Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “prototype”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,621 records · Page 90Linked to original sources
PubMed1999

Preliminary evaluation study of a prototype hollow fiber membrane for the continuous membrane autotransfusion system.

A totally new autotransfusion system has been developed utilizing a hollow fiber membrane, based upon plasmapheresis technology. Prior to fabricating the system, it was essential to evaluate the basic performance characteristics of the filter, which was designed particularly for the new system. The objective of this study was to prove or disprove that such a system would be available using this filter. An in vitro study was conducted on the filter using bovine blood. The result of the study showed that the filter could process 2-20% of hematocrit blood at a flow rate greater than 250 ml/min of inlet blood continuously. Moreover, it could concentrate 5-20% hematocrit blood to hematocrit percentages greater than 40% by a single passage through the filter. These results seemed to prove that a rapid, continuous, and compact autotransfusion system could be developed using this filter.

Blood Transfusion, Autologous↗
PubMed2003

The prototypic antidepressant drug, imipramine, but not Hypericum perforatum (St. John's Wort), reduces HPA-axis function in the rat.

Dysregulation in corticotropin-releasing hormone (CRH) secretion in the hypothalamus-pituitary-adrenal (HPA) axis may be involved in the etiology of major depressive disorder (MDD). Chronic therapy with standard antidepressant drugs, such as imipramine, can downregulate HPA axis function, indicating that the HPA axis may be an important target for antidepressant action. We tested several doses of a standardized commercial preparation of Hypericum perforatum plant extract (popularly known as St. John's Wort), a medicinal herb used for treating mild depressive symptoms, to determine whether it also modulated HPA axis function. Chronic imipramine treatment (daily injections for 8 weeks) of male Sprague-Dawley rats significantly downregulated circulating plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone compared to animals treated with saline. However, chronic St. John's Wort treatment (daily gavage for 8 weeks) had no effect on plasma ACTH or corticosterone, even at the highest doses tested. Our results confirm previous findings that imipramine may have significant peripheral HPA axis-mediated effects. However, our data does not support any role for H. perforatum in modulation of HPA axis function, suggesting that alternative pathways may be involved in mediating its antidepressant effects.

Adrenal Glands↗
PubMed2006

Automated detection of lung nodules in multidetector CT: influence of different reconstruction protocols on performance of a software prototype.

PURPOSE: To evaluate the accuracy of software for computer-aided detection (CAD) of lung nodules using different reconstruction slice thickness protocols in multidetector CT. MATERIALS AND METHODS: Raw image data sets for 15 patients who had undergone 16-row multidetector CT (MDCT) for known pulmonary nodules were reconstructed at a reconstruction thickness of 5.0, 2.0 and 1.0 mm with a reconstruction increment of 1.5, 1.0 and 0.5 mm, respectively. The "Nodule Enhanced Viewing" (NEV) tool of LungCare for computer-aided detection of lung nodules was applied to the reconstructed images. The reconstructed images were also blinded and then evaluated by 2 radiologists (A and B). Data from the evaluating radiologists and CAD was then compared to an independent reference standard established using the consensus of 2 independent experienced chest radiologists. The eligible nodules were grouped according to their size (diameter > 10, 5 - 10, < 5 mm) for assessment. Statistical analysis was performed using the receiver operating characteristic (ROC) curve analysis, t-test and two-rater Cohen's Kappa co-efficient. RESULTS: A total of 103 nodules were included in the reference standard by the consensus panel. The performance of CAD was marginally lower than that of readers at a 5.0-mm reconstruction thickness (AUC = 0.522, 0.517 and 0.497 for A, B and CAD, respectively). In the case of 2.0-mm reconstruction slices, the performance of CAD was better than that of the readers (AUC = 0.524, 0.524 and 0.614 for A, B and CAD, respectively). CAD was found to be significantly superior to radiologists in the case of 1.0-mm reconstruction slices (AUC = 0.537, 0.531 and 0.675 for A, B and CAD, respectively). The sensitivity at a reconstruction thickness of 1.0 mm was determined to be 66.99 %, 68.93 % and 80.58 % for A, B and CAD, respectively. The time required for detection was shortest for CAD at reconstruction slices of 1.0 mm (mean t = 4 min). The performance of radiologists was greatly enhanced when using CAD: sensitivity 91.26 % and 94.17 % for CAD+A and CAD+B, respectively (AUC = 0.889 and 0.917). CAD was most advantageous in the detection of nodules < 10 mm. CONCLUSION: At a 1.0-mm reconstruction thickness, CAD's ability to detect nodules < 10 mm is superior to that of radiologists and its relatively short evaluation time makes it a viable second reader.

Diagnosis, Computer-Assisted↗
PubMed1998

[Development of a surgical simulator for interventions of the paranasal sinuses. Technical principles and initial prototype].

BACKGROUND: Traditional training methods for surgeons include anatomical studies on human cadavers. Limited availability and ethical problems led to the consideration of alternatives. The surgeon's level of training could be significantly increased by a interactive training system trough computer graphics and virtual reality (VR). METHODS: Two main issues addressed are the 3-D reconstruction process and 3-D interaction to guide the surgical instruments. To provide the virtual environment, a realistic representation of the region of interest with all relevant anatomical parts is required. This model has to be suitable for computer simulation, while preserving as accurately as possible important anatomic features. Therefore the concept of creating a 3-D representation semi-automatically was developed. Textures derived from endoscopic images are superimposed on the virtual anatomic structures and provide better realism. RESULTS: Intuitive handling of the surgical instruments is ensured by using the tracking technique. The system allows navigation via a virtual camera and interaction with the virtual anatomical structures. Currently the use of a force feedback system and the simulation of deformations of tissues is critical. CONCLUSIONS: The VR based simulation system offers an alternative to conventional training methods. The future role of surgical simulation depends on overcoming the current drawbacks to provide greater interactive realism: the integration of a force feedback system to simulate the resistance of anatomical structures and the simulation of tissue deformations--both currently under development.

Artificial Intelligence↗
PubMed1989

[A prototype double coil for MR breast measurement].

The first application of a double coil for routine MR mammography is described: by this method it is possible to examine both breasts simultaneously. This is important in order to halve the time of the examination and to allow comparison of the two breasts during dynamic contrast studies. The reduction in signal-to-noise ratio, compared with a single coil and flow artifacts of the heart do not interfere with diagnosis. The axillary region is better shown than with a single coil. Examination of 22 patients with subsequent histological control has shown that the information about signal increase after the injection of Gd-DTPA obtained from single coil can be applied equally to the double coil.

Axilla↗
PubMed1993

First experience with a distraction apparatus prototype (SM-fix-phalanx distractor) for phalanges lengthening.

Since 1991 seven children aged between 5-17 years have been treated at the University Children's Hospital in Basel for 10 traumatically partially amputated phalanges with a newly developed external fixator and distractor. Through continual distraction of the osteotomy a phalanx lengthening of 3-10 mm has been achieved (on average 55% of the rest phalanx). The results of this method in distal phalanx amputation with resulting nail dystrophy (claw nail) has shown functional and cosmetic improvements. The average distraction and consolidation phases lasted 5 weeks. The after care lasted 2-12 months. As children have good distraction-histogenesis bone grafting is not necessary. A prerequisite would be, however, an intact or appropriately prepared integument. The advantage of this external fixator and distractor system is that it is suitable for the delicate anatomical structures of a child's hand. The distractor component is only necessary for a distraction step to be carried out. A further advantage of this system is the relatively light but stable construction.

Adolescent↗
PubMed2006

Observation of a simple vibrational wavepacket in a polyatomic molecule via time-resolved photoelectron velocity-map imaging: a prototype for time-resolved IVR studies.

We have prepared a coherent superposition of the two components of a Fermi resonance in the S1 state of toluene at approximately 460 cm(-1) with a approximately 1 ps laser pulse and monitored time-resolved photoelectron velocity-map images. The photoelectron intensities oscillate with time in a manner that depends on their kinetic energy, even though full vibrational resolution in the cation is not achieved. Analysis of the time-dependent photoelectron spectra enables information on the composition of the S1 wavepacket to be deduced. Such an experiment, in which a whole set of partially dispersed cation vibrational states are detected simultaneously, suggests an efficient method of studying intramolecular vibrational energy redistribution processes in excited states.

Journal Article↗
PubMed2002

First endoluminal system for transmural resection of colorectal tissue with a prototype full-thickness resection device in a porcine model.

BACKGROUND: Endoluminal transmural resection of colorectal lesions is a pivotal advance in endoscopic technology. A full-thickness resection device has been developed that functions through a combination of tissue grasping, stapling, and cutting under endoscopic guidance. This preclinical study evaluated the performance, safety, and effectiveness of the full-thickness resection device in a porcine model. METHODS: The full-thickness resection device consists of an operative handle, flexible shaft, and a resection chamber head. Eight pigs were randomized to 2 survival groups (4 each) of 14 and 28 days. The mucosa was marked electrosurgically to delineate target areas in the distal colon. A gastroscope inserted through the channel of the full-thickness resection device was advanced together with the device to the target. Targeted tissue was pulled into the resection chamber with a forceps, staples were deployed, and the isolated specimen was resected with a cutting blade. Histologic and radiographic evaluations were performed. RESULTS: All resections were transmural. Mean resected tissue diameter was 3.6 cm (1.4-5.2 cm). Mean procedure time was 30.2 (15) minutes. Minor mechanical problems required the use of replacement devices to complete 3 procedures. Resection sites were identified endoscopically and radiographically at sacrifice. In one animal, local adhesions were present. Histology evaluation disclosed resection line mucosal ulceration in 4 animals with fibroinflammatory changes consistent with healing. CONCLUSIONS: The full-thickness resection device can be used for endoluminal transmural localized resection of colorectal tissue in an animal model.

Angioplasty↗
PubMed2004

Prototypic T cell receptor and CD4-like coreceptor are expressed by lymphocytes in the agnathan sea lamprey.

All jawed vertebrates have highly diverse lymphocyte receptors, which allow discrimination between self and nonself antigens as well as the recognition of potential pathogens. Key elements of the anticipatory recombinatorial immune system in jawed vertebrates are the TCR, Ig, and MHC genes, but their ancestral genes have not been found in more basal vertebrates. In this study, we extended our analysis of the transcriptome of lymphocyte-like cells in the lamprey to identify the TCR-like and CD4-like genes. The structural features of these genes and their preferential expression in lymphocytes make them attractive candidates for ancestral TCR and CD4 genes. The TCR-like gene contains both V (variable) and J (joining) sequences in its first exon and exists as a single-copy gene that is invariant. Thus, the TCR-like gene cannot account for the receptor diversity that is required for the immune responses reported for lamprey, but it could have been easily modified to serve as an evolutionary precursor of modern TCR and Ig genes.

Amino Acid Sequence↗
PubMed2005

Viable adenovirus vaccine prototypes: high-level production of a papillomavirus capsid antigen from the major late transcriptional unit.

Safe, effective, orally delivered, live adenovirus vaccines have been in use for three decades. Recombinant derivatives of the live adenovirus vaccines may prove an economical alternative to current vaccines for a variety of diseases. To explore that possibility, we constructed a series of recombinants that express the major capsid protein (L1) of canine oral papillomavirus (COPV), a model for mucosal human papillomavirus (HPV) infection. Vaccination with virus-like particles (VLPs) composed of recombinant HPV L1 completely prevents persistent HPV infection [Koutsky, L. A., Ault, K. A., Wheeler, C. M., Brown, D. R., Barr, E., Alvarez, F. B., Chiacchierini, L. M. & Jansen, K. U. (2002) N. Engl. J. Med. 347, 1645-1651], suggesting that L1 expressed from recombinant adenoviruses might provide protective immunity. In our recombinants, COPV L1 is incorporated into adenovirus late region 5 (Ad L5) and is expressed as a member of the adenoviral major late transcriptional unit (MLTU). COPV L1 production by the most prolific recombinant is comparable to that of the most abundant adenoviral protein, hexon. COPV L1 production by recombinants is influenced by Ad L5 gene order, the specific mRNA processing signals associated with COPV L1, and the state of a putative splicing inhibitor in the COPV L1 gene. Recombinant COPV L1 protein assembles into VLPs that react with an antibody specific for conformational epitopes on native COPV L1 protein that correlate with protection in vivo. The designs of these recombinants can be applied directly to the production of recombinants appropriate for assessing immunogenicity and protective efficacy in animal models and in human trials.

Adenoviridae↗
PubMed2002

A prototypic platelet septin and its participation in secretion.

Studies are presented characterizing platelet CDCrel-1, a protein expressed to high levels by megakaryocytes and belonging to a family of conserved proteins, termed septin. Septin filaments originally were identified in yeast as essential for budding but have become increasingly associated with processes in higher eukaryotic cells involving active membrane movement such as cytokinesis and vesicle trafficking. Direct proof of an in vivo function for septins in higher eukaryotes is limited to the characterization of the Drosophila septin, termed PNUT. We present studies identifying platelet CDCrel-1 as a protein kinase substrate in the presence of known platelet agonists. The immunopurification of CDCrel-1 revealed it to be part of a macromolecular complex containing a protein involved in platelet secretion, syntaxin 4. Moreover, CDCrel-1 was localized in situ to areas surrounding platelet-storage granules. The relevance of CDCrel-1 to normal platelet function was established with the characterization of platelets from a CDCrel-1(Null) mouse. As compared with platelets from wild-type littermates, CDCrel-1(Null) platelets aggregate and release stored [14C]serotonin in the presence of subthreshold levels of collagen. These results provide new insights into the mechanisms regulating platelet secretion and identify platelet septins as a protein family contributing to membrane trafficking within the megakaryocyte and platelet.

Amino Acid Sequence↗
PubMed2003

Integrin beta cytoplasmic domain interactions with phosphotyrosine-binding domains: a structural prototype for diversity in integrin signaling.

The cytoplasmic domains (tails) of heterodimeric integrin adhesion receptors mediate integrins' biological functions by binding to cytoplasmic proteins. Most integrin beta tails contain one or two NPXYF motifs that can form beta turns. These motifs are part of a canonical recognition sequence for phosphotyrosine-binding (PTB) domains, protein modules that are present in a wide variety of signaling and cytoskeletal proteins. Indeed, talin and ICAP1-alpha bind to integrin beta tails by means of a PTB domain-NPXY ligand interaction. To assess the generality of this interaction we examined the binding of a series of recombinant PTB domains to a panel of short integrin beta tails. In addition to the known integrin-binding proteins, we found that Numb (a negative regulator of Notch signaling) and Dok-1 (a signaling adaptor involved in cell migration) and their isolated PTB domain bound to integrin tails. Furthermore, Dok-1 physically associated with integrin alpha IIb beta 3. Mutations of the integrin beta tails confirmed that these interactions are canonical PTB domain-ligand interactions. First, the interactions were blocked by mutation of an NPXY motif in the integrin tail. Second, integrin class-specific interactions were observed with the PTB domains of Dab, EPS8, and tensin. We used this specificity, and a molecular model of an integrin beta tail-PTB domain interaction to predict critical interacting residues. The importance of these residues was confirmed by generation of gain- and loss-of-function mutations in beta 7 and beta 3 tails. These data establish that short integrin beta tails interact with a large number of PTB domain-containing proteins through a structurally conserved mechanism.

Alanine↗
PubMed1974

Analysis of a simple prototypal muscle model near to and far from equilibrium.

Accurate calculations of force generated and of ATP flux, in steady isotonic contractions, are made on a simple, two-state muscle model of the sliding filament type. The objective is to illustrate the proper formulation and use of a complete and self-consistent molecular model of muscle. Otherwise, the model is not meant to be realistic. Calculations were made near equilibrium, including linear and quadratic terms in a power series expansion, and arbitrarily far from equilibrium by direct numerical solution of the appropriate differential equation in the probability of cross-bridge attachment. The results obtained from the two different methods agree where they overlap near equilibrium. The efficiency of free energy conversion is emphasized, and the relation to linear irreversible thermodynamics is pointed out.

Adenosine Triphosphate↗
PubMed1979

Immunoglobulin differentiation is dictated by repeated recombination sequences within the V region prototype gene: a hypothesis.

Analysis of the available DNA sequences of immunoglobulin light chain genes reveals a unique structural pattern. A stretch of about 15 nucleotides repeats five times within the variable (V) region gene, with few base changes. Identification of these homologous sequences is apparent in the embryonic V(lambda) gene and might also be recognized in V(kappa) genes isolated from a myeloma. Although different from each other, the V(lambda) and V(kappa) hyperhomologous sequences display a remarkable resemblance to different prokaryote sequences associated with recombinational events. The homologous sequences appear at all three sites where hypervariable regions of the mature peptide are encoded. In addition, they are located at the site where V/constant (C) recombination is supposed to take place. Consequently, a general model is proposed for immunoglobulin differentiation. The hyperhomologous loci are postulated to be comprised of recombination sequences which makes them available for a mechanism of single-stranded DNA exposure. B cell maturation begins with V/C recombination, a step that is rate limiting. The fidelity of the process is ensured by extensive DNA homology between the two embryonic subgenes of V and C. Next, an error-prone repair system is activated and thereby introduces changes into the content of the immunoglobulin gene at the exposed loci. The process ends when mutations make the recombination sequence unrecognizable as such. The model is consistent with large amounts of data and is compatible with the view that immunoglobulin diversity is being generated somatically.

Animals↗
PubMed1988

Oligomeric structure of a prototype retrovirus glycoprotein.

The structure of the Rous sarcoma virus envelope glycoprotein complex was studied by sedimentation gradient centrifugation analyses of detergent-solubilized wild-type and mutant envelope (env) gene products. These studies show that the envelope glycoprotein forms an oligomer during biosynthesis, which is most likely a trimer, and that this is the form of the complex found in virions. Our results are consistent with oligomer formation and transport out of the endoplasmic reticulum being closely linked. From analyses of mutant envelope proteins we conclude that the extracellular domain of the glycoprotein is sufficient for oligomer formation but that the transmembrane domain is required to stabilize this complex. Additional experiments suggest that interactions between external domains of the membrane-spanning, gp37 polypeptides are those most important for the formation of trimers. The significance of these observations to retroviral replication and implications for antiviral drug development are discussed.

Animals↗