Search

In our previous study, after direct administration of streptozotocin (STZ; 400 μg/g) to fetuses on day 19 of gestation, the B-cell volume in fetal pancreatic islets showed a marked decrease, but gradually recovered with electron microscopic confirmation of B-cell regeneration. However, STZ at this dose often caused fetal death. In this study, therefore, we determined whether B-cells are newly generated after treatment with STZ at a smaller dose in vivo and in vitro. For in vivo experiment, fetuses were administered STZ at 40 μg/g on day 19 of gestation. The B-cell volume in pancreatic islets decreased markedly 3 hr after the administration of STZ, but it began to increase after 6 hr. The fetal plasma insulin concentration decreased from 6 to 12 hr after the administration, but recovered after 48 hr. The cell division index in fetal pancreatic islets of the STZ-treated group began to be significantly larger after 6 hr. For in vitro experiment, fetal pancreases on day 18 of gestation were pretreated with 10 mM STZ for 6 hr and cultured for 98 hr. B-cells were completely destroyed with STZ treatment; however, as these pancreases were cultured in a medium free of STZ, B-cells began to appear and insulin secretion was detected after 48 hr. After 72 hr, the cell division index was significantly greater. These results suggest that the fetal pancreas treated with STZ has the ability to regenerate B-cells both in vivo and in vitro. © 2004 Wiley-Liss, Inc.

The present study was performed to determine when follicle-stimulating hormone (FSH) begins to promote Sertoli cell division in fetal rats, and to determine whether the effect of FSH is mediated by cAMP-dependent protein kinase (PKA). When testes from 15- to 17-day fetuses were cultured with or without FSH for 48 h, FSH did not promote Sertoli cell division in 15-day testes, but did in 16- and 17-day testes. Anti-rat FSH was injected into 16-day fetuses in utero. Twenty-four hours later, the testes of the injected fetuses and those of their intact littermates were cultured with or without FSH for 48 h. Without FSH, the Sertoli cell division index was significantly lower in anti-FSH-treated fetuses than in intact fetuses. With FSH, however, the index increased. When PKA inhibitor was added to cultures of 16-day testes with FSH, the promotion of Sertoli cell division by FSH was inhibited. We conclude that between 16 and 17 days of gestation, fetal pituitary FSH stimulates the division of Sertoli cells by activating the PKA activity.

To investigate the effect of maternal adrenocortical hormones on the development of fetal pancreatic islet cells, pregnant rats were adrenalectomised on d 6 of gestation. On d 12-16 the growth patterns of fetal insulin-producing B cells, glucagon-producing A cells, and somatostatin-producing D cells were observed histometrically. Maternal adrenalectomy resulted in growth retardation of fetal B cells on d 12-15. Maternal corticosterone therapy prevented this retardation. Maternal adrenalectomy, however, did not affect the developmental patterns of A and D cells. By Western blotting and immunohistochemistry, glucocorticoid receptors were demonstrated to be present in the islet cells from d 12 to d 15. These results suggest that maternal adrenocortical hormones, glucocorticoids in particular, maintain the early development of fetal pancreatic B cells through their specific intracellular glucocorticoid receptor.

The present study was aimed to examine the effects of follicle-stimulating hormone (FSH) on cell division of Sertoli cells from rat fetal testes and on the kinetics of 2 kinds of intermediate filaments, cytokeratin and vimentin, which comprise the cytoskeleton of Sertoli cells. Testes from rat fetuses of different ages (from day 15 to day 17 of gestation ) were cultured for 48 hr, with or without added FSH. In 15-day testes, FSH influenced neither cell division of Sertoli cells nor kinetics of intermediate filaments. In 16-day testes, FSH promoted cell division of Sertoli cells and kinetic differentiation of intermediate filaments distributed toward the lumen of the seminiferous tubules. These findings suggest that 16-day testes in culture can respond to FSH in a fashion that cell division of Sertoli cells is promoted and that intermediate filaments increase in number and change in intracellular distribution. It is concluded that FSH influences both proliferation and morphological differentiation of Sertoli cells.

Background Streptozotocin (STZ) is selectively toxic to the B cells in the pancreatic islets. It is well known that in the adult rat, STZ causes the death of B cells, and it eventually induces diabetes mellitus. The present study was conducted to detect what morphological changes could be induced in the fetal B cells following a direct injection of STZ into the fetus in utero during late pregnancy in the rat. Methods STZ (400 μg/g body weight) was injected into the fetus in utero at 10:00 on day 19 of gestation. Three, 6, 24, and 48 hr after injection, the changes in the B cells (anti-insulin serum positive cells) were examined immunohistochemically. The total volume of the B cells was measured. Electron microscopic observation was made as well. Results Six hr after STZ injection, some B cells were destroyed so that their granules were distorted and burst. Twenty-four hr after STZ injection, a large majority of the existing B cells were disintegrated, and a number of small isletlike clusters of immature cells appeared among the exocrine acini. The total volume of anti-insulin serum positive cells was strikingly decreased. At 48 hr after injection, however, the volume returned to a level that was comparable to that of their littermate controls. Conclusions The regeneration of the B cells may occur because of the high cell proliferative activity of undifferentiated cells following the destruction of the B cells caused by an injection of STZ. Anat. Rec. 247:248-252, 1997. © 1997 Wiley-Liss, Inc.

Pregnant Wistar rats were divided into 3 groups, non-operated control, adrenalectomized, and adrenalectomized and corticosterone-treated. Maternal adrenalectomy was performed on day 6 of gestation. Corticosterone therapy was made from the day at operation to the day at observation. The growth pattern of insulin-producing B-cells was observed immunohistochemically and histometrically from days 12 to 16. The results obtained were as follows: From day 12 to day 15, maternal adrenalectomy resulted in a significant retardation of the growth of insulin-positive B-cells in terms of the collective volume of the cells. Maternal corticosterone therapy prevented this retardation. On day 16, however, the growth of B-cells in collective volume overcame the suppressive effect of maternal adrenalectomy. These results suggest that the lack of adrenocortical hormones causes a retardation of B-cell growth in early development, and that, when once developed well, B-cells can grow independently of the hormones.

The age-related testicular effect on the ovarian primordia was studied by combined transplantation of fetal testes and ovaries in adult male hosts. First, ovarian primordia of 14-day fetal rats were transplanted into a renal subcapsular position of castrated or intact adult male rats. In both the castrated and the intact hosts, most of the ovarian transplants developed normally with only 3 of them having in part seminiferous tubule-like structures in addition to normal ovarian structure. Second, a 14-day ovary was combined with a fetal testis the age of which varied from 13- to 18-day, and the combination was transplanted. In the combination of a 14-day ovary and a 13-day testis, the results varied in such a way that the ovary or the testis alone developed or otherwise, both gonads developed well. In union with 15- to 18-day testes, the ovaries did not develop, although the testes developed well. These results suggest that the 14-day ovarian primordia have a slight reactiveness to androgens of host rats and that the 13-day fetal testes begin to inhibit the development of the 14-day ovaries co-transplanted with them.

This study was conducted to determine whether acute alcohol consumption in near-term pregnant rats results in constriction of the fetal ductus arteriosus (DA). Twenty milliliters per kilogram of 30% (v/v) alcohol was administered via a stomach tube 0.5, 2, 4, 6 and 12 h prior to cesarean section and fetal sacrifice, at 1.00 p.m. on the 20th gestational day (day 20.5), in experimental groups A1–A5, respectively. Controls were given water alone. The calibers of the DA and pulmonary artery (PA) were measured using the whole-body freezing method with direct exposure of the DA and PA by shaving the frozen chests of the fetuses. The DA was significantly constricted 30 min after alcohol treatment. The constriction was also observed in groups A2–A4, but not in group A5. The PA was also less markedly but significantly constricted 30 min after alcohol administration, but groups A2–A5 showed normal PA caliber. It is concluded that alcohol has a constrictive effect on the DA when administered close to the end of gestation in the rat.

Thyroids of 15-day rat fetuses prior to culture had no follicles. After 2 days in culture, regardless of added TSH in the medium, thyroids had small, colloid-storing follicles. In the follicular cells, the rER and Golgi apparatus were somewhat well developed as compared with the thyroids prior to culture. Thyroids of 17-day fetuses prior to culture were first inlaid with follicles. With TSH, 2-day cultures of 17-day thyroids showed a more marked dilation of rER and a further development of Golgi apparatus than those without TSH. These results indicate electron microscopically that TSH has no effect on the first formation of follicles as well as on the initial development of follicular cells, but that TSH can promote the further development of follicular cells themselves of once-developed follicles.

Measurements of the inner diameters (calibers) of the ductus arteriosus (DA) and pulmonary artery (PA) were made in late fetal rats and newborn rats, the latter being obtained by spontaneous or caesarean delivery. The fetal and newborn pups were frozen instantly with an acetone-dry ice mixture. The chests of these whole-body frozen pups were shaved with a surgical knife gradually from the back toward the ventral side to expose the DA and PA for measurements of their calibers. As a result, it was revealed that the DA was almost closed 180 min after birth, but that the closure and shirinkage of the DA were accelerated to some extent by caesarean delivery. On the other hand, there was no remarkable change in the PA throughout the postnatal period observed, regardless of the type of delivery, spontaneous or caesarean.

To investigate the role of growth factors (epidermal growth factor [EGF], betacellulin, and activin A) in the development of islet B cells of rat fetal pancreatic explants in vitro, pancreases from rat fetuses at day 18 of gestation were cultured for 96 hr, with or without these growth factors. Culture medium was changed every 24 hr, and the level of insulin released in the culture medium was measured. After 72 hr of culture, pancreases were examined histologically. As a result, EGF promoted cell proliferation, but reduced B cell volume. Whereas, betacellulin and activin A inhibited cell division, but promoted increased B cell volume and insulin secretion, especially activin A, which stimulated insulin release in a time dependent manner. These results suggest that EGF, betacellulin, and activin A promote pancreatic cell proliferation, islet B-cell differentiation, and islet B-cell differentiation and functional maturation, respectively, and that EGF, betacellulin, and activin A, in this order, regulate islet B-cell neogenesis.

To investigate whether teratogenicity of ethylene thiourea (ETU) is due to ETU per se or to its metabolites, rat embryos cultured in vitro were exposed to 10 and 30 micrograms/ml of ETU in the presence or absence of rat liver microsomal fraction (S9mix). In the absence of S9mix, the incidence of morphological abnormalities increased dose-dependently. In the presence of S9mix, abnormal morphogenesis was almost absent in all embryos. These findings suggest that teratogenicity of ETU is due to ETU per se.

It has been reported that when the rat fetus is treated with streptozotocin (STZ) in vivo, islet B cells are destroyed but later recover. To investigate the process of the recovery of B cells after in vitro treatment of the fetal pancreas with STZ and the role of epidermal growth factor (EGF) in the recovery of B cells, we measured the level of insulin released from the cultured fetal pancreas and examined it histologically. As a result, we immunohistologically confirmed the regeneration of B cells in the pancreas that had been cultured for 48 hr after destruction of islet B cells by STZ treatment. An immunohistologic study using proliferating cell nuclear antigen (PCNA) showed that without the addition of EGF, the cell division index was significantly higher in the STZ-treated group (STZ group) than in the untreated group (intact group), whereas with the addition of EGF, the cell division index increased in both groups, but EGF did not have a significant cell division-promoting effect on the pancreas in the STZ group. The addition of EGF caused a significant decrease in the concentration of insulin in culture medium in both groups. These results indicate that EGF has a cell growth-promoting effect on intact fetal pancreas in vitro but has the effect of inhibiting the release of insulin, and thus suggest that EGF does not trigger the regeneration of islet B cells.

This work was conducted to know whether thyroxine (T4) when injected into fetal rats would induce a constriction of the ductus arteriosus (DA). In Experiment 1, fetal rats on day 20 of gestation were given a subcutaneous injection of 1 or 10 micrograms T4 through the maternal uterine wall, and were autopsied 3 or 6 hr later. Similarly, in Experiment 2, the mother rats were given an injection of hydrocortisone (10 mg/kg) just after fetal T4 injections. In either series of experiments, uninjected littermates served as controls. According to the whole-body freezing and shaving method, the DA was exposed and calibrated under a dissecting microscope. In Experiment 1, the DAs of the T4-injected fetuses, 3 hr later, were significantly smaller in caliber than those of their controls, but recovered 6 hr later. In Experiment 2 with fetal T4 injection followed by maternal hydrocortisone injection, the DAs of the T4-injected fetuses were further smaller in caliber than those of their controls which were clearly shrunken as compared with those of controls in Experiment 1. These results indicate that T4 exerts a constrictive effect on the DA, an effect which is strengthened in the presence of hydrocortisone.

A 14 d ovarian primordium was transplanted with a fetal testis (13–18 d and 21 d of gestation) or a neonatal testis (15, 20, 30 and 45 d after birth) into the renal subcapsular position of an adult male rat. Two weeks after transplantation, transplants were examined as to the degree of ovarian and testicular differentiation. In the combination of a 14 d ovary and a 13 d testis, there were 3 types of result: either the ovary or the testis alone developed or both gonads developed well. Ovaries transplanted in union with 15–18 d testes did not develop, although the testes developed normally. Some ovaries in union with 21 d testes developed normally. In combination with infantile testes, the incidence of developed ovaries increased as the age of testes advanced. These results suggest that the 13 d fetal testes begin to suppress the development of cotransplanted 14 d ovaries, that 14–18 d fetal testes maintain such suppressive effects and that this effect gradually diminishes in infantile testes as they progress toward 45 d after birth.

The dilating effect of prostaglandin (PG) E1 and E2 on the once-constricted ductus arteriosus (DA) was examined in newborn rats. The animals were given subcutaneously PGs 3hr after caesarean delivery. The ratio of the DA to the pulmonary artery (PA) was determined 15, 30, 60, 90 and 180 min after injection. Both PGE1 and PGE2 dilated the DA for over 90 min. The maximal effect appeared 15 or 30 min after injection. The DA/PA ratio was significantly higher in PGE2 than in PGE1. In addition, another series of newborn rats were given subcutaneously PGE2 6 hr after caesarean delivery to examine the age-related changes in the DA-dilating effect. The DA/PA ratio was significantly decreased in 6-hr-old pups than in 3-hr-old pups. These findings indicate that both PGE1 and PGE2 have a dilating effect on the once-constricted DA and that the effect decreases with time.

The teratogenic potential of caffeine was examined in vitro by a whole embryo culture system (WECS) and an embryonic cell culture system (micromas teratogen assay: MTA) in the rat. In the WECS, hyperemia of the tail, and a reduction of the placental size was induced by caffeine at concentrations higher than 50 micrograms/ml; hypoplasia of the forelimb bud was induced at concentrations higher than 100 micrograms/ml; hematoma in the yolk sac and dysmorphogenesis of the fore- and hind-limb buds, prosencephalon and tail were induced by 200 micrograms/ml caffeine. In the MTA, even with 200 micrograms/ml caffeine, the toxicological parameters obtained by proliferation and differentiation assays of the midbrain and limb bud cells were almost the same as in the control. In conclusion, caffeine induced various morphological anomalies, but did not affect proliferation or differentiation of cells in these experimental systems.

The ductus arteriosus (DA) in the fetal rat was calibrated using a whole-body freezing method, 3 hr after maternal treatment with paraquat at a dose of 25 mg/kg of body weight on days 19-21 of gestation. On days 20 and 21, the DA was significantly constricted. The DA was also significantly constricted on day 19 2/3 but not on day 19 1/2. It is concluded that paraquat has a constrictive effect on the DA and that the onset of this effect occurs in the first half of day 19 of gestation.

On day 13 of gestation in Mongolian gerbil fetuses, the mesonephric (Wolffian) duct was already visible. On day 14, the anlage of the paramesonephric (Mullerian) duct was first observed close to the mesonephric duct in both sexes at the cranial part of the mesonephros. Thereafter, the paramesonephric duct grew caudally in parallel with the mesonephric duct. On day 19, the duct reached the urogenital sinus. At this stage, the anogenital distance was significantly longer in male than in female. Also in male, the mesonephric duct was increased and the paramesonephric duct was decreased in diameter compared with those in female. These suggest that both testosterone and anti-Mullerian hormone are produced in fetal Mongolian gerbils at least before day 19 of gestation.

The growth pattern of somatostatin cells was clarified immunohistochemically from day 12 to day 18 of gestation in the rat fetus. On day 12, somatostatin cells first appeared within the pancreatic anlage. The total number of somatostatin cells was gradually increased from day 12 to day 16 and rapidly increased thereafter. It may be concluded that such a sequence of events of development in somatostatin cells occurs in a fashion similar to that in B cells.

Ethylene thiourea (ETU) was administered once orally to pregnant rats on gestation day 12 at a dose of 200 mg/kg, and its concentration-time courses in the maternal plasma, amniotic fluid and embryos were investigated. The ETU concentrations in the maternal plasma and amniotic fluid reached the peak level about 2 hr after dosing, then declined gradually and had disappeared by 48 hr. In embryos, the concentration of ETU peaked at 30 min after dosing and disappeared at 48 hr. The prolonged exposure of the embryos to the high concentration of ETU in the amniotic fluid could be partially responsible for the teratogenic effect of ETU.

Pregnant rats on day 21 of gestation received a subcutaneous injection of paraquat (25 mg/kg). Two hr later, some fetuses of these rats received a subcutaneous injection of prostaglandin E2 (PGE2). The caliber of the ductus arteriosus (DA) of fetuses was measured 1 hr later. The DA of fetuses of paraquat-treated pregnant rats was significantly constricted compared with that of fetuses of control pregnant rats given physiological saline. However, the DA of PGE2-treated fetuses of paraquat-treated pregnant rats had a caliber comparable to that of control rats. The maternal plasma PGE2 level decreased following paraquat treatment. These results suggest that the decrease of maternal PGE2 level results in a constriction of the DA of fetuses.

Newborn rats delivered by cesarean section were given subcutaneously propranolol (PRO), a beta-adrenergic blocker, (1) immediately or (2) 180 min after delivery. The diameter of the ductus arteriosus (DA) of the newborn pups was calibrated at 30, 60 and 90 min after the PRO-administration. The results were as follows: (1) the DA calibers of the pups given 0.2, 1.0., 5.0 mg/kg PRO immediately after cesarean delivery remained significantly larger than those of controls in a dose-dependent manner for 30 min after treatment. In the 5 mg/kg group, the enlargement of the DA was prolonged for 90 min after treatment. (2) In untreated pups, the DA completely closed by 180 min after cesarean delivery. The DA was not affected by the administration of 5 mg/kg PRO at 3 hr after delivery. It was concluded that, PRO inhibits the spontaneous constriction of the DA, suggesting an important role of beta-adrenergic stimulation on the spontaneous closure of the DA in newborn rats.

Maternal adrenalectomy on days 14 and 15 of gestation did not alter the fetal adrenal weight 2 days later. The same operation on day 16 caused a significant increase in the adrenal weight with a hypertrophy of the cortical cells. Nevertheless, the operation on days 17 and 18 induced no change in the fetal adrenals. Subsequently on days 19 and 20, the operation resulted in a significant hypertrophy of the fetal adrenals. Fetal unilateral adrenalectomy on day 18 caused, 2 days later, significant hypertrophy of the contralateral adrenal, in contrast with no significant change after maternal adrenalectomy. This is perhaps due to the difference in the amount of fetal plasma corticoids, as evidenced by the previous reports of high concentrations of fetal plasma corticosterone on days 19 and 20. The overall results suggest that the fetal pituitary-adrenal feedback mechanism begins to appear between days 16 and 18 of gestation.

The gubernaculum consists of the gubernacular cord connected with the vas deferens and the gubernacular bulb connected with the retroabdominal wall. The cord was first distinguished on day 15 of gestation. Its length reached the peak on day 16, followed by a reduction until day 18 to be almost constant thereafter. The bulb was first distinguished on day 16, and its length was steadily increased toward term. The testis began to descend with a reduced length of the cord. By day 19, the testis descended close to the caudal part of the bulb by the sharp bending of the cord. Microscopically, the bulb consisted at first of a centrally located mesenchymal mass and of a covering layer of myoblasts. Thereafter, the mesenchymal mass was gradually shifted toward the cranial part of the bulb, trailing loose mesenchymal tissue in the caudal part of the bulb. On day 19, the mass was decreased in cell population but increased in amount of collagen fibers. It is suggested that the testicular descent starts on day 16 together with the commencement of shortening of the gubernacular cord and enlargement of the gubernacular bulb.

Adrenalectomy (ADX) of pregnant rats on day 14 or 15 of gestation did not induce any hypertrophic feature in the fetal adrenals within 2 days. ADX on day 16 significantly increased both the weight of fetal adrenals and the size of fetal adrenocortical cells in 2 days. However, ADX on day 17 induced some increase in the weight of fetal adrenals, not accompanied with any significant cortical cell enlargement within 2 days. ADX on day 18 caused no increase in either the weight of fetal adrenals or the size of cortical cells. ADX on day 19 or later also induced a highly significant increase in both the weight of fetal adrenals and the size of cortical cells. To know more clearly the pattern of the negative feedback mechanism of the fetal pituitary-adrenal axis, metopirone was injected into another series of ADX rats on each of two days after ADX and the animals were autopsied on the third day. Metopirone caused more marked hypertrophy of the fetal adrenals and cortical cells than did ADX alone performed after day 16. These results strongly support the view that the fetal pituitary-adrenal negative feedback mechanism begins to operate between days 16 and 18 of gestation.

Six groups of thyroid glands from 18-day fetal rats were explanted to organ culture for 2 days. In one group, thyroid was cultured alone and in the remaining five groups thyroid was cocultured with pituitaries from fetuses ranging in age from 17 to 21 days. In each of the groups, half of the cultures had thyrotropin-releasing hormone (TRH) added to the medium. Histometric parameters of the thyroid follicle such as diameter and cell height were used as indicators of development of the thyroid gland. When 18-day thyroid was cultured alone, addition of TRH did not accelerate development. When either one 18-day or two 17-day pituitaries were cocultured with thyroid, a significant increase in diameter and cell height was seen. Addition of TRH to the medium induced little or no further change. When the thyroid was cultured with 19- to 21-day pituitaries, a marked increase in thyroid development was observed; and the addition of TRH caused further acceleration in thyroid development. These results suggest that, in organ culture, 17- to 18-day pituitary glands can release some thyrotropin (TSH) with or without additional TRH. Older pituitaries (19- to 21-day) apparently can release an amount of TSH in the presence of TRH that is greater than their own spontaneous TSH secretion.

The critical time of onset of the reciprocal relationship between the pituitary and the thyroid in fetal rats was assessed by the appearance of goiters in fetuses after maternal treatment with goitrogen, propylthiouracil (PTU), on various days of gestation. The assessment was based on changes in the weight and histology of the fetal thyroids. The day following overnight mating was regarded as day 1 of gestation. Pregnant rats were treated with 40 mg PTU each day for two days and autopsied on the third day. The various experimental periods were days 16--18, 17--19, 18--20, 19--21, and 20--22. PTU given to pregnant rats on days 16 and 17 did not cause any change in the fetal thyroids. PTU given on days 17 and 18 caused only a slight increase of fetal "thyroid weight/body weight" ratio. In all other experimental periods (days 18--20, 19--21, and 20--22), PTU induced conspicuous goiters in fetuses, which was reflected by an increased weight of thyroids, an increased height of follicular cells, and a decreased amount of colloid stored in follicles. The results suggest that in fetal rats, the reciprocal relationship between the pituitary and the thyroid is established on approximately days 19--20 of gestation.

The time of onset of brain regulation of the pituitary-Leydig cell system in fetal rats was assessed by fetal encephalectomy, which allowed the pituitary to persist in situ. The effects of encephalectomy were compared with those of fetal hypophysectomy (surgical decapitation). The parameter for in terpretation of these effects was the collective volume of Leydig cells, measured by the method of Chalkley ('43). The normal increase in the collective volume of Leydig cells in fetuses encephalectomized on day 17 of gestation and autopsied on day 18 was not retarded, whereas that in decapitated fetuses of the same age was retarded. In all other one-day experimental periods (day 18–19, 19–20, 20–21, and 21–22), the increase in volume was retarded to approximately the same extent in encephalectomized as in decapitated fetuses. The collective volume of Leydig cells continued to increase to some extent without the brain until day 20, after which it ceased to increase. The results suggest that in fetal rats, the brain control of the pituitary-Leydig cell system begins to operate from day 18 of gestation, when the day following overnight mating was designated as day 1 of gestation.

The external genitalia in bovine fetuses were studied macroscopically, with special reference to the formation of the labia and the sexual differentiation. The age of fetuses was expressed in crown-rump length (CRL). The female urogenital fold budding on either side of the genital tubercle gradually approached the tip of the genital tubercle by the 33-cm stage and then began to enclose it with the companion fold on the other side, thus forming the labium pudendi which is equivalent to the labium minus pudendi of the human. The genital swellings, which are known to become the labia majora in the human, did not take part in the formation of the labia. They completely disappeared at the sites cranial to the genital tubercle by the l0-cm stage. The sex difference in differentiation of the external genitalia was first observed at the 2.7-cm stage, at which time in the male, the urogenital orifice and the anogenital raphe appeared at the sites caudal to the genital tubercle; in the female at the 2.9-cm stage, both structures were still not observable. The anogenital distance became clearly longer in male than in female, after 3.6-3.9-cm stages.

妊娠20日に母ラットの卵巣を除去後, 妊娠22日に剖検し, または妊娠20日の胎仔にβ-estradiol(0.02mg)を皮下注射し, 妊娠22日と生後1日に剖検して Leydig 細胞の総体積およびその組織像を検索したところ, estradial は出生前の Leydig 細胞の発達と出生後の萎縮に影響しなかった.

Development of the external genitalia in rat fetuses was studied with special reference to the formation of the labia pudenda and the determination of the stage at which the sex difference could be recognized from changes in the external structures. The urogenital fold located on either side of the external structures. The urogenital fold located on either side of the urogenital groove gradually enlarges and begins to enclose the genital tubercle with its counter fold on day 20 of gestation. Thus, the urogenital folds, which are known to become the labia minora and the prepuce of clitoris in the human, are differentiated only into the prepuce of clitoris in the rat. The genital swellings situated caudally to the urogenital folds are not well developed and come to be inconspicuously flat in situ at the end of gestation. However, the labia majora are formed by the time of puberty when the vagina opens. Therefore, it seems that the genital swellings contribute to the formation of the labia majora after birth. Sex difference in development of the external genitalia is recognized on day 17 of gestation; a small oval urogenital orifice is larger in male than in female and the genital swellings are better developed in male than in female.

To investigate the placental enlargement which accompanies maternal alcohol consumption during pregnancy, Sprague-Dawley rats were given 20% ethanol for 4 weeks prior to mating and 30% ethanol throughout gestation. Pair-fed controls received an isocaloric amount of corn starch and chow, with water ad libitum, and ad libitum controls received rat chow and water. On days 17, 18, 19 and 20 of gestation, placentas were removed for histological observation. On days 18–20, the placentas of alcohol-fed rats weighed significantly more than did those of controls, although there was no difference in weight on day 17. Giant cells in the basal zone were significantly increased in number and size in alcohol-fed rats compared to controls. Trophoblastic cells in the basal zone were significantly larger in the alcohol group than in the control groups except on day 17. The maternal blood channels in the labyrinth were wider and more filled with blood corpuscles in the alcohol group than in either control group. It is concluded that the increased weight of the placenta may be largely due to the stagnated maternal blood cells in the labyrinthine blood channels and also to the increased number and size of giant cells and the enlarged trophoblastic cells in the basal zone.

Electron microscopic examination was made on the cells of the anterior pituitaries in normal or castrated late fetal and early neonatal male rats. It was posbible to distinguish three types of granular cells in addition to celld of uncertain identity, on the basis of the diameters of granules. Type I cells had granules with a small range of diameters (40-180nm). Secretory granules of these cells were located mainly in the periphery of the cytoplasm. The cisternae of rough endoplasmic reticulum (RER) were flattened and irregularly arranged. Type II cells had somewhat larger granules (40-200nm) than type I cells. Granules of type II cells were located throughout the cytoplasm. The RER cisternae appeared as vesicular or short plates, or were grouped as lamellar stacks. Type III cells had granules with the widest range of diameters (90-360nm). Following castration, both type I cells and type III cells showed little cytological changes, but type II cells exhibited extreme changes accompanied by a marked enlargement of the RER cisternae and the Golgi complex. Such changes in type II cells were more marked in fetused than in neonatal rats, and were prevented by an injection of testosterone propionate. These observations support the view that type II cells include gonadotrophs and that the pituitary gonadotrophic activity declines just after birth in male rats.

Normally, the size of pancreatic acini is remarkably decreased after birth in the rat. Administration of water or milk on day 21 of gestation resulted in decreased acinar size a day later in intact fetuses and in fetuses decapitated immediately after administration of water or milk. The same treatments of premature newborn rats obtained by Caesarean section on day 22 of gestation induced similar effects a day later On the other hand, in starved Caesarean newborn rats, there were no histologic changes in acini. In spontaneous newborn rats which were allowed to suckle maternal milk and then starved for one day, there was an increase in acinar size as compared with that of 2-day-old normal rats. These results suggest that the fetal pancreatic acini at least near term (on day 21 of gestation) can respond to some signals conveyed from digestive tracts which have responded to exogenous stimuli, that the brain during fetal days does not play any role in digestive tract-pancreatic acini interrelations in secretion of zymogen granules and that the neonatal decrease in acinar size is caused by the intake of maternal milk.

Just before normal vaginal delivery the plasma corticosterone concentration (PCC) in fetal rats increased markedly compared with that on day 22 of gestation. The PCC was elevated 2 h after birth and then declined until 12 h after birth, when it approached the level found on day 22 of gestation. Similarly, in premature newborn rats obtained by cesarean delivery on days 21 and 22 of gestation, the PCC increased 2 to 4 h after delivery and then declined. The PCC in 22-day-old fetal rats, 30 min after ligation of the maternal blood vessels running along a uterine horn, rose markedly compared with that in fetuses in the contralateral intact horn. A similar increase in PCC was not observed in either decapitated or encephalectomized fetuses, but observed in fetuses whose umbilical cords were ligated. The rise in fetal PCC after ligation of uterine blood vessels and of umbilical cords was considerably higher than that observed after various stresses reported by other investigators and also higher than that found 60 min after maternal adrenalectomy. The rise in PCC just before and just after birth and after the ligation should not be considered as the result of stress, parturition or ligation, but may be a result of the response to other factors.

マウス副腎皮質X帯に及ぼす種々の濃度のtestosterone, progesteroneの影響を知るために30日齢のICR処女雌マウスを用いて検討した. さらに, 卵巣摘出マウスにprogesteroneを投与してその影響をも検討し, 次の成果を得た. 1) Testosterone投与では, 2.5, 1.0, 0.5, 0.1mg投与群のすべての例で, X帯は退行過程および消失様相を呈し, その形態的特微は一部の例外を除き皮・髄質境界部での膠原線維の集積であった. 2) Progesterone投与では, 2.5mg投与群で9例中8例で, X帯は退行過程および消失様相を呈していたが, 1.0mg投与群では6例中1例のみ退行したに過ぎなかった. さらに, 0.5mg投与詳でほ全例でX帯は完全に維持されていた. 消失様相の形態的特徴は一部の例外を除きX帯細胞の空胞変性化であった. 3) 卵巣除去によって内因性の影響を除いたマウスにprogesterone 2.5mgを投与した場合, 5例中4例でX帯が明瞭に維持され, 残存していた. これらの結果から, 雌マウスX帯に対するprogesteroneの退行性効果は, ほぼ卵巣を仲介するものであり, 本質的にはandrogen性であることが示唆される.

The ontogeny of the thyroid-stimulating activity of the pituitary gland associated with or dissociated from the hypothalamic control was studied in fetal rats based on electron microscopic observations of the thyroid follicular cells. The day following overnight mating was regarded as day 0 of gestation. Fetal hypophysectomy or encephalectomy (pituitary gland left intact) was performed on day 16, 17, 18 or 19, and operated fetuses were autopsied 2 days later and compared with intact littermate controls. In hypophysectomized fetuses, the weight of thyroid gland was reduced, the area ratio of "nucleus/cell" was increased and that of "rER/cytoplasm" was decreased, as compared with controls in all age groups. These changes were accompanied by shortening of microvilli on the apical surface of follicular cells, flattening of cells and shrinkage of the rER. In encephalectomized fetuses, no changes were found in all the parameters tested as compared with the controls. These electron microscopical observations support the view that the pituitary-thyroid axis in fetal rats develops independently of hypothalamic control.

ウシの胎齢1.5ヵ月の胎仔より新生仔に至るまでの第四胃胃底部の粘膜表面すなわち内面構造についてその形態学的分化行程を観察し, とくに胃小窩と胃腺の形成について走査型電子顕微鏡と復構模型を用いて精査した. 初期胎仔の第四胃表面上にはすでに多くの細かなシワをもつ, ラセンヒダが現われていた(1・5-2ヵ月). その後ヒダの表面のシワは伸長して多くの直線状の縦走する隆起となり(3-4ヵ月), 続いておのおのの直線状の隆起上のところどころに浅いくびれが現われ, その数も次第に増加して, 個々の独立した隆起を形成する. この隆起下の粘膜固有層はすでに蜂巣状の網目を示し, 間に深いくぼみを形成していた(4-5ヵ月). その後, おのおのの隆起は次第に変形して俵状になり(5-7ヵ月), さらに月齢が進むと隆起も狭くなり, その間の溝が拡大してくる(7-9ヵ月). 新生期に至るとおのおのの隆起も次第に平坦になり, 溝の一部は胃小窩として拡大する. この胃小窩の出来方には変異があり, 1例では4個の隆起が接着して, その間の溝の接点が深くくぼみ胃小窩となり, 残りの部分の溝は消失する. またこれらの隆起に背中合わせに存在する隆起間にも胃小窩ができる場合があり, このようにして隆起と隆起との間の溝は失なわれ, 胃小窩が拡大し明瞭になるように思われた.

On the 20th day of gestation in pregnant rats, the male fetuses were subjected to surgical hypophysectomy by decapitation or to intracranial paraffin injection which compressed the fetal brain. Autopsy was done on the 22nd day of gestation. The collective volume of Leydig cells in the left fetal testis was estimated by Chalkley's method. Decapitation of a fetus caused a significant retardation in increase of the collective volume of Leydig cells 2 days later. In fetuses given an intracranial paraffin injection, the Leydig cell volume was increased significantly compared with normal fetuses on the 20th day of gestation but was far smaller than that in their intact littermates. This effect of paraffin compression was completely prevented by injections of LRH. The Leydig cell volume remained extremely small in decapitated fetuses given LRH. The observations suggest that in the male rat the hypothalamus begins to govern a pituitary gonadotropic function before birth.

Pregnant rats were treated with 30 mg metopirone (M) each day for 2 days and autopsied on the third day in various gestational periods (Days 18-20, 19-21, and 20-22). Control rats were treated with saline alone (S). The adrenals of intact fetuses in M-treated dams were significantly heavier than those of intact fetuses in S-treated dams in every experimental period. In both M- and S-treated dams, the adrenals of encephalectomized (E) fetuses were lighter than those of intact littermates. However, in the experimental period of Days 18-20 and 19-21, the adrenals of E fetuses in M-treated dams were slightly but significantly heavier than those of similar E fetuses in S-treated dams. In contrast, in the experimental period Days 20-22, there was no significant difference in the weight of adrenals of E fetuses of M- and S-treated dams. These changes in fetal adrenal weight were reflected histologically in parallel changes in the size of adrenocortical cells. The observations suggest that the fetal adrenal hypertrophy following maternal treatment with metopirone can occur to some extent independent of the fetal brain, but that close to the end of gestation the hypertrophy occurs completely under the control of the fetal brain.

Granular cell indices (GCI; Dunihue and Robertson, '57) in kidneys of fetal and newborn rats were determined by examining sections stained with Bowie's technique. Some fetuses were delivered prematurely by Caesarean section a day earlier than the expected delivery, and were then nursed by a foster mother. Similarly, postmature Caesarean newborn rats were obtained; retention one day beyond the normal gestation was induced by maternal progesterone injections. The GCI was strikingly increased within a day after birth, followed by an immediate decrease thereafter. This was also observed in both premature and postmature newborn rats. It seems that this temporary increase of the GCI is not attributable solely to the age of rat, but follows only the separation from the maternal environment.

Thyroids from rat fetuses of different ages (from day 14 to day 19 of gestation) were transplanted to organ culture for 2 days, with or without added thyroid-stimulating hormone (TSH) in the medium. Thyroid tissue from 14-day fetuses that initially consisted of irregularly arranged cell cords did not form follicles when cultured in the presence or absence of TSH. Thyroids from 15- and 16-day fetuses initially consisted of epithelial cell masses. When cultured in the presence or absence of TSH they formed follicles, and a majority stored small amounts of colloid. In thyroid transplants from 17-day fetuses, the response to TSH appeared as a significant increase in the follicular diameter and cell height. Thereafter, in all transplants cultured in the presence of TSH, both the follicular diameter and the cell height were markedly greater than in the transplants cultured in the absence of added TSH. These results suggest that the initial formation of thyroid follicles is independent of TSH and that, once developed, follicles become able to respond to TSH.

麻布獣医科大学家畜解剖学教室,相模原市229反芻類においては,腹腔臓器に対する横隔膜の付着様式は,反芻に大きな意味を持つものと思われる.本研究においては,牛胎仔および新生仔を用い,とくに胃に対する付着様式をホルマリン固定した材料および胸腔•腹腔ならびに消化管への合成樹脂注入鋳型標本を観察することによって調べた.横隔膜と食道および胃との接着部では,食道尾側端および噴門部の表面には主として右脚から筋線維が分布していた.胃に対する主な付着は左脚からの筋線維によるものであった.胃に対する横隔膜の付着領域は,前方よりみて逆V型を示す.この逆V型を形成する左右両板のうち右板は,右脚からの筋線維とともに噴門付近を被い,背方に向かって第1胃前房背側面から第1胃背嚢右側背縁に至っていた.この逆V型の左板は第2胃背面より後方に向かい,第1胃背嚢左側背縁および脾臓に至っていた.両板の背後側端における連結部は,胎仔においては非常に薄く,新生仔に至って厚く,広く,強靱となった.これらの両板の間および橋状の連結部の下には,疎性の結合組織を伴なった漿膜に被われた盲管状の空隙があり,それによってその下に位置するいわゆるNICKEL et al.のいうSchleudermagenは常に横隔膜への付着から遊離していた.以上の観察結果は反芻機構の考究に一つの参考所見として役立つであろう.

Forty-nine adult male mice were starved for 1 to 7 days. All animals except 5 for control were divided into 7 groups and sacrificed group by group every day. The adrenals obtained were studied by means of histological techniques, especially of lipid and mitochondrial staining. The results and the discussion are summarized as follows.The adrenal represented significant hypertrophy in only one day's starvation and was extremely hypertrophied by the 3rd day followed by a decrease in size close to that of the control by the 5th day. No significant difference in weight of the adrenal was obtained between the 5th and the 7th day. Lipids diminished greatly in the inner cortex of the gland 2nd day. Mitochondria hypertrophied on the 2nd day and showed a decrease in size and number on the 3rd day. There were two types in the cytological changes from the 3rd day on. In one type little lipid and few mitochondria accumulated, while in the other a large amount of lipid accumulated and mitochondria hypertrophied. Sudanophillia shown in the adrenal cortical cells had an intimate relationship with the adrenal secretory activity and mitochondria were very sensitive indicators of cellular secretory activity. From this point of view, it can be supposed that the prompt release of hormonal substance in cortical cells may have occurred by the3rd day, and that the adrenal, from the 3rd dayon, showed no function, after releasing all of thesecretory substances or storing them excessively and being unable to discharge them at all. From the 5th day on, cortical atrophies and degenerations were observed here and there in the adrenals.Figs.2-6 were stained with hematoxylin-eosin, and fig.7 with Mallory-azan. Figs.8-10 show lipids in the adrenal cortex and figs.11-13 mitochondrial distribution in the adrenal cortex.Fig.2 Adrenal cortex of a control mouse.Fig.3 Adrenal cortex of a mouse starved for 3 days. Note the remarkable increase in width of the cortex.Fig.4 Adrenal cortex of a mouse starved for 7 days. Note the remarkable decrease in width of the cortex and striking atrophy of the cells, compared with those in fig.3.Fig.5 Adrenal cortex of a mouse starved for 5 days. The cortical degeneration is present.Fig.6 A portion of the cortical degeneration which occurred in the adrenal of a mouse starved for 5 days, shown under high magnification.Fig.7 A portion of the innermost part of the adrenal cortex of a mouse starved for 5 days. The special zone is present between the innermost zona fasciculata and the medulla.Fig.8 Adrenal cortex of a control mouse.Fig.9 Adrenal cortex of a mouse starved for 3 days. Note the extreme decrease in the content of lipid in the inner cortex.Fig.10 Adrenal cortex of a mouse starved for 7 days. Note the extreme accumulation of lipid. This animal died before sacrificed.Fig.11 Mitochondrial distribution in a control mouse.Fig.12 Mitochondrial distribution in a mouse starved for 3 days. Mitochondria in the inner cortex decreased in size and number.Fig.13 Mitochondrial distribution in a mouse starved for 7 days. Note the extreme accumulation of mitochondria particularly in the inner cortex.

The gonads of 9 male and 9 female fetuses of the cattle were used in this study. The fetuses are 5.7 to 45.0 cm in "crown-rump length" in males and 16.3 to 38.0 con in females. The gonads were fixed in 10% formalin and ZENKER-formol. Routine alcohol dehydration and paraffin embedding were practiced. Sections were cut at 7μ. stained with hematoxylin-eosin or HEIDENHAIN's iron alum hematoxylin, and after MASSON's trichrome method, VAN GIESON'S method and BIELSCHOWSK Y-MARESCH reticulm method. The following observations were made.Testis: There is a cuboidal layer of germ epithelium in the testis of a 5.7-cm-long fetus It becomes flattened gradually with ages. With the vascularization in the tunica albuginea, there is a remarkable increase of connective tissue fibers in the vascularized areas. The seminiferous tubules are distinctly limited by a membrana propria, exterior to which is a thin layer of small connective tissue cells forming a capsular investment. The tubules consist of two kinds of cells, i. e., indifferent cells and germ cells. The former is numerous and the latter a few. Both cells in the tubules have a tendency to increase in number, the numerical ratio between them being scarcely altered in all testes used. Interstitial cells are found sparsely at first and then form cluster-like masses with gradual vascularization.Ovary: In 16.3-cm-to 18.5-cm-long fetuses, the sex cords having a broad hand-like appearancee contain many small indlfferent cells and a few germ cells. Primary follicles increase gradually in the inner part of the cortex. In the bodies of 25-cm-and 27-cm-long fetuses, the sex cords manifested a degenerated appearance. Meanwhile, in a fetus grown 30.0-cm-long, the remarkable change is noticed with the increase in replenished sex cords. Therefore, it is presumed that the sex cords have newly been formed descending from the germ layer, or reconstructed from the parenchymal tissues in these growing stages. No interstitial cells have been found in any ovaries used.The origin of the interstitial cells in the testisand of the medullary cords in the ovary is also. discussed briefly.