bluuebunny/crossref_metadata_2025 huggingface dataset:
Migraine Headache in Patients with Sydenham's Chorea
Authors: Teixeira AL , Meira FC , Maia DP , Cunningham MC , Cardoso F
Published: June 2005

We compared the frequency of migraine among Sydenham's chorea (SC) patients, rheumatic fever (RF) patients without neurological symptoms and matched controls. Migraine was more frequent in SC patients (12/55, 21.8%) than in controls (9/110, 8.1%) and as common as in the RF group (10/55, 18.2%). Our data are in agreement with previous studies reporting higher frequency of migraine in other basal ganglia disorders, such as essential tremor and Tourette's syndrome.
Migraine Days Decline with Duration of Illness in Adolescents with Transformed Migraine
Authors: Bigal ME , Sheftell FD , Tepper SJ , Rapoport AM , Lipton RB
Published: June 2005

The aim of this study was to assess the proportion of subjects with transformed migraine (TM) who have 15 or more migraine days per month as a function of duration of chronic daily headache (CDH) in an adolescent sample. CDH is a syndrome characterized by 15 or more headache days per month. In specialty care, TM is the most common type of CDH. Most adults who meet criteria for TM do not meet the International Headache Society (IHS) criteria for chronic migraine (CM). TM criteria require 15 or more headache days per month (not necessarily migraine), with a current or past history of migraine. CM requires 15 or more migraine days per month. As TM develops, attack frequency increases and the number of migraine features diminishes. If this observation is correct, individuals who meet criteria for TM but not CM may be at a later stage in the evolution of the disease, compared with those who meet criteria for CM. We reviewed charts of 267 adolescents (13-17 years) seen in a headache centre, to identify 117 with TM. We divide subjects with TM into those with recent onset (1 year) vs. longer duration (>1 year) and examined the number of migraine days per month and demographic features. We modelled predictors of CM (>15 migraine days per month) using logistic regression. Of 117 adolescents with TM, 55 (47%) had recent-onset (<1 year) and 62 (53%) had long-duration TM. Those with recent-onset TM were much more likely also to meet criteria for CM (74.5% vs. 25.8%, P < 0.001). This was verified in the TM with medication overuse subgroup (recent onset 66.7%, vs. long duration 37%, P = 0.01) and in the TM without medication overuse subgroup (62.2% vs. 19.2%, P = 0.001). Modelling the dichotomous outcome of CM (>15 days of migraine/month) in logistic regression, CM was predicted by recent onset of CDH, recent onset of migraine (<36 months), and younger ages (15 years), but not gender or use of migraine preventive drugs or medication overuse. Among adolescents with TM, CM is more likely in individuals who are young, whose episodic headache began recently, and with CDH of recent onset. These findings suggest that early in the process of transformation, migraine is more frequent, and that as CDH evolves, fewer typical attacks of IHS migraine occur.
Prevalence, Pattern and Predictors of use of Complementary and Alternative Medicine (CAM) in Migraine Patients Attending a Headache Clinic in Italy
Authors: Rossi P , Di Lorenzo G , Malpezzi MG , Faroni J , Cesarino F , Di Lorenzo C , Nappi G
Published: June 2005

The use of complementary and alternative medicine (CAM) in migraine is a growing phenomenon about which little is known. This study was undertaken to evaluate the rates, pattern and presence of predictors of CAM use in a clinical population of patients with different migraine subtypes. Four hundred and eighty-one migraineurs attending a headache clinic were asked to undergo a physician-administered structured interview designed to gather information on CAM use. Past use of CAM therapies was reported by 31.4% of the patients surveyed, with 17.1% having used CAM in the previous year. CAM therapies were perceived as beneficial by 39.5% of the patients who had used them. A significantly higher proportion of transformed migraine patients reported CAM treatments as ineffective compared with patients suffering from episodic migraine (73.1% vs. 50.7%, P < 0.001). The most common source of a recommendation of CAM was a friend or relative (52.7%). In most cases, migraineurs' recourse to CAM treatments was specifically for their headache (89.3%). Approximately 61% of CAM users had not informed their medical doctors of their CAM use. The most common reason for deciding to try a CAM therapy was that it offered a ‘potential improvement of headache’ (47.7%). The greatest users of CAM treatments were: patients with a diagnosis of transformed migraine; those who had consulted a high number of specialists and reported a higher lifetime number of conventional medical visits; those with a comorbid psychiatric disorder; those with a high income; and those whose headache had been either misdiagnosed or not diagnosed at all. Our findings suggest that headache clinic migraine patients, in their need of and quest for care, seek and explore both conventional and CAM approaches. Physicians should be made aware of this patient-driven change in the medical climate in order to prevent misuse of healthcare resources and to be better equipped to meet patients' needs.
MR-Spectroscopic Imaging during Visual Stimulation in Subgroups of Migraine with Aura
Authors: Sándor PS , Dydak U , Schoenen J , Kollias SS , Hess K , Boesiger P , Agosti RM
Published: June 2005

Migraine pathophysiology possibly involves deficient mitochondrial energy reserve and diminished cortical habituation. Using functional magnetic resonance spectroscopic imaging (fMRSI), we studied cortical lactate changes during prolonged visual stimulation to search for different pathophysiological mechanisms in clinically distinct subgroups of migraine with aura. Eleven healthy volunteers (HV) and 10 migraine patients were investigated interictally: five with visual aura (MA) and five with visual symptoms and at least one of the following: paraesthe-sia, paresis or dysphasia (MAplus). Using MRSI (Philips, 1.5 T) 1H-spectra were repeatedly obtained from a 25 mm-thick slice covering visual and non-visual cortex, with the first and fifth measurements in darkness and the second to fourth with 8-Hz checkerboard stimulation. In MAplus lactate increased only during stimulation, only in visual cortex; in MA resting lactate was high in visual cortex, without further increase during stimulation. This is compatible with an abnormal metabolic strain during stimulation in MAplus, possibly due to dishabituation, and a predominant mitochondrial dysfunction in MA.
The effects of apigenin‐7‐O‐β‐d‐glucuronopyranoside on reflux oesophagitis and gastritis in rats
Authors: Min Y. S. , Yim S. H. , Bai K. L. , Choi H. J. , Jeong J. H. , Song H. J. , Park S. Y. , Ham I. , Whang W. K. , Sohn U. D.
Published: June 2005

1 This study evaluated the inhibitory action of apigenin‐7‐O‐β‐d‐glucuronopyranoside (AGC), apigenin, and omeprazole on reflux oesophagitis and gastritis in rats. AGC was isolated from Clerodendron trichotomum leaves.

2 Oesophagitis and gastritis were induced by surgical procedure and the administration of indomethacin, respectively. The intraduodenal (i.d.) administration of AGC decreased the volume of gastric juice and increased the gastric pH compared with apigenin and omeprazole. The acid output was more inhibited by AGC in a dose‐dependent manner than by apigenin and omeprazole. Compared with apigenin and omeprazole, AGC significantly decreased the size of gastric lesions, which were induced by exposure of the gastric mucosa to indomethacin.

3 Malondialdehyde (MDA) content, which is the end product of lipid peroxidation, was increased significantly after the induction of reflux oesophagitis. The MDA content was decreased by AGC (i.d. 3 mg kg−1), but not by either apigenin or omeprazole. This suggests that AGC has an antioxidative effect. In the oesophagitis group, the mucosal levels of glutathione (GSH) were significantly lower than that in the normal group. However, the GSH levels were preserved after administering the AGC, suggesting that AGC possesses scavenging activity.

4 In summary, AGC is more potent than apigenin and omeprazole at inhibiting reflux oesophagitis and gastritis and may therefore be a promising drug for their treatment.
Neuronal nitric oxide synthase activity in rat urinary bladder detrusor: participation in M3 and M4 muscarinic receptor function
Authors: Orman B. , Sterin‐Borda L. , Reina S. , Borda E. S.
Published: June 2005

1 The aim of this paper was to determine the different signalling cascades involved in contraction of the rat urinary bladder detrusor muscle mediated via muscarinic acetylcholine receptors (muscarinic AChR). Contractile responses, phosphoinositides (IPs) accumulation, nitric oxide synthase (NOS) activity and cyclic GMP (cGMP) production were measured to determine the reactions associated with the effect of cholinergic agonist carbachol. The specific muscarinic AChR subtype antagonists and different inhibitors of the enzymatic pathways involved in muscarinic receptor‐dependent activation of NOS and cGMP were tested.

2 Carbachol stimulation of M3 and M4 muscarinic AChR increased contractility, IPs accumulation, NOS activity and cGMP production. All of these effects were selectively blunted by 4‐DAMP and tropicamide, M3 and M4 antagonists respectively.

3 The inhibitors of phospholipase C (PLC), calcium/calmodulin (CaM), neuronal NOS (nNOS) and soluble guanylate cyclase, but not of protein kinase C and endothelial NOS (eNOS), inhibited the carbachol action on detrusor contractility. These inhibitors also attenuated the muscarinic receptor‐dependent increase in cGMP and activation of NOS.

4 In addition, sodium nitroprusside and 8‐bromo‐cGMP, induced negative relaxant effect.

5 The results obtained suggest that carbachol activation of M3 and M4 muscarinic AChRs, exerts a contractile effect on rat detrusor that is accompanied by an increased production of cGMP and nNOS activity. The mechanism appears to occur secondarily to stimulation of IPs turnover via PLC activation. This in turn, triggers cascade reactions involving CaM, leading to activation of nNOS and soluble guanylate cyclase. They, in turn, exert a modulator inhibitory cGMP‐mediated mechanism limiting the effect of muscarinic AChR stimulation of the bladder.
Differential effects of nifedipine and verapamil on non‐adrenergic non‐cholinergic relaxations at different levels of active tone: assessment of the contribution of nerve‐derived hyperpolarizing factor
Authors: Ergün Y.
Published: June 2005

1 The objective was to investigate a possible contribution of a nerve‐derived hyperpolarizing factor to the differences between non‐adrenergic non‐cholinergic (NANC) nerve‐mediated relaxations in different states of active tone in the rat gastric fundus.

2 NANC relaxations induced by electrical field stimulation (ES: 0.1, 0.5 and 1 Hz; 25 V; 1 ms; 10 s) in 40% contracted strips (S40) were greater when compared with those in 80% contracted strips (S80).

3 ES‐induced relaxations were effectively attenuated by Nω‐nitro‐l‐arginine (l‐NNA; 100 μm) in S40 and S80. Percentage reduction of the responses obtained in the presence of l‐NNA in S40 group was less than that of S80.

4 In S40 group, nifedipine (0.5–1 μm) and verapamil (0.5–1 μm) inhibited the responses to 0.1 and 0.5 Hz. Nifedipine (1 μm) and verapamil (0.5 μm) caused no change in the responses to ES in S80.

5 In S40, when l‐NNA (100 μm) and nifedipine or verapamil, either in 1 μm concentration, were administered together, the inhibition on the electrical relaxations were more than that of each drug alone.

6 In conclusion, NANC nerve‐mediated relaxations are increased when studied in an active state of 40%, and a factor, sensitive to nifedipine seems to be responsible for this distinction.
Postjunctional modulation by muscarinic M2 receptors of responses to electrical field stimulation of rat detrusor muscle preparations
Authors: Giglio D. , Delbro D. S. , Tobin G.
Published: June 2005

1 The aim of the present study was to examine the modulator influence of muscarinic M2 receptors on responses of rat urinary bladder detrusor muscle evoked by endogenous stimuli, i.e. by stimulation of the bladder innervation.

2 Responses were evoked by electrical field stimulation (EFS; 2–20 Hz, 0.8 ms, 60 V) of isolated strip preparations mounted in organ baths. The tension of the muscle strips was recorded digitally. EFS was performed by applying stimulation with either a short duration (5 s) or a longer duration (to reach peak response; approximately 20 s).

3 Effects of muscarinic receptor antagonists (muscarinic M1/M3 receptor selective: 4‐diphenylacetoxy‐N‐methylpiperidine methobromide (4‐DAMP); muscarinic M2 receptor selective: methoctramine), a β‐adrenergic antagonist (propranolol) and an adenosine receptor antagonist (8‐p‐sulfophenyltheophylline) were assessed on contractile activity and on poststimulatory relaxations.

4 Low concentrations of methoctramine (10−8 m) reduced or tended to reduce the EFS‐induced contraction, e.g. at 2 Hz by 12% while methoctramine at 10−7 m had no significant effect. In addition, in the presence of 4‐DAMP (10−9 m), which tended to inhibit contractions at all frequencies (2–20 Hz; −17 to −25%), methoctramine at 10−8 and 10−7 m induced a further reduction of the contractile responses (−5 to −10%; 2–20 Hz).

5 The β‐adrenergic receptor antagonist propranolol (10−6 m) and the adenosine receptor antagonist 8‐p‐sulfophenyltheophylline (10−6 m) both increased contractile responses by 9–21% (2–10 Hz, long duration; P < 0.05–0.001) as a consequence of antagonizing relaxatory stimuli. Neither antagonist affected the contractile responses to EFS with the short duration stimulation. Poststimulatory relaxations were reduced by 30–60% (P < 0.05) by propranolol and by 40–60% (P < 0.001) by 8‐p‐sulfophenyltheophylline, but for 8‐p‐sulfophenyltheophylline only after stimulation with the short duration.

6 In the presence of methoctramine (10−7 m), the 8‐p‐sulfophenyltheophylline‐induced increases of the contractile response to long duration EFS were significantly enhanced at 10 Hz (+12 ± 4%; P < 0.05), whereas no such enhancement of the propranolol inhibitory effect occurred in the presence of methoctramine. However, poststimulatory β‐adrenoceptor‐evoked relaxations after short duration EFS were increased by about 35% in the presence of methoctramine, but not those after long duration.

7 Thus, muscarinic M2 receptor activation inhibits adenosine receptor‐ and β‐adrenoceptor‐evoked relaxations of the rat detrusor muscle. The inhibition occurs via a transient postjunctional mechanism that mainly affects responses with a short latency.
A comparison of the effects of the 5HT1A antagonists MM‐77 and WAY‐100635 on the mouse isolated vasa deferentia
Authors: Arkle M. J. , Arkle S. , Ebenezer I. S.
Published: June 2005

1 Experiments were carried out to characterize the possible adrenergic properties of the 5‐HT1A antagonists WAY 100635 and MM‐77 using the mouse isolated vasa deferentia preparation.

2 When vasa deferentia were preincubated for 10 min in the presence of MM‐77 (10−8–10−6 m) or WAY100635 (10−8–7 × 10−7 m), a concentration‐dependent inhibition of the contractile response to submaximal electrical field stimulation (10 Hz, 50 V, 50 ms) was observed with pIC50 values of 7.05 ± 0.01 and 6.85 ± 0.1 respectively.

3 MM‐77 (10−8–10−6 m) antagonized the contractile responses of the vasa deferentia to phenylephrine (PE) (10−6–10−3 m) in a concentration‐dependent manner. Schild plots of these data were linear and yielded a mean ρA2 value of 6.81 ± 0.084. The mean slope was 1.42 ± 0.22.

4 WAY100635 (10−8–10−6 m) antagonized the contractile responses of the vasa deferentia to PE (10−6–10−3 m) in a concentration‐dependent manner. Schild plots of these data were linear and yielded a mean ρA2 value of 7.05 ± 0.08. The mean slope was 0.97 ± 0.1.

5 The results suggest that while WAY100635 acts as a competitive antagonist at α1‐adrenoceptors, MM‐77 displays non‐competitive antagonist characteristics at this receptor subtype.

6 These results may have important implications for the use of these compounds as 5‐HT1A receptor antagonists in in vivo studies.
The Process of Entrepreneurial Learning: A Conceptual Framework
Authors: Politis Diamanto
Published: June 2005

The present article seeks to advance the theoretical knowledge of entrepreneurial learning by reviewing and synthesizing available research into a conceptual framework that explains the process of entrepreneurial learning as an experiential process. The framework identifies three main components in the process of entrepreneurial learning: entrepreneurs’ career experience, the transformation process, and entrepreneurial knowledge in terms of effectiveness in recognizing and acting on entrepreneurial opportunities and coping with the liabilities of newness. Based on the arguments in the article, five major propositions were developed to refine our understanding of entrepreneurial learning. Finally, theoretical and practical implications were discussed.
The Nature of Entrepreneurial Opportunities: Understanding the Process Using the 4I Organizational Learning Framework
Authors: Dutta Dev K. , Crossan Mary M.
Published: June 2005

In this article, we drew upon insights from two rather disparate streams of literature—entrepreneurship and organizational learning—to develop an informed understanding of the phenomenon of entrepreneurial opportunities. We examined the nature of entrepreneurial opportunities from two contrasting views—Schumpeterian and Kirznerian—and delved into their ontological roots. By applying the 4I organizational learning framework to entrepreneurial opportunities, we were able to not only resolve the apparently conflicting explanations of opportunities arising out of the contrasting ontological positions but also to achieve a level of pragmatic synthesis between them. In highlighting the article's contributions to theory and practice, we suggest that just as research on entrepreneurial opportunities benefits from applying organizational learning theory, so is organizational learning informed by research arising within the field of entrepreneurship studies.
The Role of Organizational Learning in the Opportunity–Recognition Process
Authors: Lumpkin G.T. , Lichtenstein Benyamin Bergmann
Published: June 2005

Firms engage in entrepreneurship to increase performance through both strategic renewal and the creation of new venture opportunities. Organizational learning (OL) has become an effective avenue for strategic renewal. But what of creating venture opportunities—can OL enhance the process of recognizing and pursuing new ventures? This article argues that OL can strengthen a firm's ability to recognize opportunities and help equip them to effectively pursue new ventures. First, we identify three approaches to OL—behavioral, cognitive, and action. Then, we introduce a creativity–based model of opportunity recognition (OpR) that includes two phases—discovery and formation. Next, we show how each of the three types of learning is linked to the two phases of OpR. We suggest propositions that support our claim that OL enhances OpR and offer examples of firms that have used these organizational–learning approaches to more effectively recognize and pursue venture opportunities. These insights have important implications for entrepreneurial firms seeking to advance the venture–creation process.
Explorative and Exploitative Learning from External Corporate Ventures
Authors: Schildt Henri A. , Maula Markku V.J. , Keil Thomas
Published: June 2005

This study examines the antecedents of explorative and exploitative learning of technological knowledge from external corporate ventures. We compare different forms of external corporate venturing, namely corporate venture capital investments, alliances, joint ventures, and acquisitions, as alternative avenues for interorganizational learning. Furthermore, we test the effects of multiple relational characteristics on the type of learning outcomes. Our empirical analysis is based on citations in patents filed by a sample of 110 largest U.S. public information and communications technology companies during the years 1992–2000. We find that corporate venturing mode and technological relatedness have significant effects on the likelihood of explorative learning.
The economic role of Russia's subsistence agriculture in the transition process
Authors: Wehrheim Peter , Wobst Peter
Published: June 2005

In this article, we analyze the role of subsistence‐oriented agriculture in Russia in the 1990s. We start out by discussing the diverging economic effects of the growth of subsistence agriculture in Russia since the transition process started. The quantitative analysis of this sector's role is carried out by means of an applied computable general equilibrium (CGE) model applying a 1994 social accounting matrix (SAM) as base year data. The novelty of the article is to disaggregate primary agricultural production not by products but by farm types, which enables us to distinguish their institutional and economic characteristics. The model also explicitly differentiates between marketed and subsistence consumption or formal and informal marketing activities of agricultural producers. We simulate two ex post and two ex ante experiments. The results of the first backward‐looking experiment highlight that Russia's subsistence agriculture was an important buffer against further agricultural output declines during transition and, hence, against food insecurity. A simulation, which looks into the effects of a devaluation of the Russian ruble, shows that the financial crisis should have increased the relative competitiveness particularly of large‐scale crop farms versus small‐scale farms. Two forward‐looking experiments indicate that efficiency enhancing institutional change would benefit both large‐scale and small‐scale farms. However, within small‐scale agriculture, a shift from subsistence to commercial agriculture would take place.
The impact of marketing systems on soil sustainability of agriculture in developing countries: a method and an application
Authors: Castaño Jairo , Meulenberg Matthew , Van Tilburg Aad
Published: June 2005

This article is concerned with soil‐sustainability problems of agriculture in developing countries, in particular with soil erosion. The aim of our study is to develop a comprehensive model that explains the adoption of sustainable agricultural practices with respect to soil conservation. Our approach includes the following special features: (a) the model is comprehensive in that it includes a large number of institutional, personal–social, economic, and physical explanatory variables; (b) particular attention is paid to the influence of marketing systems on the adoption of sustainable agricultural practices, which to our knowledge has been neglected in past research; (c) the concept of adopting sustainable agricultural practices (ASAP) is differentiated into a limited number of basic components of soil conservation; and (d) the model is estimated by Principal Component Regression, which enhances efficient estimation of the impact of many explanatory variables on ASAP. Our model is applied to Cabuyal hillside farming in Colombia. The application demonstrates the usefulness of the proposed model. ASAP is differentiated into three basic components: soil‐disturbance control, soil‐protection practices, and run‐off control. It appears that soil‐disturbance control is particularly influenced by farmers' characteristics, such as education and managerial variables. The second component, soil‐protection practices, appears to be strongly influenced not only by farmers' managerial variables but also by their relationship with their environment, in particular marketing institutions. The third soil‐conservation component, run‐off control, is influenced by the physical characteristics of the plot and by the available farm labor. Our empirical results demonstrate the usefulness of the proposed model in designing agricultural policies, because it can determine which variables are more likely to influence the adoption of a specific type of soil conservation.
Technology choice under changing peanut policies
Authors: Price T. Jeffrey , Lamb Marshall C. , Wetzstein Michael E.
Published: June 2005

The effect of marketing quotas and price supports on technology adoption are examined for peanut production in the southeastern United States using a real options model of investment with output price and yield uncertainty. The optimal choice of peanut production technology (dryland versus irrigated) in the southeast is shown to depend on price supports and how they change. The manner in which price supports change will have an effect on the choice and rates of abandonment or adoption of production technologies.
A study of the impact of direct trade on Taiwan's fishery sector with special reference to the effect of China's WTO accession
Authors: Chiang Fu‐Sung
Published: June 2005

After Taiwan became a member of the WTO in 2002, its tariff rates for fishery products decreased by an average of 35.5% from the level in 2001. Direct imports of fishery products from China would be allowed in 2004. These tariff reductions and the relaxation of import restrictions will have a strong effect on Taiwan's fishery sector. In this paper, we present an analysis of how fishery production, prices, input usage, and welfare distribution might react to trade liberalization. In addition to evaluating the overall impact of tariff reduction on Taiwan's fishery sector, we assess the effects of China's WTO accession on the Taiwanese market. We use a fishery sector equilibrium model in which 40 products and 68 fishing activities are identified. The model also includes an import–export subsector, a factor input subsector, and a supply–demand equilibrium condition to analyze the distributions of social welfare due to trade liberalization. Three simulations are conducted to investigate the impact of tariff reductions in 2004, 2 years after Taiwan has jointed the WTO. The results indicate that Taiwan's fishery sector will be adversely affected when it encounters the extremely low import prices of certain fishery products from China. The total production of the fishery sector and its value are predicted to decrease by 4.03% and 9.96%, respectively, in 2004. Aquaculture would suffer the heaviest loss with a 7.48% reduction in the production and a 19.23% reduction in its value. The demand for labor will decrease by 8.71%. The effect is most pronounced in aquaculture in which the demand for labor will go down by 11.40% and the wage rate will decline by 14.28%. To meet the challenge of globalization, the Taiwanese fishery industry will have to diversify, and improve its operational efficiency as well as production and distribution structures for a sustainable development.
Consistency of risk premium measures
Authors: Hudson Darren , Coble Keith , Lusk Jayson
Published: June 2005

This research uses the results of a series of within‐sample experiments to elicit risk premium measures from agricultural producers. Results show that there is little consistency between measures in different contexts and using different elicitation methods, suggesting that underlying risk preferences are not consistent. These results highlight some of the difficulty with expected utility theory and risk measurement.
Risk, uncertainty, and learning in adoption of a crop innovation
Authors: Ghadim Amir K. Abadi , Pannell David J. , Burton Michael P.
Published: June 2005

Risk and uncertainty have often been suggested as causes of poor adoption of rural innovations, but empirical evidence has been scarce. This study focuses on a new crop‐type, chickpeas, in Western Australia to gather such evidence. The empirical models developed are based on a theoretical framework that conceptualizes adoption as a dynamic decision process involving information acquisition and learning‐by‐doing by growers who vary in their managerial abilities, risk preferences, and their perceptions of the profitability and riskiness of the innovation. Learning encompasses improvements in skill as well as reductions in uncertainty. An annual face‐to‐face survey of over 100 farmers was conducted over 3 years, eliciting the farmers' risk attitudes and their subjective distributions of yields and prices. Two limited dependent variable models, Tobit and Probit, are used to estimate the empirical model. There is a high degree of goodness‐of‐fit for both models. The study provides strong empirical support for the primarily economic character of the adoption decision, and highlight the importance of economic risk in the process. The two risk‐related factors with greatest impact on the adoption decision were risk aversion and relative riskiness of the innovation. Risk aversion tended to reduce adoption, and to do so to a greater extent as relative riskiness and scale increased. Results also reveal the key role that trialing of the innovation plays in adoption.
Calcium modulates endopeptidase 24.15 (EC 3.4.24.15) membrane association, secondary structure and substrate specificity
Authors: Oliveira Vitor , Garrido Paula A. G. , Rodrigues Claudia C. , Colquhoun Alison , Castro Leandro M. , Almeida Paulo C. , Shida Claudio S. , Juliano Maria A. , Juliano Luiz , Camargo Antonio C. M. , Hyslop Stephen , Roberts James L. , Grum‐Tokars Valerie , Glucksman Marc J. , Ferro Emer S.
Published: June 2005

The metalloendopeptidase 24.15 (EP24.15) is ubiquitously present in the extracellular environment as a secreted protein. Outside the cell, this enzyme degrades several neuropeptides containing from 5 to 17 amino acids (e.g. gonadotropin releasing hormone, bradykinin, opioids and neurotensin). The constitutive secretion of EP24.15 from glioma C6 cells was demonstrated to be stimulated linearly by reduced concentrations of extracellular calcium. In the present report we demonstrate that extracellular calcium concentration has no effect on the total amount of the extracellular (cell associated + medium) enzyme. Indeed, immuno‐cytochemical analyses by confocal and electron microscopy suggested that the absence of calcium favors the enzyme shedding from the plasma membrane into the medium. Two putative calcium‐binding sites on EP24.15 (D93 and D159) were altered by site‐directed mutagenesis to investigate their possible contribution to binding of the enzyme at the cell surface. These mutated recombinant proteins behave similarly to the wild‐type enzyme regarding enzymatic activity, secondary structure, calcium sensitivity and immunoreactivity. However, immunocytochemical analyses by confocal microscopy consistently show a reduced ability of the D93A mutant to associate with the plasma membrane of glioma C6 cells when compared with the wild‐type enzyme. These data and the model of the enzyme's structure as determined by X‐ray diffraction suggest that D93 is located at the enzyme surface and is consistent with membrane association of EP24.15. Moreover, calcium was also observed to induce a major change in the EP24.15 cleavage site on distinctive fluorogenic substrates. These data suggest that calcium may be an important modulator of ep24.15 cell function.
Inhibition of the D‐alanine:D‐alanyl carrier protein ligase from Bacillus subtilis increases the bacterium's susceptibility to antibiotics that target the cell wall
Authors: May Juergen J. , Finking Robert , Wiegeshoff Frank , Weber Thomas T. , Bandur Nina , Koert Ulrich , Marahiel Mohamed A.
Published: June 2005

The surface charge as well as the electrochemical properties and ligand binding abilities of the Gram‐positive cell wall is controlled by the d‐alanylation of the lipoteichoic acid. The incorporation of d‐Ala into lipoteichoic acid requires the d‐alanine:d‐alanyl carrier protein ligase (DltA) and the carrier protein (DltC). We have heterologously expressed, purified, and assayed the substrate selectivity of the recombinant proteins DltA with its substrate DltC. We found that apo‐DltC is recognized by both endogenous 4′‐phosphopantetheinyl transferases AcpS and Sfp. After the biochemical characterization of DltA and DltC, we designed an inhibitor (d‐alanylacyl‐sulfamoyl‐adenosine), which is able to block the d‐Ala adenylation by DltA at a Ki value of 232 nmin vitro. We also performed in vivo studies and determined a significant inhibition of growth for different Bacillus subtilis strains when the inhibitor is used in combination with vancomycin.
Unusual venom phospholipases A2 of two primitive tree vipers Trimeresurus puniceus and Trimeresurus borneensis
Authors: Wang Ying‐Ming , Peng Hao‐Fan , Tsai Inn‐Ho
Published: June 2005

To explore the venom diversity of Asian pit vipers, we investigated the structure and function of venom phospholipase A2 (PLA2) derived from two primitive tree vipers Trimeresurus puniceus and Trimeresurus borneensis. We purified six novel PLA2s from T. puniceus venom and another three from T. borneensis venom. All cDNAs encoding these PLA2s except one were cloned, and the molecular masses and N‐terminal sequences of the purified enzymes closely matched those predicted from the cDNA. Three contain K49 and lack a disulfide bond at C61–C91, in contrast with the D49‐containing PLA2s in both venom species. They are less thermally stable than other K49‐PLA2s which contain seven disulfide bonds, as indicated by a decrease of 8.8 °C in the melting temperature measured by CD spectroscopy. The M110D mutation in one of the K49‐PLA2s apparently reduced its edematous potency. A phylogenetic tree based on the amino‐acid sequences of 17 K49‐PLA2s from Asian pit viper venoms illustrates close relationships among the Trimeresurus species and intergeneric segregations. Basic D49‐PLA2s with a unique Gly6 substitution were also purified from both venoms. They showed edema‐inducing and anticoagulating activities. It is notable that acidic PLA2s from both venoms inhibited blood coagulation rather than platelet aggregation, and this inhibition was only partially dependent on enzyme activity. These results contribute to our understanding of the evolution of Trimeresurus pit vipers and the structure–function relationships between various subtypes of crotalid venom PLA2.
Interaction of human stefin B in the prefibrillar oligomeric form with membranes
Authors: Anderluh Gregor , Gutirrez‐Aguirre Ion , Rabzelj Sabina , Čeru Slavko , Kopitar‐Jerala Nataša , Maček Peter , Turk Vito , Žerovnik Eva
Published: June 2005

Protein aggregation is central to most neurodegenerative diseases, as shown by familial case studies and by animal models. A modified ‘amyloid cascade’ hypothesis for Alzheimer's disease states that prefibrillar oligomers, also called amyloid‐β‐derived diffusible ligands or globular oligomers, are the responsible toxic agent. It has been proposed that these oligomeric species, as shown for amyloid‐β, β2‐microglobulin or prion fragments, exert toxicity by forming pores in membranes, initiating a cascade of detrimental events for the cell. Interaction of granular aggregates and globular oligomers of an amyloidogenic protein, human stefin B, with model lipid membranes and monolayers was studied. Prefibrillar oligomers/aggregates of stefin B are shown to cause concentration‐dependent membrane leaking, in contrast to the homologous stefin A. Prefibrillar oligomers/aggregates of stefin B also increase the surface pressure at an air–water interface, i.e. they have amphipathic character and are surface seeking. In addition, they show stronger interaction with 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine and 1,2‐dioleoyl‐sn‐glycero‐3‐[phospho‐rac‐(1‐glycerol)] monolayers than native stefin A or nonaggregated stefin B. Prefibrillar aggregates interact predominantly with acidic phospholipids, such as dioleoylphosphatidylglycerol or dipalmitoylphosphatidylserine, as shown by calcein release experiments and surface plasmon resonance. The same preparations are toxic to neuroblastoma cells, as determined by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium assay, again in contrast to the homologue stefin A, which does not aggregate under any of the conditions studied. This study is aimed to contribute to the general model of cellular toxicity induced by prefibrillar oligomers of amyloidogenic proteins, not necessarily involved in pathology.
A DmpA‐homologous protein from Pseudomonas sp. is a dipeptidase specific for β‐alanyl dipeptides
Authors: Komeda Hidenobu , Asano Yasuhisa
Published: June 2005

We have determined the nucleotide sequence of a DNA fragment covering the flanking region of the R‐stereoselective amidase gene, ramA, from the Pseudomonas sp. MCI3434 genome and found an additional gene, bapA, coding for a protein showing sequence similarity to DmpA aminopeptidase from Ochrobactrum anthropi LMG7991 (43% identity). The DmpA (called l‐aminopeptidase d‐Ala‐esterase/amidase) hydrolyzes alanine‐p‐nitroanilide, alaninamide, and alanine methylester with a preference for the d‐configuration of the alanine, whereas the enzyme acts as an l‐stereoselective aminopeptidase on a tripeptide Ala‐(Gly)2, indicating a reverse stereoselectivity [Fanuel L, Goffin C, Cheggour A, Devreese B, Van Driessche G, Joris B, Van Beeumen J & Frère J‐M (1999) Biochem J341, 147–155]. A recombinant BapA exhibiting hydrolytic activity toward d‐alanine‐p‐nitroanilide was purified from the cell‐free extract of an Escherichia coli transformant overexpressing the bapA gene and characterized. The purified enzyme contained two polypeptides corresponding to residues 1–238 (α‐peptide) and 239–366 (β‐peptide) of the precursor as observed for DmpA. On gel‐filtration chromatography, BapA in the native form appeared to be a tetramer. It had maximal activity at 60 °C and pH 9.0–10.0, and was inactivated in the presence of p‐chloromercuribenzoate, N‐ethylmaleimide, dithiothreitol, Zn2+, Ag+, Cd2+ or Hg2+. The enzyme hydrolyzed d‐alanine‐p‐nitroanilide more efficiently than l‐alanine‐p‐nitroanilide the same as DmpA. Furthermore, BapA was found to hydrolyze peptide bonds of β‐alanyl dipeptides including β‐Ala‐l‐Ala, β‐Ala‐Gly, β‐Ala‐l‐His (carnosine), β‐Ala‐l‐Leu, and (β‐Ala)2 with high efficiency compared to d‐alanine‐p‐nitroanilide. β‐Alaninamide was also efficiently hydrolyzed, but the enzyme did not act on the peptides containing proteinogenic amino acids or their d‐counterparts for N‐terminal residues. Based on its unique substrate specificity, the enzyme should not be called l‐aminopeptidase d‐Ala‐esterase/amidase but β‐Ala‐Xaa dipeptidase.
7‐Ketocholesterol‐induced apoptosis
Authors: Berthier Arnaud , Lemaire‐Ewing Stéphanie , Prunet Céline , Montange Thomas , Vejux Anne , Pais de Barros Jean Paul , Monier Serge , Gambert Philippe , Lizard Gérard , Néel Dominique
Published: June 2005

Oxysterols, and particularly 7‐ketocholesterol, appear to be strongly involved in the physiopathology of atherosclerosis. These molecules are suspected to be cytotoxic to the cells of the vascular wall and monocytes/macrophages, particularly by inducing apoptosis. Previous studies have demonstrated that 7‐ketocholesterol‐induced apoptosis is triggered by a sustained increase of cytosolic‐free Ca2+, which elicits the mitochondrial pathway of apoptosis by activation of the calcium‐dependent phosphatase calcineurin, leading to dephosphorylation of the ‘BH3 only’ protein BAD. However, thorough study of the results suggests that other pathways are implicated in 7‐ketocholesterol‐induced cytotoxicity. In this study, we demonstrate the involvement of two other calcium‐dependent pathways during 7‐ketocholesterol‐induced apoptosis. The activation of the MEK→ERK pathway by the calcium‐dependent tyrosine kinase PYK 2, a survival pathway which delays apoptosis as shown by the use of the MEK inhibitor U0126, and a pathway involving another pro‐apoptotic BH3 only protein, Bim. Indeed, 7‐ketocholesterol treatment of human monocytic THP‐1 cells induces the release of Bim‐LC8 from the microtubule‐associated dynein motor complex, and its association with Bcl‐2. Therefore, it appears that 7‐ketocholesterol‐induced apoptosis is a complex phenomenon resulting from calcium‐dependent activation of several pro‐apoptotic pathways and also one survival pathway.
Mechanism of binding of serum response factor to serum response element
Authors: Huet Alexis , Parlakian Ara , Arnaud Marie‐Claire , Glandières Jean‐Marie , Valat Pierre , Fermandjian Serge , Paulin Denise , Alpert Bernard , Zentz Christian
Published: June 2005

Serum response factor (SRF) is a MADS transcription factor that binds to the CArG box sequence of the serum response element (SRE). Through its binding to CArG sequences, SRF activates several muscle‐specific genes as well as genes that respond to mitogens. The thermodynamic parameters of the interaction of core‐SRF (the 124–245 fragment of serum response factor) with specific oligonucleotides from c‐fos and desmin promoters, were determined by spectroscopy. The rotational correlation time of core‐SRF labeled with bis‐ANS showed that the protein is monomeric at low concentration (10−7 m). The titration curves for the fluorescence anisotropy of fluorescein‐labeled oligonucleotide revealed that under equilibrium conditions, the core‐SRF monomers were bound sequentially to SRE at very low concentration (10−9 m). Curve‐fitting data showed also major differences between the wild‐type sequence and the oligonucleotide sequences mutated within the CArG box. The fluorescence of the core‐SRF tyrosines was quenched by the SRE oligonucleotide. This quenching indicated that under stoichiometric conditions, core‐SRF was bound as a dimer to the wild‐type oligonucleotide, and as a monomer or a tetramer to the mutant oligonucleotides. Far‐UV CD spectra indicated that the flexibility of core‐SRF changed profoundly upon its binding to its specific target SRE. Lastly, the rotational correlation time of fluorescein‐labeled SRE revealed that formation of the specific complex was accompanied by a change in the SRE internal dynamics. These results indicated that the flexibility of the two partners is crucial for the DNA–protein interaction.
Pharmacology of vascular endothelium
Authors: Gryglewski Ryszard J.
Published: June 2005

Sir John Vane named vascular endothelium ‘the maestro of blood circulation’. Recently, ‘the maestro’ has become a target for pharmacotherapy of atherothrombotic and diabetic vasculopathies with well known cardio‐vascular drugs belonging to the families of Angiotensin Converting Enzyme inhibitors, HMG CoA reductase inhibitors or β1‐Adrenoceptor antagonists. These drugs became upgraded to a position of the pleiotropic endothelial drugs. It is not a simple verbal change in the nomenclature. It means that these drugs apart from their well defined mechanisms of action, as indicated in their regular names, in addition they act in an unknown mechanism at the level of vascular endothelium preventing angina, myocardial infarction and stroke. Many biochemical events take place in endothelial cells. I chose for a closer inspection the nitric oxide/prostacyclin defensive system to explain the endothelial pleiotropism of the drugs in question. I tried to examine the validity of this conception according to the general rule: in vitro cognitio sed in vivo veritas.
Regulation of arginase II by interferon regulatory factor 3 and the involvement of polyamines in the antiviral response
Authors: Grandvaux Nathalie , Gaboriau François , Harris Jennifer , tenOever Benjamin R. , Lin Rongtuan , Hiscott John
Published: June 2005

The innate antiviral response requires the induction of genes and proteins with activities that limit virus replication. Among these, the well‐characterized interferon β (IFNB) gene is regulated through the cooperation of AP‐1, NF‐κB and interferon regulatory factor 3 (IRF‐3) transcription factors. Using a constitutively active form of IRF‐3, IRF‐3 5D, we showed previously that IRF‐3 also regulates an IFN‐independent antiviral response through the direct induction of IFN‐stimulated genes. In this study, we report that the arginase II gene (ArgII) as well as ArgII protein concentrations and enzymatic activity are induced in IRF‐3 5D‐expressing and Sendai virus‐infected Jurkat cells in an IFN‐independent manner. ArgII is a critical enzyme in the polyamine‐biosynthetic pathway. Of the natural polyamines, spermine possesses antiviral activity and mediates apoptosis at physiological concentrations. Measurement of intracellular polyamine content revealed that expression of IRF‐3 5D induces polyamine production, but that Sendai virus and vesicular stomatitis virus infections do not. These results show for the first time that the ArgII gene is an early IRF‐3‐regulated gene, which participates in the IFN‐independent antiviral response through polyamine production and induction of apoptosis.
The impact of G‐protein‐coupled receptor hetero‐oligomerization on function and pharmacology
Authors: Maggio Roberto , Novi Francesca , Scarselli Marco , Corsini Giovanni U.
Published: June 2005

Although highly controversial just a few years ago, the idea that G‐protein‐coupled receptors (GPCRs) may undergo homo‐oligomerization or hetero‐oligomerization has recently gained considerable attention. The recognition that GPCRs may exhibit either dimeric or oligomeric structures is based on a number of different biochemical and biophysical approaches. Although much effort has been spent to demonstrate the mechanism(s) by which GPCRs interact with each other, the physiological relevance of this phenomenon remains elusive. An additional source of uncertainty stems from the realization that homo‐oligomerization and hetero‐oligomerization of GPCRs may affect receptor binding and activity in different ways, depending on the type of interacting receptors. In this brief review, the functional and pharmacological effects of the hetero‐oligomerization of GPCR on binding and cell signaling are critically analyzed.
An alcohol acyl transferase from apple (cv. Royal Gala), MpAAT1, produces esters involved in apple fruit flavor
Authors: Souleyre Edwige J. F. , Greenwood David R. , Friel Ellen N. , Karunairetnam Sakuntala , Newcomb Richard D.
Published: June 2005

Apple flavor is characterized by combinations of ester compounds, which increase markedly during fruit ripening. The final step in ester biosynthesis is catalyzed by alcohol acyl transferases (AATs) that use coenzyme A (CoA) donors together with alcohol acceptors as substrates. The gene MpAAT1, which produces a predicted protein containing features of other plant acyl transferases, was isolated from Malus pumila (cv. Royal Gala). The MpAAT1 gene is expressed in leaves, flowers and fruit of apple. The recombinant enzyme can utilize a range of alcohol substrates from short to medium straight chain (C3–C10), branched chain, aromatic and terpene alcohols. The enzyme can also utilize a range of short to medium chain CoAs. The binding of the alcohol substrate is rate limiting compared with the binding of the CoA substrate. Among different alcohol substrates there is more variation in turnover compared with Km values. MpAAT1 is capable of producing many esters found in Royal Gala fruit, including hexyl esters, butyl acetate and 2‐methylbutyl acetate. Of these, MpAAT1 prefers to produce the hexyl esters of C3, C6 and C8 CoAs. For the acetate esters, however, MpAAT1 preference depends upon substrate concentration. At low concentrations of alcohol substrate the enzyme prefers utilizing the 2‐methylbutanol over hexanol and butanol, while at high concentrations of substrate hexanol can be used at a greater rate than 2‐methylbutanol and butanol. Such kinetic characteristics of AATs may therefore be another important factor in understanding how the distinct flavor profiles of different fruit are produced during ripening.