Biomedical subjects
Publications and source records attributed to B D Patterson.
The physiology of saliva flow and hyposalivation is discussed. Drug-induced hyposalivation results in a higher incidence of dental caries, causes discomfort for denture wearers, and increases the risk of oral infections. Guidelines for preventing and treating drug-induced xerostomia are offered.
Seedlings of tomato (Lycopersicon esculentum, Mill.) varied diurnally in their sensitivity to chilling temperatures. If chilled near the end of the dark period when they were most sensitive, the time taken to kill half of the seedlings was approximately 3 days, whereas in samples taken 4 hours after the onset of dark, a period of 6 days of chilling was required. Sensitivity dropped rapidly after the onset of the light period. This rhythm was exogenously controlled by the diurnal changes in light, rather than in the temperature. The susceptibility of predawn seedlings could be reduced by exposure to light, by water stress, or by abscisic acid applied to the leaves. However, the subsequent changes in sensitivity to chilling did not correlate with stomatal aperture. Six other chilling-sensitive species showed similar diurnal changes in their chilling sensitivity.
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On the basis of polyacrylamide gradient gel electrophoresis of leaf extracts from 24 species of higher plants, two main forms of carbonic anhydrase (EC 4.2.1.1) were recognized; the "dicotyledon" type and the "monocotyledon" type. More than one band of enzyme was found on gels from most species, suggesting the possibility of carbonic anhydrase isoenzymes in higher plants.
Carbonic anhydrase (EC.4.2.1.1) was purified from leaves of the dicotyledon Pisum sativum L. (56-fold) and from leaves of the monocotyledon Tradescantia albiflora Kunth. (24-fold). The molecular weight of the Pisum enzyme was estimated to be 188,000 +/- 8,000 with subunit sizes of 28,000 +/- 3,000 and 56,600 +/- 3,500. It contained 1 mole zinc per 32,500 +/- 2,000 g protein. The molecular weight of the Tradescantia enzyme was estimated to be 42,000 +/- 2,000 with a subunit size of 27,500 +/- 2,200. It contained 1 mole zinc per 34,000 +/- 2,000 g protein. The two enzyme preparations were different in specific activity, stability in solution, and sensitivity to sulfonamides and inorganic anions. Gel electrophoresis separated each purified preparation into two active enzyme bands.
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In light-grown wheat (Triticum aestivum L.) seedlings, the amount of chloroplast and cytoplasmic ribosomal RNA increased to a maximum in the first leaf near the end of its growth and declined by about 60% in the following 3 days. While total ribosomal RNA was declining, labeled uracil was still incorporated into cytoplasmic ribosomal RNA, but the rate of incorporation into chloroplast ribosomal RNA fell by more than 80%, as did the incorporation of labeled leucine into fraction I protein. Either there is greater replacement of cytoplasmic ribosomal RNA than chloroplast ribosomal RNA in mature leaves, or chloroplasts are able to repress the incorporation of exogenous precursor when there is no net synthesis of RNA.
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Experiments have been performed to investigate whether indoleacetic acid changes the balance between the rates of synthesis of different kinds of proteins. Sub-apical sections of etiolated peas were incubated with (14)C- or (3)H-labeled amino acid, and combined to give dual-labeled tissue. Cell fractions were prepared by differential centrifugation, and the dual-labeled protein of each fraction analyzed by gel-filtration. When 2 x 10(-5)m indoleacetic acid was included with (14)C-labeled amino acid, but not with the (3)H-labeled amino acid, pronounced changes occurred in the pattern of incorporation of the (14)C label into protein. These changes were greatest in the proteins of the particulate fraction which included nuclear material. Although the pattern of incorporation of lysine was shown to be different from that of leucine, the changes induced by indoleacetic acid were quantitatively similar whichever amino acid was used as a precursor. Dual-labeled protein was further fractionated using column chromatography on DEAE-cellulose. The results suggested that the effect of indoleacetic acid may not be completely general, and that the pattern of synthesis of many proteins may be unaltered by indoleacetic acid. When tissue was preincubated with 10 mug/ml actinomycin D for 30 minutes, incorporation of amino acid into protein was reduced but not abolished. Actinomycin D did, however, prevent the changes in the pattern of protein synthesis which were induced by indoleacetic acid.
Extracts from more than 325 different plants have been tested for their effects on larvae of Aedes aegypti, and from these initial tests, 16 plants were selected for further study. Extracts from plant parts of these 16 plants were screened using tlc and the results are tabulated along with the observed biological activity.