Effects of temperature anomaly on sperm quality: A multi-center study of 33,234 men

Backgrounds

Global fertility rates continue to decline and sperm quality is a prime factor affecting male fertility. Both extreme cold and heat have been demonstrated to be associated with decreased sperm quality, but no epidemiological studies have considered human adaptation to long-term temperature. Our aim was to conduct a multi-center retrospective cohort study to investigate exposure-response relationship between temperature anomaly (TA) that deviate from long-term climate patterns and sperm quality.

Methods

A total of 78,952 semen samples measured in 33,234 donors from 6 provincial human sperm banks in China were collected. This study considered heat and cold acclimatization to prolonged exposure in humans and explored the exposure-response relationship between TAs and sperm quality parameters (sperm concentrations, sperm count, progressive motility, progressive sperm count, total motility and total motile sperm count) during the hot and cold seasons, respectively. Linear mixed models and generalized linear models were built separately for specific centers to pool in a meta-analysis to obtain the pooled effect of TA on sperm quality, considering repeated measurements data structure and spatial heterogeneity.

Results

We identified an inverted U-shaped exposure-response relationship between TA and sperm quality during the hot season. Significant negative effect of anomalous cold on sperm quality during the hot season was found after additional adjustment for Body mass index, marital status and childbearing history. The heat-related TA in hot season was significantly negatively associated with sperm concentration, progressive sperm count and total motile sperm count (all P-values<0.05). After adjusting the relative humidity, the cold-related TA in cold season was negatively associated with the sperm total motility (P-values<0.05).

Conclusions

Our results suggest both heat-related and cold-related TAs are associated with decreased sperm quality. The findings highlight the importance of reducing exposure to anomalous temperatures to protect male fertility.

Social dynamics in an isolated, confined, and extreme workplace

There can be few indoor workplaces that are more subject to the meteorological and atmospheric conditions of their locations than permanent stations on the high, inland polar plateau of Antarctica. The US Amundsen-Scott South Pole Station is such a workplace, totally isolated during the 8-9 months of the austral winter, more than 800 miles (1287 km) from the nearest other human habitation. The wintering party at the South Pole must deal with all the demands and stressors of an isolated, confined, and extreme environment without the prospect of relief from the outside world. In 1975, the seventeen men chosen to winter at the South Pole had an additional challenge. In February, as the austral winter was about to begin, a new geodesic-domed research station had just been completed. The station was the first of its kind, and the vagaries of its design and construction would be significant factors in the health and well-being of station residents as winter progressed. Potential physical and psychological problems from isolation literature are commented upon, and some significant events from this noteworthy winter are described. In addition, supporting quantitative data from current research at South Pole are used to better understand these events.

Impact of environmental factors on gastric cancer: A review of the scientific evidence, human prevention and adaptation

Globally, gastric cancer (GC) ranks fifth in prevalence and third in fatalities, and shows a distinct geographical distribution in morbidity and mortality. Such a spatial pattern indicates that environmental factors could be an important contributor to GC. We reviewed a total of 135 relevant peer-reviewed articles and other literature published 1936-2019 to investigate the scientific evidence concerning the effects of environmental factors on GC worldwide. Environmental factors affect GC from the aspects of water, soil, air, radiation, and geology. Risk factors identified include water type, water pollution, water hardness, soil type, soil pollution, soil element content, climate change, air pollution, radiation, altitude, latitude, topography, and lithology; and most of them have an adverse impact on GC. Furthermore, we found that their effects followed five common rules: (1) the leading environmental factors that affect GC incidence and mortality vary by region, (2) the same environmental factors may have different effects on GC in different regions, (3) some different environmental factors have similar effects on GC in essence, (4) different environmental factors often interact to have combined or synergistic effects on GC, and (5) environmental factors can affect human factors to have an impact on GC. Environmental factors have a great impact on GC. Human beings may prevent GC by controlling carcinogenic factors, screening high-risk populations and providing symptomatic and rehabilitative treatments. Furthermore, adaptation measures are recommended to reduce GC risk on private and public levels. Future studies should transcend existing empirical studies to develop causal relationship models and focus on vulnerable population analysis.

The curiously long absence of cooking in evolutionary thought

Beran et al. (2015, p. 1) characterized the idea that "cooked food was integral in human evolution" as a "long-held hypothesis" favored by Darwin and Engels. In fact, however, although Darwin and Engels considered the use of cooked food to be an important influence on behavior and society, neither of them suggested that its effects were evolutionary in the sense of affecting biology. Explicit discussion of the possible evolutionary impacts of cooking did not begin until the twentieth century.

Determinant of receptor-preference switch in influenza hemagglutinin

Influenza pandemic occurs when a new strain from other animal species overcomes the inter-species barriers and supports rapid human-to-human transmission. A critical prerequisite to this process is that hemagglutinin (HA) acquires a few key mutations to switch from avian receptors to human receptors. Previous studies suggest that H1 and H2/H3 HAs use different sets of mutations for the switch. This report shows that HA from the 1918 H1N1 pandemic virus (1918H1 HA) adopts the set of mutations used by H2/H3 HAs in receptor-preference switch when its 130-loop is made similar to those of H2/H3 HAs. Thus, the 130-loop appears to be the key determinant for the different mutations employed by pandemic H1 or H2/H3 HA. The correlation of the mutational routes and the 130-loop as unraveled in this study opens the door for efficient investigation of mutations required by other HA subtypes for inter-human airborne transmission.

Ancient pathogen-driven adaptation triggers increased susceptibility to non-celiac wheat sensitivity in present-day European populations

BACKGROUND

Non-celiac wheat sensitivity is an emerging wheat-related syndrome showing peak prevalence in Western populations. Recent studies hypothesize that new gliadin alleles introduced in the human diet by replacement of ancient wheat with modern varieties can prompt immune responses mediated by the CXCR3-chemokine axis potentially underlying such pathogenic inflammation. This cultural shift may also explain disease epidemiology, having turned European-specific adaptive alleles previously targeted by natural selection into disadvantageous ones.

METHODS

To explore this evolutionary scenario, we performed ultra-deep sequencing of genes pivotal in the CXCR3-inflammatory pathway on individuals diagnosed for non-celiac wheat sensitivity and we applied anthropological evolutionary genetics methods to sequence data from worldwide populations to investigate the genetic legacy of natural selection on these loci.

RESULTS

Our results indicate that balancing selection has maintained two divergent CXCL10/CXCL11 haplotypes in Europeans, one responsible for boosting inflammatory reactions and another for encoding moderate chemokine expression.

CONCLUSIONS

This led to considerably higher occurrence of the former haplotype in Western people than in Africans and East Asians, suggesting that they might be more prone to side effects related to the consumption of modern wheat varieties. Accordingly, this study contributed to shed new light on some of the mechanisms potentially involved in the disease etiology and on the evolutionary bases of its present-day epidemiological patterns. Moreover, overrepresentation of disease homozygotes for the dis-adaptive haplotype plausibly accounts for their even more enhanced CXCR3-axis expression and for their further increase in disease risk, representing a promising finding to be validated by larger follow-up studies.