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Glycerokinase occurs in ejaculated bull spermatozoa. Characteristics of the spermatozoan glycerokinase are quite similar to those of rat liver glycerokinase, except that the enzyme is firmly bound to the midpieces (mitochondria). The addition of l-glycerol-3-phosphate, as well as of free glycerol, to the washed bull spermatozoa causes both an increase in oxygen uptake and an accumulation of lactic acid. Since bull spermatozoa possess neither NAD+- nor NADP +-linked glycerol dehydrogenase, l-glycerol-3-phosphate would be formed by the action of glycerokinase as the initial step of glycerol metabolism in bull spermatozoa, followed by its oxidation to dihydroxyacetonephosphate by the mitochondrial dehydrogenase, via the glycolytic pathway. Among other animals, fowl and ram spermatozoa show high specific activity of glycerokinase. The enzyme activity is low in boar spermatozoa, and is not detectable in rabbit, human, rainbow trout, starfish and seaurchin spermatozoa.

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T. Kohsaka, H. Takahara, S. Tagami, H. Sasada and J. Masaki

Summary. Gel incubation film, which contained gelatin to prevent the diffusion of enzyme during chemical reaction and phenazine methosulfate to operate as a hydrogen acceptor between NADH and tetrazolium, was used and light microscopy revealed that lactate dehydrogenase was located in the head and tail of the spermatozoa as well as in the midpiece, whereas malate dehydrogenase was confined to the midpiece in spermatozoa of the animals examined. In goat spermatozoa, lactate dehydrogenase was associated mainly with the inner acrosomal membrane in the head, the mitochondrial matrix in the midpiece and with flagellar fibrils in the tail, whereas malate dehydrogenase was present only in the mitochondrial matrix.

Keywords: gel film histochemical technique; spermatozoa; goat; boar; water buffalo; lactate dehydrogenase; malate dehydrogenase

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M. Umezu, J. Masaki, H. Sasada and M. Ohta

Summary. A PGF-2α analogue (cloprostenol) was injected into 9 cows to synchronize oestrus. The cows were placed with or without a bull in a free-stall in groups of 3 at 46 h after the injection. Sexual behaviour was observed and serum LH concentrations were measured during the next 34 h.

The bull ejaculated with the cows in regular sequence and did not return to cows after an ejaculatory series was completed. The mating behaviour of the bull was closely related to the LH surge of the cows.

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T. Kohsaka, H. Takahara, H. Sasada, T. Kawarasaki, K. Bamba, J. Masaki and S. Tagami

Summary. Light-microscope immunocytochemistry using the peroxidase–antiperoxidase technique and a polyclonal rabbit antiserum raised against purified porcine relaxin showed that cytoplasmic immunostaining for relaxin could be visualized in the epithelial cells of the seminal vesicle. No relaxin immunoreactivity was seen in the testis, epididymis, ductus deferens, prostate or bulbo–urethral gland. A ten times higher concentration of porcine relaxin antiserum was necessary to achieve immunostaining in the seminal vesicle comparable to that in the corpora lutea of pregnant sows.

Ultrastructural examination showed that the epithelial cells of the boar seminal vesicle resembled typical protein-secreting cells with prominent rough endoplasmic reticulum and well-developed Golgi apparatus. The most striking feature of these cells was the accumulation of granules with a limiting membrane, which ranged from 200 to 600 nm in diameter and contained flocculent material of moderate electron density. Electron-microscope immunocytochemistry using the protein A-gold technique and relaxin antiserum demonstrated that the granules were the only intracellular organelles that showed immunoreactivity for relaxin.

These results indicate that a relaxin-like substance is present in boar seminal vesicles and that the subcellular site of its localization is the granules, suggesting that the seminal vesicle produces and stores a relaxin-like substance, but that it is present at much lower concentrations than in the corpora lutea of pregnant sows.

Keywords: relaxin; seminal vesicle; immunocytochemistry; boar