Functional competency of T cell antigen receptors in human thymus

The T cell antigen receptor is likely to play a role in both positive and negative selection in the thymus. Three populations of thymocytes can be distinguished by the level of expression of the CD3-alpha/beta-chain heterodimer of the T cell antigen receptor (CD3/Ti alpha/beta) complex. Cells which fail to express these receptors or express low levels of receptors are contained in a population of thymocytes which express low levels of the CD5 antigen and are predominantly CD4+/CD8+. Thus, these cells appear to be relatively immature phenotypically. In contrast, the cells which express high levels of CD3/Ti alpha/beta co-express high levels of CD5 and are predominantly contained in the more mature single positive cells which express either CD4 or CD8. With the calcium-sensitive dye, Indo-1, and immunofluorescence, we demonstrated that, despite the relative phenotypic immaturity of cells which express low levels of CD3/Ti alpha/beta, these antigen receptors are able to mediate transmembrane signaling when stimulated with CD3 monoclonal antibodies. Although increases in calcium were observed in these CD3/Ti alpha/beta-low expressing cells in response to anti-CD3, no proliferative response was observed, even in the presence of phorbol myristate acetate. Proliferative responses were observed in the more mature cells which express high levels of CD3/Ti alpha/beta. These results suggest that, rather than a defect in the functional capability of the antigen receptor complex to mediate transmembrane signaling events, cellular responses to signals generated by the antigen receptor may differ at various stages of thymocyte development.     

Prognostic significance of DNA ploidy and morphometric analyses of adenocarcinoma of the uterine cervix

In an effort to improve the prognostic accuracy of the histologic criteria used for cervical adenocarcinomas, the nuclear DNA ploidy levels, means and standard deviations of nuclear areas and amounts of lumen and neoplastic tissue were quantitated. Useful thresholds in discriminating recurrent disease, as identified by logistic regression analysis, included a DNA ploidy level of 3.0 N, a percent of lumen of 34.6% and nuclear area mean and standard deviation of 53.1 sq micron and 20.1 sq micron, respectively. These parameters should provide useful guidelines in the visual assessment of histologic features that have prognostic significance.     

Contractility, ATP, and creatine phosphate during myocardial ischaemia and reperfusion: the effects of adenosine and inhibition of adenosine catabolism in the dog heart

Provision of AMP or adenosine to heart cells during recovery from episodes of myocardial ischaemia accelerates physiological, biochemical, and structural recovery. Inhibition of adenosine loss from the tissue during ischaemia should have a similar effect. This hypothesis was tested in dog heart by infusion of adenosine and inhibitors of adenosine catabolism prior to, during, and following ischaemia. Post-ischaemic recovery of ATP and contractile function was accelerated significantly by adenosine and by inhibitors of adenosine catabolism both singly and in combination. Contractility and ATP levels during ischaemia were also increased by these inhibitors.     

Light-adaptation in the photophobic response by Stentor coeruleus

Effects of preillumination on photophobic response (light-adaptation) and recovery of the photophobic sensitivity in the dark (dark-adaptation) in Stentor coeruleus were examined. When the cells were preilluminated with white light of 7.80 W/m² for 2 min, the fluence-rate response curve of photophobic response was shifted toward higher light intensities by half an order of magnitude compared to the one without preillumination. Preillumination with a higher light intensity resulted in a further shift of the fluencerate response curve. An action spectrum for light-adaptation showed a primary peak at 610 nm and secondary peaks at 540 and 480 nm which are almost identical to the peaks observed in the photophobic action spectrum.The light-adapted cells showed a recovery of their photophobic sensing ability following dark treatment. Dark-adaptation resulted in total recovery of photophobic sensing ability in 8 minutes for the most cases examined.     

Chromosomal location, cloning and nucleotide sequence of the Bacillus subtilis cdd gene encoding cytidine/deoxycytidine deaminase

Summary The Bacillus subtilis cdd gene encoding cytidine/2-deoxycytidine deaminase has been located by transduction at approximately 225 degrees on the chromosome, and the gene order rpC-lys-cdd-aroD was established. The gene was isolated from a library of B. subtilis DNA cloned in D69 by complementation of an Escherichia coli cdd mutation. Minicell experiments revealed a molecular mass of 14000 dalton for the cytidine deaminase subunit encoded by the cloned DNA fragment. The molecular weight of the native enzyme was determined to be 58000, suggesting that it consists of four identical subunits. The nucleotide sequence of 1170 bp, including the cdd gene, was determined. An open reading frame encoding a polypeptide with a calculated molecular mass of 14800 dalton was deduced to be the coding region for cdd. The deduced amino acid composition of the 136-amino acid-long subunit shows that it contains six cysteine residues. A computer search in the GenBank DNA sequence library revealed that the 476 bp HindIII fragment containing the putative promoter region and the first ten codons of cdd is identical to the P43 promoter-containing fragment previously isolated by Wang and Doi (1984). They showed that the fragment contained overlapping promoters transcribed by B. subtilis 43 and 37 RNA polymerase holoenzymes during growth and stationary phase.Abbreviations SDS sodium dodecyl sulphate - Ap ampicillin resistance - Tet^r tetracycline resistance - Km^r kanamycin resistance     

The association of H-2Ld with human beta-2 microglobulin induces localized conformational changes in the alpha-1 and- 2 superdomain

We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2L^d molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the helical region of the alpha-1 domain. H-2L^d class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase of 34-1-2 cross-reactivity following exchange with human B2m. The H-2L^d hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2L^d molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human B2m with H-2L^d can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor.     

Metabolism of d-xylose in Schizosaccharomyces pombe cloned with a xylose isomerase gene

Summary The Escherichia coli xylose isomerase gene was transformed into Schizosaccharomyces pombe for direct d-xylose utilization. In order to understand d-xylose metabolism and determine the limiting factors on d-xylose utilization by the transformed yeast, d-xylose transport, xylose isomerization, and xylulose phosphorylation were investigated. The results indicated that low activity of xylose isomerization in the cloned yeast was the limiting step for d-xylose fermentation. An in vitro study showed that yeast proteases decreased xylose isomerase activity. Xylitol, a by-product of d-xylose fermentation, had no effect on the activity of xylose isomerase.     

Discrimination of benign versus malignant mixed tumors of the salivary gland using digital image analysis

Seven benign and four malignant mixed tumors of the salivary gland, biopsied using fine-needle aspiration, were analyzed using digital image analysis. Mean nuclear form factor, perimeter, and area were significantly increased in malignant cases. Better separation between diagnostic categories, however, was achieved by utilizing the coefficient of variation (CV) within a case rather than mean value. Form factor CV alone divided cases into nonoverlapping diagnostic categories. This quantitative analog of "pleomorphism" provided a useful marker for malignancy in mixed tumors.