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Biomedical subjects

G Stokes

Publications and source records attributed to G Stokes.

15 recordsLinked to original sources
PubMed1991

Interactions between enalaprilat and doxazosin at rat tail artery alpha 1-adrenoceptors.

Using paired isolated perfused rat tail artery segments, it was found that enalaprilat, an ACE inhibitor, augmented 1.6-fold the contractile responses to phenylephrine (PE), an alpha 1-adrenoceptor agonist. Similarly, enalaprilat potentiated 1.9-fold the alpha 1-adrenoceptor antagonist activity of doxazosin in paired rat tail artery segments. In rats treated with deoxycorticosterone acetate (DOCA) 20 mg/kg i.m. twice weekly for 5 weeks, plasma renin activity fell from a control value of 5.73 +/- 0.93 to 0.04 +/- 0.01 ng of AI/ml/h. The inhibition of circulating renin activity in these animals was associated with a loss of the potentiating effects of enalaprilat upon the alpha 1-adrenoceptor antagonist action of doxazosin. The results are interpreted as indicating that angiotensin II (AII) can modulate the functional activity of alpha 1-adrenoceptors in vascular smooth muscle.

Adrenergic alpha-Antagonists↗
PubMed1991

Investigations into interactions between doxazosin and enalaprilat at alpha 1-adrenoceptors in anaesthetized rats.

1. In anaesthetized intact Sprague-Dawley rats, the angiotensin-converting enzyme inhibitor enalaprilat, 1 mg/kg, had no significant effect on the pressor responses to the alpha 1-adrenoceptor agonist phenylephrine (PE). Doxazosin 1 mg kg was found to be a potent alpha 1-adrenoceptor antagonist. 2. The combination of enalaprilat 1 mg/kg plus doxazosin 1 mg/kg was 3.3-fold more potent in antagonizing alpha 1-adrenoceptors than doxazosin 1 mg/kg alone. 3. After treatment of rats with deoxycorticosterone acetate (DOCA) twice weekly for 5 weeks, the alpha 1-adrenoceptor antagonist action of doxazosin in anaesthetized rats was not potentiated by enalaprilat 1 mg/kg. 4. Since DOCA treatment suppresses renin activity, these findings strongly support the hypothesis that angiotensin II can modulate the functional activity of alpha 1-adrenoceptor in vascular smooth muscle.

Adrenergic alpha-Antagonists↗
PubMed1989

An in vitro study of interactions between doxazosin and enalaprilat at vascular alpha 1-adrenoceptors.

1. Isolated perfused male Sprague-Dawley rat tail artery segments were used to investigate interactions between the alpha-1-adrenoceptor antagonist, doxazosin, and the angiotensin converting enzyme (ACE) inhibitor, enalaprilat, using phenylephrine (PE) as the alpha 1-adrenoceptor agonist. 2. In concentrations of up to 10(-5) mol/L, enalaprilat had no effect on arterial responses to PE. 3. Doxazosin produced a concentration-dependent competitive alpha 1-adrenoceptor antagonism, yielding a mean pA2 value of 8.72. 4. In the continuous presence of 10(-6) mol/L enalaprilat, doxazosin with a pA2 value of 9.10 was a 2.4-fold more potent alpha 1-adrenoceptor antagonist than in the absence of enalaprilat. 5. These results are interpreted to indicate that endogenously produced angiotensin II can modulate the activity of alpha 1-adrenoceptors in vascular smooth muscle.

Adrenergic alpha-Antagonists↗
PubMed1988

Caffeine consumption and blood pressure: an epidemiological study.

A cross-sectional survey of 5147 Australians attending a health screening clinic was conducted to determine if there was an association between habitual consumption of caffeine, or particular caffeine-containing beverages, and blood pressure. The average caffeine consumption of the study population was 240 mg/day. Caffeine consumption within the last three hours was found to be associated with significantly higher mean systolic and diastolic blood pressure in both sexes after controlling for age, adiposity, first degree relatives with hypertension, serum cholesterol level, alcohol consumption and tobacco smoking. Mean systolic and diastolic blood pressures differed significantly by 4 mmHg and 2 mmHg respectively for both males and females between those who had consumed caffeine within the last three hours and those who had not consumed it within the last nine hours (p less than 0.01). Average caffeine consumption per day was not associated with blood pressure in either sex after controlling for time since caffeine consumption. Logistic regression analysis was used to estimate the relative risk of high blood pressure (treated and untreated) for the groups consuming and not consuming caffeine in the last three hours. This relative risk was significantly greater than unity in females only (p less than 0.05). After controlling for time since caffeine consumption, caffeine consumption per day was not associated with significantly increased risk of high blood pressure.

Adult↗
PubMed1987

Developing self-care skills and reducing institutionalized behaviour in a long-stay psychiatric population: the role of the nurse in behaviour modification.

This paper examines the potential for behaviour modification in the rehabilitation of chronic, long-stay psychiatric patients and the impact such procedures may have on the work role of ward-based nursing staff. Through the use of five case histories the effectiveness of behavioural analysis and modification in encouraging self-help skills and constructive activity is identified. In addition to a critical examination of the clinical and organizational factors involved in patient improvement, it is argued that behaviour modification develops the therapeutic potential of nurses. The development of the patient-teaching dimension of the nursing role not only fosters greater clinical responsibility, but also promotes both professional independence and institutional power. This is not to imply that the use of behavioural methods cannot be combined with customary nursing practices, for in many ways they provide nurses with an appropriate technology to achieve established therapeutic goals. In conclusion, it is noted that clinical success is not sufficient to ensure the acceptance of ward-based behavioural programmes. The critical issues concern conventional hospital and staff practices and institutional rigidity, not the commitment of nursing staff or patient improvement.

Aged↗
PubMed1986

Use of freshly isolated capillary endothelial cells for the immediate establishment of a monolayer on a vascular graft at surgery.

Endothelial seeding of vascular graft surfaces may lead to a less thrombogenic surface. We examined the feasibility of using microvessel endothelial cells derived from human fat for seeding purposes. Human fat was treated with collagenase for 24 minutes, washed, and purified in a Percoll gradient separation. This yielded 1.25 +/- 0.45 X 10(6) cells/gm of fat. After a 1-hour incubation on plasma-coated Dacron, 2.8 +/- 1.5 X 10(4) cells remained firmly adherent to the surface. When exposed to flow for 2 hours at a shear stress of 0 to 80 dyne/cm2, between 50% and 100% of the initially adherent cells remained adherent. Statistical analysis of this data failed to demonstrate a strong relationship between the number of adherent cells and the shear rate. Scanning electron microscopy demonstrated endothelial cells in various stages of attachment to the plasma-coated Dacron. Although most cells were still round and only focally attached to the surface, some cells were maximally flattened, forming cell-to-cell contact. Because of the high cell yield and the firm adherence characteristics, we conclude that microvessel endothelial cells may offer the possibility for confluent endothelial cell seeding of a graft at the time of surgical implantation without the need for cell culture.

Adipose Tissue↗
PubMedDate not supplied

Clinical dose-response studies with guanfacine (BS 100-141), a new antihypertensive agent.

1. Blood pressure, pulse rate, salivary flow and the degree of sedation were recorded at intervals following oral administration of single doses of guanfacine, a clonidine-like agent, to hypertensive patients. 2. Between 2 and 10 h after administration of guanfacine (3 mg or 5 mg), there were dose-related decrease in lying and standing blood pressure, together with significant reductions in pulse rate and salivary flow. 3. It is concluded that guanfacine lowers blood pressure in hypertensive patients and is probably suitable for twice daily administration, but produces xerostomia and sedation.

Antihypertensive Agents↗