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Biomedical subjects

S Carter

Publications and source records attributed to S Carter.

17 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

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↗
PubMed1977

Biochemical markers in bronchial carcinoma.

A total of 107 patients with bronchial carcinoma have been studied for the presence of potential circulating tumour markers which might be used as indicators of recurrence after primary treatment. Plasma carcinoembryonic antigen (CEA) levels were estimated in every patient and, after a preliminary hormone screening study, plasma calcitonin (CT) and parathyroid hormone (PTH) levels were assayed in 66 patients. Oat-cell tumours proved to be of particular interest in that CEA levels greater than 40 microgram/l were measured (initially or subsequently) in 40.6 percent and CT levels were elevated in 75 percent. Longitudinal studies point towards the possible use of elevated marker levels as guides to therapy when all other features of recurrent disease are lacking. It is clear that no ideal tumour marker exists for bronchial carcinoma but in an individual case an abnormal level of one or more marker substances may provide a valuable aid to treatment.

Bronchial Neoplasms↗
PubMed1977

The clinical diagnostic value of the carcinoembryonic antigen (CEA) in haematuria.

Plasma and urinary CEA levels in patients presenting with haematuria have been studied to assess whether they facilitate the differentiation between benign and malignant urothelial conditions. Plasma CEA is of no diagnostic value although, if raised, it may suggest an invasive tumour. Urinary CEA levels are only of value in the absence of urinary infection; even then, only 37% of the cases with overt urothelial tumours had raised titres. A knowledge of the urinary CEA level, therefore, would seem to contribute little to the diagnosis of patients presenting with haematuria and all patients must still be investigated by the conventional techniques of urinary bacteriology, cytology, intravenous pyelography and cystourethroscopy.

Carcinoembryonic Antigen↗
PubMed1977

Diagnostic usefulness of plasma carcinoembryonic antigen levels in acute and chronic liver disease.

Raised plasma carcinoembryonic antigen (CEA) levels were found in over 90% of 71 patients with chronic liver disease and 50% of 16 patients with acute liver damage. Levels increasing chronicity and clinical severity of disease. In individual patients, the plasma CEA level fluctuated with the clinical condition. Persistently normal levels were never found in patients with chronic liver disease in poor clinical condition. A very high level suggests a bad prognosis. If CEA is considered together with SGPT, a discriminant function can be calculated, separating patients with acute liver damage and those with an acute exacerbation of chronic active hepatitis, with a high degree of certainty. In acute damage, peak CEA levels occur later than the time of maximum liver necrosis, suggesting that the rise is not owing to release of CEA from damaged cells. There is no significant difference in CEA level between patients with and without spontaneous or surgical portosystemic shunts, suggesting that high levels are not attributable to bypass of the liver. The timing of the rise in CEA in acute liver damage suggests that raised levels may be associated with regeneration. The tendency for higher levels to occur in those patients with greater disturbances of liver function suggests altered metabolism or excretion of CEA.

Acute Disease↗