Biomedical subjects

R A Azevedo

Publications and source records attributed to R A Azevedo.

At least 19 recordsLinked to original sources

PubMed2006

Dermatan sulfate is the major metachromatic glycosaminoglycan in the integument of the anuran Bufo ictericus.

Glycosaminoglycans from the ventral and dorsal integuments of the anuran Bufo ictericus were characterized based on biochemical and histochemical methods. Dermatan sulfate is the major metachromatic glycosaminoglycan found in these tissues, but small amount of heparan sulfate was also detected. The average molecular mass of the dermatan sulfate is approximately 20 kDa, similar to the glycosaminoglycan isolated from mammalian skin. In addition, the amphibian integument contains high amounts of hyaluronic acid, especially in the ventral area. We also observed that the glycosaminoglycans occur in the anuran integument as irregular deposits through the spongious dermis and in the mast cells, as revealed by histochemical analysis using Alcian blue, dimethylmethylene blue and toluidine blue stains. The concentration and composition of glycosaminoglycans found in the amphibian integument resemble those from mammalian skin except for the higher concentration of hyaluronic acid in the amphibian tissue. Possibly, this observation indicates that the function of the sulfated glycosaminoglycan in these tissues has been preserved during evolution, although the amphibian integument and the human skin have their own particular physiology.

Animals↗

PubMed2006

Nickel elicits a fast antioxidant response in Coffea arabica cells.

The antioxidant responses of coffee (Coffea arabica L.) cell suspension cultures to nickel (Ni) were investigated. Ni was very rapidly accumulated in the cells and the accumulation could be directly correlated with the increase of NiCl(2) concentration in the medium. At 0.05 mM NiCl(2) growth was stimulated, but at 0.5 mM NiCl(2), the growth rate was reduced. An indication of alterations in the presence of reactive oxygen species was detected by an increase in lipid peroxidation at 0.5 mM NiCl(2). Catalase (CAT; EC 1.11.1.6), glutathione reductase (GR; EC 1.6.4.2), ascorbate peroxidase (APX; EC 1.11.1.11), guaiacol peroxidase (GOPX; EC 1.11.1.7) and superoxide dismutase (SOD; EC 1.15.1.1) activities were increased, particularly at earlier NiCl(2) exposure times and the activities were higher at 0.5 mM NiCl(2) for most of exposure times tested. Non-denaturing PAGE revealed one CAT isoenzyme, nine SOD isoenzymes and four GR isoenzymes. The SOD isoenzymes were differentially affected by NiCl(2) treatment and one GR isoenzyme was increased by NiCl(2). NiCl(2) at 0.05 mM did not induce lipid peroxidation and the main response appeared to be via the induction of SOD, CAT, GOPX and APX activities for the removal of the reactive oxygen species and through the induction of GR to ensure the availability of reduced glutathione.

Antioxidants↗

PubMed2006

Expression pattern of glycoconjugates in the Bidderian and ovarian follicles of the Brazilian toad Bufo ictericus analyzed by lectin histochemistry.

The Bidder's organ and ovary of the Brazilian toad Bufo ictericus were studied by light microscopy, using hematoxylin-eosin (HE) and periodic acid Schiff (PAS) staining. The expression and distribution of carbohydrate moieties was analyzed by lectin histochemistry, using 8 lectins with different carbohydrate specificities: Ulex europaeus (UEA I), Lens culinaris (LCA), Erythrina cristagalli (ECA), Arachis hypogaea (PNA), Ricinus communis (RCA I), Aleuria aurantia (AAA), Triticum vulgaris (WGA), and Glycine maximum (SBA). The results showed that the Bidderian zona pellucida presented alpha-mannose, alpha-L-fucose, beta-D-galactose, N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. The Bidderian follicular cells showed the presence of beta-D-galactose and N-acetyl-D-glucosamine. In the extracellular matrix, alpha-mannose and alpha/beta-N-acetyl-galactosamine residues were detected. The ovarian zona pellucida showed alpha-L-fucose, N-acetyl-D-glucosamine, alpha/beta-N-acetyl-galactosamine residues, and alpha-mannose and N-acetyl-D-glucosamine residues were detected in the follicular cells. Thus, the zona pellucida in both organs contains N-acetyl-D-glucosamine, and alpha/beta-N-acetyl-galactosamine residues. alpha-L-fucose residues were detected in the zona pellucida of both organs, using different lectins. Considering that beta-D-galactose residue was absent from ovary but present in the Bidder's organ, this sugar residue may play an important role in follicle development, blocking the Bidderian follicles and preventing further development of the Bidder's organ into a functional ovary.

Animals↗

PubMed2006

The aspartic acid metabolic pathway, an exciting and essential pathway in plants.

Aspartate is the common precursor of the essential amino acids lysine, threonine, methionine and isoleucine in higher plants. In addition, aspartate may also be converted to asparagine, in a potentially competing reaction. The latest information on the properties of the enzymes involved in the pathways and the genes that encode them is described. An understanding of the overall regulatory control of the flux through the pathways is undisputedly of great interest, since the nutritive value of all cereal and legume crops is reduced due to low concentrations of at least one of the aspartate-derived amino acids. We have reviewed the recent literature and discussed in this paper possible methods by which the concentrations of the limiting amino acids may be increased in the seeds.

Aspartic Acid↗

PubMed2005

Are high-lysine cereal crops still a challenge?

The essential amino acids lysine and threonine are synthesized in higher plants via a pathway starting with aspartate that also leads to the formation of methionine and isoleucine. Lysine is one of most limiting amino acids in plants consumed by humans and livestock. Recent genetic, molecular, and biochemical evidence suggests that lysine synthesis and catabolism are regulated by complex mechanisms. Early kinetic studies utilizing mutants and transgenic plants that over-accumulate lysine have indicated that the major step for the regulation of lysine biosynthesis is at the enzyme dihydrodipicolinate synthase. Despite this tight regulation, recent strong evidence indicates that lysine catabolism is also subject to control, particularly in cereal seeds. The challenge of producing crops with a high-lysine concentration in the seeds appeared to be in sight a few years ago. However, apart from the quality protein maize lines currently commercially available, the release of high-lysine crops has not yet occurred. We are left with the question, is the production of high-lysine crops still a challenge?

Crops, Agricultural↗

PubMed2005

Morphology of Bufo ictericus integument (Amphibia, Bufonidae).

Bufo ictericus integument was investigated by stereoscopic, low vacuum scanning electron microscopy, transmission electron microscopy and light microscopy. The studies revealed, that the dorsal integument surface is rougher than ventral. Three types of projections are visualized: larger rounded verrucae, smaller conical cornified tubercles, and conical short spines. Prominent verrucae are observed on the dorsal surface, being flatter on the ventral surface. The tubercles are visualized only on the dorsal surface. The verrucae are separated by grooves that may contribute spreading and retention of the glandular secretion upon the integument. The pattern of the epidermal grooves is also important for water distribution, protecting the animal against desiccation. The epidermis is composed of a stratified epithelium with intraepithelial blood vessels, where keratinocytes predominate, but flask cells, and Merkel cells also occur. In the spongious dermis, cutaneous glands are visualized. The compact dermis is a series of alternating layers of bundles of collagenous fibers, and between spongious and compact dermis there are basophilic areas that correspond to Eberth-Katschenko layer. The dorsal and the ventral surfaces of B. ictericus are morphologically distinct. The integument structure is related to the physiology of each surface and represents an adaptation to habitat, reflecting a lifestyle of the animal.

Animals↗

PubMed2004

Mandibular ramus-related Stafne's bone cavity.

Mandibular bone depressions located on the lingual/buccal aspect of the mandibular ramus are the rarest variants of the so-called Stafne's bone cavities, or major salivary gland-related depressions, with only 17 cases reported in the literature including both clinical cases and archaeological specimens. We report the case of a 14-year-old male patient who sought clinical assistance complaining of a hard expansion on the lower left premolar-molar region. Apart from a unilocular radiolucent lesion between the lower left second premolar and first molar, a panoramic radiograph showed another radiolucent lesion located in the right mandibular ramus, at the level of the mandibular foramen. Computed tomography (CT) revealed an expansile lesion in the left mandibular body, later diagnosed as a simple bone cyst through surgical exploration. The three-dimensional CT volume rendering reconstructed image showed that the second lesion, located on the lingual aspect of the ascending ramus, was an actual cortical bone defect, which was diagnosed as a mandibular ramus-related Stafne's bone cavity. Considering the young age of the patient, the size of the defect, the recognizedly slow development of mandibular bone defects and, above all, the location of the bone defect under discussion, we believe it to have a congenital rather than a developmental origin (i.e. it was caused by a focal failure during intramembranous ossification of the mandible). If this is the case, mandibular bone depressions should not be seen exclusively as salivary gland-related bone defects.

Adolescent↗

PubMed2004

Evaluation of biochemical and serological methods to identify and clustering yeast cells of oral Candida species by CHROMagar test, SDS-PAGE and ELISA.

The purpose of this work was to evaluate biochemical and serological methods to characterize and identify Candida species from the oral cavity. The strains used were five Candida species previously identified: C. albicans, C. guilliermondii, C. parapsilosis, C. krusei, C. tropicalis, and Kluyveromyces marxianus, as a negative control. The analyses were conducted through the SDS-PAGE associated with statistical analysis using software, chromogenic medium, and CHROMagar Candida (CA), as a differential medium for the isolation and presumptive identification of clinically important yeasts and an enzyme-linked immunoabsorbent assay (ELISA), using antisera produced against antigens from two C. albicans strains. This method enabled the screening of the three Candida species: C. albicans, C. tropicalis, and C. krusei, with 100% of specificity. The ELISA using purified immunoglobulin G showed a high level of cross-reaction against protein extracts of Candida species. The SDS-PAGE method allowed the clustering of species-specific isolates using the Simple Matching coefficient, S(SM) = 1.0. The protein profile analysis by SDS-PAGE increases what is known about the taxonomic relationships among oral yeasts. This methodology showed good reproducibility and allows collection of useful information for numerical analysis on information relevant to clinical application, and epidemiological and systematical studies.

Animals↗

PubMed2003

Isolation of the bifunctional enzyme lysine 2-oxoglutarate reductase-saccharopine dehydrogenase from Phaseolus vulgaris.

Lysine is catabolyzed by the bifunctional enzyme lysine 2-oxoglutarate reductase-saccharopine dehydrogenase (LOR-SDH) in both animals and plants. LOR condenses lysine and 2-oxoglutarate into saccharopine, using NADPH as cofactor and SDH converts saccharopine into alpha-aminoadipate delta-semialdehyde and glutamic acid, using NAD as cofactor. The distribution pattern of LOR and SDH among different tissues of Phaseolus vulgaris was determined. The hypocotyl contained the highest specific activity, whereas in seeds the activities of LOR and SDH were below the limit of detection. Precipitation of hypocotyl proteins with increasing concentrations of PEG 8000 revealed one broad peak of SDH activity, indicating that two isoforms may be present, a bifunctional LOR-SDH and possibly a monofunctional SDH. During the purification of the hypocotyl enzyme, the LOR activity proved to be very unstable, following ion-exchange chromatography. Depending on the purification procedure, the protein eluted as a monomer of 91-94 kDa containing only SDH activity, or as a dimer of 190 kDa with both, LOR and SDH activities, eluting together.

Molecular Weight↗

PubMed2002

Analysis of the aspartic acid metabolic pathway using mutant genes.

Amino acid metabolism is a fundamental process for plant growth and development. Although a considerable amount of information is available, little is known about the genetic control of enzymatic steps or regulation of several pathways. Much of the information about biochemical pathways has arisen from the use of mutants lacking key enzymes. Although mutants were largely used already in the 60's, by bacterial and fungal geneticists, it took plant research a long time to catch up. The advance in this area was rapid in the 80's, which was followed in the 90's by the development of techniques of plant transformation. In this review we present an overview of the aspartic acid metabolic pathway, the key regulatory enzymes and the mutants and transgenic plants produced for lysine and threonine metabolism. We also discuss and propose a new study of high-lysine mutants.

Aspartate Kinase↗

PubMed2001

Lysine metabolism in higher plants.

The essential amino acid lysine is synthesised in higher plants via a pathway starting with aspartate, that also leads to the formation of threonine, methionine and isoleucine. Enzyme kinetic studies and the analysis of mutants and transgenic plants that overaccumulate lysine, have indicated that the major site of the regulation of lysine synthesis is at the enzyme dihydrodipicolinate synthase. Despite this tight regulation, there is strong evidence that lysine is also subject to catabolism in plants, specifically in the seed. The two enzymes involved in lysine breakdown, lysine 2-oxoglutarate reductase (also known as lysine a-ketoglutarate reductase) and saccharopine dehydrogenase exist as a single bifunctional protein, with the former activity being regulated by lysine availability, calcium and phosphorylation/ dephosphorylation.

Lysine↗

PubMed2001

Antioxidant enzymes responses to cadmium in radish tissues.

To investigate the antioxidant responses of radish (Raphanus sativus L.) to cadmium (Cd) treatment, seedlings of a tolerant variety were grown in increasing concentrations of CdCl(2), ranging from 0.25-1 mM, for up to 72 h in a hydroponic system. Analysis of Cd uptake indicated that most of the Cd accumulated in the roots, but some was also translocated and accumulated in the leaves, especially at the higher concentrations of Cd used in the experiments. Roots and leaves were analysed for catalase, glutathione reductase and superoxide dismutase activities. Catalase and glutathione reductase activities increased considerably in the roots and leaves after 24 h exposure to the metal, indicating a direct correlation with Cd accumulation. The analysis of native PAGE enzyme activity staining, revealed several superoxide dismutase isoenzymes in leaves, with the two predominant isoenzymes exhibiting increases in activity in response to Cd treatment. The results suggest that in radish, the activity of antioxidant enzymes responds to Cd treatment. The main response may be via the activation of the ascorbate-glutathione cycle for the removal of hydrogen peroxide, or to ensure the availability of glutathione for the synthesis of Cd-binding proteins.

Brassica↗

PubMed1999

Quality protein maize: a biochemical study of enzymes involved in lysine metabolism.

Quality protein maize (QPM) varieties have been produced by the introduction of opaque-2 modifier genes. Two QPM varieties, BR451 and BR473, a wild type and an opaque-2 variety, have been used to study key enzymes controlling lysine metabolism in the endosperm during development. Aspartate kinase and homoserine dehydrogenase enzymes, which are involved in lysine and threonine biosynthesis, respectively, exhibited identical activity patterns during endosperm development, with a maximum specific activity at 16 days after pollination. The QPM varieties exhibited higher levels of aspartate kinase activity in the endosperm, suggesting an increased rate of lysine biosynthesis when compared to the opaque-2 and wild-type genotypes. Similar results were observed for the lysine ketoglutarate reductase and saccharopine dehydrogenase enzymes, which form a single bifunctional polypetide involved in endosperm lysine degradation. Both enzyme activities were strongly reduced in the opaque-2 maize variety when compared to the wild-type maize, whereas the QPM varieties exhibited even lower levels of lysine ketoglutarate reductase-saccharopine dehydrogenase activities when compared to the opaque-2 variety. The developmental pattern of enzyme activity showed a different profile when compared to the enzymes involved in lysine biosynthesis, with activity being detected only 12-16 days after pollination (DAP) and maximum activities approximately 24 DAP. These results also suggest that the modifier genes have intensified the effect of the opaque-2 mutation on lysine ketoglutarate reductase-saccharopine dehydrogenase. These alterations lead to an increase in soluble lysine in the endosperm of the QPM varieties when compared to the opaque-2 and wild type.

Aspartate Kinase↗

PubMed1998

Structure and regulation of the bifunctional enzyme lysine-oxoglutarate reductase-saccharopine dehydrogenase in maize.

The lysine-oxoglutarate reductase (LOR) domain of the bifunctional enzyme lysine-oxoglutarate reductase-saccharopine dehydrogenase (LOR/SDH) from maize endosperm was shown to be activated by Ca2+, high salt concentration, organic solvents and Mg2+. The Ca2+-dependent enhancement of LOR activity was inhibited by the calmodulin antagonists N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7) and calmidazolium. Limited proteolysis was used to assess the structure/function relationship of the enzyme. Digestion with elastase separated the bifunctional 125-kDa polypeptide into two polypeptides of 65 kDa and 57 kDa, containing the functional domains of LOR and SDH, respectively. Proteolysis did not affect SDH activity, while LOR showed a time-dependent and protease-concentration-dependent inactivation followed by reactivation. Prolonged digestion or increasing amounts of elastase produced a complex pattern of limit polypeptides derived from additional cleavage sites within the 65-kDa (LOR) and 57-kDa (SDH) domains. The SDH-containing polypeptides inhibited the enzymatic activity of LOR-containing polypeptides. When separated from the SDH domain by limited proteolysis and ion-exchange chromatography, the LOR domain retained its Ca2+ activation property, but was no longer activated by high salt concentrations. These results suggest that the LOR activity of the native enzyme is normally inhibited such that after modulation, the enzyme undergoes a conformational alteration to expose the catalytic domain for substrate binding.

Calcium↗

PubMed1997

The enzymology of lysine catabolism in rice seeds--isolation, characterization, and regulatory properties of a lysine 2-oxoglutarate reductase/saccharopine dehydrogenase bifunctional polypeptide.

In plant, the catabolism of lysine has only been studied in some detail in maize. The enzymes lysine 2-oxoglutarate reductase (also known as lysine alpha-ketoglutarate reductase; LOR) and saccharopine dehydrogenase (SDH), which convert lysine into saccharopine, and saccharopine into glutamic acid and 2-aminoadipate 6-semialdehyde, respectively, were isolated from immature rice seeds and partially purified through a three-step purification procedure involving ammonium sulphate precipitation, and anion-exchange and gel-filtration chromatographies, leading to a final yield of 30% for LOR and 24% for SDH. The molecular masses estimated by gel-filtration chromatography on a Sephacryl S200 column and by native non-denaturing PAGE using Ferguson plots were 203 kDa for both enzymes by gel-filtration and 202 kDa for both enzymes by native non-denaturing PAGE. A second band of LOR and SDH activities on native gels was observed for both enzymes with an estimated molecular mass of 396 kDa, which indicated a multimeric structure. Kinetic studies were consistent with an ordered sequence mechanism for LOR, where 2-oxoglutarate is the first substrate and saccharopine is the last product. The results observed for the LOR/SDH activity ratios during purification, the copurification in all three steps, the molecular masses, the relative mobilities on native non-denaturing gels and the pI estimated for LOR and SDH suggest the existence of a bifunctional polypeptide containing LOR and SDH activities.

Kinetics↗

PubMed1997

The biosynthesis and metabolism of the aspartate derived amino acids in higher plants.

The essential amino acids lysine, threonine, methionine and isoleucine are synthesised in higher plants via a common pathway starting with aspartate. The regulation of the pathway is discussed in detail, and the properties of the key enzymes described. Recent data obtained from studies of regulation at the gene level and information derived from mutant and transgenic plants are also discussed. The herbicide target enzyme acetohydroxyacid synthase involved in the synthesis of the branched chain amino acids is reviewed.

Amino Acids↗

PubMed1994

Clinical evaluation of luteal function.

OBJECTIVE: To determine the ability of luteal phase length determined by basal body temperature (BBT) pattern and a midluteal serum progesterone level to predict the result of an endometrial biopsy in a subsequent cycle. METHODS: We performed a retrospective analysis of 141 women with a history of infertility who were being evaluated for luteal function. The luteal phase length determined from a BBT chart of one menstrual cycle was compared to a single midluteal serum progesterone level from a second menstrual cycle. These findings were compared to a luteal phase endometrial biopsy performed in a third menstrual cycle. Subjects were divided into four groups depending upon luteal phase length (normal 11 or more days) and serum progesterone level (normal at least 10 ng/mL). The four groups were designated "normal," "short luteal phase," "low progesterone," and "abnormal," depending upon the results of the two tests. The frequency of in- and out-of-phase endometrial biopsy results in the four groups was compared. RESULTS: There was no difference in the occurrence of an in- or out-of-phase endometrial biopsy when the four groups were compared. CONCLUSION: Neither luteal phase length nor a single midluteal serum progesterone level was predictive of subsequent in-phase or out-of-phase endometrial biopsy.

Adult↗

PubMed1988

Lanthanum nitrate labelling of the outer cell wall surface of phagocytized Paracoccidioides loboi in human lobomycosis.

Lesioned skin tissues from a female Caiabi indian with lobomycosis were processed for routine electron microscopy using, in the initial steps, solutions containing 2% lanthanum nitrate. The pattern of tracer distribution suggests that the tracer penetrates into the cavity containing the parasite through exocytotic-like apertures situated at the cell wall outer region. The tracer also infiltrates the virtual space between the cell wall and its recovering membrane, spreading over varying areas of the outer surface of the cell wall. The contrast imparted to the pericellular macrophage space by the lanthanum nitrate enabled easy localization of fibrillar, cell wall derived material which reaches the adjacent extracellular milieu.

Adult↗