Diapause induction and duration in the phytoseiid miteTyphlodromus pyri

A photoperiod of 8L/16D for two weeks was used to distinguish between diapausing and non-diapausingTyphlodromus pyri Scheuten. A diet ofPanonychus ulmi orTetranychus urticae, or pollen ofVicia faba did not influence preovipositional periods of diapausing mites. In mid-September, 88% ofT. pyri collected from an insectary were in diapause. The critical day-length appeared to be between 12.5 and 13.5 h. Diapause duration was greatest in mites collected in September–November, becoming progressively less in mites collected later in the winter. By mid-April, ca. 50% of mites collected from the orchard and insectary oviposited promptly when cultured in the laboratory.Typhlodromus pyri eggs and larvae were present on leaves in early May. At this time, only 4% ofP. ulmi winter eggs had hatched. Diapause terminated most quickly inT. pyri kept in an 18L/6D photoperiod, followed by 24L/0D and 0L/24D. Longest preoviposition periods were recorded for mites kept in 8L/16D photoperiods.     

Co-immunolocalization of topoisomerase II and chloroplast DNA in developing,dividing and mature wheat chloroplasts

This paper describes the first localization of immunofluorescence of topoisomerase II in developing chloroplasts. In order to investigate the relationship between topoisomerase II and chloroplast DNA (ctDNA) replication during chloroplast development the 7-day-old wheat leaf was used. Topoisomerase II was immunolabelled and fluorescein tagged and the ctDNA simultaneously stained with 4,6-diamidino-2-phenylindole (DAPI) in the same sections. Topoisomerase II was detected at every stage of chloroplast development and maximal levels of topoisomerase II were found in chloroplasts at the time of ctDNA replication. Topoisomerase II was localized around the plastid periphery, exactly mirroring the position of the ctDNA. After chloroplast division both topoisomerase II and ctDNA are seen to be restricted to small discrete areas within the plastid, but at different sites. These findings strongly suggest a role for topoisomerase II in ctDNA decatenation prior to chloroplast division.     

A molecular genetic approach to the identification of isochromosomes of chromosome 21

Summary The largest class of de novo chromosomal rearrangements in Down syndrome are rea(21q21q). Classically, these rearrangements have been termed Robertsonian translocations, implying an attachment of two different chromosome 21 homologues. Additionally, a Robertsonian translocation between two chromosomes 21 cannot be distinguished from an isochromosome composed of genetically identical arms by cytogenetic analyses. Therefore, we have used molecular techniques to differentiate between true Robertsonian translocations and isochromosomes. Samples were obtained from 12 probands, ascertained for de novo rearrangements between homologous chromosomes 21 [11 rea(21q21q) and 1 rea (21;21)(q22;q22)], their parents (n = 24) and available siblings (n = 7). The parental origins of the de novo rearrangements were assigned using molecular and cytogenetic analyses. Although not statistically significant, there was a two-fold increase in the number of paternally derived de novo rearrangements (n = 8) as compared with maternally derived rearrangements (n = 4). To distinguish between rob(21q21q) and i(21q), we used restriction fragment length polymorphisms (RFLPs) spanning the length of chromosome 21. Using all informative and partially informative RFLPs, we used the method of maximum likelihood to assign the most likely rearrangement definition (i or rob) and parental origin in each family. The maximum likelihood estimates indicated that all rearrangements tested (n = 8) were isochromosomes. C-banding revealed two centromeres in three cases indicating that a U-type exchange occurred between sister chromatids in these rearrangements. Our results suggest that the majority of de novo rea(21q21q) are isochromosomes derived from a single parental chromosome 21.     

Immobilization and neutralization of Treponema pallidum attached to cultured mammalian cells

The in vitro effects of antibodies, complement, and (or) macrophages on Treponema pallidum have been previously characterized using relatively simple systems of organisms incubated with the immune components. In vivo, the more complex environment may alter immune reactivity. Experiments were performed to determine whether immobilizing and neutralizing antibodies retained their effectiveness in a more complex environment involving cultured mammalian cells. Two different protocols were used. In protocol A treponemes and normal or immune serum were mixed and added immediately to the cultured cells. In protocol B treponemes were preincubated for 18 h with cultured cells to maximize treponemal attachment; then normal or immune serum was added. With both protocols, attachment of organisms resulted in less efficient immobilization and neutralization. In further experiments, cultured cells were disrupted with Triton X, leaving cytoskeletal remnants on the vessel surface. Identical immobilization and neutralization experiments were performed in the presence of these remnants. In contrast to the findings with viable cultured cells, treponemal attachment to these nonviable remnants did not effect either antibody reaction. Attached organisms were immobilized or neutralized just as efficiently as unattached organisms. Results are discussed in terms of the altered immune reactivity in more complex in vitro environments.     

Adenosine 5'-diphosphate as an allosteric effector of phosphorylase kinase from rabbit skeletal muscle

Equilibrium binding and activity studies indicate that adenosine 5'-diphosphate binds to phosphorylase kinase with high affinity at a site, or sites, distinct from the catalytic site. Equilibrium dialysis at pH 6.8 and 8.2, with and without Mg2+, and with phosphorylated and nonphosphorylated enzyme preparations revealed approximately 8 ADP binding sites per alpha 4 beta 4 gamma 4 delta 4 hexadecamer, with Kd values ranging from 0.26 to 17 microM. Decreasing the pH from 8.2 to 6.8 or removing the Mg2+ enhanced the affinity for ADP. At pH 6.8, ADP stimulated the phosphorylase conversion and autophosphorylation activities of the nonactivated enzyme. Analogs of ADP with modifications at the 2'-, 3'-, and 5'-positions allowed determination of structural requirements for the stimulation of activity. ADP seems to alter the conformation of the beta subunit because addition of the nucleotide inhibits its dephosphorylation by phosphoprotein phosphatase and its chemical cross-linking by 1,5-difluoro-2,4-dinitrobenzene. The binding affinities and effects of ADP suggest that it may function physiologically as an allosteric effector of phosphorylase kinase.     

Activation of human thymocytes via the 50KD T11 sheep erythrocyte binding protein induces the expression of interleukin 2 receptors on both T3+ and T3- populations

Recent studies have demonstrated that the 50KD T11 molecule is a surface component of a macrophage-independent alternative pathway of human T cell activation that is unrelated to the T3/Ti antigen-MHC receptor complex. Given the expression of T11 on all human thymocytes, it was of interest to determine whether they could be activated via this pathway. The triggering of T11 by monoclonal antibodies anti-T112 and anti-T113, directed at two unique epitopes on the molecule, induced IL 2 receptor expression on both T3+ and T3- thymocytes but did not induce IL 2 production. Consequently, in contrast to peripheral blood T cells, thymocytes did not proliferate in response to anti-T112 and anti-T113 in the absence of exogenous IL 2. These studies suggest that IL 2 receptor gene activation precedes IL 2 gene activation in T cell development. The ability of the alternative pathway of T cell activation to induce IL 2 receptor expression on T3- thymocytes implies that the T11 molecule may have an important role in early thymocyte ontogeny.     

Antifungal therapy of dermatophytosis in guinea pigs and congenitally athymic rats

Guinea pigs and athymic nude (RNU/RNU) rats were used to assess the efficacy of three orally administered antifungal agents — Tolciclate, Tolnaftate, and Ketoconazole — against Trichophyton mentagrophytes dermatophytosis. All three antifungal agents inhibited the test strain of T. mentagrophytes in vitro. Antifungal agents were tested in intervention (oral therapy started 5 days after challenge) or prophylaxis (oral therapy started 5 days before challenge) protocols. Oral treatment of dermatophytosis on guinea pig skin demonstrated that Tolciclate and Tolnaftate alleviated clinical symptoms and shortened the duration of the dermatophytosis, in comparison to nontreated controls. Assessment of antifungal efficacy in the guinea pig model was time consuming (30–35 days) and variability in the duration and severity of clinical symptoms on guinea pig skin was common.Oral therapy of chronically infected athymic rats demonstrated that Tolciclate, Tolnaftate, and Ketoconazole were effective antifungal agents in vivo. Obvious improvement in clinical symptoms of dermatophytosis (i.e. less erythema and fewer lesions) was evident with all three antifungal agents within 10 days of starting oral therapy. By day 20, athymic rats that were treated with either Tolciclate or Ketoconazole showed marked clinical improvement of the chronic dermatophytosis.Chronically infected athymic rats, which lack thymus matured T-cells, are a promising new model to evaluate the efficacy of antifungal agents by culture, histology, and visual observations of clinical symptoms.     

Ta1, a novel 105 KD human T cell activation antigen defined by a monoclonal antibody

By using a murine monoclonal antibody produced against an IL 2-dependent human T cell line, we defined a T lineage-specific molecule, termed Ta1, that is expressed strongly on activated T lymphocytes of both the T4 and T8 subsets, as well as on T cell lines and clones, but only weakly on a fraction of resting T cells. SDS-PAGE analysis of immunoprecipitates from 125I-labeled, activated T cells demonstrates a single major band of apparent m.w. 105 KD under both reducing and nonreducing conditions. Unlike anti-IL 2 receptor antibodies, anti-Ta1 does not inhibit T cell proliferative responses to mitogen, antigen, or IL 2-containing medium. Moreover, anti-Ta1 has no effect on T cell-mediated cytotoxicity. Ta1 appears to be a novel human T cell-specific activation antigen that may serve as a useful marker of T cell activation in human disease.     

Ontogeny of ovine fetal liver and kidney plasma membrane insulin receptors and fetal growth

This investigation was performed to define certain characteristics of insulin-receptor interaction during the last 2 months of gestation in fetal sheep liver and kidney. Twenty-one sheep carrying a total of 46 fetuses were sacrificed at various gestational ages from 94 days to term; fetal and maternal livers and kidneys were analyzed by a radioreceptor assay for insulin binding characteristics. Specific binding of insulin to partially purified ovine fetal liver and kidney plasma membranes increased as gestation approached term, at which time specific binding was two- to fourfold greater to fetal than to maternal tissues. Associated with increased specific binding were late gestational increases in affinity of insulin for receptors in both fetal liver and kidney and an earlier increase in insulin receptor concentration in fetal kidney. These observations in fetal sheep liver and kidney are similar to reported observations in other species. However, the increase in specific binding of insulin to male fetal liver membranes was exponential; in contrast, there was no apparent increase in specific binding to female fetal liver membranes during the gestational interval surveyed. Both the weights and the vertebral column lengths of these fetuses were shown by multivariate analysis to be significantly affected by the interaction between specific binding of insulin and fetal sex. However, in 30 additional sheep fetuses we observed no difference between male and female fetuses in the increase with time in liver glycogen content. The lack of sex difference in this postreceptor event is consonant with the demonstrated dissociation between liver insulin receptors and glycogen synthesis in the late fetal rat. Our observations suggest that late gestational differences between male and female sheep fetuses in insulin specific binding to liver and, possibly, to other tissues such as cartilage, muscle, and/or fat, that are coupled to postreceptor events may account for differences in fetal growth between the sexes.