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Biomedical subjects

A Gaiti

Publications and source records attributed to A Gaiti.

At least 55 records · Page 3Linked to original sources
PubMed1976

Relationships between base-exchange reaction and the microsomal phospholipid pool in the rat brain in vitro.

The calcium-stimulated incorporation of ethanolamine, choline and L-serine into rat brain microsomal phospholipids has been investigated. The membranes were prelabeled in vitro in their choline or serine phosphoglycerides by base-exchange and then chasing experiments were done by displacing the lipid-bound base by ethanolamine, choline, or L-serine labeled with a different isotope. The results indicate that membrane phosphatidylcholine is presumably a substrate for the exchange with all the three bases, whereas phosphatidylserine exchanges only with ethanolamine and L-serine but not with choline. A small phospholipid pool (3-7% of the total available pool) is active in the calcium-dependent exchange with choline, ethanolamine, and L-serine. When the microsomal membranes are prelabeled in vitro in their phosphatidylcholine moiety through the cytidine-dependent pathway and then chasing experiments are performed with the three nitrogenous bases, as above, the small phospholipid pool is hardly detectable. In view of these and other results (Gaiti et al., FEBS Letters 49:361 1975), it is suggested that at least two different pools of phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine might exist in rat brain microsomes.

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Platelet MAO-B activity and vitamin B12 in old age dementias.

Platelet MAO-B activity, serum vitamin B12 levels, and plasma folate were measured in patients suffering from presenile (AD) and senile (SDAT) dementia of Alzheimer-type, and vascular dementia (VD). MAO-B was higher in the SDAT group than in AD and controls. An inverse relationship between MAO-B activity and vit. B12 levels was documented in the whole group and in each category studied; furthermore, MAO-B was positively related to age. All the patients were then divided into two groups, according to vit. B12 levels (Group I: less than 200 pg/mL; Group II: greater than or equal to 200 pg/mL); Group I showed a significantly higher MAO-B activity with respect to Group II. The results indicate the existence of a negative association between platelet MAO-B activity and serum levels of vitamin B12 and confirm the existence of biological differences between presenile and senile dementia of Alzheimer type.

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CSF monoamine metabolites in old age dementias.

Cerebrospinal Fluid (CSF) levels of the main metabolites of monoamines (MHPG, 5-HIAA, and HVA) were measured in patients with early onset (AD) and late-onset (SDAT) Alzheimer's disease, vascular dementia (VD), and elderly controls. Psychobehavioral assessment was carried out by means of MMSE and GBS. Mean MHPG levels did not differ from controls; 5-HIAA was lower in VD when compared to both controls and SDAT. HVA was decreased in AD, SDAT, and VD with respect to controls. Significant correlations between HVA and psycho-behavioral parameters were observed in SDAT and VD groups, whereas no relationship was documented in AD. The SDAT group was divided in SDAT-A (age at onset: greater than 65 less than or equal to 80 yr) and SDAT-B (age at onset: greater than 80 yr). SDAT-A had significantly lower CSF HVA values than SDAT-B (165 +/- 64 vs 235.7 +/- 85). SDAT-B HVA levels were similar to those observed in controls. Correlation analysis between HVA and neuropsychological variables was significant in SDAT-A, but not in SDAT-B. These results might support the evidence of SDAT heterogeneity.

Aged↗
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Comparative kinetics of oxiracetam in serum and CSF of patients with dementia of Alzheimer type.

The purpose of the study was to determine whether oxiracetam crosses the human blood-brain barrier and to evaluate its comparative kinetics in serum and in cerebro-spinal fluid (CSF). Six DAT patients, undergoing CSF collection for diagnostic purposes, received 2 g oxiracetam daily, by a 60 min i.v. infusion, for 7 days. On the last day, in four patients blood samples were collected at time 0, 30, 60 and 120 min, and lumbar drainage was performed at the end of infusion: at this time mean CSF concentration was 3.5 micrograms/ml, i.e. 4.0% of the serum one, demonstrating that oxiracetam crosses the blood-brain barrier. In two patients, blood samples were collected at time 0, 60, 120 and 240 min, and lumbar drainage was performed 60 min after the end of infusion: at this time mean CSF concentration was 2.8 micrograms/ml, i.e. 5.3% of the serum one, indicating a persistence of oxiracetam within this deep compartment. These results provide the first evidence in humans that oxiracetam penetrates the central nervous system and contribute to the understanding of its long-lasting pharmacodynamic effect in man.

Aged↗
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Serine incorporation into phospholipids in vivo and serine phosphoglyceride metabolic transformations in cerebral areas from adult and aged rats.

Serine phosphoglycerides (SPG) in the nervous tissue are synthesized by base-exchange reaction. SPG may be decarboxylated and converted into ethanolamine phosphoglycerides (EPG). This latter reaction may be followed in turn by several enzymatic reactions leading to choline phosphoglycerides (CPG) via three successive methylations. These metabolic pathways are important for several reasons and their contribution to membrane phospholipid renewal has been clearly demonstrated. Base-exchange is the only metabolic route to synthesize SPG; it was therefore possible to test this pathway in vivo by injecting labeled serine. Serine incorporation into phosphoglycerides was reduced in cortex and hippocampus from aged rat brain as compared to adult, while no change in the SPG successive metabolic transformation was found. Based on both the results presented herein and previous ones obtained in vitro the authors suggest that the reduced serine incorporation may be due to reduced uptake into cells from aged animals. This finding leads to the conclusion that the above mechanisms for partial renewal of the phospholipid molecule may play an important role in the brain structure of aged animals.

Aging↗
PubMedDate not supplied

The effect of oxiracetam treatment on alterations of lipid metabolism in brain areas from spontaneously hypertensive rats.

It has been previously demonstrated that spontaneously hypertensive adult rats (SHR) develop severe hypertension and cerebrovascular lesions on drinking 1% NaCl from weaning and that the phospholipid metabolism in the whole brain is actively altered in these lesioned animals (SHR-NaCl) as compared to SHRs which drink only water and show only sporadic cerebrovascular lesions. We have now assayed the incorporation of labelled choline, ethanolamine, glycerol and arachidonic acid into the phospholipids from the cortex and hippocampus of SHR-water and SHR-NaCl at different time intervals from injection into the lateral ventricle of the brain. A noticeable decrease of both choline and arachidonate specific activity (SA) in the phospholipids was found in the cortex and hippocampus (where the effect is most evident) from SHR-NaCl. Based on the literature and the data obtained, we suggest that in SHR-NaCl brain areas a release of choline and fatty acid also occurs from choline glycerophospholipids as a consequence of the cerebrovascular lesions caused by NaCl treatment. Even if a relatively minor loss of the amount of the lipids studied is evident from our results as compared to their entire pool, this change may be quite important if it causes a modification of the lipidic bilayer in excitable membranes. In a parallel group of SHR-NaCl animals, treated with the nootropic drug oxiracetam, we observed that the metabolic utilization of the precursors was completely restored. These experimental data favour the hypothesis that oxiracetam is effective in stimulating the phospholipid metabolism rate at levels even higher than those of the SHR-water animals.

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