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Biomedical subjects

D Whitaker

Publications and source records attributed to D Whitaker.

At least 145 records · Page 8Linked to original sources
PubMed1982

The mesothelium: a cytochemical study of "activated" mesothelial cells.

The cytochemical profile of activated mesothelial cells differs from resting cells. The reaction products of enzymes associated with oxidative mechanisms of cell respiration were easily displayed in activated mesothelial cells; in resting mesothelial cells, only enzymes of the pentose pathway were readily demonstrable. Acid hydrolases were detected in greater quantity than in resting cells, possibly reflecting an increased potential for endocytosis. In addition, the cytochemical assays indicated increased Golgi activity was reflected by the demonstration of thiamine pyrophosphatase, while the content of ribonucleic acid was also increased. These cytochemical features compare well with the ultrastructure of active mesothelial cells which possess abundant ergastoplasm and a well-developed Golgi apparatus. In comparison with peritoneal macrophages, activated mesothelial cells differ mainly in the quantity of reaction product, there being more in macrophages. The results were significantly different only in the demonstration of lipids which were never found in mesothelial cells, but were invariably present in macrophages. It is still unclear whether the acid mucopolysaccharide hyaluronic acid is produced by or merely transported through the mesothelium from the subserosal site.

Animals↗
PubMed1982

The mesothelium: its fibrinolytic properties.

We have investigated the fibrinolytic properties of the mesothelium by developing a test system in which standard tissue samples can be assessed in a comparative and semi-quantitative manner. The problem whether plasminogen activators were generated by the mesothelium itself or were transported from a subserosal site was also studied. A standard system was developed by using a uniform gelatin disc to obtain a monolayer imprint of mesothelium and subsequently incorporating several of these samples on a fibrin plate. Pure cultures of mesothelial cells were able to induce fibrinolysis.

Animals↗
PubMed1982

Detection of tissue CEA-like substance as an aid in the differential diagnosis of malignant mesothelioma.

Sections of various adenocarcinomas and malignant mesotheliomas were tested for carcinoembryonic antigen (CEA) localized in tissues by the immunoperoxidase technique; epithelial mucin was demonstrated with the PAS technique. While CEA and mucin were found in many adenocarcinomas, both were absent in the 43 cases of malignant mesothelioma we investigated. In the problem of distinguishing between adenocarcinoma and mesothelioma, the CEA-test in combination with conventional strains for mucin is a useful technique and clearly identifies most adenocarcinomas. A dual negative result for CEA and mucin, although not proving that a given lesion is a mesothelioma, adds considerable support to this histological diagnosis.

Adenocarcinoma↗
PubMed1982

The mesothelium and its reactions: a review.

The origins, nature, and reactions of the mesothelium have intrigued investigators for over 100 years. Recently, the use of sophisticated techniques has clarified earlier impressions of its development, structure, and function. The structure of mesothelium reflects its functional properties, its long slender microvilli entrapping a layer of glycosoaminoglycans, providing a frictionless free surface between the parietal and visceral serosa. Transport requirements are met by various surface modifications and both inter- and intra-cellular mechanisms occur. The presence of stomatal openings in the mesothelial membrane has been established, and they may have a major role to play in the movement of cells to and from the serosal cavities. In addition, mesothelial cells can respond to situations of increased functional demand and during the course of inflammation, the mesothelium's fibrinolytic properties are of major importance in preventing the formation of adhesions and the enhancement of healing. Of all the unanswered questions the most significant is the nature, localization, and potentialities of mesothelial precursors. A mesodermal origin is readily acknowledged, but the healing process of damaged mesothelium is less clear. It seems probable that "mature" mesothelium is one source of cell renewal, but mesenchymal cells located in the submesothelial serosa are also strong contenders. Neoplastic mesothelium can adopt a spectrum of histological appearances, reflecting its mesodermal origins. In fact, overacceptance of this concept has erroneously led to the classification of other neoplasms arising in the serosal area as mesotheliomas. Although the ocogenic sequence is still obscure, asbestos is recognized as the major etiologic agent in malignant mesotheliomas. In 1955, Hartwell described differing impressions of the peritoneum as seen through the eyes of an anatomist, an histologist, and a surgeon. In this review on the mesothelium we have attempted to unravel some of its complexities as viewed by embryologists, electronmicroscopists, cell biologists, pathologists, and oncologists.

Biological Transport↗
PubMed1980

The mesothelium; techniques for investigating the origin, nature and behaviour of mesothelial cells.

To overcome some of the difficulties encountered in studying single layers of mesothelial cells, a battery of techniques was investigated, assessed, and modified. It was found that two main methods were of value: cell monolayers and surface sections. Imprint monolayers on slides coated with 3% gelatin were considered to provide the optimal imprint for cell kinetics and cytochemical assays at room temperature. On the other hand, slides coated with agar were more satisfactory for cytochemical techniques performed at 37 degrees C. The cell-deposit techniques were excellent for studying mesothelial cells in suspension. Investigation of cultured cells was best achieved by the use of a cell-mat on coverglasses for cytochemistry, while the base of the culture vessel with its own cell-mat monolayer was best for kinetic studies. This investigation demonstrated that maximum information is only gained by employing several different techniques. It also indicates which of these will be of greatest value in assessing any one particular aspect of mesothelial pathobiology.

Animals↗
PubMed1980

The mesothelium: a histochemical study of resting mesothelial cells.

Cytochemical investigations of the resting mesothelial cells of rats are reported. The study was performed on imprint monolayers obtained from various serosal surfaces by using 3% gelatin and 1% agar-coated microscopic slides. We found only a small amount of reaction product in mesothelial cells after cytochemical demonstration of those enzymes associated with oxidative respiration; however, abundant reaction product was found when the enzymes associated with the pentose phosphate path were sought. These findings suggest that this latter respiratory mechanism may play an active role in resting mesothelial cell respiration. Enzymes associated with cell membranes such as sodium and potassium dependent ATPase and 5' nucleotidase were readily found. The "resting" mesothelial cell also had demonstrable amounts of glycogen and RNA. It is concluded that despite the morphological suggestions that the resting mesothelium is not very active metabolically (Cascarano, 1964), its histochemical profile provides good evidence of a diverse range of functional and metabolic processes. The finding of similar cytochemical profiles, irrespective of the anatomical site of the mesothelial cell sample, is considered to give credence to the concept of the mesothelium as an entity.

Animals↗
PubMed1980

A case of filariasis diagnosed on gastric cytology.

Cytological examination of gastric washings or brushing is a widely accepted technique used as a diagnostic aid in the detection of gastric malignancy. Occasionally, cytology may also provide valuable information concerning a variety of non-neoplastic disorders. This brief report is of the exceptional experience of finding numerous microfilariae of Loa loa type in a gastric lavage specimen. This observation led to appropriate further investigation and successful treatment.

Cytodiagnosis↗
PubMedDate not supplied

Malignant mesothelioma cells in sputum.

In five patients with malignant mesothelioma of pleura, malignant cells, presumably derived from intrapulmonary deposits, were found in sputum specimens. The cells presented mainly as papillary aggregates of epithelial-like cells, in most cases without specific identifiable mesothelial cell features. In one patient, the specimen was received early in the diagnostic work-up and led to a strong consideration of the diagnosis of adenocarcinoma. In the remainder, the finding was incidental, occurring after the diagnosis of mesothelioma had been established. The cases are reported to draw attention to this phenomenon, previously unreported in the cytologic literature, and to emphasize that the finding of malignant cells in sputum does not preclude the diagnosis of malignant mesothelioma.

Aged↗
PubMedDate not supplied

Changes in macular function throughout adulthood.

Recent reports suggest that the neural system is the principal cause of loss of visual function with age and that senile lenticular and pupillary changes are of minor importance. In order to investigate this neural deterioration further we measured Logmar visual acuity and photostress recovery time (PSRT) in 61 subjects over an age range of 19 to 78 years. The magnitude of the PSRT reflects the efficiency with which the visual system recovers from exposure to a glare source and is principally dependent upon the integrity of the photoreceptors and the retinal pigment epithelium. The results indicate that macular function declines significantly throughout adulthood.

Adult↗
PubMedDate not supplied

Modelling of orientation discrimination across the visual field.

In many visual tasks thresholds can be made equal across the visual field by increasing the size of peripherally presented stimuli by appropriate magnification. The parameter E2 represents the eccentricity at which foveal stimulus size must double in order to maintain performance equivalent to that at the fovea. We measured orientation discrimination for a set of line sizes at various eccentricities. Thresholds were successfully scaled by applying a scaling function estimated by a technique that requires no prior assumptions regarding the size of peripherally presented stimuli. E2 of 1.95 deg was found for orientation discrimination. From our results we were able to develop a single equation which predicts orientation discrimination thresholds for an average observer over a range of different eccentricities and line lengths.

Discrimination, Psychological↗
PubMedDate not supplied

Chromatic adaptation, perceived location, and color tuning properties.

We have studied the influence of chromatic adaptation upon the perceived visual position of a test stimulus using a Vernier alignment task. Maximum and minimum offsets in spatial position are generated when the adapting and test stimuli lie on the same and orthogonal axes in MBDKL color space, respectively. When the test stimuli lie on intermediate color axes, the measured positional shifts decrease as a function of the angular separation in color space (phi) from the adapting stimulus. At low stimulus contrasts, these shifts follow a sinusoidal function of phi and exhibit broad chromatic tuning and can be accounted for by a model in which the centroid is extracted from the linear combination of after-image, formed by the adapting stimulus, and the test stimulus. Such linear, broadband behavior is consistent with the response properties of chromatic neurons in the precortical visual pathway. At high contrast, and when adaptation gets closer to the S/(L+M) axis, the tuning functions become narrower and require sinusoids raised to increasingly higher exponents in order to describe the data. This narrowing of chromatic tuning is consistent with the tuning properties of chromatic neurons in the striate cortex, and implies the operation of a nonlinear mechanism in the combination of cone outputs.

Adaptation, Ocular↗