Effects of context on judgements of odor intensities in humans

This study evaluated whether the intensity of previously smelled odors could unintentionally influence the subsequent judgement of odor intensity. The predicted context effect was based on the adaptation- level theory. Before and 25 min after either WEAK or STRONG biasing odor concentrations, 51 subjects were required to rate the intensity of 10 different odor concentrations of California Orange Oil. After the WEAK bias, subjects judged the odor intensity as being stronger than they did after the STRONG bias. Thus the intensity of odors smelled 25 min earlier can unintentionally influence subsequent odor intensity judgement. The findings are discussed in the light of two alternative explanations, namely, a central implicit memory process and a stimulus- level-based change at the peripheral level.      

DNA base sequence changes induced by diethyl sulfate in postmeiotic male germ cells of Drosophila melanogaster

Summary The DNA base sequence changes induced by diethyl sulfate (DES) were analyzed in postmeiotic male germ cells of Drosophila melanogaster. 31 transmissible vermilion mutants were recovered in F₁ and F₂ generations, with a frequency of 2.6 × 10^–4 for the F₁, and of 1.8–13 × 10^–4 for the F₂. The results show that DES induces both base pair substitutions (93%) and deletions (7%). In accord with its relatively high ability to alkylate oxygens in DNA, the most frequent type of sequence alteration among the basepair changes are GC-AT transitions, accounting for 73% of mutations, followed by transversions AT-TA (10%). DES also induced AT-GC transitions and AT-CG transversions. Both induced deletions were intralocus deletions, not occurring between basepair repeats. No influence of neighboring bases on the mutation position was found.     

Nucleotide sequence of the D-loop region of the sperm whale (Physeter macrocephalus) mitochondrial genome

We have amplified, by the polymerase chain reaction, and have sequenced the D-loop region of the mitochondrial DNA from the sperm whale (Physeter macrocephalus). The sperm whale D-loop was aligned with D- loop sequences from four other cetaceans (Commerson's dolphin, orca, fin whale, and minke whale) and an out-group (cow). This alignment showed the sperm whale sequence to be larger than that of other cetaceans. In addition, some sequence blocks were highly conserved among all six species, suggesting roles in the functioning of mitochondrial DNA. Other blocks that were previously reported to be well conserved among cetaceans showed little sequence conservation with the sperm whale D-loop, which argues against the functional importance of these sequence blocks in cetaceans.      

Deuterostome phylogeny and the sister group of the chordates: evidence from molecules and morphology

Complete coding regions of the 18S rRNA gene of an enteropneust hemichordate and an echinoid and ophiuroid echinoderm were obtained and aligned with 18S rRNA gene sequences of all major chordate clades and four outgroups. Gene sequences were analyzed to test morphological character phylogenies and to assess the strength of the signal. Maximum- parsimony analysis of the sequences fails to support a monophyletic Chordata; the urochordates form the sister taxon to the hemichordates, and together this clade plus the echinoderms forms the sister taxon to the cephalochordates plus craniates. Decay, bootstrap, and tree-length distribution analyses suggest that the signal for inference of dueterostome phylogeny is weak in this molecule. Parsimony analysis of morphological plus molecular characters supports both monophyly of echinoderms plus enteropneust hemichordates and a sister group relationship of this clade to chordates. Evolutionary parsimony does not support chordate monophyly. Neighbor-joining, Fitch-Margoliash, and maximum-likelihood analyses support a chordate lineage that is the sister group to an echinoderm-plus-hemichordate lineage. The results illustrate both the limitations of the 18S rRNA molecule alone for high- level phylogeny inference and the importance of considering both molecular and morphological data in phylogeny reconstruction.      

A member of a novel family of yeast 'zn-finger' proteins mediates the transition from stationary phase to cell proliferation.

The cloning and molecular characterization of the GCS1 gene from the budding yeast Saccharomyces cerevisiae show that stationary phase is in fact a unique developmental state, with requirements to resume cell proliferation that can be distinct from those for maintenance of proliferation. Deletion of the GCS1 gene products a novel phenotype: stationary-phase mutant cells do not resume proliferation at a restrictive temperature of 15 degrees C, but mutant cells lacking Gcs1p that are proliferating at the permissive temperature of 29 degrees C continue to proliferate after transfer to 15 degrees C as long as nutrients are available. The GCS1 gene sequence predicts a 39 kDa polypeptide with a novel 'Zn-finger' motif. A point mutation within the finger motif produces a phenotype that mimics that of deletion of the GCS1 gene, showing that the finger motif is essential for full Gcs1p activity. Gcs1p and the products of two newly identified genes, SPS18 and GLO3, constitute a family of novel Zn-finger proteins.