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Biomedical subjects

D Rollet

Publications and source records attributed to D Rollet.

6 recordsLinked to original sources
PubMed1994

Long-term alteration in tyrosine hydroxylase mRNA levels in rat locus coeruleus after intraventricular injection of 5,6-dihydroxytryptamine.

The time course variations in tyrosine hydroxylase (TH) activity and specific mRNA were measured in the rat locus coeruleus (LC) and substantia nigra after an intracerebroventricular (i.c.v.) injection of 5,6-dihydroxytryptamine (5,6-DHT), a neurotoxin known to selectively destroy serotoninergic neurons. In this study, the TH activity and TH mRNA were both analyzed from homogenates of single tissue samples (micropunches). TH mRNA was extracted and quantified by densitometry using a northern blot method and an artificial TH RNA as an external standard. 5,6-DHT injection led to a long-lasting increase in TH activity and TH mRNA in LC but not in substantia nigra. The elevation in LC was progressive and reached its maximum value (+75%) at day 4 and day 8 after 5,6-DHT. This effect on TH activity was accompanied by a parallel change in TH mRNA whose amplitude was +57%, +81% and +45% at day 2, 4, and 8 respectively after the neurotoxin injection. Return to normal values was observed at day 16. Variations in TH activity and TH mRNA in LC were of similar amplitude. These results suggest that serotonin could be a potent modulator of TH gene expression within noradrenergic LC neurons.

5,6-Dihydroxytryptamine↗
PubMed1988

Modulation of tyrosine hydroxylase gene expression in rat brain and adrenals by exposure to cold.

The long-term changes in tyrosine hydroxylase (TH) activity induced by chronic exposure to cold in brain noradrenergic neurons of the locus coeruleus (LC) were analyzed and compared to those measured in a peripheral tissue such as adrenals. This analysis was made possible at the level of one single tissue corresponding to one animal by the use of sensitive methods that allow assay of TH activity, protein, and mRNA levels in parallel from the same homogenate. The three parameters were measured in brain structures and adrenals of rats maintained at 4 degrees C during 4 days and were compared to those of control animals kept at normal housing temperature (22 degrees C). LC of rats exposed to cold contained 200% more TH mRNA than controls. The amount of TH protein in this area rose to as much as 164% that of controls. Similarly, the activity of the enzyme increased to 140% of the normal value. Thus, these observations show that 1) the increase in TH mRNA was much higher than the increase in protein levels, and that 2) the newly synthesized molecules have about the same activity as that present under normal conditions. In contrast to the LC, no variation of these parameters was observed in the substantia nigra. In the adrenals, the variations in the different parameters were qualitatively similar to that observed in the LC, although they were quantitatively higher: TH mRNA, TH protein, and TH activity levels were respectively 330%, 182%, and 167% that of control adrenals. Altogether, these results demonstrate that exposure to cold induces an alteration in TH synthesis in brain noradrenergic neurons as well as in adrenals.

Adrenal Glands↗
PubMed1984

Immunohistochemical study of the catecholaminergic systems in the lower brain stem of the human infant.

The study of catecholaminergic (CA) systems in the lower brain stem was undertaken in the infant. A method of indirect immunohistofluorescence using antibodies to tyrosine-hydroxylase (TH) was applied to five brains from infants whose deaths had no neurological cause; two brains were submitted to fully systematic investigation. A topographical and morphocytological analysis of the CA systems was carried out on horizontal serial sections. A neuronal map is shown presenting four bulbar and four pontine sections. The disposition of the main CA groups (i.e. A1, A2, locus coeruleus) was found to be consistent with the data provided by the literature concerning the human foetus and the adult. Topographic differences and peculiarities are emphasized in the infant. Mapping of phenylethanolamine N methyltransferase (PNMT) positive neurons was performed in one plane of section of mid-medulla. This technique might usefully be applied to the exploration of putative diseases of bulbopontine CA systems, such as the sudden infant death syndrome and central blood pressure disorders.

Brain Mapping↗