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Recalcitrant Forms (recalcitrant + form)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

Effect of Cellulase Mole Fraction and Cellulose Recalcitrance on Synergism in Cellulose Hydrolysis and Binding

BIOTECHNOLOGY PROGRESS, Issue 1 2006
Tina Jeoh
Elucidating the molecular mechanisms that govern synergism is important for the rational engineering of cellulase mixtures. Our goal was to observe how varying the loading molar ratio of cellulases in a binary mixture and the recalcitrance of the cellulose to enzymatic degradation influenced the degree of synergistic effect (DSE) and degree of synergistic binding (DSB). The effect of cellulose recalcitrance was studied using a bacterial microcrystalline cellulose (BMCC), which was exhaustively hydrolyzed by a catalytic domain of Cel5A, an endocellulase. The remaining prehydrolyzed BMCC (PHBMCC) was used to represent a recalcitrant form of cellulose. DSE was observed to be sensitive to loading molar ratio. However, on the more recalcitrant cellulose, synergism decreased. Furthermore, the results from this study reveal that when an exocellulase (Cel6B) is mixed with either an endocellulase (Cel5A) or a processive endocellulase (Cel9A) and reacted with BMCC, synergism is observed in both hydrolysis and binding. This study also revealed that when a "classical" endocellulase (Cel5A) and a processive endocellulase (Cel9A) are mixed and reacted with BMCC, only limited synergism is observed in reducing sugar production; however, binding is clearly increased by the presence of the Cel5A. [source]

Progress in the development of new treatments for combined Alzheimer's and Parkinson's diseases

DRUG DEVELOPMENT RESEARCH, Issue 3 2002
Eliezer Masliah
Abstract Misfolding of synaptic molecules such as amyloid , peptide and ,-synuclein has been proposed to play a key role in the mechanisms of neurodegeneration in Alzheimer's and Parkinson's disease, respectively. Notably, the majority of patients with Alzheimer's disease also have ,-synuclein-immunoreactive Lewy bodies, and a substantial proportion of them develop a form of parkinsonism also known as Lewy body disease, that defies conventional therapies. Thus, factors involved in the pathogenesis of Alzheimer's disease might promote the development of particularly recalcitrant forms of Lewy body disease. We have shown that the amyloid , peptide 1-42, of Alzheimer's disease, promotes the toxic conversion of ,-synuclein and accelerates ,-synuclein-dependent deficits in transgenic mice. Understanding the mechanisms promoting the toxic conversion of ,-synuclein is of critical importance for the design of rationale treatments for Lewy body disease and transgenic models hold the promise for the development of such novel therapies. In this context therapies aimed at: (1) reducing amyloid , peptide 1-42 production, (2) blocking toxic ,-synuclein oligomerization (e.g., ,-synuclein, antioxidants), (3) promoting ,-synuclein protofibril degradation, and (4) protecting neurons (e.g., anti-oxidants, neurotrophic agents) against toxic ,-synuclein aggregates might prove to be significantly useful in the treatment of Lewy body disease. We characterized ,-synuclein, the non-amyloidogenic homologue of ,-synuclein, as an inhibitor of aggregation of ,-synuclein. Our results raise the intriguing possibility that ,-synuclein might be a natural negative regulator of ,-synuclein aggregation, and that a similar class of endogenous factors might modulate the toxic conversion of other molecules involved in neurodegeneration. Such an anti-amyloidogenic property of ,-synuclein in combination with other treatments might also provide a novel strategy for the treatment of neurodegenerative disorders. Drug Dev. Res. 56:282,292, 2002. © 2002 Wiley-Liss, Inc. [source]

Retention of Inorganic Nitrogen by Epiphytic Bryophytes in a Tropical Montane Forest,

BIOTROPICA, Issue 3 2005
Kenneth L. Clark
ABSTRACT We developed and evaluated a model of the canopy of a tropical montane forest at Monteverde, Costa Rica, to estimate inorganic nitrogen (N) retention by epiphytes from atmospheric deposition. We first estimated net retention of inorganic N by samples of epiphytic bryophytes, epiphyte assemblages, vascular epiphyte foliage, and host tree foliage that we exposed to cloud water and precipitation solutions. Results were then scaled up to the ecosystem level using a multilayered model of the canopy derived from measurements of forest structure and epiphyte mass. The model was driven with hourly meteorological and event-based atmospheric deposition data, and model predictions were evaluated against measurements of throughfall collected at the site. Model predictions were similar to field measurements for both event-based and annual hydrologic and inorganic N fluxes in throughfall. Simulation of individual events indicated that epiphytic bryophytes and epiphyte assemblages retained 33,67 percent of the inorganic N deposited in cloud water and precipitation. On an annual basis, the model predicted that epiphytic components retained 3.4 kg N ha/yr, equivalent to 50 percent of the inorganic N in atmospheric deposition (6.8 kg N ha/yr). Our results indicate that epiphytic bryophytes play a major role in N retention and cycling in this canopy by transforming highly mobile inorganic N (ca. 50% of atmospheric deposition is NO,3) to less mobile (exchangeable NH+4) and recalcitrant forms in biomass and remaining litter and humus. RESUMEN En este estudio se desarrollo y se evaluo un modelo para estimar la retención de nitrogeno (N) inorganico atmospherico en el dosel de un bosque tropical montano en Monteverde, Costa Rica. Primeramente, estimamos la retención de N inorganico en muestras de briófitas, grupos de epífitas, hojas de epífitas, y hojas de árboles que fueron expuestas a agua de neblina y de lluvia. Basandose en medidas de estructure del bosque y la biomasa de epífitas se derivo un modelo multi nivel de dosel, estos resultados fueron aumentados a la escala de ecosystema. El modelo fue guiado por datos meteorológicos tomados a cada hora y datos de deposición atmosféricos y las predicciónes del modelo fueron evaluadas con medidas de la lluvia indirecta (throughfall) del sitio. Las predicciónes del modelo fueron similares a los datos de campo para eventos individuales, el ciclo hidrológico anual y las fluctuaciones de N en la lluvia indirecta. La simulación de eventos individuales indicaron que las briófitas y grupos de epífitas retuvieron 33,67 por ciento de N inorganico en agua de nubes y de lluvia. Predicciónes anuales del modelo indican que los grupos de epífitas retienen 3.4 kg N ha/año, equivalente al 50 por ciento del N inorganico en la deposición atmosférica (6.8 kg N ha/año). Nuestros resultados indican que las briófitas en el dosel desempeñan un papel muy importante en la retención y ciclaje de N inorganico, porque transforman el N con alta mobilidad en N de baja mobilidad y a formas mas recalcitrantes en la biomasa, la hojarasca y el humus. [source]

Rapid improvement of recalcitrant disseminated granuloma annulare upon treatment with the tumour necrosis factor-, inhibitor, infliximab

BRITISH JOURNAL OF DERMATOLOGY, Issue 3 2005
M.S. Hertl
Summary Granuloma annulare (GA) is a chronic inflammatory disorder of unknown aetiology, which is characterized clinically by erythematous plaques preferentially localized to the distal extremities, although disseminated variants exist. In light of the chronic relapsing nature of GA and lack of satisfactory treatment options, we initiated treatment with infliximab in a patient with chronic disseminated GA that was recalcitrant to standard treatment. The 59-year-old female patient with insulin-dependent diabetes had experienced GA lesions for more than 4 years despite various systemic and topical treatments. Systemic glucocorticoids were not a therapeutic option because of the preexisting unstable insulin-dependent diabetes. Infliximab was administered intravenously at 5 mg kg,1 day,1 at weeks 0, 2 and 6 and thereafter at a monthly interval for an additional 4 months. Most of the GA plaques resolved within 4,6 weeks, leaving postinflammatory brownish macules. Newly arising plaques disappeared within 2 weeks and new GA lesions were not observed during the entire observation period of more than 16 months. Infliximab may be an additional option in the treatment of recalcitrant forms of GA as well as in other chronic granulomatous skin disorders, such as sarcoidosis and necrobiosis lipoidica. [source]