PubMed Health⌕ Search

Biomedical subjects

B Knoops

Publications and source records attributed to B Knoops.

25 records · Page 2Linked to original sources
PubMed1990

Rat sciatic nerve regeneration within an acrylic semipermeable tube and comparison with a silicone impermeable material.

Sectioned rat sciatic nerves were placed in tubes to study the regrowth of injured nerve processes. First, we characterized quantitatively the regeneration of myelinated fibers at different levels of an acrylic semipermeable tube, from two to 27 weeks postoperatively. From the fifth week, myelinated fiber counts at mid-tube level were equal to the value of an intact nerve, but at the distal part the number of fibers exceeded both mid-tube level and unsectioned nerve values. At the proximal part of the tube an important fiber disorganization was observed. Second, we have compared acrylic semipermeable and totally impermeable silicone tubes at four and 27 weeks postoperatively. In terms of the number of myelinated fibers and the surface of the endoneurium at the mid-tube level, the most effective tube was the impermeable one. This study points out the importance of the tube wall permeability in nerve regeneration.

Acrylates↗
PubMed1989

Comparison of the effects of auranofin and retinoic acid on plasminogen activator activity of peritoneal macrophages and Lewis lung carcinoma cells.

Urokinase-type plasminogen activator, a neutral proteinase, seems to play a central role in the degradation of the extracellular matrix that accompanies a number of biological phenomena including inflammatory reactions and neoplasia. The effect of auranofin and retinoic acid on the plasminogen activator activity expressed by two cell types, i.e. murine macrophages and Lewis lung carcinoma cells, has been investigated. Low concentrations of both drugs (10(-6)-10(-7) M) can inhibit in vitro the induction of plasminogen activator in macrophages stimulated by phorbol 12-myristate 13-acetate. This action occurs rapidly (15 min), is irreversible and is independent of a global cytotoxic effect. Auranofin and retinoic acid remain without effect in macrophages when added after stimulation by the phorbol ester. Both drugs are thus potent inhibitors of the induction of plasminogen activator activity in macrophages, possibly through an interaction with the protein kinase C system. The plasminogen activator activity of Lewis lung carcinoma cells, which is apparently not dependent on a protein kinase C pathway, is not influenced by auranofin or retinoic acid. These observations may contribute to explain: (1) the activity of auranofin and retinoic acid in rheumatoid arthritis, and (2) the antitumor promoting activity of retinoic acid. It would be relevant to assess whether auranofin may exhibit, like retinoic acid, an antitumor-promoting activity.

Animals↗
PubMed1989

Suloctidil increases the rat brain cortex microvascular regeneration after a lesion.

A "cavity" lesion made by aspiration in the rat occipital cortex induces a parenchymal and a vascular reaction in its vicinity. The first was mainly characterized by cellular necrosis and gliosis, the second by an increase of the vascular network. In vehicle treated rats, a 50% significant increase of the vascular network was observed around the cavity 4 days after the lesion, in comparison to the uninjured contralateral cortex. The effects of a vasoactive substance, suloctidil, on the vascular reaction was studied in the brain cortex. A single oral dose of suloctidil (30 mg/kg; 2 hours before the sacrifice) gave the same effect as the vehicle group. After 8 days of suloctidil oral administration (30 mg/kg; twice daily: 4 days before lesion and 4 days after) a significant increase (123%) of the vascular network was observed around the cavity. The hypothetical ways by which a chronic treatment of suloctidil induces this increase of the neovascularization observed after cortical lesion are discussed.

Animals↗
PubMed1987

A new in vivo model to study the influence of the microenvironment in the regeneration of the central nervous system.

In order to study the 'in vivo' regenerative capacity of the central nervous system, a semipermeable tube was placed in the axis of the lesioned nigrostriatal pathway of adult rats. In spite of a correct positioning of the tube, no growing central nervous processes were observed within the tube after 3 to 6 weeks when it was left empty. However, when the lumen of the tube was previously filled with a pre-degenerated sciatic nerve, unmyelinated and myelinated fibers were observed growing in the peripheral graft. Since the content of the tube can be modified, it appears that this model can be used to test the capability of cellular or acellular microenvironments to promote the 'in vivo' regeneration of the mammalian central nervous system fibers.

Animals↗
PubMed1987

Rat sciatic nerve regeneration in semipermeable artificial tubes.

The regeneration of the sciatic nerve in Wistar rats across a 10-mm gap, within a semipermeable chamber was examined. The sequence of regeneration can be summarized as follows: (i) formation of a fibrin-containing matrix; (ii) invasion of this matrix by fibroblasts, forming two populations defined by their relative position within the matrix; (iii) the appearance of blood vessels; (iv) bridge formation; and (v) colonization of the bridge by nerve fibers. After 4 weeks, the number of myelinated fibers and the regenerate surface were studied at midtube level. Two and four weeks after the operation, both myelinated and unmyelinated leading fibers were detected and their distances from proximal stump measured. The results approach those reported in the literature for impermeable tubes, but not those obtained for fully permeable ones.

Acrylates↗
PubMed1986

A new model for quantification of microvascular regeneration after a lesion of the rat cerebral cortex.

The purpose of this study is to validate a method for the quantification of the neovascularization in the vicinity of a lesion made in the cerebral rat cortex. A cavity, made by aspiration in the occipital cortex of young rats, induces around the lesion a parenchymal and vascular reaction. The parenchymal reaction is characterized by cellular necrosis and gliosis. The vascularization is more dense around the cavity than in normal cortex. Morphometric analysis indicates, 8 days after the lesion, a 130% increase of the total length of the vessels in comparison to the contralateral normal cortex.

Animals↗