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At least 667 records · Page 37Linked to original sources
PubMed1992

Somatostatin depleting potency of cysteamine-related thiols and amines in the rat: structure-activity relation.

Cysteamine, a potent duodenal ulcerogen, stimulates gastric acid and gastrin secretion and decreases immunoreactive somatostatin (IRS) from the gut and hypothalamus of the rat. To elucidate the structural requirements for this effect, we tested a series of cysteamine analogs for their IRS decreasing activity in comparison with their nucleophilic and reducing potencies. Adult female rats were sacrificed 4 hr after p.o. administration of the test chemicals given in molar equivalents to 30 mg/100 g of cysteamine-HCl. IRS decreasing activity in gastric mucosa, expressed as percentage of controls is listed in descending order: cystamine (55%), cysteamine (59%), 2-dimethylaminethanethiol (59%), ethylamine (66%), 1,3-propanedithiol (70%), propylamine (75%) and 3-aminothiophenol (79%). The following thiols and amines had no IRS decreasing effect (80% of controls): L-cysteine, ethanethiol, 1-propanethiol, penicillamine, dimercaprol, 1-4-dithiothreitol, ethanolamine, propionitrile, n-butyronitrile, o-, m- or p-aminophenol. The aryl 2-, 3- or 4-aminothiophenols, unlike most of their aminophenol analogs also decreased immunoreactive prolactin in the pituitary by 38 to 78%. IRS decreasing activity was independent of the reducing potency of cysteamine derivatives but was correlated significantly (r = 0.793, P < .01) with electron affinity of -SH, -NH2, -OH and -CN radicals in terminal alkyl chemicals. The structural requirement for decreasing activity is the presence of either -SH and -NH2 on a 2 to 3 carbon alkyl or aryl molecule. Both radicals when present together increase potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗
PubMedDate not supplied

[An experimental approach to determining the protective properties of drugs against ionizing radiation in low and sublethal doses].

In experiments with mice, the efficiency of radioprotective agents against acute gamma-irradiation with nonlethal and low doses (0.5-4 Gy) was estimated by nine parameters. The treatment with cystamine, cysteamine and riboxine prior to irradiation (< 2 Gy) did not influence the postirradiation values of the parameters under study. With a dose of up to 4 Gy, the effect of riboxine was noted. The determinations of the number of aberrant mitoses, cellularity and mitotic activity of the bone marrow have proved to be most informative. The data obtained are discussed with due regard for the specific effect of low-level radiation and mechanisms of the protective action of the agents under study.

Animals↗
PubMed1977

Changes in radiosensitivity induced by cyclic nucleotides and chemical radioprotection.

Cyclic AMP has a radioprotective effect and its aministration results in a significant increase in LD50/30 values in Chinese hamsters. The efficiency of these radioprotective effects is comparable to that of such radioprotective compounds as AET and cystamine + mexamine. Cyclic GMP is responsible for significant radiosensitizing effects. Changes in radiosensitivity after administration of cyclic nucleotides are both immediate and delayed and correlate closely with dose and time of administration.

5-Methoxytryptamine↗
PubMedDate not supplied

[Mechanisms of the protective action of sulfur-containing radioprotectors on the intestinal epithelium].

In studying the influence of cystamine and gammaphos on the recovery of mouse jejunum epithelium after irradiation with doses inducing intestinal form of acute radiation sickness, it was shown that the radioprotective agents did not influence D0 value for intestinal epithelium stem cells, but in crypts the number of DNA-synthesizing enterocytes that entered mitosis increased after the preventive administration of the radioprotectors. All this caused the number of cells per villus to increase and intestinal mucosa to recover more readily.

Amifostine↗
PubMedDate not supplied

[Spontaneous motor activity and physical endurance of rats during acute radiation sickness developing against a background of the use of a radioprotective agent].

Cystamine given to rats prior to irradiation with a dose of 8 Gy (LD77/30) ameliorates significantly the severity of radiation sickness and restores spontaneous motor activity by the time of clinical recovery. However, movements that require physical efforts as well as physical endurance remain decreased.

Animals↗
PubMed1975

Tumor rejection in experimental animals treated with radioprotective thiols.

In experimental animals, a systemic treatment with thiols of the mercaptoalkylamine type has affected all of five solid tumors so far investigated. (Three of the tumors were transplanted into the strain of origin.) There was either inhibition of growth or "oncodieresis," i.e., a necrosis and sloughing of tumors conducive to full recovery and repair. Mercaptoalkylamines and derivatives of the type used in our experiments are known to bind to cellular sites by a two-point attachment involving both thiol and amino groups. One of these compounds, cysteamine, was active in its native, unsubstituted form, but did not bring about oncodieresis when either the amino or thiol group, or both, were alkylated. Mercaptopropylamine, the 3-carbon homolog of cysteamine, was less active. Cystamine, a disulfide dimer of cysteamine that has no free reactive sulfhydryl, did not induce any reaction. Thioglycerol, lacking a terminal amino group, had only negligible activity. Rejection was much more striking when treatment was started on the day of inoculation than when started 7 days later. Male mice rejected better than females. Results were inferior when tow of the agents were given simultaneously or together with other radioprotectants, such as L-cysteine, glutathione, dimethyl sulfoxide, or reserpine. Tumor rejection was enhanced when the phosphorylated thioyls, S-2-(3-aminopropylamino)ethylphosphorothioic acid or S-(2-ethylguanidine)phosphorothioci acid, were given simultaneously with the radioprotective serotonin, but there was no synergy of serotonin with the nonphosphorylated compounds S-2-aminoethylisothiouronium bromide or cysteamine. Serotonin alone did not affect the tumors.

Animals↗
PubMedDate not supplied

Copper catalyzed alkaline autoxidation of selenocystamine.

In alkaline medium and in the presence of cupric ions selenocystamine undergoes autoxidation and is entirely transformed into selenohypotaurine. Among the different metal ions tested, Fe, Co, Ni, Cu, Ag, Mg, Mn, only cupric ions are effective in catalyzing the reaction. The reaction shows an optimum around pH 13. In most respects the autoxidation of selenocystamine is similar to the alkaline autoxidation of cystamine. Some data on the paper and ion exchange chromatographic behaviour of selenohypotaurine and selenotaurine are reported, as also details for the synthesis of selenotaurine.

Cations, Divalent↗
PubMedDate not supplied

[Mechanism of changes in amine binding to plasma proteins during allergy].

Blood plasma of healthy persons bound 13.13 +/- 1.07 mmol/l of p-phenylene diamine (PDA), histamine pectic index constituted 33.3 +/- 2.18%. In patients with neurodermitis and eczema both these patterns were markedly reduced. Unitiol (10(-3) mol/l) increased PDA binding and histamine level in vitro. The same concentration of cystamine decreased histamine pectic index in healthy persons. Importance of protein SH-groups in binding of amines is discussed.

Biogenic Amines↗
PubMedDate not supplied

[Radiation resistance of animals subjected to lethal irradiation with chemical protection].

The data are presented on radioresistance of mice 1, 5 and 9 months after irradiation (LD95-99/30) in conditions of protection with cystamine. It was shown that the resistance of these animals to repeated irradiation with LD50/30 is considerably lower than that of the animals not exposed previously. The radioresistance and such indices of the haemopoietic system status as quantity of caryocytes and colony-forming capacity of the bone marrow are compared.

Animals↗
PubMed1985

Evaluation of covalent antisickling compounds by PO2 scan ektacytometry.

The ektacytometer, a device to measure erythrocyte flexibility, has been used to evaluate antisickling agents that covalently modify hemoglobin S (HbS). The instrument has been adapted to produce a continuous gradient of oxygen pressure in the measuring cuvette, which permitted the rapid determination of sickle cell rigidity over the complete oxygenation range. Inspection of curves allows classification of the compounds according to their mode of action: altering oxygen affinity or increasing deoxy-HbS solubility. Reagents that modify amino groups, thiols, and histidine, as well as a crosslinking agent, were examined. The method directly evaluates deoxygenated cell deformability rather than cell shape. Many of the compounds that are effective in preventing the morphological sickling of deoxygenated sickle cells do not necessarily restore cell deformability. The method also readily detects membrane damage brought about by covalent agents that nonspecifically derivatize membrane proteins. Cystamine and pyridoxal appear to improve deformability in deoxygenated SS cells at concentrations that do not damage the membrane. This method, which examines the intact cell, fills a gap in the available experimental techniques for drug evaluation, between studies of isolated hemoglobin and in vivo studies.

Antisickling Agents↗
PubMedDate not supplied

[Application of the methods of the mathematical theory of experiments to the development of multicomponent radioprotective preparations].

A study was made of the possibility of using a mathematical theory of experiment in developing effective many-component radioprotective preparations. The preparations composed of cystamine or S-(omega-aminopropyl)-beta-aminoethyl thiophosphate, as the basis, and mexamine, ethyron and gutimine were used as an example to prove the adequacy of such an approach in solving the problems of optimization of composing the radioprotective complexes according to their efficiency and toxicity.

5-Methoxytryptamine↗
PubMedDate not supplied

[Study of the absorptive activity of the gastrointestinal tract in irradiated animals treated with radiation-protective agents].

A fluorescent uranine indicator was used to study the absorbing capacity of the gastrointestinal tract of irradiated mice and dogs. It was shown that the radioprotective agents with different mechanisms of action (for example, cystamine, para-aminopropiophenon and S-2 (3-aminopropylamino)ethylthiophosphate) exert a favourable action on the functional state of the gastrointestinal tract of irradiated mice.

Amifostine↗
PubMed1984

Protective efficacy of combined administration of lipopolysaccharide of E. coli and chemical radioprotectors under conditions of prolonged irradiation.

We investigated the protective effectiveness of the lipopolysaccharide of E. coli (LPS) in a combination with a mixture of chemical radioprotectors in female mice of the strain H at various radiation dose rates. LPS in a dose of 0.08 mg per kg of body mass was administered 1, 3, or 24 hours prior to irradiation, the radioprotective mixture (cystamine 90 mg X kg-1 + 5-methoxytryptamine 15 mg X kg-1) was administered 10 minutes before irradiation. Dose rates of 612 mGy X min-1 (irradiation time 10 to 15 minutes), 38 mGy X min-1 (3 to 4 hours), and 8.2 mGy X min-1 (27 to 29 hours) were used. The results showed that isolated administrations of LPS or of the radioprotective mixture increased the resistance of the mice against prolonged irradiation; the combined administration even enhanced the efficacy of the radioprotective action. However, this efficacy depended on the magnitude of the dose rate. At dose rates higher than 38 mGy X min-1 the effectiveness of the chemical protection prevailed, whereas at lower dose rates the biological and especially the combined protection became effective. We demonstrated a slight pyrogenic effect of LPS by measuring oxygen consumption and changes in some parameters of the hematopoiesis.

5-Methoxytryptamine↗
PubMedDate not supplied

[Mechanisms of potentiating and prolonging the radioprotective effect of multicomponent compounds].

A study was made of the effect of mexamine, etiron and gutimine on the pattern of distribution of cystamine within the body and the rate of its conversion in tissues of albino mice. It was shown that the potentiation and prolongation of the radioprotective effect is based on the ability of the complex of these preparations to inhibit the conversion of the S-containing radioprotective agent.

5-Methoxytryptamine↗
PubMed1980

Influence of radioprotective agents on the activities of isoenzymes of blood serum alkaline phosphatase in irradiated dogs.

Changes of the total serum activity of alkaline phosphatase (AP) and its bone and intestinal isoenzymes were studied in dogs gamma-irradiated by 3.0 Gy. The activities of AP isoenzymes were determined by means of a heat inactivation-inhibition method. After irradiation the serum AP activities were lower in general. In case of the bone isoenzyme the decrease was most pronounced. The changes of the total AP activity and of the intestinal isoenzyme were less distinct. The i.m. administration of the radioprotective mixture cystamine with mexamine (24 mg/kg + 4 mg/kg) before irradiation led only to a moderate reduction of the radiation-altered AP values in the dogs. The present results indicate that the radioprotective way used here renders only an unsatisfactory protection for large laboratory animals against ionizing radiation.

5-Methoxytryptamine↗
PubMed1980

Characterization of the protective effect of radioprotective substances by means of long-term changes in oxygen consumption.

A comparison of long-term hypothermic effects of radioprotective substances and their protective effectiveness was carried out in mice after acute and prolonged irradiation. As radioprotective substances were used AET, cystamine, serotonine, 5-methoxytryptamine, cysteamine-S-phosphate, sodium fluoroacetate and some double combinations of these substances. The irradiation was carried out with dose rates 38.3 and 612.5 mGy/min, the hypothermic reaction was evaluated according to total oxygen consumption, measured during 5 hours after the drug administration. The results demonstrated the existence of a correlation between the suppression of metabolic processes and both short-term and long-term protective effectiveness of radioprotective substances. The protective effectiveness of a drug is the higher, the greater decrease of oxygen consumption is induced by this substance in the investigated time interval. An analogous dependence was also demonstrated between the duration of hypothermic and radioprotective effects. The found correlation is valid for both acute and prolonged irradiation (correlation coefficient 0.79-0.87; p < 0.01).

5-Methoxytryptamine↗