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At least 1,063 records · Page 59Linked to original sources
PubMed1986

Oxytocin stimulates the apical K+ conductance in frog skin.

We measured the effects of oxytocin (0.1 U/ml) on the current (Isc) recorded through skins of Rana temporaria incubated with an isotonic K+ solution on the apical side while the transepithelial potential was clamped to zero. Under these conditions, Isc is carried by inward K+ movements. Oxytocin markedly stimulated this inward K+ current. When the spontaneous fluctuations were analyzed we found that oxytocin increased the plateau (S(1)o) of the spontaneous Lorentzian component without modifying the corner frequency (f(1)c). Addition of Ba2+ to the mucosal solution blocked Isc both in the presence and absence of oxytocin. Moreover, with mucosal Ba2+ a characteristic blocker-induced Lorentzian component appeared in the power spectrum. Analysis of this blocker-induced noise showed that oxytocin increased the number of active K+ channels in the apical membrane, while the changes in single channel current were in agreement with the expected alterations of the electrochemical driving force.

Animals↗
PubMed1994

Evaluation of a portable prototype to analyze heart rate variability.

Power spectrum analysis of heart rate fluctuations provide a quantitative noninvasive means of assessing the functioning of the cardiovascular control system. Until now the equipment used to study heart rate variability (HRV) have been complicated systems utilized mostly in research centers. Simpler systems are needed for routine clinical application. We have evaluated, through clinical practice, the usefulness of prototype equipment which allows acquisition and analysis of ECG signals by a portable electrocardiograph and a personal computer in which sophisticated software is installed. We performed one hundred forty-five recordings in twenty-two patients admitted to ICU. With this technique two different predictive patterns were detected: one concerning survivors, the other concerning nonsurvivors. Reliability, portability, simplicity and quality results are the main advantages of the system. The disadvantage is that it is difficult to perform HRV analysis in patients with ECG arrhythmia. This is because the program does not allow the choice of an arrhythmia-free section of the tachogram to analyze.

Adolescent↗
PubMed1995

L-ascorbic acid in nonenzymatic reactions. I. Reaction with glycine.

The influence of the water content, molar ratio, time and temperature on the formation of nondialysable melanoidins produced by the interaction of L-ascorbic acid and glycine has been studied. The isolated polymers have been characterized by spectrum analysis and fractionated using gel chromatography. The rate constants of the reaction for temperatures of 90 degrees C, 100 degrees C and 110 degrees C have been calculated and are (0.84 +/- 0.29) x 10(-5) x s-1, (1.33 +/- 0.14) x 10(-5) x s-1 and (5.30 +/- 0.37) x 10(-5) x s-1, respectively. The activation energy of the reaction has been determined to be 106.07 +/- 32.47 kJ/mol.

Ascorbic Acid↗
PubMed1990

Haemodynamic aspects of clinical cerebral angiography. Concurrent two vessel monitoring using transcranial Doppler ultrasound.

To overcome the technical limitations which have precluded noninvasive Doppler ultrasound in investigation of rapid cerebral haemodynamic responses in two cerebrovascular beds at the same time, we have modified a commercial 2 MHz pulsed Doppler instrument with online spectrum analysis. Two probes are activated intermittently, recording eight averaged Doppler-shifted spectra from each probe sequentially. Concurrent recordings of blood velocity in both middle cerebral arteries were performed during 25 selective iohexol carotid angiography runs in 13 patients with near normal cerebral vasculature. The technique permitted the differentiation between the specific responses confined to the recipient vascular bed, and the general responses occurring in remote brain areas as well. The specific response to iohexol was biphasic; a significant decrease in blood velocity occurred less than 4 s after the bolus entry, probably due to the high viscocity of iohexol. Between 4 and 12 s. blood velocity was significantly increased, reflecting the cerebrovascular response to hypertonic solutions. The blood velocity on the opposite side increased from less than 4 s through 45 s after iohexol. This concurs with studies using electromagnetic flowmetry, and suggests that these general responses are elicited by anxiety, discomfort and pain. Thus, no general responses were seen during angiography under general anaesthesia. Eight patients investigated during catheter flushing with normal saline showed a biphasic specific response reciprocal to that due to iohexol. A significant blood velocity peak occurred less than 4 s after the bolus entry, followed by a decrease between 4 and 60 s. The saline injections produced no pain and evoked no significant general response.

Adolescent↗
PubMed1983

Analytical procedures for diagnosis of trace element disorders.

Trace elements levels in tissues show changes in various diseases including inborn errors of metabolism. Such changes may be primary or secondary due to stress or diseases of the liver and gastrointestinal tract. Measurement of trace elements in these cases may be essential both for diagnostic and therapeutic purposes. Trace element measurements can also be useful in other areas of clinical interest including nutrition, toxicity and therapy with inorganic pharmaceutical agents. The available techniques for measuring trace elements in tissues are summarized and the various problems of each are discussed.

Electron Probe Microanalysis↗
PubMed1994

Carotid endarterectomy without arteriography: the preeminent role of the vascular laboratory.

The classic workup of patients considered for carotid endarterectomy (CE) has included contrast arteriography to delineate the nature and extent of the arterial pathology. Noninvasive testing (NIT) consisting of duplex scanning plus sound spectrum analysis is an alternative method for accurately evaluating the carotid bifurcation. The accuracy of our laboratory in comparing NIT to contrast arteriography has been established by use of the guidelines suggested by the Intersocietal Commission for the Accreditation of Vascular Laboratories. Forty-two patients underwent CE based on NIT alone. Seventeen had hemispheric transient ischemic attacks or minor strokes, six had amaurosis fugax, three had nonspecific symptoms, and 16 were asymptomatic. NIT identified a severe stenosis that was limited to the carotid bifurcation; the internal carotid artery distal to the bulb was normal. The predicted stenotic atherosclerotic lesion was confirmed at operation in all patients. One patient had a high bifurcation that required an extension of the original incision. Of three undiagnosed kinked distal internal carotid arteries found at operation, only one required surgical correction. No transient ischemic attacks, strokes, or deaths occurred postoperatively. CE can be performed in selected patients based on NIT alone, obviating the mortality, morbidity, and cost of arteriography. This algorithm demands that the NIT is unequivocal and the accuracy of the testing laboratory is established and maintained according to published standards.

Arteriosclerosis↗
PubMed1989

Predictive value of cervical bruit for the detection of obstructive lesions of the internal carotid artery. Data from 2000 patients.

Between January 1982 and June 1985, 2000 patients with either symptoms of cerebrovascular insufficiency (1873) or asymptomatic cervical bruits (127) were studied at the Surgical Department of the University of Brescia (Italy). Of these, 441 presented a mono- or bilateral cervical bruit. The value of the bruit as indicator of an obstructive pathology of the extracranial carotid artery was evaluated in comparison with the findings of Doppler spectrum analysis. A stenosis or occlusion of the internal carotid artery was present in 51% of the patients with a bruit (homolateral to the bruit in 91% of the cases) and in 9% of those without a bruit. Stenoses of a medium-high degree were those more often associated with the bruit. Both in patients with bruit and in those without bruit the age and the severity of the presenting symptoms significantly influenced the rate of association with lesions of the internal carotid artery was present in 51% of the patients with a bruit (homolateral to the bruit in 91% of the cases) and in 9% of those without a bruit. Stenoses of a medium-high degree were those more often associated with the bruit. Both in patients with bruit and in those without bruit the age and the severity of the presenting symptoms significantly influenced the rate of association with lesions of the internal carotid artery.

Adult↗
PubMed2004

Electro-encephalogram disturbances in different sleep-wake states following exposure to high environmental heat.

In this study, cerebral electrical activity or electro-encephalogram (EEG) was studied following exposure to high environmental heat, in three different age groups of freely moving rats. Each age group was subdivided into three groups: the acute heat stress group, subjected to a single exposure of 4 h at 38 degrees C in the biological oxygen demand incubator; the chronic heat stress group, exposed for 21 days, for 1 h each day, at 38 degrees C in the incubator; and the handling control group. The polygraphic sleep-wake recordings involved simultaneous recordings of cortical EEG, electro-oculogram (EOG), and electromyogram (EMG), on paper and in digital form on computer hard disk, just after the heat exposure for the acute stressed rats and on the 22nd day for the chronic stressed rats. The power spectrum was calculated for 2s epochs of the EEG signals. Quantitative analyses of EEG (qEEG) showed that, in all three age groups, changes in higher-frequency components (beta2) were significant in all sleep-wake states following both acute and chronic heat stress conditions. The power of beta2 activity in all three age groups after acute heat exposure was significantly decreased during slow wave sleep (SWS) (p < 0.05) and rapid eye movement sleep (p < 0.05), whereas the reverse was observed in the awake state (p < 0.05). Following chronic heat exposure, beta2 activity was found to increase in all three sleep-wake stages in all groups of rats (p < 0.01 for SWS in the weaning group and p < 0.05 for other data). Thus the study demonstrated that the cortical EEG is sensitive to environmental heat, and alterations in EEG frequencies in different states of mental consciousness due to high heat can be differentiated efficiently by EEG power spectrum analysis.

Animals↗
PubMed2003

Surface electromyography and mechanomyography recording: a new differential composite probe.

The objective of the study was to develop a new surface probe for differential mechanomyographic (MMG) and electromyographic (EMG) recording. Differential amplification is commonly used in electromyography to improve the signal-to-noise ratio. A new composite probe was developed with two electrodes (EMG) and two identical piezo-electric membranes (MMG) to be positioned on muscle. The probe had two built-in fixed-gain differential amplifiers: one to amplify the electric signal and the other to amplify the vibration signal. A similar non-differential MMG probe was used for comparisons. Burst muscular activity was recorded using the non-differential and differential probes and was used to test the performance of the two probes in suppressing artifacts of non-muscular origin. Power spectrum analysis of signals from the two probes showed that differential amplification significantly improved the signal-to-noise ratio in MMG recordings and significantly suppressed artifacts (power difference > 90%). The composite probe allowed simultaneous differential recording of MMG and EMG signals from the same muscular site. It recorded muscular activity more efficiently than the non-differential probe and could therefore be useful in studying fatigue and neuromuscular diseases.

Artifacts↗
PubMed1983

Neonatal 5-oxoprolinuria: difficult-to-diagnose?

A male newborn infant presented with metabolic acidosis and haemolytic anaemia. Renal tubular acidosis was suspected in the absence of amino aciduria and the patient was treated with sodium bicarbonate. Two years later, the chronic acidosis, clinical observation of developmental delay and ataxia prompted further investigational studies. 5-Oxoprolinuria was identified by gas-liquid chromatography and confirmed by mass spectrometry after an initial mass spectrum analysis reported a glutamic acid artifact. Glutathione and glutathione synthetase in erythrocytes were 25% and 5% of control values, respectively. On the basis of neonatal metabolic acidosis, without amino aciduria and an elevated reticulocyte count, a recommendation is made for blood glutathione and urine 5-oxoproline screening, followed by glutathione synthetase assay for confirmation of neonatal 5-oxoprolinuria.

Acidosis↗
PubMed1998

Dietary flavonoids interact with trace metals and affect metallothionein level in human intestinal cells.

Flavonoids are natural compounds found in food items of plant origin. The study examined systematically the interaction of structurally diverse dietary flavonoids with trace metal ions and the potential impact of dietary flavonoids on the function of intestinal cells. Spectrum analysis was first performed to determine flavonoid-metal interaction in the buffer. Among the flavonoids tested, genistein, biochanin-A, naringin, and naringenin did not interact with any metal ions tested. Members of the flavonol family, quercetin, rutin, kaempferol, flavanol, and catechin, were found to interact with Cu(II) and Fe(III). On prolonged exposure, quercetin also interacted with Mn(II). Quercetin at 1:1 ratio to Cu(II) completely blocked the Cu-dependent color formation from hematoxylin. When quercetin was added to the growth medium of cultured human intestinal cells, Caco-2, the level of metal binding antioxidant protein, metallothionein, decreased. The effect of quercetin on metallothionein was dose- and time-dependent. Genistein and biochanin A, on the contrary, increased the level of metallothionein. The interaction between dietary flavonoids and trace minerals and the effect of flavonoids on metallothionein level imply that flavonoids may affect metal homeostasis and cellular oxidative status in a structure-specific fashion.

Cadmium↗
PubMed1997

Usefulness of novel imaging modalities in diagnosis of focal nodular hyperplasia of the liver.

A 17-year-old woman was admitted because of a liver tumor found incidentally by ultrasonography. Liver function was normal and there were no markers of hepatitis viruses or malignancy. Abdominal ultrasonography, computed tomography (CT), and magnetic resonance imaging revealed a mass (2 cm in diameter) in the lateral segment of the left lobe of the liver. The lesion was not detected by hepatic arteriography. However, dynamic CT with fast scanning and dynamic CO2-enhanced ultrasonography demonstrated initial central enhancement of the mass followed by centrifugal spread of enhancement to the periphery. Color Doppler flow imaging detected a central color spot, shown to be an artery by a pulsed Doppler spectrum analysis. Fine-needle biopsy confirmed a diagnosis of focal nodular hyperplasia. Dynamic CT with fast scanning, dynamic CO2-enhanced ultrasonography, and color Doppler flow imaging were useful in detecting the vascular pattern specific to focal nodular hyperplasia. Investigation of further cases with these novel imaging modalities should help to establish a comprehensive diagnostic procedure and thus avoid unnecessary surgery for focal nodular hyperplasia, which is a completely benign lesion.

Adolescent↗
PubMed2005

A single operon-encoded form of the acetyl-CoA decarbonylase/synthase multienzyme complex responsible for synthesis and cleavage of acetyl-CoA in Methanosarcina thermophila.

Methanogens growing on C-1 substrates synthesize 2-carbon acetyl groups in the form of acetyl-CoA for carbon assimilation using the multienzyme complex acetyl-CoA decarbonylase/synthase (ACDS) which contains five different subunits encoded within an operon. In species growing on acetate ACDS also functions to cleave the acetate C-C bond for energy production by methanogenesis. A number of species of Methanosarcina that are capable of growth on either C-1 compounds or acetate contain two separate ACDS operons, and questions have been raised about whether or not these operons play separate roles in acetate synthesis and cleavage. Methanosarcina thermophila genomic DNA was analyzed for the presence of two ACDS operons by PCR amplifications with different primer pairs, restriction enzyme analyses, DNA sequencing and Southern blot analyses. A single ACDS operon was identified and characterized, with no evidence for more than one. MALDI mass spectrometric analyses were carried out on ACDS preparations from methanol- and acetate-grown cells. Peptide fragmentation patterns showed that the same ACDS subunits were present regardless of growth conditions. The evidence indicates that a single form of ACDS is used both for acetate cleavage during growth on acetate and for acetate synthesis during growth on C-1 substrates.

Acetyl Coenzyme A↗
PubMed1998

Purification and characterization of a catalase from the nonsulfur phototrophic bacterium Rhodobacter sphaeroides ATH 2.4.1 and its role in the oxidative stress response.

When challenged with reactive oxidants, the nonsulfur phototrophic bacterium Rhodobacter sphaeroides ATH 2.4.1 exhibited an oxidative stress response during both phototrophic and chemotrophic growth. Upon preincubation with 100 microM H2O2, catalase activity increased fivefold. Catalase was also induced by other forms of oxidative stress, heat-shock, ethanol treatment, and stationary-phase conditions. Only one band of catalase activity was detected after native and denaturing PAGE. The enzyme was purified 304-fold with a yield of 7%. The purified enzyme displayed a heterodimeric structure with subunits of 75 and 68 kDa, corresponding to a molecular mass of approximately 150 kDa for the native enzyme. The subunits had almost identical amino-terminal peptide sequences, sharing substantial similarity with other bacterial catalases. The enzyme exhibited an apparent Km of 40 mM and a Vmax of 285,000 U (mg protein)-1. Spectroscopic analysis indicated the presence of protoheme IX. The heme content calculated from pyridine hemochrome spectra was 0.43 mol per mol of enzyme. The enzyme had a broad pH optimum and was inhibited by cyanide, azide, hydroxylamine, 2-mercaptoethanol, and sodium dithionite. These data indicate that this catalase belongs to the class of monofunctional catalases.

Amino Acid Sequence↗
PubMed2001

Comparison of inductively coupled plasma-atomic emission spectrometry, anodic stripping voltammetry and instrumental neutron-activation analysis for the determination of heavy metals in airborne particulate matter.

The capability of three analytical techniques, inductively coupled plasma-atomic emission spectrometry (ICP-AES), anodic stripping voltammetry (ASV), and instrumental neutron-activation analysis (INAA) have been compared for the determination of Cd, Fe, Pb, and Zn in airborne particulate matter, collected on cellulose filters, from the atmosphere of the large area of Thessaloniki, Greece. Two procedures were tested for quantitative leaching of these elements from the filters before ICP-AES and ASV, digestion with aqua regia in a Teflon autoclave, after dissolution of the organic matter with HClO4 under ambient conditions, and ultrasonic extraction with a mixture of HNO3 and HCl. Validation of the leaching and digestion procedures revealed that digestion in the autoclave is more effective, especially for Fe. The concentrations of these elements over a decade in both industrial and urban areas of the investigated region are compared.

Air Pollutants↗
PubMed2003

Compatibility of staining protocols for bone tissue with Raman imaging.

We report the use of Raman microscopy to image mouse calvaria stained with hematoxylin, eosin and toluidine blue. Raman imaging of stained specimens allows for direct correlation of histological and spectral information. A line-focus 785 nm laser imaging system with specialized near-infrared (NIR) microscope objectives and CCD detector were used to collect approximately 100 x 450 micro m Raman images. Principal components analysis, a multivariate analysis technique, was used to determine whether the histological stains cause spectral interference (band shifts or intensity changes) or result in thermal damage to the examined tissue. Image analysis revealed factors for tissue components and the embedding medium, glycol methacrylate, only. Thus, Raman imaging proved to be compatible with histological stains such as hematoxylin, eosin and toluidine blue.

Animals↗
PubMed2001

Controlled release of water-soluble polymeric complexes of sorbic acid with antifungal activities.

We synthesized six water-soluble polymeric complexes of sorbic acid with polyvinylpyrrolidone of different molecular weight (mol wt). As shown by infrared absorption spectrum analysis, the complexes were formed by hydrogen bonding. The complexes (SC1, with mol wt=10 kDa, SC2 with mol wt=25 kDa, SC3 with mol wt=30 kDa, SC4 with mol wt=40 kDa, SC5 with mol wt=90 kDa, and SC6 with mol wt=360 kDa) were characterized as low mol wt (SC1, SC2, and SC3) and high mol wt (SC4, SC5, and SC6). The antifungal potencies of the complexes were tested by the macrodilution susceptibility method against environmental and clinically important fungi. Sorbic acid as well as the complexes exhibited minimum inhibitory concentrations (MICs) lower than potassium sorbate against all the strains tested. MICs of SC1, SC2, and SC3 were shown to be 2- to 4-fold lower for yeast and 1.5- to 3-fold lower than those of sorbic acid for moulds, respectively. The MICs of SC4 and SC5 against both of the Candida species tested ranged from 500 to 800 microg/ml, whereas for SC6 and sorbic acid they were about 1 mg/ml. The potencies of the high mol wt complexes against moulds were decreased by increasing the mol wt. For both of the moulds tested, the MICs of SC4 were slightly lower than those of sorbate. The MICs of sorbic acid and SC5 were equal to 300 microg/ml and 500 microg/ml respectively for Aspergillus parasiticus and for Penicillum viridicatum. The susceptibility to SC6 of all of the hyphomycetes tested was higher than that to sorbic acid. The low mol wt complexes and the sorbic acid exhibited minimal fungicidal concentrations (MFCs) 2 and 3 times higher respectively than the MICs. Sorbic acid and SC3 at a concentration of 2.5 mg/ml in an in vitro time kill curve study of Candida tropicalis were shown to be fungistatic, whereas SC1 and SC2 were fungicidal at the same concentrations. For Aspergillus parasiticus sorbic acid at 2.5 mg/ml was fungistatic for a 24-h period, whereas SC1, SC2, and SC3 were fungicidal.

Antifungal Agents↗
PubMed2002

Characteristics of a bioflocculant produced by Bacillus mucilaginosus and its use in starch wastewater treatment.

A bioflocculant, MBFA9, was produced from a strain of bioflocculant-producing bacteria isolated from a soil sample and identified as Bacillus mucilaginosus. MBFA9 had a good flocculating capability and could achieve a flocculating rate of 99.6% for kaolin suspension at a dosage of only 0.1 ml/l. The major component of MBFA9 was found to be polysaccharide composed mainly of uronic acid (19.1%), neutral sugar (47.4%) and amino sugar (2.7%). Infrared spectrum analysis showed the presence of carboxyl and hydroxyl groups in the bioflocculant. MBFA9 is nontoxic and can be used in food industries for suspended solids (SS) recovery. When applied to starch wastewater treatment, MBFA9 greatly accelerated the formation of flocs and the settling of organic particles in the presence of Ca(2+) salt. After 5 min of settling, the removal rate of SS and chemical oxygen demand were up to 85.5% and 68.5%, respectively, which is better than traditional chemical flocculants.

Bacillus↗