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C. H. CHEN, D. C. KLEIN and J. C. ROBINSON

The present report is the first in a projected series of investigations on biogenic amine-synthesizing and -degrading enzymes in trophoblast. The work is being undertaken to gain information relating to two questions. First, do the placental enzymes which degrade biogenic amines and related compounds provide an important biochemical barrier which protects the fetus against undesirable stimulation by physiological and pharmacological compounds in the maternal circulation? Secondly, do critical changes in biogenic amine metabolism in the placenta precede or accompany parturition, and might they be involved in the actual mechanism underlying the initiation of parturition?

Catechol-O-methyltransferase (COMT, E.C.2.1.1.6) is an enzyme which inactivates certain catecholamines and O-methylates 2-hydroxyoestradiol-17 β (Ball, Knuppen, Haupt & Breuer, 1971); it has been purified 66-fold from human placenta (Gugler, Knuppen & Breuer, 1970).

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C. H. Chen, D. C. Klein and J. C. Robinson

Summary.

The activity of monoamine oxidase (MAO), an enzyme which metabolizes catecholamines and indoleamines, was determined in rat placenta at various stages of gestation, in human term placenta, and in choriocarcinoma grown in culture. From Day 15 to Day 20 of gestation the specific activity (units/mg protein) of MAO in rat placenta increased at least 3-fold; from Day 20 to the time of parturition, it decreased about 50 %. The specific activity of MAO in human placenta at term was about 8 times higher than that of rat placenta at term. No MAO activity was found in choriocarcinoma grown in culture.

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F Guo, B Yang, Z H Ju, X G Wang, C Qi, Y Zhang, C F Wang, H D Liu, M Y Feng, Y Chen, Y X Xu, J F Zhong and J M Huang

The sperm flagella 2 (SPEF2) gene is essential for development of normal sperm tail and male fertility. In this study, we characterized first the splice variants, promoter and its methylation, and functional single-nucleotide polymorphisms (SNPs) of the SPEF2 gene in newborn and adult Holstein bulls. Four splice variants were identified in the testes, epididymis, sperm, heart, spleen, lungs, kidneys, and liver tissues through RT-PCR, clone sequencing, and western blot analysis. Immunohistochemistry revealed that the SPEF2 was specifically expressed in the primary spermatocytes, elongated spermatids, and round spermatids in the testes and epididymis. SPEF2-SV1 was differentially expressed in the sperms of high-performance and low-performance adult bulls; SPEF2-SV2 presents the highest expression in testis and epididymis; SPEF2-SV3 was only detected in testis and epididymis. An SNP (c.2851G>T) in exon 20 of SPEF2, located within a putative exonic splice enhancer, potentially produced SPEF2-SV3 and was involved in semen deformity rate and post-thaw cryopreserved sperm motility. The luciferase reporter and bisulfite sequencing analysis suggested that the methylation pattern of the core promoter did not significantly differ between the full-sib bulls that presented hypomethylation in the ejaculated semen and testis. This finding indicates that sperm quality is unrelated to SPEF2 methylation pattern. Our data suggest that alternative splicing, rather than methylation, is involved in the regulation of SPEF2 expression in the testes and sperm and is one of the determinants of sperm motility during bull spermatogenesis. The exonic SNP (c.2851G>T) produces aberrant splice variants, which can be used as a candidate marker for semen traits selection breeding of Holstein bulls.