Nystatin-induced increase in photocurrent in the system ‘bacteriorhodopsin proteoliposome/bilayer planar membrane’

Proteoliposomes were reconstituted from bacteriorhodopsin sheets, asolectin and cholesterol with or without nystatin. Bacteriorhodopsin-mediated electrogenesis was monitored using (1) a proteoliposome suspension and phenyldicarbaundecaborane (PCB^?) probe or (2) proteoliposomes associated with planar bilayer membrane and orthodox electrometer techniques. In the light, PCB^? was shown to be taken up by proteoliposomes. The PCB^? uptake was inhibited by addition of nystatin to an incubation mixture with proteoliposomes if they were reconstituted in the presence of nystatin. Extraproteoliposomal nystatin was without influence if nystatin was omitted from the reconstitution mixture. The nystatin-containing proteoliposomes were associated with a planar bilayer asolectin membrane in the presence of Ca²⁺. It was found that in such a system, bacteriorhodopsin generated a photocurrent charging the proteoliposome-containing (cis-side) compartment negatively and the trans-side compartment positively. The photoresponse was shown to be increased several-fold by addition of nystatin to the trans-side solution. Nystatin addition was ineffective if proteoliposomes were reconstituted without nystatin. Taking into account that nystatin forms ion-permeable pores in a membrane only if present on both sides of the membrane and that this membrane is bilayer, one can explain the above data assuming that (1) the intraproteoliposomal solution does not mix with the extraproteoliposomal one when proteoliposomes are attached to a planar black membrane and (2) the attached proteoliposomes are separated from the trans-side bathing solution by a bimolecular membrane. If this is the case, nystatin in the trans-side bathing solution and inside the attached proteoliposome can form pores across that part of the planar membrane which separates the proteoliposome interior from the trans-side solution. Through these pores, H⁺ (pumped by bacteriorhodopsin from the cis-side solution into the proteoliposome interior) or some other intraproteoliposomal ions can be equilibrated with those in the trans-side solution. As a result, the bacteriorhodopsin-generated photocurrent increases.     

Usefulness of Y-body study on bone marrow smears to demonstrate the origin of fibroblast stromal cells in allogeneic bone marrow transplantation

The value of Y-body study for assessment of stromal cell engraftment was analyzed in 25 patients submitted to allogeneic bone marrow transplantation (BMT) (sex-matched in 12 cases and sex-mismatched in 13). The study was performed weekly on bone marrow smears until day +35, and the results were compared with those obtained in a control group of 20 patients submitted to autologous BMT (12 males and 8 females). Engraftment of haemopoietic cells was documented in all cases. The results of Y-body study on the recipients' fibroblast cells showed a pattern identical to that observed prior to BMT, independent of donor's sex. On the other hand, there were no differences between allogeneic and autologous BMT recipients in regard to percentage of Y-body positive cells. These results indicate that in allogeneic BMT there is no engraftment of the fibroblastic component of bone marrow stroma.     

Use of polysaccharides to remove lipids from the protein globulin fraction of baker's yeast

The precipitation of lipid-protein complexes from the baker's yeast protein globulin fraction by polysaccharides (gum arabic and arabinogalactan) was investigated. Lipid-protein complexes were precipitated more readily with the polysaccharides under study than with other globulin fractions components. A method for the removal of lipids from the globulin fraction of baker's yeast by precipitation of the lipid-protein complexes with polysaccharides is suggested.     

Determination of nystatin component composition using HPLC and TLC with densitometry]

The component composition of nystatin produced by an improved strain of Streptomyces noursei was determined by HPLC on Milichrom chromatograph (USSR). It was shown that the antibiotic consisted of nystatins A1, A2, A3 and B and admixture substances. The data appeared to be in good agreement with the results of the complex TLC investigation, by using densitometry. The component composition of the samples was evidenced by SIEAP mass spectrometry. Physiochemical and biological characteristics of separate components are presented.     

Glutamate dehydrogenase deficiency disrupts glutamate homeostasis in hippocampus and prefrontal cortex and impairs recognition memory

Glutamate Dehydrogenase 1 (GDH), encoded by the Glud1 gene in rodents, is a mitochondrial enzyme critical for maintaining glutamate homeostasis at the tripartite synapse. Our previous studies indicate that the hippocampus may be particularly vulnerable to GDH deficiency in central nervous system (CNS). Here, we first asked whether mice with a homozygous deletion of Glud1 in CNS (CNS‐Glud1 ?/? mice) express different levels of glutamate in hippocampus, and found elevated glutamate as well as glutamine in dorsal and ventral hippocampus, and increased glutamine in medial prefrontal cortex (mPFC). l ‐serine and d ‐serine, which contribute to glutamate homeostasis and NMDA receptor function, are increased in ventral but not dorsal hippocampus, and in mPFC. Protein expression levels of the GABA synthesis enzyme glutamate decarboxylase (GAD) GAD67 were decreased in the ventral hippocampus as well. Behavioral analysis revealed deficits in visual, spatial and social novelty recognition abilities, which require intact hippocampal‐prefrontal cortex circuitry. Finally, hippocampus‐dependent contextual fear retrieval was deficient in CNS‐Glud1 ?/? mice, and c‐Fos expression (indicative of neuronal activation) in the CA1 pyramidal layer was reduced immediately following this task. These data point to hippocampal subregion‐dependent disruption in glutamate homeostasis and excitatory/inhibitory balance, and to behavioral deficits that support a decline in hippocampal‐prefrontal cortex connectivity. Together with our previous data, these findings also point to different patterns of basal and activity‐induced hippocampal abnormalities in these mice. In sum, GDH contributes to healthy hippocampal and PFC function; disturbed GDH function is relevant to several psychiatric and neurological disorders.     

Cytotoxic Effects of the Selective Ligands of Membrane Progesterone Receptors in Human Pancreatic Adenocarcinoma Cells BxPC3

Biochemistry (Moscow) - Progesterone and its synthetic analogues act on cells through different types of receptors, affecting proliferation and apoptosis. These compounds exert their effect through...     

Interactive effects of elevated temperature and CO2 levels on metabolism and oxidative stress in two common marine bivalves (Crassostrea virginica and Mercenaria mercenaria)

Marine bivalves such as the hard shell clams Mercenaria mercenaria and eastern oysters Crassostrea virginica are affected by multiple stressors, including fluctuations in temperature and CO₂ levels in estuaries, and these stresses are expected to be exacerbated by ongoing global climate change. Hypercapnia (elevated CO₂ levels) and temperature stress can affect survival, growth and development of marine bivalves, but the cellular mechanisms of these effects are not yet fully understood. In this study, we investigated whether oxidative stress is implicated in cellular responses to elevated temperature and CO₂ levels in marine bivalves. We measured the whole-organism standard metabolic rate (SMR), total antioxidant capacity (TAOC), and levels of oxidative stress biomarkers in the muscle tissues of clams and oysters exposed to different temperatures (22 and 27 °C) and CO₂ levels (the present day conditions of ~ 400 ppm CO₂ and 800 ppm CO₂ predicted by a consensus business-as-usual IPCC emission scenario for the year 2100). SMR was significantly higher and the antioxidant capacity was lower in oysters than in clams. Aerobic metabolism was largely temperature-independent in these two species in the studied temperature range (22–27 °C). However, the combined exposure to elevated temperature and hypercapnia led to elevated SMR in clams indicating elevated costs of basal maintenance. No persistent oxidative stress signal (measured by the levels of protein carbonyls, and protein conjugates with malondialdehyde and 4-hydroxynonenal) was observed during the long-term exposure to moderate warming (+ 5 °C) and hypercapnia (~ 800 ppm CO₂). This indicates that long-term exposure to moderately elevated CO₂ and temperature minimally affects the cellular redox status in these bivalve species and that the earlier observed negative physiological effects of elevated CO₂ and temperature must be explained by other cellular mechanisms.     

DNA damage causes TP53-dependent coupling of self-renewal and senescence pathways in embryonal carcinoma cells

Comment on: Wu R, et al. Clin Cancer Res 2011; 17:7359–72     

Early Diagnosis of Neurodegenerative Diseases – The Long Awaited Holy Grail and Bottleneck of Modern Brain Research – 19th HUPO BPP Workshop

The HUPO Brain Proteome Project (HUPO BPP) held its 19th workshop in Dortmund, Germany, from May 22 to 24, 2013. The focus of the spring workshop was on strategies and developments concerning early diagnosis of neurodegenerative diseases