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Biomedical subjects

A Meunier

Publications and source records attributed to A Meunier.

At least 91 records · Page 5Linked to original sources
PubMed1987

The elastic anisotropy of bone.

In modeling the anisotropic properties of hydroxyapatite (HAp), Katz found that two kinds of phenomenological relationships held among the elastic stiffness coefficients. Firstly, there are three linear combinations--(c11 + c22 + c33), (c44 + c55 + c66), (c12 + c13 + c23)--which arise naturally when computing the isotropic averages of anisotropic crystal systems over all possible spatial orientations. Secondly, the degree of elastic anisotropy in such crystal systems is characterized by two specific factors: (a) the ratio of the linear compressibility along the unique axis to that perpendicular to it, (c11 + c12 - 2c23)(c33 - c13); and (b) the ratio of the two shear moduli, c44/c66. There have been a number of experiments in recent years which have used either mechanical methods or ultrasonic techniques to measure the anisotropic elastic properties of bovine and human cortical bone. Analyses of data from these experiments show that the above relationships also play a significant role in characterizing the elastic anisotropy in bone.

Animals↗
PubMed1987

Development of a carbon-carbon hip prosthesis.

This article deals with the use of carbon-fiber-reinforced-carbon materials for the manufacture of hip prosthesis stems. It considers the manufacturing process of carbon-carbon (C-C) composites made of carbon fibers infiltrated either with dense pyrolytic carbon or silicon carbide (SiC) through chemical vapor infiltration. The chemicophysical properties of these composites are examined according to their structures. The long-term response (2 years) of cortical bone to various types of carbon-carbon was evaluated mainly for bone contact and ingrowth. Carbon-carbon coated with calcium phosphate was found to speed up the bone formation as compared to pyrolytic carbon or SiC coatings. The low modulus of elasticity of the C-C materials could be responsible for quicker bone contact as compared to a much stiffer material like sintered aluminum oxide. The biomechanical performance of C-C hip stems was assessed through (a) implantations into cadaver femurs, (b) fatigue testing, and (c) finite element analysis. These tests showed: (a) a better stress transfer as compared to a metal prosthesis having the same design, (b) no fatigue damage, (c) a computerized stem stress distribution in accordance with the fractures obtained during static mechanical testing.

Biocompatible Materials↗
PubMed1986

[Postoperative analgesia with thoracic peridural morphine in pulmonary surgery. 117 cases].

Post-operative analgesia by peridural injection of morphine in the thoracic spine was evaluated in a series of 117 successive patients with pulmonary pathology operated upon by the same surgeon. The catheters were introduced, either on the day preceding the operation or at the end of it, above or below T6-T7, after localization of the peridural space by the hanging drop technique or by loss of resistance to a liquid mandrel; 5 mg of preservative-free morphine diluted in 3 ml isotonic saline were injected. The catheter was left in situ for 3 days, then systematically removed and cultivated. Analgesia was considered excellent in 66.7% of the cases, good in 26.5% and insufficient or non-existent in 6.8%. Each dose was effective for 15 hours on average. The mean total dose administered was 18.2 mg and did not exceed 40 mg during the first three post-operative days. There was no respiratory depression requiring naloxone or mechanical ventilation. Urinary retention occurred in 62% of the patients and troublesome pruritus in 0.3%. No death attributable to the method and no neurological or infectious complication was noted. There was no problem in removing the catheter, and no redness, pain or haematoma was observed at the site of injection. In view of the potential risk of insidious and delayed respiratory depression, the patients must be closely supervised specialized by staff. This technique must not be used unless the conditions required are fulfilled.

Adult↗
PubMed1986

Circulating forms of alpha MSH in the carp and trout blood: an HPLC and RIA study.

The three forms of MSH(desacetyl-, monoacetyl-, and diacetyl) circulate in the carp and trout blood. Their proportions there are as follows: in the carp, the desacetylated form is 2.5% of total MSH and the monoacetylated form 72% of the acetylated forms of alpha MSH. In the trout, similar proportions were found: desacetyl alpha MSH was 5% of total alpha MSH and monoacetyl-, 70% of the acetylated MSHs.

Adrenocorticotropic Hormone↗
PubMed1986

Semi-automatic image-analysis applied to the quantification of bone microstructure.

Bone microstructure can be quantified by methods ranging from simple manual techniques to fully automatic image analysis systems. We describe a semi-automatic method, developed in BASIC and running on a laboratory microcomputer. Its core is based on two special algorithms for image conversion and for calculation. These two algorithms produce quantifying characteristics for any irregularly shaped structure, as defined by one or more open or closed contour lines. The quantification of these structural parameters relies only on contour line digitization. The improved efficiency of this semi-automatic method is a consequence of combining automatic calculations and human assistance. The structural parameters chosen were for a specific research project; the correlation between mechanical and microstructural properties of cortical bone, but they may readily be changed as circumstances demand.

Biomechanical Phenomena↗
PubMed1986

Proportions of mono- and diacetylated forms of alpha MSH in individual neurointermediate lobe extracts of Cyprinus carpio L.

The proportions of the mono- and diacetylated forms of alpha MSH in individual carp neurointermediate lobe (NIL) extracts, as assessed by HPLC and RIA, fluctuate within a narrow range (mono/mono- + diacetyl alpha MSH = 3-14%). These results obtained on individuals of different sex and age show that the diacetylated form predominates in the NIL of all individuals where it represents in the mean 90% of the acetylated forms. The relatively low fluctuation of the proportions of the acetylated forms suggests that the possibility for a physiological modulation of the diacetylation step may be limited in this species of fish.

Acetylation↗
PubMed1985

Separation and partial characterization by high-performance liquid chromatography and radioimmunoassay of different forms of melanocyte-stimulating hormone from fish (Cyprinidae) neurointermediate lobes.

From neurointermediate lobe (NIL) extracts of two species of Cyprinidae, Carassius auratus and Cyprinus carpio, several peptides were separated by high-performance liquid chromatography (HPLC) on a C18 muBondapak column eluted with a methanol/acetic acid/triethylamine mixture. Monitoring all fractions by radioimmunoassay (RIA) with an antibody against melanocyte-stimulating hormone (MSH) C terminal gave positive reactions for fractions 7, 11-12, 15-16, 23-24, and 25-27. For further characterization, the elution positions of these peaks were compared to those of known synthetic reference substances. Peak 7 elutes in the same position as oxidized alpha MSH, whereas peak 15-16 matches the elution position of des-acetyl alpha MSH and 23-24 that of alpha MSH. The product from peak 26-27 has several characteristics of the diacetylated form of alpha MSH: its immunoreactivity in RIA, its sensitivity to weak bases and to HCl and its mass spectrum which is identical with that of mammalian diacetyl alpha MSH. In both species, the diacetylated form is predominant in the intracellular pool. This study establishes the coexistence of three different forms of alpha MSH, a des-acetylated, monoacetylated, and diacetylated in the cyprinid NIL extracts.

Adrenocorticotropic Hormone↗
PubMed1984

Callus characteristics following intramedullary nailing with stainless steel or epoxy-carbon nails.

Biological mechanical improvements of osteosynthesis make intramedullary nailing an attractive alternative to bone plate fixation. However, little is known about stress shielding induced by intramedullary implantation of a nail. To evaluate the effect of the nail rigidity on bone healing, mid-metatarsal osteotomies were performed in sheep and fixed with either stainless steel or epoxy-carbon composite V-shaped nails. Mechanical and histomorphometric features of the callus were evaluated 4 months postoperatively. No statistical difference between the two groups were demonstrated for either mechanical or microstructural characteristics. The presence of a fibrous membrane filling the bone/nail interface and allowing sliding micromotions of the implants and the much smaller effect of nail rigidity, as compared to bone plate after implantation, were assumed to be the main reason for this uniformity. At this stage of healing, bone characteristics were more related to a nonspecific (vascular) bone remodeling phenomenon than to a stress-shielding effect.

Animals↗
PubMed1984

The effects of remodeling on the elastic properties of bone.

Cortical bone can be modeled as a complex hierarchical composite interrelating both structure and material properties on four levels of structural organization: molecular, ultrastructural, microscopic, and macroscopic. In young animals, the microstructural systems are long parallel lamellar units, plexiform bone, which in older or more mature animals converts by internal remodeling into multiple concentric lamellar units, secondary osteons, forming haversian bone. Ultrasonic wave propagation measurements performed on both plexiform and haversian bone clearly show a definitive relationship with microstructure; haversian bone can be described as a transversely symmetric material whereas plexiform bone appears to be orthotropic in nature. The anisotropy of the elastic constants are found to reflect the tissue symmetry; moreover, plexiform bone is stiffer and more rigid in all directions than is haversian bone. Similar experiments were performed on osteoporotic and osteopetrotic bone. While the results for osteoporotic bone are understandable in terms of the increased porosity, the results for the osteopetrotic bone are anomalous with respect to its density. Since Wolff, the remodeling of bone has been interpreted as a way of altering the mechanical properties to suit some need. For haversian remodeling from plexiform bone, the argument that adaptation occurs to optimize properties requires additional clarification since haversian bone appears to have inferior mechanical properties to plexiform bone.

Animals↗
PubMed1983

[Analysis of the mechanical function of the cruciate ligaments in antero-posterior knee laxity. An in vitro study].

In order to evaluate the contribution of both anterior (ACL) and posterior cruciate ligaments (PCL) in antero-posterior knee laxity, mechanical tests were performed on 31 fresh-cadaver-knees ranging from 20 to 68 years old. The joints flexed at 90 degrees in a mounting apparatus were placed in a testing machine with the tibia fixed in neutral rotation. The load-displacement curves were then analyzed. The results showed that the tensile strength of the ACL decreased greatly with age whereas its stiffness measured during anterior drawer test remained independent of age and sex. Successive resection of the antero-medial (AM) and postero-lateral (PL) bundles of the ACL demonstrated the AM bundle to be the major structure involved in the limitation of tibial displacement in the anterior drawer test. The amount of tibial shift during the anterior drawer test did not reflect the condition of the ACL, while its resection always induced a strong and significant drop in anterior knee stiffness. Dissection of the PCL was always followed by significant posterior tibial displacement during the posterior drawer test of over 10 mm, which did not permit the experimental apparatus to quantify the posterior load displacement relationship.

Adult↗
PubMed1980

[Melanotropic hormone of goldfish (Carassius auratus L.): radioimmunologic comparison with synthetic alpha-MSH].

alpha MSH from the neuro-intermediate lobe of the pituitary gland of the goldfish displays a competitive behaviour in an RIA for synthetic alpha MSH. The inhibition curves from neuro-intermediate homogenates parallel the standard curve (P < 0,01) but two major pools of immunoreactive peptides have been separated by Sephadex gel chromatography. The neuro-intermediate lobe contains 480 +/- 56 ng (S.E.M.) of immunoreactive alpha MSH.

Animals↗
PubMed1980

[Enzymatic changes after arteriography of the lower limbs (author's transl)].

Various serum enzyme activities were studied in 15 adult patients before aortography and at the 6th hour and on the first five days after investigation; and at comparable intervals in 8 adult patients who had a bilateral transfemoral arteriography. A significant rise in serum creatine phosphokinase (CPK) level was noted at the 6th hour (p < 0.01), on the 1st day (p < 0.001) and on the 2nd day (p < 0.05) after aortography. Serum aspartate-aminotransferase (ASAT) level increased significantly (p < 0.02) on the 1st day after aortography. No significant change occurred for those two enzymes after transfemoral arteriography. In both groups minor changes were noted for the other enzymes studied: lactic dehydrogenase (LDH), alanineaminotransferase (ALAT) and gamma glutamyl transpeptidase (gamma GT). Rise in CPK and ASAT levels after translumbar aortography is attributable to skeletal muscle trauma and to the retroperitoneal haematoma at the site of puncture. Agents used in anesthesia are apparently not responsible.

Adult↗