Effects of physical exercise on human circadian rhythms

Sleep and Biological Rhythms - Bright light is the principal zeitgeber for the biological clock in mammals, including humans. But there is a line of evidence that non-photic stimuli such as...     

Are there age-related differences in the song repertoire size of Eurasian blackbirds?

Most oscine bird species possess a repertoire of different song patterns, and repertoire size is thought to signal aspects of male quality. As age is assumed to be related to male quality in terms of experience and/or viability, repertoire size may be expected to reflect male age. Here, we investigated the relationship between repertoire size and age (yearlings or older) in Eurasian blackbirds, Turdus merula, a species with a large repertoire delivered in a highly variable manner. We found that older males tended to have larger repertoires than yearlings though the two age groups overlapped considerably. Thus, compared to other species with large repertoires, age-related differences in repertoire size seem rather small in male Eurasian blackbirds. We also compared repertoires of three individuals in two successive years (as yearlings and in the year following) and found a large element turnover. Our investigation revealed that this turnover was almost complete in the quiet terminating twitter part of the song. Such turnover may allow a young bird to adjust his repertoire to his neighbours?? repertoires, which could be useful for song matching interactions.     

JCV agnoprotein-induced reduction in CXCL5/LIX secretion by oligodendrocytes is associated with activation of apoptotic signaling in neurons

An indispensable role for oligodendrocytes in the protection of axon function and promotion of neuronal survival is strongly supported by the finding of progressive neuron/axon degeneration in human neurological diseases that affect oligodendrocytes. Imaging and pathological studies of the CNS have shown the presence of neuroaxonal injury in progressive multifocal leukoencephalopathy (PML), a demyelinating disease of the CNS, resulting from destruction of oligodendrocytes upon productive replication of the pathogenic neurotropic polyomavirus JC. Here, we examined the extracellular factors involved in communication between oligodendrocytes and neurons. Culturing cortical neurons with conditioned medium (CM) from rat CG4 oligodendrocytic cells that express the JCV agnoprotein showed that CXCL5/LIX, which is a chemokine closely related to the human CXCL5/ENA78 and CXCL6/GCP-2 chemokines, is essential for neuronal cell survival. We found that in CM from agnoprotein-producing CG-4 cells level of CXC5/LIX is decreased compared to control cells. We also demonstrated that a reduced expression of CXCL5/LIX by CG4 GFP-Agno cells triggered a cascade of signaling events in cortical neurons. Analysis of mitogen-activated protein kinases (MAPK) and glycogen synthase kinase (GSK3) pathways showed that they are involved in mechanisms of neuronal apoptosis in response to the depletion of CXCL5/LIX signaling. These data suggest that agnoprotein-induced dysregulation of chemokine production by oligodendrocytes may contribute to neuronal/axonal injury in the pathogenesis of PML lesions.     

Functional reconstitution and characterization of the Arabidopsis Mg2+ transporter AtMRS2-10 in proteoliposomes

Magnesium (Mg²⁺) plays critical role in many physiological processes. The mechanism of Mg²⁺ transport has been well documented in bacteria; however, less is known about Mg²⁺ transporters in eukaryotes. The AtMRS2 family, which consists of 10 Arabidopsis genes, belongs to a eukaryotic subset of the CorA superfamily proteins. Proteins in this superfamily have been identified by a universally conserved GlyMetAsn motif and have been characterized as Mg²⁺ transporters. Some members of the AtMRS2 family, including AtMRS2-10, may complement bacterial mutants or yeast mutants that lack Mg²⁺ transport capabilities. Here, we report the purification and functional reconstitution of AtMRS2-10 into liposomes. AtMRS2-10, which contains an N-terminal His-tag, was expressed in Escherichia coli and solubilized with sarcosyl. The purified AtMRS2-10 protein was reconstituted into liposomes. AtMRS2-10 was inserted into liposomes in a unidirectional orientation. Direct measurement of Mg²⁺ uptake into proteoliposomes revealed that reconstituted AtMRS2-10 transported Mg²⁺ without any accessory proteins. Mutation in the GMN motif, M400 to I, inactivated Mg²⁺ uptake. The AtMRS2-10-mediated Mg²⁺ influx was blocked by Co(III)hexamine, and was independent of the external pH from 5 to 9. The activity of AtMRS2-10 was inhibited by Co²⁺ and Ni²⁺; however, it was not inhibited by Ca²⁺, Fe²⁺, or Fe³⁺. While these results indicate that AtMRS2-10 has similar properties to the bacterial CorA proteins, unlike bacterial CorA proteins, AtMRS2-10 was potently inhibited by Al³⁺. These studies demonstrate the functional capability of the AtMRS2 proteins in proteoliposomes to study structure–function relationships.     

Budding of retroviruses utilizing divergent L domains requires nucleocapsid

We recently reported that human immunodeficiency virus type 1 (HIV-1) carrying PTAP and LYPX(n)L L domains ceased budding when the nucleocapsid (NC) domain was mutated, suggesting a role for NC in HIV-1 release. Here we investigated whether NC involvement in virus release is a property specific to HIV-1 or a general requirement of retroviruses. Specifically, we examined a possible role for NC in the budding of retroviruses relying on divergent L domains and structurally homologous NC domains that harbor diverse protein sequences. We found that NC is critical for the release of viruses utilizing the PTAP motif whether it functions within its native Gag in simian immunodeficiency virus cpzGAB2 (SIVcpzGAB2) or SIVsmmE543 or when it is transplanted into the heterologous Gag protein of equine infectious anemia virus (EIAV). In both cases, virus release was severely diminished even though NC mutant Gag proteins retained the ability to assemble spherical particles. Moreover, budding-defective NC mutants, which displayed particles tethered to the plasma membrane, were triggered to release virus when access to the cell endocytic sorting complex required for transport pathway was restored (i.e., in trans expression of Nedd4.2s). We also examined the role of NC in the budding of EIAV, a retrovirus relying exclusively on the (L)YPX(n)L-type L domain. We found that EIAV late budding defects were rescued by overexpression of the isolated Alix Bro1 domain (Bro1). Bro1-mediated rescue of EIAV release required the wild-type NC. EIAV NC mutants lost interactions with Bro1 and failed to produce viruses despite retaining the ability to self-assemble. Together, our studies establish a role for NC in the budding of retroviruses harboring divergent L domains and evolutionarily diverse NC sequences, suggesting the utilization of a common conserved mechanism and/or cellular factor rather than a specific motif.     

Direct Absorption of Methyl Mercury by Lymph

Methyl mercury is contained in fish and seafood products and is taken up into the body in food. While the central nervous system is known as a target organ, methyl mercury also induces autoimmunity and acts as a potent immunosuppressor. The aim of the present study is to know whether methyl mercury is directly absorbed by lymph. Conscious rats were infused with methyl mercury (4 mg/kg) via duodenal tubing as a single pulse infusion, followed by the continuous infusion of saline, and lymphatic fluids were continuously collected from the thoracic lymph duct every 30 min until 360 min after infusion. Mercury was detected immediately after infusion, and total mercury contents in lymph gradually increased until 90–120 min, remained steady, and then gradually decreased until 360 min; however, the amount of mercury collected during 330–360 min was about twofold higher than during 0–30 min. The amount of cumulative mercury in lymph at 360 min was 1.4 μg. In contrast, blood mercury concentration was 2.4 μg/ml 5 min after infusion, with the value at 360 min being 12.6 times higher than at 5 min. Plasma mercury concentration was 56 ng/ml at 5 min, with hundreds of nanograms per milliliter of mercury detected until 360 min. From the present study, it is concluded that some methyl mercury is directly absorbed by lymph and remains steady 6 h after infusion.     

Analysis of oligomeric stability of insulin analogs using hydrogen/deuterium exchange mass spectrometry

Insulin analog products for subcutaneous injection are prepared as solutions in which insulin analog molecules exist in several oligomeric states. Oligomeric stability can affect their onset and duration of action and has been exploited in designing them. To investigate the oligomeric stability of insulin analog products having different pharmacokinetics, we performed hydrogen/deuterium exchange mass spectrometry (HDX/MS), which is a rapid method to analyze dynamic aspects of protein structures. Two rapid-acting analogs (lispro and glulisine) incorporated deuteriums more and faster than recombinant human insulin, whereas a long-acting analog (glargine) and two intermediate-acting preparations (protamine-containing formulations) incorporated them less and more slowly. Kinetic analysis revealed that the number of slowly exchanged hydrogens (D(s)) (k<0.01 min(-1)) accounted for the difference in HDX reactivity among analogs. Furthermore, we found correlations between HDX kinetics and pharmacokinetics reported previously. Their maximum serum concentration (C(max)) was linearly correlated with D(s) (r=0.88) and the number of maximum exchangeable hydrogens (D(∞)) (r=0.89). The maximum drug concentration time (t(max)) was also correlated with reciprocals of D(s) and D(∞) (r=0.86 and r=0.96, respectively). Here we demonstrate the ability of HDX/MS to evaluate oligomeric stability of insulin analog products.     

Germ cell specific expression of Vasa in rare minnow, Gobiocypris rarus

Germ cells are set aside early with somatic cells and take roles for reproduction of species from one generation to the next generation. Vasa, a member of DEAD family is well documented as germ cell marker in the animal kingdom. Rare minnow, Gobiocypris rarus, is an emerging model fish in China to study development and toxicology, etc. A suitable germ cell marker will benefit the studies of the factors that may influence germ cell development. Here, we report the cloning and characterization of G. rarus vasa named Grvas whose protein product has the typical characteristics of Vasa proteins. RT-PCR results showed that Grvas is expressed specifically in the gonads of male and female, it is maternally deposited into the eggs for embryos and is continuously expressed in the embryos from the zygote to larvae and adult. Grvas mRNA and/or protein is restricted to the germ cells of ovary and testis. Temporal expression of Grvas mRNA is similar to that of zebrafish vasa during embryogenesis. Grvas signals are coincident with primordial germ cells. These results mean that a germ cell marker, Grvas is isolated from rare minnow and its expression is exclusively in germ cells.     

Estrogen-Dependent Uterine Secretion of Osteopontin Activates Blastocyst Adhesion Competence

Embryo implantation is a highly orchestrated process that involves blastocyst-uterine interactions. This process is confined to a defined interval during gestation referred to as the “window of embryo implantation receptivity”. In mice this receptive period is controlled by ovarian estrogen and involves a coordination of blastocyst adhesion competence and uterine receptivity. Mechanisms coordinating the acquisition of blastocyst adhesion competence and uterine receptivity are largely unknown. Here, we show that ovarian estrogen indirectly regulates blastocyst adhesion competence. Acquisition of blastocyst adhesion competence was attributed to integrin activation (e.g. formation of adhesion complexes) rather than de novo integrin synthesis. Osteopontin (OPN) was identified as an estrogen-dependent uterine endometrial gland secretory factor responsible for activating blastocyst adhesion competence. Increased adhesion complex assembly in OPN-treated blastocysts was mediated through focal adhesion kinase (FAK)- and phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways. These findings define for the first time specific regulatory components of an estrogen-dependent pathway coordinating blastocyst adhesion competence and uterine receptivity.     

Effects of regularizing sleep-wake schedules on daytime autonomic functions and psychological states in healthy university students with irregular sleep-wake habits

Sleep and Biological Rhythms - The present study examined the effects of regularizing sleep-wake schedules on sleep, autonomic function and mood/emotional and personality states in 14 habitually...