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Biomedical subjects

M A Costa

Publications and source records attributed to M A Costa.

At least 55 records · Page 3Linked to original sources
PubMed2000

Proliferation/differentiation of osteoblastic human alveolar bone cell cultures in the presence of stainless steel corrosion products.

Human osteoblastic alveolar bone cells were cultured for 28 days in control conditions and in the presence of three non-lethal concentrations of AISI 316L stainless steel (SS) corrosion products. Cells were exposed to SS corrosion products in two experimental situations: (i) in selected stages of the incubation time (during the first, second, third and fourth week of culture); and (ii) during the 28 days incubation period. Cultures were characterized for cell proliferation, total protein content, alkaline phosphatase activity (ALP) and ability to form mineralized deposits; culture media was analyzed for ionized calcium (Ca) and phosphorus (P) concentrations throughout the incubation period. The presence of SS corrosion products during the different stages of the incubation period did not significantly affect the cell proliferation; however, a significant dose-dependent deleterious effect was observed on the levels and pattern of ALP activity, concentration of ionized Ca and P in the culture medium and, also, ability to form mineralized deposits, especially in cultures exposed during the first and second week of culture (respectively, lag phase and exponential cell growth phase). Similar effects were observed in cultures exposed to the SS corrosion products during the 28 days incubation period. However, the presence of such products during the third week (when the mineralization process occurs) and, also, during the fourth week, resulted in little or no significant effects on the behavior of alveolar bone cells. Results suggested that SS corrosion products above certain non-lethal concentrations may disturb the proliferation/differentiation relationship of osteoblastic human alveolar bone cell cultures.

Journal Article↗
PubMed2000

The IgE-binding epitopes of rPar j 2, a major allergen of Parietaria judaica pollen, are heterogeneously recognized among allergic subjects.

Pollen allergens are multivalent proteins that cross-link IgE antibodies on mast or basophil cells, inducing secretion of biologic mediators, and resulting in various allergic symptoms. The IgE-binding regions of the Parietaria judaica (Pj) pollen major allergen rPar j 2 were investigated. Twenty-nine single sera from Pj-allergic subjects were tested by Western blot against five recombinant peptides. At least four putative IgE-binding epitopes were identified. The analysis of their diffusion suggested a heterogeneous IgE-binding response. In fact, 75% of the sera reacted with peptide 1-54, 48% with peptide 48-101, 24% with peptide 1-30, 7% with peptide 29-54, and none with peptide 48-76. These five peptides were analyzed with the histamine-release assay. Only peptide 48-101 was capable of inducing degranulation and release of histamine. These results suggest that the recombinant rPar j 2 allergen contains IgE epitopes that are heterogeneously recognized by sensitive patients, and that therefore the therapeutic approach based on the use of haptenic peptides needs a careful evaluation.

Allergens↗
PubMed2000

Relationship between tensile stress and plaque growth after balloon angioplasty treated with and without intracoronary beta-brachytherapy.

AIMS: We investigated the influence of tensile stress on plaque growth after balloon angioplasty with and without beta-radiation therapy. METHODS AND RESULTS: Thirty-one consecutive patients successfully treated with balloon angioplasty were analysed qualitatively and quantitatively by means of an ECG-gated three-dimensional intravascular ultrasound post-procedure and at follow-up. Eighteen patients were irradiated with catheter-based beta-radiation ((90)Sr/(90)Y source) and 13 were not (control). Studied segments were divided into 2 mm subsegments. Thus 184 irradiated and 111 non-irradiated subsegments were included. Tensile stress was calculated according to Laplace's law. The radiation dose was calculated by means of dose-volume histograms. Plaque growth was positively correlated to tensile stress in both the radiation and control groups (r=0.374, P=0.0001 and r=0.305, P=0.001). Low-dose subsegments (<6 Gy) had a significant correlation (r=0.410, P=0.0001) whereas no correlation was observed in the effective-dose subsegments (> or = 6 Gy). Multivariate analysis identified tensile stress as the only independent predictor of plaque increase in non-irradiated subsegments, whereas actual dose and plaque morphology were stronger predictors in irradiated subsegments. CONCLUSION: The results of this study suggest that plaque growth is related to tensile stress after balloon angioplasty. Intracoronary brachytherapy may alter the biophysical process on plaque growth when the prescribed dose is effectively delivered.

Aged↗
PubMed2000

Outcome from balloon induced coronary artery dissection after intracoronary beta radiation.

OBJECTIVE: To evaluate the healing of balloon induced coronary artery dissection in individuals who have received beta radiation treatment and to propose a new intravascular ultrasound (IVUS) dissection score to facilitate the comparison of dissection through time. DESIGN: Retrospective study. SETTING: Tertiary referral centre. PATIENTS: 31 patients with stable angina pectoris, enrolled in the beta energy restenosis trial (BERT-1.5), were included. After excluding those who underwent stent implantation, the evaluable population was 22 patients. INTERVENTIONS: Balloon angioplasty and intracoronary radiation followed by quantitative coronary angiography (QCA) and IVUS. Repeat QCA and IVUS were performed at six month follow up. MAIN OUTCOME MEASURES: QCA and IVUS evidence of healing of dissection. Dissection classification for angiography was by the National Heart Lung Blood Institute scale. IVUS proven dissection was defined as partial or complete. The following IVUS defined characteristics of dissection were described in the affected coronary segments: length, depth, arc circumference, presence of flap, and dissection score. Dissection was defined as healed when all features of dissection had resolved. The calculated dose of radiation received by the dissected area in those with healed versus non-healed dissection was also compared. RESULTS: Angiography (type A = 5, B = 7, C = 4) and IVUS proven (partial = 12, complete = 4) dissections were seen in 16 patients following intervention. At six month follow up, six and eight unhealed dissections were seen by angiography (A = 2, B = 4) and IVUS (partial = 7, complete = 1), respectively. The mean IVUS dissection score was 5.2 (range 3-8) following the procedure, and 4.6 (range 3-7) at follow up. No correlation was found between the dose prescribed in the treated area and the presence of unhealed dissection. No change in anginal status was seen despite the presence of unhealed dissection. CONCLUSION: beta radiation appears to alter the normal healing process, resulting in unhealed dissection in certain individuals. In view of the delayed and abnormal healing observed, long term follow up is indicated given the possible late adverse effects of radiation. Although in this cohort no increase in cardiac events following coronary dissections was seen, larger populations are needed to confirm this phenomenon. Stenting of all coronary dissections may be warranted in patients scheduled for brachytherapy after balloon angioplasty.

Angina Pectoris↗
PubMed2000

The effect of 32P beta-radiotherapy on both vessel remodeling and neointimal hyperplasia after coronary balloon angioplasty and stenting: a three-dimensional intravascular ultrasound investigation.

Intracoronary radiation is a promising therapy to decrease restenosis after percutaneous intervention. The aim of this pilot study was to determine the mechanism of intracoronary beta-radiation after balloon angioplasty and stenting in a double-blind placebo-controlled randomized fashion. Twenty-six patients were randomized to either placebo (n = 6) or 3 doses (28, 35 and 42 Gy) of beta-radiation (n = 20) using the Guidant brachytherapy system (27 mm long 32P source wire). Of these, 21 patients underwent post-procedure and 6-month follow-up three-dimensional intravascular ultrasound (IVUS) assessment. Volumetric quantification was performed by means of a semi-automated contour detection system after an ECG-gated motorized pullback IVUS imaging and three-dimensional reconstruction. We compared the volumetric changes (Delta) of total vessel volume (TVV), plaque volume (PV) and lumen volume (LV) after 6 months between placebo (dummy wire) and irradiated patients. In addition, the volume of neointimal hyperplasia was quantified within the stented segments. There was an opposite behavior of TVV and LV change between placebo (DeltaTVV = -24 mm3 and DeltaLV = -42 mm3) and irradiated (DeltaTVV = +18 mm3 and (DeltaLV = +5 mm3) patients. The mean neointimal formation within the stented segment in the irradiated patients (n = 7) was 1.9 mm3 (1.5%). Our results suggest that beta-radiation affects vessel remodeling after percutaneous intervention and inhibit neointimal formation in stented patients.

Aged↗
PubMed1999

Late coronary occlusion after intracoronary brachytherapy.

BACKGROUND: Intracoronary brachytherapy appears to be a promising technology to prevent restenosis. Presently, limited data are available regarding the late safety of this therapeutic modality. The aim of the study was to determine the incidence of late (>1 month) thrombosis after PTCA and radiotherapy. METHODS AND RESULTS: From April 1997 to March 1999, we successfully treated 108 patients with PTCA followed by intracoronary beta-radiation. Ninety-one patients have completed at least 2 months of clinical follow-up. Of these patients, 6.6% (6 patients) presented with sudden thrombotic events confirmed by angiography 2 to 15 months after intervention (2 balloon angioplasty and 4 stent). Some factors (overlapping stents, unhealed dissection) may have triggered the thrombosis process, but the timing of the event is extremely unusual. Therefore, the effect of radiation on delaying the healing process and maintaining a thrombogenic coronary surface is proposed as the most plausible mechanism to explain such late events. CONCLUSIONS: Late and sudden thrombosis after PTCA followed by intracoronary radiotherapy is a new phenomenon in interventional cardiology.

Aged↗
PubMed1999

Incidence and distribution of postcranial fractures in the prehistoric population of San Pedro de Atacama, Northern Chile.

Trauma incidence analysis in skeletal populations has been very popular among skeletal biologists during the last two decades. In this context, the work of Lovejoy and Heiple ([1981] Am. J. Phys. Anthropol. 55:529-541) has been quoted as a landmark because their analysis rested on a populational approach, avoiding simple assumptions about cause and etiology. In this study, we apply to the prehistoric population of San Pedro de Atacama, northern Chile, an approach similar to that carried out by Lovejoy and Heiple (1981). The results obtained point to a peak of risk of fractures among old people, estimated age around 45 years. The distribution of fractures by sex and age suggests that the prevailing etiology is related to accidents and not violence. When the frequencies of fractures are compared, the Libben population shows a much higher incidence than the Atacamenean population. It is suggested that this difference can be explained by peculiarities of the subsistence economies of the two populations.

Adolescent↗
PubMed1999

Influence of growth conditions on the production of xylanolytic enzymes by Aspergillus flavus.

Investigations were carried out to optimize the culture conditions for the production of xylanase and beta-xylosidase by Aspergillus flavus, a filamentous fungus isolated from soil. The production of enzymes was tolerant to a wide range of initial culture pH values. Maximum xylanase (190 U/ml) and beta-xylosidase (35 U/ml) production was obtained when the strain was grown on mineral medium supplemented with 3% (w/v) corn cob powder as the carbon source. The enzymes had optimal activities at pH values between 5.5 and 6.0 and exhibited high activity and stability under alkaline conditions.

Aspergillus flavus↗
PubMed1999

Atrial natriuretic peptide effect on NADPH-diaphorase in rat intestinal tract.

Histochemical reaction of NADPH-diaphorase (NOS-NADPH-d) was used to identify NO synthesis. A 30-min 0.1 microg microg/kg/min ANP infusion led to about a 10% and 35% increase in small and large intestine enterocytes stain respectively. This increase was abolished by a bolus of 1 mg/kg L-NAME before ANP infusion in small intestine, and partially abolished it in colon. Incubation of small and large intestine with 0.5 microM ANP increased stain at about 20%. In both tissues the preincubation with 0.1 mM L-NAME abolished the ANP effect. Incubation with 0.1 mM 8-Br-cGMP enhanced staining about 70% and 30% in small and large intestine respectively. Our results show that ANP enhances NOS-NADPH-d activity, suggesting that ANP stimulates NO synthase in enterocytes by L-arginine-NO pathway. 8-Br-cGMP mimicked the effect of ANP described above. Therefore, the guanylate cyclase-coupled natriuretic receptors, NPR-A and NPR-B, probably mediate this ANP effect.

Animals↗
PubMed1999

Regiochemical control of monolignol radical coupling: a new paradigm for lignin and lignan biosynthesis.

BACKGROUND: Although the lignins and lignans, both monolignol-derived coupling products, account for nearly 30% of the organic carbon circulating in the biosphere, the biosynthetic mechanism of their formation has been poorly understood. The prevailing view has been that lignins and lignans are produced by random free-radical polymerization and coupling, respectively. This view is challenged, mechanistically, by the recent discovery of dirigent proteins that precisely determine both the regiochemical and stereoselective outcome of monolignol radical coupling. RESULTS: To understand further the regulation and control of monolignol coupling, leading to both lignan and lignin formation, we sought to clone the first genes encoding dirigent proteins from several species. The encoding genes, described here, have no sequence homology with any other protein of known function. When expressed in a heterologous system, the recombinant protein was able to confer strict regiochemical and stereochemical control on monolignol free-radical coupling. The expression in plants of dirigent proteins and proposed dirigent protein arrays in developing xylem and in other lignified tissues indicates roles for these proteins in both lignan formation and lignification. CONCLUSIONS: The first understanding of regiochemical and stereochemical control of monolignol coupling in lignan biosynthesis has been established via the participation of a new class of dirigent proteins. Immunological studies have also implicated the involvement of potential corresponding arrays of dirigent protein sites in controlling lignin biopolymer assembly.

Amino Acid Sequence↗
PubMed1999

Production of lipase by soil fungi and partial characterization of lipase from a selected strain (Penicillium wortmanii).

Filamentous fungi from soil were screened for their ability to produce lipase. Among 56 filamentous fungi tested, one strain identified as Penicillium wortmanii was selected as the highest lipase producer. Maximum lipase production (12.5 U/ml) was obtained in 7-days cultures utilizing 5% (w/v) olive oil as the carbon source. Optimum pH and temperature for crude lipase were 7.0 and 45 degrees C, respectively. The enzyme was stable at 40 and 45 degrees C and it retained about 55% of its activity when heated at 50 degrees C for 1 hour.

Culture Media↗
PubMed1999

Late stent malapposition occurring after intracoronary beta-irradiation detected by intravascular ultrasound.

We report a case of late stent malapposition occurring 6 months after intracoronary beta-irradiation detected by three-dimensional intravascular ultrasound, in spite of good apposition immediately after the procedure. Volumetric quantification revealed that stent volume remained unchanged, whereas total vessel volume increased by 13% after 6 months within the stent area. The increase of the vessel volume took place mainly in the proximal part of the stent, where the malapposition was located.

Angioplasty, Balloon, Coronary↗
PubMed1999

Compassionate use of intracoronary beta-irradiation for treatment of recurrent in-stent restenosis.

Recurrent in-stent restenosis after balloon angioplasty poses a serious management problem. Previously g-radiation has been shown to be effective in patients with in-stent restenosis. The aim of the study was to determine the feasibility and safety of b-radiation in patients with recurrent in-stent restenosis. From May 1997 to December 1998, 18 patients were treated with balloon angioplasty (n = 8) or laser (n = 10), followed by intracoronary b-radiation at a prescribed dose of 16 Gray at 2 mm from the source, for reference diameters by quantitative coronary angiography < 3.25 mm or 20 Gray for reference diameters > or =3.25 mm. Vessels treated were as follows: left anterior descending: (n = 5); circumflex: (n = 4); right coronary artery: (n = 6); saphenous vein graft: (n = 3). Average recurrence rate was 2.4 +/- 0.7 and the restenotic length was 16 +/- 7 mm. b-radiation was successfully delivered in all patients. Two patients presented complications related to laser debulking: a non-Q wave myocardial infarction in one and a re-angioplasty due to uncovered distal dissection in another. Geographical miss, defined as an area which has been injured but not covered by the radiation source, was demonstrated in 8 patients. Seventeen patients (94%) completed the 6-month angiographic follow-up. Restenosis (> 50% Diameter Stenosis) was observed in 9 patients (53%), leading to target lesion revascularization in 8 patients (47%). Six of the 9 restenoses were located in areas with geographical miss. Intracoronary b-radiation for recurrent in-stent restenosis appears to be a safe and feasible management strategy. However, the mismatch between injured and irradiated area may lead to failure of this therapy.

Aged↗
PubMed1998

Identification of an immunodominant IgE epitope of the Parietaria judaica major allergen.

Par j 1.0101 is one of the two major allergens of the Parietaria judaica (Pj) pollen, and its three-dimensional structure was built by three-dimensional structural homology modeling. The resultant model was used to identify putative IgE binding regions. Western blot analysis of gene fragmentation products showed that the 1 to 30 region was capable of binding specific IgE from a pool of sera (n = 30) of patients allergic to Pj pollen. Using the structural model as a guide, deletion and site-directed mutagenesis of the 1 to 30 region was performed, and the amino acids involved in IgE binding were identified. In addition, a synthetic peptide covering the 1 to 30 region was capable of binding human IgE without triggering histamine release from basophils of Pj allergic patients (n = 6) and thus represents a haptenic molecule with potential use as an immunotolerant agent. This epitope is also present on the Par j 2.0101 major allergen representing a common IgE epitope. It is an immunodominant epitope, since it was capable of inhibiting 30% of all specific IgE against the Pj major allergens, and therefore, it might be a candidate for the future development of immunotherapeutics.

Allergens↗
PubMed1998

Rat tail replantation as a training model for microvascular procedures of digit replantation.

In this study we sought to evaluate the potential of rat tail replantation as a tool for very-small-vessel microvascular anastomoses. We used 10 adult Sprague-Dawley rats. The tail was completely amputated 2.0-cm distal to the base of the tail. Then the tail was replanted with anastomoses of two superficial dorsal veins from both sides and one artery. All 10 replanted tails were pink, viable, and normal-appearing at all daily inspections performed from the first to the fourteenth postoperative days. This model can provide a training tool for the acquisition of superior microvascular surgical technique for the repair of very small vessels that stimulate digital replantation.

Amputation, Traumatic↗
PubMed1998

Effects of endothelin-3 on water and sodium excretion during extracellular volume expansion.

The aim of the present study was to elucidate the role of an IV dose of endothelin-3 (ET-3) (5 ng Kg-1 min-1) on mean arterial pressure (MAP), on diuresis and natriuresis in control and in volume expanded anesthetized rats. A systemic infusion of ET-3 in normal rats (Group I) increased MAP and produced a trend of increasing diuresis, without changes in natriuresis. A 10% body weight expansion (Group II) increased diuresis and natriuresis without changes in MAP. The simultaneous infusion of ET-3 and expansion with saline (Group III) resulted in an increase in MAP, an enhanced diuretic response, and a natriuresis of similar magnitude to that observed in Group II. These results suggest that the diuresis produced by a low dose of exogenous ET-3 in control rats, is independent of sodium excretion. Furthermore, the enhanced diuresis caused by ET-3 during expansion is greater than the addition of ET-3 and expansion effects, suggesting that new mechanisms are triggered in order to maintain volume and salt homeostasis in this state.

Animals↗
PubMed1998

Effects of L-NAME and L-Arg on arterial blood pressure in normotensive and hypertensive streptozotocin diabetic rats.

The present study was designed to examine blood pressure response to nitric oxide synthase-pathway inhibition and stimulation in normotensive and hypertensive diabetic rats. Rats treated with streptozotocin (60 mg/Kg i.p.) developed high blood glucose, polyuria and slow weight gain compared with control. One group of diabetic rats developed hypertension, consequently we studied three experimental groups: control rats (C), normotensive diabetic rats (ND) and hypertensive diabetic rats (HD). Mean arterial pressure (MAP), systolic blood pressure, diastolic blood pressure and heart rate were recorded: baseline time, 30 after L-nitro arginine methyl ester (L-NAME: 1 mg/Kg i.v.) and post L-arginine (L-arg: 250 mg/Kg i.v.) injection. L-NAME induced a significantly increase in MAP in all groups. This enhancement was smaller in diabetic than in control rats. The increase in MAP in HD was significantly lower than that in ND L-arg induced a significantly decrease in MAP in all groups. This decrease was significantly attenuated in diabetic compared with control rats. The degree of hypotension in response to L-arg in diabetic groups was lower in hypertensive than that in normotensive diabetic rats. These data suggest that an impairment of nitric oxide formation could be involved in the development of hypertension in this model.

Analysis of Variance↗