Search PubMed⌕ Search

Biomedical subjects

J F Richards

Publications and source records attributed to J F Richards.

At least 37 records · Page 2Linked to original sources
PubMed1978

Corticosteroids, ornithine decarboxylase activity and the incorporation of leucine, uridine, and thymidine into mouse placenta.

The in vitro incorporation into mouse placenta of [14C]leucine, [3H]uridine, and [3H]thymidine fell between gestational days 14 and 19 by 61, 30 and 72%, respectively; ornithine decarboxylase activity fell by 75%. Injection of dexamethasone resulted on day 14 in values normally found between days 15 and 18. These changes coincided with rising activity in fetal liver of the enzyme 11 beta-hydroxysteroid:NADP oxidoreductase, which reduced the abundant 11-dehydrocorticosterone to the active hormone, corticosterone. These events appear to be part of a spectrum of effects produced by corticosteroids on fetal growth at this time, probably mediated primarily by fetal liver.

Age Factors↗
PubMed1975

Reflex epilepsy evoked by decision making.

A patient had seizures while playing chess or cards or when filling out complex forms, doing complex mathematical problems, and during certain parts of the neuropsychological testing. Seizures were myoclonic and accompanied and electroencephalographic dysrhythmia of the atypical spike and wave type. Evoked seizures were not related to visual, tactile, or auditory stimuli or clues. In chess, seizures occurred when he was on the defense and threatened. Simple decision making or physiologic stress did not evoke seizures nor did nonsequential decision making under verbal pressure. Evoking factors were complex decision making in a sequential fashion and with an element of stress or concern regarding the outcome of the decision making. Stimulus was usually nonverbal. Three major factors--decision complexity, sequential factor, and related stress or concern--may have some reciprocal relationships.

Adult↗
PubMed1975

Purification and characterization of a collagenase extracted from rabbit tumours.

A collagenase was purified from homogenates of V2 ascites-cell carcinoma growing in rabbit muscle. (NH4)2SO4 precipitation, ion-exchange and gel-filtration chromatography, and affinity chromatography (by using the CB7 CNBr) cleavage fragment of alpha 1(I) collagen linked to agarose) gave a 268000-fold purification and a sevenfold increase in total enzyme units recovered. The specific activity, defined as mumol of collagen in solution cleaved/h per mg of enzyme at 35 degrees C, WAS 1.74.2. The collagenase had a broad pH optimum from pH7.0 to 9.5, and a mol.wt. of between 33000 and 35000. It was inhibited by dithiothreitol, L-cysteine, D-penicillamine, EDTA and 1,10-phenanthroline, and by both rabbit and human serum. 3. Removal of cations by a chelating resin (Chelex 100) produced as inactive enzyme that could be reactiviated by the addition of Ca2+ ions at concentrations as low as 1muM. Other bivalent cations were not effective. 4. The purified collagenase cleaved peptides alpha2 and alpha1-CB7 (denatured polypeptides of collagen) at 37 degrees C at one site only. [alpha1 (I)]2alpha2 and [alpha1(III)]3 collagens in solution were cleaved at the same site approximately five times more rapidly than [alpha1 (II)]3. 5. An inhibitor of the enzyme in the tumour extracts, which was dissociable from the enzyme at the (NH4) 2SO4 precipitation step of purification, had a mol. wt. of between 40000 and 50000 but was distinct from the alpha1 trypsin inhibitor. 6. Studies with zonal density-gradient centrifugation suggested that the enzyme was bound to fibrillar substrate (collagen) extracellularly, but that it was not associated with enzymes originating in cell mitochondria, microsomal preparations or lysosomes.

Animals↗
PubMed1975

Prevention and treatment of non-union of slightly displaced fractures of the lateral humeral condyle in children. An end-result study.

In a ten-year study of the healing responses of thirty-one children with fresh fractures of the lateral condyle of the humerus with less than four millimeters of displacement, there were three patterns of healing. Forty-nine per cent healed rapidly in six weeks with abundant callus and periosteal new bone. Thirty-eight per cent healed slowly over eight to twelve weeks, mostly by endosteal union with little callus. Thirteen per cent had progressive displacement of the fragment in the plaster cast and required surgery to prevent non-union. Those fractures that healed had two millimeters or less of displacement of the fragment initially. Those that did not heal had an average of three millimeters of initial displacement. Established non-unions in good position that were symptomatic while the elbow was still immature were salvaged by bone-grafting, sparing the physis of the condylar fragment. The fragment united and grew with the elbow to maturity, producing an excellent end result on long-term follow-up. When the physeal plate of the ununited condylar fragment was absent, the fragment could not grow with the elbow and the result of surgery was less satisfactory.

Bone Nails↗