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Biomedical subjects

A Allen

Publications and source records attributed to A Allen.

At least 343 records · Page 19Linked to original sources
PubMed1970

The release of radioactive nucleic acids and mucoproteins by trypsin and ethylenediaminetetra-acetate treatment of baby-hamster cells in tissue culture.

Monolayers of baby-hamster kidney cells were grown on glass in tissue culture and harvested with trypsin or EDTA in order to investigate the cell surface macromolecules removed by these cell-disaggregating agents. The release of nucleic acids from the cells during the harvesting procedure was monitored by labelling the cellular RNA with [5-(3)H]uridine and the cellular DNA with [2-(14)C]thymidine. Treatment of the cells with EDTA was found to cause an increase in the permeability of the plasma membrane with 7.6% of the cellular RNA, but less than 1% of the cellular DNA, being released. Moreover, 61% of the cells harvested with EDTA were permeable to Trypan Blue. With crude trypsin, lysis of the cell occurred with the release of similar amounts of RNA and DNA amounting to about 11% of the total cellular nucleic acid. In contrast, crystalline trypsin released only 1% of the cellular nucleic acids. Since virtually all the cells (99%) after harvesting in crystalline trypsin were impermeable to Trypan Blue, this method was suitable for obtaining cell surface macromolecules without contamination by intracellular damage. [1-(14)C]Glucosamine was incorporated by the cells only into bound hexosamines and sialic acids. [By monitoring the release of radioactivity in high-molecular-weight material in such experiments a measure of the release of macromolecules containing amino sugars was obtained.] Of the total macromolecules containing amino sugars in the cells 33%, 24% and 13% were released when the cells were harvested with crude trypsin, crystalline trypsin or EDTA respectively. Crystalline trypsin also released 39% of the total sialic acid of the cell, whereas less than 1% of the cellular sialic acid was present in the EDTA-treated fraction. It is concluded that the macromolecules containing amino sugars released with crude trypsin and EDTA are likely to be heavily contaminated with intracellular material. However, the macromolecules released by crystalline trypsin appear to come from the cell surface.

Animals↗
PubMed1968

Biosynthesis of intestinal mucins. Effect of puromycin on mucoprotein biosynthesis by sheep colonic mucosal tissue.

1. Surviving sheep colonic mucosal tissue incorporated l-[U-(14)C]threonine when incubated in Krebs medium III at 37 degrees in an atmosphere of oxygen, into a well-characterized mucoprotein fraction, isolated by papain digestion of the incubated scrapings. 2. Acidic hydrolysis and chromatography of the labelled mucoprotein showed that threonine was the only constituent to become labelled. In the presence of puromycin the incorporation of l-[U-(14)C]threonine was considerably diminished (6.7 and 18.5% of control in duplicate experiments). Furthermore, puromycin also decreased incorporation of radioactivity from d-[U-(14)C]-glucose (48.0 and 31.6% of control) and (35)SO(4) (2-) (21.2 and 23.6% of control) into the mucoprotein fraction. 3. In a puromycin-inhibited system, with d-[U-(14)C]-glucose, where the overall specific radioactivity of the mucoprotein was 48% of control, the labelling of the individual monosaccharide constituents (as% of control) was: N-acetylneuraminic acid, 44%; N-glycollylneuraminic acid, 61%; hexosamines, 46%; fucose, 68%; galactose, 34%.

Animals↗
PubMed1968

The biosynthesis of intestinal mucins. The effect of salicylate on glycoprotein biosynthesis by sheep colonic and human gastric mucosal tissues in vitro.

1. Incubation of sheep colonic mucosal scrapings in Krebs-Ringer buffer for 2(1/2)hr. in the presence of salicylate (15mm) resulted in decreased incorporation of radioactivity into the epithelial glycoprotein from the following labelled precursors: 16.6mum-d-[2-(14)C]glucose (83.9% inhibition), 20mum-l-[U-(14)C]threonine (82%) and (35)SO(4) (2-)(79%). Oxygen uptake measured simultaneously was diminished to 41% of the control value. 2. At lower concentrations of salicylate (e.g. 3.75mm), incorporation of 20mum-l-[U-(14)C]threonine was little affected (3-6% inhibition), whereas utilization of 4mum-d-[U-(14)C]glucose and (35)SO(4) (2-) was inhibited (41-48% and 40-59% of the control values respectively). 3. Analysis of the papain-digested glycoprotein from tissue incubations with 16.6mum-d-[2-(14)C]glucose in the presence of salicylate (3.75mm) showed large decreases in labelling of N-acetylneuraminic acid and N-glycollylneuraminic acid residues (57% and 34% of the control values respectively) and of hexosamine constituents (glucosamine, 55% inhibition; galactosamine, 33% inhibition). Labelling of neutral sugars (galactose and fucose) was relatively little affected (9 and 11% inhibition respectively). 4. Glucose 6-phosphate transaminase and glucosamine 6-phosphate acetylase in particle-free enzyme preparations of the sheep tissue were unaffected by salicylate at the above concentrations. Acetyl-CoA synthetase was markedly inhibited. 5. Human gastric mucosa (from operation), on incubation as above, had in one experiment an oxygen consumption of 9.9mul./hr./mg. dry wt. of tissue and incorporated 5mum-d-[U-(14)C]glucose (15.8% of the total radioactivity added) into bound hexosamine (20.6% of the total radioactivity incorporated), hexoses (glucose and galactose, 5.7%) and fucose (14.2%). The presence of salicylate (15mm) decreased the incorporation of 5mum-d-[U-(14)C]glucose into the glycoprotein by 74%, all sugar constituents being affected, without influence on the rate of oxygen consumption. 6. The results suggest an inhibitory effect of salicylate on glycoprotein biosynthesis at the level of the amino sugar intermediates.

Acyltransferases↗
PubMed1968

Studies on the enzymic N-acylation of amino sugars in the sheep colonic mucosa.

1. d-[2-(14)C]Glucose, [2-(14)C]acetate, hydroxy[3-(14)C]pyruvate, [3-(14)C]pyruvate and [U-(14)C]glycine were incorporated by surviving scrapings of sheep colonic mucosal tissue into glycoprotein. 2. d-[2-(14)C]Glucose, [2-(14)C]acetate, incorporated hydroxy-[3-(14)C]pyruvate and [3-(14)C]pyruvate resulted in labelling of each of the monosaccharide residues of the glycoprotein, namely N-glycollylneuraminic acid, N-acetylneuraminic acid, galactose, fucose, glucosamine and galactosamine. [U-(14)C]Glycine was incorporated as glycyl and seryl residues of the glycoprotein. 3. Despite N-glycollylneuraminic acid being quantitatively the predominant sialic acid (N-glycollylneuraminic acid and N-acetylneuraminic acid were 8.5 and 5.2% by weight of the glycoprotein respectively) the corresponding ratio of the radio-active labelling from d-[2-(14)C]glucose in N-glycollylneuraminic acid to that in N-acetylneuraminic acid was 1.00:7.27 (expressed as percentages of the total radioactivity in the glycoprotein). Neutral sugar, hexosamine and N-acetylneuraminic acid residues of the mucoprotein were each labelled to a similar extent. 4. Similarly, the ratio of the radioactivity in N-glycollylneuraminic acid to that in N-acetylneuraminic acid in the mucoprotein from tissue incubations with [2-(14)C]-acetate was 1.0:4.0. 5. Both [2-(14)C]acetate and [2-(14)C]glucose with whole tissue led to labelling of the N-glycollyl substituent and of the main nonose skeleton of the N-glycollylneuraminic acid. In whole-tissue incubations, [3-(14)C]pyruvate was also a precursor of radioactive N-glycollylneuraminic acid. 6. Hydroxy[3-(14)C]-pyruvate and [U-(14)C]glycine caused labelling of the carbohydrate and peptide residues of the glycoprotein, but did not give rise to labelling in the N-glycollylneuraminic acid residues. 7. With a wide variety of possible N-glycollyl precursors (fructose 6-phosphate, hydroxypyruvate, glycollate and chemically synthesized glycollyl-CoA) biosynthesis of N-glycollylglucosamine was not observed in cell-free preparations.

Acetates↗
PubMed1968

Sacramento's day-treatment center for autistic children.

A report of two years' operation of a day-treatment center for autistic children is given. A brief historical review and a capsule summary regarding current concepts on autism are presented. The educational and treatment programs at the center are described, and two case vignettes illustrate the progress of the children. Highlights from group counseling sessions with the mothers of autistic children reveal the conflicts with which parents of disturbed children must deal. The two-year experience indicates that the identification of autism at an early age is crucial and that a day-treatment facility has much to offer the psychotic child and his parents.

Autistic Disorder↗