用光谱技术鉴定植物色素突变体

1983年我国报道了从γ-射线处理的“矮杆齐”大麦中得到了一株黄绿色的突变体1832C[1]。本文用光谱技术对该突变体的光合色素成分进行了鉴定。1　材料和方法　　材料为六棱裸大麦“矮杆齐”和由该品种大麦诱变形成的黄绿色突变体1832C(Mb1832C),以及作为对照的缺失Chlb的突变体大麦Chlorina-f2[2]都于3月初播种于实验田中。　　每个样品取30g新鲜的叶片,先用自来水后用蒸馏水冲洗干净。把洗净的叶片摊放在干净的纱布上吸干表面水分,剪碎,加入100mL预冷的含有0.4mol/L山梨醇、0.1mol/LTris-HCl(pH7.6)的缓冲液,用组织捣碎机先慢速捣碎1…     

Suppression of oxidative damage by Saccharomyces cerevisiae ATX2, which encodes a manganese-trafficking protein that localizes to Golgi-like vesicles.

Oxygen toxicity in Saccharomyces cerevisiae lacking the copper/zinc superoxide dismutase (SOD1) can be suppressed by overexpression of the S. cerevisiae ATX2 gene. Multiple copies of ATX2 were found to reverse the aerobic auxotrophies of sod1(delta) mutants for lysine and methionine and also to enhance the resistance of these yeast strains to paraquat and atmospheric levels of oxygen. ATX2 encodes a novel 34.4-kDa polypeptide with a number of potential membrane-spanning domains. Our studies indicate that Atx2p localizes to the membrane of a vesicular compartment in yeast cells reminiscent of the Golgi apparatus. With indirect immunofluorescence microscopy, Atx2p exhibited a punctate pattern of staining typical of the Golgi apparatus, and upon subcellular fractionation, Atx2p colocalized with a biochemical marker for the yeast Golgi apparatus. We demonstrate here that this vesicle protein normally functions in the homeostasis of manganese ions and that this role in metal metabolism is necessary for the ATX1 suppression of SOD1 deficiency. First, overexpression of ATX2 caused cells to accumulate increased levels of manganese. Second, a deletion in ATX2 caused a decrease in the apparent available level of intracellular manganese and caused sod1(delta) mutants to become dependent upon exogenous manganese for aerobic growth. Third, ATX2 was incapable of suppressing oxidative damage in cells depleted of manganese ions or lacking the plasma membrane transporter for manganese. The effect of ATX2 overexpression on manganese accumulation and oxygen resistance is similar to what we have previously reported for mutations in PMR1, which encodes a manganese-trafficking protein that also resides in a vesicular compartment. Our studies are consistent with a model in which Atx2p and Pmr1p work in opposite directions to control manganese homeostasis.     

Determination of zinc fractions in human blood and seminal plasma by ultrafiltration and atomic absorption spectrophotometry

A simple and reliable method is described which combines ultrafiltration technique with atomic absorption spectrophotometry to determine the Zn fractions in human blood plasma and seminal plasma. Ultrafiltrable, loosely bound, and firmly bound Zn can be measured using this method in the presence or absence of ethylene-diaminetetraacetic acid (EDTA). The YMT membranes for the ultrafiltration must be rinsed thoroughly before use. In contrast to Zn in blood plasma, a large part of Zn in the seminal plasma was found to be ultrafiltrabe. This method can be applied to study the physiologically active part of Zn in body fluids related to various disease states.     

Toxicity to alveolar macrophages in rats following parenteral injection of mercuric chloride

Alveolar macrophages collected by pulmonary lavage from male Fisher-344 rats at intervals (24–72 h) after HgCl₂ injection (1–5 mg/kg, sc) were analyzed by several techniques. Within 24–72 h, the macrophages showed morphological signs of activation (hypertrophy and ruffled plasma membrane). Lipid peroxidation (increased malondialdehyde concentration) was not detected until 48 h. Dose- and time-related effects of HgCl₂ on malondialdehyde concentration and time-related effects of HgCl₂ on malondialdehyde concentration and mercury content of alveolar macrophages were observed 24–72 h postinjection. Diminished cell viability occurred only at 72 h after the highest dosage of HgCl₂. This study demonstrates that the alveolar macrophage was a cellular target for mercury toxicity following parenteral exposure to HgCl₂.     

RFLP mapping of QTLs for yield and related characters in rice (Oryza sativa L.)

Quantitative triat loci (QTLs) for yield and related traits in rice were mapped based on RFLP maps from two indica/indica F₂ populations, Tesanai 2/CB and Waiyin 2/CB. In Tesanai 2/CB, 14 intervals carrying QTLs for eight traits were detected, including 3 for grain weight per plant (GWT), 2 for number of panicles per plant (NP), 2 for number of grains per panicle (NG), 1 for total number of spikelets per panicle (TNS), 1 for spikelet fertility (SF), 3 for 1000-grain weight (TGWT), 1 for spikelet density (SD), and 1 for number of first branches per main panicle. The 3 QTLs for GWT were located on chromosomes 1, 2, and 4, with 1 in each chromosome. The additive effect of the single locus ranged from 2.0 g to 9.1 g. A major gene (np4) for NP was detected on chromosome 4 within the interval of RG143–RG214, about 4cM for RG143, and this locus explained 26.1% of the observed phenotypic variance for NP. The paternal allele of this locus was responsible for reduced panicles per plant (3 panicles per plant). In another population, Waiyin 2/CB, 12 intervals containing QTLs for six of the above-mentioned traits were detected, including 3 for GWT, 2 for each of NP, TNS, TGWT and SD, 1 for SF. Three QTLs for GWT were located on chromosome 1, 4, and 5, respectively. The additive effect of the single locus for GWT ranged from 6.7 g to 8.8 g, while the dominance effect was 1.7–11.5 g. QTL mapping in two populations with a common male parent is compared and discussed.     

Analysis of wild-type and mutant p21WAF-1 gene activities.

The p21WAF-1 gene is positively regulated by the wild-type p53 protein. p21WAF-1 has been shown to interact with several cyclin-dependent kinase complexes and block the activity of G1 cyclin-dependent kinases (cdks). Mutational analysis with the p21WAF-1 gene localized a site, at amino acid residues 21 and 24 in the amino terminus of the protein, for p21WAF-1 binding to cyclins D and E. This region of the protein is conserved (residues 21 to 26) in other p21WAF-1 family members, p27kip-1 and p57kip-2. The same p21WAF-121,24 mutant also fails to bind to cyclin D1-cdk 4 or cyclin E-cdk 2 complexes in vitro, suggesting that amino acid residues 21 and 24 are important for p21WAF-1-cdk-cyclin trimeric complex interactions. The p21WAF-1 wild-type protein will suppress tumor cell growth in culture while p21WAF-1 mutant proteins with defects in residues 21 and 24 fail to suppress tumor cell growth. The overexpression of cyclin D or E in these cells will partially overcome the growth suppression of wild-type p21WAF-1 protein in cells. These results provide evidence that p21WAF-1 acts through cyclin D1-cdk4 and cyclin E-cdk2 complexes in vivo to induce the growth suppression. The p21WAF-1 binding sites for cyclins (residues 21 to 26), cdk2 (residues 49 to 71), and proliferating-cell nuclear antigen (residues 124 to 164) have all been mapped to discrete sites on the protein.     

流行性出血热患者皮肤组织内病毒抗原及免疫复合物检测与意义

应用常规病理、免疫病理及超微病理技术,对３３例流行性出血热（ＥＨＦ）患者皮肤活检标本的病理变化及病毒抗原、免疫复合物进行观察,同时与血清病毒抗原、抗体及循环免疫复合物检出情况进行比较。在２３例ＥＨＦ患者皮肤微血管内皮细胞中检出病毒抗原,部分组织中可同时检出免疫球蛋白及Ｃ３,少数组织仅能检出病毒抗原或免疫球蛋白。配对血清小也可检出ＥＨＦ病毒抗原、抗体及循环免疫复合物。组织及血清免疫复合物形成与血清补体Ｃ３水平下降有关,组织内肥大细胞脱颗粒与血清ＩｇＥ水平升高相关,提示多种变态反应参与了流行性出血热的发病机制。     

GTPase-dependent signaling in bacteria: characterization of a membrane-binding site for era in Escherichia coli.

Era is an Escherichia coli GTPase that is essential for cell viability and is peripherally associated with the cytoplasmic membrane. Both immunoelectron microscopy and subcellular-fractionation experiments have shown that Era is present in cytoplasmic as well as membrane-associated pools. These data led to speculation that the mechanism of action of Era may require cycling between membrane and cytoplasmic sites. In order to investigate this possibility, an in vitro binding assay was developed to characterize the binding of Era to membrane fractions. Competition and saturation binding experiments suggest that a site that is specific for Era and capable of binding up to 5 ng of Era per microgram of membrane protein is present in membrane preparations. The binding curve is complex, indicating that multiple equilibria describe the interaction. The binding of Era to this putative receptor is dependent on guanine nucleotides; binding cannot be measured in the absence of nucleotide, and neither ATP nor UTP can substitute. Subfractionation of cell walls showed that the guanine nucleotide-dependent binding site was present in fractions enriched in cytoplasmic membrane. These data provide evidence that Era may be involved in a GTPase-receptor-coupled membrane-signaling pathway that is essential for growth in E. coli.     

Physiological Elevations of Glucocorticoids Potentiate Glutamate Accumulation in the Hippocampus

Abstract: Glucocorticoids (GCs) are secreted during stress and can damage the hippocampus over the course of aging and impair the capacity of hippocampal neurons to survive excitotoxic insults. Using microdialysis, we have previously observed that GCs augment the extracellular accumulation of glutamate and aspartate in the hippocampus following kainic acid-induced seizures. In that study, adrenalectomized rats maintained on minimal GC concentrations were compared with those exposed to GCs elevated to near-pharmacological levels. We wished to gain insight into the physiological relevance of these observations. Thus, we have examined the effects of GCs over the normal physiological range on glutamate and aspartate profiles; this was done by implanting adrenalectomized rats with GC-secreting pellets, which produce stable and controllable circulating GC concentrations. We observe that incremental increases in GC concentrations cause incremental increases in glutamate accumulation before the kainic acid insult, as well as in the magnitude of the glutamate response to kainic acid. Elevating GC concentrations from the circadian trough to peak doubled cumulative glutamate accumulation, whereas a rise into the stress range caused a fourfold increase in accumulation. Similar, although smaller, effects also occurred with aspartate accumulation (as well as with taurine but not glutamine accumulation). These data show that the highly elevated GC concentrations that accompany neurological insults such as seizure or hypoxia-ischemia will greatly exacerbate the glutamate accumulation at that time. Furthermore, stress levels of GCs augmented glutamate accumulation even in the absence of an excitotoxic insult, perhaps explaining how sustained stress itself damages the hippocampus. Finally, even the moderately ?levated basal GC concentrations that typically occur in aged rats augmented glutamate accumulation, perhaps explaining how GCs damage the hippocampus over the course of normal aging.