Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 24
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Immunohematology ; 39(1): 15-18, 2023 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-37017598

RESUMO

Anti-M is usually a naturally occurring antibody directed against M in the MNS blood group system. It does not require exposure to the antigen from previous transfusion or pregnancy. Anti-M is usually of the immunoglobulin M (IgM) isotype, binds best at about 4°C, binds well at room temperature, and rarely binds at 37°C. As a result of its lack of binding at 37°C, anti-M is usually clinically insignificant. There have been rare cases reported of an anti-M that reacts at 37°C. Such an exceptional anti-M may cause hemolytic transfusion reactions. We report a case of a warm-reactive anti-M and the investigational process used to identify it.


Assuntos
Transfusão de Sangue , Reação Transfusional , Feminino , Gravidez , Humanos , Imunoglobulina M
2.
J Dairy Sci ; 102(3): 2698-2702, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30692006

RESUMO

Horns are living tissue and cows can use their horns for thermoregulatory purposes. We investigated the effect of the presence of horns on the metabolome of milk serum and lipidome of milk fat, to assess the physiological effect of dehorning. Milk sampling took place at low ambient temperatures of -6 to 2°C. Horned and dehorned cows were kept in a mixed herd of Holstein Friesian and Brown Swiss cows. The hypothesis was that horned cows needed to increase their metabolism to compensate for additional heat loss through the presence of their horns. No differences were observed in milk yield, milk solids, and somatic cell counts between horned and dehorned cows. For the milk metabolome, horned cows showed an upregulation of several glucogenic AA that could be transformed into glucose for energy supply and a downregulation of sugar intermediates and γ-glutamylcysteine compared with dehorned cows. The fatty acid (FA) composition in horned cows showed a shift toward decreased odd medium-chain FA (C7:0, C9:0, and C11:0) and increased cis-vaccenic acid (C18:1n-7 cis-11) and stearidonic acid (C18:4n-3). The changes in milk composition related to additional heat loss in horned cows indicate a competition in C3 metabolism for glucose synthesis and de novo FA synthesis under cold stress.


Assuntos
Cornos/fisiologia , Metaboloma , Leite/química , Animais , Regulação da Temperatura Corporal , Metabolismo dos Carboidratos , Bovinos , Ácidos Graxos/metabolismo , Feminino , Cornos/cirurgia , Lactação/fisiologia , Ácidos Oleicos/metabolismo
3.
Eur J Nutr ; 55(6): 2063-73, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26286349

RESUMO

PURPOSE: The consumption of foods rich in dietary fiber and polyunsaturated fatty acids such as nuts can contribute to a healthy diet. Therefore, the formation of fermentation end-products which might exert chemopreventive effects regarding colon cancer was investigated after an in vitro simulated digestion and fermentation of nuts using human fecal microbiota. METHODS: Fermentation supernatants (FS) and pellets (FP) were obtained after an in vitro fermentation of hazelnuts, almonds, macadamia, pistachios and walnuts. Short-chain fatty acids (SCFA) and bile acids (BA) in FS as well as fatty acids in FP were analyzed via gas chromatography. Malondialdehyde (MDA) levels in FS were determined photometrically. RESULTS: Fermentation of nuts resulted in 1.9- to 2.8-fold higher concentrations of SCFA compared to the control and a shift of molar ratios toward butyrate production. In vitro fermentation resulted in the formation of vaccenic acid (C18:1t11, 32.1 ± 3.2 % FAME; fatty acid methyl ester) and conjugated linoleic acid (c9,t11 CLA, 2.4 ± 0.7 % FAME) exclusively in fermented walnut samples. Concentrations of secondary BA deoxycholic-/iso-deoxycholic acid (6.8-24.1-fold/4.9-10.9-fold, respectively) and levels of MDA (1.3-fold) were significantly reduced in fermented nut samples compared to the control. CONCLUSION: This is the first study that demonstrates the ability of the human fecal microbiota to convert polyunsaturated fatty acids from walnuts to c9,t11 CLA as a potential chemopreventive metabolite. In addition, the production of butyrate and reduction in potential carcinogens such as secondary BA and lipid peroxidation products might contribute to the protective effects of nuts regarding colon cancer development.


Assuntos
Butiratos/química , Fermentação , Ácidos Linoleicos Conjugados/química , Nozes/química , Ácidos e Sais Biliares/metabolismo , Neoplasias do Colo/prevenção & controle , Corylus/química , Ácidos Graxos Insaturados/química , Fezes/microbiologia , Microbioma Gastrointestinal , Humanos , Concentração de Íons de Hidrogênio , Juglans/química , Macadamia/química , Malondialdeído/química , Ácidos Oleicos/química , Pistacia/química , Prunus dulcis/química , Substâncias Reativas com Ácido Tiobarbitúrico/análise
4.
Epidemiol Infect ; 136(11): 1564-75, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18198003

RESUMO

Acute parvovirus B19 infection is a risk for pregnant women. After vertical transmission the infected fetus may develop hydrops fetalis. Since B19 infection occurs mainly during childhood, children represent a main source for virus transmission. In order to determine whether certain groups in the German population show increased risks for B19 infection we analysed the seroprevalence using 6583 sera collected from adults in former Eastern and Western Germany during the German National Health Survey and 649 sera from healthy Thuringian children and adolescents. In adults the overall seroprevalence was 72.1%, rising from 20.4% in children (1-3 years) and 66.9% in adolescents (18-19 years) to 79.1% in the elderly (65-69 years). Significant differences were observed between females (73.3%) and males (70.9%) and between inhabitants of small (74.8%) and big cities (69.0%) but not between people of the former Eastern (72.8%) and Western states (72.0%) of Germany. For women during childbearing age (18-49 years) highest values were observed in those living together with two or more children (81.6%) and in women with occupational contact with children aged <6 years (88.9%). In contrast seroprevalence was significantly lower in age-matched female singles (64.8%) and in women with occupational contact with children aged >6 years and adolescents (63.8%).


Assuntos
Infecções por Parvoviridae/epidemiologia , Parvovirus B19 Humano/isolamento & purificação , Adolescente , Adulto , Fatores Etários , Idoso , Animais , Anticorpos Antivirais/sangue , Criança , Pré-Escolar , Feminino , Alemanha/epidemiologia , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Estudos Soroepidemiológicos , Fatores Sexuais , População Urbana
5.
Water Sci Technol ; 54(6-7): 347-54, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-17120668

RESUMO

Hydrologic and hydraulic modeling in the USEPA Stormwater Management Model (SWMM) were used to examine the effectiveness of typical stormwater management practices in reducing the potential for stream erosion. Fifty-year continuous simulations were used to produce flow duration curves and stream erosion rates for a variety of critical shear stress values representative of both cohesive and non-cohesive sediments. An excess shear stress erosion potential index was used to evaluate changes in erosion between undeveloped conditions of a 10 hectare watershed and four variations of post-development stormwater control. Evaluation of flow duration curves showed that when development takes place, the duration of mid- to low-range discharges increase significantly, especially when detention practices are applied. In channels with low entrainment thresholds for bed and bank materials, e.g. sands and highly erodible clays, the significant increase of the duration of mid- to low-range discharges results in erosion potential index values greater than two regardless of the detention practices used. Overcontrol detention resulted in erosion potential index values of less than one, indicating a loss of erosion potential for bed materials such as most gravels (d(s) > 6 mm) and resistant clays that have critical shear stress values greater than four Pa.


Assuntos
Cidades , Drenagem Sanitária , Modelos Teóricos , Chuva , Rios , Movimentos da Água , Simulação por Computador , Sedimentos Geológicos , Estresse Mecânico
6.
J Small Anim Pract ; 43(7): 303-7, 2002 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12137151

RESUMO

Five cats tentatively diagnosed with pituitary adenoma (four cases) or pituitary carcinoma (one case), based on computed tomography (CT) or magnetic resonance imaging, were treated with radiotherapy. Electrons were applied in four cats and electrons and photons in the fifth. Ten to 12 fractions of 3.5 to 4.0 Gy each were delivered on a Monday/Wednesday/Friday schedule. The mean total dose applied was 39 Gy. No severe acute side effects to treatment were seen. Follow-up CT examination was performed in four cats; the mass had disappeared in one cat and remained stable or slightly decreased in size in the other three. The survival times were 5.5, 8.0, 15.0, 18.0 and 20.5 months, with two cats dying of causes unrelated to the tumour. Based on these cases, radiotherapy appears to be a valuable treatment option for feline pituitary tumours.


Assuntos
Adenoma/veterinária , Carcinoma/veterinária , Neoplasias Hipofisárias/veterinária , Adenoma/radioterapia , Animais , Carcinoma/radioterapia , Gatos , Evolução Fatal , Feminino , Masculino , Neoplasias Hipofisárias/radioterapia , Sobrevida , Tomografia Computadorizada por Raios X , Resultado do Tratamento
7.
J Am Anim Hosp Assoc ; 37(5): 483-8, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11563449

RESUMO

Radiation therapy for three cases of suspect feline thymoma is described. The thymoma was controlled for 4 years in case no. 1. Case no. 2 responded well to radiation therapy but was euthanized after 2 months because of a nasal adenocarcinoma. Case no. 3 continues to do well more than 8 months after radiotherapy. Difficulties in diagnosing feline thymomas are discussed, and biological behavior as well as different treatment modalities of feline and human thymomas are compared.


Assuntos
Doenças do Gato/diagnóstico , Doenças do Gato/radioterapia , Timoma/veterinária , Neoplasias do Timo/veterinária , Animais , Doenças do Gato/patologia , Gatos , Diagnóstico Diferencial , Feminino , Masculino , Timoma/diagnóstico , Timoma/radioterapia , Neoplasias do Timo/diagnóstico , Neoplasias do Timo/radioterapia
8.
J Am Anim Hosp Assoc ; 36(1): 20-5, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10667402

RESUMO

An 18-month-old, spayed female, mixed-breed dog was referred for investigation of persistent hypercalcemia. After extensive diagnostic evaluation, a tentative diagnosis of occult lymphosarcoma (LSA) was made and the dog was euthanized. At necropsy, infection with Heterobilharzia americana was diagnosed. In endemic areas, schistosomiasis should be included in the differential diagnosis of hypercalcemia, and a fecal examination should be performed in every dog with a hypercalcemia of unknown origin.


Assuntos
Doenças do Cão/diagnóstico , Doenças do Cão/etiologia , Hipercalcemia/veterinária , Esquistossomose/veterinária , Animais , Diagnóstico Diferencial , Cães , Evolução Fatal , Feminino , Hipercalcemia/etiologia , Esquistossomose/complicações , Esquistossomose/diagnóstico
9.
J Expo Anal Environ Epidemiol ; 10(6 Pt 2): 710-22, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11138663

RESUMO

A deterministic model was developed to identify the critical input parameters needed to assess dietary intakes of young children. The model was used as a framework for understanding the important factors in data collection and data analysis. Factors incorporated into the model included transfer efficiencies of pesticide from surfaces to food, transfer efficiencies of pesticide from surfaces to hands to food, and more accurate microactivity data related to contact frequency for the three variables of interest--hands, surfaces, and food. Results from range-finding measurements of transfer efficiencies using an aqueous pesticide solution of a mixture of malathion, diazinon, and chlorpyrifos sprayed on the surfaces indicate that a higher pesticide transfer occurred from hard surfaces to food (hardwood, plastic), with low transfer from soft surfaces (carpet, cloth). Six children, all less than 4 years old, were videotaped to obtain realistic contact frequency and times for the interaction of hands, surfaces, and foods during eating meals and snacks while in their homes or day care centers. The time range of eating events varied from about 2 to 55 min, with an average of about 20 min. The average number of contact frequencies between food and hands was 19 times for each eating event, with a range of 10-40. Contacts between the surface and hand were about the same as the food and hands. Contacts between foods and surfaces ranged from 0 to 32, but only five or less of the contacts per eating event were associated with surfaces other than eating utensil. The children's microactivity data collected during the eating events, together with the laboratory results from the transfer studies, were provided as input into a Monte Carlo simulation of the dietary ingestion model. Simulation results indicate that children's handling of the food could contribute 20-80% of the total dietary intake of pesticides. Dietary exposure due to residues in the food before handling accounted for 16% and 47%, respectively, of the total mean intake from simulations for a child's consumption of an apple or banana. These results indicated that transfer efficiencies for foods on various surfaces typically found in homes as well as children's hand contacts with the food and surfaces are important as determinants of dietary exposure.


Assuntos
Dieta , Exposição Ambiental/análise , Poluentes Ambientais/análise , Contaminação de Alimentos , Resíduos de Praguicidas/análise , Pré-Escolar , Coleta de Dados/métodos , Feminino , Manipulação de Alimentos , Humanos , Lactente , Masculino , Modelos Teóricos , Fatores de Tempo , Gravação em Vídeo
11.
Am J Vet Res ; 60(8): 977-81, 1999 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10451208

RESUMO

OBJECTIVE: To determine whether healthy dogs given high doses of methylprednisolone sodium succinate (MPSS) develop gastrointestinal tract ulcers and hemorrhage. ANIMALS: 19 healthy male hound-type dogs. PROCEDURE: Dogs were assigned randomly to intravenously receive high doses of MPSS (30 mg/kg of body weight, initially, then 15 mg/kg 2 and 6 hours later, and, subsequently, every 6 hours for a total of 48 hours; n = 10) or an equal volume of saline (0.9% NaCl) solution (9). Gastroduodenoscopy was performed before and after treatment. Endoscopic evidence of gross hemorrhage in the cardia, fundus, antrum, and duodenum of each dog was graded from none (0) to severe (3), and a total stomach score was calculated as the sum of the regional gastric scores. Number of ulcers were recorded. The pH of gastric fluid and evidence of occult gastric and fecal blood were measured. Food retention was recorded. RESULTS: Gastric hemorrhage was evident in all dogs after MPSS administration and was severe in 9 of 10 dogs but not visible in any dog after saline treatment. Occult gastric blood was detected more commonly (9/10 vs 2/9), median gastric acidity was greater (pH 1 vs pH 3), and food was retained more commonly (7/10 vs 1/9) in the stomach of MPSS-treated dogs. CONCLUSIONS AND CLINICAL RELEVANCE: High doses of MPSS cause gastric hemorrhage in dogs. All dogs treated with high doses of MPSS should be treated with mucosal protectants or antacids to prevent gastric hemorrhage.


Assuntos
Doenças do Cão/induzido quimicamente , Hemorragia Gastrointestinal/veterinária , Glucocorticoides/efeitos adversos , Hemissuccinato de Metilprednisolona/efeitos adversos , Fármacos Neuroprotetores/efeitos adversos , Animais , Biópsia/veterinária , Doenças do Cão/fisiopatologia , Cães , Endoscopia Gastrointestinal/veterinária , Suco Gástrico , Hemorragia Gastrointestinal/induzido quimicamente , Hemorragia Gastrointestinal/fisiopatologia , Glucocorticoides/administração & dosagem , Concentração de Íons de Hidrogênio , Infusões Intravenosas/veterinária , Masculino , Hemissuccinato de Metilprednisolona/administração & dosagem , Fármacos Neuroprotetores/administração & dosagem , Sangue Oculto , Fotografação , Antro Pilórico/patologia , Distribuição Aleatória , Gravação de Videoteipe
12.
Am J Vet Res ; 60(8): 982-5, 1999 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10451209

RESUMO

OBJECTIVE: To determine whether administration of misoprostol prevents gastric hemorrhage in healthy dogs treated with high doses of methylprednisolone sodium succinate (MPSS). ANIMALS: 18 healthy hound-type dogs of both sexes. PROCEDURE: All dogs were given high doses of MPSS (30 mg/kg of body weight, initially, then 15 mg/kg 2 and 6 hours later, and, subsequently, q 6 h for a total of 48 hours) IV. Dogs were assigned randomly to receive concurrent treatment with misoprostol (4 to 6 microg/kg, PO, q 8 h; n = 9) or an empty gelatin capsule (9). Gastroduodenoscopy was performed before and after treatment. Hemorrhage was graded from none (0) to severe (3) for each cardia, fundus, antrum, and duodenum. A total stomach score was calculated as the sum of the regional stomach scores. Food retention was recorded, and pH of gastric fluid was determined. Gastric and fecal occult blood was measured. RESULTS: Gastric hemorrhage was evident in all dogs after MPSS administration, and its severity was similar in both groups. Median total stomach score was 6 for misoprostol-treated dogs and 5.5 for dogs given the gelatin capsule. Difference in gastric acidity, frequency of food retention, and incidence of occult blood in gastric fluid and feces was not apparent between the 2 groups. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of misoprostol (4 to 6 microg/kg, PO, q 8 h) does not prevent gastric hemorrhage caused by high doses of MPSS. Alternative prophylactic treatment should be considered.


Assuntos
Antiulcerosos/uso terapêutico , Doenças do Cão/prevenção & controle , Hemorragia Gastrointestinal/veterinária , Hemissuccinato de Metilprednisolona/efeitos adversos , Misoprostol/uso terapêutico , Fármacos Neuroprotetores/efeitos adversos , Animais , Biópsia/veterinária , Doenças do Cão/induzido quimicamente , Doenças do Cão/fisiopatologia , Cães , Endoscopia Gastrointestinal/veterinária , Feminino , Suco Gástrico , Hemorragia Gastrointestinal/induzido quimicamente , Hemorragia Gastrointestinal/prevenção & controle , Masculino , Sangue Oculto , Piloro/patologia , Distribuição Aleatória
13.
Schweiz Med Wochenschr ; 128(3): 53-63, 1998 Jan 17.
Artigo em Alemão | MEDLINE | ID: mdl-9498256

RESUMO

Systemic anaphylaxis is a potentially life-threatening clinical syndrome resulting from the release of biologically active substances such as histamine or prostaglandins upon a target organ. The aims of our study were to analyze clinical data, causative agents and follow-up in subjects with severe anaphylaxis. Of 5689 subjects who were referred from May 1994 through October 1996 to the allergy-immunology out-patient clinic of the University of Berne, 118 (2.1%; 68 females and 50 males; mean age 41 years) had experienced severe systemic anaphylaxis with hypotension, loss of consciousness or shock. 104 individuals (88.1%) showed accompanying dermal symptoms, 85 (72.0%) respiratory and 52 (44.1%) gastrointestinal signs. Causative agents were identified in 93.2% of these attacks; they included drugs (33.9%), insect stings (23.7%), foods (18.6%), exercise (8.5%), latex (7.6%), and immunotherapy (0.9%) with pollen extracts. A suspected cause could not be determined in 8 subjects. Atopy was present in 64 individuals (54%). Prior to the index anaphylaxis, 21 of 110 subjects (19.1%) with an identified cause had experienced more than one episode of anaphylaxis. Follow-up survey showed that 29 of these 110 individuals (26.4%) were accidentally reexposed to the causative agents. 19 of 24 patients (79.2%) used their emergency kits, while 5 were not equipped with. Only one severe systemic reaction occurred in a subject who intentionally reexposed himself to the identified cause of anaphylaxis. Besides cardiovascular symptoms, systemic anaphylaxis most often involves the skin and respiratory tract. Since prevention of anaphylaxis focuses upon avoidance of precipitating factors, all individuals with anaphylaxis should be referred to an allergologist for identification of the causative agents. The cause of anaphylaxis could be determined in the majority of patients with anaphylaxis. However, unexpected exposures are frequent. Thus, all patients who have had one or more episodes of anaphylaxis should carry an emergency kit for self-administration, and should be instructed in its use.


Assuntos
Anafilaxia/imunologia , Adolescente , Adulto , Idoso , Anafilaxia/epidemiologia , Anafilaxia/etiologia , Anafilaxia/prevenção & controle , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Suíça/epidemiologia
14.
Anal Bioanal Chem ; 356(1): 99-101, 1996 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15048377

RESUMO

An on-line system for the simultaneous determination of Se(IV), Se(VI) and selenomethionine (Se-Met) in aqueous samples was developed, consisting of separation by ion chromatography, microwave digestion and detection by hydride generation atomic absorption spectrometry. 8.3 mmol/l Na(2)HPO(4) (pH 9.2) was used as mobile phase for the ion chromatography, with a flow-rate of 1.5 ml/min. After the separation the sample was mixed with concentrated KBr-HCl solution and heated with microwave energy to digest Se-Met and reduce Se(VI) to Se(IV). The detection limits were 15 microg/l, 12 microg/l and 103 microg/l for Se(IV), Se(VI) and Se-Met, respectively.

15.
J Clin Endocrinol Metab ; 79(6): 1619-24, 1994 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-7527406

RESUMO

The effects of 17 beta-estradiol (E2) on the serum levels of the circulating endothelial-leukocyte, intercellular, and vascular adhesion molecules [ELAM-1, ICAM-1 (CD54), and VCAM-1] were evaluated in healthy male volunteers after single im injection of 10 mg E2 valerate. In addition, a time course of the effects of E2 on circulating adhesion molecules (AMs), cortisol serum levels, differential blood counts, and surface expression of the lymphocyte function-associated antigen-1 (CD11a/CD18), CD3, CD4, CD19, and CD25 on leukocytes was studied in another group of volunteers. A 5% decrease in circulating ICAM-1 (P = 0.045 vs. placebo) was found when a single time point (96 h after E2 injection) was studied. However, this decrease was smaller than the intrasubject (day to day) variability observed, and there was no consistent and time-dependent effect of E2 on circulating AMs. Circulating neutrophils increased 2.3-fold over baseline after E2 treatment (P = 0.0008 vs. placebo). The mean coefficients of variation for the intrasubject (day to day) and intersubject variability of circulating AMs were between 5.4-7.5% and 20-29%, respectively. Our findings indicate that the effect of E2 on circulating AMs is not distinguishable from the intrasubject variability observed after placebo treatment. Thus, an effect of E2 on adhesion molecules is unlikely to contribute to the antiatherogenic-cardioprotective effect of E2. The pronounced E2-mediated increase in neutrophils deserves further studies to elucidate its (patho-)physiological implications.


Assuntos
Moléculas de Adesão Celular/sangue , Estradiol/farmacologia , Molécula 1 de Adesão Intercelular/sangue , Adulto , Antígenos CD/sangue , Selectina E , Humanos , Hidrocortisona/sangue , Cinética , Contagem de Leucócitos , Antígeno-1 Associado à Função Linfocitária/análise , Masculino , Neutrófilos , Molécula 1 de Adesão de Célula Vascular
16.
J Card Surg ; 8(5): 541-5, 1993 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-8219534

RESUMO

Thoracic aneurysms are relatively rare in infancy. We report our experience with two such patients, one with a false aneurysm of the ascending aorta and the other with a mycotic aneurysm of the main pulmonary artery. Neck cannulation prior to sternotomy, using cannulae designed for extracorporeal membrane oxygenation, allowed entry into the mediastinum under controlled circumstances and permitted the successful repair of the aneurysms.


Assuntos
Falso Aneurisma/cirurgia , Aneurisma Infectado/cirurgia , Doenças da Aorta/cirurgia , Aspergilose/cirurgia , Artéria Pulmonar/cirurgia , Aorta/cirurgia , Ponte Cardiopulmonar , Cateterismo/métodos , Feminino , Humanos , Lactente , Pescoço , Esterno/cirurgia
19.
Mutat Res ; 159(1-2): 65-74, 1986.
Artigo em Inglês | MEDLINE | ID: mdl-3941666

RESUMO

[3H-Et]Nitrosourea was administered to male (101 X C3H) mice by i.p. injection at exposure levels of 10 mg/kg or 100 mg/kg. At intervals from 1 h to 6 days following treatment, the ratio of O6-ethylguanine to N7-ethylguanine in testis DNA averaged 1.13 following the 100 mg/kg exposure and 0.72 following the 10 mg/kg exposure. The amount of O6-ethylguanine recovered after the 100 mg/kg exposure was 40% greater than predicted from a linear extrapolation of the amount of O6-ethylguanine recovered after the 10 mg/kg exposure. We suggest that the high (100 mg/kg) exposure to ethyl nitrosourea results in depletion of the O6-alkylguanine acceptor protein within the testis and permits O6-ethylguanine to persist at higher levels than would be predicted from lower exposure data. W.L. Russell et al. (1982), W.L. Russell (1984) have found that specific-locus mutation frequencies induced in mouse spermatogonial stem cells are 5.8-fold greater after a single 100 mg/kg exposure to ethyl nitrosourea than after 10 weekly exposures to 10 mg/kg. The finding that the corresponding ratio for O6-ethylguanine formed in the testis is only 1.4 may be interpreted in a number of possible ways. If O6-ethylguanine is an important lesion for producing specific-locus mutations, then its formation in the stem cells must be at least 4-fold greater than that for the whole testis as the ENU exposure goes from 10 to 100 mg/kg: alternatively, the rate of repair of this lesion by the stem cells must decrease at least 4-fold relative to the average testicular cell. Other explanations for the difference in mutation response of the stem cells to acute vs. chronic ethyl nitrosourea-exposures include the possibility that other DNA lesions may be responsible for many of the mutations or that two hits on the DNA may be required to produce an effect.


Assuntos
Alquilantes , DNA/metabolismo , Etilnitrosoureia/toxicidade , Testículo/efeitos dos fármacos , Alquilação , Animais , DNA/genética , Relação Dose-Resposta a Droga , Etilnitrosoureia/metabolismo , Guanina/análogos & derivados , Guanina/metabolismo , Masculino , Camundongos , Espermatogônias/efeitos dos fármacos , Fatores de Tempo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...