Can Most Calcified Coronary Stenosis Be Optimized With Coronary Intravascular Lithotripsy?

Intravascular lithotripsy can be used as an effective therapy for lesion preparation in severely calcified lesions. The mechanism, as shown by optical coherence tomography, is calcium fractures. The aforementioned modification is performed with minimal risk of perforation, no-reflow and a low incidence of flow-limiting dissection and myocardial infarctions. Other techniques, such as cutting or scoring balloons and rotational atherectomy have also been shown to increase luminal diameter, but other complications, such as distal embolization, induced by these treatment modalities, are a source of concern. This review describes a single-center study of all-comer patients, including those with complex characteristics. This therapy is very effective, with a very low risk of complications. In this article, we characterize the mechanism of action of the intravascular lithotripsy catheter, its optical coherence tomography validation, clinical applications, and comparison with other calcium-modifying technologies, as well as future directions, which can be used to improve the technology.

Internal evaluation of risk stratification tool using serial procalcitonin and clinical risk factors in pediatric febrile neutropenia: The non-interventional, single institution experience prior to clinical implementation

Risk stratification of pediatric febrile neutropenia (FN) is an established concept, yet clinical risk tools misclassify nearly 5% of clinical standard-risk episodes with severe outcomes. The internal evaluation of a clinical risk tool before implementation has not been well-described. In this noninterventional cohort study, we evaluated a study decision rules (SDR) tool; a clinical risk tool with serial procalcitonin. The study standard-risk (SSR) group met clinical standard-risk criteria with two serial procalcitonin <0.4 ng/mL. The study high-risk (SHR) group met clinical high-risk criteria or clinical standard-risk with a procalcitonin ≥0.4 ng/mL. Descriptive and bivariate statistics compared the groups and outcomes. Clinical criteria alone identified 39.1% (238/608) standard-risk episodes; 5.9% (14/238) had severe events. Prospectively using the SDR, the SHR group encompassed 76.6% (92/120) of episodes; severe events occurred in 20% (3/15) of standard-risk episodes included due to elevated procalcitonin ≥0.4 ng/mL. The SHR group had more blood stream infections [21.7% (20/92) vs. 0% (0/28); P = 0.007] and intensive care admissions [13% (12/92) vs. 3.6% (1/28); P = 0.158]. In conclusion, the SDR with serial procalcitonin aided in identifying severe events in clinical standard-risk episodes, but analysis was limited. Institutions may consider similar internal evaluation methodology before FN episode risk stratification.

Rationale and design of the TUXEDO-2 India study: Ultra-Thin strUt Supraflex Cruz versus XiencE in a Diabetic pOpulation with multi-vessel disease-2

BACKGROUND

The role of percutaneous coronary interventions (PCI) in patients with diabetes mellitus and multi-vessel disease has been questioned by the results of the FREEDOM trial, which showed superiority of coronary artery bypass graft(CABG) over first generation drug-eluting stents (DES) including a reduction in mortality. In the light of safer and more efficacious stents and significantly better medical management, those results that date back to 2012 need to be revisited. TUXEDO-2 is a study designed to compare two contemporary stents in Indian diabetic patients with multi-vessel disease.

AIMS

The primary objective of the TUXEDO-2 study is to compare the clinical outcomes of PCI with ultra-thin Supraflex Cruz vs Xience when combined with contemporary optimal medical therapy (OMT) in diabetic patients with multi-vessel disease. The secondary objective is to compare clinical outcomes between a pooled cohort from both arms of the study (Supraflex Cruz + Xience; PCI arm) vs CABG based on a performance goal derived from the CABG arm of the FREEDOM trial (historical cohort). The tertiary objective is a randomized comparison of ticagrelor vs prasugrel in addition to aspirin for the composite of ischemic and bleeding events.

METHODS

In this prospective, open-label, multi-centre, 2 × 2 factorial, randomized, controlled study, 1,800 patients with diabetes mellitus and multi-vessel disease (inclusion criteria similar to FREEDOM trial) with indication for coronary revascularization will be randomly assigned to Supraflex Cruz or Xience stents and also to ticagrelor- or prasugrel- based antiplatelet strategies. All patients will receive guideline directed OMT and optimal PCI including image- and physiology-guided complete revascularization where feasible. The patients will be followed through five years to assess their clinical status and major clinical events. The primary endpoint is a non-inferiority comparison of target lesion failure at one-year for Supraflex Cruz vs Xience (primary objective) with an expected event rate of 11% and a non-inferiority margin of 4.5%. For PCI vs CABG (secondary objective), the primary endpoint is major adverse cardiac events (MACE), defined as a composite of all cause death, nonfatal myocardial infarction, or stroke at one-year and yearly up to five years, with a performance goal of 21.6%. For ticagrelor vs prasugrel (tertiary objective), the primary endpoint is composite of death, myocardial infarction, stroke, and major bleeding as per the Bleeding Academic Research Consortium (BARC) at one-year with expected event rate of 15% and a non-inferiority margin of 5%.

CONCLUSIONS

The TUXEDO-2 study is a contemporary study involving state-of-the-art PCI combined with guideline directed OMT in a complex subset of patients with diabetes mellitus and multi-vessel disease. The trial will answer the question as to whether a biodegradable polymer coated ultra-thin Supraflex Cruz stent is an attractive option for PCI in diabetic patients with multi-vessel disease. It will also help address the question whether the results of FREEDOM trial would have been different in the current era of safer and more efficacious stents and modern medical therapy. In addition, the comparative efficacy and safety of ticagrelor vs prasugrel in addition to aspirin will be evaluated. (CTRI/2019/11/022088).

Drug-coated balloon in the treatment of coronary bifurcation lesions: A hope or hype?

When compared to non-bifurcation lesions, percutaneous coronary intervention in coronary bifurcation lesions is technically demanding and has historically been limited by lower procedural success rates and inferior clinical results. Following the development of drug-eluting stents, dramatically better results have been demonstrated. In most of the bifurcation lesions, the provisional technique of implanting a single stent in the main branch (MB) remains the default approach. However, some cases require more complex two-stent techniques which carry the risk of side branch (SB) restenosis. The concept of leaving no permanent implant behind is appealing because of the complexity of bifurcation anatomy with significant size mismatch between proximal and distal MB which may drive rates of in-stent restenosis and the potential impact of MB stenting affecting SB coronary flow dynamics. With the perspective of leaving lower metallic burden, a drug-coated balloon (DCB) has been utilized to treat bifurcations in both the MB and SB. The author gives an overview of the existing state of knowledge and prospects for the future for using DCB to treat bifurcation lesions.

Effects of vedolizumab on health-related quality of life in patients with ulcerative colitis: results from the randomised GEMINI 1 trial

BACKGROUND

Health-related quality of life (HRQL) is often diminished in patients with ulcerative colitis.

AIM

To evaluate the effects of vedolizumab on HRQL in patients with ulcerative colitis.

METHODS

Using maintenance phase data from the GEMINI 1 study, an analysis of covariance model was used to calculate mean differences between the vedolizumab and placebo groups in changes from baseline to week 52 for 3 HRQL instruments: The Inflammatory Bowel Disease Questionnaire (IBDQ), 36-Item Short Form Health Survey (SF-36), and EQ-5D. Proportions of patients meeting minimal clinically important difference (MCID) thresholds for changes on these instruments were compared between treatment groups for the overall population and for clinically important subgroups. Concordance between clinical remission and remission defined using IBDQ scores was examined.

RESULTS

Compared with placebo-treated patients, vedolizumab-treated patients had greater improvements (152-201%) in IBDQ, EQ-5D visual analogue scale (VAS), and EQ-5D utility scores. Greater proportions (6.9-19.9%) of vedolizumab-treated patients than placebo-treated patients met MCID thresholds for all the instruments. Vedolizumab-treated patients with lower baseline disease activity and those without prior tumour necrosis factor (TNF) antagonist failure had greater HRQL improvements. Among 127 patients with clinical remission based on complete Mayo Clinic scores, >80% also had IBDQ remission; >70% of the 150 patients with IBDQ remission demonstrated clinical remission.

CONCLUSIONS

Vedolizumab therapy was associated with significant improvements in HRQL measures compared with placebo. Benefits were greater in patients with lower disease activity and no prior TNF antagonist failure.

Risk of developing colorectal cancer and benign colorectal neoplasm in patients with chronic constipation

BACKGROUND

Chronic constipation (CC) is a highly prevalent health problem, potentially associated with increased risk of colorectal cancer (CRCancer).

AIM

To investigate the association between CC, its severity, and CRCancer by estimating the relative risk of developing CRCancer and benign colorectal neoplasm (BCN) among severity-stratified patients with and without CC.

METHODS

Chronic constipation patients from a large retrospective US claims database were matched 1:3 with CC-free controls by demographic characteristics. CRCancer and BCN prevalence were measured over 1 year. In pre-index CRCancer- and BCN-free patients, incidence rate ratios (IRRs) of new CRCancer and BCN were calculated. Multivariate regression models adjusted for comorbidities and family history. CC patients' disease severity was rated based on CC-related resource use. IRRs for new CRCancer and BCN were estimated for CC severity groups and controls.

RESULTS

Chronic constipation (N = 28,854) and CC-free (N = 86,562) patients had mean age 61.9 years; 66.7% were female. One-year CRCancer prevalence was 2.7% and 1.7%, and BCN prevalence was 24.8% and 11.9% for CC and CC-free patients, respectively. Adjusted IRRs between CC and CC-free patients were 1.59 [95% confidence interval (CI): 1.43-1.78] and 2.60 [95% CI: 1.51-2.70] for CRCancer and BCN, respectively. Patients with severe and very severe CC had significantly greater incidence of CRCancer and BCN. At ≥ 2 and ≥ 5 years of observation, CRCancer and BCN incidence remained consistently and significantly higher for CC patients.

CONCLUSIONS

Patients with chronic constipation are associated with significantly higher prevalence and incidence of colorectal cancer and benign colorectal neoplasm than matched chronic constipation-free patients. These risks increase with the severity of chronic constipation.

Real-world assessment of therapy changes, suboptimal treatment and associated costs in patients with ulcerative colitis or Crohn's disease

BACKGROUND

Treatments for Crohn's disease (CD) and ulcerative colitis (UC) are not uniformly effective, thus necessitating dose changes, switching, and augmentation and carry adverse event risk, often requiring discontinuation, which reduces treatment benefits.

AIM

To assess continuity of and changes to initial CD and UC treatments, as well as costs associated with specific parameters defining suboptimal therapy.

METHODS

Commercial US insurance claims (2006-2010) were retrospectively analysed. CD and UC patients receiving monotherapy with 5-aminosalicylates (5-ASAs), corticosteroids (CS), immunomodulators (IM) or biologics were included. Continuity of and changes to initial (index) therapy and associated costs (2011 US$) were assessed over 12 months following therapy initiation. Suboptimal therapy included discontinuation or switch (except for CS), dose escalation, augmentation, inadequate loading (biologics only), prolonged CS use (>3 months), surgery or hospitalisation.

RESULTS

The study included 13,005 CD and 19,878 UC patients. Augmentation was a common index therapy change (~20% of 5-ASA initiators, ~40% of CS initiators, ≥40% of IM initiators and 26-55% of biologic initiators) in both CD and UC patients. Approximately 50% of CD and UC 5-ASA initiators discontinued/interrupted treatment. Approximately 80% of CD and UC patients had ≥1 suboptimal therapy marker. Mean all-cause total costs per CD patient were significantly higher in those with vs. without suboptimal therapy ($18,736 vs. $10,878; P < 0.001); in UC, the disparity was smaller ($12,679 vs. $9653; P < 0.001).

CONCLUSIONS

Frequent dose and treatment changes were observed in all classes of initial UC and CD treatments. The economic impact of suboptimal therapy among UC and CD patients is substantial.

Distinguishing the impact of dexlansoprazole on heartburn vs. regurgitation in patients with gastro-oesophageal reflux disease

BACKGROUND

Gastro-oesophageal reflux disease (GERD) is characterised by symptomatic heartburn and regurgitation. Treatment with proton pump inhibitors (PPI) effectively decreases heartburn symptoms, but their effects on symptomatic regurgitation are less clear.

AIM

To determine the impact of PPI therapy on heartburn and regurgitation severity in patients with either non-erosive GERD (NERD) or erosive oesophagitis (EE).

METHODS

Endoscopically-confirmed NERD patients received dexlansoprazole 30 or 60 mg or placebo in a randomised, blinded, 4-week study. Endoscopically-confirmed EE patients received dexlansoprazole 60 mg or lansoprazole 30 mg in two 8-week, randomised, blinded healing studies. The Patient Assessment of Upper Gastrointestinal Symptom Severity questionnaire, which includes a heartburn/regurgitation subscale, was administered to assess symptom severity at baseline, and at weeks 2 and 4 of the NERD study and at weeks 4 and 8 during the EE trials. We defined separate subscales for heartburn and regurgitation for this post-hoc analysis. Among patients with both symptoms at baseline, improvements in individual heartburn and regurgitation subscales along with the original combined heartburn/regurgitation subscale were determined.

RESULTS

In the NERD and EE studies, 661 and 1909 patients, respectively, had both heartburn and regurgitation at baseline. NERD patients receiving dexlansoprazole 30 and 60 mg experienced significantly greater improvements in symptom severity for both heartburn and regurgitation compared with placebo. EE patients receiving dexlansoprazole 60 mg had significantly greater improvements in heartburn/regurgitation and heartburn-only subscales at week 4 compared with those receiving lansoprazole.

CONCLUSIONS

Dexlansoprazole appears to be effective in improving both heartburn and regurgitation, and this improvement is maintained for the duration of treatment.

The effects of increasing body mass index on heartburn severity, frequency and response to treatment with dexlansoprazole or lansoprazole

BACKGROUND

Higher body mass index (BMI) is a recognised risk factor for gastro-oesophageal reflux disease (GERD). Data regarding the impact of BMI on proton pump inhibitor (PPI) therapy are conflicting.

AIM

To assess the impact of BMI on baseline heartburn symptom severity and frequency and response to PPI therapy in patients with non-erosive GERD (NERD) or erosive oesophagitis (EO).

METHODS

In post hoc analyses of phase 3 trial data, 621 NERD and 2692 EO patients were stratified by BMI (<25, 25 to <30 and ≥30 kg/m(2) ). NERD patients received either dexlansoprazole MR 30 mg or placebo daily for 4 weeks. EO patients received either dexlansoprazole MR 60 mg or lansoprazole 30 mg for 8 weeks. Symptom frequency and severity were assessed at baseline and subsequently by daily diary.

RESULTS

In both the NERD and EO cohorts, baseline heartburn severity increased with increasing BMI. The impact of PPI therapy on the reduction in heartburn symptom frequency and severity in both NERD and EO patients was similar across BMI categories. EO healing rates in patients treated with dexlansoprazole but not lansoprazole were higher in obese patients compared with those with a BMI <30 kg/m(2) . Differences between the PPIs were small.

CONCLUSIONS

The PPIs evaluated in this study reduced the frequency and severity of 24-h heartburn regardless of baseline BMI. In addition, because patients with higher BMI have more severe symptoms at baseline, they may experience greater therapeutic gain with dexlansoprazole (NERD and erosive oesophagitis) and possibly lansoprazole (erosive oesophagitis) treatment.

The development and validation of a Nocturnal Gastro-oesophageal Reflux Disease Symptom Severity and Impact Questionnaire for adults

BACKGROUND

Current questionnaires for assessing gastro-oesophageal reflux disease (GERD) symptoms are limited in their ability to capture nocturnal symptoms.

AIM

To develop and validate an instrument, the Nocturnal Gastro-oesophageal Reflux Disease Symptom Severity and Impact Questionnaire (N-GSSIQ), to assess severity and impact of nocturnal GERD symptoms.

METHODS

Two focus groups and 16 cognitive debriefing interviews were conducted among GERD patients to identify key issues about nocturnal symptoms. A draft instrument was tested in 196 patients at 11 clinics in the US to evaluate psychometric properties. Exploratory factor and item response theory analyses were conducted to finalize items and subscales. Internal consistency reliability, reproducibility and construct validity were examined.

RESULTS

Mean age was 45 (s.d. = 13.8) years; 76% were female and 68% were Caucasian. Patient-rated severity was mild-moderate for 69% of participants; 48% reported symptoms on two to three nights the past week. The final questionnaire includes 20 items and three subscales: Nocturnal GERD Symptoms, Morning Impact of Nocturnal GERD and Concern about Nocturnal GERD. The subscales demonstrated internal consistency reliability (Cronbach's alpha 0.84-0.94) and were significantly correlated with similar measures and disease severity (0.41-0.81; P < 0.0001).

CONCLUSION

The results support the reliability and validity of the N-GSSIQ as a measure of severity, morning impact and concern about nocturnal GERD.

Elective stenting in superior vena cava syndrome caused by idiopathic fibrosing mediastinitis: use of self-expandable wallstent

We present a case of superior vena cava obstruction caused by idiopathic fibrosing mediastinitis treated with a self-expandable Wallstent. A Gortex jump graft had been used previously, which was totally occluded. This procedure relieved symptoms and alleviated the need for re-operation.

Extrinsic obstruction of the main coronary arteries in a child with hypertrophic cardiomyopathy

Phasic narrowing of the coronary arteries on angiography is a well-known entity in both children and adults and has been described in relation to all epicardial arteries. There is a high incidence of myocardial bridges in hypertrophic cardiomyopathy. We report the case of a 6-year-old girl with hypertrophic obstructive cardiomyopathy who had extrinsic obstruction of the left main and right coronary arteries.

Localization of a human reduced folate carrier protein in the mitochondrial as well as the cell membrane of leukemia cells

IgG polyclonal antiserum was generated in New Zealand White rabbits immunized with a 16-mer peptide consisting of a specific amino acid sequence at residues corresponding to the sixth to seventh predicted transmembrane domain of the human reduced folate carrier (RFC). Using Western immunoblotting to examine the cytosolic and membrane fractions of the human CCRF-CEM T-cell lymphoblastic leukemia cell line, polyclonal antihuman RFC antiserum recognized two bands in the cytosolic fraction (approximately 60 kDa and approximately 70 kDa) on 10% polyacrylamide gels. In the membrane fraction, an approximately 60-kDa protein was identified. Comparative studies of a panel of human tumor cell lines including the HT1080 fibrosarcoma, 8805 malignant fibrous histiocytoma, and the MCF breast cancer cell lines revealed similar findings. Likewise, a recombinant approximately 60-kDa membrane protein was identified after expression of baculovirus-infected Sf9 insect cells containing cDNA of the human RFC. In the CEM-7A cell line, a variant of the CCRF-CEM cell line that overexpresses the RFC, 21-fold overexpression of the approximately 60-kDa membrane protein (RFC) was shown by Western analysis. To characterize further the cellular distribution of the human RFC, immunohistochemical analyses were performed in CCRF-CEM T-cell lymphoblastic leukemia cells. Predominantly membrane localization of the antibody reacting sites was detected; however, a cytoplasmic component was noted as well. By confocal microscopy and by immunogold electron microscopy, the cytoplasmic expression was found to be largely of mitochondrial origin. These findings were corroborated by Western immunoblotting of mitochondrial membrane isolates from the CCRF-CEM cell line, which demonstrate an approximately 60-kDa protein. The localization of the human RFC to the mitochondrial membrane is a novel finding, and it suggests a role for the mitochondrial membrane in the transport of folates.

Use of lectins as diagnostic and therapeutic tools for cancer

Within the past few years, lectins have become a well-established means for understanding varied aspects of cancer and metastasis. Evidence is now emerging that lectins are dynamic contributors to tumor cell recognition (surface markers), cell adhesion and localization, signal transduction across membranes, mitogenic stimulation, augmentation of host immune defense, cytotoxicity, and apoptosis. To advance understanding of these lectin-dependent processes, attempts are being made to discover new lectins that have one or more of these functions and to develop lectin- (or glycoconjugate-) based tools that could be used to home in on tumor cells. This review will summarize current research on the lectins and recent advances in the development of lectin-based diagnostic and therapeutic tools for cancer. Additionally, the future potential of lectin-based diagnosis and therapy is discussed.

Spontaneous hydrolysis of vasoactive intestinal peptide in neutral aqueous solution

Hydrolysis of radioiodinated vasoactive intestinal peptide (VIP) was observed in buffered aqueous solution at neutral pH and 38 degrees C. The reaction displayed apparent first-order kinetics at initial peptide concentrations below 3 nM (kobs = 1.5 x 10(-5) s-1), but the rate deviated below predicted values at higher peptide concentrations. The rate constant derived from the reaction progress curve over three half lives, starting at a concentration of 82 pM peptide, was also consistent with a first-order process. The reaction results in several products that were isolated and characterized as peptide fragments. Based on the identity of these fragments, we deduced hydrolysis at five different peptide bonds clustered between residues 17-25 of VIP. Control experiments were devised to eliminate trivial explanations for the peptide hydrolysis. Peptides representing the C-terminal segment 15-28 and the internal segment 14-22 assayed by analogous methods and under identical conditions were not degraded at a measurable rate. Sodium dodecyl sulfate and acetonitrile, agents known to influence the secondary structure of VIP, inhibited its spontaneous hydrolysis, as did chloride salts of sodium and calcium, albumin and a peptide unrelated to VIP. The rate and product distribution are inconsistent with known pathways of peptide degradation involving cyclic imide or anhydride formation at asparagine or aspartate residues. We suggest that the breakdown of VIP in dilute solutions represents an autolytic process.

Peptidolytic monoclonal antibody elicited by a neuropeptide

We report evidence that a monoclonal antibody raised by immunization with a vasoactive intestinal peptide (VIP)-carrier protein conjugate selectively hydrolyzes VIP and a fluorescence quenched decapeptide (FQ14-22D), representing the region of VIP most susceptible to autoantibody-mediated cleavage (residues 14-22). A high affinity of the antibody for VIP and a lower affinity for FQ14-22D were revealed by kinetic studies and further substantiated by potent inhibition of FQ14-22D cleaving activity by full-length VIP. Sequencing of FQ14-22D hydrolysis products indicated selective cleavage at one peptide bond. These observations suggest that antibodies induced against naturally occurring polypeptide antigens can express peptidolytic activity targeted for specific sequences in the recognition epitope.

Damage to the plasma membrane in Escherichia coli K-12 induced by far-ultraviolet radiation and its repair

Escherichia coli cells treated with low fluences of far-uv radiation (up to 90 J/m2) showed repairable damage to the plasma membrane. The loss of the ability of the cells to exclude citrate was evident from the respiratory stimulation of irradiated cells when citrate was provided exogenously. This loss of a barrier was a result of a structural disorganization of the plasma membrane as seen by freeze-etching electron microscopy. Analysis of the plasma membrane proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a characteristic loss of certain membrane proteins. When irradiated cells were incubated in glucose minimal medium at 37 degrees C for various times, a gradual recovery of membrane structure and function was observed. The recovery process was inhibited in the absence of an energy source as well as protein synthesis. The majority of the recovery occurred in the initial 1 h of the postirradiation holding. These results demonstrated that far-uv radiation at a fluence less than the D10 value had a direct or indirect effect on plasma membrane proteins, causing their release from the membrane bilayer. The lost proteins were subsequently regained by de novo protein synthesis.

Effect of diet and weight reduction in hypertension

Weight reduction by a low-energy diet and a high-polyunsaturates-, fiber- and potassium-rich diet may be independently useful to hypertensives. To study the effect of such diets, 416 hypertensives were randomized to either a low-energy cardiovasoprotective (CVP) diet (Group A; n = 106), a low-energy usual diet (Group B; n = 104), an optimal-energy CVP diet (Group C; n = 104), or an optimal-energy, usual pre-experimental diet (Group D; n = 102) plus drug therapy in a single-blind and controlled fashion. Groups A and B received significant (p less than 0.02) fewer calories per day than Groups C and D. Groups A and C also received significantly (p less than 0.02) more calories per amount of complex carbohydrates, polyunsaturates, potassium, and magnesium than did Groups B and D. Dietary compliance and drug intake was checked weekly. After 3 months, there was a significant fall in mean serum cholesterol (p less than 0.01) and mean serum triglycerides (p less than 0.05) in Group A compared with Group D. Group A and B patients had a loss of around 10kg of mean body weight, with no weight change seen in Group D. Weight loss was associated with a significant fall in systolic and diastolic pressures in both Group A (22/18mmHg) and Group B (16/13mmHg) compared with Group D at the end of the study. Group C patients also showed a significant fall in pressure (13/10mmHg) compared with Group D. Drug therapy, exercise, and salt intake were similar in all the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of far-ultraviolet radiation on the permeability of the outer membrane of Escherichia coli

Far-ultraviolet radiation (254 nm) at a dose of 10, 20, and 30 J/m2 was found to disrupt the outer membrane permeability barrier of Escherichia coli to various antibiotics, dyes, and detergents. The degree of sensitization to these agents was proportional to the radiation dose. The irradiated cells showed a significant increase in the sensitivity of hydrophilic antibiotics (ampicillin, carbenicillin, penicillin), whereas much less sensitization was found towards hydrophobic probes (kanamycin, erythromycin, rifamycin SV, crystal violet, phenol, novobiocin) and detergents (dodecyl sulfate, bile salt, Triton X-100). The biochemical data and ultrastructural analysis of the outer membrane by freeze-etching have shown that the increase in phospholipid:protein ratio after irradiation had changed the architecture of the outer membrane from a highly asymmetric bilayer structure with densely packed lipopolysaccharide--protein particles on the outer half, to one predominantly exhibiting smooth phospholipid bilayer characteristics. The structure, composition, and barrier function of the outer membrane were restored to normal within 3 h of postirradiation incubation in nonproliferative medium. During this period, the acquisition of resistance towards a hydrophilic antibiotic (ampicillin) was faster than that for a hydrophobic agent (phenol).