IFN-α-mediated Base Excision Repair Pathway Correlates with Antiviral Response Against Hepatitis B Virus Infection.

Previous studies identified APOBEC deaminases as enzymes targeting hepatitis B virus (HBV) DNA in the nucleus thus affecting its persistence. Interferon (IFN)-α treated chimpanzees and hepatitis C patients showed elevated APOBEC expression. We thus hypothesized that the responses to IFN-α treatment of chronic hepatitis B (CHB) patients is influenced by IFN-induced base excision repair (BER). CHB-treatment naïve patients, patients treated with PEGylated IFN-α, and patients with sequential treatment of Entecavior and PEGylated IFN-α were recruited. Blood and liver biopsy samples were collected before treatment and at treatment endpoint. BER genes were assessed by quantitative RT-PCR. BER gene expression levels and IFN treatment responses were correlated in patient liver biopsies. APOBEC3A, -B, -C, -D/E, and-G mRNA levels were up-regulated in IFN-treated patients. APOBEC3A expression was significantly higher in IFN-responders than in non-responders. BER genes NEIL3 was down-regulated in IFN-treated patients. APOBEC3 and BER gene expression at treatment endpoints partially correlated with the corresponding absolute DNA level or degree of HBsAg and HBV DNA decline. Our study suggests that the expression of APOBEC3A positively correlates with IFN-treatment responses in CHB patients, while NEIL3 shows negative correlation. These genes may involve to IFN mediated viral suppression and serve as biomarkers for CHB disease management.

Inter-individual variation, seasonal variation and close correlation of OGG1 and ERCC1 mRNA levels in full blood from healthy volunteers.

The mRNA levels of the nucleotide excision DNA repair gene ERCC1 and the base excision DNA repair gene OGG1 were quantified in 43 healthy volunteers in a dietary intervention trial as markers for the DNA repair capacity. Nine samples were collected from each subject over a period of 52 days. Sampling took place from January to May. The mRNA levels of OGG1 and ERCC1 correlated closely (r = 0.86, P << 0.0001) after normalization to either 18S ribosomal RNA or to beta-actin mRNA. The levels of OGG1 and ERCC1 mRNA were relatively constant within an individual with intra-individual correlation (R(2) = 0.45-0.46) in a General Linear Model. The amounts of ERCC1 and OGG1 relative to 18S RNA were doubled in May compared with January. This coincided with an increase in the monthly influx of sunlight from 18 MJ/m(2) in January to 242 MJ/m(2) in May. The mRNA levels of both ERCC1 and OGG1 were positively correlated to the average daily influx of sunlight in the previous 30 and 5 days (r = 0.49; r = 0.37, respectively, P << 0.001). There were no significant effects of the dietary interventions. The inter-individual variation was 5-10-fold, which is more than the observed 2-3-fold seasonal variation. Thus, despite seasonal variation of the individual mRNA levels, the inter-person variation is still far larger than the intra-person variation, supporting the use as biomarkers.

Retrovirus-mediated expression of the base excision repair proteins, formamidopyrimidine DNA glycosylase or human oxoguanine DNA glycosylase, protects hematopoietic cells from N,N',N"-triethylenethiophosphoramide (thioTEPA)-induced toxicity in vitro and in vivo.

Modulation of DNA damage repair activity could lead to new approaches to reduce cytotoxic side effects of chemotherapy. N,N',N"-Triethylenethiophosphoramide (thioTEPA) induces the formation of amino-ethyl adducts of guanine, resulting in imidazole ring opening [formamidopyrimidine (Fapy)] and is associated with significant myelosuppression in dose-intensive therapies. In Escherichia coli, Fapy lesions are repaired by the Fapy-DNA glycosylase (Fpg) protein. We hypothesized that the expression of the Fpg could increase resistance of hematopoietic cells to thioTEPA-induced cytotoxicity. Expression of Fpg in bone marrow (BM) cells via a retrovirus vector was associated with demonstrable 8-oxodeoxyguanosine DNA glycosylase activity. BM cells were infected with a recombinant retrovirus, SF91, containing the Fpg gene and expressing the enhanced green fluorescence protein (EGFP) via an internal ribosomal entry site element. Control mice received BM transduced with the backbone containing IRES-EGFP alone. Fpg-transduced and GFP+ BM hematopoietic cells were resistant in vitro to thioTEPA at multiple concentrations. Mice transplanted with transduced cells were treated with four doses of thioTEPA (10 mg/kg) given over 7 weeks. Despite low transduction efficiency, peripheral blood leukocytes, hemoglobin, and platelet counts of thioTEPA-treated Fpg mice were significantly higher than treated control mice (P < 0.05). In addition, after treatment, the BM, spleen, and thymic cellularity as well as the number of GFP+ progenitor cells in the BM of treated mice were significantly higher than those of control group. Selection of Fpg-transduced cells in vivo was demonstrated by an increase in the mean fluorescence intensity of peripheral mononuclear cells of Fpg mice compared with pretreatment value. In addition, a significant increase in the EGFP-bright cells was demonstrated, suggesting preferential survival of high-expressing hematopoietic cells. Similar results were demonstrated in vitro with primary BM expressing the human functional counterpart of Fpg, OGG1. These results show that expression of the Fpg or hOGG1 protein protects hematopoietic cells from thioTEPA-induced DNA damage and suggest that a high level of expression of these repair proteins is required to establish resistance to this drug. Expression of Fpg and/or OGG1 may provide an novel approach to preventing thioTEPA-induced toxicity of primary hematopoietic cells.

[Metabolism of purine compounds in psoriasis]. / Metabolizm purinovykh soedinenii pri psoriaze.

The pool of free purine derivatives and activities of the key enzymes of purine metabolism (adenosine deaminase, purine nucleoside phosphorylase, and 5'-nucleotidase) in lymphocytes, erythrocytes, and epidermis homogenates were measured in 20 normal subjects and 15 patients with psoriasis by high-performance liquid chromatography. The levels of AMP, GMP, and IMP purine monophosphates are decreased in the epidermis and red cells of psoriasis patients, whereas the final products of hypoxanthine, xanthine, and uric acid metabolism are accumulating, and the activities of ADA and PNP are increased double in the skin, all this indicating purine derivatives catabolism.

Clinical and pathological studies in cattle with hepatic disease.

In cattle with hepatic lipidosis, hepatic abscessation, leptospirosis, biliary calculi or fasciolosis, the progression of the disease was studied by serial measurements of serum total bile acid concentrations, plasma glutamate dehydrogenase, gamma-glutamyltransferase, 5'-nucleotidase and leucine aminopeptidase activities Terminalia avicennioides and by liver biopsy. Regardless of the cause of the hepatic disease, weight loss, anorexia, dullness and depression were consistent features. Signs of hepatic encephalopathy, such as blindness, head pressing, excitability, ataxia and weakness were less common and, together with pyrexia and jaundice, were grave prognostic signs. Plasma ammonia concentrations were significantly elevated compared to clinically normal cattle, but such changes were not always accompanied by a decline in plasma urea concentrations. In normal, healthy cattle, the plasma ammonia:urea concentration ratio is 9:1 and the plasma ammonia:glucose concentration is 11:1. In hepatic disease, a plasma ammonia:glucose ratio > 40:1 or plasma ammonia:urea ratio > 30:1, particularly with a rising total ketone body concentration and a declining glucose concentration, carried a guarded prognosis. The study suggested that other factors, such as hypokalaemia, alkalosis, short-chain volatile fatty acids, and false and true neuro-transmitters, may be important in the pathogenesis of hepatic coma in cattle.

Detection of trisomy 12 in CD34+ progenitor cells in a patient with B-cell chronic lymphocytic leukemia by fluorescence in situ hybridization.

B-cell chronic lymphocytic leukemia (B-CLL) is a slowly progressive disease resulting from the clonal expansion of mature B lymphocytes. The most frequent chromosomal abnormality is trisomy 12. Recently more aggressive therapeutic approaches using myeloablative therapy and autologous stem-cell support have been developed. Phase I/II studies have resulted in molecular remission and prolonged survival. One cause of relapse may be tumor-cell contamination of the transplant. We asked whether immunophenotypically identified hematopoietic progenitor cells are part of the malignant cell population in B-CLL. In a patient with trisomy 12, two subpopulations of hematopoietic progenitor cells, CD34+/CD38+ and CD34+/CD38- cells, were isolated by fluorescence-activated-cell-sorting; the sort purity was 98%. Trisomy 12 was detected in 13% of CD34+/38+ cells and in 34% of CD34+/38- cells. These data suggest that CD34+ cells are involved in the malignant clone of patients with B-CLL. The results are of significance for future strategies using autologous stem-cell transfusion.

Differential expression of transforming growth factor-beta, basic fibroblast growth factor, and their receptors in CD34+ hematopoietic progenitor cells from patients with myelofibrosis and myeloid metaplasia.

Myelofibrosis with myeloid metaplasia (MMM) is a myeloproliferative disorder characterized by clonal expansion of hematopoiesis and marrow fibrosis. Previous results from our group have shown an increased production of two potent fibrogenic factors also involved in the regulation of primitive hematopoietic cells, namely transforming growth factor-beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF), in patients with MMM. It is likely to assume that the myeloproliferation characteristic of this disease may result from an abnormal proliferation of CD34+ hematopoietic progenitors. Thus, we were particularly concerned in studying the gene and protein expression of these cytokines and their receptors in CD34+ progenitors purified from the peripheral blood of MMM patients by using semiquantitative reverse transcriptase-polymerase chain reaction and immunolabeling methods. Our data showed that the expression of TGF-beta1 is not altered in patients CD34+ cells; in contrast, the expression of TGF-beta type II receptor is significantly decreased in such cells, as compared with CD34+ cells from healthy subjects. Regarding bFGF, the very low expression of the cytokine and its type I and II receptors detected in normal CD34+ cells contrasts with that observed in patients' CD34+ cells, which is significantly higher. Our results might be a clue for a better understanding of the mechanism(s) involved in the dysregulation of hematopoiesis in MMM. Actually, the increased expression of bFGF and its receptors associated with the reduction of the TGF-beta binding receptor in CD34+ progenitors from MMM patients might facilitate the expansion of hematopoietic progenitors, not only by stimulating their growth and/or survival, but also by overcoming negative regulatory signals.

Increased numbers of primed activated CD8+CD38+CD45RO+ T cells predict the decline of CD4+ T cells in HIV-1-infected patients.

OBJECTIVE: To look for surrogate markers in HIV-1 infection that can predict the decline of CD4+ T cells. METHODS: Multiparameter flow cytometric analyses of CD8+ lymphocytes were performed. These cells were investigated for their expression of the activation marker CD38+ within the naive (CD45RA+) and primed (CD45RO+) subsets. Serial CD4 counts were plotted for each patient and the straight line that best fitted was obtained using least squares regression. Differences in rate of decline were tested using analysis of variance, after each patient was weighted by the reciprocal of the variance. RESULTS: Baseline levels of percentages of CD8+CD38+ T lymphocytes predict the CD4 decline in HIV-1-infected patients. Within the CD8+ subset, the primed CD8+CD38+CD45RO+ population was responsible for this prediction. Conversely, the naive CD8+CD38+CD45RA+ population was not predictive. Patients who initially showed a percentage of CD8+CD38+ T lymphocytes above the median (> 25%) had a more marked decline in CD4+ T cells when compared to individuals with percentages of CD8+CD38+ T lymphocytes below the median value (79.3 and 21.2 x 10(6)/l mean CD4 cell decline per year, respectively). Similarly, percentages of CD8+CD38+CD45RO+ T cells above the median value (> 7%) were also associated with a more rapid decline (69.4 and 14.2 x 10(6)/l mean CD4+ cell decline per year). These results were statistically significant after adjustment for the baseline CD4 count and beta 2-microglobulin levels. CONCLUSIONS: Percentages of activated CD8+ cells expressing CD38+ can predict the rate of decline (slope) of the CD4+ T cells. This resides in the CD45RO+ primed population. An early prediction of the CD4+ slope will allow the clinician to target treatment to those patients that are most likely to benefit.

Expression of cyclic ADP-ribose-synthetizing CD38 molecule on human platelet membrane.

CD38 is a cell surface molecule widely used as a marker for immature and activated lymphocytes. It has been recently shown that CD38 displays three enzymatic activities: hydrolysis of NAD+ to ADP-ribose, synthesis of cyclic ADP-ribose from NAD+, and hydrolysis of cyclic ADP-ribose to ADP-ribose. Thus, CD38 plays a key role in the synthesis of cyclic ADP-ribose, a calcium-mobilizing compound. We investigate here the expression and cellular localization of CD38 in human platelets using a specific monoclonal antibody. Results showed that CD38 is expressed by human platelet membranes. Moreover, we show that platelet CD38 possesses NAD glycohydrolase, ADP-ribose cyclase, and cyclic ADP-ribose hydrolase activities. This finding indicates that the calcium-mobilizing agent cyclic ADP-ribose can be synthetized by human platelets and raises the question about the possible role of CD38 expression and enzymatic activities in the signal transduction pathways leading to platelet activation.

Tnk1: a novel intracellular tyrosine kinase gene isolated from human umbilical cord blood CD34+/Lin-/CD38- stem/progenitor cells.

Degenerate PCR was employed to identify novel tyrosine kinase genes from an enriched population of human umbilical cord blood hematopoietic stem/progenitor cells. One novel tyrosine kinase gene, designated Tnk1, was cloned. The sequence of the complete Tnk1 coding region predicts a 72 kD protein. Comparison of Tnk1 to available sequences in protein databases reveals that it is most homologous to Ack, an intracellular tyrosine kinase which associates with the GTP-bound form of p21cdc42Hs. Like Ack, Tnk1 consists of an N-terminal kinase domain, a putative SH3 domain immediately C-terminal to the kinase domain, and a proline-rich C-terminal region. Analysis of Tnk1 mRNA expression demonstrates that Tnk1 is expressed in all cord blood, bone marrow and adult blood sub-populations, as well as in most of the leukemia cell lines examined (16 of 20). Hybridization to fetal multi-tissue Northern blots detected several different Tnk1 transcripts in all fetal tissues examined. In contrast, a single Tnk1 transcript was detected in only five of 16 adult tissues examined (prostate, testis, ovary, small intestine and colon). Fluorescence in situ hybridization (FISH) analysis of metaphase chromosomes localized the Tnk1 gene to the short arm of chromosome 17 (17p13.1), near the p53 locus. Thus, Tnk1 is a novel tyrosine kinase that may be involved in signalling pathways utilized broadly during fetal development, more selectively in adult tissues and in cell of the lymphohematopoietic system.

CD4+ lymphocytes in perinatal human immunodeficiency virus (HIV) infection: evidence for pregnancy-induced immune depression in uninfected and HIV-infected women.

Immune function changes during pregnancy and human immunodeficiency virus (HIV) infection. T helper function and phenotypes in HIV-infected and -uninfected pregnant and postpartum women and nonpregnant uninfected control women were studied. T helper function was assessed by interleukin-2 (IL-2) production in vitro and three-color flow cytometry. All uninfected nonpregnant subjects, 74% of uninfected pregnant subjects, and only 54% of HIV-infected pregnant subjects responded to all stimuli. All uninfected subjects 2-6 months postpartum had normal function versus 27% of infected subjects (trend P < .001). Uninfected pregnant subjects had reduced levels of CD4+CD45RA-RO+ (memory) and elevated levels of CD4+CD45RA+RO- (naive) lymphocytes. Infected pregnant subjects had elevated levels of memory, reduced levels of naive, and increased levels of CD4+HLA-DR+CD38+ (activated) lymphocytes. Increased CD4+DR+CD38+ cells correlated best with poor IL-2 function, HIV infection, and being postpartum (R2 = .79). Thus, T helper function and phenotypes are altered in pregnancy and return to baseline postpartum in uninfected but not HIV-infected women.

Self-aggregation of purified and membrane-bound erythrocyte CD38 induces extensive decrease of its ADP-ribosyl cyclase activity.

The transmembrane glycoprotein CD38 is a bifunctional enzyme that catalyzes at its ectocellular domain both the synthesis and the hydrolysis of cyclic ADP-ribose (cADPR). The complete reaction, converting NAD+ to nicotinamide and ADP-ribose, reproduces an NAD+glycohydrolase (NADase) reaction. CD38 purified from human erythrocyte membranes has been recently shown to undergo stable oligomerization induced by either NAD+ or beta-mercaptoethanol. We demonstrate that oligomerization is also triggered by reduced glutathione (GSH) and that the GSH-induced self-aggregation of purified CD38 is accompanied by extensive and comparable decrease of its ADP-ribosyl cyclase and NADase activities. GSH-induced oligomerization of CD38 and strong enzyme inactivation take place also in situ on erythrocyte membranes.

In vivo priming effects of interferon-beta ser on NK activity of peripheral blood mononuclear cells in cancer patients.

Natural killer (NK) activity was assayed in fresh peripheral blood mononuclear cells (PBMs) from cancer patients receiving interferon (IFN)-beta ser. Patients received a single intravenous injection of IFN-beta ser (90 x 10(6) IU m-2) on alternate days for 2 weeks, followed by a higher dose (180 x 10(6) IU m-2) on the same schedule. PBM NK lysis of K562 target cells was significantly increased in PBMs sampled 24 h after the initial injection (P < 0.05). At the end of the first 2 weeks of the protocol, NK cytotoxic activity of PBMs had fallen below the original baseline levels; the higher IFN dose subsequently given was without effect. However, significant increases in the proportion of CD16+ cells were seen following each injection. A positive correlation was also seen between the increased lytic activity of CD16+ NK cells and the proportion of CD38+ NK cells, but not the proportion of CD56+ NK cells. In vitro IFN-treatment of these in vivo-treated PBMs resulted in a further increase in NK activity. Pre-exposure in vivo to IFN-beta ser seems to prime the PBMs to respond to in vitro stimulation by IFN-gamma, which otherwise had no effect. Phenotypic analysis of PBMs after in vitro exposure to IFN-beta ser showed that the levels of CD16+, CD38+ and CD56+ cells did not change. All the NK activity responding to IFN-beta ser was found in the CD16+ enriched population of PBM, suggesting that it is unlikely that in vivo redistribution of CD16+ subsets representative of NK cells has occurred in the peripheral blood.

A single protein immunologically identified as CD38 displays NAD+ glycohydrolase, ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities at the outer surface of human erythrocytes.

The three ectoenzyme activities, NAD+ glycohydrolase, ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase were purified to homogeneity from solubilized human erythrocyte membranes. The purification procedure involved three sequential chromatography steps on hydroxylapatite, immobilized Cu++ and immobilized anti-CD38 monoclonal antibody resins. The final step yielded a single 46 kDa protein displaying all three enzymatic activities. Since the protein bound specifically to the anti-CD38 resin, it was immunologically identified as CD38, a 46 kDa surface antigen involved in activation and proliferation of lymphocyte populations.

An endonuclease activity in human polymorphonuclear neutrophils that removes 8-hydroxyguanine residues from DNA+.

An endonuclease that specifically removes 8-hydroxyguanine (oh8Gua) from DNA has been isolated from Escherichia coli. As the amount of oh8Gua produced in DNA of X-ray-irradiated mice is known to decrease with time after irradiation, an attempt was made to find a similar activity in human polymorphonuclear neutrophils (PMNs) using a synthetic dsDNA containing oh8Gua as a substrate. The PMN enzyme was isolated free of other DNases, and found to cleave the substrate DNA simultaneously at 2 sites, the phosphodiester bonds 5' and 3' to oh8Gua, producing free hydroxyl and phosphate groups, respectively. The enzyme showed almost no activity on DNAs containing other kinds of modified base tested or mismatched DNA. Thus human cells also contain an endonuclease that specifically removes oh8Gua residues from DNA.

Increased DNA synthesis and repair-enzyme expression in lymphocytes from patients with chronic lymphocytic leukemia resistant to nitrogen mustards.

Resistance to the nitrogen mustards in patients with chronic lymphocytic leukemia (CLL) correlates with an enhanced removal of melphalan-induced DNA interstrand cross-links. This finding suggests that DNA repair enzymes may be involved in this process. The activity of 3-methyladenine-DNA glycosylase, which can release altered bases, including adducts at the N-7 position of guanine, was increased significantly in lymphocytes from patients with resistant CLL compared with those from untreated CLL patients. Since glycosylase activity varies with cell proliferation, the amount of [3H]thymidine incorporated into DNA was determined and found to be elevated almost threefold in lymphocytes from patients with resistant CLL. The ratio of glycosylase activity to level of thymidine incorporation did not differ between these two groups of patients. Northern blot analysis of ERCC1 gene (a putative DNA repair enzyme involved in nucleotide excision repair) expression in lymphocytes from patients with CLL revealed multiple gene transcripts (1.1, 3.4, and 3.8 kilobases). In addition, analysis of two samples revealed the presence of a 2.6-kilobase transcript. The 2.6-kilobase transcript was recognized by specific RNA probes that hybridize to antisense ERCC1 transcripts. Levels of expression of the 1.1-kilobase protein encoding transcript in lymphocytes from patients with resistant CLL were increased twofold to threefold above those of untreated patients with CLL. These results indicate that increased expression of ERCC1 and increased activity of 3-methyladenine-DNA glycosylase occur with the development of resistance to the nitrogen mustards in patients with CLL, suggesting a role for enhanced DNA repair in this process.

Interference of prenatal and postnatal exposure to Ca2+-antagonist agents on rat functional development of vascular system.

Exposure to drugs during pregnancy can alter functional development of the vascular system. The present investigation was carried out in order to evaluate the effects of prenatal and postnatal exposure to Ca2+-antagonist (diltiazem, verapamil, and nimodipine) drugs on the development of rat vasomotor reactivity. Studies were carried out on pregnant female albino rats exposed from the first day of pregnancy until weaning to diltiazem and verapamil (6 and 24 mg/kg in their drinking water ad libitum) and nimodipine (3 and 12 mg/kg in their food ad libitum). After weaning, pups were exposed until the 60th day of age to the same treatment as their mothers were. Afterwards, pups from the 60th to 90th day of age were fed with a normal diet. In 30-, 60-, and 90-day-old conscious and anaesthetized pups, we evaluated the following: 1) systolic arterial blood pressure; 2) vasomotor responses elicited by various agents: L-noradrenaline (0.1, 1, and 5 micrograms/kg IV), L-isoprenaline (0.01, 0.1, and 1 micrograms/kg IV), and acetylcholine (0.01, 0.1, and 1 micrograms/kg IV) and by sinus-carotid baroreceptor stimulation; and 3) catecholamine, acetylcholinesterase, and adenosinase plasma levels. Prenatal and postnatal exposure to Ca2+-antagonist drugs significantly (P less than .05) decreased the pressor response to sinus-carotid baroreceptor stimulation and to L-noradrenaline and increased the hypotensive responses to L-isoprenaline and acetylcholine. Moreover, this type of treatment, although it induced a significant (P less than .05) decrease of catecholamine plasma levels, did not modify the acetylcholinesterase and adenosinase plasma levels in 30- and 60-day-old rats. On the 90th day of age, the evaluated parameters were not different from those of control rats. Our results showed that exposure to Ca2+ antagonists during pregnancy and the postnatal period may alter the functional development of rat vasomotor reactivity.

Uracil-DNA glycosylase in benign and malignant maturing human hematopoietic cells.

The expression of uracil-DNA glycosylase was studied in human normal hematopoietic bone marrow cells and in malignant counterparts obtained from patients with chronic granulocytic leukemia. We observed that the expression of the enzyme was highest in the proliferating granulocytic compartment (myeloblasts through myelocytes) and that it was diminished in more mature cells. Furthermore, we demonstrated that uracil-DNA glycosylase activity was higher in immature red blood cells or reticulocytes than in more mature red cells. The same tendency was also demonstrated in human malignant monoblasts, which were induced to terminal maturation by phorbol ester. It can be concluded from these results that uracil-DNA glycosylase expression is equal in benign and malignant hematopoietic progenitor cells; no selectivity towards malignant vs. benign progenitors can be expected in possible chemotherapeutic approaches relying on uracil-DNA glycosylase.

Normal levels of ATP, total nucleotides and activities of three enzymes related to nucleotide metabolism in fetal erythrocytes.

Pure fetal blood was obtained by direct-vision fetoscopy from 30 fetuses at 17-23 weeks gestation. The erythrocyte concentrations of ATP and total nucleotides and the activities of the enzymes pyrimidine-5'-nucleotide nucleosidase (Pyr5N), phosphoribosylpyrophosphate (PRPP) synthetase and adenylate kinase (AK) were analysed by established techniques to find the normal ranges for this gestational age. The ranges were relatively narrow and could serve as reference values for the prenatal diagnosis of defects in nucleotide metabolism. The results from the fetal erythrocytes were compared with the corresponding values from the maternal blood collected and analysed concurrently. The ATP and total nucleotide concentrations and the activity of Pyr5N in the fetal cells were substantially higher than those of the maternal blood. The activities of PRPP synthetase and AK were much lower. The significance of these findings is discussed.

Uracil-DNA glycosylase activity in human blood cells.

We studied uracil-DNA glycosylase activities systematically in all types of human peripheral blood cells. The highest amounts of uracil-DNA glycosylase activity were found in cells capable of using their genetic information either in DNA replicative or repair synthesis or in DNA transcription. These cells included cytotoxic/suppressor and inducer/helper T lymphocytes, B lymphocytes and monocytes. On the other hand, the peripheral blood mature end cells, erythrocytes, platelets and granulocytes, contained very little if any uracil-DNA glycosylase activity. In addition to this biological capacity, we show that the housekeeping excision repair capacity of uracil-DNA glycosylase is well maintained in human peripheral blood mononuclear cells throughout life from the neonatal period to old age.