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Biomedical subjects

G A Jones

Publications and source records attributed to G A Jones.

At least 37 records · Page 2Linked to original sources
PubMed1992

Gastric and salivary mucins inhibit angiotensin-converting enzyme. Inhibition is partly due to oligosaccharides.

Pig gastric mucin, a highly glycosylated glycoprotein, inhibits angiotensin-converting enzyme (ACE) with an IC50 of 2 mM-neutral hexose content. Pig submaxillary mucin at 2.3 mM inhibits by 73%. To determine whether the oligosaccharide moieties of the mucins contribute to this inhibition, oligosaccharides were prepared from each mucin by reductive beta-elimination and their effects on enzyme activity determined. Total oligosaccharides from gastric mucin inhibited enzyme activity with an IC50 of 0.3 mM based on the neutral hexose content of the oligosaccharide solution. Fractions isolated from gastric mucin by chromatography on DEAE-cellulose and Bio-Gel P-2 inhibited ACE with IC50 values ranging from 2 to 16 mM-oligosaccharide. Larger oligosaccharides inhibited with lower IC50 values than did smaller oligosaccharides. Fractions of average molecular mass 1100 and 740 Da prepared from submaxillary mucin inhibited with IC50 values of 40 and 80 mM-oligosaccharide respectively. Monosaccharides commonly present in serum and membrane glycoproteins were also tested for their effect on ACE. Galactose, N-acetylglucosamine, N-acetylgalactosamine and glucosamine were inhibitory. N-Acetylneuraminic acid stimulated the activity of ACE. Fucose, ethylene glycol and sucrose had no effect on the activity of the enzyme. The influences of different buffers, ion concentrations, pH and substrate structure on the effect of carbohydrate on enzyme activity were also evaluated. The extent of inhibition by the monosaccharide galactose was strongly influenced by buffer ion and substrate concentration. The effects of the oligosaccharide moieties and intact mucins were less sensitive to assay conditions.

Amino Acid Sequence↗
PubMed1992

Growth factor stimulation of phospholipase C-gamma 1 activity. Comparative properties of control and activated enzymes.

We demonstrated previously tyrosine phosphorylation-dependent modulation of phospholipase C-gamma 1 (PLC-gamma 1) catalytic activity (Nishibe, S., Wahl, M. I., Hernandez-Sotomayor, S. M. T., Tonks, N. K., Rhee, S. G., and Carpenter, G. (1990) Science 250, 1253-1256). The increase in PLC-gamma 1 catalytic activity in A-431 cells occurs rapidly, with maximal activation 5 min after epidermal growth factor (EGF) stimulation. Certain other growth factors (fibroblast growth factor, platelet-derived growth factor) also stimulate PLC-gamma 1 catalytic activity, whereas insulin does not. A similar increase in PLC-gamma 1 specific activity (2-3-fold) was observed in both soluble (cytosol) and particulate (membrane) preparations from EGF-treated cells. Tyrosine-phosphorylated PLC-gamma 1 was detected in both cytosol and membrane fractions in lysates from EGF-treated A-431 cells, but the proportion of tyrosine-phosphorylated PLC-gamma 1 was higher in the cytosol (approximately 50%) than in the membrane (approximately 20%). Because a micellar concentration of the non-ionic detergent Triton X-100 allows detection of the tyrosine phosphorylation-dependent increase in PLC-gamma 1 catalytic activity in this assay, we evaluated the kinetic properties of PLC-gamma 1, immunoprecipitated from cytosol of control or EGF-treated cells, using substrate, phosphatidylinositol 4,5-bisphosphate (PtdIns 4,5-P2), solubilized in Triton X-100 at various molar ratios. The behavior of the control enzyme differed from the EGF-activated enzyme with respect to both Ks and Km. The control enzyme has a 7.5-fold higher Ks value than the activated enzyme (1.5 mM as compared with 0.22 mM). Activation by EGF is also a positive allosteric modifier of PLC-gamma 1-catalyzed PtdIns 4,5-P2 hydrolysis, i.e. the activated enzyme displayed apparent Michalis-Menton kinetics, with a Km of 0.6 mol fraction PtdIns 4,5-P2, whereas the control enzyme displayed sigmoidal kinetics with respect to PtdIns 4,5-P2 hydrolysis. At low substrate mol fractions (e.g. 0.07), the reaction velocity of the control enzyme was 4-fold lower than the activated enzyme. However, at a high substrate mol fraction (e.g. 0.33), the estimated maximal reaction velocities (Vmax) for both forms of PLC-gamma 1 were equivalent. PLC-gamma 1 activity from both control and EGF-treated cells was stimulated by increasing nanomolar Ca2+ concentrations. Although the catalytic activity of PLC-gamma 1 from EGF-treated cells was greater than control PLC-gamma 1 at every Ca2+ concentration tested, the relative stimulation of activity was markedly greater at Ca2+ concentrations above approximately 300 nM.

3T3 Cells↗
PubMed1992

E-Speed dental film, time to take a new look?

Although various studies have indicated that there is no statistical difference in the diagnostic value between D- and E-speed films, and resolution and contrast were reported as being identical, the general acceptance of E-speed film has been slow. The dental profession is faced with a decision: Do we use the slower D-speed film that might be more "cosmetic" in appearance or use E-speed that can reduce radiation by as much as 50 percent? Recent research has indicated that 85 percent of parotid gland exposure is the result of dental radiography and carries an increased risk for meningiomas and tumors. It is the opinion of some that risk factors now dictate that only the fastest speed (E-speed) film should be used.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1991

The role of protein kinase C in the stimulation of phosphatidylcholine synthesis by phospholipase C.

The role of protein kinase C in the stimulation of phosphatidylcholine (PC) synthesis by phospholipase C was investigated. Phospholipase C treatment of Chinese hamster ovary cells (CHO) generates diacylglycerol, which is an activator of protein kinase C. The protein kinase C activator, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulated choline incorporation into two CHO cell lines, a wild-type cell line, WTB, and a mutant cell line, DTG 1-5-4. DTG 1-5-4 is a mutant defective in receptor-mediated endocytosis. A 3-h phospholipase C treatment resulted in the activation and translocation of CTP:phosphocholine cytidylyltransferase in both cell lines. TPA treatment, however, resulted in only a slight (20%) translocation of cytidylyltransferase in WTB; no detectable translocation of cytidylyltransferase was observed in DTG 1-5-4. A decrease in the phosphocholine pools was observed in response to TPA treatment in both cell lines, which indicated that the cytidylyltransferase step was being activated. Phospholipase C stimulated choline incorporation into PC even when protein kinase C had been down-regulated in both cell lines. It was concluded that phospholipase C does not activate PC synthesis by activating protein kinase C.

Animals↗
PubMed1991

Oro-antral fistula: an unusual complication of HIV-associated periodontal disease.

Oral lesions have been reported frequently in patients seropositive for human immunodeficiency virus. A case is reported of HIV-associated periodontitis complicated by necrotising stomatitis and the development of an oro-antral fistula; the role of extractions in the management of this condition is highlighted.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Morphological and biochemical evidence for elastic fibres in the Syrian hamster temporomandibular joint disc.

Elastic fibres are considered to be important for the normal biomechanical functions of the TMJ. The objective here was to correlate morphological evidence for the presence of elastic fibres in discal tissues with biochemical evidence for elastin. For light microscopy, the joints were removed en bloc, processed for paraffin embedding, sectioned and stained with resorcin-fuchsin. For biochemical study, a radioimmunoassay for desmosine was used to estimate the amount of elastin in excised articular discs. The histological preparations showed that numerous elastic fibres were present in various areas of the disc and in some of the discal attachments to surrounding bone. Radioimmunoassay also indicated that elastin was present in these tissues. Therefore, the biochemical findings support the morphological in suggesting that elastic fibres are present in the articular disc of the hamster TMJ.

Animals↗
PubMed1988

Microbial Ecology of the Gut in Laboratory Stocks of the Migratory Grasshopper, Melanoplus sanguinipes (Fab.) (Orthoptera: Acrididae).

Mean pH values in pooled samples of foregut, midgut, and hindgut from adult Melanoplus sanguinipes, which had been raised in the laboratory on barley shoots and wheat bran, were 5.15, 6.39, and 5.98, respectively. Homogenates of midgut/hindgut sections and frass (feces) yielded colony counts of bacteria by the spread plate method of 5.7 to 5.9 and 5.3 to 5.5 log(10) colonies per mg, respectively; there were no significant differences (P > 0.05) between counts obtained on several media or on media incubated aerobically or anaerobically. There was no evidence of significant populations of protozoa, fungi, or obligately anaerobic bacteria associated with the gut. A total of 168 pure strains of bacteria isolated from the gut sections were characterized and assigned to 11 taxonomic groups, including Enterococcus spp., Serratia liquefaciens, Pseudomonas spp., and Enterobacter spp. Numbers of Enterococcus spp. in the gut were 2 to 3 orders of magnitude higher than those of the other genera. Strains representing only four of the groups were recovered from bran fed to the grasshoppers; the barley shoots, which were raised in sterile soil, appeared virtually sterile. Examination of the gut wall by scanning electron microscopy revealed the presence of epimural bacteria in the foregut and hindgut but not in the midgut. The distribution of epimural cocci and bacilli differed with the gut section examined. Numerous spherical to ovoid structures up to 10 mum in diameter, which were not identified, were associated with the microvillous surface of the midgut epithelium. Acetate was present in gut, hemolymph, and frass, and it was shown that representative isolates of Enterococcus spp. and Enterobacter agglomerans produced acetate when incubated in an aqueous suspension of bran. The egestion time of solid digesta, as measured with methylene blue-stained barley shoots, was 3.0 to 5.7 h. The results show that M. sanguinipes supported extensive indigenous populations of luminal and epimural bacteria in the gut which were composed predominantly of facultatively anaerobic species; the relatively short egestion time, indicating rapid passage of digesta through the gut, was consistent with the microscopic appearance of digesta residues in frass and could account, at least in part, for the absence of a significant population of obligately anaerobic bacteria from the gut.

Journal Article↗
PubMed1988

Use of dental X rays on postirradiated patients with head and neck cancer.

As cancer therapy becomes more successful and cancer survival rates increase, the dentist will be treating more patients who have received radiation therapy for head and neck cancer. Occasionally, patients and health professionals have indicated a belief that patients who have received irradiation to the head and neck regions should not be subjected to additional radiation through dental diagnostic X-ray exposures. A literature search failed to find any references that specifically addressed this question. This study reflects the opinions of 278 radiation oncologists (400 surveyed) who responded to questions about contraindications of dental X rays for the patient with head and neck cancer.

Dental Care for Persons with Disabilities↗
PubMed1988

The acetone-butanol-ethanol fermentation.

Renewed interest in the acetone-butanol-ethanol (ABE) fermentation as a route for industrial production of butanol has been evident since the oil crisis of the 1970s. The present review includes an historical recap of the traditional industrial process and culturing practices useful in maintaining viable solvent-producing cultures, and then summarizes new and exciting research on the physiology and genetics of the microorganisms as well as process design. Most of these reports relate to improvements in solvent yield and the overall process, since traditional production is not efficient under present economic conditions. Conclusions are then made on future developments necessary for the establishment of an economically viable industrial process.

Acetone↗