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1.
Artigo em Alemão | MEDLINE | ID: mdl-33906241

RESUMO

BACKGROUND: Pompe disease is a lysosomal multisystem disorder with predominant proximal myopathy. Treatment with enzyme replacement therapy (ERT) is available requiring life-long biweekly infusions of recombinant α-glucosidase. To minimize the burden of ERT patients ask for home infusion therapy. AIMS AND METHODS: Pompe disease experts from Germany, Austria, and Switzerland discussed in two consensus meetings in 2019 and 2020 requirements for home infusion therapy, adequate execution of treatment, and the legal situation for delegating physicians. RESULTS AND DISCUSSION: Home infusion therapy is principally feasible for patients with Pompe disease if certain preconditions are fulfilled, but the decision to implement has to be made on an individual basis. The treating physician delegates the execution of ERT ad personam to nursing staff but retains full legal responsibility. Home infusion therapy has to be carried out by specially trained and qualified staff. Infusion-related risks comprise mainly allergic reactions, and adequate medical treatment must be warranted. In German-speaking countries, clear rules for conducting home infusion therapy are needed to reduce psychosocial stress for patients with Pompe disease, and providing legal certainty for delegating physicians.

2.
Fortschr Neurol Psychiatr ; 89(12): 630-636, 2021 Dec.
Artigo em Alemão | MEDLINE | ID: mdl-33561874

RESUMO

BACKGROUND: Pompe disease is a lysosomal multisystem disorder with predominant proximal myopathy. Treatment with enzyme replacement therapy (ERT) is available requiring life-long biweekly infusions of recombinant α-glucosidase. To minimize the burden of ERT patients ask for home infusion therapy. AIMS AND METHODS: Pompe disease experts from Germany, Austria, and Switzerland discussed in two consensus meetings in 2019 and 2020 requirements for home infusion therapy, adequate execution of treatment, and the legal situation for delegating physicians. RESULTS AND DISCUSSION: Home infusion therapy is principally feasible for patients with Pompe disease if certain preconditions are fulfilled, but the decision to implement has to be made on an individual basis. The treating physician delegates the execution of ERT ad personam to nursing staff but retains full legal responsibility. Home infusion therapy has to be carried out by specially trained and qualified staff. Infusion-related risks comprise mainly allergic reactions, and adequate medical treatment must be warranted. In German-speaking countries, clear rules for conducting home infusion therapy are needed to reduce psychosocial stress for patients with Pompe disease, and providing legal certainty for delegating physicians.


Assuntos
Doença de Depósito de Glicogênio Tipo II , Terapia por Infusões no Domicílio , Consenso , Terapia de Reposição de Enzimas , Alemanha , Doença de Depósito de Glicogênio Tipo II/tratamento farmacológico , Humanos
3.
Pharmaceutics ; 12(4)2020 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-32244401

RESUMO

Compaction simulators are frequently used in the formulation and process development of tablets, bringing about the advantages of flexibility, low material consumption, and high instrumentation to generate the most possible process understanding. However, their capability of resembling general aspects of rotary press compaction and their precision in simulating or mimicking sub-processes such as feeding and filling need to be systematically studied. The effect of material deformation behavior, blend composition, and feeding on tensile strength and simulation precision as compared with rotary presses of different scales is evaluated in this study. Generally, good simulation performance was found for the studied compaction simulator. Compaction profile-sensitivity was demonstrated for highly visco-plastic materials while shear-sensitivity in feeding was demonstrated for lubricated blends of ductile particles. Strategies for the compensation of both in compaction simulator experiments are presented by careful investigation of the compaction stress over time profiles and introduction of a compaction simulator-adapted shear number approach to account for differences in layout and operation mode between compaction simulator and rotary press, respectively. These approaches support the general aim of this study to provide a more straightforward determination of scaling process parameters between rotary press and compaction simulator and facilitate a quicker and more reliable process transfer.

4.
Proc Biol Sci ; 285(1872)2018 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-29445021

RESUMO

Animals that live together in groups often face difficult choices, such as which food resource to exploit, or which direction to flee in response to a predator. When there are costs associated with deadlock or group fragmentation, it is essential that the group achieves a consensus decision. Here, we study consensus formation in emigrating ant colonies faced with a binary choice between two identical nest-sites. By individually tagging each ant with a unique radio-frequency identification microchip, and then recording all ant-to-ant 'tandem runs'-stereotyped physical interactions that communicate information about potential nest-sites-we assembled the networks that trace the spread of consensus throughout the colony. Through repeated emigrations, we show that both the order in which these networks are assembled and the position of each individual within them are consistent from emigration to emigration. We demonstrate that the formation of the consensus is delegated to an influential but exclusive minority of highly active individuals-an 'oligarchy'-which is further divided into two subgroups, each specialized upon a different tandem running role. Finally, we show that communication primarily occurs between subgroups not within them, and further, that such between-group communication is more efficient than within-group communication.


Assuntos
Comunicação Animal , Formigas/fisiologia , Comportamento de Nidação , Animais , Comportamento de Escolha , Tomada de Decisões , Comportamento Social
5.
Biol Lett ; 9(5): 20130685, 2013 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-24088565

RESUMO

Organisms should invest more in gathering information when the pay-off from finding a profitable resource is likely to be greater. Here, we ask whether animal societies put more effort in scouting for a new nest when their current one is of low quality. We measured the scouting behaviour of Temnothorax albipennis ant colonies when they inhabit nest-sites with different combinations of desirable attributes. We show that the average probability of an ant scouting decreases significantly with an increase in the quality of the nest in which the colony currently resides. This means that the greater the potential gain from finding a new nest, the more effort a colony puts into gathering information regarding new nest-sites. Our results show, for the first time to our knowledge, the ability of animal societies to respond collectively to the quality of a resource they currently have at their disposal (e.g. current nest-site) and regulate appropriately their information gathering efforts for finding an alternative (e.g. a potentially better nest-site).


Assuntos
Formigas/fisiologia , Comportamento Apetitivo/fisiologia , Tomada de Decisões/fisiologia , Ecossistema , Comportamento Social , Animais , Inglaterra , Modelos Lineares
6.
PLoS One ; 8(9): e73216, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24023835

RESUMO

We present a dynamical systems analysis of a decision-making mechanism inspired by collective choice in house-hunting honeybee swarms, revealing the crucial role of cross-inhibitory 'stop-signalling' in improving the decision-making capabilities. We show that strength of cross-inhibition is a decision-parameter influencing how decisions depend both on the difference in value and on the mean value of the alternatives; this is in contrast to many previous mechanistic models of decision-making, which are typically sensitive to decision accuracy rather than the value of the option chosen. The strength of cross-inhibition determines when deadlock over similarly valued alternatives is maintained or broken, as a function of the mean value; thus, changes in cross-inhibition strength allow adaptive time-dependent decision-making strategies. Cross-inhibition also tunes the minimum difference between alternatives required for reliable discrimination, in a manner similar to Weber's law of just-noticeable difference. Finally, cross-inhibition tunes the speed-accuracy trade-off realised when differences in the values of the alternatives are sufficiently large to matter. We propose that the model, and the significant role of the values of the alternatives, may describe other decision-making systems, including intracellular regulatory circuits, and simple neural circuits, and may provide guidance in the design of decision-making algorithms for artificial systems, particularly those functioning without centralised control.


Assuntos
Comportamento Animal , Tomada de Decisões , Modelos Teóricos , Animais , Abelhas , Comportamento de Escolha , Fatores de Tempo
7.
Naturwissenschaften ; 99(12): 1067-71, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23149930

RESUMO

Of the many signals used by honey bees during the process of swarming, two of them--the stop signal and the worker piping signal--are not easily distinguished for both are mechano-acoustic signals produced by scout bees who press their bodies against other bees while vibrating their wing muscles. To clarify the acoustic differences between these two signals, we recorded both signals from the same swarm and at the same time, and compared them in terms of signal duration, fundamental frequency, and frequency modulation. Stop signals and worker piping signals differ in all three variables: duration, 174 ± 64 vs. 602 ± 377 ms; fundamental frequency, 407 vs. 451 Hz; and frequency modulation, absent vs. present. While it remains unclear which differences the bees use to distinguish the two signals, it is clear that they do so for the signals have opposite effects. Stop signals cause inhibition of actively dancing scout bees whereas piping signals cause excitation of quietly resting non-scout bees.


Assuntos
Comunicação Animal , Abelhas/fisiologia , Acústica , Animais , Som , Fatores de Tempo
8.
Int J Oncol ; 40(3): 825-32, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22108652

RESUMO

In the identification of subjects with lung cancer, increased DNA methylation of the SHOX2 gene locus in bronchial aspirates has previously been proven to be a clinically valuable biomarker. This is particularly true in cases where the cytological and histological results following bronchoscopy are undetermined. This previous case control study was conducted using research assay components and a complex work flow. To facilitate the use in a diagnostic setting, a CE marked in vitro diagnostic test kit to quantify SHOX2 DNA methylation in bronchial aspirates was developed and characterized. The presented assay for measuring SHOX2 DNA methylation in bronchial aspirates is based on two major steps: generation of bisulfite converted template DNA from patient samples followed by subsequent determination of SHOX2 biomarker methylation by real-time PCR. Individual kits for DNA preparation, real-time PCR analysis and work flow control were developed. This study describes the analytical performance (reproducibility, accuracy, interfering substances, cross-reactivity) of the in vitro diagnostic (IVD) test kit 'Epi proLung BL Reflex Assay'. In addition, the intended use of the test was validated in a clinical performance evaluation (case control) study comprised of 250 patients (125 cases, 125 controls). The results describe the test as a robust and reliable diagnostic tool for identifying patients with lung cancer using Saccomanno-fixed bronchial lavage specimens (AUC [95% confidence intervals] = 0.94 [0.91-0.98], sensitivity 78% [69-86]/specificity 96% [90-99]). This test may be used as a diagnostic adjunct to existing clinical and pathological investigations in lung cancer.


Assuntos
Biomarcadores Tumorais/genética , Metilação de DNA , Proteínas de Homeodomínio/genética , Neoplasias Pulmonares/genética , Kit de Reagentes para Diagnóstico , Idoso , Idoso de 80 Anos ou mais , Brônquios/metabolismo , Lavagem Broncoalveolar/métodos , Estudos de Casos e Controles , Reações Cruzadas , Feminino , Humanos , Neoplasias Pulmonares/diagnóstico , Masculino , Pessoa de Meia-Idade , Controle de Qualidade , Reação em Cadeia da Polimerase em Tempo Real/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
9.
Science ; 335(6064): 108-11, 2012 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-22157081

RESUMO

Honeybee swarms and complex brains show many parallels in how they make decisions. In both, separate populations of units (bees or neurons) integrate noisy evidence for alternatives, and, when one population exceeds a threshold, the alternative it represents is chosen. We show that a key feature of a brain--cross inhibition between the evidence-accumulating populations--also exists in a swarm as it chooses its nesting site. Nest-site scouts send inhibitory stop signals to other scouts producing waggle dances, causing them to cease dancing, and each scout targets scouts' reporting sites other than her own. An analytic model shows that cross inhibition between populations of scout bees increases the reliability of swarm decision-making by solving the problem of deadlock over equal sites.


Assuntos
Comunicação Animal , Abelhas/fisiologia , Comportamento de Nidação , Animais , Comportamento Animal , Tomada de Decisões , Modelos Biológicos , Modelos Neurológicos , Movimento , Inibição Neural , Neurônios/fisiologia , Comportamento Social
10.
BMC Cancer ; 10: 600, 2010 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-21047392

RESUMO

BACKGROUND: This study aimed to show that SHOX2 DNA methylation is a tumor marker in patients with suspected lung cancer by using bronchial fluid aspirated during bronchoscopy. Such a biomarker would be clinically valuable, especially when, following the first bronchoscopy, a final diagnosis cannot be established by histology or cytology. A test with a low false positive rate can reduce the need for further invasive and costly procedures and ensure early treatment. METHODS: Marker discovery was carried out by differential methylation hybridization (DMH) and real-time PCR. The real-time PCR based HeavyMethyl technology was used for quantitative analysis of DNA methylation of SHOX2 using bronchial aspirates from two clinical centres in a case-control study. Fresh-frozen and Saccomanno-fixed samples were used to show the tumor marker performance in different sample types of clinical relevance. RESULTS: Valid measurements were obtained from a total of 523 patient samples (242 controls, 281 cases). DNA methylation of SHOX2 allowed to distinguish between malignant and benign lung disease, i.e. abscesses, infections, obstructive lung diseases, sarcoidosis, scleroderma, stenoses, at high specificity (68% sensitivity [95% CI 62-73%], 95% specificity [95% CI 91-97%]). CONCLUSIONS: Hypermethylation of SHOX2 in bronchial aspirates appears to be a clinically useful tumor marker for identifying subjects with lung carcinoma, especially if histological and cytological findings after bronchoscopy are ambiguous.


Assuntos
Biomarcadores Tumorais/metabolismo , Brônquios/metabolismo , Regulação Neoplásica da Expressão Gênica , Proteínas de Homeodomínio/biossíntese , Proteínas de Homeodomínio/genética , Neoplasias Pulmonares/metabolismo , Adulto , Idoso , Broncoscopia/métodos , Carcinoma/metabolismo , Estudos de Casos e Controles , Metilação de DNA , Reações Falso-Positivas , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Hibridização de Ácido Nucleico , Sensibilidade e Especificidade
11.
Mol Cell Biol ; 30(11): 2608-20, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20368356

RESUMO

RASSF2 is a novel proapoptotic effector of K-Ras. Inhibition of RASSF2 expression enhances the transforming effects of K-Ras, and epigenetic inactivation of RASSF2 is frequently detected in mutant Ras-containing primary tumors. Thus, RASSF2 is implicated as a tumor suppressor whose inactivation facilitates transformation by disconnecting apoptotic responses from Ras. The mechanism of action of RASSF2 is not known. Here we show that RASSF2 forms a direct and endogenous complex with the prostate apoptosis response protein 4 (PAR-4) tumor suppressor. This interaction is regulated by K-Ras and is essential for the full apoptotic effects of PAR-4. RASSF2 is primarily a nuclear protein, and shuttling of PAR-4 from the cytoplasm to the nucleus is essential for its function. We show that RASSF2 modulates the nuclear translocation of PAR-4 in prostate tumor cells, providing a mechanism for its biological effects. Thus, we identify the first tumor suppressor signaling pathway emanating from RASSF2, we identify a novel mode of action of a RASSF protein, and we provide an explanation for the extraordinarily high frequency of RASSF2 inactivation we have observed in primary prostate tumors.


Assuntos
Proteínas Reguladoras de Apoptose/metabolismo , Genes ras , Proteínas Supressoras de Tumor/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Proteínas Reguladoras de Apoptose/genética , Núcleo Celular/metabolismo , Células Cultivadas , Humanos , Masculino , Pessoa de Meia-Idade , Regiões Promotoras Genéticas , Próstata/citologia , Próstata/metabolismo , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Transdução de Sinais/fisiologia , Proteínas Supressoras de Tumor/genética , Técnicas do Sistema de Duplo-Híbrido , Proteínas ras/genética , Proteínas ras/metabolismo
12.
Biotechniques ; 47(3): 737-44, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19852759

RESUMO

DNA methylation is an important epigenetic mechanism involved in fundamental biological processes such as development, imprinting, and carcino-genesis. For these reasons, DNA methylation represents a valuable source for cancer biomarkers. Methods for the sensitive and specific detection of methylated DNA are a prerequisite for the implementation of DNA biomarkers into clinical routine when early detection based on the analysis of body fluids is desired. Here, a novel technique is presented for the detection of DNA methylation biomarkers, based on real-time PCR of bisulfite-treated template with enzymatic digestion of background DNA during amplification using the heat-stable enzyme Tsp509I. An assay for the lung cancer methylation biomarker BARHL2 was used to show clinical and analytical performance of the method in comparison with methylation-specific PCR technology. Both technologies showed comparable performance when analyzing technical DNA mixtures and bronchial lavage samples from 75 patients suspected of having lung cancer. The results demonstrate that the approach is useful for sensitive and specific detection of a few copies of methylated DNA in samples with a high background of unmethylated DNA, such as in clinical samples from body fluids.


Assuntos
Biomarcadores Tumorais/análise , Líquido da Lavagem Broncoalveolar/química , Metilação de DNA , DNA de Neoplasias/análise , Proteínas de Homeodomínio/análise , Neoplasias Pulmonares/química , Proteínas do Tecido Nervoso/análise , Reação em Cadeia da Polimerase/métodos , Biomarcadores Tumorais/metabolismo , Enzimas de Restrição do DNA/metabolismo , DNA de Neoplasias/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Proteínas do Tecido Nervoso/metabolismo , Sensibilidade e Especificidade
13.
Science ; 319(5859): 104-6, 2008 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-18174445

RESUMO

The enormous progress made in functional magnetic resonance imaging technology allows us to watch our brains engage in complex cognitive and social tasks. However, our understanding of what actually is computed in the underlying cellular networks is hindered by the vast numbers of neurons involved. Here, we describe a vertebrate system, shaped for top speed, in which a complex and plastic decision is performed by surprisingly small circuitry that can be studied at cellular resolution.


Assuntos
Tomada de Decisões , Rede Nervosa/fisiologia , Neurônios/fisiologia , Perciformes/fisiologia , Animais , Atenção , Sinais (Psicologia) , Modelos Animais , Vias Neurais/fisiologia , Tempo de Reação
14.
Mol Biol Evol ; 24(12): 2763-74, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17905998

RESUMO

Transport of polypeptides across membranes is a general and essential process in every cell. This process is utilized by molecular machines composed of soluble and membrane-inserted proteins. At least one component of the molecular transport machines present in different membranes contains a subunit with a domain composed of 3 tetratricopeptide repeat (TPR) motifs. These domains are important for protein-protein interaction, for example, recognition of chaperones. To understand the evolution of these TPR domain-containing receptors involved in protein translocation, we inferred their phylogenetic relationships. We show that the evolutionary rate of these TPR domains is reduced when compared with the remaining sequence. The reduction is explained by the interaction of the TPR domains with their substrates. Based on the TPR tree, we propose that Sec72 recognizes Hsp70 and that Tom34 recognizes Hsp90. The phylogeny can further be used to assign the localization of the Toc64 isoforms to mitochondria or chloroplasts. Our findings are discussed in the context of the evolutionary development of translocation systems with focus on the occurrence of Hsp70/Hsp90-recognizing TPR domains in these machineries.


Assuntos
Membrana Celular/metabolismo , Receptores de Superfície Celular/química , Receptores de Superfície Celular/metabolismo , Sequências Repetitivas de Aminoácidos , Evolução Molecular , Humanos , Funções Verossimilhança , Modelos Genéticos , Pisum sativum/química , Filogenia , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Transporte Proteico , Saccharomyces cerevisiae/química
15.
J Biol Chem ; 282(3): 1882-90, 2007 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-17088246

RESUMO

beta-Barrel-shaped channels of the Omp85 family are involved in the translocation or assembly of proteins of bacterial, mitochondrial, and plastidic outer membranes. We have compared these proteins to understand the evolutionary development of the translocators. We have demonstrated that the proteins from proteobacteria and mitochondria have a pore diameter that is at least five times smaller than found for the Omp85 in cyanobacteria and plastids. This finding can explain why Omp85 from cyanobacteria (but not the homologous protein from proteobacteria) was remodeled to become the protein translocation pore after endosymbiosis. Further, the pore-forming region of the Omp85 proteins is restricted to the C terminus. Based on a phylogenetic analysis we have shown that the pore-forming domain displays a different evolutionary relationship than the N-terminal domain. In line with this, the affinity of the N-terminal domain to the C-terminal region of the Omp85 from plastids and cyanobacteria differs, even though the N-terminal domain is involved in gating of the pore in both groups. We have further shown that the N-terminal domain of nOmp85 takes part in homo-oligomerization. Thereby, the differences in the phylogeny of the two domains are explained by different functional constraints acting on the regions. The pore-forming domain, however, is further divided into two functional regions, where the distal C terminus itself forms a dimeric pore. Based on functional and phylogenetic analysis, we suggest an evolutionary scenario that explains the origin of the contemporary translocon.


Assuntos
Proteínas da Membrana Bacteriana Externa/química , Proteínas da Membrana Bacteriana Externa/fisiologia , Regulação Bacteriana da Expressão Gênica , Nostoc/metabolismo , Animais , Reagentes de Ligações Cruzadas/farmacologia , Proteínas de Drosophila/química , Drosophila melanogaster , Eletrofisiologia , Proteínas de Escherichia coli/química , Evolução Molecular , Modelos Biológicos , Filogenia , Conformação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Proteínas de Ligação a RNA/química
17.
J Agric Food Chem ; 54(18): 6809-13, 2006 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-16939343

RESUMO

Rates of foliar penetration of Fe(III) chelates of imidodisuccinic acid (IDHA), ligninsulfonic acid (Natrel), and citric acid (ammonium ferric citrate) were studied at 20 degrees C using a leaf disk method. After drying of the donor droplets, the humidity over the donor residues was maintained at 100% because Fe(III) chelates deliquesce only when humidity is higher than 90%. The wetting agent Glucopon 215 CSUP was added at a concentration of 0.2 g L(-1) to all donor solutions. With fully expanded stomatous broad bean leaves, penetration of Fe-IDHA followed first-order kinetics and rate constants of penetration were higher in light (0.073 h(-1)) than in the dark (0.042 h(-1)). Permeability of broad been leaves to CaCl2 was about 8 times higher than to Fe-IDHA. Doubling the Fe-IDHA concentration in the donor from 2.5 to 5 mmol L(-1) decreased rate constants of Fe-IDHA penetration by a factor of 2.2. Adding the silicon surfactant Break Thru S240 at 10 g L(-1) to the donor induced infiltration of open stomata and about 80% of the applied Fe-IDHA penetrated during droplet drying, while with Glucopon 215 CSUP stomatal infiltration was not observed. With broad bean leaves, penetration of Natrel and ammonium ferric citrate also followed first-order kinetics and rate constants were also higher in light than in the dark. Adaxial astomatous surfaces of fully expanded pear, apple, and grapevine leaves were practically impermeable to Fe-IDHA while stomatous abaxial leaf surfaces were permeable, but rate constants of penetration decreased with time and differed greatly among species. Astomatous surfaces of young unfurling grapevine and peach leaves were permeable to Fe-IDHA, but permeability of stomatous surfaces was much higher. The effect of light on permeability of stomatous leaf surfaces is attributed to the presence of aqueous pores in cuticles over guard cells, and it is suggested that permeability of these pores increases as stomata open. Consequences of these results for foliar applications of Fe chelates are discussed.


Assuntos
Compostos Férricos/metabolismo , Quelantes de Ferro/metabolismo , Luz , Folhas de Planta/metabolismo , Cloreto de Cálcio/metabolismo , Cinética , Malus , Permeabilidade , Prunus , Pyrus , Especificidade da Espécie , Fatores de Tempo , Vicia faba , Vitis
18.
Planta ; 221(5): 648-55, 2005 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15700185

RESUMO

Size selectivity of aqueous pores in Vicia leaf cuticles was investigated by measuring the penetration of calcium salts into the abaxial surface of detached leaves. Molecular weights of salts ranged from 111 g mol(-1) to 755 g mol(-1). Penetration in light at 20 degrees C and 100% humidity was a first order process and rate constants of penetration ranged from 0.39 h(-1) (CaCl2) to 0.058 h(-1) (Ca-lactobionate). Penetration was a first order process in the dark as well, but the rate constants were smaller by a factor of 1.82. Plotting logarithmatised rate constants versus anhydrous molecular weights resulted in straight lines both in light and in the dark. The slopes per hour were very similar and the average slope was -1.2 x 10(-3) mol g(-1). Hence, size selectivity was not affected by stomatal opening, and in light or darkness permeability of Vicia cuticles decreased by a factor of 2.9 when molecular weight increased from 100 g mol(-1) to 500 g mol(-1). Silver nitrate was preferentially precipitated as silver chloride in guard cells, glandular trichomes and at the base of trichomes. It was concluded that these precipitates mark the location of aqueous pores in Vicia leaf cuticles. The size selectivity of aqueous pores in Vicia leaf cuticles is small compared to that observed in poplar leaf cuticles, in which permeability decreased by a factor of 7-13 for the same range of molecular weights. It is also much smaller than size selectivity of the lipophilic pathway in cuticles. These findings suggest that active ingredients of pesticides, growth regulators and chemical inducers with high molecular weights penetrate leaves at higher rates when formulated as ions.


Assuntos
Folhas de Planta/metabolismo , Vicia faba/metabolismo , Transporte Biológico , Compostos de Cálcio/metabolismo , Peso Molecular , Permeabilidade , Folhas de Planta/anatomia & histologia , Nitrato de Prata/metabolismo , Vicia faba/anatomia & histologia , Água
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