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Biomedical subjects

A M Edwards

Publications and source records attributed to A M Edwards.

156 records · Page 9Linked to original sources
PubMed1975

Induction of delta-aminolevulinic acid synthetase in isolated rat liver cells by steroids.

The role of steroids in regulation of delta-aminolevulinic acid synthetase has been studied in isolated rat liver cell suspensions under conditions previously shown to support inducation of the enzyme by drugs. Addition of a variety of C-19 and C-21 steroids to cell suspensions resulted, after 4 to 6 hours of incubation, in 2- to 5-fold increase in the activity of delta-aminolevulinic acid synthetase as measured in liver cell homogenates. The increase was prevented by cycloheximide. The most active steroid inducers tested were pregnene or pregnane derivatives with keto or hydroxyl groups at C-3 and C-20; in particular a beta-hydroxyl group at C-20 enhanced activity. These C-21 steroids at optimal initial concentrations caused 3- to 5-fold induction over 4 hours. A number of C-19 androstene and androstane compounds caused 2- to 3-fold inducation over the same period. Hydrocortisone had no effect. For a variety of androstane and pregnane derivatives, inducation by 5alphaH steroids was as great as or greater than that by 5betaH compounds, in contrast to previous findings in chick embryo liver. Induction of delta-aminolevulinic acid synthetase by steroids in isolated liver cells was shown to be subject to feedback repression by hemin.

5-Aminolevulinate Synthetase↗
PubMed1973

Paroxysmal nocturnal hemoglobinuria in an identical twin.

The presentation of symptoms, laboratory findings and possible precipitating factors are reviewed in an 18-year-old patient with the onset of typical paroxysmal nocturnal hemoglobinuria. The opportunity was taken to study the physiology in his normal identical twin sibling who showed no hematological abnormalities on exhaustive studies, including photoscanning of the erythrocytes. These observations strengthen the evidence that PNH is an acquired disease with no basic measurable abnormalities of a hereditary or genetic nature.

Adolescent↗
PubMed1966

Distribution and dynamic state of sterols and steroids in the tissues of an insect, the roach Eurycotis floridana.

The total concentrations of sterols in the tissues of the roach, Eurycotis floridana, reared under aseptic conditions and on semisynthetic diets, are similar to, but somewhat lower than, those of tissues of vertebrates. Total concentrations of tissue sterols are relatively independent of dietary concentration of sterols whether the diet contains 0.1% cholesterol as the sole sterol, or a "minimal cholesterol" mixture (0.1% cholestanol together with 0.005% cholesterol). Under the latter conditions the cholesterol is incorporated preferentially into most tissues and remains almost exclusively unesterified, while the cholesterol-sparing sterol is esterified to varying degree, depending upon the tissue. The turnover of tissue sterols has been studied. Cholesterol of the tissues of adult insects grown on a diet containing this sterol alone may be displaced by cholestanol fed as 5% of the total diet, initially at an appreciable rate but later much less rapidly. In growing insects that have received a diet containing cholestanol together with minimal cholesterol, the unesterified cholesterol turns over slowly in all tissues and immeasurably slowly in some. The unesterified sparing sterol, on the other hand, turns over at a much greater rate. The turnover of sterols during growth is accompanied by a shift of sterols from the unesterified to the esterified pool in all tissues. The fat body of the growing insect stores sterols (apparently as their esters) that have been displaced from other tissues. The fat body of the adult does not show evidence of sterol storage. Polar derivatives of sterols are present in minor amount in all tissues of the insect, most abundantly in the mid-intestine and gastric caeca. These compounds seem likely to be C(27) steroids.

Animals↗
PubMed1965

Regional enteritis of the duodenum: a review and report of five cases.

Forty-three cases of regional enteritis of the duodenum were found in the world literature. Regional duodenitis is relatively uncommon; in one large series of 600 cases of regional enteritis only three involved the duodenum.At the University of Alberta Hospital, in a three-year period (1962 to 1965), the authors encountered five patients with regional duodenitis, demonstrating a spectrum of clinical, radiologic and pathologic characteristics of this disease. The description of these patients brings the world's total to 48 reported cases.Two of these patients had symptoms of severe duodenal obstruction and were relieved by bypass procedures and vagotomy; one required surgery because of co-existent obstructive ileal disease: and two patients have improved on corticoids and salicylazosulfapyridine without surgery.In our experience treatment with corticoids and salicylazosulfapyridine is beneficial.Four of the five patients remain in a state of mild to moderate nutritional impairment and have evidence of intestinal malabsorption. In the fifth case the period of followup is too short to permit assessment.

Adolescent↗
PubMedDate not supplied

Lysozyme photo-oxidation by singlet oxygen: properties of the partially inactivated enzyme.

This work studies the behaviour of partially inactivated lysozyme formed by the effect of singlet oxygen, which was obtained through the irradiation of the native enzyme solution with polychromatic visible light using Methylene Blue as a sensitizer. The polyacrylamide gel analysis of the partially inactivated lysozyme solution shows the presence of different protein fractions. One of them, which corresponds to 53% of the original enzyme, has the same migration as the native enzyme. The others are a mixture of fractions (47%) that show slower migration to the cathode. When this experiment is carried out in the presence of sodium dodecyl sulfate, only one fraction is obtained, which rules out the presence of covalently aggregated forms of lysozyme. The partially inactivated lysozyme has lost 74% of the fluorescence emission of the tryptophan (Trp) residues. By using the anionic quencher iodide, it is determined that 45 and 36% of the fluorescence emission arising from the native and partially inactivated enzyme, respectively, are due to Trp residues exposed to the solvent. Michaelis-Menten constants (K(in)) of 0.296 and 0.511 (mg/ml) and maximum initial rates (Vmax) of 0.295 and 0.190 (mg/ml min) are determined for the native and the partially inactivated enzyme solutions, respectively. The same inactivation profile is found when the denaturing effect of increasing urea concentration on both the native and partially inactivated lysozyme is studied. It is postulated that the partially inactivated lysozyme solution is composed of one protein fraction with enzymatic activity similar to that of the native enzyme and also of a mixture of fractions (47% of the total enzyme) with very low activity and characterized by a high tryptophan photo-oxidation.

Kinetics↗