RESUMO
Pushing capacity is a key parameter in athletic racing wheelchair performance. This study estimated the potential contribution of upper limb momentum to pushing. The question is relevant since it may affect the training strategy adopted by an athlete. A muscle-free Lagrangian dynamic model of the upper limb segments was developed and theoretical predictions of power transfer to the wheelchair were computed during the push phase. Results show that limb momentum capacity for pushing can be in the order of 40J per push cycle at 10m/s, but it varies with the specific pushing range chosen by the athlete. Although use of momentum could certainly help an athlete improve performance, quantifying the actual contribution of limb momentum to pushing is not trivial. A preliminary experimental investigation on an ergometer, along with a simplified model of the upper limb, suggests that momentum is not the sole contributor to power transfer to a wheelchair. Muscles substantially contribute to pushing, even at high speeds. Moreover, an optimal pushing range is challenging to find since it most likely differs if an athlete chooses a limb momentum pushing strategy versus a muscular exertion pushing strategy, or both at the same time. The study emphasizes the importance of controlling pushing range, although one should optimize it while also taking the dynamics of the recovery period into account.
Assuntos
Braço/fisiologia , Cadeiras de Rodas , Desempenho Atlético/fisiologia , Fenômenos Biomecânicos , Transferência de Energia , Feminino , Humanos , Masculino , Movimento , Força Muscular , Amplitude de Movimento ArticularRESUMO
Glioblastoma multiforme (GBM) is an aggressive brain tumor for which there is no cure. Overexpression of wild-type epidermal growth factor receptor (EGFR) and loss of the tumor suppressor genes Ink4a/Arf and PTEN are salient features of this deadly cancer. Surprisingly, targeted inhibition of EGFR has been clinically disappointing, demonstrating an innate ability for GBM to develop resistance. Efforts at modeling GBM in mice using wild-type EGFR have proven unsuccessful to date, hampering endeavors at understanding molecular mechanisms of therapeutic resistance. Here, we describe a unique genetically engineered mouse model of EGFR-driven gliomagenesis that uses a somatic conditional overexpression and chronic activation of wild-type EGFR in cooperation with deletions in the Ink4a/Arf and PTEN genes in adult brains. Using this model, we establish that chronic activation of wild-type EGFR with a ligand is necessary for generating tumors with histopathological and molecular characteristics of GBMs. We show that these GBMs are resistant to EGFR kinase inhibition and we define this resistance molecularly. Inhibition of EGFR kinase activity using tyrosine kinase inhibitors in GBM tumor cells generates a cytostatic response characterized by a cell cycle arrest, which is accompanied by a substantial change in global gene expression levels. We demonstrate that an important component of this pattern is the transcriptional activation of the MET receptor tyrosine kinase and that pharmacological inhibition of MET overcomes the resistance to EGFR inhibition in these cells. These findings provide important new insights into mechanisms of resistance to EGFR inhibition and suggest that inhibition of multiple targets will be necessary to provide therapeutic benefit for GBM patients.
Assuntos
Modelos Animais de Doenças , Receptores ErbB/genética , Glioblastoma/genética , Camundongos , Proteínas Proto-Oncogênicas c-met/genética , Animais , Receptores ErbB/antagonistas & inibidores , Genes Supressores de Tumor , Glioblastoma/fisiopatologia , Humanos , Camundongos TransgênicosRESUMO
Cheddar cheese in curd form is very popular in eastern Canada. It is retailed immediately after cheese manufacturing and can be maintained at room temperature for 24 h to provide better texture and mouthfeel. Subsequently, the cheese curds must be stored at 4 degrees C. The shelf life is generally 3 d. In this study, Cheddar cheese curds were produced by adding a high diacetyl flavor-producing strain (Lactococcus diacetylactis) to a thermophilic-based starter. The objective was to achieve both postacidification stability to increase the shelf life and enhanced flavor. The addition of L. diacetylactis increased processing time but did not affect cheese composition or the evolution of proteolysis and texture. During cheese manufacturing, streptococci became the dominant microflora in all cheeses, whereas populations of Lactococcus cremoris and L. diacetylactis decreased. During cheese storage, viable counts of L. diacetylactis and Streptococcus thermophilus increased but the counts of L. cremoris decreased. During cheese manufacturing and storage, the concentrations of lactic acid and diacetyl increased rapidly in cheeses produced with L. diacetylactis. Citric acid and galactose contents remained high in cheese made without L. diacetylactis. Sensory evaluation indicated that cheeses containing the L. diacetylactis strain were more flavorful and also had less sourness and could be stored at 4 degrees C for up to 7 d.
Assuntos
Queijo , Indústria de Laticínios/métodos , Tecnologia de Alimentos/métodos , Paladar , Queijo/análise , Queijo/microbiologia , Ácido Cítrico/análise , Diacetil/análise , Manipulação de Alimentos , Galactose/análise , Humanos , Concentração de Íons de Hidrogênio , Ácido Láctico/análise , Fatores de TempoRESUMO
Previous studies have shown that depletion of cardiac actin by targeted disruption is associated with increased expression of alternative actins in the mouse heart. Here we have studied the effects of transgenic overexpression of cardiac actin using the alpha-myosin heavy chain promoter. Lines carrying 7 or 8 copies of the transgene showed a 2-fold increase in cardiac actin mRNA and also displayed decreased expression of skeletal and vascular actin in their hearts. In contrast, a line with more than 250 copies of the transgene did not show a similar decrease in the expression of skeletal and vascular actin despite a 3-fold increase in cardiac actin mRNA. While the low copy number transgenic mice displayed hearts that were similar to non-transgenic controls, the high copy number transgenic line showed larger hearts with distinct atrial enlargement and cardiomyocyte hypertrophy. Further, while the low copy number transgenic mouse hearts were mildly hypocontractile when compared with non-transgenic mouse hearts, the high copy number transgenic mouse hearts were significantly so. We conclude that in the presence of a small number of copies of the cardiac actin transgene, homeostatic mechanisms involved in maintaining actin levels are active and negatively regulate skeletal and vascular actin levels in the heart in response to increased expression of cardiac actin. However, these putative mechanisms are either inoperative in the high copy number transgenic line or are countered by the enhanced expression of skeletal and vascular actin during cardiomyocyte hypertrophy.
Assuntos
Actinas/metabolismo , Cardiomegalia/etiologia , Regulação da Expressão Gênica , Miocárdio/metabolismo , Actinas/genética , Actinas/ultraestrutura , Animais , Cardiomegalia/genética , Cardiomegalia/patologia , Dosagem de Genes , Camundongos , Camundongos Transgênicos , Músculo Esquelético/metabolismo , Contração Miocárdica/genética , Miocárdio/patologia , Miocárdio/ultraestrutura , Cadeias Pesadas de Miosina/genética , Tamanho do Órgão , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismoRESUMO
In infants, sweet taste and sucking on a pacifier both have analgesic effects. Animal studies suggest that sweet taste may involve opioids, while rhythmic oral movements, as with a pacifier, increase the release of serotonin, which is involved in the gating of nociceptive afferents. The present study was designed to see if these effects produce an analgesic effect in children. Two studies were performed, during blood draws in a pediatric test center in 7- to 12-year-old children, and during vaccination at school in 9- to 11-year-old children. Using unsweetened or sweetened chewing gum, there were four groups: control, sweet, chew, and sweet plus chew. Overall, there was no effect of either sweet taste or chewing on pain responses. However, in boys sweet taste tended to increase pain ratings, but only in conjunction with chewing, while in girls sweet taste tended to decrease pain ratings in conjunction with chewing and increased them in the absence of chewing. Ratings of pain intensity and affective state were correlated. Affective state before the painful stimulus was related to pain response in the girls and in the boys in the test center, but not in the schools. In the schools, the presence of peers may have influenced the ratings.
Assuntos
Coleta de Amostras Sanguíneas/efeitos adversos , Goma de Mascar , Mastigação , Dor/etiologia , Dor/fisiopatologia , Vacinação/efeitos adversos , Criança , Feminino , Humanos , Masculino , Medição da Dor , Caracteres Sexuais , Edulcorantes/farmacologia , PaladarRESUMO
All four of the muscle actins (skeletal, cardiac, vascular, and enteric) in higher vertebrates show distinct expression patterns and display highly conserved amino acid sequences. While it is hypothesized that each of the muscle isoactins is specifically adapted to its respective tissue and that the minor variations among them have developmental and/or physiological relevance, the exact functional and developmental significance of these proteins remains largely unknown. In order to begin to assess these issues, we disrupted the skeletal actin gene by homologous recombination. All mice lacking skeletal actin die in the early neonatal period (day 1 to 9). These null animals appear normal at birth and can breathe, walk, and suckle, but within 4 days, they show a markedly lower body weight than normal littermates and many develop scoliosis. Null mice show a loss of glycogen and reduced brown fat that is consistent with malnutrition leading to death. Newborn skeletal muscles from null mice are similar to those of wild-type mice in size, fiber type, and ultrastructural organization. At birth, both hemizygous and homozygous null animals show an increase in cardiac and vascular actin mRNA in skeletal muscle, with no skeletal actin mRNA present in null mice. Adult hemizygous animals show an increased level of skeletal actin mRNA in hind limb muscle but no overt phenotype. Extensor digitorum longus (EDL) muscle isolated from skeletal-actin-deficient mice at day 2 to 3 showed a marked reduction in force production compared to that of control littermates, and EDL muscle from hemizygous animals displayed an intermediate force generation. Thus, while increases in cardiac and vascular smooth-muscle actin can partially compensate for the lack of skeletal actin in null mice, this is not sufficient to support adequate skeletal muscle growth and/or function.
Assuntos
Actinas/genética , Actinas/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/fisiologia , Animais , Animais Recém-Nascidos , Marcação de Genes , Humanos , Camundongos , Camundongos Knockout , Músculo Esquelético/ultraestrutura , Fenótipo , Isoformas de Proteínas , Células-Tronco/fisiologiaRESUMO
CONTEXT: ras gene mutations and expression of its gene product have been described in verrucous and squamous cell carcinomas. Other downstream signal-transduction mediators, extracellular signal-regulated kinases 1 and 2 (ERK-1 and ERK-2) and Raf-1, have not yet been as extensively studied. OBJECTIVE: To determine patterns of expression of ERK-1, ERK-2, and Raf-1 in verrucous and squamous cell carcinomas of the upper aerodigestive tract. DESIGN: Seventeen verrucous carcinomas and 10 squamous cell carcinomas of the upper aerodigestive tract were examined for the immunohistochemical expression of ERK-1, ERK-2, and Raf-1 product. RESULTS: Raf-1 expression was intensely expressed in the most basal portions of the epithelium in verrucous carcinomas, but was minimally expressed in the suprabasalar areas. Anti-Raf-1 staining of the squamous cell carcinomas was diffuse and patchy throughout the tumor cells and was weak in intensity. There was no geographic preference of staining. The cytoplasmic expression of both ERK-1 and ERK-2 was predominantly negative in the most basal layers of the epithelium in the verrucous carcinomas, but was positive in the suprabasalar region of the epithelium. Immunohistochemical expression of ERK-1 and ERK-2 in the squamous carcinomas was diffuse throughout the tumor. CONCLUSION: There is strong correlation of the geographic expression of these mediators of ras signal transduction in verrucous and squamous carcinomas, but the cause of these differences remains unclear at present. The expression of these mediator proteins may have potential for diagnosis, as well as in understanding the biologic behavior of these lesions.
Assuntos
Carcinoma de Células Escamosas/patologia , Carcinoma Verrucoso/patologia , Genes ras , Neoplasias Bucais/patologia , Neoplasias Faríngeas/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma de Células Escamosas/genética , Carcinoma Verrucoso/genética , Feminino , Humanos , Imuno-Histoquímica , Sistema de Sinalização das MAP Quinases , Masculino , Pessoa de Meia-Idade , Proteína Quinase 1 Ativada por Mitógeno/análise , Proteína Quinase 1 Ativada por Mitógeno/genética , Proteína Quinase 3 Ativada por Mitógeno , Proteínas Quinases Ativadas por Mitógeno/análise , Proteínas Quinases Ativadas por Mitógeno/genética , Neoplasias Bucais/genética , Mutação , Neoplasias Faríngeas/genética , Proteínas Proto-Oncogênicas c-raf/análise , Proteínas Proto-Oncogênicas c-raf/genética , Neoplasias da Língua/genética , Neoplasias da Língua/patologiaRESUMO
OBJECTIVE: To examine sex differences in the rate and symptoms of posttraumatic stress disorder (PTSD), trauma exposure, and onset patterns in youth with conduct disorder (CD). METHOD: Youth admitted to a clinical facility for severe behaviour problems completed the Diagnostic Interview for Children and Adolescents--Revised (DICA-R) to assess the presence of CD and PTSD. RESULTS: Over one-half of CD youth reported exposure to trauma, yet only 17% met criteria for PTSD. PTSD was more frequent in CD girls (28%) than in boys (10%), and girls experienced greater symptom intensity and anhedonia, difficulty feeling love or affection, and disturbance of sleep and concentration. Girls more frequently reported sexual assault, while boys were more likely to report accidents, physical assaults, and witnessing the death of a loved one. Retrospective reports indicated that PTSD tended to develop subsequent to CD. CONCLUSIONS: Exposure to trauma is common among CD youth; however, diagnostic procedures should be adapted for increased sensitivity to PTSD. The development of CD may increase the risk for PTSD, particularly in girls, by exposing youth to situations in which they are traumatized. The role of trauma in CD should be routinely examined by clinicians and warrants further research.
Assuntos
Transtorno da Conduta/complicações , Transtorno da Conduta/epidemiologia , Transtornos de Estresse Pós-Traumáticos/complicações , Transtornos de Estresse Pós-Traumáticos/epidemiologia , Adolescente , Idade de Início , Comorbidade , Transtorno da Conduta/diagnóstico , Feminino , Humanos , Acontecimentos que Mudam a Vida , Masculino , Escalas de Graduação Psiquiátrica , Índice de Gravidade de Doença , Fatores Sexuais , Transtornos de Estresse Pós-Traumáticos/diagnósticoRESUMO
Telehealth is a new technology for the delivery of health care that allows a provider to deliver health care to a client at a remote setting via full, real-time video and audio interaction (American Nurses' Association, 1996). Telehealth does not change traditional health care standards or practice. School-based health centers are designed specifically for children and offer a continuum of preventive and acute care interventions that few other health care entities can provide (School-Based Adolescent Health Care Program, 1993). Telehealth and a school-based health center were joined together in a pilot project to demonstrate the efficacy of primary care via telehealth and to determine the value of this technology to the school and community. The telehealth capability enhanced the role of the school nurse and increased access to primary care for the students. The students were quick to adapt to the technology. The role of the school nurse was essential to the success of this project.
Assuntos
Serviços de Saúde Rural/organização & administração , Serviços de Saúde Escolar/organização & administração , Serviços de Enfermagem Escolar/organização & administração , Telemedicina/organização & administração , Criança , Humanos , Projetos Piloto , Avaliação de Programas e Projetos de Saúde , TexasRESUMO
The murine Polycomb-Group (PcG) proteins Eed and Bmi1 govern axial patterning during embryonic development by segment-specific repression of Hox gene expression. The two proteins engage in distinct multimeric complexes that are thought to use a common molecular mechanism to render the regulatory regions of Hox and other downstream target genes inaccessible to transcriptional activators. Beyond axial patterning, Bmi1 is also involved in hemopoiesis because a loss-of-function allele causes a profound decrease in bone marrow progenitor cells. Here, evidence is presented that is consistent with an antagonistic function of eed and Bmi1 in hemopoietic cell proliferation. Heterozygosity for an eed null allele causes marked myelo- and lymphoproliferative defects, indicating that eed is involved in the negative regulation of the pool size of lymphoid and myeloid progenitor cells. This antiproliferative function of eed does not appear to be mediated by Hox genes or the tumor suppressor locus p16(INK4a)/p19(ARF) because expression of these genes was not altered in eed mutants. Intercross experiments between eed and Bmi1 mutant mice revealed that Bmi1 is epistatic to eed in the control of primitive bone marrow cell proliferation. However, the genetic interaction between the two genes is cell-type specific as the presence of one or two mutant alleles of eed trans-complements the Bmi1-deficiency in pre-B bone marrow cells. These studies thus suggest that hemopoietic cell proliferation is regulated by the relative contribution of repressive (Eed-containing) and enhancing (Bmi1-containing) PcG gene complexes.
Assuntos
Hematopoese/genética , Proteínas Nucleares/genética , Proteínas Proto-Oncogênicas/genética , Proteínas Repressoras/genética , Envelhecimento/genética , Envelhecimento/patologia , Animais , Divisão Celular/genética , Ensaio de Unidades Formadoras de Colônias , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Genes Homeobox , Genes Reguladores , Genes p16 , Células-Tronco Hematopoéticas/citologia , Masculino , Camundongos , Camundongos Endogâmicos C3H , Camundongos Knockout , Complexo Repressor Polycomb 1 , Complexo Repressor Polycomb 2 , Proteínas do Grupo PolycombRESUMO
This study investigated the relationship between attachment patterns and suicidal ideation in a clinical sample of adolescents. Participants (n = 116) were assessed on level of current ideation through self-report questionnaires. Lethality of methods contemplated was also rated on a subset of the sample (n = 16) who, in addition to endorsing current suicidal ideation, presented a plan on a diagnostic interview. Quality of attachment to care-givers based on a semi-structured clinical interview was assessed using Bartholomew's two-dimensional, four-category model of attachment. Categorical analyses indicated that youth with predominantly fearful or preoccupied attachment were more likely to endorse suicidal ideation than were predominantly secure or dismissing youth. Severity of suicidal ideation was positively correlated with ratings of fearfulness and negatively correlated with ratings on the secure and dismissing patterns. Greater lethality in methods of contemplated suicide was positively correlated with preoccupied tendencies. The importance of attachment theory for understanding the factors underlying suicidal ideation in troubled youth is discussed and implications for therapeutic intervention are presented.
Assuntos
Transtornos Mentais/psicologia , Apego ao Objeto , Tentativa de Suicídio/psicologia , Suicídio/psicologia , Adolescente , Colúmbia Britânica , Transtornos do Comportamento Infantil/diagnóstico , Transtornos do Comportamento Infantil/psicologia , Comorbidade , Mecanismos de Defesa , Feminino , Humanos , Masculino , Transtornos Mentais/diagnóstico , Inventário de Personalidade/estatística & dados numéricos , Psicometria , Tentativa de Suicídio/prevenção & controle , Prevenção do SuicídioRESUMO
Mammalian Polycomb group (Pc-G) genes, constituting some 5 subfamilies based on their identity to the Drosophila genes Pc, Psc, ph, esc, and E(z), appear to play critical roles in maintaining the transcriptional repression state of Hox/HOM-C genes during development. Despite increasing evidence of the important role of Hox genes in both normal hematopoiesis and leukemic transformation, little is known about the expression and possible function played by Pc-G genes in hematopoietic cells. To address this, we first examined the expression of Pc genes in purified CD34(+) human bone marrow cells by reverse transcriptase-polymerase chain reaction (RT-PCR), using degenerate primers that specifically amplify the majority of Pc genes. This analysis showed the expression of 8 different Pc genes in CD34(+) bone marrow cells, including HP1(Hsalpha), HP1(Hsgamma), the heterochromatin p25 protein, the human homologue of the murine M32 gene, and 4 novel members of this family. To assess whether Pc-G mRNA levels change during differentiation of bone marrow cells, a quantitative RT-PCR method was used to amplify the total cDNA originating from three purified subpopulations of CD34(+) bone marrow cells known to differ in their ability to grow in long-term or semisolid cultures. In sharp contrast to Hox gene expression, which is highest in the most primitive bone marrow cells, these studies show that the expression level of 8 of the 9 Pc-G genes studied (ie, HP1(Hsalpha), HP1(Hsgamma), M31, M32, M33, Mel-18, Mph1/Rae-28, and ENX-1) markedly increases with differentiation of bone marrow cells. Interestingly, BMI-1 exhibits a strikingly different pattern of expression, with high expression levels in primitive cells and very little expression in mature CD34(-) cells. Together, these results document for the first time that differentiation of human bone marrow cells is accompanied by profound changes in Pc-G gene expression levels.
Assuntos
Células da Medula Óssea/fisiologia , Proteínas de Drosophila , Regulação da Expressão Gênica , Genes Homeobox , Proteínas de Homeodomínio/fisiologia , Sequência de Aminoácidos , Sequência de Bases , Células da Medula Óssea/citologia , Diferenciação Celular/fisiologia , Proteínas de Ligação a DNA/genética , Histona-Lisina N-Metiltransferase , Humanos , Proteínas de Insetos/genética , Dados de Sequência Molecular , Nucleoproteínas/genética , Complexo Repressor Polycomb 1 , Complexo Repressor Polycomb 2 , Alinhamento de SequênciaRESUMO
Children presenting with torticollis demand thorough investigation. Atlantoaxial subluxation and rotatory fixation should be included in the differential diagnosis even in the absence of neurologic findings. We describe a 9-year-old boy with this condition associated with HLA-B27 positive seronegative spondyloarthropathy that went undiagnosed for 11 weeks. No other radiographic changes were seen, including no erosions. No neurologic findings were present. The child was treated with Halter head traction, which successfully reduced the atlantoaxial joint. This was followed by posterior C1-C2 fusion secondary to instability. Rheumatologists should be aware of this condition when examining a child presenting with torticollis.
Assuntos
Artrite/complicações , Articulação Atlantoaxial/diagnóstico por imagem , Torcicolo/diagnóstico por imagem , Torcicolo/etiologia , Artrite/cirurgia , Criança , Antígeno HLA-B27/metabolismo , Humanos , Imageamento por Ressonância Magnética , Masculino , Fusão Vertebral , Tomografia Computadorizada por Raios XRESUMO
A novel smooth muscle/myometrial-like cell line, SMU1-10, has been generated from the uterus of a H-2Kb-tsA58 transgenic mouse carrying a thermolabile SV40 large T-antigen gene. These cells grow continuously when maintained at the permissive temperature (33 degrees C) for the SV40 large T-antigen but stop dividing when placed at the non-permissive temperature (39 degrees C) and ultimately die within 3 weeks. All of the SMU1-10 cells produce smooth muscle alpha-actin (SMAA) at both 33 degrees C and 39 degrees C. A subset of the cells also contain smooth muscle gamma-actin (SMGA), a hallmark of smooth muscle differentiation, and the fraction of cells staining for this actin increases from about 1% when maintained for three days at 33 degrees C to as much as 30% at 39 degrees C over the same length of time. However, the appearance of SMGA in SMU1-10 cells appears to be regulated mainly at a post-transcriptional level since in situ hybridization indicates that all cells contain SMGA mRNA at both 33 degrees C and 39 degrees C. SMU1-10 cultures also contain smooth muscle myosin heavy chain (SM-MHC) and SM22 alpha, both of which are only found in smooth muscle of the adult mouse. Three additional smooth muscle (myometrium)-related markers, connexin 43, the thromboxane A2 receptor, and the progesterone receptor also are present in these cells. At the nonpermissive temperature for SV40 large T-antigen, the both level of SMGA mRNA and the number of cells staining for this actin are significantly increased in the presence of progesterone, a process that is similar to the upregulation of SMGA in the myometrium late in pregnancy. Overall, SMU1-10 cells provides a potentially useful in vitro model system to study smooth muscle/myometrial differentiation.
Assuntos
Proteínas dos Microfilamentos , Músculo Liso/citologia , Actinas/genética , Actinas/metabolismo , Processamento Alternativo , Animais , Northern Blotting , Linhagem Celular , Feminino , Mucosa Intestinal/metabolismo , Camundongos , Camundongos Transgênicos , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Músculo Liso/metabolismo , Músculo Liso Vascular/metabolismo , Miométrio/citologia , Miométrio/metabolismo , Cadeias Pesadas de Miosina/genética , Cadeias Pesadas de Miosina/metabolismo , Fenótipo , Gravidez , Progesterona/farmacologia , Processamento Pós-Transcricional do RNA , RNA Mensageiro/metabolismoRESUMO
The muscle actins in higher vertebrates display highly conserved amino acid sequences, yet they show distinct expression patterns. Thus, cardiac alpha-actin, skeletal alpha-actin, vascular smooth muscle alpha-actin, and enteric smooth muscle gamma-actin comprise the major actins in their respective tissues. To assess the functional and developmental significance of cardiac alpha-actin, the murine (129/SvJ) cardiac alpha-actin gene was disrupted by homologous recombination. The majority ( approximately 56%) of the mice lacking cardiac alpha-actin do not survive to term, and the remainder generally die within 2 weeks of birth. Increased expression of vascular smooth muscle and skeletal alpha-actins is observed in the hearts of newborn homozygous mutants and also heterozygotes but apparently is insufficient to maintain myofibrillar integrity in the homozygous mutants. Mice lacking cardiac alpha-actin can be rescued to adulthood by the ectopic expression of enteric smooth muscle gamma-actin using the cardiac alpha-myosin heavy chain promoter. However, the hearts of such rescued cardiac alpha-actin-deficient mice are extremely hypodynamic, considerably enlarged, and hypertrophied. Furthermore, the transgenically expressed enteric smooth muscle gamma-actin reduces cardiac contractility in wild-type and heterozygous mice. These results demonstrate that alterations in actin composition in the fetal and adult heart are associated with severe structural and functional perturbations.
Assuntos
Actinas/genética , Genes Letais , Teste de Complementação Genética , Coração/fisiologia , Animais , Testes de Função Cardíaca , Heterozigoto , Homozigoto , Intestino Delgado/química , Camundongos , Camundongos Mutantes , Músculo Liso/química , Contração Miocárdica , Miocárdio/patologia , Proteínas Recombinantes/biossíntese , Distribuição TecidualRESUMO
Embryonic stem (ES) cells are pluripotent cells derived from mouse blastocysts. ES cells can differentiate into complex embryoid bodies (EBs) which exhibit many of the characteristics of 4-10-d embryos, including areas which rhythmically contract. The expression of the four muscle isoactins was examined in EBs by using transcript-specific probes for each of the muscle actin mRNAs and selectively reactive MAbs to muscle actins. Northern blot analyses from undifferentiated ES cells and EBs after 5, 10, 15, and 20 d in suspension culture demonstrated that no muscle actin transcripts could be detected in the undifferentiated cells, whereas during differentiation, the vascular and enteric smooth muscle isoactin mRNAs were easily detected. To further define the pattern of expression polymerase chain reaction analyses were carried out on RNA isolated from individual EBs. The data indicated that all four muscle-specific actin genes are transcribed. We also demonstrated the presence of muscle actins in at least two distinct cell populations within the EBs using selectively reactive MAbs. Fibroblast-like cells exhibit significant levels of the two smooth muscle actins (vascular and enteric) localized to stress fibers. In addition, one or both of the striated muscle actins (cardiac and skeletal) are expressed in cardiomyocyte-like cells. As is the case in embryonic heart, alpha-smooth muscle actin and the striated muscle actin(s) are incorporated into well organized sarcomeres in these cardiomyocyte-like cells. Thus, differentiating EBs provide an in vitro system to study both striated and smooth muscle cell gene expression.
Assuntos
Actinas/genética , Blastocisto/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Músculos/metabolismo , Células-Tronco/metabolismo , Animais , Blastocisto/citologia , Northern Blotting , Diferenciação Celular/fisiologia , Células Cultivadas , Técnica Indireta de Fluorescência para Anticorpo , Camundongos , Músculos/embriologia , Reação em Cadeia da Polimerase , Biossíntese de Proteínas , Sondas RNA , Transcrição GênicaRESUMO
A component of hemodynamic responses during pregnancy may include structural changes in the arterial tree. Smooth muscle alpha-actin is a major structural-contractile protein of muscle cells. We observed a marked increase. In expression of actin during pregnancy in the rat aorta, suggesting a structural alteration of conduit arteries.
Assuntos
Actinas/biossíntese , Aorta/metabolismo , Músculo Liso Vascular/metabolismo , Prenhez/metabolismo , Animais , Feminino , Gravidez , Ratos , Ratos Sprague-DawleyRESUMO
Smooth muscle gamma-actin (SMGA) is an excellent marker of smooth muscle differentiation because it is essentially restricted to smooth muscle. As a first step toward unraveling the mechanisms underlying smooth muscle development and differentiation, we have examined the tissue-specific and developmental expression patterns of six constructs carrying portions of the murine SMGA gene linked to chloramphenicol acetyltransferase (CAT) in stable lines of transgenic mice. Based on the transgenic studies most, if not all, of the regulatory elements necessary for proper spatial and temporal expression of SMGA are present within a 13.7 kb segment of the SMGA gene containing 4.9 kb of upstream sequence, exon 1, intron 1, and a portion of exon 2 up to the start codon for translation. A second construct (SMGA11.6CAT) that lacks the distal 2.1 kb of upstream sequence but is otherwise identical to SMGA13.7CAT shows a similar level of smooth muscle-specific CAT activity. However, SMGA9.3CAT fusion gene containing only 571 bp of 5' flanking sequence, but otherwise identical to SMGA13.7CAT, and SMGA6.0CAT containing only the 4.9 kb upstream sequence, exon 1, and a miniintron 1 show a more than a 100-fold reduction of CAT activity in most smooth muscle-rich tissues. Furthermore, removal of most or all of intron 1 from a transgene with 571 bp of upstream sequence (SMGA2.0 CAT and SMGA0.6CAT) results in a near-complete or complete loss of activity, respectively, in all tissues. Overall, the studies suggest that upstream elements between -2.7 kb and -571 bp and elements within intron 1 are required for high levels of SMGA gene expression in an appropriate temporal-spatial fashion.
Assuntos
Actinas/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Músculo Liso/metabolismo , Actinas/genética , Animais , Cloranfenicol O-Acetiltransferase/genética , Cloranfenicol O-Acetiltransferase/metabolismo , Clonagem Molecular , Genes Reporter , Íntrons , Camundongos , Camundongos Transgênicos , Distribuição TecidualRESUMO
The physiological properties of adenosine may be essential in the control of energy metabolism for the survival of animals exposed to oxygen shortages. Accordingly, we tested the hypothesis that adenosine modulates metabolic regulation in rainbow trout and Pacific hagfish exposed to acute hypoxia. Treatment of hypoxic rainbow trout (PwO2=3.33 or 4.00 kPa) with the adenosine receptor (AR) blocker theophylline was associated with greater increases in plasma [lactate], more rapid and pronounced metabolic acidosis, higher tissue [lactate], and lower heart creatine charge and glycogen content than in the hypoxic controls. The recruitment of anaerobic metabolism in hypoxic trout treated with enprofylline, an AR blocker with very weak affinity, was intermediate to that of the hypoxic theophylline-injected and control groups. In hagfish, plasma [lactate] increased following exposure to a PwO2 of 1.33 kPa but did not increase following exposure to 3.33 kPa and, like plasma acidosis, it was greatest in the animals treated with theophylline. These findings indicate that AR blockade results in a more rapid and pronounced recruitment of anaerobic metabolism following acute hypoxic exposure, and while rainbow trout and Pacific hagfish show marked differences in their responses to hypoxia, adenosine appears to play an important protective role in both species.
RESUMO
The safety and efficacy of the sequential addition of sulfasalazine to baseline methotrexate was assessed in patients with active rheumatoid arthritis inadequately controlled by methotrexate alone. Nineteen patients were recruited in a pilot, prospective, open label, uncontrolled clinical trial. One patient was lost to follow-up, four dropped out due to toxicity, one dropped out due to inefficacy, and five violated the protocol. A modified intent-to-treat analysis was performed by carrying forward the clinical data before drop-out or protocol violation to the final visit for the 18 evaluable patients. Swollen and tender joint counts, physicians's and patient's global scores were significantly improved (p < 0.021 to 0.001). Forty-two percent of patients (8/19) demonstrated >/= 20% improvement and 26% (5/19) showed >/= 50% improvement in 4 or more clinical parameters at 6 month's follow-up. Rheumatoid factor negative patients were more likely (p < 0.025) to complete the trial. A controlled clinical trial will be necessary to determine the effectiveness of this combination and the value of sequential addition chemotherapy in patients with recalcitrant rheumatoid arthritis.