Search PubMed⌕ Search

Biomedical subjects

I Szabo

Publications and source records attributed to I Szabo.

At least 55 records · Page 3Linked to original sources
PubMed1993

Morphine treatment in vitro or in vivo decreases phagocytic functions of murine macrophages.

Studies were performed to compare in vitro and in vivo effects of morphine on the phagocytic function of murine peritoneal macrophages. Macrophage monolayers were incubated with Candida albicans for 30 min in the absence of autologous serum. Morphine added in vitro was found to decrease both the phagocytic activity (percent of phagocytic cells) and the phagocytic index (average number of ingested yeasts per cell) in a concentration-dependent manner, with maximal effects of 26% and 41%, respectively, at 10(-6) M. When morphine was administered in vivo via an implanted 75-mg pellet, there was a 22% decrease in phagocytic activity and a 40% decrease in the phagocytic index. Naltrexone completely blocked the effects of morphine both in vitro and in vivo. The results suggest that morphine is capable of interacting directly with opioid receptors on macrophages, resulting in a decrease in phagocytic function.

Animals↗
PubMed1993

A low-noise preamplifier for multisite recording of brain multi-unit activity in freely moving animals.

A novel FET instrumentation amplifier is described which, as compared to most traditional operational FET preamplifiers, is characterized by an about 7-10 times lower intrinsic electronic noise and a higher common mode rejection. This allows discrimination of single units from multi-unit recording, even if the action potential amplitudes are as small as 20-30 microV and the units are located more than 100 microns away from the electrode tips. Such a distant and chronic recording may be expected to reduce the possibility of mechanical interference with functions of neuronal membrane and its immediate environment, and may be suitable for studying changes in functional connectivities among neurons during the animal's behavior and learning.

Action Potentials↗
PubMed1993

Suppression of peritoneal macrophage phagocytosis of Candida albicans by opioids.

Receptor-selective opioid agonists have been found to suppress the capacity of macrophages to ingest opsonized sheep erythrocytes. In an effort to characterize the immunomodulatory activity of opioids further, experiments were done to examine the uptake of Candida albicans by opioid-treated murine peritoneal macrophages. It was found that treatment with morphine and selective mu, i.e., DAMGO, delta, i.e., DPDPE, and kappa, i.e., trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]benzene-acetamide methanesulfonate, receptor agonists resulted a concentration-dependent suppression of both the percentage of phagocytic cells and the average number of ingested yeasts. Antagonists selective for mu, i.e., H-D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2, delta, i.e., naltrindole, and kappa, i.e., norbinaltorphimine, opioid receptors completely blocked the respective receptor-selective agonist-induced suppression. These results suggest that the mu, delta and kappa opioid receptors can modulate macrophage function.

Amino Acid Sequence↗
PubMed1992

Gadolinium ion inhibits loss of metabolites induced by osmotic shock and large stretch-activated channels in bacteria.

Bacteria subjected to a hypotonic osmotic shock lose internal ions and also metabolites, without lysis of the cells. We show that the presence in the shock medium, at submillimolar concentrations, of the ion gadolinium, recently shown to block stretch-activated channels in Xenopus oocytes [Yang, X.-C. & Sachs, F. (1989) Science 243, 1068-1071], was sufficient to inhibit shock-induced release of metabolites such as lactose and ATP in Escherichia coli and ATP in Streptococcus faecalis. Moreover, gadolinium was observed, in patch-clamp experiments, to inhibit the giant stretch-activated channels of E. coli, S. faecalis. and Bacillus subtilis. Taken together, these data suggest that stretch-activated channels are localized in the cytoplasmic membrane of Gram-negative and Gram-positive bacteria, where they control the efflux of osmotic solutes, thus probably playing a major role in the response to hypotonic osmotic shock.

Adenosine Triphosphate↗
PubMed1992

Determination of concentrations of adenosine and other purines in human term placenta by reversed-phase high-performance liquid chromatography with photodiode-array detection: evidence for pathways of purine metabolism in the placenta.

A robust analytical method, using reversed-phase high-performance liquid chromatography with gradient elution and photodiode-array detection, was used to measure six purines and beta-NAD+ in acid-soluble extracts of samples taken from six different regions of human term placenta. Resolution of the analyte peaks in chromatographic profiles of the extracts, and the use of optimized integration, allowed simultaneous quantitation of all seven analytes from a single chromatogram. Peak purity was confirmed via on-line analysis of peak spectra, utilizing the purity parameter treatment of spectral data. Major placental purines were adenosine, inosine, hypoxanthine and adenine. Except for adenine, concentrations of the purines varied by two-fold or more between different regions of each placenta, but concentration ratios, i.e., adenosine/inosine and inosine/hypoxanthine, were similar. The findings indicate that the pathway of ATP breakdown to hypoxanthine in ischemic human term placenta is via adenosine, and that regional differences in placental concentrations of adenosine and its metabolites may result from regional differences in degree of ischemia.

Adenosine↗
PubMed1990

Measurement of hypoxanthine and xanthine in late-gestation human amniotic fluid by reversed-phase high-performance liquid chromatography with photodiode-array detection.

A robust analytical method was developed for measurement of hypoxanthine and xanthine in late-gestation human amniotic fluid by reversed-phase high-performance liquid chromatography using diodearray detection. Purity of analyte peaks was confirmed via on-line analysis of peak spectra utilizing the purity parameter treatment of spectral data. Amniotic fluid obtained by amniocentesis was deproteinized by centrifugal ultrafiltration and chromatographed on an octadecylsilica column using isocratic elution with 1% (v/v) acetonitrile in 0.05 M ammonium dihydrogenphosphate pH 6.0; hypoxanthine and xanthine were resolved, but the hypoxanthine peak was not pure. Chromatography on a column of polar endcapped octadecylsilica, using similar mobile phase conditions, yielded spectrally pure peaks of hypoxanthine xanthine. Hypoxanthine and xanthine levels in amniotic fluid from fourteen patients, gestational age 34-39 weeks, ranged from 0.56 to 2.74 microM and 1.62 to 5.52 microM, respectively.

Amniocentesis↗
PubMed1990

Cooperative mechanosensitive ion channels in Escherichia coli.

A patch-clamp investigation was carried out on giant Escherichia coli spheroplasts. The membrane exhibited stretch-induced as well as "spontaneous" activity, with similar characteristics, i.e., a large number of conductance values arising from the cooperative behavior of channels in functional clusters. It appears likely that the same molecular species are responsible for both stretch-induced and "spontaneous" current conduction; the channel multiplexes can either respond to membrane stretch or function in an activate state, presumably brought about by the previous application of the mechanical stimulus.

Cell Membrane↗
PubMed1990

Stretch-activated composite ion channels in Bacillus subtilis.

The presence of ion-conducting pores in the membrane of Bacillus subtilis giant protoplasts was discovered using the patch-clamp technique. Membrane stretch caused the activation of several conductances with values in the nS range. The observations indicate the presence of substate levels and of aggregates of channels behaving in a cooperative manner. Following repeated stretch cycles, the channels exhibited spontaneous activity. The characteristics of the electrical phenomena afterwards changed in time in a manner suggesting the decay of the giant channels into lower-conductance species, presumably corresponding to building blocks of the giant stretch-activated channels.

Bacillus subtilis↗
PubMed1989

Active-site and membrane topology of the DD-peptidase/penicillin-binding protein no. 6 of Enterococcus hirae (Streptococcus faecium) A.T.C.C. 9790.

The membrane-bound 43,000-Mr penicillin-binding protein no. 6 (PBP6) of Enterococcus hirae consists of a 30,000-Mr DD-peptidase/penicillin-binding domain and a approximately 130-residue C-terminal appendage. Removal of this appendage by trypsin proteolysis has no marked effect on the catalytic activity and penicillin-binding capacity of the PBP. Anchorage of the PBP in the membrane appears to be mediated by a short 15-20-residue stretch at the C-terminal end of the appendage. The sequence of the 50-residue N-terminal region of the PBP shows high degree of homology with the sequences of the corresponding regions of the PBPs5 of Escherichia coli and Bacillus subtilis. On this basis the active-site serine residue occurs at position 35 in the enterococcal PBP.

Amino Acid Sequence↗
PubMed1985

Loss of attachment adjacent to class II carious lesions.

The present study was designed to investigate the relationship between large open class II carious lesions and loss of periodontal attachment in 224 extracted teeth. Each tooth had a carious and a sound approximal surface. The teeth were divided into 4 groups: upper premolars, upper molars, lower premolars and lower molars each consisting of 56 teeth. Within each group, the carious lesions were divided equally between the mesial and distal surfaces. The teeth were stained and loss of attachment was measured under a stereomicroscope fitted with an ocularmicrometer. The difference in loss of attachment between carious (0.79 +/- 0.05 mm) and sound (0.76 +/- 0.04 mm) surfaces was not statistically significant. Loss of attachment was greater on the carious surface of 98 teeth, equal to in 40 teeth and less in 86 teeth than the sound surface. Mesial and distal surfaces with and without carious lesions exhibited essentially the same degree of loss of periodontal support. Upper molars and lower premolars tended towards more loss of attachment when compared with upper premolars and lower molars. The results indicate that large open class II carious lesions cannot be regarded as an important factor in the progression of attachment loss.

Bicuspid↗
PubMed1984

Responses of striatal neurons in the behaving monkey. 3. Effects of iontophoretically applied dopamine on normal responsiveness.

In order to analyse the functions of dopamine, the effects of the iontophoretic application of dopamine on the responsiveness of striatal neurons to their normal inputs were investigated in the behaving monkey. It was shown that many neurons in the putamen had responses related to movements, of for example the mouth. Iontophoretically applied dopamine decreased the spontaneous firing rates of 178 of 267 neurons (67%) tested in the putamen, caudate nucleus, and the adjacent prefrontal cortex which also receives a dopaminergic projection. Trifluoperazine, applied iontophoretically to block dopamine receptors, increased the spontaneous firing rates of some of the neurons in the prefrontal cortex, suggesting that under normal conditions in the behaving animal the release of dopamine holds the firing rates of these neurons at a low level. The median was 9 spikes/s in the present sample of striatal neurons. Application of dopamine decreased the magnitude of the movement-related responses of the striatal neurons; this decrease in the responses was of approximately the same magnitude in spikes per second as the decrease in the spontaneous firing rate of the neurons produced by the same current of dopamine. It is suggested that this type of effect of dopamine could influence the signal to noise ratio of processing within the striatum, and that changes in this signal to noise ratio produced by disturbances of dopaminergic function could contribute to the behavioral disorders produced by dysfunctions of the dopaminergic systems.

Animals↗
PubMed1984

Influence of Class II amalgam fillings on attachment loss.

176 extracted teeth restored with Class II amalgam fillings, having identical distribution regarding tooth type, jaw and proximal surface localization, were investigated. The loss of attachment was measured on stained teeth under a stereomicroscope fitted with an ocular micrometer. The cervical margins of restorations were examined with a probe. Defective cervical margins were found in 85.8% of the 176 restorations. The mean loss of attachment on the restored surfaces (1.4 mm) was significantly higher (P less than 0.001) than on the sound unrestored surfaces of the same teeth (0.9 mm). Little difference was found between mesial and distal surfaces. The restored surfaces of the lower molars showed less loss of attachment, when compared to similar surfaces of upper molars and lower premolars (P less than 0.05).

Bicuspid↗