The insertion of mesenchyme cells into the ectoderm during differentiation in Sea urchin embryos

Summary During the course of sea urchin development, from early blastula to pluteus larva, there are two major visible processes toward which all activities seem to be focused. They are the differentiation of the larval skeleton by the primary mesenchyme cells and the differentiation of the primitive gut by the secondary mesenchyme cells. These activities take place within the shell-like layer of epithelial cells, or ectodermal wall. The interactive role of the ectodermal wall with the mesenchyme cells is not yet clearly understood. A number of earlier studies have proposed that the ectoderm may have an inductive influence on the mesenchyme cells and that its inner surface forms a molecular template for guiding the mesenchyme cells. In this report, we suggest an additional role for the ectodermal wall. We show that some primary mesenchyme cells and secondary mesenchyme cells insert between the cells of the ectodermal wall in order to firmly anchor the anlage of the larval skeleton and primitive gut during differentiation. This mechanism may provide a physical basis for maintaining the stable positional relationship of the anlage during development.     

Characterization of L-threonine deaminase activity of guinea pig liver induced by a high protein diet

In a foregoing paper, we demonstrated that under equilibrated diet conditions, guinea pig liver L-threonine deaminase activity should be allocated to two distinct enzymes: a specific L-threonine deaminase without activity toward L-serine and a L-serine deaminase having a secondary activity toward L-threonine. In the present work, we observed that a high protidic diet caused an elevation of total threonine deaminase activity. Thus purification of guinea pig liver L-threonine deaminase was attempted, using ultracentrifugation, salt precipitation, heat treatment, ion exchange chromatography on DEAE Sephacel, Sephadex G 200 molecular sieve, 2 amino-2 methyl-1 propanol linked CH 4B Sepharose chromatography. The weak variations of the ratios of specific activities respectively toward L-threonine and L-serine observed at each stage of the purification procedure indicated that both activities are very likely supported by a single enzyme preexisting in the liver of guinea pigs fed an equilibrated diet. No isoenzyme was evidenced by polyacrylamide gel electrophoresis or DEAE Sephacel chromatography. Moreover, our purification procedure demonstrated that not only inducible L-threonine deaminase guinea pig liver activity was due to L-serine deaminase, but also that an initially existing specific L-threonine deaminase activity paradoxically disappeared with a protein rich diet.     

Fluorescence anisotropy from diphenylhexatriene in rat liver plasma membranes

Rat livers were fractionated to obtain intracellular membrane preparations and a highly purified preparation of bile canaliculi. The fraction containing bile canaliculi was homogenized and subfractionated to give fractions representing fragments of contiguous membrane and of canalicular microvilli. The relative purity and extent of contamination of each preparation was determined. When the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene was incorporated into aliquots of each fraction at the same probe: lipid ratio and the steady-state anisotropy of its fluorescence measured, it was found that the plasma membrane preparations were much more ordered than the intracellular membrane preparations. Of the plasma membrane preparations, that containing the canalicular microvilli was the most ordered, even allowing for any contribution of contaminants. Thus the microvillus membrane of the bile canaliculus appears to be the most ordered domain of the plasma membrane of the hepatocyte. The high order in this domain may be a factor in reducing the susceptibility to bile salt damage during bile secretion, since it is this region which is exposed to high concentrations of bile salts in vivo.     

Increase in hepatic ubiquinone on administration of diethylhexyl phthalate to the rat

It is shown for the first time that the content of ubiquinone of liver increases (2.5 fold) on dietary administration of the widely-used industrial Plasticizer diethylhexyl Phthalate to the rat. The increase is localized almost entirely in mitochondria in which the concentration of the quinone Per mg Protein is 1.7 times the control. IncorPoration of the radioactive Precursor (acetate) reveals that the biosynthesis of ubiquinone is increased in the livers of Plasticizer-administered animals. The rate of degradation is not altered.     

Allometric relations of total volumes of prolactin cells and corticotropic cells to body length in the annual cyprinodont Cynolebias whitei: effects of environmental salinity,stress and ageing

Summary An analysis of the allometric relations of the total volumes occupied by prolactin (PRL) and corticotropic (ACTH) cells (PRL volume and ACTH volume, respectively) to body length and a study of the immunocytochemical staining intensity of PRL and ACTH cells were used to determine the differences in activity of PRL and ACTH cells in freshwater-reared and in saltwater-reared Cynolebias whitei during the entire lifespan of this annual cyprinodont fish. An inflection in the allometric relation of PRL volume to body length was observed in fish of one-week old. The relatively large PRL volume in younger fish may be related to PRL cell activity before hatching. No inflections were observed in the allometric relations of PRL volume and ACTH volume to body length at the onset of maturation and the onset of ageing, indicating that the increased pituitary growth in maturing and ageing C. whitei is not the result of changes in PRL or ACTH cells. The slope of the allometric relation of PRL volume to body length in freshwater-reared fish was significantly steeper than the slope in saltwater-reared fish. The PRL volume in adult freshwater-reared fish was eight times larger than that in saltwater-reared fish of the same length. The intensity of immunocytochemical staining of saltwater PRL cells was significantly reduced. These volumetric and staining differences correspond to the low functional demand put upon PRL cells in saltwater-adapted fish. In contrast, the slope of the allometric relation of ACTH volume to body length and the intensity of immunocytochemical staining of ACTH cells were similar in freshwater-reared and in saltwater-reared fish. It is concluded that the functional demand put upon ACTH cells is similar in freshwater-reared and saltwater-reared C. whitei; the involvement of ACTH cells in the osmoregulation of the fish in both environments is similar.     

Diminished steroidogenic response of hamster granulosa cells to estrogen in vitro

Summary We have previously demonstrated that estrogen can exert inhibitory or atretogenic effects on the ovaries of both rats and rhesus monkeys in vivo. This study was designed to test whether the hamster (Mesocricetus auratus) is an appropriate model in which to test the effects of estrogens (diethylstilbestrol and estradiol-17) on steroid accumulation by ovarian granulosa cells in vitro, and whether the effects are similar to those demonstrated for other species in vivo. Immature female hamsters were injected with pregnant mare's serum gonadotropin at 28 to 30 days of age. Animals were sacrificed and follicular contents aspirated three days later. Granulosa cells were either left untreated or treated with diethylstilbestrol or estradiol (1×10^-7 M) in vitro for 72 h in the presence of androstenedione (1×10^-7 M), and in the presence or absence of serum (10%) or human follicle-stimulating hormone (20 ng/ml), and long-term accumulation of estrogen and progesterone was determined. Diethylstilbestrol inhibited accumulation of estrogen regardless of the presence or absence of follicle-stimulating hormone. In contrast, only estradiol plus follicle-stimulating hormone augmented accumulation of progesterone by granulosa cells. These findings that estrogen can be non-stimulatory or inhibitory to function of granulosa cells in vitro parallel those shown in vivo. Our experimental approach may therefore represent an appropriate model for study of the direct effects of estradiol on the function of granulosa cells.     

Calcitonin gene-related peptide immunoreactivity in airway epithelial cells of the human fetus and infant

Summary Calcitonin gene-related peptide-immunoreactive cells were identified within the epithelium of distal conducting airways in the human fetus and infant. Several peptides and amines, including calcitonin, have been identified previously within a specific population of airway epithelial cells. These cells, referred to as pulmonary neuroendocrine cells, are postulated to be airway chemoreceptors responsible for changes in ventilation and perfusion in response to changes in airway gas composition. Calcitonin gene-related peptide immunoreactive cells could be identified throughout the period of development studies (20 weeks gestation to 3 months of age), but were present in only limited numbers in less than 50% of individuals (n=23). In contrast, large numbers of calcitonin gene-related peptide immunoreactive cells were identified in 100% of infants (1–3 months, n=5) with bronchopulmonary dysplasia. The differential processing of mRNA transcribed from the calcitonin gene in neural and non-neural tissue suggests that calcitonin, rather than calcitonin gene-related peptide, is the primary product of translation in pulmonary neuroendocrine cells. However, considering the potent vasodilatory and bronchoconstrictive effects of calcitonin gene-related peptide, its presence in pulmonary neuroendocrine cells, even in small amounts, may be important in controlling pulmonary vaso- and/or bronchomotor tone. The presence of large numbers of calcitonin gene-related peptide immunoreactive cells in infants with bronchopulmonary dysplasia suggests that calcitonin gene-related peptide may be one further agent contributing to the pulmonary pathophysiology seen in this disease.     

Modulation of asialoglycoprotein binding activity in livers of pregnant or estrogen-treated rats

This report deals with the modulation of activity and expression of the hepatic asialoglycoprotein receptor, in pregnant or diethylstilbestrol-treated rats.The results show a two-fold increase in the total cell associated binding activity, both in pregnant and in estrogen-treated animals, with respect to normal values. On the contrary the surface expression was shown to be strongly enhanced only in the liver of pregnant rat. Therefore the modulation shown by this receptor system in pregnancy seems to be only partially estrogen-dependent.