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PubMedDate not supplied

Activity of adenylate cyclase and 5'-nucleotidase in the sensorimotor and limbic structures of the brain in rats after manipulatory training.

Adenylate cyclase (AC) and 5'-nucleotidase (NT) activities were measured in the limbic (amygdala, hippocampus) and sensorimotor (cortex, striatum) structures of the brain in three groups of rats: untrained rats and rats which were good and poor learners in training to perform movements involving pushing against an obstruction. After training, AC activity decreased in all structures studied. Activity decreased in the cortex and striatum to a greater extent in good learners, and in the amygdala in poor learners. NT activity decreased in all brain structures apart from the striatum, to a greater extent in rats which were less able to learn to produce movements involving prolonged pushing. The striatum was the only structure in which increases in NT activity occurred, from the lowest initial level in the control group. 1.0 +/- 0.04 microgram P(i)/mg protein/min, to 1.3 +/- 0.1 micrograms P(i)/mg protein/min in poor learners and to 2.0 +/- 0.1 micrograms P(i)/mg protein/min in good learners. Interhemisphere asymmetries in AC activity in the cortex and hippocampus were seen, along with an interhemisphere difference in NT activity in the amygdala. Thus, the activity of enzymes involved in adenine and cAMP biosynthesis changed in different ways in the limbic and sensorimotor structures of the brain, depending on the ability of rats to learn. The increase in NT activity after training of rats, which was limited to the striatum, may reflect a special role for the purinergic system in these structures in mediating sensation-regulated movements.

5'-Nucleotidase↗
PubMed1990

5'-Nucleotidase activities in sera and liver tissues of viral hepatitis patients.

In order to disclose the mechanisms involving the elevation of serum 5'-nucleotidase (5'-N) activity in viral hepatitis patients, 5'-N activities in sera and liver tissues were examined in acute and chronic hepatitis patients and compared with normal controls. Serum 5'-N activities were 0.714 +/- 0.106 nanomoles adenosine/hour/mg protein in normal individuals, 1.162 +/- 0.479 in acute hepatitis patients, and 0.845 +/- 0.530 in chronic hepatitis patients. Tissue 5'-N activities were 298.8 +/- 86.7 in normal individuals, 598.1 +/- 198.3 in acute hepatitis patients, and 462.2 +/- 91.3 in chronic hepatitis patients. Serum 5'-N activity increased significantly in acute hepatitis patients, but not in chronic hepatitis patients. Tissue 5'-N activity increased in both acute and chronic hepatitis patients. The elevation of 5'-N activity in liver tissue was not an essential factor in the elevation of serum 5'-N levels. Other factors causing the release of 5'-N from liver tissue into the blood stream are thought to be more important. It is suggested that the shedding of plasma membrane with ecto 5'-N activity due to cell damage, or leakage of bile containing high 5'-N activity were causative factors.

5'-Nucleotidase↗
PubMed2000

Activities of adenosine deaminase and 5'-nucleotidase in cancerous and noncancerous human colorectal tissues.

In order to characterize human colorectal cancer, much attention has been paid to enzyme studies. However, little is known about the correlation between the levels of key enzymes of purine nucleotide pathway and some clinical and biological indicators of tumor invasiveness and aggressiveness. Adenosine deaminase (ADA) and 5'-nucleotidase (5'-NT) were measured in cancerous and cancer-free adjacent large bowel tissues from 38 patients with colorectal carcinoma. We have analyzed the relationship between the enzyme levels and some clinical and pathological parameters. The enzymes' activities were markedly higher in primary tumors than in corresponding normal mucosae. The ADA level in tumor tissue was significantly correlated with lymph node metastasis, histologic type, tumor location, and patient's age, whereas the 5'-NT level showed a significant correlation with tumor grade and tumor location. ADA activity in tumor tissues was significantly higher in patients whose clinical course remained stable than in those with recurrent diseases. The purine metabolism and salvage pathway activity of purine nucleotides are accelerated in the cancerous human colorectal tissue. Although our findings suggest that these enzymes' activities are most likely related to the same histomorphological architecture of the tumor, the authors believe that long-term follow-up studies are needed to evaluate the prognostic value of purine enzymes for colorectal cancer.

5'-Nucleotidase↗
PubMed2005

Evidence for essential catalytic determinants for human erythrocyte pyrimidine 5'-nucleotidase.

Human erythrocyte pyrimidine 5'-nucleotidase, PN-I, catalyzes the dephosphorylation of pyrimidine nucleoside monophosphates. The enzyme also possesses phosphotransferase activity, transferring phosphate groups between pyrimidine nucleoside monophosphates and various pyrimidine nucleosides. Deficiency of the enzyme activity is associated with a hemolytic anemia. PN-I cDNA has been expressed in Escherichia coli, yielding a fully active recombinant enzyme, which was purified to homogeneity and extensively characterized. Multiple sequence alignment of PN-I and homologues proteins revealed the existence of conserved regions, whose importance in catalysis was examined by performing experiments designed to intercept covalent intermediates as strongly suggested by our previous kinetic studies. Furthermore, a functional analysis of the enzyme was carried out through site-directed mutagenesis designed on the basis of the sequence of the identified conserved regions as well as mutations observed in PN-I-deficient patients.

5'-Nucleotidase↗
PubMed2005

Enforced expression of cytosolic 5'-nucleotidase I confers resistance to nucleoside analogues in vitro but systemic chemotherapy toxicity precludes in vivo selection.

PURPOSE: Retroviral transfer of cDNA sequences that confer drug resistance can be used to protect against chemotherapy-induced hematopoietic toxicity and for the selective expansion of gene-modified cells. To successfully expand genetically engineered cells in vivo, an appropriate balance must be achieved between systemic toxicity induced by the selecting agent and the expansion of modified cells. METHOD: In this study, we investigate retroviral transfer of cytosolic 5'-nucleotidase I (cN-I) for protection and selection of gene-modified cells when treated with 2-chloro-2'-deoxyadenosine (2-CdA) and 5-fluorouracil (5-FU) alone and in combination. We also attempt to design a treatment strategy for the potential in vivo selection of cN-I-modified cells by administering 5-FU to mice prior to 2-CdA treatment. RESULTS: Our results show that cN-I can be transferred by recombinant retroviruses, and that enforced expression of cN-I protects murine fibroblast and hematopoietic progenitor cells from the cytotoxic effects of 2-CdA and/or 5-FU. Furthermore, we show that the combined administration of 5-FU and 2-CdA potentiates hematopoietic stem cell toxicity. However, the treatment also results in severe myelosuppression. CONCLUSION: These results show that while cN-I provides both protective and selective benefits to gene-modified cells in vitro, selection requires a treatment strategy that is likely too toxic to consider cN-I as an in vivo selectable marker.

5'-Nucleotidase↗
PubMed2006

Adenosine produced via the CD73/ecto-5'-nucleotidase pathway has no impact on erythropoietin production but is associated with reduced kidney weight.

CD73/ecto-5'-nucleotidase, which catalyzes the conversion of adenosine monophosphate to adenosine, has been implicated in vascular homeostasis. The aim of the present study was to evaluate the role of CD73 in erythropoietin (EPO) production and to determine its influence on basal kidney perfusion using a CD73 knockout mutant recently generated by us. Of all organs investigated, kidneys showed the most prominent CD73 activity, preferentially located in peritubular fibroblasts of the renal cortex and the glomerular mesangium. In the absence of CD73, alkaline phosphatase remained unchanged, but tissue adenosine was reduced under control conditions (by 76%) and during normobaric hypoxia (by 72%). Despite the loss of CD73 activity, EPO mRNA and plasma protein concentrations were not different under basal conditions as well as after normobaric hypoxia (8% O2) and carbon monoxide (0.1% CO) inhalation (both for 4 h). Although there were no differences in blood pressure and urine flow volume, average weight of both kidneys was reduced by 21% in the knockout (wild type 7.17+/-1.18 mg g-1 body wt, CD73-/- 5.70+/-1.91 mg g-1 body wt). Measurement of renal plasma flow and glomerular filtration revealed no significant differences when related to respective kidney weights. We conclude that adenosine derived by the extracellular CD73 pathway has no impact on EPO production under basal conditions and after hypoxic challenge but may determine kidney weight.

5'-Nucleotidase↗
PubMed2005

Adenosine deaminase and 5'nucleotidase activities in peripheral blood T cells of multiple sclerosis patients.

Multiple sclerosis (MS) is one of the most common causes of neurological disability in young and middle-aged adults and is thought to be mediated by autoreactive T cells. Activities of adenosine deaminase (ADA) and 5'(nucleotidase (5'NT), which are involved in the differentiation and maturation of the lymphoid system, were measured in peripheral blood T cells from 21 MS patients and in 23 age and sex matched healthy controls to determine whether an association existed between these enzyme abnormalities and cellular immune functions. ADA and 5'NT activities were found significantly decreased in MS patients (P < .001 and P < .01 respectively) when compared with controls. Low levels of ADA and 5'NT activities were found irrespective of whether patients had relapsing-remitting or chronic progressive MS. These findings suggest that low levels of these enzyme activities in T cells may be related to the persistent abnormalities in T cell function in the clinical course of MS.

5'-Nucleotidase↗
PubMed1976

Liver plasma membranes from essential fatty acid-deficient rats. Isolation, fatty acid composition, and activities of 5'-nucleotidase, ATPase and adenylate cyclase.

Tod determine whether changes in unsaturation of fatty acids in rat liver plasma membranes might alter activities of membrane-associated enzymes, liver plasma membranes were prepared from rats fed purified diets lacking or supplemented with essential fatty acids. Two methods of membrane purification were used. A similar degree of purification was obtained with both methods for both depleted and control membranes, as indicated by marker enzyme purification. The proportion of essential fatty acids of the linoleate series was significantly lower in phospholipids from depleted rats. The specific activity of 5'-nucleotidase was lower, and the activity, V and apparent Km for total (Na+ +K+ +Mg2+)-ATPase were higher in the depleted liver plasma membranes. Arrhenius plots of total ATPase activity showed a discontinuity at the same temperature for both the depleted and control membranes. Activity with the depleted membranes was higher at all temperatures tested. Supplementation of deficient rats with a source of essential fatty acids (corn oil) restored V and apparent Km values to normal. Adenylate cyclase activity in the presence of fluoride, glucagon or glucagon plus GTP was significantly lower in the depleted plasma membranes.

Adenosine Triphosphatases↗
PubMed1990

Increased 5'-nucleotidase activity induced by dibutyryl cyclic AMP treatment of cultured glial cells.

In an attempt to clarify the relationship between ecto-5'-nucleotidase (5'-N) activity and cell differentiation of glial cells, dibutyryl cyclic AMP (dBcAMP), which induces cell differentiation, was administrated to cultured rat glioma cells in logarithmic and confluent phases of cultivation. To evaluate the cellular differentiation, cell morphology and the number of glial fibrillary acidic protein (GFAP) positive cells were examined. Treatment with 1 mM dBcAMP decreased cell proliferation and induced cell differentiation in both the logarithmic and the confluent phases. The number of GFAP-positive cells increased with cellular aging and this tendency was enhanced by dBcAMP administration. Ecto-5'-N activity was higher in dBcAMP treated cells than in non-treated cells in both the logarithmic and the confluent phases. These findings suggest that ecto-5'-N activity of C6 glioma cells is increased by dBcAMP actions and is accompanied by cell differentiation.

5'-Nucleotidase↗
PubMed1978

Red-cell pyrimidine 5'-nucleotidase and lead poisoning.

In an effort to determine its value as a biological index of lead poisoning, we investigated the red-cell pyrimidine 5'-nucleotidase (Py5N) activity, along with the classical parameters, in 22 subjects with varying degrees of lead intoxication. In all cases, the red-cell Py5N activity was found to be decreased, even when most of the other biological tests of lead intoxication remained negative. Below the level of 150 microgram of lead per 100 ml of blood, the magnitude of the red-cell Py5N decrease was roughly proportional to the level of lead in peripheral blood. We conclude that red-cell Py5N is a convenient, reliable and sensitive index of lead exposure.

Clinical Enzyme Tests↗
PubMed1979

Study of a case with severe red-cell pyrimidine 5'-nucleotidase deficiency.

A deficiency of erythrocyte pyrimidine 5'-nucleotidase was found in a 23-year-old male suffering from severe congenital hemolytic disease. Results from exhaustive metabolic exploration are given and compared with reticulocyte-rich blood from subjects with auto-immune hemolytic disease. Evidence is given that the 20% apparent P5N residual activity corresponds to a non-specific acid phosphatase.

Adult↗
PubMed1979

Electrophoretic and kinetic studies of a mutant red cell pyrimidine 5'-nucleotidase.

Human red cell pyrimidine 5'-nucleotidase (P5N) was studied by partial purification and condensation in a patient with an extremely low red cell P5N activity and chronic hemolytic anemia. The residual P5N in the red cell of the patient was characterized by an increased Michaelis constant for cytidine 5'-monophosphate, a marked shift of the pH optimum to the acidic side, normal electrophoretic mobility and normal heat stability. These data indicate that, in this patient, severe enzyme deficiency is caused by a structural gene mutation. This variant is clearly distinguished from a previously reported case and it is designated P5N Kagoshima.

Anemia, Hemolytic, Congenital↗
PubMed1989

Pyrimidine 5'-nucleotidase deficiency: improved detection of carriers.

The activities of pyrimidine 5'-nucleotidase (P5N) and the nucleotide pools in the erythrocytes from 19 members of a Dutch family with P5N deficiency were measured. In the erythrocytes of 5 (out of 6) apparent heterozygotes (based on P5N activities), an increased amount of UDP-N-acetylhexosamines was found. This increase was also found in the erythrocytes of 2 (out of 3) questionable heterozygotes (P5N activity below normal range, but not below normal mean--2 X SD) and not in the erythrocytes of family members with a normal P5N activity nor in erythrocytes from healthy donors. We conclude that analysis of the ribonucleotide patterns, in combination with determination of P5N activity, allows a more accurate diagnosis of heterozygosity for P5N.

5'-Nucleotidase↗
PubMed1987

Cellular localization and developmental changes of deoxyribonucleoside-activated nucleotidase in the rat testis.

Specific deoxyribonucleoside-activated nucleotidase (DAN) activity showed a rapid decline during the exponential increase in testis weight between 25 and 35 days of age. Specific DAN activity in Sertoli cells was dependent on the amount of cytosol in the enzyme assay. At optimal cytosol concentration the measured value was 50 units/mg of protein. Specific DAN activity in peritubular cells, primary spermatocytes and round spermatids was 13, 3.7 and 3.1 units/mg, respectively, and was independent of the cytosol concentration in the assay.

Aging↗
PubMed1991

A comparison of the properties of 5'-nucleotidase purified from the cytosolic and synaptic plasma membrane fractions of rat forebrain.

1. 5'-Nucleotidase was purified 1247-fold from the post-microsomal supernatant (I) and 3862-fold from the synaptic plasma membrane (II) of rat brain homogenates. 2. The apparent molecular masses of I and II were 131 and 72 kDa respectively by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate and 268 and 286 kDa respectively by Sephacryl S-300 chromatography. 3. The activities of both I and II were strongly inhibited by concanavalin A but were affected differently by digestion with glycosidases. for II, these were 0.083 and 0.056 mM respectively. 5. Activities of both I and II were strongly inhibited by ATP and ADP.

5'-Nucleotidase↗
PubMed1993

Effects of adenine nucleotides on low Km 5' nucleotidase from human seminal plasma.

1. Low Km 5' nucleotidase purified from human seminal plasma has been used in this study to investigate the response of the enzyme ot adenine nucleoside di- and triphosphates in the presence of AMP and IMP as substrates. 2. In the presence of AMP, the addition of 0.5 mM ATP to the enzyme Mg-free results into the highest Vmax/Km ratio value and other experimental combinations of effectors tested cause variation of the kinetic parameters of the enzyme, indicating a control of AMP dephosphorylation by adenine nucleotides. 3. In the presence of IMP, ATP and ADP activate the enzyme but the response to various experimental combinations of effectors shows no significant difference in the kinetic properties of the enzyme, indicating a different control of the dephosphorylation of IMP.

5'-Nucleotidase↗
PubMed1978

Pyrimidine metabolism in hereditary erythrocyte pyrimidine 5' nucleotidase deficiency.

A patient with hereditary erythrocyte pyrimidine 5' nucleotidase deficiency was studied to determine the mechanism of accumulation of erythrocyte pyrimidine nucleotides. Estimates of the rate of degradation of uridine nucleotides to diffusable products imply that the high levels found in these patients could not be sustained from the degradative pathways alone. Active synthesis of uridine nucleotides was found to occur in erythrocytes from both patient and control blood samples when either uridine or orotate was used as a substrate. The circulating levels of uridine in the blood are such that sufficient nucleotides to account for the high levels seen in these patients could accumulate in the erythrocytes from biosynthetic pathways alone, quite apart from the contribution from degradation of residual ribosomal RNA. This provides scope for new therapeutic approaches; treatment with allopurinol, however, was found to result in an increase, rather than a decrease, in erythrocyte pyrimidine nucleotides.

Adolescent↗