Structural and functional analogy between pneumolysin and proaerolysin

Pneumolysin and proaerolysin are bacterial toxins that form pores in host cells by oligomerization. We propose that they may have similar structures despite a poor sequence identity. The crystal structure of proaerolysin reveals a protein composed of four domains, arranged in the shape of an elongated comma. Electron microscopy of the pneumolysin monomer shows a similar arrangement of domains. The sequence of pneumolysin recognizes the template of proaerolysin from a library of protein folds. A three-dimensional model of pneumolysin has been constructed by the comparative approach using the structure of proaerolysin. This model, together with results on the activity of site- specific mutants and the positions of antigenic sites, has been used to propose functional roles of individual domains.      

Desflurane-mediated sympathetic activation occurs in humans despite preventing hypotension and baroreceptor unloading

BACKGROUND: Increasing concentrations of desflurane result in progressive decreases in blood pressure (BP) and, unlike other currently marketed, potent volatile anesthetics, heightened sympathetic nervous system activity. This study aimed to determine whether baroreflex mechanisms are involved in desflurane-mediated sympathetic excitation. METHODS: Healthy volunteers were anesthetized with desflurane (n = 8) or isoflurane (n = 9). Heart rate (HR; measured by electrocardiograph), blood pressure (BP; measured by arterial catheter), and efferent sympathetic nerve activity (SNA; obtained from percutaneous recordings from the peroneal nerve) were monitored. Baroreflex sensitivity was evaluated at baseline while volunteers were conscious and during 0.5, 1, and 1.5 minimum alveolar concentration (MAC) anesthesia via bolus injections of nitroprusside (100 microg) and phenylephrine (150 microg) to decrease and increase BP. To prevent the BP decline with increasing depths of anesthesia, phenylephrine was infused to maintain mean BP at the 0.5 MAC level. RESULTS: The HR, BP, and SNA were similar between the groups at the conscious baseline measurement. Efferent SNA did not change during higher MAC of isoflurane, but it increased progressively as desflurane concentrations were increased beyond 0.5 MAC, despite maintaining BP at the 0.5 MAC value with phenylephrine infusions (P < 0.05). Cardiac baroslopes (based on changes in HR) were progressively and similarly decreased with increasing concentrations of isoflurane and desflurane (P < 0.05). Sympathetic baroslopes (based on SNA) decreased with increasing isoflurane concentrations but were maintained with increasing concentrations of desflurane; the response was significantly different between groups. CONCLUSIONS: The increase in basal levels of SNA with increasing concentrations of desflurane persisted despite "fixing" BP and thus is probably not due to hypotension and unloading of the baroreceptors. Further, the preservation of reflex increases in SNA to nitroprusside during desflurane indicates that desflurane preserves one component of the baroreflex in humans when BP is "fixed."     

Nutrition support for patients after cardiopulmonary bypass: required modifications of the TPN solution

Background electrolyte (BGE) systems with two coions are frequently used in capillary zone electrophoresis (CZE), especially in cases where indirect optical detection is employed. This study investigates the behavior of analytes, which possess mobilities intermediate to those of the BGE coions used. Besides the expected behavior, where the analytes provide either tailing or fronting zones, unusual behavior with extraordinary zone broadening is also observed in some cases. The explanation for this effect is that binary BGE systems involve, as a physico-chemical rule, a region where the analytes are forced by one coion to give tailing zones and simultaneously by the other coion to give fronting zones. The result of this "schizophrenic" situation is extraordinary zone broadening and deterioration of the detection record. A series of experiments is presented showing in a telling way the electromigration behavior of the discussed type of zones as well as the ways to remedy the deterioration of the peak shape by a mere slight changing of the quantitative composition of the BGE used.     

Resting respiratory tract dendritic cells preferentially stimulate T helper cell type 2 (Th2) responses and require obligatory cytokine signals for induction of Th1 immunity

Consistent with their role in host defense, mature dendritic cells (DCs) from central lymphoid organs preferentially prime for T helper cell type 1 (Th1)-polarized immunity. However, the "default" T helper response at mucosal surfaces demonstrates Th2 polarity, which is reflected in the cytokine profiles of activated T cells from mucosal lymph nodes. This study on rat respiratory tract DCs (RTDCs) provides an explanation for this paradox. We demonstrate that freshly isolated RTDCs are functionally immature as defined in vitro, being surface major histocompatibility complex (MHC) II lo, endocytosishi, and mixed lymphocyte reactionlo, and these cells produce mRNA encoding interleukin (IL)-10. After ovalbumin (OVA)-pulsing and adoptive transfer, freshly isolated RTDCs preferentially stimulated Th2-dependent OVA-specific immunoglobulin (Ig)G1 responses, and antigen-stimulated splenocytes from recipient animals produced IL-4 in vitro. However, preculture with granulocyte/macrophage colony stimulating factor increased their in vivo IgG priming capacity by 2-3 logs, inducing production of both Th1- and Th2-dependent IgG subclasses and high levels of IFN-gamma by antigen-stimulated splenocytes. Associated phenotypic changes included upregulation of surface MHC II and B7 expression and IL-12 p35 mRNA, and downregulation of endocytosis, MHC II processing- associated genes, and IL-10 mRNA expression. Full expression of IL-12 p40 required additional signals, such as tumor necrosis factor alpha or CD40 ligand. These results suggest that the observed Th2 polarity of the resting mucosal immune system may be an inherent property of the resident DC population, and furthermore that mobilization of Th1 immunity relies absolutely on the provision of appropriate microenvironmental costimuli.     

The primary aortoenteric fistula in The Netherlands--the unpublished cases

OBJECTIVE: Primary aortoenteric fistula is a rare disorder of which only four patients have been reported in the Dutch literature so far. The objective of our study was to obtain more realistic figures on the incidence of this condition, with data on the clinical presentation, diagnostic procedures, treatment and results in a group of patients not previously reported as "case histories". METHODS: A questionnaire was sent to all surgical clinics in The Netherlands. Out of 180 questionnaires, 102 have been returned reporting 27 patients to which data of eight others treated in our own institution were added. RESULTS: In all but one of these 29 patients the fistula was caused by an atherosclerotic aneurysm, the one exception being caused by an ingested cocktail pin. Gastrointestinal haemorrhage was the predominant symptom, being present in 28 of the patients, while the complete triad of haemorrhage, pain and a pulsating mass was found in only eight patients. Twenty-seven patients were treated with an in situ graft of which 14 are doing well at long term follow-up. CONCLUSIONS: Primary aortoenteric fistula is far more common than one would expect from the number of patients reported in literature. A high index of suspicion based on a complete physical examination remains the key to a correct diagnosis. Direct closure of the intestine and in situ grafting of the aorta is the treatment of first choice.     

Temperature dependence of macroscopic L-type calcium channel currents in single guinea pig ventricular myocytes

INTRODUCTION: Lowering temperature greatly reduces calcium influx through calcium channels. Studies on a number of tissues demonstrate that the peak inward current, ICa, exhibits Q10 values ranging from 1.8 to 3.5; however, it remains unclear which component(s) of calcium channel gating may give rise to this large temperature sensitivity. Components of gating that may affect channel availability include phosphorylation and changes in [Ca2+]i, processes that vary in pertinence depending on the channel examined. This study addresses this problem by examining the temperature sensitivity (from 34 degrees to 14 degrees C) of cardiac ICa under control conditions, during attenuation or activation of protein kinase A (PKA) activity, and when intracellular [Ca2+] has been elevated. METHODS AND RESULTS: ICa was studied using the whole cell configuration of the patch champ technique. In control, lowering temperature from 34 degrees to 24 degrees C resulted in a shift in the potential for maximum slope (Va) and the peak current (Ymax) toward more positive membrane potentials. The Q10 values for the decrease in Ymax and the macroscopic slope conductance (Gmax), which reflects the number of available channels, were 3.15 +/- 0.19 and 2.57 +/- 0.13, respectively. At 0 mV the Ca2+ current decayed biexponentially, and the two time constants (tau 1 and tau 2) showed Q10 values of 1.79 +/- 0.21 and 2.06 +/- 0.38, while their contribution to the total current (I1 and I2) showed a Q10 of 5.99 +/- 0.83 and 1.61 +/- 0.22. In myocytes loaded with inhibitors of the PKA cycle sufficient to inhibit the increase of ICa to 1 microM isoprenaline, the Q10 values for some of the kinetic parameters were increased with the Q10 for I1 increasing to 17.06 +/- 3.48. Stimulation of ICa by exposing myocytes to 1 microM isoprenaline reduced the temperature sensitivity of Ymax, Gmax and I1, yielding respective values of 2.00 +/- 0.18, 1.85 +/- 0.07, and 2.04 +/- 0.15. Raising [Ca2+]i to enhance Ca2+i-dependent inactivation, while affecting inactivation and activation kinetics, affected temperature sensitivity little compared to control. The Q10 for time to peak changed little under experimental conditions (2.3 to 2.4) CONCLUSIONS: Increasing the phosphorylated states of calcium channels, but not Ca2+i-dependent inactivation, reduces temperature sensitivity of certain gating parameters. The data suggest that the rate of the transitions between the unavailable and also between the various closed states are changed in the opposite direction to that induced by PKA-dependent phosphorylation. Processes, e.g., inhibitory mechanisms, may be involved to maintain channels in unavailable or "unphosphorylated" states, and it may be these that contribute to the high Q10 of macroscopic channel currents.     

A single-solenoid pulsed-magnet system for single-crystal scattering studies

We present a pulsed-magnet system that enables x-ray single-crystal diffraction in addition to powder and spectroscopic studies with the magnetic field applied on or close to the scattering plane. The apparatus consists of a single large-bore solenoid, cooled by liquid nitrogen. A second independent closed-cycle cryostat is used for cooling samples near liquid helium temperatures. Pulsed magnetic fields close to ~30 T with a zero-to-peak-field rise time of ~2.9 ms are generated by discharging a 40 kJ capacitor bank into the magnet coil. The unique characteristic of this instrument is the preservation of maximum scattering angle (~23.6°) on the entrance and exit sides of the magnet bore by virtue of a novel double-funnel insert. This instrument will facilitate x-ray diffraction and spectroscopic studies that are impractical, if not impossible, to perform using split-pair and narrow-opening solenoid magnets. Furthermore, it offers a practical solution for preserving optical access in future higher-field pulsed magnets.     

Recognition of depressed affect in hospitalized psychiatric patients: staff and patient perceptions

A comparison of self-report vs. observer rating of depressed mood in a heterogenous inpatient population revealed wide variations in concordance among diagnostic groups. Patients diagnosed as having Affective Psychosis and "Other' illnesses showed the highest correlation between four self-report scales and an observer rating scale. Patients with a diagnosis of depressive Neurosis showed only modest correlation, while Schizophrenics revealed no significant correlation, on these instruments, suggesting inconsistent communication of affect from Schizophrenic patients to observers. In contrast, when self-report scales were intercorrelated, patients in all four diagnostic categories showed highly significant correlations, indicating that they were consistently reporting their affective state on these instruments. The implications of these findings for future research as well as for practical clinical management are discussed.     

Distributed associative memory for use in scene analysis

A distributed associative memory system which is ideal for scene analysis is described. Recall of associated patterns using incomplete originals is made possible by the use of a distributed storage mechanism and a novel recall procedure. The memory is shown to store associations between patterns more efficiently than a conventional file store. The paper describes the memory structure, the recall process and its storage abilities, as well as an example of its implementation in hardware.