Imaging and manipulating molecules on a zeolite surface with an atomic force microscope.

The adsorption of neutral molecules and ions on the surfaces of zeolites was observed in real time with an atomic force microscope (AFM). Direct imaging of the surface of the zeolite clinoptilolite was possible by using a diluted tert-butyl ammonium chloride solution as a medium. Images of the crystal in different liquids revealed that molecules could be bound to the surface in different ways; neutral molecules of tert-butanol formed an ordered array, whereas tert-butyl ammonium ions formed clusters. These absorbed molecules were not rearranged by the AFM tip when used in an imaging mode. However, when a sufficiently large force was applied, the tip of the AFM could rearrange the tert-butyl ammonium ions on the zeolite surface. This demonstration of molecular manipulation suggests new applications, including biosensors and lithography.

Comparison of prostatic acid phosphatase assays.

A prospective study compared five different assays for serum prostatic acid phosphatase in the detection of carcinoma of the prostate gland. The assays included two radioimmunoassay procedures, one counterimmunoelectrophoresis procedure, and an enzymatic procedure using alpha-naphthol phosphate substrate with and without sodium tartrate inhibition. The patients' hospital records were reviewed, as were all available surgical histology slides. The patients were divided into four groups: prostatic carcinoma, benign prostatic hypertrophy, other carcinomas (besides prostatic carcinoma), and no related disease states (that would be expected to give elevated acid phosphatase levels). The results were analyzed with respect to sensitivity, specificity, predictive value of a positive result, predictive value of a negative result, and efficiency of the assays.

Severe combined immunodeficiency with thymic mast cell hyperplasia.

The autopsy finding on an infant with severe combined immunodeficiency was marked thymic mast cell hyperplasia. The clinical immune status showed a deficit in T (thymus derived) lymphocytes and low immunoglobulin levels. The autopsy showed the histologic pattern designated thymic alymphoplasia and a marked lack of development of the reticuloendothelial organs. The mast cell hyperplasia may be the result of an antigenic stimulus early in embryonic life and/or the result of mast cell differentiation at the expense of normal thymic lymphoid development caused by a genetic defect.

Cost benefit analysis of bovine mastitis in the UK.

Bovine mastitis reduces the yield and quality of milk and increases the rate of culling and veterinary costs. This reduces the profitability of farm milk production but the calculation of the extent of this economic loss is complex because of the many factors involved and deficiencies in the evidence on the relationship between the disease and various production factors. This paper examines the available evidence for the UK and provides a consistent analytical framework within which the benefits arising from reduced mastitis in dairy herds constrained by quota can be considered. It is estimated that since 1970 the farms that have followed the recommended control procedures have reduced the average annual number of cases of clinical mastitis from 135 to 40 cases/100 cows each year, while the quarters remaining uninfected for a whole year has increased from 65 to 80% of the total quarters. The costs of the main control procedures (e.g. 8.60 pounds/cow for dry-cow therapy and teat dipping or spraying) are broadly covered by the reduction in clinical mastitis, leaving the benefits of reduced subclinical infection (e.g. 3810 pounds for a 100 cow herd unconstrained by quota and achieving the average reduction in infection) as a substantial bonus. The imposition of quotas reduces the financial benefit of mastitis control but it still remains a worthwhile investment. The results of this analysis can be used to suggest maximum costs of additional new control measures produced by research. It also indicates that there is considerable value in production research which gives more precise knowledge of production systems, thus allowing producers to respond optimally to quota cuts.

Biomaterials and collagen synthesis.

A highly reactive biomaterial (clay) and a relatively nonreactive substance (silicone) were implanted separately in primarily closed incisions on the backs of rats. Collagen synthesis was determined in biopsies from each test site after 8 days. The biochemical measurements of collagen synthesis showed a significant correlation with the gross pathologic and histologic findings.