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Biomedical subjects

D M Becker

Publications and source records attributed to D M Becker.

At least 109 records · Page 6Linked to original sources
PubMed1982

Optimal conditions for the assay of lipoamide dehydrogenase in homogenized human platelets.

Widely different method have been used to assay lipoamide dehydrogenase in tissues from patients with neurological diseases. We have re-examined conditions of assay in homogenized human platelets in the light of results of optimal and inhibitory conditions others have found for the purified pig and rat liver enzymes. Optimal conditions in homogenized platelets for the forward, physiological direction were pH 8.0, 2-4 mmol/l dihydrolipoamide and 1.6-2 mmol/l NAD+ and for the reverse reaction, pH 7.3, 1.2-2 mmol/l lipoamide and 0.125-0.2 mmol/l NADH. Km values by the Lineweaver-Burke method were approximately 420 mumol/l dihydrolipoamide, 180 mumol/l NAD+, 600 mumol/l lipoamide and 27 mumol/l NADH. The optimal conditions and Km values are similar to those reported for the purified pig and rat enzymes. Assays by the present methods should therefore reflect the activity of lipoamide dehydrogenase and not the effects of substrate or cofactor inhibition nor the effects of other, interfering enzyme activities.

Blood Platelets↗
PubMed1982

A description of a means of improving ambulatory care in a large municipal teaching hospital: a new role for nurse practitioners.

We describe a nurse practitioner program that has improved ambulatory care in a large municipal teaching hospital. The significant feature of this program is an expanded role for nurse practitioners in the follow-up of patients with complicated illnesses. Benefits of this program include improved continuity of care and an easing of the house staff's service burden. Similar use of nurse practitioners at other municipal teaching hospitals would be a useful approach to problems in quality of care and continuity of care.

Florida↗
PubMed1981

Lipoamide dehydrogenase: rapid heat inactivation in platelets of patients with recessively inherited ataxia.

The activity of lipoamide dehydrogenase was abnormally heat-labile in homogenized platelets from seven patients with as recessive ataxia conforming to the syndrome of Friedreich ataxia or clinical variants. Taken together, the abnormality and previous findings of low activity and abnormal kinetic properties are compatible with a change in the conformation of the enzyme in these patients.

Blood Platelets↗
PubMed1980

The effect of delta-aminolevulinic acid on the synthesis and metabolism of GABA in rabbit brain homogenates.

The porphyrin precursor delta-aminolevulinic acid (delta-ALA) is a structural analogue of the putative amino acid neurotransmitter, gamma-aminobutyric acid (GABA). This study has demonstrated that delta-ALA has no effect on glutamate decarboxylase activity and only a small inhibitory effect of GABA aminotransferase activity. This would suggest that if accumulation of delta-ALA is related to development of the acute attack of porphyria, it is not via an effect on GABA synthesis and metabolism.

Animals↗
PubMed1979

Reduced ferrochelatase activity in fibroblasts from patients with porphyria variegata.

Ferrochelatase deficiency has been shown in both porphyria variegata (PV) and erythropoietic protoporphyria (EPP). It has been suggested that in PV there is a decrease in the enzyme, whereas in EPP the enzyme is unstable. In the present study ferrochelatase activity was measured in skin fibroblasts from three patients with PV and three normal subjects. The enzymatic activity in the patients with PV (17.5 +/- 4.5 pmoles heme formed per 10(7) fibroblasts per hour) was 50% of that of the control group (31.0 +/- 3.2 pmoles heme formed per 10(7) fibroblasts per hour). This supports the contention that the enzyme is deficient in PV and that an inactive ferrochelatase is the primary deficiency in this type of porphyria.

Fibroblasts↗
PubMed1978

Porphyria variegata--studies of an affected couple and their children.

Porphyria variegata affects approximately 1 in 200 Afrikaans-speaking people in South Africa. This paper reports the first case of a marriage between 2 people with porphyria variegata and describes investigations carried out on their 2 children, who do not exhibit any signs of the disease. The wife had suffered 1 miscarriage at 4 months' gestation.

Adult↗
PubMed1977

The neurological manifestations of porphyria: a review.

The hereditary hepatic porphyrias, PV, AIP and HC, are characterized biochemically by increased excretion of porphyrins and the porphyrin precursors ALA and PBG. They are characterized clinically by episodes of acute neurological involvement. The increased production of porphyrins and porphyrin precursors has been shown to be due to partial enzyme blocks along the heme biosynthetic pathway which results in secondary depression of the key enzyme ALA-synthetase. The neurological manifestations could therefore be related to either a decrease in essential heme-proteins or other heme-containing compounds within the nervous system, or to a toxic effect of the over-production of the porphyrin precursors ALA and PBG. There is evidence for and against both theories. Recent work from a number of research groups has shown the porphyrin precursors to have potent pharmacological effects on the nervous system, and these are possibly related to the GABA receptor and binding site-porphyrin precursor interactions. Current studies on therapy of the acute attack have concentrated on suppression of ALA-synthetase activity, and consequently, on reduced ALA and PBG production. A number of such methods of therapy have met with remarkable success and hold promise for the future treatment of the acute attack.

Acute Disease↗
PubMed1977

Reduced ferrochelatase activity: a defect common to porphyria variegata and protoporphyria.

Erythroid ferrochelatase activity has been studied in the normoblasts of patients with porphyria variegata and protoporphyria. Two methods were used for the investigation: one using intact cells and the other lysed cells, each measuring the amount of haem synthesized by normoblasts. In patients with porphyria variegata, ferrochelatase activity estimated by both methods was approximately 50% of the normal, and in protoporphyria the ferrochelatase activity was normal in intact normoblasts but was 20% of the normal in sonicated normoblasts (marrow lysates). It is suggested therefore that in porphyria variegata a dominantly inherited structural gene mutation results in an active ferrochelatase whereas in protoporphyria the genetic mutation results in an unstable ferrochelatase. The mechanism of the enzyme instability is not known though a number of postulates are discussed.

Adolescent↗
PubMed1975

The effect of porphyrin precursors on monosynaptic reflex activity in the isolated hemisected frog spinal cord.

The porphyrin precursors beta-aminolevulinic acid (beta-ALA) and porphobilinogen (PBG) which accumulate, and are excreted in the urine in increased amounts during acute attacks of porphyria, were tested for their effects on reflex activity in the isolated hemisected spinal cords of Xenopus laevis. The two compounds were found to exert an inhibitory effect on monosynaptic ventral root responses, as well as on dorsal root responses (DRR) and dorsal root potentials (DRP). The latent period for inhibition of the monosynaptic response was longer than that for the DRR and DRP. The sensitivity of the preparations to the effect of the porphyrin precursors was subject to some seasonal variation. BETA-ALA and PBG did not effect conduction in isolated sciatic nerves at a concentration of 1 mg/ml.

Aminolevulinic Acid↗
PubMedDate not supplied

Multiple genotypes, multiple phenotypes, and partial defects.

In recent years, the following ideas have been expressed: (a) that all cases of a discrete, inherited neuromuscular syndrome should prove to be due to a single biochemical defect, (b) that any single biochemical defect should give rise only to one syndrome, and (c) that an enzymatic defect cannot give rise to a disease unless there is virtual absence of activity, that is, less than 5% or 10% of the normal value. We review evidence from research in neuromuscular, neurological, and other genetic diseases of humans that suggest the contrary. There are now examples of single clinical syndromes related to each of several defects, of defects of one biochemical reaction related to two or more distinct clinical syndromes, and of partial defects associated with disease in a way that suggests a causal relationship.

Anemia, Hemolytic, Congenital↗