Biomedical subjects

M Therin

Publications and source records attributed to M Therin.

8 recordsLinked to original sources

PubMed2003

Origins of agriculture at Kuk Swamp in the highlands of New Guinea.

Multidisciplinary investigations at Kuk Swamp in the Highlands of Papua New Guinea show that agriculture arose independently in New Guinea by at least 6950 to 6440 calibrated years before the present (cal yr B.P.). Plant exploitation and some cultivation occurred on the wetland margin at 10,220 to 9910 cal yr B.P. (phase 1), mounding cultivation began by 6950 to 6440 cal yr B.P. (phase 2), and ditched cultivation began by 4350 to 3980 cal yr B.P. (phase 3). Clearance of lower montane rainforests began in the early Holocene, with modification to grassland at 6950 to 6440 cal yr B.P. Taro (Colocasia esculenta) was utilized in the early Holocene, and bananas (Musa spp.) were intensively cultivated by at least 6950 to 6440 cal yr B.P.

Agriculture↗

PubMed1996

A pilot study comparing screw-shaped implants. Surface analysis and histologic evaluation of bone healing.

The purpose of this study was to compare surface treatment and bone formation adjacent to 2 screw shaped implants of similar design manufactured by two different companies. The test implants were manufactured by SERF (Decines, France), while the controls were manufactured by Nobelpharma (Goteborg, Sweden). The surface of 3 standard 3.75 mm test and 3 standard 3.75 mm control implants were investigated by means of scanning electron microscopy (SEM), X-ray micro-analysis, electron spectroscopy for chemical analysis (ESCA) and surface topography analysis. There was a microscopic difference on the thread design (SEM). Test threads were flat at the edge, while controls appeared rounded at the edge of the threads. Tests and controls were made of commercially pure titanium, with a regular topography. Results of ESCA indicated that the carbon peak for SERF implants was slightly higher than for the Brånemark implants. 5 test and 5 control implants were installed into the epiphyseal head of the femur of 2 ewes using a standardized surgical technique. In order to stain the bone for histologic analysis, oxytetracycline injections were given 17 and 8 days before the animals were sacrificed. The animals were sacrificed 12 weeks after implant placement. Histomorphometric analysis indicated that there was an average bone to implant contact orf 68% for the test implants and 61% for the controls. There were no statistical differences between tests and controls. The preliminary results of this pilot study indicated that early bone healing for the 2 screw shaped implants investigated were similar.

Animals↗

PubMed1996

[Osteogenic capacity of a vascularized periosteal flap tubulized around a coral implant. Experimental study on sheep].

The objective of this study was to evaluate the osteogenic capacities of a vascularized periosteal flap reinforced by a bone substitute, coral, to validate the possibility of creating prefabricated bone flaps with shapes adapted to a recipient zone, while limiting the donor site sequelae. 24 periosteal flaps, with preserved vascular pedicles, were raised from the medial femoral epiphyses of 12 ewes. In the same animal, these flaps were reinforced with a cylinder of coral and a cylinder of autologous graft. After implantation for 2 or 8 weeks depending on the animal, the flaps were submitted to histopathological and histomorphometric examination. The results of this examination demonstrated a similar course of the flaps regardless of the type of reinforcement, both in terms of implant resorption and the quantity of newly formed bone.

Animals↗

PubMed1995

Experimental study of Wallstent self-expandable metal stent in ureteral implantation.

In regard to the risk of stent obstruction, there are persistent controversies concerning the use of the Wallstent self-expandable metal stents in the ureter. Only a few clinical trials have been published to date, and, from a technical point of view, no success predictors have been identified. In an experimental study using a pig model, we have shown that neither the length of the stent (5 or 10 cm) nor an initial 1-month intubation had any influence on the outcome of the stents. Among the eight implantations studied (four 5-cm and four 10-cm stents), only one 5-cm stent was perfectly patent at 35 days. In all the remaining stents, after 35 or 90 days, constant failure was related to distal narrowing at the edge of the stent, with no difference between the 5- and 10-cm stents or between the intubated and the nonintubated stents. This distal narrowing, probably attributable to a functional discrepancy between an adynamic stented ureter and a normal underlying ureter, demands extreme caution in human applications when the ureter is normally peristaltic.

Animals↗

PubMed1994

Analysis of the general features of the soft tissue response to some metals and ceramics using quantitative histomorphometry.

This article analyzes the general features of the tissue response to orthopedic biomaterials when implanted in the paraspinal muscles in rats for periods between 1 week and 1 year. Using a computer-assisted cell counting method, it was shown that the membrane thickness was a stable parameter that poorly correlated with the other histomorphometric parameters except fibrocyte distance parameters. Macrophages were significant in number only in the short term and were always located at the implant-tissue interface. At 4 weeks, the period corresponding to which macrophages disappeared, fibrocytes were found nearer the interface than at earlier periods and did not migrate for up to 52 weeks, although their densities decreased to 50% of their initial values. Therefore, it can be histomorphometrically confirmed that 1) the presence of an implant induced a delay in the healing process; 2) the immune system was not usually involved in the response to bulk metals; and 3) at early time periods, the presence of PMN cells was correlated to the long-term number of macrophages. On the contrary, the histomorphometric findings suggested that around the tested materials, a large number of macrophages did not induce an immediate or a delayed fibrocyte proliferation. If one considers that a low fibrocyte surface density is related to activated cells surrounded by a matrix high in collagen content, then the large number of macrophages induced the stimulation of collagen synthesis by the fibrocytes already included in the membrane. Accordingly, in the short-term, a high fibrocyte density and few macrophages may be a criterion for testing biocompatibility.

Animals↗

PubMed1994

Functional evaluation of polyarylamide fibers for use in a prosthesis for anterior cruciate ligament replacement in the sheep.

In order to evaluate the potential use of polyarylamide fibers as a prosthetic material for ligament replacement, resected sheep anterior cruciate ligaments were replaced by braided devices routed through a tibial tunnel and over the top of the lateral femoral condyle. Twelve sheep were used and sacrificed between 3 and 12 months. The tissue response to the implant was evaluated histologically. Morphologic features of the fibers and the abraded particles were measured by image analysis. Simultaneously, the tensile properties as well as the creep and fatigue properties of non-implanted prostheses were measured under laboratory conditions. It was shown that the polyarylamide fibers exhibited high strength, a high modulus, but low fatigue abrasion properties. At autopsy, 1 prosthesis was broken, 6 had frayed and 5 were intact. There was no adverse tissue response to the intact fibers. Inflammation was always linked to the presence of polymeric particles. A large bony ingrowth in the tibial tunnel through the prostheses strands was observed. There was no material resorption throughout the experiment. Polyarylamide fibers appear to be a suitable material for ligament replacement provided that abrasion against bone can be avoided.

Amides↗

PubMed1992

In vivo degradation of massive poly(alpha-hydroxy acids): validation of in vitro findings.

The degradation of various high-molecular-weight aliphatic polyesters derived from glycolic acid and/or lactic acid enantiomers was previously investigated in vitro. It was demonstrated that the bulk degradation mechanism proposed in the literature actually proceeds heterogeneously and proceeds faster in the centre than at the surface of large specimens. In order to compare them, similar compression-moulded specimens were implanted intramuscularly in the backs of rabbits, namely PLA50 (poly(DL-lactic acid)), PLA37.5GA25 (75% DL-lactide and 25% glycolide in the feed) and PLA75GA25 (75% L-lactide and 25% glycolide). These three intrinsically amorphous compounds exhibited faster central degradation. Furthermore, preferential degradation of glycolic acid units and induced crystallization of L-lactic acid enriched fragments were observed in the case of PLA75GA25. These findings are comparable to phenomena observed in vitro and are conclusively supported by the re-examination of some old in vivo results. Accordingly, data reported in this paper validate both the in vitro modelling and new understanding of the degradation of lactic acid/glycolic acid-based aliphatic polyesters reported previously.

Animals↗

PubMedDate not supplied

A multicentric comparison of transabdominal versus totally extraperitoneal laparoscopic hernia repair using PARIETEX meshes.

The authors report a series of 1972 inguinal hernias treated between 1993 and 1997 by the insertion of a PARIETEX mesh via either a transabdominal-preperitoneal (TAPP) (1,290 procedures) or a totally extraperitoneal TEP approach (682 procedures). Pain scores were equivalent in both groups, while the hospital stay and time to return to normal activity was lower in the TEP group than in the TAPP group (p<0.001). In both groups, the average incidence of the total reported events (complications) was around 10% with no statistical difference. This ratio seemed to compare favorably to previously published reports. Chronic pain was extremely rare (0.6% and 0.7% in the TAPP and TEP groups, respectively). Whatever the approach was, sepsis was also very rare (1/1,526 laparoscopic procedures). These findings illustrate the local tolerance of the mesh. Recurrence rates were below 1% with no statistical difference between groups. This retrospective study demonstrates the clinically apparent local tolerance of this type of mesh. Prospective and long-term clinical results will be necessary to demonstrate that the optimized short-term tolerance of PARIETEX mesh will influence the long term functional results.

Abdominal Muscles↗