Ultrastructure of the fetal rat anterior pituitary gland as term and during prolonged gestation.

The ultrastructure of the fetal rat anterior pituitary gland is described at term (day 22) and during experimentally prolonged gestation (days 23, 24, 25). The latter was achieved by daily subcutaneous injections of five mg progesterone to gravid females from the twentieth through the twenty-fourth day. Using morphological criteria for classifying pituitary cells (Moriarty, '73), six different types were observed: thyrotrophs, gonadotrophs, corticotrophs, mammotrophs, somatotrophs and non-granulated cells. During prolonged gestation (days 24 and 25 only), cells designated as corticotrophs revealed changes suggesting increased activity, i.e.,proliferation and dilation of the endoplasmic reticulum, dilated Golgi membranes and a redction of secretory granules. In addition, meconium staining , which is indicative of fetal distress, was also observed on days 24 and 25. The ultrastructural changes noted suggest an increased in corticotroph activity due to fetal hypoglycemia and hypoxia which are known to occur as a result of placental insufficiency during prolonged gestation (Roux et al., '64; Vorherr, '75; Thliveris, '76.     

Ultrastructural observations of the fetal rat heart during prolonged gestation

The ultrastructure of myocardial cells was examined from fetal rat hearts during experimentally induced prolonged gestation (GD 23, 24 and 25), and compared to those from term fetuses (GD 22) and newborn animals (N1, N2, N3). Gestation was prolonged by daily subcutaneous injections of 5 mg progesterone to gravid females on days 20 through 24. The 4 chambers of the heart were assessed individually for structural differences by morphometric analysis. Comparison between the 2 atria at each stage revealed no differences as was the case between the 2 ventricles. At term and throughout the newborn period, atrial and ventricular cells were characterised by numerous mitochondria, moderate amounts of glycogen, few lipid droplets and membrane-bounded granules, which, moreover, were peculiar to atrial tissue. During prolonged gestation (GD 24 and 25), there was a statistically significant increase in the size of mitochondria in both atria and ventricles and a reduction of membrane-bounded atrial granules. Whole heart glycogen content was also assessed, biochemically, and found reduced on GD 24 and 25. In addition to the morphological and biochemical findings, fetal rat heart weights were obtained from each designated day of prolonged gestation and compared to newborn rat hearts of comparable age. A statistically significant increase in heart weight was noted on GD 24. Meconium staining, which is indicative of fetal distress was also observed on GD 24 and 25. The morphological and biochemical changes observed suggest a response by the fetal heart to stressful conditions, namely hypoxia and hypoglycemia, which are known to exist during prolonged gestation.     

Ultrastructure of the labyrinth in the rat full-term placenta

Summary The placental labyrinth of the chorioallantoic placenta of the rat was studied with transmission and scanning electron microscopy. Full-term placentas were investigated after perfusion fixation from the maternal and fetal circulation, including thin-sectioning and freeze-fracturing.The labyrinthal three-dimensional structure was found not to be trabecular but spongious lamellar. We propose a division of the lamellae into three groups—the first, second, and third order.The trophoblastic layers are described in detail, showing a cellular layer I and two syncytial layers II and III. Layer I is found to be fenestrated and highly permeable. Layers II and III are connected by extended gap junction areas. It is suggested that the gap junctions function as a molecular sieve and represent the limiting barrier in diaplacental transport of the choriollantoic placenta.Fetal capillaries are fenestrated and endothelial cells are connected by tight junctions.The functional significance of the morphologic findings is discussed.With the support of the Deutsche Forschungsgemeinschaft. Dedicated to Prof. Dr. Drs. h.c. W. Bargmann on his 70th birthday     

Ultrastructure of human fetal mammary gland

Early cytodifferentiation of human fetal mammary gland was studied at the time of the beginning of the sexual differentiation during the sixth to eleventh developmental weeks. The gland appeared as a solid epithelial ingrowth into the underlying mesenchyme on both sides of the thoracic wall at the age of 5 weeks in both sexes. These ingrowths contained primitive glycogen-rich cells with large nuclei. The surrounding mesenchymal cells gathered around the basal lamina. These cells differentiated into fibroblasts, and collagen fibers were seen in the mesenchyme near the mammary buds. No lumina appeared within the buds during this study. Differences between the male and female mammary epithelium or mesenchyme were not observed, although androgen synthesis and secretion in the fetal testis had already begun. The close connections and concomitant differentiation of the mammary bud epithelium and mesenchyme during the early embryogenesis in this study suggest that epithelio-mesenchymal interaction plays an important role in the differentiation of human mammary gland.     

以胎儿为供体肾上腺移植的应用解剖

为提供胎儿为供体肾上腺移植的应用解剖学资料,在30具(7～9月龄)胎儿尸体标本上观测了双侧肾上腺血管的起源、支数、长度、外径以及肾上腺移植有关的血管.根据双侧肾上腺血管的观察比较,右侧肾上腺血管支数和外径都优于左侧,依据解剖学观察,以胎儿为供体行单侧肾上腺移植术宜取右侧为好.     

Ultrastructure of the anterior buccal gland of the rat

The anterior buccal gland of the rat is a mucous salivary gland which develops as a branch of the main (Stensen's) duct of the serous parotid gland, a few mm from its oral orifice. The purpose of the present study was to further characterize the mature gland by means of electron microscopy and the histochemical demonstration of myoepithelial cells. The tubuloacini were found to have intercellular extensions (canaliculi) of the lumina, prominent Golgi complexes, and mucous secretory granules with a biphasic substructure. Discharge was by exocytosis of individual granules. The tubuloacini joined directly to striated ducts; no intercalated ducts were seen. First-order excretory ducts had larger lumina and shorter columnar cells, with fewer mitochondria and basal infoldings, than the striated ducts. Myoepithelial cells invested the tubuloacini but not the ducts. The anterior buccal gland has several features that are unusual for a minor salivary gland of mucous type, and which are usually associated with serous glands such as the parotid. It should provide a particularly interesting model for investigating factors which control the differentiation of secretory and myoepithelial cells, and the glycosylation of polypeptides to form mucous secretory products.     

Ultrastructure of synaptosomes from fetal rat brain

The crude mitochondrial fraction P₂ and subfractions of P₂ were prepared from the brain stem, hemispheres and whole brain of 19-day-old fetal rats. Samples were fixed in glutaraldehyde-osmium, NaMnO₄ or by Tranzer's triple fixation method (aldehyde-chromate-dichromate-osmium) and examined by electron microscopy. The C-fraction from whole brain was the main synaptosome fraction, containing 3.2 % presynaptic terminals as counted from all membrane bound particles. The brain stem showed more presynaptic terminals than the hemisphere (2.8% versus 0.9%) suggesting a caudal-rostral maturation gradient for synaptogenesis. The maturity of the nerve endings obtained was very variable in contrast to the rather uniform synaptosomes derived from adult tissue. They varied from profiles without any substructures to mature synaptosomes displaying asymmetric synaptic junctions. Monoamine synaptosomes containing small granular vesicles were not detected in the present study, suggesting immaturity of the granular monoamine pool at this stage of development.     

Ultrastructure of the rat duodenal endocrine cells after prolonged irradiation

We propose classification of duodenal endocrine cells of intact rats based on ultrastructural signs of secretory granules and subdivided these cells into 10 basic types. The effect of long-term irradiation in a total dose of 2.5 Gy on ultrastructural organization of duodenal apudocytes was studied. Irradiation induced nonspecific changes of cell organelles in apudocytes. Differences in the ultrastructural disorganization were detected between different types of apudocyte populations and between different types of endocrine cells. Under conditions of adaptation to radiation apudocytes released the secretory product not only through molecular extrusion and exocytosis, but also via degranulation.     

Functional activity of the adrenal cortex in fetal and neonatal rabbits under normal conditions and during inhibition of the gestation dominant

The content of lipids, cholesterol, and ascorbic acid was investigated in fetuses developing during normal pregnancy and in physiologically mature newborn rabbits, and also in fetuses developing during inhibition of the gestation dominant and in physiologically immature newborn rabbits. The results showed that in the first group the functional state of the adrenal cortex was activated, as shown by a low content of lipids, cholesterol, and ascorbic acid. In a state of increased adaptive motor responses the content of these substances was reduced still further. In the second group (physiological immaturity) their content was considerably increased. It is concluded that normal antenatal development is possible during exposure to natural physiological stress.Laboratory of Age Physiology and Pathology, Institute of Normal and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Department of Histology and Embryology, Chelyabinsk Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Fedorov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 78, No. 8, pp. 35–39, August, 1974.     

Alterations in fetal rabbit prothrombin time at different stages of gestation and during asphyxia

Summary Experiments were conducted which demonstrated that prothrombin time diminishes gradually during gestation of the fetuses. The suggestion is made that this may be associated with the appearance of the prothrombin formation function of the liver. This function is not fully developed at birth but centinues maturing. This and not vitamin K deficiency is suggested as the reason for the comparatively prolonged prothrombin time seen during the first few days of independent life. Prothrombin time is greatly increased by asphyxia. Presented by Active Membet AMN SSSR Prof. A. F. Tur     

Ultrastructure of the metrial gland cell in the pregnant rat

The metrial gland cells of the pregnant rat were studied with the electron microscope from day 12 through day 15 of pregnancy. Prominent features of their fine structure included abundant granular endoplasmic reticulum, a large Golgi complex, and numerous dense granules. These granules were bounded by a single membrane and contained a dense material, smooth vesicles, and membranous whorls. It is suggested that the dense material is aggregated in the mature granules by the coalescence of smaller progranules that are derived from the Golgi apparatus. The nature and fate of these granules is discussed in relation to the possible secretion of relaxin by metrial cells.     

Mineralocorticoid function of the rat adrenal gland and thyroid hormones

Adrenal mineralocorticoid function was studied in 195 male albino Wistar rats with a different level of thyroid hormones in the organism. Aldosteronemia, aldosteronuria, and plasma renin activity were studied in in vivo experiments. In vitro experiments were carried out to study the content of aldosterone in the adrenals and its discharge into the incubation medium in euthyroid, hyper- and hypothyroid animals. Hyperthyroidization leads to manifest inhibition of the adrenal mineralocorticoid function, and suppresses aldosterone excretion in the urine and plasmic metabolic clearance in diminished formation of aldosterone in the glomerular zone. Changes of an opposite character occur in the renin-angiotensin-aldosterone system of rats after total thyroidectomy. Injection of small doses of thyroxine also reduces aldosterone production in the adrenals of thyroidectomized animals. It is shown that an excess of endogenous thyroxine in the organism produces an inhibiting effect not only on the level of aldosterone production and secretion, but, to a definite measure, also on the level of the possible realization of its peripheral action.