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At least 685 records · Page 38Linked to original sources
PubMed2006

A finite shell element for heart mitral valve leaflet mechanics, with large deformations and 3D constitutive material model.

This paper presents a shell finite element formulation appropriate for simulating the heart valve leaflet mechanics, including three-dimensional (3D) stress and strain effects. A 4-node mixed-interpolation shell is formulated in convected coordinates. This shell model is made capable of handling arbitrary 3D material models by use of an algorithm that satisfies the shell stress assumption at every element integration point. A method for tracking the fiber direction is incorporated. The resulting shell element operates under the same conditions as a standard 4-node shell element with 5 degrees of freedom per node, but extends the modeling capabilities to handle large-deformation and anisotropic behavior.

Biomechanical Phenomena↗
PubMed2006

Discrimination and characterization of environmental strains of Escherichia coli by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS).

A rapid and reliable bacterial source tracking (BST) method is essential to counter risks to human health posed by fecal contamination of surface waters. Genetic fingerprinting methods, such as repetitive sequence based-PCR (rep-PCR), have shown promise as BST tools but are time-consuming and labor-intensive. In this work, we investigate the ability of MALDI-TOF-MS to characterize and discriminate between closely related environmental strains of Escherichia coli and to classify them according to their respective sources. We compared the performance of a rapid MALDI-TOF-MS-based method to a commonly used rep-PCR-based method that employs the BOX-A1R primer. Among the criteria evaluated were repeatability and the ability of each method to group E. coli isolates according to their respective sources. Our data suggest that the MALDI-TOF-MS-based approach has a lower repeatability level compared to rep-PCR but offers an improved ability to correctly assign E. coli isolates to specific source groups. In addition, we have identified five biomarkers that appear conserved among avian species. We conclude that MALDI-TOF-MS may represent a promising, novel and rapid approach to addressing the problem of fecal contamination of surface waters and warrants further investigation.

Animals↗
PubMed2005

Manganese-enhanced MRI of rat spinal cord injury.

The potential of the manganese-enhanced MRI (MEI) technique in labeling the intact neuronal circuitry of rat spinal cord was examined. Experiments were conducted on normal and injured cords at 9.4-T magnetic field strength using an implantable rf coil. The contrast agent manganese (Mn) was locally delivered within the parenchyma at a dose of 25 mmol/L in 10 nL. The transport, uptake and accumulation of Mn in tissue were then followed remotely on T1-weighted images that were acquired serially from the cord. In MEIs of normal cord, Mn was observed to be transported in directions both rostral and caudal to the site of injection. In the cord that was subjected to hemisection, signal enhancement was on the contralesional side of the cord, but not at the ipsilesional side. The sensitivity and specificity of the MEI technique in labeling the neurons that are functional were also validated with a traditional track-tracing method using biotinylated dextran amine.

Animals↗
PubMed2006

Magnetic resonance imaging of functional Schwann cell transplants labelled with magnetic microspheres.

There is increasing interest in the use of magnetic resonance imaging (MRI) methods for tracking the fate of labelled cells in vivo post-implantation. The majority of studies have employed cell labels based on nanometer-sized ultrasmall dextran-coated iron oxide particles (USPIO), which are detected through signal hypointensity in T2-weighted images. Although sensitive to MR detection, these labels can be difficult to distinguish from other sources of signal loss in vivo and can be diluted by cell division. Recently, a micron-sized cell label has been described that is much more sensitive to MR detection and which allows detection of single labels in vivo. We show here that glial cells readily take up this label in culture and that the labelled Schwann cells can be detected in vivo by MRI following their implantation into a demyelinated lesion in the rat spinal cord. Signal loss due to the label is sufficiently great that the labelled cells can easily be distinguished from surrounding haemorrhage at the lesion site. Subsequent histological analysis of the lesion area showed that the transplanted cells were remyelinating the demyelinated axons, demonstrating that the labelled cells retained their biological function and that the majority of the label had remained within the transplanted cells.

Animals↗
PubMed2006

Tissue-engineered peripheral nerve grafting by differentiated bone marrow stromal cells.

Bone marrow stromal cells are multipotential stem cells that contribute to the differentiation of tissues such as bone, cartilage, fat and muscle. In the experiment, we found that bone marrow stromal cells can be induced to differentiate into cells expressing characteristic markers of Schwann cells, such as S-100 and glial fibrillary acidic protein, promoting peripheral nerve regeneration. Tissue-engineered bioartificial nerve grafting of rats by differentiated bone marrow stromal cells was applied for bridging a 10 mm-long sciatic nerve defect. Twenty-eight inbred strains of female F344 rats weighing 160 approximately 200 g were randomly divided into four nerve grafting groups, with seven rats in each group. Differentiated bone marrow stromal cell-laden group: poly(lactic-co-glycolic) acid tubes with an intrinsic framework were seeded with syngeneic bone marrow stromal cells which were induced for 5 days; Schwann cell-laden group: poly(lactic-co-glycolic) acid tubes with an intrinsic framework were seeded with syngeneic Schwann cells; acellular group: poly(lactic-co-glycolic) acid tubes were only filled with an intrinsic framework; autografts group. Three months later, a series of examinations was performed, including electrophysiological methods, walking track analysis, immunohistological staining of nerves, immunostaining of S-100 and neurofilament, and axon counts. The outcome indicated that bone marrow stromal cells are able to differentiate into Schwann-like cells and Schwann-like cells could promote nerve regeneration. Bone marrow stromal cells may be potentially optional seed cells for peripheral nerve tissue engineering because of abilities of promoting axonal regeneration.

Animals↗
PubMed2006

Limited brain diffusion of the glucocorticoid receptor agonist RU28362 following i.c.v. administration: implications for i.c.v. drug delivery and glucocorticoid negative feedback in the hypothalamic-pituitary-adrenal axis.

The experiments described herein present a method for tracking diffusion of the glucocorticoid receptor agonist RU28362 in brain following i.c.v. drug administration. A useful property of glucocorticoid receptor is that it is primarily cytoplasmic when unbound and rapidly translocates to the nucleus when bound by ligand. Thus, removal of endogenous glucocorticoids by adrenalectomy allows us to identify brain regions with activated glucocorticoid receptor after i.c.v. glucocorticoid receptor agonist treatment by examining the presence or absence of nuclear glucocorticoid receptor immunostaining. We have previously demonstrated that an i.p. injection of 150 microg/kg RU28362 1 h prior to restraint stress is sufficient to suppress stress-induced hypothalamic-pituitary-adrenal axis hormone secretion [Ginsberg AB, Campeau S, Day HE, Spencer RL (2003) Acute glucocorticoid pretreatment suppresses stress-induced hypothalamic-pituitary-adrenal axis hormone secretion and expression of corticotropin-releasing hormone hnRNA but does not affect c-fos mRNA or fos protein expression in the paraventricular nucleus of the hypothalamus. J Neuroendocrinol 15:1075-1083]. We report here, however, that in rats i.c.v. treatment with a high-dose of RU28362 (1 microg) 1 h prior to stressor onset does not suppress stress-induced hypothalamic-pituitary-adrenal axis activity. We then performed a series of experiments to examine the possible differences in glucocorticoid receptor activation patterns in brain and pituitary after i.c.v. or i.p. treatment with RU28362. In a dose-response study we found that 1 h after i.c.v. injection of RU28362 (0.001, 0.1 and 1.0 microg) glucocorticoid receptor nuclear immunoreactivity was only evident in brain tissue immediately adjacent to the lateral or third ventricle, including the medial but not more lateral portion of the medial parvocellular paraventricular nucleus of the hypothalamus. In contrast, i.p. injection of RU28362 produced a uniform predominantly nuclear glucocorticoid receptor immunostaining pattern throughout all brain tissue. I.c.v. injection of the endogenous glucocorticoid receptor agonist, corticosterone (1 microg) also had limited diffusion into brain tissue. Time-course studies indicated that there was not a greater extent of nuclear glucocorticoid receptor immunostaining present in brain after shorter (10 or 30 min) or longer (2 or 3 h) intervals of time after i.c.v. RU28362 injection. Importantly, time-course studies found that i.c.v. RU28362 produced significant increases in nuclear glucocorticoid receptor immunostaining in the anterior pituitary that were evident within 10 min after injection and maximal after 1 h. These studies support an extensive literature indicating that drugs have very limited ability to diffuse out of the ventricles into brain tissue after i.c.v. injection, while at the same time reaching peripheral tissue sites. In addition, these studies indicate that significant occupancy of some glucocorticoid receptor within the paraventricular nucleus of the hypothalamus and pituitary is not necessarily sufficient to suppress stress-induced hypothalamic-pituitary-adrenal axis activity.

Analysis of Variance↗
PubMed2005

Vaccinations in pneumonia (VIP): pneumococcal and influenza vaccination patterns among patients hospitalized for pneumonia.

BACKGROUND: Although the CDC ACIP (Advisory Committee on Immunization Practices) recommends that appropriate inpatients receive pneumococcal and influenza vaccines, adult vaccination rates for these remain low. We therefore examined perihospitalization vaccination rates for high-risk pneumonia inpatients. METHODS: A retrospective chart review of all pneumonia patients admitted to one community hospital from 6/1/95 to 5/31/96. Vaccination history, co-morbidity, mortality, and prior and subsequent pneumonia admissions were recorded. Primary care providers and nursing homes were contacted to complete and verify vaccine histories. RESULTS: For 173 total admissions (160 subjects), vaccine histories were documented in the hospital chart in less than 0.5% of patients. While 97% had indications for both vaccines at the time of admission, no vaccines were given in the hospital and less than 5% had documented vaccinations during the subsequent 3 years. CONCLUSIONS: Despite clear indications, few patients had documented vaccination at any time. These data lend urgency to the recommendation that pneumococcal and influenza vaccines should be routinely administered to pneumonia inpatients at discharge. Furthermore, they illustrate the need for an improved method for tracking individual adult vaccinations.

Aged↗
PubMed1994

The accuracy of computed tomography in the diagnosis of blunt small-bowel perforation.

BACKGROUND: Computed tomography (CT) is commonly used to evaluate patients with possible blunt intra-abdominal injury. One of its reported weaknesses is failure to demonstrate intestinal trauma. However, CT accuracy in identifying blunt small-bowel perforation has not been adequately assessed. PATIENTS AND METHODS: We tracked 883 consecutive stable trauma victims who had abdominal CT because of equivocal physical findings. Initial "wet reading" results were compared with laparotomy findings and patient outcome. RESULTS: Small-bowel perforation occurred in 26 patients (3%). Twenty-four had CT abnormalities suggesting the injury. Twelve had CT findings considered diagnostic: contrast extravasation (n = 5) and/or extraluminal air (n = 11). One additional patient was thought to have free air on CT, but had no intestinal injury at laparotomy. Another 12 patients had CT scans that were non-diagnostic but suggestive: free fluid without solid organ injury (n = 10), or small-bowel thickening (n = 4) or dilatation (n = 3). Two patients with small-bowel injuries had normal CT scans. Of 857 patients without small-bowel disruption, 802 had normal abdominal CT scans, and 55 had 67 CT findings suggesting intestinal injury. Thus, CT diagnosed small-bowel perforation with a sensitivity of 92%, a specificity of 94%, and negative and positive predictive accuracies of 100% and 30%, respectively. The test had an overall accuracy (validity) of 94%. CONCLUSIONS: Blunt small-bowel injury is uncommon. When it is present, abdominal CT is usually abnormal. CT findings in intestinal perforation can be subtle and nonspecific. Any unexplained abnormality on CT after blunt abdominal trauma may signal the presence of intestinal perforation and warrants close clinical observation or further diagnostic tests.

Adolescent↗
PubMed2003

Measurements of protein-protein interactions by size exclusion chromatography.

A method is presented for determining second virial coefficients (B(2)) of protein solutions from retention time measurements in size exclusion chromatography. We determine B(2) by analyzing the concentration dependence of the chromatographic partition coefficient. We show the ability of this method to track the evolution of B(2) from positive to negative values in lysozyme and bovine serum albumin solutions. Our size exclusion chromatography results agree quantitatively with data obtained by light scattering.

Algorithms↗
PubMed2000

The kinetics of periodate oxidation of carbohydrates: a calorimetric approach.

A calorimetric approach is described for analysing the kinetics of periodate oxidation on a series of monosaccharidic substrates. Rate constants at several temperatures were calculated from the calorimetric decay curves that are proportional to the rate of conversion. Arrhenius plots provided the activation parameters for the various carbohydrates and a linear correlation was found between the values of enthalpy and entropy of activation. The dependence of the values of kinetic rates on stereochemistry is interpreted in terms of conformational probability of the reactive state. The suitability of the calorimetric method to track the kinetic process of slow reactions is emphasised, in particular its ability to monitor, directly and continuously, the course of the reaction.

Calorimetry↗
PubMed2004

Acute pancreatitis after EUS-guided FNA of solid pancreatic masses: a pooled analysis from EUS centers in the United States.

BACKGROUND: The aim of this study was to determine the frequency and the severity of pancreatitis after EUS-guided FNA of solid pancreatic masses. A survey of centers that offer training in EUS in the United States was conducted. METHODS: A list of centers in which training in EUS is offered was obtained from the Web site of the American Society for Gastrointestinal Endoscopy. Designated program directors were contacted via e-mail. The information requested included the number of EUS-guided FNA procedures performed for solid pancreatic masses, the number of cases of post-procedure pancreatitis, and the method for tracking complications. For each episode of pancreatitis, technical details were obtained about the procedure, including the location of the mass, the type of fine needle used, the number of needle passes, and the nature of the lesion. RESULTS: Nineteen of the 27 programs contacted returned the questionnaire (70%). In total, 4909 EUS-guided FNAs of solid pancreatic masses were performed in these 19 centers over a mean of 4 years (range 11 months to 9 years). Pancreatitis occurred after 14 (0.29%): 95% CI[0.16, 0.48] procedures. At two centers in which data on complications were prospectively collected, the frequency of acute pancreatitis was 0.64%, suggesting that the frequency of pancreatitis in the retrospective cohort (0.26%) was under-reported (p=0.22). The odds that cases of pancreatitis would be reported were 2.45 greater for the prospective compared with the retrospective cohort (95% CI[0.55, 10.98]). The median duration of hospitalization for treatment of pancreatitis was 3 days (range 1-21 days). The pancreatitis was classified as mild in 10 cases, moderate in 3, and severe in one; one death (proximate cause, pulmonary embolism) occurred after the development of pancreatitis in a patient with multiple comorbid conditions. CONCLUSIONS: EUS-guided FNA of solid pancreatic masses is infrequently associated with acute pancreatitis. The procedure appears to be safe when performed by experienced endosonographers. The frequency of post EUS-guided FNA pancreatitis may be underestimated by retrospective analysis.

Acute Disease↗
PubMed2002

Osmotic loading to determine the intrinsic material properties of guinea pig knee cartilage.

Few methods exist to study cartilage mechanics in small animal joints due to the difficulties associated with handling small tissue samples. In this study, we apply an osmotic loading method to quantify the intrinsic material properties of articular cartilage in small animal joints. Cartilage samples were studied from the femoral condyle and tibial plateau of two-month old guinea pigs. Swelling strains were measured using confocal fluorescence scanning microscopy in samples subjected to osmotic loading. A histochemical staining method was developed and calibrated for quantification of negative fixed charge density in guinea pig cartilage. Site-matched swelling strain data and fixed charge density values were then used with a triphasic theoretical model for cartilage swelling to determine the uniaxial modulus of the cartilage solid matrix. Moduli obtained in this study (7.2 MPa femoral condyle; 10.8 MPa, tibial plateau) compare well with previously reported values for the tensile moduli of human and other animal cartilages determined from uniaxial tension experiments. This study provides the first available data for material properties and fixed charge density in cartilage from the guinea pig knee and suggests a promising method for tracking changes in cartilage mechanics in small animal models of degeneration.

Animals↗
PubMed2005

Bioluminescent imaging of ubiquitin ligase activity: measuring Cdk2 activity in vivo through changes in p27 turnover.

Optical imaging of reporter molecules such as firefly luciferase has become a popular method of tracking and visualizing cells in living animals. Many biological processes involve ubiquitin ligases, which target specific proteins for destruction under specific sets of conditions. Importantly, the motifs recognized by different ubiquitin ligases are often modular and can be used to target foreign proteins for destruction in cis. We recently fused the Cdk inhibitor p27, which is polyubiquitylated by a Skp2-containing ubiquitin ligase if phosphorylated by cdk2 to firefly luciferase. The resulting fusion protein, p27-Luc, was induced by cdk2 inhibitors in living cells grown in culture or in nude mice. This article describes protocols for validation of p27-Luc in cell culture using siRNA against cdk2 (or its partner cyclin A) and for imaging cells producing p27-Luc grown in transparent hollow fibers after treatment with cdk2 inhibitory drugs in vivo. These approaches should be generalizable to other ubiquitin-ligase substrate pairs.

Animals↗
PubMed1999

The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections.

BACKGROUND: An ever increasing demand to evaluate the effect of dietary supplements on specific health conditions by use of a "significant scientific" standard has prompted the publication of this study. OBJECTIVE: To study the effect of megadose Vitamin C in preventing and relieving cold and flu symptoms in a test group compared with a control group. DESIGN: Prospective, controlled study of students in a technical training facility. SUBJECTS: A total of 463 students ranging in age from 18 to 32 years made up the control group. A total of 252 students ranging in age from 18 to 30 years made up the experimental or test group. METHOD: Investigators tracked the number of reports of cold and flu symptoms among the 1991 test population of the facility compared with the reports of like symptoms among the 1990 control population. Those in the control population reporting symptoms were treated with pain relievers and decongestants, whereas those in the test population reporting symptoms were treated with hourly doses of 1000 mg of Vitamin C for the first 6 hours and then 3 times daily thereafter. Those not reporting symptoms in the test group were also administered 1000-mg doses 3 times daily. RESULTS: Overall, reported flu and cold symptoms in the test group decreased 85% compared with the control group after the administration of megadose Vitamin C. CONCLUSION: Vitamin C in megadoses administered before or after the appearance of cold and flu symptoms relieved and prevented the symptoms in the test population compared with the control group.

Adolescent↗
PubMed2002

[Deflation of breast implants, pre-filled with saline or hydrogel. Results and analysis of 650 treated patients].

SUBJECT: The main mechanical side effect of saline or hydrogel filled implants is deflation. The aim of this study was to analyse the prosthetic deflation rate in the last 7 years in the plastic surgery unit of Toulouse. PATIENTS AND METHODS: We tracked 650 patients operated on between july 1993 and july 2000 (representing 1117 primary implants) which we separated in two groups: the first group contained patients in need of breast reconstruction; the second group contained all the patients with implants placed for aesthetic or breast asymMetry reasons. For each of the two groups we determined the number and the type of implants, as well as the rate and the mean delay after which deflation occurred. RESULTS: During this period, we've determined that: rate of deflation of group 1 (reconstruction) is highest than group 2 (aesthetic), despite sort of implant; rates of deflation of pre-filled hydrogel implants are highest than rates of deflation of pre-filled saline implants. DISCUSSION: Only a few series concerning implants deflation have been described in the literature. We can find a large difference in results which vary from 2 to 76%. We were surprised by the result of our series with a rate of deflation up to 15% with a medium follow-up 5 years in both groups and a mean delay before the fourth year. Deflation's factors are numerous: type of sterilisation, rippling, texture, valve's incompetence, prosthetic patch, guarantee control and iatrogenic causes. Because the silicone gel implants (the one uncomplicated by deflation) were taken off the french market, the saline implants tried to supplant them but without satisfactory results. CONCLUSIONS: With the unacceptable rate deflation of implants in our study, the return in the french market of silicone gel implants seems us an acceptable alternative.

Adolescent↗
PubMed1999

Synchronization of oestrous cycles in sable antelope.

Techniques for manipulating the oestrous cycle of sable antelope, Hippotragus niger, were evaluated in a captive population of 24 females maintained at the Smithsonian Institution's Conservation and Research Center in Front Royal, VA, USA. A secondary objective was to demonstrate the effectiveness of fecal steroid monitoring techniques as a non-invasive method of tracking experimental manipulations. Controlled Internal Drug Releasing (CIDR) devices designed for cattle (type B, reduced in length by 5 cm to fit the sable antelope's smaller reproductive tract) were more effective than CIDR devices designed for goats (type G) at delivering progesterone into circulation, and maintained serum progesterone at levels up to 86.1+/-7.8% of normal luteal concentrations in females whose spontaneous ovarian activity had been inhibited with melengestrol acetate. Serum progesterone and fecal progestagen measurements were highly correlated (P<0.05). Synchronization treatments of prostaglandin (PG) F2alpha alone and in combination with modified CIDR-B devices (12-day insertion interval) were both effective in inducing synchronized ovulation, however the PGF2alpha/modified CIDR-B treatment resulted in more precise synchrony and a shorter latency to ovulation than did PGF2alpha alone. In a separate experiment to characterize the temporal relationship between synchronization treatment, behavioral oestrus and ovulation, onset of behavioral oestrus occurred 34.1+/-5.7 h following PGF2alpha/modified CIDR-B treatment. Mean duration of the induced oestrus was 24.9+/-4.3 h. The first detectable rise in fecal progestagens occurred 5.1+/-1.0 and 4.1+/-1.0 days following PGF2alpha/modified CIDR-B treatment in groups of females housed with and without an adult male, respectively, indicating that the presence of a male did not accelerate the onset of the induced cycle.

Administration, Intravaginal↗
PubMed1998

Recombinant DNA techniques for bioremediation and environmentally-friendly synthesis

A number of new recombinant DNA techniques have been developed for genetically engineered microorganisms for biodegradation of environmental contaminants or for the synthesis of small molecules. These techniques include new expression vectors to carry the heterologous genes into the host organism, new mechanisms to control gene expression, containment mechanisms to control persistence of genetically-engineered microorganisms, application of site-directed and random mutagenesis to increase the substrate range or activity of biodegradative enzymes, and methods to track genetically-engineered microorganisms.

Journal Article↗