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Biomedical subjects

G Laroche

Publications and source records attributed to G Laroche.

At least 55 records · Page 3Linked to original sources
PubMed1989

Expanded polytetrafluoroethylene prostheses as secondary blood access sites for hemodialysis: pathological findings in 29 excised grafts.

The popularity of expanded polytetrafluoroethylene (PTFE) arteriovenous fistulas for hemodialysis access is increasing. The low infection rate, low thrombogenicity and low body reactivity make it an important blood access for patients on routine hemodialysis. The authors examined 29 PTFE graft fistulas surgically excised from patients on hemodialysis for one or more of the following complications: infection 7, 2 with associated hemorrhage; thrombosis 9; aneurysm 11, 3 with associated thrombosis; stenosis 5, 3 with associated thrombosis; hemorrhage 4 and arterial steal 2. The explanted prostheses were reinforced Gore-tex in 20, Gore-tex thin wall in 1, Impra I in 4, Impra II in 3 and Vitagraft in 1. It was also noted that the implants failed in the short term mainly because of infection, in the medium term mainly because of thrombosis and stenosis, and in the long term usually because of aneurysm.

Adult↗
PubMed1989

Biologic and structural evaluation of 80 surgically excised human umbilical vein grafts.

Human umbilical vein is a valuable alternative to autogenous saphenous vein in lower-limb revascularization. However, the long-term patency is not as good. To understand better the reasons for this, the authors studied the biologic and structural changes occurring in 80 segments of human umbilical vein (HUV) grafts excised from 70 patients. Morphologic, histologic and scanning electron microscopy examinations were performed on each specimen. It was noted that increasing duration of implantation was associated with greater encapsulation and less surrounding inflammatory reaction. Twenty-six percent of clinically noninfected grafts were found to harbour bacteria. Bacteremic colonization was often in the folds of the luminal surface. As a result of these findings, the authors emphasize the need for complete excision of clinically infected grafts. Anastomoses between HUV segments are discouraged because they are associated with a high frequency of infection and a corresponding decrease in duration of implantation. Delamination of the wall was common, and such sites may represent areas at risk for further degradation. Continued surveillance of the biologic and structural changes occurring in excised grafts remains an important method in increasing our understanding of the evolutive complications of HUV grafts.

Adult↗
PubMed1988

Study of the effect of poly(L-lysine) on phosphatidic acid and phosphatidylcholine/phosphatidic acid bilayers by raman spectroscopy.

The effect of polylysine (PLL) on dimyristoylphosphatidic acid (DMPA), on dimyristoyl-phosphatidylcholine (DMPC), and on mixtures of these lipids was investigated by Raman spectroscopy. These results show that long polylysine (Mr approximately 200,000) increases the stability of the acyl chain matrix of DMPA to form a more closely packed structure with a stoichiometry of one lysine residue per PA molecule. On the other hand, short PLL (Mr 4000) destabilizes the PA bilayer, and the complex formed undergoes a gel to liquid-crystalline transition at a lower temperature than of the pure lipid. For both cases, we have observed that bound polylysine adopts a beta-sheet conformation as opposed to the alpha-helical structure previously found for dipalmitoylphosphatidylglycerol/long PLL complexes [Carrier, D., & Pézolet, M. (1984) Biophys. J. 46, 497-506]. The difference in the thermal behavior of complexes of DMPA with long and short polylysines is believed to be associated with the fact that in the complex the long polypeptide adopts the beta-sheet conformation over the whole range of temperatures investigated while the short one undergoes a change of conformation from beta-sheet of random coil upon heating. Therefore, the conformation of the lipid-bound polypeptides depends on the nature of the polar head group of the lipid, not only on its net charge, and it affects considerably the thermotropism of the lipid. On the other hand, both long and short polylysines show no affinity for phosphatidylcholine since the temperature profiles of DMPC and of DMPC/PLL complexes exhibit exactly the same behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimyristoylphosphatidylcholine↗
PubMed1986

The virgin, modified, human, umbilical vein graft: morphologic characteristics and mechanical properties.

The authors used macrophotography, endoscopy, roentgenography, light microscopy, and transmission and scanning electron microscopy to assess the morphologic characteristics of 37 virgin, human, umbilical vein grafts. The specimens showed deep longitudinal folds (22%) and multiple transverse folds of the intimal surface (27%), irregularity of wall thickness (41%) and intimal breakdown exposing thrombogenic layers of the vein wall to blood (19%). The mechanical properties also studied were dynamic compliance, Young's modulus, breaking strength and breaking strain. The mean dynamic compliance was 6.44 X 10(-4) mm Hg-1 (SD = 2.02 X 10(-4) mm Hg-1, i.e., 31%), which is in agreement with results of others. The specimens showed great variability in Young's modulus, breaking strength and breaking strain. The structural deficiencies and variable mechanical properties of human umbilical vein grafts require investigation to determine their effect on patency rates due to increased thrombogenicity and thus to establish whether there are potential hazards associated with their use.

Biomechanical Phenomena↗
PubMed1982

Raynaud's phenomenon in forestry workers in Quebec.

A survey of 1540 forestry workers in Quebec found a prevalence of Raynaud's phenomenon of 30.5% among chain-saw users and 8.7% among nonusers. Prevalence was related directly to duration of use of the chain-saw. The mean interval (+/- the standard deviation) between the time the chain-saw was first used and the onset of Raynaud's phenomenon was 7.8 +/- 5.6 years. After 20 years of chain-saw use over 50% of the population had Raynaud's phenomenon. Relative risks among those using a chain-saw for more than 10 years were 3.60 for nonsmokers and 6.55 for smokers. Other factors associated with the phenomenon included a family history of nonoccupational Raynaud's phenomenon, previous injuries to the arms, climate and type of residence during the wood-cutting season. Decreased work capacity, interference with leisure activities and changes in professional orientation often resulted from this disease. These problems should be taken into account when disability compensation is being considered.

Adult↗