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Biomedical subjects

G Cruciani

Publications and source records attributed to G Cruciani.

At least 37 records · Page 2Linked to original sources
PubMed1998

Enhancement of radiation response by paclitaxel in mice according to different treatment schedules.

PURPOSE: The aim of our study was to determine if paclitaxel could be used as a radiosensitizer in vivo. MATERIALS AND METHODS: Paclitaxel was tested as a single agent and combined with an X-ray treatment. Paclitaxel was administered i.p. in doses from 30 to 120 mg/kg b.w. to (C3D2F1) mice bearing spontaneous mammary carcinoma. Tumor growth delay (TGD) or tumor control dose (TCD50, radiation dose needed to induce local tumor control in 50% of irradiated animals) and moist desquamation dose (MDD50, radiation dose needed to induce serious moist desquamation in 50% of the non-tumor-bearing feet) were the endpoints. DNA flow cytometric analysis was performed. RESULTS: DNA analysis demonstrated a G2/M block of tumor cells and a depletion of cells in S phase, with a maximum at 24 h from paclitaxel administration. Administering paclitaxel, in graded doses, 15 min before a 10-Gy X-ray treatment resulted in a linear regression line, almost parallel to that with paclitaxel alone, with a growth delay of about 6 days. In contrast, varying the X-ray dose with a constant paclitaxel injection (45 mg/kg b.w.) treatment showed some degree of synergism as the linear regression curves diverged. Interval time and sequence between paclitaxel administration and a 10 Gy X-ray treatment did not influence TGD. Protocols with paclitaxel at 30, 45, or 60 mg/kg were combined with radiation treatments at various doses (from 10 to 65 Gy). Values of TCD50 varied from 50.8 Gy for X-ray alone to 31.8 Gy for paclitaxel 60 mg/kg + X-ray. No differences were observed among MDD of different protocols. CONCLUSIONS: These results suggest that, under some conditions, paclitaxel combined with radiation can show superadditive effects and this result combined with the lack of severe normal tissue damage indicate that a favorable therapeutic gain can be obtained.

Animals↗
PubMed1998

Greater antitumor efficacy of paclitaxel administered before epirubicin in a mouse mammary carcinoma.

Combined treatment with paclitaxel and anthracyclines is increasingly being tested in clinical practice. Epirubicin is in general administered before paclitaxel. We have investigated, using a murine mammary adenocarcinoma, whether the efficacy and toxicity of this combination is influenced by treatment sequence, different time intervals and dose intensity. The tumor was transplanted into the right hind foot of C3D2F1 female mice. Paclitaxel was administered i.p. in doses ranging from 15 mg/kg to 75 mg/kg and epirubicin (i.p. or i.v.) in doses from 9 mg/kg to 30 mg/kg. The hepatic and peritoneal toxicity observed with epirubicin administration increased in combined treatments (stronger with i.p. than i.v. epirubicin administrations) and was dose-dependent. When paclitaxel and epirubicin were administered simultaneously or paclitaxel was given 24 h before epirubicin, the same tumor growth delays were obtained in all groups. A smaller effect was observed when paclitaxel was administered 24 h after epirubicin. Increasing the epirubicin or paclitaxel dose led to higher tumor growth delays but also an increased toxicity. In conclusion, in this experimental model, the administration of 45 mg/kg paclitaxel before 15 mg/kg epirubicin was very effective and the increased toxicity can be limited by introducing an interval of 24 h between drug administrations. These results should be considered when designing clinical trials.

Animals↗
PubMed1998

Multivariate analysis of experimental and computational descriptors of molecular lipophilicity.

Two experimental (log P, R(Mw)) and 17 calculation descriptors for molecular lipophilicity (fragmental, atom-based or based on molecular properties) were investigated by multvariate analysis for a database of 159 compounds including both simple structures as well as more complex drug molecules. Principal component analysis (PCA) of the entire database exhibits a clustering of chemical groups; preciseness of clustering corresponds to chemical similarity. Thus, diversity searching in databases might effectively be performed by PCA on the basis of calculated log P. The comparative validity check of experimental and computational procedures by regression analysis and PCA was performed with a chemically balanced, reduced data set (n = 55) representing 11 chemical groups with 5 members each. Regression of experimental descriptors (log Poct versus RMW) proves that chromatographic data, obtained under well-defined experimental conditions, can be used as valid substitutes for log P. Regression of calculated versus experimental lipophilicity data shows a superiority of fragmental over atom-based methods and approaches based on molecular properties, as indicated by correlation coefficients, slopes and intercepts. In addition, PCA revealed that fragmental methods (Rekker-type, KOWWIN, KLOGP) sense the compound ranking in log P data to almost the same extent as experimental approaches. For atom-based procedures and CLOGP, both the comparability of absolute values and the sensing of the compound ranking in the database are slightly less. This trend is more pronounced for the methods based on molecular properties, with the exception of BLOGP.

Chromatography, Thin Layer↗
PubMed1998

Moderate and large doses of ethanol differentially affect hepatic protein metabolism in humans.

The intake of approximately 70 g of alcohol impairs liver protein metabolism in healthy humans. To establish the threshold at which alcohol impairs hepatic protein metabolism in humans we compared the effects of 500 mL of water (control study), 300 (28.4 g ethanol) or 750 mL (71 g ethanol) of table wine on hepatic protein metabolism in three groups of healthy nonalcoholic volunteers. Hepatic protein metabolism was estimated (L-[1-14C]leucine infusion) by measuring the fractional secretory rates of albumin and fibrinogen during the overnight postabsorptive state (basal) and the subsequent administration of water or two different amounts of wine (300 or 750 mL) given with a liquid glucose-lipid-amino acid meal. During the meal, water did not affect fibrinogen fractional secretory rate and increased albumin fractional secretory rate by approximately 50% (P < 0.01). The 300 mL of wine increased albumin secretory rate by only approximately 20% (P < 0.01 vs. basal, P < 0.04 vs. water) and did not affect fibrinogen secretory rate. The 750 mL of wine profoundly impaired hepatic protein metabolism, decreasing the fractional secretory rates of albumin (P < 0.01 vs. water and 300 mL wine) and fibrinogen (P < 0.04 vs. water and 300 mL of wine) below the postabsorptive values. These results demonstrate that a moderate dose of alcohol (28 g, approximately 2 drinks) slightly affects postprandial hepatic protein metabolism by blunting the meal-induced increase in albumin synthesis, whereas it does not interfere with fibrinogen synthesis as do higher doses.

Adult↗
PubMed1997

A strategy for the incorporation of water molecules present in a ligand binding site into a three-dimensional quantitative structure--activity relationship analysis.

Water present in a ligand binding site of a protein has been recognized to play a major role in ligand-protein interactions. To date, rational drug design techniques do not usually incorporate the effect of these water molecules into the design strategy. This work represents a new strategy for including water molecules into a three-dimensional quantitative structure-activity relationship analysis using a set of glucose analogue inhibitors of glycogen phosphorylase (GP). In this series, the structures of the ligand-enzyme complexes have been solved by X-ray crystallography, and the positions of the ligands and the water molecules at the ligand binding site are known. For the structure-activity analysis, some water molecules adjacent to the ligands were included into an assembly which encompasses both the inhibitor and the water involved in the ligand-enzyme interaction. The mobility of some water molecules at the ligand binding site of GP gives rise to differences in the ligand-water assembly which have been accounted for using a simulation study involving force-field energy calculations. The assembly of ligand plus water was used in a GRID/GOLPE analysis, and the models obtained compare favorably with equivalent models when water was excluded. Both models were analyzed in detail and compared with the crystallographic structures of the ligand-enzyme complexes in order to evaluate their ability to reproduce the experimental observations. The results demonstrate that incorporation of water molecules into the analysis improves the predictive ability of the models and makes them easier to interpret. The information obtained from interpretation of the models is in good agreement with the conclusions derived from the structural analysis of the complexes and offers valuable insights into new characteristics of the ligands which may be exploited for the design of more potent inhibitors.

Binding Sites↗
PubMed1997

Chemometric methodologies in a quantitative structure-activity relationship study: the antibacterial activity of 6-aminoquinolones.

The paper illustrates the chemometric strategies appropriate for extracting information from a large amount of biological data regarding the antibiotic activity of 6-aminoquinolones. The unique framework based on principal component analysis, projection onto latent structures, and response surface methodologies permits the structure-activity correlations to be shown and to suggest new compounds for further testing. The low activity of the suggested molecules points out the limitations of quantitative structure-activity relationship models when the training set is not properly designed in order to balance all the structural variations taken into account.

Aminoquinolines↗
PubMed1997

Smart region definition: a new way to improve the predictive ability and interpretability of three-dimensional quantitative structure-activity relationships.

This report describes a new methodology aimed at grouping 3D-QSAR interaction energy descriptors into regions of neighbor variables bearing the same chemical and statistical information. These regions represent the structural variability of the series better than individual descriptor variables and can advantageously replace them in the chemometric analysis. The algorithm used to generate such regions is described, together with their application for improving the quality of GOLPE variable selection. The method is illustrated on a series of 47 glucose analogues, inhibitors of glycogen phosphorylase b, and is shown to improve both the predictive ability and the interpretability of the 3D-QSAR models obtained, comparing favorably with other methods previously described.

Algorithms↗
PubMed1997

Reliability of comparative molecular field analysis models: effects of data scaling and variable selection using a set of human synovial fluid phospholipase A2 inhibitors.

The effects of data pretreatment, data scaling, and variable selection on three-dimensional quantitative structure-activity relationships derived by comparative molecular field analysis (CoMFA) using the GRID energy function were studied in detail for a set of inhibitors of the human synovial fluid phospholipase A2 (HSF-PLA2). The quality of the models was evaluated for predictive power and ability to map the receptor binding site by (a) comparison of predicted and experimental activities using cross-validation and external validation sets and (b) comparison of the regions selected in space in the CoMFA models with a crystal structure of a HSF-PLA2-inhibitor complex, with optimized comparative binding energy analysis (COMBINE) models (Ortiz et al., 1995) and with structure-activity relationships derived previously for different sets of compounds. It is found that (1) data scaling and dielectric modeling strongly influence CoMFA results. Unscaled data and a uniform dielectric constant of 4 are well suited to GRID-CoMFA studies for the present compound set. (2) The GOLPE and Q2-GRS variable selection methods select variables in roughly the same regions in Cartesian space, but they produce different models in chemometric space and differ in their sensitivity to data scaling and pretreatment and their tendency to overfitting. (3) CoMFA models are consistent with COMBINE models in that they identify approximately the same intermolecular interactions as relevant for activity. Our study provides support for the qualitative receptor-mapping properties of CoMFA models and for the validity of variable selection when applied with care and also provides guidelines for how to evaluate the quality of CoMFA models.

Enzyme Inhibitors↗
PubMed1997

GRID/GOLPE 3D quantitative structure-activity relationship study on a set of benzamides and naphthamides, with affinity for the dopamine D3 receptor subtype.

In the search for drugs against schizophrenia and depression without extrapyramidal side effects, compounds that selectively antagonize the dopamine D3 receptor subtype are thought to be a solution. In order to create a model with which the D3 activity can be predicted and that can generate new ideas for future synthesis, we performed a comparative molecular field analysis (CoMFA). In our model 30 ligands were described quantitatively in the GRID program, and the model was optimized by selecting only the most informative variables in the GOLPE program. We found the predictive ability of the model to increase significantly when the number of variables was reduced from 25110 to 784. A Q2 of 0.65 was obtained with the final model, confirming the predictive ability of the model. By studying the PLS coefficients in informative 3D contour plots, ideas for the synthesis of new compounds can be generated.

Algorithms↗
PubMed1997

Nicotinamide counteracts alcohol-induced impairment of hepatic protein metabolism in humans.

We have recently shown that a large amount of wine (750 mL, approximately 70 g of alcohol) markedly impairs postprandial hepatic protein metabolism in healthy subjects. This is probably due to the shift in the intracellular redox state (increased NADH/NAD+) induced by ethanol oxidation. If this hypothesis is true, the administration of nicotinamide (NAD+ precursor) should provide NAD+ in excess and thus correct the NADH/NAD+ abnormalities and prevent the ethanol hepatotoxicity. Whole-body protein metabolism and the fractional secretory rates of hepatic (albumin, fibrinogen) and extra-hepatic (immunoglobulin G, IgG) plasma proteins were measured in the basal postabsorptive and in the absorptive states in 15 healthy subjects, that had been assigned to three groups matched for age and body mass index. During the absorptive state (intragastric meal), the three groups received water (control), 750 mL of wine, or 750 mL of wine + 1.25 g of nicotinamide, respectively. The redox state was estimated by determining the plasma lactate/pyruvate ratio. Compared with the basal state, wine alone increased the lactate/pyruvate ratio twofold and depressed the fractional secretory rates of albumin and fibrinogen (P < 0.01 vs. control and nicotinamide); nicotinamide reduced the effects of wine on the lactate/pyruvate ratio (P < 0.02 vs. wine alone) and prevented the reduction of albumin and fibrinogen secretory rates (P > 0.05 vs. control). These results indicate that nicotinamide counteracts the acute hepatotoxic effects of ethanol by ameliorating the redox state.

Adult↗
PubMed1997

Cisplatin-gemcitabine combination in advanced non-small-cell lung cancer: a phase II study.

PURPOSE: The nucleoside analog, gemcitabine, has shown activity as a single agent in the treatment of metastatic non-small-cell lung cancer (NSCLC). Its combination with cisplatin in preclinical models suggested synergy between the two drugs. The aim of the study was to evaluate the clinical efficacy and toxicity of the cisplatin-gemcitabine combination in advanced NSCLC. PATIENTS AND METHODS: Forty-eight consecutive previously untreated NSCLC patients entered the trial from January to June 1994. The median age was 60 years (range, 37 to 70) and performance status (PS) was 0 or 1; 22 patients had unresectable stage III disease (21 stage IIIB and one stage IIIA) and 26 had stage IV disease. Gemcitabine 1 g/m2 was administered weekly (days 1, 8, and 15) followed by a 1-week rest and cisplatin 100 mg/m2 on day 2 of each 28-day cycle. Survival and response were determined in accordance with the intention-to-treat principle in all enrolled patients. RESULTS: Of 48 assessable patients, one (stage IV) had a complete response (CR) and 25 achieved a partial response (PR). The overall response rate was 54% (95% confidence interval [CI], 40% to 68%). Thrombocytopenia was the main side effect, with 52% of patients experiencing grade III to IV toxicity, which was usually short-lived and responsible for the omission of gemcitabine administration on day 15 in 50% of chemotherapy courses. The median survival time was 61.5 weeks (95% CI, 40 to 71). CONCLUSION: The combination of gemcitabine and cisplatin induced a high response rate in both stage IIIB and IV NSCLC, with modest side effects. The regimen deserves further careful evaluation in a phase III prospective randomized trial.

Adult↗
PubMed1996

Contribution of amino acids and insulin to protein anabolism during meal absorption.

The contribution of dietary amino acids and endogenous hyperinsulinemia to prandial protein anabolism still has not been established. To this end, leucine estimates ([1-14C]leucine infusion, plasma alpha-ketoisocaproic acid [KIC] specific activity [SA] as precursor pool SA) of whole-body protein kinetics and fractional secretory rates (FSRs) of albumin, fibrinogen, antithrombin III, and immunoglobulin G (IgG) were measured in three groups of healthy volunteers during intragastric infusion of water (controls, n = 5), liquid glucose-lipid-amino acid (AA) meal (meal+AA, n = 7), or isocaloric glucose-lipid meal (meal-AA, n = 7) that induced the same insulin response as the meal+AA. The results of this study demonstrate that 1) by increasing (P < 0.01) whole-body protein synthesis and decreasing (P < 0.01) proteolysis, dietary amino acids account for the largest part (approximately 90%) of postprandial protein anabolism; 2) the ingestion of an isocaloric meal deprived of amino acids exerts a modest protein anabolic effect (10% of postprandial protein anabolism) by decreasing amino acid oxidation and increasing (P < 0.01) albumin synthesis; 3) albumin FSR is increased (approximately 20%) by postprandial hyperinsulinemia (meal-AA) and additionally increased (approximately 50%) by amino acid intake (meal+AA); 4) IgG FSR is stimulated (approximately 40%) by amino acids, not by insulin; and 5) fibrinogen and antithrombin III FSR are not regulated by amino acids or insulin.

Administration, Oral↗
PubMed1995

A novel strategy for improving ligand selectivity in receptor-based drug design.

A major desirable characteristic of many drugs is their ability to interact specifically with only one variety of the target receptor among many others. It is remarkable that, even when accurate three dimensional structures for the target biomolecules are available, there is no well-established methodology to describe their differences and use them for the design of selectively-interacting compounds. This work presents a novel method that uses multivariate GRID descriptors and principal component analysis (PCA) with the aim of revealing the most relevant structural and physicochemical differences between biomacromolecules related to receptor selectivity. The methodology is described through an example involving the study of bacterial (Escherichia coli) and recombinant human varieties of the dihydrofolate reductase (EC 1.5.1.3, DHFR) enzyme. This analysis easily unveils the most important regions on these biomolecules which should be taken into consideration for the design of selectively interacting compounds.

Binding Sites↗
PubMed1995

Glucose analogue inhibitors of glycogen phosphorylase: from crystallographic analysis to drug prediction using GRID force-field and GOLPE variable selection.

Several inhibitors of the large regulatory enzyme glycogen phosphorylase (GP) have been studied in crystallographic and kinetic experiments. GP catalyses the first step in the phosphorylysis of glycogen to glucose-l-phosphate, which is utilized via glycolysis to provide energy to sustain muscle contraction and in the liver is converted to glucose. alpha-D-Glucose is a weak inhibitor of glycogen phosphorylase form b (GPb, K(i) = 1.7 mM) and acts as a physiological regulator of hepatic glycogen metabolism. Glucose binds to phosphorylase at the catalytic site and results in a conformational change that stabilizes the inactive T state of the enzyme, promoting the action of protein phosphatase 1 and stimulating glycogen synthase. It has been suggested that in the liver, glucose analogues with greater affinity for glycogen phosphorylase may result in a more effective regulatory agent. Several N-acetyl glucopyranosylamine derivatives have been synthesized and tested in a series of crystallographic and kinetic binding studies with GPb. The structural results of the bound enzyme-ligand complexes have been analysed together with the resulting affinities in an effort to understand and exploit the molecular interactions that might give rise to a better inhibitor. Comparison of the N-methylacetyl glucopyranosylamine (N-methylamide, K(i) = 0.032 mM) with the analogous beta-methylamide derivative (C-methylamide, K(i) = 0.16 mM) illustrate the importance of forming good hydrogen bonds and obtaining complementarity of van der Waals interactions. These studies also have shown that the binding modes can be unpredictable but may be rationalized with the benefit of structural data and that a buried and mixed polar/non-polar catalytic site poses problems for the systematic addition of functional groups. Together with previous studies of glucose analogue inhibitors of GPb, this work forms the basis of a training set suitable for three-dimensional quantitative structure-activity relationship studies. The molecules in the training set are void of problems and potential errors arising from the alignment and bound conformations of each of the ligands since the coordinates were those determined experimentally from the X-ray crystallographic refined ligand-enzyme complexes. The computational procedure described in this work involves the use of the program GRID to describe the molecular structures and the progam GOLPE to obtain the partial least squares regression model with the highest prediction ability. The GRID/GOLPE procedure performed using 51 glucose analogue inhibitors of GPb has good overall predictivity [standard deviation of error predictions (SDEP) = 0.98 and Q(2) = 0.76] and has shown good agreement with the crystallographic and kinetic results by reliably selecting regions that are known to affect the binding affinity.

Journal Article↗
PubMed1995

6-Aminoquinolones: a new class of quinolone antibacterials?

A series of quinolone- and 1,8-naphthyridone-3-carboxylic acids, designed by previous QSAR studies and characterized by an amino group at the C-6 position instead of the usual fluorine atom, were synthesized for the first time and evaluated for in vitro antibacterial activity. All of the synthesized compounds maintain good activity against Gram-negative bacteria (Pseudomonas aeruginosa excluded), and those compounds having a thiomorpholine group as the C-7 substituent also have good activity against Gram-positive bacteria. Some aspects of structure-activity relationships associated with the C-1, C-5, C-7, and C-8 substituents are also discussed. Derivatives 18g and 38g displayed the best activity with geometric mean MICs of 0.45 and 0.66-0.76 micrograms/mL against Gram-negative and Gram-positive bacteria, respectively. This antimicrobial activity reflects their ability to inhibit bacterial DNA-gyrase. The results of this study show that, while the C-6 fluorine is still the preferred substituent, good activity can still be obtained by replacing it with an amino group.

4-Quinolones↗
PubMed1995

Ethanol impairs post-prandial hepatic protein metabolism.

The effects of acute ethanol ingestion on whole body and hepatic protein metabolism in humans are not known. To simulate social drinking, we compared the effects of the association of a mixed meal (632 kcal, 17% amino acids, 50% glucose, 33% lipids) with a bottle of either table wine (ethanol content 71 g) or water on the estimates ([1-14C]-leucine infusion) of whole body protein breakdown, oxidation, and synthesis, and on the intravascular fractional secretory rates (FSR) of hepatically (albumin, fibrinogen) and extrahepatically (IgG) synthesized plasma proteins in two randomized groups (ethanol n = 7, water n = 7) of healthy nonalcoholic volunteers. Each study was carried out for 8 h. Protein kinetics were measured in the overnight post-absorptive state, over the first 4 h, and during a meal infusion (via a nasogastric feeding tube at constant rate) combined with the oral ingestion of wine or water, over the last 4 h. When compared with water, wine ingestion during the meal reduced (P < 0.03) by 24% the rate of leucine oxidation, did not modify the estimates of whole body protein breakdown and synthesis, reduced (P < 0.01) by approximately 30% the FSR of albumin and fibrinogen, but did not affect IgG FSR. In conclusion, 70 g of ethanol, an amount usual among social drinkers, impairs hepatic protein metabolism. The habitual consumption of such amounts by reducing the synthesis and/or secretion of hepatic proteins might lead to the progressive development of liver injury and to hypoalbuminemia also in the absence of protein malnutrition.

Blood Glucose↗