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Biomedical subjects

L Costa

Publications and source records attributed to L Costa.

At least 55 records · Page 3Linked to original sources
PubMed1999

Efficacy of two techniques for endodontic instrumentation.

The aim of the present study was to compare the quality of preparation in curved and straight root canals employing 2 techniques, i.e. the step-back technique and the technique of Goerig, Michelich and Schultz. One hundred and thirty single-rooted human teeth were employed throughout. The walls of the root canals of these teeth were painted. Following instrumentation the roots were sectioned longitudinally. The sections were observed under a stereoscopic microscope SZ40 with a grid fitted in the eyepiece. The efficacy of instrumentation was evaluated using area of paint removed as the end-point. Statistical significance of the data was tested with the chi square test employing the Epi Info 5 software. There was no statistically significant difference between techniques for straight canals. The technique of Goerig, Michelich and Schultz was more effective than the step-back technique in the apical third of curved canals.

Chi-Square Distribution↗
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↗
PubMed1997

Turkey rhinotracheitis virus and Escherichia coli experimental infection in chickens: histopathological, immunocytochemical and microbiological study.

The aim of this study was to evaluate the response of chickens to a combined infection with turkey rhinotracheitis virus (TRTV) and Escherichia coli O78:K80. Groups of specific-pathogen-free chickens were inoculated by eyedrop and intranasal routes with TRTV and/or E. coli O78:K80. Presence of E. coli O78:K80, histopathological changes and tissue distribution of viral antigen in the respiratory tract of chickens were evaluated. Dual infection resulted in increased severity of clinical signs, and macroscopic and microscopic lesions compared with those groups given single infections. All 36 chickens inoculated with TRTV plus E. coli O78:K80 showed severe rhinitis. Moreover, periorbital edema and fibrinous airsacculitis and pericarditis were observed in one of the three chickens inoculated with both agents and sacrificed at day 5 p.i. In addition, purulent material in the air spaces of the cranial bones was seen in three of the six animals from the same group sacrificed at days 5 and 7 p.i. The distribution of viral antigen in tissues was similar in groups inoculated with TRTV and TRTV plus E. coli, but viral antigen was detected only in main bronchi of chickens from the latter group. The quantity of E. coli O78:K80 isolated from the nasal cavity was greater in the group given dual infection. The results obtained suggest that TRTV may act as primary agent, enhancing E. coli multiplication. The lesions observed in the group inoculated with both agents could correspond to an initial stage of swollen head syndrome (SHS) and contribute to the hypothesis that SHS could be due to a mixed infection with TRTV and E. coli.

Animals↗
PubMed1997

Quantitative electroencephalographic differences associated with alcohol, cocaine, heroin and dual-substance dependence.

Resting electroencephalographic (EEG) activity was evaluated in 88 drug-dependent inpatients, abstinent 1-6 months, and 14 non-drug-dependent controls. The patients were assigned to one of four groups using DSM-III-R criteria: alcohol-dependent (n = 12), cocaine-dependent (n = 21), heroin-dependent (n = 19), or dual alcohol- and cocaine-dependent (n = 36). The analysis revealed significant differences between the five subject groups in high- and low-frequency beta power, but not in other frequency bands. Beta power was significantly greater in the alcohol-dependent and cocaine-dependent groups relative to non-drug-dependent controls. These group differences did not correlate with quantity/frequency measures of alcohol or cocaine use, family history, personality, mood, or demographic characteristics. The similar increases in EEG beta found in alcohol- and cocaine-dependent patients do not suggest a direct drug effect. Rather, they suggest the existence of a common premorbid variable or a complex interaction between alcohol/drug use and other variables.

Adult↗
PubMed1997

Juxta-adrenal malignant schwannoma.

A case of malignant schwannoma occurring in an 11-year-old boy is described. To our knowledge, this is the third case of malignant juxta-adrenal schwannoma reported in the literature. It was misdiagnosed at the onset of the disease as a post-traumatic renal hematoma. Angiography revealed that the tumor derived its blood supply from collateral vessels of the aorta, splenic, and left gastric arteries. An analysis of the diagnosis, clinical course, and prognostic factors of this rare tumor is performed.

Child↗
PubMed1997

Asymptomatic HIV-infected women: preliminary study of quantitative EEG activity and performance on a continuous performance test.

Several studies have examined the electrophysiological correlates of human immunodeficiency virus (HIV) infection in medically asymptomatic men. Although the rates of HIV infection are increasing at a greater rate in women than men, there have been no publications to date of electrophysiological functioning in HIV-infected women. In the present study, quantitative electroencephalographic (qEEG) activity was measured in 22 women (11 asymptomatic HIV-seropositive and 11 HIV-seronegative) utilizing a procedure comprised of three auditory continuous performance tests and a set of qEEG components derived from principal components analysis. No significant group differences were found in qEEG or in performance on the continuous performance tests; however, task-related differences were detected across groups between simple and complex language tasks in EEG fast beta power, delta power, and a left-hemisphere principal components analysis-derived EEG component. In examining the electrophysiological correlates of HIV infection, researchers might employ a similar methodology while increasing the sample size and varying the task modality or difficulty.

Adult↗
PubMed1996

Unacceptable biodegradation of polyethylene in vivo.

The chemical characterization of 19 retrieved ultra-high-molecular-weight polyethylene tibial plateaux, six new ones and one raw bar was performed by means of infrared spectroscopy. The surface and bulk oxidation and biodegradation indexes were calculated. The raw bar has a measurable oxidation, which increases on the bulk and on the surfaces of the new plateaux. In the retrieved plateaux, the average oxidation index increases further both on the bulk and on the surfaces; the worse values were present on the worn area. Similar results were found for the biodegradation index. The data show that the biotic in vivo degradation is promoted by the oxidation present on the new plateaux and that it occurs through a different mechanism, abiotic thermal-, photo-, gamma-radiation oxidation, evaluated by the oxidation index.

Aged↗
PubMed1996

Speech outcomes of a prolonged-speech treatment for stuttering.

It has been shown that people who stutter can speak with greatly reduced stuttering after treatments that use variations of Goldiamond's (1965) prolonged-speech (PS). However, outcome research to date has not taken account of several important issues. In particular, speech outcome measures in that research have been insufficient to show that lasting relief from stuttering has been achieved by clients outside the clinic for meaningful periods. The present study used extensive speech outcome measures across a variety of situations in evaluating the outcome of an intensive PS treatment (Ingham, 1987). The speech of 12 clients in this treatment was assessed on three occasions prior to treatment and frequently-on eight occasions-after discharge from the residential setting. For 7 clients, a further assessment occurred at 3 years posttreatment. Concurrent dependent measures were percent syllables stuttered, syllables per minute, and speech naturalness. The dependent measures were collected in many speaking situations within and beyond the clinic. Dependent measures were based on speech samples of substantive duration, and covert assessments were included in the study. Detailed data were presented for individual subjects. Results showed that 12 subjects who remained with the entire 2-3-year program achieved zero or near-zero stuttering. The majority of subjects did not show a regression trend in %SS or speech naturalness scores during the posttreatment period, either within or beyond the clinic. Some subjects showed higher posttreatment %SS scores during covert assessment than during overt assessment. Results also showed that stuttering was eliminated without using unusually slow and unnatural speech patterns. This treatment program does not specify a target speech rate range, and many clients maintained stutter-free speech using speech rates that were higher than the range typically specified in intensive PS programs. A significant correlation was found between speech rate and perceived posttreatment speech naturalness.

Adolescent↗