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K Gohari

Publications and source records attributed to K Gohari.

At least 19 recordsLinked to original sources
PubMed1986

The Golgi apparatus during epithelial differentiation: a quantitative morphological study of maturation compartments in keratinised epithelium from hamster cheek pouch mucosa.

Stereological and other morphometric techniques have been used to investigate the quantitative morphological characteristics of the Golgi complex in defined basal, spinous and granular layers of hamster cheek pouch epithelium. As the cell migrates between basal and granular layers, there are reductions in the volumetric, numerical and surface densities of Golgi per unit volume of epithelial cell cytoplasm. When these density estimates are related to the average cell, the average granular cell has a higher number of Golgi complexes with a greater cisternal and associated vesicular volume and membrane surface area than the average basal cell. Both the volume and surface area of individual Golgi systems are smaller in the average granular cell when compared with the average basal cell. We suggest that these structural alterations are associated with the increased secretory activity of spinous and granular cells which is primarily effected by the production of membrane-coating granules, organelles which are probably responsible for producing the intercellular permeability barrier. These changes are also accompanied by increases in the amounts of rough endoplasmic reticulum and plasma membrane, supporting the proposition that the epithelial cell becomes increasingly metabolically active as it differentiates.

Animals↗
PubMed1985

A quantitative ultrastructural study of alterations in the area of the basal cell-stromal interface during experimental oral carcinogenesis.

Because of its topographical location, the basal cell in carcinomas must play a significant role in the invasion of adjacent tissues. We have analysed the proportion of the basal cell plasma membrane in direct contact with the adjacent lamina propria during in vivo oral carcinogenesis. Samples of hamster cheek-pouch mucosa treated with DMBA were assigned to hyperplasia, dysplasia and carcinoma groups using strictly defined histopathological criteria. Electron micrographs of basal cells were subjected to stereological intersection counting to provide estimates of the proportion of the total basal cell membrane in contact with the connective tissue (SSBM,PM). In untreated controls, a mean value of 9% was obtained, whereas, for DMBA-induced hyperplasias, dysplasias and carcinomas, values were 8%, 12% and 16% respectively. Statistically, SSBM,PM values were significantly elevated in dysplasias and carcinomas. The changes in this parameter may reflect an increased motility in the transforming basal cell prior to and concomitant with cellular invasion, and may prove to be of value as a structural indicator of malignant transformation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

An ultrastructural morphometric study of cellular and nuclear volume alterations during experimental oral carcinogenesis.

Cellular and nuclear pleomorphism are features of epithelial dysplasia, a premalignant alteration found in many stratified squamous epithelia including those of the oral mucosa. In the present report we have applied morphometric techniques to evaluate alterations in cellular and nuclear volume during epithelial differentiation in experimentally-induced oral carcinogenesis. Hamster cheek pouches treated with DMBA were biopsied and assigned to hyperplasia, dysplasia and carcinoma groups with untreated pouches being used as controls. Following a rigorous sampling scheme, electron micrographs from defined basal, spinous and granular strata were obtained and cellular and nuclear volumetric estimates obtained by a combination of direct measurement and stereological intersection counting. In all strata, nuclear, cytoplasmic and cellular volumes were lowest in the normal control group and were increased in all experimental groups. Volumetric estimates obtained for carcinogen-treated groups were generally between 2 to 3 times higher than for the control group which indicates that cellular and nuclear hypertrophy occurs in conjunction with the epithelial hyperplasia and proliferation induced by the chemical carcinogen. We also describe the application of the pathological alteration ratio (PAR), a parameter which is independent of methodological variables, and which was consistently elevated in our experimental study. This was also applied to a number of reports in the literature which describe morphometric alterations in cellular or nuclear parameters in a variety of human lesions. Within any particular group of lesions, PAR values were generally higher for carcinomas than for other benign conditions. We conclude that cellular and nuclear hypertrophy occurs not only during experimental carcinogenesis but also in human benign and malignant lesions. With the advent of computer-based automated image analysers, measurements of certain structural features on sectioned tissues may have a role in histopathological diagnosis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

A morphometric study of alterations in rough endoplasmic reticulum during differentiation in stratified squamous epithelium.

Stereological techniques were applied to investigate several structural parameters characterising the rough endoplasmic reticulum (RER) during differentiation in hamster cheek-pouch epithelium. Mucosal samples from five Syrian golden hamsters were obtained and processed for electron microscopy. Following a strict sampling regime, micrographs were obtained from defined basal, spinous and granular layers, and subjected to stereological point and intersection counting procedures. This enabled volume and surface densities, and volume-to-surface ratios of RER to be determined for each cellular layer. From previous estimates of the mean cytoplasmic volume of the "average" basal, spinous and granular cell in this tissue, it was possible to calculate the absolute volume and surface area of RER present in these average cells. Both volume and surface densities of RER decreased between basal and granular layers, whereas the total volume and surface area present in the average spinous and granular cell were both higher than in the average basal cell. These data suggest that RER is being synthesised during epithelial differentiation. In view of the role of the RER in the production of exportable proteins, it is possible that increased amounts of this organelle are required to synthesise the enzymes and glycoproteins found in membrane-coating granules, since these are also seen with increasing frequency in successively higher strata.

Animals↗
PubMed1984

Hemidesmosomal dimensions and frequency in experimental oral carcinogenesis: a stereological investigation.

Connective tissue invasion by carcinomas results in a variety of morphological changes at the epithelial-connective tissue junction. In this report, hemidesmosomal size (-delta) and frequency (Ns) were quantified using established stereological methods. Following treatment of hamster cheek pouches with the chemical carcinogen DMBA, lesions defined as hyperplasias, dysplasias and carcinomas were evaluated using electron microscopical techniques. Untreated pouches served as controls. Stereological intersection counting procedures were used to quantify hemidesmosomes at the epithelial-connective tissue junction. During carcinogenesis, hemidesmosomal diameter decreased progressively, although the reductions were not statistically significant. Hemidesmosomal frequency also decreased progressively between control and carcinoma groups. Normal basal plasma membranes possessed approximately 8 hemidesmosomes/micron 2 whereas values were reduced to approximately 3/micron 2 in the carcinoma group. The reductions in hemidesmosomal frequency during carcinogenesis may reflect an increased motility of basal epithelial cells and a decreased adherence of basal cells to the adjacent lamina propria. The specificity of this alteration in the pathogenesis of malignancy can be readily determined by the application of stereological methods to various neoplastic and non-neoplastic lesions.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

A qualitative ultrastructural study of the intercellular spaces between epithelial cells treated in vivo with DMBA.

One of the features of epithelial dysplasia at the histological level is known as "loss of cellular adherence" in which adjacent epithelial cells appear more widely separated from each other than in normal tissues. In this study we examine the effects of the carcinogen DMBA on the epithelium of the hamster cheek-pouch with particular emphasis on the dimensions of the intercellular spaces. DMBA-induced lesions were processed for electron microscopy and assigned to hyperplasia, dysplasia and carcinoma groups, using defined criteria on toluidine blue-stained 1 micron Araldite sections. Untreated pouches were used as a control. At the light-microscopical level, intercellular spaces in hyperplastic epithelium appeared similar to those present in untreated tissue but increased progressively in dysplastic and carcinomatous lesions. Spaces were generally wider between basal and spinous cells than between granular cells, although wide variations were observed between tissue blocks demonstrating similar histological features and also within adjacent areas of the same block. At the ultrastructural level, untreated and hyperplastic tissue showed only occasional focal separations of adjacent plasma membranes; these spaces were more frequent between cells of lower strata. In sections from dysplasias and carcinomas, spaces were always extensive and were occupied by numerous villous or foliate membrane-bound cytoplasmic extensions. These were often attached to each other by desmosomes of apparently normal morphology but of a lower frequency than in untreated epithelium. The increased epithelial separation as indicated by the increased intercellular spaces during chemical carcinogenesis may be a result of any or all of the following factors: desmosomal disruption or their failure to develop; the production of cell-surface molecules which are less adhesive; inflammatory oedema and direct alterations on intercellular junctions and cell-surface components by infiltrating inflammatory cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Alterations in the volume of the intercellular space between epithelial cells of the hamster cheek-pouch: quantitative studies of normal and carcinogen-treated tissues.

The present report investigated the extent of the epithelial dysplastic feature known as "loss of cellular adherence" at the ultrastructural level by quantifying the volume of the intercellular space during hamster cheek-pouch carcinogenesis. Following topical application of DMBA to cheek-pouches, lesions were classified as hyperplasia, dysplasia and carcinoma, with untreated pouches serving as a control. Stereological point counting procedures were used to determine the volume density of intercellular space in defined basal, spinous and granular layers for each group. In general, progressive increases in volume density were detected within each stratum during carcinogenesis. These results indicate that increasing separation of epithelial cells occurs during carcinogenesis, although it is not yet known whether this results from loss of cohesion between specialised (i.e., desmosomal) or nonspecialised membrane areas. In addition, a simple indicator of pathological alteration, the Pathological Alteration Ratio (PAR), is described and was used to evaluate existing published data for intercellular spaces in various oral mucosal conditions. Values of the PAR were found to be substantially higher in carcinogen-treated epithelia than in reports describing changes in wound healing, lichen planus and leukoplakia simplex. These objective techniques are of value for investigating the pathogenesis of diseased epithelium and may find applications in the diagnosis of oral premalignant lesions.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Desmosomes in hamster cheek pouch epithelium: their quantitative characterization during epithelial differentiation.

Desmosomes in stratified squamous epithelia appear to exhibit quantitative alterations during differentiation. In this work we use stereological and other morphometric methods to quantify these structures in epithelial cells from defined basal, spinous and granular strata. Hamster cheek pouch mucosa from five animals was processed for electron microscopy using strictly standardized techniques and a stratified random sampling procedure was used to obtain micrographs of cells from basal, spinous and granular layers. Stereological intersection counting techniques were used to determine for each layer the relative surface area of plasma membrane occupied by desmosomes (Ss), the number of desmosomes per unit surface area of plasma membrane (Ns), the mean individual desmosomal diameter (delta) and the mean individual desmosomal surface area (s). In addition, estimates of nuclear volume were obtained by direct measurement of nuclear profiles and volume-to-surface ratios were obtained by a combination of point and intersection counting, which enabled estimates for the volume (Vcell) and plasma membrane surface area (SPM) of the 'average' cell within each stratum to be acquired. Using this information, it was then possible to calculate both the total surface area (S) and the number (N) of desmosomes on the plasma membranes of average cells. The parameters Ss and Ns showed progressive increases between basal and granular layers, whereas values for delta and s were lower in granular cells when compared with basal and spinous cells. The parameters Vcell, SPM, S and N all increased progressively and significantly during differentiation. Between basal and granular layers, the mean cell volume and surface area had each increased approximately threefold, whereas the surface area and number of desmosomes on the average cell plasma membrane had increased approximately seven- and eleven-fold, respectively. Granular cells thus possess more numerous desmosomes, which occupy a greater proportion of the plasma membrane area but which are individually smaller, when compared with basal and spinous layers.

Animals↗
PubMed1984

Ultrastructural morphometric of gap junctions during differentiation of stratified squamous epithelium.

The presence of gap junctions in stratified epithelia has now been extensively documented, but there have been few attempts to quantify them. In the present report, samples of hamster cheek pouch mucosa were processed for electron microscopy and electron micrographs from defined basal, spinous and granular layers were obtained. Using a combination of direct measurement and stereological intersection counting techniques, the relative surface areas of peripheral gap junctions (i.e. those in direct contact with the epithelial plasma membrane) and annular gap junctions (i.e. those present as complete, approximately circular profiles within the epithelial cell cytoplasm) were determined. Following estimation of the plasma membrane surface area of 'average' epithelial cells from each of the defined strata, relative values were transformed into absolute data. Data from peripheral and annular junctions were pooled to provide an estimate of total gap junctions area. Relative surface area estimates were similar for peripheral, annular and total gap junctions, in that values were invariably highest in the spinous layer and lowest in the granular layer. Absolute data indicate that there is more than a threefold increase in the area of membrane differentiated into gap junctions in the average spinous cell when compared with the average basal cell. Values for total gap-junctional areas in the average granular cell are reduced somewhat with respect to the average spinous cell and this is effected by a decrease in the area of peripheral gap junctions. We conclude that there is synthesis of gap junctions between basal and spinous cells, which is followed by evidence of degradation between spinous and granular cells. The magnitude of the estimates of area is comparable to those obtained from other stratified and non-stratified epithelia and it would thus appear that gap junctions may play a significant role in cellular control processes in all viable epithelial strata.

Animals↗
PubMed1984

Some aspects of desmosomal morphology during differentiation of hamster cheek pouch epithelium.

Desmosomes function as intercellular attachment devices. In keratinised epithelia, squames are shed from the surface and these are replaced by less differentiated cells of the basal or parabasal layers, which migrate progressively towards the surface. In order to perform these migratory activities, cellular movement must occur, with the implication that cells must be able to make and break their desmosomal attachments. The present study investigates desmosomal ultrastructure with the objective of suggesting mechanisms by which desmosomes are altered during differentiation. The majority of desmosomes in basal, spinous and granular layers were similar in morphology, with differences being quantitative rather than qualitative. Desmosomes appeared to be more frequent and of smaller dimensions in granular cells when compared with those present on cells from lower strata. Upon keratinisation, desmosomal cytoplasmic structural specialisations disappeared and the intercellular contact layer became more prominent. A number of features which might represent desmosomal formation or synthesis were observed in nucleated cellular layers. These included an apparent budding or fusing of attachment plaques from existing desmosomes. Asymmetrical attachment plaques were prevalent with a markedly reduced number of tonofilaments associated with one plaque or an attachment plaque which was generally or locally reduced in electron density. Other appearances suggested that de novo desmosomal formation occurred as a result of the production of either single or paired attachment plaques, often containing fine filaments extending for a short distance into the cytoplasm. In view of the increased frequency of desmosomes in granular cells, the majority of these desmosomal abnormalities may represent synthetic rather than degradative activities.

Animals↗
PubMed1983

Stereological studies of differentiation in hamster cheek pouch epithelium: variations in the volume and frequency of mitochondria.

The present report describes quantitative studies of mitochondria from stratified squamous epithelial cells from hamster cheek pouch mucosa in differentiating compartments. Mucosa was processed for electron microscopy and, using strict sampling procedures, electron micrographs of epithelium from defined basal, spinous and granular strata were acquired. Using stereological and other morphometric methods, the volume density, numerical density and volume-to-surface ratio of mitochondria were estimated in each cellular layer, and these data were transformed into absolute values characterising the average cell in these layers. The results suggest that both volumetric and numerical densities of mitochondria decreased progressively during epithelial differentiation; conversely, the total volume and number of mitochondria present in granular cells were consistently higher than in basal cells, as was the volume of individual mitochondria. These quantitative changes may reflect functional alterations in the metabolism of epithelial cells during differentiation and provide a base line for further work on experimental epithelial biology and pathology.

Animals↗
PubMed1983

Volumetric alterations in tonofibrils during epithelial differentiation in hamster cheek pouch mucosa.

The present report describes the use of stereological procedures to evaluate the volume of tonofibrils present in defined epithelial strata undergoing differentiation. Hamster cheek pouch epithelium was processed for electron microscopy and, following strict sampling procedures, micrographs were obtained from basal, spinous and granular layers. Using stereological point counting techniques, the volume density of tonofibrils present in unit volume of epithelial cytoplasm was determined for each layer. From previously determined estimates of cytoplasmic volume in this tissue, it was possible to calculate the absolute volume of tonofibrils present in the 'average' epithelial cell of each layer. The results describe essentially similar volume density data for each of the layers investigated. However, estimates of tonofibril volume in the 'average' cell increase more than threefold between basal and granular layers. It is concluded that as the epithelial cell differentiates through spinous and granular strata, synthesis of tonofilaments may occur.

Animals↗
PubMed1982

Towards economy of effort in quantitative ultrastructural pathology: efficient sampling schemes for studying experimental carcinogenesis.

Hamster cheek pouch mucosa was painted with DMBA in order to compare samples of epithelium at different pathological stages of carcinogenesis. Stereological methods were applied to ultrathin sections of tissue to estimate one ultrastructural index of change, the surface ratio of lamina densa compared with the overlying plasma membrane of cells in stratum basale. Analysis of variance techniques were then employed to isolate and quantify the contributions which different levels of sampling (animals, tissue blocks, microscopic fields) made to the total observed variation in this surface ratio. Economical sampling schemes for future use were calculated from the sampling variances by taking into account the relative costs at each sampling level. Though illustrated by means of the hamster cheek pouch-DMBA model, our results are pertinent to many other experimental models for quantitative histopathology.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Cellular and nuclear volumetric alterations during differentiation of normal hamster cheek pouch epithelium.

The aim of this investigation was to determine whether volumetric changes occurred in differentiating layers of stratified squamous epithelium. Samples of cheek pouch mucosa from 5 hamsters were obtained, prepared for electron microscopy using carefully controlled methods, and electron micrographs obtained from defined basal, spinous and granular layers of the epithelium. Stereological point counting procedures were used to determine the ratio of nucleus to cytoplasm for each of the defined cell layers. From direct measurement of nuclear profiles, major and minor axes were transformed to diameters of circles of equivalent area and it was thus possible to obtain an estimate of nuclear volume. Using the previously determined nuclear-cytoplasmic ratio, the volume of cytoplasm and hence cell volume, could be estimated for the cell layers. Between basal and granular layers, nuclear-cytoplasmic ratios decreased from 0.42 to 0.08, whereas cytoplasmic and cellular volumes increased progressively from 248 to 1052 microns 3 and from 352 to 1144 microns 3, respectively. Nuclear axial ratios were highest in the granular layers. These methods can be used in a variety of comparative ultrastructural studies of epithelia, and will also prove valuable in generating additional biological information from more conventionally presented stereological data.

Animals↗
PubMed1982

Stereological methods for quantifying cell surface specializations in epithelia, including a concept for counting desmosomes and hemidesmosomes.

We present stereological procedures for morphometric evaluation of intercellular junctions appearing in ultrathin sections of epithelia. A model representing desmosomes and hemidesmosomes as flat, circular discs differentiated within the plasma membrane of epithelial cells forms a basis for estimating number per unit volume of tissue or per unit area of cell surface. Methods for estimating relative surfaces are also provided. Consideration is given to problems of tissue sampling, varying feature size and finite section thickness. The procedures are improvements over earlier estimates of number per unit area of section or per unit length of membrane. Worked examples of calculations are included and methods are illustrated further by reference to quantitative studies of hamster cheek pouch epithelium during experimental carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

A quantitative study of lamina densa alterations in hamster cheek pouch carcinogenesis.

Lesions produced by topical application of 0.5 per cent. DMBA to the hamster cheek pouch epithelium were classified as hyperplasia, dysplasia and carcinoma groups using strict histological criteria. Untreated epithelium served as a control. Tissue samples from five animals in each group were processed for electron microscopy and electron micrographs from the epithelial-connective tissue junction were obtained from 5 blocks per animal. The micrographs were subjected to stereological intersection counting to determine the relative surface (SSLD, BM) of lamina densa which was in normal relationship to the basal cell plasma membranes. Quantitative results indicated a progressive loss of lamina densa during carcinogenesis and this was accompanied by the extrusion of pseudopodia from the basal cells through the gaps. The pseudopodia were frequently related to peripheral cytoplasmic microfilaments. Quantitative data confirmed the progressive nature of this loss, with values for SSLD,BM being of the order of 98 per cent., 88 per cent., 76 per cent, and 42 per cent. for normal epithelium and for the hyperplastic, dysplastic and carcinomatous lesions respectively. The loss of lamina densa is discussed in relation to the specificity of the response and to the development of features indicative of motility in transforming cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Quantitative studies of hemidesmosomes during progressive DMBA carcinogenesis in hamster cheek-pouch mucosa.

The present study was designed to establish whether there are changes in hemidesmosomal distribution during defined stages of chemical carcinogenesis in hamster cheek-pouch epithelium. 0.5% DMBA in liquid paraffin was applied thrice weekly to hamster pouches and tissue samples were obtained at regular intervals and assigned to hyperplastic, dysplastic and carcinomatous groups on the basis of histological criteria. Untreated pouches served as controls. Following a strict sampling regime, electron micrographs were obtained from the epithelial-connective tissue junction and, using stereological intersection counting, the relative surface area of basal plasma membrane (BPM) occupied by hemidesmosomes was estimated. In normal epithelium 40% of the BPM is occupied by hemidesmosomes. During carcinogenesis, values decrease progressively and significantly to 35% in hyperplasia, 28% in dysplasia and 13% in carcinoma. A decrease in the relative area of hemidesmosomes would therefore appear to contribute to the increased motility of epithelial cells during a connective-tissue invasion and cellular metastasis.

9,10-Dimethyl-1,2-benzanthracene↗