Capillary electrophoretic behavior of milk proteins in the presence of non-ionic surfactants

The electrophoretic behavior of alpha-lactalbumin and beta-lactoglobulins (A and B) in the presence of non-ionic surfactants was studied by capillary electrophoresis (CE), using a poly(ethylene glycol) coated capillary column. The surfactants (Tween 20, Brij 35 and 78) were used as buffer additives. The separation is based on the difference in the strength of protein-surfactant association complexes, which results in a change of the effective electrophoretic mobility. The modification of the electrophoretic mobilities of proteins was observed and this variation permitted the estimation of the interaction between protein and surfactant. The effect of surfactant type and concentration on the migration behavior of protein in CE is discussed. It is found that the retention behavior of the milk proteins (the alpha-lactalbumin and the beta-lactoglobulins) in CE is very different. The pH of the buffer and the surfactant type influence significantly the protein-surfactant interactions.

Endoscopic sclerotherapy with fibrin glue as compared with polidocanol to prevent early esophageal variceal rebleeding

BACKGROUND/AIMS

Endoscopic sclerotherapy is of proven benefit for patients after esophageal variceal bleeding, but is associated with substantial local and systemic complications. Since fibrin glue is a promising agent for endoscopic sclerotherapy of esophageal varices, we compared its safety and efficacy in patients after esophageal variceal bleeding.

PATIENTS AND METHODS

In a randomized, controlled trial, 36 patients with an acute episode of variceal bleeding were endoscopically treated with either polidocanol (18 patients) or fibrin glue (18 patients) by intravariceal injections within 12 h of admission. Tissue compatibility, incidence of various complications, episodes of rebleeding and overall survival rates were investigated.

RESULTS

Rebleeding, especially from enrollment to day 28, was less common in the fibrin group (p=0.046), and all patients treated with fibrin glue survived for more than 28 days, whereas five patients treated with polidocanol died within this period. The incidence of sclerotherapy-induced ulcers was significantly lower in the fibrin group than in the polidocanol group (p=0.001), and major complications such as perforation or ulcer bleeding were observed only in the polidocanol group. There were no complications in any group due to activation of systemic coagulation, fibrinolysis or clinically relevant pulmonary embolization.

CONCLUSIONS

We conclude that fibrin glue is an efficient and safe agent for endoscopic sclerotherapy of bleeding esophageal varices, especially in the immediate posthemorrhagic period.

[Importance of endoscopic hemostasis in peptic ulcer hemorrhage in a teaching hospital]

INTRODUCTION

The results of endoscopic treatment for bleeding peptic ulcers in a teaching hospital are little reported. Most studies are published by a limited number of specialized authors with a reported success rate of 76-83%. The aim of this study is to evaluate the success rate in a teaching hospital.

PATIENTS AND METHOD

We retrospectively studied 150 patients hospitalized in our service between 1994 and 1995. They comprised 59 females (median age 80.5 [24-93] years) and 91 males (median age 61.5 [26-98]). 49% were aged 70 or over. 39 patients (29%) had a past history of peptic ulcer disease, the others being admitted for an initial episode of bleeding ulcer. Biopsies for urease test were obtained in 84 patients. In this group the prevalence of Helicobacter pylori infection was respectively 88% and 58% in subjects with a history of ulcer disease and in those with an initial episode of bleeding ulcer. 46% and 54% respectively had taken nonsteroidal anti-inflammatory drugs during the previous weeks. Neither of these two risk factors was present in 9 patients without a previous history of ulcer disease; they were present in none of those with a history.

RESULTS

All patients underwent emergency esogastroduodenoscopy; 48 underwent endoscopic hemostasis. 12 gastroenterologists were involved in these procedures. The definitive success rate is 81%. The success rate for a first hemostasis for a posterior bulbar ulcer is 41% vs 88% for the other localizations, a difference which is statistically significant (p = 0.002). Endoscopic hemostasis showed a higher failure rate where the bleeding stigmata was a spurting vessel (44% vs 18%) but this was not significant (p = 0.18).

CONCLUSION

Endoscopic treatment for bleeding peptic ulcer is effective in a teaching hospital. The technique shows a higher failure rate for posterior bulbar ulcers. In view of the risk of recurrence, patients should be kept in hospital after a first procedure.

[Comparison of treatment outcome for non-variceal upper gastrointestinal hemorrhage using endoscopic obliteration methods and traditional methods in patients over 60]

Authors present results of therapy of patients over 60 treated because of nonvariceal upper gastrointestinal bleeding in General Surgery Department in Oświecim. In 1991-1993 47 patients underwent non-endoscopic therapy. In 1994-1996 endoscopic obliteration with 0.01% epinephrine or 1% polidocanol in patients over 60 was applied. In the group over 60 more often concomitant diseases (cardiovascular, diabetes, atherosclerosis) were noted. Similar endoscopic obliteration efficacy (90% vs. 91%) in patients aged under and over 60 was observed. Patients treated with endoscopic obliteration underwent urgent operation twice rarely then conservative management (6.7% vs. 13%). They obtained less quantity of blood (2.23 vs. 3.4 unit). Their hospital stay was shorter (9 vs. 13 days). In both kind of therapy, mortality in patients over 60 was higher then under 60, but less often in group undergone endoscopic obliteration (traditional treatment 28% vs. 6%, endoscopic 15% vs. 2%).

CONCLUSIONS

1. Reason of worse therapy results of upper gastrointestinal bleeding among patients aged over 60 was great number of concomitant diseases. 2. Efficacy of endoscopic obliteration 0.01% epinephrine and 1% polidocanol was independent from age. 3. Application of endoscopic obliteration improved results of therapy in patients aged over 60.

The diagnosis and treatment of intratesticular varicocele

A case of varicocele is reported. The dilated veins were situated in the left testis. The diagnosis required color Doppler sonography. Successful treatment was performed by transcatheter embolization of the left spermatic vein. The control sonogram revealed complete regression. A literature search yielded only three previous cases of intratesticular varicocele. No data were found on the treatment of this entity.

Polidocanol sensitivity--a possible tool in the differentiation of Malassezia spp

In recent years, the genus Malassezia was reclassified based on molecular data; in addition to M. furfur, M. pachydermatis and M. sympodialis, four new species (M. globosa, M. obtusa, M. restricta, M. slooffiae) were described. Primary keys for routine identification have recently been presented. Polidocanol was shown to have specific inhibitory effects against Malassezia spp. In an agar diffusion test, type strains of all Malassezia species were incubated with polidocanol concentrations between 0.01% and 10%. M. furfur strains were most resistant, with minimal inhibitory concentrations (MIC) ranging from 7.5% to 10%. Inhibitory concentrations of the other strains were lower by at least one factor of ten. Most sensitive were strains of M. pachydermatis (0.05%). In a further test, polidocanol-containing olive oil was used to determine the sensitivity of Malassezia furfur and M. sympodialis. Again, the inhibitory concentrations for strains of M. sympodialis were one tenth of those found for M. furfur. In addition to its antifungal effects, polidocanol might therefore be a useful tool in differentiating Malassezia species.

Lipase-based quantitation of triacylglycerols in cellular lipid extracts: requirement for presence of detergent and prior separation by thin-layer chromatography

A protocol, based on the use of Pseudomonas lipase, is presented to measure quantitatively the amount of triacylglycerols in extracts from cultured cells of tissues. Since the lipase also acts on di- and monoacylglycerols, separation of the extracts by thin-layer chromatography is recommended. In order to allow the lipase-catalyzed hydrolysis to proceed efficiently, lipid extracts or eluates from silica scrapings were mixed with the detergent Thesit [dodecylpoly(ethylene glycol ether)], prior to drying. After dissolution of the dried residues in water, the amount of triacylglycerols was quantified using Pseudomonas sp. lipase, glycerol kinase, glycerol-phosphate oxidase, and peroxidase. The activity of the latter enzyme was followed either colorimetrically in the presence of 4-aminoantipyrine and 2,4,6-tribromo-3-hydroxybenzoic acid or fluorimetrically in the presence of homovanillic acid.

Resolution of the diastereomers of a large synthetic peptide by capillary electrophoresis using nonionic surfactants

A capillary electrophoretic method was developed for the determination of the diastereomeric composition of the bradykinin B2 antagonist, SB-238592-DB. The nonionic surfactant Brij 35 was demonstrated to be suitable for the baseline resolution of the three diastereoisomers of SB-238592-DB in the presence of a low pH phosphate buffer and small volume percentages of acetonitrile.

Heterologous expression, purification, and properties of diol dehydratase, an adenosylcobalamin-dependent enzyme of Klebsiella oxytoca

Recombinant adenosylcobalamin-dependent diol dehydratase of Klebsiella oxytoca overexpressed in Escherichia coli was purified to homogeneity. The enzyme has a low solubility and was extracted from the crude membrane fraction with 1% Brij 35 in a high recovery. Subsequent chromatography on DEAE-cellulose resulted in 4.9-fold purification of the enzyme in an overall yield of 65%. The enzyme thus obtained showed specific activity comparable to that of the wild-type enzyme of K. oxytoca. The apparent molecular weight determined by nondenaturing gel electrophoresis on a gradient gel was 220,000. The enzyme consists of equimolar amounts of the three subunits with apparent Mr of 60,000 (alpha), 30,000 (beta), and 19,000 (gamma). Therefore, the subunit structure of the enzyme is most likely alpha2beta2gamma2. The recombinant enzyme was also separated into components F and S upon DEAE-cellulose chromatography in the absence of substrate. Components F and S were identified as the beta subunit and alpha2gamma2 complex, respectively. Apparent Km for adenosylcobalamin, 1,2-propanediol, glycerol, and 1,2-ethanediol were 0.83 microM, 0.08 mM, 0.73 mM, and 0.56 mM, respectively. The three genes encoding the subunits of diol dehydratase were overexpressed individually or in various combinations in Escherichia coli. The alpha and gamma subunits mutually required each other for correct folding forming the soluble, active alpha2gamma2 complex (component S). Expression of the beta subunit in a soluble, active form (component F) was promoted by coexpression with both the alpha and gamma subunits, probably by coexistence with component S. These lines of evidence indicate that each subunit mutually affects the folding of the others in this heterooligomer enzyme.

Effect of calcium ions on rat osseous plate alkaline phosphatase activity

Rat osseous plate alkaline phosphatase is a metalloenzyme with two binding sites for Zn2+ (sites I and III) and one for Mg2+ (site II). This enzyme is stimulated synergistically by Zn2+ and Mg2+ (Ciancaglini et al., 1992) and also by Mn2+ (Leone et al., 1995) and Co2+ (Ciancaglini et al., 1995). This study was aimed to investigate the modulation of enzyme activity by Ca2+. In the absence of Zn2+ and Mg2+, Ca2+ had no effects on the activity of Chelex-treated, Polidocanol-solubilized enzyme. However, in the presence of 10 microM MgCl2, increasing concentration of Ca2+ were inhibitory, suggesting the displacement of Mg2+ from the magnesium-reconstituted enzyme. For calcium-reconstituted enzyme, Zn2+ concentrations up to 0.1 microM were stimulatory, increasing specific activity from 130 U/mg to about 240 U/mg with a K0.5 = 8.5 nM. Above 0.1 microM Zn2+ exerted a strong inhibitory effect and concentrations of Ca2+ up to 1 mM were not enough to counteract this inhibition, indicating that Ca2+ was easily displaced by Zn2+. At fixed concentrations of Ca2+, increasing concentrations of Mg2+ increased the enzyme specific activity from 472 U/mg to about 547 U/mg, but K0.5 values were significantly affected (from 4.4 microM to 38.0 microM). The synergistic effects observed for the activity of Ca2+ plus magnesium-reconstituted enzyme, suggested that these two ions bind to the different sites. A model to explain the effect of Ca2+ on the activity of the enzyme is presented.

[Value of the emergency therapeutic endoscopy in gastrointestinal hemorrhage]

The experience in therapeutic digestive endoscopy is presented using injection technique with adrenalin-polidocanol of gastrointestinal hemorrhage lesions. One hundred and twenty nine patients were treated endoscopically; the medium age was 60 years; in almost 80% of the cases, peptic ulcer disease were found. The effectiveness was 91.4% when one session procedure was used and in some cases two sessions were applied, giving a final total arrest of hemorrhage of 95.3%. The total mortality still remain high (16.3%) even without bleeding, due to coexisting poor general conditions of the patients. The technique of endoscopic injection is reviewed and the final results of our work are presented.

Remarkable inhibitory effects of hybrid liposomes on the growth of HL-60 cells coupled to induction of apoptosis

The hybrid liposomes (90 mol% DMPC/10 mol% C12(EO)10 or C12(EO)12) have a highly inhibitory effect on the growth of tumor cells (HL-60). The induction of apoptosis by the hybrid liposomes in HL-60 cells was revealed on the basis of flow cytometry and DNA electrophoresis.

Randomised trial of single and repeated fibrin glue compared with injection of polidocanol in treatment of bleeding peptic ulcer

BACKGROUND

Although injection treatments for ulcer haemostasis seem to be effective, recurrent bleeding remains a serious problem. Large randomised clinical trials are required to show differences between treatment modalities for gastrointestinal bleeding. The aim of this study was to compare the safety and efficacy of repeated endoscopic injection of fibrin glue (FG) with that of single endoscopic injection of polidocanol in the prevention of recurrent bleeding.

METHODS

854 patients with active gastroduodenal bleeding (spurting, oozing), or ulcers with a visible non-bleeding vessel, were randomly assigned one of three endoscopic treatments: single application of polidocanol 1%, single application of FG, or daily repeated application of FG until the visible vessel had disappeared. All patients were pretreated with local injection of epinephrine (1/10,000), and had daily repeat endoscopies until the vessel observed at initial endoscopy was no longer visible.

FINDINGS

Recurrent bleeding rates among the 790 patients in whom the rates could be assessed were 58 (22.8%) of 254 in the polidocranol group, 51 (19.2%) of 266 in the FG-single group, and 41 (15.2%) of 270 in the FG-repeated group. The difference between FG-repeated treatment and polidocanol was significant (p = 0.036). Treatment failed, making other treatments (including surgery) necessary, in 34 (13.0%) of 261 in the polidocanol group, 34 (12.4%) of 274 in the FG-single group, and 21 (7.7%) of 274 in the FG-repeated group. The difference between FG-repeated treatment and polidocanol was significant (p = 0.046). The 30-day-mortality rates were low in all three treatment groups (polidocanol 4.7%; FG-single treatment 5.3%, FG-repeated treatment 4.3%). The safety profiles of the three treatment strategies were similar.

INTERPRETATION

Repeated injection with FG glue is significantly more effective than injection with polidocanol 1% in the treatment of bleeding from gastroduodenal ulcers.

Comparison of polidocanol and tetracycline in the sclerotherapy of testicular hydrocele and epididymal cyst

OBJECTIVE

To compare the effects and side-effects of polidocanol and tetracycline when used as sclerosants for testicular hydrocele and epididymal cyst.

PATIENTS AND METHODS

Forty-five men (median age 67 years, range 42-81) with 46 hydroceles or epididymal cysts were assessed. After puncture and aspiration, the empty sac was instilled with either polidocanol or tetracycline, assigned randomly. Patients recorded any treatment-associated pain on a visual analogue scale.

RESULTS

At 9 months of follow-up, nine of 17 men were cured after sclerotherapy with polidocanol compared with 17 of 20 men treated with tetracycline (P < 0.05). Tetracycline produced some pain for 3 days after treatment while polidocanol therapy was almost pain-free. Re-instillation should be considered for recurrences. At the follow-up after 35 months, 16 of 18 men treated with polidocanol and 20 of 22 men treated with tetracycline were satisfied with the outcome.

CONCLUSION

Both polidocanol and tetracycline are useful sclerosants for treating testicular hydrocele and epididymal cyst. We prefer polidocanol as a first choice in older patients because there were few short-term side-effects.

Nitric oxide-mediated vasorelaxation induced by sodium polyoxyethylene laurylether sulfate

Ingestion of surfactants is known to cause hemodynamic changes with decreased total vascular resistance. Motivated by this clinical observation, we investigated the direct effects of a common anionic surfactant, sodium polyoxyethylene laurylether sulfate (LES), on isolated ring segments of rat thoracic aorta. LES did not produce any vasocontractile responses, but relaxed ring segments precontracted with 10(-6) M phenylephrine in a concentration-dependent manner. This LES-induced vasorelaxation was significantly reduced by the removal of endothelium or pretreatment with N(G)-nitro-L-arginine methylester hydrochloride, methylene blue, or oxyhemoglobin to the same degree, but was not affected by pretreatment with indomethacin. A further study measuring NO2- plus NO3- (NO(x), total metabolites of NO) in the medium of calf pulmonary artery endothelial (CPAE) cells, a cultured cell line, revealed that LES caused a significant increase in NO(x) production. On the other hand, in a study measuring intracellular Ca2+ in fura-2-loaded CPAE cells, LES caused a significant increase in intracellular Ca2+. These results suggest that LES causes endothelium-dependent vasorelaxation via a NO-mediated signaling pathway, which might be due to Ca2+ mobilization.

Preservation of the native structure and function of Ca2+-ATPase from sarcoplasmic reticulum: solubilization and reconstitution by new short-chain phospholipid detergent 1,2-diheptanoyl-sn-phosphatidylcholine

The properties of Ca2+-ATPase purified and reconstituted from rabbit skeletal sarcoplasmic reticulum (SR) has been studied in comparison with the preparations obtained by the commonly used detergent poly(oxyethylene)8-lauryl ether (C12E8) and the bile salt detergents cholate and deoxycholate. 1,2-Diheptanoyl-sn-phosphatidylcholine (DHPC) has been shown to be excellent for solubilizing a wide variety of membrane proteins [Kessi, Poiree, Wehrli, Bachofen, Semenza and Hauser (1994) Biochemistry 33, 10825-10836]. The DHPC method consistently gave higher yields of purified Ca2+-ATPase with a greater specific activity than the methods with C12E8, cholate, or deoxycholate. DHPC and C12E8 were superior to cholate and deoxycholate in active enzyme yields and specific activity. DHPC-solubilized Ca2+-ATPase purified on a density gradient retained the E1Ca-E1(*)Ca conformational transition, whereas the enzyme from the C12E8 purification did not retain this transition. The coupling of Ca2+ transported to ATP hydrolysed in the DHPC-purified enzyme was maximal and matched the values obtained with native SR, whereas the coupling was much lower for the C12E8-purified enzyme. The specific activity of Ca2+-ATPase reconstituted into dioleoylphosphatidylcholine vesicles with DHPC was up to 2-fold greater than that achieved with C12E8, and is comparable to that measured in the native SR. Finally, the dissociation of Ca2+-ATPase into monomers by DHPC preserved the ATPase activity, whereas similar dissociation by C12E8 gave only one-sixth the activity of that obtained with DHPC. These studies show that the Ca2+-ATPase solubilized, purified and reconstituted with DHPC is superior to that obtained with C12E8 in significant ways, making it a preparation suitable for detailed studies on the mechanism of ion transport and the role of protein-lipid interactions in the function of membrane proteins.

Endoscopic variceal ligation versus endoscopic variceal ligation and endoscopic sclerotherapy: a prospective randomized study

OBJECTIVE

To compare endoscopic variceal ligation (EVL) with a combination of EVL and endoscopic scelerotherapy (EST) in the secondary prophylaxis of esophageal variceal bleeding.

METHODS

Fifty patients with esophageal varices due to cirrhosis of the liver (38), noncirrhotic portal fibrosis (7), or extrahepatic portal venous obstruction (5) were included in the study. These 50 patients were randomized to receive either EVL alone or a combination of EVL and EST for variceal eradication. Twenty-one patients received EVL alone (group A), and 23 patients received EVL and EST (group B). In group B, EVLs were performed until the varices were reduced to grade II size, and, subsequently, these patients underwent low-dose sclerotherapy with 1% polidocanol until variceal eradication was achieved.

RESULTS

Combined EVL and EST treatment eradicated the varices in a significantly greater number of patients then EVL alone (87% vs. 24%; p < 0.05). However, significantly more endoscopic sessions were required with combined treatment than with EVL alone (5.87 +/- 2.32 vs. 4.28 +/- 1.82; p < 0.05). Rebleeding episodes before variceal eradication were similar in the two groups (19% vs. 22%). The complications were similar in both the EVL and the EVL-plus-EST group, ie., deep ulcers (16% vs. 20%), transient dysphagia (20% vs. 32%), and stricture (4% vs. 8%).

CONCLUSION

Thus, combined EVL and EST treatment eradicates varices in a significantly larger number of patients than EVL alone, with no extra complications.

[Complete gastric wall necrosis after endoscopic sclerotherapy for a gastric ulcer with visible arterial stump]

HISTORY AND CLINICAL FINDINGS

A 43-year-old man with a gastric ulcer was admitted because of sudden onset of epigastric pain, cold sweats and dizziness. He had tachycardia (100/min); his blood pressure was 120/80 mm Hg: his epigastrium was tender to palpation. There were no tarry stools.

INVESTIGATIONS

Haemoglobin concentration was 12.7 g/dl. WBC count 17,900/microliter. Gastroscopy revealed residual haematin and an ulcer with an arterial stump at the angular fold.

TREATMENT AND COURSE

3 ml epinephrine, diluted 1:20,000, and 13 ml of 1% polidocanol were injected around the arterial stump, most of the latter solution flowing back into the gastric lumen from the rather hard ulcer base. Haematemesis four days later necessitated laparotomy followed by gastrectomy with reconstruction and a Roux-Y anastomosis because of complete necrosis of the gastric wall. Histological examination of the surgical specimen showed chronic scarred gastric ulcer and ulcerating pangastritis with haemorrhagic necrosis of the wall and associated peritonitis, caused by accidental injection of polidocanol into the artery.

CONCLUSION

Since the tissue-sparing injection of epinephrine, fibrin glue or salt solution is alone effective in the endoscopic treatment of bleeding gastroduodenal ulcers, polidocanol should not be injected as well.

Treatment of bleeding esophageal varices with cyanoacrylate and polidocanol, or polidocanol alone: results of a prospective study in an unselected group of patients with cirrhosis of the liver

BACKGROUND AND STUDY AIMS

Data concerning the results with emergency and further elective therapy of esophageal varices using polidocanol and cyanoacrylate, or polidecanol alone, in an unselected group of patients with liver cirrhosis have not previously been available. The aim of the present prospective study was to evaluate acute and repeated cyanoacrylate and polidocanol therapy in the emergency and long-term elective management of esophageal varices.

METHODS

In accordance with the protocol of the present prospective study, acutely bleeding esophageal varices of grades 1 to 3 were treated endoscopically with polidocanol injection, while grade 4 varices, large solitary varices (over 5 mm) and otherwise uncontrollable cases of variceal bleeding were treated by injection of cyanoacrylate and polidocanol. Over a period of 62 months, 112 patients (65 men, 47 women) with acute bleeding from esophageal varices due to cirrhosis of the liver (69% alcohol-related) underwent a total of 245 treatment sessions in hospital. The average age of the patients was 62.0 +/- 12.3 years (58.1% were 60 or older). Hepatic function corresponded to Child-Pugh class A in 38 patients (33.9%), Child-Pugh class B in 68 patients (60.7%), and Child-Pugh class C in six (4.5%).

RESULTS

Sixty-eight patients (60.7%) were treated with polidocanol alone, and 44 (39.3%) with cyanoacrylate and polidocanol. Acute hemostasis was achieved in all cases. In 5.7% of the sclerotherapy procedures, bleeding ulcers were observed, and a pleural effusion was seen in one case. The hospital mortality rate was 24.1%, resulting from the bleeding in 2.7% and due to liver failure in the remaining cases. Recurrent bleeding occurred within 24 hours in four patients (3.6%), and during the later course of the hospital stay in a further 11 patients (9.8%). The mean survival time was 13.7 +/- 17.7 months. Over the entire observation period of 23 +/- 21 months, 67 patients died (59.8%); the cause of death was hemorrhage in 4.5%, the underlying hepatic disease in 65.7%, and non-hepatic causes in 29.8%. Recurrent bleeding occurred in 58 patients (51.7%). The cumulative survival rate in the patients treated with cyanoacrylate and polidocanol was 66 +/- 15% and 26 +/- 32% after one and five years, respectively, and 56 +/- 13% and 33 +/- 19% in those treated with polidocanol alone.

CONCLUSIONS

Endoscopic treatment of esophageal varices with cyanoacrylate and polidocanol, or polidocanol alone, is effective in controlling bleeding, and the complication rate is tolerable. The short-term and long-term mortality rates are determined largely by the underlying liver disease.

Gel filtration chromatographic studies of the isolated membrane domain of band 3

We have investigated the oligomeric state of the membrane domain of band 3 (MDB3) in non-ionic detergent solution using Sepharose CL-4B gel filtration chromatography to study the hydrodynamic properties of the protein as a function of its concentration. The studies were performed in a C12E9 (polyoxyethylene-9-lauryl ether) buffer containing phosphatidylcholine and sodium chloride, which significantly slow a dilution-induced band 3 conformational change, and an associated aggregation process. Under these conditions native MDB3 eluted predominantly as a single Gaussian peak with a Stokes radius of 76 +/- 14 A, at all protein concentrations studies between 0.2 and 12 microM. This value agrees with the calculated Stokes radius (74 A) determined from the crystal structure of the MDB3 dimer. The Stokes radius of the MDB3 monomer was obtained experimentally by treating native MDB3 with 0.5% SDS, and exchanging the SDS for C12E9 on the Sepharose column. SDS-treated MDB3 showed two peaks whose ratio was strongly dependent on applied protein concentration. The peak representing the largest material had a Stokes radius of 69.7 +/- 14 A, which is essentially the same as the native MDB3 dimer. The peak representing the smaller material had a Stokes radius of 36 +/- 9 A, and was assigned as the MDB3 monomer in C12E9. Evidence is discussed which indicates that the C12E9 monomer specifically self-associates to form a functional MDB3 dimer. We conclude that native MDB3 exists as a stable dimer in mixed micellar solutions composed of C12E9 and phosphatidylcholine, and that the dimer can be dissociated to monomers only by denaturation.

Proteolytic potential of human neutrophil membranes

A synergistic role for proteases in the degradation of extracellular matrix proteins has been proposed. Plasma membrane was isolated from a neutrophil homogenate, on a sucrose gradient, and shown to activate gelatinolysis when purified 92 kDa gelatinase was added to the medium. This stimulatory activity was enhanced by the addition of phorbol 12-myristate 13-acetate (PMA), in a dose-dependent manner, and was partially sensitive to phenylmethylsulfonyl fluoride treatment. The effect was abolished by the addition of 1 M KCl or 0.05% Brij 35 extraction. Both elastase and urinary type plasminogen activator were shown to be involved in the process. Moreover, upon neutrophil stimulation by PMA, 92 kDa gelatinase, as elastase, became associated with the plasma membrane, as shown by a subcellular fractionation experiment. These in vitro observations suggest that human neutrophils may be able, in vivo, to recruit endogenous or exogenous proteinases to mediate proteolysis associated with diapedesis and chemotactism during the inflammation process.

Regulation of beta-lactamase synthesis as a novel site of action for suppression of methicillin resistance in Staphylococcus aureus

Nearly all clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) produce beta-lactamase as well as an additional low-affinity penicillin-binding protein called PBP2a or PBP2', the main factor for mediating methicillin resistance. Polidocanol (PDO), a dodecyl polyethyleneoxide ether, resensitizes clinical isolates of MRSA to methicillin; in addition, their resistance to benzylpenicillin (BP) is reduced. The action of PDO is based on the inhibition of the induced syntheses of PBP2a and beta-lactamase. Induction in our study was performed with 2-(2'-carboxyphenyl)benzoyl-6-aminopenicillanic acid (CBAP). Inducible PBP2a production in MRSA strains is under the control of the same regulatory system which is responsible for the induction of beta-lactamase synthesis. BlaR1, a membrane-spanning protein with a penicillin sensor and a signal transducer domain represents the starting point of this induction cascade. Based on its amphiphilic properties, it is likely that the action of PDO is located in the bacterial membrane. Therefore we investigated the possibility that BlaR1 might be the main target for PDO action. We were able to detect the BlaR1 sensor domain in resistant staphylococcal cells even in the noninduced state by fluorography. In a competition assay, CBAP was bound specifically, with a high affinity to the penicillin sensor. Moreover, the binding of CBAP was very stable. As concerns PDO, no significant interaction with the penicillin binding site of BlaR1 was detectable. This is why the BlaR1 transducer domain is thought to be the actual target area of PDO. In this case, PDO would interfere with the transmission of the signal, generated by the receptor binding of CBAP, through the membrane via BlaR1 into the staphylococcal cell. This assumption could be confirmed by the analysis of the concentration-effect relationship, whereafter PDO does not work as a competitive, but as a noncompetitive antagonist of CBAP. Our results demonstrate that BlaR1 could be an attractive new target for the development of new drugs to overcome methicillin resistance.