Successful establishment of Wolbachia in Aedes populations to suppress dengue transmission

Genetic manipulations of insect populations for pest control have been advocated for some time, but there are few cases where manipulated individuals have been released in the field and no cases where they have successfully invaded target populations. Population transformation using the intracellular bacterium Wolbachia is particularly attractive because this maternally-inherited agent provides a powerful mechanism to invade natural populations through cytoplasmic incompatibility. When Wolbachia are introduced into mosquitoes, they interfere with pathogen transmission and influence key life history traits such as lifespan. Here we describe how the wMel Wolbachia infection, introduced into the dengue vector Aedes aegypti from Drosophila melanogaster, successfully invaded two natural A. aegypti populations in Australia, reaching near-fixation in a few months following releases of wMel-infected A. aegypti adults. Models with plausible parameter values indicate that Wolbachia-infected mosquitoes suffered relatively small fitness costs, leading to an unstable equilibrium frequency <30% that must be exceeded for invasion. These findings demonstrate that Wolbachia-based strategies can be deployed as a practical approach to dengue suppression with potential for area-wide implementation.

Dysbindin (DTNBP1) and the biogenesis of lysosome-related organelles complex 1 (BLOC-1): main and epistatic gene effects are potential contributors to schizophrenia susceptibility

BACKGROUND

The DTNBP1 gene, encoding dysbindin, has been strongly implicated in schizophrenia (SZ) susceptibility by a series of independent genetic association and gene expression studies. Among its known functions, dysbindin is part of a protein complex, termed the biogenesis of lysosome-related organelles complex 1 (BLOC-1), the molecular components of which might be involved in the regulation of vesicular trafficking and dendrite branching.

METHODS

A systematic investigation of the other seven BLOC-1 genes (MUTED, PLDN, CNO, SNAPAP, BLOC1S1, BLOC1S2, and BLOC1S3) for evidence of association with SZ was undertaken in a sample of 373 SZ cases and 812 control subjects. Possible epistasis between combinations of BLOC-1 genes, including DTNBP1, was tested with a novel method of investigating for gene-gene interaction. Quality control measures were incorporated into genotyping strategy, and all results were corrected for multiple testing to prevent false positive results.

RESULTS

We identified significant evidence of association between BLOC1S3 and SZ (odds ratio = 1.45, confidence interval = 1.13-1.86, p = .0028, corrected p = .0389). We also report evidence for epistatic interaction between DTNBP1 and MUTED contributing to SZ in the absence of a significant main effect at MUTED (p = .0009, corrected p = .0252). Single marker and epistasis results remained significant after correction for multiple testing.

CONCLUSIONS

Together these data provide evidence for the involvement of the BLOC-1 protein complex in SZ pathogenesis.

Evidence for association and epistasis at the DAOA/G30 and D-amino acid oxidase loci in an Irish schizophrenia sample

The D-amino acid oxidase (DAO) signaling pathway has been implicated in schizophrenia pathogenesis. This may be mediated through modulation of NMDA function by DAO, which is in turn activated by DAO activator (DAOA, formerly G72). Chumakov et al. (2002); PNAS 99: 13675-13680, identifying the novel schizophrenia susceptibility gene DAOA/G30 and a number of independent studies have since reported evidence of association between the DAOA and DAO genes and schizophrenia. However, at least two studies have failed to replicate the epistatic interaction between these loci described in the original report and there have been differences in the associated alleles/haplotypes reported at each locus. In this study, we performed association and epistasis analyses of the DAOA/G30 and DAO loci in a sample of 373 cases with DSM-IV schizophrenia/schizoaffective disorder and 812 controls from the Republic of Ireland. Corrected for the number of tests performed, we found evidence for association between markers at both genes and schizophrenia: DAOA/G30 (P = 0.005, OR = 1.34 (1.09, 1.65)) and DAO (P = 0.003, OR = 1.43 (1.12, 1.84). The data suggest that evidence for association at DAO (marker rs2111902) is more consistent than previously realized, particularly in Caucasian schizophrenia populations. We identified evidence for epistatic interaction between the associated SNPs at DAOA and DAO genes in contributing to schizophrenia risk (OR = 9.3 (1.4, 60.5). Based on these data, more systematic investigation of genes involved in DAO signaling is required.

d-Amino acid oxidase (DAO) genotype and mood symptomatology in schizophrenia

A series of genetic studies have identified the D-amino acid oxidase (DAO) gene as potentially contributing to schizophrenia susceptibility. An interacting gene, D-amino acid oxidase activator (DAOA) has also been implicated and it has been suggested that variation at these genes may influence the efficiency of glutamate gating at N-methyl-D-aspartate-type (NMDA) receptors. However, recent data suggests that DAOA may influence susceptibility to mood episodes across the spectrum of psychotic disorders rather than contributing to a specific psychosis phenotype. The aim of this study was to determine whether risk variation at DAO is similarly associated with affective or other clinical symptoms in psychosis. We have previously reported association between risk variation at DAO and schizophrenia in an Irish case-control sample. In this study we investigated the relationship between a defined genetic risk variant at DAO and PANSS-derived clinical symptom factors in a sample of 249 patients using principal component and Kruskal-Wallis analyses. Carriers of the DAO risk variant scored significantly higher on the 'depression/anxiety' factor than non-carriers (H=9.02, d.f.=2, p=0.01). These data suggest a potential role for DAO in susceptibility to depressive symptoms in schizophrenia, but a more general role for DAO in affective disorders cannot be excluded.

Functional genetic analysis of mutations implicated in a human speech and language disorder

Mutations in the FOXP2 gene cause a severe communication disorder involving speech deficits (developmental verbal dyspraxia), accompanied by wide-ranging impairments in expressive and receptive language. The protein encoded by FOXP2 belongs to a divergent subgroup of forkhead-box transcription factors, with a distinctive DNA-binding domain and motifs that mediate hetero- and homodimerization. Here we report the first direct functional genetic investigation of missense and nonsense mutations in FOXP2 using human cell-lines, including a well-established neuronal model system. We focused on three unusual FOXP2 coding variants, uniquely identified in cases of verbal dyspraxia, assessing expression, subcellular localization, DNA-binding and transactivation properties. Analysis of the R553H forkhead-box substitution, found in all affected members of a large three-generation family, indicated that it severely affects FOXP2 function, chiefly by disrupting nuclear localization and DNA-binding properties. The R328X truncation mutation, segregating with speech/language disorder in a second family, yields an unstable, predominantly cytoplasmic product that lacks transactivation capacity. A third coding variant (Q17L) observed in a single affected child did not have any detectable functional effect in the present study. In addition, we used the same systems to explore the properties of different isoforms of FOXP2, resulting from alternative splicing in human brain. Notably, one such isoform, FOXP2.10+, contains dimerization domains, but no DNA-binding domain, and displayed increased cytoplasmic localization, coupled with aggresome formation. We hypothesize that expression of alternative isoforms of FOXP2 may provide mechanisms for post-translational regulation of transcription factor function.

Neurocognition and suicidal behaviour in an Irish population with major psychotic disorders

OBJECTIVES

Although neurocognitive deficits are seen as core to schizophrenia the association between suicidality and neurocognition has received little attention. Our aim was to examine the relationship between neurocognitive variables and suicidal behaviour in patients with schizophrenia and schizoaffective disorder.

METHODS

Seventy-eight patients with DSM-IV diagnoses of schizophrenia or schizoaffective disorder were categorised as either having attempted suicide or not having attempted suicide based on clinical interview and chart review. Attempters and non-attempters were compared on an extensive neuropsychological battery examining pre-morbid and current general cognitive functioning, episodic memory, and executive functioning.

RESULTS

Suicide attempters tended to out perform non-attempters across all areas of executive functioning, and showed significantly better performances on measures of attention and verbal fluency. After controlling for relevant clinical and demographic variables, the differences between attempters and non-attempters remained significant for measures of attention (F = 4.97, p = 0.03) and verbal fluency (F = 4.28, p = 0.04).

CONCLUSION

This study adds to existing data that suicide attempters with schizophrenia or schizoaffective disorder may have higher cognitive functioning than non-attempters. In particular, the preservation of higher executive function may influence the ability to initiate and plan suicidal behaviour.

Lifelong learning in ethical practice: a challenge for continuing medical education

BACKGROUND

Formal education in the identification, analysis, and resolution of ethical issues in clinical practice is now an essential component of undergraduate and postgraduate medical education. Physicians educated before the 1980s have had little or no formal education in ethics. This article describes a project for assessing the content and format appropriate for the continuing education needs of practicing physicians.

METHODS

A questionnaire and follow-up facilitated small-group discussions with a physician ethicist around case-based problems were used to identify the ethical issues in practice where participants felt the need for continuing education.

RESULTS

The project confirmed that practitioners had very little formal ethics in medical school and less since starting practice despite encountering ethical issues. The most frequently used method of learning about ethics was informal discussion among those who have the same lack of formal education. Physicians did not feel that they needed a "very high" level of confidence and competence in handling ethical issues, even those commonly encountered. Participants indicated strongly that they lacked a systematic approach to the identification and analysis of ethical issues and suggest incorporation of the ethical component into regular CME.

FINDINGS

In spite of the small study population and the volunteer nature of the participants, the project demonstrated the identification of ethics content for CME similar to that used in medical education. Further work is needed to assess objective needs for ethics education in addition to the perceived needs of clinicians.

Ethics in an aging society: challenges for oral health care

Health and aging are deeply meaningful and complex realities. The demographic reality of the Canadian population in the 21st century requires an in-depth understanding of the health care goals of older people, an analysis of the attitudes toward older people that affect societal decision making and the educational and policy changes required to effect positive change. Viewing these issues through the lens of oral health care allows an analysis of health care goals for the older population. A look at representative cases where oral health needs were not met uncovers some of the attitudes and values about oral health, the goals of health care and the unique circumstances of older people that present barriers to appropriate care.

Pediatricians' experience of ethical dilemmas in practice: implications for education

OBJECTIVE

To determine Canadian pediatricians' experience with ethical dilemmas, to relate this information to proposed curriculum for residency training in Canada, and to determine pediatricians' self-assessment of adequacy of training in ethical issues and the means used in practice to resolve dilemmas.

METHOD

A single-pass questionnaire was mailed to all 1,220 pediatrician members of the Canadian Pediatric Society.

RESULTS

From the 363 questionnaires (30 per cent) that were returned, 43 per cent of respondents had received formal ethics education in their training. Approximately half of respondents judged their training as adequate. Responses confirmed the themes of futile treatment, demands for and refusal of treatment by parents, uncertainty regarding withdrawing or withholding treatments, conflicts over judgments about the right thing to do, and dilemmas regarding the role of the child and adolescent. Respondents relied mainly on informal discussion with colleagues to resolve their dilemmas in practice.

CONCLUSIONS

Core residency and continuing physician education need a valid epidemiological description of ethical issues encountered in practice. Educational approaches to the development of ethical knowledge, skills, and attitudes must be validated as there is a tendency to rely on case precedent and peer judgment. Perceived competence in handling ethical issues and dilemmas must be tested against accepted standards. Emerging ethical issues such as resource allocation, peer review, managed care, and technological and scientific advances must be regularly incorporated into both residency education and continuing medical education.

Tamoxifen induces TGF-beta 1 activity and apoptosis of human MCF-7 breast cancer cells in vitro

We report here that the antiestrogen tamoxifen (TAM) induces cell death in human breast cancer cell line MCF-7. We assessed the type of cell death induced by TAM in this breast cancer cell line on the basis of morphological and biochemical characteristics. Dying cells showed morphological characteristics of apoptosis, such as chromatin condensation and nuclear disintegration. DNA isolated from these cells revealed a pattern of distinctive DNA bands on agarose gel. The DNA fragmentation in MCF-7 cells induced by TAM could also be detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin end labeling. Northern blot hybridization revealed a substantial increase in the amounts of TRPM-2 and TGF-beta 1 mRNAs in MCF-7 cells after treatment with TAM. In contrast, the mRNA level of the estrogen-induced pS2 gene was strongly suppressed. The biological activity of TGF-beta was increased at least fourfold in the media from MCF-7 cells treated with TAM. The results presented in this study suggest that TAM induces apoptosis of MCF-7 cells and it may be mediated by the secretion of active TGF-beta.

Rotational dynamics of luteinizing hormone receptors on bovine and ovine luteal cell plasma membranes

To determine whether LH receptor rotational diffusion is similar in closely related species, we compared the rotational correlation times of LH receptors on bovine CL membranes with those of LH receptors on sheep small luteal cells and luteal cell plasma membranes using time-resolved phosphorescence anisotropy techniques. After binding of erythrosin isothiocyanate (ErITC)-derived bovine LH (bLH), ErITC-ovine LH (oLH), or ErITC-hCG, there was no difference in the initial and final anisotropy at 4 degrees C, 15 degrees C, 25 degrees C, and 37 degrees C, indicating that the bLH receptor was rotationally immobile on the time scale of our experiments. On these same membrane preparations, the epidermal growth factor (EGF) receptor occupied by ErITC-murine EGF exhibited temperature-dependent rotational correlation times of 80 +/- 5 microseconds, 111 +/- 7 microseconds, 254 +/- 4 microseconds, and > 1000 microseconds at 4 degrees C, 15 degrees C, 25 degrees C, and 37 degrees C, respectively. Slower rotational times for EGF receptor observed at higher temperatures suggested the occurrence of temperature-dependent receptor aggregation. Like the bLH receptor, the oLH receptor on intact cells and on CL plasma membranes was rotationally immobile on the time scale of our experiments when occupied by ErITC-hCG. However, the oLH-occupied receptors on small luteal cells and on luteal cell membranes had comparable rotational correlation times at 37 degrees C. These results suggest that bLH receptors are present in large, rotationally immobile structures, whereas the receptor-containing structure formed on ovine luteal cells depends on whether that receptor is occupied by hCG or oLH. Also, despite the similarities between reproductive function in these species, the LH-occupied receptor appears to be organized differently in the plasma membranes of these hormone-responsive luteal cells.

Rotational dynamics of luteinizing hormone receptors and MHC class I antigens on murine Leydig cells

We have examined the molecular motions of luteinizing hormone (LH) receptor and the Major Histocompatibility Complex Class I antigen on murine Leydig cells. Using time-resolved phosphorescence anisotropy methods, erythrosin (ErITC)-derivatized ovine luteinizing hormone (oLH) bound to the LH receptor appears rotationally mobile with rotational correlation times of 19.6 +/- 1.3 microseconds, 13.3 +/- 2.4 microseconds, 9.5 +/- 0.7 microseconds and 4.7 +/- 0.5 microseconds at 4 degrees C, 15 degrees C, 25 degrees C and 37 degrees C, respectively. Rotational correlation times for human chorionic gonadotropin (hCG)-occupied LH receptors were similar to those of the ErITC-oLH occupied receptor at each temperature. In addition, both oLH- and hCG-occupied LH receptors were laterally mobile in fluorescence photobleaching recovery experiments with diffusion coefficients at 29 degrees C of (5.8 +/- 0.9) x 10(-10) cm2 s-1 and (2.9 +/- 0.4) x 10(-10) cm2 s-1, respectively. We also measured the rotational correlation time of Class I antigen on murine Leydig cells using ErITC-derivatized 34-12-2S, an anti-Class I monoclonal antibody. Because there was no decay of the anisotropy function at 4 degrees C, 15 degrees C, 25 degrees C or 37 degrees C in the absence of oLH or following preincubation of Leydig cells with 1 nM oLH, it appears that Class I is rotationally immobile on the 1 ms timescale of our experiments. This result is consistent with the presence of Class I antigen in large molecular weight structures and may be the result of Class I self-aggregation. Further, treatment of cells with anti-Class I antibody had no effect on either basal or oLH-stimulated testosterone secretion. Thus, it appears that this anti-Class I antibody is not LH-mimetic on murine Leydig cells.

Chronic fracture dislocations of the proximal interphalangeal joint. Treatment by the "S" Quattro

The "S" Quattro has proved its value in the treatment of acute displaced comminuted intraarticular phalangeal fracture dislocations. We have used the system to treat five cases of chronic fracture-dislocation or subluxation of the PIP joint. At an average follow-up period of 16.4 months, there was a mean increase in the range of movement of the injured joint by 75 degrees. We recommend this technique for selected cases.

Spontaneous apoptosis of cells prepared from the nonregressing corpus luteum

At the end of a nonconception estrous cycle, the sheep corpus luteum undergoes involution (luteolysis), a process thought to involve apoptotic deletion of cells. It is not yet clear which of the heterogeneous luteal cell types is involved or what mechanisms drive the apoptotic progression. We examined intact paraffin-embedded corpora lutea (in situ terminal dUTP nick end-labeling method) and found direct evidence for apoptotic deletion of cells during luteolysis, but not in healthy, nonregressing corpora lutea. We then sought to implement in vitro models to dissect apoptotic mechanisms in the constituent cells of the corpus luteum. Cells prepared using standard collagenase dispersion of corpus luteum were evaluated for evidence of apoptosis (DNA laddering) by direct agarose gel electrophoresis, a method that obviates the need for DNA extraction, so allowing examination of relatively few cells (< or = 0.5 x 10(6)). When cells were prepared from nonregressing corpus luteum for in vitro manipulation, a population(s) of cells undergoing spontaneous apoptosis was detected. Apoptosis was inhibited by Zn2+ (5 mM), by the tyrosine phosphatase inhibitor sodium orthovanadate (100 microM), or by maintenance at 4 degrees C. It appears that simple collagenase digestion of intact corpus luteum removes a subset of constituent cells from their survival signal, leading to rapid initiation of endonuclease activity and apoptotic cell death. Identification of the required survival factors and their actions is being pursued to facilitate development of appropriate in vitro models for this endocrine system.

Class I major histocompatibility complex antigens are not associated with the LH/CG receptor on ovine luteal cells

We have examined the rotational dynamics of the luteinizing hormone (LH) receptor on day 10 intact ovine small luteal cells and isolated plasma membranes using polarized fluorescence depletion (PFD). This technique measures rotational correlation times which are proportional to the in-membrane volume of a protein and are useful for examining changes in protein size due to receptor aggregation or protein-protein interactions. Eosin isothiocyanate (EITC)-derivatized ovine LH (EITC-oLH) bound to the LH receptor on luteal cell plasma membranes had a rotational correlation time of 20 +/- 6 microseconds, while that for EITC-human chorionic gonadotropin (EITC-hCG)-occupied LH receptors was 46 +/- 13 microseconds. Slower rotational times for EITC-oLH and EITC-hCG, 63 +/- 19 and 87 +/- 20 microseconds, respectively, were obtained on intact ovine luteal cells. These results indicate that the LH receptor exists as a larger molecular mass complex when binding hCG than oLH, a difference which could be attributable to hCG-induced LH-receptor interaction with additional membrane protein(s). One candidate protein for such an interaction is the Major Histocompatibility Complex (MHC) Class-I antigen. However, the rotational correlation time of EITC-anti-MHC Class-I antibody (SBU I) Fab fragments was 247 +/- 34 microseconds, indicating that MHC Class I is located in complexes larger than those identified by EITC-OLH or EITC-hCG. Preincubation of plasma membranes with 1 nM unlabeled oLH or hCG had no significant effect on this rotational correlation time. Further, treatment of cells with SBU I had no affect on either basal or oLH-stimulated progesterone secretion. Thus it appears that the ovine luteal LH-receptor is not associated with MHC Class I and that antibody-induced aggregation of MHC Class I does not cause an LH-mimetic response.

Nail gun injuries

The nail gun is a potentially dangerous device that is commonly used in the construction industry to drive various sizes of nails into wood or concrete. These devices appear to be used without sufficient training and they can be easily obtained by the general public. We report a series of injuries caused by nail guns. The pattern of these injuries and the mechanism of their production suggest that the safety mechanisms on the guns and the protective clothing worn by operators of the guns do not prevent injuries. We call for a review of operator training and the design of both the safety mechanism of nail guns and the protective clothing worn by operators. If necessary, modifications should be introduced to reduce the likelihood and severity of such potentially serious injuries.

Molecular dynamics of luteinizing hormone receptors on rat luteal cells

To better understand the in situ organization of the luteinizing hormone receptor on rat luteal cells, we have examined the molecular motions of this receptor following binding of ovine luteinizing hormone (oLH) or human chorionic gonadotropin (hCG). Fluorescence photobleaching recovery (FPR) measurements of LH receptor lateral diffusion were performed using tetramethylrhodamine isothiocyanate (TRITC)-derivatized oLH or hCG as a probe. These experiments indicate that TRITC-oLH occupied LH receptors on luteal cells obtained from superovulated female rats have a lateral diffusion coefficient D of (1.7 +/- 0.6).10(-10) cm2s-1 at 27 degrees C with fluorescence recovery after photobleaching of 46 +/- 5%. In similar experiments, binding of TRITC-hCG caused a significant decrease in LH receptor lateral diffusion; fluorescence recovery after photobleaching was less than 20%. To determine whether hCG-occupied receptors might exist in large aggregates, we measured the rotational correlation times (RCT) of hCG and oLH bound to the LH receptor on intact cells using single cell polarized fluorescence depletion (PFD). At 4 degrees C, LH receptors occupied by eosin isothiocyanate (EITC)-hCG exhibited a slower RCT (64 microseconds) than did receptors occupied by EITC-oLH (43 microseconds). At this temperature both TRITC-oLH and TRITC-hCG occupied LH receptors were laterally immobile. These FPR and PFD results suggest that the molecular motions of the luteal cell LH receptor are significantly modulated by the subtle structural differences in various bound gonadotropins.

Gonad protection in young orthopaedic patients

OBJECTIVE

To determine whether gonad shields are correctly positioned on the pelvic radiographs of children with slipped capital femoral epiphysis.

DESIGN

Retrospective study of radiographs taken of children treated by in situ pinning of slipped capital femoral epiphysis between 1 January 1983 and 31 December 1988.

SETTING

Three teaching hospitals in north west England.

PATIENTS

32 patients with complete set of radiographs.

RESULTS

An average of 10.8 anteroposterior pelvic radiographs plus 8.9 lateral hip radiographs had been performed per patient. Gonad shields had been completely omitted in 137 (40%) anteroposterior pelvic radiographs performed on the 32 patients at the time of completion of the study. In 100 (29%) the gonad shields were adequately protecting the gonads, but in 109 (31%) the gonad shields were not protecting the gonads due to incorrect positioning of the shield. The incorrect positioning of the gonad shields was more commonly found in girls than boys (64 vs 45; p less than 0.012), presumably because of the difficulty in determining gonadal position in relation to surface landmarks. Absence of gonad shields was also more commonly seen in girls (82 v 55; p less than 0.005), but this is not easily explained.

CONCLUSIONS

Gonad shields are not protecting the gonads in a large percentage of anteroposterior pelvic radiographs (71%) because they have been omitted or inadequately placed. This avoidable excess radiation exposure to the gonads, combined with the inability to shield the gonads in lateral hip radiographs and the large number of radiographs performed, results in the gonads receiving a higher dose of radiation than may otherwise be the case, and may increase the potential for disease in the future offspring of these patients.

Morphometric quantification of mitochondria in the two steroidogenic ovine luteal cell types

Progesterone secretion is regulated by different mechanisms in large and small steroidogenic ovine luteal cells. Large cells secrete approximately 7-fold more progesterone in an unstimulated state than small cells. Since cholesterol side-chain cleavage, which is catalyzed by an inner mitochondrial membrane enzyme complex, is a major rate-limiting step in progesterone synthesis, mitochondrial components were quantified in the two steroidogenic cell types throughout the estrous cycle. Corpora lutea collected on Days 4 (n = 4), 8 (n = 4), 12 (n = 5), and 16 (n = 6) of the estrous cycle were prepared for electron microscopy. Volume densities of cell types within corpora lutea and mitochondrial densities within cell types were estimated by point-counting; nuclear and cytoplasmic volume densities were estimated by planimetric analysis. A total of 570 micrographs (magnification 5300 X) were analyzed. Large cell volume density was unchanged during the cycle (35 +/- 1%) while small cell volume density increased (p less than 0.05) from 13 +/- 1% on Day 4 to 20 +/- 3% on Day 12. Large cell mitochondrial volume density increased (p less than 0.05) from 13 +/- 1% on Day 4 to 23 +/- 1% on Day 16 accompanied by an increase in cytoplasmic volume density such that nuclear to cytoplasmic ratio increased (p less than 0.05) from 1:14 to 1:34 between Days 4 and 16. Small cell mitochondrial volume density increased from 11 +/- 1% on Day 4 to 14 +/- 1% (p less than 0.05) for the rest of the cycle while the nuclear to cytoplasmic ratio remained at 1:14.(ABSTRACT TRUNCATED AT 250 WORDS)

Progesterone production, LH receptors, and oxytocin secretion by ovine luteal cell types on days 6, 10 and 15 of the oestrous cycle and day 25 of pregnancy

Corpora lutea were collected from sheep on Days 6, 10, and 15 of the oestrous cycle and Day 25 of pregnancy and dissociated into single cell suspensions. Purified preparations of large and small luteal cells were prepared by elutriation on all days except Day 6. Basal progesterone production by large cells was 6-8-fold higher than by small cells (36-65 vs 6-9 fg/cell/min). Oxytocin secretion was maximal on Day 6 (1.0 fg/cell/min) and declined thereafter. The number of receptors for LH increased between Day 6 and Day 10 and the two cell types had an equal number of receptors on Days 10 and 15 (19,000-23,000). Large cells on Day 25 of pregnancy had fewer receptors (12,000) than did small cells (26,000). Progesterone secretion by small luteal cells from all days examined was stimulated by LH (0.01-1000 ng/ml) in a dose-dependent manner; maximum sensitivity to LH occurred on Day 10. Despite the presence of receptors for LH on large cells, LH failed to stimulate progesterone production. Basal production of progesterone by large and small cells, and the response of small cells to LH, was not influenced by day examined. Re-combinations of large and small cells from Day 10 synergized to increase progesterone secretion. Prostaglandin E-2 (0.1-1000 ng/ml) did not stimulate progesterone secretion by large or small cells.

Prostaglandin F2 alpha-induced functional luteolysis: interactions of LH, prostaglandin F2 alpha and forskolin in cyclic AMP and progesterone synthesis in isolated rat luteal cells

The acute antigonadotrophic action of prostaglandin F2 alpha (PGF2 alpha) was examined in dispersed luteal cell preparations from immature superluteinized rat ovaries. Cell suspensions prepared by collagenase digestion and purification over a Percoll density gradient were incubated for 1 h in Eagle's minimum essential medium in the presence and/or absence of LH, PGF2 alpha, N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate (dbcAMP) and forskolin. Medium was assayed for total progesterone and adenosine 3',5'-cyclic monophosphate (cAMP). Luteal cell preparations showed typical steroidogenic (progesterone) responses to LH, mimicked by both dbcAMP and forskolin. Whilst the threshold LH dose to increase cAMP synthesis was greater than that for progesterone (100 micrograms/l compared with 1 microgram/l), 24 mumol forskolin/l was the threshold dose for both cAMP and progesterone responses. Furthermore, combined doses of LH and forskolin synergistically raised cAMP yet produced less than additive increases in progesterone. Similarly, combinations of dbcAMP plus forskolin produced less than additive progesterone increases. These data suggest that forskolin may not act as a simple mimic of LH. Prostaglandin F2 alpha dose-dependently inhibited forskolin-induced cAMP and progesterone synthesis and also inhibited progesterone synthesis induced by dbcAMP. These data suggest that the antigonadotrophic effect of PGF2 alpha has more than one locus of action, i.e. it both inhibits an adenylate cyclase event associated with cAMP generation and blunts the cellular response to cAMP. The present uncertainty over the exact locus of forskolin's action within the adenylate cyclase complex limits further delineation of the inhibitory action of PGF2 alpha on LH-responsive adenylate cyclase.