Infant loss during and after male replacement in gibbons

According to the sexual selection hypothesis, infanticide during resident male replacement is an adaptive strategy that has evolved because the killing of unweaned offspring sired by previous males shortens the inter‐birth intervals of the mothers whose infants are targeted and thereby increases the reproductive fitness of the perpetrator. To test this hypothesis, we describe previously unreported cases of primary male replacement for two gibbon species (Hylobates lar and Nomascus nasutus), and review all other reported cases of primary male replacement in gibbons. Overall, infants were present in nearly half of all cases (16/33, 48%) and of the 18 infants present during replacement, 50% (N = 9) disappeared within 2 months of the event. In four of the five cases where there was sufficient demographic information to identify the likely sire of the subsequent offspring of females that lost infants, the new male was believed to be the sire. Infants were also less likely to die or disappear if the new male and original resident male were possible kin. However, there was no significant difference in the age of infants between those that died or disappeared following replacement and those that survived to weaning (p = .630). Our review of takeover‐related infant loss in gibbons confirms that periods of male instability are risky for unweaned infants and that replacing males benefit from infant loss. Nevertheless, variability in the context of infant loss and difficulties related to data collection in the field make it difficult to test competing hypotheses concerning the mechanisms and functions of infanticide in the small apes.     

Multiple histone modifications in euchromatin promote heterochromatin formation by redundant mechanisms in Saccharomyces cerevisiae

Background  

Methylation of lysine 79 on histone H3 by Dot1 is required for maintenance of heterochromatin structure in yeast and humans. However, this histone modification occurs predominantly in euchromatin. Thus, Dot1 affects silencing by indirect mechanisms and does not act by the recruitment model commonly proposed for histone modifications. To better understand the role of H3K79 methylation gene silencing, we investigated the silencing function of Dot1 by genetic suppressor and enhancer analysis and examined the relationship between Dot1 and other global euchromatic histone modifiers.     

Electroantennogram responses of the Mediterranean fruit fly, Ceratitis capitata to identified volatile constituents from calling males

Fifty-six compounds from the odor of calling, sexually mature, laboratory reared males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) were isolated by headspace trapping on Tenax columns and identified using GC/MS techniques (69 total compounds were detected). Electroantennogram responses (EAGs) to 54 of the 56 identified compounds as well as 5 analogs were tested on both sexes. Significant differences between the sexes in their responsiveness were found in 9 of the 54 identified compounds tested. There was no correlation between the amplitude of the EAG response and the relative abundance of compound identified from headspace analysis. Of the five major identified components, three elicited relatively small EAG responses, while two elicited large EAGs compared to the hexan-1-ol standard. The relative ranking of EAG responses were: methyl and ethyl hexenoates and hexanoates > C₄–C₆ esters and/or acetates > ethyl and methyl octenoates > monoterpenes > sesquiterpenes > C₂–C₅ acetates, alcohols and ketones. Behavioral bioassays on each of the five major identified components as well as a blend of six of the compounds showed some degree of attractancy to virgin females which in some cases approached the response to a pheromonal standard (male odors absorbed onto filter paper). These results are discussed in relationship to the insect's antennal sensitivity to putative pheromone components and/or allomonal components and to other reported C. capitata pheromone studies.

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Résumé Cinquante-six composés de l'odeur de mâles de C. capitata Weidemann, élevés en laboratoire, sexuellement mûrs et en appel, ont été isolés par piégeage sur colonnes tenax et identifiés par la technique GC/MS (69 composés avaient été détectés en tout). Les électroantennogrammes (EAGs) ont été examinés chez les deux sexes pour 54 des 56 composés identifiés et 5 de leurs analogues. Des différences significatives entre les sexes ont été observées pour 9 des 54 composés identifiés. Il n'y avait pas de corrélation entre l'ampleur de l'EAG et l'abondance relative du composé lors de son isolement. Pour les 5 principaux composés identifiés, 3 ont induit des EAGs relativement faibles, tandis que 2 étaient importants, par comparaison avec l'Hexane-1-ol utilisé comme témoin. Le classement relatif des EAG a été: hexénoates et hexanoates d'éthyl et de méthyl C₄–C₆ esters et/ou acétates octénoates d'éthyl ou de méthyl monoterpènes sesquiterpènes C₂–C₅ acétates, alcools et kétones. Les expériences de comportement avec chacun des 5 composés principaux identifiés, comme avec des mélanges de 6 composés ont mis en évidence une attraction des femelles vierges qui dans quelques cas avoisine la réponse à la phéromone témoin (odeur du mâle absorbée sur papier filtre). Ces résultats sont discutés en fonction de la sensibilité de l'antenne d'insexte aux composés supposés de la phéromone et aux composés allomonaux, et en fonction des autres études connues sur les phéromones de C. capitata.

     

Evolution after gene duplication: models, mechanisms, sequences, systems, and organisms

Gene duplication is postulated to have played a major role in the evolution of biological novelty. Here, gene duplication is examined across levels of biological organization in an attempt to create a unified picture of the mechanistic process by which gene duplication can have played a role in generating biodiversity. Neofunctionalization and subfunctionalization have been proposed as important processes driving the retention of duplicate genes. These models have foundations in population genetic theory, which is now being refined by explicit consideration of the structural constraints placed upon genes encoding proteins through physical chemistry. Further, such models can be examined in the context of comparative genomics, where an integration of gene-level evolution and species-level evolution allows an assessment of the frequency of duplication and the fate of duplicate genes. This process, of course, is dependent upon the biochemical role that duplicated genes play in biological systems, which is in turn dependent upon the mechanism of duplication: whole genome duplication involving a co-duplication of interacting partners vs. single gene duplication. Lastly, the role that these processes may have played in driving speciation is examined.     

Polymeric C-terminal cross-linked material from type-I collagen. A modified method for purification, anomalous behaviour on gel filtration, molecular weight estimation, carbohydrate content and lipid content.

Polymeric cross-linked C-terminal peptide material (poly-alpha 1CB6) from mature bovine tendon type-I collagen was prepared and purified by a modification of the method previously described [Light & Bailey (1980) Biochem. J. 185, 373-381]. Poly-alpha 1CB6 was shown to exhibit concentration-dependent aggregation effects on gel filtration due to interaction with a filtration medium. The material had an amino acid content that was very similar to a mixture of alpha 1CB6 and alpha 1CB5. The material was shown to be polydisperse with a mol.wt. range of 50 000-350 000, but chromatographic fractions were relatively homogeneous over this molecular weight range with respect to amino-acid composition. The heterogeneity of the material was not due to incomplete CNBr peptide cleavage, as poly-alpha 1CB6 did not contain detectable quantities of methionine. The material showed no discrete bands on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis but gave a constant blue stain throughout the molecular weight range described above. Lipid analysis showed that the partially purified material contained elevated levels of stearate when compared to the crude CNBr-digested starting material. This may indicate the specific association of a stearic-acid-rich lipid with the peptide material. On carbohydrate analysis poly-alpha 1CB6 was shown to contain only galactose and glucose at levels of 0.72 and 0.28% respectively. The carbohydrate and amino acid analyses indicated that (alpha 1CB6)2-(alpha 1CB5)1 may be the basic cross-linked structural unit of poly-alpha 1CB6)2-(alpha 1CB5)1 units, although the carbohydrate analysis indicated that the higher molecular weight oligomers may be enriched in alpha 1CB6.     

Identification and characterization of mutations responsible for a runaway replication phenotype of plasmid R1

Initiation of replication of the resistance plasmid R1 is carefully regulated by the two negatively acting factors, CopA and CopB. It is shown here that the temperature-dependent runaway-replication phenotype of an R1 plasmid mutant is caused by two point mutations in each of the promoters for the genes of these control factors. Expression of the two genes is affected in the following way: (1) one C-to-T transition in the putative -35 box of the copB-repA operon creates a two- to three-fold stronger promoter from which expression is temperature-dependent; (2) another C-to-T transition in a G + C-rich area immediately downstream from the -10 box of the copA promoter reduces expression of the copA gene three-fold. The phenotypic consequences of the two mutations are discussed in the light of the current model for R1 replication control.     

Refolding of serine proteinases

Bovine trypsinogen and chymotrypsinogen were successfully refolded as the mixed disulfide of glutathione using cysteine as the disulfide interchange catalyst. The native structures were regenerated with yields of 40%-50% at pH 8.6 and 4 degrees C, and the half-time for the refolding was approximately 60-75 min. We then refolded threonine-neochymotrypsinogen, which is a two-chain structure held together by disulfide bonds and produced on cleavage of Tyr 146-Thr 147 in native chymotrypsinogen [Duda CT, Light A, J Biol Chem 257 9866-9871, 1982]. Neochymotrypsinogen was denatured and fully reduced, and the thiols were converted to the mixed disulfide of glutathione. The two polypeptide fragments, representing the amino- and carboxyl-terminal domains, were separated on Sephadex G-75. Mixtures of the polypeptide fragments varying in the ratio of their concentration from 1:5 to 5:1 were refolded with yields of 21-28%. The lack of dependence on the concentration of either fragment and the relatively high yields suggest independent folding of the amino- and carboxyl-terminal domains. When the globular structures of the domains formed, they then interacted with one another and produced the native intermolecular disulfide bridge and the proper geometry of the active site.     

Sepharose-bound trypsin and activated sepharose-bound trypsinogen. Studies with small and large substrates

Several enzymic and physical properties of Sepharose-bound trypsin and activated Sepharose-bound trypsinogen have been compared to those of the soluble enzyme. Sepharose-bound trypsinogen could be activated to the same extent as soluble trypsinogen; the release of the activation peptide and formation of the active site occurred as expected in the presence of catalytic amounts of trypsin. With synthetic substrates, the relative activity and pH dependence of both immobilized trypsin preparations were essentially identical and nearly the same as the soluble enzyme. Sepharose-trypsin also formed an inactive complex with soybean trypsin inhibitor, with 85% of the active sites participating. In contrast, the activity of Sepharose-trypsin with chymotrypsinogen and with trypsinogen as substrates was only 40% that of soluble trypsin. There is evidence for some catalytic heterogeneity of active sites of bound trypsin; probably those sites buried within the gel have a limited catalytic efficiency with macromolecular substrates. The immobilized enzyme is more stable than the soluble enzyme at elevated temperatures and to concentrated urea, and denaturation by urea at pH 8 is fully reversible since the loss of molecules by autolysis is eliminated.