In vitro growth of murine T cells. IV. Use of T-cell growth factor to clone lymphoid cells

Murine bone marrow cells can suppress the in vitro primary antibody response of normal spleen cells without apparent cytotoxicity. The bone marrow cells suppress the response to both T-dependent (SRBC) and T-independent (DNP-Ficoll) antigens. When bone marrow cells are fractionated on a sucrose density gradient, the suppressive activity is found in the residue rather than the lymphocyte fraction. The suppressive activity is either unaffected or enhanced by treatment with anti-T- and anti-B-cell serums. Pretreatment of mice with phenylhydrazine which reduces the number of pre-B cells did not reduce the suppressive activity of their bone marrow cells. Suppressive activity is abolished by irradiation of the marrow cells in vitro with 1000 R prior to assay. The activity is present in the marrow of thymus deficient (nude) mice, infant mice, and mice which have been made polycythemic by transfusion. Furthermore, the suppressor cell can phagocytize iron carbonyl particles, is slightly adherent to plastic and Sephadex G-10, and can bind to EA monolayers. We conclude that the suppressor cell is not a mature lymphocyte or granulocyte nor a member of the erythrocytic series, but is likely to be an immature cell possibly of the myeloid series. We speculate on the physiologic role of this cell.     

Asymmetry of the phospholipid bilayer of rat liver endoplasmic reticulum

The phospholipids of intact microsomal membranes were hydrolysed 50% by phospholipase C of Clostridium welchii, without loss of the secretory protein contents of the vesicle, which are therefore not permeable to the phospholipase. Phospholipids extracted from microsomes and dispersed by sonication were hydrolysed rapidly by phospholipase C-Cl. welchii with the exception of phosphatidylinositol. Assuming that only the phospholipids of the outside of the bilayer of the microsomal membrane are hydrolysed in intact vesicles, the composition of this leaflet was calculated as 84% phosphatidylcholine, 8% phosphatidylethanolamine, 9% sphingomyelin and 4% phosphatidylserine, and that of the inner leaflet 28% phosphatidylcholine, 37% phosphatidylethanolamine, 6% phosphatidylserine and 5% sphingomyelin. Microsomal vesicles were opened and their contents released in part by incubation with deoxycholate (0.098%) lysophosphatidylcholine (0.005%) or treatment with the French pressure cell. Under these conditions, hydrolysis of the phospholipids by phospholipase C-Cl. welchii was increased and this was mainly due to increased hydrolysis of those phospholipids assigned to the inner leaflet of the bilayer, phosphatidylethanolamine and phosphatidylserine. Phospholipase A₂ of bee venom and phospholipase C of Bacillus cereus caused rapid loss of vesicle contents and complete hydrolysis of the membrane phospholipids, with the exception of sphingomyelin which is not hydrolysed by the former enzyme.     

Changing behavior of surface immunoglobulin on mouse B lymphocytes during immune development: I. LPS-induced changes in the lateral mobility of B lymphocyte surface immunoglobulins on two populations which express different surface immunoglobulin phenotypes

The redistribution of surface membrane immunoglobulin molecules (sIg) was studied in two functionally distinct populations of mouse splenic B lymphocytes, namely, those bearing membrane IgM(IgG^?) and those bearing IgG. Brief exposure to mitogenic doses of bacterial lipopolysaccharide (LPS) produced direct but differential effects on the subsequent ability of specific antibodies to induce this redistribution on each cell type. Studied as a function of temperature, antibody-induced redistribution of sIgM on cells previously exposed to LPS was observed to occur at temperatures lower than the temperatures required for similar sIgM redistribution on lymphocytes not exposed to LPS. In contrast, mitogen-treated sIgG⁺ cells demonstrated an opposite and long-lasting effect (at least 40 hr), requiring higher temperatures to allow sIgG movement comparable to that seen on untreated sIgG-bearing lymphocytes. Thus, we conclude that LPS interacts with both IgM⁺(IgG^?) and IgG⁺ lymphocytes, but that such interactions produced different membrane effects on each B-cell subset. This membrane change can therefore be useful as a quasi-functional differentiation marker. Furthermore, differences in sensitivity to cellular activation by LPS seen between sIgM-bearing (sIgG^?) and sIgG-bearing B cells may be a reflection of such direct, although different, membrane effects.     

Recent increase in body size of the American marten Martes americana in Alaska

Using museum specimens, we studied recent changes in skull size of the American marten Martes americana , in continental Alaska. In Alaska, global warming has resulted in milder winters that may contribute to an improved food supply in the wild. In the present study, we tested the hypothesis that body size of the marten had increased during the second half of the 20th century, in response to global warming. We found that skull size, and by implication body size, increased significantly during the second half of the 20th century, possibly due to an improved food supply and/or lower metabolic demands in winter. Improved food availability in winter may result from the improved nutritional conditions for prey, and/or from increased access to prey resulting from a longer snow-free season. Longitude had a significant positive effect on skull size and a significant negative effect on teeth size. In Alaska, the climate is milder along the western coast and becomes harsher inland. Hence, the milder climate was associated with larger body size providing further support for our prediction that body size of the American marten was influenced by food availability and reduced energy expenditure. The negative relationship between longitude and teeth size may indicate a trend towards a larger prey in inland marten populations, but we have no data to support or refute this hypothesis.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 701–707.     

Carnitine transport by rat kidney cortex slices: stimulation by dibutyryl cyclic AMP+.

The transport of carnitine by rat kidney cortex slices against a concentration gradient has been demonstrated. Similarities to other transport systems included a linear period of uptake, as well as indications of saturability of the system with increasing concentrations of substrate. The transport of carnitine was inhibited by anoxia, and carbonyl cyanide-m-chloro-phenylhydroxazone (CCC1P), an uncoupler of oxidative phosphorylation. Carnitine uptake was stimulated approximately 50% when kidney slices were treated with dibutyryl cAMP.     

A semiautomated fluorometric determination of 5-hydroxyindoles in the nanogram range

Automated determinations of 5-hydroxytryptamine and its main metabolite, 5-hydroxyindoleacetic acid, have been described (Technicon autoanalyzer). The determinations are based on an extraction procedure from deproteinized tissue extracts or cerebrospinal fluid by means of butanolheptane mixtures. The indoles are transferred from the organic phase to a water phase and determined fluormetrically with the cysteine-o-phthaldialdehyde method. The method is highly sensitive: solutions containing 1 ng/ml can be reproducibly determined. Twenty samples per hour can be passed through the system. The determination of both 5-hydroxyindoles is performed with the same manifold.     

Development of membrane-potential responsiveness by myeloid leukemia cells during neutrophilic differentiation

The ability of a myeloid leukemia cell line (HL-60) to undergo membrane electrical potential changes was followed during neutrophilic differentiation induced by 2 compounds. Membrane-potential changes were induced with 12-O-tetradecanoylphorbol 13-acetate (TPA) or formyl-methionyl-leucyl-phenylalanine (FMLP) and were monitored by flow cytometry. The magnitude of the membrane-potential response to TPA increased in a more uniform manner as the population of cells matured than did acquisition of mature morphology or ability to undergo the respiratory burst in response to TPA. The response to TPA and FMLP of HL-60 cells, maximally induced to differentiate by dimethylsulfoxide, closely resembled that of neutrophils. Thus, HL-60 cells may be a useful tool in the study of the relation between membrane depolarization and subsequent cellular activation.     

Analysis of the effects of cesium ions on potassium channel currents in biological membranes

Cesium ions block potassium channels in biological membranes in a voltage dependent manner. For example, external cesium blocks inward current with little or no effect on outward current. Consequently, it produces a characteristic N-shaped current-voltage relationship. We have modeled this result by single file diffusion of ions in a narrow channel spanning the membrane with a special blocking site in the channel for cesium ions. The model enables us to make detailed comparisons of the effects of cesium on potassium channels in different types of biological membranes.     

Space use and genetic structure do not maintain color polymorphism in a species with alternative behavioral strategies

Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics, and evolutionary maintenance of alternative strategies in color polymorphic species. Despite the prevalence of color polymorphic species as model systems in evolutionary biology, the interaction between space use and genetic structuring of morphs within populations has rarely been examined. Here, we assess the spatial and genetic structure of male throat color morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male color morphs do not differ in morphology but differ in aggressive and antipredator behaviors as well as androgen levels. Despite these behavioral and endocrine differences, we find that color morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to nonrandom pre‐ or postcopulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure, and nonrandom mating do not appear to be primary mechanisms maintaining color polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with color polymorphism.     

A near-infrared method for studying hydration changes in aqueous solution: Illustration with protease reactions and protein denaturation

Proteins undergoing protease reactions, heat denaturation, or interactions with sodium dodecyl sulfate (SDS) were used to demonstrate the effectiveness of a near-infrared method for the quantitative study of changes in hydration or water binding during such processes. The spectra of different proteins showed that the liberation of $\text{COO}{}^{\mathrm{?}}\text{and NH}{}_3{}^{\mathrm{+}}$ groups during a protease reaction is associated with a large increase in hydration and excluded volume. On the basis of experiments with model compounds, other spectral changes, including development of continuum absorbance between 1.55 and 1.85 μm and a band with a peak near 2.1 μm, were also attributed to the liberation of these groups. After heat denaturation or in the presence of SDS, the rate of proteolytic hydrolysis was markedly increased, consistent with the view that some preliminary denaturation is necessary for protease activity. The validity of the hydration changes calculated for protease reactions was supported by model studies with l-lysine, and with poly-l-lysine before and after hydrolysis. The near-infrared spectrum of the protein substrate with no added protease was largely unaffected by heat treatment alone, indicating that the hydration as such was not changed to a large extent by the structural modifications of denaturation. In contrast to the protease reaction, the interactions between SDS and the proteins resulted in a decrease in hydration. Results of this paper are compared with those obtained from other methods. Some unique advantages of the near-infrared method for the study of hydration changes during reactions in aqueous solution are described.