Microwaves induce an increase in the frequency of complement receptor-bearing lymphoid spleen cells in mice.

A single 30-min exposure of mice to 2450 MHz microwaves (12 to 15 mW/g body weight) in an environmentally controlled waveguide facility induced a significant increase in the proportion of complement-receptor positive lymphoid cells in the spleen. This effect was further enhanced by repeated (three times) exposures, which in addition produced a significant increase in the proportion of Ig+ cells. The proportion of theta-positive cells and the total number of spleen cells remained unchanged.     

Effect of microwaves (2450-MHz) on the immune system in mice: studies of nucleic acid and protein synthesis

CBA/J adult male mice were given single or triple exposures to 2450-mHz microwaves in an environmentally controlled wave guide facility. The average absorbed dose rate for a single exposure varied from 12 to 15 mW/g. Sham-exposed mice served as controls. Lymphoid cells were collected and tested for metabolic activity on days 3, 6, and 9 following a single exposure, and on days 9, 12, and 16 following triple exposures on days 0, 3, and 6. Cells were cultured in vitro for four hours to seven days before their metabolic rates were assayed. Under these conditions, microwaves failed to produce any detectable change in deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein synthesis, as measured by the incorporation of methyl(3H)-thymidine (3H-TDR) (DNA substrate), 3H-uridine (3H-UR) (RNA substrate), and 3H-leucine (protein substrate) by spleen, bone marrow, and peripheral blood lymphocytes (PBL) in vitro. These data suggest that microwave-induced increases in the frequency of complement-receptor (CR)- or surface-immunoglobulin (sIg)-bearing cells were not associated with a concomitant increase in cell proliferation and/or protein synthesis, and favor the concept that microwaves under these conditions stimulate already existing B-cell precursors for maturation.     

Studies on non-H-2-linked lymphocyte-activating determinants. IV. Ontogeny of the Mls product on murine B cells.

The minor lymphocyte stimulating (Mls) locus codes for lymphocyte activating determinants (LADs) on murine B lymphocytes, but not T lymphocytes. This observation was strengthened by a series of techniques which allow deletion and addition of T and B cells. These included the use of cytotoxic antisera such as anti-Thy 1.2, anti-MTLA, anti-MBLA, and complement, and the use of a goat anti-μ antisera, and finally the use of a fluorescence activated cell sorter (FACS).The studies in this report document the organ distribution and the ontogenetic appearance of the surface LADs on the surface of B lymphocytes from DBA/2N (H-2^d, Mls^a) and CBA/J (H-2^k, Mls^d) mice. Adult-like ability to stimulate H-2 identical BALB/c (H-2^d, Mls^b) and C3H/He (H-2^k, Mls^c) responder cells appeared at about 4–5 weeks of age. Inability of neonatal cells to induce an Mls-defined MLC was found not to be due to a low frequency of B lymphocytes or to the presence of suppressor cells, but due to the absence of the Mls-coded LADs on their surface. These data support the concept that the Mls-coded LADs are present on adult B lymphocytes and are specific markers of B-cell differentiation, which is preceded by membrane IgM and the δ homologue of human IgD, Ia, and the receptor for the third component of complement.     

Size-frequency estimates of secondary production byMysis relicta in Lakes Michigan and Huron

Data from five Great Lakes studies ofMysis relicta populations were reanalyzed to calculate secondary production estimates using the size-frequency method. Production estimates (P) ranged from 0.25 to 3.2 g dry weight m^–2 yr^–1. Average annual biomass {xxB} and mean annual density (xxD) were 0.11–1.11 g dry weight/ m² and 25–434 animals/ m², respectively. P:{xxB} ratios varied only between 2.2 and 3.3. Maximum and minimum biomass values within a study varied by a factor of 519 for one study but by less than 17 for the others. Highest estimates of P, {xxB} and {xxD} were calculated for collections from a 50-m station in Lake Michigan despite the larger populations suspected to be present at greater depths sampled in the other studies. These conservative estimates provide a basis for scaling trophic interactions involvingM. relicta and emphasize findings by previous workers that night-time sampling with vertical net hauls is the best available technique for quantitative studies ofM. relicta populations in the Great Lakes.     

Surface immunoglobulin on rabbit lymphoid cells. III. Double expression and separate endocytosis of surface immunoglobulin allotypes on heterozygous lymphocytes demonstrated by immunoelectron microscopic labeling.

The expression of immunoglobulin b locus (k chain) allotypes on the surface of rabbit peripheral blood lymphocytes (PBL's) is examined using an indirect double immunoelectron microscopic labeling technique. Ferritin and whelk hemocyanin individually conjugated to allotypically specific IgG are used as ultrastructurally identifiable molecular markers. These indicators are coupled to lymphocyte surface immunoglobulin (Ig) allotypic determinants by an antiallotype antibody linkage. Human red blood cells, conjugated with IgG of a specific allotype and used as test cells, demonstrate the absolute specificity and high efficiency of the ultrastructural labeling technique. Specific labeling on rabbit PBL's shows that 65–75% of the cells are positive for surface Ig. Lymphocytes from homozygous donors (b4b4 or b6b6) are labeled specifically with only the appropriate allotypic labeling system. Thirty-three percent of the PBL's from heterozygous donors (b4b6) express both allotypes (allelic inclusion) on the cell surface; the remaining proportion of Ig-bearing cells have only one detectable allotype present (allelic exclusion). We conclude that approximately 50% of the Ig-bearing PBL's demonstrate allelic inclusion for the b locus allotypes. On allelically included heterozygous lymphocytes, both allotypic determinants can undergo specific endocytosis. Endocytosis of one allotype on heterozygous cells can be induced by stimulation with antiallotypic serum without affecting the surface appearance of the other allelic marker (separate endocytosis).     

Magnesium binding in the digesta of the chicken.

Two experiments involving laying hens and mature roosters were carried out to determine the effect of pH on the ultrafilterable fraction of Mg((Mg)u) present in the digesta along the gastrointestinal tract. Concurrently, the approximate molecular weight of the (Mg)u was determined. The average pH's for laying hens were: crop 4.88, proventriculus 5.27, ventriculus 4.77, duodenum 5.57, jejunum 6.15, ileum 7.82, and colon 6.65. Similar pH values were obtained for mature roosters. The (Mg)u fraction decreased significantly in the ileum where the pH was greater than 7.00. However, treating the ileal digesta with an acid pH buffer released about 70% of the nonfilterable Mg. The molecular weight of the (Mg)u was found to be less than 700, suggesting that the Mg was present in digesta as an inorganic salt or as an organic complex of low molecular weight.     

Studies on rabbit lymphocytes in vitro: XVII. Kinetics of reversible concanavalin a stimulation and restimulation of blast transformation after blocking with α-methyl-d-mannopyranoside

The stimulation of transformation of rabbit peripheral blood lymphocytes by Concanavalin A (ConA) has a narrow dose optimum, is reversible by α-d-methyl-mannopyranoside (MAM) and cultures that have been stimulated and reversed may be restimulated by removal of the blocking saccharide and re-addition of ConA. The kinetics of the stimulatory dose of ConA, the blocking dose of MAM, and the time of stimulation and blocking indicate a competitive binding of lymphocyte receptors and blocking saccharide for ConA. Most of the lymphocytes that respond to ConA become enlarged during the first 16–24 h after stimulation, although fully developed ‘blast’ cell transformation and mitosis do not occur until after approx. 40 h. Lymphocytes that are held in vitro prior to ConA stimulation gradually lose the ability to respond to ConA stimulation (delayed stimulation). Morphologic and metabolic analysis of ConA-stimulated and MAM blocked cultures demonstrate (1) that RNA synthesis gradually decreases in blocked cultures at a time that it is increasing in stimulated cultures; (2) that cells enlarged after ConA stimulation become smaller following MAM inhibition; (3) that the ability of blocked cells to be restimulated by ConA gradually decreases following MAM block (delayed restimulation). Lymphocyte activation requires the continued presence of the stimulant for consumation of the transformation process, and activated cells that have been blocked have a temporary ability to respond to restimulation at a time when cells that have not been preactivated are unable to respond. The requirement of increasing amounts of blocking MAM to reverse stimulation by ConA as the time of contact of ConA with the cells in culture increases is consistent with the concept that internalization, or stripping of mitogen or cellular receptors is the important cellular event initiating transformation. Blocking is achieved by permitting re-externalization of lectin or cell surface receptors. Stimulation requires the continued internalization or stripping of newly formed receptors by reaction with the stimulating mitogen during the entire culture period prior to initiation of DNA synthesis.     

Studies on rabbit lymphocytes in vitro : XX. Demonstration of cells reactive to more than one mitogen by mixed sequential stimulation

Rabbit peripheral blood lymphocyte (PBL) cultures stimulated by ConA and then blocked by the addition of competing sugar or antiserum after 6–15 h of ConA prestimulation respond to restimulation by PHA or PWM to a much greater extent than to continuous stimulation or delayed stimulation with PHA or PWM. This effect of mixed lectin sequential stimulation indicates that many of the same PBLs will respond to more than one mitogen, but that some cells require preactivation by one mitogen in order to respond fully to another mitogen. Thus, the number of PBLs which respond to PHA or PWM alone is much less than the number which respond following pretreatment with ConA when the pretreatment effect of ConA alone is blocked. Rabbit PBLs do not respond to LPS and preactivation by ConA does not prepare rabbit PBLs to respond to LPS.     

Production and characterization of monoclonal antibodies to rabbit lymphocyte subpopulations. I. Tissue immunofluorescence and flow cytometric analysis

Nine monoclonal antibodies to rabbit T cells and B subpopulations have been generated from three separate fusions of spleen cells from mice immunized with fractionated populations of rabbit lymphocytes. These monoclonal antibodies, as well as a previously described rabbit T cell monoclonal antibody, 9AE10, have been analyzed by immunofluorescence staining on frozen tissue sections of rabbit thymus, spleen, and appendix. This screening method permits rapid identification of the lymphocyte subdomains in each tissue which is not possible by other screening methods. Each monoclonal antibody selected has a unique tissue staining pattern. Flow cytometric analysis of these monoclonal antibodies, using indirect immunofluorescence techniques on thymocytes, splenocytes, and PBL, revealed varying percentages of positive cells and individual mean fluorescence intensities indicating different epitope densities for each antigen. These monoclonal antibodies are now being used to characterize normal lymphocyte function and the role of specific lymphocyte subpopulations in experimental disease models in the rabbit.