Oxygen inhibition of nitrate uptake is a general regulatory mechanism in nitrate respiration

It has recently been demonstrated that oxygen inhibits nitrate uptake by denitrifying Pseudomonas aeruginosa. The purpose of the present investigation was to determine if this novel mechanism of regulation is universal for the regulation of nitrate respiration in other widely divergent species of bacteria. Nitrate transport by whole cell suspensions was completely and reversibly inhibited in 11 out of 12 species tested, whereas nitrate reduction by cell-free extracts was not affected by oxygen or was only partially inhibited in some cases. These results indicate that oxygen inhibition of nitrate uptake is a general regulatory phenomenon.     

Genes for serum amyloid A proteins map to Chromosome 7 in the mouse

Summary Several restriction fragment length variants have been detected among inbred strains using a mouse serum amyloid A cDNA clone. Five variants were shown to segregate as a single genetic unit and were mapped to Chromosome 7 between the glucose phosphate isomerase locus (Gpi-1) and the pink eye dilution locus (p) using recombinant inbred and congenic strains. The finding that no major MspI or BclI restriction fragments were shared between digests of DNAs from a Chromosome 7 congenic strain and its inbred partner, indicate that most, and probably all, sequences detected with the probe are clustered on Chromosome 7. Aneuploid mapping was used to show that the serum amyloid A gene complex (Saa) is proximal to the Chromosome 7 breakpoint in T(7;X)1Ct, a translocation in which the middle third of Chromosome 7 is inserted into the X-chromosome. A survey of inbred strains revealed a single common Saa haplotype and eight rare haplotypes. The complex distribution of 14 different variants suggests that recombination may have played a role in haplotype evolution.This work was supported by grants GM18684 and CA33093 from the National Institute of General Medical Sciences and the National Cancer Institute, respectively.     

Influence of the solvent on the conformational-dependent properties of random-coil polypeptides. I. The mean-square of the end-to-end distance and of the dipole moment

Conformational energies for the N-acetyl-N'-methylamides of the 20 natural amino acids were calculated, including the solvent effects, as functions of the angles phi and psi for rotation of the main chain and for six positions chi 1 of the C alpha-C beta bond in the side chain (fixed values for chi 2, chi 3, ...). The computed energies were used to evaluate the mean-square end-to-end distance and mean-square dipole moment of homopolypeptides of the 20 natural amino acids. Ten proteins and three enzymes of current interest were also studied. Slight differences in both properties are found on taking the effects of solvent into consideration. Comparison with other computational and experimental results is made.     

An "epidemic" model of sexual intercourse prevalences for black and white adolescents

In adolescence (12-16 years), the prevalence of sexual intercourse increases each year. To explain the increasing yearly prevalences, we propose a recursive equation model of onset of adolescent sexual intercourse. The model allows for an "epidemic" process (the transmission of sexuality from a nonvirgin to a virgin) and a nonepidemic process (two virgins progressing to sexual intercourse). The model also requires that virgin females be pubertally mature before they will progress to sexual intercourse. Adequate fits were obtained to the intercourse prevalences for both black and white respondents. Comparisons of alternative models established that the full model was superior to models that omitted either the nonepidemic process or the requirement of females' pubertal maturation. The model was able to fit both white and blacks simultaneously, assuming equal transition probabilities in both races. Hence, we propose the hypothesis that race differences in sexual intercourse prevalence may be strongly influenced by the age of initiation of the "epidemic" process and by race difference in females' rates of pubertal maturation. The results suggested that most new cases of sexual intercourse arose from the epidemic process and that males were more prone to progress to intercourse, given an opportunity.     

The development of epidermal feet in preparation for metamorphosis in an insect

Insect epidermal cell surfaces can be seen by scanning electron microscopy after removal of the basal lamina. This let us study surface changes in the 5th larval stage of Calpodes ethlius (Lepidoptera, Hesperiidae) in preparation for metamorphosis at the end of the stadium, in particular changes in the basal cell processes or feet, intercellular lymph spaces, filopodia and hemidesmosomes. The feet develop in three phases, initiation, elongation and contraction. Initial growth begins immediately after ecdysis and continues until commitment to pupation 66 hr later. During this phase the feet are randomly oriented. Elongation and orientation begin after commitment to pupation. Orientation is probably achieved by selective survival and growth of those feet that are axially oriented rather than by reorientation. As the larva shortens to the pupal form late in the stadium, contraction of the feet occurs and the cells become columnar. The feet finally disappear as the cells rearrange themselves into new positions in the pupal epidermis. The lateral margins of the feet are united by adhesions even when their interdigitations are most complex. The adhesions separate an intercellular lymph space from the haemolymph. The lymph space remains small through most of the stadium, but enlarges with the loss of lateral junctions as the feet contract and eventually extends along most of the length of the columnar cells. Filopodia then form and span the gaps between the cells as though they have been induced by the separation and loss of lateral cell to cell contact. Scanning electron microscopy also shows that hemidesmosomes reflect the axial alignment of the cells even before the orientation of the feet. The hemidesmosome plaques are linear structures having a constant width of 0.15 - 0.2 mum and variable length. They arise in short sections and lengthen by the linear addition of more sections with the same width. Late in the stadium they lose their axial alignment and may become branched.     

Epstein-Barr virus BZLF1 trans-activator specifically binds to a consensus AP-1 site and is related to c-fos.

Two regions of the Epstein-Barr virus BZLF1 trans-activator protein have sequence similarity to the c-fos protein. Part of the similarity corresponds to the region of c-fos which is similar to the DNA binding domain of c-jun and GCN-4. The structure of the exon which contains this region in c-fos and BZLF1 is also highly conserved between the two genes. Complete BZLF1 protein and a C terminal fragment were prepared either as purified fusion proteins or by in vitro translation from a BZLF1 cDNA. Gel retardation and DNase footprinting assays using these proteins show that BZLF1 is a sequence specific DNA binding protein capable of binding to a target sequence which contains a consensus AP-1 site.     

A second nonrandom translocation, der(16)t(1;16)(q21;q13), in Ewing sarcoma and peripheral neuroectodermal tumor

The majority of Ewing sarcomas and peripheral neuroectodermal tumors (PNET) that have been karyotyped contain a specific translocation, t(11;22)(q23;q11). We report here a second nonrandom translocation, der(16)t(1;16)(q21;q13), in 2 of 20 cases of Ewing sarcoma (seven previously unreported) and 2 of 7 cases of PNET (all previously unreported). All cases with this translocation also contained the t(11;22). Comparison of C-banding patterns in tumor and peripheral lymphocyte karyotypes in one case indicated that the likely breakpoints were 1q21 and 16q13. The presence of this translocation in cell lines will enable further investigation of the molecular events important in the pathogenesis of Ewing sarcoma and PNET.     

Influence of the solvent on the conformational-dependent properties of random coil polypeptides. II. Mean square optical anisotropies and Kerr constants

Mean square optical anisotropies and molar Kerr constants were calculated for homopolypeptides of the 20 natural amino acids and of several enzymes and proteins in the random-coil state. The effect of hydration was taken into account in constructing the molecular potential that gives the conformational energies as a function of the rotational angles phi and psi of the backbone and chi(1) of the side chain. The Rotational Isomeric State model was used in calculated energies, the Valence Optical Scheme and the matrix calculus technique of Flory being employed in the evaluation of the optical properties. The results are compared with calculations for the same substances that were performed without taking into account the solvent, as well as with other similar studies. The Kerr constant is confirmed as being one of the most sensitive properties of a given polypeptide to the residue class and to the sequence of those residues.