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Biomedical subjects

M Rizzi

Publications and source records attributed to M Rizzi.

At least 91 records · Page 5Linked to original sources
PubMed1993

In vivo analysis of glucose-induced fast changes in yeast adenine nucleotide pool applying a rapid sampling technique.

Transition from glucose limitation to glucose excess in Saccharomyces cerevisiae leads to a fast change from complete to partial oxidative metabolism. To determine rapid changes of in vivo concentrations of yeast metabolites, occurring in the range of seconds after a glucose injection, a fast sampling technique was developed. A harvesting device with negligible dead space and highly efficient inactivation and extraction steps was applied to analyze the behavior of the physiological concentrations of adenine nucleotides as the dynamic response to fast changing glucose concentrations. Adenine nucleotides were selected as appropriate references due to their high turnover rates (in the range of seconds). During the first 5 s after a glucose pulse to a continuous chemostat culture, a significant decrease (30%) in ATP concentration and a coincident rise of ADP and AMP values were found. A further advantage of this technique is the high sampling frequency (5 s) and the long-term sterility ensuring recurrent harvesting.

Adenine Nucleotides↗
PubMed1993

Adoptive immunotherapy of advanced melanoma patients with interleukin-2 (IL-2) and tumor-infiltrating lymphocytes selected in vitro with low doses of IL-2.

Freshly isolated tumor-infiltrating lymphocytes (TIL) from stage IV melanoma patients were cultured for 2 weeks with low doses of interleukin-2 (IL-2; 120 IU/ml), to select potentially for tumor-specific lymphocytes present in the neoplastic lesion, followed by high doses (6000 IU/ml) to achieve lymphocyte expansion. TIL were serially analyzed for their expansion, phenotype and cytotoxic activity against autologous and allogenic tumor cells. A preferential lysis of autologous melanoma cells was obtained in long-term cultures of 7/13 cases (54%), while the remaining ones showed a major-histocompatibility-complex-unrestricted, lymphokine-activated-killer(LAK)-like activity at the time of in vivo injection. Sixteen patients with metastatic melanoma were infused with TIL (mean number: 6.8 x 10(9), range: 0.35 x 10(9)-20 x 10(9)) and IL-2 (mean dose: 130 x 10(6) IU, range: 28.8 x 10(6)-231 x 10(6) IU); 1 complete and 3 partial responses were observed in 12 evaluable patients (response rate 33%). In all responding patients, injected TIL showed an in vitro preferential lysis of autologous tumor cells, while in no cases were TIL with LAK-like activity associated with a clinical response. The mean autologous tumor cytotoxic activity of TIL at the time of in vivo injection was significantly higher in responding patients in comparison to nonresponding ones, suggesting that a marked and preferential cytolysis of autologous tumor cells is associated with the therapeutic efficacy of TIL.

Adult↗
PubMed1993

Extracellular somatostatin measured by microdialysis in the hippocampus of freely moving rats: evidence for neuronal release.

Intracerebral microdialysis combined with a sensitive and specific radioimmunoassay was used to monitor the neuronal release of somatostatin (somatostatin-like immunoreactivity, SLI) in the dorsal hippocampus of freely moving rats. The sensitivity of the radioimmunoassay was optimized to detect < 1 fmol/ml. The basal concentration of SLI in 20-min dialysate fractions (5 microliters/min) collected 24 h after probe implantation was stable over at least 200 min. The spontaneous efflux dropped by 54 +/- 6.4% (p < 0.05) when Ca2+ was omitted and 1 mM EGTA added to the Krebs-Ringer solution and by 65.5 +/- 3.2% (p < 0.05) in the presence of 1 microM tetrodotoxin. Depolarizing concentrations of the Na+ channel opener veratridine (6.25, 25, 100 microM) induced 11 +/- 2 (p < 0.05), 17 +/- 2 (p < 0.05), and 21 +/- 5 (p < 0.01) fold increase in SLI concentration, respectively, during the first 20 min of perfusion. The effect of 100 microM veratridine was blocked by coperfusion with 5 microM tetrodotoxin (p < 0.01) and reduced by 79% (p < 0.01) in the virtual absence of Ca2+. Neuronal depolarization by 20 min of perfusion with Krebs-Ringer solution containing 25 and 50 mM KCl and proportionally lowered Na+ increased the dialysate SLI 4.4 +/- 1 (p < 0.05) and 17 +/- 3 (p < 0.01) fold baseline, respectively. Ten micromolar ouabain, a blocker of Na+,K(+)-ATPase, increased the dialysate SLI 15-fold baseline, on average (p < 0.05), during 80 min of perfusion. The results demonstrate the suitability of brain microdialysis for monitoring the neuronal release of SLI and for studying its role in synaptic transmission.

Animals↗
PubMed1993

Binding of bovine basic pancreatic trypsin inhibitor (Kunitz) as well as bovine and porcine pancreatic secretory trypsin inhibitor (Kazal) to human cathepsin G: a kinetic and thermodynamic study.

The effect of pH and temperature on kinetic and thermodynamic parameters for the binding of the bovine basic pancreatic trypsin inhibitor (Kunitz inhibitor; BPTI) as well as bovine and porcine pancreatic secretory trypsin inhibitor (Kazal inhibitor; bovine and porcine PSTI, respectively) to human cathepsin G (EC 3.4.21.20) has been investigated. The affinity of the macromolecular inhibitors examined for cathepsin G is characterized by an endothermic, entropy-driven, behaviour, and shows the following trend: BPTI > bovine PSTI > porcine PSTI. The affinity difference of BPTI as well as of bovine and porcine PSTI for cathepsin G is mostly accounted for by changes in the values of the apparent dissociation rate constant for the proteinase:inhibitor complex destabilization. On increasing the pH from 4.5 to 9.5 (at 25.0 degrees C), the affinity of BPTI, as well as bovine and porcine PSTI for cathepsin G increases thus reflecting the acidic-pK shift of the His-57 catalytic residue from approximately 6.9 in the free enzyme to approximately 5.0 in the serine proteinase:inhibitor complexes. The BPTI as well as the bovine and porcine PSTI binding properties of cathepsin G have been analyzed in parallel with those of related serine (pro)enzyme/macromolecular inhibitor systems. Considering the known molecular models, the observed binding behaviour of BPTI as well as that of bovine and porcine PSTI to cathepsin G has been related to the inferred stereochemistry of the serine proteinase/inhibitor contact region(s).

Animals↗
PubMed1993

Structural studies on the loggerhead sea turtle (Caretta caretta) myoglobin.

The primary structure of myoglobin from the loggerhead sea turtle (Caretta caretta) has been determined; the protein consists of 153 amino acid residues. The ferric loggerhead sea turtle myoglobin has been crystallized in a form suitable for X-ray structural investigations. The crystals were grown at pH 8.0, in 0.05 M tris/HCl buffer, using 3.2 M ammonium sulfate as precipitating agent, at 4 degrees C, and belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell constants a = 37.2 A, b = 61.1 A, c = 75.2 A (one molecule, 17,000 M(r), in the asymmetric unit). A molecular replacement solution was found for the loggerhead sea turtle myoglobin crystals using sperm whale myoglobin structure as search model. The R-factor value, after molecular replacement, is 0.387, for the data in the 15-3.3 A resolution range. The results here reported are the basis for the first X-ray crystallographic investigation on a reptile myoglobin, and indicate a strong overall structural similarity between the loggerhead sea turtle and mammalian (i.e. sperm whale) myoglobins.

Amino Acid Sequence↗
PubMed1993

Pulmonary toxicity of recombinant interleukin-2 plus lymphokine-activated killer cell therapy.

The aim of the present investigation was to evaluate lung toxicity in 15 patients affected by metastatic melanoma of different sites, and treated with recombinant interleukin-2 (rIL-2) plus lymphokine-activated killer (LAK) cells The treatment regimen included a first and a second course of rIL-2, separated by four consecutive daily leukaphereses. Autologous LAK cells were reinfused during the second course. Lung function was monitored before and after each rIL-2 administration. In the 12 patients who could be followed until completion of the therapy, spirometric parameters and transfer factor of the lungs for carbon monoxide (TLCO) decreased significantly during the first rIL-2 course, remained stable during leukapheresis, and declined significantly further during the second rIL-2 course. In the second phase, chest radiography documented some degree of pulmonary oedema, ranging from interstitial oedema to frank pulmonary oedema. A significant dose-dependent correlation was found between the cumulative rIL-2 dose and the decline in TLCO in the first course of therapy. Moreover, patients who developed symptomatic respiratory insufficiency (World Health Organisation grade III or IV) during the second course of therapy received a higher number of LAK cells than those who did not. The data support the hypothesis that LAK cells have an additional toxic effect on the lung.

Adult↗
PubMed1992

Chronic infusion of quinolinic acid in rat striatum: effects on discrete neuronal populations.

The intrastriatal infusion of relatively low doses of quinolinic acid (Quin, 4-10 nmol/h) for 1 or 2 weeks induced time-dependent degeneration of neuronal cells. We examined the effects of these infusions on discrete cellular populations. The distribution of somatostatin (SOM)-positive neurons labelled by immunocytochemistry or by NADPH-diaphorase histochemistry and of cholinergic cells stained by acetylcholinesterase was quantified in the peripheral portion of the lesioned area. SOM-positive cells did not appear selectively spared by Quin infusion. The proportion of SOM- and NADPH-diaphorase-positive neurons killed by exposure to Quin was similar to or higher than the percentage of total neurons degenerated (from 30 to 85%). A selective sparing of cholinergic cells was observed in all conditions examined; perfusion of 6 nmol/h for a week induced 65% of cell death while not more than 30% of cholinergic neurons were killed. Thus, the neurochemical similarity between the degenerative effects of intrastriatal Quin and Huntington's disease (HD) did not appear confirmed by the chronic perfusion of low doses of Quin for SOM-positive neurons, whereas an analogy between Quin's effects and HD was suggested by the pattern of AChE staining.

Acetylcholinesterase↗
PubMed1992

A kinetic study of immobilized lipase catalysing the synthesis of isoamyl acetate by transesterification in n-hexane.

Isoamyl acetate was synthesized by lipase-catalyzed transesterification of ethyl acetate in n-hexane. The selectivity and rates of ester formation decreased when water content of the immobilized enzyme exceeded 3% (w/w). Experimental observations clearly indicate that the substrates as well as the product (ethanol) act as dead-end inhibitors. A ping-pong bi-bi mechanism with competitive inhibition by substrates and products is proposed that predicts the experimental observation satisfactorily.

Enzymes, Immobilized↗
PubMed1992

Somatostatin release is enhanced in the hippocampus of partially and fully kindled rats.

The release of somatostatin (somatostatin-like immunoreactivity) from hippocampal slices during the development of hippocampal kindling in rats was measured under resting and depolarizing conditions. Preliminary experiments in naive rats showed that the spontaneous efflux of somatostatin (4.0 +/- 0.3 fmol/ml every 10 min) was independent of external Ca2+ but was reduced to 71.5 +/- 6% of baseline (P < 0.05) during 20 min incubation with 5 microM tetrodotoxin. Neuronal depolarization with 25, 50 and 100 mM KCl induced a Ca(2+)-dependent somatostatin release, respectively 4.3 +/- 0.4, 16.7 +/- 1.6 and 22.0 +/- 1.3 times baseline (P < 0.01). Veratridine caused a dose-dependent Ca2+ and tetrodotoxin (5 microM) sensitive release ranging from 6.5 +/- 0.1 to 13.0 +/- 1.4 times baseline at 1.4 microM and 50 microM respectively (P < 0.01). One week after the last of three consecutive stage 5 seizures (full seizure expression) or 48 h after the last stage 2 stimulation (preconvulsive stage), 50 mM KCl-induced somatostatin release was significantly higher (1.8 +/- 0.1, P < 0.01) than in shams (animals implanted with electrodes but not stimulated) in the stimulated and contralateral hippocampus. Somatostatin release measured under resting conditions was increased by 1.5 times in the stimulated hippocampus at stage 2 (P < 0.05) and by 2.2 and 1.7 times in both hippocampi at stage 5 (P < 0.01). Forty-eight hours after the induction of a single afterdischarge no significant changes were found in either spontaneous or 50 mM KCl-induced release of somatostatin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Serine proteinase inhibition by the cyclic thiolic compound YS3025: a crystallographic study.

In order to unravel the serine proteinase inhibition mechanism by cyclic thiolic compounds, the X-ray crystal structure of bovine alpha-chymotrypsin inhibited by 3-[2-(2-thiophencarboxythio)]-propanoyl-4-thioazolidin carboxylic acid (YS3025) has been studied by means of difference Fourier techniques and refined at 2.8 A resolution (R-factor = 0.174). The thiophencarbonyl moiety of YS3025 is covalently linked, in the acyl-enzyme complex, to Ser195 OG atom of bovine alpha-chymotrypsin, and located at the entrance of the proteinase primary specificity subsite (S1). The present data confirm previous hypotheses raised on the inhibition mechanism of serine proteinases, based on solution studies of human leukocyte elastase in the presence of the YS3025 parent compound 2-[3-thiophencarboxythio]-N-[dihydro-2(3H)- thiophenone-3-il]-propionamide (MR889).

Binding Sites↗
PubMed1991

Changes in pre- and postsynaptic components of noradrenergic transmission in hippocampal kindling in rats.

We investigated whether modifications in noradrenergic neurotransmission occurred during the development of hippocampal kindling in rats. We measured the release of [3H]norepinephrine (NE) induced by field-electrical stimulation, NE-stimulation of inositol phosphates [( 3H]IP) accumulation in the presence of LiCl and isoproterenol-induced accumulation of cAMP in hippocampal slices taken from rats electrically kindled at stages 2 and 5 in the dorsal hippocampus. One week after the last of at least 3 consecutive stage 5 seizures or 48 h after the last stage 2 stimulation, 2 min electrical stimulation of stratum pyramidale CA1-CA3 or dentate gyrus (DG) slices from kindled and contralateral hippocampi induced frequency-dependent NE release (respectively 2, 4 and 8 times spontaneous release measured at 2, 5 and 10 Hz) which did not significantly differ from that observed in shams (implanted with electrodes but not stimulated). Basal release of NE from kindled and sham-treated rats did not differ either. Isoproterenol induced a dose-dependent increase above basal cAMP concentration ranging from 40% at 0.01 microM to 180% at 10 microM (P less than 0.01, Dunnett's test) which did not differ between stages 2 and 5 and sham-hippocampi. NE (1-1000 microM) induced a dose-dependent, prazosin-sensitive increase in [3H]IP accumulation in the hippocampal slices. A significantly higher increase was found at stages 2 (P less than 0.05, Tukey's test) and 5 (P less than 0.05 and P less than 0.01, Tukey's test) compared to shams at all doses studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Binding mode of azide to ferric Aplysia limacina myoglobin. Crystallographic analysis at 1.9 A resolution.

The binding mode of azide to the ferric form of Aplysia limacina myoglobin has been studied by X-ray crystallography. The three-dimensional structure of the complex has been refined at 1.9 A resolution to a crystallographic R-factor of 13.9%, including 126 ordered solvent molecules. Azide binds to the heme iron, at the sixth co-ordination position, and is oriented towards the outer part of the distal site crevice. This orientation is stabilized by an ionic interaction with the side-chain of Arg66 (E10) which, from an outer orientation in the 'aquo-met' ligand-free myoglobin, folds back towards the distal site in the presence of the anionic ligand. In the absence of a hydrogen bond donor residue at the distal E7 position in Aplysia limacina myoglobin, a different polar residue, Arg66 at the E10 topological position, has been selected by molecular evolution in order to grant ligand stabilization.

Animals↗
PubMed1991

A peptidase-resistant cyclic octapeptide analogue of somatostatin (SMS 201-995) modulates seizures induced by quinolinic and kainic acids differently in the rat hippocampus.

Electroencephalographic (EEG) seizures were measured in rats after intrahippocampal injection of 120 nmol quinolinic acid into the stratum radiatum CA1 or 0.19 nmol kainic acid in the dentate gyrus or in the stratum radiatum. Injection of 5 micrograms SMS 201-995, a peptidase-resistant cyclic octapeptide analogue of somatostatin, into the stratum radiatum, 15 min before quinolinic acid, did not significantly modify the number of seizures and the total time in seizures. Five micrograms SMS 201-995 injected into the stratum radiatum reduced the number of seizures induced by kainic acid in the same area and the total time spent in seizures by 58% and 75%, respectively (Student's t-test; P less than 0.01). In both instances the latency to the first ictal episode was not significantly modified. Lesions of the medial septum, which reduced the activity of choline-o-acetyl-transferase (CAT) in the dorsal hippocampus by greater than 90% after one week did not significantly affect seizures induced by quinolinic acid. In rats lesioned in the medial septum, 5 micrograms SMS 201-995 reduced the total time spent in seizures by 43%, without changing the number of ictal episodes and raised the latency to the first quinolinic acid-induced seizure by 53% (ANOVA 2 x 2, P less than 0.05) but had no effect on these measures in the corresponding sham-operated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Salpingoscopy in patients with contralateral ectopic pregnancy.

Patients who experience a tubal pregnancy have a poor prognosis in terms of reproductive potential and are at increased risk of a repeat EP. Salpingoscopy is a new endoscopic technique that allows the detection of abnormalities of the tubal mucosa. In seven patients with a follow-up longer than 6 months, an IUP occurred only in patients with a normal ampullary mucosa, whereas a recurrent tubal pregnancy occurred in the patient that conceived with an abnormal tubal mucosa. These preliminary results suggest that salpingoscopy may constitute an important prognostic factor in these patients.

Adult↗
PubMed1991

Nerve cell death induced in vivo by kainic acid and quinolinic acid does not involve apoptosis.

We investigated whether in vivo excitotoxicity was mediated by a mechanism of programmed cell death called apoptosis. Neurotoxic doses of kainic acid (1.2 nmol) and quinolinic acid (120 nmol) were unilaterally injected in the dorsal hippocampus of anesthetized rats. Eight or 16 h later the animals were killed and DNA was extracted from the injected hippocampi. DNA from mouse thymocytes exposed to methylprednisolone (10(-5) M for 6 h at 37 degrees C) was used as a positive control of apoptotic cells. No typical 'ladder' of DNA fragments (multimers of approximately 200 Kb) which characterizes apoptosis was seen in hippocampal cells after toxic doses of kainic or quinolinic acid, as assessed by agarose gel electrophoresis. This suggests that hippocampal nerve cell death induced in vivo by the excitotoxins is not mediated by apoptosis.

Animals↗
PubMed1991

[Use of buprenorphine after right hepatectomy].

Ten patients who underwent surgery (5 right hepatectomy and 5 colectomy) for cancer participated in a clinical controlled study. They were treated with buprenorphine (i.v. slow infusion) to relieve postsurgical pain. We found an increased urinary excretion of this drug in patients who underwent hepatectomy as compared with patients who underwent colectomy. However no differences in the occurrence of side-effects and/or in the therapeutic effect were observed between the two groups. We conclude that buprenorphine can be effectively and safely used also in patients with a resection of liver parenchyma.

Adenocarcinoma↗
PubMed1989

Cardiac output with CO2 rebreathing method in CAPD patients.

The aim of this study is to evaluate cardiac output (CO) with CO2 rebreathing method (RCO2) in patients (pts) on CAPD. We have studied 15 pts on CAPD from at least 6 months, the mean (+/- SD) age was 55 +/- 4 years, mean (+/- SD) hemoglobin was 10 +/- 2 gr/dl. The respiratory tests excluded obstructive or restrictive broncopneumopathies. Electrocardiograms and B-mode echocardiograms were normal. RCO2 was evaluated using the FICK formula: CO = VCO2/CvCO2 - CaCO2 where VCO2 is CO2 production; CvCO2 is the CO2 content in venous mixed blood; CACO2 is arterial CO2. VCO2 was obtained by collecting expired air into a Douglas bag during respiration at rest for 4 minutes. CvCO2 was obtained after 10-15 seconds of respiration in a mixture of 7% CO2 in O2. CaCO2 was obtained at CO2 end-tidal capnogram. RCO2 was performed in CAPD with full and empty abdomen. The mean (+/- SD) CO was 2.3 +/- 1.04 l/min with both full and empty abdomen, values below those theoretically calculated, taking into account the age and body surface (4.7 +/- 0.6 l/min P less than 0.0005). The reduction of CO is not induced by left ventricular insufficiency, but such phenomenon could be attributed to a redistribution of body fluid between intra and extracellular, in favour of the intracellular compartment. Therefore the increase in hematocrit and total plasma proteins can be fictitious.

Aged↗