Unusual association of 'chloride cells' with another cell type in the skin of the glass catfish, Kryptopterus bicirrhis

Cutaneous biology and diseases of fish

The normal structure and function of the piscine integument reflects the adaptation of the organism to the physical, chemical, and biological properties of the aquatic environment, and the natural history of the organism. Because of the intimate contact of fish with the environment, cutaneous disease is relatively more common in fish than in terrestrial vertebrates and is one of the primary disease conditions presented to the aquatic animal practitioner. However, cutaneous lesions are generally nonspecific and may be indicative of disease that is restricted to the integument or a manifestation of systemic disease. Regardless, a gross and microscopic examination of the integument is simple to perform, but is highly diagnostic and should always be included in the routine diagnostic effort of the aquatic animal practitioner, especially since various ancillary diagnostic procedures are either not practical or lack predictive value in fish. The purpose of this article is to provide an overview of normal cutaneous biology prior to consideration of specific cutaneous diseases in fish.

A study of the morphology of the gills of an extreme alkalinity and hyperosmotic adapted teleost Oreochromis alcalicus grahami (Boulenger) with particular emphasis on the ultrastructure of the chloride cells and their modifications with water dilution. A SEM and TEM study

The general gill morphology of Oreochromis alcalicus grahami, a teleost adapted to high salinity and hyperosmosis, is basically similar to that of other teleostean fish. The species has four pairs of gill arches, all of which have well developed filaments. Each of the arches (holobranchs) has two rows of filaments (hemibranchs). Bilaterally situated secondary lamellae branch from the central axis of the filaments. The lamellae reach their maximum size at the middle of the filament, gradually decrease in size and eventually disappear towards the tip of the filament, which is bare. The leading edge of the gill filament and the immediate interlamellar space is covered by a stratified epithelium consisting of pavement cells, mucous cells, chloride cells and undifferentiated cells. The surface of these cells is made up of concentric microridges. The chloride cells were found only on the primary epithelium (filamental epithelium) and very rarely on the secondary epithelium (lamellar epithelium). Two types of chloride cells were observed in the gills of Oreochromis. The superficial chloride cells have fewer mitochondria concentrated towards the basal aspect of the cell, and a network of tubules towards the apical surface and are less electron dense. These cells intercommunicate with the water through an apical pore. The deep chloride cells have numerous diffuse mitochondria intercalated between a fine profuse tubular network and are more electron dense. These cells are covered by one or more layers of pavement cells and thus do not have access to the external surface. After gradual dilution of the lake water in which the fish were kept, both types of chloride cells remained topographically and ultrastructurally distinct. However, in both kinds of cell the mitochondria decreased in number and size. Initially there was an increase in the diameter and the degree of interdigitation of the tubules followed by a gradual decrease. An increase in the quantity of rough endoplasmic reticulum, particularly at the perinuclear region of the cell, was noted. The morphometric analysis of the branchial system indicated that the gills of Oreochromis are well adapted for gas exchange by having numerous and relatively long gill filaments with a high lamellar density. These features provide a large surface for gas exchange which, when coupled with the notably thin water-blood barrier of an average thickness of only 0.83 micro, would facilitate efficient absorption of oxygen by the gills. Oreochromis alcalicus was observed to be incapable of adapting to freshwater. This may have been due to the progressive degeneration of the chloride cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Submandibular duct salivary bladder of the rat

This investigation is a light and electron microscopic description of the submandibular duct salivary bladder of the rat, a dilation of the distal end of the main excretory duct. The wall of the bladder consists of a mucosa with pseudostratified epithelium, a submucosal layer of connective tissue, and an underlying layer of striated muscle. The pseudostratified columnar epithelium lining the bladder is composed of three cell types: light cells, dark cells, and basal cells. The lamina propria contains bundles of collagen, attenuated fibrocytes, capillaries with fenestrated endothelia, and nerve fibers which enter the epithelial layer. The capillaries of the submucosa are not fenestrated. The morphology of the wall of this structure provides evidence that the primary fluid of the submandibular gland is modified in the bladder by transepithelial fluid and ion transport.

New ultrastructure of rat RPE cells: basal intracytoplasmic tubules

Retinal pigment epithelial cells have prominent basal folds facing Bruch's membrane. In addition to folds I have observed intracytoplasmic tubules 60-90 nm in diameter in the basal cytoplasm of rat pigment epithelial cells. The tubules arise from the basal plasma membrane and open to the extracellular space. The tubules are most evident when intravenous horseradish peroxidase is used as a tracer. The tracer leaks out of the fenestrated choriocapillaris, into the extracellular space of the pigment epithelium and into the tubules. Electron microscopy at 1000 KV (High Voltage Electron Microscopy) confirms the tubular nature of these structures and their continuity with folds or the plasma membrane facing Bruch's membrane. The tubules are also observed in tissue not infiltrated with peroxidase. Morphometry shows that the tubules occupy about 21% of the surface area of the basal plasma membrane. Tubules appear plentiful where folds are reduced, and reduced where folds are plentiful; the tubules may be a different conformation of the normally slit-like fold extracellular space. The tubules are observed in all quadrants of the retina; centrally and peripherally; in young and adult rats and in pigmented and albino rats. The tubule's function may be linked to that of the folds, from which many of them arise.

Ultrastructure of marine teleost gill epithelia: SEM and TEM study of the chloride cell apical membrane

This paper deals with the structure of gill epithelia in the sole, Solea solea, as revealed by transmission and scanning electron microscopy. In this marine teleost the chloride cell and its accessory cell form a cellular complex. Apically the plasma membranes of these cells are loosely juxtaposed, thus forming a leaky epithelium covering a large part of the gill.