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Biomedical subjects

A Walter

Publications and source records attributed to A Walter.

At least 55 records · Page 3Linked to original sources
PubMed1998

[Experiences with "reversed tip and snip" phacoemulsification].

UNLABELLED: The endothelial cell count after phacoemulsification serves as a sensitive indicator for the level of corneal traumatization caused by different phacoemulsification techniques concerning the used phacotime and phacoenergy/s. PATIENTS: In a prospective and randomized study, the "reversed tip and snip" technique and the "divide and conquer" technique were performed in groups of 30 patients each. The corneal endothelial cell count was measured preoperatively as well as 4 weeks and 3 months postoperatively. In a second study the phacotime and phacoenergy used/second and the endothelial cell loss were compared between patients 1-30 and 31-60 who were operated on with the "reversed tip and snip" technique, demonstrating the learning curve of this technique. RESULTS: The endothelial cell count showed significant (P < 0.001) reduction by about 10% after the "reversed tip and snip" technique and by about 15% after the "divide and conquer" technique. The latter produced significantly greater cell loss. The phacotime (mean: 22-17) and phacoenergy/s (mean: 23-16) were reduced significantly (P < 0.05) when patients 1-30 were compared with 31-60. CONCLUSION: The "reversed tip and snip" phacoemulsification technique produces less endothelial cell loss than the "divide and conquer" technique. There is a short learning curve by using the "reversed tip and snip" technique.

Aged↗
PubMed1998

Limitations of imaging choroidal tumors in vivo by optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) produces two-dimensional cross-sectional images with a longitudinal resolution of 10 microns. Its capacity for imaging retinal structure has been shown in a variety of diseases. There are no reports on its capacity and limitations in imaging choriocapillary and choroidal structures. METHODS: Twenty-two patients with the diagnosis of malignant melanoma of the choroid were submitted to OCT. We used a prototype and a commercial device, both with an 850-nm superluminescent diode with a band-width of 30 nm (reported longitudinal resolution 10 microns). The images were evaluated for retinal thickness, changes in retinal pigment epithelium, subretinal fluid accumulation and changes in choriocapillary or choroidal reflectivity. RESULTS: Retinal edema and detachment found on biomicroscopic examination for fluorescein angiography was detected by OCT in all such cases. In 2 of 22 cases small retinal detachments were detected only by OCT. Tumor extension through the retinal pigment epithelium was not seen in this series, either by biomicroscopy or by OCT. The pattern of choroidal or choriocapillary reflectivity was nonspecifically lower than that of normal choroid, but did not yield any additional information about tumor histology. When normal retina was present, the OCT appearance of a malignant melanoma resembled that of normal choroid. CONCLUSION: OCT may provide information about the retinal structure overlying prominent tumors and the extent of adjacent retinal detachment. In its present state of development, OCT is of little value in the differential diagnosis of choroidal tumors. Its potential value for the follow-up of shallow tumors needs further investigation.

Adult↗
PubMed1998

Effect of microbial phytase on zinc bioavailability and cadmium and lead accumulation in growing rats.

This study evaluated the effect of increasing levels of dietary microbial phytase on the bioavailability of zinc and the accumulation of cadmium and lead in growing rats. Five groups of seven albino rats (initial average weight 47 g) were housed individually and fed phytate-rich diets (7 g/kg) based on maize, soya bean meal, corn starch and soya bean oil over a 4-week experimental period. The basal diet contained 24 mg zinc (native concentration), 10 mg lead as Pb(CH3COO)2.3H2O and 5 mg cadmium as CdCl2 per kg and was supplemented with 0, 250, 500, 1000 and 2000 U phytase from Aspergillus niger per kg diet. Supplementation of microbial phytase significantly increased apparent zinc absorption. Differences in zinc bioavailability due to supplementation of the diet with microbial phytase were evident in zinc concentration in plasma, femur and testes as well as in the percentage unsaturated plasma zinc binding capacity and the activity of the zinc metalloenzyme alkaline phosphatase. Cadmium concentrations in liver and kidneys were not significantly altered in response to the different dietary treatments. There was a tendency for femur lead concentration to be increased in response due to the phytase supplementation.

6-Phytase↗
PubMed1998

[Tyndallometry in patients with diabetic macular edema before and after central laser coagulation].

BACKGROUND: It is known that the breakdown of the blood-retina-barrier (BRB) as well as the blood-aqueous-barrier (BAB) is one of the earliest pathopysiological changes in the diabetic eye. Some previous studies confirmed a statistically significant increase of flare values of the aqueous humor in eyes with diabetic retinopathy which is lineary correlated with the protein concentration. This study investigated the effect of a central laser photocoagulation in eyes with clinically significant macular edema on the permeability of the blood-aqueous-barrier (BAB). PATIENTS AND METHODS: We included 22 eyes of 22 patients with diabetes mellitus suffering from clinically significant macular edema determined by fluorescence angiography giving an indication for central laser treatment. Two measurements of aqueous flare were taken, the first before laser photocoagulation (grid with about 100 coagulations) and the second 6 to 8 weeks after treatment. RESULTS: The flare values before treatment were 11.4 +/- 4.1 phc/ms (4.9-23.8) and after treatment 10.0 +/- 3.5 phc/ms (5.7-16.7). There was a significant difference between both measurements (p = 0.039). CONCLUSIONS: The protein concentration of the aqeoues humor is a parameter which allows to characterize the permeability of the BAB. The central laser photocoagulation seems to seal the vessels.

Aged↗
PubMed1998

Effect of citric acid supplements to a maize-soya diet on the in vitro availability of minerals, trace elements, and heavy metals.

The aim of the present study was to evaluate the effect of increasing supplements of citric acid (CTA) on the in vitro availability of mineral (Ca, Mg), trace elements (Mn, Zn) and heavy metals (Pb, Cd). Phytaterich diets (0.8%) based on maize, soybean meal, corn starch and soybean oil (containing 5.0 g Ca, 1.2 g Mg, 50 mg Mn, 22 mg Zn, 10 mg Pb and 5 mg Cd per kg diet) were supplemented with 0, 1, 2, 3 and 4% of CTA. All diets were treated in a multi-enzyme in vitro system followed by equilibrium dialysis after peptic and pancreatic digestion. Under the conditions investigated, dietary addition of CTA enhanced dialysability of calcium, magnesium, manganese and zinc. Furthermore, a dose-dependent increase of lead and cadmium dialysability due to CTA supplementations was evident.

Animal Feed↗
PubMed1997

Patterns of failure in children with medulloblastoma: effects of preirradiation chemotherapy.

PURPOSE: To evaluate the effects of preirradiation chemotherapy on patterns of failure in children with medulloblastoma. METHODS AND MATERIALS: Fifty-three patients (pts) with medulloblastoma were given preirradiation chemotherapy as initial postoperative treatment at St. Jude Children's Research Hospital from November 1984 to September 1993. Patients < or = 3 years of age (n = 23) received chemotherapy (CH) with delayed craniospinal irradiation (CSI). Children > or = 3 years with more advanced disease (T3b-T4, M+ or measurable residual after resection) were given CH followed by CSI (30 patients). Chemotherapy regimen depended on protocol, but usually included cis- or carboplatin and etoposide, +/- cyclophosphamide and vincristine. RESULTS: Actuarial overall survival and event-free survival rates are 60% (95% confidence interval [41,79]) and 37% [19,55] at 5 years. Children < or = 3 at diagnosis: six of 23 pts completed CH without progression and received consolidative CSI; all six are alive with no evidence of disease (NED) at 2.4-9.1 years. Seventeen patients progressed during CH and were then given CSI. Sites of progression during CH were posterior fossa (PF) in 11 patients, neuraxis (NEUR) in 4, and PF+NEUR in 2. Following CSI, 7 patients are alive NED at 2.0-8.6 years; 10 patients died of progressive disease. Eleven patients had M0 disease at diagnosis; 8 (73%) progressed during CH, 3 in the neuraxis. Children > or = 3 at diagnosis: 20 of 30 patients completed pre-CSI CH without progression; 15 are alive NED at 1.3-9.2 years, and 5 showed post-CSI progression in the PF (n = 3), in the NEUR (n = 1) and in bone marrow (n = 1). Ten of the 30 (33%) patients progressed on CH (6 in NEUR, 4 in PF); 5 are alive and NED or with stable disease. Seventeen patients had M0 disease at diagnosis; 3 out of 17 (18%) progressed during CH, 2 in NEUR and 1 in an extraneural site. In the total group of 30 patients, 11 have had disease recurrence after completion of XRT. The actuarial rate of failure was 23 +/- 9% for the patients < or = 3 years of age and 21 +/- 8% for the older children when evaluated at 4 months after diagnosis (at the completion of chemotherapy in the older children but during the ongoing chemotherapy in the younger children). CONCLUSIONS: In patients presenting with M0 disease and receiving pre-CSI chemotherapy, the risk of neuraxis progression seems to increase with duration of chemotherapy. The sites of progression during preirradiation chemotherapy are nearly equally divided between posterior fossa and other neuraxis sites. CSI salvage of patients progressing on chemotherapy is possible in approximately 50% of patients. Following CSI, neuraxis progression is more frequent than posterior fossa relapse.

Adolescent↗
PubMed1997

EMBO fellows go home.

Explore the source record for details and available documents.

Academies and Institutes↗
PubMed1997

[Ceramic-to-ceramic combination. Relic or renaissance?].

More than 20 years after the introduction of the alumina-alumina bearing system for total hip replacements (THRs) in Germany, this combination still only accounts for a small percentage of the conventional combinations with polyethylene cups. Follow-up examinations of ceramic-ceramic THRs with early alumina quality result in an extreme range of linear wear rates from 30 nm to 3.7 mm per year. Simulator tests confirm the potential for minimal debris generation but also show the sensitivity of the system to malpositioning and un-smooth repositioning.

Aluminum Oxide↗
PubMed1997

[Comparative tribological studies of Chirulen, Hylamer and Enduron combined with A1203].

The creep and wear behaviour of Chirulen, Hylamer and Enduron, materials which differ only in their manufacturing procedures, was examined and compared. Chirulen is manufactured by being pressed into form by plates, whereas Hylamer and Enduron are shaped by tubes. Hylamer differs from Enduron in that intermediate material processing is undertaken with the goal of improving the initial material. The wear and deformation rate was determined by means of the ring-on-disc testing device after 360,000 cycles and after 1.0 x 10(6) cycles, respectively. The static tests for the determination of wear were carried out at a contact stress of 5.62 MPa and a testing time of 100 h in analogy to the ring-on-disc tests. Chirulen and Hylamer demonstrated comparable wear with a tendency toward a lower wear rate in Hylamer, while Enduron presented a clearly higher wear rate.

Biocompatible Materials↗
PubMed1997

Food safety training needs exist for staff and consumers in a variety of community-based homes for people with developmental disabilities.

OBJECTIVE: To determine staff and consumer-focused food safety training needs in community-based homes for people with developmental disabilities as well as dietitians' perceptions of food-handling practices in these homes. DESIGN: Direct-care staff and dietitians were surveyed according to a modified Dillman method using a mailed, self-administered questionnaire. Main outcome measures included food-handling knowledge, attitudes, and practices of staff and consumers as reported by staff and dietitians; critical control points in safe food preparation in the homes based on the Hazard Analysis and Critical Control Point system; and learning preferences of staff and consumers. SUBJECTS: A 10% probability sample of direct-care staff in homes for people with developmental disabilities in western Massachusetts and a nonprobability sample of dietitians who work with this population were surveyed. Results are reported from 132 and 18 respondents, respectively. STATISTICAL ANALYSES PERFORMED: Descriptive statistics, chi 2 statistic, and the Fisher's exact test. RESULTS: Staff knowledge of safe food preparation is lacking in several areas, including storage and handling procedures. Although staff and consumers do not always follow safe food-handling practices, the staff reported that they follow recommended food-handling practices more often than the dietitians reported they do. Most staff and dietitians reported that staff and consumers had never attended a food safety training program, but that all of the critical control points surveyed would be somewhat helpful if they were included in a food safety workshop. APPLICATIONS: A food safety training program would be beneficial for staff and consumers. Programs should be geared to staff and include ideas and materials for consumers. Consumer modules could then be adapted to individual learning levels by direct-care staff in the homes. The Safe Food at Home workshop was developed on the basis of the results of this study and incorporates the approaches described in this article.

Adult↗
PubMed1997

DNA binding studies and influence on the activity of DNA topoisomerases of bis-netropsins: different effects of analogs containing cis and trans ethylene linkers.

Binding to DNA and synthetic duplex polymers of two bifunctional netropsins and effects on supercoiled plasmid DNA as well as their inhibitory potency on DNA topoisomerases have been investigated. Characteristic differences were found in the DNA binding properties of the two bis-netropsins containing a cis and trans tether as reflected by CD, thermal melting and sedimentation measurements. CD results indicate, that the bis-netropsins interact with DNA by a two-step binding mode depending on the ligand concentration. The trans bis-netropsin may form stable complexes with different DNA's at high salt concentration, whereas for cis bis-netropsin DNA complexes the second binding step is completely abolished. The variations in the DNA binding ability of trans and cis bis-netropsin show a close relationship to the differences observed in their inhibitory effects on DNA topoisomerases. It appeared that trans bis-netropsin more strongly blocks topoisomerase activity than the cis isomer and represents the most potent inhibitor of DNA gyrase. Differences in the DNA. binding ability of the bis-netropsins and their inhibitory potency on topoisomerase activity are explained in terms of bidentate and monodentate binding mode of the trans and cis isomer, respectively.

Binding, Competitive↗
PubMed1997

Low-grade astrocytoma: a decade of experience at St. Jude Children's Research Hospital.

PURPOSE: To evaluate the impact of primary tumor site, age at diagnosis, extent of resection, and histology on progression-free survival (PFS) in pediatric low-grade astrocytoma. PATIENTS AND METHODS: Medical, pathologic, and imaging information were reviewed for 142 children (ages 2 months to 19 years) with low-grade astrocytoma treated between January 1984 and July 1994. Gross total resection (GTR) was attempted for cerebellar and cerebral hemisphere tumors, with biopsy or less aggressive resection used predominantly for tumors in other sites. Surgery was followed by observation in 107 cases, radiation therapy in 31, and chemotherapy in four. RESULTS: The overall survival rate was 90% +/- 3% (SE) at 4 years. PFS was significantly better for patients with cerebellar and cerebral hemisphere tumors (n = 75) than those with tumors in all other sites (P = .0006). Within the former group, there was no significant difference in PFS for patients in whom GTR was achieved versus those with incomplete resections (4-year estimates, 89% and 77%, respectively). Histology (juvenile pilocytic v astrocytoma not otherwise specified [NOS]) was not related to PFS in an analysis that controlled for tumor site and patient age. Patients younger than 5 years at diagnosis had a significantly poorer PFS than older children, regardless of histology (P < .03) or tumor site (P < .002). Treatment for progressive/recurrent disease was effective in a majority of patients, but appeared more successful in patients with hemispheric than thalamic or hypothalamic tumors. CONCLUSION: The overall survival in this series of pediatric low-grade astrocytomas is excellent. Age at diagnosis and tumor location, but not histology, had a significant impact on PFS. Efforts to improve treatment outcome should focus on young patients (< 5 years) and on those with central midline tumors. The majority of patients with completely resected hemispheric tumors were monitored without further therapy, which supports attempted GTR of cerebral and cerebellar hemisphere low-grade astrocytoma.

Adolescent↗
PubMed1997

[Requirements of optimal working conditions and patient-centered care in hospital nursing].

Nursing--a human service increasing in size and significance--is facing deep changes. The organization of hospital wards is also influenced by these profound changes. The aim of this psychological research project sponsored by the German Federal Ministry for Education and Science, Research and Technology (BMBF) and part of the Saxonian Public Health Association was to determine the external and individual working conditions that put the personnel's health at risk, particularly in regard to burnout syndromes. Investigations should show possibilities in work organization that minimize such risks. Organizational designs have to ensure high quality levels of nursing care, as well as high quality of working conditions in nursing for the individual employee. This empirical study presents the results of an investigation of 53 medical, surgical and intensive care units of 7 Saxonian hospitals with 336 employees of the nursing departments. The size of the hospital, the service profile, the nursing standards and the organizational conditions of the nursing service influence work pressure and working attitude.

Burnout, Professional↗
PubMed1996

DNA index of glial tumors in children. Correlation with tumor grade and prognosis.

BACKGROUND: Although DNA index (DI) has prognostic significance in a variety of pediatric malignancies, there are few data regarding its utility in central nervous system (CNS) tumors. We have previously shown that patients with hyperdiploid medulloblastoma have a significantly better survival than those whose tumors are diploid. Here, we examine the effect of DI and tumor grade on the progression free survival (PFS) of 57 patients with a variety of glial neoplasms. METHODS: DI was determined by flow cytometry on freshly obtained tumor tissue from the initial diagnostic specimens; a DI = 1.0 was defined as diploid (DIP), 1.0 < DI < 1.1 as near diploid (NDIP), and DI > 1.1 as hyperdiploid (HYP). Tumors were histologically graded according to the World Health Organization classification. RESULTS: There were 21 Grade I tumors, 20 Grade II, 8 Grade III, and 8 Grade IV. Among the 41 low grade tumors (Grade I-II), 39 were DIP or NDIP, and 2 were HYP. Among the 16 high grade tumors (Grade III-IV), 9 were DIP, 2 NDIP, and 5 HYP. The 4-year PFS of low grade tumors was 70% (standard deviation [SD] 12%) versus 8% (SD 7%) for high grade tumors. There was a significant correlation between low grade tumor histology and a DIP/NDIP DI (P = 0.015), and univariate analysis suggested improved PFS was associated with DIP/NDIP tumors (P = 0.05). However, DI did not remain a significant prognostic factor after being stratified by tumor grade (P = 0.87). CONCLUSIONS: Unlike medulloblastoma, DI is not an independent prognostic factor in pediatric glial tumors.

Adolescent↗
PubMed1996

Blood-flow sensing by anionic biopolymers.

Using 23Na-NMR techniques we could show that the polyanion proteoheparan sulfate integrated into the membrane of endothelial cells may serve as "flow sensor'. Based on its viscoelastic properties, heparan sulfate proteoglycan is present as a random coil under "no flow' conditions, whereby most of its polyanionic sites undergo intramolecular hydrogen bonding. With increasing flow the macromolecule becomes unfolded into a filamentous structure. Additional anionic binding sites to which Na+ ions from the blood bind are released by this shear stress-dependent conformational change. The Na+ binding triggers the signal transduction chain for a vasodilatory vessel reaction. Decrease in flow effects, for reasons of the intramolecular elastic recoil forces of the macromolecules, an entropic coiling, the release of Na+ ions and thus an interruption of the signal chain. Proteoheparan sulfate adsorbed onto a hydrophobic surface in physiological Krebs solution at pH 7.3 demonstrated clearly its characteristic as a Na+ sensor. While Ca2+ ions modulated the adsorption (promotion with increasing Ca2+ concentrations) by changing the conformation of the sensor molecule, the adsorbed amount was determined preferably by the Na+ concentration. K+ and Mg2+ ions showed slightly desorbing properties with increasing concentrations. Thus, it may be concluded that Na+ ions play the role as "first messenger' in flow-dependent vasodilation.

Biopolymers↗
PubMed1996

Anionic biopolymers as blood flow sensors.

The finding of flow-dependent vasodilation rests on the basic observation that with an increase in blood flow the vessels become wider, with a decrease the vascular smooth muscle cells contract. Proteoheparan sulphate could be the sensor macromolecule at the endothelial cell membrane-blood interface, that reacts on the shear stress generated by the flowing blood, and that informs and regulates the vascular smooth muscle cells via a signal transduction chain. This anionic biopolyelectrolyte possesses viscoelastic and specific ion binding properties which allow a change of its configuration in dependence on shear stress and electrostatic charge density. The blood flow sensor undergoes a conformational transition from a random coil to an extended filamentous state with increasing flow, whereby Na+ ions from the blood are bound. Owing to the intramolecular elastic recoil forces of proteoheparan sulphate the slowing of a flow rate causes an entropic coiling, the expulsion of Na+ ions and thus an interruption of the signal chain. Under physiological conditions, the conformation and Na+ binding proved to be extremely Ca(2+)-sensitive while K+ and Mg2+ ions play a minor role for the susceptibility of the sensor. Via counterion migration of the bound Na+ ions along the sensor glycosaminoglycan side chains and following Na+ passage through an unspecific ion channel in the endothelial cell membrane, the signal transduction chain leads to a membrane depolarization with Ca2+ influx into the cells. This stimulates the EDRF/NO production and release from the endothelial cells. The consequence is vasodilation.

Biosensing Techniques↗