Ornithine Decarboxylase Activity Levels Research Articles

Brain Neurons Express Ornithine Decarboxylase‐Activating Antizyme Inhibitor 2 with Accumulation in Alzheimer's Disease

Polyamines are small cationic molecules that in adult brain are connected to neuronal signaling by regulating inward-rectifier K(+)-channels and different glutamate receptors. Antizyme inhibitors (AZINs) regulate the cellular uptake of polyamines and activate ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine synthesis. Elevated levels of ODC activity and polyamines are detected in various brain disorders including stroke and Alzheimer's disease (AD). We originally reported a novel brain- and testis-specific AZIN, called AZIN2, the distribution of which we have now studied in normal and diseased human brain by in situ hybridization and immunohistochemistry. We found the highest accumulation of AZIN2 in a pearl-on-the-string-like distribution along the axons in both the white and gray matter. AZIN2 was also detected in a vesicle-like distribution in the somas of selected cortical pyramidal neurons. Double-immunofluorescence staining revealed co-localization of AZIN2 and N-methyl D-aspartate-type glutamate receptors (NMDARs) in pyramidal neurons of the cortex. Moreover, we found accumulation of AZIN2 in brains affected by AD, but not by other neurodegenerative disorders (CADASIL or Lewy body disease). ODC activity is mostly linked to cell proliferation, whereas its regulation by AZIN2 in post-mitotically differentiated neurons of the brain apparently serves different purposes. The subcellular distribution of AZIN2 suggests a role in vesicular trafficking.

Ornithine decarboxylase activity in tumor cell lines correlates with sensitivity to cell death induced by histone deacetylase inhibitors

Inhibitors of histone deacetylases (HDAC) show significant promise as targeted anticancer agents against a variety of hematologic and solid tumors. HDAC inhibitors arrest the growth of primary cells, but they induce apoptosis or differentiation of tumor cells. Although the precise mechanism is unknown, differences in cell cycle checkpoints and chromatin structure may be responsible. Cellular polyamines regulate both cell cycle progression and chromatin structure. In tumors, polyamines are abundantly produced because of increased activity of the rate-limiting enzyme in polyamine synthesis, ornithine decarboxylase (ODC). To determine if polyamines contribute to the cellular response to HDAC inhibitors, we inhibited ODC activity with alpha-difluoromethylornithine. Polyamine depletion increased resistance to apoptosis induced by HDAC inhibitors. In addition, we found that ODC activity levels correlated with sensitivity to HDAC inhibitors in a panel of tumor cell lines. We conclude that polyamines participate in the cellular response to HDAC inhibitors and that ODC activity correlates with sensitivity to HDAC inhibitor-induced apoptosis. Thus, elevated polyamine levels might be a biomarker for tumor sensitivity to HDAC inhibitor-induced apoptosis. These findings warrant clinical evaluation of tumor samples to determine if high ODC activity levels predict sensitivity to HDAC inhibitors.

Genetic and biochemical changes in colorectal carcinoma in relation to morphologic characteristics.

A distinct genetic pathway may be involved in the development of polypoid and flat colorectal cancers, two morphologically different cancer subtypes. The present study was undertaken to clarify whether different combinations of some genetic alterations commonly involved (such as K-ras and p53 gene mutations) may exist between polypoid and flat types. In addition, to investigate any different proliferative behavior between the two distinct types of colorectal cancer, we tested the enzymatic activity of ornithine decarboxylase (ODC). A total of 29 polypoid type and 21 flat type colorectal cancers were selected for this study. We investigated K-ras and p53 mutations by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) and single strand conformational polymorphism (PCR-SSCP) analysis, respectively. A radiometric method was used to evaluate ODC activity. K-ras and p53 gene mutations were present in 30 and 48% of cases, respectively. A significant association between the p53 mutation and the flat type of colorectal cancer was detected; on the contrary, no significant difference in frequency of K-ras mutation between polypoid and flat type colorectal cancer was found. A statistically significant difference in ODC activity levels was observed between polypoid and flat types. Moreover, we found that ODC activity was significantly higher in neoplastic tissue than in surrounding normal mucosa in polypoid type colorectal cancer. Different mutation patterns and proliferative behavior were observed in polypoid and flat colorectal malignant tumors. Further studies will be required to ascertain whether the distinct growth appearance of colorectal cancer can affect the outcome and prognosis of patients with this type of malignant disease.

Polyamine levels of human colorectal adenocarcinomas are correlated with tumor stage and grade.

Cellular proliferation and differentiation are regulated by polyamines and their rate-limiting enzyme ornithine decarboxylase (ODC), both of which are correlated with tumor growth, but their role in differentiation is less clear. We investigated the correlation of ODC activity and polyamine levels with tumor stage and grade with respect to sample recruitment. We determined ODC activity ([(14)C]CO(2) release), polyamines (HPLC), and histological staging and grading (TNM classification) of tissue samples from 64 patients with colorectal adenocarcinomas. We found the concentrations of putrescine, spermidine, and N(1)-acetyl-spermidine and the ODC activity in tumor tissue to be twice as high as in adjacent normal mucosa. A critical parameter affecting ODC activity was ischemic time, which significantly reduced ODC activity levels in tumors (threefold) and in the surrounding normal tissue (ninefold) when the ischemic period exceeded 1 h. By contrast, polyamine content was not affected by ischemia. Total polyamine and spermine concentrations were higher in T3 and T4 than in T2 tumors, but putrescine was higher in T4 than in T3 and T2 tumors. There were significantly higher levels of total polyamines and spermine in moderately differentiated (G2) than in poorly differentiated (G3) tumors. The lower spermidine/spermine ratio in G2 (0.44) compared with that in G3 (0.64) tumors suggests the involvement of the polyamines in colonic cell differentiation. Polyamine content is thus correlated with the tumor stage.

Ornithine Decarboxylase of Stagonospora (Septoria) nodorum Is Required for Virulence toward Wheat

A knockout strain of Stagonospora (Septoria) nodorum lacking the single ornithine decarboxylase (ODC) allele has been created by targeted gene replacement. A central region of the S. nodorum ODC gene was isolated by polymerase chain reaction using degenerate oligonucleotides and used to probe a lambda genomic library. The gene was sequenced and the encoded ODC protein sequence was shown to be similar to those from other fungi. The functionality of the S. nodorum ODC was confirmed by complementation of an Aspergillus nidulans mutant (puA) strain devoid of ODC activity, restoring growth in the absence of exogenous polyamines. Sporulation of the transformants was reduced suggesting abberant regulation of the S. nodorum gene in A. nidulans. Transformation-mediated gene replacement was used to create strains which were auxotrophic for putrescine and lack ODC coding sequences. Pathogenicity studies on these mutants showed that they are greatly reduced in virulence compared with non-disrupted transformants. This confirms that the strains carrying an ODC disruption cannot obtain sufficient polyamines from the host plant for normal growth and, thus, that fungal ODC may be a suitable target for chemical intervention.

Ornithine decarboxylase activity and its gene expression are increased in benign hyperplastic prostate.

Ornithine decarboxylase (ODC) is the first key enzyme in the polyamine biosynthesis pathway. Polyamine is believed to participate in cellular proliferation and differentiation. To study the relationship between ODC and the pathogenesis of benign prostatic hyperplasia (BPH), the polyamine levels, ODC activities, and expression of ODC mRNA in benign hyperplastic and normal human prostates were assayed. Polyamine contents and ODC activities in tissue extracts were determined by reverse-phase high-performance liquid chromatography and spectrophotometric procedures, respectively. The ODC mRNA levels were assayed by Northern blot analysis. The contents of putrescine, spermidine, and spermine in BPH tissues were 2.2, 3.4, and 6.0 times higher than those in normal tissues, respectively; the ODC activity of BPH tissue was about 3.2 times higher than in normal tissue; the expression level of ODC mRNA in the BPH tissues was greater than that of normal tissues. The findings imply that 1) the increased ODC activity and polyamine content in prostatic tissue may correlate with the pathogenesis of BPH, and 2) the high level of ODC activity is induced by the overexpression of ODC mRNA.

GABAergic system in the developing mammalian retina: dual sources of GABA at early stages of postnatal development

In the present work, we have characterized the maturation of the GABAergic system in mammalian retina. Immunoreactivity for GABA, GAD (glutamic acid decarboxylase, EC 4.1.1.15) -65 and -67 in the adult rat retina was localized in cells in the inner nuclear and ganglion cell layers. This pattern was established around postnatal day 8 and included transient GABA and GAD-67 expression in horizontal cells. GAD activity was very low at P1 and P4, increasing after P8, reaching maximal activity by P21 and decreasing to attain adult values by P30. GABA content was approximately constant from P1 to P13, increasing thereafter to reach adult levels. GAD protein content increased progressively with postnatal development and the two isoforms could be distinguished at P8.The disparity between retinal GABA content vs presence and activity of the synthesizing enzyme, led us to investigate the alternative pathway for GABA synthesis that utilizes putrescine as a substrate. Highest levels of ornithine decarboxylase activity (the limiting step for putrescine synthesis) were found between P1 and P4, decreasing to very low levels after P13. The same pattern was observed for putrescine content in the retina. Highest amounts were found at P1, that decreased and remained constant after P13. Additionally, approximately 40% of tritiated putrescine incorporated by P1, P4 and adult retinas was converted into GABA.Our results suggest the existence of two different sources of GABA in mammalian retina, one that uses glutamate as a precursor and predominates in the mature nervous system and another that utilizes putrescine and is present transiently at early developmental stages.

Chronic Ethanol Treatment Leads to Increased Ornithine Decarboxylase Activity

Recent research has focused on the N-methyl-D-aspartate receptor system as a major site of ethanol action in the brain and specifically on compensatory changes in the expression of the polyamine-sensitive NR2B subunit. Therefore, we examined the effects of chronic ethanol treatment on polyamine homeostasis in the rat brain. Wistar rats were made dependent by ethanol vapor inhalation. This caused a rise in hippocampal ornithine decarboxylase (ODC) activity that was correlated with the appearance of physiological dependence. ODC activity returned to control levels within 3 days of ethanol withdrawal. Enzyme activity also increased in the cerebral cortex, striatum, and cerebellum of the ethanol-dependent rats. The concentration of the polyamines (putrescine, spermidine, and spermine) in the hippocampus was increased in ethanol-dependent rats. Injection of the ODC inhibitor, alpha-difluoromethylornithine (500 mg/kg) at the onset of withdrawal resulted in a significant reduction in the severity of withdrawal behaviors. The level of ODC activity and the severity of withdrawal behaviors were positively correlated. Perturbed polyamine homeostasis may represent an important molecular component in the initiation of ethanol withdrawal behaviors in the ethanol-dependent rat.

Chronic Ethanol Treatment Leads to Increased Ornithine Decarboxylase Activity: Implications for a Role of Polyamines in Ethanol Dependence and Withdrawal

Recent research has focused on the N-methyl-D-aspartate receptor system as a major site of ethanol action in the brain and specifically on compensatory changes in the expression of the polyamine-sensitive NR2B subunit. Therefore, we examined the effects of chronic ethanol treatment on polyamine homeostasis in the rat brain. Wistar rats were made dependent by ethanol vapor inhalation. This caused a rise in hippocampal ornithine decarboxylase (ODC) activity that was correlated with the appearance of physiological dependence. ODC activity returned to control levels within 3 days of ethanol withdrawal. Enzyme activity also increased in the cerebral cortex, striatum, and cerebellum of the ethanol-dependent rats. The concentration of the polyamines (putrescine, spermidine, and spermine) in the hippocampus was increased in ethanol-dependent rats. Injection of the ODC inhibitor, alpha-difluoromethylornithine (500 mg/kg) at the onset of withdrawal resulted in a significant reduction in the severity of withdrawal behaviors. The level of ODC activity and the severity of withdrawal behaviors were positively correlated. Perturbed polyamine homeostasis may represent an important molecular component in the initiation of ethanol withdrawal behaviors in the ethanol-dependent rat.

Transcription Factor ZBP-89 Regulates the Activity of the Ornithine Decarboxylase Promoter

Appropriate cellular levels of polyamines are required for cell growth and differentiation. Ornithine decarboxylase is a key regulatory enzyme in the biosynthesis of polyamines, and precise regulation of the expression of this enzyme is required, according to cellular growth state. A variety of mitogens increase the level of ornithine decarboxylase activity, and, in most cases, this elevation is due to increased levels of mRNA. A GC box in the proximal promoter of the ornithine decarboxylase gene is required for basal and induced transcriptional activity, and two proteins, Sp1 and NF-ODC1, bind to this region in a mutually exclusive manner. Using a yeast one-hybrid screening method, ZBP-89, a DNA-binding protein, was identified as a candidate for the protein responsible for NF-ODC1 binding activity. Three lines of evidence verified this identification; ZBP-89 copurified with NF-ODC1 binding activity, ZBP-89 antibodies specifically abolished NF-ODC1 binding to the GC box, and binding affinities of 12 different double-stranded oligonucleotides were indistinguishable between NF-ODC1, in nuclear extract, and in vitro translated ZBP-89. ZBP-89 inhibited the activation of the ornithine decarboxylase promoter by Sp1 in Schneider's Drosophila line 2, consistent with properties previously attributed to NF-ODC1.

Inhibition of cell growth in CaCO2 cells by the polyamine analogue N1,N12-bis(ethyl)spermine is preceded by a reduction in MYC oncoprotein levels.

The polyamine analogue N1,N12bis(ethyl)spermine (BESpm) is a potent inhibitor of cell proliferation and is representative of a class of agents currently in clinical trials. Previous studies have demonstrated that BESpm treatment can produce a decrease in the mRNA levels of the protooncogene c-myc resulting from decreased transcription. Investigation into the mechanism of the antiproliferative effect of BESpm in the colon cancer cell line CaCO2 indicated that significant reduction in MYC protein, but not c-myc mRNA levels, preceded cytostasis. Specificity of the downregulation of MYC expression by BESpm treatment was demonstrated by comparison to effects on the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase (SSAT) and the polyamine biosynthetic enzyme ornithine decarboxylase (ODC). SSAT activity rapidly increased while levels of ODC activity decreased after BESpm treatment. Measurement of intracellular polyamines demonstrated significant uptake of the analogue after 24 hours, which was concurrent with a reduction of spermine and spermidine levels. Thus, cellular uptake of BESpm mediated a reduction of polyamine levels that was associated with a decrease of MYC protein at the post-transcriptional level.

Effects of eicosanoids on lipopolysaccharide-induced ornithine decarboxylase activity and polyamine metabolism in the mouse liver

Background/Aims: During endotoxic shock, arachidonic acid is released from the inflammatory cell membranes and is metabolized to form eicosanoids, which modify the deleterious effects of lipopolysaccharide (LPS) on liver function, However, it is not known which protaglandins (PGs) or leukotrienes (LTs) are produced or how they affect the LPS-treated liver. As LPS treatment elevates hepatic ornithine decarboxylase (ODC) activity and affects the polyamine levels of the mouse liver, this study was carried out to examine the effects of eicosanoids and their inhibitors on the induction of ODC activity and polyamine levels in the LPS-treated mouse liver.Methods: LPS in the presence or absence of other drugs was intraperitoneally administered to 6-week-old mice and the livers were then removed. The hepatic ODC activity, polyamine levels, and level of ODC mRNA were determined.Results: The levels of LPS-induced ODC activity, the putrescine (PUT) and N1-acetylspermidine (A-SPD) were reduced by the administration of PGE1. ODC activity was enhanced by the administration of corticosteron, AA-2414 (an antagonist of thromboxane (TX) A2) and TXB2, whereas the A-SPD level was reduced by corticosterone and AA-2414 treatment. The level of ODC mRNA changed in parallel with the change in OdC activity.Conclusions: PGE1 may reduce the LPS-induced production of inflammation-accelerating cytokines and reduce the level of ODC activation. Corticosterone and AA-2414 treatment may attenuate the LPS-induced production of eicosanoids, and enhance the LPS-induced ODC activation. It is possible that the eicosanoids produced by LPS treatment inhibit ODC activation during endotoxic shock.

Alpha-difluoromethylornithine-resistant cell lines obtained after one-step selection of Leishmania mexicana promastigote cultures.

Proliferation of Leishmania mexicana promastigotes in synthetic medium can be blocked by the depletion of intracellular polyamine pools induced by the presence of D,L-alpha-difluoromethylornithine (DFMO), a specific and irreversible inhibitor of ornithine decarboxylase (ODC). Here we report that DFMO-resistant cell lines growing normally at DFMO levels of 10 mM have been obtained from non-proliferating cultures after a single-step selection in the presence of high concentrations of the drug. The DFMO-resistant promastigotes underwent a morphological transformation into an 'amastigote-like' form after incubation for several hours at gradually increasing temperatures up to 35 degrees C. The uptake of DFMO was not significantly altered in the drug-resistant cell lines but in both cases (promastigote and 'amastigote-like' forms) the ODC specific activity was increased approx. 15-fold over the normal enzymic levels found in the wild-type Leishmania. The enzyme affinities for its substrate and for DFMO gave very similar values in the drug-resistant promastigotes and the wild-type parasites. In contrast, ODC from the 'amastigote-like' Leishmania showed a higher affinity for ornithine and a decreased capacity for the binding of DFMO. An 80-fold amplification of the ODC gene and a corresponding increase in its transcripts have been detected in both DFMO-resistant Leishmania cell lines. The drug-resistant phenotypes with their characteristic morphologies, the increased levels of ODC activity and the amplification of the ODC gene have been stable for at least 6 months in the absence of selective pressure.

The modulation effect of vitamin E on prostaglandin E 2 level and ornithine decarboxylase activity at the promotion phase of lung tumorigenesis in mice

The present study was undertaken to investigate a mechanism of the inhibitory effect of vitamin E in urethane-induced lung tumorigenesis in mice. We assayed ornithine decarboxylase (ODC) activity and the prostaglandin E 2 (PGE 2) level in lung at 8 weeks after urethane injection (promotion phase). Excessive vitamin E feeding or indomethacin treatment suppressed the urethane-induced increase in ODC activity, while exogenous PGE 2 overcame the effect of vitamin E on ODC activity. Furthermore, the amount of PGE 2 and the level of ODC activity were well correlated. These results indicate that the vitamin E-induced decrease in PGE 2 level probably contributes to the inhibition of ODC induction and the prevention of tumor development in the lung.

Comparison of ultraviolet light-induced skin carcinogenesis and ornithine decarboxylase activity in sencar and hairless SKH-1 mice fed a constant level of dietary lipid varying in corn and coconut oil.

To investigate the effect of various levels of corn oil and coconut oil on ultraviolet (UV) light-induced skin tumorigenesis and ornithine decarboxylase (ODC) activity, Sencar and SKH-1 mice were fed one of three 15% (weight) fat semipurified diets containing three ratios of corn oil to coconut oil: 1.0%:14.0%, 7.9%:7.1%, and 15.0%:0.0% in Diets A, B, and C, respectively. Groups of 30 Sencar and SKH-1 mice were fed one of the diets for three weeks before UV irradiation; then both strains were UV irradiated with an initial dose of 90 mJ/cm2. The dose was given three times a week and increased 25% each week. For Sencar mice (irradiated 33 wks for a total dose of 48 J/cm2), tumor incidence reached a maximum of 60%, 60%, and 53% for Diets A, B, and C, respectively, with an overall average of one to two tumors per tumor-bearing animal. For the SKH-1 mice (irradiated 29 wks for a total dose of 18 J/cm2), all diet groups reached 100% incidence by 29 weeks, with approximately 12 tumors per tumor-bearing mouse. No significant effect of dietary corn oil/coconut oil was found for tumor latency, incidence, or yield in either strain. The effect of increasing corn oil on epidermal ODC activity in chronically UV-irradiated Sencar and SKH-1 mice was assessed. Three groups of mice from each strain were fed one of the experimental diets and UV irradiated for six weeks. Sencar mice showed no increase in ODC activity until six weeks of treatment, when the levels of ODC activity in the UV-irradiated mice fed Diet A were significantly higher than those in mice fed Diet B or Diet C: 1.27, 0.55, and 0.52 nmol/mg protein/hr, respectively. In the SKH-1 mice, ODC activity was increased by the first week of UV treatment, and by three weeks of treatment a dietary effect was observed; ODC activity was significantly higher in mice fed Diet C (0.70 nmol/mg protein/hr) than in mice fed Diet A (0.18 nmol/mg protein/hr). Although there was no significant effect of dietary corn oil/coconut oil on UV-induced tumor incidence, the data indicate that chronically UV-irradiated hairless SKH-1 mice are more susceptible to UV-induced skin carcinogenesis than Sencar mice and that this susceptibility is correlated with increased in ODC activity, a parameter of cell proliferation.

Chemopreventive effects of taurine on diethylnitrosamine and phenobarbital-induced hepatocarcinogenesis in male F344 rats.

Modifying effects of taurine, a naturally occurring organosulfur compound, on diethylnitrosamine (DEN) and phenobarbital (PB)‐induced hepatocarcinogenesis were examined in rats. Male F344 rats, 5 weeks old, were divided into 8 groups. Rats of groups 1 through 5 were given i.p. injections of DEN (100 mgAg body weight) once a week for 3 weeks from one week after the start of the experiment. Of them, animals of group 2 received taurine mixed in a basal diet at a concentration of 2000 ppm for the initial 4 weeks, and those of groups 3 and 5 were given the agent starting 4 weeks after the beginning of experiment until the end (24 weeks). Rats in groups 1, 4, 7 and 8 were kept on the basal diet throughout the experiment (24 weeks). Group 6 was given taurine throughout the experiment and group 8 was treated as a vehicle control. Animals of groups 1,2, 3 and 7 received PB in drinking water at a dose of 500 ppm from one week after the end of carcinogen or vehicle treatment. Liver neoplasms were recognized only in DEN‐treated groups. The incidence and average number of liver neoplasms of group 3 were significantly lower than those of group 1. The number of glutathione S‐transferase placenta! form (GST‐P)‐positive foci of group 2 or 3 was significantly smaller than that of group 1 (P < 0.01 or P < 0,005). The average and unit areas of GST‐P‐positive foci in groups 2 and 3 were also significantly smaller than those in group 1 (P< 0.005 and P< 0.0001, P< 0.0001 and P< 0.001, respectively). In this study, the level of ornithine decarboxylase activity in non‐neoplastic liver tissue was reduced by taurine treatment in both the initiation and postinitiation phases. These results suggest that taurine could be a chemopreventive agent for liver neoplasia.

Insulin Signaling in Chick Embryos Exposed to Alcohol

Although insulin is known to be an important generator of regulatory signals during fetal growth and development, neither the immediate nor long-term effects of alcohol (ethanol) on insulin action are well understood. In the rat, fetal exposure to alcohol has been shown to be correlated with a subsequent abnormal response to a glucose load in the neonate and adult. Further, fetal hypoplasia secondary to maternal alcohol consumption is correlated with decreased placental glucose transport and with a lowering of the glucose levels in fetal tissues. However, the fetal effects of alcohol cannot be completely overcome by glucose/caloric supplementation, suggesting that factors other than glucose transport are involved. Using an embryonic chick model that negates the factors of maternal/placental metabolism and transport, the current study found that fetal alcohol exposure markedly increased insulin binding in developing tissue, but had little effect on the binding of the insulin-like growth factors. Competitive binding experiments revealed a marked increase in insulin receptor numbers, but no change in binding affinity as a result of the alcohol exposure. Basal uptake of 2-deoxyglucose by fetal tissue was lowered by alcohol exposure, but incubation with exogenous porcine insulin (1 x 10(-7) M) resulted in a significant increase in glucose uptake by the alcohol-exposed embryos. The increases in insulin binding and in insulin-dependent glucose uptake notwithstanding, exogenous insulin could not induce normal levels of ornithine decarboxylase activity in embryonic cells previously exposed to alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)

PC12 Variants with Altered Ornithine Decarboxylase Expression Patterns Exhibit Altered Signal Transduction Capabilities

Nerve growth factor (NGF) induced differentiation of primary and permanent neuronal cell cultures is accompanied by a rapid and transient induction of ornithine decarboxylase (ODC) mRNA and enzymatic activity; a similar ODC induction accompanies mitogenic effectors in many additional cell types. In an effort to assess the role of ODC activity in neuronal cell biology, we have used the ODC suicide substrate inhibitor difluoromethylornithine (DFMO) to select PC12 cell variants with altered ODC expression patterns and characterized the resulting phenotypes. The variants fall into three distinct classes based upon their patterns of ODC mRNA and ODC activity levels; however, all are severely compromised in their ability to respond properly to NGF treatment. Following NGF treatment, none of the variants exhibits any morphological differentiation. In addition, none of the variants is capable of properly inducing either c-fos mRNA (an "immediate early" response) or GAP-43 mRNA (a "late" response) following NGF treatment. Our data suggest that altered ODC metabolism can lead to inactivation of element(s) active very early in the normal NGF signal transduction cascade.

Signaling Pathways Regulating Ornithine Decarboxylase Activity in the Embryonic Chicken

The pathways regulating ornithine decarboxylase (ODC) activity in the chick embryo were studied to determine which kinase-signaling pathways regulate ODC activity levels during development. Insulin-dependent tyrosine kinase, protein kinase C and cAMP-dependent protein kinase were activated by the addition of insulin, tetradecanoylphorbol-12,13-acetate, and forskolin, respectively. All three drugs increased ODC activity and forskolin combined with insulin increased ODC activity above the increase caused by either drug alone. These results suggest that all three signaling pathways regulate ODC activity during development and that common intermediates exist among the pathways downstream of the kinases.

Elevated ornithine decarboxylase activity and polyamine levels during early development in the brine shrimp Artemia franciscana

AbstractRehydrated Artemia cysts were assayed for ornithine decarboxylase (ODC) activity and levels of putrescine, spermidine, and spermine during pre‐emergent development, emergence and hatching. Low but detectable ODC activity levels increased significantly within 2 hr, suggesting de novo synthesis of ODC protein and representing one of the earliest enzymatic biochemical markers in post dormancy development. ODC activity increased 100‐fold during preemergent development (occurring in the absence of an increase in tissue polyamine content). This increase in enzyme activity occurs in the relative absence of DNA synthesis but may be related to an enhanced polyamine synthetic capacity necessary for other physiological processes such as early transcriptional and translational activity. A second, higher ODC activity peak (correlated with a significant increase in polyamines) prior to hatching may be related to DNA synthesis and other biochemical processes associated with hatching of stage 1 nauplii and is correlated with increasing ecdysteroid titres reported previously. Putrescine and spermidine levels were significantly higher than spermine levels (2.5, 2.65, and 0.13 μmoles/g dry weight) at the onset of rehydration. High endogenous polyamines levels in encysted embryos are most likely available for use in metabolic processes associated with early differentiation. Polyamine levels increased significantly just prior to emergence and continued increasing throughout hatching. Spermidine to spermine ratios (&gt;18) should reflect high rates of overall biosynthetic processes throughout preemergence, emergence, and hatching. © Wiley‐Liss, Inc.