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Biomedical subjects

M Morton

Publications and source records attributed to M Morton.

At least 19 recordsLinked to original sources
PubMed1992

Tetrodotoxin-insensitive sodium channels in a cardiac cell line from a transgenic mouse.

The electrophysiological properties of a cardiac cell line (MCM1) originating from a transgenic mouse were characterized. The dominant current in these cells is a sodium current that is insensitive to concentrations of tetrodotoxin (TTX) up to 100 microM. It activates and inactivates rapidly with half-maximal activation at -40 mV and half-maximal inactivation at -79 mV. This sodium current is reduced by agents that increase intracellular adenosine 3',5'-cyclic monophosphate (cAMP) and activate cAMP-dependent protein kinase including isoproterenol, 8-bromo-cAMP, and isobutylmethylxanthine. The phenylalkylamine desmethoxyverapamil blocks the TTX-insensitive sodium current in MCM1 cells in both tonic and use-dependent fashion. Membrane depolarization enhances this block. It is proposed that the TTX-insensitive sodium current in these cells may be similar in origin to the embryonic type of TTX-insensitive sodium current described in other cardiac and skeletal muscle preparations.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Oral cancer and precancer: after-care and terminal care.

This paper looks at the social and psychological effects of cancer on patients and their families, and discusses the support and after-care required by a patient who has been treated for an oral cancer. The role of the dental practitioner in the maintenance of oral health and comfort is discussed, and the management of the side-effects of the different treatment modalities is described. The particular problems and needs of patients, and the relatives of patients, in the terminal stages of oral cancer are also discussed.

Aftercare↗
PubMed1984

Left ventricular size, output, and structure during guinea pig pregnancy.

We investigated left ventricular (LV) hemodynamics, pressure-volume relations, and morphometry to determine what cardiac changes characterize pregnancy in the guinea pig. Time-bred virgin guinea pigs were paired by weight with unbred controls. Hemodynamic studies and LV pressure-volume relations were obtained on days 59-68 of the 68-day gestation. Weight of control sows increased from 817 to 902 g (P less than 0.01) and pregnant sows from 810 to 1,251 g (P less than 0.01). LV weights were not different. When indexed for maternal weight minus uterus and contents, pregnancy produced increases in O2 consumption, +48% (P less than 0.01); cardiac output, +32% (P less than 0.05); and stroke volume, +46% (P less than 0.025). Passive LV pressure-volume curves (dP/dV) were shifted to the right (P less than 0.025), but dP/dV at constant pressure was unchanged. Using a thin-walled spherical model, elastic modulus at constant stress was not different. The percent LV inter- and intracellular volumes and myocyte myofibril and organelle volumes were unchanged during pregnancy. In the guinea pig, pregnancy increases LV output, stroke volume, and size without changes in LV mass, morphometry, or elastic modulus.

Animals↗
PubMed1984

Physical activity and osteoporosis in post-menopausal women.

Osteoporosis is an accepted fact of the female's aging process. This decrease in bone mass is most often linked to a lack of estrogen; however, prolonged inactivity is also known to cause atrophy in both muscle and bone. The purpose of this study was to investigate the relationship between the degree of osteoporosis and the physical activity levels of a group of post-menopausal women. Forty women between the ages of 60-69 yr were selected at random from a group of volunteers. The possible existence of a correlation between cortical diameter and activity level was investigated by using linear-model analysis. The width of the cortex may be related to many factors in addition to activity level. Some of the more important factors also considered were height, weight, ponderal index, age, years since taking estrogen, and total metacarpal diameter. The inclusion of these terms in the linear-model analysis allowed for an accounting of variability as associated with variables that could not be held constant. The variables showing the most significant relationships with the cortical diameter were the activity level and the use of estrogen. The relationships investigated through the linear-model analysis do not need to be independent. It is possible that combinations of these variables act to retard or enhance osteoporosis. Therefore, because the primary concern of the investigators was the relationship between physical activity and osteoporosis, a t-test was performed comparing the 10 most active women with the 10 most sedentary.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1982

The effect of acute elevation of blood pressure on myocardial performance during enflurane and enflurane with nitrous oxide anaesthesia in man.

Myocardial performance was assessed by a noninvasive method, when arterial pressure was raised acutely in eleven healthy subjects, awake and anaesthetized with equipotent (1 MAC) doses of either enflurane (Group 1) or enflurane with nitrous oxide 70 per cent. (Group 2). With anaesthesia, there was a significant and equal decrease in the indices of myocardial performance (p less than 0.05) in both groups with pressure elevation when compared to awake controls. The results are similar to those observed in subjects with depressed myocardial function due to either ischaemic heart disease or halothane anaesthesia.

Adolescent↗
PubMed1980

Baroreflex control of heart rate in man awake and during enflurane and enflurane--nitrous oxide anesthesia.

Baroreflex control of heart rate was assessed by means of a pressor test in two groups of subjects while awake and at two levels of anesthesia with enflurane (Group I) and enflurane-nitrous oxide (Group II). In the awake control situation, calculated mean slopes (+/- SD) were 23 +/- 8 (Group I) and 25 +/- 11 (Group II). There was no significant difference between the groups. During enflurane anesthesia (Group I) mean slopes were significantly depressed to 5 +/- 5 at 1 MAC and 6 +/- 6 at 0.8 MAC. During enflurane-nitrous oxide anesthesia (Group II), slopes were significantly depressed to 5 +/- 3 at 1 MAC and 6 +/- 4 at 0.9 MAC. There was no significant difference between the extents of depression in the two groups. It is concluded that both enflurane anesthesia and enflurane-nitrous oxide anesthesia at 1 MAC produce significant depression of baroreflex control of heart rate in man.

Adolescent↗
PubMed1977

Mortality and the concentration of elements in tap water in county boroughs in England and Wales.

To explain the associations of water hardness and air temperature with area differences in ischaemic heart disease mortality, samples of tap water were obtained from homes in 61 county boroughs in England and Wales, and the concentration of calcium and 12 other elements was estimated. Multiple regressions were calculated with the death rates from various causes as dependent variables and with the concentration of the elements in the tap water, mean annual temperature, mean annual rainfall, and a socioeconomic index as independent variables. The well known negative association between water hardness and ischaemic heart disease was shown to be due to calcium, and none of 12 other elements examined appeared to contribute significantly to the association. Area differences in other causes of death also showed an association with calcium. There was little association between temperature and ischaemic heart disease.

Adult↗
PubMed1977

Pulmonary tissue concentrations of ethchlorvynol after intravenous injection.

Noncardiogenic pulmonary edema has been reported to follow the intravenous use of ethchlorvynol (Placidyl) in both human clinical and animal experimental situations. In a further attempt to define ethchlorvynol-pulmonary tissue inter-relations, we measured ethchlorvynol concentrations in venous and arterial blood and lung and liver tissue of dogs after intravenous injection of 15 to 25 mg of the drug per kg of body weight. In 10 dogs, the mean +/- SEM lung concentrations 1, 3, and 5 min after injection were 70 +/- 20, 50 +/- 13, and 24 +/- 9 mug per g of tissue, respectively. Simultaneous mean +/- SEM venous contrations were 75 +/- 40, 29+/-5, and 22 +/- 5 mug per ml of blood, respectively. During minutes 1 and 3, the liver concentrations were lower than those found in the lung. In an additional 3 dogs, injection of ethchlorvynol into the portal vein led to higher concentrations (at all sample times) in the liver when compared to the lung. In vitro lung slice studies using ethchlorvynol labeled with iodine-131 revealed no active energy-dependent uptake. Intravenously administered ethchlorvynol rapidly fluxes into and out of lung tissue, apparently following the laws of diffusion.

Animals↗