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Biomedical subjects

W C Reeves

Publications and source records attributed to W C Reeves.

At least 109 records · Page 6Linked to original sources
PubMed1991

Occurrence and evolutionary significance of a California encephalitis-like virus in Aedes squamiger (Diptera: Culicidae).

More than 12,000 Aedes increpitus Dyar and 4,600 Aedes squamiger (Coquillett) were tested for the presence of arboviruses to test the hypothesis that there is a coevolutionary relationship between Aedes (Ochlerotatus) mosquitoes and California serogroup viruses. Five strains of a California encephalitis-like virus were isolated from adults reared from larvae of Ae. squamiger collected in January 1989 from a coastal salt marsh at Morro Bay, San Luis Obispo County, California. Viruses were isolated in Vero cell cultures and serotyped by cross-neutralization tests. These isolates represent the first arboviruses isolated from this species. On the basis of morphology, Aedes squamiger has been included in the Aedes stimulans group of the subgenus Ochlerotatus. Other species within the Ae. stimulans group are vectors of California (CAL) serogroup viruses elsewhere in North America. Analysis of isozyme variability supports the inclusion of Ae. squamiger in the Ae. stimulans group and suggests that coastal populations of Ae. increpitus are the closest California relatives of Ae. squamiger. Recovery of virus from Ae. squamiger reinforces the relationship between CAL serogroup viruses and Aedes (Ocherlotatus) mosquitoes. However, the failure to isolate virus from large samples of Ae. increpitus from coastal and low elevation inland habitats suggests a complex evolutionary history involving both vertical and horizontal transmission mechanisms.

Aedes↗
PubMed1991

Myocardial imaging artifacts caused by mitral valve annulus calcification.

Knowledge of imaging artifact of myocardial perfusion studies with thallium-201 is critical for improving the diagnostic accuracy of coronary artery disease. Three patients are described who underwent exercise or pharmacologic stress thallium-201 imaging studies and had a moderate, fixed myocardial perfusion defect (scar) involving the posterolateral and inferoposterior walls of the left ventricle. This was an imaging artifact caused by a heavily calcified mitral valve annulus.

Aged↗
PubMed1991

Isolation of Jamestown Canyon virus from boreal Aedes mosquitoes from the Sierra Nevada of California.

More than 28,000 mosquitoes in four genera were collected from high elevation (greater than or equal to 1,000 m) areas of California during 1988-89 and tested for virus by plaque assay in Vero cells. Viruses were serogrouped by enzyme immunoassay and serotyped by cross-neutralization. Six strains of Jamestown Canyon virus in the California serogroup were isolated from three species of boreal Aedes in the Aedes communis group of the subgenus Ochlerotatus. All isolates were from mosquitoes collected in Alpine County at approximately 2,300 m elevation in the Sierra Nevada. These included one virus from a pool of male Aedes cataphylla collected in immature stages, which is evidence for vertical transmission; four viruses from adult female Ae. communis (sens. lat.); and one virus from adult female Aedes hexodontus. These are the first isolations of viruses from boreal Aedes mosquitoes in California and the first reported isolations of Jamestown Canyon virus from Ae. cataphylla or Ae. hexodontus.

Aedes↗
PubMed1991

Isolation of Northway serotype and other Bunyamwera serogroup bunyaviruses from California and Oregon mosquitoes, 1969-1985.

Eight previously untyped Bunyamwera serogroup bunyaviruses that had been isolated from mosquitoes collected in California and Oregon between 1969 and 1985, were identified by cross-neutralization tests. Four viruses from Anopheles freeborni and a virus from Aedes sierrensis collected in Butte County in the Central Valley of California in 1970-71 were shown to belong to the Northway serotype. The existence of a Northway serotype virus in California had been inferred from previous serologic surveys of deer and horses, but these are the first Northway serotype viruses to be identified from the contiguous United States or from An. freeborni. This is also the first isolation of any virus from Ae. sierrensis. Two viruses from Culiseta inornata collected in Umatilla County, Oregon in 1969 may represent a new serotype in the Bunyamwera serocomplex of the Bunyamwera serogroup. The name "Stanfield" is proposed for this serotype, which is closely related to the Cache Valley and Northway bunyavirus serotypes. A virus from Ae. taeniorhynchus collected in San Diego County, California in 1985 was confirmed to belong to the Main Drain serotype. Previously, Main Drain serotype viruses in California have been associated principally with Culicoides variipennis.

Aedes↗
PubMed1991

Experimental studies to determine the susceptibility to infection with St. Louis encephalitis virus of five species of Panamanian mosquitoes.

The susceptibility to infection with a Panamanian isolate of St. Louis encephalitis (SLE) virus was evaluated in Culex quinquefasciatus, Haemagogus equinus, Mansonia dyari, Sabethes cyaneus and Deinocerites pseudes. When fed on blood-virus suspensions using the hanging drop or pledget technique, the median infective dose (ID50) of SLE virus for colonized strains of Cx. quinquefasciatus and Hg. equinus was 10(2.8) plaque forming units (PFU)/2 microliters and 10(3.5) PFU/2 microliters, respectively. The susceptibility of F1 and F2 Cx. quinquefasciatus females was similar to the colonized strain by the same technique. When fed on viremic chicks, the ID50 for both Cx. quinquefasciatus and Hg. equinus was 10(0.5) PFU/2 microliters. These results and successful transmission trials indicate that both of these species have the potential to serve as vectors of SLE virus in Panama. Because of their poor feeding response, complete susceptibility profiles were not obtained for the other 3 species tested. They appear to be less susceptible than Cx. quinquefasciatus and Hg. equinus, although Ma. dyari was readily infected after engorging on a blood-virus suspension with a titer of 10(3.0) PFU/2 microliters.

Animals↗
PubMed1991

Considerations for conducting epidemiologic case-control studies of cancer in developing countries.

The challenges involved in conducting epidemiologic studies of cancer in developing countries can be and often are unique. This article reports on our experience in performing a case-control study of invasive cervical cancer in four Latin American countries (Columbia, Costa Rica, Mexico, and Panama), the summary medical results of which have been published in a previous issue of this journal (1). The study involved a number of principal activities--mainly selecting, conducting interviews with, and obtaining appropriate biologic specimens from 759 cervical cancer patients, 1,467 matched female controls, and 689 male sex partners of monogamous female subjects. This presentation provides an overview of the planning and methods used to select the subjects, conduct the survey work, and obtain complete and effectively unbiased data. It also points out some of the important advantages and disadvantages of working in developing areas similar to those serving as locales for this study.

Case-Control Studies↗
PubMed1990

Occurrence of IgA and IgG antibodies to select peptides representing human papillomavirus type 16 among cervical cancer cases and controls.

We used an enzyme-linked immunosorbent assay to test sera from 186 cases of invasive cervical cancer and 172 age-matched controls for IgG and IgA antibodies to an human papillomavirus 16 E7 peptide and to peptide 245, representing an epitope in E2. Cases had significantly higher mean absorbance values than controls for both immunoglobulin isotypes to E7 and elevated mean values for IgG to peptide 245. Since absorbances were not normally distributed we analyzed cervical cancer risk for seropositive and seronegative women. Of the traditional cervical cancer risk factors, cigarette smoking, educational level, number of pregnancies, time interval since last Papanicolaou smear, and age at first intercourse influenced the distribution of seropositivity to some of the viral antigens. Adjusting for these variables, the odds ratios of cervical cancer associated with IgG to E7 was 5.28 [95% confidence (95% CI) = 2.4-11.6] and that with IgA to E7 was 2.67 (95% CI = 1.3-5.3). IgG to peptide 245 was less strongly associated, odds ratio 1.68 (95% CI = 1.2-3.3), and IgA to peptide 245 was not significantly associated with disease. These findings suggest that antibodies to E7 are markers for invasive cervical cancer. However, seropositivity correlated poorly with clinical state, survival, or the presence of human papillomavirus DNA in the cancer tissue.

Antibodies, Viral↗
PubMed1990

Injectable contraceptives and risk of invasive cervical cancer: evidence of an association.

In a case-control study conducted in Latin America, the relationship of injectable contraceptive (IC) use to risk of invasive cervical cancer was analyzed while controlling for a variety of other risk factors, including female and spouse sexual behavior and infection with human papillomaviruses (HPV). Thirty-two cases and 82 controls reported ever having used IC. Women reporting use of IC for less than 5 years had an adjusted RR of 0.5 (95% Cl = 0.3-0.9), but users for 5 or more years had an RR of 2.4 (95% Cl = 1.0-5.7). The effect of prolonged IC use was stronger for women reporting first use 10 or more years before interview (adjusted RR = 3.4, 95% Cl = 1.1-24.9) and more than 5 years since last use (adjusted RR = 5.3, 95% Cl = 1.1-10.0). Cervical cancer risk associated with prolonged IC use was particularly high among women who reported never having had a Pap smear or having had one 2 or more years before interview (adjusted RR = 6.3, 95% Cl = 2.1-18.7). The reduced cervical cancer risk associated with short-term use of IC may reflect intensive Pap smear screening as the method is initiated. Although hampered by small numbers, these results suggest an adverse effect of prolonged IC use on cervical cancer risk, particularly among women who cease participation in screening programs after terminating usage, and indicate that long-term IC users should be monitored for cervical disease until more conclusive results are available.

Case-Control Studies↗
PubMed1990

Association of oral contraceptive use and human papillomaviruses in invasive cervical cancers.

In a study of 197 cases of histologically confirmed invasive cervical cancer, 61% of biopsies were positive for human papillomavirus (HPV) DNA by Southern or dot-blot hybridization. An association between detection of HPV DNA and oral contraceptive use was observed when HPV-positive and -negative cases were compared. Women reporting recent or long-term (greater than 4 yrs) oral contraceptive use were at 2.3 and 2.9-fold increased risks of HPV positivity, respectively. An increased risk of HPV positivity was also associated with formal education and with urban residence, while long-term smoking was negatively associated with HPV detection. A non-significant trend of increasing risk of HPV positivity with increasing number of sexual partners of the women and of the male partners of monogamous women was observed. Detection of HPV DNA was not associated with other cervical cancer risk factors examined, including age at first coitus, number of pregnancies, and Pap smear screening history. Our findings suggest either an interaction between HPV infection and oral contraceptive use in the genesis of cervical cancer or an increased expression of HPV genome in neoplasms of oral contraceptive users. These observations also support a multifactorial model of cervical cancer causation.

Adult↗
PubMed1990

Exacerbation of doxorubicin cardiotoxicity by digoxin administration in an experimental rabbit model.

The relationship between digoxin administration and the development of doxorubicin cardiomyopathy was evaluated in a chronic experimental rabbit model. We graded the myocardial pathology by conventional light microscopic histologic techniques. Additionally, myocardial fibrosis was quantified by hydroxyproline determinations and myocardial cellular damage by technetium-99m pyrophosphate uptake. Twenty-four rabbits were studied: 6 control, 6 doxorubicin-treated, and 12 digoxin-doxorubicin-treated. Mortality in the digoxin-doxorubicin group was 50%. All other rabbits lived throughout the entire experiment. The severest grades of histologic lesions were seen only in the digoxin-doxorubicin group. Myocardial hydroxyproline content was greater (p less than 0.05) in the digoxin-doxorubicin group than in the doxorubicin or control groups. Myocardial technetium-99m pyrophosphate content was also significantly greater (p less than 0.05) in the digoxin-doxorubicin group than in controls. In conclusion, the pretreatment and continued administration of digoxin, together with doxorubicin, increased the severity of myocardial damage and reduced longevity in this experimental model of doxorubicin cardiotoxicity.

Animals↗
PubMed1990

Sexual behavior, venereal diseases, hygiene practices, and invasive cervical cancer in a high-risk population.

A case-control study of 759 women with invasive cervical cancer and 1430 controls in four Latin American countries evaluated risk in relation to sexual behavior, histories of specific venereal diseases, and hygiene practices. Early age at first sexual intercourse and increasing number of sexual partners were associated with significantly increased risks even after adjustment for their mutual effects. Risk increased to a twofold excess among women reporting first intercourse at 14 to 15 years of age compared with 20+ years. The number of steady sexual partners was a more important predictor of risk than the number of nonsteady partners, particularly before age 30, possibly reflecting the need for prolonged or repeated exposures to a transmissible agent, or different methods of protection against sexually transmitted diseases or pregnancy. Reported frequency of intercourse was not generally associated with risk, except among women reporting increased frequencies before 20 years of age. Histories of gonorrhea or crab lice were associated with increased risk, but histories of other venereal diseases were not significant predictors. No consistently increased risks were detected for women reporting specific hygiene or douching habits, except the practice of washing the genitalia infrequently during menstruation. These results provide support for a period of increased susceptibility to carcinogens during adolescence, and suggest that this may be an important determinant of the high incidence of cervical cancer in Latin America.

Adolescent↗
PubMed1990

Human T-cell lymphotropic virus type I and neurologic disease in Panama, 1985 and 1986.

Human T-cell lymphotropic virus type I (HTLV-I) causes adult T-cell leukemia and has recently been associated with HTLV-associated myelopathy/tropical spastic paraparesis. The HTLV-I is endemic throughout the Caribbean basin and parts of South America, and HTLV-associated myelopathy/tropical spastic paraparesis also seems to be common in this area. This 2-year study, 1985 and 1986, was designed to evaluate the occurrence of HTLV-I infection in all newly diagnosed cases of selected neurologic diseases in Panama City, Panama. Six (8%) of 71 patients had antibody to HTLV-I detected by immunofluorescence, enzyme-linked immunosorbent assay, radioimmunoassay, and Western blot assays; 5 patients' conditions were diagnosed as spastic paraparesis, and all 5 were seropositive and also had HTLV-I antibody in cerebrospinal fluid. The remaining seropositive patient had multiple sclerosis, and no antibody was detected in her cerebrospinal fluid. Clinical and electrophysiologic studies indicated that HTLV-I-associated spastic paraparesis is a multifocal, primarily demyelinating disease that principally involves the spinal cord.

Adult↗
PubMed1990

Oral contraceptive use and risk of invasive cervical cancer.

A case-control study of 759 invasive cervical cancer patients and 1430 controls in Panama, Costa Rica, Colombia and Mexico enabled an evaluation of risk in relation to oral contraceptive use. Overall use was associated with a 21% nonsignificant elevation in risk, with some further increases in risk for more extensive durations of use. Although risks were similar for recent and non-recent users (RRs = 1.3 versus 1.2), recent long-term users were at highest risk (RR for 5+ years use = 1.7, 95% Cl 1.1-2.6). Relationships were similar for women with and without a recent Pap smear, arguing against detection bias. There was little evidence that other risk factors, including smoking and detection of human papillomaviruses (HPV), altered the effects of oral contraceptives. The risk associated with oral contraceptives was significantly increased for adenocarcinomas (RR = 2.2), whereas for squamous cell tumours the effect was minimal (RR = 1.1). These results provide some support for an adverse effect of oral contraceptives on cervical cancer risk, although possibly limited only to a subpopulation of cases.

Adenocarcinoma↗
PubMed1990

Echocardiographic contrast in two-dimensional echocardiography: new applications for an old technique?

Although Gramiak and Shah first introduced the technique of using contrast enhanced two-dimensional echocardiography in 1968, it has seen a resurgence of new and varied applications. Three of the areas of interest are in the use of microbubble enhanced contrast agents to evaluate: (1) regional myocardial blood flow; (2) regional myocardial function; and (3) myocardial ischemic areas and infarct size. Whether these new approaches will have applications and value in the clinical laboratory is still a matter of conjecture. The objective of this review is to briefly summarize the potential uses and the advantages and disadvantages of each application.

Animals↗
PubMed1990

Quantification of acute aortic regurgitation by color Doppler flow in an experimental animal model.

Color Doppler flow studies were performed on ten anesthetized open-chest dogs. Acute aortic regurgitation was created in the dogs by a special valve-spreading catheter. The magnitude of valvular regurgitation was determined by aortic electromagnetic flow recordings of regurgitant fraction. Arbitrarily-designated grades of aortic regurgitation: mild (4%-10%), moderate (11%-30%), and severe ( greater than 30%) were assigned on the basis of electromagnetic flow. We attempted to obtain studies of varying degrees of AR in each animal. Mean regurgitant fraction for the three grades were 6.8 +/- 0.6% (n = 11), 22.0 +/- 2.4% (n = 7), and 40.4 +/- 2.5 (n = 20), respectively (each P less than 0.05). By color Doppler flow assessment, the ratio of regurgitant jet height to the left ventricular dimension at the junction of the left ventricular outflow tract and the aortic annulus (JH/LVOH) was measured in each study. AR was classified by Doppler as grade I (mild), 1%-24%; II (moderate), 25%-64%; and III (severe), greater than or equal to 65% jet height/left ventricular outflow tract height. Color Doppler flow correlated well with flowmeter assessment of regurgitant fraction. Color Doppler flow tests had a calculated sensitivity of 88%, specificity of 83%, and predictive value of 85% for significant (moderate + severe) aortic regurgitation. Our data support the concept that this method of color Doppler flow assessment provides a quantitative noninvasive evaluation of aortic regurgitation.

Animals↗
PubMed1990

Evaluation of a technique for avoiding inadvertent myocardial laceration in an experimental canine model: expansion of the role of two-dimensional echocardiography.

An experimental animal model was utilized to evaluate the role of simultaneous two-dimensional echocardiography combined with a modified electrocardiographic monitoring technique for improving the safety of pericardiocentesis. This technique avoids the hazards of placing the sharp pericardiocentesis needle against the heart in order to determine its location against the epicardial surface. This technique was evaluated in eight dogs in over 100 aspiration attempts. Cardiac trauma occurred only in a single incidence with the use of a 20-gauge cannula. A detailed description of this procedure is provided in the text.

Animals↗