Prevalence and intensity of Thelazia spp. (Nematoda: Thelazioidea) in a Musca autumnalis (Diptera: Muscidae) population from Central Alberta

A face fly (Musca autumnalis) population near Wetaskiwin, central Alberta, Canada, was sampled 9 times from 26 July to 29 September 1988 for the early larval stages of Thelazia spp. Of 426 female flies examined, 159 (37%) contained Thelazia spp. (almost exclusively T. skrjabini), with an average worm burden of 4.2 larvae per infected fly. Prevalence ranged from 17 to 56% over 9 collections. This is the first report of Thelazia skrjabini in flies from western North America and the highest Thelazia prevalence in face flies yet reported in North America. The face fly population was also parasitized by Heterotylenchus autumnalis, with a prevalence of 5.5%.     

Direct evidence for the interaction between papaverine and alpha 2-adrenergic receptors in canine platelets

The effects of papaverine on specific [3H]-yohimbine binding to canine platelet alpha 2-adrenergic receptors and on the platelet aggregation were assessed and compared with those of verapamil. Both compounds concentration-dependently inhibited [3H]-yohimbine binding with KI values for respective compounds of 0.39 +/- 0.05 microM (n = 3) and 15 +/- 0.19 microM (n = 3). In the presence of either compound KD values in Scatchard analysis of the equilibrium ligand binding increased in concentration-dependent manner, whereas Bmax did not change, indicating competitive inhibition of the ligand binding by these compounds. (-)-Epinephrine (3 microM) potentiation of adenosine diphosphate (ADP, 0.1 microM) aggregation was inhibited by papaverine with IC50 of 11 +/- 3.6 microM (n = 4). In the same experiments verapamil inhibited the platelet aggregation with lower IC50 (3.1 +/- 0.87 microM, n = 4) in comparison with that for papaverine. These results suggest that papaverine, like verapamil, inhibits physiological response of canine platelets through alpha-adrenergic receptor stimulation by direct interaction with the receptors.     

The STE4 and STE18 genes of yeast encode potential beta and gamma subunits of the mating factor receptor-coupled G protein

The STE4 and STE18 genes are required for haploid yeast cell mating. Sequencing of the cloned genes revealed that the STE4 polypeptide shows extensive homology to the beta subunits of mammalian G proteins, while the STE18 polypeptide shows weak similarity to the gamma subunit of transducin. Null mutations in either gene can suppress the haploid-specific cell-cycle arrest caused by mutations in the SCG1 gene (previously shown to encode a protein with similarity to the alpha subunit of G proteins). We propose that the products of the STE4 and STE18 genes comprise the beta and gamma subunits of a G protein complex coupled to the mating pheromone receptors. The genetic data suggest pheromone-receptor binding leads to the dissociation of the alpha subunit from beta gamma (as shown for mammalian G proteins), and the free beta gamma element initiates the pheromone response.     

The role of adherent accessory cells in the generation of effector suppressor T cells

The role of accessory cell populations in the generation of effector suppressor (Ts3) cells was studied. By using an in vitro culture system, it was previously determined that the induction of NP-specific effector suppressor activity requires T cells, antigen, and an anti-idiotypic B cell population. We now demonstrate that the generation of Ts3 cells in this system also requires accessory cells. The accessory population appears to play a role in the processing and presentation of antigen. These antigen-presenting accessory cells are required early in the induction phase of Ts3 generation. These accessory cells can present NP coupled to immunogenic or non-immunogenic polypeptide carriers, including polymers of L-amino acids. However, NP coupled to polymers of poorly metabolized D-amino acids fail to induce suppressor T cell generation. Furthermore, the data demonstrate that an H-2 homology must exist between the Ts3 precursors and the antigen-presenting cell population if suppressor activity is to be generated. We also characterize the differential genetic restrictions that govern the induction of Ts3 cells that control suppression of either T cell or B cell responses. The data suggest that although I-J region encoded gene products control the induction and effector phases of suppressor cell activity as measured on T cell responses, the suppression of B cell responses appear to be controlled by I-A gene products. Possible cellular mechanisms that might explain these findings are discussed.     

Effects of various compounds on growth of yeast cells of Histoplasma capsulatum

Summary A number of compounds were screened for their effects on growth of the yeast cells ofHistoplasma capsulatum. Included were penicillin and related compounds, sulfhydryl inhibitors, various organic sulfur compounds recently synthesized for the first time, and compounds structurally related to the required metabolites, thiamine and cystine or cysteine. Cephalothin was the only one of the penicillin related compounds which inhibited growth. This occurred only when a high concentration (8.3 × 10^–4 M) was used. Of the analogues of cystine tested, allylglycine had the greatest inhibitory effect on growth of the yeast cells in the synthetic medium, but it failed to inhibit growth in a complex medium containing peptones and plasma. Among the sulfhydryl inhibitors, the maleimides were the most effective, producing complete inhibition of growth in the peptone medium at 10µg/ml or less. At subinhibitory concentrations the cultures tended to become mycelial. The action of the maleimides was reversed by cystine over a range of concentrations. At low concentrations, some of the disulfide derivatives of thiamine stimulated growth equally as well as thiamine, but at concentrations of 100 to 150µg/ml, they completely inhibited growth. On the basis of results obtained to date, three classes of the new organic sulfur compounds being tested offer promise as sources of potentially useful chemotherapeutic agents. These classes, which differ widely in structure, are as follows: the benzyl decylaminoethyl disulfides, the acyl disulfides, and the trithiopercarbamates.This investigation was supported by Public Health Service Research Grant AI-03524 from the National Institute of Allergy and Infectious Diseases.     

Molecular analysis of the yeast VPS3 gene and the role of its product in vacuolar protein sorting and vacuolar segregation during the cell cycle

vps3 mutants of the yeast Saccharomyces cerevisiae are impaired in the sorting of newly synthesized soluble vacuolar proteins and in the acidification of the vacuole (Rothman, J. H., and T. H. Stevens. Cell. 47:1041-1051; Rothman, J. H., C. T. Yamashiro, C. K. Raymond, P. M. Kane, and T. H. Stevens. 1989. J. Cell Biol. 109:93-100). The VPS3 gene, which was cloned using a novel selection procedure, encodes a low abundance, hydrophilic protein of 117 kD that most likely resides in the cytoplasm. Yeast strains bearing a deletion of the VPS3 gene (vps3-delta 1) are viable, yet their growth rate is significantly reduced relative to wild-type cells. Temperature shift experiments with strains carrying a temperature conditional vps3 allele demonstrate that cells rapidly lose the capacity to sort the vacuolar protein carboxypeptidase Y upon loss of VPS3 function. Vacuolar morphology was examined in wild-type and vps3-delta 1 yeast strains by fluorescence microscopy. The vacuoles in wild-type yeast cells are morphologically complex, and they appear to be actively partitioned between mother cells and buds during an early phase of bud growth. Vacuolar morphology in vps3-delta 1 mutants is significantly altered from the wild-type pattern, and the vacuolar segregation process seen in wild-type strains is defective in these mutants. With the exception of a vacuolar acidification defect, the phenotypes of vps3-delta 1 strains are significantly different from those of mutants lacking the vacuolar proton-translocating ATPase. These data demonstrate that the acidification defect in vps3-delta 1 cells is not the primary cause of the pleiotropic defects in vacuolar function observed in these mutants.     

Nucleotide sequence of the chromosomal gene coding for the aminoglycoside 6-adenylyltransferase from Bacillus subtilis Marburg 168

Gene aadK of Bacillus subtilis is 855 bp long and codes for aminoglycoside 6-adenylyltransferase.     

Response of murine bone marrow granulocyte-macrophage colony-forming units to hyperthermia in situ

A detailed understanding of how bone marrow stem cell progenitors are affected by heat is prerequisite to predicting how whole-body or regional hyperthermia protocols may affect bone marrow function. This investigation reports the reproductive integrity of murine tibial bone marrow granulocyte-macrophage colony-forming units (CFU-GM) after in situ hyperthermia. Heat was applied by water bath immersion of the leg of male BALB/c mice anesthetized with 90 mg/kg pentobarbital given subcutaneously. Tibial and rectal temperatures were monitored in representative animals by microthermocouples (tip diameter approximately 100 microns). By approximately 3 min after immersion of the limb, marrow temperature was within 0.3 degree C of water bath temperature (O'Hara et al., Int. J. Hyperthermia 5, 589-601, 1989) and was within 0.1 degree C by 5 min after immersion. The CFU-GM were cultured in "lung-conditioned" McCoy's 5A medium supplemented with 15% fetal calf serum and 0.3% Bacto agar. In situ heating of tibial marrow to exposure temperatures of 42, 42.5, 43, 44, and 45 degrees C gave D0's (+/- 95% CI) of 91 +/- 44, 44 +/- 27, 27 +/- 2.2, 16 +/- 6, and 7 +/- 4 min, respectively. Heating to 41.5 degrees C for up to 180 min did not result in cytotoxicity. Development of thermotolerance after approximately 100 min of heating was apparent by the presence of a "resistant tail" of the 42 degrees C survival curve. A plot of D0 vs water bath temperature was bimodal with an inflection point at approximately 42.5 degrees C. The inactivation enthalpy for temperatures above 42.5 degrees C was 586 kJ/mol (140 kcal/mol) and for temperatures below 42.5 degrees C was estimated to be 1205 kJ/mol (288 kcal/mol). These results show that CFU-GM can be heated predictably in situ, can be inactivated with thermal exposures as low as 42 degrees C, and are capable of developing thermotolerance. These findings underscore the necessity to understand stem cell inactivation by hyperthermia in situ prior to widespread implementation of clinical hyperthermia protocols where bone marrow may be included in the treatment field.