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Biomedical subjects

D G Baker

Publications and source records attributed to D G Baker.

173 records · Page 10Linked to original sources
PubMed1967

Relative importance of reradiation, convection, and transpiration in heat transfer from plants.

For a plant of average spectral properties and average diffusion resistance (2 sec/cm), diurnal variations in the energy dissipated by reradiation, convection, and transpiration have been explicitly calculated and plotted for certain environmental conditions as measured at St. Paul, Minnesota. These conditions represent the environments of characteristic types of days and of characteristic types of leaves. In all situations reradiation is overwhelmingly the dominant mode of heat transfer.A new method for the calculation of Bowen's ratio is also presented which gives results in very good agreement with older procedures. For certain individual leaves the energy dissipated by convection is found to be greater than that dissipated by transpiration. For a crop as a whole, however, transpiration is found to be by far the most important.

Journal Article↗
PubMedDate not supplied

Establishment and validation of an isolated rat lung model for pulmonary metabolism studies.

An isolated rat lung model was established and validated for use in pulmonary metabolism studies. During the establishment phase of the study, several problems were encountered and overcome in order to maintain the lungs in physiological condition. In the validation phase of the study, the lungs were removed, ventilated and perfused from 34 male Fischer 344 rats. After an equilibration period, lungs were ventilated and perfused for up to 4 h. Morphological, biochemical and functional parameters were evaluated to validate the physiological condition of the lungs. Morphological parameters included wet/dry lung weight ratios and gross and histological scoring for edema. Biochemical parameters included assays for tissue ATP and reduced glutathione content, glutathione reductase activity and glucose utilization. Functional parameters included changes in lung tidal volume, dynamic compliance and airway resistance. Results indicated that edema formation was only detected histologically, that lungs remained nearly biochemically normal for 210 min and that pulmonary function declined to about 80-90% of normal. Overall, these findings indicated that the isolated, perfused rat lung remained in acceptable physiological condition for ca. 210 min. This period of time should be adequate for conducting pulmonary metabolism studies with a variety of exogenous compounds.

Adenosine Triphosphate↗
PubMedDate not supplied

Hepatic toxicity and recovery of Fischer 344 rats following exposure to 2-aminoanthracene by intraperitoneal injection.

Humans may be exposed to 2-aminoanthracene (2-AA), a substituted polycyclic aromatic hydrocarbon, and a recognized mutagen and carcinogen, through oral and respiratory routes from contact with a variety of environmental sources. For the present study, we sought to evaluate hepatic damage and recovery in Fischer 344 rats following multiple i.p. injections of 5 mg of 2-AA. Rats were injected weekly for up to 5 weeks. Subgroups were then allowed to recover for 1, 5, or 9 weeks, and biochemical and pathologic changes were evaluated. We observed that weight gains were reduced relative to controls for all groups receiving > or = 2 injections. Serum enzyme levels indicative of liver damage were evident and included alterations in serum aspartate aminotransferase, alkaline phosphatase, total protein, albumin, and globulin. These alterations usually returned to normal by 5 weeks following cessation of 2-AA administration. In contrast, histologic liver changes, including hepatocyte hypertrophy, biliary hyperplasia with oval cell proliferation, altered foci, nodular hyperplasia, and one hepatocellular adenoma became more severe with time. This experiment demonstrates patterns of hepatic damage and recovery in rats exposed to 2-AA.

Adenoma↗
PubMedDate not supplied

Suppression of arylamine toxicity in the Fischer-344 rat following ingestion of a complex mixture.

The toxic effects of a mixture of 2-aminoanthracene (2-AA), benzanthracene (BA), and dinitropyrene isomers (DNP), and the toxic effects of these compounds individually, were investigated in the Fischer-344 rat following dietary exposure via a powdered basal diet. Animals were sacrificed at 14-, 30-, and 80-days of dietary exposure. Exposure to dietary 2-AA alone induced anorexia, cachexia, variable mortality, and altered serum chemistry profiles in the F-344 rat. Reduced lymphocyte counts were also shown in rats exposed to 2-AA. A temporal pattern of effect of 2-AA dietary exposure was observed in the progression of hepatic lesions in exposed animals. Dietary exposure to either DNP isomers or BA at a 10-fold higher concentration in the diet, relative to 2-AA, did not induce detectable toxic responses. However, exposure of rats to a mixture of 2-AA, BA, and DNP isomers (100 mg/kg, 1.0 g/kg, and 1.0 g/kg of diet, respectively) resulted in the attenuation of toxic effects when compared to exposure of F-344 rats to 2-AA alone. These results indicate that the toxic effects of 2-AA are suppressed by co-administration of DNP and BA and suggest that compound interactions need to be considered when predicting the toxic potential of specific environmental pollutants.

Alanine Transaminase↗
PubMedDate not supplied

Binding of synovial fluid proteins to monosodium urate crystals in vitro.

Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS PAGE) and western blot techniques were used to analyze proteins adsorbed in vitro to synthetic monosodium urate crystals (MSUC) from a variety of gouty biologic fluids. Distinct differences in adsorbed proteins were found in comparing synovial fluid (SF) with serum or plasma, particularly at 220 kD and below 19 kD. Further studies should consider the importance of the synovial milieu. Patterns of proteins adsorbed to MSUC from the SF of all 12 patients with gout were similar. A considerable number of polypeptides appeared to be selectively adsorbed. Of these, polypeptides associated with fibronectin, C1q and IgM were identified by immunotransblotting. The experiments also demonstrated that the overall polypeptide patterns obtained by SDS PAGE of eluates from MSUC exposed to SF were unaffected by heating MSUC to 180 degrees C, as well as by the volume of SF in the incubation mixture.

Adsorption↗