Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “interaction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources
PubMed1979

Interactions of cartilage proteoglycans with hyaluronate. Inhibition of the interaction by modified oligomers of hyaluronate.

Oligomers of hyaluronic acid were prepared by digestion of hyaluronic acid from rooster combs with testicular hyaluronidase (hyaluronate 4-glycanohydrolase, EC 3.2.1.35), leech head hyaluronidase (hyaluronate 3-glycanohydrolase, EC 3.2.1.36), and with fungal hyaluronidase (hyaluronate lyase from Streptomyces hyalurolyticus). The oligomers were fractionated by gel permeation, using Sephadex G-50. Oligomers isolated after incubation of the hyaluronic acid with the testicular hyaluronidase were further modified. To prepare oligomers with N-acetylglucosamine at both ends, terminal nonreducing glucuronic acid residues were removed with beta-glucuronidase. Reducing terminal N-acetylglucosamine residues were removed by reaction under mildly alkaline conditions. The reducing terminal N-acetylglucosamine residues were also reduced with sodium borohydride to form N-acetylglucosaminitol. The potentials of the various oligosaccharides to bind to the proteoglycan from bovine nasal septum cartilage were estimated by determining their effectiveness as inhibitors of the proteoglycan-hyaluronate interaction. The present study shows that, to bind maximally to the proteoglycan, the hyaluronate oligosaccharide must be at least 10 sugar residues in length and be terminated at the nonreducing and reducing ends with a glucuronate residue and an N-acetylglucosamine residue, respectively. Sugar residues extended beyond this basic decasaccharide, do not interact with the hyaluronate binding site on the proteoglycan.

Animals↗
PubMed1979

The interaction of a tyrosyl residue and carboxyl groups in the specific interaction between Streptomyces subtilisin inhibitor and subtilisin BPN'. A chemical modification study.

An ultraviolet absorption difference spectrum that is typical of a change in ionization state (pKa 9.7 leads to greater than 11.5) of a tyrosyl residue has been observed on the binding between Streptomyces subtilisin inhibitor (SSI) and subtilisin BPN' [EC 3.4.21.14] at alkaline pH, ionic strength 0.1 M, at 25 degrees C (Inouye, K., Tonomura, B., and Hiromi, K., submitted). When the complex of SSI and subtilisin BPN' is formed at an ionic strength of 0.6 M and pH 9.70, the characteristic features of the protonation of a tyrosyl residue in the difference spectrum are diminished. These results suggest that the pKa-shift of a tyrosyl residue observed at alkaline pH and lower ionic strength results from an electrostatic interaction. Nitration of tyrosyl residues of SSI and of subtilisin BPN' was performed with tetranitromethane (TNM). By measurements of the difference spectra observed on the binding of the tyrosyl-residue-nitrated SSI and the native subtilisin BPN', and on the binding of the native SSI and the tyrosyl-residue-nitrated subtilisin BPN' and alkaline pH, the tyrosyl residue in question was shown to be one out of the five tyrosyl residues of pKa 9.7 of the enzyme. This tyrosyl residue was probably either Tyr 217 or Tyr 104 on the basis of the reactivities of tyrosyl residues of the enzyme with TNM and their locations on the enzyme molecule. Carboxyl groups of SSI were modified by covalently binding glycine methyl ester with the aid of water-soluble carbodiimide, in order to neutralize the negative charges on SSI. In the difference spectrum which was observed on the binding of subtilisin BPN' and the 5.3-carboxyl-group-modified SSI at alkaline pH, the characteristic features of the protonation of a tyrosyl residue were essentially lost, and the difference spectrum is rather similar to that observed on the binding of the native SSI and the enzyme at neutral pH. This phenomenon indicates that the pKa of a tyrosyl residue of the enzyme is shifted upwards by interaction with carboxyl group(s) of SSI on the formation of the enzyme-inhibitor complex.

Amino Acids↗
PubMed1965

Clinical effects of interaction between drugs. Review of points at which drugs can interact.

The prescribing of mixtures is unfortunately traditional and has a psychological appeal, which is being encouraged by many manufacturers. Doctors must have a sound working knowledge of the mode of action of modern drugs in order to use them effectively and safely, particularly when they are used together.In this context ;drug' means any biologically active substance. Interaction between drugs can be inapparent (if equal and opposite), antagonistic or synergistic. This includes summation and potentiation.INTERACTION BETWEEN DRUGS CAN ARISE IN A VARIETY OF WAYS: directly; in the intestine or other absorptive site; in transit; at the receptor or at another site in the same biological system; by accelerating or slowing drug metabolism; or by influencing excretion.Most of these mechanisms are considered in detail in this Symposium. With greater understanding of underlying mechanisms many of the untoward interactions now being increasingly reported might be foreseen and avoided.

Drug Synergism↗
PubMed1984

Interaction between bacterial metabolites and some pesticides. I. Interaction between the phenolic compounds produced by Pseudomonas acidovorans and the herbicide Venzar.

The phenolic compounds produced by Pseudomonas acidovorans interacted with the herbicide Venzar changing its phytotoxicity. Bioassay with Chlorella vulgaris and lettuce showed that the interaction of the bacterial phenols and Venzar was synergistic or antagonistic depending on the concentration of the phenolic compounds its chemical structure and pH of the environment. The humic-like polymers isolated from the bacterial culture reduced to a small extent the phytotoxicity of Venzar. It was found that [C14]-labelled Venzer was incorporated into the bacterial humic-like compounds due to the action of the enzymatic system of the bacteria.

Chlorella↗
PubMed1980

The Chédiak-Higashi syndrome; the nature of the giant neutrophil granules and their interactions with cytoplasm and foreign particulates. I. Progressive enlargement of the massive inclusions in mature neutrophils. II. Manifestations of cytoplasmic injury and sequestration. III. Interactions between giant organelles and foreign particulates.

Defective bactericidal functioning of polymorphonuclear leukocytes (PMNs) from patients with the Chédiak-Higashi syndrome (CHS) has been related in previous reports to a failure of the giant granules characteristics of the disorder to participate in degranulation after uptake of foreign particulates by neutrophils. However, the reason massive CHS inclusions do not fuse with and discharge their contents into phagocytic vacuoles has not been defined. The problem is particularly puzzling because it has been postulated that the hugh organelles in CHS neutophils originate by fusion of small azurophilic granules in promyelocytes and myelocytes. The present series of investigations into the cytopathology of the CHS has employed electron microscopy and ultrastructural cytochemistry to characterize the progressive enlargement of the hugh bodies in mature PMNs, their interaction with cytoplasmic constituents resulting in various manifestations of cell injury, and their response to foreign particulates. Each study clarifies abnormal features of the giant organelles essential to the understanding of their role in the defective bactericidal function of CHS neutrophils. The first report demonstrates that most of the hugh inclusions in PMNs are not primary lysosomes. The interaction and fusion of giant azurophilic granules with each other, with normal-sized primary and secondary granules, and with cytoplasmic components converts the massive primary granules into huge secondary lysosomes. Transformation to secondary hysosomes represents a critical alteration in the state of the giant granules that underlies their damaging influence on the cytoplasm and loss of reactivity wtih phagocytic vacuoles.

Adolescent↗
PubMed1980

Dynamics of lipid-protein interactions. Interaction of apolipoprotein A-II from human plasma high density lipoproteins with dimyristoylphosphatidylcholine.

ApoA-II and dimyristoylphosphatidylcholine (DMPC) spontaneously associate to give three different complexes whose structures are determined by the initial reactant concentration and by the reaction temperature with respect to Tc (23.9 degrees C), the gel to liquid crystalline transition temperature of DMPC. At an initial lipid to protein ratio of 45/1, a single complex (2.29 x 10(5) daltons) is quantitatively formed at all temperatures between Tc - 4 degrees C and Tc + 6 degrees C. When the 45/1 complex is mixed with DMPC liposomes there is lipid exchange but no net transfer of lipid, so that the structure of the complex remains unaltered. At an initial molar ratio of 100 to 300:1, the reaction scheme is more complex. At 24 degrees C a 240/1 complex (1.5 x 10(6) daltons) is formed from a precursor 75/1 complex (3.43 x 10(5) daltons) if excess (approximately 300 mol/mol) lipid is present. The 75/1 complex exhibits lipid exchange in the presence of added DMPC liposomes at 24 degrees C, and both the 75/1 and the 240/1 complex can be converted to smaller protein-rich complexes in the presence of added apoA-II. These results suggest that the initial lipid/protein ratio and the physical state of a lipid or lipid . protein complex determines the composition and structure of the resulting complex and support the view that lipid-protein interactions are stronger than protein-protein or lipid-lipid interactions.

Apolipoprotein A-II↗
PubMed1981

Mycoplasma-lymphocyte interactions: Ir gene control of mitogenesis and a paradoxical interaction with thy-1 bearing cells.

A novel interaction occurs between mycoplasmas and lymphocytes whereby the mycoplasmas behave as multivalent ligands and, following attachment to the lymphocyte plasma membrane, redistribute to one pole of the cell. This mycoplasma-capping event is accompanied by co-capping of certain specific lymphocyte surface antigens. Mycoplasma capping occurs on both lymphoblastoid cells and resting lymphocytes. There is a high degree of correlation between mycoplasma capping on resting (splenic) lymphocytes and blast transformation of these cells. This appears to be a general phenomenon, and many different mycoplasma species are mitogenic for lymphocytes from a number of animal species, including human. In the mouse, mycoplasma-induced triggering does not appear to be influenced by H-2 differences and the primary lymphocyte triggered is the B cell. In other animal species T cells or B and T cells are stimulated. The importance of these interactions with reference to mycoplasma pathogenesis will be discussed.

Animals↗
PubMed1982

[Interaction of phospholipids with 3-oxosteroid-delta 1-dehydrogenase in adsorptional model biomembranes. Interaction of the enzyme from Mycobacterium rubrum with liposomes].

A comparative study of the activity of 3-oxosteroid-delta 1-dehydrogenase from Mycobacterium rubrum 121 in solution and after interaction with liposomes prepared from phospholipids of the same microorganism was carried out. It was demonstrated that at pH 6.6 the enzyme activity in the presence of liposomes is increased. The dependence of this effect on the amount of phospholipids and protein in the system, on the ratio and on the time of their coincubation was established. The activating effect of liposomes is not changed by Mg2+ or EDTA. The crucial role in the enzyme association with the phospholipid matrix belongs to electrostatic bonds which are destroyed upon increase in the ionic strength within the physiological range. The enzyme transition to the free state is accompanied by a fall in the activity. The possible role of these interactions in regulation of enzymatic activity in the cell is discussed.

Adsorption↗
PubMed1978

Interaction of metal ions with nucleic acids. Interaction of copper(II) with inosine and its derivatives.

1. The interaction of copper(II) with inosine, 2'-deoxyinosine, 1-methylinosine, 7-deazainosine, 6-methoxypurine riboside and IMP was examined. 2. Copper binds with the purine base of the nucleosides, and in IMP also with the phosphate group. Non interaction with ribose hydroxyl groups was observed. 3. In non-aqueous medium, the main site of copper binding is N-7 of inosine and 1-methylinosine, and additionally N-1 in 6-methoxypurine riboside. 4. In aqueous medium, coordination of copper with N-1 and N-7 of inosine and IMP is pH-dependent. 5. Formation of either a five-membered copper chelate with N-7 and oxygen at C-6, or a four-membered chelate of the type C(6)-O-Cu-N(1), is rather unlikely. 6. The crystalline copper-IMP complex [Cu(C10H11O8N4P).(H2O)] contains presumably two copper atoms coordinated in different manner. The phosphate group and N-7, but not the carbonyl oxygen, participate in the complex formation.

Chemical Phenomena↗
PubMed1979

Interaction of troponin subunits. The interaction between the inhibitory and tropomyosin-binding subunits.

The interaction of troponin-I and troponin-T was demonstrated by circular dichroism and gel filtration. Troponin-I gives a negative circular dichroism band between 300 and 260 nm while troponin-T gives two weak positive bands, one at 290 nm and the other at 263 nm. When troponin-I and troponin-T were mixed, the complex produced a strong negative circular dichroism band with a maximum around 280 nm. This band was most intense with a molar ratio of troponin-T to troponin-I of 1:1. The intensity of the band was 2.4 times that expected from the separate components. The interaction was independent of salt concentration from 0.15 to 0.5 M KCl. Gel filtration on Sephacryl S-200 showed that a stable 1:1 complex was formed between troponin-T and troponin-I. When troponin-C was added to the complex of troponin-T.troponin-I; the reconstituted troponin had a circular dichroism spectrum identical to that of native troponin. The oxidation state of troponin-I was important in reconstituting troponin. Oxidized troponin-I produced less change in the near ultraviolet circular dichroism when added to troponin-T and the troponin-C than did reduced troponin-I. This showed the subunits were not assembled correctly with oxidized troponin-I. When the reconstituted complex was reduced, the circular dichroism was restored to that of native troponin. Troponin reconstituted with oxidized troponin-I did not confer calcium sensitivity on actomyosin ATPase; activity was restored by reducing the complex.

Circular Dichroism↗
PubMed1994

Thermal inactivation of tryptophan synthase. Stabilization by protein-protein interaction and protein-ligand interaction.

This study investigates effects of ligands on thermal inactivation of the tryptophan synthase alpha and beta 2 subunits alone and in the alpha 2 beta 2 complex. Addition of pyridoxal phosphate to the apo-beta 2 subunit increases the temperature of one-half inactivation (Ti) from 52 to 77 degrees C. Ligands that promote association of the alpha and holo-beta 2 subunits markedly stabilize the more temperature-labile alpha subunit in the alpha 2 beta 2 complex from irreversible thermal denaturation. The combination of a beta 2 subunit ligand (L-serine) with an alpha subunit ligand (alpha-glycerol 3-phosphate) raises the inactivation temperature (Ti) of the alpha subunit in the holo-alpha 2 beta 2 complex from 54 to 66 degrees C. In contrast, values of Ti for inactivation of the alpha and beta subunits in the holo-alpha 2 beta 2 complex are more similar to respective values for the isolated alpha subunit (50 degrees C) and holo-beta 2 subunit (77 degrees C). Surprisingly, the addition of L-serine results in a larger decrease in the Ti of the beta 2 subunit in the holo-alpha 2 beta 2 complex (78 degrees C-->64 degrees C) than in Ti of the holo-beta 2 subunit alone (77 degrees C-->71 degrees C). The observation that ligands have different effects on the isolated and associated subunits provides evidence that the alpha and beta 2 subunits do not fully dissociate during thermal inactivation of the alpha 2 beta 2 complex at pH 7.8 and at approximately 0.1 ionic strength. Our results demonstrate that linkage between protein-ligand interactions and protein-protein interactions affects the conformational stability of the tryptophan synthase alpha 2 beta 2 complex.

Apoenzymes↗
PubMedDate not supplied

The interactive patient: a multimedia interactive educational tool on the World Wide Web.

To develop a physician-friendly continuing medical education tool for use on the World Wide Web, and to improve physicians' clinical and history taking skills, developers at Marshall University designed a multimedia interactive patient encounter for a Web server. Any physician with access to the Internet can use this program to take a history, perform a physical examination, order laboratory and radiologic studies, and submit a diagnosis and treatment plan. The system evaluates the user's performance electronically and delivers CME credits by mail. The Interactive Patient has been embraced by the medical community, with many institutions providing links to this new tool and hundreds of physicians using it. The enthusiasm of most users demonstrates that combining education with fun enhances the learning experience.

Attitude to Computers↗
PubMed1995

Determination of analgesic interaction between acetaminophen and d-propoxyphene obtained by means of the surface of synergistic interaction.

The analgesic effects of acetaminophen, p.o., (ACE) and d-propoxyphene, s.c., (PROP) administered either separately or in 24 different combinations were determined in a model of pain-induced functional impairment in the rat. This allowed us to detect the analgesic interaction profile of the combinations. Furthermore, we set out to determine the optimal degree of enhancement obtained with a specific combination of the above drugs by means of the surface of synergistic interaction (SSI) of the combinations. This parameter was calculated from the total analgesic effect produced by the combination after having subtracted the analgesic effect produced by each drug alone. The ED50s for ACE and PROP were 286.1 +/- 1.4 mg/kg and 66.3 +/- 1.2 mg/kg, respectively. Over the dose ranges used, the analgesic activities of both ACE and PROP tended to be smaller than those of their respective combinations. Furthermore, 11 combinations showed various degrees of enhancement (p<0.01), while the others (13) exhibited additive analgesic effects. The combination of ACE (562.3 mg/kg) and PROP (56.2 mg/kg) produced the maximum analgesic effect. However,5 combinations of ACE with PROP (177.8-56.2, 316.2-10.0, 316.2-17.8, 316.2-56.2 and 562.3-10.0 mg/kg) produced the highest enhancement. The SSI clearly showed which combination of these analgesic drugs produced the highest degree of enhancement in the rat. This study shows that a specific combination ratio of analgesic drugs can produce optimum enhancement of their analgesic effects.

Acetaminophen↗
PubMed1997

Use of confocal microscopy to localize the SHBG interaction with human breast cancer cell lines--a comparison with serum albumin interaction.

This work has allowed a comparison between the interaction of two principal plasma estradiol-binding proteins, serum albumin and Sex Hormone Binding Globulin (SHBG), with human breast cancer cells in culture (MCF-7 and MDA-MB 231), using a protocol which protects the integrity of cell structure. We showed that serum albumin was highly internalized by cells whereas SHBG interacted essentially at the plasma membrane level, and this whatever the contents of the receptor estrogen cells. If, by its high plasma concentration, serum albumin is internalized in a non-specific way and can thus fit into intracellular traffic, SHBG, by its membrane binding, seems to have a specific action toward target cells.

Breast Neoplasms↗
PubMedDate not supplied

Studies on interactions between traditional herbal and Western medicines. IV: lack of pharmacokinetic interactions between Saiko-ka-ryukotsu-borei-to and carbamazepine in rats.

The possibility of pharmacokinetic interactions between Saiko-ka-ryukotsu-borei-to extract powder (TJ-12), a widely used traditional Chinese herbal (Kampo) medicine, and carbamazepine (CBZ), an important anti-epileptic drug, was examined in rats. There were no significant differences in the serum protein binding of CBZ and carbamazepine- 10,11-epoxide (CBZ-E), its active metabolite, at two concentrations (1 and 10 Bg/ml) between twogroups pretreated orally with the vehicle andTJ-12 suspension (1 g/kg/d, p.o.) for 1 week. One-week repeated pretreatment with TJ- 12 (1 g/kg/d) did not influence liver weight, contents of cytochromes P450 and b5 in hepatic microsomes or the formation rate of CBZ-E from CBZ by its microsomes, while pretreatment with phenobarbital (80 mg/kg/d, i.p.) significantly increased these parameters. Neither a single nor 1-week repeated oral pretreatment with TJ-12 (1 g/kg/d) affected the plasma concentration-time profile and any pharmacokinetic parameter of CBZ or CBZ-E after oral administration of CBZ (50 mg/kg). These results indicated that oral co-administration of TJ-12 with CBZ has no effect ofthe pharmacokinetics of CBZ or CBZ-E in rats. Concomitant treatment with TJ- 12 and CBZ appears to be pharmacokinetically safe in humans.

Animals↗
PubMed2001

Interaction of cyanine dyes with nucleic acids. XXI. Arguments for half-intercalation model of interaction.

The spectral luminescent properties of two groups of monomethine cyanine dyes were studied in the presence of DNA. The first group included five dyes with 5,6-methylenedioxy-[d]-benzo-1,3-thiazole heterocycle and their unsubstituted analogs. Five monomethine pyrylium cyanines and their N-methyl-pyridine analogs were included in the second group. In each pair the pyrylium and pyridine dyes had similar geometry but differed in charge density distribution. The results presented some evidence in favor of the half-intercalation interaction mode between the studied dyes and DNA. When the benzothiazole residue had the lowest electron donor ability between the two heterocycles in the dye molecule, its substitution with the bulky methylenedioxy group led to a significant decrease in fluorescence enhancement of the dye-DNA complex. On the contrary, when the substituents that create steric hindrance (e.g., methylenedioxy and methyl groups) were introduced into the heterocycle with the higher electron donor ability, the fluorescence enhancement value of the dye-DNA complex was virtually unchanged. The changes in the Stock's shift values upon the formation of the dye-DNA complexes were in agreement with the proposed half-intercalation model. Interestingly, in the dye-DNA complexes the pyrylium dyes probably resided in a place similar to the pyridine ones. It is possible that the benzothiazole (or benzooxazole) ring intercalated between the DNA bases and the pyrylium (or pyridine) residue was located in the DNA groove closer to the phosphate backbone.

Animals↗
PubMed1982

Physiologically based pharmacokinetics of drug-drug interaction: a study of tolbutamide-sulfonamide interaction in rats.

A blood flow rate-limited pharmacokinetic model was developed to study the effect of sulfonamide on the plasma elimination and tissue distribution of 14C-tolbutamide (TB) in rats. The sulfonamides (SA) used were sulfaphenazole (SP), sulfadimethoxine (SDM), and sulfamethoxazole (SMZ). The tissue-to-plasma partition coefficients (Kp) of all tissues studied, i.e., lung, liver, heart, kidney, spleen, G.I. tract, pancreas, brain, muscle, adipose tissue, and skin, increased in the presence of SA, but except for brain, liver, and spleen, the tissue-to-plasma unbound concentration ratio (Kp,f) of other tissues did not show a significant alteration. This suggested that the tissue binding of TB is not affected by SA and that the increase of Kp is due mainly to the displacement of plasma protein-bound TB by SA. The concentrations of TB in several tissues and plasma were predicted by a physiologically based pharmacokinetic model using in vitro plasma binding and metabolic parameters, the plasma-to-blood concentration ratio and the tissue-to-plasma unbound concentration ratios having been determined from both the tissue and plasma concentrations of TB at the beta-phase after intravenous administration of TB and the plasma free fraction. The predicted concentration curves of TB in each tissue and in plasma showed good agreement with the observed values except for the brain, for which the predicted concentrations were lower than the observed values in the early time period. In the SP- and SDM-treated rats, the predicted free concentration of TB in the target organ, the pancreas, at 6 h was six times higher than that of the control rats. From these findings, it is suggested that physiologically based pharmacokinetic analysis could be generally useful to predict approximate plasma and tissue concentrations of a drug in the presence of drug-drug interaction.

Animals↗