Search PubMed⌕ Search

Biomedical subjects

G H Thomas

Publications and source records attributed to G H Thomas.

At least 109 records · Page 6Linked to original sources
PubMed1981

Direct quantitation of glycosaminoglycans in 2 mL of urine from patients with mucopolysaccharidoses.

Glycosaminoglycans in urine from patients representing the major different mucopolysaccharidoses were separated and measured by use of a procedure that requires only 2 mL of urine. The compounds were resolved by two-dimensional electrophoresis on cellulose acetate plates and made visible by staining with Alcian Blue. They were identified by co-migration with standard glycosaminoglycans, by digestion with specific glycosidases, and by specific degradation with HNO2. They were quantitated by comparing the absorbance of eluates of the stained spots to appropriate standard curves for each glycosaminoglycan. This study revealed additional findings. About half of the patients excreted small amounts of heparin. Further, the keratan sulfate in samples from Morquio's disease patients migrated differently from authentic keratan sulfate unless digested with chondroitinase ABC. Our results for these diseases are in harmony with earlier reports.

Electrophoresis, Cellulose Acetate↗
PubMed1980

A new R-banding technique in clinical cytogenetics.

Currently, standard methods of chromosome banding detect an abnormality in some 10%--15% of all patients referred for a cytogenetic study. Higher resolution by the study of the less contracted chromosomes with or without cell synchronization techniques may yield higher frequencies in the future. On the other hand, use of more complicated methodology adds to the time and expense needed for the study. The method of 5' bromodeoxyuridine pretreatment of cells in culture is commonly used to study the replication behavior of X chromosomes, and is known to demonstrate R bands along the other chromosomes. We have modified this technique with the addition of a cell synchronization step and evaluated several variables that are of importance in a clinical service laboratory setting. The method offers a simple way to obtain quality R-banded karyotypes. The advantages and limitations, based on our study of 120 consecutive cultures, are described.

Acridines↗
PubMed1980

A severe infantile sialidosis: clinical, biochemical, and microscopic features.

An infant boy is described whose clinical findings include congenital ascites, hepatosplenomegaly, postnatal growth failure, dysostosis multiplex, delayed development, pericardial effusion, and the nephrotic syndrome. Death occurred before he reached 2 years of age. Evidence indicates that these abnormalities resulted from an autosomal recessive inherited deficiency of neuraminidase.

Ascites↗
PubMed1980

Complex chromosome rearrangements. Report of a new case and literature review.

A complex and unique, apparently balanced translocation involving three autosomes and an X in a phenotypically abnormal child is described. Family studies using glucose 6 phosphate dehydrogenase as a marker provided biochemical evidence of non-random expression of this Xq locus and suggested that this de novo abnormality in the proband could be paternal in origin--the first such instance to be recorded.

Abnormalities, Multiple↗
PubMed1979

Xeroderma pigmentosum variants have a slow recovery of DNA synthesis after irradiation with ultraviolet light.

Human cells (normal and xeroderma pigmentosum variant) irradiated with ultraviolet light and pulse-labelled with [3H]thymidine underwent transient decline and recovery of molecular weights of newly synthesized DNA and rates of [3H]thymidine incorporation. The ability to synthesize normal-sized DNA recovered more rapidly in both cell types than thymidine incorporation. During recovery cells steadily increased in their ability to replicate normal-sized DNA on damaged templates. The molecular weight versus time curves fitted exponential functions with similar rate constants in normal and heterozygous xeroderma pigmentosum cells, but with a slower rate in two xeroderma pigmentosum variant cell lines. Caffeine added during the post-irradiation period eliminated the recovery of molecular weights in xeroderma pigmentosum variant but not in normal cells. The recovery of the ability to synthesize normal-sized DNA represents a combination of a number of cellular regulatory processes, some of which are constitutive, and one of which is altered in the xeroderma pigmentosum variant such that recovery becomes slow and caffeine sensitive.

Caffeine↗
PubMed1979

Evidence for removal at different rates of O-ethyl pyrimidines and ethylphosphotriesters in two human fibroblast cell lines.

The potent carcinogen, ethylnitrosourea, has been shown to ethylate oxygens, in preference to nitrogens, in the DNA of cultured cells. We have now studied the removal of seven ethyl derivatives in replicating cells. The following findings are reported. 1) The absolute amounts of 02-EtT, 04-EtT and 02-EtC are decreased in cellular DNA after correction for cell growth. However the rate of decrease diminishes after approximately 20 hr and after more than two cell doublings 20--40% of each derivative persists. This decrease is presumed to be due to enzymes since these derivatives are stable in isolated DNA. 2) The amount of ethyl phosphotriesters remains almost unchanged during 72 hr of cell culture. 3) The unstable purine derivatives, 7-EtG and 3-EtA, are both removed from cellular DNA with a rate faster than can be accounted for by the lability of the glycosyl bond. 4) Both GM 637 fibroblasts and Xeroderma pigmentosum fibroblasts (12-RO) (XP-12) have similar ability to remove ethyl products, except for O6-ethyl G which persists to a greater extent in XP12 cells. 5) The implications of the in vivo persistence of ethylated bases is discussed in regard to recent demonstrations that O2-EtT, O4-ET, O2-EtC and O6-EtG are all mutagenic.

Alkylation↗
PubMed1979

Characterization of neuraminidase activity of cultured human fibroblasts.

Investigations have been carried out to establish the enzymatic properties and specificities of the neuraminidase of cultured human fibroblasts. Homogenates of these cells cleaved the actylated derivative of neuraminic acid from fetuin, N-acetylneuraminyllactose and 2-(3' methoxyphenyl)-N-acetyl-alpha-neuraminic acid. Maximum activity occurred between pH 4.2 and 4.6 in sodium acetate buffer. The Km values were 3.6 . 10(-4) M, 3.0 . 10(-3) M and 1.1 . 10(-3) M, respectively, against fetuin, N-acetylneuraminyllactose and 2-(3'methoxyphenyl)-N-acetyl-alpha-neuraminic acid. Against the first two substrates, the rate of hydrolysis fell below the expected value as the cell homogenate was diluted with water or 10 mM NaCl. Dilution with 8 mg/ml bovine serum albumin prevented the deviation and yielded the expected linear decrease. After the first 2-h incubation, the rate of hydrolysis decreased from the initial linear rate. The enzyme(s) was partially or completely inactivated by sonication at 20 kHz, freeze-thaw treatment, incubation at 52 degrees C or storage for 48 h at -70 degrees C. Suspension of the fibroblasts in water for 10 min at room temperature, followed by homogenization with a tissue grinder, yielded preparations that were suitable for the assay of the neuraminidase activity.

Cells, Cultured↗
PubMed1979

Partial trisomy 4q resulting from a familial 4/3 translocation.

A case of trisomy 4q resulting from a balanced paternal translocation is described. Phenotypic similarity of cases with similar break points included hypoplastic nasal alae, short philtrum and pursed lips, and prominent ears. The birth of the proband was preceded by unexplained infertility, oligospermia in the father, and increased fetal wastage. Each of these features is an appropriate indication for cytogenetic analysis. If such an analysis had been done, the unbalanced translocation state in a liveborn, handicapped child could have been anticipated.

Child, Preschool↗
PubMed1979

Neuraminidase deficiency in the original patient with the Goldberg syndrome.

Homogenates of cultured skin fibroblasts from a non-ambulatory, 20-year-old male with cherry-red spots, corneal clouding, seizures, mental retardation, dysostosis multiplex, dwarfism, coarse facies and loss of vision, originally described by Goldberg et al. (1971), have diminished neuraminidase activity and an excess of neuraminic acid-rich compounds. Specifically, these cells have 2-17% normal neuraminidase when measured with 2-(3' methoxyphenyl)-N-acetyl-alpha-neuraminic acid, N-acetyl-neuramin-lactose and fetuin. Activities of 12 other lysosomal enzymes were either at or above the range of normal control fibroblasts. Total neuraminic acid concentration was 44.3 nmol/mg protein versus an average control value of 14.2. It is concluded that the Goldberg syndrome should be considered, along with mucolipidosis I and the cherry-red spot -- myoclonus syndrome, as resulting from a primary neuraminidase deficiency.

Abnormalities, Multiple↗