Structure and mechanism of the evolutionarily unique plant enzyme chalcone isomerase

Chalcone isomerase (CHI) catalyzes the intramolecular cyclization of chalcone synthesized by chalcone synthase (CHS) into (2S)-naringenin, an essential compound in the biosynthesis of anthocyanin pigments, inducers of Rhizobium nodulation genes, and antimicrobial phytoalexins. The 1.85 A resolution crystal structure of alfalfa CHI in complex with (2S)-naringenin reveals a novel open-faced beta-sandwich fold. Currently, proteins with homologous primary sequences are found only in higher plants. The topology of the active site cleft defines the stereochemistry of the cyclization reaction. The structure and mutational analysis suggest a mechanism in which shape complementarity of the binding cleft locks the substrate into a constrained conformation that allows the reaction to proceed with a second-order rate constant approaching the diffusion controlled limit. This structure raises questions about the evolutionary history of this structurally unique plant enzyme.

Developmental and light-regulated post-translational control of 3-hydroxy-3-methylglutaryl-CoA reductase levels in potato

In plants, the first committed step in the cytosolic pathway for biosynthesis of isoprenoids is catalysed by 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR). We have added an eight amino-acid-residue epitope tag to a potato (Solanum tuberosum L.) HMGR isoform and expressed this novel protein (HMGR-FLAG) in transgenic plants. Despite high levels of transcript accumulation in all leaf stages of transgenic plants, high levels of HMGR-FLAG protein were found only in apical meristematic tissue, suggesting post-translational regulation of potato HMGR affected by plant development. Protein immunoblots, and determination of enzymatic activity and transcript accumulation in the HMGR-FLAG transgenic and the non-transgenic parental plant lines, show that HMGR levels decrease dramatically in the dark. Again, the mechanism of this control occurs at a post-translational level. After 2.5 h in darkness, levels of HMGR-FLAG are approximately one-half of those in plants in the light; protein levels recover rapidly when dark-treated plants are returned to the light. In non-transgenic plants, hmg transcript levels are reduced in the dark, whereas dark treatments do not affect transgene hmg transcripts expressed under the control of a constitutive promoter. Furthermore, transcripts for HMGR-FLAG remain associated with polyribosomes in dark-treated tissues. Addition of inhibitors of cysteine proteases during microsomal protein extraction is required for recovery of immunoreactive HMGR-FLAG. The epitope-tagged isozyme has been used to show for the first time that a regulated decrease in plant HMGR activity correlates closely with a loss of the HMGR protein. We have used whole plants to demonstrate that developmental and light-regulated control of HMGR occurs post-translationally in vivo.

Post-transcriptional regulation of phenylalanine ammonia-lyase expression in tobacco following recovery from gene silencing

Introduction of a bean phenylalanine ammonia-lyase (PAL) transgene into tobacco plants results in epigenetic post-transcriptional gene silencing which is unstable, such that after self-pollination first generation progeny may become PAL over-expressors. The change from gene silencing to PAL over-expression is accompanied by a loss of cytosine methylation of the PAL transgene and reduced methylation of the endogenous tobacco PAL2 gene, but not the PAL1 gene. These changes are associated with the appearance of high levels of bean PAL and tobacco PAL2 transcripts in the total RNA fraction from PAL over-expressing plants. However, tobacco PAL2 transcripts are inefficiently recruited into polysomes, and tobacco PAL2 protein is not detected in leaves of PAL over-expressing or wild-type lines. Thus, in spite of the post-transcriptionally controlled increase in tobacco PAL2 transcripts in PAL over-expressors, the increased PAL activity is primarily the result of the increase in bean PAL transcripts and corresponding enzymatic activity. These results reveal a complex cross-talk between expression of the PAL transgene and the corresponding endogenous PAL genes at the levels of transcription, transcript stability and polysomal recruitment during sense transgene-mediated silencing and subsequent over-expresson of PAL in tobacco.

Attenuation of pulmonary vascular hypertension and cardiac hypertrophy with sitaxsentan sodium, an orally active ET(A) receptor antagonist

Effects of sitaxsentan (TBC11251), an orally active, highly selective antagonist of endothelin A receptors, were examined on the development and maintenance of pulmonary hypertension, pulmonary vascular remodeling, and cardiac hypertrophy in the rat. The pulmonary vasoconstrictor response to acute hypoxia (10% O(2)for 90 min) was prevented with sitaxsentan (5 mg/kg infused iv 10 min prior to the onset of hypoxia) while BQ-788 (a specific endothelin B receptor antagonist) was without effect. The same dose of sitaxsentan delivered iv 50 min after the onset of hypoxia reversed the established pulmonary vasoconstriction. In a 2-week model of hypoxia using 10% O(2), treatment with sitaxsentan (15 mg/kg per day in drinking water) attenuated pulmonary hypertension and the associated right ventricular hypertrophy, and prevented the remodeling of small pulmonary arteries (50-100 microM) without affecting systemic arterial blood pressure or heart rate. Institution of sitaxsentan treatment (15 and 30 mg/kg per day in drinking water) for 4 weeks after 2 weeks of untreated hypoxia produced a significant, dose dependent reversal of the established pulmonary hypertension, right heart hypertrophy, and pulmonary vascular remodeling despite continued hypoxic exposure. Sitaxsentan blocked increased plasma endothelin levels in the prevention protocol but did not affect the established elevated levels in the intervention study. Sitaxsentan dose dependently (10 and 50 mg/kg per day in the drinking water) attenuated right ventricular systolic pressure, right heart hypertrophy, and pulmonary vascular remodeling observed 3 weeks after a single subcutaneous injection of monocrotaline. These findings support the hypothesis that endothelin-1 plays a significant role in the development of pulmonary hypertension, pulmonary vascular remodeling, and the associated cardiac hypertrophy, and further suggest that specific endothelin-A receptor blockade may be useful in the treatment of pulmonary hypertension of diverse etiologies.

Reduction of pulmonary mast cells in areas of acute inflammation in calves with Mannheimia (Pasteurella) haemolytica pneumonia

Mast cells in the left cranial pulmonary lobe of colostrum-deprived neonatal calves were quantified 2 and 6 h after intrabronchial inoculation with Mannheimia (Pasteurella) haemolytica A1. The mast cells were detected (1) immunohistochemically with a mouse anti-human mast cell tryptase monoclonal antibody, and (2) by metachromatic staining with low pH toluidine blue. A greater number of mast cells was demonstrated by the second method than by the first. At 6 h after inoculation, but not at 2 h, the number of mast cells was significantly reduced at the site of the main lesions. Treatment of calves with a sialyl Lewis mimetic (TBC1269) did not appreciably affect the results at 6 h.

Multiple selectin blockade with a small molecule inhibitor downregulates liver chemokine expression and neutrophil infiltration after hemorrhagic shock

BACKGROUND

The purpose of this study was to investigate the regulatory effect of a small molecule selectin inhibitor in the liver by examining the functional, structural, and survival response of animals subjected to hemorrhagic shock and to determine the liver infiltration of neutrophils and the regulation of chemokine expression. Selectins play an important role in the development of the lesions associated with ischemia/reperfusion and hemorrhagic shock. Blocking individually the selectin family of adhesion molecules with monoclonal antibodies has resulted in better organ function and survival. To our knowledge, there are no studies demonstrating the beneficial effect of multiple selectin blockade with a small molecule inhibitor under conditions of hemorrhagic shock.

METHODS

Forty-eight Sprague-Dawley rats were subjected to hemorrhagic shock. Three groups of animals were included (n = 16/group), i.e., the sham, control, and treated groups, which received a small molecule selectin inhibitor (TBC-1269) at 25 mg/kg body weight after the bleeding began. The following parameters were evaluated: fluid requirements during resuscitation, liver injury tests (aspartate aminotransferase, alanine aminotransferase), liver histology and myeloperoxidase, and macrophage inflammatory protein-2 mRNA and cytokine-induced neutrophil chemoattractant mRNA in liver tissue, and animal survival at 3 days. Statistical analysis included Student's t test and analysis of variance when indicated.

RESULTS

Significant improvement in liver function and histology was noted in the treated group. Survival was also improved, although it is not known whether liver failure was the most proximate cause of lethality. Infiltration of neutrophils, measured by tissue myeloperoxidase, was significantly decreased in livers of treated animals. No significant changes were noted in fluid requirements. The small molecule selectin inhibitor group showed a down-regulating effect on liver macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant mRNA expression associated with less accumulation of neutrophils in the liver.

CONCLUSION

This study supports the role that selectins play in the pathogenesis of hemorrhagic shock. The mechanism of protection seen after multiple selectin blockade (TBC-1269) centered, in part, around the infiltration of liver neutrophils, probably dependent on the induction of macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant mRNA expression in liver tissue.

Microsurgical reconstruction of basal cell carcinoma defect of the face: a multidisciplinary approach

This article describes a 73-year-old white man with a history of dizziness secondary to profound anemia who presented with a large basal cell carcinoma of the left front temple region. A multidisciplinary approach to the extirpation and reconstruction of this defect is presented with a review of histopathologic features and outcomes of basal cell carcinoma excision.

Basal activity of the hypothalamic-pituitary-adrenal axis and cognitive function in anorexia nervosa

Anorexia nervosa is associated with abnormalities in neuroendocrine function including sustained hypercortisolism, which has been shown elsewhere to be associated with impairment of function in learning, memory and attention. Cognitive impairment has also been observed in anorexia nervosa. These effects may be mediated in part through cortisol effects on the hippocampus, which is dense with glucocorticoid receptors. We investigated the association between cortisol levels and cognitive function in anorexia nervosa by measuring both 24-hour urinary cortisol counts and performance on tasks of learning, memory and attention in patients suffering from the disorder. Cortisol secretion was shown to be significantly higher in the patient group than in a matched control group and patients were also shown to be impaired in memory and attention. However, no correlations were found between the cognitive deficits and cortisol measures. It is suggested that more sensitive profiling of cortisol levels throughout the circadian cycle may be useful in future studies of cognitive function in anorexia nervosa.

Inhibition of adhesion of human neutrophils and eosinophils to P-selectin by the sialyl Lewis antagonist TBC1269: preferential activity against neutrophil adhesion in vitro

BACKGROUND

Leukocyte rolling on vascular endothelium is mediated by selectins and their carbohydrate-containing counterligands. The tetrasaccharide sialyl Lewis(x) (sLe(x)) binds to all 3 selectins, so compounds that mimic sLe(x) are potential antagonists.

OBJECTIVE

Our purpose was to examine the ability of the sLe(x) mimetic TBC1269 to inhibit binding of human neutrophils and eosinophils to P-selectin.

METHODS

Expression of the primary P-selectin ligand, P-selectin glycoprotein ligand-1 (PSGL-1), was examined on neutrophils and eosinophils, and their adhesion to immobilized P-selectin was examined under both static and dynamic conditions in the presence and absence of TBC1269.

RESULTS

Neutrophils and eosinophils expressed PSGL-1, with eosinophils expressing about twice as much as neutrophils. In the absence of TBC1269, both cell types adhered avidly to P-selectin under static and dynamic conditions. For neutrophils, preincubation of P-selectin-coated plates with TBC1269 (1 to 1000 microgram/mL) resulted in concentration-dependent decreases in neutrophil adhesion, with significant inhibition seen at concentrations >/=100 microgram/mL. Eosinophil adhesion to P-selectin was more refractory to inhibition by TBC1269 and was only partially inhibited at the highest concentration tested (1000 microgram/mL). Two structurally related control compounds, TBC1900 and TBC746, had no effect when tested at similar concentrations.

CONCLUSION

These data indicate that an sLe(x) mimetic can exhibit cell type-specific differences in potencies with respect to antagonism of P-selectin adhesion. Although this may in part be the result of differences in PSGL-1 expression, the discrepancy in potencies may also be due to other differences, including carbohydrate composition and binding affinity of PSGL-1.

Activation tagging in Arabidopsis

Activation tagging using T-DNA vectors that contain multimerized transcriptional enhancers from the cauliflower mosaic virus (CaMV) 35S gene has been applied to Arabidopsis plants. New activation-tagging vectors that confer resistance to the antibiotic kanamycin or the herbicide glufosinate have been used to generate several tens of thousands of transformed plants. From these, over 30 dominant mutants with various phenotypes have been isolated. Analysis of a subset of mutants has shown that overexpressed genes are almost always found immediately adjacent to the inserted CaMV 35S enhancers, at distances ranging from 380 bp to 3.6 kb. In at least one case, the CaMV 35S enhancers led primarily to an enhancement of the endogenous expression pattern rather than to constitutive ectopic expression, suggesting that the CaMV 35S enhancers used here act differently than the complete CaMV 35S promoter. This has important implications for the spectrum of genes that will be discovered by this method.

Genetic heterogeneity in Prevotella intermedia, Prevotella nigrescens, Prevotella corporis and related species isolated from oral and nonoral sites

Prevotella intermedia (43 isolates), Prevotella nigrescens (55) and Prevotella corporis (8) from oral and nonoral sites were distinguished by species-specific DNA fragments, after hybridization of DNA fragments with ribosomal RNA (ribotyping). Eight strains previously identified as P. intermedia did not have these specific fragments. P. nigrescens, P. intermedia and P. corporis formed separate clusters in dendrograms constructed using clustering with an unweighted pair group method with arithmetic averages of similarity values derived from ribotype patterns, with 10 subclusters in P. intermedia isolates and 26 in P. nigrescens. Nine groups of P. intermedia isolates and 6 of P. nigrescens shared identical patterns. Specific ribotypes or species were not associated with particular diseases when all isolates were analyzed. However, results from organisms isolated by one laboratory using consistent clinical reporting indicated that P. intermedia was associated with more severe forms of periodontitis and P. nigrescens with mild to moderate disease.

Age-related cognitive deficits mediated by changes in the striatal dopamine system

OBJECTIVE

The study examined the influence of losses in dopaminergic function on age-related cognitive deficits.

METHOD

Eleven healthy subjects (21-68 years of age) completed a set of cognitive tasks used to assess perceptual speed and episodic memory. D(2) receptor binding was measured in the caudate and the putamen by using positron emission tomography.

RESULTS

A gradual age-related deterioration was found for all cognitive tasks and for D(2) binding in both striatal structures. Statistical control of D(2) binding eliminated the age-related cognitive variation, whereas residual effects of D(2) binding were seen after the analysis controlled for age.

CONCLUSIONS

D(2) receptor binding is a more important factor than chronological age in accounting for variation in cognitive performance across the adult lifespan. Changes in dopaminergic neurotransmission play an important role in aging-related cognitive decline.

Antibiotic resistance and prevalence of beta-lactamase in Haemophilus influenzae isolates-a surveillance study of patients with respiratory infection in Saudi Arabia

Haemophilus influenzae was isolated from patients with respiratory tract infections in five centers in Saudi Arabia. All of the 129 isolates tested by MIC agar dilution were fully susceptible to ceftazidime and ciprofloxacin but 13.2% were resistant to ampicillin, 7% to tetracycline, 5.4% to chloramphenicol, 3.9% to roxithromycin, and 1.6% to amoxicillin/clavulanic acid. Seventeen (13.2%) of all isolates produced TEM-1 type beta-lactamase, the majority (82%) characterized as biotype I or II with 4 (23.5%) encapsulated and belonging to serotype b. There was a clear distinction between the prevalence of beta-lactamase production in hospital patients (26.3% of 19 isolates) compared with community based patients (10.9% of 110 isolates). In addition, we report an increase in the prevalence of beta-lactamase negative, ampicillin intermediate strains (BLNAI) compared to previous studies in this defined geographical region. Changes in the frequency and nature of antimicrobial resistance in common respiratory pathogens confirms the need to maintain surveillance.

Substrate preferences of caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferases in developing stems of alfalfa (Medicago sativa L.)

Caffeic acid/5-hydroxyferulic acid 3/5-O-methyltransferase (COMT, EC 1.2.1.68) catalyzes at least two reactions in lignin biosynthesis. Of its two supposed substrates in the lignin pathway, COMT from most sources methylates 5-hydroxyferulic acid (5HFA) with two to three times higher activity than caffeic acid (CafA). The ratio of activity for 5HFA compared with CafA increases with the developmental age of alfalfa (Medicago sativa L.) stem internodes, from approximately 1:1 in young (third and fourth) internodes to 2:1 in mature (seventh and eighth) internodes. This observation, together with immunoblot analysis using antiserum raised against recombinant alfalfa COMT, suggests the presence of a different form of COMT, having preference for CafA compared with 5HFA, in young internodes. This apparently new O-methyltransferase (COMT II) was separated from the previously characterized COMT (COMT I) by anion exchange and hydrophobic interaction chromatography. COMT I, but not COMT II, was found in mature internodes. COMT II was not recognized by anti-(COMT I) serum. Furthermore, in addition to substrate preference, COMT II differed from COMT I in native relative molecular mass, pH optimum, and its very low K(m) for CafA. The possible physiological role of COMT II is discussed.

Dissection of malonyl-coenzyme A decarboxylation from polyketide formation in the reaction mechanism of a plant polyketide synthase

Chalcone synthase (CHS) catalyzes formation of the phenylpropanoid chalcone from one p-coumaroyl-CoA and three malonyl-coenzyme A (CoA) thioesters. The three-dimensional structure of CHS [Ferrer, J.-L., Jez, J. M., Bowman, M. E., Dixon, R. A., and Noel, J. P. (1999) Nat. Struct. Biol. 6, 775-784] suggests that four residues (Cys164, Phe215, His303, and Asn336) participate in the multiple decarboxylation and condensation reactions catalyzed by this enzyme. Here, we functionally characterize 16 point mutants of these residues for chalcone production, malonyl-CoA decarboxylation, and the ability to bind CoA and acetyl-CoA. Our results confirm Cys164's role as the active-site nucleophile in polyketide formation and elucidate the importance of His303 and Asn336 in the malonyl-CoA decarboxylation reaction. We suggest that Phe215 may help orient substrates at the active site during elongation of the polyketide intermediate. To better understand the structure-function relationships in some of these mutants, we also determined the crystal structures of the CHS C164A, H303Q, and N336A mutants refined to 1.69, 2.0, and 2.15 A resolution, respectively. The structure of the C164A mutant reveals that the proposed oxyanion hole formed by His303 and Asn336 remains undisturbed, allowing this mutant to catalyze malonyl-CoA decarboxylation without chalcone formation. The structures of the H303Q and N336A mutants support the importance of His303 and Asn336 in polarizing the thioester carbonyl of malonyl-CoA during the decarboxylation reaction. In addition, both of these residues may also participate in stabilizing the tetrahedral transition state during polyketide elongation. Conservation of the catalytic functions of the active-site residues may occur across a wide variety of condensing enzymes, including other polyketide and fatty acid synthases.

Altering expression of cinnamic acid 4-hydroxylase in transgenic plants provides evidence for a feedback loop at the entry point into the phenylpropanoid pathway

Pharmacological evidence implicates trans-cinnamic acid as a feedback modulator of the expression and enzymatic activity of the first enzyme in the phenylpropanoid pathway, L-phenylalanine ammonia-lyase (PAL). To test this hypothesis independently of methods that utilize potentially non-specific inhibitors, we generated transgenic tobacco lines with altered activity levels of the second enzyme of the pathway, cinnamic acid 4-hydroxylase (C4H), by sense or antisense expression of an alfalfa C4H cDNA. PAL activity and levels of phenylpropanoid compounds were reduced in leaves and stems of plants in which C4H activity had been genetically down-regulated. However, C4H activity was not reduced in plants in which PAL activity had been down-regulated by gene silencing. In crosses between a tobacco line over-expressing PAL from a bean PAL transgene and a C4H antisense line, progeny populations harboring both the bean PAL sense and C4H antisense transgenes had significantly lower extractable PAL activity than progeny populations harboring the PAL transgene alone. Our data provide genetic evidence for a feedback loop at the entry point into the phenylpropanoid pathway that had previously been inferred from potentially artifactual pharmacological experiments.

Altering expression of cinnamic acid 4-hydroxylase in transgenic plants provides evidence for a feedback loop at the entry point into the phenylpropanoid pathway

Pharmacological evidence implicates trans-cinnamic acid as a feedback modulator of the expression and enzymatic activity of the first enzyme in the phenylpropanoid pathway, L-phenylalanine ammonia-lyase (PAL). To test this hypothesis independently of methods that utilize potentially non-specific inhibitors, we generated transgenic tobacco lines with altered activity levels of the second enzyme of the pathway, cinnamic acid 4-hydroxylase (C4H), by sense or antisense expression of an alfalfa C4H cDNA. PAL activity and levels of phenylpropanoid compounds were reduced in leaves and stems of plants in which C4H activity had been genetically down-regulated. However, C4H activity was not reduced in plants in which PAL activity had been down-regulated by gene silencing. In crosses between a tobacco line over-expressing PAL from a bean PAL transgene and a C4H antisense line, progeny populations harboring both the bean PAL sense and C4H antisense transgenes had significantly lower extractable PAL activity than progeny populations harboring the PAL transgene alone. Our data provide genetic evidence for a feedback loop at the entry point into the phenylpropanoid pathway that had previously been inferred from potentially artifactual pharmacological experiments.

Upregulation of lung chemokines associated with hemorrhage is reversed with a small molecule multiple selectin inhibitor

BACKGROUND

Hemorrhage can modify the leukocyte-endothelial cell response leading to tissue injury. The selectin family of adhesion molecules and chemokines mediate the leukocyte-endothelial cell interaction, resulting in neutrophil sequestration and activation. This work studies whether a small molecule inhibitor of selectins can ameliorate the effect of hemorrhage on chemokine expression and neutrophil infiltration in the lung. We also aimed to assess the regulatory effect of this small molecule inhibitor of selectins in the lung functional and structural response of animals subjected to hemorrhagic shock.

STUDY DESIGN

We subjected 36 Sprague-Dawley rats to uncontrolled hemorrhagic shock for a period of 150 minutes. Three groups of animals were included (n = 12 per group)-the sham, control, and treated groups, with the latter receiving a small molecule selectin inhibitor (TBC-1269) at 25 mg/kg, which was given after tail artery transection. The following measurements were evaluated: fluid requirements during resuscitation for 150 minutes; PO2/FIO2 ratio, lung water, and lung histology, lung myeloperoxidase and lung macrophage inflammatory protein-2 (MIP-2) mRNA and cytokine induced neutrophil chemoattractant mRNA at 6 hours. Statistical analysis included Student's t-test and ANOVA.

RESULTS

There was significant improvement in lung function as expressed by PO2/FIO2 ratio and wet to dry lung water ratio in the treated group. There were no significant changes in fluid requirements between the three groups. Neutrophil infiltration, measured by tissue myeloperoxidase, was significantly (p < 0.05) decreased in the lungs of the treated animals. Lung histology was considerably improved in the treated group. The small molecule selectin inhibitor had a profound downregulating effect on macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant as expressed in lung tissue.

CONCLUSIONS

Our study confirms the key role that selectins play in the pathogenesis of hemorrhagic shock. The multiple selectin blockade allowed for better function and structure of the lung. The mechanism of protection may be secondary to the downregulation of chemokine expression and neutrophil infiltration.

Cross-talk between the signal pathways for pathogen-induced systemic acquired resistance and grazing-induced insect resistance

Reducing phenylpropanoid biosynthesis in transgenic tobacco compromises systemic acquired resistance (SAR) to tobacco mosaic virus, while increasing phenylpropanoid biosynthesis enhances SAR. Surprisingly, transgenic tobacco plants compromised in SAR exhibit more effective grazing-induced systemic resistance to larvae of Heliothis virescens, whereas induced insect resistance is compromised in transgenic plants with elevated phenylpropanoid levels. Levels of the phenylpropanoid-derived signal salicylic acid are directly correlated with overall phenylpropanoid biosynthesis in this series of transgenic plants. Moreover, while pathogen-induced SAR is almost completely compromised in salicylic acid-deficient plants expressing the bacterial nahG salicylate hydroxylase gene, these plants show enhanced grazing-induced insect resistance compared to wild-type. Hence, suppression of grazing-induced insect resistance is mediated at least in part by salicylic acid and likely reflects salicylic acid inhibition of the synthesis and action of the wound signal jasmonic acid. We propose that the dual functions of salicylic acid contribute to a signal poise which constrains constitutive expression of disease and insect resistance mechanisms, and reciprocally switches their selective activation.

Endothelin antagonists: substituted mesitylcarboxamides with high potency and selectivity for ET(A) receptors

We have previously disclosed the discovery of 2,4-disubstituted anilinothiophenesulfonamides with potent ET(A)-selective endothelin receptor antagonism and the subsequent identification of sitaxsentan (TBC11251, 1) as a clinical development compound (Wu et al. J. Med. Chem. 1997, 40, 1682 and 1690). The orally active 1 has demonstrated efficacy in a phase II clinical trial of congestive heart failure (Givertz et al. Circulation 1998, 98, Abstr. #3044) and was active in rat models of myocardial infarction (Podesser et al. Circulation 1998, 98, Abstr. #2896) and acute hypoxia-induced pulmonary hypertension (Chen et al. FASEB J. 1996, 10 (3), A104). We now report that an additional substituent at the 6-position of the anilino ring further increases the potency of this series of compounds. It was also found that a wide range of functionalities at the 3-position of the 2,4,6-trisubstituted ring increased ET(A) selectivity by approximately 10-fold while maintaining in vitro potency, therefore rendering the compounds amenable to fine-tuning of pharmacological and toxicological profiles with enhanced selectivity. The optimal compound in this series was found to be TBC2576 (7u), which has approximately 10-fold higher ET(A) binding affinity than 1, high ET(A)/ET(B) selectivity, and a serum half-life of 7.3 h in rats, as well as in vivo activity.

Development of a screening tool for detecting undernutrition and dietary inadequacy among rural elderly in Malaysia: simple indices to identify individuals at high risk

Undernutrition and the consumption of poor diets are prevalent among elderly people in developing countries. Recognising the importance of the early identification of individuals at high nutritional risk, this study aimed to develop a simple tool for screening. A cross-sectional study was conducted on 11 randomly selected villages among the 62 in Mersing District, Malaysia. Undernutrition was assessed using body mass index, plasma albumin and haemoglobin on 285 subjects. Dietary inadequacy (a count of nutrients falling below two-thirds of the Recommended Dietary Allowances) was examined for 337 subjects. Logistic regression analysis was performed to identify significant predictors of undernutrition and dietary inadequacy from social and health factors, and to derive appropriate indices based on these predictions. The multivariate predictors of undernutrition were 'no joint disease', 'smoker', 'no hypertension', 'depended on others for economic resource', 'respiratory disease', 'perceived weight loss' and 'chewing difficulty', with a joint sensitivity of 56% and specificity of 84%. The equivalent predictors of dietary inadequacy were 'unable to take public transport', 'loss of appetite', 'chewing difficulty', 'no regular fruit intake' and 'regularly taking less than three meals per day', with a joint sensitivity of 77% and specificity of 47%. These predictions, with minor modification to simplify operational use, led to the production of a simple screening tool. The tool can be used by public health professionals or community workers or leaders as a simple and rapid instrument to screen individual at high risk of undernutrition and/or dietary inadequacy.

Flavonoids and isoflavonoids - a gold mine for metabolic engineering

Flavonoid-derived plant natural products have long been known to function as floral pigments for the attraction of insect pollinators, as signal molecules for beneficial microorganisms in the rhizosphere, and as antimicrobial defense compounds. New functions for flavonoid compounds continue to be found, particularly in plant-microorganism signaling, and there has been an explosion of interest in flavonoids and isoflavonoids as health-promoting components of the human diet. The flavonoid and isoflavonoid pathways are probably the best characterized natural product pathway in plants, and are therefore excellent targets for metabolic engineering. Manipulation of flavonoid biosynthesis can be approached via several strategies, including sense or antisense manipulation of pathway genes, modification of the expression of regulatory genes, or generation of novel enzymatic specificities by ra-tional approaches based on emerging protein structure data. In addition, activation tagging provides a novel approach for the discovery of uncharacterized structural and regulatory genes of flavonoid biosynthesis.

Use it or lose it: engaged lifestyle as a buffer of cognitive decline in aging?

Data from the Victoria Longitudinal Study were used to examine the hypothesis that maintaining intellectual engagement through participation in everyday activities buffers individuals against cognitive decline in later life. The sample consisted of 250 middle-aged and older adults tested 3 times over 6 years. Structural equation modeling techniques were used to examine the relationships among changes in lifestyle variables and an array of cognitive variables. There was a relationship between changes in intellectually related activities and changes in cognitive functioning. These results are consistent with the hypothesis that intellectually engaging activities serve to buffer individuals against decline. However, an alternative model suggested the findings were also consistent with the hypothesis that high-ability individuals lead intellectually active lives until cognitive decline in old age limits their activities.