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Biomedical subjects

R H Stevens

Publications and source records attributed to R H Stevens.

At least 91 records · Page 5Linked to original sources
PubMed1981

Analysis of human anti-diphtheria antibodies by isoelectric focusing: evidence for restricted clonal heterogeneity of anti-fragment A antibodies.

The in vivo human humoral response to diphtheria toxoid-tetanus toxoid booster immunization was studied by isoelectric focusing analysis of sera obtained after immunization. The anti-diphtheria toxoid (immunoglobulin G [IgG]-Dip), anti-fragment A (IgG-Frag A), and anti-tetanus toxoid antibodies from 20 donors post-booster immunization were focused by using agarose isoelectric focusing and visualized by development with radiolabeled antigens. The quantities of the IgG-Dip and IgG-Frag A antibodies correlated with the number of bands seen on the isoelectric focusing pattern in that more bands were found in the spectrotypes of donors with high serum levels of antibody. No difference was apparent in the antibody spectrotypes obtained from sera of donors at successive times post-booster immunization. Individual heterogeneity of the different donors' spectrotypes was often found for IgG-Frag A antibodies, but a close comparison of several different donors revealed antibodies with the same spectrotype patterns. Thus, individual clones of antibody were revealed in humans after in vivo immunization, particularly when antibodies against antigens of restricted epitope size were analyzed. Additionally, the sharing of certain antibody spectrotypes among several individuals raised the possibility that certain antibody clones may be preferentially expressed in the human population.

Antibody Specificity↗
PubMed1981

Adenosine and guanosine 3',5' cyclic monophosphate phosphodiesterase activities in rat small and large bowel following single and multiple exposure to 1,2-dimethylhydrazine.

The hydrolytic activities of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) phosphodiesterases (PDE) in rat large and small bowel tissue were determined after exposure to the colon carcinogen 1,2-dimethylhydrazine (DMH). Immediate increases in the cAMP-PDE activities were found in the tissues after a single exposure to the chemical which returned towards normal while chronic exposure resulted in no visible changes. The increased cAMP-PDE activities may be the factor responsible for the diminished intracellular cAMP concentrations found after exposure to the carcinogen. In contrast, the cGMP-PDE activities changed little in the colon and increased in the small bowel, suggesting that the determinant for the increases in the concentration cGMP was the activation of guanylate cyclase enzymes following exposure to DMH. Ratios of cAMP to cGMP and cAMP-PDE to cGMP-PDE in the colon showed major changes after carcinogenic insult by the DMH, suggesting that such measurements might serve as useful markers for exposure to environmental toxicants.

1,2-Dimethylhydrazine↗
PubMed1981

Immunoglobulin-bearing cells are a target for the antigen-induced inhibition of pokeweed mitogen-stimulated antibody production.

In vivo immunization with tetanus toxoid causes the appearance of B cells in the circulation that can produce IgG-antitetanus toxoid antibody in vitro after stimulation by T cells and pokeweed mitogen. Addition of soluble tetanus toxoid to these cultures, however, causes a profound inhibition of the in vitro IgG, but not IgM, antitetanus toxoid antibody production. Treatment of the lymphocytes with 10 microgram of tetanus toxoid for as little as 1 hr at 37 degrees C was sufficient to promote this antigen-specific inhibition. The antigen could be added, however, as late as 3 days after the culture initiation for the inhibition to be observed. Cell separation studies indicated that the inhibitory activity could be found in both the E-rosette positive and E-rosette negative populations. Further studies on the non-E-rosetting cells showed that: 1) inhibition induced in antigen-treated cells could not be transferred to untreated cells; 2) adherent cells were not responsible for the inhibition; 3) treatment of the surface Ig+ cells with antigen was sufficient for the inhibitory effects; and 4) in vivo generated lymphoblastoid cells that produce IgG-antitetanus toxoid antibody in vitro but are surface Ig- were not inhibited by soluble antigen. The results in this study thus indicate that cells in both the E-rosette positive and negative subsets can be responsible for the antigen-induced inhibition of in vitro antibody production observed in the majority of immunized donors.

Animals↗
PubMed1981

Lymphocyte dysfunction in chronic graft-versus-host disease.

Three recipients of HLA-identical bone marrow transplants developed chronic graft-versus-host disease (cGVHD) and hypergammaglobulinemia. All three had evidence of abnormal B-lymphocyte function, including a polyclonal increase in immunoglobulins (Ig), antinuclear antibodies, rheumatoid factor, lymphocytotoxins, and increased immune complexes. T-lymphocyte function was also abnormal, including decreased mitogen reactivity and delayed cutaneous hypersensitivity. The cellular basis of these immune abnormalities was studied in an in vitro system in which we analyzed spontaneous pokeweed mitogen (PWM) driven Ig synthesis. Multiple defects in both T- and B-lymphocyte function were detected. In contrast to normal B cells, circulating B cells from all three patients with cGVHD spontaneously synthesized in vitro greater than 200 ng of IgG and in two of the three greater than 175 ng of IgM. This increase in spontaneous Ig synthesis was not due to a deficiency of regulatory cells, since T cells from the three patients suppressed spontaneous Ig synthesis in a normal fashion. In contrast to this increased spontaneous Ig synthesis, the response of the patients' B cells to PWM-driven Ig synthesis was normal. Using the PWM system we demonstrated several defects in these patients' T cells, including increased suppressor activity and decreased helper cell activity. These data indicate that some patients with cGVHD have multiple defects in both T- and B-cell function that may contribute to their profound immune deficiency.

Adolescent↗
PubMed1980

Isotype-specific human B lymphocytes that produce immunoglobulin E in vitro when stimulated by pokeweed mitogen.

Normal human peripheral blood lymphocytes can be stimulated by PWM and T cells to produce IgE in vitro. Between 4% and 10% of circulating B lymphocytes were found to bear noncytophilic membrane IgE. In contrast, limiting diluton analysis of active B cell precursor frequency revealed that only about 1 in 50,000 B cells was responsible for the synthesis of IgE in vitro. Variation inthe precursor frequency was primarily responsible for differences in the amount of IgE produced in vitro by different individuals while the amount of IgE produced per precursor cell was relatively constant. B lymphocytes with surface IgM, IgG, or IgE were depleted. Depletion of IgE-bearing cells decreased IgE production 70% to 83% while IgM-bearing-cell removal lowered IgE synthesis by 59% to 72%. Dual removal of IgM- and IgE-bearing cells did not give an additive effect. IgE- and IgM-positive B cells showed enhanced IgE synthesis of 327% and 182%, respectively. The consequences of crosslinking different surface isotypes on subsequent IgE production were also assessed. Anti-epsilon treatment inhibited IgE production up to 68% while anti-mu treatment decreased it by up to 38%. Thus only a very limited subset of B lymphocytes is responsible for PWM and T cell-dependent IgE synthesis in vitro and those cells probably bear both surface IgE and IgM.

Adult↗
PubMed1980

Profile of multiple lymphocyte functional defects in acquired hypogrammaglobulinemia, derived from in vitro cell recombination analysis.

Immunoregulatory defects in patients can be assigned to B cells, T helper cells, or T suppressor cells by means of a modification of the in vitro PWM-stimulated Ig biosynthesis assay. When lymphocyte subpopulations from patient and normal are recombined, multiple internal comparisons within a single experiment reveal the functional activity of each subpopulation. By this technique we studied nine adult patients with acquired panhypogammaglobulinemia and one with isolated IgG deficiency. Low total Ig production by the B cell fraction was demonstrated in seven of the nine panhypogammaglobulinemic patients. In four of these seven, IgG and IgA secretion was markedly reduced compared with IgM. In the two patients with normal total Ig production, elevated IgM compensated for lower IgA and IgG. The one patient with no surface Ig+ cells had a B cell defect, but no T cell defect. Reduced T help and excessive T suppression characterized two of the four patients with the most severe B cell defects. Three patients were anergic by delayed hypersensitivity skin testing and failed to sensitize to DNCB, but the patient with the most severe T cell defects in vitro was not among them. One of these three patients showed a mild T cell help defect and suppressor excess and the other two had pure B cell defects. Thus, anergy and T regulator function were not correlated. In three instances where hypersuppression was more evident by adding patient unfractionated cells than by adding patient T cells, suppression by the T depleted fraction could be demonstrated. No cases of radiation-resistant T suppression were revealed among the seven patients tested. Subnormal total protein synthesis, noted in six of seven patients with low Ig production, was invariably less marked than the Ig defect and often affected both T and B cells. One additional patient with pure IgG deficiency of 2 yr duration was essentially normal in her in vitro lymphocyte function. The general applicability of this experimental design for analysis of positive or negative immunoregulatory abnormalities is emphasized.

Adult↗
PubMed1980

In utero effects of 1,2-dimethyl hydrazine on adenosine and guanosine 3',5'-cyclic monophosphate content in rat fetal intestine.

Sperm positive 12-14-day pregnant Holtzman rats were exposed to a single subcutaneous injection (20 mg/kg body wt) of 1,2-dimethylhydrazine (DMH). Two days post-exposure, the fetal intestinal tissues were examined for their content and metabolic activities for cyclic 3',5'-adenosine monophosphate (cAMP) and cyclic 3',5'-guanosine monophosphate (cGMP). The in utero exposure to the carcinogen resulted in lowering the intracellular content of cAMP and increasing cGMP. The decreased levels of cAMP may be accounted for the finding of a corresponding increase in its breakdown by its phosphodiesterases; however, associated with the increase in cGMP was correspondingly an increase in its phosphodiesterases, suggesting the activities for synthesis of this cyclic nucleotide may be the major factor for its elevated concentration. These observations indicate that DMH may cross the placental barrier and can effect the intracellular cyclic nucleotide concentrations in the fetal tissues as well as acting as a colorectal carcinogen in the adult rat. The changes in the cyclic nucleotide levels were toward the direction expected for an increased cell proliferation; consequently, further investigations are suggested to determine whether a hyperproliferative state is induced by the DMH in the already rapidly dividing fetal intestinal tissue.

Animals↗
PubMed1980

Evidence for a defective mitochondrial membrane in 1,2-dimethylhydrazine-induced colon adenocarcinoma in rat: enhanced lipid peroxidation potential in vitro.

Enhanced lipid peroxidation potential was measured in Holtzman rat colon tumors induced by chronic subcutaneous injection of 1,2-dimethyl-hydrazine as compared with normal colonic tissue. The peroxidation potentials were determined in the mitochondrial cellular components by measuring the ferrous-ascorbate induced formation of malondialdehyde. The tumor mitochondria were found to peroxidize at a rate 8-10-fold higher than the comparable normal tissue components. In addition, we found that the mitochondria from the cancer cells exhibited reduced NADH-cytochrome c reductase activity. These observations suggest an involvement of non-enzymatic free radical flux in DMH-induced carcinogenesis, which may be the result of structurally altered mitochondrial membranes.

Adenocarcinoma↗
PubMed1980

Intracellular adenosine and guanosine 3',5'-cyclic monophosphate concentrations in rat small and large bowel following single and multiple exposures to 1,2-dimethylhydrazine.

The adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) levels were determined in the small and large intestinal tissue of rats that had been exposed to single and chronic administration of the colon carcinogen 1,2-dimethylhydrazine (DMH). A single subcutaneous injection of DMH resulted in a decrease in the intracellular concentration of cAMP and increase in cGMP beyond the levels which had been measured in the unexposed intestinal tissue and DMH induced intestinal adenocarcinomas. Recovery to normal concentrations of the cyclic nucleotides occurred within 30 days. Multiple exposures resulted in maintaining reduced levels of cAMP while cGMP was also found to be lowered upon the chronic administration. A possible explanation for these observations is the expansion of the crypt cell population consisting of replicating intestinal cells that occurs upon exposure to the carcinogen. These findings suggest that cyclic nucleotide alterations may represent a characteristic of the precancerous state of intestinal tissue and indicates further studies are warranted to determine whether these changes may serve as a useful marker in a screening program for colon cancer.

Adenocarcinoma↗
PubMed1980

Biological and chemical characterization of endotoxin from Capnocytophaga sputigena.

An endotoxin was isolated from Capnocytophaga sputigena strain 4 by a modification of the hot phenol-water method. The extraction procedure yielded a lipopolysaccharide which accounted for approximately 1.5% of the dry weight of the cells. The material was composed of 18.6% lipid (as C(15) fatty acid), 46.5% neutral sugar including 9.6% hexose, 18.3% 6-deoxy sugar, 1.0% 2-keto-3-deoxy sugar, and 4.8% heptose. Hexosamine, protein, and phosphorus were found in quantities amounting to 9.0, 2.9, and 2.0% of the dry weight, respectively. No pentose or nucleic acid was detected. Acid hydrolysis resulted in the release of the constituent sugars and the formation of an insoluble precipitate. The lipopolysaccharide was tested for numerous biological activities characteristic of endotoxins. The pyrogenicity was relatively low; the fever index 40 was 17 mug, and 10 mug was required to give the characteristic biphasic fever response. The toxicity of the extract was very low, with a 50% chicken embryo lethal dose of 15.6 mug and a 50% mouse embryo lethal dose of greater than 8 mg. Similarly, the C. sputigena endotoxin had modest effects on leukocytes when compared with endotoxin standards from other organisms. The extract exhibited little or no mitogenicity when tested on mouse spleen lymphocytes. It was not toxic to human peripheral polymorphonuclear leukocytes and caused the release of only a small (13%) portion of lysosomal enzymes. Although the C. sputigena lipopolysaccharide caused significant activation of mouse peritoneal macrophages, the dose required was twice that of an Escherichia coli endotoxic standard. However, the Limulus amoebocyte lysate clotting activity of the lipopolysaccharide was comparable to that of an Serratia marcescens lipopolysaccharide standard, and passive hemagglutination tests revealed that 1 mug of the lipopolysaccharide was capable of sensitizing 1 ml of a 2% sheep erythrocyte suspension for agglutination with an antiserum prepared against C. sputigena whole cells.

Animals↗
PubMed1980

Detection of a fibroblast proliferation inhibitory factor from Capnocytophaga sputigena.

The addition of a sonic extract of Capnocytophaga sputigena to the culture fluid to human fibroblasts resulted in an inhibition of cell proliferation. The inhibition was dose-related (200 micrograms/ml caused a 90% inhibition, and 1,000 micrograms/ml caused a complete cessation of growth). The growth inhibition was not due to alterations in culture medium, pH or ionic strength, or to the effects of the C. sputigena lipopolysaccharide.

Cell Division↗