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At least 901 records · Page 50Linked to original sources
PubMed1991

The physiology of congenital heart disease: assessment by Doppler color flow mapping.

The use of Doppler echocardiography is a routine part of the noninvasive assessment of the patient with heart disease. In children with congenital heart disease, pulsed- and continuous-wave Doppler echocardiographic techniques provide accurate, reproducible hemodynamic data relative to structural defects. Doppler color flow imaging, however, allows for qualitative assessment of blood flow patterns, which may give important insights into the changing physiology of the newborn infant or that of a patient in the medical or surgical intensive care settings. Ten cases are presented in which this flow information is instructive in understanding the physiological sequelae of congenital heart disease.

Adolescent↗
PubMed1994

Reticulocytes: biological variations and reference limits.

The reticulocyte count is a good index of erythropoietic activity. Automated methods, mainly flow cytometry, have made the counting easier, more accurate and reproducible. The data presented describe the counting of reticulocytes in 1219 apparently healthy subjects of both sexes who came for a periodic health examination. Their ages varied from 4 to over 60 years. The reticulocytes were counted with a flow cytometer (Sysmex R-3000) with Auramine-O as fluorochrome. There was no statistical difference between boys and girls aged 4-19 years. However, the reticulocyte count was significantly higher in men than in women over 20 years of age. The reticulocyte count was affected neither by the menstrual cycle in girls at puberty, nor by oral contraceptives and the menopause in women. No effect of moderate smoking was observed in either sex. Reference limits of the reticulocyte counts (percentage and absolute value) according to age and sex and the three types of reticulocytes are provided.

Adolescent↗
PubMed1989

A simple intravenous infusion method in rodents for determining the potency of anticonvulsants acting through GABAergic mechanisms.

A simple method of intravenous infusion of convulsant drugs (pentetrazol and bicuculline) into the tail vein of rats has been used to determine seizure threshold and construct log-dose seizure threshold response curves for several anticonvulsant drugs (diazepam, phenobarbitone, pentobarbitone, chlormethiazole and valproate). It has been shown that an index of the dose required to increase seizure threshold by 50% (TI50) can be obtained using small numbers of animals. The advantages of this method over that of the subcutaneous pentetrazol method are several: small numbers of animals required, speed and reproducibility. The data also demonstrate the concordance between TI50 values obtained using pentetrazol and bicuculline as the convulsant agent. It is suggested that this method can be used routinely in screens of anticonvulsant drugs thought to work through GABAergic mechanisms.

Animals↗
PubMed1993

The effects of inhibitors of sarcoplasmic reticulum function on the systolic Ca2+ transient in rat ventricular myocytes.

1. The effects of thapsigargin, ryanodine and caffeine were examined on systolic Ca2+ transients in indo-1-loaded rat ventricular myocytes. 2. Thapsigargin (1-10 microM) decreased the magnitude of the Ca2+ transient. This was accompanied by a decrease of the rate constant of decay of the transient. 3. Ryanodine (1-10 microM) decreased the magnitude of the Ca2+ transient. Initially there was no change in the rate of decay but further reduction of the magnitude was accompanied by a slowing. 4. Caffeine (0.5-10 mM) decreased the magnitude of the Ca2+ transient and its rate of decay. These effects were graded with caffeine concentration. 5. For a given submaximal reduction of the magnitude of the Ca2+ transient, the effect on the rate of decay was greatest for thapsigargin, least for ryanodine and intermediate for caffeine. 6. The above data are reproduced by a model in which all three agents decrease the magnitude of the Ca2+ transient by decreasing the calcium content of the sarcoplasmic reticulum (SR) (thapsigargin by inhibiting the Ca2+ pump and ryanodine and caffeine by increasing the leak of Ca2+ from the SR). The decreased contribution of the SR will thereby slow relaxation. The fact that thapsigargin inhibits the SR Ca2+ pump accounts for the observation that, for a given decrease of amplitude, it has more effect than the other agents on the rate of decay. The difference between caffeine and ryanodine is suggested to arise because caffeine potentiates Ca2+ release from the SR and thereby attenuates the effect of the decreased SR calcium content on the magnitude of the Ca2+ transient.

Animals↗
PubMed1995

Reduced effect of pH on skinned rabbit psoas muscle mechanics at high temperatures: implications for fatigue.

1. Inhibition of actomyosin function by decreased pH has been proposed to account for much of the depression of muscle function during fatigue. The clearest support for this hypothesis has been from studies of skinned skeletal muscle fibre mechanics at low temperatures (< or = 15 degrees C). 2. We re-examined the effect of decreased pH (7.0-6.2) on skinned mammalian skeletal fibre mechanics at low (10 degrees C) and high (30 degrees C) temperatures, using recently developed protocols that allow reproducible mechanical data to be obtained at higher temperatures. 3. At 10 degrees C we duplicated previous observations of a significant inhibition of maximum shortening velocity (Vmax) and isometric tension (Po) by acidosis. In contrast, at the higher temperature, we found only a very minimal effect of acidosis on Vmax and a threefold reduction in the decrease in Po. 4. Thus at temperatures only slightly below physiological for mammalian skeletal muscle systems, pH plays a much less important role in the process of muscle fatigue at the cross-bridge level than has been suggested by data obtained at physiologically unrealistic temperatures.

Acidosis↗
PubMed2004

Functional interaction between extracellular sodium, potassium and inactivation gating in HERG channels.

We have studied the interaction between extracellular K(+) (K(+)(o)) and extracellular Na(+) (Na(+)(o)) in human ether-à-go-go related gene (HERG)-encoded K(+) channels expressed in Chinese hamster ovary (CHO-K1) cells, using the whole-cell voltage clamp technique. Prior studies indicate that Na(+)(o) potently inhibits HERG current (IC(50) 3 mm) by binding to an outer pore site, and also speeds recovery from inactivation. In this study, we sought to explore the relationship between the Na(+)(o) effect on recovery and Na(+)(o) inhibition of HERG current, and to determine whether inactivation gating plays a critical role in Na(+)(o) inhibition of HERG current. Na(+)(o) concentration-response relationships for current inhibition and speeding of recovery were different, with Na(+)(o) less potent at speeding recovery. Na(+)(o) inhibition of HERG current was relieved by physiological [K(+)](o), while Na(+)(o) speeded recovery from inactivation similarly in the absence or presence of physiological [K(+)](o). To examine the link between Na(+)(o) block and inactivation using an independent approach, we studied hyperpolarization-activated currents uncoupled from inactivation in the S4-S5 linker mutant D540K. Depolarization-activated D540K currents were inhibited by Na(+)(o), while hyperpolarization-activated currents were augmented by Na(+)(o). This result reveals a direct link between Na(+)(o) inhibition and a depolarization-induced conformational change, most likely inactivation. We attempted to simulate the disparate concentration-response relationships for the two effects of Na(+)(o) using a kinetic model that included Na(+)(o) site(s) affected by permeation and gating. While a model with only a single dynamic Na(+)(o) site was inadequate, a model with two distinct Na(+)(o) sites was sufficient to reproduce the data.

Animals↗
PubMedDate not supplied

Noninvasive imaging of oral premalignancy and malignancy.

Early detection of cancer and its precursors remains the best way to ensure patient survival and quality of life. Our specific aim is to test a multimodality approach to noninvasive diagnostics of oral premalignancy and malignancy. In the hamster cheek pouch model (120 hamsters), in vivo optical coherence tomography (OCT) and optical Doppler tomography (ODT) map epithelial, subepithelial, and vascular change throughout carcinogenesis. In vivo multiwavelength multiphoton (MPM) and second-harmonic generated (SHG) fluorescence techniques provided parallel data on surface and subsurface tissue structure, specifically collagen presence and structure, cellular presence, and vasculature. Images are diagnosed by two blinded, prestandardized investigators using a scale from 0 to 6 for all modalities. After sacrifice, histopathology is evaluated on a scale of 0 to 6. Imaging data are reproducibly obtained with good accuracy. Carcinogenesis-related structural and vascular changes are clearly visible to tissue depths of 2 mm. Sensitivity (OCT/ODT alone, 71 to 88%; OCT+MPMSHG, 79 to 91%) and specificity (OCT alone, 62 to 83%; OCT+MPMSHG, 67 to 90%) compare well with conventional techniques. Our conclusions are that OCT/ODT and MPM/SHG are promising noninvasive in vivo diagnostic modalities for oral dysplasia and malignancy.

Animals↗
PubMedDate not supplied

Noninvasive measurement of cell volume changes by negative staining.

To maintain the intracellular concentration of ions and small molecules on osmotic challenges, nature has developed highly sophisticated transport systems for regulating water and ion content. An ideal measurement technique for volume changes of cells during osmotic challenges has to fulfil two requirements: it has to be osmotically inert, and it should allow online monitoring of cell volume changes. Here, a simple fluorescence microscopy-based approach is presented. Using fluorescein as a negative stain, it is possible to monitor cell volume changes without affecting the functionality of cell membranes and cell osmolarity. Measurement of Madine-Darby canine kidney (MDCK) cells after hypo- and hyperosmotic challenges reveals the main advantages of this approach: besides providing precise and reproducible quantitative data on reversible cell volume changes, the viability of the cells can be assessed directly by the appearance of stain in the cytoplasm. This becomes evident especially after hypo-osmotic challenge of glutaraldehyde-treated cells, which become leaky after fixation, followed by a massive volume change. This new approach represents a very sensitive measurement technique for cell volume changes resulting from water or ion flux, and thus seems to be an ideal tool for studying cell volume regulatory processes.

Animals↗
PubMed1995

Antifungal susceptibility testing of yeasts: evaluation of technical variables for test automation.

The technical parameters for antifungal susceptibility testing with Candida species were reexamined to determine the optimal conditions for testing with semiautomated preparations of broth microdilution cultures, automated spectrophotometric readings of the cultures, and dose-response and endpoint determinations by means of a computer spreadsheet. Tests were based on proposed standard method M27P of the National Committee for Clinical Laboratory Standards for antifungal agents. RPMI 1640 broth with extra glucose to a final concentration of 2% gave higher and more reproducible drug-free control readings without affecting susceptibility endpoint readings. An inoculum of 8 x 10(4) yeasts per ml prepared from a carbon-limiting broth culture without further standardization was found to give optimal control readings after 48 h of incubation at 37 degrees C. For flucytosine, fluconazole, itraconazole, and ketoconazole, endpoints based on 50% growth inhibition (50% inhibitory concentration) gave the minimum variation with inoculum size and the fewest endpoint differences with RPMI 1640 medium obtained from two different suppliers. The 50% inhibitory concentration was also the optimal endpoint for fluconazole and ketoconazole susceptibilities in comparison with broth macrodilution MICs determined by the method of the National Committee for Clinical Laboratory Standards. Intralaboratory reproducibility was determined by retrospective analysis of replicate results for isolates retested at random over a 2-year period. This approach showed less favorable reproducibility than has been reported from purpose-designed, prospective antifungal susceptibility studies, but it may better reflect real-life test reproducibility. Susceptibility data for 616 clinical isolates of yeasts, representing 16 Candida and Saccharomyces spp., confirmed the tendency of Candida lusitaniae isolates to show relatively low susceptibilities to amphotericin B, the tendency of Candida krusei isolates to show low flucytosine and fluconazole susceptibilities, and the presence of some isolates in the species Candida albicans, Candida glabrata, and Candida tropicalis with low susceptibilities to azole derivative antifungal agents. The study demonstrates the value of automation and standardization in all stages of yeast susceptibility testing, from plate preparation to data analysis.

Antifungal Agents↗
PubMed2006

In silico model as a tool for interpretation of intestinal infection studies.

In nutrition research the number of human in vivo experiments is limited because of the many restrictions and the high costs of testing in humans. Up to now predictive computer models aiming to enhance research have been rare or too complex, with many nonmeasurable adjustable parameters. This study aimed to develop a basic physicochemical computer model for a first quantitative interpretation of results obtained from in vivo intestinal experiments with bacteria. This new modeling approach is validated with results obtained from gut infection studies in vivo. The design of the model is described, and its ability to reproduce experimental data is evaluated. The model predictions are compared with new experimental data. The phenomena that take place in the gastrointestinal tract are summarized by model constants for growth, adherence, and release of bacteria. Although the model is far from describing all details and many processes in the intestine are combined, the model calculation results lead to reasonable conclusions and interesting hypotheses. One of these hypotheses concluded from the model outcomes is that Escherichia coli bacteria have a much lower intestinal growth rate in humans than in rats. Extra laboratory validation experiments proved the reliability of this hypothesis predicted by the model. In addition, the known protective effect of dietary calcium and detrimental effect of clindamycin on the growth and adherence of Salmonella bacteria could be quantified. From these results it is clear that the model enhances the interpretation of in vivo gastrointestinal experiments and will facilitate research trajectories towards new functional foods that improve resistance to pathogenic bacteria in humans.

Animals↗
PubMed2002

Sensitive in situ monitoring of a recombinant bioluminescent Yersinia enterocolitica reporter mutant in real time on Camembert cheese.

Bioluminescent mutants of Yersinia enterocolitica were generated by transposon mutagenesis using a promoterless, complete lux operon (luxCDABE) derived from Photorhabdus luminescens, and their production of light in the cheese environment was monitored. Mutant B94, which had the lux cassette inserted into an open reading frame of unknown function was used for direct monitoring of Y. enterocolitica cells on cheeses stored at 10 degrees C by quantifying bioluminescence using a photon-counting, intensified charge-coupled device camera. The detection limit on cheese was 200 CFU/cm(2). Bioluminescence of the reporter mutant was significantly regulated by its environment (NaCl, temperature, and cheese), as well as by growth phase, via the promoter the lux operon had acquired upon transposition. At low temperatures, mutant B94 did not exhibit the often-reported decrease of photon emission in older cells. It was not necessary to include either antibiotics or aldehyde in the food matrix in order to gain quantitative, reproducible bioluminescence data. As far as we know, this is the first time a pathogen has been monitored in situ, in real time, in a "real-product" status, and at a low temperature.

Cheese↗
PubMed2003

Protective levels of diphtheria-neutralizing antibody induced in healthy volunteers by unilateral priming-boosting intranasal immunization associated with restricted ipsilateral mucosal secretory immunoglobulin a.

Subunit intranasal vaccines offer the prospect of inducing combined systemic-mucosal immunity against mucosally transmitted infections such as human immunodeficiency virus. However, although human studies have demonstrated the induction of active immunity, secretory immunoglobulin A (sIgA) responses are variable, and no study has demonstrated protection by accepted vaccine-licensing criteria as measured by direct toxin-neutralizing activity. Using the genetically inactivated mutant diphtheria toxoid CRM(197) in a bioadhesive polycationic polysaccharide chitosan delivery system, we found that a single nasal immunization was well tolerated and boosted antitoxin neutralizing activity in healthy volunteers, which could be further boosted by a second immunization. The neutralizing activity far exceeded accepted protective levels and was equivalent to that induced by standard intramuscular vaccine and significantly greater than intranasal immunization with CRM(197) in the absence of chitosan. A striking but unexpected observation was that although unilateral intranasal immunization induced circulating antitoxin antibody-secreting cells, a nasal antitoxin sIgA response was seen only after the second immunization and only in the vaccinated nostril. If these data are reproduced in larger studies, an intranasal diphtheria vaccine based on CRM(197)-chitosan could be rapidly licensed for human use. However, a restricted sIgA response suggests that care must be taken in the priming-boosting strategy and clinical sampling techniques when evaluating such vaccines for the induction of local mucosal immunity.

Administration, Intranasal↗
PubMed2003

Multilocus sequence typing of Staphylococcus aureus with DNA array technology.

A newly developed oligonucleotide array suited for multilocus sequence typing (MLST) of Staphylococcus aureus strains was analyzed with two strain collections in a two-center study. MLST allele identification for the first strain collection fully agreed with conventional strain typing. Analysis of strains from the second collection revealed that chip-defined MLST was concordant with conventional MLST. Array-mediated MLST data were reproducible, exchangeable, and epidemiologically concordant.

Alleles↗
PubMed2006

Recognition of transmembrane segments in proteins: review and consistency-based benchmarking of internet servers.

Membrane proteins perform a number of crucial functions as transporters, receptors, and components of enzyme complexes. Identification of membrane proteins and prediction of their topology is thus an important part of genome annotation. We present here an overview of transmembrane segments in protein sequences, summarize data from large-scale genome studies, and report results of benchmarking of several popular internet servers.

Algorithms↗
PubMed1990

Approximation of various canine left ventricular end-systolic relations by a cylinder model.

Assuming a linear end-systolic force-length relation and a cylindrical geometry of the left ventricle (LV), we have developed a mathematical model (cylinder model) and derived formulas for LV end-systolic force-diameter (Fes-Des), stress-diameter (Ses-Des), pressure-diameter (Pes-Des), and pressure-cylinder volume (Pes-Ves) relations. To assess the validity of this model for the study of the intact LV, eight healthy beagles were instrumented with ultrasonic crystals to measure LV diameter and wall thickness and a micromanometer to measure LV pressures. Preload was altered by vena caval occlusion. Contractility was increased by addition of Ca2+. Fes-Des relation was nearly linear under control contractility, whereas after addition of Ca2+ this relation became concave toward the diameter axis. Linear approximation was more accurate for this relation than for the Pes-Des and Pes-Ves relations in control contractility. Predictions from the model formulas more accurately reproduced observed data in the Pes-Des (P less than 0.01) and Pes-Ves (P less than 0.001) relations than those from linear regression equations, whereas the model predictions for the Ses-Des relation were as accurate as those of a linear regression equation. Although the slope of the Fes-Des relation increased with inotropic stimulation, diameter intercepts of this relation did not change. Thus the present results obtained under control contractility were consistent with assumptions of the model. This cylinder model might provide reasonable approximations for various canine LV end-systolic relations.

Animals↗
PubMed2004

Aortic valve stenosis: fatal natural history despite normal left ventricular function and low invasive peak-to-peak pressure gradients.

For many years, the severity of valvular aortic stenosis (AS) was evaluated mainly on the basis of cardiac catheterization. In many centers, the handy peak-to-peak transvalvular pressure difference or 'peak-to-peak gradient' in relation to left ventricular function was used as a crucial feature in taking a decision regarding valve substitution. In a prospective study during the period 1994-1997, 150 consecutive patients with AS were examined systematically using cardiac catherization as well as transthoracic (TTE) and transesophageal echocardiography. The study was performed in order to compare the diagnostic accuracy and reproducibility of the three modalities with the purpose of improving our evaluation strategy. We found that the three methods were able to determine the aortic valve area with similar accuracy and reproducibility. The data thus support earlier papers and the currently recommended strategy of managing most patients on the basis of TTE since this approach is more rapid and gentle to the patients. In accordance with the past policy of our department, however, considerable weight was put on the invasive data during the study period. Thus, 12 patients with invasive peak-to-peak gradient <50 mm Hg and no severe depression of left ventricular function were not offered valve replacement, despite symptoms and significant valve area reductions. At 2.5 years of follow-up, 6 had died, 3 of severe heart failure, 2 while awaiting scheduled valve replacement, and 1 during aortocoronary bypass surgery. Another 3 patients later experienced further symptom progression and underwent successful aortic valve replacement. In the remaining 3 patients, all free from coronary stenoses and other valvular heart disease than AS, heart failure symptoms had worsened considerably during continued medical therapy. In conclusion, we do not recommend consideration of the peak-to-peak gradient in the process of deciding whether or not AS patients should receive valve replacement. A low peak-to-peak gradient does not exclude severe AS, even in the presence of preserved left ventricular function.

Aged↗
PubMed1995

[Cepstrum analysis in voice disorders].

Objective data and reproducible procedures are increasingly demanded for assessment and long-term comparison in voice disturbances. Well-known electroacoustic methods like formant analysis, autocorrelation and inverse filtering have been applied for this purpose, though without leaving experimental stage. The cepstrum analysis presented here permits an easy and distinct separation of glottal pitch and filter function of the vocal tract. In this study, 112 normal and hoarse voices were analyzed. The sum of amplitudes of the first cepstral pitch peaks differed significantly between the different degrees of hoarseness (0-3). Disturbances producing hoarseness, however, could not be sufficiently differentiated by the method in its present state.

Adult↗
PubMed2006

Higher level chromatic mechanisms for image segmentation.

We used a noise-masking paradigm to investigate the number and properties of chromatic mechanisms involved in image segmentation. Observers were presented with a pattern of dynamic random squares, each independently modulated along a certain direction in DKL color space, either in the isoluminant plane or in the L - M luminance plane. A signal consisting of a rectangular region of squares, oriented horizontally or vertically, was added to the noise. The signal squares were spatially and temporally aligned to the noise squares, excluding the possibility of phase offsets to mediate segmentation performance. Noise and signal color directions were independently varied, and the signal contrast was measured at which an observer could reliably indicate the orientation of the signal. In a second set of experiments, the noise was simultaneously varying in two directions, symmetrically arranged around the signal direction. Masking was generally highest when signal and noise were modulated along the same direction and minimal for orthogonal noise. No difference was found between signals modulated along cardinal directions or intermediate directions. However, measured tuning widths critically depended on the type of noise: Noise modulated along one direction results in narrow tuning, whereas two-sided noise results in broad tuning. A chromatic detection model with multiple broadly tuned mechanisms successfully accounts for the experimental findings, both for narrow and broad tuning curves. Models with four broadly tuned cardinal mechanisms or multiple narrowly tuned mechanisms failed to reproduce the data. Our results suggest an important role for multiple, broadly tuned mechanisms in image segmentation.

Artifacts↗