Magnesium bioavailability from mineral water. A study in adult men.

OBJECTIVE: To assess magnesium enteral absorption from a magnesium-rich mineral water. DESIGN: Experimental study. SETTING: Department of Nuclear Medicine, Brugmann Hospital, Brussels, Belgium. SUBJECTS: Ten healthy male volunteers in the age range 25-42 y. INTERVENTION: Each subject completed two sessions in a random order. At one session, they received an oral load of 300 ml of water (containing 1.2 mmol Mg), traced with (28)Mg, and at the other session they received an intravenous injection of (28)Mg, in order to take into account the metabolism of endogenous magnesium. The dietary consumption was further noted on a weekly diary. RESULTS: The mean bioavailability was 59.1% (s.d.+/-13.6). Magnesium absorption and age were significantly inversely correlated (r=-0.68, P=0.035). CONCLUSION: Magnesium-rich mineral water is a reliable source of magnesium. Our observation of decreased magnesium absorption with age deserves further investigations. SPONSORSHIP: The study was sponsored by SEV, Bourg la Reine, France.

Correlation between inhibition, working memory and delimited frontal area blood flow measure by 99mTc-Bicisate SPECT in alcohol-dependent patients.

Recently detoxified non-neurological alcoholic patients appear to be impaired in cognitive tasks measuring inhibitory processes as well as working memory (involving storage and manipulation of information). The aim of this study was to investigate in alcoholic participants the relationship between these two cognitive functions and regional cerebral blood flow (rCBF) studied at rest in regions of interest selected on the basis of recent PET studies which explored inhibitory and working memory in normal subjects. Twenty non-neurological alcoholic patients and 20 normal volunteers were selected for a neuropsychological exploration, including assessment of inhibition processes (by means of the Hayling test) and working memory (by means of the Alpha-span task). rCBF of alcoholics was also evaluated with a semi-quantitative method using a 99mTc-Bicisate single photon emission computed tomography (SPECT) procedure. Alcoholic patients performed worse than controls in the alphabetical condition of the Alpha-span task (involving manipulation and storage of information), and on the Hayling test. Significant correlation emerged between inhibition performance and both the bilateral inferior (left BA 47, r = -0.40; right BA 47, r = -0.599) and median frontal gyrus (left BA 10, r = -0.55; right BA 10, r = -0.59), but not with the region of reference (occipital/cerebellum, r = -0.13). Coordination of storage and manipulation was correlated with bilateral median frontal (left BA 10/46, r = -0.50; right BA 10/46, r = -0.45), but not with bilateral parietal area (left BA 7, r = -0.12, right BA 7, r = -0.18). These results suggest a relationship between inhibition and working memory deficits in alcoholic patients, and regional rCBF measured in frontal areas. Clinical implications of these data related to alcohol relapse are discussed.

Quantitative EEG in subcortical neglect.

Right-sided capsulo-lenticular strokes may cause left visuo-spatial neglect. The neural mechanism most frequently evoked to account for the occurrence of related cognitive disorders is remote cortical dysfunction in the posterior part of the right hemisphere. We studied 33 patients with capsulo-lenticular stroke, with (n = 16) or without (n = 17) associated subcortical neglect. A 20-channel EEG cartography system was used. Four regions of interest were delineated on the topographic map. Absolute delta and thêta amplitude peaks were obtained, as well as left-to-right ratios between activities in homologous regions of interest. The population was subdivided into two groups according to the presence or absence of neglect. Delta activity was higher in neglect patients than in patients without neglect, but the magnitude of delta activity differences between the two groups of patients did not depend on the site. The left-to-right ratio of delta activity between posterior homologous regions was lower in neglect patients, suggesting that right posterior dysfunction producing an imbalance between these regions might contribute to the emergence of the attention disorder.

Pathogenesis of subcortical visuo-spatial neglect. A HMPAO SPECT study.

The pathophysiology of neuropsychological disorders due to right deep-seated hemispheric lesions remains a debated point. We undertook this study to check the hypothesis according to which remote cortical dysfunction could be responsible for the occurrence of neglect. Twenty-eight patients presenting with a right-sided subcortical stroke were studied. A neuropsychological battery of tests suitable for assessment of possible visuo-spatial neglect was performed as well as HMPAO SPECT. Neglect was observed in 15 cases out of 28. The lesion's site (at CT and/or MRI) did not allow discrimination between patients without neglect and patients with neglect. The latter however could be distinguished from the former by the presence of a remote decrease in cortical blood flow in the right temporo-parietal region. By suggesting that cortical involvement is necessary for the occurrence of neglect, the results were interpreted according to a network approach in which subcortical neglect is attributed to a cortical deprivation from afferent input in the posterior part of the brain.

Remote cortical dysfunction as a possible cause of subcortical neglect? A regional cerebral blood flow study.

Cortical remote effects of right deep-seated lesions were studied with two cerebral blood flow measurement methods (two-dimensional xenon-133 inhalation and 99mTc HMPAO SPECT) in a population of 13 right-handed stroke patients. A neuropsychological battery of tests suitable for assessment of possible visual neglect was performed. Neglect was present in 7 cases. A regional cortical hypoperfusion was observed in all patients. However, in neglect patients it was more extended and involved the right inferior parietal region suggesting a causal relationship between cortical dysfunction and neuropsychological deficit. This finding supports the model attributing neglect to a unilateral attention-arousal defect in a cortico-limbic-reticular loop.

Cerebral blood flow in just detoxified alcohol dependent patients. A 99 m Tc-HMPAO-SPECT study.

Chronic alcohol abuse is responsible for several organic brain disorders. However, even the most characteristic of them are largely underdiagnosed by routine procedures. Therefore, there is need for sensitive, noninvasive and low-cost diagnostic procedures. 99m-Tc-HMPAO-SPECT could be an interesting candidate in this indication, because it estimates the distribution of the cerebral blood flow and the metabolic activity of the brain with a good resolution. We used this technique in 17 healthy volunteers and in a sample of 50 patients dependent on alcohol, without other major physical or mental disorder. SPECT was performed during the attendance of these patients in an inpatient detoxification program. We observed abnormal SPECT in 34 patients, but only in 2 volunteers (p < 0.001). The main abnormality was heterogeneity of the distribution of the tracer. SPECT abnormalities appear to be due nor to withdrawal syndrome, nor to medication. On the contrary, they are correlated with stigmata of heavy alcoholism. Furthermore, a genetic vulnerability to alcohol was suspected because SPECT abnormalities are more frequent in patients with an history of drinking problems in their relatives.

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density.

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by 153Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMDDPA into BMDDXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.

Contribution of remote cortical dysfunction to the pathogenesis of subcortical aphasia: A (99m)Tc-HMPAO SPECT study.

Remote cortical effects of deep-seated lesions were studied by (99m)Tc-hexamethyl-propylenenamine oxime single-photon emission computed tomography at about 50 days after stroke in a population of 16 right-handed aphasic patients. A left-sided regional cortical hypoperfusion was present in all cases. Significant relations were observed between the severity of verbal expression disorders and the degree of regional cortical flow decrease, suggesting that, from a given level of remote dysfunction, the affected cortical areas no longer would be able to play their functional role in language elaboration. There was no difference between the degree of cortical hypoperfusion, whether the morphological lesion was of thromboembolic or hemorrhagic origin.

Predictors of the variation of the ejection fraction during exercise in patients with and without coronary heart disease.

The aim of this study was to determine the factors influencing the different response of the ejection fraction (EF) of the left ventricle at exercise observed in patients with and without significant coronary heart disease. We have studied 98 patients referred for coronary angiography (82 men, 16 women), of whom 49 patients had a previous myocardial infarction and 71 patients had significant coronary heart disease. Exercise testing was performed and combined with a cardiac blood pool imaging at equilibrium. The variation of the EF between rest and peak exercise (delta EF) was measured. Twelve clinical, exercise-related, isotopic, and coronary arteriographic variables were examined in a linear univariate and statistical analysis. In the univariate regression, seven variables were significant regressors on the delta EF. In the multivariate regression, only four variables were significant regressors on the delta EF. Three independent predictors were found: the rate-pressure product, the ST depression, and the occurrence of a previous myocardial infarction. These three independent predictors reflect the myocardial functional reserve.

Lack of evolution of the cerebral blood flow during clinical recovery of a stroke.

Cerebral blood flow and clinical parameters were studied in 30 stroke patients at 15th, 30th, 60th, 90th days after the cerebral insult (Xenon 133 inhalation method). The clinical improvement was not accompanied by a progressive normalization of the CBF at rest. No relationship was found between the clinical data and the CBF values; either on the affected hemisphere or on the contralateral one. It is concluded that measurement of the CBF at rest has no predictive value as regards further clinical evolution.

Longitudinal study of calcium and bone metabolism in paraplegic patients.

A longitudinal study of bone and calcium metabolism in 28 patients with spinal chord lesion shows an enhancement of bone calcium accretion, generalized to the whole skeleton. The bone calcium turnover rate is more increased in the non-paralysed area during the first 2 months.