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1.
Rev Gastroenterol Mex (Engl Ed) ; 85(4): 461-471, 2020.
Article in English, Spanish | MEDLINE | ID: mdl-32863095

ABSTRACT

There has been a recent increase in the consumption of cow's milk substitutes, specifically plant-based beverages, which have erroneously been named "plant milks". Plant-based beverages do not have a standard of identity, and so their nutritional composition can vary from one brand to another, even within the same category. The aim of the present narrative review was to produce a technical opinion to serve as a frame of reference for sustaining the recommendation of soy plant-based beverages. Nutrition and gastroenterology experts that belong to the Asociación Mexicana de Gastroenterología jointly commented on and analyzed themes on plant-based beverages, and on soy drinks in particular, including their nutritional characteristics, consumption in children, and potential growth and development alterations, as well as soy drink consumption in adults and its association with gastrointestinal alterations and other conditions. Plant-based beverages, including those made from soy, are not a replacement for breastmilk or breastmilk substitutes. Soy beverages are considered safe and can enrich the varied diet of its consumers, as long as they are considered an additional liquid portion of the diet. They can be ingested by adults and children above two years of age that present with cow's milk protein allergy or lactose intolerance.


Subject(s)
Soy Milk , Adult , Animals , Child , Diet , Guidelines as Topic , Humans , Male , Rabbits
2.
Curr Oncol ; 26(Suppl 1): S43-S52, 2019 11.
Article in English | MEDLINE | ID: mdl-31819709

ABSTRACT

Background: To date, the role of adjuvant systemic therapy in stages ii and iii colon cancer remains a topic of interest and debate. The objective of the present review was to assess the most recent data, specifically addressing methods of risk stratification, duration of therapy, and future directions. Methods: PubMed and medline were searched for literature pertinent to adjuvant chemotherapy in either stage ii or stage iii colorectal cancer. Summary: Locoregional disease, histopathology, age, laterality, and a number of other biologic and molecular markers appear to have a role in disease risk stratification. The duration of adjuvant therapy for stage iii disease can vary based on risk factors, but use of adjuvant therapy and duration of therapy in stage ii disease remain controversial. Future directions should include genomic assays and improved study design to provide concrete evidence about the duration of adjuvant folfox or capox and about other types of chemotherapy and immunotherapy.


Subject(s)
Chemotherapy, Adjuvant/methods , Colonic Neoplasms/drug therapy , Duration of Therapy , Humans , Neoplasm Staging , Risk Factors
3.
Acta ortop. mex ; 33(4): 211-216, jul.-ago. 2019. tab, graf
Article in Spanish | LILACS | ID: biblio-1284942

ABSTRACT

Resumen: Introducción: La artrodesis subastragalina o astrágalo calcánea, es un procedimiento de estabilización quirúrgica en la patología aislada de la articulación subastragalina que no responde a tratamiento conservador, su objetivo es obtener una fusión sólida de la articulación para eliminar o aminorar el dolor y mejorar la función, normalizando la distribución de cargas del pie y su alineación. Existen variables estudiadas que interfieren en el resultado quirúrgico de los pacientes tratados con artrodesis subastragalina como son: el tabaquismo, edad, sexo, artrosis, IMC, rehabilitación, material de osteosíntesis y la técnica quirúrgica. Objetivo: Conocer los factores pronósticos asociados a los resultados de la artrodesis subastragalina. Material y métodos: Estudio retrospectivo, longitudinal, descriptivo con revisión de expedientes y elaboración de estadística descriptiva de casos tratados de Agosto de 2012 a Enero de 2016 con artrodesis subastragalina para identificar factores pronósticos que afecten el resultado. Resultados: Se analizaron 29 pies, reportándose una artrodesis exitosa en 21 casos (72.4%), en 82.8% la técnica quirúrgica fue adecuada. La tasa de complicaciones fue de 20.7%. En la escala de la Sociedad Ortopédica Americana de Pie y Tobillo (AOFAS) 55.2% se reportaron como resultado muy bueno, 27.6% bueno y sólo 17.2% regular, se encontraron como factores asociados el sexo y la rehabilitación postoperatoria al buen resultado. Discusión: La artrodesis subastragalina brinda alivio en cuanto al dolor y mejoría en alineación, en nuestro servicio este procedimiento presenta una tasa de éxito de 72.4%, entre los factores asociados con significancia estadística fue la rehabilitación y el sexo.


Abstract: Introduction: Subtalar arthrodesis is a surgical stabilization procedure in the isolated pathology of the subastragaline joint that does not respond to conservative treatment, its goal is to obtain a solid fusion of the joint to eliminate or improve pain and function, normalizing the distribution of foot loads and alignment of the foot. There are studied variables that interfere with the surgical outcome of patients treated with subtalar arthrodesis such as: smoking, age, sex, osteoarthritis, BMI, rehabilitation, osteosynthesis material and surgical technique. Objective: To know the prognostic factors associated with the results of subastragaline arthrodesis. Material and methods: Retrospective, longitudinal, descriptive study with review of files and conducting descriptive statistics of treated cases of August 2012- Jan 2016 with subtalar arthrodesis to identify predictive factors affecting the outcome. Results: 29 feet were analyzed, reporting a successful arthrodesis in 21 cases (72.4%), in 82.8% the surgical technique was adequate. The complication rate was 20.7% On the AOFAS scale 55.2% were reported as a very good result, 27.6% good and only 17.2% regular. The factors associated with good outcome were sex and postoperative rehabilitation. Discussion: The subtalar arthrodesis provides improvement in pain and alignment, at our service this procedure presents a success rate of 72.4%, among the factors associated with statistical significance was rehabilitation and sex.


Subject(s)
Humans , Osteoarthritis/surgery , Subtalar Joint , Prognosis , Arthrodesis , Retrospective Studies , Treatment Outcome , Fracture Fixation, Internal
4.
Acta Ortop Mex ; 33(4): 211-216, 2019.
Article in Spanish | MEDLINE | ID: mdl-32246590

ABSTRACT

INTRODUCTION: Subtalar arthrodesis is a surgical stabilization procedure in the isolated pathology of the subastragaline joint that does not respond to conservative treatment, its goal is to obtain a solid fusion of the joint to eliminate or improve pain and function, normalizing the distribution of foot loads and alignment of the foot. There are studied variables that interfere with the surgical outcome of patients treated with subtalar arthrodesis such as: smoking, age, sex, osteoarthritis, BMI, rehabilitation, osteosynthesis material and surgical technique. OBJECTIVE: To know the prognostic factors associated with the results of subastragaline arthrodesis. MATERIAL AND METHODS: Retrospective, longitudinal, descriptive study with review of files and conducting descriptive statistics of treated cases of August 2012- Jan 2016 with subtalar arthrodesis to identify predictive factors affecting the outcome. RESULTS: 29 feet were analyzed, reporting a successful arthrodesis in 21 cases (72.4%), in 82.8% the surgical technique was adequate. The complication rate was 20.7% On the AOFAS scale 55.2% were reported as a very good result, 27.6% good and only 17.2% regular. The factors associated with good outcome were sex and postoperative rehabilitation. DISCUSSION: The subtalar arthrodesis provides improvement in pain and alignment, at our service this procedure presents a success rate of 72.4%, among the factors associated with statistical significance was rehabilitation and sex.


INTRODUCCIÓN: La artrodesis subastragalina o astrágalo calcánea, es un procedimiento de estabilización quirúrgica en la patología aislada de la articulación subastragalina que no responde a tratamiento conservador, su objetivo es obtener una fusión sólida de la articulación para eliminar o aminorar el dolor y mejorar la función, normalizando la distribución de cargas del pie y su alineación. Existen variables estudiadas que interfieren en el resultado quirúrgico de los pacientes tratados con artrodesis subastragalina como son: el tabaquismo, edad, sexo, artrosis, IMC, rehabilitación, material de osteosíntesis y la técnica quirúrgica. OBJETIVO: Conocer los factores pronósticos asociados a los resultados de la artrodesis subastragalina. MATERIAL Y MÉTODOS: Estudio retrospectivo, longitudinal, descriptivo con revisión de expedientes y elaboración de estadística descriptiva de casos tratados de Agosto de 2012 a Enero de 2016 con artrodesis subastragalina para identificar factores pronósticos que afecten el resultado. RESULTADOS: Se analizaron 29 pies, reportándose una artrodesis exitosa en 21 casos (72.4%), en 82.8% la técnica quirúrgica fue adecuada. La tasa de complicaciones fue de 20.7%. En la escala de la Sociedad Ortopédica Americana de Pie y Tobillo (AOFAS) 55.2% se reportaron como resultado muy bueno, 27.6% bueno y sólo 17.2% regular, se encontraron como factores asociados el sexo y la rehabilitación postoperatoria al buen resultado. DISCUSIÓN: La artrodesis subastragalina brinda alivio en cuanto al dolor y mejoría en alineación, en nuestro servicio este procedimiento presenta una tasa de éxito de 72.4%, entre los factores asociados con significancia estadística fue la rehabilitación y el sexo.


Subject(s)
Arthrodesis , Osteoarthritis , Subtalar Joint , Fracture Fixation, Internal , Humans , Osteoarthritis/surgery , Prognosis , Retrospective Studies , Treatment Outcome
5.
Rev. clín. esp. (Ed. impr.) ; 218(3): 115-120, abr. 2018. tab
Article in Spanish | IBECS | ID: ibc-174240

ABSTRACT

Objetivos. Blastocystis hominis (B. hominis) es uno de los parásitos intestinales más frecuentemente aislados en el ser humano. Puede producir sintomatología gastrointestinal o, en la mayoría de los casos, permanecer asintomático. Existen dudas sobre el carácter patógeno del parásito. El objetivo de este estudio fue analizar las características clínicas y epidemiológicas de la parasitación por B. hominis, con y sin otras coparasitaciones. Pacientes y métodos. Estudio observacional retrospectivo de aislamientos de B. hominis en heces, desde octubre del 2004 hasta marzo del 2016 en una Unidad de Medicina Tropical. Se revisó a todos los pacientes con parasitación exclusiva, o no, por B. hominis. Resultados. Se estudió a 3.070 pacientes. En 570 (18%) se diagnosticó infección por B. hominis, de los que en 245 (43%) representó el único aislamiento; 325 (57%) presentaron otras coparasitaciones (Entamoeba hystolitica o dispar, Strongyloides stercoralis, uncinarias y Schistosoma sp.). El síntoma principal fue dolor abdominal (41,8%). En un 31,2% el parásito se detectó en el cribado de enfermedades importadas en pacientes asintomáticos. De los que recibieron tratamiento con metronidazol, un 78,2% mejoró y en el 82,6% los parásitos se negativizaron. Conclusiones. La parasitación por B. hominis es una de las enfermedades más frecuentes en nuestra Unidad de Medicina Tropical. La mayoría de los pacientes están asintomáticos o bien la clínica puede ser atribuida a otras parasitaciones. En aquellos casos en los que persisten los síntomas sin poder ser atribuidos a otras causas, es recomendable un tratamiento específico


Objectives. Blastocystis hominis (B. hominis) is one of the most common intestinal parasites isolated in humans. The parasite can cause gastrointestinal symptoms or, in most cases, remain asymptomatic. There are issues concerning the parasite's pathogenic character. The aim of this study was to analyse the clinical and epidemiological characteristics of the parasite infection by B. hominis, with or without other parasitic co-infections. Patients and methods. An observational retrospective study was conducted of B. hominis isolates in faeces from October 2004 to March 2016 in a tropical medicine unit. We reviewed all patients with a parasite infection, exclusively or not by B. hominis. Results. We studied 3070 patients, 570 (18%) of whom were diagnosed with B. hominis infection, which was the only isolate in 245 (43%) of the 570 patients. A total of 325 (57%) patients presented other parasitic co-infections (Entamoeba histolytic or Entamoeba dispar, Strongyloides stercoralis, hookworm and Schistosoma spp.). The main symptom was abdominal pain (41.8%). In 31.2% of cases, the parasite was detected in the imported diseases screening of asymptomatic patients. Of those who underwent treatment with metronidazole, 78.2% improved. The parasite was neutralised in 82.6% of the patients. Conclusions. Parasite infection by B. hominis is one of the most common diseases in our tropical medicine unit. Most patients are asymptomatic, or their symptoms can be attributed to other parasite infections. In those cases in which symptoms persist without being able to attribute them to other causes, a specific treatment is recommended


Subject(s)
Humans , Male , Female , Child, Preschool , Child , Adolescent , Young Adult , Adult , Middle Aged , Aged , Intestinal Diseases, Parasitic/epidemiology , Blastocystis Infections/epidemiology , Blastocystis hominis/isolation & purification , Metronidazole/therapeutic use , Abdominal Pain/etiology , Trimethoprim, Sulfamethoxazole Drug Combination/therapeutic use , Retrospective Studies , Intestinal Diseases, Parasitic/drug therapy , Medical History Taking/methods , Intestinal Diseases, Parasitic/urine , Schistosomiasis/urine , Microfilariae , Microfilariae/parasitology , Spain/epidemiology , Feces/parasitology
6.
Rev Clin Esp (Barc) ; 218(3): 115-120, 2018 Apr.
Article in English, Spanish | MEDLINE | ID: mdl-29455921

ABSTRACT

OBJECTIVES: Blastocystis hominis (B. hominis) is one of the most common intestinal parasites isolated in humans. The parasite can cause gastrointestinal symptoms or, in most cases, remain asymptomatic. There are issues concerning the parasite's pathogenic character. The aim of this study was to analyse the clinical and epidemiological characteristics of the parasite infection by B. hominis, with or without other parasitic co-infections. PATIENTS AND METHODS: An observational retrospective study was conducted of B. hominis isolates in faeces from October 2004 to March 2016 in a tropical medicine unit. We reviewed all patients with a parasite infection, exclusively or not by B. hominis. RESULTS: We studied 3070 patients, 570 (18%) of whom were diagnosed with B. hominis infection, which was the only isolate in 245 (43%) of the 570 patients. A total of 325 (57%) patients presented other parasitic co-infections (Entamoeba histolytic or Entamoeba dispar, Strongyloides stercoralis, hookworm and Schistosoma spp.). The main symptom was abdominal pain (41.8%). In 31.2% of cases, the parasite was detected in the imported diseases screening of asymptomatic patients. Of those who underwent treatment with metronidazole, 78.2% improved. The parasite was neutralised in 82.6% of the patients. CONCLUSIONS: Parasite infection by B. hominis is one of the most common diseases in our tropical medicine unit. Most patients are asymptomatic, or their symptoms can be attributed to other parasite infections. In those cases in which symptoms persist without being able to attribute them to other causes, a specific treatment is recommended.

8.
Toxicol Appl Pharmacol ; 248(2): 122-33, 2010 Oct 15.
Article in English | MEDLINE | ID: mdl-20659491

ABSTRACT

Diethyldithiophosphate (DEDTP) is a metabolite formed by biotransformation of organophosphorous (OP) compounds that has a longer half-life than its parental compound. Here we evaluate the effects of DEDTP on human CD4+ T lymphocytes. In vitro exposure to DEDTP (1-50µM) decreased [(3)H]thymidine incorporation in resting cells and increased CD25 surface expression without altering cell viability. DEDTP treatment inhibited anti-CD3/anti-CD28 stimulation-induced CD4+ and CD8+ T cell proliferation determined by CFSE dilution. Decreased CD25 expression and intracellular IL-2 levels were correlated with this defect in cell proliferation. IL-2, IFN-γ and IL-10 secretion were also reduced while IL-4 secretion was not altered. Increased phosphorylation of SOCS3 and dephosphorylation of STAT5 were induced by DEDTP after as little as 5min of exposure. In addition, DEDTP induced phosphorylation of ERK, JNK and p38 and NFAT nuclear translocation. These results suggest that DEDTP can modulate phosphorylation of intracellular proteins such as SOCS3, which functions as a negative regulator of cytokine signalling, and that DEDTP exposure may thus cause T cells to fail to respond to further antigen challenges.


Subject(s)
CD4-Positive T-Lymphocytes/drug effects , Lymphocyte Activation/drug effects , Organothiophosphates/toxicity , Pesticides/toxicity , Receptors, Interleukin-2/metabolism , Signal Transduction/drug effects , CD28 Antigens/metabolism , CD4-Positive T-Lymphocytes/immunology , Cell Proliferation/drug effects , Cytokines/metabolism , Humans , Interleukin-2 Receptor alpha Subunit/metabolism , Organothiophosphates/metabolism , Phosphorylation/drug effects , STAT5 Transcription Factor/metabolism , Suppressor of Cytokine Signaling 3 Protein , Suppressor of Cytokine Signaling Proteins/metabolism
9.
Pediatr Transplant ; 14(6): 746-52, 2010 Sep 01.
Article in English | MEDLINE | ID: mdl-20412508

ABSTRACT

The aim of the study was to evaluate the efficacy and safety of the conversion of MMF to EC-MPS in pediatric renal transplant recipients. We included 12 patients with stable graft function who were receiving MMF treatment. In the first visit, a complete medical examination was performed, which included a GSRS, a nine-point pharmacokinetic profile, samples for renal, liver and hematological tests and evaluation of IMPDH2 gene expression. The patients were transferred to an equimolar dose of EC-MPS. Two wk later, a clinical evaluation and blood collection, as in the first visit were performed. There was no change in serum creatinine, leukocyte count, serum albumin, or transaminase levels, but we found a statistically significant reduction of hemoglobin after conversion (13.2 +/- 1.6 g/dL with MMF vs. 12.5 +/- 1.3 g/dL when receiving EC-MPS). The GSRS total mean score was 16 +/- 12 with MMF vs. 8 +/- 5 with EC-MPA (p < 0.05). There was no statistically significant difference between formulations in the gene expression of IMPDH 2, in the AUC(0-12h) or in C(max). However, peak concentration occurred later with EC-MPS.


Subject(s)
Drug Substitution , Immunosuppressive Agents/pharmacokinetics , Kidney Transplantation , Mycophenolic Acid/analogs & derivatives , Mycophenolic Acid/pharmacokinetics , Adolescent , Area Under Curve , Child , Female , Humans , Immunosuppressive Agents/therapeutic use , Kidney Transplantation/immunology , Male , Mycophenolic Acid/therapeutic use , Prospective Studies , Tablets, Enteric-Coated
10.
J Virol ; 72(2): 1203-9, 1998 Feb.
Article in English | MEDLINE | ID: mdl-9445019

ABSTRACT

R13-1 is an intertypic recombinant virus in which the left-hand 18% of the herpes simplex virus type 1 (HSV-1) genome is replaced by homologous sequences from HSV-2. R13-1 is nonneurovirulent and defective in DNA replication in neurons. The defect was localized to the UL5 open reading frame by using marker rescue analysis (D. C. Bloom and J. G. Stevens, J. Virol. 68:3761-3772, 1994). To provide conclusive evidence that UL5 is the only HSV-2 gene involved in the restricted replication phenotype of R13-1, we have characterized the phenotype of a recombinant virus (IB1) in which only the UL5 gene of HSV-1 was replaced by HSV-2 UL5. Data from 50% lethal dose determinations and the in vivo yields of virus suggested that IB1 has the same phenotypic characteristics as R13-1. UL5 is the helicase component of a complex with helicase and primase activities. All three subunits of this complex (UL5, UL8, and UL52) are required for viral DNA replication in all cell types. The intertypic complex HSV-2 UL5-HSV-1 UL8-HSV-1 UL52 was purified and biochemically characterized. The primase activity of the intertypic complex was 10-fold lower than that of HSV-1 UL5-HSV-1 UL8-HSV-1 UL52. The ATPase activity was comparable to that of the HSV-1 enzyme complex, and although the helicase activity was threefold lower, this did not interfere with the synthesis of leading strands by the HSV polymerase. One explanation for these findings is that the interactions between the subunits of the helicase-primase intertypic complex that are important for the full function of each subunit are inappropriate or weak.


Subject(s)
DNA Helicases/genetics , Gene Expression Regulation, Viral , Simplexvirus/physiology , Virus Replication/genetics , Animals , Chlorocebus aethiops , DNA Primase , DNA, Recombinant , Genome, Viral , Neurons/virology , Vero Cells , Viral Proteins
11.
J Mol Biol ; 267(5): 1089-103, 1997 Apr 18.
Article in English | MEDLINE | ID: mdl-9150398

ABSTRACT

RNA-protein interactions between bacteriophage Qbeta plus strand RNA and the components of the Qbeta replicase system were studied by deletion analysis. Internal, 5'-terminal and 3'-terminal deletions were assayed for template activity with replicase in vitro. Of the two internal binding sites previously described for replicase, we found that the S-site (map position 1247 to 1346) could be deleted without any significant effect on template activity, whereas deletion of the M-site (map position 2545 to 2867) resulted in a strong inactivation and a high salt sensitivity of the residual activity. Binding complexes of the deletion mutant RNAs with the different proteins involved in Qbeta RNA replication were analysed by electron microscopy. The formation of looped complex structures, previously reported and explained as simultaneous interactions with replicase at the S and the M-site, was abolished by deleting the S-site but, surprisingly, not by deleting the M-site. The same types of complexes observed with replicase were also formed with purified protein S1 (the alpha subunit of replicase), suggesting that these internal interactions with Qbeta RNA are mediated by the S1 protein. The Qbeta host factor, a protein required for the template activity of the Qbeta plus strand, was reported earlier to form similar complexes by binding to the S and M-sites (or adjacent sites) and in addition to the 3'-end, resulting in double-looped structures. The patterns of looped complexes observed with the deletion mutant RNAs suggest that the binding of host factor might not involve the S and M-sites themselves but adjacent downstream sites. An additional internal host factor interaction near map position 2300 was detected with several mutant RNAs. Qbeta RNA molecules with 3'-truncations formed 3'-terminal loops with similar efficiency as wild-type RNA, indicating that recognition of the 3'-end by host factor is not dependent on a specific 3'-terminal base sequence.


Subject(s)
Allolevivirus/enzymology , Carrier Proteins/metabolism , Q beta Replicase/metabolism , RNA, Viral/metabolism , Ribosomal Proteins/metabolism , Allolevivirus/genetics , Binding Sites , Carrier Proteins/ultrastructure , Integration Host Factors , Mutagenesis , Nucleic Acid Conformation , Q beta Replicase/ultrastructure , RNA, Viral/ultrastructure , RNA-Dependent RNA Polymerase/metabolism , RNA-Dependent RNA Polymerase/ultrastructure , Ribosomal Proteins/ultrastructure , Sequence Deletion , Substrate Specificity , Transcription, Genetic
12.
J Mol Biol ; 243(5): 811-5, 1994 Nov 11.
Article in English | MEDLINE | ID: mdl-7966301

ABSTRACT

In order to identify the structural elements important for the activity of the Q beta minus strand RNA as a template for Q beta replicase, a series of minus strand RNAs with internal or external deletions were prepared by in vitro transcription from suitable expression plasmids. The template activities of the deletion mutants were determined by single-round replication assays using purified replicase holoenzyme or core enzyme (lacking subunit alpha) in vitro. Two elements of RNA structure and/or sequence important for template activity were found. The first is a segment in the 5'-terminal region (map segment 4078 to 4132) containing a potential stem-loop structure, whose sequence was previously recognized to be highly conserved in the small variant MDV-1 RNA and suggested to be involved in its template recognition. The second element is defined by two partially complementary sequence segments in the 3'-terminal region (map positions 557 to 576 and 24 to 35), that appear to be engaged in long-range base-pairing and may form the stem of a large secondary structure domain, whose branches are not necessary for template recognition. The results obtained with replicase holoenzyme and core enzyme were identical within the accuracy of the method. They confirm the absence of any role of S1 protein in the interaction of replicase with minus strand RNA and further emphasize the profound difference in the interactions of replicase with the plus and minus strand.


Subject(s)
Allolevivirus/genetics , Q beta Replicase/metabolism , RNA Phages/metabolism , Base Sequence , Gene Deletion , Molecular Sequence Data , Plasmids , RNA, Double-Stranded/genetics , Sequence Alignment , Templates, Genetic
13.
J Mol Biol ; 232(2): 512-21, 1993 Jul 20.
Article in English | MEDLINE | ID: mdl-8345521

ABSTRACT

Our earlier work on the recognition of Q beta plus strand RNA by replicase had shown by RNase degradation and by electron microscopic techniques that specific binding interactions occurred at two internal sites, the S-site and the M-site, but not at the 3'-end, i.e. the site of initiation of synthesis. Using essentially similar methods, we have found now for binding complexes of replicase with the minus strand a completely different pattern, namely considerable terminal binding, whereas binding to internal sites was without detectable specificity. In the case of plus strand complexes, simultaneous binding at the two internal sites and at a terminal site could be demonstrated by electron microscopy after initiation of RNA synthesis in the presence of host factor, GTP and ATP. A variant plus strand RNA containing a 490 nucleotide duplication near the 5'-end resulted in similar double-looped complexes, however with an elongated free arm, showing that the protein-bound terminal site was the 3'-end of the RNA. Interestingly, the same two-looped structures were also found for complexes consisting of plus strand RNA and host factor without replicase. This suggests that the role of the host factor on the plus strand template is to bring the 3'-end into the proximity of the S-site/M-site domain, where replicase can initiate on it. In contrast, the 3'-end of the minus strand appears to be directly available to the enzyme.


Subject(s)
Coliphages/enzymology , Q beta Replicase/metabolism , RNA, Double-Stranded/metabolism , RNA, Viral/metabolism , Nucleic Acid Hybridization , Q beta Replicase/ultrastructure , RNA, Double-Stranded/ultrastructure , RNA, Viral/ultrastructure
14.
Mutagenesis ; 7(2): 125-35, 1992 Mar.
Article in English | MEDLINE | ID: mdl-1579068

ABSTRACT

The goal of this study was the development of a mutagenicity assay in V79 cells using Pseudomonas toxin A (PTA) as a selective agent and to compare it with the V79/hypoxanthineguaninephosphoribosyl transferase (HGPT) assay. PTA inhibits protein synthesis by covalently modifying elongation factor 2 (EF-2). Mutations in the EF-2 gene, in genes responsible for the modification of EF-2, and also in genes for the transport of the toxin into the cells, lead to PTA resistance. This involvement of several genes might explain the relatively high spontaneous mean mutation frequency of (122.7 +/- 38.8) x 10(-6) in growing cells (2 micrograms PTA/ml) as compared with (3.97 +/- 4.68) x 10(-6) in the HGPRT test (10 micrograms thioguanine/ml), where only mutations in the HGPRT gene lead to resistance. Methyl methanesulphonate, methyl nitroso urea and UV light were directly mutagenic in the V79/PTA assay. Aflatoxin B1 was mutagenic in the presence of an S9 mix. Benzidine, procarbazine, 2-acetylaminofluorene (2-AAF) and 4-acetylaminofluorene (4-AAF) were positive in the V79/PTA test when rat hepatocytes were used for metabolic activation. Using cells treated together with those used for the PTA assay, benzidine, 2-AAF and 4-AAF were negative in the V79/HGPRT test, while procarbazine was found to be positive under these test conditions. Hexamethyl phosphoramide (HMPA) was tested in the presence of rat hepatocytes and was negative in both test systems. Phorbol-12-myristate-13-acetate was highly cytotoxic, but did not induce mutations at the PTA resistance loci. In conclusion, it was demonstrated that the V79/PTA assay is an easy and sensitive method to screen for gene mutations in mammalian cells.


Subject(s)
ADP Ribose Transferases , Bacterial Toxins , Exotoxins/pharmacology , Mutagenicity Tests/methods , Virulence Factors , Aflatoxin B1/toxicity , Animals , Biomarkers , Cell Line , Cricetinae , Drug Resistance , Hypoxanthine Phosphoribosyltransferase/pharmacology , Methyl Methanesulfonate/toxicity , Methylnitrosourea/toxicity , Mutation , Tetradecanoylphorbol Acetate/toxicity , Ultraviolet Rays , Pseudomonas aeruginosa Exotoxin A
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