ISSN:0731-5724    

DOI:10.1080/07315724.1985.10738065

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

The electrocardiogram was recorded and serum and bulk myocardial electrolytes were determined in male Sprague Dawley rats, subjected to dietary magnesium deficiency for various periods, to assess the time course of development and cessation of the enhanced arrhythmogenic action of isoproterenol (150 micrograms/kg, subcutaneously) and to establish possible relationships between electrolyte changes and severe ventricular dysrhythmias. Ventricular fibrillation occurred within 60 min following isoproterenol injection in 25, 25, 62.5, 50, and 62.5% of rats on magnesium deficient diet for 4, 7, 11, 15, and 19 days (N = 8), respectively, and resulted in death in most animals (83%). Reintroduction of normal chow following a 30-day period on magnesium-deficient diet normalized serum magnesium (from 1.42 +/−0.23 to 1.90 +/−0.08 mEq/liter, mean +/−SD) but did not significantly reduce the incidence of ventricular fibrillation. Magnesium deficiency did not produce statistically significant alterations in bulk myocardial content of sodium, potassium, magnesium, and calcium. However, sodium was elevated and potassium diminished in hearts from rats that died in ventricular fibrillation, but not in those that had recovered. Magnesium-deficient rats sacrificed 30 min after isoproterenol injection, that is before the occurrence of ventricular fibrillation, exhibited hypomagnesemia and hypokalemia as well as elevated sodium and diminished potassium and magnesium in the myocardium. In contrast, rats on Purina Chow exhibited hypermagnesemia, but also showed hypokalemia and diminished cardiac potassium. The results indicate that magnesium deficiency enhances the arrhythmogenic propensity of isoproterenol and that the development of ventricular fibrillation is preceded by serum and myocardial electrolyte alterations.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720081

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

To evaluate changes in magnesium levels with treadmill exercise-induced coronary insufficiency, 59 consecutive patients were studied. In addition to electrocardiographic monitoring, hematocrit, total protein, whole blood, serum and red blood cell magnesium determinations were made before and after exercise testing. Fifteen patients had positive exercise test, 18 did not complete, and 26 had negative exercise test. There was no significant difference in the serum and red blood cell magnesium on the basis of stress test results for ischemia. Although whole blood magnesium, hematocrit, and total proteins increased (P less than .05) in both groups, we did not find a significant change in magnesium homeostasis.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720072

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

Twenty type A male students were compared to nineteen type B male students (all in apparently good health), before and after exposure to combined stress (noise and task). Before stress, red blood cell (RBC) Zn concentration is higher (P less than .05) and Zn excretion lower (P less than .05) in type A than in type B people. After stress, type A subjects exhibit changes that are larger and more significant than those of type B individuals. After stress, the type A group shows an important increase of urinary catecholamines (P = 2.10(−5), serum free fatty acids, and urinary Zn (P = .001); a slight increase in plasma magnesium (P less than .05); and a small but significant decrease in RBC Mg (P less than .02). These results suggest that type A subjects are more sensitive to stress than are type B people and more readily lose their intracellular Mg, the rise in plasma Mg being a transient one, probably consecutive to the cellular loss. The present observations are in good agreement with published data: ie, the psychological characteristics of type A personalities; their greater susceptibility to ischemic heart disease, which has been associated with Mg deficiency; the possible role of hypomagnesemia in the pathogenesis of hypertension and coronary vasospasm; and the high RBC Zn levels found in hypertensive patients.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720073

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

Epidemiological studies indicate a strong relationship between dietary Mg intake and the incidence of sudden cardiac death. The mechanism by which dietary Mg leads to an increased incidence of cardiovascular disease is unknown but may involve alteration of electrolyte balance. In the present study, tissue electrolyte levels and myocardial pathology were investigated in adult hamsters fed a diet containing no added Mg. Control animals were fed the same diet supplemented with Mg or standard laboratory chow. Hamsters were killed after 4, 8, 12, or 18 days on the test diet, and levels of Na, K, Ca, and Mg were measured in the serum, myocardium, bone, and kidney. The earliest change induced by the test diet was a decrease of the serum Mg and an increase in the Na concentration of the myocardium and other tissues. Following the rise in myocardial Na, the myocardial Ca rose, attaining a fourfold increase by 18 days. K fell in heart and kidney, but not significantly. Although there was no significant change in myocardial Mg, foci of myocardial necrosis, considered to be typical of acute severe Mg deficiency, were found. Myocardial necrosis and the increase in myocardial Ca occurred in parallel. Because of the pattern of observed changes in electrolyte levels, and the potential role of Ca in myocardial injury, the occurrence of myocardial necrosis in these Mg-deficient hamsters is attributable to the increased level of myocardial Ca, rather than to any change in intracellular Mg levels. It is postulated that reduced extracellular Mg levels increase [Na]i through reduction of sarcolemmal (Na+ + K+)-ATPase activity. This would lead to an increase in [Ca]i through Na-Ca exchange.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720074

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

In a single case study of a moderately trained, healthy man, physiologic changes during a marathon are reported. Blood was drawn prior to the race, at 1 hour and 2 hours into the race, at the end of the race, and after 1 hour of recovery. By 1 hour into the race, norepinephrine, epinephrine, and dopamine had increased nearly nine-fold, two-fold and five-fold, respectively. After 1 hour of recovery, epinephrine had returned to the pre-race value but norepinephrine and dopamine were still elevated. Cortisol increased gradually and was more than doubled by the end of the race. It was still elevated after 1 hour of recovery. White blood cells gradually increased, reaching their maximum value at the end of the race; a four-to-five-fold increase. Thromboxane B2, which had an inverse relationship to serum magnesium, was below the pre-race value for the first 2 hours but increased nine-fold by the end of the race. Serum magnesium increased from 1.44 meq/l to 1.68 meq/l at 2 hours into the marathon, dropped to 1.07 meq/l by the end of the race, and returned to its pre-race value by 1 hour of recovery. The decrease in serum magnesium at the end of the race may be associated with increased plasma free fatty acid levels.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720075

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

Dietary intake levels of calcium and magnesium, as well as calcium/magnesium ratios, were assessed for 12 age/sex groups of the U.S. population through use of USDA's 1977-78 Nationwide Food Consumption Survey. Results indicated that a majority of the U.S. population consumed less than recommended amounts (NRC-RDA) of both calcium and magnesium. Approximately 60% of 0 to 5 year olds and 40% of 6 to 11 year olds had average daily calcium intakes of less than 800 mg, while 60 and 85% of the male and female adolescents, respectively, had intakes below the recommended level of 1,200 mg/day. Approximately 80 to 85% of the adult female groups and 50 to 65% of the adult male groups had average intakes below recommended levels. With the exception of children ages 0 to 5 years, the average daily magnesium intakes of all age/sex classes were below the NRC-RDA. Magnesium consumption was particularly low among adolescent females, adult females, and elderly men, with 85, 80-85 and 75%, respectively, of the population groups having average magnesium intakes below their respective NRC-RDA. Furthermore, the majority of the population groups did not consume appropriate proportions of these two minerals to obtain optimal calcium/magnesium ratios. While adolescent females and adult females had more appropriate ratio values than other segments of the population, these ratios principally resulted from their very low intakes of calcium. The most inappropriate calcium/magnesium ratios, observed for children, male adolescents, and young adult males, were, in general, due to their more appropriate calcium intakes and their low magnesium intakes.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720076

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

The USDA's 1977-1978 Nationwide Food Consumption Survey was utilized to assess dietary intake levels of cholesterol, fatty acids, sodium, and potassium by several age/sex groups of the U.S. population. Results indicated that mean cholesterol intakes for all male age groups of 12 yr and older exceeded 300 mg/day while the mean intakes of females and children were less than 300 mg/day. However, approximately 30% of each age group of adult females exceeded 300 mg cholesterol per day and only about one-third of the adult males had average intakes of less than 300 mg/day. Between 39% and 44% of total kilocalories were obtained from fat consumption with saturated fatty acids contributing 13-15%, polyunsaturated fatty acids contributing 5-6% and oleic acid contributing 12-14% of total kilocaloric intake. We found that 90% of children ages 6-11 yr and adult females had saturated fatty acids intakes of less than 40 gm/day; 90% of all men had intakes of less than 55 gm/day. At least 90% of all age/sex groups averaged intakes of polyunsaturated fatty acids of less than 26 gm/day. Average daily sodium intakes for each age/sex group (excluding table salt) were within the limits considered safe and adequate. However, approximately 4% of each age group of adult females and about 25% of each of the three younger adult male groups had average sodium intakes of 4000 mg/day or more. Average daily potassium intakes were somewhat low, ranging from 1584 mg/day for children ages 0-5 yr to 2735 mg/day for males ages 51-64 yr.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720077

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

Eight normotensive obese subjects participated in an inpatient study designed to determine the effect of a constant sodium intake (150 mEq) on the renin-aldosterone axis during 12 weeks of weight reduction. Two 800-calorie (3,200 kj) ketogenic diets, differing in carbohydrate content (10 g vs 70 g) were used for the study. Supine and upright plasma renin activity (PRA) and serum aldosterone (SA) were determined at the baseline and every 4 weeks. Total body water (TBW) was determined by the tritiated water technique at the baseline and 12 weeks after dieting. Extracellular water (ECW) was determined by 77Br space. Routine serum chemistries were obtained at 2-week intervals. Analysis of variance indicated no significant differences in the PRA and SA between the two diets. At the baseline, while on a self-selected 150 mEq sodium diet, there was a 3- to 4-fold increase in PRA after 2 h of ambulation (supine PRA 0.83 +/−0.22 increased to 3.41 +/−0.96 ng/ml/h). After the hypocaloric diets were instituted, the absolute values for PRA in the supine and upright positions declined. However, the magnitude of the postural response (3- to 4-fold increase) remained unchanged during the 12 weeks of weight reduction. There was no decline in the absolute values for supine or upright SA, during the entire study. Weight loss was significant (from 102.56 +/−6.0 to 81.7 +/−3.7 kg; P less than .001) and was accompanied by a mean +/−SE reduction in the TBW of 3.01 +/−0.88 liters (P less than .011).(ABSTRACT TRUNCATED AT 250 WORDS)

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720078

出版商:Routledge    

年代:1985

数据来源: Taylor

摘要:

To examine the effect of chloride-containing potassium supplements on chloride titrator estimates of dietary sodium intake, we gave normal subjects diet containing 10, 100, or 200 mEq/d sodium in random order either as such, or supplemented with one of two potassium supplements. One regimen consisted of potassium 45 mEq/d with 12 mEq/d chloride and 33 mEq/d of citrate and gluconate; the other contained 48 mEq/d potassium and 48mEq/d chloride. Increased potassium intake with either supplemented regimen resulted in increased 24-hour potassium excretion, which was manifested in only the diurnal collections. Increased chloride intake resulted in increased urinary chloride excretion both during the day and at night. At all chloride intakes, urinary sodium and chloride excretion were highly correlated. The 48 mEq/d chloride intake generated a relationship with the same slope but with a different intercept from the other two regimens. The highest chloride intake resulted in a greater chloride titrator reading; however, the relationship was sufficiently predictable that adjustments in interpretation could be easily made. We conclude that if daily potassium chloride intake is known, chloride titrators continue to be reliable tools for estimating dietary sodium intake.

ISSN:0731-5724    

DOI:10.1080/07315724.1985.10720079

出版商:Routledge    

年代:1985

数据来源: Taylor