RESUMEN
BACKGROUND: Bimatoprost ophthalmic solution 0·03% is approved in several countries for the treatment of eyelash hypotrichosis. Previous trials were limited to 4 months of treatment and primarily idiopathic hypotrichosis. OBJECTIVES: To evaluate the long-term safety and efficacy of bimatoprost in patients with idiopathic or chemotherapy-induced hypotrichosis. METHODS: This multicentre, double-masked, randomized, parallel-group study included two 6-month treatment periods [treatment period 1 (TP1) and treatment period 2 (TP2)]. Patients with idiopathic hypotrichosis were randomized to three treatment groups: (i) bimatoprost (TP1 and TP2); (ii) bimatoprost (TP1) and vehicle (TP2); and (iii) vehicle (TP1) and bimatoprost (TP2). Patients with chemotherapy-induced hypotrichosis were randomized to two treatment groups: (i) bimatoprost or vehicle (TP1) and (ii) bimatoprost (TP2). Primary end point was a composite of at least a one-grade improvement in investigator-assessed Global Eyelash Assessment and at least a three-point improvement in patient-reported Eyelash Satisfaction Questionnaire Domain 2 at month 4. Secondary measures included digitally assessed eyelash characteristics. RESULTS: The primary efficacy end point was met in both populations (idiopathic responder rate was 40·2% for bimatoprost vs. 6·8% for vehicle; postchemotherapy responder rate was 37·5% for bimatoprost vs. 18·2% for vehicle). Efficacy by month 6 was maintained (idiopathic) or enhanced (postchemotherapy) at 12 months. Treatment effects were maintained for approximately 2 months but markedly diminished 4-6 months following treatment cessation in patients with idiopathic hypotrichosis. No drug-related serious adverse events were reported. CONCLUSIONS: Daily treatment with bimatoprost ophthalmic solution 0·03% for 1 year was effective and well tolerated in patients with idiopathic and chemotherapy-induced hypotrichosis.
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Bimatoprost/administración & dosificación , Fármacos Dermatológicos/administración & dosificación , Pestañas/patología , Enfermedades de los Párpados/tratamiento farmacológico , Hipotricosis/tratamiento farmacológico , Soluciones Oftálmicas/administración & dosificación , Administración Oftálmica , Bimatoprost/efectos adversos , Fármacos Dermatológicos/efectos adversos , Método Doble Ciego , Enfermedades de los Párpados/patología , Femenino , Humanos , Hipotricosis/inducido químicamente , Hipotricosis/patología , Masculino , Persona de Mediana Edad , Soluciones Oftálmicas/efectos adversos , Resultado del TratamientoRESUMEN
A case of localized tracheobronchial primary amyloidosis masquerading as "bronchial asthma" is presented. Computed tomography of the chest and fiberoptic bronchoscopy image are included. Tracheobronchial primary amyloidosis is a rare, but potentially curable cause of airway obstruction mimicking asthma.
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Amiloidosis/diagnóstico , Asma/diagnóstico , Enfermedades Bronquiales/diagnóstico , Enfermedades de la Tráquea/diagnóstico , Diagnóstico Diferencial , Humanos , Masculino , Persona de Mediana EdadAsunto(s)
Virus del Dengue , Dengue/terapia , Dengue/diagnóstico , Dengue/transmisión , Humanos , IndiaAsunto(s)
Fluoroquinolonas/efectos adversos , Torsades de Pointes/inducido químicamente , Adulto , Diagnóstico Diferencial , Femenino , Humanos , India , Síndrome de QT Prolongado/inducido químicamente , Síndrome de QT Prolongado/diagnóstico , Torsades de Pointes/diagnóstico , Tuberculosis Pulmonar/tratamiento farmacológicoRESUMEN
OBJECTIVE: Tuberculosis is a major public health problem in India. Haematological changes associated with tuberculosis have been incompletely investigated. To the best of our knowledge, there is no comprehensive study assessing the haematological abnormalities in these patients from the Indian subcontinent. In the present study, we have compared peripheral blood and bone marrow findings in patients with disseminated/miliary tuberculosis (DTB/MTB) as well as pulmonary tuberculosis (PTB). An attempt has also been made to assess the effect of antituberculosis therapy on the haematologic abnormalities. MATERIAL AND METHODS: Thirty two patients with disseminated/miliary tuberculosis and 23 patients with pulmonary tuberculosis were prospectively studied to determine the various haematological manifestations in tuberculosis and the effect of antituberculosis therapy. All patients received standard antituberculosis treatment. They were subjected to a detailed haemogram including peripheral blood examination, which was repeated on completion of antituberculosis therapy. Bone marrow aspiration and biopsy was also done in all patients before starting antituberculosis treatment. RESULTS: Normocytic normochromic anaemia was the most common abnormality observed in all the groups and subgroups (DTB/MTB 84%, PTB 86%). Other haematological abnormalities of the white blood cells include leucopenia (DTB/MTB 25%, PTB 0%; p < 0.02), neutropenia (DTB/MTB 22%, PTB 0%; p < 0.04), lymphocytopenia, monocytopenia, leukocytosis, neutrophilia, lymphocytosis and monocytosis. Pancytopenia was observed only in patients with disseminated/miliary tuberculosis (p < 0.05). Thrombocytopenia was more common in patients with disseminated/miliary tuberculosis (p < 0.007), whereas thrombocytosis was more common in patients with pulmonary tuberculosis (p < 0.04). The patients of disseminated/miliary tuberculosis with granulomas in the bone marrow had certain significant differences as compared to patients without granulomas. These patients showed severe anaemia, peripheral monocytopenia and bone marrow histiomonocytosis. The haemogram reverted to normal with antituberculosis therapy in these patients. CONCLUSIONS: In view of the varied haematological abnormalities observed in patients with tuberculosis in this part of the world, it is concluded that the differential diagnosis of tuberculosis should be entertained in patients with varied haematological disorders.
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Enfermedades Hematológicas/etiología , Tuberculosis Miliar/complicaciones , Tuberculosis Pulmonar/complicaciones , Adulto , Antituberculosos/uso terapéutico , Médula Ósea/efectos de los fármacos , Femenino , Enfermedades Hematológicas/sangre , Enfermedades Hematológicas/tratamiento farmacológico , Humanos , India , Masculino , Estudios Prospectivos , Tuberculosis Miliar/sangre , Tuberculosis Miliar/tratamiento farmacológico , Tuberculosis Pulmonar/sangre , Tuberculosis Pulmonar/tratamiento farmacológicoAsunto(s)
Infecciones Oportunistas Relacionadas con el SIDA/tratamiento farmacológico , Infecciones Oportunistas Relacionadas con el SIDA/epidemiología , Tuberculosis Pulmonar/tratamiento farmacológico , Tuberculosis Pulmonar/epidemiología , Fármacos Anti-VIH/uso terapéutico , Antituberculosos/uso terapéutico , Humanos , India/epidemiologíaRESUMEN
The objective of the study was to validate and refine the APACHE II (acute physiology and chronic health evaluation II) prognostic system in the Indian context. We prospectively collected data on 79 patients admitted in the medical intensive care unit. We have studied APACHE II and 11 other physiological variables and sought to improve the risk prediction by developing a new score to be governed by the rule of thumb at the bed side. The new score included the following five variables: pH and serum albumin at admission and heart rate, bilirubin and Glasgow coma scale at 48 hours. A score below 3.5 was independently associated with a statistically significant increase in the risk of hospital death. This model resulted in a pseudo r2 of 0.43 in comparison to pseudo r2 of 0.02 and 0.12 for APACHE II scores on the day of admission and after 48 hours, respectively.
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APACHE , Enfermedad Crítica , Estudios de Cohortes , Femenino , Humanos , Modelos Logísticos , Masculino , Persona de Mediana Edad , Pronóstico , Estudios ProspectivosRESUMEN
Transbronchial lung biopsy using the fibreoptic videobronchoscope was carried out in 25 patients with diffuse pulmonary disease. There were no serious complications. Satisfactory specimens were obtained in 20 of the 25 patients. A histological diagnosis was made in 10 patients. The problems of interpreting pulmonary fibrosis have been highlighted. Fibreoptic transbronchial lung biopsy is a safe and useful adjunct to the diagnosis of diffuse parenchymal pulmonary disease.
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Enfermedades Pulmonares/patología , Pulmón/patología , Adulto , Biopsia/métodos , Broncoscopía/métodos , Femenino , Tecnología de Fibra Óptica , Humanos , Masculino , Persona de Mediana EdadRESUMEN
The exact role of fibre-optic bronchoscopy (FOB) and CT of the chest in the diagnosis of patients presenting with haemoptysis and a normal or non-localizing chest radiograph has not been clearly defined. A study was designed to evaluate 50 patients presenting with haemoptysis and a normal or non-localizing chest radiograph using FOB and high-resolution computed tomography (HRCT). A definitive diagnosis was established in 17 (34%) patients. The aetiologies included bronchiectasis (24%), bronchial adenoma (6%), tuberculosis (2%) and bronchitis (2%). The diagnosis was made by HRCT in 15 (30%) patients, while FOB was diagnostic in five (10%) patients. The diagnosis was made by HRCT and FOB in all patients with focal airway abnormalities. Therefore, HRCT effectively delineated abnormalities of both the central and peripheral airways. It is concluded that CT should be obtained prior to FOB in all patients presenting with haemoptysis and a normal or non-localizing chest radiograph.
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Broncoscopía , Hemoptisis/diagnóstico , Radiografía Torácica , Tomografía Computarizada por Rayos X , Adenoma/diagnóstico , Adolescente , Adulto , Anciano , Neoplasias de los Bronquios/diagnóstico , Bronquiectasia/diagnóstico , Bronquitis/diagnóstico , Femenino , Hemoptisis/diagnóstico por imagen , Humanos , Masculino , Persona de Mediana Edad , Sensibilidad y Especificidad , Tuberculosis/diagnósticoRESUMEN
Measurement of intracellular drug levels in cell culture systems can be of predictive value in establishing rational clinical dosage schedules. Such in vitro measurements carried out with anti-HIV agents of the 2',3'-dideoxynucleoside (ddN) class have shown that many of the pharmacologically active ddNTP metabolites of these agents have relatively long intracellular half-lives and little or no host-cell cytotoxicity. As a consequence, replication of drug-exposed cells continues at an unperturbed rate so that a systematic dilution error occurs in the measurement of ddNTP decay half-times. The aim of this study is to present a simple general formulation for the correction of measured t1/2-values for ddNTPs and for other agents with similar intracellular pharmacokinetic properties. Two factors of practical interest emerge: first, the error is greater for agents with slow intracellular clearance rates than for agents with rapid rates; and second, for cell lines with long doubling times, the measured t1/2-values approach more closely to the true t1/2-values, until with the extreme case (quiescent or "G(o)" cells), the observed and true decay times are identical. The greatest dilution errors are seen with adenodine-based agents such as ddATP and 2'-F-ddATP, while the smallest errors are seen with rapidly cleared agents of the dideoxythymidine class.
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Adenosina Trifosfato/análogos & derivados , Fármacos Anti-VIH/farmacocinética , Nucleótidos de Desoxiadenina/farmacocinética , Adenosina Trifosfato/farmacocinética , Células Cultivadas , Técnicas de Cultivo , Didesoxinucleótidos , Semivida , HumanosRESUMEN
The anti-human immunodeficiency virus (anti-HIV) agent 2',3'-didehydro-3'-deoxythymidine (D4T), like other 2',3'-dideoxynucleosides, requires conversion to its 5'-triphosphate to exert its pharmacological effect. Although D4T-triphosphate is unusually potent as an inhibitor of HIV-1 reverse transcriptase, the phosphorylation of the drug at low dose levels is inefficient because of its low affinity as an alternate substrate for the initial phosphorylation enzyme thymidine kinase. Because thymidine kinase is under feedback regulatory control by the physiological deoxynucleoside-5'-triphosphate dTTP, we examined the effect on D4T phosphorylation and thus, potentially, on its antiviral activity, of a variety of agents that lower intracellular dTTP pools. We found that agents that inhibit the de novo pyrimidine biosynthetic pathway have the ability to increase D4T phosphorylation, the most effective being two inhibitors of thymidylate formation, methotrexate and 5-fluoro-2'-deoxyuridine, compounds that block the enzymes dihydrofolate reductase and thymidylate synthetase, respectively. Because HIV itself lacks the capacity to synthesize dTTP and the other deoxynucleoside triphosphates essential for viral replication, combinations of D4T with modulatory agents that deplete host-cell dTTP, unlike conventional anti-HIV drug monotherapy directed solely at viral enzymes, have the ability to inhibit replication of mutant HIV strains as well as of wild-type virus.
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Compuestos de Bifenilo/farmacología , Desoxiguanosina/farmacología , Floxuridina/farmacología , Metotrexato/farmacología , Inhibidores de la Transcriptasa Inversa/metabolismo , Ribonucleósidos/farmacología , Estavudina/metabolismo , Nucleótidos de Timina/biosíntesis , Amidas , Biotransformación , Línea Celular , VIH/efectos de los fármacos , Transcriptasa Inversa del VIH , VIH-1/enzimología , Humanos , Hidroxiurea/farmacología , Cinética , Modelos Biológicos , Fosforilación , Pirazoles , ADN Polimerasa Dirigida por ARN/metabolismo , Inhibidores de la Transcriptasa Inversa/química , Ribosa , Estavudina/química , Timidina Quinasa/metabolismo , Células Tumorales CultivadasRESUMEN
Fazarabine has shown activity in the panel of 60 cultured human tumor lines of the National Cancer Institute. COMPARE analyses relating correlation coefficients of other anticancer drugs with those of fazarabine suggest that this agent operates through a similar mode of action to that of cytarabine. Studies have been carried out both in culture and in vivo to examine the mechanism of action of fazarabine in P388 murine and Molt-4 human lymphoblasts. Authentic fazarabine nucleotide standards were prepared by chemical and enzymatic methods and characterized on HPLC by comparison to related pyrimidine nucleoside-5'-phosphates as well as by enzymatic digestion. Fazarabine inhibited the incorporation of labeled thymidine into DNA without influencing the synthesis of RNA or protein. Deoxycytidine overcomes this inhibition of DNA synthesis and also prevents the cytotoxicity of the drug to lymphoblasts, probably by competing for fazarabine uptake and metabolism. Fazarabine was rapidly phosphorylated in both cell lines; in P388 cells it was incorporated into DNA, where it continued to undergo the same type of ring opening and degradation as the free nucleoside. Alkaline elution studies demonstrated that exposure to the agent resulted in the formation of alkaline labile sites. Fazarabine also inhibited the methylation of deoxycytidine residues in DNA, but this effect was less pronounced than that produced by 5-azacytidine. Taken together, these studies suggest that fazarabine probably acts by arresting the synthesis and/or altering the structural integrity or functional competence of DNA.
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Antimetabolitos Antineoplásicos/uso terapéutico , Azacitidina/análogos & derivados , Linfocitos/efectos de los fármacos , Animales , Antimetabolitos Antineoplásicos/metabolismo , Azacitidina/antagonistas & inhibidores , Azacitidina/metabolismo , Azacitidina/uso terapéutico , Supervivencia Celular/efectos de los fármacos , ADN de Neoplasias/biosíntesis , ADN de Neoplasias/genética , Desoxicitidina/farmacología , Humanos , Leucemia P388/tratamiento farmacológico , Linfocitos/metabolismo , Ratones , Ratones Endogámicos , Fosforilación , Células Tumorales CultivadasRESUMEN
Incorporation of 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ddA), a recently developed anti-HIV agent, into the cellular DNA of human MOLT-4 cells has been compared with the DNA incorporation seen with fialuridine (FIAU; 1-[2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl]-5-iodouracil), a potent anti-hepatitis B (anti-HBV) nucleoside analogue recently found to cause severe hepatic toxicity in human subjects. At equimolar concentrations (10 microM), incorporation of F-ddA was less than 1% of that for FIAU, a difference attributable to the lack of a 3'-hydroxyl group in the former compound and a consequent inability of F-ddA, unlike FIAU, to form DNA internucleotide linkages.
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Antivirales/metabolismo , Arabinofuranosil Uracilo/análogos & derivados , ADN/metabolismo , Didesoxiadenosina/análogos & derivados , Arabinofuranosil Uracilo/metabolismo , Línea Celular , Didesoxiadenosina/metabolismo , HumanosAsunto(s)
Displasia Fibrosa Poliostótica/diagnóstico , Hipoparatiroidismo/diagnóstico , Adulto , Gluconato de Calcio/administración & dosificación , Femenino , Displasia Fibrosa Poliostótica/complicaciones , Estudios de Seguimiento , Humanos , Hipoparatiroidismo/complicaciones , Hipoparatiroidismo/tratamiento farmacológico , IndiaRESUMEN
Twenty male diabetic patients (age range, 40-60 years) with normal autonomic function were studied to determine the prevalence of silent myocardial ischemia on exercise as well as ambulatory electrocardiography. The presence and extent of silent myocardial ischemia was also correlated with the severity of atherosclerotic coronary artery disease as determined by coronary angiography. A cohort of 20 matched non-diabetic patients were also included in the study. Silent myocardial ischemia was detected in 50% of the diabetic patients on exercise electrocardiography and in 35% on ambulatory electrocardiography compared with 10% and 5% in non-diabetics by the two methods, respectively (P < 0.01 and P < 0.05, respectively). On exercise testing in diabetic patients, silent myocardial ischemia was detected in 64% of the patients with three-vessel disease, 50% of the patients with two-vessel disease and 20% of the patients with one-vessel disease whereas in non-diabetic patients silent myocardial ischemia was detected in only 18% of the patients with three-vessel disease (P < 0.05) and in none of the patients with two- or one-vessel disease. On ambulatory electrocardiography, only patients (both diabetic and non-diabetic) with three-vessel disease manifested silent myocardial ischemia. Total ischemic burden was similar in both the diabetic and non-diabetic patients. We conclude that silent myocardial ischemia occurs in diabetic patients with coronary artery disease more frequently even in the absence of autonomic dysfunction and the prevalence of silent myocardial ischemia is higher in patients with severe degree of coronary artery disease.
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Complicaciones de la Diabetes , Electrocardiografía Ambulatoria , Prueba de Esfuerzo , Isquemia Miocárdica/complicaciones , Adulto , Presión Sanguínea/fisiología , Estudios de Casos y Controles , Estudios de Cohortes , Enfermedad de la Arteria Coronaria/diagnóstico , Enfermedad de la Arteria Coronaria/fisiopatología , Diabetes Mellitus/epidemiología , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Persona de Mediana Edad , Isquemia Miocárdica/diagnóstico , Isquemia Miocárdica/epidemiología , Isquemia Miocárdica/fisiopatología , Prevalencia , Estudios Prospectivos , Índice de Severidad de la Enfermedad , Volumen Sistólico/fisiología , Factores de TiempoRESUMEN
The anti-human immunodeficiency virus agents 2',3'-dideoxyadenosine (ddAdo) and 2'-beta-fluoro-2',3'-dideoxyadenosine (2'-beta-F-ddAdo) are rapidly converted, both in vitro and in vivo, to the corresponding inosine analogs by the widely distributed enzyme adenosine deaminase (EC 3.5.4.4). We have determined the effects of the potent adenosine deaminase inhibitor 2'-deoxycoformycin (2'-dCF) on ddAdo and 2'-beta-F-ddAdo metabolism in MOLT-4 cells and on ddAdo antiviral activity in the ATH8 test system. At levels as low as 5 nM in the incubation medium, 2'-dCF effectively blocks the extracellular deamination of both agents, thus permitting their rapid cellular uptake as the unchanged parent compounds, rather than as the less lipid-soluble 2',3'-dideoxyinosine or 2'-beta-fluoro-2',3'-dideoxyinosine. The result is a significant increase in intracellular levels of the pharmacologically active forms 2',3'-dideoxyadenosine-5'-triphosphate and 2'-beta-fluoro-2',3'-dideoxyadenosine-5'-triphosphate. The effect becomes maximal over the range of 50-250 nM 2'-dCF and declines to control levels when extracellular 2'-dCF levels exceed 1 microM. This decrease in ddAdo and 2'-beta-F-ddAdo phosphorylation with higher levels of the inhibitor appears to result from intracellular penetration of 2'-dCF and consequent inhibition of intracellular deamination, a critical step in the activation of both agents through the 5'-nucleotidase pathway. In anti-human immunodeficiency virus assays, a 2.2-fold increase in ddAdo antiviral potency was seen at 2'-dCF levels of 20 and 50 nM.
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Didesoxiadenosina/análogos & derivados , Didesoxiadenosina/farmacología , VIH/efectos de los fármacos , Pentostatina/farmacología , Inhibidores de la Adenosina Desaminasa , Línea Celular , Didanosina/farmacocinética , Didesoxiadenosina/metabolismo , Didesoxiadenosina/farmacocinética , Sinergismo Farmacológico , IMP Deshidrogenasa/antagonistas & inhibidores , Fosforilación/efectos de los fármacos , Ribavirina/farmacologíaRESUMEN
Fecal samples submitted for virus examination over July 1990 to June 1991 from children < 3 years of age were examined by electron microscopy (EM), virus culture (VC), and enzyme immunoassay [EIA, group-reactive and adenovirus (Ad) 40/41 specific; Cambridge BioScience] to compare the detection rate of adenovirus from pediatric fecal specimens. Ad isolates of serotypes 1-7 grown in HEp-2 or primary rhesus monkey kidney cells were identified by neutralization. Graham 293 cell cultures were used only when specimens were found to be positive for Ad by EM, type-specific Ad40/41 EIA, and for isolates not identified by neutralization. Ads grown in 293 cells were identified by DNA restriction endonuclease analysis. Of the 1187 specimens examined, 105 (9%) were found to be positive for Ad. VC detected 93, while 12 additional positives were detected by EM or EIA. The relative sensitivity of VC, EIA, and EM for the 105 specimens was 89% (93), 45% (47), and 35% (37), respectively. Among the 105 positive specimens, enteric Ad, nonenteric Ad, and untypeable Ad were 28% (29), 65% (68), and 7% (8), respectively. Of 37 EM positives, 62% (23) were enteric Ad; 27% (10) were nonenteric including serotypes 2, 3, 4, 5, 12, and 31, with 4, 1, 1, 2, 1, and 1 isolates of each type positive, respectively; and 11% (4) were detectable only by EM. Five isolates were identified as variant of Ad 2(3), Ad 3(1) and Ad 31(1). Over a 1-year period, a single Ad41 variant strain was the most frequently detected enteric Ad in Winnipeg, Manitoba, Canada.(ABSTRACT TRUNCATED AT 250 WORDS)
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Infecciones por Adenovirus Humanos/virología , Adenovirus Humanos/aislamiento & purificación , Heces/microbiología , Adenovirus Humanos/clasificación , Línea Celular , Preescolar , Humanos , Técnicas para Inmunoenzimas , Lactante , Recién Nacido , Microscopía Electrónica , Mapeo Restrictivo , Sensibilidad y Especificidad , Serotipificación , Ultracentrifugación , Cultivo de VirusRESUMEN
The abilities of hybridization probes to detect all human adenovirus types and to identify enteric adenovirus types were evaluated. The efficiency of hybridization was compared to other tests currently in routine laboratory use on clinical specimens from young children with gastroenteritis. Probes were derived from various regions of the adenovirus types 2 and 41 genomes, and were evaluated by hybridization with a series of DNA quantities from 1 microgram to 10 pg of one adenovirus type from each human subgenus, lambda phage, and HEp 2 cells. The sensitivity of hybridization with the HPII probe (92.7%), containing the conserved hexon gene, compared well with EM (54.6%), culture and neutralization (45.5%), and enzyme immunoassay (61.8%). The sensitivity of detection of enteric adenovirus isolates by the cloned Bg/II D fragment probe (92.9%) and by a synthetic probe (85.7%), manufactured from type-specific sequences of the Ad41 hexon gene were comparable to Ad40/Ad41 specific enzyme immunoassay (84.6%). Hybridization was found to be a sensitive method of adenovirus detection in comparison to traditional methods of laboratory diagnosis. Synthetic oligonucleotides enable specific detection of individual enteric adenovirus types. Hybridization had additional advantages over other tests in identifying cases of infection with more than one adenovirus type and in allowing an estimate of the concentration of adenovirus in the specimen.
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Infecciones por Adenoviridae/diagnóstico , Adenovirus Humanos/clasificación , Sondas de Oligonucleótidos , Infecciones por Adenoviridae/epidemiología , Adenovirus Humanos/aislamiento & purificación , Secuencia de Bases , Niño , ADN Viral/análisis , Heces/microbiología , Gastroenteritis/microbiología , Humanos , Técnicas para Inmunoenzimas , Manitoba/epidemiología , Microscopía Electrónica , Datos de Secuencia Molecular , Pruebas de Neutralización , Hibridación de Ácido Nucleico/métodos , Sondas de Oligonucleótidos/síntesis química , Sensibilidad y Especificidad , Cultivo de VirusRESUMEN
Cyclopentenyl cytosine (CPEC) exhibits oncological activity in murine and human tumor cells and has now entered Phase I clinical trials. Its mode of action as an antitumor agent appears to be inhibition by its triphosphate (CPEC-TP) of CTP synthase, the enzyme which converts UTP to CTP. In an attempt to elucidate the mechanism of resistance to CPEC, a murine leukemia cell line resistant to CPEC (L1210/CPEC) was developed by N-methyl-N-nitro-N-nitrosoguanidine-induced mutagenesis and subsequent selection by cultivation of the L1210 cells in the presence of 2 microM CPEC. Resistant clones were maintained in CPEC-free medium for 6 generations before biochemical studies were performed. The resistant clone selected for further studies was approximately 13,000-fold less sensitive to growth inhibition by CPEC than the parental cells, and the concentration of CPEC required to deplete CTP in the resistant cells was 50-fold higher than in the sensitive cells. A comparison of the kinetic properties of CTP synthase from sensitive and resistant cells indicated alteration in the properties of the enzyme from the latter; the median inhibitory concentration for CPEC-TP increased from 2 to 14 microM, Km for UTP decreased from 126 to 50 microM, and Vmax increased 12-fold from 0.2 to 2.3 nmol/mg/min. Northern blot analyses of polyadenylated RNA from the resistant and sensitive cells indicated a 3-fold increase in transcripts of the CTP synthase gene in the resistant line. Consistent with these alterations in the properties of the enzyme, the resistant cells exhibited significantly expanded CTP and dCTP pools (4- 5-fold) when compared with the sensitive cells. No change was observed, however, in the properties of uridine-cytidine kinase, the enzyme responsible for the initial phosphorylation of CPEC; despite this, however, cellular uptake of CPEC was greatly decreased, and phosphorylation of CPEC and its incorporation into RNA were 10-fold less than in the parental cells. These latter observations are most readily explained by feedback inhibition by the increased CTP levels of the resistant cells of uridine-cytidine kinase and/or of the membrane transport process used for initial entry of CPEC.