Effects of Dose on the Induction of Dominant-Lethal Mutations and Heritable Translocations with Ethyl Methanesulfonate in Male Mice

Genetic damage by ethyl methanesulfonate (EMS) in male mice was measured at doses ranging from 50 to 300 mg/kg with dominant-lethal mutations and reciprocal translocations as endpoints. No appreciable increase in dominant-lethal mutations was detected following a dose of 100 mg/kg. Dominant lethals induced by EMS were convincingly detected only after a dose of 150 mg/kg, but in the translocation experiment an increase in the genetic effect was detectable at the 50 mg/kg dose. It is likely that dominant lethals had also been induced at the 50 and 100 mg/kg doses, but were not detected due to the relative insensitivity of the dominant..lethal procedure. Thus, for detection of low levels of EMS-induced chromosome breakage, translocations are a much more reliable endpoint than are dominant-lethal mutations. A procedure for large-scale screening of induced translocations is described.—The dominant-lethal dose-response curve, plotted on the basis of living embryos as a percentage of the control value, is clearly not linear as it is markedly concave downward. Similarly, the translocation dose-response curve showed a more rapid increase in the number of translocations with dose than would be expected on the basis of dose-square kinetics. It is clear for both of these endpoints that the effectiveness of EMS in inducing chromosome breakage is proportionately much lower at low doses.     

Nitrogen and phosphorus release from decaying water milfoil

To evaluate the net N and P contribution to water from herbicide-killed aquatic weeds, water milfoil containing 1.5% N and 0.30% P was killed with endothal and allowed to decompose, in the dark, in water only or sediment-water systems. Changes with time in dry weight, total N and P, and organic C in the plant material, and organic and inorganic forms of N and P in the water were determined. Plant decompostion was limited by N. Inorganic N was released by the sediment, and decomposition was more rapid when sediment was present. A smaller N requirement for decomposition under conditions of low O₂ was postulated as a possible explanation of the more rapid decomposition observed in the absence of aeration. The presence of plant P in excess of decomposition requirements resulted in rapid accumulation of organic P, followed by inorganic P, in the water. Organic N appeared in the water early in the experiments, but was depleted rapidly, and inorganic N was apparently immobilized as soon as it was formed. In the presence of sediment, organic N and inorganic P levels were much lower. On treating of water milfoil with herbicide, rapid P release can be expected. This P can either be utilized in further biomass production or be sorbed by the sediment. Insufficient data were available to reach definite conclusions regarding N. It would appear, however, that N release from decaying weeds is much slower than P.     

Gibberellins and early growth in seedlings of Phaseolus vulgaris

Summary 1. Amounts of gibberellin extractable from young bean seedlings using phosphate buffer, and following acid hydrolysis, or protease treatment, have been examined and compared with those obtained using methanol extraction. 2. Considerable differences in the amounts of gibberellins extractable are found for different batches of material. The level of extracted gibberellin is less for dry seeds and for 1-day old seedlings than for seedlings 4 days old. Before germination, the amounts of free, buffer-soluble, gibberellins are low, but these rise rapidly in the postgermination period. 3. The appearance of large amounts of free gibberellins in the cotyledons, believed to represent the conversion of bound forms, is not dependent upon the presence of the embryonic axis, since removal of this at planting has only a small effect on the amount of gibberellin extractable at day 4. There is evidence for synthesis of new gibberellin in the intact seedling by day 4. 4. amylase activity in the cotyledons also develops in the absence of the embryo, but the high levels of activity shown by intact seedlings are not reached in cotyledons cultured in absence of the embryo.     

Carving The Palm: The Role of Metaphor in Mayawo Marriage Rituals

…With metaphor we experience the metamorphosis of both language and reality. Paul Ricoeur. ‘Creativity in Language’. The Philosophy of Paul Ricoeur. pp. 132–133 (1973).     

In vitro differentiation of rabbit blastocyst cells

Summary Six- and seven-day post-coitus (p.c.) rabbit embryos have been cultured in an attempt to establish a trophectodermal cell line. Results indicate that cells with epithelial characteristics (i.e. positive staining for cytokeratin) will survive in culture until Passage 3. At that time a fibroblastlike cell becomes predominant. In addition, we have found that the presence of the inner cell mass is required for embryo explants often results in the development of cells that spontaneously contract. These cells stain positively for myosin, which indicates that they may be precardiac cells. Maximum diastolic potential was −59±1.2 mV and the threshold potential was −53±2.3 mV. Spontaneously contracting cells did not respond to atropine, acetylcholine, epinephrine, isoproterenol, or propranolol. Action potential seems to be a result of an inward calcium current, because the beating rate is decreased in a dose-related manner with the calcium channel blocker verapamil, whereas the voltage-sensitive sodium channel blocker tetrodotoxin was without effect. This work was supported by grants HD21302, HD07069, DK31091, and HL37320 from the National Institutes of Health, Bethesda, MD, with additional support from a University of Alabama at Birmingham Cardviovascular Research and Training Center Award.     

Dissimilarity for partially ranked data and its application to cover-abundance data

Cover-abundance estimates are commonly employed in phytosociological investigations to record the performance of species. Because the coded values are on an ordinal scale of measure, various authors have suggested that some transformation is necessary before such values can be used for classification and ordination. However, it is not clear that transformation is a sufficient treatment, and it would seem preferable to use ordinal data directly. In this paper we examine such direct use of partial rankings and show that several dissimilarity measures can be defined for this case without invoking any transformations. They include dissimilarity measures associated with various rank correlation measures and with distances between strings; all the measure are variant forms of Hausdorf's interset distance. Certain other kinds of data, such as those employing dominant and subdominant species and the dry-weight-rank estimation of biomass, are also on an ordinal scale and could be analysed using similar techniques.To illustrate the approach, a string dissimilarity measure is used to analyse a set of data from Slovakian grasslands which appear to reflect a simple gradient. The original data were recorded with 10 classes of performance and are analysed using hierarchical and nondeterministic, overlapping, classifications.     

A new DNA marker (D4S90) is located terminally on the short arm of chromosome 4, close to the Huntington disease gene

Genetic linkage studies have mapped Huntington's disease (HD) to the distal portion of the short arm of chromosome 4 (4p16.3), 4 cM distal to D4S10 (G8). To date, no definite flanking marker has been identified. A new DNA marker, D4S90 (D5), which maps to the distal region of 4p16.3, is described. The marker was used in a genetic linkage study in the CEPH reference families with seven other markers at 4p16. The study, together with knowledge of the physical map of the region, places D4S90 as the most distal marker, 6 cM from D4S10. A provisional linkage study with HD gave a maximum lod score of 2.14 at a θ of 0.00 and no evidence of linkage disequilibrium. As D4S90 appears to be located terminally, it should play an important role in the accurate mapping and cloning of the HD gene.