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M. H. JOHNSON

Hypophysectomy does not destroy the blood-testis barrier of the adult rat (Setchell, Voglmayr & Waites, 1969; Johnson, 1970), but the development of the barrier in the impubertal animal (Days 6 to 30 post partum) occurs at the same time as other changes known to depend on secretions of the anterior pituitary (Setchell, Scott, Voglmayr & Waites, 1969). Administration of oestrogens to young male rats is known to depress secretion of gonadotrophins and its effect on the development of the blood-testis barrier is investigated in this paper.

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Four schedules of oestradiol benzoate injection in arachis oil were used (Table 1). At least five mice on each schedule were killed at Days 3, 15 and 25 post partum. The testes were examined for intratubular staining by acriflavine (20 mg/kg subcutaneously 5 hr before autopsy) as an indication of barrier

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M. H. JOHNSON

It has been known for many years that fresh serum from non-immunized animals causes lysis and immobilization of spermatozoa of some species (Metchnikoff, 1900) and complement is evidently involved in these reactions (Chang, 1947). Complement is usually fixed during antibody-antigen reactions, and later experiments, using complement fixation (Edwards, 1960), immune fluorescence (Beck, Edwards & Young, 1962; Symons, 1967), mixed conglutination (Lachmann, Sell & Spooner, 1965) and mixed antiglobulin (Edwards, 1967), indicated that a complement-fixing antibody might be involved in the antispermatozoal activity of serum. Fresh normal serum also lyses the germinal cells of the testis (Spooner, 1964), and this reaction can be detected by mixed conglutination (Lachmann et al., 1965). In contrast with these observations, Brown, Glynn & Holborow (1963), Pokorna, Vojtiskova, Rychlikova & Chutna (1963) and Mancini (1967) all failed to detect reactions between serum and spermatozoa by immune fluorescence. The present work re-examines the question of the

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M. H. JOHNSON

Summary.

Current concepts of the macromolecular organization of membranes and of ways in which membrane organization may change during membrane fusion are considered briefly. The properties of the sperm membrane at different phases of its development up to fertilization are then examined in the light of this more general model.

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M. H. JOHNSON

Cadmium exerts a selective toxic effect on the blood vessels of the testis and caput epididymidis (Gunn, Gould & Anderson, 1963; Chiquoine, 1964; Mason & Young, 1967) and investigations into the changes in blood flow and vascular permeability suggest that the primary site of action is the end-arterial bed (Niemi & Kormano, 1965; Waites & Setchell, 1966; Clegg & Carr, 1966; Gupta, Barnes & Skelton, 1967). The resulting ischaemia and interstitial oedema then cause failure of spermatogenesis (Mason & Young, 1967). Dye studies suggest that a barrier exists at the tubular as well as the vascular level (Kormano, 1967a, b), and the presence of this barrier is essential for the production of a testicular fluid differing in composition from serum (Setchell, 1967; Setchell, Dawson & White, 1968; Johnson & Setchell, 1968). The present study shows that, in the untreated guinea-pig
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M. H. JOHNSON

Summary.

Immunological damage induced by iso-immunization of guinea-pigs with testis in adjuvant is most readily observed in the rete testis and vasa efferentia and is less frequently present in the testis and epididymis. Possible reasons for the greater vulnerability of the rete testis and vasa efferentia are discussed. The testis shows interstitial inflammation and an invasion of tubules by eosinophils and mononuclear cells. The tubular barrier to acriflavine, and possibly also to γ-globulin, partially breaks down during the invasive phase of initial damage but is restored before normal spermatogenesis is re-established. It is suggested that the occurrence of testicular damage is dependent upon the immune response, of whatever type(s), overcoming the protective effect of the blood-testis barrier.

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M. H. Nasr-Esfahani and M. H. Johnson

Summary. Transferrin promotes development of mouse embryos through the two-cell block in vitro. Uptake of transferrin into blastocysts was shown to occur by both receptor-mediated and nonspecific pathways, but neither pathway was used to a detectable extent by embryos before the eight-cell stage. Conversely, the dialysis of culture medium, non-permissive for development through the two-cell block, against a solution of transferrin rendered it capable of supporting development. It was therefore concluded that transferrin exerts its supportive effect on development in vitro via its chelating effects.

Keywords: hydrogen peroxide; transferrin; embryo; reactive oxygen species; mouse

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S. R. M. Holmberg and M. H. Johnson

Summary. The transport of methionine into unfertilized and fertilized mouse eggs appears to involve active transport mechanisms with similar V max, K m, substrate specificity and independence from Na+. An exchange diffusion system with a similar amino acid specificity to the uptake system has also been found in both types of egg. An estimate of 6·5 fmol has been made for the size of the total internal pool of exchangeable amino acids.

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M. H. JOHNSON and B. P. SETCHELL

There is little information on the accessibility of the seminiferous tubule to serum proteins and especially to the glycoprotein hormones or to immunoglobulins. The secretions of ram seminiferous tubules may be collected from the rete testis by inserting a cannula via the vasa efferentia (Voglmayr, Scott, Setchell & Waites, 1967), and this paper reports the results of an analysis of these secretions for protein and immunoglobulin.

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The Biuret reaction was used to determine the total protein concentration of rete testis fluid collected at different times of the year from rams showing wide seasonal variation in spermatogenesis. The values for rams showing active spermatogenesis were not different from those with poor spermatogenesis (Table 1). The protein content was much lower than that of testicular lymph,

Present address: Ian Clunies Ross Animal Research Laboratory, C.S.I.R.O.

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R. K. W. Smith and M. H. Johnson

Summary. The third (4-cell) and fourth (8-cell) cell cycles of early mouse development have been analysed in populations of blastomeres synchronized to the preceding cleavage division. DNA content was measured microdensitometrically. The entry of blastomeres into these cell cycles showed considerable heterogeneity both within and between individual embryos. This heterogeneity was greater in the fourth than in the third cell cycle. The component phases of the third cell cycle were estimated as G, = 1 h, S = 7 h, and G2 + M = 2–5 h, and those of the fourth cell cycle as G1 = 2 h, S = 7 h, and G2 + M = 1–3 h.

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M. H. SLOAN and A. D. JOHNSON

Rabbit oviduct secretions have been analysed following ligation (David, Brackett, Garcia & Mastroianni, 1969), flushing (Olds & VanDemark, 1957) or cannulation of the genital tract (Holmdahl & Mastroianni, 1965). Data obtained from ligation have been questioned because of possible occlusion of the blood supply and histological damage. Flushing has the limitation of one sample per animal, so that any change with treatment or stage cannot be verified. This study was designed to determine if the secretions of a cannulated oviduct differ from those of the intact oviduct of the same individual.

A 6 cm-long silastic cannula (1·57 mm i.d., 2·4 mm o.d.) was inserted through a mid-ventral incision into the fimbriated end of one oviduct of each of twenty virgin does. The cannula was surrounded by a velour cuff 2 mm wide placed 1 cm from the tip. About three stitches were taken into