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R. ELIASSON

Summary.

The oxygen consumption of human spermatozoa has been determined polarographically with Clark electrodes both in whole semen and in a buffered Ringer solution. Washing of the spermatozoa caused an average decrease of 13% in the number of live cells. The oxygen consumption of the spermatozoa was two to three times higher in the Ringer solution than in the whole semen (P<0·001).

If the washed spermatozoa were returned to their own seminal plasma, the oxygen consumption also returned to the original level. These results indicated that human seminal plasma normally contains a factor that depresses sperm respiration.

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R. DEANESLY

Summary.

The rapid decidualization of the endometrial stroma, which begins while the guinea-pig blastocyst is still passing through the uterine epithelium, has been compared in serial sections with the decidualization following thread traumatization in the same or similar uteri. In both cases there are localized alkaline phosphatase reactions, but blastocyst implantation leads to formation of a decidua which within the first 24 hr, is more organized and differentiated than the corresponding traumatic deciduoma. The passage of the guinea-pig blastocyst through the uterine epithelium does not involve cell destruction or phagocytosis and the decidual changes in the stroma must be attributed to specific blastocyst activity.

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R. YANAGIMACHI

Mammalian ovarian oocytes can mature in vitro when liberated from Graafian follicles and placed in appropriate culture media. This was first demonstrated in the rabbit (Pincus & Enzmann, 1935, 1937; Chang, 1955a, b) and has been confirmed in a variety of animals (see Donahue, 1972; Biggers, 1973; Fowler & Edwards, 1973).

According to Jagiello (1969), 80 to 100% of guinea-pig oocytes isolated from ovaries of adult females in the middle (Days 5 to 8) of their oestrous cycle resume meiosis upon culture and may reach metaphase II by 14 hr of culture. Unfortunately, Jagiello gave no detailed information of the techniques which she used for isolation and culture of the oocytes and did not determine whether the oocytes matured in vitro were fertilizable. This paper describes a method of culturing

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R. JONES

As yet, there is little knowledge as to the possible side effects of vasectomy on the function of the epididymis. In rats and bulls, it has been reported that vasectomy causes a spermatocoele to develop at the site of ligation on the vas deferens or in the epididymis (Amann & Almquist, 1962; Igboeli & Rakha, 1970; Hooker & Gilmore, 1972); in other species, notably the rabbit, this does not occur (Macmillan, Desjardins, Kirton & Hafs, 1968; Paufler & Foote, 1969). Some reports have claimed that vasectomy causes atrophy of the testis and disruption of spermatogenesis (Laumas & Uniyal, 1967; Sacher & Schilling, 1973) but most workers agree that, at least in the early stages, vasectomy only affects the terminal parts of the epididymis. It is not known what influence this might have

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R. Jones

Summary. Monoclonal antibodies to antigens located on surface and intracellular membranes of spermatozoa from the rat cauda epididymidis have been used as probes to assess the purity of putative plasma membrane fractions. Spermatozoa were demembranated by shearing forces generated on a vortex-mixer. Immunofluorescence and ultrastructural analysis of vortex-mixed spermatozoa showed that they were denuded of approximately 90% of surface membrane. Areas of acrosomal membranes were also removed. Crude plasma membranes were recovered in low-speed wash fluids and fractionated on a 13–23% Nycodenz density gradient. Three bands containing membrane vesicles were resolved. Absorption curves and direct binding assays using monoclonal antibodies specific for acrosomal membranes, mitochondrial membranes and fibrous sheath showed relatively strong binding to bands 1 and 2 but weak binding to band 3. Conversely a monoclonal antibody specific for a surface membrane antigen bound strongly to band 3 and weakly to bands 1 and 2. Identification on immunoblots of the antigens recognized by the monoclonal antibodies revealed that band 3 was positive for surface membrane antigens but gave no reaction for intracellular antigens. However, bands 1 and 2 were strongly positive for intracellular components. The results suggest that vortex-mixing is a simple and efficient means of removing the plasma membrane from spermatozoa and that a membrane fraction can be recovered from a Nycodenz density gradient that is enriched 40- to 50-fold in surface antigens.

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R. D.

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R. YANAGIMACHI

With some important exceptions (Chang & Hancock, 1967), fertilization of mammalian eggs is species-specific in that the eggs of a species can be penetrated only by spermatozoa of the same species. The analysis of the species-specificity of fertilization is very difficult when in-vivo systems are used. In-vitro systems, on the other hand, eliminate many factors and enable us to examine directly the interactions between the eggs and spermatozoa.

Barros (1968) inseminated rat eggs in vitro with capacitated golden hamster spermatozoa and found that only one out of 294 eggs had been penetrated. In this egg, two spermatozoa had penetrated the zona pellucida but failed to enter the vitellus. On the other hand, none of 280 mouse eggs inseminated in vitro with capacitated hamster spermatozoa were found to be penetrated.

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R. DEANESLY

Summary.

Ovo-implantation in the guinea-pig on the 6th to 7th day post coitum is not affected by ovariectomy on days 3 to 7 p.c. If the ovaries are removed on the 2nd day after mating, however, implantation does not occur unless at least one injection of progesterone is given. In the ovariectomized guinea-pigs, the embryos develop normally for several days but may regress after day 14 unless progesterone is supplied, permitting further growth. No evidence was found of delayed implantation.

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R. YANAGIMACHI

Summary.

When hamster epididymal spermatozoa were incubated in vitro in the presence of follicular fluid in Tyrode's solution for 3 hr or more, they became fully capacitated. The majority of the capacitated spermatozoa had lost the acrosome cap, and they displayed an extremely vigorous motility. When placed in contact with freshly ovulated eggs in vitro, the spermatozoa started to enter the zona pellucida of the eggs as early as 10 min after insemination; sperm penetration through the zona pellucida, however, occurred most often between 30 and 50 min after insemination. The follicular fluid markedly reduced its spermcapacitating potency when diluted with a large volume of Tyrode's solution. Cumulus oophorus cells, their matrix, corona radiata cells and the eggs had no potency to induce functional capacitation of the spermatozoa. Follicular fluids of four different species were tested. In respect to their potency to capacitate hamster spermatozoa, the fluids of three species could be arranged in the following order: hamster>mouse >rat. Rabbit follicular fluid was totally ineffective.

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R. ELIASSON

Summary.

Determinations of aspartate and alanine aminotransferase activity in human semen were carried out by the spectrophotometric and colorimetric methods. It was found that the occurrence of interfering substances in semen makes the spectrophotometric method unsuitable without prior partial purification of the enzyme. The mean activity determined colorimetrically in 417 samples of human semen was 320 Sigma-Frankel units/ml (s.e.m. ±8, range 10 to 1070) for aspartate aminotransferase and 30 units/ml (s.e.m. ±3, range 0 to 97, n = 40) for alanine aminotransferase. As regards aspartate aminotransferase, the activity of this enzyme was highest at +60° C. Pyridoxal phosphate increased the activity, particularly if added to semen samples with initially low activity. Gel electrophoresis of seminal plasma showed one band migrating towards the anode. However, in homogenized spermatozoa the bulk of enzyme migrated towards the cathode and only a weak band could be demonstrated on the side of the anode.