The impact of a high-dependency unit on the workload of an intensive care unit

While there has been recent support for high-dependency unit development, there are few data reporting the impact of such development on existing critical care facilities. Therefore the aim of this study was to examine the workload and capacity constraints of an adult general intensive care unit before and after the development of an adjacent high-dependency unit. Following the opening of the high-dependency unit, the total number of patients admitted increased by 49%. On the high-dependency unit, more elderly patients were admitted for longer and more frequently following midweek elective surgery. On the intensive care unit, patients' initial severity of illness was lower and their duration of admission decreased; fewer patients were admitted directly from the general wards. The financial benefits of high dependency care may be eroded by the increased use of the critical care services.

Relationship of blood thromboxane-B2 (TxB2) with lipid peroxides and effect of vitamin E and placebo supplementation on TxB2 and lipid peroxide levels in type 1 diabetic patients

OBJECTIVE

To study the effect of vitamin E supplementation on platelet hyperaggregability in type 1 diabetic patients.

RESEARCH DESIGN AND METHODS

Written informed consent according to the Institutional Review Board on Human Experimentation guidelines was obtained from diabetic patients (n = 29) and their age-matched normal siblings (n = 21) to participate in this study. Diabetic patients were supplemented with DL-alpha-tocopherol (vitamin E) capsule (orally, 100 IU/day) or placebo for 3 months in a double-blind clinical trial. Alternate diabetic patients were assigned to vitamin E or placebo during regular visits to the clinic. Fasting blood was collected from each diabetic patient before the start and after the vitamin E or placebo supplementation. Platelet aggregability was assessed by competitive enzyme-linked immunosorbent assay of the blood TxB2 (a stable thromboxane metabolite). Plasma vitamin E and MDA (malondialdehyde, a product of lipid peroxidation) was assessed by high-performance liquid chromatography. Data were analyzed statistically on 12 diabetic patients on vitamin E and 12 on placebo supplementation.

RESULTS

Diabetic patients (n = 29) had 62% higher (P < 0.05) levels of TxB2 and 15% higher levels (P < 0.05) of MDA in comparison to normal subjects (n = 21). Plasma TxB2 levels had a significant correlation with MDA levels (r = 0.45, P < 0.02) but not with the HbA1 (r = -0.08), glucose (r = -0.13), duration of diabetes (r = -0.04), or age (r = 0.12) of diabetic patients. Vitamin E supplementation lowered MDA levels by 30% (P < 0.04), TxB2 levels by 51% (P < 0.03), and triglyceride levels by 22% (P < 0.04) in diabetic patients. There were no differences in these parameters before versus after placebo supplementation.

CONCLUSIONS

The elevated blood level of TxB2 (hyperaggregability of platelets) is significantly related to the level of lipid peroxidation products (oxidative stress) in type 1 diabetic patients. Supplementation of modest doses of vitamin E (100 IU/day) significantly lowers blood TxB2 and lipid peroxidation products levels in type 1 diabetic patients.

Prevalence of urinary tract symptoms in long-standing type 1 diabetes mellitus

The purpose of this study was to evaluate the prevalence of urinary tract symptoms in a population-based cohort of 109 young adult patients with Type 1 diabetes mellitus with onset at < 16 years versus 208 sex- and age-matched controls. A validated postal questionnaire was used (response rate 87.2% in diabetic patients vs 77.4% in controls). Diabetic female patients had been treated more often than controls with antibiotics for urinary tract infections (UTI): 35/48 and 39/82 respectively; p < 0.01. Diabetic female patients with HbA1c > 9.0% did not have significantly more treated UTIs than those with HbA1c < or = 9.0%. Diabetic female patients had more social problems than controls in daily life because of urinary tract problems (11/48 and 3/82 respectively; p < 0.005) and used clamps to prevent wetting more often than did controls (5/48 vs 1/82, p < 0.05), whereas diabetic male patients never used condoms to prevent wetting. In conclusion, female but not male diabetic patients with long-standing Type 1 diabetes mellitus had increased frequency of treated UTIs. Urinary tract problems also interfered with normal social activities in female diabetic patients who had a greater need for clamps to prevent wetting.

Cholesterol-Streptolysin O Interaction: An EM Study of Wild-Type and Mutant Streptolysin O

We present transmission electron microscopical data from negatively stained specimens of cholesterol following interaction with the thiol-activated bacterial toxin streptolysin O (SLO) (wild-type and a number of cysteine substitution mutants), with and without chemical modification of the cysteine residues. Two experimental systems were used, one with an aqueous suspension of cholesterol microcrystals and the other with immobilized thin planar cholesterol crystals attached to a carbon film. In both systems the wild-type SLO and two cytolytically active mutants, Cys 530 --> Ala (C530A) and Ser 101 --> Cys (S101C), readily generated the characteristic SLO arc- and ring-like oligomers on the surface of cholesterol microcrystals and immobilized planar cholesterol crystals. An underlying array of bound toxin can sometimes be detected. In the presence of high concentrations of SLO monomer, extensive sheet-like networks of linked oligomers extend from the microcrystals. The SLO mutant Thr250 --> Cys (T250C), which also possesses a relatively high cytolytic activity, has been found to create ring-like toxin oligomers somewhat more slowly than wild-type SLO, but the linear monomolecular layer array of cholesterol-bound toxin is more readily detected. With mutant Asn402 --> Cys (N402C), which has approximately 10% cytolytic activity compared to wild-type SLO, the formation of ring-like oligomers is markedly reduced, with incomplete arcs and the parallel arrays predominating. Chemical modification of the functional cysteine groups of SLO mutants T250C and N402C completely inhibits the formation of toxin oligomers, but does not prevent the ability of these mutants to bind to cholesterol as a linear array. Such chemical modification is also known to abolish hemolysis/cytolysis. For both mutant T250C and N402C the parallel array of bound SLO adopts an orientation that appears to be determined by the underlying lattice of the crystalline cholesterol. The cholesterol-binding of biotinylated SLO mutant N402C was confirmed by labeling in suspension with 5-nm streptavidin-conjugated colloidal gold particles. Removal of the maltose-binding protein from the SLO fusion products increases the order of the monolayer array of biotinylated SLO bound to cholesterol crystals. Overall, our data support the concept that there is sterospecific binding of the SLO monomer to crystalline cholesterol bilayers, prior to oligomer formation. With the mutants tested, cysteine modification does not prevent binding to cholesterol, but subsequent release and oligomer formation are blocked. Copyright 1998 Academic Press.

Improved recovery of antibiotic-stressed microorganisms on inclusion of saponin in aerobic blood culture media

The recovery rates and times to detection of microorganisms isolated from two similar blood culture media, one containing saponin, were compared. A total of 2117 blood cultures were analysed in a prototype automated blood culture system. Significantly more gram-positive organisms (P<0.05) and gram-negative organisms (P<0.05), including Enterobacteriaceae (P<0.05) were recovered from the lytic medium. Average time to detection in the lytic medium was 15.8 h, compared to 22.7 h in the other medium (P<0.001). The improved recovery of microorganisms was most pronounced in blood samples obtained from patients being treated with antibiotics at the time of venesection. In vitro experiments on antibiotic affected bacteria confirmed the protective effect of saponin.

Effects of altering the time of administration and the time frame of quality of life assessments in clinical trials: an example using the EORTC QLQ-C30 in a large anti-emetic trial

Previous studies conducted by our group suggested that the ability to demonstrate an impact of emesis control on quality of life might depend upon when an quality of life instrument was administered in relation to chemotherapy and on the time frame of the questionnaire. This study was conducted to address this issue. Six hundred and fifty patients receiving moderately emetogenic chemotherapy in a randomized trial comparing a variety of anti-emetic regimens were allocated to four different modes of administration (days 4 and 8; 3 and 7 day time frames) of the QLQ-C30. Patients who completed the questionnaire at the time of maximal impact of chemotherapy (day 3) were more likely to report deterioration in quality of life. Patients who completed questionnaires at day 8 were more likely to report deterioration in quality of life if their questionnaire had a 7 day time frame rather than a 3 day time frame. Patients receiving more effective anti-emetic therapy had better quality of life. It was concluded that better anti-emetic control improves quality of life after moderately emetogenic chemotherapy. In studying quality of life in situations where the impact of treatment waxes and wanes, careful attention needs to be paid to scheduling the administration of questionnaires and to their time frame.

Assembly mechanism of the oligomeric streptolysin O pore: the early membrane lesion is lined by a free edge of the lipid membrane and is extended gradually during oligomerization

Streptolysin O (SLO) is a bacterial exotoxin that binds to cell membranes containing cholesterol and then oligomerizes to form large pores. Along with rings, arc-shaped oligomers form on membranes. It has been suggested that each arc represents an incompletely assembled oligomer and constitutes a functional pore, faced on the opposite side by a free edge of the lipid membrane. We sought functional evidence in support of this idea by using an oligomerization-deficient, non-lytic mutant of SLO. This protein, which was created by chemical modification of a single mutant cysteine (T250C) with N-(iodoacetaminoethyl)-1-naphthylamine-5-sulfonic acid, formed hybrid oligomers with active SLO on membranes. However, incorporation of the modified T250C mutant inhibited subsequent oligomerization, so that the hybrid oligomers were reduced in size. These appeared as typical arc lesions in the electron microscope. They formed pores that permitted passage of NaCl and calcein but restricted permeation of large dextran molecules. The data indicate that the SLO pore is formed gradually during oligomerization, implying that pores lined by protein on one side and an edge of free lipid on the other may be created in the plasma membrane. Intentional manipulation of the pore size may extend the utility of SLO as a tool in cell biological experiments.

Streptolysin O: a proposed model of allosteric interaction between a pore-forming protein and its target lipid bilayer

Streptolysin O, a polypeptide of 571 amino acids, belongs to the family of thiol-activated toxins that permeabilize animal cell membranes. The protein binds as a monomer to membrane cholesterol. Binding involves a conserved region close to the C-terminus and triggers subsequent polymerization into large arc- and ring-shaped structures surrounding pores of up to 30 nm. Besides the C-terminus, a distantly located region spanning residues 213-305 is involved in oligomerization and in membrane insertion. Here, we searched for conformational effects of monomer binding to the latter functionally important region. To this end, single cysteine substitution mutants were produced and derivatized with the polarity-sensitive fluorophore acrylodan. Fluorimetric measurements revealed that binding of the monomer to membranes is accompanied by distinct environmental changes at amino acid residues 218, 248, 266, and 277. Conspicuously, the environment of residues 218 and 266 became more hydrophilic, suggesting movement of these residues out of hydrophobic protein pockets. Upon oligomerization, further alterations in all side-chain environments were observed. The membrane-bound monomer thus differs in conformation from both the monomer in solution and the subunit of the oligomer. The putative binding site of the molecule is linked to remote domains involved in oligomerization and membrane insertion in an apparently allosteric fashion. It is proposed that allostery is responsible for restricting oligomerization to the membrane-bound state of the toxin.

Results of a phase III, double-blind, placebo-controlled trial of megestrol acetate modulation of P-glycoprotein-mediated drug resistance in the first-line management of small-cell lung carcinoma

The objective of this study was to determine if the addition of megestrol acetate (MA), a modulator of P-glycoprotein-mediated drug resistance, to first-line cytotoxic therapy in patients with limited and advanced stage small-cell lung cancer (SCLC) would improve median time to disease progression and median overall survival. Secondary outcomes evaluated were response rates and patient symptom profile. Between 1992 and 1995, 130 eligible patients were randomized in a double-blind fashion to receive standard first-line therapy consisting of alternating courses of cyclophosphamide/doxorubicin/vincristine and etoposide/cisplatin (and thoracic radiotherapy for limited stage patients), along with either placebo or MA 160 mg t.i.d. for 8 days commencing 3 days before initiation of each cycle of chemotherapy. Treatment was continued for a maximum of six cycles. A total of 130 eligible patients were randomized, 65 to each arm. Fifty-two per cent of patients had limited disease and 48% had advanced disease. The median time to disease progression in limited stage disease was 46 weeks in the placebo arm and 43 weeks in the MA arm (P = 0.71) and in advanced stage disease was 28 weeks in the placebo arm and 27 weeks in the MA arm (P = 0.92). The median overall survival in limited stage disease was 75 weeks in the placebo arm and 75 weeks in the MA arm (P = 0.56) and in advanced stage disease was 41 weeks in the placebo arm and 39 weeks in the MA arm (P = 0.96). There was no consistent statistical difference in response rates or patient symptom profiles between the two treatment arms. The addition of MA, in the dose and schedule used, to standard first-line cytotoxic therapy in SCLC did not result in a significant improvement in response rates, symptom profile, median time to disease progression or overall survival.

Delayed immediate implants: alveolar bone changes during the healing period

Delaying the placement of immediate fixtures by 6-8 weeks after extraction of the natural dentition allows for the elimination of associated infective processes, the achievement of maximum osteoblastic activity that theoretically could help the osseointegration process and complete wound covering that simplifies the placement of grafts or membranes. This study examines the healing associated with 21 fixtures in 14 patients. The fixtures were placed into sockets 6-8 weeks after tooth extraction without the use of barrier membranes or bone substitutes. Measurements were taken immediately prior to fixture placement and 3-6 months later at the abutment placement. Alveolar bone height, the remaining socket depth and diameter and the depth to which a 3.75 mm fixture could be inserted into the socket were measured. After fixture placement the vertical and horizontal measurements from the cover screw to the surrounding alveolar bone and the distance from the cover screw to the CEJ of the adjacent tooth were recorded. All fixtures were integrated at exposure with 1 failure during the follow-up period. The distance from the cover screw to the buccal plate decreased by a mean of 2.17 mm. There was an increase in the mean vertical bone height at all 4 surfaces. When horizontal defects were present, the mean vertical distance decreased from 2.5 +/- 0.37 mm to 0.36 +/- 0.64 mm. When horizontal defects were absent, the mean vertical distance decreased from 3.86 +/- 0.58 mm to 0.48 +/- 0.25 mm. There was also a marked decrease in the horizontal distance between the bone margin and the surface of the fixture from 1.6 +/- 1.73 mm to 0.02 +/- 0.02 mm. These results indicate a strong tendency for the defects to fill-in the horizontal plane and for bone growth to occur in the vertical plane to the height of the cover screw. In conclusion the delayed immediate placement of fixtures has a good short-term prognosis with bone regeneration occurring around the defect without the use of barrier membranes or bone substitutes.

Intervention with the hypoxic tumor cell sensitizer etanidazole in the combined modality treatment of limited stage small-cell lung cancer. A one-institution study

PURPOSE

We report the toxicity, patterns of failure and survival of a cohort of patients with limited disease (LD) small-cell lung cancer (SCLC) treated with combined radiation and chemotherapy. During the course of thoracic irradiation, we added intravenous (i.v.) etanidazole (SR-2508, a third-generation 2-nitroimidazole) as a hypoxic cell sensitizer in an attempt to reduce the primary local failure rate and improve survival.

METHODS AND MATERIALS

Between July 1988 and August 1990, 30 consecutive patients with limited disease SCLC were enrolled and treated on a Phase II protocol receiving a standard combination chemotherapy regimen utilizing i.v. cisplatin 25 mg/m2/day x 3 days, i.v. etoposide 100 mg/m2/day x 3 days alternating with intravenous cyclophosphamide 1000 mg/m2/day, intravenous doxorubicin 15 mg/m2, and intravenous vincristine 2 mg (CAV) to a total of six cycles every 3 weeks. Radiotherapy and etanidazole were started after the first cycle of chemotherapy. Etanidazole was administered intravenously at a dose of 2 g/m2 three times per week for a total of 30 g/m2 during the course of thoracic radiation that delivered 50.00 Gy tumor dose in 25 fractions in an overall time of 6 weeks.

RESULTS

The overall response rate of the primary lesion in the thorax was 96% (CR + PR), with 64% complete responses. The median time to treatment failure was 18 months. Of the patients that have relapsed, only 18% failed in the thorax (alone or concomitant with other sites). This is a marked improvement compared to the 40-50% rate reported in the literature. The 2-year crude survival was 46%. The 3- and 5-year crude survival rate with no evidence of disease was 33 and 30%, respectively. We have observed a 10% increase in the incidence of transient etanidazole related peripheral neuropathies compared to previous etanidazole studies not utilizing systemic chemotherapy. There was no increased incidence of radiation esophagitis, pulmonary toxicity, or nephro- or myelotoxicity over and above what has been routinely observed with this radio/chemotherapy regimen. There were no treatment related deaths.

CONCLUSION

The moderate increase in etanidazole-related transient peripheral neuropathies could have been related to the concomitant use of etanidazole with vincristine and cisplatin. Although the almost 50% improvement in the incidence of tumor failure rate in the thorax in this small group of patients did not correlate with an equal marked improvement in their survival, the 5-year survival outcome in our series is at least equal or better than the best reports in the literature of larger clinical trials. We believe there is sufficient data from this study, particularly the improvement of local tumor control, to warrant a large randomized controlled clinical trial, using the most current systemic chemotherapy with concomitant thoracic irradiation with or without the most effective available hypoxic cell cytotoxic/sensitizer.

Bacterial cytolysin perturbs round window membrane permeability barrier in vivo: possible cause of sensorineural hearing loss in acute otitis media

The passage of radioiodinated streptolysin-O (SLO) and albumin through the round window membrane (RWM) was studied in vivo. When applied to the middle ear, SLO became quantitatively entrapped in this compartment and no passage to the cochlea occurred. However, flux of radioiodinated albumin through the toxin-damaged RWM was observed. We propose that the passage of noxious macromolecules, such as proteases, from a purulent middle-ear effusion may be facilitated by pore-forming toxins, resulting in cochlear damage and sensorineural hearing loss.

Cysteine-specific radioiodination of proteins with fluorescein maleimide

A protocol is described for coupling of carrier-free iodine to protein sulfhydryl groups via fluorescein maleimide. 125I is first coupled to fluorescein maleimide in the presence of chloramine T. Iodination is stopped with sodium thiosulfate, and the iodine-substituted fluorescein maleimide is reacted with free cysteines of the protein. Excess label is then removed by gel-permeation chromatography. The procedure avoids exposition of the protein to oxidative conditions and does not require purification of the labeled carrier reagent. Suitability of the method for a given protein can be evaluated spectrophotometrically without employing radioactivity. It can be applied under denaturing conditions and may be particularly useful with mutant proteins carrying engineered single cysteine residues at sites that are not functionally critical.

Staphylococcal alpha-toxin: formation of the heptameric pore is partially cooperative and proceeds through multiple intermediate stages

Staphylococcal alpha-toxin is a 293 residue polypeptide that assembles into pore-forming heptamers, residues 118-140, thereby inserting to form an amphipathic beta-barrel in the lipid bilayer. Fluorometric analyses were here conducted using cysteine-substitution mutants site-specifically-labeled at positions 35 or 130 with the environmentally-sensitive fluorophore acrylodan. In conjunction with functional assays, three conformational states of the heptamer were defined, which may represent transitional configurations of the toxin molecule along its way to membrane insertion and pore formation. The first was the freshly assembled, SDS-sensitive heptamer alpha7*a, where a minor alteration in the environment of H35 with no change in the environment of the membrane-inserting stem domain was observed. In transition stage alpha7*b, the stem domain moved from a hydrophilic to a more hydrophobic environment, due to protein-protein interaction. Transition to alpha7*c involved a cooperative effect, in which residue 35 was forced by a neighboring molecule into a markedly hydrophobic environment. At this stage, the heptamers acquired SDS stability. The final pore conformation alpha7 resulted when the stem domain inserted into the lipid bilayer, an event that was driven by H35 within the respective protomer. A model thus evolved in which cooperative forces first lever H35 into a position that subsequently drives the pore-forming sequence within each respective protomer into the membrane. In accord with this model, when hybrid heptamers were formed between a functionally defective H35 substitution mutant and active toxin, only the latter inserted their pore-forming domain into the membrane. In a satisfying functional correlate, pores of reduced size were then generated.

Transmembrane beta-barrel of staphylococcal alpha-toxin forms in sensitive but not in resistant cells

Staphylococcal alpha-toxin is a 293-residue, single-chain polypeptide that spontaneously assembles into a heptameric pore in target cell membranes. To identify the pore-forming domain, substitution mutants have been produced in which single cysteine residues were introduced throughout the toxin molecule. By attaching the environmentally sensitive dye acrylodan to the sulfhydryl groups, the environment of individual amino acid side chains could be probed. In liposomes, a single 23-amino acid sequence (residues 118-140) was found to move from a polar to a nonpolar environment, indicating that this sequence forms the walls of the pore. However, periodicity in side chain environmental polarity could not be detected in the liposomal system. In the present study, the fluorimetric analyses were extended to physiological target cells. With susceptible cells such as rabbit erythrocytes and human lymphocytes, the 23 central amino acids 118-140 were again found to insert into the membrane; in contrast to the previous study with liposomes, the expected periodicity was now detected. Thus, every other residue in the sequence 126-140 entered a nonpolar environment in a striking display of an amphipathic transmembrane beta-barrel. In contrast, human granulocytes were found to bind alpha-toxin to a similar extent as lymphocytes, but the heptamers forming on these cells failed to insert their pore-forming domain into the membrane. As a consequence, nonfunctional heptamers assembled and the cells remained viable. The data resolve the molecular organization of a pore-forming toxin domain in living cells and reveal that resistant cells can prevent insertion of the functional domain into the bilayer.

Fatigue in patients with cancer: results with National Cancer Institute of Canada Clinical Trials Group studies employing the EORTC QLQ-C30

The purpose of this study was to examine the factors which affect the level of fatigue among patients participating in clinical trials in which this symptom had been assessed with the EORTC QLQ-C30. Data were assembled from 2390 patients in ten clinical trials in which the QLQ-C30 had been used to assess baseline and on-study quality of life. The relationship between the level of fatigue reported by the patients on the fatigue scale of this questionnaire and patient and disease characteristics was assessed in univariate and multivariate cross-sectional analyses. In addition, changes in fatigue scores were compared in a longitudinal analysis among patients on two arms of an anti-emetic trial whose emesis control was markedly different. Baseline fatigue levels differed substantially among patients taking part in the different trials. Factors associated with greater fatigue severity on univariate analysis included: female gender, presence of metastatic disease, and poorer performance status. In addition, on multivariate analyses the oldest patients were found to have less fatigue, as were patients with breast cancer, while patients with ovarian and lung cancer experienced greater fatigue. Patients on the arm of the anti-emetic trial in which emesis was better controlled showed significantly less increase in fatigue after receiving chemotherapy. The fatigue scale of the QLQ-C30 appears to provide a useful approach to assessing this important symptom. The relationships found between fatigue and patient and disease characteristics need further exploration as does the degree to which the QLQ-C30 fully captures this dimension of quality of life.

Phase III double-blind comparison of dolasetron mesylate and ondansetron and an evaluation of the additive role of dexamethasone in the prevention of acute and delayed nausea and vomiting due to moderately emetogenic chemotherapy

PURPOSE

To compare the efficacy of dolasetron and ondansetron in controlling nausea and vomiting in the first 24 hours; to evaluate the efficacy when dexamethasone is added to either drug in the first 24 hours; and to extend these comparisons over 7 days in patients receiving moderately emetogenic chemotherapy.

PATIENTS AND METHODS

This was a multicenter, double-blind, randomized study with six parallel arms that used a 2 x 2 factorial design in chemotherapy-naive patients. In arm 1, dolasetron (2.4 mg/kg) was given intravenously (I.V.) prechemotherapy, followed 24 hours later by oral dolasetron (200 mg once daily) for 6 days. Arms 2 and 3 consisted of dolasetron and dexamethasone 8 mg I.V., followed 24 hours later by oral dexamethasone (8 mg once daily) in one arm, and oral dexamethasone and dolasetron in the other, also for 6 days. In arms 4, 5, and 6, ondansetron (32 mg I.V. or 8 mg orally twice daily) was administered in a similar manner to arms 1, 2, and 3 before and 24 hours after chemotherapy. Mean nausea severity (MNS) was assessed on a visual analog scale (VAS) in a daily diary.

RESULTS

Of 703 patients enrolled, 696 were eligible. There were 343 dolasetron- and 353 ondansetron-treated patients; 57% of dolasetron-treated patients had complete protection in the first 24 hours versus 67% of patients who received ondansetron (P = .013). MNS was also more pronounced on the dolasetron arm (P = .051). Sixty-seven percent of patients who received added dexamethasone in the first 24 hours had complete protection, compared with 55% without dexamethasone (P < .001). MNS was significantly reduced with the addition of dexamethasone (P < .001). At 7 days, dolasetron and ondansetron had equivalent complete protection rates (36% and 39%, respectively). With the addition of dexamethasone, 48% of patients compared with 28% had complete protection (P < .001). MNS was significantly improved with added dexamethasone (P < .001).

CONCLUSION

At the doses used, dolasetron was significantly less effective than ondansetron at controlling nausea and vomiting in the first 24 hours in patients receiving moderately emetogenic chemotherapy, but there was no demonstrable difference between both drugs over 7 days. The addition of dexamethasone significantly improved the efficacy of both drugs in the first 24 hours and over 7 days.

Mode of primary binding to target membranes and pore formation induced by Vibrio cholerae cytolysin (hemolysin)

Vibrio cholerae cytolysin (VCC) is produced by many non-choleratoxigenic strains of V. cholerae, and possibly represents a relevant pathogenicity determinant of these bacteria. The protein is secreted as a pro-toxin that is proteolytically cleaved to yield the active toxin with a molecular mass of approximately 63 kDa. We here describe a simple procedure for preparative isolation of mature VCC from bacterial culture supernatants, and present information on its mode of binding and pore formation in biological membranes. At low concentrations, toxin monomers interact with a high-affinity binding site on highly susceptible rabbit erythrocytes. This as yet unidentified binding site is absent on human erythrocytes, which are less susceptible to the toxin action. At higher concentrations, binding of the toxin occurs to both rabbit and human erythrocytes in a non-saturable manner. Cell-bound toxin monomers oligomerize to form supramolecular structures that are seen in the electron microscope as apparently hollow funnels, and oligomerization correlates functionally with the appearance of small transmembrane pores. Osmotic protection experiments indicate that the toxin channels are of finite size with a diameter of 1-2 nm. The mode of action of VCC closely resembles that of classical pore-forming toxins such as staphylococcal alpha-toxin and the aerolysin of Aeromonas hydrophila.