Disturbed gut microbiota and bile homeostasis in Giardia-infected mice contributes to metabolic dysregulation and growth impairment

Although infection with the human enteropathogen Giardia lamblia causes self-limited diarrhea in adults, infant populations in endemic areas experience persistent pathogen carriage in the absence of diarrhea. The persistence of this protozoan parasite in infants has been associated with reduced weight gain and linear growth (height-for-age). The mechanisms that support persistent infection and determine the different disease outcomes in the infant host are incompletely understood. Using a neonatal mouse model of persistent G. lamblia infection, we demonstrate that G. lamblia induced bile secretion and used the bile constituent phosphatidylcholine as a substrate for parasite growth. In addition, we show that G. lamblia infection altered the enteric microbiota composition, leading to enhanced bile acid deconjugation and increased expression of fibroblast growth factor 15. This resulted in elevated energy expenditure and dysregulated lipid metabolism with reduced adipose tissue, body weight gain, and growth in the infected mice. Our results indicate that this enteropathogen's modulation of bile acid metabolism and lipid metabolism in the neonatal mouse host led to an altered body composition, suggesting how G. lamblia infection could contribute to growth restriction in infants in endemic areas.

Rapid Implementation and Evaluation of Virtual Health Training in a Subspecialty Hospital in British Columbia, in Response to the COVID-19 Pandemic

Introduction: Adoption of virtual health (VH) solutions in healthcare has been challenging; this changed rapidly after implementation of physical distancing measures due to the COVID-19 pandemic. In response to the pandemic, British Columbia's Children's and Women's sub-specialty hospitals rapidly trained and scaled up support to equip staff and clinicians to use VH. Methods: Ninety-minute live online training workshops and frequently updated online support materials were offered for 6 weeks. Training was monitored via feedback collected at training sessions and a brief post-training survey. After training completion, a second survey was circulated to measure utilization outcomes and experiences with VH. Results: Eight hundred and ninety-five participants representing 82% of staff requiring support were trained through 101 sessions; 348 (38.9%) and 272 (30.4%) responses were collected for the monitoring and outcome surveys, respectively. Overall, 89% agreed that training was relevant to their needs; participants indicated average 58.1% (SD = 26.6) and 60.6% (SD = 25.2) increase in knowledge and confidence in VH after training; 90.1% had booked or conducted VH sessions. Increase in confidence was more pronounced in participants with lesser previous exposure to VH, but number of sessions conducted post-training and percentage of successful sessions were independent of previous exposure. For future training and support, participants suggested subject-tailored trainings, asynchronous trainings, and availability of experienced users. Discussion: Training is key to success of VH implementation. Moving forward, core competencies in VH should be developed to support standardization and allow for evaluation and quality improvement. Incorporation of VH training in continuous professional development and onboarding is also highly recommended.

Implementation study of a 5-component pediatric early warning system (PEWS) in an emergency department in British Columbia, Canada, to inform provincial scale up

Background

The rapid identification of deterioration in the pediatric population is complex, particularly in the emergency department (ED). A comprehensive multi-faceted Pediatric Early Warning System (PEWS) might maximize early recognition of clinical deterioration and provide a structured process for the reassessment and escalation of care. The objective of the study was to evaluate the implementation fidelity, effectiveness, and utility of a 5-component PEWS implemented in the ED of an urban public general hospital in British Columbia, Canada, and to guide provincial scale up.

Methods

We used a before-and-after design to evaluate the implementation fidelity, effectiveness, and utility of a 5-component PEWS (pediatric assessment flowsheet, PEWS score, situational awareness, escalation aid, and communication framework). Sources of data included patient medical records, surveys of direct care staff, and key-informant interviews. Data were analyzed using mixed-methods approaches.

Results

The majority of medical records had documented PEWS scores at triage (80%) and first bedside assessment (81%), indicating that the intervention was implemented with high fidelity. The intervention was effective in increasing vital signs documentation, both at first beside assessment (84% increase) and throughout the ED stay (> 100% increase), in improving staff’s self-perceived knowledge and confidence in providing pediatric care, and self-reported communication between staff. Satisfaction levels were high with the PEWS scoring system, flowsheet, escalation aid, and to a lesser extent with the situational awareness tool and communication framework. Reasons for dissatisfaction included increased paperwork and incidence of false-positives. Overall, the majority of providers indicated that implementation of PEWS and completing a PEWS score at triage alongside the Canadian Triage and Acuity Scale (CTAS) added value to pediatric care in the ED. Results also suggest that the intervention is aligned with current practice in the ED.

Conclusion

Our study shows that high-fidelity implementation of PEWS in the ED is feasible. We also show that a multi-component PEWS can be effective in improving pediatric care and be well-accepted by staff. Results and lessons learned from this pilot study are being used to scale up implementation of PEWS in ED settings across the province of British Columbia.

Promoting cross-jurisdictional primary health care research: developing a set of common indicators across 12 community-based primary health care teams in Canada

AimTo describe the process by which the 12 community-based primary health care (CBPHC) research teams worked together and fostered cross-jurisdictional collaboration, including collection of common indicators with the goal of using the same measures and data sources. BACKGROUND: A pan-Canadian mechanism for common measurement of the impact of primary care innovations across Canada is lacking. The Canadian Institutes for Health Research and its partners funded 12 teams to conduct research and collaborate on development of a set of commonly collected indicators. METHODS: A working group representing the 12 teams was established. They undertook an iterative process to consider existing primary care indicators identified from the literature and by stakeholders. Indicators were agreed upon with the intention of addressing three objectives across the 12 teams: (1) describing the impact of improving access to CBPHC; (2) examining the impact of alternative models of chronic disease prevention and management in CBPHC; and (3) describing the structures and context that influence the implementation, delivery, cost, and potential for scale-up of CBPHC innovations.FindingsNineteen common indicators within the core dimensions of primary care were identified: access, comprehensiveness, coordination, effectiveness, and equity. We also agreed to collect data on health care costs and utilization within each team. Data sources include surveys, health administrative data, interviews, focus groups, and case studies. Collaboration across these teams sets the foundation for a unique opportunity for new knowledge generation, over and above any knowledge developed by any one team. Keys to success are each team's willingness to engage and commitment to working across teams, funding to support this collaboration, and distributed leadership across the working group. Reaching consensus on collection of common indicators is challenging but achievable.

Assessment of scalability of evidence-based innovations in community-based primary health care: a cross-sectional study

BACKGROUND

In 2013, the Canadian Institutes of Health Research funded 12 community-based primary health care research teams to develop evidence-based innovations. We aimed to explore the scalability of these innovations.

METHODS

In this cross-sectional study, we invited the 12 teams to rate their evidence-based innovations for scalability. Based on a systematic review, we developed a self-administered questionnaire with 16 scalability assessment criteria grouped into 5 dimensions (theory, impact, coverage, setting and cost). Teams completed a questionnaire for each of their innovations. We analyzed the data using simple frequency counts and hierarchical cluster analysis. We calculated the mean number and standard deviation (SD) of innovations that met criteria within each dimension that included more than 1 criterion. The analysis unit was the innovation.

RESULTS

The 11 responding teams evaluated 33 evidence-based innovations (median 3, range 1-8 per team). The innovations focused on access to care and chronic disease prevention and management, and varied from health interventions to methodological innovations. Most of the innovations were health interventions (n = 21), followed by analytical methods (n = 4), conceptual frameworks (n = 4), measures (n = 3) and strategies to build research capacity (n = 1). Most (29) met criteria in the theory dimension, followed by impact (mean 22.3 [SD 5.6] innovations per dimension), setting (mean 21.7 [SD 8.5]), cost (mean 17.5 [SD 2.1]) and coverage (mean 14.0 [SD 4.1]). On average, the innovations met 10 of the 16 criteria. Adoption was the least assessed criterion (n = 9). Most (20) of the innovations were highly ranked for scalability.

INTERPRETATION

Scalability varied among innovations, which suggests that readiness for scale up was suboptimal for some innovations. Coverage remained largely unaddressed; further investigation of this critical dimension is necessary.

Leishmania exosomes and other virulence factors: Impact on innate immune response and macrophage functions

Leishmania parasites are the causative agents of the leishmaniases, a collection of vector-borne diseases that range from simple cutaneous to fatal visceral forms. Employing potent immune modulation mechanisms, Leishmania is able to render the host macrophage inactive and persist inside its phagolysosome. In the last few years, the role of exosomes in Leishmania-host interactions has been increasingly investigated. For instance, it was reported that Leishmania exosome release is augmented following temperature shift, a condition mimicking parasite's entry into its mammalian host. Leishmania exosomes were found to strongly affect macrophage cell signaling and functions, similarly to whole parasites. Importantly, these vesicles were shown to be pro-inflammatory, capable to recruit neutrophils at their inoculation site exacerbating the pathology. In this review, we provide the most recent insights on the role of exosomes and other virulence factors, especially the surface protease GP63, in Leishmania-host interactions, deepening our knowledge on leishmaniasis and paving the way for the development of new therapeutics.

Exosome Secretion by the Parasitic Protozoan Leishmania within the Sand Fly Midgut

Despite several studies describing the secretion of exosomes by Leishmania in vitro, observation of their formation and release in vivo has remained a major challenge. Herein, we show that Leishmania constitutively secretes exosomes within the lumen of the sand fly midgut through a mechanism homologous to the mammalian pathway. Through egestion experiments, we demonstrate that Leishmania exosomes are part of the sand fly inoculum and are co-egested with the parasite during the insect's bite, possibly influencing the host infectious process. Indeed, co-inoculation of mice footpads with L. major plus midgut-isolated or in-vitro-isolated L. major exosomes resulted in a significant increase in footpad swelling. Notably, co-injections produced exacerbated lesions through overinduction of inflammatory cytokines, in particular IL-17a. Our data indicate that Leishmania exosomes are an integral part of the parasite's infectious life cycle, and we propose to add these vesicles to the repertoire of virulence factors associated with vector-transmitted infections.

Active suppression of intestinal CD4(+)TCRαβ(+) T-lymphocyte maturation during the postnatal period

Priming of the mucosal immune system during the postnatal period substantially influences host–microbial interaction and susceptibility to immune-mediated diseases in adult life. The underlying mechanisms are ill defined. Here we show that shortly after birth, CD4 T cells populate preformed lymphoid structures in the small intestine and quickly acquire a distinct transcriptional profile. T-cell recruitment is independent of microbial colonization and innate or adaptive immune stimulation but requires β7 integrin expression. Surprisingly, neonatal CD4 T cells remain immature throughout the postnatal period under homeostatic conditions but undergo maturation and gain effector function on barrier disruption. Maternal SIgA and regulatory T cells act in concert to prevent immune stimulation and maintain the immature phenotype of CD4 T cells in the postnatal intestine during homeostasis. Active suppression of CD4 T-cell maturation during the postnatal period might contribute to prevent auto-reactivity, sustain a broad TCR repertoire and establish life-long immune homeostasis.

The mechanisms governing the ontogeny and maturation of the mucosal immune system during the postnatal period are not well understood. Here the authors characterize the homing kinetic, anatomical distribution and maturation of early intestinal CD4 T cells and provide insights into active T-cell suppression during the postnatal period.

MODELING THE HEART BEAT, CIRCLE OF WILLIS AND RELATED CEREBRAL STENOSIS USING AN EQUIVALENT ELECTRONIC CIRCUIT

In this study, the cardiovascular system is modeled using an equivalent electronic system focusing on the circle of Willis (COW). COW supports adequate blood supply to the brain. Each cardiovascular artery is modeled using electrical elements such as resistor, capacitor and inductor. MATLAB Simulink software was used to obtain the left and right ventricles pressure as well as pressure distribution at efferent arteries of the COW. Firstly, the normal operation of the system was shown then the stenosis of cerebral arteries was induced in the circuit and the effects were studied. In the normal condition, the difference between pressure distribution of right and left efferent arteries (left and right anterior cerebral arteries (ACA-A2), left and right middle cerebral arteries (MCA), left and right posterior cerebral arteries (PCA-P2) was calculated to see the effect of anatomical difference between left and right sides of supplying arteries of COW. In stenosis cases, the effect of internal carotid artery (ICA) occlusion on efferent arteries pressure was investigated. The model results were verified by comparing to the clinical observation reported in the literature.

Heart sound segmentation based on homomorphic filtering

BACKGROUND

Phonocardiography, the digital recording of heart sounds, is becoming increasingly popular as a primary detection system for diagnosing heart disorders and is relatively inexpensive. The electrocardiogram (ECG) is often used when recording the phonocardiogram in order to help identify the systolic and diastolic components. In this study, a heart sound segmentation algorithm has been developed which automatically separates the heart sound signal into these component parts.

METHODS

100 patients with normal and abnormal heart sounds were studied. The algorithm uses homomorphic filtering to produce time-domain intensity envelopes of the heart sounds and separates the sounds into four overlapping parts: the first heart sound, the systolic period, the second heart sound and the diastolic period.

RESULTS

The performance of the algorithm was evaluated using 14,000 cardiac periods from 100 digital phonocardiographic recordings, including normal and abnormal heart sounds. In tests, the algorithm was over 93 percent correct in detecting the first and second heart sounds.

CONCLUSION

The automatic segmentation algorithm presented uses wavelet decomposition and reconstruction to select a suitable frequency band for envelope calculations and has been found to be effective in segmenting phonocardiogram signals into four component parts without using an ECG reference.

Combining numerical and clinical methods to assess aortic valve hemodynamics during exercise

Computational simulations have the potential to aid understanding of cardiovascular hemodynamics under physiological conditions, including exercise. Therefore, blood hemodynamic parameters during different heart rates, rest and exercise have been investigated, using a numerical method. A model was developed for a healthy subject. Using geometrical data acquired by echo-Doppler, a two-dimensional model of the chamber of aortic sinus valsalva and aortic root was created. Systolic ventricular and aortic pressures were applied as boundary conditions computationally. These pressures were the initial physical conditions applied to the model to predict valve deformation and changes in hemodynamics. They were the clinically measured brachial pressures plus differences between brachial, central and left ventricular pressures. Echocardiographic imaging was also used to acquire different ejection times, necessary for pressure waveform equations of blood flow during exercise. A fluid-structure interaction simulation was performed, using an arbitrary Lagrangian-Eulerian mesh. During exercise, peak vorticity increased by 14.8%, peak shear rate by 15.8%, peak cell Reynolds number by 20%, peak leaflet tip velocity increased by 47% and the blood velocity increased by 3% through the leaflets, whereas full opening time decreased by 11%. Our results show that numerical methods can be combined with clinical measurements to provide good estimates of patient-specific hemodynamics at different heart rates.

Modeling of cerebral aneurysm using equivalent electrical circuit (Lumped Model)

The circle of Willis (CoW) is a key asset in brain performance as it supports adequate blood supply to the brain. The lumped method (electrical equivalent circuits) is a useful model to simulate the process of the human cardiovascular system. In this study, the whole cardiovascular system is modeled, using an equivalent electrical circuit to investigate an aneurysm in an artery. The cerebrovascular system consists of 29 compartments, which includes the CoW. Each vessel is modeled by a resistor, a capacitor and an inductor. Using MATLAB Simulink, the left and right ventricles are modeled by controlled voltage sources and diodes. The effects of the left internal carotid artery aneurysm (Fusiform) on the pressure of the efferent arteries in the circle of Willis are studied. The modeling results are entirely in agreement with the available clinical observations. The results of the present study may have clinical implications for modeling different cardiovascular diseases, such as arterial stiffness and atherosclerosis.

Immunomodulatory impact of leishmania-induced macrophage exosomes: a comparative proteomic and functional analysis

Released by many eukaryotic cells, the exosomes are 40-100 nm vesicles shown to operate over the complex processes of cell-cell communication. Among the metazoan cell lineages known to generate exosomes is the mononuclear phagocyte lineage, a lineage that parasites such as Leishmania are known to subvert as host cells. We previously reported that mouse macrophage signaling and functions are modified once co-incubated with exoproteome of Leishmania promastigotes. Using mass spectrometry analysis, we were curious to further compare the content of purified exosomes released by the J774 mouse macrophage cell line exposed or not to either LPS or to stationary phase Leishmania mexicana promastigotes. Collectively, our analyses resulted in detection of 248 proteins, ∼50-80% of which were shared among the three sources studied. Using exponentially modified protein abundance index (emPAI) and network analyses, we found that the macrophage exosomes display unique signatures with respect to composition and abundance of many functional groups of proteins, such as plasma membrane-associated proteins, chaperones and metabolic enzymes. Moreover, for the first time, L. mexicana surface protease GP63 is shown to be present in exosomes released from J774 macrophages exposed to stationary phase promastigotes. We observed that macrophage exosomes are able to induce signaling molecules and transcription factors in naive macrophages. Finally, using qRT-PCR, we monitored modulation of expression of multiple immune-related genes within macrophages exposed to exosomes. We found all three groups of exosomes to induce expression of immune-related genes, the ones collected from macrophages exposed to L. mexicana sharing properties with exosomes collected from macrophage left unexposed to any agonist. Overall, our results allowed depicting that protein sorting into macrophage-derived exosomes depends upon the cell status and how such distinct protein sorting can in turn impact the functions of naive J774 cells.

[Diagnosis and evaluation of hepatitis C virus among haemodialysis patients]

Hepatitis C is a health problem worldwide. The World Health Organization estimates that 3% of world's population is infected with hepatitis C virus (HCV). In haemodialysis patients, the prevalence reaches 80% in some countries. In Morocco, HCV prevalence is 32% according to the Moroccan register of dialysis. The natural history of hepatitis C infection in chronic haemodialysis patients is characterized by a silent evolution. There are different methods to diagnose HCV and they are becoming increasingly sensitive. There are indirect tests for antibodies to HCV: these are reproducible but false negatives are common and there is direct testing of viral RNA: this is more sensitive but not always available and is more expensive. The use of these tests has been categorized through new recommendations from learned societies. However, the evaluation of liver disease is still controversial and liver biopsy remains the gold standard. This paper reviews the approaches for diagnosing and evaluating hepatitis C in haemodialysis patients.

The Kt/V by ionic dialysance: Interpretation limits

The availability of hemodialysis machines equipped with online clearance monitoring (OCM) allows frequent assessment of dialysis efficiency and adequacy without the need for blood samples. Accurate estimation of the urea distribution volume (V) is required for Kt/V calculated from OCM to be consistent with conventional blood sample-based methods. A total of 35 patients were studied. Ionic dialysance was measured by conductivity monitoring. The second-generation Daugirdas formula was used to calculate the Kt/V single-pool (Kt/VD). Values of V to allow comparison between OCM and blood-based Kt/V were determined using Watson formula (VWa), bioimpedance spectroscopy (Vimp), and blood-based kinetic data (Vukm). Comparison of Kt/Vw ocm calculated by the ionic dialysance and Vw (Kt/Vw ocm) with Kt/VD shows that using VW leads to significant systematic underestimation of dialysis dose by 24%. Better agreement between Kt/V ocm and Kt/VD was observed when using Vimp and Vukm. Bio-impedancemetry and the indirect method using the second-generation Daugirdas equation are two methods of clinical interest for estimating V to ensure greater agreement between OCM and blood-based Kt/V.

[Benign intracranial hypertension in a hemodialysis patient: consider the fistula]

Benign intracranial hypertension (BIH) is a syndrome characterized by the abnormal elevation of the intracranial pressure in the absence of a mass lesion or hydrocephalus, and with normal composition of the cerebrospinal fluid. We report a case of BIH in a chronic hemodialysis patient with no signs of intraocular inflammation or neurologic abnormalities. Treatment with acetazolamide followed by corticosteroids failed to improve the signs of BIH. However, after correction of the radiocephalic arteriovenous fistula of the left upper extremity, which demonstrated excessive flow, BIH symptoms completely disappeared.

CONCLUSION

When managing BIH in a hemodialysis patient, consider the fistula.

Predictors of early vascular-access failure in patients on hemodialysis

Vascular access management is key and critical in the successful management of hemodialysis patients, and an arteriovenous fistula (AVF) is considered the access of choice. This study was conducted between January 2007 and October 2009 at the Military Hospital in Rabat. Data on 115 patients who underwent 138 AVFs were retrospectively studied. Wrist AVF was the most common site of use. The primary course was uncomplicated in 63% of the patients, while primary failure occurred in 23.9% of the patients. Presence of diabetes was the most important risk factor for primary failure.

Myelodysplastic syndrome and extracapillary glomerulonephritis: is there a link?

Introduction: The association of myelodysplastic syndrome and extracapillary glomerulonephritis is exceptional. Only two other cases have been reported. Reported case: A 52-year-old patient with a history of myelodysplastic syndrome developed rapidly progressive glomerulonephritis. Renal biopsy identified extracapillary glomerulonephritis.Discussion: The association of myelodysplastic syndrome with glomerulopathy is rare and often regarded as fortuitous. Only a few cases are described in literature on the subject. A relationship between the two diseases is possible but the causal link between these two diseases remains unknown. Conclusion: The notion that myelodysplastic syndrome may be associated with various glomerular nephropathies involves looking for renal disease in this haematologic disorder.

Temperature-induced protein secretion by Leishmania mexicana modulates macrophage signalling and function

Protozoan parasites of genus Leishmania are the causative agents of leishmaniasis. These digenetic microorganisms undergo a marked environmental temperature shift (TS) during transmission from the sandfly vector (ambient temperature, 25-26°C) to the mammalian host (37°C). We have observed that this TS induces a rapid and dramatic increase in protein release from Leishmania mexicana (cutaneous leishmaniasis) within 4 h. Proteomic identification of the TS-induced secreted proteins revealed 72 proteins, the majority of which lack a signal peptide and are thus thought to be secreted via nonconventional mechanisms. Interestingly, this protein release is accompanied by alterations in parasite morphology including an augmentation in the budding of exovesicles from its surface. Here we show that the exoproteome of L. mexicana upon TS induces cleavage and activation of the host protein tyrosine phosphatases, specifically SHP-1 and PTP1-B, in a murine bone-marrow-derived macrophage cell line. Furthermore, translocation of prominent inflammatory transcription factors, namely NF-κB and AP-1 is altered. The exoproteome also caused inhibition of nitric oxide production, a crucial leishmanicidal function of the macrophage. Overall, our results provide strong evidence that within early moments of interaction with the mammalian host, L. mexicana rapidly releases proteins and exovesicles that modulate signalling and function of the macrophage. These modulations can result in attenuation of the inflammatory response and deactivation of the macrophage aiding the parasite in the establishment of infection.

Comparative study of the ability of Leishmania mexicana promastigotes and amastigotes to alter macrophage signaling and functions

Leishmania alternates between two morphologically different stages, promastigotes and amastigotes. While the majority of reports focused on how the promastigote form can alter macrophage (Mphi) signaling and function, fewer reports investigated signaling alterations mediated by amastigotes, and there is a lack of comparative studies. In this study, we performed a comparison between the ability of both forms of the parasite to alter Mphi signaling and functions. Here, we show that both promastigotes and amastigotes were able to rapidly activate host protein tyrosine phosphatases (PTPs), importantly the Src homology 2 domain-containing PTP (SHP-1). However, we found that PTP-1B is specifically activated by promastigote but not amastigote infection and that lmcpb(-/-) promastigotes were no longer able to activate PTP-1B. We also show a similarity in the way promastigotes and amastigotes inactivate the transcription factors (TFs) STAT-1alpha and AP-1, but we show differences in the modulation of NF-kappaB, with promastigotes cleaving the p65 subunit, generating a smaller p35 subunit, and amastigotes fully degrading the p65 subunit with no p35 production. Importantly, we show that the cysteine proteinase LmCPb plays a key role in the alteration of NF-kappaB, STAT-1alpha, and AP-1 by promastigote and amastigote infections, ultimately leading to the inability of these TFs to translocate to the nucleus in response to gamma interferon (IFN-gamma) stimulation and thus contributing to the ability of both parasite forms to effectively block IFN-gamma-mediated nitric oxide (NO) production in Mphis.

Regulation of macrophage nitric oxide production by the protein tyrosine phosphatase Src homology 2 domain phosphotyrosine phosphatase 1 (SHP-1)

Nitric oxide (NO) is a potent molecule involved in the cytotoxic effects mediated by macrophages (MØ) against microorganisms. We previously reported that Src homology 2 domain phosphotyrosine phosphatase 1 (SHP-1)-deficient cells generate a greater amount of NO than wild-type cells in response to interferon-gamma (IFN-gamma). We also reported that the Leishmania-induced MØ SHP-1 activity is needed for the survival of the parasite within phagocytes through the attenuation of NO-dependent and NO-independent mechanisms. In the present study, we investigated the role of SHP-1 in regulating key signalling molecules important in MØ NO generation. Janus tyrosine kinase 2 (JAK2), mitogen-activated extracellular signal-regulated protein kinase kinase (MEK), extracellular signal-regulated kinases 1 and 2 (Erk1/Erk2) mitogen-activated protein kinases, p38 and stress-activated mitogen-activated protein kinases/c-Jun NH(2)-terminal kinase (SAPK/JNK) were examined in immortalized bone marrow-derived MØ (BMDM) from both SHP-1-deficient motheaten mice (me-3) and their respective littermates (LM-1). The results indicated that Erk1/Erk2 and SAPK/JNK are the main kinases regulated by SHP-1 because the absence of SHP-1 caused an increase in their phosphorylation. Moreover, only Apigenin, the specific inhibitor of Erk1/Erk2, was able to block IFN-gamma-induced inducible nitric oxide synthase (iNOS) transcription and translation in me-3 cells. Transcription factor analyses revealed that in the absence of SHP-1, activator protein-1 (AP-1) was activated. The activation of AP-1, and not nuclear factor-kappaB (NF-kappaB) or signal transducer and activator of transcription-1 alpha (STAT-1 alpha), may explain the enhanced NO generation in SHP-1-deficient cells. These observations emphasize the involvement of the MAPKs Erk1/Erk2 and SAPK/JNK in NO generation via AP-1 activation. Collectively, our findings suggest that SHP-1 plays a pivotal role in the negative regulation of signalling events leading to iNOS expression and NO generation. Furthermore, our observations underline the importance of SHP-1-mediated negative regulation in maintaining NO homeostasis and thus preventing the abnormal generation of NO that can be detrimental to the host.

On the optimality of the genetic code, with the consideration of coevolution theory by comparison of prominent cost measure matrices

Statistical and biochemical studies have revealed non-random patterns in codon assignments. The canonical genetic code is known to be highly efficient in minimizing the effects of mistranslation errors and point mutations, since it is known that when an amino acid is converted to another due to error, the biochemical properties of the resulted amino acid are usually very similar to those of the original one. In this study, using altered forms of the fitness functions used in the prior studies, we have optimized the parameters involved in the calculation of the error minimizing property of the genetic code so that the genetic code outscores the random codes as much as possible. This work also compares two prominent matrices, the Mutation Matrix and Point Accepted Mutations 74-100 (PAM(74-100)). It has been resulted that the hypothetical properties of the coevolution theory of the genetic code are already considered in PAM(74-100), giving more evidence on the existence of bias towards the genetic code in this matrix. Furthermore, our results indicate that PAM(74-100) is biased towards the single base mistranslation occurrences in second codon position as well as the frequency of amino acids. Thus PAM(74-100) is not a suitable substitution matrix for the studies conducted on the evolution of the genetic code.

gp49B1-alpha(v)beta3 interaction inhibits antigen-induced mast cell activation

We have identified the integrin alpha(v)beta3 as a ligand for mouse gp49B1, thus identifying a new class of ligand for a member of the family of inhibitory immunoreceptors that bear C2-type immunoglobulin-like domains. The specific interaction was shown by both cell-protein and cell-cell binding assays. In addition, we found that the interaction of alpha(v)beta3 with gp49B1 on bone marrow-derived mouse mast cells inhibited antigen-induced immunoglobulin E-mediated cell activation. Because neither gp49B1 nor alpha(v)beta3 exhibit substantive allelic variation, their newly appreciated interaction may reflect an innate pathway for down-regulating the activity of mast cells.

A novel element and a TEF-2-like element activate the major histocompatibility complex class II transactivator in B-lymphocytes

Major histocompatibility complex (MHC) class II molecules play a central role in immune responses, and transcription of this family of genes requires the MHC class II transactivator (CIITA). CIITA has four promoters, which are transcribed in a tissue-specific manner. CIITA promoter III is constitutively active in mature B-lymphocytes. This report now describes the minimal 319-base pair promoter region necessary for maximal transcriptional activity in B-lymphocytes. Ultraviolet light and dimethylsulfate in vivo genomic footprinting analyses reveal five occupied DNA sequence elements present in intact B-lymphocytes. Functional analysis of these elements using promoter deletions and site-specific mutations demonstrates that at least two of the sites occupied in vivo are critical for transcriptional activity. In vitro protein/DNA analysis suggests that one of the sites is a TEF-2-like element and the other is occupied by a novel transcription activator. In addition, nuclear factor-1 associates with the promoter both in vivo and in vitro. In myeloma cell lines, loss of CIITA transcription correlates with a completely unoccupied CIITA promoter III. These findings suggest that CIITA transcription in B-lymphocytes is activated through at least two strong promoter elements, while loss of expression in myeloma cells is mediated through changes in promoter assembly.