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Biomedical subjects

R P Siraganian

Publications and source records attributed to R P Siraganian.

At least 19 recordsLinked to original sources
PubMed1992

Gonadotropin-releasing hormone antagonists with N omega-triazolylornithine, -lysine, or -p-aminophenylalanine residues at positions 5 and 6.

In order to be used as fertility regulators in humans, gonadotropin releasing hormone (GnRH) antagonists must be extremely potent and long acting and exhibit negligible side effects such as stimulating histamine release. To this aim, we have recently synthesized a series of analogues with the standard Ac-DNal1-DCpa2-DPal3 substitutions, where the N omega-amino function of ornithine, lysine, or p-aminophenylalanine (Aph) was converted to the aminotriazolyl (atz) derivatives at positions 5 and 6 with further modifications at positions 7 and 10. The analogues were tested for their ability to bind to pituitary cell membranes, to release histamine in a mast cell assay, to inhibit luteinizing hormone (LH) secretion by castrated male rats or cultured pituitary cells, and to interfere with the ovulation in intact female rats. While the subcutaneous (sc) injection of 50 micrograms of Azaline A (7, [Ac-DNal1,DCpa2,DPal3,Lys5(atz),DLys6++ +(atz),ILys8,DAla10]GnRH) dissolved in 0.2 mL of an aqueous media significantly inhibited LH release in the castrated male rat for 24 h, the same dose of Azaline B (11), [Ac-DNal1,DCpa2,DPal3,Aph5(atz),DAph6++ +(atz),ILys8,DAla10]GnRH, inhibited LH release for 72 h. A similar long duration of action was observed for Antide ([Ac-DNal1,DCpa2,DPal3,Lys5(Nic),DLys6(Nic ),ILys8,DAla10]GnRH) but not for Nal-Glu ([Ac-DNal1,DCpa2,DPal3,Arg5,4-(pmethoxybenzoy l)-D-2-Abu6,DAla10]GnRH). In the same paradigm, a 5-fold dilution of the peptide (50 micrograms in 1 mL) and the use of three injection sites rather than one resulted in significantly shorter duration of action for most of the peptides tested. This suggested that long duration of action might be the result of slow release from the injection site(s). In order to investigate this possibility, Nal-Glu and Azaline B were injected intravenously (i.v.) at three doses (10, 50, 250 micrograms) to castrated male rats. At all doses, both peptides significantly lowered LH levels for 8 h. By 24 h, Nal-Glu (250 micrograms) and Azaline B (50 and 250 micrograms) still measurably inhibited LH secretion. Finally, only Azaline B (250 micrograms) was still active at 48 h. These findings demonstrate that subtle structural modifications will yield peptides with different half-lives after iv administration. These findings led us to investigate the effects of other structural modifications on duration of action. We observed that systematic substitutions at positions 7 (NMeLeu) and 10 (Pro9-NHEt, and Gly-NH2) were found to be deleterious. Of interest was the observation that only the DAla10-NH2 substitution led to long duration of action and enzymatic stability under the conditions tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1979

Allergenic and biologic activity of commercial preparations of house dust extract.

The endotoxin, protein nitrogen unit (PNU) content, and allergenic activity of seven different extracts of house dust were determined. The PNU content varied from 1,600 to 44,000 PNU/ml. The endotoxin content as measured by the limulus assay varied from 450 to 500,000 ng/ml. Pyrogenic activity was present by rabbit fever assay and correlated well with the limulus assay. There was no correlation between endotoxin and PNU content of the different dust preparations. Leukocytes from 15 patients with a clinical history of allergy to dust were used for histamine release studies. The allergenic activity did not correlate with the PNU or endotoxin content of the different house dust preparations. The dust extracts could be divided into three groups according to their activities: three extracts which were the most reactive (30% histamine release with 0.12 to 0.39 PNU/ml), two which were about 20 times less active (4.75 to 6.43 PNU/ml for 30% histamine release), and a final group of two which were about 600 times less active. The leukocytes of three out of 15 patients failed to release histamine with one of these least reactive extracts. The reactivity pattern of five of the dust preparations appeared to correlate, suggesting that the different preparations contained the same allergens. Reactivities of two of the other extracts correlated poorly, and the reactivity of the least reactive sample did not correlate with six out of the seven preparations. Therefore, some dust preparations contain significant endotoxin-like material. Wide variations in the endotoxin, PNU content, allergenic activity, and reactivity patterns of different dust preparations were observed.

Adult↗
PubMed1979

Characterization of mouse allergens.

The major allergens present in mouse skin, serum, and urine have been identified. Skin extracts, serum, and urine were chromatographed, and the activities of the fractions were monitored by histamine release from the leukocytes of individuals sensitive to mice. Fractionation of skin extracts revealed two major allergens. The large allergen has a molecular weight of approximately 67,000 daltons and by biochemical and immunochemical criteria appears to be identical to mouse albumin. The smaller molecular weight allergen is approximately 17,000 daltons. The same two allergens are also found in mouse serum and mouse urine. Histamine release by leukocytes of individuals allergic to mice demonstrated that some individuals react predominantly to the large allergen, some to the small allergen, and one group of patients reacts to both allergens.

Albumins↗
PubMed1979

Interferon-induced enhancement of IgE-mediated histamine release from human basophils requires RNA synthesis.

Incubation of human leukocytes with certain viruses results in the enhancement of IgE-mediated release of histamine. This enhancement is produced by interferon. The present experiments show that an induction period of 6 to 9 hr and new RNA synthesis are required for interferon to enhance histamine release. This points to the possibility that interferon may exert its antiviral and histamine-release enhancing activities by acting through a common pathway.

Allergens↗
PubMed1979

Mechanisms of mouse mast cell activation and inactivation for IgE-mediated histamine release.

The IgE-mediated histamine release from mouse mast cells requires Ca++, is optimal at 37 degrees C, and is enhanced by phosphatidylserine. The rate of release is relatively slow. The mast cells can be activated to release histamine by either anti-IgE or anti-Fab antibodies and, in the case of cells from sensitized mice, by the immunizing antigen. The incubation of mast cells with antigen in the absence of Ca++ or phosphatidylserine fails to release histamine. Such cells are desensitized to the further addition under optimal conditions of the same antigen. Desensitization is antigen specific, requires optimal levels of antigen, and occurs at both 30 degrees and 37 degrees C. In contrast, anti-IgE desensitizes all IgE-mediated histamine release reactions.

Animals↗
PubMed1978

The mechanism of basophil histamine release in patients with periodontal disease.

Histamine release from washed peripheral blood basophils of thirty-three subjects with varying degrees of periodontal disease was studied. Dental plaque, serum and basophil leucocytes were collected from individual patients. There was no histamine release when autologous, washed sonicated plaque was added to leucocytes. However, the incubation of autologous plaque with serum at 37 degrees C for 30 min generated a factor which induced histamine release from basophils. This serum factor was stable to heat (56 degrees C, 30 min), eluted from a Sephadex G-100 column at a volume corresponding to a molecular weight of approximately 16,000 daltons and its action was inhibited by antibody to C5. This factor, therefore, is probably C5a. There was a variation in the degree of histamine release seen with the leucocytes of different donors. This variability was a property of the basophil rather than a function of the serum. Basophils from patients with gingival indices of 0.5 to 1.0 had significantly more histamine release than basophils from patients with gingival indices of less than 0.5 or greater than 1.5 (P less than 0.001). These experiments demonstrate that dental plaque activates serum to form C5a which in turn releases histamine from basophils. However, these experiments do not indicate a role for IgE in this reaction since the direct interaction of plaque with basophils did not cause histamine release. The release of mediators from mast cells could play an important role in the induction of the inflammatory response in periodontal disease.

Adolescent↗
PubMed1977

Enhancement of IgE-mediated histamine release from human basophils by viruses: role of interferon.

Human leukocytes maintained in culture are induced to release histamine when exposed to ragweed antigen E or anti-IgE. Leukocyte cultures incubated with virus (i.e. HSV-1, Influenza A, and Adeno-1) but not exposed to ragweed antigen E or anti-IgE fail to release histamine. If, however, leukocyte cultures are first exposed to virus and then to ragweed antigen E or anti-IgE, significant enhancement of histamine release occurs. Both infectious and inactivated virus enhance histamine release and the degree of enhancement is related to the concentration of virus and the length of the incubation. Tissue culture fluid harvested 8 h after exposure of leukocytes to virus contains a soluble factor which is capable of enhancing histamine release when added to fresh leukocyte cultures. This factor has all the properties of interferon including species specificity and cannot be dissociated from the antiviral activity of interferon. Moreover, both known inducers of interferon (poly I:poly C) and standard preparations of interferon are capable of enhancing histamine release. The enhancement of histamine release by interferon represents a new biological role for interferon.

Adenoviridae↗
PubMed1977

Automated histamine analysis for in vitro allergy testing. II. Correlation of skin test results with in vitro whole blood histamine release in 82 patients.

The recently developed sensitive, automated histamine assay system was applied for in vitro allergy testing. The simplified method for histamine release from whole heparinized blood was used. Aliquots of blood and allergen were incubated for one hour at 37 degrees C, and each supernatant was then analyzed for histamine release. Nine common pollen and environmental allergens were used at three 10-fold dilutions for in vitro testing with the use of 20 ml of blood. Intradermal skin tests were correlated with the whole blood histamine release in 82 patients who had received no immunotherapy. A scoring system for the histamine results was developed to take into consideration the results with multiple allergen concentrations. When the skin test was strongly positive (greater than or equal to 3 + at 100 protein nitrogen units [PNU]/ml), the whole blood histamine release was positive in 89% of the tests. In contrast, when the skin test was negative ( less than 1 + at 100 PNU/ml), the histamine release was also negative in 99.8% of the cases. When the skin test was 1 +, the histamine release from whole blood was positive in 6% of the tests; and when the skin test was 2+, the whole blood results were positive in 32%. The accuracy, precision, and sensitivity of the automated histamine assay allow its application for the clinical study of allergic patients.

Allergens↗
PubMed1977

Complement-induced histamine release from human basophils. III. Effect of pharmacologic agents.

Human serum activated with zymosan generates a factor (C5a) that releases histamine from autologous basophils. Previously we have presented evidence that this mechanism for C5a-induced release differs from IgE-mediated reactions. The effect of several pharmacologic agents known to alter IgE-mediated release was studied to determine whether they have a similar action on serum-induced release. Deuterium oxide (D2O), which enhances allergic release, inhibited in a concentration-dependent fashion the serum-induced reaction at incubation temperatures of 25 and 32 degrees C. The colchicine-induced inhibition was not reversed by D2O. Cytochalasin B, which gives a variable enhancement of IgE-mediated release, had a marked enhancing effect on the serum-induced reaction in all subjects tested. The following agents known to inhibit the IgE-mediated reaction also inhibited serum-induced release at 25 degrees C: colchicine, dibutyryl cyclic AMP, aminophylline, isoproterenol, cholera toxin, chlorphenesin, diethylcarbamazine, and 2-deoxy-D-glucose. These results suggest that the serum-induced release is modulated by intracellular cyclic AMP, requires energy, and is enhanced by the disruption of microfilaments. The lack of an effect by D2O would suggest that microtubular stabilization is not required. The data can be interpreted to indicate that IgE- and C5a-mediated reactions diverge at a late stage in the histamine release pathway.

Aminophylline↗
PubMed1977

Noncytotoxic IgE-mediated release of histamine and serotonin from murine mastocytoma cells.

Cultured murine mastocytoma (AB-CBF1-MCT-1) cells were stimulated to release endogenous or incorporated histamine or serotonin by an IgE-mediated mechanisms without loss of viability. Stimulation was achieved by incubation of the cells with rat IgE-anti-IgE, rat IgE-anti-light chain, fluoresceinated rat IgE-anti-fluorescein, IgE-enriched mouse anti-ovalbumin-ovalbumin, or covalently linked dimers of rat IgE, at doses similar to those optimal for normal peritoneal mast cells. Active cell metabolism and Ca++ were required to obtain release. Despite the latter, no dose of the calcium ionophore, A23187, could be found which caused release without concomitant cytotoxicity. Phosphatidylserine did not enhance release.

Animals↗
PubMed1977

Mechanism of histamine release by formyl methionine-containing peptides.

Small, acylated, methionine-containing peptides release histamine from human basophils. The characteristics of this reaction were compared to that of C5a- and IgE-induced release. fMet peptide-induced release requires Ca++ and is inhibited by EDTA in a manner similar to IgE- and C5a-mediated reactions. The fMet-Phe-Met-initiated reaction is complete within 2 min at temperatures of 25, 30, and 37 degrees C; but does not occur at 0 degrees C. There was a large variation in the capacity of leukocytes from different donors to release histamine with fMet peptides. However, there was no correlation in the capacity of leukocytes to release histamine with fMet-Phe-Met and their release with C5a or anti-IgE. The release by fMet-Phe-Met (but not by C5a or anti-IgE) was reversibly inhibited by a nonreleasing tripeptide. Leukocytes could be desensitized to the action of active fMet-peptide by preincubation with the peptide in the absence of cations. After washing, these cells released normally with C5a or anti-IgE. Conversely, cells desensitized to the action of C5a- or IgE-mediated reactions released normally with fMet peptides. There was cross-desensitization between different active peptides, and inactive peptides could not desensitize the leukocytes. Pharmacologic agents had similar effects on C5a and fMet peptide-induced release (e.g., lack of enhancement with deuterium oxide; enhancement with cytochalasin B; and inhibition with aminophylline and dibutyryl cyclic AMP). Therefore, histamine release with fMet peptides is initiated by their binding to and activation of a specific receptor on the basophil; the reaction beyond that point is similar to the C5a-mediated reaction.

Complement C5↗
PubMed1976

Automated histamine analysis for in vitro allergy testing. I. A method utilizing allergen-induced histamine release from whole blood.

A sensitive, automated, histamine assay system has been developed and applied for in vitro allergy testing. Nine common pollen and environmental allergens were used at three log dilutions for in vivo studies utilizing small volumes of blood (15-20 ml). The clinical evaluation was correlated with the results of the histamine release. two different procedures were utilized. The first is the commonly used histamine release from washed leukocytes. There was excellent correlation between the clinical evaluation and the results of histamine release from washed leukocytes in 17 different individuals. The second and simpler method utilized whole heparinized blood which might better reflect the immunologic reaction which occurs in vivo. Aliquots of blood and allergen were incubated for 1 hr at 37 degrees C and each supernatant was then analyzed for histamine release. There was excellent correlation between the two tests in 29 patients tested by both the whole blood and washed leukocyte methods. There was also good correlation between the clinical evaluation of the patients amd the intro tests. The precision, accuracy, and sensitivity of the automated histamine assay make feasible its routine application in the clinical study of allergic patients.

Allergens↗
PubMed1976

Complement-induced histamine release from human basophils. II. Mechanism of the histamine release reaction.

The activation of human serum complement by incubation with zymosan generates C5a which releases histamine from autologous basophils. The characteristics of the C5a-induced histamine release were investigated. It is similar to IgE-mediated reactions in requiring Ca++ and in being inhibited by EDTA. However, it has marked differences from IgE-mediated reactions. C5a, at all concentrations, released histamine completely in less than 2 min. The C5a reaction has a narrow pH optimum that antigen-induced release and occurs well at 17 degrees to 37 degreesC but not at 0 degreesC. The optimal reaction temperature is 25 degrees to 30 degrees C. Unlike the antigen-induced release, no two-stage activation with C5a for the release of histamine could be demonstrated. There was additive release between C5a- IgE-mediated reactions. Leukocytes could be desensitized to the C5a-mediated reaction by 1) incubating the cells at 37 degrees C for 45 min, 2) pretreating the leukocytes with activated serum in the presence of EDTA, and 3) adding the activated serum to the leukocytes at 0 degrees C before transferring to the optimal reaction temperatures. Cells desensitized to the complement-induced release have normal reactions to IgE-mediated histamine release. In parallel experiments, cells from allergic donors desensitized for IgE-mediated reactions by incubation with antigen under sub-optimal conditions release histamine normally upon the addition of C5a. The results indicate that histamine release by C5a involves a mechanism of basophil activation that is different from the pathway involved in the IgE-induced reaction.

Antigens↗
PubMed1976

Histamine release by chemotactic, formyl methionine-containing peptides.

Certain formyl dipeptides and tripeptides containing methionine released histamine from human basophils at concentrations of 10(-4) to 10(-7) M. However, N-formyl amino acids did not release histamine. Tripeptides, in general, were more active than dipeptides. An acyl group was required for histamine release although an N-terminal position for Met was not essential. Histamine release from human basophils by these peptides correlated well with their chemotactic activity for rabbit leukocytes.

Animals↗
PubMed1976

Histamine release from cultured human basophils: lack of histamine resynthesis after antigenic release.

Human peripheral basophils can be maintained in cultured for up to 72 hr. These cells retain their functional integrity as judged by total histamine content and by their ability to release histamine by an IgE-mediated reaction in response to a specific antigen challenge. Cells cultured after suboptimal antigenic challenge could be activated to release histamine upon the addition of antigen. In contrast, cells culture after supra-optimal antigenic challenge did not fully recover their ability to release histamine even after 24 hr. With a variety of culture conditions, it was impossible to demonstrate any net synthesis of histamine in cells. Cells cultured after depletion of their stores by reaction with antigen did not show any net histamine formation. The experiments suggest that the basophil in peripheral blood is functionally an end-stage cell and can participate in the histamine release reaction only once.

Antigens↗