Variation in Lipid Content of Strains of Histoplasma capsulatum Exhibiting Different Virulence Properties for Mice

Nielsen, H. S., Jr. (Duke University Medical Center, Durham, N.C.). Variation in lipid content of strains of Histoplasma capsulatum exhibiting different virulence properties for mice. J. Bacteriol. 91:273-277. 1966.-Lipid content and virulence were studied in six isolates of Histoplasma capsulatum in an attempt to determine whether or not the two factors could be correlated in this fungus. Virulence was evaluated by injecting dba line 1 male mice intracerebrally with 2.8 x 10(4) infective yeast-phase units and recording organ involvement and spontaneous deaths occurring in a 20-day period. Yeast cells were extracted with mixtures of ethyl alcohol-diethyl ether (3:1, v/v), and the total extractable lipid, as determined by solubility in petroleum ether, was separated into acetone-soluble and phospholipid fractions by acetone precipitation. Neutral lipids were measured directly by weighing, whereas total phospholipids were calculated after the colorimetric determination of phosphorus. The mixed phosphatides of two isolates, differing in virulence, were separated into five fractions by use of a column of silicic acid and Hyflo Super-Cel. In the six isolates studied, neither total extractable lipid, acetone-soluble lipid, nor phospholipid showed a quantitative correlation with virulence. Phosphatidylserine, cephalin, phosphoinositides, and sphingolipids were present in essentially the same amounts in the two strains investigated; however, a lecithin fraction was absent in the less virulent form. These data suggest that the quantity of phosphatidylcholine demonstrated for a given isolate of H. capsulatum may provide some insight as to its virulence, although such a relationship is lacking for total lipid, the acetone-soluble fraction, and the combined phospholipids of yeast-phase growth.     

Why do males of the dance flyEmpis borealis refuse to mate? The importance of female age and size

Empis borealisfemales form swarms, and males carrying a nuptial gift come to swarms to mate. Males either mated with one of the females (accepted swarms) or left swarms without mating (refused swarms). Males mated with the younger (low wing-wear) and relatively larger females in accepted swarms. They seemed to be able to judge the relative size of the females but to ignore their absolute size. Visiting males stayed shorter in accepted swarms as female size variation increased. This probably reflects their greater ease in choosing a mate among females of relatively different sizes. Females in accepted swarms tended to be larger and to have less worn wings than females in rejected swarms.     

Food limitation and social regulation in a red fox population

This study evaluates a conceptual model on functional and numerical response to short-term fluctuating vole populations of a red fox ( Vulpes vulpes L.) population in south-central Sweden. The model assumes that this particular population is located in between socially regulated stable populations to the south and direct food-limited populations to the north. The model predicts: (1) food availability as the primary factor for limiting fox numbers, causing reduced rates of reproduction and survival during years of low vole densities, and (2) density-dependent regulation during years of increasing and high vole densities resulting in increased group sizes within territories of fixed dimensions. During 1973–1980 data were obtained from 1216 fox scats, 874 fox carcasses, 63 tagged foxes, nine radio-collared females and from yearly den counts in an area of 130 km², Eight predictions of the model were tested. These concerned the occurrence of small rodents in fox diet, fluctuations in the density of foxes, variations in the number of fox litters, the effect on reproduction of providing supplemental food during January–May, the proportion of vixens bearing a litter different years, dispersal of young males relative to that of young females throughout the vole cycle, and variations in mortality rates of young males and females. All tests were in favour of the conceptual model, and contradictory to alternative models.     

The influence of creosote compounds on the aerobic degradation of toluene

The inhibiting effect of 14 typical creosote compounds on the aerobic degradation of toluene was studied in batch experiments. Four NSO-compounds (pyrrole, 1-methylpyrrole, thiophene, and benzofuran) strongly inhibited the degradation of toluene. When the NSO-compounds were present together with toluene, little or no degradation of toluene was observed during 16 days of incubation, compared with a total removal of toluene within 4 days when the four compounds were absent. Indole (an N-compound) and three phenolic compounds (phenol, o-cresol, and 2,4-dimethylphenol) also inhibited the degradation of toluene, though the effect was much weaker that of the four NSO-compounds. O-xylene, p-xylene, naphthalene and 1-methylnaphthalene seemed to stimulate the degradation even though the influence was very weak. No effects of benzothiophene (an S-compound) and quinoline (an N-compound) were observed. Benzofuran (an O-compound) was identified as the compound that most inhibited the degradation of toluene. An effect could be detected even at low concentrations (40 g/l).Abbreviations bf benzofuran - bt benzothiophene - dmp 2,4-dimethylphenol - GC gas chromatograph - ind indole - mnap 1-methylnaphthalene - MAH monoaromatic hydrocarbons - mpyr 1-methylpyrrole - nap naphthalene - o-cre o-cresol - o-xyl o-xylene - phe phenol - pyr pyrrole - p-xyl p-xylene - tol toluene - thi thiophene - qui quinoline     

Simultaneous triple-immunogold staining of virus and host cell antigens with monoclonal antibodies of virus and host cell antigens in ultrathin cryosections

Summary The mechanism of intracellular maturation and sorting of herpes simplex virus type I glycoproteins is not known in details. To elucidate the intracellular sorting of viral glycoproteins and their possible interaction with the cytoskeleton, a method for simultaneous immunogold staining of three antigens in ultrathin cryosections is described. Each antigen is stained by an indirect technique using mouse monoclonal IgG as first layer, rabbit antimouse IgG as second and gold-conjugated goat anti-rabbit IgG as third layer antibody. After each staining cycle the paraformaldehyde vapour at 80° C for 30 min. This destroys the free antigen combining sites of the second and the third layer IgG and abolish contaminating staining. Simultaneous triple-staining is documented with three mouse monoclonal antisera specific for 1) herpes simplex virus type 1 glycoprotein C, 2) glycoprotein D and 3) - and -tubulin as primary antibodies. Labelling for virus glycoproteins was found in some Golgi vesicles and close to the cytoplasmic microtubules as well as on the cell surface and on intracytoplasmic and extracellular virus particles.Presented in part at the 9th European Congress on Electron Microscopy, York, England, September 4–9, 1988