Biomedical subjects

T Farkas

Publications and source records attributed to T Farkas.

At least 73 records · Page 4Linked to original sources

PubMed1994

Neonatal enucleation induces cross-modal changes in the barrel cortex of rat. A behavioural and electrophysiological study.

The present study was undertaken to determine whether neonatal enucleation leads to functional changes in the somato-sensory system and whether it has any behavioural effects. Binocular enucleation was performed on newborn rats. The effects of enucleation were tested versus controls in a rectangular maze on 10 successive days starting on postnatal day 80. Immediately after the 10-day behavioural study session, electro-physiological experiments were performed on 5 enucleated and 5 control rats. All the whiskers of the remaining animals were clipped off on both sides, and these animals continued the maze running for four additional sessions. The behavioural study demonstrated that the maze performance achieved by the neonatally enucleated animals was better than that of the controls. This suggested that cross-modal compensatory changes took place in other sensory systems, presumably somatosensory too. This was supported by the result of the experiment preceded by bilateral vibrissa clipping. The electrophysiological experiments clearly revealed that functional changes took place in the somatosensory system of enucleated rats. In these animals, the cells in some barrels (C1 and E3) displayed enlarged receptive fields, while in an other barrel (A3) an increased angular sensitivity for deflection of its related whisker was observed. This combined study clearly demonstrates that neonatal enucleation is able to induce cross-modal compensatory changes in the somatosensory system of the rat.

Animals↗

PubMed1994

Platelet membrane fluidity and plasma malondialdehyde levels in Alzheimer's demented patients with and without family history of dementia.

Platelet membrane fluidity (PMF) was measured with three different fluorescent probes, 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), 3-(p-phenyl-1,3,5-hexatrienyl)phenyl-propionic acid (DPH-PA), which labeled different parts of the bilayer (the hydrophobic core and the positively and negatively charged regions, respectively) in Alzheimer's disease (AD) patients with and without a family history of dementia, and in a control group. In support of earlier findings in the literature, significantly increased PMF was found by the application of DPH in both groups with AD. The use of the fluorescence probe TMA-DPH, however, revealed no differences between the groups. In contrast, significant rigidification was observed with DPH-PA, but only in the AD group with a positive family history of dementia. The plasma malondialdehyde levels appeared to be similar in each group. Our findings are discussed in light of the controversies regarding the value of PMF measurements in AD.

Aged↗

PubMed1994

Secretion of phospholipase A2 induced by interactions of human platelets with monocytes.

Phospholipase A2 (PLA2) activity was found and measured in the cell-free supernatants of human mononuclear cells (monocytes and lymphocytes) cultured with platelets for 48 h at 37 degrees C. The relative molecular mass of purified, calcium-dependent PLA2 was 14 kD. The amount of PLA2 in the supernatants correlated positively with the number of monocytes and platelets in the cultures. Electron microscopically, direct cell-to-cell interactions of monocytes and platelets were observed. Cultivation of suspensions of human mononuclear cells with platelets in serum-free medium was found to be an efficient way to produce and purify human secretable PLA2. In the release of secretable PLA2 in peripheral blood, the interactions between platelets and monocytes may play a considerable role.

Blood Platelets↗

PubMed1994

Role of phospholipid molecular species in maintaining lipid membrane structure in response to temperature.

The compositions and physical states of the liver phospholipids of fish and phospholipids of shrimps adapted to relatively constant but radically different temperatures were investigated. There were no measurable differences in their gross fatty acid compositions of phospholipids from the species obtained from identical temperature. Saturated-to-unsaturated fatty acid ratio did not show any convincing difference. Docosahexaenoic acid (22:6) did not seem to participate in the process of adaptation. Cold adaptation was coincidental with oleic acid (18:1) accumulation, preferentially in the phosphatidylethanolamine. In the experiment with rats, it has been found that the fish oil fed rats showed a similarity in their liver phospholipid fatty acid composition like fish liver phospholipids. Determination of molecular species composition of phosphatidylcholine and phosphatidylethanolamine revealed a 4- to 5-fold and 10-fold increase in the level of 18:1/22:6 and 18:1/20:5 species respectively in favor of cold adaptation. Phospholipids from cold-adapted species showed a more fluid structure than that of warm-adapted species near the C-2 segment of the bilayer, but not in the deeper regions. Phospholipids from the rat livers did not show any change irrespective of diet. Phosphatidylcholines from rat liver, fish liver or shrimps did not show any difference among them in their fluidity irrespective of their environmental conditions or diet. An appropriate combination (75:25) of phosphatidylcholine from rat liver with phosphatidylethanolamines from cold adapted species showed a drastic fluidization at the C-2 segment, in comparison with their phosphatidylcholines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Increased proportion of docosahexanoic acid and high lipid peroxidation capacity in erythrocytes of stroke patients.

BACKGROUND AND PURPOSE: Intracellular accumulation of lipid peroxides that derive from the autoxidation of membrane polyunsaturated fatty acids reduces the deformability of erythrocytes contributing to the hemorheological disturbances observed in acute cerebral ischemia. The present study deals with the biochemical background of increased lipid peroxidation capacity in the erythrocytes of stroke patients. METHODS: A complete clinical and laboratory assessment was made of 24 men and 18 women (aged 50 to 78 years; 64.5 +/- 13.9 years, mean +/- SD) who had an ischemic hemispheric lesion of the brain. Lipid peroxide content, lipid peroxidation capacity, superoxide dismutase activity, and fatty acid composition of erythrocytes were compared in stroke patients and 22 healthy subjects matched for age. The lipid peroxide content of the erythrocytes was estimated before and after the autoxidative test; the results were expressed as nanomoles of malondialdehyde per gram of hemoglobin. The increase of the lipid peroxide content in the erythrocytes during the autoxidative test measures the lipid peroxidation capacity. RESULTS: In comparison with healthy subjects (1.45 +/- 0.30 nmol MDA/g Hb per 24 hours), the lipid peroxidation capacity was found to be significantly higher (4.18 +/- 0.41 nmol MDA/g Hb per 24 hours) (P < .01) in the erythrocytes of stroke patients. The stroke patients could be divided into two groups on the basis of lipid peroxidation capacity of their erythrocytes. Twenty patients had erythrocytes with high lipid peroxidation (< 4 nmol MDA/g Hb per 24 hours), and 22 patients had very high lipid peroxidation capacity (> 4 nmol MDA/g Hb per 24 hours). There was no significant difference in superoxide dismutase activity in the erythrocytes of patients compared with healthy subjects. Before the autoxidative test was conducted, the fatty acid composition in the erythrocytes of stroke patients with very high lipid peroxidation capacity was measured and found to be generally normal; only the proportion of docosahexanoic acid (22:6 n-3) was markedly (P < .01) increased. CONCLUSIONS: The results suggest that the erythrocytes of ischemic stroke patients with very high lipid peroxidation capacity displaying an abnormal fatty acid composition are much more vulnerable to lipid peroxidation. The increased proportion of docosahexanoic acid and the high lipid peroxidation capacity of erythrocytes play a pathogenetic role and explain the hemorheological disturbances observed in the microcirculation of stroke patients.

Aged↗

PubMed1994

Ethanol-induced signal transducing mechanism associated with a transient antiviral state in human amniotic cells.

Short-term effects of ethanol on human amnion cells were investigated by studying the cellular signaling processes and the replication of vesicular stomatitis virus. Treatment of human amniotic cells with ethanol transiently triggers the breakdown of inositol phospholipids, stimulates intracellular [Ca2+]i mobilization and activates the translocation of protein kinase C. Activation of this signal transduction mechanism is associated with the development of an antiviral state, as proven by studying 3H-uridine incorporation into the RNA of vesicular stomatitis virus. Induction of the antiviral state in human amniotic cells correlates with the solubility of the alcohols in the lipid membrane of the cells.

Amnion↗

PubMed1993

Molecular and structural composition of phospholipid membranes in livers of marine and freshwater fish in relation to temperature.

The compositions and physical states of the liver phospholipids of marine and freshwater fish adapted to relatively constant but radically different temperatures were investigated. Fish adapted to low temperature (5-10 degrees C) accumulated more unsaturated fatty acids than those in a warm (25-27 degrees C) environment. There were no measurable differences in the gross fatty acid compositions of the total liver phospholipids from identical thermal environments. Docosahexaenoic acid (22:6) did not seem to participate in the process of adaptation. Cold adaptation was coincidental with oleic acid (18:1) accumulation, preferentially in the phosphatidylethanolamine. Determination of the molecular species composition of phosphatidylethanolamine revealed a 2- to 3-fold and 10-fold increase in the level of 18:1/22:6 and 18:1/20:5 species, respectively. ESR spectroscopy revealed a 7-10% compensation in the ordering state of native phospholipids with temperature. Combination of 16:0/22:6 phosphatidylcholine with phosphatidylethanolamines of cold-adapted marine fish showed a drastic fluidization near the C-2 segment of the bilayer, but not in the deeper regions. An appropriate combination (75:25) of phosphatidylcholines from warmth-adapted marine fish with phosphatidylethanolamines from cold-adapted marine fish mimicked a 100% adaptational efficacy in the C-2 segment as compared with the phosphatidylethanolamines of warmth-adapted marine fish. A specific role of 18:1/22:6 phosphatidylethanolamine in controlling membrane structure and physical state with thermal adaptation is proposed.

Acclimatization↗

PubMed1993

Compensation of a sensory deficit inflicted upon newborn and adult animals. A behavioural study.

Somatosensory deprivation (bilateral vibrissa clipping) was performed on newborn (P1) and adult (P80) rats and, on 10 successive days starting on day 81, the effect of sensory deprivation was tested in a rectangular maze versus controls. The maze performance (the time to reach the goal-box with food reward) of the P80 animals was significantly poorer than that of P1 animals. The tests repeatedly demonstrated, however, that the maze performance achieved by the P1 animals was better than that of the controls. This behavioural study clearly revealed that early sensory deprivation induced (probably cross-modal) compensatory changes in other sensory systems.

Aging↗

PubMed1992

Dietary manipulation with high marine fish oil intake of fatty acid composition and arachidonic acid metabolism in rat cerebral microvessels.

Male weanling Wistar rats were maintained on one of two semisynthetic diets, differing only in the type of oil used: (i) 10% by weight marine fish oil (MFO group) containing 20% eicosapentaenoic acid (EPA) and 17% docosahexaenoic acid (DHA), or (ii) 10% by weight sunflower oil (SFO group). The control group was kept on standard diet for 4 weeks. Blood-free microvessels were isolated from brain cortex by a rapid micromethod, and their fatty acid composition was determined by gas chromatography. It was found that the proportion of n-3 fatty acids (including EPA and DHA) increased significantly in the microvessels of the MFO group, accompanied by a decrease of the n-6 fatty acid series. The changes in fatty acid composition of endothelial cells were not significant in the SFO group in comparison to the control. The amounts of lipoxygenase and cyclooxygenase metabolites were determined. Dietary fish oil decreased the percentage of total products of arachidonate by 50%, while the SFO diet had no effect on it. The amount of lipoxygenase products in the MFO group decreased significantly from 16931 +/- 3131 dpm to 6399 +/- 357 dpm/300 mg wet weight of brain. Significantly less PGF-1 alpha, PGF-2 alpha and 12-hydroxyheptadecatrienoic acid (HHT) were found in the capillaries of MFO treated animals, in comparison to the SFO group. The ratios of vasoconstrictor and vasodilator metabolites of arachidonate cascade were not modified by the diets. Our results suggest that fish oil diet reduces the arachidonate cascade in cerebral microvessels. This effect may explain for the efficiency of n-3 fatty acids in vascular diseases.

6-Ketoprostaglandin F1 alpha↗

PubMed1992

Isolation of chicken anaemia virus from broiler chickens.

Chicken anaemia virus (CAV) infection was demonstrated, by both serology and virus isolation, in 1- to 6-week-old broiler chickens originated from various parent flocks in Hungary. Total losses in the broiler flocks were estimated at 7 to 8% and about 25% of the chickens failed to reach target body mass by the 7th week of life. The clinical signs, postmortem lesions and histopathological changes of the affected chickens were similar to those of naturally occurring CAV-induced infectious anaemia of young chickens. In MDCC-MSB1 cell cultures, a chloroform-resistant virus smaller than 50 nm in diameter, resistant to heating at 70 degrees C for 30 min, and antigenically very closely related to the Cux-1 strain of CAV was isolated from the liver of naturally diseased broilers. This virus isolate was designated the Bia strain of CAV. Inoculation of susceptible 1-day-old SPF chicks with a CAV-positive liver extract from naturally diseased broilers caused pathological changes characteristic of CAV infection, namely impaired growth, severe anaemia with atrophy of the bone marrow, marked atrophy of the lymphoid organs and petechial haemorrhages throughout the body. A quite similar pathological syndrome was also induced by inoculation of 1-day-old SPF chicks with the MDCC-MSB1 cell-culture-propagated new Bia strain of CAV. The CAV was successfully reisolated from the livers of experimentally inoculated birds, and antibodies to the reference Cux-1 strain of CAV were also demonstrated by the indirect immunofluorescence test in sera of naturally diseased and experimentally inoculated chickens. No antibodies were found against infectious bursal disease virus, reticuloendotheliosis virus, Marek's disease herpesvirus as well as avian adenoviruses and reoviruses. The reported disease of young broiler chickens was associated with natural infection of a new isolate of CAV. On the basis of its physicochemical, antigenic and pathogenic characteristics, this virus is similar to other strains of CAV isolated from chickens in other countries.

Anemia↗

PubMed1991

Modulation of the beta-adrenergic response in cultured rat heart cells. I. Beta-adrenergic supersensitivity is induced by lactate via a phospholipase A2 and 15-lipoxygenase involving pathway.

Incubation of rocker-cultured neonatal rat heart cells with 3 mM L(+)-lactate led to a sharp increase in the sensitivity of cardiomyocytes to the beta-adrenergic agonist isoprenaline, as measured by their chronotropic response. This effect was accompanied by a reduction in the arachidonic acid content of the total phospholipids. The phospholipase A2-activator melittin as well as free arachidonic acid induced this supersensitivity to the same degree. On the other hand, the L(+)-lactate-evoked supersensitivity could be blocked by the phospholipase A2 inhibitors mepacrine and n-bromophenacyl-bromide, suggesting an involvement of phospholipase A2 in the process of beta-adrenergic sensitization. The sensitizing action of arachidonic acid was blocked by the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid, but not by the cyclo-oxygenase inhibitor indomethacin. Supersensitivity was likewise evoked by 15-S-hydroxyeicosatetraenoic acid (15-S-HETE), but not by 5-S-HPETE or 5-S-HETE. These findings suggest that the phospholipase A2-15-lipoxygenase pathway plays a role in the induction of beta-adrenergic supersensitivity in the cultured cardiomyocytes and point to a new physiological role of the lipoxygenase product 15-S-HETE.

Acetophenones↗

PubMed1990

The fatty acid constitution and ordering state of membranes in dominant temperature-sensitive lethal mutation and wild-type Drosophila melanogaster larvae.

The ordering state and changes in fatty acid composition of microsomal (MS) and mitochondrial (MC) membranes of two dominant temperature-sensitive (DTS) lethal mutations and the wild-type Oregon-R strain larvae of Drosophila melanogaster have been studied at 18 and 29 degrees C and after temperature-shift experiments. The membranes of wild-type larvae have a stable ordering state, with "S" values between 0.6 (18 degrees C) and 0.5 (29 degrees C) in both membranes which remained unchanged in shift experiments, although the ratios of saturated/unsaturated fatty acids were changed as expected. The strongly DTS mutation 1(2) 10DTS forms very rigid membranes at the restrictive temperature (29 degrees C) which cannot be normalized after shift down, while shift up or development at the permissive temperature results in normal ordering state. This mutant is less able to adjust MS and MC fatty acid composition in response to the growth temperature than the wild type. The less temperature-sensitive 1(2)2DTS allele occupies an intermediate state between Oregon-R and 1(2)10DTS in both respects. We assume and the genetical data suggest that the DTS mutant gene product is in competition with the wild-type product, resulting in a membrane structure which is not able to accommodate to the restrictive temperature.

Alleles↗

PubMed1989

Phospholipase C and phospholipase A2 are involved in the antiviral activity of human interferon-alpha.

Treatment of human amniotic cells (UAC) with human interferon-alpha (Hu-IFN alpha) or phorbol myristate acetate (PMA) resulted in translocation of protein kinase C (PK-C) activity from the cytosol fraction to that of the membranes. Analysis of 32P incorporation into phospholipid fractions and studies of alterations in fatty acid content for the major phospholipids of IFN-treated cells suggest that phospholipases C and A2 are activated by Hu-IFN alpha. Addition of neomycin (an inhibitor of phospholipase C), as well as mepacrine (an inhibitor of phospholipase A2) to IFN-treated cells inhibited the antiviral activity of Hu-IFN alpha in the vesicular stomatitis virus (VSV)-UAC system used. These observations indicate that (i) activation of PK-C and (ii) diacylglycerol formation, arachidonic acid and/or lysophosphatidylcholine release are important steps in the mechanism of action of IFN.

Amnion↗

PubMed1989

Simultaneous presence of platelet activating factor, leukotriene B4, prostaglandin F1 alpha and F2 alpha in the supernatant of human neutrophils treated with phospholipase A2 of human monocytes.

The simultaneous presence of platelet-activating factor, leukotriene B4, prostaglandin F1 alpha and F2 alpha are detectable in the supernatant of human neutrophil granulocytes treated with phospholipase A2 of human monocytes. This enzyme is suspected to play an important role in the pathomechanism of inflammation.

Dinoprost↗

PubMed1989

Interferon (IFN)-like antiviral effect is induced by unspecific cross-linking of cell surface receptors.

Treatment of human amniotic cells (UAC) with Cytodex 1 (DEAE-dextran) results in the development of an antiviral state of the cells, as proven by studying (i) the cytopathic effect and (ii) [3H]uridine incorporation into the RNA of vesicular stomatitis virus (VSV) after VSV infection. The same treatment transiently triggers the breakdown of inositol phospholipids and activates the translocation of protein kinase C (PKC). On the basis of these data it can be suggested that cross-linking of cell surface receptors by a solid carrier bearing covalently bound positive charges may result in IFN-like effects.

Antiviral Agents↗

PubMed1989

Effect of sodium on [3H]ethylketocyclazocine binding to opioid receptors in frog brain membranes.

The specific binding of [3H]ethylketocyclazocine to frog brain membrane preparation was enhanced in the presence of sodium ions administered as NaCl, both at 0 degree C and at room temperature. The optimal NaCl concentration was 25 mM at 0 degree C and 50 mM at 24 degrees C. MgCl2 inhibited the [3H]ethylketocyclazocine binding. Two binding sites (high and low affinity) were established with [3H]ethylketocyclazocine as ligand by equilibrium binding studies. Addition of NaCl increased the Bmax of the low-affinity site more than that of the high-affinity site at both temperatures. Affinities were higher at 0 degree C than at 24 degrees C. The KD values were not significantly influenced by sodium ions. The dissimilarities between the rat and frog brain opioid receptors in [3H]ethylketocyclazocine binding are attributed to the different lipid composition of the two membranes.

Animals↗

PubMed1989

Manipulation of plasma membrane physical state affects desaturase activity in rat lymphocytes.

Thymocytes, obtained from young rats, were incubated in the presence of either diheptadecanoylphosphatidylcholine or dioleylphosphatidylcholine vesicles and desaturation of either [1-14C]stearic acid or [1-14C]linoleic acid was followed in the endoplasmic reticulum. Incubation with diheptadecanoylphosphatidylcholine resulted in an accumulation of heptadecanoic acid in the plasma membrane, but not in the endoplasmic reticulum and mitochondria, and an increase in membrane ordering as assessed by diphenylhexatriene fluorescence polarization. A shift to higher temperature of the phase separation in the plasma membrane was also observed. Both delta 9 and delta 6 desaturase activities were enhanced in these cells, with delta 6 responding more intensly. Accumulation of oleic acid in the plasma membrane could not be observed when the cells were incubated in the presence of dioleylphosphatidylcholine vesicles, but all the membranes separated, including the microsomes, became more fluid. This can be attributed to removal of cholesterol by the vesicles. Fluidization of plasma membrane and endoplasmic reticulum depressed the conversion of stearate to oleate and linoleate to gamma-linolenate. It is concluded that there is an exchange of information between the plasma membrane and the endoplasmic reticulum in order to maintain the proper fluidity relationships and that this occurs without transfer of lipids from the former to the latter.

Animals↗

PubMed1988

The use of fibrin adhesive in the repair of chondral and osteochondral injuries.

Fibrin adhesive proved to be useful in the reattachment of chondral and osteochondral fragments. Its use is based on sound biological principles. It offers a number of advantages over internal fixation; it causes no further damage to the cartilage, even small chondral fragments can be reattached and a second operation for the removal of metalwork is unnecessary. Its bonding strength provides only contact stability, so that immobilization in plaster for 3 weeks is always necessary. In the last 5 years we have used fibrin adhesive in 28 patients for the fixation of 39 chondral or osteochondral fragments. Of these, 26 cases were followed up for periods of 6 months to 5 years. Twelve patients were examined arthroscopically; 9 of them showed complete healing of the fragments, and only 3 slight localized degenerative changes. In 15 cases we were able to see radiological healing. All except two showed union of the fragments and restoration of the joint surface. In view of our results fibrin adhesive can be recommended for the operative management of cartilage injuries.

Adolescent↗