Fulminant Mycoplasma pneumoniae pneumonia.

The frequency of fulminant pneumonia due to Mycoplasma pneumoniae is relatively rare despite the high prevalence of Mycoplasma species infection in the general population. We recently encountered such a case and have reviewed the English-language literature on cases of M pneumoniae pneumonia that have resulted in respiratory failure or death. Due to host factors or on epidemiologic grounds, fulminant cases seem to be more common in young healthy adults, in males, and possibly in smokers among the 46 patients we found. An enhanced host cellular immune response may be responsible for the development of severe cases. A spectrum of small airways disease is characteristic, including cellular bronchiolitis and bronchiolitis obliterans with and without organizing pneumonia. Based largely on anecdotal experience, corticosteroid use may be salutary in patients with respiratory failure. For reasons that are not well known, the incidence of pulmonary thromboembolism is increased in fatal cases.     

Activation of the lutropin/choriogonadotropin receptor in MA-10 cells leads to the tyrosine phosphorylation of the focal adhesion kinase by a pathway that involves Src family kinases

We show that activation of the endogenous or recombinant lutropin/choriogonadotropin receptor (LHR) in mouse Leydig tumor cells (MA-10 cells) leads to the tyrosine phosphorylation of the focal adhesion kinase (FAK) and one of its substrates (paxillin). Using specific antibodies to the five tyrosine residues of FAK that become phosphorylated, we show that activation of the LHR increases the phosphorylation of Tyr576 and Tyr577, but it does not affect the phosphorylation of Tyr397, Tyr861, or Tyr925. Because FAK is a prominent substrate for the Src family of tyrosine kinases (SFKs) we tested for their involvement in the LHR-mediated phosphorylation of FAK-Tyr576. Src is not detectable in MA-10 cells, but two other prominent members of this family (Fyn and Yes) are present. The LHR-mediated phosphorylation of FAK-Tyr576 is readily inhibited by PP2 (a pharmacological inhibitor of SFKs) and by dominant-negative mutants of SKFs. Moreover, activation of the LHR in MA-10 cells results in the stimulation of the activity of Fyn and Yes, and overexpression of either of these two tyrosine kinases enhances the LHR-mediated phosphorylation of FAK-Tyr576. Studies involving activation of other G protein-coupled receptors, overexpression of the different Galpha-subunits, and the use of second messenger analogs suggest that the LHR-induced phosphorylation of FAK-Tyr576 in MA-10 cells is mediated by SFKs, and that this family of kinases is, in turn, independently or cooperatively activated by the LHR-induced stimulation of Gs and Gq/11-mediated pathways.     

Southern blot analysis of HLA-DP gene polymorphisms in Caucasoid rheumatoid arthritis (RA) patients and controls

Despite extensive analysis of the incidence ofHLA-DR andHLA-DQ allele frequencies in defined autoimmune disease groups, there is very little information available onHLA-DP allele frequencies. This is largely becauseHLA-DP typing has until recently been restricted to primed lymphocyte typing (PLT). However, allelic polymorphism of theHLA-DP subregion can now be studied by Southern blot analysis or genotyping withDPA1 andDPB1 probes. By direct counting of allele-specific DNA fragments, we have analyzed the frequencies of five majorDP genotypes (DPw1, DPw2, DPw3/6, DPw4, andDPw5), in a large number of Caucasoid rheumatoid arthritis (RA) patients (n=74), and controls (n=91). The predicted frequency ofDP alleles in both patient and control groups was comparable to PLT-determinedDP allele frequencies in normal Caucasoids. However, the gene frequency ofDPw4 was increased in the RA patients, with 51% of the patients studied scoring asDPw4, 4 homozygotes. With the exception of one possible combination (DPw5 andDRw6) in the controls, no significant linkage disequilibrium was detected betweenDP andDR alleles in either patient or control groups. Thus the prevalence ofDPw4 in the RA patients is independent of any disease association with theDR loci, and may represent a new class II association with RA.     

Critical Structure Sparing in Stereotactic Ablative Radiotherapy for Central Lung Lesions: Helical Tomotherapy vs. Volumetric Modulated Arc Therapy

Background

Helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) are both advanced techniques of delivering intensity-modulated radiotherapy (IMRT). Here, we conduct a study to compare HT and partial-arc VMAT in their ability to spare organs at risk (OARs) when stereotactic ablative radiotherapy (SABR) is delivered to treat centrally located early stage non-small-cell lung cancer or lung metastases.

Methods

12 patients with centrally located lung lesions were randomly chosen. HT, 2 & 8 arc (Smart Arc, Pinnacle v9.0) plans were generated to deliver 70 Gy in 10 fractions to the planning target volume (PTV). Target and OAR dose parameters were compared. Each technique’s ability to meet dose constraints was further investigated.

Results

HT and VMAT plans generated essentially equivalent PTV coverage and dose conformality indices, while a trend for improved dose homogeneity by increasing from 2 to 8 arcs was observed with VMAT. Increasing the number of arcs with VMAT also led to some improvement in OAR sparing. After normalizing to OAR dose constraints, HT was found to be superior to 2 or 8-arc VMAT for optimal OAR sparing (meeting all the dose constraints) (p = 0.0004). All dose constraints were met in HT plans. Increasing from 2 to 8 arcs could not help achieve optimal OAR sparing for 4 patients. 2/4 of them had 3 immediately adjacent structures.

Conclusion

HT appears to be superior to VMAT in OAR sparing mainly in cases which require conformal dose avoidance of multiple immediately adjacent OARs. For such cases, increasing the number of arcs in VMAT cannot significantly improve OAR sparing.     

Neuroleptics antagonize a calcium-activated potassium channel in airway smooth muscle

We examined the effect of neuroleptics on Ca-activated K channels from dog airway smooth muscle cells. Because these agents inhibit a variety of other Ca-mediated processes, it seemed possible that they might also inhibit Ca-activated K channels. In excised, inside-out patches, several neuroleptics potently and reversibly inhibited the K channel from the internal but not the external surface of the patch. Measurements of the effect on open probability and open- and closed-state durations support a simple kinetic model in which neuroleptics bind to and block the open channel. Inhibition by neuroleptics was moderately voltage dependent, with blockers less potent at hyperpolarizing voltages. The relationship between voltage and the dissociation constant for the blocker suggests that the binding site is one-third of the way across the channel's electrical field. Equilibrium dissociation constants for the drug-channel complex were: haloperidol, 1.0 +/- 0.1 microM; trifluoperazine, 1.4 +/- 0.1 microM; thioridazine, 2.4 +/- 0.1 microM; and chlorpromazine, 2.0 microM. This rank-order potency is different from their potency as calmodulin inhibitors, which suggests that neuroleptics bind to the channel rather than a calmodulin-channel complex.     

The Src Homology 2 Domain-Containing Adapter Protein B (SHB) Regulates Mouse Oocyte Maturation

SHB (Src homology 2 domain-containing adapter protein B) is involved in receptor tyrosine kinase signaling. Mice deficient in the Shb gene have been found to exhibit a transmission ratio distortion with respect to inheritance of the Shb null allele among offspring and this phenomenon was linked to female gamete production. Consequently, we postulated that Shb plays a role for oocyte biology and thus decided to investigate oocyte formation, meiotic maturation, and early embryo development in relation to absence of the Shb gene. Oogenesis was apparently accelerated judging from the stages of oocyte development on fetal day 18.5 and one week postnatally in Shb −/− mice; but in adulthood ovarian follicle maturation was impaired in these mice. Completion of meiosis I (first polar body extrusion) was less synchronized, with a fraction of oocytes showing premature polar body extrusion in the absence of Shb. In vitro fertilization of mature oocytes isolated from Shb +/+, +/− and −/− mice revealed impaired early embryo development in the −/− embryos. Moreover, the absence of Shb enhanced ERK (extracellular-signal regulated kinase) and RSK (ribosomal S6 kinase) signaling in oocytes and these effects were paralleled by an increased ribosomal protein S6 phosphorylation and activation. It is concluded that SHB regulates normal oocyte and follicle development and that perturbation of SHB signaling causes defective meiosis I and early embryo development.     

Does fitness level modulate the cardiovascular hemodynamic response to exercise?

Subjects with greater aerobic fitness demonstrate better diastolic compliance at rest, but whether fitness modulates exercise cardiac compliance and cardiac filling pressures remains to be determined. On the basis of maximal oxygen consumption (VO2max), healthy male subjects were categorized into either low (LO: VO2max=43+/-6 ml.kg-1.min-1; n=3) or high (HI: VO2max=60+/-3 ml.kg-1.min-1; n=5) aerobic power. Subjects performed incremental cycle exercise to 90% Vo(2max). Right atrial (RAP) and pulmonary artery wedge (PAWP) pressures were measured, and left ventricular (LV) transmural filling pressure (TMFP=PAWP-RAP) was calculated. Cardiac output (CO) and stroke volume (SV) were determined by direct Fick, and LV end-diastolic volume (EDV) was estimated from echocardiographic fractional area change and Fick SV. There were no between-group differences for any measure at rest. At a submaximal workload of 150 W, PAWP and TMFP were higher (P<0.05) in LO compared with HI (12 vs. 8 mmHg, and 9 vs. 4 mmHg, respectively). At peak exercise, CO, SV, and EDV were lower in LO (P<0.05). RAP was not different at peak exercise, but PAWP (23 vs. 15 mmHg) and TMFP (12 vs. 6 mmHg) were higher in LO (P<0.05). Compared with less fit subjects, subjects with greater aerobic fitness demonstrated lower LV filling pressures during exercise, whereas SV and EDV were either similar (submaximal exercise) or higher (peak exercise), suggesting superior diastolic function and compliance.     

Regulation of Gi by the CB1 cannabinoid receptor C-terminal juxtamembrane region: structural requirements determined by peptide analysis

A CB1 cannabinoid receptor peptide fragment from the C-terminal juxtamembrane region autonomously inhibits adenylyl cyclase activity in a neuroblastoma membrane preparation. The cannabinoid receptor antagonist, SR141716A, failed to block the response. The peptide was able to evoke the response in membranes from Chinese hamster ovary (CHO) cells that do not express the CB1 receptor. These studies are consistent with a direct activation of Gi by the peptide. To test the importance of a BXBXXB sequence, Lys403 was acetylated, resulting in a peptide having similar affinity but reduced efficacy. N-Terminal truncation of Arg401 resulted in a 6-fold loss of affinity, which was not further reduced by sequential truncation of up to the first seven amino acids, four of which are charged. N-Terminal-truncated peptides exhibited maximal activity, suggesting that Gi activation can be conferred by the remaining amino acids. Truncation of the C-terminal Glu417 or substitution of Glu417 by a Leu or of Arg401 by a Norleucine reduced activity at 100 microM. The C-terminal juxtamembrane peptide was constrained to a loop peptide by placement of Cys residues at both terminals and disulfide coupling. This modification reduced the affinity 3-fold but yielded near-maximal efficacy. Blocking the Cys termini resulted in a loss of efficacy. Circular dichroism spectropolarimetry revealed that all C-terminal juxtamembrane peptide analogues exist in a random coil conformation in an aqueous environment. A hydrophobic environment (trifluoroethanol) failed to induce alpha-helix formation in the C-terminal juxtamembrane peptide but did so in less active peptides. The anionic detergent sodium dodecyl sulfate induced alpha-helix formation in all analogues except the loop peptide, where it induces a left-handed PII conformation. It is concluded that alpha-helix formation is not required for Gi activation.     

An association between the acute phase response and patterns of antigen induced T cell proliferation in juvenile idiopathic arthritis

The aim of this research was to determine whether all memory T cells have the same propensity to migrate to the joint in patients with juvenile idiopathic arthritis. Paired synovial fluid and peripheral blood mononuclear cell proliferative responses to a panel of antigens were measured and the results correlated with a detailed set of laboratory and clinical data from 39 patients with juvenile idiopathic arthritis. Two distinct patterns of proliferative response were found in the majority of patients: a diverse pattern, in which synovial fluid responses were greater than peripheral blood responses for all antigens tested; and a restricted pattern, in which peripheral blood responses to some antigens were more vigorous than those in the synovial fluid compartment. The diverse pattern was generally found in patients with a high acute phase response, whereas patients without elevated acute phase proteins were more likely to demonstrate a restricted pattern. We propose that an association between the synovial fluid T cell repertoire and the acute phase response suggests that proinflammatory cytokines may influence recruitment of memory T cells to an inflammatory site, independent of their antigen specificity. Additionally, increased responses to enteric bacteria and the presence of αEβ7 T cells in synovial fluid may reflect accumulation of gut associated T cells in the synovial compartment, even in the absence of an elevated acute phase response. This is the first report of an association between the acute phase response and the T cell population recruited to an inflammatory site.