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Biomedical subjects

J C Mott

Publications and source records attributed to J C Mott.

30 records · Page 2Linked to original sources
PubMed1971

Angiotensin II-like activity in circulating arterial blood in immature and adult rabbits.

1. Angiotensin II-like activity was estimated from the contraction of the rat ascending colon superfused with arterial blood in an extracorporeal circuit. The colon was calibrated by infusion of synthetic angiotensin II amide (Hypertensin, CIBA Ltd).2. Resting levels of angiotensin II-like activity were obtained by comparison of the length of a rat colon preparation superfused alternately with blood from an intact and from a nephrectomized rabbit.3. The resting levels of angiotensin II-like activity reached a maximum value of about 1.6 ng/ml. at 10-14 days of age, and thereafter declined to the adult value of 0.23 ng/ml. Rabbits of less than 100 g body weight had resting levels in the same range as adults.4. Removal of 25% of the calculated blood volume induced five times greater increments in arterial angiotensin II-like activity in immature than in adult rabbits (1.68 +/- 0.26 S.E. of mean ng/ml. compared with 0.34 +/- 0.08 S.E. of mean ng/ml.).5. No evidence was obtained that the high levels of angiotensin II-like activity encountered in immature rabbits were attributable to a slower rate of inactivation of angiotensin by tissues.6. The pronounced activity of the renin-angiotensin system demonstrated by these experiments in immature rabbits especially during haemorrhage is consistent with the suggestion that this system is of particular importance in cardiovascular control in early life.

Age Factors↗
PubMed1969

The kidneys and arterial pressure in immature and adult rabbits.

1. The effect of stepwise haemorrhage on arterial pressure in adult and immature (9-15 days old) rabbits lightly anaesthetized with sodium pentobarbitone is described.2. Bethanidine (1 or 3 mg/kg) lowered initial arterial pressure but did not impair the maintenance of arterial pressure in immature or adult rabbits during stepwise haemorrhage.3. Arterial pressure was only slightly lower in nephrectomized than in intact adult rabbits; in some immature rabbits nephrectomy caused a substantial fall of resting arterial pressure. This fall was largest in animals of low body weight and low haematocrit. Nephrectomy reduced the ability of both immature and adult rabbits to maintain arterial pressure during haemorrhage.4. Arterial pressure fell more precipitately on stepwise haemorrhage in adult rabbits in which the carotid sinus and depressor nerves had been cut than in intact rabbits. No such difference was seen in immature rabbits despite the fact that initial arterial pressure was higher in denervated animals at all ages.5. The responses to stepwise haemorrhage were compared in dummy operated and nephrectomized immature and adult rabbits with carotid sinus and depressor nerves cut to minimize changes of sympathetic tone. Under these conditions the presence or absence of kidneys made no significant difference in the response to stepwise bleeding in adult rabbits. In immature rabbits maintenance of arterial pressure was greatly impaired in the absence of the kidneys.6. The results suggest that a pressor mechanism of renal origin may be relatively more important in the maintenance of arterial pressure in the face of haemorrhage in immature than in adult rabbits.7. Resting arterial pressure in small and anaemic immature rabbits may partly depend on the presence of the kidneys. At birth arterial pressure is higher in rabbits of higher haematocrit but this relationship reverses in the second week of life when the haematocrit level is falling.

Age Factors↗
PubMed1968

Acute effects of haemorrhage on the composition of arterial blood in immature and adult rabbits, kittens and cats.

1. The fall of haematocrit after stepwise bleeding in rabbits and young kittens was not accompanied by an equivalent fall of plasma nitrogen. The relative failure of plasma nitrogen to decrease after haemorrhage was not attributable to the entry of diffusible nitrogen into the circulation.2. Plasma protein recovery by a combination of stepwise bleeding and viviperfusion was such as to yield values for the whole body/great vessel haematocrit ratio (F(cells)) in the normal range in adult cats but significantly below the normal range in young kittens and rabbits. If viviperfusion was not preceded by stepwise bleeding F(cells) in the normal range was obtained in young kittens and rabbits.3. The results of electrophoretic examination of pre- and post-haemorrhagic plasma were consistent with the entry of fresh protein into the circulation after haemorrhage occurring preferentially in the albumin fraction, but increase of albumin/globulin ratio was small in adult cats.4. It was concluded that the fall of haematocrit after haemorrhage in young kittens and rabbits was mainly due to the entry of protein rich tissue fluid into the circulation. In adult cats, however, the haematocrit did not always fall and any such fall may have been partly due to a shift of plasma from the periphery to the great vessels.5. The bearing of these observations on the validity of calculation of blood volume from red cell mass and haematocrit during stepwise haemorrhage was considered.

Animals↗
PubMed1968

The effect of haemorrhage on haemoglobin concentration, blood volume and arterial pressure in kittens and cats.

1. The arterial haemoglobin concentration in kittens less than 24 hr old was inversely related to body weight. There was about twice as much haemoglobin/unit body weight at birth as in adult cats. Haemoglobin concentrations were minimal at 3-6 weeks of age.2. In animals lightly anaesthetized with sodium pentobarbitone, arterial pressure rose from 52 mm Hg at birth in kittens to 133 mm Hg in adult cats. Blood volume decreased from 73 ml./kg at birth to 60 ml./kg in adults.3. When kittens less than a fortnight old were subjected to stepwise blood letting, arterial pressure fell proportionately with blood volume; in older kittens and in cats, arterial pressure was less well maintained at similar proportionate reductions of blood volume than in young kittens.4. The responses to haemorrhage of kittens and cats were compared with those of rabbits similarly treated and with those of adult cats anaesthetized with urethane and chloralose reported in the literature.

Aging↗
PubMed1967

The relation of blood volume to body weight and arterial haemoglobin levels in rabbits.

1. Relative blood volume (ml./kg) of rabbits calculated from total circulating haemoglobin and blood haemoglobin concentration decreases rapidly during the first few weeks of life and more slowly thereafter.2. In anaemic rabbits over 1 kg body weight, relative blood volume is significantly increased.3. Rabbits under 1 kg body weight have larger blood volumes than would be expected from their anaemia alone, were the relationship deduced in rabbits over 1 kg in body weight applicable. Blood volume was not related to haemoglobin concentration in these immature rabbits.

Anemia, Hypochromic↗
PubMedDate not supplied

Interventionalists' guide to the patient's experience of lower extremity arterial occlusive disease.

This article is intended as a guide for all who propose to intervene in patients with symptomatic lower extremity arterial occlusive disease. It reviews the natural history of and therapies for intermittent claudication. The results of a survey of claudicants are summarized; this survey gathered data on claudicants' general health, comorbid conditions, symptoms of claudication, and functional abilities. Respondents predicted a 20% improvement in their ability to perform instrumental activities of daily living (eg, walking several blocks, climbing one flight of stairs, performing household tasks) if lower extremity symptoms were relieved. This level of improvement is consistent with that reported in the literature following revascularization. The conclusion is that patients with claudication have modest goals with respect to improvement following vascular intervention. More data should be collected on the functional outcomes of vascular intervention so that patients can make better informed choices regarding treatment of symptomatic lower extremity arterial occlusive disease.

Activities of Daily Living↗