Acute, High Dose Metformin Therapy at Reperfusion Decreases Infarct Size in the High-Risk Aging Heart

Elderly patients (age > 75) sustain larger infarcts with greater mortality from ST elevation myocardial infarcts (STEMI) despite successful reperfusion treatment. Elderly age remains an independent risk despite correction for clinical and angiographic variables. The elderly represent a high-risk population and may benefit from treatment in addition to reperfusion alone. We hypothesized that modulation of cardiac signaling and metabolism with acute, high dose metformin given at reperfusion would exhibit additional cardioprotection. Using a translational aging murine model (22-24-month C57BL/6J mice) of in vivo STEMI (45 min artery occlusion with reperfusion for 24 hours); treatment acutely at reperfusion by high dose metformin decreased infarct size and enhanced contractile recovery, demonstrating cardioprotection in the high-risk aging heart.

Mode of delivery following obstetric anal sphincter injury: a 7-year retrospective review and follow-up cohort survey

INTRODUCTION AND HYPOTHESIS

Limited evidence exists regarding long-term outcomes following birth after prior obstetric anal sphincter injury (OASI). This article set out to describe outcomes following birth after OASI by reviewing the grades of tear, endoanal ultrasound (EAUS) findings, subsequent delivery outcomes and long-term symptoms.

METHODS

This study was conducted in two parts. The first involved a retrospective review of all OASI at a tertiary hospital in Australia over 7 years (2013-2019 inclusive) where the patient underwent a subsequent delivery. Following this, a retrospective cohort survey of this group was performed.

RESULTS

There were 27,284 vaginal births and 828 OASIs (3.03%); 247 (29.8%) had at least one subsequent birth by January 2021. Vaginal delivery occurred in 68%; recurrence of OASI was 5.4%. There were 90 responses (36.4%) to the follow-up survey. EAUS had been performed in 87.5%; none demonstrated a defect. Vaginal birth was the preferred mode for 77.8%; this occurred in 64%. The majority had high levels of satisfaction, this related to communication rather than the mode of delivery itself. Ongoing faecal or flatal incontinence was reported by 12%. There was no statistically significant difference in St Mark's incontinence scores between modes of birth.

CONCLUSIONS

In our unit most women who sustain OASI will have a subsequent vaginal delivery in future pregnancies. The majority remain asymptomatic at long-term follow-up with no statistically significant difference in incontinence scores regardless of mode of delivery. The rate of recurrent OASI was 5.4%.

O030 Image-analysis algorithm to determine quality of cold perfusion in kidney transplantation

Introduction

Surgeon assessment of visual ‘quality of perfusion’ (QOP) influences kidney discard and predicts transplant outcome. However, this assessment is subjective and bias-prone.

We aimed to design an application utilising a smartphone camera to make this assessment objective and enhance decision making.

Methods

The QOP in photographs of backbench kidneys was graded from 1 (ideal) to 5 (very poor) by three independent surgeons. A training cohort was used to develop an image-analysis algorithm, which was validated in a separate cohort.

Results

Analysing surgeon scores of 174 kidney images revealed that inter-rater agreement was good for kidneys displaying the best (rated 1) and worst (rated 4 or 5) QOP. However, for intermediate scores inter-rater agreement was poor. Inter-rater agreement between surgeons decreased as they graded more images; as surgeons fatigued, their ability to classify images worsened. A training cohort (n=174 kidneys) was used for algorithm development. First, small regions within each image were mapped within the CEILAB colour-space, where well-perfused and poorly perfused areas show clear separation. To generate a score for each kidney these regions are compared with ideally flushed kidney tissue. Testing our algorithm (validation cohort - n=29 kidneys) revealed strong correlation between image-analysis QOP score and surgeon assessment, r=0.789 (0.587–0.899), P<0.001.

Conclusion

Surgeon inter-rater agreement on kidney QOP is low for kidneys with borderline QOP and worsens with fatigue. We provide a QOP score utilising an image-analysis algorithm, which correlates with surgeon scoring. With additional images and training this could provide an objective, numerical, point-of-care assessment of organ quality.

Take-home message

Current visual assessment of transplant organ quality is subjective and bias-prone. This body of work attempts to create a point-of-care image-analysis application to provide an objective numeric organ quality score.

The Interaction of mTOR and Nrf2 in Neurogenesis and Its Implication in Neurodegenerative Diseases

Neurogenesis occurs in the brain during embryonic development and throughout adulthood. Neurogenesis occurs in the hippocampus and under normal conditions and persists in two regions of the brain—the subgranular zone (SGZ) in the dentate gyrus of the hippocampus and the subventricular zone (SVZ) of the lateral ventricles. As the critical role in neurogenesis, the neural stem cells have the capacity to differentiate into various cells and to self-renew. This process is controlled through different methods. The mammalian target of rapamycin (mTOR) controls cellular growth, cell proliferation, apoptosis, and autophagy. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is a major regulator of metabolism, protein quality control, and antioxidative defense, and is linked to neurogenesis. However, dysregulation in neurogenesis, mTOR, and Nrf2 activity have all been associated with neurodegenerative diseases such as Alzheimer’s, Huntington’s, and Parkinson’s. Understanding the role of these complexes in both neurogenesis and neurodegenerative disease could be necessary to develop future therapies. Here, we review both mTOR and Nrf2 complexes, their crosstalk and role in neurogenesis, and their implication in neurodegenerative diseases.

Abstract 12111: Metformin Maintains Mitochondrial Integrity and Preserve Heart From Ischemia Reperfusion Injury Through Sestrin2-AMPK Signaling

Introduction: Metformin activates AMP-activated protein kinase (AMPK) to improve cardiac function during ischemia and reperfusion (I/R). We reported that Sestrin2 (Sesn2) is associated with AMPK and maintains oxidative phosphorylation (OXPHOS) under I/R stress. The role of age-related Sesn2-AMPK signaling in the beneficial actions of metformin on ischemic insults remains unknown.

Hypothesis: Metformin maintains mitochondrial integrity and limits cardiac damage caused by ischemic insults through the Sesn2-AMPK signaling pathway.

Methods: Young (3-6 months) and aged (22-24 months) C57BL/6J wild type mice, and 3 months of Sesn2 f/f and cardiomyocyte-specific Sesn2 knockout (cSesn2 -/- ) C57BL/6J mice were subjected to 45 minutes of ischemia followed by 2 mM metformin injection 5 minutes before 24-hour of reperfusion. Cardiac function and myocardial infarction were determined with echocardiography and 2,3,5-triphenyl tetrazolium chloride staining. Immunoblotting determines the mechanism of metformin in modulating Sesn2 to preserve mitochondrial OXPHOS components. The Seahorse XF Analyzer examined the mitochondrial respiratory functions.

Results: Metformin administration can significantly improve cardiac function and reduce myocardial infarction size during I/R conditions in both young and aged wild-type C57BL/6J mice. Intriguingly, the beneficial effects of metformin administration on cardiac function and myocardial infarction were significantly blunted in the cSesn2 -/- versus Sesn2 f/f C57BL/6J mice. The immunoblotting showed metformin treatment augmented mitochondrial OXPHOS Complex II levels in young/aged wild type, and Sesn2 f/f but not cSesn2 -/- heart during I/R stress. Moreover, the mitochondrial respiration data displayed that metformin treatment improved the respiration rate of mitochondrial states 2 and 3μ in the isolated cardiomyocytes from Sens2 f/f but not from cSesn2 -/- mouse hearts under I/R stress conditions.

Conclusions: Metformin can stabilize age-related Sesn2 levels in cardiomyocytes and improve cardiac function under I/R stress through maintaining mitochondrial integrity. Metformin is a potential therapeutic drug for ischemic heart disease in the elderly.

O3 Ex vivo normothermic machine perfusion facilitates gymnotic delivery of RNA interference therapeutics in donor kidneys

Introduction

Normothermic machine perfusion (NMP) of donor kidneys prior to transplantation provides a platform for delivery of novel therapeutics to optimize organ quality. This includes RNA interference (RNAi) therapeutics e.g. antisense oligonucleotides (ASO) that block detrimental microRNAs. The intracellular kinetics of RNAi therapeutics are crucial for their pharmacological effect, however, it remains poorly understood. NMP provides an ideal platform to investigate this further.

Method

During NMP, human kidneys (n = 12) were treated for 6 hours with a fluorescently-labelled ASO designed to block microRNA-24-3p activity. Biopsies were taken at 0, 2, 4, and 6 hours. Kidney sections were stained with antibodies against early endosomes (Rab5), late endosomes (Rab7), RNA-induced silencing complexes (GW182) and lysosomes (LAMP2). Confocal microscopy images were obtained and co-localisation quantified using Hugyens™ software following batch deconvolution. The global transcriptomic impact of ASO therapy was also assessed using RNA sequencing.

Result

Following 2 hours of NMP, ASO was primarily found in tubular epithelial cells. Co-localisation studies revealed ASO uptake via endocytosis and endosomal sorting occurring during NMP. This was followed by cytoplasmic escape and co-localisation of ASO with GW182 proteins. This pattern of co-localisation was not seen in scrambled sequence or cold perfusion controls. RNAseq analysis revealed a decrease in inflammatory pathways and upregulation of microRNA-24-3p targets.

Discussion

This is the first study to demonstrate NMP facilitates gymnotic ASO delivery directly into the RISC, whereby, it blocks microRNA-mediated mRNA silencing and increases bioavailability of protective targets. This study highlights the capacity of NMP to re-programme gene expression in donor kidneys using RNAi therapeutics.

Take-home Message

Ex vivo normothermic machine perfusion of donor kidneys provides a unique window of opportunity prior to transplantation when we can deliver therapies to improve the quality of the organ. Novel genetic therapies designed to protect kidneys against ischemia reperfusion injury could potentially increase organ utilisation and improve post-transplant outcomes for the many patients on the kidney transplant waiting list.

Alterations in mitochondrial dynamics with age-related Sirtuin1/Sirtuin3 deficiency impair cardiomyocyte contractility

Sirtuin1 (SIRT1) and Sirtuin3 (SIRT3) protects cardiac function against ischemia/reperfusion (I/R) injury. Mitochondria are critical in response to myocardial I/R injury as disturbance of mitochondrial dynamics contributes to cardiac dysfunction. It is hypothesized that SIRT1 and SIRT3 are critical components to maintaining mitochondria homeostasis especially mitochondrial dynamics to exert cardioprotective actions under I/R stress. The results demonstrated that deficiency of SIRT1 and SIRT3 in aged (24–26 months) mice hearts led to the exacerbated cardiac dysfunction in terms of cardiac systolic dysfunction, cardiomyocytes contractile defection, and abnormal cardiomyocyte calcium flux during I/R stress. Moreover, the deletion of SIRT1 or SIRT3 in young (4–6 months) mice hearts impair cardiomyocyte contractility and shows aging‐like cardiac dysfunction upon I/R stress, indicating the crucial role of SIRT1 and SIRT3 in protecting myocardial contractility from I/R injury. The biochemical and seahorse analysis showed that the deficiency of SIRT1/SIRT3 leads to the inactivation of AMPK and alterations in mitochondrial oxidative phosphorylation (OXPHOS) that causes impaired mitochondrial respiration in response to I/R stress. Furthermore, the remodeling of the mitochondria network goes together with hypoxic stress, and mitochondria undergo the processes of fusion with the increasing elongated branches during hypoxia. The transmission electron microscope data showed that cardiac SIRT1/SIRT3 deficiency in aging alters mitochondrial morphology characterized by the impairment of mitochondria fusion under I/R stress. Thus, the age‐related deficiency of SIRT1/SIRT3 in the heart affects mitochondrial dynamics and respiration function that resulting in the impaired contractile function of cardiomyocytes in response to I/R.

O59: USE OF DEXTRAN 40 FOLLOWING PANCREAS TRANSPLANT MAY REDUCE EARLY INFLAMMATION AND SIGNIFICANT BLEEDING COMPARED TO A HEPARIN-BASED PROTOCOL

Introduction

Dextran 40 (D40) is a synthetic colloid with anticoagulant properties, which is commonly used instead of heparin following pancreas transplantation, however there is a lack of evidence over which is more effective. Graft thrombosis and pancreatitis, which may be mediated through micro or macrothrombosis within the graft, remain significant complications following pancreas transplantation. We hypothesised that D40 reduces inflammation through its antithrombotic pro-microcirculatory effects. We aimed to evaluate D40 compared to a heparin-based protocol by comparing post-operative complications and post-transplant levels of inflammation.

Method

Data were collected retrospectively for pancreas transplant patients between December 2009 and August 2018 – 26 patients had been treated with the pre-Dextran protocol and 37 had received D40. Post-operative complications and inflammatory markers (WCC, CRP and amylase) on post-operative days 1, 2, 3 and 7 were compared between the two groups. Potential confounders were also recorded.

Result

Patients in the D40 group had similar thrombosis rates but were less likely to have had substantial post-operative bleeding compared to the heparin-based protocol. The group who received D40 had significantly lower CRP and WCC on days 2, 3 and 7. The differences on days 3 and 7 remained when the results were adjusted for the significant confounders - cold ischaemic time and donor age.

Conclusion

D40 appears to be as effective as IV heparin at preventing graft thrombosis following pancreas transplant, and to confer a reduced risk of bleeding. It may also reduce post-operative inflammatory processes, leading to reduced graft pancreatitis.

Take-home message

Using Dextran 40 as an anticoagulant after pancreas transplantation is as effective as IV heparin at preventing graft thromboses and has a reduced risk of bleeding.

O67: PERFUSATE GLUCOSE REFLECTS TISSUE GLYCOGENATION DURING LIVER PERFUSION

Introduction

Normothermic machine perfusion (NMP) is a method of organ preservation that aims to replicate the physiological environment, achieved by perfusing the livers with a blood-based perfusate at physiological inflow pressures and temperature. NMP also permits viability assessment through evaluation of the perfusate flow rates through the portal vein and hepatic artery. In addition to this, biochemical assessment and perfusate gas analysis can be performed to provide insights into the metabolic activity of the liver.

Method

Discarded human liver grafts (n=6), were perfused for 24 hours. Core biopsies and perfusate samples were taken from each liver at 5 distinct time intervals over 24 hours. Core biopsies were fixed and stained with periodic acid-Schiff and analysed with Leica software to provide a quantitative estimate of the hepatocellular glycogen content.

Result

Hepatic glycogen concentration rose during the first hour, followed by a steady decline thereafter until the end of perfusion. Contrary to our initial hypothesis that glucose concentration within the circuit would show an inverse relationship to glycogen stores in the liver cells, we found that glucose concentration closely followed the same trend.

Conclusion

Change in hepatocyte glycogen content provides an important insight into the synthetic function of a liver destined for transplant. Our research suggests that glucose concentration can be used as a surrogate marker for the synthetic function of a liver on NMP and provides valuable information on the glycogen-synthesising capability of the hepatocytes. In future, this could potentially aid the decision-making process with regards to liver graft transplant viability.

Take-home message

Perfusate glucose concentration could provide an insight into the viability of liver transplants

O25: TARGETING THE RENAL TUBULAR EPITHELIUM WITH ANTI-MIRNA THERAPY: A POTENTIAL MECHANISM FOR MINIMISING ISCHAEMIA REPERFUSION INJURY

Introduction

Ischaemia reperfusion injury (IRI) is an unavoidable, significant consequence of renal transplantation. MicroRNAs are small, non-coding RNA molecules that regulate multiple downstream mRNA targets. MiRNA-21-5p and miRNA-24-3p have been previously implicated in IRI. Antisense oligonucleotides (ASOs) block specific microRNAs, with previous work by our group demonstrating their delivery to kidneys using normothermic machine perfusion. Imaging these kidneys revealed ASO localisation around proximal tubule epithelial cells (PTECs). This project aimed to characterise ASO blockade against miRNA-21-5p and miRNA-24-3p in PTECs.

Method

HKC8 cells, a human PTEC cell line, were used throughout these experiments. Cells were placed in a hypoxic incubator for 24hrs, followed by 6hrs of reoxygenation to mimic IRI. HKC8s were transfected with ASOs using lipofectamine. RT-qPCR and Western Blots were used to evaluate expression of antioxidant targets, SOD2 and HMOX1.

Result

MiRNA-21-5p and miRNA-24-3p levels were high throughout hypoxia and reoxygenation. Single blockade with anti-miRNA-21-5p resulted in a significant increase in its downstream target SOD2 (P<0.05). Anti-miRNA-24-3p treatment resulted in no change in either of its downstream targets, HMOX1 or SOD2. This was reflected in the failure of dual blockade to produce a synergistic effect on the shared target, SOD2.

Conclusion

Anti-miRNA-21-5p results in a significant increase of SOD2, which is well characterised as protective during IRI. Anti-miRNA-24-3p appears to have no effect on PTECs, contrary to previous work in endothelial cells, perhaps suggesting a cell specific response of microRNAs. Normothermic machine perfusion could be used to deliver dual ASOs; allowing simultaneous targeting of different kidney cell types.

Take-home message

The delivery of anti-miRNA-21-5p therapy pre-transplant, using normothermic machine perfusion, has the potential to reduce ischaemia reperfusion injury and improve kidney transplant outcomes.

Multidisciplinary guidelines for the management of paediatric tracheostomy emergencies

Temporary and permanent tracheostomies are required in children to manage actual or anticipated long-term ventilatory support, to aid secretion management or to manage fixed upper airway obstruction. Tracheostomies may be required from the first few moments of life, with the majority performed in children < 4 years of age. Although similarities with adult tracheostomies are apparent, there are key differences when managing the routine and emergency care of children with tracheostomies. The National Tracheostomy Safety Project identified the need for structured guidelines to aid multidisciplinary clinical decision making during paediatric tracheostomy emergencies. These guidelines describe the development of a bespoke emergency management algorithm and supporting resources. Our aim is to reduce the frequency, nature and severity of paediatric tracheostomy emergencies through preparation and education of staff, parents, carers and patients.

Confronting Goffman: how can mental health nurses effectively challenge stigma? A critical review of the literature

This paper critically reviews the issues and questions surrounding the ways in which mental health nurses can best address stigma in the 21st century. It begins with a brief discussion of the nature and definition of the term stigma and explores some of the theoretical basis behind it before drawing out potential flaws in the theory and using this as the basis for an exploration of the way in which stigma is formed and shaped by public and professional attitudes. The discussion then turns to the underlying principles of contemporary mental health legislation and evaluates the tensions between various strands of UK legislation, the way in which risk is perceived and managed by practitioners, and whether risk-averse practice perpetuates stigma. This leads onto the question of how mental health law itself might contribute to the perpetuation of stigma by removing power and responsibility from the hands of service users. Finally, the discussion concludes with some suggestion about how a future change in the principles of mental health law might alter the way in which mental health problems are perceived and allow nurses to practice in a way that is less focussed on risk management and places more emphasis on recovery.

Build your own infection control link nurse: an innovative study day

Infection control is everyone's business and it is important that all members of staff observe good infection control practice. An effective infection control link nurse system has been shown to support and develop this approach. The strength of ward-based infection control link nurses depends upon their effectiveness as role models and their ability to influence practice on their wards and beyond. In addition, the degree of respect they command from their peers and colleagues and the amount and quality of knowledge they possess is crucial. This paper describes an innovative approach taken in Mid-Essex, which allowed infection control link nurses to assess their capabilities and limitations in communicating with and influencing colleagues. In addition, we show how quantitative measures may be made available by this approach. Such measures may be used to explain to management how particular areas of infection control practice (e.g. the need for infection control link nurses to have more authority and more 'muscle') may be important.

"A little encouragement": health services and domestic violence

The aim of this study was to identify those elements of health care which women who have experienced domestic violence consider to represent quality care and explore opportunities for an area health service to improve its service delivery to these women. To do this nine focus groups were conducted with six urban and three rural groups, recruited from Women's Support Services and Refuges, and 65 women participated. A trained facilitator conducted the focus groups with a representative from each participating organisation. Audiotapes were transcribed then coded using a thematic analysis approach. Analysis of the tapes revealed six opportunities for improvement of health services. Improve services to Aboriginal women; increase access to services; promote available services; improve the health service environment; educate service providers; and provide specialist health services. A major theme to emerge was the importance of a supportive environment where women were supported to make choices for their future.

An examination of senior nursing roles: challenges for the NHS

Wellhouse NHS Trust moved its inpatient services to the new Barnet General Hospital in 1997 and merged with Chase Farm Hospital NHS Trust in 1999. To assist with the trust's management of resulting changes in care provision, a short project was conducted to examine the nursing services provided by ward managers (20) and senior nurses (27), that is nurses who undertake specialist/ advanced nursing practice. The project also aimed to present the views of the stakeholders (66) with regard to nursing in the trust and nurse-led services. The project involved two stages of data collection--focus groups and postal questionnaires. The project provided a great deal of information about the nursing service within the trust: a profile of the senior nurses, roles and responsibilities, skills and competencies, training and development, and support needs for their roles. The findings considered a number of issues: (i) employment--diversity of grading for posts; (ii) work roles--conflicts in role composition; (iii) stakeholders--perspectives of stakeholders on nursing. It is anticipated that the findings are not unique to the one trust and that they will contribute to the development of new clinical career pathways for senior nurses within the trust.

Alcohol and drug use in second-year medical students at the University of Leeds

OBJECTIVE

In view of recent media attention concerning the high level of alcohol and drug use reported in a group of newly qualified junior doctors, the aim of the present study was to assess the alcohol and drug habits of a group of current medical students.

METHODS

Information about alcohol and illicit drug use was obtained from 136 second-year medical students (46 men, 90 women) at the University of Leeds by means of a personally administered questionnaire. Levels of anxiety and depression were also assessed.

RESULTS

86% of the students drank alcohol and among those who drank, a high proportion (52.6% of the men and 50.6% of the women), exceeded the recommended weekly limit of alcohol consumption of 21 units for men and 14 units women per week). Illicit drug use was reported by 33.1% of students (28.3% of men, 35.6% of women). The drug most commonly used was cannabis. According to the Hospital Anxiety and Depression (HAD) scale, 41.2% of the students (37% of men, 43.3% of women) had anxiety ratings within the clinically significant range (HAD scale> 8); 9.5% of students demonstrated clinically significant levels of depression (HAD scale> 8). However, these high levels of anxiety and depression did not correlate with high levels of alcohol consumption or drug use.

A review of senior nurses' roles in an acute trust

The relationship between the managerial and clinical roles of senior nurses should be given more attention. Senior nurses believe some colleagues do not understand their role and feel they need more support.

Domestic violence: examining nurses' and doctors' management, attitudes and knowledge in an accident and emergency setting

Despite the increasing awareness of the important role that Accident and Emergency (A&E) personnel have in the diagnosis and management of domestic violence victims, there is limited knowledge about the nurses' or doctors' knowledge of or attitudes to domestic violence in Australian health care settings. In addition nursing and medical staff still receive very little training in working with domestic violence victims. This study was conducted to examine the existing knowledge, attitudes to and management strategies for domestic violence victims among 111 nurses and doctors in two rural and two country hospitals. The findings indicate that A&E staff recognise the importance of their role in the identification and management of domestic violence victims. Despite this they do not have all the skills necessary to deal effectively with the problem or to be able to access local resources for assistance. Education programs should focus on direct questioning techniques, and recognition of risk factors and protocols to provide guidelines for police involvement.

Domestic violence experienced by women attending an accident and emergency department

The aim of the study was to establish the extent and severity of domestic violence experienced by women attending the accident and emergency department of a large teaching hospital in Newcastle. The data were collected over a five-week period in 1992. All women between 17 and 80 years, attending the emergency or ambulatory areas between 8 a.m. and midnight, were asked to complete a confidential structured interview. A total of 401 women participated in the study, representing 82 per cent of eligible women approached. Each participant was asked if she had ever been physically hurt by someone close to her. Questions were asked to determine the relationship to the perpetrator, the type and cause of injury, treatment necessary and help sought. Seven (1.7 per cent, 95 per cent confidence interval (CI) 0.46 to 3.02) of the women surveyed were attending the hospital as a direct result of an incident of domestic violence, and 100 women (25 per cent, CI 21 to 29) had experienced domestic violence at some time. Bruising, fractures and cuts were the most common forms of injury, with the most common locations being the head, face and chest. Weapons, such as guns and knives, were used in 20 per cent of the incidents. A considerable number of the women (68 per cent) did not seek help at the time of their injuries. As a substantial proportion of women have experienced domestic violence in their lives, accident and emergency workers should receive training in recognising and assisting victims of domestic violence.

Impaired reception of nonverbal cues in women with premenstrual tension syndrome

The ability to perceive nonverbal facial cues was tested in 30 White, middle-class females. Pre- and post-menses responses of 15 subjects diagnosed as having Premenstrual Tension Syndrome (PMS) were compared to the responses of age-matched controls. Each subject was asked to interpret videotaped facial cues of individuals engaged in a gambling task. Interpretive ability fluctuated during the menstrual cycle and was significantly impaired during the premenstrual phase.

Physiological and isotopic aspects of photosynthesis in peperomia

Physiological and isotopic aspects of several Peperomia species were investigated. All but one species had C(3)-like stomatal behavior, in that stomata were open during the day and closed during the night. In these species, most atmospheric CO(2) uptake occurred during the day. Concurrent with this stomatal behavior, there were Crassulacean acid metabolism-like acid fluctuations in most species. Carbon and hydrogen isotope ratios of cellulose nitrate from Peperomia reflect their physiological behavior. The delta(13)C values of cellulose nitrate from Peperomia species were similar to values observed in C(3) plants and consistent with the daytime uptake of exogeneous CO(2) via the C(3) photosynthetic pathway. The deltaD values of cellulose nitrate from Peperomia species approach those of Crassulacean acid metabolism plants. These elevated deltaD values are caused by fractionations occurring during biochemical reactions and not as a consequence of water relations.

Gamma-aminobutyric acid is not likely a physiological prolactin-inhibiting factor

Basal plasma prolactin concentration is controlled by tonic inhibition. The major prolactin-inhibiting factor (PIF) is believed to be dopamine. Factors other than dopamine have also been suggested as possible physiological PIF. One of the major candidates for the nondopaminergic PIF is considered to be gamma-aminobutyric acid (GABA). We have carefully examined the possible physiological role of GABA by monitoring, at every 2 min, the circulating prolactin concentration after GABA administration, in conscious freely moving rats. GABA (0.1 or 1 g/kg) had no significant direct effect on plasma prolactin in rats in which the dopaminergic receptors were completely blocked by pimozide, nor in hypophysectomized rats in which a pituitary had been grafted under the kidney capsule and was therefore removed from any hypothalamic influence. The effects of bicuculline, a GABA-receptor-blocking agent, was examined in order to find out whether a tonic inhibition is exerted by GABA after elimination of tonic dopaminergic inhibition on prolactin secretion. The pimozide-treated rat in which the dopaminergic tone is completely eliminated did not show any prominent elevation of plasma prolactin concentration after bicuculline (300 micrograms/kg) administration. However, GABA did have an inhibitory effect in a primary pituitary cell monolayer culture system. Therefore, we conclude that GABA does not play a significant role as a physiological PIF and that the inhibitory effect of GABA in vitro is of a pharmacological nature.

Temporal and other effects of catechol estrogens on prolactin secretion in the rat

Temporal alterations in plasma prolactin levels caused by the administration of 2-hydroxyestradiol and 2-hydroxyestrone (100 microgram/kg) into the right atrium of freely-moving conscious male rats were examined. The catechol estrogens were given in a single bolus via an indwelling cannula and plasma prolactin concentration was monitored by taking blood samples every 2 min. A pulsatile elevation of plasma prolactin occurred approximately 4 h after the injection of 2-hydroxyestradiol and a small increase was also observed when it was administered to rats bearing a Silastic capsule containing estradiol. 2-Hydroxyestrone had no effect in untreated male rats but produced a 5- to 6-fold elevation in plasma prolactin level 4 h after its administration to rats implanted with estradiol. It is proposed that 2-hydroxyestrone suppresses the action of estradiol on prolactin secretion from the pituitary and that the accumulated hormone is released when the concentration of this catechol estrogen falls below a critical level. A longer latent period was required to produce an elevation in plasma prolactin levels by 2-hydroxyestradiol than by estradiol.