Carbamoyl-phosphate synthetases from Neurospora crassa. Immunological relatedness of the enzymes from Neurospora, bacteria, yeast, and mammals

Neurospora crassa contains two carbamoyl-phosphate synthetases: a mitochondrial enzyme (CPS-A) which supplies carbamoyl phosphate for arginine biosynthesis, and a nuclear enzyme whose product is used for the synthesis of pyrimidines. We have prepared antiserum against a highly purified preparation of the large subunit of CPS-A and have used the antiserum to demonstrate that the large subunit is, like most mitochondrially localized proteins, initially synthesized as a higher molecular weight precursor. The CPS-A antiserum cross-reacts with the nuclear enzyme, allowing us to identify the product of the complex N. crassa pyr-3 genetic locus as a protein with a subunit molecular weight of 180,000. Finally, we have found that the CPS-A antiserum also cross-reacts with carbamoyl-phosphate synthetases from bacteria, yeast, and mammals. The immunological relatedness of carbamoyl-phosphate synthetases from such diverse species suggests that the protein sequences required for carbamoyl phosphate production have been highly conserved during the course of evolution.     

A Study in Neo‐conservative Populism: Richard Trudgen's Why Warriors Lie Down and Die

First appearing in 2000, and with 20,000 copies sold as it entered its sixth printing in 2004, Richard Trudgen's Why Warriors Lie down and Die is a minor publishing phenomenon. Although scholarly forums have generally ignored the book, Christian media outlets, the popular press and neo‐conservative political activists have enthusiastically received and promoted it. An examination of the merits of Why Warriors Lie down and Die suggests that its popularity is only partly explained by original observations or insights on the part of the author. The most important explanation, and implication, of the book's remarkable take‐up lies in the opportune way in which it corresponds with now ascendant neo‐conservative political perspectives on indigenous policy.     

The Redox Biochemistry of Protein Sulfenylation and Sulfinylation

Controlled generation of reactive oxygen species orchestrates numerous physiological signaling events (Finkel, T. (2011) Signal transduction by reactive oxygen species. J. Cell Biol. 194, 7–15). A major cellular target of reactive oxygen species is the thiol side chain (RSH) of Cys, which may assume a wide range of oxidation states (i.e. −2 to +4). Within this context, Cys sulfenic (Cys-SOH) and sulfinic (Cys-SO₂H) acids have emerged as important mechanisms for regulation of protein function. Although this area has been under investigation for over a decade, the scope and biological role of sulfenic/sulfinic acid modifications have been recently expanded with the introduction of new tools for monitoring cysteine oxidation in vitro and directly in cells. This minireview discusses selected recent examples of protein sulfenylation and sulfinylation from the literature, highlighting the role of these post-translational modifications in cell signaling.     

Assay of DNA-RNA hybrids by S1 nuclease digestion and adsorption to DEAE-cellulose filters.

A fast and accurate assay procedure for DNA-RNA hybrids is described in which exhaustive digestion of unhybridized DNA with S1 nuclease is followed by binding of hybrids to filter discs of DEAE-cellulose. The digested DNA can be efficiently washed from the filters so that background levels of 0.1-0.2% of input tracer DNA can be achieved, in contrast to the much higher (approximately 1-5%) backgrounds obtained using TCA precipitation procedures. Short duplexes, as small as 36 nucleotides in length, which are inefficiently bound to hydroxyapatite, are quantitatively bound to the DEAE-cellulose filters.     

Latitudinal variation in population structure of wintering Pacific Black Brant

ABSTRACT.   Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant ( Branta bernicla nigricans ). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.     

Thymus-dependent in vivo suppression of IgE synthesis in a murine IgE-secreting hybridoma

In previous studies we demonstrated that BALB/c mice bearing ascitic tumors of the IgE-secreting hybridoma B53 (epsilon, kappa, anti-dinitrophenyl) developed large numbers of Lyt-1-2+ Fc epsilon R(+) T lymphocytes (T cells with membrane Fc receptors) in response to the elevated serum IgE concentration. The development of Fc epsilon R(+) T lymphocytes was followed by a progressive decrease in the levels of serum IgE in spite of continued proliferation of the hybridoma cells. This sequence of events suggested that the IgE-secreting hybridoma triggered a suppressive immunoregulatory circuit of the host that inhibited IgE expression by the hybridoma cells. The present studies were undertaken to investigate the basis for the subsequent decline in serum IgE levels in mice with B53 tumors and to identify host factors that might be involved in this process. We observed that ascitic B53 cells recovered at increasing time points from BALB/c mice exhibited a selective decline in steady state levels and rates of synthesis of epsilon-heavy chain protein and mRNA. The expression of kappa-light chain protein and mRNA appeared relatively unchanged. The decrease in epsilon-heavy chain gene expression did not occur when B53 tumors were passaged in nu+/nu+ mice or in BALB/c mice depleted of Lyt-2+ cells (suppressor/cytotoxic cell lineage), but did occur in nu+/nu+ mice reconstituted with neonatal BALB/c thymus and in BALB/c mice depleted of L3T4+ cells (helper/inducer cell lineage). That Fc epsilon R(+) T lymphocytes were directly involved in the inhibition of IgE expression was supported by the earlier and more pronounced inhibition of B53 IgE in mice infused with Fc epsilon R(+) T lymphocytes. We conclude from these findings that: 1) the decline in serum IgE levels that occurs toward the end of each generation of in vivo passage of the B53 hybridoma is due to decreased production of IgE by the hybridoma cells, 2) the decreased production of IgE is due to a selective loss of epsilon mRNA expression, 3) the decrease production of IgE by B53 cells is dependent on the presence of Lyt-2+ cells, and 4) Fc epsilon R(+) T lymphocytes participate in the mechanism by which IgE production is suppressed.     

The effect of water and nitrogen amendments on photosynthesis,leaf demography,and resource-use efficiency in Larrea tridentata,a desert evergreen shrub

Summary In the Chihuahuan Desert of southern New Mexico, both water and nitrogen limit the primary productivity of Larrea tridentata, a xerophytic evergreen shrub. Net photosynthesis was positively correlated to leaf N, but only in plants that received supplemental water. Nutrient-use efficiency, defined as photosynthetic carbon gain per unit N invested in leaf tissue, declined with increasing leaf N. However, water-use efficiency, defined as the ratio of photosynthesis to transpiration, increased with increasing leaf N, and thus these two measures of resource-use efficiency were inversely correlated. Resorption efficiency was not significantly altered over the nutrient gradient, nor was it affected by irrigation treatments. Leaf longevity decreased significantly with fertilization although the absolute magnitude of this decrease was fairly small, in part due to a large background of insect-induced mortality. Age-specific gas exchange measurements support the hypothesis that leaf aging represents a redistribution of resources, rather than actual deterioration or declining resource-use efficiency.     

Corrective recombination of mouse immunoglobulin kappa alleles in Abelson murine leukemia virus-transformed pre-B cells.

Previous characterization of mouse immunoglobulin kappa gene rearrangement products cloned from murine plasmacytomas has indicated that two recombination events can take place on a single kappa allele (R. M. Feddersen and B. G. Van Ness, Proc. Natl. Acad. Sci. USA 82:4792-4797, 1985; M. A. Shapiro and M. Weigert, J. Immunol. 139:3834-3839, 1987). To determine whether multiple recombinations on a single kappa allele can contribute to the formation of productive V-J genes through corrective recombinations, we have examined several Abelson murine leukemia virus-transformed pre-B-cell clones which rearrange the kappa locus during cell culture. Clonal cell lines which had rearranged one kappa allele nonproductively while maintaining the other allele in the germ line configuration were grown, and secondary subclones, which subsequently expressed kappa protein, were isolated and examined for further kappa rearrangement. A full spectrum of rearrangement patterns was observed in this sequential cloning, including productive and nonproductive recombinations of the germ line allele and secondary recombinations of the nonproductive allele. The results show that corrective V-J recombinations, with displacement of the nonproductive kappa gene, occur with a significant frequency (6 of 17 kappa-producing subclones). Both deletion and maintenance of the primary (nonfunctional) V-J join, as a reciprocal product, were observed.     

Hensen's node,but not other biological signallers,can induce supernumerary digits in the developing chick limb bud

Summary The purpose of this study was to determine whether the organizer regions of early avian and amphibian embryos could induce supernumerary (SN) wing structures to develop when they were grafted to a slit in the anterior side of stage 19–23 chick wing buds. Supernumerary digits developed in 43% of the wings that received anterior grafts of Hensen's node from stage 4–6 quail or chick embryos; in addition, 16% of the wings had rods of SN cartilage, but not recognizable SN digits. The grafted quail tissue did not contribute to the SN structures. When tissue anterior or lateral to Hensen's node or lateral pieces of the area pellucida caudal to Hensen's node were grafted to anterior slits, the wings usually developed normally. No SN structures developed when Hensen's nodes were grafted to posterior slits in chick wing buds. Wings developed normally when pieces of the dorsal lip of the blastopore from stage 10–11.5 frog (Xenopus laevis and Rana pipiens) embryos were grafted to anterior slits. No SN digits developed when other tissues that have limb-inducing activity in adult urodele amphibians [chick otic vesicle, frog (Rana pipiens) lung and kidney] or that can act as heteroinductors in neural induction (rat kidney, lung, submaxillary gland and urinary bladder; mouse liver and submaxillary gland) were grafted to anterior slits in chick wing buds. SN digits also failed to develop following preaxial grafts of chick optic vesicles. These results suggest that although the anteroposterior polarity of the chick wing bud can be influenced by factors other than the ZPA (e.g., Hensen's node, retinoids), the wing is not so labile that it can respond to a wide variety of inductively-active tissues.