Stock‐specific variation of trophic position,diet and environmental stress markers in Atlantic salmon Salmo salar during feeding migrations in the Baltic Sea

This study investigated stock‐specific variation in selected ecophysiological variables during the feeding migrations of Atlantic salmon Salmo salar in the Baltic Sea. Oxidative stress biomarkers and EROD (ethoxyresorufin‐O‐deethylase, Cyp1A enzyme) activity were used as indicators of possible environmental stress and stable isotopes as determinants of diet and trophic position. Latvian S. salar stocks Daugava and Gauja had distinct stable‐isotope signatures compared to the other stocks, indicating differences in migration patterns, residency or arrival times, or dietary specialization among stocks. Salmo salar originating from Daugava and Gauja also had lower catalase enzyme activity than the other stocks. Post‐smolts originating from rivers of the Gulf of Finland had elevated EROD activities compared to fish of the same age from Bothnian Bay rivers, which could indicate exposure to organochlorine pollutants. No other stock‐specific differences in oxidative stress biomarkers were found. The study demonstrates how genetic, oxidative stress biomarker, EROD and stable‐isotope data may be combined to study trophic position, prey prevalence and environmental stress of mixed S. salar stocks foraging in the sea.     

A comparison of the isoenzymes of Trypanosoma (Duttonella) vivax isolates from East and West Africa

The genetic diversity in 13 stocks and clones of Trypanosoma vivax from East and West Africa was compared by isoenzyme analysis. The Ugandan and West African stocks and clones showed a very high degree of genetic similarity to each other but they differed from the Kenyan stocks and clones. Two haemorrhagic stocks, IL 2337 (Galana, Kenya) and IL 3067 (Bamburi, Kenya), showed a high degree of similarity in enzyme banding patterns in electrophoresed preparations. One of the Kenyan stocks, M1D 627, differed in most of its enzyme banding patterns from all the other stocks and clones used.     

Electrophoretic variation in multiple recessive tester, T, stock mice

The multiple recessive tester stock, homozygous for seven recessive visible markers, has been used since the 1950s in the specific locus test of mutagenicity in the mouse. The stock was developed by W.L. Russell in Oak Ridge, sent to the MRC Radiobiology Unit (Harwell) in 1953 and then passed to Research Triangle Institute (RTI) in 1988. Stocks are maintained by random mating in all three centres. and in addition stocks that have been selected for homozygosity at certain enzyme and protein markers are kept at both Harwell and RTI. The extent of electrophoretic variation was investigated in the random bred tester stocks at Harwell in 1981 and 1990, and in both random bred and fixed tester stocks at RTI in 1990. Altogether 44 loci were scored and eight of these (Acy-1, Es-3, Gpi-1, Hba, Hbb, Idh-1, Mod-1 and Pgd) have been polymorphic in one or more colonies at various times. Three loci (Es-3, Hbb and Mod-1) had low levels of polymorphism in 1981 and had become monomorphic by 1990. Despite this slight loss of variation, overall the tester stocks show considerable variability. The proportion of polymorphic loci and mean heterozygosity is of the same order of magnitude as island populations of wild mice or other isolated random bred laboratory populations. Contamination of tester stocks with other stocks can be ruled out, and thus tester stocks can be considered to be characteristic island populations. The retention of an appreciable amount of genetic variability in tester stocks is of practical importance in designing new mutation tests involving these mice. When using these stocks, care must be taken to ensure that they are homozygous for the loci under test.     

Variation between human and animal isolates of Giardia as demonstrated by DNA fingerprinting

Five Giardia stocks collected from animals and man in Alberta, Canada, were compared by DNA fingerprinting. Although many DNA bands were common to all stocks, differences in the DNA banding patterns were seen. These same stocks had previously been shown to be identical by restriction enzyme cleavage of genomic DNA.     

Quantitative Genetics of Postponed Aging in Drosophila Melanogaster. II. Analysis of Selected Lines

Quantitative genetic analyses of Drosophila melanogaster stocks with postponed aging have suffered from the problem of a lack of certainty concerning patterns of allelic differentiation. The present experiments were designed to alleviate this difficulty by selecting for enhanced levels of characters known to be related to postponed aging. Selection successfully increased the degree of differentiation of postponed aging stocks with respect to starvation resistance and fecundity, but persistent additive genetic variance suggested that selection did not result in fixation of alleles. The artificially selected stocks were subjected to crosses to test for patterns of dominance and maternal effects. There was little evidence for these effects in the inheritance of the characters underlying postponed aging, even with the increased differentiation of the selected stocks.     

Malic enzyme type VII isoenzyme as an indicator of suramin resistance in Trypanosoma evansi

This study analysed the suramin sensitivity of 29 stocks of Trypanosoma evansi isolated from Egypt, Sudan, and Indonesia and compared the results with the isoenzyme banding patterns of 20 soluble enzymes in these stocks of T. evansi. The results showed that the type VII banding pattern of malic enzyme was found only in T. evansi stocks which were highly resistant to suramin.     

Enzyme variation among clones of Trypanosoma cruzi

The genetic relationships within and between stocks of Trypanosoma cruzi were studied by the in vitro isolation of clones and sub-clones and by the comparison of their isoenzyme patterns in thin-layer starch-gel electrophoresis. Altogether 13 clones and 36 sub-clones were isolated from stocks CL89 and Y207 of T. cruzi. Employing the enzymes L-alanine aminotransferase (ALAT), L-aspartate aminotransferase (ASAT), glucose phosphate isomerase (GPI), malic enzyme (ME), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), and phosphoglucomutase (PGM), two zymodemes, B and C, emerged among the clones with distinct banding patterns. These zymodemes were consistently distinguished by ALAT, ASAT, GPI, G6PD, 6PGD, and PGM and the differences in enzyme profiles were simultaneously reflected in all six enzyme systems. That the enzymic characters as genetic determinants are stable was demonstrated after recloning and successive replica-platings, i.e., the distinct enzyme patterns remained consistent and homogeneous, the siblings retained the enzyme profiles of their parental clones, and no segregation of the enzyme patterns was observed. Our data from clone and sub-clone examinations show that the isoenzymes act as labels to characterize T. cruzi stocks. Furthermore, enzyme variation was demonstrated among clones isolated from stock CL89.     

Is Tree Species Diversity or Species Identity the More Important Driver of Soil Carbon Stocks,C/N Ratio,and pH?

We explored tree species diversity effects on soil C stock, C/N ratio, and pH as compared with effects of tree species identity. We sampled forest floors and mineral soil (0–40 cm) in a diversity gradient of 1–5 tree species composed of conifers and broadleaves in Bia?owie?a Forest, Poland. Diversity was a weaker driver than identity of soil C stocks, C/N ratio, and pH in the soil profile. However, there were significant non-additive effects of diversity and significant effects of identity on C stock and C/N ratio within different parts of the soil profile. More diverse forests had higher C stocks and C/N ratios in the 20–40 cm layer, whereas identity in terms of conifer proportion increased C stocks and C/N ratios only in forest floors. A positive relationship between C stocks and root biomass in the 30–40 cm layer suggested that belowground niche complementarity could be a driving mechanism for higher root carbon input and in turn a deeper distribution of C in diverse forests. Diversity and identity affected soil pH in topsoil with positive and negative impacts, respectively. More diverse forests would lead to higher soil nutrient status as reflected by higher topsoil pH, but there was a slight negative effect on N status as indicated by higher C/N ratios in the deeper layers. We conclude that tree species diversity increases soil C stocks and nutrient status to some extent, but tree species identity is a stronger driver of the studied soil properties, particularly in the topsoil.     

Expression of genes coding NGF and BDNF human proteins in embryos of transgenic stocks of Drosophila melanogaster

Transgenic Drosophila stocks were selected. These stocks contained human ngf and bdnf genes under Drosophila heat-shock promoter. The expression of foreign genes during Drosophila development was demonstrated with Northern and whole mount hybridization.     

The characterization of Chilean and Bolivian Trypanosoma cruzi stocks from Triatoma infestans by isoelectrofocusing

Culture forms of 12 Chilean and 9 Bolivian Trypanosoma cruzi stocks were compared isoenzymatically by the following enzymes: non-specific esterase, phosphoglucomutase, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, and alcohol dehydrogenase. On the basis of the electrophoretic mobility of these enzymes the stocks were classified into two main groups. Ten Chilean stocks were characterized as group II; two stocks showed enzyme patterns of group I. In contrast, five Bolivian stocks were classified as belonging to group I, the other four to group II. The results show that the two groups of T. cruzi overlap in Triatoma infestans suggesting that both groups of T. cruzi are infective for man. The classification of stocks into two groups is discussed in the light of published results of Brazilian T. cruzi stocks. A strong association of groups with the transmission cycles as it seems to be in Brazil does not exist in Chile and Bolivia.     

Genetics of Biomphalaria glabrata: Linkage analysis of genes for pigmentation,enzymes, and resistance to Schistosoma mansoni

The snail, Biomphalaria glabrata, is a major intermediate host of the human blood fluke, Schistosoma mansoni, in the Americas. The inheritance and linkage relationships of a gene enabling adult snails to resist infection by a Puerto Rican strain of the parasite were analyzed using two laboratory stocks that differed in susceptibility, pigmentation, and five electrophoretically detectable enzyme markers. Segregation ratios in second-generation intraspecific hybrids between susceptible (M-stock) and resistant (10-R2-stock) snails indicate that the susceptibility gene is not linked to the enzyme (ACON-1, ACP, EST-2, PEP-2, PGD) or pigmentation loci studied. These seven loci assort independently of one another. Observed rates of infection among F1 and F2 progeny are consistent with Richards' finding that adult susceptibility to the PR-1 strain of S. mansoni is controlled by a single locus with resistance dominant. No association between allozymes of acid phosphatase and snail susceptibility to PR-1 was seen in the snail-parasite combinations studied.     

The suitability of restriction fragment length polymorphisms as genetic markers in maize

Summary Strain identification in Zea mays by restriction fragment length polymorphism should be feasible due to the high degree of polymorphism found at many loci. The polymorphism in maize is apparently higher than that currently known for any other organism. Five randomly selected maize inbred lines were examined by Southern filter hybridization with probes of cloned low copy sequences. Typically, several alleles could be distinguished among the inbred lines with any one probe and an appropriately selected restriction enzyme. Despite considerable polymorphism at the DNA level, 16 RFLP markers in three inbred lines of maize were examined for six to 11 generations and found be stable. Mapping of RFLP markers in maize can be accelerated by the use of B-A translocation stocks, which enable localization of a marker to chromosome arm in one generation. The use of recombinant inbred lines in further refinement of the map is discussed.     

Changes in carbon, nutrients and stoichiometric relations under different soil depths, plant tissues and ages in black locust plantations

To investigate influences of forest plantations on soil nutrient properties, biomass accumulation, major nutrient elements (NPK) and their stoichiometric couplings in different tissues and aged plants, and correlations between major nutrient contents in soils and in foliage of plants, 5-, 10-, 15- and 20-year-old plantations of black locust (Robinia pseudoacacia L.) and farmland were selected. Black locust plantations increased soil organic carbon (SOC) and N stocks by 23–327 and 23–119 %, respectively, in the 0–10 cm top soil layer compared to those in farmland. Soil C:N, C:P, C:K, N:P, N:K and P:K ratios were 10.1, 22.9, 0.7, 2.2, 0.7 and 0.03, respectively. These ratios were higher in the 0–10 cm soil layer than those in the 10–20 cm soil layer and increased under older plantations. Higher C contents in stem, N contents in leaf, the largest C pools in stem and N pools in root in 20-year-old plantation were observed. Correspondingly, the highest C:N, C:P and C:K and the lowest N:P and N:K ratios in stem, decreased C:N and C:P ratios in older trees were found. No strong correlations were observed between element contents in soils and in leaves of black locust trees. These results suggest that black locust plantations can increase soil nutrient concentrations, SOC and N stocks resulting in changes in element stoichiometric relations. CNPK contents and their stoichiometries vary with tissues and tree ages of black locust. No strong coupling relations exist between major nutrient element contents in the top soil and in foliage of black locust.     

Studies on parasitemia courses and mortality in mice infected with genetically distant Trypanosoma cruzi clonets.

The biological characterization of bloodstream forms of eleven Trypanosoma cruzi cloned stocks, corresponding to two genetically similar clonets (19 and 20) and one distant clonet (39), according to multilocus enzyme electrophoresis analysis, showed dissimilar parasitemia in an experimental isogenic mouse model. While clonet 39 stocks gave low parasitemias, clonets 19 or 20 stocks gave high parasitemias, independently of the inocula (10(2) and 10(4) bloodstream forms) used. High parasitemia did not always associate with greater mortality. Statistical studies on mortality using a low inocula showed significantly higher mortality with clonet 39 stocks when compared to clonets 19 or 20 stocks. Finally, in order to confirm the identity of each stock studied, typing by molecular karyotype was performed before inoculating mice.     

Glycosidase and phosphatase activities in U-937 and some clones and sublines

1. The activities of nine glycosidases, lysozyme and acid and alkaline phosphatases were compared in the histiocytic lymphoma cell line U-937 and a set of clones and sublines derived from this line. 2. The patterns of the different enzyme activities and selected enzyme ratios have been used as a method to distinguish between different clones and sublines. 3. Sublines with high lysozyme levels were rich in most cell-bound glycosidases. 4. During long-term growth distinct enzyme patterns of individual lines were preserved. 5. The enzyme pattern during a cell culture growth cycle was basically stable.     

Histological study of the development and sex differentiation of the gonad in the European eel

The histological structure of the gonads was studied in yellow eels sampled from a coastal lagoon and from stocks reared in an aquaculture plant showing different sex ratios. Gonad development related to body size rather than to age and underwent an intermediate stage characterized by a structure of an early testis but containing oogonia and oocytes. This gonad was called the Syrski organ and the stage juvenile ambisexual. Ovaries were found in eels from 22–30 cm in length, possibly derived from undifferentiated gonads or from Syrski organs. Fully differentiated testes were found in eels >35 cm, derived from Syrski organs. These observations support the results of previous research. From elvers and in eels up to 15–16 cm in length, growth of the gonadal primordium is due to primordial germ cell migration. In eels > 15 cm multiplication of primordial cells begins. Oogonial clones were found in eels > 18 cm in length, whilespermatogonium B clones were observed in eels >30 cm in length. The dynamics of sex differentiation was different among stocks with different ultimate sex ratios: ovaries were found in shorter eels in stocks with a prevalence of females, in longer eels in stocks with a prevalence of males. This result supports the hypothesis of a metagametic (environmental) sex determination. The somatic cells in contact with germ cells and those in the interstitium appeared early during gonad development and preceded germ cell differentiation. This suggests that somatic cells are the targets of the environmental factors influencing sex differentiation.     

Modelling the patterns of dispersion of length at age in teleost fishes

The patterns of dispersion of length at age were analysed in 142 samples representing 115 stocks, 72 species and seven orders of teleost fishes. The coefficients of variation i.e. the ratios of the standard deviations to the mean lengths, declined with age in 85 samples, did not vary significantly with age in 50 samples and increased with age in seven samples. A rapid exponential decline in the coefficients of variation of length with age was a dominant characteristic of most short-lived stocks. Conversely, in most long-lived stocks, the coefficients of variation of length remained relatively constant, declined gradually, or increased slightly with age. It is proposed that the patterns of dispersion of length at age can be modelled empirically as a function of longevity. The probable sources of the observed patterns, including the intrinsic variability of life-history parameters between individuals and the impact of social interactions, are discussed.     

Quantitative analysis of the amount of larval serum protein-1 (LSP-1) synthesized by flies with different doses of the LSP-1 coding sequences

Larval serum protein-1 (LSP-1) and LSP-2 are the major proteins of Drosophila larval serum. The amount of LSP-1 synthesized is strictly proportional to the number of LSP-1 genes present within the range 1-10. The normal number in female flies is 6. Flies with extreme amounts of LSP-1 were, by our criteria, as fit as the wild type. The ratio of LSP-2:LSP-1 was analyzed in 169 different stocks and was constant in 164 of these. The significantly different ratios in five stocks were all due to the lack of one of the LSP-1 gene products.     

Linkage disequilibrium in natural populations of Trypanosoma cruzi (flagellate), the agent of Chagas' disease

We have studied linkage disequilibrium in natural populations of Trypanosoma cruzi, the agent of Chagas' disease, by analyzing (i) a set of 524 stocks from the whole geographical range of the parasite, characterized at four gene loci coding for enzymes; (ii) a subsample of 121 stocks characterized at 12 enzyme loci; and (iii) a subset of 386 stocks from six locations in Bolivia, characterized by four enzyme loci. Our results show that the linkage disequilibrium reaches the maximum possible value, given the observed allelic frequencies, for almost all the locus pairs. This result is most consistent with the hypothesis that genetic recombination is absent or very rare in T. cruzi natural populations. Partition of the linkage disequilibrium variance for the six Bolivian populations shows that both inter- and intrapopulation components are substantial and that the relationships among the components are D2IS less than D2ST, and D'2IS less than D'2ST. These inequalities are interpreted as the result of an interplay between genetic drift, rare or absent mating, and clonal selection in generating linkage disequilibrium in T. cruzi populations.