Biomedical subjects

P Molnár

Publications and source records attributed to P Molnár.

6 recordsLinked to original sources

PubMed1992

Effect of different subtypes of cognition enhancers on long-term potentiation in the rat dentate gyrus in vivo.

The effect of four drugs considered as cognition enhancers on the amplitude of the population spikes and on the long-term potentiation (LTP) evoked by perforant path stimulation was investigated in rat dentate gyrus in vivo. LTP was characterized by the absolute increase in the amplitude of the population spikes, which were expressed in mV, contrary to the widely used percentage value, because the absolute increase was independent of the pretetanus level, whereas the percentage increase was found to be negatively correlated with it. Intravenous administration of the drugs (piracetam 500 mg/kg, hydergine 2 mg/kg, vinpocetine 0.1 and 5 mg/kg and physostigmine 0.01 and 0.1 mg/kg) did not influence the amplitude of the population spikes itself. Piracetam and hydergine did not have an effect on LTP, while vinpocetine and physostigmine altered LTP in a similar manner. The higher doses of the two latter drugs, administered 5 min before tetanic stimulation, induced a significant potentiation of LTP, whereas a significant inhibition of LTP was obtained when the drugs were administered 30 min before tetanic stimulation. Based on the results obtained from guinea pig hippocampal slices, an LTP-potentiating effect of all compounds tested could have been anticipated, but this was not supported by our data. The apparent contradiction between the in vivo and in vitro results is discussed.

Animals↗

PubMed1992

Inhibition of hippocampal field potentials by GYKI 52466 in vitro and in vivo.

GYKI 52466 is a specific antagonist of the neuronal excitation mediated by the non-NMDA type excitatory amino acid receptors, at several sites in the central nervous system. The experiments presented here show that the drug has a dose-dependent, slowly developing, long-lasting and reversible inhibitory action on the field potentials recorded from the CA1 region of the rat hippocampus, in vitro. Its action is similar to that of the well-known non-NMDA receptor blocker, CNQX. When the stimulus intensity-dependence of the population spikes was investigated, both drugs shifted the input-output curves in a parallel manner, while the maximum responses were only slightly depressed at the doses applied. With i.v. application, GYKI 52466 also inhibited the hippocampal field potentials recorded from the CA1 region of anesthetized rats dose-dependently. The inhibition was relatively weak compared to the effect found in earlier studies in the spinal cord, by the same doses. Four mg/kg i.v., a doses which is able to block spinal reflexes completely, caused an only about 20% depression of the recorded responses in the hippocampal CA1 area.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1992

Chronic intestinal lymphocytic microphlebitis.

The authors report two cases of a peculiar microphlebitis of the intestines, similar to that described by Saraga and Costa quite recently [5]. The patients had undergone hemicolectomy because of evolving ileus caused by cecal polyps or lipohyperplasia, respectively. Pseudomembranous-ulcerative inflammation of the cecum and variously intense lymphocytic infiltrates of numerous small submucosal veins and venules of the intestines were found in both cases. Thrombosis occurred very rarely in the affected vessels, although sometimes it was found in deeper and larger veins. Arteries, lymphatics, mesenterial veins and lymph nodes were normal. Parts of the distal ileum and ascending colon displayed the phlebitic changes without mucosal alterations. The authors hypothesize that it was not the abnormal local circulation, but some hitherto not fully clarified immunological disorder that resulted in the disease. In contrast to the claim of Saraga and Costa [5], it is suggested that thrombosis of the small veins does not have a significant role in the development of the lesions, but a complex process that includes the entry of antigens via the altered mucosa followed by an immunogenic inflammatory response of the small veins is responsible for the pathogenesis.

Adult↗

PubMed1979

Auto-shaping or orienting?

Four experiments were carried out to study the development of the orienting response (OR) under different experimental conditions in the cat and rat. In Experiment I and II (cat) and Experiment IV (rat) classical CS-US pairing was used (with food, shock and water reinforcers, respectively). In Experiment III (cat) an instrumental pedal press response was brought under the control of a discriminative signal. In all four experiments the auditory CS was spatially discontiguous with reinforcement in order t o separate CS directed orienting responses from US related activities. Exposure to CS signalling food or water caused the animals to orient to it throughout conditioning (up to 700 trials) and this overt responding was absent if CS predicted aversive reinforcers. OR was consistently followed by goal (US) directed anticipatory activities. It is proposed that the CS directed auto-shaped response ("sign-tracking") is identical with the conditional orienting response, and that the spatio-temporal patterning of behaviors is influenced both by CS and US.

Animals↗

PubMedDate not supplied

[Changes in antiproteolytic activity in the blood and cervical mucus after superovulation stimulation].

The function of proteins, peptides, proteases and inhibitors of proteases in modulations of regulation mechanisms of gonadotrophins during the development of ovarian folicles has not been fully explained up to now. We can see difference reactions of ewes to superovulation stimulations in oestrous and anoestrous periods as shown by the variation of the antiproteolytic activity of blood plasma and cervical mucus. Trypsin is used as a model for serine protease, and trypsin inhibitory activity (TIA) was measured from the reduced rate of trypsin hydrolysis of the chromogenic substrate N-alpha-tosyl-L-arginine-4-nitroanilide (TAPA, Bartík et al., 1974). Full hydrolytic activity was determined as a change in absorbency at 405 nm = 1.0 after ten-minute incubation at 25 degrees C and pH = 8.1, and inhibition was expressed in percentage of full activity. Statistical analyses were performed by Student's t-test. Twenty-three ewes in anoestrus and twenty-eight ewes in oestrus were included in this experiment. They were of the Slovak Merino breed, two to three years old, with the mean live weight of thirty to forty kg. The ewes were treated with Ageline vaginal sponges (20 mg chlorsuperlutin/sponge) to provide for synchronization of ovarian activity, in the interval of eleven to twelve days. After removal of sponges, the ewes were stimulated for superovulation as shown in Tab. I. Heparinized blood plasma samples were stored at -25 degrees C. Low molecular TIA activities were determined in HClO4--treated blood plasma. Samples of cervical mucus were taken on cotton-wool tampons which were evaluated in 0.2 M Tris-HCl buffer, pH = 8.1. Figs. 1-6 shows TIA changes in blood plasma and cervical mucus on particular days. Fig. 7 shows the mean values of controls (I-initial) after synchronization (A) and after stimulation (S). TIA changes were different in anoestrous and oestrous periods. Differences in TIA changes in blood plasma and cervical mucus in oestrous period suggested certain local regulation mechanisms of synthesis and/or secretion of this activity in the cervix. Some values of TIA were maximum at the time of expected heat or ovulation and may be some of the factor(s) which influenced fertility of females after superovulation stimulations.

Animals↗

PubMedDate not supplied

[Antiproteolytic activity of blood and cervical mucus in sheep after hormonal ovarian stimulation and gamma ray irradiation (2.45 Gy) during anestrus].

The antiproteolytic activities of the blood plasma (BP) and cervical mucus (CM) determined as trypsin inhibiting activities (TIA) where trypsin served as a model serine protease, were variable after superovulatory stimulations of ewes and after their gamma irradiation (2.45 Gy). TIA's were determined from the reduction in the bovine trypsin hydrolysis of the low-molecular chromogenic substrate N-alpha-tosyl-L-arginyl-p-nitro anilide (TAPA) (Bartík et al., 1974). The inhibition was expressed in per cent when delta A405 = 1.0 for 10-minute incubation at 25 degrees C, pH = 8.05, 0.2 mol/l tris-HCl buffer, was taken as 100%. Student's t-test was used for the statistical evaluation. A hundred ewes of the Merino breed were applied Agelin vaginal tampons (20 mg chlor-superlutin per head) on day 1 for 10 days in the anoestric period (May). A part of these ewes were subjected to whole-body gamma irradiation on days 6 to 11. When the irradiation was completed and the tampons were taken out, the ewes (three to four years old lambing ewes, yearling ewes) were stimulated to superovulations by an administration of 1500 IU serum gonadotropin (SG) or 450 IU follicle stimulating hormone (FSH). These parameters were followed in the subsequent 5-6 days: BP TIA (Figs. 1 and 4), fraction of low-molecular BP (n) TIA (Figs. 2 and 5), CM TIA (Figs. 3 and 6). Fig. 7 shows the average values of the results. The lambing ewes and yearling ewes had various responses to irradiation and superovulatory stimulation. Gamma irradiation eliminated the increase in BP TIA (P < 0.001) in the ewes after stimulations (Fig. 1a, b). The yearling ewes showed nonsignificant changes (ns) as their responses to SG stimulations and gamma irradiation, but the responses on the particular days of the trial were different (Fig. 1c, d--FSH stimulation). Similar changes were observed in the BP nTIA fraction. The changes in the average values of CM TIA were nonsignificant in the lambing ewes, the gamma irradiation reduced CM TIA only after FSH stimulation (P < 0.002). The amount of cervical mucus decreased after stimulations and irradiation, the thickness of ovarian epithelium and muscles was reduced in the particular parts, differently in lambing ewes and in yearling ewes.(ABSTRACT TRUNCATED AT 400 WORDS)

Anestrus↗