Biochemical characterization of plasma membrane isolated from human skeletal muscle

AbstractSpecific components of ion translocation systems were studied in excitable plasma membranes isolated from normal human muscle. Na+ - K+ ATPase and ouabain-sensitive K+ phosphatase activities were 8.9 ± 1 μmol Pih per mg protein and 96 ± 9 nmolmin per mg protein, respectively. Scatchard analysis of equilibrium binding assays with [3H]ouabain showed non-linear curves consistent with high- and low-affinity sites (estimated Kd 3 nM and 0.22 μM). Two families of receptors with different affinities for a tritiated TTX derivative (estimated Kd 0.4 and 4 nM) were also identified suggesting the existence in human muscle of at least two classes of voltage-dependent Na+ channels. In addition (+)-[methyl-3H]PN200-110, a potent Ca2+ antagonist used for labeling voltage-dependent Ca2+ channels, was observed to bind to a homogeneous population of receptors in the plasma membrane (Kd = 0.2 nM)

CCN3 and calcium signaling

The CCN family of genes consists presently of six members in human (CCN1-6) also known as Cyr61 (Cystein rich 61), CTGF (Connective Tissue Growth Factor), NOV (Nephroblastoma Overexpressed gene), WISP-1, 2 and 3 (Wnt-1 Induced Secreted Proteins). Results obtained over the past decade have indicated that CCN proteins are matricellular proteins, which are involved in the regulation of various cellular functions, such as proliferation, differentiation, survival, adhesion and migration. The CCN proteins have recently emerged as regulatory factors involved in both internal and external cell signaling. CCN3 was reported to physically interact with fibulin-1C, integrins, Notch and S100A4. Considering that, the conformation and biological activity of these proteins are dependent upon calcium binding, we hypothesized that CCN3 might be involved in signaling pathways mediated by calcium ions. In this article, we review the data showing that CCN3 regulates the levels of intracellular calcium and discuss potential models that may account for the biological effects of CCN3

Renal infarction in an adolescent carrier of the sickle cell trait.

editorial reviewedWe report the case of a 15-year-old teenager, carrier of the sickle cell trait (haemoglobin AS), who presented a renal infarction. Besides, the patient also presented a renal ectopia. It is tempting to link these two particularities and the ischemic attack. The kidney is a target of this hemoglobinopathy, in its homozygous and possibly even heterozygous form. However, the analysis of the literature does not retain renal vascular accidents as a complication of sickle cell trait. Kidney position abnormalities also do not appear to be a contributing factor. It is, however, necessary to be attentive in adult heterozygous subjects to a faster than normal decline in glomerular filtration. The search for other risk factors (hypertension, diabetes, dyslipaemia) is desirable. The implementation of specific monitoring requires additional work

Acute experimental glomerulonephritis induced by the glomerular deposition of circulating polymerid IgA-Concanavalin A complexes

The perfusion of polymeric or secretory IgA-Concanavalin A complexes into the aorta of rats led to a mannose-dependent binding of both IgA and lectin to the glomerular capillary wall, as shown by double immunolocalization experiments, by quantitative analysis of the amount of radiolabeled complexes bound per g of kidney, and by blocking experiments with the corresponding carbohydrate. Rats injected with amounts of those complexes as low as 500 ?g developed, one hour later, a focal and segmental proliferative glomerulonephritis characterized by the deposition of injected complexes and of rat C3 and rat fibrin/ fibrinogen in most glomeruli ; focal thrombosis and small areas of necrosis in 10 to 15% of glomeruli, confined to the periphery of a single lobule of the tuft and segmental infiltration of these glomeruli by polymorphonuclear leucocytes and platelets. At the same time, many mesangial cells exhibited a hyperactive appearance, and red blood cells were noted in tubular lumens. In contrast, rats similarly injected with either monomeric IgA-ConA complexes, multimeric or secretory IgA-peanut agglutinin complexes or polymeric or monomeric IgA aggregates of comparable apparent molecular weight did not develop obvious glomerular lesions within one hour. The data indicate that preformed polymeric IgA-ConA complexes can specifically bind to glomerular structures in vivo and trigger acute glomerular lesions locally, analogous to those observed in some glomerular diseases associated with a cryoglobulinemia

Vitamin D-Resistant Rickets and Cinacalcet—One More Favorable Experience

Hereditary vitamin D-resistant rickets (HVDRR) is an autosomal recessive disorder characterized by early onset of severe rickets, with a complete triad of clinical, biochemical and skeletal abnormalities. Homozygous or heterozygous mutations in the vitamin D receptor (VDR) gene leading to complete or partial target organ resistance to the action of 1α, 25-dihydroxyvitamin D3 (the active form of vitamin D) are responsible for HVDRR. Theoretically the therapeutic goal is to overcome this tissue resistance, and to normalize calcium and phosphate homeostasis. Practically, the treatment could be oriented to correct the secondary hyperparathyroidism to avoid long-term negative impact on bone health. The conventional therapeutic strategy (high-dose calcium plus active vitamin D metabolites) gives variable responses in magnitude and duration. We report a case of HVDRR with heterozygous mutation in the VDR gene, neonatal alopecia, and a severe clinical phenotype diagnosed at the age of 30 months who showed unsatisfactory response to traditional therapy. The short-term responsiveness to cinacalcet was encouraging, with adequate correction of phosphate-calcium homeostasis and significant improvement of clinical and radiological status at 6 months of treatment

Differential axonal transport of individual Na, K-ATPase catalytic ([alpha]) subunit isoforms in rat sciatic nerve

Three isoforms of the Na, K-ATPase catalytic ([alpha]) subunit are present in neurons, demonstrated by in situ hybridization of neurons and Western blot of nerve. We used Western blot with antibodies specific for [alpha]1, [alpha]2 and [alpha]3 peptides to measure the accumulation of individual peptides at a ligature on the sciatic nerve. [alpha]1 peptide accumulated with kinetics suggesting rapid axonal transport of that isoform within nerve. [alpha]2 and [alpha]3 peptides did not accumulate at the ligature. These studies provide insight into the dynamics of axonal Na, K-ATPase isoforms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30641/1/0000283.pd

Acidocétose diabétique chez l’enfant: aspects épidémiologiques et pronostiques

Introduction: au Congo, les données concernant l'acidocétose diabétique (ACD) chez l'enfant sont anciennes et rares. Notre étude avait pour objectifs de décrire les caractéristiques sociodémographiques de l'ACD et d'identifier les facteurs de risque de décès. Méthodes: de Janvier 2013 à Juin 2016, nous avons réalisé une étude analytique portant sur l'ACD chez l'enfant au CHU de Brazzaville. Les variables sociodémographiques, cliniques, paracliniques et évolutives ont été étudiées. Les tests de Chi-2, de Fischer et l'odds ratios ont servi pour l'analyse univariée et le modèle de régression logistique pour l'analyse multivariée. Résultats: sur 172 enfants hospitalisés pour un diabète, 55(31%) l'étaient pour une acidocétose. Il s'agissait de 33(60%) filles, l'âge moyen: 11,1± 4,9 ans (extrêmes 1 mois et 17 ans), 61,8% des parents avaient un bas niveau socioéconomique. L'acidocétose était révélatrice dans 67,2 % de cas. Le diagnostic avant l'hospitalisation était erroné: 50%. Le facteur déclenchant était souvent infectieux (52,7%). La létalité était de 12,7%. Les facteurs de risque de décès en analyse univariée étaient : l'âge < 5 ans (p=0,000006), le délai de consultation supérieur à 7 jours (p= 0,001), la déshydratation sévère (p = 0,0006), les troubles hémodynamiques (p= 0,0006), la dénutrition sévère (p= 0,02), le Glasgow < 9 (p= 0,007) et la diarrhée (p= 0,001). Conclusion: l'importance et la gravité de l'acidocétose imposent des mesures de prévention axées sur la sensibilisation, l'information, l'éducation et la maîtrise des facteurs de risque de décès

The inhibition of CHO-K1-BH4 cell proliferation and induction of chromosomal aberrations by brevetoxins in vitro

Brevetoxins (PbTxs) are highly potent trans-syn polyether neurotoxins produced during blooms of several species of marine dinoflagellates, most notably Karenia brevis. These neurotoxins act on voltage-sensitive sodium channels prolonging the active state. During red tides, the commercial fishing and tourism industries experience millions of dollars of lost revenue. Human consumption of shellfish contaminated with PbTxs results in neurotoxic shellfish poisoning (NSP). Additionally, blooms of K. brevis are potentially responsible for adverse human health effects such as respiratory irritation and airway constriction in coastal residents. There is little information regarding the full range of potential toxic effects caused by PbTxs. Recent evidence suggests that PbTxs are genotoxic substances. The purpose of this study was to determine if PbTxs could induce chromosomal aberrations and inhibit cellular proliferation in CHO-K1-BH4 cells, and if so, could the damage be negated or reduced by the PbTx antagonist brevenal. Results from the chromosomal aberrations assay demonstrated that PbTxs are potent inducers of CHO-K1-BH4 chromosome damage. Results from the inhibition of cellular proliferation assays demonstrated that PbTxs inhibit the ability of CHOK1- BH4 cells to proliferate, an effect which can be reduced with brevenal. Originally published Food and Chemical Toxicology, Vol. 44, No. 7, July 200

Medical genetics

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38266/1/28_ftp.pd

Pyrethroids and Nectar Toxins Have Subtle Effects on the Motor Function, Grooming and Wing Fanning Behaviour of Honeybees (Apis mellifera)

Sodium channels, found ubiquitously in animal muscle cells and neurons, are one of the main target sites of many naturally-occurring, insecticidal plant compounds and agricultural pesticides. Pyrethroids, derived from compounds found only in the Asteraceae, are particularly toxic to insects and have been successfully used as pesticides including on flowering crops that are visited by pollinators. Pyrethrins, from which they were derived, occur naturally in the nectar of some flowering plant species. We know relatively little about how such compounds—i.e., compounds that target sodium channels—influence pollinators at low or sub-lethal doses. Here, we exposed individual adult forager honeybees to several compounds that bind to sodium channels to identify whether these compounds affect motor function. Using an assay previously developed to identify the effect of drugs and toxins on individual bees, we investigated how acute exposure to 10 ng doses (1 ppm) of the pyrethroid insecticides (cyfluthrin, tau-fluvalinate, allethrin and permethrin) and the nectar toxins (aconitine and grayanotoxin I) affected honeybee locomotion, grooming and wing fanning behaviour. Bees exposed to these compounds spent more time upside down and fanning their wings. They also had longer bouts of standing still. Bees exposed to the nectar toxin, aconitine, and the pyrethroid, allethrin, also spent less time grooming their antennae. We also found that the concentration of the nectar toxin, grayanotoxin I (GTX), fed to bees affected the time spent upside down (i.e., failure to perform the righting reflex). Our data show that low doses of pyrethroids and other nectar toxins that target sodium channels mainly influence motor function through their effect on the righting reflex of adult worker honeybees