Purification and substrate specificity of an endopeptidase from the human oral spirochete Treponema denticola ATCC 35405, active on furylacryloyl-Leu-Gly-Pro-Ala and bradykinin.
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An endopeptidase was purified to homogeneity from the cell extracts of Treponema denticola ATCC 35405 (a human oral spirochete) by a procedure that comprised dialysis, anion exchange fast protein liquid chromatography (FPLC), hydroxylapatite FPLC, immobilized metal affinity FPLC, FPLC chromatofocusing, and two consecutive gel permeation FPLC steps. The enzyme is a 62-kDa protein with an isoelectric point of 6.5-7.0. Experiments with enzyme inhibitors suggest that this enzyme is a metallopeptidase and that its activity is not dependent on sulfhydryl or serine residues. The enzyme is active on furylacryloyl-Leu-Gly-Pro-Ala (FALGPA; pH optimum near 6.25), bradykinin (Bk), and several Bk-related peptides. In FALGPA, the cleavage site is the Leu-Gly bond. An imino acid is absolutely necessary in position P'2. The shortest hydrolyzed peptide was FALGPA, the hydrolysis of which is strongly and competitively inhibited by Bk (Ki = 5.0 microM). The pyrophosphate ion and phosphoramidon also inhibited the hydrolysis of FALGPA. The enzyme does not hydrolyze all typical synthetic collagenase substrates, Azocoll, Azocasein, or Type I and Type IV collagens, or any other proteins tested. In Bk-related peptides, the hydrolyzed bond was Phe5-Ser6. Since a Bk antagonist and a Bk-potentiating pentapeptide also were good substrates, it is possible that the enzyme hydrolyzes Bks and related peptides only because of the coincidental, specific amino acid sequence of those substrates. A proposal is made that since a substantial portion of the amino acid sequence of FALGPA is present in collagen (and additionally acknowledging that the furylacryloyl residue structurally resembles that of proline), the natural substrates of this enzyme may be small, soluble collagen fragments produced by other enzymes from periodontal connective tissue, and that such peptides are important for the nutrition and pathogenicity of T. denticola. (+info)
Cyrmenins, new beta-methoxyacrylate inhibitors of the electron transport. Production, isolation, physico-chemical and biological properties.
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New antibiotic compounds, named cyrmenins, were isolated from the culture broth of strains of the myxobacteria Cystobacter armeniaca and Archangium gephyra. The compounds belong to the group of beta-methoxyacrylate (MOA) inhibitors and are the first naturally occuring nitrogen-linked MOAs. The cyrmenins show nearly the same antifungal activity as strobilurin A, but are less toxic in a growth inhibition assay with L929 mouse cells. Cyrmenins inhibit NADH oxidation by submitochondrial particles from beef heart. Investigations by difference spectroscopy showed that cyrmenin B1 blocks the electron transport within the cytochrome bc1-segment (complex III) of the respiratory chain. (+info)
Effect of several factors on the mechanical properties of pressure-sensitive adhesives used in transdermal therapeutic systems.
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The effects of coating thickness, type of adhesive, and type and concentration of enhancer on the mechanical properties of two acrylic pressure-sensitive adhesives (PSAs) were investigated using a 2(4) factorial design and an optimization technique. Sixteen formulations containing 0% or 10% of either caprylic acid or methyl laurate in two different PSAs, namely Duro-Tak 87-2196 and Duro-Tak 87-2097, were prepared. The adhesive properties of these laminates were evaluated by applying the 90 degrees Dynamic Adhesive Strength Peel Test (90 degrees DASPT) and 1800 Release Liner Peel Test (180 degrees RLPT). Coating thickness, concentration of enhancer, and type of adhesive did affect the 90 degrees DASPT. For the 180 degrees RLPT, the most significant factors were coating thickness and concentration of enhancer, with a strong interaction observed between the two. Coating thickness and concentration of enhancer were also used to create mathematical models that correlated these factors with the mechanical properties of the PSAs. For this purpose, the optimization technique 3(2) was applied. It was found that the correlation of the above factors can be adequately described with polynomial equations, which can be used for predicting the mechanical properties of the laminates containing the above PSAs and methyl laurate (0%-10%). (+info)
Posterior capsule opacification after implantation of a hydrogel intraocular lens.
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AIM: To compare the degree of posterior capsule opacification (PCO) in eyes with a hydrophilic hydrogel intraocular lens (IOL) with that in eyes with a hydrophobic acrylic IOL. METHODS: Ninety five patients underwent a hydrogel IOL implantation in one eye and an acrylic IOL implantation in the opposite eye. The PCO value of these patients was measured using the Scheimpflug videophotography system at 1, 6, 12, 18, and 24 months postoperatively. The rate of neodymium:YAG (Nd:YAG) laser posterior capsulotomy and visual acuity were also evaluated. RESULTS: The mean PCO value in the hydrogel group increased significantly (p<0.0001), while that in the acrylic group did not show significant change. The PCO value in the hydrogel group was significantly greater than that in the acrylic group throughout the follow up period. Kaplan-Meier survival analysis determined that the Nd:YAG capsulotomy rate in the hydrogel group was significantly higher than that in the acrylic group (p<0.0001). Mean visual acuity in the hydrogel group decreased significantly with time (p<0.0001), and became significantly worse than that in the acrylic group at 18 and 24 months postoperatively. CONCLUSION: Posterior capsule opacification in eyes with a hydrophilic hydrogel IOL is significantly more extensive than that in eyes with a hydrophobic acrylic IOL, and results in a significant impairment of visual acuity. (+info)
Influence of storage conditions and type of plasticizers on ethylcellulose and acrylate films formed from aqueous dispersions.
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PURPOSE: To investigate the influence of storage conditions and types of plasticizers on the properties and stability of ethylcellulose and polymethacrylate films and to elucidate the mechanism for the changes observed. METHODS: Films were prepared from Surelease, Aquacoat and Eudragit L 30D dispersions by the casting method. The effects of different plasticizers on the morphology, transparency, mechanical property and water vapour permeability of the prepared films were studied. The film samples were exposed to storage conditions of 30 degrees C and 50 or 75 %RH. Samples were removed at pre-determined time intervals for mechanical testing and analysis of plasticizer content in the films. RESULTS: It was found that films prepared from aqueous ethylcellulose dispersions were relatively weaker and more brittle than acrylate films. Acrylate films did not show any significant change in mechanical property when stored at high humidity. However, the properties of ethylcellulose films stored at high humidity varied depending on the type of plasticizers present. CONCLUSIONS: The changes in mechanical property of ethylcellulose films on storage were mainly attributed to the loss of plasticizers during storage, causing further coalescence of ethylcellulose films and to a smaller extent, reduction in moisture content of the film. (+info)
Potential renoprotective effects of the angiotensin receptor blocker eprosartan: a review of preliminary renal studies.
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The importance of the renin-angiotensin-aldosterone system (RAAS) in the pathogenesis of hypertension and in renal disease, particularly in patients with diabetes, has become increasingly evident. Pharmacological blockade of the RAAS offers potential for the therapeutic management of these pathologies. Angiotensin converting enzyme (ACE) inhibitors and angiotensin II (AII) receptor blockers have been shown to exhibit effectiveness in the treatment of hypertension. AII receptor blockers have a renal protective effect owing to their ability to reduce systemic blood and intraglomerular pressures. Eprosartan is a chemically distinct AII blocker, which displays a dual mode of action whereby it blocks both pre- and postsynaptic AT(1) receptors, potentially benefiting patients with hypertension and renal disease. In addition, evidence suggests that eprosartan is well tolerated by both healthy subjects and patients with varying degree of renal impairment, such that the dose does not need to be modified in patients with mild to moderate renal impairment. Results from preliminary studies demonstrates that eprosartan doses will below those required for blood pressure control have a pronounced effect on the kidney and do not compromise renal autoregulatory mechanisms. Therefore, eprosartan may have a benefit in the prevention or delay of renal damage in hypertensive patients with renal impairment, although this remains to be determined in a clinical setting. (+info)
Ethyl acrylate risk assessment with a hybrid computational fluid dynamics and physiologically based nasal dosimetry model.
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Cytotoxicity in the nasal epithelium is frequently observed in rodents exposed to volatile organic acids and esters by inhalation. An interspecies, hybrid computational fluid dynamics and physiologically based pharmacokinetic (CFD-PBPK) dosimetry model for inhaled ethyl acrylate (EA) is available for estimating internal dose measures for EA, its metabolite acrylic acid (AA), and EA-mediated reductions in tissue glutathione (GSH). Nasal tissue concentrations of AA were previously used as the dose metric for a chronic Reference Concentration (RfC) calculation with this compound. However, EA was more toxic than expected, based on calculated tissue AA concentrations. Unlike AA, EA causes depletion of tissue GSH. We have developed an RfC for EA using tissue GSH depletion in the olfactory epithelium as the primary measure of nasal tissue dose. The hybrid CFD-PBPK model was refined to improve the accuracy of simulations for GSH in rat olfactory tissues. This refined model was used to determine the concentration for continuous human exposures to EA predicted to reduce nasal GSH levels to the same extent as seen in rats exposed to EA at the no-observed-effect level (NOEL). Importantly, AA concentrations in the human nasal olfactory epithelium at the proposed chronic RfC were predicted to be lower than the AA concentrations estimated in the rat at the NOEL. Thus, a chronic RfC based on maintaining GSH in the human nasal olfactory epithelium at levels equivalent to the rat NOEL would also provide an adequate margin of safety with respect to AA concentrations in nasal tissues. (+info)
BACKGROUND: Angiotensin type 1 receptor (AT(1)R) blockers (ARB) have been shown to reduce the incidence of type 2 diabetes mellitus by an unknown molecular mechanism. The peroxisome proliferator-activated receptor-gamma (PPARgamma) is the central regulator of insulin and glucose metabolism improving insulin sensitivity. We investigated the regulation of PPARgamma function by ARBs. METHODS AND RESULTS: The ARBs irbesartan and telmisartan (10 micromol/L) potently enhanced PPARgamma-dependent 3T3-L1 adipocyte differentiation associated with a significant increase in mRNA expression of the adipogenic marker gene adipose protein 2 (aP2), as measured by quantitative real-time polymerase chain reaction (irbesartan: 3.3+/-0.1-fold induction; telmisartan: 3.1+/-0.3-fold induction; both P<0.01). Telmisartan showed a more pronounced induction of aP2 expression in lower, pharmacologically relevant concentrations compared with the other ARBs. The ARB losartan enhanced aP2 expression only at high concentrations (losartan 100 micromol/L: 3.6+/-0.3-fold induction; P<0.01), whereas eprosartan up to 100 micromol/L had no significant effects. In transcription reporter assays, irbesartan and telmisartan (10 micromol/L) markedly induced transcriptional activity of PPARgamma by 3.4+/-0.9-fold and 2.6+/-0.6-fold (P<0.05), respectively, compared with 5.2+/-1.1-fold stimulation by the PPARgamma ligand pioglitazone (10 micromol/L). Irbesartan and telmisartan also induced PPARgamma activity in an AT1R-deficient cell model (PC12W), demonstrating that these ARBs stimulate PPARgamma activity independent of their AT(1)R blocking actions. CONCLUSIONS: The present study demonstrates that a specific subset of ARBs induces PPARgamma activity, thereby promoting PPARgamma-dependent differentiation in adipocytes. The activation of PPARgamma demonstrates new pleiotropic actions of certain ARBs, providing a potential mechanism for their insulin-sensitizing/antidiabetic effects. (+info)