OBJECTIVE

To determine whether the photopic negative response (PhNR) of the electroretinogram (ERG) is reduced in patients with primary open angle glaucoma (POAG).

METHODS

ERGs were recorded with DTL electrodes from 62 normal subjects (16 to 82 years), 18 POAG patients (47 to 83 years) and 7 POAG suspects (46 to 73 years) to brief flashes (<6 ms), and also in a few subjects to long (200 ms) red, full-field ganzfeld flashes delivered on a rod-saturating blue background. At the time of ERG measurements, the intraocular pressures of most of the patients were controlled medically. Visual field sensitivities were measured with the Humphrey C24-2 threshold test and optic nerve head cup-to-disc ratio (C/D) was determined by binocular indirect ophthalmoscopy.

RESULTS

ERGs of normal subjects contained a slow negative potential following the a- and b-waves, the PhNR, that increased slightly in latency with age. The a- and b-wave amplitudes and implicit times of POAG patients were similar to age-matched controls. In contrast, their PhNRs were small or virtually absent. PhNR amplitudes were reduced even when visual sensitivity losses were small, and were correlated significantly (P < 0.05) with mean deviation (MD), corrected pattern SD (CPSD), and C/D across the population of POAG patients whose MD losses ranged from 1 to 13 dB, CPSDs from 0 to 11 dB and C/Ds from 0.6 to 0.9. PhNRs of most POAG suspects also were small.

CONCLUSIONS

PhNR amplitudes in POAG patients are smaller than those of normal subjects. PhNR amplitudes are reduced when visual field sensitivity losses are mild and become even smaller as sensitivity losses increase. There is a potential role for the PhNR in early detection and possibly in monitoring the progression of glaucomatous damage.

In Streptococcus pneumoniae, the first four genes of the capsule locus (cpsA to cpsD) are common to most serotypes. By analysis of various in-frame deletion and site-directed mutants, the function of their gene products in capsular polysaccharide (CPS) biosynthesis was investigated. We found that while CpsB, C and D are essential for encapsulation, CpsA is not. CpsC and CpsD have similarity to the amino-terminal and carboxy-terminal regions, respectively, of the autophosphorylating protein-tyrosine kinase Wzc from Escherichia coli. Alignment of CpsD with Wzc and other related proteins identified conserved Walker A and B sequence motifs and a tyrosine rich domain close to the carboxy-terminus. We have shown that CpsD is also an autophosphorylating protein-tyrosine kinase and that point mutations in cpsD affecting either the ATP-binding domain (Walker A motif) or the carboxy-terminal [YGX]4 repeat domain eliminated tyrosine phosphorylation of CpsD. We describe, for the first time, the phenotypic impact of these two mutations on polysaccharide production and show that they affect CPS production differently. Whereas a mutation in the Walker A motif resulted in loss of encapsulation, mutation of the tyrosines in the [YGX]4 repeat domain resulted in an apparent increase in encapsulation and a mucoid phenotype. These data suggest that autophosphorylation of CpsD at tyrosine attenuates its activity and reduces the level of encapsulation. Additionally, we demonstrated that CpsC is required for CpsD tyrosine phosphorylation and that CpsB influences dephosphorylation of CpsD. These results are consistent with CpsD tyrosine phosphorylation acting to negatively regulate CPS production. This has implications for the function of CpsC/CpsD homologues in both Gram-positive and Gram-negative bacteria and provides a mechanism to explain regulation of CPS production during pathogenesis.

OBJECTIVE

To evaluate the role and ability of optical coherence tomography (OCT) to detect differences in peripapillary retinal nerve fiber layer (RNFL) thickness between normal and glaucomatous eyes and also between different severities of glaucoma.

METHODS

This cross-sectional observational study included 160 eyes of 160 healthy subjects and 134 eyes of 134 patients with primary open-angle glaucoma (POAG). Peripapillary RNFL thickness was measured on OCT using the fast RNFL thickness protocol. The RNFL thickness parameters used for evaluation included average RNFL thickness and inferior, superior, nasal, and temporal RNFL thickness. The glaucomatous eyes were subdivided into three subgroups on the basis of visual field defects and a fourth subgroup of eyes blinded by glaucoma. RNFL thickness parameters were compared among the normal eyes and the glaucoma subgroups. Correlation of global visual field indices with RNFL thickness parameters was also performed.

RESULTS

The average RNFL in control subjects, early glaucoma, moderate glaucoma, severe glaucoma, and blind glaucoma were 102.30 +/- 10.34, 77.68 +/- 15.7, 66.07 +/- 15.5, 53.65 +/- 14.2, and 44.93 +/- 4.95 microm, respectively. There was a significant difference in all RNFL thickness parameters between normal and all glaucoma subgroups (P < 0.001). Average and inferior RNFL thicknesses showed the highest area under the receiver operating characteristic curve, with 0.905 and 0.862 for normal versus early glaucoma, 0.705 and 0.722 for early versus moderate glaucoma, 0.737 and 0.717 for moderate versus severe glaucoma, and 0.635 and 0.584 for severe versus blind glaucoma. Both mean deviation (MD) and corrected pattern standard deviation (CPSD) showed a significant correlation with all the RNFL thickness parameters in eyes with glaucoma (P < 0.001).

CONCLUSIONS

RNFL thickness measured on OCT may serve as useful adjuncts in accurately and more objectively distinguishing normal from glaucomatous eyes, even in the early stages of glaucoma and may help to differentiate various severities of glaucoma. Average and inferior RNFL thicknesses are among the most efficient parameters for distinguishing such a differentiation. RNFL thicknesses in eyes blinded by glaucoma provide an estimate of the component of the RNFL thickness, which is not related to visual function.

OBJECTIVE

To compare the abilities of scanning laser polarimetry (SLP), optical coherence tomography (OCT), short-wavelength automated perimetry (SWAP), and frequency-doubling technology (FDT) perimetry to discriminate between healthy eyes and those with early glaucoma, classified based on standard automated perimetry (SAP) and optic disc appearance. To determine the agreement among instruments for classifying eyes as glaucomatous.

METHODS

One eye of each of 94 subjects was included. Healthy eyes (n = 38) had both normal-appearing optic discs and normal SAP results. Glaucoma by SAP (n = 42) required a repeatable abnormal result (glaucoma hemifield test [GHT] or corrected pattern standard deviation [CPSD] outside normal limits). Glaucoma by disc appearance (n = 51) was based on masked stereoscopic photograph evaluation. Receiver operating characteristic (ROC) curve areas, sensitivities, and specificities were calculated for each instrument separately for each diagnosis.

RESULTS

The largest area under the ROC curve was found for OCT inferior quadrant thickness (0.91 for diagnosis based on SAP, 0.89 for diagnosis based on disc appearance), followed by the FDT number of total deviation plot points of < or =5% (0.88 and 0.87, respectively), SLP linear discriminant function (0.79 and 0.81, respectively), and SWAP PSD (0.78 and 0.76, respectively). For diagnosis based on SAP, the ROC curve area was significantly larger for OCT than for SLP and SWAP. For diagnosis based on disc appearance, the ROC curve area was significantly larger for OCT than for SWAP. For both diagnostic criteria, at specificities of>> or =90% and>> or =70%, the most sensitive OCT parameter was more sensitive than the most sensitive SWAP and SLP parameters. For diagnosis based on SAP, the most sensitive FDT parameter was more sensitive than the most sensitive SLP parameter at specificities of>> or =90% and>> or =70% and was more sensitive than the most sensitive SWAP parameter at specificity of>> or =70%. For diagnosis based on disc appearance at specificity of>> or =90%, the most sensitive FDT parameter was more sensitive than the most sensitive SWAP and SLP parameters. At specificity>> or = 90%, agreement among instruments for classifying eyes as glaucomatous was poor.

CONCLUSIONS

In general, areas under the ROC curve were largest (although not always significantly so) for OCT parameters, followed by FDT, SLP, and SWAP, regardless of the definition of glaucoma used. The most sensitive OCT and FDT parameters tended to be more sensitive than the most sensitive SWAP and SLP parameters at the specificities investigated, regardless of diagnostic criteria.

CpsA, CpsB, CpsC, and CpsD are part of a tyrosine phosphorylation regulatory system involved in modulation of capsule synthesis in Streptococcus pneumoniae and many other gram-positive and gram-negative bacteria. Using an immunoblotting technique, we observed distinct laddering patterns of S. pneumoniae capsular polysaccharides of various serotypes and found that transfer of the polymer from the membrane to the cell wall was independent of size. Deletion of cps2A, cps2B, cps2C, or cps2D in the serotype 2 strain D39 did not affect the ability to transfer capsule to the cell wall. Deletion of cps2C or cps2D, which encode two domains of an autophosphorylating tyrosine kinase, resulted in the production of only short-chain polymers. The function of Cps2A is unknown, and the polymer laddering pattern of the cps2A deletion mutants appeared similar to that of the parent, although the total amount of capsule was decreased. Loss of Cps2B, a tyrosine phosphatase and a kinase inhibitor, resulted in an increase in capsule amount and a normal ladder pattern. However, Cps2B mutants exhibited reduced virulence following intravenous inoculation of mice and were unable to colonize the nasopharynx, suggesting a diminished capacity to sense or respond to these environments. In D39 and its isogenic mutants, the amounts of capsule and tyrosine-phosphorylated Cps2D (Cps2D approximately P) correlated directly. In contrast, restoration of type 2 capsule production followed by deletion of cps2B in Rx1, a laboratory passaged D39 derivative containing multiple uncharacterized mutations, resulted in decreased capsule amounts but no alteration in Cps2D approximately P levels. Thus, a factor outside the capsule locus, which is either missing or defective in the Rx1 background, is important in the control of capsule synthesis.

Four genes, cpsA-cpsD, at the 5' end of the capsular polysaccharide (CPS) biosynthesis locus are conserved in nearly all of the 90 known serotypes of Streptococcus pneumoniae. In the present study, the impact that mutations in cpsA, cpsB, and cpsD have on CPS production and on virulence in mice infected via systemic and intranasal routes was investigated. Strains exhibiting rough colony morphologies (in which either the cpsB or cpsD gene had been deleted) were avirulent, but a smooth, partially encapsulated strain (in which the cpsA gene had been deleted) was as virulent as the wild-type strain. Interestingly, mucoid strains containing mutations affecting the [YGX](3)-repeat domain of CpsD were unable to cause bacteremia after intranasal challenge of CD1 mice, even though such strains were capable of killing BALB/c mice after intraperitoneal challenge. In our model, the ability of S. pneumoniae to regulate, via CpsD phosphorylation, CPS production was required for its transition from the lung to the bloodstream.

We showed previously that a mutant strain of group B Streptococcus (GBS) defective in capsule production was avirulent. This study describes the derivation of an unencapsulated mutant from a highly encapsulated wild-type strain of type III GBS, COH1, by transposon mutagenesis with Tn916 delta E. The mutant, COH1-13, was sensitive to phagocytic killing by human leukocytes in vitro and was relatively avirulent in a neonatal rat sepsis model compared with the wild-type strain. No capsular polysaccharide was evident in the cytoplasm or on the cell surface of the mutant strain. The Tn916 delta E insertion site in COH1-13 was mapped to the same chromosomal location as the Tn916 insertion site in the unencapsulated type III mutant COH31-15 reported previously. Nucleotide sequencing of DNA flanking the insertion site in COH1-13 revealed an open reading frame, designated cpsD, with significant homology to the rfbP gene of Salmonella typhimurium. RfbP encodes a galactosyl transferase enzyme that catalyses the transfer of galactose to undecaprenol phosphate, the initial step in O-polysaccharide synthesis. A particulate fraction of a lysate of wild-type strain GBS COH1 mediated the transfer of galactose from UDP-galactose to an endogenous acceptor. The galactose-acceptor complex partitioned into organic solvents, suggesting it is lipid in nature or membrane-associated. Galactosyl transferase activity was significantly reduced in the unencapsulated mutant strain COH1-13. These results, together with the similarity in deduced amino acid sequence between cpsD and rfbP suggest that cpsD encodes a galactosyl transferase essential for assembly of the GBS type III capsular polysaccharide.

OBJECTIVE

To detect and estimate the rate of progression of visual field loss in subjects with glaucoma who undergo long-term automated perimetric visual field testing.

METHODS

Automated visual field data were obtained for subjects with glaucomatous visual field loss and a minimum of seven threshold field tests over at least 4.5 years. Univariate linear regression was performed with respect to mean deviation (MD), corrected pattern standard deviation (CPSD), mean thresholds of clusters corresponding to the Glaucoma Hemifield Test (GHT), and thresholds of 52 individual test locations. Subjects were classified as progressive or stable (unchanged or improved) based on the slope and statistical significance of these parameters. Adjusted P values were used to maintain the overall type 1 error at 5%.

RESULTS

One hundred ninety-one subjects with a mean follow-up period of 7.1 years (range, 4.5 to 10.5 years) and a mean number of visual field tests of 9.5 (range, 7 to 16) were included. Twenty-four subjects (12.6%) showed progression in MD (mean slope [95% confidence interval], -1.26 [-1.50, -1.01] dB/year), and 27 (14.1%) showed progression in CPSD (mean slope [95% confidence interval], 0.71 [0.58, 0.84] dB/year). Thirty-five subjects (18.3%) had>> or = 1 progressive GHT cluster. The mean slope in progressive clusters ranged from -1.51 [-1.82, -1.20] to -2.84 [-3.39, -2.29] dB/year. Thirty-six subjects (18.8%) had>> or = 1 progressive individual test locations. Fifty-two subjects (27.2%) were classified as progressive based on progression of CPSD,>> or = 1 cluster and/or>> or = 1 point.

CONCLUSIONS

Fewer than 1 in 3 subjects progressed by any one of the criteria for progression over an average of 7.1 years. Rates of progression that could be statistically confirmed were in the range of approximately 1 to 5 dB/year, depending on the number of fields, the variability over time, and the parameter assessed (global indices, GHT clusters, or individual points). No correlation between initial visual field status and the rate of progression was found. A minimum of approximately 5 years of follow-up with annual perimetry would be required to detect significant changes in the visual field by linear regression.

The capacity of Streptococcus pneumoniae to produce capsular polysaccharide (CPS) is essential for virulence. The CPS biosynthesis proteins CpsB, CpsC, and CpsD function to regulate CPS production via tyrosine phosphorylation of CpsD. This mechanism of regulating CPS production is important for enabling S. pneumoniae to cause invasive disease. Here, we identify mutations affecting the attachment of CPS to the cell wall. These mutations were located in cpsC, such that CpsC functioned independently from CpsD tyrosine phosphorylation. These mutants produced WT levels of CPS, but were unable to cause bacteremia in mice after intranasal challenge. This finding suggests that cell-wall attachment of CPS is essential for invasive pneumococcal disease; production of WT levels of CPS alone is not sufficient. We also show that cpsB mutants, which lack the phosphotyrosine-protein phosphatase, produced less CPS than the WT strain, but attached substantially more CPS to their cell wall. Thus, the phosphorylated form of CpsD promotes attachment of CPS to the cell wall.

Most isolates of Streptococcus pneumoniae are mixed populations of transparent (T) and opaque (O) colony phenotypes. Differences in the production of capsular polysaccharide (CPS) between O and T variants were accentuated by changes in the environmental concentration of oxygen. O variants demonstrated a 5.2- to 10.6-fold increase in amounts of CPS under anaerobic compared to atmospheric growth conditions, while CPS production remained low under all conditions for T variants. Increased amounts of CPS in O compared to T pneumococci were associated with increased expression of cps-encoded proteins. The inhibitory effect of oxygen on expression of CPS in O variants correlated with decreased tyrosine phosphorylation of CpsD, a tyrosine kinase and regulator of CPS synthesis. Modulation of CpsD expression and its activity by tyrosine phosphorylation may allow the pneumococcus to adapt to the requirements of both colonization, where decreased CPS allows for adherence, and bacteremia, where increased CPS may be required to escape from opsonic clearance. In patients with invasive infection, paired isolates from the same patient were shown to have predominantly a T colony phenotype without phosphotyrosine on CpsD when cultured from the nasopharynx, and an O phenotype that phosphorylates CpsD in response to oxygen when cultured from the blood. Differences in the availability of oxygen, therefore, may be a key factor in allowing for the selection of distinct phenotypes in these two host environments.

OBJECTIVE

To introduce a new method, derived from the Glaucoma Staging System (GSS), for classifying glaucomatous visual field defects.

METHODS

Four sample groups composed respectively of 471 (sample #1), 128 (sample #2), 185 (sample #3), and 131 (sample #4) patients with either ocular hypertension or chronic glaucoma were considered. The GSS 2 uses both the MD and CPSD/CLV or PSD/LV perimetric indices to classify visual field defect in 6 stages and in 3 types (generalized, localized, and mixed). The formulas were determined using sample #1. A new borderline stage was created, on the basis of sample #2. The relationship between the PSD/LV and CPSD/CLV values was studied on sample #3 to verify the possibility of using the uncorrected indices instead of the CPSD/CLV. The relationship with other classification methods was studied on sample #4.

RESULTS

The GSS 2 showed a strong level of association with the AGIS and the Hodapp-Parrish-Anderson methods in staging defect severity. A good correlation was also found with a classification based on the Bebie curve.

CONCLUSIONS

The GSS 2 was able to correctly classify both damage severity and perimetric defect type in the sample studied, using either the corrected or uncorrected visual field indices. It is a quick and easy method, and its formulas can be introduced in any software.

The first four genes of the capsule locus (cps) of Streptococcus pneumoniae (cpsA to cpsD) are common to most serotypes. We have previously determined that CpsD is an autophosphorylating protein-tyrosine kinase, demonstrated that CpsC is required for CpsD tyrosine-phosphorylation, and shown that CpsB is required for dephosphorylation of CpsD. In the present study we show that CpsB is a novel manganese-dependent phosphotyrosine-protein phosphatase that belongs to the PHP (polymerase and histidinol phosphatase) family of phosphoesterases. We also show that an S. pneumoniae strain with point mutations in cpsB, affecting one of the conserved motifs of CpsB, is unencapsulated and appears to be morphologically identical to a strain in which the cpsB gene had been deleted.

OBJECTIVE

To evaluate the effect of Ginkgo biloba extract (GBE) on preexisting visual field damage in patients with normal tension glaucoma (NTG).

METHODS

Prospective, randomized, placebo-controlled, double-masked cross-over trial.

METHODS

Twenty-seven patients with bilateral visual field damage resulting from NTG.

METHODS

Patients received 40 mg GBE, administered orally, three times daily for 4 weeks, followed by a wash-out period of 8 weeks, then 4 weeks of placebo treatment (identical capsules filled with 40 mg fructose). Other patients underwent the same regimen, but took the placebo first and the GBE last. Visual field tests, performed at baseline and at the end of each phase of the study, were evaluated for changes.

METHODS

Change in visual field and any ocular or systemic complications.

RESULTS

After GBE treatment, a significant improvement in visual fields indices was recorded: mean deviation (MD) at baseline versus MD after GBE treatment, 11.40 +/- 3.27 dB versus 8.78 +/- 2.56 dB (t = 8.86, P = 0.0001, chi-square test); corrected pattern standard deviation (CPSD) at baseline versus CPSD after GBE treatment, 10.93 +/- 2.12 dB versus 8.13 +/- 2.12 dB (t = 9.89, P = 0.0001, chi-square test). No significant changes were found in intraocular pressure, blood pressure, or heart rate after placebo or GBE treatment. Any ocular and systemic side effects were recorded for the duration of the trial.

CONCLUSIONS

Ginkgo biloba extract administration appears to improve preexisting visual field damage in some patients with NTG.

OBJECTIVE

In this twofold study, part 1 aimed to determine whether the playing of high resistance wind instruments elevates intraocular pressure (IOP) and if so, to investigate the mechanism of IOP elevation and whether its magnitude differs while playing high resistance versus low resistance instruments. The purpose of part 2 was to evaluate whether high resistance players have a greater incidence of glaucomatous changes than other musicians.

METHODS

Three case reports and a cross-sectional study.

METHODS

Two players of high resistance instruments and one player of high and low resistance wind instruments participated in part 1 of the study. Nine high resistance wind players, 12 low resistance wind players, and 24 nonwind players were recruited among professional musicians in the Boston area to participate in part 2.

METHODS

In part 1, IOP and uveal thickness changes were measured by pneumatonometry and ultrasound biomicroscopy in two participants playing their high resistance wind instruments (trumpet and oboe) and in a third participant playing both high (trumpet) and low (clarinet and saxaphone) resistance instruments. Each musician in part 2 underwent medical and musical history, measurement of IOP, Humphrey visual field testing, slit-lamp examination, gonioscopy, and dilated examination.

METHODS

Intraocular pressure and uveal thickness changes, and visual field loss and optic nerve head appearance were the main parameters measured in part 1 and part 2, respectively.

RESULTS

In part 1, pneumatonometry showed IOP elevation dependent on the force of blowing, and ultrasound biomicroscopy revealed uveal thickening associated with IOP elevation. The magnitude of IOP elevation was dependent on the amount of expiratory resistance provided by the particular instrument. Part 2 showed that life hours of high resistance wind instrument playing had a significant relationship to abnormal visual field (P = 0.03) and corrected pattern standard deviation (CPSD) scores (P = 0.007) in univariate logistic regression and univariate linear regression, respectively. A 0.011-unit increase in CPSD for each 1000 life hours of high resistance wind playing was found.

CONCLUSIONS

High and low resistance wind musicians experience a transient rise in their IOP while playing their instruments as a result least in part of uveal engorgement. The magnitude of IOP increase is greater in high resistance wind players versus low resistance wind players. High resistance wind musicians had a small but significantly greater incidence of visual field loss (abnormal fields and increased CPSD scores) than other musicians, which was related to life hours of playing. The cumulative effects of long-term intermittent IOP elevation during high resistance wind instrument playing may result in glaucomatous damage, which could be misdiagnosed as normal-tension glaucoma.

In Streptococcus pneumoniae, CpsB, CpsC, and CpsD are essential for encapsulation, and mutants containing deletions of cpsB, cpsC, or cpsD exhibit rough colony morphologies. CpsD is an autophosphorylating protein-tyrosine kinase, CpsC is required for CpsD tyrosine phosphorylation, and CpsB is a phosphotyrosine-protein phosphatase. We have previously shown that autophosphorylation of CpsD at tyrosine attenuates its activity and consequently reduces the level of encapsulation and negatively regulates CPS production. In this study, we further investigated the role of the carboxy-terminal (YGX)(4) repeat domain of CpsD in encapsulation. A CpsD truncation mutant in which the entire (YGX)(4) repeat domain was removed was indistinguishable from a strain in which the entire cpsD gene had been deleted, indicating that the carboxy-terminal (YGX)(4) tail is required for CpsD activity in capsular polysaccharide production. Double mutants having a single tyrosine residue at position 2, 3, or 4 in the (YGX)(4) repeat domain and lacking CpsB exhibited a rough colony morphology, indicating that in the absence of an active protein-tyrosine phosphatase, phosphorylation of just one of the tyrosine residues in the (YGX)(4) repeat was sufficient to inactivate CpsD. When various mutants in which CpsD had either one or combinations of two or three tyrosine residues in the (YGX)(4) repeat domain were examined, only those with three tyrosine residues in the (YGX)(4) repeat domain were indistinguishable from the wild-type strain. The mutants with either one or two tyrosine residues exhibited mucoid colony morphologies. Further analysis of the mucoid strains indicated that the mucoid phenotype was not due to overproduction of capsular polysaccharide, as these strains actually produced less capsular polysaccharide than the wild-type strain. Thus, the tyrosine residues in the (YGX)(4) repeat domain are essential for normal functioning of CpsD.

Tyrosine phosphorylation is associated with polysaccharide synthesis in a number of Gram-positive and Gram-negative bacteria. In Streptococcus pneumoniae, CpsB, CpsC, and CpsD affect tyrosine phosphorylation and are critical for the production of a mature capsule in vitro. To characterize the interactions between these proteins and the phosphorylation event they modulate, cps2B, cps2C, and cps2D from the capsule type 2 S. pneumoniae D39 were cloned and expressed both individually and in combination in Escherichia coli. Cps2D purified from E. coli was not phosphorylated unless it was co-expressed with its cognate transmembrane domain, Cps2C. Purified phosphorylated Cps2D had tyrosine kinase activity and could phosphorylate both dephosphorylated Cps2D and an exogenous substrate (poly-Glu-Tyr) in the absence of ATP. Cps2B exhibited phosphatase activity against both purified phosphorylated Cps2D and p-nitrophenyl phosphate. An additional role for Cps2B as an inhibitor of Cps2D phosphorylation was demonstrated in both co-expression experiments in E. coli and in vitro experiments where it blocked the transphosphorylation of Cps2D even in the presence of the phosphatase inhibitor sodium orthovanadate. cps2C and cps2D deletion mutants in S. pneumoniae produced no detectable mature capsule during laboratory culture. Both were avirulent in systemic mouse infections and were unable to colonize the nasopharynx, suggesting that the failure to produce capsule was not dependent on the environment. Based on these results, we propose a model for capsule regulation where CpsB, CpsC, CpsD, and ATP form a stable complex that enhances capsule synthesis.

OBJECTIVE

To study blood pressure (BP), intraocular pressure (IOP), and mean ocular perfusion pressure (MOPP) in patients with untreated normal tension glaucoma (NTG), and to investigate the relationship between circadian MOPP fluctuation and visual field status at initial presentation.

METHODS

IOP and BP were evaluated in hospital over 24 hours in 132 patients with NTG, with measurements taken every 2 hours between 12 PM and 10 AM the following day, except for the period between 12 and 6 AM, during which measurements were taken every 3 hours. MOPP was calculated from the 24-hour IOP and BP data. Patients were classified into three groups-nondippers, dippers, and overdippers-corresponding to the degree of reduction in their nocturnal mean arterial pressure (MAP) compared with their diurnal MAP. IOP and systemic and ocular hemodynamic parameters were compared among the groups. The correlations between circadian MOPP fluctuation and visual field scores (mean deviation [MD] and corrected pattern standard deviation [CPSD]) at initial presentation were analyzed.

RESULTS

Forty-one (31.1%) of the patients with NTGs were classified into the nondipper group, 36 (27.2%) into the dipper group, and 55 (41.7%) into the overdipper group. Marked circadian MOPP fluctuation was noted in the overdipper group (P < 0.05). Circadian MOPP fluctuation showed positive associations with visual field indices at initial diagnosis of NTG (P < 0.05, R2 = 0.056 with MD, R2 = 0.038 with CPSD).

CONCLUSIONS

Marked circadian MOPP fluctuation was associated with nocturnal BP reduction. Circadian MOPP fluctuation may be a risk factor for the development of NTG.

OBJECTIVE

To determine which machine learning classifier learns best to interpret standard automated perimetry (SAP) and to compare the best of the machine classifiers with the global indices of STATPAC 2 and with experts in glaucoma.

METHODS

Multilayer perceptrons (MLP), support vector machines (SVM), mixture of Gaussian (MoG), and mixture of generalized Gaussian (MGG) classifiers were trained and tested by cross validation on the numerical plot of absolute sensitivity plus age of 189 normal eyes and 156 glaucomatous eyes, designated as such by the appearance of the optic nerve. The authors compared performance of these classifiers with the global indices of STATPAC, using the area under the ROC curve. Two human experts were judged against the machine classifiers and the global indices by plotting their sensitivity-specificity pairs.

RESULTS

MoG had the greatest area under the ROC curve of the machine classifiers. Pattern SD (PSD) and corrected PSD (CPSD) had the largest areas under the curve of the global indices. MoG had significantly greater ROC area than PSD and CPSD. Human experts were not better at classifying visual fields than the machine classifiers or the global indices.

CONCLUSIONS

MoG, using the entire visual field and age for input, interpreted SAP better than the global indices of STATPAC. Machine classifiers may augment the global indices of STATPAC.

Spectral analysis of backscattered intravascular ultrasound (IVUS) data has demonstrated the ability to characterize plaque. We compared the ability of spectral parameters (e.g., slope, midband fit and y-intercept), computed via classic Fourier transform (CPSD), Welch power spectrum (WPSD) and autoregressive (MPSD) models, to classify plaque composition. Data were collected ex vivo from 32 human left anterior descending coronary arteries. Regions-of-interest (ROIs), selected from histology, comprised 64 collagen-rich, 24 fibrolipidic, 23 calcified and 37 calcified-necrotic regions. A novel quantitative method was used to correlate IVUS data with corresponding histologic sections. Periodograms of IVUS samples, identified for each ROI, were used to calculate spectral parameters. Statistical classification trees (CT) were computed with 75% of the data for plaque characterization. The remaining data were used to assess the accuracy of the CTs. The overall accuracies for normalized spectra with CPSD, WPSD and MPSD were, respectively, 84.7%, 85.6% and 81.1% (training data) and 54.1%, 64.9% and 37.8% (test data). These numbers were improved to 89.2%, 91.9% and 89.2% (training) and 62.2%, 73% and 59.5% (test) when the calcified and calcified-necrotic regions were combined for analysis. Most CTs misclassified a few fibrolipidic regions as collagen, which is histologically acceptable, and the unnormalized and normalized spectra results were similar.

OBJECTIVE

The authors estimated the prevalence and rates of progressive visual field loss in glaucoma patients followed annually for a median of 6.3 years.

METHODS

Linear regression was used to estimate rates of progression of mean deviation, corrected pattern standard deviation (CPSD), clusters of locations based on the Glaucoma Hemifield Test (GHT), and location specific changes in C-30-2 fields of the Humphrey Analyzer.

RESULTS

Sixty-seven eyes of 56 patients whose first two consecutive fields were abnormal on GHT were included. Almost all patients were under treatment or had undergone surgery for glaucoma. Visual field deteriorated in 19 (28%) eyes based on worsening of one or more CPSD, GHT clusters, or individual test locations (regression slopes significantly different from zero). Corrected pattern standard deviation deteriorated in 5 eyes, at least one GHT cluster deteriorated in 17 eyes, and one or more individual test locations deteriorated in 15 eyes. For those whose visual field deteriorated, CPSD increased by 0.9 dB/year. Glaucoma Hemifield Test clusters declined by between 1.4 and 2.4 dB/year. Deterioration at individual locations ranged from 1.0 to 5.0 dB/year. Age, but not baseline visual field severity, was predictive of further visual field loss. The odds ratio for the association between progressive visual field loss and thinning of the nerve fiber layer was 1.81 (95% confidence interval: 0.52, 6.33), and 3.78 (95% confidence interval: 0.80, 18.16) for the association between progressive visual field loss and optic disc changes during follow-up based on masked photograph readings.

CONCLUSIONS

Less than one in three eyes of patients with glaucoma had any progressive field loss. Average changes in threshold sensitivities of less than 1 dB/year could not be detected with seven fields done over 6 years. Larger changes or increased frequency of visual field testing would need to occur before smaller changes could be detected statistically.

Mannose-binding lectin (MBL) is a serum protein that has been demonstrated to activate the classical complement pathway and to function directly as an opsonin. Although MBL deficiency is associated with a common opsonic defect and a predisposition to infection, the role of the protein in bacterial infection remains unclear. We have investigated MBL binding to Neisseria meningitidis serogroup B1940 and three isogenic mutants, and the subsequent activation of the two major isoforms of C4 (C4A and C4B) by an associated serine protease, MASP. The mutants lacked expression of the capsular polysaccharide (siaD-), the lipo-oligosaccharide (LOS) outer core that prevented LOS sialylation (cpsD-), or both capsule and LOS outer core (cps-). Using flow cytometry, it was possible to detect strong MBL binding to the cps- and cpsD- mutants over a wide range of concentrations. In contrast, minimal or no MBL binding was detected on the parent organism, with binding to siaD- only at higher MBL concentrations. C4 was activated and bound by mutants that had previously bound MBL/MASP, but there was no significant difference in the amounts of C4A and C4B bound. When sialic acid residues were removed from the parent organism by neuraminidase treatment, the binding of both MBL and C4 increased significantly. Our results suggest that MBL may bind to and activate complement on these encapsulated organisms, and the major determinants of these effects are the LOS structure and sialylation.

Forty group B Streptococcus (GBS) isolates obtained from Europe and the United States previously reported to be nontypeable (NT) by capsule serotype determination were subjected to buoyant density gradient centrifugation. From nearly half of the isolates capsule-expressing variants could be selected. For characterization of the remaining NT-GBS isolates, the capsule operon (cps) was amplified by the long-fragment PCR technique and compared by restriction fragment length polymorphism (RFLP) analysis. The patterns from serotype reference isolates (n = 32) were first determined and used as a comparison matrix for the NT-GBS isolates. Using two restriction enzymes, SduI and AvaII, cluster analysis revealed a high degree of similarity within serotypes but less than 88% similarity between serotypes. However, serotypes III and VII were each split in two distant RFLP clusters, which were designated III(1) and III(2) and VII(1) and VII(2), respectively. Among the isolates that remained NT after repeated Percoll gradient selections, two insertional mutants were revealed. Both were found in blood isolates and harbored insertion sequence (IS) elements within cpsD: one harbored IS1548, and the other harbored IS861. All other NT-GBS isolates could, by cluster analysis, be referred to different serotypes by comparison to the RFLP reference matrix. In pulsed-field gel electrophoresis of SmaI-restricted chromosomal DNA, patterns from allelic type 1 and 2 isolates were essentially distributed in separate clusters in serotypes III and VII. A covariation with insertion sequence IS1548 in the hylB gene was suggested for serotype III, since allelic type III(1) harboring IS1548 in hylB, clustered separately. The variation in serotype VII was not dependent on the presence of IS1548, which was not detected at any position in the type VII chromosome.

OBJECTIVE

To compare the results of the water drinking test between glaucomatous eyes with and without visual field progression.

METHODS

Retrospective analysis of 76 eyes of 76 open angle glaucoma patients followed for a mean period of 26.0 (SD 13.8) months. Patients were submitted to the water drinking test at the beginning of the follow up period. Reliable achromatic automated perimetry tests performed during the studied period were used to characterise visual field progression. All subjects were under clinical therapy and had an intraocular pressure (IOP) lower than 17 mm Hg monitored by isolated measurements during the follow up period. The results of the water drinking test were compared between glaucomatous eyes with and without visual field progression.

RESULTS

Twenty eight eyes reached definite visual field progression. There were no significant differences in the mean age, sex, race, basal IOP, number of antiglaucomatous drugs, initial mean deviation (MD), and corrected pattern standard deviation (CPSD) between eyes that showed visual field progression and the ones who did not progress. A significant difference of 1.9 (SD 0.6) mm Hg (p = 0.001, analysis of covariance; 95% CI 0.8 to 3.0) was observed between glaucomatous eyes that showed visual field deterioration and glaucomatous eyes that did not progress. A significant difference of 16.8% (SD 4.6%) in the mean percentage of IOP variation was also observed between the two groups (p<0.001, analysis of covariance; 95% CI 7.7 to 26.0).

CONCLUSIONS

Mean IOP peak and percentage of IOP variation during water drinking test were significantly higher in patients with visual field progression compared with patients who did not progress.

OBJECTIVE

To evaluate the quality of life in glaucomatous patients using two different questionnaires: the medical outcomes study 36-item short-form health survey (MOS SF-36) and Viswanathan et al's questionnaire and to compare these two questionnaires.

METHODS

Seventy-seven patients with glaucoma were consecutively selected. Two force-choice questionnaires were administered to each patient. Viswanathan et al's questionnaire was related to visual disability and the second was related to the quality of life from the MOS 36-item short-form health survey. Both questionnaires were evaluated among all the considered patients and the results were compared. Then the questionnaire which did the best evaluation was used to test the quality of life in three different subgroups based on the mean deviation of the worse eye. Mann-Whitney non parametric test and Spearman's r coefficient were used and a P value less than 0.05 was considered to be statistically significant. A linear regression model was used.

RESULTS

In the entire group (n = 77) the Mean Deviation (MD) was -6.5 +/- 6.8 dB (mean +/- standard deviation) and Corrected Pattern Standard Deviation (CPSD) was 4.7 +/- 4.1 dB. The score of the Viswanathan et al's questionnaire was 8.3 +/- 2.4, while MOS SF-36 score ranged from 60.5% to 100% (mean score %). A significant (P < 0.0001) correlation was found between the score of the Viswanathan et al's questionnaire and MD (r = 0.79), Pattern Standard Deviation (PSD) (r = -0.68) and CPSD (r = -0.61).

CONCLUSIONS

Viswanathan et al's questionnaire was more useful than MOS SF-36, both for the score and for the velocity to use. Furthermore Viswanathan et al's questionnaire was more significantly correlated to visual field MD.