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.

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.

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.

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.

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.

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.

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.

The present study was conducted to clarify the histological differentiation of the adrenal cortex of the bovine fetus and to determine the time when the sudanophilic lipid appears for the first time in the adrenal gland. Twenty bovine fetuses, from 13 to 43cm in C.R.L., collected at a slaughter house in Osaka were used in this study. Fixed with 10% formalin, one of the adrenals of each fetus was paraffin-sectioned at 7μ in thickness and stained by several methods; the other was frozen-secti ned at 25μ and stained with Sudan IV-hematoxylin. The observations are summarized as follows. At the stage of a 13-cm C. R. L., the cortical parenchyma was composed of irregular cell cords alone. At that of a 16-cm C.R.L., beneath the capsule were revealed rather slightly smalloepitheloid cells grouped in spherical clusters. A layer of these clusters of cells is to be termed zona glom-erulosa. By the stage of a 24-cm C. R. L., the spherical clusters beneath the capsule developed further and expanded horizontally along the capsule with widening connective tissue spaces among them. The cells of z. glomerulosa were smaller and stained darker than those of z. fasciculata. Histolo-gical differentiation of the adrenal cortex of the bovine fetus seemed to be almost completed essen-tially by the stage of a 30-cm C. R. L., because little changes were found in the gland after this stage. Few sudanophilic lipid droplets were found in the parenchyma of the adrenal cortex of a 19-cm-long fetus. In a 24-cm-long fetus, however, sudanophilic droplets were contained in some cortical rPlls, especially in the glomerular and the inner fasciculate cells in considerable abundance. From the stageof a 27-cm C. R. L., on all adrenals contained lipid droplets in the cortex with no exception. From the stage of a 27-cm C.R.L. on, lipid droplets gradually increased their size and number in the glomerular cells. As the lipid contained in the adrenocortical cellsis said to have an intimate relatiorship with hormone production, it may be concluded presumably from the above observations that the adrenal of the bovine fetus may shows in some manner the hormone-formation or the secretory activity, at least after the growth stage of a 27-cm C. R. L.

Thyroids of 26 bovine fetuses, 10.0 to 64.5 cm in crown-rump length, were histologically examined. The number, body length, and estimated age of the fetuses are shown in table 1. The glands were fixed in Zenker-formol and embedded in paraffin. Paraffin sections were stained with hematoxylin-eosin and by Masson's trichrome method, Mallory-azan method, PAS technique, and LILLIE's silver impregnation.In a 10-cm fetus, the thyroid consisted of undifferentiated epithelial cells arranged in very irregular cords. In a few of these cells, the cytoplasm contained colloid droplets, which were also seen in intercellular spaces. No follicles were present, In 12.5-and 13.2-cm fetuses, a few very young follicles with a colloid mass in the lumen were developed in the cords and spherical groups of cells, most of which were loaded with colloid droplets located in juxtanuclear portion or far from the nucleus, or polarized toward the capillary surface. From the stage of 16.3cm onwards, the whole thyroid consisted generally of follicles of widely varying size which grew progressively together with an increase in amount of colloid stored in them which stained mostly blue or occasionally yellow or red by the azan method, except the peripheral portions of the gland which presented indifferent patterns showing irregular cell masses and very young follicles.Argyrophilic granules demonstrated by LILLIE's silver impregnation appeared in fetuses 16.5cm in body length and older, first in cells of small follicles and then in these of medium-sized follicles and of interfollicular undifferentiated epithelial masses. Follicles were formed first in irregu'ar cell cords and, thereafter, separated by encircling of argyrophilic fibers, growing by mitotic proliferation of cells, together with their fellows developing from interfollicular undifferentiated epithelial cells.Most cells of the developing follicles contained PAS-positive, occasionally argyrophilic, granules in the apical portion of the cytoplasm being ready to cast them off into the lumen. With the advance of fetal age, colloid substances became to be seen frequently in the interstitial tissues in variable amount. They may be extravasations pushed out of ruptured follicles or passing through degenerating colloid cells in the follicular epithelium from the lumen.

Morphologic and volume changes of the pancreatic islets during perinatal days in the rat were studied.During 3 days at the end of fetal life, the islet cells containing Gomori's aldehydepositive β granules gradually increased in number and in degree of granulation. The total volume of islets sharply increased at term.After birth, the total volume of the islets did not increase. The size of islet cells was markedly reduced. The number of β granules in islet cells markedly increased. These observations would support the view of some limitations of insulin secretion under a normal physiologic condition at least during the first 3 days after birth in the rat.

The adrenals of rat fetuses obtained from mothers whose pregnancy was prolonged by injection of progesterone were compared with those of fetuses in normal pregnancy and of neonatals, with particular reference to the weight, ascorbic acid content and histology.During normal pregnancy, the fetal adrenal weight steadily increased up to the 21st day of pregnancy, showing an especially pronounced rise from the 20th to 21st day of pregnancy. From the 21st to 22nd day, there was no reliable in crease in fetal adrenal weight. After birth, the adrenal of neonatals was lighter and cortical cells were smaller than those in the fetal stage. Ascorbic acid content increased on the 22nd day of pregnancy, showing little fluctuation after birth. Osmiophilic materials increased in amount. When pregnancy was prolonged for 2 or 3 days, the fetal adrenals did not show atrophy, but gained weight, with a fall in ascorbic acid content. Osmiophilic materials were fewer than in the normal neonatals.The adrenals of progesterone-treated mothers did not show any significant change, neither in weight nor in ascorbic acid content, as compared to those of the normal untreated mothers. Progesterone, when injected to the newborn rats, failed to induce a distinct alteration in adrenal weight and histology, but caused a slight decrease in ascorbic acid content.It is concluded that the retardation of fetal adrenal growth does not occur in prolonged pregnancy.

The amount of liver fat just before birth and just after birth in the rat was determined by weighing crude fat extracted with chloroform-methanol. The liver fat in rat fetuses tended to be decreased in amount toward birth. After birth, it was remarkably increased. In fetuses retained experimentally beyond the normal gestation, it showed a slight increase. In premature newborns obtained by Caesarean section, it was increased significantly in a short period of 6hrs. after the delivery.

On the 20th day of pregnancy in the rat, decapitation, adrenalectomy or thyroidectomy of a fetus was performed in utero. Some decapitated fetuses were given a subcutaneous injection of cortisone acetate or extract of bovine thyroids. On the 22nd day of pregnancy, the fat content of the fetal liver was determined by the weight of crude fat extracted with chloroform-methanol. Remarkable increase of the fat content in the fetal liver followed decapitation. This increase was prevented partially by injected cortisone, but not by injected thyroidal extract. The increase of liver fat, though less than the recorded increase in decapitated fetuses, also followed adrenalectomy. The increase did not follow thyroidectomy. The observations suggest that the effect of decapitation on the liver fat involves in part the adrenal deficiency.

Two hr after birth, newborn rats were given a subcutaneous injection of 0.01 mg estradiol benzoate dissolved in 0.05 ml sesame oil. Other siblings were given sesame oil alone. Autopsy was performed on days 1, 2 and 3 after birth. Gravimetric and histologic examinations of the adrenals from these animals and from normal littermate controls were made together with the determination of plasma corticosterone concentrations. In all the three groups of rats, estrogen-treated, oil-treated and non-treated, the weight of the adrenal glands declined with a concomitant decrease in the plasma corticosterone concentrations. The results indicate that estradiol benzoate, when given after birth, does not prevent the neonatal adrenal from shrinking.

On day 14 of fetal life in the rat, Mullerian (paramesonephric) duct in both sexes was first observed close to Wolffian (mesonephric) duct. Its caudal end joined Wolffian duct at about the level of the middle of gonadal anlage. Thereafter, Mullerian duct became independent of Wolffian duct through its whole length. Therefore, the main part of Mullerian duct may be formed by budding from Wolffian duct. On day 16, the anogenital distance in male started to increase with thickening of Wolffian duct and disappearance of Mullerian duct. Castration of male fetuses on day 19 stopped later masculinizing development. Therefore, it is clear that the fetal testis is an organ crucial for the masculinization of the urogenital tract as it activates the secretion of masculinizing hormone(s).

The main purpose of this study was to examine the relationship between the lung alveolar development and the fetal adrenal activity, by means of fetal bilateral adrenalectomy. The bubble stability ratio (BSR), to detect the changes in the amount of pulmonary surfactant, was determined in the lungs of rat fetuses and neonates or fetuses retained in utero beyond the normal gestation period. Histologic examination of lung alveolar tissue was also performed. The BSR in normal rats was gradually increased toward term and was still high at 2hr after birth, followed by a subsequent decline in the 1st and the 2nd day after birth. This change was in parallel with the histologic observation that the alveolar walls became progressively thinner whereas the number of great alveolar cells showed a prenatal increase followed by a postnatal decrease. Prolongation of gestation, induced by a maternal injection of progesterone, maintained the late fetal state in the BSR and the lung histology. Fetal adrenalectomy caused a decline in the BSR and a retardation in histologic differentiation of the fetal lung alveolar tissue. These effects were overcome by giving corticosterone to the adrenalectomized fetuses. The results support the view that the fetal adrenal gland participates in the development of great alveolar cells and the surfactant production before birth.

Hypothalamus-independent negative feedback mechanism of the pituitary-thyroid axis was studied by electron microscopic observation of thyroid follicular cells of encephalectomized or hypophysectomized fetal rats under hypothyroidism induced by propylthiouracil (PTU). Fetal hypophysectomy or encephalectomy was performed on day 19 of gestation. Mother rats were given either a daily amount of 40 mg PTU or saline alone on the day of operation and on the next day. On day 21, their fetuses were obtained. As a result, PTU induced marked goiters even in encephalectomized fetuses, the goiters being comparable in weight to those induced in littermate intact fetuses. Electron microscopically, the follicular lumen was narrowed, microvilli were lengthened with a marked increase in number, and rER was extremely expanded. Follicular cells often confined colloid droplets and lysosomes. Fetal hypophysectomy, even in PTU-treatment, caused a reduction in the thyroid weight, accompanied by flattening of follicular cells, shortening of microvilli, widening of follicular lumen, and shrinkage of rER. These findings would support the view that the negative feedback mechanism of the pituitary-thyroid axis can operate without the hypothalamus in fetal rats.

Thyroid C cells in fetal rats on days 21 and 22 of gestation had well-developed rough endoplasmic reticule (RER) and Golgi complexes and numerous secretory granules. The granules had vascular polarity in their location and some of them were attached to the cell membranes. Fetal hypophyseoprivia by subtotal decapitation (SD) caused fetal hypercalcemia, accompanied by a wide variation in electron density of the secretory granules, an increase in number of flattened RER and a further development of Golgi complexes. These changes in fine structure suggest a rise in calcitonin-producing activity of C cells, probably in response to hypercalcemia. Fetal thyroidectomy caused fetal hypocalcemia, probably owing to parathormone deficiency. TSH therapy of SD fetuses neither prevented the fetal hypercalcemia nor repaired the cytologic changes in C cells. GH therapy of SD fetuses partially prevented the hypercalcemia between day 20 and day 21 of gestation, but not between day 21 and day 22. Cytologic repair was not observed. Propylthiouracil injected into fetuses influenced neither the C cell's structure nor the plasma calcium levels. The observations suggest that the fetal hypercalcemia and the rise in secretory activity of C cells induced by fetal SD are not solely due to a deficiency of fetal pituitary TSH. The role of pituitary GH is questionable. Deficiencies of other brain factors should be considered as contributing to the observations.

Male and female fetal rats were gonadectomized in utero on the 20th day of gestation. Two days after the operation, the pituitaries were observed histologically in order to examine the changes of the population of basophilic cells. The gonadectomy of a male fetus caused a significant increase in the per cent of basophilic cells, whereas that of a female fetus induced no significant change. Since the increase in the relative number of basophilic cells following gonadectomy has already been accepted to be intimately related to the increased production of gonadotrophic hormones, the present results strongly suggest that the feedback mechanism between the pituitary and the gonad is already operated before birth in males but not in females. There is a definite sex difference in development of the pituitary-gonadal axis during the fetal life.