Fetal hypophysis as the main source of serum TSH in fetal rat

Decapitation performed at days 17-18 leads to a drastic drop (82%) in blood TSH of 19 and 21-day-old rat fetuses below the mother's level. 125I-TSH injected at 21 days into the mother's bloodstream is not found in fetal blood. The fetal hypophysis is the main source of fetal plasmatic TSH.     

Fetal rat brain hemisphere tissue in nonadherent stationary organ culture

Summary A simple organ culture system for brain tissue is described. Fragments of fetal rat brain hemisphere tissue are explanted to multiwell dishes base-coated with semisolid agar. In this system nonadherent organ culture can be performed for at least 50 days. Cell migration, biochemical and morphological differentiation and the formation of a layered architecture seem to mimic some of the phenomena occurring in the developing rat brain in vivo. The fragments may therefore be a useful organ culture model for nervous tissue.     

Changes in the level of ACTH in the fetal hypophysis. A study in the rat toward the end of gestation]

The isolated adrenal cell method for bioassay of ACTH was employed in order to determine the ACTH content of the hypophysis of the rat foetus, in late pregnancy. The ACTH concentration decreases between 17 days 8 h and 17 days 15 h, then it increases regularly until the term. This evolution is correlated with the change in the fluorescence intensity of the corticotrophs and with the modification of the adrenocortical activity.     

Immunoactive TSH in the amniotic fluid of the rat

Summary Amniotic fluid was obtained from 19-day-old rat fetuses by aspiration. Pooled samples measured at 4 different dilutions demonstrated parallelism with standard rat TSH. It is concluded that rat amniotic fluid has TSH immunoactivity.This work was supported by Hong Kong University Research Grant No. 335/034/5727.The authors wish to acknowledge with thanks the gift of rat TSH RIA kit from Dr A. F. Parlow and the Rat Pituitary Programme of NIAMDD.     

Development of the innervation of the urogenital complex in the fetal mouse

Summary The developing urogenital complex of the fetal mouse was studied by means of silver impregnation and electron microscopy. These studies showed that: 1) the mesonephric field is innervated during prenatal stages (Wolffian nerve); 2) nerve penetration precedes the differentiation of the gonads and related ducts; and 3) the Wolffian nerve arises during the earliest stages from the first pair of abdominal rami communicantes. The identity between the fetal Wolffian nerve and the nerve of the suspensory ligament (higher pathway) of the adult is discussed.     

Inhibition of TSH-stimulated thyroid hormone release and potentiation of TRH-stimulated TSH release by indomethacin in perifusion systems of rat thyroids and pituitaries

Summary Using indomethacin (Ind), a prostaglandin, synthesis inhibitor, in vivo experiments in rats and in vitro experiments with perifusion systems of rat thyroids and pituitaries were conducted. After 35 days of intragastric infusion of Ind, serum TSH levels were markedly increased, the thyroid was swollen and, as a consequence, T₃ and T₄ levels were normal. The T₃ release from perifused rat thyroids under continuous stimulation with 10 mU/ml TSH was inhibited significantly (p<0.01) by 1.0×10^–6 M Ind. On the other hand, the TSH release from perifused rat pituitaries under TRH stimulation was enhanced conspicuously by Ind. It was concluded that Ind decelerated thyroid hormone release from the thyroid and accelerated TSH release from the pituitary in perifusion systems.     

Differential removal of insulin-like growth factor binding proteins in rat serum by solvent extraction procedures

Solvent extraction of serum and other biological fluids at an acidic pH is a convenient method to remove the insulin-like growth factor binding proteins (IGFBPs); however, an incomplete removal of IGFBPs can occur and this can potentially interfere with the radioimmunoassay of insulin-like growth factors (IGFs). This study compared the removal of IGFBPs from normal adult rat serum and 5-day old neonatal rat serum by acid-gel filtration, and three solvent extraction methods, i.e., acid-ethanol (AE), acid-cryo-ethanol (ACE) and formic acid-acetone (FAA) treatments by western ligand blotting and slot-blotting analysis. In adult rat serum all three extraction methods removed nearly 75% of total IGFBPs present. For the neonatal serum, AE and FAA were very inefficient in eliminating the IGFBPs, while ACE was somewhat better, as it removed nearly 30% of IGFBPs. Ligand blots of extracted samples showed that IGFBPs of lower size range, 24 to 32 kDa (IGFBP-4, IGFBPs-1 and-2), were resistant to solvent extraction. Acid-gel filtration, in contrast, eliminated >95% of IGF-binding components in both sera. Determination of IGF-I concentrations in samples after gel filtration and extraction methods revealed lower IGF-I values in neonatal serum in acid extracted samples. These data caution against using solvent extractions for IGFBP removal in fetal/neonatal serum.     

Ontogenic development of peptide hormones in the mammalian fetal pancreas

Summary The ontogeny of insulin, glucagon, PP and somatostatin in the mammalian fetal pancreas has been examined in recent years largely by immunocytochemistry and in some instances by radioimmunoassay. Complete ontogenic data are available only for the rat, human pig and sheep. Figure 3 compares the time of appearance of the endocrine cell-types within the fetal pancreas when the periods of gestation of the four species are converted to a uniform scale. The striking ontogenic difference in the rat probably reflects the immaturity of the rodent fetus at birth compared with the human, pig and sheep. In the fetal pancreas, differences in cell number of glucagon and PP cells in the dorsal and ventral lobes become apparent from an early gestational period. Factors responsible for the functional and structural maturation of the fetal pancreatic endocrine cells and the processes involved in pancreatic organogenesis are poorly understood. Studies in these areas would have clinical implications since it may be possible in the future to employ agents for selective replication of fetal -cells for transplantation in patients with Type I diabetes, bearing in mind that such cells must have the capacity to respond to normal stimuli and repressors when transplanted. The presence of the other islet cell-types may be obligatory for these appropriate responses. This would require a more complete knowledge of those factors which produce the normal selectivity of the four hormonal cell-types.     

Effect of epidermal growth factor on growth and maturation of fetal and neonatal rat small intestine in organ culture

Summary Small intestinal explants from pre- and post-natal rats were incubated in an organ culture system in the absence and presence of epidermal growth factor (EGF). The rate of synthesis of small intestinal DNA and protein as well as the activity of lactase and alkaline phosphatase increased rapidly between 17 and 20-day gestational age, whereafter they declined. The maximal incorporation of³H-thymidine and¹⁴C-alanine into DNA and protein, respectively, was significantly stimulated by EGF (100 ng/ml). EGF had no effect on the activity of either lactase or alkaline phosphatase in the small intestinal explants.Acknowledgment. The project was supported by grants from the Veterans Administration Research Service. The authors wish to thank Dr. M. C. Geokas, Chief, Department of Medicine, Veterans Administration Medical Center, Martinez, CA, for providing us with excellent laboratory facilities and for his encouragement in this study.     

Intracellular localization of alpha-fetoprotein and serum albumin in the central nervous system of the rat during fetal and postnatal development]

The morphological localisation of alphafetoprotein (AFP), serumalbumin (SA), transferrin and immunoglobulins (IgG) has been studied in the developing central nervous system of the Rat by immunocytochemical methods. Evidence is presented of a highly selective staining for AFP and SA, both proteins exhibiting the same topographical distribution. Practically all the areas of the brain and the spinal cord are stained at a given moment of the developmental process. The labeling is cytoplasmic and in the neuronal elements extends to their axonic and dendritic prolongations. The localization of AFP and SA in the nervous system may be related to the well known binding properties of these proteins for varied substances (estrogen and/or fatty acids). The morphological data presented here suggest that both proteins may be actively involved in the uptake of such substances by the cellular structures of the nervous tissue.     

The dopaminergic innervation as observed by immunohistochemistry using anti-dopamine serum in the rat cerebral cortex

Summary By using an antiserum raised against dopamine bound to bovine serum albumin, thinner dopamine-labeled nerve terminals were visualized immunohistochemically within neocortical areas, in addition to well-documented dopaminergic innervation into the prefrontal and limbic cortices.This study was supported in part by a Grant-in-Aid for Scientific Research on Priority Areas, Japanese Ministry of Education, Science, Culture (No. 62623002).     

The dopaminergic innervation as observed by immunohistochemistry using anti-dopamine serum in the rat cerebral cortex

By using an antiserum raised against dopamine bound to bovine serum albumin, thinner dopamine-labeled nerve terminals were visualized immunohistochemically within neocortical areas, in addition to well-documented dopaminergic innervation into the prefrontal and limbic cortices.     

The effect of gonadotropic hormones and the fetal hypophysis on testosterone production by the testis of 18 day mouse fetuses in organ culture]

The production of testosterone (measured by radioimmuno-assay) by the 18-day-old mouse fetal testis may be stimulated specifically by ovine LH (1 ng, p less than 0.005) and HCG in organ culture. A stimulation by FSH is observed only with high doses (10 mug, p less than 0.0005). Prolactin and ACTH have no effect. Age-matched fetal pituitaries increase significantly the testosterone production in the culture medium (p less than 0.0005).     

Enzyme immunometric assay for the determination of pregnancy associated plasma protein A (PAPP-A) with the antigen as solid phase (conjoint IEMA)

Summary Purified pregnancy associated plasma protein A (PAPP-A) can be effectively bound to polystyrene microtitre plates. This immobilized antigen competes with the added serum PAPP-A of unknown concentration for the limited amount of peroxidase-labeled monospecific anti-PAPP-A antibody incubated simultaneously. The sensitivity is 0.2 WHO unit/ml and non-specific binding is 1.0%.Acknowledgments. My thanks go to the Janggen-Pöhn-Stiftung, St. Gallen, Switzerland, for the reception of a fellowship grant which enabled this work to be carried out. I would also like to thank Arnold Klopper, Professor of Reproductive Endocrinology, for many stimulating discussions, Garry Luke for excellent technical assistance, and the Department of Medical Illustration of the University of Aberdeen for the preparation of the graphics. The donkey serum was generously supplied by the Scottish Antibody Production Unit, Carluke, Lanarkshire.     

Inhibition of phosphoenolpyruvate carboxykinase by 6-phosphogluconate in rat liver

Summary Various concentrations of 6-phosphogluconate inhibit rat liver phosphoenolpyruvate carboxykinase activity. 0.04 mM 6-phosphogluconate, which is the concentration found in vivo, caused a 50% inhibition of 6-phosphoenolpyruvate carboxykinase activity. 6-Phosphogluconate lowered the V_max of the enzyme and increased the concentration of phosphoenolpyruvate required to achieve one-half of the maximum velocity. The role of 6-phosphogluconate as a regulator of the coordination of fluxes through three metabolic pathways is discussed.     

Supramarginal cells in the rat pituitary cleft revealed by scanning electron microscopy

Summary An unusual cell type consisting of free elements widely scattered over the marginal epithelium of the rat pituitary cleft is revealed by SEM. Most of these supramarginal cells characteristically have irregularly shaped cell bodies from which thin branched processes extend. Supramarginal cells bear resemblances to Kolmer (epiplexus) cells and to supraependymal cells of the brain ventricles. Their ultrastructural features make it probable that supramarginal cells are phagocytes, and can be regarded as scavengers of the cleft. Considering the close topographical association between the hypophysial cleft and the floor or the 3rd ventricle, supramarginal cells may be members of the motile macrophagic Kolmer cells populating the ventricular surfaces of the brain.Work supported by grants from MPI-60%-193/84