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Biomedical subjects

G Wolf

Publications and source records attributed to G Wolf.

At least 181 records · Page 10Linked to original sources
PubMed1999

[Stimulation of Schwann cell growth and axon regeneration of peripheral nerves by the immunosuppressive drug FK 506].

BACKGROUND: Nerve allografts are highly antigenic and, thus, require the continuous use of immunosuppressive drugs. The immunosuppressant Cyclosporine A was used in most studies. More recently, the immunosuppressive effect of FK 506 on peripheral nerve allografts and xenografts has been studied, and the drug has been found to prevent rejection successfully. However, neurotoxic complications have been noted in the central and peripheral nervous system although an increased rate of axonal regeneration has also been shown. METHODS: Schwann cells were cultured from the sciatic nerve of the rat. The effect of 100 microM FK 506 administered daily on these cultures was assessed over a period of seven days and compared to an untreated control group of cultures. To visualize a direct effect of FK 506 on Schwann cells, the changes in intracellular calcium were recorded using fluorescence imaging of primary rat Schwann cell cultures loaded with Fluo-3. Regeneration of autologous nerve grafts was assessed in a rat model clinically and morphometrically after daily administration of 0.6 mg FK 506/kg body weight. RESULTS: FK 506 increases the number of Schwann cells in culture significantly compared to the control group, while the fibrocyte population is decreased. FK 506 caused a transient increase of intracellular calcium levels of cultured cells. A significantly higher axon count was observed in the FK 506-treated grafts after two weeks of regeneration compared with controls. Additionally, less myelin debris was evident in the FK 506 treated group after two weeks compared with the control group. Good regeneration was noted in all grafts after six weeks of regeneration. CONCLUSION: The increased axon counts and decreased myelin debris in the FK 506 grafts after two weeks indicate an accelerated Wallerian degeneration and increased axon sprouting into the graft initially. FK 506 promotes axonal regeneration through binding to FKBP-12, thus activating GAP-43 (growth associated protein) and the TGF beta 1-pathway (transforming growth factor). In addition, the increase of the intracellular calcium may induce Schwann cell proliferation via Calmodulin which in turn promotes axonal regeneration.

Animals↗
PubMed1999

[Effect of pre-degeneration of peripheral nerves on plasticity of cultivated Schwann cells and their cell number in vitro].

Predegeneration of peripheral nerve grafts is known to improve axonal regeneration in the sciatic nerve of the rat. Predegeneration involves sectioning the donor nerve in situ for a period of time prior to harvesting in order to allow Wallerian degeneration to take place. It is suggested that proliferating Schwann cells are responsible for this regeneration-promoting effect due to an increased production and accumulation of trophic factors. The aim of this study was to evaluate whether the proliferation of Schwann cells is increased after various predegeneration periods and whether predegeneration does affect the production of trophic factors. The rat's sciatic nerve was transsected distal to the spinal ganglion. Predegeneration was allowed to take place for one, two, three and four days and one, two and three weeks, respectively. The nerve was resected and prepared for Schwann cell cultivation. Cells cultivated from the contralateral untreated nerve served as control. S100 immunostaining, nerve-growth factor (NGF), and N-cadherin were used to characterize Schwann cells. Viability was assessed by fluoresceine fluorescence staining. Proliferation index was determined by BrdU DNA incorporation. Cultivation of cells harvested from predegenerated nerves indicated an increased proliferation of Schwann cells compared to the control. Proliferation effects depended on the period of predegeneration. A higher cell yield was obtained as early as 24 hours and up to three weeks after predegeneration. Optimal proliferation was seen after one week of predegeneration. The rapid expansion of Schwann cell populations oppressed the development of contaminating fibroblasts. NGF and N-cadherin were expressed by all S100-positive cells. Predegeneration did not affect viability. The determined high mitotic activity of predegenerated Schwann cells in combination with an early onset of proliferation may explain the regenerating-promoting effect of predegenerated nerve grafts. The expression of both NGF and N-cadherin in the predegenerated cultures indicates a high level of plasticity with dedifferentiation capacity, which in turn promotes neural regeneration. Predegeneration allows a proliferation of Schwann cells without concomitant pharmacological treatment. Thus, predegeneration of peripheral nerves is considered to be a highly efficacious method if a high yield of activated Schwann cells is desired within a short period of time. This may become relevant in the future of repair of peripheral nerve lesions, when autologous Schwann cells with their capacity to provide neurotrophines and cell adhesion molecules are used as cellular prostheses to bridge nerve gaps.

Animals↗
PubMed1999

Successful implantation of Schwann cells in acellular muscles.

Acellular muscle grafts can support axonal regeneration over short gaps. Due to the lack of viable Schwann cells in the grafts, failure of regeneration is evident with increasing gap lengths. To create a biological nerve conduit, Schwann cells were implanted into acellular muscle. The grafts were then incubated in vitro and assessed histologically and morphometrically. For cultivation of the Schwann cells, rat sciatic nerves were allowed to predegenerate to obtain a high cell yield. Rat gracilis muscles were harvested and made acellular by a liquid nitrogen treatment. After Schwann cell implantation, the muscles were incubated in vitro for 2, 5, and 7 days. S100-immunostaining, NGF, and N-cadherin, characterized the Schwann cells within the muscle. Viability was assessed by fluoresceine-fluorescence staining. Proliferation was determined by BrdU-DNA incorporation. Cell implantation did not to affect Schwann cell viability. Cells were seen throughout the entire length of the muscle basal lamina. They aligned and formed a cell column. Immunostained for S-100, implanted cells showed 100 percent staining. N-cadherin and NGF were expressed by all of the S-100 positive cells. Predegeneration is considered to be a highly efficacious method, if a high yield of activated Schwann cells is required. The successful implantation of the cells into an acellular muscle provides the possibility of a biologic conduit, offering the advantage of large basal lamina tubes serving as a pathway for regenerating axons. It also provides the beneficial effects of viable Schwann cells that produce neurotrophic and neurotropic factors to support axonal regeneration. Functional outcomes require evaluation in further in vivo studies.

Animals↗
PubMed1999

Acellular muscle with Schwann-cell implantation: an alternative biologic nerve conduit.

Denatured or acellular muscle grafts are known to support axonal regeneration. With increasing gap length, failure of regeneration is evident, due to the lack of viable Schwann cells in the graft. The authors created a biologic nerve conduit, in a rat sciatic nerve model, by implanting cultured Schwann cells into an acellular gracilis muscle. Autologous nerve grafts and acellular muscle grafts without Schwann cells served as controls. After 6 weeks, regeneration was assessed clinically, histologically, and morphometrically. Polymerase chain reaction (PCR) analysis showed that the implanted Schwann cells remained viable within the graft. Good regeneration was noted in the muscle-Schwann cell group, while regeneration in the muscle grafts without Schwann cells was significantly impaired. The muscle-Schwann cell graft demonstrated systematic and organized regeneration, including the proper orientation of regenerated fibers. The number of axons regenerating through the muscle-Schwann cell grafts was significantly increased, compared with the acellular muscle without Schwann cells. Implantation of Schwann cells into acellular muscle thus provided a biologic conduit with large basal lamina tubes, as a pathway for regenerating axons. The positive effects of Schwann cells, producing neurotrophic and neurotropic factors, supported axonal regeneration.

Animals↗
PubMed1999

Chromosomal alterations in peripheral lymphocytes of female cabin attendants.

PURPOSE: To analyse lymphocyte chromosomes from female cabin attendants flying the North Atlantic route. MATERIALS AND METHODS: Peripheral lymphocytes from 58 cabin attendants and 29 controls, all female, were cultured and analyzed for structural chromosomal aberrations and sister chromatid exchanges (SCE). Cytogenetic data from 56 age-matched females from Berlin investigated between 1994 and 1996 as part of routine medical checks were used as an additional control group. RESULTS: The mean frequencies of dicentric and ring chromosomes per 1000 cells amount to 1.3+/-0.2 in cabin attendants, 1.4+/-0.2 in ground personnel and 1.3+/-0.2 in the Berlin control group. Sister chromatid exchanges were found at mean frequencies of 7.0+/-0.1, 6.8+/-0.1 and 6.8+/-0.2 per cell respectively in the three groups. CONCLUSIONS: When compared with controls, cabin attendants have no elevation of the frequencies of dicentric and ring chromosomes and SCE.

Adolescent↗
PubMed1999

Cytogenetic investigations in flight personnel.

During long-distance flights at high altitudes flight personnel are exposed to cosmic radiation. In order to determine whether there are biological effects of such low dose radiation exposure in aircrew, chromosomal aberrations were investigated in 59 female cabin attendants and a matched control group of 31 members of station personnel. The mean number of dicentric chromosomes amounts to 1.3 (95% CI 1.0-1.6) per 1000 cells in cabin attendants and 1.4 (95% CI 1.0-1.9) per 1000 cells in controls. In an additional control group of 56 female clerks from Berlin the mean frequency of dicentric chromosomes was 1.3 (95% CI 1.0-1.6). Neither in dicentric frequency and distribution nor in other aberrations was a significant difference between the groups of flight and station personnel found. The high frequency of multi-aberrant cells was remarkable in flight personnel as well as in station personnel. The reason for this phenomenon is unknown and needs further investigation.

Adult↗
PubMed1999

The molecular mechanism of the stimulation of adipocyte differentiation by a glucocorticoid.

The glucocorticoid dexamethasone (dex) stimulates differentiation of cultured preadipocytes of the 3T3-L1 cell line to adipocytes. The preadipocytes express a gene termed preadipocyte factor 1 (pref-1). The pref-1 gene product is abundant in preadipocytes but completely absent in adipocytes. Constitutive expression of pref-1 blocks differentiation of adipocytes, as does a soluble 50 kDa fragment of the pref-1 protein. It appears that dex mediates adipogenesis by down-regulating expression of pref-1.

Adipocytes↗
PubMed1999

The role of oxysterols in cholesterol homeostasis.

Cholesterol biosynthesis is regulated by transcription factors named steroid regulatory element-binding proteins. A newly discovered transcription factor, LXR, regulates the catabolic degradation of cholesterol by activation of the gene controlling cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in the formation of bile acids. Excessive dietary cholesterol leads to increased oxysterol formation. Oxysterol binds to LXR and thereby induces transcription of cholesterol 7 alpha-hydroxylase, thus increasing the removal of cholesterol as bile acids.

Animals↗
PubMed1999

A case of human vitamin A deficiency caused by an inherited defect in retinol-binding protein without clinical symptoms except night blindness.

Two German siblings were found to suffer from night blindness and mild retinal dystrophy but no other clinical symptoms of vitamin A deficiency. Even though they had no detectable plasma retinal-binding protein (RBP) and their plasma retinol was exceedingly low, they showed normal physiologic functions and growth. Their RBP gene was found to harbor two point mutations. Their post-prandial plasma levels of retinyl esters were normal, and it is likely that they derived their tissue retinol from retinyl esters.

Adaptation, Physiological↗
PubMed1999

Vasoactive factors and tubulointerstitial injury.

Morphological changes of the tubulointerstitial architecture are a major determinant in the progression of chronic renal disease. The evolution of the tubulointerstitial lesion includes early tubular hypertrophy, recruitment of inflammatory cells into the tubulointerstitial space, and proliferation of interstitial fibroblasts resulting in the irreversible changes of tubular atrophy and tubulointerstitial fibrosis. Many of these diverse effects are mediated by autocrine or paracrine release of growth factors, cytokines, and chemokines. Proteinuria, reduction in functional renal mass per se, alterations in tubular fluid reabsorption, and well as hemodynamic changes in the injured kidney may all stimulate local release of such growth factors. A more recent conception is that vasoactive substances, traditionally viewed to be only involved in the regulation of vascular tone, could actually mediate many of these functions of the more 'classical' growth factors and cytokines. In this regard, one of the most intensively studied vasoactive substances is angiotensin II which has been linked to the progression of renal disease by a host of mechanisms, including the induction of tubular hypertrophy and proliferation of interstitial fibroblasts. There is also increasing evidence that other vasoconstrictive factors such as endothelins and eicosanoids are involved in pathophysiological changes leading eventually to tubulointerstitial fibrosis. On the other hand, natriuretic peptides may exert antifibrogenic properties. Although interference with the renin angiotensin system is currently the only treatment being effective in attenuating the loss of function in patients with chronic renal insufficiency, it is likely that future studies will also investigate the role of other vasoactive substances in the progression of human chronic renal disease.

Angiotensin II↗
PubMed1999

The expression of proUK in Escherichia coli: the vgb promoter replaces IPTG and coexpression of argU compensates for rare codons in a hypoxic induction model.

The expression of the proUK gene was improved by the coexpression of the argU gene cloned in a moderate copy number vector. As the proUK gene contains 2% AGG/AGA codons, which is much higher than the normal frequency in E. coli, about 0.14%-0.21%, the argU gene cloned in a multicopy plasmid was coexpressed with the proUK expression vector in our experiments. In E. coli strain BL21(DE3), IPTG is known to induce the expression of T7 RNA polymerase gene and this enzyme can transcribe the proUK gene under the control of the T7 promoter leading to expression of proUK. To replace IPTG by a cheaper alternative on a large scale, we constructed a plasmid in which the vgb promoter--which is known to be activated by the onset of hypoxic conditions--controls the T7RNA polymerase gene expression. Low oxygen conditions were then used to activate the vgb promoter causing T7RNA polymerase gene expression and finally leading to the expression of proUK as inactive inclusion bodies. Our experiments on a large scale in a bioreactor show that the expression of proUK accounts for about 30% of total protein after about 6 h of anaerobic cultivation, so the presented model represents an economical alternative to IPTG induction.

Bacterial Proteins↗
PubMed1999

Remote microscopy through the internet.

A fully robotic microscope Axioplan2 (Zeiss) and CCD camera (RGB-Sony) mounted on this microscope have been connected to a computer dedicated as an Internet server. This server is available by means of an Internet browser with an interpreter of the Java programming language. We have used Java technology for remote control this full-motorized telemicroscope. The Java program for microscope control is automatically downloaded and started when the user selects the Web site of the corresponding microscope server with his Internet browser. At the client's side, there is no need for any additional software except for what is included in Netscape Navigator 3.0, Microsoft Explorer 3.0 or its later versions. Our remote microscope can be remotely controlled from any place in the world through the Internet. The user can move the microscope stage, change the magnification or can execute any other microscope operations by pressing the related buttons of the downloaded telemicroscopy client program. The microscope server receives the commands from the client program, executes the operation on the microscope and after every new command distributes the next microscope image to the connected telemicroscopy clients. There are also software modules which allow marking a field of interest in the image and discuss. Every Internet user can control the remote microscope and discuss the images with others who have direct access to the Internet on-line, or are connected by modem or ISDN. The quality of the transferred microscopic images and response time is sufficient for practical use. No complicated installation processes are necessary and the system is easy to use. The system design makes every pathologist, who is the Internet user, to be a possible consultant.

Internet↗
PubMed1999

Glutathione levels in primary glial cultures: monochlorobimane provides evidence of cell type-specific distribution.

Because glutathione (GSH) levels in glia play an important role in cellular defense against oxidative and nitrosative stress, the present study was designed to study GSH levels in the primary glial cell cultures. Here we used fluorescence microscopy and spectroscopy with monochlorobimane for measurement of intracellular glutathione content. Monochlorobimane showed high specificity for GSH with very little binding to protein sulphydryls as ascertained from the low fluorescence intensity of the protein fraction of the cells as well as from the low fluorescence of the GSH-depleted cells. The formation of the monochlorobimane-glutathione conjugate was observed to be enzymatically catalyzed as seen from its higher rate of formation in the presence of cell homogenate. A monochlorobimane concentration of 60 microM was used for conjugation of cellular GSH; at higher mBCl concentrations there was no appreciable increase in fluorescence. Therefore, cultures were treated with 60 microM mBCl for an incubation time of 20 min (beyond this time, export of the bimane-glutathione adduct was significantly large) and examined by fluorescence microscopy. This adduct could be fixed with a mixture of paraformaldehyde and glutaraldehyde, and excellent fixation was observed with 4% paraformaldehyde and 0.2% glutaraldehyde. Analysis of the fluorescence images revealed differences in fluorescence intensity between astro- and microglial cells, which were identified by glial fibrilliary acidic protein and OX42 staining, respectively. Microglial cells isolated from primary glial cultures were found to have higher GSH content than astrocytes. Biochemical determination of GSH levels in microglia isolated from primary glial cultures corroborated this fact. From our findings it seems that owing to the greater intracellular concentration of reactive oxygen and nitrogen species to which microglia are subjected, especially under conditions of inflammation, this cell type is fortified with higher GSH levels as a means to combat oxidative and nitrosative stress.

Animals↗
PubMed1999

[Endoscopic treatment of lacrimal duct stenoses using a KTP laser--report of initial experiences].

BACKGROUND: Since four years, endoscopes with which the mucosa and disorders of the lacrimal drainage system can be examined directly, are available. The wish to treat lacrimal disorders with endoscopes and laser have remained. PATIENTS AND METHODS: Between January 1996 and February 1997. 12 patients with acquired lacrimal stenosis were treated with an Hyb:Erbium-YAG-laser and 32 patients were treated with a KTP-laser (quasi-cw mode, wavelength 532 nm and 10 W power). Five patients were treated for lower canaliculus stenosis and seven patients for postsaccal stenosis with the Hyb:Erbium-YAG-laser. 32 patients with postsaccal stenosis were treated with the KTP-laser to perform a bony window of 5 x 5 mm. Bicanalicular intubation into the nose was performed and was left for at least three months. RESULTS: The longest follow up period was 30 months while the shortest was 13 months in the Hyb:Erbium-YAG-laser group. Treatment was successful in four cases with a canalicular stenosis, but restenosis occurred in all cases of postsaccal stenosis and in one case of canalicular stenosis and required a conventional DCR. In the KTP-laser group 25 patients are patent and have no symptoms, 4 patients have watering cold weather and 3 patients had a restenosis. Follow-up range between 2 months and 12 months. CONCLUSIONS: The Hyb:Erbium-YAG-laser is successful in thin membranes and small restenosis. With the KTP-laser a successful transcanalicular laser assisted DCR is possible.

Aged↗
PubMed1999

[Selection of BVDV genotype II isolates using a monoclonal antibody and FACS analysis].

The infection of cattle with the bovine viral diarrhea virus (BVDV) in Germany is gaining attention and guidelines for the "protection of cattle farms against BVDV infections" were passed in 1997. New investigations about the damages induced by BVDV infections as well as the new occurrence of so-called BVDV genotypes (BVDV I and II) made the problems to become aware. The newly described BVDV genotype considerably differs both genetically and antigenetically from the up to now known BVD-viruses (BVDV I). The subdivision in BVDV genotypes I and II is based on genomic differences, which are determined by sequence analyses of different parts of the viral genome. Here, we describe the classification of BVDV in genotypes using a monoclonal antibody and indirect immunofluorescence with flow cytometry (FACS) based analysis. The suitability of the mab WB160 (Central Veterinary Laboratory, Weybridge; UK) for the classification of both BVDV-genotypes was first checked using genetically defined BVDV isolates. While all BVDV I isolates (n = 20) reacted with high fluorescence signals, the mab WB160 could not detect any of the defined BVDV II isolates (n = 20). Subsequently, 505 BVDV field strains isolated between 1993-1997 were screened for both genotypes using the mab WB160 and FACS analysis. 33 (6.5%) of the BVDV isolates were classified as BVDV II.

Animals↗