Nonrecombinant Meiosis I Nondisjunction in Saccharomyces Cerevisiae Induced by Trna Ochre Suppressors

The presence of the tRNA ochre suppressors SUP11 and SUP5 is found to induce meiosis I nondisjunction in the yeast Saccharomyces cerevisiae. The induction increases with increasing dosage of the suppressor and decreases in the presence of an antisuppressor. The effect is independent of the chromosomal location of SUP11. Each of five different chromosomes monitored exhibited nondisjunction at frequencies of 0.1%-1.1% of random spores, which is a 16-160-fold increase over wild-type levels. Increased nondisjunction is reflected by a marked increase in tetrads with two and zero viable spores. In the case of chromosome III, for which a 50-cM map interval was monitored, the resulting disomes are all in the parental nonrecombinant configuration. Recombination along chromosome III appears normal both in meioses that have no nondisjunction and in meioses for which there was nondisjunction of another chromosome. We propose that a proportion of one or more proteins involved in chromosome pairing, recombination or segregation are aberrant due to translational read-through of the normal ochre stop codon. Hygromycin B, an antibiotic that can suppress nonsense mutations via translational read-through, also induces nonrecombinant meiosis I nondisjunction. Increases in mistranslation, therefore, increase the production of aneuploids during meiosis. There was no observable effect of SUP11 on mitotic chromosome nondisjunction; however some disomes caused SUP11 ade2-ochre strains to appear white or red, instead of pink.     

Towards a physical map of the Drosophila melanogaster genome: mapping of cosmid clones within defined genomic divisions.

A physical map of the D. melanogaster genome is being constructed, in the form of overlapping cosmid clones that are assigned to specific polytene chromosome sites. A master library of ca. 20,000 cosmids is screened with probes that correspond to numbered chromosomal divisions (ca. 1% of the genome); these probes are prepared by microdissection and PCR-amplification of individual chromosomes. The 120 to 250 cosmids selected by each probe are fingerprinted by Hinfl digestion and gel electrophoresis, and overlaps are detected by computer analysis of the fingerprints, permitting us to assemble sets of contiguous clones (contigs). Selected cosmids, both from contigs and unattached, are then localized by in situ hybridization to polytene chromosomes. Crosshybridization analysis using end probes links some contigs, and hybridization to previously cloned genes relates the physical to the genetic map. This approach has been used to construct a physical map of the 3.8 megabase DNA in the three distal divisions of the x chromosome. The map is represented by 181 canonical cosmids, of which 108 clones in contigs and 32 unattached clones have been mapped individually by in situ hybridization to chromosomes. Our current database of in situ hybridization results also includes the beginning of a physical map for the rest of the genome: 162 cosmids have been assigned by in situ hybridization to 129 chromosomal subdivisions elsewhere in the genome, representing 5 to 6 megabases of additional mapped DNA.     

The use of hydrophobic synthetic glycosides as acceptors in glycosyltransferase assays

A general method is described for the assay of glycosyltransferase activity, which makes use of synthetic glycoside acceptors attached to hydrophobic aglycones. The products formed by incubation of an enzyme with acceptor and radiolabelled sugarnucleotide can then be rapidly (one minute) separated from interfering radioactivity by adsorption on to reverse-phase C-18 cartridges. After aqueous washing, products are easily isolated by elution with methanol. The utility of the method for the assay of (1–4)galactosyltransferase, (1–2)fucosyltransferase andN-acetylglucosaminyltransferase I and V is demonstrated.     

Responses of plasma human atrial natriuretic factor to high intensity submaximal exercise in the heat

No data exists regarding responses of human atrial natriuretic factor (ANF) to exercise in the heat. The purpose of this study was to examine the responses of plasma ANF to high intensity submaximal (71% +/- 0.9 VO2max) exercise in the heat over an eight day acclimation period. Fourteen healthy males volunteered to participate in the study. Subjects performed intermittent exercises on a treadmill (0% grade) during 50 min of each 100 min trial in an environmental chamber maintained at 41.2 +/- 0.5 degrees C, 39.0 +/- 1.7% relative humidity. Blood was obtained from an antecubital vein after standing 20 min in the heat prior to exercise, and immediately after exercise. Measures were compared on days 1, 4 and 8. ANF did not change pre- to post-exercise nor did it change over the eight day heat acclimation period despite other heat acclimation adaptations. Conversely, plasma aldosterone (ALDO), renin activity (PRA) and cortisol (COR) all increased (p less than 0.05) pre- to post-exercise on each day but again no changes were observed over the eight day period. These data support that ANF may not increase when ALDO and PRA increases are observed.     

Studies on the Tissue Distribution of the Puromycin-Sensitive Enkephalin-Degrading Aminopeptidases

An antiserum generated to the soluble form of the rat brain puromycin-sensitive enkephalin-degrading aminopeptidase was used to determine the tissue distribution of the soluble and membrane-associated forms of this enzyme. All tissues examined contained significant levels of the soluble enzyme form, with this enzyme accounting for greater than 90% of the arylamidase activity in brain, heart, and skeletal muscle. Native gel electrophoresis coupled with activity staining as well as inhibition studies were used to confirm the presence of this enzyme in various tissues. Serum was found not to contain this particular aminopeptidase. In contrast to the results obtained with the soluble enzyme form, brain was the only tissue found to contain the membrane-associated enzyme form. Although all tissues contained membrane-associated aminopeptidase activity only the brain enzyme could be maintained in solution in the absence of detergent. In addition, the brain membrane-associated enzyme could be distinguished from the membrane-associated aminopeptidase activity in other tissues on the basis of its sensitivity to inhibition by puromycin.     

Influence of maize root mucilage on soil aggregate stability

This study was undertaken to determine the effects of root exudates on soil aggregate stability. Root mucilage was collected from two-month old maize plants (Zea mays L.) Mucilage and glucose solutions were added at a rate of 2.45 g C kg⁻¹ dry soil to silty clay and silt loam soils. Amended soils, placed in serum flasks, were incubated for 42 d with a drying-wetting cycle after 21 d. Evolved CO₂ was measured periodically as well as the water-stable aggregates and soluble sugar and polysaccharide content of the soil. In mucilage-amended soils CO₂ evolution started with a lag phase of 2–3 days, which was not observed in glucose-amended soils. There was then a sharp increase in evolved CO₂ up to day 7. During the second incubation period there were only small differences in evolved C between treatments. Incorporation of mucilage in both soils resulted in a spectacular and immediate increase in soil aggregate stability. Thereafter, the percent of water-stable aggregates quickly decreased parallel to microbial degradation. On completion of the incubation, aggregate stability in the silty clay soil was still significantly higher in the presence of mucilage than in the control. This work supports the assumption that freshly released mucilage is able to stick very rapidly to soil particles and may protect the newly formed aggregates against water destruction. On the silty clay, microbial activity contributes to a stabilization of these established organo-mineral bounds.     

In vitro clonal multiplication of the actinorhizal plant Comptonia peregrina

Micropropagation of the actinorhizal plant Comptonia peregrina of the Myricaceae was achieved successfully by the induction of root buds in excised root culture with cytokinin (1.0 M benzyladenine). Excised root segments with initiated root buds were subcultured in Woody Plant Medium (WPM) lacking growth regulators, developing extensive callus which subsequently gave rise to multiple adventitious buds. Shoot elongation was facilitated by transfer of calluses to more aerated conditions. Root initiation was induced on shoots by brief treatment with auxin (<1 M indolebutyric acid) and transfer to WPM for plantlet development. Controlled light and aeration in liquid medium were critical conditions for successful micropropagation.     

The genetics and expression of an esterase locus inAnopheles gambiae

The main polymorphic system of esterase isoenzymes in adults of the G3 laboratory strain ofAnopheles gambiae consists of two to five major bands of activity per individual. The bands are designated 5S, 5F, 13, 14, and 15. In genetic crosses, the genes which coded for the bands assorted as three codominant alleles, Est A, Est B, and Est C, at a single autosomal locus. Homozygotes for the Est C allele were significantly underrepresented among backcross progeny. The developmental pattern of esterase expression was examined. Esterase gene expression in embryos was first detectable between 2 and 12 hr after oviposition. The initiation or termination of expression of some of the bands corresponded to boundaries between developmental stages. Most of the esterase fractions were not specifically localized within the tissues tested, with the exception of a series of bands which were restricted largely to adult male testes.