Biomedical subjects
Publications and source records attributed to J B Stevens.
The provision of health care is as much a matter of social and political arrangements as of medical science, and thus varies greatly from country to country, reflecting the values of different societies. Janet Stevens looks at the values implicit in the French service, and contrasts them with those of the NHS.
The critical care nurse confronts ethical dilemmas in practice on a regular basis. Problems concerning treatment issues, allocation of resources, and collegial disputes are common. Knowledge of available resources can assist the nurse in dealing with these dilemmas.
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Polychlorinated dibenzo-p-dioxin's (PCDD) behavior in the agricultural food chain was modeled in this study. The source of PCDD was a municipal solid waste (MSW) incinerator. Of the farm livestock investigated only the beef cow and the milk cow were shown to contribute significant amounts of PCDD to humans. Milk was the single highest dietary source of PCDD. Comparison of the calculated human dose of PCDD from the agricultural food chain with an estimate human PCDD dose from inhalation of contaminated air revealed that the agricultural food chain could be responsible for a vast majority of the dose to an individual impacted by these facilities. Thus, these data suggest that operating MSW facilities in agricultural areas may result in enhanced PCDD exposure to individuals via the agricultural food chain. The data also suggest that milk and beef may be good sentinels to evaluate environmental impacts of these facilities.
Cell viability, cytochrome P-450 content, cell respiration, and lipid peroxidation were all investigated as a function of oxygen tension in adult rat hepatocytes in short-term culture (less than 9 h). The various oxygen tensions used in this study were obtained by equilibrating culture medium with air, air + nitrogen, or air + oxygen. Cell viability, as assessed by trypan blue exclusion, was significantly greater at all time points tested when hepatocytes were cultured in Ham's F12 medium containing 132 microM O2, as compared to medium equilibrated with air (220 microM O2) or air + oxygen (298 microM O2). Cells cultured in 220 microM O2 (air) also exhibited a gradual loss of cytochrome P-450, so that by 9 h of incubation less than 60% of the active material remained. This loss of P-450 was minimized when cells were cultured in 163 microM O2 and abolished when cells were cultured in 132 microM O2. The 132 microM O2 exposure conditions also maintained cell respiration at the 1 h incubation values, whereas there was a continuous loss in cell respiration over time when the cells were cultured in either 220 microM O2 (air) or 298 microM O2 (air:O2). These cytotoxicity findings may be related to oxidative cell damage inasmuch as it was additionally demonstrated that lipid peroxidation (as measured by malondieldehyde equivalents) was consistantly lower in hepatocytes cultured in air:N2 as compared to air or air:O2. These results suggest that hepatocyte culture in low oxygen tension improves not only cell viability but also maintains other functional characteristics of the cell.
Xanthine dehydrogenase (EC 1.2.1.37) was purified approximately 1000-fold from liver homogenates of adult male Sprague-Dawley rats. Enzyme recovery was good (greater than 20% of the starting activity was obtained), and the homogeneously pure enzyme had a molecular mass of approximately 300,000 Da. The purified protein exhibited a specific activity of 2470 units/mg protein and spectral properties identical to those of the best preparations of this enzyme reported by other investigators. Routine preparations of this enzyme also possess higher dehydrogenase:oxidase ratios (typically between 5 and 6) than do other xanthine dehydrogenase preparations so far reported in the literature. Maximum dehydrogenase:oxidase ratios, greater than 10, could be obtained from this procedure if only peak dehydrogenase fractions from the chromatography columns were saved. The present small-scale purification method, which can be completed in 48-60 h, utilizes ammonium sulfate fractionation, Sephadex G-200 column chromatography, Blue Dextran-Sepharose column chromatography, and preparative gel electrophoresis.
The rare earth metals cerium, lanthanum, and neodymium each were evaluated in an in vitro cytotoxicity assay system using adult, male Sprague-Dawley rat pulmonary alveolar macrophages. Both the soluble chloride form of these metals and their insoluble metal oxides were studied. For comparison purposes, the cytotoxicities of cadmium chloride and cadmium oxide were also quantified in this test system. In general, regardless of the cytotoxicity parameter measured, i.e., cell viability, lysosomal enzyme leakage, or changes in cell surface morphology, cadmium was more toxic to these cells than were the rare earth metals. Of the rare earth metals studied, only lanthanum chloride (LC50 = 52 microM), cerium chloride (LC50 = 29 microM), and neodymium oxide (LC50 = 101 microM) displayed significant cytotoxicity in this test system. Cadmium chloride exhibited an LC50 value of 28 microM, whereas the LC50 value for cadmium oxide was found to be 15 microM. These findings suggest that rare earth metal fumes should be considered as cytotoxic to lung tissue and therefore potentially fibrogenic.
Aqueous formaldehyde was stabilized in pH 7 phosphate buffer with excess sodium bisulfite of fixed and known concentration. The 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) procedure described previously was used to determine excess bisulfite colorimetrically. The slope of the calibration line (absorbance at 412 nm vs. formaldehyde concentration) is -0.350 A.U./ug CH2O/mL (correlation coefficient: 0.9995). The precision of the method at the 95% confidence level is indicated by the mean percentage relative error (1.81 +/- 1.67) and mean percentage standard error (0.42 +/- 0.39). Gaseous formaldehyde of known concentrations (ppm) in air was absorbed from air samples in pH 7 buffer and determined by the DTNB method. For the determination of formaldehyde in air, the precision and accuracy were demonstrated at the 95% confidence level by the mean percentage relative error (5.04 +/- 3.2), the mean percentage standard error (1.72 +/- 1.0), the mean percentage recovery (99.9 +/- 2.7), and the mean percentage absolute error (1.86 +/- 1.6). The graphic comparison of air concentration found vs. air concentration calculated shows a slope of 0.993 ppmfound/ppmcalcd (correlation coefficient: 0.9993).
Pulmonary alveolar macrophages were isolated from adult, male New Zealand white rabbits by bronchial lavage and exposed to cadmium chloride in vitro. The observed cell sensitivity to this metal was highly dependent upon the incubation conditions used as well as the cytotoxic index selected. An LC50 value, as measured by dye exclusion (erythrosin B), was determined to be 390 microM when these cells were exposed to cadmium in Ham's F12 culture medium for 8 hr at 35 degrees C. The presence of fetal calf serum in the medium (10%; v/v) enhanced this toxicity slightly, LC50 = 235 microM, as did raising the incubation temperature to 37 degrees C, LC50 = 201 microM. No effect on cadmium toxicity was observed when the culture medium was made deficient in Cu, Zn, and Fe, nor was there any effect observed when Hepes buffer was substituted for the bicarbonate/carbon dioxide buffering system. Measurements of cadmium-109 uptake by pulmonary alveolar macrophages were consistent with and could explain, at least in part, the above observations of cytotoxicity. In the standard culture system (an 8-hr exposure period at 35 degrees C in Ham's F12 culture medium plus serum), the appearance in the culture medium of two lysosomal enzyme activities, acid phosphatase and cathepsin D, paralleled cell death. In addition, an EC50 value of 102 microM was found for cadmium when cell respiration (O2 uptake) was measured; an EC50 value of 31 microM was found for cadmium when cell function (engulfment of killed yeast particles) was followed; and scanning electron microscopic studies showed cell membrane changes (loss of fine structure and blebbing) at cadmium concentrations as low as 30 microM. These findings suggest that loss of cell function and/or changes in cell morphology are more sensitive measurements of macrophage exposure to cadmium than is either cell death, lysosomal enzyme release, or cell respiration.
Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.
In vitro exposure of adult rat alveolar macrophages to either paraquat or diquat resulted in concentration dependent cytotoxicity (cell death). The herbicide paraquat, however was statistically significantly more potent toward these cells than was diquat. The LC50 value for paraquat (8-h exposure, 37 degrees C) was determined to be 0.94 mM [95% confidence interval (C.I.) 0.79-1.12 mM], whereas the corresponding LC50 value for diquat was 1.97 mM (C.I. 1.58-2.51 mM). Interestingly, diquat was shown to enter these cells to a much greater extent than was paraquat. The latter data, while seemingly contradictory to the above findings, is consistent with other reported findings in this study that show that cell respiration, as measured by loss of oxygen consumption, was more sensitive to diquat than it was to paraquat. Also, only paraquat cytotoxicity was found to be dependent on oxygen tension and could be altered by the presence of antioxidant enzymes in the culture medium. Both compounds, however, were found to be equipotent toward purified mitochondria. Both paraquat and diquat were able to uncouple oxidative phosphorylation and induce active oxygen species (superoxide anions and hydrogen peroxide) from this organelle. It is concluded that free-radical pathology is the most likely mechanism of action by which paraquat is cytotoxic toward these cells, but that diquat poisoning probably originates from some other mode of action.
The determination of atmospheric sulfur dioxide as aqueous bisulfite using 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) was validated as a simple, rapid and reliable procedure. Standard sulfur dioxide concentrations in air (0-2.6 ppm) were generated by means of a permeation device. Sulfur dioxide from air samples was absorbed in pH 7 phosphate buffer and determined as bisulfite. The mean percentage recovery of sulfur dioxide is 101.4; the slope of the validation line determined by linear regression analysis (calculated vs. found) is 1.014 ppm found/calculated (1.4% absolute error; 0.9976 correlation coefficient).
Leukemic cells from 17 dogs with spontaneous leukemia were stained with leukocyte alkaline phosphatase, alpha naphthyl acetate esterase with and without fluoride, peroxidase, and periodic acid-Schiff. Cytochemistry was necessary for identification or confirmation of leukemic cell type in most dogs and resulted in changing the light microscopic morphologic diagnosis in eight of 17 dogs. Leukemic cell types diagnosed were myelomonocytic leukemia in seven dogs, monocytic leukemia in five dogs, lymphocytic leukemia in four dogs, and myelocytic leukemia in one dog.
One hundred nineteen hepatic tissue samples from 117 Bedlington Terriers were divided into 6 groups depending on the severity of histopathologic hepatic changes. Group 0 comprised dogs with microscopically normal livers. Group I dogs had copper-positive, lipofuscin-containing lysosomes present in centrilobular hepatocytes. Microfoci of hepatic necrosis, in addition to the increased numbers of the copper-positive, lipofuscin-containing lysosomes in centrilobular and periportal hepatocytes, were present in group II dogs. Group III dogs had more copper-positive, lipofuscin-containing lysosomes present translobularly and morphologic changes consistent with chronic active hepatitis. Mixed micro- or macronodular cirrhosis and translobular presence of copper-positive, lipofuscin-containing lysosomes characterized group IV dogs. Dogs in group V had massive hepatic necrosis and morphologic changes that were consistent with the changes in group III and IV dogs. Histochemical staining for copper was useful in making the microscopic diagnosis of this disease and was shown to be necessary in early diagnosis (group I) when other clinical and pathologic values associated with this syndrome were not consistently abnormal. Copper histochemical stains varied in sensitivity. Timm's silver sulfide was more sensitive for copper than was rubeanic acid, which was more sensitive than rhodanine staining. The brown pigment associated with the copper in the lysosomes was shown to be lipofuscin pigment with the aid of histochemical staining with orcein, Prussian blue, periodic acid-Schiff, and acid-fast stains together with fluorescent microscopy (excitation maxima: 365 nm; emissions: 420 + nm). Since these were positive only in later stages of the hepatic disease, they were not especially useful in its early diagnosis. The severity of the histopathologic hepatic changes was shown to increase with age and was associated with increasing hepatic copper concentration. These observations illustrate that this inherited, chronic hepatic degeneration in the Bedlington Terrier is progressive. Clinical chemical tests were diagnostically useful only in later stages of the disease. Alanine transaminase activity was of most value, but was not always abnormal, even when severe hepatic damage was present. Clinical signs of hepatic disease were seen in dogs in groups III, IV, and V. Death due to hepatic failure occurred only in dogs in groups III, IV, and V. Hemosiderin was present in increased amounts in the liver, bone marrow, spleen, and lymph nodes of affected Bedlington Terriers, indicating that a possible defect in iron metabolism and/or an increase in RBC turnover existed.(ABSTRACT TRUNCATED AT 400 WORDS)
When the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridylium) was administered to adult rat pulmonary alveolar macrophages (PAM) in primary culture, both a time-dependent and a dose-dependent cytotoxic response (cell death) was observed. An LD50 value of 1 mM was calculated when these cells were exposed to paraquat in vitro for 12 h in Ham's F12 culture medium at 30 degrees C. Cell death was accompanied by the formation of TBA-reactive substances (lipid peroxidation) and was potentiated by hyperoxia (95% O2). In a 95% O2-5% CO2 atmosphere, an LD50 value of 0.1 mM was calculated. In addition, the presence of superoxide dismutase in the culture medium (1700 units/ml) inhibited the cytotoxic response. Since [14C]paraquat was not absorbed into these cells, extracellular superoxide anion radical formation was investigated as the cause of the observed cell death. Paraquat (0.5 mM) was found to stimulate extracellular O-2 generation, from PAM, but only in nonactivated cells. A sevenfold enhancement over the resting rate of radical generation was observed in the presence of paraquat. No increase in the O-2 generation rate of activated macrophages was observed upon the addition of paraquat to the culture medium. These data indicate that paraquat is cytotoxic to the pulmonary alveolar macrophage and further suggest that this cytotoxicity is mediated, at least in part, by an excess, extracellular production of active oxygen species. Implications of these findings with respect to the currently accepted hypothesis of paraquat poisoning in vivo are discussed.
Cytochemical staining for leukocyte alkaline phosphatase(LAP), nonspecific esterase (NSE), nonspecific esterase with fluoride inhibition (NSE-F), periodic acid Schiff (PAS) reactivity, and peroxidase (PO) was valuable in identification of the neoplastic cell type in 10 leukemic cats. Staining both blood and bone marrow smears was often necessary for making the correct diagnosis. Cytochemical staining resulted in changing the morphologic diagnosis of leukemia in two of the 10 cats. Also, increased LAP activity, probably a marker for myelocytic leukemia in the cat, was observed in bone marrow cells from three nonleukemic, FeLV-positive cats.
The high dose intravenous glucose tolerance test and concurrent immunoreactive serum insulin and glucagon levels were measured and the results related to the presence or absence of pancreatic insular amyloid in 16 cats, seven of which were known to be diabetic. Control values for all parameters were established using seven additional clinicopathologically normal cats. Nine of the 16 cats had normal fasting blood glucose levels (less than 120 mg/dl) and impaired glucose tolerance. These cats had attenuated (3/9) or normal (6/9) 0 to 5 minute glucose-stimulated insulin secretion, rising 45 to 60 minute insulin secretion (7/9), low mean insulin/glucose ratio, and normal mean serum glucagon. Three of the nine cats with impaired glucose tolerance had insular amyloidosis. These three cats had significantly higher mean blood glucose levels during the glucose tolerance test than did cats with impaired glucose tolerance and no insular amyloid deposits. Also, these three cats accounted for three of the four longest glucose disappearance one-half times (T1/2S), three of the four lowest glucose disappearance coefficients, and three of the four lowest 0 to 5 minute insulin responses. The seven diabetic cats (fasting blood glucose levels greater than 120 mg/dl) had either low to low normal (6/7) or above normal (1/7) fasting insulin levels, no insulin response to intravenous glucose stimulation (6/7), and elevated mean serum glucagon levels. Insular amyloid was present in six of the seven diabetic cats. Three diabetic cats with marked insular amyloid deposits had glucose disappearance T1/2 and K (coefficient) values, serum insulin levels, serum glucagon levels, and insulin/glucose ratios which were not significantly different from the other three diabetic cats with slight to moderate insular amyloidosis. These results confirm a strong association between the occurrence, but not the extent of insular amyloidosis and diabetes mellitus in adult diabetic cats, although amyloid replacement of pancreatic islets does not appear to be the primary diabetogenic event. Rather, these results appear to be consistent with our hypothesis that insular amyloid deposition is a morphologic marker of primary B-cell dysfunction that is basic to the pathogenesis of the diabetic condition, and is reflected clinically by impaired glucose tolerance.
Degenerative joint disease and inflammation of the synovial membrane were produced in the left stifle of 16 dogs by severing the cranial cruciate ligament. Arthrotomy only was performed on the right stifle. Synovial membrane from these joints was histologically examined at 1, 2, 8, and 13 weeks after surgical operation. Similar tissue was obtained from 4 healthy dogs for comparison. Inflammatory changes in the synovium of the left stifle progressed with time and were prominent at 8 weeks postoperatively; subsynovial fibrosis was greatest at 13 weeks. Inflammation of the synovial membrane and subsynovial tissue was characterized by synovial cell hypertrophy and hyperplasia, plasma cell and lymphocyte infiltration, and increased vascularization of the subsynovial region.