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11.
Summary In a population of Allium stracheyi
Baker (2n=14) growing in Darjeeling both diploids and polyploids occur. The diploids contain B-chromosomes varying from 2–10 in number. Polyploids are conspicuous by absence of B-chromosomes. These in diploids are found in the pollen mother cells and also in the pollen, and some are provided with subterminal constriction.Diploid individuals when brought from Darjeeling to Calcutta (i. e. from temperate to tropical regions) became polyploid within a month and the B-chromosomes were simultaneously lost. In order to confirm this unexpected result, the transfer experiment has been repeated thrice with fresh collections in each case and selection of diploid bulbs after cytological observation. In all cases the result has been the same. In rare cases one or two B-chromosomes were found in the polyploid cells which might represent intermediate steps of the disappearance.B-chromosomes in diploids possibly help the individual to compete with polyploids by enlarging the adaptive capacity.The sudden polyploidisation by transfer from the mountains to the plains might have been the result of a shock due to the temperature difference. The high temperature may be deleterious for the reproduction of B-chromosomes, and their degeneration products possibly contribute to cytoplasmic changes and the spindle disturbances which effect polyploidisation. 相似文献
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14.
Purification of Mitochondrial Glutamate Dehydrogenase from Dark-Grown Soybean Seedlings 总被引:13,自引:2,他引:11
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Proteins in extracts from cotyledons, hypocotyls, and roots of 5-d-old, dark-grown soybean (Glycine max L. Merr. cv Williams) seedlings were separated by polyacrylamide gel electrophoresis. Three isoforms of glutamate dehydrogenase (GDH) were resolved and visualized in gels stained for GDH activity. Two isoforms with high electrophoretic mobility, GDH1 and GDH2, were in protein extracts from cotyledons and a third isoform with the lowest electrophoretic mobility, GDH3, was identified in protein extracts from root and hypocotyls. Subcellular fractionation of dark-grown soybean tissues demonstrated that GDH3 was associated with intact mitochondria. GDH3 was purified to homogeneity, as determined by native and sodium dodecyl sulfate-polyacrylamide gels. The isoenzyme was composed of a single 42-kD subunit. The pH optima for the reductive amination and the oxidative deamination reactions were 8.0 and 9.3, respectively. At any given pH, GDH activity was 12- to 50-fold higher in the direction of reductive amination than in the direction of the oxidative deamination reaction. GDH3 had a cofactor preference for NAD(H) over NADP(H). The apparent Michaelis constant values for [alpha]-ketoglutarate, ammonium, and NADH at pH 8.0 were 3.6, 35.5, and 0.07 mM, respectively. The apparent Michaelis constant values for glutamate and NAD were 15.8 and 0.10 mM at pH 9.3, respectively. To our knowledge, this is the first biochemical and physical characterization of a purified mitochondrial NAD(H)-dependent GDH isoenzyme from soybean. 相似文献
15.
Kanika Misra Arun B. Banerjee Subhankar Ray Manju Ray 《Molecular and cellular biochemistry》1996,156(2):117-124
Two enzymes, one NADPH-dependent and another NADH-dependent which catalyze the reduction of methylglyoxal to acetol have been isolated and substantially purified from crude extracts of Escherichia coli K12 cells. Substrate specificity and formation of acetol as the reaction product by both the enzymes, reversibility of NADH-dependent enzyme with alcohols as substrates and inhibitor study with NADPH-dependent enzyme indicate that NADPH-dependent and NADH-dependent enzymes are identical with an aldehyde reductase (EC 1.1.1.2) and alcohol dehydrogenase (EC 1.1.1.1) respectively. The Km for methylglyoxal have been determined to be 0.77 mM for NADPH-dependent and 3.8 mM for NADH-dependent enzyme. Stoichiometrically equimolar amount of acetol is formed from methylglyoxal by both NADPH- and NADH-dependent enzymes. In phosphate buffer, both the enzymes are active in the pH range of 5.8–6.6 with no sharp pH optimum. Molecular weight of both the enzymes were found to be 100,000 ± 3,000 by gel filtration on a Sephacryl S-200 column. Both NADPH- and NADH-dependent enzymes are sensitive to sulfhydryl group reagents. 相似文献
16.
Pei-Wen Chiang SuQing Wang Paul Smithivas Woo-Joo Song Saravanan Ramamoorthy Joseph Hillman Sheryl Puett Margaret L. Van Keuren Eric Crombez Arun Kumar Thomas W. Glover Diane E. Miller Chun-Hui Tsai C.Clare Blackburn Xiao-Ning Chen Zhiguang Sun Jan-Fang Cheng Julie R. Korenberg David M. Kurnit 《Genomics》1996,34(3):328
17.
Carola Borries Volker Sommer Arun Srivastava 《International journal of primatology》1994,15(3):421-443
We studied grooming among adults of a one-male multifemale troop of free-ranging Hanuman langurs (Presbytis entellus)living near Jodhpur, India, for 9 years. The 11–13 females devoted about 6% of their day to allogrooming. Adult males, whose
tenures averaged 2.2 years, were transient figures in the troop's history, as reflected by their rather peripheral role in
the grooming network. Females groomed males 4–40 times more frequently (1006 episodes) than vice versa- (176 episodes). Adult
females received 97% of all grooming from other adult females (6655 episodes). Although females exhibited an age- inversed
dominance hierarchy, they did not compete for grooming access to particular troop mates. Dyads of all possible rank differences
occurred as frequently as expected: 51% of grooming was directed up the hierarchy and 49% down it. Young, high- ranking individuals
gave and received significantly more grooming than the oldest, low- ranking females did. The pattern seemed to be influenced
by kin selection because of the presumably high degree of female relatedness. They invested most in troopmates with the highest
reproductive value, i.e., the youngest individuals. This trend was coupled with a preference of closest kin (mothers and daughters).
Reciprocity was the outstanding feature since all adult females groomed and were groomed by all others. Such a tight social
net might establish the necessary cohesion during frequent territorial disputes with neighboring troops. 相似文献
18.
Amaresh Chandra M. Thungapathra Kallash C. Upadhyaya 《Journal of plant biochemistry and biotechnology.》1994,3(1):31-35
The calcium binding protein, calmodulin Is involved in regulating various cellular and biochemical processes. A gene tor calmodulin (CaM) has been Isolated from a genomic library of Arabidopsis thaliana constructed in ; EMBL-4 using a heterologous cDNA probe from electric eel. One of the positive clones was characterized and the region containing the calmodulin gene sequences was Identified, excised using appropriate restriction enzymes and subcloned Into a plasmid vector. The genomic clone contains a complete copy of the calmodulin gene. A comparison of the nucleotide sequence of the part of the clone with those of the other plant and animal systems confirms that the clone In fact contains the calmodulin gene sequences. Southern hybridization ulling the calmodulin gene sequences as a probe reveals the presence of more than one copy of the calmodulin gene. The results of this investigation taken together with those Iff the other. indicate that the calmodulin gene belongs to a small mutigene family consisting of atieast four member. In the Arabidopsis genome. 相似文献
19.
When Chlorella vulgaris 11h, Chlorella vulgaris C-l, Chlamydomonasreinhardtii, Chlamydomonas moewusii, Scenedesmus obliquus, orDunaliella tertiolecta were illuminated in with 0.5 mM NaHCO3,the pH of the medium increased in a few minutes from 6 to about9 or 10. The alkalization, which was accompanied by O2 evolution,was dependent on light, external dissolved inorganic carbon(DIC) as HCO-3, and algae grown or adapted to a low, air-levelCO2 in order to develop a DIC concentrating mechanism. Therewas little pH increase by algae without a DIC concentratingprocess from growth on 3% CO2 in air. Photosynthetic O2 evolutionwithout alkalization occurred using either internal DIC or externalCO2 at acidic pH. The PH increase stopped between pH 9 to 10,but the alkalization would restart upon re-acidification betweenpH 6 and 8. Alkalization was suppressed by the carbonic anhydraseinhibitors, acetazolamide, ethoxyzolamide or carbon oxysulfide.The pH increase appeared to be the consequence of the externalconversion of HCO3 into CO2 plus OH during photosynthesisby cells with a high affinity for CO2 uptake. Cells grown onhigh CO2 to suppress the DIC pump, when given low levels ofHCO3 in the light, acidified the medium from pH 10 to7. Air adapted Scenedesmus cells with a HCO3 pump, aswell as a CO2 pump, alkalized the medium very rapidly in thelight to a pH of over 10, as well as slower in the dark or inthe light with DCMU or without external DIC and O2 evolution.Alkalization of the medium during photosynthetic DIC uptakeby algae has been considered to be part of the global carboncycle for converting H2CO3 to HCO3 and for the formationof carbonate salts by calcareous algae from the alkaline conversionof bicarbonate to carbonate. These processes seem to be a consequenceof the algal CO2 concentrating process.
1Present address: Department of Biology, Faculty of Science,Niigata University, Niigata, 950-21 Japan. 相似文献
20.
Arun Agrawal 《Human ecology: an interdisciplinary journal》1993,21(3):261-279
This paper describes and then analyzes the decision-making arrangements that prevail among the Raikas—nomadic shepherds from Western India. The paper suggests, using a simple analytical framework, that the existing distribution of decision-making during migration helps the Raikasto utilize available economies of scale, represent the different interest groups in their collectives, and control their decision-makers. At the same time, the ordinary shepherds in the camp are able to extract a comfortable subsistence from a complex and harsh environment by delegating much of their decision-making responsibilities to the leaders in the camp. To the extent shepherds in other parts of the world migrate over long distances and must confront similar issues of delegation of responsibilities and control over decision-makers, the analysis holds general relevance. 相似文献