Biomedical subjects

W A Foster

Publications and source records attributed to W A Foster.

At least 37 records · Page 2Linked to original sources

PubMed1990

Gonotrophic cycle duration, population age structure, and onset of sugar feeding and insemination of Aedes triseriatus (Diptera: Culicidae).

During two successive summers, laboratory-reared Aedes triseriatus (Say) were marked and released into two woodlots in central Ohio. Several cohorts of two groups of mosquitoes were marked and released: blood-engorged, 10-12-d-old females and unfed, 2-d-old females. The parity of marked mosquitoes captured during daily biting collections were used to estimate the duration of the gonotrophic cycle. The parity rate of unmarked mosquitoes, in conjunction with the cycle estimate, yielded data on age structure and daily survival. Information on the onset of insemination and sugar feeding also was obtained. The mean and median duration of the first gonotrophic cycle, based on females released after blood feeding and later finding the collector, was 12 d. Unfed females required a median of about 8 d to feed on sugar, mate, and locate the collector, but required 22-32 d to sugar feed, mate, find a natural host, become parous, and then find the collector. The median duration of the natural gonotrophic cycle was estimated to take 14 d during warm (22 degrees C) weather. The parity rate of the natural population remained between 29 and 51% during the last 3 mo of each summer. The high proportion parous indicated that daily survival rate of unmarked females was above 0.9. Marked females moved between woodlots for distances as far as 400 m and were more likely to emigrate from the small woodlot than the large one.

Aedes↗

PubMed1990

Micrometeorologic factors affecting field host-seeking activity of adult Dermacentor variabilis (Acari: Ixodidae).

Fifteen micrometeorologic or microenvironmental parameters, including temperature, moisture, wind, and solar radiation, were repeatedly measured at 1 m and 2.5 cm aboveground, in the litter layer, and in the soil concurrently with drag samples of questing American dog tick, Dermacentor variabilis (Say), in five plots (1 by 10 m) in Delaware County, Ohio. Multivariate statistical analyses of the resultant data showed that ambient temperature was the best general predictor of adult tick host seeking under the observed ranges of the observed parameters. Multivariate procedures included forward stepwise multiple regressions and principal components analyses. Solar radiation was covariant with ambient temperature but was much less predictive. A suppression of questing activity with increased ambient temperature was evident at the highest observed temperatures, implying an upper temperature limit for this activity.

Analysis of Variance↗

PubMed1990

Tests of Sabethes cyaneus leg paddle function in mating and flight.

Both sexes of the mosquito Sabethes cyaneus have conspicuous midleg paddles of unknown function. These paddles are displayed prominently by males during courtship. However, we found that paddle removal reduced successful mating of females, not males. Males without paddles approached and courted females normally, but females without paddles were rarely approached by males. Paddle removal appeared not to alter flight, and paddleless females oviposited in the manner characteristic of Sabethes, suggesting that the paddles do not aid in hovering or rapid reverse flight. We conclude that paddles of females are used in attracting males but that their function in males remains undetermined.

Animals↗

PubMed1987

Rapid, quantitative microassay for the monokine respiration inhibitory factor.

The murine monokine respiration inhibitory factor (RIF) induces lesions at Complex I and Complex II of the mitochondrial electron transport chain (ETC) of tumor cells; these lesions in the ETC appear closely linked with cytostasis of the targets. In this report we describe the use of the sensitive murine mammary adenocarcinoma line EMT-6 in a colorimetric microassay for the effects of RIF on the ETC and target replication. The participation of cytolytic molecules in this assay system was excluded because of the resistance of the target to their effects. The endpoint for the assay was the ETC-mediated reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to its colored formazan. The two major coupling sites of MTT in the ETC of EMT-6 cells are shown to be proximal to Coenzyme Q, detected either by malate oxidation through Complex I or succinate oxidation through Complex II. The assay was sensitive to both RIF-induced lesions at these dehydrogenases and to the cytostasis-linked reduction in target cell number. The assessment of ETC lesions by this microassay correlated directly with that determined by the less sensitive polarimetric assay based on oxygen consumption. We demonstrate the application of this microassay to parameters for the production of RIF by activated murine macrophages, and to initial molecular characterization of this mediator.

Animals↗

PubMed1987

Tumoricidal effector mechanisms of murine BCG-activated macrophages. I. Parameters of production and initial characterization of a cytolytic factor serologically related to necrosin.

Previous studies have shown that peritoneal macrophages from mice chronically infected with Bacillus Calmette-Guérin (BCG) become highly cytotoxic for tumor targets upon further in vitro triggering with a variety of agents. In the current studies, achievement of this activated state was characterized by the production and release of a cytotoxin, herein termed cytolytic factor (CF), which appeared in the fluid phase. Production/release of CF by the macrophage required transcription, translation, glycosylation, and an intact secretory apparatus, as evident from inhibition by treatment with actinomycin-D, cycloheximide, tunicamycin, and monensin, respectively, prior to and during triggering with lipopolysaccharide (LPS). CF obtained by culture of BCG-activated macrophages appeared rapidly in the supernatant after triggering. Using the actinomycin-D-treated L-929 or EMT-6 targets in a microassay, CF secreted by macrophages cultured in low molecular weight serum components was detected as an approximately 150-kD component on Sephacryl S-200. CF demonstrated a spectrum of cytotoxic activity against a number of tumor and normal targets in vitro. Its lytic activity appeared equally effective whether the targets were cultured in medium containing fetal calf serum (FCS) or in Neuman-Tytell medium without serum during the assay. CF was moderately sensitive to treatment with TLCK and TAME; however, its activity in serum and apparent molecular weight distinguish it from a moiety obtained from BCG-activated murine macrophages and previously described. A rabbit heteroantiserum raised against highly purified necrosin, a product of the murine macrophage cell line J774.1, was extremely effective in neutralizing the biological activity of CF.

Animals↗

PubMed1986

Effector mechanisms of human monocyte-mediated tumor cytotoxicity in vitro: biochemical, functional, and serological characterization of cytotoxins produced by peripheral blood monocytes isolated by counterflow elutriation.

Human peripheral blood monocytes, isolated in high purity by centrifugal counterflow elutriation from normal donors, release cell toxins, herein termed human monocyte toxins (HMTs) upon further stimulation in vitro. The principal form of HMTs produced by these human peripheral blood monocytes has been subjected to biochemical, functional, and serological characterization. By molecular sieving on Sephacryl S-200, HMTs can be resolved into two molecular weight classes. The larger, termed alpha, has a molecular weight of about 120,000, and the smaller, termed beta, has a molecular weight of about 65,000. The beta class is by far the most predominant species and has been further characterized. Chromatofocusing of beta-HMT indicates a slightly acidic nature, since this species is eluted at pH 5.8. Functional characterization of beta-HMT suggests that it is not a trypsin-like protease, since neither alpha,N-tosyl-L-lysylchloromethylketone nor alpha,N-tosyl-L-arginyl methyl ester are capable of causing significant inhibition of the cell-lytic activity of the molecule. Furthermore, cell lysis induced by beta-HMT appears to be independent of oxygen-dependent mechanisms, since catalase is incapable of blocking lysis, and since hydrogen peroxide and superoxide anion are not produced in detectable amounts during lysis. Finally, beta-HMT does not appear to be an arginase, since it is active in arginine-containing medium and further addition of arginine to the assay medium does not inhibit lysis significantly. beta-HMT is serologically related to recombinant human tumor necrosis factor (rHuTNF), since its cell lytic activity can be blocked by a rabbit antiserum against rHuTNF. However, much higher levels of this antiserum are required to achieve neutralization than are required to neutralize a comparable number of cell lytic units of rHuTNF. Furthermore, the results of preliminary immunoprecipitation experiments using the rabbit anti-rHuTNF antiserum suggest that a peptide in the Mr 60,000-70,000 range is recognized by this serum, whereas no signal at Mr 17,000 corresponding to rHuTNF is detectable. Thus, human peripheral blood monocytes can be triggered to release cell toxins, the principal form of which, beta-HMT, appears to be functionally distinct from the cytotoxic proteases reported in the murine system and appears to be molecularly distinct from, but serologically related to rHuTNF.

Chromatography, Gel↗

PubMed1985

Tests of ultrasonic emissions on mosquito attraction to hosts in a flight chamber.

Five ultrasonic devices generating fundamental frequencies of 20-70 kHz were tested for their efficacy in repelling mosquitoes. Four species (Anopheles quadrimaculatus, Aedes aegypti, Ae. triseriatus and Haemagogus equinus), were used in a flight chamber in which females must fly upwind against the direction of the sound waves and around the ultrasonic devices to reach a trap downwind of a source of human breath and skin emanations. Repellency was rated by the number of mosquitoes entering the trap during a series of 5 min tests. For all species there was no significant difference between the numbers trapped when the devices were switched on or off, when all devices were tested simultaneously. Tests of individual devices against Ae. aegypti also failed to show a repellent effect.

Animals↗

PubMed1983