Measurement of 3-hydroxy-3-methylglutaryl-CoA lyase activity in amniotic cells and in chorionic villi.
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Amino Acid Metabolism, Inborn Errors↗
Biomedical subjects
V Barash
Publications and source records attributed to V Barash.
Familial carnitine deficiency: further evidence for autosomal recessive transmission with variable expression.
Carnitine deficiency occurring in families has been rarely reported and the genetic transmission has not yet been clearly elucidated. Five members of one family showing marked heterogeneity of carnitine deficiency states are presented. In three patients, there was no correlation between measurable carnitine levels in serum and muscle and the clinical findings. The parents, who are remote relatives from an isolated village in Kurdistan (Iraq), had low muscle carnitine levels; however, they were asymptomatic. One son, with systemic carnitine deficiency causing muscle weakness and recurrent episodes of severe hepatic encephalopathy, died at 3 years of age. His brother had mild proximal muscle weakness associated with low muscle carnitine levels. He was successfully treated with L-carnitine and prednisone. A daughter is asymptomatic, but with low serum and muscle levels of carnitine. The marked heterogeneity of carnitine deficiency states within one family, where both parents had low muscle carnitine levels, suggests an autosomal recessive inheritance with variable expression.
Carnitine↗
Pyruvate carboxylase activity in chorionic villi: possibility of application to prenatal diagnosis.
Pyruvate carboxylase (PC) activity was assayed in 27 chorionic villi samples (CVS) obtained at 9-12 weeks of gestation. The kinetic properties of the CVS enzyme were similar to those of liver PC; more than 75% of PC activity was recovered in the mitochondrial fraction of CVS. Apparent Km for pyruvate, ATP, acetyl CoA and HCO3- in the presence of saturation concentrations of the other reactants, were 0.3, 0.44, 0.015 and 6.0 mmol/l, respectively. The optimum pH was 7.5-8.0. The activity of PC in CVS was 3.2 +/- 0.3 nmol/min/mg protein, which is severalfold higher than that of amniotic fluid fibroblasts.
Cell Fractionation↗
Placental function in maternal-fetal fat transport in diabetes.
High levels of triglycerides (TG) and free fatty acids (FFA) in maternal plasma, in diabetes, promote fat passage to the fetus. In the streptozotocin-diabetic rat a significant correlation exists between maternal plasma and fetal tissue lipid contents, as shown by the accretion of labeled fatty acids or linoleate used as markers of maternal fat transfer. The passage of lipids through the placenta is not direct--this organ serves as an interim storage barrier with its lipid content increasing in proportion to the maternal TG and FFA level. Very low density lipoprotein (VLDL) TG are taken up with the aid of lipoprotein lipase as evident from TG = glycerol exchange when doubly labeled VLDL-TG are presented to the placenta. Esterification rate of albumin-bound FFA is considerably higher indicating that the rate of TG lipolysis is rate limiting and that the FFA are the main precursor of the placental lipids. The uptake of both FFA and VLDL-TG is associated with the retention of a substantial amount of FFA in the placenta. The size of the FFA pool corresponds to the size of the extracellular fluid space. The FFA cannot be eluted by repeated washing, suggesting that they are membrane bound. Placental slices with prelabeled TG gradually release FFA into the medium upon reincubation with FFA-free albumin, indicating that TG and FFA traverse the placenta in part by a sequential process of esterification and lipolysis and in part by diffusion as FFA. The latter are probably moving from the maternal to the fetal side within the interfacial capillary membrane lipids.
Animals↗
Placental glycogen accumulation and maternal-fetal metabolic responses in hyperglycaemic non-diabetic rats.
The effect of maternal hyperglycaemia on glycogen and triglyceride accumulation in the feto-placental unit of non-diabetic rats was studied. Hyperglycaemia was induced by continuous infusion of a 400 g/l glucose solution at the rate of 2-4 g/hr/kg, from day 18.5-20.5 of gestation. Hyperglycaemic mothers were hyperinsulinaemic; their fetuses were hyperglycaemic but their insulin levels were comparable with those of control pregnant rats (infused with a 50 g/l glucose solution at the same rate). Fetal pancreas insulin content in the hyperglycaemic fetuses was pronouncedly reduced. The hyperglycaemia produced an approximately 2-fold increase in placental glycogen content in association with increased activities of placental glycogen synthase and phosphorylase. Maternal serum triglycerides fell concomitant with the hyperglycaemia. Placental triglyceride content of hyperglycaemic rats did not change significantly, whereas up to a 2-fold increase in maternal and fetal liver triglyceride concentration was observed. There was no change in fetal and placental weight. Since we have shown previously an increase in both placental glycogen and triglycerides in diabetic rats with hyperglycaemia, concomitant with elevation of plasma triglycerides and free fatty acids, the present experiments demonstrate that these 2 factors causing placental glycogen and triglyceride accumulation can be dissociated. On the other hand, maternal and fetal liver triglycerides accumulate in the hyperglycaemic rats probably as a result of local de vovo lipogenesis.
Animals↗
Effect of L-DOPA on glucose oxidation and incorporation into glycogen in discrete brain regions of the rat.
Previous reports in which the [14C]deoxyglucose mapping technique was used, have demonstrated that systemic administration of L-DOPA can either increase or decrease glucose utilization in various brain regions. However, in the striatum, which contains a high concentration of dopamine, no conclusive results were found using this technique. In the present study we attempted, by implicating a different technique, to evaluate the effect of L-DOPA on glucose metabolism in the striatum. This approach is based on in vitro measuring of glucose oxidation to CO2 and its incorporation to glycogen. Rats were injected with carbidopa (100 mg/kg) and 1 h later with L-DOPA (50 mg/kg). The rats were sacrificed by decapitation 1 h after L-DOPA injection and the following brain regions were assayed for glucose oxidation to CO2 and its incorporation to glycogen: striatum, hypothalamus, hippocampus and prefrontal cortex. A significant increase of glucose oxidation of 50% was found in the striatum and hippocampus, while no change was demonstrated in the hypothalamus and cortex. The incorporation of glucose to glycogen was markedly reduced in the striatum and hippocampus while no change was found in the hypothalamus or cortex. The present results demonstrate that L-DOPA treatment increases glucose metabolism in specific brain areas. The mechanism involved might be an increase in cellular uptake of glucose and/or activation of enzymes participating in glucose metabolic pathways.
Animals↗
Fetal diabetes in rats and its effect on placental glycogen.
The role of fetal insulin in placental glycogen accumulation, which occurs despite insulin deficiency in maternal diabetes, was studied in rats. Streptozotocin was injected into fetuses of non-diabetic and streptozotocin-diabetic mothers on days 19.5 and 20.5 of gestation, causing fetal hypoinsulinaemia and pancreatic insulin depletion. Placental glycogen content of either 1.6 mg/g in non-diabetic rats or 6.5 mg/g in diabetic rats was not affected by fetal streptozotocin treatment. Glycogen distribution was also measured in the placenta to assess the effect of fetal hypoinsulinaemia on glycogen content in its fetal segment. The glycogen concentration ratio between the fetal and maternal segments in diabetic rats was approximately 0.3 and increased to approximately 0.5 in diabetic rats, without being affected by fetal hypoinsulinaemia. There was no significant effect of fetal hypoinsulinaemia on the activities of placental glycogen synthase or glycogen phosphorylase, both in non-diabetic and diabetic rats. Fetal hypoinsulinaemia was associated, however, with a marked decrease in fetal liver glycogen together with a decrease in fetal liver weight, which was more pronounced than the decrease in fetal body weight. Administration of insulin to the streptozotocin-treated fetuses restored the impaired glycogen synthesis (measured by incorporation of U-[14C]-glucose and 3H2O in the fetal liver) without affecting glycogen synthesis in the placenta.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Incorporation of [14C]glucose into alpha-1,4 bonds of glycogen by leukocytes and fibroblasts of patients with type III glycogen storage disease.
In two patients assay of alpha-1,6-amyloglucosidase activity by incorporation of [14C]glucose into glycogen revealed normal activity in leukocytes, erythrocytes, and fibroblasts, whereas no activity was detected in liver and muscle. No activity in any tissue was found when enzyme activity was assayed by following the release of glucose from a phosphorylase limit dextrin. Labeling of glycogen by incubation with crude tissue homogenates according to the protocol used for the [14C]glucose method and subsequent degradation of the outer portion of the polysaccharide molecule with beta-amylase showed that with tissues from normal controls more than 90% of the label of the glycogen was retained in the limit dextrin. When fibroblasts or leukocytes of the patients served as enzyme source up to 80% of the label was released after incubation with beta-amylase or phosphorylase a. Addition of Tris to the assay inhibited enzyme activity in fibroblast homogenates of the patients and of controls to the same extent and had no effect on the distribution of the label between supernatant and limit dextrin after beta-amylolysis of the labeled glycogen. A pH curve performed with fibroblast preparations from the patients and a normal control did not reveal differences in the effect of changes in pH on [14C]glucose incorporation. We propose that incorporation of [14C]glucose into glycogen by the enzyme present in the patients' cells was into alpha-1,4 linkages in glycogen.
Cells, Cultured↗
Mechanism of placental glycogen deposition in diabetes in the rat.
The metabolic basis for glycogen accumulation in the placenta of rats with diabetes induced by streptozotocin on day 12 of pregnancy was studied on days 15 and 20. On day 15 glycogen content of the placenta was 1.5-fold higher in the diabetic than in the control rats and this difference increased to greater than fivefold on day 20 of gestation whether calculated per g tissue or per total placenta. Accumulation of glycogen was associated with increased specific activities of both glycogen synthase and phosphorylase. The activities of these enzymes regulating synthase and phosphorylase activities and the activity of acid alpha-glucosidase were not significantly affected by diabetes. Glucose-6-phosphate concentration of the placenta was 67 and 23 nmol/g in diabetic and control rats, respectively. Incubation of placental homogenates with glucose increased the rate of inactivation of phosphorylase and activation of glycogen synthase. These results indicate that the enhanced glucogenesis in diabetes is not due to changes in the activities of these enzymes, as measured in vitro under standard conditions. The factors promoting glycogen accumulation in vivo are related to the abundance of glucose and glucose-6-phosphate as substrates for glycogen synthesis, which may also cause an increase in the activity ratio glycogen synthase a/phosphorylase a. In addition, the high intracellular glucose-6-phosphate concentration is likely to enable glycogen synthase b to contribute to glycogen synthesis.
Animals↗
Correction by bromocriptine of hypothalamic dysfunction and post-prandial hypoglycaemic symptoms in a 31-year-old woman.
A 31-year old female presented with recurrent episodes of post-prandial hypoglycaemic symptoms. Basal serum levels of ACTH, cortisol, GH, insulin and glucagon were normal. An adrenaline test demonstrated a normal peripheral response. An exercise test failed to produce ACTH, cortisol or FFA responses. Insulin (0.1 u/kg)-induced-hypoglycaemia failed to elevate serum ACTH, cortisol or GH. Metyrapone and ACTH tests were normal, demonstrating adequate hypophyseal and adrenal function. These findings suggested that the patient suffered from hypothalamic dysfunction. Bromocriptine (Parlodel, 7.5 mg/d for 5 weeks) resulted in an improved general condition, accompanied by a decrease in sugar consumption. Following treatment, FFA, ACTH and cortisol responses to exercise test were normal, as were ACTH, cortisol and GH responses to insulin-induced hypoglycaemia. It is concluded that bromocriptine may be useful in the treatment of post-prandial hypoglycaemic symptoms associated with hypothalamic dysfunction.
Adult↗
Congenital lactic acidosis associated with pyruvate carboxylase deficiency.
Two cases of congenital lactic acidosis associated with pyruvate carboxylase deficiency are described. One 2-mo-old infant had a fulminant clinical course with extremely severe intractable acidosis and died after 48 h in hospital. The second infant, aged 2 1/2 mo, had a milder clinical course, characterized by moderate acidosis and frequent convulsive episodes. He died at the age of 3 mo due to respiratory arrest following prolonged status epilepticus. Pyruvate carboxylase activity in liver biopsy specimens obtained from the two patients was 1 and 50% of normal, respectively. Both patients failed to respond to treatment, including massive doses of thiamine and high serum levels of lactate and pyruvate were found throughout their illnesses. Cerebral autopsy performed in both cases was unremarkable. Absence of neuropathological findings ruled out the possibility of Leigh's disease.
Acidosis↗
Regulation of glycogen synthetase and phosphorylase phosphatase activities in rat adipose tissue.
Incubation of a rat adipose tissue homogenate causes a time and temperature dependent activation of glycogen synthetase (UDP glucose:glycogen 4-alpha-glucosyltransferase) and simultaneous inactivation of phosphorylase (1,4-alpha-D-glucan: orthophosphate alpha-glucosyltransferase, EC 2.4.1.1). Activation of glycogen synthetase at 15 and 23 degrees C was preceded by a lag period. The duration of the lag period could not be correlated with significant changes in phosphorylase activity. Addition of glucose and methylxanthines caused an increase in the rates of glycogen synthetase activation and phosphorylase inactivation. The effect on glycogen synthetase activation was mainly on the linear phase. Addition of AMP inhibited phosphorylase inactivation and accelerated glycogen synthetase activation. Addition of muscle phosphorylase alpha caused a prolongation of the lag period which lasted until phosphorylase alpha activity had decreased to the level originally present in the preparation. It is concluded that in adipose tissue activation of glycogen synthetase is not dependent on prior inactivation of phosphorylase and that other factors should be looked for to explain the lag period preceding glycogen synthetase activation.
Adenosine Monophosphate↗
Adipose tissue glycogen synthetase. I. Kinetic properties.
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Adenosine Triphosphate↗
Solubilization of mycoplasma membranes by the nonionic detergent Triton X-100.
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Journal Article↗
Localization of glycogen in the placenta of diabetic rats: a light and electron microscopic study.
The ultrastructure of the placentae on day 20 of gestation was studied in rats made diabetic by streptozotocin injection on day 13 of gestation. In the placentae of control rats most of the glycogen was found in the glycogen cells, while some of it was localized to the labyrinth trophoblastic layers. In the diabetic rats a marked increase in glycogen content, together with higher numbers of glycogen cells in the junctional zone, was seen. Glycogen was also stored in other cell types of this zone, as well as in all cell types of the placental labyrinth of the diabetic animals.
Animals↗
Cytosolic fatty acid binding proteins in rat placenta.
Placentae from 21 days pregnant rats were assayed for long-chain fatty acid binding activity. Oleate binding activity, associated with a low-molecular-weight protein fraction resembling liver fatty acid binding protein (FABP or 'Z' protein), could be demonstrated after removal of serum albumin by fractionation of the placental cytosol on Sephadex G-75. The fatty acid binding activity in the placenta was 2 to 4 per cent of the FABP activity present in rat liver.
Animals↗
Ring 18 chromosome with mental retardation, hemidysmorphism, and mitochondrial encephalomyopathy.
A 2 1/2-year-old female is reported with ring 18 chromosome syndrome. The chromosomal abnormality was found in all examined leukocytes and cultured skin fibroblasts. Besides the usual clinical characteristics of this syndrome, two additional features are described that have not been reported previously: right hemidysmorphism, including hypertrophy of the tongue and lower extremity; coloboma of the lower right side of the gums; atretic external right ear canal; and hypotonia with mitochondrial encephalomyopathy associated with excessive ketonemia during normal food intake and a large increase after overnight fast.
Brain Diseases↗
Mobilization of placental glycogen in diabetic rats.
Since glycogen accumulates in the placenta in diabetes and does not appear to be susceptible, in general, to the effect of fasting, the capacity of catecholamines to elicit glycogenolysis was investigated in non-diabetic and diabetic rats. Injection of epinephrine or isoproterenol caused a decrease in placental glycogen within 20 min in non-diabetic, 20 day pregnant rats, in association with the rise in serum glucose and lactate. Incubation with isoproterenol induced glycogenolysis in placental slices from non-diabetic and diabetic rats, nearly commensurate with lactate production. This effect of isoproterenol was concentration dependent and of similar magnitude in non-diabetic and diabetic rat placentas. Glucagon was ineffective in inducing placental glycogenolysis in vivo or in vitro. Protracted stimulation of the catecholamine receptor by the administration of cholera toxin effected a pronounced decrease in placental glycogen, percentagewise higher in diabetic than non-diabetic rats. These results show that placental glycogen is amenable to mobilization by hormonal stimuli effecting phosphorylase activation.
Animals↗