Under aerobic conditions the addition of (C2N5)2N(N[O]NO)-.Na+(DEA/NO), S-nitroso-N-acetyl penicillamine and nitric oxide (NO)-saturated buffer, but not S-nitroso-L-glutathione, to dopamine solutions resulted in dopamine o-semiquinone formation that was dependent on the formation of a NO/oxygen intermediate. High pressure liquid chromatography (HPLC) electrochemical analysis of dopamine demonstrated that the DEA/NO-induced oxidation of dopamine was abrogated in the presence of the antioxidants, ascorbate and glutathione. NO spontaneously released from DEA/NO decreased [3H]dopamine accumulation in primary cultures of mesencephalic neurons in a dose-dependent fashion. In contrast, [3H] gamma-aminobutyric acid uptake by mesencephalic neurons tested under the same conditions was unchanged. When DEA/NO was added to incubation buffer that contained [3H]dopamine and the antioxidant, ascorbate or glutathione, [3H]dopamine uptake was also inhibited. These data excluded that oxidation of extracellular [3H]dopamine by the intermediates of the NO/O2 reaction could have caused this decrease. Instead, NO may have acted directly on a not yet identified target operative in the regulation of dopamine storage and release. Analysis of the rate constants for the NO reaction with ascorbate, glutathione and dopamine revealed that dopamine quinone formation was delayed by the presence of antioxidants. Since the formation of NO as well as neurotransmitter release are activated during ischemia reperfusion injury, it is possible that prolonged NO exposure could deplete antioxidants and facilitate the oxidation of dopamine and thereby cause neurotoxicity.

Animals↗

PubMedDate not supplied

Reaction kinetics for nitrosation of cysteine and glutathione in aerobic nitric oxide solutions at neutral pH. Insights into the fate and physiological effects of intermediates generated in the NO/O2 reaction.

The critical regulatory function of nitric oxide (NO) in many physiologic processes is well established. However, in an aerobic aqueous environment NO is known to generate one or more reactive and potentially toxic nitrogen oxide (NOx) metabolites. This has led to the speculation that mechanisms must exist in vivo by which these reactive intermediates are detoxified, although the nature of these mechanisms has yet to be elucidated. This report demonstrates that among the primary bioorganic products of the reaction of cellular constituents with the intermediates of the NO/O2 reaction are S-nitrosothiol (S-NO) adducts. Anaerobic solutions of NO are not capable of nitrosating cysteine or glutathione, while S-NO adducts of these amino acids are readily formed in the presence of O2 and NO. Investigation of the kinetics for the formation of these S-NO adducts has revealed a rate equation of d[RSNO]/dt = kSNO[NO]2[O2], where kSNO = (6 +/- 2) x 10(6) M-2S-1, a value identical to that for the formation of reactive intermediates in the autoxidation of NO. Competition studies performed with a variety of amino acids, glutathione, and azide have shown that cysteine residues have an affinity for the NOx species that is 3 orders of magnitude greater than that of the nonsulfhydryl amino acids, and > 10(6) times greater than that of the exocyclic amino groups of DNA bases. The dipeptide alanyltyrosine reacts with the intermediates of the NO/O2 reaction with an affinity 150 times less than that of the sulfhydryl-containing compounds. Furthermore, Chinese hamster V79 lung fibroblasts depleted of glutathione display enhanced cytotoxicity on exposure to NO.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Curling's ulcer in association with staphylococcal scalded skin syndrome in the neonate.

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Anti-Bacterial Agents↗

PubMedDate not supplied

Protective effects of trans-13-APT, a thromboxane receptor antagonist, in endotoxemia.

The effect of the thromboxane A2/prostaglandin H2 (TxA2/PGH2) receptor antagonist trans-7[2-(p-hydroxyphenethylamino)-cyclopentyl]-heptanoic acid (trans-13-APT) on certain pathogenic sequelae of endotoxic shock and associated changes in arachidonic acid metabolism in the rat was investigated. trans-13-APT, an analog of 13-azaprostanoic acid, was synthesized and found to block human platelet aggregation induced by the thromboxane mimetic U46619. Pretreatment with trans-13-APT did not significantly alter the elevations in plasma immunoreactive (i) TxB2 or iPGE, 0.5 or 4 h after the intravenous administration of Salmonella enteritidis endotoxin. However, in the trans-13-APT-pretreated group, 4 h after administration of the endotoxin, plasma i6-keto-PGF1 alpha was significantly (p less than 0.05) reduced to 1.2 +/- 0.3 ng/ml (n = 17) compared with vehicle-treated rats (2.4 +/- 0.5 ng/ml; n = 18). The elevation in plasma i6-keto-PGF1 alpha seen 0.5 h (n = 17/group) after endotoxin infusion was not altered by trans-13-APT. trans-13-APT also significantly (p less than 0.05) attenuated the endotoxin-induced fall in platelet count (135 +/- 27 X 10(3)/mm3 vs. 350 +/- 65 X 10(3)/mm3 and hypoglycemia (73 +/- 9 vs. 97 +/- 7 mg/dl), but not the leukopenia. Since the reticuloendothelial system may be an important source of iTxB2 and i6-keto-PGF1 alpha during endotoxemia, in vitro studies were conducted with adherent peritoneal cells. High concentrations of trans-13-APT (50 and 100 microM) significantly reduced (p less than 0.05) basal but not endotoxin-induced synthesis of iTxB2 and i6-keto-PGF1 alpha by isolated adherent rat peritoneal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

Improvement in organ blood flow by inhibition of thromboxane synthetase during experimental endotoxic shock in the rat.

Endotoxic shock is associated with increased metabolism of arachidonic acid to thromboxane (Tx) and prostaglandins. This investigation examined the effects of two structurally dissimilar inhibitors of (Tx) synthetase on Salmonella enteritidis endotoxin (LPS) (15 mg/kg)-induced alterations in cardiac output and organ blood flow in Long-Evans rats. An imidazole derivative, 7(1-imidazolyl) heptanoic acid (7-IHA), and sodium -(E)-3-[4-(3-pyridyl-methyl)phenyl]-2-methacrylate (OKY-1581) were injected intravenously at 30 and 5 mg/kg, respectively, 30 min before injection with endotoxin. Cardiovascular function was assessed 30 min post-LPS with Sr-85 labeled microspheres under light ether anesthesia. Injection of endotoxin caused a 60% decrease in cardiac output (34.0 +/- 2.7 ml/min/100 g body weight in control rats) and a 38.9% decrease in systolic arterial pressure. Both Tx synthetase inhibitors significantly (p less than 0.05) attenuated the decrease in cardiac output, although only 7-IHA improved blood pressure. Pretreatment with 7-IHA or OKY-1581 significantly (p less than 0.05) attenuated the LPS-induced decrease in renal perfusion. Lung nutrient blood flow (1.1 +/- 0.2 ml/min/g lung) decreased nearly 70% in shock. Both Tx synthetase inhibitors prevented this reduction. LPS shock resulted in approximately a 30% decrease in brain blood flow. 7-IHA significantly (p less than 0.05) improved flow, while OKY-1581 was without apparent effect. Splanchnic blood flow was likewise improved by 7-IHA and OKY-1581. Liver blood flow, 55% less than values of the control group in shock (p less than 0.05), was returned to values of the controls by both inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylates↗

PubMedDate not supplied

Parenteral glutathione monoester enhances tissue antioxidant stores.

Glutathione (GSH) is a potent endogenous antioxidant that protects major organs from oxidant injury. However, present nutrition regimens may inadequately support tissue stores of this tripeptide during critical illness. To determine whether GSH reserves can be enhanced in vivo with intravenous (IV) supplements, rats underwent central venous catheterization, were given chow and water ad libitum during a 2-day recovery period, and were then randomized to receive one of three treatments as an IV bolus: (1) dextrose, (2) glutathione (GSH), or (3) glutathione monoethyl ester. GSH monoethyl ester is transported into cells more easily than is GSH. Tissue and plasma samples were analyzed for GSH at 2 and 4 hours after drug administration. Liver, renal, and ileal mucosal GSH were significantly increased in the GSH-monoethyl ester rats compared with dextrose-treated animals. In addition, plasma GSH was dramatically increased after monoester injection. In contrast, GSH administration depressed liver GSH stores and did not significantly affect GSH concentration in the other organs analyzed. Plasma GSH concentration was elevated 2 hours after GSH administration. We conclude that: (1) the monoethyl ester of glutathione can be used in vivo to enhance tissue and plasma GSH concentration and (2) IV GSH administration does not significantly increase tissue GSH levels and may paradoxically depress hepatic GSH in normal rats. Because the malnourished and critically ill are likely to have depleted GSH stores, nutrition strategies that include the provision of GSH monoester may lend additional support to those organs that are at risk for injury from oxygen free radicals during catabolic states.

Animals↗

PubMedDate not supplied

Hyperthermic sensitization by the radical initiator 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH). I. In vitro studies.

AAPH (2,2'-azobis-(2-amidinopropane dihydrochloride)) is a water-soluble, heat-labile azo compound which undergoes thermal decomposition to produce carbon-centred free radicals. These carbon-centred radicals might be directly cytotoxic or may react with oxygen to produce potentially cytotoxic alkoxyl and peroxyl radicals. The rate of free radical production as a result of AAPH thermal decomposition increases with increasing temperature. We have evaluated the efficacy of AAPH as a heat sensitizer for Chinese hamster V79 cells by the clonogenic assay. AAPH (50 mM) was not cytotoxic to V79 cells at 37 degrees C for exposures up to 3 h. In contrast, AAPH (50 mM) was found to markedly sensitize cells exposed to 42, 43 and 45 degrees C. For a 75 min exposure to 42 degrees C alone, cell survival was reduced to 9 x 10(-1); however, a 75 min exposure at 42 degrees C+AAPH resulted in survival of 5.5 x 10(-4). For 43 and 45.5 degrees C heating, cell survival was potentiated by AAPH at the 1% survival level by 4.1 and 1.4-fold, respectively. AAPH was also found to sensitize both hypoxic cells and thermotolerant cells. These findings would encourage in vivo evaluation of AAPH (or analogues) as a temperature-dependent heat sensitizer. AAPH represents a new class of heat sensitizers which may have use in unravelling the mechanism(s) of heat killing and may have utility in local hyperthermia treatment.

Amidines↗

PubMedDate not supplied

Non-specific and specific stimulation of resistance against Leishmania donovani in C57BL/6 mice.

Stimulation by intravenous injections of glucan, a beta 1,3 polyglucose, provided a significant degree of resistance in mice against Leishmania donovani. The response of C57BL/6 animals was dose-dependent. A single glucan injection before or after infection induced significant resistance but to a lesser degree than two or three injections. Immunization by injections of formalin-killed promastigotes with glucan via the subcutaneous or intravenous routes provided greater resistance than glucan or dead parasites alone against subsequent infection with viable parasites. Subcutaneous immunization with promastigotes from cultures passaged 10 times in vitro and those from cultures maintained for 25 passages elicited a similar degree of resistance against infection and induced positive skin test responsiveness against leishmanial antigen prior to infection.

Adjuvants, Immunologic↗

PubMedDate not supplied

Transforming growth factor beta 1 alters rat peritoneal macrophage mediator production and improves survival during endotoxic shock.

Transforming Growth Factor beta 1 (TGF-beta 1) is a potent anti-inflammatory cytokine involved in wound healing. Because of its anti-inflammatory actions, the effects of TGF-beta 1 were studied in vitro on rat macrophage inflammatory mediator production and in vivo on Salmonella enteritidis endotoxin (LPS) induced lethality. TGF-beta 1's effect on stimulated rat peritoneal macrophage (MO) production of prostacyclin and nitric oxide were assessed via measurement of their stable metabolites, 6-keto-PGF-1 alpha and nitrite, respectively. TGF-beta 1 (10 ng/ml) pretreatment (3 hours) resulted in significant reductions (p < 0.05) of LPS (50 micrograms/ml) stimulated, lipid A (1 and 10 micrograms/ml) stimulated, arachidonic acid (16 microM) stimulated, and Ca++ ionophore (10 microM) stimulated MO 6-keto-PGF 1 alpha production. These data suggest that TGF-beta 1 inhibits LPS stimulated MO 6-keto-PGF-1 alpha production by acting at, or distally to, phospholipase A2, possibly at the level of cyclooxygenase in the arachidonic acid cascade. In a similar study, TGF-beta 1 pretreatment led to a significant (p < 0.05) reduction of LPS stimulated MO nitrite production. In subsequent studies, the effects of TGF-beta 1 were studied in vivo on rats challenged with lethal doses of LPS. Rats pretreated with TGF-beta 1 (250 ng/rat i.v.) exhibited a significant increase (p < 0.01, n = 15 rats/group) in mean survival time compared to control rats. The increased survival time of TGF-beta 1 pretreated rats with LPS shock may be due, in part, to altered production of MO mediators.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

Protection from radiation-induced alopecia with topical application of nitroxides: fractionated studies.

PURPOSE: Hair loss resulting from irradiation of the head and neck or from whole brain irradiation often leads to cosmetic, social, and psychological problems for the radiotherapy patient. Few successful clinical interventions are available. We have shown that nitroxides (stable free radicals) afford radiation protection against single-dose radiation-induced alopecia in a guinea pig model. Here we determine if topical nitroxide application provides protection from fractionated radiation treatment. MATERIALS AND METHODS: Two symmetrical and contralateral areas (3 x 5 cm) of skin on the dorsal trunk of guinea pigs were shaved to a hair length of 0.25 cm. A 2 mL solution containing 70 mg/mL nitroxide (Tempo or Tempol) in 70% ethanol was topically applied to the skin surface of one side; 70% ethanol was applied to the contralateral (control) side 10 minutes before irradiation. Animals were placed in a special jig that held skin without decreasing blood flow to the treatment area and fractionated external beam radiation (7 Gy) was delivered daily for eight fractions over 10 days via a 4 MeV linear accelerator. Alopecia (hair density) was scored weekly for 13 to 14 weeks after radiotherapy, using a standardized reference with respect to hair loss and regrowth in the treatment field. RESULTS: After radiation treatment, dry desquamation and gradual hair loss were observed for both control and nitroxide-treated skin; however, over weeks 4 to 11 postirradiation hair loss was much more pronounced in control animals when compared with nitroxide-treated animals. Hair density measurements for Tempol treatment over weeks 9 to 13 were approximately 75% compared with measurements in controls of approximately 25%. Tempo-treated animals exhibited hair density values of approximately 90% compared with 12% in controls over weeks 11 to 14. Tempol and Tempo treatments resulted in significant radioprotection. Histologic evaluation showed that radiation treatment alone in ethanol controls resulted in a marked decrease in the number of hair follicles and poor development of remaining follicles; however, nitroxide pretreatment resulted in no appreciable decrease in hair follicles and hair follicles appeared mature. This was also observed in unirradiated ethanol controls. Electron paramagnetic resonance studies revealed that topical nitroxide application did not result in measurable systemic concentrations of either drug. CONCLUSIONS: The results of this study suggest that topical application of nitroxides may be useful in a clinical setting to reduce the undesirable toxicity of radiation-induced alopecia.

Administration, Topical↗