Gut microbiota-gonadal axis: the impact of gut microbiota on reproductive functions.

The influence of gut microbiota on physiological processes is rapidly gaining attention globally. Despite being under-studied, there are available data demonstrating a gut microbiota-gonadal cross-talk, and the importance of this axis in reproduction. This study reviews the impacts of gut microbiota on reproduction. In addition, the possible mechanisms by which gut microbiota modulates male and female reproduction are presented. Databases, including Embase, Google scholar, Pubmed/Medline, Scopus, and Web of Science, were explored using relevant key words. Findings showed that gut microbiota promotes gonadal functions by modulating the circulating levels of steroid sex hormones, insulin sensitivity, immune system, and gonadal microbiota. Gut microbiota also alters ROS generation and the activation of cytokine accumulation. In conclusion, available data demonstrate the existence of a gut microbiota-gonadal axis, and role of this axis on gonadal functions. However, majority of the data were compelling evidences from animal studies with a great dearth of human data. Therefore, human studies validating the reports of experimental studies using animal models are important.

Effect of source filter interaction on isolated vowel-consonant-vowel perception.

Source-filter interaction explains the drop in pitch in voiced consonant due to constriction in the vocal tract during vowel-consonant-vowel (VCV) production. In this work, a perceptual study is conducted where the pitch contour in the voiced consonant region is modified to four different levels and a listening test is performed to assess the naturalness of the VCVs synthesized with the modified pitch contour. The listening test with 30 listeners shows no statistically significant difference between the naturalness of the original and synthesized VCVs with modified pitch indicating that pitch drop due to source-filter interaction may not be critical for the perceived naturalness of VCVs.

Provision, uptake and cost of cardiac rehabilitation programmes: improving services to under-represented groups.

OBJECTIVES: To estimate UK need for outpatient cardiac rehabilitation, current provision and identification of patient groups not receiving services. To conduct a systematic review of literature on methods to improve uptake and adherence to cardiac rehabilitation. To estimate cost implications of increasing uptake of cardiac rehabilitation. DATA SOURCES: Hospital Episode Statistics (England). Hospital Inpatient Systems (Northern Ireland). Patients Episode Database for Wales. British Association for Cardiac Rehabilitation/British Heart Foundation surveys. Cardiac rehabilitation centres. Patients from general hospitals. Electronic databases. REVIEW METHODS: The study analysed hospital discharge statistics to ascertain the population need for outpatient cardiac rehabilitation in the UK. Surveys of cardiac rehabilitation programmes were conducted to determine UK provision, uptake and audit activity, and to identify local interventions to improve uptake. Data were also examined from a trial estimating eligibility for cardiac rehabilitation and non-attendance. A systematic review of interventions to improve patient uptake, adherence and professional compliance in cardiac rehabilitation was conducted. Estimated costs of improving uptake were identified from national survey, systematic review and sampled cardiac rehabilitation programmes. RESULTS: In England, Wales and Northern Ireland nearly 146,000 patients discharged from hospital with primary diagnosis of acute myocardial infarction, unstable angina or following revascularisation were potentially eligible for cardiac rehabilitation. In England in 2000, 45-67% of these patients were referred, with 27-41% attending outpatient cardiac rehabilitation. If all discharge diagnoses of ischaemic heart disease were considered, nearly 299,000 patients would be potentially eligible and in England rates of attendance and referral would be 22-33% and 13-20% respectively. Rates of referral and attendance were similar in Wales, but somewhat lower in Northern Ireland. It was found that referral and attendance of older people and women at cardiac rehabilitation tended to be low. It was also suggested that patients from ethnic minorities and those with angina or heart failure were less likely to be referred to or join programmes. A wide range of local interventions suggested awareness of the problem of uptake. In an NHS-funded randomised controlled trial, possibly representing more optimal protocol-led care, medical and nursing staff identified 73-81% of patients with acute myocardial infarction as eligible for cardiac rehabilitation. Excluded patients tended to be older with more severe presentation of cardiac disease. Experiences of patients suggested that uptake may be improved by addressing issues of motivation and relevance of rehabilitation to future well-being, co-morbidities, site and time of programme, transport and care for dependents. Systematic review of studies supported the use of letters, pamphlets or home visits to motivate patients and the use of trained lay visitors. Self-management techniques showed some value in promoting adherence to lifestyle changes. Studies examining professional compliance found that professional support for practice nurses may have value in the coordination of postdischarge care. Average costs in 2001 of cardiac rehabilitation to the health service per patient completing a cardiac rehabilitation programme were about GBP350 (staff only) and GBP490 (total). If services were modelled on an intermediate multidisciplinary configuration with three to five key staff, approximately 13% more patients could be treated with the same budget. Depending on staffing configuration an approximate 200-790% budget increase would be required to provide cardiac rehabilitation to all potentially eligible patients. CONCLUSIONS: Provision of outpatient cardiac rehabilitation in the UK is low and little is known about the capacity of cardiac rehabilitation centres to increase this provision. There is an uncoordinated approach to audit data collection and few interventions aimed at improving the situation have been formally evaluated. Motivational communications and trained lay volunteers may improve uptake of cardiac rehabilitation, as may self-management techniques. Experience of low-cost interventions and good practice exists within rehabilitation centres, although cost information frequently is not reported. Increased provision of outpatient cardiac rehabilitation will require extra resources. Further trials are required to compare the cost-effectiveness of comprehensive multidisciplinary rehabilitation with simpler outpatient programmes, also research is needed into economic and patient preference studies of the effects of different methods of using increased funding for cardiac rehabilitation. An evaluation of a range of interventions to promote attendance in all patients and under-represented groups would also be useful. The development of standards is suggested for audit methods and for eligibility criteria, as well as regular and comprehensive data collection to estimate the need for and provision of cardiac rehabilitation. Further areas for intervention could be identified through qualitative studies, and the extension of low-cost interventions and good practice within rehabilitation centres. Regularly updated systematic reviews of relevant literature would also be useful.

Endothelial dysfunction in chronic renal failure: roles of lipoprotein oxidation and pro-inflammatory cytokines.

BACKGROUND: Chronic renal failure (CRF) is associated with an increased risk of ischaemic heart disease (IHD), but the mechanisms responsible are controversial. We investigated the relationship of two sets of candidate mechanisms-indices of LDL oxidation and markers of inflammatory activity-with vascular endothelial dysfunction (VED). METHODS: We carried out cross-sectional analysis of 23 dialysed and 16 non-dialysed CRF patients, 28 healthy controls, and 20 patients with stable angina and normal renal function. The following were determined: (i) LDL oxidation by Cu(2+) and ultraviolet light, serum autoantibodies to oxidized LDL (oxLDL); (ii) forearm flow-mediated vasodilatation, plasma concentrations of adhesion molecules, and von Willebrand factor (vWF); and (iii) circulating levels of TNF-alpha and IL-6, C-reactive protein (CRP), and fibrinogen. RESULTS: Endothelium-dependent vasodilatation (EDV) was lower in angina, pre-dialysis, and dialysis CRF patients than in controls (all P<0.005). Compared with controls, vWf (P<0.005) and adhesion molecules (vCAM-1, P<0.005; iCAM-1, P=0.01; E-selectin, P=0.05) were raised in dialysis, and vCAM-1 (P=0.01) in pre-dialysis CRF patients. Dialysed patients had lower HDL cholesterol (P=0.01) and higher triglyceride (P=0.05) than controls, but LDL-oxidation was similar in all groups. Autoantibodies to oxLDL were raised in angina (P<0.005) and pre-dialysis (P=0.006), but were absent in most dialysed patients. Concentrations of IL-6, TNF-alpha, CRP and fibrinogen were elevated in CRF compared with control and angina patients (P<0.005). In the whole population, IL-6 and TNF-alpha correlated negatively with EDV, HDL cholesterol, and positively with triglyceride, blood pressure, vWf, iCAM-1, vCAM-1 and E-selectin (r=-0.43 to +0.70, all P<0.05). CONCLUSIONS: Endothelial dysfunction is unrelated to LDL oxidation, suggesting that LDL oxidation might not be a major cause of VED in CRF. In contrast VED was more severe in CRF than in angina patients and is associated with increased acute-phase proteins and plasma cytokines, demonstrating a chronic inflammatory state. These observations may explain the VED and increased IHD risk of patients with CRF.

End systolic pressure-length relations in halothane anaesthetised dogs: effects of regional ischaemia and inotropic agents.

STUDY OBJECTIVE: The aim was to investigate the effects of regional myocardial ischaemia, calcium, and verapamil on (a) the hysteresis and (b) slope and length axis intercept of the left ventricular end systolic pressure-length relationship. DESIGN: Segment length in myocardium supplied by the left anterior descending coronary artery was measured in anaesthetised dogs using sonomicrometry. Three levels of regional myocardial ischaemia were produced by stenosis and occlusion of the left anterior descending artery (ischaemia 1, ischaemia 2, and occlusion). A snare placed around the descending thoracic aorta was used to obtain temporary aortic occlusions. SUBJECTS: Seven open chested mongrel dogs were used, weight 17 kg (range 16-20). MEASUREMENTS AND MAIN RESULTS: After abrupt release of temporary aortic occlusions, end systolic lengths were greater than before the occlusion in the normal myocardium. This hysteresis was abolished by regional myocardial ischaemia. However, hysteresis was insensitive to calcium and verapamil. The length axis intercept of the end systolic pressure-length relationship was increased during ischaemia 2, during coronary occlusion, and after administration of verapamil; its slope was increased after coronary occlusion. CONCLUSIONS: (1) Viscoelastic properties of the myocardium make a major contribution to hysteresis of the end systolic pressure-length relationship; and (2) the length axis intercept of this relationship is not constant and its slope does not appear to be a sensitive indicator of regional myocardial contractility during regional ischaemia.

Influence of halothane on contraction at positive membrane potentials in single cells isolated from guinea-pig ventricular muscle.

Actions of halothane were investigated under voltage-clamp conditions in single cells from guinea-pig ventricular muscle. Contraction (measured by an optical method) evoked by step depolarization to 0 mV was consistently reduced by halothane. At positive membrane potentials (+60 mV) 2% halothane did not cause a consistent depression of peak contraction, and in the majority of cells contraction was enhanced. Two per cent halothane increased the time-to-peak contraction at +60 mV. However, when a pre-pulse to 0 mV was applied to inactive calcium current through L-channels, any effect of 2% halothane on the time-to-peak of contraction was reduced or abolished. A halothane-induced increase in time-to-peak contraction was also observed at membrane potentials in the range of the action potential plateau (+20 and +40 mV). In double-pulse experiments contraction during a 'test' depolarization to +60 was measured following a 'conditioning' depolarization to 0 mV. Contraction at +60 mV was slightly reduced at brief interpulse intervals (less than 400 ms) following the 'conditioning' depolarization to 0 mV, and recovered as the interval was prolonged; in cells exposed to halothane contraction at +60 mV was no longer influenced by the interval between the pulses. Isoflurane (3.2%) had qualitatively similar but less potent effects than halothane on contraction at +60 mV. These observations are consistent with the suggestion that mechanisms for calcium entry may vary with the membrane potential: at 0 mV, the major pathway for calcium entry may be through halothane-sensitive L-type calcium channels, while at +60 mV entry may be through additional pathways which are relatively resistant to halothane. Actions of halothane on the time-to-peak of contraction may be accounted for by its influence on the sarcoplasmic reticulum to decrease net uptake and release of calcium. These actions of halothane might be of importance during the action potential plateau.

Isoflurane depresses membrane currents associated with contraction in myocytes isolated from guinea-pig ventricle.

The influence of isoflurane on membrane currents, action potentials, and contraction was investigated in single cells isolated from guinea-pig ventricle. Isoflurane (1.65-4.45%) reduced the action potential duration at 20% and 90% repolarization times. When step depolarizations were applied under voltage-clamp conditions, there was a depression by isoflurane both of the second inward (calcium) current and of the contraction (measured by an optical method). Isoflurane also depressed "tail" currents, which were recorded on repolarization following a voltage-clamp step to 0 mV and which are thought to be activated by cytosolic calcium. Additional actions of isoflurane were investigated using a paired-pulse protocol. The observations were consistent with a reduction by isoflurane of calcium release. This action together with the reduction of calcium influx during the second inward current would contribute to the negative inotropic effect of isoflurane.

Effects of halothane on membrane currents associated with contraction in single myocytes isolated from guinea-pig ventricle.

1. The effects of halothane on electrical activity and contraction were investigated in single myocytes isolated from guinea-pig ventricle. 2. Halothane depressed the plateau and shortened the duration of action potentials. 3. Halothane also reduced the amplitude of inward calcium currents and of additional inward current activated by cytosolic calcium under voltage-clamp conditions. 4. Contractions (measured by an optical technique) accompanying either action potentials or calcium currents were reduced by halothane. However, the extent of attenuation of contraction was greater than when a similar level of calcium channel blockade was induced by application of verapamil. 5. Actions of halothane on calcium-activated tail currents in double-pulse experiments were consistent with reduction by halothane of the cytosolic calcium transient, perhaps as a consequence of reduced uptake of calcium into sarcoplasmic reticulum stores. 6. It is concluded that the actions of halothane on inward currents contribute to its effects on action potentials. The reduction in contraction caused by halothane may result partly from a reduced influx of calcium to trigger contraction, and partly by a reduced release of calcium from sarcoplasmic reticulum stores.

Influence of halothane on electrical coupling in cell pairs isolated from guinea-pig ventricle.

1. The actions of halothane on electrical coupling between cells were investigated in cell pairs isolated from guinea-pig ventricular muscle. 2. Under voltage-clamp conditions a step depolarization applied to one cell caused a similar change in potential in the second. Application of halothane led to the appearance of double peaks in inward current evoked by step depolarizations. These observations were interpreted in terms of uncoupling of the cells leading to escape of the second cell from the influence of the voltage-clamp in the first cell. 3. This suggestion that uncoupling in the presence of halothane led to differences in electrical activity in the two cells was confirmed in experiments in which independent electrodes were used to measure membrane potential in the two cells. 4. The voltage responses of both cells of the pair were recorded in response to constant current pulses. Administration of halothane led to abolition of the response recorded from the second cell while that of the first was enhanced. The actions are consistent with an action of halothane on gap junctions to block electrical coupling. 5. Qualitatively similar observations, consistent with electrical uncoupling, were observed with isoflurane. 6. These findings may be significant in relation to the arrhythmogenic actions of halothane.

Hysteresis of left ventricular end ejection pressure-dimension relations after acute pressure loading in the intact canine heart.

The left ventricular end systolic pressure-volume relation of the isolated canine heart is linear and independent of the loading conditions. The effects of acute pressure loading on the left ventricular end ejection pressure-length relations were studied in the intact canine heart. The lengths of two wall segments of the left ventricle parallel to the minor axis were measured with pairs of miniature piezoelectric crystals. At two levels of filling pressure, with and without control of heart rate, acute increases in left ventricular afterload were produced for six successive beats by occluding the thoracic aorta. After abrupt release of this occlusion, at left ventricular end diastolic pressure less than 10 mmHg, end ejection lengths were longer than before the occlusion for both segments despite the same or lower end ejection pressures. When heart rate was not controlled the mean(SD) difference in end ejection length was 0.46(0.21) mm (n = 100). When heart rate was controlled by atrial pacing after autonomic blockade the difference was 0.37(0.11) mm (n = 80). In contrast, at left ventricular end diastolic pressure greater than 10 mmHg there was no significant difference between end ejection lengths before and after release of the aortic occlusion. Gradual release of the aortic occlusion over 4-5 beats produced clockwise hysteresis of the left ventricular end ejection pressure-length relation when left ventricular end diastolic pressure was less than 10 mmHg. No hysteresis occurred when left ventricular end diastolic pressure was greater than 10 mmHg. Hysteresis of the end systolic pressure-dimension relation was also seen when major and minor axis dimensions of the left ventricular were measured.(ABSTRACT TRUNCATED AT 250 WORDS)