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Biomedical subjects

G C Smith

Publications and source records attributed to G C Smith.

At least 253 records · Page 14Linked to original sources
PubMed1989

Surveillance of St. Louis encephalitis virus vectors in Grand Junction, Colorado, in 1987.

Grand Junction, Colorado, was the site of a St. Louis encephalitis (SLE) outbreak in 1985. Epidemiologic and ecologic investigations in 1985 and 1986 suggested that Culex tarsalis may not have been the exclusive vector in the outbreak and that Cx. pipiens may have contributed to transmission as an accessory vector. A limited field study in 1987 generally confirmed observations from 1986 that Cx. pipiens was more abundant than Cx. tarsalis in late summer when SLE virus transmission normally occurs. In both years, infection rates in Cx. tarsalis were higher than in Cx. pipiens, but in 1987 the only SLE virus isolate from Cx. pipiens was obtained early in the season. Truck trap collections showed that Cx. pipiens was the principal vector species collected, comprising 86% of the total. Light trap collections underestimated the population of Cx. pipiens; gravid trap collections gave a closer approximation of the relative proportions of Cx. pipiens and Cx. tarsalis in the vector mosquito population after midsummer.

Animals↗
PubMed1988

A novel method for nucleic acid sequence determination.

We describe a novel sequencing methodology which should be readily and completely automated. The method relies on fragmentation of a nucleotide or deoxynucleotide sequence into short fragments, and subsequent quantitation of the fragments by hybridization to oligo-deoxynucleotides on a solid support. The original sequence may be reconstructed from the resulting table of fragment frequencies. We present a specific protocol which would allow practical implementation of this approach.

Base Sequence↗
PubMed1988

Observations on dopamine receptor antagonists and gastric ulceration associated with experimental anorexia cachexia.

Gastric ulceration is frequently reported to occur in tumour-bearing animals and man, even when such tumours are not associated with organs of digestion. That central and peripheral dopamine (DA) containing neurones may be relevant to this phenomenon, is supported by the fact that the DA receptor antagonists domperidone (0.1 and 0.05 mg/kg) and pimozide (0.1 mg/kg) were observed to prevent gastric ulceration commonly reported in rats bearing the Walker 256 carcinosarcoma. Daily administration of these drugs prevented the formation of ulcers similar to those observed in vehicle-treated animals. These results demonstrate that DA neurone function is important in the formation of gastric ulcers in tumour-bearing animals and suggest that such compounds may be useful in cancer management.

Animals↗
PubMed1988

i.r. Beta-endorphin, corticosterone, cholesterol and triglyceride concentrations in rat plasma after stress, cingulotomy or both.

Plasma i.r. beta-endorphin, corticosterone, cholesterol and triglyceride concentrations were determined in male Sprague-Dawley rats after exposure to running or swimming stressors or after surgical ablation of the cingulum bundle. While cingulotomy alone altered only the plasma triglyceride concentrations, the combination of cingulotomy plus running stress significantly increased plasma i.r. beta-endorphin and triglyceride concentrations above those seen in animals receiving only a running stress. Triglyceride concentrations in cingulotomy plus swimming stress were significantly elevated above those in animals receiving a severe stress only. While the exposure to running and swimming increased plasma beta-endorphin significantly above control levels, plasma corticosterone was not affected by these stressors. Changes in plasma cholesterol and triglycerides were also differentially affected by cingulotomy or stress exposure. These results indicate that various stress hormones are affected differentially by exposure to various experimental procedures which are employed as stressors.

Animals↗
PubMed1988

Facilitation of cancer-associated anorexia by cholecystokinin.

Cholecystokinin octapeptide (CCK-8, 5 micrograms/kg) was injected i.p. into male Sprague-Dawley rats bearing the Walker 256-carcinosarcoma, or into non-tumour bearing controls, on a 20-h food deprivation schedule. Food and water intake and body weight maintenance were monitored for 15 days after tumour implantation and compared to that of tumour-bearing animals not injected with CCK-8. Food intake was significantly reduced for the duration of the two 4-day periods of CCK-8 injection, indicating that behavioural tolerance to this peptide did not occur. The severity of anorexia and body weight loss in tumour-bearing animals was significantly greater than that observed in non-tumour bearing controls, for the first 13 days of observation. These results indicate that endogenous peptides, such as CCK, may function in tumour-bearing animals to enhance the anorexia and wasting which typifies the anorexia cachexia syndrome.

Animals↗
PubMed1988

Cingulotomy in the rat fails to block opiate withdrawal effects but elevates stress-induced plasma beta-endorphin.

1. Male, albino, Sprague Dawley rats underwent surgical cingulotomy or sham operation and were then implanted with subcutaneous morphine pellets or exposed to forced running. 2. The conditions of cingulotomy or forced running alone did not cause a significant increase in plasma i.r. Beta endorphin concentrations. 3. The combined treatment of cingulotomy plus forced running caused a significant elevation of plasma beta-endorphin concentrations. 4. The cingulum is involved in the elicitation of stress hormone responses in the rat.

Animals↗
PubMed1988

Psychoanalysis today.

Psychoanalysis as a theory has permeated Western culture in a way that often no longer is conscious. Psychoanalysis as a practice has had a more visible and stormy progress. A similar fate has befallen behavioural, biological, cognitive and social psychology, and it is argued that the attractiveness of reductionism acts to prevent critical appraisal of psychoanalysis and of the other paradigms.

Biological Psychiatry↗
PubMed1988

Indomethacin, but not oxygen tension, affects the sensitivity of isolated neonatal rabbit ductus arteriosus, but not aorta, to noradrenaline.

The effects of increasing oxygen tension from fetal to neonatal levels and of incubation in the cyclo-oxygenase inhibitor, indomethacin, on the response of isolated rings of neonatal rabbit ductus arteriosus and aorta to noradrenaline were studied in vitro. Increasing oxygen tension did not affect the sensitivity, as measured by the pEC50, of either vessel to noradrenaline. Incubation with indomethacin increased ductal sensitivity to noradrenaline tenfold, but had no effect on the aortic response. Since indomethacin caused the ductus arteriosus to contract (by the removal of dilator prostaglandins), the effect of increased muscular tone per se on the response to noradrenaline was investigated by eliciting a contracture by potassium induced depolarisation. This procedure did not alter the vessel's sensitivity to noradrenaline and reduced its maximum response (indomethacin had increased the maximum response). It is concluded that intramurally synthesised cyclo-oxygenase products, most probably prostaglandins, attenuate the sensitivity of the ductus arteriosus to noradrenaline.

Animals↗
PubMed1988

Entomologic studies after a St. Louis encephalitis epidemic in Grand Junction, Colorado.

In 1986, after a St. Louis encephalitis epidemic in Grand Junction, Colorado, in 1985, vector mosquitoes in the city were surveyed to correlate their bionomics and infection rates with the occurrence of human disease. No human cases were reported, but mosquito surveillance disclosed St. Louis encephalitis virus in Culex tarsalis and Culex pipiens pipiens. Mosquitoes were collected with gravid traps designed to attract Cx. p. pipiens and with Centers for Disease Control light traps. Culex p. pipiens was the predominant vector mosquito collected and was captured chiefly in gravid traps. The Culex tarsalis population emerged and expanded approximately one month earlier than did the Cx. p. pipiens population. Consequently, Cx. p. pipiens was the predominant vector species after August. Infection rates throughout the surveillance period (June to September) were severalfold higher in Cx. tarsalis than in Cx. p. pipiens; however, in late summer, diminished numbers of Cx. tarsalis and a persistent population of Cx. p. pipiens resulted in relatively larger numbers of infected Cx. p. pipiens. Thus, the participation of Cx. p. pipiens as a St. Louis encephalitis vector would have been underestimated in previous studies employing light traps alone. These studies provide further evidence that Cx. p. pipiens-associated urban St. Louis encephalitis and rural Cx. tarsalis-associated St. Louis encephalitis cycles may coexist in the West.

Animals↗
PubMed1988

Vitamin D-dependent calcium binding protein in rat uterus: differential effects of estrogen, tamoxifen, progesterone, and pregnancy on accumulation and cellular localization.

The present studies were undertaken to characterize the expression of calcium binding protein (CaBP or calbindin-D9k) in uterine tissues. Using immunohistochemical techniques, calbindin-D9k was localized to the uterine (luminal) epithelium of pregnant rats, but not present in the uterine epithelium of nonpregnant rats. Calbindin was found also in the uterine smooth muscle and endometrial stromal cells of pregnant animals. These latter localizations were reproduced in uteri of 21-day-old nonpregnant rats by administration of tamoxifen or physiological doses of estrogens. Estrogen and tamoxifen produced half-maximal increases of uterine calbindin at daily doses of 0.1 and 10 micrograms, respectively, and maximal responses at 0.3 and 40 micrograms/day. Testosterone and progesterone, at doses which increased the growth of the uterus, did not induce calbindin-D, and both hormones blocked estradiol's effect on uterine calbindin-D appearance. The epithelial localization of calbindin in pregnant uteri was not reproduced in nonpregnant animals by either estradiol (3 micrograms/day) or progesterone (1 mg/day). The localization of calbindin in uterine epithelium during pregnancy appears to be dependent upon an as yet unknown factor. In view of the large surface area of the luminal epithelium in pregnant animals, and the pregnancy-related expression of calbindin in these cells, we propose that uterine epithelium plays an important role in transport of calcium during pregnancy.

Animals↗
PubMed1988

Importation of Aedes albopictus and other exotic mosquito species into the United States in used tires from Asia.

Between May 18 and December 4, 1986, 79 seagoing containers and their contents of 22,051 used tires were inspected for adult mosquitoes as well as eggs and larvae. Of the total inspected, 5,507 tires (25%) contained significant amounts of water. No adults or eggs were found. Fifteen tires contained mosquito larvae that were identified as Ae. albopictus, Ae. togoi, Culex pipiens complex, Tripteroides bambusa and Uranotaenia bimaculata. The infestation rate for all species was 6.8 infested tires per 10,000 tires (wet and dry) inspected. Aedes albopictus larvae were most frequently collected, occurring at a rate of 20 infested wet tires per 10,000 inspected.

Aedes↗
PubMed1987

Further studies on the neurochemical specificity of 6-hydroxydopamine as compared to radiofrequency lesions.

Despite the large volume of literature during the past 15 years addressing the problem concerning the neurochemical specificity of 6-hydroxydopamine (6-OHDA), there is still disagreement over this issue. While some claim that the catecholamine-specific effects of this drug can be maximized by controlling the dose injected, others claim that all doses of 6-OHDA produce non-specific damage (NSD), thereby contraindicating its use in experimental paradigms. In the present study, we examined the degree of neurochemical specificity of 6-OHDA by comparing the volume of proximal accumulation to that of NSD, produced by 6-OHDA (2 microliter of 8 micrograms/microliter) or radiofrequency (RF) lesions (60 degrees C for 50 s and 45 degrees C for 30 s), placed in the medial forebrain bundle. The volume of NSD and accumulation produced by 6-OHDA was significantly less than that produced by large RF lesions which had a similar effect on the gross behaviour of albino rats. Smaller RF lesions produced similar volumes of NSD but less amine accumulation than did 6-OHDA, and did so without affecting normal behaviour. The ratio of NSD to accumulation in 6-OHDA treated rats was 3/1, while large and small RF lesions produced a NSD/accumulation ratio of 15/1. The present study introduces a novel method of determining the degree of neurochemical specificity which can be achieved with 6-OHDA and reveals that it is several magnitudes more neurochemically specific than RF lesions.

Animals↗
PubMed1987

MPTP, impairment of motor performance and amine accumulation in Macaca fascicularis.

The selective neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was injected (IV) into monkeys (Macaca fascicularis) in two different injection regimes. With the small dose regime, one monkey was injected with 0.25 mg/kg, every other day, over a 16 day period. In the large dose regime, another monkey was injected with 0.5 mg/kg every other day, over an 8 day period. While the time required for drug delivery was varied between animals, the total dose delivered was 2 mg/kg in both animals. Before, during and for 14 days after the course of drug administration both animals were assessed on several motor function tests. The animal receiving the small dose regime showed normal motor performance on all tests for the duration of the study, however, the monkey receiving the large dose regime displayed progressive akinesia, muscular rigidity, and aphagia. In fact, impairment was so severe that this animal had to be force fed and maintained with daily oral L-dopa. Fluorescent histochemical assessment of forebrain in both monkeys revealed that striatal tissue was totally devoid of fluorescence in both cases. Large, swollen axons in the internal capsule, hypothalamus and midbrain were visible only in the severely impaired animal. These results suggest that, as with other neurotoxins, degeneration associated increases in amines may be important in the aetiology of Parkinson-like motor impairment produced by selective neurotoxins.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1987

Epidemiologic aspects of a St. Louis encephalitis outbreak in Mesa County, Colorado.

An epidemic of St. Louis encephalitis in 1985 in Mesa County, Colorado, led to 17 cases, including one fatality. Risk was associated with advanced age and residence in Grand Junction, the county's principal city. A trend was observed toward higher risk in females. However, increased risk in females was not associated with higher infection rates (increased exposure). Capture enzyme immunoassays detected specific immunoglobulin M (IgM) and immunoglobulin A after infection. A serosurvey of Grand Junction residents disclosed an infection rate of 4.0%, indicating that 1,123 epidemic St. Louis encephalitis infections may have occurred in the city. Evidence of previous St. Louis encephalitis virus infection was found in 11.2% of survey respondents who had neutralizing antibody to the virus without specific IgM. The prevalence of St. Louis encephalitis virus antibody was similar to rates observed in serosurveys undertaken 30 years earlier, indicating that the level of endemic St. Louis encephalitis transmission in the city had not changed appreciably in that interval.

Adolescent↗
PubMed1987

Epizootic vesicular stomatitis in Colorado, 1982: epidemiologic and entomologic studies.

An epizootic of vesicular stomatitis (VS) caused by the New Jersey serotype of VS virus affected livestock and humans in 14 western states in 1982-1983. Epidemiological observations were made on at least 10% of the cattle in 4 dairy herds that were located in the vicinity of Grand Junction, Colorado. High rates of neutralizing antibody to the New Jersey serotype were seen in all cattle regardless of whether livestock in the dairy had clinical VS or a decrease in mild production. Antibody titers remained high in these cattle for as long as 2 years after the epizootic. No virus isolations were made from 32 humans with clinical signs compatible with viral disease. Entomological information was obtained during the epizootic from 23 premises in northwestern Colorado. Insect collections yielded 4 isolates from Culicoides spp. midges, 2 from C. variipennis, and 1 each from C. stellifer and C. (Selfia) spp. This is the first report of VS virus isolations from field-collected Culicoides.

Aedes↗
PubMed1987

Epizootic vesicular stomatitis in Colorado, 1982: epidemiologic studies along the northern Colorado front range.

Epidemiologic evaluations were made of farm personnel on vesicular stomatitis-affected premises along the front range of the Rocky Mountains in Colorado during the 1982 epizootic. A similar antibody prevalence was noted to that of veterinarians and research and regulatory personnel who were involved with the same epizootic. Risk of infection resulted from intimate physical contact with infected horses or cows. Incidence and infection rates in horses were 45%; rates in cows were much lower, only 5%. Some epidemiologic clues were gained by a detailed study of an equine ranch. The pasture was incriminated as the area of highest risk, where 100% infection rates were noted. Horses in open pens and barns were at lower risk. Severe clinical disease in horses resulted in higher neutralizing antibody titers than inapparent or mild infection. Maternal antibody was detected in foals up to 4 months of age, and the level of antibody in the foal was a reflection of the dam's antibody level.

Agricultural Workers' Diseases↗