Peter Harris

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 heart and pulmonary vasculature of the llama (Lama glama)

Heath, D., Smith, P., Williams, D., Harris, P., Arias-Stella, J., and Krüger, H. (1974).Thorax, 29, 463-471. The heart and pulmonary vasculature of the llama (Lama glama). A qualitative and quantitative histological study was made of the pulmonary trunk and muscular pulmonary arteries of a male and a pregnant female llama born and living at an altitude of 4,720 m above sea-level in the Peruvian Andes. A similar study was made on the fetal llama. The individual cardiac chambers of the two adults were weighed. Our results show that in the adult llama there is no hypertrophy of the right ventricle or of the media of the pulmonary trunk or small pulmonary arteries. This appears to be of evolutionary significance in respect of survival at high altitude and suggests that the llama does not have a sustained significant pulmonary hypertension. The pulmonary arteries of the fetal llama are thick-walled and we associate this with the physiological pulmonary hypertension of fetal life.

Clara Cells in the Llama

A study was made by light and electron microscopy of the Clara cells of two llamas born and bred at an altitude of 4,720 m in the Peruvian Andes. The Clara cells were numerous and prominent with big apical caps, many of which had been extruded into the terminal bronchioles. On electron microscopy the caps were found to contain vesicular endoplasmic reticulum. Previous studies have shown this to contain dipalmitoyl lecithin, a known pulmonary surfactant. Acute exposure to a simulated altitude of 4,270 m has been reported to increase surface tension in lung extracts of mice. Hence it may be that an animal, such as the llama, chronically exposed to high altitude requires a persistent secretion of pulmonary surfactant.