Morphology-Voltage-P-wave duration (MVP) score in prediction of incident atrial fibrillation in an elderly epidemiologic cohort

Background

Interatrial block (IAB) on electrocardiography (ECG) and reduced P wave voltage reflect atrial abnormalities which may contribute to development of atrial fibrillation (AF).

Purpose

We aimed to assess the value of a recently proposed ECG risk score that combines the morphology, voltage and length of the P wave (MVP score) for prediction of incident AF in a prospective population-based setting.

Material and methods

The study population is based on the large, prospective Malmö Preventative Project (MPP) cohort. We included subjects without a history of AF, with a readable ECG in sinus rhythm and an echocardiography performed in 2002–2006 (n=983, mean age 70±5 years, 38% females). Median follow-up was 4.2 (IQR 3.7–4.8) years. ECGs were digitally processed using the Glasgow algorithm. Advanced IAB (aIAB) was defined as a P-wave ≥120 ms and biphasic morphology (+/−) in inferior leads, partial IAB (pIAB) as P-wave ≥120 ms and a monophasic positive morphoology in inferior leads. MVP score was calculated based on the P-wave morphology in inferior leads, voltage in lead 1, and P-wave duration (Table 1).Incident AF events (n=66, 7%) were obtained from the Swedish Hospital Discharge Register and Cause of Death Register. Cox regression analysis and Kaplan Meier curve analysis were used to study the association of echocardiographic and P-wave characteristics with the risk of new onset AF.

Results

At baseline the mean MVP score was 1±1, none of the subjects had MVP score above 4. MVP score correlated with left atrial (LA) area: Pearson r=0.192, p<0.001. After adjustment for age, gender and LA enlargement expressed as LA area >20 cm2, new onset AF was associated with MVP score 4 (HR 6.17, 95% CI 1.76–21.64 compared to those with MVP score <4, Figure 1). Neither aIAB (univariate HR 1.93 CI 95% 0.82–4.56), nor pIAB (univariate HR 1.16 CI 95% 0.52–2.55) predicted incident AF.

Conclusion

In a population-based elderly epidemiological cohort, the ECG-based MVP score was significantly associated with incident AF, independently of LA enlargement.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): The Swedish Heart-Lung Foundation

Nuclear factor I-A regulates diverse reactive astrocyte responses after CNS injury

Reactive astrocytes are associated with every form of neurological injury. Despite their ubiquity, the molecular mechanisms controlling their production and diverse functions remain poorly defined. Because many features of astrocyte development are recapitulated in reactive astrocytes, we investigated the role of nuclear factor I-A (NFIA), a key transcriptional regulator of astrocyte development whose contributions to reactive astrocytes remain undefined. Here, we show that NFIA is highly expressed in reactive astrocytes in human neurological injury and identify unique roles across distinct injury states and regions of the CNS. In the spinal cord, after white matter injury (WMI), NFIA-deficient astrocytes exhibit defects in blood-brain barrier remodeling, which are correlated with the suppression of timely remyelination. In the cortex, after ischemic stroke, NFIA is required for the production of reactive astrocytes from the subventricular zone (SVZ). Mechanistically, NFIA directly regulates the expression of thrombospondin 4 (Thbs4) in the SVZ, revealing a key transcriptional node regulating reactive astrogenesis. Together, these studies uncover critical roles for NFIA in reactive astrocytes and illustrate how region- and injury-specific factors dictate the spectrum of reactive astrocyte responses.

Pilot GWAS of caries in African-Americans shows genetic heterogeneity

BACKGROUND

Dental caries is the most common chronic disease in the US and disproportionately affects racial/ethnic minorities. Caries is heritable, and though genetic heterogeneity exists between ancestries for a substantial portion of loci associated with complex disease, a genome-wide association study (GWAS) of caries specifically in African Americans has not been performed previously.

METHODS

We performed exploratory GWAS of dental caries in 109 African American adults (age > 18) and 96 children (age 3-12) from the Center for Oral Health Research in Appalachia (COHRA1 cohort). Caries phenotypes (DMFS, DMFT, dft, and dfs indices) assessed by dental exams were tested for association with 5 million genotyped or imputed single nucleotide polymorphisms (SNPs), separately in the two age groups. The GWAS was performed using linear regression with adjustment for age, sex, and two principal components of ancestry. A maximum of 1 million adaptive permutations were run to determine empirical significance.

RESULTS

No loci met the threshold for genome-wide significance, though some of the strongest signals were near genes previously implicated in caries such as antimicrobial peptide DEFB1 (rs2515501; p = 4.54 × 10- 6) and TUFT1 (rs11805632; p = 5.15 × 10- 6). Effect estimates of lead SNPs at suggestive loci were compared between African Americans and Caucasians (adults N = 918; children N = 983). Significant (p < 5 × 10- 8) genetic heterogeneity for caries risk was found between racial groups for 50% of the suggestive loci in children, and 12-18% of the suggestive loci in adults.

CONCLUSIONS

The genetic heterogeneity results suggest that there may be differences in the contributions of genetic variants to caries across racial groups, and highlight the critical need for the inclusion of minorities in subsequent and larger genetic studies of caries in order to meet the goals of precision medicine and to reduce oral health disparities.

A Chimeric Antibody against ACKR3/CXCR7 in Combination with TMZ Activates Immune Responses and Extends Survival in Mouse GBM Models

Glioblastoma (GBM) is the least treatable type of brain tumor, afflicting over 15,000 people per year in the United States. Patients have a median survival of 16 months, and over 95% die within 5 years. The chemokine receptor ACKR3 is selectively expressed on both GBM cells and tumor-associated blood vessels. High tumor expression of ACKR3 correlates with poor prognosis and potential treatment resistance, making it an attractive therapeutic target. We engineered a single chain FV-human FC-immunoglobulin G1 (IgG₁) antibody, X7Ab, to target ACKR3 in human and mouse GBM cells. We used hydrodynamic gene transfer to overexpress the antibody, with efficacy in vivo. X7Ab kills GBM tumor cells and ACKR3-expressing vascular endothelial cells by engaging the cytotoxic activity of natural killer (NK) cells and complement and the phagocytic activity of macrophages. Combining X7Ab with TMZ allows the TMZ dosage to be lowered, without compromising therapeutic efficacy. Mice treated with X7Ab and in combination with TMZ showed significant tumor reduction by MRI and longer survival overall. Brain-tumor-infiltrating leukocyte analysis revealed that X7Ab enhances the activation of M1 macrophages to support anti-tumor immune response in vivo. Targeting ACKR3 with immunotherapeutic monoclonal antibodies (mAbs) in combination with standard of care therapies may prove effective in treating GBM.

Nutritional depletion of total mixed rations by European starlings: Projected effects on dairy cow performance and potential intervention strategies to mitigate damage

European starlings are an invasive bird species in North America that are known to cause damage to commercial dairies through the consumption of total mixed rations (TMR) destined for dairy cows. We hypothesized that large foraging flocks of starlings alter the physical composition of TMR, and that this change may be significant enough to affect milk production. To better determine if production losses could potentially occur in commercial dairies as a consequence of feed consumption by foraging flocks of starlings, we conducted controlled feeding experiments using a TMR sourced from a commercial dairy that is chronically plagued with seasonal starling damage. European starlings selected the high-energy fraction of the TMR and reduced starch and crude fat availability. Using the dairy National Research Council production model equations, the nutritional changes measured in the controlled feeding experiments could potentially reduce the productivity of dairies. Model output suggests that for Holsteins producing 32 kg of milk/d, total required net energy intake (NE_I) was 31.5 Mcal/d. Within the reference TMR, NE_I supplied was 29.3 Mcal/d, whereas within the starling-consumed TMR NE_I supplied was 27.7 Mcal/d. Following our nutrition experiments, we assessed the efficacy of pelleted feed as a deterrent strategy for bird damage management in commercial dairies. Six different pelleted feed treatments of differing diameter were offered to starlings. All pellets of 0.95 cm diameter or larger inhibited starling consumption by ≥79%.

Validation of the Vectra H1 portable three-dimensional photogrammetry system for facial imaging

Three-dimensional (3D) surface imaging using stereophotogrammetry has become increasingly popular in clinical settings, offering advantages for surgical planning and outcome evaluation. The handheld Vectra H1 is a low-cost, highly portable system that offers several advantages over larger stationary cameras, but independent technical validation is currently lacking. In this study, 3D facial images of 26 adult participants were captured with the Vectra H1 system and the previously validated 3dMDface system. Using error magnitude statistics, 136 linear distances were compared between cameras. In addition, 3D facial surfaces from each system were registered, heat maps generated, and global root mean square (RMS) error calculated. The 136 distances were highly comparable across the two cameras, with an average technical error of measurement (TEM) value of 0.84mm (range 0.19-1.54mm). The average RMS value of the 26 surface-to-surface comparisons was 0.43mm (range 0.33-0.59mm). In each case, the vast majority of the facial surface differences were within a ±1mm threshold. Areas exceeding ±1mm were generally limited to facial regions containing hair or subject to facial microexpressions. These results indicate that 3D facial surface images acquired with the Vectra H1 system are sufficiently accurate for most clinical applications.

Protease-triggered siRNA delivery vehicles

The safe and efficacious delivery of membrane impermeable therapeutics requires cytoplasmic access without the toxicity of nonspecific cytoplasmic membrane lysis. We have developed a mechanism for control of cytoplasmic release which utilizes endogenous proteases as a trigger and results in functional delivery of small interfering RNA (siRNA). The delivery approach is based on reversible inhibition of membrane disruptive polymers with protease-sensitive substrates. Proteolytic hydrolysis upon endocytosis restores the membrane destabilizing activity of the polymers thereby allowing cytoplasmic access of the co-delivered siRNA. Protease-sensitive polymer masking reagents derived from polyethylene glycol (PEG), which inhibit membrane interactions, and N-acetylgalactosamine, which targets asialoglycoprotein receptors on hepatocytes, were synthesized and used to formulate masked polymer-siRNA delivery vehicles. The size, charge and stability of the vehicles enable functional delivery of siRNA after subcutaneous administration and, with modification of the targeting ligand, have the potential for extrahepatic targeting.

Producer survey of bird-livestock interactions in commercial dairies

The objective of this producer survey was to identify and estimate damage caused by bird-livestock interactions in commercial dairies. The interactions between birds and livestock have previously been implicated in causing economic damage while contributing to the environmental dissemination of microorganisms pathogenic to livestock and humans. Very little research exists to help producers understand what bird species use dairies, why they use dairies, or the scope and nature of damage created as a result of bird-livestock interactions. To better characterize these interactions, we surveyed dairy operators within Pennsylvania, New York, and Wisconsin. Survey results suggest that the most common and destructive bird species found on commercial dairies are invasive to North America, and their use of dairies is associated with the loss of cattle feed, increased operating costs, and an increase in dairies self-reporting Salmonella spp. and Mycobacterium avium ssp. paratuberculosis. Cattle feed loss estimates generated from this survey were used to parameterize an input-output (IO) economic model using data from 10 counties in the state of Pennsylvania (Bedford, Berks, Blair, Bradford, Chester, Cumberland, Franklin, Lancaster, Lebanon, and Somerset). This IO model allowed us to estimate direct, indirect, and induced economic effects of feed loss from bird damage to dairies within these counties. The IO model output suggests that feed loss costs Pennsylvania between $4.11 and $12.08 million (mean $10.6 million) in total economic damage, with approximately 43 to 128 jobs (mean 112) forgone statewide in 2009.

The effects of UV radiation and antioxidants on life span and lipid peroxidation in the rotifer Asplanchna brightwelli

Lipid peroxidation (LP) rates and life span were determined in control and in ulraviolet (UV) irradiated rotifers of the species Asplanchna brightwelli. UV irradiation administered at 6 h of life significantly increased the rate of LP as the rotifers aged; it also produced a significant shortening of rotifer life span. Pretreatment with 20 microg/ml of vitamin E blocked the increase in LP and the decrease in life span induced by UV radiation. The antioxidant synergist 3,3'-thiodipropionic acid had no such UV-protective effect. These results indicate that the decrease in life span caused by UV radiation may be mediated through the production of lipid peroxides.

Expression of prostaglandin G/H synthase (PGHS) and heat shock protein-70 (HSP-70) in the corpus luteum (CL) of prostaglandin F2 alpha-treated immature superovulated rats

In this study we examined the mechanism of corpus luteum (CL) regression by measuring changes in expression of prostaglandin G/H synthase-1 (PGHS-1) and -2 (PGHS-2) in day 4 CL and inducible heat shock protein 70 (HSP-70) in day 4 and day 9 CL of immature superovulated rats. The rats were superovulated and treated with 500 microg of prostaglandin F2alpha (PGF2alpha) on day 4 or day 9 after CL formation. Ovaries and serial blood samples were removed during the 24-hour period following treatment. Plasma progesterone was determined by radioimmunoassay while mRNA abundance and protein expression were assessed by semiquantitative RT-PCR and immunoblot analysis, respectively. One hour after PGF2alpha, both day 4 and day 9 rats exhibited a significant decrease in progesterone secretion; however, there was a greater decrease in day 9 rats. In ovarian samples removed on day 4, there was a significant increase in mRNA for PGHS-2 at 1 hour after PGF2alpha. PGHS-1 mRNA content remained unchanged. Immunoblot analyses showed an increase in PGHS-2 protein expression only at 8 h. There were no changes in PGHS-1 protein expression. In day 9 rats, ovarian HSP-70 protein levels increased by 50% after PGF2alpha injection; however, on day 4 there was no change in expression of this protein over the sampling period. These results suggest that expression of PGHS-2 may be involved in inhibiting progesterone production and that expression of HSP-70 may be required for complete CL regression in the rat.

Treatment with prostaglandin F2alpha increases expression of prostaglandin synthase-2 in the rat corpus luteum

Recent studies indicate that the corpus luteum (CL) may be a source of prostaglandin F2alpha (PGF2alpha) for regression. We investigated expression of mRNA and protein for prostaglandin G/H synthase (PGHS) in the CL of immature superovulated rats following administration of PGF2alpha. We observed an increase in mRNA for PGHS-2, the induced isoform, at 1 h and protein at 8 and 24 h after treatment. One hour after PGF2alpha, there was also a progressive decrease in plasma progesterone concentration. There were no changes, however, in expression of PGHS-1, the constitutive isoform, over the 24 h sampling period. These results indicate that PGHS-2 increases following PGF2alpha treatment and that expression of this enzyme in the rat CL may contribute to the luteolytic mechanism.

Phenanthrenequinone disrupts progesterone production in rat luteal cells

The ability of the environmental contaminant phenanthrene (PH) and its photooxidized product phenanthrenequinone (PHQ) to disrupt progesterone secretion was examined in a model system of in vitro suspensions of luteal cells from the rat. Treatment with PHQ dramatically inhibited luteinizing hormone (LH) stimulated progesterone secretion. PHQ also generated a significant increase in reactive oxygen species (ROS). In the absence of LH, however, PHQ stimulated a small increase in basal progesterone secretion. The parent compound, PH, did not alter progesterone or ROS release. Since there is evidence that PHQ lowers the activity of nitric oxide synthase (NOS) and that nitric oxide (NO) affects progesterone production, we examined the response to the NOS inhibitors N-monomethyl-L-arginine, Zn protoporphyrin-9, and aminoguanidine in luteal cells. However, there was no effect of these agents on LH stimulated progesterone secretion. These results indicated that PHQ is a potent disrupter of progesterone secretion and should perhaps be considered in assessing the risk of PH to humans.

High-fructose feeding of streptozotocin-diabetic rats is associated with increased cataract formation and increased oxidative stress in the kidney

We examined the effects of high-fructose (FR) feeding on the development of diabetic complications in the lens and the kidney of streptozotocin (STZ)-diabetic rats. Male Wistar Furth rats were treated with one of two doses of STZ (HIGH STZ, 55 mg/kg body weight; MOD STZ, 35 mg/kg body weight) or vehicle alone (SHAM) and were then assigned to a control (CNTL) or 400 g FR/kg diet for 12 weeks. At the end of the study, body weight, plasma glucose and insulin concentrations differed among STZ groups (HIGH v. MOD v. SHAM, P < 0.001) but did not differ due to diet. Plasma FR concentrations were significantly higher in FR-fed v. CNTL-fed groups (P < 0.0001) and in HIGH-STZ groups v. MOD-STZ and SHAM groups (P < 0.0004 and P < 0.0001 respectively). Focal length variability of the lens, a quantitative measure of cataract formation, was increased in the HIGH STZ, FR group compared with the HIGH STZ, CNTL group (P < 0.01). The concentration of H2O2 in kidney microsomes was significantly higher in HIGH STZ, FR rats v. HIGH STZ, CNTL rats (P < 0.01). Micro-albuminuria was not observed in any of the groups examined, and there was no evidence of extensive histological damage in the kidney from any rats. Under conditions of severe hyperglycaemia, high FR intake promotes the development of cataracts in the lens of the eye, and results in increased concentrations of substances indicative of oxidative stress in the kidney. Although FR has been suggested as a carbohydrate source for diabetics, a high FR diet coupled with hyperglycaemia produces effects that may promote some of the complications associated with diabetes.

Oxidative stress in hypopituitary dwarf mice and in transgenic mice overexpressing human and bovine GH

Growth hormone (GH) stimulates metabolic activity. The purpose of this study was to examine whether it is involved in the aging process by increasing oxidative stress. Inorganic peroxides and lipid peroxides were measured in kidney and liver samples in dwarf mice that are deficient in GH, prolactin and thyrotropin and in transgenic mice that produce high levels of GH. In normal male mice, there was an increase in inorganic peroxides in the kidney with age. Levels were lower in old male dwarfs when compared with normal male mice of similar age. Unexpectedly, concentrations of inorganic peroxides were frequently lower in transgenic male and female mice expressing extra copies of GH than in normal controls. Lipid peroxide concentrations were more variable. Transgenic animals expressing bovine GH had the highest levels of lipid peroxides. In dwarfs, kidney levels were similar to those of normal mice but concentrations in the liver were more variable. This study does not indicate that the decrease in life span in transgenic mice producing high levels of GH is due to an increase of oxidative stress. Rather, it suggests that expression of extra copies of the GH gene may lead to a compensatory increase in antioxidant protection.

A consideration of some notable aging theories

Aging is characterized as a breakdown process and the relevant events occur after reproduction, when the force of natural selection declines. Studies on the life histories of species reveal that there is an association between resource allocation and longevity and that the aging process is retarded when animals are protected from the deleterious consequences of excess metabolic activity. Although the extent to which aging is caused by environmental or genetic factors is unresolved, our understanding of the field has been enriched by the rapid development of the tools of molecular biology. In his pioneering work, Alex Comfort has postulated a hierarchical clock system as a descriptive paradigm of the aging process, and investigations at the molecular level are bringing to light evidence of a genetic link to life span that seems consistent with Comfort's model. It appears however, that the appropriate context for these mechanistic observations of functional decline is in the postreproductive period.

Luteotropic and luteolytic mechanisms in the bovine corpus luteum

The function of the corpus luteum (CL) is a key element in many reproductive processes including ovulation, length of the estrous cycle, recognition of pregnancy and embryo survival in all mammalian species. The main function of the CL is to produce progesterone which acts on its tissues to prepare them for successful pregnancy. The CL is controlled by numerous biological compounds which provide luteotropic support during the estrous cycle and pregnancy and for inducing luteolysis at the end of the cycle The purpose of this paper is to review the mechansims responsible for controlling the endocrine function of this tissue in the bovine ovary.

Intracellular regulation of progesterone secretion by the superoxide radical in the rat corpus luteum

In this study we examined the prospect that the superoxide radical (SOR) is involved in the mechanism by which LH stimulates progesterone secretion in the rat corpus luteum (CL). Treatment of dispersed CL cells with low doses of LH or a SOR-generating system (xanthine-xanthine oxidase) resulted in a significant increase in progesterone release and SOR production. High doses of each treatment were inhibitory. SOR generation also decreased hCG binding. To determine whether SOR may be required for progesterone secretion, dispersed cells were electroporated with antioxidant enzymes [superoxide dismutase (SOD) and catalase (CAT)] and treated with either low (50 ng) stimulatory or high (20 micrograms) inhibitory doses of LH. At 50 ng LH, insertion of SOD or CAT dose-dependently inhibited progesterone secretion. However, at high doses of LH (20 micrograms), which are associated with high levels of SOR, electroporation of SOD or CAT produced the opposite response. This stimulatory response of SOD or CAT on progesterone release was also dose related. These results indicate that SOR may be involved in the mechanisms that stimulate as well as those that inhibit progesterone release. The effect on progesterone secretion appears to be dose related, with small increases associated with stimulation and high levels involved in inhibition of secretion.

Generation of free radicals and messenger function

Free radicals are toxic agents that are produced as by-products of metabolic activity. A number of antioxidant mechanisms work to protect cells from damage. Recent evidence indicates, however, that free radicals and related oxidants such as hydrogen peroxide may also have a beneficial role, working as messengers to control cell function. These agents are generated in response to agonists, production is regulated by intracellular signal pathways, and they appear to be used to control particular cellular processes. Free radicals may perform these functions in a number of cell types. Also, they are produced in muscles and there is evidence that they may work as messengers in smooth muscle cells.

Stimulation of progesterone secretion in dispersed cells of rat corpora lutea by antioxidants

Antioxidants were used to investigate the role of free radicals in control of luteal steroidogenesis. Corpora lutea from pseudopregnant rats were enzymatically dispersed, the cells were incubated with antioxidants, and progesterone production was measured. Addition of the antioxidants nordihydroguaiaretic acid (NDGA), butylated hydroxytoluene (BHT), and the gonadotropin luteinizing hormone (LH) resulted in a dose-dependent increase in progesterone secretion. However, the response pattern to these treatments differed with the age of the corpora lutea, and unlike LH neither NDGA nor BHT treatment resulted in an increase in the intracellular second messenger cAMP. Nevertheless, LH and antioxidant-induced progesterone stimulation could be blocked by the addition of either aminoglutethimide or ketoconazole, cytochrome P450 side-chain cleavage (cytochrome P450 SCC) enzyme inhibitors, which prevent the conversion of cholesterol to pregnenolone and thus block steroid hormone synthesis. Also, unlike exposure to LH, exposure to antioxidants resulted in an additional increase in progesterone production in luteal tissue saturated with 25 hydroxycholesterol, a soluble cholesterol analog which serves as a substrate for cytochrome P450 SCC. This study suggests that the site of antioxidant action in affecting progesterone secretion may be at the cytochrome P450 SCC enzyme. Based on these results and on studies in other steroid hormone-producing cells, it appears that free radicals may be involved in regulating synthesis by modulating activity of cytochrome P450 SCC enzyme in rat luteal tissue.

Studies on the mechanism controlling generation of superoxide radical in luteinized rat ovaries during regression

The mechanism regulating the luteolytic release of superoxide radical (SOR) was examined in prostaglandin F2 alpha (PGF2 alpha)-treated rats. Tail vein injection of PGF2 alpha caused a rapid increase in SOR in mitochondria and plasma membrane samples prepared from luteinized rat ovaries. The peak in the mitochondria preceded that in the plasma membrane, and both occurred before progesterone concentrations decreased in the blood. The amount of SOR produced was greater when samples from the plasma membrane, mitochondria, and cytosol were combined. In plasma membrane samples, SOR generation was lowered by inhibitors of intracellular signaling pathways, but not by cyanide, which blocks electron transport in respiratory enzymes. In mitochondria samples, however, SOR was blocked by cyanide, but not by inhibitors of intracellular signaling enzymes. The addition of phospholipase-A2, phorbol myristate acetate (protein kinase-C activator), or arachidonic acid stimulated SOR production in plasma membrane samples from ovaries of control rats, and phorbol myristate acetate and arachidonic acid inhibited LH-stimulated progesterone secretion in dispersed rat luteal cells. Also, when mitochondria prepared from ovaries of PGF2 alpha-treated rats were added to dispersed corpus luteum cells, there was an increase in SOR generation and an inhibition of LH-stimulated cAMP formation and progesterone secretion. These results indicate that SOR production in the corpus luteum after PGF2 alpha treatment is generated by several subcellular components. Formation in the plasma membrane may be initiated by SOR generation from the mitochondria and regulated by intracellular signaling pathways. Our results indicate that formation of SOR may lead to the disruption of LH stimulation of progesterone secretion.

Alterations in free radical activity in aging Drosophila

Drosophila were examined to see if there is an increase in damage associated with free radical activity in older flies. The levels of superoxide radical and of lipid peroxides were higher in membrane samples from older flies. Also, in older Drosophila there was a significant decrease in membrane fluidity, as determined by fluorescence polarization, and an increase in ATP-dependent calcium uptake. In homogenates from whole flies, the concentration of inorganic peroxides and activity of the proteolytic enzyme, cathepsin B, increased with age. During their lifetime, vestigial wing Drosophila displayed a greater level of free radical activity than wild-type flies and a significantly shorter life span (26.7 +/- 0.7 days vs. 34.4 +/- 1.0, p < 0.01). These results indicate that the level of oxidative stress is closely coupled to cellular damage and to life span, and they indicate that free radicals may play a central role in the aging process in Drosophila.

Plasma membrane changes in the rat corpus luteum induced by oxygen radical generation

The luteolytic mechanism was investigated in rat corpora lutea (CL). This study focused on the changes that occur in the plasma membrane. Previous experiments with rat luteal cells indicated that in vitro generation of superoxide radicals by xanthine oxidase disrupted LH-stimulated cAMP production and progesterone secretion similar to the effect of prostaglandin F2 alpha, the luteolytic hormone. In the present study, we observed that xanthine oxidase treatment of plasma membrane samples from CL caused a large decrease in fluidity, which also occurs during prostaglandin F2 alpha-induced luteolysis. This fluidity change was blocked by catalase, bromophenacyl bromide, an inhibitor of phospholipase-A activity, indomethacin, and free radical scavengers, and it was reversed by removal of FFA from the membrane. In addition, xanthine oxidase treatment caused phospholipid breakdown, formation of neutral lipids, a burst of inorganic peroxides, and a sustained rise in the level of lipid peroxides. These results indicate that free radical generation causes several changes that disrupt the plasma membrane of CL cells, and they raise the possibility that phospholipid breakdown could be involved in the mechanism that inhibits LH stimulation of steroidogenesis during luteolysis.

Changes in superoxide radical formation, lipid peroxidation, membrane fluidity and cathepsin B activity in aging and spawning male Chinook salmon (Oncorhynchus tschawytscha)

Superoxide radical (SOR) formation in the brain and the liver of male Chinook salmon (Oncorhynchus tschawytscha) increased in mitochondrial and plasma membrane samples as they aged. In 2-year-old salmon, spawning also lead to a significant elevation in SOR formation in mitochondrial and plasma membrane samples. The rise in this free radical was associated with an increase in lipid peroxidation, a decrease in plasma membrane fluidity, and an elevation in cathepsin B activity in the brain and liver. In 2-year-old spawning salmon, the changes in these parameters was greater than in 2-year-old non-spawning salmon. These observations suggest that free radical levels increase with aging and during spawning and indicate that these changes may be involved in cellular degeneration. In addition, these results support the suggestion that cellular degeneration accelerates during the spawning process.

Isolation and characterization of deteriosomes from rat liver

Deteriosomes, a new class of microvesicles, have been isolated from rat liver tissue. These microvesicles are similar to those isolated previously from plant tissue [Yao et al., Proc Natl Acad Sci USA 88:2269-2273, 1991] in that they are nonsedimentable and enriched in membrane catabolites, particularly products of phospholipid degradation. Liver deteriosomes range in size from 0.05 microns to 0.11 microns in radius. They are also much more permeable than microsomal membrane vesicles indicating that the deteriosome bilayer is perturbed. The data are consistent with the proposal that deteriosomes are formed from membranes by microvesiculation and that they represent an intermediate stage of membrane deterioration. Furthermore, liver deteriosomes were found to contain phospholipase A2 activity. This suggests that they not only serve as a means of moving destabilizing macromolecular catabolites out of membranes into the cytosol but also possess enzymatic activity. The fact that the specific activity of phospholipase A2 is higher in deteriosomes than in deteriosome-free cytosol suggests that some of the enzymatic activity traditionally assumed to be cytosolic may in fact be associated with deteriosomes.

Oxygen radicals and the control of ovarian corpus luteum function

The superoxide radical (SOR) and other reactive oxygen species form in cells during the course of respiration as well as in response to various stimuli. Although well known for their damaging effects, these agents can also work beneficially to control cell function. The present review examines the evidence that oxygen radicals and H2O2 may regulate steroid hormone biosynthesis in the ovarian corpus luteum. Recent findings indicate that luteal cells can employ reactive oxygen species at specific sites in controlling the production of progesterone over the course of the reproductive cycle and in inhibiting its synthesis during regression at the end of the cycle. These studies indicate that oxygen radicals and related compounds may function as intracellular regulators of steroidogenesis in the corpus luteum.

Stimulation of phospholipase A2 by xanthine oxidase in the rat corpus luteum

The ability of the superoxide radical (SOR) generated by xanthine oxidase to activate phospholipase A2 (PLA2) was examined in microsomes prepared from luteinized rat ovaries. Treatment of microsomes with xanthine oxidase resulted in a rapid burst in SOR formation followed by an increase in PLA2 activity. Stimulation of PLA2 activity was dose related and similar in microsomes prepared from control or prostaglandin F2 alpha (PGF2 alpha)-treated rats. Activation was inhibited by the antioxidants, vitamin E and nordihydroguaiaretic acid, and by superoxide dismutase and catalase, which metabolize SOR and H2O2 to remove reactive oxygen species from the cell. The stimulation of PLA2 activity by xanthine oxidase was dependent upon the addition of calcium ions, and it was highest in samples in which cytosol was added to membranes. These results indicate that the SOR and/or H2O2 may mediate PLA2 activation, which may be involved in the luteolytic process.

Superoxide radical formation and associated biochemical alterations in the plasma membrane of brain, heart, and liver during the lifetime of the rat

Plasma membrane samples from rat brain, heart, and liver were examined for biochemical changes with age. A rise in superoxide radical (SOR) levels was followed by increases in thiobarbituric acid reactive substances and decreases in membrane fluidity with age. The earliest rise in SOR formation appeared in the plasma membrane from the brain. With age, protein synthesis also decreased significantly in tissue homogenates from brain and heart but was unchanged in the liver. Exposure of plasma membrane samples to in vitro-elevated SOR levels stimulated formation of lipid peroxides, as indicated by the thiobarbituric acid test, and resulted in a decrease in membrane fluidity in each tissue and in a decline in protein synthesis in brain and heart. Changes in brain lipid peroxidation and in membrane fluidity in brain and heart as a result of SOR supplementation were further enhanced due to age. In addition, the mechanism of SOR formation was examined in plasma membrane samples from the brain. SOR generation was Ca(2+)-sensitive, blocked by superoxide dismutase or vitamin E and inhibited by both indomethacin, a cyclooxygenase inhibitor, and bromophenacyl bromide, a phospholipase A2 inhibitor. These results show significant increases in SOR formation and biochemical alterations in plasma membranes from brain, heart, and liver in aging rats. SOR formation appears to be enzyme-mediated and elevated levels of this oxygen radical could be involved in membrane breakdown in older rats.

Rapid plasma membrane changes in superoxide radical formation, fluidity, and phospholipase A2 activity in the corpus luteum of the rat during induction of luteolysis

Early luteolytic changes in the plasma membrane of luteal cells were examined in the rat. Treatment with prostaglandin F2 alpha in vivo caused a rapid transient increase in superoxide radical formation and a decrease in fluidity in plasma membrane samples prepared from luteinized rat ovaries. These alterations preceded detection of a significant fall in plasma progesterone concentration. The rise in superoxide radical was not accompanied by changes in activities of free radical scavenging enzymes. Within the first hour of prostaglandin treatment, there was also a significant increase in the activity of phospholipase A2 and ATP-dependent calcium uptake in the membrane samples. These experiments indicate that one of the initial sites affected by the luteolytic process appears to be the plasma membrane. The changes include a transient rise in production of superoxide radicals, which may cause membrane changes that are responsible for disrupting corpus luteum function in the rat.

The effects of ambient temperature on life span, lipid peroxidation, superoxide dismutase, and phospholipase A2 activity in Drosophila melanogaster

Aging changes were examined in Drosophila melanogaster. Lifespan was determined in two strains of male and female Drosophila raised at 19 degrees, 24 degrees, and 29 degrees C. The results show an inverse relationship between lifespan and temperature. In addition, lipid peroxidation rates and superoxide dismutase activity were measured in homogenates and phospholipase A2 activity was determined in crude membrane samples prepared from this species. Temperature was found to be directly correlated with the rate of lipid peroxidation in each group. The longest-lived group, wild-type females, exhibited the lowest rate of lipid peroxidation at each temperature; whereas the shortest-lived group, vestigial wing males, displayed the highest rates of lipid peroxidation. Older (40-53 day) vestigial wing males also exhibited significantly higher superoxide dismutase activity than younger vestigial wing males (0-5 day) and higher phospholipase A2 activity than wild-type females of the same age. These results indicate that there is an association between lipid peroxidation rates and lifespan in Drosophila, and that aging changes may include an increase in superoxide dismutase and phospholipase A2 activity. These findings agree with the hypothesis that free radicals are involved in the aging process in Drosophila.

Biochemical changes associated with the mechanism controlling superoxide radical formation in the aging rotifer

Levels of the superoxide radical (SOR) and lipid peroxides were measured and found to increase during aging in the short-lived rotifer, Asplanchna brightwelli. Life-span was altered by changes in environmental temperature, absence of light, diet restriction, exposure to ultraviolet radiation, and addition of vitamin E to the diet. Each of the conditions that lengthened life-span decreased SOR and lipid peroxide levels, and each condition that shortened life-span increased levels of SOR and lipid peroxides. Additional experiments indicated that on the third day of age, there was a significant increase in Ca2+ uptake and phospholipase A2 activity in membrane samples and an elevation in superoxide dismutase and catalase activity in rotifer homogenates. In addition, SOR concentration was inhibited by the addition of bromophenacyl bromide and indomethacin to membrane samples. By day 5 there was also a significant increase in the lysosomal enzyme, alpha-mannosidase. The results of this study indicate that levels of the SOR and lipid peroxides are coupled to rotifer life-span and that activation of phospholipase A2 may contribute to the elevation of these agents in older animals.

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.

Studies on prostaglandin and luteolysis in the pseudopregnant rabbit

The ability of pulsatile infusion of prostaglandin F2 alpha (PGF2 alpha) or 13, 14-dihydro prostaglandin F2 alpha to induce corpus luteum regression was examined in the pseudopregnant rabbit. Each prostaglandin was infused in 5, 1-hour pulses (1 per 6 hours) during a 25-hour period starting day 9 or 10 of pseudopregnancy. Although both prostaglandins were capable of inhibiting progesterone secretion, pulse administration was no more effective than continuous infusion. To determine if PGF2 alpha was released into the systemic circulation during spontaneous luteolysis, starting day 12 of pseudopregnancy serial blood samples were collected every 90 minutes from the jugular vein. Prostaglandin F levels remained steady (1-2 ng/ml over the collection period with no apparent increase associated with functional luteolysis. Although prostaglandins may be involved in luteolysis in the rabbit, the present results suggest that it is unlikely that PGF2 alpha by itself is responsible for the sustained fall in progesterone secretion at the end of the pseudopregnancy.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.