Cystine Deprivation Induces Oligodendroglial Death: Rescue by Free Radical Scavengers and by a Diffusible Glial Factor

Abstract: In this study we examined the effect on oligodendroglial survival of exogenous cystine deprivation. Oligodendroglia isolated from mixed glial primary cultures derived from brains of 1-day-old rats, and then grown for 3 days, were markedly dependent on extracellular cystine for survival. The EC₅₀ values for cystine for a 24-h exposure ranged from 2 to 65 µ M . After 6 h of cystine deprivation, the cellular glutathione level decreased to 21 ± 13% of the control. Free radical scavengers (α-tocopherol, ascorbate, idebenone, and N-tert -butyl-α-phenylnitrone) were protective against cystine deprivation but had no effect on the glutathione level. An iron chelator, desferrioxamine mesylate, also was protective. These findings suggest that intracellular hydroxyl radicals are important for this toxicity. In contrast to the observations in 3-day-old cultures, the dependence on exogenous cystine for cell viability was not observed consistently in oligodendroglia cultured for 6 days before the onset of cystine deprivation. Several observations suggested that this loss of cystine dependence was due to a diffusible factor. Sensitivity to the toxicity of cystine deprivation in day 6 cultures increased as the volume of medium was increased from 0.3 to 2 ml. Furthermore, preincubation of cystine-depleted medium with astrocyte cultures eliminated the toxicity of the cystine deprivation. HPLC assay of the conditioned cystine-depleted medium showed no significant change in cystine or cysteine concentration. We conclude that oligodendroglia are highly susceptible to cystine deprivation in day 3 cultures and that this susceptibility is due to the accumulation of intracellular free radicals in the setting of glutathione depletion. The resistance of day 6 oligodendroglial cultures is caused at least in part by a diffusible factor.     

Variability in several ecologic-physiologic traits of different populations of the Asiatic Arctic suslik Citellus parryi]

In several geographic populations of the Arctic ground squirrel C. parryi, studies have been made on changes in oxygen consumption during decrease of the ambient temperature from 25 to 3-4 degrees, thermal preference, hemoglobin content of the blood and composition of the adipose tissue (both brown and white, subcutaneous and visceral). Significant shifts of these indices were found. In animals from various parts of the species area, different sensitivity to cooling was found, as indicated by determinations of oxygen consumption at different temperatures and the prefered temperature: different hemoglobin content of the blood was also found together with differences in the level of two unsaturated fatty acids - the oleic and linoleic ones. Comparison of these data with similar results obtained on various populations of the Siberian ground squirrel C. undulatus revealed obvious differences between these close species with respect to the indices studied.     

In-depth Profiling and Quantification of the Lysine Acetylome in Hepatocellular Carcinoma with a Trapped Ion Mobility Mass Spectrometer

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death worldwide with limited therapeutic options. Comprehensive investigation of protein posttranslational modifications in HCC is still limited. Lysine acetylation is one of the most common types of posttranslational modification involved in many cellular processes and plays crucial roles in the regulation of cancer. In this study, we analyzed the proteome and K-acetylome in eight pairs of HCC tumors and normal adjacent tissues using a timsTOF Pro instrument. As a result, we identified 9219 K-acetylation sites in 2625 proteins, of which 1003 sites exhibited differential acetylation levels between tumors and normal adjacent tissues. Interestingly, many novel tumor-specific K-acetylation sites were characterized, for example, filamin A (K865), filamin B (K697), and cofilin (K19), suggesting altered activities of these cytoskeleton-modulating molecules, which may contribute to tumor metastasis. In addition, we observed an overall suppression of protein K-acetylation in HCC tumors, especially for enzymes from various metabolic pathways, for example, glycolysis, tricarboxylic acid cycle, and fatty acid metabolism. Moreover, the expression of deacetylase sirtuin 2 (SIRT2) was upregulated in HCC tumors, and its role of deacetylation in HCC cells was further explored by examining the impact of SIRT2 overexpression on the proteome and K-acetylome in Huh7 HCC cells. SIRT2 overexpression reduced K-acetylation of proteins involved in a wide range of cellular processes, including energy metabolism. Furthermore, cellular assays showed that overexpression of SIRT2 in HCC cells inhibited both glycolysis and oxidative phosphorylation. Taken together, our findings provide valuable information to better understand the roles of K-acetylation in HCC and to treat this disease by correcting the aberrant acetylation patterns.     

普通小麦栽培品种丰抗13的4B—1D染色体易位的鉴定

通过细胞学观察,在普通小麦栽培品种“丰抗13”和“京红1号”的杂交后代中,发现有多价体出现,这就表明有染色体易位发生。为进一步弄清究竟是哪条染色体发生了易位,我们采用单体测交方法,观察鉴定所有各单体系F_1的花粉母细胞第一次减数分裂中期Ⅰ(以下简称PMCs中Ⅰ)染色体构型。从鉴定结果发现,凡2n=42的F_1 PMCs中Ⅰ出现19~Ⅱ 1~Ⅳ,而2n=41的F_1PMCs中Ⅰ的染色体构型不同,单体与易位有关的两个单体系4B和1D F_1 PMCs中的Ⅰ构型中有部分呈现为19个二价体加1个三价体,即19~Ⅱ 1~Ⅲ,没有单价体,而其余各单体系F_1 PMCs中Ⅰ构型则表现为18个二价体,1个四价体和1个单价体,即18~Ⅱ 1~Ⅰ 1~Ⅳ。因此,可以肯定“丰抗13”存在1个染色体易位,其有关染色体就是4B和1D。     

Proteolytic processing of Blattella germanica vitellin during early embryo development

In the eggs of the cockroach Blattella germanica, vitellin (Vt) utilization is initiated 4 days postovulation by the proteolytic processing of its three subunits. These reactions yield a specific set of peptides that are consumed by the developing embryo. A yolk proteinase activity, believed central to this processing event, has been investigated. First expressed at day 3 postovulation, just prior to Vt's processing, its specific activity with synthetic substrates increased four-fold to 18-fold through day 6. In addition, a mixing experiment showed that these proteinases(s) can also process Vt's large subunits in vitro. A relationship between Vt processing and proteinase specific activity was also noted with two B. germanica translocation heterozygotes, which displayed differences in the extent of Vt processing. One group of eggs (group A) failed to process any Vt subunit. A second group (B) processed the M_r 102,000 subunit but not the M_r 95,000. A third group (C) processed their Vt normally. Proteinase specific activities in the yolk of translocant's eggs at day 6 mirrored the extent of processing, being highest in group C eggs and effectively absent from the yolk of group A eggs. Eggs defective in Vt processing also contained arrested embryos. It is concluded that the yolk proteinase activity described here participates in Vt processing at day 4 postovulation. Microscopic examination of yolk obtained from eggs of wild type females showed that, as processing began in vivo (day 4), the yolk granules also underwent an abrupt decrease in size from diameters of 15–30 μm to 3–10 μm. Yolk granules of those translocant's eggs that were defective in Vt processing did not undergo this size decrease, suggesting that granule reorganization and Vt proteolysis may be linked functionally.     

Comparative study of different variants of Actinomyces roseoflavus producing the polyene antibiotic roseofungin

The respiration chain in the membranes of whole Actinomyces roseoflavus (var. roseofungini) cells from the parent and secondary cultures is sensitive to KCN, non-sensitive to Triton X-100 treatment removing the antibiotic roseofungin from the cells, and has a very high for the bacteria respiration control. When the cells are in contact with atomic tritium at the temperature of liquid nitrogen, roseofungin is tritiated and binds to A. roseoflavus isolated membranes and whole cells, mostly to those of the parent culture as compared to the secondary culture. A fraction of membranes which lost NADH dehydrogenase in the course++ of purification was isolated from the cells disintegrated in the frozen state.     

Comparative effectiveness of various antibiotics in the treatment of patients with meningococcal meningitis]

The results of treating 322 patients with various forms of meningococcal infection accepted to a hospital within a year are presented. The patients were divided into 3 groups by the character of etiotropic therapy. The patients of group I were treated with benzylpenicillin and those of group 2 were treated with levomycetin sodium succinate. Group 3 included the patients, the therapy of whom with the above two antibiotics failed and they were subjected to treatment with cefazolin, cefotaxime, amikacin and other broad spectrum antibiotics. Benzylpenicillin generally proved to be the drug of choice in the antibacterial therapy of meningococcal infection. In comparison to levomycetin (chloramphenicol) it provide more rapid clinical recovery of the patients and normalization of the indices of the cerebrospinal fluid. Only failure of benzylpenicillin therapy was considered as an indication to the broad-spectrum antibiotics to be in the complex treatment of the patients. As additional methods for estimating the efficacy of antibacterial therapy it was recommended to employ calculation of the integral indices of hemograms (the leukocyte index of intoxication and the hematologic index of intoxication).     

A threshold result for an epidemiological model

A threshold parameter R ₀ is identified for an SIRS epidemiological model which has nonlinear incidence and a distributed delay for transfer out of the removed class. For R ₀ < 1, the disease free equilibrium is proved to be the global attractor for all solutions.Research supplied in part by NSERC A-8965     

cGMP-binding centers in photoreceptor membranes

The binding of cGMP by structural components of bovine rod outer segments was studied. The discs and plasma membranes were shown to contain two types of the specific binding sites for cGMP which are distinct from cyclic GMP phosphodiesterase. The sites have a "high" and "low" (Kd = 0.1 divided by 0.35 and 1.5 divided by 2.0 X 10(-6) M respectively) affinity for cGMP. They belong to membraneous integral proteins presumably associated with phospholipids. Their affinity for cGMP is controlled by GTP and calmodulin.