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Biomedical subjects

J E Watson

Publications and source records attributed to J E Watson.

At least 109 records · Page 6Linked to original sources
PubMed1977

Identification of glutamate chain lengths of endogenous folylpoly-gamma-glutamates in rat tissues.

A simplified procedure for the determination of the glutamate chain lengths of endogenous tissue folate is described. Natural pteroylpoly-gamma-glutamates in tissue extracts, irrespective of their one-carbon moiety, were converted by a reductive cleavage procedure to a homologous series of p-aminobenzoylpoly-gamma-glutamates, differing only in glutamate chain length. Desalting and concentration of the extracts were achieved by absorbing the derivatives on active charcoal followed by their elution with ethanol:ammonia. Aminobenzoylpolyglutamates were separated by DEAD-cellulose chromatography and quantitated by a colorimetric procedure for primary aromatic amines. The major endogenous folates in rat liver and kidney were pteroylpentaglutamate derivatives with smaller amounts of pteroyltetra- and hexaglutamate.

Animals↗
PubMed1977

Uptake and metabolism of [3H]folate by normal and by vitamin B-12- and methionine-deficient rats.

The uptake of an injected dose of [3H]folic acid and its metabolism to pteroylpoly-gamma-glutamate forms by the livers and kidneys of vitamin B-12- and methionine-deficient and -supplemented rats were investigated. The initial hepatic uptake of the labeled folate dose was the same in deficient and supplemented animals, demonstrating no involvement of vitamin B-12 or methionine in folate transport. At longer time periods, a decreased hepatic net uptake of labeled folate was observed in the deficient animals compared to supplemented animals, and this was directly correlated with the decreased ability of the deficient animals to synthesize pteroylpolyglutamates. The absolute rate of loss of labeled pteroylmonoglutamate from liver was the same in deficient and supplemented animals. These data are best explained by a modification of the 'methyl trap' hypothesis for the interrelationship of vitamin B-12 and folate metabolism. Vitamin B-12 deficiency can lead to lowered levels of 5-methyltetrahydrofolate:homocysteine methyltransferase, creating a functional folate deficiency by 'trapping' an increased proportion of folate as the methyl derivative. In addition, as methyltetrahydrofolate is a poor substrate for folylpoly-gamma-glutamate synthetase, there is a decreased synthesis of pteroylpolyglutamates, the forms of the vitamin that are preferentially retained by tissues. This results in decreased tissue folate levels under conditions of vitamin B-12 deficiency. Vitamin B-12 and methionine deficiency had no significant effect on the distribution of endogenous pteroylpolyglutamates in rat liver and kidney, although total endogenous folate in rat liver was reduced by about 60%. The distribution of labeled pteroylpolyglutamates in rat liver and kidney 48 h after the tracer dose of [3H]folate closely resembled the endogenous distribution in these tissues.

Animals↗
PubMed1976

The effect of muscle extracts on the contracture response of skeletal muscle to acetylcholine.

Preincubation of normal rat soleus muscles in vitro with homogenates prepared from mixed leg muscles which had been denervated 4 days previously resulted in an increase in the contracture response to acetylcholine. After 30 min incubation a 1.5-fold increase was observed. Homogenates of normally innervated muscles did not increase the response. The active principles of the denervated muscles were found to reside in the "cytosol" fraction. An approximately 2-fold increase was observed upon incubation with the cytosol for 30 min; incubation for longer periods resulted in a subsequent decrease in the response. The effect of the denervated muscle cytosol was concentration-dependent and heat-labile. Normal muscle cytosol also increased the soleus muscle response to acetylcholine but this fraction was less effective than denervated muscle cytosol. The response of control muscles incubated in Krebs-Henseleit solution was found to decrease with time. Commercially obtained phospholipases C and D increased the response of normal soleus muscles approximatley 2-fold. Phospholipase A, lipase, trypsin, collagenase and a bacterial protease had no effect, lysozyme produced a small but consistent increase in the response to acetylcholine.

Acetylcholine↗
PubMed1976

Interpretation of aspiration tests in local anesthetic injections.

Three young adult laboratory rabbits were anesthetized with a barbiturate and their abdominal cavities were surgically opened to expose a variety of blood vessels. A number of veins and arteries were penetrated with 25- and 27-gauge needles attached to standard dental aspirating cartridge-type syringes. Aspiration tests were performed and the results were recorded. No differences in the performance of aspiration were detected with the two gauges of needles. Where the aperture of the needle lay unobstructed and wholly within a vein greater than 1.5 mm in diameter or within any artery, it was impossible not to aspirate blood even with a peer technique. In certain circumstances, false-negative and misleading positive readings are possible. Recommendations for a clinically reliable aspirating technique have been given and four grades of positive result described. Absolutely infallible interpretation of results is impossible but, provided the aspirating technique itself is sound, intelligent evaluation of observed effects should result in very few errors of interpretation.

Anesthesia, Local↗
PubMed1975

Locomotory adaptations in a free-lying brachiopod.

Magadina cumingi inhabits an environment of high current energy and mobile sediments by using its pedicle in Pogo-stick fashion as an elevating device. This type of progression is associated with pedicle musculature different from that of attached and other free-lying forms, and some diagnostic differences in muscle attachment areas are evident in preservable hard parts.

Animals↗
PubMed1975

Studies of folic acid compounds in nature. IV. Folic acid compounds in soybeans and cow milk.

Folate compounds in soybean and cow's mild were identified by Sephadex chromatography and differential microbiological assaymsoybean contained mainly monoglutamates (ca. 52%), some diglutamates (ca. 16%), and polyglutamates (pentaglutamates representing the major portion). 5-CHO-H4PteGlun(1-6) constituted 65-70% of total folate activity; Cow's milk contained monoglutamates (60%) and polyglutamates (ranging from di- to hepta-conjugates). In contrast to soybean, 90-95% of milk folate was in the 5-CH3h4pteGlun(1-7) form.

Animals↗