Acta vitaminologica et enzymologica最新文献

Anti-alpha-amylase is a protein characterized by an antienzymatic activity in the sense that it prevents hydrolysis of the alpha--1,4 glycoside bond of starch. Such action could be exploited for reducing the caloric value of the diet. We studied the in-vivo effectiveness of large doses of anti-alpha-amylase extracted from white beans (Phaseolus vulgaris). The growth rate of rats was clearly impaired, the blood pictures and biochemistry showed modifications, and the internal organ histology revealed alterations in the liver and kidney.

To estimate the antirachitic activity of human and bovine milk, we developed a modern biochemical method for determining vitamin D metabolites in milk. Vitamin D metabolites were assayed from milk whey and from whole milk. Milk whey yielded poor recovery of both endogenous and added vitamin D, suggesting a marked loss of vitamin D activity to milk fat during homogenization and separation of the milk whey. A method for assaying the vitamin D metabolites in whole milk involves 1) lipid extraction, 2) cold methanol and ether precipitation, 3) alkaline backwash to reduce the amount of interfering lipids, 4) an efficient reverse-phase preparative purification, 5) an additional silica purification for vitamin D, 6) an analytical high-performance liquid chromatography, and 7) separate sensitized protein-binding assays for vitamin D and 25-hydroxyvitamin D. The method for whole milk resulted in good recovery of added vitamin D, and levels of assayed metabolites and their calculated antirachitic activity agreed well with earlier reports, that is, about 10-50 IU of vitamin D activity per liter.

Xanthurenic acid (XA), kynurenic acid (KA) and creatinine in fasting urine were determined by reversed phase high pressure liquid chromatography in order to investigate the distortion of tryptophan metabolites in diabetes mellitus. The results of ten patients with non-insulin dependent diabetes mellitus and ten normal healthy subjects were compared. No tryptophan load test was performed in this study, because tryptophan loading produces further latent shortage of active vitamin B6 which results in exacerbation of the disease. The ratios of XA to KA and to creatinine were 0.35 +/- 0.099 (mean +/- S.D.) and 0.99 +/- 0.321 in the diabetic patients. The corresponding figures in the normal subjects were 0.17 +/- 0.064 and 0.55 +/- 0.22. Both ratios were significantly higher in the diabetic patients than in normal subjects (p less than 0.001 and p less than 0.01, respectively). This means that XA was excessively excreted in diabetic patients resulting in distortion of tryptophan metabolism. Our findings indicated that the ratios are useful to monitor excess XA excretion and also for detection of diabetes.

3,7,11,15-Tetramethyl-2,4,6,10,14-hexadecapentaenoic acid (E5166), a synthetic analog of retinoic acid, increased 2-deoxy-D-glucose (2DG) uptake in a dose and time-dependent manner in mouse fibroblasts, Swiss 3T3 cells. Kinetic analysis of 2DG uptake showed that the Vmax for 2DG uptake by E5166-treated cells was greater than that of the control, while the Km values were essentially the same. Most of the E5166-stimulated 2DG uptake was suppressed by cycloheximide, although part of the stimulation always remained despite of the cycloheximide treatment. These results suggest that E5166-induced stimulation of 2DG uptake is due to the increase in the synthesis and recycle of hexose transporters (carriers) in Swiss 3T3 cells.

Maltitol is a disaccharide molecule with special physico-chemical characteristics due to a glycosidic bond which is not easily split by the natural disaccharidases. The present study was designed to evaluate the effects of a prolonged feeding with maltitol on growing rats. Acceptability, caloric yield, intestinal absorption and metabolic effects have been determined.

Using a 2 X 2 factorial design, we evaluated the possible interaction of vitamin A deficiency and excess fluoride in rat dentin and bone. Simultaneous presence of excess fluoride plus vitamin A deficiency resulted in a significant decrease in bone fluoride concentration compared to the presence of excess fluoride alone. Vitamin A deficiency alone significantly reduced calcium concentration in dentin formed during the deficient period.

Twenty-eight women with postmenopausal osteoporosis were studied in a double-blind trial aimed to compare the effects of a one-year treatment with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), estradiol valerate (E2) and placebo. Patients were divided into 4 groups: group 1 was given 1,25(OH)2D3 alone, group 2 was given E2 alone, group 3 was given 1,25(OH)2D3 + E2, group 4 received a placebo. The evaluation of the effects of the treatments included clinical examination of patients, the measurement of a number of biochemical parameters, such as plasma and urinary calcium and phosphate, urinary hydroxyproline, serum alkaline phosphatase, the measurement of intestinal calcium absorption and bone mineral content (BMC) and a histomorphometric study of bone biopsies from the iliac crest. The best clinical results were obtained in the patients who were given 1,25(OH)2D3 alone; appreciable results were also noticed in the patients who were given E2 alone or in combination with 1,25(OH)2D3, while patients in the placebo group worsened. BMC decreased in the placebo group and increased, although non significantly, in the patients treated with 1,25(OH)2D3 or E2 or both. The histomorphometric study showed a significant increase in the mean trabecular diameter in patients treated with 1,25(OH)2D3 alone or in combination with E2. Changes in the volume density of trabecular bone paralleled those in BMC. The results of the trial indicate that 1,25(OH)2D3 is an effective therapeutic agent in postmenopausal osteoporosis.

The effects of a mineral-vitamin-sugar preparation has been tested on a group of volley ball players under training. Plasma electrolytes (Na, K, Cl), erythrocyte electrolyte content, plasma lactate concentration and erythrocyte water content have been determined before and after a training session in three different experimental situations: a) controls; b) acute treatment with the energy stimulator; c) chronic treatment (8 days) with a similar preparation of the energy stimulator. The results are indicative of a significantly lower lactate production and a more stable electrolyte concentration after treatment with respect to the control data.

The incorrect use of the terms vitamin overdosage and overload, hypervitaminosis and dysvitaminosis gives rise to errors in the classification and evaluation of their etiology and pathogenesis. Vitamin overdosage and overload are observed with every vitamin and produce high blood and tissue levels of the vitamin itself; however, the overdosage can be obtained only upon administration of high doses of a vitamin, while vitamin overload may originate from a variety of factors. Hypervitaminoses are known for vitamin A and D; they are accompanied by high blood levels, but are characterized by a specific symptomatology. The term dysvitaminosis comprises "every alteration of the physiological status of the vitamin, in terms of both its deficiency and its surplus". These considerations provide a unitary view of vitamin pathology and lead to the following proposal of an etiopathogenetic classification of dysvitaminoses: class A) dysvitaminoses due to overload, class B) dysvitaminoses due to deficiency. Each class in turn may be divided into congenital and acquired syndromes. In class A) the congenital syndromes are still not well known, the acquired syndromes comprise those with hypervitaminosis (hypervitaminosis A and D) and those without hypervitaminosis (for the other vitamins). In class B) the congenital syndromes comprise diseases produced by inborn enzymatic errors and by other etiologies, the acquired syndromes can be distinguished in physiological (age, pregnancy, etc.) and pathological (nutritional, iatrogenic, etc.) ones. On this basis hypervitaminoses A and D can be considered as non obligatory dysvitaminoses due to overload; their origin has a complex etiology, since the liposolubility of the vitamins and the prolonged use of high dosages are not the only factors responsible for the hypervitaminosis.

Bilirubin react with flavins under both aerobic and anaerobic conditions. Under anaerobic conditions these substances behave as a redox-system in solution, riboflavin functioning as an electron acceptor and bilirubin as an electron donor. The reaction products are the leuco-form of riboflavin and biliverdin. On the basis of the dependence of the optical spectrum and of the reaction rate on pH it can be assumed that bilirubin reacts in the anionic form. Under anaerobic conditions a reversible reaction occurs leading to a dynamic equilibrium of the reactants. The products were identified and determined by optical spectroscopy, chromatography and potentiometry. Excretion of biliverdin in the stool of new-born infants was orientatively monitored during the phototherapy of hyperbilirubinemia, after the administration of small doses of riboflavin. It has been found that excretion of biliverdin increases during the phototherapy. The possibility of utilizing the described reaction for an improvement in the phototherapy of new-born infant hyperbilirubinemia is discussed.