Showing papers on "Thiamine published in 1975"

Subacute necrotizing encephalomyelopathy. Clinical, ultrastructural, biochemical and therapeutic studies in an infant.

Abstract: Grobe, H., v. Bassewitz, D. B., Dominick, H.-Chr. and Pfeiffer, R. A. (Departments of Paediatrics and of Medical Cell Biology, University of Munster, Munster, and Institute of Human Genetics, Medical School, Lubeck, BRD). Subacute necrotizing en-cephalomyelopathy. Clinical, ultrastructural, biochemical and therapeutic studies in an infant. Acta Paediatr Scand, 64: 755, 1975.–Subacute necrotizing encephalomyelopathy (SNE) has been observed in an infant with regressing psychomotor development. The concentrations of alanine, pyruvate and lactate were increased in the serum and blood as well as in the cerebrospinal fluid. Pyruvate carboxylase activity was reduced in the liver tissue. An inhibitor of thiamine-pyrophosphate-ATP-phosphotransferase was present in the urine. Thiamine treatment was followed by a decrease of serum alanine and blood pyruvate and lactate, but there was no clinical improvement during a period of 17 months. Ultrastructural investigations revealed high glycogen levels in liver tissue and skeletal muscle. These findings contrast with decreased gluconeogenesis, which is suggested by the diminished pyruvate carboxylase activity. Therefore it is concluded that reduced hepatic pyruvate carboxylase activity is not the primary cause of SNE.

Pyruvate Dehydrogenase Phosphatase Deficiency: A Cause of Congenital Chronic Lactic Acidosis in Infancy

Abstract: A male child presented on the first day of life with metabolic acidosis with elevated blood lactate (15 mM), pyruvate (0.4 mM), and free fatty acid (1.3 mM) levels and a blood pH of 7.16. The severity of the acidosis was diminished by intravenous administration of glucose in large doses and by bicarbonate. On two occasions, when the acidosis was particularly severe, peritoneal dialysis using an acetate buffer was required. Restriction of the dietary intake of saturated fatty acids or treatment with nicotinic acid also appeared to diminish the severity of acidosis. No improvement was achieved by the administration of thiamine or biotin. Tissues taken at postmortem showed normal activity of gluconeogenic enzymes and pyruvate dehydrogenase. The activity of pyruvate dehydrogenase in tissue homogenates preincubated with ATP was reduced by 60-75% both in liver of the patient and of the controls because of the inactivation of the enzyme by pyruvate dehydrogenase kinase. Addition of Ca++ and Mg++ to the inactivated enzyme caused a prompt return of the activity to normal in controls but not in the patient. This defect, which was apparent in muscle and liver but not in brain, we attribute to a markedly reduced activity of pyruvate dehydrogenase phosphatase in the patient.

Decreased metabolism in vivo of glucose into amino acids of the brain of thiamine-deficient rats after treatment with pyrithiamine.

Abstract: — Thiamine deficiency produced by administration of pyrithiamine to rats maintained on a thiamine-deficient diet resulted in a marked disturbance in amino acid and glucose levels of the brain. In the two pyrithiamine-treated groups of rats (Expt. A and Expt. B) there was a significant decrease in the levels of glutamate (23%, 9%) and aspartate (42%, 57%), and an increase in the levels of glycine (26%, 27%) in the brain, irrespective of whether the animals showed signs of paralysis (Expt. A) or not (Expt. B). as a result of thiamine deficiency. A significant decrease in the levels of γ-aminobutyrate (22%) and serine (28%) in the brain was also observed in those pyrithiamine-treated rats which showed signs of paralysis (Expt. A). Threonine content increased by 57% in Expt. A and 40% in Expt. B in the brain of pyrithiamine-treated rats, but these changes were not statistically significant. The utilization of [U-14C]glucose into amino acids decreased and accumulation of glucose and [U-14C]glucose increased significantly in the brain after injection of [U-14C]glucose to pyrithiamine-treated rats which showed abnormal neurological symptoms (Expt. A). The decrease in 14C-content of amino acids was due to decreased conversion of [U-14C]glucose into alanine, glutamate, glutamine, aspartate and γ-aminobutyrate. The flux of [14C]glutamate into glutamine and γ-aminobutyrate also decreased significantly only in the brain of animals paralysed on treatment with pyrithiamine. The decrease in the labelling of, amino acids was attributed to a decrease in the activities of pyruvate dehydrogenase and α-oxoglutarate dehydrogenase in the brain of pyrithiamine-treated rats. The measurement of specific radioactivity of glucose, glucose-6-phosphate and lactate also indicated a decrease in the activities of glycolytic enzymes in the brain of pyrithiamine-treated animals in Expt. A only. It was suggested that an alteration in the rate of oxidation in vivo of pyruvate in the brain of thiamine-deficient rats is controlled by the glycolytic enzymes, probably at the hexokinase level. The lack of neurotoxic effect and absence of significant decrease in the metabolism of [U-14C]glucose in the brain of pyrithiamine-treated animals in Expt. B were probably due to the fact that animals in Expt. B were older and weighed more than those in Expt. A, both at the start and the termination of the experiments.

Thiamine phosphate metabolism and possible coenzyme-independent functions of thiamine in brain.

Abstract: — The effect of depolarization of rat brain cortex slices on the relative distribution of thiamine among its various phosphate esters and on the efflux of thiamine was studied as a probe of possible coenzyme-independent neurophysiological functions of thiamine. Electrical pulses for 30 min increased lactate production but did not affect the levels of thiamine esters. Depolarization with 41 mM-potassium decreased thiamine diphosphate by only 3 percent (P= 0.05). Thiamine triphosphate levels (TTP) were unaffected by depolarization but doubled during incubation for 1 h in which time efflux of 40 percent of the total thiamine from the slices as unesterified thiamine occurred. Depolarization by potassium released a small but highly variable portion of the thiamine content of superfused cortex slices above the basal rate of efflux. The basal efflux was partially sodium dependent. Thiamine efflux was unaffected by acetylcholine, ouabain, or tetrodotoxin, compounds previously reported to increase thiamine efflux. The incorporation of 32P1 into the endogenous thiamine phosphates of cortex slices was studied. Incorporation into thiamine diphosphate reached only 20 percent of the specific activity of its precursor, ATP, after 2h of incubation while the incorporation into TTP approached equilibrium with ATP in 15-30 min indicating that the TTP pool was the most rapidly turning over of the thiamine phosphates. The data suggest that only a small portion of the TDP pool undergoes rapid turnover and serves as a precursor for TTP. The rapid turnover of TTP phosphoryl groups is consistent with specific functions for this compound related to its potential for phosphorylation reactions. An analog of TTP with the β, γ oxygen bridge replaced by a methylene group decreased TDP levels and increased thiamine when incubated with cortex slices, but did not effect thiamine monophosphate or triphosphate levels indicating inhibition of thiamine pyrophosphokinase.

Thiamine increases the specific activity of human liver branched chain α-ketoacid dehydrogenase

Abstract: THIAMINE pyrophosphate (TPP), the active derivative of vitamin B1, functions as a coenzyme in dehydrogenase reactions such as the oxidative decarboxylation of α-ketoisovaleric (KIV), α-keto-β-methylvaleric (KMV) and α-ketoisocaproic (KIC) acids in humans1. Impairment of these reactions produces the group of disorders known as maple syrup urine disease2,3. In the classic form of the disease, the ketoacids and their amino acid precursors accumulate in homozygous affected individuals and depress the function of the central nervous system early in life. Therapy involves restriction of branched chain amino acids in the diet to decrease their concentrations in the body fluids4. Further reduction in plasma leucine, isoleucine and valine has been achieved by supplementing this diet with thiamine for patients with partial (60%) and severe (95%) reduction in enzyme activity5,6. Other investigators found no effect in patients lacking all enzyme activity7,8. We are seeking an explanation for the clinical response at the enzyme level and have already reported that branched chain α-ketoacid dehydrogenase activity was increased in peripheral white blood cells. This occurred after 3 weeks of oral thiamine treatment in patients with 5% activity and in normal controls5. In contrast, activity in mitochondrial inner membranes from cultured normal and mutant skin fibroblasts was not stimulated directly by TPP/Mg2+, but was prolonged by the presence of TPP/Mg2+, suggesting that the cofactor increases the half life of the dehydrogenase complex. We have now found that thiamine supplementation of normal diets increases normal human liver branched chain α-ketoacid dehydrogenase activity.

Thiamine absorption in the rat. ii. intestinal alkaline phosphatase activity and thiamine absorption from rat small intestine in-vitro and in-vivo.

Abstract: The correlations between intestinal alkaline phosphatase (IAP) activity and thiamine absorption and glucose absorption were studied in the rat. An everted sac in-vitro technique was used in adult rats whereas in-vitro experiments were performed in young rats 10 days old. All incubation experiments were done with 14-C-labeled thiamine. The patterns of IAP activity along the small intestines differed greatly between young and adult rats but were closely paralleled by the distribution of active thiamine transport in adult rats and thiamine absorption in young rats, respectively. When IAP was specifically inhibited in adult rats by L-phenylalanine active thiamine transport in-vitro was abolished. No correlation was found between IAP activity and active transport or glucose in-vitro, nor did inhibition of the enzyme in any way affect glucose transport capacity. It is suggested that the enzyme intestinal alkalinephosphatase is involved in the process of active thiamine absorption.

Brain lipid composition of immature thiamine-deficient and undernourished rats.

Abstract: — The brain lipid composition of 25-day-old offspring of rats exposed to dietary thiamine (vitamin B1) deficiency from the 14th day of gestation was examined and compared to normal and pair-fed (undernourished) controls. Thiamine-deprived rats displayed neurological signs and a marked diminution of growth at 25 days of age. No changes in brain lipids of either whole brain or selected brain areas (brain stem, cerebellum, diencephalon) which were distinct from the effects of undernutrition (pair-fed controls) were observed in the thiamine-deficient group. Undernutrition, as exemplified by the pair-fed control group produced a highly significant depression of all lipids expressed per total brain and a significant deficit of whole brain and regional lipid, cerebroside and cholesterol concentrations indicating a deficiency in myelinogenesis. Ganglioside NeuNAc concentration was shown to be significantly greater in whole brain and certain brain areas of the same group while no changes were evident in total phospholipid concentration and the distribution of individual phospholipids. The implications of these findings in terms of the pathophysiology of thiamine-deficiency encephalopathy and undernutrition in early life are discussed.

Effects of thiamine antagonists on nerve conduction. I. Actions of antimetabolites and fern extract on propagated action potentials.

Abstract: To assess the hypothesis that thiamine is directly involved in the permeability changes at the sodium channel during nerve conduction, the effects of thiamine antagonists on lobster giant axon resting and action potentials were determined. Thiamine antimetabolites, in millimolar concentrations, reversibly decreased the maximum rate of rise and amplitude of the action potential while increasing its duration. In particular, thiamine tert-butyl disulfide (TTBD) elicited the formation of pronounced shoulders during repolarization, lengthening the action potential by 2-50 times, depending on dose. Antimetabolites also depolarized the resting membrane, but this change was poorly reversible and may indicate a dual mechanism for antimetabolite action. An extract of the fern, Pteris aquilina, reversibly decreased the maximum rate of rise of the action potential and depolarized the resting potential. It also elevated and prolonged the action potential after-depolarization, sometimes causing repetitive activity. The strength of these actions was correlated with the antithiamine potency of the extract, and was diminished by addition of thiamine to the extract.

An improved procedure for the determination of thiamine.

Abstract: A modified thiochrome procedure for the assay of thiamine is described. It eliminates the use of ion-exchange columns and elutions with hot, saturated potassium chloride solution that are employed in most other methods. The times required for extraction and dephosphorylation have been examined critically and shortened.

Effects of thiamine antagonists on nerve conduction. II. Voltage clamp experiments with antimetabolites

Abstract: Thiamine antimetabolites were externally applied to voltage clamped squid giant axons to investigate the possible role of thiamine in nerve conduction. Phenylthiazinothiamine, in concentrations as low as 250 muM, reduced peak early current and steady-state current, with the depression of the former being two to five times greater than that of the latter. Peak transient and steady-state conductances were about equally depressed by thiamine tert-butyl disulfide (2 mM) and L-586944-00P07 (5-10 mM). None of the antimetabolites produced an appreciable change in the kinetics of Na+ activation, K+ activation, or Na+ inactivation. Thiamine itself, applied externally up to 30 mM, had no appreciable effect on either the magnitude or time course of the ionic currents. Although these data are consistent with the hypothesis that thiamine may be involved in nerve conduction, they probably reflect a nonspecific stabilizing interaction of this class of compound with the axon membrane. Taken in this light, the hypothesis that thiamine plays a direct role in Na+ channel permeability changes must be reevaluated.

Purification and properties of thiamine pyrophosphokinase from parsely leaf

Abstract: Thiamine pyrophosphokinase was purified about 8,000-fold from extracts of parsely leaves. The enzyme, as prepared, was homogenous on polyacrylamide gel electrophoresis. The molecular weight of the enzyme, estimated by gel filtration with Sephadex G-150, was approximately 30,000. In 0.05 M Tris-HCl, the enzymic activity showed a pH optimum over a range of 8 to 9. A least squares analyses of Lineweaver-Burk and Hofstee plots gave Km values of 0.8mM and 0.15mum for ATP and thiamine, respectively. Thiamine homologues and analogues so far tested, except for cetyl thiamine, were all inactive as substrates. The enzyme was specific for ATP and Mg++, although to a lesser extent a combination with other ribonucleoside triphosphates or divalent cations could replace them. SH reagents, such as PCMB, NEM and iodoacetamide, were potent inhibitors of the enzyme. The inhibition was prevented by the addition of dithiothreitol. Inorganic pyrophosphate exhibited striking inhibition. TMP could not replace thiamine as the substrate, whereas it inhibited the TPP formation from thiamine. These findings are consistent with the views that TMP is not directly converted to TPP but after being dephosphorylated by the action of a monoesterase, thiamine is pyrophosphorylated with ATP by thiamine pyrophosphokinase (EC 2.7.6.2) to form TPP and thus give a clear evidence regarding the mechanism of TPP formation in plant tissues.

A nutritional survey in the elderly: blood and urine vitamin levels.

Abstract: In this survey of vitamin levels in 93 acute geriatric admissions to hospital, none had a completely normal nutritional profile. Twenty-two patients had over 50% of test abnormal and for all patients the average % of abnormal tests was 29%. The most common abnormalities were albumin, leucocyte vitamin C, vitamin E, carotene and nicotinic acid where over 50% of patients had abnormal results. Transferrin and vitamin A levels were abnormal in over 30% of patients while there was little evidence for riboflavin or thiamine malnutrition. It is postulated that an inadequate dietary intake, due to disease or to physical and mental deterioration was the most likely cause of these multiple nutritional abnormalities.

Process for producing pyruvic acid by fermentation

Abstract: Improved method for producing pyruvic acid by fermentation of pyruvic acid producing mutants of the strain Candida lipolytica which require methionine and thiamine for growth.