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Biomedical subjects

C Townsend

Publications and source records attributed to C Townsend.

36 records · Page 2Linked to original sources
PubMed1989

Intravenous morphine infusion (IMF) to drug-naive, conscious rats evokes bradycardic, hypotensive effects, but pressor actions are elicited after IMF to rats previously given morphine.

Hemodynamic (blood pressure and heart rate) responses of conscious drug-naive rats were studied following intravenous (i.v.) infusion of sterile saline, morphine sulphate, and then naloxone hydrochloride, as well as of other groups previously injected with morphine sulphate. Those groups chronically given morphine sulphate received twice daily injections of morphine sulphate (5 mg/kg, s.c. per injection) for 3 or 6 days before testing with the i.v. infusion of morphine sulphate. Drugs were infused (135 microL/min) through an indwelling femoral venous catheter via a Harvard infusion pump, and blood pressure was recorded from the abdominal aorta via a femoral arterial catheter. Other pretreatment studies were done to determine the receptor mechanisms mediating the blood pressure responses of drug-naive and chronic morphine-treated rats, whereby equimolar doses (0.32 mumol) of specific receptor antagonists were given as a bolus i.v. injection 5 min after saline but before subsequent infusion with morphine sulphate. Intravenous infusion of morphine sulphate (7.5 mg/kg total over 15 min) to drug-native rats caused a transient but precipitous fall in mean arterial pressure and mean heart rate with an associated rise in mean pulse pressure; these effects were blocked in other groups pretreated with atropine. Interestingly, however, rats chronically injected with morphine sulphate for 3 days previously evoked a transient pressor response when subsequently infused i.v. with morphine sulphate, actions that were blocked in other groups when pretreated i.v. with 0.32 mumol of phentolamine, yohimbine, prazosin, or guanethidine. A greater and persistent pressor response occurred following morphine infusion to groups of rats previously injected over 6 days with morphine sulphate, which was associated with tachycardia during the later stages of the 15-min morphine sulphate infusion period. The prolonged pressor and tachycardic responses of this 6-day chronically injected group were completely blocked in another group pretreated i.v. with both phentolamine and propranolol (0.32 mumol). The results suggest that morphine sulphate infusion to conscious, drug-naive rats evokes classical hypotensive effects due to decreases in mean heart rate caused by activation of parasympathetic vagal activity. With 3 or 6 days of chronic morphine sulphate administration beforehand, subsequent i.v. infusion of morphine sulphate evoked pressor actions felt to be caused by a progressive activation of the sympathetic nervous system.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1981

Photocoagulation for optic disc new vessels in diabetes mellitus.

The effects of treatment by argon laser and xenon arc photocoagulation in 165 diabetic patients with optic disc new vessel formation have been studied retrospectively. Visual acuity and degree of new vessel formation have been assessed over a period of between six months and seven years of follow-up (mean 23 months). Visual acuity improved in 36% of treated eyes and remained unchanged in 34%. Improvement was most marked in those with initially poor acuity (less than 6/36). There was no association between improvement in visual acuity and regression of disc vessels, the latter occurring in 79% of treated eyes. Only 6% of eyes became blind during the period of follow-up, principally as a result of vitreous haemorrhage and retinal detachment. There was no difference between the results produced by the use of separate or combined argon laser and xenon arc photocoagulation on the regression of disc new vessels. However, our results suggest that argon laser treatment was more effective than xenon arc photocoagulation in improving visual acuity. These findings suggest that either form of treatment or a combination offers considerable benefit in the management of proliferative diabetic retinopathy, even when very severe at presentation.

Adult↗
PubMed1981

Evidence for functional endothelial cell damage in early diabetic retinopathy.

Two aspects of endothelial cell function were examined in two matched groups of male insulin-dependent diabetics, six with background retinopathy and seven without retinopathy. Leakage of fluorescein from the retinal capillaries was estimated by vitreous fluorophotometry. In addition, factors VIII/von Willebrand (vWF) and VIII-related antigen (VIII-RAG), which are synthesized by the endothelial cells, were measured, together with VIII-antihaemophilic factor (VIII-AHF). The patients without retinopathy had normal leakage of fluorescein in the macula (mean +/- SEM: 1.10 +/- 0.10 g X 10(-8)/ml) and the posterior vitreous (0.45 +/- 0.11 g X 10(-8)/ml), and normal circulating levels of vWF (123% of a normal reference plasma +/- 18%), VIII-RAG (137 +/- 14%) and VIII-AHF (112 +/- 18%). In contrast, the patients with background retinopathy showed higher leakage of fluorescein in the macula (6.34 +/- 1.74 g X 10(-8)/ml; p less than 0.01), and the posterior vitreous (3.09 +/- 0.94 g X 10(-8)/ml; p less than 0.02), as well as increased levels of vWF (177 +/- 16%; p less than 0.05). There was a trend towards increased VIII-RAG (195 +/- 24%; p less than 0.1), but not VIII-AHF (126 +/- 13%). Alterations of endothelial cell function thus accompany the development of retinopathy. It cannot be said from the present study whether these alterations also precede the appearance of retinopathy.

Adult↗
PubMed1981

Xenon arc and argon laser photocoagulation in the treatment of diabetic disc neovascularization. Part 1. Effect on disc vessels, visual fields, and visual acuity.

Xenon arc and argon laser photocoagulation are equally effective in producing regression of disc neovascularization and maintaining visual acuity. Xenon has more destructive effects on the visual field and electroretinogram, but is more comfortable because retrobulbar anaesthesia is used and more convenient to the patient because fewer treatment sessions are needed.

Adult↗
PubMed1980

Xenon arc photocoagulation for the treatment of diabetic maculopathy. Interim report of a multicentre controlled clinical study.

The results of a randomised controlled clinical study in the treatment of diabetic maculopathy are reported. Ninety-nine patients with two similarly affected eyes had one--chosen by random procedure--treated, while the other was left as an untreated control. Visual acuity was maintained in the treated eyes, while it deteriorated in the untreated eyes, reaching over 2 lines difference after 4 years. The difference in deterioration was significantly less in treated than in untreated eyes at each assessment. After 4 years the difference between the 2 eyes was greatest in those with initially good vision. There was no difference in visual acuity in patients whose initial vision was less than 6/36. Only 9 treated but 25 control eyes lost vision to blindness (P less than 0.001). It is concluded that maculopathy is a treatable form of diabetic retinopathy if treated before severe visual loss occurs.

Adult↗
PubMed1978

Photocoagulation in diabetic retinopathy: II. Methodology.

There is now evidence from clinical trials that patients with diabetic retinopathy have their visual lives prolonged by photocoagulation. However, the exact indications for treatment have not yet been established and are undergoing continuous reevaluation. For many years, the presence of fibrous tissue either on the optic disc or the retina was considered to be a contraindication to treatment. However, recently treatment has been possible using gentle photocoagulation. It is hoped that over the next few years the exact indications for treatment will be established. It may be found in the future that the treatment of patients with maculopathy by panretinal photocoagulation and focal treatment and similarly patients with a few peripheral new vessels, by panretinal photocoagulation may prevent further progression and remove the necessity for treatment. It is important to limit as much as possible the number of visits to the opththalmologist that the patient must make. It is therefore important to establish a technique that requires as few treatment sessions as possible. Ultimately, follow up should be done by the well trained physician. The difficulty with the development of this type of technique is that diabetic retinopathy is a progressive disease and therefore new abnormal areas may well develop in patients who have had seemingly adequate treatment. Also, relatively mild background retinopathy or maculopathy may progress ultimately to proliferative retinopathy. However, with improvements in technique and establishment of safe treatment regimens, the goal of single treatment may be achieved.

Diabetic Retinopathy↗
PubMed1978

Photocoagulation in diabetic retinopathy: III. Complications.

We have reviewed the unwanted effects that follow the treatment of diabetic retinopathy with photocoagulation. Complications are uncommon, and those side effects that occur regularly are acceptable in relation to the benefits to be gained from treatment.

Diabetic Retinopathy↗
PubMed1975

Osteosarcoma. Results of treatment employing adjuvant immunotherapy.

The treatment of patients with osteosarcoma continues to result in few survivors despite advances in surgery and radiotherapy. Since the primary site of failure is pulmonary, it is apparent that a systemically active adjuvant must be employed if a cure is to be achieved. Because of the experimental evidence for an immune response against osteosarcoma and because of the potential systemic activity of the immune system, a trial of postoperative adjuvant immunotherapy was begun. Seventeen patients received immunotherapy consisting of BCG and an allogeneic tumor cell vaccine following surgical removal of all gross tumors. Eighteen per cent (3/17) of the patients who received immunotherapy remained alive and free of disease compared to 0/12 who did not. An analysis of the 14 patients with recurrence, revealed that the median time to recurrence was 3.0 months in both groups. It is, therefore, apparent that at the time of initiation of immunotherapy subclinical metastasis must already have been present. Therefore, on the basis of this study we conclude that adjuvant chemotherapy should be employed to further reduce the tumor cell burden in order for immunotherapy to be effective for osteosarcoma.

Antigens, Neoplasm↗
PubMedDate not supplied

The effects of learners on waiting times and patient satisfaction in an ambulatory teaching practice.

Data regarding waiting times and times with nurses and physicians were recorded for 656 patients visiting a large family practice unit. Patients also provided estimates of their own waiting times and ratings of the acceptability of these waits. The data were analyzed to assess whether any differences exist in terms of waiting times, times with providers, and waiting time satisfaction for patients seen by clinical clerks (medical students), resident physicians, and attending physicians. Consultation times were longer for patients seen by learners, but waiting times were shorter for these patients. Importantly, there were no significant differences in terms of patient satisfaction with consultation time or waiting time satisfaction. Thus, while learners made a noticeable impact on consultation time, the overall effect on the patient booking system was marginal, and there was no negative impact on patient wait time satisfaction. To control for unevenness of type of providers assigned to the different services, only intermediate assessments are included in this study. The conclusions should not be generalized for other types of services.

Appointments and Schedules↗