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At least 595 records · Page 33Linked to original sources
PubMed2003

Monocytes and neutrophils from tuberculosis patients are insensitive to anti-inflammatory effects triggered by the prototypic formyl peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP).

Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis where formyl peptides, which are cleavage products of bacterial and mitochondrial proteins, are present. In this study, we demonstrated that interferon gamma (IFN)-gamma and interleukin (IL)-10 induced the overexpression of the receptor for the Fc portion of IgG I (FcgammaRI) in monocytes from tuberculosis (TB) patients, showing that these cells respond to IFN-gamma and IL-10 signals. We also demonstrated that lower doses of IL-10 render monocytes from TB patients less responsive to higher doses of the cytokine. Although the prototypic formyl peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) is a well-known proinflammatory agonist, we have demonstrated previously that preincubation of monocytes with FMLP inhibited the up-regulation of FcgammaRI induced by IFN-gamma or IL-10. This effect was not observed in monocytes from TB patients. FMLP also induced the down-regulation of the expression of FcgammaRI in monocytes that had been activated already with IFN-gamma. However, this effect of FMLP was not observed in monocytes from TB patients and supernatants from monocytes obtained from these patients were incapable of inducing the down-regulation of FcgammaRI. In contrast to normal donors, supernatants from FMLP-treated neutrophils from TB patients did not modify the basal level of expression of FcgammaRI in monocytes from normal donors. In conclusion, in this study we demonstrated the existence of two novel mechanisms that may contribute to the pathological effects generated by M. tuberculosis: the enhancement of FcgammaRI in response to IFN-gamma and IL-10, and the unresponsiveness to the anti-inflammatory effects induced by formyl peptides.

Cells, Cultured↗
PubMed1999

Light-guided tracheal intubation using a prototype illuminated flexible catheter through the intubating laryngeal mask.

We evaluated the efficacy of a newly developed prototype illuminated flexible catheter to facilitate tracheal intubation through the intubating laryngeal mask and compared this light-guided technique with the conventional blind tracheal intubation through the intubating laryngeal mask. The illuminated flexible catheter consists of a completely flexible thin plastic catheter, a bulb attached to its distal end, a 15-mm concentric adapter at its proximal end connected with a battery and a power switch. The device is placed into a silicone tracheal tube in such a way that the bulb protrudes from the distal end of the tracheal tube. One hundred adult patients, ASA I-III, scheduled to undergo propofol/fentanyl/atracurium anaesthesia for elective surgery were studied. All participants underwent a randomized double comparative cross over trial with respect to the tracheal intubation technique through the intubating laryngeal mask. The light guided tracheal intubation was performed as follows; the tracheal tube preloaded with the illuminated flexible catheter was inserted through the intubating laryngeal mask and by observing the glow in the neck was advanced into the trachea. Whenever resistance was felt during insertion, appropriate adjusting manoeuvres were performed. The intubating laryngeal mask was inserted successfully in all patients. The success rate for the blind and light-guided technique was 91% and 100%, respectively (P = 0.003). The mean (+/- SD) duration including appropriate intubating laryngeal mask placement and tracheal intubation, was significantly lower in the light-guided tracheal intubation technique, than with the blind tracheal intubation (31 +/- 8 s vs. 43 +/- 18 s; P < 0.0001). We conclude that the use of an illuminated flexible catheter carries advantages either in optimizing the intubating laryngeal mask position in the laryngopharynx or in achieving a quick and safe light-guided advancement from laryngopharynx into the trachea.

Adult↗
PubMed1999

The performance of foreign medical graduates on the National Board of Medical Examiners (NBME) standardized patient examination prototype: a collaborative study of the NBME and the Educational Commission for Foreign Medical Graduates (ECFMG).

OBJECTIVES: The purpose of the study was to explore foreign medical graduates' (FMGs) performance on a clinical skills (SPX) examination. The National Board of Medical Examiners (NBME) is in the process of developing an SPX for potential use in the United States Medical Licensing Examination (USMLE). The Educational Commission for Foreign Medical Graduates (ECFMG) is developing the Clinical Skills Assessment (CSA) as an additional requirement for FMGs who wish to be certified by ECFMG. DESIGN: Thirty-three FMGs and 151 United States medical students (USMSs) took the SPX during the winter of 1996 as part of the ongoing pilot studies conducted by the NBME. Four clinical skill areas were assessed: history-taking, physical examination, communication and interpersonal skills. The examination used in this research consisted of 12 cases. The examination utilizes standardized patients (SPs) who are trained to document examinee behaviours and evaluate the communication component of the test. The SPs were also trained to evaluate the English proficiency of the candidates. Candidates were also administered the Test of Spoken English developed by the Educational Testing Services (ETS). SETTING: The examination was conducted in one medical school which served as an SPX centre for NBME pilot studies. SUBJECTS: Thirty-three foreign medical students and 151 US medical students. RESULTS: The indications were that the majority of candidates in both groups felt the examination was moderately fair but 78% of FMGs felt moderately pressed for time, vs. 80% of the USMSs who did not feel pressed for time. Reliabilities obtained for the various SPX components were somewhat higher for the FMGs reflecting the heterogeneity of this group. CONCLUSIONS: The NBME-ECFMG collaborative study yielded important information regarding the NBME SPX prototype as a performance measure for FMGs.

Clinical Competence↗
PubMed2003

The monolithic fetal pacemaker: prototype lead design for closed thorax deployment.

Prenatal sudden cardiac death and hydrops fetalis are often due to complete heart block. However, no pacing modality exists for intrauterine application for fetal bradycardia. A prototype lead for a novel fetal pacemaker has been developed and used in a direct pacing model. It has been demonstrated that the lead can be safely and successfully deployed using a hypochondriac and transdiaphragmatic or subxiphoid approach. Pacing with ventricular capture was evident with the widening of QRS duration from 50.2 +/- 9.8 to 95.1 +/- 12.8 ms (P = 0.0001). Further studies by echocardiogram revealed an increase in the pulse with pacing, confirming pacing. This study documents proof-of-concept for closed thorax over-the-wire deployment of a novel lead design applicable to fetal pacing. By combining the lead design with microcircuitry and a small power source, it is possible to create a monolithic fetal pacemaker system capable of being deployed in utero.

Animals↗
PubMed1996

A prototypic intracellular calcium antagonist, TMB-8, protects cultured cerebellar granule cells against the delayed, calcium-dependent component of glutamate neurotoxicity.

The effect(s) of a prototypic intracellular Ca2+ antagonist, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8), on glutamate-induced neurotoxicity was investigated in primary cultures of mouse cerebellar granule cells. Glutamate evoked an increase in cytosolic free-Ca2+ levels ([Ca2+]i) that was dependent on the extracellular concentration of Ca2+ ([Ca2+]o). In addition, this increase in [Ca2+]i correlated with a decrease in cell viability that was also dependent on [Ca2+]o. Glutamate-induced toxicity, quantified by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) staining, was shown to comprise two distinct components, an "early" Na+/Cl(-)-dependent component observed within minutes of glutamate exposure, and a "delayed" Ca(2+)-dependent component (ED50 approximately 50 microM) that coincided with progressive degeneration of granule cells 4-24 h after a brief (5-15 min) exposure to 100 microM glutamate. Quantitative analysis of cell viability and morphological observations identify a "window" in which TMB-8 (at > 100 microM) protects granule cells from the Ca(2+)-dependent, but not the Na+/Cl(-) -dependent, component of glutamate-induced neurotoxic damage, and furthermore, where TMB-8 inhibits glutamate-evoked increases in [Ca2+]i. These findings suggest that Ca2+ release from a TMB-8-sensitive intracellular store may be a necessary step in the onset of glutamate-induced excitotoxicity in granule cells. However, these conclusions are compromised by additional observations that show that TMB-8 (1) exhibits intrinsic toxicity and (2) is able to reverse its initial inhibitory action on glutamate-evoked increases in [Ca2+]i and subsequently effect a pronounced time-dependent potentiation of glutamate responses. Dantrolene, another putative intracellular Ca2+ antagonist, was completely without effect in this system with regard to both glutamate-evoked increases in [Ca2+]i and glutamate-induced neurotoxicity.

Animals↗
PubMed2003

Genetic approaches in the clinical investigation of complex disorders: malnutrition, inflammation, and atherosclerosis (MIA) as a prototype.

Despite major research efforts and improvements in dialysis technology, patients with end-stage renal disease (ESRD) experience an extremely high mortality, which seems to be increasingly related to cardiovascular disease. Cardiovascular disease has been linked to the presence of systemic inflammation and malnutrition (MIA syndrome), in addition to the high prevalence of traditional risk factors observed in ESRD patients. Since the mechanisms underlying the development of these complications of ESRD are largely unknown, new strategies for identification of risk factors, pathophysiologic pathways, and targets for intervention are warranted. Although the combined impact of MIA complications seems to determine the extremely poor clinical outcome in the ESRD patients, there are significant unexplained individual differences in the development of the MIA syndrome, implying that genetic differences might play a role. The vast information generated by the advances in molecular genetics offers a great opportunity to analyze the causes of differences not only in our susceptibility to (or protection from) various diseases, but also in the age of onset, severity of illness, and in the way our bodies respond to treatment. In this review, we summarize an integrated approach in the investigation of complex disorders, requiring the interactive collaboration between laboratory, clinical, and epidemiologic resources using the MIA syndrome as a prototype. We focus on the application of common genetic variations (single nucleotide polymorphisms [SNPs]) in association with studies to generate potential risk profiling using data from multiple vulnerability genes. The appropriate application of this approach may be essential in the early identification of high-risk individuals and groups of patients for whom specific therapeutic interventions are indicated, thus creating a tailor-made clinical management for the future.

Arteriosclerosis↗
PubMed2000

Computational flow study of the continuous flow ventricular assist device, prototype number 3 blood pump.

A computational fluid dynamics study of blood flow in the continuous flow ventricular assist device, Prototype No. 3 (CFVAD3), which consists of a 4 blade shrouded impeller fully supported in magnetic bearings, was performed. This study focused on the regions within the pump where return flow occurs to the pump inlet, and where potentially damaging shear stresses and flow stagnation might occur: the impeller blade passages and the narrow gap clearance regions between the impeller-rotor and pump housing. Two separate geometry models define the spacing between the pump housing and the impeller's hub and shroud, and a third geometry model defines the pump's impeller and curved blades. The flow fields in these regions were calculated for various operating conditions of the pump. Pump performance curves were calculated, which compare well with experimentally obtained data. For all pump operating conditions, the flow rates within the gap regions were predicted to be toward the inlet of the pump, thus recirculating a portion of the impeller flow. Two smaller gap clearance regions were numerically examined to reduce the recirculation and to improve pump efficiency. The computational and geometry models will be used in future studies of a smaller pump to determine increased pump efficiency and the risk of hemolysis due to shear stress, and to insure the washing of blood through the clearance regions to prevent thrombosis.

Computer Simulation↗
PubMedDate not supplied

An in vitro biomechanical comparison of a prototype intramedullary pin-plate with a dynamic compression plate for equine metacarpophalangeal arthrodesis.

OBJECTIVES: To compare the biomechanical properties of a prototype intramedullary pin-plate (IMPP) implant specifically designed for equine metacarpophalangeal (MCP) arthrodesis with a dynamic compression plate (DCP) system. STUDY DESIGN: In vitro biomechanical testing of paired cadaveric equine forelimbs with a simulated traumatic disruption of the suspensory apparatus, stabilized by one of two methods for MCP arthrodesis. ANIMAL POPULATION: Twenty-one pairs of adult equine cadaveric forelimbs. METHODS: Each forelimb had the distal sesamoidean ligaments severed to create a disrupted suspensory apparatus. For each forelimb pair, the MCP joint was stabilized with the IMPP in one limb, and a DCP in the other limb. Seven matching limb pairs were tested in axial compression in a single cycle to failure, 7 matching limb pairs were tested in torsion in a single cycle to failure, and 7 matching limb pairs were fatigued tested in axial compression. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: The mean yield load, yield stiffness, and failure load (axial compression, torsional loading) was significantly greater for the IMPP compared with the DCP system. Mean cycles to failure for axial compression was significantly greater for the IMPP compared with the DCP system. Significance in all tests was P<.0001. CONCLUSION: The IMPP was superior to the DCP system in resisting the biomechanical forces most likely to cause failure of MCP joint arthrodesis. CLINICAL RELEVANCE: The IMPP implant should be considered for MCP arthrodesis in horses with traumatic disruption of the suspensory apparatus. The specific design of the IMPP implant may facilitate equine MCP arthrodesis and avoid convalescent complications related to cyclic fatigue.

Animals↗
PubMed2002

Tirapazamine: prototype for a novel class of therapeutic agents targeting tumor hypoxia.

Preclinical models in vitro and in vivo have shown that tumor hypoxia alters the malignant cell phenotype, selecting for p53 mutations, stimulating angiogenesis and metastasis, and markedly reducing the efficacy of both radiotherapy and chemotherapy. Similarly, clinical studies measuring pretreatment tumor oxygen status confirm that the presence of hypoxia confers a negative impact on local control, disease-free survival, and overall survival. Despite these data and extensive past research efforts, the promise of developing selective hypoxic-cell sensitizers has been largely unfulfilled. In contrast, tirapazamine is the rationally designed prototype for a new class of therapeutic agents targeting tumor hypoxia: hypoxic cytotoxins. Tirapazamine is bioreductively activated in hypoxic cells and has been shown to potentiate the cytotoxicity of radiation and a number of chemotherapeutic drug classes, in particular platinum compounds and taxanes. This article reviews the preclinical and clinical development of tirapazamine, as well as current trials in non-small cell lung cancer designed to provide proof of principle for this new category of cancer therapeutics.

Carcinoma, Non-Small-Cell Lung↗
PubMed2002

Analysis of errors in medical rapid prototyping models.

Rapid prototyping (RP) is a relatively new technology that produces physical models by selectively solidifying UV-sensitive liquid resin using a laser beam. The technology has gained a great amount of attention, particularly in oral and maxillofacial surgery. An important issue in RP applications in this field is how to obtain RP models of the required accuracy. We investigated errors generated during the production of medical RP models, and identified the factors that caused dimensional errors in each production phase. The errors were mainly due to the volume-averaging effect, threshold value, and difficulty in the exact replication of landmark locations. We made 16 linear measurements on a dry skull, a replicated three-dimensional (3-D) visual (STL) model, and an RP model. The results showed that the absolute mean deviation between the original dry skull and the RP model over the 16 linear measurements was 0.62 +/- 0.35 mm (0.56 +/- 0.39%), which is smaller than values reported in previous studies. A major emphasis is placed on the dumb-bell effect. Classifying measurements as internal and external measurements, we observed that the effect of an inadequate threshold value differs with the type of measurement.

Algorithms↗
PubMed2002

[Connections between attachment prototypes and relationship patterns].

Connections between attachment styles and relationship patterns are studied on 32 female psychotherapy patients. Our study gives first hints to a connection between attachment variables, assessed by the German version of the Adult Attachment Prototype Rating (AAPR) and predominant relationship patterns, assessed by the Core Conflictual Relationship Theme Method (CCRT) developed by Luborsky, if both methods are used independently. Subsamples according to the attachment styles show differences in CCRT variables.

Adult↗
PubMed1998

Biliary stenting with a prototype expandable Teflon endoprosthesis.

BACKGROUND AND STUDY AIMS: A new balloon-expandable Teflon endoprosthesis was developed for endoscopic placement in the biliary tree. After deployment to its maximum diameter the stent is hardened by exposure to UV light. We present our preliminary results with a prototype 18 Fr prosthesis. PATIENTS AND METHODS: Three patients with a distal common bile duct obstruction due to unresectable pancreatic head carcinoma were treated with this stent. Insertion of the stent was the only palliative procedure. Patients were followed up until stent dysfunction or death. RESULTS: Stent placement was successful in all patients and no procedural complications occurred. Distal migration occurred in one patient, clogging of the stent after 149 days in another. CONCLUSION: In patients with a malignant biliary stricture this newly developed expandable endoprosthesis is effective in relieving obstructive jaundice. The technique has potential advantages over placement of current expandable metal mesh stents.

Aged↗
PubMed1998

[A remote access system for inquiry of centrally stored data on patients suspected of malignant hyperthermia . A prototypical development for the Internet].

OBJECTIVES: Malignant hyperthermia (MH) is an inherited, potentially life-threatening syndrome of the skeletal muscles. It is a life-threatening complication of anaesthesia with a high mortality (8-10%). The risk of the patient during anaesthesia due to an overlooked predisposition for MH can be reduced by organisational measures, such as, all data of MH-susceptible patients and their families known in Germany must be brought together in a central register, MH-relevant data of patients must be readily retrievable, optional oral advice for those making an inquiry must be available. METHODS: To achieve this goal, a client-server system has been implemented: Standard Multimedia personal computers installed at the user's (anaesthetist's) site, linked to the Internet, will act as clients. On a server, relevant data of patients concerning MH-susceptibility are integrated in a central database. The newly developed software of this project ensures the legally prescribed data security on the server and the data routes. At the client's site, standard software together with automatically installed programmes from the server using Java applets ensure easy use and maintenance. IMPLEMENTATION: The total system was implemented and tested. Its functionality and high availability was demonstrated during this test period. Relevant aspects of data security were successfully examined by the data security officer of the University Hospitals of Baden-Württemberg. The user can optionally call a multifunctional teleconference which secures on-line advice if needed. This system demonstrates a safe and quick retrieval of MH relevant data of patients via Internet while at the same time guaranteeing all aspects of data protection and security. CONCLUSION: A prototypical database access system is described. It ensures safe access to patient data via Internet, while guaranteeing all aspects of data security.

Computer Communication Networks↗
PubMed1986

[Prototype of an ophthalmoscope for studying an upright image with light amplification].

The instrument described here is the prototype of a direct ophthalmoscope with amplification of available light. The beam path has already been published and patented under reference number 3124305. It does not require drug-induced mydriasis, reduces light toxicity of the retina, and facilitates examination of pre-eclamptic and other patients who are sensitive to light. With this ophthalmoscope it may be possible to demonstrate the autofluorescence of the hyalocytes, described by Cremer-Bartels and Balacz.

Fluorescence↗
PubMed1995

Prototype instruments for endoscopic microsurgery: technical note.

The authors describe a concept of converting microsurgical instruments into endoscopes and demonstrate prototype devices. These instruments combine the benefits of microsurgery (multiple instruments, tactile feedback, bimanual manipulation, magnification) with those of endoscopy (minimally invasiveness, indirect line of vision).

Animals↗
PubMed2003

The spatial logistic map as a simple prototype for spatiotemporal chaos.

A spatial extension of the logistic map-termed spatial logistic map-is found to display the same basic universality classes as the commonly studied diffusively coupled logistic lattice despite being vastly simpler. By analyzing the escape rates and the Lyapunov spectra it is shown that the main attractors of the spatial logistic map are stable and hence that it is a good candidate for serving as a prototype for the class of coupled map lattices which it is a part of. The spatial logistic map is then employed to provide an analytical derivation for the recently discovered linear scaling of the wavelength under increasing coupling ranges.

Journal Article↗
PubMed2004

Prototype reflectivity analyses of hydrogen storage levels in single-walled carbon nanotubes.

A prototype case study is presented that examines the level of hydrogen content in H-SWNTs using the Surface Plasmon Resonance technique. The damping effect and the angular shift in the resonance minimum of an SWNT-gold interface due to the presence of hydrogen is analyzed using a parametric model, which is based on the concept of an effective permittivity. The new approach provides for a non-invasive analysis of the level of hydrogen content in H-SWNTs and is potentially extendable to other carbon-based hydrogen storage materials.

Journal Article↗
PubMed1993

Extracting prototypical facial images from exemplars.

A computer graphic method for extracting a natural image of an individual's facial prototype, or average appearance, from a number of different images of that individual is presented. The process improves upon previous photographic and computational techniques. Synthesis of a person's average expression and pose from a sample of images is derived in an automatic and quantitative way. Possible uses of composite faces produced in this manner in psychological investigations of facial qualities (eg attractiveness) and in applied areas such as telecommunication are pointed out.

Attention↗