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Biomedical subjects

L Levine

Publications and source records attributed to L Levine.

At least 253 records · Page 14Linked to original sources
PubMed1977

Stimulation of phospholipase activity and prostaglandin biosynthesis by melittin in cell culture and in vivo.

Melittin, a membrane-active peptide of bee venom, as well as synthetic melittin, stimulated the biosynthesis of prostaglandins by mouse transformed fibroblasts (MC5-5), human fibroblasts (D550), rabbit aorta endothelial cells (CLO), rat lung type II alveolar pneumocytes (L-2) and rabbit smooth muscle cells (R-I). The melittin peptides also stimulated the release of arachidonic acid from the cellular phospholipids of MC5-5 cells. The stimulated prostaglandin biosynthesis by MC5-5 cells was inhibited by indomethacin and dexamethasone. Dexamethasone inhibited also the release of arachidonic acid by MC5-5 cells. In mice, intraperitoneal inoculation of melittin increased 13,14-dihydro-15-keto-PGE2 levels in peripheral blood. Prior injections of the mice with indomethacin prevented the melittin-induced increase in this PGE2 metabolite.

Animals↗
PubMed1976

Stimulation of prostaglandin synthesis by bradykinin and thrombin and their mechanisms of action on MC5-5 fibroblasts.

Transformed mouse fibroblasts, in which [3H]arachidonic acid was incorporated in the cellular lipids, released radioactive materials into the medium when stimulated by bradykinin and thrombin. Most of this released radioactivity was found in the landins; the remainder was present in the arachidonic acid fraction. When the cells stimulated by serum or when they were mechanically manipulated, not only prostaglandins but also high levels of arachidonic acid were released. Anti-inflammatory steroids, which decrease the availability of arachidonic acid, inhibited the stimulated release of prostaglandins caused by the vasoactive agents, suggesting that bradykinin and thrombin stimulated prostaglandin synthesis by increasing deacylation of the phospholipids. The efficiency of the conversion of the released arachidonic acid into prostaglandins appears to reflect the cellular proximity of the phospholipid deacylating activity and prostaglandin synthesizing system.

Arachidonic Acids↗
PubMed1976

Stimulation of prostaglandin biosynthesis by vasoactive substances in methylcholanthrene-transformed mouse BALB/3T3.

Prostaglandins E2 and F2alpha are present in the culture medium of methylcholanthrene-transformed mouse BALB/3T3 cells. The production of these prostaglandins is stimulated when the cells are incubated in the presence of serum, arachidonic acid, thrombin, and bradykinin, or if they are mechanically manipulated. Whereas the appearance of prostaglandins resulting from the latter four treatments is complete in several minutes, in the presence of serum the prostaglandin levels are still increasing ever after 2 hours. Stimulation by all of these treatments is additive. Indomethacin inhibits these stimulations, suggesting that the production of prostaglandins results from de novo biosynthesis.

Animals↗
PubMed1976

Prostaglandin production by methylcholanthrene-transformed mouse BALB/3T3: inhibition by cytochalasin B.

Cytochalasin B inhibits the production of prostaglandins by serum-, thrombin-, and bradykinin-stimulated MC5-5 cells. The serum-stimulated release of arachidonic acid from cellular phospholipids also is inhibited. Cytochalasin B does not affect the cells' prostaglandin synthetase activity when exogenous arachidonic acid is present. Deacylation of phospholipids may be the step affected by cytochalasin B possibly as a result of disruption of microfilament organization. Colchicine and vinblastine, two drugs that can disrupt microtubule organization, do not inhibit prostaglandin production by cells.

Animals↗
PubMed1976

Inhibition of arachidonic acid release from cells as the biochemical action of anti-inflammatory corticosteroids.

Serum stimulates the production of prostaglandins by transformed mouse fibroblasts. Hydrocortisone (cortisol) inhibits this stimulation. The half-maximal inhibition occurs at 6x10-9 M. Studies with cells labeled with [3H]arachidonic acid in their lipids show that the stimulation by serum results in the release of arachidonic acid from the cellular lipids, mostly phospholipids. Hydrocrotisone inhibits this release but does not inhibit the production of prostaglandins from exogenously supplied arachidonic acid. This inhibition of arachidonic acid release from phospholipids may be the mechanism for the anti-inflammatory action of corticosteroids.

Administration, Topical↗
PubMed1976

Effective degree of mydriasis with phenylephrine and tropicamide.

The mydriatic effects of several concentrations of phenylephrine and of tropicamide were studied in 84 young adults for 90 min following topical instillation. Pupillary diameter was estimated (a) under ambient photopic illumination and (b) when illumination was increased to that associated with direct ophthalmoscopy. Evaluation was made of the "degree of mydriasis," i.e., the difference in pupillary diameter between the eye receiving the mydriatic agent and the contralateral control eye when the pupillary light reflex was stimulated. In subjects with light or hazel irides, phenylephrine caused maximal dilatation in 60 to 75 min, mean values being 5.6 mm with 1 drop of 2%, 6.0 mm with 2 drops of 2.5%, and 7.1 mm with 1 drop of 10%. Maxiumum degrees of mydriasis were 3.0 mm with 2 drops of 2.5% and 3.1 mm with 1 drop of 10%. With 0.5% tropicamide, maximum diameter was 8.0 mm in 30 min in subjects with light, hazel, or brown irides, and the maximum degree of mydriasis was 5.0 mm. It is concluded that when a mydriatic agent is used to facilitate intraocular visualization, neither specification in terms of (a) maximum diameter under ambient illumination nor (b) degree of mydriasis provides optimal characterization. It is suggested that the "clinically effective diameter," i.e., pupillary diameter under illumination corresponding to that to be used during examination, would be the most useful specification.

Adaptation, Ocular↗
PubMed1976

A study of applicants to colleges of optometry in the U.S.

A statistical summary of numbers of applicants and applications to U.S. colleges of optometry, dentistry, and medicine is presented for the six academic years, 1969-70 through 1974-75. Attention is drawn to changes during the five-year interval in numbers of (a) professional schools, (b) total applicants, (c) total applications, (d) applicants accepted, (e) applicants per acceptance, (f) percent of applicants accepted, and (g) applications per individual. Absolute numbers are listed in tabular form and, to facilitate interdisciplinary comparison, in relative numbers in a series of figures. Concerns raised by the trends revealed are outlined.

Humans↗
PubMed1976

Prostaglandin synthetase systems of rabbit tissues and their inhibition by nonsteroidal anti-inflammatory drugs.

Prostaglandin synthetase activities in the microsomal fractions of seven rabbit tissues have been partially characterized. All of the microsomal preparations required arachidonic acid, hydroquinone and reduced glutathione for enzymatic activity. The synthetic systems of the renal medulla were most active followed by microsomal preparations from the renal cortex, lung, brain, spleen, uterus and heart. Three structurally distinct nonsteroidal anti-inflammatory drugs, indomethacin, flufenamic acid and aspirin, inhibited the production of prostaglandins by these microsomes. The effectiveness of these drugs depended on the concentration of substrate. When assayed under identical experimental conditions, the inhibiting activity of each of these drugs for the synthetase of each of the tissues was the same.

Animals↗
PubMed1976

Biosynthesis of prostaglandins in rabbit renal cortex.

Prostaglandin biosynthetic activity has been found in the microsomal fractions prepared from rabbit renal cortex. The cortex preparation requires arachidonic acid as substrate and hydroquinone and reduced glutathione as cofactors for enzymatic activity and is inhibited by indomethacin. The biosynthetic capacity of the washed microsomes of cortex ranges from one third to equal that of the washed microsomes of medulla. A partially purified medullary cytoplasmic factor and crystalline hemoglobin can stimulate greatly the synthetase activity in the microsomes of the medulla, but they have no effect on the activity of cortical microsomes.

Animals↗
PubMed1976

The effects of hydroquinone, hematin and heme-containing proteins on prostaglandin biosynthesis by methylcholanthrene-transformed mouse BALB/3T3 fibroblasts.

Cultured methylcholanthrene-transformed 3T3 mouse fibroblasts secrete large amounts of prostaglandin into the medium. Prostaglandin biosynthesis by these cells can be stimulated by arachidonic acid and, to a much lesser extent, by glutathione and porphyrin. In the presence of hydroquinone, prostaglandin production is increased; the most striking increases are seen at concentrations that are lethal. Porphyrins, when added to cells in the presence of lethal levels of hydroquinone, inhibit stimulation of prostaglandin E2 synthesis but stimulate the production of prostaglandin F2alpha.

Animals↗
PubMed1975

Purification and regulatory properties of chicken heart prostaglandin E 9-ketoreductase.

Prostaglandin E 9-ketoreductase was purified from chicken heart by ammonium sulfate fractionation, and DEAE-Sephadex, hydroxylapatite and phosphocellulose chromatography. Two peaks of activity were resolved during the phosphocellulose chromatographic step. Both peaks were stimulated by a substance that was not bound to the phosphocellulose column. This stimulatory substance was destroyed by treatment with phosphodiesterase and 0.1 M NaOH. It was heat-stable (100 degrees, 2 min), nondialyzable, and resistant to treatment with pronase, ribonuclease, and deoxyribonuclease; but it was dialyzable after heating or digestion with pronase. Sodium pyrophosphate also enhanced the activities of the prostaglandin E 9-ketoreductases as did angiotensin I; but not angiotensin II. In the presence of 3':5'-cyclic AMP, AMP, or several other ribonucleotides, the enhancing effects of the natural stimulatory substance, sodium pyrophosphate or angiotensin I were blocked, but these ribonucleotides themselves had little effect on the enzymes activity. The substrate specificities of the two prostaglandin E 9-ketoreductases were also studied. Both the 9-keto group and the 15-keto group of 15-ketoprostaglandin F2 alpha could be converted to the corresponding hydroxyl group; the 15-keto group was reduced faster than the 9-keto group. Prostaglandin D2, a prostaglandin with a 9-hydroxyl and an 11-keto group, could not be converted to prostaglandin F2 alpha nor could cyclohexanone be converted to cyclohexanol by the prostaglandin E 9-ketoreductase.

Alcohol Oxidoreductases↗
PubMed1975

Prostaglandins in the rheumatic diseases.

The prostaglandins may participate in the pathogenesis of the inflammatory rheumatic diseases by acting as mediators of inflammation and in promoting bone resorption. Levels of PGB (presumed to arise from PGE) in synovial fluids are elevated in the majority of a group of patients with inflammatory rheumatic diseases, as compared to similar patients treated with aspirin and indomethacin and patients with osteoarthritis. Rheumatoid synovium produces large amounts of PGE2 in organ culture. In addition, fibroblast cell lines derived from rheumatoid synovia synthesize more PGE and more cAMP than do cells from normal synovia or skin. The media from rheumatoid synovial organ cultures contain large quantities of bone-resorbing activity toward mouse calvaria in vitro. The bone resorption can be accounted for by PGE2 produced by the synovia, because the activity and PG synthesis are inhibited by more than 90% by incubation of the tissue with indomethacin, because it is quantitatively extractable into ether, and because it bears a relationship to the concentrations of PGE2 present, as measured by radioimmunoassay.

Arthritis, Rheumatoid↗
PubMed1975

Metabolism of prostaglandins E, A, and C in serum.

Three prostaglandin-metabolizing enzymes were detected in human serum. One enzyme was a dehydrase that converted prostaglandin E to prostaglandin A, the second was a prostaglandin A isomerase that converted prostaglandin A to prostaglandin C and the third was a prostaglandin C isomerase that converted prostaglandin C to prostaglandin B. All three were inactivated by sulfhydryl blocking agents. In human serum, only prostaglandin C isomerase had high activity, whereas the two other enzymes had very low activity. In rabbit serum both isomerases were very active, but dehydrase activity could not be detected. Prostaglandin C isomerase activity was also found in crystallized human serum albumin and rabbit serum albumin.

Animals↗
PubMed1975

Prostaglandin metabolism. II. Identification of two 15-hydroxyprostaglandin dehydrogenase types.

Homogenates of several mammalian tissues were measured by radioimmunoassay for 15-hydroxyprostaglandin dehydrogenase activity. Two types of enzyme activity were detected. One, which used NAD-plus as cofactor much more effectively than NADP-lus, was found in monkey lung, heart, liver, kidney, and spleen and in chicken heart and dog lung. A second type, which uses NADP-plus as a cofactor more effectively than NAD-plus, was found in monkey and human brain and red blood cells and in swine kidney. These two types of 15-hydroxyprostaglandin dehydrogenase were partially purified from monkey brain and chicken heart. In addition to different cofactor requirements, the two partially purified enzymes could be distinguished by chromatographic properties, their relative affinities for prostaglandin I2 and F2alpha, and their sensitivities to inhibition by reduced pyridine nucleotides, thyroid hormones, and prostaglandin B2.

Alcohol Oxidoreductases↗
PubMed1975

Distribution of prostaglandin E 9-KETOREDUCTASE AND TYPES I and II 15-hydroxyprostaglandin dehydrogenase in swine kidney medulla and cortex.

Prostaglandin E 9-ketoreductase, NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (type I), and NADP+-dependent 15-hydroxyprostaglandin dehydrogenase (type II) have been partially purified from swine renal medulla and cortex. Eleven times more NAD+-dependent 15-hydroxyprostaglandin dehydrogenase activity was found in the cortex than in the medulla. On the other hand, about twice as much NADP+-dependent dehydrogenase activity was found in the medulla than in the cortex. The prostaglandin 9-ketoreductase activities were equally distributed in the swine kidney cortex and medulla.

Alcohol Oxidoreductases↗