Scanning electron microscopic study of hyalocytes in the guinea pig eye

The ultrastructure and distribution of hyalocytes were examined in guinea pig eyes by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hyalocytes were distributed randomly on the vitreous surface of the retinal inner limiting membrane, where they were elongated in shape with a spherical perikaryon and a few stout processes. On the epithelial surface of the ciliary body, however, the cells were stellate with some short processes. The cells of both regions included typical dense hyalocyte granules in the cytoplasm. The surface morphology of hyalocytes indicates that the cells are wandering macrophages. The abundance of free cells in the ciliary body epithelium suggests that the area is a site for the emigration of hyalocytes or their precursors from the ciliary stroma. The homogeneous population of hyalocytes in the posterior part of the eyeball may be useful for experimental studies of the cell in vivo or their isolation for study in vitro.     

Co-localization of vasoactive intestinal polypeptide and neuropeptide Y immunoreactivities in the nerve fibers of the rat adrenal gland

The co-localization of Vasoactive Intestinal Polypeptide (VIP) with Neuropeptide Y (NPY) or its C-flanking peptide (C-PON) was investigated with immunocytochemistry methods in the adrenal gland of the rat. Most of the VIP immunoreactive (+) nerve fibers found in the capsule/glomerular zone also exhibited NPY or C-PON immunoreactivity (IR). We found that at least two populations of VIP varicose nerve fibers can be observed, the most prevalent exhibited both VIP/NPY or VIP/C-PON IR and the other which was rather scarce lacked NPY or C-PON IR. In the superficial cortex VIP/NPY or VIP/C-PON IR nerve fibers were often associated with capsular or subcapsular vascularization and extended into the zona glomerulosa. In the deeper layers of the adrenal cortex radial fibers were closely associated with the inner vascularization of the zona fasciculata and reticularis. In the adrenal medulla NPY or C-PON immunoreactivity was associated with ganglion neurons as well as chromaffin cells; these last cells were always VIP (-). VIP and NPY/C-PON IR could be co-localized in catecholaminergic nerve terminals of the adrenal cortex but not in the adrenal medulla.     

An electron microscopic study of intestinal metaplasia in human gallbladder.

Areas of intestinal metaplastic epithelium in gallbladders removed by cholecystectomies performed for gallstones were studied with the electron microscope. Three gallbladders contained areas of goblet cells and endocrine enterochromaffin-like cells and one gallbladder also Paneth cells. The goblet cells contained mucin granules of slightly variable size and shape and relatively great electron lucency. The intervening columnar epithelial cells contained various amounts of electron-lucent mucin granules. The round or oval enterochromaffin-like cells rested on the basement membrane, and in these cells the small, round, electron-opaque secretory granules were located in the infranuclear region. The supranuclear cytoplasm of the Paneth cells in the intestinalized epithelium contained typical large, round secretory granules. The fine structures of the various cells in the metaplastic epithelium bore resemblance to those of the cells in the intestinalized stomach mucosa.     

Immunohistochemical evidence of vasoactive intestinal polypeptide-containing neurons and nerve fibers in sympathetic ganglia

Neurons and nerve fiber networks showing immunoreactivity for vasoactive intestinal polypeptide have been observed in some sympathetic ganglia with the help of the indirect immunofluorescence technique. Antisera to tyrosine hydroxylase and dopamine β-hydroxylase were used to identify catecholamine cells on consecutive sections. In the coeliac-superior mesenteric ganglion complex and the inferior mesenteric ganglion of the guinea-pig very dense networks of vasoactive intestinal polypeptide-positive varicose nerve fibers were observed around the principal ganglion cells. Only very few immunofluorescent fibers were seen in relation to the small intensely fluorescent cells. Occasionally some immunoreactive principal ganglion cells were found. In the same ganglia of the rat a considerably less dense network of vasoactive intestinal polypeptide-positive nerve fibers was present. The superior cervical ganglia of both species contained only a few vasoactive intestinal polypeptide-immunofluorescent fibers and no positively reacting cells were found.     

Coexistence of vasoactive intestinal polypeptide- and substance P-like immunoreactivities in the tongue of the guinea pig

Vasoactive intestinal polypeptide (VIP)- and substance P (SP)-like immunoreactivities were examined in the tongue of the guinea pig by using the double immunofluorescence method. Coexistence of VIP- and SP-like immunoreactivities was suggested in many nerve fibers innervating the lingual salivary glands, as well as in a few intralingual ganglionic cells.     

Immunoelectron microscopic study of tyrosine hydroxylase immunoreactive nerve fibers and ganglion cells in the rat adrenal gland

The present immunocytochemical study used an antiserum to tyrosine hydroxylase (TH), the first enzyme in the biosynthetic pathway of catecholamines, and revealed TH immunoreactivity in the ganglion cells and in the varicose nerve fibers of the cortex and medulla in the rat adrenal gland. TH immunoreactive nerve fibers in the cortex and medulla contained large and small granular vesicles, and also small clear vesicles. The immunoreactive nerve fibers were in close apposition to cortical cells in the cortex and in apposition to smooth muscle cells of blood vessels in both the cortex and medulla. Furthermore, TH immunoreactive nerve fibers were sometimes in close apposition to pericytes of blood vessels in the cortex and chromaffin cells in the medulla. The present results suggest that the catecholaminergic nerve fibers in the rat adrenal gland may be both intrinsic and extrinsic in origin.     

An electron microscopic study on substance P-like immunoreactive nerve fibers in the pars distalis of the adenohypophysis in the dog.

The pars distalis of the adenohypophysis has recently been proved to be innervated by substance P-like immunoreactive nerve fibers in the monkey and the dog. The present study investigated immuno-electron microscopically the morphology of these nerve fibers and their relationship to anterior pituitary gland cells in the dog. The nerve fibers were unmyelinated and varicose. Direct contacts between them and every cell type of the gland could be ascertained, including folliculostellate cells. Typical synapses were identified on somatotropes and corticotropes. Most of them were of asymmetrical type with round to oval small clear vesicles and scattered large dense-cored vesicles. Occasional symmetrical type synapses were also seen. The results imply that substance P-like immunoreactive nerve fibers have an effector role in the pars distalis of the dog.     

An electron microscopic study of absorption of peroxidase conjugated immunoglobulin G by guinea pig visceral yolk sac in vitro,

In the guinea pig and some other animals, passive immunity is conferred on the developing fetus by passage of immunoglobulin from mother to fetus across the yolk sac. In order to examine the cytological pathway involved in immunoglobulin transport, guinea pig visceral yolk sacs from late in gestation were exposed in vitro to peroxidase-conjugated guinea pig immunoglobulin G (IgG-HRP). Tissue was then fixed, incubated to show the site of localization of peroxidase reaction product and prepared for electron microscopy. The results suggested that the first step in the uptake of IgG-HRP by yolk sac is attachment of the protein to the surface coats of endocytic invaginations at the apical surfaces of the endodermal cells. The endocytic vesicles then appear to pinch off from the surface and move deeper into the cytoplasm. Some of the small endocytic vesicles fuse with large apical vacuoles, which often contain large amounts of reaction product. Other small endocytic vesicles pinch off from the surface, move deeper into the cytoplasm and fuse with the lateral plasmalemma; their protein content is emptied into the intercellular space by exocytosis. From the intercellular spaces the protein presumably diffuses across the basement membrane and connective tissue spaces and enters the vitelline capillary bed. It is postulated that the latter cellular pathway, involving small vesicles and the intercellular spaces, is utilized by those immunoglobulins which are transferred intact across the yolk sac endoderm.     

Immunoelectron microscopic localization of relaxin in endometrial gland cells of the pregnant guinea pig

Endometrial gland cells in uteri from late-pregnant guinea pigs (day 60 to parturition) resembled typical protein-secreting cells. Extensive rough endoplasmic reticulum and well-developed Golgi complexes were evident. The most striking features of endometrial gland cells were accumulations of large (≈ 0.5 μm in diameter), dense, membrane-bounded granules. The granules were located in the supranuclear region of the cell and frequently occurred in close proximity to the plasma membrane adjacent to the lumen of the gland. Thin sections of endometrial gland cells treated with relaxin antiserum and either colloidal gold-protein A or colloidal gold-goat antirabbit IgG demonstrated that the granules contained relaxin. These studies provide additional evidence that the uterus of the guinea pig produces relaxin and support the hypothesis that uterin relaxin may play an important role in pregnancy and parturition in the guinea pig.     

Immunoelectron microscopic study of tyrosine hydroxylase immunoreactive nerve fibers and ganglion cells in the rat adrenal gland.

The present immunocytochemical study used an antiserum to tyrosine hydroxylase (TH), the first enzyme in the biosynthetic pathway of catecholamines, and revealed TH immunoreactivity in the ganglion cells and in the varicose nerve fibers of the cortex and medulla in the rat adrenal gland. TH immunoreactive nerve fibers in the cortex and medulla contained large and small granular vesicles, and also small clear vesicles. The immunoreactive nerve fibers were in close apposition to cortical cells in the cortex and in apposition to smooth muscle cells of blood vessels in both the cortex and medulla. Furthermore, TH immunoreactive nerve fibers were sometimes in close apposition to pericytes of blood vessels in the cortex and chromaffin cells in the medulla. The present results suggest that the catecholaminergic nerve fibers in the rat adrenal gland may be both intrinsic and extrinsic in origin.     

A light and electron microscopic study on pulpal nerve fibers in the lower incisor of the mouse.

Light and electron microscopic studies were made on pulpal nerve fibers in mouse lower incisors, typical continuously growing teeth. Serial sections, from the apex of the odontogenic sheath to the incisal edge of the apical foramen, were examined by light microscopy to identify myelinated fibers passing through the apical foramen. The fine structure of the pulpal nerves was examined by electron microscopy at three sites: 1) the level at the incisal edge of the apical foramen; 2) a level 5 mm incisal from the apex of the odontogenic sheath; and 3) the level where the incisor comes out of the alveolar bone. No myelinated fibers were found passing through the apical foramen; they were also lacking at the three levels of the pulp. At level 2, unmyelinated axons were seen in close contact with smooth muscle fibers of arterioles. At level 3, nerve fibers were difficult to distinguish from processes of fibroblasts and odontoblasts. Degenerating axons were present in Schwann cells, and fine unmyelinated axons running through the odontoblast cell layer were seen. Various types of unmyelinated axons were observed in the apical region (level 1). These axons were classified into 6 types on the basis of their fine structures: Type I, bundles of unmyelinated axons completely or partly ensheathed by Schwann cell cytoplasm (mature type); Type II, bundles of unmyelinated axons in a space formed by a Schwann cell membrane (regenerating type); Type III, bundles of unmyelinated axons ensheathed not by a Schwann cell, but merely by a basal lamina (regenerating type); Type IV, single axons in direct contact with the basal lamina (regenerating or terminal type); Type V, naked, electron-dense axons with many vesicles and mitochondria (growth cone-like type); and Type VI, electron opaque axons, due to loss of axonal organellae (degenerating type). The significance of these structures is discussed in relation to the continuous growth of the rodent incisor.     

An electron microscopic study of pig liver viability after extracorporeal storage.

The effects of hyperbaric oxygenation and ambient pressure oxygenation on the viability of pig liver stored in the Vickers'' transportable organ storage unit were assessed by electron microscopy. It was found that hyperbaric oxygenation resulted in marked liver damage in contrast to ambient pressure storage. Although electron microscopy proved to be a sensitive method for detecting damage induced by unsuitable storage protocols consideration is given to the possibility that other changes, which may not be detectable by electron microscopy, limit the success of liver storage.     

Synaptology and sources of vasoactive intestinal polypeptide and substance p containing axons of the cat celiac ganglion. An experimental electron microscopic immunohistochemical study

We have examined the possible origin of vasoactive intestinal polypeptide (VIP) and substance P-containing axons and the synapses formed by these axons in the celiac ganglion of the cat, by means of ultrastructural immunohistochemistry combined with various surgical lesions.Axons containing VIP as well as those immunopositive for substance P, formed axo-dendritic and axosomatic synapses with principal ganglion cells. After transaction of the superior mesenteric nerve numerous degenerated axonal profiles could be found in the celiac ganglion. Some of these contained VIP immunoreactivity. By contrast in alternate sections stained with substance P antibody only intact axons were labelled.Bilateral vagotomy resulted in the appearance of degenerating axonal profiles in the celiac ganglion, some of which could be stained with substance P antiserum but not with VIP antiserum. Following removal of dorsal root ganglia (Th₆-Th₁₂) from both sides, a large number of degenerated axons were found, many of which were immunopositive for substance P but not for VIP.We conclude that the peripheral input to the celiac ganglion contains VIP fibers which form synapses with principal ganglion cells. Substance P-containing fibers reach the celiac ganglion via the vagal nerve as well as from the dorsal root ganglia, and they form synapses with the principal ganglion cells. It is proposed that the VIP and the substance P-containing axons are involved in two different peripheral reflex loops.