Aggressive wear-debris pseudotumor following total hip replacement.
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Aged↗
Biomedical subjects
M Palmer
Publications and source records attributed to M Palmer.
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.
Animals↗
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.
2-Naphthylamine↗
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.
Antineoplastic Combined Chemotherapy Protocols↗
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.
Journal Article↗
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.
Anti-Bacterial Agents↗
Thrombocytopenia after rattlesnake envenomation.
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Adult↗
Haematological and non-haematological toxicity after 5-fluorouracil and leucovorin in patients with advanced colorectal cancer is significantly associated with gender, increasing age and cycle number. Tomudex International Study Group.
5-Fluorouracil (5-FU) has been widely used for over 30 years. Recently, investigators have described interactions between toxicity with 5-FU and age and gender. Pharmacokinetics of infusional 5-FU are known to be gender dependent, with drug clearance being lower in females. The full impact of age and gender on both toxicity and response has not been fully explored and is worthy of further investigation. 439 patients were entered into a phase III trial comparing a novel thymidylate synthase (TS) inhibitor Tomudex (raltitrexed, formerly ZD1694) with 5-FU and leucovorin (LV) for the treatment of advanced colorectal cancer. Approximately 20-24% of patients in each treatment group were aged 70 years or older and 41% of the patients were female. In a multiple regression analysis, female patients receiving 5-FU + LV experienced significantly more grade 3/4 leucopenia, whilst those receiving raltitrexed had more rises in transaminase levels. Grade 3/4 leucopenia and mucositis were significantly correlated with age (especially > 70 years) only in patients receiving 5-FU + LV. Patients receiving 5-FU + LV were significantly more at risk of experiencing grade 3/4 haematological and non-haematological toxicity in the first three cycles than patients receiving raltitrexed. Female gender and increased age predict for increased grade 3/4 toxicity in patients receiving modulated 5-FU. Further studies with modulated 5-FU which utilise a modified dose reduction schema for female patients, or patients aged 70 years or over, may be appropriate.
Adult↗
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.
Adult↗
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.
Adolescent↗
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.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
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.
APACHE↗
Pore-forming bacterial cytolysins.
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Animals↗
Reducing the supply of illicit drugs.
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Editorial↗
Accumulation of amphotericin B in human macrophages enhances activity against Aspergillus fumigatus conidia: quantification of conidial kill at the single-cell level.
A cytofluorometric assay that allowed assessment of damage to phagocytosed Aspergillus fumigatus conidia at the single-cell level was developed. After ingestion by monocyte-derived macrophages (MDMs), conidia were reisolated by treatment of the cells with streptolysin O, a pore-forming toxin with lytic properties on mammalian cells but not on fungi. The counts obtained by staining of damaged conidia with propidium iodide and quantification by cytofluorometry correlated with colony counts. By the use of this method, we demonstrate that MDMs differentiated in vitro by low-dose granulocyte-macrophage colony-stimulating factor and gamma interferon have only a limited capacity to damage Aspergillus conidia in vitro. The killing rate 12 h after phagocytosis was found to be only 10 to 15%. However, intracellular loading of the phagocytes with amphotericin B (AmB) dose dependently enhanced the anticonidial activity. Preincubation of macrophages with only 1 microg of AmB per ml resulted in an uptake of 18 fg of AmB/cell, leading to killing rates of 50 to 60%. The experimental protocol provides a new tool for the rapid quantification of anticonidial activity against A. fumigatus in vitro. Intracellular accumulation of AmB may represent an important factor underlying the efficacy of this antifungal drug in the prophylaxis and treatment of Aspergillus infections.
Amphotericin B↗
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.
Albumins↗
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.
Child↗