Search PubMed⌕ Search

Biomedical subjects

J W Davis

Publications and source records attributed to J W Davis.

At least 289 records · Page 16Linked to original sources
PubMed1974

Characterization of persistent Modoc viral infections in Syrian hamsters.

Adult Syrian hamsters were readily infected by intranasal inoculation with Modoc virus. Viremias were detected 2 to 6 days after infection and peak viremia titers (10(6.2) plaque-forming units/ml of blood) occurred 4 days postinoculation. All infected animals developed neutralizing and hemagglutination-inhibiting antibodies by 7 days, and complement-fixing antibodies by 14 days postinoculation. High titers of antibodies persisted for at least 4 months. Modoc virus was recovered from throat swabs at 7 days postinoculation, but not at 14 days or later. Urine samples were positive for virus throughout a 12-week observation period. Isolation of virus from lungs and kidneys of one and three animals, respectively, at 151 to 221 days after inoculation confirmed chronic infection. Viral isolations were made only when organs were cultivated in vitro and were unsuccessful by tests on 10% homogenates of the organs. Horizontal viral transmission of virus by infected hamsters that were viruric was demonstrated in only 1 of 27 normal hamsters that were cocaged for 4 weeks under crowded conditions. General failure to obtain horizontal viral transmission may relate to rapid inactivation of virus in excreted urine. Vertical viral transmission was not demonstrated from five chronically infected female hamsters to their 34 offspring. However, if primary infection occurred during pregnancy, the progeny were either stillborn or died shortly after birth, and thus appeared to represent transplacental viral transmission.

Animals↗
PubMed1974

Modoc viral infections in the deer mouse Peromyscus maniculatus.

The pathogenesis of Modoc virus and its mechanism of transmission were investigated in Peromyscus maniculatus gambeli (deer mouse) as a model to understand the natural history of this virus. Animals were readily infected by the intranasal or subcutaneous route of inoculation. Virus could be detected by direct isolation techniques in many organs and body fluids during the first 7 to 9 days after intranasal inoculation. Increases in viral titers were detectable first in lungs and then the spleen, salivary-submaxillary glands, and lymph nodes. Viremias were low titered and ephemeral. Virus was recovered from urine and throat swabs 4 to 6 days and 4 to 7 days after inoculation, respectively. Serum dilution neutralization, hemagglutination inhibition, or complement fixation antibodies were detected in sera of some animals 13 days after infection and in all animals after 20 days. Antibodies persisted for the 168-day period of observation. Persistent viral infection was demonstrable by in vitro culturing of lungs or pooled lungs, salivary glands, and kidneys from 14 of 69 mice that were sacrificed from 1 to 6 months after intranasal inoculation. Attempts to demonstrate horizontal or vertical transmission of Modoc virus among mice were generally unsuccessful. Female deer mice infected with virus before mating passed maternal antibodies to their young.

Animals↗
PubMed1973

A new enzymatic assay for guanosine 3':5'-cyclic monophosphate and its application to the ductus deferens of the rat.

A sensitive enzymatic procedure has been developed for the determination of guanosine 3':5'-cyclic monophosphate (cyclic GMP). It is based on the conversion of cyclic GMP to GMP by cyclic nucleotide phosphodiesterase and on the transfer of (32)P from [gamma-(32)P]ATP to GMP by the action of a specific ATP:GMP phosphotransferase (EC 2.7.4.8). The [(32)P]GDP is separated from the remaining [(32)P]ATP by enzymatic degradation of ATP by myosin and by precipitation of the (32)P(i) formed. The reaction blank, which is mostly caused by the nucleotide content of the enzymes, is doubled by about 0.1 pmol of cyclic GMP. The procedure has advantages in speed and/or accuracy over other methods in current use. Cyclic nucleotide concentrations were studied in the ductus deferens of the rat; two agents were used, carbachol and norepinephrine, which cause contraction. Incubation with 0.1 mM carbachol caused a 3-fold increase in cyclic GMP content, which was maximal about 2 min after carbachol addition. Cyclic AMP concentrations were not significantly changed. Addition of 0.01 mM norepinephrine increased cyclic GMP content by about 25% within 1 min and by 40% within 3 min; cyclic AMP concentrations were only slightly increased. A 3-min incubation with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine (0.1 mM) doubled the cyclic GMP content and increased cyclic AMP concentration by 50%.

Adenosine Diphosphate↗
PubMed1973

In vitro studies with Modoc virus in Vero cells: plaque assay and kinetics of growth, neutralization, and thermal inactivation.

A sensitive and quantitative assay system is described for plaquing Modoc virus in Vero cells. Neutralizing antibodies to Modoc virus could be detected by using this in vitro system by their interference with viral plaque formation. Virus was readily neutralized within 30 min at 37 C by a 1:10 dilution of hyperimmune hamster serum. The rate of neutralization and the total amount of virus neutralized was not altered significantly by the addition of 20 U of guinea pig complement to the hyperimmune hamster serum. A study of the growth of Modoc virus in Vero cells is also presented. After an initial latent period of 20 h, viral titer increased exponentially for 20 h. By 83 h after infection, 8,000 plaque-forming units of virus were detected per cell. The stability of viral infectivity in phosphate-buffered saline at pH 7.4 was evaluated. No reduction in viral titer was detected after 3 days at 7 or 22 C. A continuous decrease in infectivity at 37 C was observed, however, throughout the observation period.

Animals↗