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Biomedical subjects

W Schneider

Publications and source records attributed to W Schneider.

At least 73 records · Page 4Linked to original sources
PubMed2001

The prevention of occupational hand dermatitis in bakers, confectioners and employees in the catering trades. Preliminary results of a skin prevention program.

Occupational skin diseases (OSD) are among the most frequent occupational diseases (OD). Compared to other occupations, bakers, confectioners and employees in the catering trades are at a high risk of developing OSD. In January 1999, the interdisciplinary Skin Disease Prevention Program in the Baking, Hotel and Catering Industries (SDPP) conducted by the Department of Dermatology and Allergology at the Friedrich Schiller University, Jena, in cooperation with the Research Center for Applied System Safety and Industrial Medicine, Erfurt, and the technical experts at the Social Insurance for the Food Industry and Related Professions (Berufsgenossenschaft für Nahrungsmittel und Gaststätten--(BGN)), Erfurt, was initiated. Following detailed analysis of the occupational exposure of the employees and their personal occupational disease history, the patients' diagnosis and therapy was re-evaluated and supplemented if necessary. Individual skin care and protection regimes were demonstrated and practically trained. Skin care and protection products were supplied. Skin-care and protection seminars were offered to volunteering participants. From January to December 1999, 29 affected employees were examined in the OSD clinic. 22 employees (76%) suffered from irritant contact dermatitis. The follow-up data of 11 employees are available. In 8 employees (73%), the skin disease improved or disappeared. Moreover, in 1 employee (9%), the skin condition was stabilized even though he continued working. In only 2 employees (18%) did the skin condition worsen. These preliminary results showed that most of the OSD were due to lack of or unsuitable skin care and protection. The program will be extended to cover a larger number of food industry employees with OSD.

Adolescent↗
PubMed2001

Prolonged cold preservation augments vascular injury independent of renal transplant immunogenicity and function.

BACKGROUND: While prolonged cold ischemia has detrimental effects on graft survival, the mechanisms remain unclear. We tested whether or not cold preservation enhances intragraft inflammatory responses and vascular injury. METHODS: Rat renal grafts were cold preserved in University of Wisconsin solution for 2, 4, 6, 12, 24, and 48 hours, and then transplanted into syngeneic recipients and harvested after 24 hours. Frozen sections were examined histologically and stained for vascular cellular adhesion molecule-1 (VCAM-1), platelet-endothelial cell adhesion molecule-1 (PECAM-1), major histocompatibility complex (MHC) class II, tissue factor, leukocyte function associated molecule-1 (LFA-1), very late antigen-4 (VLA-4), as well as for inflammatory cells. RESULTS: Function did not differ between isografts preserved for shorter (2 to 6 hours) or longer times (12 to 24 hours). Neutrophil influx and that of LFA-1-positive cells showed similar increases in all groups. Compared with short preservation groups, the long preserved grafts had more VLA-4-positive ED-1+ monocytic infiltrates adjacent to vessels expressing VCAM-1 (P < or = 0.001). Increased preservation duration had no effect on infiltration with recipient ED-2+ macrophages, MHC class II-positive cells, or dendritic cells. Decreased color intensity and continuity of PECAM-1 staining indicated loss of endothelial integrity in grafts preserved for longer than six hours. Intensity in VCAM-1 staining increased progressively in grafts preserved for more than six hours and was localized predominantly on the endothelium of elastic vessels. Endothelial cells, vascular smooth muscle cells, and monocytes expressed increasingly more tissue factor in grafts preserved for more than six hours, revealing enhanced intragraft procoagulant capacity. Furthermore, grafts with preservation times of more than six hours developed more severe vascular endothelial injury and worse tubular necrosis scores (P < or = 0.001) compared with grafts with shorter preservation times. CONCLUSIONS: Because of the prominent vascular injury, strategies for endothelial protection should be attempted in grafts with long preservation times in clinical renal transplantation.

Animals↗
PubMed2001

[Endovascular therapy of renal artery stenosis: technical results with the Palmaz-Corinthian stent].

OBJECTIVE: To evaluate the technical performance and delivery characteristics of the Palmaz-Corinthian stent for endovascular therapy of atherosclerotic renovascular disease. METHODS: 61 patients underwent implantation of 76 Palmaz-Corinthian (PC) stents in 72 arteries. 50 original PC and 26 PC stents with the modified IQ-design were employed. The indications comprised primary stenting of ostial (n = 49) or truncal (n = 1) stenosis or occlusion (n = 3), and selective stenting following complicated (dissection, n = 4) or unsuccessful (n = 8) angioplasty. The remaining stents were placed in patients with recurrent stenosis (n = 5) or acute aortic dissection (n = 2) involving the renal artery. Mean severity and length of stenosis were 81.3% and 9.8 mm, respectively. 39 lesions were rated eccentric or calcified. Data on technical success, complication rate, delivery characteristics and ease of placement compared to standard renal stents were retrieved from a prospective multicenter registry. RESULTS: Stent delivery was successful in all patients, major complications were not reported. Stent placement was suboptimal in 7 of 72 cases: 4 stents were located too distally in the renal artery, necessitating proximal coaxial overstenting in 2 cases. The distal part of the stenosis was incompletely covered and the orifice of a segmental branch inappropriately overstented in one case each. One stent was dislodged from the balloon, resulting in stent protrusion in the aortic lumen. Significant residual stenosis after stenting was not observed. Overall stent deliverability, trackability and potential repositioning inside the stenosis were rated positive, radio-opacity was rated superior for the IQ design. CONCLUSION: Technical performance and delivery characteristics of the Palmaz-Corinthian stent have been significantly improved compared to the Palmaz design, allowing mostly correct placement in renal artery stenoses with a low complication rate.

Angiography, Digital Subtraction↗
PubMed2001

[Electrophysiological methods for diagnosis of entrapment syndromes of peripheral nerves].

Summary. Apart from clinical findings, the diagnosis of compression syndromes of peripheral nerves is based on electrophysiological investigations. This includes the determination of nerve conduction velocities, distal motor latency and electromyography, which gives a qualitative indication of the condition of nerves and their related muscles. In the 1980s, new methods were developed for quantifying the diagnoses of nerve lesions and their recovery. Due to the development of new software, we can now carry out these investigations with commercial equipment. The macro-EMG and the motor-unit-estimation give information about the size and number of activated motor units of muscles. One needs a special needle which derives single-fibre- and macro-potentials for recording of the macro-EMG. The single-fibre-potential is used for triggering. The motor-unit-estimation represents a non-invasive method to determine the approximate number of motor units. Multiple point stimulation of the nerve is used to determine action potentials which are registered by surface electrodes. Afterwards, the medians of amplitudes and areas of motor unit action potential are defined and must be divided by the corresponding value of maximal compound muscle action potential for estimating motor units. In this way, the extent of nerve damage can be determined exactly. Additionally, a post-operative follow-up is possible. Furthermore, these methods give information about regeneration processes after nerve damage and their recovery after reconstruction and transplantation. From our point of view, these methods should be included in investigation routinely.

Decompression, Surgical↗
PubMed2001

Revascularization of tissue-engineered nerve grafts and invasion of macrophages.

Nonneural derived nerve conduits fail to support regeneration over larger gaps due to lacking viable Schwann cells. Thus, tissue engineering of nerves is focusing on implantation of viable Schwann cells into suitable scaffolds. We established grafts made from acellular muscles and veins, respectively, seeded with cultured Schwann cells. As timing of revascularization is crucial to determine Schwann cell survival and depending axonal regeneration we studied establishment of vascular architecture in a rat sciatic nerve model (2-cm gap) after 3, 5, 7, and 10 days postoperatively, using albumin bound Evans blue. Additionally, macrophage recruitment was immunohistochemically assessed. Engineered grafts showed a delayed revascularization, starting between day 5 and 7 in comparison to normal autografts, that revascularized by day 3. Macrophage recruitment in autologous nerve grafts was evident by day 3. The engineered groups revealed no macrophage invasion until day 7. As Schwann cells survive up to 7 days in autologous grafts without blood supply, depending purely on diffusion, establishment of vascular structure between day 5 and 7 is rapid enough to support Schwann cell survival in engineered grafts. As these grafts are lacking Wallerian degeneration delayed macrophage invasion may not impair degeneration-dependent regeneration, but presence of macrophage derived or induced growth factors may be decreased.

Animals↗
PubMed2001

Left ventricular function in mice lacking the AT2 receptor.

OBJECTIVES: The role of the AT2 receptor in the heart is incompletely understood. We investigated left ventricular performance in AT2 receptor knockout mice, with and without deoxycorticosterone acetate (DOCA)-salt treatment. Given the putative opposing functions of the AT1 and AT2 receptor, we also analysed AT1 receptor expression in the left ventricle. METHODS: We used a miniaturized conductance-manometer system to measure pressure-volume loops for analysing left ventricular performance under baseline conditions and after increasing peripheral vascular resistance. We determined left ventricular AT1-receptor expression by RNase-protection assays. RESULTS: In AT2 receptor knockout mice, end-systolic and end-diastolic volumes were lower than in wild-type mice, so that pressure-volume loops were shifted leftward. Left ventricular systolic and diastolic kinetics were not different between the groups. AT2 receptor knockout mice and wild-type mice both stabilized their reduced stroke volume after laparatomy as peripheral resistance was increased. DOCA-salt treatment increased elastance in AT2 receptor knockout mice, compared to controls. Furthermore, AT2 receptor knockout mice had a steeper increase in dP/dtmax. Left ventricular AT1 receptor gene expression was increased in AT2 receptor knockout mice and was not down-regulated in response to DOCA-salt treatment. Finally, the hearts of AT2 receptor knockout mice were smaller than controls, but increased in size in response to DOCA-salt treatment. CONCLUSIONS: AT2 receptor knockout mice displayed no major changes in left ventricular function at baseline or in response to DOCA-salt treatment, compared to wild-type mice. The AT2 receptor may be important to AT1 receptor expression in response to DOCA-salt challenge and may have some influence on cardiac growth responses.

Animals↗
PubMed2001

Tissue engineering of peripheral nerves: A comparison of venous and acellular muscle grafts with cultured Schwann cells.

Bioengineering is considered to be the laboratory-based alternative to human autografts and allografts. It ought to provide "custom-made organs" cultured from patient's material. Venous grafts and acellular muscle grafts support axonal regeneration only to a certain extent because of the lack of viable Schwann cells in the graft. We created a biologic nerve graft in the rat sciatic nerve model by implanting cultured Schwann cells into veins and acellular gracilis muscles, respectively. Autologous nerve grafts and veins and acellular muscle grafts without Schwann cells served as controls. After 6 and 12 weeks, regeneration was assessed clinically, histologically, and morphometrically. The polymerase chain reaction analvsis showed that the implanted Schwann cells remained within all the grafts. The best regeneration was seen in the control; after 12 weeks the number of axons was increased significantly compared with the other grafts. A good regeneration was noted in the muscle-Schwann cell group, whereas regeneration in both of the venous grafts and the muscle grafts without Schwann cells was impaired. The muscle-Schwann cell graft showed a systematic and organized regeneration including a proper orientation of regenerated fibers. The venous grafts with Schwann cells showed less fibrous tissue and disorganization than the veins without Schwann cells, but failed to show an excellent regeneration. This might be attributed to the lack of endoneural-tube-like components serving as scaffold for the sprouting axon. Although the conventional nerve graft remains the gold standard, the implantation of Schwann cells into an acellular muscle provides a biologic graft with basal lamina tubes as pathways for regenerating axons and the positive effects of Schwann cells producing neurotrophic and neurotropic factors, and thus, supporting axonal regeneration.

Animals↗
PubMed2001

Treatment of bone-marrow oedema of the talus with the prostacyclin analogue iloprost. An MRI-controlled investigation of a new method.

Bone marrow oedema syndrome of the talus is a rare cause of pain in the foot, with limited options for treatment. We reviewed six patients who had been treated with five infusions of 50 microg of iloprost given over six hours on five consecutive days. Full weight-bearing was allowed as tolerated. The foot score as described by Mazur et al was used to assess function before and at one, three and six months after treatment. The mean score improved from 58 to 93 points. Plain radiographs were graded according to the Mont score and showed grade-I lesions before and after treatment, indicating that no subchondral fracture or collapse had occurred. MRI showed complete resolution of the oedema within three months. We conclude that the parenteral administration of iloprost may be used in the treatment of this syndrome.

Adult↗
PubMed2001

STEP--a System for Teaching Experimental Psychology using E-Prime.

Students in psychology need to learn to design and analyze their own experiments. However, software that allows students to build experiments on their own has been limited in a variety of ways. The shipping of the first full release of the E-Prime system later this year will open up a new opportunity for addressing this problem. Because E-Prime promises to become the standard for building experiments in psychology, it is now possible to construct a Web-based resource that uses E-Prime as the delivery engine for a wide variety of instructional materials. This new system, funded by the National Science Foundation, is called STEP (System for the Teaching of Experimental Psychology). The goal of the STEP Project is to provide instructional materials that will facilitate the use of E-Prime in various learning contexts. We are now compiling a large set of classic experiments implemented in E-Prime and available over the Internet from http://step.psy.cmu.edu. The Web site also distributes instructional materials for building courses in experimental psychology based on E-Prime.

Humans↗
PubMed2000

Neuroma: a donor-age independent source of human Schwann cells for tissue engineered nerve grafts.

Schwann cells are used in combination with biological matrices as tissue engineered nerve grafts in animal models offering a new therapeutic approach for treatment of lesions of the peripheral nervous system. A high yield of human Schwann cells from adult donors is only achieved by pharmacological stimulation, which should, however, be avoided in clinical therapy. Here, we establish cultures of activated human Schwann cells which were isolated from peripheral nerve neuroma which developed after a median nerve lesion. To allow nerve reconstruction neuroma have to be resected. Such neuroma tissue is virtually predegenerated and shows activation of Schwann cells, implying good adherence and high mitotic activity. This allows, irrespective of donor age, growing within a short time period and without any pharmacological treatment.

Adult↗
PubMed2000

Cooper minima in the photoemission spectra of solids.

Variations of the photoionization cross section of valence states as a function of interatomic distance are studied by means of atomic and solid-state density functional approaches and compared with photoemission data. In contrast to the free atom case, a series of Cooper minima is found for 4d, 5d, and 5f states in Pd, Ag, Au, and U metals. The discovered fundamental phenomenon is of high importance for the correct interpretation of photoemission data.

Journal Article↗
PubMed2000

Composition, synthesis, and assembly of the embryonic chick retinal basal lamina.

To study the biology of basal laminae in the developing nervous system the protein composition of the embryonic retinal basal lamina was investigated, the site of synthesis of its proteins in the eye was determined, and basal lamina assembly was studied in vivo in two assay systems. Laminin, nidogen, agrin, collagen IV, and XVIII are major constituents of the retinal basal lamina. However, only agrin is synthesized by the retina, whereas the other matrix constituents originate from cells of the ciliary body, the lens, or the optic disc. The synthesis from extraretinal tissues infers that the retinal basal lamina proteins must be shed from their tissues of origin into the vitreous body and from there bind to receptor proteins provided by the retinal neuroepithelium. The fact that all proteins typical for the retinal basal lamina are abundant in the vitreous body and a new basal lamina is only formed when the vitreous body was directly adjacent to the retina is consistent with the contention of the vitreous body having a function in retinal basal lamina formation. Basal lamina assembly was also studied after disrupting the retinal basal lamina by intraocular injection of collagenase. The basal lamina regenerated after chasing the collagenase with Matrigel, which served as a collagenase inhibitor. The basal lamina was reconstituted within 6 h. However, the regenerated basal lamina was located deeper in the retina than normal by reconstituting along the retracted neuroepithelial endfeet demonstrating that these endfeet are the preferred site of basal lamina assembly.

Agrin↗
PubMed2000

Cryopreservation of peripheral nerve grafts.

The utilization of viable biological nerve graft substitutes and nerve allografts raises the problem of nerve storage. To clarify this, rat sciatic nerve segments were harvested and stored in Dulbecco's modified eagle medium. The segments were divided into three groups. In the first group, no cryoprotectant was added, whereas the second had 10% dimethyl sulfoxide (DMSO) added as cryoprotectant. These two groups of nerve segments were subjected to controlled freezing. In a third group, segments were frozen uncontrolled in liquid nitrogen (-196 degrees C). All nerves were replanted orthotopically. Fresh conventional autografts (fourth group) served as control group. Histologically, freezing did not affect the structural elements such as basal lamina tubes and perineurial tissue. Morphometrically, all cryopreserved grafts had significantly reduced axon counts and less myelinization than did controls. Cryoprotected nerves (group 2) showed no different morphometric parameters compared with the group without DMSO (group 1). Controlled freezing was superior to uncontrolled freezing (group 3). Impaired regeneration was attributed mainly to delayed Wallerian degeneration and slower revascularization. Moreover, decreased survival of resident Schwann cells in the graft may impair regeneration due to the lack of neurotrophic, neurotropic, and attachment factors in early regeneration. Grafts subjected to controlled freezing support axonal regeneration to a certain extent, but further studies are required to assess various cooling patterns, cryoprotectants, and graft revascularization.

Animals↗