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Biomedical subjects

F Masi

Publications and source records attributed to F Masi.

At least 19 recordsLinked to original sources
PubMed2006

Microcirculation as a novel marker of membrane biocompatibility.

BACKGROUND: It is possible to consider microcirculation as a kind of OwitnessO of the complex biological reactions triggered by the dialytic treatment. The reactivity of microcirculation to the dialytic stress may represent a measure of the overall biocompatibility of the membrane. In this study we tested the hypothesis that different synthetic membranes may have different biological effects, particularly related to microcirculation. SUBJECTS AND METHODS: In this crossover study, we observed 16 chronically hemodialyzed patients. All patients were treated with the EVAL membrane; we recorded the TcPO2 during the second treatment of the week. All patients were then switched to the hf-PS membrane. During the study observation we did not change the dialytic prescription or the pharmacologic treatment. RESULTS: From the beginning of the session until 90O, the behavior of TcPO2 is similar for both the membranes. From 120O to the end of the treatment in sessions with the EVAL membrane, the TcPO2 values come back to the starting level, whereas in the treatments with hf-PS the TcPO2, the values remain at a lower level; there was a significant difference between EVAL and hf-PS in the values recorded. Arterial blood gas values of paO2 and paCO2 are quite similar in the treatments with both the membranes, without any significant difference. CONCLUSIONS: The analysis of microcirculation by means of TcPO2 measurement is a useful tool to obtain a OclinicalO measure of biocompatibility of the dialytic treatment and different membranes may have different impacts on TcPO2.

Aged↗
PubMed2003

Acquisition of a palatable-food-sustained appetitive behavior in satiated rats is dependent on the dopaminergic response to this food in limbic areas.

Rats exposed to repeated unavoidable stress show decreased dopamine output in the nucleus accumbens shell (NAcS) and do not acquire vanilla sugar (VS)-sustained appetitive behavior (VAB). Rats treated with lithium for 3 weeks also show decreased NAcS dopamine output, yet they acquire VAB. Feeding a novel palatable food increases extraneuronal dopamine levels in the NAcS and medial prefrontal cortex (mPFC) in rats. In order to investigate the role of food-induced dopamine release in VAB acquisition, we studied by microdialysis the dopaminergic response in the NAcS and mPFC to the presentation and consumption of VS in satiated control rats, and in satiated rats exposed to repeated stress or lithium treatment. The dopaminergic response to VS was also studied in rats familiar with VS, or that had acquired VAB. In control rats, VS feeding was accompanied by increased dopamine output in the NAcS and mPFC, and one-trial habituation to this effect developed in the NAcS. Rats exposed to a 7-day stress showed reduced interest in VS pellets, and when fed VS they did not show a dopaminergic response in the NAcS and mPFC. Lithium-treated rats rapidly ate VS pellets and showed increased dopamine output in the NAcS and mPFC, with no habituation in the NAcS response. Rats familiar with VS and rats that had already learned VAB ate VS pellets. The first group showed a lower dopaminergic response to VS consumption than the control group, but the latter showed no dopaminergic response in the NAcS and mPFC. We propose that the limbic dopaminergic response to a novel palatable food plays a role in associative learning and that it is predictive of the competence to learn an appetitive behavior. Moreover, in our experimental conditions a phasic increase in mesolimbic dopamine no longer signals the VS stimulus once it has become a reinforcer in an appetitive task.

Animals↗
PubMed2002

Dizocilpine infusion has a different effect in the development of morphine and cocaine sensitization: behavioral and neurochemical aspects.

The stimulation of glutamate receptors plays a relevant role in the development of behavioral sensitization to psychostimulants, while less clear results have been obtained on their role in morphine sensitization. We addressed this issue by comparing the development of cocaine and morphine sensitization under a continuous s.c. infusion of the N-methyl-D-aspartate (NMDA) antagonist dizocilpine (0.1 mg/kg/24 h). Moreover, we studied the expression of NMDA and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor subunits in discrete limbic areas of rats sensitized to morphine or cocaine with or without the concomitant dizocilpine infusion. It was observed that dizocilpine infusion did not prevent the development of morphine sensitization, while it prevented the development of tolerance to morphine-induced analgesia. Finally, morphine-sensitized animals did not present any modification in the subunit expression of glutamate receptors in the brain areas examined. In agreement with previous results, we found that dizocilpine infusion prevented the development of cocaine sensitization. Moreover, we observed that rats sensitized to cocaine presented a significant increase in the levels of GLUR1, NR1 and NR2B, in the nucleus accumbens, and of NR2B in the hippocampus compared to control animals. Such modifications were absent in rats administered cocaine under dizocilpine infusion. We conclude that: (i) morphine sensitization is a neuroadaptive phenomenon which does not appear to require NMDA receptor activity in order to develop; (ii) cocaine sensitization is clearly dependent on NMDA receptor activity, as dizocilpine infusion prevented the occurrence of glutamate receptors modifications as well as the development of sensitization.

Animals↗
PubMed2001

Dopamine output in the nucleus accumbens shell is related to the acquisition and the retention of a motivated appetitive behavior in rats.

Chronic stress exposure consistently impairs the reactivity to aversive and pleasurable stimuli in rats; these behavioral modifications are associated with a decrease in dopamine output in the nucleus accumbens shell (NAcS). However, when rats that have already acquired an appetitive behavior are exposed to chronic stress, they develop an impaired reactivity to avoidable aversive stimuli while retaining the appetitive behavior. The dissociation between these two behavioral traits was used to study whether the decreased dopaminergic activity in the NAcS was connected to either of the two deficits. Dopamine output was studied through microdialysis as dopamine accumulation following re-uptake inhibition by cocaine. When rats that had previously acquired the appetitive behavior were exposed to chronic stress, they showed a dopaminergic transmission in the NAcS similar to that of controls and significantly higher than that of chronically stressed animals. Thus, dopamine output in the NAcS was consistently associated to the acquisition and maintenance of appetitive behavior, while the expression of a deficit in avoidance appeared to be independent of it.

Animals↗
PubMed2001

Long-term behavioral and neurochemical effects of chronic stress exposure in rats.

Rats exposed to acute unavoidable stress develop a deficit in escaping avoidable aversive stimuli that lasts as long as unavoidable stress exposure is repeated. A 3-week exposure to unavoidable stress also reduces dopamine (DA) output in the nucleus accumbens shell (NAcS). This study showed that a 7-day exposure to unavoidable stress induced in rats an escape deficit and a decrease in extraneuronal DA basal concentration in the NAcS. Moreover, animals had reduced DA and serotonin (5-HT) accumulation after cocaine administration in the medial pre-frontal cortex (mPFC) and NAcS, compared with control animals. After a 3-week exposure to unavoidable stress, escape deficit and reduced DA output in the NAcS were still significant at day 14 after the last stress administration. In the mPFC we observed: (i) a short-term reduction in DA basal levels that was back to control values at day 14; (ii) a decrease in DA accumulation at day 3 followed by a significant increase beyond control values at day 14; (iii) a significant reduction in 5-HT extraneuronal basal levels at day 3, but not at day 14. Finally, a significant decrease in 5-HT accumulation following cocaine administration was present in the NAcS and mPFC at day 3, but not at day 14. In conclusion, a long-term stress exposure induced long-lasting behavioral sequelae associated with reproducible neurochemical modifications.

Animals↗
PubMed2001

A study of the antidepressant activity of Hypericum perforatum on animal models.

The treatment of non-selected depressed patients with a hydro-alcoholic extract of Hypericum perforatum has been reported to have an efficacy similar to that of classical antidepressants. The effects of H. perforatum on three animal depression models have been studied: (a) an acute form of escape deficit (ED) induced by unavoidable stress; (b) a chronic model of ED, which can be maintained by the administration of mild stressors on alternate days; (c) a model of anhedonia based on the finding that repeated stressors prevent the development of appetitive behavior induced by vanilla sugar in satiated rats fed ad libitum. H. perforatum: (i) acutely protects animals from the sequelae of unavoidable stress; (ii) reverts the chronic escape deficit state maintained by repeated stressors and (iii) preserves the animal's capacity to acquire motivated appetitive behavior. Exposure to chronic stress not only induces escape deficit, but also decreases extraneuronal levels of dopamine in the nucleus accumbens shell; both behavioral and neurochemical effects are reverted by long-term treatment with antidepressants. Three-week treatment with H. perforatum reverted the chronic stress effect on extraneuronal dopamine in the nucleus accumbens. A consistent body of data in the literature suggests that, among the components of H. perforatum extract, hyperforin is the compound (or one of the compounds) responsible for the antidepressant activity. We compared the efficacy of the total extract with the efficacy of hyperforin after p.o. administration. In the acute-escape deficit model, hyperforin showed a potency of about ten times that of the total extract in protecting rats from the sequelae of unavoidable stress. Thus, hyperforin appears to be the most likely active component responsible for the antidepressant activity of H. perforatum.

Animals↗
PubMed2001

Constructed wetlands for wastewater treatment in central Italy.

The performance of 4 constructed wetlands designed by IRIDRA Srl and operating in Tuscany (central Italy) has been monitored during the last three years. The 4 treatment systems have different sizes and characteristics: one single stage secondary treatment (150 p.e.); two secondary treatment plants with effluent reuse: one small (60 p.e) and the other big (350 p.e.); a tertiary treatment of effluents from an activated sludge plant with high hydraulic load fluctuation (5-500 p.e.). Due to geographical and economic constraints the four systems have high hydraulic and organic loading rates, neverthless the systems show very good removal performance of COD (62-95%), especially the ones with higher inflow COD concentrations (87-95%). Interesting results concerning also removal percentage of MBAS (42-88%) and ammonium (42-85%) were obtained, even though NH4+ concentration in the outflows of some of the plants, doesn't always comply with Italian quality standards.

Conservation of Natural Resources↗
PubMed2000

Long-term lithium administration abolishes the resistance to stress in rats sensitized to morphine.

Morphine sensitized rats appear protected from the sequelae of an unavoidable stress: when exposed to stress (after a 7-day morphine wash-out) and then tested for escape, they perform like naive animals. This protection appears similar to that induced by chronic imipramine treatment, as it is antagonized by the inhibition of D(1)-dopamine receptors before exposure to unavoidable stress. Repeated unavoidable stress induces in rats a condition characterized by hyporeactivity to noxious stimuli and reverted by long-term antidepressant treatments, and this state is regarded as an experimental model of depression. The resistance to stress in morphine sensitized rats could be considered as the behavioral counterpart of the sensitivity to stress in control rats, i.e. as a model of mania. The aim of the present study was to validate such a putative model by studying whether the resistance to stress induced by morphine sensitization would respond to a long-term administration of lithium, the reference antimanic drug. Long-term lithium treatment induces in rats a condition of hyporeactivity to noxious stimuli, accompanied by decreased levels of dopamine in the nucleus accumbens shell. In morphine sensitized rats chronic lithium abolished the resistance to stress, but it did not modify the D(1)-dopamine receptor mediated response to morphine, nor did it modify the levels of extraneuronal dopamine in the nucleus accumbens shell. Thus, lithium treatment abolished the resistance to stress in morphine sensitized rats, conferring predictive validity to the paradigm. Moreover, it did so through a mechanism which appeared to be independent of D(1)-dopamine receptor activity.

Animals↗
PubMed2000

Rats sensitized to morphine are resistant to the behavioral effects of an unavoidable stress.

In agreement with the results of other authors, rats sensitized to morphine and challenged with 5 mg/kg of morphine after 7 days of wash-out showed intense stereotyped movements, the expression of which was selectively antagonized by SCH 23390. Sensitized rats were exposed to an unavoidable stress (which consistently produces an escape deficit in control animals) after 3, 7 and 21 days of morphine wash-out. Twenty-four hours after the unavoidable stress, animals were tested for their capacity to escape and their performance was compared to that of control-stressed and naive rats. Morphine sensitization completely prevented the development of escape deficit. This protective effect was similar to that induced by a chronic imipramine treatment and, like the effect of imipramine, it was antagonized by the administration of SCH 23390 before the unavoidable stress. However, it was not affected by the administration of naloxone. Moreover, when rats presenting a clear-cut escape deficit, induced by a 10-day treatment with SKF 38393, were exposed to the morphine sensitization protocol, a complete recovery of their capacity to avoid a noxious stimulus was observed. Finally, the down-regulation of both the number of D(1)-dopamine receptors and of the coupled adenylyl cyclase activity in the pre-frontal cortex (PFC) produced by long-term SKF 38393 administration was reverted by the superimposed morphine sensitization. Thus, the condition of morphine sensitization appears to share several common effects with chronic imipramine treatment.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed2000

Acquisition of an appetitive behavior reverses the effects of long-term treatment with lithium in rats.

Rats exposed to a long-term treatment with lithium chloride develop a deficit of avoidance accompanied by a reduction in the basal levels of extraneuronal dopamine and in dopamine accumulation in the nucleus accumbens shell after acute uptake inhibition. Such a condition is similar to that of an experimental model of depression induced by exposing rats to a chronic stress procedure. Rats exposed to chronic stress are also unable to acquire an appetitive behavior sustained by a highly palatable food. Thus, it was studied whether rats fed a diet containing lithium would develop an appetitive behavior induced by a pure hedonic stimulus. Rats on the lithium diet developed a clear-cut escape deficit condition accompanied by a decreased dopamine output in the nucleus accumbens shell; nevertheless, they learned the appetitive behavior within a similar period to controls. The development of the appetitive behavior coincided with the recovery of the capacity to avoid a noxious stimulus and with the return of the dopaminergic transmission in the nucleus accumbens shell to values similar to those of control rats. It may be concluded that the mechanism of action underlying the behavioral and neurochemical sequelae of a chronic stress is distinct from that of the analogous effects produced by lithium.

Animals↗
PubMed1999

The effects of long-term administration of rubidium or lithium on reactivity to stress and on dopamine output in the nucleus accumbens in rats.

Rubidium and lithium are alkali metals belonging to the same periodic series as sodium, potassium and cesium. In the present report the effects of lithium and rubidium on animal reactivity to stressful stimuli and on dopamine output in the nucleus accumbens were studied. A dose-response curve with rubidium, administered acutely before exposure to unavoidable stress, showed a maximal protective activity on escape deficit development at the dose of 0. 41 mEq/kg. Rubidium injected at doses of 0.008-0.08 mEq/kg 72 h before the unavoidable stress had the same efficacy as the acute 0. 41 mEq/kg dose. Tolerance to the effect of rubidium developed after 9 days of treatment and, on day 15, rats presented a spontaneous escape deficit. The acute effect of lithium, administered for 3.5 days at the dose of 0.8 mEq/kg, i.p. twice a day before the exposure to unavoidable stress, was analogous to that of rubidium, but after repeated treatment a spontaneous escape deficit developed. Rats showing an escape deficit secondary to chronic stress also presented decreased extraneuronal dopamine concentrations in the nucleus accumbens. Accordingly, microdialysis studies showed significantly lower extracellular dopamine levels in rats chronically treated with lithium or rubidium compared to control animals. Cocaine (5 mg/kg i. p.) administered acutely increased extracellular dopamine concentrations in control rats, as well as in rats chronically stressed or chronically treated with lithium or rubidium. However, the dopamine increase was significantly higher in controls compared to the other groups. In conclusion, long-term treatment with lithium or rubidium, or the exposure to chronic stress, produced a condition of behavioral hypo-reactivity accompanied by a decreased dopamine output in the nucleus accumbens.

Animals↗
PubMed1999

A chronic stress that impairs reactivity in rats also decreases dopaminergic transmission in the nucleus accumbens: a microdialysis study.

Chronic stress induces in rats a decreased reactivity toward noxious stimuli (escape deficit), which can be reverted by antidepressant treatments. The present study reports that this condition of behavioral deficit is accompanied by a decreased level of extracellular dopamine in the nucleus accumbens shell. To assess whether this finding was the result of a decreased release or of an enhanced removal of dopamine, we acutely administered cocaine, and 2 h later d-amphetamine, to stressed and control rats. The increases in dopamine output observed in stressed animals after cocaine administration were significantly lower than those observed in control rats; whereas the total amount of dopamine released after d-amphetamine administration was similar in both groups of rats. These data suggest a reduced activity of dopaminergic neurons as the possible mechanism underlying dopamine basal level reduction in stressed animals. It is interesting that the stress group showed a locomotor response to cocaine not different from control rats, thus suggesting a condition of sensitization to dopamine receptor stimulation. Imipramine administered daily concomitantly with stress exposure completely reverted the escape deficit condition of chronically stressed rats. Moreover, stressed rats treated with imipramine showed basal and cocaine stimulated levels of extraneuronal dopamine similar to those observed in control animals.

Adrenergic Uptake Inhibitors↗
PubMed1995

Lactate versus bicarbonate on-line hemofiltration: a comparative study.

In this study, 6 chronic anuric uremic patients underwent lactate hemofiltration (HF) with a substitution fluid, prepared in bags, for 3 months and bicarbonate HF, with continuous on-line preparation of the substitution fluid, for 3 months. We determined Na+, Cl-, K+, total calcium (Ca), ionized calcium (Ca2+), phosphate, intact parathormone (I-PTH), pH, PCO2, PO2, and HCO3- in plasma before, during, and after the treatment, as well as Ca, Ca2+, phosphate, and I-PTH in the ultrafiltrate. Moreover, heart rate (HR) and mean arterial pressure (MAP) were continually recorded during the procedure. Furthermore, the patients underwent echocardiographic study before and after the session. In comparison with lactate, bicarbonate HF caused a significant increase in HCO3- and a decrease in K+ plasma concentrations. This was detectable, with lower significance, even 44 h after the end of the treatment. At the end of the long interdialytic period (68 h after the end of the treatment), no significant difference was detectable. pH and PCO2 showed a significant but transient increase during HF. The other parameters investigated did not differ significantly between the two methods.

Adult↗
PubMed1993

Dislipemia in patients undergoing continuous ambulatory peritoneal dialysis: pharmacological therapy (simvastatin) versus hemodialysis.

Peritoneal dialysis can worsen dislipemia, which is frequent in chronically uremic patients. In order to verify the therapeutic possibilities, we retrospectively studied 20 chronically uremic patients who had been previously treated with continuous ambulatory peritoneal dialysis (CAPD) and who had developed an IV-type dislipemia. Twelve have continued CAPD treatment and have been simultaneously treated with simvastatin; 8 have withdrawn from CAPD and have begun HD, without any antidislipemic pharmacological support. The results, after 3, 6, 12, and 18 months of treatment, showed the following: in patients treated with CAPD and simvastatin, highly significant decreases were noted in total cholesterol (T-cho) and triglycerides (TG) (p < 0.001), and highly significant increases were noted in HDL-cholesterol (HDL-cho) (p < 0.005) and apolipoprotein-A1 (Apo-A1) (p < 0.01). In patients treated with HD, only slightly significant decreases were noted in T-cho (p < 0.01) and TG (p < 0.02), a slightly significant increase in Apo-A1 (p < 0.05), and no significant change in HDL-cho. Apolipoprotein-B showed no change in the two groups. Therefore, patients undergoing CAPD, with dislipemia only, can continue the treatment, because simvastatin is capable of correcting dislipemia, while those patients who have displemia as well as other complications strictly due to CAPD must abandon treatment and must be transferred to extracorporeal methods.

Female↗
PubMed1990

Improvement of continuous arteriovenous hemofiltration (CAVH) and hemofiltration (HF) efficiency by adding hemoperfusion (HP).

Aiming to improve the efficiency of the blood purification convective methods either with spontaneous (CAVH) or with pump-assisted (HF) extracorporeal circulation we inserted after the hemofilter a cartridge containing 70 g of collodion-coated activated charcoal (CAC) microencapsulated, obtaining so hemofiltration and hemoperfusion in series (HF+HP). The obtained results show that in both methods HP addition gives a negligible increase of urea clearance and a practically null increase of phosphate clearance, whereas creatinine and uric acid clearances increase is remarkable especially, in percentage, with low blood flows (CAVH). In the HF+HP system we have also been studying B2-microglobulin (B2-M) clearance aiming at examining the possibility of increasing the removal of substances with higher molecular weight. We have been finding HP addition increases further on B2-M clearance already high in HF. Therefore we think HP addition to convective methods is an interesting step in the attempt to carry out highly efficient blood purification methods.

Creatinine↗
PubMed1989

[Hemofiltration and hemoperfusion performed in series for the purpose of removing beta 2 microglobulin].

With the objective to develop most efficient method for Beta-2-microglobulin elimination, the authors, using extracorporeal circulation placed behind the haemofilter a capsule containing 70 g of collodion coated with activated medicinal charcoal. This combination was used in 3 haemofilters made from different membranes. The results showed polysulphon to be the highest efficiency membrane out of those tested for Beta-2 microglobulin elimination. In combination with haemoperfusion, its efficiency increases significantly. Even if haemoperfusion increases efficiency by considerable percentage, the Beta-2 microglobulin elimination using other types of membranes lasts long and the total clearance remains low.

Adult↗
PubMed1987

[Hormonal, beta-endorphin and renin activity changes in man during partial immersion, as a therapeutic method, in water at 38 degrees C].

This research was carried out to define the effects on men of head-out water immersion in a bath at 38.41 +/- 0.04 degrees C (mean +/- S.E.) with a method similar to that used for therapeutical rehabilitation and time of immersion of 30 minutes. Beta-endorphin, renin activity, aldosterone, cortisol, HGH, FSH, LH, TSH, T3, T4 and prolactin haematic levels were analysed. Seventeen healthy subjects (fourteen males and three females), aged 21-65 years (mean age 29.8 +/- 2.6) were studied. Water immersion caused a decrease in FSH and LH haematic concentrations; no significant changes occurred in beta-endorphin, renin activity, aldosterone, prolactin, cortisol, HGH, TSH, T3, T4 and FTI values. Thirty minutes after the end of immersion, FSH and LH levels returned to pre-immersion values. The probable pathogenesis of these observations is suggested.

Adult↗