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At least 1,261 records · Page 70Linked to original sources
PubMed1997

Myasthenia gravis as a prototype autoimmune receptor disease.

Myasthenia gravis (MG) is an organ-specific autoimmune disease in which autoantibodies against nicotinic acetylcholine receptors (AChR) at the postsynaptic membrane cause loss of functional AChR and disturbed neuromuscular transmission. The immunopathogenic mechanisms responsible for loss of functional AChR include antigenic modulation by anti-AChR antibodies, complement-mediated focal lysis of the postsynaptic membrane, and direct interference with binding of acetylcholine to the AChR or with ion channel function. The loss of AChR and subsequent defective neuromuscular transmission is accompanied by increased expression of the different AChR subunit genes, suggesting a role for the target organ itself in determining susceptibility and severity of disease. Experimental autoimmune myasthenia gravis (EAMG) is an animal model for the disease MG, and is very suitable to study the immunopathogenic mechanisms leading to AChR loss and the response of the AChR to this attack. In this article the current concepts of the structure and function of the AChR and the immunopathological mechanisms in MG and EAMG are reviewed.

Animals↗
PubMed2005

Noninvasive monitoring of changes in structural cancellous bone parameters with a novel prototype micro-CT.

Characterization of trabecular bone structures requires necropsy of animals followed by a labor-intense histomorphometric or ex vivo micro-CT analysis. We tested the novel vivaCT40 from Scanco Medical AG (Bassersdorf, Switzerland), which allows monitoring such changes repeatedly in anesthetized rats and mice. Postmenopausal osteoporosis: in 8-month-old ovariectomized (OVX) rats, the vivaCT40 was capable of picking up the decrease in trabecular bone volume and trabecular thinning as well as the decrease in the number of trabecular elements as a function of time. The bone anabolic effects of parathyroid hormone [hPTH(1-34)], which resulted in an increase in trabecular thickness but not their number, as well as the bone protective effect of the two antiresorptive agents zoledronic acid (ZA) and 17-alpha ethinylestradiol (aEE), were detected correctly with the vivaCT40. Adjuvans arthritis: the vivaCT40 allowed measuring trabecular bone loss caused by periarticular inflammation in a rat model of adjuvans arthritis and demonstrated the bone protective effect of dexamethasone (DM). In addition, it was possible to image the subtle erosive lesions in subchondral bone caused by the inflammatory processes. Tumor osteolysis: the vivaCT40 allowed monitoring of the progressive osteolytic response following the local administration of 4T1luc2000 tumor cells into the tibia metaphysis of nude mice. The potent protective effect of ZA on tumor osteolysis was demonstrated. In summary, the new vivaCT40 can monitor the effects of known agents and diseases such as osteoporosis, inflammatory arthritis, and tumor invasion on 3-D trabecular microarchitecture accurately, repeatedly, reliably, and quickly in anesthetized rats and mice. The scanner represents a breakthrough for noninvasive imaging and structural measurements in small rodents.

Animals↗
PubMed2000

Breast imaging using an amorphous silicon-based full-field digital mammographic system: stability of a clinical prototype.

An amorphous silicon-based full-breast imager for digital mammography was evaluated for detector stability over a period of 1 year. This imager uses a structured CsI:TI scintillator coupled to an amorphous silicon layer with a 100-micron pixel pitch and read out by special purpose electronics. The stability of the system was characterized using the following quantifiable metrics: conversion factor (mean number of electrons generated per incident x-ray), presampling modulation transfer function (MTF), detector linearity and sensitivity, detector signal-to-noise ratio (SNR), and American College of Radiology (ACR) accreditation phantom scores. Qualitative metrics such as flat field uniformity, geometric distortion, and Society of Motion Picture and Television Engineers (SMPTE) test pattern image quality were also used to study the stability of the system. Observations made over this 1-year period indicated that the maximum variation from the average of the measurements were less than 0.5% for conversion factor, 3% for presampling MTF over all spatial frequencies, 5% for signal response, linearity and sensitivity, 12% for SNR over seven locations for all 3 target-filter combinations, and 0% for ACR accreditation phantom scores. ACR mammographic accreditation phantom images indicated the ability to resolve 5 fibers, 4 speck groups, and 5 masses at a mean glandular dose of 1.23 mGy. The SMPTE pattern image quality test for the display monitors used for image viewing indicated ability to discern all contrast steps and ability to distinguish line-pair images at the center and corners of the image. No bleeding effects were observed in the image. Flat field uniformity for all 3 target-filter combinations displayed no artifacts such as gridlines, bad detector rows or columns, horizontal or vertical streaks, or bad pixels. Wire mesh screen images indicated uniform resolution and no geometric distortion.

Female↗
PubMed2004

Abl: the prototype of oncogenic fusion proteins.

Since it was first recognized, chronic myeloid leukemia (CML) has always represented a unique model to understand the molecular mechanisms underlying the onset and progression of a leukemic process. CML was the first recognized form of cancer to have a strong association with a recurrent chromosomal abnormality, the t(9;22) translocation, which generates the so-called Philadelphia (Ph)-chromosome. Twenty years later, this abnormality was shown to cover a specific molecular defect, a hybrid BCR-ABL gene, strongly implicated in the pathogenesis of the disease through the production of a protein with a constitutive tyrosine-kinase activity. Although we still lack a complete definition of all the transformation pathways activated by Bcr-Abl, the recent introduction into clinical practice of tyrosine kinase inhibitor represents a major breakthrough to the management of CML and, furthermore, promises to usher in molecularly targeted therapy for other types of leukemia, lymphoma and cancer.

Apoptosis↗
PubMed1997

[Transtracheal monitoring of the recurrent laryngeal nerve. Prototype of a new tube].

A new sensing device for the continuous intraoperative monitoring of the recurrent laryngeal nerve is presented. It is based on a double ballooned endotracheal tube including stimulating and tracing electrodes. The system is characterised by three advantages: 1) it is atraumatic, 2) it is operating completely outside the operating field (extraterritorially), 3) nerve function is being monitored continuously from the time of intubation to the time of extubation. The presented system has been evaluated in piglets. First results in humans will be available shortly.

Animals↗
PubMed1997

[An implantable piezoelectric hearing aid transducer for inner ear hearing loss. I: Development of a prototype].

Implantable hearing aids can form the basis of new surgical techniques for dealing with hearing problems originating in the inner ear, provided they are fully implantable. Accordingly, a comprehensive, interdisciplinary, combined project was initiated at the ENT clinic of the University of Tübingen which was to conclude with operations to improve hearing via fully implantable hearing aids. A novel electromechanical transducer for implantable hearing aids based on the piezoelectric principle is described. Unlike the piezoelectric transducers reported so far, this transducer does not rely on the bimorphic principle but on a circle-shaped, heteromorphic combination system consisting of a piezoceramic disc and metal membrane. The transducer can be hermetically sealed and is designed for implantation into the mastoid. Transfer of mechanical oscillations to an ossicle in the middle ear is effected by a directly fixed coupling rod or via suitable coupling elements. The transducer is highly tuned with a resonance frequency at the upper end of the spectral transfer range (greater than 10 kHz). Below this resonance and down to low frequencies, the frequency response of elongation is smooth with amplitudes of around 20 nm. At low and middle frequencies of up to 1 kHz, these vibration amplitudes correspond to sound-pressure levels of around 90 dB SPL. At higher frequencies of up to 10 kHz, the output level increases to about 130 dB SPL. Nonlinear distortions are also very small at the highest levels (less than 0.1%) throughout the whole transfer range. Electric power consumption at maximum levels is in the range of a few microwatts and is therefore significantly lower than that of electromagnetic systems. Particularly, this makes it possible to use the transducer in fully implantable hearing aids for rehabilitation of sensorineural hearing loss.

Cochlear Implants↗
PubMed2007

[Polycystic ovary syndrome. Prototype of a cardio-metabolic syndrome].

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting women in the reproductive age and is a major cause of anovulation, hyperandrogenism and infertility. Since obesity and insulin resistance are predominant features of women with PCOS, a variety of metabolic disturbances are associated. There is a marked increase in the risk of developing type-2 diabetes in these patients and a majority of women with PCOS will subsequently harbour an enhanced cardiovascular risk.

Cardiovascular Diseases↗
PubMed2001

[Ethical conflicts in involuntary treatment of schizophrenic patients; decision-making and in influential factors in three prototype cases].

Three case reports of patients with schizophrenia were presented to a sample of 520 persons (25.1% psychiatrists, 3.7% psychologists, 8.1% social workers, 14.6% nurses, and 48.6% others). The decisions for involuntary admission to a psychiatric hospital and involuntary treatment were questioned. In case 1 (young man, first episode, delusions, extreme social withdrawal), 71.7% supported admission to hospital and 62.7% were in favor of neuroleptic treatment. In case 2 (woman with disorganized syndrome beating her 74-year-old mother), 84.6% supported hospitalization and 78.8% neuroleptics. In case 3 (relapsed multi-episode patient, increasingly neglected, delusional, and socially withdrawn), 56.3% supported hospitalization and 52.7% neuroleptics. Generally, psychiatrists' decisions were very similar to those of other professionals and laypersons, while social workers more often rejected involuntary treatment. After professional status, multivariate analyses revealed older age as the most significant variable for support of involuntary treatment. Frequency of experience with mentally ill persons were only weak predictors or not significant.

Adolescent↗
PubMed1997

[Rapid prototyping. Construction of a model in the preoperative planning of reconstructive pelvic interventions].

X-ray or CT images allows only a limited three-dimensional orientation in presurgical planning. Especially for the planning of internal hemipelvectomies with custom-made endoprosthesis and for peri-acetabular osteotomies a high-grade orientation is necessary. This orientation is improved by a 3D CT-controlled manufactured 1:1 model of the pelvis. This enables and exact classification of defect and deformity, planning of resection planes, design of the suitable custom-made implant and simulation of the operation technique as preoperative quality control.

Adult↗
PubMed2003

A transporter of Escherichia coli specific for L- and D-methionine is the prototype for a new family within the ABC superfamily.

An ABC-type transporter in Escherichia coli that transports both L- and D-methionine, but not other natural amino acids, was identified. This system is the first functionally characterized member of a novel family of bacterial permeases within the ABC superfamily. This family was designated the methionine uptake transporter (MUT) family (TC #3.A.1.23). The proteins that comprise the transporters of this family were analyzed phylogenetically, revealing the probable existence of several sequence-divergent primordial paralogues, no more than two of which have been transmitted to any currently sequenced organism. In addition, MetJ, the pleiotropic methionine repressor protein, was shown to negatively control expression of the operon encoding the ABC-type methionine uptake system. The identification of MetJ binding sites (in gram-negative bacteria) or S-boxes (in gram-positive bacteria) in the promoter regions of several MUT transporter-encoding operons suggests that many MUT family members transport organic sulfur compounds.

ATP-Binding Cassette Transporters↗