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D. AMIR

Summary.

Sperm smears prepared from different parts of the genital tract of two bulls 12 and 21 days after the start of oral treatment with ethylene dibromide (4 mg EDB/kg body weight on alternate days), showed a distribution of abnormal spermatozoa, which indicates that EDB affected the shape of the spermatozoa during maturation in the epididymis and during spermiogenesis.

After administration to four bulls of labelled [3H]- or [14C]EDB, either orally or by injection, labelled spermatozoa were obtained in the ejaculates collected from about 1 week after the first oral dose or injection until 2 to 3 weeks after the last oral dose or injection. The highest percentage of abnormal spermatozoa resulting from the treatment was found when the radioactivity of the spermatozoa was lowest or nil.

It appears that the spermicidal action of EDB is not direct on the sperm cells but occurs during the process of spermiogenesis and through the absorptive and/or secretory functions of the epididymis.

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D. AMIR

Division of Animal Reproduction, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan, Israel

(Received 20th January 1975)

It has been reported that the administration of ethylene dibromide, either orally or by injection, to bulls induced malformations in the heads of ejaculated spermatozoa collected from about 3 weeks after the start of the treatment (Amir & Volcani, 1965; Amir & Ben-David, 1973). These malformations persisted for about 3 weeks, and then spermatozoa with normal-shaped heads appeared in the ejaculates. Since head malformations in spermatozoa can occur as a result of testis dysfunction (Gustafsson, 1966), it is possible to study the mechanism of sperm formation in the testis by following the various stages of interference by ethylene dibromide in the normal process of spermatogenesis. However, individual differences should be determined before the physiological significance of ethylene dibromide action is considered. In the present study, the release of spermatozoa with

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D. AMIR and H. SCHINDLER

Summary.

Rates of fructolysis and oxygen uptake were measured in suspensions of ram spermatozoa containing various concentrations of lactate at different pH. It was found that lactate by itself causes a reversible depression of the metabolic rate, the magnitude of the effect being dependent on the lactate concentration.

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H. SCHINDLER and D. AMIR

The effect of different sperm doses on the conception rate has been studied by Salamon (1962), Gancev (1963) and Kareta, Osikowski & Wierzbowski (1966), but without relation to a possible effect of time of insemination. Jones, Martin & Lapwood (1969) and Entwistle & Martin (1972) studied the effect of restricted sperm doses (100 × 106 and 50 × 106 spermatozoa) and, by relating the results to vaginal mucus score, found that the highest conception rate occurred in ewes with a copious, clear or cloudy mucus at the time of insemination. On the other hand, in recent work in this laboratory (Amir & Schindler, 1972), it was shown that with the use of 300 to 500 × 106 freshly ejaculated spermatozoa, single inseminations of ewes were of uniform and high efficiency almost throughout oestrus. The present study was undertaken in order to investigate the possibility that the time

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D. Amir and U. Lavon

Summary.

Protein changes in epididymal and ejaculated spermatozoa were studied in bulls treated orally on alternate days with a total of 10 doses (each of 4 mg/kg body weight) of ethylene dibromide. No significant changes were found in the total nitrogen, amino acid or lipoprotein contents of the spermatozoa collected either from the epididymis 1 day after the last dose, or from ejaculates 9-13 days after the end of the treatment. Significant changes were found in the percentage composition of amino acids of the sperm proteins and lipoproteins but the changes differed in the caput, cauda and ejaculated spermatozoa.

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D. AMIR and H. SCHINDLER

It is generally accepted that in cattle the conception rate depends upon the time of insemination in relation to the time of ovulation, considering the unequal life-span of the gametes and the time necessary for sperm transport and capacitation (Asdell, 1955). Accordingly, practical recommendations have been put forward as to the time during oestrus when insemination will result in the optimum conception rate (Salisbury & VanDemark, 1961).

Studies made in ewes gave variable results, with the optimum time for insemination coinciding with the first half of oestrus (Sinclair, 1957; Morrant & Dun, 1960; Restall, 1963; Jones, Martin & Lapwood, 1968; Mattner & Braden, 1969), mid-oestrus (Kardymovic, Marsakova & Pavljucek, 1934; Carbonero-Bravo, 1955) or the later stages of oestrus (Anderson, 1941; Restall, 1961; Schindler, Eyal & Volcani, 1961; Steklenev, 1961).

In view of the potential

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D. AMIR and H. SCHINDLER

Summary.

The rates of oxygen consumption and fructolysis were measured in suspensions of washed spermatozoa at concentrations ranging from 1×109 to 7×109/ml. Within that range the respiratory rate was independent of sperm concentration, provided that the oxygen diffusion was adequate. Similarly, the rate of fructolysis under anaerobic conditions and constant pH was not influenced by high sperm densities.

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D. DRORI, D. AMIR and Y. FOLMAN

Summary.

Male rats mated infrequently had consistently larger coagulating glands containing more fructose than unmated males, and the concentration of fructose in these glands was higher in four out of five experiments. However, males mated frequently had smaller glands and lower fructose content than males mated infrequently.

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F. Tasseron, D. Amir and H. Schindler

Although a fertilization rate similar to that of fresh semen has been obtained with frozen ram semen (Colas, 1975), a low lambing rate is reported in the majority of the studies so far published (Salamon & Visser, 1974). The low fertility of the frozen ram semen has been attributed to a failure of sperm transport in the female (Lightfoot & Salamon, 1970), to a reduced viability of the spermatozoa in the genital tract of the ewe (Mattner, Entwistle & Martin, 1969), or, at least in part, to the acrosomal damage caused by freezing (Watson & Martin, 1972).

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U. LAVON, R. VOLCANI, D. AMIR and D. DANON

There are a few reports on the changes in specific gravity (s.g.) during maturation and ageing of spermatozoa. Lindahl & Kihlström (1952) found the s.g. of bull spermatozoa to range between 1·240 and 1·334. The s.g. decreased from 1·2867 to 1·2668 when three consecutive ejaculates were collected. Lindahl & Thunqvist (1965) found a value of 1·10 to 1·12 for the s.g. of bull epididymal spermatozoa and a value of 1·21 to 1·33 for ejaculated spermatozoa. Assuming that spermatozoa from the epididymis and from later ejaculates are younger than those from the first ejaculates, they suggested that the s.g. of spermatozoa increases with maturation and ageing.

Spermatozoa were taken from different parts of the bull testis in order to ascertain whether their s.g.