Economic evaluation of antimicrobial usage surveillance in livestock.

There is increased pressure by governments and industry to develop national surveillance programmes to evaluate antimicrobial usage (AMU) in animals. This article presents a methodological approach to cost-effectiveness analysis of such programmes. Seven objectives are proposed for AMU surveillance in animals: quantifying use, finding trends, detecting hotspots, identifying risk factors, encouraging research, evaluating the impact of policies and diseases, and demonstrating compliance with regulations. Achieving these objectives would assist in making decisions about potential interventions, help to generate trust, incentivise the reduction of AMU and decrease the risk of antimicrobial resistance. The cost-effectiveness of each objective can be found by dividing the cost of the programme by the performance indicators of the surveillance required to meet the objective concerned. The precision and accuracy of surveillance outputs are suggested here as useful performance indicators. Precision depends on the level of surveillance coverage (SC) and surveillance representativeness (SR). Accuracy is influenced by the quality of farm records and SR. The authors argue that there is an increase in marginal cost for each unit increase of SC, SR and data quality. This is caused by the increasing difficulty of recruiting farmers due to potential barriers such as staff capacity, capital availability, computing literacy and availability, and geographical differences, among other factors. A simulation model was conducted to test the approach, using the quantification of AMU as the primary objective, and to provide evidence of the application of the law of diminishing returns. Cost-effectiveness analysis can be used to support decisions on the level of coverage, representativeness and data quality required in such AMU programmes.

Les gouvernements tout comme le secteur de l'élevage exercent une pression croissante pour que des programmes nationaux de surveillance soient élaborés afin d'évaluer l'utilisation d'agents antimicrobiens (UAM) chez les animaux. Cet article présente une approche méthodologique permettant de réaliser l'analyse coût-efficacité de ces programmes. Sept objectifs sont proposés pour la surveillance de l'UAM chez les animaux : quantifier cette utilisation, relever les tendances, détecter les situations d'utilisation intensive, déceler les facteurs de risque, encourager la recherche, évaluer l'impact des politiques et des maladies et démontrer la conformité avec les réglementations. La réalisation de ces objectifs de surveillance permettra de prendre des décisions éclairées sur les interventions à mener, contribuera à mettre en place un climat de confiance, encouragera à réduire l'UAM et atténuera le risque d'apparition d'antibiorésistances. Le ratio coût-efficacité de chaque objectif peut être déterminé en divisant le coût du programme par les indicateurs de performance de la surveillance requise pour chacun des objectifs examinés. Les auteurs considèrent que la précision et l'exactitude des résultats de la surveillance sont des indicateurs de performance utiles à cet effet. La précision dépend du niveau de couverture de la surveillance (CS) et de sa représentativité (RS). L'exactitude est fonction de la qualité des registres d'élevage et de la RS. D'après les auteurs, chaque accroissement unitaire de la CS, de la RS et de la qualité des données donne lieu à une augmentation du coût marginal. Celle-ci s'explique par la difficulté croissante de recruter des éleveurs pour cette activité, en raison d'obstacles tels que le manque d'effectifs, la disponibilité de capitaux, le manque de compétences et d'équipements informatiques et les différences géographiques, entre autres facteurs potentiels. Un modèle de simulation a été mis en oeuvre pour tester cette approche à partir de l'objectif principal (la quantification de l'UAM), et pour apporter des éléments démontrant l'application de la loi des rendements décroissants dans ce domaine. L'analyse coût-efficacité peut être utilisée pour étayer les décisions concernant la couverture, la représentativité et la qualité des données requises pour les programmes de surveillance de l'UAM.

Los gobiernos y la industria vienen presionando cada vez más para la implantación de programas nacionales de vigilancia destinados a evaluar el uso de agentes antimicrobianos (UAM) en los animales. Los autores presentan una solución metodológica para analizar la relación costo-eficacia de tales programas. En primer lugar proponen un conjunto de siete objetivos que deben cumplirse al vigilar el UAM en los animales: cuantificar el uso, detectar tendencias, localizar áreas de "gran intensidad" de uso, determinar los factores de riesgo, alentar la investigación, evaluar la repercusión de las políticas y las enfermedades y comprobar la observancia de los reglamentos. El logro de estos objetivos ayudaría a decidir sobre posibles intervenciones y a generar confianza, supondría un incentivo para reducir el UAM y atenuaría el riesgo de que surgieran resistencias a estos productos. Para cada objetivo es posible determinar la relación costo-eficacia dividiendo el costo del programa por los indicadores de desempeño de la vigilancia requerida para cumplir el objetivo en cuestión. Los autores proponen utilizar la precisión y exactitud de los resultados de la vigilancia como útiles indicadores de desempeño. La precisión depende del nivel de cobertura y de representatividad de la vigilancia. En la exactitud, por su parte, influyen la calidad de los archivos de las explotaciones pecuarias y la representatividad de la vigilancia. Los autores postulan que cada aumento unitario de la cobertura y la representatividad de la vigilancia y de la calidad de los datos se acompaña de un aumento correspondiente del costo marginal. Ello se explica por la creciente dificultad que presenta la participación de ganaderos en el proceso, debida a su vez a posibles barreras en aspectos como la dotación de personal, el capital disponible, los conocimientos en informática y el acceso a ordenadores o las diferencias geográficas, entre otros factores. Para ensayar el método y probar que se aplica el principio de los rendimientos decrecientes, los autores emplearon un modelo de simulación, utilizando como principal objetivo la cuantificación del UAM. El análisis de la relación costo-eficacia puede ser utilizado como herramienta auxiliar para tomar decisiones sobre el nivel de cobertura, representatividad y calidad de los datos que se necesita en este tipo de programas de vigilancia del UAM.

Unfolded protein response-induced dysregulation of calcium homeostasis promotes retinal degeneration in rat models of autosomal dominant retinitis pigmentosa.

The molecular mechanism of autosomal dominant retinitis pigmentosa (ADRP) in rats is closely associated with a persistently activated unfolded protein response (UPR). If unchecked, the UPR might trigger apoptosis, leading to photoreceptor death. One of the UPR-activated cellular signaling culminating in apoptotic photoreceptor cell death is linked to an increase in intracellular Ca(2+). Therefore, we validated whether ADRP retinas experience a cytosolic Ca(2+) overload, and whether sustained UPR in the wild-type retina could promote retinal degeneration through Ca(2+)-mediated calpain activation. We performed an ex vivo experiment to measure intracellular Ca(2+) in ADRP retinas as well as to detect the expression levels of proteins that act as Ca(2+) sensors. In separate experiments with the subretinal injection of tunicamycin (UPR inducer) and a mixture of calcium ionophore (A231278) and thapsigargin (SERCA2b inhibitor) we assessed the consequences of a sustained UPR activation and increased intracellular Ca(2+) in the wild-type retina, respectively, by performing scotopic ERG, histological, and western blot analyses. Results of the study revealed that induced UPR in the retina activates calpain-mediated signaling, and increased intracellular Ca(2+) is capable of promoting retinal degeneration. A significant decline in ERG amplitudes at 6 weeks post treatment was associated with photoreceptor cell loss that occurred through calpain-activated CDK5-pJNK-Csp3/7 pathway. Similar calpain activation was found in ADRP rat retinas. A twofold increase in intracellular Ca(2+) and up- and downregulations of ER membrane-associated Ca(2+)-regulated IP3R channels and SERCA2b transporters were detected. Therefore, sustained UPR activation in the ADRP rat retinas could promote retinal degeneration through increased intracellular Ca(2+) and calpain-mediated apoptosis.

Central projections of intrinsically photosensitive retinal ganglion cells in the macaque monkey.

Circadian rhythms generated by the suprachiasmatic nucleus (SCN) are entrained to the environmental light/dark cycle via intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin and the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP). The ipRGCs regulate other nonimage-forming visual functions such as the pupillary light reflex, masking behavior, and light-induced melatonin suppression. To evaluate whether PACAP-immunoreactive retinal projections are useful as a marker for central projection of ipRGCs in the monkey brain, we characterized the occurrence of PACAP in melanopsin-expressing ipRGCs and in the retinal target areas in the brain visualized by the anterograde tracer cholera toxin subunit B (CtB) in combination with PACAP staining. In the retina, PACAP and melanopsin were found to be costored in 99% of melanopsin-expressing cells characterized as inner and outer stratifying melanopsin RGCs. Two macaque monkeys were anesthetized and received a unilateral intravitreal injection of CtB. Bilateral retinal projections containing colocalized CtB and PACAP immunostaining were identified in the SCN, the lateral geniculate complex including the pregeniculate nucleus, the pretectal olivary nucleus, the nucleus of the optic tract, the brachium of the superior colliculus, and the superior colliculus. In conclusion, PACAP-immunoreactive projections with colocalized CtB represent retinal projections of ipRGCs in the macaque monkey, supporting previous retrograde tracer studies demonstrating that melanopsin-containing retinal projections reach areas in the primate brain involved in both image- and nonimage-forming visual processing.

Improved ventilation-perfusion matching by abdominal insufflation (pneumoperitoneum) with CO2 but not with air.

BACKGROUND: Pneumoperitoneum (PP) by CO2-insufflation causes atelectasis however with maintained or even improved oxygenation. We studied the effect of abdominal insufflation by carbon dioxide (CO2) and air on gas exchange during PP. METHODS: Twenty-seven anesthetized pigs were studied during PP with insufflations to 12 mmHg by either 1/CO2, 2/ air or 3/CO2 during intravenous nitroprusside infusion (SNP) (N.=9 in each group). In 3 pigs in each group, gamma camera technique (SPECT) was used to study ventilation and perfusion distributions, in another 6 pigs an inert-gas technique (MIGET) was used for assessing ventilation-perfusion matching (VA/Q). Measurements were made during anesthesia before and after 60 minutes of PP. RESULTS: CO2-PP caused a shift of blood flow away from dependent, non-ventilated (atelectatic) to ventilated regions. Air-PP caused smaller, and SNP-PP even less shift of lung blood flow. Shunt decreased during CO2-PP (6 ± 1% compared to baseline 9 ± 2%, P<0.05), did not change during Air-PP (10 ± 2%) and increased during SNP-PP (16 ± 2%, P<0.05). PaO2 increased from baseline 35 ± 2 to 41 ± 3 kPa during CO2-PP and decreased to 32 ± 3 kPa during Air-PP and to 27 ± 3 kPa during SNP-PP (P<0.05 for all three comparisons). PaCO2 increased during CO2- and SNP-PP. CONCLUSION: CO2-PP enhanced the shift of blood flow towards better ventilated areas of the lung compared to Air-PP and SNP blunted the effects seen with CO2-PP. SNP may thus have blunted and CO2 potentiated vasoconstriction, by hypoxic pulmonary vasoconstriction or another mechanism.

No additive effects of inhaled iloprost and prone positioning on pulmonary hypertension and oxygenation in acute respiratory distress syndrome.

BACKGROUND: In acute respiratory distress syndrome (ARDS), pulmonary hypertension is associated with a poor prognosis. Prone position is effective to improve oxygenation whereas inhaled iloprost can treat pulmonary hypertension. However, combination of these interventions has not been examined before. The hypothesis was that this combination had additive effects on oxygenation and pulmonary hemodynamics as compared with each intervention alone. METHODS: In a prospective, randomized cross-over study, ten pigs were anesthetized, intubated and ventilated with volume controlled ventilation. Carotid, jugular venous and pulmonary artery catheters were inserted. ARDS was induced with oleic acid (0.20 mL/kg). Measurements were repeated in randomized different sequences of prone or supine positions with or without iloprost inhalation (220 ng/kg/min) (four combinations). Systemic and pulmonary arterial pressures; arterial and mixed venous blood gases; and Qs/Qt and the resistances were recorded. RESULTS: Iloprost decreased pulmonary artery pressures (for MPAP: P=0.034) in both supine (37±10 vs. 31±8 mmHg; P<0.05) and prone positions (38±9 vs. 29±8 mmHg; P<0.05); but did not obtain a significant improvement in oxygenation in both positions. Prone position improved the oxygenation (p<0.0001) compared to supine position in both with (361±140 vs. 183±158 mmHg, P<0.05) or without iloprost application (331±112 vs. 167±117 mmHg, P<0.05); but did not achieve a significant decrease in MPAP. CONCLUSION: Although iloprost reduced pulmonary arterial pressures, and prone positioning improved oxygenation; there are no additive effects of the combination of both interventions on both parameters. To treat both pulmonary hypertension and hypoxemia, application of iloprost in prone position is suggested.

Improved ventilation-perfusion matching with increasing abdominal pressure during CO(2) -pneumoperitoneum in pigs.

BACKGROUND: CO(2) -pneumoperitoneum (PP) is performed at varying abdominal pressures. We studied in an animal preparation the effect of increasing abdominal pressures on gas exchange during PP. METHODS: Eighteen anaesthetized pigs were studied. Three abdominal pressures (8, 12 and 16 mmHg) were randomly selected in each animal. In six pigs, single-photon emission computed tomography (SPECT) was used for the analysis of V/Q distributions; in another six pigs, multiple inert gas elimination technique (MIGET) was used for assessing V/Q matching. In further six pigs, computed tomography (CT) was performed for the analysis of regional aeration. MIGET, CT and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia and after 60 min on each of the three abdominal pressures. SPECT was performed three times, corresponding to each PP level. RESULTS: Atelectasis, as assessed by CT, increased during PP and in proportion to abdominal pressure [from 9 ± 2% (mean ± standard deviation) at 8 mmHg to 15 ± 2% at 16 mmHg, P<0.05]. SPECT during increasing abdominal CO(2) pressures showed a shift of blood flow towards better ventilated areas. V/Q analysis by MIGET showed no change in shunt during 8 mmHg PP (9 ± 1.9% compared with baseline 9 ± 1.2%) but a decrease during 12 mmHg PP (7 ± 0.9%, P<0.05) and 16 mmHg PP (5 ± 1%, P<0.01). PaO(2) increased from 39 ± 10 to 52 ± 9 kPa (baseline to 16 mmHg PP, P<0.01). Arterial carbon dioxide (PCO(2) ) increased during PP and increased further with increasing abdominal pressures. CONCLUSION: With increasing abdominal pressure during PP perfusion was redistributed more than ventilation away from dorsal, collapsed lung regions. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction mediated by increasing PCO(2) .

Ventilation-perfusion distributions and gas exchange during carbon dioxide-pneumoperitoneum in a porcine model.

BACKGROUND: Carbon dioxide (CO2)-pneumoperitoneum (PP) of 12 mm Hg increases arterial oxygenation, but it also promotes collapse of dependent lung regions. This seeming paradox prompted the present animal study on the effects of PP on ventilation-perfusion distribution (V/Q) and gas exchange. METHODS: Fourteen anaesthetized pigs were studied. In seven pigs, single photon emission computed tomography (SPECT) was used for spatial analysis of ventilation and perfusion distributions, and in another seven pigs, multiple inert gas elimination technique (MIGET) was used for detailed analysis of V/Q matching. SPECT/MIGET and central haemodynamics and pulmonary gas exchange were recorded during anaesthesia before and 60 min after induction of PP. RESULTS: SPECT during PP showed no or only poorly ventilated regions in the dependent lung compared with the ventilation distribution during anaesthesia before PP. PP was accompanied by redistribution of blood flow away from the non- or poorly ventilated regions. V/Q analysis by MIGET showed decreased shunt from 9 (sd 2) to 7 (2)% after induction of PP (P<0.05). No regions of low V/Q were seen either before or during PP. Almost no regions of high V/Q developed during PP (1% of total ventilation). Pa(o2) increased from 33 (1.2) to 35.7 (3.2) kPa (P<0.01) and arterial to end-tidal Pco2 gradient (Pae'(co2) increased from 0.3 (0.1) to 0.6 (0.2) kPa (P<0.05). CONCLUSIONS: Perfusion was redistributed away from dorsal, collapsed lung regions when PP was established. This resulted in a better V/Q match. A possible mechanism is enhanced hypoxic pulmonary vasoconstriction.

Development of atelectasis and arterial to end-tidal PCO2-difference in a porcine model of pneumoperitoneum.

BACKGROUND: Intraperitoneal insufflation of carbon dioxide (CO2) may promote collapse of dependent lung regions. The present study was undertaken to study the effects of CO2-pneumoperitoneum (CO2-PP) on atelectasis formation, arterial oxygenation, and arterial to end-tidal PCO2-gradient (Pa-E'(CO2)). METHODS: Fifteen anaesthetized pigs [mean body weight 28 (SD 2) kg] were studied. Spiral computed tomography (CT) scans were obtained for analysis of lung tissue density. In Group 1 (n=5) mechanical ventilation (V(T)=10 ml kg (-1), FI(O2)=0.5) was applied, in Group 2 (n=5) FI(O2) was increased for 30 min to 1.0 and in Group 3 (n=5) negative airway pressure was applied for 20 s in order to enhance development of atelectasis. Cardiopulmonary and CT data were obtained before, 10, and 90 min after induction of CO2-PP at an abdominal pressure of 12 mmHg. RESULTS: Before CO2-PP, in Group 1 non-aerated tissue on CT scans was 1 (1)%, in Group 2 3 (2)% (P<0.05, compared with Group 1), and in Group 3 7 (3)% (P<0.05, compared with Group 1 and Group 2). CO2-PP significantly increased atelectasis in all groups. PaO2/FI(O2) fell and venous admixture ('shunt') increased in proportion to atelectasis during anaesthesia but CO2-PP had a varying effect on PaO2/FI(O2) and shunt. Thus, no correlation was seen between atelectasis and PaO2/FI(O2) or shunt when all data before and during CO2-PP were pooled. Pa-E'(CO2), on the other hand correlated strongly with the amount of atelectasis (r2=0.92). CONCLUSIONS: Development of atelectasis during anaesthesia and PP may be estimated by an increased Pa-E'(CO2).

One-lung ventilation induces hyperperfusion and alveolar damage in the ventilated lung: an experimental study.

BACKGROUND: One-lung ventilation (OLV) increases mechanical stress in the lung and affects ventilation and perfusion (V, Q). There are no data on the effects of OLV on postoperative V/Q matching. Thus, this controlled study evaluates the influence of OLV on V/Q distribution in a pig model using a gamma camera technique [single-photon emission computed tomography (SPECT)] and relates these findings to lung histopathology after OLV. METHODS: Eleven anaesthetized and ventilated pigs (V(T)=10 ml kg(-1), Fio2=0.40, PEEP=5 cm H2O) were studied. After lung separation, OLV and thoracotomy were performed in seven pigs (OLV group). During OLV and in a two-lung ventilation (TLV), control group (n=4) ventilation settings remained unchanged. SPECT with (81m)Kr (ventilation) and (99m)Tc-labelled macro-aggregated albumin (perfusion) was performed before, during, and 90 min after OLV/TLV. Finally, lung tissue samples were harvested and examined for alveolar damage. RESULTS: OLV affected ventilation and haemodynamic variables, but there were no differences between the OLV group and the control group before and after OLV/TLV. SPECT revealed an increase of perfusion in the dependent lung compared with baseline (49-56%), and a corresponding reduction of perfusion (51-44%) in non-dependent lungs after OLV. No perfusion changes were observed in the control group. This resulted in increased low V/Q regions and a shift of V/Q areas to 0.3-0.5 (10(-0.5)-10(-0.3)) in dependent lungs of OLV pigs and was associated with an increased diffuse alveolar damage score. CONCLUSIONS: OLV in pigs results in a substantial V/Q mismatch, hyperperfusion, and alveolar damage in the dependent lung and may thus contribute to gas exchange impairment after thoracic surgery.

Strychnine, but not PMBA, inhibits neuronal nicotinic acetylcholine receptors expressed by rabbit retinal ganglion cells.

Strychnine is considered a selective competitive antagonist of glycine gated Cl- channels (Saitoh et al., 1994) and studies have used strychnine at low micromolar concentrations to study the role of glycine in rabbit retina (Linn, 1998; Protti et al., 2005). However, other studies have shown that strychnine, in the concentrations commonly used, is also a potent competitive antagonist of alpha7 nicotinic acetylcholine receptors (nAChRs; Matsubayashi et al., 1998). We tested the effects of low micromolar concentrations of strychnine and 3-[2'-phosphonomethyl[1,1'-biphenyl]-3-yl] alanine (PMBA), a specific glycine receptor blocker (Saitoh et al., 1994; Hosie et al., 1999) on the activation of both alpha7 nAChRs on retinal ganglion cells and on ganglion cell responses to a light flash. Extracellular recordings were obtained from ganglion cells in an isolated retina/choroid preparation and 500 microM choline was used as an alpha7 agonist (Alkondon et al., 1997). We recorded from brisk sustained and brisk transient OFF cells, many of which have been previously shown to have alpha7 receptors (Strang et al., 2005). Further, we tested the effect of strychnine, PMBA and alpha-bungarotoxin on the binding of tetramethylrhodamine alpha-bungarotoxin in the inner plexiform layer. Our data indicates that strychnine, at doses as low as 1.0 microM, can inhibit the alpha7 nAChR-mediated response to choline, but PMBA at concentrations as high as 0.4 microM does not. Binding studies show strychnine and alpha-bungarotoxin inhibit binding of labeled alpha-bungarotoxin in the IPL. Thus, the effects of strychnine application may be to inhibit glycine receptors expressed by ganglion cell or to inhibit amacrine cell alpha7 nAChRs, both of which would result in an increase in the ganglion cell responses. Further research will be required to disentangle the effects of strychnine previously believed to be caused by a single mechanism of glycine receptor inhibition.

Anesthetic considerations in patients with previous thoracic surgery.

PURPOSE OF THE REVIEW: This review presents an overview of the different problems and challenges after thoracic surgery. It covers the pathophysiological changes that may occur regularly in the early and late period following surgery. In addition, surgical complications with anesthesiological implications for diagnosis, treatment and prevention are discussed, and consequences for anesthesia in further major and thoracic surgical procedures are shown. RECENT FINDINGS: During the last decade, complications in the early period following surgery after thoracotomy have increasingly moved into the focus caused by their high morbidity and mortality. These problems, such as hemorrhagia and bronchopleural fistulas, are important because they call for a prompt revision or even an emergency operation. The therapy of acute bleeding follows general anesthesiological guidelines whereas the bronchopleural fistula demands methods to prevent aspiration pneumonia as a first priority. In the late period following surgery, typical cardiac and pulmonary modifications can be described that persist and have anesthesiological implications in the case of further surgery. Recent literature, however, lacks clear recommendations regarding anesthesiological management and practice for these cases. SUMMARY: Current literature presents no general recommendations on how to manage patients after recent thoracic surgery. Therefore it is necessary to find an individual strategy to handle possible complications and well known pathophysiological changes. Knowledge and understanding of the etiology, the pathophysiology and the risk factors of the perioperative period, allows prevention and target intervention aimed at reducing morbidity and mortality following surgery.

[Is the pneumoperitoneum minimally invasive during laparoscopic colonic surgery?]. / Ist das Pneumoperitoneum bei Kolonresektion wirklich minimalinvasiv? Standpunkt aus anästhesiologischer Sicht.

The importance of laparoscopic colonic surgery has increased considerably in the past decade. However, a minimally invasive operation with induction of pneumoperitoneum does not imply a minimally invasive anaesthesia. The haemodynamic effects of intraperitoneal carbon dioxide insufflation depend an the extent of intraabdominal pressure elevation, severity of preexisting cardiopulmonary diseases, alterations of arterial PCO (2) and pH, volume state of the patient and co-medications. In addition, positioning of the patient for laparoscopic colonic surgery and endocrinological reactions during and after induction of pneumoperitoneum may significantly affect systemic and pulmonary haemodynamics. Intraabdominal operations may impair respiratory function independent from anaesthesia. Preoperative evaluation of the high risk patient is of utmost importance. Assessment of expiratory PCO (2), extended cardiopulmonary monitoring and maintenance of intraabdominal pressure in the range of 5 - 7 mmHg are recommended during laparoscopic colonic surgery.

Cost-minimization study comparing Simulect vs. Thymoglobulin in renal transplant induction.

PURPOSE: Based on the data of clinical trial CHI-F-02 comparing the efficacy and safety of basiliximab (Simulect) vs. anti-thymocyte globulin (Thymoglobulin) in renal transplant induction, we carried out an economic evaluation. METHOD: This pharmacoeconomic study was a cost-minimization study, i.e. given the equivalent efficacy of the products, the strategy that minimized the cost of care was considered better. The cost of care was analyzed from the hospital perspective. MATERIAL: This 'piggyback' study of 100 patients estimated the direct medical costs incurred over 6 months of use of two strategies for renal transplant induction therapy. Direct medical costs are those of utilized medical resources: medications, hospital stays, dialysis, and physician visits and investigations not scheduled in the protocol. RESULTS: In the Simulect arm, significant reductions were found in the initial hospital stay duration and number of infectious episodes. Therefore, although the average cost of treatment was slightly higher with Simulect) than with Thymoglobulin (2964 vs. 2298 Euros), the cost of the initial hospitalization was significantly lower in the Simulect arm (10 907 vs. 11 967 Euros; p = 0.02). Furthermore the mean cost of infectious episodes was significantly lower in the Simulect arm (1056 vs. 1790 Euros, p = 0.03). Cytomegalovirus infection accounted for a significantly smaller proportion of this cost in the Simulect arm than in the Thymoglobulin arm (30% vs. 53%, p = 0.001). CONCLUSION: This study showed direct medical cost savings of 1159 Euros per patient in the Simulect arm, which more than compensated for the higher price of this immunosuppressive drug.

Usage of triptans among migraine patients: an audit in nine GP practices.

A retrospective audit was carried out to investigate triptan usage over a period of one year among 360 adult patients with migraine in nine GP practices in the UK and the Republic of Ireland. Data from patient records were analysed, in conjunction with replies to a questionnaire about patients' perceptions of their migraine and its treatment. The majority of patients included in the audit were women (83%), and most patients (81%) were aged between 35 and 64 years. Most patients in the audit population (60%) were in the lowest band of triptan usage (1-36 tablets prescribed over 12 months); 7% had moderate usage (37-53 tablets). A minority of patients appeared to be taking triptans in higher quantities: about 15% of patients had been prescribed 54-94 triptan tablets over a year, 9% had received prescriptions for 95-149 tablets and 7% had received prescriptions for 150 or more tablets. These results indicated that some migraine patients were using triptans at higher than expected rates, and suggested that some patients might have been using their prescribed triptans inappropriately to treat a headache that they incorrectly perceived as migraine (e.g. chronic daily headache). Analyses were carried out to identify predictors of high usage. Predictors identified included the use of several other (non-triptan) medications to treat conditions other than migraine, one triptan dose being reported as sufficient to treat an attack, patient's perception of all headaches as migraine and lack of concern about taking too much medication. Patients identified as using triptans at a higher than expected rate can be called in for review of migraine diagnosis, identification of possible causes of any increased frequency of attacks, and investigation of suspected non-migrainous headaches, such as chronic daily headache and medication-induced headaches. For GPs, such actions would help achieve and maintain a high standard of care for their migraine patients, thus helping to contribute towards meeting the demands of the clinical governance agenda. Audit of triptan usage may also offer financial benefits for the practice, since helping patients to avoid the inappropriate use of triptans could lead to reductions in the overall costs of triptan prescribing within the practice. The high usage predictors could be developed into a checklist of potential indicators for GPs to identify patients who may become high users if prescribed triptans and who might require closer monitoring. We recommend that patients identified as having a potential for high usage should be routinely reviewed, every 3-6 months, to ensure that they are using triptans appropriately to treat migraine. Although triptans are generally safe and well tolerated, unnecessary use of any medication should be avoided.

A central role for the T1 domain in voltage-gated potassium channel formation and function.

To interpret the recent atomic structures of the Kv (voltage-dependent potassium) channel T1 domain in a functional context, we must understand both how the T1 domain is integrated into the full-length functional channel protein and what functional roles the T1 domain governs. The T1 domain clearly plays a role in restricting Kv channel subunit heteromultimerization. However, the importance of T1 tetramerization for the assembly and retention of quarternary structure within full-length channels has remained controversial. Here we describe a set of mutations that disrupt both T1 assembly and the formation of functional channels and show that these mutations produce elevated levels of the subunit monomer that becomes subject to degradation within the cell. In addition, our experiments reveal that the T1 domain lends stability to the full-length channel structure, because channels lacking the T1 containing N terminus are more easily denatured to monomers. The integration of the T1 domain ultrastructure into the full-length channel was probed by proteolytic mapping with immobilized trypsin. Trypsin cleavage yields an N-terminal fragment that is further digested to a tetrameric domain, which remains reactive with antisera to T1, and that is similar in size to the T1 domain used for crystallographic studies. The trypsin-sensitive linkages retaining the T1 domain are cleaved somewhat slowly over hours. Therefore, they seem to be intermediate in trypsin resistance between the rapidly cleaved extracellular linker between the first and second transmembrane domains, and the highly resistant T1 core, and are likely to be partially structured or contain dynamic structure. Our experiments suggest that tetrameric atomic models obtained for the T1 domain do reflect a structure that the T1 domain sequence forms early in channel assembly to drive subunit protein tetramerization and that this structure is retained as an integrated stabilizing structural element within the full-length functional channel.

Endocrine effects of dopexamine vs. dopamine in high-risk surgical patients.

OBJECTIVES: To compare the endocrine effects of dopexamine and dopamine on prolactin (PRL), dihydroepiandrosterone sulfate (DHEAS), cortisol, thyrotropin (TSH), and peripheral thyroid hormone serum concentrations in surgical patients at risk of developing postoperative complications because of hypoperfusion of various organ systems. DESIGN AND SETTING: A prospective, randomized, placebo-controlled, blinded clinical trial in an adult surgical intensive care unit in a university hospital. PATIENTS: Thirty-two male surgical risk patients undergoing elective major abdominal surgery. INTERVENTIONS: Patients were randomized to receive placebo ( n=8), dopexamine (0.5 microg kg(-1) min(-1), n=8), dopexamine (1 microg kg(-1) min(-1), n=8) or dopamine (5 microg kg(-1) min(-1), n=8) on the first postoperative day. MEASUREMENTS AND RESULTS: All patients received either a placebo or catecholamine infusion for 24 h. Blood samples were obtained every 2 h for the next 2 days. PRL, DHEAS, cortisol, TSH, triiodothyronine, thyroxin, free triiodothyronine, and free thyroxin serum concentrations were determined by radioimmunoassay or luminescence immunoassay. Dopexamine (0.5 microg kg(-1) min(-1)) had no effects on serum concentrations of PRL or TSH. Higher doses of dopexamine (1 microg kg(-1) min(-1)) suppressed PRL secretion significantly, but not TSH. In contrast, infusion of dopamine (5 microg kg(-1) min(-1)) completely inhibited PRL and TSH secretion. DHEAS, cortisol, and thyroid hormone serum concentrations were not affected by either dopexamine or dopamine infusion. Measurements of hemodynamic parameters, peripheral oxygen saturation, diuresis, blood gases, and standard laboratory parameters were repeated hourly. Significant differences were not found between placebo, dopexamine (0.5 microg kg(-1) min(-1)) and dopamine (5 microg kg(-1) min(-1)) group. Dopexamine at 1 microg kg(-1) min(-1) increased the heart rate significantly. CONCLUSIONS: Routine postoperative optimizing of men undergoing abdominal surgical procedures with dopexamine at higher doses or dopamine induces at least partial hypopituitarism, which may possibly affect postoperative morbidity.

Inhibiting transthyretin amyloid fibril formation via protein stabilization.

Transthyretin (TTR) amyloid fibril formation is observed systemically in familial amyloid polyneuropathy and senile systemic amyloidosis and appears to be the causative agent in these diseases. Herein, we demonstrate conclusively that thyroxine (10.8 microM) inhibits TTR fibril formation efficiently in vitro and does so by stabilizing the tetramer against dissociation and the subsequent conformational changes required for amyloid fibril formation. In addition, the nonnative ligand 2,4,6-triiodophenol, which binds to TTR with slightly increased affinity also inhibits TTR fibril formation by this mechanism. Sedimentation velocity experiments were employed to show that TTR undergoes dissociation (linked to a conformational change) to form the monomeric amyloidogenic intermediate, which self-assembles into amyloid in the absence, but not in the presence of thyroxine. These results demonstrate the feasibility of using small molecules to stabilize the native fold of a potentially amyloidogenic human protein, thus preventing the conformational changes, which appear to be the common link in several human amyloid diseases. This strategy and the compounds resulting from further development should prove useful for critically evaluating the amyloid hypothesis--i.e., the putative cause-and-effect relationship between TTR amyloid deposition and the onset of familial amyloid polyneuropathy and senile systemic amyloidosis.

FAP mutations destabilize transthyretin facilitating conformational changes required for amyloid formation.

Functional transthyretin (TTR) can be transformed into amyloid by partial acid denaturation yielding a monomeric amyloidogenic intermediate which self-associates. The amyloidogenic intermediate has substantial beta-sheet structure with non-native but defined tertiary structure. pH-dependent proteolysis sensitivity studies have identified portions of TTR which become disordered and solvent-exposed in the amyloidogenic intermediate. These include the C-strand-loop D-strand portion of TTR which moves away from the core of the beta-sandwich fold. Mutations that are associated with early onset-amyloid disease (familial amyloidotic polyneuropathy; FAP) function by destabilizing tetrameric TTR in favour of the monomeric amyloidogenic intermediate which has a rearranged C-strand-loop D-strand region. In most cases the FAP mutations do not significantly alter the native folded structure, but instead act on the denaturation pathway by a mechanism that is not completely understood. Interestingly, mutations have also been characterized which strongly stabilize tetrameric TTR and make amyloid formation very difficult at pHs accessible in vivo.

Site-directed alterations to the geometry of the aspartate transcarbamoylase zinc domain: selective alteration to regulation by heterotropic ligands, isoelectric point, and stability in urea.

Structural aspects requisite for allosteric function in the regulatory chain of aspartate transcarbamoylase were explored by site-specific amino acid insertion or substitution within the zinc domain in the region of contact between the catalytic and regulatory chains. Amino acid substitution at two positions yielded enzymes which retained a maximum velocity similar to that of the wild-type enzyme but responded differently from the native enzyme in the presence of regulatory nucleoside triphosphates. A change of zinc coordinate amino acid C109 to histidine and a change of E119 to aspartic acid resulted in enzymes which demonstrated synergistic inhibition by CTP and UTP but not inhibition by CTP in either phosphate buffer or a morpholino-based tri-partate (TP) buffer at pH 7. At pH 8.3, where there is a higher proportion of T-state conformers in the native enzyme, the mutants diverged from their similar kinetic behavior. C109H remained an enzyme which was not inhibited by CTP but was still inhibited by CTP+UTP. E119D was inhibited by both CTP and CTP+UTP. Activation of the mutants by ATP was found to vary either with pH or with phosphate as a buffer component. C109H was activated by ATP in phosphate, while in TP at either pH 7 or 8.3 its activation by ATP was diminished or absent. E119D was activated by ATP in phosphate at pH 7 or in TP at pH 8.3, but not in TP at pH 7. In TP at pH 7, where neither mutant was activated by ATP, the S values and Hill coefficients of the unliganded mutant enzymes resembled those of the ATP-liganded wild-type enzyme. While neither mutation would be predicted to alter the net charge of the holoenzyme, differences in the isoelectric point of the mutants were observed if phosphate was present. This result suggests that the isoelectric point of aspartate transcarbamoylase is conformationally dependent and that the mutants exist in an altered conformation. In addition, the stabilities of both mutant holoenzymes were reduced substantially from those of the wild-type enzyme in 4 M urea. C109H was more stable at pH 8.25 in a Tris buffer; E119D was more stable at pH 7 in the phosphate buffer. Potential effects of these mutations on the active site chemistry and geometry are discussed.

Histopathology: its role in the diagnosis of a child with intussusception.

Spontaneous expulsion of a small portion of the intestinal mucosa per rectum, in an infant, associated with ileocolic intussusception is an extremely rare condition. This appears to be the first report of such a clinical presentation. The initial diagnosis was raised by the histopathologist following examination of the eliminated piece of tissue. Subsequent barium enema and laparotomy confirmed the diagnosis and the ileocolic intussusception was successfully reduced. This unusual presentation, together with a review of the pertinent literature, is discussed. Our findings indicate that both the clinicians and histopathologists should be aware of this phenomenon and stress the importance of the histological examination of any unusual faecal matter. This may prove to be a simple, quick and cheap method of investigation of this condition.