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Biomedical subjects

T C Theoharides

Publications and source records attributed to T C Theoharides.

At least 109 records · Page 6Linked to original sources
PubMed1990

Serotonin release from rat brain mast cells in vitro.

Mast cells are primarily localized in connective tissues, where they secrete numerous mediators. They have also been identified in the mammalian central nervous system on the basis of their histochemical and morphological properties, but their role there remains unknown. A perfusion system was used to investigate in vitro mediator release from rat brain mast cells. Compound 48/80, the classic mast cell secretagogue of connective tissue mast cells, induced dose-dependent and non-cytotoxic release of serotonin, histamine and beta-hexosaminidase from mast cells in the rat thalamus and hypothalamus, but not in the cerebellum which was used as a negative control. Detailed studies were performed on thalamic mast cells, which were identified on the basis of metachromasia with Toluidine Blue and Safranin-positive staining with the Alcian Blue/Safranin technique. Their secretion was characterized by: (a) parallel release of serotonin, histamine and beta-hexosaminidase; (b) lack of dependence on extracellular calcium; (c) susceptibility to inhibition by disodium cromoglycate; and (d) lack of lactate dehydrogenase release. These results indicate that the morphology and secretory characteristics of thalamic mast cells resemble those of connective tissue mast cells. The ability of brain mast cells to secrete their mediators is discussed in the context of their possible involvement in brain pathophysiology.

Animals↗
PubMed1990

Histochemical and ultrastructural characteristics of rat brain perivascular mast cells stimulated with compound 48/80 and carbachol.

Mast cells, known for their involvement in allergic reactions where they secrete numerous chemicals in response to immunoglobulin E and specific antigens, have recently been localized in the central nervous system. The function of these brain mast cells has remained speculative as they have not been the subject of any combined functional or detailed morphological studies. Here it is shown that these cells are primarily perivascular and stain metachromatically with Toluidine Blue, but red with Alcian Blue counterstained with Safranin, indicating that they contain proteoglycans quite similar to those of peritoneal, but not mucosal mast cells. Intracardiac administration of the classic mast cell secretagogue, compound 48/80, or the acetylcholine analog, carbachol, caused ultrastructural changes in brain mast cells consistent with secretion, but without exocytosis. However, it is known that the same concentration of carbachol has no effect on homogeneic peritoneal mast cells. These results indicate that brain mast cells share histochemical characteristics with serosal mast cells, but differ in their reactivity to secretagogues, and apparently in the mechanism of secretion. Their ability to respond to neurotransmitters and their distinct mechanism of secretion, which may be selective, expands their possible role in brain pathophysiology.

Animals↗
PubMed1990

Mast cell activation in sterile bladder and prostate inflammation.

Sterile inflammation of the bladder has often been associated with interstitial cystitis (IC), a urologic condition of unknown etiology, predominantly affecting young and middle-aged females, for which no effective therapy is known. Recent reports have indicated that IC is associated with an increased number of bladder mast cells. Here we report the case of a middle-aged man with chronic sterile hematuria, dysuria and lower abdominal pain associated with a high number of bladder and prostate mast cells. Following therapeutic transurethral resection of the trigone area, bladder neck and prostate, samples of bladder and prostate were examined with light and electron microscopy and contained many mast cells (about 150 cells/mm2) which were not degranulated. Nevertheless, mast cells contained many altered granules and urinary levels of histamine were elevated, implying secretion without exocytosis. These findings are discussed in the context of the pathophysiology of IC and possible therapeutic interventions.

Cystitis↗
PubMed1990

Progesterone triggers selective mast cell secretion of 5-hydroxytryptamine.

Mast cells are involved in allergic reactions where they secrete numerous mediators in response to immunoglobulin E and antigen. However, they have recently been implicated in neuroinflammatory conditions with a higher prevalence in women, and there have been clinical reports of progesterone anaphylaxis. When tested on purified rat peritoneal mast cells, progesterone alone stimulated release only of 5-hydroxytryptamine (serotonin) in a dose- and time-dependent manner. Serotonin release by progesterone was exceptional because it was not accompanied by histamine release or degranulation and was either augmented or unaffected by drugs which inhibit secretion induced by the classic mast cell secretagogue, compound 48/80. These findings indicate that mast cells are capable of selective serotonin secretion, previously shown only after pretreatment with certain tricyclic drugs, and may be involved in neuroendocrine syndromes.

Animals↗
PubMed1989

Histamine2 (H2)-receptor antagonists in the treatment of urticaria.

Urticaria may develop in response to a number of stimuli such as allergic reactions, drugs, cold, pressure, stings and, most interestingly, neuropsychological upheavals. Classical treatment has utilised H1-receptor antagonists, in view of the fact that histamine released from local mast cells acts on H1-receptors on the vasculature and participates in the pathophysiology of this syndrome. More recently, H2-receptor antagonists have also been tried, alone or in combination, with encouraging results. The question still remains why H2-receptor antagonists should have any beneficial effect since H2-receptors are mostly present on exocrine cells and on T-suppressor lymphocytes, where they are stimulatory, or mast cells, where they are auto-inhibitory. Possible explanations may include the ratio of H1- to H2-receptors on local vasculature and the effect of H2-antagonists on responses elicited through nervous system activity via cholinergic or neuropeptidergic neurons. Finally, evidence is presented that certain tricyclic H-receptor antagonists may have powerful inhibitory effects on secretion from both peripheral and central nervous system mast cells, as well as from neurons. The possible role of H3-receptors in this process is also discussed. At present, the available evidence does not justify the routine use of H2-antagonists in the treatment of urticaria.

Histamine H2 Antagonists↗
PubMed1988

High-affinity benzodiazepine binding sites on rat peritoneal mast cells and RBL-1 cells: binding characteristics and effects on granule secretion.

High-affinity binding sites for benzodiazepines are present in a wide range of tissues other than brain, and appear to be pharmacologically distinct from central nervous system receptors. Binding sites have been reported on rat peritoneal mast cells, but specificity of binding and functional effects have not been addressed in these cells. Using the specific radioligand [3H]-Ro5-4864, which binds to peripheral but not central binding sites, we characterized binding to rat peritoneal mast cells and the related cell line, RBL-1 cells, and effects on granule secretion. Studies in rat peritoneal mast cells disclosed one class of saturable binding sites with a dissociation constant of KD = 5.29 +/- 1.26 nM (mean +/- SE) and maximal binding Bmax = 357 +/- 113 fmol/10(6) cells. Competition studies showed that IC50 for Ro5-4864 was 15.7 nM, for PK11195 was 10.9 nM, for diazepam was 191 nM, and for clonazepam was greater than 10(-5) M. Studies in RBL-1 cells also showed one class of saturable binding sites with KD = 1.11 +/- 0.72 nM and Bmax = 177 +/- 69 fmol/10(6) cells; specificity was similar to peritoneal mast cells. Incubation of peritoneal mast cells with Ro5-4864 (10(-10)-10(-5) M) for 60 min, or with 10(-6) M for 0-60 min, showed no change in histamine or serotonin release either in unstimulated mast cells or those stimulated by compound 48/80 or substance P. Experiments with the fluorescent dye Quin-2 showed no change in free intracellular calcium levels in peritoneal mast cells after incubation with Ro5-4864 ranging from 10(-10) to 10(-6) M.

Animals↗
PubMed1987

Synaptic alterations in the acoustic cortex of the rat following insulin-induced hypoglycemia.

Hypoglycemia was induced by intracarotid insulin infusions in adult Lewis rats. Electron microscopy of the acoustic cortices in these animals revealed that hypoglycemia provoked marked morphological and morphometric alterations in the pre- and postsynaptic terminals present, as well as in the astrocytic processes seen. The number of the synaptic vesicles in the "active zone" of the synapses was dramatically decreased, with most of the vesicles loosely dispersed in the entire presynaptic profile. Some of the pre- and postsynaptic terminals were enlarged and contained dilated cisternae of smooth endoplasmic reticulum, as well as mitochondria exhibiting a marked internal disorganization. The synaptic clefts in a large number of synapses were dilated and contained fibrillary material. The most striking morphological alterations seen involved a membrane discontinuity of the postsynaptic terminal and was found mostly in the synapses of the superficial layer of the acoustic cortex. Most of the morphological alterations observed in the acoustic cortex following uncomplicated hypoglycemia are seen in sensitive areas of the brain after ischemia or hypoxia.

Animals↗
PubMed1986

Immune defects in chronic renal impairment: evidence for defective regulation of lymphocyte response by macrophages from patients with chronic renal impairment on haemodialysis.

Cellular mechanisms contributing to impaired lymphocyte proliferative responses in chronic renal impairment (CRI) were investigated using peripheral blood mononuclear cells (PBMC) from 25 patients receiving haemodialysis. Impaired T cell proliferative responses to phytohaemagglutinin were demonstrated. The hyporeactive PBMC from patients with CRI suppressed the responses of PBMC from normals to a greater degree than did control PBMC. This immunosuppression was reversed significantly by depleting adherent monocytes (M phi). To further determine if these impairments might be critically dependent on cell-cell contact, M phi from an additional 10 patients on haemodialysis were examined for ability to support B and T cell colony formation in semi-solid cultures stimulated by Staphylococcus protein A (SpA). When compared to normal controls, significantly fewer B and T cell colonies were observed with M phi from CRI patients than when autologous M phi were used. Also, T cells from patients were significantly less effective than controls in supporting B cell colony growth. Decreased T and B cell colony responses in patients were not due to a primary abnormality of these cells, since allogeneic mixing experiments showed that B and T cells from patients were able to form a sufficient number of colonies when control M phi or T cells from normals were used as accessory and helper cells. These findings suggest that although M phi-mediated suppressor activity is an important mechanism contributing to impaired lymphocyte responsiveness in patients with chronic renal impairment on haemodialysis, additional or related abnormalities in M phi 'accessory' function may also exist.

Adult↗
PubMed1985

Differential release of serotonin without comparable histamine under diverse conditions in the rat mast cell.

Pretreatment of mast cells with various psychotropic agents was shown to permit preferential release of serotonin without substantial release of histamine or massive degranulation. Differential release involved both endogenous, granule-stored serotonin, and exogenous radiolabeled serotonin that had been taken up by the cell. This phenomenon occurred in mast cells stimulated to secrete with suboptimal concentrations of the classic mast cell secretagogue compound 48/80, was associated with drugs of several different structures and known mechanisms of action, and could be inhibited by certain prostaglandins. Furthermore, differential release of serotonin occurred in mast cells of retired breeders without the use of drugs or other exogenous agents. Light microscopic studies of mast cells undergoing differential release showed minimal degranulation, indicating that most of the serotonin release did not occur via classic exocytosis. The ability of mast cell to selectively release serotonin, by a mechanism unlike that occurring in allergic anaphylactic secretion, constitutes one of the first instances of differential release from secretory cells, suggests a new mechanism of release of secretory products, and expands the potential role of mast cells in the pathophysiology of the body.

Age Factors↗
PubMed1983

Induction of mast cell secretion by parathormone.

The biologically active fragment of human parathormone (PTH) and intact bovine PTH were found to induce secretion of both serotonin and histamine from rat peritoneal mast cells in vitro. Release of serotonin and histamine was demonstrated with 25 units/ml PTH or higher. This level is within the higher limits of the elevated PTH levels found in advanced uremia. Mast cell secretion by PTH was dose, time and energy dependent and was not cytotoxic. Although mast cell activation was independent of extracellular calcium, it required intracellular calcium, thus resembling the action of certain other peptide secretagogues. Intradermal injection of PTH induced immediate increases in vascular permeability suggesting that PTH could induce mast cell secretion in vivo. Light and electron microscopic observations confirmed mast cell degranulation by exocytosis. These results demonstrate that elevated levels of PTH can induce mast cell secretion in vitro and in vivo and suggest a possible role for mast cells in the pathophysiology of non-allergic disease states.

Animals↗
PubMed1983

Defective elicitation of delayed-type hypersensitivity in W/Wv and SI/SId mast cell-deficient mice.

Previous studies have indicated that cutaneous mast cells are involved in the elicitation of delayed-type hypersensitivity (DTH) in mice. Mast cells are thought to be required in DTH to release serotonin to open gaps between endothelial cells, allowing entrance of effector cells into the tissue. Two different strains of mice with independent genetic defects that lead to a substantial mast cell deficiency (W/Wv and SI/SId), and their normal littermate +/+ controls, were studied for their ability to express DTH. Both strains were shown to be deficient in serotonin-containing mast cells at skin sites of preferential elicitation of DTH in normal mice, such as the ear or footpad. Defective DTH was found in both mast cell-deficient strains by using two different systems: 1) sheep erythrocyte-induced footpad DTH, and 2) picryl chloride-induced contact sensitivity ear swelling responses. Adoptive transfer experiments demonstrated that abnormal DTH in mast cell-deficient mice was due to a defect in the elicitation of DTH, rather than a defect in the induction of effector T cells. In these experiments, the ability to elicit DTH could be transferred to normal +/+ mice with sensitized cells from mast cell-deficient mice, but sensitized cells from +/+ mice could not transfer DTH responsiveness to mast cell-deficient mice. In addition, no defects in numbers of epidermal Langerhans cells or in antigen-presenting cell function were found in W/Wv or SI/SId mice. We therefore concluded that abnormal elicitation of DTH in W/Wv and SI/SId mice was probably due to their mast cell deficiency. The inability of mast cell-deficient mice to express DTH was overcome when sensitized T cells and specific antigen were placed in the extravascular tissues by local passive transfer. These results suggest that mast cell release of vasoactive mediators, such as serotonin, is required in DTH to allow effector T cells to leave the intravascular space, enter the tissues, and become activated by antigen to release chemoattractant lymphokines that recruit a nonspecific infiltrate of inflammatory cells.

Animals↗
PubMed1982

Affinity chromatography with specific antibody increases activity and retains antigenicity of ornithine decarboxylase.

An affinity chromatography column with antibody specific to ornithine decarboxylase (ODC) was employed successfully for the retention and subsequent partial elution of ODC with enhanced activity and retention of antigenicity. This may be a useful procedure for further attempts to produce antiserum for identification and characterizations of ODC in vitro and in vivo.

Animals↗
PubMed1982

Serotonin storage pools in basophil leukemia and mast cells: characterization of two types of serotonin binding protein and radioautographic analysis of the intracellular distribution of [3H]serotonin.

We studied binding of serotonin to protein(s) derived from rat basophil leukemia (RBL) cells and mast cells. We found two types of serotonin binding protein in RBL cells. These proteins differed from one another in molecular weight and eluted in separate peaks from sephadex G-200 columns. Peak I protein (KD = 1.9 X 10(-6) M) was a glycoprotein that bound to concanavalin A (Con A); Peak II protein (KD1 = 4.5 X 10(-8) M; KD2 = 3.9 X 10(-6) M) did not bind to Con A. Moreover, binding of [3H]serotonin to protein of peak I was sensitive to inhibition by reserpine, while binding of [3H]serotonin to protein of peak II resisted inhibition by that drug. Other differences between the two types of binding protein were found, the most significant of which was the far more vigorous conditions of homogenization required to extract peak I than peak II protein. Neither peak I nor peak II protein resembled the serotonin binding protein (SBP) that is found in serotonergic neurons of the brain and gut. Electron microscope radioautographic analysis of the intracellular distribution of [3H]serotonin taken up in vitro by RBL cells or in vivo by murine mast cells indicated that essentially all of the labeled amine was located in cytoplasmic granules. No evidence for a pool in the cytosol was found and all granules were capable of becoming labeled. The presence of two types of intracellular serotonin binding proteins in these cells may indicate that there are two intracellular storage compartments for the amine. Both may be intragranular, but peak I protein may be associated with the granular membrane while peak II protein may be more free within the granular core. Different storage proteins may help to explain the differential release of amines from mast cell granules.

Animals↗