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Biomedical subjects

R G Davidson

Publications and source records attributed to R G Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1977

Prenatal diagnosis of metachromatic leukodystrophy by electrophoretic and immunologic techniques.

Electrophoretic examination of extracts of cultured amniotic fluid cells from a pregnancy at risk for metachromatic leukodystrophy (MLD) showed absence of arylsulfatase A (AS-A) activity. Immunodiffusion with anti-human AS-A immune serum failed to show enzymatically active arcs of immune precipitate. Electrophoretic studies and quantitative assay of extracts of organs from the aborted fetus confirmed the diagnosis of MLD. Electrophoresis of amniotic fluid from this and one additional fetus with MLD showed an arylsulfatase pattern qualitatively and quantitatively indistinguishable from normal. In both normal and MLD fluids, the AS-A band was replaced by a band with lower anodal mobility. Only the anodal band of normal amniotic fluid, however, reacted with the anti-AS-A immune serum in immunoelectrophoresis. Assay of amniotic fluic with p-nitrocatechol sulfate (PNCS) as a substrate showed marked deficiency of "AS-A" activity in the fluids from the two MLD pregnancies. An optimal procedure for prenatal detection of MLD should include electrophoresis of extracts of cultured amniotic fluid cells with visual demonstration of absence of AS-A activity. Immunologic techniques applied to cell-free amniotic fluid may be of help in the rapid identification of the fetal genotypes.

Amniocentesis↗
PubMed1976

Hypophosphatasia: a developmental anomaly of alkaline phosphatase?

This report deals with quantitative and qualitative investigations of alkaline phosphatase in two unrelated infants with the severe infantile form of hypophosphatasia. Both affected infants had no detectable leukocyte alkaline phosphatase activities and both sets of parents and one sibling tended to have low but variable leukocyte enzyme activities. Normal duodenal juice alkaline phosphatase activity was present in the one patient in whom it was measured and a wide range of variation in enzymic activity was observed in the stools. There was no significant difference in the stool enzyme activity between both patients with hypophosphatasia (42.01 +/- 9.77 U) and control infants (40.55 +/- 6.29 U). However, the heterozygous parents had values significantly lower than the control adults (2.10 +/- 0.47 as compared with 19.10 +/- 4.44 U). Intestinal bacteria did not contribute significantly to the stool alkaline phosphatase activity. Enzyme activity was present in the bile of one of the patients and nearly absent in that of the other. Three "inducers" of alkaline phosphatase were given to both patients (phenobarbital, vitamin A, and corticosteroid). No clinical improvement or rise in serum alkaline phosphatase activity was observed during the trial of therapy with these agents. However, a significant increase in the activity of serum acid phosphatase was demonstrated during the course of vitamin A administration, suggesting an in vivo action of vitamin A on the lysosomes through decreasing the stability of the membrane and releasing acid phosphatase to the serum. Quantitative determination of tissue alkaline phosphatases from autopsy tissues was highly variable: no activity was found in bone, lungs, or spleen of either infant; there was a discrepancy in liver and kidney alkaline phosphatase values (zero in one patient and present in the other) and activity was present in the intestinal mucosa of both. Qualitative analysis of kidney, liver, and intestinal alkaline phosphatase revealed some differences between the patients and control subjects in heat inactivation and phenylalanine inhibition (Table 3). Starch gel electrophoresis of the liver preparation of one patient disclosed a single band which had greater mobility than that of six control subjects matched for age. Liver extracts from a premature and from full term newborns showed two bands. The single band of the patient's liver enzyme corresponded to the newborn's fast moving component. In addition, the intestinal enzyme prepared from the same patient had an extra band when compared with age-matched control subjects.

Acid Phosphatase↗
PubMed1976

Studies on complementation of beta hexosaminidase deficiency in human GM2 gangliosidosis.

Complementation of beta hexosaminidase A (hex A) deficiency was obtained by Sendai virus-mediated somatic cell hybridization of cultured skin fibroblasts from two unrelated patients with Tay-Sachs disease (TSD) and one patient with Sandhoff-Jatzkewitz disease (SJD). The newly formed hex A was identified by its electrophoretic mobility in three different systems, heat lability, and reactivity with an antiserum against the unique antigenic determinant, alpha of hex A. The percentage of heterokaryons obtained by virus treatment of TSD and SJD fibroblast mixtures showed good correlation with the observed percentage of hex A activity. It is concluded that, in these two forms of GM2 gangliosidosis, beta hexosaminidase deficiency results from two different mutations. All of the current models of beta hexosaminidase structure are compatible with the observed complementation. No complementation was detected in 13 Sendai virus-induced fusions of cultured skin fibroblasts from seven unrelated patients with SJD. The enzyme deficiency in these patients may be due to very similar allelic mutations, not capable of undergoing complementation; or to different structural mutations, all coding for unstable beta hexosaminidase molecules.

Acetylglucosaminidase↗
PubMed1975

A familial F/G translocation [t(p-; 22q+)] observed in three generations.

A family is described in which a translocation between chromosomes 20 and 22 has been observed in three generations. Two first cousins with remarkably similar malformations and mental retardation have identical karyotypes which, after chromosome banding, were interpreted as partially trisomic for the short arm of chromosome No. 20.

Abnormalities, Multiple↗
PubMed1970

Genetic polymorphisms of human mitochondrial glutamic oxaloacetic transaminase.

In a survey of 860 unselected human placental extracts, three variants of mitochondrial glutamic oxaloacetic transaminase were found, all of which were common enough to be considered polymorphisms. Family studies showed that this enzyme is under the control of nuclear rather than mitochondrial DNA.

Aspartate Aminotransferases↗