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At least 127 records · Page 7Linked to original sources
PubMed1995

Early mother-child relationship. The Copenhagen model of early preventive intervention towards mother-infant relationship disturbances.

The development of interactive patterns in the first year of life has been studied in healthy mother-infant pairs and in infants whose mothers have psychiatric or psychosocial problems, interfering with their relation to the child. During the first 3 months a relationship develops in healthy mother-infant pairs characterized by an intimate interchange of signals and responses between mother and child. The baby develops a basic pattern of social relating. During the next months the baby begins to expect the mother to fulfil it's wishes and still the mother adapts to and supports the baby's expanding capacities and needs. A beginning sense of self and not-self develops. At 10-12 months the infant is able to move around trying to examine everything within range. At this age the infant senses that there exist other wills and minds than it's own. The child looks at the mother and reads her expressions for "yes", "no", and "maybe". The mother can stop or encourage her child by verbal and body signals. At 12-18 months the child has developed a secure attachment apt to protect the child against later adversities. The development during the first year of life may be seriously disturbed if the mother cannot adapt to and support the baby's signals and needs. Relationship disturbances in the first year of life may be related to maternal or infant problems: Low birth weight babies, irritable babies with low stimulus tolerance and babies with withdrawal reactions following maternal alcoholism or drug abuse during pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[The relationship between work and vision in a preventive medicine context: the initial guidelines for a correct ergonomic ophthalmological approach proposed by the Italian Group for the Study of the Relationships between Work and Vision (G.I.L.V.). I. The presentation].

Modern technology poses numerous and complex problems concerning the implications for health in the work/vision relationship. While many of the hypotheses made in the past about the possibility of serious eye alterations in non-industrial workers have not been confirmed by recent investigations, considerable attention is at present being addressed to the short- and long-term effects of office work, especially in the case of tasks requiring prolonged visual effort "at near point". The prevalence of asthenopia in such workers is rather high, between 40 and 80%. The considerable specificity of the symptoms and the shortcomings in assessment of exposure in most of the research done so far has meant that no clear and unequivocal causal relationship between work involving intense visual effort and onset of asthenopia has been established. Nevertheless, from an analysis of the literature three main guidelines for a correct ergophthalmologic assessment can be identified: a) ophthalmologic assessments that will detect any transitory inefficiencies of the accommodation and convergence system; b) specific analysis of the technical and illumination conditions with special attention to the distribution of the natural and artificial light sources; c) quantification of airborne pollutants that have a potential irritative effect on the "ocular surface". Other environmental parameters that could be considered are electric and magnetic fields in the vicinity of VDTs and PCs and the microclimate of the workplace.

Ergonomics↗
PubMedDate not supplied

[The relationship between work and vision in a preventive medicine context: the initial guidelines for a correct ergonomic ophthalmological approach proposed by the Italian Group for the Study of the Relationship between Work and Vision (G.I.L.V.). II. The method].

In view of the numerous problems concerning the relationship between work and vision, the Italian Group for the Study of Work/Vision Relationships has developed a document that sets out initial guidelines for environmental monitoring and health surveillance in ergophthalmology. Particular emphasis is given to fact-finding inspections and collection of subjective assessments that will enable the occupational health physician to identify any adverse factors in the working environment and assess the visual effort of the operators. The importance of cooperation between occupational health physicians and ophthalmologists in the various phases of ergophthalmological assessment is stressed. An analytical list is provided of the parameters that the ophthalmologist should measure during eye examination as well as the appropriate assessments that the occupational health physician should perform if an ophthalmological specialist is not available. Suggestions for periodic controls on the basis of visual effort and ophthalmological status are made. It is the task of the occupational health physician to establish the fitness or otherwise of the patients for the job, and for this the Group is preparing further documents.

Environmental Monitoring↗
PubMed2007

Quantitative structure-activity relationship study of bitter di- and tri-peptides including relationship with angiotensin I-converting enzyme inhibitory activity.

Bitterness represents a major challenge in industrial application of food protein hydrolysates or bioactive peptides and is a major factor that controls the flavor of formulated therapeutic products. The aim of this work was to apply quantitative structure-activity relationship modeling as a tool to determine the type and position of amino acids that contribute to bitterness of di- and tri-peptides. Datasets of bitter di- and tri-peptides were constructed using values from available literature, followed by modeling using partial least square (PLS) regression based on the three z-scores of 20 coded amino acids. Prediction models were validated using cross-validation and permutation tests. Results showed that a single-component model could explain 52 and 50% of the Y variance (bitterness threshold) of bitter di- and tri-peptides, respectively. Using PLS regression coefficients, it was determined that hydrophobic amino acids at the carboxyl-terminus and bulky amino acid residues adjacent to the carboxyl terminal are the major determinants of the intensity of bitterness of di- and tri-peptides. However, there was no significant (p > 0.05) correlation between bitterness of di- and tri-peptides and their angiotensin I-converting enzyme-inhibitory properties.

Amino Acid Sequence↗
PubMed1992

Comparative toxicity of four chlorinated dibenzo-p-dioxins (CDDs) and their mixture. Part III: Structure-activity relationship with increased plasma tryptophan levels, but no relationship to hepatic ethoxyresorufin o-deethylase activity.

Male Sprague-Dawley rats were treated with an LD20, an LD50, and an LD80 of 2,3,7,8-tetrachlorodibenzo-p-dioxin (tetra-CDD), 1,2,3,7,8-pentachlorodibenzo-p-dioxin (penta-CDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (hexa-CDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (hepta-CDD), respectively, and a mixture of the four homologues where each CDD was represented at one-fourth its previously established LD20, LD50, and LD80, respectively. Plasma tryptophan levels, liver ethoxyresorufin O-deethylase (EROD) activities, and liver weights were determined at 2 and 8 days after treatment. Plasma tryptophan levels were dose-dependently elevated, particularly at 8 days after treatment, by as much as 75% over control levels. EROD activity in CDD-treated animals was induced 27- to 28-fold, as compared with vehicle-treated controls, but did not show any dose-response. Liver weights were also significantly increased by the CDD treatments, but the increase was not dose related. There was no correlation between plasma tryptophan levels, a biomarker of acute toxicity of CDDs, and EROD activity, a biomarker of arylhydrocarbon (Ah) receptor-mediated enzyme induction. It is concluded that the acute toxicity of CDDs, which correlates and shows perfect structure-activity relationship with reduced activities of key enzymes of intermediary metabolism, and the induction of enzymes by much lower doses of CDDs in the liver, have different mechanisms of action.

Animals↗
PubMed2005

Quantitative structure-activity relationship and quantitative structure-pharmacokinetics relationship of 1,4-dihydropyridines and pyridines as multidrug resistance modulators.

PURPOSE: The aim of this study was to develop quantitative structure-activity/pharmacokinetic relationships (QSAR/QSPKR) for a series of synthesized 1,4-dihydropyridines (DHPs) and pyridines as P-glycoprotein (P-gp) inhibitors. METHODS: Molecular descriptors of test compounds were generated by 3D molecular modeling using SYBYL and KowWin programs. Forward inclusion coupled with multiple linear regression (MLR) was used to derive a QSAR equation for Ca2+ channel binding. A multivariate statistical technique, partial least square (PLS) regression, was applied to derive a QSAR model for P-gp inhibition and QSPKR models. Cross-validation using the "leave-one-out" method was performed to evaluate the predictive performance of models. RESULTS: For Ca2+ channel binding, the MLR equation indicated a good correlation between observed and predicted values (R2 = 0.90), and cross-validation confirmed the predictive ability of the model (Q2 = 0.67). For P-gp reversal, the model obtained by PLS could account for most of the variation in P-gp inhibition (R2 = 0.76) with fair predictive performance (Q2 = 0.62). Nine structurally related 1,4-DHP drugs were used for QSPKR analysis. The models could explain the majority of the variation in clearance (R2 = 0.90), and cross-validation confirmed the prediction ability (Q2 = 0.69). CONCLUSION: QSAR/QSPKR models were developed, and the QSAR models were capable of identifying synthesized 1,4-DHPs and pyridines with potent P-gp inhibition and reduced Ca2+ channel binding. The QSPKR models provide insight into the contribution of electronic, steric, and lipophilic factors to the clearance of DHPs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Relationship between disease activity and dose-response relationships with beta interferon therapies in the treatment of multiple sclerosis.

Beta-interferon (IFNbeta) therapy in patients with multiple sclerosis has proven efficacious in the treatment of multiple sclerosis (MS). Numerous studies have demonstrated a decrease in relapse rates, decreases in new gadolinium enhanced lesions, slowed accumulation of disability, and decreases in the accumulation of lesion burden on T2 weighted MRI scans. There has been a heterogeneity of responsiveness to IFNbetas in individual patients. Responsiveness to IFNbeta therapy is discussed in view of pre-existing disease activity. Disease activity can be objectively measured using the frequency and volume of new gadolinium enhancing lesions. Disability may be dependent upon lesion location, frequency, and by the intensity of inflammation within lesions. The presence of a dose-response relationship with IFNbeta therapy in MS is supported by available data. Evidence is reviewed supporting the argument that responsiveness to IFNbeta therapy depends, in part, on pre-existing disease activity.

Adjuvants, Immunologic↗
PubMed2001

Structure-activity relationships in platelet-activating factor (PAF). 11-From PAF-antagonism to phospholipase A(2) inhibition: syntheses and structure-activity relationships in 1-arylsulfamido-2-alkylpiperazines.

1-Benzoyl-2-alkyl piperazines are strong inhibitors of Group I and II secreted PLA(2)s. An improvement of their activity was obtained by replacing the amide function by a sulfamide and by introduction of electrodonor substituents on the para position of the benzenesulfonyl moiety. Neither the position on one of the carbon of the piperazine ring nor the absolute configuration of this carbon have an effect on the affinity for one or the other group of PLA(2), but the lipophilicity remains for these series an essential parameter. In addition structure-activity relationships allow new hypothesis on interaction of these piperazine derivatives with the catalytic site of PLA(2)s.

Animals↗
PubMed1980

Quantitative structure-pharmacokinetic relationships derived on antibacterial sulfonamides in rats and its comparison to quantitative structure-activity relationships.

Quantitative structure-pharmacokinetic relationships have been derived for a series of substituted 2-sulfapyridines. Pharmacokinetic parameters, such as elimination rate constant (ke), clearance (Cl), and protein-binding constant (Kassoc), have been determined in rats. The observed variation is statistically significant, explained by changes in the lipophilic (deltaRm), electronic (pKa), and steric effects (I, ES) of the substituents. The obtained correlations are discussed with respect to the previously derived correlations for the antibacterial activity of these compounds. A scale up of the results opens up the possibility of a rational synthesis of highly active sulfonamides with special pharmacokinetic properties because lipophilicity influences strongly the pharmacokinetic properties, whereas no influence on the degree of antibacterial effect is observed. Steric substituent influence is opposite on specific binding to bacterial enzymes and unspecific binding to serum proteins.

Animals↗
PubMed2002

Structure-activity relationships of a novel class of endothelin-A receptor antagonists and discovery of potent and selective receptor antagonist, 2-(benzo[1,3]dioxol-5-yl)-6-isopropyloxy-4-(4-methoxyphenyl)-2H-chromene-3-carboxylic acid (S-1255). 1. Study on structure-activity relationships and basic structure crucial for ET(A) antagonism.

A novel series of endothelin-A (ET(A)) selective receptor antagonists having a 2H-chromene skeleton are described. A lead compound, 2-(benzo[1,3]dioxol-5-yl)-2H-chromene-3-carboxylic acid (3), was found by modifications of our own angiotensin II antagonist. A structure-activity relationship (SAR) study of 3 reveals that the structural requirements essential for potent and selective ET(A) receptor binding affinity are the m,p-methylenedioxyphenyl, carboxyl, and isopropoxy groups at the 2-, 3-, and 6-positions, respectively, on the (R)-2H-chromene skeleton. The substituent at the 4-position is also important for improving the activity, and various hydrophobic functional groups of 6-9 A such as liner, branched, and cyclic aliphatic groups, unsubstituted and substituted aryl groups, and even halogen atoms were acceptable. These results suggest that (R)-2-(benzo[1,3]dioxol-5-yl)-6-isopropoxy-2H-chromene-3-carboxylic acid, formula 108, is the crucial basic structure to be recognized by the ET(A) receptor. The most potent compound is (R)-48 (S-1255), which binds to the ET(A) receptor with an IC(50) value of 0.19 nM and is 630-fold selective for the ET(A) receptor than for the ET(B) receptor. This compound has 55% oral bioavailability in rats. On the basis of the SAR, the roles of each substituent in the receptor binding are discussed.

Animals↗
PubMed1997

Synthesis and structure-activity relationships of a new model of arylpiperazines. 2. Three-dimensional quantitative structure-activity relationships of hydantoin-phenylpiperazine derivatives with affinity for 5-HT1A and alpha 1 receptors. A comparison of CoMFA models.

A series of 48 bicyclohydantoin-phenylpiperazines (1-4) with affinity for 5-HT1A and alpha 1 receptors was subjected to three-dimensional quantitative structure-affinity relationship analysis using comparative molecular field analysis (CoMFA), in order to get insight into the structural requirements that are responsible for 5-HT1A/alpha 1 selectivity. Good models (high cross-validation correlations and predictive power) were obtained for 5-HT1A and alpha 1 receptors. The resulting 3D-QSAR models rationalize steric and electrostatic factors which modulate binding to 5-HT1A and alpha 1 receptors. A comparison of these models gives an additional understanding for 5-HT1A/alpha 1 selectivity: (a) Substitution at the ortho position by a group with negative potential is favorable to affinity for both receptors. (b) The meta position seems to be implicated in 5-HT1A/alpha 1 selectivity. While the 5-HT1A receptor is able to accommodate bulky substituents in the region of its active site, the steric requirements of the alpha 1 receptor are more restricted (optimum volume of substituent 11-25 A3). (c) For both receptors the para position represents a region where the volume accessible by the ligands is limited. (d) The hydantoin moiety and the side chain length seem to modulate not only the affinity but also 5-HT1A/alpha 1 selectivity. The 3D-QSAR models reveal an useful predictive information for the design of new selective ligands.

Animals↗
PubMedDate not supplied

Structure-activity relationships for contact allergenic potential of gamma,gamma-dimethyl-gamma-butyrolactone derivatives. 2. Quantitative structure-skin sensitization relationships for alpha-substituted-alpha-methyl-gamma,gamma-dimethyl-gamma-butyrolactone s.

A skin sensitization cross-challenge dataset for a series of alpha-(X-substituted-methyl)-gamma,gamma-dimethyl-gamma-butyrolactones is analyzed in terms of the relative alkylation index (RAI) model. The data analyzed consist of guinea pig sensitization response data for tests in which one lactone derivative is used for the induction stage and then the animals are challenged with another lactone derivative to elicit the response. RAI values are based on calculated log P (octanol/water) values together with measured relative rate constants for reactions of the lactones with n-butylamine to form alpha-methylene-gamma,gamma-dimethyl-gamma-butyrolactone. Plots of biological response against RAI for induction (RAIi) for sets of data in which the same compound is used for challenge have the double-sigmoid shape typical of sensitization response--RAIi plots, with some points in the overload region. Relative elicitation potential (REP) values, defined in terms of the biological response when sensitized animals are challenged with the compound in question relative to the response when the same animals are challenged with a chosen reference compound, are obtained. Consistent with the RAI model, plots of REP against RAIc, the RAI value corresponding to challenge, are linear and the slopes of plots corresponding to different reference compounds are, within the limits of experimental error, in the same ratio as the REP values of the reference compounds. Finally, multiple linear regression analysis gives a quantitative structure-activity relationship (QSAR) covering the complete set of cross-challenge data, relating the biological responses to the RAIi and RAIc values.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed2005

Structure-activity relationship study of some triazolinone based compounds with antagonistic balanced activity on angiotensin II receptor subtypes AT1 and AT2. A three-dimensional quantitative structure-activity relationship investigation.

Angiotensin II (AII) receptor antagonists have attracted much attention as anti-hypertensive agents in recent times following the discovery of side effects associated with angiotensin converting enzyme (ACE) inhibitors. Various lead structures of the compounds of this category are reported in the literature. Studying the structure-activity relationships (SAR) for such compounds has been a fascination for scientists and efforts have been made to identify the essential physico-chemical requirements for the angiotensin type 1 (AT1) receptor selective, angiotensin type 2 (AT2) receptor selective and some AT,/ AT2 balanced antagonistic activity compounds. With an aim to identify the structural requirements for balanced activity and differentiate between the features individually responsible for AT1 and AT2 antagonistic activities, a quantitative SAR (QSAR) analysis was carried out on a series of triazolinone based balanced AII receptor antagonists. The statistically significant equations with r > 0.88, chance < 0.01, q2 > 0.60 and F values at least three times greater than those reported were obtained for both AT1 and AT2 receptor subtypes antagonistic activities. A comparative study of the parameters responsible for AT1 and AT2 receptor antagonistic activities is carried out in order to identify the features that can be modulated to obtain balanced compounds. It has been observed that the most reliable equations obtained in the study show the contribution of hydrophobic parameters: logarithm of partition coefficient (logP), thermodynamic parameters: bend energy (Eb), and electronic parameters: electronic energy (Eelec) parameters towards AT1 anatgonistic activity, and thermodynamic parameters: total energy (E), steric parameters: principal moment of inertia along the Y-axis (PMIY) and electronic parameters: electronic energy (Eelec) parameters towards AT2 antagonistic activity. The parameter Eelec is common but its effect towards the two activities is opposite, negative for AT1 and positive for AT2.

Angiotensin II Type 2 Receptor Blockers↗
PubMed1988

Underestimation of dose--response relationship with particular reference to the relationship between the dietary intake of mercury and its concentration in blood.

Wide discrepancies have been observed between controlled and uncontrolled intake studies of the relationship of blood mercury concentration to intake of mercury. The probable reason for the apparent discrepancies is that the within-subject variation of mercury intake in the uncontrolled studies was almost certainly considerably larger than the within-subject variation in blood mercury concentration; in these circumstances, the apparent slope obtained from a linear regression of blood mercury on intake will invariably be much smaller than the true slope. Studies of the exposure or intake of any substance should therefore include a consideration of the likely within-subject variation in the exposure or intake relative to that in the effect.

Analysis of Variance↗
PubMed2001

Structure-activity relationship (SAR) studies on oxazolidinone antibacterial agents. 2. Relationship between lipophilicity and antibacterial activity in 5-thiocarbonyl oxazolidinones.

5-Thiourea and 5-dithiocarbamate oxazolidinones were synthesized as a continuation of research on 5-thiocarbonyl oxazolidinone antibacterial agents considering the hydrophobic parameters of the molecule. The structure-activity relationship (SAR) study revealed that the antibacterial activity on 5-thiocarbonyl oxazolidinones was significantly affected by the lipophilicity, especially the calculated log P value and the balance between 5-hydrophilic (or hydrophobic) substituent and hydrophobic (or hydrophilic) substituents on the benzene ring. Some of 5-thiocarbonyl oxazolidinones were found to have good in vitro antibacterial activity against gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE).

Anti-Bacterial Agents↗
PubMed1999

Parabolic quantitative structure-activity relationships and photodynamic therapy: application of a three-compartment model with clearance to the in vivo quantitative structure-activity relationships of a congeneric series of pyropheophorbide derivatives used as photosensitizers for photodynamic therapy.

An open three-compartment pharmacokinetic model was applied to the in vivo quantitative structure-activity relationship (QSAR) data of a homologous series of pyropheophorbide photosensitizers for photodynamic therapy (PDT). The physical model was a lipid compartment sandwiched between two identical aqueous compartments. The first compartment was assumed to clear irreversibly at a rate K0. The measured octanol-water partition coefficients, P(i) (where i is the number of carbons in the alkyl chain) and the clearance rate K0 determined the clearance kinetics of the drugs. Solving the coupled differential equations of the three-compartment model produced clearance kinetics for each of the sensitizers in each of the compartments. The third compartment was found to contain the target of PDT. This series of compounds is quite lipophilic. Therefore these drugs are found mainly in the second compartment. The drug level in the third compartment represents a small fraction of the tissue level and is thus not accessible to direct measurement by extraction. The second compartment of the model accurately predicted the clearance from the serum of mice of the hexyl ether of pyropheophorbide a, one member of this series of compounds. The diffusion and clearance rate constants were those found by fitting the pharmacokinetics of the third compartment to the QSAR data. This result validated the magnitude and mechanistic significance of the rate constants used to model the QSAR data. The PDT response to dose theory was applied to the kinetic behavior of the target compartment drug concentration. This produced a pharmacokinetic-based function connecting PDT response to dose as a function of time postinjection. This mechanistic dose-response function was fitted to published, single time point QSAR data for the pheophorbides. As a result, the PDT target threshold dose together with the predicted QSAR as a function of time postinjection was found.

Animals↗
PubMed1990

Chromosomal analysis and phylogenetic relationships in the Drosophila nasuta subgroup. I. Phylogenetic relationships within the Drosophila sulfurigaster species complex.

Phylogenetic relationships within the Drosophila sulfurigaster species-complex, which belongs to the D. nasuta subgroup, were investigated on the basis of chromosomal constitution and morphology. D. pulaua is thought to be the most ancestral species, from which D. s. sulfurigaster and D. s. bilimbata derived in one branch and D. s. albostrigata and D. s. neonasuta in another branch.

Animals↗
PubMed1994

Phylogenetic relationships among extant classes of echinoderms, as inferred from sequences of 18S rDNA, coincide with relationships deduced from the fossil record.

In spite of the rich fossil record and multiple descriptions of morphological and embryological characteristics, the origin and subsequent evolution of echinoderms remain highly controversial issues. Using sequence data derived from 18S rDNA, we have investigated the phylogenetic relationships among five extant classes of echinoderms--namely, crinoids, asteroids, ophiuroids, echinoids, and holothurians. Almost complete sequences of 18S rDNA were determined for one species in each class, and phylogenetic trees were constructed both by the neighbor-joining method and by the maximum-likelihood method, with a hemichordate as an outgroup. The trees constructed by these methods support the hypothesis that the phylum Echinodermata can be subdivided into two subphyla, Pelmatozoa and Eleutherozoa. The class Holothuroidea, which has been the subject of debate with respect to whether the members are primitive or advanced echinoderms, did not occupy a primitive position but had an affinity for the class Echinoidea. Since both trees gave different branching topologies for the order of emergence of asteroids and ophiuroids, it seems likely that these two groups emerged within a very short period of time. A rough estimate of the timing of the divergence of the five classes from the present molecular analysis coincided with that deduced from the fossil record.

Animals↗