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  • Author: B. H. ERICKSON x
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B. H. ERICKSON

Summary.

The morphogenesis of the Leydig cells and germ cells of the pig during the first 130 days after birth is described in relation to estimates of cellular radiosensitivity. Boars aged 1 to 30 days were exposed totally to 200 r of gamma rays and the effects on the Leydig cells and germ cells were determined before and after puberty. The number of gonocytes (primitive germ cells) declined to 10% of the control values by Day 30 after irradiation, but at Day 60 some recovery was evident. Postpubertally, an average of 23% of the seminiferous tubules seen in transverse section in the irradiated testes exhibited radiation damage which was presumably permanent. Average sperm production was 47% of the control value. Increased numbers of crenated nuclei and a delay in morphogenesis were noted among the Leydig cells before puberty. Urinary steroid output of the irradiated boars equalled or exceeded that of the non-irradiated boars and it is assumed that 200 r of gamma rays effected no permanent damage among the Leydig cells.

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B. H. ERICKSON

Summary.

Qualitative observations of forty-nine bovine foetuses taken at varying stages of gestation revealed the following: (1) the germinal ridge is established at the 32nd day of gestation; (2) due to the formation of the tunica albuginea of the primitive testis, foetal sex is distinguishable by Day 39; (3) meiosis begins in ovaries at 75 to 80 days post coitum; (4) oogonial mitosis is discontinued by 150 to 170 days; (5) the majority of the oocytes have attained their stage of rest (pachytene) and are enveloped in primordial follicles by Day 170; and (6) vesicular follicles appear in ovaries at Day 250 of gestation.

Total germ-cell numbers, based on volumetric determinations or direct counts, increased from a low of approximately 16,000 at Day 50 to a high of 2,700,000 at Day 110. From Day 110 numbers declined abruptly to 107,000 at Day 170 and the ovaries of four foetuses at 270 days of gestation (average length of gestation, 283 days) contained an average of 68,000 ± 21,000 germ cells.

Seventy prenatally irradiated (400 R, whole-body to dam) and twenty-five non-irradiated heifers were slaughtered at either 9 or 23 months of age. Microscopic examinations of their ovaries revealed that irradiation was apparently without effect during the interval of 17 to 59 days of gestation, and of questionable effect during the interval of 59 to 119 days of gestation. Irradiation administered during the 119 to 154-day interval, however, diminished germ-cell numbers by an average of 68%. From Day 154 to term, irradiation was again without effect. The mitotically active oogonium was probably the cell affected during the interval of 59 to 119 days of gestation and the drastic germinal decline during the 119- to 154-day interval was believed to be related to the progression of oocytes from zygotene to pachytene, a transition during which the oocyte under normal conditions is highly susceptible to death.

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A. A. Moura and B. H. Erickson

A study was conducted to determine whether basal or GnRH-stimulated concentrations of FSH, LH, testosterone, androstenedione and oestradiol measured from 2 months to 12 months of age were correlated with size and histology of the testes of Angus bulls at 12 months of age. Three blood samples per month were taken from 24 calves at 1.5 h intervals to establish basal hormone concentrations. On the following day, calves received 0.05 μg of GnRH kg−1 body mass and were bled 1.5 h and 3.0 h later. At 12 months of age, bulls were castrated and testes were measured and prepared for histological analysis. Yearling testis diameter was related to GnRH-stimulated testosterone at 3 months (r = 0.48, P < 0.05). Basal FSH at all ages between 2 months and 12 months was correlated with yearling testis diameter (r = −0.53, P < 0.05, to r= −0.74, P < 0.01). In addition, basal FSH, measured at 2 and 3 months and between 8 and 12 months, was related to number of Sertoli cells per testis (r= −0.47, P < 0.05, to r= −0.53, P < 0.05), number of round spermatids per A1 spermatogonium (r = −0.48, P < 0.05, to r = −0.60, P < 0.01) and number of round spermatids per Sertoli cell (r=−0.50, P < 0.05, to r=−0.64, P < 0.01). Similarly, prepubertal concentrations of GnRH-stimulated FSH between 2 months and 12 months of age were correlated with testis diameter (r = non-significant, to r= −0.71, P < 0.01) and cell ratios in the seminiferous tubules (r = non-significant, to r= −0.61, P < 0.01). Thus, prepubertal hormone secretion could serve as a meaningful index of the potential sperm-producing capacity of the yearling bull.

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B. H. VICKERY, G. I. ERICKSON and J. P. BENNETT

Summary.

The minimal effective daily oral dose of α-chlorohydrin in the male Sprague-Dawley rat to prevent fertilization in the female following mating was found to be 2·5 mg/kg/day. The time to take effect and the time of recovery after withdrawal decreased and increased, respectively, as the dose was increased. With doses of up to 10 mg/kg/day, the sterility could not be accounted for on the basis of changes in the histology or weight of the male reproductive organs or accessory glands. The motility of spermatozoa recovered from the female tract the morning after mating was inhibited and, although normal numbers were recovered from the uterus, very few had entered the oviducts. When semen was collected from the uterus of a female 3 to 4 hr after mating with a treated male and transferred directly into the ovarian bursa of an unmated female, the spermatozoa were capable of fertilization. Semen from untreated males, transferred in the same fashion, caused acceleration of egg transport in the oviducts which was not observed with the semen from treated males. Inhibition of sperm transport is assumed to be a major factor in prevention of fertilization and may, at least in part, be mediated through a change in the constituents of semen of treated males. The disparate effect on egg transport, implying effects on oviducal musculature, suggests the involvement of prostaglandins or similar smooth muscle stimulants in the mechanism.