Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle

Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle.     

Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability

We have analyzed nucleic acid and amino acid sequence alignments of a variety of voltage-sensitive ion channels, using several methods for phylogenetic tree reconstruction. Ancient duplications within this family gave rise to three distantly related groups, one consisting of the Na+ and Ca++ channels, another the K+ channels, and a third including the cyclic nucleotide-binding channels. A series of gene duplications produced at least seven mammalian homologues of the Drosophila Shaker K+ channel; clones of only three of these genes are available from all three mammalian species examined (mouse, rat, and human), pointing to specific genes that have yet to be recovered in one or another of these species. The Shaw-related K+ channels and the Na+ channel family have also undergone considerable expansion in mammals, relative to flies. These expansions presumably reflect the needs of the high degree of physiological and neuronal complexity of mammals. Analysis of the separate domains of the four-domain channels (Ca++ and Na+) supports their having evolved by two sequential gene duplications and implies the historical existence of a functional two-domain channel.      

Intensified Tuberculosis Case Finding among Malnourished Children in Nutritional Rehabilitation Centres of Karnataka,India: Missed Opportunities

Background

Severe acute malnutrition (SAM) is the most serious form of malnutrition affecting children under-five and is associated with many infectious diseases including Tuberculosis (TB). In India, nutritional rehabilitation centres (NRCs) have been recently established for the management of SAM including TB. The National TB Programme (NTP) in India has introduced a revised algorithm for diagnosing paediatric TB. We aimed to examine whether NRCs adhered to these guidelines in diagnosing TB among SAM children.

Methods

A cross-sectional study involving review of records of all SAM children identified by health workers during 2012 in six tehsils (sub-districts) with NRCs (population: 1.8 million) of Karnataka, India.

Results

Of 1927 identified SAM children, 1632 (85%) reached NRCs. Of them, 1173 (72%) were evaluated for TB and 19(2%) were diagnosed as TB. Of 1173, diagnostic algorithm was followed in 460 (37%). Among remaining 763 not evaluated as per algorithm, tuberculin skin test alone was conducted in 307 (41%), chest radiography alone in 99 (13%) and no investigations in 337 (45%). The yield of TB was higher among children evaluated as per algorithm (4%) as compared to those who were not (0.3%) (OR: 15.3 [95%CI: 3.5-66.3]). Several operational challenges including non-availability of a full-time paediatrician, non-functioning X-ray machine due to frequent power cuts, use of tuberculin with suboptimal strength and difficulties in adhering to a complex diagnostic algorithm were observed.

Conclusion

This study showed that TB screening in NRCs was sub-optimal in Karnataka. Some children did not reach the NRC, while many of those who did were either not or sub-optimally evaluated for TB. This study pointed to a number of operational issues that need to be addressed if this collaborative strategy is to identify more TB cases amongst malnourished children in India.     

Organotypic brain-slice cultures from adult rats: approaches for a prolonged culture time

Animal experiments are widely used in neurobiological and neuropharmacological research. Today, juvenile brain organotypic slice cultures have partially replaced in vivo experiments, but there is no adequate in vitro counterpart for the adult brain. The present study was aimed at the long-term culture of physiologically intact hippocampal slices from adult rats, by improving the conditions for preparation and culture, and the development of a new culture medium. A cerebrospinal fluid (CSF)-like medium was used, which was modified with a variety of supplements, including energy precursors, free-radical scavengers, and compounds known to inhibit neurotoxicity. The population spike amplitude (PSA) was used as a measure of viability, and amplitudes larger than 1mV indicated viable cultures. The addition of MK-801 during slice preparation improved PSA values during the first two days in vitro (DIV). Ascorbic acid and insulin prolonged the culture time up to DIV 4. FK-506 and vitamin E, alone or in combination, supported slice culture up to DIV 5. An increase in ATP, unless combined with vitamin E, and/or insulin, increased culture time up to DIV 6. Vitamins B(1), B(2), B(12) and D(2) had no effect. The modified CSF-like medium developed in this study permits the culture of adult hippocampal tissue for at least 6 days.     

Risks and Benefits of Nalmefene in the Treatment of Adult Alcohol Dependence: A Systematic Literature Review and Meta-Analysis of Published and Unpublished Double-Blind Randomized Controlled Trials

Background

Nalmefene is a recent option in alcohol dependence treatment. Its approval was controversial. We conducted a systematic review and meta-analysis of the aggregated data (registered as PROSPERO 2014:CRD42014014853) to compare the harm/benefit of nalmefene versus placebo or active comparator in this indication.

Methods and Findings

Three reviewers searched for published and unpublished studies in Medline, the Cochrane Library, Embase, ClinicalTrials.gov, Current Controlled Trials, and bibliographies and by mailing pharmaceutical companies, the European Medicines Agency (EMA), and the US Food and Drug Administration. Double-blind randomized clinical trials evaluating nalmefene to treat adult alcohol dependence, irrespective of the comparator, were included if they reported (1) health outcomes (mortality, accidents/injuries, quality of life, somatic complications), (2) alcohol consumption outcomes, (3) biological outcomes, or (4) treatment safety outcomes, at 6 mo and/or 1 y. Three authors independently screened the titles and abstracts of the trials identified. Relevant trials were evaluated in full text. The reviewers independently assessed the included trials for methodological quality using the Cochrane Collaboration tool for assessing risk of bias. On the basis of the I2 index or the Cochrane’s Q test, fixed or random effect models were used to estimate risk ratios (RRs), mean differences (MDs), or standardized mean differences (SMDs) with 95% CIs. In sensitivity analyses, outcomes for participants who were lost to follow-up were included using baseline observation carried forward (BOCF); for binary measures, patients lost to follow-up were considered equal to failures (i.e., non-assessed patients were recorded as not having responded in both groups). Five randomized controlled trials (RCTs) versus placebo, with a total of 2,567 randomized participants, were included in the main analysis. None of these studies was performed in the specific population defined by the EMA approval of nalmefene, i.e., adults with alcohol dependence who consume more than 60 g of alcohol per day (for men) or more than 40 g per day (for women). No RCT compared nalmefene with another medication. Mortality at 6 mo (RR = 0.39, 95% CI [0.08; 2.01]) and 1 y (RR = 0.98, 95% CI [0.04; 23.95]) and quality of life at 6 mo (SF-36 physical component summary score: MD = 0.85, 95% CI [−0.32; 2.01]; SF-36 mental component summary score: MD = 1.01, 95% CI [−1.33; 3.34]) were not different across groups. Other health outcomes were not reported. Differences were encountered for alcohol consumption outcomes such as monthly number of heavy drinking days at 6 mo (MD = −1.65, 95% CI [−2.41; −0.89]) and at 1 y (MD = −1.60, 95% CI [−2.85; −0.35]) and total alcohol consumption at 6 mo (SMD = −0.20, 95% CI [−0.30; −0.10]). An attrition bias could not be excluded, with more withdrawals for nalmefene than for placebo, including more withdrawals for safety reasons at both 6 mo (RR = 3.65, 95% CI [2.02; 6.63]) and 1 y (RR = 7.01, 95% CI [1.72; 28.63]). Sensitivity analyses showed no differences for alcohol consumption outcomes between nalmefene and placebo, but the weight of these results should not be overestimated, as the BOCF approach to managing withdrawals was used.

Conclusions

The value of nalmefene for treatment of alcohol addiction is not established. At best, nalmefene has limited efficacy in reducing alcohol consumption.     

Kidney pathology precedes and predicts the pathological cascade of cerebrovascular lesions in stroke prone rats

Introduction

Human cerebral small vessel disease (CSVD) has been hypothesized to be an age-dependent disease accompanied by similar vascular changes in other organs. SHRSP feature numerous vascular risk factors and may be a valid model of some aspects of human CSVD. Here we compare renal histopathological changes with the brain pathology of spontaneously hypertensive stroke-prone rats (SHRSP).

Material and Methods

We histologically investigated the brains and kidneys of 61 SHRSP at different stages of age (12 to 44 weeks). The brain pathology (aggregated erythrocytes in capillaries and arterioles, microbleeds, microthromboses) and the kidney pathology (aggregated erythrocytes within peritubular capillaries, tubular protein cylinders, glomerulosclerosis) were quantified separately. The prediction of the brain pathology by the kidney pathology was assessed by creating ROC-curves integrating the degree of kidney pathology and age of SHRSP.

Results

Both, brain and kidney pathology, show an age-dependency and proceed in definite stages whereas an aggregation of erythrocytes in capillaries and arterioles, we parsimoniously interpreted as stases, represent the initial finding in both organs. Thus, early renal tubulointerstitial damage characterized by rather few intravasal erythrocyte aggregations and tubular protein cylinders predicts the initial step of SHRSPs'' cerebral vascular pathology marked by accumulated erythrocytes. The combined increase of intravasal erythrocyte aggregations and protein cylinders accompanied by glomerulosclerosis and thrombotic renal microangiopathy in kidneys of older SHRSP predicts the final stages of SHRSPs'' cerebrovascular lesions marked by microbleeds and thrombotic infarcts.

Conclusion

Our results illustrate a close association between structural brain and kidney pathology and support the concept of small vessel disease to be an age-dependent systemic pathology. Further, an improved joined nephrologic and neurologic diagnostic may help to identify patients with CSVD at an early stage.     

N-Terminal pyroglutamate formation of Aβ38 and Aβ40 enforces oligomer formation and potency to disrupt hippocampal long-term potentiation

Pyroglutamate (pGlu)-modified amyloid peptides have been identified in sporadic and familial forms of Alzheimer's disease (AD) and the inherited disorders familial British and Danish Dementia (FBD and FDD). In this study, we characterized the aggregation of amyloid-β protein Aβ37, Aβ38, Aβ40, Aβ42 and ADan species in vitro, which were modified by N-terminal pGlu (pGlu-Aβ3-x, pGlu-ADan) or possess the intact N-terminus (Aβ1-x, ADan). The pGlu-modification confers rapid formation of oligomers and short fibrillar aggregates. In accordance with these observations, the pGlu-modified Aβ38, Αβ40 and Αβ42 species inhibit hippocampal long term potentiation of synaptic response, but pGlu-Aβ3-42 showing the highest effect. Among the unmodified Aβ peptides, only Aβ1-42 exhibites such propensity, which was similar to pGlu-Aβ3-38 and pGlu-Aβ3-40. Likewise, the amyloidogenic peptide pGlu-ADan impaired synaptic potentiation more pronounced than N-terminal unmodified ADan. The results were validated using conditioned media from cultivated HEK293 cells, which express APP variants favoring the formation of Aβ1-x, Aβ3-x or N-truncated pGlu-Aβ3-x species. Hence, we show that the ability of different amyloid peptides to impair synaptic function apparently correlates to their potential to form oligomers as a common mechanism. The pGlu-modification is apparently mediating a higher surface hydrophobicity, as shown by 1-anilinonaphtalene-8-sulfonate fluorescence, which enforces potential to interfere with neuronal physiology.     

A three-dimensional colocalization RNA interference screening platform to elucidate the alternative lengthening of telomeres pathway

A high-content colocalization RNA interference screen based on automatic three-color confocal fluorescence microscopy was developed to analyze the alternative lengthening of telomeres (ALT) pathway. Via this pathway telomerase-negative cancer cells can maintain their telomeres and with it their unlimited proliferative potential. A hallmark of ALT cells is the colocalization of promyelocytic leukemia (PML) nuclear bodies with telomeres to form ALT-associated PML nuclear bodies (APBs). In our screen, the presence of APBs was used as a marker to identify proteins required for the ALT mechanism. A cell-based assay and an automatic confocal image acquisition procedure were established. Using automatic image analysis based on 3D parametric intensity models to identify APBs, we conducted an unbiased and quantitative analysis of nine different candidate genes. A comparison with the literature and manual analysis of the gene knockdown demonstrates the reliability of our approach. It extends the available repertoire of high-content screening to studies of cellular colocalizations and allows the identification of candidate genes for the ALT mechanism that represent possible targets for cancer therapy.