Autogenous translational operator recognized by bacteriophage T4 DNA polymerase.

The synthesis of the DNA polymerase of bacteriophage T4 is autogenously regulated. This protein (gp43), the product of gene 43, binds to a segment of its mRNA that overlaps its ribosome binding site, and thereby blocks translation. We have determined the Kd of the gp43-operator interaction to be 1.

Selenium accumulation and elimination in mallards.

Selenium accumulation and loss were measured in adult mallards (Anas platyrhynchos) fed selenomethionine during two experiments. In Experiment 1, both sexes were fed a diet containing 10 ppm selenium for 6 weeks, followed by 6 weeks on untreated feed. Selenium accumulation in liver and muscle of females was described by C = A(1-e-bt).

Evidence for a functional and anatomical relationship between the lateral septum and the hypothalamus in the control of flank marking behavior in Golden hamsters.

Golden hamsters with established dominant/subordinate relationships communicate their social status by rubbing pheromone-producing flank glands against objects in the environment. This behavior, called flank marking, is controlled by vasopressin-sensitive neurons localized to the anterior hypothalamus. Vasopressinergic magnocellular neurons in the nucleus circularis and medial aspect of the supraoptic nucleus are thought to be a source of neurotransmitter for the initiation of flank marking.

Third chronological supplement to the carcinogenic potency database: standardized results of animal bioassays published through December 1986 and by the National Toxicology Program through June 1987.

This paper is the third chronological supplement to the Carcinogenic Potency Database that first appeared in this journal in 1984. We report here results of carcinogenesis bioassays published in the general literature between January 1985 and December 1986, and in Technical Reports of the National Toxicology Program between June 1986 and June 1987. This supplement includes results of 337 long-term, chronic experiments of 121 compounds, and reports the same information about each experiment in the same plot format as the earlier papers, e.

DSM-III and DSM-III-R schizotypal symptoms in borderline personality disorder.

The frequency of DSM-III and DSM-III-R schizotypal personality disorder (SPD) symptoms and diagnosis was explored in 39 inpatients classified as borderline by the Diagnostic Interview for Borderlines (DIB) and 19 inpatient major depressive disorder (MDD) controls. Most SPD symptoms in all groups, except the nondepressed borderlines, derived from social-interpersonal items. By DSM-III, 24 borderlines (62%) but only six controls (32%) had cognitive-perceptual SPD symptoms (P = .

Dietary carcinogens, environmental pollution, and cancer: some misconceptions.

Various misconceptions about dietary carcinogens, pesticide residues, and cancer causation are discussed. The pesticides in our diet are 99.99% natural, since plants make an enormous variety of toxins against fungi, insects, and animal predators.

Natural chemicals, synthetic chemicals, risk assessment, and cancer.

The administration of chemicals at the maximum tolerated dose (MTD) in standard animal cancer tests is postulated to increase cell division (mitogenesis), which in turn increases rates of mutagenesis and thus carcinogenesis. The animal data are consistent with this mechanism, because a high proportion--about half--of all chemicals tested (whether natural or synthetic) are indeed rodent carcinogens. We conclude that at the low doses of most human exposures, where cell killing does not occur, the hazards to humans of rodent carcinogens may be much lower than is commonly assumed.

Application of entropy measures derived from the ergodic theory of dynamical systems to rat locomotor behavior.

Measures of complexity derived from ergodic theory of dynamical systems were developed and applied to an exemplary data set describing locomotor movements of rats in a bounded space. A symbolic dynamical system was obtained by partitioning the event space into equally probable partition elements, using a k-dimensional tree. The measures calculated from the symbolic sequences included the topological entropy (ht)--i.

Selection of the initiator tRNA by Escherichia coli initiation factors.

We have developed a new technique, called 'toeprinting,' which has allowed a study of the tRNA-binding properties of Escherichia coli translation initiation complexes. In response to natural mRNAs, the initiator tRNA and a variety of elongator tRNAs bind to the same tRNA-binding site on the 30S ribosomal subunit as long as a cognate codon is present near the Shine and Dalgarno sequence. The selection of the initiator tRNA in 30S initiation complexes is accomplished by initiation factors IF2 and IF3.

Biochemical characterization of the fibronectin binding sites for IgG.

Plasma fibronectin (Fn) is a constituent of cryoglobulins and has been shown to interact with immune complexes. In a previous report we demonstrated that Fn specifically bound to IgG immobilized on a solid matrix. To localize and biochemically characterize the sites on the Fn molecule involved in this interaction, Fn was enzymatically cleaved with subtilisin and subjected to IgG affinity chromatography.

Dual translational initiation sites control function of the lambda S gene.

Lysis gene S of phage lambda has a 107 codon reading frame beginning with the codons Met1-Lys2-Met3. Genetic data have suggested that translational initiation occurs at both Met1 and Met3, generating two polypeptides, S107 and S105 respectively. We have proposed a model in which the proper scheduling of lysis depends on the partition of translational initiations between the two start codons.

Location and molecular cloning of the structural gene for the deoxyguanosine triphosphate triphosphohydrolase of Escherichia coli.

The structural gene for deoxyguanosine triphosphate triphosphohydrolase (dGTPase) (EC 3.1.5.

Identification of a T4 gene required for bacteriophage mRNA processing.

A ribonucleolytic activity that cleaves within the Shine/Dalgarno sequences of the bacteriophage T4 motA and ORF2 mRNAs was recently described. We have identified additional sites of processing within several other ribosome binding sites, including two sites in the polycistronic frd transcript. Deletion mutants (farP) that overproduce the product of frd are defective in this mRNA processing.

Human plasma fibronectin as a substrate for human urokinase.

An early event in malignant transformation is the increased expression of proteases, such as plasminogen activator, which can degrade surrounding extracellular matrices, thereby conferring an advantage for tumour cell invasion and metastasis. The present studies provide evidence that plasma fibronectin (Fn), which is a component of the extracellular matrix, is a direct substrate for the plasminogen activator urokinase (UK). Human plasma Fn was incubated with human UK under plasminogen-free conditions.

Ribosome-binding sites and RNA-processing sites in the transcript of the Escherichia coli unc operon.

The polycistronic mRNA encoding the nine genes of the unc operon of Escherichia coli was studied. We demonstrated the ribosome-binding capabilities of six of the nine unc genes, uncB, uncE, uncF, uncH, uncA, and uncD, by using the technique of primer extension inhibition or "toeprinting." No toeprint was detected for the other genes, uncI, uncG, and uncC.

Interspecies extrapolation in carcinogenesis: prediction between rats and mice.

Interspecies extrapolation in carcinogenesis is studied by evaluating prediction from rats to mice and from mice to rats. The Carcinogenic Potency Database, which includes 3500 cancer tests conducted in rats or mice on 955 compounds, is used for the analysis. About half of the chemicals tested for carcinogenicity are positive in at least one test, and this proportion is similar when rats and mice are considered separately.

Granular cell odontogenic cyst: a unicystic ameloblastoma with late recurrence as follicular ameloblastoma.

This report is a follow-up of the original case of granular cell odontogenic cyst described by Gold and Christ in 1970. The lesion, originally treated by enucleation in 1965, recurred 18 years later as a follicular ameloblastoma with prominent plexiform and acanthomatous histologic patterns. No histologic evidence of granular cells was noted in the recurrent lesion.

Summary of carcinogenic potency and positivity for 492 rodent carcinogens in the carcinogenic potency database.

A tabulation of carcinogenic potency (TD50) by species for 492 chemicals that induce tumors in rats or mice is presented. With the use of the Carcinogenic Potency Database, experimental results are summarized by indicating in which sex-species groups the chemical was tested and the respective evaluations of carcinogenicity. A comparison of three summary measures of TD50 for chemicals with more than one positive experiment per species shows that the most potent TD50 value is similar to measures that average values or functions of values.