Characterization of AAT1: a gene involved in the regulation of amino acid transport in Saccharomyces cerevisiae.

A new class of Saccharomyces cerevisiae mutants (aat1 - amino acid transport) has been identified. These mutants are unable to grow on rich medium or on minimal medium supplemented with certain amino acids (isoleucine, methionine, phenylalanine, tyrosine or valine). This phenotype is directly linked to the presence of the leu2 allele in these strains: aat1 LEU2 organisms grow normally on all media tested.

Vibrotactile masking: effects of stimulus onset asynchrony and stimulus frequency.

Vibrotactile thresholds for the detection of a 50-ms vibratory stimulus on the thenar eminence of the hand were measured in the presence of and in the absence of a 700-ms suprathreshold vibratory masking stimulus. When thresholds were measured in the presence of the masking stimulus, stimulus onset asynchrony (SOA) was varied so that backward, simultaneous, and forward masking could be measured. The amount of masking, expressed as threshold shift, was greatest when the test stimulus was presented near the onset or offset of the masking stimulus.

The measurement of loudness in individual children and adults by absolute magnitude estimation and cross-modality matching.

Twelve adults and 11 children (age range 4-7 years) performed absolute magnitude estimation of the apparent lengths of lines and the loudnesses of 1000-Hz tones as well as cross-modality matching between loudness and apparent line length. Consistent with the notion that children and adults have similar impressions of loudness, there were no major differences between the absolute magnitude estimation (AME) and cross-modality matching (CMM) data of the adults and children. A direct comparison between the exponents for loudness by AME and CMM was made when a correction factor was employed to eliminate the effects of idiosyncratic use of numbers from the AME exponents.

Development of Iiyanassa obsoleta embryos after equal distribution of polar lobe material at first cleavage.

Ilyanassa obsoleta embryos cleave unequally via the formation of polar lobes, which contain materials essential for the development of larval shell, foot, operculum, statocysts, and eyes. Polar lobe material is shunted to the CD cell during first cleavage and to the D cell during second cleavage. Treatment with cytochalasin B (CB) before first cleavage prevents the formation of the polar lobe and leads to equal cleavage and the equal distribution of lobe material.

Cell proliferation in chick oral membrane lags behind that of adjacent epithelia at the time of rupture.

Radioautographic analysis showed that ectoderm and endoderm cells in chick oral membrane continued to label with tritiated thymidine through the period of rupture, but their frequency of labeling was significantly lower than those of adjacent epithelia. Frequency of labeling increased in adjacent ectoderm and endoderm, while oral membrane rates remained relatively low, suggesting that growth in the membrane lags relative to adjacent epithelia. Relatively greater proliferation in adjacent epithelia could generate tension and pull apart the thinned oral membrane.

Binding of amphiphilic peptides to a carboxy-terminal tryptic fragment of calmodulin.

Calmodulin (CaM) fragments 1-77 (CaM 1-77) and 78-148 (CaM 78-148) were prepared by tryptic cleavage of CaM. CaM 78-148 exhibited Ca2+-dependent binding to mastoparan X, Polistes mastoparan, and melittin with apparent dissociation constants less than 0.2 microM as judged from changes in the fluorescence spectrum and anisotropy of the single tryptophan residue of each of these cationic, amphiphilic peptides.

Remarriage as a coping response for widowhood.

Consideration and use of remarriage as a response to cope with the death of a husband was examined in 39 women who had been widowed and had subsequently remarried, 192 widows who had considered remarriage but had not yet remarried, and 420 widows who had not considered remarriage. Controlling for age, we found that women who had remarried reported fewer current concerns than did the other two groups. Furthermore, we found that women who retrospectively recalled the most concerns immediately after the death of the spouse were the ones who eventually remarried.

Familiarity and organization of category terms in semantic memory.

In order to determine production frequencies for various category terms, 219 college students were asked to generate category terms (e.g. Automobiles, Vegetables, Relatives) during a 4-rain period.

Cross-category structure in semantic memory.

In Experiment I, subjects made similarity judgments about all 56 category terms listed in the Battig and Montague (1969) norms. These judgments were then subjected to a hierarchical clustering analysis. Experiment II demonstrated that the relations among the category labels are very similar to the relations among the high dominance exemplars of these categories.

Visual and semantic factors in recognition from long-term memory.

In recognition tests, physical and semantic relationships between targets and distractors have been shown, in separate manipulations, to affect the latency of subject's decision. Recognition was tested for distractors which were visually similar or dissimilar to targets and which belonged to the target categories or to nontarget categories in order to examine the interaction of these dimensions. Rejection latency was longer for target category than for nontarget category distractors.