No abstract

Mammalian spermatogenesis is a complex biological process occurring in the seminiferous tubules in the testis. This process represents a delicate balance between cell proliferation, differentiation, and apoptosis. In most mammals, the testicles are kept in the scrotum 2 to 7°C below body core temperature, and the spermatogenic process proceeds with a blood and oxygen supply that is fairly independent of changes in other vascular beds in the body. Despite this apparently well-controlled local environment, pathologies such as varicocele or testicular torsion and environmental exposure to low oxygen (hypoxia) can result in changes in blood flow, nutrients, and oxygen supply along with an increased local temperature that may induce adverse effects on Leydig cell function and spermatogenesis. These conditions may lead to male subfertility or infertility. Our literature analyses and our own results suggest that conditions such as germ cell apoptosis and DNA damage are common features in hypoxia and varicocele and testicular torsion. Furthermore, oxidative damage seems to be present in these conditions during the initiation stages of germ cell damage and apoptosis. Other mechanisms like membrane-bound metalloproteinases and phospholipase A2 activation could also be part of the pathophysiological consequences of testicular hypoxia.

No abstract

Overlap of primary studies among systematic reviews (SRs) is one of the main methodological challenges when conducting overviews. If not assessed properly, overlapped primary studies may mislead findings, since they may have a major influence either in qualitative analyses or in statistical weight. Moreover, overlapping SRs may represent the existence of duplicated efforts. Matrices of evidence and the calculation of the overall corrected covered area (CCA) are appropriate methods to address this issue, but they seem to be not comprehensive enough. In this article we present Graphical Representation of Overlap for

No abstract

Introduction: Evidence about COVID-19 and pregnancy has rapidly increased since December 2019, making it difficult to make rigorous evidence-based decisions. The objective of this overview of systematic reviews is to conduct a comprehensive analysis of the current evidence on prognosis of COVID-19 in pregnant women. Material and methods: We used Living OVerview of Evidence (L•OVE) platform for COVID-19, which continually retrieves studies from 46 data sources (including Pubmed/MEDLINE, Embase, other electronic databases, clinical trials registries, preprint repositories, among other sources relevant to COVID-19), mapping them into PICO questions. The search covered the period from the inception date of each database to September 13, 2020. We included systematic reviews assessing outcomes of pregnant women with COVID-19 and/or their newborns. Two authors independently screened the titles and abstracts, assessed full-texts to select the studies that met the inclusion criteria, extracted data, and appraised the risk of bias of each included systematic review. We measured the overlap of primary studies included among the selected systematic reviews by building a matrix of evidence, calculating the corrected covered area, and assessing the level of overlapping for every pair of systematic reviews. Results: Our search yielded 1132 references. 52 systematic reviews met inclusion criteria and were included in this overview. Only one review had a low risk of bias, three had an unclear risk of bias, and 48 had a high risk of bias. Most of the included reviews were highly overlapped among each other. In the included reviews, rates of maternal death varied from 0% to 11.1%, admission to intensive care from 2.1% to 28.5%, preterm deliveries before 37 weeks from 14.3% to 61.2%, and cesarean delivery from 48.3% to 100%. Regarding neonatal outcomes, neonatal death varied from 0% to 11.7% while the estimated infection status of the newborn varied between 0% and 11.5%. Conclusions: Only one of 52 systematic reviews had a low risk of bias. Results were heterogenous and the overlap of primary studies was frequently very high between pairs of systematic reviews. High quality evidence syntheses of comparative studies are needed to guide future clinical decisions.

This article is part of a collaborative methodological series of narrative reviews on biostatistics and clinical epidemiology. This review aims to present basic concepts about the minimal clinically important difference and its use in the field of clinical research and evidence synthesis. The minimal clinically important difference is defined as the smallest difference in score in any domain or outcome of interest that patients can perceive as beneficial. It is a useful concept in several aspects since it links the magnitude of change with treatment decisions in clinical practice and emphasizes the primacy of the patient’s perception, affected by endless variables such as time, place, and current state of health, all of which can cause significant variability in results.

High-altitude hypoxia generates spermiogram impairment due to germinal epithelium, Leydig cells, sperm and seminal plasma alterations, but precise mechanisms involved are unknown. The objective of this work was to analyse the effect of normobaric hypoxia on the morphology of testicular interstitium and some associated molecular and hormonal factors. Twenty-four mice were exposed to normobaric hypoxia (8.1% inspired oxygen fraction) during 20 days. The effects on body weight, testicular weight, vascularisation, testosterone, HIF1-α and VEGF were analysed at different periods of exposure and compared to controls. Hypoxic mice had lower body weight than mice kept in normoxia. Testicular weight raised significantly the 1st day, but remained normal during the rest of experiment. Number of blood vessels per field and mean diameter of vessels were higher in hypoxic mice. Plasmatic and testicular testosterone raised during first 24 h of hypoxia, but decreased on the 5th day. Vascular/interstitial ratio (proportion of interstice occupied by blood vessels) duplicated at the end of the experiment. Most substantial early effects of hypoxia were testicular oedema, increase in number and diameter of blood vessels and elevation of plasmatic and testicular testosterone. Normobaric hypoxia generates similar effects to those induced by hypobaric hypoxia.