Higher alpha diversity and Lactobacillus blooms are associated with better engraftment after Fecal Microbiota Transplant in Inflammatory Bowel Disease

Background

Fecal Microbiota Transplant (FMT) has proven effective in treating recurrent Clostridioides difficile infection (rCDI) and has shown some success in treating inflammatory bowel diseases (IBD). There is emerging evidence that host engraftment of donor taxa is a tenet of successful FMT. However, there is little known regarding predictors of engraftment. We undertook a double-blind, randomized, placebo-controlled pilot study to characterize the response to FMT in children and young adults with mild to moderate active Crohn's disease (CD) and ulcerative colitis (UC).

Results

Subjects with CD or UC were randomized to receive antibiotics and weekly FMT or placebo in addition to baseline medications. The treatment arm received seven days of antibiotics followed by FMT enema and then capsules weekly for seven weeks. We enrolled four subjects with CD and 11 with UC, ages 14-29 years. Due to weekly stool sampling, we were able to create a time series of alpha diversity, beta diversity and engraftment as they related to clinical response. Subjects exhibited a wide range of microbial diversity and donor engraftment as FMT progressed. Specifically, engraftment ranged from 26% to 90% at week 2 and 3% to 92% at two months. Consistent with the current literature, increases over time of both alpha diversity (p< 0.05) and donor engraftment (p< 0.05) correlated with improved clinical response. Additionally, our weekly time series enabled an investigation into the clinical and microbial correlates of engraftment at various time points. We discovered that the post-antibiotic but pre-FMT time point, often overlooked in FMT trials, was rich in microbial correlates of eventual engraftment. Greater residual alpha diversity after antibiotic treatment was positively correlated with engraftment and subsequent clinical response. Interestingly, a transient rise in the relative abundance of Lactobacillus was also positively correlated with engraftment, a finding that we recapitulated with our analysis of another FMT trial with publicly available weekly sequencing data.

Conclusions

We found that higher residual alpha diversity and Lactobacillus blooms after antibiotic treatment correlated with improved engraftment and clinical response to FMT. Future studies should closely examine the host microbial communities pre-FMT and the impact of antibiotic preconditioning on engraftment and response.

Phenotypes of disease severity in a cohort of hospitalized COVID-19 patients: Results from the IMPACC study

BACKGROUND

Better understanding of the association between characteristics of patients hospitalized with coronavirus disease 2019 (COVID-19) and outcome is needed to further improve upon patient management.

METHODS

Immunophenotyping Assessment in a COVID-19 Cohort (IMPACC) is a prospective, observational study of 1164 patients from 20 hospitals across the United States. Disease severity was assessed using a 7-point ordinal scale based on degree of respiratory illness. Patients were prospectively surveyed for 1 year after discharge for post-acute sequalae of COVID-19 (PASC) through quarterly surveys. Demographics, comorbidities, radiographic findings, clinical laboratory values, SARS-CoV-2 PCR and serology were captured over a 28-day period. Multivariable logistic regression was performed.

FINDINGS

The median age was 59 years (interquartile range [IQR] 20); 711 (61%) were men; overall mortality was 14%, and 228 (20%) required invasive mechanical ventilation. Unsupervised clustering of ordinal score over time revealed distinct disease course trajectories. Risk factors associated with prolonged hospitalization or death by day 28 included age ≥ 65 years (odds ratio [OR], 2.01; 95% CI 1.28-3.17), Hispanic ethnicity (OR, 1.71; 95% CI 1.13-2.57), elevated baseline creatinine (OR 2.80; 95% CI 1.63- 4.80) or troponin (OR 1.89; 95% 1.03-3.47), baseline lymphopenia (OR 2.19; 95% CI 1.61-2.97), presence of infiltrate by chest imaging (OR 3.16; 95% CI 1.96-5.10), and high SARS-CoV2 viral load (OR 1.53; 95% CI 1.17-2.00). Fatal cases had the lowest ratio of SARS-CoV-2 antibody to viral load levels compared to other trajectories over time (p=0.001). 589 survivors (51%) completed at least one survey at follow-up with 305 (52%) having at least one symptom consistent with PASC, most commonly dyspnea (56% among symptomatic patients). Female sex was the only associated risk factor for PASC.

INTERPRETATION

Integration of PCR cycle threshold, and antibody values with demographics, comorbidities, and laboratory/radiographic findings identified risk factors for 28-day outcome severity, though only female sex was associated with PASC. Longitudinal clinical phenotyping offers important insights, and provides a framework for immunophenotyping for acute and long COVID-19.

FUNDING

NIH.

Direct care nurses' perceptions of their roles in clinical research: An integrated review of the literature

PURPOSE

To review the extant literature relevant to perceptions by direct care nurses toward clinical research endeavors.

DESIGN

An integrative review guided by the socioecological model was conducted.

METHODS

Five databases were searched to identify relevant peer-reviewed articles; there was no limitation on publication date.

FINDINGS

The final sample (N = 9) was systematically appraised. Numerous barriers to direct care nurses' ability to perform study activities on clinical research trials were encountered at all levels: (1) personal-comprehension, education, and training; (2) interpersonal-communication issues within or from the study team, failure to advocate for the patient; (3) organizational-lack of leadership support, knowledge, and time; and (4) community-insufficient guidance and oversight by research-governing bodies.

CONCLUSIONS

Direct care nurses report numerous barriers to completing protocol-administered activities for their patients participating in clinical research. A dearth of robust research exists in describing the reasons for, or persistence of, barriers faced by direct care nurses to assisting with research, and there have been little to no interventions to address them.

CLINICAL RELEVANCE

As translational research evolves and becomes more complex, there is the need to ensure both the care of clinical research participants and the integrity of the research. Direct care nurses are critical to this endeavor, and potential barriers they face may have significant ramifications for the research enterprise. Recognition of these barriers and eventual interventions designed to address them are needed.

Peripheral vascular access from the arms for invasive cardiac investigation using ultrasound guidance

Introduction

Vascular access for invasive cardiac investigations has traditionally been gained from the femoral vessels, however, a “radial-first” approach has become increasingly popular for coronary interventions [1]. Transradial access has shown lower complication rates, shorter admission times, and reduced healthcare costs for coronary interventions [4]. A “superior” approach via the jugular and subclavian veins have been reported for electrophysiology (EP) studies and radiofrequency catheter ablation (RFCA) but is associated with an increased risk of complications such as pneumo- and haemothorax [9].

Purpose

EP procedures often require the use of both venous and arterial catheters, and the potential advantage of non-femoral peripheral access is yet to be investigated. This study was performed to provide comprehensive anatomical evidence that the vessels of the arms are suitable for use during EP procedures, as assessed by vascular ultrasound.

Methods

A portable ultrasound device was used to measure the diameter of the brachial artery, brachial vein, basilic vein & cephalic vein on the left and right upper limbs of 63 healthy adult volunteers. Measurements were also taken of the circumference at the elbow and at the mid-bicep level on both arms. A subgroup of 15 volunteers had additional measurements taken of the same veins and artery on both arms with a tourniquet at the upper bicep level.

Results

The basilic vein was found to have the largest diameter with a median of 4.6 mm and 4.5 mm (right and left diameter, respectively), followed by the cephalic (median of 3.1 and 3.0 mm) and the brachial vein (median of 2.8 mm for both arms). 100% of volunteers had at least one vein that was equal to a 3 mm diameter (which would allow for a 8F sheath insertion), with 98% having 2 suitable veins and &gt;80% having 3 suitable venous vessels. More than 90% had a suitable diameter of more than 3 mm for both the right and left brachial artery. There was significant correlation between gender, and basilic vein and brachial artery diameters. There was no correlation between BMI, height, weight and elbow or bicep circumference.

Conclusion

To our knowledge, this is the first study to investigate the feasibility of adopting peripheral access in the electrophysiology lab. 100% of volunteers examined had one vein which was at least 3mm in size and would be suitable for 8F sheath insertion. We demonstrate the anatomic evidence that the vessels in the arm are capable of housing the size of sheath and catheters commonly used in the EP lab.

Funding Acknowledgement

Type of funding sources: None. Figure 2. measurementsFigure 3. Vessel diameters

Development and Preliminary Evaluation of a Quality-of-Life Questionnaire for Adults with Neurofibromatosis Type 1 (NF1-AdQOL)

BACKGROUND

Neurofibromatosis type 1 (NF1) is a variable and unpredictable multisystem genetic disorder which predisposes to medical complications, cognitive impairment and disfigurement, of all which can impact negatively upon the health related quality of life (HRQOL) of affected adults.

OBJECTIVES

To develop and validate a disease specific HRQOL adult questionnaire to evaluate effects of NF1 from the patient's viewpoint.

METHODS

The NF1 adult HRQOL questionnaire (NF1-AdQOL) was developed based on patient interviews (n=8), survey of clinicians and piloting of the questionnaire. Adults with NF1 (n=114, 18-40 years) were recruited from three Australian genetics clinics and completed the NF1-AdQOL, Skindex-29 and Short Form-36v2 (SF-36v2) questionnaires. An exploratory factor analysis of the NF1-AdQOL was conducted to assess construct validity. Convergent and discriminant validity of the NF1-AdQOL was determined by using the multi-trait multi-method with Skindex-29 and SF-36v2 scores.

RESULTS

Factor analysis indicated that 62.7% of the common variance could be explained by three factors labelled as 'emotions associated with cosmetic appearance' (12 items), 'social functioning and learning' (11 items) and 'physical symptoms' (8 items). NF1-AdQOL had good internal consistency (Cronbach's α = 0.96). Convergent validity was confirmed by moderate associations with similarly named scales of the Skindex-29 and SF-36v2. Results from all HRQOL questionnaires indicated overall healthy HRQOL for young adults with NF1.

CONCLUSIONS

NF1-AdQOL is a relatively valid, feasible and fairly easy to read tool to measure QOL in adults with NF1. Further evaluation is required to determine its test-retest reliability, responsiveness and validity in larger adult NF1 cohorts.

Patient-Customized Oligonucleotide Therapy for a Rare Genetic Disease

Genome sequencing is often pivotal in the diagnosis of rare diseases, but many of these conditions lack specific treatments. We describe how molecular diagnosis of a rare, fatal neurodegenerative condition led to the rational design, testing, and manufacture of milasen, a splice-modulating antisense oligonucleotide drug tailored to a particular patient. Proof-of-concept experiments in cell lines from the patient served as the basis for launching an "N-of-1" study of milasen within 1 year after first contact with the patient. There were no serious adverse events, and treatment was associated with objective reduction in seizures (determined by electroencephalography and parental reporting). This study offers a possible template for the rapid development of patient-customized treatments. (Funded by Mila's Miracle Foundation and others.).

The Unique Role of the Pediatric Clinical Research Nurse in Anesthesia: An Interdisciplinary Collaboration

This article describes the distinctive function of the pediatric clinical research nurse (CRN) in the anesthesia setting. The pediatric CRN in anesthesia acts as a liaison between families and the research team and is the major nexus between the principal investigator or anesthesiologist on a study, and the collaborating surgeons from many different departments. This is unique because the CRNs collaborate with physicians in specialties that can include plastics, urology, neurosurgery, orthopaedics, otolaryngology, cardiology, critical care, and many other departments. The profession requires a breath of knowledge ranging from clinical understanding of diseases, surgical procedures, and recovery to cognitive and developmental stages, to expertise in the research protocol process. Our objective was to describe these specialized activities of the pediatric anesthesia CRN, with focus on care coordination, communication, and continuity of care. Defining this role will enhance the quality of clinical research conducted by the CRN in anesthesia and may influence the development of novel medical treatments.

Knowledge, perception and practice of self-medication among premedical and basic science undergraduate medical students

Aims and Objective: Responsible self-medication is recognized as an important component of self-care. Medical students are in a unique position as they cannot yet legally prescribe medicines but their knowledge about and exposure to medicines increase as they progress through their course. Xavier University School of Medicine in Aruba admits students mainly from the United States, Canada and other countries to the undergraduate medical course. The present study was carried out to study the knowledge, perceptions and practice of self-medication among premedical and undergraduate medical students.Materials and Methods: The study was conducted during June and July 2016 using a questionnaire which had been used previously.  Knowledge and perceptions were studied by noting the respondents’ degree of agreement with asset of 40 statements. The use of selected classes of medicines for self-medication during the preceding one-year period was studied. The knowledge, perception and total scores were calculated and compared among different subgroups of respondents. Age, gender, nationality and semester of study of the respondents were noted.Results: Eighty-five of the 125 students enrolled (69.1%) participated. The mean knowledge, perception and total scores were 73.45, 62.75 and 136.2 (maximum possible scores were 105, 95 and 200 respectively). There was no significant difference in scores among subgroups of respondents. Analgesics, skin ointments, antipyretics and anti-allergics were commonly used for self-medication. Over half the respondents had used some form of self-medication during the preceding year.      Conclusion: The present study provides preliminary information regarding self-medication practices among both premedical and basic science medical students. Further studies on factors influencing and information sources used during self-medication can be conducted. Asian Journal of Medical Sciences Vol.7(5) 2016 63-68

Uptake of health monitoring and disease self-management in Australian adults with neurofibromatosis type 1: strategies to improve care

Lifelong health monitoring is recommended in neurofibromatosis type 1 (NF1) because of the progressive and unpredictable range of disabling and potentially life-threatening symptoms that arise. In Australia, strategies for NF1 health surveillance are less well developed for adults than they are for children, resulting in inequalities between pediatric and adult care. The aims of this study were to determine the uptake of health monitoring and capacity of adults with NF1 to self-manage their health. Australian adults with NF1 (n = 94, 18-40 years) participated in a semi-structured interview. Almost half reported no regular health monitoring. Thematic analysis of interviews identified four main themes as to why: (i) did not know where to seek care, (ii) unaware of the need for regular monitoring, (iii) futility of health monitoring as nothing can be done for NF1, and (iv) feeling healthy, therefore monitoring unnecessary. Overall, there were low levels of patient activation, indicating that adults with NF1 lacked knowledge and confidence to manage their health and health care. Findings are discussed in the context of service provision for adults with NF1 in New South Wales, Australia.

Maintaining the genuine structure of 2D materials and catalytic nanoparticles at atomic resolution

The recent development of atomic resolution, low dose-rate electron microscopy allows investigating 2D materials as well as catalytic nano particles without compromising their structural integrity. For graphene and a variety of nanoparticle compositions, it is shown that a critical dose rate exists of <100 e(-)/Å(2) s at 80 keV of electron acceleration that allows maintaining the genuine object structures including their surfaces and edges even if particles are only 3 nm large or smaller. Moreover, it is demonstrated that electron beam-induced phonon excitation from outside the field of view contributes to a contrast degradation in recorded images. These degradation effects can be eliminated by delivering electrons onto the imaged area, only, by using a Nilsonian illumination scheme in combination with a suitable aperture at the electron gun/monochromator assembly.

Clathrates of TETROL: selective inclusion of methylcyclohexanones in their energetically unfavorable axial methyl conformations

TETROL, surprisingly, includes 3- and 4-methylcyclohexanone exclusively in their energetically disfavoured axial conformations.

Primary CNS posttransplant lymphoproliferative disease (PTLD): an international report of 84 cases in the modern era

We performed a multicenter, International analysis of solid organ transplant (SOT)-related primary central nervous system (PCNS) posttransplant lymphoproliferative disease (PTLD). Among 84 PCNS PTLD patients, median time of SOT-to-PTLD was 54 months, 79% had kidney SOT, histology was monomorphic in 83% and tumor was EBV+ in 94%. Further, 33% had deep brain involvement, 10% had CSF involvement, while none had ocular disease. Immunosuppression was reduced in 93%; additional first-line therapy included high-dose methotrexate (48%), high-dose cytarabine (33%), brain radiation (24%) and/or rituximab (44%). The overall response rate was 60%, while treatment-related mortality was 13%. With 42-month median follow-up, three-year progression-free survival (PFS) and overall survival (OS) were 32% and 43%, respectively. There was a trend on univariable analysis for improved PFS for patients who received rituximab and/or high-dose cytarabine. On multivariable Cox regression, poor performance status predicted inferior PFS (HR 2.61, 95% CI 1.32-5.17, p = 0.006), while increased LDH portended inferior OS (HR 4.16, 95% CI 1.29-13.46, p = 0.02). Moreover, lack of response to first-line therapy was the most dominant prognostic factor on multivariable analysis (HR 8.70, 95% CI 2.56-29.57, p = 0.0005). Altogether, PCNS PTLD appears to represent a distinct clinicopathologic entity within the PTLD spectrum that is associated with renal SOT, occurs late, is monomorphic and retains EBV positivity.

Perceptions of HPV and cervical cancer among Haitian immigrant women: implications for vaccine acceptability

INTRODUCTION

Women in Haiti and throughout the Haitian Diaspora shoulder a disproportionate burden of cervical cancer morbidity and mortality. The widespread Human Papillomavirus (HPV) vaccination holds promise for helping to attenuate this disparity. However, previous research has not fully examined Haitian women's perceptions of, and barriers to, HPV vaccination, which is essential for informing future intervention. The current paper aims to fill this gap.

METHODS

As part of ongoing Community-Based Participatory Research (CBPR) efforts, we conducted a series of focus groups with Haitian immigrant women in Little Haiti, the predominantly Haitian neighborhood in Miami, Florida, U.S. Focus group questions assessed women's knowledge and beliefs about cervical cancer and HPV, their opinions of vaccines in general, their knowledge and perceptions of the HPV vaccine specifically and health communications preferences for cervical cancer prevention.

RESULTS

Among the participants who had heard of HPV, many held misconceptions about virus transmission and did not understand the role of HPV in the development of cervical cancer. Virtually all participants expressed support for vaccines in general as beneficial for health. Some women had heard of the HPV vaccine, primarily as the result of a contemporary popular media campaign promoting the Gardasil® vaccine. Physician recommendation was commonly mentioned as a reason for vaccination, in addition to having more than one sex partner. Women felt the HPV vaccine was less appropriate for adolescent girls who are presumed as not sexually active. Women indicated a strong preference to obtain health information through trusted sources, such as Haitian physicians, Haitian Community Health Workers, and especially Kreyol-language audiovisual media.

DISCUSSION

Study findings indicate a need for culturally and linguistically appropriate educational initiatives to promote awareness of HPV and its role in cervical cancer, the importance of vaccination against the virus, explicitly differentiating HPV from HIV and providing specific information about vaccine safety.

CONCLUSION

In the U.S., there is a substantial lack of educational information available in Haitian about HPV and cervical cancer. This gap results in missed opportunities to promote disease prevention through vaccination and regular screening. Addressing such gaps is essential for achieving health equity among Haitian immigrant women and other, similarly underserved women, who are disproportionately burdened by cervical cancer.

Responses to handling and confinement stressors in juvenile great sturgeon Huso huso

The effects of acute stressors on physiological responses of juvenile great sturgeon or beluga Huso huso L. were investigated in two experiments. In the first experiment, fish were handled by placing them in containers at either low density (LD, one fish l(-1)) or high density (HD, four fish l(-1)) for 60 s. Concentrations of plasma cortisol, glucose and lactate were determined from blood collected at 0, 1, 3, 6 and 12 h after application of the stressor. Plasma cortisol concentrations increased after the disturbance in H. huso from both handling treatments, but changes were not significant. Plasma glucose rose significantly by 22.9 and 31.6% in LD and HD handling treatments, respectively, after 3 h. Significant increases in plasma lactate occurred within 1 h in both treatment groups, but that of the HD group was much higher. In the second experiment, fish were held at two different densities, LD (2 kg m(-2) tank bottom surface area) and HD (7 kg m(-2)), for 8 weeks and then subjected to an aerial emersion handling stressor in a net for 60 s; blood samples were taken before handling (resting, 0 h) and at 1, 3, 6 and 9 h after handling. Plasma cortisol increased significantly in fish from the HD treatment from 8.8 +/- 0.3 to 19.2 +/- 2.4 ng ml(-1) (mean +/-s.e.) by 1 h after stress, but post-handling changes in the LD group were not significant. Significant increases in both plasma glucose and lactate were observed by 1 h in both treatment groups, with peak levels of plasma glucose evident at 3 h [69.4 +/- 2.9 and 60.9 +/- 1.7 mg dl(-1) (mean +/-s.e.) in LD and HD groups, respectively]. Plasma glucose levels were significantly higher in the LD group than in the HD group at 3 and 6 h. Post-handling haemoglobin content increased by 1 h and white blood cell numbers were reduced by 3 and 6 h in the HD treatment group compared with resting values, but changes in these blood features in the LD group were not significant. Acute handling did not affect haematocrit in either treatment. The results suggest that H. huso is relatively resistant to handling and confinement, and could tolerate normal hatchery practices associated with aquaculture. Because changes in cortisol concentrations were relatively low compared with those in most teleosts, glucose and lactate concentrations may be more useful as stress indicators in juvenile H. huso. This study also demonstrated that prior exposure to a chronic stressor, specifically high stocking density, could alter the physiological response to subsequent acute handling in H. huso.

The self-concept of children and adolescents with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a genetic disorder associated with cognitive deficits, learning problems, medical complications and cosmetic disfigurement. Despite the wide-ranging impact of NF1, very few studies have examined the psychosocial adjustment of individuals with NF1, and in particular, self-concept. The aims of this study were threefold: (i) to examine the self-concept of children and adolescents with NF1; (ii) to compare the self-concept of children with NF1 (NF1 only), children with NF1 and learning difficulties [NF1 + LA (low achievement)], and children with NF1 and attention deficit hyperactivity disorder (ADHD) (NF1 + ADHD); and (iii) to examine the academic self-concept of these three groups relative to objective criteria - academic achievement and teacher ratings of academic competence.

METHODS

Measures of self-concept, academic achievement and intelligence were administered to 49 children and 26 adolescents with NF1. Parents and teachers completed behavioural rating scales.

RESULTS

The majority of children and adolescents with NF1 reported positive global self-concept, with some exceptions on specific domains. Children and adolescents with NF1 reported significantly poorer self-concept for physical abilities. Adolescents also reported significantly poorer self-concept for mathematics and general self when compared with normative mean values. Clinical severity of NF1 was not a significant predictor of self-concept for physical appearance or physical abilities. Despite a significant difference between NF1 only, NF1 + LA and NF1 + ADHD groups on measures of academic achievement and teacher ratings of academic competence, there was no significant difference between the groups for academic domains of self-concept, or any other domain of self-concept. All three groups reported inflated academic self-perceptions relative to objective criteria.

CONCLUSION

Children and adolescents with NF1 are most likely to develop negative self-concepts about their physical and sporting abilities. Inflated academic self-perceptions are discussed in light of the positive illusory bias, which may serve as an adaptive or protective function.

Seeing through the blind! Ability of hospital staff to differentiate morphine from placebo, in neonates at a placebo controlled trial

AIM

To investigate whether professional training and/or clinical experience affect the ability of caregiver to assess clinical signs of pre-emptive morphine analgesia.

METHODS

In the Neurological Outcomes & Pre-emptive Analgesia In Neonates trial preterm infants undergoing mechanical ventilation were randomized to receive continuous infusion, either of morphine or placebo blinded. Staff from centres in Sweden (Stockholm and Orebro) completed an assessment form.

RESULTS

A total of 360 assessment forms were collected from 52 neonates. In 59% of the cases, caregivers correctly identified patients group. Comparable proportion of answers were correct between physicians, nurses and assistant nurses (63, 60 and 54%, respectively, p = 0.60). Staff with Neonatal intensive care unit experience <1 year identified 63%, as compared to 65% for working 1-5 year, and 55% that has been working >5 years (p = 0.28). Staff's ability to correctly identify group assignment was reduced by amount of additional morphine (p < 0.01) and severity of illness (p = 0.01).

CONCLUSIONS

Clinical medical staffs, including neonatologists, have great difficulties in assessing the presence and severity of pain. Further studies should focus on the methods for assessment of prolonged pain in preterm neonates, define the effects of adequate analgesia, and investigate the clinical factors that may alter neonatal responses to acute and prolonged pain.

Optimizing phase contrast in transmission electron microscopy with an electrostatic (Boersch) phase plate

Imaging of weak amplitude and phase objects, such as unstained vitrified biological samples, by conventional transmission electron microscopy (TEM) suffers from poor object contrast since the amplitude and phase of the scattered electron wave change only very little. In phase contrast light microscopy the imaging of weak phase objects is greatly enhanced by the use of a quarter-wave phase plate, which produces high signal contrast by shifting the phase of the scattered light. An analogous quarter-wave plate for the electron microscope, designed as an electrostatic einzel lens, was proposed by Boersch in 1947 but the small dimensions of the device have impeded its realization up to now. We here present the first fabrication and application of a miniaturized electrostatic einzel lens driven as TEM quarter-wave phase plate. Phase modulation is generated by the electrostatic field confined to the inside of a microstructured ring electrode. This field affects the phase velocity of the unscattered part of the electron wave. By varying its strength the phase shift of the primary beam can be adjusted to pi/2, producing strong phase contrast independent of spatial frequency. The phase plate proves to be mechanically stable and does not impair image quality, in particular it does not reduce the high-resolution signal. The expected residual lens effect of the einzel lens is minimal. Our microlens is supported by conducting rods arranged in a threefold symmetry. This particular geometry provides optimized single-sideband signal transfer for spatial frequencies otherwise obstructed by the supporting rods.

Five additional genes are involved in clavulanic acid biosynthesis in Streptomyces clavuligerus

An approximately 12.5-kbp region of DNA sequence from beyond the end of the previously described clavulanic acid gene cluster was analyzed and found to encode nine possible open reading frames (ORFs). Involvement of these ORFs in clavulanic acid biosynthesis was assessed by creating mutants with defects in each of the ORFs. orf12 and orf14 had been previously reported to be involved in clavulanic acid biosynthesis. Now five additional ORFs are shown to play a role, since their mutation results in a significant decrease or total absence of clavulanic acid production. Most of these newly described ORFs encode proteins with little similarity to others in the databases, and so their roles in clavulanic acid biosynthesis are unclear. Mutation of two of the ORFs, orf15 and orf16, results in the accumulation of a new metabolite, N-acetylglycylclavaminic acid, in place of clavulanic acid. orf18 and orf19 encode apparent penicillin binding proteins, and while mutations in these genes have minimal effects on clavulanic acid production, their normal roles as cell wall biosynthetic enzymes and as targets for beta-lactam antibiotics, together with their clustered location, suggest that they are part of the clavulanic acid gene cluster.

Applications of gene replacement technology to Streptomyces clavuligerus strain development for clavulanic acid production

Cephamycin C production was blocked in wild-type cultures of the clavulanic acid-producing organism Streptomyces clavuligerus by targeted disruption of the gene (lat) encoding lysine epsilon-aminotransferase. Specific production of clavulanic acid increased in the lat mutants derived from the wild-type strain by 2- to 2.5-fold. Similar beneficial effects on clavulanic acid production were noted in previous studies when gene disruption was used to block the production of the non-clavulanic acid clavams produced by S. clavuligerus. Therefore, mutations in lat and in cvm1, a gene involved in clavam production, were introduced into a high-titer industrial strain of S. clavuligerus to create a double mutant with defects in production of both cephamycin C and clavams. Production of both cephamycin C and non-clavulanic acid clavams was eliminated in the double mutant, and clavulanic acid titers increased about 10% relative to those of the parental strain. This represents the first report of the successful use of genetic engineering to eliminate undesirable metabolic pathways in an industrial strain used for the production of an antibiotic important in human medicine.

Genes specific for the biosynthesis of clavam metabolites antipodal to clavulanic acid are clustered with the gene for clavaminate synthase 1 in Streptomyces clavuligerus

Portions of the Streptomyces clavuligerus chromosome flanking cas1, which encodes the clavaminate synthase 1 isoenzyme (CAS1), have been cloned and sequenced. Mutants of S. clavuligerus disrupted in cvm1, the open reading frame located immediately upstream of cas1, were constructed by a gene replacement procedure. Similar techniques were used to generate S. clavuligerus mutants carrying a deletion that encompassed portions of the two open reading frames, cvm4 and cvm5, located directly downstream of cas1. Both classes of mutants still produced clavulanic acid and cephamycin C but lost the ability to synthesize the antipodal clavam metabolites clavam-2-carboxylate, 2-hydroxymethyl-clavam, and 2-alanylclavam. These results suggested that cas1 is clustered with genes essential and specific for clavam metabolite biosynthesis. When a cas1 mutant of S. clavuligerus was constructed by gene replacement, it produced lower levels of both clavulanic acid and most of the antipodal clavams except for 2-alanylclavam. However, a double mutant of S. clavuligerus disrupted in both cas1 and cas2 produced neither clavulanic acid nor any of the antipodal clavams, including 2-alanylclavam. This outcome was consistent with the contribution of both CAS1 and CAS2 to a common pool of clavaminic acid that is shunted toward clavulanic acid and clavam metabolite biosynthesis.

Cerebral blood flow velocity in patients with subclinical portal-systemic encephalopathy

Alterations in cerebral blood flow (CBF) are implicated in the etiology of portal-systemic encephalopathy. We hypothesized that CO2 reactivity of the cerebral circulation may be impaired in subjects with chronic liver disease (CLD) who also had subclinical portal-systemic encephalopathy (SPSE). We compared the relationship between PETCO2 and cerebral blood flow velocity in 10 patients with CLD with those of 10 healthy control subjects. Middle cerebral artery mean blood flow velocity (MCAMFV) was measured using transcranial Doppler during rest, hyperventilation, and hypoventilation. The degree of SPSE was quantified by using psychometric testing. Patients with CLD had poorer psychometric test scores compared with control subjects. Patients with CLD had lower PETCO2, MCAMFV, and blood pressure values and higher heart rates, differing from control subjects in all ventilation states. However, CO2 reactivity, the rate of change in MCAMFV to changes in ventilation (expressed as percent change in CBF velocity per mm Hg change in PETCO2) was similar for both groups (4.6% +/- 0.6% vs 4.2% +/- 0.5% for patients with CLD versus control subjects, P = 0.15).

IMPLICATIONS

Psychometric test scores in patients with chronic liver disease revealed subclinical impairment compared with control subjects. Transcranial Doppler measurements of middle cerebral artery blood flow with varying PETCO2 were conducted, but the CO2 response of patients with liver disease was within the range of control subjects.