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Biomedical subjects

M Timmer

Publications and source records attributed to M Timmer.

13 recordsLinked to original sources
PubMed2006

Culturing of glial and neuronal cells on polysialic acid.

Although peripheral nerves exhibit regeneration capacities after transection injuries, the success of nerve repair depends crucially on the length of the gap. In addition to autologous nerve grafting as the conventional neurosurgical treatment to overcome long gaps, alternative strategies are needed. Numerous experimental studies have been undertaken to find the optimal material for production of artificial prostheses, which can be introduced as conduits between the nerve stumps. The current study follows the aim to establish polysialic acid (polySia), a homopolymer of alpha2,8-linked sialic acid residues, as a novel, biocompatible, and bioresorbable material for nerve tissue engineering. As a first step towards this goal, protocols for efficient coating of cell culture dishes with soluble polySia were established. In addition, primary nerve cells which are candidates for reconstructive therapies, including neonatal and adult Schwann cells, neural progenitor cells, spinal ganglionic neurons and motoneurons were cultured on polySia substrates. Cultures were evaluated with regard to cell survival and cell proliferation capacities. polySia turned out to be stable under cell culture conditions, and induced degradable and degradation products had no negative effects on cell cultures. Furthermore, polySia revealed its compatibility for several cell types derived from rat embryonic, postnatal and adult nervous tissue when used as a substrate.

Animals↗
PubMed2004

Fibroblast growth factor-20 promotes the differentiation of Nurr1-overexpressing neural stem cells into tyrosine hydroxylase-positive neurons.

Stem cells are currently considered as alternative cell resources for restorative transplantation strategies in Parkinson's disease. However, the mechanisms that induce differentiation of a stem cell toward the dopaminergic phenotype are still partly unknown thus hampering the production of dopaminergic neurons from stem cells. In the past, FGF-20 has been found to promote the survival of ventral mesencephalic (VM) dopaminergic (DA) neurons in culture. We hereby provide evidence that FGF-20, a growth factor of the FGF family, is expressed in the adult and 6-OHDA-lesioned striatum and substantia nigra, but is not expressed by VM glia or DA neurons, suggesting that FGF-20 may work on DA neurons in a paracrine- or target-derived manner. We also found that co-culture of Nurr1-NSCs with Schwann cells overexpressing FGF-20 induced the acquisition of a neuronal morphology by the NSCs and the expression of tyrosine hydroxylase (TH) as assessed by immunocytochemistry, cell ELISA, and Western blot analysis. RT-PCR showed, that both, Schwann cells and Nurr1-NSCs (differentiated or not), expressed the FGF-1 receptor suggesting that both direct and indirect actions of FGF-20 are possible. We show that differentiated Nurr1 cells retained both neuronal morphology and TH expression after transplantation into the striatum of 6-OHDA-lesioned postnatal or adult rats, but that neuritogenesis was only observed after postnatal grafts. Thus, our results suggest that FGF-20 promotes the differentiation of Nurr1-NSCs into TH-positive neurons and that additional factors are required for the efficient differentiation of DA neurons in the adult brain.

Animals↗
PubMed2003

Axonal regeneration across long gaps in silicone chambers filled with Schwann cells overexpressing high molecular weight FGF-2.

Basic fibroblast growth factor (FGF-2) has been shown to enhance the survival and neurite extension of various types of neurons including spinal ganglion neurons. In addition, endogenous FGF-2 and FGF receptors are upregulated following peripheral nerve lesion in ganglia and at the lesion site. FGF-2 protein is expressed in different isoforms (18 kDa, 21 kDa, 23 kDa) and differentially regulated after nerve injury. In the rat we analyzed the regenerative capacity of the high molecular weight (HMW) FGF-2 isoforms (21/23 kDa) to support the regeneration of the axotomized adult sciatic nerve across long gaps. The nerve stumps were inserted into the opposite ends of a silicone chamber resulting in an interstump gap of 15 mm. Silicone tubes were filled with Matrigel or a mixture of Schwann cells (SC) and Matrigel. SC were prepared from newborn rats and transfected to overexpress HMW FGF-2. Four weeks after the operation procedure, channels were analyzed with regard to tissue cables bridging both nerve stumps and myelinated axons distal to the original proximal nerve stump. Peripheral nerves interposed with HMW Schwann cells displayed significantly enhanced nerve regeneration, with the greatest number of tissue cables containing myelinated axons and the highest number of myelinated axons. These results suggest that a cellular substrate together with a source of a trophic factor could be a promising tool to promote nerve regeneration and, therefore, become useful also for a clinical approach to repair long gaps.

Animals↗
PubMed1999

Process steps for the preparation of purified fractions of alpha-lactalbumin and beta-lactoglobulin from whey protein concentrates.

Fractions enriched with alpha-lactalbumin (alpha-la) and beta-lactoglobulin (beta-lg) were produced by a process comprising the following successive steps: clarification-defatting of whey protein concentrate, precipitation of alpha-lactalbumin, separation of soluble beta-lactoglobulin, washing the precipitate, solubilization of the precipitate, concentration and purification of alpha-la. The present study evaluated the performance of the process, firstly on a laboratory scale with acid whey and then on a pilot scale with Gouda cheese whey. In both cases soluble beta-lg was separated from the precipitate using diafiltration or microfiltration and the purities of alpha-la and beta-lg were in the range 52-83 and 85-94% respectively. The purity of the beta-lg fraction was higher using acid whey, which does not contain caseinomacropeptide, than using sweet whey. With the pilot scale plant, the recoveries (6% for alpha-la; 51% for beta-lg) were disappointing, but ways of improving each step in the process are discussed.

Cheese↗
PubMed1993

[Lyme borreliosis].

Explore the source record for details and available documents.

Dose-Response Relationship, Drug↗
PubMed1977

Hepatitis syphilitica. A clinico-pathological study of 25 cases.

Specific histological alterations have been observed in 23 of the 25 patients with early syphilis with laboratory findings suggesting liver damage. Treponema has been detected in the areas of liver lesion in 70 per cent of the patients. Control examination carried out after penicillin therapy showed regression of the alterations. On the basis of the findings authors assert that treponema might induce hepatitis in early syphilis differing from liver damage of other origin.

Female↗
PubMed1975

Early syphilitic hepatitis.

17 out of 175 cases of early syphilis had clinical, biochemical, and immunological evidence of liver damage. Before penicillin therapy the histological appearance of the liver was abnormal in 14 of the 15 patients from whom biopsy specimens were obtained. In 7 cases, treponemes were seen in the liver. After two months' penicillin therapy the extent and severity of the histological abnormality was reduced. In the repeat liver-biopsy specimens obtained after penicillin treatment no treponemes could be demonstrated. It is suggested that the hepatitis found in these 17 cases of early syphilis was produced by treponemes.

Adult↗
PubMed1975

Syphilitic hepatitis: clinical, immunological and morphological aspects.

In 17 out of 176 cases of early syphilis (seropositive syphillis I; syphilis II) liver function tests yielded a positive result. In these patients a significant increase in the serum IgG, IgM and coeruloplasmin levels and a decrease in t4e transferrin level was found. The concentrations of alpha-2-macroglobulin and of beta-1-C-globulin were practically uneffected. Liver biopsy revealed hepatitis of variable severity in 13 patients with focal necroses or a proliferative process effecting the walls of the central veins, the arterioles and the branches of the portal vein. In 7 cases the presence of Treponema in the liver was demonstrated.

Adult↗