A gene (Bmn) controllingβ-mannosidase activity in the mouse is located in the distal part of chromosome 3

A gene (Bmn) with a major effect on -mannosidase activity in kidney and liver of the house mouse was revealed by assay with the synthetic substratep-nitrophenyl--d-mannoside. Activity is low in DBA/2J and CSB mice and high in C57BL/6J mice. By the use of the BXD series of recombinant inbred strains and by crosses between C57BL and CSB, it was possible to map the gene to the distal part of chromosome 3 by demonstration of linkage to a gene for cadmium resistance,cdm, as well as to theAdh-3 locus.This work was supported by Swedish Natural Science Research Council Project B-BU 2992-108.     

Quantitative comparison of Fusarium oxysporum competitiveness in relation to carbon utilization

Abstract The competitive saprophytic interaction between pathogenic and non-pathogenic strains of Fusarium oxysporum was investigated by studying their ability to competitively colonize sterilized soil. It was demonstrated that carbon was the first limiting substrate of Fusarium oxysporum growth in sterilized soil. Moreover, the efficiency with which glucose was utilized in the formation of propagules varied from one strain to another. Results of competitiion experiments showed that a linear relationship existed between the ratio of inoculum densities at the plateau (carrying capacity) and the ratio of inoculum densities incorporated into non-amended sterilized soil. The slope of the regression line indicated the competitiveness index, i.e. the competitiveness of a non-pathogenic strain in relation to that of a pathogenic strain. This parameter could be related to the yield coefficient of the strains in glucose-amended soil.     

Plasmid content in Yersinia pestis strains of different origin

Plasmid content in 242 Yersinia pestis strains from various natural plague foci of the U.S.S.R. and other countries was studied. Of these strains, 172 (71%) were shown to carry three plasmids described previously of about 6, 45-50 and 60 MDa, respectively. Twenty strains (8%) from different foci harboured additional cryptic plasmids, most often of about 20 mDa in size. Plasmid pPst displayed considerable constancy of its molecular mass. On the contrary, size variations of pCad (45-49 MDa) and, especially, pFra (60-190 MDa) were found. Molecular mass of these plasmids correlated with the host strain origin.     

The effectiveness of some Indonesian strains of Rhizobium on four tropical legumes

Nodules were collected from 14 legume species from the Indonesian Islands of South Sulawesi, Java and Sumatra. Their rhizobia were isolated and growth characteristics, nodulation ability and nitrogen fixing effectiveness were assessed against recommended commercially available Australian strains. The test legumes wereMacroptilium atropurpureum Urb. cv. Siratro,Vigna unguiculata (L.) Walp. cv Eureka,Centrosema pubescens Benth cv. Belalto andDesmodium heterocarpon (L) DC. A significant portion of the native rhizobial isolates were of the fast growing type. Dry matter and total nitrogen production forM. atropurpureum andV. unguiculata was highest when inoculated with native strains while the commerical strains produced superior dry matter production forC. pubescens andD. heterocarpon. However the total nitrogen production of native and commercial strains was not significantly different for the latter two legumes. The study indicated that a potential exists for developing inocula from local Rhizobium strains.     

Comparative study of embryonic thermoresistance of two inbred strains of the medaka (Oryzias latipes)

Summary By using inbred strains (HO4C and HB32C) of the medaka,Oryzias latipes, the involvement of genetic factor(s) in the determination of thermoresistance of fish was investigated. The thermoresistance of embryos of the medaka was quantitated by the fraction of the embryos surviving 1 day after heat treatment. At early stages of development (st. 13 and st. 20–21), the HO4C strain was more resistant than the HB32C strain. At st. 20–21, the HO4C strain was more resistant than the HB32C strain at all temperatures used (42, 43, and 44°C). At later stages of development (st. 27 and st. 32), however, the HB32C strain was more resistant than the HO4C strain.The results of genetic cross experiments raised the following possibilities; the thermoresistance of embryos at early developmental stages can be lowered by some factor(s) inherited in the HO4C strain and/or increased by those in the HB32C strain. By contrast, the sensitivity of embryos at later stages of development was not affected by factor(s) of their parents, but by their own genetic constitution.     

Dietary modulation of α-amylase activity in eight geographical strains of Sitophilus oryzae and Sitophilus zeamais

Rank transformation of specific activity values of -amylase across four strains of Sitophilus oryzae (L.) and four strains of S. zeamais Motschulsky indicates that levels of these predominant enzymes are highest in adults feeding on hulled barley or long-grain brown rice. Intermediate activity levels are found in weevils feeding on yellow corn (maize) and lowest levels are found in wheat-fed weevils. Although extracts prepared from barley contain inhibitory activity against two purified isoamylases from S. oryzae, levels of the naturally-occurring -amylase inhibitors against these two enzymes are about 2.2-fold and 6.1-fold, respectively, more concentrated in wheat. Ingestion of these amylase inhibitors and formation of an inactive enzyme:inhibitor complex with previously secreted amylase may account for the lower activity of amylase in weevils of both species feeding on wheat. Amylase levels across all strains feeding on a given diet are about 2-fold higher in S. oryzae than in S. zeamais. Significant differences in activity levels were also found between strains in both species. Since -amylase is a predominant digestive hydrolase in these species, the degree to which cereal diets affect amylase levels may indicate their suitability as potential hosts.

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Résumé La transformation de rang des valeur d'activité spécifique de l'-amylase de 4 souches de S. oryzae et de 4 souches de S. zeamais montre que les niveaux les plus élevés de ces enzymes prédominantes s'observent chez les adultes nourris d'orge mondé ou de riz brun á grains longs. Des niveaux intermédiaires d'activité ont été obtenus chez les insectes élevés sur maïs jaune, et les niveaux les plus faibles chez ceux élevés sur blé. Bien que les extraits préparés à partir d'orge présentent une activité inhibitrice de deux isoamylases purifiées de S. oryzae, les niveaux des inhibiteurs naturels -amylase de ces deux enzymes sont environ respectivement 2,2 et 6,1 fois plus concentrés dans le blé. L'ingestion de ces inhibiteurs d'amylase et la formation d'un complexe enzyme inactive/inhibiteur avec l'amylase secrétée antérieurement, peut rendre compte de la plus faible activité de l'amylase chez les charançons consommant du blé. Le niveau d'amylase de S. oryzae est 2 fois plus élevé que celui de S. zeamais pour toutes les souches élevées sur un régime donné. Des niveaux d'activité significativement différents ont été trouvés suivant les souches pour chacune des deux espèces. Puisque l'amylase est la principale hydrolase digestive de ces espèces, l'intensité de la modification des teneurs en amylase par la consommation de céréales peut indiquer leur adéquation comme hôtes potentiels.

     

Variation in alpha-L-fucosidase properties among 28 inbred mouse strains: Six strains have high enzyme activity and heat-stabile enzyme with a variant pH-activity curve; twenty-two strains have low activity and heat-labile enzyme

Alpha-L-fucosidase in tissues of 28 inbred mouse strains varied with respect to three properties: high or low heat stability, a pH-activity curve with high or low relative activity at pH 2.8, and high or low activity. Alpha-L-fucosidase from six strains (A/J, BDP/J, LP/J, P/J, SEA/GNJ, and 129/J) had high heat stability, high pH 2.8 relative activity, and high activity, whereas the other 22 strains all had low heat stability, low pH 2.8 relative activity, and low activity. The heat-stability difference was seen in all organs tested (brain, liver, kidney, spleen, heart, skeletal muscle, lung, and testis) for two heat-stabile strains (P/J and 129/J) and four heat-labile strains (C57 BL/6J, C3H/HeJ, DBA/2J, and BALB/cJ) studied in detail. The findings suggested that two structural variants of alpha-L-fucosidase, probably genetically determined, exist in these 28 inbred mouse strains, although the presence of linkage disequilibrium between alleles of tightly linked structural and regulatory genes could not be excluded.This work was supported by grants from the National Institutes of Health (NS-15281 and NS-11766), the Muscular Dystrophy Association (H. Houston Merritt Clinical Center for Muscular Dystrophy and Related Diseases), the March of Dimes Birth Defects Foundation, and a generous gift from the Alexander Rapaport Foundation.     

Comparison of glucokinase in C3H/He and C58 mice that differ in their hepatic activity

Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gk^a and Gk^b, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K _m values for MgATP^2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.).     

Isolation and cryopreservation of O-methylthreonine-resistant Rosa cell lines altered in the feedback sensitivity of l-threonine deaminase

O-Methylthreonine (OMT) inhibits the growth of plated Rosa cells (ID₅₀6·10^-6M). Isoleucine is able to reverse efficiently and specifically this OMT toxicity. From OMT-resistant colonies occurring at a frequency of 1.58·10^-7 variants per cell plated at 10^-4M OMT, the variant strains OMT^R-1 and OMT^R-2 were isolated, cloned via protoplasts and characterized. Both variants were ten times more resistant to OMT than the wildtype and were cross-resistant to another isoleucine analog, dl-4-thiaisoleucine. The resistant variants retained their resistance after storage for three years in liquid nitrogen. Both resistant strains were stable for several months when subcultured in the absence of OMT although it was shown in a reconstitution experiment that wildtype cells overgrow OMT^R-2 variant cells if co-cultivated for many passages in drug-free medium. One case of instability was observed upon long-term subculturing in drug-free medium: the strain OMT^R-1D^* partially lost phenotypic properties. Resistance to OMT was followed qualitatively by a new method based on inhibition-zone formation in cell suspensions plated in agar medium. The OMT-resistant variants showed a reduction in sensitivity of the enzyme l-threonine deaminase to feedback inhibition by isoleucine, a decreased stability of l-threonine deaminase when stored at-18°C or incubated at +55°C and a two- to threefold increase of the free isoleucine pool within the cells. The genetical events and the biochemical mechanisms which might lead to the observed stable and biochemically defined character are discussed with particular reference to the high ploidy level of the Rosa cell line.Abbreviations OMT l-O-methylthreonine - TD l-threonine deaminase