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Biomedical subjects

K M Gibson

Publications and source records attributed to K M Gibson.

At least 91 records · Page 5Linked to original sources
PubMed1995

gamma-Aminobutyric acid (GABA) metabolism in mammalian neural and nonneural tissues.

4-Aminobutyric acid (GABA), a major inhibitory neurotransmitter of mammalian central nervous system, is found in a wide range of organisms, from prokaryotes to vertebrates. GABA is widely distributed in nonneural tissue including peripheral nervous and endocrine systems. GABA acts on GABAA and GABAB receptors. GABAA receptors are ligand-gated chloride channels modulated by a variety of drugs. GABAB receptors are essentially presynaptic, usually coupled to potassium or calcium channels, and they function via a GTP binding protein. In neural and nonneural tissues, GABA is metabolized by three enzymes--glutamic acid decarboxylase (GAD), which produces GABA from glutamic acid, and the catabolic enzymes GABA-transaminase (GABA-T) and succinic semialdehyde dehydrogenase (SSADH). Production of succinic acid by SSADH allows entry of the GABA carbon skeleton into the tricarboxylic acid cycle. Alternate sources of GABA include putrescine, spermine, spermidine and ornithine, which produce GABA via deamination and decarboxylation reactions, while L-glutamine is an additional source of glutamic acid via deamination. GAD from mammalian brain occurs in two molecular forms, GAD65 and GAD67 (referring to subunit relative molecular weight (Mr) in kilodaltons). These different forms of GAD are the product of different genes, differing in nucleotide sequence, immunoreactivity and subcellular localization. The presence and characteristics of GAD have been investigated in a wide variety of nonneural tissues including liver, kidney, pancreas, testis, ova, oviduct, adrenal, sympathetic ganglia, gastrointestinal tract and circulating erythrocytes. In some tissues, one form (GAD65 or GAD67) predominates. GABA-T has been located in most of the same tissues, primarily through histochemical and/or immunochemical methods; GABA-T is also present in a variety of circulating cells, including platelets and lymphocytes. SSADH, the final enzyme GABA catabolism, has been detected in some of the tissues in which GAD and GABA-T have been identified, although the presence of this enzyme has not been in mammalian pancreas, ova, oviduct, testis or sympathetic ganglia.

Animals↗
PubMed1995

Enzymatic and immunologic identification of succinic semialdehyde dehydrogenase in rat and human neural and nonneural tissues.

We have identified succinic semialdehyde dehydrogenase protein in rat and human neural and nonneural tissues. Tissue localization was determined by enzymatic assay and by western immunoblotting using polyclonal antibodies raised in rabbit against the purified rat brain protein. Although brain shows the highest level of succinic semialdehyde dehydrogenase activity, substantial amounts of enzyme activity occur in mammalian liver, pituitary, heart, and ovary. We further demonstrate the absence of succinic semialdehyde dehydrogenase enzyme activity and protein in brain, liver, and kidney tissue samples from an individual affected with succinic semialdehyde dehydrogenase deficiency, thereby verifying the specificity of our antibodies.

Aldehyde Oxidoreductases↗
PubMed1994

The detection of 3-methylglutarylcarnitine and a new dicarboxylic conjugate, 3-methylglutaconylcarnitine, in 3-methylglutaconic aciduria.

Two patients, diagnosed with 3-methylglutaconic aciduria, who presented with diverse clinical and metabolic manifestations, were studied. Glycine conjugation as a possible detoxification mechanism in these two patients yielded negative results. Carnitine conjugates were however detected. 3-Methylglutarylcarnitine was observed in the urine of both patients, while one of the patients excreted detectable quantities of 3-methylglutaconylcarnitine, a previously unknown metabolite. The presence of this metabolite in urine samples from one patient and the apparent correlation between administered carnitine and the conjugate excretion profile seems to indicate that carnitine may play an important role in future therapeutic programmes.

Acidosis↗
PubMed1994

Pre- and postnatal diagnosis of succinic semialdehyde dehydrogenase deficiency using enzyme and metabolite assays.

We report our cumulative experience for the prenatal diagnosis of succinic semialdehyde dehydrogenase (SSADH) deficiency in seven 'at-risk' pregnancies from four unrelated families. Prenatal diagnosis was performed by determination of 4-hydroxybutyric acid (4-HBA) concentration in amniotic fluid using isotope-dilution gas chromatography-mass spectrometry in conjunction with assay of SSADH activity in biopsied chorionic villus and/or cultured amniocytes. In three of four pregnancies predicted as affected, confirmation was obtained by demonstration of deficient SSADH activity in fetal tissues. Our results suggest that determination of 4-HBA concentration in amniotic fluid combined with enzyme determination in cultured or biopsied tissue represents a reliable method for the prenatal diagnosis of SSADH deficiency.,

Aldehyde Oxidoreductases↗
PubMed1994

Screening for defects of branched-chain amino acid metabolism.

Screening for defects of branched-chain amino acid metabolism is a sequential process involving clinical evaluation of the patient, plasma carnitine determination, urinary organic acid analysis, and enzyme studies in cultured or isolated peripheral cells. This report will summarize clinical and metabolite features and enzymological methods available for the diagnosis of the more common defects of branched-chain amino acid metabolism, including isovaleryl-CoA dehydrogenase deficiency, 3-methylcrotonyl-CoA carboxylase deficiency, 3-methylglutaconic aciduria due to 3-methylglutaconyl-CoA hydratase deficiency and other less well characterized defects, 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, and 2-methylacetoacetyl-CoA thiolase deficiency. Newer enzymatic methodologies utilizing NaH14CO3 fixation coupled assays are described which allow for the estimation of six enzyme activities in the catabolic pathways of L-leucine and L-isoleucine catabolism. These coupled assays facilitate the rapid identification of five of the six enzyme abnormalities described above. Their ease of use should allow them to be implemented in any laboratory which screens for inborn errors of metabolism.

Amino Acid Metabolism, Inborn Errors↗
PubMed1994

Neurological manifestations of organic acid disorders.

Neurological manifestations are very common and can be the leading and/or presenting feature in organic acid disorders, sometimes in the absence of metabolic derangement. Review of the time course and presentation of neurological disease in organic acid disorders reveals characteristic clinical findings of ataxia, myoclonus, extrapyramidal symptoms, metabolic stroke and megalencephaly. A group of organic acid disorders presents exclusively with neurological symptoms. These include glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type I), succinic semialdehyde dehydrogenase deficiency (4-hydroxybutyric aciduria), mevalonic aciduria, N-acetylaspartic aciduria (Canavan disease) and L-2-hydroxyglutaric aciduria. As a group these "cerebral" organic acid disorders appear to remain often undiagnosed and their true incidence is much less well-known than that of the "classical" organic acid disorders. Unfortunately, stringent guidelines for a clinical preselection of neuropaediatric patients to be investigated for organic acid disorders cannot be provided. Today, screening for neurometabolic disorders should be as comprehensive as possible and include determinations of amino acids, purines and pyrimidines and markers of peroxisomal function in addition to organic acid analysis.

Brain Diseases, Metabolic↗
PubMed1994

D-2-hydroxyglutaric aciduria in neonate with seizures and CNS dysfunction.

D-2-Hydroxyglutaric aciduria was documented in a newborn who presented with seizures, hypotonia, cortical blindness, a movement disorder, and developmental delay. Her clinical presentation differs from that of patients with L-2-hydroxyglutaric aciduria and a single previously reported patient with D-2-hydroxyglutaric aciduria. Cerebrospinal fluid levels of gamma-aminobutyric acid were elevated, while biogenic amine metabolites were normal. The movement disorder in our patient and in those with L-2-hydroxyglutaric aciduria suggests involvement of the basal ganglia in the disease process. Prenatal diagnosis of an affected fetus was accomplished during a subsequent pregnancy.

Basal Ganglia Diseases↗
PubMed1994

A new syndrome with ethylmalonic aciduria and normal fatty acid oxidation in fibroblasts.

We describe four Italian male infants with a novel clinical phenotype characterized by orthostatic acrocyanosis, relapsing petechiae, chronic diarrhea, progressive pyramidal signs, mental retardation, and brain magnetic resonance imaging abnormalities. The first symptoms appeared after the termination of breast-feeding and introduction of formula feeding. Marked persistent 2-ethylmalonic aciduria was associated with abnormal excretion of C4-C5(n-butyryl-, isobutyryl-, isovaleryl-, and 2-methylbutyryl-)acylglycines and acylcarnitines and with intermittent lactic acidosis. Short- and branched-chain plasma acylcarnitine levels were also elevated. 2-Ethylmalonic aciduria is generally regarded as being indicative of a defect in fatty acid oxidation. Extensive studies of cultured fibroblasts failed to reveal such a defect. The observation of intermittent urinary excretion of 2-ethylhydracrylic acid pointed to involvement of the isoleucine R pathway in ethylmalonate biosynthesis. This hypothesis was tentatively corroborated by the biochemical responses to an oral isoleucine challenge in two patients. However, fibroblast studies showed normal oxidation rates of (14C)isoleucine (ul), indicating that this is not a defect of isoleucine oxidation expressed in skin fibroblasts. In one of two patients tested, cytochrome c oxidase activity was partially reduced (45%) in cultured fibroblasts. This unique clinical and biochemical phenotype identifies a new metabolic encephalopathy of yet undetermined cause.

Acyl-CoA Dehydrogenase↗
PubMed1994

3-Methylglutaconic aciduria in the Iraqi-Jewish 'optic atrophy plus' (Costeff) syndrome.

Eleven new patients of Iraqi-Jewish origin with bilateral optic atrophy, neurological abnormalities ('optic atrophy plus' syndrome) and 3-methylglutaconic aciduria (type III) are described. Clinical abnormalities in decreasing order of frequency were bilateral optic atrophy, extrapyramidal signs, spasticity, ataxia, dysarthria and cognitive deficit. An association with age was found only for spasticity. Spasticity, extrapyramidal signs and optic atrophy frequently led to major disability, in contrast to ataxia, dysarthria and cognitive deficit. The combined excretion of 3-methylglutaconic and 3-methylglutaric acid ranged between 9 and 187 mmol/mol creatinine. The primary enzymatic defect possibly may reside in the mitochondrial respiratory chain.

Adolescent↗
PubMed1994

Holocarboxylase synthetase deficiency: a treatable metabolic disorder masquerading as cerebral palsy.

A 20-month-old boy of Jewish-Turkish origin presented with severe metabolic acidosis. He was born prematurely and had bacteremia during the neonatal period. Scaly skin eruption, developmental delay, generalized muscular hypertonia, and mild ventriculomegaly were noted during the 1st year. Holocarboxylase synthetase deficiency was diagnosed, and biotin and carnitine were administered. The skin rash and the organic aciduria resolved within several days, and at 30 months, his psychomotor development was appropriate for age. Metabolic evaluation should be performed in patients with combined neurologic and dermatologic symptoms even when medical history suggests a nonmetabolic etiology.

Biotin↗
PubMed1994

Tiglylglycine excreted in urine in disorders of isoleucine metabolism and the respiratory chain measured by stable isotope dilution GC-MS.

Tiglyglycine (TG), an intermediate product of the catabolism of isoleucine, is increased in the urine of patients with beta-ketothiolase deficiency or with disorders of propionate metabolism. It is also implicated as a useful diagnostic marker in disorders of the respiratory chain. We present a method for the synthesis of TG and tiglyl[13C, 15N]glycine and the development of a stable isotope dilution mass spectrometric assay for TG. We compare data from controls with that from subjects with beta-ketothiolase deficiency and propionyl-CoA carboxylase deficiency, and with six patients with enzyme-confirmed disorders of the respiratory chain. TG was increased in the urine from all of the patient groups. The increased TG excretion did not persist in one patient with a respiratory chain defect, which suggests that, in some patients, multiple sample analysis may be necessary to identify a respiratory chain defect. This is the first urinary compound to be implicated as a potential marker of disorders of the respiratory chain.

Acetyl-CoA C-Acyltransferase↗
PubMed1994

A survey of persisting leg and/or foot pain in vascular surgery patients.

Two surveys were performed on more than 100 postoperative peripheral vascular procedure patients in order to ascertain the incidence and extent of prolonged lower limb pain. There was a significant number of patients who continued to experience moderate or greater degrees of disability associated with their pain at more than 7 months postoperatively. A multidisciplinary approach to the management of peripheral vascular patients is discussed.

Australia↗
PubMed1993

3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL). Cloning of human and chicken liver HL cDNAs and characterization of a mutation causing human HL deficiency.

3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL) catalyzes the final step of ketogenesis, an important pathway of mammalian energy metabolism. HL deficiency is an autosomal recessive inborn error in man leading to episodes of hypoglycemia and coma. Using the N-terminal peptide sequence of purified chicken liver HL, we designed degenerate sequence primers and amplified an 89-base pair (bp) chicken liver HL cDNA fragment. Longer cDNA clones for chicken (1384 bp) and human (1575 bp) HL were obtained by library screening. The peptide sequence predicted from the chicken clone contains two peptides from purified chicken HL. Mature human and chicken HL are 298-residue peptides. The sequence of the human clone predicts a 27-residue mitochondrial leader and a 31.6-kDa mature HL peptide. Human fibroblast and liver RNA contain a single 1.7-kilobase HL message. Two Acadian French-Canadian siblings with HL deficiency were homozygous for a 2-base pair deletion within the Ser-69 codon (S69fs(-2)), predicted to result in a truncated nonfunctional HL peptide lacking a complete active site. S69fs(-2) was not present in 12 other HL-deficient patients of 10 other ethnic origins, showing that HL deficiency is genetically heterogeneous.

Amino Acid Sequence↗