Acacipetalin in Acacia constricta from north America

Acacipetalin, previously known only from the African legumes Acacia sieberiana var. woodii and Acacia hebeclada, has been isolated from an American species of the genus, Acacia constricta.     

Structural gene sets active in embryos and adult tissues of the sea urchin

Structural gene sequences active in a variety of sea urchin adult and embryo tissues are compared. A single-copy ³H-DNA fraction, termed mDNA, was isolated, which contains sequences complementary to the messenger RNA present on gastrula stage polysomes. Gastrula message sequences are 50 fold concentrated in the mDNA compared to total single-copy DNA. mDNA reactions were carried out with excess mRNA from blastula, pluteus, exogastrula, adult ovary, tubefoot, intestine, and coelomocytes, and with excess total mature oocyte RNA. A single-copy ³H-DNA fraction totally devoid of gastrula message sequences, termed null mDNA, was also reacted with these RNAs. Large differences in the extent of both mDNA and null mDNA reaction with the various RNAs were observed, indicating that in each state of differention a distinct set of structural genes is active, generally characterized by several thousand specific sequences. The complexity of gastrula mRNA was shown in previous work to be about 17 × 10⁶ nucleotides. In units of 10⁶ nucleotides, the complexities of the RNA sequence reacting with mDNA and with null mDNA in each tissue are, respectively, as follows: intestine mRNA; 2.1 and 3.7; coelomocyte mRNA: 3.5 and ≤1.4; tubefoot mRNA: 2.7 and ≤0.4; ovary mRNA: 13 and 6.7; oocyte total RNA: 17 and 20; blastula mRNA: 12 and 15; pluteus mRNA: 14 and ≤0.6; exogastrula mRNA: 14 and ≤0.6. The total complexity of each mRNA population is the sum of these values, as verified for several cases by reactions with total single-copy DNA. A relatively small set of mRNAs, the complexity of which is about 2.1 × 10⁶ nucleotides, appears to be shared by several of the tissues studied.     

Interpersonal relationships and personal space: Research review and theoretical model

This article reviews research concerning interpersonal distance as a function of interpersonal relationships, attraction, and reactions to spatial invasion. To integrate research findings, we propose a simple model, based on the idea that people seek an optimal distance from others that becomes smaller with friends and larger for individuals who do not expect to interact. The model describes comfort-discomfort as a function of interaction distance in three situations: interacting friends, interacting strangers, and strangers who do not expect interaction. These three personal space profiles are discussed in terms of qualifying variables, such as seated vs. standing interaction, sex composition of the dyad, intimacy of conversation topics, and situational variables.A version of the theoretical section of this article was presented at the 82nd annual convention of the American Psychological Association in a symposium entitled Getting Close: Personal Space and Privacy, New Orleans, 1974. An earlier version of the material appears in a book by Irwin Altman (1975).     

Double-label autoradiography on polyacrylamide gels with 3H and 14C

A method of autoradiography is deseribed which allows discrimination between ³H- and ¹⁴C-labeled materials on polyacrylamide gels. The method relies on a very simple procedure for switching from fluorography to autoradiography which results in a decrease in ¹⁴C detection sensitivity of about 10-fold but a concomitant decrease in ³H sensitivity of over 800-fold. With the proper ratio of ³H to ¹⁴C radioactivities, there is little or no “spillover” of one isotope during the detection of the other. No special equipment is required.     

DNA sequence organization in the genomes of five marine invertebrates

The arrangement of repetitive and non-repetitive sequence was studied in the genomic DNA of the oyster (Crassostrea virginica), the surf clam (Spisula solidissima), the horseshoe crab (Limulus polyphemus), a nemertean worm (Cerebratulus lacteus) and a jelly-fish (Aurelia aurita). Except for the jellyfish these animals belong to the protostomial branch of animal evolution, for which little information regarding DNA sequence organization has previously been available. The reassociation kinetics of short (250-300 nucleotide) and long (2,000-3,000 nucleotide) DNA fragments was studied by the hydroxyapatite method. It was shown that in each case a major fraction of the DNA consists of single copy sequences less than about 3,000 nucleotides in length, interspersed with short repetitive sequences. The lengths of the repetitive sequences were estimated by optical hyperchromicity and S1 nuclease measurements made on renaturation products. All the genomes studied include a prominent fraction of interspersed repetitive sequences about 300 nucleotides in length, as well as longer repetitive sequence regions.     

CYP3 a likely candidate for the structural gene of ISO-2 cytochrome C in Saccaromyces cerevisiae.

Mutations specific for iso-2 cytochrome c were obtained in strains bearing a deletion of the structural gene of iso-1-cytochrome c. In this genetic context the mutations entail an inability to grow on glycerol. One of these mutants was shown to have a modified iso-2-cytochrome c as witnessed by its lack of stability and modified chromatographic behaviour. Genetic studies showed the mutations to be allelic to the mutation cyp3-15 previously identified by Clavilier $\text{et al.}$ (1) as a specific enhancer of iso-2-cytochrome c synthesis. The simplesthypothesis to explain the results is that the CYP3 locus is the structural gene for iso-2-cytochrome c.     

Reversion of the gal3 mutation of Escherichia coli: Partial deletion of the insertion sequence

Summary The gal3 mutation of E. coli is an insertion of a DNA sequence, 1,100 base pairs in length, into the operator-promoter region of the galactose operon. This mutation reverts spontaneously to gal⁺ by excision of the insertion to produce stable, inducible revertants, or by tandem duplications of the gal operon to produce unstable, constitutive revertants. The nature of a third class of revertants, which are stable and constitutive, is the subject of the present study.The stable, constitutive class of revertants included approximately 30% of all gal⁺ revertants obtained from a gal3() strain. Although the constitutive reversions could be transduced by , the efficiency was found to be extremely poor and the rare transductants which did appear seemed to originate from abnormal transducing particles. It was concluded that these reversions were not normally packaged by .In order to facilitate the packaging of these reversions, the chlD-pgl region was deleted from the parent gal3() strain. Unexpectedly, the gal3 mutation in the majority of these deletions reverted to produce stable, constitutive reversions exclusively. The explanation proposed was that the chlD-pgl deletions had also removed part of the gal operator-promoter up to the gal3 insertion, so that simple excisions of the insertion yielded stable, constitutive revertants by connecting the gal structural genes to a different promoter. These revertants were not considered to be true representatives of the stable, constitutive class. The specificity of deletion end-points at the insertion was found only in the gal3() strain, and not in gal ⁺, gal ⁺(), or gal3 strains. Moreover, the frequency of spontaneous chlD-pgl deletions increased 10- to 15-fold in presence of the gal3 insertion.A gal phage bearing a true stable, constitutive reversion (gal ^c 200) was isolated from the revertant strain by subsequent deletion of the chlD-pgl segment (31). Electron micrographs of gal ⁺ and gal ^c 200 31(chlD pgl) DNA heteroduplexes were interpreted to indicate that the stable, constitutive reversion had arisen by a deletion of 3/4 of the gal3 insertion sequence.The main conclusions are: (i) the stable, constitutive reversions of gal3 can arise by partial deletions of the insertion sequence, apparently by elimination of the nucleotide sequence which causes polarity; (ii) the chlD-pgl deletions may exhibit preferential termination at the right extremity of the gal3 insertion in presence of prophage ; and (iii) the gal3 insertion appears to inhibit the production of gal particles by providing a nucleotide sequence which is recognized and degraded by a specific endonuclease. It is suggested that inhibition of transducing particle formation by gal3 and the preferred termination of deletions at gal3 might represent related phenomena.