Spermidine-induced destabilization of ornithine decarboxylase (ODC) is mediated by accumulation of antizyme in ODC-overproducing variant cells

The mechanism of spermidine-induced destabilization of ornithine decarboxylase (ODC) was examined in newly isolated ODC-overproducing variant cells by use of an in vitro ODC degrading system. The cells accumulated ODC protein in the presence of alpha-difluoromethylornithine. Addition of spermidine to the medium accelerated degradation of ODC protein concomitantly with induction of antizyme, a regulatory protein that binds to ODC, inhibiting its activity. Both the acceleration of ODC degradation and the induction of antizyme were inhibited by cycloheximide, but not by actinomycin D. ODC was degraded rapidly in extracts from spermidine-treated cells. The rate of ODC degradation correlated with the amount of antizyme in the extracts, and the degradation activity was abolished by treatment of the extracts with anti-antizyme antibody. Thus, antizyme induced by spermidine was essential for the accelerated degradation of ODC in the cells. ODC was phosphorylated in the cells, probably at serine residue 303 in the first internal PEST region. ODC phosphorylation occurred even when its new synthesis was inhibited by cycloheximide. Antizyme accelerated the degradations of both dephosphorylated ODC and native ODC.     

The effect of CC14 on uterine ornithine decarboxylase (ODC) in the rat. Inhibition by CC14 of the induction of ODC by E2 and o,p'DDT

The oral administration of carbon tetrachloride (CC14) to ovariectomized rats markedly inhibited the elevation of uterine decarboxylase (ODC) by estradiol-17beta (E2) and by 1-(o-chlorophenyl)-1-(p-chlorophenyl)-2,2,2-trichloroethane (o,p'DDT). The inhibition of ODC induction by CC14 does not appear to be mediated by the formation of an inhibitor of ODC activity. CC14 treatment caused no observable alteration in the uterine cytosolic E2 receptor. Namely, there was no alteration by CC14 in the number of E2 binding sites, in the affinity of the receptor for E2 or in the sedimentation constant of the 8S receptor. Furthermore, the possibility that CC14 inhibition of ODC induction is a resultant of an initial stimulation of this uterine enzyme by CC14 was excluded. The potential inhibitory effect of CC14 by direct of indirect route on uterine protein synthesis is discussed.     

The proopiocortin (adrenocorticotropin/beta-lipoprotein) gene is located on chromosome 2 in humans

The proopiocortin gene is located on chromosome 2 in humans. A 13-kb DNA fragment containing proopiocortin gene sequences was identified in human cells while proopiocortin-related genes sequences of 9.8 and 6.2 kb were present in mouse cells. In human-mouse cell hybrids which contained reduced numbers of human chromosomes and a complete set of mouse chromosomes, the 9.8- and 6.2-kb fragments were always present while the 13-kb fragment segregated with human chromosome 2 and the chromosome 2 enzyme markers acid phosphatase-1 (ACP1), malate dehydrogenase-1 (MDHI), and isocitrate dehydrogenase-1 (IDH1). Analysis of a single cell hybrid with a broken chromosome 2 indicates that the proopiocortin and ACP1 genes are closely linked and in the distal region of the short arm of chromosome 2.     

A highly polymorphic CA/GT repeat in intron 3 of the human urokinase receptor gene (PLAUR)

We describe the first highly polymorphic microsatellite marker for the human urokinase plasminogen activator receptor gene (PLAUR). The urokinase receptor (uPAR) has a central role in cancer invasion and metastasis, which may enable the development of new anti-metastatic therapies. Analysis of the marker genotypes in colorectal cancer cell lines revealed three alleles that were not detected in a series of healthy control individuals, which encourages further genetic study of the role of uPAR in cancer.     

Small ligands that neither bind to nor alter the structure of d(GA x TC)n sequences in DNA

Three minor-groove binding ligands have been used to study the characteristics of two d(GA x CT)n DNAs embedded in longer DNA fragments. The binding of mithramycin, netropsin or Thia-Net to these sequences has been studied using DNAse I footprinting. None of these ligands appeared to bind to d(GA x CT)5 nor to d(GA x CT)22 extensively, although with mithramycin some protected bonds were detected at the very edge of these sequences. In general, these small ligands did not enhance the DNAse I cleavage patterns at the alternating d(GA x CT)n flanking sequences located near DNA regions where the drug was bound. The d(GA x CT)n sequences could act as a rigid block in which it is not easy to propagate structural changes, whereas other sequences flanking the binding sites showed cleavage enhancements.     

The untranslated first exon ''exon 0S'' of the rat estrogen receptor (ER) gene

Occasionally, ipsilateral ischemia develops following the groin insertion of an intra-aortic balloon catheter. Various treatment options have evolved, and include replacing the catheter in the opposite groin, removing it completely, or performing a femorofemoral bypass to deliver blood flow below the catheter. Outlined in this paper is a simple method to restore blood flow to a threatened limb, during femoral artery exploration, in the presence of an intra-aortic balloon. This method is also appropriate for optimal positioning of the balloon catheter prior to femorofemoral bypass.     

A composite regulatory element in the first intron of the estrogen-responsive very low density apolipoprotein II gene

Over 12 years, from 1984 to 1995, we conducted a prospective study of overall and malaria specific mortality among three rural populations in the Sahel, savanna and forest areas of Senegal. The emergence of chloroquine resistance has been associated with a dramatic increase in malaria mortality in each of the studied populations. After the emergence of chloroquine resistance, the risk of malaria death among children 0-9 years old in the three populations was multiplied by 2.1, 2.5 and 5.5, respectively. This is the first study to document malaria mortality at the community level in Africa before and after the emergence of chloroquine resistance. Findings suggest that the spread of chloroquine resistance has had a dramatic impact on the level of malaria mortality in most epidemiological contexts in tropical Africa.     

Characterization of Ca(2+) flows essential in ornithine decarboxylase induction by L-asparagine in rat hepatoma cells using Ca(2+) flow inhibitors

L-Asparagine stimulates bi-directional Ca(2+) flows and induces ornithine decarboxylase in Reuber H-35 hepatoma cells. Previously it has been shown that these effects are completely, but reversibly inhibited by lanthanum chloride. In this study we examined the role(s) of Ca(2+) flows using more specific Ca(2+) flow inhibitors. It was shown that ornithine decarboxylase induction was inhibited by CdCl(2) and verapamil at concentrations above 1 mu M and 100 mu M respectively, but was unaffected by as much as 300 mu M NiCl(2), 1 mM nifedipine, or 10 mu M omega-conotoxin. Enzyme induction was blocked by the Ca(2+)-ATPase pump antagonists vanadate and Compound 48/80 in a dose-dependent manner. These results, taken together with the observations that extracellular Ca(2+) is essential for enzyme induction but a substantial elevation of cytoplasmic [Ca(2+)] is not, suggest that Ca(2+) inflow independent of the receptor-activated Ca(2+) channels, and the Ca(2+)-ATPase mediated Ca(2+) out-flow, are both important factors in the action of L-asparagine.     

Polyamines and regulation of spermatogenesis: selective stimulation of late spermatogonia in transgenic mice overexpressing the human ornithine decarboxylase gene

Polyamines are believed to participate in the induction of cell growth, differentiation, and proliferation, but their role in spermatogenesis has remained obscure. Two transgenic mouse lines (K2 and K15) that overexpress the human ornithine decarboxylase (ODC) gene coding for a rate-controlling enzyme in polyamine biosynthesis and, hence, contain high levels of tissue putrescine have been used to study the stage-specific role of ODC in spermatogenesis. In K2 mice with 30-fold testicular ODC overexpression, [3H]thymidine incorporation at stages I-VI of the cycle of the seminiferous epithelium was significantly above the control level. This may reflect a specific stimulation of DNA synthesis in type A4, intermediate, and type B spermatogonia. The K15 mice that have about 70-fold ODC overexpression showed an elevation of DNA synthesis only at stage V of the cycle, suggesting a specific dependence of type B spermatogonia on putrescine. In K15 mice, [3H]thymidine incorporation of stage VIII tubule segments was decreased, suggesting that excess amounts of putrescine selectively inhibit meiotic DNA synthesis. We propose that putrescine has strictly selective local stimulatory and inhibitory actions during spermatogenic DNA synthesis, and that its excess amounts ultimately may lead to decreased fertility.     

Isolation and sequence analysis of the orotidine-5'-phosphate decarboxylase gene (URA3) of Candida utilis. Comparison with the OMP decarboxylase gene family

The URA3 gene of Candida utilis encoding orotidine-5'-phosphate decarboxylase enzyme was isolated by complementation in Escherichia coli pyrF mutation. The deduced amino-acid sequence is highly similar to that of the Ura3 proteins from other yeast and fungal species. An extensive analysis of the family of orotidine-5'-phosphate decarboxylase is shown. The URA3 gene of C. utilis was able to complement functionally the ura3 mutation of Saccharomyces cerevisiae.