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Biomedical subjects

L Costa

Publications and source records attributed to L Costa.

At least 19 recordsLinked to original sources
PubMed2000

Generalized schmidt decomposition and classification of three-quantum-Bit states

We prove for any pure three-quantum-bit state the existence of local bases which allow one to build a set of five orthogonal product states in terms of which the state can be written in a unique form. This leads to a canonical form which generalizes the two-quantum-bit Schmidt decomposition. It is uniquely characterized by the five entanglement parameters. It leads to a complete classification of the three-quantum-bit states. It shows that the right outcome of an adequate local measurement always erases all entanglement between the other two parties.

Journal Article↗
PubMed2000

Biochemical markers and skeletal metastases.

BACKGROUND: Skeletal metastases are common occurrences in patients with malignancies such as breast and prostate carcinoma, but they are difficult to diagnose nonradiologically, and treatment is difficult to follow clinically. Recent developments suggest that biochemical markers of bone remodeling, such as the bone collagen breakdown product N-telopeptide and the bone formation marker known as bone specific alkaline phosphatase, hold great promise as clinical tools for the management of patients with metastatic bone disease. METHODS: Serum levels of the bone formation marker known as bone specific alkaline phosphatase (BAP), along with serum levels of the bone collagen breakdown product carboxyterminal telopeptide of Type I collagen (ICTP) and urine levels of pyridinoline (PYD), deoxypridinoline (DPD), and N-telopeptide (NTx), were measured in a large cohort of patients with newly diagnosed or progressive cancer of the breast, prostate, lung, and other sites. Bone marker levels were correlated with the presence or absence of bone scan-documented metastases; metastatic disease extension in terms of the number of skeletal sites involved; and the type of lesion, whether blastic or lytic. Sites examined included the pelvis, spine, skull, ribs, and long bones. RESULTS: All of the bone markers examined, including BAP and NTx, were abnormally elevated in a high proportion of patients with confirmed metastases to bone. Urine NTx levels and bone specific alkaline phosphatase were significantly correlated with the number of skeletal sites involved, and a significant correlation between marker level and extent of skeletal involvement was also observed. In addition, both markers were higher in patients with a blastic disease presentation than in patients with osteolytic lesions. CONCLUSIONS: Biochemical markers of bone resorption and bone formation are abnormally raised in the blood and urine of patients with metastatic bone disease. Markers of bone collagen breakdown, such as N-telopeptide, as well as markers of osteoblast function, such as bone specific alkaline phosphatase, appear to be of use in assessing and managing patients with malignancies that metastasize to bone. In this study, both NTx and BAP showed a significant correlation with both the presence of bone metastases and the extent of skeletal involvement. Biochemical markers of bone remodeling can also be used to guide decision making regarding the treatment of metastatic bone disease and to determine the effectiveness of therapy for patients with cancer to bone whose broad-based symptoms make it difficult to discern true response to therapy.

Alkaline Phosphatase↗
PubMed2000

Frontal P300 decrements, alcohol dependence, and antisocial personality disorder.

BACKGROUND: The purpose of this study was to examine the independent and interactive effects of alcohol dependence, antisocial personality disorder (ASPD), and age on brain function. METHODS: P300 event-related potentials (ERPs) were recorded from 393 alcohol-dependent and 170 non-alcohol-dependent adults while they performed a visual oddball task. The two subject groups were further subdivided based upon age and the presence/absence of ASPD. RESULTS: Alcohol dependence was associated with a significant P300 amplitude decrement at anterior electrode sites only. Antisocial personality disorder was also associated with reduced P300 amplitudes at anterior electrode sites; however, the effects were only significant among subjects 30 years of age or younger. To validate this association between ASPD and P300 amplitude a correlational analysis was performed; the correlation between anterior P300 amplitude and the total number of childhood conduct disorder and adult ASPD symptoms was significant. CONCLUSIONS: The P300 amplitude decrement found at anterior electrode sites among subjects with ASPD is consistent with the results of numerous ERP, neuroimaging, or neuropsychologic studies of anterior brain function. Our study is unique in suggesting that the effects of ASPD on anterior brain function are best detected during early adulthood. The study also suggests that the detrimental neurophysiologic effects of alcohol dependence predominantly involve the anterior brain.

Adolescent↗
PubMed1999

Transcriptional up-regulation of paxillin expression by heregulin in human breast cancer cells.

Activation of heregulin (HRG) signaling has been implicated in the development of aggressive phenotype in breast cancer cells. The mechanisms through which HRG regulates the progression of breast cancer cells to a more invasive or motile phenotype are currently unknown. Because the process of cell migration must involve dynamic changes in the formation of new focal adhesions at the leading edge and dissolution of preexisting focal points, we explored the potential HRG regulation of paxillin, a major component of focal adhesion. Here, we report that HRG stimulation of noninvasive breast cancer MCF-7 cells resulted in the up-regulation of paxillin mRNA and protein. The observed HRG stimulation of paxillin mRNA expression was completely blocked by actinomycin D (a transcriptional inhibitor) as well as by cycloheximide (a protein synthesis inhibitor), suggesting the involvement of an inducible protein factor(s) and transcriptional regulation of paxillin mRNA by HRG. Extension of these observations to other HRG-responsive human cell lines also demonstrated that HRG has a significant capacity to up-regulate the paxillin expression. Furthermore, the levels of paxillin expression were closely linked with the coexpression of human epidermal growth factor receptor 2 (HER2)/HER3 receptors in breast cancer cell lines and in grade III human breast tumors. This study is the first demonstration of regulation of paxillin expression by a polypeptide growth factor, and it suggests a potential role for paxillin in the HER2 pathway in breast cancer.

Breast Neoplasms↗
PubMed1999

Prevalence of Haemophilus parasuis serovars isolated in Spain from 1993 to 1997.

From 1993 to 1997, 327 strains of Haemophilus parasuis were isolated from spanish swine in our Diagnostic Laboratory and 174 strains (53.2%) were serotyped. Four serotypes, sv. 5 (18.4%), sv 4 (16%), sv. 2 (9.2%) and sv. 13 (8%) were the most frequently isolated and 29.3% of the studied strains were classified as non typable. The results obtained indicate that the distribution of the serotypes in Spain is very similar to that found by other researchers in Germany, Australia, Canada and alike to that found in the United States.

Animals↗
PubMed1999

Residual thickness of root in first maxillary premolars with post space preparation.

It has been suggested that, to ensure tooth strength, a minimum of 1 mm of root wall thickness should be left after post preparations. The purpose of this study was to determine the instrument diameter that will not affect this measurement in maxillary first premolars. Post preparations were made in 106 teeth with one and two root canals at a working depth equal to the anatomical crown length, with 0.70, 0.90, 1.10, 1.30, 1.50, and 1.70 mm diameter instruments. Sections were cut perpendicular to the long axis of the tooth at the cervical and apical ends of each preparation, and the minimum width of residual root was measured on each wall, at both sites. A binocular microscope with a micrometer eyepiece was used. At the cervical level of the preparation, no group showed a wall thickness < 1 mm. Data for the apical sections was statistically analyzed, and the corresponding confidence limits were calculated with 95% confidence on the mean. The results show that the minimum residual thickness was only preserved when 0.70 mm instruments were used in single-canal roots and when 1.10 mm or smaller instruments were used for two-canal roots. This seemingly anomalous result occurs because fluting on both the mesial and distal sides of the root impinge on single canals, whereas dual canals are buccally or lingually displaced to an area of thicker root diameter.

Bicuspid↗
PubMed1999

Ureterovascular hydronephrosis in children: is pyeloplasty always necessary?

OBJECTIVE: To evaluate the efficacy of the vessel transposition technique in ureterovascular hydronephrosis in children. METHODS: Over a 25-year period, we treated 111 patients with 112 instances of ureterovascular hydronephrosis. In order to determine the obstructive effect of the vessels, we performed an intraoperative diuretic test. Using this approach, 61 patients judged to have only vascular pyeloureteral junction obstruction underwent vessel transposition. However, 50 patients in whom the intraoperative diuretic test proved doubtful needed pyeloplasty. RESULTS: Surgical success was achieved in 98% of the patients. Only 1 child treated by vessel transposition had an unsatisfactory outcome which necessitated a subsequent pyeloplasty for persistent hydronephrosis. This was due to a previously unrecognized intrinsic pyeloureteral junction obstruction. CONCLUSION: Based on our clinical experience, the intraoperative diuretic test has proven to be a safe and effective diagnostic tool in children with ureterovascular hydronephrosis. Its use may contribute to treating some cases of ureterovascular hydronephrosis without resorting to pyeloplasty.

Adolescent↗
PubMed1998

Determining the similarity of deformable shapes.

Determining the similarity of two shapes is a significant task in both machine and human vision systems that must recognize or classify objects. The exact properties of human shape similarity judgements are not well understood yet, and this task is particularly difficult in domains where the shapes are not related by rigid transformation. In this paper we identify a number of possibly desirable properties of a shape similarity method, and determine the extent to which these properties can be captured by approaches that compare local properties of the contours of the shapes, through elastic matching. Special attention is devoted to objects that possess articulations, i.e. articulated parts. Elastic matching evaluates the similarity of two shapes as the sum of local deformations needed to change one shape into another. We show that similarities of part structure can be captured by such an approach, without the explicit computation of part structure. This may be of importance, since although parts appear to play a significant role in visual recognition, it is difficult to stably determine part structure. We also show novel results about how one can evaluate smooth and polyhedral shapes with the same method. Finally, we describe shape similarity effects that cannot be handled by current approaches.

Algorithms↗
PubMed1998

In vivo UHMWPE biodegradation of retrieved prosthesis.

Sixty-two ultra high molecular weight polyethylene prosthetic components (PEs) (31 tibial plateaux and 31 cups), sterilised by gamma rays or ethylene oxide (EtO), were retrieved after 1-12 years depending on different medical reasons and were studied by FTIR spectroscopy with derivatisation of oxidised species. Esters, acids and hydroperoxides were found under the surface of the EtO sterilised PEs up to 2 mm depth. The behaviour of gamma ray sterilised PEs is more complex due to the oxidation following the sterilisation process. Ester and acid formation might arise from the diffusion of components of synovial liquid or from the oxidation process, whereas hydroperoxide formation is thought to be due to the oxidation. Abrasion and delamination process is discussed considering the topological distribution of degradation products.

Aged↗
PubMed1998

Markers of bone resorption in patients treated with pamidronate.

Pyridinoline (PYD), deoxypyridinoline (DPD), and N-telopeptide (NTX) are markers of bone resorption. In cancer patients with bone metastases, NTX is more often elevated than either of the pyridinolines. Bisphosphonates inhibit osteoclasts and their treatment decreases skeletal complications of malignancy. The aim of this study was to correlate urinary PYD, DPD, and NTX levels with clinical events in patients receiving pamidronate. 25 cancer patients with lytic bone disease were treated with monthly pamidronate combined with endocrine or chemotherapy; 27 others were on placebo. Twenty-four hour urines were collected at baseline, 1, 3 and 6 months. NTX values were determined by enzyme-linked immunosorbent assay (ELISA); PYD and DPD values were determined by reverse phase high performance liquid chromatography (HPLC). Two hour urines were also collected weekly for 21 patients. The greatest difference as a result of pamidronate treatment was observed in NTX values. Maximum suppression was achieved 2 weeks after treatment. Of the 25 patients who received pamidronate, 21 had initially elevated NTX values. 12 of the 21 finished with normal NTX values, whilst 9/21 had NTX values which remained abnormally elevated. The proportions of patients with fractures between these two subgroups approached statistical significance (P = 0.07) while the proportions with bony disease progression were significant (P = 0.03, Fisher's exact test). Measuring NTX levels appears useful in monitoring bisphosphonate therapy of bone metastases. The goal of treatment should be to normalise NTX excretion.

Aged↗
PubMed1998

Antigenic diversity of hepatitis B virus strains of genotype F in Amerindians and other population groups from Venezuela.

The adw4 subtype of hepatitis B virus (HBV) belongs to a unique genomic group (genotype F) representing the original HBV strains from the New World. Data regarding the prevalence of this subtype among HBV carriers in South America are, however, scarce, and those concerning HBV genotype F are based on only a few samples from Latin America. In this study, serum samples were obtained from 141 hepatitis B surface antigen (HBsAg) carriers from Amerindians and urban populations from Venezuela. The HBsAg subtype was identified with monoclonal antibodies in 105 samples, and the HBV genotype was identified by reverse-phase hybridization with DNA fragments in 58 samples. The adw4 subtype was highly prevalent in the population studied (75%); among the Amerindians, the prevalence was 97%. The adw2 subtype was also present (10%), while other subtypes (ayw3 and ayw4) were only occasionally found. The HBV subtype was associated with the expected genotype in most cases (80%), and thus genotype F was highly prevalent. Sequencing of viral strains that gave genotypes unpredicted by the HBsAg subtyping confirmed seven of them as belonging to not previously described genotype-subtype associations: namely, adw2 and ayw4 within genotype F.

Amino Acid Substitution↗
PubMed1998

Smooth pursuit eye movement dysfunction in substance-dependent patients: mediating effects of antisocial personality disorder.

Smooth pursuit eye movements were evaluated in 21 healthy volunteers and 126 patients meeting criteria for one of the following DSM-III-R dependence diagnoses: alcohol (n = 10), cocaine (n = 44), heroin (n = 34), or dual alcohol and cocaine (n = 38). A significant reduction in tracking accuracy was found in the heroin and the dually dependent groups relative to controls. Interestingly, the eye movement dysfunction in the drug-dependent groups was no longer detectable when the effects of antisocial personality disorder were statistically removed. The magnitude of the dysfunction also correlated with several antisocial personality-related features, including an increased number of criminal charges and months of incarceration, increased problems associated with drug abuse, and lower intellectual functioning. The relationship demonstrated presently between antisocial personality disorder and eye movement dysfunction may have implications beyond studies of substance dependence.

Adult↗
PubMed1998

13th Meeting of the Scientific Group on Methodologies for the Safety Evaluation of Chemicals (SGOMSEC): alternative testing methodologies for organ toxicity.

In the past decade in vitro tests have been developed that represent a range of anatomic structure from perfused whole organs to subcellular fractions. To assess the use of in vitro tests for toxicity testing, we describe and evaluate the current status of organotypic cultures for the major target organs of toxic agents. This includes liver, kidney, neural tissue, the hematopoietic system, the immune system, reproductive organs, and the endocrine system. The second part of this report reviews the application of in vitro culture systems to organ specific toxicity and evaluates the application of these systems both in industry for safety assessment and in government for regulatory purposes. Members of the working group (WG) felt that access to high-quality human material is essential for better use of in vitro organ and tissue cultures in the risk assessment process. Therefore, research should focus on improving culture techniques that will allow better preservation of human material. The WG felt that it is also important to develop and make available relevant reference compounds for toxicity assessment in each organ system, to organize and make available via the Internet complete in vivo toxicity data, including human data, containing dose, end points, and toxicokinetics. The WG also recommended that research should be supported to identify and to validate biological end points for target organ toxicity to be used in alternative toxicity testing strategies.

Animal Testing Alternatives↗
PubMed1998

Dual-energy X-ray absorptiometry in osteonecrosis of the femoral head.

UNLABELLED: Osteonecrosis of the hip classically produces a heterogeneous density in the femoral head, although the bone marrow ischemia extends down to the femoral neck and trochanters. Also, bone insufficiency fractures due to diffuse bone loss have been implicated in the genesis of osteonecrosis. OBJECTIVES: To use dual-energy X-ray absorptiometry to quantify the bone changes produced by osteonecrosis of the hip and to compare bone mineral density values in patients with osteonecrosis of the hip and in controls. METHODS: Bone mineral density was measured at the femoral neck (total femoral neck, Ward's triangle, and trochanter), femoral head and lumbar spine using dual-energy X-ray absorptiometry (DPX, L Lunar) in 22 patients with osteonecrosis of the hip and in 22 age- and sex-matched controls. RESULTS: In the patients with osteonecrosis, bone mineral density on the affected side was higher than on the opposite side at the femoral head (+18%), femoral neck (+7%), and Ward's triangle (+6%) and lower at the trochanter (-4%). These differences were most marked at the more advanced end of the osteonecrosis spectrum. As compared to age-specific normative values, the osteonecrosis patients had moderately decreased bone mineral density values at the lumbar spine (-0.53 +/- 1.1 SD or -6 +/- 1.5%) and at the femoral neck on the normal side (-0.9 +/- 1.4 SD or 12 +/- 1.8%). As compared to the controls, bone mineral density was significantly decreased at Ward's triangle (-25%; P: 0.04) and nonsignificantly decreased at the lumbar spine (-4.7%; P: 0.15) and at the femoral neck (-15%; P: 0.09).

Absorptiometry, Photon↗
PubMed1998

[Molecular diagnosis in an Argentinian family with multiple endocrine neoplasia type-1 (MEN-1)].

MEN-1 is a hereditary autosomal dominant syndrome characterized by the involvement of parathyroid glands, pancreatic islet cells and anterior pituitary gland. Today molecular genetics permit gene carrier analysis to compare the data obtained with the clinical biochemical tests. The twenty living members of the first, second and third generation of a family with MEN-1 were studied to determine the presence of genetic markers in MEN-1 loci 11q13, by linkage analysis and in affected individuals by biochemical tests and clinical examination. Two very informative polymorphic markers immediately flanking the MEN-1 gene on chromosome 11 band q13 were detected: PYGM and D11S987, haplotypes segregated by two members of the second generation, inherited from their father and two of the third generation: the affected one and one presymptomatic. The third generation had the affected member with renal stones and elevated PTH, PRL and glucagon. The presymptomatic carrier of MEN-1 allele showed elevated PTH. Among the members who inherited the normal allele we found one with elevated gastrin, one with elevated glucagon and one with elevated PTH, all asymptomatic. Of one Argentine family studied, molecular diagnosis allowed us to detect one presymptomatic carrier in the members at risk. As suggested by the available literature, accuracy of molecular diagnosis seems to make it the test of choice to exclude those members at risk for MEN-1 inheriting the normal allele.

Adult↗