Synthesis of neoglycoconjugates and oligosaccharides with potential anti-Helicobacter pylori activity

The significance of carbohydrate-protein interactions in many biological phenomena is now widely acknowledged and carbohydrate based pharmaceuticals are under intensive development. The interactions between monomeric carbohydrate ligands and their receptors are usually of low affinity. To overcome this limitation natural carbohydrate ligands are often organized as multivalent structures. Therefore, artificial carbohydrate pharmaceuticals should be constructed on the same concept, as multivalent carbohydrates or glycoclusters. Infections of specific host tissues by bacteria, viruses, and fungi are among the unfavorable disease processes for which suitably designed carbohydrate inhibitors represent worthy targets. The bacterium Helicobacter pylori colonizes more than half of all people worldwide, causing gastritis, gastric ulcer, and conferring a greater risk of stomach cancer. The present medication therapy for H. pylori includes the use of antibiotics, which is associated with increasing incidence of bacterial resistance to traditional antibiotics. Therefore, the need for an alternative treatment method is urgent. In this study, four novel synthesis procedures of multivalent glycoconjugates were created. Three different scaffolds representing linear (chondroitin oligomer), cyclic (γ-cyclodextrin), and globular (dendrimer) molecules were used. Multivalent conjugates were produced using the human milk type oligosaccharides LNDFH I (Lewis-b hexasaccharide), LNnT (Galβ1-4GlcNAcβ1-3Galβ1-4Glc), and GlcNAcβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glc all representing analogues of the tissue binding epitopes for H. pylori. The first synthetic method included the reductive amination of scaffold molecules modified to express primary amine groups, and in the case of dendrimer direct amination to scaffold molecule presenting 64 primary amine groups. The second method described a direct procedure for amidation of glycosylamine modified oligosaccharides to scaffold molecules presenting carboxyl groups. The final two methods that were created both included an oxime-linkage on linkers of different length. All the new synthetic procedures synthesized had the advantage of using unmodified reducing sugars as starting material making it easy to synthesize glycoconjugates of different specificity. In addition, the binding activity of an array of neoglycolipids to H. pylori was studied. Consequently, two new neolacto-based structures, Glcβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-Cer and GlcAβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-Cer, with binding activity toward H. pylori were discovered. Interestingly, N-methyl and N-ethyl amide modification of the GlcAβ1-3Galβ1-4GlcNAcβ1-3Galβ1-4Glcβ1-Cer glucuronic acid residue resulted in more effective H. pylori binding epitopes than the parent molecule.

Genomic Profiling of Gastric Cancer

Gastric cancer is the fourth most common cancer and the second most common cause of cancer-related death worldwide. Due to lack of early symptoms, gastric cancer is characterized by late stage diagnosis and unsatisfactory options for curative treatment. Several genomic alterations have been identified in gastric cancer, but the major factors contributing to initiation and progression of gastric cancer remain poorly known. Gene copy number alterations play a key role in the development of gastric cancer, and a change in gene copy number is one of the fundamental mechanisms for a cancer cell to control the expression of potential oncogenes and tumor suppressor genes. This thesis aims at clarifying the complex genomic alterations of gastric cancer to identify novel molecular biomarkers for diagnostic purposes as well as for targeted treatment. To highlight genes of potential biological and clinical relevance, we carried out a systematic microarray-based survey of gene expression and copy number levels in primary gastric tumors and gastric cancer cell lines. Results were validated using immunohistochemistry, real-time qRT-PCR, and affinity capture-based transcript (TRAC) assay. Altogether 192 clinical gastric tissue samples and 7 gastric cancer cell lines were included in this study. Multiple chromosomal regions with recurrent copy number alterations were detected. The most frequent chromosomal alterations included gains at 7q, 8q, 17q, 19q, and 20q and losses at 9p, 18q, and 21q. Distinctive patterns of copy number alterations were detected for different histological subtypes (intestinal and diffuse) and for cancers located in different parts of the stomach. The impact of copy number alterations on gene expression was significant, as 6-10% of genes located in the regions of gains and losses also showed concomitant alterations in their expression. By combining the information from the DNA- and RNA-level analyses many novel gastric cancer-related genes, such as ALPK2, ENAH, HHIPL2, and OSMR, were identified. Independent genome-wide gene expression analysis of Finnish and Japanese gastric tumors revealed an additional set of genes that was differentially expressed in cancerous gastric tissues compared with normal tissue. Overexpression of one of these genes, CXCL1, was associated with an improved survival of gastric cancer. Thus, using an integrative microarray analysis, several novel genes were identified that may be critically important for gastric carcinogenesis. Further studies of these genes may lead to novel biomarkers for gastric cancer diagnosis and targeted therapy.

GATA Transcription Factors in Tissue Homeostasis and Pathology of the Gastrointestinal Tract and Liver

Mammalian gastrointestinal tract and liver are self-renewing organs that are able to sustain themselves due to stem cells present in their tissues. In constant, inflammation-related epithelial damage, vigorous activation of stem cells may lead to their uncontrolled proliferation, and further, to cancer. GATA-4, GATA-5, and GATA-6 regulate cell proliferation and differentiation in many mammalian organs. Lack of GATA-4 or GATA-6 leads to defective endodermal development and cell differentiation. GATA-4 and GATA-5 are considered the ones with tumor suppressive functions, whereas GATA-6 is more related to tumor promotion. In the digestive system their roles in inflammation and tumor-related molecular pathways remain unclear. In this study, we examined the GATA-related molecular pathways involved in normal tissue organization and renewal and in inflammation-related epithelial repair in the gastrointestinal tract and liver. The overall purpose of this study was to elucidate the relation of GATA factors to gastrointestinal and hepatic disease pathology and to evaluate their possible clinical significance in tumor biology. The results indicated distinct expression patterns for GATA-4, GATA-5, and GATA-6 in the human and murine gastrointestinal tract and liver, and their involvement in the regulation of intestine-specific genes. GATA-5 was confined to the intestines of suckling mice, suggesting an association with postnatal enzymatic changes. GATA-4 was upregulated in bowel inflammation concomitantly with TGF-β signaling. In gastrointestinal tumors, GATA-4 was restricted to benign neoplasias of the stomach, while GATA-6 was detected especially at the invasive edges of malignant tumors throughout the gut. In the liver, GATA-4 was upregulated in pediatric tumors along with erythropoietin (Epo), which was detected also in the sera of tumor patients. Furthermore, GATA-4 was enhanced in areas of vigorous hepatic regeneration in patients with tyrosinemia type I. These results suggest a central role for GATA-4 in pediatric tumor biology of the liver. To conclude, GATA-4, GATA-5, and GATA-6 are associated with normal gastrointestinal and hepatic development and regeneration. The appearance of GATA-4 along with TGF-β-signaling in the inflammatory bowel suggests a protective role in the response to inflammation-related epithelial destruction. However, in extremely malignant pediatric liver tumors, GATA-4 function is unlikely to be tumor-suppressing, probably due to the nature of the very primitive multipotent tumor cells. GATA-4, along with its possible downstream factor Epo, could be utilized as novel hepatic tumor markers to supplement the present diagnostics. They could also serve a function in future biological therapies for aggressive pediatric tumors.

Gastric motility: Measurement, symptoms and therapy

Gastric motility disorders, including delayed gastric emptying (gastroparesis), impaired postprandial fundic relaxation, and gastric myoelectrical disorders, can occur in type 1 diabetes, chronic renal failure, and functional dyspepsia (FD). Symptoms like upper abdominal pain, early satiation, bloating, nausea and vomiting may be related to gastroparesis. Diabetic gastroparesis is related to autonomic neuropathy. Scintigraphy is the gold standard in measuring gastric emptying, but it is expensive, requires specific equipment, and exposes patients to radiation. It also gives information about the intragastric distribution of the test meal. The 13C-octanoic acid breath test (OBT) is an alternative, indirect method of measuring gastric emptying with a stable isotope. Electrogastrography (EGG) registers the slow wave originating in the pacemaker area of the stomach and regulating the peristaltic contractions of the antrum. This study compares these three methods of measuring gastric motility in patients with type 1 diabetes, functional dyspepsia, and chronic renal failure. Currently no effective drugs for treating gastric motility disorders are available. We studied the effect of nizatidine on gastric emptying, because in preliminary studies this drug has proven to have a prokinetic effect due to its cholinergic properties. Of the type 1 patients, 26% had delayed gastric emptying of solids as measured by scintigraphy. Abnormal intragastric distribution of the test meal occurred in 37% of the patients, indicating impaired fundic relaxation. The autonomic neuropathy score correlated positively with the gastric emptying rate of solids (P = 0.006), but HbA1C, plasma glucose levels, or abdominal symptoms were unrelated to gastric emptying or intragastric distribution of the test meal. Gastric emptying of both solids and liquids was normal in all FD patients but abnormal intragastric distribution occurred in 38% of the patients. Nizatidine improved symptom scores and quality of life in FD patients, but not significantly. Instead of enhancing, nizatidine slowed gastric emptying in FD patients (P < 0.05). No significant difference appeared in the frequency of the gastric slow waves measured by EGG in the patients and controls. The correlation between gastric half-emptying times of solids measured by scintigraphy and OBT was poor both in type 1 diabetes and FD patients. According to this study, dynamic dual-tracer scintigraphy is more accurate than OBT or EGG in measuring gastric emptying of solids. Additionally it provides information about gastric emptying of liquids and the intragastric distribution of the ingested test meal.

Synthesis of neoglycopeptides and analyses of their biodistributionin vivo to identify tissue specific uptake and novel putative membrane lectins

Complex typeN-linked oligosaccharides derived from fetuin, fibrinogen and thyroglobulin were coupled to acetyltyrosine affording a series of neoglycopeptides with retention of terminal structures and the beta-anomeric configuration of their reducing endN-acetylglycosamine residue. The neoglycopeptides thus synthesized could be labelled to high specific activities with125I in the aromatic side chain of tyrosine. Analysis of the fate of these neoglycopeptides in conjunction with inhibition with asialofetuin and oligosaccharides of defined structure in micein vivo revealed the uptake of galactosylated biantennary compound by kidneys, in addition to the known itinerary of triantennary galactosylated complex oligosaccharide from fetuin to liver and the galactosylated biantennary chain with fucosylation in the core to bone marrows. On the other hand, the agalacto, aglucosamino biantennary chains with and without fucosylation in the core region are taken up by submaxillary glands while the conserved trimannosyl core with fucose is primarily concentrated in stomach tissue. These studies thus define new routes for the uptake of complexN-linked glycans and also subserve to identify lectins presumably involved in their recognition.

Enzymatic cross-linking of β-casein and its impact on digestibility and allergenicity

Protein modification via enzymatic cross-linking is an attractive way for altering food structure so as to create products with increased quality and nutritional value. These modifications are expected to affect not only the structure and physico-chemical properties of proteins but also their physiological characteristics, such as digestibility in the GI-tract and allergenicity. Protein cross-linking enzymes such as transglutaminases are currently commercially available, but also other types of cross-linking enzymes are being explored intensively. In this study, enzymatic cross-linking of β-casein, the most abundant bovine milk protein, was studied. Enzymatic cross-linking reactions were performed by fungal Trichoderma reesei tyrosinase (TrTyr) and the performance of the enzyme was compared to that of transglutaminase from Streptoverticillium mobaraense (Tgase). Enzymatic cross-linking reactions were followed by different analytical techniques, such as size exclusion chromatography -Ultra violet/Visible multi angle light scattering (SEC-UV/Vis-MALLS), phosphorus nuclear magnetic resonance spectroscopy (31P-NMR), atomic force (AFM) and matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS). The research results showed that in both cases cross-linking of β-casein resulted in the formation of high molecular mass (MM ca. 1 350 kg mol-1), disk-shaped nanoparticles when the highest enzyme dosage and longest incubation times were used. According to SEC-UV/Vis-MALLS data, commercial β-casein was cross-linked almost completely when TrTyr and Tgase were used as cross-linking enzymes. In the case of TrTyr, high degree of cross-linking was confirmed by 31P-NMR where it was shown that 91 % of the tyrosine side-chains were involved in the cross-linking. The impact of enzymatic cross-linking of β-casein on in vitro digestibility by pepsin was followed by various analytical techniques. The research results demonstrated that enzymatically cross-linked β-casein was stable under the acidic conditions present in the stomach. Furthermore, it was found that cross-linked β-casein was more resistant to pepsin digestion when compared to that of non modified β-casein. The effects of enzymatic cross-linking of β-casein on allergenicity were also studied by different biochemical test methods. On the basis of the research results, enzymatic cross-linking decreased allergenicity of native β-casein by 14 % when cross-linked by TrTyr and by 6 % after treatment by Tgase. It can be concluded that in addition to the basic understanding of the reaction mechanism of TrTyr on protein matrix, the research results obtained in this study can have high impact on various applications like food, cosmetic, medical, textile and packing sectors.

Ruokauskomukset Mosambikin maaseudun raskaana olevilla ja imettävillä naisilla

Ihmisille ympäri maailmaa on tyypillistä valita tiettyjä ruokia suuremmasta valikoimasta syömäkelpoista ruokaa ja luoda mieltymyksiä sekä kieltoja joitakin ruokia kohtaan. Näitä ilmiöitä kutsutaan ruokauskomuksiksi ja ne ovat tärkeä osa kulttuuria. Niiden taustalla on usein terveydelliset perustelut tai sosiaalinen arvostus yhteisössä. Afrikassa on todettu olevan paljon erilaisia ruokauskomuksia, jotka kohdistuvat usein raskaana oleviin ja imettäviin naisiin sekä lapsiin, ryhmään, joka on fysiologisesti erityisen herkässä elämänvaiheessa. Ravitsemustilan tai ruokaturvan ollessa heikko, mahdollisilla ruokauskomuksilla voi olla merkittävät seuraukset erityisesti tämän väestönosan terveydentilaan. Aliravitsemus ja virheravitsemus ovat edelleen suuria ongelmia Afrikassa ja muissa kehittyvissä maissa. Tämän työn tavoitteena oli tutkia laadullisin menetelmin, onko erityisesti raskaana olevilla ja imettävillä naisilla Keski-Mosambikin maaseudulla, Zambézian maakunnassa, ruokauskomuksia, mitä ne mahdollisesti ovat, sekä arvioida voiko ruokauskomuksilla olla ravitsemuksellista merkitystä. Menetelminä oli 5 ryhmähaastattelua kolmessa kylässä ja 10 yksilöhaastattelua kahdessa kylässä. Tutkittavat olivat 12–78-vuotiaita naisia ja heitä oli yhteensä 27. Tulkkaus, tutkimusaiheen sensitiivisyys ja haastattelijan kokemattomuus aiheuttivat haasteita haastatteluiden toteutukseen. Tämän vuoksi menetelmää muokattiin ja se vaihdettiin ryhmähaastattelusta yksilöhaastatteluun tutkimuksen aikana. Ruokauskomukset vaihtelivat sekä kylien välillä että kylien sisällä, joskin niistä löytyi samantyyppisiä pääpiirteitä. Työssä todettiin, että raskaana oleviin ja imettäviin naisiin kohdistui tutkimusalueella ruokauskomuksia. Raskauden aikana tuli välttää pääasiassa proteiinipitoisia ruokia, kuten lihaa ja kalaa ja puolestaan suosia kasvisten, hedelmien ja viljatuotteiden käyttöä. Linnun munien syöntiä sekä suositeltiin että kehotettiin välttämään raskauden aikana. Raskauden aikana ilmeni lisäksi tietoinen tapa vähentää kassavapuuron tai ruuan syömistä kokonaisuudessaan. Imetyksen aikana ei vältetty juuri mitään ruokia, vaan suositeltiin kookosta ja kasviksia. Suurin osa perusteluista liittyi äidin ja lapsen terveyteen. Perustelut voitiin jakaa seuraaviin ryhmiin: lisää äidinmaidon tuotantoa; aiheuttaa vatsakipua äidillä; pitää yllä kuntoa ja estää vatsan kasvua; äidistä tulee vahva, terve ja hän saa vitamiineja; lapsen ulkonäkö muuttuu; lapsesta tulee terve ja vahva; lapsen käyttäytyminen muuttuu; aiheuttaa keskenmenon; aiheuttaa vaikean tai helpon synnytyksen. Ruokauskomukset ja terveysviranomaisilta tullut valistus oli osittain sekoittunut keskenään. Lähes kaikki naiset kertoivat noudattavansa näitä ruokauskomuksia. Muutamat naiset kertoivat suositeltavien ruokien kohdalla, että ruokien saatavuus tekee noudattamisen joskus vaikeaksi. Proteiinipitoisten ruokien välttäminen voi lisätä proteiinialiravitsemuksen riskiä ja syömisen vähentäminen saattaa lisätä riskiä saada riittämättömästi energiaa raskauden aikana. Suositeltavat ruuat todennäköisesti edistävät terveyttä. Tutkielman perusteella voitiin todeta, että vieraassa kulttuurissa tutkiminen vaatii tutkimusmenetelmältä paljon. Tärkeää on menetelmän joustavuus, jotta sitä voi muuttaa tutkimuskentällä toimivampaan ja luotettavampaan muotoon. Johtopäätöksenä todettiin, että suositeltavin menetelmä tutkittaessa ruokauskomuksia tällä tutkimusalueella olisi ollut yksilöhaastattelut, jossa olisi ollut mahdollisimman vähän osallistujia ja osallistujat olisivat olleet samaa sukupuolta ja saman ikäisiä. Terveyden ja ravitsemuksen kannalta on tärkeää, että ruokauskomuksista ollaan tietoisia ja väestön ruokauskomuksia tutkitaan alueittain, koska ne voivat vaihdella merkittävästi jopa kylien tai ihmisryhmien sisällä.

Structure and activity cyclase activated of OK-GC: A kidney receptor-guanylate cyclase activated by guanylin peptides

Uroguanylin, guanylin, and lymphoguanylin are small peptides that activate renal and intestinal receptor guanylate cyclases (GC). They are structurally similar to bacterial heat-stable enterotoxins (ST) that cause secretory diarrhea. Uroguanylin, guanylin, and ST elicit natriuresis, kaliuresis, and diuresis by direct actions on kidney GC receptors. A 3,762-bp cDNA characterizing a uroguanylin/guanylin/ST receptor was isolated from opossum kidney (OK) cell RNA/cDNA. This kidney cDNA (OK-GC) encodes a mature protein containing 1,049 residues sharing 72.4�75.8% identity with rat, human, and porcine forms of intestinal GC-C receptors. COS or HEK-293 cells expressing OK-GC receptor protein were activated by uroguanylin, guanylin, or ST13 peptides. The 3.8-kb OK-GC mRNA transcript is most abundant in the kidney cortex and intestinal mucosa, with lower mRNA levels observed in urinary bladder, adrenal gland, and myocardium and with no detectable transcripts in skin or stomach mucosa. We propose that OK-GC receptor GC participates in a renal mechanism of action for uroguanylin and/or guanylin in the physiological regulation of urinary sodium, potassium, and water excretion. This renal tubular receptor GC may be a target for circulating uroguanylin in an endocrine link between the intestine and kidney and/or participate in an intrarenal paracrine mechanism for regulation of kidney function via the intracellular second messenger, cGMP.

Structure and activity of OK-GC: a kidney receptor guanylate cyclase activated by guanylin peptides

Uroguanylin, guanylin, and lymphoguanylin are small peptides that activate renal and intestinal receptor guanylate cyclases (GC). They are structurally similar to bacterial heat-stable enterotoxins (ST) that cause secretory diarrhea. Uroguanylin, guanylin, and ST elicit natriuresis, kaliuresis, and diuresis by direct actions on kidney GC receptors. A 3,762-bp cDNA characterizing a uroguanylin/guanylin/ST receptor was isolated from opossum kidney (OK) cell RNA/cDNA. This kidney cDNA (OK-GC) encodes a mature protein containing 1,049 residues sharing 72.4-75.8% identity with rat, human, and porcine forms of intestinal GC-C receptors. COS or HEK-293 cells expressing OK-GC receptor protein were activated by uroguanylin, guanylin, or ST13 peptides. The 3.8-kb OK-GC mRNA transcript is most abundant in the kidney cortex and intestinal mucosa, with lower mRNA levels observed in urinary bladder, adrenal gland, and myocardium and with no detectable transcripts in skin or stomach mucosa. We propose that OK-GC receptor GC participates in a renal mechanism of action for uroguanylin and/or guanylin in the physiological regulation of urinary sodium, potassium, and water excretion. This renal tubular receptor GC may be a target for circulating uroguanylin in an endocrine link between the intestine and kidney and/or participate in an intrarenal paracrine mechanism for regulation of kidney function via the intracellular second messenger, cGMP.

Expression of the receptor guanylyl cyclase C and its ligands in reproductive tissues of the rat: A potential role for a novel signaling pathway in the epididymis

Guanylyl cyclase C (GC-C) is a membrane-associated form of guanylyl cyclase and serves as the receptor for the heat-stable enterotoxin (ST) peptide and endogenous ligands guanylin, uroguanylin, and lymphoguanylin. The major site of expression of GC-C is the intestinal epithelial cell, although GC-C is also expressed in extraintestinal tissue such as the kidney, airway epithelium, perinatal liver, stomach, brain, and adrenal glands. Binding of ligands to GC-C leads to accumulation of intracellular cGMP, the activation of protein kinases G and A, and phosphorylation of the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel that regulates salt and water secretion. We examined the expression of GC-C and its ligands in various tissues of the reproductive tract of the rat. Using reverse transcriptase and the polymerase chain reaction, we demonstrated the presence of GC-C, uroguanylin, and guanylin mRNA in both male and female reproductive organs. Western blot analysis using a monoclonal antibody to GC-C revealed the presence of differentially glycosylated forms of GC-C in the caput and cauda epididymis. Exogenous addition of uroguanylin to minced epididymal tissue resulted in cGMP accumulation, suggesting an autocrine or endocrine activation of GC-C in this tissue. Immunohistochemical analyses demonstrated expression of GC-C in the tubular epithelial cells of both the caput epididymis and cauda epididymis. Our results suggest that the GC-C signaling pathway could converge on CFTR in the epididymis and perhaps control fluid and ion balance for optimal sperm maturation and storage in this tissue.

NMR Structure Implications of Enhanced Efficacy of Obestatin Fragment Analogs

Obestatin is a more recently discovered hormone that is encoded by the ghrelin gene and produced in the stomach and gut. We report NMR analysis on synthetic Obestatin (OB23), a 23 residue peptide, along with three overlapping fragments of the same in methanol solvent as a first step towards structure activity relationship. Selective substitutions on the promising N-terminal and middle fragments of obestatin have been carried out in order to improve the efficacy and potency. In the N-terminal fragment two peptides were obtained by the replacement of Gly (8) with a-aminoisobutyric acid (Aib, U) and Phe (F5) with Cyclohexylalanine (Cha). In case of the middle fragment both Gly (3) and Gly (8) were replaced with Aib residues. The rationale being, these unusual amino acids could provide protection from immediate degradation and aid structure stabilization. Our previous studies showed that the N-terminal and the middle fragment were unstructured and hence this substitution would directly evaluate the effect of structure on the activity of these fragment analogs. Detailed NMR analysis clearly demonstrates formation of helical secondary structure in all the peptide analogues and provides justification for relative activities reported by our group previously (Nagaraj et al. 2009).

Helicobacter pylori DprA alleviates restriction barrier for incoming DNA

Helicobacter pylori is a Gram-negative bacterium that colonizes human stomach and causes gastric inflammation. The species is naturally competent and displays remarkable diversity. The presence of a large number of restriction-modification (R-M) systems in this bacterium creates a barrier against natural transformation by foreign DNA. Yet, mechanisms that protect incoming double-stranded DNA (dsDNA) from restriction enzymes are not well understood. A DNA-binding protein, DNA Processing Protein A (DprA) has been shown to facilitate natural transformation of several Gram-positive and Gram-negative bacteria by protecting incoming single-stranded DNA (ssDNA) and promoting RecA loading on it. However, in this study, we report that H. pylori DprA (HpDprA) binds not only ssDNA but also dsDNA thereby conferring protection to both from various exo-nucleases and Type II restriction enzymes. Here, we observed a stimulatory role of HpDprA in DNA methylation through physical interaction with methyltransferases. Thus, HpDprA displayed dual functional interaction with H. pylori R-M systems by not only inhibiting the restriction enzymes but also stimulating methyltransferases. These results indicate that HpDprA could be one of the factors that modulate the R-M barrier during inter-strain natural transformation in H. pylori.

Metal nanoparticles as better protein-aggregation prevention agents than chaperones

Prevention or suppression of protein aggregation is of great importance in the context of protein storage, transportation and delivery. Traditionally chaperones or other chemically active agents are used to stop or diffuse native protein aggregation. We have used gold nanoparticles to prevent thermal aggregation of alcohol dehydrogenase (ADH), a protein that maintains the alcohol level in the liver and stomach. A light-scattering assay has been used to investigate the effect of gold nanoparticles on thermal aggregation of ADH and the result of our study has been summarized in Fig. 1. The scattered light intensity from the solution containing ADH decreases when 45 nm gold nanoparticles are added prior to heating (thermal denaturation) the solution, which indicates prevention of aggregation. The aggregation of the protein is suppressed to the extent of 96% with picomolar concentration of 45 nm gold nanoparticles while micromolar amounts of other proteins and biological substances are necessary to achieve the same effect. The extent varies with the size and the concentration of the gold NPs for the same protein concentration.

El Matadero de Esteban Echeverría, o la inauguración de los mataderos

Resumen: En el presente texto retomamos y reconocemos el carácter de ‘texto fundante’ que El Matadero de Esteban Echeverría tiene en nuestra cultura argentina. Analizamos lo enraizado del texto conectándolo hacia atrás, con los orígenes de la gauchesca, y hacia adelante, con su culminación y con sus proyecciones, incluso en diversas disciplinas. Luego podemos centrarnos en el tema de la violencia como recurrente no solo literario, y precisar el sentido en que la tomamos. Sostenemos que la violencia de El Matadero ya estaba presente, de manera velada, en otras obras de Echeverría; no tanto por su tematización, sino porque figurativiza, de manera muy acorde con la ideología románticas, razón y corazón, considerado éste no como exclusiva sede de sentimientos, sino como víscera, y de allí sus equivalentes, como el estómago y el matambre. Esta parte visceral no accede a mayor formulación, porque no entra en el programa de la estética en boga. Desde este punto de vista, releo las quejas debidas al sufrimiento del corazón, y entiendo el llanto y el descontento de otro modo. Hay lamento porque nada, al menos en el terreno literario, brinda salida a ese fondo vivo, no esquemático y que le resulta abyecto, porque encierra un modo y un contenido que no puede reconocer como propios. Asociado con esta cara puesta en sombra, inopinadamente, El matadero vuelve a ser texto fundante, pero de otra parte de la literatura argentina: de lo marginal, que no puede sumarse a proyectos, y que muy pocos dicen.

Preliminary studies on food and feeding habits of Polypterus endlicheri and Polypterus senegalus in Lake Chad

The food and feeding habits of Polyprerus cncllicheri and Polypterus senegalus was carried out in the months of September to October. The food of 33 Polypierus endlicheri as observed include Tilapia species (89.3%), Eutropius niloticus (28.6%), Mayfly nymph (39.3%), Dragon fly larva (56.6%) fish remains (21.4%) and detritus (7.1%). The food of27 Polypterus senegalus as observed include Tilapia sp (88.4%), Eutropius niloticus (27.9%), may fly nymph (23.3%), Dragonfly nymph (34.9%) remains (21.1%) detritus (23.3%). (9 page document) The percentage occurrence of food item found in the stomach of Polypterus endlieheri is 93.3% while that of Polyprerus senegalus is 67.4%. The dominance of Tilapia sp was establish in the study, and there is no significant difference between the feeding habit of Polypterus endlicheri and Polyprerus senegalus.