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Biomedical subjects

A Kulik

Publications and source records attributed to A Kulik.

27 records · Page 2Linked to original sources
PubMed1996

Activation of P2-purino-, alpha 1-adreno and H1-histamine receptors triggers cytoplasmic calcium signalling in cerebellar Purkinje neurons.

The cytoplasmic calcium concentration ([Ca2+]i) was measured from Purkinje neurons in acutely prepared cerebellar slices. Neurons were loaded with calcium indicator Fura-2 by 40-min slice incubation in Tyrode solution containing 5 microM Fura-2/AM and 0.02% pluronic-F127. Bath applications of ATP (100 microM), epinephrine (10 microM) and histamine (100 microM) triggered a transient increase of [Ca2+]i in Purkinje neurons. ATP-induced [Ca2+]i elevation in Purkinje neurons was mimicked by ADP, but not AMP or adenosine pointing to the involvement of P2Y metabotropic purinoreceptors. Epinephrine-triggered [Ca2+]i responses were blocked by the selective alpha 1-antagonist prazosin and were mimicked by the alpha 1-adrenoreceptor agonist phenylephrine, and were not affected by beta- and alpha 2-adrenoreceptor agonists (isoproterenol and clonidine) and antagonists (propranolol and yohimbine). Histamine-induced [Ca2+]i responses demonstrated specific sensitivity to selective H1 antagonist chlorpheniramine, and were not sensitive to H2 and H3 histamine receptors modulators. The [Ca2+]i responses to all three agonists persisted in Ca(2+)-free extracellular media and were blocked by slice preincubation with thapsigargin (500 nM). We conclude that cerebellar Purkinje neurons are endowed with metabotropic P2 gamma purinoreceptors, alpha 1-adrenoreceptors and H1 histamine receptors which mediate the generation of intracellular [Ca2+]i signals via activation of Ca2+ release from inositol-1,4,5-trisphosphate-sensitive intracellular stores.

Adenosine Triphosphate↗
PubMed1996

Sub-population of capsaicin sensitive primary afferent neurons in thoracic, lumbar and sacral dorsal root ganglion in young rats revealed by stimulated cobalt uptake.

The number of dorsal root ganglion (DRG) neurons, the relative number of capsaicin sensitive DRG cells and the diameter distribution of these neurons were investigated in the thoracic 11, lumbar 5 and sacral 1 DRG ganglia in young rats. The capsaicin sensitivity of DRG cells was shown by the stimulated cobalt uptake technique in in vitro conditions. Cobalt labelled and non-labelled neurons were counted using the dissector method. Our results show that the total number of DRG cells in the Th11, L5 and S1 segments (4200-6500 per ganglion) were not significantly different from each other and about 8% of these cells were capsaicin sensitive in the segments studied. These findings also show that the capsaicin sensitive DRG cells belong to the small diameter DRG cell population. Control experiments on neonatally capsaicin injected animals indicate that the capsaicin stimulated cobalt uptake provides selective and specific staining of capsaicin sensitive DRG neurons.

Animals↗
PubMed1996

Connections of the torus semicircularis and oliva superior in the frog, Rana esculenta: a Phaseolus vulgaris leucoagglutinin labeling study.

The afferent and efferent connections of the frog principal nucleus (TP) of torus semicircularis (TOS) and superior olive (SO) were examined by employing the anterograde and retrograde transport patterns of Phaseolus vulgaris leucoagglutinin (PHA-L). After injecting the tracer into these nuclei it was found that the TP projected to the ipsilateral posterior and central thalamic nuclei, all subdivisions of the bilateral TDS and the ipsilateral nucleus isthmi (NI). In the rhombencephalon the projection was restricted mainly to the contralateral SO and the cochlear nucleus (CN). Retrogradely labeled cells were found in most of the areas that contained anterogradely labeled terminals. The termination areas of the SO fibers were similar to the projections of fibers of TP origin in the diencephalic and in the mesencephalic auditory centers. A strong projection was followed into the contralateral SO; the CNs received fibers at both sides. Caudally to the SO the reticular formation, the spinal nucleus of the trigeminal nerve, the solitary nucleus and the dorsal column nuclei were supplied by the fibers of the SO origin. Retrogradely labeled cells were found in the TOS, tegmental nuclei, solitary nucleus, dorsal column nuclei and in the spinal nucleus of the trigeminal nerve. Our results indicate that the frog auditory pathway is more complex at the level of the secondary and tertiary fiber projections than has been previously recognized.

Afferent Pathways↗
PubMed1994

Biosynthetic capacities of actinomycetes. 2. Juglomycin Z, a new naphthoquinone antibiotic from Streptomyces tendae.

A new juglomycin-type antibiotic was identified by a HPLC-diode array screening technique in the culture filtrate of Streptomyces tendae Tü 901/8c. Juglomycin Z (1) differs from all other known juglomycin compounds by an additional methyl group in position 3 of the naphthoquinone ring system. Juglomycin Z is antibiotically active against Gram-positive and Gram-negative bacteria and against yeasts.

Anti-Bacterial Agents↗
PubMed1994

Mesencephalic projections of the cochlear nucleus in the frog, Rana esculenta.

The lectin Phaseolus vulgaris leucoagglutinin was injected into chochlear nucleus in order to study the trajectory and projections of the auditory pathway in the frog. A strong contralateral and a weak ipsilateral fiber bundle representing the lemniscus lateralis could be followed to the torus semicircularis. The following areas of termination could be discerned in the mesencephalon: (1) Each of the five subnuclei of the torus semicircularis received fibers from the cochlear nucleus, the largest number of fibers terminated in the principal nucleus. (2) Nuclei of the mesencephalic tegmentum were supplied by fibers from the cochlear nucleus on both sides. (3) The nucleus isthmi was innervated by a few small caliber fibers, and (4) the nucleus visceralis secundarius was richly supplied by large caliber fibers. Two ill-defined neuron groups in the mesencephalic tegmentum, the nucleus reticularis isthmi (5) and (6) the nucleus profundus mesencaphali were conspicuously outlined by the terminals of auditory fibers. Their positions suggested homology to the mammalian nucleus of the lemniscus lateralis. (7) A few fibers and boutons were labelled in the fifth and sixth layers of the optic tectum. Retrogradely labelled cells were found in the nucleus laminaris of the torus semicircularis and in the nuclei of mesencephalic tegmentum. Our results indicate that the frog auditory pathway is more complex at the level of the secondary fiber projections than has been previously recognized. The retrogradely labelled neurons suggest a descending control of the cochlear nucleus from higher structures of the auditory pathway.

Affinity Labels↗
PubMed1989

Measurement of sympathetic nerve activity in the unanesthetized rat.

A new system was developed in our laboratory to continuously monitor intra-arterial pressure, heart rate, and sympathetic nerve activity in unanesthetized rats. The animals were prepared 24 h before the start of the experiments. Sympathoneural traffic was measured at the level of splanchnic nerve. The amplitude of the spikes recorded at this level was utilized to express sympathetic nerve activity. The amplitude of the residual electroneurogram signal present 30 min after the rats were killed was 32 +/- 2 mV (mean +/- SE; n = 11). For analysis, these background values were subtracted from values determined in vivo. The nerve we studied contains postganglionic fibers, since electrical activity decreased in response to ganglionic blockade with pentolinium (1.25 mg/min iv for 4 min). The amplitude of spikes fell by 43 +/- 4% (n = 4). Sympathetic nerve activity was highly reproducible at a 24-h interval (104 +/- 26 vs. 111 +/- 27 mV for the amplitude of spikes; n = 11). Dose-response curves to the alpha 1-stimulant methoxamine and to bradykinin were established in four rats. The increase in blood pressure induced by methoxamine caused a dose-dependent fall in sympathetic nerve activity, whereas the blood pressure reduction resulting from bradykinin was associated with a dose-dependent activation of sympathetic drive. These data therefore indicate that it is possible with out system to accurately measure sympathetic nerve activity in the awake rat, together with intra-arterial pressure and heart rate.

Animals↗