Biomedical subjects

J C Carlson

Publications and source records attributed to J C Carlson.

At least 37 records · Page 2Linked to original sources

PubMed1990

Alterations in phospholipase A2 activity during luteal regression in pseudopregnant and pregnant rats.

The activity of phospholipase A2 was measured in microsomes prepared from ovaries of superovulated pseudopregnant rats during spontaneous and prostaglandin F2 alpha-induced regression and during regression in pregnant rats. Microsome samples were incubated at 40 C for 90 min in Tris buffer (pH 8.3) with 1.0 mM CaCl2 added. The substrate, radiolabeled phosphatidylcholine, was incorporated into liposomes. During spontaneous regression, there was a significant 2- to 4-fold increase in phospholipase A2 activity, when compared with levels at mid-pseudopregnancy (days 8-9). This elevation was correlated with a significant decrease in plasma progesterone concentration. On day 6 or 7 of pseudopregnancy, treatment of rats with luteolytic doses of prostaglandin F2 alpha also caused a significant increase in phospholipase A2 activity, which remained elevated throughout the 72-h sampling period. In pregnant rats there was a small but significant rise in phospholipase A2 activity after parturition. These results indicate that the activity of phospholipase A2 increases during luteal regression in pregnant and pseudopregnant rats and that it could be involved in the mechanism that causes the loss in progesterone secretion.

Animals↗

PubMed1989

Superoxide radical production in plasma membrane samples from regressing rat corpora lutea.

Plasma membrane samples prepared from regressing rat corpora lutea were examined for production of the superoxide radical. A procedure was developed to purify membrane samples that were enriched approximately 15-fold with the plasma membrane marker enzyme, and superoxide radical levels were determined using electron spin resonance to measure Tiron semiquinone. During prostaglandin F2 alpha-induced and spontaneous regression, there was a significant increase in formation of superoxide radical that was not observed in plasma membrane samples from nonregressing corpora lutea. Plasma membrane incubation experiments indicated that the increase in production was temperature sensitive and reduced with inhibitors of phospholipase A2 and cyclooxygenase. Addition of superoxide dismutase or vitamin E abolished superoxide radical formation in vitro. Following the rise in superoxide radical levels during regression, there was also a significant decrease in the activity of the plasma membrane enzyme, Na+-K+ ATPase. These results indicate that the production of superoxide radical increases in plasma membrane samples prepared from regressing rat corpora lutea and that this increase is mainly due to the products of phospholipase A2 and cyclooxygenase activity.

Animals↗

PubMed1989

Plasma membrane changes during corpus luteum regression.

Structural and biochemical changes were examined in the plasma membrane of luteal cells during corpus luteum regression. Structural alterations as indicated by an increase in the liquid-crystalline to gel phase transition temperature and a decrease in plasma membrane fluidity were observed during luteolysis in microsomes and in plasma membranes prepared from prostaglandin F2 alpha-treated rats, when samples were examined by wide angle x-ray diffraction and fluorescence polarization. In addition, a significant increase in activity of the lipolytic enzyme phospholipase A2 appeared during incubation of plasma membrane samples and dispersed luteal cells at 40 degrees C in the presence of 1.0 mM CaCl2. Similar incubation conditions also produced a drop in human chorionic gonadotropin (hCG) binding in luteal samples from prostaglandin F2 alpha-treated rats. These results indicate that during luteolysis there are important structural changes in the plasmalemma of regressing luteal cells. These alterations appear related to an increase in phospholipase A2 activity and a decrease in hCG receptors. These modifications may account for the decrease in function during corpus luteum regression.

Animals↗

PubMed1989

The effects of prolactin and prostaglandin F2 alpha on plasma membrane changes during luteolysis in the rat.

The ability of PRL to modify prostaglandin F2 alpha (PGF2 alpha)-induced membrane changes during functional corpus luteum regression was examined in the pseudopregnant rat. Fluorescence polarization studies conducted 24 h after sc injection of PGF2 alpha revealed a marked and significant increase in the polarization parameter, which is suggestive of reduced plasma membrane fluidity. At the same time, there was a decrease in hCG binding and a significant increase in apparent phospholipase-A2 activity during incubation of dispersed rat luteal cells. Each of these changes was attenuated when the animals were pretreated with PRL 30 min before PGF2 alpha. The decrease in plasma progesterone caused by PGF2 alpha treatment was also inhibited by PRL. PGF2 alpha also stimulated a significant polarization increase in dispersed cells prepared from ovaries removed 1 h after injection of this luteolytic agent, although this effect could not be demonstrated in plasma membrane samples. These results indicate that PRL and PGF2 alpha affect the same membrane pathway in the rat corpus luteum and that this pathway appears to be closely coupled to luteal cell function.

Animals↗

PubMed1988

Impairment of gonadotropin binding occurs during membrane rigidification in plasma membrane samples prepared from regressed rat corpora lutea.

The effect upon human chorionic gonadotropin (hCG) binding of a 90-min incubation of plasma membranes prepared from the corpora lutea of control and prostaglandin F2 alpha injected rats was studied. After incubation for 90 min with 1 mM CaCl2 at 40 degrees C, single point hCG binding assays at room temperature revealed a significant decrease in the degree of binding of approximately 50% in membrane samples prepared from regressed corpora lutea. The binding decrease in regressed samples did not occur if the incubation temperature was reduced to 35 degrees C or if calcium ion was replaced with magnesium. Scatchard analyses indicated that the decrease in binding capacity was the result of a loss of gonadotropin receptors rather than an affinity shift. Specific activities of two membrane-bound enzymes (Na+-K+ ATPase, 5'-nucleotidase) did not change in a correlative fashion during the incubation. In previous studies the same in vitro conditions caused a substantial and significant decrease in membrane fluidity, as determined by fluorescence polarization. Thus it appears that the membrane rigidification is of a specific nature and interferes with gonadotropin binding during luteolysis.

Animals↗

PubMed1987

Changes in superoxide radical and lipid peroxide formation in the brain, heart and liver during the lifetime of the rat.

The free radical theory of aging was examined by measuring the formation of superoxide radical (SOR) and the level of lipid peroxides in various tissues of the aging rat. A significant increase in SOR production was seen in mitochondria prepared from the brain and the heart as rats aged. An elevation in the level of lipid peroxidation was also found in whole tissue homogenates of the brain and the liver. Vitamin E concentrations in the blood rose rapidly in young rats and remained steady except for a non significant drop in old animals. These results suggest that age-related degeneration of various tissues in the rat may be due to a rise in free radical production in the mitochondria.

Aging↗

PubMed1987

Association between lipid peroxidation and life-modifying factors in rotifers.

The rate of lipid peroxidation (LP) was measured in rotifers reared under conditions of continuous darkness (D:D), dietary restriction, vitamin E supplementation, or elevated temperatures. D:D, diet restriction, and vitamin E supplementation increased life span and caused a significant decline in LP; elevated temperatures decreased life span and increased LP. The addition of physiological levels of malonaldehyde, a product of LP, did not alter life span. The dietary uptake of Paramecia, the food source for rotifers, did not change under the conditions of D:D, vitamin E supplementation, and elevated temperatures. These results suggest that the LP process is inversely related to longevity in the rotifer and that it appears to be involved in the aging process.

Aging↗

PubMed1987

Involvement of phospholipase A activity in the plasma membrane of the rat corpus luteum during luteolysis.

Plasma membrane samples prepared from corpora lutea (CL) of control and prostaglandin F2 alpha-treated rats were incubated with radiolabeled phosphatidylcholine for 90 min at 40 C with 1 mM CaCl2 to test for the presence of phospholipase A2 activity. At the end of the incubation period, labeled arachidonic acid cleaved from the 2 position of the phospholipid moiety had accumulated to 10.7 +/- 2.4% (mean +/- SE) of the initially added radioactivity in the prostaglandin F2 alpha-treated samples, with 3.7 +/- 1.2% appearing in the controls. Arachidonic acid production was inhibited by calcium chelation and by the phospholipase A2 inhibitor bromophenacyl bromide, indicating heightened activity of phospholipase A2 in CL plasma membranes undergoing regression. Unexpectedly, radiolabeled lysophosphatidylcholine was produced in regressed membrane samples at a similar rate, suggesting the induction of phospholipase A1 activity as well. To determine if the membrane rigidification that occurs with regressed membrane samples under the same incubation conditions is caused by the hydrolysis products of phospholipase activity, fluorescence polarization experiments with the probe trans-parinaric acid were conducted. Washing of incubated membrane samples with fatty acid-free BSA, which selectively removes free fatty acids and lysophosphatides from the bilayer, resulted in a restoration of the fluidity to levels recorded at the onset of the incubation. These results suggest that the previously described decreases in CL plasma membrane fluidity and hCG binding in vitro during luteolysis are caused by a synergistic effect of calcium ion and hydrolysis products of phospholipase A activity.

Animals↗

PubMed1987

Standardized endosonographic evaluation of prostate cancer: receiver-operator-characteristic analysis.

A standardized endosonographic numeric method has been developed for the detection of prostate cancer. Eighty-six men were examined with a 5-MHz, 96-element linear-array probe. Mean gray-scale amplitudes were produced by a semiautomatic method for periprostatic fat and regions of interest within the external portion of the prostate gland that were visually suspicious for prostate cancer. Mean gray-scale amplitude ratios of visually abnormal areas of prostate to periprostatic fat (Ap/Af) were calculated. Pathologic confirmation of disease was obtained in all patients. Three different numeric Ap/Af ratios were compared with digital palpation and subjective visual interpretation of sonograms. The numeric method resulted in a consistently higher specificity, accuracy, and positive predictive value when compared with palpation and subjective interpretation. The initial results suggest that this technique may also detect atypical hyperplasia.

Adenocarcinoma↗

PubMed1986

Progesterone secretion by primary cultures of rat luteal cells.

Primary cultures were prepared from ovaries of immature rats that had been superovulated. The dispersed luteal cells attached to growth surfaces, formed monolayers and secreted progesterone. Progesterone accumulation in the medium was most pronounced in the first week of culturing. Removal of serum from the medium resulted in a progressive decline in progesterone concentration in the culture medium which reached basal levels by 5 hours. In medium without serum, the addition of hCG, FSH or prolactin stimulated an increase in progesterone secretion within 1 hour. Also cholera toxin stimulated a significant increase in progesterone levels in the medium. Prior exposure of cultures to estradiol for 3 days did not augment the response to hCG and inhibited the ability of cholera toxin to stimulate progesterone secretion. These results indicate that the steroidogenic function of rat luteal cells can be studied in culture and that a number of hormones rapidly stimulate the secretion of progesterone from these cells.

Animals↗

PubMed1985

Association of lipid peroxidation during luteal regression in the rat and natural aging in the rotifer.

Lipid peroxides (LP) were measured in whole homogenates and membrane fractions from luteinized rat ovaries and in homogenates of aging rotifers. There was a significant increase in the accumulation of LP as plasma progesterone levels declined during luteal regression. Lipid peroxide levels also increased with age in rotifers. This study indicates that lipid peroxide accumulation is associated with cellular breakdown and suggests that the rat corpus luteum may be used as a mammalian aging model.

5'-Nucleotidase↗

PubMed1985

Calcium-regulated plasma membrane rigidification during corpus luteum regression in the rat.

Plasma membrane fractions were prepared from ovaries of superovulated rats and examined for structural changes during luteolysis. Using fluorescence polarization, we observed a rapid rigidification in vitro of samples obtained from ovaries undergoing spontaneous or prostaglandin F2 alpha-induced regression. The rigidification, manifested by a 72% polarization increase over 50 min, is calcium and calmodulin dependent, temperature sensitive and protein mediated. This increase in polarization did not appear in fractions from nonregressing ovaries; however, addition of phospholipase A2 caused virtually identical changes in polarization results as in samples prepared from regressing ovaries. These results suggest that calcium-calmodulin-dependent phospholipase A2 plays a role in membrane deterioration during luteolysis.

Animals↗

PubMed1984

Alterations in the cellular membranes of regressing rat corpora lutea.

Wide angle x-ray diffraction and fluorescence polarization were used to determine the structural properties of membranes from rat luteal cells. Examination of a plasma membrane fraction by x-ray diffraction revealed a significant increase in the gel phase melting temperature during luteal regression. The membrane fluidity of this fraction as well as that of a preparation of microsomes was also studied by fluorescence polarization. Using a fluorescent probe, membrane fluidity was observed to decrease during luteolysis. The temporal correlation between structural changes in the membrane and decreased progesterone secretion suggests that alterations in the physical properties of cellular membranes may be involved in the process of luteal cell regression.

Animals↗

PubMed1983

The effect of prolactin pretreatment on prostaglandin F2 alpha-associated structural changes in membranes from rat corpora lutea.

The ability of prolactin treatment to antagonize the luteolytic effect of prostaglandin F2 alpha (PGF2 alpha) was examined in the rat. Animals were superovulated, treated with PGF2 alpha and various doses of prolactin. Plasma progesterone concentrations were measured to assess luteal function. Microsomes were prepared from ovarian homogenates and examined by wide-angle x-ray diffraction for evidence of structural changes in the cellular membranes during luteolysis. In addition, the concentrations of various lipids were analyzed for alterations in membrane lipid composition. In preparations from control animals, all of the membrane lipid was in the liquid-crystalline phase at body temperature. However, in samples from PGF2 alpha-treated rats, portions of the bilayer underwent a structural alteration from liquid-crystalline to gel phase. This phase transition was not accompanied by significant changes in the relative concentrations of various lipids. Prolactin treatment was effective in inhibiting this membrane breakdown in a dose-dependent manner. These results suggest that PGF2 alpha and prolactin may control luteal function by affecting membrane structure.

Animals↗

PubMed1983

Behavioral and clinical profiles of Tourette's disease: a comprehensive overview.

A brief review of Gilles de la Tourette's disease is presented. The initial part gives an overview of major signs, symptoms displayed, and diagnosis in addition to certain minor concomitant features. The latter conditions included appetite, adaptive function, learning disorders, sexual behavior, sleep disturbances, speech pathology, and tic-related injury. Neurological manifestations, infectious etiology, and genetics were discussed. Treatment modalities are outlined and description of various drug therapy is given in conjunction with rationale of pharmacotherapy and possible underlying mechanism of action. Drug-induced Tourette's-like syndrome was also summarized.

Acetylcholine↗

PubMed1983

A study of the interaction between progesterone and membrane lipids.

The ability of progesterone to associate with phospholipid was examined in a model membrane system. Molecular interaction was assessed by measuring the enthalpy of the phase transition of dipalmitoylphosphatidylcholine liposomes by differential scanning calorimetry. The response was compared to cholesterol, a constituent of cellular membranes. Unlike cholesterol, progesterone caused minimal disruption of the phospholipid bilayer phase properties at concentrations ranging from 5-33 mol %. However, it interacted with the phospholipid to a greater degree when cholesterol was included in the liposomes. These results indicate that progesterone can intercalate into phospholipid bilayers containing cholesterol, and raise the prospect that there may be some diffusion of the hormone across the plasma membrane.

Calorimetry, Differential Scanning↗

PubMed1982

Luteolysis-induced changes in phase composition and fluidity of bovine luteal cell membranes.

X-ray diffraction, fluorescence polarization of trans-parinaric acid, and fluorescence photobleaching recovery of dioctadecyltrimethyneindolecarbocyanine have been used to characterize the phase composition and liquid phase fluidity of bovine luteal cell membranes and membrane lipids for functional corpora lutea collected at midcycle and for regressing corpora lutea collected after treatment with prostaglandin F2 alpha. These results support previous observations of gel phases in microsomal preparations of regressed luteal cells at physiological temperatures and further suggest that the plasma membrane may be the main source of this gel phase. Analysis of the overall lipid composition of the microsomal preparations from these cells indicates a role for sphingomyelin, in the presence of cholesterol, for the generation of a gel phase at physiological temperatures.

Animals↗

PubMed1982

Evidence of membrane changes during regression in the bovine corpus luteum.

Microsomal membranes prepared from bovine corpora lutea (CL) were examined by wide angle x-ray diffraction to determine if there were structural changes in the cellular membranes during regression. In samples prepared from CL removed at midcycle, all of the membrane lipid was in the liquid crystalline phase at body temperature. However, examination of microsomes prepared from regressing luteal tissue revealed a phase transition in which a portion of the lipid bilayer was in a gel phase at body temperature. Coincident with this physical change was a decline in CL function. These results indicate that there are structural changes that occur at the submicroscopic level in cellular membranes during luteal regression, which appear to be related to the loss in cellular function.

Animals↗