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Biomedical subjects

B H Robinson

Publications and source records attributed to B H Robinson.

At least 127 records · Page 7Linked to original sources
PubMed1992

Analysis of encoding efficiency in MR imaging of velocity magnitude and direction.

The efficiency of balanced versus unbalanced techniques for phase-angle-based velocity magnitude and direction imaging is investigated. Methods having balanced flow-encoding gradients (gradients in positive and negative directions with a zero center of gravity) are compared with unbalanced methods. For three-dimensional imaging, a currently used balanced method is the six-point technique having opposed gradients pairs for each orthogonal direction. A currently used unbalanced method is a four-point null technique which has three orthogonal gradients and an additional acquisition having no specific flow encoding to correct the baseline (null) phase. In the gradient-limited case of slow flow and perfusion, the balanced method is predicted to have higher velocity magnitude-to-noise ratio per time (SNRV) by a factor of 1.63, with similar results for velocity direction. In the wraparound-limited case of faster flows and motions, similar results are found when a null acquisition is added to the balanced method. This results in a seven-point balanced method having an SNRV 1.51 times that of the four-point unbalanced method. If null phases are within the [-pi/2,pi/2] interval, this additional null acquisition is unnecessary. Other four-point methods are also considered. These results indicate that, in general, balanced methods have advantages over unbalanced methods for velocity imaging.

Blood Flow Velocity↗
PubMed1992

Fatal combined defects in mitochondrial multienzyme complexes in two siblings.

A female child suffering from intrauterine growth retardation was born by caesarean section at 32 weeks. In the immediate newborn period there was a metabolic acidosis but this resolved. Hypotonia, muscular weakness and poor respiratory effort were evident and the child died at 6 days of age. A previous male sibling had died at 3 months of age after similar symptoms with seizures and a dysmyelination disorder. Post-mortem examination of both children showed damage to the basal ganglia. Defects in the activities of the pyruvate dehydrogenase complex, cytochrome oxidase and succinate cytochrome c reductase were found in cultured skin fibroblasts. Similar defects were found in isolated muscle mitochondria but not in isolated liver mitochondria from the patient. Immunoblotting for cytochrome oxidase showed that the multienzyme complex was not assembled in muscle and skin fibroblast mitochondria, but was assembled in liver mitochondria. Similar results were obtained in cultured skin fibroblast mitochondria for complex I of the mitochondrial respiratory chain. This is the first occasion that multiple defects have been demonstrated both in tissue and in culture skin fibroblasts in mitochondrial respiratory chain complexes.

Abnormalities, Multiple↗
PubMed1992

Nonviability of cells with oxidative defects in galactose medium: a screening test for affected patient fibroblasts.

Diagnosis of respiratory chain defects in cultured skin fibroblasts is a difficult diagnostic procedure. We investigated the feasibility of using survival of skin fibroblasts in culture medium with galactose as the major carbon source as a method of quickly diagnosing cell lines that were compromised in oxidative metabolism. We found that cells from patients with most forms of cytochrome oxidase deficiency, cells with complex I deficiency, cells with multiple respiratory chain defects and cells with severe pyruvate dehydrogenase (PDH) complex deficiency failed to survive when subcultured into galactose (5 mM) medium. Cells from patients with Lebers hereditary optic neuropathy (LHON), Kearns-Sayre syndrome (KSS), myoclonus-epilepsy-lactic acidosis-stroke (MELAS), the hepatic form of cytochrome oxidase deficiency, and mild PDH complex deficiency survived well in galactose (5 mM)-containing medium. This could be used as a rapid screening test for skin fibroblasts with major oxidative defects.

Cell Line↗
PubMed1992

Heteroplasmic mtDNA mutation (T----G) at 8993 can cause Leigh disease when the percentage of abnormal mtDNA is high.

A female infant showing lacticacidemia, hypotonia, and neurodegenerative disease died at 7 mo of age. Autopsy revealed lesions typical of Leigh disease, both in the basal ganglia and in the brain stem. A maternal aunt and uncle died 1 year and 5 mo, respectively, after following a similar clinical course, while another uncle, presently 33 years of age, has retinitis pigmentosa and ataxia and is mentally retarded. PCR restriction-digest analysis of mtDNA isolated from the proband revealed a T-to-G change at position 8993, creating a new AvaI restriction site. The mutation present in the ATP 6 gene results in the substitution of an arginine residue for a leucine. The indexed patient had greater than 95% abnormal mtDNA in her skin fibroblasts, brain, kidney, and liver tissues, as measured by laser densitometry. The maternal aunt who died at age 1 year had greater than 95% abnormal mtDNA in her lymphoblasts. The uncle with retinitis pigmentosa had 78% and 79% abnormal mtDNA in his skin fibroblasts and lymphoblasts, respectively, while an asymptomatic maternal aunt and her son had no trace of this mutation. The mother of the index case had 71% and 39% abnormal mtDNA in her skin fibroblasts and lymphoblasts, respectively, showing that the heteroplasmy can be variable, on a tissue-specific basis, within one individual. This shows that mtDNA mutations at 8993 can produce the clinical phenotype of Leigh disease in addition to the phenotype of ataxia and retinitis pigmentosa described by Holt et al.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA, Mitochondrial↗
PubMed1992

Role strain and depression in employed married Black mothers.

During the past several decades, the rate of participation in the labor force among married women with children has increased steadily. This trend coincides with an increase in the rate of reported psychological distress among women and an increase in researchers' interest in the psychological consequences of married mothers in the work force. Black women have historically and in significant numbers worked outside the home. The authors discuss the major concerns of employed Black mothers, identify areas where mental health professionals might intervene and identify coping strategies for Black women managing multiple roles.

Adaptation, Psychological↗
PubMed1991

Determination of the cDNA sequence for the human mitochondrial 75-kDa Fe-S protein of NADH-coenzyme Q reductase.

A human-hepatoma cDNA lambda gt11 expression library was probed with an antibody to holoenzyme complex I (NADH-CoQ reductase) of the respiratory chain. One of the 30 antibody positive clones was purified to homogeneity, amplified by the polymerase chain reaction (PCR), subcloned and sequenced. It proved to be highly similar to the cDNA sequence for the bovine 75-kDa Fe--S protein. Using the sequence obtained from this library, both sense and antisense oligonucleotides were constructed and used to probe a human kidney cDNA library using PCR amplification with oligonucleotides that flank the polylinker region of the lambda phage. Two further cDNA clones were obtained which overlapped and covered the entire cDNA sequence of 2526 bp. The encoded protein of 727 amino acids has 21 amino acids that differ from the bovine-protein sequence. Northern blot analysis of mRNA from fibroblasts of complex-I deficient patients revealed no abnormalities. We show that this Fe--S protein has significant similarity with (a) the gamma chain of the hydrogen hydrogenase of Alcaligenes eutrophus and (b) the A chain of the formate dehydrogenase of Methanobacterium formicum.

Amino Acid Sequence↗
PubMed1991

Reverse enzyme synthesis in microemulsion-based organo-gels.

Lipase from three different sources has been immobilised in microemulsion-based gels (MBGs) with retention of catalytic activity. Such lipase-containing MBGs prove to be novel solid-phase catalysts for use in apolar organic solvents such as n-heptane. Using these systems, preparative-scale synthesis of a wide variety of esters under mild conditions was possible with products easily isolated and obtained in high yield. Stereoselective esterification of octan-2-ol was observed for all three lipases with Chromobacterium viscosum (CV) lipase yielding product with an enantiomeric excess of 92%. Repeated usage of a CV lipase-containing MBG resulted in a visually unchanged gel whose activity was 75% of the initial value after 30 days. The sectioned MBGs were well suited for use in column flow reactors and were also found to be effective esterification catalysts at temperatures as low as -20 degrees C.

Catalysis↗
PubMed1991

Infant-onset progressive myoclonus epilepsy.

We report the clinical, electroencephalographic, neurophysiologic, and neuroimaging findings in eight children with infant-onset progressive myoclonus epilepsy, all of whom had muscle biopsies performed as as part of the diagnostic evaluation. Each child had myoclonic seizures, generalized tonic-clonic seizures, and neurologic regression or marked developmental delay. Four children died before 3 years of age. Electroencephalograms in seven children showed an abnormally slow background with bilateral multifocal paroxysmal discharges but no burst suppression pattern or photoparoxysmal response. Muscle biopsy specimens were submitted for histopathology and respiratory-chain enzyme studies. Nonspecific abnormalities on light microscopy or electron microscopy were found in seven samples, including increased subsarcolemmal deposits of mitochondria or morphologic mitochondrial changes, but no ragged-red fibers were seen. Respiratory-chain enzyme studies were performed on five samples and in three children (all of whom had a history of elevated lactate in serum or cerebrospinal fluid), there were low levels of rotenone-sensitive reduced nicotinamide adenine dinucleotide (NADH) cytochrome c reductase characteristic of a defect in the complex I part of the respiratory-chain pathway. This study has shown that infant-onset progressive myoclonus epilepsy can be distinguished from other myoclonic epilepsy syndromes of infancy by clinical and electrographic features. Furthermore, respiratory-chain enzyme defects are a relatively common cause of infant-onset progressive myoclonus epilepsy. The absence of ragged-red fibers on muscle histopathology does not preclude a mitochondrial enzyme abnormality.

Biopsy↗
PubMed1991

Pairing students for community health nursing home visits.

Faculty paired community health nursing (CHN) students for home visits to reduce students' anxiety and enhance their learning of the nursing process. The pairing method involved 60 students over a three-semester period. The process is described and advantages and disadvantages are analyzed. The net results are favorable. Faculty found that students' fear of entering an unfamiliar home was supplanted by a sense of challenge at working collaboratively with a peer. Furthermore, the pairing experience increased students' confidence in making decisions about client care and offered them more physical safety when visiting high-crime urban settings. Students felt positive about the increased safety and expressed greater confidence in their CHN role and their application of the nursing process.

Community Health Nursing↗
PubMed1991

Pyruvate dehydrogenase deficiency due to a 20-bp deletion in exon II of the pyruvate dehydrogenase (PDH) E1 alpha gene.

A 20-bp deletion in the last exon of the pyruvate dehydrogenase (PDH) E1 alpha gene was found in a severely affected female patient diagnosed with PDH deficiency. PDH-complex activity in the patient's fibroblasts was 22% of that in normal controls. The mutation was characterized using PCR techniques with both patient cDNA and genomic DNA, followed by sequencing of the products. E1 beta cDNA sequence was found to be the same as that in controls. The deletion causes a frameshift and the occurrence of a premature stop codon. Western blot analysis revealed an extra band migrating just above the PDH E1 beta band. Northern blot analysis showed normal levels of both E1 alpha and E1 beta message when probed with the respective cDNAs. However, a larger intermediate-size transcript was observed for this patient in the E1 beta blot. The 20-bp deletion was not found in either parent's genomic DNA, and hence we conclude that the mutation must have occurred de novo, either in the germ-line cells or immediately following fertilization.

Amino Acid Sequence↗
PubMed1990

Isolation, characterization and chromosomal localization of cDNA clones for the E1 beta subunit of the pyruvate dehydrogenase complex.

A full-length cDNA clone for the E1 beta subunit of the human pyruvate dehydrogenase (PyrDH) complex was isolated from a human skin fibroblast cDNA library. When sequenced, it showed differences from the nucleotide sequence already published [Koike, K., Ohta, S., Urata, Y., Kagawa, Y. & Koike, M. (1988) Proc. Natl Acad. Sci. USA 85, 41-45], such that 19 amino acids were different in the translated open reading frame. Northern blotting of human fibroblast cell lines revealed a major mRNA species of 1.6 kb and a weaker band of 5.5 kb. In a series of nine PyrDH-complex-deficient cell lines from patients with this deficiency, no patients had severely reduced amounts of mRNA, but there was one patient cell line with an increased amount of abnormal-size mRNA. Chromosome localization carried out with DNA blots from man-mouse hybrid cell lines indicated that the E1 beta subunit of pyruvate dehydrogenase is located on chromosome 3. A motif AXGXXXXGL(R/K)X15(D/E)Q was found in common with a variety of other oxo-acid oxidoreductases, but its function is not known.

Amino Acid Sequence↗
PubMed1990

Congenital lactic acidosis due to a defect of pyruvate dehydrogenase complex (E1). Clinical, biochemical, nerve biopsy study and effect of therapy.

We report an 8-year-old patient with clinical features suggesting Leigh's syndrome and with a decreased activity of the E1 component of the pyruvate dehydrogenase complex in cultured skin fibroblasts. A nerve biopsy showed the presence of severe peripheral neuropathy, rarely described in the literature. The partial correction of lactic acidosis with oral sodium bicarbonate chronic therapy may result in a slow evolution of the clinical symptoms.

Acidosis, Lactic↗
PubMed1990

Defects in the E2 lipoyl transacetylase and the X-lipoyl containing component of the pyruvate dehydrogenase complex in patients with lactic acidemia.

Three patients with chronic lacticacidemia and deficiency of the pyruvate dehydrogenase complex demonstrated in cultured skin fibroblasts showed abnormalities on Western blotting with anti-pyruvate dehydrogenase complex antiserum which were not located in the E1 (alpha and beta) component of the complex. One of these patients had an enzymatically demonstrable deficiency in the E2 dihydrolipoyl transacetylase segment of the complex and very low observable E2 protein component on Western blotting of fibroblast proteins. The other two patients had abnormalities observable in the X component but no observable reduction in either E1, E2, or E3 enzymatic activities. One patient appeared to have a missing X component while the other had two distinct bands where X should be on Western blotting of fibroblast proteins. All three patients appeared to have severe clinical sequelae resulting from these defects. This is the first time that defects in either the E2 or the X component of the pyruvate dehydrogenase complex have been observed in the human population.

Acetyltransferases↗
PubMed1990

Effect of lipoic acid in a patient with defective activity of pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, and branched-chain keto acid dehydrogenase.

Lactic acidosis and accumulation of 3-hydroxybutyrate and other citric acid cycle intermediates were found in an infant with a lethal syndrome of metabolic acidosis and renal tubular acidosis. Nevertheless, the patient was relatively well for 4 mo of life. The activity of the pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase, and branched-chain keto acid dehydrogenase were all reduced to levels 9 to 29% of control. In contrast, the activity of lipoamide dehydrogenase was normal. The conversion of 1-14C-leucine and 1-14C-valine to 14CO2 and of U-L-14C-valine to its major metabolic product 3-hydroxyisobutyric acid by fibroblasts derived from the patient was less than 5% of control. Cultivation of the patient's fibroblasts in medium enriched with lipoic acid markedly improved these in vitro conversions of leucine and valine.

3-Hydroxybutyric Acid↗
PubMed1990

3-Oxothiolase activities and [14C]-2-methylbutanoic acid incorporation in cultured fibroblasts from 13 cases of suspected 3-oxothiolase deficiency.

Cultured fibroblasts from 13 patients with organic aciduria suggesting 3-oxothiolase deficiency were studied by measuring first the capacity of the isoleucine degradative pathways in whole cells, as the incorporation of 1-[14C]-2-methylbutanoic acid into macromolecules, and, second, the activity of 3-oxothiolase in cell homogenates using specific 3-oxoacyl-CoA substrates to identify the different enzymes. Nine patients showed low incorporation by the macromolecular labeling assay, as well as deficiency of 2-methylacetoacetyl-CoA thiolase. In this group of patients, low activity by the macromolecular labeling assay was associated with clinically severe symptoms, and vice versa. Two patients showed reduced macromolecular labeling, but apparently normal 3-oxothiolase. Finally, two patients showed normal activities by either test, the reason for their particular organic aciduria being unknown. In conclusion, occurrence of urinary 2-methyl-3-hydroxybutyric acid and/or tiglyglycine is not an unequivocal indicator of the absence of the thiolase that metabolizes 2-methylacetoacetyl-CoA. Measurement of 1-[14C]-2-methylbutanoic acid incorporation in cultured fibroblasts adds important information in studying possible defects of the isoleucine catabolic pathway.

Acetyl-CoA C-Acyltransferase↗