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W Meier-Ruge

Publications and source records attributed to W Meier-Ruge.

149 records · Page 9Linked to original sources
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Morphometry of axon cytoskeleton at internodal regions of rat sciatic nerve during aging.

BACKGROUND: Nerve endings undergo a lifespan morphofunctional modulation which is reported to be markedly impaired with aging. Neurone structural remodelling is in charge of processes occurring in the nerve cell soma, however the axonal transportation of organelles and molecules by cytoskeletal elements plays a very important role in the morphological rearrangements taking place at peripheral compartments. OBJECTIVE: To assess the involvement of axonal ultrastructure in the reported age-related decline of slow axoplasm flow mechanisms, we carried out a morphometric study of axon cytoskeleton in aging. METHODS: Female Wistar rats (3, 12 and 30 months of age) were anesthetized and perfused with saline followed by a fixation solution (glutaraldehyde 5% + formalin 2% in 0.1 cacodylate buffer pH 7.4). The excised sciatic nerves were processed according to conventional electron microsopic procedures. Axons sectioned perpendicularly to their longitudinal axis at the internodal region (mean axoplasm area: 18.25-26.5 microm(2)) were sampled by a systematic random procedure. The overall number of neurofilaments (No.Nfs) and microtubules (No.Mts) per total axoplasm area analysed, the numeric density (number/microm(2) of axoplasm area) of neurofilaments (NaNfs) and microtubules (NaMts), the myelin thickness, the number of myelin lamellae and the R proportion [No. Nfs/(No.Nfs + No.Mts)] were the parameters measured by computer-assisted semiautomatic methods. RESULTS: No.Nfs, NaNfs, myelin thickness and the number of myelin lamellae did not change between 12 and 30 months of age, while a significant increase of these parameters was found in a comparison with younger rats. No.Mts and NaMts were significantly increased at 12 vs. 3 as well as at 30 vs. 12 months of age, respectively. R proportion did not show any difference due to age. CONCLUSIONS: The present findings support that the dynamic condition of the axonal cytoskeleton appears to be preserved at a high extent in aging. Thus, the intra-axonal defective spacing of cytoskeletal elements (e.g. neurofilaments), rather than their number, is proposed to contribute to the decline of the slow axonal transport of organelles and molecules reported in aging.

Actin Cytoskeleton↗
PubMedDate not supplied

The significance of glucose turnover in the brain in the pathogenetic mechanisms of Alzheimer's disease.

This paper presents a comprehensive survey of the pathogenesis and pathophysiology of Alzheimer's disease (AD). Two mechanisms are of etiological importance in the development of a degenerative dementing brain disease: 1. Lesions in the mitochondrial genome that are caused by free radicals. Primary degenerative AD is characterized by a tendency to acquire random lesions within mitochondrial DNA that are produced by free radicals. The consequence of these lesions is a decrease in glucose turnover and a decline in oxidative phosphorylation. Point mutations on chromosome 21 are hypothesized to increase the susceptibility of mitochondrial DNA to lesions created by free radicals. 2. Ischemic brain lesions as well as traumatic brain damage cause an increase in the release of excitotoxic amino acids (glutamate, aspartate, etc.). These neurotransmitters increase CA(+2) influx into the nerve cell and significantly lower energy production. From a pathogenetic point of view, AD is characterized by a decrease in glucose turnover in the brain. The progression of AD can be monitored by F18- deoxyglucose PET studies. This technique also allows the recognition of patients who are prone to develop AD. The actual development of a cognitive deficit is a threshold phenomenon that occurs if glucose turnover in the hippocampus or temporoparietal cortex drops below a critical level of about 40% of the level of age-matched controls. The low glucose turnover in AD causes a cholinergic deficit by decreasing the synthesis of AcCoA, which is used by choline acetyltransferase in the acetylation of choline to acetylcholine. The decrease in glucose turnover also reduces oxidative phosphorylation. The resulting decrease in ATP triggers the hyperphosphorylation of tau protein by activating protein kinase 40erk. The hyperphosphorylation leads to the development of paired helical filaments. The generation of beta amyloid and the loss of neuronal synapses are also caused by a decrease in oxidative phosphorylation, since beta amyloid precursor proteins are not inserted into the membranes of nerve cells in the absence of a sufficient amount of ATP. This results in the generation of intact beta amyloid molecules and leads to amyloidosis in the brains of patients with Alzheimer's disease.

Aged↗
PubMedDate not supplied

[Experimental plasmin arthritis].

It is known, that plasmin is capable of specifically activating the complement factors C1 q and C3. In addition plasmin can activate procollagenase to collagenase. Since both mechanisms could possibly play a decisive role in the pathogenesis of rheumatoid arthritis, we have carried out animal experiments to investigate the primary role of plasmin in the development of arthritis. Twenty-two rabbits were subjected to intraarticular injection with an equal dose of plasmin on days 1, 4, and 8. An aspirate was taken on day 9 for a white cell count and a histological investigation of the synovial tissue. Already after a single dose of 0.25 CU plasmin an inflammatory reaction was clearly observed. Increasing amounts of plasmin (2.5 and 12.5 CU) caused an increased inflammatory response. On the basis of these results, it is discussed whether the observed arthritic reaction after plasmin injection is caused by complement activation. Possible analogies with rheumatoid arthritis are discussed.

Animals↗