Growth and photosynthetic down-regulation in Coffea arabica in response to restricted root volume

Coffee (Coffea arabica L.) plants were grown in small (3-L), medium (10-L) and large (24-L) pots for 115 or 165 d after transplanting (DAT), which allowed different degrees of root restriction. Effects of altered source : sink ratio were evaluated in order to explore possible stomatal and non-stomatal mechanisms of photosynthetic down-regulation. Increasing root restriction brought about large and general reductions in plant growth associated with a rising root : shoot ratio. Treatments did not affect leaf water potential or leaf nutrient status, with the exception of N content, which dropped significantly with increasing root restriction even though an adequate N supply was available. Photosynthesis was severely reduced when plants were grown in small pots; this was largely associated with non-stomatal factors, such as decreased Rubisco activity. At 165DAT contents of hexose, sucrose, and amino acids decreased in plants grown in smaller pots, while those of starch and hexose-P increased in plants grown in smaller pots. Photosynthetic rates were negatively correlated with the ratio of hexose to free amino acids, but not with hexose content. Activities of acid invertase, sucrose synthase, sucrose-P synthase, fructose-1,6- bisphosphatase, ADP-glucose pyrophosphorylase, starch phosphorylase, glyceraldehyde-3-P dehydrogenase, PPi : fructose-6-P 1-phosphotransferase and NADP : glyceraldehyde-3-P dehydrogenase all decreased with severe root restriction. Glycerate-3-P : Pi and glucose-6-P : fructose-6-P ratios decreased accordingly. Photosynthetic down-regulation was unlikely to have been associated directly with an end-product limitation, but rather with decreases in Rubisco. Such a down-regulation was largely a result of N deficiency caused by growing coffee plants in small pots.

Performance and egg quality of laying hens fed diets containing aflatoxin, fumonisin and adsorbent

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Crystal structure of human PNP complexed with guanine

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. PNP is a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. More recently, the 3-D structure of human PNP has been refined to 2.3 Angstrom resolution, which allowed a redefinition of the residues involved in the substrate-binding sites and provided a more reliable model for structure-based design of inhibitors. This work reports crystallographic study of the complex of Human PNP:guanine (HsPNP:Gua) solved at 2.7 Angstrom resolution using synchrotron radiation. Analysis of the structural differences among the HsPNP:Gua complex, PNP apoenzyme, and HsPNP:immucillin-H provides explanation for inhibitor binding, refines the purine-binding site, and can be used for future inhibitor design. (C) 2003 Elsevier B.V. All rights reserved.

Crystallographic structure of PNP from Mycobacterium tuberculosis at 1.9 angstrom resolution

Even being a bacterial purine nucleoside phosphorylase (PNP), which normally shows hexameric folding, the Mycobacterium tuberculosis PNP (MtPNP) resembles the mammalian trimeric structure. The crystal structure of the MtPNP apoenzyme was solved at 1.9 Angstrom resolution. The present work describes the first structure of MtPNP in complex with phosphate. In order to develop new insights into the rational drug design, conformational changes were profoundly analyzed and discussed. Comparisons over the binding sites were specially studied to improve the discussion about the selectivity of potential new drugs. (C) 2004 Elsevier B.V. All rights reserved.

Crystal structure of human PNP complexed with hypoxanthine and sulfate ion

Purine nucleoside phosphorylase (PNP) is a ubiquitous enzyme, which plays a key role in the purine salvage pathway, and PNP deficiency in humans leads to an impairment of T-cell function, usually with no apparent effects on B-cell function. Human PNP has been submitted to intensive structure-based design of inhibitors, most of them using low-resolution structures of human PNP. Here we report the crystal structure of human PNP in complex with hypoxanthine, refined to 2.6 Angstrom resolution. The intermolecular interaction between ligand and PNP is discussed. (C) 2004 Elsevier B.V. All rights reserved.

Structure of human PNP complexed with ligands

Purine nucleoside phosphorylase (PNP) is a key enzyme in the purine-salvage pathway, which allows cells to utilize preformed bases and nucleosides in order to synthesize nucleotides. PNP is specific for purine nucleosides in the beta-configuration and exhibits a strong preference for purines containing a 6-keto group and ribosyl-containing nucleosides relative to the corresponding analogues. PNP was crystallized in complex with ligands and data collection was performed using synchrotron radiation. This work reports the structure of human PNP in complex with guanosine (at 2.80 angstrom resolution), 3' deoxyguanosine (at 2.86 angstrom resolution) and 8-azaguanine (at 2.85 angstrom resolution). These structures were compared with the PNP-guanine, PNP-inosine and PNP-immucillin-H complexes solved previously.

Determining the structural basis for specificity of ligands using crystallographic screening

Crystallographic screening has been used to identify new inhibitors for potential target for drug development. Here, we describe the application of the crystallographic screening to assess the structural basis of specificity of ligands against a protein target. The method is efficient and results in detailed crystallographic information. The utility of the method is demonstrated in the study of the structural basis for specificity of ligands for human purine nucleoside phosphorylase (PNP). Purine nucleoside phosphorylase catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. This enzyme is a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. This methodology may help in the future development of a new generation of PNP inhibitors.

Evaluation of the antigenotoxicity of polysaccharides and beta-glucans from Agaricus blazei, a model study with the single cell gel electrophoresis/Hep G2 assay

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structural basis for inhibition of human PNP by immucillin-H

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. PNP is a target for inhibitor development aiming at T-cell immune response modulation. This work reports on the crystallographic study of the complex of human PNP-immucillin-H (HsPNP-ImmH) solved at 2.6 Angstrom resolution using synchrotron radiation. Immucillin-H (ImmH) inhibits the growth of malignant T-cell lines in the presence of deoxyguanosine without affecting non-T-cell tumor lines. ImmH inhibits activated normal human T cells after antigenic stimulation in vitro. These biological effects of ImmH suggest that this agent may have utility in the treatment of certain human diseases characterized by abnormal T-cell growth or activation. This is the first structural report of human PNP complexed with immucillin-H. The comparison of the complex HsPNP-ImmH with recent crystallographic structures of human PNP explains the high specificity of immucillin-H for human PNP. (C) 2003 Elsevier B.V. All rights reserved.

Estrutura dos grânulos de amido de milho normal e ceroso

Visando obter informações a respeito da estrutura dos grânulos, amidos de milho normal e ceroso foram isolados e submetidos à ação da a-amilase e amiloglucosidase. Para elucidar a estrutura dos grânulos, os resíduos desta hidrólise foram submetidos à cromatografia de permeção em gel Sephadex G-50, diretamente e após sucessivas digestões enzimáticas com pululanase e b-amilase. Os resultados mostraram que existem diferenças nos resíduos dos amidos de milho ceroso e normal, tratados com a-amilase e amiloglucosidase. No resíduo do amido de milho ceroso, os perfis de eluição mostraram duas frações a 290 e 350 ml (picos I e II) respectivamente, que não eram suscetíveis ao ataque da a-amilase e amiloglucosidase, indicando que estas frações faziam parte das zonas cristalinas do amido. Estas frações também faziam parte das áreas cristalinas no amido normal. A presença do pico V à 390 ml na a-glucana do amido de milho normal sugeriu que além das duas frações não suscetíveis à hidrólise existia outra que também participava das zonas cristalinas deste amido como regiões não suscetíveis às enzimas formando, consequentemente, rede cristalina fortemente associada. A presença deste pico a 390 ml sugeriu arranjo cristalino distinto entre o amido de milho ceroso e o normal.

Ambient pH Controls Glycogen Levels by Regulating Glycogen Synthase Gene Expression in Neurospora crassa. New Insights into the pH Signaling Pathway

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação da mutagenicidade e antimutagenicidade de um biopolímero extraído do microorganismo Agrobacterium radiobacter em camundongos Swiss

A presente pesquisa avaliou a ação mutagênica e antimutagênica de um biopolímero de glucose extraído da Agrobacterium radiobacter (Biopolímero de Agrobacterium radiobacter). O experimento foi realizado com camundongos Swiss machos divididos em oito grupos. O tratamento com o biopolímero foi realizado por gavage em dose única concomitante a uma dose de solução tampão fosfato nos grupos de avaliação da mutagenicidade, ou ao agente indutor de danos no DNA, ciclofosfamida, na concentração de 50 mg/kg (peso corpóreo - p.c.), nos grupos de avaliação da antimutagenicidade. Utilizou-se o teste de micronúcleo em sangue periférico e a coleta de sangue foi realizada 24 e 48 h após a aplicação das substâncias-teste. A análise estatística demonstrou que o biopolímero não possui atividade mutagênica e que é efetivo em prevenir danos no DNA. As porcentagens de redução de danos nos grupos de antimutagenicidade foram de 83,9%, 89,1% e 103,1% em 24 h e 101,24%, 98,14% e 120,64% em 48 h para as doses de 75, 150 e 300mg/kg (p.c.), respectivamente. A alta porcentagem de redução de danos associada à ausência de efeitos mutagênicos indica, além da atividade quimioprotetora, a possibilidade do biopolímero ser um alimento funcional candidato à utilização como co-adjuvante na quimioterapia para prevenir efeitos colaterais.

Quadro seroproteico como auxílio diagnóstico na anemia hemolítica imunomediada em cães

No presente protocolo experimental, determinaram-se os proteinogramas séricos, por intermédio da eletroforese em gel de poliacrilamida contendo duodecil sulfato de sódio (SDS-PAGE), de 120 cães com raças e idades variadas e atendidos junto ao Hospital Veterinário Governador Laudo Natel da FCAV/Unesp, com o objetivo principal de comparar diferentes frações seroproteicas em estados anêmicos regenerativos, arregenerativos, imunomediados primários e secundários. Os referidos animais foram distribuídos em cinco grupos experimentais: grupo 1: 20 cães de controle; grupo 2: 28 cães com anemia regenerativa não imune; grupo 3: 27 cães com anemia arregenerativa não imune; grupo 4: 10 cães com anemia hemolítica imunomediada primária; grupo 5: 35 cães com anemia hemolítica imunomediada secundária. A técnica SDS-PAGE permitiu o fracionamento de 24 proteínas, cujos pesos moleculares (PM) variaram de 18.000 a 165.000 daltons (Da). Os cães com AHIM primária e secundária apresentaram 24 frações proteicas em seus traçados eletroforéticos, enquanto que cães de controle (1) e portadores de anemia regenerativa (2) e arregenerativa (3) de natureza não imune apresentaram 23 frações de proteínas, cuja proteína de peso molecular 68.000Da não foi encontrada. Dessa forma, 23 frações proteicas foram detectadas e revelaram-se comuns aos proteinogramas dos cães de controle e daqueles dos quatro grupos experimentais. Destas, identificaram-se nominalmente 11 frações proteicas, e as demais foram estudadas com base nos seus respectivos pesos moleculares. em relação aos cães de controle, os anêmicos (grupos 2, 3, 4 e 5) apresentaram maiores concentrações de transferrina sérica e entre estes os animais portadores da AHIM primária. Todos os cães anêmicos apresentaram teores séricos de haptoglobina e fosforilase significativamente maiores que os controles, enquanto que a concentração sérica de ceruloplasmina foi significativamente maior nestes. Tais achados analisados em conjunto agregam informações adicionais úteis à elucidação das AHIMs em cães.

Structural characterization of the cell wall D-glucans isolated from the mycelium of Botryosphaeria rhodina MAMB-05

Three D-glucans were isolated from the mycelium of the fungus Botryosphaeria rhodina MAMB-05 by sequential extraction with hot-water and hot aqueous KOH (2% w/v) followed by ethanol precipitation. Following their purification by gel permeation chrornatography on Sepharose CL-4B, the structural characteristics of the D-glucans were determined by FT-IR and C-13 NMR spectroscopy and, after methylation, by GC-MS. The hot-water extract produced a fraction designated Q(1A) that was a beta-(1 -> 6)-D-glucan with the following structure:[GRAPHICS]The alkaline extract, when subjected to repeated freeze-thawing, yielded two fractions: KIP (insoluble) that comprised a beta-(1 -> 3)-D-glucan with beta-D-glucose branches at C-6 with the structure:[GRAPHICS]and K1SA (soluble) consisting of a backbone chain of alpha-(1 -> 4)-linked D-glucopyranosyl residues substituted at O-6 with alpha-D-glucopyranosyl residues:[GRAPHICS](c) 2008 Elsevier Ltd. All rights reserved.

Sulfonation and anticoagulant activity of botryosphaeran from Botryosphaeria rhodina MAMB-05 grown on fructose

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)