Brain stem death induces pro-inflammatory cytokine production and cardiac dysfunction in sheep model

Introduction

Organs procured following brain stem death (BSD) are the main source of organ grafts for transplantation. However, BSD is associated with inflammatory responses that may damage the organ and affect both the quantity and quality of organs available for transplant. Therefore, we aimed to investigate plasma and bronchoalveolar lavage (BAL) pro-inflammatory cytokine profiles and cardiovascular physiology in a clinically relevant 6-h ovine model of BSD.

Methods

Twelve healthy female sheep (37–42 Kg) were anaesthetized and mechanically ventilated prior to undergoing BSD induction and then monitored for 6 h. Plasma and BAL endothelin-1 and cytokines (IL-1β, 6, 8 and tumour necrosis factor alpha (TNF-α)) were assessed by ELISA. Differential white blood cell counts were performed. Cardiac function during BSD was also examined using echocardiography, and cardiac biomarkers (A-type natriuretic peptide and troponin I were measured in plasma.

Results

Plasma concentrations big ET-1, IL-6, IL-8, TNF-α and BAL IL-8 were significantly (p < 0.01) increased over baseline at 6 h post-BSD. Increased numbers of neutrophils were observed in the whole blood (3.1 × 10⁹ cells/L [95% confidence interval (CI) 2.06–4.14] vs. 6 × 10⁹ cells/L [95%CI 3.92–7.97]; p < 0.01) and BAL (4.5 × 10⁹ cells/L [95%CI 0.41–9.41] vs. 26 [95%CI 12.29–39.80]; p = 0.03) after 6 h of BSD induction vs baseline. A significant increase in ANP production (20.28 pM [95%CI 16.18–24.37] vs. 78.68 pM [95%CI 53.16–104.21]; p < 0.0001) and cTnI release (0.039 ng/mL vs. 4.26 [95%CI 2.69–5.83] ng/mL; p < 0.0001), associated with a significant reduction in heart contractile function, were observed between baseline and 6 h.

Conclusions

BSD induced systemic pro-inflammatory responses, characterized by increased neutrophil infiltration and cytokine production in the circulation and BAL fluid, and associated with reduced heart contractile function in ovine model of BSD.

Endothelin receptor antagonist improves donor lung function in an ex vivo perfusion system

BACKGROUND

A lung transplant is the last resort treatment for many patients with advanced lung disease. The majority of donated lungs come from donors following brain death (BD). The endothelin axis is upregulated in the blood and lung of the donor after BD resulting in systemic inflammation, lung damage and poor lung graft outcomes in the recipient. Tezosentan (endothelin receptor blocker) improves the pulmonary haemodynamic profile; however, it induces adverse effects on other organs at high doses. Application of ex vivo lung perfusion (EVLP) allows the development of organ-specific hormone resuscitation, to maximise and optimise the donor pool. Therefore, we investigate whether the combination of EVLP and tezosentan administration could improve the quality of donor lungs in a clinically relevant 6-h ovine model of brain stem death (BSD).

METHODS

After 6 h of BSD, lungs obtained from 12 sheep were divided into two groups, control and tezosentan-treated group, and cannulated for EVLP. The lungs were monitored for 6 h and lung perfusate and tissue samples were processed and analysed. Blood gas variables were measured in perfusate samples as well as total proteins and pro-inflammatory biomarkers, IL-6 and IL-8. Lung tissues were collected at the end of EVLP experiments for histology analysis and wet-dry weight ratio (a measure of oedema).

RESULTS

Our results showed a significant improvement in gas exchange [elevated partial pressure of oxygen (P = 0.02) and reduced partial pressure of carbon dioxide (P = 0.03)] in tezosentan-treated lungs compared to controls. However, the lungs hematoxylin-eosin staining histology results showed minimum lung injuries and there was no difference between both control and tezosentan-treated lungs. Similarly, IL-6 and IL-8 levels in lung perfusate showed no difference between control and tezosentan-treated lungs throughout the EVLP. Histological and tissue analysis showed a non-significant reduction in wet/dry weight ratio in tezosentan-treated lung tissues (P = 0.09) when compared to control.

CONCLUSIONS

These data indicate that administration of tezosentan could improve pulmonary gas exchange during EVLP.

Socio-economic inequalities in fragility fracture outcomes: a systematic review and meta-analysis of prognostic observational studies

Individuals with low socio-economic status (SES) have a higher risk of dying following hip fracture compared with individuals with high SES. Evidence on social inequalities in non-hip fractures is lacking as well as evidence on the impact of SES on health-related quality of life post fracture.

INTRODUCTION

Fragility fractures, especially of the hip, cause substantial excess mortality and impairment in health-related quality of life (HRQoL). This systematic review and meta-analysis aimed to investigate the association between socio-economic status (SES) and post-fracture mortality and HRQoL.

METHODS

PubMed, EMBASE and CINAHL databases were searched from inception to the last week of November 2018 for studies reporting an association between SES and post-fracture mortality and/or HRQoL among people aged ≥ 50 years. Risk ratios (RRs) were meta-analyzed using a standard inverse-variance-weighted random effects model. Studies using individual-level and area-based SES measures were analyzed separately.

RESULTS

A total of 24 studies from 15 different countries and involving more than one million patients with hip fractures were included. The overall risk of mortality within 1-year post-hip fracture in individuals with low SES was 24% higher than in individuals with high SES (RR 1.24, 95% CI 1.19 to 1.29) for individual-level SES measures, and 14% (RR 1.14, 95% CI 1.09 to 1.19) for area-based SES measures. The quality of the evidence for the outcome mortality was moderate. Using individual SES measures, we estimated the excess HRQoL loss to be 5% (95% CI - 1 to 10%) among hip fracture patients with low SES compared with high SES.

CONCLUSIONS

We found a consistently increased risk of post-hip fracture mortality with low SES across SES measures and across countries with different political structures and different health and social care infrastructures. The impact of SES on post-fracture HRQoL remains uncertain due to sparse and low-quality evidence.

Global strategy for asthma management and prevention: GINA executive summary

Asthma is a serious health problem throughout the world. During the past two decades, many scientific advances have improved our understanding of asthma and ability to manage and control it effectively. However, recommendations for asthma care need to be adapted to local conditions, resources and services. Since it was formed in 1993, the Global Initiative for Asthma, a network of individuals, organisations and public health officials, has played a leading role in disseminating information about the care of patients with asthma based on a process of continuous review of published scientific investigations. A comprehensive workshop report entitled "A Global Strategy for Asthma Management and Prevention", first published in 1995, has been widely adopted, translated and reproduced, and forms the basis for many national guidelines. The 2006 report contains important new themes. First, it asserts that "it is reasonable to expect that in most patients with asthma, control of the disease can and should be achieved and maintained," and recommends a change in approach to asthma management, with asthma control, rather than asthma severity, being the focus of treatment decisions. The importance of the patient-care giver partnership and guided self-management, along with setting goals for treatment, are also emphasised.

Role of membrane curvature in mechanoelectrical transduction: Ion carriers nonactin and valinomycin sense changes in integral bending energy

We describe the phenomenon of mechanoelectrical transduction in macroscopic lipid bilayer membranes modified by two cation-selective ionophores, valinomycin and nonactin. We found that bulging these membranes, while maintaining the membrane tension constant, produced a marked supralinear increase in specific carrier-mediated conductance. Analyses of the mechanisms involved in mechanoelectrical transduction induced by the imposition of a hydrostatic pressure gradient or by an amphipathic compound chlorpromazine reveal similar changes in the charge carrier motility and carrier reaction rates at the interface(s). Furthermore, the relative change in membrane conductance was independent of membrane diameter, but was directly proportional to the square of membrane curvature, thus relating the observed phenomena to the bilayer bending energy. Extrapolated to biological membranes, these findings indicate that ion transport in cells can be influenced simply by changing shape of the membrane, without a change in membrane tension.

The correlation between asthma control and health status: the GOAL study

The present study examined the association between guideline-derived asthma control and health-related quality of life, assessed using the Asthma Quality of Life Questionnaire (AQLQ), in patients with uncontrolled asthma whose treatment was directed towards achieving the highest possible level of control. The present randomised, double-blind, parallel-group study compared the efficacy of fluticasone propionate (FP) and salmeterol/fluticasone propionate combination (SFC) in achieving two composite, guideline-derived measures of control: total control (TC) and well-controlled (WC) asthma. Not achieving these levels was classed as not well-controlled (NWC). Doses were augmented until patients achieved TC or reached the maximum dose. This dose was maintained for the remainder of the study. AQLQ was assessed at baseline and at each clinic visit. AQLQ scores improved throughout the study, reaching near-maximal levels in patients achieving TC and WC, and 52-week mean scores in the three control groups were statistically significantly different. Clinically meaningful improvements (mean change from baseline) were: TC group (SFC 1.9, FP 1.8), WC (SFC 1.5, FP 1.5) and NWC (SFC 1.0, FP 0.9). In conclusion, the treatment aimed at controlling asthma improves the health-related quality of life to levels approaching normal. The difference in Asthma Quality of Life Questionnaire scores between total control and well-controlled confirms that patients distinguish even between these high levels of control.

Cost-effectiveness of asthma control: an economic appraisal of the GOAL study

BACKGROUND

The Gaining Optimal Asthma ControL (GOAL) study has shown the superiority of a combination of salmeterol/fluticasone propionate (SFC) compared with fluticasone propionate alone (FP) in terms of improving guideline defined asthma control.

METHODS

Clinical and economic data were taken from the GOAL study, supplemented with data on health related quality of life, in order to estimate the cost per quality adjusted life year (QALY) results for each of three strata (previously corticosteroid-free, low- and moderate-dose corticosteroid users). A series of statistical models of trial outcomes was used to construct cost effectiveness estimates across the strata of the multinational GOAL study including adjustment to the UK experience. Uncertainty was handled using the non-parametric bootstrap. Cost-effectiveness was compared with other treatments for chronic conditions.

RESULT

Salmeterol/fluticasone propionate improved the proportion of patients achieving totally and well-controlled weeks resulting in a similar QALY gain across the three strata of GOAL. Additional costs of treatment were greatest in stratum 1 and least in stratum 3, with some of the costs offset by reduced health care resource use. Cost-effectiveness by stratum was 7600 pound (95% CI: 4800-10,700 pound) per QALY gained for stratum 3; 11,000 pound (8600-14,600 pound) per QALY gained for stratum 2; and 13,700 pound (11,000-18,300 pound) per QALY gained for stratum 1.

CONCLUSION

The GOAL study previously demonstrated the improvement in total control associated with the use of SFC compared with FP alone. This study suggests that this improvement in control is associated with cost-per-QALY figures that compare favourably with other uses of scarce health care resources.

[Effect of long-term treatment with inhaled budesonide on adult height of children with asthma]

INTRODUCTION

Short-term studies have shown that inhaled corticosteroids may retard the growth of children with asthma. The effect of long-term treatment on adult height is, however, uncertain.

MATERIAL AND METHODS

We conducted a prospective study of children with asthma to examine the effect of long-term treatment with inhaled budesonide on adult height. We report on 211 children who have attained adult height: 142 asthmatic children treated with budesonide, 18 asthmatic control patients who have never received inhaled corticosteroids, and 51 healthy siblings of patients in the budesonide group, who also served as controls.

RESULTS

The children in the budesonide group attained adult height after a mean of 9.2 years of budesonide treatment (range 3-13 years) at a mean daily dose of 412 micrograms (range 110-877 micrograms). The mean cumulative dose of budesonide was 1.35 g (range 0.41-3.99 g). The mean differences between the measured and target adult heights were +0.3 cm (95% confidence intervals: -0.6; +1.2 cm) for the children treated with budesonide, -0.2 cm (95% confidence intervals: -2.4; +2.1 cm) for the control children with asthma, and +0.9 cm (95% confidence intervals: -0.4; +2.2 cm) for the healthy siblings. The adult height depended significantly (p < 0.001) on the child's height before budesonide treatment. Although growth rates were significantly reduced during the first years of budesonide treatment, these changes were not significantly associated with adult height.

DISCUSSIONS

Children with asthma who have received long-term treatment with inhaled budesonide attain normal adult height.

[Pediatric pulmonology]

Paediatric pulmonology (paediatric respiratory medicine) concerns such lung diseases in children as asthma, pneumonia, cystic fibrosis, primary ciliary dyskinesia, chronic interstitial pneumonia, bronchopulmonary dysplasia and congenital abnormalities. This specialty has been approved as an official subsection of the European Confederation of Specialists in Paediatrics (CESP) and acknowledged by the European Union of Medical Specialists (UEMS). A training syllabus has been defined and training centres in all EU countries, including Denmark, have been identified and approved by the local paediatric organisations. The training syllabus emphasises routine in the clinical diagnosis and treatment of the diseases, as well as methods such as lung function in all age groups, bronchoscopy, biopsy, and others. This article summarises the status of this specialty, and the training syllabus, and highlights key research questions.

Site-specific charge interactions of alpha-conotoxin MI with the nicotinic acetylcholine receptor

We have tested the importance of charge interactions for alpha-conotoxin MI binding to the nicotinic acetylcholine receptor (AChR). Ionic residues on alpha-conotoxin MI were altered by site-directed mutagenesis or by chemical modification. In physiological buffer, removal of charges at the N terminus, His-5, and Lys-10 had small (2-4-fold) effects on binding affinity to the mouse muscle AChR and the Torpedo AChR. It was also demonstrated that conotoxin had no effect on the conformational equilibrium of either receptor, as assessed by the effects of the noncompetitive antagonist proadifen on conotoxin binding and, conversely, the effect of conotoxin on the affinity of phencyclidine, proadifen, and ethidium. Conotoxin displayed higher binding affinity in low ionic strength buffer; neutralization of Lys-10 and the N terminus by acetylation blocked this affinity shift at the alphadelta site but not at the alphagamma site. It is concluded that Ctx residues Lys-10 and the N terminal interact with oppositely charged receptor residues only at the alphadelta site, and the two sites have distinct arrangements of charged residues. Ethidium fluorescence experiments demonstrated that conotoxin is formally competitive with a small cholinergic ligand, tetramethylammonium. Thus, alpha-conotoxin MI appears to interact with the portion of the binding site responsible for stabilizing agonist cations but does not do so with a cationic residue and is, consequently, incapable of inducing a conformational change.

Calcium binding to calmodulin leads to an N-terminal shift in its binding site on the ryanodine Receptor

The skeletal muscle calcium release channel, ryanodine receptor, is activated by calcium-free calmodulin and inhibited by calcium-bound calmodulin. Previous biochemical studies from our laboratory have shown that calcium-free calmodulin and calcium bound calmodulin protect sites at amino acids 3630 and 3637 from trypsin cleavage (Moore, C. P., Rodney, G., Zhang, J. Z., Santacruz-Toloza, L., Strasburg, G., and Hamilton, S. L. (1999) Biochemistry 38, 8532-8537). We now demonstrate that both calcium-free calmodulin and calcium-bound calmodulin bind with nanomolar affinity to a synthetic peptide matching amino acids 3614-3643 of the ryanodine receptor. Deletion of the last nine amino acids (3635-3643) destroys the ability of the peptide to bind calcium-free calmodulin, but not calcium-bound calmodulin. We propose a novel mechanism for calmodulin's interaction with a target protein. Our data suggest that the binding sites for calcium-free calmodulin and calcium-bound calmodulin are overlapping and, when calcium binds to calmodulin, the calmodulin molecule shifts to a more N-terminal location on the ryanodine receptor converting it from an activator to an inhibitor of the channel. This region of the ryanodine receptor has previously been identified as a site of intersubunit contact, suggesting the possibility that calmodulin regulates ryanodine receptor activity by regulating subunit-subunit interactions.

Identification of the sites of incorporation of [3H]ethidium diazide within the Torpedo nicotinic acetylcholine receptor ion channel

The binding sites of ethidium, a noncompetitive antagonist of the nicotinic acetylcholine receptor (nAChR), have been localized in the Torpedo nAChR in the desensitized state by use of a photoactivatible derivative, [(3)H]ethidium diazide. At 10 microM [(3)H]ethidium diazide, incorporation into the alpha-, beta-, and delta-subunits was inhibited by the presence of phencyclidine (PCP). Within the alpha-subunit, the incorporation was mapped to a 20-kDa fragment beginning at alphaSer-173 and containing the first three transmembrane segments, alphaM1, alphaM2, and alphaM3. Further digestion of this fragment generated two fragments with PCP-inhibitable incorporation, one containing alphaM1 and one containing both alphaM2 and alphaM3. Within alphaM2, specific incorporation was present in alphaLeu-251 and alphaSer-252, residues that have been previously shown to line the lumen of the ion channel. Digestion of the delta-subunit with S. aureus V8 protease generated a 14-kDa and a 20-kDa fragment, both of which began at Ile-192 and contained PCP-inhibitable labeling. The 14-kDa fragment, containing deltaM1 and deltaM2, was further digested to generate a 3-kDa fragment, containing deltaM2 alone, with PCP-inhibitable incorporation. Digestion of the 20-kDa fragment, which contained deltaM1, deltaM2, and deltaM3, generated two fragments with incorporation, one containing the deltaM1 segment and the other containing deltaM2 and deltaM3. These results establish that in the desensitized state of the nAChR, the high-affinity binding site of ethidium is within the lumen of the ion channel and that the bound drug is in contact with amino acids from both the M1 and M2 hydrophobic segments.

Electrostatic interactions regulate desensitization of the nicotinic acetylcholine receptor

To determine the importance of electrostatic interactions for agonist binding to the nicotinic acetylcholine receptor (AChR), we examined the affinity of the fluorescent agonist dansyl-C6-choline for the AChR. Increasing ionic strength decreased the binding affinity in a noncompetitive manner and increased the Hill coefficient of binding. Small cations did not compete directly for dansyl-C6-choline binding. The sensitivity to ionic strength was reduced in the presence of proadifen, a noncompetitive antagonist that desensitizes the receptor. Moreover, at low ionic strength, the dansyl-C6-choline affinities were similar in the absence or presence of proadifen, a result consistent with the receptor being desensitized at low ionic strength. Similar ionic strength effects were observed for the binding of the noncompetitive antagonist [(3)H]ethidium when examined in the presence and absence of agonist to desensitize the AChR. Therefore, ionic strength modulates binding affinity through at least two mechanisms: by influencing the conformation of the AChR and by electrostatic effects at the binding sites. The results show that charge-charge interactions regulate the desensitization of the receptor. Analysis of dansyl-C6-choline binding to the desensitized conformation using the Debye-Hückel equation was consistent with the presence of five to nine negative charges within 20 A of the acetylcholine binding sites.

Aminotriarylmethane dyes are high-affinity noncompetitive antagonists of the nicotinic acetylcholine receptor

A series of aminotriarylmethane dyes were examined for binding to the nicotinic acetylcholine receptor (AChR) from Torpedo californica. Several compounds were found to bind to the noncompetitive antagonist site of the AChR as demonstrated by inhibition of [3H]phencyclidine binding; apparent KD values ranged from 50 nM to >100 microM. One dye with high affinity, crystal violet, revealed a greater than 200-fold fluorescence enhancement upon binding the AChR. Using fluorescence to measure binding, we determined that one crystal violet bound per receptor with a dissociation constant of 100 nM; in the presence of the agonist carbamylcholine this value decreased to 10 nM. The KD for [3H]acetylcholine binding likewise was decreased in the presence of crystal violet. These results are consistent with preferential binding of crystal violet to the desensitized conformation of the AChR. Crystal violet binding blocked agonist-induced 22Na ion efflux from AChR-rich vesicles. It is concluded that crystal violet and other dyes of similar structure bind to the high-affinity noncompetitive antagonist site of the AChR associated with the channel lumen. Because of their optical properties, crystal violet and several of the other homologous dyes are likely to be useful ligands for further characterization of the AChR channel. Structure-activity comparison of the various dyes suggests the importance of nonquaternary nitrogens in binding the pore. Additional steric bulk on amines or at meta positions increase or have neutral effect on affinity, suggesting that steric considerations alone do not limit high affinity for the binding site.

Interaction of D-tubocurarine analogs with the 5HT3 receptor

D-Tubocurarine is a potent competitive antagonist of two members of the ligand-gated ion channel family, the muscle-type nicotinic acetylcholine receptor (AChR) and serotonin type-3 receptor (5HT3R). We have used a series of analogs of D-tubocurarine to determine the effects of methylation, stereoisomerization and halogenation on the interaction of D-tubocurarine with the 5HT3R. The affinities of the analogs for the 5HT3R span a 200-fold concentration range and fall into three broad groups. The first group, with affinity constants (Ki) < 150 nM, consists of D-tubocurarine and analogs modified at the nitrogens or 7' hydroxyl. The fact that these compounds all have high affinity for the 5HT3R suggests that these portions of the ligand do not make interactions with the receptor that are critical for high-affinity binding. The second group, with Ki's in the 1-5 microM range, consists of analogs modified at the 12'-hydroxyl or the adjacent 13'-carbon, which suggests that this portion of the ligand makes interactions that are important for high-affinity binding. The third, very low affinity, group is a compound with altered stereoconfiguration at the 1 carbon, demonstrating the importance of proper configuration of the antagonist in ligand-receptor interactions. For the most part, this pattern of selectivity is similar to that for the AChR, suggesting that the structures of the ligand-binding sites of these two receptors share common structural features.

[Peroral drug administration to children--are there any problems?]

Children's compliance with orally administered medicine is described. Five hundred questionnaires were given to the parents of children at their first visit at the out-patient clinic with a response from 484. Three hundred and ninety-seven children had been treated with oral medication in the form of liquid formulation or tablets, 257 within the previous year. Of these, 43.2% reported difficulties in taking the medication. Only 8.5% of the treatments had been interrupted. The main cause of the problems were the medications' taste and difficulties with swallowing tablets. The problems were more pronounced among the younger children. The administration of tablets was more difficult than the administration of liquids. There was no relationship between the problems and frequency of dosing, duration of treatment, severity of illness, social status of the parents, or the parents' age. In conclusion, prescription of better tasting mixtures and chewable tablets may reduce the problems associated with administering oral medication to children.

Interaction of d-tubocurarine analogs with the mouse nicotinic acetylcholine receptor. Ligand orientation at the binding site

The binding of d-tubocurarine and several of its analogs to the mouse nicotinic acetylcholine receptor (AChR) was measured by competition against the initial rate 125I-alpha-bungarotoxin binding to BC3H-1 cells. The changes in affinity due to methylation or halogenation at various functional groups on d-tubocurarine was measured to both the high affinity (alphagamma-site) and the low affinity site (alphadelta-site). We show that quaternization by methylation of the 2'-N ammonium group enhances the affinity for both the acetylcholine binding sites of mouse AChR, whereas this change does not affect affinity for the Torpedo AChR sites. The effect of N-methylation suggests the presence of interactions with the ammonium moiety that cannot be readily attributed to the known conserved residues thought to stabilize this functional group. Methylation of both the 7'- and 12'-phenols produced net affinity changes at both sites. The changes resulted from contributions at both the 7'- and the 12'-positions; however, these effects were dependent on whether the ammoniums were also methylated. Substitution of bromine or iodine at the 13'-position decreased the affinity considerably to the high affinity alphagamma-site of mouse AChR, whereas the affinity for the Torpedo alphagamma-site was slightly increased. Furthermore, binding to the mouse AChR was unaffected by the conformational state, whereas these ligands strongly preferred the desensitized conformation of the Torpedo AChR. Comparison of binding changes upon 13'-halogenation to the changes in amino acid residues at the ACh binding sites of the mouse and Torpedo AChR shows mouse residue Ile-gamma116 as likely to be involved in interacting with the 13'-position of d-tubocurarine. It is predicted that this residue is involved in the conformational equilibrium between the resting and desensitized conformations.

Quinacrine and ethidium bromide bind the same locus on the nicotinic acetylcholine receptor from Torpedo californica

Quinacrine is a noncompetitive antagonist of the nicotinic acetylcholine receptor (AChR) which displays severalfold fluorescent enhancement upon binding to AChR-rich membranes from Torpedo californica electric organ. It is demonstrated that the fluorescence enhancement comprises two components: specific interaction at a high-affinity binding site on the AChR, and interaction with the lipid bilayer. The interaction with the lipid bilayer can be attenuated by other noncompetitive antagonists, but at concentrations substantially higher than those required for binding to the AChR. It is further shown that quinacrine can inhibit the binding of [3H]phencyclidine and [3H]ethidium in a manner fully consistent with simple competitive inhibition. The data support a model for high-affinity quinacrine binding to the same, single locus of the acetylcholine receptor as phencyclidine and ethidium. This site is likely within the lumen of the ion channel.

Interaction between ryanodine and neomycin binding sites on Ca2+ release channel from skeletal muscle sarcoplasmic reticulum

Neomycin is a potent inhibitor of skeletal muscle sarcoplasmic reticulum (SR) calcium release. To elucidate the mechanism of inhibition, the effects of neomycin on the binding of [3H]ryanodine to the Ca2+ release channel and on its channel activity when reconstituted into planar lipid bilayer were examined. Equilibrium binding of [3H]ryanodine was partially inhibited by neomycin. Inhibition was incomplete at high neomycin concentrations, indicating noncompetitive inhibition rather than direct competitive inhibition. Neomycin and [3H]ryanodine can bind to the channel simultaneously and, if [3H]ryanodine is bound first, the addition of neomycin will slow the dissociation of [3H]ryanodine from the high affinity site. Neomycin also slows the association of [3H]ryanodine with the high affinity binding site. The neomycin binding site, therefore, appears to be distinct from the ryanodine binding site. Dissociation of [3H]ryanodine from trypsin-treated membranes or from a solubilized 14 S complex is also slowed by neomycin. This complex is composed of polypeptides derived from the carboxyl terminus of the Ca2+ release channel after Arg-4475 (Callaway, C., Seryshev, A., Wang, J. P., Slavik, K., Needleman, D. H., Cantu, C., Wu, Y., Jayaraman, T., Marks, A. R., and Hamilton, S. L. (1994) J. Biol. Chem. 269, 15876-15884). The proteolytic 14 S complex isolated with ryanodine bound produces a channel upon reconstitution into planar lipid bilayers, and its activity is inhibited by neomycin. Our data are consistent with a model in which the ryanodine binding sites, the neomycin binding sites, and the channel-forming portion of the Ca2+ release channel are located between Arg-4475 and the carboxyl terminus.

Interaction of d-tubocurarine analogs with the Torpedo nicotinic acetylcholine receptor. Methylation and stereoisomerization affect site-selective competitive binding and binding to the noncompetitive site

Analogs of d-tubocurarine were used to determine the individual effects of methylation, stereoisomerization, and halogenation of d-tubocurarine on the affinity for each of the two acetylcholine (ACh) binding sites of the Torpedo nicotinic acetylcholine receptor (AChR) and for the noncompetitive antagonist site. Eight analogs were synthesized, including three new compounds: 7'-O-methyl-chondocurarine, 12'-O-methyl-chondocurarine, and 13'-bromo-d-tubocurarine. The two ACh sites differ in their affinities for d-tubocurarine by 400-fold, as shown by inhibition of [3H]ACh binding, whereas the affinity ratio for metocurine, the trimethylated derivative of d-tubocurarine, is reduced to 30 due to a decreased affinity for the high affinity site. Binding analysis of five d-tubocurarine analogs demonstrates that methylation of the phenols alone is responsible for the observed changes in affinity. Substitution with bromine or iodine at the 13'-position affected affinity at both sites with a net increase in site selectivity. Stereoisomers of d-tubocurare had decreased affinity for only the high affinity ACh site. Thus, the ring systems, including the 12'- and 13'-positions and the 1-position stereocenter, appear to be important in discriminating between the two ACh binding sites. Desensitization of the AChR was measured by increased affinity for [3H]phencyclidine. Binding to only the single, high affinity acetylcholine binding site, comprised by the alpha gamma-subunits, was required for partial desensitization of the AChR by d-tubocurarine and its analogs. Stronger desensitization, to the same extent observed in the presence of the agonist carbamylcholine, occurred upon binding by iodonated or brominated d-tubocurarine. Interaction of the analogs at the noncompetitive antagonist site of the AChR was also measured by [3H]phencyclidine binding. The bis-tertiary ammonium analogs of either the d- or l-stereoisomers bound to the noncompetitive antagonist binding site of the AChR with 100-fold higher affinity than the corresponding quaternary ammonium analogs.

Site-selective photoaffinity labeling of the Torpedo californica nicotinic acetylcholine receptor by azide derivatives of ethidium bromide

Three azido derivatives of ethidium bromide, a potent noncompetitive antagonist of the nicotinic acetylcholine receptor from Torpedo californica, were synthesized, namely 8-azido-ethidium chloride, 3-azido-ethidium chloride, and 3,8-diazido-ethidium chloride. These derivatives were tested for their ability to interact with the noncompetitive antagonist binding site and the acetylcholine binding sites on the acetylcholine receptor. The derivatives bound to the noncompetitive antagonist site with 2-5-fold lower affinity than did ethidium bromide, as determined by competitive inhibition of [3H]phencyclidine binding, indicating a moderate effect of the azide groups upon binding. Inhibition of [3H]-acetylcholine binding by ethidium and its azide derivatives indicated differential binding to the two agonist sites, with high affinity binding to the same site that exhibits high affinity for d-tubocurarine. Photoaffinity labeling by these derivatives revealed reaction with the alpha and gamma subunits that was specific for the acetylcholine binding sites. Inhibition of labeling by d-tubocurarine showed reaction with alpha subunits at both of the acetylcholine binding sites, whereas reaction with the gamma subunit was consistent with reaction only at the site with high affinity for d-tubocurarine. There was no corresponding reaction with the delta subunit, which forms part of the second acetylcholine binding site, despite reaction with the apposing alpha subunit. The azides, therefore, display preferential reaction with the gamma subunit. The selectivity of the reaction must reflect structural differences between the two sites, and subsequent determination of the labeled site(s) should reveal the nature of the differences.

[Budesonide administered via Turbuhaler and a nebulator]

Two hundred and forty-one children with perennial asthma had their normal dose of budesonide (administered via Nebuhaler) reduced by 50%. Asthma control deteriorated in 126 patients to such an extent that budesonide had to be increased to the normal dose. During a subsequent two week run-in these 126 patients were treated with their normal dose of budesonide via Nebuhaler. Thereafter 64 were randomized to treatment with their normal budesonide therapy and 62 to treatment with half their normal budesonide dose via Turbuhaler for nine weeks. Asthma symptoms, peak-flow measurements, and beta 2-agonist use were recorded. Pulmonary function tests, exercise tests and 24 hour urine sample collections were performed. There were no differences between the groups in any of the parameters studied during run-in or during the study period, except for use of beta 2-agonist, which was significantly lower in the Turbuhaler-treated group. We conclude that Turbuhaler is more effective than Nebuhaler in the treatment of asthma. Therefore the dose of budesonide should be reduced when patients are switched from Nebuhaler to Turbuhaler treatment.

Structure of the noncompetitive antagonist-binding site of the Torpedo nicotinic acetylcholine receptor. [3H]meproadifen mustard reacts selectively with alpha-subunit Glu-262

[3H]Meproadifen mustard, an affinity label for the noncompetitive antagonist site of the nicotinic acetylcholine receptor (AChR), specifically alkylates the AChR alpha-subunit when the acetylcholine-binding sites are occupied by agonist (Dreyer, E. B., Hasan, F., Cohen, S. G., and Cohen, J. B. (1986) J. Biol. Chem. 261, 13727-13734). In this report, we identify the site of alkylation within the alpha-subunit as Glu-262. AChR-rich membranes from Torpedo californica electric organ were reacted with [3H]meproadifen mustard in the presence of carbamylcholine and in the absence or presence of nonradioactive meproadifen to define specific alkylation of the noncompetitive antagonist site. Alkylated alpha-subunits were isolated and subjected to chemical or enzymatic cleavage. When digests with CNBr in 70% trifluoroacetic acid or 70% formic acid were fractionated by gel filtration high performance liquid chromatography (HPLC), specifically labeled material was recovered in the void volume fractions. Based upon NH2-terminal sequence analysis, for both digests, the void volume fractions contained a fragment beginning at Gln-208 before the M1 hydrophobic sequence, whereas the sample from the digest in trifluoroacetic acid also contained as a primary sequence a fragment beginning at Thr-244 and extending through the M2 hydrophobic sequence. Sequence analysis revealed no release of 3H for the sample from digestion in formic acid, whereas for the trifluoroacetic acid digest, there was specific release of 3H in cycle 19, which would correspond to Glu-262. This site of alkylation was confirmed by isolation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reversed-phase HPLC of a specifically labeled fragment from an endoproteinase Lys-C digest of the alkylated alpha-subunit. NH2-terminal amino acid sequencing revealed release of 3H at cycle 20 from a fragment beginning at Met-243 and extending into the M3 hydrophobic sequence. Because [3H]meproadifen mustard contains, as its reactive group, a positively charged quaternary aziridinium ion, Glu-262 of the alpha-subunit is identified as a contributor to the cation-binding domain of the noncompetitive antagonist-binding site and thus of the ion channel.

[Dietary treatment of diabetes mellitus. Background and rationale for recommendations in the 1990's]

Individual dietary regulation is still an important part of all forms of treatment of diabetes. In insulin dependent diabetes (IDDM) it is rational to advise the patient 1) to arrange his diet so that this results in a low glycaemic response, which implies a relatively high intake of dietary fibre and polysaccharides, 2) to distribute the food into 5-6 daily meals and 3) to consume a low-fat diet. This prevents too pronounced postprandial hyperglycaemia and hypoglycaemia between meals. Simultaneously, insulin sensitivity is increased and not only the insulin requirement but also peripheral hyperinsulinism tend to be reduced. Dietary regulation in IDDM is thus a compensation for the defective synchronization of variations in the plasma levels of glucose and insulin in the present day forms of insulin therapy. Nine out of ten diabetic patients are non-insulin dependent (NIDDM). The great majority are obese, 50% have essential hypertension and just as many have dyslipidaemia (raised serum triglyceride and reduced serum high density lipoprotein (HDL)-cholesterol). The condition is characterized pathophysiologically by insulin resistance in muscle, fat and liver tissue and delayed and frequently reduced glucose-stimulated secretion of insulin. The most important element in dietary regulation in NIDDM is, therefore, reduction of the energy content of the food with the object of achieving and maintaining reduction in weight. Even moderate reduction, in the majority of NIDDM patients, will have the effect that metabolism of carbohydrates and lipids becomes approximately normal on account of considerable increase in insulin sensitivity and to a lesser degree increased secretion of insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

d-Tubocurarine binding sites are located at alpha-gamma and alpha-delta subunit interfaces of the nicotinic acetylcholine receptor

The competitive nicotinic antagonist d-[3H]tubocurarine was used as a photoaffinity label for the acetylcholine binding sites on the nicotinic acetylcholine receptor (AcChoR) from Torpedo. Irradiation with 254-nm UV light of AcChoR-rich membranes equilibrated with d-[3H]tubocurarine resulted in covalent incorporation into the alpha, gamma, and delta subunits that could be blocked by alpha-bungarotoxin or by carbamoylcholine. The concentrations of d-[3H]tubocurarine required for half-maximal specific incorporation into the gamma and delta subunits were 40 nM and 0.9 microM, respectively, consistent with the dissociation constants for the high- and low-affinity binding sites (Kd = 35 nM and 1.2 microM). The concentration dependence of incorporation into alpha subunit was biphasic and consistent with labeling of both the high- and low-affinity d-tubocurarine binding sites. The specific photolabeling of each AcChoR subunit was inhibited by carbamoylcholine with appropriate dose dependence. These results establish that, in addition to the alpha subunits, the gamma and delta subunits also contribute directly to the acetylcholine binding sites and that each binding site is at an interface of subunits. Because the AcChoR subunits are homologous and are arranged pseudosymmetrically about a central axis, the photolabeling results are inconsistent with an arrangement of subunits in the AcChoR rosette of alpha beta alpha gamma delta and indicate that either the gamma or delta subunit resides between the alpha subunits.

Identification of a cytoplasmic region of the Torpedo nicotinic acetylcholine receptor alpha-subunit by epitope mapping

Analysis of the binding of monoclonal antibodies (mAbs) by Torpedo nicotinic acetylcholine receptor (AChR) has demonstrated that a region of the alpha-subunit between alpha-156 and alpha-179 is exposed on the cytoplasmic surface of the nicotinic post-synaptic membrane. A panel of mAbs was produced that recognized sodium dodecyl sulfate-denatured subunits of the Torpedo AChR. Antibodies recognizing alpha-subunit were distinguished in terms of their ability to bind alpha-subunit fragments generated by Staphylococcus aureus V8 protease: an 18-kDa fragment beginning at Val-46, a 20-kDa fragment beginning at Ser-173/Ser-162, and a 10 kDa fragment beginning at Asn-339. Three mAbs, selected for binding to each of the V8-protease alpha-subunit fragments, respectively, were characterized in detail. The location of epitopes recognized by both anti-V8-18 and anti-V8-20 mAbs was determined to be within alpha-156 to alpha-179 by isolation of small immunoreactive peptides from proteolytic digests of the alpha-subunit, while the mAb reactive to V8-10 was bound to an epitope within alpha-339 to alpha-386. Quantitative evaluation of binding of the anti-V8-18 and anti-V8-20 mAbs to overlapping synthetic peptides corresponding to alpha-147 to alpha-179 localized the epitopes to distinct portions of this region. Further screening of the panel of mAbs using these synthetic peptides revealed three additional mAbs that bind in this region. The mAbs that bound the three distinct V8-protease alpha-subunit fragments were shown to bind to native AChR by indirect immunofluorescence on frozen sections of Torpedo electric organ. Binding to the native AChR was to the cytoplasmic surface of the AChR since the mAbs could bind to AChR in native vesicles, in which the AChR is oriented right-side-out, only after permeabilization of the vesicles by alkaline treatment or after scrambling of the orientation of the AChR by solubilization and reconstitution into liposomes. The location of the mAb-binding sites at the cytoplasmic surface of the AChR was visualized directly by freeze-etch immunoelectron microscopy. The identification of alpha-156 and alpha-179 as containing a cytoplasmic exposed sequence implies the existence of two non-hydrophobic transmembrane sequences between the site of N-glycosylation (Asn-141) and Cys-192, a site alkylated by the cholinergic affinity labels.

Visualization of the cytoplasmic surface of Torpedo postsynaptic membranes by freeze-etch and immunoelectron microscopy

The synapse-specific Mr 43,000 protein (43K protein) and the acetylcholine receptor were visualized by freeze-etch immunoelectron microscopy in preparations of purified Torpedo postsynaptic membranes. Vesicles were immobilized on glass and then sheared open by sonication to expose the cytoplasmic surface. Membranes were labeled with monoclonal antibodies to the 43K protein or the acetylcholine receptor. The cytoplasmic surface was devoid of filamentous structure, and the 43K protein and the cytoplasmic projection of the acetylcholine receptor were associated with prominent surface particles. Acetylcholine receptor and 43K protein, in membrane surfaces in direct contact with glass coated with polyornithine, segregated into dense particle aggregates separated by smooth membrane patches, whereas those in contact with glass coated with Alcian Blue underwent little or no detectable rearrangement. After treatment of vesicles at alkaline pH to remove the 43K protein, the cytoplasmic surfaces were still covered by a dense array of particles that were more uniform in shape and appeared slightly shorter than those seen on unextracted membranes, but similar in height to the extracellular projection. Monoclonal antibodies to the acetylcholine receptor labeled these particles, while antibodies to 43K protein did not. We conclude that the 43K protein is in direct association with the receptor and that complexes of the receptor and 43K protein can undergo surface-induced lateral redistribution. In addition, the cytoplasmic projection of the acetylcholine receptor is sufficiently large to be readily detected by freeze-etch electron microscopy and is similar in height to the extracellular projection.

Location of ligand-binding sites on the nicotinic acetylcholine receptor alpha-subunit

The portions of the Torpedo californica nicotinic acetylcholine receptor (AChR) alpha-subunit that contribute to the allosteric antagonist-binding site and to the agonist-binding site have been localized by affinity labeling and proteolytic mapping. [3H]Meproadifen mustard was employed as an affinity label for the allosteric antagonist-binding site and [3H]tubocurare as a photoaffinity label for the agonist-binding site. Both labels were found in a 20-kDa proteolytic fragment generated from the AChR alpha-subunit by Staphylococcus aureus V8 protease. This 20-kDa peptide also contains the 3H-labeled 4-(N-maleimido)-alpha-benzyltrimethylammonium iodide-reactive site and binds 125I-alpha-bungarotoxin. N-terminal sequencing established that the 20-kDa fragment began at Ser-173 of the alpha-subunit. Fluorescein isothiocyanate-conjugated concanavalin A could be bound to the second of the two major V8 cleavage products, an 18-kDa peptide. This peptide was also sensitive to treatment with endo-beta-N-acetyl-glucosaminidase H, consistent with the presence of N-linked carbohydrate on this fragment. The N terminus of this peptide was found to be Val-46 of the alpha-subunit sequence. Experiments designed to map disulfide bonds within the AChR alpha-subunit indicate that no bonds exist between the 18-kDa fragment (containing Cys-128 and Cys-142) and the 20-kDa fragment (containing Cys-192, Cys-193, and Cys-222). These results establish that the 20-kDa fragment contributes to both the acetylcholine and the allosteric antagonist-binding sites, whereas there is no evidence that the 18-kDa fragment is part of either site.

Functional activation of beta-adrenergic receptors by thiols in the presence or absence of agonists

Treatment of beta-adrenergic receptor with dithiothreitol (DTT) or other thiol compounds caused its functional activation in the presence or absence of agonist ligands. Such activation was observed in reconstituted unilamellar phospholipid vesicles that contained beta-adrenergic receptors, purified to greater than or equal to 95% homogeneity from turkey erythrocyte plasma membranes, and the stimulatory GTP-binding protein of the adenylate cyclase system (Gs) purified from rabbit liver. Incubation of the vesicles with 2-10 mM DTT at 0 degrees C for 1 h increased the rate (4-5-fold) and the extent (3-4-fold) of activation of Gs by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) binding, an effect about equivalent to the addition of beta-adrenergic agonists. Treatment with DTT also markedly potentiated the ability of agonists to stimulate GTP gamma S binding, increasing the initial rate about 10-fold. DTT treatment was as effective as agonist in stimulating GTPase activity, and maximal stimulation was obtained when DTT-treated vesicles were assayed in the presence of agonist. Other thiol compounds produced effects similar to those of DTT but were at least 10-fold less potent. Stimulation of GTP gamma S binding or GTPase activity required active receptor, and treatment of the receptor with DTT prior to reconstitution also increased its efficacy. There was no effect of DTT on Gs alone. Thus, the site of action of DTT appears to be on the beta-adrenergic receptor itself, and the reduction of disulfides and the binding of agonist act synergistically to activate the receptor. DTT treatment made the receptor more labile to thermal denaturation. Inclusion of cholesterol or cholesteryl-hemisuccinate (5-25%) in the vesicles protected the reduced receptor against such denaturation and enhanced its recovery during reconstitution. No effect of cholesterol or cholesteryl-hemisuccinate was observed on the stability of the nonreduced receptor, which was comparable to that observed in native membranes.

Reconstitution of catecholamine-stimulated binding of guanosine 5'-O-(3-thiotriphosphate) to the stimulatory GTP-binding protein of adenylate cyclase

The stimulatory GTP-binding protein (Gs) of adenylate cyclase, purified from rabbit liver, and beta-adrenergic receptors, partially purified 1000-4000-fold from turkey erythrocyte plasma membranes, were coreconstituted into unilamellar phospholipid vesicles. The molar ratio of Gs to receptors in the vesicles varied from 3 to 10 in different preparations, as measured by guanosine 5'-O-(3-[35S]thiotriphosphate) [( 35S]GTP gamma S) binding to Gs and [125I]iodocyanopindolol binding to receptors. Activation of reconstituted Gs by GTP gamma S was stimulated up to 10-fold by the addition of the beta-adrenergic agonist (-)-isoproterenol. Activation was assayed functionally by reconstitution with the catalytic unit of adenylate cyclase. Because of the relative purity of this preparation, the quasi-irreversible binding of [35S]GTP gamma S could also be measured in the vesicles and was shown to parallel the functional activation of Gs under all conditions. Most of the assayable Gs in the vesicles could interact with the receptors and undergo agonist-stimulated activation. Agonist-stimulated activation and [35S]GTP gamma S binding were complete in less than 3 min, even under suboptimal conditions, and could go to completion in less than 20 s under maximal stimulation. Agonist-stimulated binding did not require appreciable free Mg2+ (less than 0.1 mM). Activation in the absence of agonist was stimulated by free Mg2+, but maximal activation took up to 10 min in the presence of 50 mM MgCl2. Reconstitution increased the stability of Gs to thermal denaturation. The addition of beta-adrenergic agonist further stabilized Gs, presumably by the formation of a stable agonist-receptor-Gs complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Reconstitution of catecholamine-stimulated guanosinetriphosphatase activity

beta-Adrenergic receptors were partially purified from turkey erythrocyte membranes by alprenolol-agarose chromatography to 0.25-2 nmol/mg of protein, and the stimulatory guanosine 5'-triphosphate (GTP) binding protein of adenylate cyclase (Gs) was purified from rabbit liver. These proteins were reconstituted into phospholipid vesicles by addition of phospholipids and removal of detergent by gel filtration. This preparation hydrolyzes GTP to guanosine 5'-diphosphate (GDP) plus inorganic phosphate (Pi) in response to beta-adrenergic agonists. The initial rate of isoproterenol-stimulated hydrolysis is approximately 1 mol of GTP hydrolyzed min-1 X mol-1 of Gs. This low rate may be limited by the hormone-stimulated binding of substrate, since it is roughly equal to the rate of binding of the GTP analogue guanosine 5'-O-(3-[35S] thiotriphosphate) [( 35S]GTP gamma S) to Gs in the vesicles. Activity in the absence of agonist, or in the presence of agonist plus a beta-adrenergic antagonist, is 8-25% of the hormone-stimulated activity. Guanosinetriphosphatase (GTPase) is not saturated at 10 microM GTP, and the response to GTP is formally consistent either with the existence of multiple Km's or of a separate stimulatory site for GTP. The GTPase activity of Gs in vesicles is also stimulated by 50 mM MgCl2 in the presence or absence of receptor. Significant GTPase activity is not observed with Lubrol-solubilized Gs, although [35S]-GTP gamma S binding is increased by Lubrol solubilization.

Functional reconstitution of beta-adrenergic receptors and the stimulatory GTP-binding protein of adenylate cyclase

A procedure for the functional reconstitution of beta-adrenergic receptors and the stimulatory guanine nucleotide-binding protein (G/F) of adenylate cyclase in phospholipid vesicles is described. beta-Adrenergic receptors were solubilized from turkey erythrocyte plasma membranes and reconstituted into phospholipid vesicles by the addition of dimyristoyl phosphatidylcholine and removal of detergent by gel filtration. This procedure restored the ability to bind [125I]iodohydroxybenzylpindolol and [3H]dihydroalprenolol. Purified rabbit hepatic G/F that was added to the receptor vesicles could be stably activated by guanosine 5'-[3-thio]triphosphate at a low rate, and this activation was increased up to 4-fold in the presence of beta-adrenergic agonists. This stimulation of the activation of G/F was specific for beta-adrenergic agonists and could be specifically blocked by beta-adrenergic antagonists. Stimulation was proportional to the concentration of vesicles containing active beta-adrenergic receptor. Under optimal conditions, 5 to 6 molecules of G/F were activated per receptor, indicating that catalytic activation of G/F by receptor was reconstituted.

Serum concentrations of theophylline in children treated with two daily doses of a sustained-release theophylline preparation

Over a 3-month period 22 asthmatic children were treated with a sustained-release theophylline preparation (Nuelin Retard, Riker) in twice-daily doses. During the first 2 weeks of treatment slight side-effects were observed in 14 children. Over the remaining 10-week period only four children experienced minor-side-effects. Serum theophylline levels 4 hours after tablet administration were measured three times and serum levels just before tablet administration were measured once during the observation period. The average difference between the serum levels of theophylline just before tablet administration and the corresponding serum value 4 hours afterwards was 4.2 microgram/ml. The serum values 4 hours after tablet administration showed an insignificant fall throughout the period and patient compliance was assessed as good. When the average requirements of theophylline in mg/kg found by Wyatt et al. (15) (Table 2) were used as initial doses, few dosage adjustments were necessary and no serum values were greater than 26.2 microgram/ml, but in order to avoid serum levels above 20 microgram/ml initial doses should be decreased about 10% and final adjustment made with the aid of serum theophylline measurement under steady state conditions. In children, Nuelin Retard given in two daily doses is capable of maintaining a constant therapeutic serum concentration for the whole 24-hour period.

Effects of ergotamine on isolated human vessels

In isolated human mesenteric and crural veins, ergotamine induced long-lasting contractions. These contractions were resistant to repeated wash-out and were not affected by alpha-adrenoceptor blockade, but could be abolished by removal of extracellular calcium or by the presence of the calcium-blocker nifedipine. In contrast to its effect on human mesenteric and crural veins, ergotamine had no contractile effect, but a marked relaxant effect on mesenteric arteries mediated via blockade of alpha-receptors. The ergotamine-induced contraction was not affected by indomethacin (0.28--2.8 microM) nor was it influenced by serotonin (5-HT). In both mesenteric and crural veins, the ergotamine-induced contraction was diminished by the 5-HT blocking agent, methysergide. In veins, development of tachyphylaxis to 5-HT was demonstrated. It is concluded that ergotamine has a direct contractile effect on isolated human mesenteric and crural veins. These effects are dependent on unhindered influx of extracellular calcium and are at least partly mediated via 5-HT receptors. In mesenteric arteries, ergotamine acted as an alpha-adrenoceptor blocker, and had no contractant effect.

Stability of DNA/ANTI-DNA complexes. IV. Complement fixation

We describe an in vitro assay to study complement fixation of antibody/dsDNA immune complexes formed from SLE sera and radiolabeled dsDNA. The method measures the amount of radiolabeled dsDNA which is part of an immune complex bound to red blood cells via the C3b complement component receptor. The assay is dependent upon active complement, red blood cells, and anti-dsDNA antibodies, but it is independent of the red blood cell donor (type O) and the age of the red blood cells (up to 10 days). The method has been compared in some detail with the Farr assay with respect to the antibody/dsDNA ratio in the immune complexes and the relative stability of the complexes as measured by their resistance to dissociation by excess unlabeled dsDNA. Our results indicate that multiple binding of antibodies to dsDNA is required for complement fixation, and that a significant percentage of those antibodies which fix complement are of high avidity. Finally, a double label assay using both [3H]- and [14C]-dsDNA indicates that the complement fixing potential of the anti-dsDNA antibodies in an SLE serum is strongly influenced by the order of mixing of the isotopes with the serum. The DNA isotope which is added to the serum first is considerably more effective at fixing complement than the isotope which is added 1 h later. The implications of these results with respect to the pathogenesis of SLE are discussed.

Dialysis encephalopathy in a non-dialysed uraemic boy treated with aluminium hydroxide orally

Brain aluminium concentration has been found significantly higher in patients dying with dialysis encephalopathy than in uraemic patients without this syndrome, and it has previously been reported only in haemodialysed patients. We report a case of high brain aluminium concentration in a uraemic boy showing symptoms of severe encephalopathy. He was never dialysed but only treated with aluminium hydroxide orally. Baluarte reported corresponding symptoms in nondialysed uraemic children, but brain aluminium concentrations were not reported. His patients as well as our had very high levels of parathormone which may play a role in the resorption and distribution of aluminium. Aluminium preparations should be avoided in children with renal failure.