PubMed Health⌕ Search

Biomedical subjects

L Pawlowski

Publications and source records attributed to L Pawlowski.

14 recordsLinked to original sources
PubMed1999

An inverted repeat triggers cytosine methylation of identical sequences in Arabidopsis.

The Wassilewskija (WS) strain of Arabidopsis has four PAI genes at three sites: an inverted repeat at one locus plus singlet genes at two unlinked loci. These four genes are methylated over their regions of DNA identity. In contrast, the Columbia (Col) strain has three singlet PAI genes with no methylation. To test the hypothesis that the WS inverted repeat locus triggers methylation of unlinked identical sequences, we introduced this locus into the Col background by genetic crosses. The inverted repeat induced de novo methylation of all three unmethylated Col PAI genes, with methylation efficiency varying with the position of the target locus. These results, plus results with inverted repeat transgenes, show that methylation is communicated by a DNA/DNA pairing mechanism.

Arabidopsis↗
PubMed1985

Ro 11-2465 (cyan-imipramine), citalopram and their N-desmethyl metabolites: effects on the uptake of 5-hydroxytryptamine and noradrenaline in vivo and related pharmacological activities.

Ro 11-2465 (cianopramine, cyan-imipramine) and citalopram (CIT), putative antidepressant drugs, are very potent and selective 5-hydroxytryptamine (5-HT) uptake inhibitors in vitro. This study investigated the effects of these drugs and their desmethyl metabolites, Ro 12-5419 (desmethylcianopramine, cyan-desipramine) and desmethylcitalopram (DCIT), respectively, on the uptake of 5-HT and noradrenaline (NA) in vivo [protection against H 77/77 (4, alpha-dimethyl-metatyramine)-induced displacement of 5-HT and NA] and on related pharmacological activities. All the investigated drugs antagonized H 77/77-induced displacement of 5-HT in the rat brain, though the effects of the metabolites were considerably weaker than those of the parent compounds. The H 77/77-induced displacement of brain NA in rats and mice was antagonized only by Ro 12-5419 and Ro 11-2465. All the drugs potentiated the pressor response to 5-HT in pithed rats; however, Ro 12-5419 and particularly Ro 11-2465 could also block the response when used in higher doses (greater than or equal to 0.1 mg/kg). Only Ro 12-5419 and Ro 11-2465 were able to potentiate the pressor response to NA. Ro 12-5419 also potentiated thyrotropin releasing hormone (TRH) hyperthermia and antagonized reserpine hypothermia in mice; Ro 11-2465 potentiated the TRH hyperthermia only. CIT and DCIT were inactive in both these tests. Of all the four drugs only CIT and Ro 12-5419 considerably stimulated the hind limb flexor reflex in spinal rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Effect of harmine and brain lesions on apomorphine induced motor activity.

Application of harmine (10 mg/kg IP) 30 min before apomorphine decreased the motoric effects of the latter. Following harmine an increase in 5-HT and a decrease in 5-HIAA in different brain regions have been found. Injection of 5,6-DHT into nucleus medianus raphe 7 days before the experiment caused a significant increase of the apomorphine effect. Harmine pretreatment reduced this escessive motility as well as additional lesion of the substantia nigra with 6-OH-DA. Lesion induced by 6-OH-DA alone was without significant effect on the hypermotility following apomorphine. Application of PCPA 3 days before testing elicited an increase of apomorphine-induced hypermotolity which could be abolished by preceding harmine application. The experiments demonstrate the inhibitory effect of the central serotoninergic system on the apomorphine syndrome as well as the serotoninergic-dopaminergic interaction in hypermotility.

5,6-Dihydroxytryptamine↗
PubMedDate not supplied

The influence of serotonergic agents on the body temperature.

The effects of serotonin precursors, tryptophan (TP) and L-5-hydroxytryptophan (5-HTP), administered together with peripheral decarboxylase inhibitor -- Ro 4-4602 on the rectal body temperature of rats was studied. TP caused a significant hypothermia which was prevented by pretreatment with p-chlorophenylalanine (PCPA), the serotonin synthesis inhibitor. 5-HTP did not influence the body temperature or slightly decreased it. However, the significant hypothermizing effect of 5-HTP was observed in rats pretreated with spiroperidol, haloperidol or phenoxybenzamine. Methysergide or cyproheptadine -- compounds regarded as potent serotonin receptor blockers -- did not prevent the TP-induced hypothermia. In methysergide pretreated rats 5-HTP produced a considerable hyperthermia. Cyproheptadine did not influence the effects of 5-HTP on the body temperature. The results obtained suggest that cyproheptadine and methysergide fail to block those central serotonin receptors which produce hypothermia after their stimulation.

5-Hydroxytryptophan↗