Genetic control of effector cell characteristics: con A-induced suppressor cells carry H-2 I region encoded determinants.

Activation of splenic lymphocytes with Con A leads to the formation of suppressor cells capable of interfering with the activity of several polyclonal B-cell-activating substances. Thus, these suppressor cells, or their products, most probably act directly on B cells. Suppressor cells could be recovered from the effluent cell population of nylon wool columns, and they were absent from the spleens of athymic nude mice. Furthermore, they were absent from the thymus of normal as well as cortison-treated mice. Cortisone treatment did not abolish the formation of Con A-induced suppressor cells in the spleen. Treatment of activated suppressor cells with antisera specific for distinct products of the H-2 I region revealed that they carried I-J cell surface antigens. We conclude that the suppressor cells in our test system, which unlike other Con A-induced suppressor cell populations have a direct effect on B cells, had antigenic characteristics similar to those previously described for I-J carrying suppressor cells.     

The fine structure of psychrophilic and mesophilic Rhodotorula rubra

Transmission electron microscopy of thin sections of two mesophilic and a psychrophilic Rhodotorula rubra revealed structures normally associated with yeast. The capsule of all three strains was thicker in the cells grown in glucose than those grown in glucose-free media. The cell wall of all three strains showed more lamellae in the cells grown in a medium containing glycerol. Budding was of the Rhodoturula type. Endoplasmic reticula running parallel to the nucleus were commonly observed in the psychrophiles but not in the mesophiles. In the psychrophile, in association with the plasmalemma, lomasomes and plasmalemmasomes were observed. Giant mitochondria were commonly seen in the cells grown in a fermentable carbohydrate-free medium. Vacuoles were mostly empty.     

The effects of chemotactic factors on the adhesiveness of rabbit neutrophil granulocytes.

A range of chemotactic factors has been shown to affect the adhesion of rabbit peritoneal neutrophil granulocytes to cultured endothelial cells and to serum-coated glass. At chemotactically optimal concentrations, α_s-casein, β-casein, alkali denatured human serum albumin (HSA) and several synthetic formyl-peptides reduced the number of adherent neutrophils after 30 min to around 50% of control values. These effects were still observed after neutrophils, but not endothelium or serum-coated glass had been exposed to chemotactic factors and washed before use in assays. Two non-chemotactic analogues, native HSA and a non-formyl-peptide were ineffective. The dose responses for adhesion after 30 min in the presence of α_s-casein and formyl-methionyl-leucyl-phenylalanine (FMLP) were found to be inversely related to those for migration towards these substances. After incubation for 60 min in high (10^?8–10^?7 M) concentrations of FMLP, neutrophil adhesion was found to be enhanced. Neutrophil aggregation was also affected by the presence of chemotactic factors in a similar time- and dose-dependent manner to the adhesion to substratum assays. Using FMLP, it was also shown that the timing of the adhesive changes depended on the concentration of chemotactic factor present.     

Long-lasting synaptic potentials and the modulation of synaptic transmission.

Long-lasting postsynaptic potentials (PSPs) generated by decreases in membrane conductance (permeability) have been reported in many types of neurons. We investigated the possible role of such long-lasting decreases in membrane conductance in the modulation of synaptic transmission in the sympathetic ganglion of the bullfrog. The molecular basis by which such conductance-decrease PSPs are generated was also investigated. Synaptic activation of muscarinic cholinergic receptors on these sympathetic neurons results in the generation of a slow EPSP (excitatory postsynaptic potential), which is accompanied by a decrease in membrane conductance. We found that the conventional "fast" EPSPs were increased in amplitude and duration during the iontophoretic application of methacholine, which activates the muscarinic postsynaptic receptors. A similar result was obtained when a noncholinergic conductance-decrease PSP--the late-slow EPSP--was elicited by stimulation of a separate synaptic pathway. The enhancement of fast EPSP amplitude increased the probability of postsynaptic action potential generation, thus increasing the efficacy of impulse transmission across the synapse. Stimulation of one synaptic pathway is therefore capable of increasing the efficacy of synaptic transmission in a second synaptic pathway by a postsynaptic mechanism. Furthermore, this enhancement of synaptic efficacy is long-lasting by virtue of the long duration of the slow PSP. Biochemical and electrophysiological techniques were used to investigate whether cyclic nucleotides are intracellular second messengers mediating the membrane permeability changes underlying slow-PSP generation. Stimulation of the synaptic inputs, which lead to the generation of the slow-PSPs, increased the ganglionic content of both cyclic AMP and cyclic GMP. However, electrophysiological analysis of the actions of these cyclic nucleotides and the actions of agents that affect their metabolism does not provide support for such a second messenger role for either cyclic nucleotide.     

Differentiation of the formaldehyde-induced fluorescent products of noradrenaline and dopamine by microspectrofluorometry

Synopsis The influence of concentration of dopamine and noradrenaline on the spectral characteristics of their formaldehyde-induced fluorophore, together with the influence of duration of reaction with formaldehyde, has been investigated in a model system. No substantial differences between fluorescence spectra of the amine fluorophores were observed. Accordingly, the influence of hydrochloric acid and ammonia vapours on the fluorophores was investigated. A shift to shorter wavelengths in the excitation maximum of each fluorophore was observed after a brief exposure to hydrochloric acid vapour; more prolonged exposure resulted in a pronounced shift back to longer wavelengths in the case of noradrenaline but no substantial change was observed with dopamine. Brief exposure to hydrochloric acid vapour resulted in a substantial increase in the rate of fading of the noradrenaline fluorophore on exposure to exciting radiation. It is suggested that this offers a convenient way of differentiating the amines.     

Types of beta-lactamase determined by plasmids in gram-negative bacteria.

Two species of beta-lactamase determined by plasmids in enteric bacteria that show some resemblance to TEM enzymes are described. Both are distinct from all other plasmid-mediated beta-lactamases and differ from the TEM beta-lactamases in ability to hydrolyze some substrates, in isoelectric point, in immunological specificity, and in susceptibility to inhibition. One of the enzyme species, mediated by plasmid p453, has been briefly described previously. We have discovered that this beta-lactamase, designated SHV-1, is unique in its response to inhibition by the sulfhydryl group reagent p-chloromercuribenzoate, because the hydrolysis of cephaloridine but not that of benzylpenicillin is affected. This enzyme is found in a variety of plasmid types which were transferred from several bacterial species collected from a wide geographic range. The other enzyme species is novel; only a single plasmid determining this kind of beta-lactamase (designated HMS-1) has been detected.     

Purification of murine oncornaviral phosphoproteins using alkyl agarose derivatives..

Methods for the purification of both murine mammary tumor (type B) and murine leukemia (type C) oncornaviral phosphoproteins are described, in which chromatography on alkyl-agarose derivatives is used as the primary fractionation step. Gel filtration or ion exchange chromatography on phosphocellulose was the only subsequent step required for the purification of the type B and type C viral proteins, respectively. The two-step protocols also resulted in the co-purification of a low molecular weight core protein from each virus. Recoveries of the viral proteins purified by this method, based on per cent contribution of individual polypeptides to total virion proteins, were 70% or greater. Radioimmunocompetition analysis of the purified murine mammary tumor virus major core protein as well as analysis of the RNA binding properties of purified low molecular weight type C virus proteins suggests that neither antigenic reactivity nor specific RNA binding characteristics are altered by the purification protocols. The availability of these procedures should aid studies on the possible function and immunochemical properties of the native murine oncornaviral phosphoproteins and may also be extended to the purification of other oncornaviral proteins.     

Human Territoriality: An Ecological Reassessment

The question of human territoriality has frequently been debated, but most previous discussions have not sufficiently emphasized ecological variables as major factors determining territoriality. We argue that current theories in sociobiology, especially the model focusing on economic defendability of resources, need to be considered in analyzing human territoriality. According to this model, territoriality is expected to occur when critical resources are sufficiently abundant and predictable in space and time, so that costs of exclusive use and defense of an area are outweighed by the benefits gained from resource control. This model is developed, and then applied to several locally adapted human populations (Northern Ojibwa, Basin-Plateau Indians, and Karimojong). Variations in territorial responses for these groups seem to accord with the predictions of the economic defendability model . [territoriality, resource defense, human ecology, sociobiology, spatial organization]     

New syntheses of deuterated protoporphyrin-IX derivatives for heme protein nmr studies

An efficient total synthesis of 1,5-di(trideuteromethyl)protoporphyrin-IX (3) dimethyl ester from monopyrrole precursors is described, the synthesis proceeding through crystalline tripyrrene and a,c-biladiene salt intermediates. The 2- and 4-vinyl groups in (3) are formed from the corresponding (2-chloroethyl) substituents by way of base-promoted dehydrochlorination. In protio solvents, this synthetic step is shown to exchange out preferentially deuterons in the 1-methyl group, and this observation is exploited in an efficient synthesis of the 1,3-di(trideuteromethyl)protoporphyrin-IX (22) dimethyl ester from 2,4-diacetyldeuteroporphyrin-IX (20) dimethyl ester (which is in turn accessible from commercially available protoporphyrin-IX (5)). Thus, basic exchange in deuterated solvent of (20) gives the deuterated analog, which after reduction and dehydration gives the 1,3-di(trideuteromethyl)protoporphyrin-IX analog (22), in which the vinyl H₂ and propionic CH₂·CO functions have also become deuterated.     

On the study of two interacting populations one of which acts independently of the other

Many ecological and biological systems can be studied in terms of a bivariate stochastic branching process, {X ₁ (t), X ₂ (t)}, each of whose components (or populations) varies in magnitude according to the laws of a generalized birth-death process. Of particular interest is such a model in which the birth and death rates of the first population,X ₁, are constant while those of the second population,X ₂, exhibit a functional dependence upon the magnitude of the first. It is shown, first, that the existence of the stochastic mean of a birth death process implies the existence of all higher moments. The values of all the factorial moments of such a process are then determined. The moments of the dependent population of the bivariate process are given in terms of its expectation and the joint probability density function of the process is determined. It is possible, therefore, to use Bayesian techniques to infer conclusions about the independent population, given information about the variation of the dependent one.