High- and Low-Affinity α-[3H]Amino-3-Hydroxy-5-Methylisoxazole-4-Propionic Acid ([3H]AMPA) Binding Sites Represent Immature and Mature Forms of AMPA Receptors and Are Composed of Differentially Glycosylated Subunits

Abstract: Quantitative α-[³H]amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid ([³H]AMPA) binding autoradiography was performed on frozen-thawed sections from rat brain after preincubation at 0 or 35°C for 1 h. Preincubation at 35°C instead of 0°C resulted in a selective decrease of [³H]AMPA binding assayed at a low concentration of [³H]-AMPA (50 nM) and an enhancement of binding at a high concentration (500 nM). The decrease in [³H]AMPA binding after preincubation at 35°C was accompanied with the loss of the lighter organelles of P3 (microsomal) fractions. These organelles were found to contain a small subpopulation of AMPA/GluR receptors exhibiting a high affinity for [³H]AMPA(K_D～14 nM), whereas heavier organelles exhibited lower affinity for AMPA (K_D～190 nM). This small subpopulation of AMPA/GluR receptors contained almost exclusively a structurally distinct species of GluR2/3 subunits with an apparent molecular mass of 103.5 kDa (assessed with anti-GluR2/3, C-terminal antibodies). Experiments using two deglycosylating enzymes, N-glycopeptidase F and endoglycosidase H, clearly indicated that the 103.5-kDa species represented a partially unglycosylated form of GluR2/3 subunits containing the high-mannose type of oligosaccharide moiety, whereas receptors present in synaptosomal fractions were composed of subunits with complex oligosaccharides. A similar result was obtained by using an antibody recognizing the N-terminal domain of GluR2(4). The same enzymatic treatment indicated that GluR1 subunits also exhibited a partially glycosylated form. These data indicate that high-affinity [³H]AMPA binding sites represent nonsynaptic, intracellular membrane-bound AMPA receptors that differ from synaptic receptors by at least the glycosylation state of GluR2 (and GluR1) subunits. In addition, our results provide a relatively simple way of assessing changes in two spatially and structurally distinct [³H]AMPA binding/GluR sites.     

Nanovehicles in the improved treatment of infections due to brain-eating amoebae

International Microbiology - Pathogenic free-living amoebae are known to cause fatal central nervous system infections with extremely high mortality rates. High selectivity of the blood–brain...     

Cyclic variations of gonad development of snow trout,Schizopyge niger from the river Jhelum of Kashmir Himalaya

The aim of the present study was to know the cyclic changes in gonadal maturation and to investigate the various developmental stages of oocytes and testicular germ cells of snow trout, Schizopyge niger. A total of 316 fish specimens were procured from three sites of river Jhelum during November 2016 to October 2017 and the histological analysis of their gonad was carried out. The results of the present study indicates that the male population was found significantly (p < 0.05) higher compared to female population and were reported as (1.6:1; M:F). The highest mean GSI value was recorded in male (12.24 ± 0.89) during the month of March and for female (13.74 ± 0.92) also in the month of March, which indicated that the gonadal development reached its peak during this month. The highest mean oocyte diameter was 1.04 ± 0.20 mm observed in March, showing that the oocyte reached its maturity during this month. Histological study of ovary revealed the evidence of vitellogenic yolk granule stage and ripe mature stage from December to April. While in case of male, four stages of spermatogenesis were distinguished and spermatozoa were highly abundant in the months of March and April. Mean ± SE of absolute fecundity was 3,224 ± 421 eggs and also, the relative fecundity was 69 egg/g body weight. Based on the results of GSI and the analysis of gonad histology, it was observed that the peak breeding season of S. niger occurred in the month of March. It was also noted that spawning period of this fish begins in the month of February and lasts till April with a peak breeding season in the month of March. The present study will provide a baseline information about the appropriate peak breeding of the fish, which will be useful for artificial breeding as well for prevention of fishing from natural habitat.     

Cognitive and Kidney Function: Results from a British Birth Cohort Reaching Retirement Age

Background

Previous studies have found associations between cognitive function and chronic kidney disease. We aimed to explore possible explanations for this association in the Medical Research Council National Survey of Health and Development, a prospective birth cohort representative of the general British population.

Methods

Cognitive function at age 60–64 years was quantified using five measures (verbal memory, letter search speed and accuracy, simple and choice reaction times) and glomerular filtration rate (eGFR) at the same age was estimated using cystatin C. The cross-sectional association between cognitive function and eGFR was adjusted for background confounding factors (socioeconomic position, educational attainment), prior cognition, and potential explanations for any remaining association (smoking, diabetes, hypertension, inflammation, obesity).

Results

Data on all the analysis variables were available for 1306–1320 study members (depending on cognitive measure). Verbal memory and simple and choice reaction times were strongly associated with eGFR. For example, the lowest quartile of verbal memory corresponded to a 4.1 (95% confidence interval 2.0, 6.2) ml/min/1.73 m² lower eGFR relative to the highest quartile. Some of this association was explained by confounding due to socioeconomic factors, but very little of it by prior cognition. Smoking, diabetes, hypertension, inflammation and obesity explained some but not all of the remaining association.

Conclusions

These analyses support the notion of a shared pathophysiology of impaired cognitive and kidney function at older age, which precedes clinical disease. The implications of these findings for clinical care and research are important and under-recognised, though further confirmatory studies are required.     

Primary Amoebic Meningoencephalitis Caused by Naegleria fowleri: An Old Enemy Presenting New Challenges

First discovered in 1899, Naegleria fowleri is a protist pathogen, known to infect the central nervous system and produce primary amoebic meningoencephalitis. The most distressing aspect is that the fatality rate has remained more than 95%, despite our advances in antimicrobial chemotherapy and supportive care. Although rare worldwide, most cases have been reported in the United States, Australia, and Europe (France). A large number of cases in developing countries go unnoticed. In particular, religious, recreational, and cultural practices such as ritual ablution and/or purifications, Ayurveda, and the use of neti pots for nasal irrigation can contribute to this devastating infection. With increasing water scarcity and public reliance on water storage, here we debate the need for increased awareness of primary amoebic meningoencephalitis and the associated risk factors, particularly in developing countries.     

Soluble ST2 Associates with Diabetes but Not Established Cardiovascular Risk Factors: A New Inflammatory Pathway of Relevance to Diabetes?

Preliminary data mostly from animal models suggest the sST2/IL-33 pathway may have causal relevance for vascular disease and diabetes and thus point to a potential novel inflammatory link to cardiometabolic disease. However, the characterisation of sST2 levels in terms of metabolic or vascular risk in man is completely lacking. We sought to address this gap via a comprehensive analysis of risk factor and vascular correlates of sST2 in a cross-sectional study (pSoBid). We measured sST2 in plasma in 639 subjects and comprehensively related it to cardiovascular and diabetes risk factors and imaged atherosclerosis measures. Circulating sST2 levels increased with age, were lower in women and in highest earners. After adjusting for age and gender, sST2 levels associated strongly with markers of diabetes, including triglycerides [effect estimate (EE) per 1 standard deviation increase in sST2∶1.05 [95%CI 1.01,1.10]), liver function (alanine aminotransaminase [ALT] and γ-glutamyl transferase [GGT]: EE 1.05 [1.01,1.09] and 1.13 [1.07,1.19] respectively), glucose (1.02 [1.00,1.03]) and sICAM-1 (1.05 [1.02,1.07]). However, sST2 levels were not related to smoking, cholesterol, blood pressure, or atheroma (carotid intima media thickness, plaque presence). These results suggest that sST2 levels, in individuals largely without vascular disease, are related principally to markers associated with diabetes and ectopic fat and add support for a role of sST2 in diabetes. Further mechanistic studies determining how sST2 is linked to diabetes pathways may offer new insights into the inflammatory paradigm for type 2 diabetes.     

School absenteeism as an adjunct surveillance indicator: experience during the second wave of the 2009 H1N1 pandemic in Quebec, Canada

Background

A school absenteeism surveillance system was implemented in the province of Quebec, Canada during the second wave of the 2009 H1N1pandemic. This paper compares this surveillance approach with other available indicators.

Method

All (3432) elementary and high schools from Quebec were included. Each school was required to report through a web-based system any day where the proportion of students absent for influenza-like illness (ILI) exceeded 10% of current school enrolment.

Results

Between October 18 and December 12 2009, 35.6% of all schools met the 10% absenteeism threshold. This proportion was greater in elementary compared to high schools (40% vs 19%) and in smaller compared to larger schools (44% vs 22%). The maximum absenteeism rate was reached the first day of reporting or within the next two days in 55% and 31% of schools respectively. The first reports and subsequent peak in school absenteeism provincially preceded the peak in paediatric hospitalization by two and one weeks, respectively. Trends in school surveillance otherwise mirrored other indicators.

Conclusion

During a pandemic, school outbreak surveillance based on a 10% threshold appears insufficient to trigger timely intervention within a given affected school. However, school surveillance appears well-correlated and slightly anticipatory compared to other population indicators. As such, school absenteeism warrants further evaluation as an adjunct surveillance indicator whose overall utility will depend upon specified objectives, and other existing capacity for monitoring and response.     

Genome-wide study of gene variants associated with differential cardiovascular event reduction by pravastatin therapy

Statin therapy reduces the risk of coronary heart disease (CHD), however, the person-to-person variability in response to statin therapy is not well understood. We have investigated the effect of genetic variation on the reduction of CHD events by pravastatin. First, we conducted a genome-wide association study of 682 CHD cases from the Cholesterol and Recurrent Events (CARE) trial and 383 CHD cases from the West of Scotland Coronary Prevention Study (WOSCOPS), two randomized, placebo-controlled studies of pravastatin. In a combined case-only analysis, 79 single nucleotide polymorphisms (SNPs) were associated with differential CHD event reduction by pravastatin according to genotype (P<0.0001), and these SNPs were analyzed in a second stage that included cases as well as non-cases from CARE and WOSCOPS and patients from the PROspective Study of Pravastatin in the Elderly at Risk/PHArmacogenomic study of Statins in the Elderly at risk for cardiovascular disease (PROSPER/PHASE), a randomized placebo controlled study of pravastatin in the elderly. We found that one of these SNPs (rs13279522) was associated with differential CHD event reduction by pravastatin therapy in all 3 studies: P = 0.002 in CARE, P = 0.01 in WOSCOPS, P = 0.002 in PROSPER/PHASE. In a combined analysis of CARE, WOSCOPS, and PROSPER/PHASE, the hazard ratio for CHD when comparing pravastatin with placebo decreased by a factor of 0.63 (95% CI: 0.52 to 0.75) for each extra copy of the minor allele (P = 4.8 × 10(-7)). This SNP is located in DnaJ homolog subfamily C member 5B (DNAJC5B) and merits investigation in additional randomized studies of pravastatin and other statins.     

Rac1 accumulates in the nucleus during the G2 phase of the cell cycle and promotes cell division

Rac1 regulates a wide variety of cellular processes. The polybasic region of the Rac1 C terminus functions both as a plasma membrane-targeting motif and a nuclear localization sequence (NLS). We show that a triproline N-terminal to the polybasic region contributes to the NLS, which is cryptic in the sense that it is strongly inhibited by geranylgeranylation of the adjacent cysteine. Subcellular fractionation demonstrated endogenous Rac1 in the nucleus and Triton X-114 partition revealed that this pool is prenylated. Cell cycle-blocking agents, synchronization of cells stably expressing low levels of GFP-Rac1, and time-lapse microscopy of asynchronous cells revealed Rac1 accumulation in the nucleus in late G2 and exclusion in early G1. Although constitutively active Rac1 restricted to the cytoplasm inhibited cell division, activated Rac1 expressed constitutively in the nucleus increased the mitotic rate. These results show that Rac1 cycles in and out of the nucleus during the cell cycle and thereby plays a role in promoting cell division.     

The nitric oxide (NO)-sensing repressor NsrR of Neisseria meningitidis has a compact regulon of genes involved in NO synthesis and detoxification

We have analyzed the extent of regulation by the nitric oxide (NO)-sensitive repressor NsrR from Neisseria meningitidis MC58, using microarray analysis. Target genes that appeared to be regulated by NsrR, based on a comparison between an nsrR mutant and a wild-type strain, were further investigated by quantitative real-time PCR, revealing a very compact set of genes, as follows: norB (encoding NO reductase), dnrN (encoding a protein putatively involved in the repair of nitrosative damage to iron-sulfur clusters), aniA (encoding nitrite reductase), nirV (a putative nitrite reductase assembly protein), and mobA (a gene associated with molybdenum metabolism in other species but with a frame shift in N. meningitidis). In all cases, NsrR acts as a repressor. The NO protection systems norB and dnrN are regulated by NO in an NsrR-dependent manner, whereas the NO protection system cytochrome c' (encoded by cycP) is not controlled by NO or NsrR, indicating that N. meningitidis expresses both constitutive and inducible NO protection systems. In addition, we present evidence to show that the anaerobic response regulator FNR is also sensitive to NO but less so than NsrR, resulting in complex regulation of promoters such as aniA, which is controlled by both FNR and NsrR: aniA was found to be maximally induced by intermediate NO concentrations, consistent with a regulatory system that allows expression during denitrification (in which NO accumulates) but is down-regulated as NO approaches toxic concentrations.