Evolution of epitopes on human and nonhuman primate lymphocyte cell surface antigens

The T- and B-cell surface polypeptides detected by an international workshop panel of 100 mouse monoclonal antibodies (M.Ab) were biochemically defined by radioimmunoprecipitation. Eight T-cell-associated molecules and eight B-cell-associated molecules were identified by multiple antibodies in the panel. Clusters of antibodies specific for the same polypeptide were then compared for their reactivity against peripheral blood mononuclear cells (PBMC) from 11 nonhuman primate species. All the major T- and B-cell antigens present in humans were also expressed in some nonhuman primates. M.Ab to the same antigen were found to react with distinct epitope groups that differed in their phylogenetic distribution. Some epitopes were highly conserved, while other epitopes on the same molecule were only expressed in hominoids and were not detected in old world and new world monkeys. Our detailed analysis of the phylogeny of 37 T-cell antigen epitopes on ten different molecules revealed there was no clear correspondence between the number of epitopes shared and evolutionary distance. Rather the data suggest that parallelism with back mutation may be a common mechanism in the evolution of T-cell antigens. The data also show that the tissue distribution of T-cell antigens can differ between primate species; for example, M.Ab to human Tp45 Tla-Qa-like antigens that did not react with human PBMC did react with PBMC from new world monkeys.     

Les effets de recristallisation sur la paroi des Involutinidae (Foraminifères) triasiques

The different types of recrystallization which can be observed in the Triassic involutinids should be considered in the taxonomic treatment of this foraminiferal family. If the diagenetic modifications of the test are neglected the same form could be placed into different suborders. Our inclusion of the genusTriasina Majzon in the Involutinidae proposed earlier on purely morphologic grounds, seems to be supported by the fact that the same types of recrystallization exist inTrocholina, Involutina undTriasina.     

A model describing photosynthesis in terms of gas diffusion and enzyme kinetics

Summary A model predicting net photosynthesis of individual plant leaves for a variety of environmental conditions has been developed. It is based on an electrical analogue describing gas diffusion from the free atmosphere to the sites of CO₂ fixation and a Michaelis-Menten equation describing CO₂ fixation. The model is presented in two versions, a simplified form without respiration and a more complex form including respiration. Both versions include terms for light and temperature dependence of CO₂ fixation and light control of stomatal resistance. The second version also includes terms for temperature, light, and oxygen dependence of respiration and O₂ dependence of CO₂ fixation.The model is illustrated with curves based on representative values of the various environmental and biological parameters. These curves relate net photosynthesis to light intensity, [CO₂], [O₂], temperature, and resistances to CO₂ uptake. The shape of the [CO₂]-net photosynthesis curves depends on the total diffusion resistance to CO₂ uptake and the Michaelis constant for CO₂ uptake. The curves range from typical Michaelis-Menten to Blackman types.The model is combined with a model of leaf energy exchange permitting simultaneous estimation of net photosynthesis and transpiration. The combined model is illustrated with curves relating transpiration to photosynthesis under a wide variety of environmental conditions. Environmental regimes yielding maximum efficiency of water use are identified for the given assumptions and biological parameters.     

Analysis for Antigenic Similarities Among the 30S Ribosomal Proteins of Escherichia coli

Antiserum was made against a single 30S protein, 30S-7. The amount of complement fixed by total 30S protein in the presence of this antiserum indicated that protein 30S-7 was the major antigen in the mixture of proteins. Each of the 30S ribosomal proteins was tested for cross-reactivity with anti-30S-7. This was done by determining if any of the other 30S proteins inhibited complement fixation by 30S-7. None of the other 30S proteins was found to inhibit complement fixation by 30S-7, indicating that 30S-7 is antigenically distinct from the other proteins.     

Change in Properties of Physarum polycephalum Amoebae During Extended Culture

During two years of passage, several myxamoebal strains of Physarum polycephalum changed with regard to their properties in crosses and plaque morphology. These changes have been correlated with increased nuclear deoxyribonucleic acid content.     

Freeze-thaw-refreeze cycle to prepare lymphocytes for HLA antibody detection or tissue typing

Human lymphocytes stored in the frozen state may be thawed, placed on cytotoxicity plates, refrozen, rethawed and used for screening sera or tissue-typing of the cells. The simple procedure described uses only a ?90 °C refrigerator for both freezing and storage of the cells. The technique permits a laboratory to collect a variety of cells over a long period, so that a set of test plates with cells from 10 to 20 donors can be prepared when a convenient number of donor cells are available. Also, the refrozen cells in cytotoxicity test plates may be warmed to the temperature of dry ice for 24 hr, returned to the refrigerator set at a slightly lower temperature, and at a later time, these cells may be thawed and used for serum screening. In view of these results, it appears possible to ship the refrozen cells from one laboratory to another using simple dry ice storage during the transfer. Negative reactions due to soluble antigens in the suspending sera can be obviated by washing out these sera and replacing them with medium 199 or alternatively, fetal calf serum can be used to replace the human serum in the suspending media.     

Osmotic alterations of the lysosomal system during rat liver perfusion: Reversible suppression by insulin and amino acids

Livers from nonfasted rats were perfused in situ under conditions known from previous studies in this laboratory to increase or decrease overall endogenous proteolysis. At the termination of the experiments, lysosomal alterations were evaluated by the increase in free acid phosphatase or N-acetyl-β-D-glucosaminidase that occurred when tissue homogenates were subjected to osmotic shock in hypotonic sucrose. In control perfusions, osmotic sensitivity increased spontaneously over unperfused values, reaching maximum by 60 min or earlier. Additions of insulin, amino acid mixtures, or cycloheximide in amounts known to suppress proteolysis prevented this spontaneous perfusion effect or, when added at 60 min, rapidly reversed it. Glucagon alone during perfusion did not increase osmotic sensitivity further; however, stimulation with glucagon was observed when the perfusion effect was suppressed by insulin or cycloheximide. Anoxia, induced by gassing with nitrogen instead of oxygen, markedly reduced the perfusion effect and also doubled the amount of free acid phosphatase in the initial isotonic homogenates. Total acid phosphatase activities in the perfusion experiments were not significantly different from unperfused values and, with the exception of the anoxia perfusions, the amounts of free enzyme present in the initial isotonic sucrose homogenates did not change.     

Dehydrogenation of a phosphonate substrate analogue by glycerol 3-phosphate dehydrogenase

S-(+)-3,4-Dihydroxybutylphosphonic acid, an isosteric analogue of sn-glycerol 3-phosphate, was synthesized stereospecifically and shown to be an effective substrate for rabbit muscle glycerol 3-phosphate dehydrogenase (sn-glycerol 3-phosphate-NAD(+) oxidoreductase, EC 1.1.1.8). Non-isosteric phosphonate analogues of sn-glycerol 3-phosphate showed neither substrate nor inhibitory activity with the enzyme.     

Isolation and partial characterization of carbonic anhydrase from erythrocytes of Meleagris gallopavo

Summary A soluble enzyme with carbonic anhydrase activity has been isolated from domestic turkey(Meleagris gallopavo) erythrocytes and purified by chloroformethanol precipitation, ammonium sulfate fractionation and gel filtration on a Sephadex G-75 column. Analytical polyacrylamide gel disc electrophoresis showed one major and two minor bands. The specific activity for the CO₂ hydration reaction was approximately 2000 Wilbur-Anderson units/mg protein at 0°C. The presence of the reducing agents 2-mercaptoethanol or dithioerythritol was required throughout the procedure. Upon removal of the 2-mercaptoethanol by dialysis the activity was lost but could be restored by addition of the reducing agent. The enzymatic activity was inhibited by acetazolamide,p-chloromercuribenzoate ando-iodosobenzoate. Esterase activity was detected withp-nitrophenylacetate as the substrate. The molecular weight of the enzyme was determined as 31,000 by gel filtration and 34,000 ± 2000 with analytical ultracentrifugation. Atomic absorption spectroscopy indicated the presence of zinc in the ratio of one mole of zinc per one mole of enzyme.