2,351 research outputs found

    Deciphering the Structure, Growth and Assembly of Amyloid-Like Fibrils Using High-Speed Atomic Force Microscopy

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    Formation of fibrillar structures of proteins that deposit into aggregates has been suggested to play a key role in various neurodegenerative diseases. However mechanisms and dynamics of fibrillization remains to be elucidated. We have previously established that lithostathine, a protein overexpressed in the pre-clinical stages of Alzheimer's disease and present in the pathognomonic lesions associated with this disease, form fibrillar aggregates after its N-terminal truncation. In this paper we visualized, using high-speed atomic force microscopy (HS-AFM), growth and assembly of lithostathine protofibrils under physiological conditions with a time resolution of one image/s. Real-time imaging highlighted a very high velocity of elongation. Formation of fibrils via protofibril lateral association and stacking was also monitored revealing a zipper-like mechanism of association. We also demonstrate that, like other amyloid ß peptides, two lithostathine protofibrils can associate to form helical fibrils. Another striking finding is the propensity of the end of a growing protofibril or fibril to associate with the edge of a second fibril, forming false branching point. Taken together this study provides new clues about fibrillization mechanism of amyloid proteins

    Evolution of Plant Nucleotide-Sugar Interconversion Enzymes

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    Nucleotide-diphospho-sugars (NDP-sugars) are the building blocks of diverse polysaccharides and glycoconjugates in all organisms. In plants, 11 families of NDP-sugar interconversion enzymes (NSEs) have been identified, each of which interconverts one NDP-sugar to another. While the functions of these enzyme families have been characterized in various plants, very little is known about their evolution and origin. Our phylogenetic analyses indicate that all the 11 plant NSE families are distantly related and most of them originated from different progenitor genes, which have already diverged in ancient prokaryotes. For instance, all NSE families are found in the lower land plant mosses and most of them are also found in aquatic algae, implicating that they have already evolved to be capable of synthesizing all the 11 different NDP-sugars. Particularly interesting is that the evolution of RHM (UDP-L-rhamnose synthase) manifests the fusion of genes of three enzymatic activities in early eukaryotes in a rather intriguing manner. The plant NRS/ER (nucleotide-rhamnose synthase/epimerase-reductase), on the other hand, evolved much later from the ancient plant RHMs through losing the N-terminal domain. Based on these findings, an evolutionary model is proposed to explain the origin and evolution of different NSE families. For instance, the UGlcAE (UDP-D-glucuronic acid 4-epimerase) family is suggested to have evolved from some chlamydial bacteria. Our data also show considerably higher sequence diversity among NSE-like genes in modern prokaryotes, consistent with the higher sugar diversity found in prokaryotes. All the NSE families are widely found in plants and algae containing carbohydrate-rich cell walls, while sporadically found in animals, fungi and other eukaryotes, which do not have or have cell walls with distinct compositions. Results of this study were shown to be highly useful for identifying unknown genes for further experimental characterization to determine their functions in the synthesis of diverse glycosylated molecules

    Association of nutritional status and serum albumin levels with development of toxicity in patients with advanced non-small cell lung cancer treated with paclitaxel-cisplatin chemotherapy: a prospective study

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    <p>Abstract</p> <p>Background</p> <p>A frequent manifestation of advanced NSCLC is malnutrition, even though there are many studies which relate it with a poor survival, its relation with toxicity has not yet been consistently reported. The aim of this study was to associate malnutrition and albumin serum levels with the occurrence of chemotherapy-induced toxicity in cisplatin plus paclitaxel chemotherapy-treated NSCLC.</p> <p>Methods</p> <p>We prospectively evaluated 100 stage IV NSCLC patients treated with paclitaxel (175 mg/m<sup>2</sup>) and cisplatin (80 mg/m<sup>2</sup>). Malnutrition was assessed using SGA prior treatment. Neutrophil Lymphocyte Ratio (NLR) and the Platelet Lymphocyte Ratio (PLR) were used to determine the presence of systemic inflammatory response (SIR) and were related to the development of toxicity. Toxicity was graded according to NCI CTCAE version 3.0 after two chemotherapy cycles.</p> <p>Results</p> <p>Median age was 58 ± 10 years, 51% of patients were malnourished, 50% had albumin ≤3.0 mg/mL. NLR ≥ 5 was associated with basal hypoalbuminemia (mean ranks, 55.7 vs. 39 p = 0.006), ECOG = 2 (47.2 vs. 55.4 p = 0.026) and PLR ≥ 150 were significantly related with a basal body mass index ≤20 (56.6 vs. 43.5; p = 0.02) and hypoalbuminemia (58.9 vs. 41.3; p = 0.02). Main toxicities observed after 2 cycles of chemotherapy were alopecia (84%), nausea (49%), neuropathy (46%), anemia (33%), lymphopenia (31%), and leukopenia (30%). Patients malnourished and with hypoalbuminemia developed more chemotherapy-induced toxicity overall when compared with those without malnutrition (31 vs 22; <it>p </it>= 0.02) and normal albumin (mean ranks, 62 vs 43; <it>p </it>= 0.002), respectively. Hypoalbuminemia was associated with anemia (56 vs 47; <it>p </it>= 0.05), fatigue (58 vs 46; <it>p </it>= 0.01), and appetite loss (57.1 vs 46.7; <it>p </it>= 0.004) compared with normal albumin. PLR ≥ 150 was related with the development of toxicity grade III/IV (59.27 vs. 47.03 p = 0.008) and anemia (37.9 vs 53.8 p = 0.004).</p> <p>Conclusion</p> <p>SIR parameters were associated with malnutrition, weight loss and hypoalbuminemia. Chemotherapy-induced toxicity in NSCLC patients treated with paclitaxel and cisplatin was associated with malnutrition and hypoalbuminemia. Early nutritional assessment and support might confer beneficial effects.</p

    Preferential Entry of Botulinum Neurotoxin A Hc Domain through Intestinal Crypt Cells and Targeting to Cholinergic Neurons of the Mouse Intestine

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    Botulism, characterized by flaccid paralysis, commonly results from botulinum neurotoxin (BoNT) absorption across the epithelial barrier from the digestive tract and then dissemination through the blood circulation to target autonomic and motor nerve terminals. The trafficking pathway of BoNT/A passage through the intestinal barrier is not yet fully understood. We report that intralumenal administration of purified BoNT/A into mouse ileum segment impaired spontaneous muscle contractions and abolished the smooth muscle contractions evoked by electric field stimulation. Entry of BoNT/A into the mouse upper small intestine was monitored with fluorescent HcA (half C-terminal domain of heavy chain) which interacts with cell surface receptor(s). We show that HcA preferentially recognizes a subset of neuroendocrine intestinal crypt cells, which probably represent the entry site of the toxin through the intestinal barrier, then targets specific neurons in the submucosa and later (90–120 min) in the musculosa. HcA mainly binds to certain cholinergic neurons of both submucosal and myenteric plexuses, but also recognizes, although to a lower extent, other neuronal cells including glutamatergic and serotoninergic neurons in the submucosa. Intestinal cholinergic neuron targeting by HcA could account for the inhibition of intestinal peristaltism and secretion observed in botulism, but the consequences of the targeting to non-cholinergic neurons remains to be determined

    The formation of human populations in South and Central Asia

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    By sequencing 523 ancient humans, we show that the primary source of ancestry in modern South Asians is a prehistoric genetic gradient between people related to early hunter-gatherers of Iran and Southeast Asia. After the Indus Valley Civilization’s decline, its people mixed with individuals in the southeast to form one of the two main ancestral populations of South Asia, whose direct descendants live in southern India. Simultaneously, they mixed with descendants of Steppe pastoralists who, starting around 4000 years ago, spread via Central Asia to form the other main ancestral population. The Steppe ancestry in South Asia has the same profile as that in Bronze Age Eastern Europe, tracking a movement of people that affected both regions and that likely spread the distinctive features shared between Indo-Iranian and Balto-Slavic languages

    Shape Variation in Aterian Tanged Tools and the Origins of Projectile Technology: A Morphometric Perspective on Stone Tool Function

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    BACKGROUND: Recent findings suggest that the North African Middle Stone Age technocomplex known as the Aterian is both much older than previously assumed, and certainly associated with fossils exhibiting anatomically modern human morphology and behavior. The Aterian is defined by the presence of 'tanged' or 'stemmed' tools, which have been widely assumed to be among the earliest projectile weapon tips. The present study systematically investigates morphological variation in a large sample of Aterian tools to test the hypothesis that these tools were hafted and/or used as projectile weapons. METHODOLOGY/PRINCIPAL FINDINGS: Both classical morphometrics and Elliptical Fourier Analysis of tool outlines are used to show that the shape variation in the sample exhibits size-dependent patterns consistent with a reduction of the tools from the tip down, with the tang remaining intact. Additionally, the process of reduction led to increasing side-to-side asymmetries as the tools got smaller. Finally, a comparison of shape-change trajectories between Aterian tools and Late Paleolithic arrowheads from the North German site of Stellmoor reveal significant differences in terms of the amount and location of the variation. CONCLUSIONS/SIGNIFICANCE: The patterns of size-dependent shape variation strongly support the functional hypothesis of Aterian tools as hafted knives or scrapers with alternating active edges, rather than as weapon tips. Nevertheless, the same morphological patterns are interpreted as one of the earliest evidences for a hafting modification, and for the successful combination of different raw materials (haft and stone tip) into one implement, in itself an important achievement in the evolution of hominin technologies

    Reconstructing the Deep Population History of Central and South America

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    We report genome-wide ancient DNA from 49 individuals forming four parallel time transects in Belize, Brazil, the Central Andes, and the Southern Cone, each dating to at least 9,000 years ago. The common ancestral population radiated rapidly from just one of the two early branches that contributed to Native Americans today. We document two previously unappreciated streams of gene flow between North and South America. One affected the Central Andes by 4,200 years ago, while the other explains an affinity between the oldest North American genome associated with the Clovis culture and the oldest Central and South Americans from Chile, Brazil, and Belize. However, this was not the primary source for later South Americans, as the other ancient individuals derive from lineages without specific affinity to the Clovis-associated genome, suggesting a population replacement that began at least 9,000 years ago and was followed by substantial population continuity in multiple regions

    A randomized, controlled trial of 3.0 mg of liraglutide in weight management

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    BACKGROUND Obesity is a chronic disease with serious health consequences, but weight loss is difficult to maintain through lifestyle intervention alone. Liraglutide, a glucagonlike peptide-1 analogue, has been shown to have potential benefit for weight management at a once-daily dose of 3.0 mg, injected subcutaneously. METHODS We conducted a 56-week, double-blind trial involving 3731 patients who did not have type 2 diabetes and who had a body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) of at least 30 or a BMI of at least 27 if they had treated or untreated dyslipidemia or hypertension. We randomly assigned patients in a 2:1 ratio to receive once-daily subcutaneous injections of liraglutide at a dose of 3.0 mg (2487 patients) or placebo (1244 patients); both groups received counseling on lifestyle modification. The coprimary end points were the change in body weight and the proportions of patients losing at least 5% and more than 10% of their initial body weight. RESULTS At baseline, the mean (±SD) age of the patients was 45.1±12.0 years, the mean weight was 106.2±21.4 kg, and the mean BMI was 38.3±6.4; a total of 78.5% of the patients were women and 61.2% had prediabetes. At week 56, patients in the liraglutide group had lost a mean of 8.4±7.3 kg of body weight, and those in the placebo group had lost a mean of 2.8±6.5 kg (a difference of -5.6 kg; 95% confidence interval, -6.0 to -5.1; P&lt;0.001, with last-observation-carried-forward imputation). A total of 63.2% of the patients in the liraglutide group as compared with 27.1% in the placebo group lost at least 5% of their body weight (P&lt;0.001), and 33.1% and 10.6%, respectively, lost more than 10% of their body weight (P&lt;0.001). The most frequently reported adverse events with liraglutide were mild or moderate nausea and diarrhea. Serious events occurred in 6.2% of the patients in the liraglutide group and in 5.0% of the patients in the placebo group. CONCLUSIONS In this study, 3.0 mg of liraglutide, as an adjunct to diet and exercise, was associated with reduced body weight and improved metabolic control. (Funded by Novo Nordisk; SCALE Obesity and Prediabetes NN8022-1839 ClinicalTrials.gov number, NCT01272219.)
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