ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718428

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

The various definitions of neonatal hypocalcemia (NHC) are critically examined. The authors review the known and less known complications of NHC and of its treatment. They emphasize the need for a definition of NHC in terms of serum ionized rather than total calcium concentrations, the rationale for treating symptomatic NHC, as well as the need for further research in infants with asymptomatic NHC.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718429

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

A comprehensive and critical review of the evidence relating magnesium (Mg) deficiency to alcohol consumption reveals several important types of interactions. First, alcohol acts acutely as a Mg diuretic, causing a prompt, vigorous increase in the urinary excretion of this metal along with that of certain other electrolytes. Second, with chronic intake of alcohol and development of alcoholism, the body stores of Mg become depleted. During the late stages of alcoholism, the urinary excretion of Mg may become diminished as a physiological response to reduced intake and reduction of body stores. A number of aspects of the clinical syndrome of alcoholism contribute to and intensify that already existing reduction in body Mg stores. Third, a number of manifestations of alcoholism are believed due to effects of Mg deficiency, and some therapeutic benefit has been suggested from treatment of alcoholic patients with Mg. Finally, relatively little attention has been paid to the possible value of Mg administration as a preventive measure to forestall or minimize the deleterious effects of chronic use of alcohol or to prevent the development of cancer than can occur in this setting.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718430

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

Magnesium is unique among biological cations. Its volume change from hydrated cation to atomic ion is over an order of magnitude larger than that of any other biological cation. This volume change presents particular problems for a magnesium transport system and suggests that these systems may be significantly different from other classes of ion transport systems. Detailed study of Mg2+ transport in complex organisms is limited by severe technical problems. However, molecular genetic techniques have enabled the isolation of three Mg2+ transport systems from the Gram-negative bacterium Salmonella typhimurium. The MgtA and MgtB transport systems are members of the P-type ATPase superfamily of transporters but possess unique characteristics among members of this family. The CorA transport protein is the first member of an entirely new class of transport proteins. In addition, another completely new family of Mg2+ transport proteins have been identified that is present in both Gram-negative and Gram-positive bacteria. Characterization of these transporters should provide substantial insight into Mg2+ transport and cellular Mg2+ homeostasis.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718431

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

Stress intensifies release of catecholamines and corticosteroids that increase survival of normal animals when their lives are threatened. When magnesium (Mg) deficiency exists, stress paradoxically increases risk of cardiovascular damage including hypertension, cerebrovascular and coronary constriction and occlusion, arrhythmias and sudden cardiac death (SCD). In affluent societies, severe dietary Mg deficiency is uncommon, but dietary imbalances such as high intakes of fat and/or calcium (Ca) can intensify Mg inadequacy, especially under conditions of stress. Adrenergic stimulation of lipolysis can intensify its deficiency by complexing Mg with liberated fatty acids (FA), A low Mg/Ca ratio increases release of catecholamines, which lowers tissue (i.e. myocardial) Mg levels. It also favors excess release or formation of factors (derived both from FA metabolism and the endothelium), that are vasoconstrictive and platelet aggregating; a high Ca/Mg ratio also directly favors blood coagulation, which is also favored by excess fat and its mobilization during adrenergic lipolysis. Auto-oxidation of catecholamines yields free radicals, which explains the enhancement of the protective effect of Mg by anti-oxidant nutrients against cardiac damage caused by beta-catecholamines. Thus, stress, whether physical (i.e. exertion, heat, cold, trauma–accidental or surgical, burns), or emotional (i.e. pain, anxiety, excitement or depression) and dyspnea as in asthma increases need for Mg. Genetic differences in Mg utilization may account for differences in vulnerability to Mg deficiency and differences in body responses to stress.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718432

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

To determine whether: 1) short-term dietary elevation in magnesium (Mg) intake could alter serum ionized Mg (IMg2+), total Mg (TMg); % ionized Mg (% IMg2+) and other cations; and 2) different formulated preparations of Mg oxide (MgO) in the presence and absence of phosphate could alter serum IMg2+, TMg, % IMg2+ and other cations in Mg-loaded subjects.A randomized, triple cross-over study was performed on a rigorously defined group of normal male volunteers. Eighteen males were administered diets containing four to five times the United States recommended daily allowance (USRDA) of Mg followed by a randomization of three different MgO preparations, in the presence or absence of phosphate, containing equimolar amounts (12.34 mmol) of elemental Mg. Forty age-matched volunteers served as reference range controls. Specific ion selective electrodes were utilized to measure IMg2+, ionized calcium (ICa2+), sodium (Na+) potassium (K+) and hydrogen ion concentration (H+). Measurement of urinary excretion of Mg as well as TMg were determined by atomic absorption spectroscopy.Diets enriched with different oral formulations of Mg given for 6 days result in significant elevations in serum IMg2+ and % IMg2+ but not TMg, ICa2+, K+ or H+ in normal subjects. Although such Mg-loaded subjects demonstrate significant elevation in urinary excretion of Mg, no further changes in IMg2+, TMg or any of the serum cations were produced by ingestion of either of the three MgO preparations. Subjects showing normally low basal levels of serum IMg2+, (

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718433

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

Suspicions that mild zinc deficiency is common among the elderly cannot be confirmed or refuted because definitive indicators of zinc status are lacking. The goal of this study was to document the clinical responsiveness of parameters of zinc status in a group of older adults consuming a carefully controlled diet: first moderately low in zinc (3.97 mg/day for 15 days) and then high in zinc (28.19 mg/day for 6 days).Fifteen older adults (mean age = 66.6 yrs) volunteered to consume a marginally zinc-deficient diet for 15 days followed by 6 days of zinc repletion. Plasma concentrations of erythrocyte metallothionein and the enzyme 5′-nucleotidase, as well as levels of zinc, alkaline phosphatase, copper and ceruloplasmin were measured before and after zinc depletion and repletion.Plasma zinc levels were not altered during the study. Alkaline phosphatase (AP) values did not change in the expected direction, although a small decrease in AP following zinc repletion was statistically significant. Erythrocyte metallothionein results followed a pattern similar to that of alkaline phosphatase, little change, but a small, statistically significant drop after zinc repletion. As expected, there were no diet-associated changes in plasma copper and ceruloplasmin levels. In contrast, plasma concentrations of the enzyme 5′-nucleotidase decreased (p<0.01) from 2.7 +/−0.5 to 1.1 +/−0.5 U during zinc depletion and increased (p<0.05) to 2.2 +/−0.4 U after 6 days of repletion.Mild zinc deficiency is difficult to detect. In this study, traditional indicators such as plasma zinc and alkaline phosphatase did not change as would be expected in response to alterations in zinc intake. Likewise, erythrocyte metallothionein did not respond to altered zinc intakes as expected but this factor may reflect long-standing or more severe zinc depletion and thus requires additional study. Activity of the enzyme 5′-nucleotidase appears responsive to acute changes in zinc intake; however, more work is needed to define how well these activities will reflect zinc intake in other types of subjects.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718434

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

The purpose of this study was to determine the plasma, erythrocyte, and mononuclear blood cell (MBC) magnesium concentrations in patients with chronic, severe hypomagnesemia due to a chronic magnesium-wasting tubulopathy.Six patients with Bartter's syndrome and five patients with magnesium-wasting tubulopathy were compared with normal subjects. We determined magnesium in plasma, erythrocytes, and MBCs.Patients with chronic magnesium-wasting tubulopathy had a significantly lower plasma magnesium concentration than controls, but erythrocyte magnesium concentration and MBC magnesium concentration and content did not differ significantly between patients and controls.Two disorders with chronic magnesium-wasting tubulopathies are associated with a low plasma magnesium concentration but normal erythrocyte and MBC magnesium.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718435

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

To determine if later renal conservation occurs in calcium (Ca) and magnesium (Mg) excretion after morning caffeine-induced increases in urinary Ca and Mg excretion.Before-after trial of caffeine abstinance and consumption was conducted on two consecutive days in a metabolic ward while subjects ate a controlled diet containing 11.3 mmol Ca and 12.7 mmol Mg. 17 healthy males and females, ages 17-41 yr volunteered. Two caffeine doses of 3 mg/kg lean body mass caffeine were consumed at 7 and 10 a.m. on second day. Salivary caffeine concentrations and urinary Ca, Mg, sodium and creatinine excretion were measured.Salivary caffeine peaked at 4.7 umol/mL at 11:30 a.m. and declined with a half-life of 7.3 hours. Urinary Ca and Mg were elevated significantly (p = 0.01 and p = 0.04) for six h after the second caffeine dose. Caffeine had no significant effect on urinary calcium or magnesium excretion between 4 p.m. and 1 a.m. Between 1 and 4 a.m., urinary Ca and Mg excretion was decreased after caffeine (p = 0.04 and p = 0.01). Creatinine excretion was not different at any time.Nighttime compensatory renal conservation was insufficient to offset morning caffeine-induced mineral losses, resulting in net 24-hour urinary increases of 0.32 mmol Ca and 0.16 mmol Mg.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718436

出版商:Routledge    

年代:1994

数据来源: Taylor

摘要:

The study investigated lithium-sodium countertransport in erythrocytes of normal female volunteers during different phases of the menstrual cycle or during administration of oral contraceptives.Ten normally menstruating, and eight oral contraceptive using, normal female subjects were studied over at least one cycle. Erythrocyte lithium-sodium countertransport was determined using. standard, previously validated methods at different phases of the menstrual cycle. Hematological, electrolyte, blood pressure and other transport measures were also made and these were related to the self-reported incidence of premenstrual symptomatology.A correlation, (p<0.02), was found between lithium-sodium countertransport rate and the premenstrual symptom severity score but only in the premenstrual phase. There was no correlation between any of the electrolyte, blood pressure or hematological data and lithium-sodium countertransport rate nor between it and other ion transport measures. Pre-menstrual symptomatology was conspicuously absent from those subjects taking oral contraceptives. Cyclical fluctuations in normally menstruating women, and differences between them and oral contraceptive users, were seen in lithium-sodium countertransport rate although the groups were too small to show statistical significance.Care was taken to exclude influences due to circadian, dietary and diurnal variations and the present results show somewhat less within-individual variability in erythrocyte lithium-sodium countertransport during the menstrual cycle than do other reports in the literature. Some interesting features were observed which justify a much larger scale study than the present pilot experiment which should involve a larger number of subjects studied over more than one cycle and in particular a more detailed study of the ovulatory phase.

ISSN:0731-5724    

DOI:10.1080/07315724.1994.10718437

出版商:Routledge    

年代:1994

数据来源: Taylor