In vitro and in vivo regulation of chloroplast glyceraldehydes-3-phosphate dehydrogenase isozymes from Chenopodium rubrum. I. Purification and properties of isozymes

Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GPD, EC 1.2.1.13) was purified from leaves of Chenopodium rubrum L. Aggregated (≥ 10⁶) and disaggregated (165 × 10³) molecular weight forms were obtained by gel filtration in the presence of NAD⁺ and NADP⁺, respectively. The disaggregated enzyme was separated into two isozymes by inverse ammonium sulphate gradient solubilization: "NADP-GPD I" was homotetrameric (subunit molecular weight 39 × 10³); "NADP-GPD II" was heterotetrameric (subunit molecular weights 39 × 10³ and 43 × 10³). Isoelectric focusing of the isozymes, both aggregated and disaggregated, revealed two isoelectric forms in each case, at 4.3 and 7.7. Chloroplast GPD was "NADP-suppressed" in crude extracts due to partial oxidation, incubation with dithioerythritol restored full activity.     

Lymphocyte transformation to connective tissue antigens in adult and juvenile rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, systemic lupus erythematosus, and a nonarthritic control population

Transformation of peripheral blood lymphocytes after exposure to connective tissue antigens was measured in patients with adult (n = 35) and juvenile rheumatoid arthritis (n = 34), osteoarthritis (n = 21), ankylosing spondylitis (n = 15), and systemic lupus erythematosus (n = 26) and in control subjects (n = 36). The connective tissue antigens included homologous cartilage-type proteoglycan, cyanogen bromide-derived peptides of type I, II, and III collagens, and type I and II helical collagens. Lymphocyte transformation was not detected in the osteoarthritic and control groups, with one exception. Sensitization to at least one connective tissue antigen was detected in approximately one-third of the rheumatoid arthritic and lupus patients and in one-quarter of the juvenile rheumatoid patients. In ankylosing spondylitis, positive responses occurred to proteoglycan in 20% of patients tested but never to collagens or peptides. Sensitivity to proteoglycan was detected only in ankylosing spondylitis except for one patient with juvenile rheumatoid arthritis. In patients with systemic lupus erythematosus and both forms of rheumatoid arthritis, lymphocyte transformation was usually more frequently detected to peptides than to the helical collagens. In adult rheumatoid arthritis, type II peptides elicited an elevated number of responses (14%) as did type I (9%) and III (8%) peptides to lesser degrees. Responses to type I (4%) and II (4%) helical collagens were infrequent. Rheumatoid arthritic patients usually exhibited sensitivity to only one antigen and lymphocyte transformation was often detected when the arthritis was improving. In juvenile rheumatoid arthritis, lymphocyte transformation was detected to peptides of type I (16%), II (9%), and III (29%) collagens and to helical type I (12%) and II (8%) collagens. In systemic lupus erythematosus, sensitization was detected to peptides of type I (13%), II (20%), and III (14%) collagens and to helical type I collagen (18%) but not type II collagen. Simultaneous sensitivity to several antigens often occurred in both systemic lupus erythematosus and juvenile rheumatoid arthritis. Examination of individual patients in all three rheumatic disease groups revealed that immune sensitivity developed to collagen peptides rather than to the helical molecules, particularly in the case of type II collagen. Thus, some patients with inflammatory arthritis exhibit immune responses to connective tissue components which are, as a group, characteristic for each type of arthritis. These responses, which were not obviously associated with disease activity, may develop as a result of inflammation or trauma which destroys connective tissue and exposes molecules, in either a native or degraded state, to cells of the immune system. Expression of sensitivity to these tissue antigens may contribute to the chronicity of the inflammatory arthritides.     

A model of the role of natural killer cells in immune surveillance — II

The functioning of natural killer (NK) cells as immune surveillance effector cells against tumors is explored. In part I (J. Math. Biol. 12, 363-373 (1981], it was predicted that susceptible tumors would be eliminated if they have parameter lambda 0 value negative. They would not be eliminated if lambda 0 greater than 0. As the lambda 0 less than 0 result was local, one expected either that tumors of all sizes with lambda 0 less than 0 will be eliminated (global stability) or that tumor population will go to zero if in a domain of attraction of the critical point which is not all of the positive orthant. In this paper, the second is shown to be true. The general results are illustrated by a specific model.     

The Distribution of Crossovers along Unreplicated Lambda Bacteriophage Chromosomes

The distribution of crossovers along unreplicated chromosomes of bacteriophage lambda has been examined by determining the density distributions and genotypes of particles in the progenies of crosses of density-labeled by ordinary parents in the presence of genetic blocks to replication. The Red and Rec systems combined produce crossovers primarily near the ends (especially the right end) of the chromosome. Removal of the generalized lambda recombination functions by red and gam mutations results in loss of these terminal crossovers; coupled with this loss is a disappearance of the differential dependence of recombination frequencies in terminal and central intervals on DNA synthesis. Removal of the bacterial system by a recA mutation results in severe depression of crossing over among unreplicated phage, with the few recombinants produced by the lambda system occurring near the right end.     

Electron-paramagnetic-resonance studies on cobalt(II) carbonic anhydrase–sulphonamide complexes

Sulphonamide adducts of three Co(II) carbonic anhydrases were investigated by e.p.r. (electron paramagnetic resonance) at helium temperatures. The highly anisotropic 9 GHz spectra exhibited only three distinct features, with g values between 6.3 and 1.5. Such spectra arise from an electronic state with effective spin S'=(1/2), indicating that the high-spin (S=3/2) ground level is split into two spin doublets differing in energy by an amount large compared with the microwave quantum, but small in relation to thermal energies at ambient temperature. This situation would occur in a tetrahedral system suffering a large rhombic distortion. Calculations based on this model accounted for apparent discrepancies in integrated spectral intensities, and yielded magnetic moments in good agreement with independent measurements, especially in the case of certain small Co(II) complexes resembling the enzyme adducts in their e.p.r. signals. Precise sets of g values, reflecting a particular co-ordination geometry, were found to be representative of each enzyme variant and the type of sulphonamide inhibitor, whether benzocyclic or heterocyclic. A series of substituted benzene sulphonamides bound to the same enzyme gave rise to closely similar spectra despite a wide range of pK(i) values. Thus benzocyclic and heterocyclic sulphonamides were evidently held in the active-site cleft in characteristic orientations irrespective of side chains that might considerably influence the total binding strength. Visible absorption spectra of various sulphonamide adducts at room temperature showed a similar pattern of inhibitor dependence to the e.p.r. spectra, suggesting a correspondence between the co-ordination structures in liquid and frozen solution. E.p.r. spectra of the sulphonamide complexes were remarkable not only for their range of g values, but also for their variations in line-width and spin-lattice relaxation behaviour. Addition of glycerol to the medium produced marked enhancement in resolution, owing to the creation of a more homogeneous frozen matrix. The non-uniform spin relaxation was probably a consequence of the large anisotropy in effective g tensor.     

Metabolic Regulation by Homoserine in Escherichia coli B/r

A mathematical analysis of branched pathway regulation has led to the prediction of a novel homoserine control in Escherichia coli B. Experimental support for such control is presented in this paper. Homoserine, the precursor of both threonine and methionine, inhibits nicotinamide adenine dinucleotide phosphate (NADP(+))-specific glutamate dehydrogenase (EC 1.4.1.4), the enzyme catalyzing the first reaction in ammonia assimilation. Physiological and biochemical evidence for this effect are offered. Homoserine depresses the growth rate of the organism, and glutamate, the product of the inhibited reaction, reverses this effect. The NADP(+)-specific glutamate dehydrogenase activity in cell-free extracts is inhibited by homoserine, and this inhibition parallels the restriction of growth rate. These effects are found in other enteric bacteria which share a similar overall pattern of control for the amino acids derived from aspartate. On the other hand, a sampling of more distantly related species which have different pathways and/or regulatory patterns provides no evidence for homoserine inhibition of the glutamate dehydrogenase reaction.     

Simple Medium for Pigment Production by the Erythrasma Diphtheroid

A simple method for the isolation and identification of the causative diphtheroid of erythrasma, Corynebacterium minutissimum, utilizes Muiller-Hinton Agar.     

A note on the diffusion approximation for single neuron firing problems

Summary This paper presents a well-known stochastic model used to describe the firing or discharge pattern of a single neuron in terms of various input processes, and shows how the potential level of the neuron can be given by means of a diffusion equation approximation. There is a discussion of the adequacy of this approximation, and the paper concludes with a brief discussion of first passage time problems.Supported in part by a grant from the Alfred P. Sloan Foundation to the Committee on Mathematical Biology and by a grant of the Statistical Branch, Office of Naval Research to the Department of Statistics, University of Chicago.