Extending the kinetic solution of the classic Michaelis-Menten model of enzyme action

The principal aim of studies of enzyme-mediated reactions has been to provide comparative and quantitative information on enzyme-catalyzed reactions under distinct conditions. The classic Michaelis-Menten model (Biochem Zeit 49:333, 1913) for enzyme kinetic has been widely used to determine important parameters involved in enzyme catalysis, particularly the Michaelis-Menten constant (K (M) ) and the maximum velocity of reaction (V (max) ). Subsequently, a detailed treatment of the mechanisms of enzyme catalysis was undertaken by Briggs-Haldane (Biochem J 19:338, 1925). These authors proposed the steady-state treatment, since its applicability was constrained to this condition. The present work describes an extending solution of the Michaelis-Menten model without the need for such a steady-state restriction. We provide the first analysis of all of the individual reaction constants calculated analytically. Using this approach, it is possible to accurately predict the results under new experimental conditions and to characterize and optimize industrial processes in the fields of chemical and food engineering, pharmaceuticals and biotechnology.

The rational reconstruction of the research program on classic rationalism: Locke and the empiricist approach

This article intends to rationally reconstruct Locke`s theory of knowledge as incorporated in a research program concerning the nature and structure of the theories and models of rationality. In previous articles we argued that the rationalist program can be subdivided into the classical rationalistic subprogram, which includes the knowledge theories of Descartes, Locke, Hume and Kant, the neoclassical subprogram, which includes the approaches of Duhem, Poincare and Mach, and the critical subprogram of Popper. The subdivision results from the different views of rationality proposed by each one of these subprograms, as well as from the tools made available by each one of them, containing theoretical instruments used to arrange, organize and develop the discussion on rationality, the main one of which is the structure of solution of problems. In this essay we intend to reconstruct the assumptions of Locke`s theory of knowledge, which in our view belongs to the classical rationalistic subprogram because it shares with it the thesis of the identity of (scientific) knowledge and certain knowledge.

Hemihypoglossal-facial neurorrhaphy after mastoid dissection of the facial nerve: Results in 24 patients and comparison with the classic technique

OBJECTIVE: Hypoglossal-facial neurorrhaphy has been widely used for reanimation of paralyzed facial muscles after irreversible proximal injury of the facial nerve. However, complete section of the hypoglossal nerve occasionally results in hemiglossal dysfunction and interferes with swallowing and speech. To reduce this morbidity, a modified technique with partial section of the hypoglossal nerve after mastoid dissection of the facial nerve (HFM) has been used. We report our experience with the HFM technique, retrospectively comparing the outcome with results of the classic hypoglossal-facial neurorrhaphy. METHODS: A retrospective review was performed in 36 patients who underwent hypoglossal-facial neurorrhaphy with the classic (n = 12) or variant technique (n = 24) between 2000 and 2006. Facial Outcome was evaluated with the House-Brackmann grading system, and tongue function was evaluated with a new scale proposed to quantify Postoperative tongue alteration. The results were compared, and age and time between nerve injury and surgery were correlated with the outcome. RESULTS: There was no significant difference between the two techniques concerning facial reanimation. A worse outcome of tongue function, however, was associated with the classic technique (Mann-Whitney U test; P < 0.05). When HFM was used, significant correlations defined by the Spearman test were identified between preoperative delay (p = 0.59; P = 0.002) or age (p = 0.42; P = 0.031) and results of facial reanimation evaluated with the House-Brackmann grading system. CONCLUSION: HFM is as effective as classic hypoglossal-facial neurorrhaphy for facial reanimation, and it has a much lower morbidity related to tongue function. Better results are obtained in younger patients and with a shorter interval between facial nerve injury and surgery.

Primary retroperitoneal lipoma: A soft tissue pathology heresy? Report of a case with classic histologic, cytogenetics, and molecular genetic features

Adipose tissue tumors of the retroperitoneum showing no identifiable cytologic atypia are usually classified as lipoma-like well-differentiated liposarcoma. Whether a subset of these tumors represents true examples of retroperitoneal lipoma remains a controversial subject, because the diagnostic liposarcoma cells may be of difficult identification, even after extensive sampling. Herein, we describe a large retroperitoneal lipoma with classic histopathologic, cytogenetic, molecular cytogenetic, and molecular genetic features. Extensive morphologic inspection showed no evidence of cytologic atypia. Cytogenetic analysis performed on fresh tissue material revealed the classic lipoma chromosome t(3;12)(q27;q14-15). Fluorescence in situ hybridization on multiple sections excluded the presence of MDM2 and CDK4 amplification, but showed HMGA2 balanced rearrangement in most cells. Reverse-transcriptase polymerase chain reaction followed by sequencing analysis confirmed the presence of the HMGA2-LPP fusion gene, a characteristic and the most common fusion product found in lipoma. The patient has been followed for 2.5 years without evidence of recurrence or metastasis. These results indicate that retroperitoneal lipomata do exist, but their diagnosis must rely on stringent histologic, cytogenetic, and molecular genetic analysis.

Effect of casting atmosphere on the shear bond strength of a ceramic to Ni-Cr and Ni-Cr-Be alloys

The success of metal-ceramic restorations depends on an optimal bond between metal and ceramic. This study evaluated the effect of 3 casting atmospheres on the metal-ceramic bond strength (MCBS) of 2 Ni-Cr alloys, with beryllium (Fit Cast V) and without beryllium (Fit Cast SB). Sixty acrylic resin patterns (8 mm long and 5 mm diameter) were obtained using a fluorocarbon resin matrix. Wax was used to refine the surface of acrylic resin patterns that were invested and cast in an induction casting machine under normal, vacuum, and argon atmospheres at a temperature of 1340ºC. The castings were divested manually and airborne-particle abraded with 100-µm aluminum-oxide. Ten castings were obtained for each group. The IPS Classic V ceramic was applied (2 mm high and 5 mm diameter). The shear bond strength was tested in a mechanical testing machine with a crosshead speed of 2.0 mm/min. The MCBS data (MPa) were subjected to 2-way analysis of variance (α=0.05). There was no statistically significant difference (p>0.05) between the alloys or among the casting atmospheres. Within the limitations of this study, it may be concluded that the presence of beryllium and the casting atmosphere did not interfere in the MCBS of the evaluated metal-ceramic combinations

Termogravimetria: um novo enfoque para a clássica determinação de cálcio em cascas de ovos

The use of thermoanalytical data in sample preparation is described as a tool to catch the students' attention to some details that can simplify both the analysis and the analytical procedure. In this case, the thermal decomposition of eggshells was first investigated by thermogravimetry (TGA). Although the classical procedures suggest long exposure to high temperatures, the TGA data showed that the decomposition of organic matter takes place immediately when the sample is heated up to 800 °C under air atmosphere. After decomposition, the calcium content was determined by flame atomic emission photometry and compared with the results obtained using classical volumetric titration with EDTA.

Análise das relações taxonômicas e sistemáticas entre espécies de triatomíneos (Hemiptera, Reduviidae) de colônias mantidas pelo Serviço Especial de Saúde de Araraquara, inferida de seqüências do 16S rDNA mitocondrial

Foram analisadas seqüências de nucleotídeos do gene 16S do rDNA mitocondrial em 14 populações de triatomíneos mantidos em colônias no insetário SESA de Araraquara- SP, comparando-as com seqüências do mesmo gene disponíveis no GenBank. Os fragmentos variaram de 311 a 317 pb com baixa variação intra-específica entre as distâncias genéticas (0% a 0,6%), exceto para os relacionamentos entre espécimes de Triatoma sordida (1%) e espécimes de T. brasiliensis (1,3%) atribuídos a populações geográficas diferentes. A parafilia de Rhodniini e do gênero Panstrongylus foi evidenciada pelas analises, confirmando resultados anteriores entre estes e os estreitos relacionamentos de R. prolixus com R. robustus e de T. infestans e T. platensis. O relacionamento entre T. maculata e T. pseudomaculata não foi solucionado, uma vez que, esses táxons apareceram tanto em monofilia quanto em parafilia: T. pseudomaculata (SESA) está agrupado com T. maculata (seqüência do GenBank) e associados a T . brasiliensis (SESA), enquanto T. maculata (SESA) aparece agrupado com T. pseudomaculata do SESA e do GenBank. Os resultados evidenciam a utilidade do gene 16S como marcador de espécies de triatomíneos e sua importância em questões de sistemática e taxonomia. Há necessidade de novos estudos envolvendo outros marcadores associados a caracteres sistemáticos clássicos de morfologia, ecologia e comportamento para decisões sistemáticas adequadas uma vez, que teriam impacto não apenas sistemático mas, para as estratégias de controle.

Epidemiological and ecological aspects related to malaria in the area of influence of the lake at Porto Primavera dam, in western São Paulo State, Brazil

A study was carried out in the area of influence of the Porto Primavera Hydroelectric Power Station, in western São Paulo State, to investigate ecological and epidemiological aspects of malaria in the area and monitor the profile of the anopheline populations following the environmental changes brought about by the construction of the lake. Mosquitoes captured were analyzed by standardized indicator species analysis (ISA) before and during different flooding phases (253 m and 257 m elevations). The local human population was studied by means of parasitological (thin/thick blood smears), molecular (PCR) and serological tests. Serological tests consisted of Enzyme Linked Immunosorbent Assay (ELISA) with synthetic peptides of the circumsporozoite protein (CSP) from classic Plasmodium vivax, P. vivax variants (VK247 and "vivax-like"), P. malariae and P. falciparum and Indirect Immunofluorescence Assay (IFA) with asexual forms of P. vivax, P. malariae and P. falciparum. The results of the entomological survey indicated that, although the Anopheles darlingi population increased after the flooding, the population density remained very low. No malaria, parasite infection or DNA was detected in the inhabitants of the study area. However, there was a low frequency of antibodies against asexual forms and a significant prevalence of antibodies against P. vivax, P. vivax variants, P. falciparum and P. malariae; the presence of these antibodies may result from recent or less recent contact with human or simian Plasmodium (a parallel study in the same area revealed the existence of a sylvatic cycle). Nevertheless, these results suggest that, as in other places where malaria is present and potential vectors circulate, the local epidemiological conditions observed could potentially support the transmission of malaria in Porto Primavera Lake if infected individuals are introduced in sufficient numbers. Further studies are required to elucidate the phenomena described in this paper.

Comparação entre o método clássico de Gibson e Cooke e o teste da condutividade no suor em pacientes com e sem fibrose cística

OBJETIVO: Comparar os valores de cloro no suor obtidos pelo teste quantitativo da iontoforese pela pilocarpina (teste clássico) com os valores de condutividade no suor obtidos pelo sistema de coleta por Macroduct® em pacientes com e sem fibrose cística (FC). O custo e tempo despendidos na execução de cada teste foram também analisados. MÉTODOS: O teste do suor pelas duas técnicas foi realizado simultaneamente, em pacientes com e sem FC. Os pontos de corte para a condutividade para excluir ou diagnosticar FC foram < 75 e > 90 mmol/L, respectivamente, e, para o teste clássico, cloro < 60 e > 60 mmol/L. RESULTADOS: Cinquenta e dois pacientes com FC (29 do sexo masculino e 23 do sexo feminino; de 1,5 a 18,2 anos) realizaram o teste do suor pelas duas técnicas, apresentando valores medianos de cloro e condutividade no suor de 114 e 122 mmol/L, respectivamente. Em todos eles, a condutividade foi > 95 mmol/L, o que conferiu ao teste 100% de sensibilidade (IC95% 93,1-100). Cinquenta pacientes sem FC (24 do sexo masculino e 26 do sexo feminino; de 0,5 a 12,5 anos) apresentaram valores medianos de cloro e condutividade no suor de 15,5 e 30 mmol/L, respectivamente. Em todos os casos, a condutividade foi < 70 mmol/L, o que conferiu ao teste 100% de especificidade (IC95% 92,9-100). O tempo despendido na execução dos testes foi significativamente menor com o teste da condutividade, e o seu custo também foi inferior. CONCLUSÕES: O teste da condutividade apresentou alta sensibilidade e especificidade, e houve boa correspondência entre os testes. O tempo de execução foi mais rápido e o custo inferior na aplicação do teste da condutividade em relação ao teste clássico.

Evaluation of a recombinant p24 antigen for the detection of Feline Immunodeficiency Virus-specific antibodies

Feline Immunodeficiency Virus is a worldwide infection and is considered a significant pathogen. The diagnosis of FIV infections is mainly based on commercially available rapid tests that are highly expensive in Brazil, hence it is rarely performed in the country. Furthermore, lentiviruses grow slowly and poorly in tissue cultures, making the production of viral antigen by classic means and thus the establishment of FIV immunodiagnosis impracticable. In order to deal with this, recombinant DNA techniques were adopted to produce the protein p24, a viral capsid antigen. The protein's reactivity evaluation analyzed by Western blot indicated that this recombinant antigen can be a useful tool for the immunodiagnostic of FIV infections.

On the interference of clinical outcome on rabies transmission an perpetuation

Rabies is a viral zoonotic infectious disease that affects mammals and is caused by genotypes/species of the Lyssavirus genus (Rhabdoviridae, Mononegavirales), with the genotype 1 (classic rabies virus - RABV) being the most prevalent. Despite continuous efforts, rabies is still an incurable disease that causes thousands of deaths amongst humans worldwide. Due to a wide range of hosts and the different evolutionary paths of RABV in each host, several host-specific variants have arisen in an ongoing process. The result of RABV replication in nervous tissues may lead to two opposite clinical outcomes, i.e., paralytic/dumb form and encephalitic/furious one. The paralytic form creates dead-end hosts mainly amongst herbivores, while the furious form of the disease allows for augmented transmission when manifested in gregarious carnivores, as their natural aggressive behavior is accentuated by the disease itself. The aim of this article is to propose a theoretical model intended to explore how the rabies virus intrinsically modulates the immune system of different host classes, the pathological changes that the virus causes in these animals and how these elements favor its own perpetuation in nature, thus providing a basis for better prediction of the patterns this disease may present.

Variabilidade espacial da textura de um Argissolo Vermelho Amarelo sob cultivo de pastagem e vegetação nativa

O conhecimento da variabilidade espacial dos atributos de um solo sob diferentes coberturas auxilia o estudo das alterações ocorridas em razão do manejo. O objetivo deste trabalho foi determinar, com uso da estatística clássica e geoestatística, a variabilidade espacial das frações texturais de um solo cultivado com pastagem e vegetação nativa. Amostras de solo foram coletadas na profundidade de 0-0,20m, nos pontos de cruzamento de uma malha, com intervalos regulares de 10m, totalizando 64 pontos em cada área. Na área de pastagem, as frações areia grossa e total apresentaram valores médios maiores em relação à vegetação nativa e correlações negativas com as altitudes dos pontos amostrais nas duas áreas. Todas as frações texturais apresentaram dependência espacial de moderada a alta nas duas áreas e com o patamar definido, com exceção da areia fina e do silte na pastagem. Grande parte dessa variabilidade ocorre em função da erosão hídrica.

Saúde e adolescentes: possibilidades de violência simbólica

Este artigo se propõe a analisar o tipo de relação que as Unidades de Saúde estabelecem com os adolescentes no município de Fortaleza, CE, na perspectiva da violência simbólica de Pierre Bourdieu. Para tanto, foram organizados seis grupos focais constituídos de profissionais das Unidades Básicas de Saúde da Família. O número de participantes variou de 10 a 15 pessoas. Os critérios de escolha das Unidades foram: aquelas que já realizaram algum projeto de promoção à saúde ou prevenção de doenças com adolescentes; que possuem profissionais que são reconhecidos por desenvolverem atendimento junto aos adolescentes. As falas do grupo foram anotadas e transcritas por um observador independente. O material coletado foi analisado de acordo com os critérios clássicos da análise de conteúdo. Os resultados mostraram que há uma descrença na implantação de políticas públicas para a saúde na adolescência e que a sustentabilidade de programas e projetos fica fragilizada pela ausência dessa estrutura de apoio às ações no cuidado aos adolescentes

Prontuários, para que servem?: representação dos coordenadores de equipe dos capsi a respeito do valor e da utilidade dos prontuários

INTRODUÇÃO: o artigo procura compreender como os Coordenadores dos Centros de Atenção Psicossocial Infantojuvenil (CAPSi) do Estado de São Paulo percebem o valor e a utilidade dos prontuários do usuários do serviço. Atualmente, os prontuários obedecem a claros princípios éticos. São muitas as pesquisas que se utilizam de prontuários e vários os estudos que se propõem a aperfeiçoá-los uma vez que são considerados ferramenta de primeira importância no âmbito da saúde. Cabe, entretanto, indagar se esses instrumentos são valorizados e se suas utilidades percebidas pelas equipes de saúde mental no exercício real de suas práticas. O trabalho descreve e analisa as percepções dos Coordenadores dos CAPSi-SP a respeito da utilidade dos prontuários para a equipe de saúde e para os usuários. MÉTODO: foi entrevistado um Coordenador de cada um dos 19 dos CAPSi do Estado de São Paulo. As respostas foram analisadas de acordo com os procedimentos clássicos da Análise de Conteúdo. RESULTADOS: os prontuários são percebidos como valiosos instrumentos de trabalho e sua importância destacada como instrumento de intervenção e de acompanhamento clínicos. Sua relevância é assinalada como dispositivo que possibilita a articulação e a comunicação dos membros das equipes técnicas dos CAPSi. Por outro lado, não é percebida qual a utilidade que eles teriam para o usuário. A contradição nos níveis de importância alocada à utilidade dos prontuários quando se trata da equipe técnica ou dos usuários enseja uma discussão aprofundada sobre a natureza da clínica em saúde mental praticada nos CAPSi

HTLV-1 Tax Specific CD8+ T Cells Express Low Levels of Tim-3 in HTLV-1 Infection: Implications for Progression to Neurological Complications

The T cell immunoglobulin mucin 3 (Tim-3) receptor is highly expressed on HIV-1-specific T cells, rendering them partially ""exhausted'' and unable to contribute to the effective immune mediated control of viral replication. To elucidate novel mechanisms contributing to the HTLV-1 neurological complex and its classic neurological presentation called HAM/TSP (HTLV-1 associated myelopathy/tropical spastic paraparesis), we investigated the expression of the Tim-3 receptor on CD8(+) T cells from a cohort of HTLV-1 seropositive asymptomatic and symptomatic patients. Patients diagnosed with HAM/TSP down-regulated Tim-3 expression on both CD8(+) and CD4(+) T cells compared to asymptomatic patients and HTLV-1 seronegative controls. HTLV-1 Tax-specific, HLA-A*02 restricted CD8(+) T cells among HAM/TSP individuals expressed markedly lower levels of Tim-3. We observed Tax expressing cells in both Tim-3(+) and Tim-3(-) fractions. Taken together, these data indicate that there is a systematic downregulation of Tim-3 levels on T cells in HTLV-1 infection, sustaining a profoundly highly active population of potentially pathogenic T cells that may allow for the development of HTLV-1 complications.