Comparative pappus micromorphology of edelweiss (Leontopodium,Gnaphalieae, Asteraceae) with implications for taxonomy,ecology and evolution

We analysed pappus characters in 31 of the c. 34 accepted Leontopodium spp. (edelweiss). Micromorphological pappus character states were useful for discriminating between individual species and intrageneric groups. The pappus differs in number, length, breadth, surface structure, colour and the tips of the bristles. Several features characterize single species, for example a unique fan‐like tip that is only found in L. franchetii. Leontopodium section Nobilia is supported by unusual pappus characters. Experimental evidence shows that the pappus of Leontopodium, previously thought to be caducous, is well suited for wind dispersal of the fruit. One clear trend is that species growing in sparsely vegetated, high‐altitude regions often have more numerous and longer pappus bristles, particularly on the female flowers.     

Auto-tumor recognition following in vitro induction of MHC antigen expression on solid human tumors: stimulation of lymphocytes and generation of cytotoxicity against the original MHC-antigen-negative tumor cells

Summary Expression of major histocompatibility complex (MHC) class I antigens was induced in eight out of nine freshly prepared tumor cell suspensions by exposure to interferon (IFN) and tumor necrosis factor (TNF) in vitro. The untreated, class-I-antigen-negative, and the treated, antigen-positive, cells of three tumors (one breast carcinoma, one plasmocytoma and one ovarian carcinoma) were compared for the capacity to stimulate autologous and allogeneic blood lymphocytes, to generate auto-tumor cytotoxicity and for sensitivity to the lytic effect induced in autologous mixed lymphocyte tumor cell culture (MLTC). The MHC class I-negative cells did not stimulate, while the cells induced for expression of antigens did. On the other hand, when the autologous cytotoxic cells were generated in the MLTC by the class I antigen-positive tumor cells the class I-negative tumor cells were also damaged. Lysis of the class-I-positive tumor cells was abrogated by the W6/32 monoclonal antibody directed against the monomorphic part of the class I molecules.     

Patterns of isozyme variation between maize and Mexican annual teosinte

Isozyme variation in 94 accessions of Mexican maize (Zea mays ssp. mays) and 37 collections of Mexican annual teosinte (Z. mays ssp. mexicana and var. parviglumis) are compared. Variety parviglumis (a predominantly wild plant) shows a closer genetic relationship to maize than does ssp. mexicana (a weedy teosinte often found in maize fields). The isozyme data suggest that maize and Z. mays var. parviglumis share a more recent common ancestor than either of these taxa share with other members of the genus Zea. In this sense, the isozyme data support the theory that maize is a domesticated form of teosinte. Isozyme data provide no evidence for independent origin of Mexican maize races from different taxa of teosinte. Isozyme analysis suggests that gene flow between maize and ssp. mexicana exists, but that it is highly restricted and more probably goes from weed into crop. Maize and var. parviglumis are isozymically too similar and too variable to allow patterns of gene flow between them (if any) to be discerned. The maize- teosinte complex does not fit a model applied to some other crops in that (I) weedy teosinte (ssp. mexicana) does not appear to be a hybrid of the wild form (var. parviglumis,) and maize and (2) the weedy form does not act as a genetic bridge between wild form and crop.     

Allozyme Frequency Changes Associated with Selection for Increased Grain Yield in Maize (ZEA MAYS L.)

Frequency changes of alleles at eight enzyme loci were monitored in four long-term maize selection experiments. The results indicate that changes in frequencies of the alleles at these loci are associated with changes due to selection for improved grain yield. The frequencies changed more than is consistent with the hypothesis of selective neutrality. In addition, significant deviations from a random-drift model were nearly always accompanied by significant linear trends as would result if allozyme frequencies respond to directional selection. Evaluations of linkages and linkage disequilibria in the selected populations indicate that the eight enzyme loci responded independently as selection progressed.     

Hybridization and evolution in Picradeniopsis (Compositae)

The predominantly allopatric species of the genusPicradeniopsis, P. oppositifolia andP. woodhousei, are distinct in morphological, in phenolic and terpeniod chemical, and in cytological aspects (n = 24 andn = 12, respectively). In an area of sympatry in northeastern New Mexico, interbreeding occurs frequently with the production of morphologically intermediate hybrids. Morphological and phenolic chemical data from 191 plants in 40 isolated parental populations and from 91 plants in four hybrid populations are of limited value in determining the nature of this hybridization, but meiotic configurations of 12_II and 12_I and low pollen viabilities of 1–11% in the hybrids indicate that they are all of the F₁ generation (with one possible backcross). The absence of observed introgression, and therefore the absence of gene flow between the two taxa, strengthens the case for taxonomic recognition of two species in the genus. Comparisons of the morphology, phenolic and terpenoid chemistry, and cytology of parents and F₁ hybrids suggest that the tetraploid,P. oppositifolia, has arisen by allopolyploidy from a cross betweenP. woodhousei and an unknown diploid species. An extrapolated morphological and chemical reconstruction of this putative diploid parent is advanced.     

The Mechanism of the Gram Reaction I. The Specificity of the Primary Dye

Dyes of all major types were tested for their suitability as the primary dye in the Gram stain. When a counterstain was not used, some dyes of all types were found to differentiate Gram-positive from Gram-negative organisms. When a counterstain was used, these dyes were found to vary greatly in their suitability. Those dyes found to be good substitutes for crystal violet were: Brilliant green, malachite green, basic fuchsin, ethyl violet, Hoffmann's violet, methyl violet B, and Victoria blue R. All are basic triphenylmethane dyes. Acid dyes were generally not suitable. Differences in the reaction of Gram-positive and Gram-negative cells to Gram staining without the use of iodine were observed and discussed but a practical differentiation could not be achieved in this manner. Certain broad aspects of the chemical mechanism of dyes in the gram stain are discussed.     

The integration of microarray information in the drug development process

In the past year, microarray technologies have moved beyond the proof-of-principle stage. Microarrays are now being used for genome-wide expression monitoring, large-scale polymorphism screening and mapping, and for the evaluation of drug candidates.     

Chest pain with nondiagnostic electrocardiogram in the emergency department: a randomized controlled trial of two cardiac marker regimens

BACKGROUND: Early detection of acute myocardial infarction (AMI) may save lives. In the emergency setting, it is unclear whether the early use of certain cardiac markers (myoglobin and cardiac troponin I [cTnI]) assists in making appropriate decisions whether to admit or discharge patients with chest pain of possible ischemic cause who have nondiagnostic electrocardiograms (ECGs). We performed a study to determine whether the addition of new cardiac markers in the emergency department results in improved clinical decisions. METHODS: A single-blind randomized controlled trial was conducted between June 1997 and June 1998 in a tertiary care emergency department in Kingston, Ont. Of 296 patients aged 30 years or more who presented to the emergency department with chest pain and nondiagnostic ECGs, 146 were randomly assigned to the intervention group (determination of baseline creatine kinase [CK] level, CK MB fraction and cTnI level, and myoglobin level at baseline and at 2 hours) and 150 to the control group (determination of baseline CK level and CK MB fraction). Outcome measures included the rate of admission to the inpatient cardiology service and length of stay in the emergency department. RESULTS: Of the 296 patients, 34 (11.5%) received a diagnosis of AMI in the emergency department, and 92 (31.1%) had chest pain of noncardiac cause. Patients in the intervention group were less likely than those in the control group to be admitted to the cardiology service (67 [45.9%] v. 81 [54.0%]). The absolute difference in the proportion (8.1% [95% confidence interval -3.3 to 19.5]), although potentially important clinically, was not statistically significant. The length of stay in the emergency department was essentially the same in the 2 study groups. At 30 days, the proportions of patients with a diagnosis of recurrent angina (58.2% in the intervention group and 58.0% in the control group) and AMI (12.3% and 14.7%) were also similar. INTERPRETATION: The optimal cardiac marker panel to be used in the emergency department remains unknown. The addition of serial testing of myoglobin with cTnI confirmation to the standard panel did not substantially change the clinical management or outcomes of patients presenting with chest pain and nondiagnostic ECGs.