Complementation analysis of the inorganic carbon concentrating mechanism of Chlamydomonas reinhardtii

Summary Six independently isolated mutants of Chlamydomonas reinhardtii that require elevated CO₂ for photoautotrophic growth were tested by complementation analysis. These mutants are likely to be defective in some aspect of the algal concentrating mechanism for inorganic carbon as they exhibit CO₂ fixation and inorganic carbon accumulation properties different from the wild-type. Four of the six mutants defined a single complementation group and appear to be defective in an intracellular carbonic anhydrase. The other two mutations represent two additional complementation groups.Abbreviations HS high salt medium which has 13 mM phosphate at pH 6.8 - HSA high salt plus 36 mM acetate medium - YA high salt medium with 4 g yeast extract per L and 36mM acetate - Arg arginine - cia^- CO₂ accumulation mutants that cannot grow on low CO₂ - C_i inorganic carbon (CO₂+HCO _- ³ ) - CA carbonic anhydrase - mt mating type Supported in part by the McKnight Foundation and by NSF grant PCM 8005917 and published as journal article 11924 from the Michigan State Agriculatural Experiment Station     

夏季高温对水牛瘤胃代谢的影响

利用南京地区夏季炎热的自然条件,连续两年在高温季节(7—8月)进行实验。第一年(系列Ⅰ)的实验动物为四头装置瘤胃瘘管的空怀母水牛,研究高温初期(27.5～33.4℃)和持续高温期(28.0～35℃)对水牛瘤胃消化代谢的影响。第二年实验(系列Ⅱ)利用三头装置瘤胃瘘管的海仔母水牛重复高温(26～35.3℃)实验。 夏季高温期间,实验水牛的呼吸率、瘤胃温度和直肠温度升高,采食量减少,饮水量增加,瘤胃液流速减缓。高温初期出现瘤胃代谢升高[总挥发性脂肪酸(TVFA)和氨氮(NH_3-N)浓度及乙酸/丙酸(A/P)比率升高]。但在持续高温情况下,水牛的采食和瘤胃代谢均明显抑制。采取瘤胃内降温措施(投入冰袋)或冷水淋浴,均能迅速降低呼吸率、直肠和瘤胃温度,恢复采食和反刍,并缓解瘤胃代谢的抑制。提示动物机体参与调节瘤胃代谢的变化,并为改善水牛夏季的饲养管理提供生理学依据。     

低温对大鼠骨骼肌能量代谢的影响——Ⅰ.高能磷酸化合物含量的变化

本实验选择对低温比较敏感的骨骼肌组织作为实验对象。将19只大鼠随机分成3组,其右后肢经冷冻处理使组织温度分别达 5℃、0℃及-5℃,于复温后不同时间测定骨骼肌中四种高能磷酸化合物AMP,ADP、ATP及CP的含量。结果表明,大鼠骨骼肌组织中高能磷酸化合物含量随冷冻时组织最低温度的下降而不同程度的减少,并且具有明显的时相过程。复温后即刻至4小时下降迅速,4～12小时三组值较为接近,其后随时间延长而明显分离。 5℃组恢复得早而且明显,0℃组恢复程度次于 5℃组,-5℃组含量下降最明显而且几乎不恢复。提示:低温使骨骼肌组织能量的产生和贮存过程受到影响。     

亲和层析法分离腺苷结合蛋白质

本文报告一种新的腺苷亲和层析凝胶的合成方法。利用这种凝胶可从大鼠心脏、肝脏及小牛主动脉平滑肌的水溶部份分离出几种腺苷结合蛋白质,其亚基分子量(据SDS-PAGE)分别为35,000、37,000、46,000、43,000及15,300Dal。现已证明,35,000Dal蛋白质是乳酸脱氢酶及苹果酸脱氢酶,43,000Dal蛋白质是腺苷激酶,46,000Dal蛋白质可能是S-腺苷同型半胱氨酸水解酶。15,000Dal蛋白质前人未有报道。它对腺苷具有高度特导性和亲和力,推测是腺苷的细胞内受体和/或载体。测定了这种低分子量腺苷结合蛋白质的氨基酸组成及某些物理常数:pI=6.5;沉降系数2.42S,微分比容0.727cm~3/g,与腺苷复合物的解离常数K_D=2.3μM。     

Superior resolution of gamma-crystallins from microdissected eye lens by cation-exchange high-performance liquid chromatography

A novel procedure is presented for the rapid quantitative analysis of eye lens gamma-crystallins and beta s-crystallin by ion-exchange high-performance liquid chromatography on Synchropak CM300. At least six different gamma-crystallin gene products can be resolved from the soluble fraction of calf lens extract. This method is applicable to the analysis of microsections from individual lenses, and can be used to rapidly characterize spatial variations in gamma-crystallin composition which occur with aging and cataractogenesis.     

Maximal exercise capacity in adolescent European and Amerindian high-altitude natives

Forty-seven highland natives were given maximal exercise tests on a treadmill ergometer at 3,600 m. The subjects were grouped into four subsamples on the basis of ethnicity (European vs. Aymara) and age (young vs. old adolescent). Two-way ANOVA indicated that VO2max adjusted for body size did not differ significantly between ethnic groups but was significantly larger in older than younger boys within each ethnic group (p less than .05). This finding does not support the hypothesis that Amerindian highland natives have adapted genetically to hypoxia but is consistent with the hypothesis that the relatively high VO2max's of highlanders are acquired by developmental adaptation. Several measures of ventilation and oxygen transport capacity differed significantly between ethnic groups, suggesting that growing European and Aymara boys may respond somewhat differently to the stress of high-altitude hypoxia. However, despite these differences, VO2max, an integrated measure of the overall functional capacity of the oxygen transport system, did not differ significantly between ethnic groups, suggesting that both groups are equally capable of meeting the body's oxygen requirements during maximal exercise at high altitude.     

Purification of human plasma retinol-binding protein by hydrophobic interaction chromatography

Human plasma retinol-binding protein has been purified to homogeneity by a simple method that requires an ammonium sulfate fractionation, a hydrophobic interaction chromatography on phenyl-Sepharose, which dissociates the complex between retinol-binding protein and its carrier, transthyretin, and a gel filtration on Sephadex G-50. The yield of pure protein is comparable or higher than that obtained with the more complex procedures previously reported.     

A mechanism for rich-medium inhibition of the repair of daughter-strand gaps in the deoxyribonucleic acid of UV-irradiated Escherichia coli K12 uvrA

Ultraviolet-irradiated Escherichia coli K12 uvrA(B,C) cells show higher survival if plated on minimal growth medium (MM) rather than on rich growth medium (RM). This phenomenon has been referred to as 'minimal medium recovery' (MMR). UV-irradiated (4 J/m2) uvrA cells showed a similar rate of protein synthesis, whether incubated in MM or RM, however, they showed a severe depression in DNA synthesis when incubated in MM that lasted for about 30 min, and the normal rate of DNA synthesis was not reestablished until about 60 min after irradiation. When a sample of these same cells was switched to RM immediately after UV-irradiation, there was only a slight slowing of DNA synthesis, and the normal rate of synthesis was reestablished by 60 min. An additional mmrA mutation or growth retardation by valine blocked both this extra DNA synthesis in RM, and the inhibitory effect of RM on survival. These findings suggest that the absence of a marked delay in DNA synthesis observed in RM may be responsible for the inhibitory effect of RM on the survival of UV-irradiated excision-deficient cells. Two hypotheses, which are not mutually exclusive, are proposed and supported by data to explain why a fast rate of DNA synthesis after UV-irradiation partially inhibits postreplication repair and enhances cell lethality.     

Changes in synthetic activity of cell walls during the cell cycle in a synchronous culture of Catharanthus roseus

The incorporation rates of [¹⁴C] glucose into various fractions of the cell walls and into the sugar constituent of each fraction were investigated in a synchronous culture of Catharanthus roseus (L.) G. Don in order to elucidate the synthetic aspects of the cell walls during the cell cycle. Changes in the incorporation of radioactivity were closely correlated with changes in the amount of each cell wall fraction as well as with those in sugar composition as reported previously (S. Amino et al. Physiol. Plant. 60: 326–332, 1984). The specific activity of galactose was higher than that of other sugars throughout the cell cycle, and a temporary increase in the incorporation of radioactivity into all cell wall fractions except cellulose was observed just before the increase in cell numbers. The synthetic activities may play key roles in the regulation of cell wall polysaccharide dynamics during the cell cycle.     

Uptake of free amino acids by the diatom,Melosira mediocris

Individual ¹⁴C-labelled amino acids are rapidly removed from dilute solution in artificial sea water (0.2 mol 1^–1) by suspensions of Meliosira medocris. The rate of disappearance of radioactivity corresponds closely to removal of primary amines as determined by measurement of the rate of decrease of fluorescamine-positive material. Net removal of naturally occurring free amino acids from the sea water habitat from which the alga was isolated is demonstrated using high performance liquid chromatography. Removal of amino acids from natural sources makes a significant contribution to the carbon requirements of the alga as well as supplying significant amounts of amino nitrogen.