Reduced formation of phosphatidic acid upon B-cell receptor triggering of mouse B-lymphocytes lacking Bruton's tyrosine kinase

Btk deficient (BtkM) mouse B-lymphocytes do not proliferate when stimulated with anti-immunoglobulin (anti-Ig) antibodies. In order to characterize the molecular basis of this unresponsiveness we have compared early signal transduction pathways triggered by ligating the B cell antigen receptor (BCR) of purified resting B cells from normal C57BL/6 (wild-type) and BtkM mice on C57BL/6 background. BCR-induced signalling events that occur during the first few minutes of activation, such as bulk tyrosine phosphorylations, mitogen-activated protein kinase (MAPK) activation, PI3-kinase dependent PKB/Akt kinase phosphorylation/activation and PLCgamma2 tyrosine phosphorylation are comparable in wild type and BtkM B cells. However, the initial extracellular calcium influx is reduced and the BCR-induced accumulation of phosphatidic acid (PA) display a more transient profile in the BtkM cells. BCR ligation did not induce detectable phosphatidyl-choline PLD activity, suggesting that the reduced PA is owing to a reduction in the phospho-inositide hydrolysis. These findings further support the notion that the proliferative defect of Btk deficient mouse B cells in response to anti-immunoglobulin stimulation stems from a failure to sustain phospholipase-dependent signalling.

Bruton's tyrosine-kinase-deficient murine B lymphocytes fail to enter S phase when stimulated with anti-immunoglobulin plus interleukin-4

One of the earliest recognized defects of B cells carrying the xid mutation in the gene encoding for Bruton's tyrosine kinase (Btk) was their inability to proliferate in response to anti-immunoglobulin plus interleukin (IL)-4 stimulation. Previous attempts to define the stage at which this proliferative block occurred using xid B cells provided dissimilar results. We decided to reinvestigate this question using B cells from C57BL/6-Btk-protein-deficient (BtkM) mice. Upon stimulation with anti-IgM and IL-4, BtkM cells increase in size and up-regulate early activation markers such as CD69 and B7-2, however, they do not progress into the cell cycle further than a very early G1 stage. They down-regulate the cyclin-dependent kinase (cdk) inhibitor p27 to some extent but fail to up-regulate the G1-phase cyclins D2 and E and the retinoblastoma protein (pRb) remains hypo-phosphorylated. While approximately 25% of the wild-type cells enter S phase after 36 h stimulation, only 1% of the BtkM cells do so. The proliferative responsiveness of the BtkM cells is restored when the phorbol ester phorbol 12,13-di-butyrate (PDBu) is added to the anti-IgM plus IL-4 cultures. Collectively, our data demonstrate that a dramatically reduced frequency of responsive cells underlies the low proliferation of anti-IgM plus IL-4-stimulated Btk-deficient B cells and point towards an early block in the G1 phase due to inadequate activation of a pathway that regulates PKC activation.

Randomized comparison of aztreonam and cefuroxime in gram-negative upper urinary tract infections

In order to evaluate the efficacy and safety of aztreonam in hospitalized patients with upper urinary tract infections (UTI), a comparative clinical study with cefuroxime was performed. 62/60% (aztreonam/cefuroxime) of the patients had a complicating factor, mostly obstructive uropathy. I.v. bolus injections were used at a dose of 1 g aztreonam or 1.5 g cefuroxime t.i.d., for a mean of 8.2 days (range: five to 14 days) except in patients with bacteraemia, who received a mean of 10.3 days (range: seven to 13 days) of therapy. 89% of the patients treated with aztreonam and 87% of those who received cefuroxime showed clinical cure and the bacteriological cure rate at one week post-therapy was 70% and 73% in the respective groups. The relapse/reinfection rate was high with both drugs; bacteriological cure at one month post-therapy was only 43% after aztreonam and 40% after cefuroxime. This suggests that these infections may need longer treatment times. Superinfections, mostly asymptomatic urinary colonization, occurred in 7% and 3%, respectively, and adverse reactions in 23% and 12%, respectively, of the patients treated with aztreonam or cefuroxime, the majority being mild and reversible and only 3% and 3%, respectively, requiring discontinuation of the therapy. The t 1/2 for aztreonam following a 1 g i.v. bolus was 2.0 h in six patients with creatinine clearance above 80 ml/min and 3.0 h in seven patients with creatinine clearance between 35-75 ml/min.

Outbreak of giardiasis: effect of a new antiflagellate drug, tinidazole

We describe here an intensive outbreak of mostly symptomatic (90%) Giardia lamblia infestation in a Swedish student group visiting the U.S.S.R. A new antiflagellate drug, ethyl (2-(2-methyl-5-nitro-1-imidazolyl)ethyl) sulphone, tinidazole, Pfizer, was given in a dosage of 150 mg twice daily for seven days to 10 healthy volunteers and to 24 students infested with G. lamblia. The drug was found to be effective in curing giardiasis and in eradicating G. lamblia from the intestinal tract. All the students with symptomatic giardia infestation became free from gastrointestinal disturbance, usually soon after treatment was started. None of the 24 students had G. lamblia in their stools after tinidazole treatment was discontinued or at follow-up. No side effects of the drug were seen and all of the subjects tolerated it very well.