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Biomedical subjects

G Toffano

Publications and source records attributed to G Toffano.

At least 145 records · Page 8Linked to original sources
PubMed1980

Interactions of GM1 ganglioside with crude rat brain neuronal membranes.

The binding of GM1 ganglioside to crude preparations of rat brain neuronal membranes was studied, the following results being obtained: (a) the binding process followed a biphasic kinetics, which displayed a break at 0.07-0.08 x 10(-6) M GM1 concentration; (b) the features of the binding process at GM1 concentrations below the break and, over the break, above 10(-6) M appeared to be different. Below the break the process proceeded slowly and brought a stable and irreversible association of GM1 molecules to the membranes. Over 10(-6) M the process was much more rapid and caused GM1 molecules to interact in such a way that they were releasable by washing and could exchange with newly added free ganglioside; (c) the two binding processes displayed the characteristics of a saturation phenomenon; (d) in both cases, GM1 taken up was freely available to galactose oxidase, indicating that the oligosaccharide chains protrude from the membrane surface. We postulate that GM1 occurs, below and above the break, in different physical forms, each of them having a different mechanism of interaction with the membrane. Above 10(-6) M GM1 interacts as micelles, and the basis of the micelle-membrane interaction is a fusion process. Below the break, in the 10(-8)--10(-7) M range, the binding is the result of hydrophobic interactions between sites on the membrane and the hydrophobic portion of individual ganglioside molecules, most likely in the monomeric form.

Animals↗
PubMed1980

Lysophosphatidylserine-induced release of intra-cellular amines in mice.

In the presence of mouse plasma, lysophosphatidylserine stimulates histamine secretion from isolated mast cells. The extensive modification of carbohydrate metabolism produced by lysophosphatidylserine in mice was largely prevented by the antihistaminic drug, pyrilamine. However, to prevent completely the change in carbohydrate metabolism induced by lysophosphatidylserine the administration of an antihistamine and an adrenoceptor antagonist was required. It is concluded that the effect of lysophosphatidylserine in mice is due to release of intracellular amines. Histamine and catecholamines are involved.

Animals↗
PubMed1980

Cyclic nucleotides in medulloblastomas: correlative study of tumoral and cerebrospinal fluid levels.

The tumoral and cerebrospinal fluid (CSF) levels of cyclic nucleotides and of the main adrenergic metabolites (homovanillic acid and 5-hydroxyindoleacaetic acid) were investigated in a group of children with posterior fossa medulloblastomas. A longitudinal evaluation of CSF change of cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), and adrenergic metabolites before and after surgical removal of the tumor mass is presented. Some preliminary patterns concerning correlative levels in the neoplastic tissue are discussed. The relevant increase of cGMP in medulloblastoma specimens and in CSF samples operation and the rapid decrease in the CSF after surgical removal of the tumor seem to suggest a possible role of cyclic nucleotides in the neoplastic growth of these tumors. (Neurosurgery, 7: 359-362, 1980).

Blood-Brain Barrier↗
PubMed1979

Pharmacological effects of phosphatidylserine liposomes: the role of lysophosphatidylserine.

1. Unique among the phospholipids, phosphatidylserine depresses brain energy metabolism when injected intravenously into mice in the form of sonicated liposomes. The possibility that this effect results from a metabolic transformation of phosphatidylserine is examined in this paper. 2. A strong enhancement of the phosphatidylserine effect is induced by the incubation of liposomes with rat serum. Similar phosphatidylserine activation is observed after the incubation of the phospholipid with purified phospholipase A2 from pancreas. In both cases phosphatidylserine is split into the deacylated derivative, lysophosphatidylserine. 3. Lysophosphatidylserine reproduces with greater efficacy the effect of phosphatidylserine on brain energy metabolism. Other lysophospholipids are not effective. 4. It is concluded that the pharmacological effects of phosphatidylserine liposomes is due to the generation of lysophosphatidylserine.

Animals↗
PubMed1979

Pharmacological effects of phosphatidylserine liposomes: regulation of gylcolysis and energy level in brain.

1 The accumulation of glucose in the brain produced by the administration of phosphatidylserine liposomes into mice has been studied by measurement of the cerebral contents of glycolytic intermediates and high-energy compounds. 2 With a normal supply of oxygen to the brain, inhibition of glycolysis is indicated mainly at the phosphofructokinase step. The ratio of glucose-6-phosphate to fructose-1,6-diphosphate increased, whereas the levels of pyruvate and especially lactate decreased. 3 Under conditions of cerebral ischaemia, the administration of phosphatidylserine delays glycogen mobilization and ATP use. As a consequence of decreased energy utilization, the brain adenylate energy charge remains at a high level. 4 It is concluded that the phosphatidylserine-induced glucose accumulation in the brain is due to reduced energy expenditure and therefore to a decrease in carbohydrate consumption. The inhibition of glycolysis by the high level of adenylate energy charge is probably the control mechanism explaining the decreased carbohydrate utilization.

Adenine Nucleotides↗
PubMed1979

Lack of counteracting effect of liposomes on benserazide-induced hyperprolactinemia.

Benserazide induces an increase of serum prolactin in man, possibly as the result of an impairment of the dopamine effect on the pituitary and/or on the outer median eminence caused by the inhibition on L-dopa decarboxylase. On the other hand, liposomes obtained from bovine brain cortex phospholipids reduced serum prolactin possibly through an effect of phosphatidylserine on dopamine biosynthesis at the level of tyrosine hydroxylase. Benserazide, given orally (125 mg) to 5 normal subjects, induced an increase of serum prolactin that did not change when 300 mg of phospholipid liposomes were given intravenously 60 min later. An increase of L-dopa synthesis does not seen to be capable to overcome the effects of the decarboxylase inhibition.

Adult↗
PubMed1978

Brain cortex phospholipids liposomes effects on CSF HVA, 5-HIAA and on prolactin and somatotropin secretion in man.

Liposomes obtained from bovine brain cortex phospholipids (BC-PL), which display several effects on brain function in mice, have been administered intravenously (200 mg) to healthy subjects at various times before diagnostic lumbar puncture. HVA and 5-HIAA concentrations in CSF have been evaluated with the aim of assessing changes of monoamines metabolism. An increase of HVA occurs after 2 hours from BC-PL administration, reaching its peak after 6--7 hours. The finding is interpreted as an index of an increased turnover of brain DA. 5-HIAA changes are less impressive and a smaller increase of the metabolite is observed. They cannot correctly be related to brain changes of serotonin metabolism, since 5-HIAA originates also from the spinal cord. No effects are observed on the secretion of prolactin, but somatotropin increases sharply between 2 and 7 hours from treatment, suggesting the possibility of an activation of the dopaminergic pathway, stimulating STH secretion.

Adolescent↗
PubMed1978

Purification of an endogenous protein inhibitor of the high affinity binding of gamma-aminobutyric acid to synaptic membranes of rat brain.

In a medium without Na+, gamma-aminobutyric acid (GABA) binds at 0 degrees to freshly prepared crude synaptic membranes from rat cerebral cortex with an apparent dissociation constant of 218 nM. An endogenous inhibitor of the Na+-independent GABA binding was removed from these membranes by freezing and thawing and by repeated washing with Tris citrate buffer (50 mM, pH 7.1) containing 0.01% Triton X-100. As a result, the crude synaptic membranes bind GABA at 0 degrees with two dissociation constants, 20 nM and 111 nM. The endogenous inhibitor is a thermostable (95 degrees for 15 min) acidic protein of approximately 1.5 X 10(4) daltons. It was purified (about 500-fold) with a series of procedures including gel chromatography on Sephadex G-100 and ion exchange chromatography on Dowex 50W-X8 (H+). Recombination of the purified endogenous inhibitor with crude synaptic membrane preparations deprived of the endogenous inhibitor showed that the purified inhibitor blocked noncompetitively the sites for high-affinity GABA binding. A role of this endogenous regulator in the functional of GABA-ergic synapses is discussed.

Animals↗