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W. Holtz and D. Smidt

Institut für Tierzucht und Haustiergenetik der Universität Göttingen, 34 Göttingen, Albrecht-Thaer-Weg 1, West-Germany

In all mammals studied so far, with the possible exception of man, it has been shown that sperm cells emerging from the testis have to pass through at least part of the epididymis before they acquire the ability to fertilize (Bedford, Calvin & Cooper, 1973; Bedford, 1974).

The literature regarding the fertilizing capacity of spermatozoa collected from different segments of the epididymis in laboratory animals has been summarized by Paufler & Foote (1968) and Orgebin-Crist (1969). Little information is available for the large domestic species although bulls have been successfully inseminated with spermatozoa from the cauda epididymidis (Lardy & Ghosh, 1952; Barker, 1954; Igboeli & Foote, 1968).

The present experiments were therefore conducted to examine the fertilizing capacity of spermatozoa from different regions of the epididymis in the domestic pig.

Epididymides were obtained by castrating sexually rested

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W. HOLTZ and R. H. FOOTE

Cannulation of the ductus deferens for collection of epididymal spermatozoa has been performed successfully in rams, bulls and boars (White, Larsen & Wales, 1959; Amann, Hokanson & Almquist, 1963; Bennett & Rowson, 1963; Tadmor, Schindler & Kempenich-Pinto, 1969; Wierzbowski & Wierzchos, 1969). Our attempts to adapt reported procedures directly to the rabbit failed because the cannula frequently became blocked soon after its insertion. A branched cannula was developed which consisted of a silicone rubber tube (Silastic, Dow Corning) 30 cm long, 1·02 mm i.d. and 1·65 mm o.d. A smaller tube (0·64 mm i.d. and 1·19 mm o.d.) of the same material was connected laterally 3 to 5 mm from the end of the cannula that was to be inserted into the ductus deferens (Text-fig. 1). This arrangement permitted flushing, and reduced the time spermatozoa

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R. H. F. Hunter, W. T. Huang and W. Holtz

Aliquots of ejaculated boar semen containing known numbers of spermatozoa were deposited into the caudal isthmus or rostral ampulla of the Fallopian tubes of gilts at, or immediately after, ovulation to assess regional influences on the rate of capacitation. Eggs were recovered during a second intervention 4, 5, 6 or 7 h after surgical insemination and were examined by phase-contrast microscopy. Results were obtained from ten animals in each of the 4-, 5- and 6-h groups and from eight animals in the 7-h group. With two exceptions, fertilized eggs were not recovered until 6 h after insemination into the isthmus, the proportion (45.6%) being significantly greater than the corresponding figure (1.4%) for ampullary insemination (P < 0.001). Similarly, the proportion of fertilized eggs recovered 7 h after insemination into the isthmus (58.7%) was significantly greater than after ampullary insemination (21.9%; P < 0.01). Numbers of spermatozoa associated with the zona pellucida remained low in all these instances, with mean figures per egg ranging from 0.3 to 3.8. Insemination into the isthmus gave a 1–2 h advantage in fertilization compared with insemination into the ampulla. Although relative rates of sperm cell progression to the site of fertilization may have contributed to this, there is strong evidence that rates of capacitation differ significantly in the respective portions of the Fallopian tube. Therefore, attention was focused on: (1) the viscous glycoprotein secretion in the caudal isthmus acting to remove seminal plasma from the sperm surface; and (2) the phase of sperm head binding to the isthmus epithelium. Gradients in local endocrine modulation by the adjacent ovary offer one explanation for the functional specialization of different regions of the Fallopian tubes.

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M Saleh, M Shahin, W Wuttke, M Gauly and W Holtz

The present investigation addresses the pharmacokinetics of human chorionic gonadotropin (hCG), intramuscularly (i.m.) administered to goats. Nine pluriparous does of the Boer goat breed, 2–6 years of age and weighing 45–60 kg, were administered 500 IU hCG (2 ml Chorulon) deep into the thigh musculature 18 h after superovulatory FSH treatment. Blood samples were drawn from the jugular vein at 2 h intervals for the first 24 h, at 6 h intervals until 42 h, and at 12 h intervals until 114 h after administration. After centrifugation, plasma hCG concentrations were determined by electrochemiluminescence immunoassay. Pharmacokinetical parameters were as follows: lag time, 0.4 (s.e.m. 0.1) h; absorption rate constant, 0.34 (s.e.m. 0.002) h; absorption half-life, 2.7 (s.e.m. 0.5) h; elimination rate constant, 0.02 (s.e.m. 0.002) h; biological half-life, 39.4 (s.e.m. 5.1) h; and apparent volume of distribution, 16.9 (s.e.m. 4.3) l. The plasma hCG profile was characterized by an absorption phase of 11.6 (s.e.m. 1.8) h and an elimination phase of 70.0 (s.e.m. 9.8) h, with considerable individual variation in bioavailability and pharmacokinetical parameters. Biological half-life was negatively correlated (P<0.05) with peak concentration (r=−0.76), absorption rate constant (r=−0.78), and elimination rate constant (r=−0.87). The results indicate that after rapid absorption, hCG remains in the circulation for an extended period. This has to be taken into account when assessing the stimulatory response to hCG treatment on an ovarian level.

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R. H. F. Hunter, W. Holtz and P. J. Henfrey

Department of Agricultural Zoology, School of Agriculture, University of Edinburgh, U.K. and Department of Animal Science, University of Göttingen, West Germany