Occurrence of B-chromosomes in diploid Allium stracheyi Baker and their elimination in polyploids

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.     

Reduction of methylglyoxal in Escherichia coli K12 by an aldehyde reductase and alcohol dehydrogenase

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 K_m 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.     

Weaving a tight social net: Allogrooming in free-ranging female langurs (Presbytis entellus)

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.     

Side reactions in the synthesis of phosphotyrosine-containing peptides

Summary A series of phosphopeptides Tyr(PO₃H₂)-Val-Pro-Xxx-Leu (Xxx=Met, Met(O), Nle, Dab or Cys), derived from the native platelet-derived growth factor- receptor (PDGF-) sequence, has been prepared to study their interaction with the src-homology 2 (SH2) domains of the p85 subunit of PI3 kinase. The phosphopeptides were synthesized using Fmoc methodology incorporating N-Boc dibenzyl-protected phosphotyrosine (Boc-Tyr[PO₃(Bzl)₂]) as the N-terminal amino acid, since the benzyl groups can be removed during resin cleavage with TFA. Only peptides containing methionine were found to exist partially as S-benzyl sulfonium salts after TFA cleavage from the resin. The desired peptide could be obtained from the S-benzyl sulfonium salt by hydrogenolysis.     

Alkalization of the Medium by Unicellular Green Algae during Uptake Dissolved Inorganic Carbon

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 HCO^–₃ 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 ofHCO^–₃ in the light, acidified the medium from pH 10 to7. Air adapted Scenedesmus cells with a HCO^–₃ 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 HCO^–₃ 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.     

Mobility and cooperation among nomadic shepherds: The case of theRaikas

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.     

Disposition kinetics of ML-1035 sulfoxide enantiomers and the prochiral sulfide in rats

ML-1035, 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N-[2-(diethylamino)ethyl]benzamide, is a sulfoxide compound and a racemic gastroprokinetic agent with a chiral center at the sulfur atom. We have investigated the disposition kinetics of (R)-ML-1035 sulfoxide (R) and (S)-ML-1035 sulfoxide (S) after the single enantiomers and the racemic mixture were administered to rats in separate experiments. There was no noticeable chiral inversion after either enantiomer dose. Both enantiomers were rapidly absorbed. After dosing with enantiomers or with the racemate, the resulting plasma concentration-time curve of R was closely parallel to that of S in both intravenous and oral experiments, suggesting that the two enantiomers have approximately the same disposition kinetics. After intravenous enantiomer doses, only S underwent conversion to sulfide, suggesting that sulfidation in the liver is enantioselective. However, the enantioselective sulfidation after intravenous dosing did not introduce a difference in the global plasma disposition profiles between R and S, since the reduction reaction is a minor metabolic process. Other metabolic reactions such as sulfonation and mono-N-desethylations were not enantioselective. After oral administration, conversion to sulfide was observed for both enantioners, implicating the existence of a nonhepatic pathway in sulfidation. Administration of a prochiral sulfide dose was associated with an enantioselective sulfoxidation, in which the R/S concentration ratios increased as a function of time. In addition, enantiomeric interaction causing changes in pharmacokinetic parameters was observed after the oral racemate dose, while the interaction is negligible after an intravenous racemate dose, indicating a route dependency in enantiomeric interaction. © 1993 Wiley-Liss, Inc.