Inter- and intra-population variations in diapause attribute of the two-spotted spider mite,Tetranychus urticae Koch,in Japan

Populations of the two-spotted spider mite, Tetranychus urticae Koch collected from various localities and from various host plants in Japan showed wide variations in diapause attribute. Diapause percentages at 18°C/9L15D varied from nearly 100% in the north to 0% in the south-west. At intermediate latitudes the mites showed wide inter-population variations. Populations on herbaceous hosts in vinyl- or glass-houses gave significantly lower incidence of diapause than those on roses and deciduous fruit trees. Presence of winter hosts and better host quality under protected environments seemed to favour non-diapausing mites. The temperature threshold for diapause expression also varied widely among local populations. Northern populations consistently had higher and less variable thresholds than populations at intermediate latitudes with thresholds between 15 and 18°C. Inbred lines derived from a population in Kyoto exhibited a wide variation in diapause percentage at 18°C. These results show that diapause in T. urticae is a quantitative threshold trait and that populations in central Japan consist of a variety of genotypes with different diapause traits. This might provide a genetic source for adaptation to local and temporal variations in environmental conditions.     

A simplified method for the determination of nitric oxide in biological solutions.

A new simplified procedure for determination of nitric oxide (NO) in biological solutions is described utilizing a new reducing system of nitric oxide prior to chemiluminescence. Advantages of the new method makes heating of the reducing solution unnecessary and avoids cooling and condensation of generated vapors. Only traces of acid with a high boiling point are used. The method permits analysis of small sample volumes (200 microL). The basal production of nitric oxide by freshly harvested endothelial cells ranged from 100 to 880 picomoles.     

Fidelity of mammalian DNA replication and replicative DNA polymerases.

Current models suggest that two or more DNA polymerases may be required for high-fidelity semiconservative DNA replication in eukaryotic cells. In the present study, we directly compare the fidelity of SV40 origin-dependent DNA replication in human cell extracts to the fidelity of mammalian DNA polymerases alpha, delta, and epsilon using lacZ alpha of M13mp2 as a reporter gene. Their fidelity, in decreasing order, is replication greater than or equal to pol epsilon greater than pol delta greater than pol alpha. DNA sequence analysis of mutants derived from extract reactions suggests that replication is accurate when considering single-base substitutions, single-base frameshifts, and larger deletions. The exonuclease-containing calf thymus DNA polymerase epsilon is also highly accurate. When high concentrations of deoxynucleoside triphosphates and deoxyguanosine monophosphate are included in the pol epsilon reaction, both base substitution and frameshift error rates increase. This response suggests that exonucleolytic proofreading contributes to the high base substitution and frameshift fidelity. Exonuclease-containing calf thymus DNA polymerase delta, which requires proliferating cell nuclear antigen for efficient synthesis, is significantly less accurate than pol epsilon. In contrast to pol epsilon, pol delta generates errors during synthesis at a relatively modest concentration of deoxynucleoside triphosphates (100 microM), and the error rate did not increase upon addition of adenosine monophosphate. Thus, we are as yet unable to demonstrate that exonucleolytic proofreading contributes to accuracy during synthesis by DNA polymerase delta. The four-subunit DNA polymerase alpha-primase complex from both HeLa cells and calf thymus is the least accurate replicative polymerase. Fidelity is similar whether the enzyme is assayed immediately after purification or after being stored frozen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genome modifications in protoplast-derived tobacco plants: Contents of repetitive DNA sequences

Plasticity of the tobacco genome was studied by testing the DNAs of protoplast-derived regenerants with three different repetitive DNA sequences by the method of quantitative DNA/DNA hybridizations. A large population of 91 regenerants belonging to 35 different protoclones was analysed and a high degree of heterogeneity in the contents of the different DNA repeats was detected. The contents of middle repetitive sequences of two types were more stable or changed in the same direction, while the highly repetitive sequence varied independently and displayed a significant reduction in comparison with the two other sequences. Comparing the variation within the subpopulations of plants of the same clonal origin and the variation among the protoclones led to a conclusion that the pre-existing DNA variability in the starting plant material and/or thein vitro stress during the very early stages of protoclone regeneration played a decisive role in the formation of modified genomes in regenerants.     

Temporal relationships betweenZea mays,ostrinia nubilalis (Lep.: Pyralidae) and endophyticBeauveria bassiana

The entomopathogenic fungus,Beauveria bassiana (Balsamo) Vuillemin, was applied to whorl-stage (V7) corn,Zea mays L., by foliar application of a granular formulation of corn grits containing conidia or by injection of a conidial suspension. All plants were infested with European corn borer larvae,Ostrinia nubilalis (Hübner), at the V7 (whorl), V12 (late-whorl), or V17 (pretassel) stage of plant development. Plants infested at whorl and late-whorl stages had significantly more European corn borer tunneling than did plants infested at the pretassel stage. The percentage of plants colonized byB. bassiana did not differ significantly among the whorl, late-whorl, and pretassel stages. As the plants matured,B. bassiana was isolated from different plant areas, with the pith more frequently colonized than the leaf collars. Foliar application ofB. bassiana provided immediate suppression ofO. nubilalis in those plants infested at whorl stage. The reduced efficacy ofB. bassiana at the intermediate plant stages relative to efficacy at harvest is discussed. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

PAS IV, an integral membrane protein of mammary epithelial cells, is related to platelet and endothelial cell CD36 (GP IV).

PAS IV is a 78-kDa (bovine) to 80-kDa (human) integral membrane glycoprotein of unknown function which is found in mammary epithelial cells. We now report the purification of human PAS IV and native bovine PAS IV from the milk fat globule membrane (MFGM), a preparation of apical plasmalemma from epithelial cells of lactating mammary tissue. N-Terminal sequence analyses of human and bovine PAS IV revealed homology to the N-terminal sequence of the 88-kDa human endothelial and platelet glycoprotein CD36. The similarity of MFGM PAS IV to platelet CD36 was further established by immunoblots of purified platelet CD36 and MFGM PAS IV with MFGM PAS IV specific antiserum. The removal of N-linked oligosaccharides from PAS IV and CD36 by treatment with endoglycosidase F reduced the apparent Mr of both proteins to approximately 57,000. These data suggest that PAS IV and CD36 are similar if not identical polypeptides that undergo cell type specific glycosylation.     

In vivo inhibition of cholesterol uptake in rabbit aortas by 7-ketocholesterol.

The iv injection of 7-ketocholesterol into rabbits, made soluble by combining with bile salts, inhibited cholesterol uptake by the aorta. However, the inhibition was not as marked or as uniform as previously demonstrated in in vitro experiments. This difference may have been the result of lower plasma concentrations of 7-ketocholesterol in the injected animals. Gastric feeding of 7-ketocholesterol failed to inhibit aortic cholesterol uptake, probably because of inadequate plasma concentrations of the inhibitory steroid. The results suggest that the mechanism of 7-ketocholesterol on aortic cholesterol uptake is through competitive inhibition.     

Actinomyces streptomycini mutant blocked in streptidine biosynthesis]

Mutant 170 not capable of forming streptidine and streptomycin was obtained using chemical mutagenes. This mutant can produce streptomycin only with suplementation of exogenous streptidine. Experiment with labeled C14-streptidine showed its specific incorporation in streptidine moiety of streptomycin molecule.