胁迫处理对林生山黧豆蛋白质多肽及其含量的影响

应用二维电泳技术,分析了经水分胁迫（ＰＥＧ）、盐分胁迫（ＮａＣｌ）和热激（４０℃）处理后林生山黧豆（ＬａｔｈｙｒｕｓｓｙｌｖｅｓｔｒｉｓＬ．）体内蛋白质多肽及其含量的变化。有些蛋白质经ＰＥＧ、ＮａＣｌ和热激处理后可以产生相同的变化。两种不同的胁迫因子对某些蛋白质的影响有一定的共同性。特定的胁迫条件可以造成特定的影响。不同胁迫因子对同一蛋白质多肽可以造成不同的影响。胁迫下蛋白质的变化可能与林生山黧豆抵抗和适应胁迫条件的能力以及体内非蛋白质氨基酸的代谢有关     

Thermotolerance induced by heat shock in Chlorella

Thermotolerance in cultures of Chlorella zofingiensis was induced by heat shock treatment at supraoptimal temperatures (40and 45 °C for 30 min). Thermotolerance was assayed by two methods: the survival of the cells at 70 °C and the growth of diluted cultures at 35 and 45 °C. A culture without heat shock treatment was unable to grow at 45 °C. According to eletrophoretic analyses, the synthesis of proteins of 95, 73, 60, 43 and 27 kDa was induced by heat shock treatment. The large molecular weight proteins (95, 73, 60 and43 kDa) were present in non-heat treated cells, but the heat shock treatment increased their quantity in cells. The synthesis of a low molecular weight protein (27 kDa) was induced by heat shock treatment. The induced thermotolerance could be inhibited by the presence of an 80S ribosomal translation inhibitor, cycloheximide(CHI). The first 12 amino acid residues from the N-terminus of the27 kDa heat shock induced protein are Val-Glu-Trp-Try-Gly-Pro-Asn-Arg-Ala-Lys-Phe-Leu. This revised version was published online in August 2006 with corrections to the Cover Date.     

HhaI and HpaII DNA methyltransferases bind DNA mismatches, methylate uracil and block DNA repair.

The hydrolytic deamination of 5-methylcytosine (5-mC) to thymine (T) is believed to be responsible for the high mutability of the CpG dinucleotide in DNA. We have shown a possible alternate mechanism for mutagenesis at CpG in which HpaII DNA-(cytosine-5) methyltransferase (M.HpaII) can enzymatically deaminate cytosine (C) to uracil (U) in DNA [Shen, J.-C., Rideout, W.M., III and Jones, P.A., Cell, 71, 1073-1080, (1992)]. Both the hydrolytic deamination of 5-mC and enzymatic deamination of C create premutagenic DNA mismatches (G:U and G:T) with the guanine (G) originally paired to the normal C. Surprisingly, we found that DNA-(cytosine-5) methyltransferases have higher affinities for these DNA mismatches than for their normal G:C targets and are capable of transferring a methyl group to the 5-position of U, creating T at low efficiencies. This binding by methyltransferase to mismatches at the recognition site prevented repair of G:U mismatches by uracil DNA glycosylase in vitro.     

The effect of nitroimidazoles on glucose utilization and lactate accumulation in mouse brain

The radiation sensitizers misonidazole (MISO) and desmethylmisonidazole (DMM) can produce central and peripheral neuropathy in patients and laboratory animals. Behavioral and pathological investigations have indicated that in the central nervous system this primarily involves the cochlear and vestibular systems. Nitroimidazoles can also interfere with glycolysis in vitro under aerobic and anaerobic conditions. In the present work we have studied the effect of MISO or DMM on lactate production and glucose utilization in mouse brain. It is observed that these compounds result in a 25% inhibition of lactate production in brain slices relative to the control at a 10 mM level. Additionally, MISO (1.0 mg/g/day) or DMM (1.4 mg/g/day) were administered daily (oral) for 1, 4, 7, or 14 days to examine the effect of these two drugs on the regional glucose utilization in C3Hf mouse brain. Five microcuries of 2-deoxy[14C]glucose was given following the last drug dose and autoradiographs of serial brain sections were made and analyzed by a densitometer. Following a single dose of either MISO or DMM, no significant differences in glucose uptake were observed when compared with controls. However, following 4, 7, and 14 doses the rate of glucose utilization was significantly reduced in the intoxicated animals. Larger reductions were measured in specific regions including the posterior colliculus, cochlear nuclei, vestibular nuclei, and pons with increasing effects observed at later stages. These results share a degree of correspondence with the regional brain pathology produced by these nitroimidazoles.     

Histogenesis of the pituitary in rainbow trout (Salmo gairdneri) in different ambient salinities with particular reference to the rostral pars distalis

Summary The pituitary gland is first evident in rainbow trout two weeks before hatching. Differentiation of prolactin and ACTH cells is not marked until 3–4 days after hatching when the follicular arrangement of the prolactin cells become apparent. There is no difference in the time of development of either prolactin or ACTH cells in larvae reared in different ambient salinities despite marked changes in tissue ion and water content. This suggests that prolactin and ACTH do not play the osmo- and iono-regulatory roles in larval rainbow trout that they are considered to play in adult salmonids.The work was supported by a grant-in-aid of research from the National Research Council of Canada     

Select growth of human T lymphocytes in single phase semisolid culture.

Selective growth and clonal proliferation of human T lymphocytes can be achieved by using a single-phase semi-solid methylcellulose system without the requirement of preincubation with lectins. Significant proliferation, however, depends upon the continued presence of Con A or PHA, but not pokeweed mitogen or lipopolysaccharide within the methylcellulose. This procedure eliminates nonspecific agglutination by lectins and allows for direct visualization of colonies and their specific removal and subsequent cloning in liquid phase. Optimal growth and production of colonies greater than 40-cell size require 3 to 9 days. Individual cells can be identified on the basis of E rosette formation and absence of surface immunoglobulin or ability to phagocytize latex particles. Moreover, proliferation is inhibited by antithymocyte but not anti-B cell sera and can be demonstrated with peripheral blood T and MOLT-4 cells, but not with B or Raji cells. Finally, colony formation is not enhanced by the presence of 2-mercaptoethanol. The clonal proliferation of human T lymphocytes has wide application in the study of both antigen recognition and lymphocyte alterations in specific diseases.     

Resolution of optical isomers by high-pressure liquid chromatography: The separation of benzo[a]pyrene trans-diol derivatives

The optical isomers of (±)r-7,t-8-dihydroxy-7,8-dihydrobenzo[a]pyrene and its synthetic precursor (±)r-7,t-8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene were resolved as their di-(−)menthoxyacetates using high-pressure liquid chromatography. Saponification of the resolved diesters yielded the corresponding enantiomers. The specific rotation, CD spectra, and ORD curves are reported. The resolution of these optical isomers permits detailed studies on the enzymatic intermediates and the mechanism of benzo[a]pyrene activation to its carcinogenic form. The method is of general usefulness for the resolution of optical isomers.     

Myocardial calcium cycling defect in furazolidone cardiomyopathy.

We have previously demonstrated that in furazolidone-induced congestive heart failure in turkeys the specific Ca(2+)-ATPase activity of myocardial sarcoplasmic reticulum (SR) is 60% increased in compensation for a 50% depression in net Ca(2+)-sequestration activity. This study tested the hypothesis that SR Ca(2+)-uptake and Ca(2+)-ATPase activities were uncoupled in this cardiomyopathy because of increased Ca(2+)-release channel activity. A novel microassay was used to monitor Ca2+ transport by myocardial homogenates using the fluorescent Ca2+ dye indo 1 to indicate extravesicular ionized Ca2+. The method is applied to cyropreserved biopsy specimens of myocardium and requires only 50 mg tissue. Both SR Ca(2+)-pump and SR Ca(2+)-channel activity were estimated using the channel-inhibitor ruthenium red (RR) and the mitochondrial inhibitor sodium azide. The specificity of the RR inhibition was confirmed using ryanodine. Cardiomyopathy was induced in 2-week-old turkey poults by the addition of 0.07% furazolidone to their feed for 4 weeks. Compared with controls, myocardial maximal Ca(2+)-channel activity relative to maximal Ca(2+)-pump activity was 22% greater and duration of Ca(2+)-channel activity was 100% increased. However, the heart failure birds had 43 and 53% decreases in absolute maximal Ca(2+)-pumping and Ca(2+)-channel activities, respectively. The abnormal Ca(2+)-channel activity resulted in 200% greater time before initiation of net Ca2+ sequestration and 700% greater final myocardial Ca2+ concentrations. For all birds, the Ca(2+)-accumulating activity was highly correlated with Ca(2+)-release activity (all p less than 0.05). These data indicate that in this animal model of congestive heart failure there is defective SR Ca(2+)-channel function resulting in abnormal Ca2+ homeostasis.(ABSTRACT TRUNCATED AT 250 WORDS)