Localisation of carbonic anhydrase in the sperm storing regions of the domestic hen oviduct.

In the female bird sperm is stored in a quiescent mode, but full motility is needed for successful fertilisation. Regulation of sperm motility is thus of vital interest and the pH is a factor of importance. For this reason the localisation of carbonic anhydrase in the vagina, uterovaginal junction and infundibulum was studied with a histochemical method. Carbonic anhydrase catalyses the reaction CO2 + H2O <--> H+ + HCO3- and is known to take significant part in acid-base regulation in the body. The enzyme was found in all regions with the highest activity, both cytoplasmic and membrane-bound, in the non-ciliated cells of the uterovaginal surface epithelium. Intense membrane-bound activity was also found in the infundibular grooves and glands with slightly less in the sperm storage tubules and vaginal epithelium. Occasionally cytoplasmic and nuclear staining was seen. Changes in pH affect sperm motility and our results provide the first evidence for cellular mechanisms that makes rapid changes of the pH possible in these regions. Judging from the distribution of carbonic anhydrase we suggest two possible functions: (1) increasing pH and/or adding bicarbonate ions to stimulate sperm motility needed for the transfer to the storage sites and at fertilisation, and (2) a lowering of the pH in the sperm storage sites to keep the sperm quiescent during storage.

Platyphylloside: Metabolism and digestibility reductionin vitro.

The metabolism of platyphylloside [(5S)-5-hydroxy-1,7-bis-(4-hydroxyphenyl)-3-heptanone-5-O-ß-D-glucopyranosidel]-known to reduce digestibility-was studiedin vitro in sheep rumen liquor. Platyphylloside is hydrolyzed to 5-hydroxy-3-platyphyllone [(5S)-5-hydroxy-1,7-bis-(4-hydroxyphenyl)-3-heptanone], which is reduced to centrolobol [1,7-bis-(4-hydroxyphenyl)-3-heptanol], via 3-platyphyllone [7-bis-(4-hydroxyphenyl)-3-heptanone]. The digestibility-reducing effect was shown to be correlated with the concentration of centrolobol.

Chemical defense in birch. Platyphylloside: A phenol fromBetula pendula inhibiting digestibility.

Extracts of Scandinavian birch (Betula pendula Roth) buds and internodes of varying twig diameters have been investigated for their inhibitory effect on ruminant digestibility in vitro. The predominant inhibitory effect was observed in extracts containing the phenol platyphylloside, 5-hydroxy-1,7-bis-(4-hydroxy-phenyl)-3-heptan-one-3-O-ß-D-glucopyranoside. Isolation of the pure compound and incubation with rumen inocula showed that digestibility was negatively related to the concentration. Significant effect was measured below the concentration naturally occurring in birch (0.8% of dry matter). Another isolated compound, the closely related rhododendrin, 4-(4-hydroxyphenyl)-2-butanol-2-O-ß-D-glucopyranoside, did not depress digestibility within the concentrations found in birch. An important phenol of buds, apigenin-4',7-dimethylether, did not have any measurable effect on digestibility, while a nonphenolic fraction of bud extract had a slight inhibitory effect on digestibility. Implications for browsers feeding on birch are briefly discussed.