The interaction of bothropstoxin-I (Lys49-PLA(2)) with liposome membranes

Bothropstoxin-I (BthTx-I) is a Lys49-PLA(2) from the venom of the snake Bothrops jararacussu, which permeabilizes biological and artificial membranes by a mechanism independent of lipid hydrolysis. This mechanism has been investigated by studying the interaction of nine single tryptophan BthTx-I mutants with negatively charged phospholipid membranes. Changes in the solvent exposure of the tryptophan in each mutant were evaluated comparing the rate of chemical modification (k(mod)) by bromosuccinamide with the maximum intrinsic tryptophan fluorescence emission wavelength (lambda(max)) in buffer and in the presence of 10% DMPA/90% DPPC liposomes. No changes in lambda(max). were observed, whereas k(mod) values for tryptophans at positions 7, 10, 31 and 125 were significantly reduced in the presence of lipids, suggesting that bound phospholipid decreases solvent accessibility at these positions. Since the half-lives of the fluorescence and chemical modification effects differ by at least six orders of magnitude, these results suggest that the bound phospholipid may interact with multiple locations on the protein surface over micro- to millisecond timescales. (C) 2009 Elsevier Ltd. All rights reserved.

Molecular View of the Interaction between iota-Carrageenan and a Phospholipid Film and Its Role in Enzyme Immobilization

Proteins incorporated into phospholipid Langmuir-Blodgett (LB) films are a good model system for biomembranes and enzyme immobilization studies. The specific fluidity of biomembranes, an important requisite for enzymatic activity, is naturally controlled by varying phospholipid compositions. In a model system, instead, LB film fluidity may be varied by covering the top layer with different substances able to interact simultaneously with the phospholipid and the protein to be immobilized. In this study, we immobilized a carbohydrate rich Neurospora crassa alkaline phosphatase (NCAP) in monolayers of the sodium salt of dihexadecylphosphoric acid (DHP), a synthetic phospholipid that provides very condensed Langmuir films. The binding of NCAP to DHP Langmuir-Blodgett (LB) films was mediated by the anionic polysaccharide iota-carrageenan (iota-car). Combining results from surface isotherms and the quartz crystal microbalance technique, we concluded that the polysaccharide was essential to promote the interaction between DHP and NCAP and also to increase the fluidity of the film. An estimate of DHP:iota-car ratio within the film also revealed that the polysaccharide binds to DHP LB film in an extended conformation. Furthermore, the investigation of the polysaccharide conformation at molecular level, using sum-frequency vibrational spectroscopy (SFG), indicated a preferential conformation of the carrageenan molecules with the sulfate groups oriented toward the phospholipid monolayer, and both the hydroxyl and ether groups interacting preferentially with the protein. These results demonstrate how interfacial electric fields can reorient and induce conformational changes in macromolecules, which may significantly affect intermolecular interactions at interfaces. This detailed knowledge of the interaction mechanism between the enzyme and the LB film is relevant to design strategies for enzyme immobilization when orientation and fluidity properties of the film provided by the matrix are important to improve enzymatic activity.

Interaction of adrenocorticotropin peptides with microheterogeneous systems - A fluorescence study

Adrenocorticotropin (ACM) and alpha-melanocyte stimulating hormone (alpha-MSH) are peptides which present many physiological effects related to pigmentation, motor and sexual behavior, learning and memory, analgesia, anti-inflammatory and antipyretic processes. The 13 amino acid residues of alpha-MSH are the same initial sequence of ACM and due to the presence of a tryptophan residue in position 9 of the peptide chain, fluorescence techniques could be used to investigate the conformational properties of the hormones in different environments and the mechanisms of interaction with biomimetic systems like sodium dodecyl sulphate (SDS) micelles, sodium dodecyl sulphate-poly(ethylene oxide) (SDS-PEO) aggregates and neutral polymeric micelles. In buffer solution, fluorescence parameters were typical of peptides containing tryptophan exposed to the aqueous medium and upon addition of surfactant and polymer molecules, the gradual change of those parameters demonstrated the interaction of the peptides with the microheterogeneous systems. From time-resolved experiments it was shown that the interaction proceeded with conformational changes in both peptides, and further information was obtained from quenching of Trp fluorescence by a family of N-alkylpyridinium ions, which possess affinity to the microheterogeneous systems dependent on the length of the alkyl chain. The quenching of Trp fluorescence was enhanced in the presence of charged micelles, compared to the buffer solution and the accessibility of the fluorophore to the quencher was dependent on the peptide and the alkylpyridinium: in ACTH(1-21) highest collisional constants were obtained using ethylpyridinium as quencher, indicating a location of the residue in the surface of the micelle, while in alpha-MSH the best quencher was hexylpyridinium, indicating insertion of the residue into the non-polar region of the micelles. The results had shown that the interaction between the peptides and the biomimetic systems where driven by combined electrostatic and hydrophobic effects: in ACTH(1-24) the electrostatic interaction between highly positively charged C-terminal and negatively charged surface of micelles; and aggregates predominates over hydrophobic interactions involving residues in the central region of the peptide; in alpha-MSH, which presents one residual positive charge, the hydrophobic interactions are relevant to position the Trp residue in the non-polar region of the microheterogeneous systems. (C) 2008 Elsevier B.V. All rights reserved.

A study of the interaction between operator style and machine capability for a hydraulic mining excavator

This paper presents a case study that explores how operator digging style juxtaposes with mechanical capability for a class of hydraulic mining excavators. The relationships between actuator and digging forces are developed and these are used to identify the excavator's capability to apply forces in various directions. Two distinct modes of operation are examined to see how they relate to the mechanical capabilities of the linkage and to establish if one has merit over the other. It is found that one of these styles results in lower loading of the machine.

Mapping changes in coastline geomorphic features using Landsat TM and ETM+ imagery: examples in southeastern Brazil

Multitemporal Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) imagery was used to assess coastline morphological changes in southeastern Brazil. A spectral linear mixing approach (SLMA) was used to estimate fraction imagery representing amounts of vegetation, clean water (a proxy for shade) and soil. Fraction abundances were related to erosive and depositional features. Shoreline, sandy banks (including emerged and submerged banks) and sand spits were highlighted mainly by clean water and soil fraction imagery. To evaluate changes in the coastline geomorphic features, the fraction imagery generated for each data set was classified in a contextual approach using a segmentation technique and ISOSEG, an unsupervised classification. Evaluation of the classifications was performed visually and by an error matrix relating ground-truth data to classification results. Comparison of the classification results revealed an intense transformation in the coastline, and that erosive and depositional features are extremely dynamic and subject to change in short periods of time.

Geospatial clustering in data-rich environments: Features and issues

Geospatial clustering must be designed in such a way that it takes into account the special features of geoinformation and the peculiar nature of geographical environments in order to successfully derive geospatially interesting global concentrations and localized excesses. This paper examines families of geospaital clustering recently proposed in the data mining community and identifies several features and issues especially important to geospatial clustering in data-rich environments.

Management of brachial plexus region tumours and tumour-like conditions: relevant diagnostic and surgical features in a consecutive series of eighteen patients

Tumours of the brachial plexus region are rare and most publications are case reports or studies with a small series of patients. The aim of this study is to present our experience in managing these lesions. We review 18 patients with tumours in the brachial plexus region submitted to surgical treatment in a 6 year period, including their clinical presentation, neuro-imaging data, surgical findings and outcome. The tumours comprised a heterogeneous group of lesions, including schwannomas, neurofibromas, malignant peripheral nerve sheath tumour (MPNST), sarcomas, metastases, desmoids and an aneurysmal bone cyst. The most common presentation was an expanding lump (83.33%). Eleven tumours were benign and 7 were malignant. Neurofibromatosis was present in only 2 patients (11.11%). Gross total resection was achieved in 14 patients and sub-total resection in the others. Only 3 patients presented with new post-operative motor deficits. The incidence of complications was low (16.5 %). The majority of tumours were benign and most of them could be excised with a low incidence of additional deficits. Some of the malignant tumours could be controlled by surgery plus adjuvant therapy, but this category is still associated with high morbidity and mortality rates.

Metabolic syndrome features small, apolipoprotein A-I-poor, triglyceride-rich HDL3 particles with defective anti-apoptotic activity

The metabolic syndrome (MetS) phenotype is typically characterized by visceral obesity, insulin resistance, atherogenic dyslipidemia involving hypertriglyceridemia and subnormal levels of high density lipoprotein-cholesterol (HDL-C), oxidative stress and elevated cardiovascular risk. The potent antioxidative activity of small HDL3 is defective in MetS [Hansel B, et al. J Clin Endocrinol Metab 2004;89:4963-71]. We evaluated the functional capacity of small HDL3 particles from MetS subjects to protect endothelial cells from apoptosis induced by mildly oxidized low-density lipoprotein (oxLDL). MetS subjects presented an insulin-resistant obese phenotype, with hypertriglyceridemia, elevated apolipoprotein B and insulin levels, but subnormal HDL-C concentrations and chronic low grade inflammation (threefold elevation of C-reactive protein). When human microvascular endothelial cells (HMEC-1) were incubated with oxLDL (200 jig apolipoprotein B/ml) in the presence or absence of control HDL subfiractions (25 mu g protein/ml), small, dense HDL3b and 3c significantly inhibited cellular annexin V binding and intracellular generation of reactive oxygen species. The potent anti-apoptotic activity of small HDL3c particles was reduced (-35%; p < 0.05) in MetS subjects (n = 16) relative to normolipidemic controls (n = 7). The attenuated anti-apoptotic activity of HDL3c correlated with abdominal obesity, atherogenic dyslipidemia and systemic oxidative stress (p < 0.05), and was intimately associated with altered physicochemical properties of apolipoprotein A-I (apoA-I-poor HDL3c, involving core cholesteryl ester depletion and triglyceride enrichment. We conclude that in MetS, apoA-I-poor, small, dense HDL3c exert defective protection of endothelial cells from oxLDL-induced apoptosis, potentially reflecting functional anomalies intimately associated with abnormal neutral lipid core content. (c) 2007 Elsevier Ireland Ltd. All rights reserved.

Histological features of acute tubular necrosis in native kidneys and long-term renal function

There are few studies on the relationship between the morphology of acute tubular necrosis (ATN) in native kidneys and late functional recovery. Eighteen patients with acute renal failure (ARF) who had undergone renal biopsy were studied. All had the histological diagnosis of ATN and were followed for at least six months. Clinical characteristics of ARF were analyzed, and histological features were semi-quantitatively evaluated (tubular atrophy, interstitial inflammatory infiltrate, interstitial fibrosis, and ATN). According to the maximal GFR achieved during the follow-up, patients were divided into two groups: complete recovery (GFR >= 90 mL/min/1.73 m(2)) and partial recovery (GFR < 90 mL/min/1.73 m(2)). Only 39% of the patients achieved complete recovery. Patients with partial recovery achieved their maximal GFR (63 +/- 9 mL/min/1.73 m(2)) 37 +/- 14 months after ARF, a period of time similar to those patients with complete recovery (i.e., 54 +/- 22 months). Patients with partial recovery had more severe ARF: oliguria was more frequent (90 versus 17%, p < 0.01), and they had higher peak creatinine (13.85 +/- 1.12 versus 8.95 +/- 1.30 mg/dL, p = 0.01), and longer hospitalization (45 +/- 7 versus 20 +/- 4 days, p = 0.03). No single histological parameter was associated with partial recovery, but the sum of all was when expressed as an injury index [4.00 (2.73-5.45) versus 2.00 (1.25-3.31), p < 0.05]. In conclusion, among patients with atypical ATN course, those with more severe ARF and tubule-interstitial lesions are more prone to partial recovery.

Psychoses of epilepsy: A study comparing the clinical features of patients with focal versus generalized epilepsies

In the literature, psychosis of epilepsy (POE) has been described as one of the most frequent psychiatric comorbidities of epilepsy, occurring particularly in association with temporal lobe epilepsy. However, the presence of such psychiatric disorders among patients with idiopathic generalized epilepsies has also been mentioned. In this study, we evaluated the clinical features of psychotic disorders in a series of patients with temporal lobe epilepsy related to mesial temporal sclerosis (TLE-MTS) and juvenile myoclonic epilepsy with the aim of describing and comparing the clinical patterns of the psychotic symptoms in such frequent and important epilepsy syndromes. POE occurred most frequently in patients with TLE-MTS (P=0.01), but no differences were observed between the groups with respect to the subtypes and core symptoms of psychoses. The clinical implications of POE in both epilepsy syndromes are discussed. (C) 2011 Elsevier Inc. All rights reserved.

The interaction between N-category and N-ratio as a new tool to improve lymph node metastasis staging in gastric cancer: Results of a single cancer center in Brazil

Background: Depth of tumor invasion (T-category) and the number of metastatic lymph nodes (N-category) are the most important prognostic factors in patients with gastric cancer. Recently, the ratio between metastatic and dissected lymph nodes (N-ratio) has been established as one. The aim of this study is to evaluate the impact of N-ratio and its interaction with N-category as a prognostic factor in gastric cancer. Methods: This was a retrospective study in which we reviewed clinical and pathological data of 165 patients who had undergone curative surgery at our institution through a 9-year period. The exclusion criteria included metastases, gastric stump tumors and gastrectomy with less than 15 lymph nodes dissected. Results: The median age of the patients was 63 years and most of them were male. Total gastrectomy was the most common procedure and 92.1% of the patients had a D2-lymphadenectomy. Their 5-year overall survival was 57.7%. T-category, N-category, extended gastrectomy, and N-ratio were prognostic factors in overall and disease-free survival in accordance with univariate analysis. In accordance with TNM staging, N1 patients who have had NR1 had 5-year survival in 75.5% whereas in the NR2 group only 33% of the cases had 5-year survival. In the multivariate analysis, the interaction between N-category and N-ratio was an independent prognostic factor. Conclusion: Our findings confirmed the role of N-ratio as prognostic factor of survival in patients with gastric cancer surgically treated with at least 15 lymph nodes dissected. The relationship between N-category and N-ratio is a better predictor than lymph node metastasis staging. (C) 2010 Elsevier Ltd. All rights reserved.

Neck Nerve Trunks Schwannomas: Clinical Features and Postoperative Neurologic Outcome

Objectives/Hypothesis: To analyze clinical and epidemiological features of neck nerve schwannomas, with emphasis on the neurologic outcome after surgical excision sparing as much of nerve fibers as possible with enucleation technique. Study Design: Retrospective study. Methods: Review of medical records from 1987 to 2006 of patients with neck nerve schwannomas, treated in a single institution. Results: Twenty-two patients were identified. Gender distribution was equal and age ranged from 15 to 61 years (mean: 38.6 years). Seven vagal, four brachial plexus, four sympathetic trunk, three cervical plexus, and two lesions on other sites could be identified. Most common symptom was neck mass. Local or irradiated pain also occurred in five cases. Median growing rate of tumors was 3 mm per year. Nerve paralysis was noted twice (a vagal schwannoma and a hypoglossal paralysis compressed by a vagal schwannoma). Different techniques were employed, and seven out of nine patients kept their nerve function (78%) after enucleation. No recurrence was observed in follow-up. Conclusions: Schwannomas should be treated surgically because of its growing potential, leading to local and neural compression symptoms. When possible, enucleation, which was employed in 10 patients of this series, is the recommended surgical option, allowing neural function preservation or restoration in most instances. This is especially important in the head and neck, where denervation may have a significant impact on the quality of life.

A transgenic mouse model that recapitulates the clinical features of both neonatal and adult forms of the skin disease epidermolytic hyperkeratosis

Keratins are the major structural proteins of keratinocytes, which are the most abundant cell type in the mammalian epidermis. Mutations in epidermal keratin genes have been shown to cause severe blistering skin abnormalities. One such disease, epidermolytic hyperkeratosis (EHK), also known as bullous congenital ichthyosiform erythroderma, occurs as a result of mutations in highly conserved regions of keratins K1 and K10. Patients with EHK first exhibit erythroderma with severe blistering, which later is replaced by thick patches of scaly skin. To assess the effect of a mutated K1 gene on skin biology and to produce an animal model for EHK, we removed 60 residues from the 2B segment of HK1 and observed the effects of its expression in the epidermis of transgenic mice. Phenotypes of the resultant mice closely resembled those observed in the human disease, first with epidermal blisters, then later with hyperkeratotic lesions. In neonatal mice homozygous for the transgene, the skin was thicker, with an increased labeling index, and the spinous cells showed a collapse of the keratin filament network around the nuclei, suggesting that a critical concentration of the mutant HK1, over the endogenous MK1, was required to disrupt the structural integrity of the spinous cells. Additionally, footpad epithelium, which is devoid of hair follicles, showed blistering in the spinous layer, suggesting that hair follicles can stabilize or protect the epidermis from trauma. Blisters were not evident in adult mice, but instead they showed a thick, scaly hyperkeratotic skin with increased mitosis, resulting in an increased number of corneocytes and granular cells. Irregularly shaped keratohyalin granules were also observed. To date, this is the only transgenic model to show the typical morphology found in the adult form of EHK.

Beach water table fluctuations due to wave run-up: Capillarity effects

High-frequency beach water table fluctuations due to wave run-up and rundown have been observed in the field [Waddell, 1976]. Such fluctuations affect the infiltration/exfiltration process across the beach face and the interstitial oxygenation process in the beach ecosystem. Accurate representation of high-frequency water table fluctuations is of importance in the modeling of (1) the interaction between seawater and groundwater, more important, the effects on swash sediment transport and (2) the biological activities in the beach ecosystem. Capillarity effects provide a mechanism for high-frequency water table fluctuations. Previous modeling approaches adopted the assumption of saturated flow only and failed to predict the propagation of high-frequency fluctuations in the aquifer. In this paper we develop a modified kinematic boundary condition (kbc) for the water table which incorporates capillarity effects. The application of this kbc in a boundary element model enables the simulation of high-frequency water table fluctuations due to wave run-up. Numerical tests were carried out for a rectangular domain with small-amplitude oscillations; the behavior of water table responses was found to be similar to that predicted by an analytical solution based on the one-dimensional Boussinesq equation. The model was also applied to simulate the water table response to wave run-up on a doping beach. The results showed similar features of water table fluctuations observed in the field. In particular, these fluctuations are standing wave-like with the amplitude becoming increasingly damped inland. We conclude that the modified kbc presented here is a reasonable approximation of capillarity effects on beach water table fluctuations. However, further model validation is necessary before the model can confidently be used to simulate high-frequency water table fluctuations due to wave run-up.