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M Botta

Publications and source records attributed to M Botta.

At least 37 records · Page 2Linked to original sources
PubMed2000

Syntheses and relaxation properties of mixed gadolinium hydroxypyridinonate MRI contrast agents.

The tripodal ligand tris[(3-hydroxy-1-methyl-2-oxo-1,2- didehydropyridine-4-carboxamido)ethyl]amine (TREN-Me-3,2-HOPO) forms a stable Gd3+ complex that is a promising candidate as a magnetic resonance imaging (MRI) contrast agent. However, its low water solubility prevents detailed magnetic characterization and practical applicability. Presented here are a series of novel mixed ligand systems that are based on the TREN-Me-3,2-HOPO platform. These new ligands possess two hydroxypyridinone (HOPO) chelators and one other chelator, the latter of which can be easily functionalized. The ligands described use salicylamide, 2-hydroxyisophthalamide, 2,3-dihydroxyterephthalamide, and bis(acetate) as the derivatizable chelators. The solution thermodynamics and relaxivity properties of these new systems are presented. Three of the four complexes (salicylamide-, 2-hydroxyisophthalamide-, and 2,3-dihydroxyterephthalamide-based ligands) possess sufficient thermodynamic stability for in vivo applications. The relaxivities of the three corresponding Gd3+ complexes range from 7.2 to 8.8 mM-1 s-1 at 20 MHz, 25 degrees C, and pH 8.5, significantly higher than the values for the clinically employed polyaminocarboxylate complexes (3.5-4.8 mM-1 s-1). The high relaxivities of these complexes are consistent with their faster rates of water exchange (< 100 ns), higher molecular weights (> 700), and greater numbers of inner-sphere coordinated water molecules (q = 2) relative to those of polyaminocarboxylate complexes. A mechanism for the rapid rates of water exchange is proposed involving a low energy barrier between the 8- and 9-coordinate geometries for lanthanide complexes of HOPO-based ligands. The pathway is supported by the crystal structure of La[TREN-Me-3,2-HOPO] (triclinic P1: Z = 4, a = 15.6963(2) A, b = 16.9978(1) A, c = 17.1578(2) A, alpha = 61.981(1) degrees, beta = 75.680(1) degrees, gamma = 71.600(1) degrees), which shows both 8- and 9-coordinate metal centers in the asymmetric unit, demonstrating that these structures are very close in energy. These properties make heteropodate Gd3+ complexes promising candidates for use in macromolecular contrast media, particularly at higher magnetic field strengths.

Contrast Media↗
PubMed2000

Design and realization of a tailor-made enzyme to modify the molecular recognition of 2-arylpropionic esters by Candida rugosa lipase.

Within a research project aimed at probing the substrate specificity and the enantioselectivity of Candida rugosa lipase (CRL), computer modeling studies of the interactions between CRL and methyl (+/-)-2-(3-benzoylphenyl)propionate (Ketoprofen methyl ester) have been carried out in order to identify which amino acids are essential to the enzyme/substrate interaction. Different binding models of the substrate enantiomers to the active site of CRL were investigated by applying a computational protocol based on molecular docking, conformational analysis, and energy minimization procedures. The structural models of the computer generated complexes between CRL and the substrates enabled us to propose that Phe344 and Phe345, in addition to the residues constituting the catalytic triad and the oxyanion hole, are the amino acids mainly involved in the enzyme-ligand interactions. To test the importance of these residues for the enzymatic activity, site-directed mutagenesis of the selected amino acids has been performed, and the mutated enzymes have been evaluated for their conversion and selectivity capabilities toward different substrates. The experimental results obtained in these biotransformation reactions indicate that Phe344 and especially Phe345 influence CRL activity, supporting the findings of our theoretical simulations.

Base Sequence↗
PubMed2000

[GdPCP2A(H(2)O)(2)](-): a paramagnetic contrast agent designed for improved applications in magnetic resonance imaging.

A novel ligand based on a pyridine-containing macrocycle bearing two acetic and one methylenephosphonic arms (PCP2A) has been synthesized. An efficient synthesis of PCP2A is based on the macrocyclization reaction between 2,6-bis(chloromethyl)pyridine and a 1,4, 7-triazaheptane derivative bearing a methylenephosphonate group on N-4. The Gd(III) complex of PCP2A displays characteristic properties which make it a very promising contrast agent for improved applications in magnetic resonance imaging. In fact it shows (i) a very high stability constant (log K(GdPCP2A) = 23.4) which should guarantee against the in vivo release of toxic free Gd(III) ions and free ligand molecules and (ii) a relaxivity that is about 2 times higher than the values reported for contrast agents currently used in the clinical practice. Its high relaxivity is the result of the presence of two water molecules in the inner coordination sphere and a significant contribution from water molecule(s) hydrogen bonded to the phosphonate group. Moreover, the inner sphere water molecules are involved in an exchange with the bulk water which is relatively fast. This property is important for the attainment of an even higher relaxivity once the molecular reorientation rate of the [GdPCP2A(H(2)O)(2)](-) moiety is lengthened by means of conjugation to a macromolecular substrate.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed2000

Phase II study of vinorelbine with protracted fluorouracil infusion as a second- or third-line approach for advanced breast cancer patients previously treated with anthracyclines.

PURPOSE: To evaluate the feasibility and activity of vinorelbine in association with protracted infusional fluorouracil in patients with advanced breast cancer who were previously treated with anthracycline-containing regimens. PATIENTS AND METHODS: Eighty-three consecutive patients were entered onto the study. Forty-three patients experienced treatment failure or relapse after anthracycline-based, first-line chemotherapy for advanced disease and 29 experienced treatment failure or relapse after first- and second-line approaches; 11 patients experienced progressive disease within 6 months of completion of adjuvant anthracycline therapy. Sites of involvement were as follows: liver involvement, 42 patients (50.6%); lung 24 (28.9%); bone, 49 (59.0%); and skin/lymph nodes, 21 (25.3%). Treatment consisted of vinorelbine 30 mg/m(2) administered on days 1 and 15 every 28 days and fluorouracil 200 mg/m(2)/d given continuously over a 24-hour period. RESULTS: Toxicity was recorded for 441 cycles. The scheme was well tolerated: grade 1/2 nausea/vomiting occurred in 13 patients (15.6%), grade 1/2 diarrhea in nine (10.8%), and grade 2/3 stomatitis in six (7.2%). Three patients (3.6%) experienced grade 3/4 leukopenia and four (4.8%) experienced grade 2/3 anemia. Grade 2/3 neurologic toxicity was observed in three cases (3.6%), and grade 2/3 hand-foot syndrome was observed in three (3.6%). The median relative dose-intensity was 92% and 100% for vinorelbine and fluorouracil, respectively. Six patients (7.2%) attained a complete clinical response and 45 (54.2%) attained a partial response, for an overall response rate of 61.4% (95% confidence interval, 50.9% to 71.9%). Twenty-one patients (25.3%) obtained disease stabilization, and 11 (13.3%) experienced disease progression. Median time to progression in responding patients was 15 months; median overall survival of the entire population was 22 months. CONCLUSION: Vinorelbine associated with protracted infusional fluorouracil is an active and manageable scheme in advanced breast cancer patients previously treated with anthracyclines. The response obtained is durable.

Adult↗
PubMed2000

Non-covalent conjugates between cationic polyamino acids and GdIII chelates: a route for seeking accumulation of MRI-contrast agents at tumor targeting sites.

Three novel Gd chelates containing on their external surface pendant phosphonate and carboxylate groups, which promote the interaction with the positively charged groups of polyornithine and polyarginine, have been synthesized. Their solution structures have been assessed on the basis of 1H- and 31P-NMR spectra of the Eu and Yb analogues. A thorough investigation of the relaxometric (1H and 17O) properties of the Gd chelates has been carried out and the observed relaxivities have been accounted for the sum of three contributions arising from water molecules in the first, second, and outer coordination layers, respectively. It has been found that the occurrence of a tight second coordination coating renders the dissociation of the water molecule directly coordinated to the Gd ion more difficult. The binding interactions between the negatively charged Gd chelates and the positively charged groups of polyornithine (ca. 140 residues) and polyarginine (ca. 204 residues) have been evaluated by means of the proton relaxation enhancement (PRE) method. Although the binding interaction decreases markedly in the presence of competitive anions in the solution medium, the affinity is strong enough that in blood serum it is possible to meet the conditions where most of the chelate is bound to the polyamino acid substrate. On this basis one may envisage a novel route for a MRI location of tumors as it is known that positively charged polyamino acids selectively bind to tumors having a greater negative charge than non-tumor cells.

Chelating Agents↗
PubMed2000

Computer simulations of enantioselective ester hydrolyses catalyzed by Pseudomonas cepacia lipase.

On the basis of the X-ray crystal structure of the lipase from Pseudomonas cepacia (PcL)-an enzyme representative for a whole family of Pseudomonas lipases (lipase PS, SAM-2, AK 10, and others with a high degree of homology with PcL)-a computational study was performed to rationalize both the enantioselectivity and substrate specificity (tolerance) displayed by this lipase in the enantioselective hydrolysis of racemic esters 1a-12a from various secondary aromatic alcohols. The major goal of this project was the development of a binding model for PcL which is able to rationalize the experimental findings to predict "a priori the enantioselective behavior of PcL toward a wider range of substrates. A two-step modeling procedure, namely, docking experiments followed by construction of tetrahedral intermediates, was used for the simulation of the involved enzyme-substrate recognition/hydrolysis processes. The study of the recognition process (docking experiments) led to unambiguous identification of the binding geometry for the two enantiomeric series of substrates, but did not suggest a definitive interpretation of the behavior of PcL. Taking into consideration the stereoelectronic requirements of the enzymatic hydrolysis reaction, both the enantioselectivity and tolerance of the enzyme were then explained through the study of the tetrahedral intermediates, in turn constructed from the calculated docking geometries of 1a-12a.

Burkholderia cepacia↗
PubMed2000

Ternary Gd(III)L-HSA adducts: evidence for the replacement of inner-sphere water molecules by coordinating groups of the protein. Implications for the design of contrast agents for MRI.

Two novel gadolinium(III) chelates based on the structure of the heptadentate macrocyclic 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) ligand have been synthesized and their relaxometric and luminescent properties thoroughly investigated. They contain two water molecules in the inner coordination sphere in fast exchange with the bulk solvent and bear either a p-bromobenzyl or a p-phosphonatomethylbenzanilido substituent for promoting further interaction with macromolecular substrates. Upon interaction with human serum albumin the expected relaxation enhancement is not observed owing to displacement of the two inner-sphere water molecules of the complexes by a donor atom (likely from a carboxylate group) on the protein and possibly the phosphate anion of the buffered solution, respectively. We modeled the observed behavior by measuring the decrease of the relaxation rate of the water protons upon addition of malonate anion to aqueous solutions of the complexes. Conversely, no change in the hydratation state of the Gd(III) center for both complexes has been observed when the substrate for the formation of the macromolecular adduct is represented by poly-beta-cyclodextrin.

Contrast Media↗
PubMed2000

Research on anti-HIV-1 agents. Investigation on the CD4-Suradista binding mode through docking experiments.

Sulfonated distamycin (Suradista) derivatives exhibit anti-HIV-1 activity by inhibiting the binding of the viral envelope glycoprotein gp120 to its receptor (CD4). With the aim to propose a possible binding mode between Suradistas and the CD4 macromolecule, molecular docking experiments, followed by energy minimization of the complexes thus obtained, were performed. Computational results show that ligand binding at the CD4 surface involves two or three positively charged regions of the macromolecule, in agreement with the results of X-ray crystallographic analysis of a ternary complex (CD4/gp120/neutralizing antibody) recently reported in the literature. Our findings account well for the structure-activity relationship found for Suradista compounds.

Anti-HIV Agents↗
PubMed2000

Intra-arterial continuous infusion for treatment of pancreatic and biliary tract cancer.

BACKGROUND: Systemic chemotherapy does not satisfactorily improve the poor prognosis of pancreas and biliary tract cancer unresectable or metastatic to the liver. Intra-arterial infusion of antineoplastic agents can give higher concentrations to the tumor and slighter concentrations to the whole body, with a potential of efficacy and lower toxicity, due to the hepatic clearance. METHODS: Based on a safe and ambulatorial technique of transcutaneous arterial port implantation, this study was designed to evaluate feasibility and toxicity of 5-fluorouracil (5-FU) intra-arterial continuous infusion combined with systemic gemcitabine with dose escalation. Seventeen patients affected by pancreatic (14) or biliary tract (3) cancer received up to six cycles of treatment. Treatment consisted of intravenous gemcitabine on d 1 and 8 and intra-arterial 5-FU continuous infusion on d 1-14 every 21 d. Dose-escalation levels were 900 and 1000 mg/m2 for gemcitabine and 8, 10, 12, 15, and 17 mg/kg/d for 5-FU. Consecutive cohorts of three patients were planned at each dose level. RESULTS: Gastrointestinal toxicity (vomiting and diarrhea [3rd-4th degree] and gastritis), constituted the dose-limiting toxicity, with a maximum-tolerated dose of 1000 mg/m2 for gemcitabine and 15 mg/kg/d for 5-FU. Hematological toxicity was present in a minority of patients. No patient had acute or later complications such as arterial thrombosis related to the implanted arterial port, sclerosis cholangitis, or chemical cholecistitis. CONCLUSION: 5-Fluorouracil intra-arterial continuous infusion, combined with systemic gemcitabine, seems to be a feasible and safe regimen that could give interesting results in pancreatic cancer.

Aged↗
PubMed2000

Fibroblast growth factors and their inhibitors.

Fibroblast growth factors (FGFs) are members of a family of polypeptides synthesized by a variety of cell types during the processes of embryonic development and in adult tissues. FGFs have been detected in normal and malignant cells and show a biological profile that includes mitogenic and angiogenic activity with a consequent crucial role in cell differentiation and development. To activate signal transduction pathways, FGFs use a dual receptor system based on tyrosine kinases and heparan sulfate (HS) proteoglycans. Based on these considerations, a variety of inhibitors able to block the interactions between FGFs and their receptors have been designed and investigated for their biological properties related to antiangiogenesis and antitumor activity. In this paper, in addition to an extensive description of the FGF family members, we report several compounds acting as FGF inhibitors by direct interaction with the growth factors. Suramin and other diverse polyanionic polysulfated and polysulfonated compounds are described, with a particular focus on suradistas. For this class of molecules, by means of molecular modeling procedures, a binding model to FGF-2 has been proposed and the structure-activity relationships of suradistas have been analyzed on the basis of the computational model described.

Angiogenesis Inhibitors↗
PubMed2000

[Left atrium rupture after non-penetrating injury to the back].

Survival after cardiac rupture associated with blunt thoracic trauma is very uncommon. In these patients successful management demands a high index of suspicion of cardiac injury. A case of a 24-year-old woman who presented unconscious and shocked in the emergency room after motorcycle trauma strictly limited to her back is reported. Rib and sternal fractures were absent; the typical signs of cardiac tamponade were not found. Therefore the suspicion of cardiac chamber rupture was not immediate and the cardiologist was consulted after several diagnostic exams. Transthoracic echocardiography showed a pericardial effusion with clots and initial cardiac tamponade. The patient was transferred to the operating room and a large hemopericardium was disclosed. Two lacerations were noticed: the first pericardial, near the inferior vena cava, and the second one in the posterior wall of the left atrium. It is possible that the associated pericardial tear and pericardial clots could have contributed to survival. After surgical repair, carried out during cardiopulmonary bypass, the recovery was quick and complete. This case report confirms the possibility of heart chamber rupture after blunt chest trauma even in the absence of obvious thoracic lesion and it shows that the presentation could be very insidious without a "classic" clinical picture of cardiac tamponade. In front of an unexplained shock after nonpenetrating thoracic trauma, a rupture of the heart chambers should be suspected and echocardiography is mandatory. In the emergency room environment pericardiocentesis should be performed only with a quickly available cardiac surgery or in the presence of overwhelming hemodynamic failure.

Adult↗
PubMed1999

Further hypotensive metabolites from Verbesina caracasana.

After the isolation of caracasanamide and caracasandiamide, further hypotensive components of Verbesina caracasana were shown to be N3-prenylagmatine, N1-3',4'-dimethoxycinnamoylagmatine, agmatine and galegin (prenylguanidine). The structures were assigned on the basis of the spectral data of both metabolites and products from their alkaline hydrolyses. A pharmacological analysis of these products is also presented.

Animals↗
PubMed1999

Novel hypotensive agents from Verbesina caracasana. 6. Synthesis and pharmacology of caracasandiamide.

Caracasandiamide, a second hypotensive agent isolated from Verbesina caracasana, is the cyclobutane dimer (truxinic type) of the previously reported 1-[(3, 4-dimethoxycinnamoyl)amino]-4-[(3-methyl-2-butenyl)guanidino]butane (caracasanamide) (Delle Monache, G.; et al. BioMed. Chem. Lett. 1992, 25, 415-418). The structure was confirmed by synthesis starting from beta-truxinic acid obtained by photoaddition of 3, 4-dimethoxycinnamic acid. The dimer was coupled with 2 mol of prenylagmatine to give caracasandiamide in satisfactory yield. By contrast, the direct photodimerization of caracasanamide was unsuccessful. Caracasandiamide, assayed by the iv route in anesthetized rats at doses ranging from 50 to 3200 microgram/kg of body weight, was found to have no appreciable effect on heart rate. At lower doses, the drug stimulates breathing and increases cardiac inotropism, stroke volume, and cardiac output, thus augmenting blood pressure and aortic flow. At higher doses, caracasandiamide depresses breathing likely through central neurogenic mechanisms (not involved in the cardiovascular effects), continues to stimulate cardiac inotropism, and induces, by reducing peripheral vascular resistance, arterial hypotension with reduction of both aortic flow and stroke volume. These cardiovascular effects appear to involve complex interactions at the level of the peripheral beta(1)-, beta(2)-, and alpha(2)-adrenoreceptor-dependent as well as M(2)- and M(4)-cholinergic receptor-dependent transductional pathways both in cardiovascular myocells and at the level of the postganglionic sympathetic endings (with reserpine- and guanethidine-like mechanisms). The cardiovascular effects of caracasandiamide, different from those of caracasanamide, do not depend on significant actions on the central nervous system and on baroreflex pathways. In a similar manner and more effective than caracasanamide, caracasandiamide may be considered a hypotensive and antihypertensive drug. It is devoid of some of the negative side effects, e.g., reflex tachycardia and decreased cardiac inotropism, which are shown by the majority of the most common antihypertensive and vasodilator drugs.

Animals↗
PubMed1999

A unified and quantitative receptor model for the microtubule binding of paclitaxel and epothilone.

[formula: see text] Paclitaxel and epothilone represent the two major classes of antimicrotubule agents that promote tubulin polymerization and, presumably, mitotic arrest during cell division. A common minireceptor binding site model at beta-tubulin has been constructed for these structurally divergent compounds. Utilizing 20 amino acids identified in photoaffinity labeling experiments, the 3-D model correlates measured and predicted Ki's with r = 0.99 and rms(delta Gcalc-delta Gexp) = 0.2 kcal/mol. In addition, the model predicts the affinity of compounds not used in the training set and explains much of the SAR for the paclitaxel and epothilone families.

Antineoplastic Agents↗
PubMed1999

Synthesis and biological evaluation of 2-methoxy- and 2-methylthio-6-[2'-alkylamino)ethyl]-4(3H)-pyrimidinones with anti-rubella virus activity.

The synthesis of a new family of antiviral compounds, 2-methoxy-, and 2-methylthio-6-[(2'-alkylamino)ethyl]-4(3H)-pyrimidinones, has been accomplished. The activity of these agents against positive strand (rubella virus and sindbis virus) and negative strand (vesicular stomatitis virus) RNA viruses is reported. Some of these compounds are efficient and selective inhibitors of rubella virus.

Animals↗