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  • 1
    ISSN: 1432-2048
    Keywords: Cell suspension culture ; Chalcone isomerase ; Elicitor ; Enzyme induction ; Phaseolus (chalcone isomerase) ; Phytoalexin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Approximately fourfold increases in the extractable activity of the enzyme chalcone isomerase (CHI, EC 5.5.1.6) were observed within 24 h of treatment of cell suspension cultures of Phaseolus vulgaris with a crude elicitor preparation heatreleased from the cell walls of the bean pathogen Colletotrichum lindemuthianum. The induction of CHI activity was highly dependent upon elicitor concentration, with maximum induction occurring in two discrete concentration ranges. A basal half-life for CHI〉32 h in control cultures was determined by labelling with 2H from 2H2O followed by analysis of the equilibrium distribution of enzyme activity in CsCl density gradients. Comparative density labelling indicated that at both the lower and higher effective elicitor concentrations, the induced appearance of CHI activity was the result of an apparent initial activation of pre-existing enzyme followed by an increase in the rate of de-novo synthesis of the enzyme as compared with non-elicited controls. The increased appearance of the enzyme over the first 8 h in elicitor-treated cultures was inhibited by cycloheximide, cordycepin and actinomycin D. The results are discussed in relation to the mechanisms of co-ordinate enzyme induction operating in French-bean cell cultures exposed to fungal elicitors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Chalcone synthase ; Colletotrichum ; Elicitor ; Phaseolus ; Phenylalanine ammonia-lyase ; Phytoalexin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In wounded cotyledons ofPhaseolus vulgaris L. the accumulation of the 5-hydroxy isoflavonoids kievitone and 2′-hydroxygenistein precedes the major increases in the levels of the 5-deoxy compounds phaseollin and coumestrol. Increased phytoalexin levels are preceded by transient increases in the extractable activities of L-phenylalanine ammonia-lyase (EC 4.3.1.5.), chalcone synthase and chalcone isomerase (EC 5.5.1.6.). Accumulation of phytoalexins, above wounded control levels, is observed following treatment of excised cotyledons or hypocotyls with crude or fractionated elicitor preparations heat-released from the cell walls ofColletotrichum lindemuthianum. Chalcone synthase levels are also induced in cotyledons, although crude elicitor and all fractions suppress L-phenylalanine ammonia-lyase activity in both tissues. Kievitone is the major phytoalexin induced in cotyledons, whereas in hypocotyls phaseollin predominates. Patterns of phytoalexin accumulation have been studied in response to varying concentrations of the crude and fractionated elicitor; 5-hydroxy isoflavonoid accumulation is highly dependent upon elicitor concentration, the dose-response curves for kievitone accumulation showing maxima at around 1 μg glucose equivalents per cotyledon, minima at 2–3 μg equivalents and increasing induction at higher concentrations. Similar patterns are observed for L-phenylalanine ammonia-lyase and chalcone synthase levels, although the overall extent of these changes is masked by the high wound response. Accumulation of 5-deoxy isoflavonoids above control levels requires high elicitor concentrations; no experimental conditions were found under which phaseollin accumulated to higher levels than kievitone in cotyledons during the first 48 h after elicitation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 32 (1980), S. 195-199 
    ISSN: 1432-0827
    Keywords: Bone ; Diabetes ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A simple instrument is described which measures the breaking strength of rat bones. The apparatus yields reproducible results and is suitable for use in measuring the strength of bones from both large and small animals. Diabetic rat femurs were more fragile and required less force to break in contrast to those from diabetic rats treated with insulin or normal rats. Daily insulin treatment significantly improved the bone cortical thickness and enhanced their capacity to withstand pressure, although these did not reach the level of the normal controls. The amount of force required to break the bone appears to be related to its cortical thickness and mass.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0827
    Keywords: Aluminum ; Parathyroid hormone ; Bone ; Renal failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Bone aluminum, quantitative bone histology, and plasma parathyroid hormone (PTH) were compared in 29 patients undergoing chronic hemodialysis. Histologic techniques included double tetracycline labeling and histochemical identification of osteoclasts and osteoblasts. Bone aluminum was measured chemically by flameless atomic absorption spectrophotometry, and histochemically. When measured chemically, the bone aluminum was 67±46 (SD) mg/kg dry weight (normal 2.4±1.2 mg/kg); histochemically, aluminum was present at 2.9±4.4% of trabecular surface. The biochemical and histochemical results agreed well (r=0.80,P〈0.001). No double tetracycline labels were seen at the mineralization front where aluminum was deposited, indicating cessation of mineralization at these sites. The osteoblast surface correlated positively with plasma PTH (r=0.67,P〈0.001) and negatively with bone aluminum level (r=−0.42,P〈0.05). Multiple linear regression showed a correlation of aluminum with osteoblasts additional to that of PTH, consistent with a direct effect of aluminum in depressing osteoblast numbers. Though a relationship between PTH and chemically determined bone aluminum level could not be demonstrated, there was a negative correlation between osteoclast count and aluminum, and the nine patients with severe hyperparathyroid bone disease had lower chemically determined aluminum levels than the other patients. These results suggest that aluminum (a) directly inhibits mineralization, (b) is associated with decreased PTH activity and hence osteoblast numbers, and (c) directly reduces osteoblast numbers. In addition to inducing severe, resistant osteomalacia, aluminum appears to contribute to the mild osteomalacia commonly seen in renal failure, characterized by extensive thin osteoid and low tetracycline and osteoblast surfaces.
    Type of Medium: Electronic Resource
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