Effectiveness training type on body composition and metabolic parameters in adolescents with obesity: review

No systematic reviews had analyzedthe most effective training for adolescents with obesity, thus, the aim of our review was to understand whether aerobic, resistance, or combinate, is appropriate for improving body composition, and factors associated with obesity in adolescents. We followed PRISMA methods, in the Pubmed, SCOPUS, and Web of Science databases, using the terms Obesity, teenager, fat mass, body mass index, body mass, intervention, aerobic, resistance, training and physical activity. Subsequently, titles and abstracts were read to filter the articles. Of the 3585 results found, 10 articles were selected with protocols of 3 to 4 weekly training sessions of 15 to 60 minutes, with interventions of 4 to 12 weeks. All types of training were beneficial for anthropometric and biochemical improvement, only resistance training (RT) has a significant difference for muscle mass compared to aerobic training (AT). Even though of the small number of studies with this type of comparison, it is still unclear which type of training is better or whether the two done concurrently would be a better alternative. According to our findings adolescents who want to maximize the effect of exercise on anthropometric variables should ideally perform aerobic and endurance exercises, but significant benefit can be achieved through any type of exercise, and if it were to have a significant differentiation within muscle mass the resistance exercise may be ideal to achieve this goal(AU)

En este artículo de revisión, fue analizado cual es el método de entrenamiento que es más efectivo para adolescentes con obesidad, de allí, a que nuestro objetivo en esta revisión es definir cual de los protocolos de entrenamiento (aeróbico, de resistencia o combinado) es mas apropiado para mejorar la composición corporal y otros factores asociados con la obesidad en adolescentes. Siguiendo los métodos de PRISMA se realizó la búsqueda en las bases de datos de, Pubmed, SCOPUS, y Web os Science, utilizando términos de obesidad, adolescentes, masa grasa, índice de masa corporal, masa corporal, intervención, ejercicio aeróbico, ejercicio de resistencia, ejercicio combinado y actividad física, subsecuentemente se leyeron títulos y resúmenes para filtrar los artículos. De los 3585 artículos encontrados, 10 artículos fueron seleccionados con protocolos de 3 a 4 días a la semana, donde cada sesión era de 15 a 60 minutos, con intervenciones entre 4 y 12 semanas. Todos los tipos de entrenamiento fueron beneficiosos para mejorar composición corporal y parámetros bioquímicos, el ejercicio de resistencia demuestra tener diferencia con relación a los otros dos protocolos de entrenamiento donde post-intervención consiguen mejorar la masa muscular. Debido al número pequeño de estudios aun la información es poco clara sobre cual protocolo es más efectivo y así poder elegir una alternativa mas adecuada. De acuerdo con los hallazgos realizar ejercicios aeróbicos y/o combinados mejoran la composición corporal a nivel de masa grasa, y el ejercicio de resistencia demuestra mejorar musculatura en adolescentes con obesidad(AU)

Estrés y depresión en docentes de una institución pública de enseñanza / Estresse e depressão em docentes de uma instituição pública de ensino / Stress and depression in teachers from a public education institution

OBJETIVOS: Analizar la presencia de estrés y signos indicativos de depresión en docentes de una institución pública de enseñanza. MATERIAL Y MÉTODOS: Estudio analítico, realizado con 163 docentes de una institución pública de enseñanza. Se aplicó Escala de estrés percibido-EEP e inventario de depresión de Beck-IDB. RESULTADOS: De los 163 participantes, 108 (66,3%) eran del género masculino, 64 (39,3%) con rango de edad de 30 a 39 años, 79 (48,5%) tenían una renta salarial de más de 15 salarios (en el caso de las mujeres). La mayoría presentó título de maestro, 84 (51,5%). Se identificaron niveles mínimos de estrés en hombres, 73 (67,0%) y 34 (63,0%) en mujeres. 87 (79,8%) mujeres y 35 (64,8%) hombres presentaron un nivel de depresión mínima. Hubo diferencias significativas en los escores de estrés y depresión entre los sexos. Se observó una correlación positiva moderada entre las escalas. CONCLUSIÓN: Los docentes con niveles mínimo y leve están sujetos a presentar estrés y depresión, mereciendo atención por parte de las instituciones

OBJETIVOS: Analisar a presença de estresse e sinais indicativos de depressão em docentes de uma instituição pública de ensino. MATERIAL E MÉTODOS: Estudo analítico, realizado com 163 docentes de uma instituição pública de ensino. Aplicou-se Escala de Estresse Percebido-EEP e Inventário de Depressão de Beck-IDB. RESULTADOS: Dos 163 participantes, 108 (66,3%) eram do gênero masculino, 64 (39,3%) com faixa etária de 30 a 39 anos, 79 (48,5%) tinham uma renda salarial de mais de 15 salários mínimos, 80 (49,1%) referiram cor parda. A maioria apresentou título de mestre, 84 (51,5%). Identificaram-se níveis mínimos de estresse em homens, 73 (67,0%) e 34 (63,0%) em mulheres. 87 (79,8%) mulheres e 35 (64,8%) homens apresentaram nível de depressão mínima. Houve diferença significativa nos escores de estresse e depressão entre os sexos. Observou-se uma correlação positiva moderada entre as escalas. CONCLUSÃO: Os docentes com níveis mínimo e leve estão sujeitos a apresentarem estresse e depressão, merecendo atenção por parte das instituições

OBJECTIVES: To analyze the presence of stress and signs indicative of depression in teachers of a public educational institution. MATERIALS AND METHODS: An analytical study was conducted with 163 teachers from a public educational institution. The Perceived Stress Scale-EEP and Beck-IDB Depression Inventory were applied. RESULTS: Of the 163 participants, 108 (66.3%) were males, 64 (39.3%) were between 30 and 39 years of age, 79 (48.5%) had a wage income of more than 15 wages minimum, 80 (49.1%) reported brown color. The majority had a master's degree, 84 (51.5%). Minimal levels of stress were identified in men, 73 (67.0%) and 34 (63.0%) in women. 87 (79.8%) women and 35 (64.8%) men had minimal depression. There was a significant difference in the stress and depression scores between the sexes. There was a moderate positive correlation between the scales. CONCLUSION: Teachers with minimal and light levels are subject to stress and depression, deserving attention from the institutions

Infection Patterns Induced in Naive Adult Woodchucks by Virions of Woodchuck Hepatitis Virus Collected during either the Acute or Chronic Phase of Infection.

UNLABELLED: The infectivity of hepadnavirus virions produced during either acute or chronic stages of infection was compared by testing the ability of the virions of woodchuck hepatitis virus (WHV) to induce productive acute infection in naive adult woodchucks. Serum WHV collected during acute infection was compared to virions harvested from WHV-infected woodchucks during either (i) early chronic infection, when WHV-induced hepatocellular carcinoma (HCC) was not yet developed, or (ii) late chronic infection, when established HCC was terminal. All tested types of WHV inoculum were related, because they were collected from woodchucks that originally were infected with standardized WHV7 inoculum. Despite the individual differences between animals, the kinetics of accumulation of serum relaxed circular DNA of WHV demonstrated that the virions produced during early or late chronic infection are fully capable of inducing productive acute infection with long-lasting high viremia. These findings were further supported by the analysis of such intrahepatic markers of WHV infection as replicative intermediate DNA, covalently closed circular DNA, pregenomic RNA, and the percentage of WHV core antigen-positive hepatocytes measured at several time points over the course of 17.5 weeks after the inoculation. In addition, the observed relationship between the production of antibodies against WHV surface antigens and parameters of WHV infection appears to be complex. Taken together, the generated data suggest that in vivo hepadnavirus virions produced during different phases of chronic infection did not demonstrate any considerable deficiencies in infectivity compared to that of virions generated during the acute phase of infection. IMPORTANCE: The generated data suggest that infectivity of virions produced during the early or late stages of chronic hepadnavirus infection is not compromised. Our novel results provided several lines of further evidence supporting the idea that during the state of chronic infection in vivo, the limitations of hepadnavirus cell-to-cell spread/superinfection (observed recently in the woodchuck model) are not due to the diminished infectivity of the virions circulating in the blood and likely are (i) related to the properties of hepatocytes (i.e., their capacity to support hepadnavirus infection/replication) and (ii) influenced by the immune system. The obtained results further extend the understanding of the mechanisms regulating the persistence of hepadnavirus infection. Follow-up studies that will further investigate hepadnavirus cell-to-cell spread as a potential regulator of the chronic state of the infection are warranted.

Superinfection with woodchuck hepatitis virus strain WHVNY of livers chronically infected with strain WHV7.

UNLABELLED: The determinants of the maintenance of chronic hepadnaviral infection are yet to be fully understood. A long-standing unresolved argument in the hepatitis B virus (HBV) research field suggests that during chronic hepadnaviral infection, cell-to-cell spread of hepadnavirus is at least very inefficient (if it occurs at all), virus superinfection is an unlikely event, and chronic hepadnavirus infection can be maintained exclusively via division of infected hepatocytes in the absence of virus spread. Superinfection exclusion was previously shown for duck HBV, but it was not demonstrated for HBV or HBV-related woodchuck hepatitis virus (WHV). Three woodchucks, which were chronically infected with the strain WHV7 and already developed WHV-induced hepatocellular carcinomas (HCCs), were superinfected with another WHV strain, WHVNY. Six weeks after the superinfection, the woodchucks were sacrificed and tissues of the livers and HCCs were examined. The WHVNY superinfection was demonstrated by using WHV strain-specific PCR assays and (i) finding WHVNY relaxed circular DNA in the serum samples collected from all superinfected animals during weeks one through six after the superinfection, (ii) detecting replication-derived WHVNY RNA in the tissue samples of the livers and HCCs collected from three superinfected woodchucks, and (iii) finding WHVNY DNA replication intermediates in tissues harvested after the superinfection. The results are consistent with the occurrence of continuous but inefficient hepadnavirus cell-to-cell spread and superinfection during chronic infection and suggest that the replication space occupied by the superinfecting hepadnavirus in chronically infected livers is limited. The findings are discussed in the context of the mechanism of chronic hepadnavirus infection. IMPORTANCE: This study aimed to better understand the determinants of the maintenance of chronic hepadnavirus infection. The generated data suggest that in the livers chronically infected with woodchuck hepatitis virus, (i) hepadnavirus superinfection and cell-to-cell spread likely continue to occur and (ii) the virus spread is apparently inefficient, which is consistent with the interpretation that a limited number of cells in the livers facilitates the spread of hepadnavirus. The limitations of the cell-to-cell virus spread most likely are mediated at the level of the cells and do not reflect the properties of the virus. Our results further advance the understanding of the mechanism of chronic hepadnavirus infection. The significance of the continuous but limited hepadnavirus spread and superinfection for the maintenance of the chronic state of infection should be further evaluated in follow-up studies in order to determine whether blocking the virus spread would facilitate the suppression of chronic hepadnavirus infection.

Artemisinin resistance in rodent malaria--mutation in the AP2 adaptor µ-chain suggests involvement of endocytosis and membrane protein trafficking.

BACKGROUND: The control of malaria, caused by Plasmodium falciparum, is hampered by the relentless evolution of drug resistance. Because artemisinin derivatives are now used in the most effective anti-malarial therapy, resistance to artemisinin would be catastrophic. Indeed, studies suggest that artemisinin resistance has already appeared in natural infections. Understanding the mechanisms of resistance would help to prolong the effective lifetime of these drugs. Genetic markers of resistance are therefore required urgently. Previously, a mutation in a de-ubiquitinating enzyme was shown to confer artemisinin resistance in the rodent malaria parasite Plasmodium chabaudi. METHODS: Here, for a mutant P. chabaudi malaria parasite and its immediate progenitor, the in vivo artemisinin resistance phenotypes and the mutations arising using Illumina whole-genome re-sequencing were compared. RESULTS: An increased artemisinin resistance phenotype is accompanied by one non-synonymous substitution. The mutated gene encodes the µ-chain of the AP2 adaptor complex, a component of the endocytic machinery. Homology models indicate that the mutated residue interacts with a cargo recognition sequence. In natural infections of the human malaria parasite P. falciparum, 12 polymorphisms (nine SNPs and three indels) were identified in the orthologous gene. CONCLUSION: An increased artemisinin-resistant phenotype occurs along with a mutation in a functional element of the AP2 adaptor protein complex. This suggests that endocytosis and trafficking of membrane proteins may be involved, generating new insights into possible mechanisms of resistance. The genotypes of this adaptor protein can be evaluated for its role in artemisinin responses in human infections of P. falciparum.

MDR1-associated resistance to artesunate+mefloquine does not impair blood-stage parasite fitness in a rodent malaria model.

If drug-resistant malaria mutants are less fit than sensitive forms, they will wane over time when active drug pressure is removed and the overall sensitivity to the drug may be restored. However, most studies addressing this issue have been largely retrospective. Here, we undertook a predictive study, using mutant rodent malaria parasites resistant to the Artemisinin combination treatment (ACT) version of artesunate+mefloquine (ATN+MF) to gain insights about their ability to compete with ATN+MF-sensitive forms in untreated hosts. Previously, Plasmodium chabaudi parasites resistant to ATN+MF were selected in vivo through prolonged passaging in mice under increasing doses of the two drugs, and shown to harbour duplication of the mdr1 gene. Here, the resistant parasite, AS-ATNMF1, was mixed with its progenitor AS-ATN in different proportions and each mixture was injected into mice that were left untreated. Absolute percentage parasitaemias and the proportion of each parasite were then monitored by microscopy and proportional sequencing, respectively, every two days for a period of 14days. AS-ATNMF1 outperformed its progenitor AS-ATN over the whole sampling period regardless of the relative starting proportion of each parasite clone. In order to assess if consecutive sub-inoculations could have been responsible for the apparent fitness gain of the resistant parasite, its growth was compared to that of AS-ATN27P, a parasite which was passaged the same number of times as AS-ATNMF1, but left untreated. Although small fluctuations in the proportion of each parasite were observed through time, the relative abundance of each on the last day of sampling (Day 14) was virtually identical to that of the starting inoculum. We conclude that there is no fitness cost associated with MDR1-associated ATN+MF resistance in vivo. These observations offer the first insights about the within-host dynamics between ACT-resistant and -sensitive parasites in absence of drug pressure.

Quantitative genome re-sequencing defines multiple mutations conferring chloroquine resistance in rodent malaria.

BACKGROUND: Drug resistance in the malaria parasite Plasmodium falciparum severely compromises the treatment and control of malaria. A knowledge of the critical mutations conferring resistance to particular drugs is important in understanding modes of drug action and mechanisms of resistances. They are required to design better therapies and limit drug resistance.A mutation in the gene (pfcrt) encoding a membrane transporter has been identified as a principal determinant of chloroquine resistance in P. falciparum, but we lack a full account of higher level chloroquine resistance. Furthermore, the determinants of resistance in the other major human malaria parasite, P. vivax, are not known. To address these questions, we investigated the genetic basis of chloroquine resistance in an isogenic lineage of rodent malaria parasite P. chabaudi in which high level resistance to chloroquine has been progressively selected under laboratory conditions. RESULTS: Loci containing the critical genes were mapped by Linkage Group Selection, using a genetic cross between the high-level chloroquine-resistant mutant and a genetically distinct sensitive strain. A novel high-resolution quantitative whole-genome re-sequencing approach was used to reveal three regions of selection on chr11, chr03 and chr02 that appear progressively at increasing drug doses on three chromosomes. Whole-genome sequencing of the chloroquine-resistant parent identified just four point mutations in different genes on these chromosomes. Three mutations are located at the foci of the selection valleys and are therefore predicted to confer different levels of chloroquine resistance. The critical mutation conferring the first level of chloroquine resistance is found in aat1, a putative aminoacid transporter. CONCLUSIONS: Quantitative trait loci conferring selectable phenotypes, such as drug resistance, can be mapped directly using progressive genome-wide linkage group selection. Quantitative genome-wide short-read genome resequencing can be used to reveal these signatures of drug selection at high resolution. The identities of three genes (and mutations within them) conferring different levels of chloroquine resistance generate insights regarding the genetic architecture and mechanisms of resistance to chloroquine and other drugs. Importantly, their orthologues may now be evaluated for critical or accessory roles in chloroquine resistance in human malarias P. vivax and P. falciparum.

Genomewide scan reveals amplification of mdr1 as a common denominator of resistance to mefloquine, lumefantrine, and artemisinin in Plasmodium chabaudi malaria parasites.

Multidrug-resistant Plasmodium falciparum malaria parasites pose a threat to effective drug control, even to artemisinin-based combination therapies (ACTs). Here we used linkage group selection and Solexa whole-genome resequencing to investigate the genetic basis of resistance to component drugs of ACTs. Using the rodent malaria parasite P. chabaudi, we analyzed the uncloned progeny of a genetic backcross between the mefloquine-, lumefantrine-, and artemisinin-resistant mutant AS-15MF and a genetically distinct sensitive clone, AJ, following drug treatment. Genomewide scans of selection showed that parasites surviving each drug treatment bore a duplication of a segment of chromosome 12 (translocated to chromosome 04) present in AS-15MF. Whole-genome resequencing identified the size of the duplicated segment and its position on chromosome 4. The duplicated fragment extends for ∼393 kbp and contains over 100 genes, including mdr1, encoding the multidrug resistance P-glycoprotein homologue 1. We therefore show that resistance to chemically distinct components of ACTs is mediated by the same genetic mutation, highlighting a possible limitation of these therapies.

Experimental evolution, genetic analysis and genome re-sequencing reveal the mutation conferring artemisinin resistance in an isogenic lineage of malaria parasites.

BACKGROUND: Classical and quantitative linkage analyses of genetic crosses have traditionally been used to map genes of interest, such as those conferring chloroquine or quinine resistance in malaria parasites. Next-generation sequencing technologies now present the possibility of determining genome-wide genetic variation at single base-pair resolution. Here, we combine in vivo experimental evolution, a rapid genetic strategy and whole genome re-sequencing to identify the precise genetic basis of artemisinin resistance in a lineage of the rodent malaria parasite, Plasmodium chabaudi. Such genetic markers will further the investigation of resistance and its control in natural infections of the human malaria, P. falciparum. RESULTS: A lineage of isogenic in vivo drug-selected mutant P. chabaudi parasites was investigated. By measuring the artemisinin responses of these clones, the appearance of an in vivo artemisinin resistance phenotype within the lineage was defined. The underlying genetic locus was mapped to a region of chromosome 2 by Linkage Group Selection in two different genetic crosses. Whole-genome deep coverage short-read re-sequencing (Illumina Solexa) defined the point mutations, insertions, deletions and copy-number variations arising in the lineage. Eight point mutations arise within the mutant lineage, only one of which appears on chromosome 2. This missense mutation arises contemporaneously with artemisinin resistance and maps to a gene encoding a de-ubiquitinating enzyme. CONCLUSIONS: This integrated approach facilitates the rapid identification of mutations conferring selectable phenotypes, without prior knowledge of biological and molecular mechanisms. For malaria, this model can identify candidate genes before resistant parasites are commonly observed in natural human malaria populations.

Experimental evolution of resistance to artemisinin combination therapy results in amplification of the mdr1 gene in a rodent malaria parasite.

BACKGROUND: Lacking suitable alternatives, the control of malaria increasingly depends upon Artemisinin Combination Treatments (ACT): resistance to these drugs would therefore be disastrous. For ACTs, the biology of resistance to the individual components has been investigated, but experimentally induced resistance to component drugs in combination has not been generated. METHODOLOGY/PRINCIPAL FINDINGS: We have used the rodent malaria parasite Plasmodium chabaudi to select in vivo resistance to the artesunate (ATN)+mefloquine (MF) version of ACT, through prolonged exposure of parasites to both drugs over many generations. The selection procedure was carried out over twenty-seven consecutive sub-inoculations under increasing ATN+MF doses, after which a genetically stable resistant parasite, AS-ATNMF1, was cloned. AS-ATNMF1 showed increased resistance to ATN+MF treatment and to artesunate or mefloquine administered separately. Investigation of candidate genes revealed an mdr1 duplication in the resistant parasites and increased levels of mdr1 transcripts and protein. There were no point mutations in the atpase6 or ubp1genes. CONCLUSION: Resistance to ACTs may evolve even when the two drugs within the combination are taken simultaneously and amplification of the mdr1 gene may contribute to this phenotype. However, we propose that other gene(s), as yet unidentified, are likely to be involved.

Tricotilomania: dificuldades diagnósticas e relato de dois casos / Trichotillomania: difficulties in diagnosis and report of two clinical cases

OBJETIVO: Relatar dois casos de tricotilomania, um transtorno psiquiátrico ainda subdiagnosticado e que pode estar associado a problemas sociais e clínicos relevantes. Pretende-se destacar as características clínicas, discutindo as implicações do diagnóstico precoce para a evolução dos pacientes. DESCRIÇÃO DO CASO: Uma adolescente com diagnóstico de tricotilomania "pura" e outra menina cujo quadro estava associado ao transtorno obsessivo-compulsivo. Embora com o tratamento, a evolução de ambas tenha sido favorável, houve demora significativa para estabelecer o diagnóstico e encaminhá-las a um serviço de saúde mental, com prejuízos escolares e sociais. COMENTÁRIOS: A tricotilomania difere dos quadros benignos e transitórios de arrancar cabelos observados nos primeiros anos de vida e ainda é subdiagnosticada. A vergonha dos sintomas observada nos portadores e o desconhecimento por parte dos profissionais de saúde contribuem para essa situação. O quadro pode ser grave, particularmente se acompanhado de tricofagia. Profissionais da saúde precisam identificar o transtorno precocemente e encaminhar as crianças para tratamento especializado antes das possíveis complicações clínicas e repercussões psicossociais.

OBJECTIVE: To report two cases of trichotillomania, an underdiagnosed psychiatric disorder that may be associated with important social and clinical problems. The clinical features will be highlighted considering the implications of early diagnosis on patients' outcome. CASE DESCRIPTION: An adolescent with isolated trichotillomania and another girl whose symptoms were associated with obsessive-compulsive disorder are described. Although both patients presented a favorable outcome with treatment, there was a significant delay in establishing the diagnosis and in referring them to a mental health service, leading to negative impact in educational and social domains. COMMENTS: Trichotillomania differs from the benign and transitory hair pulling habits observed in the first years of life, and it is still underdiagnosed. The embarrassment related the patients' symptoms and the lack of knowledge of health professionals contribute to this situation. The condition may be severe, particularly if associated with trichophagia. Health care professionals need to identify the disorder early and refer these children to specialized treatment before clinical complications and psychosocial problems occur.

Plasmodium chabaudi: efficacy of artemisinin + curcumin combination treatment on a clone selected for artemisinin resistance in mice.

Recent studies have proposed curcumin as a potential partner for artemisinin in artemisinin combination therapies to treat malaria infections. The efficacy of curcumin alone and in combination with artemisinin was evaluated on a clone of Plasmodium chabaudi selected for artemisinin resistance in vivo. The addition of piperine as an enhancer of curcumin activity was also tested. Results indicated that curcumin, both alone and in combination with piperine had only a modest antimalarial effect and was not able to reverse the artemisinin-resistant phenotype or significantly affect growth of the tested clone when used in combination with artemisinin. This is in contrast with previous in vivo work and calls for further experimental evaluation of the antimalarial potential of curcumin.

Plasmodium falciparum from Pará state (Brazil) shows satisfactory in vitro response to artemisinin derivatives and absence of the S769N mutation in the SERCA-type PfATPase6.

OBJECTIVE: To evaluate the in vitro efficacy of artesunate (ATN) and artemether (ATH) against Plasmodium falciparum isolates from the Brazilian Amazon state of Pará and to search for mutations and/or altered copy numbers in the putative resistance-associated pfcrt, pfmdr1 and pfATPase6 genes. METHODS: In vitro efficacy of ATN and ATH was successfully measured in 56 freshly collected P. falciparum isolates, using a conventional WHO microtest with minor modifications. Single nucleotide polymorphisms (SNPs) in the same isolates were inspected using DNA sequencing and/or PCR-RFLP. We used real-time quantitative PCR to assess gene copy numbers. RESULTS: ATN and ATH geometric mean IC(50)s were 0.85 nm, 95% CI (0.55-1.15) and 3.0 nm, 95% CI (1.5-4.5), respectively. There was extremely limited diversity of pfcrt and pfmdr1 genotypes and three SNPs were identified in the pfATPase6 gene: one T to A synonymous mutation at nucleotide 2694 and two non-synonymous (both G to A) mutations at nucleotides 110 and 1916, causing predicted aminoacid shifts of arginine to lysine and of glycine to aspartate, respectively. The previously reported S769N mutation was not detected in any of the isolates inspected. In addition, no gene amplifications were detected in a subset of eight isolates. CONCLUSION: Artemisinin derivatives display satisfactory in vitro activity locally and the pfATPase6 gene is distinct from that reported in French Guiana, suggesting that those haplotypes have not been introduced regionally.

Resistance to thapsigargin-induced intracellular calcium mobilization in a multidrug resistant tumour cell line.

A multidrug resistant (MDR) cell line, derived from the human leukaemic cell K562 and selected for its resistance to Vincristine, was shown to be resistant to Thapsigargin (TG). A concentration of 50 nM TG was toxic to K562 cells whereas the MDR cell line, known as Lucena I cells, survived unaffected for up to seven days in culture. Similarly, no intracellular Ca2+ mobilization was observed in the MDR cell line treated with TG. This effect was not a result of TG extrusion by P glycoprotein (Pgp), as no mobilization was observed even in the presence of the Pgp inhibitors Verapamil (5 microM) and Cyclosporin A (0.16 microM). In the present study, both cell lines expressed comparable levels of Bcl-2 making it unlikely that Bcl-2 was involved in this process. Similarly, no overexpression of the endoplasmic reticulum Ca2+ ATPase (SERCA) could be detected in the MDR cell line and Ca2+ uptake by vesicles of the two cell types were equally sensitive to TG. These results confirm that MDR cells do not mobilize Ca2+ in the presence of TG but go against the possibility that this might be due to TG extrusion or to the overexpression of a resistant SERCA isoform.