Sleep replay of awake experience in the cortex and hippocampus has been proposed to be involved in memory consolidation. However, whether temporally structured replay occurs in the cortex and whether the replay events in the two areas are related are unknown. Here we studied multicell spiking patterns in both the visual cortex and hippocampus during slow-wave sleep in rats. We found that spiking patterns not only in the cortex but also in the hippocampus were organized into frames, defined as periods of stepwise increase in neuronal population activity. The multicell firing sequences evoked by awake experience were replayed during these frames in both regions. Furthermore, replay events in the sensory cortex and hippocampus were coordinated to reflect the same experience. These results imply simultaneous reactivation of coherent memory traces in the cortex and hippocampus during sleep that may contribute to or reflect the result of the memory consolidation process.

A health risk appraisal function has been developed for the prediction of stroke using the Framingham Study cohort. The stroke risk factors included in the profile are age, systolic blood pressure, the use of antihypertensive therapy, diabetes mellitus, cigarette smoking, prior cardiovascular disease (coronary heart disease, cardiac failure, or intermittent claudication), atrial fibrillation, and left ventricular hypertrophy by electrocardiogram. Based on 472 stroke events occurring during 10 years' follow-up from biennial examinations 9 and 14, stroke probabilities were computed using the Cox proportional hazards model for each sex based on a point system. On the basis of the risk factors in the profile, which can be readily determined on routine physical examination in a physician's office, stroke risk can be estimated. An individual's risk can be related to the average risk of stroke for persons of the same age and sex. The information that one's risk of stroke is several times higher than average may provide the impetus for risk factor modification. It may also help to identify persons at substantially increased stroke risk resulting from borderline levels of multiple risk factors such as those with mild or borderline hypertension and facilitate multifactorial risk factor modification.

BACKGROUND

Studies have documented the underrepresentation of women and blacks in clinical trials, and their recruitment is now federally mandated. However, little is known about the level of participation of elderly patients. We determined the rates of enrollment of patients 65 years of age or older in trials of treatment for cancer.

METHODS

We analyzed data on 16,396 patients consecutively enrolled in 164 Southwest Oncology Group treatment trials between 1993 and 1996 according to sex, race (black or white), and age under 65 years or 65 or older. These rates were compared with the corresponding rates in the general population of patients with cancer, derived from the 1990 U.S. Census and from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program for the period from 1992 through 1994. Fifteen types of cancer were included in the analysis.

RESULTS

The overall proportions of women and blacks enrolled in Southwest Oncology Group trials were similar to or the same as the estimated proportions in the U.S. population of patients with cancer (women, 41 percent and 43 percent; blacks, 10 percent and 10 percent, respectively). In contrast, patients 65 years of age or older were underrepresented overall (25 percent vs. 63 percent, P<0.001) and in trials involving all 15 types of cancer except lymphoma. The underrepresentation was particularly notable in trials of treatment for breast cancer (9 percent vs. 49 percent, P<0.001). The findings were similar when data on patients who were 70 years of age or older were analyzed, when 15 trials that excluded older patients were eliminated from the analysis, and when community-based enrollment was analyzed separately from enrollment at academic centers.

CONCLUSIONS

There is substantial underrepresentation of patients 65 years of age or older in studies of treatment for cancer. The reasons should be clarified, and policies adopted to correct this underrepresentation.

The sifting and winnowing of DNA sequence that occur during evolution cause nonfunctional sequences to diverge, leaving phylogenetic footprints of functional sequence elements in comparisons of genome sequences. We searched for such footprints among the genome sequences of six Saccharomyces species and identified potentially functional sequences. Comparison of these sequences allowed us to revise the catalog of yeast genes and identify sequence motifs that may be targets of transcriptional regulatory proteins. Some of these conserved sequence motifs reside upstream of genes with similar functional annotations or similar expression patterns or those bound by the same transcription factor and are thus good candidates for functional regulatory sequences.

Concurrently with or shortly after their synthesis on ribosomes, numerous specific proteins are unidirectionally translocated across or asymmetrically integrated into distinct cellular membranes. Thereafter, subpopulations of these proteins need to be sorted from each other and routed for export or targeted to other intracellular membranes or compartments. It is hypothesized here that the information for these processes, termed "protein topogenesis," is encoded in discrete "topogenic" sequences that constitute a permanent or transient part of the polypeptide chain. The repertoire of distinct topogenic sequences is predicted to be relatively small because many different proteins would be topologically equivalent-i.e., targeted to the same intracellular address. The information content of topogenic sequences would be decoded and processed by distinct effectors. Four types of topogenic sequences could be distinguished: signal sequences, stop-transfer sequences, sorting sequences, and insertion sequences. Signal sequences initiate translocation of proteins across specific membranes. They would be decoded and processed by protein translocators that, by virtue of their signal sequence-specific domain and their unique location in distinct cellular membranes, effect unidirectional translocation of proteins across specific cellular membranes. Stop-transfer sequences interrupt the translocation process that was previously initiated by a signal sequence and, by excluding a distinct segment of the polypeptide chain from translocation, yield asymmetric integration of proteins into translocation-competent membranes. Sorting sequences would act as determinants for posttranslocational traffic of subpopulations of proteins, originating in translocation-competent donor membranes (and compartments) and going to translocation-incompetent receiver membranes (and compartments). Finally, insertion sequences initiate unilateral integration of proteins into the lipid bilayer without the mediation of a distinct protein effector. Examples are given for topogenic sequences, either alone or in combination, to provide the information for the location of proteins in any of the intracellular compartments or for the asymmetric orientation of proteins and their location in any of the cellular membranes. Proposals are made concerning the evolution of topogenic sequences and the relationship of protein topogenesis to the precellular evolution of membranes and compartments.

Glioblastoma (GBM) is among the most aggressive of human cancers. A key feature of GBMs is the extensive network of abnormal vasculature characterized by glomeruloid structures and endothelial hyperplasia. Yet the mechanisms of angiogenesis and the origin of tumour endothelial cells remain poorly defined. Here we demonstrate that a subpopulation of endothelial cells within glioblastomas harbour the same somatic mutations identified within tumour cells, such as amplification of EGFR and chromosome 7. We additionally demonstrate that the stem-cell-like CD133(+) fraction includes a subset of vascular endothelial-cadherin (CD144)-expressing cells that show characteristics of endothelial progenitors capable of maturation into endothelial cells. Extensive in vitro and in vivo lineage analyses, including single cell clonal studies, further show that a subpopulation of the CD133(+) stem-like cell fraction is multipotent and capable of differentiation along tumour and endothelial lineages, possibly via an intermediate CD133(+)/CD144(+) progenitor cell. The findings are supported by genetic studies of specific exons selected from The Cancer Genome Atlas, quantitative FISH and comparative genomic hybridization data that demonstrate identical genomic profiles in the CD133(+) tumour cells, their endothelial progenitor derivatives and mature endothelium. Exposure to the clinical anti-angiogenesis agent bevacizumab or to a γ-secretase inhibitor as well as knockdown shRNA studies demonstrate that blocking VEGF or silencing VEGFR2 inhibits the maturation of tumour endothelial progenitors into endothelium but not the differentiation of CD133(+) cells into endothelial progenitors, whereas γ-secretase inhibition or NOTCH1 silencing blocks the transition into endothelial progenitors. These data may provide new perspectives on the mechanisms of failure of anti-angiogenesis inhibitors currently in use. The lineage plasticity and capacity to generate tumour vasculature of the putative cancer stem cells within glioblastoma are novel findings that provide new insight into the biology of gliomas and the definition of cancer stemness, as well as the mechanisms of tumour neo-angiogenesis.

BACKGROUND

Use of computed tomography (CT) for diagnostic evaluation has increased dramatically over the past 2 decades. Even though CT is associated with substantially higher radiation exposure than conventional radiography, typical doses are not known. We sought to estimate the radiation dose associated with common CT studies in clinical practice and quantify the potential cancer risk associated with these examinations.

METHODS

We conducted a retrospective cross-sectional study describing radiation dose associated with the 11 most common types of diagnostic CT studies performed on 1119 consecutive adult patients at 4 San Francisco Bay Area institutions in California between January 1 and May 30, 2008. We estimated lifetime attributable risks of cancer by study type from these measured doses.

RESULTS

Radiation doses varied significantly between the different types of CT studies. The overall median effective doses ranged from 2 millisieverts (mSv) for a routine head CT scan to 31 mSv for a multiphase abdomen and pelvis CT scan. Within each type of CT study, effective dose varied significantly within and across institutions, with a mean 13-fold variation between the highest and lowest dose for each study type. The estimated number of CT scans that will lead to the development of a cancer varied widely depending on the specific type of CT examination and the patient's age and sex. An estimated 1 in 270 women who underwent CT coronary angiography at age 40 years will develop cancer from that CT scan (1 in 600 men), compared with an estimated 1 in 8100 women who had a routine head CT scan at the same age (1 in 11 080 men). For 20-year-old patients, the risks were approximately doubled, and for 60-year-old patients, they were approximately 50% lower.

CONCLUSIONS

Radiation doses from commonly performed diagnostic CT examinations are higher and more variable than generally quoted, highlighting the need for greater standardization across institutions.

Three mutants have been isolated in which the normal 24-hour rhythm is drastically changed. One mutant is arrhythmic; another has a period of 19 hr; a third has a period of 28 hr. Both the eclosion rhythm of a population and the locomotor activity of individual flies are affected. All these mutations appear to involve the same functional gene on the X chromosome.

Data will be reviewed using the acoustic startle reflex in rats and humans based on our attempts to operationally define fear vs anxiety. Although the symptoms of fear and anxiety are very similar, they also differ. Fear is a generally adaptive state of apprehension that begins rapidly and dissipates quickly once the threat is removed (phasic fear). Anxiety is elicited by less specific and less predictable threats, or by those that are physically or psychologically more distant. Thus, anxiety is a more long-lasting state of apprehension (sustained fear). Rodent studies suggest that phasic fear is mediated by the amygdala, which sends outputs to the hypothalamus and brainstem to produce symptoms of fear. Sustained fear is also mediated by the amygdala, which releases corticotropin-releasing factor, a stress hormone that acts on receptors in the bed nucleus of the stria terminalis (BNST), a part of the so-called 'extended amygdala.' The amygdala and BNST send outputs to the same hypothalamic and brainstem targets to produce phasic and sustained fear, respectively. In rats, sustained fear is more sensitive to anxiolytic drugs. In humans, symptoms of clinical anxiety are better detected in sustained rather than phasic fear paradigms.

In areas 17 and 18 of the cat visual cortex the firing probability of neurons, in response to the presentation of optimally aligned light bars within their receptive field, oscillates with a peak frequency near 40 Hz. The neuronal firing pattern is tightly correlated with the phase and amplitude of an oscillatory local field potential recorded through the same electrode. The amplitude of the local field-potential oscillations are maximal in response to stimuli that match the orientation and direction preference of the local cluster of neurons. Single and multiunit recordings from the dorsal lateral geniculate nucleus of the thalamus showed no evidence of oscillations of the neuronal firing probability in the range of 20-70 Hz. The results demonstrate that local neuronal populations in the visual cortex engage in stimulus-specific synchronous oscillations resulting from an intracortical mechanism. The oscillatory responses may provide a general mechanism by which activity patterns in spatially separate regions of the cortex are temporally coordinated.

The objective of the U.K. Prospective Diabetes Study is to determine whether improved blood glucose control in type II diabetes will prevent the complications of diabetes and whether any specific therapy is advantageous or disadvantageous. The study will report in 1998, when the median duration from randomization will be 11 years. This report is on the efficacy of therapy over 6 years of follow-up and the overall incidence of diabetic complications. Subjects comprised 4,209 newly diagnosed type II diabetic patients who after 3 months' diet were asymptomatic and had fasting plasma glucose (FPG) 6.0-15.0 mmol/l. The study consists of a randomized controlled trial with two main comparisons: 1) 3,867 patients with 1,138 allocated to conventional therapy, primarily with diet, and 2,729 allocated to intensive therapy with additional sulfonylurea or insulin, which increase insulin supply, aiming for FPG < 6 mmol/l; and 2) 753 obese patients with 411 allocated to conventional therapy and 342 allocated to intensive therapy with metformin, which enhances insulin sensitivity. In the first comparison, in 2,287 subjects studied for 6 years, intensive therapy with sulfonylurea and insulin similarly improved glucose control compared with conventional therapy, with median FPG at 1 year of 6.8 and 8.2 mmol/l, respectively (P < 0.0001). and median HbA1c of 6.1 and 6.8%, respectively (P < 0.0001). During the next 5 years, the FPG increased progressively on all therapies (P < 0.0001) with medians at 6 years in the conventional and intensive groups, FPG 9.5 and 7.8 mmol/l, and HbA1c 8.0 and 7.1%, respectively. The glycemic deterioration was associated with progressive loss of beta-cell function. In the second comparison, in 548 obese subjects studied for 6 years, metformin improved glucose control similarly to intensive therapy with sulfonylurea or insulin. Metformin did not increase body weight or increase the incidence of hypoglycemia to the same extent as therapy with sulfonylurea or insulin. A high incidence of clinical complications occurred by 6-year follow-up. Of all subjects, 18.0% had suffered one or more diabetes-related clinical endpoints, with 12.1% having a macrovascular and 5.7% a microvascular endpoint. Sulfonylurea, metformin, and insulin therapies were similarly effective in improving glucose control compared with a policy of diet therapy. The study is examining whether the continued improved glucose control, obtained by intensive therapy compared with conventional therapy (median over 6 years HbA1c 6.6% compared with 7.4%), will be clinically advantageous in maintaining health.

Small-probe contact dot surface analysis, with all explicit hydrogen atoms added and their van der Waals contacts included, was used to choose between the two possible orientations for each of 1554 asparagine (Asn) and glutamine (Gln) side-chain amide groups in a dataset of 100 unrelated, high-quality protein crystal structures at 0.9 to 1.7 A resolution. For the movable-H groups, each connected, closed set of local H-bonds was optimized for both H-bonds and van der Waals overlaps. In addition to the Asn/Gln "flips", this process included rotation of OH, SH, NH3+, and methionine methyl H atoms, flip and protonation state of histidine rings, interaction with bound ligands, and a simple model of water interactions. However, except for switching N and O identity for amide flips (or N and C identity for His flips), no non-H atoms were shifted. Even in these very high-quality structures, about 20 % of the Asn/Gln side-chains required a 180 degrees flip to optimize H-bonding and/or to avoid NH2 clashes with neighboring atoms (incorporating a conservative score penalty which, for marginal cases, favors the assignment in the original coordinate file). The programs Reduce, Probe, and Mage provide not only a suggested amide orientation, but also a numerical score comparison, a categorization of the marginal cases, and a direct visualization of all relevant interactions in both orientations. Visual examination allowed confirmation of the raw score assignment for about 40 % of those Asn/Gln flips placed within the "marginal" penalty range by the automated algorithm, while uncovering only a small number of cases whose automated assignment was incorrect because of special circumstances not yet handled by the algorithm. It seems that the H-bond and the atomic-clash criteria independently look at the same structural realities: when both criteria gave a clear answer they agreed every time. But consideration of van der Waals clashes settled many additional cases for which H-bonding was either absent or approximately equivalent for the two main alternatives. With this extra information, 86 % of all side-chain amide groups could be oriented quite unambiguously. In the absence of further experimental data, it would probably be inappropriate to assign many more than this. Some of the remaining 14 % are ambiguous because of coordinate error or inadequacy of the theoretical model, but the great majority of ambiguous cases probably occur as a dynamic mix of both flip states in the actual protein molecule. The software and the 100 coordinate files with all H atoms added and optimized and with amide flips corrected are publicly available.

Epileptic encephalopathies are a devastating group of severe childhood epilepsy disorders for which the cause is often unknown. Here we report a screen for de novo mutations in patients with two classical epileptic encephalopathies: infantile spasms (n = 149) and Lennox-Gastaut syndrome (n = 115). We sequenced the exomes of 264 probands, and their parents, and confirmed 329 de novo mutations. A likelihood analysis showed a significant excess of de novo mutations in the ∼4,000 genes that are the most intolerant to functional genetic variation in the human population (P = 2.9 × 10(-3)). Among these are GABRB3, with de novo mutations in four patients, and ALG13, with the same de novo mutation in two patients; both genes show clear statistical evidence of association with epileptic encephalopathy. Given the relevant site-specific mutation rates, the probabilities of these outcomes occurring by chance are P = 4.1 × 10(-10) and P = 7.8 × 10(-12), respectively. Other genes with de novo mutations in this cohort include CACNA1A, CHD2, FLNA, GABRA1, GRIN1, GRIN2B, HNRNPU, IQSEC2, MTOR and NEDD4L. Finally, we show that the de novo mutations observed are enriched in specific gene sets including genes regulated by the fragile X protein (P < 10(-8)), as has been reported previously for autism spectrum disorders.

The observation that purified yeast glutamine synthetase is rapidly inactivated in a thiol-containing buffer yet retains activity in crude extracts containing the same thiol led to our discovery of an enzyme that protects against oxidation in a thiol-containing system. This novel antioxidant enzyme was shown to reduce hydroperoxides and, more recently, peroxynitrite with the use of electrons provided by a physiological thiol like thioredoxin. It defined a family of proteins, present in organisms from all kingdoms, that was named peroxiredoxin (Prx). All Prx enzymes contain a conserved Cys residue that undergoes a cycle of peroxide-dependent oxidation and thiol-dependent reduction during catalysis. Mammalian cells express six isoforms of Prx (Prx I to VI), which are classified into three subgroups (2-Cys, atypical 2-Cys, and 1-Cys) based on the number and position of Cys residues that participate in catalysis. The relative abundance of Prx enzymes in mammalian cells appears to protect cellular components by removing the low levels of peroxides produced as a result of normal cellular metabolism. During catalysis, the active site cysteine is occasionally overoxidized to cysteine sulfinic acid. Contrary to the general belief that oxidation to the sulfinic state is an irreversible process in cells, studies on the fate of the overoxidized Prx species revealed a mechanism by which the catalytically active thiol form is recovered. This sulfinic reduction is a slow, ATP-dependent process that is specific to 2-Cys Prx isoforms. This reversible overoxidation may represent an adaptation unique to eukaryotic cells that accommodates the intracellular messenger function of H(2)O(2), but experimental validation of such speculation is yet to come.

Gating current (Ig) has been studied in relation to inactivation of Na channels. No component of Ig has the time course of inactivation; apparently little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement during a pulse and comparing it to OFF charge after the pulse. The OFF:ON ratio is near 1 for a pulse so short that no inactivation occurs, and the ratio drops to about one-third with a time course that parallels inactivation. Other correlations between inactivation and immobilization are that: (a) they have the same voltage dependence; (b) charge movement recovers with the time coures of recovery from inactivation. We interpret this to mean that the immobilized charge returns slowly to "off" position with the time course of recovery from inactivation, and that the small current generated is lost in base-line noise. At -150 mV recover is very rapid, and the immobilized charge forms a distinct slow component of current as it returns to off position. After destruction of inactivation by pronase, there is no immobilization of charge. A model is presented in which inactivation gains its voltage dependence by coupling to the activation gate.

Since its conception three decades ago, the idea that the striatum consists of a dorsal sensorimotor part and a ventral portion processing limbic information has sparked a quest for functional correlates and anatomical characteristics of the striatal divisions. But this classic dorsal-ventral distinction might not offer the best view of striatal function. Anatomy and neurophysiology show that the two striatal areas have the same basic structure and that sharp boundaries are absent. Behaviorally, a distinction between dorsolateral and ventromedial seems most valid, in accordance with a mediolateral functional zonation imposed on the striatum by its excitatory cortical, thalamic and amygdaloid inputs. Therefore, this review presents a synthesis between the dorsal-ventral distinction and the more mediolateral-oriented functional striatal gradient.

Plasmid ColE1, like many other small non-conjugative plasmids, is present in multiple copies (about 15 per chromsome equivalent) in Escherichia coli cells. Because of their high copy number, the replication of such plasmids has been described as 'relaxed', even though there is good evidence that it is strictly controlled: ColE1 derivatives have characteristic but different copy numbers and ColE1 copy-number mutants have been characterised. No plasmid-specified protein is essential for the replication of ColE1 and related plasmids, as extensive replication can occur in chloramphenicol-treated cells, in plasmid-free chloramphenicol-treated cells transfected with a hybrid ColE1/phage replicon and in vitro in extracts derived from plasmid-free cells. Nevertheless, it is possible that a plasmid-specified protein is involved in ColE1 replication control in viable cells. Here we show that deletion of a given non-essential region from ColE1-like plasmids results in a raised copy number. Such plasmids are stably maintained and have their copy number returned to normal when a complementing plasmid is present in the same cell, indicating that a plasmid-specified diffusible gene product regulates the plasmid content of ColE1-containing cells. Deletion of the equivalent region from the cloning vector pBR322 gives a derivative which has a raised copy number and which has also lost its origin for conjugal transfer; unlike pBR322, it cannot be mobilised.

Neoplastic cells simultaneously harbor widespread genomic hypomethylation, more regional areas of hypermethylation, and increased DNA-methyltransferase (DNA-MTase) activity. Each component of this "methylation imbalance" may fundamentally contribute to tumor progression. The precise role of the hypomethylation is unclear, but this change may well be involved in the widespread chromosomal alterations in tumor cells. A main target of the regional hypermethylation are normally unmethylated CpG islands located in gene promoter regions. This hypermethylation correlates with transcriptional repression that can serve as an alternative to coding region mutations for inactivation of tumor suppressor genes, including p16, p15, VHL, and E-cad. Each gene can be partially reactivated by demethylation, and the selective advantage for loss of gene function is identical to that seen for loss by classic mutations. How abnormal methylation, in general, and hypermethylation, in particular, evolve during tumorigenesis are just beginning to be defined. Normally, unmethylated CpG islands appear protected from dense methylation affecting immediate flanking regions. In neoplastic cells, this protection is lost, possibly by chronic exposure to increased DNA-MTase activity and/or disruption of local protective mechanisms. Hypermethylation of some genes appears to occur only after onset of neoplastic evolution, whereas others, including the estrogen receptor, become hypermethylated in normal cells during aging. This latter change may predispose to neoplasia because tumors frequently are hypermethylated for these same genes. A model is proposed wherein tumor progression results from episodic clonal expansion of heterogeneous cell populations driven by continuous interaction between these methylation abnormalities and classic genetic changes.

BACKGROUND

Circulating levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are elevated in diabetic patients. We assessed the role of glucose in the regulation of circulating levels of IL-6, TNF-alpha, and interleukin-18 (IL-18) in subjects with normal or impaired glucose tolerance (IGT), as well as the effect of the antioxidant glutathione.

RESULTS

Plasma glucose levels were acutely raised in 20 control and 15 IGT subjects and maintained at 15 mmol/L for 5 hours while endogenous insulin secretion was blocked with octreotide. In control subjects, plasma IL-6, TNF-alpha, and IL-18 levels rose (P<0.01) within 2 hours of the clamp and returned to basal values at 3 hours. In another study, the same subjects received 3 consecutive pulses of intravenous glucose (0.33 g/kg) separated by a 2-hour interval. Plasma cytokine levels obtained at 3, 4, and 5 hours were higher (P<0.05) than the corresponding values obtained during the clamp. The IGT subjects had fasting plasma IL-6 and TNF-alpha levels higher (P<0.05) than those of control subjects. The increase in plasma cytokine levels during the clamping lasted longer (4 hours versus 2 hours, P<0.01) in the IGT subjects than in the control subjects, and the cytokine peaks of IGT subjects after the first glucose pulse were higher (P<0.05) than those of control subjects. On another occasion, 10 control and 8 IGT subjects received the same glucose pulses as above during an infusion of glutathione; plasma cytokine levels did not show any significant change from baseline after the 3 glucose pulses.

CONCLUSIONS

Hyperglycemia acutely increases circulating cytokine concentrations by an oxidative mechanism, and this effect is more pronounced in subjects with IGT. This suggests a causal role for hyperglycemia in the immune activation of diabetes.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal (GI) tract. They are defined here as KIT (CD117, stem cell factor receptor)-positive mesenchymal spindle cell or epithelioid neoplasms primary in the GI tract, omentum, and mesentery. GISTs typically present in older individuals and are most common in the stomach (60-70%), followed by small intestine (20-25%), colon and rectum (5%), and esophagus (<5%). Benign tumors outnumber the malignant ones by a wide margin. Approximately 70% of GISTs are positive for CD34, 20-30% are positive for smooth muscle actin (SMA), 10% are positive for S100 protein and <5% are positive for desmin. The expression of CD34 and SMA is often reciprocal. GISTs commonly have activating mutations in exon 11 (or rarely exon 9 and exon 13) of the KIT gene that encodes a tyrosine kinase receptor for the growth factor named stem cell factor or mast cell growth factor. Ligand-independent activation of KIT appears to be a strong candidate for molecular pathogenesis of GISTs, and it may be a target for future treatment for such tumors. Other genetic changes in GISTs discovered using comparative genomic hybridization include losses in 14q and 22q in both benign and malignant GISTs and occurrence in various gains predominantly in malignant GISTs. GISTs have phenotypic similarities with the interstitial cells of Cajal and, therefore, a histogenetic origin from these cells has been suggested. An alternative possibility, origin of pluripotential stem cells, is also possible; this is supported by the same origin of Cajal cells and smooth muscle and by the common SMA expression in GISTs. GISTs differ clinically and pathogenetically from true leiomyosarcomas (very rare in the GI tract) and leiomyomas. The latter occur in the GI tract, predominantly in the esophagus (intramural tumors) and the colon and rectum (muscularis mucosae tumors). They also differ from schwannomas that are benign S100-positive spindle cell tumors usually presenting in the stomach. GI autonomic nerve tumors (GANTs) are probably a subset of GIST. Other mesenchymal tumors that have to be separated from GISTs include inflammatory myofibroblastic tumors in children, desmoid, and dedifferentiated liposarcoma. Angiosarcomas and metastatic melanomas, both of which are often KIT-positive, should not be confused with GISTs.

There are many strains of the agents that cause transmissible spongiform encephalopathies (TSEs) or 'prion' diseases. These strains are distinguishable by their disease characteristics in experimentally infected animals, in particular the incubation periods and neuropathology they produce in panels of inbred mouse strains. We have shown that the strain of agent from cattle affected by bovine spongiform encephalopathy (BSE) produces a characteristic pattern of disease in mice that is retained after experimental passage through a variety of intermediate species. This BSE 'signature' has also been identified in transmissions to mice of TSEs of domestic cats and two exotic species of ruminant, providing the first direct evidence for the accidental spread of a TSE between species. Twenty cases of a clinically and pathologically atypical form of Creutzfeldt-Jakob disease (CJD), referred to as 'new variant' CJD (vCJD), have been recognized in unusually young people in the United Kingdom, and a further case has been reported in France. This has raised serious concerns that BSE may have spread to humans, putatively by dietary exposure. Here we report the interim results of transmissions of sporadic CJD and vCJD to mice. Our data provide strong evidence that the same agent strain is involved in both BSE and vCJD.

The intranuclear position of many genes has been correlated with their activity state, suggesting that migration to functional subcompartments may influence gene expression. Indeed, nascent RNA production and RNA polymerase II seem to be localized into discrete foci or 'transcription factories'. Current estimates from cultured cells indicate that multiple genes could occupy the same factory, although this has not yet been observed. Here we show that, during transcription in vivo, distal genes colocalize to the same transcription factory at high frequencies. Active genes are dynamically organized into shared nuclear subcompartments, and movement into or out of these factories results in activation or abatement of transcription. Thus, rather than recruiting and assembling transcription complexes, active genes migrate to preassembled transcription sites.

The level of genetic variation of human immunodeficiency virus type 1 (HIV-1), a member of the lentivirus genus of the Retroviridae family, is high relative to that of retroviruses in some other genera. The high error rates of purified HIV-1 reverse transcriptase in cell-free systems suggest an explanation for this high genetic variation. To test whether the in vivo rate of mutation during reverse transcription of HIV-1 is as high as predicted by cell-free studies, and therefore higher than that rates of mutation of retroviruses in other genera, we developed an in vivo assay for detecting forward mutations in HIV-1, using the lacZ alpha peptide gene as a reporter for mutations. This system allows the rates and types of mutations that occur during a single cycle of replication to be studied. We found that the forward mutation rate for HIV-1 was 3.4 x 10(-5) mutations per bp per cycle. Base substitution mutations predominated; G-to-A transition mutations were the most common base substitution. The in vivo mutation rates for HIV-1 are three and seven times higher than those previously reported for two other retroviruses, spleen necrosis virus and bovine leukemia virus, respectively. In contrast, our calculated in vivo mutation rate for HIV-1 is about 20-fold lower than the error rate of purified HIV-1 reverse transcriptase, with the same target sequence. This finding indicates that HIV-1 reverse transcription in vivo is not as error prone as predicted from the fidelity of purified reverse transcriptase in cell-free studies. Our data suggest that the fidelity of purified HIV-1 reverse transcriptase may not accurately reflect the level of genetic variation in a natural infection.

The Global Burden of Diseases, Injuries, and Risk Factors Study 2015 provides an up-to-date synthesis of the evidence for risk factor exposure and the attributable burden of disease. By providing national and subnational assessments spanning the past 25 years, this study can inform debates on the importance of addressing risks in context.

We used the comparative risk assessment framework developed for previous iterations of the Global Burden of Disease Study to estimate attributable deaths, disability-adjusted life-years (DALYs), and trends in exposure by age group, sex, year, and geography for 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks from 1990 to 2015. This study included 388 risk-outcome pairs that met World Cancer Research Fund-defined criteria for convincing or probable evidence. We extracted relative risk and exposure estimates from randomised controlled trials, cohorts, pooled cohorts, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. We developed a metric that allows comparisons of exposure across risk factors-the summary exposure value. Using the counterfactual scenario of theoretical minimum risk level, we estimated the portion of deaths and DALYs that could be attributed to a given risk. We decomposed trends in attributable burden into contributions from population growth, population age structure, risk exposure, and risk-deleted cause-specific DALY rates. We characterised risk exposure in relation to a Socio-demographic Index (SDI).

Between 1990 and 2015, global exposure to unsafe sanitation, household air pollution, childhood underweight, childhood stunting, and smoking each decreased by more than 25%. Global exposure for several occupational risks, high body-mass index (BMI), and drug use increased by more than 25% over the same period. All risks jointly evaluated in 2015 accounted for 57·8% (95% CI 56·6-58·8) of global deaths and 41·2% (39·8-42·8) of DALYs. In 2015, the ten largest contributors to global DALYs among Level 3 risks were high systolic blood pressure (211·8 million [192·7 million to 231·1 million] global DALYs), smoking (148·6 million [134·2 million to 163·1 million]), high fasting plasma glucose (143·1 million [125·1 million to 163·5 million]), high BMI (120·1 million [83·8 million to 158·4 million]), childhood undernutrition (113·3 million [103·9 million to 123·4 million]), ambient particulate matter (103·1 million [90·8 million to 115·1 million]), high total cholesterol (88·7 million [74·6 million to 105·7 million]), household air pollution (85·6 million [66·7 million to 106·1 million]), alcohol use (85·0 million [77·2 million to 93·0 million]), and diets high in sodium (83·0 million [49·3 million to 127·5 million]). From 1990 to 2015, attributable DALYs declined for micronutrient deficiencies, childhood undernutrition, unsafe sanitation and water, and household air pollution; reductions in risk-deleted DALY rates rather than reductions in exposure drove these declines. Rising exposure contributed to notable increases in attributable DALYs from high BMI, high fasting plasma glucose, occupational carcinogens, and drug use. Environmental risks and childhood undernutrition declined steadily with SDI; low physical activity, high BMI, and high fasting plasma glucose increased with SDI. In 119 countries, metabolic risks, such as high BMI and fasting plasma glucose, contributed the most attributable DALYs in 2015. Regionally, smoking still ranked among the leading five risk factors for attributable DALYs in 109 countries; childhood underweight and unsafe sex remained primary drivers of early death and disability in much of sub-Saharan Africa.

Declines in some key environmental risks have contributed to declines in critical infectious diseases. Some risks appear to be invariant to SDI. Increasing risks, including high BMI, high fasting plasma glucose, drug use, and some occupational exposures, contribute to rising burden from some conditions, but also provide opportunities for intervention. Some highly preventable risks, such as smoking, remain major causes of attributable DALYs, even as exposure is declining. Public policy makers need to pay attention to the risks that are increasingly major contributors to global burden.

Bill & Melinda Gates Foundation.