A high-throughput microtiter plate-based calcium assay for the study of protease-activated receptor 2 activation.
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Aniline Compounds↗
Biomedical subjects
B Walker
Publications and source records attributed to B Walker.
Strategies for the inhibition of serine proteases.
Serine proteases have been shown to play a multifarious role in health and disease. As a result, there has been considerable interest in the design and development of synthetic inhibitors of these enzymes. In view of their diverse roles in biological processing events, one of the great challenges in such endeavours has been the need to produce compounds with exquisite selectivity. Inhibitor design has been broadly guided by the use of either peptide- or heterocyclic-based compounds, designed to exploit the known substrate specificity characteristics of individual enzymes. This review describes the thinking and strategies employed in such efforts.
Animals↗
System dynamics and action research in aged care.
This paper documents an Action Research project undertaken to implement a Continuity of Care Model in an Extended Care Centre. System Dynamics modelling and group-modelling techniques were used to examine and improve patient length of stay (LOS). Several indicators of success of the project are noted. They included the reduction of LOS, improvements in teamwork and staff morale, and various systemic adaptations in other parts of the health care sector. Upstream providers responded to the reductions in patient numbers by swamping the Centre with intractable patients. This effectively reduced up-stream providers' LOS, and returned the Centre's LOS to pre-intervention levels.
Aged↗
Sustained dysfunction of antiviral CD8+ T lymphocytes after infection with hepatitis C virus.
Hepatitis C virus (HCV) sets up persistent infection in the majority of those exposed. It is likely that, as with other persistent viral infections, the efficacy of T-lymphocyte responses influences long-term outcome. However, little is known about the functional capacity of HCV-specific T-lymphocyte responses induced after acute infection. We investigated this by using major histocompatibility complex class I-peptide tetrameric complexes (tetramers), which allow direct detection of specific CD8+ T lymphocytes ex vivo, independently of function. Here we show that, early after infection, virus-specific CD8+ T lymphocytes detected with a panel of four such tetramers are abnormal in terms of their synthesis of antiviral cytokines and lytic activity. Furthermore, this phenotype is commonly maintained long term, since large sustained populations of HCV-specific CD8+ T lymphocytes were identified, which consistently had very poor antiviral cytokine responses as measured in vitro. Overall, HCV-specific CD8+ T lymphocytes show reduced synthesis of tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) after stimulation with either mitogens or peptides, compared to responses to Epstein-Barr virus and/or cytomegalovirus. This behavior of antiviral CD8+ T lymphocytes induced after HCV infection may contribute to viral persistence through failure to effectively suppress viral replication.
Acute Disease↗
A study of the anti-invasive properties of N-alpha-phthalimidomethyl-ketomethylene tripeptide-based metalloprotease inhibitors.
We have developed matrix metalloprotease (MMP) inhibitors based on synthetic peptides incorporating a non-cleavable peptide-bond isostere at the site of the putative scissile bond. These inhibitors, N-alpha-phthaloyl-Gly-psi(CO-CH2)-Leu-Tyr-Ala-NH2 (Pht-G-CH2-LYA-NH2) and N-alpha-phthaloyl-Gly-psi(CO-CH2)-Leu-Tic-Ala-NH2 (Pht-G-CH2-LTcA-NH2) were kinetically evaluated against the type IV collagenases, gelatinase A (MMP-2) and B (MMP-9), and compared with an exactly analogous chelating-based inhibitor, N-alpha-mercaptoacetyl-Leu-Tyr-Ala-NH2 (HSCH2CO-LYA-NH2). The peptide inhibitors were also tested for their anti-invasive effects on breast carcinoma cell lines using a modification of the Boyden chamber assay. Gelatin zymography was utilized to identify gelatinolytic activities present in media removed from cultured breast cancer cells. Of the two N-alpha-phthalimidomethyl-ketomethylene peptide-based inhibitors, Pht-G-CH2-LYA-NH2 proved the more effective inhibitor of MMP-2 and MMP-9 (Ki 34.27 and 45.75 microM, respectively). However, when tested against two breast cancer cell lines, T47D and MDA-MB-231, both inhibitors were able to effectively reduce tumour cell invasion through a type IV collagen matrix by up to 91.2%. Of particular interest was the observation that Pht-G-CH2-LYA-NH2 was the most potent inhibitor of invasion by the highly aggressive MDA-MB-231 cells, despite the cells' relative lack of active secreted metalloprotease activity. The results obtained from this kinetic and anti-invasive analysis of the new inhibitors suggest that compounds incorporating the N-alpha-phthalimidomethyl-ketomethylene peptide-bond isostere may have potential for development as new agents with anti-metastatic properties.
Algorithms↗
Synthesis and kinetic evaluation of peptide alpha-keto-beta-aldehyde-based inhibitors of trypsin-like serine proteases.
New, synthetic peptide analogues bearing a C-terminal basic alpha-keto-beta-aldehyde moiety were prepared as novel inhibitors of the trypsin-like serine proteases. The compounds, Ac-Leu-Leu-Arg-COCHO, Ac-Arg-Gln-Arg-COCHO and Boc-Val-Leu-Lys-COCHO were evaluated kinetically against trypsin and three other trypsin-like serine proteases, tryptase, plasmin and thrombin, all of which are implicated as mediators of important disease processes. Results illustrate that alpha-keto-beta-aldehydes are potent inhibitors, with similar potency to comparable peptide aldehydes, and intriguingly, appearto act, in some instances, by a novel mechanism of action. Ac-Leu-Leu-Arg-COCHO, an analogue of the natural product leupeptin, is a potent, tight-binding inhibitor of trypsin (Ki(final) = 1.9 microM), plasmin (Ki(final) = 4.9 microM) and tryptase (Ki(final) = 1.2 microM) and an irreversible inactivator of thrombin (k2nd 4,500 M(-1).min(-1)). Boc-Val-Leu-Lys-COCHO was found to be a tight-binding inhibitor of its target protease plasmin (Ki(final) = 3.1 microM) and was inactive against thrombin. Ac-Arg-Gln-Arg-COCHO was a slow-binding inhibitor of tryptase (Ki(final) = 1.6 microM) and also irreversibly inactivated trypsin (k2nd = 8,920 M(-1) min(-1)). Peptides or peptidomimetics with a C-terminal basic alpha-keto-beta-aldehyde function thus provide a useful new molecular template for the development of new therapeutic agents against a wide range of disorders, such as coagulopathies and asthma, which may be mediated by the aberrant activity of trypsin-like serine proteases.
Aldehydes↗
Observers' reaction to parent-child intimacy.
A study was carried out to examine how people react to acts of intimacy between parent and child. Based on an extensive series of studies reported in 1998 by Reis who found less intimate interactions between two men who are friends than between men or women or between two women who are friends, it was reasoned that intimacy between two males may violate norms of our culture, so it was predicted that people would react less favorably to intimacy between father and son than to intimacy between father and daughter, mother and daughter, or mother and son. Men (n = 19) and women (n=26), most of whom were 18-24 years of age, read versions of a mother or father having an intimate interaction (lap-sit, hair-stroke, hug/kiss) with an 11-yr.-old daughter or son and then rated the act on a 7-point scale from good to bad. As predicted, the undergraduates rated intimate interactions between father and son less favorably than those between father and daughter, mother and daughter, and mother and son.
Adult↗
Evaluation of a model of intervention to create a visually enriched environment.
Within a day resource for people with learning disabilities 'stand-alone' signing training proved ineffectual to sustain lasting change in the formalised gestural behaviours of carers. Consideration was given to setting conditions pre- and post-training and a new model of delivery evolved, designed in partnership with day resource staff. Aims of intervention were to promote the adoption and active use of signing as an aid to communication and move towards a partnership framework which values the role of carers as co-facilitators and lessens dependency on the therapist. This paper describes and evaluates a training model which was found to be successful in translating knowledge into changes in practice and discusses the critical factors which should be built into future interventions.
Caregivers↗
Environmental health and antisocial behavior: implications for public policy.
Antisocial behavior persists as a preeminent public policy issue in the United States. A more critical assessment of both the policies and the programs designed to address this problem is necessary, and new risk factors for antisocial behavior need to be investigated. Sufficient evidence exists to hypothesize that exposure to neurotoxins may be a risk factor for antisocial behavior. Neurotoxins such as lead have been demonstrated to affect the cognitive development of children, and impaired cognition is accepted as a risk factor for antisocial behavior. Little consideration has been given, however, to the possible link between neurotoxins and human behavior. This paper presents a biologically and socially plausible justification for this association, reviews the supporting evidence, and emphasizes the need for additional investigation of the phenomenon. Elucidation of this risk factor may lead to new strategies for preventing or mitigating antisocial behaviors among youth and adults.
Antisocial Personality Disorder↗
Inhibition of Escherichia coli glucosamine synthetase by novel electrophilic analogues of glutamine--comparison with 6-diazo-5-oxo-norleucine.
A series of electrophilic glutamine analogues based on 6-diazo-5-oxo-norleucine has been prepared, using novel synthetic routes, and evaluated as inhibitors of Escherichia coli glucosamine synthetase. The gamma-dimethylsulphonium salt analogue of glutamine was found to be one of the most potent inactivators of this enzyme yet reported, with an apparent second order rate constant (k2/Ki) of 3.5 x 10(5) M(-1) min(-1).
Antimetabolites, Antineoplastic↗
Partial characterization of a novel cathepsin L-like protease from Fasciola hepatica.
A 30-kDa protease, purified previously from Fasciola hepatica, was sequenced and the first 15 N-terminal residues were found to be 100% homologous to a region in the protein Fcp1c, which was cloned and expressed from F. hepatica. This terminal region was also 53 and 54% identical to two other cathepsin L-like proteases isolated from the same source. The 30-kDa protease demonstrated a specificity different from humancathepsin L when assayed with novel peptidyl enediones of the type Z-Phe-Ala-CH&dbond;CH(2)-CO(2)R (where R = Me/Et/Bu(t)). The ethyl ester peptide was a more efficient inhibitor of the protease than the corresponding methyl ester. This is in contrast to bovine cathepsin B and human cathepsin L where both are more readily inhibited by the methyl, rather than the ethyl ester peptide. These differences in the inhibition of the novel parasite protease may allow it to be exploited as a chemotherapeutic target.
Amino Acid Sequence↗
Asymmetric preference of serine proteases toward phosphonate and phosphinate esters.
We have previously reported the asymmetric synthesis of (alpha-aminoalkyl) diphenylphosphonate and phosphinate derivatives designed as inhibitors of chymotrypsin- and elastase-like proteases. This paper reports the first kinetic evaluation of individual epimers of the (alpha-aminoalkyl) diphenylphosphonates as inactivators of chymotrypsin, cathepsin G and neutrophil elastase (HNE). Results show that the (R)-epimers consistently function as more potent irreversible inactivators of their respective target proteases than the corresponding (S)-epimers. Additionally, phosphinate analogues were found to be consistently superior to their diphenylphosphonate counterparts. For example, Cbz. Phe(P)(OPh)-(CH(2))(2)-CO(2)Et inactivates cathepsin G approximately 45-fold more rapidly (k(i)/K(i) = 1.2 x 10(5) M(-1). min(-1)) than the analogous Cbz.Phe(P)(OPh)(2) (2.6 x 10(3) M(-1). min(-1)). Similarly, Cbz.Val(P)(OPh)-(CH(2))(2)-CO(2)Et was found to inactivate HNE some 3-fold more efficiently than Cbz.Val(P)(OPh)(2) (6.5 x 10(3) and 2.0 x 10(3) M(-1). min(-1), respectively).
Cathepsin G↗
Characterization of the affinity of streptavidin toward a peptide sequence previously identified as a target substrate for biotinylation by the escherichia coli biotin holoenzyme synthetase, BirA.
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Amino Acid Sequence↗
Development of laminin receptor agonists: identification of important functional residues by alanine scanning.
An antagonist of cellular adhesion and motility, acetyl-C-[S-Acm]-VIGYSGDRC-[S-Acm]-NH(2) (mEGF(33-42)), shares homology with the agonist sequence CDPGYIGSR-NH(2). It has been proposed that the latter peptide binds to the high affinity 67 kDa laminin receptor. Both peptides have equal affinities for the receptor and similar conformations have been derived for both. We have examined the importance of individual non-homologous residues with respect to receptor binding and antagonistic properties of mEGF(33-42). Alanine scanning of non-conserved residues in the N-terminal half of mEGF(33-42) caused loss of biological activity with respect to cell attachment, receptor binding and migratory response. Substitution of alanine for serine (position 6) caused loss of laminin-specific cell attachment and receptor binding activities. However, the peptide did stimulate migration suggesting that this peptide may be a non-specific stimulator of migration. In contrast, alanine substitution for the C-terminal Cys-S-Acm had no apparent effect on the attachment or receptor binding activities of the peptide but generated an agonist from the antagonist parent. Comparison of the modelled folds of the alanine containing peptides revealed the presence of significant helical content in those peptides capable of stimulating migration and suggests that a reduction in bulk in the N-terminal residues is not conducive to adopting a productive binding conformation.
Alanine↗
Evaluation of dipeptide alpha-keto-beta-aldehydes as new inhibitors of cathepsin S.
A series of dipeptidyl alpha-keto-beta-aldehydes (glyoxals), prepared by solid-/solution-phase chemistries, were assessed for their inhibitory activity against cathepsin S, a lysosomal cysteine protease implicated in a number of important pathophysiological processes. The inhibitor Cbz-Phe-Leu-COCHO, which exhibits slow-binding kinetic characteristics, was found to be almost 400-fold more selective for cathepsin S (K(i) = 0.185 nM) than for cathepsin B (76 nM) and is, to our knowledge, the most potent, reversible, synthetic cathepsin S inhibitor reported to date.
Aldehydes↗
Development of peptidyl alpha-keto-beta-aldehydes as new inhibitors of cathepsin L--comparisons of potency and selectivity profiles with cathepsin B.
We have utilized previously known substrate and inhibitor specificity profiles for the lysosomal cysteine protease, cathepsin L, to design a new series of putative inhibitors of this enzyme, based on di- and tri-peptidyl alpha-keto-beta-aldehydes. Kinetic evaluation of these compounds revealed Z-Phe-Tyr(OBut)-COCHO, with a Ki 0.6 nM, to be the most potent, synthetic reversible inhibitor of cathepsin L reported to date.
Aldehydes↗
Ecology. The value of nature and the nature of value.
Ecosystems are capital assets: When properly managed, they yield a flow of vital goods and services. Relative to other forms of capital, however, ecosystems are poorly understood, scarcely monitored, and--in many important cases--undergoing rapid degradation. The process of economic valuation could greatly improve stewardship. This potential is now being realized with innovative financial instruments and institutional arrangements.
Australia↗
Potent new leucine aminopeptidase inhibitor of novel structure synthesised by a modified Wadsworth-Emmons (Horner) Wittig procedure.
The use of a leucine-derived alpha-keto-beta-aldehyde (glyoxal) as a substrate in the Horner-Emmons (Wadsworth) Wittig reaction has enabled the synthesis of (Z)-7-methyl-5(S)-amino-4-oxo-methyl-oct-2-eneoate. This novel compound is a potent inhibitor (Ki = 76 nM) of leucine aminopeptidase and provides an interesting new template for the development of metallopeptidase inhibitors.
Chemistry, Organic↗