Effects on the right ventricle, pulmonary vasculature, and carotid bodies of the rat of exposure to, and recovery from, simulated high altitude

Three groups of 10 adult male Wistar albino rats were studied. The first was kept for five weeks in a hypobaric chamber exposed to a barometric pressure of 380 mmHg, equivalent to a simulated altitude of 5,500 m above sea level. The second was exposed to the same barometric pressure for five weeks and then allowed to recover in room air for a further period of five weeks. The third group acted as controls and was kept at normal barometric pressure throughout. At necropsy right ventricular weight was expressed as an inverse ratio of left ventricular weight (LV/RV ratio). The thickness of the media of the pulmonary trunk was expressed as a ratio of that of the aorta. The volumes of the carotid bodies were measured by applying Simpson's rule to histological sections. In the first group, exposed to chronic hypoxia without relief, there was hypertrophy of the right ventricle and media of the pulmonary trunk and there was an increase of carotid body volume, as compared with the values obtained in the controls. In the recovery group these three measurements had returned almost to normal. The results appear to be applicable to hypoxic cor pulmonale in man. They suggest that hypoxia rapidly produces pulmonary hypertension and its morbid anatomical associations while recovery is equally rapid once the hypoxic stimulus is removed.

Post-mortem size and structure of the human carotid body

The weights of the carotid bodies have been measured in an unselected group of 40 successive cases coming for routine necropsy. Although the mean weight of the carotid bodies was higher in those subjects with emphysema or Pickwickian syndrome, this difference did not reach a level of statistical significance. Nevertheless, in a group of two patients with cor pulmonale and one with the Pickwickian syndrome the mean weight of the carotid bodies was significantly higher than that of the rest. Such observations would be consistent with enlargement of the glomic tissue in response to chronic hypoxia. In addition to these observations there was a significant correlation between the size of the carotid bodies and the weights of the left and right ventricles separately, while there was a substantially higher correlation between the weights of the carotid bodies and the combined weights of the two ventricles. Should such a correlation be determined by a causative link between these two measurements, a new metabolic role of glomic tissue will have to be considered. The histology of the carotid bodies was studied and differential cell counts were carried out in 21 cases. Enlargement of the carotid bodies was not accompanied by any change in the differential cell count, except that in one case with `cor pulmonale' and large carotid bodies areas of hyperplasia showed a predominance of the dark variety of type 1 (chief) cell.

The permeation of non-electrolytes through the single barnacle muscle cell

The rate of movement of non-electrolytes and tritiated water (THO) across the muscle cell membrane of the giant barnacle Balanus nubilus has been studied and permeability coefficient calculated. The rate of permeation is more closely related to the oil-water partition coefficient than to size of the molecule or degree of hydrogen bonding. Calculations based on efflux from an ideal cylinder suggest that the membrane acts as a significant barrier to movement of these molecules. The cell was unable to concentrate dimethyl sulphoxide (DMSO); the steady state was reached at about 60% of the extracellular concentration. The energies of activation for water, urea and DMSO are 7.5, 20.3 and 26.1 kcal/mol. At 4 degrees C the apparent pore size measured with urea, glycerol and DMSO was 3.5 A. At 25 degrees C the apparent pore size for urea and glycerol is unchanged but that for DMSO is 14 A.

Microanatomy of glomic tissue of the pulmonary trunk

Glomic tissue occurs at the bifurcation of the pulmonary trunk. There is controversy as to its derivation, blood supply, and function. It has been regarded as one of the coronary glomera supplied by the intertruncal branch of the left coronary artery. On the other hand, it has been described as the true glomus pulmonale supplied by blood from the pulmonary trunk. The purpose of this article is to draw attention to its existence and to establish its microanatomical structure.