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Academies and Institutes↗
Biomedical subjects
A Walter
Publications and source records attributed to A Walter.
[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↗
[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↗
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↗
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↗
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↗
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↗
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↗
Reversal of the Z- to B-conformation of poly(dA-dT) center dot poly(dA-dT) induced by netropsin and distamycin A.
Poly(dA-dT) center dot poly(dA-dT) which adopts the Z-form at 5 M NaCl in presence of 95 mM Ni2+ions is reversed to the B-conformation by the nonintercalating drugs netropsin (Nt) and distamycin A (Dst). The drug-induced reversal from the Z-to B-form of poly(dA-dT) center dot poly(dA-dT) is evidenced by CD spectral changes at characteristic wavelengths around 295 nm and 248 nm. The drug-induced conformational transition is accompanied by a slow kinetic process. The results suggest the preference of these AT-specific drugs for the B-form and the inability of Nt and Dst to form a stable complex with the Z-form of poly(dA-dT) center dot poly(dA-dT).
Bacterial Proteins↗
[Agee endoscopic operation of carpal tunnel syndrome in comparison with open surgical technique].
In the course of a prospective randomised study, 120 patients underwent a carpal tunnel release procedure. The follow-up documentation included 101 patients. 54 patients had the conventional open procedure, including epineural neurolysis of the median nerve. 47 patients were treated with the Agee endoscopic procedure. The documentation included: patients age, sex, profession, duration of treatments, disablement, return to the activities of daily life (ADL) and pre- and postoperative neurological symptoms and postoperative complications. The electroneurographical measurements were performed preoperatively and nine months after operation by the same neurologist. The open and endoscopic carpal tunnel release procedures are described and the study results are reported. None of the 101 patients had wound-healing impairments. Clinical and neurological follow-up examinations did not reveal any signs of injured nerves or tendons. The study shows that the endoscopic group returned to work significantly earlier compared to the control group. At the same time, the Agee group had reduced postoperative pain symptoms. Regarding the long-term results, no significant difference between both groups was found. Based on the electrophysiological results, the study shows that epineural neurolysis of the median nerve is not necessary.
Arthroscopes↗
In vivo isoproterenol treatment leads to downregulation of the mRNA encoding the cAMP response element binding protein in the rat heart.
The expression of different myocardial regulatory proteins is altered in human heart failure, e.g., beta 1-adrenoceptors, G-proteins and others. Similar changes in rats after 4 days treatment with isoproterenol led to the hypothesis of the cAMP pathway involved in these changes. In different cell types cAMP-dependent transcriptional activation is mediated by the cAMP-response element binding protein (CREB) which was recently shown to be expressed and phosphorylated in the human heart. Here, by the reverse transcriptase-polymerase chain reaction two alternatively spliced isoforms of CREB mRNA were found to be expressed in rat ventricles. Both isoforms were down-regulated in the ventricles of rats treated in vivo with isoproterenol (2.4 mg/kg per day) for 4 days proposing a possible mechanism involved in expressional changes mentioned above.
Adrenergic beta-Agonists↗
Antiphospholipid antibody binding to bilayer-coated glass microspheres.
Thrombosis, recurrent fetal loss, and thrombocytopenia are clinical manifestations associated with circulating antibodies that recognize cardiolipin (CL)- or phosphatidylserine (PS)-dependent antigens. Enzyme-linked immunosorbent assays (ELISAs) are generally used to determine the presence and specificity of antiphospholipid antibodies (aPLs). However, the presentation of the phospholipid antigen in the ELISA assay is unknown. In this study, we determined the specificity of three mouse monoclonal aPLs for phospholipid bilayer membranes. These monoclonal aPLs had been characterized by ELISA to have different specificities for CL and PS and were designated BA3B5C4 (CL+/PS+), 3SB9b (CL-/PS+), and D11A4 (CL+/PS-). Bilayers composed of 0-100% PS or CL in phosphatidylcholine (PC) were formed on the surface of 1.6 microns diameter glass microspheres to permit analysis by flow cytometry. BA3B5C4 and 3SB9b bound specifically to both PS- and CL-containing bilayers, and binding increased with increasing percentage of anionic phospholipid. The threshold for PS-dependent binding was 20 mol% PS for both BA3B5C4 and 3SB9b. For CL-dependent binding, the threshold was below 25 mol% CL for both of these antibodies. Binding to PS-containing bilayers was tested as a function of ionic strength for BA3B5C4 and 3SB9b. The ionic strength dependence of the binding suggested that the intermolecular attractive forces between anti-PS antibodies and PS-containing bilayers are predominantly multiple weak electrostatic bonds. D11A4 bound only to bilayers composed of 100% PS and 100% PC, and this antibody did not bind to CL-containing bilayers. The binding specificities of these aPLs to bilayer membranes suggest that, in this system, the conformation of the epitope involving CL, and perhaps PS, is different from that expressed in the routine clinical ELISA. Two of the monoclonal antibodies reacted in this model system at the low levels of PS typically externalized in the plasma membranes of activated platelets, apoptopic lymphocytes, and senescent red blood cells: thus, these surfaces are plausible candidates for the site of pathologically relevant antibody interactions.
Cardiolipins↗
Neurourologic consequences of accidental intrathecal vincristine: a case report.
Inadvertent intrathecal administration of vincristine results in severe neurotoxicity. Motor and sensory bladder dysfunction have been reported but the long-term urologic consequences are unknown due to the associated high mortality. We report a case of accidental intrathecal vincristine administration with patient survival and follow-up of 24 months. The child developed a lower motor neuron neuropathic bladder requiring intermittent self-catheterization of the bladder. Urinary tract management of these children should be based on the urodynamic findings.
Child↗
Identification of estrogen regulated genes in Fe33 rat hepatoma cells by differential display polymerase chain reaction and their hormonal regulation in rat liver and uterus.
We applied the differential display RT-PCR (ddRT-PCR) technology to identify estrogen-regulated hepatic genes in the estrogen receptor expressing rat hepatoma cell line Fe33. Three genes of known sequences were detected by the ddRT-PCR approach: IGF binding protein-1 (IGFBP-1), vitamin D-dependent calcium-binding protein (CaBP9k) and major acute phase protein (MAP). Effects of ethinyl estradiol on the mRNA levels of these genes were confirmed by "Northern-blot" analysis. If given in combination with dexamethasone and glucagon, ethinyl estradiol caused 40-, 15- and 11-fold increases in the mRNA steady state level of IGFBP-1, CaBP9k and MAP, respectively, in Fe33 cells 24 h after addition of hormone. Besides ethinyl estradiol, the partial estrogen agonist OH-tamoxifen caused dose dependent effects on expression of MAP and IGFBP-1. Estrogen regulation of the respective genes and the modulatory effects of progesterone (10 mg/animal/day) were studied in ovariectomized rats treated subcutaneously for 14 days with 1 microgram/animal/day estradiol. "Northern-blot" analysis of liver RNA revealed a 6-fold stimulation of IGFBP-1 mRNA levels in estradiol-treated compared to vehicle-treated rats and a weak but detectable increase of MAP mRNA steady state level (1.6-fold) upon estradiol administration. No effect of estradiol treatment could be monitored for CaBP9k in rat liver. Modulatory effects of progesterone on estradiol-stimulated expression in the liver could be monitored for IGFBP-1 only. In an extension of our investigation on the expression of the three genes in rat liver, we determined their expression and hormonal regulation in the uterus of the same animals. In the uterus, estradiol caused an increase in CaBP9k mRNA. In contrast, IGFBP-1 mRNA levels increased dramatically upon progesterone administration, whereas no effect of estradiol treatment could be detected. MAP mRNA levels increased only after coadministration of estradiol and progesterone. In conclusion, the ddRT-PCR proved to be a powerful method to identify estrogen-regulated genes. The study on the hormonal regulation of three genes stimulated by estrogen in Fe33 cells revealed similarities and differences in their regulation in vivo and in vitro.
Acute-Phase Proteins↗
Transpapillary and transmural drainage of pancreatic pseudocysts.
BACKGROUND: Endoscopic drainage of pseudocysts using the transpapillary and transmural approaches has been reported. We evaluated endoscopic drainage in 53 patients with symptomatic pancreatic pseudocysts in whom conservative management had failed. METHODS: After preliminary endoscopic retrograde pancreatography, transpapillary drainage was attempted in 33 patients with pseudocysts that communicated with the main pancreatic duct. Transmural drainage of pseudocysts in contact with the stomach or duodenal wall was attempted in the remaining 20 patients and in 4 patients selected for combined transpapillary and transmural drainage. The cause of pseudocysts was chronic pancreatitis in 92%. The median pseudocyst size was 7.0 cm (range, 2 to 16). RESULTS: Endoscopic drainage was technically successful in 50 patients (94%), of whom 47 had complete pseudocyst resolution. Complications occurred in 11% and included gallbladder puncture (n = 1) and bleeding (n = 2) after transmural drainage, and pancreatitis (n = 1) after transpapillary drainage; stent clogging resulted in abscess formation in 2 patients. Mean follow-up was 22 months (range, 1 to 70); pseudocysts recurred in 11 patients (23%), of whom 7 were successfully re-treated endoscopically. CONCLUSION: Both transpapillary and transmural pseudocyst drainage are highly effective in patients with pseudocysts demonstrating suitable anatomy for these endoscopic techniques.
Adult↗
Stereotactic injection of herpes simplex thymidine kinase vector producer cells (PA317-G1Tk1SvNa.7) and intravenous ganciclovir for the treatment of progressive or recurrent primary supratentorial pediatric malignant brain tumors.
This study will evaluate the safety and efficacy of in vivo gene transfer of the herpes simplex thymidine kinase (HSV-Tk1) gene using PA317/G1Tk1SvNa.7 vector producer cells (VPC) in pediatric patients with progressive or recurrent primary supratentorial malignant brain tumors. Insertion of the HSV-Tk1 gene confers a sensitivity to the anti-herpes drug ganciclovir. It has been demonstrated that the direct injection of HSV-Tk vector producer cells into growing tumors in animals can result in their complete destruction with ganciclovir therapy. This selective destruction of growing tumors in situ is thought to result from the transfer of the HSV-Tk gene into the tumor cells and the production of toxic ganciclovir metabolites which result from the interaction of HSV-Tk and ganciclovir. This procedure can result in the cure of some experimental animals with limited systemic toxicity due to selective gene transfer into tumors. This clinical trial will focus on maximizing the relative number of vector producer cells to the tumor mass by stereotactically injecting VPCs into the tumor mass. Children with progressive or recurrent primary supratentorial malignant brain tumor which is accessible to stereotactic injection will be evaluated for the extent and location(s) of their disease before being entered into the study. Fifteen days after stereotactic injection of the tumor mass, ganciclovir will be administered at 5 mg/kg IV b.i.d. for 14 days. Upon completion of the treatment with HSV-Tk1 vector producer cells and ganciclovir, the patient will be followed monthly for the first three months, then every two months for the next twenty-one months, and annually for life thereafter.
Adolescent↗
Monoclonal IgM antiphosphatidylserine antibody reacts against cytoskeleton-like structures in cultured human umbilical cord endothelial cells.
PROBLEM: It has been proposed that antibodies against phospholipid-dependent antigens (aPLs), induce recurrent pregnancy loss and thrombosis through modulation of endothelial cell function, yet aPLs have not been conclusively shown to bind with endothelial cells. METHOD: Using indirect immunofluorescence we investigated the anti-endothelial cell reactivity of three monoclonal antibodies that differentiate between the phospholipids cardiolipin (CL) and phosphatidylserine (PS): BA3B5C4 (CL+/PS+); 3SB9b (CL-/PS+); and D11A4 (CL+/PS-). Cultured umbilical cord endothelial cells were prepared without fixation or with cold acetone fixation. RESULTS: None of the aPLs reacted with endothelial cells prepared without fixation. 3SB9B reacted strongly with cytoskeletal-like components in acetone-fixed cells, whereas BA3B5C4 and D11A4 were unreactive. The cytoskeletal-like binding of 3SB9b was completely blocked by a monoclonal antibody against vimentin, whereas antibodies against tubulin or actin were not inhibitory. Lipid extraction of the cells destroyed the 3SB9b reactive antigen without affecting the reactivity of anti-vimentin. CONCLUSION: These results suggest that phospholipid-dependent antigenic determinants are not expressed on the surface of resting endothelial cells but that a PS-dependent antigenic determinant is associated with endothelial cell intermediate filaments.
Animals↗
[Effect of the manufacturing process on creep and wear properties of UHMWPE (ultra-high molecular weight polyethylene)].
The creep and wear behaviour of pressed UHMWPE and extruded UHMWPE was compared, taking Chirulen and extruded UHMWPE of the Lennite type as examples. Using the ring-on-disc test, the wear and deformation volumes per 360,000 cycles were determined. The static tests were performed at surface pressures of 5.62 MPa and 9.37 MPa, while the test duration was 41.86 and 100 hours, respectively. The surface pressures result from the axial forces of 900 N and 1500 N, respectively, and a ring surface analogous to the DIN 58,835 and ISO 6474 standards. Between conventionally pressed and the extruded UHMWPE material differences of up to 350% in the sums of wear and deformation were found. It was noted that already at low surface pressures the extruded UHMWPE is more susceptible to creep deformation than is the conventionally pressed material, and that this effect dramatically increases at high surface pressures.
Biomechanical Phenomena↗