Immunochemical aspects of the screening of gene expression

Different immunochemical methods of gene expression screening in the heterologous system are described. Special attention is paid to the technique of in situ screening and to the methods of the product detection in lysates and cell colony replicas on the basis of immunoblot, immunodot, immunoprecipitation and immunochemical analysis on plates. The data on cell lysis, solid-phase immobilization and sensitivity of different immunochemical methods are discussed.     

Methodological aspects of shift-work research

A major issue in shift-work research is to understand the possible ways in which shift work can impact performance and health. Nearly all body functions, from those of the cellular level to those of the entire body, are circadian rhythmic. Disturbances of these rhythms as well as the social consequences of odd work hours are of importance for the health and well-being of shift workers. This article reviews a number of common methodological issues which are of relevance to epidemiological studies in this area of research. It discusses conceptual problems regarding the use of the term "shift work," and it underscores the need to develop models that explain the mechanisms of disease in shift workers.     

Methodological aspects of scaling in biology

Interest in the scaling approach to problems of biological design has increased dramatically in the past few years. But thus far no systematic attempt has been made to review the possible pitfalls attendant upon this approach. As a beginning, the problems which can arise from rounding exponents, or taking standard errors at face value, or expressing dependent variables in ratio form are discussed. There follows a discussion of fitting specific functions to scaling data, of the special needs for documentation and of the potential value to be derived from suitable computer programs in scaling studies. Finally, the possible difficulties of demonstrating global optimization in biological systems, the risks of dimensional analysis and the value and nature of scaling models are discussed.     

The micronucleus test. Methodological aspects

Changes in the cellular compositiion of bone marrow were studied in relation to dose of Trenimon® and time after treatment. Strong mutagenic effects caused a partial depletion of the marrow cavities of nucleated blood cell precursors, with subsequent retention of newly formed erythrocytes and inundation with peripheral blood. The influence of these changes on the results of micronucleus scoring was investigated in a time-effect and a dose-effect study using three different methods of evaluation, relating the incidence of micronuclei to (a) nucleated cells, (b) all erythrocytes, and (c) polychromatic erythrocytes. Conclusions are drawn on the practical use of the micronucleus test system. The simplest scoring procedure, namely relating micronucleated polychromatic erythrocytes to a given total number of erythrocytes, was very efficient in the range of low mutagenic effects and therefore well suited for safety screening wherease dose-effect studies comprising very high mutagenic effects required the application of a modified method of scoring.     

Methodological aspects of the problem of nonmonotonic dose-effect dependence

Considered are the methodological bases of two radiobiological theories—target theory and structural-metabolic theory. The target theory states the existence in the cell of a biologically significant structure (sensitive volume) and the monotonic “dose-effect“ dependence. In the structural-metabolic theory at the molecular level the unity of structure and metabolism is postulated. Discussed is the role of homeostatic mechanisms in the nonmonotonicity of the “time-effect” dependence. The nonmonotonicity of the “dose-effect” dependence for metabolic and functional parameters of cells and tissues is stipulated by the non-monotonicity in time of the metabolic and functional response to the action of ionizing radiation.     

Quantitative expression of maize HSPs: genetic dissection and association with thermotolerance

Summary In higher plants, within-species qualitative polymorphism for heat shock proteins (HSPs) is extremely rare, even between genotypes showing different heritable levels of thermotolerance. Here we have explored the amount of quantitative variability in HSP synthesis in maize. We have analyzed the quantitative expression of the typical HSPs in a set of recombinant inbreds (RIs) derived from the f₁ hybrid between a thermotolerant (T232)- and a thermosensitive (CM37)-genotype, characterized for about 200 mapped RFLP loci. Significant differences were detected in the level of expression of five HSPs, and their frequency distribution in the RI population is that of a quantitative trait. Subsequent mapping of loci controlling the characters, based on RFLP analysis, confirmed the multigenic control of HSP expression: the regression analysis of the band intensities of each variant HSP on RFLPs revealed, for the different HSPs, a minimum number of three to eight quantitative trait loci (QTLs) accounting for a high proportion (0.35–0.60) of the genetic variability of these bands. An analysis of the correlation between the variability of HSPs and that of cellular membrane stability, a cellular component of thermotolerance, did not reveal any significant association of the two parameters.     

Methodological aspects of serological diagnosis in leptospirosis

The results of serological study for leptospirosis of 515 blood serum specimens from patients coming to different clinics of the Republic of Bangladesh, are presented. The sera were tested in microagglutination test. To exclude intergroup reactions and to enhance reliability of results, immunoglobulin classes were determined with the use of cysteine as a reducing agent and immunoabsorption test. In 51 patients (9.9%) antileptospiral antibodies were detected in titers from 1:20 to 1:1600 against pathogenic leptospires of different serological groups.     

Population genetic variation in genome-wide gene expression

Evolutionary biologists seek to understand which traits display variation, are heritable, and influence differential reproduction, because such traits respond to natural selection and underlie organic evolution. Selection acts upon individual differences within a population. Whether individual differences within a natural population include variation in gene expression levels has not yet been addressed on a genome-wide scale. Here we use DNA microarray technology for measuring comparative gene expression and a refined statistical analysis for the purpose of comparing gene expression levels in natural isolates of the wine yeast Saccharomyces cerevisiae. A method for the Bayesian analysis of gene expression levels is used to compare four natural isolates of S. cerevisiae from Montalcino, Italy. Widespread variation in amino acid metabolism, sulfur assimilation and processing, and protein degradation-primarily consisting of differences in expression level smaller than a factor of 2-is demonstrated. Genetic variation in gene expression among isolates from a natural population is present on a genomic scale. It remains to be determined what role differential gene expression may play in adaptation to new or changing environments.     

Reprogrammed genetic decoding in cellular gene expression

Reprogrammed genetic decoding signals in mRNAs productively overwrite the normal decoding rules of translation. These "recoding" signals are associated with sites of programmed ribosomal frameshifting, hopping, termination codon suppression, and the incorporation of the unusual amino acids selenocysteine and pyrrolysine. This review summarizes current knowledge of the structure and function of recoding signals in cellular genes, the biological importance of recoding in gene regulation, and ways to identify new recoded genes.