Search PubMed⌕ Search

Biomedical subjects

D L Nelson

Publications and source records attributed to D L Nelson.

At least 505 records · Page 28Linked to original sources
PubMed1977

Spontaneous cell-mediated cytotoxicity by human peripheral blood lymphocytes in vitro.

With isolated subpopulations of human peripheral blood mononuclear cells, spontaneous cell-mediated cytotoxicity (SCMC) and antibody-dependent cellular cytotoxicity (ADCC) were demonstrated to be functions of a population of surface immunoglobulin (sIg)-negative, Fc receptor-positive lymphocytes. Organ distribution studies revealed that SCMC and ADCC effector cell activity occurred in parallel, being present in spleen and absent in tonsils. Treatment of effector cells with trypsin significantly inhibited SCMC but not ADCC and this inhibition was not reversed by short-term incubation in autologous plasma. These results demonstrate that SCMC and ADCC involve different cytotoxicity mechanisms and are consistent with two subsets of effector cells with separate functional capabilities or a single effector cell mediating both forms of cytotoxicity through separate mechanisms.

Antibodies↗
PubMed1976

Biochemical studies of the excitable membrane of Paramecium aurelia. I. 45Ca2+ fluxes across resting and excited membrane.

The characteristics of Ca2+ transport across the excitable membrane of Paramecium aurelia were studied by measuring 45Ca2+ influx and efflux. The intracellular concentration of free Ca2+ in resting P. aurelia was at least ten times less than the extracellular concentration. Ca2+ influx was easily measurable at 0 degrees C, but not at 23 degrees C. The influx of 45Ca2+ was stimulated by the same conditions which cause membrane depolarization and ciliary reversal. Addition of Na+ and K+ (which stimulate ciliary reversal) resulted in a 10-fold increase in the rate of Ca2+ influx. An externally applied, pulsed, electric field (1-2 mA/cm2 of electrode surface), caused the rate of Ca2+ influx to increase 3-5 times, with the extent of stimulation dependent on the current density and the pulse width. Ca2+ influx had the characteristics of a passive transport system and was associated with the chemically or electrically triggered Ca2+ "gating" mechanism, which has been studied electrophysiologically. In contrast, Ca2+ efflux appeared to be catalyzed by an active transport system. With cells previously loaded at 0 degrees C with 45Ca2+, Ca2+ efflux was rapid at 23 degrees C, but did not occur at 0 degrees C. This active Ca2+ efflux mechanism is probably responsible for maintaining the low internal Ca2+ levels in unstimulated cells.

Azides↗
PubMed1976

Secretory component deficiency. A disorder of the IgA immune system.

We studied a 15-year-old boy with chronic intestinal candidiasis who had normal serum IgA levels without IgA in his secretions. There was an elevated number of peripheral blood lymphocytes bearing surface IgA. In addition, the lymphocytes cultured in vitro with pokeweed mitogen produced IgA as well as other immunoglubulins. Despite this evidence of normal IgA synthetic capacity, the patient had greatly diminished levels of IgA in the saliva and jejunal fluid, and, as estimated by 14C-L-leucine incorporation, could not synthesize IgA locally at intestinal-mucosal sites. Finally, the patient had no detectable free secretory component in saliva or jejunal fluid in contrast to normal persons and to patients with IgA deficiency. The basis of this disorder is probably a defect in the homing of IgA precursor cells to secretory sites or in the selective proliferation/differentiation of IgA cells at such sites.

Adolescent↗
PubMed1976

Specific B-cell antigens associated with gluten-sensitive enteropathy and dermatitis herpetiformis.

Gluten-sensitive enteropathy (G.S.E.) and dermatitis herpetiformis (D.H.) are associated with an increased frequency of the histocompatability antigen HLA-B8. These diseases were found to be even more strongly associated with a specific B-lymphocyte surface antigen recognised by maternal antisera. Two antisera (B-1 and W-1) reacted with B lymphocytes form G.S.E. and D.H. patients. Antiserum B-1 reacted with cells from thirteen of sixteen G.S.E. patients and from fifteen of nineteen D.H. patients, while antiserum W-1 reacted with cells from fifteen of sixteen G.S.E. patients and from fifteen of fifteen D.H. patients. None of the sera tested reacted with B lymphocytes from thirty-seven normal individuals, whether or not they were HL8-B8 positive. The identification of this specific antigen provides further insight into the pathogenesis of G.S.E. and D.H. and might form the basic of a diagnostic test for these diseases.

Adolescent↗
PubMed1976

Amphipathic amines affect membrane excitability in paramecium: role for bilayer couple.

Amphipathic amines and local anesthetics stimulated reversal of the ciliary beating direction in wild-type Paramecium. Ca++ influx across the surface membrane and the consequent increase in internal Ca++ causes ciliary reversal and backward swimming. Mutant cells of the "Pawn" class, which lack a "gating" mechanism for regulating Ca++ influx, did not swim backwards in the presence of local anesthetics. Local anesthetics stimulated the passive efflux of K+ but had no effect on the active transport of K+ or Ca++. Apparently passive influx of Ca++ also was stimulated by local anesthetics as evidenced by their effects on swimming direction. These data can be interpreted in terms of the "bilayer couple" hypothesis of Sheetz and Singer [(1974) Proc. Nat. Acad. Sci. USA 71, 4457-4461]: amphipathic drugs affect cells by asymmetric insertion into one face of the lipid bilayer. As predicted by this hypothesis, the drugs' effects were seen only after a short time lag, and quaternary amines were less effective than tertiary amines. The effect on behavior was caused by any of several amphipathic cations, and the relative potency was a function of their hydrophobicity. Amphipathic anions, which according to the hypothesis would insert into the opposite face of the lipid bilayer, had little effect on ciliary reversal. Asymmetric perturbation of the lipid bilayer with amphipathic cations may trigger the opening of the Ca++ gate.

Amines↗
PubMed1976

The Sézary syndrome: a malignant proliferation of helper T cells.

The Sézary syndrome is a frequently lethal disease characterized by circulating malignant cells of thymus-derived (T)-cell origin. The capacity of circulating malignant lymphocytes from patients with this syndrome to synthesize immunoglobulins and to function as helper or suppressor cells regulating immunoglobulin synthesis by bone marrow-derived (B) lymphocytes was determined. Peripheral blood lymphocytes from normal individuals had geometric mean immunoglobulin synthetic rates of 4,910 ng for IgM, 1,270 ng for IgA, and 1,625 ng for IgG per 2 X 10(6) cells in culture with pokeweed mitogen for 7 days. Purified normal B cells had geometric mean synthetic rates of 198 ng for IgM, 145 ng for IgA, and 102 ng for IgG. Leukemic cells from patients with the Sézary syndrome produced essentially no immunoglobulins. Adding normal T cells to normal B cells restored their immunoglobin producing capacity. Leukemic cells from four of five patients tested had a similar capacity to help immunoglobulin synthesis by purified normal B cells. Additionally, Sézary cells from one patient studied induced a nearly 10-fold increase in IgA synthesis by lymphocytes from a child with ataxia telangiectasia and selective IgA deficiency. Furthermore, these Sézary cells induced more than a 500-fold increase in IgG and IgA synthesis by lymphocytes from a child with Nezelof's syndrome. When Sézary cells were added to normal unfractionated lymphocytes, they did not suppress immunoglobulin biosynthesis. In addition, unlike the situation observed when large numbers of normal T cells were added to purified B cells, there was no depression of immunoglobulin synthesis at very high malignant T-cell to B-cell ratios. These data support the view that Sézary T cells do not express suppressor cell activity. The results presented in this paper suggest that neoplastic lymphocytes from the majority of patients with the Sézary syndrome originate from a subset of T cells programmed exclusively for helper-like interactions with B cells in their production of immunoglobulin molecules.

Adult↗
PubMed1976

Pictorial superiority effect.

Pictures generally show superior recognition relative to their verbal labels. This experiment was designed to link this pictorial superiority effect to sensory or meaning codes associated with the two types of symbols. Paired-associate stimuli consisted of simple pictures or of their labels, with list items selected either from the same conceptual category or from different conceptual categories. In addition, schematic or visual similarity among the pictures was either high or low. At two rates of presentation equal amounts of conceptual interference were produced for pictures and their labels. High schematic similarity eliminated the pictorial superiority effects at the slow rate and completely reversed it at the fast rate. These results suggest that the meaning representations for simple pictures and their labels may be identical, and that the pictorial superiority effect is related to the qualitative superiority of the sensory codes for pictures.

Concept Formation↗
PubMed1976

The effector cells in human peripheral blood mediating mitogen-induced cellular cytotoxicity and antibody-dependent cellular cytotoxicity.

The identity of the effector cells in human peripheral blood capable of mediating mitogen-induced cellular cytotoxicity (MICC) and antibody-dependent cellular cytotoxicity (ADCC) was investigated utilizing effector cell populations consisting of purified polymorphonuclear leukocytes, macrophages, lymphocytes, and cell surface immunoglobulin (sIg)-negative and sIg-positive lymphocyte subpopulations obtained by Sephadex anti-Fab immunoabsorbent column fractionation techniques. Chicken erythrocytes (CRBC) and Chang liver cells were used as target cells in both cytotoxicity assays. With CRBC targets MICC was mediated by polymorphonuclear leukocytes, macrophages, sIg-positive lymphocytes (B cells), and sIg-negative lymphocytes. On the contrary, with Chang liver cells as targets, MICC was mediated only by lymphocytes, and effector cells occurred exclusively in sIg-negative lymphocyte subpopulations containing thymus-derived lymphocytes (T cells). Further purification of sIg-negative lymphocyte subpopulations on antigen-antibody coated plastic surfaces yielded a nonadherent T lymphocyte population depleted of Fc receptor-bearing lymphocytes that was capable of mediating MICC against both CRBC and Chang cell targets. With use of CRBC targets, ADCC was mediated by polymorphonuclear leukocytes, macrophages, and sIg-negative lymphocyte subpopulations. However, with Chang cell targets, ADCC was mediated only by lymphocytes, and effector cells were present only in sIg-negative lymphocyte subpopulations. SIg-positive lymphocytes (B cells) and T lymphocytes were not effective in mediating ADCC against either CRBC or Chang cell targets. These studies demonstrate that the nature of the target cell employed in MICC and ADCC reactions is of critical imporatnce in defining the effector cell(s) capable of mediating cytotoxicity.

Animals↗
PubMed1976

Distribution and properties of adrenergic storage vesicles in nerve terminals.

The subcellular distribution of adrenergic storage vesicles was determined in rat spleen, heart and superior cervical ganglion and in dog spleen using dopamine-beta-hydroxylase (DBH) as a marker for vesicle membranes and norepinephrine (NE) as a marker for the soluble contents of the storage vesicles. Density gradient centrifugation revealed populations of vesicles in the rat heart and spleen with equilibrium densities of 1.05 and 1.15 g/ml. There was a consistent shoulder on the low-density peak at a density of 1.08 g/ml. Several populations of NE-and DBH-containing vesicles were also found in homogenates of dog spleen. In homogenates of superior cervical ganglia, most of the NE was nonsedimentable while the DBH activity formed a broad poorly resolved band within the gradient. Although NE and DBH were present in each of several populations of vesicles in nerve terminals of rat and dog organs, the ratio of NE/DBH varied as a function of the species and organ examined. Mitochondrial contamination did not, as has been previously claimed, influence the distribution of DBH which was observed. Both light and heavy vesicles were able to take up and retain NE-[3H].

Animals↗
PubMed1976

Differential effects of nerve impulses on adrenergic storage vesicles in rat heart.

The effects of increasing and decreasing activity in sympathetic neurons on light (D420 = 1.05) and heavy (D420 = 1.15) populations of adrenergic vesicles have been determined. Norepinephrine (NE) was used as a marker for the soluble contents of the vesicles, and dopamine beta-hydroxylase was used as a marker for the vesicle membranes. Cold exposure was used to increase activity in the sympathetic nervous system. A 40% decrease in the NE content of the rat heart with no change in the activity of dopamine beta-hydroxylase was observed after 70 minutes at 5 degrees C. The fall in NE content was completely blocked by pretreating the animals with chlorisondamine. Separation of light and heavy populations of vesicles was achieved with linear sucrose density gradients. Cold stress of 70 minutes duration led to a marked decrease in the NE content of the light vesicles. Blocking adrenergic nerve impulses with chlorisondamine resulted in an increase in total NE in the heart but had no effect on dopamine beta-hydroxylase activity. The initial effect of chlorisondamine was to increase the NE content of the light vesicles. The administration of alpha-methyl-p-tyrosine for 6 hours caused an approximately equal loss of NE from both vesicle populations. The decrease in total heart NE was about 25% and could be prevented by pretreating the animals with chlorisondamine. These results suggest that the light vesicle fraction is involved in the rapid or short-term responses to changes in nerve impulse frequency. Changes in the NE content of the heavy vesicles in rat heart were seen only after longer times, suggesting that these particles may function only as auxiliary storage sites for the neurotransmitter.

Animals↗
PubMed1975

Constrictive pericarditis, intestinal lymphangiectasia, and reversible immunologic deficiency.

A patient with constrictive pericarditis, secondary intestinal lymphangiectasia, and protein-losing enteropathy was demonstrated to have the characteristic immunologic deficiency associated with intestinal lymphangiectasia: hypogammaglobulinemia, lymphocytopenia, cutaneous anergy, impaired allograft rejection. and diminished in vitro lymphocyte proliferative responses. Following surgical correction of the cardiac abnormality, the intestinal lymphangiectasia and protein-losing gastroenteropathy resolved and was accompanied by a slow but progressive return of normal immune function. This documented reversal of the immunologic deficiency in intestinal lymphangiectasia supports the concept that the immune defect in this syndrome is due to the excessive loss of lymphocytes and immunoglobulins into the gastrointestinal tract.

Adolescent↗
PubMed1975

The pathogenesis of gluten-sensitive enteropathy.

Gluten-sensitive enteropathy is characterized by flattening of intestinal villi and malabsorption caused by the toxic effect of gluten, a wheat protein. Gluten activates an endogenous mechanism of toxicity that may be the local mucosal immune system: local mucosal immunoglobulin and antigluten antibody production occur soon after gluten ingestion. Approximately 80% of patients with this disease possess HL-A8, a second segregant series antigen. This association also occurs in dermatitis herpetiformis, a disease with vesicular skin lesions and gluten-sensitive flattening of intestinal villi. The association suggests that the fundamental abnormality in enteropathy is a binding reaction involving gluten protein and a binding site on a cell surface, determined in part by the histocompatibility gene; this reaction then results in a local mucosal immune response to gluten. Alternatively, the fundamental abnormality may be the presence of an abnormal immune-response gene linked to the HL-A8 gene or acting in concert with it; this immune-response gene results in local mucosal production of antigluten antibody.

Adult↗
PubMed1975

Sensory and meaning features in stimulus recognition and associative retrieval.

Three experiments addressed the problem of isolating the effects of sensory similarity on subprocesses involved in coding paired associates. In the first, the standard recognition-recall procedure was used and stimulus similarity, concreteness, and frequency were varied. However, because of concern with the validity of this recognition procedure as a measure of functional stimulus contact, an alternative was developed. This alternative led to the second study in which only stimulus similarity was manipulated. In the third experiment, similarity was varied, and the pairs were either associatively compatible, unrelated, or incompatible. The results using the new procedure indicated that similarity consistently disrupted functional stimulus contact but not associative retrieval. By contrast, associative relatedness facilitated both subprocesses.

Adolescent↗