. de J. (1978). Thorax, 33,[335][336][337][338][339][340][341][342][343][344] Structural basis for the changing physical properties of human pulmonary vessels with age. Circumferential strips of pulmonary vessel wall were obtained at necropsy from the major arterial and venous branches at the lung hilum in patients aged 7-87 years.The extensibility of these strips was measured using the tension balance method of Harris et al. (British Heart Journal, 1965, 27, 651-659). The vessels were then bisected, and half of each strip was submitted for structural analysis using morphometric methods on paraffin sections stained to show the collagen, elastin, and muscle content. The other halves of the formalin-fixed vessel strips were examined chemically to determine their collagen content by estimation of the total hydroxyproline content. The thickness of the vessel media was measured microscopically on all of the sections examined.Quantitative measurements were made on 42 arteries and 37 veins. Contrary to expectation, there was a steady fall in medial collagen content with increasing age in arteries and veins. The decrease in collagen content was similar in the morphometric and chemical studies and was statistically significant. The thickness of the vessel media did not change significantly with age.The pulmonary artery and vein strips were less extensible in the older age groups, the main change occurring in the elastic phase of the vascular stress/strain curves. It is suggested that changes in the elastic tissue at a molecular and lamellar level are responsible for the increasing stiffness of pulmonary vessels rather than changes in the medial collagen content.

1. We have studied the extensibility of circumferential strips of main pulmonary artery and large pulmonary veins obtained at post mortem from patients of all ages, dying from conditions other than heart and lung disease. 2. The vessel strips were submitted to increasing loads in a tension balance. The pulmonary arteries were found to be readily extensible. This extensibility became less with increasing age. The pulmonary veins were virtually inextensible at all ages. 3. It is postulated that the large extraparenchymal pulmonary veins have a capacitative role in supplying blood from the lungs to the left atrium. This may be accomplished by their collapsible nature, as they have little capability of distension.

Previous studies have shown that the functionally enigmatic pineal "synaptic" ribbons are structurally a heterogeneous group of organelles consisting of rodlike ribbons sensu stricto, spherules, and intermediate forms. As ribbons and spherules react differently under various experimental conditions, these organelles were studied qualitatively and quantitatively during the postnatal period in guinea pigs. It was found that the pinealocytes were highly differentiated at birth and contained all three forms of "synaptic" structures. Ribbons and intermediate forms were more abundant than spherules and exhibited a striking increase in number on postnatal days 1 and 2; this increase was followed by a distinct trough and by a second peak at days 12 and 13, after which their numbers declined to reach adult levels by day 20. The spherules were small in number at birth and did not show the large immediate postnatal increase observed for the ribbons and intermediate forms. Instead there was a steady numerical increase up to day 12 (absolute number) or day 15 (relative numbers), followed by a decrease to adult level by day 20. Whereas during the early postnatal period (days 1 to 3) the majority of pinealocytes were characterized by ribbons and intermediate forms, with increasing age spherule-bearing pinealocytes increased in number. As ribbons and spherules were usually not found in the same pinealocyte, the present findings are interpreted to mean that ribbons and spherules characterize different types of pinealocytes showing an inverse numerical development postnatally. Developmentally intermediate forms behave like ribbons.

(1974). Thorax, 29,[567][568][569][570] Cardiovascular dynamics in women during the menstrual cycle and oral contraceptive therapy. Measurements of pulmonary blood flow and cardiac output have been made in 31 healthy women during the follicular and luteal phases of their menstrual cycle using nitrous oxide whole body plethysmography. The women were divided into three groups: 12 women were receiving oestrogen-progestogen contraceptive pills, 8 were receiving progestogen-only pills, and 11 were using either alternative methods of contraception or none at all. There was no significant difference in the values of cardiac index, pulmonary arterial distensibility, heart rate or systemic blood pressure during the two phases of the menstrual cycle in any of the three groups. When the three groups were compared the cardiac output showed the most significant difference, being greatest in the oestrogen-progestogen group, the progestogenonly group occupying an intermediate position. An increased cardiac output might play a part in the development of systemic hypertension in some women receiving oral contraceptives and could also add a risk to women with pre-existing heart disease.An increased cardiac output has been reported in women receiving the oestrogen-progestogen contraceptive pill (Walters and Lim, 1969, 1970), while changes have been noted in both plasma and lung capillary volumes and in blood vessel distensibility during the luteal phase of the normal menstrual cycle (Seaton, 1972). We have now studied the pulmonary haemodynamics of women receiving both combined and progestogen-only contraceptive pills using nitrous oxide (N2O) body plethysmography. PATIENTS AND METHODSThirty-one healthy, normotensive women were studied: 11 (group 1) were using either no contraception (5) or methods other than the pill (6); 12 (group 2) were taking combined oestrogen-progestogen contraceptive pills; and 8 (group 3) were taking progestogen-only oral contraceptives (Table I). Patients were recruited from a local family planning clinic with the exception of five control patients who were not using any form of contraception and were recruited from the hospital staff.The three groups were studied concurrently under identical conditions. The subjects were studied on two separate occasions during their menstrual cycle--between 7 and 10 days after, and one to four days before the onset of bleeding-with the exception of four women taking the progestogen-only preparation who had grossly irregular and unpredictable bleeding and were studied at an interval of four weeks.Arterial blood pressure was measured with a mercury sphygmomanometer after the subject had been lying at rest for 10 minutes. Heart rate was determined from the electrocardiogram during plethysmography. N20 BODY PLETHYSMOGRAPHY Readings were taken with the patient in the supine position. All patients were trained to perform the respiratory manoeuvre in an identical manner and to maintain constant air flow during slow exhalation.Pulmonary capillary blood flow was measured by th...