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Biomedical subjects

S Martin

Publications and source records attributed to S Martin.

At least 559 records · Page 31Linked to original sources
PubMed1989

[Plastic surgery of the anterior cruciate ligament: experimental study of intra-articular aramid fibers in dogs].

The authors explored the possibility of replacing an anterior cruciate ligament with an aramid fiber (Kevlar) implant. This study was performed in intra-articular site in 9 dogs and the average implantation period was 5 months. Studies were carried out by macroscopic, photon microscopy, and electron microscopy examination of the samples obtained at the time the animals were sacrificed. Clinical and radiographic studies of the knees were performed in order to assess functional consequences. Overall, the results showed a partial or complete rupture of 10 neoligaments out of the 17 studied ligaments; on the other hand, osseous anchorage and reintegration in the intra-articular zone appeared satisfactory. Kevlar fiber only partially meets the performance specifications for an artificial ligament intended to serve as an anterior cruciate ligament substitute. Some positive results have encouraged the authors to carry on further this experimental study.

Animals↗
PubMed1989

[Bone integration within calcium phosphate ceramic by creation of posterior inter-articular lumbar spine fusions in dogs].

Following earlier experiments in which several calcium phosphate ceramics were tested, the aim of this study was to evaluate bone integration within a macroporous biphasic calcium ceramic (M.B.C.P.) in comparison to autologous bone grafts, by producing posterior lumbar spine fusions in dogs. Five dogs were used. 40 posterior lumbar joints were exposed; 38 articular surfaces were removed, 27 M.B.C.P. and 5 autologous bone grafts were implanted; 6 joints were kept free of implant for control purposes. Fixation with a metal rod was performed using Luque's method. Tetracycline was used for a double marking of bone growth. Joints were removed at 4 weeks in 1 dog, 8 weeks in two and 13 weeks in the remaining 2 dogs. Demineralized and non demineralized sections were examined. After 1 month, sections with M.B.C.P. showed early signs of mineralization of the scar tissue between the biomaterial and one of the facets of the joint. Fluoroscopy revealed an absence of bone growth in the pores at the center of the ceramic implant. After 3 months, a number of M.B.C.P. blocks had become integrated into both sides of the joint; however some microfractures in the biomaterial with discontinuity between the mineralized areas was seen. Macroporous calcium phosphate ceramic leads to revascularization allowing bone reconstruction. Similarities in the kinetics and mechanisms of bone integration between the ceramic and autologous bone grafts are demonstrated.

Animals↗
PubMed1989

[Comparative study of bioactive calcium phosphate ceramics after implantation in spongy bone in dogs. Histologic, ultrastructural and electron probe microanalysis].

An experimental model of posterior spine arthrodesis in dogs was created using 3 types of calcium phosphate biomaterials already known for their applications as bone substitutes, namely: hydroxyapatite (HA), which is not readily resorbable; highly resorbable tricalcium phosphate (TCP); and a mixture of HA and TCP (BCP), the resorbability of which depends on the proportion of HA and TCP. The BCP implants had a macroporous structure, whilst the HA and TCP implants were used in dense form. The creation of macropores increases the surface exchange area, thus enabling the osseous colonization processes. By carefully removing the posterior articular facets it was possible to remove the articular surfaces and to fit into each appropriate location a block a few millimeters in diameter. The anatomopathological assessment was performed using histological methods, transmission electron microscopy, and energy dispersion microprobe analysis. Our results indicate that calcium phosphate ceramics may be used as bone substitutes for carrying out arthrodeses, provided (1) immediate immobilization using a spine containment technique is effected; (2) their chemical composition is sufficiently stable over time; (3) they are sufficiently bioactive so as to allow their colonization and replacement by bone.

Animals↗
PubMed1989

An evaluation of Fecatwin/Feca EIA; a faecal occult blood test for detecting colonic neoplasia.

A combination guaiac and immunological test Fecatwin/Feca EIA for the detection of faecal occult blood was used in the investigation of 535 symptomatic patients in order to assess the value of this combined test in the detection of colorectal neoplasia. The addition of the immunological part of the test led to an improvement in specificity for colorectal cancer from 80% to 91% and an increase in the positive predictive value of the test for colorectal cancer from 14% to 24%. However, there was a fall in sensitivity from 75% to 67%. There was no substantial advantage in the addition of the immunological part of the test to justify the extra laboratory workload incurred.

Colonic Neoplasms↗
PubMed1989

Macroporous calcium phosphate ceramic performance in human spine fusion.

With a background of experimental studies on macroporous biphasic calcium phosphate (MBCP) in canine spine fusion, MBCP was investigated in 11- to 18-year-old patients with scoliosis treated by spinal fusion. Twelve cases were chosen for whom enough bone graft was difficult to obtain (severe neurologic scoliosis and osteogenesis imperfecta). MBCP blocks were used in combination with a specific strong fixation (Cotrel-Dubousset instrumentation). Clinical and roentgenogram assessments were performed up to 24 months. In two cases, biopsies were obtained. Histologic, ultrastructural, and microanalysis studies demonstrated the effectiveness of MBCP implants combined with a strong stabilization as bone graft substitutes for spine fusion. Clinical and biologic assessments were normal, and the histologic and ultrastructural evaluation demonstrated the bioactivity and the osteoconduction of this material. Partial resorbability of the MBCP blocks involved lamellar bone formation at the expense of the ceramic.

Adolescent↗
PubMed1989

[Artificial respiration at home--an exceptional form of intensive care].

A couple with a child suffering from transverse lesion of the spinal cord with respiratory paralysis were greatly interested in taking care of him at home. After making technical and organisational preparations we transferred the child to his home with a respiratory machine. The child has now been at home for 3 years. Although the successful course of this home respirator treatment shows the correctness of our decision, we look upon such a procedure as an exception.

Child↗
PubMed1988

Fast disassembly of microtubules induced by Mg2+ or Ca2+.

The extent and rate of disassembly of microtubules induced by the addition of high concentrations of magnesium and calcium have been measured. At 25 degrees C, the rate constant for microtubule disassembly increases more than ten-fold on increasing [Mg2+] from 4.0 to 20 mM. The process is even more sensitive to [Ca2+], showing similar enhancement on increasing [Ca2+] from 0.5 to 8 mM. Electron microscopy indicates that the disassembly is an end-dependent process. Complete microtubule disassembly occurs at concentrations in excess of 10 and 2 mM for Mg2+ and Ca2+, respectively; this suggests the importance of binding to weak sites for both ions. The sensitivity to ionic composition explains the wide variations in the published values for k-, under varying conditions. The results indicate the potential range of microtubule disassembly rates which may be encountered under different conditions in vitro and in vivo. The highest values of k- (ca. 3000 s-1) would imply microtubule shortening rates in excess of 100 um per minute.

Animals↗
PubMed1988

The conformation of calmodulin: a substantial environmentally sensitive helical transition in Ca4-calmodulin with potential mechanistic function.

The conformation of Ca4-calmodulin in solution, as assessed by far-UV peptide circular dichroism, contains significantly less alpha-helix than the proposed X-ray crystal structure. We now show that Ca4-calmodulin adopts significant additional helical structure in solution in the presence of a helicogenic solvent (50%, v/v, aqueous 2,2,2-trifluoroethanol or 50%, v/v, methylpentane-5,5-diol). We suggest that the long continuous helix (residues 66-92 of the crystal structure) is not necessarily a normal feature of the calmodulin structure in solution, and may be due in part to the conditions of crystallisation. This result is supported by time-resolved tyrosine fluorescence anisotropy studies indicating that Ca4-calmodulin in solution is an essentially compact globular structure which undergoes isotropic rotational motion. We conclude that, under appropriate ionic and apolar environmental conditions, Ca4-calmodulin undergoes a substantial helical transition, which may involve residues in the central region of the molecule. Such a transition could have an important function in determining specificity and affinity in interactions of calmodulin with different target sequences of Ca2+-dependent regulatory enzymes.

Animals↗
PubMed1988

Effect of anti-ER antibodies within the ER lumen of living cells.

We describe the production and partial characterization of 12 monoclonal antibodies raised against a preparation of endoplasmic reticulum membranes obtained from Xenopus laevis liver. Four of the antibodies cross-react with liver melanocytes; two of the antibodies recognize extracellular antigens, whilst the remaining six recognize antigens present in hepatocytes. The concentrations of these latter antigens increase markedly in livers stimulated by estrogen. Western blotting analysis revealed that the six anti-hepatocyte monoclonal antibodies recognize at least five different antigens whose molecular weights are 14K, 18K, 19K, 43K, and 125K. The possible functional involvement of the various antigens in the secretory pathway was investigated using Xenopus oocytes as a surrogate secretory system. The mRNAs coding for the monoclonal antibodies were injected into oocytes and the resulting immunoglobulin chains were translated and assembled into active anti-ER antibodies inside the lumen of the ER. The effect on secretion was then observed. Our data indicate that the binding of antibodies to most antigens of the endoplasmic reticulum membrane may result in a blockage of secretion.

Animals↗
PubMed1988

Ultrastructure of junctional epidermolysis bullosa in Belgian foals.

Ultrastructural examination of a mechanobullous disease of probable hereditary nature in Belgian foals, confirmed light microscopic findings that separation of the dermo-epidermal junction occurred through the lamina lucida of the basement membrane, leaving the intact lamina densa adherent to the dermis and the plasmalemma of the basal epithelial cells intact. The location of the cleft and the presence of small hemidesmosomes in adjacent intact skin are additional characteristics which make this condition similar to junctional epidermolysis bullosa of man.

Animals↗