Arachidonic acid, but not its metabolites, is essential for FcgammaR-stimulated intracellular killing of Staphylococcus aureus by human monocytes

Since arachidonic acid (AA) production by phospholipase A2 (PLA2) is essential for the Fcgamma receptor (FcgammaR)-mediated respiratory burst and phagocytosis of opsonized erythrocytes by monocytes and macrophages, we focused in this study on the role of AA and its metabolites in the FcgammaR-stimulated intracellular killing of Staphylococcus aureus by human monocytes. The results revealed that the PLA2 inhibitors, but not inhibitors of cyclo-oxygenase and lipoxygenase, markedly suppressed the FcgammaR-mediated killing process. The production of O-2 by monocytes upon FcgammaR cross-linking was inhibited by 4-bromophenacyl bromide in a dose-dependent fashion, indicating that inhibition of PLA2 activity impairs the oxygen-dependent bactericidal mechanisms of monocytes, which could be partially restored by addition of exogenous AA and docosahexaenoic acid, but not myristic acid. These polyunsaturated fatty acids, but not myristic acid, stimulated the intracellular killing of S. aureus by monocytes, although not as effectively as FcgammaR cross-linking. Furthermore, FcgammaR cross-linking stimulated the release of AA from monocytes. Studies with selective inhibitors revealed that the FcgammaR-mediated activation of PLA2 is dependent on Ca2+ and tyrosine kinase activity. Together these results indicate a key role for PLA2/AA, but not its major metabolites, in mediating the FcgammaR-stimulated intracellular killing of S. aureus by monocytes.     

Incidence of delirium and associated mortality in hematopoietic stem cell transplantation patients.

Delirium has been associated with a high risk of mortality in medical patients. Despite the high incidence of delirium in patients who undergo hemapoietic stem cell transplantation (HSCT), delirium as a risk factor for death has not been examined in this population. Thirty adult patients undergoing HSCT who were admitted to the University of Iowa Blood and Marrow Transplantation Program inpatient unit were assessed prospectively from 1 to 2 weeks before transplantation, throughout their inpatient stay, and at 100 days after transplantation. The Delirium Rating Scale and Memorial Delirium Assessment Scale were used twice weekly during the inpatient period to assess delirium severity and occurence. Patients' self-reports of medical history, computerized medical records, and neuropsychological and psychiatric assessments were used to identify pretransplantation risk factors. The incidence of delirium (Delirium Rating Scale score >12 or Memorial Delirium Assessment Scale score >or=8) was 43% and occurred with highest frequency in the first 2 weeks after transplantion. The presence of delirium at any point during hospitalization after transplantation and transplant type (allogeneic) were highly predictive of mortality (p < .0005; odds ratios, 14.0 and 14.4). In conclusion, this study highlights the importance of monitoring for delirium during the acute recovery period after transplantation and suggests that early or even prophylactic treatment for delirium should be studied. Studies to determine the factors that connect delerium soon after transplantation to mortality are highly warranted.     

Enhanced viral clearance in interleukin-18 gene-deficient mice after pulmonary infection with influenza A virus

T helper 1 driven immune responses facilitate host defence during viral infections. Because interleukin-18 (IL-18) mediates T helper 1 driven immune responses, and since mature IL-18 is up-regulated in human macrophages after influenza virus infection in vitro, it has been suggested that IL-18 plays an important role in the immune response to influenza. To determine the role of IL-18 in respiratory tract infection with influenza, IL-18 gene-deficient (IL-18(-/-)) and normal wildtype mice were intranasally inoculated with influenza A virus. Influenza resulted in an increase in constitutively expressed IL-18 in the lungs of wildtype mice. The clearance of influenza A was inhibited by IL-18, as indicated by reduced viral loads on day 8 and day 12 after infection in IL-18(-/-) mice. This enhanced viral clearance correlated with increased CD4(+) T-cell activation in the lungs as reflected by CD69 expression on the cell surface. Surprisingly, interferon-gamma (IFN-gamma) levels were similar in the lungs of IL-18(-/-) mice and wildtype mice. Intracellular IFN-gamma staining revealed similar expression levels in lung-derived natural killer cells, CD4(+) and CD8(+) T cells, indicating that IFN-gamma production is IL-18-independent during influenza virus infection. Tumour necrosis factor-alpha production by CD4(+) T cells was significantly lower in IL-18(-/-) mice than in wildtype mice. Our data indicate that endogenous IL-18 impairs viral clearance during influenza A infection.     

Estimation of the genetic contribution of presenilin-1 and -2 mutations in a population-based study of presenile Alzheimer disease

Two closely related genes, the presenilins ( PS ), located at chromosomes 14q24.3 and 1q42.1, have been identified for autosomal dominant Alzheimer disease (AD) with onset age below 65 years (presenile AD). We performed a systematic mutation analysis of all coding and 5'-non-coding exons of PS -1 and PS -2 in a population-based epidemiological series of 101 unrelated familial and sporadic presenile AD cases. The familial cases included 10 patients of autosomal dominant AD families sampled for linkage analysis studies. In all patients mutations in the amyloid precursor protein gene ( APP ) had previously been excluded. Four different PS -1 missense mutations were identified in six familial cases, two of which where autosomal dominant cases. Three mutations resulted in onset ages above 55 years, with one segregating in an autosomal dominant family with mean onset age 64 years (range 50-78 years). One PS -2 mutation was identified in a sporadic case with onset age 62 years. Our mutation data provided estimates for PS -1 and PS -2 mutation frequencies in presenile AD of 6 and 1% respectively. When family history was accounted for mutation frequencies for PS -1 were 9% in familial cases and 18% in autosomal dominant cases. Further, polymorphisms were detected in the promoter and the 5'-non-coding region of PS -1 and in intronic and exonic sequences of PS -2 that will be useful in genetic association studies.      

Functional polymorphism of IgG FcRII (CD32) on human neutrophils.

In this study we demonstrate that Fc gamma RII on polymorphonuclear cells (PMN) (i) mediates binding of immune complexes, and (ii) is polymorphic, similar to the polymorphism described for monocytes and platelets. This was demonstrated in an adherence assay of PMN to activated human umbilical vein endothelial cells (HUVEC). Precoating of activated HUVEC with a mouse IgG1 monoclonal antibody (mAb) ENA1, which is highly reactive with activated HUVEC, caused an enhanced adhesion in 11 of 15 experiments using PMN from different donors. Enhanced adhesion of the PMN corresponded with expression of a high-responder (HR) Fc gamma RII on monocytes isolated from the same donor, as identified by anti-CD3-induced T-cell proliferation. These data led to the conclusion that Fc gamma RII on PMN is polymorphic. This conclusion was, furthermore, supported by immunofluorescence (IF) studies using a new mAb 41H16, which selectively reacts with the HR allotype of Fc gamma RII.     

Cloning and functional characterization of a novel connexin expressed in somites of Xenopus laevis.

Connexin-containing gap junctions play an essential role in vertebrate development. More than 20 connexin isoforms have been identified in mammals. However, the number identified in Xenopus trails with only six isoforms described. Here, identification of a new connexin isoform from Xenopus laevis is described. Connexin40.4 was found by screening expressed sequence tag databases and carrying out polymerase chain reaction on genomic DNA. This new connexin has limited amino acid identity with mammalian (<50%) connexins, but conservation is higher (approximately 62%) with fish. During Xenopus laevis development, connexin40.4 was first expressed after the mid-blastula transition. There was prominent expression in the presomitic paraxial mesoderm and later in the developing somites. In adult frogs, expression was detected in kidney and stomach as well as in brain, heart, and skeletal muscle. Ectopic expression of connexin40.4 in HEK293 cells, resulted in formation of gap junction like structures at the cell interfaces. Similar ectopic expression in neural N2A cells resulted in functional electrical coupling, displaying mild, asymmetric voltage dependence. We thus cloned a novel connexin from Xenopus laevis, strongly expressed in developing somites, with no apparent orthologue in mammals.     

L1 knockout mice show dilated ventricles, vermis hypoplasia and impaired exploration patterns

L1 is a neural cell adhesion molecule mainly involved in axon guidance and neuronal migration during brain development. Mutations in the human L1 gene give rise to a complex clinical picture, with mental retardation, neurologic abnormalities and a variable degree of hydrocephalus. Recently, a transgenic mouse model with a targeted null mutation in the L1 gene was generated. These knockout (KO) mice show hypoplasia of the corticospinal tract. Here we have performed further studies of these KO mice including magnetic resonance imaging of the brain, neuropathological analysis and behavioral testing. The ventricular system was shown to be abnormal with dilatation of the lateral ventricles and the 4th ventricle, and an altered shape of the Sylvius aqueduct. Additionally, the cerebellar vermis of the KO mice is hypoplastic. Their exploratory behavior is characterized by stereotype peripheral circling reminiscent of that of rodents with induced cerebellar lesions.      

A randomised,double-blind comparison of milnacipran and imipramine in the treatment of depression

This multicentre, double-blind, randomised trial in 109 patients compared the efficacy and tolerance of the novel selective serotonin and noradrenaline reuptake inhibitor (SNRI) antidepressant milnacipran (50 mg twice daily, n=53) with the established tricyclic agent imipramine (75 mg twice daily, n=56) over a period of 6 weeks, in patients with major depression (Montgomery-Asberg depression rating score (MADRS) > or =25). Initiation of antidepressant medication was conducted during a 2-week period of hospitalisation, after a 3- to 7-day washout period. Concomitant psychiatric medication was limited to lorazepam, cyamemazine, chloral hydrate and long-term uncomplicated lithium therapy. Assessment for efficacy using the MADRS and Hamilton rating scales of depression, a visual analogue scale and global evaluation revealed both agents to be highly effective (P=0.0001) in this group of patients. Milnacipran was found to be of similar efficacy to imipramine. Tolerance, assessed by physiological and biochemical examinations with routine inventory and spontaneous report of adverse events, revealed a clear advantage for milnacipran. The incidence of anticholinergic events with milnacipran was about half that with imipramine and the overall incidence of adverse events by either reporting method was markedly lower with milnacipran than with imipramine. Furthermore, the patient drop-out rate with imipramine was double that experienced with milnacipran. Milnacipran appears to possess equal antidepressant efficacy to imipramine but with markedly superior tolerance. Therefore, milnacipran constitutes an important new treatment option in major depression.     

Autoimmunity to sperm antigens in vasectomized men.

Sera from vasectomized men were tested for the presence of antibodies directed against sperm antigens. A high percentage (about 55%) of the vasectomized men developed agglutinating antibodies. A lower percentage (22%) also developed low titres of antibodies to human protamine, as detected in the indirect IFT on swollen sperm heads and 22% developed cytotoxic antibodies. A correlation was found between the presence of anti-protamine antibodies and the presence of agglutinating and of cytotoxic antibodies. This correlation, and also the fact that they developed after vasectomy, indicates that the formation of antibodies against human protamine is a result of an autoimmune response to spermatozoa. The indirect IFT was also performed on 'normal' unswollen spermatozoa. All the sera were positive at least on one of the sperm antigens located in the acrosome, equator, or post-nuclear region, but no increase nor decrease in titre was found after vasectomy.