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Biomedical subjects

R J Stephens

Publications and source records attributed to R J Stephens.

At least 91 records · Page 5Linked to original sources
PubMed1982

Characterization of isolated Fe-loaded rat hepatocytes prepared by collagenase perfusion.

Hepatocytes from livers of rats loaded by Fe-dextran treatment were isolated by an in situ collagenase perfusion technique and evaluated for their biochemical, cytochemical, and morphological characteristics in cell culture. Iron loads 15 times higher than in normal rat liver cells isolated in the same way were retained in the preparations with 40% present as hemosiderin. A simple centrifugation-mathematical approach is described for the calculation of Fe content in the hepatocyte (95%) and reticuloendothelial (5%) fractions in the isolates. The cells were cultured for 22 h without loss of protein synthesis capability or significant changes in cell count, viability, endogenous glutamate-oxaloacetate transaminase (GOT) or Fe and were morphologically similar in most respects to unloaded (normal) hepatocytes similarly cultured. Studies are in progress to assess the utility of these preparations as a model for Fe mobilization from Fe-loaded animals.

Animals↗
PubMed1982

Vaginal delivery in patients with a prior cesarean section.

To assess the risks and benefits of vaginal delivery in patients with prior cesarean section, the English literature on this subject from 1950 to 1980 was reviewed. The following conclusions were reached: 1) Properly conducted vaginal delivery after cesarean section is relatively safe, with a 0.7% incidence of uterine rupture, 0.93 perinatal mortality, and no maternal deaths due to uterine rupture. 2) Of those patients allowed a trial of labor, 66.7% were successfully delivered vaginally. Successful vaginal delivery occurred in 74.2% of those patients with a nonrecurrent indication for their previous cesarean section and in 33.3% of those patients whose indication for previous cesarean section was cephalopelvic disproportion. Sixty-seven percent of those patients with a prior vaginal delivery versus 47.1% of those patients without a prior vaginal delivery subsequently delivered vaginally. 3) A classic uterine scar clearly increases the probability of uterine rupture. However, the precise magnitude of the increased risk cannot be accurately determined. 4) Certain basic safety requirements such as available operating room facilities and adequate personnel for careful observation are mandatory, but other management policies that remain controversial include use of regional anesthesia, oxytocin administration, timing of hospital admission, artificial rupture of membranes, mode of delivery, proper method to evaluate the uterine scar, and delivery of fetuses in breech presentation and twins. 5) A policy of selective vaginal deliveries among patients with prior cesarean sections will result in cost reductions due to decreased postpartum hospitalization.

Cesarean Section↗
PubMed1981

Rapid OTAN method for localizing unsaturated lipids in lung tissue sections.

The OTAN treatment, which is the only histochemical method available at present for the simultaneous localization of hydrophobic and hydrophilic unsaturated lipids in tissue sections, requires unduly long exposure to OsO4 and use of free-floating sections, which makes handling the sections difficult and often results in their loss or damage. Simple modifications using OsO4 treatment at 37 C and slide-mounted sections eliminate the practical drawbacks of the existing method and provide as good or better localization in less than one-eight of the time. The modified method is applicable to fixed as well as fresh frozen tissues.

1-Naphthylamine↗
PubMed1980

Behavioural and neurochemical proteins of 1-[1-([indol-3-yl] methyl) piperid-4-yl]-3-benzoylurea (Wy 25093) in rodents.

Wy 25093 is a novel, selective and potent inhibitor of the neuronal 5-hydroxytryptamine (5-HT) uptake process in vitro and in vivo. The compound was more potent than clomipramine and fluoxetine as an inhibitor of 5-HT uptake in vitro and did not significantly inhibit catecholamine uptake. In addition, Wy 25093 potentiated the behavioural syndrome induced by 5-hydroxytryptophan (5-HTP) and antagonised the hyperactivity produced by p-chloroamphetamine (P-CA). WY 25093 antagonised the (P-CA)-induced depletion of 5-HT in rat brain and reduced the probenecid-induced increase in rat brain 5-hydroxyindole-3-acetic acid (5-HIAA). Acute administration of the agent to rats resulted in reduced 5-HIAA levels without affecting 5-HT; chronic treatment with the compound produced decreases in the levels of both 5-HIAA and 5-HT. It is concluded that Wy 25093 is a selective and potent inhibitor of the neuronal re-uptake process for 5-HT both in vitro and in vivo, and may possess potential antidepressant activity.

5-Hydroxytryptophan↗
PubMed1978

Cytologic responses of postnatal rat lungs to O3 or NO2 exposure.

At the level of exposure employed (approximately 14.0 ppm NO2 or 0.85 ppm O3) epithelial cells at the juncture of the terminal airways and proximal alveoli have previously been shown to be seriously injured or destroyed in maturing (35 days of age or older) and adult lungs. Subsequent repair results in the formation of a tissue nodule at this location. In contrast, postnatal rats between birth and weaning have been shown to be highly resistant to the cytotoxic effects of both NO2 and O3. Prior to wearning, exposure to O3 resulted in little or no injury when examined with either the light or electron microscope, and only minor injury and loss of cilia from epithelial cells lining the terminal airways was noted after NO2 exposure. Subsequent to weaning at 20 days of age, however, there was a progressive increase in the cellular response in both the terminal airways and proximal alveoli after exposure to either oxidant gas. A plateau in the response is reached at approximately 35 days of age and continues until the animals are approximately 1 year old. The data are discussed in terms of current theories on endogenous antioxidant mechanisms.

Animals↗
PubMed1977

Acute leukaemia after busulphan.

During a double-blind study of two years' cytotoxic chemotherapy with busulphan or cyclophosphamide in patients who had had resection of carcinoma of the bronchus the long-term effects of these two drugs were also studied. Four of the 243 patients treated with busulphan developed leukaemia compared with none of the 234 treated with cyclophosphamide and none of the 249 on placebo. None of these four patients received radiotherapy or other cytotoxic chemotherapy before leukaemia was diagnosed, and all four were among the 19 patients who developed pancytopenia while taking busulphan, five to eight years before leukaemia became clinically apparent. These findings suggest that busulphan is leukaemogenic, though its mode of action is uncertain.

Acute Disease↗
PubMed1977

An improved method for the histochemical localization of glucose-6-phoshate dehydrogenase in animal and plant tissues.

An improved procedure is reported for the histochemical localization of glucose-6-phosphate dehydrogenase in fresh-frozen sections of animal and plant tissues. Used in this procedure are an incubation medium and an inert high-molecular-weight polyvinyl alcohol as a stabilizer to check enzyme diffusion. The incubation medium consists of 10 mg each of nicotinamide adenine dinucleotide phosphate and nitroblue tetrazolium chloride and 60 mg of glucose-6-phosphate per 20 ml of 22% polyvinyl alcohol solution in 0.2 M Tris-maleate buffer, pH 7.2. Use of this medium has given consistent results with the tissues tested. Because the use of an electron-transfer agent in the incubation medium often resulted in enzyme diffusion, its use in glucose-6-phosphate dehydrogenase localization is considered undersirable. Incubation time of 15 to 30 min for animal tissue and 20 to 45 min for plant tissue of 37degreesC was found to be optimal for producing the characteristic blue formazan at the reaction sites.

Adrenal Cortex↗
PubMed1976

Erythropoiesis in the yolk sac of the bat Tadarida brasiliensis cynocephala.

The process of erythropoiesis and vasculogenesis in the yolk sac of the bat (Tadarida brasiliensis cynocephala) has been studied through the use of both light and electron microscopy. Stem cells arise from the leading edge of the migrating splanchnic mesoderm and transform into primitive erythroblasts. Differentiation involves either contact or association with the endodermal cells, since all erythropoietic activity occurs on the endodermal side of the expanding vascular bed, and many of the cells are in close apposition to the lateral or basal plasma membranes of the endodermal cells. Endodermal cells also phagocytize developing primitive erythroblasts during the later stage of the process when erythropoiesis is subsiding in the yolk sac. Cells destined to become the endothelium of the expanding vascular bed also arise from the leading edge of the migrating splanchnic mesoderm. Their process of differentiation involves the development of cytoplasmic extensions that may surround a group of differentiating erythroblasts, enclosing them in the newly formed lumen of the blood vessel. The cytoplasmic extensions make contact and develop junctional complexes with similar processes from other cells to complete the lumen of the lengthening vascular bed. Cells of the granulocyte series or megakaryocytes are not observed in the yolk sac of the bat as has been described in certain other species.

Animals↗
PubMed1976

5-year follow-up of cytotoxic chemotherapy as an adjuvant to surgery in carcinoma of the bronchus.

This report gives the 5-year findings of a double-blind study of long-term cytotoxic chemotherapy as an adjuvant to surgery in patients receiving busulphan or cyclophosphamide for carcinoma of the bronchus compared with a group receiving a placebo. Of 243 patients initially allocated busulphan, 234 cyclophosphamide and 249 placebo, 28%, 27% and 34% respectively were alive at 5 years. There were significant associations between mortality from bronchial carcinoma and histological involvement of the resected intrathoracic nodes and the histology of the tumour. Haematological toxicity, especially thrombocytopenia, was frequent and severe in the busulphan series, and low platelet counts continued long after chemotherapy was stopped.

Bronchial Neoplasms↗
PubMed1976

Renewal of the terminal bronchiolar epithelium in the rat following exposure to NO2 or O3.

Rats were exposed to either NO2 or O3 to determine whether nonciliated cells (Clara cells) could divide and differentiate into ciliated cells in the terminal bronchioles. Dividing cells were labeled with tritiated thymidine, visualized in the light and electron microscopes using autoradiographic techniques, and studied for up to 15 days after labeling. Electron microscopic autoradiography 1 hour after injection of tritiated thymidine showed that all labeled cells in the terminal bronchioles were nonciliated. However, 4 days after injection of tritiated thymidine, 67.8 per cent of the labeled cells were nonciliated and 32.2 per cent were ciliated. Light microscopic autoradiography showed that the new labeled ciliated cell population was stable for up to 15 days. These results indicate that nonciliated cells divide and the sister cells may form new ciliated and nonciliated cells. Thus, nonciliated cells can act as progenitor cells for the terminal bronchiolar epithelium.

Animals↗