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Biomedical subjects

B Dubuc

Publications and source records attributed to B Dubuc.

7 recordsLinked to original sources
PubMed1993

Evaluation of the surface roughness of cystine stones using a visible laser diode scattering approach.

To understand the processes of fragmentation and the chemical reactivity of solids, proper characterization of surface topography is crucial. This paper describes a non-destructive technique of quantifying the surface roughness of cystine renal stones, using visible laser diode scattering and fractal geometry. Fragments of cystine stones were mounted on microscope slides and coated by a carbon-sputtering apparatus. The slides were placed under a dynamic active-vision system, using a visible laser diode to measure three-dimensional surface coordinates. The data obtained were analyzed by fractal geometry. Surface fractal dimensions were determined by the variation method. The results showed that the surface of a compact-size sample can be evaluated quantitatively. The technique is valuable for the accurate presentation of surfaces in three dimensions.

Cystine↗
PubMed1991

Receptive fields and properties of a new cluster of mechanoreceptor neurons innervating the mantle region and the branchial cavity of the marine mollusk Aplysia californica.

The rostral LE cluster (rLE) is a new set of mechanoreceptor neurons of the abdominal ganglion innervating the mantle area, the branchial cavity, the gill and the siphon of the marine mollusk Aplysia californica Cooper. We have compared the organization of rLE cell receptive fields with that of three other clusters of sensory neurons in the abdominal ganglion (LE, RE and RF) that we have reanalysed. There is extensive overlap of receptive fields from the four populations of sensory cells, and the most exposed areas of the mantle are the most densely innervated. The sensory threshold is similar for all groups. The action potentials of the LE, rLE and RE neurons are broadened by serotonin and the peptide SCPB and narrowed by dopamine and FMRFamide. The RF group does not show the same kind of sensitivity to these neuromodulators. The synaptic outputs of the LE and rLE neurons undergo similar synaptic depression and homosynaptic and heterosynaptic facilitation. We estimate that 100 mechanoreceptor neurons innervate the entire mantle and siphon skin, gill and branchial cavity of Aplysia. The degree of their convergence onto various interneurons and motor neurons mediating the gill- and siphon-withdrawal reflex and other reflexes is under investigation.

Animals↗
PubMed1987

Surface studies of calcium oxalate dihydrate single crystals during dissolution in the presence of urine.

Single crystals of Calcium Oxalate Dihydrate (COD) were grown from solution under controlled release of the reacting ions. Dissolution of COD was studied at different pH levels and in different dilutions of urine. The descriptors of the contour were determined during dissolution of COD using a quantitative morphological technique. The shape parameters and surface ruggedness were determined from Fourier and fractal analysis. The results obtained give quantitative information on the dissolution kinetics and the surface geometry of COD crystals in normal and diluted urine. Dissolution inhibition and morphological changes of COD crystals during dissolution were attributed to selective adsorption of urine non-ionic macromolecules on the crystal stepped surface. Surface etching of COD was found to depend on urine dilution and time of incubation. The data obtained suggest that the geometric structure of the surface is likely to be a potential factor in understanding crystal aggregation in stone formation.

Calcium Oxalate↗
PubMed1981

Pulmonary function loss in Vermont granite workers. A long-term follow-up and critical reappraisal.

Previous studies of Vermont granite workers averred that pulmonary function loss was occurring at 2 to 3 times the normal rate. The excess loss was attributed to the current, relatively low concentrations of dust prevailing in the stone sheds. Because the Vermont State Health Department had traditionally provided surveillance of granite workers to detect evidence of occupationally related illness, we offered pulmonary function screening to any currently employed worker. Spirometric data from the first 150 workers, compared with data from the previous studies, showed a large increase in the FVC and a smaller increase in the FEV1. We therefore undertook a survey of the entire stone shed work force, as well as of retired workers tested previously. The results in 487 current workers indicated an overall increase in FVC from 1974 to 1979 of 0.540 L, and an increase in FEV1 of 0.030 L: predicted losses based on the previous studies were 0.350 to 0.400 L in FVC and 0.250 to 0.350 L in the FEV1. Analysis of data in various subgroups, such as retired workers or those with more than 20 yr of work experience, also showed increases in FVC, and either slight gains or minimal losses in FEV1. The possible reasons for apparent improvement in pulmonary function are discussed. We concluded that technical deficiencies in the previous studies led to exaggerated and erroneous estimates of loss. At this time, the actual decrement in pulmonary function values for exposed granite workers is not known and requires further investigation. Because the newly proposed, stricter standard, for silica was importantly influenced by the previous studies, we believe that adoption of this standard would be premature.

Air Pollutants↗