Cerebral Metabolic Changes Related to Oxidative Metabolism in a Model of Bacterial Meningitis Induced by Lipopolysaccharide.

BACKGROUND: Cerebral mitochondrial dysfunction is prominent in the pathophysiology of severe bacterial meningitis. In the present study, we hypothesize that the metabolic changes seen after intracisternal lipopolysaccharide (LPS) injection in a piglet model of meningitis is compatible with mitochondrial dysfunction and resembles the metabolic patterns seen in patients with bacterial meningitis. METHODS: Eight pigs received LPS injection in cisterna magna, and four pigs received NaCl in cisterna magna as a control. Biochemical variables related to energy metabolism were monitored by intracerebral microdialysis technique and included interstitial glucose, lactate, pyruvate, glutamate, and glycerol. The intracranial pressure (ICP) and brain tissue oxygen tension (PbtO2) were also monitored along with physiological variables including mean arterial pressure, blood glucose, lactate, and partial pressure of O2 and CO2. Pigs were monitored for 60 min at baseline and 240 min after LPS/NaCl injection. RESULTS: After LPS injection, a significant increase in cerebral lactate/pyruvate ratio (LPR) compared to control group was registered (p = 0.01). This increase was due to a significant increased lactate with stable and normal values of pyruvate. No significant change in PbtO2 or ICP was registered. No changes in physiological variables were observed. CONCLUSIONS: The metabolic changes after intracisternal LPS injection is compatible with disturbance in the oxidative metabolism and partly due to mitochondrial dysfunction with increasing cerebral LPR due to increased lactate and normal pyruvate, PbtO2, and ICP. The metabolic pattern resembles the one observed in patients with bacterial meningitis. Metabolic monitoring in these patients is feasible to monitor for cerebral metabolic derangements otherwise missed by conventional intensive care monitoring.

Competitive displacement of sodium caseinate by low-molecular-weight emulsifiers and the effects on emulsion texture and rheology.

Low-molecular-weight (LMW) emulsifiers are used to promote controlled destabilization in many dairy-type emulsions in order to obtain stable foams in whippable products. The relation between fat globule aggregation induced by three LMW emulsifiers, lactic acid ester of monoglyceride (LACTEM), saturated monoglyceride (GMS), and unsaturated monoglyceride (GMU) and their effect on interfacial protein displacement was investigated. It was found that protein displacement by LMW emulsifiers was not necessary for fat globule aggregation in emulsions, and conversely fat globule aggregation was not necessarily accompanied by protein displacement. The three LMW emulsifiers had very different effects on emulsions. LACTEM induced shear instability of emulsions, which was accompanied by protein displacement. High stability was characteristic for emulsions with GMS where protein was displaced from the interface. Emulsions containing GMU were semisolid, but only low concentrations of protein were detected in the separated serum phase. The effects of LACTEM, GMS, and GMU may be explained by three different mechanisms involving formation of interfacial α-gel, pickering stabilization and increased exposure of bound casein to the water phase. The latter may facilitate partial coalescence. Stabilizing hydrocolloids did not have any effect on the LMW emulsifiers' ability to induce protein displacement.

Gaussian Process-based prediction of memory performance and biomarker status in ageing and Alzheimer's disease-A systematic model evaluation.

Neuroimaging markers based on Magnetic Resonance Imaging (MRI) combined with various other measures (such as genetic covariates, biomarkers, vascular risk factors, neuropsychological tests etc.) might provide useful predictions of clinical outcomes during the progression towards Alzheimer's disease (AD). The use of multiple features in predictive frameworks for clinical outcomes has become increasingly prevalent in AD research. However, many studies do not focus on systematically and accurately evaluating combinations of multiple input features. Hence, the aim of the present work is to explore and assess optimal combinations of various features for MR-based prediction of (1) cognitive status and (2) biomarker positivity with a multi-kernel learning Gaussian process framework. The explored features and parameters included (A) combinations of brain tissues, modulation, smoothing, and image resolution; (B) incorporating demographics & clinical covariates; (C) the impact of the size of the training data set; (D) the influence of dimensionality reduction and the choice of kernel types. The approach was tested in a large German cohort including 959 subjects from the multicentric longitudinal study of cognitive impairment and dementia (DELCODE). Our evaluation suggests the best prediction of memory performance was obtained for a combination of neuroimaging markers, demographics, genetic information (ApoE4) and CSF biomarkers explaining 57% of outcome variance in out-of-sample predictions. The highest performance for Aß42/40 status classification was achieved for a combination of demographics, ApoE4, and a memory score while usage of structural MRI further improved the classification of individual patient's pTau status.

Expression patterns of CD44 and CD44 splice variants in patients with rheumatoid arthritis.

OBJECTIVES: It has been suggested that CD44 is involved in the pathogenesis of rheumatoid arthritis (RA). By alternative splicing, numerous CD44 isoforms can be generated which may play different roles the inflammatory process. We therefore studied the expression of various CD44 splicevariants in the circulation and synovial tissue of patients with RA and correlated expression with clinical features. METHODS: Expression of distinct CD44 splice variants was analysed by FACS in peripheral monocytes of 46 RA patients and 36 healthy controls. Expression of CD44 splice variants in synovial tissue of RA and OA patients was analysed by immunohistochemistry and the effects of blocking CD44v4 on RA-fibroblast like synoviocytes (FLS) were studied. RESULTS: On monocytes, the expression of CD44 and CD44v3 was significantly lower in patients with erosive disease than in those without radiographic progression (p<0.05 for CD44 and p<0.01 for CD44v3). CD44v6 on monocytes was significantly associated with the clinical disease activity index (r=0.34, p<0.05) and CRP-levels (r=0.37, p<0.02). Immunhistochemical analyses revealed that most variants were expressed to a significantly higher extent in RA than in OA synovial membranes. Particularly the variants CD44v4, CD44v6 and CD44v7-8 were highly expressed in the RA lining and also abundantly in the endothelium. Blocking CD44v4 in RA-FLS reduced the proliferation to 68±8% (p<0.02) when compared to control experiments and led to a reduction in IL-1ß mRNA expression (p<0.05). CONCLUSIONS: Expression of CD44 splice variants is generally increased in the synovial lining of RA patients when compared to OA. The inverse association of CD44v3 expression on monocytes with the development of erosive disease and the functional impacts of CD44v4 blockade in RA-FLS suggests a pathogenetic role of this splice variants which needs to be further investigated.

Colonic Health in Hospitalized Horses Treated with Non-Steroidal Anti-Inflammatory Drugs - A Preliminary Study.

Non-steroidal anti-inflammatory drugs (NSAIDs) can cause right dorsal colitis, but longitudinal clinical studies are lacking. This study investigates whether NSAID treated horses develop right dorsal colonic pathology in a clinical setting. Non-gastrointestinal hospitalized horses treated with NSAIDs >4 days, and untreated hospital-owned teaching horses and non-gastrointestinal client-owned hospitalized horses were included. All horses were monitored over time with clinical examinations (focusing on presence of colic, depression, reduced appetite, unstructured feces), ultrasonographic intestinal wall measurements, fecal occult blood tests (semi-quantitative results), and blood analysis (total protein and albumin concentrations, white blood cell and neutrophil counts). Outcomes were recorded as "ultrasonographically thickened right dorsal colon (RDC) walls", "colitis" and "right dorsal colitis". Findings over time were compared to baseline values and to control horses. Seventeen NSAID treated horses and 5 controls were included. NSAID treated horses developed thickened RDC walls (4/9), and subclinical and mild colitis (9/11) and right dorsal colitis (4/10), whereas all control horses remained healthy. The first changes were identified on treatment day 2. RDC walls of treated horses were significantly thicker compared to their own baseline values and compared to control horses. In conclusion, presumptive colon pathology was identified with a high incidence, starting early in the course of treatment, but with low severity. Appropriate monitoring should be advised throughout NSAID treatment. Additional research for noninvasive diagnostic tests for colon pathology is required.

Role of reticular activation in the modulation of intracortical synchronization.

During aroused states of the brain, electroencephalographic activity is characterized by fast, irregular fluctuations of low amplitude, which are thought to reflect desynchronization of neuronal activity. This phenomenon seems at odds with the proposal that synchronization of cortical responses may play an important role in the processing of sensory signals. Here, activation of the mesencephalic reticular formation (MRF), an effective way to "desynchronize the electroencephalogram," was shown to facilitate oscillatory activity in the gamma frequency range and to enhance the stimulus-specific synchronization of neuronal spike responses in the visual cortex of cats.

T cells against a bacterial heat shock protein recognize stressed macrophages.

Heat shock proteins are evolutionarily highly conserved polypeptides that are produced under a variety of stress conditions to preserve cellular functions. A major antigen of tubercle bacilli of 65 kilodaltons is a heat shock protein that has significant sequence similarity and cross-reactivity with antigens of various other microbes. Monoclonal antibodies against this common bacterial heat shock protein were used to identify a molecule of similar size in murine macrophages. Macrophages subjected to various stress stimuli including interferon-gamma activation and viral infection were recognized by class I-restricted CD8 T cells raised against the bacterial heat shock protein. These data suggest that heat shock proteins are processed in stressed host cells and that epitopes shared by heat shock proteins of bacterial and host origin are presented in the context of class I molecules.

Precisely synchronized oscillatory firing patterns require electroencephalographic activation.

Neuronal response synchronization with millisecond precision has been proposed to serve feature binding in vision and should therefore, like visual experience, depend on central states. Here we test this hypothesis by examining the occurrence and strength of response synchronization in areas 17 and 18 of anesthetized cats as a function of central states. These were assessed from the frequency content of the electroencephalogram, low power in the delta and high power in the gamma frequency ranges (here 20-70 Hz) being considered as a signature of activated states. We evaluated both spontaneous state changes and transitions induced by electrical stimulation of the mesencephalic reticular formation. During states of low central activation, visual responses were robust but lacked signs of precise synchronization. At intermediate levels of activation, responses became synchronized and exhibited an oscillatory patterning in the range of 70-105 Hz. At higher levels of activation, a different pattern of response synchronization and oscillatory modulation appeared, oscillation frequency now being in the range of 20-65 Hz. The strength of response synchronization and oscillatory modulation in the 20-65 Hz range increased with further activation and was associated with a decrease in oscillation frequency. We propose that the oscillatory patterning in the 70-105 Hz range is attributable to oscillatory retinothalamic input and that a minimal level of activation is necessary for cortical neurons to follow this oscillatory pattern. In contrast, the synchronization of responses at oscillation frequencies in the 20-65 Hz range appears to result from intracortical synchronizing mechanisms, which become progressively more effective as central activation increases. Surprisingly, enhanced synchronization and oscillatory modulation in the gamma frequency range were not associated with consistent increases in response amplitude, excluding a simple relation between central activation and neuronal discharge rate. The fact that intracortical synchronizing mechanisms are particularly effective during states of central activation supports the hypothesis that precise synchronization of responses plays a role in sensory processing.

Neuronal assemblies: necessity, signature and detectability.

The ease with which highly developed brains can generate representations of a virtually unlimited diversity of perceptual objects indicates that they have developed very efficient mechanisms to analyse and represent relations among incoming signals. Here, we propose that two complementary strategies are applied to cope with these combinatorial problems. First, elementary relations are represented by the tuned responses of individual neurons that acquire their specific response properties (feature selectivity) through appropriate convergence of input connections in hierarchically structured feed-forward architectures. Second, complex relations that cannot be represented economically by the responses of individual neurons are represented by assemblies of cells that are generated by dynamic association of individual, featureselective cells. The signature identifying the responses of an assembly as components of a coherent code is thought to be the synchronicity of the respective discharges. The compatibility of this hypothesis is examined in the context of recent data on the dynamics of synchronization phenomena, the dependence of synchronization on central states and the relations between the synchronization behaviour of neurons and perception.

Outbreak of Tuberculosis in a Colony of Rhesus Monkeys (Macaca mulatta) after Possible Indirect Contact with a Human TB Patient.

Simian tuberculosis is one of the most important bacterial diseases of non-human primates. Outbreaks of tuberculosis have been reported in primate colonies almost as long as these animals have been used experimentally or kept in zoological gardens. Significant progress has been made in reducing the incidence of tuberculosis in captive non-human primates, but despite reasonable precautions, outbreaks continue to occur. The most relevant reason is the high incidence of tuberculosis (TB) amongst the human population, in which tuberculosis is regarded as an important re-emerging disease. Furthermore, many non-human primate species originate from countries with a high burden of human TB. Therefore, Mycobacterium tuberculosis remains a significant threat in animals imported from countries with high rates of human infection. We report an outbreak of tuberculosis among a group of rhesus monkeys (Macaca mulatta) living in a closed, long-term colony. The outbreak coincided with reactivation of a TB infection in a co-worker who never had direct access to the animal house or laboratories. Eleven of 26 rhesus monkeys developed classical chronic active tuberculosis with typical caseous granulomata of varying size within different organs. The main organ system involved was the lung, suggesting an aerosol route of infection. Such an outbreak has significant economic consequences due to animal loss, disruption of research and costs related to disease control. Precautionary measures must be improved in order to avoid TB in non-human primate colonies.

Human herpesvirus-6 immunoglobulin G antibodies in patients with multiple sclerosis.

OBJECTIVE: To further investigate a possible correlation between human herpesvirus-6 (HHV-6) infection and multiple sclerosis by analyzing the level of HHV-6 antibodies in MS patients and healthy controls. MATERIALS AND METHODS: A total of 189 serum samples from patients with multiple sclerosis (MS) in different disease stages and 190 serum samples from healthy controls matched for age and sex were analyzed for HHV-6 antibodies using a competitive ELISA. RESULTS: There was no difference between HHV-6 IgG titers in MS patients and controls. Two of the controls were seronegative for HHV-6 versus to none of the MS-patients. There was no apparent difference in HHV-6 titers from patients in different disease stages. CONCLUSION: This study cannot support the theory that HHV-6 is a contributing factor to the development of MS, although a seroprevalence study like this would not disclose whether a late primary infection (in puberty) with HHV-6 might affect the development of MS.

Frequencies of IFN gamma- and IL-4-producing cells during Mycobacterium bovis BCG infection in two genetically susceptible mouse strains: role of alpha/beta T cells and NK1.1 cells.

Frequencies of IFN gamma- and IL-4-producing spleen cells in response to Mycobacterium bovis BCG infection were determined in C57BL/6 and BALB/c mice. Both mouse strains express equal innate susceptibility to M. bovis BCG (Bcgs), but differ in their NK1.1 and T-cell activities. M. bovis BCG infection induced higher frequencies (f approximately 1/500) of antigen-induced IFN gamma-secreting spleen cells in C57BL/6 mice as compared to BALB/c mice (f approximately 1/8000). Concanavalin A stimulated almost equal numbers of IFN gamma-secreting cells in both mouse strains (f approximately 1/50). Treatment with anti-NK1.1 mAb of M. bovis BCG-infected C57BL/6 mice did not alter frequencies of IFN gamma-secreting cells. Equally low numbers of antigen-induced IL-4-producing cells (f approximately 1/3000) were determined in both C57BL/6 and BALB/c mice during M. bovis BCG infection and treatment of C57BL/6 mice with anti-NK1.1 mAb had no measurable effect on IL-4 producers. Finally, frequencies of IFN gamma-producing cells were markedly reduced (10-fold) in M. bovis BCG-infected TCR-beta-/- gene deletion mutants as compared to their heterozygous controls. Our findings verify that M. bovis BCG infection primarily induces IFN gamma-secreting alpha/beta T cells of TH1 type and show that the frequencies of these IFN gamma producers differ in the two Bcgs mouse strains C57BL/6 and BALB/c.

The superantigen exfoliative toxin induces cutaneous lymphocyte-associated antigen expression in peripheral human T lymphocytes.

Several immune-mediated dermatoses including psoriasis and atopic dermatitis can be exacerbated by bacterial infections. Superantigen producing bacteria can be isolated from skin lesions of these dermatoses. Consistent with superantigen effects, skewed T cell receptor variable gene usage has been demonstrated within these lesions. Therefore, the question arises whether superantigen induce a skin-seeking phenotype within peripheral T cells. In this study, we investigated the in vitro influence of the V beta 2-selective superantigen exfoliative toxin from Staphylococcus aureus on the expression of the cutaneous lymphocyte-associated antigen on peripheral T lymphocytes of healthy donors. We demonstrate that exfoliative toxin dramatically upregulates cutaneous lymphocyte-associated antigen expression on T cell receptor V beta 2+ lymphocytes. Up to 69% of V beta 2+ lymphocytes expressed cutaneous lymphocyte-associated antigen after 5 days of in vitro culture. Additionally, exfoliative toxin also increased cutaneous lymphocyte-associated antigen expression in CD3+ T cell receptor V beta 2- lymphocytes indicating a different effect as caused by the superantigen-T cell receptor V beta 2 interaction. Our findings suggest influence of bacterial superantigens on T lymphocyte skin homing in vivo.

Epitopes of the mycobacterial heat shock protein 65 for human T cells comprise different structures.

T cell recognition of foreign antigens is a result of a ternary complex between T cell receptor, nominal peptide and major histocompatibility complex molecule. It has been proposed that the nominal peptide, which is presented by accessory cells to T cells, has a characteristic structure which can be predicted on the basis of physicochemical criteria. To further study this aspect, we stimulated T cells from normal human blood donors with synthetic peptides (each of approximately 15 amino acids in length) from the heat shock protein 65 of Mycobacterium tuberculosis-M. bovis. We found that while the characterization of certain epitopes follows commonly used predictions, other epitopes cannot be predicted by known methods.

Immunity to mycobacteria: possible role of alpha/beta and gamma/delta T lymphocytes.

Immunity to pathogenic mycobacteria is mediated by T lymphocytes. The possible contribution of CD4 alpha/beta T cells, CD8 alpha/beta T cells and gamma/delta T cells as well as the possible role of interleukin-mediated macrophage activation and target cell lysis through direct cell contact is discussed. Furthermore, attempts to define mycobacterial antigens for T lymphocytes with particular emphasis on heat shock proteins are described. The data currently available suggest complex interactions between different T-cell types in immunity to mycobacteria.

Isolated congenital absence of the pericardium: clinical presentation, diagnosis, and management.

BACKGROUND: Congenital absence of the pericardium (CAP) is a rare clinical entity. METHODS: We identified from the two hospital databases all patients with isolated CAP, reviewed their data, and invited them for prospective clinical evaluation with electrocardiography, chest x-ray findings (CXR), echocardiography, and magnetic resonance imaging (MRI). RESULTS: Ten patients (3 males, 7 females) presented at a median age of 21 years (range, 2-53 years) with paroxysmal stabbing chest pain, largely nonexertional (9), and heart murmur with an abnormal CXR (1). Three patients had partial and 7 had complete CAP (all 7 had marked lateral displacement of the cardiac apex). CXR combined with MRI were key to establishing the diagnosis; a "tongue" of lung tissue interposing between the main pulmonary artery and aorta was the most consistent diagnostic feature. Four patients underwent pericardioplasty, 3 for debilitating symptoms and 1 for left atrial appendage herniation, followed by improvement or resolution of symptoms. At a mean of 10.5 years from presentation all patients were alive. No complications were seen in the nonsurgical group. CONCLUSIONS: Isolated CAP has a common presentation pattern with periodic stabbing chest pain mimicking coronary artery disease. CXR and MRI are required for definitive diagnosis. Symptomatic patients with the complete form may benefit from pericardioplasty.

Numbers of IFN-gamma-producing cells against ESAT-6 increase in tuberculosis patients during chemotherapy.

ESAT-6 is a specific Mycobacterium tuberculosis complex antigen and strong inducer of interferon-gamma (IFN-gamma) production by T cells from tuberculosis patient T-cells. We studied the frequency of IFN-gamma producing cells reacting to ESAT-6 during anti-tuberculosis chemotherapy. The numbers of IFN-gamma producing cells in the peripheral blood were higher in tuberculosis patients after discharge from specific anti-tuberculosis chemotherapy, compared with untreated patients. These results indicate that monitoring specific M. tuberculosis antigen reactivity during anti-tuberculosis chemotherapy may avoid premature termination of treatment and resistant strains.

Performance of whole blood IFN-gamma test for tuberculosis diagnosis based on PPD or the specific antigens ESAT-6 and CFP-10.

OBJECTIVE: To evaluate the QuantiFERON-TB test in BCG-vaccinated, non-BCG-vaccinated and tuberculosis (TB) patient donor groups, and to compare its diagnostic performance with that of a blood test based on the Mycobacterium tuberculosis specific antigens ESAT-6 and CFP-10. DESIGN: Analysis of the IFN-gamma responses of whole blood cells from BCG-vaccinated or non-BCG-vaccinated donors or patients with tuberculosis, stimulated with PPD, ESAT-6 or CFP-10 antigens, and evaluation of the specificity and sensitivity of the test. RESULTS: None of the non-vaccinated donors showed positive responses to M. tuberculosis-PPD, ESAT-6 or CFP-10. In BCG-vaccinated donors, 9/19 (47%) donors responded to the QuantiFERON-TB test based on M. tuberculosis-PPD, whereas 2/19 (10.5%) responded to either ESAT-6 or CFP-10. Comparable levels of sensitivity were obtained with the QuantiFERON-TB test based on M. tuberculosis-PPD (79%) and ESAT-6 or CFP-10 antigens (72%). CONCLUSION: Our results demonstrate that the whole blood test based on M. tuberculosis-PPD did not efficiently distinguish BCG-vaccinated donors from individuals with disease due to M. tuberculosis. The introduction of new recombinant antigens specific for M. tuberculosis, such as ESAT-6 or CFP-10, should increase the specificity of the whole blood test and enable discrimination between TB infection, atypical mycobacterial reactivity and reactivity due to BCG vaccination. Such a test would provide a quantum improvement over the current practice of using the tuberculin skin test for TB control and elimination.

Serum and plasma fragments of C-telopeptides of type I collagen (CTX) are stable during storage at low temperatures for 3 years.

BACKGROUND: Control of pre-analytical variables is essential for successful application of biological markers, including bone resorption markers, in clinical trials and routine use. The effect of storage temperature on stability of bone resorption markers have not been subject of systematically investigation, and therefore the present study was set out to determine the stability of C-telopeptides of type I collagen (CTX) in serum and plasma samples stored frozen for 3 years. METHODS: The serum and plasma levels of CTX were determined in samples aliquoted and stored frozen for up to 3 years. RESULTS: No significant decrease could be detected in neither serum nor plasma samples after 3 years of storage at -20, -80 or -150 degrees C. However, at elevated temperature, i.e. 4 and 37 degrees C, improved stability of CTX was observed in EDTA plasma samples compared to serum. CONCLUSIONS: CTX is stable in frozen serum and plasma samples for up to 3 years. EDTA plasma might be the preferred matrix due to improved stability at elevated temperatures.

High-frequency oscillations (20 to 120 Hz) and their role in visual processing.

Oscillatory firing of neurons in response to visual stimuli has been observed to occur with different frequencies at multiple levels of the visual system. In the cat retina, oscillatory firing patterns occur with frequencies in the range of 60 to 120 Hz (omega-oscillations). These millisecond-precise temporal patterns are transmitted reliably to the cortex and may provide a feed-forward mechanism of response synchronization. In the cortex, visual responses often show oscillatory patterning with frequencies between 20 and 60 Hz (gamma-oscillations), which are not phase locked to the stimulus onset and therefore do not show up in regularly averaged evoked potentials. Gamma-oscillatory responses synchronize with millisecond precision over long distances and are mediated by the reciprocal corticocortical connectivity. Modulatory systems like the ascending reticular activating system facilitate synchronization and increase the strength of gamma-oscillations. During states of such functional cortical activation, the dominant frequency of the EEG is shifted from lower frequencies in the delta-/theta-range to higher frequencies in the gamma-range. Therefore, functional states indicate different degrees of temporal precision with which large neuronal populations interact. Response synchronization also depends on relations of global stimulus features. This suggests that millisecond-precise neuronal interactions serve as a fundamental mechanism for visual information processing.