Search PubMed⌕ Search

Biomedical subjects

F Nagy

Publications and source records attributed to F Nagy.

At least 91 records · Page 5Linked to original sources
PubMed1995

Bladder augmentation with detubularized intestinal segment.

The authors report on 9 cases of bladder augmentation with detubularized intestinal segments. The capacity of the contracted bladder was increased in 4 cases; care was taken to prevent the development of an hour-glass bladder. In a young female patient a caecal-ileal segment was applied so that in case of a possible future pregnancy the mesentery should not hinder the growth of the uterus. In 4 cases hypertonic neurogenic bladders were augmented with intestinal segments, thus the further destruction of the kidneys could be avoided. In one case the reflux was hindered by a Kock valve, but stagnation developed above the valve, therefore it was eliminated and replaced by a 15 cm intestinal segment. In one case the uninhibited neurogenic bladder was augmented, the resistance of the urethra increased as a result of which the patient stayed dry between self-catheterizations. Attention is called upon the metabolic disturbances and increased risk of infection following intestinal implantations.

Cystectomy↗
PubMed1995

Characterization of membrane-bound small GTP-binding proteins from Nicotiana tabacum.

We have cloned nine cDNAs encoding small GTP-binding proteins from leaf cDNA libraries of tobacco (Nicotiana tabacum). These cDNAs encode distinct proteins (22-25 kD) that display different levels of identity with members of the mammalian Rab family: Nt-Rab6 with Rab6 (83%), Nt-Rab7a-c with Rab7 (63-70%), and Nt-Rab11a-e with Rab11 (53-69%). Functionally important regions of these proteins, including the "effector binding" domain, the C-terminal Cys residues for membrane attachment, and the four regions involved in GTP-binding and hydrolysis, are highly conserved. Northern and western blot analyses show that these genes are expressed, although at slightly different levels, in all plant tissues examined. We demonstrate that the plant Rab5, Rab6, and Rab11 proteins, similar to their mammalian and yeast counterparts, are tightly bound to membranes and that they exhibit different solubilization characteristics. Furthermore, we show that the yeast GTPase-activating protein Gyp6, shown to be specifically required to control the GTP hydrolysis of the yeast Ypt6 protein, could interact with tobacco GTP-binding proteins. It increases in vitro the GTP hydrolysis rate of the wild-type Nt-Rab7 protein. In addition, it also increases, at different levels, the GTP hydrolysis rates of a Nt-Rab7m protein with a Rab6 effector domain and of two other chimaeric Nt-Rab6/Nt-Rab7 proteins. However, it does not interact with the wild-type Nt-Rab6 protein, which is most similar to the yeast Ypt6 protein.

Amino Acid Sequence↗
PubMed1994

A receptor with GABAC-like pharmacology in invertebrate neurones in culture.

We have characterized in crustacean neurones in culture a receptor for gamma-aminobutyric acid (GABA) which conforms to the pharmacological profile of the proposed type-C GABA receptor (GABAC) found in the vertebrate retina. It is associated with a chloride-selective ion channel and is blocked by picrotoxin. It is neither inhibited by bicuculline nor activated by baclofen, while diazepam and phenobarbital are without modulatory effect. Like the GABAC-like receptor of the vertebrate retina it is activated by the folded GABA analogue cis-4-aminocrotonic acid (CACA). Desensitization is moderate allowing for a more sustained action of GABA. Single channel recordings revealed a bicuculline-resistant GABA- and CACA-activated chloride channel with a conductance about eight times higher than that described for the bicuculline-resistant GABA receptor channel from the rat retina.

Animals↗
PubMed1994

Developmental, hormonal, and pathogenesis-related regulation of the tobacco class I beta-1,3-glucanase B promoter.

The class I beta-1,3-glucanases are antifungal vacuolar proteins implicated in plant defense that show developmental, hormonal, and pathogenesis-related regulation. The tobacco enzymes are encoded by a small gene family with members derived from ancestors related to the present-day species Nicotiana sylvestris and N. tomentosiformis. We studied the expression in transgenic tobacco plants of a chimeric beta-glucuronidase (GUS) reporter gene fused to 1.6 kb of upstream sequence of the tobacco class I beta-1,3-glucanase B (GLB) gene, which is of N. tomentosiformis origin. Expression of the GUS reporter gene and the accumulation of class I beta-1,3-glucanase and its mRNA showed very similar patterns of regulation. In young seedlings the reporter gene was expressed in the roots. In mature tobacco plants it was preferentially expressed in lower leaves and roots and was induced in leaves by ethylene treatment and by infection with tobacco mosaic virus (TMV). Furthermore, it was down-regulated in cultured leaf discs by combinations of the hormones auxin and cytokinin. Histological studies of GUS activity showed that the GLB promoter shows highly localized expression in roots of seedlings. It is also expressed in a ring of cells around necrotic lesions induced by TMV infection, but not in cells immediately adjacent to the lesions or in the lesions themselves. The results of deletion analyses suggest that multiple positive and negative elements in the GLB promoter regulate its activity. The region from -1452 to -1193 containing two copies of the heptanucleotide AGCCGCC, which is highly conserved in plant-stress and defense-related genes, is necessary for high level expression in leaves. Additional regions important for organ-specific and regulated expression were: -568 to -402 for ethylene induction of leaves; -402 to -211 for expression in lower leaves and cultured leaf discs and for TMV induction of leaves; and -211 to -60 for expression in roots.

Cytokinins↗
PubMed1994

Ribosome-deficient plastids affect transcription of light-induced nuclear genes: genetic evidence for a plastid-derived signal.

Transcription of ten nuclear genes was analysed in the albostrians mutant of barley (Hordeum vulgare L.). The lack of plastid ribosomes in white seedlings of this mutant results in a complex alteration of nuclear gene expression at the transcriptional level. We found a strong reduction in the accumulation of mRNAs transcribed from nuclear genes encoding chloroplast enzymes involved in the Calvin cycle, the chlorophyll a/b binding protein, and the cytosolic enzyme nitrate reductase. In contrast, the levels of transcripts of the genes encoding the cytosolic glycolytic enzymes glyceraldehyde phosphate dehydrogenase and phosphoglycerate kinase were slightly enhanced. Accumulation of chalcone synthase mRNA even reaches much higher levels in white than in green leaves. Ribosome-deficient plastids were combined by crossing with a nuclear genotype heterozygous for the albostrians allele. Analysis of transcript levels in F1 plants having the same nuclear genotype and differing only with respect to their content of normally developed chloroplasts versus undifferentiated mutant plastids, provided strong genetic evidence for the plastid being the origin of a signal (chain) involved in regulation of nuclear gene expression. Results of run-on transcription in isolated nuclei demonstrated that the plastid signal acts at the level of transcription; it does not interfere with gene regulation in general. Mechanisms triggering nuclear gene expression in response to light operate in white mutant leaves: the very low levels of mRNAs derived from nuclear genes encoding chloroplast proteins and the strongly enhanced level of chalcone synthase mRNA were both light inducible. Also the negative regulation of leaf thionein gene expression by light is observed in white albostrians seedlings.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Nucleus↗
PubMed1994

Phenotype of the fission yeast cell cycle regulatory mutant pim1-46 is suppressed by a tobacco cDNA encoding a small, Ran-like GTP-binding protein.

Mutations in which the onset of mitosis is uncoupled from the completion of DNA replication has recently been described. Characterization of these mutants led to the identification of Pim1/Spi1 in fission yeast and RCC1/Ran proteins in mammalian cells. Their Saccharomyces cerevisae homologues, the MTR1/CNR1 proteins, appear to be involved in controlling RNA metabolism and transport. Here the isolation and partial characterization of plant cDNA clones which encode proteins homologous to the mammalian/fission yeast/budding yeast Ran/Spi/CNR proteins are reported. Higher plants appear to contain more than one gene per haploid genome which codes for Ran proteins. These genes are expressed in different plant tissues, including root tips and stems, known to contain mitotically active cells. The tobacco Ran-like proteins, like their mammalian and yeast homologues, are soluble proteins which are found in the cytoplasm and in the nucleus. In addition, it has been shown that overexpression of the tobacco Nt-Ran-A1 cDNA suppressed the phenotype of the temperature-sensitive fission yeast pim1-46 mutant. These results suggest that the plant Ran genes can be functionally equivalent to the mammalian/fission yeast/budding yeast Ran/Spi/CNR genes and that they may play a role: (i) in maintaining a coordinated cell cycle; (ii) in controlling RNA metabolism and transport in higher plants; and/or (iii) in protein import into the nucleus.

Amino Acid Sequence↗
PubMed1994

Light-regulated modification and nuclear translocation of cytosolic G-box binding factors in parsley.

Functional cell-free systems may be excellent tools with which to investigate light-dependent signal transduction mechanisms in plants. By evacuolation of parsley protoplasts and subsequent silicon oil gradient centrifugation of lysed evacuolated protoplasts, we obtained a highly pure and concentrated plasma membrane-containing cytosol. Using GT- and G-box DNA elements, we were able to demonstrate a specific localization of a pool of G-box binding activity and factors (GBFs) but not one of GT-box binding activity in this cytosolic fraction. The DNA binding activity of the cytosolic GBFs is modulated in vivo as well as in vitro by light and phosphorylation/dephosphorylation activities. The regulation of cytosolic G-box binding activity by irradiation with continuous white light and phosphorylation correlates with a light-modulated transport of GBFs to the nucleus. This was shown by a GBF-antibody cotranslocation assay in permeabilized, cell-free evacuolated parsley protoplasts. We propose that a light-regulated subcellular displacement of cytosolic GBFs to the nucleus may be an important step in the signal transduction pathway coupling photoreception to light-dependent gene expression.

Base Sequence↗
PubMed1994

A rhythmic modulatory gating system in the stomatogastric nervous system of Homarus gammarus. I. Pyloric-related neurons in the commissural ganglia.

1. Operation of the pyloric neural network in the crustacean stomatogastric ganglion (STG) depends on constant firing of modulatory inputs from anterior ganglia. We have identified two bilaterally symmetrical pairs of these inputs in the commissural ganglia (COGs) of the European rock lobster Homarus gammarus. During operation of the pyloric CPG, they fired in pyloric time, out of phase with the pyloric pacemakers. 2. One of the pair was the commissural pyloric (CP) neuron and the other was homologous to the P neuron described in the spiny lobster Panulirus interruptus. We describe their morphology and location in the COG. The CP neuron projected to the STG via the superior esophageal nerve (son) and the stomatogastric nerve (stn), whereas the P neuron projected via the inferior esophageal nerve (ion) and stn. 3. To determine the total number of commissural neurons projecting to the STG, we used cobalt and Lucifer yellow backfilling from their cut axons in the stn. With the ion cut, there were between 8 to 12 labeled somata in each COG including CP cell body, whereas only 2 somata (including P) were labeled with the son cut. Among these neurons, CP and P appeared to be the only commissural neurons that fired in pyloric time and projected in the STG on the pyloric network. 4. The CP neuron produced monosynaptic excitatory postsynaptic potentials (EPSPs) on the pyloric dilator (PD), lateral pyloric (LP), and inferior cardiac (IC) neurons, whereas the P neuron produced monosynaptic EPSPs on all pyloric motoneurons but IC. The P neuron was gamma-aminobutyric acid immunoreactive, and the P-derived EPSPs in pyloric neurons were reversibly blocked by bicuculline, picrotoxin, and D-tubocurarine. 5. The CP and P neurons were electrically coupled, and modification of membrane potential in either one of them appreciably changed the firing frequency of the coupled neuron. 6. A negative-feedback loop from the pyloric anterior burster (AB) interneuron provoked simultaneous rhythmic inhibitions in the P and CP neurons. Together with the electrical coupling, the rhythmic inhibition contributed to synchronize firing of the two commissural neurons. 7. The following papers in the series of describe the modulatory and rhythmic control exerted by the P and CP neurons over the pyloric pattern generator.

Animals↗
PubMed1994

A rhythmic modulatory gating system in the stomatogastric nervous system of Homarus gammarus. II. Modulatory control of the pyloric CPG.

1. In the European rock lobster, Homarus gammarus, two bilaterally symmetrical pairs of commissural neurons, P and commissural pyloric (CP), evoke excitatory postsynaptic potentials in the neurons of the pyloric motor network. The present paper shows that the two commissural neurons also exert a modulatory control over the pyloric network. 2. The P and CP neurons were active during ongoing pyloric rhythms. Ongoing pyloric activity was terminated when the neurons were hyperpolarized to inhibit their firing. 3. When the pyloric network was quiescent, depolarizing either the P or CP neuron induced a robust pyloric rhythm. 4. We studied the actions of the P and CP neurons on individual pyloric neurons isolated in situ from network interactions by a photoinactivation techniques. The P neuron induced oscillatory properties in the pacemaker pyloric dilator (PD) neurons and the motor neuron, ventricular dilator (VD), whereas the CP neuron induced rhythmogenic properties in all the network neurons but VD. Together, the P-CP neurons modulated the entire pyloric network. The modulatory effects of the P-CP neurons did not outlast the duration of their discharge. 5. The P and CP neurons also controlled the firing frequency of all the pyloric neurons. They may, in addition, control phasing of the constrictor neurons discharges, but this effect was state-dependent and occurred only when the pyloric central pattern generator was functioning weakly. Their role in providing flexibility to the network operation appeared relatively limited. 6. We conclude that the P and CP neurons are good candidates for insuring long-term maintenance of pyloric network activity patterns.

Animals↗
PubMed1994

A rhythmic modulatory gating system in the stomatogastric nervous system of Homarus gammarus. III. Rhythmic control of the pyloric CPG.

1. Two modulatory neurons, P and commissural pyloric (CP), known to be involved in the long-term maintenance of pyloric central pattern generator operation in the rock lobster Homarus gammarus, are members of the commissural pyloric oscillator (CPO), a higher-order oscillator influencing the pyloric network. 2. The CP neuron was endogenously oscillating in approximately 30% of the preparations in which its cell body was impaled. Rhythmic inhibitory feedback from the pyloric pacemaker anterior burster (AB) neuron stabilized the CP neuron's endogenous rhythm. 3. The organization of the CPO is described. Follower commissural neurons, the F cells, and the CP neuron receive a common excitatory postsynaptic potential from another commissural neuron, the large exciter (LE). When in oscillatory state, CP in turn excites the LE neuron. This positive feedback may maintain long episodes of CP oscillations. 4. The pyloric pacemaker neurons follow the CPO rhythm with variable coordination modes (i.e., 1:1, 1:2) and switch among these modes when their membrane potential is modified. The CPO inputs strongly constrain the pyloric period, which as a result may adopt only a few discrete values. This effect is based on mechanisms of entrainment between the CPO and the pyloric oscillator. 5. Pyloric constrictor neurons show differential sensitivity from the pyloric pacemaker neurons with respect to the CPO inputs. Consequently, their bursting period can be a shorter harmonic of the bursting period of the pyloric pacemakers neurons. 6. The CPO neurons seem to be the first example of modulatory gating neurons that also give timing cues to a rhythmic pattern generating network.

Animals↗
PubMed1994

BICUCULLINE/BACLOFEN-INSENSITIVE GABA RESPONSE IN CRUSTACEAN NEURONES IN CULTURE

Neurones were dissociated from thoracic ganglia of embryonic and adult lobsters and kept in primary culture. When gamma-aminobutyric acid (GABA) was applied by pressure ejection, depolarizing or hyperpolarizing responses were produced, depending on the membrane potential. They were accompanied by an increase in membrane conductance. When they were present, action potential firing was inhibited. The pharmacological profile and ionic mechanism of GABA-evoked current were investigated under voltage-clamp with the whole-cell patch-clamp technique. The reversal potential of GABA-evoked current depended on the intracellular and extracellular Cl- concentration but not on extracellular Na+ and K+. Blockade of Ca2+ channels by Mn2+ was also without effect. The GABA-evoked current was mimicked by application of the GABAA agonists muscimol and isoguvacine with an order of potency muscimol>GABA>isoguvacine. cis-4-aminocrotonic acid (CACA), a folded and conformationally restricted GABA analogue, supposed to be diagnostic for the vertebrate GABAC receptor, also induced a bicuculline-resistant chloride current, although with a potency about 10 times lower than that of GABA. The GABA-evoked current was largely blocked by picrotoxin, but was insensitive to the GABAA antagonists bicuculline, bicuculline methiodide and SR 95531 at concentrations of up to 100 µmol l-1. Diazepam and phenobarbital did not exert modulatory effects. The GABAB antagonist phaclophen did not affect the GABA-induced current, while the GABAB agonists baclophen and 3-aminopropylphosphonic acid (3-APA) never evoked any response. Our results suggest that lobster thoracic neurones in culture express a chloride-conducting GABA-receptor channel which conforms to neither the GABAA nor the GABAB types of vertebrates but shows a pharmacology close to that of the novel GABAC receptor described in the vertebrate retina.

Journal Article↗
PubMed1994

On the ultrastructure of the spermatozoa in the Siberian hamster (Phodopus sungorus campbelli).

Spermatozoa of the Siberian hamster were examined using transmission and scanning electron microscopy. The sperm are approximately 119 microns in length and exhibit a falciform head typical of murine rodents. A rod-like structure runs almost the entire length of the subacrosomal space within the subacrosomal cytoskeleton. Scrolls of redundant nuclear membrane are consistently asymmetric on concave and convex sides of the sperm head with the convex side presenting much more elaborate whorls. Mitochondria in the middle piece number approximately 133 pairs and present either one or two distinct cross-sectional profiles. Determining the number of mitochondrial pairs is presented as a means of distinguishing among the various species or subspecies of Phodopus. Viewed in longitudinal section, the annulus also presents two different configurations; one profile is cuneiform, the other semilunar. The axonemal complex is typical of most rodent sperm flagellae. Dense fibers 1, 5 and 6 are substantially larger and fiber 9 is somewhat larger in diameter than the rest.

Animals↗
PubMed1994

Muscarinic modulation of a pattern-generating network: control of neuronal properties.

The aim of this article is to investigate the cellular mechanisms underlying cholinergic modulation of the pyloric network in the stomatogastric ganglion (STG) of the Cape lobster Jasus Ialandii. Bath application of the muscarinic agonists muscarine, oxotremorine, and pilocarpine on the STG activates a rhythmic pattern from a quiescent pyloric network. The mechanisms of this modulation were investigated on individual pyloric neurons isolated both from synaptic interactions within the network (by photoinactivation of most of the presynaptic neurons and pharmacological blockade of the remaining synapses) and from central inputs (by a sucrose block of the input nerve). All three muscarinic agonists activated bursting and plateau properties of all the neurons comprising the pyloric network. The activation was dose dependent, and was blocked by the muscarinic antagonists atropine, pirenzepine, and scopolamine. The oscillatory behavior triggered by the muscarinic stimulation was specific to each type of pyloric neuron. The isolated neuron AB had the shortest oscillation period and depolarizing phase. The constrictor neurons (LP, PY, IC) were the slowest oscillators, and only oscillated upon hyperpolarizing current injection. Under muscarinic modulation, the individual bursting activities of the isolated pyloric neurons were of the same type as their activities when isolated from the network but modulated by central inputs (Bal et al., 1988). The VD neuron is an exception since it was a rapid oscillator in the latter situation and became a slow oscillator when modulated by a single muscarinic agonist. To determine the relative importance of the muscarinic-dependent bursting properties of the individual pyloric neurons in the operation of the intact network, a progressive reconstruction of the synaptic circuitry was attempted. We found that under certain conditions of muscarinic modulation a new composite pacemaker could be created, composed of the electrically coupled VD, AB, and PD neurons. This can result in the generation of new pyloric patterns that were very sensitive to the membrane potential of individual network neurons. The data also confirmed that, in a rhythmic "pattern-generating network," the pacemaker role may not be definitely attributed to a given neuron but instead could be assigned to other neurons by modulation of their respective oscillatory capabilities.

Animals↗
PubMed1993

[Autoimmune hemolytic anemia in ulcerative colitis].

Out of the 215 regularly controlled patients Coombs positive anaemia developed in two during the course of ulcerative colitis. Hemolysis was manifested clinically only in one of the two cases. Steroid therapy was effective in the first and combined with azathioprine in the second case. Their experiences with the simultaneous appearance of these diseases are being discussed on the bases of previous data.

Adult↗
PubMed1993

The circadian oscillator is regulated by a very low fluence response of phytochrome in wheat.

Expression of genes encoding the light-harvesting chlorophyll a/b binding proteins of photosystem II (Cab) in etiolated wheat seedlings is controlled by phytochrome and a circadian clock. Even photoconversion of <1% of phytochrome to its active form, which can be achieved by moonlight, induces the expression of the Cab genes, particularly that of the Cab-1 gene, in circadian fashion. Thus, this reaction shows the characteristics of a low and a very low fluence response. A single far-red light pulse given to an etiolated seedling is sufficient for a persistence of the circadian oscillation of the Cab-1 mRNA level for at least 100 h. Subsequent red (R) or long-wavelength far-red (RG9) light irradiations alter the free running rhythm. These observations indicate a change in sensitivity to phytochrome and/or a control by stable phytochrome. The latter hypothesis is supported by the observation that the level of Cab-1 mRNA is increased or decreased by a second R or RG9 light pulse, respectively.

Journal Article↗
PubMed1993

A 61 bp enhancer element of the tobacco beta-1,3-glucanase B gene interacts with one or more regulated nuclear proteins.

We show that a 61 bp fragment derived from the promoter region of the tobacco class I beta-1,3-glucanase GLB gene enhances transcription in Nicotiana plumbaginifolia protoplasts independent of orientation relative to the start of transcription. This fragment leads to a cooperative stimulation of transcription when combined with the cauliflower mosaic virus 35S as-1 enhancer element. The GLB enhancer contains two copies of the sequence AGCCGCC, which is conserved in several genes showing expression patterns similar to the GLB gene, as well as a sequence identical at 6 of 7 bp. Point mutations in these three sequences eliminate the enhancer activity of the 61 bp fragment. Nuclear extracts prepared from leaves of tobacco plants contain one or more putative transcription factors that interact specifically with the GLB enhancer. This factor was much less abundant in nuclear extracts prepared from upper leaves of untreated tobacco plants than in nuclear extracts prepared from upper leaves of ethylene-treated plants or from lower leaves. Since beta-1,3-glucanase genes are expressed at very low levels in upper leaves of tobacco plants, at higher levels in lower leaves, and are induced in all leaves after treatment of plants with the stress hormone ethylene, we conclude that the enhancer element interacts with one or more transcription factors whose binding activity is correlated with gene expression in vivo.

Base Composition↗
PubMed1993

Technetium-99m hexamethylpropylene amine oxime labelled leucocyte scintigraphy in ulcerative colitis and Crohn's disease.

Technetium-99m hexamethylpropylene amine oxime labelled leucocyte scintigraphy (LS) was performed on 45 occasions in 30 patients with ulcerative colitis and on 53 occasions in 34 patients with Crohn's disease. Serial images were taken following re-injection of the labelled leucocytes. The segmental extent of the inflammation and the grade of the leucocyte uptake were calculated, and compared with the laboratory results and colonoscopy findings. The sensitivity and specificity of LS proved higher in ulcerative colitis (87% and 93%) than in Crohn's disease (53% and 89% in cases with large intestine involvement, and 82% and 100% in cases with small intestine involvement). The activity of the process determined by LS correlates with the alpha 2-globulin level (r = 0.47), fibrinogen level (r = 0.50), fS iron level (r = -0.57), sedimentation (r = 0.44), leucocyte count (r = 0.38), platelet count (r = 0.34) and Best index (r = 0.31) in ulcerative colitis, but not in Crohn's disease.

Adolescent↗