Halophytes – A resource for the future

Wetlands Ecology and Management -     

Subcellular Localization of Enzymes of Carbon and Nitrogen Metabolism in Nodules of Medicago sativa

Alfalfa (Medicago sativa L. cv. Vernal) nodules were separatedinto host plant fractions and fractions of rhizobial originby differential centrifugation and sedimentation equilibriumcentrifugation. Both NAD- and NADP-linked isocitrate dehydrogenase(70%, 90%) and glutamate dehydrogenase activities (90%, 83%)were located primarily (percent total nodule activity) in thefractions of plant origin and their specific activities werehighest in the fractions of plant origin. More than 50% of thenodules' total activity of both glutamine synthetase and NAD-glutamatesynthase and greater than 90% of the total glutamate oxaloacetatetransaminase activity was located in plant fractions. However,the fractions of rhizobial origin had the highest specific activitiesof glutamine synthetase and glutamate synthase. (Received September 5, 1981; Accepted December 7, 1981)     

Reducing HIV Risk among Transgender Women in Thailand: A Quasi-Experimental Evaluation of the Sisters Program

Transgender women are particularly at risk of HIV infection, but little evidence exists on effective HIV prevention strategies with this population. We evaluated whether Sisters, a peer-led program for transgender women, could reduce HIV risks in Pattaya, Thailand. The study used time-location sampling to recruit 308 transgender women in Pattaya into a behavioral survey in 2011. Coarsened exact matching was used to create statistically equivalent groups of program participants and non-participants, based on factors influencing likelihood of program participation. Using multivariable logistic regression, we estimated effects of any program participation and participation by delivery channel on: condom use at last sex; consistent condom and condom/water-based lubricant use in the past 3 months with commercial, casual, and regular partners; and receipt of HIV testing in the past 6 months. Program coverage reached 75% of the population. In a matched sub-sample (n = 238), participation in outreach was associated with consistent condom/water-based lubricant use with commercial partners (AOR 3.22, 95% CI 1.64–6.31). Attendance at the Sisters drop-in center was associated with receiving an HIV test (AOR 2.58, 95% CI 1.47–4.52). Dedicated transgender-friendly programs are effective at reducing HIV risks and require expansion to better serve this key population and improve HIV prevention strategies.     

下丘脑外侧区注射TRH对大鼠胃酸分泌的影响

本文采用连续收集胃腔灌流法,观察下丘脑外侧区(LHA)注射促甲状腺激素释放激素(TRH)对大鼠胃酸分泌的影响,并分析TRH在LHA促进胃酸分泌的作用机制。结果表明:(1)LHA注射TRH(1μg)明显地刺激胃酸分泌;(2)预先向LHA注射酚妥拉明(10μg)、美多心安(5μg)及胃泌素抗体1μl(1:640)并不影响TRH的泌酸作用,如预先向LHA注射阿托品(5μg)则可消除TRH的泌酸效应;(3)垂体摘除及肾上腺切除均不影响TRH的泌酸作用;(4)隔下迷走神经切断后,LHA注入TRH的泌酸效应仍然出现,但持续时间显著缩短;腹腔交感神经节摘除后,TRH仍能促进胃酸分泌,但分泌量少而平稳。以上结果提示:LHA是TRH中枢泌酸效应的有关结构之一,其中枢机制是通过胆碱能M受体中介的,腹腔交感神经节和膈下迷走神经是TRH泌酸效应的传出途径。前者引起的泌酸反应出现较早且引起泌酸高峰,但持续时间短;后者则引起低平的持续分泌。     

Effects of Acifluorfen on Endogenous Antioxidants and Protective Enzymes in Cucumber (Cucumis sativus L.) Cotyledons

The herbicide acifluorfen (2-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoate) causes strong photooxidative destruction of pigments and lipids in sensitive plant species. Antioxidants and oxygen radical scavengers slow the bleaching action of the herbicide. The effect of acifluorfen on glutathione and ascorbate levels in cucumber (Cucumis sativus L.) cotyledon discs was investigated to assess the relationship between herbicide activity and endogenous antioxidants. Acifluorfen decreased the levels of glutathione and ascorbate over 50% in discs exposed to less than 1.5 hours of white light (450 microeinsteins per square meter per second). Coincident increases in dehydroascorbate and glutathione disulfide were not observed. Acifluorfen also caused the rapid depletion of ascorbate in far-red light grown plants which were photosynthetically incompetent.

Glutathione reductase, dehydroascorbate reductase, superoxide dismutase, ascorbate oxidase, ascorbate free radical reductase, peroxidase, and catalase activities rapidly decreased in acifluorfen-treated tissue exposed to white light. None of the enzymes were inhibited in vitro by the herbicide. Acifluorfen causes irreversible photooxidative destruction of plant tissue, in part, by depleting endogenous antioxidants and inhibiting the activities of protective enzymes.

     

中华白蛉的自育性研究

现场及实验室结果表明,我国黄土高原的大多数中华白蛉(Phlebotomus chinensis)应属自育性品系,它通常在羽化后、吸血前经交配能依靠腹节内脂肪体发育卵泡,一般在产卵后始行吸血。其生理性状是:胃内无血、腹节内有大量块状或条状脂肪体。羽化24小时后,附腺内有暗色颗粒,卵巢内有发育的卵泡。在25℃士1℃下它的生活史分快、慢两型。快型从卵至成虫仅需44—50夭,慢型需要以四龄幼虫滞育,其长短随滞育期而定,最长的滞育期达301天。观察了白蛉幼虫在饥饿状态下对自育性的影响。此外,还比较了吸血白蛉与自育性白蛉的妊卵数。吸血白蛉的妊卵数约较自育性的高出1/5。这种自育性品系的中华白蛉在自然居群约内占92%、主要栖于洞穴内为野栖种类。本文对自育性中华白蛉的生态及其防制策略作了分析和讨论。     

Phytochrome control of its own accumulation and leaf expansion in tentoxin- and norflurazon-treated mung bean seedlings

Primary leaves of 4-day-old, dark-grown mung bean [ Vigna radiata (L.) Wilczek cv. Berken] seedlings were exposed to 24 h of white light (200 μmol m⁻² s⁻¹) which was terminated by a 15 min, phytochrome-saturating red or far-red light exposure. Phytochrome content (in vivo and in vitro) and leaf area were monitored during the subsequent dark period. Red light treatments resulted in lower phytochrome content and greater leaf expansion than did far-red treatments. Phytochrome accumulation and leaf expansion were less in norflurazon- (no carotenoids and very low Chl) than in tentoxin- (very low Chl) treated leaves. After 3 days of darkness, leaf expansion was about 25% greater and phytochrome content was about 50% less in red- than in far-red-treated leaves of all treatments. These effects generally took longer to develop in norflurazon- than in tentoxin-treated tissues. Norflurazon-treated tissues exposed to long white light periods apparently do not as accurately reflect phytochrome-controlled photomorphogenic events of green tissues as do tentoxin-treated tissues of mung bean seedlings.     

Light control of extractable nitrate reductase activity in higher plants

Light regulation of extractable nitrate reductase (NR) activity of higher plants is complicated by: 1) involvement of several photoreceptors, 2) differences in the relative importance of the several photoreceptors among species and among developmental stages of the same species, 3) two types of effects – alteration of activity of existing NR and influences on de novo synthesis of NR, and 4) differing forms of NR within the same species. The interrelationships of all of these factors are not clear. It may be that each system will have to be understood separately before a general model can be developed. Immunochemical quantification of NR from systems exposed to varied light regimes may enhance our understanding of this area. Currently few general conclusions can be made; however, we think that the following statements are true or are usually true: (1) Phytochrome influences extractable NR activity by the low irradiance response and high irradiance response in etiolated tissues. (2) In de-etiolated tissues phytochrome can influence NR activity decay at the end of a light period by the low irradiance response. (3) The phytochrome equilibrium or the absolute level of P_fr influences extractable NR activity in green tissues under white light. (4) Blue light influences extractable NR activity through phytochrome and another, unknown, blue light-absorbing pigment. Flavins may be involved in vitro in reactivation of inactivated NR. (5) Photosynthesis does not directly influence the induction of the forms of NR that require substrate and light for induction. (6) In some tissues there appears to be a close link between nitrite-reducing and nitrate-reducing capabilities. (7) Much circumstantial evidence from kinetic and protein-synthesis-inhibitor studies and the only available immunochemical data indicate that light induces de novo synthesis of NR, resulting in increased extractable activity.     

Glucocorticoid activation of a calcium-dependent endonuclease in thymocyte nuclei leads to cell death

Dexamethasone and corticosterone kill mouse thymocytes, as measured by eosin uptake, after several hours of in vitro incubation. This killing requires RNA and protein synthesis, because it is inhibited by cycloheximide, emetine, or actinomycin D. An earlier event than cell death is the extensive fragmentation of nuclear DNA into oligonucleosomal subunits; this fragmentation also requires RNA and protein synthesis. The DNA cleavage results from the action of an endonuclease that preferentially cleaves DNA in the linker regions between nucleosomes. This endonuclease is found constitutively in the nuclei of thymocytes and some other cells, and requires calcium and magnesium ions for its activation; if isolated fresh thymocyte nuclei are incubated with these ions, as much as 77% of their DNA is cleaved within 90 min. Thus, the protein for which synthesis is necessary for glucocorticoid-induced thymocyte death is not the endonuclease itself, but is in some way involved in its activation; we suggest that it may be part of a system for transporting calcium into the nucleus. The endonuclease is inhibited by zinc, which also prevents thymocyte death. It appears that glucocorticoids cause thymocyte death by activating an enzyme that rapidly and extensively degrades DNA. This "death from within" is biochemically and morphologically different from toxic or accidental cell death, such as that induced by azide, heat, or antibody and complement treatment. Although mature T cells also contain the endogenous endonuclease, they lack the glucocorticoid-inducible mechanism for activating it, and are thus glucocorticoid-resistant.