PubMed Health⌕ Search

Biomedical subjects

S Carter

Publications and source records attributed to S Carter.

At least 19 recordsLinked to original sources
PubMed1992

Contribution of adenosine to isoproterenol-stimulated prostacyclin production in rabbit heart.

This study investigated adenosine's contribution to isoproterenol-stimulated prostacyclin production, measured as 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) output, and mechanical function in the isolated rabbit heart perfused with Krebs-Henseleit buffer. The isoproterenol-induced increase in 6-keto-PGF1 alpha was diminished by adenosine (10 microM), the A1 receptor antagonist 1,3-dipropyl, 8-cyclopentylxanthine (DPCPX 0.06 microM), and the A2 receptor agonist CGS-21680 (0.6 microM); CGS-21680 did not decrease heart rate (HR) or myocardial contractility (dP/dt(max)). The isoproterenol-induced increase in 6-keto-PGF1 alpha was potentiated by the A1 receptor agonist 1-deaza,2-chloro,N6-cyclopentyladenosine (DCCA, 0.6 microM) and the A2 receptor antagonist 3,7-dimethyl,1-propargylxanthine (DMPX, 6 microM). The isoproterenol-induced increase in dP/dt(max) and HR was diminished by adenosine, DCCA, and DMPX. DPCPX enhanced dP/dt(max) and HR and prevented the decrease by adenosine and DCCA of the isoproterenol-induced increase in HR and dP/dt(max); the increase by DCCA but not the decrease by adenosine in 6-keto-PGF1 alpha output was abolished. DMPX abolished the effect of adenosine and CGS-21680 to reduce isoproterenol-stimulated 6-keto-PGF1 alpha. These data suggest that adenosine generated in response to isoproterenol attenuates its effect on HR and dP/dt(max) through A1 receptors and on prostacyclin synthesis via A2 receptors.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Role of duplex scanning for the detection of atherosclerotic renal artery disease.

To assess the accuracy of renal artery duplex scanning for the purpose of diagnosing atherosclerotic renal artery stenosis, we compared the findings of renal arteriograms to the results of duplex scanning in 41 patients. Using an increase of renal artery peak systolic flow velocity of greater than 180 cm/sec, duplex scanning was able to discriminate normal from diseased renal arteries with a sensitivity of 95% and a specificity of 90%. Using the principle that blood flow velocity across a stenosis is roughly proportional to the degree of stenosis, it appeared that a ratio of the peak velocity in the renal artery to the aorta (RAR) of greater 3.5 predicted a greater than 60% diameter reduction of that renal artery, which is felt to be a significant stenosis. Forty-eight vessels were classified as having a greater than 60% diameter reduction by arteriography. Using the RAR of greater than 3.5, duplex scanning agreed in 44 renal arteries (sensitivity 92%). In the 26 renal arteries where arteriography showed a less than 60% diameter reduction, duplex scanning agreed in 16 vessels and correctly detected a focal narrowing in nine of the remaining ten vessels. Ten of 11 occluded renal arteries were correctly identified by duplex scanning. Duplex scanning determined the location of the renal artery lesion with an accuracy of 95% (kappa 0.74). Since duplex scanning can accurately demonstrate and locate focal renal artery stenosis, we believe it may become an accurate screening test for renovascular hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

The effect of partial coating with hydroxyapatite on bone remodeling in relation to porous-coated titanium-alloy dental implants in the dog.

For inhibition of crestal bone resorption due to stress shielding and disuse atrophy, an hydroxyapatite (HA) plasma coating was added to the coronal portion of partially porous-coated endosseous dental implants. These implants, as well as control non-HA-coated implants were placed in healed mandibular premolar extraction sites in dogs for a 72-week period of function. Histological examination showed that both implant designs became securely fixed by bone ingrowth into the porous-coated apical region of the implants. The plasma-sprayed HA coating resulted in significantly greater bone height formation and maintenance next to the coronal portion of the implant compared with non-HA-coated implants of similar design. In addition, significant resorption of the 20-to-50-microns-thick plasma-sprayed HA coating occurred over the 18-month period of function.

Alloys↗
PubMed1989

Detection of feline calicivirus antigens in the joints of infected cats.

Twelve specific pathogen free cats were used to investigate the role of calicivirus in causing lameness. These were divided into two groups each of six cats; one group of cats had previously been vaccinated, the other had not. Three cats in each group were given live vaccine virus (F9 related) by the subcutaneous route and two in each group were challenged intranasally with field virus (A4), either four or seven days before euthanasia. The other two cats were controls. Virus was isolated from the oropharynx of five cats and the conjunctiva of a single cat. Four of these cats had been given the field virus and two the vaccine strain; the latter two cats had been previously immunised and had high circulating neutralising antibodies to calicivirus. No virus was isolated from the joints of any cat but immunofluorescence examination revealed viral antigens within the synovial macrophages of 14 joints from five cats, three having been given the field virus and two the vaccine virus seven days before euthanasia. Immunofluorescence also demonstrated the presence of immunoglobulin and complement within synovial macrophages suggesting that the virus was in the form of an immune complex. No lameness was reported in any cat and the synovial histological changes were minimal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Characteristics of males at a public health department contraceptive service.

To effectively confront teenage pregnancy, the characteristics, attitudes, and behaviors of males, along with females, need to be better understood. This pilot study examined young males who visited the family planning clinic of a public health department to obtain free condoms. Questionnaires were distributed over a 4-week period. Nearly 30% of males reported having sex 11+ times a month. However, an equal proportion reported having sex three or fewer times in the same interval. Most males reported using condoms during sex, although one quarter reported use as "seldom." The health department was a major source of condoms and was positively evaluated because condoms were free and there were "no questions asked." Only one third of the males reported using another method of contraception. Results suggest a major role of the health department in condom availability and the potential need for contraceptive services for males.

Contraceptive Devices, Male↗
PubMed1989

Clinical experience using the Wolf Piezolith device at 2 British stone centers.

Machines using the principle of piezoelectric extracorporeal shock wave lithotripsy have been developed. This has allowed the prospect of painless treatment for renal and ureteral calculi. The experience with use of 2 Wolf Piezolith machines for 1 year is presented. Different second generation lithotriptors have varying techniques of production of shock waves and different imaging methods. The Wolf Piezolith device uses ultrasound imaging and piezoelectric crystals for shock wave generation. Between June 1987 and May 1988, 545 patients 5 to 84 years old were treated with the Wolf Piezolith device. Of these patients 2-month followup data are available for 367 (398 renal units). Outpatient treatment was used routinely. For renal calculi complete fragmentation (into particles less than 2 mm. in size) was achieved in 94 per cent of the patients, with 53 per cent being completely free of stone at 2 months. For ureteral stones treated in situ the best results were obtained in the upper and lower ureter. Over-all, 62 per cent of the patients required more than 1 treatment, with the number of treatment sessions required increasing with the size of the stone treated. Morbidity was low. Ultrasound imaging has proved to be as effective as x-ray imaging. Compared to Dornier HM-3 lithotripsy, installation and running costs were low. The machine offers a favorable alternative to first generation lithotriptors.

Adolescent↗
PubMed1989

Vascular smooth muscle responsiveness to noradrenaline and phenylephrine following experimental heart failure in dogs.

Adrenergic vascular responsiveness was assessed in the dorsal pedal artery and the saphenous vein in dogs before and after the development of congestive heart failure (CHF). Following development of severe CHF, both noradrenaline and phenylephrine could produce a greater maximum tension and a shift of the resultant concentration-effect curve to the left compared to the curves seen before the development of CHF. The saphenous vein was more sensitive than the dorsal pedal artery to both agonists before CHF. After CHF, the sensitivity difference to noradrenaline increased significantly but it remained unaltered to phenylephrine. Relative to noradrenaline, phenylephrine became more potent on the artery at peak CHF, whereas the potency ratio was unchanged in the saphenous vein at peak CHF. Prazosin was a competitive antagonist only against phenylephrine prior to CHF; competitive antagonism was not seen against noradrenaline or following CHF. Prazosin was less effective in antagonising noradrenaline induced contractions, as shown by an increase in IC50 values. These results are consistent with increased tissue sensitivity to adrenergic agents during CHF. The greater potency of phenylephrine in the artery at peak CHF suggests the presence of a greater proportion of alpha 1 adrenoceptors, which is consistent with the decrease in effectiveness of prazosin after the development of CHF.

Animals↗
PubMed1989

Project SMART parent program: preliminary results of a chronic disease risk reduction trail.

Project SMART Parent Program is a school-based healthy lifestyle promotion program designed to reduce chronic disease risk in adults and to provide a health-conscious home environment for children through the adoption of healthy lifestyle by their parents. Parents in the high involvement condition received comprehensive health status appraisals, and a program designed to reduce dietary fat intake, and increase aerobic activity levels. Parents in the low involvement condition received only the comprehensive health status appraisals. ANCOVA, using treatment condition as the independent variable and change scores as the dependent variables, were used to assess program outcomes. At the first posttest measure, the intervention group compared to the control group had a significantly greater decrease in blood cholesterol, a greater gain in aerobic fitness, a greater weight loss, and a greater decrease in body fat. At the second posttest measure, the intervention group had significantly greater gain in aerobic fitness, a greater decrease in body fat, a greater decrease in systolic blood pressure, and a marginally significant decrease in weight. Preliminary results provide strong support for the effectiveness of the Parent Program in reducing chronic disease risks.

Adolescent↗
PubMed1989

The biology of human immunodeficiency virus-1 IIIB infection in the chimpanzee: in vivo and in vitro correlations.

Human immunodeficiency virus (HIV)-1 IIIB infection of chimpanzees leads to a compartmentalized, nonpathogenic in vivo and in vitro relationship with the virus. The absence of an acquired immunodeficiency syndrome (AIDS)-like disease in over 100 chimpanzees persistently infected may be related to some or all of the findings reported here. Further characterizing these possible host adapative mechanisms may be critical in both understanding pathogenesis, as well as elucidating novel mechanisms for therapeutic and/or the preventive strategies for AIDS in humans.

Acquired Immunodeficiency Syndrome↗
PubMed1988

In vivo regulation of beta-adrenergic receptors on mononuclear leukocytes and heart. Assessment of receptor compartmentation after agonist infusion and acute aortic constriction in guinea pigs.

In animals injected with a bolus of isoproterenol, beta-adrenergic receptors in both mononuclear leukocytes (MNL) and heart were sequestered away from the cell surface, and the time course (0-120 min) and dose-response patterns were similar in the two tissues. In guinea pigs given a constant infusion of isoproterenol, 0.15 mg/(kg.h), down-regulation of total receptor number occurred more quickly and to a greater extent in the MNL than in the heart. We also compared receptor sequestration after aortic constriction-induced acute heart failure. Negligible sequestration (9%) of beta-adrenergic receptors occurred in the MNL of animals treated in this manner, whereas the number of receptors in the sarcolemmal fraction decreased 61%. This selective sequestration of cardiac receptors may result from the action of high concentrations of norepinephrine (which is selective for beta 1 over beta 2 receptors) present at sympathetic nerve-cardiac cell synapses. We conclude that although receptor redistribution occurs similarly in MNL and heart in response to a circulating nonselective agonist, beta-adrenergic receptor redistribution may occur selectively in the heart in response to such stimuli as aortic constriction-induced acute heart failure that activate the sympathetic nervous system.

Adenylyl Cyclases↗
PubMed1986

Uptake pathways for amino acids in mouse intestine.

This paper characterizes amino acid (AA) uptake pathways in an everted-sleeve preparation of mouse jejunum. AA uptake is linear with time for 2-4 min, depending on the particular AA and its uptake rate. Escape of tracer to the serosal surface is still negligible at these times. Errors due to metabolism of labeled AAs to volatile products can be minimized by using 14C- rather than 3H-labeled AAs and by not drying tissues before counting. The dependence of AA uptake on concentration shows saturable kinetics, with apparent Km values in the range 1-4 mM. By 25 or 50 mM an uptake plateau is reached for leucine, lysine, methionine, and methylaminoisobutyric acid but not for aspartic acid, histidine, or proline. Proline kinetics are the result of a saturable Na+-dependent component, a linear diffusional component, and possibly a small saturable Na+-independent component. The Na+-dependent component of uptake for six AAs averages 83% of the total at 0.01 mM and 54% at 25 or 50 mM. Leucine and D-glucose exhibit modest (32%) cross-inhibition of Na+-dependent uptake. For the same six AAs we determined the percent inhibition of both the Na+-dependent and the Na+-independent components by the other AAs. These results suggest the presence of at least five or six AA uptake pathways in mouse jejunum: distinct Na+-dependent pathways for acidic, basic, and neutral AAs and for imino acids; a shared Na+-independent pathway for basic and neutral AAs; and possibly a Na+-independent pathway for acidic AAs. Comparisons of AA uptake pathways in mouse, rabbit, and rat intestine reveal many similarities but also some differences.

Amino Acids↗