Cell types in the fetal pars tuberalis of the human adenohypophysis at mid-gestation

Summary The pars tuberalis of the adenohypophysis was investigated in three human fetuses at mid-gestation by electron microscopy or immunohistochemistry. In addition to gonadotrophs and thyrotrophs, identified by immunohistochemistry and ultrastructural morphology, electron microscopy revealed the existence of an additional differentiated cell type closely resembling pars tuberalis-specific cells known from other species. The role of this cell type in the human endocrine regulation remains to be elucidated.     

Viviparity and the maternal-embryonic relationship in the coelacanth Latimeria chalumnae

Synopsis Embryos of Latimeria chalumnae develop in well-vascularized compartments in the uterine region of the right oviduct. Compartments conform to the shape of their embryos and yolksacs; they represent a stable, gestation-induced oviductal modification. Late-term pups possess large, flaccid, vascular yolksacs almost devoid of yolk. The sac is in close contact with, but does not adhere to, the lumenal uterine surface. A massive vascular plexus occurs in the wall of the compartment at the site of contact with the yolksac; together they constitute a non-adherent, transposable placenta. The exterior surface of the yolksac is bounded by an attenuated, single-layered, squamous epithelium that surrounds an intercommunicating bed of cortical sinuses. The cortex of the sac is composed mostly of connective tissue stroma. The inner surface is bounded by a layer of yolk-digesting merocytes. Residual yolk occurs as yolk platelets that include yolk crystals. The interior surface of the sac is invested by an uniquely specialized vitelline circulation; no connection seems to exist between the interior of the yolksac and gut. The uterine wall consists of: (1) a lumenal surface composed of an anastomosing network of capillaries with a layer of attenuated, very thin, squamous epithelium, (2) a well-vascularized connective tissue stroma, (3) alternating transverse and longitudinal layers of smooth muscle, also well-vascularized, and (4) an external epithelial layer. Comparison of egg dry weight (184 g) with the estimated dry weights of a late-term pup (171 to 239 g) and a neonate (200 to 280 g) reveals a weight change of – 7 to + 30% and + 9 to + 52%, respectively. This is indicative of matrotrophy. In one female specimen, 19 remarkably large ovulated eggs were found and in another about 30 somewhat smaller ovarian ones. These are many more than ever could be accommodated in the uterine space. During the early and middle phases of development, embryos must be lecithotrophic, using their yolk reserves, with oophagy of fragmented supernumerary eggs as the most probable source of additional nutrients. The well-developed embryonic gut contains brown, amorphous yolk-like material. The limited amount of metachromatic secretory product of the uterine glands can play little or no role in embryonic nutrition.     

胎儿脾内B淋巴细胞发育的研究

本文利用一系列抗体和免疫组织化学,在冰冻切片上对不同胎龄(9～38周)的脾,比较观察了淋巴组织形成过程中,B细胞膜抗原的变化。结果发现胎儿脾内T、B淋巴细胞集聚是沿血管分布的,开始为集落样,随着淋巴细胞不断增加,则分别发育为脾小结和动脉周围淋巴鞘。B细胞由集落发展为脾小结时,膜抗原出现一系列变化,如Leu14和BA-1由弱阳性到阳性,OKB-2和Tac由阴性转变为阳性。其他的各种SIg,HLA-DR也有相应改变,这些膜抗原表达的变化,提示B细胞向成熟方面发育,但未发育为浆细胞,脾小结内也未见有生长中心。T细胞数量由少到多,但染色强度没有改变,这是因为T细胞不在脾内发育,而且进入外周淋巴器官的T细胞,功能上是成熟的。     

Müllerian inhibiting substance in reproduction and cancer.

During embryogenesis normal male phenotypic development requires the action of Müllerian Inhibiting Substance (MIS) which is secreted by Sertoli cells of the fetal testis. As testes differentiate in genetic (XY) males, they produce MIS which causes regression of the Müllerian ducts, the anlagen of the female reproductive tract. Soon thereafter, testicular androgens stimulate the Wolffian ducts. In females, on the other hand, MIS is not produced by grandulosa cells until after birth, before which, estrogens induce Müllerian duct development, while the Wolffian ducts passively atrophy in the absence of androgenic stimulation. High serum MIS levels in males are maintained until puberty, whereupon they fall to baseline levels. In females MIS is undetectable in serum until the peripubertal period when values approach the baseline levels of males. This distinct pattern of sexual and ontogenic expression presupposes and requires tight regulation. MIS may play a role in gonadal function and development. Our laboratory has shown that an important role for ovarian MIS is to inhibit oocyte meiosis, perhaps providing maximal oocyte maturation prior to selection for ovulation and subsequent fertilization. Furthermore, Vigier et al. (Development 100:43-55) have recently obtained evidence that MIS may influence testicular differentiation, coincident with inhibition of aromatase activity. Current structure-function studies demonstrate that MIS, like other growth regulators in its protein family, requires proteolytic cleavage to exhibit full biological activity. MIS can be inhibited by epidermal growth factor. This antagonism, which is common to all MIS functions so far investigated, is associated with inhibition of EGF receptor autophosphorylation. We have provided evidence that bovine MIS can inhibit female reproductive tract tumors arising in adults.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gene Expression of Tyrosine Hydroxylase in the Developing Fetal Brain

Tyrosine hydroxylase, aromatic L-amino-acid decarboxylase, and dopamine beta-hydroxylase activities were studied in the developing fetal rat brain. A delay of 2-3 days between the detection of the tyrosine hydroxylase and the aromatic L-amino-acid decarboxylase and dopamine beta-hydroxylase activities was observed. For this reason, the expression of tyrosine hydroxylase mRNA was studied. Tyrosine hydroxylase mRNA was visualized in the whole brain from 13 days of gestation, but the largest increase of the expression was observed in the hypothalamus. These results are discussed in terms of the relative gene expressions of the three enzymes involved in the biosynthesis of catecholamines and phenolamines in nervous tissues.     

Ontogeny and organization of the stationary non-lymphoid cells in the human thymus

Summary Ontogenetic differentiation of the human thymus was investigated in 50 embryos by means of light and electron microscopic methods in an attempt to clarify the morphogenesis of the complicated microecology of thymic tissue. At the 8th gestational week (g.w.), the primordium of the thymus contains almost exclusively undifferentiated epithelial cells. At the 10th g.w., the epithelial cells in the central part are spindle-shaped. During the subsequent weeks the cortical region of the thymus becomes separated into lobes by mesenchymal septa containing hemopoietic precursor cells and large electronlucent cells with irregularly shaped nuclei. The latter cells are also found in the deeper presumptive medullary regions of the thymus; they differentiate into interdigitating reticulum cells (IDC). The permeation of the medulla of the thymus by non-epithelial IDC occurs concurrently with the formation of cortical and medullary epithelial cells. Between the 12th and 14th g.w. the cortical and medullary differentiation is completed. At this time-stage cortical small lymphocytes differ in morphological shape from medullary lymphocytes, the latter acquiring the appearance of immunocompetent T cells and establishing intimate contact with the IDC.These findings indicate that the thymic cortex and medulla contain different epithelial cells. In addition, the thymic medulla displays cells characterized by the morphology of typical interdigitating reticulum cells of peripheral lymphoid tissue. The structural pattern of the thymus is correlated to morphologically differing lymphoid cell populations in the cortical and medullary regions.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft and by the Sonderforschungsbereich 111The authors dedicate this paper to Professor Helmut Leonhardt on the occasion of his 60th birthday. The authors also appreciate the excellent technical assistance of Mrs. I. Knauer, Mrs. H. Waluk and Mrs. H. Siebke     

A hit deconstruction approach for the discovery of fetal hemoglobin inducers

Beta-hemoglobinopathies such as sickle cell disease represent a major global unmet medical need. De-repression of fetal hemoglobin in erythrocytes is a clinically validated approach for the management of sickle cell disease, but the only FDA-approved medicine for this purpose has limitations to its use. We conducted a phenotypic screen in human erythroid progenitor cells to identify molecules with the ability to de-repress fetal hemoglobin, which resulted in the identification of the benzoxaborole-containing hit compound 1. This compound was found to have modest cellular potency and lead-like pharmacokinetics, but no identifiable SAR to enable optimization. Systematic deconstruction of a closely related analog of 1 revealed the fragment-like carboxylic acid 12, which was then optimized to provide tetrazole 31, which had approximately 100-fold improved cellular potency compared to 1, high levels of oral exposure in rats, and excellent solubility.     

Ultrastructural and functional development of macrophages in the dermal tissue of rat fetuses

Summary After about 12 days of gestation, fetal macrophages begin to appear in the subepidermal mesenchyme of rat fetuses. The macrophages are ultrastructurally characterized by cytoplasmic vacuoles, abundant polyribosomes and long filopodia. Immunocytologically, they possess Fc and complement (C3) receptors on the cell surface and are capable of immune phagocytosis, Latex or carbon phagocytosis, and glass adherence. From 15 days of gestation, lysosomal granules and miropinocytic vesicles gradually develop, together with an enlargement of Golgi complexes, whereas the number of polysomes and the number and size of cytoplasmic vacuoles are gradually reduced when gestation ends. Finally, the macrophages become amoeboid. Non-specific esterase and endogenous peroxidase activities are always absent in these macrophages. In culture experiments with cell suspensions prepared from the mesenchyme, fetal macrophages show a similar maturation process. Autoradiography with ³H-thymidine demonstrates a high proliferative capacity of the macrophages, particularly during the fetal stage.Supported by Grant-in-Aid for Cancer Research from the Ministry of Education, Science and Culture, Japan (No. 401057)     

Ossification in the hand and foot of the macaque (Macaca nemistrina). I. General features.

The appearance of the secondary centers of ossification was investigated in hand and foot radiographs of 112 fetal and neonatal Macaca nemestrina and a maturational index calculated using a scoring system that differentiated between the initial and later stages of ossification. Cumulative incremental curves of skeletal maturation, constructed by plotting the maturational indices against gestational age, demonstrated three distinct periods of ossification: the First Acceleration when primary centers appear, the Plateau, and the Second Acceleration when the secondary centers ossify. Similar curves are constructed for human prenatal and postnatal ossification. The results are also compared with those reported for M. mulatta, and the bases of the observed differences are discussed. Compared with other primates, the fetal and neonatal macaque shows a developmental precocity which may be an ontogenetic adaptation to the socioecological setting of terrestrial life.     

Funktionsentwicklung der thyrotropen Zellen der Adenohypophyse des Goldhamsters

Zusammenfassung Die Entwicklung der thyrotropen Zellen in der Adenohypophyse des Goldhamsters wurde an Schnittserien untersucht. Zur Klärung der Frage, inwieweit zwischen dem Beginn der thyrotropen Aktivität und der Funktionsaufnahme der fetalen Schilddrüse ein zeitlicher Zusammenhang besteht, wurden die fetalen Schilddrüsen in die Untersuchung einbezogen. Ausgewertet wurden in erster Linie Präparate, die — nach Aufoxydation der für das thyrotrope Hormon charakteristischen Cystingruppen — mit Alcianblau (pH 0,3) und Dichlorpseudoisocyanin gefärbt worden waren.Thyrotrope Zellen treten in der fetalen Goldhamsterhypophyse erstmals am 14. Tag (untersuchtes Stadium: 13d 17 h) auf. Es sind große, längsoval-birnenförmige bis polygonale Zellen, welche häufig über einen sockelartig ausgezogenen Zellfortsatz mit einer Kapillarwand in Kontakt treten. Das färbbare granuläre Material ist hauptsächlich in der Zellperipherie konzentriert, wodurch es zu einer charakteristischen, scharfen Konturierung dieser Zellen kommt.Zu demselben Zeitpunkt zeigt die fetale Schilddrüsenanlage als erste Zeichen der spezifischen Funktionsaufnahme Follikel- und Kolloidbildung.Während der weiteren Entwicklung nimmt die Zahl der thyrotropen Zellen stetig zu. Zellform und -große sowie die Art der Granulation bleiben dabei nahezu unverändert. An den ältesten untersuchten Stadien (14 Tage p.p.) sind als gonadotrop zu charakterisierende Zellen noch nicht eindeutig nachweisbar.

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Development of function of the thyrotropin secreting cells in the pituitary gland of the golden hamster

Summary The development of thyrotropin secreting cells in the pituitary gland of the golden hamster has been investigated in serial sections. With regard to the relationship between the beginning of thyrotropic activity in the fetal pituitary gland and onset of function in the fetal thyroidea the latter also has been investigated. Thyrotropic cells have been identified by staining with alicanblue (pH 0.3) or dichlorpseudoisocyanin after oxidation with performic acid or potassium permanganate. These reactions are based upon the relative high cystine content of TSH. Thyrotropic cells firstly are to be seen the 14th day of fetal life. These large cells of oval or angular form often have contact with the wall of a sinusoid via a long cytoplasmatic process. The grannies of the thyrotrophs show a marked tendency to be more concentrated at the cell borders giving the cell a characteristic hard outline. At the same time the thyroideaanlage shows first signs of specific function as represented by forming of follicles and production of colloid. During the further development the number of thyrotrophs increases. Form and size of the TSH-cells and the kind of granulation of these cells do not change. In the oldest stages examined (14th day p.p.) gonadotropic cells could not be identified.

Sasse (1968) konnte weiterhin zeigen, wie es etwa zum selben Zeitpunkt zu einem plötzlichen Anstieg der Aktivität der Glucose-6-Phosphat-Dehydrogenase und der cytoplasmatischen RNS in den Schilddrüsenepithelien kommt. Die Bedeutung der G-6-P-DH liegt in der Bereitstellung der für die Nucleinsäuresynthese notwendigen Pentosen über den Pentose-Phosphat-Cyclus (Sasse, 1968). Die plötzliche Steigerung der Aktivitätsrate der G-6-P-DH beruht möglicherweise auf der zum gleichen Zeitpunkt einsetzenden thyrotropen Aktivität des HVL. Hierauf weist jedenfalls die in vitro an Gewebsschnitten beobachtete spezifische Stimulierung des Pentose-Phosphat-Cyclus nach TSH-Zusatz hin (Condliffe und Robbins, 1967). Die Bedeutung des thyrotropen Hormons für die Synthese der Ribonucleotide in der fetalen Schilddrüse wird auch durch Befunde unterstrichen, nach denen TSH eine Umwandlung des glatten agranulären in das rauhe, d. h. mit Ribosomen besetzte, endoplasmatische Retikulum bewirkt. Wesentlicher Mechanismus scheint dabei zu sein, daß durch TSH eine Funktionsumstellung der DNS von der Phase reiner Proliferation auf die Entwicklung der spezifischen Schilddrüsenfunktion, d.h. der thyroidealen Hormonsynthese bewirkt wird (Szentágothai et al., 1968).