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Biomedical subjects

N Sarda

Publications and source records attributed to N Sarda.

47 records · Page 3Linked to original sources
PubMed1986

Differential pulse voltammetry in vivo with working carbon fiber electrodes: 5-hydroxyindole compounds or uric acid detection?

Differential pulse voltammetry was performed in rats chronically implanted with carbon fiber electrodes in the caudate (n.Cd) and raphe dorsalis (n.RD) nuclei. The electrochemical signal obtained at the +300 mV potential (peak 3) in animals implanted for more than one week (long term chronic conditions, greater than 7 days) could be dependent upon the extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in n.Cd and n.RD. This result was obtained despite the tendency of Pargyline to increase n.Cd and n.RD endogenous concentrations of Uric Acid (UA) measured by High Performance Liquid Chromatography (HPLC). In contrast, in animals implanted for less than one week (short term chronic conditions, less than 7 days) peak 3 recorded in the same structure could be dependent upon extracellular fractions of 5-HIAA and UA since consecutive injections of Pargyline and Allopurinol are necessary to suppress this signal. The source of extracellular UA measured in brain by voltammetry, in such short term chronic conditions, might result from surgical trauma.

Animals↗
PubMed1985

Phospholipid methylase activity, [3H]S-adenosyl-L-homocysteine binding, and S-adenosyl-L-methionine and S-adenosyl-L-homocysteine levels in rat brain during maturation.

The changes in activity of phospholipid methyltransferase I and [3H]S-adenosyl-L-homocysteine ([3H]SAH) binding were determined in cortical membrane preparations from newborn rats and rats 1, 2, and 8 months old. The activity of phospholipid methyltransferase I and the [3H]SAH binding were significantly greater (respectively, +30 and +40%) in newborn rats than in 1-, 2-, and 8-month-old rats. The methylated products at days 1 and 30 were identical. These changes in methyltransferase activity may be correlated with variations in concentration of S-adenosyl-L-methionine (SAM) and SAH. The endogenous SAM level was higher and the SAH level was lower in newborn compared with adult rats. These data suggested that the processes of methylation were favored in newborn rats. The modifications observed after treatment with L-homocysteine reinforced this hypothesis.

Animals↗
PubMed1985

[Differential pulse voltammetry: focus on the measurement of 5-hydroxyindole compounds and uric acid in the brain].

The electrochemical signal obtained at the +300 mV potential (peak 3) in rats implanted for more than one week could be dependent upon extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in caudate and raphe dorsalis nuclei. In contrast, in rats implanted for less than one week, this signal could be dependent upon extracellular fractions of 5-HIAA and uric acid since consecutive injections of Pargyline and Allopurinol are necessary to suppress it.

Animals↗
PubMed1984

Diurnal variations of S-adenosyl-L-methionine and adenosine content in the rat pineal gland.

S-adenosylmethionine and adenosine levels in the rat pineal gland were determined by high-performance liquid chromatography after fractionation of the pineal extracts. The concentration of S-adenosylmethionine follows a circadian rhythm and is about three times higher during the day (2.5 nmol/gland) than the night (1.1 nmol/gland). The variations in the level of adenosine are apparently more complex. Over the 24 hours period there are two maxima at 03.00 (120 pmol/gland) and 15.00 hrs (100 pmol/gland) and one minimum at 09.00 hrs (50 pmol/gland). In addition, only an ultradian rhythm with a period of 12 hrs and an acrophase of 3 hrs can be evinced by computer analysis.

Adenosine↗
PubMed1984

Effect of S-adenosyl-L-homocysteine upon sleep in p-chlorophenylalanine pretreated rats.

S-Adenosyl-L-homocysteine (7 mg/kg), administered to PCPA-pretreated rats, was able to restore normal SWS and PS quantities, as well as circadian rhythms. This effect was at its maximum when SAH was injected 48 h after PCPA (400 mg/kg). These results are discussed in terms of post-synaptic synergetic control by SAH of serotonergic and noradrenergic nerve terminals via the periventricular system and caudal medulla in relation to environmental input.

Animals↗
PubMed1984

Autoradiographic localization of [14C]8-S-adenosyl-L-homocysteine in rat brain.

Following intracarotid injection of [14C]8-S-adenosyl-L-homocysteine ( [14C]SAH) in the rat, radioactivity was localized by autoradiographic detection in the circumventricular organs, such as the pineal gland, choroid plexuses and area postrema, which lie outside the blood-brain barrier. HPLC analysis indicated a decrease of [14C]SAH radioactivity in these structures from 1 to 45 min, after injection. These results are discussed and related to the known pharmacological properties of SAH.

Animals↗
PubMed1983

A comparison of the effects of S-adenosyl-L-homocysteine on sleep in normal and pinealectomized rats.

S-adenosyl-L-homocysteine (SAH) was administered to normal and pinealectomized rats previously implanted with electrodes for polygraphic recording. In normal rats, injected at 17.00 h, 7 mg/kg SAH induced a significant increase of paradoxical sleep (PS) during the night. When injected at 09.00 or 19.00 h, no effect was observed. In pinealectomized rats, SAH had no significant effect on PS amounts but seemed to resynchronize the PS rhythm. Thus, the pineal gland plays an important role in SAH effect. The results are discussed with reference to different mechanisms within the rat pineal gland and a possible implication of beta-adrenergic receptors.

Animals↗
PubMed1983

In vivo elevation of mouse brain S-adenosyl-L-homocysteine after treatment with L-homocysteine.

Intraperitoneal coadministration of adenosine and L-homocysteine markedly increased S-adenosyl-L-homocysteine in whole mouse brain, but further investigations showed that this elevation could also be produced following administration of L-homocysteine alone. The noted increase was maximal (+1325%) 10 min after treatment, remaining at about this level for 30-40 min before returning to control values after 180 min. Cerebral adenosine levels were decreased after treatment with L-homocysteine, adenosine, or these two substances in combination.

Adenosine↗
PubMed1982

The regional concentrations of S-adenosyl-L-methionine, S-adenosyl-L-homocysteine, and adenosine in rat brain.

The concentrations of S-adenosyl-L-methionine (SAM), S-adenosyl-L-homocysteine (SAH), and adenosine (Ado) were determined in whole brain and rat brain regions by HPLC. The whole brain contains, respectively, 22 nmol, 1 nmol, and 65 nmol of SAM, SAH, and Ado per g of wet tissue. Their distribution indicated that SAM and SAH levels are highest in brainstem, whereas the Ado level is highest in cortex. With aging the SAM concentrations decrease in whole brain, brainstem, and hypothalamus (-25%) and SAH levels increase by 90% in striatum and by 160% in cerebellum, while Ado levels are increased in all regions by 100--180%.

Adenosine↗
PubMedDate not supplied

Pharmacokinetics and metabolism of S-adenosyl-L-homocysteine, in rats and dog.

Tissue distribution, metabolism and excretion of 14C-S-adenosyl-L-homocyteine were investigated in rat after oral and intraperitoneal administration. The radioactivity was distributed rapidly to the tissues. The urine was the major route of excretion: respectively 32% and 52% of radioactivity were excreted in 48 h urine after oral and intraperitoneal administration. Analysis of urine by HPLC showed that the major part of the radioactivity could be identified as uric acid. Absorption and pharmacokinetic parameters were determined in dog after oral and intravenous administration. The experimental data were fitted to a biexponential equation from a two-compartment open model.

Animals↗