Glycogen metabolism in the capillary endothelium. Electron histochemical study of glycogen synthetase and phosphorylase in the pecten capillary of the chick

Glycogen synthetase and phosphorylase activities in the pecten capillary of the chick were studied electron histochemically. Polyglucose particles synthesized by glycogen synthetase or phosphorylase in the pecten capillary were demonstrated to be amorphous. They were located in the cytoplasmic matrix of the endothelium and expanded it widely. The endothelial cell of the pecten capillary plays a role in glycogenesis as well as glycogenolysis and may require substantial energy to its important transport functions.     

Electron histochemical study on synthesis and breakdown of glycogen in the rabbit cornea.

Glycogen synthetase and phosphorylase activity was studied in the rabbit cornea electron histochemically. Glycogen synthetase and phosphorylase were located in the cytoplasmic matrices of the corneal epithelium, but glycogen synthetase was found to be mainly in the superficial half of the epithelium, and phosphorylase mainly in the deep layer. Since the cells in the deep layer of the corneal epithelium contain rich cytoplasmic organelles which have carbohydrate metabolism from glycogen or glucose through the Embden-Meyerhof pathway to the TCA cycle, glycogen synthesized in the superficial half of the corneal epithelium by glycogen synthetase may be transferred to the deep layer of the epithelium and broken down by phosphorylase. Phosphorylase in the superficial half of the corneal epithelium may break down overproduced glycogen so as to avoid the deposition of a large number of glycogen particles for maintenance of corneal transparency.     

Electron histochemical study of phosphorylase system in choroidal melanoma.

4 choroidal melanomas have been studied by electron histochemical techniques for phosphorylase activity. Of the 4 melanomas studied, 2 were spindle B and 2 were epitheloid cell types. Electron micrographs of the tumour cells incubated in the medium revealed that polyglucose particles synthesized by phosphorylase and branching glycosyltransferase were found in both spindle B and epitheloid cells. Synthesized polyglucose particles in both spindle B and epitheloid cells showed 2 patterns. The one was fine granular form and the other was the deposition of amorphous particles which greatly expanded the cytoplasmic matrices. Melanophages in both cell types also showed 2 patterns of synthesized polyglucose particles, fine granular and amorphous. It is concluded that both phosphorylase and branching glycosyltransferase are active in both spindle B and epithelioid cells of choroidal melanomas and their melanophages. It is also indicated that there is no difference in glycolysis among these cells of melanomas.     

A histochemical study of epithelial mucin in the chick chorioallantois

Histochemical methods demonstrate the accumulation of two types of mucous inclusion in the allantoic epithelial cells of the chick embryo. One type of inclusion contains a sialomucin that is PAS-reactive, unstained by Alcian blue and other anionophilic dyes and is susceptible to digestion by Vibrio cholerae neuraminidase. The second inclusion contains an apparent sulfomucin which is Alcianophilic at pH 1.0, unstained by anionophilic dyes after a methylation-demethylation sequence and resistant to testicular hyaluronidase. This sulfomucin exhibits PAS reactivity after desulfation procedures. Both types of mucus occur in individual cells and are normal components of the chorioallantois. Accumulation of the inclusions is enhanced by lowering the pH of the allantoic fluid or as a result of organ transplantation.     

Asymmetrical developmental pattern of uptake of lucifer yellow into amacrine cells in the embryonic chick retina

Whole chick embryo eyes between embryonic day 10.5 and 12 (E10.5–E12) were incubated in a solution of Lucifer Yellow and examined in frozen sections. Starting around day 10.5, brightly stained cells were observed in the innermost part of the inner nuclear layer. Their size, shape and location suggest that most of them represent a subclass of amacrine cells.A distinct spatio-temporal development of Lucifer Yellow-staining of this subpopulation of cells within the inner nuclear layer between E10.5 and E12 is revealed in detail using 3-dimensional models of Lucifer Yellow-stained eyes. The staining can be first observed at a specific location at the ventro-posterior side not far from the fundus. It then spreads radially in a complex pattern reaching the ora serrata first on the ventro-posterior side, then sequentially reaching into the dorso-posterior, the ventro-anterior and finally the dorso-anterior quadrants of the retina. Our results suggest that a horizontal (posterior-anterior) axis and a vertical (ventro-dorsal) axis function as a coordinate system during differentiation of the tissue.We conclude that there are precise spatio-temporal patterns of Lucifer Yellow-staining which most probably reflect spatio-temporal patterns of cell differentiation within the chicken retina. The correlation of these findings with other data on spatio-temporal patterns during differentiation of the chicken retina is discussed.     

The growth of the chick retina after hatching.

In autoradiographs of the retina from two-week old chicks injected with tritiated thymidine during the first week after hatching, the labelled cells were found mainly in the extreme periphery of the retina and the ciliary epithelium of the pars plana. The pattern of labelling in the extreme periphery resembles that observed (Fujita and Horii, '63) in retinae exposed to tritiated thymidine during embryonic development. The mechanisms underlying the histogenesis of retinal cells during growth at the extreme periphery in young stages may be the same as those which operate during embryonic devolopment.     

Scanning electron microscopy of developing photoreceptors in the chick retina.

Photoreceptor morphogenesis in the sensory retina of chicks of 2 to 20 days incubation age was studied by scanning electron microscopy (SEM) and correlative transmission electron microscopy (TEM). At 9.5 days spherical inner segments extend into the subretinal space (optic ventricle). They are randomly arranged with chiefly smooth surfaces and contain centrioles, polyribosomes and microtubules. Microvilli project primarily from Müller cells. By the twelfth day immature ellipsoid and myoid regions have formed. Microvilli are abundant on the lateral surfaces of inner segments and extend over the entire spherical surface by the fifteenth day. Occasional cilia with surrounding depressions at their bases were also observed. Inner segments are more symmetrically arranged due to close proximity of photoreceptor cells. Inner segments elongate during the sixteenth day; many display a transitional ovoid form. Microvilli become less numerous but some persist as calycal processes. By the eighteenth day, conical shaped outer segments appear. Thereafter, all photoreceptor cells are comparable to those in the mature retina. Abundant microvilli on the external surface of the sensory retina suggest a supportive role in supplying adequate nutrition to the sensory retina during morphogenesis. The establishment and continual development of the ellipsoid and myoid appear to be primarily responsible for the elongation of photoreceptor cells.     

Displaced ganglion cells in the chick retina

New morphological and cytological data on the displaced ganglion cells (DGCs) in the chick retina are presented. Analysis of the topographic distribution, cellular number, dendritic field, perikaryon size and ultrastructural characteristics are included. The DGCs were found predominantly in the peripheral retina. The sizes of the DGCs, 18-42 microns, observed either by Normarsky's interferential contrast or by silver impregnation techniques, spanned the size range of the other retinal neurons. The results support the hypothesis that DGCs, in the chick retina, may constitute a specific morphofunctional system, and therefore they might not be considered as neurons that fail to attain the normal location of ganglion cells during the developmental process of migration.     

Microcalcifications in the anterior pituitary gland of the fetus and the newborn: a histochemical and immunohistochemical study

Calcified concretions are a normal and constant finding in the anterior pituitary gland of fetuses and newborns. Their light and electron microscopic characteristics have been recently reported by the authors. In this study, undecalcified and decalcified sections from 20 neonatal and 60 fetal anterior pituitary glands were studied by histochemical and immunohistochemical methods to further clarify their nature and mechanism of formation. All the glands revealed homogeneous and/or laminar calcifications located either within the interstitium or follicular structures. They were composed of a diastase-resistant periodic acid-Schiff-positive carbohydrate-rich matrix. The Feulgen method for DNA was negative. Their core frequently reacted to Alcian blue and epithelial membrane antigen (EMA). EMA also stained the apical membranes of adjacent epithelial cells. Other immunostains (vimentin, keratin, and pituitary hormones) were negative. The positive staining for Alcian blue and EMA and the negative staining with the Feulgen method for DNA suggest that the core of the calcifications consists of acidic mucosubstances and EMA-positive proteinaceous material previously secreted by viable pituitary cells. The EMA-negative periphery of the concretions probably develops from further extracellular peripheral mineralization that leads to larger, sometimes laminated psammoma bodies. The occurrence of pituitary calcifications in states of adult physiological and pathological hyperprolactinemia suggests that the marked proliferation of lactotrophs occurring during the fetal life play an important role in the pathogenesis of the fetal and neonatal concretions.     

On the synaptogenic sequence in the chick retina

Study of the developing chick retina with the electron microscope revealed that dyad ribbon synapses begin to form in the inner plexiform layer before synaptic ribbons begin to appear in photoreceptor terminals of the outer plexiform layer. This centrifugal (inner to outer) sequence of synaptogenesis in the predominantly cone retina of the chick differs from the centripetal sequence that has been reported for the predominantly rod retinas of the mouse and rat. This difference does not favor the hypothesis, suggested by others, that the photo-receptor may influence the maturation of inner retinal elements. The different patterns of synaptogenesis are discussed briefly with reference to anatomical differences between the retinas of different species.     

Light- and focus-dependent expression of the transcription factor ZENK in the chick retina.

Ocular growth and refraction are regulated by visual processing in the retina. We identified candidate regulatory neurons by immunocytochemistry for immediate-early gene products, ZENK (zif268, Egr-1) and Fos, after appropriate visual stimulation. ZENK synthesis was enhanced by conditions that suppress ocular elongation (plus defocus, termination of form deprivation) and suppressed by conditions that enhance ocular elongation (minus defocus, form deprivation), particularly in glucagon-containing amacrine cells. Fos synthesis was enhanced by termination of visual deprivation, but not by defocus and not in glucagon-containing amacrine cells. We conclude that glucagon-containing amacrine cells respond differentially to the sign of defocus and may mediate lens-induced changes in ocular growth and refraction.