PubMed Health⌕ Search

Biomedical subjects

A C Vasconcelos

Publications and source records attributed to A C Vasconcelos.

At least 19 recordsLinked to original sources
PubMed2006

Cellular proliferation, differentiation and apoptosis in polyether-polyurethane sponge implant model in mice.

The integration of implanted material to host organism requires spatial and temporal organization of several cellular processes, such as proliferation, differentiation and apoptosis. Despite the clinical relevance of these processes, there is little information regarding the sequence of such events in synthetic matrices. Here, we present a combination of techniques used to characterize the fibrovascular response in subcutaneous polyether-polyurethane sponge implants in mice at days 4, 7, 10 and 14 postimplantation. The AgNOR technique was modified and used as a surrogate marker for proliferating and activated cells invading the implant. The number of AgNOR-stained cells increased progressively from day 4 (606+/-76) to day 14 (2146+/-71) postimplantation. The number of TUNEL-positive (apoptotic index) cells also increased progressively from day 4 (459+/-40) to day 14 (1157+/-119) postimplantation. However, the ratio of TUNEL-labeled/proliferating cells had its highest peak in the early phase of the process remaining stable until day 14. Using Picrosirius staining it was shown that thin collagen increased from day 4, peaking at day 10 and falling markedly at day 14, whereas dense collagen increased progressively during the whole period. These experiments hold potential to investigate not only distinct phases of tissue repair induced by synthetic matrices but also to study underlying mechanisms involved.

Animals↗
PubMed2003

Apoptosis in canine distemper.

Canine distemper is a systemic viral disease characterized by immunosuppression followed by secondary infections. Apoptosis is observed in several immunosuppressive diseases and its occurrence on canine distemper in vivo has not been published. In this study, the occurrence of apoptosis was determined in lymphoid tissues of thirteen naturally infected dogs and nine experimentally inoculated puppies. Healthy dogs were used as negative controls. Samples of lymph nodes, thymus, spleen and brain were collected for histopathological purposes. Sections, 5 microm thick, of retropharingeal lymph nodes were stained by HE, Shorr, Methyl Green-Pyronin and TUNEL reaction. Shorr stained sections were further evaluated by morphometry. Canine distemper virus nucleoprotein was detected by immunohistochemistry. Retropharingeal lymph nodes of naturally and experimentally infected dogs had more apoptotic cells per field than controls. In addition, DNA from thymus of infected dogs were more fragmented than controls. Therefore, apoptosis is increased in lymphoid depletion induced by canine distemper virus and consequently play a role in the immunosuppression seen in this disease.

Animals↗
PubMed2003

Apoptosis in the cerebellum of dogs with distemper.

Canine distemper virus (CDV) may induce multifocal demyelination in the central nervous system of infected dogs. The pathogenesis of this process is not clear. The present work identifies the presence of apoptotic cells in white and grey matter of dogs'cerebellum, naturally infected with CDV. Fifteen dogs with clinical signs of canine distemper that tested positive for CDV nucleoprotein were used. Brain specimens were processed and embedded in paraffin. Sections 5 microm thick were stained with hematoxylin-eosin and Shorr. Other sections were submitted to TUNEL reaction and to immunohistochemistry for CDV nucleoprotein detection. Acute and chronic demyelinated plaques were observed in the white matter, while apoptosis occurred particularly in the granular layer of grey matter. Apoptosis seems to play an important role in the pathogenesis of canine distemper demyelination.

Animals↗
PubMed1999

Effect of growth hormone and induced IGF-I release on germ cell population and apoptosis in the bovine testis.

Bovine growth hormone has been used in dairy cattle to increase milk production,but it also increases the twin parturition rate. This effect is mediated by insulin-like growth factor-I (IGF-I), which prevents follicular atresia by hindering apoptosis of granulosa cells. The action of GH and IGF-I on testicular function remains unclear. The goal of this study, therefore, was to verify the effects of short-term administration of GH and induced IGF-I release on the number of testicular germ cells, testicular morphology, and apoptosis in the bovine testis. Twenty Zebu bulls were split into 2 groups. The bulls in Group 1 (n = 10) were treated with 2 subcutaneous injections of bovine GH (500 mg/bull) 7 d apart. Group 2 bulls (n = 10) received placebos under the same protocol. All of the bulls were slaughtered 14 d after the start of treatment. Fragments of the testis were collected, fixed in Bouin's solution, embedded in paraffin, and the sections stained with hematoxilin and eosin. The paraffin-embedded sections were also used for in situ detection of apoptotic cells. Blood samples were collected at slaughter to measure serum levels of IGF-I, FSH and LH. Neither the number of Stage I seminiferous epithelium germ cells and the morphometric parameters (tubular diameter, seminiferous epithelium height, and volumetric proportions of structural components) nor the blood levels of FSH and LH showed a significant difference between the 2 groups. However, the treated animals showed an increase in serum IGF-I (P<0.01). Apoptotic germ cells were detected in the testis of both groups, showing the same pattern and a stage-specific apoptosis pattern. Most of the labeled cells were spermatocytes. The localization of apoptotic germ cells did not differ between groups. These results suggest that short-term administration of GH does not affect bovine spermatogenesis in adult bulls.

Animals↗
PubMed1998

Spinach cytosolic fructose-1,6-bisphosphatase: I. Its organ-specific and developmental expression characteristics.

Spinach (Spinacia oleracea) cytosolic fructose-1,6-bisphosphatase (FBPase) was purified and the final preparation of protein has a specific activity of about 45 units/mg protein and a single band of molecular mass of 39 kDa. Polyclonal antibody against the protein did not cross-react with chloroplast FBPase, but showed strong cross-reactivity with all plant cytosolic FBPases tested. Studies of the FBPase expression characteristics at early stages of development demonstrated that it was controlled at both the transcriptional and translational levels, and its mRNA was detected even in etiolated cotyledons. This suggests that the expression is not light-inducible. A single transcript was detected in all spinach tissues tested. Western blot analysis revealed two protein bands in the etiolated cotyledons: one was the same size as that present in the mature leaf, and the other slightly smaller. A high enzyme activity was detected in etiolated cotyledons, especially compared to protein levels in Western blots. Expression of the cytosolic FBPase gene during leaf development showed no change in the steady-state level of mRNA, but the protein level and enzyme activity were higher in mature leaves than in young ones, suggesting that the increase in FBPase activity during development is due to an increase in protein synthesis. Young roots showed low enzyme activity, but an unexpectedly high activity was detected in old fiber roots.

Antibodies↗
PubMed1998

Spinach cytosolic fructose-1,6-bisphosphatase: II. Light effect on its expression.

The effect of light on the expression of spinach (Spinacia oleracea) cytosolic fructose-1,6-bisphosphatase (FBPase) was determined by the level of mRNA, protein content, and enzyme activity. It was found that its expression and activity were constant and stable during normal daily conditions as well as under continuous light or dark conditions. However, two different mRNAs were detected; one transcript was expressed all the time, while the other was detected only during prolonged dark periods. Analysis of the expression of the mRNAs at the protein level using an activity gel showed that this "darkness-specific" mRNA encoded a separate, distinct polypeptide. Thus, our data suggest that cytosolic FBPase is encoded by a small multigene family.

Blotting, Southern↗
PubMed1998

[Comparison of methods to test the "in vitro" cytotoxicity of biocompatible materials].

OBJECTIVE: A comparison of the sensitivity of the agar diffusion method with that of extraction using cell-lines RC-IAL (fibroblastic of rabbit kidney) and HeLa (epithelial carcinoma cells from the cervix uteri of the human uterus), in the in vitro evaluation of materials of medical and hospital. MATERIALS AND METHODS: Fifteen samples chosen at random, from among the already known positives and negatives in our stock, were tested and identified as cotton, form, latex, cellulose and acrylic. Besides the samples mentioned, many SDS (GIbco) concentrations were tested experimentally in RC-IAL and HeLa cell cultures. RESULTS: Of the 50 samples tested, 44(88%) were positive by both methods. However, when the SDS were compared by using the two methods, positive results were noted in the concentrations of from 0.5 to 0.05 microgram/ml in the agar diffusion ans extraction methods. A cytotoxic effect was only noted in the concentrations of up to 0.25 microgram/ml. CONCLUSION: When the SDS was used, differences favorable to the agar diffusion method were observed in the two cell lines, in two concentrations; that is, the sensitivity of this method was quantitatively greater on inspection than that of the extraction method, as well as being the simpler method to use.

Animals↗
PubMed1996

Physical association of KAB1 with plant K+ channel alpha subunits.

K+ channel proteins contain four alpha subunits that align along a central axis perpendicular to membranes and form an ion-conducting pore. Recent work with K+ channels native to animal membranes has shown that at least some members of this protein family also have four beta subunits. These structural components of the holoenzyme each form tight associations with the cytoplasmic portion of an alpha subunit. We have cloned an Arabidopsis cDNA (KAB1) that encodes a polypeptide sharing 49% amino acid identity with animal K+ channel beta subunits. In this study, we provide experimental evidence that the KAB1 polypeptide forms a tight physical association with the Arabidopsis K+ channel alpha subunit, KAT1. An affinity-purified KAB1 fusion protein was immobilized to a support resin and shown to sequester selectively the KAT1 polypeptide. In addition, polyclonal antibodies raised against KAB1 were shown to immunoprecipitate the KAT1 polypeptide as a KAT1-KAB1 protein complex. Immunoblot analysis demonstrated that KAB1 is expressed in Arabidopsis seedings and is present in both membrane and soluble protein fractions. The presence of KAB1 (a soluble polypeptide) in both soluble and membrane protein fractions suggests that a portion of the total amount of native KAB1 is associated with an integral membrane protein, such as KAT1. The presence of KAB1 in crude protein fractions prepared from different Arabidopsis plant organs was evaluated. High levels of KAB1 protein were present in flowers, roots, and leaves. Immunoblot analysis of protein extracts prepared from broad bean leaves indicated that the KAB1 expression level was 80-fold greater in guard cells than in mesophyll cells. Previous studies of the in situ transcription pattern of KAT1 in Arabidopsis indicated that this alpha subunit is abundantly present in leaves and, within the leaf, exclusively present in guard cells. Thus, KAB1 was determined to be expressed in plant organs (leaves) and cell types (guard cells) that are sites of KAT1 expression in the plant. The in situ expression pattern of KAB1 suggests that it may associate with more than one type of K+ channel alpha subunit. Sequence analysis indicates that KAB1 may function in plant K+ channels as an oxidoreductase. It is postulated that beta subunits native to animal K+ channels act as regulatory subunits through pyridine nucleotide-linked reduction of alpha polypeptides. Although the KAB1 primary structure is substantially different from that of animal beta subunits, amino acid motifs critical for this catalytic activity are retained in the plant beta subunit.

Amino Acid Sequence↗
PubMed1995

Apoptosis as a cause of death in chicken embryos inoculated with Newcastle disease virus.

Eleven-day-old chicken embryos were inoculated by the allantoic route with the GB strain of Newcastle disease virus (NDV). At 0, 24, 36 and 42 h post-inoculation (p.i.), the brain and heart tissues were harvested for DNA extraction, and the thymus and the brain were fixed and processed for light and electron microscopy. At 42 h p.i., most of the embryos had died; however, no histopathological changes could be seen in the embryos at any stage of infection. DNA extracted from the brain cells started showing fragmentation at 24 h p.i., and from the heart muscle cells at 36 h p.i. Electron microscopy of the brain and thymus showed condensation of the nuclear chromatin, apoptotic bodies, various forms of crescent formation and some evidence of necrosis. Fragmentation of cellular DNA, crescent formation and apoptotic bodies are the typical signs of cells undergoing apoptosis. We suggest that apoptosis of the heart and brain is probably a cause of death of chicken embryos in acute Newcastle disease infection.

Animals↗
PubMed1995

Apoptosis in chicken embryos induced by the infectious bursal disease virus.

Fifteen-day-old fertile eggs (specific pathogen-free) were inoculated with the infectious bursal disease virus (IBDV) by the allantoic route and were opened and examined 2, 4 or 6 days later. The bursas of Fabricius (BFs) were collected and processed for DNA extraction, flow cytometry, and light and electron microscopy. Cellular DNA was subjected to electrophoresis on 1.5% agarose gel and stained with ethidium bromide. Intense internucleosomal DNA fragmentation was detected in IBDV-infected bursas. Cytograms from cell suspensions derived from infected BFs displayed an increased population of cells with either high density and small size (apoptotic cells) or small size and high uptake of ethidium bromide (necrotic cells). Light and electron microscopical examination of the IBDV-infected BFs revealed death of lymphoid cells without surrounding inflammatory reaction, but with condensation of nuclear chromatin, crescent formation, and nuclear and cellular fragmentation. These data indicated that infection of chicken embryos with IBDV induced apoptosis in bursal lymphoid cells.

Animals↗
PubMed1995

Evidence that plant K+ channel proteins have two different types of subunits.

Plant K+ channel proteins have been previously characterized as tetramers of membrane-spanning alpha subunit polypeptides. Recent studies have identified a 39-kD, hydrophilic polypeptide that is a structural component of purified animal K+ channel proteins. We have cloned and sequenced an Arabidopsis thaliana cDNA encoding a 38.4-kD polypeptide that has a sequence homologous to the animal K+ channel beta subunit. Southern and northern analyses indicate the presence of a gene encoding this cDNA in the Arabidopsis genome and that its transcription product is present in Arabidopsis cells. To our knowledge, this is the first report to document the presence of K+ channel beta subunits in plants.

Amino Acid Sequence↗
PubMed1994

Newcastle disease virus-induced apoptosis in chicken peripheral blood lymphocytes.

Chicken peripheral blood lymphocytes (PBL) were infected with the GB strain of Newcastle disease virus (NDV). At 0, 1.5 and 3 h postinfection, PBL were stained with acridine orange-ethidium bromide and examined for apoptotic and necrotic indices under a UV microscope. At the end of 3 h, the cells were pelleted and were either fixed for electron microscopy or used for DNA extraction. Infected cells showed a significant amount of apoptosis and necrosis when compared with controls. Electron microscopy of the infected cells also showed characteristics of apoptosis, i.e. apoptotic bodies, margination of chromatin with crescent formation and fusion of cells. DNA extracted from virus-infected cells showed extensive fragmentation. Based on these findings it is concluded that NDV, in addition to causing necrosis in chicken lymphocytes, can induce apoptosis.

Acridine Orange↗
PubMed1994

Apoptosis induced by infectious bursal disease virus.

Chicken peripheral blood lymphocytes (PBLs) show morphological and biochemical features of apoptosis (programmed cell death) when infected in vitro with infectious bursal disease virus (IBDV). DNA extracted from IBDV-infected lymphocytes displayed an intense laddering pattern when visualized after agarose gel electrophoresis. IBDV-infected PBLs had significantly higher apoptotic and necrotic indices measured by acridine orange-ethidium bromide staining than did control lymphocytes. Electron micrographs of the IBDV-infected PBLs revealed features typical of apoptosis such as peripheral condensation of chromatin, blebbing of the plasma membrane and fragmentation of the nucleus and of the cell leading to the formation of apoptotic bodies. These findings indicate that IBDV, in addition to causing necrosis, can also induce apoptosis in avian lymphocytes in vitro.

Animals↗
PubMed1989

The transit peptide of a chloroplast thylakoid membrane protein is functionally equivalent to a stromal-targeting sequence.

The role of transit peptides in intraorganellar targeting has been studied for a chlorophyll a/b binding (CAB) polypeptide of photosystem II (PSII) and the small subunit of ribulose-1,5-bisphosphate carboxylase (RBCS) from Pisum sativum (pea). These studies have involved in vitro import of fusion proteins into isolated pea chloroplasts. Fusion of the CAB transit peptide to RBCS mediates import to the stroma, as evidenced by assembly of RBCS with chloroplast-synthesized large subunit (RBCL) to form holoenzyme. Similarly, fusion of the RBCS transit peptide to the mature CAB polypeptide mediates import and results in integration of the processed CAB protein into the thylakoid membrane. Correct integration was indicated by association with PSII and assembly with chlorophyll to form the light-harvesting chlorophyll a/b protein complex (LHCII). We interpret these results as evidence that the CAB transit peptide is functionally equivalent to a stromal-targeting sequence and that intraorganellar sorting of the CAB protein must be determined by sequences residing within the mature protein. Our results and those of others suggest that import and integration of CAB polypeptides into the thylakoid proceeds via the stroma.

Biological Transport↗
PubMed1989

Isolation of a cDNA encoding mitochondrial citrate synthase from Arabidopsis thaliana.

We isolated a cDNA clone from Arabidopsis thaliana encoding the TCA cycle enzyme, citrate synthase. The plant enzyme displays 48% and 44% amino acid residue similarity with the pig, and yeast polypeptides, respectively. Many proteins, including citrate synthase, which are destined to reside in organelles such as mitochondria and chloroplasts, are the products of the nucleocytoplasmic protein synthesizing machinery and are imported post-translationally to the site of function. We present preliminary investigations toward the establishment of an in vitro plant mitochondrial import system allowing for future studies to dissect this process in plants where the cell must differentiate between mitochondria and chloroplast and direct their polypeptides appropriately.

Amino Acid Sequence↗
PubMed1989

Purification and characterization of mitochondrial citrate synthase.

Mitochondrial citrate synthase was purified from leaves of Pisum sativum L. cv Progress 9. A three step purification was employed using ATP-Sepharose affinity chromatography which resulted in a 600-fold enrichment. Enzyme activity was assayed spectrophotometrically during greening of etiolated leaves under constant white light illumination. An increase (1.4 fold) in citrate synthase activity was observed in response to light. Immunoblot analysis of the same samples indicated a constant steady state level of citrate synthase on a per milligram protein basis. These investigations provide supportive evidence for the ability of this trichloroacetic acid cycle enzyme to be active in photosynthesizing tissue.

Journal Article↗
PubMed1982

Leaf water potential, stomatal resistance, and photosynthetic response to water stress in peach seedlings.

Individual groups of peach (Prunus persica [L.] Batsch) seedlings stressed to -17, -26 and -36 bars recovered to control levels within 1, 3, and 4 days, respectively. Stomatal resistance was significantly correlated with both leaf water potential and net photosynthesis. In seedlings stressed to -52 bars, leaf water potential and stomatal resistance recovered sooner than net photosynthesis, despite recovery of 0(2) evolution at a rate similar to leaf water potential. Therefore, some nonstomatal factor other than reduction in photochemical activity must be responsible for the lag in recovery of CO(2) assimilation following irrigation.

Journal Article↗