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Biomedical subjects

R D Stark

Publications and source records attributed to R D Stark.

36 records · Page 2Linked to original sources
PubMed1972

Daily requirement of oxygen to reverse pulmonary hypertension in patients with chronic bronchitis.

We have shown previously in patients with chronic bronchitis that correction of the hypoxaemia by continuous administration of oxygen substantially reduced the pulmonary hypertension by reversal of structural changes in the pulmonary resistance vessels. We have now demonstrated that such improvements may occur with less than continuous oxygen. Treatment with oxygen for 18 hours daily significantly decreased pulmonary arterial pressure and pulmonary vascular resistance. Oxygen therapy for 15 hours a day also decreased pulmonary vascular resistance; such a regimen is practicable in the home, is consistent with a working day free from the constraints of an oxygen supply, and should reduce the number of episodes of congestive cardiac failure.

Adult↗
PubMed1970

The vascular responses of the spleen to intravenous infusions of catecholamines, angiotensin and vasopressi in the anaesthetized cat.

1. Splenic arterial flow and splenic weight were recorded in cats anaesthetized with sodium pentobarbitone. The responses of the spleen to catecholamines, angiotensin and vasopressin were investigated.2. Catecholamines caused responses mediated by alpha- and beta-adrenoceptors in the arteriolar smooth muscle, but only insignificant beta-adrenoceptor responses could be elicited from the capsular smooth muscle. The difficulties in elucidating the mechanism of action of catecholamines on arteriolar smooth muscle are discussed.3. Angiotensin caused marked vasoconstriction, but contraction of the capsular smooth muscle was less marked. Vasopressin caused vasoconstriction but had no effect on capsular smooth muscle. Thus these peptides constrict the resistance vessels but produce much weaker contraction of the capsule.4. These responses are discussed in relation to the splenic responses to acute haemorrhage.

Acute Disease↗
PubMed1969

Vascular responses of the spleen to rapid haemorrhage in the anaesthetized cat.

1. Splenic blood flow, splenic weight and arterial pressure were recorded in cats anaesthetized with sodium pentobarbitone. The mechanisms of the splenic contraction and vasoconstriction which followed rapid haemorrhage were investigated.2. When splenic arterial pressure was decreased progressively by mechanical occlusion of the coeliac artery, the decrease in splenic blood flow was proportional to the decrease in pressure; splenic weight did not change.3. After denervation of the spleen and adrenalectomy, haemorrhage resulted in a decrease in splenic flow which was similar to but slower than that in the innervated spleen; there was no splenic contraction. After splenic denervation, adrenalectomy and nephrectomy, haemorrhage caused a smaller decrease in flow but this response was still greater than that expected as a consequence of the reduced arterial pressure.4. Infusions of small doses of angiotensin caused splenic vasoconstriction with little change in splenic weight. Larger doses reduced both flow and weight.5. The splenic flow and weight responses to stimulation of the sympathetic nerves remained unimpaired when splenic blood flow was substantially reduced for 1-2 hr by haemorrhage.6. It is concluded that after a rapid haemorrhage, the splenic contraction is due only to activity of the splenic nerves and the adrenal medullae. The decrease in splenic flow is due to the reduction in arterial pressure, activity of the splenic nerves and the adrenal medullae, and the actions of angiotensin and some unidentified vasoconstrictor substance.

Adrenalectomy↗
PubMed1968

Vascular responses of the spleen to nerve stimulation during normal and reduced blood flow.

1. The splenic artery flow, the splenic weight and the arterial blood pressure were recorded in cats anaesthetized with sodium pentobarbitone.2. Oscillations in splenic artery flow and splenic weight were observed. Following occlusion and release of the splenic artery, there was a brief increase in flow to above the pre-occlusion level and the oscillations in flow were greatly increased in amplitude. It is suggested that the brief increase is a consequence of the reduction of arterial pressure and that the oscillations are due to synchronization of rhythmic activity of smooth muscle within the spleen.3. Stimulation of the splenic nerves resulted in decreases in splenic artery flow and splenic weight. The size of the responses varied with the frequency of stimulation and maximum responses in both flow and weight were obtained at about 3 impulses/sec.4. After stimulation for 10 min, the splenic weight response was maintained while the flow response showed some recovery towards the control level.5. When the splenic artery flow was reduced to about half the control level for periods up to 2 hr, the flow and weight responses to stimulation of the splenic nerves remained unchanged; the significance of this after a haemorrhage is discussed.6. Intravenous administration of atropine or propranolol did not affect the responses to nerve stimulation. After phenoxybenzamine, nerve stimulation caused a smaller decrease in splenic weight, while the splenic artery flow increased to above the control level. This increase was unaffected by atropine but abolished by propranolol.

Animals↗
PubMed1967

The effect of haemorrhage on hepatic artery and portal vein flows in the anesthetized cat.

1. In cats anaesthetized with pentobarbitone, the hepatic artery and portal vein flows and pressures were recorded simultaneously.2. Removal of blood from the animal did not cause a decrease in the hepatic artery flow unless the arterial pressure fell below 80 mm Hg. In contrast, the portal vein flow fell markedly.3. After restoration of the blood, the hepatic artery flow increased to above the pre-haemorrhage level, while portal vein flow returned only partly towards the control level.4. It is concluded that haemorrhage causes a vasodilation in the hepatic artery vascular bed and a vasoconstriction in the vascular beds drained by the portal vein. By this means, the oxygen supply to the liver is maintained as far as possible.

Animals↗
PubMedDate not supplied

Management of life-threatening epistaxis in a Jehovah's Witness.

The religious beliefs of Jehovah's Witnesses forbid them to receive blood or blood products. We report a case of life-threatening epistaxis in a Jehovah's Witness, causing severe anaemia (Hb 2.7 g/dl). The successful management of this case and literature relating to this are discussed.

Anemia↗
PubMedDate not supplied

The development of a family nurse practitioner programme in Botswana.

The Family Nurse Practitioner Programme, offered through the National Health Institute in Botswana, Africa, is the result of a collaborative effort between the Ministry of Health of the Government of Botswana and the United States Agency for International Development. This one-year post-basic nursing programme evolved from a national commitment to expand and upgrade primary health care services. The curriculum, based on service needs and reflecting national development priorities, has been designed to increase the relevance of nursing education to the social and health needs of the people.

Botswana↗
PubMedDate not supplied

The relationship between breathlessness and ventilation during steady-state exercise.

In clinical studies on breathlessness, the relationship between breathlessness and ventilation is a convenient way of summarizing the responses of single subjects or groups of subjects. This relationship is usually based on measurements during progressive exercise. The objective of this study was to determine whether the relationship was maintained in different conditions or whether breathlessness could alter independently of ventilation. Six healthy subjects undertook progressive exercise so that the relationship of breathlessness to ventilation could be described; the reproducibility was established. The same subjects also undertook exercise at two constant workloads. After 4 min, stable values of ventilation were achieved but the breathlessness scores continued to increase (p less than 0.05). These findings show that the relationship between breathlessness and ventilation may be disturbed without external intervention, and this provides further evidence that breathlessness is not simply a sensing of the ventilation achieved.

Adult↗