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F Santangelo

Publications and source records attributed to F Santangelo.

At least 55 records · Page 3Linked to original sources
PubMed1991

Role of a calf thymus preparation in the degradation of native and reductively methylated low density lipoprotein.

1. The clearance of low density lipoprotein (LDL) is mediated by a specific LDL receptor pathway and by an alternative metabolic pathway that is responsible for the receptor-independent LDL catabolism. 2. This alternative catabolism can be studied in vivo using a preparation of chemically modified LDL that are reductively methylated. 3. Recently we showed that a calf thymus protein extract affects the cholesterol metabolism via activation of LDL catabolism. 4. The aim of this study was to investigate whether in vivo the specific LDL receptor pathway and the independent LDL receptor pathway are affected by thymus treatment. 5. The results obtained injecting in rats native and chemically modified 125I-LDL to probe the receptor independent pathway, show that the thymus gland decreases serum cholesterol by activation of the specific LDL receptor pathway. 6. This effect is mainly evident in liver and kidney that represent organs in which the specific LDL receptors are widely present.

Animals↗
PubMed1990

Effects of 5-hydroxytryptamine on the firing rates of neurons of the lateral vestibular nucleus in the rat.

5-hydroxytryptamine (5-HT) was delivered microiontophoretically (20-80 nA) to cells of the lateral vestibular nucleus of anaesthetized rats to test its influence on the spontaneous activity of single neurons. 5-HT increased the rate of firing of 94% of the units tested. The enhancement persisted for up to 700 s after the end of the 5-HT ejection and the maximum magnitude of the excitation (10-3400%) showed a hyperbolic correlation (rho = 0.86) with background firing. In 43% of units the enhancement was preceded by a short-lasting (less than 105 s) depression of the neuronal firing rate, the magnitude of which was unrelated to the background mean firing rate. Both components of the 5-HT response were dose-dependent. Only the excitatory responses were antagonized by metergoline, methysergide and ketanserin. The putative 5-HT agonist, 5-methoxy-N,N-dimethyltryptamine, applied microiontophoretically, depressed the background firing rate and was not antagonized by methysergide. These results demonstrate that 5-HT modifies the responsiveness of vestibular neurons and suggest that at least two mechanisms and maybe two types of receptors are activated by 5-HT in this nucleus.

Action Potentials↗
PubMed1990

Effects of motor cortex and single muscle stimulation on neurons of the lateral vestibular nucleus in the rat.

The neuronal responses to stimulation of motor cortical sites and of forelimb single muscles were studied in the lateral vestibular nucleus of anaesthetized rats. Of the 228 neurons tested for response to stimulation of contralateral motor cortex, 63% responded to cortical sites controlling extensor muscles and 30% to those controlling flexors. The corresponding figures for responders to ipsilateral stimulation were 34 and 21%. Vestibulospinal units responded to cortical sites controlling extensor and flexor muscles whereas the remaining lateral vestibular nucleus neurons, very reactive to cortical sites controlling extensor muscles, responded little to contralateral and not at all to ipsilateral cortical sites controlling flexor muscles. The effects evoked by contralateral cortical sites controlling extensors varied, those induced by cortical sites controlling flexors were inhibitory in 77% of cases. The responses to ipsilateral motor cortex stimulation differed not so much by cortical sites controlling extensor or flexor muscles as by whether the neuron was in the dorsal or ventral zone of the lateral vestibular nucleus: mixed in the former, all inhibitory in the latter. Of the lateral vestibular nucleus units tested for response to stimulation of ipsilateral or contralateral forelimb distal muscles, only 11% responded. All the vestibulospinal units responsive to muscle stimulation lay in the dorsal zone of the nucleus. The remainder, dorsal or ventral, were not responsive to contralateral muscles. Single lateral vestibular nucleus cells influenced both by ipsilateral muscle and by contralateral motor cortex made up 24% of the pool, vestibulospinal and non-vestibulospinal. They fell into three groups: responsive to one or both structures but responding more strongly to combined stimulation; responsive to each of the two structures but showing a response to combined stimulation not significantly different from that evoked by the cortex alone; responsive only to combined stimulation. The lateral vestibular nucleus units included in these three groups accounted for 29% of those tested for response to extensor muscles and cortical sites controlling extensors and 15% of those tested for response to flexor muscles and cortical sites controlling flexors. Twenty-five per cent of the vestibulospinal neurons responded both to contralateral muscles and to ipsilateral motor cortex stimulation but none of the non-vestibulospinal neurons responded to both. All the responders to both were in the dorsal zone of the lateral vestibular nucleus and responded to extensor stimuli, always in the same way. These results indicate that motor cortex output exerts a major influence on lateral vestibular nucleus discharges, while the muscle afferents have a modulatory influence on the lateral vestibular nucleus responses to cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1990

Effects of glutamate on the serotonin-induced responses of vestibular neurons.

The aim of this work was to verify whether and how spontaneous or glutamate(GLU)-induced enhancements of the neuronal firing rate modified the responsiveness of the vestibular neurons to microiontophoretic application of serotonin (5-HT). During experiments performed on anaesthetized Wistar rats the responses to 5-HT applications were studied in neurons of the lateral vestibular nucleus identified by the antidromic activation upon stimulation of the vestibulospinal tract. The magnitude (in percent) of the 5-HT induced excitatory responses decreased (hyperbolic correlation, r = 0.91) when the background mean firing rate was enhanced spontaneously or by long-lasting application of GLU. Even in high-discharging units, the response never changed its sign. The trend to a depression of the response to 5-HT in function of the background discharge was observed when either the enhancement of firing occurred spontaneously and it was induced by an application of GLU, no significant difference (F-test) being found between the two cases. It is concluded that serotoninergic afferents can exert a strong control upon the vestibular neurons when the background activity is depressed, and only a weak influence when the neuronal firing is enhanced by other excitatory afferents. It remains to verify whether the type of interference observed between GLU and 5-HT is specific or can be also detected between 5-HT and other excitatory neuromediators.

Animals↗
PubMed1989

Purification and characterization of a calf thymus protein active on lipid metabolism.

1. This work concerns the purification of a calf thymus protein that increases the binding of human 125I-labeled low density lipoprotein (LDL) on both human skin fibroblasts and a special line of rat liver cells, BRL 3A. 2. It was found that the thymus gland affects cholesterol metabolism via an activation of the LDL receptor pathway. 3. Moreover, the thymus protein active on the LDL receptor pathway has a different amino acid composition and molecular weight from other well-characterized thymic peptides.

Amino Acids↗
PubMed1989

Thymus fraction (FIII) effect on cholesterol metabolism: modulation of the low density lipoprotein receptor pathway.

1. A heat stable protein fraction from calf thymus is able to determine a marked drop of total serum cholesterol and B apoproteins in rats fed a cholesterol enriched diet. 2. It is known that the catabolism of low density lipoprotein (LDL) cholesterol is mediated by the existence of high affinity surface receptor on membrane cells. 3. The purpose of the present paper is to verify if the heat stable thymus protein fraction is able to affect the LDL receptor pathway in vitro. 4. The results obtained show that the protein calf thymus is able to increase human and rat LDL catabolism.

Adult↗
PubMed1988

The effect of L-carnitine on the apolipoprotein pattern of rats fed a cholesterol-rich diet.

1. L-Carnitine was administered to hypercholesterolemic rats for eight days, after which the blood was collected by intracardiac puncture and lipoproteins were collected by preparative ultracentrifuge. 2. The chemical composition of lipoproteins of normal rats and hypercholesterolemic rats before and after L-carnitine treatment was determined. 3. The total serum B and E apoproteins were assayed by rocket electrophoresis, while apoproteins in VLDL, IDL, LDL and HDL were determined by densitometric scanning of SDS and TMU polyacrylamide disc gel electrophoresis. 4. The results obtained showed that the L-carnitine treatment tends to restore to normal values both the chemical composition of lipoproteins and the apoproteins pattern of rats fed on a diet enriched with cholesterol.

Animals↗
PubMed1987

Integration of cortical and peripheral information in the lateral vestibular nucleus in the cat.

Neuronal discharges in the lateral vestibular nucleus (LVN) of the cat were studied during stimulation of a forelimb muscle and of a site in the contralateral motor cortex (area 4) capable of activating the same muscle. About one third of the LVN units were reactive to both stimulations or at least responded to one (cortex or muscle) but modified the response pattern when the other was stimulated also. The patterns evoked by a muscle were mostly enhanced on simultaneous stimulation of the cortical zone controlling the same muscle and vice versa. Only in the dorsal division the excitatory responses to muscle stimulation were depressed by simultaneous cortical stimulation. Some functional implications are proposed.

Afferent Pathways↗
PubMed1987

The serum lipoprotein pattern of water buffalo (Bubalus bubalis).

1. The serum lipoprotein pattern of water buffalo was studied by means of electrophoresis and the lipoproteins were isolated by ultracentrifugation on the basis of their hydrated density. 2. High density lipoproteins (HDL) showed a higher level of cholesterol than did the other lipoproteins. Moreover, the level of phospholipids was higher in HDL than in very low density lipoproteins (VLDL). 3. The buffalo B100 apoprotein was similar to that of man and rat. Three apoproteins similar to human apo E, apo AI and AII were found in buffalo HDL, buffalo VLDL contained essentially apo B protein.

Animals↗
PubMed1987

The serum apo B and apo E in rats following cholesterol diet and thymus treatment.

The serum levels of apo B and apo E in rats fed on a diet rich in cholesterol before and after thymus treatment were determined by the authors. The diet enriched with cholesterol increases the serum levels of apo E and of the large and small species of apo B. After treatment the large apo B and the small one strongly decrease, while apo E increases further. These data support the hypothesis that the dropping of total cholesterol, after thymus treatment, cannot be ascribed to apo E decrease but possibly to B-apoproteins.

Animals↗
PubMed1986

Synthesis and chemical properties of ibopamine and of related esters of N-substituted dopamines--synthesis of ibopamine metabolites.

The therapeutic usefulness of intravenously infused dopamine in congestive heart failure and in shock prompted us to synthesize a wide series of 3,4-O-diesters of dopamine and N-substituted derivatives to obtain an orally active dopamine-like prodrug having adequate absorption and duration of action. The pharmacological results and in particular, the hemodynamic studies in the dog led to the selection of ibopamine, i.e. the 3,4-diisobutyryl ester of N-methyldopamine and to its development as a useful drug for the chronic treatment of congestive heart failure. The choice of ibopamine from among several analogs was also influenced by other favourable properties such as good chemical stability in pharmaceutical formulations and in the biopharmaceutical phases of the absorption, and fast enzymatic activation of the prodrug by plasma and peripheral tissue esterases; the latter property appeared desirable to avoid any accumulation in the central nervous system and consequent undesired side effects. The isomeric mixture of 3-O- and 4-O-isobutyrates of N-methyldopamine as well as the main conjugated metabolites, i.e. the 3-O- and 4-O-sulphate and 4-O-beta-glucuronide of N-methyldopamine were synthesized as analytical references in metabolic studies and for the investigation on their pharmacokinetic and pharmacological properties. Dopamine O-sulphates were also prepared using the methods developed for the corresponding N-methyl derivatives.

Biotransformation↗