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Biomedical subjects

W C Reeves

Publications and source records attributed to W C Reeves.

At least 163 records · Page 9Linked to original sources
PubMed1987

Evaluation of myocardial perfusion and coronary vascular resistance following withdrawal of chronic nitroglycerin treatment in rabbits.

This investigation was performed to determine whether the abrupt withdrawal of chronically administered nitroglycerin (NTG) alters coronary vascular resistance and myocardial perfusion in an experimental rabbit model. New Zealand white rabbits received 2 inches of topical NTG (2%) applied 3 times daily over a 6 week period. Forty hours after abrupt withdrawal of NTG left ventricular blood flow was assessed by the radioactive microsphere technique. Coronary resistance was significantly increased in NTG-withdrawal rabbits at the baseline (21.5 +/- 3.1) compared to controls (13.5 +/- 1.2) and remained elevated after ergonovine administration at both the early (NTG-withdrawal: 20.9 +/- 3.5 vs controls 12.6 +/- 1.5) and late (NTG-withdrawal: 17.1 +/- 3.1 vs controls: 11.6 +/- 0.9) sampling periods. Neither ergonovine nor indomethacin significantly altered blood flow compared to earlier values. However, the NTG-withdrawal rabbits exhibited significantly lower blood flow to the left ventricle compared to controls after ergonovine administration at both early (NTG-withdrawal: 4.80 +/- 0.72 ml/min/gram vs controls: 6.98 +/- 0.79 ml/min/gram) and late (NTG-withdrawal: 5.30 +/- 0.80 ml/min/gram vs controls: 7/52 +/- 0.66 ml/min/gram) sampling periods and also following indomethacin administration (NTG-withdrawal: 4.24 +/- 0.46 ml/min/gram vs controls: 7.52 +/- 1.26 ml/min/gram). Electrocardiographic evidence of myocardial ischemia was noted in the NTG-withdrawal rabbits following intracardiac injection of microspheres. These studies show that increased sensitivity of NTG-withdrawal rabbits to ergonovine or microsphere injection is associated with increased coronary vascular resistance. However, severe myocardial ischemia was not observed.

Animals↗
PubMed1986

Enzootic bovine rotavirus is not a source of infection in Panamanian cattle ranchers and their families.

Vaccination of humans against rotavirus (RV) diarrhea may be accomplished by oral immunization with attenuated animal strains known to be antigenically very similar to human strains. To define better the degree of infectivity in nature of these animal strains for humans, we conducted surveillance for RV infection/diarrhea in 180 farm workers, their 161 family contacts, and the 566 animals (512 cattle, 35 pigs, and 19 sheep) on 14 farms in rural Panama. No correlation between the high infection rates in farm workers (72%) and their family contacts (78%) and in cattle (56%) could be demonstrated. Heads of families with four or more children with RV infection experienced a twofold greater rate of RV infection compared with heads of families of similar size without RV infection. Despite the close similarity between human and bovine RV, in Panama intrafamilial (particularly child-to-child or child-to-parent) rather than interspecies transmission appeared to be the most important route for the spread of this highly infectious virus.

Age Factors↗
PubMed1986

Acute hemorrhagic conjunctivitis epidemic in Colon, Republic of Panama.

Acute hemorrhagic conjunctivitis has caused numerous outbreaks throughout Africa and Asia since it was first recognized in 1969 but did not involve the New World until 1981. This unprecedented outbreak reached Colon, Panama during August 1981 and by October 8,401 cases had been reported (14% of Colon's population). In October the Gorgas Memorial Laboratory and Ministry of Health conducted a survey in Colon to collect descriptive data on household living units, epidemiologic and clinical data from residents, and venous blood from all residents one year or older. The survey sampled 127 households and interviewed 608 people (1% of Colon's homes and 1% of the population). Overall 336 (55%) study subjects recalled having conjunctivitis. Disease rates differed according to residence; poor sectors of the city had 67% attack rates, lower class 52%, middle class 34%, and upper class 13%. Within each sector adults were more likely than children to be index cases, and communal bathrooms and household crowding were the most important risk factors for acute hemorrhagic conjunctivitis. Between 4-20% of people denying acute conjunctivitis had antibody to enterovirus 70 and may represent asymptomatic cases.

Adolescent↗
PubMed1986

Air conditioning and television as protective factors in arboviral encephalitis risk.

In California, the advent of television and air conditioned housing has coincided with a general decrease in mosquito-borne viral encephalitis cases in humans in the past 25 years. During this same period, levels of vector populations, virus activity in vectors, birds, and horses has been high at times. Air conditioning and television encourage persons to remain indoors during summer evenings, the primary time when infected Culex tarsalis transmit western equine encephalomyelitis and St. Louis encephalitis viruses. The attack rates for these 2 diseases in 33 counties in the central valley of California, 1945-1982, were compared with the prevalence of household air conditioning and television. Encephalitis rates were negatively associated with television ownership in both cross-sectional and longitudinal analysis. Moreover, individual counties which experienced the most rapid increase in household television ownership had the greatest decline in encephalitis rates. A telephone survey conducted in Kern County revealed that air conditioner and television utilization times corresponded closely to the feeding times of Cx. tarsalis, and respondents indicated a preference to remain indoors during this time because of these appliances. It is concluded that changed behavioral patterns may protect from vector-borne diseases and be complementary to vector control programs.

Air Conditioning↗
PubMed1985

Effect of diltiazem and ibuprofen on right ventricular hypertrophy in an experimental model of hypoxic pulmonary hypertension.

The effectiveness of diltiazem, a slow channel calcium blocker, ibuprofen, a nonselective inhibitor of prostanoid synthesis, and the selective inhibition of thromboxane A2 with imidazole and UK-38,485 in retarding the development of right ventricular (RV) hypertrophy was assessed in a rat model of chronic hypoxic pulmonary hypertension. Both ibuprofen and diltiazem significantly reduced RV hypertrophy in the chronically hypoxic rat. In contrast, selective inhibition of thromboxane A2 was ineffective in reducing RV hypertrophy. The beneficial effect of ibuprofen was unrelated to inhibition of thromboxane A2. Furthermore, thromboxane A2 did not appear to be involved in the development of RV hypertrophy in this experimental model of hypoxic pulmonary hypertension.

Animals↗
PubMed1985

Case control study of cervical cancer in Herrera Province, Republic of Panama.

A previous survey found the average annual age-adjusted incidence of cervical cancer in Herrera Province, Panama, to be 79/100,000, exceeding any other reported world rate. In an effort to clarify the reasons for this excessive occurrence, a case-control study was conducted among patients diagnosed between 1974-1980. Sixty-six percent of cervical cancer patients from Herrera Province were alive and were contacted by the study team; of these 91% were successfully interviewed and provided serum specimens. The total study encompassed 156/169 surviving patients and 309 age-neighborhood matched controls. Sexual promiscuity was uncommon, but it exerted a major effect, with those reporting 4 or more life-time sex partners being at a 4-fold excess risk compared to those reporting only one partner. First intercourse at a young age was common (21% began sexual activity prior to age 16) but it failed to alter risk once number of partners was taken into account. Oral contraceptive use was associated with a 2-fold excess risk and this was not substantially affected by controlling for sexual parameters. Thirty-three percent of the study subjects had anti-herpes-simplex type-2 antibody as measured by both neutralization and radioimmunoassays. Although results of the neutralization test were not predictive of risk, women with a radioimmunoassay indicative of HSV-2 infection were at a 40% excess risk for cervical cancer after adjustment for sexual characteristics.

Adult↗
PubMed1985

Coronary artery spasm after abrupt withdrawal of nitroglycerin in rabbits.

The potential for abrupt withdrawal of nitroglycerin (NTG) to create coronary artery spasm was assessed in New Zealand white rabbits. In the control setting, electrocardiograms were taken from 7 anesthetized rabbits. The administration of intravenous ergonovine did not provoke ST-segment shifts or arrhythmias. Two inches of topical NTG (2%) was applied 3 times daily to a shaved area on the back of each rabbit over a 6-week period. Forty hours after abrupt withdrawal of NTG, intravenous ergonovine and indomethacin were given. Six of 7 rabbits had electrocardiographic changes: ventricular tachycardia in 2, ventricular fibrillation in 1, and significant (1 mm or more) ST-segment shifts in 5 rabbits. Three rabbits died. Sixty-four hours after NTG administration the remaining 4 rabbits were reexamined. One had baseline electrocardiographic evidence of severe myocardial ischemia. Repeat ergonovine and indomethacin testing in the others revealed ventricular tachycardia progressing to asystole in 1, premature ventricular complexes in 1, and ST-segment elevation in another. Two of the remaining 4 rabbits died. Eighty-two hours after NTG administration the remaining 2 rabbits were found dead in their cages. Nitroblue tetrazolium studies revealed extensive myocardial infarction in both animals. Additional studies were performed in 10 normal rabbits. Neither ergonovine nor indomethacin induced ST-segment shifts or arrhythmias in this control population.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Herpes simplex virus type 2 and human papillomavirus type 16 in cervicitis, dysplasia and invasive cervical carcinoma.

Sera and biopsies of cervical lesions from 55 women with benign or malignant disease were analyzed for evidence of infection with herpes simplex virus type 2 (HSV-2) or human papillomavirus (HPV). In addition, information regarding known risk factors for cervical cancer was obtained by interview. The sera were tested for HSV-2 antibodies and the biopsies were tested for HPV or HSV DNA sequences by Southern blot hybridization. HSV-2 sequences were detected in 2/13 (15%) invasive neoplasms and in 1/12 (7%) benign lesions. Under non-stringent conditions of hybridization, reactions with HPV DNA were detected in biopsies of 2/17 (12%) inflammatory lesions, 6/12 (50%) intraepithelial neoplasms and 13/20 (65%) invasive neoplasms. All but one of the positive biopsies of invasive cancer, but only 4/11 biopsies of non-invasive lesions, contained HPV-16 DNA as determined by stringent hybridization conditions. Women with cervical cancer possessed the risk factors associated with the disease. Cigarette smoking and the presence of HPV-16 DNA were the most prominent risk factors. No evidence of an interaction between HSV-2 and HPV-16 was found among the cases of invasive cervical cancer.

Adult↗
PubMed1985

Evidence of immunity induced by naturally acquired rotavirus and Norwalk virus infection on two remote Panamanian islands.

For better understanding of the role of humoral immunity in ameliorating infections with rotavirus (RV) and Norwalk virus (NW), 305 Cuna Indians living on two isolated islands located off Panama's Carribean coast were surveyed daily for diarrhea over a seven-month period. Nine (8%) of 108 persons with a baseline RV antibody titer of greater than 1:4 developed RV infection compared with 70 (46%) of 151 persons with a baseline RV antibody titer of less than 1:4 (P less than .001). Thirty-eight (25%) of 151 persons of all ages with baseline RV antibody titer of less than 1:4 had at least one episode of RV diarrhea compared with 6 (6%) of 108 persons who had baseline RV antibody titers of greater than 1:4 (P less than .001). Thirty-two (47%) of 68 persons of all ages who had a baseline NW antibody titer of less than 1:100 developed NW infection compared with 30 (13%) of 237 persons with a baseline NW titer of greater than 1:100 (P less than .001). The high NW and RV infection rates and the excellent levels of protection provided by specific preexisting humoral antibody to these agents should promote activities aimed at developing vaccines for preventing these infections.

Age Factors↗
PubMed1985

Risk factors for fatal childhood diarrhea: a case-control study from two remote Panamanian islands.

Between September 1979 and March 1980, distinguishing features between fatal and nonfatal cases of diarrhea caused by the same etiologic agents were sought in a case-control investigation of Cuna Indian children living on the San Blas Islands located off Panama's Caribbean coast. The eight fatal cases of diarrhea (four associated with rotavirus, one with Giardia lamblia, and three without identifiable pathogens), which occurred in a cohort of 186 children aged less than five years who were followed for seven months, were matched with 24 contemporaneously occurring nonfatal cases of diarrhea. Weight-for-length measurements falling below the 90th percentile of the reference standard, reliance on traditional rather than equally as available Western medicine, and failure to receive oral rehydration solution were significantly more common among fatal than nonfatal cases. Incorporating traditional medicine men with their long-standing village-wide authority into expanded community health education programs that emphasize the importance of early treatment of diarrhea with oral rehydration solution would probably reduce mortality associated with diarrheal illness in this population.

Child, Preschool↗
PubMed1985

Ineffectiveness and toxicity of BCG vaccine for the prevention of recurrent genital herpes.

One hundred fifty-five patients with genital herpes were enrolled in a double-blind, placebo-controlled trial comparing 0.1 ml of intradermal BCG vaccine with placebo for the prevention of recurrent episodes of genital herpes. The mean rate or recurrence over 9 months of prospective follow-up was 0.528 recurrences per month in BCG recipients compared with 0.392 recurrences per month in placebo recipients (not significant). The BCG vaccine also failed to influence the duration of lesions in the first recurrent episode of genital herpes after vaccination. Six patients were given a second inoculation of BCG vaccine, and persistent cutaneous granulomas were noted in three of these six patients. Intradermal inoculation with BCG does not appear to affect the natural history of genital herpes, and repeated inoculations can be toxic.

Adult↗
PubMed1985

Effect of normal mosquito extracts upon arbovirus recoveries from mosquito pools.

Titers of Turlock (TUR) and Hart Park (HP) viruses were reduced to undetectable levels when virus was mixed with a triturated suspension of uninfected (normal) 4th instar larvae of Culex tarsalis prior to plaque assay in cell culture. There was a linear relationship between the number of larvae in the pool and the titer of virus recoverable. Virus was undetectable when 1,000-10,000 PFU of either agent was added to pools that contained 25 or more larvae. Suspensions of up to 25 adult male or female Cx. tarsalis had little effect on detectable viral titers while pupal suspensions had an intermediate effect. The inhibitory effect of normal larval extracts on viral infectivity could be counteracted by use of polycations or a high pH buffer. A similar reduction in titer of TUR virus was observed with extracts of larvae of Aedes melanimon or Anopheles franciscanus. Larval extracts of Cx. tarsalis similarly reduced titers of California and St. Louis encephalitis viruses but not western equine encephalomyelitis virus. These findings may have significant bearing on the interpretation of transovarial transmission attempts in which pooled larvae are assayed for virus.

Aedes↗
PubMed1985

The childhood health effects of an improved water supply system on a remote Panamanian island.

The incidence of diarrhea, respiratory disease, and skin infections was prospectively determined after the introduction of a system which distributed unlimited quantities of high quality fresh water to each of the 150 housing units on Tupile, an island devoid of fresh water located off Panama's Caribbean coast and inhabited by 1,500 Cuna Indians. Tupile residents used 7.1 liters of water/person/day compared to the 2.3 usage rate of inhabitants on Achutupo, the control island. Despite ready availability of water in each household, Tupile residents continued to store water in contaminated vessels prior to use. Forty percent of stored water samples tested on Tupile and 45% on Achutupo were contaminated with E. coli organisms. There were 4.7 episodes/child year (E/Y) of acute diarrhea on Tupile compared with the 3.5 rate on Achutupo. The rotavirus infection rate on Tupile was 0.8 E/Y compared with 0.2 E/Y on Achutupo. Infection rates for Norwalk virus, respiratory syncytial virus and Coxsackie B 1-6 viruses were similar on both islands. Respiratory disease rates were high on both islands (2.2 E/Y on Tupile, 2.7 E/Y on Achutupo). Achutupo had much higher rates of impetigo and scabies (0.6 E/Y and 2.5 E/Y, respectively) than Tupile (0.2 E/Y and 1.4 E/Y). Provision of the water distribution system had a beneficial effect on the incidence of water-washed diseases (impetigo and scabies), but at best had no effect on diarrheal disease.

Child↗