Novel mutations in ubiquitin-specific protease 26 gene might cause spermatogenesis impairment and male infertility

Aim： To study the incidence of single nucleotide polymorphisms in ubiquitin-specific protease 26 （USP26） gene and its involvement in idiopathic male infertility in China. Methods： Routine semen analysis was performed. Infertility factors such as immunological, infectious and biochemical disorders were examined to select patients with idiopathic infertility. DNA was isolated from peripheral blood of the selected patients and control population, which were examined for mutations using polymerase chain reaction-single strand conformation polymorphism analysis. Furthermore, nucleotide sequences were sequenced in some patients and controls. Results： Of 41 infertile men, 9 （22.0%, P = 0.01） had changes in USP26 gene on the X chromosome. A compound mutation （364insACA; 460G→A） was detected in 8 patients （19.5%, P = 0.01） and a 1044T→A substitution was found in 1 patient （2.4%, P 〉 0.05）. All three variations led to changes in the coding amino acids. Two substitutions predict some changes： 460G→ A changes a valine into an isoleucine, and 1044T → A substitutes a leucine for a phenylalanine. Another insertion of three nucleotides ACA causes an insertion of threonine. No other changes were found in the remaining patients and fertile controls. Conclusion： The USP26 gene might be of importance in male reproduction. Mutations in this gene might be associated with male infertility, and might negatively affect testicular function. Further research on this issue is in progress.

The expression of Usp26 gene in mouse testis and brain

Deubiquitinating enzymes （DUBs） play an important role in ubiquitin-dependent processes as negative regulators of protein ubiquitination. Ubiquitin-specific protease 26 （USP26） is a member of this family. The expression of Usp26 in mammalian testis and in other tissues has yet to be fully elucidated. To study the expression of Usp26 mRNA and protein in various murine tissues, reverse transcription （RT）-PCR and immunohistochemistry analyses were carried out. The RT-PCR analysis showed that the Usp26 transcript was expressed in all of the tested tissues. USP26 protein localization was examined by immunohistochemistry, and it was shown that USP26 was not detectable at 20 days postpartum, with the expression restricted to the cytoplasm of condensing spermatids （steps 9-16）, Leydig cells and nerve fibers in the brain. In addition, the USP26 protein was detected at moderate levels in myocardial ceils, the corpus of epidydimis, epithelium of the renal tubules and the seminal gland of postnatal day 35 mice. Its spatial and temporal expression pattern suggests that Usp26 may play an important role in development or function of the testis and brain. Further research into these possibilities is in progress.

Hepatic Cyp1a2 Expression Reduction during Inflammation Elicited in a Rat Model of Intermittent Hypoxia

Background： Intermittent hypoxia （IH） is a key element of obstructive sleep apnea （OSA） that can lead to disorders in the liver. In this study, IH was established in a rat model to examine its effects on the expression of hepatic cytochrome P450 （CYP） and CYP regulators, including nuclear receptors. Methods： Hematoxylin and eosin staining was conducted to analyze the general pathology of the liver of rats exposed to IH. The messenger RNA （mRNA） expression levels of inflammatory cytokines, CYPs, nuclear factor-κB （NF-κB）, and nuclear factors in the liver were measured by quantitative reverse transcription polymerase chain reaction. Results： We found inflammatory infiltrates in the liver of rats exposed to IH. The mRNA expression level of interleukin-1beta was increased in the liver of the IH-exposed rats （0.005 ± 0.001 vs. 0.038 ± 0.008, P = 0.042）, whereas the mRNA expression level of Cyp1a2 was downregulated （0.022 ± 0.002 vs. 0.0050 ± 0.0002, P = 0.029）. The hepatic level of transcription factor NF-κB was also reduced in the IH group relative to that in the control group, but the difference was not statistically significant and was parallel to the expression of the pregnane X receptor and constitutive androstane receptor. However, the decreased expression of the glucocorticoid receptor upon IH treatment was statistically significant （0.056 ± 0.012 vs. 0.032 ± 0.005, P = 0.035）. Conclusions： These results indicate a decrease in expression of hepatic CYPs and their regulator GR in rats exposed to IH. Therefore, this should be noted for patients on medication, especially those on drugs metabolized via the hepatic system, and close attention should be paid to the liver function of patients with OSA-associated IH.

Effect of artificial tribological layer on sliding wear behavior of H13 steel

An artificial tribological layer was formed on the worn surface during sliding,through supplying MoS_2,Fe_2O_3 or their equiponderant mixtures onto the sliding interface of H13/GCr15 steels.The effect of this tribological layer on the wear behavior of H13 steel was studied.The worn surfaces and subsurfaces of H13 steel were thoroughly characterized by using X-ray diffraction（XRD）,scanning electron microscopy（SEM）and energy dispersive spectrometry（EDS）;the wear mechanisms were explored.The research results demonstrated that tribological layer did not exist during sliding of H13 steel with no additive,but it formed with the addition of MoS_2,Fe_2O_3 or their equiponderant mixtures.When there was no tribological layer,the wear rate rapidly increased with an increase of the load.In this case,adhesive and abrasive wear prevailed.As the additives were supplied,the artificial tribological layer was observed to be immediately formed and stably existed on worn surfaces.This tribological layer presented an obvious protective function from wear and friction.Hence,the wear rate and friction coefficient were significantly decreased.MoS_2 as tribological layer seemed to present more obvious protective function than Fe_2O_3.By supplying their mixture,the artificial tribological layer possessed not only the load-carrying capacity of Fe_2O_3,but also the lubricative capacity of MoS_2.These two simultaneous capacities could improve the friction and wear properties of H13 steel further.