Kinetics of reappearance of suppressed allotypes in multiheterozygous rabbits (author's transl)

Heterozygous rabbits of genotype a1n81f73g74/a2n82f71g75 were injected at birth with anti-al antiserum. The suppression of the VHa1 allotype resulted in a similar concommitant suppression of the constant region allotypes coded by genes of the same allogroup as a1. After 3 to 4 months the suppressed allotypes were re-expressed in measurable amounts. At 6 months in the 3 suppressed animals, the proportion of suppressed allotypes (S) to the non-suppressed ones (NS) was higher among colostrum and serum IgA (50% S, 50% NS) than among IgG for IgM. Among these two latter classes the proportion S/(S + NS) remained low (about 15% S, 85% NS) over an 18 month period in two out of three suppressed rabbits. In the third one, the proportion S/(S + NS) among IgG molecules increased to increasing concentration of S allotypes is not compensated by a decrease in concentrations of NS allotypes. The study of these phenomena could bring a better understanding of mechanisms involved in regulation of Ig synthesis and in allotype suppression.     

Relationships between soil urease activity and other properties of some tropical wetland rice soils

Ten Philippine wetland rice soils differing widely in pH, texture and organic matter were studied to determine relationships between urease activity and other soil properties. Simple correlation analyses of urease activity with soil properties indicated that urease activity was correlated highly significantly with total N (r = 0.91)^**, and organic C (r = 0.89^**) but was not significantly correlated with CEC, Clay, pH active Fe or active Mn content. From multiple regression analyses it was observed that organic matter content of soils measured by organic C and total N accounted for most of the variation in urease activity.     

Determination of antibiotics in different water compartments via liquid chromatography-electrospray tandem mass spectrometry

The mechanisms by which BCG exerts its antitumour activity remain unclear. Attachment of BCG to the bladder via FN has been shown to be an important step in initiating its antitumorigenic activity. The mechanism(s) by which BCG operates requires LAK cells, BCG-activated killer cells, T lymphocytes (CD4) helper cells and CD8 suppressor/cytotoxic cells) and monocytes. The optimal route of administration is intravesical. The efficacy of a BCG vaccine depends on the viability, dose and strain. Differences in efficacy and side-effects have not been shown between different strains. Low-dose regimens successfully protect from recurrences, with fewer side-effects. The initial schedule of BCG is a course of six instillations in 6 weeks; when the patient fails this course, two possibilities arise. The first is maintenance therapy; response rates improve but there is more local and systemic toxicity. The second is a further 6-week course, and this seems most useful in those with a sustained response to the initial treatment. The clinical response to BCG therapy can be monitored using cytokine measurements or p53 determinations. Toxicity remains a major problem in BCG treatment and triple antituberculosis combination therapy should be given for 3 months in those with severe systemic side-effects. The use of prophylactic isoniazid is not recommend to decrease side-effects. The clinical results of BCG have been good, with success rates of 58-100%, with a minimal follow-up of one year in prophylaxis. BCG seems superior to intravesical therapy, but at the cost of inducing more adverse effects. BCG is not indicated for low- and intermediate-risk patients, in whom chemotherapy is the first choice. BCG can also be used to eliminate tumour after an incomplete TUR, or in patients who are unfit for surgery, with a 60-70% success rate. The primary and best treatment for CIS is intravesical BCG; encouraging results have been reported, with success rate of 42-83% after a minimal follow-up of one year. Although currently BCG seems to be the choice for high-risk superficial TCC, many questions remain unanswered, especially about the mechanism(s) of action, the optimal dose and clinical schedule.     

A room-based diagnostic imaging system for measurement of patient setup

A room-based diagnostic x-ray imaging system for routine measurement of radiotherapy patient orientation has been developed. The system consists of a pair of room-mounted x-ray tubes and a portable imager consisting of an orthogonal pair of phosphor screens, a mirror/lens system, a CCD camera, and computer software for comparing images of the patient to reference images. Orthogonal pairs of images can be acquired quickly and with relatively little exposure, allowing correction of patient setup on a daily basis. This could limit patient setup error to the uncertainty in the measurement and repositioning processes, a potentially significant improvement over the present standard.     

Direct percutaneous transluminal coronary angioplasty in acute myocardial infarction. Predictors of short-term outcome and the impact of coronary stenting. Study Group of The Arbeitsgemeinschaft Leitender Kardiologischer Krankenhaus?rzte (ALKK)

BACKGROUND: Direct percutaneous transluminal coronary angioplasty (PTCA) is widely accepted in the treatment of acute myocardial infarction since excellent results had been reported from several small randomized trials. Less favourable results were observed in large-scale registries. In particular, the use of stents in acute myocardial infarction has become common practice without documented evidence of clinical efficacy. METHODS: Data were analysed from a registry of all consecutive percutaneous transluminal coronary angioplasty procedures from 62 centres in Germany, including 2331 direct percutaneous transluminal coronary angioplasty in acute myocardial infarction from July 1994 to April 1997. RESULTS: The overall angiographic success rate of percutaneous transluminal coronary angioplasty, defined as complete antegrade perfusion of the infarct vessel, was 87%. In-hospital mortality was 11.2%. The most important predictor of death was the presence of cardiogenic shock in 15% of patients, of whom 52% died. Mortality in patients without shock was 3.9%. Failed percutaneous transluminal coronary angioplasty was associated with a mortality of 36%. Further independent predictors of death were older age, multivessel disease, and anterior myocardial infarction. Stents were used in 4.1% of the procedures in 1994, increasing to 53% in 1997. However, this was not accompanied by improved clinical outcome. Mortality with coronary stenting was 9.9% vs 11.6% without stents (ns). CONCLUSIONS: Direct percutaneous transluminal coronary angioplasty is a valuable treatment strategy in acute myocardial infarction, although the results are less exceptional than reported from some highly specialized centres. Failed percutaneous transluminal coronary angioplasty seems to be harmful, thus outweighing much of the benefit from successful procedures. Stents did not improve the clinical outcome significantly, despite technically successful placement in 98%. Mortality from cardiogenic shock continues to be excessively high despite direct PTCA.     

Direct exposure to gallium arsenide upregulates costimulatory activity of murine macrophages

Gallium arsenide (GaAs) is an intermetallic semiconductor compound used in the electronics industry. Acute exposure of animals to GaAs systemically suppresses several immune functions while paradoxically causing inflammation at the exposure site. We investigated the effect of GaAs on costimulatory activity of murine peritoneal macrophages, 5 days after ip exposure. Costimulation by macrophages was determined by activation of CD4(+) helper T cell hybridomas to secrete interleukin-2 in the presence of immobilized monoclonal anti-CD3 antibody. Both peritoneal exudate cells (PEC) and resident peritoneal cells exposed to GaAs provided greater costimulation to the T cells than vehicle control cells. Resident peritoneal cells exposed to GaAs were also more efficient than latex bead-exposed cells, indicating that phagocytosis alone did not cause the GaAs effect. Double immunofluorescence staining and flow cytometric analysis revealed that GaAs-exposed PEC had increased cell surface expression of costimulatory B7-1 and B7-2 molecules and intracellular adhesion molecule-1 (ICAM-1) compared to controls. In addition to these molecules, resident peritoneal macrophages exposed to GaAs also expressed significantly higher levels of heat-stable antigen (HSA). Monoclonal antibodies specific for these costimulatory molecules significantly inhibited T cell activation, demonstrating that the molecules on GaAs-exposed cells were functional. In contrast, GaAs did not upregulate costimulatory molecules on splenic macrophages. These findings suggest that direct GaAs exposure improves macrophage costimulatory activity, possibly by activating the cells, which may contribute to respiratory inflammation caused by inhalation of GaAs particles.     

An assessment of the reliability of in-service gappedsilicon-carbide distribution surge arresters

Although gapped silicon carbide arresters are no longer purchased by electricity authorities, they still form the majority of the very large number of distribution arresters in service in Australia and many other countries. Most of the arresters of this type are now over ten years old and many are much older. So the question must be asked-what is to be done with this ageing and outdated class of arresters? Extensive Australian studies in the 1960s had revealed that internal degradation resulting from inadequate seals was the predominant cause of failure of gapped silicon carbide arresters. This paper describes the results of a recent investigation. Electrical testing showed that after about 10 years of service, there is a marked upturn in the number of arresters with unsatisfactory insulation resistance, and after about 13 years of service, a marked upturn in the number of arresters with reduced power frequency sparkover level. Inspection of the internal components of dismantled arresters confirmed that the likelihood of significant degradation increased markedly with years of service, and was evident in almost 75% of arresters with 13 years or more of service. The authors therefore recommend that all gapped silicon carbide arresters with 13 or more years of service be progressively replaced by modern metal oxide arresters