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Background and Materials and methods: In order to clarify and reveal the morphological characteristics of yak placentomes, placentomes obtained from 151 to 180 days of pregnant yaks were observed using light microscopy and scanning and transmission electron microscopy. Results: The results indicated that sessile, dome-shaped yak placentomes seemed to have a relatively complex villous-crypt architecture pattern. There was a straight maternal plate beneath the placentome. Plentiful uterine glands and a dense cellular layer were present in the endometrium lamina propria close to the maternal plate. Trophoblast giant cells appeared to have similar ultrastructure features to these in other ruminants, including abundant mitochondria, an extensive array of rough endoplasmic reticulum, advanced Golgi complex and many specific secretory granules. Trophoblast giant cells could also secrete neutral and acid glycoconjugates. Furthermore, numerous glycoconjugates were distributed in the connective zones between mononuclear trophoblast cells and crypt epithelial cells as well as in maternal connective tissues. Mononucleate trophoblast cells, which had abundant microvilli that interdigitated with the corresponding microvilli arising from the crypt epithelial cells, had numerous mitochondria and vesicles, but there were no glycoconjugates. Conclusions: The morphological structures of yak placentomes were similar to those of other bovid genera; however, certain differences were observed. These findings might provide morphological evidence for evolutionary relationships between different bovid genera.

Background: This study aimed to investigate the expression and localisation of fol­licle stimulating hormone receptor/growth hormone receptor/luteinising hormone receptor (FSHR/GHR/LHR) in different tissues and examine the regulatory effects of FSHR/GHR/LHR in the reproductive organs of female yaks during luteal phase. Materials and methods: The quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry assays were utilised to analyse the expression and localisation of FSHR/GHR/LHR in different tissues on female yaks. Results: The qRT-PCR results showed that the mRNA expressions of FSHR/GHR/ /LHR were significantly different in the non-reproductive organs (p < 0.01); the highest expression level was observed in the kidney, cerebellum and lung, whereas the lower expression level was observed in the liver and spleen. Im­munohistochemistry assay results showed that FSHR/GHR/LHR were located in kidney tubules, Purkinje cells, cerebellar medulla, alveolar cells and hepato­cytes. In addition, the expression levels of FSHR and GHR were considerably higher than LHR in the reproductive organs of female yaks during luteal phase (p < 0.01). FSHR/GHR/LHR were located in cardiac muscle cells, cerebellar medulla, and theca cell lining of reproductive organs. Furthermore, the expression level of FSHR was higher than those of GHR and LHR in all examined tissues. Conclusions: Therefore, the expression and localisation of FSHR/GHR/LHR possibly helped to evaluate the effects of them in tissue specific expression on female yaks, investigate the function and mechanism of FSHR/GHR/LHR in the reproductive organs of female yaks during luteal phase. (Folia Morphol 2018; 77, 2: 301–309)

Cold-inducible RNA binding protein (CIRP) is over-expressed during cold and many other stresses, and could regulate the adaptation to hypothermia. In the present investigation, the objective was to determine the expression of CIRP in adult yak heart, liver, spleen, lung, kidney, brain, ovary, testis and skin by relative quantitative real time polymerase chain reaction (RT-PCR), Western blot and immunohistochemistry from mRNA and protein levels. The CIRP open reading frame encoding was cloned from the domestic yak brain. Results of RT-PCR and Western blot showed the high expression level of CIRP in the heart, kidney, brain, testis and skin, and the lower expression level of CIRP in the lung. Immunohistochemical staining showed CIRP was expressed in the nucleus of neuronal cells, spermatogonia, primary spermatocytes and epidermal cells, and in the cytoplasm of the residual tissues. These observations may provide new data to understand and further study the important role of CIRP protein in the plateau adaptation of the domestic yak on long-term evolution.

Background: Heat shock protein 60 (Hsp60) play important roles in protecting testicular development and production of sperms. This study was conducted to investigate Hsp60 gene expression and localization in testicular development to ascertain its influence on infertility and in different tissues of the male cattle-yak and yak. A total of 54 cattle (24 cattle-yak and 30 yak) were examined. Materials and methods: Hsp60 mRNA of cattle-yak was cloned first and amino acid variations were found leading to differences at protein spatial structure compare with the yak. Real-time quantitative PCR (RT-qPCR) analysis revealed that Hsp60 mRNAs expression were different in cattle-yak and yak. Results: The results showed disparity in Hsp60 expression among different tissues and in different developmental stages of the testis. High Hsp60 expression was observed in juvenile and adult testicles. Moreover, Hsp60 expression in cattle-yak was significantly higher than yak (p < 0.01). The location of Hsp60 in tissue and testis was detected by immunohistochemistry (IHC) and immunofluorescence (IF). The results demonstrated that Hsp60 proteins located in epithelial cells, spermatocytes, sperm cells and mesenchymal cells. Conclusions: The Hsp60 proteins are expressed in different tissues, and the highest expression level was observed in the testis of the cattle-yak, which suggests that infertility of cattle-yak have some correlation with up-regulation of Hsp60.

The fore- and hindlimb of yak have been studied by the gross anatomical methods and standard histological techniques. The artery of ungula was also determined by X-ray and acrylonitrile-butadiene-styrene casting. Anatomical features of the forelimb of yak resemble those of hindlimb, including hoof periphery, hoof coronal, hoof wall, hoof sole, and hoof sphere. The forelimb and hindlimb are almost the same in histological structure. The epidermis comprised all 5 strata: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum and stratum basale. The papillary layers and dermal lamellae contained a variable amount of capillary as well as collagen and elastic fibres. Many venules and arteriovenous anastomosis were distributed among the reticular layer. Subcutaneous tissue was composed of rich adipose and connective tissue in hoof periphery, hoof coronal, and, especially, hoof sphere. Major arteria in forelimb of yak include arteria digitalis palmaris communis III and arteriae digitales palmares propriae III and IV axialis. Those in hindlimb include arteria digitalis plantaris communis III and arteria digitalis plantaris propria III and IV axialis. Our findings highlight the main morphological features of yak and provide a morphological basis useful to researchers using yak hoof.

Background: Platelet derived growth factors (PDGFs) are key components of autocrine and paracrine signalling, both of which play important roles in mammalian developmental processes. PDGF expression levels also relate to oxygen levels. The characteristics of yak PDGFs, which are indigenous to hypoxic environments, have not been clearly described until the current study. Materials and methods: We amplified the open reading frame encoding yak (Bos grunniens) platelet derived growth factor-alpha (PDGFA) from a yak skin tissue cDNA library by reverse transcriptase polymerase chain reaction (PCR) using specific primers and Sanger dideoxy sequencing. Expression of PDGFA mRNA in different portions of yak brain tissue (cerebrum, cerebellum, hippocampus, and spinal cord) was detected by quantitative real-time PCR (qRT-PCR). PDGFA protein expression levels and its location in different portions of the yak brain were evaluated by western blot and immunohistochemistry. Results: We obtained a yak PDGFA 755 bp cDNA gene fragment containing a 636 bp open reading frame, encoding 211 amino acids (GenBank: KU851801). Phylogenetic analysis shows yak PDGFA to be well conserved, having 98.1% DNA sequence identity to homologous Bubalus bubalus and Bos taurus PDGFA genes. However, 8 nucleotides in the yak DNA sequence and 4 amino acids in the yak protein sequence differ from the other two species. PDGFA is widely expressed in yak brain tissue, and furthermore, PDGFA expression in the cerebrum and cerebellum are higher than in the hippocampus and spinal cord (p > 0.05). PDGFA was observed by immunohistochemistry in glial cells of the cerebrum, cerebellum, and hippocampus, as well as in pyramidal cells of the cerebrum, and Purkinje cell bodies of the hippocampus, but not in glial cells of the spinal cord. Conclusions: The PDGFA gene is well conserved in the animal kingdom; however, the yak PDGFA gene has unique characteristics and brain expression patterns specific to this high elevation species.