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Biomedical subjects

W C Reeves

Publications and source records attributed to W C Reeves.

At least 181 records · Page 10Linked to original sources
PubMed1985

Aerial adulticiding for the suppression of Culex tarsalis in Kern County, California, using low volume propoxur: 2. Impact on natural populations in foothill and valley habitats.

A low volume formulation of propoxur wettable powder suspended in larvicidal oil was evaluated on 4 occasions in Kern Co., California during 1983 using fixed and rotary wing aerial application systems. Culex tarsalis abundance was suppressed significantly by all sprays, although reduction below the virus maintenance threshold of 30 females per trap night was achieved only at one foothill site. Western equine encephalomyelitis virus minimum infection rates decreased significantly after serial applications on 2 occasions at a valley site. However, virus persisted in the spray zone at minimum infection rates of greater than 1 per 1000 Cx. tarsalis females tested and transmission of virus to sentinel chickens continued. The parity rates were reduced significantly at 2 semi-isolated foothill sites, but not at a valley site where elevated autogeny rates increased the reproductive age of the host-seeking population. Spraying during late afternoon by helicopter resulted in better control than early morning applications by fixed wing aircraft at a valley site.

Aircraft↗
PubMed1984

Cervical cancer in the Republic of Panama.

Cervical cancer is more common in Latin America than elsewhere in the world. Previous work indicated that Panama also had a high incidence of cervical cancer and that the disease clustered in rural Herrera Province; to document this and collect detailed information on risk factors, the authors established a population-based Cervical Cancer Registry in Panama. Cervical cancer cases diagnosed between 1974 and 1979 were identified by visiting every major hospital in the country. The registry abstracted epidemiologic, clinical, and other information from patients' hospital charts. It recorded an age-adjusted invasive cervical cancer incidence of 28.4/100,000 between 1974 and 1979; rural Herrera Province supported the highest rate (79.1/100,000), while urban Panama Province had a low rate (24.6/100,000); in situ disease followed a similar pattern (48.7/100,000 in Herrera Province and 17.6/100,000 in Panama Province). Women born in Herrera Province retained high cervical cancer rates irrespective of residence at diagnosis (64.7/100,000), while women from Panama Province had low rates (12.4/100,000) which were comparable to those seen in US whites. In addition to having high cancer rates, women from Herrera Province developed invasive disease at an unusually young age; women between 35 and 39 years of age had an incidence of 151/100,000.

Adolescent↗
PubMed1984

Experimental transovarial transmission of St. Louis encephalitis virus by Culex and Aedes mosquitoes.

Colonized and field-collected female Culex tarsalis, infected with St. Louis encephalitis, (SLE) virus by intrathoracic inoculation or by feeding on a viremic host, transmitted virus to their F1 adult and/or larval progeny when reared at 18(+/- 1) degree C but not when reared at 27(+/- 1) degrees C. The minimal infection rates (MIR) for different populations of Cx. tarsalis ranged from 1:32 to less than 1:250 (mean = 1:121) for larval progeny and from 1:32 to less than 1:1, 989 (mean = 1:1,571) for adult progeny. SLE virus also was transmitted transovarially by colonized and field-collected populations of Culex pipiens (mean MIRs = 1:340 and 1:1,815 for larval and adult progeny, respectively) and by a field population of Culex quinquefasciatus (MIR = 1:500 and less than 1:246 for larval and adult progeny, respectively), but not by colonized strains of Cx. quinquefasciatus and Culex peus. SLE virus was not recovered in tests on 5,522 Cx. tarsalis and 4,798 Cx. quinquefasciatus that were collected as larvae or pupae from field sites in Southern California and reared to adults at 18 degrees C in the laboratory. Transovarial transmission of SLE virus by Aedes epactius was confirmed and extended to a closely related species, Aedes atropalpus. Efforts to demonstrate transovarial transmission of SLE virus by Aedes melanimon, Aedes sierrensis, and Aedes triseriatus were unsuccessful. Aedes dorsalis, Cx. peus, and Toxorhynchites amboinensis were equally sensitive hosts for viral isolation when inoculated with suspensions of larvae transovarially infected with SLE virus.

Aedes↗
PubMed1983

The release of thromboxane A2 and prostacyclin following experimental acute pulmonary embolism.

The contributions of thromboxane A2 (TXA2) and prostacyclin (PGI2) to the effects of acute pulmonary embolism were evaluated in 18 open-chest rabbits. All rabbits received autologous whole-blood-clot embolus (.4 cc) by way of a catheter in the right ventricle. Pulmonary artery (PA) and left atrial (LA) pressures, and aortic flow (AOQ) were recorded. The stable metabolites of TXA2 (TXB2) and PGI2 (6-Keto PGF1) were assayed by radioimmunoassay at pre- and post-embolization periods (+5, +10, +20, +30, and +40 minutes). Significant elevations of pulmonary vascular resistance (PVR) (normalized), PA pressure, and reduction of AOQ were noted comparing pre-embolus to +5 minute time intervals. A negative correlation was reached between PGI2 and AOQ at +40 minutes (p less than .05). Five of the 13 rabbits died prematurely. At +5 minutes these 5 rabbits had higher PVR (p less than .001) and lower AOQ (p less than .01) than their living counterparts. At +10 minutes AOQ was still significantly lower (p less than .005) and TXB2 was higher (p less than .05) in the premature death group. We conclude that TXB2 is significantly but transiently elevated early following acute pulmonary embolism and may contribute to mortality. In contrast PGI2 does not appear to play an immediate role in the hemodynamic events following embolization but does rise to significant levels later in the course possibly in an attempt to compensate for reduced flow.

6-Ketoprostaglandin F1 alpha↗
PubMed1983

Comparison of biological properties of St. Louis encephalitis and Rio bravo viruses.

St. Louis encephalitis (SLE) virus, an arbovirus, and Rio Bravo (RB) virus, a non-arthropod-borne virus, are flaviviruses which cross-react in neutralization tests. Several of their biological properties were compared. Viral growth curves revealed that greater than 99% of infectious SLE (Parton) virus remained cell-associated in Vero cells but was released slowly into the medium of infected BHK-21 cells. In contrast, RB (M-64) virus was released upon maturation into the fluids of Vero and BHK-21 cell cultures. Fortyfold more SLE virus than RB virus adsorbed to monolayer cultures of Aedes dorsalis cells. SLE but not RB virus replicated and reached high titers (10(8) pfu/ml) in Ae. dorsalis cell cultures maintained in media which were expected to enhance recovery of RB virus. Further, SLE but not RB virus replicated in cultured bat epithelial cells and primary duck embryo cells incubated at 42 degrees C. Clearly, the prototype strains of RB and SLE viruses are distinct viruses. Both the classification of RB virus in the genus flavivirus and the antigenic relationship between RB and SLE viruses require further clarification.

Aedes↗
PubMed1983

Historical perspectives on California encephalitis virus in California.

CEV is primarily associated with Ae. melanimon as its maintenance host and vector in California. A few species of lagomorphs and rodents will develop a transient viremia when infected. Infection of domestic mammals and man is frequent but rarely results in a clinical disease. Extensive field and laboratory studies lead to the conclusion that CEV probably is a mosquito virus that is partially adapted to a narrow range of vertebrate hosts but is not reliant on vertebrates for its continuous existence. JCV has many similarities to CEV in California in that it is dependent on one mosquito, Cu. inornata, as its vector and, as far as is known, the same group of mammalian species as for CEV serve as hosts for JCV.

Aedes↗
PubMed1982

Myocardial hydroxyproline reduced by early administration of methylprednisolone or ibuprofen to rabbits with radiation-induced heart disease.

The ability of methylprednisolone (MP) and ibuprofen (IB) to reduce the severity of the late state of radiation-induced heart disease was assessed in 57 New Zealand white rabbits. Before and shortly after cardiac irradiation, 15 rabbits received i.v. MP, 30 mg/kg twice daily for 3 days, and 15 others received IB, 12.5 mg/kg twice daily for 2 days. No drug was administered to 14 irradiated rabbits, and neither irradiation nor drugs were administered to 13 rabbits that served as controls, All 15 rabbits treated with MP and 13 of the 15 treated with IB lived for 100 days. Only seven of the untreated, irradiated rabbits lived that long. Longevity of each treated group of rabbits was better (p less than 0.01 and 0.05) than that of the untreated, irradiated rabbits. Surviving rabbits were killed 100 days after irradiation. Pericarditis (p less than 0.05) and pericardial effusion (p less than 0.01) were less frequent in the treated, irradiated groups than in the untreated, irradiated rabbits. At least some rabbits in each irradiated group had microscopic evidence of myocardial fibrosis. The fibrosis was quantitated by determination of myocardial hydroxyproline concentrations (MHP). MHP concentration in the untreated, irradiated rabbits was greater than in those treated with MP (p less than 0.05) or IB (p less than 0.01) and in the untreated, unirradiated rabbits (p less than 0.01). Early administration of MP or IB retarded the development of myocardial fibrosis, pericarditis and pericardial effusion, and improved survival in this experimental model of radiation-induced heart disease.

Animals↗
PubMed1982

Transovarial and trans-stadial transmission of California encephalitis virus in Aedes dorsalis and Aedes melanimon.

California encephalitis (CE) virus was transmitted transovarially by its natural vectors, Aedes dorsalis and Aedes melanimon following infection by intrathoracic inoculation. Virus was recovered from adult Ae. melanimon reared from eggs that were stored for up to 19 months and exposed to repeated freezing and thawing. Neither time since oviposition nor storage conditions affected infection rates in surviving embryos. Survival rates were highest in eggs stored at 4 degrees C. Transovarial infection with CE virus did not affect survival of embryos, larvae or adults. However, transovarially infected larvae took longer to develop than did their uninfected siblings.

Aedes↗
PubMed1982

Stabilized infection of California encephalitis virus in Aedes dorsalis, and its implications for viral maintenance in nature.

Three populations of Aedes dorsalis were selected which transmitted California encephalitis (CE) virus vertically to over 90% of their progeny. Infected progeny in these subpopulations transmitted virus at similar rates through five generations; females from the last generation transmitted virus by bite to suckling mice. These high rates of vertical transmission appeared to be due to the development of a stabilized infection with CE virus rather than to genetic selection for a more efficient transmitter or for a mutant strain of virus. In developed nonstabilized infections and transmitted virus vertically to approximately 20% of their progeny. The existence of stabilized infections of CE virus in vector populations and its implications for the natural history of CE virus and on the Fine and LeDuc model are discussed.

Aedes↗
PubMed1982

Evaluation of the efficiency of transovarial transmission of California encephalitis viral strains in Aedes dorsalis and Aedes melanimon.

California encephalitis (CE) virus was transmitted transovarially by its natural vector, Aedes melanimon. Vertical transmission rates ranged from 13-26% in geographical populations of Ae. melanimon infected with CE virus by intrathoracic inoculation. No consistent pattern of transmission rates was detected for location or time of year mosquito collection. Vertical transmission rates ranged from 9-29% in Aedes dorsalis inoculated with CE viral strains isolated from Ae. melanimon collected in California. The month or year of viral isolation had no effect on the efficiency of vertical transmission. However, a viral strain isolated from the Owens Valley was less efficiently transmitted than strains from the Sacramento Valley, and strains from the San Joaquin Valley were intermediate in efficiency. Filial infection rates were highest in first ovarian cycle progeny and declined with increasing ovarian cycles in both Ae. dorsalis and Ae. melanimon.

Aedes↗
PubMed1982

Sensitivity to carbon dioxide in mosquitoes infected with California serogroup arboviruses.

Ten species of mosquitoes became sensitive to CO2 following intrathoracic (i.t.) inoculation of California encephalitis (CE) virus. These included field-collected Aedes melanimon, Aedes nigromaculis and Culiseta incidens and laboratory-colonized strains of Aedes dorsalis, Aedes triseriatus, Anopheles freeborni, Culex peus, Culex pipiens pipiens, Culex pipiens quinquefasciatus and Culex tarsalis. Another California serogroup virus, Jerry Slough (= Jamestown Canyon) (JS), also induced CO2 sensitivity in nearly 100% of infected female Ae. dorsalis, Ae. melanimon and Cx. tarsalis. Sensitivity to CO2 developed in Ae. dorsalis and Cx. tarsalis within 3 days after i.t. inoculation of CE virus, remained at a high level through day 10 after inoculation and decreased gradually with time until by 30 days post-inoculation nearly all mosquitoes were nonsensitive. In contrast, Ae. dorsalis infected transovarially with CE virus were not CO2 sensitive. There was homologous but no heterologous interference to the development of CO2 sensitivity when Ae. dorsalis infected transovarially with CE virus were inoculated with CE or JS viruses. Two other bunyaviruses, Main Drain and Turlock, produced CO2 sensitivity in 3-10% and 0%, respectively, of infected Ae. dorsalis, Ae. melanimon and Cx. tarsalis. Two toga-viruses, St. Louis encephalitis and western equine encephalomyelitis, did not induce CO2 sensitivity in Ae. dorsalis and Cx. tarsalis.

Aedes↗