Taxonomy ofNeurolaena (Asteraceae-Heliantheae)

A taxonomic treatment of the tropical genusNeurolaena (tribeHeliantheae, subtribeGalinsoginae) is rendered. Ten species are recognized: the widespread, annual, weedy,N. lobata and nine relatively rare, relictual, shrubby or small tree species, mostly restricted to southern Mexico and Central America. Distributional maps, key to species, and complete synonymy are presented. A chromosomal and chemical review is also provided.     

Interaction of phlorizin and sodium with the renal brush-border membraned-glucose transporter: Stoichiometry and order of binding

Summary The order and stoichiometry of the binding of phlorizin and sodium to the renal brush-border membraned-glucose transporter are studied. The experimental results are consistent with a random-binding sites is one-to-one. When the kinetics of phlorizin binding are measured as a function of increasing sodium concentration no significant variation is found in the apparent number of binding sites; however, the apparent binding constant for phlorizin decreases rapidly from approximately 16 m at [Na]=0 to 0.1 m at [Na]=100mm and approaches 0.05 m as [Na]. The experimental data are fit to a random carrier-type model of the coupled transport of sodium andd-glucose. A complete parameterization of the phlorizin binding properties of this model under sodium equilibrium conditions is given.     

Leaf thickness and carbon isotope composition in the Crassulaceae

Summary Measurements of leaf thickness and ¹³C value were obtained for twenty species and three intergeneric hybrids of the Crassulaceae. The data include plants growing in their native habitats and also in greenhouse cultivation. There is a strong relationship between leaf thickness and leaf ¹³C values. The plants with the thickest leaves of ca. 7 to 11 mm had ¹³C values ranging from -11.5 to -13.8. Plants with leaves that were thinner than 2.0 mm all had ¹³C values that were more negative than -23. Plants having intermediate leaf thickness possessed intermediate ¹³C values. The leaf tissue of four genotypes spanning the range of leaf thicknesses all exhibited a two-fold or greater nocturnal increase in titratable acidity. It appears that the differences in leaf thickness and ¹³C values among the tested species are genetically determined.     

The use of a fabric softener in the reconstitution of mummified tissue prior to paraffin wax sectioning for light microscopical examination

A method of reconstituting mummified tissues using the fabric softener "Comfort" is described. Routine histological paraffin wax sections were prepared following overnight treatment at room temperature with a 0.2% solution of this substance in isotonic saline. A comparison of results obtained by this method is made with those obtained using Ruffer's and Sandison's solutions. Nuclear stains gave poor results whereas connective tissue stains demonstrated their respective fibers by all rehydration methods.     

Point mutations at the thymidine kinase locus in L5178Y mouse lymphoma cells II. Test validation and interpretation

The L5178Y Mouse Lymphoma TK assay was studied extensively to determine if this mammalian cell assay for gene mutations at the thymidine kinase (TK) locus could provide valid, interpretable determinations of mutagenic potential, and whether this information is of value in the safety evaluation of chemicals. We first determined that test-derived TFT^R mutants were phenotypically stable, possessing little or no thymidine kinase activity as measured by labeled thymidine uptake, but demonstrating 100% cross resistance to bromodeoxyuridine. Common solvent vehicles such as acetone, dimethylsulfoxide and ethanol were shown to produce little cytotoxicity and no mutagenic activity when present at 1% levels. Out of a total of 10 noncarcinogens tested, all were negative when results were analyzed by a 2-sample log_et test on control and treated mutant count means. Of the 13 putative animal carcinogens tested, 10 were positive, 2 were negative (auramine O and sodium phenobarbital), and 1 showed sporadic activity (hydrazine sulfate) in the TK assay on the basis of test-derived t statistics. 2 compounds, 1,2-epoxybutane and ICR 191, which have been described as Ames positive non-carcinogens, were also positive in the TK assay. Although this sampling of a total of 29 compounds is insufficient for precise estimations of expected false-positive or false-negative frequencies, these data indicate the TK assay can be expected to detect a majority of carcinogens as mutagens including some missed by more established point-mutation assays.     

Cryopreservation of human peripheral blood stem cells: optimal cooling and warming conditions

Peripheral blood stem cells are being used to reconstitute human bone marrow function after ablative therapy of blast transformation of chronic myelogenous leukemia. Studies were undertaken to establish the optimum cooling and warming conditions of the preservation of colonyforming activity in the peripheral blood of patients with CML.The results show that maximum recovery of CFU-c activity occurs after cooling at 3 °C/min, an average of 50% better than the recovery following cooling at 1 °C/min. CFU-c recovery decreased with decreasing warming rate, but high recovery was obtained with warming rates as low as 10 °C/ min. Viable cell count did not correlate with CFU-c recovery, therefore it represents a poor index for quality control.These results suggest that for clinical purposes bulk samples in flat bags with high surface area to volume ratios, frozen at a rate of 3 °C/min and thawed as rapidly as possible, should give maximum recovery of stem cell activity.