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Biomedical subjects

W C Stewart

Publications and source records attributed to W C Stewart.

At least 145 records · Page 8Linked to original sources
PubMed1988

Transpupillary argon laser cyclophotocoagulation in the treatment of glaucoma.

Twenty-seven patients with glaucoma, which could not be controlled with maximum tolerable medication and standard laser techniques, underwent transpupillary argon laser cyclophotocoagulation. Only six patients (22.3%) had a successful outcome, and the postoperative course in many cases was complicated by an additional, sustained increase in intraocular pressure. Notwithstanding these results, the procedure may be useful occasionally to preclude the need for conventional glaucoma surgery.

Adolescent↗
PubMed1983

Incidence of pelvic inflammatory disease in clinical trials with Cu-7 (intrauterine copper contraceptive): a statistical analysis.

Pelvic inflammatory disease (PID) was recorded for 365 of 10,760 women using the Cu-7 for up to 48 months during clinical investigations in the United States. This involved a total exposure of 242,169 woman-months, or some 20,000 woman-years. The overall incidence of PID was 18 cases/1000 woman-years. Incidence was inversely related to age and to duration of use. It was statistically significantly greater in parous subjects than in nulliparous, after stratifying for age. The estimated rates in this study do not differ markedly from those in most other prospective investigations.

Age Factors↗
PubMed1982

End-point dilution-fluorescent antibody technique for cloning hog cholera virus.

Hog cholera virus was cloned by incubating selected pretitrated dilutions of the virus on PK-15 cell cultures for 2 hours. After a thorough washing, the coverslip cell cultures were overlaid with medium containing 0.1% hog cholera immune serum to prevent secondary foci. Forty-eight hours later, the cultures were vigorously washed and maintenance medium containing 5% bovine fetal serum was added. When examined by the fluorescent antibody technique 18 hours later, single plaques were observed in some cultures with no evidence of secondary foci. The virus clone subsequently yielded a homogeneous population of hog cholera virus that retained the characteristics of the parent strain; pathogenicity of the virus clone in pigs was demonstrated, and specific immunofluorescence occurred in infected cell cultures stained with fluorescein isothiocyanate-labeled antibody. The method used gave reasonable assurance of the cloned virus' freedom from extraneous agents.

Classical Swine Fever Virus↗
PubMed1981

Field evaluation of enzyme-linked immunosorbent assay for detection of antibody to African swine fever virus.

The enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to African swine fever virus was evaluated under field conditions in the Dominican Republic. A total of 3,402 swine serums were tested by ELISA. All ELISA-positive serums (n = 224) and 426 of 2,760 ELISA-negative serums were retested by indirect immunofluorescence (IIF). There were no antibodies to ASF virus detected by IIF in ELISA-negative serums. By IIF, antibodies were detected in only a small portion of the ELISA-positive serums. The specificity and sensitivity of ELISA and IIF were investigated and discussed. It appears that poor quality serums had an effect in ELISA results. Detection of immunoglobulin (Ig) G and IgM classes of antibodies in the ELISA and IIF-positive serums were also performed and related to longevity of African swine fever virus infection. The ELISA is recommended as an efficient method in testing large number of serums; positive results are to be retested by IIF.

African Swine Fever↗
PubMed1980

Bovine viral diarrhea infection in pregnant swine.

Twenty pregnant gilts (5 groups of 4) were infected experimentally with 1 of 4 strains of bovine viral diarrhea virus (BVDV) administered intranasally-orally. Blood specimens were taken from the gilts on postinfection day (PID) 7 and cultured for virus. Serum specimens, obtained on PID 21 and at termination of the experiment, were tested for neutralizing antibodies. At 90 to 112 days of gestation, the gilts were euthanatized and their fetuses were examined for evidence of intrauterine infection. Evidence of infection was demonstrated in all of the gilts, either by isolation of BVDV at PID 7 or subsequently by detection of neutralizing antibody titers. Intrauterine infection was confirmed in one of 20 gilts by isolation of BVDV, detection of neutralizing antibodies, and demonstration of microscopic lesions in the fetuses. The microscopic lesions were characterized as nonsuppurative meningitis and choroiditis. Clinical signs of disease were not seen in the infected fetuses. Of 8 gilts exposed to strains of BVDV pathogenic for cattle, 1 gilt developed intrauterine infection, 2 gilts were found barren, and 3 gilts had significantly fewer fetuses than copora lutea.

Animals↗
PubMed1980

Isolation of pseudorabies virus from trigeminal ganglia of a latently infected sow.

A 2-year-old sow with a relatively low virus-neutralization (VN) titer (1:8) against pseudorabies virus (PRV) was brought to the National Animal Disease Center for observation and study. The sow was kept in isolation for approximately 6 weeks, and repeated nasal and tonsillar swabs for virus isolation and blood samples for VN tests were obtained during this interval. At the end of 5 weeks' observation, the sow was injected IM with 200 mg of dexamethasone and was euthanatized 1 week later. Parts of the two trigeminal ganglia, tonsillar tissue, and nasal secretions were cultured in porcine kidney cells. The rest of the trigeminal ganglia was extracted with phenol and tested for presence of the PRV-DNA genome by hybridization with tritiated complementary RNA. The PRV was isolated from the trigeminal ganglia only, and the PRV genome was demonstrated in the same tissue. This latently infected sow was a potential shedder of PRV.

Animals↗
PubMed1980

Persistent hog cholera infection detected during virulence typing of 135 field isolates.

During the hog cholera (HC) eradication program in the United States, 135 field isolates were characterized by inoculation into specific-pathogen-free pigs. This gave origin to the classification of 61 (45%) as high virulent, 37 (27%) as low virulent, 29 (22%) as avirulent or immunizing, and 8 (6%) as capable of causing persistent infection. The persistent infections caused by the eight isolates were of long durtion, lasting in one instance to 152 days. The persistently infected pigs remained relatively free of clinical signs of HC but had high concentrations of HC virus (HCV) in their blood. When 6 of these pigs were given a second inoculation (with the virulent Ames strain of HCV), 2 died while the health status of 4 remained unchanged.

Animals↗
PubMed1979

Thermal inactivation of hog cholera virus in ham.

Experiments were conducted to determine the temperatures required to inactivate hog cholera virus (HCV) in fresh ham after 1 minute and in cured and processed (canned) ham after 90 minutes. A momentary or "flash" temperature of 71 C for 1 minute caused inactivation of the virus in 15 of 15 cubes (2 cm3) of ham. Hog cholera virus was destroyed in 21 of 21 canned hams (weighing 0.91 kg each) when an internal temperature of 65 C was sustained for 90 minutes. Pigs were found to be more sensitive than tissue culture cells for detecting viable HCV in heat-processed fresh hams. Virus was isolated by tissue culture technique only from those hams exposed to temperatures below 61 C. The relative concentration of HCV in unheated cured hams of experimentally infected pigs varied over a wide range; these pigs were inoculated with the virulent Ames strain and were killed on postinfection day 6 or 7.

Animals↗
PubMed1978

Agar-gel immunodiffusion assay for pseudorabies virus antibody.

Soluble antigen prepared from pseudorabies virus-infected embryonic pig kidney cells was used to demonstrate the presence of pseudorabies virus antibodies in sera taken from naturally and experimentally infected swine. Antibody could be detected by agar-gel immunodiffusion as early as 14 days postexposure and was demonstrable at least 3 months after experimental infection (the longest period tested). The reliability of the agar-gel immunodiffusion test was comparable to that of the microtitration serum-virus neutralization test commonly used in diagnostic laboratories. One advantage of the agar-gel immunodiffusion test was that severely hemolyzed and cytotoxic serum samples could be tested with confidence. The test is simple, rapid, and inexpensive and could be easily adopted by diagnostic laboratories that receive requests for pseudorabies virus antibody determinations in swine sera.

Animals↗
PubMed1977

Tween 80: a marker for differentiation of hog cholera and bovine viral diarrhea viruses.

Markers for differentiating hog cholera and bovine viral diarrhea viruses were studied using Tween 80, chloroform, trichlorotrifluoroethane and tri (n-butyl) phosphate. Attenuated A and virulent Ames strains of hog cholera virus were employed. Moreover, the NADL PK-15 cell culture adopted strain and low cell culture passaged Purdue strain of bovine viral diarrhea virus were used. These viruses were reacted with 2,500 micrograms/ml of Tween 80 for one hour at 37 degrees C. When attenuated A and virulent Ames strains of hog cholera virus with titers greater than 10(6) and 10(5) plaque forming units respectively, were reacted with Tween 80 the titer of each strains was reduced by approximately 10(4) plaque forming units of virus. When either strain of bovine viral diarrhea virus was reacted with Tween 80, virus was not detected.

Animals↗
PubMed1977

Isolation of a new porcine enterovirus in the United States.

A cytopathogenic virus isolated from an Iowa farm pig with diarrhea was identified as a member of Group 5 of the porcine enteroviruses. Clinical signs observed in other pigs in the herd were diarrhea, debilitation and gauntness. Morbidity and mortality rates were approximately 50% and 3% respectively.A Group 5 porcine enterovirus had not been previously isolated in North America according to the Western Hemisphere Committee on Animal Virus Characterization.

Animals↗
PubMed1976

Natural infection of pigs with bovine viral diarrhea virus and its differential diagnosis from hog cholera.

Natural infection of pigs with bovine viral diarrhea virus (BVDV) through contact with infected cattle has caused problems in diagnosing hog cholera (HC). Low cross-reacting serum antibody titers against HC caused by BVDV infection were found in clinically normal pigs as well as those suspected of having HC. Bovine viral diarrhea virus was isolated from specimen tissues and initially identified as HC virus (HCV), using the fluorescent antibody cell culture technique. Additional cell cultures, as well as pig and calf trials, were necessary to identify it as BVDV. The isolate caused clinical signs of illness in the calves, whereas the pigs remained healthy. Bovine viral diarrhea virus may be detected in tissue sections or isolated in cell cultures and confirmed as HCV, using the HC fluorescent antibody conjugate. Laboratories performing the neutralization test for HC should use discretion when interpreting HC titers unless BVD titers are determined on the same serums.

Animals↗
PubMed1976

Porcine encephalomyelitis caused by hemagglutinating encephalomyelitis virus.

Six epizootics of encephalomyeltis in suckling pigs in Minnesota were attributed to infection with hemagglutinating encephalomyelitis virus. The disease occurred in 74 litters of pigs and was characterized by sudden onset of tremors, inappetence, weakness, atazia, and hyperesthesia, with high morbidity and case fatality rate. Pathologic changes consisted of marked nonsuppurative, nondemyelinating encephalomyelitis characterized by perivascular mononuclear cuffing, gliosis, neuronal death, and satellitosis. Clinical disease was limited principally to suckling pigs during a single farrowing period and did not recur in the herds involved during the ensuing 18 months.

Animals↗
PubMed1976

Sensitivity of swine buffy coat culture to infection with hog cholera virus.

The susceptibility of swine buffy coat (BC) cultures inoculated with hog cholera (HC) virus in the presence of homologous antiserum was greater than that of a pig kidney (PK-15) cell line similarly inoculated. The virus was isolated from BC cultures grown in the presence of 0.1% hyperimmune serum, whereas it could not be consistently recovered from the PK-15 cell line in which hyperimmune serum concentrations exceeded 0.025%. Maximal viral titers in BC culture were reached between postinoculation days 4 and 8. Peak titers were not influenced by the age of cells at infection or dose of virus. Data were present in support of the hypothesis that the decrease of HC viral isolations in BC cultures from HC epizootics was related to lessened use of attenuated vaccines.

Animals↗