Summer versus winter: the impact of the seasons on oocyte quality in in vitro fertilization cycles.

OBJECTIVE: The aim of this study was to determine the effects of seasons (winter vs. summer) on oocyte quality in infertile women undergoing ovulation induction for in vitro fertilization. METHODS: This retrospective cross-sectional study assessed 155 cycles of in vitro fertilization-induced ovulation in women, with 71 and 84 cycles occurring in the summer and winter, respectively. Oocytes were evaluated for quality, with 788 and 713 assessed during summer and winter, and classified according to Nikiforov's categories: (a) category I, good quality; (b) category 2, medium quality; and (c) category 3, low quality. RESULTS: Thickened zona pellucida (p<0.001), increased perivitelline space (p<0.001), oocyte shape abnormalities (p=0.01), and the presence of refractile bodies (p<0.0001) were more frequent in the summer cycles, whereas cytoplasmic granularity (p<0.001) was more frequent in the winter cycles. In winter, we observed a higher frequency of category 3 (p<0.001) and category 2 (p<0.001) oocytes and a lower frequency of category 1 (p<0.001) oocytes. CONCLUSION: Oocyte dysmorphisms were found in 70-80% of cases and were more common in winter. The main features include a thickened zona pellucida, enlarged perivitelline space, irregular shape, and cytoplasmic granularity. This implies better-quality oocytes in the summer than in the winter. However, retrospective studies have limitations due to data collection biases and potential confounding variables such as diet and exercise. Future research is needed to confirm these findings and explore the underlying mechanisms.

A inserção da Medicina Veterinária em uma Residência Multiprofissional em Saúde da Família e Comunidade: um relato de experiência

Objetivou-se com o presente trabalho descrever a experiência vivenciada por residentes da Medicina Veterinária (MV) durante pandemia da COVID-19. Trata-se de um relato de experiência sobre a inserção de residentes da MV no Programa de Residência Multiprofissional em Saúde da Família e Comunidade (PRMSFC) na Atenção Básica (AB) do município de João Pessoa - PB, durante o período de março de 2021 a fevereiro de 2022. Os primeiros desafios encontrados foram atividades concentradas em consultas, testagens e vacinações, e a falta de informação sobre o trabalho da MV. Os territórios das Unidades de Saúde da Família (USF) caracterizaram-se por áreas com desmatamento, urbanização, falta de saneamento básico, acúmulo de lixo, presença de animais de rua, agrícolas, sinantrópicos e peçonhentos. Nas USF foram observados casos de diversas zoonoses, como esporotricose, toxoplasmose e acidentes com animais peçonhentos. Foram realizadas ações de educação em saúde e articulações com outros serviços. Alguns problemas que limitaram a inserção da MV foram ausência de médicos veterinários na AB, dificuldades com a preceptoria e AB centrada no atendimento ambulatorial. A presença da MV na AB mostrou-se importante para o diagnóstico, notificação, promoção e prevenção em saúde de doenças e agravos da interface ambiente-animal-ser humano.

Summer versus winter: the impact of the seasons on oocyte quality in in vitro fertilization cycles

SUMMARY OBJECTIVE: The aim of this study was to determine the effects of seasons (winter vs. summer) on oocyte quality in infertile women undergoing ovulation induction for in vitro fertilization. METHODS: This retrospective cross-sectional study assessed 155 cycles of in vitro fertilization-induced ovulation in women, with 71 and 84 cycles occurring in the summer and winter, respectively. Oocytes were evaluated for quality, with 788 and 713 assessed during summer and winter, and classified according to Nikiforov's categories: (a) category I, good quality; (b) category 2, medium quality; and (c) category 3, low quality. RESULTS: Thickened zona pellucida (p<0.001), increased perivitelline space (p<0.001), oocyte shape abnormalities (p=0.01), and the presence of refractile bodies (p<0.0001) were more frequent in the summer cycles, whereas cytoplasmic granularity (p<0.001) was more frequent in the winter cycles. In winter, we observed a higher frequency of category 3 (p<0.001) and category 2 (p<0.001) oocytes and a lower frequency of category 1 (p<0.001) oocytes. CONCLUSION: Oocyte dysmorphisms were found in 70-80% of cases and were more common in winter. The main features include a thickened zona pellucida, enlarged perivitelline space, irregular shape, and cytoplasmic granularity. This implies better-quality oocytes in the summer than in the winter. However, retrospective studies have limitations due to data collection biases and potential confounding variables such as diet and exercise. Future research is needed to confirm these findings and explore the underlying mechanisms.

Barreiras ao emprego de refugiados no Brasil e seus impactos na integração de longo prazo / Barreras en el empleo de refugiados en Brasil y sus impactos en la integración a largo plazo / Barriers towards the refugee employment in Brazil and their impacts on long-term integration

Resumo Este artigo visa compreender como barreiras individuais, nacionais e organizacionais e suas inter-relações impactam o emprego de refugiados no mercado de trabalho brasileiro, com base na teoria da estrutura relacional da gestão da diversidade de Syed e Özbilgin (2009). Por meio de um paradigma interpretativo, abordagem qualitativa e utilizando uma pesquisa descritiva, o estudo foi realizado com oito refugiados com emprego formal na cidade de São Paulo, Brasil. As descobertas do estudo indicam a prevalência de barreiras nacionais sobre a exclusão de emprego para os refugiados, podendo potencializar fatores excludentes em níveis individual e organizacional. O governo brasileiro configurou-se como um dos principais obstáculos nacionais à integração, tendo papel particularmente importante na estrutura relacional. A pesquisa apresenta suas contribuições ao defender a condição do refugiado como inerente a uma extensão da diversidade. Ao lançar luz sobre as perspectivas dos refugiados acerca da realidade organizacional brasileira, o artigo propõe soluções que visem, por parte dos formuladores de políticas e organizações, minimizar impactos que as diferentes barreiras proporcionam à integração eficaz desses grupos nas organizações brasileiras.

Resumen Este artículo tiene como objetivo comprender cómo las barreras individuales, nacionales y organizacionales y sus interrelaciones impactan en el empleo de refugiados en el mercado laboral brasileño, con base en la teoría de la estructura relacional de Syed y Özbilgin (2009) de gestión de la diversidad. A través de un paradigma interpretativo, un enfoque cualitativo y utilizando una investigación descriptiva, el estudio se llevó a cabo con ocho refugiados con empleo formal en la ciudad de São Paulo, Brasil. Los hallazgos del estudio indican la prevalencia de barreras nacionales de exclusión del empleo para los refugiados, que pueden aprovechar los factores de exclusión a nivel individual y organizacional. El gobierno brasileño se ha convertido en uno de los principales obstáculos nacionales para la integración, ya que juega un papel particularmente importante en la estructura relacional. La investigación presenta sus aportes defendiendo la condición de refugiado como inherente a una extensión de la diversidad. Al arrojar luz sobre las perspectivas de los refugiados sobre la realidad organizacional brasileña, el artículo propone soluciones que apuntan, por parte de los políticos y las organizaciones, a minimizar los impactos de las diferentes barreras en la integración efectiva de estos grupos en las organizaciones brasileñas.

Abstract This article seeks to analyze how individual, national and organizational barriers and their interrelationships impact the employment of refugees in the Brazilian labor market, based on the theory of the relational structure of diversity management of Syed and Özbilgin (2009). Through an interpretative paradigm, a qualitative approach, and the use of descriptive research, this study was conducted with eight refugees formally employed in the city of São Paulo, Brazil. The findings of this study indicate the prevalence of national barriers over job exclusion for refugees, which may potentiate exclusion factors at the individual and organizational level. The Brazilian government appeared as one of the main national obstacles to integration, playing a particularly important role in the relational structure. This research presents its contributions to regard the refugee's condition as inherent to an extension of diversity. By shedding light on the perspectives of refugees about the Brazilian organizational reality, the article proposes solutions for policy makers and organizations in order to minimize the impacts that the different barriers provide to the effective integration of these groups in Brazilian organizations.

Bone density and quality in patients treated with direct-acting oral anticoagulants versus warfarin.

INTRODUCTION: Direct-acting oral anticoagulants (DOACs) are therapeutic alternatives to warfarin that act independently of vitamin K, thus not affecting bone matrix formation. The aim of this study was to compare bone mineral density (BMD) and microarchitecture in patients treated with DOACs versus warfarin. METHODS: Cross-sectional, observational study in patients using oral anticoagulants for >1 year and a paired control group (CG). Based on the type of anticoagulant used, the patients were grouped into a DOAC (DOACG) or warfarin (WG) group. All patients filled out a questionnaire and underwent BMD evaluation and trabecular bone score (TBS) measurement. RESULTS: In all, 150 patients were included (50 patients in each group). The mean age was 60.49 ± 7.48 years, and most participants were men (64%). The most frequent comorbidities were hypertension, dyslipidemia, and hyperglycemia (comparison between groups p > 0.05). Low bone mass was diagnosed in 42%, 50%, and 66% of the patients in the CG, DOACG, and WG, respectively (p = 0.012). On logistic regression analysis, BMD was associated with body mass index (BMI; odds ratio [OR] 0.846, 95% confidence interval [CI] 0.763-0.926, p = 0.001), creatinine level (OR 0.024, 95%CI 0.001-0.434, p = 0.017), and TBS value (OR 17.777, 95%CI 4.526-96.903, p = 0.000). The mean TBS decreased progressively from the CG to the DOACG and WG (1.328 ± 0.112, 1.264 ± 0.138, and 1.203 ± 0.112, respectively, p < 0.001). On multivariate linear regression, negative predictors of TBS included warfarin use (-0.06, 95%CI -0.11 to -0.02, p = 0.006), BMI (-0.01, 95%CI -0.01 to -0.00, p < 0.001), and hyperglycemia (-0.07, 95%CI -0.11 to -0.03, p = 0.003), while positive predictors were an active IPAQ classification (0.06, 95%CI 0.01-0.11, p = 0.029) and family history of hip fracture (0.07, 95%CI 0.01-0.14, p = 0.029). CONCLUSION: Patients using anticoagulants have lower BMD and TBS values compared with controls. This negative effect on bone was more pronounced with warfarin, but was also seen with DOACs.

Trabecular bone score (TBS) and bone mineral density in patients with long-term therapy with warfarin.

In this study, we compared patients using the anticoagulant warfarin for more than a year with a control group with similar characteristics but without using the drug. We demonstrated worse BMD and bone quality by trabecular bone score (TBS) in patients using warfarin for more than 1 year. PURPOSE: Evaluate the bone mineral density (BMD) and the trabecular bone score (TBS) of patients taking warfarin for more than 1 year compared with a control group. METHODS: Male patients aged 25-65 years in warfarin use for more than 1 year were included. Patients answered a questionnaire regarding lifestyle habits and realized a dual X-ray densitometry (DXA) (lumbar spine and hip), and TBS was evaluated. RESULTS: From the 96 patients invited, 33 patients accepted to participate and comprised the warfarin group (WG), and 3 were excluded. The control group (CG) was composed of 21 individuals matched by age and race. The mean age of WG was 57.0 ± 7.6 and in the CG 54.0 ± 10.6 years (p = 0.095). The BMD in WG was lower than that in the CG in all sites (spine p < 0.001, total hip p = 0.001, and femoral neck p = 0.005). A longer time of warfarin use increased the likelihood of having low BMD (OR = 1.239, CI 1.064-1.674, p = 0.01), whereas high BMI decreased it (OR = 0.732, CI 0.533-0.918, p = 0.03). The TBS was lower in WG than the CG (p = 0.04). Lower TBS was associated with hypertension in both groups and to the hip BMD (neck and total) (p < 0.005) in the WG. In the multivariate analysis, only hypertension (- 0.10, CI - 0.17 to - 0.03, p = 0.008) and total hip BMD ( 0.26, CI 0.07-0.46, p = 0.009) influenced TBS. CONCLUSION: We demonstrated an association between worsening of BMD and bone quality in patients taking warfarin for more than 1 year.

Prevalence and clinical aspects of Otodectes cynotis infestation in dogs and cats in the Semi-arid region of Paraíba, Brazil

Background: Infestation by Otodectes cynotis is one of the main causes of external otitis in small animals, causing greatdisconfort and predisposition to secondary bacterial or fungal infections, with relevant importance in the small animalmedicine. In dogs, a small number of this parasite in the ears may cause inflammation, while in cats, otoacariasis accountsfor half of the external otitis cases. Due to the insufficiency of data about the prevalence of this disease in the Northeastregion of Brazil, the purpose of the present study was to evaluate the prevalence and clinical aspects of O. cynotis in dogsand cats from the Semi-arid region of Paraíba, Brazil.Materials, Methods & Results: The research was conducted in the municipality of Sousa, Paraíba State, Brazil. A total of102 dogs and 152 cats had their external ear canals examined by bilateral otoscopy, using an otoscope with a veterinarycone that allows inspection of the external ear canal. Parasitological swabs were also used to determine the prevalence ofparasitism by Otodectes cynotis. Samples collected in swabs were stored in a 70% alcohol preservative solution and sentto the Laboratory of Veterinary Parasitology, in wich were examinated on direct research, using microscopes in the 10xobjective (magnification of 100x). In all animals, clinical examinations were performed and their owners answered anepidemiological questionnaire to collect information about food and sanitary management. During the clinical examination,characteristics such as otopodal reflex, and the presence of pruritus and/or cerumen were also evaluated. The prevalence ofdogs and cats positive for O. cynotis was 33.3% (34/102) and 52.6% (80/152), respectively. Bilateral infestations occurredin 52.9% (18/34) of the positive dogs. Most of the positive animals showed evidence of the mite in both tests, Otoscopy +Swab [dogs: 58.8% (20/34) and cats: 66.2% (53/80)].Discussion: A high prevalence of...(AU)

Prevalence and clinical aspects of Otodectes cynotis infestation in dogs and cats in the Semi-arid region of Paraíba, Brazil

Background: Infestation by Otodectes cynotis is one of the main causes of external otitis in small animals, causing greatdisconfort and predisposition to secondary bacterial or fungal infections, with relevant importance in the small animalmedicine. In dogs, a small number of this parasite in the ears may cause inflammation, while in cats, otoacariasis accountsfor half of the external otitis cases. Due to the insufficiency of data about the prevalence of this disease in the Northeastregion of Brazil, the purpose of the present study was to evaluate the prevalence and clinical aspects of O. cynotis in dogsand cats from the Semi-arid region of Paraíba, Brazil.Materials, Methods & Results: The research was conducted in the municipality of Sousa, Paraíba State, Brazil. A total of102 dogs and 152 cats had their external ear canals examined by bilateral otoscopy, using an otoscope with a veterinarycone that allows inspection of the external ear canal. Parasitological swabs were also used to determine the prevalence ofparasitism by Otodectes cynotis. Samples collected in swabs were stored in a 70% alcohol preservative solution and sentto the Laboratory of Veterinary Parasitology, in wich were examinated on direct research, using microscopes in the 10xobjective (magnification of 100x). In all animals, clinical examinations were performed and their owners answered anepidemiological questionnaire to collect information about food and sanitary management. During the clinical examination,characteristics such as otopodal reflex, and the presence of pruritus and/or cerumen were also evaluated. The prevalence ofdogs and cats positive for O. cynotis was 33.3% (34/102) and 52.6% (80/152), respectively. Bilateral infestations occurredin 52.9% (18/34) of the positive dogs. Most of the positive animals showed evidence of the mite in both tests, Otoscopy +Swab [dogs: 58.8% (20/34) and cats: 66.2% (53/80)].Discussion: A high prevalence of...

Knowledge management for the sustainable development of the semi-arid region in Northeastern Brazil / Gerenciamento do conhecimento para o desenvolvimento sustentável da região semiárida no Nordeste do Brasil

The objective of this study was to analyze the knowledge management perception in managers of a public university in the Brazilian Northeastern Semiarid Region, especially their tactical and strategic processes to produce knowledge about this region. The analysis was conducted according to the perspective of administrators at this university with a view to the sustainable development of the region. This was a qualitative descriptive study. All data were collected through structured interviews, using a questionnaire based on the Knowledge Management Diagnosis as a structuring model. Results showed that Knowledge Management is still a maturing practice. However, knowledge management is making institutional changes feasible and generating organization capacity to implement solutions and promote the sustainable development of the semi-arid region in the Northeastern Brazil.(AU)

O objetivo deste estudo foi analisar a percepção da gestão do conhecimento em gestores de uma universidade pública na Região Semiárida do Nordeste brasileiro, especialmente seus processos táticos e estratégicos para produzir conhecimento sobre esta Região. A análise foi conduzida segundo a perspectiva de administradores nesta universidade tendo em vista o desenvolvimento sustentável da região. Este foi um estudo qualitativo. Todos os dados foram coletados por meio de entrevistas estruturadas, usando um questionário baseado no Diagnóstico de Gestão do Conhecimento como modelo estruturante. Os resultados mostraram que a Gestão do Conhecimento é uma prática que está amadurecendo. Entretanto, a gestão do conhecimento está viabilizando mudanças institucionais e gerando capacidade da organização para implementar soluções e promover o desenvolvimento sustentável da região semiárida no Nordeste do Brasil.(AU)

Knowledge management for the sustainable development of the semi-arid region in Northeastern Brazil / Gerenciamento do conhecimento para o desenvolvimento sustentável da região semiárida no Nordeste do Brasil

ABSTRACT: The objective of this study was to analyze the knowledge management perception in managers of a public university in the Brazilian Northeastern Semiarid Region, especially their tactical and strategic processes to produce knowledge about this region. The analysis was conducted according to the perspective of administrators at this university with a view to the sustainable development of the region. This was a qualitative descriptive study. All data were collected through structured interviews, using a questionnaire based on the Knowledge Management Diagnosis as a structuring model. Results showed that Knowledge Management is still a maturing practice. However, knowledge management is making institutional changes feasible and generating organization capacity to implement solutions and promote the sustainable development of the semi-arid region in the Northeastern Brazil.

RESUMO: O objetivo deste estudo foi analisar a percepção da gestão do conhecimento em gestores de uma universidade pública na Região Semiárida do Nordeste brasileiro, especialmente seus processos táticos e estratégicos para produzir conhecimento sobre esta Região. A análise foi conduzida segundo a perspectiva de administradores nesta universidade tendo em vista o desenvolvimento sustentável da região. Este foi um estudo qualitativo. Todos os dados foram coletados por meio de entrevistas estruturadas, usando um questionário baseado no Diagnóstico de Gestão do Conhecimento como modelo estruturante. Os resultados mostraram que a Gestão do Conhecimento é uma prática que está amadurecendo. Entretanto, a gestão do conhecimento está viabilizando mudanças institucionais e gerando capacidade da organização para implementar soluções e promover o desenvolvimento sustentável da região semiárida no Nordeste do Brasil.

Overexpression of mTOR and p(240-244)S6 in IDH1 Wild-Type Human Glioblastomas Is Predictive of Low Survival.

PI3K/Akt/mTOR pathway activation is a hallmark of high-grade gliomas, which prompted clinical trials for the use of PI3K and mTOR inhibitors. However, the poor results in the original trials suggested that better patient profiling was needed for such drugs. Thus, accurate and reproducible monitoring of mTOR complexes can lead to improved therapeutic strategies. In this work, we evaluated the expression and phosphorylation of mTOR, RAPTOR, and rpS6 in 195 human astrocytomas and 30 normal brain tissue samples. The expression of mTOR increased in glioblastomas, whereas mTOR phosphorylation, expression of RAPTOR, and expression and phosphorylation of rpS6 were similar between grades. Interestingly, the overexpression of total and phosphorylated mTOR as well as phosphorylated rpS6 (residues 240-244) were associated with wild-type IDH1 only glioblastomas. The expression and phosphorylation of mTOR and phosphorylation of rpS6 at residues 240-244 were associated with a worse prognosis in glioblastomas. Our results suggest that mTOR and rpS6 could be used as markers of overactivation of the PI3K-mTOR pathway and are predictive factors for overall survival in glioblastomas. Our study thus suggests that patients who harbor IDH1 wild-type glioblastomas might have increased benefit from targeted therapy against mTOR.

O controle da tradução pela via mTOR nos mecanismos de tumorigênese em gliomas / The control of the translation mechanisms in the mTOR pathway in tumorigenesis gliomas

A síntese de novas proteínas é um processo essencial para a proliferação celular e, portanto, as vias de controle da tradução podem exercer um papel chave na tumorigênese. O controle da tradução pela via de mTOR é bem conhecido e, interessantemente, mutações genéticas encontradas em diversos tipos tumorais, incluindo gliomas e glioblastomas, levam a uma super-ativação de mTOR. A proteína mTOR forma os complexos mTORC1 (formado pelas proteínas mTOR e Raptor, entre outras) e mTORC2 (formado pelas proteínas mTOR e Rictor, entre outras). O primeiro complexo é susceptível ao inibidor rapamicina e está relacionado ao controle da tradução, proliferação, autofagia e hipóxia. Já mTORC2 é insensível a rapamicina e regula eventos relativos à adesão e migração celulares. A ativação de elementos de mTORC1 em tumores foi amplamente observada na literatura, no entanto, existem poucos trabalhos observando a expressão destas proteínas em gliomas, um tipo tumoral que ainda hoje apresenta altos índices de morbidade. Já a expressão de proteínas do complexo mTORC2 em tumores humanos foi pouco estudada. A rapamicina, tem sido utilizada atualmente em ensaios clínicos de terapia anti-tumoral. No entanto, a resistência à rapamicina pode ser observada, reduzindo a eficácia do tratamento, o que poderia estar relacionado com a presença do complexo mTORC2. Assim, a atividade de mTOR, bem como a expressão de proteínas dos complexos mTORC1 e 2 (como Raptor e Rictor, respectivamente) em gliomas poderia contribuir para orientar uma conduta terapêutica diferencial para um tipo tumoral que apresenta baixa responsividade às terapias atuais. Utilizando um tissue microarray de 190 casos de gliomas de diferentes graus, pudemos observar uma alta expressão das proteínas da via de PI3K/mTOR, que aumentavam com a progressão da doença. Por outro lado, o componente do complexo mTORC2, Rictor, apresentou expressão que diminuía com a progressão tumoral. Observando a sobrevida global dos indivíduos acometidos, verificamos uma correlação estatisticamente significativa em pAKT e mTOR, aonde os indivíduos que tinham uma menor expressão sobreviviam mais do que aqueles que tinha uma expressão alta destas proteínas. Quando utilizamos mais de uma proteína da via para realizar as análises de sobrevida, estes resultados ficaram mais evidentes, mostrando que estas proteínas poderiam ser aplicadas para estimativas de prognóstico. Em conjunto, nossos dados evidenciam a importância da via de PI3K/mTOR na progressão tumoral em glioblastomas e sugere que inibidores desta via sejam potenciais alvos terapêuticos para este tipo tumoral.

The synthesis of new proteins is a key process for cell proliferation, thus translation control may play a role in tumorigenesis. The control of the translation by the mTOR pathway is well known and, interestingly, genetic mutations found in several tumor types, including gliomas and glioblastomas, lead to an over-activation of mTOR. mTOR forms the complexes mTORC1 (formed by the proteins mTOR and Raptor, among others) and mTORC2 (formed by Rictor and mTOR proteins, among others). The first complex is susceptible to the inhibitor rapamycin and is related to the control of translation, proliferation, autophagy and hypoxia. mTORC2 is insensitive to rapamycin and regulates events related to cell adhesion and migration. mTORC1 activation in tumors has been widely reported in the literature, however, there are few studies looking at the expression of these proteins in gliomas, a tumor type that still has high morbidity. The expression of mTORC2 proteins in human tumors hasn't been extensively approached. Rapamycin is currently in use in clinical trials for antitumor therapy. However, resistance to rapamycin may be observed, reducing the effectiveness of treatment, which could be related to the pres ence of mTORC2. Thus, the activity of mTOR and protein expression of complexes mTORC1 and 2 in gliomas may help to guide a therapeutic differential for a tumor type that has low responsiveness to current therapies. Using a tissue microarray of 190 cases of gliomas of different degrees, we observed a high expression of the proteins of the PI3K/mTOR pathway, which increases with disease progression. On the other hand, the component of the mTORC2 complex, Rictor, showed decreased expression in tumor progression. Observing global survival of the affected individuals, we found a statistically significant correlation in pAkt and mTOR, where individuals who had a lower expression survived longer than those who had a high expression of these proteins. When using more than one protein of the pathway to perform the survival analyzes, the results were more evident, indicating that these proteins could be applied to estimate disease prognosis. Together, our data show the importance of the PI3K/mTOR pathway in tumor progression in glioblastomas and suggests that inhibitors of this pathway are potential therapeutic agents for this tumor type.

Aggregation of integrins and RhoA activation are required for Thy-1-induced morphological changes in astrocytes.

Thy-1, a cell adhesion molecule abundantly expressed in mammalian neurons, binds to a beta(3)-containing integrin on astrocytes and thereby stimulates the assembly of focal adhesions and stress fibers. Such events lead to morphological changes in astrocytes that resemble those occurring upon injury in the brain. Extracellular matrix proteins, typical integrin ligands, bind to integrins and promote receptor clustering as well as signal transduction events that involve small G proteins and cytoskeletal changes. Here we investigated the possibility that the cell surface protein Thy-1, when interacting with a beta(3)-containing integrin on astrocytes, could trigger signaling events similar to those generated by extracellular matrix proteins. DI-TNC(1) astrocytes were stimulated with Thy-1-Fc immobilized on beads, and increased RhoA activity was confirmed using an affinity precipitation assay. The effect of various inhibitors on the cellular response was also studied. The presence of Y-27632, an inhibitor of Rho kinase (p160ROCK), a key downstream effector of RhoA, significantly reduced focal adhesion and stress fiber formation induced by Thy-1. Similar effects were obtained when astrocytes were treated with C3 transferase, an inhibitor of RhoA. Alternatively, astrocytes were transfected with an expression vector encoding fusion proteins of enhanced green fluorescent protein with either the Rho-binding domain of Rhotekin, which blocks RhoA function, or the dominant-negative N19RhoA mutant. In both cases, Thy-1-induced focal adhesion formation was inhibited. Furthermore, we observed that RhoA activity after stimulation with soluble Thy-1-Fc molecule was augmented upon further cross-linking using protein A-Sepharose beads. The same was shown by cross-linking beta(3)-containing integrin with anti-beta(3) antibodies. Together, these results indicate that Thy-1-mediated astrocyte stimulation depended on beta(3) integrin clustering and the resulting increase in RhoA activity.

Regulation of Rho family GTPases by cell-cell and cell-matrix adhesion.

Integrins and cadherins are transmembrane adhesion receptors that are necessary for cells to interact with the extracellular matrix or adjacent cells, respectively. Integrins and cadherins initiate signaling pathways that modulate the activity of Rho family GTPases. The Rho proteins Cdc42, Rac1, and RhoA regulate the actin cytoskeleton. Cdc42 and Rac1 are primarily involved in the formation of protrusive structures, while RhoA generates myosin-based contractility. Here we examine the differential regulation of RhoA, Cdc42, and Rac1 by integrin and cadherin signaling. Integrin and cadherin signaling leads to a decrease in RhoA activity and activation of Cdc42 and Rac1. When the normal RhoA suppression is antagonized or RhoA signaling is increased, cells exhibited impaired spreading on the matrix protein fibronectin and decreased cell-cell adhesion. Spreading on fibronectin and the formation of cell-cell adhesions is decreased in cells expressing dominant negative forms of Cdc42 or Rac1. These data demonstrate that integrins and cadherins regulate Rho proteins in a comparable manner and lead us to speculate that these changes in Rho protein activity participate in a feedback mechanism that promotes further cell-matrix or cell-cell interaction, respectively.

Regulation of Rho family GTPases by cell-cell and cell-matrix adhesion

Integrins and cadherins are transmembrane adhesion receptors that are necessary for cells to interact with the extracellular matrix or adjacent cells, respectively. Integrins and cadherins initiate signaling pathways that modulate the activity of Rho family GTPases. The Rho proteins Cdc42, Rac1, and RhoA regulate the actin cytoskeleton. Cdc42 and Rac1 are primarily involved in the formation of protrusive structures, while RhoA generates myosin-based contractility. Here we examine the differential regulation of RhoA, Cdc42, and Rac1 by integrin and cadherin signaling. Integrin and cadherin signaling leads to a decrease in RhoA activity and activation of Cdc42 and Rac1. When the normal RhoA suppression is antagonized or RhoA signaling is increased, cells exhibited impaired spreading on the matrix protein fibronectin and decreased cell-cell adhesion. Spreading on fibronectin and the formation of cell-cell adhesions is decreased in cells expressing dominant negative forms of Cdc42 or Rac1. These data demonstrate that integrins and cadherins regulate Rho proteins in a comparable manner and lead us to speculate that these changes in Rho protein activity participate in a feedback mechanism that promotes further cell-matrix or cell-cell interaction, respectively