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P M Rees

Publications and source records attributed to P M Rees.

12 recordsLinked to original sources
PubMed1978

Histology and ultrastructure of the carotid sinus in experimental hypertension.

Histological studies including electron microscopy were performed on the carotid sinuses of dogs with renal hypertension of 17 to 82 days duration or hypertension of two years secondary to aortic coarctation. Physiological abnormalities in the baroreceptors including resetting had been demonstrated before death. Histologically there were no qualitative or quantitative differences in the intrasinus nerve fibers of the hypertensive animals compared tp controls with normal blood pressures, and there was no evidence that baroreceptor degeneration occurred as a consequence of the hypertension. Structural lesions confined to the intima were evident in the sinus walls of some of the renal hypertensive animals whereas the dogs with coarctation showed more advanced sinus wall changes including medial calcification and enlargement of the vascular lumen.

Animals↗
PubMed1976

Baroreflex sensitivity and carotid sinus dimensions in dogs with coarctation.

Baroreflex sensitivity (BRS) has not been assessed in coarctation, though it is diminished in renal and essential hypertension. Previous experimental studies of coarctation have dealt primarily with renal mechanisms of hypertension, and have relied on constricting the aorta in adult animals. We banded the thoracic aorta in newborn puppies, and performed studies 2 yr later. Blood pressure (BP) elevations, abundant chest wall collaterals, the absence of heart failure, and subsequent necropsy confirmed the full syndrome of natural coarctation in all dogs. Transient BP elevations were induced in conscious, unrestrained dogs with intravenous phenylephrine injections. Reflex bradycardia was quantitated by plotting each pulse interval in microseconds against BP of the preceding beat, and expressing BRS as the linear regression coefficient (slope) in ms/mmHg. Mean BRS in 10 dogs with coarctation did not differ significantly (P greater than 0.1) from 8 normal controls. Carotid sinus diameter (CSD) was also assessed. Carotid arteries were fixed in vivo by prolonged exposure to glutaraldehyde to prevent contraction, then were excised and measured in a calibrated microscope. Mean CSD in 10 dogs with coarctation was significantly greater (P less than 0.01) than in 10 control dogs. The unexpectedly normal BRS in experimental coarctation may be due to changes in CSD induced by hypertension; such changes may only develop in growing animals. Experimental studies of coarctation should use a preparation that mimics the natural lesion.

Animals↗
PubMed1975

Carotid baroceptor re-setting in the hypertensive dog.

1. The behaviour of forty-four single carotid baroreceptor fibres from nine dogs with normal blood pressure was contrasted with that of forty-seven single fibres from nine dogs with renal (nephrectomy--clip) hypertension. 2. It was found that in response to a square-wave pressure step, the mean steady-state threshold pressure was 99.23 mmHg for the normotensive dogs and 129.13 mmHg for the hypertensive dogs. 3. The degree of re-setting appeared to correlate with the duration of the hypertension but was not seen until an animal had been hypertensive for more than 4 days. 4. In one animal, hypertensive for 7 weeks but whose blood pressure returned towards normal after removal of the clip, the receptor characteristics was normal. 5. No change in the gain of the receptor sensitivity was seen. 6. Light-microscopy and electron miscroscopy of the opposite (non-perfused) carotid sinus revealed no differences in the fibre morphology or density between the hypertensive and normotensive animals (a random sampling, four normal and six hypertensive).

Animals↗
PubMed1967

The distribution of biogenic amines in the carotid bifurcation region.

1. The distribution of phenolic amines in the carotid body and of adrenergic nerves in the arterial walls of the carotid bifurcation region was investigated histochemically using the phenolic amine-formaldehyde gas condensation reaction, with supplementary electron microscopical examination. Studies were conducted on normal rabbits and on rabbits after superior cervical ganglionectomy.2. The glomus cells of the carotid body contain phenolic amines. The cellular amine persists after long-term sympathetic ganglionectomy.3. The blood vessels supplying the carotid body receive an adrenergic innervation which disappears following superior cervical ganglionectomy.4. The walls of the carotid sinus contain adrenergic nerve fibres derived from the superior cervical ganglion.5. There is no penetration of the arterial tunica media by vasomotor fibres in any part of the carotid bifurcation region.6. Ultimate terminations of adrenergic nerves upon smooth muscle occur across the medio-adventitial border of the common, internal and external carotid arterial walls but only in relation to smooth-muscle cells in the adventitia of the carotid sinus wall.

Amines↗