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R Bijlsma

Publications and source records attributed to R Bijlsma.

33 records · Page 2Linked to original sources
PubMed1995

Genetic variation in Phoca vitulina (the harbour seal) revealed by DNA fingerprinting and RAPDs.

Genetic variation in two harbour seal (Phoca vitulina) populations from the Dutch Wadden Sea and Scotland was examined by RAPD analysis and DNA fingerprinting. For comparison a population of grey seals (Halichoerus grypus) was studied. The RAPD method revealed a very low number of polymorphic bands. The multilocus DNA fingerprinting technique showed very low levels of variation both within and between populations of the harbour seals. For one probe a significant difference in variation between populations was demonstrated. The estimated average heterozygosity, however, diverged more strongly between the two harbour seal populations because of more frequent occurrence of rare alleles in the Scottish population. Low levels of genetic variation seem to be characteristic for the subspecies Phoca vitulina vitulina, but not for all marine mammals in the North Sea, as the grey seal population showed significantly higher variation.

Animals↗
PubMed1993

The adult component of selection in Drosophila melanogaster: some aspects of early-remating activity of females.

As an important factor of the adult component of selection, mating behaviour was studied in Drosophila melanogaster, with emphasis on non-virgin females. We found that 30-50 per cent of the females in a laboratory population will remate within 6 h of first mating under no-choice conditions. This high percentage of early rematings was not due to the continuous confinement of the females with males but indicated a rapid return of receptivity of a significant proportion of the females. Remating behaviour was significantly influenced by both the genotype of the female and the genotype of her two successive partners. Age of females was only important insofar as it concerned young, 1 or 2-day old, females. These females showed less remating than older females. Willingness to remate was also affected by the number of sperm stored. Females that had been inseminated by less fertile males, i.e. males that had already mated two or three times, showed higher remating percentages than females inseminated by more fertile males. Notwithstanding this sperm effect, females were estimated to remate approximately every second day. It is suggested that a high frequency of remating and the resulting sperm competition are significant components of Drosophila life-history.

Animals↗
PubMed1992

Duplication of the structural gene for glucosephosphate isomerase and phosphogluconate dehydrogenase in Scabiosa columbaria and their phylogenetic implications in the dipsacaceae.

Zymograms of glucosephosphate isomerase (GPI) and phosphogluconate dehydrogenase (PGD) revealed three isozymes for each enzyme in the plant species Scabiosa columbaria. Intergenic heterodimers are formed between the polypeptides coded by Gpi-1 and Gpi-2 and between those coded by Pgd-1 and Pgd-2, indicating that a GPI and a PGD locus have been duplicated in the past. The ancestral genes assort independently with their duplicated gene, suggesting that the duplications have originated from a process of translocation. Linkage was found only between Gpi-1 and Pgd-2 and between Gpi-2 and Pgd-1, suggesting that the duplicated loci were located on the same translocated chromosomal segment. Both duplications are present in all other examined species of Scabiosa and in Cephalaria and Knautia, two other genera of the Dipsacaceae. The genera Succisa and Dipsacus, also belonging to the Dipsacaceae, do not show Gpi-1 activity, making Gpi-2 and Pgd-1 the most likely ancestral genes. In Succisa, the isozymes of Gpi-1 and Gpi-2 either overlap or Gpi-1 has been silenced. The combined results suggest that a chromosomal segment containing Gpi-2 and Pgd-1 has been translocated before the divergence of Scabiosa, Cephalaria, Knautia, and Succisa.

Genes, Plant↗
PubMed1992

On the developmental theory of ageing. II. The effect of developmental temperature on longevity in relation to adult body size in D. melanogaster.

Flies from a wild type strain of Drosophila melanogaster, previously kept at 25 degrees C, were reared at either 20, 25 or 29 degrees C. As expected, developmental time and adult body size decreased with increasing temperature. Adult longevity of flies reared at 25 degrees C was slightly greater than that of flies raised at 20 or 29 degrees C when measured at all three temperatures. This may reflect the laboratory history of the strain. On the whole, it appeared that longevity was independent of adult body size. These results support our previous conclusion (Zwaan et al., 1991) that developmental time and body size are not causally related to longevity in 'environmental' studies. It is stressed, that genetic analysis is needed to investigate the reputed correlation between development and ageing.

Aging↗
PubMed1992

Interaction between the Adh and alpha Gpdh loci in Drosophila melanogaster: adult survival at high temperature.

The role of high temperature resistance in the world-wide cline of Adh and alpha Gpdh allele frequencies of Drosophila melanogaster was investigated. Experimental strains were used with different combinations of Adh and alpha Gpdh alleles but with similar genetic background. The survival time of adult males, reared at different pre-adult temperatures, was measured at 35 degrees C. To investigate the relationship between survival and protein content, triglycerides content and ADH and alpha GPDH enzyme activity, the latter characters were measured before and after 12 h exposure to 35 degrees C. Three-way ANOVA of survival at 35 degrees C showed significant effects of rearing temperature and Adh genotype, interaction between Adh and alpha Gpdh, interaction between Adh and rearing temperature and interaction between Adh, alpha Gpdh and rearing temperature, alpha GPDH enzyme activity did not change significantly. Although protein content, triglycerides content and ADH enzyme activity decreased significantly at 35 degrees C, no correlation was observed between survival and these traits. It is concluded that the world-wide cline of Adh and alpha Gpdh allele frequencies cannot simply be explained by the genotypic differences in resistance to high temperature of adult Drosophila melanogaster.

Alcohol Dehydrogenase↗
PubMed1991

On the developmental theory of ageing. I. starvation resistance and longevity in Drosophila melanogaster in relation to pre-adult breeding conditions.

The developmental theory of ageing predicts a positive correlation between developmental time and adult longevity. Experiments that vary larval density and food level have been carried out to test this prediction. The results show differences in viability, developmental time, starvation resistance and adult longevity. It is concluded that pre-adult developmental time is not a causal factor for the determination of adult longevity in Drosophila melanogaster. The observed variation in adult longevity is discussed in relation to viability selection and changed adult physiology.

Aging↗
PubMed1991

Polymorphism at the Adh and alpha Gpdh loci in Drosophila melanogaster: effects of rearing temperature on developmental rate, body weight, and some biochemical parameters.

The role of developmental time in the world-wide cline of Adh and alpha Gpdh allele frequencies of Drosophila melanogaster, and the relationship with weight and some biochemical characters, were investigated. Experimental strains were constructed with different combinations of Adh and alpha Gpdh alleles but with similar genetic background. Developmental time, adult weight, protein-and triglyceride-content, and ADH and alpha GPDH enzyme activity were measured at a rearing temperature of 20, 25 and 29 degrees C. Genotype effects were found in all studied characters. In general the developmental times of genotypes were: AdhFF less than AdhFS less than AdhSS and alpha GpdhFF greater than alpha GpdhFS = alpha GpdhSS. Developmental time and adult weight were strongly affected by rearing temperature. Triglyceride content and ADH and alpha GPDH enzyme activity were slightly affected by temperature. Interactions between genotype and temperature effects were found for developmental rate, adult weight and protein content. No trade off was observed between developmental time on the one hand and adult weight, protein- and triglyceride-content, and ADH and alpha GPDH enzyme activity on the other hand. It is argued that developmental rate differences might be one of the underlying mechanisms of the world-wide cline of the Adh and alpha GPdh allele frequencies.

Alcohol Dehydrogenase↗
PubMed1988

The alcohol dehydrogenase polymorphism in Drosophila melanogaster: fitness measurements and predictions under conditions with no alcohol stress.

The relative fitnesses of the different Adh genotypes under normal laboratory conditions and in the absence of alcohol stress were estimated in Drosophila melanogaster according to Prout's method. The larval component (viability) did not reveal fitness differences between the genotypes but for the adult component significant differences were observed. The female adult component (fecundity) showed an overdominant pattern: both homozygous genotypes showed a relative fitness significantly lower than the heterozygous genotype. For the male adult component (virility) also differences were observed. The homozygous SS genotype showed a lower relative fitness than the other two genotypes. Predictions for gene frequency changes based on the estimated fitness values do show a reasonably good correspondence with frequency changes actually observed in a number of experimental cage populations and indicate a globally stable equilibrium around a frequency of the F allele of 0.40-0.70. The relevance of these fitness estimates, obtained under conditions with no alcohol stress, for the explanation of the Adh polymorphisms observed in nature is discussed.

Alcohol Dehydrogenase↗
PubMed1983

The effect of DDT on the polymorphism at the G6pd and Pgd loci in Drosophila melanogaster.

For the degradation of DDT and other chlorohydrocarbon insecticides energy in the form of NADPH is needed which for the greater part is supplied by the pentose phosphate shunt. Therefore the influence of DDT on the polymorphism at the G6pd and Pgd loci in Drosophila melanogaster was investigated by studying its effect on egg to adult survival and adult survival. The results show the existence of significant differences in fitness between the different genotypes of the two loci for both components. It is found that the effect of DDT supplementation differs significantly from the effect of sodium octanoate addition. DDT treatment also increases the activity of the pentose phosphate shunt as measured by the activity of G6PD and 6PGD. In larvae a 50% increase in activity is found and in adults a 100% increase. As there is little doubt that the activities of G6PD and 6PGD are somehow correlated with the fitness of flies, the data are discussed in relation to the in vitro and in vivo differences in activity between the different allozymes of both G6PD and 6PGD.

Animals↗
PubMed1982

Collateral pathways in lumbar epidural venography. Report of three cases.

Opacification of collateral pathways other than the central channels is very rare in lumbar epidural venography. Two cases of opacification of the inferior mesenteric vein following extravasation of contrast medium at the tip of the lateral sacral vein catheter are reported. One case is presented in which filling of normal parametrial venous plexuses and the left ovarian vein occurred as a consequence of incompetent or absent valves in the internal iliac vein. The literature containing comparable collateral flow patterns in disease is reviewed. The significance of the phlebographic features in our cases is discussed.

Back Pain↗
PubMed1980

Polymorphism at the G6pd and 6Pgd loci in Drosophila melanogaster. IV. Genetic factors modifying enzyme activity.

Different homozygous lines of similar genotype with respect to G6pd and 6Pgd were shown to have different enzyme activities for G6PD and 6PGD. Crosses between high and low lines suggested that there were modifying genes present on the autosomes, while others were probably located on the X chromosome. Allelic variation within each electrophoretic class of G6pd and 6Pgd might, however, also have contributed to this variation. An experiment on adaptation to sodium octanoate demonstrated that in adapted flies selection for lower enzyme activity had occurred, which provided further evidence for the existence of genetic differences in activity. Furthermore, a strong positive correlation between the activities of G6PD and 6PGD was found for each genotype. Since no correlation was found between MDH and the two enzymes G6PD and 6PGD, it could be concluded that this correlation was probably rather specific for G6PD and 6PGD. Interaction between genotypes with respect to activity was also found. It was shown that the variation at 6Pgd influenced the activity of G6PD within a genotype. The data are discussed in relation to fitness differences presented in foregoing articles.

Adaptation, Physiological↗
PubMed1979

Polymorphism at the G6pd and 6Pgd loci in Drosophila melanogaster. III. Developmental and biochemical aspects.

The electrophoretic variants of G6PD and 6PGD isolated from the Bogota Drosophila melanogaster population were characterized developmentally and biochemically. Changes in in vitro enzyme activity during development were comparable to those found for other dehydrogenases: an increase in the larval and adult stage and a decrease in the pupal stage. During the whole life cycle the "S" enzyme of both loci showed a higher activity than the "F" enzyme. MgCl2 had a stimulating effect on the activity of both enzymes whereas their heat stability was decreased. The allozymes of 6PGD had different Vmax's but were comparable with respect to Km values, pH optimum, and stability at 45 C. the allozymes of G6PD showed different Vmax's and differed in stability at 35 C, but had similar Km values and pH optima. As the difference in stability was probably due to differences in molecular structure of the allozymes, the differences in activity found at high pH and high MgCl2 concentration were most probably due to this difference in stability.

Animals↗