Effect of age and high blood pressure on baroreflex sensitivity in man

The purpose of this study was to relate baroreflex sensitivity to age and arterial pressure in 61 male and 20 female untreated subjects, aged 19-66 years, whose mean arterial pressures ranged from 70 to 150 mm Hg. In this selected group of subjects there was no correlation between age and arterial pressure. The index of sensitivity used was the increase in pulse interval which occurs reflexly in response to a rise in systolic pressure induced by the intravenous injection of phenylephrine and is measured as the increase in pulse interval in milliseconds per mm Hg rise in systolic blood pressure. It ranged from 1.9 to 48.9 msec/mm Hg. Increasing age and arterial pressure act independently to reduce baroreflex sensitivity. Eight subjects who had normal blood pressure at the time of testing but whose pressure had been elevated in the past, had reflex sensitivities significantly less than expected in persons of the same age and mean arterial pressure. The heart rate in these subjects was not significantly different from that in the controls; the heart rate of the 12 hypertensive subjects aged under 40 years was significantly faster than that of age-matched normotensive subjects but not that of older hypertensive subjects.

Interaction between ABO and rhesus blood groups, the site of origin of gastric cancers, and the age and sex of the patient

ABO and Rhesus blood group data have been examined for 1,680 patients treated for gastric cancer in four London hospitals. The risk of developing gastric cancer was estimated to be 16% higher for group A subjects than for group O subjects, in close agreement with many previous reports throughout the world. More detailed analysis failed to support the suggestion that there was any special correlation between either ABO or Rhesus blood groups and the site of origin of the tumour within the stomach or the sex or age of the patient. Male predominance among the patients was noted to be greater at ages 40-69 years than at other ages and greater for tumours of the upper two thirds of the stomach than for tumours that arose distally.

The mechanism of carcinogenesis by the neutral fraction of cigarette smoke condensate

Sixteen groups, each of 50 Swiss female SPF mice, were treated thrice weekly with various combinations of 3,4-benzopyrene (BP) and/or the neutral fraction of cigarette smoke (NF) in acetone applied to the skin. Some groups received one carcinogen, some the other and some a mixture of the two. Skin tumour incidence rates were found to increase both with the dose of NF and with the dose of BP. With BP alone a threshold dose was found beyond which a very heavy incidence rate of malignant skin tumours occurred. After correction of the results for intercurrent deaths it was found that when NF and BP are applied together as a mixture they do not act independently in the production of malignant skin tumours but interact positively. This suggests that some of the components of NF act as cocarcinogens rather than as complete carcinogens. Treatment with NF appeared to increase the incidence of malignant lymphomas. The data were not suitable for deciding whether the various treatments influenced the rates of incidence of internal tumours of other types, for example, lung tumours.

The effect of the age of mice on the incidence of skin cancer

The plausibilities of two hypotheses explaining the increased cancer incidence rate in old age caused by a constant dose of carcinogen were compared using a mouse skin painting experiment in which two groups of mice started treatment at different ages. It was shown that the hypothesis of the increased rate being caused simply by increased vulnerability of old animals was not as plausible as the alternative hypothesis of the carcinogen acting to some extent cumulatively.

Comparative carcinogenicity for mouse-skin of smoke condensates prepared from cigarettes made from the same tobacco cured by two processes

Bright tobacco grown in Mexico was either flue-cured and redried (FC) or air-cured and bulk-fermented (AC). Both FC and AC were made into cigarettes standardized for draw resistance. FC and AC cigarettes were smoked under similar conditions in a smoking machine (one 2-second 25 ml. puff per minute down to a 20 mm. butt length). Condensates were kept at 0-4° C. until applied to the skin of mice.Three groups of 400 female Swiss mice were treated as follows: Group 1- thrice weekly application of 60 mg. FC in 0.25 ml. acetone to the clipped dorsal skin: Group 2- similar treatment with AC; Group 3-thrice weekly application of 0.25 ml. acetone only.Chemical analysis of the 2 tobaccos and 2 condensates revealed only small differences in composition and it is noteworthy that the concentration of reducing sugars was almost as high as in the AC tobacco as in the FC tobacco.The risk of development of skin tumours, particularly malignant skin tumours, was higher in FC-treated mice than in AC-treated mice (p < 0.01), but the difference may have been due to the use of equal weights of condensates rather than the use of extracts from equal numbers of cigarettes, since the AC cigarettes produced more condensate. The rates of detection of pulmonary tumours also varied between groups (p < 0.01) but this does not necessarily imply that the incidence rates of pulmonary tumours varied. There was no evidence that the detection or incidence rates of any other neoplasms, including malignant lymphoma, were affected by treatment with either of the condensates.