Biomedical subjects

M Rizzi

Publications and source records attributed to M Rizzi.

At least 73 records · Page 4Linked to original sources

PubMed1995

Structure of a complex of two plasma proteins: transthyretin and retinol-binding protein.

The three-dimensional structure of the complex formed by two plasma proteins, transthyretin and retinol-binding protein, was determined from x-ray diffraction data to a nominal resolution of 3.1 angstroms. One tetramer of transthyretin was bound to two molecules of retinol-binding protein. The two retinol-binding protein molecules established molecular interactions with the same transthyretin dimer, and each also made contacts with one of the other two monomers. Thus, the other two potential binding sites in a transthyretin tetramer were blocked. The amino acid residues of the retinol-binding protein that were involved in the contacts were close to the retinol-binding site.

Amino Acid Sequence↗

PubMed1995

Reptile heme protein structure: X-ray crystallographic study of the aquo-met and cyano-met derivatives of the loggerhead sea turtle (Caretta caretta) myoglobin at 2.0 A resolution.

The X-ray crystal structures of the aquo-met and cyano-met derivatives of the loggerhead sea turtle (Caretta caretta) myoglobin have been determined at 2.0 A resolution (R = 0.182, and 0.178, respectively). The results here reported, representing the first reptile globin solved by X-ray crystallography, have been analyzed in parallel with data for related monomeric hemoproteins, and indicate a strong overall structural similarity between the loggerhead sea turtle and mammalian myoglobins, reflected by the 63% amino acid identity of their primary structures. The root-mean-square deviation between the entire polypeptide backbones of loggerhead sea turtle and sperm whale myoglobins, after structure superposition, is 0.83 A. Upon cyanide binding to the protein distal site, the iron-bound water molecule present in the aquo-met form is displaced by the incoming ligand. Cyanide is oriented towards the inner part of the heme distal site forming a Fe-C-N angle of 133 degrees.

Animals↗

PubMed1995

Functional effects of D-Phe-c[Cys-Tyr-D-Trp-Lys-Val-Cys]-Trp-NH2 and differential changes in somatostatin receptor messenger RNAs, binding sites and somatostatin release in kainic acid-treated rats.

In situ hybridization histochemistry for somatostatin receptors-1, -2, -3 and -4 section and receptor autoradiography using [125I]CGP 23996, [125I]somatostatin-28, [125I]seglitide and [125I]Tyr3 octreotide were carried out to determine the expression of somatostatin receptor messenger RNAs and binding sites in the hippocampus and cerebral cortex of rats 21 days following generalized limbic seizures induced by subcutaneous injection of 12mg/kg kainic acid. In control rats, somatostatin-1 to somatostatin-4 receptor messenger RNAs were found in the pyramidal layer and granule cell layer of the dentate gyrus. After kainate treatment, the CA1 subfield displayed a selective decrease in somatostatin-3 and somatostatin-4 receptor hybridization signals of 35 and 41%, respectively, whereas no changes were observed in the remaining hippocampal areas. Somatostatin-1 and somatostatin-2 receptor messenger RNA expression in the hippocampus remained unaffected by kainate treatment. No effect of kainate was observed in the expression of somatostatin receptor messenger RNAs in the cerebral cortex. In control rats, the selective somatostatin-2 receptor ligands, [125I]seglitide and [125I]Tyr3 octreotide and the non-selective somatostatin receptor ligands [125I]CGP 23996 and [125I]somatostatin-28, labelled preferentially the stratum oriens and radiatum CA1, the granule and molecular layers of the dentate gyrus and the deep layers of the cerebral cortex. [125I]somatostatin-28 and [125I]CGP 23996 labelled sites were selectively decreased by 32 and 39%, respectively, in the stratum radiatum CA1 after kainate treatment. [125I]CGP 23996 binding was also decreased by 35% in the stratum oriens CA1 and by 36% on average in the stratum oriens and radiatum CA3. [125I]seglitide and [125I]Tyr3 octreotide binding was not affected by kainate in any hippocampal region. The granule and molecular layers of the hippocampus and the layers IV-VI of the cerebral cortex did not show changes in binding sites for any of the radioligands analysed. A 18 and 35% decrease in the spontaneous and 50 mM KCl-induced somatostatin release from hippocampal slices was found two days after kainate, a likely reflection of neuronal cell loss. No differences in somatostatin release were observed 21 days after kainate treatment. At this latter time, the rats had an enhanced susceptibility to tonic-clonic seizures induced by intraperitoneal injection of 30 mg/kg pentylenetetrazol, a subconvulsant dose in naive rats. Bilateral infusion of 6 micrograms RC 160, a selective somatostatin-2 receptor agonist, in the dentate gyrus 21 days after kainate, significantly reduced (P < 0.05) the number of animals with tonic-clonic seizures induced by pentylenetetrazol.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1995

Prognostic role of laparoscopic salpingoscopy of the only remaining tube after contralateral ectopic pregnancy.

OBJECTIVE: To evaluate the prognostic value of laparoscopic salpingoscopy in detecting patients who are at increased risk for a repeat ectopic pregnancy (EP). DESIGN: Patients with secondary infertility after a previous contralateral salpingectomy for EP were evaluated by laparoscopy with tubal perfusion and salpingoscopy of the only remaining tube. Subsequent reproductive outcome was evaluated and correlated to laparoscopic and salpingoscopic findings. SETTING: Department of Obstetrics and Gynecology of the Catholic University, a tertiary care university center in Rome, Italy. PATIENTS: Eighteen patients submitted to laparoscopy and salpingoscopy after a previous salpingectomy for EP. INTERVENTION: A two- to three-puncture laparoscopy with tubal perfusion and salpingoscopy. MAIN OUTCOME MEASURE: Reproductive outcome after a mean follow-up of 42.6 months. RESULTS: Salpingoscopy revealed a normal tubal mucosa in 13 patients (72%) and intra-ampullary adhesions in 5 patients (28%). Eight of the 13 patients with a normal mucosa conceived an intrauterine pregnancy. In the 5 patients with intra-ampullary adhesions, there were 3 repeat EPs, with one patient having first a term pregnancy and then a repeat EP. The presence of peritubal adhesions at laparoscopy was not of prognostic significance. CONCLUSION: Direct visualization of the ampullary mucosa by salpingoscopy can allow the detection of intraluminal adhesions that put the patient at increased risk for a repeat EP.

Adult↗

PubMed1995

Correlation between the American Fertility Society classifications of adnexal adhesions and distal tubal occlusion, salpingoscopy, and reproductive outcome in tubal surgery.

OBJECTIVE: To compare the prognostic value of salpingoscopy with a current classification system of adnexal adhesions and distal tubal occlusion in patients with tubal infertility undergoing reconstructive tubal surgery. DESIGN: Prospective clinical study. SETTING: Department of Obstetrics and Gynecology of the Catholic University, a tertiary care University Center in Rome, Italy. PATIENTS: Fifty-five infertile patients with either adnexal adhesions (29 patients) or hydrosalpinx (26 patients) undergoing reconstructive tubal surgery. INTERVENTIONS: Salpingoscopy performed concomitantly to salpingo-ovariolysis or salpingoneostomy at the time of either operative laparoscopy or laparotomy using microsurgical techniques. MAIN OUTCOME MEASURES: Salpingoscopic findings were compared with a current classification system of adnexal adhesions and distal tubal occlusion. The patients were followed for a mean follow-up of 49 months; the pregnancy rates achieved were correlated with the salpingoscopic findings and the classification system used. RESULTS: There was a significant correlation between the salpingoscopic grade and the occurrence of a term pregnancy for both the salpingo-ovariolysis and salpingoneostomy groups of patients. There was no significant correlation between the classification system used and the occurrence of a term pregnancy for both groups of patients. CONCLUSION: Salpingoscopy plays an important role in selecting the patients who may benefit the most from reconstructive tubal surgery.

Adnexal Diseases↗

PubMed1995

Pulmonary toxicity of alpha tumor necrosis factor in patients treated by isolation perfusion.

We studied pulmonary function in 22 patients affected by in-transit metastases from cutaneous melanoma and metastases from soft tissue sarcoma of the limbs who were treated with isolation perfusion in extracorporeal circulation with rTNF alpha at doses ranging from 0.5 to 4 mg/m2 in mild hyperthermia. Seventeen patients suffered from respiratory insufficiency which required assisted ventilation (7 mechanical ventilation for 1 day, 8 for 2 days and 2 patients on synchronized intermittent mandatory ventilation). Spirometric parameters recorded 7 to 15 days after treatment did not change from baseline values; in contrast, lung transfer factor for carbon monoxide significantly declined in a dose dependent fashion. These data confirm that rTNF alpha administered by isolation perfusion technique induces pulmonary side effects. Further studies are required to better define time course and reversibility of impairment in pulmonary function.

Adult↗

PubMed1994

Adaptive changes in the NMDA receptor complex in rat hippocampus after chronic treatment with CGP 39551.

Chronic treatment of adult rats with DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic carboxyethylester (CGP 39551) (30 mg/kg orally for 12 days) induced a significant increase, 72 h after the last dose, in the N-methyl-D-aspartate (NMDA)-sensitive [3H]glutamate binding in the hippocampal pyramidal layer (stratum oriens CA1, CA3: +51% on average; stratum radiatum CA1, CA3: +40% on average; stratum pyramidale CA1: +20%, CA3: +55%) and in the dentate gyrus (+43%) compared to vehicle-injected animals, as assessed by quantitative receptor autoradiography. Similar results were obtained using the NMDA receptor antagonist, [3H]DL-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid (CGP 39653). Saturation experiments showed that the increase in [3H]CGP 39653 binding was due to the maximum number of receptors, without changes in affinity. The same regimen did not alter [3H]N-(1-[2-thienyl]-cyclohexyl)-3,4-piperidine (TCP) binding to the ion channel coupled to the receptor but prevented D-serine (5 microM)-induced enhancement of [3H]glutamate binding. NMDA (3-300 microM) enhanced [3H]noradrenaline release from hippocampal slices, and 7-Cl-kynurenic acid (5-100 microM) and (+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclo-hepten-5,10-imine maleate (MK 801) (0.03-0.3 microM), antagonists at the glycine site and ion channel respectively, antagonized this effect to the same extent in CGP 39551-treated rats and controls. Chronic CGP 39551 did not affect the neurotoxic potency of quinolinic acid, a selective agonist at the NMDA receptor, injected in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗

PubMed1994

Structure of the sulfide-reactive hemoglobin from the clam Lucina pectinata. Crystallographic analysis at 1.5 A resolution.

The crystal structure of the aquo-met form of the sulfide-reactive hemoglobin (component I) from the gill of the symbiont-harboring mollusc, Lucina pectinata, has been solved and refined at 1.5 A resolution, based on synchrotron radiation X-ray diffraction data, and employing molecular replacement techniques. The crystallographic R-factor, calculated for the data in the 15.0 to 1.5 A resolution range, is 0.170, with highly regular stereochemical parameters for the protein model, and including 131 water molecules. The monomeric hemoglobin I chain consists of 142 amino acid residues, which have been partly identified on the basis of the crystallographic analysis. The molecule is characterized by an unusual distribution of aromatic residues, particularly in the region surrounding the distal site in the heme pocket. The heme distal residue is Gln(64)E7, while other notable amino acid substitutions include Trp(21)B2, Phe(29)B10, Leu(46)CD3, Phe(68)E11 and Trp(75)E18. An amino acid insertion (Ser44) is observed between sites CD1 and CD2. In the aquo-met protein, a water molecule is present at the sixth coordination position of the heme iron, and hydrogen bonded to Gln(64)E7. Simple model building shows that a dioxygen molecule, bound to ferrous protein, would contact with its free atom the ring edge of Phe(29)B10, being thus stabilized at the coordination site by an aromatic-electrostatic interaction. Similarly, the unique packing and organization of aromatic residues in the surroundings of the heme distal site is proposed as the molecular basis of the very high affinity of Lucina pectinata hemoglobin I for hydrogen sulfide, considered as one of the two physiological ligands of the protein.

Amino Acid Sequence↗

PubMed1994

Crystallization of the macromolecular complex transthyretin-retinol-binding protein.

Single crystals of the macromolecular complex transthyretin-retinol-binding protein have been obtained. Transthyretin is a carrier of the hormone thyroxine in plasma whereas retinol-binding protein is the specific transporter of the alcohol form of vitamin A in the same medium. This macromolecular complex is found under physiological conditions in plasma and is believed to play an important physiological role. The complex can be formed in vitro by proteins purified from different species. Our crystals are grown with chicken retinol-binding protein complexed to human transthyretin. They are grown by equilibrium dialysis versus 2.3 M ammonium sulphate, 3% ethylene glycol buffered with 0.1 M succinate (pH 5.5). Their space group is I222 (or I2(1)2(1)2(1)) with unit cell parameters a = 222.4 A, b = 163.4 A and c = 55.5 A. Using a conventional X-ray source, we have collected a complete data set of the crystals to a nominal resolution of 3.1 A.

Animals↗

PubMed1994

Enhanced neuropeptide Y release in the hippocampus is associated with chronic seizure susceptibility in kainic acid treated rats.

We measured the release of neuropeptide Y (NPY) from hippocampal slices of rats at various times after limbic seizures induced by a subcutaneous injection of 12 mg/kg kainic acid (KA). Two days after KA, 100 mM KCl induced a 1.6 +/- 0.2-fold increase in NPY release compared to saline-injected rats (P < 0.05), while spontaneous and 50 mM KCl-induced release were unchanged. Thirty days after KA, the spontaneous and 100 mM KCl-induced efflux of NPY was enhanced 2-fold on average (P < 0.01) compared to controls, while no significant differences were found using 50 mM KCl. Tissue concentration of NPY was raised 2.2 +/- 0.2 times (P < 0.01) 30 days after KA. Thirty days after KA, the rats showed enhanced susceptibility to tonic-clonic seizures, assessed using a normally subconvulsive dose of pentylenetetrazol (PTZ; 30 mg/kg). A selective antibody (Ab) raised against NPY in a rabbit was infused bilaterally for three days in the CA3 area and dentate gyrus (DG) of the dorsal hippocampus of rats treated 30 days before with KA. This significantly reduced (P < 0.05) the number of animals with tonic-clonic seizures induced by 30 mg/kg PTZ, compared to KA treated rats which received the inactivated Ab. The Ab was ineffective in naive rats injected with a full convulsive dose of PTZ (55 mg/kg). The present results show that neuronal release of NPY is enhanced in the hippocampus after limbic seizures induced in rats by KA. This effect persists for at least 30 days and may contribute to the chronically enhanced susceptibility to seizures after injection of this toxin.

Animals↗

PubMed1994

Changes in the ADP-ribosylation status of some hippocampal proteins are linked to kindling progression.

The N-methyl-D-aspartate (NMDA) receptors are a class of excitatory amino acid receptors in the brain which are important for the induction of kindling and kindling-like phenomena. Post hoc sodium nitroprusside-induced ADP ribosylation of some proteins (particularly a p43 and a p39 protein) in homogenates from stimulated hippocampus was reduced at preconvulsive stage II and stage V (tonic-clonic seizures) of dentate gyrus kindling compared with controls. This effect, which probably reflects enhanced endogenous ADP ribosylation, depends on the progressive activation of the NMDA receptors and on the generation of nitric oxide (NO). The early occurrence and the persistence of these modifications suggest they may be associated to the long-lasting changes in neuronal function induced by kindling.

2-Amino-5-phosphonovalerate↗

PubMed1994

Correlation Between AFS Classification Systems of Adnexal Adhesions and Distal Tubal Occlusion, Tubal Mucosa at Salpingoscopy and Reproductive Outcome of the Patient

From November 1988 to December 1991, 45 infertile patients underwent salpingo-ovariolysis and/or salpingoneostomy during laparotomy or laparoscopy. Findings at surgery were scored according to the AFS classification. Salpingoscopy was performed to evaluate the status of the ampullary mucosa. The mean age of the patients was 29.5 years and the mean length of infertility prior to surgery was 4.4 years. All patients were contacted by phone to obtain information on reproductive outcome with a minimum period of 18 months of follow-up. Statistical analysis of data was performed using the Fisher's exact test. AFS scores were not correlated with reproductive outcome, while the status of the tubal mucosa at salpingoscopy was significantly correlated with reproductive outcome.

Journal Article↗

PubMed1993

Functional, spectroscopic and structural properties of haemoglobin from chamois (Rupicapra rupicapra) and steinbock (Capra hircus ibex).

The functional and spectroscopic properties of chamois (Rupicapra rupicapra) and steinbock (Capra hircus ibex) haemoglobin (Hb) have been studied with special reference to the action of allosteric effectors and temperature. Moreover, the amino acid sequences of the N-terminal segments of the alpha- and beta-chains have been determined. The present results indicate that chamois and steinbock Hbs display a low affinity for O2, which appears to be modulated in vivo by Cl- ions rather than 2,3-bisphosphoglycerate. The Bohr effect for O2 binding to chamois and steinbock Hb is higher than for reindeer and bovine Hbs, being similar to that of human Hb. Moreover, the temperature-dependence of oxygenation appears intermediate between that of human and reindeer Hbs. E.p.r. and absorption spectroscopic properties of the ferrous nitrosylated derivative of chamois and steinbock Hbs suggest that both haemoproteins are in a low-affinity conformation even in the absence of InsP6. The reduced effect of polyphosphates on the functional and spectroscopic properties of chamois and steinbock Hb agree with amino acid differences in the N-terminal segment of the beta-chains (i.e. the deletion of Val(NA1) and the replacement of His(NA2), present in human Hb, and Gln(NA2), present in horse Hb, by Met). The molecular mechanism modulating the basic reaction of O2 with chamois and steinbock Hb may be linked to specific physiological needs related to the high-altitude habitats of these two animals.

Amino Acid Sequence↗

PubMed1993

Electrical kindling of the hippocampus is associated with functional activation of neuropeptide Y-containing neurons.

The release of neuropeptide Y (NPY) was measured from hippocampal slices of rats at stage 2 (preconvulsive stage) and stage 5 (full seizure expression) of electrical kindling of the dorsal hippocampus (upper blade of the dentate gyrus). Spontaneous release in naive rats (9.0 +/- 0.8 fmol/ml every 10 min) was independent of external Ca2+ but was reduced by 38 +/- 3.6% (P < 0.05) during 20 min incubation with 5 microM tetrodotoxin. Spontaneous efflux in naive rats did not differ from that in shams (implanted with electrodes but not stimulated) or in rats kindled to stage 2 and stage 5. Twenty-five, 50 and 100 mM KCl induced a concentration-dependent release of NPY (P < 0.05 and P < 0.01 at 25 and 50-100 mM respectively) from slices of shams. The effect of 100 mM KCl was reduced by 94 +/- 1% (P < 0.01) in the absence of Ca2+. Two days after the last stage 2 stimulation and 1 week after the last stage 5 seizure, NPY release was significantly larger than in shams at all KCl concentrations in the stimulated and contralateral hippocampus (P < 0.05 and P < 0.01). Forty-eight hours after one single after-discharge and 1 month after the last stage 5 seizure, 50 mM KCl induced a significantly larger release of NPY in the stimulated and contralateral hippocampus (P < 0.01 and P < 0.05), although the effect was less than during kindling.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1993

X-ray crystal structure of ferric Aplysia limacina myoglobin in different liganded states.

The X-ray crystal structure of the ligand-free ferric form of Aplysia limacina myoglobin (pH 6.0) has been refined at 1.7 A resolution (R = 15.1%), and its cyanide, thiocyanate and imidazole derivatives studied by difference Fourier techniques at atomic resolution. The crystallographic R-factors of the three different derivatives reported are 16.1%, 16.1% and 15.6% at 1.8 A, 2.0 A and 2.0 A resolution, respectively. The present results have been analyzed in parallel with previous crystallographic studies on the molecular structures of the fluoride and azide derivatives of ferric Aplysia limacina myoglobin. Ligand binding to the distal site of the heme pocket results in different networks of hydrogen bonds involving to various degrees the bound ligand, residue Arg(66)E10, the heme propionate III, ordered water molecules and/or protein backbone atoms from the CD region. In particular, Arg(66)E10 stabilizes the bound ligand and compensates for the absence of the hydrogen bond donor residue HisE7, commonly present in oxygen-carrying globins.

Animals↗

PubMed1993

Inhibition of serine proteinases belonging to the chymotrypsin superfamily by the cyclic thiolic compound YS3025: a comparative crystallographic study.

The synthetic cyclic thiolic compound 3-[2-(2-thiophencarboxythio)]-propanoyl-4-thiazolidin carboxylic acid (YS3025) acts as an effective inhibitor of bovine alpha-chymotrypsin. In the present communication YS3025 binding studies are extended to bovine beta-trypsin and porcine pancreatic elastase, by means of crystallographic difference Fourier techniques. For all the enzymes considered, the thiopencarbonyl moiety of YS3025 is located at the entrance of the inhibited proteinase primary specificity pocket (S1), covalently linked to the catalytic Ser195 OG atom, and forming an acyl-enzyme complex. These observations allow to select between alternative binding (and inhibition) mechanisms for YS3025 and related molecules to serine proteinases belonging to the chymotrypsin superfamily.

Animals↗

PubMed1993

Crystal structure of a distal site double mutant of sperm whale myoglobin at 1.6 A resolution.

The three-dimensional structure of sperm whale myoglobin His64(E7)-->Val,Thr67(E10)-->Arg double mutant has been studied by X-ray crystallography at 1.6 A resolution, and refined to a crystallographic R-factor of 0.197. The Arg67(E10) side chain is extended in the direction of the ligand binding site, and its NH1 atom is at a distance of 3.11 A from the NH1 atom of Arg45(CD3), which is also pointing towards the distal site. Both are kept in this position by hydrogen bonding and electrostatic interactions with a solvent sulfate ion, located amongst the two, on the protein surface. No liganded water molecule is present at the sixth coordination position of the Fe(III) heme.

Animals↗

PubMed1993

Anti-somatostatin antibody enhances the rate of hippocampal kindling in rats.

A somatostatin-specific antibody (Ab) (1:250) was continuously infused into the stimulated dorsal hippocampus of rats from 4 days before to 26 days after the beginning of kindling or until the first stage 5. Controls received boiled Ab. The number of stimulations to the first stage 5 were reduced by 41 +/- 4% (P < 0.01, Student's t-test) in animals infused with the Ab compared to controls. The cumulative after-discharge in the stimulated hippocampus was slightly, although not significantly, reduced. Kindling was not affected when the Ab was infused only during the first 10 stimulations (stage 2). Histological analysis showed no neurotoxic effects in the hippocampus as a consequence of Ab infusion.

Animals↗