Dynamics of efflux pumps in antimicrobial resistance, persistence, and community living of Vibrionaceae

The marine bacteria of the Vibrionaceae family are significant from the point of view of their role in the marine geochemical cycle, as well as symbionts and opportunistic pathogens of aquatic animals and humans. The well-known pathogens of this group, Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, are responsible for significant morbidity and mortality associated with a range of infections from gastroenteritis to bacteremia acquired through the consumption of raw or undercooked seafood and exposure to seawater containing these pathogens. Although generally regarded as susceptible to commonly employed antibiotics, the antimicrobial resistance of Vibrio spp. has been on the rise in the last two decades, which has raised concern about future infections by these bacteria becoming increasingly challenging to treat. Diverse mechanisms of antimicrobial resistance have been discovered in pathogenic vibrios, the most important being the membrane efflux pumps, which contribute to antimicrobial resistance and their virulence, environmental fitness, and persistence through biofilm formation and quorum sensing. In this review, we discuss the evolution of antimicrobial resistance in pathogenic vibrios and some of the well-characterized efflux pumps' contributions to the physiology of antimicrobial resistance, host and environment survival, and their pathogenicity.

Functional Roles of the Conserved Amino Acid Sequence Motif C, the Antiporter Motif, in Membrane Transporters of the Major Facilitator Superfamily

The biological membrane surrounding all living cells forms a hydrophobic barrier to the passage of biologically important molecules. Integral membrane proteins called transporters circumvent the cellular barrier and transport molecules across the cell membrane. These molecular transporters enable the uptake and exit of molecules for cell growth and homeostasis. One important collection of related transporters is the major facilitator superfamily (MFS). This large group of proteins harbors passive and secondary active transporters. The transporters of the MFS consist of uniporters, symporters, and antiporters, which share similarities in structures, predicted mechanism of transport, and highly conserved amino acid sequence motifs. In particular, the antiporter motif, called motif C, is found primarily in antiporters of the MFS. The antiporter motif's molecular elements mediate conformational changes and other molecular physiological roles during substrate transport across the membrane. This review article traces the history of the antiporter motif. It summarizes the physiological evidence reported that supports these biological roles.

Inhibition of Multidrug Efflux Pumps Belonging to the Major Facilitator Superfamily in Bacterial Pathogens

Bacterial pathogens resistant to multiple structurally distinct antimicrobial agents are causative agents of infectious disease, and they thus constitute a serious concern for public health. Of the various bacterial mechanisms for antimicrobial resistance, active efflux is a well-known system that extrudes clinically relevant antimicrobial agents, rendering specific pathogens recalcitrant to the growth-inhibitory effects of multiple drugs. In particular, multidrug efflux pump members of the major facilitator superfamily constitute central resistance systems in bacterial pathogens. This review article addresses the recent efforts to modulate these antimicrobial efflux transporters from a molecular perspective. Such investigations can potentially restore the clinical efficacy of infectious disease chemotherapy.

The Major Facilitator Superfamily and Antimicrobial Resistance Efflux Pumps of the ESKAPEE Pathogen Staphylococcus aureus

The ESKAPEE bacterial pathogen Staphylococcus aureus has posed a serious public health concern for centuries. Throughout its evolutionary course, S. aureus has developed strains with resistance to antimicrobial agents. The bacterial pathogen has acquired multidrug resistance, causing, in many cases, untreatable infectious diseases and raising serious public safety and healthcare concerns. Amongst the various mechanisms for antimicrobial resistance, integral membrane proteins that serve as secondary active transporters from the major facilitator superfamily constitute a chief system of multidrug resistance. These MFS transporters actively export structurally different antimicrobial agents from the cells of S. aureus. This review article discusses the S. aureus-specific MFS multidrug efflux pump systems from a molecular mechanistic perspective, paying particular attention to structure-function relationships, modulation of antimicrobial resistance mediated by MFS drug efflux pumps, and direction for future investigation.

First report of a multidrug-resistant Salmonella enterica Serovar Infantis carrying pESI megaplasmid isolated from marine shrimp in India

BACKGROUND

Non-typhoidal Salmonella enterica (NTS) in seafood is an important human health concern. An emerging strain of NTS serovar Infantis carrying a megaplasmid pESI and resistant to multipe drugs has been responsible for frequent food-borne human infections worldwide.

METHODS

S. enterica strain JS5 was isolated from a sample of shrimp from the retail market on XLD agar after enrichment in the RV medium. The genomic DNA was isolated and sequenced using the Illumina platform. The draft whole genome sequence of Salmonella Infantis JS5 revealed the presence of a plasmid.

RESULTS

The genome size was 4,977,731 bp with 4663 open reading frames. The bacterium harboured a megaplasmid similar to the pESI plasmid reported in the emerging S. Infantis. The 285 kb plasmid contained the characteristic genes of the pESI plasmids, such as the mercury operon, yersiniabactin siderophore operon, fimbriae, toxin-antitoxin systems and the hypothetical protein backbone. The antibiotic resistance genes tet(A), dfrA14, aadA, qacEdelta1, and sul1 were detected. To the best of our knowledge, this is the first report on pESI plasmid carrying S. Infantis from India.

Search for New Physics in Electronic Recoil Data from XENONnT

We report on a blinded analysis of low-energy electronic recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 ton liquid xenon target reduced the background in the (1, 30) keV search region to (15.8±1.3)  events/(ton×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 ton-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.

Membrane Efflux Pumps of Pathogenic Vibrio Species: Role in Antimicrobial Resistance and Virulence

Infectious diseases caused by bacterial species of the Vibrio genus have had considerable significance upon human health for centuries. V. cholerae is the causative microbial agent of cholera, a severe ailment characterized by profuse watery diarrhea, a condition associated with epidemics, and seven great historical pandemics. V. parahaemolyticus causes wound infection and watery diarrhea, while V. vulnificus can cause wound infections and septicemia. Species of the Vibrio genus with resistance to multiple antimicrobials have been a significant health concern for several decades. Mechanisms of antimicrobial resistance machinery in Vibrio spp. include biofilm formation, drug inactivation, target protection, antimicrobial permeability reduction, and active antimicrobial efflux. Integral membrane-bound active antimicrobial efflux pump systems include primary and secondary transporters, members of which belong to closely related protein superfamilies. The RND (resistance-nodulation-division) pumps, the MFS (major facilitator superfamily) transporters, and the ABC superfamily of efflux pumps constitute significant drug transporters for investigation. In this review, we explore these antimicrobial transport systems in the context of Vibrio spp. pathogenesis and virulence.

<i>Staphylococcus aureus</i> antimicrobial efflux pumps and their inhibitors: recent developments

<abstract> <p>The microorganism <italic>Staphylococcus aureus</italic> is a notorious causative agent of bacterial infection. The widespread presence of this pathogen has caused significant morbidity and mortality rates in clinical healthcare settings and communities. Due to its increasingly frequent recalcitrant nature towards clinically available antimicrobial agents, the bacterium poses a considerable public health crisis. A significant bacterial mechanism of antimicrobial agent resistance includes multidrug efflux pump systems. These antimicrobial efflux determinants translate into several large superfamilies of transporters that share related amino acid sequences, similarities in three-dimensional structures, modes of energization, and solute transport catalysis across the membrane. Because of their ubiquitous nature and functional role in virulence, these multidrug transporters make good targets for inhibition. This review briefly summarizes recent key findings regarding multidrug efflux activity and modulation in the MATE, SMR, and MFS transporters.</p> </abstract>

Broadband, millimeter-wave antireflection coatings for large-format, cryogenic aluminum oxide optics

We present two prescriptions for broadband ($ {\sim} 77 - 252\;{\rm GHz} $), millimeter-wave antireflection coatings for cryogenic, sintered polycrystalline aluminum oxide optics: one for large-format (700 mm diameter) planar and plano-convex elements, the other for densely packed arrays of quasi-optical elements-in our case, 5 mm diameter half-spheres (called "lenslets"). The coatings comprise three layers of commercially available, polytetrafluoroethylene-based, dielectric sheet material. The lenslet coating is molded to fit the 150 mm diameter arrays directly, while the large-diameter lenses are coated using a tiled approach. We review the fabrication processes for both prescriptions, then discuss laboratory measurements of their transmittance and reflectance. In addition, we present the inferred refractive indices and loss tangents for the coating materials and the aluminum oxide substrate. We find that at 150 GHz and 300 K the large-format coating sample achieves $ (97 \pm 2)\% $ transmittance, and the lenslet coating sample achieves $ (94 \pm 3)\% $ transmittance.

Current trends in tendinopathy: consensus of the ESSKA basic science committee. Part I: biology, biomechanics, anatomy and an exercise-based approach

Chronic tendinopathies represent a major problem in the clinical practice of sports orthopaedic surgeons, sports doctors and other health professionals involved in the treatment of athletes and patients that perform repetitive actions. The lack of consensus relative to the diagnostic tools and treatment modalities represents a management dilemma for these professionals. With this review, the purpose of the ESSKA Basic Science Committee is to establish guidelines for understanding, diagnosing and treating this complex pathology.

Neutrophil swarming and extracellular trap formation play a significant role in Alum adjuvant activity

There are over 6 billion vaccine doses administered each year, most containing aluminium-based adjuvants, yet we still do not have a complete understanding of their mechanisms of action. Recent evidence has identified host DNA and downstream sensing as playing a significant role in aluminium adjuvant (aluminium hydroxide) activity. However, the cellular source of this DNA, how it is sensed by the immune system and the consequences of this for vaccination remains unclear. Here we show that the very early injection site reaction is characterised by inflammatory chemokine production and neutrophil recruitment. Intravital imaging demonstrates that the Alum injection site is a focus of neutrophil swarms and extracellular DNA strands. These strands were confirmed as neutrophil extracellular traps due to their sensitivity to DNAse and absence in mice deficient in peptidylarginine deiminase 4. Further studies in PAD4−/− mice confirmed a significant role for neutrophil extracellular trap formation in the adjuvant activity of Alum. By revealing neutrophils recruited to the site of Alum injection as a source of the DNA that is detected by the immune system this study provides the missing link between Alum injection and the activation of DNA sensors that enhance adjuvant activity, elucidating a key mechanism of action for this important vaccine component.

Researchers have identified the mechanism of action in which aluminium hydroxide (alum) boosts the efficacy of co-administered vaccines. In this study, James Brewer and colleagues from the University of Glasgow, UK, studied the effects of alum co-administration in a mouse model, finding that the compound induces immune cells, called neutrophils, to swarm around the site of immunization and produce neutrophil extracellular traps (NETs). NETs, webs of DNA and cell contents formed under certain conditions of neutrophil cell death, immobilize pathogens and promote their elimination. This study builds on previous research and demonstrates that alum artificially stimulates this pathway to boost the adaptive immune response to vaccine antigens, increasing their immunogenicity. The authors also suggest further study into neutrophil components as potential therapeutic agents.

Mitochondrial epileptic encephalopathy, 3-methylglutaconic aciduria and variable complex V deficiency associated with TIMM50 mutations

Mitochondrial encephalopathies are a heterogeneous group of disorders that, usually carry grave prognosis. Recently a homozygous mutation, Gly372Ser, in the TIMM50 gene, was reported in an abstract form, in three sibs who suffered from intractable epilepsy and developmental delay accompanied by 3-methylglutaconic aciduria. We now report on four patients from two unrelated families who presented with severe intellectual disability and seizure disorder, accompanied by slightly elevated lactate level, 3-methylglutaconic aciduria and variable deficiency of mitochondrial complex V. Using exome analysis we identified two homozygous missense mutations, Arg217Trp and Thr252Met, in the TIMM50 gene. The TIMM50 protein is a subunit of TIM23 complex, the mitochondrial import machinery. It serves as the major receptor in the intermembrane space, binding to proteins which cross the mitochondrial inner membrane on their way to the matrix. The mutations, which affected evolutionary conserved residues and segregated with the disease in the families, were neither present in large cohorts of control exome analyses nor in our ethnic specific exome cohort. Given the phenotypic similarity, we conclude that missense mutations in TIMM50 are likely manifesting by severe intellectual disability and epilepsy accompanied by 3-methylglutaconic aciduria and variable mitochondrial complex V deficiency. 3-methylglutaconic aciduria is emerging as an important biomarker for mitochondrial dysfunction, in particular for mitochondrial membrane defects.

Challenges of optimizing glycaemic control in children with Type 1 diabetes: a qualitative study of parents' experiences and views

AIMS

To explore the difficulties parents encounter in trying to achieve clinically recommended blood glucose levels and how they could be better supported to optimize their child's glycaemic control.

METHODS

In-depth interviews were conducted with 54 parents of children with Type 1 diabetes (≤ 12 years). Data were analysed thematically.

RESULTS

Parents described being reluctant and finding it difficult to keep their child's blood glucose levels consistently within clinically recommended ranges. As well as worrying about their child's ability to detect/report hypoglycaemia, parents highlighted a multitude of factors that had an impact on their child's blood glucose levels and over which they could exercise little control. These included: leaving their child with other caregivers who could not be trusted to detect hypoglycaemia; difficulties remotely monitoring and regulating their child's food consumption and activity; and physical and social changes accompanying childhood development. Most parents used two sets of blood glucose targets, with clinically recommended targets employed when their child was in their immediate care and higher targets when in the care of others. Parents described health professionals as lacking understanding of the difficulties they encountered keeping blood glucose within target ranges and needing more empathetic, tailored and realistic advice.

CONCLUSION

It is not parents' fear of hypoglycaemia in isolation that leads to decisions to raise their child's blood glucose but, rather, parental fear in conjunction with other factors and considerations. Hence, to improve diabetes management in children, these factors may need to be addressed; for instance, by training others in diabetes management and using new technologies. Changes to consultations are also recommended.

Ocular complications and loss of vision due to herpes zoster ophthalmicus in patients with HIV infection and a comparison with HIV-negative patients

The aim of the work is to describe the occurrence of ocular complications and loss of vision due to herpes zoster ophthalmicus (HZO) in HIV-positive patients who received early antiviral therapy for HZO. This is a post hoc analysis of prospectively collected data. Twenty-four HIV-positive patients with HZO were included in this report; male to female ratio was 3.8:1; mean age was 33.5 (±14.9) years. The visual outcome was good, with 14/24 patients having 6/6 vision; severe vision loss (≤6/60) occurred in only 2/24. There was no statistical difference in the visual outcome between the HIV-positive and -negative patients ( P = 0.69), although severe vision loss was more likely in HIV-infected patients. The ocular complications of HZO in HIV-infected patients were: reduced corneal sensation (17/24), corneal epithelial lesions (14/24), uveitis (12/24), elevated intraocular pressure (10/24) and extra-ocular muscle palsy (3/24). The severity of rash was similar in the two groups but multidermatomal rash occurred only in HIV-infected patients (4/24). There was no difference in the occurrence of ocular complications of HZO between HIV-positive and HIV-negative patients. HZO associated ocular complications and visual loss is low in HIV-infected patients if treated with HZO antiviral therapy and was comparable with HIV-negative patients. Early institution of HZO antiviral therapy is recommended to reduce ocular complication and vision loss.

When jurisdictional boundaries become barriers to good patient care

Canada is a pioneer in remote cancer care delivery to underserved populations; however, it is trailing behind on policies that would support clinicians in providing care using distance technologies. The current policy framework is disjointed, and discussions by professional boards about online jurisprudence associated with licensure appear to be regressive. We hope that by addressing the discrepancies in interjurisdictional practice and focusing on the key issue of "where therapy resides," we will be able to nudge dialogue and thinking closer toward the reasoning and recommendations of national telehealth organizations. We present this discussion of jurisdictional issues and e-health practice in the context of a pan-Canadian online support program developed for cancer patients and family members. Although the present paper uses online support groups as a springboard to advocate for e-health, it ultimately addresses a broader audience: that of all Canadian health care stakeholders.

Evaluation of CancerChatCanada: a program of online support for Canadians affected by cancer

BACKGROUND

Professional-led cancer support groups can improve quality of life and address unmet needs, but most Canadians affected by cancer do not have access to or do not make use of cancer support groups. A collaborative interdisciplinary team developed, operated, and evaluated Internet-based, professional-led, live-chat support groups (osgs) for cancer patients, caregivers, and survivors across Canada.

OBJECTIVE

Our study aimed to report participant and participation characteristics in the pan-Canadian initiative known as CancerChatCanada, and to understand participant perspectives about the quality of communication and professional facilitation, overall satisfaction, and psychosocial benefits and outcomes.

METHODS

Participants in osgs provided informed consent. Participant and participation characteristics were gathered from program data collection tools and are described using frequencies, means, and chi-squares. Patient, survivor, and caregiver perspectives were derived from 102 telephone interviews conducted after osg completion and subjected to a directed qualitative content analysis.

RESULTS

The 55 professional-led osgs enrolled 351 participants from 9 provinces. More than half the participants came from rural or semirural areas, and more than 84% had no received previous cancer support. The attendance rate was 75%, the dropout rate was 26%, and 80% of participants were satisfied or very satisfied. The convenience and privacy of osgs were benefits. Meaningful communication about important and difficult topics, kinship and bonding with others, and improved mood and self-care were perceived outcomes.

CONCLUSIONS

Our results demonstrate that this collaborative initiative was successful in increasing reach and access, and that pan-Canadian, professional-led osgs provide psychosocial benefit to underserved and burdened cancer patients, survivors, and family caregivers.

A practical approach to incidental findings in neuroimaging research

OBJECTIVE

We describe the systematic approach to incidental findings (IFs) used at the Mind Research Network (MRN) where all MRI scans receive neuroradiologist interpretation and participants are provided results.

METHODS

From 2004 to 2011, 8,545 MRI scans were acquired by 45 researchers. As mandated by MRN's external institutional review board, all structural sequences were evaluated by a clinical neuroradiologist who generated a report that included recommendations for referral if indicated. Investigators received a copy of their participants' reports, which were also mailed to participants unless they specifically declined. To better understand the impact of the radiology review process, a financial analysis was completed in addition to a follow-up phone survey to characterize participant perceptions regarding receiving their MRI scan results.

RESULTS

The radiologist identified IFs in 34% of the 4,447 participants. Of those with IFs (n = 1,518), the radiologist recommended urgent or immediate referral for 2.5% and routine referral for 17%. For 80.5%, no referral was recommended. Estimated annual cost for this approach including support for the neuroradiologist, medical director, and ancillary staff is approximately $60,000 or $24/scan. The results of the retrospective phone survey showed that 92% of participants appreciated receiving their MRI report, and the majority stated it increased their likelihood of volunteering for future studies.

CONCLUSIONS

Addressing IFs in a cost-effective and consistent manner is possible by adopting a policy that provides neuroradiology interpretation and offers participant assistance with clinical follow-up when necessary. Our experience suggests that an ethical, institution-wide approach to IFs can be implemented with minimal investigator burden.

Development of mu rhythm in infants and preschool children

Mu rhythm is an idling rhythm that originates in the sensorimotor cortex during rest. The frequency of mu rhythm, which is well established in adults, is 8-12 Hz, whereas the limited results available from children suggest a frequency as low as 5.4 Hz at 6 months of age, which gradually increases to the adult value. Understanding the normal development of mu rhythm has important theoretical and clinical implications since we still know very little about this signal in infants and how it develops with age. We measured mu rhythm over the left hemisphere using a pediatric magnetoencephalography (MEG) system in 25 infants (11-47 weeks), 18 preschool children (2-5 years) and 6 adults (20-39 years) for two 5-min sessions during two intermixed conditions: a rest condition in which the hands were at rest, and a prehension condition in which the subject squeezed a pipette with his/her right hand. In all participants, mu rhythm was present over the frontoparietal area during the rest condition, but was clearly suppressed during the prehension condition. Mu rhythm peak frequency, determined from the amplitude spectra, increased rapidly as a function of age from 2.75 Hz at 11 weeks to 8.25 Hz at 47 weeks (r2 = 0.83). It increased very slowly during the preschool period (3.1 ± 0.9 years; 8.5 ± 0.54 Hz). The frequency in these children was, however, lower than in adults (10.3 ± 1.2 Hz). Our results show a rapid maturation in spontaneous mu rhythm during the first year of life.

Separation of antigens by immunological specificity: Use of disulphide-linked antibodies as immunosorbents

1. gamma-Globulin concentrates of antisera prepared against ovalbumin and human serum albumin were thiolated and cross-linked to form insoluble polymers. 2. These immunosorbents were of low solubility and of high capacity for homologous antigen. 3. The high specificity of these immunosorbents was demonstrated by fractionation of various binary mixtures of fluorescent ovalbumin, (131)I-labelled human serum albumin, lysozyme and ribonuclease.

Separation of antigens by immunological specificity: Use of cellulose-linked antibodies as immunosorbents

1. Immunosorbents were prepared by coupling activated aminocellulose with the gamma-globulin concentrates of antisera prepared against ovalbumin and human serum albumin. 2. The immunosorbents were low in solubility, but high in capacity for homologous antigens. 3. The high specificity of these immunosorbents was demonstrated by their use in fractionating various mixtures of fluorescent ovalbumin, (131)I-labelled human serum albumin, lysozyme and ribonuclease.

Mediators released from LPS-challenged lungs induce inflammatory responses in liver vascular endothelial cells and neutrophilic leukocytes

The systemic inflammatory response plays an important role in the progression of acute lung injury (ALI) to multiple organ dysfunction syndrome (MODS). However, the role of lung-derived inflammatory mediators in induction of the inflammatory response in remote organs is poorly understood. To address the above, we investigated the effects of lung inflammation on induction of inflammatory response(s) in the liver in vitro. Inflammation in mouse lungs was induced by intranasal administration of lipopolysaccharide (LPS; 1 mg/ml) followed by mechanical ventilation using the isolated perfused mouse lung method to obtain and characterize lung perfusate from the pulmonary circulation. LPS administration to mouse lungs resulted in an increased release of inflammation-relevant cytokines and chemokines into the perfusate (Luminex assay) compared with the saline-controls. Subsequently, primary mouse liver vascular endothelial cells (LVEC) or mouse polymorphonuclear leukocytes (PMN) in vitro were stimulated with the perfusate obtained from saline- or LPS-challenged lungs and assessed for various inflammation-relevant end points. The obtained results indicate that stimulation of LVEC with perfusate obtained from LPS-challenged lungs results in 1) reactive oxygen species (ROS) production; 2) activation of NF-kappaB; and 3) expression of E-selectin, ICAM-1, and VCAM-1 and a subsequent increase in PMN rolling and adhesion to LVEC. In addition, perfusate from LPS-challenged lung induced activation of PMN with respect to increased ROS production and upregulation of cell surface levels of adhesion molecules MAC-1 and VLA-4. Heat-inactivation of the perfusate obtained from LPS-challenged lungs was very effective in suppressing increased proadhesive phenotype (i.e., E-selectin and ICAM-1 expression) in LVEC, whereas targeted inhibition (immunoneutralization) of TNF-alpha and/or IL-6 in LPS-lung perfusate had no effect. Taken together, these findings indicate that multiple proinflammatory mediators (proteinaceous in nature) released from inflamed lungs act synergistically to induce systemic activation of circulating PMN and promote inflammatory responses in liver vascular endothelial cells.

MEG response to median nerve stimulation correlates with recovery of sensory and motor function after stroke

OBJECTIVE

Hemiparesis due to damage by stroke in primary motor cortex (MI) or its underlying projections presents a problem for functional neuroimaging technologies that attempt to evaluate the neurophysiological basis for restoration of motor function. Traditional assessments of MI function require patients to move their fingers, hands, or limbs, which can be either impossible or markedly compromised after stroke. We recently demonstrated in normal subjects that magnetoencephalography (MEG), a non-invasive neuromagnetic functional imaging technique, detects neuronal response elicited by electrical median nerve stimulation in MI, as well as primary somatosensory cortex (SI). In the present study, we used the MEG response from median nerve stimulation to investigate the recovery of primary motor and somatosensory in acute ischemic stroke patients.

METHODS

Twelve patients with unilateral ischemic strokes that affected sensorimotor functions of their hand were studied in the acute stage (4.4+/-1.2 days, mean+/-SD) and during a 1-month follow-up (38.6+/-5.6 days, except for one patient's follow-up done 6 month after stroke).

RESULTS

Among the multiple cortical sources localized after median nerve stimulation, one source localized to SI and another localized to the vicinity of MI. Changes in the source strengths of the first component post-stimulus of MI and SI correlated with the extent of recovery of sensorimotor functions as determined by neurological exams.

CONCLUSIONS

This study provides a novel way of indirectly assessing MI function using MEG during the acute stroke phase, when many patients often cannot perform motor tasks due to paralysis.

Pathogenesis of infectious diarrhea

A brief overview of some of the main features involved in normal physiological bi-directional absorption and secretion of fluid in the gut is given, including the nature and cellular location of key enzymes, ion pumps, symports, antiports and diffusion channels; the microanatomy of intestinal villous vasculature and the dynamics of villus blood flow, which together generate hypertonic zones in villus tip regions; and the production, differentiation, escalator movement (from crypt to villus tip) and subsequent shedding of intestinal epithelial cells. (Neural and hormonal mechanisms that regulate normal mucosal ion transport are not discussed.) The manner in which Vibrio cholerae, several pathotypes of Escherichia coli, several Salmonella serotypes, rotavirus, Campylobacter species, Shigella dysenteriae, Yersinia species and Clostridium difficile perturb these mechanisms and cause diarrhea, is discussed. Throughout the article, the main emphasis is on experimental studies designed to elucidate biological mechanisms and (where relevant) the microbial determinants responsible for diarrheal disease. Allusions are also made to the involvement of host responses such as the inflammatory response, the production and release of potent cytokines and accelerated homeostatic responses (such as increased rates of crypt cell division seen in some infections), and the role that they play in pathophysiological fluid secretion.

Osteoporosis: A possible aetiological factor in the development of Scheuermann's disease

The aim of this study was to test the hypothesis that spinal osteoporosis is an aetiological factor in the development of Scheuermann's disease in adolescents. Clinical and radiological data was collected on 12 individuals with Scheuermann's disease (SD). Lumbar spine bone mineral density (L2-4) was measured using dual energy X-ray absorptiometry. Age and sex-matched adolescents were used as controls. The number of standard deviations from the mean of age and sex-matched controls were calculated. In regards to results, SD patients demonstrated high bone densities of between 1 and 1.5 standard deviations above the mean of age-matched controls. These results suggest that osteoporosis is not an aetiological factor in Scheuermann's disease and that bone density measurements may indeed be higher than aged-matched controls in the general population.

Sources on the anterior and posterior banks of the central sulcus identified from magnetic somatosensory evoked responses using multistart spatio-temporal localization

A Multi-Start Spatio-Temporal (MSST) multidipole localization algorithm was used to study sources on the anterior and posterior banks of the central sulcus localized from early somatosensory magnetoencephalography (MEG) responses. Electrical stimulation was applied to the right and left median nerves of 8 normal subjects. Two sources, one on the anterior and one on the posterior bank of the central sulcus, were localized from 16 data sets (8 subjects, 2 hemispheres). Compared with the more traditional practice of single-dipole fits to peak latencies, MSST provided more reliable source locations. The temporal dynamics of the anterior and posterior central sulcus sources, obtained using MSST, showed considerable temporal overlap. In some cases, the two sources appeared synchronous. On the other hand, in the traditional single-dipole peak-latency fit approach, there is no time course other than a focal dipole moment activated only at the selected peak latency. The same group of subjects also performed a motor task involving index-finger lifting; the anterior central sulcus source obtained from electrical median nerve stimulation localized to the same or similar region in the primary motor area identified from the finger-lift task. The physiological significance of the anterior central sulcus source is discussed. The findings suggest that one can test the integrity of cortical tissue in the region of primary motor cortex using electrical somatosensory stimulation.

Sources on the anterior and posterior banks of the central sulcus identified from magnetic somatosensory evoked responses using multistart spatio-temporal localization

A Multi-Start Spatio-Temporal (MSST) multidipole localization algorithm was used to study sources on the anterior and posterior banks of the central sulcus localized from early somatosensory magnetoencephalography (MEG) responses. Electrical stimulation was applied to the right and left median nerves of 8 normal subjects. Two sources, one on the anterior and one on the posterior bank of the central sulcus, were localized from 16 data sets (8 subjects, 2 hemispheres). Compared with the more traditional practice of single-dipole fits to peak latencies, MSST provided more reliable source locations. The temporal dynamics of the anterior and posterior central sulcus sources, obtained using MSST, showed considerable temporal overlap. In some cases, the two sources appeared synchronous. On the other hand, in the traditional single-dipole peak-latency fit approach, there is no time course other than a focal dipole moment activated only at the selected peak latency. The same group of subjects also performed a motor task involving index-finger lifting; the anterior central sulcus source obtained from electrical median nerve stimulation localized to the same or similar region in the primary motor area identified from the finger-lift task. The physiological significance of the anterior central sulcus source is discussed. The findings suggest that one can test the integrity of cortical tissue in the region of primary motor cortex using electrical somatosensory stimulation.

Multistart algorithms for MEG empirical data analysis reliably characterize locations and time courses of multiple sources

We applied our newly developed Multistart algorithm (M. Huang et al., 1998, Electroencephalogr. Clin. Neurophysiol. 108, 32-44) to high signal-to-noise ratio (SNR) somatosensory responses and low SNR visual data to demonstrate the reliability of this analysis tool for determining source locations and time courses of empirical multisource neuromagnetic data. This algorithm performs a downhill simplex search hundreds to thousands of times with multiple, randomly selected initial starting parameters from within the head volume, in order to avoid problems of local minima. Two subjects participated in two studies: (1) somatosensory (left and right median nerves were stimulated using a square wave pulse of 0.2 ms duration) and (2) visual (small black and white bull's-eye patterns were presented to central and peripheral locations in four quadrants of the visual field). One subject participated in both of the studies mentioned above and in a third study (i.e., simultaneous somatosensory/visual stimulation). The best-fitting solutions were tightly clustered in high SNR somatosensory data and all dominant regions of activity could be identified in some instances by using a single model order (e.g., six dipoles) applied to a single interval of time (e.g., 15-250 ms) that captured the entire somatosensory response. In low SNR visual data, solutions were obtained from several different model orders and time intervals in order to capture the dominant activity across the entire visual response (e.g. , 60-300 ms). Our results demonstrate that Multistart MEG analysis procedures can localize multiple regions of activity and characterize their time courses in a reliable fashion. Sources for visual data were determined by comparing results across several different models, each of which was based on hundreds to thousands of different fits to the data.

Effects of intranasal challenge with group A beta haemolytic streptococcus M type 49 in Swiss albino mice

Mice are susceptible to natural infections with streptococci and therefore can serve as suitable animal models to study experimental streptococcal infections. In an earlier study, we had shown the development of pharyngeal colonization, antibody response and histopathological changes in the heart following intranasal (IN) challenge with a rheumatogenic serotype of group A beta haemolytic streptococcus, the M type 18. To determine if nonpharyngitis associated serotypes can also elicit similar responses, 30 Swiss albino mice were challenged intranasally with 2 x 10(7) colony forming units of a skin associated serotype of group A beta haemolytic streptococcus, the M type 49. Pharyngeal colonization varied from 64% (n = 30) in the first week to 69% (n = 16) during the fourth week after IN challenge. Eleven (36.7%) of the 30 animals studied showed antibody response to DNase B (ADNB) with peak titers varying from 150 to 1200 units. Wide variations were seen in ADNB titers in individual mice. Histopathological evidence for cardiac lesions were seen in three animals. The changes were mild and varied from mild to chronic endocardial inflammation to calcification. The study shows that Swiss albino mice are also susceptible to IN challenge with skin associated strains of GABHS and therefore can serve as useful models to study the effects of experimental infection with diverse serotypes of GABHS.

Generation of vector-insensitive dig-labeled probes from large cosmid library inserts using PCR

We have devised a general method for producing vector-insensitive probes from clones in which insert DNA (ca. 40 kb) could not be amplified in one piece nor be excised from the vector sequence. The method involves PCR and vector-specific primers in combination with restriction digestion and ligation. It yields specific PCR products that could subsequently be labeled using DIG-11-dUTP in a single-cycle PCR. In colony blot hybridization, the probes were specific for the insert DNA from which the probe was derived and, importantly, did not detect vector sequences.

Iterative selection from a Salmonella typhimurium cosmid library can lead to the isolation of an atypically small plasmid

We have constructed a DNA library from a virulent Salmonella typhimurium strain, in an avirulent strain. The process of selecting the components of interest from the library involved iterative growth in liquid culture. This resulted, after four cycles, in the culture becoming homogeneous for a single plasmid, which was much smaller than the average size for the library. We have identified the larger precursor of this plasmid which has two regions of sufficient homology to allow recombination resulting in the formation of the small plasmid. S. typhimurium carrying the small plasmid have a smaller genetic burden than other members of the library and survive better in spent culture medium, facilitating selection on repeated subculture. Such rapid adventitious selection has important implications for isolation of clones of interest from genomic libraries.

Pharyngeal colonisation, ADNB response and development of cardiac lesions in mice following intranasal inoculation with group A beta haemolytic streptococcus M type 18

Swiss albino mice from a randomly bred colony were inoculated intranasally with 1.6, 2 or 2.4 x 10(7) colony forming units of a mid-logarithmic phase culture of group A beta haemolytic streptococcus M type 18 for 3 days, 6 days or once a week respectively for three weeks. Pharyngeal colonisation could be observed in 67 (59.8%) of 112 mice on 4th day after inoculation and 14 (38%) of the 37 mice on 21st day. Out of 27 mice tested for determination of antibodies to deoxyribonuclease B at regular intervals for 98 days, 15 (55.5%) showed responses, with maximum titers varying from 50 units to 4800 units in individual mice. Histopathological evidence for cardiac lesions were seen in five (3.03%) of the 165 animals studied. These included one case of severe endocarditis, two cases of endocarditis with valvular lesions and one case with non-specific lymphocyte infiltration in the heart. One other animal showed subendocardial oval nodular aggregates. Although the cellular nature of these lesions were not determined, this study shows that Swiss albino mice can serve as suitable animal models to study experimental streptococcal infections. However these are preliminary observations and are to be confirmed and revalidated by further controlled experiments.

Ototoxicity resulting from intracochlear perfusion of Streptococcus pneumoniae in the guinea pig is modified by cefotaxime or amoxycillin pretreatment

Acute changes in the electrophysiology and ultrastructure of the organ of Corti were studied after microperfusion of c. 5 x 10(6) CFU of serotype 2 Streptococcus pneumoniae D39 or Escherichia coli K-12 directly into the scala tympani of guinea pigs. Hearing loss was assessed by recording the auditory nerve compound action potential response to a 10 kHz tone pip. Mean hearing loss 3 h after pneumococcal perfusion (n = 4) was 44 dB, compared to 6 dB after E. coli perfusion (n = 4) (P<0.001). After pneumococcal perfusion, scanning electron microscopy revealed damage to hair cell stereocilia and cratering of the apical surface of supporting cells. Intraperitoneal injection of 100 mg/kg cefotaxime (n = 4) or 100 mg/kg amoxycillin (n = 4) 30 min before perfusion of pneumococci significantly reduced mean hearing loss to 23 dB (P=0.01) or 20 dB (P=0.01), respectively, and diminished ultrastructural damage. The data suggest that if pneumococci invade the inner ear during meningitis, cochlear deafness may rapidly ensue.

A role for pneumolysin but not neuraminidase in the hearing loss and cochlear damage induced by experimental pneumococcal meningitis in guinea pigs

We investigated the roles of pneumolysin and neuraminidase in the pathogenesis of deafness and cochlear damage during experimental pneumococcal meningitis. Anesthetized guinea pigs were inoculated intracranially with 7.5 log10 CFU of either (i) wild-type Streptococcus pneumoniae D39 (n = 8), (ii) PLN-A, a defined isogenic derivative of D39 deficient in pneumolysin (n = 5), or (iii) deltaNA1, a new derivative of D39 deficient in neuraminidase constructed by insertion-duplication mutagenesis of the nanA gene (n = 5). To quantify hearing loss, the auditory nerve compound action potential evoked by a tone pulse was recorded from the round window membrane of the cochlea every 3 h for 12 h. The organ of Corti was intravitally fixed for subsequent examination by high-resolution scanning and transmission electron microscopy. All animals sustained similar meningeal inflammatory responses. PLN-A induced significantly less hearing loss than D39 over the frequency range of 3 to 10 kHz. Levels of mean hearing loss at 10 kHz 12 h postinoculation were as follows: D39, 50 dB; deltaNA1, 52 dB (P = 0.76 versus D39), and PLN-A, 12 dB (P < 0.0001 versus D39). The mean rates of hearing loss at 10 kHz were 4.4 dB/h for D39, 4.3 dB/h for deltaNA1, and just 1.0 dB/h for PLN-A (P < 0.0001 versus D39). Suppurative labyrinthitis was universal. PLN-A induced the accumulation of less protein in the cerebrospinal fluid (P = 0.04 versus D39). Infection with D39 and deltaNA1 induced significant damage to the reticular lamina, the sensory hair cells, and supporting cells of the organ of Corti. By contrast, after infection with PLN-A, the organ of Corti appeared virtually intact. Pneumolysin seems to be the principal cause of cochlear damage in this model of meningogenic deafness. No clear pathogenic role was demonstrated for neuraminidase.