[Perioperative pharmacological circulatory support in daily clinical routine]

Perioperative phases of hypotension are associated with an increase in postoperative complications and organ damage. Whereas some years ago hemodynamic stabilization was primarily carried out by volume supplementation, in recent years the use and dosing of cardiovascular-active substances has significantly increased. But like intravascular volume therapy, also substances with a cardiovascular effect have therapeutic margins, and thus, potential side effects. This review article discusses indications for each cardiovascular-active agent, weighing up advantages and disadvantages. Special attention is paid to the question how to administrate them: central venous catheter vs. peripheral indwelling venous cannula. The authors come to the conclusion that it is not a question of whether it is principally allowed to apply cardiovascular-active drugs via peripheral veins but more importantly, what should be taken into consideration if a peripheral venous access is used. This article provides concise recommendations.

Urine neutrophil gelatinase-associated lipocalin predicts outcome and renal failure in open and endovascular thoracic abdominal aortic aneurysm surgery

Urine neutrophil gelatinase–associated lipocalin (uNGAL) has been evaluated as a biomarker for AKI detection and adverse outcome in open and endovascular thoracoabdominal aortic aneurysm surgery. This observational, retrospective study included 52 patients. UNGAL was measured peri-operatively (48 h) and correlated with AKI requiring dialysis, tracheotomy and adverse outcome. Mean patients’ age was 64.5 years. A total of 26.9% (n = 14) developed AKI, and 21.1% (n = 11) required dialysis, tracheotomy rate was 19.2% (n = 10) and in-hospital mortality rate was 7.6% (n = 4). uNGAL levels were related to AKI requiring dialysis at ICU (p = 0.0002), need for tracheotomy at baseline and admission on ICU (p = 0.0222, p = 0.0028, respectively), as well as adverse discharge modality (p = 0.0051, p = 0.0048, respectively). Diagnostic quality was good for uNGAL levels at admission to ICU regarding AKI requiring dialysis (sensitivity: 81.8% [48.2–97.7]; specificity: 87.8% [73.8–95.9]; area under the curve (AUC): 0.874 [0.752–0.949]). The diagnostic quality of uNGAL was favorable for the prediction of tracheotomy (sensitivity: 70.0% [34.8–93.3]; specificity: 83.3% [68.6–93.0]; AUC: 0.807 [0.674–0.903]) and adverse discharge (sensitivity: 77.8% [40.0–97.2]; specificity: 83.7% [69.3–93.2]; AUC: 0.817 [0.685–0.910]). uNGAL may be valuable as an post-operative predictor of AKI and adverse outcome after open and endovascular TAAA repair.

Impact of age on the clinical outcomes of major trauma

PURPOSE

In view of demographic changes over the past few decades, the average age of trauma patients is progressively increasing. We therefore aimed to summarize the specific characteristics of geriatric trauma and to identify potential fields for further research to improve the care of elderly trauma patients.

METHODS

Review of the literature.

RESULTS

Due to the diverse risk factors (e.g., pre-existing conditions, limited physiological reserve), geriatric patients are prone to developing severe complications, even after less severe trauma. Yet, age is not considered as the only predictor of worse outcomes, and it should not be considered the only criterion for limiting care in those patients. It is crucial that age-specific treatment guidelines are developed to optimize the outcomes for senior trauma patients. Based on the current literature, these guidelines should emphasize the importance of field triage directly to a trauma center, along with the activation of the trauma team. Furthermore, early intensive monitoring, aggressive resuscitation, and time of surgical intervention are of upmost importance to reduce mortality.

CONCLUSION

The impact of several factors [age, premedical conditions (PMC), decreased physiological reserves, and impaired immune function] on the post-traumatic course of elderly trauma patients needs to be clarified in future experimental and clinical studies for the early identification of geriatric high-risk patients and for the development of age-adapted therapeutic strategies.

Single-channel analysis of the anion channel-forming protein from the plant pathogenic bacterium Clavibacter michiganense ssp. nebraskense

The anion channel protein from Clavibacter michiganense ssp. nebraskense (Schürholz, Th. et al. 1991, J. Membrane Biol. 123: 1-8) was analyzed at different concentrations of KCl and KF. At 0.8 M KCl the conductance G(V(m)) increases exponentially from 21 pS at 50 mV up to 53 pS at V(m) = 200 mV, 20 degrees C. The concentration dependence of G(V(m)) corresponds to a Michaelis-Menten type saturation function at all membrane voltage values applied (0-200 mV). The anion concentration K(0.5), where G(V(m)) has its half-maximum value, increases from 0.12 M at 50 mV to 0.24 M at 175 mV for channels in a soybean phospholipid bilayer. The voltage dependence of the single channel conductance, which is different for charged and neutral lipid bilayers, can be described either by a two-state flicker (2SF) model and the Nernst-Planck continuum theory, or by a two barrier, one-site (2B1S) model with asymmetric barriers. The increase in the number of open channels after a voltage jump from 50 mV to 150 mV has a time constant of 0.8 s. The changes of the single-channel conductance are much faster (<1 ms). The electric part of the gating process is characterized by the (reversible) molar electrical work DeltaG(theta) (el) = rhoZ(g)FV(m) approximately -1.3 RT, which corresponds to the movement of one charge of the gating charge number Z(g) = 1 across the fraction rho = DeltaV(m)/V(m) = 0.15 of the membrane voltage V(m) = 200 mV. Unlike with chloride, the single channel conductance of fluoride has a maximum at about 150 mV in the presence of the buffer PIPES (>/=5 mM, pH 6.8) with K(0.5) approximately 1 M. It is shown that the decrease in conductance is due to a blocking of the channel by the PIPES anion. In summary, the results indicate that the anion transport by the Clavibacter anion channel (CAC) does not require a voltage dependent conformation change of the CAC.

Massive Blutung nach Hysterektomie - Einsatz von rekombinantem Faktor VIIa

MEDICAL HISTORY

A 38-yr-old woman suffered from excessive blood loss after elective removal of the uterus because of a leiomyoma. The surgical attempt to stop the bleeding failed. The laboratory evaluation before surgery showed normal coagulation parameters (aPTT 23.4 sec, TPZ > 100 %, platelet count 267 000/microl).

DEVELOPMENT

Despite treatment with the plasminogen activator inhibitor Tranexamic Acid (2 x 500 mg) and 10 units of concentrated platelets as well as 31 units of fresh frozen plasma and 31 units of red blood cell concentrates the bleeding continued. Reaching an cumulative blood loss of 15 000 ml the patient developed ventricular fibrillation necessitating cardiac resuscitation including defibrillation and application of epinephrine 7 mg. At this point systolic blood pressure decreased from 90 to 70 mm Hg, the core temperature was 31,9 degrees C. After successful resuscitation (systolic blood-pressure 90 mm Hg after 15 min) the bleeding started again with a blood loss of 2000 ml requiring 3 units of fresh frozen plasma and 3 red cell concentrates Use of recombinant activated Factor VII (r.FVIIa): 6 mg (300 KiU) r.FVIIa have been applied (92 microg/kgKG [4.6 KiE/kg]). Within 10 minutes the bleeding stopped. More transfusions were not necessary. The patient left the intensive care unit 8 days after the operation without neurological deficit.

CONCLUSION

The use of recombinant Factor VIIa may stop excessive haemorrhage, even if the cause is unknown.

Impact of tobacco smoking on platelet function in apheresis products in vitro

BACKGROUND AND OBJECTIVES

The aim of this study was to analyse the platelet function, over a 5-day time-period, of apheresis-derived platelet concentrates obtained from smokers and non-smokers.

MATERIALS AND METHODS

Smoker and non-smoker plateletpheresis products were investigated on days 1, 3 and 5 of storage. Receptor expression (as evaluated by flow cytometry) and the platelet aggregation response were measured.

RESULTS

There was only a slight loss of platelet function in apheresis products from smokers compared to non-smokers.

CONCLUSIONS

Smoking does not significantly change the quality of platelet preparations. The current practice, of not to exclude smokers from platelet donation, can be continued.

[Massive transfusion of washed red blood cells: acid-base and electrolyth changes for different wash solutions]

OBJECTIVE

The composition of normal saline (NaCl), the standard wash solution for cell saver autotransfusion, is considerably different from physiologic plasma values in small infants. Therefore, we investigated acid-base and electrolyte changes during massive cell saver autotransfusion with different wash solutions in young pigs.

METHODS

After approval by the animal protection authorities 15 young pigs (weight 10.6 +/- 1.1 kg, blood volume 848 +/- 88 ml, mean+/-SD) underwent 15 cycles of cell saver autotransfusion (Haemolite 2plus, Haemonetics). For each cycle, 100 ml arterial blood was withdrawn, washed with NaCl, physiologic multielectrolyte solution (PME, V Infusionslösung 296 mval Elektrolyte, Baxter) or physiologic erythrocyte protection solution (PEP, 3.2 % gelatine, pH 7.40, cHCO3 24 mmol/l), and then retransfused. Analyses of acid-base, electrolyte, and hematologic parameters were performed for systemic and washed blood samples.

RESULTS

For NaCl there was a progressive decrease in systemic pH, HCO3 and base excess (BE) and an increase in chloride values (Cl) (p < 0.05). Use of PME slightly decreased pH (n. s.), whereas HCO3, BE and Cl remained stable. PEP slightly increased pH, HCO3 and BE, and decreased Cl (n. s.). Free hemoglobin increased in NaCl and PME (p < 0.05) and was below baseline in PEP (n. s.). Lactic acid course was comparable in all groups.

CONCLUSIONS

The use of NaCl as wash solution for massive autotransfusion resulted in metabolic acidosis caused by dilution of HCO3 and increased Cl values. Fewer systemic acid-base and electrolyte changes were observed, when blood was washed with PME or PEP. The decreased hemoglobin release with PEP is possibly due to a gelatine specific electrostatic surface coating of erythrocyte membranes. For massive transfusion of washed red blood cells, physiologic multielectrolyte solution and physiologic erythrocyte protection solution should be preferred to NaCl, especially for small infants.

[Aseptic central venous catheter exchange with a guide wire]

Central venous catheters are exchanged in cases of malfunction, suspected infections, or when another catheter type is required. It can be replaced by new venipuncture or using a guide wire. The guide wire technique should be used with a defective catheter or when the catheter type is to be changed. It is contraindicated at exit site infections or proven or suspected catheter infections. Due to possible cross contamination of new by old catheter material meticulous aseptic technique is required. A detailed description of the process of catheter exchange using a guide wire with special regard to the aseptic technique is given.

Acid-base, electrolyte and metabolite concentrations in packed red blood cells for major transfusion in infants

METHODS

Acid-base, electrolyte and metabolite concentrations were determined in 100 U of packed red blood cells (RBC) preserved in extended-storage media to be used for major transfusion in paediatric and cardiac surgery.

RESULTS

In fresh RBC, low pH, bicarbonate (cHCO3-), base excess (BE) and high glucose values were observed all outside the physiological range. With lengthening storage duration, values of pH, cHCO3-, BE, sodium and glucose decreased and carbon dioxide, potassium and lactic acid concentrations increased [mean +/- SD (range): storage duration 6.7 +/- 3.8 (1-17) days, pH 6.79 +/- 0.1 (6.53-6.99); mmol.l-1: cHCO3- 11.1 +/- 1.5 (6.2-14.5), BE - 29.2 +/- 4.1 ([-39.4] - [-20.9]), potassium 20.5 +/- 7.8 (4.2-43.6), glucose 24.1 +/- 6.1 (16.7-29.2), lactic acid 9.4 +/- 4 (4.3-21.4)].

CONCLUSION

Massive and rapid transfusion of RBC may lead to a severe burden of hydrogen ions, carbon dioxide, potassium, glucose and lactic acid and this can be avoided by cell saver blood processing, when autologous erythrocytes from the operative field are saved and substrate load and storage lesions from packed red blood cells are minimized in one step by washing.

Protective effects of plasma replacement fluids on erythrocytes exposed to mechanical stress

Haemoglobin release from 40 suspensions of packed red blood cells in modified fluid gelatin, 4% albumin solution, 6% hydroxyethyl starch and normal saline was investigated in vitro during circulation with a roller pump from a heart-lung machine for 120 min at a flow rate of 2.5 l.min-1 at room temperature. The lowest haemoglobin release was obtained with erythrocytes in modified fluid gelatin, whereas free haemoglobin concentrations became progressively higher with albumin, hydroxyethyl starch and normal saline [median free haemoglobin (interquartile range) after 120 min circulation: gelatin 493 (360-601) mg.l-1, albumin 692 (590-1111) mg.l-1, hydroxyethyl starch 1121 (692-1518) mg.l-1, normal saline 1178 (881-1757) mg.l-1, p < 0.001]. Modified fluid gelatin appears to have potent erythrocyte protective properties similar to those of albumin. This effect could decrease mechanical haemolysis during extracorporeal circulation or cell saver autotransfusion if modified fluid gelatin is used as part of a priming solution or as an additive in wash solutions.

Evaluation of modulations in heart rate variability caused by a composition of herbal extracts

The purpose of this prospective, placebo-controlled, randomized double-blind study was the examination of changes of the basic vegetative rhythms due to Cardiodoron, a composition of extracts of blossoms from Primula officinalis and Onopordon acanthium and from the herbs of Hyoscyamus niger. In its clinical use it is known as a modulating medicine in the treatment of functional disturbances of the cardiovascular system. With use of Holter monitoring, 24-h ECG recordings were obtained from 100 healthy subjects of whom 50 took the composition and 50 a placebo. Heart rate variability was evaluated from the 24-h ECGs by means of a power spectral analysis based on the Fast Fourier Transformation (FFT). Regulative influences on the rhythmic system due to the medicine were found. After four weeks of medication half of the verum group showed a tendency to an increased variability in the low and high frequency range at night (LFn: 0.04-0.15 Hz, HFn: 0.15-0.4 Hz) in contrast to the placebo group. The mean heart rate at night (HRn) showed a tendency towards a normalization in the verum group: in subjects with a low HRn the heart rate was increased and in subjects with a high HRn the heart rate was decreased. This effect could not be observed in the placebo group. After two further weeks without any medication this difference between verum and placebo was abolished.

Haemodynamic, acid-base and electrolyte changes during plasma replacement with hydroxyethyl starch or crystalloid solution in young pigs

We investigated haemodynamic, acid-base and electrolyte changes during almost total plasma replacement with hydroxyethyl starch (HES) and physiological balanced electrolyte solution (PBE) by using a cell saver in ten young pigs. In the PBE group an additional 3550 (444) ml crystalloid solution [Mean (SD)] was infused over the course of the study in order to maintain pulmonary capillary wedge pressure. Plasma protein levels decreased in both groups and the colloid osmotic pressure increased in HES and decreased in PBE. At the end of the study, body weight [HES 10.4 (1), PBE 13.1 (1.4) kg, P < 0.01] and lactic acid concentration [HES 0.9 (0.3), PBE 2.9 (1. 3) mmol.l -1, P < 0.01] was higher and tissue oxygen delivery [HES 327 (22), PBE 89 (29) ml.min.m2, P < 0.01] was lower in the PBE group. There were only moderate acid-base changes in both groups, but at the end, anion gap was significant lower in HES. In conclusion, maintenance of colloid osmotic pressure close to the physiological range of infants seems to be advantageous during major paediatric surgery.

[The effect of a nasal spray consisting of a standardized mixture of citrus limon (succus) and an aqueous extract of Cydonia oblongata (fructus) on nasal mucociliary clearance]

In a three-way-crossover study in 18 healthy male and female subjects aged from 20 to 49 years the influence of a 1% and 3% solution of a standardized composition of Citrus limon, succus, and extract from Cydonia oblonga, fructus (Gencydo) on the intranasal mucociliar clearance was investigated after multiple administration. The pH of the solution was about pH 2.3-3.2. The dose regimen consisted of 20 puffs (0.13 ml per puff) in each nostril within 24 h, which was by factor 3-10 higher than the usual therapeutic dosage of 2-6 puffs per nostril and 24 h. The mucociliar transport time was measured by a modified saccharin test, where 1 microliter of a 3-molar aqueous sodium saccharinate solution was applicated at the inferior nasal turbinate 1 cm from its anterior end using a glass capillary microliter pipet. This test was performed at screening examination, before each administration period, directly after each 24 h treatment period and 24 h after the end of each treatment. The time of initial taste perception could be defined with high precision by the volunteer since it appeared very spontaneously. Neither after intranasal administration of the 1% and 3% Citrus/Cydonia solution nor after placebo solution a prolongation of the perception time was found. It could be concluded that there is no measurable influence of the test products on the intranasal ciliar function.

Alteration of anion gap during almost total plasma replacement with synthetic colloids in piglets

In ten piglets (body weight 8.2-11.6 kg), acid base, electrolyte and anion gap changes were investigated during almost total plasma replacement with hydroxyethyl starch (HES) and modified fluid gelatin (GEL) in saline solution using a cell saver autotransfusion technique. During the study, there were only moderate acid base changes, but marked disturbances in anion balance. At study end, the mean chloride concentration was significantly higher (mmol/l: normal values 97-108, HES 116 +/- 1.5, GEL 108 +/- 1.1, p < 0.01) and the mean anion gap was significantly lower in the HES group in comparison to the GEL group (mmol/l: normal values 5-14, HES 3 +/- 1.7, GEL 11.9 +/- 0.9, p < 0.01). It is concluded that plasma replacement with electroneutral HES, but not with negatively charged GEL, can lower the anion gap irrespective of the underlying disease. This can be misleading when the anion gap is used for differential diagnosis of metabolic acidosis in patients after large volume infusion of synthetic colloids.

The initiation of the muscle action potential

The specific functional properties of the nicotinic acetylcholine receptors (AChR) and the particular oligomeric membrane organization of AChR are suggested to be the basis for the steep electrical depolarisation, required for the initiation of the postsynaptic action potentials causing muscle contraction and discharge of electric organs. The dimer (M(r) approximately 580,000) and the monomer (M(r) approximately 290,000) of the detergent-solubilized, affinity-purified AChR of Torpedo californica electrocytes exhibit different channel conductances and larger oligochannels. Patch clamp data of the dimer, reconstituted in large lipid vesicles, show that the dimer is a double-channel protein causing single-channel events of conductance G(D) = 84 +/- 6 pS at 0.11 M K+ and 0.1 mM Ca2+ at 293 K (20 degrees C). At the same ionic conditions the vesicle-reconstituted monomer, if prevented from aggregation, exhibits a channel conductance, G(M) = 42 +/- 3 pS, which is only half of that of the dimer. The dimer conductivity event thus reflects the synchronous switching of its two constituent monomeric parts. The K(+)-conductance of the reconstituted Torpedo dimer is the same, and shows the same inhibitory Ca(2+)-dependence, as that of the Torpedo AChR expressed in Xenopus laevis oocytes (Imoto et al., Nature, 324, 670-674, 1986). In terms of Ca(2+)-binding, reducing K(+)-transport, the equilibrium constant is KCa = 0.48 mM at 0.11 m K+, 20 degrees C; G0([Ca]-->0) = 98 +/- 6 pS and G infinity ([Ca]-->infinity) = 27 +/- 6 pS. The ratio G0/G infinity and an estimate of the lateral surface area of the channel vestibule yields about 16 negatively charged groups in an average distance of 1.8 nm. These negative charges cause an accumulation of K+ ions in the channel vestibule by a factor of about 4. Our results and the comparison with the oocyte data reveal that it is also the dimer which is the physiological opening-closing unit of the AChR in the oocyte membrane. The larger macrochannel events are multiples of the dimer or of the monomer conductances. The occurrence of such oligochannels from AChR protein oligomers could guarantee the steep electrical depolarisation necessary to generate the action potential by the Na(+)-channel system.

[Clinical relevance of incidental prostate carcinoma. A retrospective study]

Between July 1973 and December 1992, 5156 men underwent either TURP (n = 4259) or open prostatectomy (n = 897) because of infravesical obstruction supposedly due to benign prostatic hyperplasia (BPH). In this retrospective study, 86 men in whom an incidental carcinoma of the prostate had been found were followed up. Thirty-seven cases had been classified as pT1a tumor and 49 cases as pT1b tumor; 73 patients had undergone TURP and 13 open surgery. The mean age of the patients was 70.6 years (range 54-89). Twenty-seven patients (73%) with a pT1a tumor and 19 patients (38.8%) with a pT1b carcinoma received no further treatment. Radical prostatectomy was performed in four cases, one of pT1a and three of pT1b tumor. In all other cases the patients received androgen deprivation, and in four cases external radiotherapy was applied. With a mean follow-up of 5 years (range 17-229 months) 48 patients died (55.8%). The median survival was 73 months (95% CI: 52; 89). Compared to the overall population in the same age range, the standard mortality rate (SMR) was 1.72 and 2.05 (95% CI: 1.23; 2.21 and 1.46; 2.64 respectively) using the "Allgemeine Sterbetafel" of the Federal Republic of Germany (1949-1951 and 1986-1988). Using the log-rank test (P = 0.5, two-sided) no difference in survival was found between patients staged pT1a and pT1b. Ten of 48 patients dead at the time of evaluation died of prostate cancer. This means that 20.8% (pT1a n = 3; pT1b n = 7) of the patients succumbed to progressive disease during follow-up. All four patients who underwent radical prostatectomy are free of tumor at time of this evaluation. These results are in accordance with other studies. In younger men with incidental carcinoma of the prostate and life expectancy of more than 10 years, radical surgery of the prostate should be recommended.

Purification of the CIC-0 chloride channel from Torpedo california electroplax identification of a phosphorylation site for cAMP-dependent protein kinase

The voltage-gated chloride channel (CIC-0) from the electric organ of Torpedo californica was purified by immunoaffinity chromatography. A polyclonal antibody was shown to specifically recognize the CIC-0 channel (M(r) 85,000-90,000) in a Western blot of total membrane proteins. As monitored by immunoprecipitation, the formation of antibody-antigen complexes in solution strongly depends on the detergent composition. The highest yield of precipitated CIC-0 was obtained from an incubation mixture containing both an anionic detergent, cholate or lauryl sulfate, and the zwitterionic detergent CHAPS. In contrast, immuno-precipitation of CIC-0 was largely reduced when cholate was exchanged for the nonionic detergent Triton x-100, suggesting that the efficient formation of immuno-complexes is favored by negatively charged detergent. In initial immunopurification experiments, in addition to CIC-0 a major contaminating polypeptide of M(r) approximately 115,000 was copurified, which represents the SITS-binding protein [Jentsch et al. (1989) Biochem. J. 261, 155]. Purification of CIC-0 could be increased from about 35% up to 60% homogeneity when immunoaffinity chromatography was performed in the presence of N-acetylglucosamine. Therefore the highly glycosylated SITS-binding protein most likely interacts with the CIC-0 protein via its carbohydrate parts. The purified CIC-0 channel was found to be phosphorylated by PKA in vitro to a level of 0.35-0.4 mol of phosphate incorporated per mol of CIC-0. Proteolytic digestion with endoproteinase GluC and HPLC-separation revealed two major phosphopeptides, which could be identified by amino acid sequence analysis as different size fragments of the same consensus phosphorylation site. Comparison of the peptide sequences with the deduced protein sequence of CIC-0 [Jentsch et al. (1990) Nature 348, 510; O'Neill et al. (1991) Biochem. Biophys. Acta 1129, 131] indicates serine 600 as the phosphorylated residue. Therefore, our results provide strong evidence that CIC-0 is phosphorylated at this single site by PKA in vitro.

Critical dependence of the solubilization of lipid vesicles by the detergent CHAPS on the lipid composition. Functional reconstitution of the nicotinic acetylcholine receptor into preformed vesicles above the critical micellization concentration

The critical concentration of free detergent [Dw]c, which is necessary for lipid vesicle solubilization, is widely believed to be near to the critical micellization concentration (CMC) of the detergent. Here it is shown that [Dw]c and the critical detergent/lipid ratio Rc(M) in the mixed micelles strongly depend on the lipid composition. In agreement with the concept of packing constraints, phospholipids with a large head-group were solubilized by the detergent CHAPS at low CHAPS concentrations, for example [Dw]c = 0.27 mM for phosphatidyl-inositol and [Dw]c = 2.3 mM for phosphatidylcholine, T = 293 K (20 degrees C). In contrast, phospholipids (PL) with a small head-group required larger [CHAPS] values for (mixed) micelle formation: [Dw]c = 3.2 mM for phosphatic acid (PA) and [Dw]c = 5.2 mM for a mixture of palmitoyloleoylphosphatidylcholine (POPC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), POPC:PE:PG = 30:60:10 (mol.-%). Values obtained for the partition coefficient K = Rc(M)/[Dw]c ranged from K = 0.12 mM-1 for dimyristoylphosphatidylcholine to K = 1.1 mM-1 for (soy) phosphatidylcholine:phosphatidylglycerol (50:50). After addition of 30 mol.-% cholesterol (Ch) or with dipalmitoylphosphatidylcholine below T = 308 K (35 degrees C), [Dw]c is > 10 mM, which is far above the CMC = 4 mM. This indicates that CHAPS micelles are formed before vesicle solubilization begins. The analysis of vesicle solubilization was a prerequisite for the controlled reconstitution of protein membrane proteins. AChR proteins reconstituted into preformed PL/Ch-vesicles at [Dw] > CMC had a 4-5 time higher value of Li-influx compared to reconstitutions from completely solubilized lipid and proteins indicating a higher efficiency of right-side out AChR incorporation.

[Iodine-induced hyperthyroidism in urology caused by using roentgen contrast media. Risks and prevention]

The presence of functionally autonomous portions of the thyroid is a precondition for the occurrence of iodine-induced hyperthyroidism after the administration of i.v. contrast media, in the form either of latent immunogenic hyperthyroidism (Basedow's disease) or of localized or diffuse autonomy. The normal thyroid can compensate an iodine excess in multiple ways. In the malfunctioning thyroid, however, autoregulation mechanisms may fail, resulting in complicated forms of hyperthyroidism. In Germany autonomy-correlated hyperthyroidism occurs much more often than in other countries in which sufficient alimentary iodine is present. Especially in elderly patients with long-standing nodular goitres, there is an elevated risk of iodine-induced hyperthyroidism arising from thyroidal autonomy. These cases may differ from those seen in younger patients. An existing hyperthyroidism may worsen dramatically after administration of contrast media. To prevent an iodine-induced thyrotoxic crisis, contrast media should only be given to patients with latent of manifest hyperthyroidism when vital indications are present, and then only after thyrostatics have been administered. To evaluate the morphology of the renal collecting system and ureter in these cases a retrograde rather than an intravenous pyelography should be performed. When this is combined with determination of serum creatinine and creatinine clearance, functional and morphological evaluation, respectively, of the upper urinary tract are possible.

Indanyloxyacetic acid-sensitive chloride channels from outer membranes of skeletal muscle

In mature mammalian muscle, the chloride conductance of the membrane is an important factor in the regulation of excitability. Up to now, no ligand was available for the biochemical characterization of muscle chloride channels. In order to localize and characterize these channels, we have used indanyloxyacetic acid (IAA)-94, a ligand previously used for epithelial Cl- channels (Landry, D. W., Reitman, M., Cragoe, E. J., Jr., and Al-Awqati, Q. (1987) J. Gen. Physiol. 90, 779-798; Landry, D. W., Akabas, M. H., Redhead, C., Edelman, A., Cragoe, E. J., Jr., and Al-Awqati, Q. (1989) Science 244, 1469-1472). IAA induced myotonic responses when microinjected into mature mouse muscle fibers, indicating a blockade of Cl- channels from the cytoplasmic side. Membrane vesicles were prepared from rabbit skeletal muscle and separated by sucrose gradient centrifugation. Fractions obtained (in the order of increasing density) were sarcolemma (SL), T-tubules (TT), sarcoplasmatic reticulum (SR), and triads and mitochondria (TR/M). The fraction enriched for SL was characterized by high specific binding capacity for [3H]saxitoxin (Na+ channel), whereas TT-rich fractions bound [3H]PN 200-110 (dihydropyridine receptor) with high specific activity. Upon patch-clamping of lipid supplemented vesicles, IAA-sensitive Cl- channels were found in the SL fraction but not in the SR. Highest specific activities in electrical diffusion potential sensitive 36Cl transport and [3H]IAA-94 binding were found in the SL. SL vesicles were solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate and subjected to IAA-Sepharose affinity chromatography. Specifically bound protein was eluted with 100 microM IAA-94 and either analyzed by SDS-gel electrophoresis or reconstituted into phospholipid vesicles. The eluate contained four polypeptides (specifically bound, mapp 110-120 and 60 kDa; unspecifically bound mapp 67 and 50 kDa) and was highly enriched for IAA-sensitive chloride channels as shown by patch-clamping after reconstitution. The IAA-sensitive 100/280-picosiemens chloride channels of the sarcolemma are likely to be responsible for its major chloride conductance and thereby for the stabilization of resting potential.

Functional reconstitution of the nicotinic acetylcholine receptor by CHAPS dialysis depends on the concentrations of salt, lipid, and protein

The detergent CHAPS was found to be the preferable surfactant for the efficient purification and reconstitution of the Torpedo californica nicotinic acetylcholine receptor (AChR). The main result is that the incorporation of the AChR proteins into lipid vesicles by CHAPS dialysis was strongly dependent on the salt and protein concentrations. As monitored by sucrose gradients, by electron microscopy, and by agonist-induced lithium ion flux, the best reconstitution yields were obtained in 0.5 M NaCl at a protein concentration of 0.5 g/L and in 0.84 M NaCl at 0.15 g/L protein. Electron micrographs of receptor molecules, which were incorporated into vesicles, showed single, nonaggregated dimer (M(r) = 580,000) and monomer (M(r) = 290,000) species. CHAPS dialysis at NaCl concentrations less than 0.5 M largely reduced the receptor incorporation concomitant with protein aggregation. Electron micrographs of these preparations revealed large protein sheets or ribbons not incorporated into vesicles. The analysis of static and dynamic light scattering demonstrated that the detergent-solubilized AChR molecules aggregate at low lipid contents (less than or equal to 500 phospholipids/AChR dimer), independent of the salt concentration. AChR proteins eluted from an affinity column with a solution containing 8 mM CHAPS (but no added lipid) still contained 130 +/- 34 tightly bound phospholipids per dimer. The aggregates (about 10 dimers on the average) could be dissociated by readdition of lipid and, interestingly, also by increasing the CHAPS concentration up to 15 mM. This value is much higher than the CMC of CHAPS = 4.0 +/- 0.4 mM, which was determined by surface tension measurements. The data clearly suggest protein-micelle interactions in addition to the association of monomeric detergents with proteins. Furthermore, the concentration of the (free) monomeric CHAPS at the vesicle-micelle transformation in 0.5 M NaCl ([Dw]c = 3.65 mM) was higher than in 50 mM NaCl ([Dw]c = 2.8 mM). However, it is suggested that the main effect of high salt concentrations during the reconstitution process is an increase of the fusion (rate) of the ternary protein/lipid/CHAPS complexes with mixed micelles or with vesicular structures, similar to the salt-dependent fusion of vesicles.

Lipid-protein surface films generated from membrane vesicles: selfassembly, composition, and film structure

Lipid-protein films at the air-water interface were generated from a variety of native vesicles and from vesicles derived from lipid extracts. A technique is described which is particularly suitable for the generation of films from small amounts of material at high yield and velocity. In all instances, 10 microliters vesicle suspensions containing 25 micrograms protein yield at least 50 cm2 film area at a constant surface pressure of 12 mN/m within minutes. Upon formation, surface films are separated from vesicles by use of shear forces. Complete separation is demonstrated by electron microscopy and surface pressure-area diagrams. The latter confirms previous conclusions that surface films generated from lipid vesicles are organized as a monolayer. Analysis of lipid-protein surface layers reveals that their lipid to protein ratios match those of the vesicles used, within a factor of two, irrespective of whether films are generated at high or low surface pressure. Surface denaturation of membrane proteins is shown to be effectively prevented when the film is generated and held at high surface pressure (greater than or equal to 15 mN/m). Upon surface pressure jumps from high to low values, denaturation kinetics revealed activation areas of 1.5 (+/- 0.2) nm2.

Anion channel forming activity from the plant pathogenic bacterium Clavibacter michiganense ssp. nebraskense

The plant pathogenic bacterium Clavibacter michiganense ssp. nebraskense secretes an anion channel forming activity (CFA) into the culture field. The CFA inserts spontaneously into planar lipid membranes when culture fluid of this species is added to the aqueous phase of the bilayer chamber. The channels formed are highly anion selective. The conductance decreases for larger anions (Cl- greater than SCN- greater than SO2-(4] and is practically zero for gluconate. The channels show a unique voltage dependence: (i) The single-channel conductance increases linearly with voltage up to 200 mV saturating at 250 mV with 25 +/- 1 pS (300 mM KCl). The channel is closed at negative voltage relative to the side of insertion (diode-type I-V curve). (ii) The average number of open channels also increases with voltage. The Poisson distribution of channel numbers indicates independent opening of the channels. Channel activity can be abolished by protease treatment of the planar bilayer. The channels can be blocked by indanyloxyacetic acid (IAA-94) and by pH greater than 10. The CFA was purified yielding one major band on the SDS gel with a relative molecular mass of 65,000. The putative involvement of the CFA in the toxicity of this plant pathogen is discussed and compared to other toxins like colicins and to the diptheria toxin group.

The nematocyst extract of Hydra attenuata causes single channel events in lipid bilayers

The nematocyst extract of Hydra attenuata causes single conductance events in reconstituted planar lipid membranes as well as in inside-out patches derived from liposomes. The smallest single channel conductance level of the toxins is 110 pS. The conductance levels increase stepwise with time up to 2000 pS. These large conductance jumps indicate channel cooperativity. If the membrane-voltage is changed from positive to negative values, the single channel events become undefined and noisy, indicating major reorganizations of the proteins which form the channels. The molecular properties of the ionophoric component(s) of the nematocyst extract may help explain the observed macroscopic effects, such as hemolysis of human erythrocytes, after addition of the nematocyst extract.

Miscibility of octyl glucoside-phosphatidylcholine micellar solutions. Partition of the nicotinic acetylcholine receptor into the surfactant-rich phase

Phospholipid phosphatidylcholines (PC) and the nonionic detergent octyl glucoside (OG) were found to form a miscibility gap in aqueous solution at a molar ratio [OC]T/[PC]T=2.6-2.4. This ratio is just below the critical ratio for the formation of vesicles. At [PC] greater than 1.3 g/l the transition from micelles to vesicles is not direct but via a surfactant-rich phase (SRP). The various stability regions are summarized in a phase diagram. Though the partition coefficient gamma=[Db]/[Dw] increases markedly with temperature, the critical ratio for the phase separation R(c) is biased to higher detergent concentrations. This behaviour can be explained by increased motion of the hydrocarbon moiety at higher temperatures. The different phases are investigated by light microscopy, nuclear magnetic resonance and thin-layer chromatography. The miscibility gap of PC/OG is compared to the lamellar phase of Triton X-114; the miscibility gap has implications for membrane protein reconstitution and can be used for membrane protein purification. The Torpedo californica nicotinic acetylcholine receptor (n-AcChR) was found to partition into the SRP.

The cromolyn binding protein constitutes the Ca2+ channel of basophils opening upon immunological stimulus

Ca2+ channel opening has been proposed to be induced in the plasma membrane of mast cells and basophils upon crosslinking their Fc epsilon receptors. Here we report direct conductance measurements on planar lipid bilayers containing membrane components of rat basophils (RBL-2H3 line). These studies identify the Ca2+ channel-forming membrane component as the cromolyn binding protein [CBP, in which cromolyn is the anti-asthmatic drug 1,3-bis(2-carboxy-chromon-5-yloxy)-2-hydroxypropane]. Planar membranes were first formed from lipid vesicles containing unfractionated plasma membrane components prepared from RBL-2H3 cells. Conductance of these bilayers was induced by crosslinking IgE bound to the Fc epsilon receptors of this membrane by a specific polyvalent antigen. Channel conductance in the presence of only Ca2+ ions (2 mM) was 2 pS. When only sodium ions were present (150 mM), conductance was 10 pS. Upon addition of Ca2+ (2 mM) to the Na+ ion-containing solution, the conductance decreased from 10 pS to that of the Ca2+ ions--namely, 2pS. Open channel times were in the range of several hundred milliseconds. Conductance amplitudes and time characteristics were independent of the applied voltage. As our earlier studies revealed the essential role of the CBP in Ca2+ conductance of basophil membranes, we formed planar bilayers containing this isolated protein alone. Crosslinking of the CBP by a monoclonal antibody specific to it resulted in the appearance of channel conductances. All characteristics of these channels exhibited great similarity to those observed in planar membranes containing unfractionated RBL-2H3 membrane components. Moreover, in the latter membranes, the monoclonal anti-CBP antibody induced channel conductances that display an even closer similarity to those observed in membranes containing CBP alone. Conductances of both types of planar membranes, irrespective of the mode of activation used, were inhibited by cromolyn. Furthermore, the conductance induced in RBL membranes by polyvalent antigen was inhibited on dissociation of the crosslinked aggregates by a monovalent hapten. The detailed resemblance in channel behavior observed in experiments with the two types of planar bilayers provides compelling evidence that the CBP is the essential and sufficient component forming Ca2+ channels in basophil plasma membranes.