The requirements for G1 checkpoint progression of Trypanosoma brucei S 427 clone 1.

Trypanosoma brucei S 427 clone 1 accumulated in G1 when incubated under growth-limiting conditions. Further incubation of the G1-restricted organisms in medium containing 10% fetal bovine serum (FBS) and 2 mM hydroxyurea resulted in their reversible arrest after a G1 checkpoint beyond which serum was not required for progress into and through S. Progress of the G1-restricted T. brucei through the G1 checkpoint was linear and required continuous incubation with exogenous serum growth factors. These were principally low and high density lipoproteins; both lipoproteins triggered G1 progression in a dose- and time-dependent manner whilst their removal by immunoaffinity chromatography severely reduced the capacity of FBS to stimulate G1 progression. Serum-induced progress of T. brucei through G1 was Ca(2+)-independent, but required gene transcription, protein synthesis, and continuous kinase activity that was inhibited by tyrphostin 51 and DAPH 1 which typically inhibit epidermal growth factor receptor protein tyrosine kinase activity. The tyrphostin 51-sensitive catalytic activity was not required for T. brucei protein synthesis, glycolysis, or S phase progression but was required for tyrosine phosphorylation of several polypeptides, none of which was specifically associated with serum-induced G1 progression.

Effect of gramicidin on methanogenesis by various methanogenic bacteria.

Methanogenesis by Methanobacterium thermoautotrophicum strains was extremely sensitive to gramicidin, total inhibition being observed at 0.2 mug/ml. In contrast, methane synthesis by Methanococcus voltae, Methanogenium marisnigri, Methanosarcina mazei, and Methanospirillum hungatei were resistant to the highest concentrations of gramicidin tested (40 mug/ml), although spheroplasts of Methanospirillum hungatei were extremely sensitive. Other species tested showed intermediate sensitivity to gramicidin, methanogenesis inhibition occurring at 4 to 20 mug/ml.

Monoclonal anti-B produced by the immunization of mice with soluble salivary glycoproteins.

IgM and IgG mouse monoclonal antibodies with specificity for the blood group B determinant have been produced by immunization of mice with a partially purified salivary glycoprotein. These antibodies have been characterized and one of the IgM antibodies showed potential as a grouping reagent. The ready availability of these salivary blood group substances offers the potential to produce a wide range of related monoclonal antibodies.

Mouse monoclonal anti-N. II. Physicochemical characterization and assessment for routine blood grouping.

The precise physicochemical conditions under which two examples of mouse monoclonal anti-N can be used as blood grouping reagents have been defined. The antibodies were shown to belong to the IgG1 and IgG2b subclasses respectively and both reacted within discrete ranges of temperature and pH with optimal reactions occurring at 20 degrees C or less and pH 8.5. Under these conditions and at concentrations of 2-3 micrograms/ml, the antibodies were used, in parallel with conventional polyclonal antisera, to type a series of random blood donors. The results obtained with one of the monoclonal antibodies and the polyclonal reagents were in perfect agreement and the monoclonal antibody was judged to have considerable potential as an N-grouping reagent.

Mouse monoclonal anti-N. I. Production and serological characterization.

Two examples of mouse monoclonal anti-N are described. The antibodies were derived from mice immunized with sialoglycoprotein extracts of group O MM ss erythrocyte membranes and the probable stimulus for immunization was glycophorin B associated N-antigen. Both antibodies reacted as direct agglutinins but appeared to recognize different epitopes with one having a greater dependence on sialic acid. The antibodies could prove to be valuable alternatives to those reagents used currently for N-blood grouping.

Recurrent pulmonary thromboembolism presenting with cardiac arrhythmias.

Pulmonary emboli seldom recur, and when recurrence does occur it is not associated with permanent sequelae unless there is progressive pulmonary arterial hypertension. Five patients with clinical and perfusion lung scan evidence of recurrent pulmonary embolism presented with abnormal cardiac rhythms without evidence of progressive pulmonary hypertension. Twenty-four-hour ambulatory electrocardiographic monitoring was valuable in diagnosis and in assessing the effectiveness of treatment. Although palpitation was the main complaint, other symptoms included tiredness, mild exertional dyspnoea, and chest discomfort unrelated to effort. Symptomatic improvement coincided with objective evidence of improvement from repeat lung scans and 24-hour ECG records. Antiarrhythmic agents controlled the arrhythmias but were subsequently withdrawn without the return of symptoms. Four of the five patients continued to take anticoagulants for two years. We believe that these five patients represent a group of patients with recurrent pulmonary emboli and a recognisable clinical picture dominated by arrhythmias unrelated to progressive pulmonary arterial hypertension. Long-term anticoagulant treatment was associated with clinical improvement.