The specific recognition of DNA modifications by repair endonucleases was used to characterize the DNA damage induced by photosensitizers in the presence of visible light. Under cell-free conditions, chemically unrelated photosensitizers (methylene blue, acridine orange, proflavin, riboflavin, hematoporphyrin) induce the same type of DNA damage. It is characterized by a high number of base modifications sensitive to the repair endonuclease FPG protein (formamidopyrimidine-DNA glycosylase), while both the number of DNA strand breaks and the number of sites of base loss (sensitive to exonuclease III or endonuclease IV) is low. Therefore the damage is markedly different from that induced by hydroxyl radicals. Mechanistically, the generation of the base modifications sensitive to FPG protein involves singlet oxygen in some, but possibly not all cases, as substituting D2O for H2O increases the reaction yield six-fold in the case of methylene blue, but only 1.4-fold in the case of acridine orange. In plasmids from Salmonella typhimurium strains treated with methylene blue or acridine orange plus light and from Escherichia coli strains treated with acridine orange or proflavin plus light, the same type of damage was observed as under cell-free conditions. In L1210 mouse leukemia cells exposed to acridine orange plus light, the numbers of modifications sensitive to FPG protein and exonuclease III were quantified, in addition to strand breaks, by a modified alkaline elution assay. Again, the number of base modifications sensitive to FPG protein was found to be several-fold higher than the number of strand breaks and sites of base loss. It has to be concluded that the DNA damage in the intact cells is not mediated by hydroxyl radicals or cellular nucleases, but by the same mechanism as operates under cell-free conditions with these agents.

The crystal structure of chicken egg white riboflavin-binding protein, determined to a resolution of 2.5 A, is the prototype of a family that includes other riboflavin- and folate-binding proteins. An unusual characteristic of these molecules is their high degree of cross-linking by disulfide bridges and, in the case of the avian proteins, the presence of stretches of highly phosphorylated polypeptide chain. The structure of chicken egg white riboflavin-binding protein is characterized by a ligand-binding domain and a phosphorylated motif. The ligand-binding domain has a fold that appears to be strongly conditioned by the presence of the disulfide bridges. The phosphorylated motif, essential for vitamin uptake, is made up of two helices found before and after the flexible phosphorylated region. The riboflavin molecule binds to the protein with the isoalloxazine ring stacked in between the rings of Tyr75 and Trp156. This geometry and the proximity of other tryptophans explain the fluorescent quenching observed when riboflavin binds to the protein.

Diet is important in triggering the symptoms of irritable bowel syndrome (IBS). This study investigated the impact of dietary guidance on the symptoms, quality of life and habitual diet of patients with IBS. Forty-six patients who fulfilled the Rome III criteria for the diagnosis of IBS were included. Of these patients, 17 completed the entire study. Each patient attended three sessions (~45 min in duration) and received individual guidance on their dietary management. The patients were asked to complete the following questionnaires prior to receiving the dietary guidance, and at least 3 months subsequently: The Birmingham IBS symptom score questionnaire, the IBS Quality of Life (IBS-QOL) questionnaire, the Short-Form Nepean and Dyspepsia Index (SF‑NDI) and the MoBa Food Frequency Questionnaire (MoBa FFQ). The time at which patients completed the questionnaires following dietary guidance ranged from 3-9 months (median, 4 months). The total IBS symptom scores were reduced once the patients had received dietary guidance (P=0.001). The total score for the quality of life, as assessed by the IBS‑QOL and the SF-NDI, increased significantly following the dietary guidance sessions (P=0.003 and P=0.002, respectively). There were no statistical differences in the intake of calories, carbohydrate, fiber, protein, fat or alcohol in the patients with IBS following dietary guidance. There were increases in the consumption of dairy products, β-carotene, retinol equivalents, riboflavin, vitamin B12 and calcium, although only the increase in vitamin B12 consumption was statistically significant. There was a significant reduction in the consumption of certain fruits and vegetables that were rich in highly fermentable short-chain carbohydrates, disaccharides, monosaccharides and polyols, as well as insoluble fibers. In conclusion, three 45-min dietary guidance sessions, administered by a nurse, reduced the symptoms and improved the quality of life of patients with IBS, and resulted in an adequate intake of vitamins and minerals. Individual dietary guidance is a cost-effective option for the management of IBS.

Mucosal associated invariant T (MAIT) cells are an innate-like T cell subset prevalent in humans and distributed throughout the blood and mucosal sites. Human MAIT cells are defined by the expression of the semi-invariant TCRα chain TRAV1-2/TRAJ12/20/33 and are restricted by the non-polymorphic major histocompatibility complex (MHC) class I-like molecule, MHC-related protein 1, MR1. MAIT cells are activated by small organic molecules, derived from the riboflavin biosynthesis pathway of bacteria and fungi, presented by MR1. Traditionally, MAIT cells were thought to recognize a limited number of antigens due to usage of an invariant TCRα chain and restriction by a non-polymorphic MHC molecule. However, recent studies demonstrate that the TCR repertoire of MAIT cells is more heterogeneous, suggesting there is a more diverse array of MR1 antigens that MAIT cells can recognize. In response to infected cells, MAIT cells produce the pro-inflammatory cytokines, IFN-γ and TNF, and are cytolytic. Studies performed in MR1-deficient mice suggest that MAIT cells can provide anti-bacterial control within the first few days post-infection, as well as contribute to enhanced adaptive immunity in murine models of respiratory infections. In humans, the role of MAIT cells is unclear; however, evidence points to interplay between MAIT cells and microbial infections, including Mycobacterium tuberculosis. Given that MAIT cells are pro-inflammatory, serve in early control of bacterial infections, and appear enriched at tissue sites where microbes interface and gain access to the body, we postulate that they play an important role in antimicrobial immune responses. In this review, we discuss the most recent studies on the function and phenotype of MAIT cells, including their TCR diversity and antigenic repertoire, with a focus on the contribution of human MAIT cells in the immune response to microbial infection.

Animal source foods (ASF) can provide micronutrients in greater amounts and more bioavailable forms compared to plant source foods, but their intake is low in many poor populations. However, the impact of ASF on micronutrient status of undernourished populations has not been assessed. Supplemental meat (60-85 g/d), milk (200-250 mL/d) or energy (isocaloric with the meat and milk, 240-300 kcal/d) were randomly assigned to 555 undernourished school children aged 5-14 y in a rural malaria-endemic area of Kenya, at one school meal daily for one school year. Blood and stool samples were collected at baseline and after 1 y to assess stool parasites, malaria, hemoglobin, serum or plasma C-reactive protein, ferritin, iron, zinc, copper, vitamin B-12, folate and retinol, and erythrocyte riboflavin. At baseline, there was a high prevalence of micronutrient deficiencies (iron, zinc, vitamins A and B-12 and riboflavin), yet plasma ferritin was low in few children, and none had low serum copper. At the end of the year of supplementation, plasma vitamin B-12 concentrations were significantly increased in children fed the Meat or Milk meal; prevalence of severe plus moderate deficiency fell from 80.7% at baseline to 64.1% in the Meat group and from 71.6 to 45.1% in the Milk group, respectively. No significant improvement was observed in the status of other micronutrients compared to the Energy and Control groups, although malaria and other infections may have obscured effects. Supplementation with small amounts of meat or milk reduced the high prevalence of vitamin B-12 deficiency in these children.

BACKGROUND

The purpose of this paper was to report the results of transepithelial corneal collagen cross-linking (CXL) with modified riboflavin and ultraviolet A irradiation in patients affected by keratoconus, each with thinnest pachymetry values of less than 400 μm (with epithelium) and not treatable using standard de-epithelialization techniques.

METHODS

Sixteen patients affected by progressive keratoconus with thinnest pachymetry values ranging from 331 μm to 389 μm underwent transepithelial CXL in one eye using a riboflavin 0.1% solution in 15% Dextran T500 containing ethylenediamine tetra-acetic acid 0.01% and trometamol to enhance epithelial penetration. The patients underwent complete ophthalmological examination, including endothelial cell density measurements and computerized videokeratography, before CXL and at one day, one week, and one, 6, and 12 months thereafter.

RESULTS

Epithelial healing was complete in all patients after one day of use of a soft bandage contact lens. No side effects or damage to the limbal region was observed during the follow-up period. All patients showed slightly improved uncorrected and spectacle-corrected visual acuity; keratometric astigmatism showed reductions (up to 5.3 D) and apical ectasia power decreased (K(max) values reduced up to 4.3 D). Endothelial cell density was unchanged.

CONCLUSIONS

Application of transepithelial CXL using riboflavin with substances added to enhance epithelial permeability was safe, seemed to be moderately effective in keratoconic eyes with ultrathin corneas, and applications of the procedure could be extended to patients with advanced keratoconus.

OBJECTIVE

To evaluate the 1-year results of keratoconic eyes with thin corneas that were treated by a hypo-osmolar riboflavin solution and ultraviolet A collagen cross-linking (CXL).

METHODS

Retrospective, nonrandomized study.

METHODS

setting: Department of Ophthalmology, Carl Gustav Carus University Hospital, Dresden, Germany. study population: Thirty-two eyes of 29 patients with progressive keratoconus and a corneal thickness of less than 400 μm (without the epithelium). intervention: Application of a hypo-osmolar riboflavin solution to the cornea after its de-epithelization followed by ultraviolet A collagen cross-linking. main outcome measures: Thirty-two eyes with a follow-up within 1 year were evaluated before and after the procedure. Examinations comprised an evaluation of visual acuity, corneal topography, slit-lamp microscopy, and corneal thickness measurements.

RESULTS

Before surgery, the mean corneal thickness (with the epithelium) was 382.3 ± 41.9 μm, and after the removal of epithelium, the thickness of the cornea was reduced to 337.0 ± 51.9 μm. After the application of the hypo-osmolar riboflavin solution, this value increased to 451.8 ± 46.7 μm. Before surgery, the mean K-value of the apex of the keratoconus was 65.6 ± 11.2 diopters, and 1 year after treatment, this value remained unchanged at 64.9 ± 11.0 diopters (P = .839). Mean best-corrected visual acuity at the time of the treatment was 0.63 ± 0.37 logarithm of the minimal angle of resolution, and 1 year after the treatment, this value was not statistically different (0.59 ± 0.42 logarithm of the minimal angle of resolution; P = .662). At the last follow-up examination, which was 1 year after the procedure, all corneas were transparent, without any scarring lesions in the stroma.

CONCLUSIONS

The results of our study, using hypo-osmolar riboflavin solution in a cross-linking procedure of thin corneas, show a stability of keratoconus one year after cross-linking. Application of the hypo-osmolar riboflavin solution preserved cross-linked corneas from developing stromal scars.

We report the selective detection of single nitric oxide (NO) molecules using a specific DNA sequence of d(AT)(15) oligonucleotides, adsorbed to an array of near-infrared fluorescent semiconducting single-walled carbon nanotubes (AT(15)-SWNT). While SWNT suspended with eight other variant DNA sequences show fluorescence quenching or enhancement from analytes such as dopamine, NADH, L-ascorbic acid, and riboflavin, d(AT)(15) imparts SWNT with a distinct selectivity toward NO. In contrast, the electrostatically neutral polyvinyl alcohol enables no response to nitric oxide, but exhibits fluorescent enhancement to other molecules in the tested library. For AT(15)-SWNT, a stepwise fluorescence decrease is observed when the nanotubes are exposed to NO, reporting the dynamics of single-molecule NO adsorption via SWNT exciton quenching. We describe these quenching traces using a birth-and-death Markov model, and the maximum likelihood estimator of adsorption and desorption rates of NO is derived. Applying the method to simulated traces indicates that the resulting error in the estimated rate constants is less than 5% under our experimental conditions, allowing for calibration using a series of NO concentrations. As expected, the adsorption rate is found to be linearly proportional to NO concentration, and the intrinsic single-site NO adsorption rate constant is 0.001 s(-1) μM NO(-1). The ability to detect nitric oxide quantitatively at the single-molecule level may find applications in new cellular assays for the study of nitric oxide carcinogenesis and chemical signaling, as well as medical diagnostics for inflammation.

OBJECTIVE

In migraine, an interictal reduction of mitochondrial energy metabolism and a preventive effect of high-dose riboflavin were reported. To explore the relation between the two, we tested if the therapeutic response to riboflavin is associated with specific mitochondrial DNA (mtDNA) haplogroups. We focused our attention on haplogroup H, which is known to differ from others in terms of energy metabolism.

METHODS

Sixty-four migraineurs completed a 4-month open trial with riboflavin (400 mg QD) and were genotyped blindly for mtDNA haplogroups.

RESULTS

Forty patients responded to riboflavin treatment and 24 were nonresponders. The mtDNA haplogroup H was found in 29 subjects (20 migraine without aura, 9 migraine with aura). Riboflavin responders were more numerous in the non-H group (67.5%). Conversely, nonresponders were mostly H (66.7%). The difference between the two groups was significant (chi(2) = 7.07; p = 0.01). The presence of aura had no influence on riboflavin's effectiveness (chi(2) = 0.113; p = 0.74) and was not associated with a particular haplogroup (chi(2) = 0.55; p = 0.46).

CONCLUSIONS

In this pharmacogenetic study, riboflavin appears to be more effective in patients with migraine with non-H mitochondrial DNA haplotypes. The underlying mechanisms are unknown, but could be related to the association of haplogroup H with increased activity in complex I, which is a major target for riboflavin. Our results may have ethnic implications, since haplogroup H is chiefly found in the European population.

Type B lactic acidosis is a rare complication of hematologic malignancies. The exact mechanism of this process is not well understood. Because caregivers may not be aware of the association of type B lactic acidosis with hematologic malignancies, it may go unrecognized as a cause of acidosis in these patients. We report the cases of 7 patients with type B lactic acidosis who were cared for by members of the Brown Medical School Hematology/Oncology Division. Of the 7 patients reported, 5 had lymphomas and 2 had chronic lymphocytic leukemia. One of the lymphomas was a T-cell lymphoma. Of the patients we were able to evaluate, there did not seem to be a unique cluster of differentiation marker in association with type B lactic acidosis. We also review 14 additional cases, most reported since 2001. From our review of the literature, we suggest that a deficiency of thiamine or riboflavin may play a more pivotal role than previously recognized in the development of type B lactic acidosis associated with malignancy. Further investigation should be undertaken to learn if thiamine or riboflavin replacement might be useful in treating this disorder.

Mushrooms have been consumed since earliest history; ancient Greeks believed that mushrooms provided strength for warriors in battle, and the Romans perceived them as the "Food of the Gods." For centuries, the Chinese culture has treasured mushrooms as a health food, an "elixir of life." They have been part of the human culture for thousands of years and have considerable interest in the most important civilizations in history because of their sensory characteristics; they have been recognized for their attractive culinary attributes. Nowadays, mushrooms are popular valuable foods because they are low in calories, carbohydrates, fat, and sodium: also, they are cholesterol-free. Besides, mushrooms provide important nutrients, including selenium, potassium, riboflavin, niacin, vitamin D, proteins, and fiber. All together with a long history as food source, mushrooms are important for their healing capacities and properties in traditional medicine. It has reported beneficial effects for health and treatment of some diseases. Many nutraceutical properties are described in mushrooms, such as prevention or treatment of Parkinson, Alzheimer, hypertension, and high risk of stroke. They are also utilized to reduce the likelihood of cancer invasion and metastasis due to antitumoral attributes. Mushrooms act as antibacterial, immune system enhancer and cholesterol lowering agents; additionally, they are important sources of bioactive compounds. As a result of these properties, some mushroom extracts are used to promote human health and are found as dietary supplements.

OBJECTIVE

To examine effects of race and predictors of socioeconomic status (SES) on nutrient-based diet quality and their contribution to health disparities in an urban population of low SES.

METHODS

Data were analyzed from a sample of the Healthy Aging in Neighborhoods of Diversity Across the Life Span (HANDLS) Study participants examining effects of age, sex, race, income, poverty income ratio, education, employment, and smoking status on nutrient-based diet quality as measured by a micronutrient composite index of nutrient adequacy ratios and a mean adequacy ratio. Regression models were used to examine associations and t tests were used to look at racial differences.

METHODS

African American and white adults ages 30 to 64 years residing in 12 predefined census tracts in Baltimore, Maryland.

RESULTS

Sex, age, education, poverty income ratio, and income were statistically significant predictors of diet quality for African Americans, while sex, education, and smoking status were statistically significant for whites. African Americans had lower mean adequacy ratio scores than whites (76.4 vs. 79.1). Whites had significantly higher nutrient adequacy ratios scores for thiamin, riboflavin, folate, B12, vitamins A and E, magnesium, copper, zinc, and calcium, while African Americans had higher vitamin C scores.

CONCLUSIONS

Education significantly impacted diet quality in the HANDLS sample, but race cannot be discounted. Whether the racial differences in diet quality are indicative of cultural differences in food preferences, selection, preparation, and availability, or disparities in socioeconomic status remains unclear.

A novel, 68 amino acid long flavoprotein called dodecin has been discovered in the proteome of Halobacterium salinarum by inverse structural genomics. The 1.7 A crystal structure of this protein shows a dodecameric, hollow sphere-like arrangement of the protein subunits. Unlike other known flavoproteins, which bind only monomeric flavin cofactors, the structure of the dodecin oligomer comprises six riboflavin dimers. The dimerization of these riboflavins along the re-faces is mediated by aromatic, antiparallel pi staggering of their isoalloxazine moieties. A unique aromatic tetrade is formed by further sandwiching of the riboflavin dimers between the indole groups of two symmetry-related Trp36s. So far, the dodecins represent the smallest known flavoproteins. Based on the structure and the wide spread occurrences in pathogenic and soil eubacteria, a function in flavin storage or protection against radical or oxygenic stress is suggested for the dodecins.

A novel phenol hydroxylase (PheA) that catalyzes the first step in the degradation of phenol in Bacillus thermoglucosidasius A7 is described. The two-protein system, encoded by the pheA1 and pheA2 genes, consists of an oxygenase (PheA1) and a flavin reductase (PheA2) and is optimally active at 55 degrees C. PheA1 and PheA2 were separately expressed in recombinant Escherichia coli BL21(DE3) pLysS cells and purified to apparent homogeneity. The pheA1 gene codes for a protein of 504 amino acids with a predicted mass of 57.2 kDa. PheA1 exists as a homodimer in solution and has no enzyme activity on its own. PheA1 catalyzes the efficient ortho-hydroxylation of phenol to catechol when supplemented with PheA2 and FAD/NADH. The hydroxylase activity is strictly FAD-dependent, and neither FMN nor riboflavin can replace FAD in this reaction. The pheA2 gene codes for a protein of 161 amino acids with a predicted mass of 17.7 kDa. PheA2 is also a homodimer, with each subunit containing a highly fluorescent FAD prosthetic group. PheA2 catalyzes the NADH-dependent reduction of free flavins according to a Ping Pong Bi Bi mechanism. PheA2 is structurally related to ferric reductase, an NAD(P)H-dependent reductase from the hyperthermophilic Archaea Archaeoglobus fulgidus that catalyzes the flavin-mediated reduction of iron complexes. However, PheA2 displays no ferric reductase activity and is the first member of a newly recognized family of short-chain flavin reductases that use FAD both as a substrate and as a prosthetic group.

OBJECTIVE

The molecular biology revolution has led to a significant improvement in our understanding of biological and physiological processes. Such expansion of knowledge has also covered the field of intestinal absorption of water-soluble vitamins and is the subject of this review.

RESULTS

Impressive progress has been made in the understanding of the mechanisms and regulation of transport of water-soluble vitamins at the cellular and molecular levels. In addition, the 5' regulatory regions of the genes that encode a number of the involved transporters have been cloned and characterized in vitro and in vivo in transgenic mice, thus providing important information about transcriptional regulation of these events. Furthermore, confocal imaging of live intestinal epithelial cells has led to significant progress in understanding the mechanisms involved in intracellular trafficking and membrane targeting of the carrier proteins and how clinical mutations lead to interference with transport. Finally, the identification in the large intestine of efficient and specialized carrier-mediated systems that are capable of absorbing a number of the bacterially synthesized vitamins (thiamin, folate, biotin, riboflavin, pantothenic acid) has raised the possibility that this source of vitamins may play a role in regulating (fine tuning) the normal body homeostasis of these vitamins, and especially the vitamin level in the local colonocytes.

CONCLUSIONS

Water-soluble vitamin absorption involves regulated and specific mechanisms. Interference with the function of these mechanisms may lead to deficiency. The large intestine is capable of absorbing water-soluble vitamins that are synthesized by the normal microflora.

OBJECTIVE

The objectives of the present study were to describe food and nutrient intakes in children aged 9 and 18 months, and to assess tracking of intakes between these two ages.

METHODS

Participants were 177 children of first-time mothers from the control arm of the Melbourne Infant Feeding Activity and Nutrition Trial (InFANT) Program. Dietary intake was collected at 9 and 18 months using three 24 h diet recalls. Tracking was assessed for food and nutrient intakes using logistic regression analysis and estimating partial correlation coefficients, respectively.

RESULTS

Although overall nutrient intakes estimated in this study did not indicate a particular risk of nutrient deficiency, our findings suggest that consumption of energy-dense, nutrient-poor foods occurred as early as 9 months of age, with some of these foods tracking highly over the weaning period. Intakes of healthier foods such as fruits, vegetables, dairy products, eggs, fish and water were also relatively stable over this transition from infancy to toddlerhood, along with moderate tracking for riboflavin, iodine, fibre, calcium and iron. Tracking was low but close to ρ=0.3 for zinc, magnesium and potassium intakes.

CONCLUSIONS

The tracking of energy-dense, nutrient-poor foods has important implications for public health, given the development of early eating behaviours is likely to be modifiable. At this stage of life, dietary intakes are largely influenced by the foods parents provide, parental feeding practices and modelling. This study supports the importance of promoting healthy dietary trajectories from infancy.

Colostrum composition and management were surveyed via sample and data collection from 55 dairy farms in Pennsylvania. Colostrum samples were analyzed for fat, protein, lactose, total solids, ash, Ig, lactoferrin, water- and fat-soluble vitamins, and minerals. Mean percentages of fat, protein, and lactose in colostrum were 6.7, 14.9, and 2.5, respectively. Concentrations of IgG1, IgG2, IgA, IgM, and lactoferrin were 35.0, 6.0, 1.7, 4.3, and 0.8 mg/mL, respectively. Mean concentrations of fat-soluble vitamins, including retinol, tocopherol, and beta-carotene, were 4.9, 2.9, and 0.7 microg/g, respectively. Mean concentrations of water-soluble vitamins were 0.34, 0.90, 4.55, 0.60, 0.15, 0.21, and 0.04 microg/mL for niacin, thiamine, riboflavin, vitamin B12, pyridoxal, pyridoxamine, and pyridoxine, respectively. Mean concentrations (mg/kg) of selected minerals in colostrum were also determined (Ca 4,716; P 4,452; Mg 733; Na 1,058; K 2,845; Zn 38; Fe 5.3; Cu 0.3; S 2,595; and Mn 0.1). The findings of this study revealed that the mean concentrations of most nutrients in colostrum have increased when compared with values previously reported. Results also showed that management practices have improved over time, particularly with regard to colostrum storage and feeding. Additionally, we observed that herd size influenced colostrum management and quality. It can be inferred, based on these findings, that although improvements have been made with regard to colostrum management and quality, there is still a need to educate producers on issues related to storage and timely feeding of colostrum to increase passive transfer and decrease the rate of calf morbidity and mortality.

OBJECTIVE

To evaluate the effects of corneal cross-linking on keratocytes and collagen fibres in human corneas.

METHODS

Fifteen corneal buttons were examined. Ten were from patients with keratoconus submitted to penetrating keratoplasty and five of them were treated with cross-linking 6 months before penetrating keratoplasty. Five normal corneal buttons from healthy donors were used as controls. All samples were prepared for TUNEL assay and Western blot analysis for the detection of keratocyte apoptosis and immunohistochemical analysis for the morphological evaluation of keratocytes and collagen fibre diameter.

RESULTS

Normal corneas exhibited no TUNEL-positive keratocytes and keratoconic and cross-linked corneas showed moderate apoptotic cells mainly in the anterior part of the stroma. This apoptotic trend was confirmed by the cleavage of poly (ADP-ribose) polymerase assessed using Western blot. The Ki-67 staining showed a significant increase in the keratocyte proliferation in cross-linked corneas compared with normal and keratoconus. In cross-linked corneas CD34-positive keratocytes were regularly distributed throughout the whole corneal stroma as in the control, and keratoconus was associated with patchy loss of immunoreactivity. The immunohistochemical analysis of collagen type I showed a significant increase in fibre diameter of cross-linked corneas compared with control and keratoconus.

CONCLUSIONS

Corneal cross-linking leads to keratocyte damage; after 6 months a repopulation by proliferating cells, a distribution of CD34-positive keratocytes as in control and an increase in collagen fibre diameter were observed. These modifications are the morphological correlate of the process leading to an increase in biomechanical stability.

Oxidative stress is involved in the development of many chronic diseases. One of the main factors involved in oxidative stress reduction is increased antioxidant potential. Some nutrients such as vitamin C, vitamin E and carotenoids are known to act as antioxidants; however, riboflavin is one of the neglected antioxidant nutrients that may have an antioxidant action independently or as a component of the glutathione redox cycle. Herein, studies that have examined the antioxidant properties of riboflavin and its effect on oxidative stress reduction are reviewed. The results of the reviewed studies confirm the antioxidant nature of riboflavin and indicate that this vitamin can protect the body against oxidative stress, especially lipid peroxidation and reperfusion oxidative injury. The mechanisms by which riboflavin protects the body against oxidative stress may be attributed to the glutathione redox cycle and also to other possible mechanisms such as the conversion of reduced riboflavin to the oxidised form.

OBJECTIVE

To investigate relationships between a wide range of macro- and micronutrients, including antioxidant vitamins, and the three main types of cataract in older people.

METHODS

Population-based cross-sectional study.

METHODS

Two thousand nine hundred people aged 49 to 97 years living in an urban community near Sydney, Australia.

METHODS

Food frequency questionnaires and lens photography.

METHODS

Lens photographs were graded for presence and severity of cortical, nuclear, and posterior subcapsular cataracts.

RESULTS

Higher intakes of protein, vitamin A, niacin, thiamin, and riboflavin were associated with reduced prevalence of nuclear cataract. After adjusting for multiple known cataract risk factors, the odds ratios for those in the highest intake quintile groups compared to those in the lowest intake quintiles were 0.5 (95% confidence interval [CI], 0.3-0.8) for protein, 0.5 (95% CI, 0.3-0.9) for vitamin A, 0.6 (95% CI, 0.4-0.9) for niacin, 0.6 (95% CI, 0.4-0.9) for thiamin, and 0.5 (95% CI, 0.3-0.9) for riboflavin. Intake of polyunsaturated fats was associated with reduced prevalence of cortical cataract. No nutrients were associated with posterior subcapsular cataract.

CONCLUSIONS

The nucleus of the lens is particularly sensitive to nutrient deficiencies. Protein, vitamin A, niacin, thiamin, and riboflavin protected against nuclear cataract in this study.

The luminescence (lux) operon (luxICDABEG) of the symbiotic bacterium Vibrio fischeri is regulated by the transcriptional activator LuxR and two acyl-homoserine lactone (acyl-HSL) autoinducers (the luxI-dependent 3-oxo-hexanoyl-HSL [3-oxo-C6-HSL] and the ainS-dependent octanoyl-HSL [C8-HSL]) in a population density-responsive manner called quorum sensing. To identify quorum-sensing-regulated (QSR) proteins different from those encoded by lux genes, we examined the protein patterns of V. fischeri quorum-sensing mutants defective in luxI, ainS, and luxR by two-dimensional polyacrylamide gel electrophoresis. Five non-Lux QSR proteins, QsrP, RibB, AcfA, QsrV, and QSR 7, were identified; their production occurred preferentially at high population density, required both LuxR and 3-oxo-C6-HSL, and was inhibited by C8-HSL at low population density. The genes encoding two of the QSR proteins were characterized: qsrP directs cells to synthesize an apparently novel periplasmic protein, and ribB is a homolog of the Escherichia coli gene for 3,4-dihydroxy-2-butanone 4-phosphate synthase, a key enzyme for riboflavin synthesis. The qsrP and ribB promoter regions each contained a sequence similar to the lux operon lux box, a 20-bp region of dyad symmetry necessary for LuxR/3-oxo-C6-HSL-dependent activation of lux operon transcription. V. fischeri qsrP and ribB mutants exhibited no distinct phenotype in culture. However, a qsrP mutant, in competition with its parent strain, was less successful in colonizing Euprymna scolopes, the symbiotic host of V. fischeri. The newly identified QSR genes, together with the lux operon, define a LuxR/acyl-HSL-responsive quorum-sensing regulon in V. fischeri.

ATP-binding cassette (ABC) transporters, composed of importers and exporters, form one of the biggest protein superfamilies that transport a variety of substrates across the membrane, powered by ATP hydrolysis. Most ABC transporters are composed of two transmembrane domains and two cytoplasmic nucleotide-binding domains. Also, importers from prokaryotes usually have extra solute-binding proteins in the periplasm that are responsible for the binding of substrates. Structures of importers have been reported that suggested a two-state model for the transport mechanism. Energy-coupling factor (ECF) transporters belong to a new class of ATP-binding cassette importers. Each ECF transporter comprises an energy-coupling module consisting of a transmembrane T protein (EcfT), two nucleotide-binding proteins (EcfA and EcfA'), and another transmembrane substrate-specific binding S protein (EcfS). Despite the similarities with ABC transporters, ECF transporters have different organizational and functional properties. The lack of solute-binding proteins in ECF transporters differentiates them clearly from the canonical ABC importers. Previously reported structures of the EcfS proteins RibU and ThiT clearly demonstrated the binding site of substrate riboflavin and thiamine, respectively. However, the organization of the four different components and the transport mechanism of ECF transporters remain unknown. Here we present the structure of an intact folate ECF transporter from Lactobacillus brevis at a resolution of 3 Å. This structure was captured in an inward-facing, nucleotide-free conformation with no bound substrate. The folate-binding protein FolT is nearly parallel to the membrane and is bound almost entirely by EcfT, which adopts an L shape and connects to EcfA and EcfA' through two coupling helices. Two conserved XRX motifs from the coupling helices of EcfT have a vital role in energy coupling by docking into EcfA-EcfA'. We propose a transport model that involves a substantial conformational change of FolT.

Isoniazid (INH) is an essential drug used to treat tuberculosis. The mycobactericidal agents are INH adducts [INH-NAD(P)] of the pyridine nucleotide coenzymes, which are generated in vivo after INH activation and which bind to, and inhibit, essential enzymes. The NADH-dependent enoyl-ACP reductase (InhA) and the NADPH-dependent dihydrofolate reductase (DfrA) have both been shown to be inhibited by INH-NAD(P) adducts with nanomolar affinity. In this paper, we profiled the Mycobacterium tuberculosis proteome using both the INH-NAD and INH-NADP adducts coupled to solid supports and identified, in addition to InhA and DfrA, 16 other proteins that bind these adducts with high affinity. The majority of these are predicted to be pyridine nucleotide-dependent dehydrogenases/reductases. They are involved in many cellular processes, including S-adenosylmethionine-dependent methyl transfer reactions, pyrimidine and valine catabolism, the arginine degradative pathway, proton and potassium transport, stress response, lipid metabolism, and riboflavin biosynthesis. The targeting of multiple enzymes could, thus, account for the pleiotropic effects of, and powerful mycobactericidal properties of, INH.