Defoliation-Induced Stress in Nodules of White Clover: II. IMMUNOLOGICAL AND ENZYMIC MEASUREMENTS OF KEY PROTEINS

Changes in key nodule proteins following defoliation of whiteclover plants were assessed by measurements of enzyme activitiesand by use of antibodies to specific nodule proteins. Defoliation caused major declines in protein and leghaemoglobinlevels and in the activities of invertase, sucrose synthase,UDP glucose pyrophosphorylase, aspartate amino transferase,glutamine synthetase, phosphoenolpyruvate carboxylase, and malatedehydrogenase. In continuously defoliated plants the activities of these noduleenzymes continued to decline throughout the course of the 17d experiment. In plants defoliated once and then allowed toregrow new leaves, nodule enzyme activities declined for 7 to10 d before increasing again to control levels by the end ofthe experiment. In this single defoliation/recovery treatmentonly the activities of PEP carboxylase and glutamine synthetasedeclined to a greater extent than the general decline in proteincontent. Alcohol dehydrogenase, increased in specific activityfollowing a single defoliation and only declined in nodulesof continuously defoliated plants. Amino peptidase activity declined in concert with other enzymeactivities described above. Endopeptidase activity, in contrast,increased significantly after 4 d following either a singleor continuous defoliation. In the plants allowed to regrow newleaves endopeptidase activity declined to control levels again,whereas in plants continuously defoliated the activity rose5-fold. However, endopeptidase increased only after significantdeclines in protein and other enzyme activities had alreadyoccurred. Western immunoblotting confirmed that the declines in glutaminesynthetase activity and leghaemoglobin levels were due to thedisappearance of antigen. Declines in nitrogenase componentsI and II indicated that bacteroid proteins were affected bydefoliation over the same time-scale as host plant encoded proteins.As new leaves grew and nodule N₂ fixation was reestablished,these specific nodule proteins were again detectable by immunoblotting. Key words: Trifolium repens, white clover, defoliation, nodules, enzymes, antibodies     

Regeneration of Vitamin A Deficient Rat Tracheal Epithelium After Mild Mechanical Injury

Mild mechanical abrasion of tracheal epithelium of Vitamin A deficient rats removed the superficial cells and spared basal cells which divided to repopulate the damaged area. The proliferative cells passed through a period of DNA synthesis with the greatest numbers of thymidine incorporating cells in samples labelled 22 h after injury. A peak of cell division occurred at 32 h and there was no further DNA synthesis or cell division. The area of wounding exhibited squamous metaplasia while normal pseudostratified muco-ciliary structure was retained by adjacent epithelium which had not been injured. The data indicates that squamous metaplasia in the respiratory epithelium in longstanding Vitamin A deficiency is due to redirected differentiation of basal cells and is seen only after mitotic activity has occurred.     

Macromolecules in brachiopod shells: characterization and diagenesis

An immunological investigation was conducted of soluble intra-crystalline macromolecules isolated from living and fossil brachiopod shells, which had previously been used for an immunologically based study of phylogeny (serotaxonomy). The soluble intra-crystalline macromolecules comprised 0.03% by weight of the extant shell material. Bulk analysis and gel electrophoresis indicated that the organic material is predominantly glycoprotein, and contains up to 30% by weight carbohydrate. Treatment of the macromolecules with periodate and proteinase K revealed that antibodies were raised predominantly against the carbohydrate moieties. Using a specially adapted dot blot immunobinding assay (DIBA) the decay in immunological signal over geological time was determined. Pleistocene shells have lost between 99 and 99.9% of immunological reactivity, and original antigenic determinants form a declining proportion of total organic matter. It is suggested that condensation reactions between amino acids and sugars account for the rapid destruction of determinants; this has important implications for the direction of future studies on fossil macromolecules. □ Serotaxonomy, biomolecular palaeontology, glycoproteins, melanoidins, brachiopods.     

Peripheral endothelial cells are not reliable in differentiating primary benign and malignant hepatocellular lesions in fine needle aspirates of the liver

The distinction of hepatocellular carcinoma (HCC) from benign lesions of the liver in fine needle aspiration (FNA) specimens can be problematic. In an attempt to separate well-differentiated HCC from benign hepatocellular lesions, the presence of tissue fragments displaying peripheral endothelial cells (PE) has been proposed in a previous study as a useful feature in favour of malignancy. In this study, we evaluated slides from 59 cases of liver masses undergoing FNA (19 HCC, 40 benign) and evaluated them for the presence of tissue fragments containing PE. We found that 90% of cases of HCC contained tissue fragments in which PE were either focally present or abundant. However, 68% of cases containing only benign hepatocytes also contained tissue fragments in which PE were at least focally present. In addition, it appears that within the group of benign lesions, the presence of PE was related to the overall cellularity of the specimen rather than the specific nature of the lesion. Thus, the presence of PE in tissue fragments does not, in isolation, appear to be a useful morphological feature for the separation of benign and malignant hepatocellular lesions in FNA material.