Search PubMed⌕ Search

Biomedical subjects

R L Jones

Publications and source records attributed to R L Jones.

At least 343 records · Page 19Linked to original sources
PubMed1979

Characterization of GDP-Fucose: Polysaccharide Fucosyl Transferase in Corn Roots (Zea mays L.).

The peripheral root cap cells of corn (cv. SX-17A) secrete a fucose-rich, high molecular weight, polysaccharide slime via the dictyosome pathway. To study the synthesis of this polysaccharide, a technique for isolating and assaying GDP-fucose:polysaccharide fucosyl transferase activity was developed. Corn roots were excised from germinated seeds, incubated 12 hours at 10 C in water, and ground in 100 millimolar Tris or Pipes buffer (pH 7.0) with or without 0.5 molar sucrose. The membrane-bound enzyme was solubilized by sonication in the presence of 2 molar urea and 1.5% (v/v) Triton X-100 and assayed by monitoring the incorporation of GDP-[(14)C]fucose into endogenous acceptors. Optimum enzyme activity is expressed at pH 7.0 and 30 C in the presence of 0.8% (v/v) Triton X-100. The enzyme does not require divalent cations for activation and is inhibited by concentrations of MnCl(2) or MgCl(2) greater than 1 millimolar. Corn root cap slime will serve as an exogenous acceptor for the enzyme if it is first hydrolyzed in 5 millimolar trifluoroacetic acid for 60 minutes at 18 pounds per square inch, 121 C. This procedure prepares the acceptor by removing terminal fucose residues from the slime molecule. Kinetics of fucose release during hydrolysis of native slime and in vitro synthesized product suggests that the two polymers possess similar linkages to fucose.

Journal Article↗
PubMed1979

Intracellular Localization of GDP-Fucose: Polysaccharide Fucosyl Transferase in Corn Roots (Zea mays L.).

The intracellular site of synthesis of the fucose-rich polysaccharide slime secreted by corn roots was localized by monitoring the distribution of GDP-fucose:polysaccharide fucosyl transferase activity in subcellular fractions of corn roots. Root tip sections were chopped in the presence of 0.56 molar sucrose and 100 millimolar Tris (pH 7.0). After a brief centrifugation, the homogenate was applied to a Sepharose 4B column (1.5 x 30 cm). The turbid, particulate portion of the supernatant fraction eluted at the void volume. Ninety per cent of the enzyme activity was found in the pooled particulate fractions. The particulate fraction was purified on linear sucrose gradients. Gradient fractions were characterized by buoyant density, 280 nanometer absorbance, electron microscope observation, and distributions of NADH-cytochrome c oxidoreductase and fucosyl transferase activities.TWO PEAKS OF FUCOSYL TRANSFERASE ACTIVITY WERE OBSERVED: one in fractions rich in smooth endoplasmic reticulum, and another in fractions rich in dictyosome cisternae and dictyosome vesicles. The data suggest that the synthesis of corn root slime begins in the endoplasmic reticulum and is completed in the dictyosomes prior to secretion; however, the possibility that more than one fucosyl transferase exists in corn roots is discusses.

Journal Article↗
PubMed1979

Reduced fibrinogen survival in diabetes mellitus. A reversible phenomenon.

Fibrinogen survival and turnover were examined in 15 adult-onset diabetic patients. (125)I-labeled fibrinogen was prepared from each patient during the period of poor carbohydrate control, or hyperglycemic period, and fibrinogen survival determined. Improved control was established in each patient and during this euglycemic period, fibrinogen survival was determined simultaneously with (125)I-fibrinogen saved from the hyperglycemic period and (131)I-labeled fibrinogen prepared from the patient during the euglycemic period. The results confirm reduced fibrinogen survival in hyperglycemic diabetic patients and demonstrate reversal of the fibrinogen abnormality when euglycemia is achieved. The results of the double-label experiments in the euglycemic period suggest that the fibrinogen molecule is not altered functionally and that an abnormal plasma or vascular environment is a more likely basis for reduced fibrinogen survival during hyperglycemia. Electrophoretic and chromatographic experiments demonstrated no gross chemical differences between the fibrinogens prepared from the hyperglycemic and euglycemic periods and normal fibrinogen. Fibrinogen survival gave a better correlation with serial glucose measurements than with correction of hemoglobin A(Ic) levels indicating that the reduced fibrinogen survival noted in diabetics is a rapidly reversible phenomenon. During the hyperglycemic period, pharmacological intervention with aspirin and dipyrimadole was attempted to examine the role of platelets in reduced fibrinogen survival. No significant change in fibrinogen survival was observed. Heparin infusion during hyperglycemia normalized the fibrinogen kinetics of hyperglycemic diabetic patients, suggesting that reduced fibrinogen survival during hyperglycemia is secondary to an effect on thrombin or one of its antagonists.

Adult↗
PubMed1979

Large-scale preparation of highly purified pyrogen-free human growth hormone for clinical use.

A method is described for the large-scale isolation of highly purified human growth hormone for therapeutic use. The hormone was extracted from frozen pituitary glands under mildly alkaline conditions. Purification was effected by gel filtration and ion-exchange chromatography. The final product was pyrogen-free and had a potency of 2.5 i.u./mg measured by bioassay against the current international standard. The yield of growth hormone/gland was approximately 5 mg.

Chromatography, Gel↗
PubMed1979

Rhodotorulic acid--investigation of its potential as an iron-chelating drug.

The use of rhodotorulic acid (RA) as an iron-chelating drug was suggested by experiments in hypertransfused rats in which urinary and fecal iron excretion were significantly enhanced in response to RA. The toxicity of the drug appears to be minimal at a parenteral dose less than 250 mg/kg. An increased excretion of zinc was the only notable side effect of the drug at the doses used. When administered i.v. to humans, RA was only 16% more effective than desferrioxamine (DF). Pharmacokinetic studies showed that RA persisted in the bloodstream of dogs 6 times longer than desferrioxamine after an intravenous injection. Accordingly RA was evaluated as a potential repository drug. While animal experiments were encouraging, human subjects experienced a painful local reaction to RA administered either i.m. or s.c. as a suspension in physiological saline. Accordingly it appears that RA is best looked at as a second line drug, unless a means can be found to obviate local inflammatory reactions.

Adult↗
PubMed1979

Chelation therapy in beta-thalassemia major: a one-year double blind study of 2,3-dihydroxybenzoic acid.

A year-long double-blind study of 2,3-dihydroxybenzoic acid (2,3-DHB) given orally at a dose of 25 mg/kg four times per day was undertaken in 15 patients with beta-thalassemia major. 2,3-DHB and placebo (mannitol) were tolerated to an equal degree and there were no signs of drug toxicity at the end of 1 year. Efficacy in terms of retardation of iron accumulation could be documented using serial liver biopsies, serum ferritin determinations, or clinical laboratory assessment. Serum iron values increased, as did the iron binding capacity, in the group receiving 2,3-DHB. The increase in iron binding capacity was due to drug interference with the method of determination. Because of the greater efficacy of slow infusions of desferrioxamine in chelating iron when administered slowly, the clinic has shifted its emphasis toward further evaluation of that compound. Nevertheless, in view of the minimal toxicity of 2,3-DHB, further work appears warranted to define its role in the treatment of iron-overload.

Administration, Oral↗
PubMed1978

A comparison of prostaglandin F2alpha and three 16-aryloxy analogues on the isolated rabbit jejunum.

Three 16-aryloxy analogues of PGF2alpha are potent, full agonists on the isolated rabbit jejunum. Their actions are more prolonged than that of PGF2alpha, and radioactive tracer studies with one of the analogues reveal a slower wash-out of the analogue compared to PGF2alpha, under superfusion conditions. During the prolonged contractile response diminished responses to PGF2alpha were obtained: this effect was investigated in terms of receptor desensitization. The actions of these analogues were also investigated on the isolated guinea-pig ileum and the rabbit oviduct in vivo.

Animals↗
PubMed1978

Role of Cation and Anion Uptake in Salt-stimulated Elongation of Lettuce Hypocotyl Sections.

The role of cation and anion uptake in salt-stimulated growth of light-grown, GA(3)-treated lettuce (Lactuca sativa L.) hypocotyl sections was investigated. Potassium chloride (10 mm) causes a 2-fold increase in the growth rate of GA(3)-treated hypocotyl sections without affecting the growth rate of sections incubated in the absence of GA(3). Salt uptake is the same in both treatments, and furthermore the uptake of cation and anion is stoichiometric during the first 24 hours under all incubation conditions. The importance of the anion for cation uptake is demonstrated in experiments with benzenesulfonate(-) and iminodiacetate(2-). When K(+) and Na(+) are supplied only as the benzenesulfonate and iminodiacetate salts, growth and cation uptake are markedly reduced compared to KCl and NaCl. Calculation of the osmotic potential of salt-treated sections based on measurement of K(+) and Cl(-) uptake suggests that the observed increase in tissue osmolality is a result of salt uptake. Similarly, uptake of ions can account for the shift in water potential when sections are incubated in 10 mm KCl. We conclude that the change in growth rate of light-grown, GA(3)-treated sections caused by the addition of KCl or NaCl to the incubation medium results solely from decreased water potential of the tissue due to ion uptake.

Journal Article↗
PubMed1978

Effects of age on regional residual volume.

Forty-one normal non-smokers between the ages of 20 and 80 were studied to determine if the increased residual volume, known to occur with aging, results from increased residual volume throughout, or only in specific regions of the lung. The subjects were dividied into groups consisting of 20-29, 30-39, 40-49, 50-69, and 70+ yr. Measurements of regional residual volume to regional total lung capacity ratio (RVr/TLCr) were made using zenon-133 and a multidetector analysis system in which five zones (from top to bottom) were analyzed in each lung. Closing volume was also measured. The subjects were in the sitting position for all studies. The results showed regardless of age, the RVr/TLCr was higher at the top than at the bottom of the lung. In addition, the ratio of upper to lower RVr/TLCr was not significantly different between any of the age groups. The results can be explained if airways throughout the lung close at higher volumes as age increases, or if altered emptying sequences within regions occur due to retarded emptying of highly compliant lung regions.

Adult↗
PubMed1978

Definition of prostaglandin-sensitive arterial constrictor systems.

The effects of a number of prostaglandins on the systemic arterial circulations of the sheep, pig, dog, cat, rabbit and rat have been investigated. It is suggested that all of the species may possess, in addition to a PGE2-sensitive dilator system, a PGD2-sensitive constrictor system, and that 13,14-dihydro-15-oxo PGD2 is a potent and selective agonist on this system. The dog and the pig also have an endoperoxide-sensitive constrictor system activated by the 11,9-(epoxymethano) analogue of PGH2 and, of particular note, ICI 79939 and its 11-oxo analogue. These latter substances also contract the rabbit aorta strip and the guinea pig tracheal chain and aggregate human platelets. A number of PGF2alpha analogues show certain other distinctive cardiovascular actions.

Animals↗
PubMed1977

Relation between pulsus paradoxus and pulmonary function in patients with chronic airways obstruction.

The relation of pulsus paradoxus to chronic, stable obstructive disease of the airways has not previously been described. Pulsus paradoxus was observed in 66% of 68 patients with such disease but in none of 14 healthy individuals. There was a significant correlation between the degree of pulsus paradoxus and the forced expiratory volume in 1 second (FEV1) in the subgroup of patients with bronchial asthma but not in the subgroup with chronic bronchitis or emphysema, or both. There was no correlation between the degree of pulsus paradoxus and the degree of hyperinflation in either group. Hence factors other than hyperinflation contribute importantly to the decrease in systolic pressure that occurs at full inflation of the lungs.

Adult↗