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PubMed1996

Adaptive morphological changes of the intestinal mucosa in orthotopic ileal bladder. Short-term and long-term evaluation.

The morphology of the mucosa of orthotopic ileal bladders in place for 3 months to 4 years was studied in biopsies obtained at random from 12 patients. A mucosal flattening, a reorganization of the lining epithelium and a disappearance of the fenestrated areas of blood capillaries were found. Enterocytes progressively stratified and acquired poorly differentiated features, along with loss of microvilli, reduction of the apical fuzzy glycocalyx and enlargement of intercellular spaces. Goblet cells at short-term evaluation were actively involved in mucous synthesis and secretion. Metabolic acidosis was slight both in short-term postoperative periods-under alkaline therapy- and in long-term postoperative periods-when therapy was suspended. It can be concluded that, firstly, urine contact determines in such reservoirs a condition of acute irritation and, secondly, environmental changes induce the ileal mucosa to develop a new phenotype probably better suited to a protective rather than absorptive function.

Aged↗
PubMed2002

Selection, design, and characterization of a new potentially therapeutic ribozyme.

An in vitro selection was designed to identify RNA-cleaving ribozymes predisposed for function as a drug. The selection scheme required the catalyst to be trans-acting with phosphodiesterase activity targeting a fragment of the Kras mRNA under simulated physiological conditions. To increase stabilization against nucleases and to offer the potential for improved functionality, modified sequence space was sampled by transcribing with the following NTPs: 2'-F-ATP, 2'-F-UTP, or 2'-F-5-[(N-imidazole-4-acetyl) propylamine]-UTP, 2'-NH2-CTP, and GTP. Active motifs were identified and assessed for their modified NMP and divalent metal dependence. The minimization of the ribozyme's size and the ability to substitute 2'-OMe for 2'-F and 2'-NH2 moieties yielded the motif from these selections most suited for both nuclease stability and therapeutic development. This motif requires only two 2'-NH2-Cs and functions as a 36-mer. Its substrate sequence requirements were determined to be 5'-Y-G-H-3'. Its half-life in human serum is >100 h. In physiologically relevant magnesium concentrations [approximately 1 mM] its kcat = 0.07 min(-1), Km = 70 nM. This report presents a novel nuclease stable ribozyme, designated Zinzyme, possessing optimal activity in simulated physiological conditions and ready for testing in a therapeutic setting.

Base Sequence↗
PubMed1997

Sharp diffraction peaks from chaotic structures.

Recently various models for spatially chaotic structures have been proposed. We study the diffraction patterns produced by plane chaotic waves incident on one-dimensional chaotic point scatterers. The spacing between the scatterers and the dynamics of the incident wave are given by a logistic map or standard map. We find a sharp diffraction peak when the incident dynamics is produced by the same map as the structure of the spatial configuration. The diffraction pattern is symmetric about the incident direction only if the map dynamics is invertible. Diffraction patterns with chaotic incident waves have a large signal-to-noise ratio and are well suited for pattern identification. We discuss possible applications to the scattering of microwaves from aperiodic structures. (c) 1997 American Institute of Physics.

Journal Article↗
PubMed2006

Evaluation of ultrasound lung comets by hand-held echocardiography.

BACKGROUND: Ultrasound lung comets (ULCs) are a clinically useful sign of extravascular lung water. They require very limited technology (2 D-echo), and a short learning curve. The aim of the present study is to compare ULCs information obtained by experienced echocardiologists using a full feature echocardiographic platform and by inexperienced sonographers using a hand-held echocardiography system. METHODS: 20 consecutive in-hospital patients underwent, within 15' and in random order, 2 ultrasound examinations for ULCs by 2 observers with different specific expertise and different technology: 1) "high-tech veteran": ULCs assessment with full feature echocardiographic platform (HP Sonos 7500 Philips Medical Systems, Andover, MA, USA) by a trained echocardiologist, with > or =2 years expertise in ULCs assessment and accredited by the European Association of Echocardiography; 2) and a "low-tech beginner": ULCs assessment with hand-held echocardiography (Optigo; Philips, Andover, MA) by an echocardiographer with very limited (30') dedicated training on ULCs assessment. In each patient, ULC score was obtained by summing the number of comets from each of the scanning spaces in the anterior right and left hemithorax, from the second to the fifth intercostal space. RESULTS: There was a significant, tight correlation (r = .958, p < 0.001) between the 2 observations in the same patient by "high-tech veteran" and "low-tech beginner". CONCLUSION: ULCs are equally reliable in the hands of highly experienced echocardiologists using full feature echocardiographic platforms and in the hands of absolute beginners with miniaturized, compact, and battery-equipped echocardiographic systems. From the technological and expertise viewpoint, ULCs are the "kindergarten" of echocardiography, ideally suited for bedside evaluation of patients with both known or suspected heart failure.

Aged↗
PubMed1986

Two modes of processing visual information: implications for assessing visual impairment.

The recognition of visual detail and the ability to orient spatially to visual stimuli are apparently subserved by distinct modes of processing, termed "focal" and "ambient," respectively. Current clinical techniques are well suited to evaluate aspects of focal vision, but do little to evaluate ambient visual functions. As a result, the impairment of ambient functions may be difficult to specify or may be overestimated. Implications for the development of assessment techniques for ambient functions are discussed.

Humans↗
PubMed1990

A statistical model of the VA/Q distribution.

A "blocks model" is proposed to model the distribution of the ventilation-perfusion ratio (VA/Q distribution). This model is developed from statistical principles and enables the estimated VA/Q distribution to be interpreted in a straightforward and intuitive manner. Estimation of parameters of the blocks model uses a constrained weighted least-squares procedure. Although developed initially to estimate VA/Q distributions from data generated by the multiple inert gas elimination technique (P. D. Wagner, H. A. Saltzman, and J. B. West, J. Appl. Physiol. 36: 588-599, 1974), the blocks method is applicable to any problem in which the unknown distribution is related to the data through an ill-posed integral equation and is particularly suited for problems in which the data are scarce. The method is illustrated with several examples--hypothetical data representing a wide range of VA/Q distributions as well as some real data.

Computer Simulation↗
PubMed1994

Subdural monitoring in the evaluation of children for epilepsy surgery.

Noninvasive assessment of children with chronic epilepsy is often imprecise and localization of seizure foci requires intracranial electroencephalographic monitoring. Subdural electrodes provide coverage of large areas of neocortex and are ideally suited for evaluating children with intractable epilepsy and to functionally map critical cortex. This report discusses the role of subdural electroencephalography in the evaluation of childhood epilepsy.

Brain Mapping↗
PubMed2003

Radiography in the assessment of musculoskeletal conditions.

Plain film radiography is the most widely used imaging technique for diagnosing and monitoring the progression of chronic inflammatory and degenerative joint diseases. Advanced imaging techniques that are better suited for detecting soft-tissue inflammation are available, but they are more costly and some of them may expose the patient to higher doses of radiation. Plain film radiographs are inexpensive, easy to generate, can be compared with baseline and prospective films, and provide a permanent, reproducible record. Radiographs can easily detect the features that are specific to various rheumatological disorders, and serial radiography can be used to assess response to therapy by measuring erosions, joint space narrowing, and other disease-specific features. This chapter discusses the use of radiography for diagnosing and differentiating various rheumatic joint diseases, specifically rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis and osteoarthritis. The most frequently used scoring systems that are used to assess and monitor the severity and progression of these disorders are briefly described.

Arthritis, Psoriatic↗
PubMed1996

Lead and Helium Isotope Evidence from Oceanic Basalts for a Common Deep Source of Mantle Plumes

Linear arrays in lead isotope space for mid-ocean ridge basalts (MORBs) converge on a single end-member component that has intermediate lead, strontium, and neodymium isotope ratios compared with the total database for oceanic island basalts (OIBs) and MORBs. The MORB data are consistent with the presence of a common mantle source region for OIBs that is sampled by mantle plumes. 3He/4He ratios for MORBs show both positive and negative correlation with the 206Pb/204Pb ratios, depending on the MORB suite. These data suggest that the common mantle source is located in the transition zone region. This region contains recycled, oceanic crustal protoliths that incorporated some continental lead before their subduction during the past 300 to 2000 million years.

Journal Article↗
PubMed2004

Microstructural characterization of cyanobacterial mats from the McMurdo Ice Shelf, Antarctica.

The three-dimensional structures of two types of cyanobacterium-dominated microbial mats from meltwater ponds on the McMurdo Ice Shelf were as determined by using a broad suite of complementary techniques, including optical and fluorescence microscopy, confocal scanning laser microscopy, scanning electron microscopy with back-scattered electron-imaging mode, low-temperature scanning electron microscopy, and microanalyitical X-ray energy dispersive spectroscopy. By using a combination of the different in situ microscopic techniques, the Antarctic microbial mats were found to be structures with vertical stratification of groups of cyanobacteria and mineral sediments, high contents of extracellular polymeric substances, and large void spaces occupied by water. In cyanobacterium-rich layers, heterocystous nostocalean and nonheterocystous oscillatorialean taxa were the most abundant taxa and appeared to be intermixed with fine-size deposits of epicellular silica and calcium carbonate. Most of the cyanobacterial filaments had similar orientations in zones without sediment particles, but thin filaments were tangled among thicker filaments. The combination of the microscopic techniques used showed the relative positions of biological and mineral entities within the microbial mats and enabled some speculation about their interactions.

Antarctic Regions↗
PubMed2003

Stereotactic imaging for radiotherapy: accuracy of CT, MRI, PET and SPECT.

CT, MRI, PET and SPECT provide complementary information for treatment planning in stereotactic radiotherapy. Stereotactic correlation of these images requires commissioning tests to confirm the localization accuracy of each modality. A phantom was developed to measure the accuracy of stereotactic localization for CT, MRI, PET and SPECT in the head and neck region. To this end. the stereotactically measured coordinates of structures within the phantom were compared with their mechanically defined coordinates. For MRI, PET and SPECT, measurements were performed using two different devices. For MRI, T1- and T2-weighted imaging sequences were applied. For each measurement, the mean radial deviation in space between the stereotactically measured and mechanically defined position of target points was determined. For CT, the mean radial deviation was 0.4 +/- 0.2 mm. For MRI, the mean deviations ranged between 0.7 +/- 0.2 mm and 1.4 +/- 0.5 mm, depending on the MRI device and the imaging sequence. For PET, mean deviations of 1.1 +/- 0.5 mm and 2.4 +/- 0.3 mm were obtained. The mean deviations for SPECT were 1.6 +/- 0.5 mm and 2.0 +/- 0.6 mm. The phantom is well suited to determine the accuracy of stereotactic localization with CT, MRI, PET and SPECT in the head and neck region. The obtained accuracy is well below the physical resolution for CT, PET and SPECT, and of comparable magnitude for MRI. Since the localization accuracy may be device dependent, results obtained at one device cannot be generalized to others.

Humans↗
PubMed1997

Cubby. A medical virtual environment based on multiscreen movement parallax.

In this paper a desktop virtual reality system named Cubby is described. Cubby is based on self-induced, head-coupled movement parallax on three orthogonal screens. It is argued that this system is better suited to medical practice than Immersive VR solutions or single screen Desktop VR systems. Whilst Cubby is currently limited to visualisation it opens up possibilities of direct instrumental manipulation and as such could prove useful as a medical simulator.

Computer Simulation↗
PubMed1992

Septic discitis resulting from Escherichia coli urosepsis.

Septic discitis refers to a primary suppurative process involving the intervertebral disc space and occurs as a result of hematogenous invasion or contamination by pyogenic organisms. A case of septic discitis is described in a 77-year-old woman following an episode of Escherichia coli urosepsis. Despite bed rest, an orthosis, and appropriate antibiotics, the patient ultimately had to undergo surgical disc removal. The diagnosis of septic discitis is often made in the context of other diseases that share common clinical and laboratory findings. Magnetic resonance imaging appears well suited for diagnostic confirmation of septic discitis. Needle biopsy and aspiration results should be used to determine the appropriate choice of antibiotic for this disease process.

Aged↗
PubMed2006

Characterisation of stationary phases in subcritical fluid chromatography by the solvation parameter model. II. Comparison tools.

This study is an investigation of numerical and graphical tools for the comparison of the chromatographic stationary phases previously characterized with the solvation parameter model [C. West, E. Lesellier, J. Chromatogr. A, in press]. Numerous methods are presented and discussed: the coefficient ratio comparison, principal component analysis (PCA) and calculation of the distance. The coefficient ratio comparison allows to estimate the weight of a particular type of interaction relative to dispersive interactions, but is not practical when a lot of chromatographic systems need to be compared. The principal component analysis is mainly used to reduce the set of correlated variables, but is not useful for non correlated variables such as the solvation parameters. The distance calculation is an interesting tool to measure the differences between two systems but suffers from a confusion between two notions: the difference in the type of interactions involved in the chromatographic system and the intensity of these interactions. Finally, we chose to associate each stationary phase to a vector in a five-dimensional space, according to a method proposed by Ishihama and Asakawa [Y. Ishihama, N. Asakawa, J. Pharm. Sci., 88(12) (1999) 1305] for the comparison of lipophilicity scales. Thus, the angles between the different vectors are used to compare the selectivities of the stationary phases, and the lengths of the vectors are used to compare the relative intensities of the interactions. This method was applied to different alkyl phases characterized in subcritical fluid chromatography (SubFC). The angle values are well suited to the description of the differences in chromatographic behaviour. As expected, a small angle value is obtained between C8, C12 and C18, when a greater one is noticed between C4 and the longer chain length alkyl bonded phases, showing the different acidity and basicity of the C4 phase. Moreover, a satisfactory correlation is obtained between the length of the vectors and the carbon number of the alkyl chain. The differences between classical alkyl-bonded silica phases and polar-embedded alkyl-bonded phases or fluorinated phases are also conveniently evidenced. Finally, graphical tools are investigated and a new type of representation, based in part on a radar plot, is proposed. This plot allows the comparison of stationary phases without reducing the number of studied variables. The comparisons based on this method are consistent with the observed chromatographic behaviour of the phases compared.

Adsorption↗
PubMed1998

Virtual endoscopy for planning and simulation of minimally invasive neurosurgery.

OBJECTIVE: This article demonstrates the usefulness and the problems of present-state software for virtual endoscopy as a tool for the planning and simulation of minimally invasive neurosurgical procedures. METHODS: The software Navigator (General Electric Medical Systems, Buc, France) was applied for virtual endoscopic visualization of three-dimensional magnetic resonance data sets of healthy volunteers and neurosurgical patients, using a clinical magnetic resonance scanner (1.5-T Signa Hispeed; General Electric Medical Systems). Classical approaches for minimally invasive procedures were simulated. RESULTS: Virtual endoscopy provided impressive three-dimensional views of intracranial and intracerebral cavities, with visualization of many anatomic details of the brain's inner and outer surfaces. The method proved to be especially suited for the simulation and planning of operations of intraventricular lesions, for which the technical limitations of the present state of development of this method have fewer implications. However, the present state of technology, as described in this article, has two major shortcomings: 1) the blood vessels cannot be visualized together with the brain tissue and cranial nerves; and 2) different tissue compartments cannot be stained in their original coloring, which would facilitate their recognition and thus orientation in space by anatomic landmarks. Another important disadvantage at this stage is time consumption for many single working steps. CONCLUSION: Virtual endoscopy is a promising tool for teaching and training in intracranial neuroanatomy as well as for planning and simulation of minimally invasive (e.g., endoscopic), mainly intraventricular, operations. Direct clinical application is, at this stage of development, limited by several technical shortcomings of visualization and quantification of distances and modeling of surfaces.

Cerebral Ventricles↗
PubMed2002

Acetylcholine released from cholinergic nerves contributes to cutaneous vasodilation during heat stress.

Nitric oxide (NO) contributes to active cutaneous vasodilation during a heat stress in humans. Given that acetylcholine is released from cholinergic nerves during whole body heating, coupled with evidence that acetylcholine causes vasodilation via NO mechanisms, it is possible that release of acetylcholine in the dermal space contributes to cutaneous vasodilation during a heat stress. To test this hypothesis, in seven subjects skin blood flow (SkBF) and sweat rate were simultaneously monitored over three microdialysis membranes placed in the dermal space of dorsal forearm skin. One membrane was perfused with the acetylcholinesterase inhibitor neostigmine (10 microM), the second membrane was perfused with the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME; 10 mM) dissolved in the aforementioned neostigmine solution (l-NAME(Neo)), and the third membrane was perfused with Ringer solution as a control site. Each subject was exposed to approximately 20 min of whole body heating via a water-perfused suit, which increased mean body temperature from 36.4 +/- 0.1 to 37.5 +/- 0.1 degrees C (P < 0.05). After the heat stress, SkBF at each site was normalized to its maximum value, identified by administration of 28 mM sodium nitroprusside. Mean body temperature threshold for cutaneous vasodilation was significantly lower at the neostigmine-treated site relative to the other sites (neostigmine: 36.6 +/- 0.1 degrees C, l-NAME(Neo): 37.1 +/- 0.1 degrees C, control: 36.9 +/- 0.1 degrees C), whereas no significant threshold difference was observed between the l-NAME(Neo)-treated and control sites. At the end of the heat stress, SkBF was not different between the neostigmine-treated and control sites, whereas SkBF at the l-NAME(Neo)-treated site was significantly lower than the other sites. These results suggest that acetylcholine released from cholinergic nerves is capable of modulating cutaneous vasodilation via NO synthase mechanisms early in the heat stress but not after substantial cutaneous vasodilation.

Acetylcholine↗
PubMed1984

Quantitative histochemistry in pathology and toxicology. An evaluation of the original two-wave length method of Ornstein.

A quantitative histochemical procedure for use in general pathologic and toxicologic studies, based on the original two-wave length microdensitometric method of Ornstein, has been developed. Basic mathematical formulas and necessary parameters have been derived from Ornstein's calculations. A computer simulation of the behavior of these equations in analyzing a photometric field demonstrated the importance of careful choice of working wave lengths for both reference wave length (lambda ref) and correction wave length (lambda cor), the importance of minimizing "empty space" in the photometric field, and the importance of accuracy and stability of transmission readings. An easy procedure for choosing lambda ref and lambda cor is described. The effects of mounting media, varying chromophores analyzed, internal glare, and measuring diaphragms and monochromator in the photometric apparatus are assessed. This method is compared with a scanning technique, and the formulas employed are related to alternative calculations done by Patau. The application of this two-wave length method is well suited to accurately determine extinction values from tissues and cytologic specimens at varying powers of magnification utilizing a variety of histochemical chromophores, which makes the method ideally applicable to general purpose use in pathologic and toxicologic studies.

Computers↗
PubMed2005

[Ultrasound evaluation of the acromioclavicular joint. A comparison with magnetic resonance imaging].

INTRODUCTION: Ultrasound is useful in detecting acromioclavicular pathologies in cases of trauma, inflammations and degenerative changes in sports medicine. Many studies compare joint space and capsular dimensions of symptomatic and asymptomatic patients. However, no study has examined the reproducibility and reliability of these measurements. The aim of this study was to evaluate the reliability of ultrasonographic measurements in assessing the acromioclavicular joint. MATERIALS AND METHODS: 27 acromioclavicular joints of 15 healthy subjects were examined by T1 weighted magnetic resonance imaging (MRI) to determine the normal limits of joint space (a) and joint capsule (b). These measurements were compared to standardised ultrasonographic (11 Mhz) measurements, which were repeated three times. RESULTS: The mean difference between MRI and ultrasound measurements was 1.5 +/- 1.3 mm and 1.3 +/- 1.2 mm for distance a and b, respectively. Reproducibility of ultrasonographic measurements was high with a mean standard deviation of 0.3 +/- 0.2 mm and 0.4 +/- 0.3 mm for distance a and b, respectively. CONCLUSION: Due to low costs, safety and wide availability ultrasonography is suited for the evaluation of the acromiocalvicular joint. However, when interpreting the results measurement errors, limitations in resolution of the system used, and the anatomy of the acromioclavicular joint and its anatomic variants have to be taken into consideration.

Acromioclavicular Joint↗