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At least 433 records · Page 24Linked to original sources
PubMed1994

[The effect of preclotting and collagen coating on endothelializing rate and thrombogenesity of Dacron grafts in the canine thoracic aorta].

Although high porosity knitted Dacron is generally recognized to have superior healing characteristics over woven Dacron, its porosity must be controlled at the clinical operation. This can be achieved with several materials, including geratin, insoluble collagen, albumin, and fibrin. We made atherocollagen coated graft using EX-313 as a new crosslinking agent. The purpose of this study is to compare the endothelializing rate and thrombogenesity of Dacron grafts coated by atherocollagen in the canine thoracic aorta with preclotting grafts with blood or albumin. Five groups were studied: Control group (n = 10), without preclotting; A-P group (n = 8), preclotting with albumin; B-P group (n = 5), preclotting with blood; W-C group (n = 5), atherocollagen coating with low cross-linkage; S-C group (n = 7), atherocollage coating with high cross-linkage. Thoracic aorta was replaced with 8 mm graft in length of 5.0 to 5.5 cm using temporary bypass with anthron tube. Grafts were harvested 3 months following implantation, and the endothelized surface ratio was calculated by microscopic line sampling method. Endothelized surface ratio of Control group, A-P group B-P group, W-C group and S-C group were 85%, 55%, 67%, 93% and 85%, respectively. Endothelized surface ratio of W-C group and S-C group were higher (p < 0.05) than those of A-P group, B-P group. There were thrombus in non-epithelized area. We conclude that atherocollagen coated graft had superior antithrombogenesity compared to albumin or blood preclotting graft.

Animals↗
PubMed1994

Anthralin: how does it act and are there more favourable derivatives?

Anthralin is still the most effective and safest therapeutic agent for treatment of psoriasis. Our data may assist toward an understanding of its mode of action and introduce new derivatives, more antiproliferative and less toxic than anthralin in vitro. Anthralin exerts a direct effect on keratinocytes and leukocytes. In time-lapse studies it significantly prolonged the prophase of mitotic keratinocytes in subtoxic doses and suppressed the expression of keratin 6 mRNA in the immediately suprabasal layer of psoriatic epidermis in vivo. Anthralin inhibits the transformation of lymphocytes and the release of reactive oxygen species from activated leukocytes, in vitro. We provide evidence that these effects of anthralin are mediated by protein kinase C. Twelve new hydrophilic derivatives of anthralin, including a 1,8-dimethoxy compound, as well as C-2 and C-10 substituted anthrones were tested on human keratinocytes. The antiproliferative effect of those derivatives bearing lacton rings at a C-10, consisting of 4, 5, or 6 C atoms, exceeded that of anthralin and were equally or less cytotoxic than the parent drug. These compounds had no pro-drug character in vitro, since they did not metabolize via anthralin, as shown by HPLC. These data indicate that there may be anthralin derivatives with more favourable properties for topical therapy than anthralin itself.

Anthralin↗
PubMed1995

Genetic factors controlling responsiveness to skin tumor promotion in mice.

Two genetic models that could explain all of the current data are depicted in Figure 4, although it should be stressed that proof of any model will require additional genetic analyses. The first model (Model A) indicates that one or more loci controlling responsiveness to TPA are also responsible for directly controlling responsiveness to other classes of skin tumor promoters such as BzPo and Chr. We have called this locus the Pms locus (for skin tumor promotion sensitivity). The differences between compounds in the magnitude of their promoting ability may reside in the inability to activate a full set or compliment of Pms loci. Genetic differences may reside in a critical Pms locus that is necessary for tumor promotion by all chemical promoters. Alternatively, the current data could be interpreted as showing that different genes responsible for high sensitivity to promotion by diverse promoting agents act on a pathway(s) common to promotion in mouse epidermis (Model B). In this case, the Pms locus would represent a common biochemical/molecular pathway where different responses mediated by different types of promoters ultimately converge and lead to the process of tumor promotion in mouse skin. Directly testing either of the above models will require analyses of progeny from appropriate segregating crosses among the various stocks and strains used in the present study. Model B could help explain several experimental observations. First, SSIn mice, while still retaining a fairly high sensitivity to skin tumor promotion with Chr relative to other inbred strains (i.e., DBA/2, C57BL/6), have lost their increased sensitivity to this anthrone derivative relative to SENCAR mice. SSIn were developed through a process of inbreeding starting with the current outbred SENCAR and employing a selection scheme using DMBA initiation and TPA promotion similar to that originally devised by Boutwell (1964). Second, C57BL/6 mice, although relatively resistant to TPA, chrysarobin and BzPo, are somewhat peculiar in their high resistance to standard promotion protocols using TPA (DiGiovanni et al., 1991). Indirectly, these observations suggest that different genes may regulate some responses to particular types of promoting agent. For example, perhaps the induction of a oxidant response by phorbol esters would represent a specific response to this class of tumor promoters. A testable prediction from these observations is that it may be possible to selectively breed for mouse lines more sensitive and/or resistant to specific classes of promoting agents.

Animals↗
PubMed1979

[Hydroxyethyl starch (HAS 450/0.7) in human plasma and liver. Course of concentration and histological changes].

In 12 patients 1,000 ml hydroxyethyl starch (Mw 450,000, degree of substitution 0.7) was infused intravenously. A liver biopsy was performed in 10 patients undergoing abdominal surgery 30 minutes to 28 days after the infusion. The liver tissue was investigated by light and electron microscopy. The plasma level of hydroxyethyl starch decreased to 4.8% of the initial concentration 28 days after the infusion (Anthron method). Single intracellular vacuoles were shown by electron microscopy 30 minutes after the end of infusion in Kupffer's cells only. However, 6 to 28 days after infusion intracellular vacuoles were demonstrated in parenchymal liver cells, Kupffer's cells, interstitial histiocytes and to a lesser degree in the cells of the small bile ducts. The pathogenic importance of the portracted elimination from the plasma and the liver storage is unknown.

Adult↗
PubMed1995

[Mechanism of action of sennosides].

A review of the recent progress in the study of the mode of action of the sennosides, the active constituents of the senna drug, is presented. An interaction between rhein anthrone, the active metabolite of the sennosides, and the immune cells of the colon is suggested as a base for laxative activity.

Anthraquinones↗
PubMed1977

The glycogen-depleting effect of aqueous estrone on the cerebral hemispheres of the chick embryo.

Aqueous estrone (10 to 50 pigrams/egg) was injected into the albumen of the 13 day chick embryo. The control solution and estrone carrier was 0.1 ml bacteriostatic saline. The KOH-alcohol-Anthrone colorimetric method was used to determine glycogen. 20 or more pigrams estrone/egg lowered the mean cerebral glycogen significantly (P less than 0.01) after 24 hours duration in a non-dosage-dependent manner. The glycolytic effect was demonstrated by the 20.0 pigram dosage after 120 hours duration.

Animals↗
PubMed1986

Biodegradable microspheres. IV: Factors affecting the distribution and degradation of polyacryl starch microparticles.

Polyacryl starch microparticles have been suggested as lysosomotropic drug carriers. In this paper we report the study of the distribution and elimination of polyacryl starch microparticles after intravenous administration in mice. The half-life of the particles in the circulation is short (less than 5 min) and they are efficiently taken up by the reticuloendothelial (RES) system, mainly in the liver (50-90%). The stability of the particles, as studied both in vitro (with serum and lysosome preparations) and in vivo (via the elimination from the liver), depends on two factors, the amount of initiator of the polymerization process (N,N,N',N'-tetramethylethylenediamine, TEMED) and the degree of derivatization of the starch. TEMED, used for the polymerization of the acryl groups forming the hydrocarbon chains, determines the number and the length of the cross-links between the starch molecules. The results indicate that large amounts of TEMED induce the formation of particles with many and short cross-links, which are easily degraded and dissolved in serum and more rapidly eliminated from the liver. The stability in serum can be improved by coadministration of soluble starch. Prolonged treatment of the starch with acrylic acid glycidyl ester leads to a high degree of derivatization and, consequently, to less degradable particles remaining in the lysosomes of the RES. The extent of biodegradation of the polyacryl starch particles could be anticipated from in vitro degradation of the monomers (acryloylated starch) with amyloglucosidase.

Animals↗
PubMed1990

Perfusion of rat colon with sennosides, rhein and rheinanthrone. Concentration-related histamine release.

Rat colon perfused intraluminally in vitro and in vivo released histamine into the perfusates. Histamine release was increased by rhein 0.1-10 micrograms/ml and much more by rheinanthrone 0.1-10 micrograms/ml but not by sennosides A or B 1-10 micrograms/ml. The effect of rhein and rheinanthrone was reduced by tritoqualine 20 mg/kg. This raises the possibility that laxation by senna and its derivatives involves histamine formation.

Animals↗
PubMed1991

A rapid method for the estimation of prostaglandin E2 in intestinal tissues using fluorescence derivatization.

A sensitive spectrofluorimetric method is described to determine small quantities of prostaglandin E2 in complex biological systems as intestinal tissues. The method is based on a solid phase extraction combined with a coupling with a fluorescent marker and measuring the derivatization product by fluorescence densitometry. After mixing the tissue with an ice-cold perchloric acid solution, adjusting the pH, centrifugation and filtration steps, the prostaglandins are retained on a solid phase extraction C18 disposable column. They are eluted with diethylether, derivatized with 4-bromomethyl-7-methoxy-coumarin using potassium carbonate as condensating agent and finally analysed using fluorescence densitometry on silica gel TLC plates. Applying this method, amounts down to 5 ng (per gram wet tissue) could be measured in intestinal tissues, the s.e.m. for replicated total analysis being less than 15%. The foregoing method is applied for the determination of PGE2 released in the intestinal wall under the influence of laxatives.

Animals↗
PubMed1987

The release and percutaneous permeation of anthralin products, using clinically involved and uninvolved psoriatic skin.

The release and permeation of 1% Westragel and 1% Westrastick and three commercial 1% anthralin products were investigated in vitro with the use of a Franz diffusion cell unit. An inert Teflon membrane with a mesh opening of 74 mu was used for measuring the rate of release. Involved psoriatic and uninvolved human skin collected from the same subjects were used for the permeation study. The permeation of danthron and dianthrone, the major degradation products of anthralin, was also studied with the use of microemulsion gels of 1% danthron and 1% dianthrone, which were prepared in the same way as 1% Westragel. The penetrating anthralin, danthron, and dianthrone were stabilized by a modified receptor fluid, and sample solutions were analyzed by a high-power liquid chromatography method. Involved psoriatic skin was found to be much more permeable to anthralin than was uninvolved psoriatic skin. The slow permeation rate of anthralin, danthron, and dianthrone through normal skin and uninvolved skin indicates that the stratum corneum is the rate-limiting barrier. In involved psoriatic skin, the release rate of anthralin from the topical product becomes the rate-determining step. Large individual variations were found in the permeation of anthralin through involved psoriatic skin, suggesting that the permeation rate of anthralin also may depend on the disease state of psoriatic patients. The anthralin molecule, possessing both hydrophilic and lipophilic centers, diffused significantly faster than did danthron and dianthrone. Westragel, 1%, showed the highest diffusion rate as well as the highest driving force when compared to other commercial 1% anthralin products. This suggests that 1% Westragel may be an optimal design, especially for short-contact anthralin therapy.

Anthracenes↗
PubMed2000

Triplet-state energies and substituent effects of excited aroyl compounds in the gas phase.

Triplet-state energy values obtained from the gas phase are still scarce. In this study, the triplet-state energies of 58 aroyl compounds, introduced as gas chromatographic peaks at atmospheric pressure and typically 473 K, have been determined from the 0-0 bands of their n --> pi* type phosphorescence spectra in excited nitrogen. Correlations of those gas-phase triplet-state energies with Hammett constants could be observed for substituted acetophenones, benzaldehydes and benzophenones.

Acetophenones↗
PubMed2000

Quantitative changes of dianthrones, hyperforin and flavonoids content in the flower ontogenesis of Hypericum perforatum.

Samples of Hyperici herba were obtained by harvesting Hypericum perforatum L. in different plant development stages. The relation of flower development phases in the drug's flower fraction was examined. The HPLC method was then employed for the analysis of the content of secondary metabolites in different flower ontogenesis phases. The content of dianthrones, derivatives of quercetin and hyperforin increased from the first bud phases (0.29%, 0.80%, and 2.47%, respectively) to flowers just opened (1.04%, 4.23% and 6.60%, respectively). The content of dianthrones and quercetin glycosides then decreased (in unripe fruits 0.11% and 0.08%, respectively), whereas the amounts of hyperforin increased to 8.07% in fruits. The content of I3,II8-biapigenin increased from 0.21% in small buds to 1.04% in buds just before opening and has then decreased gradually to a value of 0.02% in fruits. Rutin was not detected in the samples.

Anthracenes↗
PubMed1989

[Senna-containing laxatives: excretion in the breast milk?].

The excretion of rhein, a cathartic with active metabolite from sennosides, was investigated in breast milk samples of 15 post-partum women for at least 24 h after the intake of a therapeutic dose (15 mg sennosides/day) of a standardized, fiber containing senna laxative (Agiolax). Rhein was analyzed by a HPLC-method with a lower limit of detection at 1 ng/ml rhein, taking into account a possible binding as monoglucuronide and monosulfate. Maximal concentrations up to 27 ng/ml and in 89% values below 10 ng/ml were measured. Related to the daily milk volume, 73% of the women excreted less than 2 ng rhein/day. Based on median values, 0.017% of the sennoside intake (calculated as rhein) was excreted in breast milk. The amount of rhein transmitted to the infant is therefore 0.3% of the rhein intake of the mother. This is far below the oral rhein dose necessary for inducing a laxative effect. Accordingly, none of the breast-fed infants (n = 8) showed any difference in stool consistency in comparison with the non breast-fed infants.

Adult↗
PubMed2005

Structure and kinetics of a transient antibody binding intermediate reveal a kinetic discrimination mechanism in antigen recognition.

Induced fit is a predominant phenomenon in protein-ligand interactions, yet it is invariably attributed without establishing the existence, let alone the structure, of the initial, low-affinity encounter complex. We determined the crystal structure of the encounter complex on the pathway of ligand binding by IgE antibody SPE7. We show that this complex is formed by a wide range of ligands that initially bind with identical affinity. Nonspecific ligands rapidly dissociate, whereupon the antibody isomerizes to a nonbinding isomer. Specific ligand complexes, however, slowly isomerize to give a high-affinity complex. This isomerization involves backbone and side-chain rearrangements of up to 14 A and the formation of specific hydrogen bonds. The postbinding conformational switch, combined with the prebinding isomerization to an energetically favorable nonbinding isomer, results in a "kinetic discrimination" mechanism that mediates selective binding, by a factor of >10(3), between highly related ligands that initially bind with the same affinity. This model may apply to proteins that bind multiple ligands in a specific manner or other proteins that, although capable of binding many ligands, are activated by only a few.

Anthracenes↗
PubMed1998

Cloning, nucleotide sequence, and expression in Escherichia coli of levansucrase genes from the plant pathogens Pseudomonas syringae pv. glycinea and P. syringae pv. phaseolicola.

Plant-pathogenic bacteria produce various extracellular polysaccharides (EPSs) which may function as virulence factors in diseases caused by these bacteria. The EPS levan is synthesized by the extracellular enzyme levansucrase in Pseudomonas syringae, Erwinia amylovora, and other bacterial species. The lsc genes encoding levansucrase from P. syringae pv. glycinea PG4180 and P. syringae pv. phaseolicola NCPPB 1321 were cloned, and their nucleotide sequences were determined. Heterologous expression of the lsc gene in Escherichia coli was found in four and two genomic library clones of strains PG4180 and NCPPB 1321, respectively. A 3. 0-kb PstI fragment common to all six clones conferred levan synthesis on E. coli when further subcloned. Nucleotide sequence analysis revealed a 1,248-bp open reading frame (ORF) derived from PG4180 and a 1,296-bp ORF derived from NCPPB 1321, which were both designated lsc. Both ORFs showed high homology to the E. amylovora and Zymomonas mobilis lsc genes at the nucleic acid and deduced amino acid sequence levels. Levansucrase was not secreted into the supernatant but was located in the periplasmic fraction of E. coli harboring the lsc gene. Expression of lsc was found to be dependent on the vector-based Plac promoter, indicating that the native promoter of lsc was not functional in E. coli. Insertion of an antibiotic resistance cassette in the lsc gene abolished levan synthesis in E. coli. A PCR screening with primers derived from lsc of P. syringae pv. glycinea PG4180 allowed the detection of this gene in a number of related bacteria.

Amino Acid Sequence↗
PubMed1995

A new enzymatic method for the determination of inulin.

A new enzymatic method for the determination of inulin in plasma and urine, using inulase (EC 3.2.1.7), fructokinase (EC 2.7.1.4), phosphoglucoisomerase (EC 5.3.1.9) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) is described. The assay is based on the hydrolysis of inulin or Inutest (INutest which is the injectable form of inulin), by inulase and the determination of fructose released. The assay was linear up to 2 g/L of Inutest. The within-batch and between batch coefficients of variation were 2.3% and 2.2%, respectively. Recovery of added Inutest from plasma and urine was 98-102%. There was no interference from glucose (27.7 mmol/L), fructose (1.7 mmol/L) or mannose (1.7 mmol/L). When inulin clearance (using this method) and thiosulphate clearance were compared in 37 patients the inulin clearance was 9.3 mL/min (12%) lower than the thiosulphate clearance. We conclude that this enzymatic method is a simple and specific method.

Anthracenes↗