Context and Considerations for the Development of Community-Informed Health Communication Messaging to Support Equitable Uptake of COVID-19 Vaccines Among Communities of Color in Washington, DC

BACKGROUND

Communities of color have been disproportionately impacted by COVID-19. We explored barriers and facilitators to COVID-19 vaccine uptake among African American, Latinx, and African immigrant communities in Washington, DC.

METHODS

A total of 76 individuals participated in qualitative interviews and focus groups, and 208 individuals from communities of color participated in an online crowdsourcing contest.

RESULTS

Findings documented a lack of sufficient, accurate information about COVID-19 vaccines and questions about the science. African American and African immigrant participants spoke about the deeply rooted historical underpinnings to their community's vaccine hesitancy, citing the prior and ongoing mistreatment of people of color by the medical community. Latinx and African immigrant participants highlighted how limited accessibility played an important role in the slow uptake of COVID-19 vaccines in their communities. Connectedness and solidarity were found to be key assets that can be drawn upon through community-driven responses to address social-structural challenges to COVID-19 related vaccine uptake.

CONCLUSIONS

The historic and ongoing socio-economic context and realities of communities of color must be understood and respected to inform community-based health communication messaging to support vaccine equity for COVID-19 and other infectious diseases.

Anticholinergic medicines in an older primary care population: a cross-sectional analysis of medicines' levels of anticholinergic activity and clinical indications

WHAT IS KNOWN AND OBJECTIVES

Adverse clinical outcomes have been associated with cumulative anticholinergic burden (to which low-potency as well as high-potency anticholinergic medicines contribute). The clinical indications for which anticholinergic medicines are prescribed (and thus the 'phenotype' of patients with anticholinergic burden) have not been established. We sought to establish the overall prevalence of prescribing of anticholinergic medicines, the prevalence of prescribing of low-, medium- and high-potency anticholinergic medicines, and the clinical indications for which the medicines were prescribed in an older primary care population.

METHODS

This was a cross-sectional analysis of a cohort study of Australian early-career general practitioners' (GPs') clinical consultations - the Registrar Clinical Encounters in Training (ReCEnT) study. In ReCEnT, GPs collect detailed data (including medicines prescribed and their clinical indication) for 60 consecutive patients, on up to three occasions 6 months apart. Anticholinergic medicines were categorized as levels 1 (low-potency) to 3 (high-potency) using the Anticholinergic Drug Scale (ADS).

RESULTS

During 2010-2014, 879 early-career GPs (across five of Australia's six states) conducted 20 555 consultations with patients aged 65 years or older, representing 35 506 problems/diagnoses. Anticholinergic medicines were prescribed in 10·4% [95% CIs 9·5-10·5] of consultations. Of the total anticholinergic load of prescribed medicines ('community anticholinergic load') 72·7% [95% CIs 71·0-74·3] was contributed by Level 1 medicines, 0·8% [95% CIs 0·5-1·3] by Level 2 medicines and 26·5% [95% CIs 24·8-28·1] by Level 3 medicines. Cardiac (40·0%), Musculoskeletal (16·9%) and Respiratory (10·6%) were the most common indications associated with Level 1 anticholinergic prescription. For Level 2 and 3 medicines (combined data), Psychological (16·1%), Neurological (16·1%), Musculoskeletal (15·7%) and Urological (11·1%) indications were most common.

WHAT IS NEW AND CONCLUSION

Anticholinergic medicines are frequently prescribed in Australian general practice, and the majority of the 'community' anticholinergic burden is contributed by 'low'-anticholinergic potency medicines whose anticholinergic effects may be largely 'invisible' to prescribing GPs. Furthermore, the clinical 'phenotype' of the patient with high anticholinergic burden may be very different to common stereotypes (patients with urological, psychological or neurological problems), potentially making recognition of risk of anticholinergic adverse effects additionally problematic for GPs.

Dating violence, childhood maltreatment, and BMI from adolescence to young adulthood

BACKGROUND AND OBJECTIVES

This study tested whether dating violence (DV) victimization is associated with increases in BMI across the transition from adolescence to young adulthood and whether gender and previous exposure to child maltreatment modify such increases.

METHODS

Data were from participants (N = 9295; 49.9% female) in the National Longitudinal Study of Adolescent Health. BMI was calculated from measured height and weight at waves 2, 3, and 4 of the study. DV victimization was measured at waves 2, 3, and 4 by using items from the revised Conflict Tactics Scales. Linear regression by using generalized estimating equations with robust SEs was used to test the association. Models were stratified according to gender and history of child maltreatment.

RESULTS

From baseline to wave 4, BMI increased on average 6.5 units (95% confidence interval [CI]: 6.2-6.7) and 6.8 units (95% CI: 6.5-7.1) among men and women, respectively, and nearly one-half (45.5% of men; 43.9% of women) reported DV at some point. In stratified models, DV victimization (β: 0.3 [95% CI: 0.0-0.6]) independently predicted BMI increase over time in women. Exposure to childhood sexual abuse magnified the increase in BMI associated with DV victimization (β: 1.3 [95% CI: 0.3-2.3]). No other types of childhood maltreatment were significant modifiers of the DV-BMI association. Violence victimization was not associated with BMI among men.

CONCLUSIONS

Screening and support for DV victims, especially women who have also experienced childhood maltreatment, may be warranted to reduce the likelihood of health consequences associated with victimization.

Intermittent hypoxia-induced increases in reactive oxygen species activate NFATc3 increasing endothelin-1 vasoconstrictor reactivity

Sleep apnea (SA), defined as intermittent respiratory arrest during sleep, is associated with increased incidence of hypertension, peripheral vascular disease, stroke, and sudden cardiac death. We have shown that intermittent hypoxia with CO2 supplementation (IH), a model for SA, increases blood pressure and circulating ET-1 levels, upregulates lung pre-pro ET-1 mRNA, increases vasoconstrictor reactivity to ET-1 in rat small mesenteric arteries (MA) and increases vascular reactive oxygen species (ROS). NFAT activity is increased in the aorta (AO) and MA of mice exposed to IH in an ET-1-dependent manner, and the genetic ablation of the isoform NFATc3 prevents IH-induced hypertension. We hypothesized that IH causes an increase in arterial ROS generation, which activates NFATc3 to increase vasoconstrictor reactivity to ET-1. In support of our hypothesis, we found that IH increases ROS in AO and MA. In vivo administration of the SOD mimetic tempol during IH exposure prevents IH-induced increases in NFAT activity in mouse MA and AO. We found that IH causes an NFATc3-dependent increase in vasoconstrictor reactivity to ET-1, accompanied by an increase in vessel wall [Ca²⁺]. Our results indicate that IH exposure causes an increase in arterial ROS to activate NFATc3, which then increases vasoconstrictor reactivity and Ca²⁺ response to ET-1. These studies highlight a novel regulatory pathway, and demonstrate the potential clinical relevance of NFAT inhibition to prevent hypertension in SA patients.

Psychosocial distress and stroke risk in older adults

BACKGROUND AND PURPOSE

To investigate the association of psychosocial distress with risk of stroke mortality and incident stroke in older adults.

METHODS

Data were from the Chicago Health and Aging Project, a longitudinal population-based study conducted in 3 contiguous neighborhoods on the south side of Chicago, IL. Participants were community-dwelling black and non-Hispanic white adults, aged 65 years and older (n=4120 for stroke mortality; n=2649 for incident stroke). Psychosocial distress was an analytically derived composite measure of depressive symptoms, perceived stress, neuroticism, and life dissatisfaction. Cox proportional hazards models examined the association of distress with stroke mortality and incident stroke over 6 years of follow-up.

RESULTS

Stroke deaths (151) and 452 incident strokes were identified. Adjusting for age, race, and sex, the hazard ratio (HR) for each 1-SD increase in distress was 1.47 (95% confidence interval [CI]=1.28-1.70) for stroke mortality and 1.18 (95% CI=1.07-1.30) for incident stroke. Associations were reduced after adjustment for stroke risk factors and remained significant for stroke mortality (HR=1.29; 95% CI=1.10-1.52) but not for incident stroke (HR=1.09; 95% CI=0.98-1.21). Secondary analyses of stroke subtypes showed that distress was strongly related to incident hemorrhagic strokes (HR=1.70; 95% CI=1.28-2.25) but not ischemic strokes (HR=1.02; 95% CI=0.91-1.15) in fully adjusted models.

CONCLUSIONS

Increasing levels of psychosocial distress are related to excess risk of both fatal and nonfatal stroke in older black and white adults. Additional research is needed to examine pathways linking psychosocial distress to cerebrovascular disease risk.

Latent constructs in psychosocial factors associated with cardiovascular disease: an examination by race and sex

This study examines race and sex differences in the latent structure of 10 psychosocial measures and the association of identified factors with self-reported history of coronary heart disease (CHD). Participants were 4,128 older adults from the Chicago Health and Aging Project. Exploratory factor analysis (EFA) with oblique geomin rotation was used to identify latent factors among the psychosocial measures. Multi-group comparisons of the EFA model were conducted using exploratory structural equation modeling to test for measurement invariance across race and sex subgroups. A factor-based scale score was created for invariant factor(s). Logistic regression was used to test the relationship between the factor score(s) and CHD adjusting for relevant confounders. Effect modification of the relationship by race-sex subgroup was tested. A two-factor model fit the data well (comparative fit index = 0.986; Tucker-Lewis index = 0.969; root mean square error of approximation = 0.039). Depressive symptoms, neuroticism, perceived stress, and low life satisfaction loaded on Factor I. Social engagement, spirituality, social networks, and extraversion loaded on Factor II. Only Factor I, re-named distress, showed measurement invariance across subgroups. Distress was associated with a 37% increased odds of self-reported CHD (odds ratio: 1.37; 95% confidence intervals: 1.25, 1.50; p-value < 0.0001). This effect did not differ by race or sex (interaction p-value = 0.43). This study identified two underlying latent constructs among a large range of psychosocial variables; only one, distress, was validly measured across race-sex subgroups. This construct was robustly related to prevalent CHD, highlighting the potential importance of latent constructs as predictors of cardiovascular disease.

Adapting evidence-based strategies to increase physical activity among African Americans, Hispanics, Hmong, and Native Hawaiians: a social marketing approach

INTRODUCTION

Using a social marketing approach, we studied how best to adapt proven, evidence-based strategies to increase physical activity for use with underserved racial or ethnic groups.

METHODS

We conducted focus groups with low-income Hispanic women in Texas, Hmong parents and their children in California, low-income African American women and men in the Mississippi Delta, and Native Hawaiian college students in Hawaii. We also interviewed key leaders of these communities. Topics of discussion were participants' perceptions about 1) the benefits of engaging in physical activity, 2) the proposed evidence-based strategies for increasing each community's level of physical activity, and 3) the benefits and barriers to following the proposed interventions for increasing physical activity. A total of 292 individuals participated in the study.

RESULTS

All groups considered that being physically active was part of their culture, and participants found culturally relevant suggestions for physical activities appealing. Overwhelmingly, strategies that aimed to create or improve social support and increase access to physical activity venues received the most positive feedback from all groups. Barriers to physical activity were not culturally specific; they are common to all underserved people (lack of time, transportation, access, neighborhood safety, or economic resources).

CONCLUSION

Results indicate that evidence-based strategies to increase physical activity need to be adapted for cultural relevance for each racial or ethnic group. Our research shows that members of four underserved populations are likely to respond to strategies that increase social support for physical activity and improve access to venues where they can be physically active. Further research is needed to test how to implement such strategies in ways that are embraced by community members.

Giving and receiving of gifts between pharmaceutical companies and medical specialists in Australia

BACKGROUND

This study investigated the 'gift-relationship' between pharmaceutical companies and doctors.

METHODS

The study was based on a survey questionnaire of 823 medical specialists from across Australia. The aim of this study was to investigate gifts offered to medical specialists in Australia by pharmaceutical companies, financial support actively sought by medical specialists for activities other than research and to consider what is ethically appropriate.

RESULTS

A high percentage of specialists received offers of food (96%), items for the office (94%), personal gifts (51%) and journals or textbooks (50%). Most specialists were invited to product launches, symposia or educational events (75-84%) and 52% received offers of travel to conferences. A high proportion of offers were accepted (66-79%) except invitations to product launches (49%), sponsored symposia (53%) and offers of travel that included partners (27%). Fifteen per cent of specialists requested financial support from pharmaceutical companies for activities and items, including conferences, travel, educational activities, salaries and donations to specific funds. The study outlined guidelines on gifts from pharmaceutical companies and differing standards applying to gifts and grants for travel. We found that, although most gifts and requests for support complied with professional and pharmaceutical industry guidelines, some--including personal gifts, tickets to sporting events, entertainment and travel expenses for specialists' partners--did not.

CONCLUSION

To ensure that physicians' judgements are free from real or perceived influence from industry and to maintain public trust, we support a shift towards more conservative standards on gifts and support for travel evident in recent guidelines.

Concentrations of oestrone sulphate during pregnancy in milk from Jersey and Friesian dairy cows differing in milk yields and composition

Oestrone sulphate concentrations were measured by radioimmunoassay in milk samples obtained weekly during pregnancy from Jersey and Friesian cows, with each breed grazed at two different stocking rates. Mean milk yields differed significantly (P<0.05) between the four herds, while mean percentage milk fat and protein values differed significantly (P<0.05) between the two breeds. In all four herds, oestrone sulphate concentrations in milk rose progressively during pregnancy from a mean value of approximately 80-100 pg/ml at 60-80 days of pregnancy to a plateau value of approximately 1 ng/ml at 181-200 days. In non-pregnant cows, oestrone sulphate concentrations in milk ranged from non-detectable to 110 pg/ml, with a mean +/- s.e.m. value of 59 +/- 4 pg/ml. There was considerable variation in milk oestrone sulphate concentrations between cows in each herd, and oestrone sulphate concentrations could also fluctuate markedly within cows from week to week. Despite this variation, the concentration of oestrone sulphate in 98% of milk samples obtained after 120 days of pregnancy was greater than the highest concentration found in milk from non-pregnant cows. Measurement of oestrone sulphate concentrations in milk samples taken at least 120 days after mating or insemination may provide an alternative, non-invasive means of determining or confirming pregnancy in New Zealand dairy cows.

The robustness of faecal steroid determination for pregnancy testing Kaimanawa feral mares under field conditions

AIMS

To investigate the utility of faecal oestrone sulphate (OS) concentrations for detecting pregnancy in mares during behavioural studies of feral horses, in which the collection and preservation of samples is not immediate.

METHODS

Oestrone sulphate concentrations were measured in fresh dung samples collected from 153 free-roaming Kaimanawa mares throughout the year. In addition, multiple samples were taken from the same pile to investigate the reliability of diagnosis from a single sample, as well as the influence of time until preservation on OS concentrations. Samples were also taken before and after a 10mm simulated rainfall event to test for dilution of OS concentrations by rain. Oestrone sulphate concentrations in all samples were measured using an enzyme immunoassay.

RESULTS

From approximately 150 to 250 days of gestation, OS concentrations were consistently >80 ng/g in mares which subsequently foaled. Mares which did not foal and had low faecal OS concentrations in multiple samples throughout the year had faecal OS concentrations of 31+/-13 ng/g (mean+/-s.d.) with an upper 95% confidence limit of 57 ng/g. Mares sampled from 1 week before to 1 month after behavioural oestrus, and that did not foal in the previous and subsequent seasons, had OS concentrations of 37+/-32 ng/g (mean+/-s.d.) with an upper 95% confidence limit of 100 ng/g. The standard error of oestrone sulphate concentrations in multiple samples from the same dung pile ranged from 1 to 37% of the mean. This large within-pile variation, however, did not result in incorrect diagnoses from single samples unless mares were within 18 days of parturition. Keeping samples at ambient temperatures for up to 16 hours did not affect OS concentrations. Simulated rainfall caused a 17% mean reduction in OS concentrations, but did not change pregnancy diagnoses.

CONCLUSIONS

Faecal OS concentrations >100 ng/g were indicative of pregnancy in Kaimanawa mares. For mares more than 150 days post-mating, OS concentrations <57 ng/g were indicative of non-pregnancy, while concentrations between 57 and 100 ng/g provided an inconclusive diagnosis. A single sample from each dung pile collected within 16 hours of defecation was sufficient to accurately diagnose pregnancy in mares 150-250 days post conception.

CLINICAL RELEVANCE

Measurement of OS concentrations in dung samples was a reliable and robust indicator of pregnancy status in feral mares 150-250 days post mating. This corresponds approximately to the period from May to August, given the seasonal breeding pattern in this population. This method of determining pregnancy status is suitable for field use in behavioural and demographic studies of wild horse populations.

Pregnancy status determination in mares using a rapid lateral flow test for measuring serum oestrone sulphate

AIMS

To develop a means of determining pregnancy status in horses based on measuring serum oestrone sulphate (OS) concentrations using a rapid lateral flow immunoassay, and to determine the assay's effectiveness using a visual end-point.

METHODS

Serum samples from mares >100 days post-mating (n=701) were assayed using a nitrocellulose membrane-based lateral flow immunoassay device. The device was developed using membrane-bound 1,3,5 (10)-estratrien-3-ol-17-one conjugated to bovine serum albumin as the capture antigen, and an OS-detection monoclonal antibody coupled to colloidal gold as the visible detection reagent. Concentrations of the coating antigen and OS monoclonal antibody were optimised so that the working range would allow pregnancy status to be determined from a visual end-point. The test was run by adding 0.1 ml serum to the sample well of a plastic cassette encasing the test membrane. As the serum migrated along the membrane, a test dot and control line were generated on it within 5-10 min. The intensity of the test dot was inversely proportional to the concentration of OS in the serum sample being tested. Results were compared with those from a validated OS enzyme immunoassay (EIA) and subsequent foaling or return to oestrus of the mares.

RESULTS

Serum samples with OS concentrations <10 ng/ml, indicative of non-pregnancy in mares >100 days post-mating, generated a test end-point consisting of a highly visible test dot and control line, whereas serum OS concentrations >50 ng/ml, indicative of pregnancy, generated a control line only. The test correctly identified 384/389 (98.7%) non-pregnant mares tested, and 303/312 (97.1%) pregnant mares tested that were >100 days post-mating. The lateral flow test devices were stable for at least 12 months when stored at 4 degrees C, sealed in aluminium pouches with desiccant.

CONCLUSION

This novel, rapid, easy-to-use, lateral flow immunoassay offers a practical alternative to traditional laboratory- based immunoassays for measuring serum OS concentrations in mares for determining their pregnancy status.

Transfusion thresholds and other strategies for guiding allogeneic red blood cell transfusion

BACKGROUND

Most clinical practice guidelines recommend restrictive red cell transfusion practices with the goal of minimising exposure to allogeneic blood (from an unrelated donor). The purpose of this review is to compare clinical outcomes in patients randomised to restrictive versus liberal transfusion thresholds (triggers).

OBJECTIVES

To examine the evidence on the effect of transfusion thresholds, on the use of allogeneic and/or autologous blood, and the evidence for any effect on clinical outcomes.

SEARCH STRATEGY

Trials were identified by: computer searches of OVID Medline (1966 to December 2000), Current Contents (1993 to Week 48 2000), and the Cochrane Controlled Trials Register (2000 Issue 4). References in identified trials and review articles were checked and authors contacted to identify any additional studies.

SELECTION CRITERIA

Controlled trials in which patients were randomised to an intervention group or to a control group. Trials were included where the intervention groups were assigned on the basis of a clear transfusion "trigger", described as a haemoglobin (Hb) or haematocrit (Hct) level below which a RBC transfusion was to be administered.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed using criteria proposed by Schulz et al. (1995). Relative risks of requiring allogeneic blood transfusion, transfused blood volumes and other clinical outcomes were pooled across trials using a random effects model.

MAIN RESULTS

Ten trials were identified that reported outcomes for a total of 1780 patients. Restrictive transfusion strategies reduced the risk of receiving a red blood cell (RBC) transfusion by a relative 42% (RR=0.58: 95%CI=0.47,0.71). This equates to an average absolute risk reduction (ARR) of 40% (95%CI=24% to 56%). The volume of RBCs transfused was reduced on average by 0.93 units (95%CI=0.36,1.5 units). However, heterogeneity between these trials was statistically significant (p<0.00001) for these outcomes. Mortality, rates of cardiac events, morbidity, and length of hospital stay were unaffected. Trials were of poor methodological quality.

REVIEWER'S CONCLUSIONS

The limited published evidence supports the use of restrictive transfusion triggers in patients who are free of serious cardiac disease. However, most of the data on clinical outcomes were generated by a single trial. The effects of conservative transfusion triggers on functional status, morbidity and mortality, particularly in patients with cardiac disease, need to be tested in further large clinical trials. In countries with inadequate screening of donor blood the data may constitute a stronger basis for avoiding transfusion with allogeneic red cells.

Factors influencing the uptake of technologies to minimize perioperative allogeneic blood transfusion: an interview study of national and institutional stakeholders

BACKGROUND

Alternatives to allogeneic blood transfusion exist and are being used to varying extents in Australian hospitals. Evidence on effectiveness and cost-effectiveness is generally inconclusive and provides a suboptimal basis for policy development.

AIM

To describe the influences on uptake of transfusion technologies as perceived by national and institutional stakeholders.

METHODS

Qualitative interview study. Interview transcripts were coded and analysed independently by at least two researchers. Participants had opportunity to comment on their transcript and the manuscript.

RESULTS

A total of 71 interviews were conducted with representatives of the media, specialist medical societies, consumer special interest groups, the Australian Red Cross Blood Service (ARCBS), government, private health insurers, technology manufacturers, prominent clinicians in the area and a sample of clinicians drawn from hospitals with variable use of blood-saving technologies. Technical advances and acceptance of lower transfusion triggers were identified as the main influences on the decrease in use of allogeneic blood transfusion in the past decade. Participants indicated that patients were most aware and supportive of autologous predonation. Participants noted that 'enthusiasts' were involved in educating about the need for alternatives, negotiating resourcing and maintaining the use of a technology. Funding mechanisms were seen as main barriers to use of alternatives. A discrepancy was noted in the rigour of evaluation and regulation of pharmaceuticals and devices/procedures.

CONCLUSIONS

Uptake of blood transfusion technologies by institutions was dependent mostly on funding arrangements and the presence of an 'enthusiast'. Critical review of the evidence for effectiveness or cost-effectiveness of these technologies was rarely mentioned. Opportunities exist for evidence-based medicine principles to play a greater role in policy decisions in this area.

Anti-fibrinolytic use for minimising perioperative allogeneic blood transfusion

BACKGROUND

Concerns regarding the safety of transfused blood have prompted re-consideration of the use of allogeneic (blood from an unrelated donor) blood transfusion.

OBJECTIVES

To assess the effects of the anti-fibrinolytic drugs aprotinin, tranexamic acid, and epsilon aminocaproic acid, on peri-operative red blood cell (RBC) transfusion.

SEARCH STRATEGY

We searched MEDLINE (to May 1998), EMBASE (to December 1997), web sites of international health technology assessment agencies (to May 1998). References in identified trials and review articles were checked and authors contacted to identify any additional studies.

SELECTION CRITERIA

Randomised controlled trials of anti-fibrinolytic drugs in adults scheduled for non-urgent surgery.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

We found 61 trials of aprotinin (7027 participants). Aprotinin reduced the rate of RBC transfusion by a relative 30% (RR=0.70: 95%CI: 0.64 to 0.76). The average absolute risk reduction (ARR) was 20.4% (95%CI: 15.6% to 25.3%). On average, aprotinin use saved 1.1 units of RBC (95%CI: 0.69 to 1.47) in those requiring transfusion. Aprotinin also significantly reduced the need for re-operation due to bleeding (RR=0.40: 95%CI: 0.25 to 0.66). We found 18 trials of tranexamic acid (TXA) (1,342 participants). TXA reduced the rate of RBC transfusion by a relative 34% (RR=0.66: 95%CI: 0.54 to 0.81). This represented an ARR of 17.2% (95%CI: 8.7% to 25.7%). TXA use resulted in a saving of 1.03 units of RBC (95%CI: 0.67 to 1.39) in those requiring transfusion. We found four trials of epsilon aminocaproic acid (EACA) (208 participants). EACA use resulted in a statistically non-significant reduction in RBC transfusion (RR=0.48: 95%CI: 0.19 to 1.19). Comparisons between agents Eight trials made 'head-to-head' comparisons between TXA and aprotinin. There was no significant difference between the two drugs in the rate of RBC transfusion: RR=1.21 (95%CI: 0.83 to 1.76) for TXA compared to aprotinin. Adverse Effects Aprotinin did not seem to be associated with an excess risk of adverse effects, including thrombo-embolic events (thrombosis RR=0.64: 95%CI: 0.31 to 1.31) and renal failure (RR=1.19: 95%CI: 0.79 to 1.79). Fewer data were available for TXA and EACA.

REVIEWER'S CONCLUSIONS

From this review it appears that aprotinin reduces the need for red cell transfusion, and the need for re-operation due to bleeding, without serious adverse effects. However, there was significant heterogeneity in trial outcomes, and some evidence of publication bias. Similar trends were seen with TXA and EACA, although the data were rather sparse. The poor evaluation of these latter drugs is unfortunate as results suggest they may be equally as effective as aprotinin, but are significantly cheaper. The evidence reviewed here supports the use of aprotinin in cardiac surgery. Further small trials of this drug are not warranted. Future trials should be large enough to compare the efficacy and cost-effectiveness of aprotinin with that of TXA and EACA.

Desmopressin for minimising perioperative allogeneic blood transfusion

BACKGROUND

Public concerns regarding the safety of transfused blood have prompted re-consideration of the use of allogeneic (from an unrelated donor) red blood cell (RBC) transfusion, and a range of techniques designed to minimise transfusion requirements.

OBJECTIVES

To examine the evidence for the efficacy of desmopressin (1-deamino-8-D-arginine-vasopressin), in reducing perioperative blood loss and the need for red cell transfusion in patients who do not have congenital bleeding disorders.

SEARCH STRATEGY

Articles were identified by: computer searches of OVID MEDLINE, EMBASE, and Current Contents (to August 2000) and web sites of international health technology assessment agencies (to May 1998). References in the identified trials and review articles were checked and authors contacted to identify additional studies.

SELECTION CRITERIA

Randomised controlled parallel group trials in which adult patients, scheduled for non-urgent surgery, were randomised to DDAVP, or to a control group, who did not receive the intervention.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed using criteria proposed by Schulz et al. (1995) and Jadad et al. (1996). The principal outcomes were: the number of patients exposed to red cells, and the amount of blood transfused. Other clinical outcomes are detailed in the review.

MAIN RESULTS

Fourteen trials of DDAVP (N=1034) reported data on the proportion of patients exposed to allogeneic RBC transfusion. In subjects treated with DDAVP the relative risk of exposure to peri-operative allogeneic blood transfusion was 0.98 (95%CI: 0.88 to 1.10) compared with control. In DDAVP-treated patients the relative risk of requiring re-operation due to bleeding was 0.56 (95%CI: 0.18 to 1.73). There was no statistically significant effect overall for mortality and non-fatal myocardial infarction in DDAVP-treated patients compared with control (RR=1.53: 95%CI: 0.58 to 4.05) and (RR=1.52: 95%CI: 0.67 to 3.49) respectively.

REVIEWER'S CONCLUSIONS

There is no convincing evidence that desmopressin minimises perioperative allogeneic RBC transfusion in patients who do not have congenital bleeding disorders. These data suggest that there is no benefit of using DDAVP as a means of minimising perioperative allogeneic RBC transfusion. This meta-analysis had 90% power to detect a relative risk reduction of at least 17% for receiving a red cell transfusion at alpha = 0.05 (two-sided).

Use of interventions to minimise perioperative allogeneic blood transfusion in Australia. A survey by the International Study of Perioperative Transfusion (ISPOT) Study Group

OBJECTIVE

To investigate use of interventions to minimise need for perioperative transfusion of allogeneic blood in surgical units in Australia.

DESIGN

Two questionnaire-based surveys of practice.

SETTING

All hospitals in Australia, 1996-1997.

PARTICIPANTS

Survey 1: all Australian hospitals that have at least 50 beds and undertake surgery; Survey 2: surgical units identified as using the interventions.

MAIN OUTCOME MEASURES

Reported rates of use of the various interventions (preoperative autologous donation, acute normovolaemic haemodilution [ANH], cell salvage, and drugs); use of guidelines; and perceptions about the appropriateness of current levels of use.

RESULTS

Survey 1 was returned by 349 of 400 hospitals (87%) and Survey 2 by 324 of 578 surgical units (56%). Preoperative autologous donation was most widely used (70% of hospitals), most commonly in units performing orthopaedic or vascular surgery (65% and 37%, respectively). Cell salvage and ANH were used by 27% and 24% of hospitals, respectively, most often in units performing cardiothoracic (40% and 44%, respectively) and vascular surgery (29% and 15%, respectively). These three interventions were used significantly more in private than in public hospitals (P < 0.05). Use of printed guidelines was uncommon. Respondents considered that autologous transfusion techniques should be used more widely because of their perceived efficacy and concerns about safety of allogeneic blood. Perceived barriers to greater use included lack of surgeon or physician interest, uncertain scheduling of surgery in public hospitals and cost (cell salvage). Drugs to minimise blood loss were used by fewer than 10% of hospitals.

CONCLUSIONS

Interventions to minimise the need for perioperative allogeneic blood transfusion (apart from drugs) are widely used in Australia. However, enthusiasm for intraoperative techniques of re-infusing autologous blood needs to be assessed against the evidence of their efficacy and cost-effectiveness.

Enzymeimmunoassay of oestrone sulphate concentrations in faeces for non-invasive pregnancy determination in mares

AIM

To determine the suitability of measuring faecal oestrone sulphate (OS) by enzymeimmunoassay as a means of determining pregnancy status in mares bred under New Zealand conditions.

METHODS

An antibody-coated microtitre plate-based enzymeimmunoassay was used to determine the concentration of OS in faecal and plasma samples obtained from pregnant and non-pregnant mares.

RESULTS

In non-pregnant mares, the mean faecal OS concentration was 34 ng/g, and the value three standard deviations above this was 80 ng/g. None of 427 faecal samples collected from 116 non-pregnant mares over a l-year period had an OS concentration >80 ng/g. Only five samples from three mares had an OS concentration >65 ng/g, the value two standard deviations above the mean non-pregnant value. Analysis of faecal OS concentrations in 532 faecal samples collected from 39 pregnant mares showed that as pregnancy progressed, an increasing proportion of faecal samples had OS concentrations >80 ng/g. None of the mares 150 days or more pregnant had faecal OS concentrations <50 ng/g, and 204/220 samples obtained from these mares had faecal OS concentrations >80 ng/g. Following foaling or foetal death, elevated faecal OS concentrations returned quickly to non-pregnant levels. The mean +/- s.e.m. plasma level of OS in five mares bled daily throughout one oestrous cycle was 1.7 +/- 0.2 ng/ml. Sixty-eight blood samples from pregnant mares bled up to five times between 92 days after mating and foaling all had plasma OS concentrations >30 ng/ml, with 64/68 being >50 ng/ml.

CONCLUSIONS

This study shows that measuring faecal OS concentrations by enzymeimmunoassay offers a convenient, accurate, non-invasive means of determining pregnancy status in mares from 150 days after mating onwards. Mares with faecal OS concentrations <50 ng/g can be considered not pregnant, while mares with faecal OS concentrations >80 ng/g can be considered pregnant. Those few mares returning a faecal OS concentration between 50 and 80 ng/g should be retested to obtain a conclusive result. Measuring plasma OS concentrations allows pregnancy status to be determined earlier (from 100 days after mating). Moreover, the discrimination between non-pregnant and pregnant levels is greater for OS in plasma than in faeces.

CLINICAL RELEVANCE

Measurement of OS concentrations in faeces provides an alternative and non-invasive means of determining pregnancy status in mares from 150 days after mating.

Evaluation of antibody- and antigen-coated enzymeimmunoassays for measuring oestrone-3-glucuronide concentrations in urine

A monoclonal antibody to oestrone-3-glucuronide (OG) was generated and incorporated into antigen- and antibody-coated competitive enzymeimmunoassays (EIAs) using OG-, 6-ketoestrone-6-O-carboxymethyl-oxime (OCMO) and oestrone-3-hemisuccinate (OHS) as the steroid coating antigens or 'tracers' in each format respectively. In the coated-antigen format, standard curves with the lowest mean values (pg/well) for sensitivity (1.1 +/- 0.1), mid-point (ED50; 8.2 +/- 0.7) and high-point (ED20; 31 +/- 2) were obtained using OCMO coupled to bovine serum albumin (BSA) as the coating antigen, and horseradish peroxidase (HRP) as the enzyme label coupled directly to the monoclonal antibody. Standard curves generated using enzyme-labelled OG, OCMO and OHS as 'tracers' in the antibody-coated EIA format were all similar, but had higher mean sensitivity, ED50 and ED20 values than those obtained in the optimal coated-antigen format. In both EIA formats alkaline phosphatase (AP) was found to be inferior to HRP as an enzyme label. Measurement of OG concentrations in early morning urine samples from women with natural, regular menstrual cycles, using the antigen-coated EIA, demonstrated the characteristic elevation in OG concentrations associated with the onset of the urinary LH surge. This technically straightforward and robust antigen-coated EIA may be of interest to laboratories with a requirement to measure OG concentrations in urine, or other biological samples.

Application of enzymeimmunoassay to measure oestrone sulphate concentrations in cow's milk during pregnancy

The characteristics of antigen- and antibody-coated enzymeimmunoassay (EIA) formats to measure oestrone sulphate (OS) were studied using a murine monoclonal antibody as the primary antibody. In an antigen-coated format the most sensitive EIA (9 fmol/well) was achieved using 6-ketoestrone-6-O-carboxymethyloxime (OCMO) coupled to bovine serum albumin (BSA), as the coating antigen, and horseradish peroxidase (HRP), as the enzyme label. In an antibody-coated format, comparable sensitivity could be achieved using HRP conjugated to either OCMO, oestrone-3-glucuronide (OG) or oestrone-3-hemisuccinate (OHS) as the steroid 'tracer'. In both the antigen- and antibody-coated formats replacing HRP with alkaline phosphatase (AP) markedly aggravated the assay sensitivity. The antigen-coated EIA format was used to measure OS concentrations in cow's milk directly without an initial defatting step, and a progressive increase in OS concentrations in milk as pregnancy progressed was observed. Median OS concentrations rose from 1.1 nmol/l at days 70-99 of pregnancy (n = 44) to 3.2 nmol/l at days 140-160 (n = 92). Oestrone sulphate concentrations in milk from non-pregnant cows (n = 51) ranged from non-detectable to 1.3 nmol/l with a median value of 0.4 nmol/l. Only 5% of cows 120 or more days pregnant had milk OS concentrations within the range of values found in milk from non-pregnant cows. Accurate discrimination of non-pregnant and pregnant cows can thus be achieved on the basis of OS concentrations in milk samples taken at least 120 days after mating/insemination. This EIA for OS may have a role in the dairy industry as an alternative non-invasive means of determining pregnancy status in cows.

A model for follicle selection and the determination of ovulation rate in the ewe

A model for folliculogenesis is proposed that is based as far as possible on a knowledge of physiological, rather than anatomical, changes taking place during follicle development. The model is therefore functional, rather than descriptive, and consists of five classes of follicles that have been defined by their dependency and sensitivity to gonadotrophins. These classes are: primordial, committed, gonadotrophin-responsive, gonadotrophin-dependent and ovulatory. The model is an attempt to encourage discussion and to promote the integration of morphological models of folliculogenesis with recent advances in the molecular endocrinology of the ovarian follicle. Two hypotheses for the mechanisms that determine ovulation rate are developed in light of the model. In the first, multiple ovulation results when the viability of gonadotropin-dependent follicles is enhanced. In the second, multiple ovulation is caused by increasing the number of gonadotrophin-responsive follicles available for further development; this results from the increasing rate of folliculogenesis and the throughput of follicles. The final section of this paper examines how these two hypothetical mechanisms, which are not mutually exclusive, appear to account for most of the known genetical and environmental effects on ovulation rate of sheep. In particular, the effects of nutrition, genotype, exogenous gonadotrophins, immunity to both oestrogens and androgens, and immunity to inhibin are discussed.

Inhibin production in vitro by granulosa cells from Booroola ewes which were either homozygous or non-carriers of a fecundity gene influencing their ovulation rate

The production of inhibin by granulosa cells was studied in vitro using cells from follicles of various sizes and health. Follicles were recovered on Days 10-13 of the oestrous cycle, from Booroola x Romney ewes which were homozygous (FF) carriers or non-carriers (++) of the fecundity (F) gene. Inhibin was measured using a bioassay based on the suppression of follicle-stimulating hormone (FSH) output by cultured pituitary cells from ovariectomized Romney ewes and, in some instances, for comparative purposes, by radioimmunoassay also. Geometric mean inhibin production by granulosa cells from nonatretic follicles increased with increasing follicle diameter, during the first 24 h of culture, for both genotypes. The geometric mean production of inhibin by cells from nonatretic 3-4.5 mm diameter FF follicles (the largest follicles found in FF ewes), was significantly higher (P less than 0.05) than that by cells from non-atretic 3-4.5 mm diameter ++ follicles, but similar to that of cells from non-atretic greater than or equal to 5 mm diameter ++ follicles. The production of oestradiol-17 beta by cells cultured in the presence of testosterone (1 microgram/ml) followed a pattern similar to cellular inhibin production. There was a positive linear correlation between inhibin and oestradiol-17 beta production during the first 24 h of culture, for both genotypes. In addition to acting as a substrate for oestradiol-17 beta synthesis, testosterone generally had a slight, stimulatory effect on inhibin production.(ABSTRACT TRUNCATED AT 250 WORDS)

Oocyte production and ovarian steroid concentrations of immature rats in response to some commercial gonadotrophin preparations

Four commercial gonadotrophin preparations, namely Folligon, F.S.H.-P., Folltropin and Ovagen, were examined for their effects on oocyte production and ovarian steroid concentrations in immature rats. The ratios of the FSH to LH concentrations of the preparations, determined by radioreceptor assays, were Folligon 5, F.S.H.-P. 18, Folltropin 49 and Ovagen 1090. Forty-eight hours after administering each gonadotrophin preparation to immature rats, ovulation was induced by injection of chorionic gonadotrophin. Twenty-four hours later, oocytes were recovered from the oviducts and counted. Oocytes were produced after injection of chorionic gonadotrophin following a single injection of Folligon (10-50 i.u.). However, no oocytes were produced in response to the other gonadotrophin preparations unless they were administered by continuous infusion (30-1000 micrograms day-1). When given by injection (Folligon) or infusion (others), the gonadotrophin preparations all promoted a dose-dependent increase in mean oocyte production, except at the highest doses when mean oocyte numbers either remained unchanged or declined significantly in the cases of Folligon and F.S.H.-P. The highest mean numbers of oocytes produced in response to Folltropin (48 +/- 9 oocytes, mean +/- s.e.m.) and Ovagen (47 +/- 7) were greater than those attained with Folligon (21 +/- 6) or F.S.H.-P. (31 +/- 5). Mean ovarian weights also increased in a dose-dependent fashion in response to each of the gonadotrophin preparations. Measurements of ovarian steroid concentrations 48 h after the onset of gonadotrophin treatment (i.e. immediately prior to ovulation induction with chorionic gonadotrophin) showed that the gonadotrophin preparations markedly influenced the ratios of ovarian oestradiol-17 beta and androgen (androstenedione plus testosterone) concentrations. At low doses the gonadotrophin preparations increased the ratio of oestradiol-17 beta to androgens, but at the highest doses, with the exception of Ovagen, the ratio was reduced relative to peak values. Co-infusion of ovine LH (NIADDK-oLH-25; 10-20 micrograms day-1) with Ovagen (250 micrograms day-1) or ovine FSH (10 micrograms day-1, NIADDK-oFSH-17), both low in LH content, increased the mean number of oocytes produced and also the ovarian oestradiol-17 beta:androgen concentration ratio. However, with 40 micrograms LH day-1, the oestradiol-17 beta:androgen ratio fell due to a continued increase in mean ovarian androgen concentrations and a decrease in mean ovarian oestradiol-17 beta concentration. The mean number of oocytes produced also fell significantly.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of oestradiol-17 beta, progesterone or bovine follicular fluid on the plasma concentrations of FSH and LH in ovariectomized Booroola ewes which were homozygous carriers or non-carriers of a fecundity gene

The plasma concentrations of FSH and LH were measured in ovariectomized Booroola FF and ++ ewes before and after treatment with subcutaneous implants of oestradiol-17 beta (0, 2 or 8 cm Silastic capsules; 5 ewes/genotype per dose) or progesterone (0, 1 or 3 Silastic envelopes; 5 ewes/genotype per dose) or subcutaneous injections of steroid-free bovine follicular fluid (bFF; 0, 0.5, 1.0, 2.5 or 5 ml; 4 ewes/genotype per dose). During the first 50 h after implantation of oestradiol or progesterone, or the first 24 h after bFF treatment, the FSH and LH concentrations in plasma were not different between the genotypes although there were significant effects of the steriods and bFF with respect to dose (P less than 0.05). At 6 days after steroid implantation, no gene-specific effects were noted for the plasma concentrations of FSH although significant effects of dose of oestradiol (P less than 0.01) but not progesterone were noted. Also at 6 days after steroid implantation, no gene-specific differences in the pulsatile patterns (i.e. peak frequency or amplitude) of plasma LH concentrations were noted although there were significant effects of steriod dose (P less than 0.05) on frequency and/or amplitude. It is concluded that the higher ovulation-rate in FF than ++ Booroola ewes is unlikely to be due to gene-specific differences in the sensitivity of the hypothalamic-pituitary axis to ovarian hormones.

Studies of the effectiveness of gonadotrophin-releasing hormone, steroids and follicular fluid in modulating ovine gonadotrophin output in vivo and in vitro

Gonadotrophin-releasing hormone (GnRH) readily stimulated LH output by sheep pituitary cells in vitro, and raised plasma LH concentrations in vivo in sheep, in a dose-dependent fashion. However, increases in FSH levels were only marginal by comparison. Dose-dependent decreases in sheep pituitary cell FSH output and in plasma FSH concentrations were caused by sheep follicular fluid and oestradiol-17 beta in vitro, and by bovine follicular fluid and oestradiol benzoate in vivo. In contrast, LH concentrations were only reduced slightly at the higher doses of these reagents. Cumulative suppressive effects of follicular fluid and oestradiol-17 beta (oestradiol benzoate) on FSH levels were observed both in vitro and in vivo. The transient positive feedback effect of oestradiol benzoate on FSH output negated the suppressive effect of bovine follicular fluid on plasma FSH concentrations. Progestagens, androgens and catechol oestrogens also suppressed mean FSH output in vitro, though not as effectively as oestradiol-17 beta. While only 1-5 pg/ml of oestradiol-17 beta was needed to suppress significantly mean FSH output in vitro, greater than 500 pg/ml of the other steroids was required. Seminal plasma inhibin-like peptide failed to suppress mean FSH output by cultured sheep pituitary cells at doses from 1 pg/ml to 500 ng/ml. At higher doses, both FSH and LH output was suppressed and this was accompanied by morphological deterioration of the cells. It is suggested that, to raise plasma FSH concentrations with a view to increasing ovulation rates in sheep, the development of means to reduce the negative feedback effects of steroids, notably oestradiol-17 beta, and inhibin on FSH secretion may be a more appropriate pharmacological strategy than increasing pituitary exposure to GnRH.

Binding characteristics of 125I-labelled human FSH to granulosa cells from Booroola ewes which were homozygous, heterozygous or non-carriers of a major gene(s) influencing their ovulation rate

At 37 degrees C 125I-labelled human (h) FSH (NIAMDD-hFSH-I-3) bound rapidly to granulosa cells from Booroola and Romney ewes with 50% maximum binding achieved after 3 min and equilibrium being reached within 45 min, irrespective of whether the cells were obtained from the FF, F+ or ++ Booroola genotypes or from Romney ewes. Binding of 125I-labelled FSH followed second order kinetics and there was no effect of follicle diameter (1-2.5 mm vs greater than or equal to 3 mm). Irrespective of breed, genotype or follicle size, the mean (+/- s.e.m.) calculated association rate constant, (ka) was 7.3 (+/- 0.8) x 10(5) litres mol-1 sec-1 (n = 12). Dissociation of receptor bound 125I-labelled hFSH was less than 5% after 30 min and low but variable (i.e. between 0 and 30%) after 2-6 h irrespective of breed, genotype or follicle size. No gene-specific differences were noted in binding specificity between F+ and ++ genotypes: studies were not performed with cells from FF ewes because of insufficient cells. The binding of 125I-labelled hFSH could be displaced with sheep FSH (NIH-FSH-S16; 10% cross-reaction) and FSH-P (2.5% cross-reaction) but other sheep pituitary hormones and hCG showed little or no cross-reaction (less than or equal to 0.1%). The calculated binding capacities (Bmax) and equilibrium dissociation constants (Kd) for 125I-labelled hFSH binding to granulosa cells did not differ between the Booroola genotypes or between Booroola or Romney follicles of different diameter (i.e. 1-2.5 mm; or greater than or equal to 3 mm). The overall mean +/- s.e.m. (n = 24) Bmax and Kd values were 16.7 +/- 0.8 fm/mg protein (i.e. approximately 800 available receptor binding sites/cell) and 1.1 +/- 0.1 nM respectively. Collectively, these findings suggest that the earlier maturation of follicles in FF or F+ ewes compared to ++ ewes is unlikely to be due to gene-specific differences in the FSH binding characteristics of the granulosa cells.

Differences in the plasma concentrations of FSH and LH in ovariectomized Booroola FF and ++ ewes

During 12 sampling days before ovariectomy the mean plasma FSH but not LH concentrations in FF ewes were higher (P less than 0.01) than those in ++ ewes (16 ewes/genotype). After ovariectomy increases in the concentrations of FSH and LH were noted for ewes of both genotypes within 3-4 h and the rates of increase of FSH and LH were 0.18 ng ml-1 h-1 and 0.09 ng ml-1 h-1 respectively for the first 15 h. From Days 1 to 12 after ovariectomy, the overall mean +/- s.e.m. concentrations for FSH in the FF and ++ ewes were 8.1 +/- 0.6 and 7.1 +/- 0.4 ng/ml respectively and for LH they were 2.7 +/- 0.3 and 2.1 +/- 0.2 ng/ml: these differences were not statistically significant (P = 0.09 for both FSH and LH; Student's t test). However, when the frequencies of high FSH or LH values after ovariectomy were compared with respect to genotype over time, significant F gene-specific differences were noted (P less than 0.01 for both FSH and LH; median test). In Exp. 2 another 21 ewes/genotype were blood sampled every 2nd day from Days 2 to 60 after ovariectomy and the plasma concentrations of FSH and LH were more frequently higher in FF than in ++ ewes (P less than 0.01 for FSH and LH). The F gene-specific differences in LH concentration, observed at 21-36 days after ovariectomy were due to higher mean LH amplitudes (P less than 0.025) but not LH peak frequency in FF than in ++ ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Consequences of increasing or decreasing plasma FSH concentrations during the preovulatory period in Romney ewes

Romney ewes were infused with ovine FSH (NIADDK-oFSH-16) for 48 h from the initiation of luteolysis with cloprostenol. Doses of 2.5 or 5 micrograms/h which partly or completely prevented the normal preovulatory decline in plasma FSH concentrations caused a significant increase in mean ovulation rates. Ovulation rates were not increased significantly if the FSH (5 micrograms/h) was infused for only 20 h starting from the initiation of luteolysis or 24 h later. Infusion of a less potent and relatively impure preparation of FSH (i.e. FSH-P) at 0.5 mg/h for 48 h after cloprostenol treatment also increased the mean ovulation rate significantly. However, if the FSH-P was given for only the first 24 h, or if the start of the infusion was delayed for more than 12 h, mean ovulation rates were not increased significantly. Infusion of LH (NIADDK-oLH-25, 5 micrograms/h) for 48 h from the initiation of luteolysis decreased the mean ovulation rate significantly. Administration of bovine follicular fluid to suppress plasma FSH concentrations below normal during the first 24 h after cloprostenol injection did not delay oestrus. However, oestrus was delayed by approximately 2 days if plasma FSH concentrations were reduced by bovine follicular fluid 24 h after the initiation of luteolysis. As ovulation rate increased, the mean weight of individual corpora lutea of each ewe decreased. In ewes with a single ovulation, most corpora lutea weighed greater than 600 mg, but as the ovulation rate increased the proportion of corpora lutea present weighing less than 400 mg rose steadily.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in gonadotrophin-stimulated cyclic AMP production by granulosa cells from booroola x merino ewes which were homozygous, heterozygous or non-carriers of a fecundity gene influencing their ovulation rate

Granulosa cells from follicles of different sizes from Booroola x Merino ewes which were homozygous (FF), heterozygous (F+) or non-carriers(++) of a fecundity gene were obtained 0-48 h after cloprostenol injection on Day 10 of the oestrous cycle. The highest mean amounts of cAMP produced by the cells did not differ between the genotypes. However, in the ++ ewes it was attained by cells from follicles greater than or equal to 5 mm in diameter, whereas in F+ and FF ewes it was attained by cells from follicles 3-4.5 mm in diameter. Cells from 1-2.5-mm diameter follicles of FF ewes were more sensitive to FSH and LH than were corresponding cells from F+ or ++ ewes. Granulosa cells from greater than or equal to 5 mm diameter follicles of ++ ewes 12-24 h after injection of cloprostenol had a lower mean response to FSH and LH than did cells obtained 0-6 or 36-48 h after cloprostenol. No such effect of time was evident for cells from any size of follicles obtained from F+ or FF ewes. In 1-2.5-mm diameter follicles, the mean aromatase activity of granulosa cells from ++ and F+ ewes was similar, but significantly lower than that of cells from FF ewes. In 3-4.5 mm diameter follicles, the mean aromatase activity of cells from F+ and FF ewes was similar, and significantly higher than that of cells from ++ ewes. For all 3 genotypes, there was a significant positive relationship between FSH or LH stimulation of granulosa cell cAMP production and cellular aromatase activity.

Differences in gonadotrophin concentrations and pituitary responsiveness to GnRH between Booroola ewes which were homozygous (FF), heterozygous (F+) and non-carriers (++) of a major gene influencing their ovulation rate

The mean plasma concentrations of FSH and LH were significantly higher in FF ewes than in ++ ewes with those F+ animals being consistently in between. These gene-specific differences were found during anoestrus, the luteal phase and during a cloprostenol-induced follicular phase, suggesting that the ovaries of ewes with the F-gene are more often exposed to elevated concentrations of FSH and LH than are the ovaries of ewes without the gene. The gene-specific differences in LH secretion arose because the mean LH amplitudes were 2-3 times greater in FF compared to ++ ewes with the LH amplitudes for F+ ewes being in between. The LH pulse frequencies were similar. In these studies the pulsatile nature of FSH secretion was not defined. The pituitary contents of LH during the luteal phase, were similar in all genotypes whereas for FSH they were significantly higher in the F-gene carriers compared to ++ ewes. The pituitary sensitivity to exogenous GnRH (0.1, 0.5 and 25 micrograms i.v.) was related to genotype. Overall the LH responses to GnRH were lower in FF ewes than in ++ ewes with the results for the F+ ewes being in between. The FSH responses to all GnRH doses in the FF genotype were minimal (i.e. less than 2-fold). In the other genotypes a greater than 2-fold response was noted only at the highest GnRH dose (i.e. 25 micrograms). Treatment of FF and F+ but not ++ ewes with GnRH eventually led to a reduced FSH output, suggesting that the pituitary responses to endogenous GnRH were being down-regulated in the F-gene carriers whereas this was not the case in the non-carriers. Collectively these data confirm that peripheral plasma and the pituitary together with the ovary are compartments in which F-gene differences can be observed. In conclusion, these findings raise the possibility that F-gene-specific differences may also extend to the hypothalamus and/or other regions of the brain.

Gonadotrophins, fecundity genes and ovarian follicular function

The Booroola Merino is a sheep breed having a major gene(s) (F) influencing its ovulation-rate. Homozygous (FF), heterozygous (F+) and non-carriers (++) of the gene have ovulation-rates of greater than or equal to 5, 3 or 4 and 1 or 2 respectively with the durations of each oestrous cycle and oestrous behaviour being similar in all genotypes. Although the principal site(s) of gene expression are obscure, FF genotypes have mean plasma concentrations of FSH and LH which are higher than in the F+ ewes, which in turn are higher than in the ++ animals. Thus, the FF and F+ animals provide a unique system in which to examine ovarian function under continual exposure to elevated gonadotrophin concentrations. At the ovarian level, F gene-specific differences in follicular development and function were noted. In small follicles (0.1-1.0 mm dia.), the basal levels of cAMP and the in vitro synthesis of cAMP, progesterone, androstenedione and oestradiol-17 beta in response to LH and FSH were significantly influenced by genotype (FF greater than F+ greater than ++; P less than 0.05). In larger follicles (1-4.5 mm dia.) the granulosa cells from FF and F+ ewes were more responsive to FSH and/or LH than in ++ ewes with respect to cAMP synthesis and they also had higher levels of aromatase activity. In vivo, the ovarian secretion-rates of oestradiol from greater than or equal to 5 ("oestrogenic") follicles in FF ewes, 3-4 such follicles in F+ ewes, and 1-2 such follicles in ++ animals during the follicular phase were similar. In FF and F+ ewes, the preovulatory follicles ovulated at a smaller diameter (i.e. 3-5 mm) than in ++ ewes (greater than 5 mm diam.) and also produced smaller corpora lutea. Thus, after continual exposure to elevated levels of gonadotrophins, follicles may synthesize steroid and mature at smaller diameters compared to those exposed to normal levels of FSH and LH.

Influence of follicular health on the steroidogenic and morphological characteristics of bovine granulosa cells in vitro

In 24-h cultures, steroid production by cells from non-atretic follicles increased with increasing follicular diameter. Cells from atretic follicles, of all sizes, produced low amounts of oestradiol-17 beta, but very high amounts of progesterone, relative to cells from non-atretic follicles. Increasing the culture period to 72 h caused little change in daily progesterone and oestradiol-17 beta production by granulosa cells from atretic follicles. In contrast, in cells from non-atretic follicles, daily progesterone production increased and daily oestradiol-17 beta production decreased to the levels observed with cells from atretic follicles. Dibutyryl cyclic AMP (1.0 mM) significantly stimulated progesterone production by cells from atretic, but not from non-atretic, follicles. Testosterone (1 microgram/ml) had no effect on progesterone production by cells from atretic follicles, while oestradiol-17 beta, oestrone, testosterone, androstenedione and 5 alpha-dihydro-testosterone (0-1000 ng/ml) each significantly suppressed progesterone production by cells from non-atretic follicles in a dose-dependent manner. Morphometric analysis revealed few subcellular differences between cells from non-atretic and atretic follicles. Mean cell volume was significantly higher for cells from atretic compared to non-atretic follicles, but the mean volumes of the major subcellular components were not influenced by follicle health. The mean surface area of the plasma and nuclear membrane, and granular endoplasmic reticulum was also significantly higher in cells from atretic compared to non-atretic follicles.

125I-labelled hCG binding characteristics in theca interna and other tissues from Romney ewes and from Booroola x Romney ewes with and without a major gene influencing their ovulation rate

Specific receptors for 125I-labelled hCG in ovarian follicle wall were located in the theca interna. No specific binding of 125I-labelled hCG was found in theca externa and/or stromal tissue. The kinetics of 125I-labelled hCG binding to theca interna followed second order kinetics with calculated association rate constants (ka +/- s.d.) of 1.57 +/- 0.16 X 10(6) and 0.57 +/- 0.02 X 10(6) litres mol-1 sec-1 at 37 degrees C and 22 degrees C respectively. Dissociation of specifically bound 125I-labelled hCG from theca interna was minimal at 37 degrees C and 22 degrees C. The binding of 125I-labelled hCG to theca interna could be displaced with PMSG, FSH-P and sheep LH but other sheep pituitary hormones and LH-releasing hormone showed little or no cross-reaction. The calculated binding capacities (Bmax) and equilibrium dissociation constants (Kd) for 125I-labelled hCG binding to theca interna did not differ between Romney ewes and Booroola x Romney ewes with and without the fecundity (F) gene on Day 10 of the oestrous cycle, during anoestrus or at 36 h after an injection of cloprostenol on Day 10 of the oestrous cycle. When the data for Day 10 and anoestrus were pooled, the median (range) Bmax and Kd values in non-atretic follicles (greater than or equal to 3 mm diameter) were 12.0 (5.1-23.5) fmol/mg protein and 0.10 (0.05-0.16) nM respectively. At 36 h after cloprostenol injection the respective median (range) Bmax and Kd values in non-atretic follicles (greater than or equal to 3 mm diam.) increased to 46.9 (28.4-70.3) fmol/mg protein and 0.23 (0.13-0.65) nM respectively. In corpora lutea the hCG binding characteristics were similar in all the above breeds/genotypes. On Day 10 of the cycle, the mean Bmax but not the mean Kd value was significantly higher (P less than 0.01) than the corresponding value at 36 h after cloprostenol injection. In granulosa cells, from follicles of greater than or equal to 5 mm diameter of Romney and Booroola x Romney (++) ewes and from follicles of greater than or equal to 3 mm diameter of Booroola x Romney (F+) ewes, the hCG binding characteristics were similar. In granulosa cells from smaller sized follicles from the above breeds/genotypes, no specific hCG binding was noted.

Differences in ovarian activity between booroola X merino ewes which were homozygous, heterozygous and non-carriers of a major gene influencing their ovulation rate

Differences in the function and composition of individual ovarian follicles were noted in Booroola Merino ewes which had previously been segregated on at least one ovulation rate record of greater than 5 (FF ewes, N = 15), 3-4 (F+ ewes, N = 18) or less than 3 (++ ewes, N = 18). Follicles in FF and F+ ewes produced oestradiol and reached maturity at a smaller diameter than in ++ ewes. In FF (N = 3), F+ (N = 3) and ++ (N = 3) ewes, the respective mean +/- s.e.m. diameters for the presumptive preovulatory follicles were 3.4 +/- 0.3, 4.1 +/- 0.2 and 6.8 +/- 0.3 mm and in each of these follicles the respective mean +/- s.e.m. numbers of granulosa cells (X 10(6)) were 1.8 +/- 0.3, 2.2 +/- 0.3 and 6.6 +/- 0.3. During a cloprostenol-induced follicular phase, the oestradiol secretion rates from FF ewes with 4.8 +/- 0.4 'oestrogenic' follicles, F+ ewes with 3.2 +/- 0.2 'oestrogenic' follicles and ++ ewes with 1.5 +/- 0.02 'oestrogenic' follicles were not significantly different from one another. Moreover, the mean total numbers of granulosa cells from the 'oestrogenic' follicles from each genotype were identical, namely 5.4 X 10(6) cells. Irrespective of genotype the mean weight of each corpus luteum was inversely correlated to the ovulation rate (R = 0.91, P less than 0.001). Collectively, these findings support the notion that the maturation of greater than or equal to 5 follicles in FF ewes and 3-4 follicles in F+ ewes may each be necessary to provide a follicular-cell mass capable of producing the same quantity of oestradiol as that from 1-2 preovulatory follicles in ++ ewes.

Use of bovine follicular fluid to increase ovulation rate or prevent ovulation in sheep

Romney ewes were injected intramuscularly once or twice daily for 3 days with 0, 0.1, 0.5, 1 or 5 ml of bovine follicular fluid (bFF) treated with dextran-coated charcoal, starting immediately after injection of cloprostenol to initiate luteolysis on Day 10 of the oestrous cycle. There was a dose-related suppression of plasma concentrations of FSH, but not LH, during the treatment period. On stopping the bFF treatment, plasma FSH concentrations 'rebounded' to levels up to 3-fold higher than pretreatment values. The mean time to the onset of oestrus was also increased in a dose-related manner by up to 11 days. The mean ovulation rates of ewes receiving 1.0 ml bFF twice daily (1.9 +/- 0.2 ovulations/ewe, mean +/- s.e.m. for N = 34) or 5.0 ml once daily (2.0 +/- 0.2 ovulations/ewe, N = 25) were significantly higher than that of control ewes (1.4 +/- 0.1 ovulations/ewe, N = 35). Comparison of the ovaries of ewes treated with bFF for 24 or 48 h with the ovaries of control ewes revealed no differences in the number or size distribution of antral follicles. However, the large follicles (greater than or equal to 5 mm diam.) of bFF-treated ewes had lower concentrations of oestradiol-17 beta in follicular fluid, contained fewer granulosa cells and the granulosa cells had a reduced capacity to aromatize testosterone to oestradiol-17 beta and produce cyclic AMP when challenged with FSH or LH. No significant effects of bFF treatment were observed in small (1-2.5 mm diam.) or medium (3-4.5 mm diam.) sized follicles. Ewes receiving 5 ml bFF once daily for 27 days, from the onset of luteolysis, were rendered infertile during this treatment period. Oestrus was not observed and ovulation did not occur. Median concentrations of plasma FSH fell to 20% of pretreatment values within 2 days. Thereafter they gradually rose over the next 8 days to reach 60% of pretreatment values where they remained for the rest of the 27-day treatment period. Median concentrations of plasma LH increased during the treatment period to levels up to 6-fold higher than pretreatment values. When bFF treatment was stopped, plasma concentrations of FSH and LH quickly returned to control levels, and oestrus was observed within 2 weeks. The ewes were mated at this first oestrus and each subsequently delivered a single lamb.

FSH influences follicle viability, oestradiol biosynthesis and ovulation rate in Romney ewes

Injection of steroid-free bovine follicular fluid (bFF; 2 X 5 ml s.c. 12 h apart) into anoestrous ewes lowered plasma FSH concentrations by 70% and after 24 h had significantly (P less than 0.01) reduced the number of non-atretic follicles (greater than or equal to 1 mm diam.) without influencing the total number of follicles (greater than 1 mm diam.) compared to untreated controls. Hourly injections of FSH (10 micrograms i.v. NIH-FSH-S12) for 24 h did not influence the number of non-atretic follicles but did negate the inhibitory effects of bFF on follicular viability. Hourly injections of FSH (50 micrograms i.v., NIH-FSH-S12) + bFF treatment for 24 h significantly increased the total number of non-atretic follicles, and particularly the number of medium to large non-atretic follicles (greater than 3 mm diam.) compared to the untreated controls (both P less than 0.01). The 10 micrograms FSH regimen (without bFF) significantly increased aromatase activity in granulosa cells from large (greater than or equal to 5 mm diam.; P less than 0.01) but not medium (3-4.5 mm diam.) or small (1-2.5 mm diam.) follicles compared to controls. The 10 micrograms FSH + bFF regimen had no effect on granulosa-cell aromatase activity compared to the controls. However, the 50 micrograms FSH plus bFF regimen increased the aromatase activity of granulosa cells from large, medium and small non-atretic follicles 2.6-, 8.3- and greater than or equal to 11-fold respectively compared to that in the control cells. Ewes (N = 11) that ovulated 2 follicles had significantly higher plasma FSH concentrations from 48 to 24 h and 24 to 0 h before the onset of a cloprostenol-induced follicular phase (both P less than 0.01) than in the ewes (N = 12) that subsequently ovulated one follicle. Hourly FSH treatment (1.6 micrograms i.v., NIAMDD-FSH-S15) for 24 h but not for any 6 h intervals between 48 and 24 h or 24 and 0 h before a cloprostenol-induced luteolysis also resulted in significant increases (P less than 0.05) in the number of ewes with 2 ovulations.(ABSTRACT TRUNCATED AT 400 WORDS)

Gonadotrophin-stimulated cyclic AMP production by granulosa cells from Booroola x Romney ewes with and without a fecundity gene

The influence of follicular size and health on FSH and LH stimulation of cAMP production by granulosa cells in vitro was studied in cells from Booroola X Romney ewes, with (F+) and without (++) a fecundity gene. The granulosa cells were obtained 0-48 h after the initiation of luteolysis on Day 10 of the oestrous cycle by cloprostenol. The highest mean amounts of cAMP produced by granulosa cells challenged with FSH or LH were not significantly different between the genotypes. However, they were achieved using granulosa cells from follicles greater than 3-4 mm in diameter in F+ ewes but from follicles greater than 4 mm in diameter in ++ ewes. Follicles may thus attain ovulatory maturity at a smaller diameter in F+ ewes than in ++ ewes. Granulosa cells from most atretic follicles gave a poor cAMP response to FSH or LH, compared to cells from non-atretic follicles. Granulosa cell responsiveness to FSH was independent of the time the cells were recovered after cloprostenol treatment in F+ ewes, but not in ++ ewes. Cellular responsiveness to LH was independent of time for sheep of both genotypes. There was a significant positive relationship for sheep of both genotypes between the level of aromatase activity in granulosa cells and cellular responsiveness to FSH and LH.

Influence of follicular atresia on LH-induced cAMP and steroid synthesis by bovine thecae interna

The aim of the present study was to examine the interrelationships between the luteinizing hormone (LH) receptor, the LH-induced changes in adenosine cyclic 3', 5'-monophosphate (cAMP) and steroid synthesis in theca interna tissue of large antral follicles (greater than or equal to 8 mm diameter) from oestrous cycling cows. Three distinct types of theca interna were identified (types I, II and III), all of which contained an LH receptor: type I was capable of secreting increased amounts of cAMP dehydroepiandrosterone, androstenedione and testosterone when exposed to LH; type II was capable of secreting increased amounts of cAMP and progesterone but not the androgens when exposed to LH; type III was incapable of cAMP or steroid synthesis when exposed to LH. Follicles with type I thecae contained: a full complement of granulosa cells; high intrafollicular concentrations of oestradiol; and granulosa cells with a high capacity to metabolise testosterone to oestradiol. These follicles were considered to be non-atretic structures. Follicles with types III thecae contained: fewer granulosa cells; low intrafollicular concentrations of oestradiol; and granulosa cells with a low capacity to metabolise testosterone to oestradiol. Moreover, follicles with type III thecae contained the highest concentrations of progesterone and the lowest concentrations of androstenedione and testosterone. These follicles were considered to be severely atretic structures. Follicles with type II thecae contained granulosa cell populations and progesterone, and androgen concentrations which were intermediate between those with thecae of types I and III. These follicles were considered to be at an intermediate stage of atresia.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovarian activity in Booroola X Romney ewes which have a major gene influencing their ovulation rate

A marked difference in both the function and composition of individual ovarian follicles was noted in Booroola X Romney ewes (6-7 years of age) which had previously been segregated on at least one ovulation rate record of 3-4 (F + ewes, N = 21) or less than 3 (++ ewes, N = 21). Follicles in F + ewes produced oestradiol and reached maturity at a smaller diameter than in ++ ewes. In F+ ewes (N = 3), the presumptive preovulatory follicles were 4.4 +/- 0.5 (s.e.m.) mm in diameter and contained 2.1 +/- 0.3 X 10(6) (s.e.m.) granulosa cells, whereas in ++ ewes (N = 3), such follicles were 7.3 +/- 0.3 mm in diameter and contained 6.5 +/- 0.8 X 10(6) cells. During a prostaglandin (PG)-induced follicular phase, the secretion rate of oestradiol from ovaries containing 3 presumptive preovulatory follicles in F + ewes was similar to that from ovaries with only one such follicle in ++ ewes. We suggest that the putative 'gene effect' in F + ewes is manifested during early follicular development and that it may be mediated via an enhanced sensitivity of granulosa cells to pituitary hormones. As a consequence, the development of 3 preovulatory follicles in F + ewes may be necessary to provide a cell mass capable of producing the same quantity of oestradiol as that from one preovulatory follicle in ++ ewes.

Effect of follicular atresia on inhibin production by bovine granulosa cells in vitro and inhibin concentrations in the follicular fluid

The ability of bovine granulosa cells to produce inhibin and to synthesize oestradiol-17 beta increased with increasing follicle size in healthy but not atretic follicles. Granulosa cells from small (less than or equal to 5 mm diam.) healthy follicles were indistinguishable from cells of atretic follicles in terms of their ability to produce inhibin and to aromatize androgen. However, granulosa cells from healthy and atretic follicles, irrespective of size, differed markedly in their morphological appearance after culture for 24 h. Testosterone (1 microgram/ml) stimulated inhibin production by granulosa cells from healthy and atretic follicles while FSH (100 ng/ml) stimulated inhibin production by granulosa cells from healthy follicles only. The relative ability of granulosa cells from different sizes of healthy and atretic follicles to produce inhibin in vitro was reflected in inhibin concentrations in follicular fluid. There was a significant positive correlation between inhibin concentration in follicular fluid and the number of granulosa cells per follicle. There was also a significant positive correlation between follicular diameter and inhibin concentration in follicular fluid, but only in healthy follicles. These findings show that both follicular size and atresia influence follicular inhibin production.

Increase in ovulation rate after active immunization of sheep with inhibin partially purified from bovine follicular fluid

Four Romney ewes were actively immunized with a partially purified preparation of inhibin derived from bovine follicular fluid and their ovulation rates in four successive oestrous cycles were compared with those of four ewes receiving adjuvant alone. The ovulation rates of the ewes immunized with the inhibin preparation were significantly higher than those of the control ewes (2.06 +/- 0.16 (S.E.M.) vs 1.31 +/- 0.06 ovulations/ewe, n = 4). Plasma concentrations of FSH and LH, measured in blood samples taken three times a week for 11 weeks, during which time each ewe was immunized three times, were not significantly different between the two treatment groups. These results suggest that active immunization with inhibin-enriched follicular fluid may be a potential means of increasing fecundity in sheep.

Some aspects of thecal and granulosa cell function during follicular development in the bovine ovary

The patterns of ovarian follicular development and the steroidogenic properties of individual follicles (greater than or equal to 2 mm diam.) were assessed in Angus cows from Day - 5 until Day + 1 of the oestrous cycle (oestrus = Day 0). Individual follicles were judged to be healthy or atretic using a new classification system incorporating assessments of thecal vascularity and colour, the number of granulosa cells, the presence or absence of debris in follicular fluid and the status of the oocyte. The results suggest that the theca interna of small antral follicles (less than 5 mm diam.) responds to LH and synthesizes androstenedione before the granulosa cells develop an appreciable ability to metabolize androgen to oestrogen. Regardless of follicle size, the output of thecal androstenedione per unit mass of tissue remained unchanged in healthy but not in atretic follicles. On a per cell basis, aromatase activity increased in granulosa cells from healthy but not from atretic follicles with increasing follicle size. Peak levels of aromatizing activity were consistently observed in dominant oestrogen-enriched follicles on Day 0 although similar activity was also observed in some healthy follicles (greater than or equal to 8 mm diam.) on other days of the cycle. Early atresia in bovine follicles was characterized by an absence or lowering of aromatase activity in granulosa cells which always preceded any reduction in the thecal steroidogenic response to LH. It was estimated that between 20 and 60 antral follicles (greater than or equal to 2 mm diam.) per cow may respond to LH by synthesizing androgen whereas only 1-3 follicles (greater than 5 mm diam.) have granulosa cells capable of metabolizing androstenedione or testosterone to oestradiol.

Seasonal differences in ovarian activity in cows

The plasma concentrations of LH and prolactin and various parameters of ovarian function were examined in cows on known days of the oestrous cycle during May and June (autumn and winter) and during October (spring). Luteinizing hormone peak frequency and plasma prolactin concentrations were significantly higher in October than during the May-June period (LH, P less than 0.05; prolactin, P less than 0.01). The mean diameters of large healthy follicles (greater than or equal to 8 mm diameter) and the dominant oestrogen-secreting follicles were significantly larger (P less than 0.01 for both follicle types) and each follicle contained more granulosa cells (both P less than 0.01) in May-June than in October. The LH responsiveness of theca interna with respect to androstenedione production and the levels of aromatase activity in granulosa cells did not differ with time of year. The corpora lutea were heavier (P less than 0.05) and secreted more progesterone (P less than 0.01) in May-June than in October. It is concluded that seasonal differences in ovarian activity exist in cows and that these differences are probably the consequence of seasonal differences in gonadotrophin secretion.

[125I]hCG binding to bovine thecal tissue from healthy and atretic antral follicles

[125I]hCG binding to thecal tissue from healthy bovine follicles was examined and compared to [125I]hCG binding to other bovine ovarian tissues. [125I]hCG bound specifically to theca interna but not to theca externa. Binding to theca interna was a time- and temperature-dependent process, the rate of association obeying second-order kinetics with calculated rate constants of 1.97 +/- 0.13 X 10(5) and 0.85 +/- 0.04 X 10(5) 1 M-1 sec-1 at 37 and 22 degrees C, respectively. The dissociation of [125I]hCG from theca interna was a slow biphasic process with only 40% of specifically bound [125I]hCG being liberated after 8 h at 37 degrees C. Unlabelled hCG and LH, but not FSH, prolactin, GH, TSH or GnRH, inhibited [125I]hCG binding to theca interna. The specific binding of [125I]hCG to theca interna was saturable and equilibrium binding data produced a linear plot when fitted to the Woolf equation. The equilibrium dissociation constant (Kd) and maximum binding capacity (Bmax) calculated from Woolf plots were 0.21 +/- 0.02 nM (mean +/- SEM) and 34 +/- 4 fmoles/mg protein, respectively. Constants for [125I]hCG binding to granulosa cells and luteal tissue, respectively, were 0.29 +/- 0.02 and 0.31 +/- 0.04 nM for the Kd values and 32 +/- 6 and 116 +/- 13 fmoles/mg protein for the Bmax values. [125I]hCG binding constants for small (less than 8 mm dia.) and large (greater than or equal to 8 mm dia.) follicles (healthy or atretic) were not significantly different. In addition, there was no difference in the [125I]hCG binding constants of healthy and atretic follicles (large or small).(ABSTRACT TRUNCATED AT 250 WORDS)

Steroidogenesis by bovine theca interna in an in vitro perifusion system

The aims of these studies were: to examine the steroidogenic responses of perifused bovine theca interna to varying flow rates of media and varying amounts of luteinizing hormone (LH), and to compare the steroidogenic outputs of theca interna from follicles of differing size and health with those of other ovarian tissues. The results showed that the outputs of androstenedione by thecae interna from healthy but not atretic follicles, with or without stimulation by LH, were amplified by the flow rate of media. Steroidogenesis by perifused theca interna was also influenced by the mass and concentration of LH as well as by the duration of exposure to LH. When expressed on a per unit mass basis, the outputs of androstenedione from LH-primed thecae interna from small (2-5.5 mm diameter), medium (6-9.5 mm diameter) and large (greater than or equal to 10 mm diameter) healthy follicles were comparable. But when the above data were expressed per total mass of theca interna, the androstenedione output increased significantly with increasing follicular diameter (P less than 0.01). Under the experimental conditions employed, the fraction of androstenedione produced by thecal tissue as a percentage of the total output of progesterone, androstenedione, testosterone and estradiol was 82%, whereas the progesterone, testosterone and estradiol fractions were 1%, 15% and 2%, respectively. By contrast, the granulosa cell output of progesterone, androstenedione, testosterone and estradiol were 79%, 0%, 0% and 21%, respectively. When this cell type was supplied with saturating amounts of androstenedione, it contributed greater than or equal to 90% of the total quantity of estradiol by the two cell types in isolation.

Changes in gonadotrophin secretion and ovarian antral follicular activity in seasonally breeding sheep throughout the year

Overall, significantly more antral follicles greater than or equal to 1 mm diameter were present in Romney ewes during anoestrus than in the breeding season (anoestrus, 35 +/- 3 (mean +/- s.e.m.) follicles per ewe, 23 sheep; Day 9-10 of oestrous cycle, 24 +/- 1 follicles per ewe, 22 sheep; P less than 0.01), although the mean numbers of preovulatory-sized follicles (greater than or equal to 5 mm diam.) were similar (anoestrus, 1.3 +/- 0.2 per ewe; oestrous cycle, 1.0 +/- 0.1 per ewe). The ability of ovarian follicles to synthesize oestradiol did not differ between anoestrus and the breeding season as assessed from the levels of extant aromatase enzyme activity in granulosa cells and steroid concentrations in follicular fluid. Although the mean plasma concentration of LH did not differ between anoestrus and the luteal phase of the breeding season, the pattern of LH secretion differed markedly; on Day 9-10 of the oestrous cycle there were significantly more (P less than 0.001) high-amplitude LH peaks (i.e. greater than or equal to 1 ng/ml) in plasma and significantly fewer (P less than 0.001) low amplitude peaks (less than 1 ng/ml) than in anoestrous ewes. Moreover, the mean concentrations of FSH and prolactin were significantly lower during the luteal phase of the cycle than during anoestrus (FSH, P less than 0.05, prolactin, P less than 0.001). It is concluded that, in Romney ewes, the levels of antral follicular activity change throughout the year in synchrony with the circannual patterns of prolactin and day-length. Also, these data support the notion that anovulation during seasonal anoestrus is due to a reduced frequency of high-amplitude LH discharges from the pituitary gland.

Effect of infusion of PGI-2, 6-keto-PGF-1 alpha and PGF-2 alpha on luteal function in the pregnant rat

Prostacyclin (PGI-2), 6-keto-PGF-1 alpha and PGF-2 alpha were infused continuously for 6 h into the dorsal aorta of rats 8 days pregnant. PGF-2 alpha (10 micrograms/h) significantly reduced plasma progesterone concentrations by 66% and luteal tissue concentrations of pregnenolone and progesterone by 78% and 95% respectively. Plasma concentrations of 20 alpha-dihydroprogesterone remained unchanged whilst luteal tissue concentrations rose 2-fold. Plasma progesterone concentrations were significantly reduced to 50% by PGI-2 (10 micrograms/h) but were unaffected by 6-keto-PGF-1 alpha (10 or 100 micrograms/h). Neither PGI-2 (10 micrograms/h) nor 6-keto PGF-1 alpha (10 or 100 micrograms/h) had any significant effect on plasma concentrations of 20 alpha-dihydroprogesterone or on luteal tissue concentrations of pregnenolone, progesterone or 20 alpha-dihydroprogesterone. Arterial blood pressure was unaffected by PGF-2 alpha and 6-keto-PGF-1 alpha, but was significantly reduced by PGI-2 at infusion rates greater than or equal to 60 micrograms/h.

Inhibin production by bovine ovarian tissues in vitro and its regulation by androgens

No detectable amounts of inhibin were produced by cultured ovarian stroma or luteal tissue. Follicular tissue produced inhibin in vitro and removal of the granulosa cells from the follicle wall caused inhibin production to fall by 80%. Granulosa cells alone had the greatest ability of any ovarian cell type to produce inhibin in vitro, and are probably the major site of follicular inhibin production. Cyproterone acetate at concentrations of 35 and 350 microM inhibited basal and testosterone (3.5 microM)-stimulated inhibin production by cultured intact follicle wall and granulosa cells. In addition, each concentration of cyproterone acetate inhibited progesterone but not oestradiol-17 beta production by the follicle wall and granulosa cell cultures. The synthetic, non-aromatizable androgens, methylestrenolone and mesterolone, at concentrations of 5 and 25 microM, mimicked the effect of testosterone and stimulated granulosa cell inhibin production, methylestrenolone being the more potent. These findings provide further evidence that androgens regulate follicular inhibin and progesterone production and that these may be receptor-mediated processes, and suggest that inhibin production may be a general property of androgenic compounds. Preliminary examination of the physicochemical characteristics of inhibin indicated that the inhibin activity of bovine granulosa cell culture medium was (a) retained by an Amicon XM100A filter with a nominal molecular weight cut-off point of 100 000; and (b) destroyed by heating to 80 degrees C for 30 min.

Gonadotrophin and steroid concentrations in bovine follicular fluid and their relationship to follicle size

The concentrations of LH, FSH and prolactin, and oestradiol-17 beta, androstenedione, testosterone and progesterone were measured in follicular fluid from small, medium and large bovine follicles. As follicle size increased, there was a significant increase in median fluid concentrations of prolactin (2-fold) and oestradiol-17 beta (14-fold) and a significant decrease in concentrations of LH (to 73%), androstenedione (to 30%) and testosterone (to 10%). There was no relationship between follicle size and fluid concentrations of FSH or progesterone, or between fluid concentrations of FSH and the relative concentrations of androgen and oestradiol-17 beta. As follicle size increased there was a significant increase in the proportion of follicles in which follicular fluid concentrations of oestradiol-17 beta exceeded those of androgen. There was a significant relationship between follicular fluid concentrations of prolactin and progesterone; as fluid prolactin concentrations increased, the maximum concentration of progesterone observed decreased.

Regulation of inhibin production by bovine ovarian cells in vitro

The regulation of ovarian inhibin production was investigated using a rat pituitary cell culture system as a bioassay for inhibin activity. Bovine follicular granulosa cells produced inhibin in vitro provided that the culture medium contained serum. The stimulatory factor(s) present in serum is unlikely to be gonadotrophins, because bovie LH and/or FSH failed to stimulate inhibin production when added to medium devoid of serum. Luteinization of granulosa cells in culture was accompanied by a reduction in their inhibin production and an inverse relationship existed between inhibin and progesterone production by granulosa cells. Bovine corpus luteum cells in culture failed to produce detectable amounts of inhibin. Androgens stimulated granulosa cell inhibin production with testosterone and 5 alpha-dihydrotestosterone being more potent than androstenedione. The androgens did not stimulate inhibin production by luteal cells. Progesterone inhibited granulosa cell inhibin production but oestrogens had no effect. Measurement of steroids and inhibin in fluid from individual follicles indicated that as follicle size increased, concentrations of oestradiol-17 beta increased, testosterone and inhibin decreased and progesterone remained unchanged. The stimulatory effect of testosterone on inhibin production in vitro together with the parallel changes in follicular fluid concentrations of testosterone and inhibin suggest that ovarian inhibin production in vivo may be controlled, at least in part, through androgens modifying granulosa cell inhibin production. The inhibitory effect of progesterone on granulosa cell inhibin production may be more important in regulating ovarian inhibin production at the time of granulosa cell luteinization and CL formation. The stimulatory effect of androgens on granulosa cell inhibin production might also be a means by which androgens promote follicular atresia.