Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have demonstrated earlier that the per sperm creatine-N-phosphotransferase (CK) activity was increased in oligospermic vs. normospermic men. The increased sperm CK activity is related to higher concentrations of cellular CK, which may indicate a defect of cytoplasmic extrusion during spermatogenesis. In the present work, we examined whether in spermatozoa, similar to muscle, there is a change in the synthesis of B-CK and M-CK isoforms during cellular differentiation. In 109 normospermic and 50 oligospermic specimens (sperm concentrations 60.6 +/- 3.7 vs. 8.8 +/- 1.3 million sperm/ml; all values expressed as mean +/- SEM), the relative concentrations of the M-CK isoform (M-CK/M-CK + B-CK) were 27.2% +/- 2.1% vs. 6.7% +/- 0.9% (P less than 0.001). The per sperm CK activities showed comparable differences (0.21 +/- 0.02 vs. 0.89 +/- 0.1 CK IU/100 million sperm; P less than 0.001) in the two groups, and there was a close correlation between per sperm CK activities and M-CK concentrations (R = 0.69, P less than 0.001, N = 159). This indicates that the loss of cytoplasm and the commencement of M-CK isoform synthesis are related events during the last phase of spermatogenesis, also that the incidence of spermatozoa with incomplete cellular maturation is higher in oligospermic specimens. In characterizing the M-CK, we found that sperm (unlike muscle tissue) lack the MB hybrid of CK dimers. However, in the presence of muscle M-CK, the muscle-sperm MB-CK hybrid has formed. Thus in sperm and muscle the M-CK isoforms are structurally different, whereas the B-CKs are apparently homologous.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Spermatogenesis-related change in the synthesis of the creatine kinase B-type and M-type isoforms in human spermatozoa. 233 74

The demonstration that phosphocreatine is used as an energy source by rat PRL-secreting pituitary tumours prompted the study of the enzyme creatine kinase in both rat and human pituitary tumours. Rats treated with diethylstilbestrol developed greatly enlarged pituitaries and hyperprolactinaemia. Total creatine kinase was significantly increased and fractionation on diethylaminoethyl Sephadex showed that the 'brain' form was increased, whereas the 'muscle' and mitochondrial forms showed no change. Exposure to large concentrations of oestradiol caused similar changes in creatine kinase which increased over a period of 25 weeks. The total creatine kinase content of a series of human pituitary tumours was highly variable, but the mean value of 183 +/- 46 (SEM) units per gram protein was significantly higher than the mean for normal pituitary tissues (28.4 +/- 2.9). The brain:muscle isozyme ratio was measured in six human PRL-secreting tumours with a mean of 3.47 +/- 0.73, significantly higher than in 'non-functional' tumours (1.57 +/- 0.29) or normal tissue (1.77 +/- 0.28). Three of four GH-secreting tumours had a ratio below 0.6. The highest ratio found (8.66) was in an ACTH-secreting tumour. Previous reports have shown that oestradiol rapidly induces brain creatine kinase in oestrogen responsive tissues. This is not the case with the rat pituitary gland or oestrogen responsive human tumour cells in culture. Chronic oestrogen treatment, however, does increase creatine kinase in the proliferating gland and many human pituitary tumours have increased enzyme activity. These results suggest that the phosphocreatine/ATP system and in particular the brain isozyme of creatine kinase are of particular importance in lactotropes.
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PMID:Increased creatine kinase activity in pituitary tumours of rat and man. 303 50