PubMed Health⌕ Search

Biomedical subjects

H S Johnston

Publications and source records attributed to H S Johnston.

At least 19 recordsLinked to original sources
PubMed1992

The hamster harderian gland: a combined scanning and transmission electron microscopic investigation.

Scanning electron microscopy of the epithelial cells of the female hamster harderian gland reveals a range of surface features. Some cells exhibit a uniform covering of microvilli while others, often with swollen apices, are relatively devoid of microvilli. Surface pitting is frequent for all cells; pits represent regions of exocytotic lipid vacuole release. A similar range of surface appearances occurs in the male gland but here cells with uniform microvilli represent type I cells (characterised by small lipid vacuoles) while swollen cells with sparse microvilli are type II cells (characterised by large lipid vacuoles). It is suggested that different cell forms represent a single cell type in varying activity states. Luminal debris is often marked, consisting chiefly of lipids. Solid porphyrin accretions, sometimes surrounded by neutrophils, are numerous in female (but not male) glands. Interstitial mast cells are also numerous in the female gland. The gland contains fenestrated capillaries and extensive lymphatics. The duct of the gland, which has received little attention, possesses ciliated cells, nonciliated cells and basal cells. Ciliated cells possess kinocilia and relatively tall thin microvilli, as well as some lipid vacuoles. Nonciliated cells bear shorter microvilli, apically located mucoid granules, and lamellar formations of smooth endoplasmic reticulum. The basal cells are squat and pyramidal; their lateral walls, which interdigitate with the main duct cell types, show pronounced folding.

Animals↗
PubMed1987

The Harderian gland, its secretory duct and porphyrin content in the woodmouse (Apodemus sylvaticus).

The Harderian gland of the woodmouse (Apodemus sylvaticus) consists of tubules lined by a single layer of epithelial cells with a surrounding layer of myoepithelial cells. The epithelium contains two cell types, one with numerous small, clear, lipid vacuoles (Type I), the other with large electron-dense ones (Type II). Each type is further subdivided into cells where the smooth endoplasmic reticulum exhibits pronounced vacuolation (Ia and IIa). The lipid vacuoles frequently coalesce and are released by exocytosis. They possess a multilamellar cap; similar multilamellar whorls (without a vacuole) are also seen. Polytubular complexes are a feature of Type II cells; tubules are in continuity with the smooth endoplasmic reticulum. Peroxisomes are also present. Fenestrated capillaries occur frequently in the interstitium, and (where no myoepithelial cell intervenes) the basal surface of the gland epithelial cell is covered with microvilli. There is no morphologically distinct duct system within the gland. The extraglandular duct is lined by columnar epithelium except at the opening on to the nictitating membrane where there is stratified squamous epithelium, with melanocytes and nests of mucus-secreting cells. The porphyrin content of the gland is low and solid intraluminal deposits are not seen.

Animals↗
PubMed1986

The prevention of porphyrin loss from tissues during routine histological processing: quantitative studies on the Harderian gland.

The rodent Harderian gland is an important site of porphyrin biosynthesis and storage. Porphyrins are visible at the light and electron microscope level as large intraluminal accretions, as large interstitial accretions surrounded by foreign body giant cells, or as small interstitial deposits within free macrophages. Since porphyrins are soluble in a wide range of solvents, it is important to employ histological routines which minimize porphyrin loss during processing in addition to giving good tissue preservation. In this quantitative investigation, these requirements were optimally achieved with fixation in 3% buffered glutaraldehyde and the use of amyl acetate as a clearing agent.

Animals↗
PubMed1986

Quantitative studies on the effects of hormones on structure and porphyrin biosynthesis in the harderian gland of the female golden hamster. II. The time course of changes after ovariectomy.

The Harderian gland of the golden hamster is an important model of porphyrin biosynthesis. In the female, ovariectomy leads to changes in porphyrin production and gland structure. The present study demonstrates that these changes are progressive and independent of age and environmental factors which may have similar effects. Porphyrinogenic enzyme activity decreases with time after ovariectomy while tubule wall degeneration and neutrophilic infiltration increase. Tubule degeneration leads in turn to porphyrin stores (normally intraluminal) occurring increasingly in the interstitial tissue of the gland, either as large accretions surrounded by foreign body giant cells or as small deposits inside individual free macrophages. Between 20-30 weeks after ovariectomy, the frequency of mitotic figures begins to increase accompanied by a transient rise in porphyrinogenic enzyme activity. Mast cell numbers (both in the gland and its capsule) increase markedly with time after ovariectomy.

5-Aminolevulinate Synthetase↗
PubMed1985

Electron microscopic morphometric studies on the resting and secreting nasal (salt) glands of the domestic duck. I. Standardisation of the fixation procedure.

In order to perform morphometric analysis of the nasal (salt) glands of domestic duck it was necessary to standardise the regime of fixation and processing for this tissue. This paper reports the results of these experiments in which the nasal glands of nine groups of ducks were perfused by fixatives containing various concentrations of glutaraldehyde; each group included three secreting ducks and three non-secreting control ducks. Fixative osmolality ranged from 300-825 m-osmol. The resulting effects on the electron microscopical appearances of mitochondria and intercellular spaces were assessed. The fixative finally selected as most satisfactory for both control and secreting tissue contained 3.5% glutaraldehyde and 3% dextran in sodium cacodylate buffer, giving an osmolality range of 580-650 m-osmol.

Animals↗
PubMed1985

Interstitial porphyrins and tubule degeneration in the hamster Harderian gland.

The Harderian glands of rodents manufacture and store porphyrins and are increasingly used as models for porphyrin biosynthesis. Although porphyrins are normally stored as solid intraluminal accretions, interstitial deposits also occur; in the Harderian gland of the female hamster these are found frequently in ovariectomised or aged animals. The present study (employing double-embedding techniques) suggests that interstitial porphyrin deposits are the result of degenerative processes which conform to an escalating pattern. Initially, tubule epithelial and myoepithelial cells become greatly attenuated and there is neutrophil invasion. Secondly, tubule walls disappear leaving previously intraluminal porphyrin stores free within the interstitium. Finally, large interstitial porphyrin accretions become surrounded by foreign body giant cells or are broken down into smaller deposits within free macrophages. These are often associated with plasma cells. Infiltration of the interstitium by lymphocytes may also occur. It may be that the abnormal localisation of porphyrin in the interstitium (i) evokes an immune response and (ii) is related to elevated blood porphyrin levels found in these animals.

Animals↗
PubMed1985

The Harderian gland, its secretory duct and porphyrin content in the Plains mouse (Pseudomys australis).

The Harderian gland of the Australian Plains mouse (Pseudomys australis) consists of tubules lined by a single layer of epithelial cells with a surrounding meshwork of myoepithelial cells. The epithelium contains three types of cell. Type I cells, characterised by their many large apical lipid vacuoles, are comparable with cells reported in other rodents. Secretion is exocytotic and, to a lesser extent, apocrine. Type II cells are highly distinctive with extremely large mitochondria arranged in stacks and whorls. Unusually for Harderian glands, these cells possess prominent conventional Golgi complexes and lysosomes. Cytoplasmic 'slashes', possible vacuole-precursors, are also present. Type III cells have few distinguishing features and may be resting cells. They are occasionally binucleate and mitotic figures occur. The gland contains stored porphyrins, chiefly protoporphyrin, in the form of solid intraluminal accretions. There is a marked sex difference, with females having higher levels of porphyrin than males. Among the components of the interstitial tissue are mast cells, plasma cells and porphyrin-containing macrophages. The secretory duct contains large quantities of cell debris, including nuclei, and is lined by columnar cells with single large apical vacuoles. The outer opening of the duct is lined by mucus-secreting cells and stratified squamous epithelium.

Animals↗
PubMed1983

The Harderian gland, its secretory duct and porphyrin content in the mongolian gerbil (Meriones unguiculatus).

The Harderian gland, its secretory duct and porphyrin content were examined in the mongolian gerbil (Meriones unguiculatus). The gland consisted of tubules lined by a single layer of epithelial cells and a myoepithelial network. The tubule cells were often binucleate and possessed lipid vacuoles in the apical half of the cell, a corona of granular endoplasmic reticulum surrounding the nucleus, and cytoplasmic 'slashes'. The latter are probably derived from dense membranous couplets and may be precursors of the lipid vacuoles. Holocrine and merocrine secretion was observed. Interstitial cells included plasma cells, mast cells and (predominantly) melanocytes which render the gland black. The gland was surrounded by a collagen capsule and an outer layer of highly attenuated (possibly endothelioid) cells. Within the gland, the secretory duct was lined by a single layer of normal tubule cells. Outside the gland, the duct enlarged to form an ampulla, from which clefts led off to deep crypts. The ampulla and clefts were lined by cells with small dense apical granules and stubby microvilli; some possessed lipid vacuoles. The crypts were lined by serous cells with active Golgi regions. At the duct opening, ampullary cells became squamous and goblet cells occurred. Geometric crystalloid deposits (with a layered structure of 7.6 nm periodicity) occurred at cleft-crypt junctions. Islets of extra-glandular ductal tissue were occasionally found within the gland. Porphyrins were detectable both by chemical assay and fluorescence microscopy. There was a trend for female glands to have a higher content than males. Solid intraluminal accretions of porphyrin and/or lipid were present.

Animals↗
PubMed1982

Mast cells in the hamster Harderian gland: sex differences, hormonal control and relationship to porphyrin.

The Harderian gland of the female golden hamster contains an average of forty times more mast cells in the interstitial tissue than the male gland. A similar sex difference occurs in the connective tissue capsule of the gland. Mast cell numbers in the male Harderian gland increase greatly between two and five months after castration, reaching levels comparable to those found in the female. This postcastrational rise in mast cell numbers is prevented by androgen administration; furthermore, if mast cell numbers are allowed to increase in castrates, subsequent androgen administration will reverse the rise. There is no obvious relationship between mast cell numbers in the Harderian gland of the female hamster and the porphyrin content of the gland.

Androgens↗