Sequence analysis of the 17-kilodalton-antigen gene from Rickettsia rickettsii.

DNA obtained from the Sheila Smith strain of Rickettsia rickettsii was digested to completion with the restriction endonucleases BamHI and SalI and ligated with the plasmid vector pUC19. The ligation mixture was used to transform Escherichia coli. A total of 465 bacterial clones were screened for antigen production with hyperimmune rabbit serum. One of the reactive clones, containing a recombinant plasmid designated pSS124, was solubilized and subjected to immunoblot analysis and revealed expression of a 17-kilodalton protein reactive with anti-R. rickettsii serum that comigrated with an antigen from R. rickettsii. A 1.6-kilobase PstI-BamHI fragment from pSS124 was subcloned and continued to direct synthesis of the 17-kilodalton antigen. The nucleotide sequence was determined for this 1.6-kilobase subclone, which encompassed the gene encoding the polypeptide as well as flanking regions containing potential regulatory sequences. The open reading frame consisted of 477 nucleotides that specified a 159-amino-acid protein with a calculated molecular weight of 16,840. The deduced amino acid sequence contained a hydrophobic sequence near the amino terminus that resembled signal peptides described for E. coli. The carboxy terminus was hydrophilic in nature and probably contained the exposed epitopes.     

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.     

Major histocompatibility (B) complex and sex effects on the phytohaemagglutinin wattle response

The influence of the major histocompatibility (B) complex and sex on the phytohaemagglutinin (PHA) wattle response was studied in 136 segregants (B2/B2, B2/B5 and B5/B5) of a fourth generation cross between inbred lines 6(1) and 15(1). At 6 weeks of age, chickens were injected with 100 micrograms purified PHA-P. Wattle thickness measurements were taken 4, 24, 48, 72 and 96 h after injection. Analysis of variance showed that 4 h after injection, males had a significantly higher response than females but the sex-genotype interaction was also significant. Females had higher responses than males 24 and 48 h after injection as a consequence of more rapid development and earlier resolution of the reaction in males. B2/B2 chickens had significantly lower responses than B5/B5 chickens 72 and 96 h after injection, signifying a faster late resolution phase in the B2/B2 genotype. The developmental and early resolution phases of the PHA wattle response were influenced by sex while the late resolution phase was influenced by B genotype.     

Allometric Root/Shoot Relationships and Predicted Water Uptake for Desert Succulents

Root morphology, shoot morphology, and water uptake for Agavedeserti and Ferocactus acanthodes of various sizes were studiedusing allometric relationships (y = ax^b) and a previously developedwater uptake model. Shoot surface area increased with shootvolume with an exponent b of 0.75 for both species. Root lengthand the ground area explored by the roots increased with shootsurface area with b's of 0.72 for A. deserti and 0.92 for F.acanthodes. Various sized individuals had about the same ratioof root length to explored ground area, with higher values occurringfor A. deserti. Predicted water uptake averaged over the exploredground area was approximately constant over a 10⁴-fold rangein shoot surface area, suggesting that shoot size confers nointraspecific competitive advantage for water uptake. For theroot lengths per explored ground area observed in the field,water uptake was predicted to be 85 per cent of maximal; wateruptake could be increased by the production of more rain roots.When differences in shoot volume were accounted for by allometry,small plants had relatively less shoot surface area and relativelymore root length per shoot volume than did large plants, whichmay be important for the water relations of seedling establishment. Agave deserti, Ferocactus acanthodes, allometry, desert succulents, root distribution, root length, seedling growth, seedling establishment, shoot surface area, shoot volume, water uptake     

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.