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Biomedical subjects

P Vera

Publications and source records attributed to P Vera.

At least 55 records · Page 3Linked to original sources
PubMed1994

Dynamic study of insole materials simulating real loads.

A new methodology of biomechanical analysis of materials for shoe inserts is presented. This methodology is based on the determination of the loads applied to the materials in real situations and its simulation by means of a dynamic testing machine. Both the rigidity and the energy-absorbing characteristics of the materials are investigated as a function of frequency. This methodology is applied to the study of several commercially available viscoelastic materials intended for shoe inserts in the treatment and prevention of degenerative joint diseases. The influence of thickness is investigated as well as the frequency-dependent behavior of the materials studied. Significant differences between materials and different behavior as a function of thickness and frequency were found. Poron materials were found to have the lowest rigidity, good for adequate pressure distribution, while Noene showed the highest energy absorption. A careful selection of the thickness of Sorbothane was found to be necessary for avoiding flattening of the material.

Adult↗
PubMed1993

cDNA cloning of viroid-induced tomato pathogenesis-related protein P23. Characterization as a vacuolar antifungal factor.

A 23-kD pathogenesis-related protein (P23) is induced in tomato (Lycopersicon esculentum Mill, cv Rutgers) plants when infected with citrus exocortis viroid. This protein is homologous to the salt-induced tomato NP24 protein (I. Rodrigo, P. Vera, R. Frank, V. Conejero [1991] Plant Mol Biol 16: 931-934). Further characterization of P23 has shown that this protein accumulates in vacuoles in association with dense inclusion bodies. In vitro assays indicated that the purified P23 protein inhibits the growth of several phytopathogenic fungi. P23-coding cDNA clones were isolated from viroid-induced and ethylene-induced libraries. Southern analysis showed that at least two genes could encode P23 or P23-related products. The accumulation of P23 protein correlated with the accumulation of its mRNA. Sequence analysis revealed significant differences in both coding and downstream untranslated regions between the cDNA sequences corresponding to the viroid-induced P23 and the salt stress-induced NP24 proteins.

Amino Acid Sequence↗
PubMed1993

Design and development of a new general purpose stereotaxic device.

This paper describes the design and development of a new device which allows the surgeon to locate an internal point following two X-ray views with an image intensifier. Three dimensional coordinates of the target point are directly estimated by means of two ring-and-bead sights and no computer calculations are necessary. After the location of the target point it is possible to choose any track to it by means of the rotation of an arc and the circumferential sliding of the arc. The system reduces radiation doses and it can be used for many purposes such as percutaneous discectomies and chemonucleolysis, biopsies and screw insertion of interlocking nails.

Bias↗
PubMed1992

Biomechanical consequences of callus development in Hoffmann, Wagner, Orthofix and Ilizarov external fixators.

A theoretical analysis by a finite elements model (FEM) of some external fixators (Hoffmann, Wagner, Orthofix and Ilizarov) was carried out. This study considered a logarithmic progress of callus elastic characteristics. A standard configuration of each fixator was defined where design and application characteristics were modified. A comparison among standard configurations and influence of every variation was made with regard to displacement and load transmission at the fracture site. An experimental evaluation of standard configurations was performed with a testing machine. After experimental validation of the theoretical model was achieved, an application of physiological loads which act on a fractured limb during normal gait was analysed. A minimal contribution from an external fixator to the total rigidity of the bone-callus-fixator system was assessed when a callus showing minimum elastic characteristics had just been established. Insufficient rigidity from the fixation devices to assure an adequate immobilization during the early stages of fracture healing was verified. However, regardless of the external fixator, callus development was the overriding element for the rigidity of the fixator-bone system.

Biomechanical Phenomena↗
PubMed1991

Identification of the viroid-induced tomato pathogenesis-related (PR) protein P23 as the thaumatin-like tomato protein NP24 associated with osmotic stress.

P23, a 23 kDa pathogenesis-related (PR) protein, was purified from citrus exocortis viroid (CEVd)-infected tomato leaves. Partial amino acid sequencing of this protein including the N-terminal and nine additional tryptic fragments covering about 50% of its primary structure revealed extensive homologies to the members of the family of plant thaumatin-like proteins. Sequence alignment revealed that tomato P23 is the previously described NP24 protein found to be associated to osmotic stress in tomato. In view of this fact the possible role of pathogenesis-related P23 protein as a component of a general mechanism of response of the plant is discussed.

Amino Acid Sequence↗
PubMed1991

Degradation of tobacco pathogenesis-related proteins : evidence for conserved mechanisms of degradation of pathogenesis-related proteins in plants.

Tobacco (Nicotiana tabacum L.) leaves were found to contain an extracellular proteinase that endoproteolytically cleaves tobacco pathogenesis-related (PR) proteins. This proteinase was partially purified from tobacco leaves and characterized as an aspartyl proteinase with a pH optimum around pH 3 and a molecular mass of 36,000 to 40,000 daltons. In vitro, the enzyme cleaved purified tobacco and tomato PR proteins into discrete fragments. The characteristics of this proteinase were similar to pepsin and identical to those displayed by a previously described tomato 37-kilodalton aspartyl proteinase active against tomato PR proteins (I Rodrigo, P Vera, V Conejero [1989] Eur J Biochem 184: 663-669), suggesting that these extracellular proteases could play a role in a conserved mechanism for PR protein turnover in plants.

Journal Article↗
PubMed1990

Effect of Ethephon on Protein Degradation and the Accumulation of ;Pathogenesis-Related' (PR) Proteins in Tomato Leaf Discs.

The effect of ethephon (2-chloroetylphosphonic acid) on the degradation of proteins and on the induction of Lycopersicon esculentum pathogenesis-related (PR) proteins was studied in tomato leaf discs. The rate of ribulose, -1,5-bisphosphate carboxylase/oxygenase (Rubisco) degradation was maximal in discs after 48 hours of incubation with 1 millimolar ethephon, leading to complete disappearance of Rubisco after 96 hours. This effect was correlated with an increase in PR protein synthesis and the induction of the previously reported alkaline proteolytic enzyme PR-P69 (P Vera, V Conejero [1988] Plant Physiol 87: 58-63). In vivo pulse-chase experiments demonstrated that ethephon not only affected Rubisco content but that of many other (35)S-labeled proteins as well, indicating that ethylene activates a general and nonspecific mechanism of protein degradation. This effect was partially inhibited in vivo by the action of pCMB, a selective inhibitor of cysteine-proteinases such as P69. These data reinforce the hypothesis that P69 and perhaps other PR proteins are involved in the mechanism of accelerated protein degradation activated by ethylene.

Journal Article↗
PubMed1989

Degradation of tomato pathogenesis-related proteins by an endogenous 37-kDa aspartyl endoproteinase.

As a response to the stress induced by different afflicting agents, tomato plants (Lycopersicon esculentum) produce the so-called 'pathogenesis-related' proteins. Here we report the degradation of some of these proteins by a constitutive endoproteolytic activity that co-distributes with pathogenesis-related proteins in the intercellular spaces of tomato leaves infected with citrus exocortis viroid. This endoproteinase was purified, showing a pH optimum of 2.5-3.5, a Mr of 37,000 and selective inhibition by pepstatin. In crude homogenates, the enzyme does not seem to degrade other cellular proteins. This specificity indicates that the proteinase might be involved in the extracellular degradative pathway of pathogenesis-related proteins and in the regulation of their biological function.

Aspartic Acid Endopeptidases↗
PubMed1989

Immunogold localization of the citrus exocortis viroid-induced pathogenesis-related proteinase p69 in tomato leaves.

Citrus exocortis viroid induces in tomato plants (Lycopersicon esculentum) synthesis and accumulation of a pathogenesis-related protein (P69) previously reported to be a proteinase (Vera P, Conejero V [1988] Plant Physiol 87: 58-63). By immunogold/transmission electron microscopy, we have studied the distribution of this protein in thin sections of parenchymatous leaf tissue. The enzyme was present intra- and extracellularly. The intracellular location was limited to the vacuole and was always associated with engulfed cell material. When extracellularly located, the enzyme was associated with a dispersed, electron-dense material in the intercellular spaces. This latter location was confirmed after analysis of intercellular washing fluids obtained by vacuum infiltration of leaves. These observations provide new data for the understanding of viroid pathogenesis and the biological role of the pathogenesis-related proteinase P69.

Journal Article↗
PubMed1988

Pathogenesis-related proteins of tomato : p-69 as an alkaline endoproteinase.

An endoproteinase induced by citrus exocortis viroid has been purified from tomato (Lycopersicon esculentum Mill, cv "Rutgers") leaves. The proteinase corresponds to one of the major pathogenesis-related proteins of tomato plants and was designated proteinase P-69 as it has a molecular weight of 69,000 to 70,000. The proteinase was purified in four steps: (NH(4))(2)SO(4) fractionation, chromatography on Bio-Gel P-60, DEAE-Sepharose chromatography, and casein-Sepharose affinity chromatography. The proteinase had a pH optimum of 8.5 to 9.0 when assayed with either fluorescein thiocarbamoyl derivative (FTC)-casein or FTC-ribulose 1,5-bisphosphate carboxylase/oxygenase as substrates. The proteinase activity was inhibited by pCMB and strongly activated by calcium and magnesium ions as well as by DTT. When analyzed by electrofocusing, the activity showed a pI around 9.0.

Journal Article↗
PubMed1982

Comparative effects of semisynthetic D-5-vinyl-2-thiooxazolidone and water-extracted rapeseed meal in the rat.

The toxic effect of two levels of semisynthetic D-5-vinyl-2-thiooxazolidone (VTO) (0.006 and 0.0012%) was compared in rats with that of 0.005% of the same substance present in 'detoxified' rapeseed meal (DRSM). Diets containing 10% protein as casein (control group) or DRSM were tested. Growth rates and protein efficiency ratio with DRSM were slightly less than in the controls. VTO did not affect the growth rate and seems to increase the protein efficiency ratio. Liver and thyroid weights were normal in rats fed DRSM. VTO increased liver weight independently of the concentration in the diet. The The effect on thyroid weight was proportional to VTO concentration, and the glands reached weights twice or three times that of normal. Both levels of semisynthetic VTO led to damage of the hepatic parenchyma. Liver weight was increased. Animals receiving DRSM did not show differences either in liver weight or histology compared to the controls. Thyroid histology of animals fed VTO or DRSM showed smaller follicles lined by tall cells and reduction of lumenal colloid. These changes were more severe in animals fed VTO. It is postulated that both VTO and isothiocyanate may decrease thyroid hormone production which in turn stimulates TRH and TSH release leading to glandular hyperplasia and hypertrophy.

Animals↗
PubMedDate not supplied

Dynamic MR urography in urinary tract obstruction: implementation and preliminary results.

BACKGROUND: Recent studies have demonstrated magnetic resonance (MR) capabilities in evaluating renal morphology and function in patients with urinary obstruction. The objective of this report is to support the introduction of dynamic MR renography on any MR equipment. METHODS: A custom-made device of vials filled with different concentrations of gadolinium was studied by combinations of T1-weighted gradient-echo sequences and coils. We compared the capabilities of two coils (phased array vs. standard body), the properties of dynamic sequences, and the effects of increasing concentrations of gadolinium on signal intensity. In a second section, we designed MR urography plug-ins of Image J (DICOM image software) for the analysis of dynamic studies. RESULTS: Optimized gradient-echo sequences acquired with a phased array body coil produced acceptable quality images with a linear relation between signal intensity and the lowest concentrations of gadolinium. In vitro measurements showed loss of linearity above 8 mmol/L. CONCLUSION: Theoretical calculation and data from the literature suggest that the gadolinium dose to the patient should not exceed one-fourth of the usual one (0.025 mmol/kg). Postprocessing using Image J software and the specifically designed plug-ins was validated. The collection of plug-ins is now available on the Internet.

Adult↗
PubMedDate not supplied

[Total gastrectomy in newborn infant].

Total gastrectomy is rarely indicated in childhood and when necessary it involves multiple ulterior therapeutic problems, mainly nutritional, which need a meticulous physiological approach to avoid further complications, as illustrated by the following patient who, at age 15 months, was submitted to total gastric resection, Y en Roux esophagojejunal anastomosis and splenectomy, because of peritonitis secondary to dehiscence of a recent esophagogastric anastomosis for partial gastric resection due to gastric volvulus and necrosis, which in turn were associated to diaphragmatic relaxation. The patient was admitted to our hospital one month later with signs of acute calorie-protein malnutrition (W/A 60% and W/H 68%, NCHS standards) requiring combined parenteral and enteral nutritional support (via central venous catheter and jejunostomy tube for 15 and 35 days respectively) together with intramuscular vitamin B 12, oral iron and oral vitamin supplements before it became possible to fed him only by mouth. Prophylaxis against Streptococcus pneumonia infections with monthly benzatin penicillin was also instituted. Mean daily weight increases of 16 g, W/A 68% and W/H 74% were thus achieved before hospital discharge, without evidence of dumping syndrome nor alkaline reflux.

Gastrectomy↗