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Biomedical subjects

R J Stephens

Publications and source records attributed to R J Stephens.

At least 109 records · Page 6Linked to original sources
PubMed1975

Construction and implantation of a cannula system for repeated injections into localized regions of the rat brain.

The construction and method of implantation of a brain cannula for chronic use in rats is described. All the components of the cannula system are easily made from stainless steel tubing and no machined parts are required. The use of a metal key eliminates the need for tapped holes during implantation. Although little time is required to prepare each animal the system remains firmly fixed to the skull and allows injections to be made accurately into selected brain areas.

Animals↗
PubMed1975

Survey of the sputum cytology service in England and Wales.

Of the 231 laboratories carrying out sputum cytology in England and Wales, information on the staffing, laboratory procedures, workload, records, and results for the year 1971 was obtained from 228 (98.7%) by means of a questionnaire, which was completed in 1973 in 81% of the laboratories and at the end of 1972 in the remainder. At the time the questionnaire was completed, the number of laboratories per region offering a service ranged from 6 to 25. Most of the processing of specimens was done by technicians and non-medical screeners (technicians without recognized qualifications) and most of the microscopy by pathologists and technicians. Papanicolaou and/or haematoxylin and eosin stains were used in 97% of the laboratories. During 1971, the number of specimens tested per laboratory ranged from 9 to 6000. A median of 381 specimens and 165 patients were tested per laboratory. Almost all specimens were submitted by hospitals and chest clinics and only 1% by general practitioners. An estimated median of 6.5% of all cytological specimens were sputum, most of the remainder being cervical smears. Laboratories varied greatly in their positive (0%-24%) and doubtful positive (0%-27%) rates. An estimated 63 000 patients had their sputum tested in 1971, and about 6300 had positive reports, rather less than one-quarter of all patients diagnosed as having lung cancer in England and Wales in 1971. The cost of the service was estimated to be of the order of pound375 000 at 1974 prices; that is, pound2.50 per specimen or pound6.00 per patient tested. An improved service might best be provided by district general hospital laboratories testing at least 1000 specimens per year so that a high level of accuracy in reporting could be assurred. A large proportion of the microscopy might be done by non-medical graduates and technicians under the supervision of pathologists.

Cervix Uteri↗
PubMed1974

Early response of lung to low levels of ozone.

The epithelial response in the terminal bronchioles and alveoli was examined after exposure to approximately 0.5 and 0.9 ppm ozone (O(3)). Loss of ciliated cells from the terminal bronchiole was pronounced after 6 to 10 hours of exposure; however, nonciliated cells were resistant to injury from O(3). In contrast, type 1 alveolar lining cells were very sensitive to O(2) and were severely damaged or removed from significant areas of the proximal alveoli after as little as 2 hours of exposure to 0.5 ppm. The basement lamina was left devoid of an epithelium with the exception of type 2 cells, which were very resistant and retained a relatively normal appearance. Under continuous exposure, repair of the lesion area was accomplished in approximately 48 hours through proliferation of the type 2 cells. The new cells were cuboidal at first but subsequently became more squamous in appearance. Exposure for 8 to 10 hours followed by residence in clean air resulted in a proliferative response at 48 hours, about equal to that observed after continuous exposure.

Adaptation, Physiological↗
PubMed1973

Renewal of alveolar epithelium in the rat following exposure to NO2.

This research was undertaken to study the kinetics of Type 2 cell division and the fate of the Type 2 sister cell following exposure to NO(2). To accomplish this, male rats were exposed to NO(2). Dividing cells were labeled with (3)H-TdR and studied with autoradiographic technics in the light and electron microscopes for up to 72 hours after labeling. The kinetics of cell division were determined from a curve constructed from the percent of labeled mitotic figures. The fate of the Type 2 sister cells was determined by studying tissues at 24, 48 and 72 hours after labeling with (3)H-TdR. The results show that Type 2 cells may divide and the sister cells transform into Type 1 cells. These data support an interpretation of the mechanism for cell renewal of the alveolar epithelium in which Type 2 cells are the progenitor cells for Type 1 cells.

Animals↗
PubMed1973

Cell division of alveolar macrophages in rat lung following exposure to NO2.

The purpose of this research was to study cell division of alveolar macrophages following exposure of rats to NO(2). Dividing cells were labeled with (3)H-TdR and studied for 12 hours after labeling. The kinetics of cell division were determined from a curve constructed from the percent of labeled mitotic figures. Dividing alveolar macrophages were localized in alveoli near the openings of terminal bronchioles. There were no morphologic differences observed between labeled and unlabeled macrophages. Estimates of the durations of the various phases of the cell cycle gave approximate values of: G(2), 1 hour; t(2), 1.8 hour; M, 2.8 hours; and S, 5.8 hours. This evidence, combined with that of others, is compatible with an interpretation for alveolar cell renewal in which marrow-derived cells enter the alveoli and become macrophages. While in the alveoli, the cells may divide and thus increase their numbers. Eventually the macrophages are extruded from the alveoli. Alveolar macrophages were classified as a dividing, transient renewing cell population.

Animals↗
PubMed1973

Cytologic changes in dogs lungs induced by chronic exposure to ozone.

Beagle dogs exposed for 8 hours a day to 3 ppm O(3) for 18 months showed cytologic changes that indicate metabolic alterations. The endoplasmic reticulum of the type 2 alveolar epithelial cells in the proximal alveoli were frequently dilated and contained a moderately electron-dense substance having a periodicity of approximately 754 A. This condition was accompanied by a substantial reduction in the lamellar membranes in the characteristic lamellar bodies of the type 2 cells, suggesting a sequestering of protein in the endoplasmic reticulum. In addition, endothelial cells contained paracrystalline arrays of cytoplasmic membranes not observed in control animals.

Animals↗