Mecanismos de ação e controle da digestão de proteínas e peptídios em humanos

This review aims to report the major control mechanisms of protein and peptides digestion of special interest in human patients. Regarding protein assimilation its digestive process begins at the stomach with some not so indispensable actions comparatively to those of duodenal/jejunal lumen. However even the intestine processes are partially under gastric secretion control. Proteolytic enzyme activities are related to protein structure and amino acid constituents, tertiary and quartenary structures need HCl - denaturation prior to enzymatic hydrolysis. Thereafter the exopeptidases are guided by either NH 2 (aminopeptidases) or COOH (carboxypeptidases) terminals of the molecule while endopeptidases are oriented by the specific amino acids constituents of the peptide. Both dietary and luminal secreted proteins and polypeptides undergo to either limited or complete proteolysis resulting basic or neutral free-amino acids (40%) or dioctapeptides. The brush border peptidases continue to degrade oligopeptide to di-tripeptides and neutral free-amino acids. Some peptides are uptaked by the enterocytes whose cytosolic peptidases complete the hydrolysis. Hence the digestive products flowing in the portal vein are mainly free-amino acids from either luminal or cytosolic hydrolysis and some di-tripeptides intactly absorbed. Both mechanical and chemical processes of digestion are under neural (vagal), neuroendocrinal(acetilcholine),endocrinal(gastrin, secretin and cholecystokinin) or paracrinal (histamine) controls. The gastric phase (hydrochloric acid and pepsinogen secretions) is activated by gastrin, histamine and acetilcholine which respond to both dietary-amino acids (tryptophan and phenylalanine) and mechanic distention of stomach. The pancreatic secretion is stimulated by either cephalic or gastric phases and has influence on the intestinal phase of digestion. The intestinal types of cells S and I release secretin and cholecystokinin respectively in response of acid quimo (cells S) or amino acids and peptides (cells I) in the lumen. Secretin stimulates the releasing of water, bicarbonate and enteropeptidases whereas cholecystokinin acts on pancreatic enzymes.

Vas Deferens Surface Epithelium of Agouti paca: Fine Structural Features

The surface epithelium of the vas deferens of Agouti paca, a wild and large South American rodent, was basically formed by principal and basal cells being only the principal cells related to endocytosis processes and also secretion taking base on their cytoplasmic ultrastructural features. Principal cell of vas deferens epithelium were characterized mainly by presence of vesicles with several shapes, sizes and internalized content at their apical cytoplasm occurring smaller pits and pale small vesicles seen next to the apical brush border of microvillus. Moreover, coated vesicles, smooth surface vesicles and great vesicles; multivesicular bodies, endosomes and lysosomes were seen. Presence of an apocrine secretory apparatus was also viewed, showing apical cytoplasmic expansions protruding into the vas deferens luminal compartment. The basal flattened cells, without luminal surface contact, occurred next to the basement membrane of the ductus, and did no exhibit special ultrastructural features.

Características regionais sobre a ultra-estrutura das células principais do epitélio do ducto epididimal de Agouti paca

The principal (P) cells of epididymidis surface epithelium of Agouti paca were related to processes of adsorptive endocvtosis and phase-fluid endocvtosis, as well as protein secretion apparently also occur. These findings had been proposed on the base the cytoplasmic ultrastructural features of P cells in which were seen an expressive number of vesicles with several shapes, sizes and internalized content occurring also smaller pits and pale small vesicles located next to the apical brush border of microvilli. Moreover, occurred coated vesicles, smooth surface vesicles and great vesicles; multivesicular bodies, endosomes and lysosomes mainly viewed on supranuclear and apical positions. Presence of an appocrine secretory pathway was characterized in P cells through the occurrence of apical cytoplasmic expansions, protruding into the ducts epididymidis lumina) compartment.

Desenvolvimento pós-embrionário do intestino médio de Dermatobia hominis (Linnaeus Jr.) (Diptera, Cuterebridae)

Dermatobia hominis (Linnaeus, 1781) midgut is internally lined by an epithelium of polytenic cells, some low others prismatic with well developed brush border. Their apical portion are enlarged by secretory vesicles, forming button-like structures that are pinched off to the lumen, some accompained by the nucleus characterizing apocrine and holocrine secretions. This epithelium is gradually renewed by small, non polytenic regenerative cells, found scattered at its basal portion. At the end of the third instar the metamorphosis begins. The epithelial cells present signs of degeneration and at the first day of pupation the regenerative cells increase in number. By the 5th day of pupation these regenerative cells, besides being increased in number, differentiate themselves into two layers: one similar to the dense conective tissue that sustainning the larval epithelium is pinched off to the midgut lumen forming the yellow bodies; the other, develops right under it as the imaginal epitelium. The disorganized muscles bundles of the midgut wall, are invaded by phagocytes. At the end of pupation the midgut has a low prismatic epithelium with brush-border. In the adult, the torax portion of the midgut has prismatic homogeneously basophilic epithelium while in the abdominal portion the epithelium is made of high prismatic cells full of small vacuoles. The larval midgut epithelium suffers programmed cell death non compatible with apoptose. During the metamorphosis the midgut lenght diminishes from 31mm in the larva to 14mm in the adult.

Mecanismos de absorção de aminoácidos e oligopeptídios. Controle e implicações na dietoterapia humana

The mechanisms involved in the absorption of amino acids and oligopeptides are reviewed regarding their implications in human feedings. Brush border and basolateral membranes are crossed by amino acids and di-tripeptides by passive (facilitated or simple diffusion) or active (Na + or H + co-transporters) pathways. Active Na +-dependent system occurs mainly at brush border and simple diffusion at basolateral, both membranes have the passive facilitated transport. Free-amino acids use either passive or active transport systems whereas di-tripeptides do mainly active (H + co-transporter). Brush border have distinctive transport system for amino acids and di-tripeptides. The former occurs mainly by active Na + dependency whereas the later is active H +-dependent with little affinity for tetra or higher peptides. Free amino acids are transported at different speed by saturable, competitive carriers with specificity for basic, acidic or neutral amino acids. Di and tripeptides have at least two carriers both electrogenic and H +-dependent. The basolateral membrane transport of amino acids is mostly by facilitated diffusion while for di-tripeptides it is an active anion exchange associated process. The main regulation of amino acids and di-tripeptide transport is the presence o substrate at the mucosal membrane with higher the substrate higher the absorption. Di and tripeptides are more efficiently absorbed than free amino acids which in turns are better absorbed than oligopeptides. So di-tripeptides result in better N-retention and is particularly useful in cases of lower intestinal absorption capacity. The non-absorbed peptides are digested and fermented by colonic bacteria resulting short-chain fatty acids, dicarboxylic acids, phenolic compounds and ammonia. Short-chain fatty acid provides energy for colonocytes and bacteria and the ammonia not fixed by bacteria returns to the liver for ureagenesis.

Morphology of the vas deferens of the budgerigar (Melopsittacus undulatus)

A morphological study of the budgerigar vas deferens was conducted to demonstrate the electron-microscopic features of its epithelial lining. The analysis showed that the vas deferens of the budgerigar was found to be of a tubular and serpentine structure, continuous with the epididymal region and lined with stereo ciliated pseudostratified epithelium, which contained folds projecting into the tubular lumen and a characteristic brush border. The epithelium consists of ciliated and non-ciliated cells with different electron densities. Ciliated cells were characterized by two morphologically distinct configurations: some cells were columnar and other ciliated cells were longer, thinner and dark. Non-ciliated cells showed apical cytoplasmic expansions, which projected into the tubular lumen as protrusions.

Ultrastructural features of the lining epithelium of the vas deferens of Agouti paca

The epididymal epithelium of Agouti paca, a wild South American rodent, was basically formed by principal and basal cells. Principal cells were closely related to processes of adsorptive endocytosis, phasefluid endocytosis and also secretion originating from their cytoplasmic ultrastructural features. Principal cells were also characterized by the presence of vesicles of several shapes, sizes and internalized content occurring in smaller pits, pale small vesicles next to the apical brush border of microvillus, as well as coated vesicles, smooth surface vesicles and great vesicles. Multivesicular bodies, endosomes and lysosomes were mainly observed in supranuclear position. Moreover, presence of an apocrine secretory process was demonstrated by the occurrence of apical cytoplasmic expansions projecting into the vas deferens luminal compartment. Basal flattened cells without luminal surface contact occurred next to the basement membrane of the ductus, and did no exhibit special ultrastructural features.

Bacillus thuringiensis Cry1Ia10 and Vip3Aa protein interactions and their toxicity in Spodoptera spp. (Lepidoptera)

The polyphagous pests belonging to the genus Spodoptera are considered to be among the most important causes of damage and are widely distributed throughout the Americas'. Due to the extensive use of genetically modified plants containing Bacillus thuringiensis genes that code for insecticidal proteins, resistant insects may arise. To prevent the development of resistance, pyramided plants, which express multiple insecticidal proteins that act through distinct mode of actions, can be used. This study analyzed the mechanisms of action for the proteins Cry1Ia10 and Vip3Aa on neonatal Spodoptera frugiperda, Spodoptera albula, Spodoptera eridania and Spodoptera cosmioides larvae. The interactions of these toxins with receptors on the intestinal epithelial membrane were also analyzed by binding biotinylated toxins to brush border membrane vesicles (BBMVs) from the intestines of these insects. A putative receptor of approximately 65. kDa was found by ligand blotting in all of these species. In vitro competition assays using biotinylated proteins have indicated that Vip3Aa and Cry1Ia10 do not compete for the same receptor for S. frugiperda, S. albula and S. cosmioides and that Vip3Aa was more efficient than Cry1Ia10 when tested individually, by bioassays. A synergistic effect of the toxins in S. frugiperda, S. albula and S. cosmioides was observed when they were combined. However, in S. eridania, Cry1Ia10 and Vip3Aa might compete for the same receptor and through bioassays Cry1Ia10 was more efficient than Vip3Aa and showed an antagonistic effect when the proteins were combined. These results suggest that using these genes to develop pyramided plants may not prove effective in preventing the development of resistance in S. eridiana. © 2012 Elsevier Inc.

Análise morfológica e histoquímica do corpo gorduroso e dos túbulos de Malpighi de operárias adultas de Scaptotrigona postica (Latreille, 1807) (Hymenoptera, Apidae) tratadas com fipronil e ácido bórico

Pós-graduação em Ciências Biológicas (Biologia Celular e Molecular) - IBRC

Avaliação da toxicidade de resíduos industriais e urbanos aplicados na agricultura

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Interações das proteínas Cry1Ia10 e Vip3Aa de Bacillus thuringiensis e toxicidade para larvas de Spodoptera spp. (Lepidoptera: Noctuidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos da interação e toxicidade das proteínas Cry1 e Vip3A de Bacillus thuringiensis em Diatraea saccharalis (Fabr., 1794) (Lepidoptera: Crambidae)

Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

Morphology and histochemistry of the digestive tract in carnivorous freshwater Hemisorubim platyrhynchos (Siluriformes: Pimelodidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Interação de proteínas Vip3A e Cry1la10 de Bacillus thuringiensis com atividade inseticida a lepidópteros-praga

Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

Uso de probiótico e óleos essenciais na ração sobre a microbiota intestinal, atividade de enzimas digestivas e a expressão de genes relacionados aos processos de digestão e absorção de nutrientes em frangos

Pós-graduação em Zootecnia - FCAV