RESUMEN
Prejudices can lead to discrimination, social exclusion, and violence particularly among young male adults. Previous findings suggest that the degree of holding prejudices is linked to low levels of empathy, while low levels of empathy have been associated with alexithymia, the inability to experience one's own feelings. We tested the hypothesis that the impact of a lack of empathy on reporting blatant and subtle prejudices is moderated by the inability to identify one's own feelings. In a sample of n = 136 young male adults aged 21 years (mean = 21.5 years; sd = 0.3), we conducted correlation and moderator analyses to determine possible relationships between prejudices, empathy, and alexithymia as assessed by self-report questionnaires. Prejudices were assessed by the Blatant and Subtle Prejudice Scale (BSPS), empathy was assessed by the German modified version of the Interpersonal Reactivity Index (IRI), and alexithymia by the 20-item Toronto Alexithymia Scale (TAS-20). Self-reported empathy levels were correlated with the strength of subtle and blatant prejudices. The moderation analyses revealed that the negative association between empathy and subtle prejudice increased with decreasing alexithymia. The negative association between empathy and blatant prejudice, on the other hand, was significant only for participants with low levels of alexithymia. These results suggest that empathy can limit the expression of blatant and to some degree also subtle prejudice when subjects are capable to identify their own feelings in a group of young males.
Asunto(s)
Emociones , Empatía , Adulto , Síntomas Afectivos , Humanos , Masculino , Prejuicio , Encuestas y Cuestionarios , Adulto JovenRESUMEN
Bone autografting remains the clinical model of choice for resolving problematic fractures. The precise mechanisms through which the autograft promotes bone healing are unknown. The present study examined the hypothesis that cells within the autograft secrete osteogenic factors promoting the differentiation of mesenchymal stem cells (MSCs) into osteoblasts. Particles of human bone ("chips") were recovered at the time of joint replacement surgery and placed in culture. Then, conditioned media were added to cultures of human, adipose-derived MSCs under both basal and osteogenic conditions. Contrary to expectation, medium conditioned by bone chips reduced the expression of alkaline phosphatase and strongly inhibited mineral deposition by MSCs cultured in osteogenic medium. Real time PCR revealed the inhibition of collagen type I alpha 1 chain (Col1A1) and osteopontin (OPN) expression. These data indicated that the factors secreted by bone chips inhibited the osteogenic differentiation of MSCs. However, in late cultures, bone morphogenetic protein-2 (BMP-2) expression was stimulated, suggesting the possibility of a delayed, secondary osteogenic effect.
Asunto(s)
Células Madre Mesenquimatosas/citología , Osteoblastos/citología , Osteogénesis , Comunicación Paracrina , Tejido Adiposo/citología , Adulto , Anciano , Fosfatasa Alcalina/genética , Fosfatasa Alcalina/metabolismo , Huesos/metabolismo , Diferenciación Celular , Células Cultivadas , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Cadena alfa 1 del Colágeno Tipo I , Medios de Cultivo Condicionados/farmacología , Femenino , Humanos , Masculino , Células Madre Mesenquimatosas/efectos de los fármacos , Células Madre Mesenquimatosas/metabolismo , Persona de Mediana Edad , Osteoblastos/metabolismo , Osteopontina/genética , Osteopontina/metabolismoRESUMEN
Allogeneic hematopoietic stem cell transplantation (HSCT) is a well-established curative therapy for various malignant and non-malignant diseases. Successful outcome after allogeneic HSCT has been associated with donor chimerism (DC). However, the detection of residual host cells or mixed hemopoietic chimerism (MC) has indicated that donor chimerism is not obligatory following HSCT. More recently, fluorescence in situ hybridization (FISH) analysis has been applied to engraftment studies for the identification of polymorphic or sex chromosomes. In this study, chimerism status was evaluated in 48 sex-mismatched HSCT pediatric patients (17 women/31 men, mean age: 9.02 +/- 3.95 years, range: 2-19) by FISH and the effect of DC or MC on outcome and long-term disease-free survival was documented. The stem cell source was bone marrow in all cases. All of the donors were human leucocyte antigen-identical siblings. FISH was performed on 156 specimens between days +13 and +1878. Donor chimerism was found in 47.9% (23/48) and MC was found in 52.1% (25/48) of the patients. Fifteen of 48 (31.25%) patients died, of whom 12 (80%) were MC and three patients (20%) were DC. The difference in chimerism status (MC or DC) was statistically significant between those patients who died and those still alive (chi(2) = 6.813; P = 0.009).
Asunto(s)
Trasplante de Células Madre Hematopoyéticas , Quimera por Trasplante , Adolescente , Adulto , Niño , Preescolar , Enfermedad Injerto contra Huésped/etiología , Trasplante de Células Madre Hematopoyéticas/mortalidad , Humanos , Hibridación Fluorescente in Situ , Análisis de Supervivencia , Trasplante Homólogo/efectos adversosRESUMEN
Tramadol is a weak opioid agonist and an inhibitor of the reuptake of noradrenaline and serotonin. This study was undertaken to assess a possible pharmacological interaction of ondansetron, a serotonin-3 (5-hydroxytryptamine-3, 5-HT3) antagonist, and tramadol in an animal model for acute pain. Sixty-three male albino mice were randomly given saline, tramadol (10, 20, and 40 mg kg(-1)), ondansetron (1, 2, and 4 mg kg(-1)), or ondansetron (1, 2, and 4 mg kg(-1)) and tramadol (20 mg kg(-1), given 10 min after ondansetron injection) intraperitoneally. Each mouse was assessed twice for tail-flick latency before saline or drug administration and 15, 30, 60, 90, and 120 min thereafter. Tramadol (10 mg kg(-1)) had no effect on pain threshold levels of mice, but tramadol doses of 20 or 40 mg kg(-1) increased pain threshold levels in a dose-dependent manner (p < 0.01 for 20 mg kg(-1) and p < 0.001 for 40 mg kg(-1)). Ondansetron doses of 1, 2, or 4 mg kg(-1) alone had no effect on pain threshold levels of mice. Tramadol (20 mg kg(-1)) and ondansetron (1, 2, and 4 mg kg(-1)) increased pain threshold levels at all doses (p < 0.001 for 1 and 2 mg kg(-1) ondansetron and p < 0.01 for 4 mg kg(-1) ondansetron). The pain threshold levels of mice given tramadol (20 mg kg(-1)) alone or tramadol and ondansetron (p > 0.05 for 1, 2, and 4 mg kg(-1)) were similar. Our results indicate that ondansetron-a 5-HT3 selective antagonist-does not decrease the analgesic effectiveness of tramadol in mice, which may be the result of different mechanisms involving 5-HT3 receptors.
Asunto(s)
Analgésicos Opioides/farmacología , Ondansetrón/farmacología , Umbral del Dolor/efectos de los fármacos , Antagonistas de la Serotonina/farmacología , Tramadol/farmacología , Analgesia , Animales , Interacciones Farmacológicas , Masculino , Ratones , Ratones Endogámicos , Dimensión del DolorRESUMEN
The prevalence of and risk factors for hypertension were determined among habitants in the European side of Istanbul who are 25 years and older. Eight administrative districts were selected with the method of simple random sampling. The participants were selected through systematic calling from address lists. Between 17 and 22 June 2002, the questionnaires were applied to the participants in a face-to-face interview; then arterial blood pressures, body weights and heights of the participants were measured. Of 423 adults participating in the study, 35.5% were hypertensive; 35.9% were obese, 27.9% were overweight and 2.1% were underweight. Risk factors for hypertension such as age, gender, educational status, social security, family history of hypertension and cardiovascular disease, medical history of diabetes and congestive heart failure, smoking and alcohol use, and body mass index in the hypertensive and non-hypertensive groups were investigated by means of logistic regression analysis. Age [odds ratio (OR): 5.20, 95% confidence interval (CI): 2.18-12.40], body mass index (OR: 2.22, 95% CI: 1.57-3.16) and smoking (OR: 0.72, 95% CI: 0.55-0.95) were found to be correlated with hypertension. The results showed that the prevalence of hypertension was high in Istanbul, and obesity, being overweight and advanced age were the risk factors for hypertension.
Asunto(s)
Hipertensión/epidemiología , Adulto , Anciano , Consumo de Bebidas Alcohólicas/epidemiología , Índice de Masa Corporal , Comorbilidad , Diabetes Mellitus/epidemiología , Dieta , Femenino , Humanos , Estilo de Vida , Masculino , Persona de Mediana Edad , Obesidad/epidemiología , Prevalencia , Factores de Riesgo , Fumar/epidemiología , Encuestas y Cuestionarios , Turquía/epidemiología , Población UrbanaRESUMEN
Spigelian hernia is a rare lateral ventral abdominal hernia. These clinically elusive hernias are treacherous and have a real risk of strangulation. We present a patient with a strangulation of the small bowel and appendix in a right spigelian hernia, which was accurately demonstrated by spiral computerised tomography preoperatively and successfully treated with primary suturing reinforced with polypropylene mesh. With a high index of suspicion and the use of modern radiological technique, these "bewildering" hernias can be diagnosed and repaired relatively safely.
Asunto(s)
Apéndice/cirugía , Hernia Ventral/cirugía , Vólvulo Intestinal/cirugía , Intestino Delgado/cirugía , Laparotomía/métodos , Mallas Quirúrgicas , Apéndice/diagnóstico por imagen , Femenino , Estudios de Seguimiento , Hernia Ventral/complicaciones , Hernia Ventral/diagnóstico por imagen , Humanos , Vólvulo Intestinal/complicaciones , Vólvulo Intestinal/diagnóstico por imagen , Intestino Delgado/diagnóstico por imagen , Persona de Mediana Edad , Cuidados Preoperatorios , Medición de Riesgo , Tomografía Computarizada por Rayos X , Resultado del TratamientoRESUMEN
The combination of venlafaxine and tramadol was compared with the single use of these agents to investigate the antinociceptive effect on paw withdrawal latency (PWL) to paw pressure in rats with neuropathic pain. Rats were divided into 4 groups: group 1 received saline (0.2 ml i.p.); group 2 received venlafaxine (22 mg/kg i.p.); group 3 received tramadol (20 mg/kg i.p.); and group 4 received venlafaxine + tramadol. No statistically significant changes were observed in the saline and venlafaxine groups with respect to PWL in the lesioned paw. However, tramadol produced a significant antinociceptive effect on the lesioned paw at 30 min compared with the saline and venlafaxine groups. A more potent antinociceptive effect was observed in the tramadol + venlafaxine group, beginning at 60 min and lasting for 1 h. The combination of venlafaxine + tramadol was more effective in increasing the pain threshold in this animal model of neuropathic pain than either of these drugs administered alone.
Asunto(s)
Analgésicos/farmacología , Ciclohexanoles/farmacología , Neuropatía Ciática/tratamiento farmacológico , Tramadol/farmacología , Animales , Modelos Animales de Enfermedad , Sinergismo Farmacológico , Quimioterapia Combinada , Masculino , Umbral del Dolor/efectos de los fármacos , Presión , Ratas , Ratas Sprague-Dawley , Neuropatía Ciática/fisiopatología , Clorhidrato de VenlafaxinaRESUMEN
This study is a field study with cross-section and case control conducted in the Kucukcekmece Region of Istanbul between June 1999 and February 2000. Four hundred and ninety three dwellings selected by a simple random sampling method were visited. From a population of 2187, 58 people, after filling in a questionnaire were suspected to have epilepsy. Following an interview, neurological examination and an electroencephalogram (EEG) 17 were diagnosed as having epilepsy. Lifetime epilepsy prevalence was 0.8%. 41.2% of the 17 epilepsy cases had partial epilepsy ( n= 7), 47.0% had generalized (n = 8) and in 11.8% seizures could not be classified ( n= 2). The risk factors for epilepsy in the control group ( n= 125) from the same region and those with epilepsy were investigated by means of logistic regression analyses. Educational status (odds ratio : 1.82, 95% confidence interval : 1.13-2.94; P= 0.01), profession (OR : 0.76, 95% CI : 0.60-0.97; P= 0.03), history of epilepsy in the family (OR : 0.67, 95% CI : 0.47-0.94; P= 0.02) were determined to be correlated with epilepsy. The results have drawn attention to the fact that individuals should be informed about epilepsy.
Asunto(s)
Epilepsia/epidemiología , Población Rural/estadística & datos numéricos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Casos y Controles , Áreas de Influencia de Salud , Niño , Preescolar , Estudios Transversales , Electroencefalografía , Epilepsia/diagnóstico , Femenino , Humanos , Lactante , Masculino , Persona de Mediana Edad , Prevalencia , Estudios Retrospectivos , Encuestas y Cuestionarios , Turquía/epidemiologíaRESUMEN
In this study, we investigated smoking addiction and some risk factors among university students in Istanbul. A questionnaire survey of 236 university students studying in Istanbul Medical Faculty (n: 148) and other faculties (n: 88) was performed with cross-sectional and responding-under-observation methods in March-May 1999. Thirty-six per cent of the university students with mean age 24.0 (2.9 were addicted to smoking (n: 85): 41.3% males and 26.7% females; 67.5% were using imported and 32.5% were using local product cigarettes. Of the subjects, 18.1% were smoking 1-10 cigarettes a day, 61.4% 11-20 cigarettes a day and 20.5% more than 20 cigarettes a day. When alcohol and smoking addiction were compared with logistic regression analysis, with respect to gender, age, school, parents' educational levels, living style and the sources of income, the risk factor for alcohol addicts was found to be more 2.54 times than smoking addicts (OR = 2.54, 95% CI = 1.38-4.67; p = 0.003). The study has emphasized the association of alcohol and smoking addiction in university students and the prevalence of smoking addiction among adolescent females.
Asunto(s)
Conducta Adictiva/etnología , Fumar/etnología , Estudiantes/estadística & datos numéricos , Adulto , Distribución por Edad , Consumo de Bebidas Alcohólicas/epidemiología , Áreas de Influencia de Salud , Estudios Transversales , Femenino , Humanos , Masculino , Prevalencia , Análisis de Regresión , Factores de Riesgo , Muestreo , Sensibilidad y Especificidad , Distribución por Sexo , Fumar/epidemiología , Encuestas y Cuestionarios , Turquía/epidemiología , UniversidadesRESUMEN
Agmatine is an endogenous polyamine metabolite formed by decarboxylation of L-arginine. In this study, the effect of agmatine on tonic pain was compared to its effect on phasic pain by using the formalin and tail-flick (TF) tests in mice. When administered intraperitoneally (ip), agmatine (37.5-300 mg/kg) exhibited a decrease in nociceptive behaviours in the first and second phase of the formalin test, which is a tonic pain model. The alpha(2) adrenoceptor antagonist yohimbine blocked the effect of agmatine in Phase 2 but did not change its effect in Phase 1. In the TF test, there was no significant change in the behaviour of agmatine-administered (75-300 mg/kg) animals. As a result, agmatine appears to have an analgesic effect on tonic rather than phasic pain, and alpha(2) receptors seem partly to have a role in the antinociceptive effect of agmatine on tonic pain.
Asunto(s)
Agmatina/farmacología , Analgésicos/farmacología , Dimensión del Dolor/efectos de los fármacos , Agmatina/administración & dosificación , Analgésicos/administración & dosificación , Animales , Formaldehído , Inyecciones Intraperitoneales , Masculino , Ratones , Desempeño Psicomotor/efectos de los fármacos , Tiempo de Reacción/efectos de los fármacos , Receptores Adrenérgicos alfa 2/efectos de los fármacosRESUMEN
Nabumetone is a nonsteroidal anti-inflammatory (NSAI) drug which is known to cause less gastrointestinal damage than other NSAI drugs. This study was performed to evaluate whether nabumetone treatment might alter the vascular aberrations related to inflammation in a rat model of adjuvant-induced arthritis. Nabumetone treatment (120 or 240 mg x kg(-1) x day(-1), orally) was initiated on the 15th day of adjuvant inoculation and continued for 14 days. Arthritic lesions, vascular contractile and relaxant responses and gastroduodenal histopathological preparations were evaluated 29 days after adjuvant inoculation. The contractile responses of aortic rings to phenylephrine and KCl were increased in grade 2 arthritic rats. In grade 3 arthritis only the phenylephrine contractility was decreased. The relaxant responses to acetylcholine and sodium nitroprusside were decreased in grades 2 and 3. In healthy rats, nabumetone did not change the vascular responses. After treatment of arthritic rats with nabumetone, both the contractile and relaxant response of the aortic rings returned to normal, and arthritic score and paw swelling were reduced. Gastroduodenal histopathology did not show erosions or ulcers in any of the groups. In conclusion, nabumetone improved the systemic signs and vascular alterations in experimental arthritis without showing any gastrointestinal side effects.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacología , Aorta Torácica/efectos de los fármacos , Butanonas/farmacología , Vasoconstricción/efectos de los fármacos , Vasodilatación/efectos de los fármacos , Animales , Antiinflamatorios no Esteroideos/uso terapéutico , Artritis Experimental/tratamiento farmacológico , Butanonas/uso terapéutico , Masculino , Nabumetona , Ratas , Ratas WistarRESUMEN
Because the pain sensation is subjective, it is difficult to evaluate the responses to analgesic drugs. Some analgesics that affect the central nervous system are known to change the pupil diameter. The pupil diameter is a more objective criterion that shows the drug effect. We studied the relation between the pupil diameter and analgesia responses to morphine and antidepressants by using the selective micro-receptor agonist morphine (2 and 4 mg/kg), the noradrenaline reuptake inhibitor desipramine (7.5 and 10 mg/kg), the mixed serotonergic and noradrenergic uptake inhibitor and cholinergic receptor antagonist amitriptyline (2.5 and 5 mg/kg), and the selective serotonin reuptake inhibitor sertraline (2.5 and 5 mg/kg) in mice. Both monocular microscopy to assess pupil measurement and the hot-plate test to assess nociceptive thresholds were used in the same animals. We found that morphine played an important role in both mydriasis and analgesia, whereas amitriptyline and desipramine had a greater effect on pupil response than on nociception. Sertraline produced antinociception without causing a change in pupil diameter. As a result, although the pupil response is an important criterion in evaluating the analgesic effect of morphine, it is not possible to put forward the same criterion for the antidepressant drugs. Because different neurotransmitters are involved in pupil and pain mechanisms of antidepressant drugs, it is difficult to evaluate the analgesic response with the pupil diameter.
Asunto(s)
Analgésicos Opioides/farmacología , Antidepresivos/farmacología , Morfina/farmacología , Dolor/prevención & control , Pupila/efectos de los fármacos , Amitriptilina/farmacología , Analgesia , Animales , Desipramina/farmacología , Masculino , Ratones , Midriasis , Dolor/fisiopatología , Dimensión del Dolor , Umbral del Dolor/efectos de los fármacos , Sertralina/farmacología , Factores de TiempoRESUMEN
The effect of a leukotriene D(4) receptor antagonist, (3-(3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl(3-dimethyl amino-3-oxo propyl)thio)methyl)thio) propanoic acid (L-660,711; MK-571), was investigated on nociceptive responses in mice using three different assays: acetic-acid-induced abdominal constrictions, formalin response and tail-flick test. MK-571 (8-32 mg/kg, i.v.) produced dose-dependent protection against acetic-acid-induced abdominal constriction (ED(50)=30 mg/kg). The compound (10-80 mg/kg, i.p.) was also effective, in a dose-dependent manner, on the second phase of the formalin response (ED(50)=26 mg/kg). However, it had no effect on the first phase of the formalin response and in the tail-flick test. Naloxone (1 mg/kg, i.v.), an opioid antagonist, almost completely blocked the antinociceptive effect of MK-571 in both acetic-acid-induced abdominal constriction and the second phase of the formalin test. These results provide evidence for an antinociceptive action of MK-571 at peripheral sites and suggest that opioid mechanisms are involved.
Asunto(s)
Analgésicos/farmacología , Antagonistas de Leucotrieno , Antagonistas de Leucotrieno/farmacología , Proteínas de la Membrana , Propionatos/farmacología , Quinolinas/farmacología , Receptores de Leucotrienos , Receptores Opioides/metabolismo , Dolor Abdominal/inducido químicamente , Dolor Abdominal/prevención & control , Acetatos , Analgésicos/uso terapéutico , Animales , Temperatura Corporal/efectos de los fármacos , Antagonistas de Leucotrieno/uso terapéutico , Masculino , Ratones , Naloxona/farmacología , Antagonistas de Narcóticos/farmacología , Dimensión del Dolor/efectos de los fármacos , Propionatos/uso terapéutico , Quinolinas/uso terapéuticoRESUMEN
Irrigation with antibiotic solutions is frequently used in penile prosthesis surgery to avoid infection. We carried out a prospective study to determine the degree of absorption of gentamicin after intracavernous irrigation in 10 patients who underwent penile implantation surgery. All obtained values were below the toxic level of 10 micrograms/ml and decreased gradually within a few hours. We concluded that highly concentrated gentamicin solutions could be used with safety for intracavernous irrigation.
Asunto(s)
Antibacterianos/farmacocinética , Gentamicinas/farmacocinética , Prótesis de Pene , Absorción , Anciano , Antibacterianos/administración & dosificación , Gentamicinas/administración & dosificación , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Irrigación TerapéuticaRESUMEN
The effect of protein energy malnutrition (PEM) in the children on serum levels of total thyroxine (TT4), total triodothyronine (TT3) and thyrotropin (TSH) were evaluated. There were 107 children aged 2 to 60 months in the malnutrition group and 54 healthy age and sex matched controls. Serum TT4 and TT3 were all reduced in the malnutrition group. This decrease in TT3 was more significant (p < 0.01) in severe malnutrition than in mild PEM. Serum TSH levels in the malnutrition and control groups were similar. These results suggest that the children remained euthyroid and represent an adaptive response to protein energy malnutrition.
Asunto(s)
Desnutrición Proteico-Calórica/sangre , Tirotropina/sangre , Tiroxina/sangre , Triyodotironina/sangre , Estudios de Casos y Controles , Preescolar , Femenino , Humanos , Lactante , Masculino , Valores de Referencia , Pruebas de Función de la Tiroides , Glándula Tiroides/metabolismo , Glándula Tiroides/fisiologíaRESUMEN
A new method for the production of ascorbate free radicals is established. The radical is produced from ascorbate in deionized water by applying constant potential electrolysis under a nitrogen atmosphere. Prior to electrolysis, a cyclic voltammogram (CV) of the ascorbic acid was obtained. Electrolysis potentials were selected as the oxidation peak potential of the ascorbic acid obtained by CV. The detection of the radical was done by electron spin resonance (esr) and uv spectroscopies.
Asunto(s)
Ácido Ascórbico/análogos & derivados , Ácido Ascórbico/farmacología , Electroquímica , Electrólisis , Espectroscopía de Resonancia por Spin del Electrón/métodos , Radicales Libres , Espectrofotometría UltravioletaRESUMEN
gamma-Radiation-induced single-strand break formation (ssb) in polyadenylic acid (poly(A] has been determined in Ar and N2O-saturated aqueous solution in the presence of different concentrations of t-butanol. Strand breaks were monitored by a low-angle laser light-scattering technique. The efficiencies for strand breakage caused by solvated electrons, hydrogen atoms and OH radicals have been found to be 0.25, 0.20 and 7.8 per cent, respectively. The efficiency of OH radicals depends only slightly on pH (pH 5.0, 7.5 and 9.0) and is independent of the presence of salt (0.01 mol dm-3 NaC1O4) and of the irradiation temperature (20 degrees C and 70 degrees C). The efficiency of OH for ssb formation obtained in this work with poly(A) is much smaller than that of poly(dA). This is explained by the different molecular conformations of the sugar moiety of poly(A) (3'-endo) and poly(dA) (2'-endo). With increasing t-butanol concentration more strand breaks are formed than expected from simple homogeneous competition kinetics of poly(A) and t-butanol for OH radicals. This result is considered to be due to nonhomogeneous reaction kinetics in the above-mentioned competition. The rate constants for the reaction of OH and H with poly(A) have been determined.
Asunto(s)
Poli A/efectos de la radiación , Algoritmos , Radicales Libres , Rayos gamma , Hidrógeno , Hidróxidos , Radical Hidroxilo , Rayos Láser , Conformación de Ácido Nucleico/efectos de los fármacos , Dispersión de Radiación , Tetranitrometano , AguaRESUMEN
Peroxyl radicals of poly(U), poly(A), and single- and double-stranded DNA have been produced by photolysing H2O2 in oxygenated aqueous solution in presence of the substrates. The peroxyl radicals are formed by the reaction of OH radicals with the polynucleotides followed by addition of oxygen. The lifetime of the peroxyl radicals and the rate constant of their reactions with the thiols cysteamine, glutathione and dithiothreithol have been measured by time-resolved e.s.r. spectroscopy. The unusually long lifetimes range from 0.2 to 3.3 s. The activation energy for the decay for all four substrates is 10.3 +/- 1 kcal/mol (43 kJ mol-1). The reaction rate constants with the thiols range from k = 0.8 X 10(4) to 1.3 X 10(5) dm3 mol-1 s-1. The reactions of the thiols with the peroxyl radical of poly(U) are known to prevent strand break formation. This shows that the peroxyl radicals of poly(U) observed by e.s.r. are intermediates in the pathway leading to strand break formation.