Ionoregulatory physiology of two species of African lungfishes Protopterus dolloi and Protopterus annectens

Basic ionoregulatory physiology was characterized in two species of African lungfish, slender African lungfish Protopterus dolloi and West African lungfish Protopterus annectens , largely under aquatic conditions. There were no substantive differences between the two species. Plasma [Na], [Cl] and [Ca] were only 60–80% of those typical of freshwater teleosts, and plasma Ca activity was particularly low. Unidirectional Na and Cl influx rates from water were also very low, only c . 10% of teleost values, whereas unidirectional Ca influx rates were comparable with teleost rates. Protopterus spp. were fed a 3% ration of bloodworms every 48 h. The bloodworm diet provided similar amounts of Na and Ca as uptake from water, but almost no Cl. Efflux rates of Na and Cl through the urine were greater than via the faeces, whereas the opposite was true for Ca. Net ion flux measurements and ionic balance sheet calculations indicated that (1) both water and dietary uptake routes are important for Na and Ca acquisition; (2) the waterborne route predominates for Cl uptake; (3) unidirectional ion effluxes across the body surface (gills and skin) rather than urine and faeces are the major routes of loss for Na, Cl and Ca. Tissues (muscle, liver, lung, kidney, intestine and heart) and plasma ions were also examined in P. dolloi 'terrestrialized' in air for up to 5 months, during which plasma ion concentrations (Na, Cl, Ca and Mg) did not change and there were only a few alterations in tissue ions, that is, increased [Na] in intestine, decreased [Cl] in kidney and increased [Ca] in liver and kidney.     

Infection of CD127+ (interleukin-7 receptor+) CD4+ cells and overexpression of CTLA-4 are linked to loss of antigen-specific CD4 T cells during primary human immunodeficiency virus type 1 infection

We recently found that human immunodeficiency virus (HIV)-specific CD4+ T cells express coreceptor CCR5 and activation antigen CD38 during early primary HIV-1 infection (PHI) but then rapidly disappear from the circulation. This cell loss may be due to susceptibility to infection with HIV-1 but could also be due to inappropriate apoptosis, an expansion of T regulatory cells, trafficking out of the circulation, or dysfunction. We purified CD38+++CD4+ T cells from peripheral blood mononuclear cells, measured their level of HIV-1 DNA by PCR, and found that about 10% of this population was infected. However, a small subset of HIV-specific CD4+) T cells also expressed CD127, a marker of long-term memory cells. Purified CD127+CD4+ lymphocytes contained fivefold more copies of HIV-1 DNA per cell than did CD127-negative CD4+ cells, suggesting preferential infection of long-term memory cells. We observed no apoptosis of antigen-specific CD4+ T cells in vitro and only a small increase in CD45RO+CD25+CD127dimCD4+ T regulatory cells during PHI. However, 40% of CCR5+CD38+++ CD4+ T cells expressed gut-homing integrins, suggesting trafficking through gut-associated lymphoid tissue (GALT). Furthermore, 80% of HIV-specific CD4+ T cells expressed high levels of the negative regulator CTLA-4 in response to antigen stimulation in vitro, which was probably contributing to their inability to produce interleukin-2 and proliferate. Taken together, the loss of HIV-specific CD4+ T cells is associated with a combination of an infection of CCR5+ CD127+ memory CD4+ T cells, possibly in GALT, and a high expression of the inhibitory receptor CTLA-4.     

FERM domain phosphoinositide binding targets merlin to the membrane and is essential for its growth-suppressive function

The neurofibromatosis type 2 tumor suppressor protein, merlin, is related to the ERM (ezrin, radixin, and moesin) family of plasma membrane-actin cytoskeleton linkers. For ezrin, phosphatidylinositol 4,5-bisphosphate (PIP(2)) binding to the amino-terminal FERM domain is required for its conformational activation, proper subcellular localization, and function, but less is known about the role of phosphoinositide binding for merlin. Current evidence indicates that association with the membrane is important for merlin to function as a growth regulator; however, the mechanisms by which merlin localizes to the membrane are less clear. Here, we report that merlin binds phosphoinositides, including PIP(2), via a conserved binding motif in its FERM domain. Abolition of FERM domain-mediated phosphoinositide binding of merlin displaces merlin from the membrane and releases it into the cytosol without altering the folding of merlin. Importantly, a merlin protein whose FERM domain cannot bind phosphoinositide is defective in growth suppression. Retargeting the mutant merlin into the membrane using a dual-acylated amino-terminal decapeptide from Fyn is sufficient to restore the growth-suppressive properties to the mutant merlin. Thus, FERM domain-mediated phosphoinositide binding and membrane association are critical for the growth-regulatory function of merlin.     

Autophagy deregulation in neurodegenerative diseases - recent advances and future perspectives

Autophagy is an evolutionarily conserved homeostatic process for the turnover of cellular contents, organelles and misfolded proteins through the lysosomal machinery. Recently, the involvement of autophagy in the pathophysiology of neurodegenerative diseases has attracted considerable interest because autophagy deregulation has been linked to some of these neurodegenerative disorders. This interest is further heightened by the demonstration that various autophagic pathways, including macroautophagy and chaperone-mediated autophagy, are implicated in the turnover of proteins that are prone to aggregation in cellular or animal disease models. These observations have stimulated new awareness in the pivotal role of the autophagic pathways in neurodegenerative disease pathophysiology, and have sparked extensive research aimed at deciphering the mechanisms by which autophagy is altered in these disorders. Here, we summarize the latest advances in our understanding of the role of autophagy deregulation in Parkinson's, Alzheimer's and Huntington's disease.     

Scapinin-induced inhibition of axon elongation is attenuated by phosphorylation and translocation to the cytoplasm

Scapinin is an actin- and PP1-binding protein that is exclusively expressed in the brain; however, its function in neurons has not been investigated. Here we show that expression of scapinin in primary rat cortical neurons inhibits axon elongation without affecting axon branching, dendritic outgrowth, or polarity. This inhibitory effect was dependent on its ability to bind actin because a mutant form that does not bind actin had no effect on axon elongation. Immunofluorescence analysis showed that scapinin is predominantly located in the distal axon shaft, cell body, and nucleus of neurons and displays a reciprocal staining pattern to phalloidin, consistent with previous reports that it binds actin monomers to inhibit polymerization. We show that scapinin is phosphorylated at a highly conserved site in the central region of the protein (Ser-277) by Cdk5 in vitro. Expression of a scapinin phospho-mimetic mutant (S277D) restored normal axon elongation without affecting actin binding. Instead, phosphorylated scapinin was sequestered in the cytoplasm of neurons and away from the axon. Because its expression is highest in relatively plastic regions of the adult brain (cortex, hippocampus), scapinin is a new regulator of neurite outgrowth and neuroplasticity in the brain.     

Piperine Reverses Chronic Unpredictable Mild Stress-Induced Behavioral and Biochemical Alterations in Rats

Previous studies in our laboratory have demonstrated that piperine produced antidepressant-like action in various mouse models of behavioral despair, which was related to the serotonergic system. The present study aimed to examine the behavioral and biochemical effects of piperine in rats exposed to chronic unpredictable mild stress (CUMS). The results showed that CUMS caused depression-like behavior in rats, as indicated by the significant decrease in sucrose consumption and increase in immobility time in the forced swim test. In addition, it was found that serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) contents in the hippocampus and frontal cortex were significantly decreased in CUMS-treated rats. Treating the animals with piperine significantly suppressed behavioral and biochemical changes induced by CUMS. The results suggest that piperine produces an antidepressant-like effect in CUMS-treated rats, which is possibly mediated by increasing 5-HT and BDNF contents in selective brain tissues.     

Comparative genomics of methicillin-resistant Staphylococcus aureus ST239: distinct geographical variants in Beijing and Hong Kong

Background

The ST239 lineage is a globally disseminated, multiply drug-resistant hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA). We performed whole-genome sequencing of representative HA-MRSA isolates of the ST239 lineage from bacteremic patients in hospitals in Hong Kong (HK) and Beijing (BJ) and compared them with three published complete genomes of ST239, namely T0131, TW20 and JKD6008. Orthologous gene group (OGG) analyses of the Hong Kong and Beijing cluster strains were also undertaken.

Results

Homology analysis, based on highest-percentage nucleotide identity, indicated that HK isolates were closely related to TW20, whereas BJ isolates were more closely related to T0131 from Tianjin. Phylogenetic analysis, incorporating a total of 30 isolates from different continents, revealed that strains from HK clustered with TW20 into the ‘Asian clade’, whereas BJ isolates and T0131 clustered closely with strains of the ‘Turkish clade’ from Eastern Europe. HK isolates contained the typical φSPβ-like prophage with the SasX gene similar to TW20. In contrast, BJ isolates contained a unique 15 kb PT1028-like prophage but lacked φSPβ-like and φSA1 prophages. Besides distinct mobile genetic elements (MGE) in the two clusters, OGG analyses and whole-genome alignment of these clusters highlighted differences in genes located in the core genome, including the identification of single nucleotide deletions in several genes, resulting in frameshift mutations and the subsequent predicted truncation of encoded proteins involved in metabolism and antimicrobial resistance.

Conclusions

Comparative genomics, based on de novo assembly and deep sequencing of HK and BJ strains, revealed different origins of the ST239 lineage in northern and southern China and identified differences between the two clades at single nucleotide polymorphism (SNP), core gene and MGE levels. The results suggest that ST239 strains isolated in Hong Kong since the 1990s belong to the Asian clade, present mainly in southern Asia, whereas those that emerged in northern China were of a distinct origin, reflecting the complexity of dissemination and the dynamic evolution of this ST239 lineage.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-529) contains supplementary material, which is available to authorized users.     

Cellular mechanisms in intermittent hypoxia-induced cardiac damage in vivo

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH) during sleep, is increasingly recognized as an independent risk factor of cardiovascular diseases. OSA is associated with changes in the levels of circulating oxidative stress/inflammatory markers and dyslipidemia, supporting their mediating roles in cardiovascular pathogenesis. Our aims were to investigate the effect of IH on heart tissue using an IH-exposed rat model and to explore the potential mechanisms involved in the occurrence of cardiac damage. Male Sprague–Dawley rats were exposed to IH and intermittent normoxia as control and sacrificed after 2 or 4 weeks. IH for 4 weeks caused elevation in serum malondialdehyde and cytokine-induced neutrophil chemoattractant-1 and reduction in serum adiponectin levels. In contrast, cardiac oxidative stress and pro-inflammatory markers were suppressed while cardiac adiponectin and cholesterol levels were elevated after IH exposure for 4 weeks. In parallel, there was an increase in apoptosis in the heart of IH-exposed rats, demonstrated by elevations of Bax and cleaved caspase-3 protein and TUNEL staining. Cardiac damage was further evident with decreased arterial vessel and capillary densities, increased cardiac fibrosis, and the loss of troponin I. Our data demonstrated that IH exposure paradoxically caused systemic oxidative and inflammatory responses and cardioprotective responses, i.e., anti-oxidative and anti-inflammatory responses. Despite such a local compensatory protective mechanism, cardiac damage was observed that might be due to IH-induced cholesterol accumulation in the heart and caspase-dependent apoptosis.