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Biomedical subjects

J Abrantes

Publications and source records attributed to J Abrantes.

6 recordsLinked to original sources
PubMed2001

Spatial reconstruction of the human motion based on images of a single camera.

The inverse dynamic analysis procedures used in the study of the human gait require that the kinematics of the supporting biomechanical model is known beforehand. The first step to obtain the kinematic data is the reconstruction of human spatial motion, i.e., the evaluation of the anatomic points positions that enables to uniquely define the position of all anatomical segments. In photogrammetry, the projection of each anatomical point is described by two linear equations relating its three spatial coordinates with the two coordinates of the projected point. The need for the image of two cameras arises from the fact that three equations are necessary to find the original spatial position of the anatomical point. It is shown here that the kinematic constraint equations associated with a biomechanical model can be used as the extra set of equations required for the reconstruction process, instead of the equations associated with the second camera. With this methodology, the system of equations arising from the point projections and biomechanical model kinematic constraints are solved simultaneously. Since the system of equations has multiple solutions for each image, a strategy based on the minimization of the cost function associated to the smoothness of the reconstructed motion is devised, leading to an automated computer procedure enabling a unique reconstruction.

Biomechanical Phenomena↗
PubMed2001

Spatial reconstruction of human motion by means of a single camera and a biomechanical model.

The value of the results of the inverse dynamic analysis procedures used in the study of human tasks is dependent on the quality of the kinematic and kinetic data supplied to the biomechanical model that supports it. The kinematic data, containing the position, velocity and acceleration of all anatomical segments of the biomechanical model, result from the reconstruction of human spatial motion by means of the evaluation of the anatomic points positions that enable to uniquely define the position of all anatomical segments. Furthermore, the motion data must be kinematically consistent with the structure of the biomechanical model used in the analysis. The traditional photogrammetric methodologies used for the spatial reconstruction of the human motion require images of two or more calibrated and synchronized cameras. This is due to the fact that the projection of each anatomical point is described by two linear equations relating its three spatial coordinates with the two coordinates of the projected point. The need for the image of another camera arises from the fact that a third equation is necessary to find the original spatial position of the anatomical point. The methodology proposed here substitutes the projection equations of the second camera with the kinematic constraint equations associated with a biomechanical model in the motion reconstruction process. In the formulation the system of equations arising from the point projections and biomechanical model kinematic constraints, representing the constant length of the anatomical segments, are solved simultaneously. Because the system of equations has multiple solutions for each image, a strategy based on the minimization of a cost function associated to the smoothness of the reconstructed motion is devised. It is shown how the process is implemented computationally avoiding any operator intervention during the motion reconstruction for a given time period. This leads to an automated computer procedure that ensures the uniqueness of the reconstructed motion. The result of the reconstruction process is a set of data that is kinematically consistent with the biomechanical model used. Through applications of the proposed methodology to several sports exercises its benefits and shortcomings are discussed.

Biomechanical Phenomena↗
PubMed1999

A phase I study of paclitaxel for mobilization of peripheral blood progenitor cells.

We conducted a phase I trial to determine the dose and schedule of paclitaxel, when given together with filgrastim, which would optimally promote mobilization of stem cells with tolerable toxicity. Dose escalation began at 275 mg/m2 3 h infusion. Dose-limiting neuropathy was observed at the 300 mg/m2 dose level. A second dose escalation was conducted utilizing 24 h infusion schedules, beginning at 225 mg/m2. Dose escalation was continued by 25 mg/m2 increments to 300 mg/m2, at which dose neuropathy was again dose-limiting. The recommended dose and schedule of paclitaxel for the purpose of mobilization of stem cells, when given together with filgrastim, are 275 mg/m2 as a 24 h infusion. The median stem cell yield after this dose of paclitaxel was 6.6 x 10(6) CD34+ cells/kg/apheresis (range 3.6 x 10(6)-7.7 x 10(6)).

Adult↗
PubMed1998

Staphylococcal strains involved in bovine mastitis are inhibited by Staphylococcus aureus antimicrobial peptides.

The inhibitory activity of five bacteriocin (Bac)-producer strains of Staphylococcus aureus was tested against bacteria pathogenic for cattle. Sixty-five epidemiologically unrelated strains of Staph. aureus involved in bovine mastitis were used as indicators in an agar diffusion test. Bacteriocins produced by four strains could inhibit only a limited number of test organisms. However, all 65 indicator strains proved to be susceptible to the combined action of both bacteriocins encoded by pRJ9, a Bac plasmid found in strain A53. Therefore, the bacteriocins produced by this strain may represent new antimicrobial peptides with potential applications in the prevention and treatment of bovine mastitis.

Animals↗
PubMedDate not supplied

Adjuvant sequential dose-dense doxorubicin, paclitaxel, and cyclophosphamide (ATC) for high-risk breast cancer is feasible in the community setting.

PURPOSE: This study evaluated the feasibility, when given in the community, of dose-dense, sequential ATC (doxorubicin, paclitaxel, cyclophosphamide) as adjuvant therapy for breast cancer with four or more metastatic axillary lymph nodes. PATIENTS AND METHODS: Patients were recruited after definitive breast cancer surgery if four or more axillary nodes were involved by metastatic cancer and if distant metastases were not present on computed tomographic scan or bone scan. Forty patients received doxorubicin, 90 mg/m2 every 14 days for three cycles; paclitaxel, 250 mg/m2 every 14 days for three cycles; and cyclophosphamide, 3 g/m2 every 14 days for three cycles with filgrastim support. Chemotherapy was administered by the referring physician. RESULTS: Mean dose intensity was 99% for doxorubicin, 96% for paclitaxel, and 99% for cyclophosphamide. Grade 3 toxicities included mucositis (13%), nausea/vomiting (10%), neuropathy (13%), and myalgia/arthralgia (10%). Thirteen patients had neutropenic fever. One patient developed acute leukemia. Three relapses have occurred. Ninety percent of patients are alive and disease-free at a median follow-up of 24 months. DISCUSSION: ATC can be administered in the community at full doses with acceptable toxicity. Preliminary efficacy data suggest that this high-dose, intensively scheduled regimen warrants comparison with standard therapy for high-risk patients.

Adult↗