Search PubMed⌕ Search

Biomedical subjects

V E Anderson

Publications and source records attributed to V E Anderson.

At least 91 records · Page 5Linked to original sources
PubMed1989

Lactate dehydrogenase displays absolute stereospecificity in the transfer of the prochiral hydrogen of NADH.

The frequency of nonstereospecific hydride transfers to and from the C-4 of NAD+ by porcine heart lactate dehydrogenase has been determined to be less than 1 out of every 10(7) hydride transfers, using a method employing a dynamic equilibrium which allows for the detection of extremely rare (less than 1 in 10(8] nonstereospecific transfers. A detailed protocol is presented. The inability to detect unequivocally a nonstereospecific transfer either to or from the si face of the nicotinamide ring (pro-4S hydrogen to NADH) indicates that the transition state for the more favorable transfer of the pro-4R hydrogen is at least 10 kcal/mol lower in energy.

Animals↗
PubMed1989

Isotope effects on the crotonase reaction.

The primary, alpha-secondary, beta-secondary, and beta'-secondary deuterium and primary 18O kinetic isotope effects on V/K for the dehydration of [(3S)-3-hydroxybutyryl]pantetheine by bovine liver crotonase (enoyl-CoA hydratase, EC 4.2.1.17) have been determined by the equilibrium perturbation method. The primary deuterium and 18O kinetic isotope effects are 1.61 and 1.051, respectively. The secondary deuterium effects at C-2, C-3, and C-4 are 1.12, 1.13, and 1.00 per H, respectively. The large 18O isotope effect suggests C-O bond cleavage is largely rate determining but is consistent with either an E1cb or E2 mechanism with a large amount of carbanion character. The beta-secondary effect is a factor of 1.05 greater than the equilibrium isotope effect, indicating that this C-H bond is less stiff in the affected transition state or that its motion is coupled to the reaction coordinate motion. Analytical solutions to the differential equations describing uni-uni equilibrium perturbations are presented.

Animals↗
PubMed1989

Isotope effects on binding of NAD+ to lactate dehydrogenase.

The isotope effect on binding [4-2H]NAD+ and [4-3H]NAD+ to lactate dehydrogenase has been shown to be 1.10 +/- 0.03 by whole molecule isotope ratio mass spectrometry and 1.085 +/- 0.01 by 3H/14C scintillation counting. These values demonstrate that specific interactions of the nicotinamide ring with the enzyme make the C-H bond at C-4 less stiff in the binary complex.

Animals↗
PubMed1989

Citrate synthase stabilizes the enethiolate of acetyldithio coenzyme A.

Citrate synthase catalyzes the slow condensation of acetyldithio-CoA [Ac(= S)CoA] with oxalacetate to form thiocitrate [Wlassics, I.D., Stille, C., & Anderson, V.E. (1988) Biochim. Biophys. Acta 952, 269]. During the transient approach to steady state an observable amount of the dithioester absorbance disappears. The amplitude of the decrease in absorbance corresponds to 0.32, 0.03, and 0.02 enzyme equiv at pH 8.3, 7.5, and 6.6, respectively. The difference spectra from before and after the transient exhibit the dithioester lambda max at 306 nm. Acid quenching of a stiochiometric reaction between Ac(= S)CoA and citrate synthase following the transient quantitatively regenerates Ac(= S)CoA, indicating carbon-carbon bond formation had not yet occurred. The apparent first-order rate constant of the transient is independent of Ac(= S)CoA concentration and increases with decreasing pH, being 0.007, 0.016, and 0.04 s-1 at pH 8.3, 7.5, and 6.6, respectively. 2-Fluoroacetyldithio-CoA is a better inhibitor of citrate synthase, Ki = 300 nM, and substrate, Vmax = 2 X 10(-3) s-1, than Ac(= S)CoA. 1H NMR experiments indicate that citrate synthase catalyzes the exchange of the alpha-hydrogens of Ac(= S)CoA with turnover numbers of 0.13 and 0.54 s-1 at pD 7.9 and 7.2, respectively. Analysis of the proton and deuterium decoupled 13C NMR spectra of [2-13C]Ac(= S)CoA that has exchanged 37% of the alpha-hydrogens in the presence of citrate synthase indicates that the relative proportions of CH3, CH2D, CHD2, and CD3 were 0.29, 0.39, 0.25, and 0.07, respectively. This statistical distribution indicates each exchange event is independent. The data indicate that citrate synthase stabilizes the ionized form of Ac(= S)CoA by 5 kcal/mol relative to the un-ionized form, that the ionized dithioester is on the reaction pathway, and that below pH 8.3 the slow carbon-carbon bond forming reaction is responsible for the 10(6) decrease in Vmax caused by substituting sulfur for oxygen in the thioester carbonyl.

Acyl Coenzyme A↗
PubMed1989

Benign familial neonatal convulsions linked to genetic markers on chromosome 20.

Recurrent seizures, commonly known as epilepsies, occur in 1.7% of the general population by age 40. The factors that initiate or underlie seizures are not well understood, but trauma, infectious disease and genetics have been implicated. An understanding of the molecular basis of seizures would shed light on the basic mechanisms of neuronal homeostasis and allow new therapeutic strategies to be explored. Here, we report the mapping of an epilepsy gene to a specific chromosomal region, on the basis of cosegregation of two closely-linked DNA markers with a form of epilepsy known as benign familial neonatal convulsions (BFNC2, 12120 in ref. 3). The linked markers confirm the genetic basis and autosomal dominant inheritance of this trait, and localize the gene causing BFNC in this family to the long arm of chromosome 20. This regional placement is the first step towards the isolation of a gene involved in neuronal activity in the human brain.

Chromosome Mapping↗
PubMed1988

Coenzyme A dithioesters: synthesis, characterization and reaction with citrate synthase and acetyl-CoA:choline O-acetyltransferase.

Acyl dithioesters of CoA have been synthesized by transesterification. The alpha-hydrogens have a spectrally determined pKa of 12.5 +/- 0.14. The hydroxide catalyzed enolization rate is estimated to be 600 M-1.s-1. The absorbance of the dithioester, lambda max = 306 nm, can be used to monitor both the condensation and transesterification reactions that use CoA-Ac as a substrate. For citrate synthase at pH 7.4 Vmax = (4.0 +/- 0.4).10(-4) s-1 and Km = 53 +/- 7.5 microM, which are 2.10(-6) and 3.3-times the Vmax and Km values observed for CoAS-Ac, while for Ac-CoA: choline O-acetyltransferase (EC 2.3.1.6) at pH 7.0 Vmax = (1.1 +/- 0.2).10(-2) mumol.s-1.(mg protein)-1 and Km = 83 +/- 33 microM, which are 0.077 and 10-times the values observed with CoAS-Ac, respectively. The CoA dithioesters are stable at low pH, but hydrolyze with a second-order rate constant of 8.2.10(-2) M-1.s-1 at pH 11.4. The spectral properties of these dithioesters should allow these analogs to be used as probes of the structure of enzyme bound intermediates.

Acyl Coenzyme A↗
PubMed1987

Complex segregation analysis of febrile convulsions.

Complex segregation analysis was performed on 467 nuclear families ascertained through febrile-convulsion probands. The probands were identified as having their first febrile convulsion while residents of Rochester, MN, during the years 1935-64. Parents and first- and second-degree relatives of probands were identified through the Olmsted County, MN, record-linkage system. Diagnoses of convulsive activity were made from review of medical records. The genetic models investigated included both single-major-locus and polygenic models, with likelihoods computed jointly on children and parents as well as being conditioned on parental phenotype. Possible heterogeneity was investigated by means of analyses of frequency of febrile convulsions in the proband. Analyses of the entire data set indicated that the single-major-locus models could be rejected. The most parsimonious model for these data was the pure polygenic (or common familial environment) model with a large heritable component (68% +/- 7%). However, when families were partitioned on the basis of frequency of febrile convulsions in the proband, significant heterogeneity was present. Our results indicated that the polygenic model was strongly corroborated in families of probands with a single febrile convulsion. In families of probands with multiple febrile convulsions, evidence was consistent with a single-major-locus model with nearly dominant seizure susceptibility.

Child, Preschool↗
PubMed1986

Reduced plasma haptoglobin and urinary taurine in familial seizures identified through the multisib strategy.

The multisib (MS) sampling strategy was used for detecting possible genetic influences on a complex and heterogeneous disorder. The MS strategy increases the likelihood of selecting pedigrees for single genetic factors and allows the efficient analysis of data. The collection of complete pedigrees will procure additional data, but at a large marginal expense. The MS ascertainment procedure was applied to seizure disorders by examination of taurine excretion levels and by conducting two-dimensional gel electrophoresis of plasma proteins. Reduced taurine excretion (proposed to be genetically controlled) was found to associate with seizures, particularly in those individuals with a generalized spike and wave (GSW) EEg, or in families with a GSW-seizure history. Examination of two-dimensional gels showed hypohaptoglobinemia in several seizure patients [Panter et al, 1984]. The frequency of hypohaptoglobinemia is greatly increased in familial seizure cases, and may also be genetically controlled. Thus the MS strategy has proven successful in identifying kindreds in which specific physiological alterations may contribute toward the complex phenotype of seizures.

Adult↗
PubMed1986

Seizures and myoclonus in patients with Alzheimer's disease.

We reviewed 81 patients with dementia and autopsy findings of Alzheimer's disease (AD) to identify patients with seizures or myoclonus after onset of dementia. Eight (10%) had seizures, and eight others (10%) had myoclonus. The incidence of seizures was 10 times more than expected in a reference population. Seizures occurred in any stage of AD, but myoclonus was often a late manifestation. Both seizures and myoclonus, individually or together, are manifestations of AD and may be seen at any time in the course of the illness.

Aged↗
PubMed1986

Genetic heterogeneity in the epilepsies.

There is ample evidence for genetic and other heterogeneity in the mechanisms leading to epilepsy. Animal models of epilepsy show that genetic factors can influence the hypersensitivity of neurons. In the human, there are over 140 Mendelian traits (including disorders of amino acids, enzymes, hormones, and vasculature) that increase the risk of seizures. Furthermore, systems with an intermediate optimum (such as blood clotting and blood glucose) involve a number of mechanisms under independent genetic control, and it is reasonable to assume that the same principle applies to neuronal excitability. Finally, genetic variation can be expected in any of the factors that are altered in the origin of seizures: neuronal inhibition, inactivation of excitatory neurotransmitters, feedback control, and seizure generalization. One goal of future research is to define etiological subtypes on the basis of biochemical data or other factors. Meanwhile, it is possible to analyze currently available indicators of phenotypic variability (age at onset of seizures, family history of seizures, seizure type, EEG pattern, and history of antecedent factors such as fever or trauma) to address the following questions: Do any phenotypic groups have different sibling risks for seizures? How much phenotypic variability is seen among affected siblings of each defined group of probands (index cases)? Do any groups of probands show significant biochemical differences? Within a specific group, do isolated and familial cases show the same phenotype? Within a presumed single entity, will linkage marker studies show further heterogeneity? With such data in hand, certain strategies can be recommended. Complex segregation analysis of family data will permit a test of alternative models for genetic transmission. Linkage studies of selected large families (using recombinant DNA probes) will establish the genetic map location of any single-locus major factor. Selected samples of multiplex families (with several affected siblings) will concentrate the likelihood of genetic factors and will permit the detection of biochemical factors that might be significant in only a few families. Biochemical and other hypotheses can be tested in a panel of twin pairs concordant or discordant for epilepsy. The search for genetic heterogeneity clearly has implications for diagnosis, prognosis, therapy, and genetic counseling, as well as for other research studies on the basic mechanisms of the epilepsies.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1985

Distribution of reaction intermediates on chicken liver fatty acid synthase.

The distributions of covalent intermediates in the reaction cycle catalyzed by chicken liver fatty acid synthase were studied. In isotope-trapping experiments, 30% of [1-14C] acetyl-enzyme and 6.7% of [2-14C]malonyl-enzyme are converted to long-chain fatty acids, indicating the initiation reaction is partially random. The 3-hydroxybutyryl intermediate is located on the tryptic peptide which contains the 4'-phosphopantetheine (greater than 90%), while the C4-C18 saturated intermediates are distributed both on this peptide and on the peptide that contains the active cysteine. The ratio of intermediates on the two peptides is about unity for chain lengths less than C14, but the amount on the active cysteine progressively decreases for chain lengths of C14, C16, and C18 with trypsinized enzyme. The distributions of carbon chain lengths for the saturated or 3-keto intermediates when acetoacetyl-labeled trypsinized enzyme is incubated with limiting malonyl coenzyme A or NADPH, respectively, show large fractions both of unreacted enzyme and of C16 or longer intermediates. A detailed analysis suggests that the initial condensation and reduction steps are slower than the analogous reactions with longer chain length intermediates. The 3-keto intermediate comprises over 70% of each chain length intermediate detected when NADPH is the limiting substrate, indicating the reduction of the 3-keto intermediates is at least 2 times slower than the reduction of the unsaturated intermediates.

Acetyl Coenzyme A↗
PubMed1985

Hypohaptoglobinemia associated with familial epilepsy.

In select kindreds afflicted with familial idiopathic epilepsy, most individuals suffering seizures also have low levels of the plasma hemoglobin-binding protein, haptoglobin. This hypohaptoglobinemia may be causally associated with a tendency to develop epilepsy. Our experimental results indicate that artificially-induced hypohaptoglobinemia in mice causes retarded clearance of free hemoglobin from the central nervous system, and that such free hemoglobin may engender the peroxidation of brain lipids. We hypothesize that hypohaptoglobinemia, either inherited, or acquired via traumatic processes, may prevent efficient clearance of interstitial hemoglobin from the central nervous system, thereby predisposing these people to encephalic inflammation and the appearance of seizure disorders.

Adult↗
PubMed1985

The risk of seizure disorders among relatives of children with febrile convulsions.

We studied the risk for seizure disorders among relatives of probands with febrile convulsions. The risk for febrile convulsions was raised in siblings, offspring, and nieces and nephews of probands. Risks to siblings were higher if one or both parents also had febrile convulsions, or the proband had no identified neurologic abnormality before the febrile convulsion, if the proband had recurrent febrile convulsions, or the febrile convulsions were complex. The risk for epilepsy was raised in siblings of probands, but not in other relatives. If the proband had febrile convulsions followed by epilepsy, risk to siblings for febrile convulsions and for epilepsy was significantly higher than when probands had either condition alone.

Adolescent↗
PubMed1984

Reaction intermediate analogues for enolase.

A number of compounds that appear to be analogues of the aci form of the normal carbanion intermediate are good inhibitors of yeast enolase. These include (3-hydroxy-2-nitropropyl)phosphonate (I), the ionized (pK = 8.1) nitronate form of which in the presence of 5 mM Mg2+ has a Ki of 6 nM, (nitroethyl)phosphonate (III) (pK = 8.5; Ki of the nitronate in the presence of 5 mM Mg2+ = 1 microM), phosphonoacetohydroxamate (IV) (pK = 10.2; Ki with saturating Mg2+ for the ionized form = 15 pM), and (phosphonoethyl)nitrolate (VII) (Ki at 1 mM Mg2+ = 14 nM). The oxime of phosphonopyruvate (VI) has a pH-independent Ki of 75 microM. I, IV, VI, and VII are slow binding inhibitors. All of these compounds are trigonal at the position analogous to C-2 of 2-phosphonoglycerate and contain a phosphono group, but a negatively charged metal ligand at the position isosteric with the hydroxyl attached to C-3 of 2-phosphoglycerate (as in IV) appears to contribute more to binding than a nitro group isosteric with the carboxyl of 2-phosphoglycerate (I and III). These data support the carbanion mechanism for enolase and suggest that the 3-hydroxyl of 2-phosphoglycerate is directly coordinated to Mg2+ prior to being eliminated to give phosphoenolpyruvate.

Indicators and Reagents↗
PubMed1984

Stereochemistry of the reactions catalyzed by chicken liver fatty acid synthase.

The stereochemistry of the four partial reactions catalyzed by chicken liver fatty acid synthase that lead to the synthesis of palmitic acid has been determined. The reduction of acetoacetyl-CoA to 3-hydroxybutyryl-CoA by NADPH proceeds with the transfer of the pro-4S hydrogen of NADPH to form D-3-hydroxybutyryl-CoA. During the subsequent dehydration of D-3-hydroxybutyryl-CoA the pro-2S hydrogen and the 3-hydroxyl group are removed in a syn elimination to form crotonyl-CoA. Crotonyl-CoA is reduced to butyryl-CoA by NADPH, with the transfer of the pro-4R hydrogen of NADPH to the pro-3R position in butyryl-CoA and the transfer of a solvent hydrogen to the pro-2S position. The occurrence of the syn dehydration, when combined with the results of a previous study [ Sedgwick , B., & Cornforth , J. W. (1977) Eur. J. Biochem. 75, 465-479], implies that the condensation of the enzyme-bound malonyl moiety with the enzyme-bound saturated fatty acid to form a 3-keto intermediate proceeds with inversion at C-2 of the malonyl. The stereochemistry of the hydration was derived from an analysis of the spin-spin coupling constant of 3-hydroxy[2-2H]butyric acid benzylamides obtained from 3-hydroxy[2-2H]butyryl-CoA synthesized by fatty acid synthase. The elucidation of the stereochemistry of the reduction of crotonyl-CoA relied on the previously established stereochemistry of pork liver acyl-CoA dehydrogenase. The source of all 28 prochiral hydrogens of the palmitic acid synthesized by chicken liver fatty acid synthase was inferred from the results of this work.

Acyl Coenzyme A↗
PubMed1984

Energy absorption in cylinders containing an off-axis linear source.

An analytical model for evaluating the absorption of gamma rays by cylindrical tissues has been developed. This model introduces the case of an off-axis linear source of radiation inside the cylinder. The total energy absorbed by the tissue for different source strengths, absorption properties of the tissues, and the aspect ratio of the length of the cylinder to its radius have been evaluated.

Gamma Rays↗