Biomedical subjects
Publications and source records attributed to T Gordon.
Female wistar rats were given cadmium sulfide in various concentrations in their chow (26 mg CdS/kg feed and 52 mg CdS/kg feed). After a three month trial no significant changes in blood pressure could be seen. The pulse frequencies showed the falling tendency with increasing weight, as already seen in healthy rats.
Female wistar rats were given cadmium sulfide in various concentrations in their chow (26 mg CdS/kg feed and 52 mg tcdS/kg feed). After a three month trial no significant changes in blood pressure could be seen. The pulse frequencies showed the falling tendency with increasing weight, as already seen in healthy rats.
1. The sensitivity to acetylcholine (ACh) of the fast posterior latissimus dorsi (PLD) and slow anterior latissimus dorsi (ALD) during embryonic development was studied and compared. The sensitivities were expressed as a ratio of the maximal tetanic tension and tension developed in response to ACh. 2. Up to the 17th day of incubation both muscles are sensitive to ACh to a similar extent; at the 18th day the sensitivity of the PLD muscle decreases and continues to do so until hatching and thereafter. 3. Since the decrease in sensitivity of PLD muscles takes place a few days after innervation, it is suggested that this is caused by activity of the motor nerve. To test this curare (dTc) and hemicholinium (HC-3), drugs that interfere with neuromuscular transmission, were injected into the yolk sac of the embryos when nervemuscle connections are usually established. In the curare and HC-3 treated embryos the desensitization of the PLD muscles did not take place. 4. The distribution of endplates on PLD muscles from drug treated 20-21 day old embryos was compared to that of untreated controls. Whereas control PLD muscles have only one band of endplates, muscles from curarized embryos and HC-3 treated embryos have several bands of endplates, and many muscle fibres with multiple innervation were found. 5. It is suggested that nerve fibres which make connections with PLD muscle fibres bring about a decline in chemosensitivity by releasing more transmitter, and thereby prevent further nerve muscle connections from being made along the same muscle fibre.
1. The role of innervation of the differentiation of contractile speeds was studied in the slow anterior latissimus dorsi (ALD) and fast posterior latissimus dorsi (PLD) muscle of the chick. 2. These muscles become innervated during the 12th and 15th day of embryonic development. At this time both muscles contract and relax extremely slowly and their contractile speeds are very similar. By the 18th day their contraction and relaxation becomes more rapid. It is at this time that the contractile characteristics of both muscles also become very different from each other, ALD being about 3 times slower than PLD. Thus innervation percedes differentiation of contractile speeds by several days. 3. The influence of innervation on the contractile characteristics of developing slow and fast muscles was studied during muscle regeneration in adults. When a slow ALD muscle was minced and implanted in place of a fast PLD the newly regenerated ALD became innervated by a PLD nerve and resembled a fast PLD. Conversely, when PLD muscles were minced and replaced ALD the regenerated PLD was innervated by ALD nerve and became slow. 4. Histological examination revealed that the regenerated ALD became focally innervated, and the regenerated PLD multiply innervated. 5. Thus, the contractile speeds are not predetermined properties of the muscle fibre. Both contractile characteristic and the pattern of innervation of developing muscles are determined by the motor nerve.
During the first 18 years of the Framingham Study there was a substantial decrease (39 per cent ) in the number of men smoking cigarettes and a moderate decrease (22 per cent) in the number of women smoking cigarettes. Except for a greater tendency of diabetic patients to quit smoking, there were no significant differences at baseline between smokers who quit and smokers who continued smoking. After quitting there was a short-term rise in weight for men. This rise led only to trivial changes in blood pressure and serum cholesterol levels. There was a beneficial impact on long-term vital capacity trends from quitting smoking.
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Precursors of sudden death were sought in men--1838 civil servants in Albany, New York, and 2282 residents of Framingham, Massachusetts--under continuous surveillance for 16 years. In men 45-74 years old there were 234 deaths attributed to coronary heart disease (CHD) of which 109 occurred within one hour of onset of symptoms. More than half of all deaths due to CHD occurred outside the hospital and about 80 per cent of these were sudden. Most were unheralded by prior symptoms of CHD. Persons at high risk of death from CHD, including sudden death, can be identified long before the terminal unexpected catastrophe. The same precursive stigmata exist in persons subject ot coronary attacks whether or not immediately fatal. The risk of sudden death in these two populations was positively correlated with high blood pressure, the electrocardiographic pattern of left ventricular enlargement, obesity, and heavy cigarette usage. Sudden death is a common and possibly incidental expression of lethal coronary heart disease. The potential candidate for sudden death cannot be confidently distinguished from the individual who succumbs more slowly of myocardial infarction. The inescapable conclusion is that the prevention of sudden death requires the prevention of coronary attacks.
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In children from an industrial area with a high degree of lead, zinc and cadmium pollution, the lead levels in blood and hair increased with increasing lead fall-out, and the cadmium concentration in the urine increased with increasing zinc fall-out. Children from the center of town presented significantly higher lead values in the blood and hair samples and, significantly lower urine lead concentration than those children investigated, living in the peripheral districts of the industrial town. The lead content of blood and hair samples corresponded to the various lead immission levels encountered. The results give rise to the supposition that biological cadmium interactions are influenced by simultaneous lead uptake.
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