Preface

Molecular and Cellular Biochemistry -     

Current clinical laboratory practice: investigation of plasma lipids--which tests and when?

Clinical interest in the lipoproteins stems mainly from the association between serum cholesterol concentrations and coronary heart disease. Investigations of lipoproteins should be performed in patients with premature coronary heart disease, with a strong family history of coronary heart disease, or with certain cutaneous stigmata of hyperlipoproteinaemia and when fasting serum samples are seen to be lipaemic. Family studies should be performed in appropriate cases to identify relatives at increased risk of developing coronary heart disease. Patients with conditions known to cause secondary hyperlipoproteinaemia should be investigated if they fall into one of these categories but only after treatment of the underlying condition. Non-specialist laboratories should be able to measure total cholesterol and triglyceride concentrations and high density lipoprotein cholesterol concentrations. Lipoprotein electrophoresis has a limited role in such laboratories and is not necessary as a routine procedure. Specialist laboratories should in addition be able to measure individual lipoproteins and identify apolipoprotein E phenotypes.     

Sickness and Healing: An Anthropological Perspective

Sickness and Healing: An Anthropological Perspective. Robert A. Hahn. New Haven, CT: Yale University Press, 1995 (cloth and paper), viii. 327 pp.     

Real-time analysis of the assembly of ligand, receptor, and G protein by quantitative fluorescence flow cytometry.

We describe a general approach for the quantitative analysis of the interaction among fluorescent peptide ligands (L), receptors (R), and G proteins (G) using fluorescence flow cytometry. The scheme depends upon the use of commercially available fluorescent microbeads as standards to calibrate the concentration of fluorescent peptides in solution and the receptor number on cells in suspension. We have characterized a family of fluoresceinated formyl peptides and analyzed both steady-state and dynamic aspects of ligand formyl peptide-receptor interactions in digitonin-permeabilized human neutrophils. Detailed receptor-binding studies were performed with the pentapeptide N-formyl-Met-Leu-Phe-Phe-Lys-fluorescein. Equilibrium studies showed that GTP [S] caused a loss of binding affinity of approximately two orders of magnitude, from approximately 0.04 nM (LRG) to approximately 3 nM (LR), respectively. Kinetic studies revealed that this change in affinity was principally due to an increase in the dissociation rate constants from approximately 1 x 10(-3) s-1 (LRG) to approximately 1 x 10(-1) s-1 (LR). In contrast, the association rate constants in the presence and absence of guanine nucleotide (approximately 3 x 10(7) s-1 M-1) were statistically indistinguishable and close to the diffusion limit. In the presence of guanine nucleotide (LR), the kinetic data were adequately fit by a single-step reversible-binding model. In the absence of guanine nucleotides, not all receptors have rapid access to G to form the LRG ternary complex. Mathematically, those R that have rapid access to G are either precoupled to R or the association of G with R is fast compared to the association of L with R. The physiological consequences of coupling heterogeneity are discussed.     

Exopolysaccharide-producing strains of thermophilic lactic acid bacteria cluster into groups according to their EPS structure

AIMS: To compare galactose-negative strains of Streptococcus thermophilus and Lactobacillus delbrueckii subspecies bulgaricus isolated from fermented milk products and known to produce exopolysaccharides (EPSs). METHODS AND RESULTS: The structures of the EPSs were determined using nuclear magnetic resonance (NMR) and their genetic relationships determined using restriction endonuclease analysis (REA) and random amplification of polymorphic DNA (RAPD). Similar groupings were apparent by REA and RAPD, and each group produced an EPS with a particular subunit structure. CONCLUSION: Although none of the strains assimilated galactose, all inserted a high proportion of galactose into their EPS when grown in skimmed milk, and fell into three distinct groups. Significance and Impact of the Study: This information should help in an understanding of genetic exchanges in lactic acid bacteria.     

Statistical analysis of in situ hybridization data: Derivation and use of the Zmax test

There are many situations in which grain distributions resulting from in situ hybridization of radioactively labeled probes to unique genes should be subjected to a statistical analysis. However, the problems posed by analysis of in situ hybridization data are not straightforward, and no completely satisfying method is currently available. We have developed a procedure in which the major and any number of minor site(s) of hybridization may be specifically located and the significance of each tested. This Z_max procedure first tests the overall distribution for departure from randomness and then identifies significantly overlabeled whole chromosomes (or chromosome arms or other large segments), a process that may be repeated to pinpoint significantly overlabeled regions within these chromosomes. We describe in detail the derivation of the Z_max statistic, present tables of significant Z_max levels, and show with examples how Z_max is used in tests of significance of in situ hybridization data.