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Biomedical subjects

L Xi

Publications and source records attributed to L Xi.

At least 19 recordsLinked to original sources
PubMed2006

Inhibition of telomerase enhances apoptosis induced by sodium butyrate via mitochondrial pathway.

Telomerase activation represents an early step in carcinogenesis. Increased telomerase activity in cervical cancer suggests a potential target for the development of novel therapeutic drugs. The aim of this study is to investigate the impact of telomerase activity on the biological features of HeLa cells and the possible mechanisms of enhanced apoptosis rate induced by sodium butyrate after telomerase inhibition. We introduced vectors encoding dominate negative (DN)-hTERT, wild-type (WT)-hTERT, or a control vector expressing only a drug-resistance marker into HeLa cells. Thus we assessed the biological effects of telomerase activity on telomere length, cell proliferation, chemosensitivity and radiosensitivity. In order to understand the mechanisms in which DN-hTERT enhances the apoptosis induced by sodium butyrate, we detected the release status of cytochrome c and apoptosis inducing factor (AIF) from mitochondria. Ectopic expression of DN-hTERT resulted in inhibition of telomerase activity, reduction of telomere length, decreased colony formation ability, and loss of tumorigenicity in nude mice. Moreover, DN-hTERT transfected HeLa cells with shortened telomeres were more susceptible to multiple chemotherapeutic agents and radiation. WT-hTERT transfected HeLa cells with longer telomeres exhibited resistance to radiation and chemotherapeutic agents. Our data demonstrate that elevated release level of cytochrome c and AIF from mitochondria might contribute to the enhanced apoptosis in DN-hTERT transfected HeLa cells after treatment with sodium butyrate. Inhibition of telomerase might serve as a promising adjunctive therapy combined with conventional therapy in cervical cancer.

Animals↗
PubMed2006

Antitumor activities of the four sesquiterpene lactones from Elephantopus scaber L.

AIM: To evaluate antitumor activity of sesquiterpene lactones (scabertopin (ES-2), isoscabertopin (ES-3), deoxyelephantopin (ES-4), isodeoxyelephantopin (ES-5)) isolated from Elephantopus scaber L. in vitro and in vivo. METHODS: SMMC-7721, Caco-2 and HeLa cell lines were treated with ES-2,3,4,5. Cell viability was determined by MTT assay. Agarose gel electrophoresis was used to detect DNA fragmentation. To evaluate in vivo antitumor activity of ES-4, experimental murine tumor model was used. RESULTS: It was shown that ES-2, ES-4, ES-5 exhibited significant antitumor effect in vitro in a concentration-dependent manner. However, the effect of ES-3 on the growth of tested cell lines was relatively weak. In HeLa cells exposed to ES-4 for 48 h, morphological changes and DNA ladder pattern evidencing on apoptosis were detected. ES-4 revealed in vivo antitumor activity. CONCLUSION: Antitumor activity of studied sesquiterpene lactones may be due, at least in part, to induction of apoptosis in vitro. ES-4 possesses also antitumor activity in vivo.

Antineoplastic Agents, Phytogenic↗
PubMed2005

Effects of lorazepam on fear-potentiated startle responses in man.

Sudden intense sensory stimuli elicit a cascade of involuntary responses, including a short-latency skeletal muscular response ('eyeblink startle response') and longer-latency autonomic responses. These responses are enhanced when subjects anticipate an aversive event compared to periods when subjects are resting ('fear potentiation'). It has been reported previously that the anxiolytic diazepam can suppress fear-potentiation of the eyeblink startle response in human volunteers. The present experiment aimed to confirm and extend these observations by examining the effect of another benzodiazepine, lorazepam, on the eyeblink and skin conductance components of the acoustic startle, and on fear-potentiation of these responses. Eighteen male volunteers participated in three weekly sessions in which they received oral treatment with placebo, lorazepam (1 mg) and lorazepam (2 mg), according to a balanced three-period, crossover, double-blind design. Two hours after ingestion of the treatments, electromyographic responses of the orbicularis oculi muscle and skin conductance responses were evoked by sound pulses during alternating periods in which the threat of an electric shock (electrodes attached to the subject's wrist) was present (THREAT) and absent (SAFE). The THREAT condition was associated with significant increase in the amplitude of the electromyographic (EMG) and skin conductance responses; there were also increases in baseline skin conductance, the number and amplitude of 'spontaneous' skin conductance fluctuations and self-rated anxiety. Lorazepam attenuated the effect of THREAT on self-rated anxiety and on the amplitude of the EMG response, but had no significant effect on fear-potentiation of the skin conductance responses. These results extend previous findings of the effect of diazepam on the fear-potentiated eyeblink startle response to lorazepam, and suggest that fear-potentiation of the later autonomic component of the startle response may be less sensitive to benzodiazepines than the fear-potentiated eyeblink response and self-rated anxiety.

Acoustic Stimulation↗
PubMed2004

Pharmacokinetics of total and unbound ertapenem in healthy elderly subjects.

Ertapenem is a new once-a-day parenteral carbapenem antimicrobial agent. The pharmacokinetics of unbound and total concentrations of ertapenem in plasma were investigated in elderly subjects and compared with historical data from young adults. In a single- and multiple-dose study, healthy elderly males and females (n = 14) 65 years old or older were given a 1-g intravenous (i.v.) dose once daily for 7 days. Plasma and urine samples collected for 24 h on days 1 and 7 following administration of the 1-g doses were analyzed by reversed-phase high-performance liquid chromatography. Areas under the concentration-time curve from 0 h to infinity (AUC(0- infinity )) for elderly females and males were similar following administration of 1-g single i.v. doses, and thus, the genders were pooled in subsequent analyses. Concentrations in plasma and the half-life of ertapenem were generally higher and longer, respectively, in elderly subjects than in young adults. The mean AUC(0- infinity ) of total ertapenem in the elderly was 39% higher than that in young subjects following administration of a 1-g dose. The differences were slightly greater for the mean AUC(0- infinity ) of unbound ertapenem (71%). The unbound fraction of ertapenem in elderly subjects ( approximately 5 to 11%) was generally greater than that in young adults ( approximately 5 to 8%). As in young adults, ertapenem did not accumulate upon multiple dosing in the elderly. The pharmacokinetics of ertapenem in elderly subjects, while slightly different from those in young adults, do not require a dosage adjustment for elderly patients.

Adult↗
PubMed2003

Influence of dietary cobalt source and concentration on performance, vitamin B12 status, and ruminal and plasma metabolites in growing and finishing steers.

Sixty Angus steers, averaging 274 kg, were used to evaluate the effects of Co source and concentration on performance, vitamin B12 status, and metabolic characteristics of steers. Treatments consisted of 0 (control, analyzed 0.04 mg Co/kg), 0.05, 0.10, and 1.0 mg of supplemental Co/kg of DM from CoCO3 or 0.05 and 0.10 mg of supplemental Co/kg of DM from Co propionate. Steers were individually fed a growing diet for 56 d followed by a high-concentrate finishing diet. Performance was not affected by Co supplementation during the growing phase. During the finishing phase, ADFI (DM basis) and ADG were higher (P < 0.05) for the entire finishing phase, and gain:feed was higher (P < 0.10) over the first 56 d for Co-supplemented steers. Steers supplemented with 0.10 mg Co/kg as Co propionate had higher (P < 0.05) ruminal propionate and lower (P < 0.05) acetate molar proportions than steers receiving 0.10 Co/kg as CoCO3 during the growing phase. Supplemental Co increased (P < 0.10) molar proportion of propionate during the finishing phase. Plasma vitamin B12 was higher (P < 0.05) in Co-supplemented steers by d 56 of the growing phase and remained higher (P < 0.10) throughout the study. Control steers had higher (P < 0.05) plasma methylmalonic acid on d 56 of the growing phase and on d 28, 56, and 112 of the finishing phase than steers receiving supplemental Co. Steers supplemented with Co had higher plasma glucose at d 56 (P < 0.01), 84 (P < 0.10), and 112 (P < 0.01) of the finishing phase. Steers supplemented with 0.10 mg Co/kg as Co propionate had higher plasma glucose than those receiving 0.10 mg Co/kg as CoCO3 at d 28 of the growing phase (P < 0.05) and d 28 of the finishing phase (P < 0.10). Final body weight and hot carcass weight were lower (P < 0.10) in steers receiving the control diet, whereas other carcass characteristics were not affected by dietary Co. Average daily gain and feed efficiency for the entire finishing phase did not differ among Co-supplemented steers. However, increasing supplemental Co above 0.05 mg/kg DM (total diet Co = 0.09 mg/kg) resulted in increased (P < 0.01) plasma (linear) and liver (quadratic) vitamin B12 concentrations and decreased (quadratic, P < 0.10) plasma methylmalonic acid concentrations toward the end of the finishing phase. These results suggest that finishing steers require approximately 0.15 mg Co/kg of DM. Vitamin B12 status was not affected by Co source; however, the two Co sources seemed to affect certain metabolites differently.

Animals↗
PubMed2002

Pharmacokinetics of ertapenem in healthy young volunteers.

Ertapenem (INVANZ) is a new once-a-day parenteral beta-lactam antimicrobial shown to be effective as a single agent for treatment of various community-acquired and mixed infections. The single- and multiple-dose pharmacokinetics of ertapenem at doses up to 3 g were examined in healthy young men and women volunteers. Plasma and urine samples collected were analyzed using reversed-phase high-performance liquid chromatography with UV detection. Ertapenem is highly bound to plasma protein. The protein binding changes from approximately 95% bound at concentrations of <50 micro g/ml to approximately 92% bound at concentrations of 150 micro g/ml (concentration at the end of a 30-min infusion following the 1-g dose). The nonlinear protein binding of ertapenem resulted in a slightly less than dose proportional increase in the area under the curve from 0 h to infinity (AUC(0- infinity )) of total ertapenem. The single-dose AUC(0- infinity ) of unbound ertapenem was nearly dose proportional over the dose range of 0.5 to 2 g. The mean concentration of ertapenem in plasma ranged from approximately 145 to 175 micro g/ml at the end of a 30-min infusion, from approximately 30 to 34 micro g/ml at 6 h, and from approximately 9 to 11 micro g/ml at 12 h. The mean plasma t(1/2) ranged from 3.8 to 4.4 h. About 45% of the plasma clearance (CL(P)) was via renal clearance. The remainder of the CL(P) was primarily via the formation of the beta-lactam ring-opened metabolite that was excreted in urine. There were no clinically significant differences between the pharmacokinetics of ertapenem in men and women. Ertapenem does not accumulate after multiple once-daily dosing.

Adult↗
PubMed2001

Markers for carcinogenicity among butadiene-polymer workers in China.

We examined a spectrum of genotoxic and other outcomes in 41 butadiene-polymer production workers and 38 nonexposed controls, in China, to explore the role of butadiene in human carcinogenesis. Among butadiene-exposed workers, median air exposure was 2 ppm (6-h TWA), due largely to intermittent high-level exposures. Compared to unexposed subjects, butadiene-exposed workers had greater levels of hemoglobin N-(2,3,4-trihydroxybutyl)valine (THBVal) adducts (P<0.0001), and adduct levels tended to correlate, among butadiene-exposed workers, with air measures (P=0.03). Butadiene-exposed workers did not differ, however, from unexposed workers with respect to frequency of uninduced or diepoxybutane-induced sister chromatid exchanges, aneuploidy as measured by fluorescence in situ hybridization of chromosomes 1, 7, 8 and 12, glycophorin A variants or lymphocyte hprt somatic mutation. Also among the exposed, greater THBVal levels were not associated with increases in uninduced sister chromatid exchanges, aneuploidy, glycophorin A, or hprt mutations. Butadiene-exposed workers had greater lymphocyte (P=0.002) and platelet counts (P=0.07) and lymphocytes as a percent of white blood cells were moderately correlated with greater THBVal levels (Spearman's rho=0.32, P=0.07). Among butadiene-exposed workers, several serum cytokines correlated with THBVal adduct levels. Overall, the study demonstrated exposure to butadiene in these workers, by a variety of short-term and long-term measures, but did not show specific genotoxic effects, at the chromosomal or gene levels, related to that exposure.

Air Pollutants, Occupational↗
PubMed2001

Mitogen-activated protein kinases mediate heat shock-induced delayed protection in mouse heart.

We determined the role of p38 mitogen-activated protein kinase (MAPK), 72-kDa heat shock protein (HSP72), and antioxidant enzymes in whole body heat stress (HS)-induced cardioprotection in mouse hearts. Adult male mice were treated with either HS or anesthesia only. At 0.5, 48, 72, or 120 h later, the hearts were subjected to 20 min of global ischemia and 30 min of reperfusion in Langendorff mode. A significant protection against ischemia-reperfusion injury was observed 48 h after HS as demonstrated by: 1) reduction in infarct size; 2) decrease in leakage of lactate dehydrogenase; and 3) enhanced postischemic ventricular contractile function. No such protection was observed at other post-HS time points. HS caused an ~25% increase in phosphorylated c-Jun NH2-terminal kinase (JNK) but not p38 MAPK in the heart during the first 2-h post-HS time period. Cardioprotection was abolished by the MAPK inhibitor SB-203580, which also partially suppressed the HS-induced JNK phosphorylation. The protective effect was associated with a two- to threefold increase in HSP72 protein accumulation, but not antioxidant enzyme activities (catalase and Cu/Zn and Mn SOD) in the myocardium. Although HSP72 levels remained high 72 h after HS, the cardioprotection had already disappeared. We conclude that HS induces a transient delayed cardioprotection at 48 h after thermal stress in mice which appears to be mediated via a MAPK-signaling pathway.

Animals↗
PubMed2001

[Establishment and application of a data management program for BY 960 ambulatory blood pressure monitoring system].

Report of ambulatory blood pressure monitoring may contain a large number of data which is very important for the clinical studies on subjects' blood pressure. Most of the ambulatory blood pressure monitoring systems in use at present are lacking in database managing function, which is very inconvenient to the research work. In accordance with the characteristics of BY 960 ambulatory blood pressure monitoring system (produced by Shenzhen NewEra Tech Co., Ltd.), a set of data management program was established. It can automatically transfer the ambulatory data to database sets and is confirmed to be a practical tool for the research work.

Blood Pressure Monitoring, Ambulatory↗
PubMed2000

Pivotal role of nitric oxide in delayed pharmacological preconditioning against myocardial infarction.

The phenomenon of 'ischemic preconditioning' (IP) has been vigorously investigated during the past 15 years. As our knowledge on the possible protective mechanisms of IP has been increasingly expanded, novel approaches based on preconditioning with pharmacological agents have recently emerged. Two drugs have been used to induce delayed preconditioning against myocardial infarction caused by ischemia/reperfusion. One of the drugs was monophosphoryl lipid A (MLA)--a detoxified derivative of lipopolysaccharide from gram-negative strains; and another drug was RC552--a novel synthetic glycolipid that mimics the chemical structure of MLA. We have shown that pretreatment of adult mice with MLA or RC552 (350 microg/kg) 24 h prior to the global ischemia and reperfusion in the isolated perfused heart attenuated myocardial injury. Infarct size was significantly reduced in MLA or RC552-treated groups as compared with the vehicle-treated group. The delayed cardioprotection was associated with a moderate but significant increase of nitric oxide level in the ischemic myocardium. Treatment with S-methylisothiourea (3 mg/kg), a selective inhibitor of inducible nitric oxide synthase (iNOS) abolished MLA or RC552-induced delayed protection. In addition, neither MLA nor RC552 reduced infarct size in iNOS knockout mice. Our findings suggest that both MLA and RC552 are able to induce delayed myocardial preconditioning via iNOS-dependent pathway.

Adjuvants, Immunologic↗
PubMed2000

Microcalorimetric investigation of the toxic action of Cd(2+) on Rhizopus nigricans growth.

The microcalorimetric bioassay for acute cellular toxicity is based on metabolic heat production from cultured cells. Microcalorimetry is a quantitative, inexpensive, and versatile method for toxicology research. The biological response to toxicants is the inhibition of the heat production rate in cells and toxicity is expressed as the concentration of toxicant that is 50% effective in this inhibition (IC(50)). In this paper, the effect of Cd(2+) on Rhizopus nigricans growth was investigated at 25 degrees C. The relationship between growth rate constants (k) and concentration of Cd(2+) (C) shows a logarithmic normal distribution, and described as k=1. 2742x10(61)exp[-1.810x10(-3)(C+283.0)(2)], and IC(50) is 0.72 microg/ml. These signals are readily obtained by an LKB 2277-204 heat conduction microcalorimeter.

Cadmium↗
PubMed2000

Inducible nitric oxide synthase mediates delayed myocardial protection induced by activation of adenosine A(1) receptors: evidence from gene-knockout mice.

BACKGROUND: The mechanism of delayed preconditioning induced by activation of adenosine A(1) receptors (A(1)ARs) is not fully understood. We determined the role of inducible nitric oxide synthase (iNOS) in mediating adenosine-induced late cardioprotection using pharmacological inhibitors and iNOS gene-knockout mice. METHODS AND RESULTS: Adult male mice were treated with saline or an A(1)AR agonist, 2-chloro-N(6)-cyclopentyladenosine (CCPA). Twenty-four hours later, the hearts were perfused in Langendorff mode and subjected to 30 minutes of global ischemia followed by 30 minutes of reperfusion. 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.1 mg/kg IP) and S-methylisothiourea (SMT; 3 mg/kg IP) were used to block A(1)ARs and iNOS, respectively. Infarct size (IS) was measured by triphenyltetrazolium chloride staining, and iNOS expression was measured by Western blots. Myocardial IS was reduced from 24.0+/-3. 2% in the saline group to 12.2+/-2.5% in CCPA-treated mice (P<0.05). The infarct-reducing effect of CCPA was abrogated by DPCPX (29.3+/-3. 4%) and SMT (32.3+/-2.6%) and was absent in mice with targeted ablation of iNOS (23.9+/-1.6%). CCPA produced improvement in postischemic end-diastolic pressure, developed pressure, and rate-pressure product, which was also blocked by DPCPX and SMT. Increased iNOS protein expression observed in CCPA-treated hearts was diminished by DPCPX. CONCLUSIONS: Selective activation of A(1)ARs produces delayed cardioprotection against ischemia/reperfusion injury in the mouse. Increased iNOS expression concomitant with the lack of protective effect of A(1)AR activation in iNOS gene-knockout mice suggests a direct cause-and-effect relationship of iNOS in adenosine-induced late cardioprotection.

Adenosine↗
PubMed2000

Genotoxic markers among butadiene polymer workers in China.

While 1,3-butadiene is carcinogenic in rodents, cancer causation in humans is less certain. We examined a spectrum of genotoxic outcomes in 41 butadiene polymer production workers and 38 non-exposed controls, in China, to explore the role of butadiene in human carcinogenesis. Because in vitro studies suggest that genetic polymorphisms in glutathione S-transferase enzymes influence genotoxic effects of butadiene, we also related genotoxicity to genetic polymorphisms in GSTT1 and GSTM1. Among butadiene-exposed workers, median air exposure was 2 p.p.m. (6 h time-weighted average), due largely to intermittent high level exposures. Compared with unexposed subjects, butadiene-exposed workers had greater levels of hemoglobin N-(2,3,4-trihydroxybutyl)valine (THBVal) adducts (P < 0.0001) and adduct levels tended to correlate, among butadiene-exposed workers, with air measures (P = 0.03). Butadiene-exposed workers did not differ, however, from unexposed workers with respect to frequency of uninduced or diepoxybutane-induced sister chromatid exchanges, aneuploidy as measured by fluorescence in situ hybridization of chromosomes 1, 7, 8 and 12, glycophorin A variants or lymphocyte hprt somatic mutation. Also among the exposed, greater THBVal levels were not associated with increases in uninduced sister chromatid exchanges, aneuploidy, glycophorin A or hprt mutations. Butadiene-exposed workers had greater lymphocyte (P = 0.002) and platelet counts (P = 0.07) and lymphocytes as a percentage of white blood cells were moderately correlated with greater THBVal levels (Spearman's phi = 0.32, P = 0.07). Among butadiene-exposed workers, neither GSTM1 nor GSTT1 genotype status predicted urinary mercapturic acid butanediol formation, THBVal adducts, uninduced sister chromatid exchanges, aneuploidy or mutations in the glycophorin A or hprt genes. Overall, the study demonstrated exposure to butadiene in these workers, by a variety of short-term and long-term measures, but did not show specific genotoxic effects, at the chromosomal or gene levels, related to that exposure.

Adult↗
PubMed2000

Dietary copper effects on lipid metabolism and circulating catecholamine concentrations in finishing steers.

Forty-eight Angus and Hereford x Angus steers were used to determine the effects of copper (Cu) on lipid and catecholamine metabolism. Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of 0 (control, no supplemental Cu), 10, or 40 mg of supplemental Cu (from Cu2(OH)3Cl)/kg DM. Steers were fed a corn silage-soybean meal-based growing diet for 42 d. Animals were then switched to a high-concentrate finishing diet and remained on the same dietary treatments. On d 70, indwelling jugular catheters were nonsurgically inserted into five steers per treatment. Blood samples were obtained from steers after a 24-h period of feed withdrawal, 1 h after feeding, and after i.v. administration of norepinephrine and were subsequently analyzed for nonesterified fatty acid (NEFA) and catecholamine concentrations. Average daily gain over the finishing period was higher (P < 0.06) in steers receiving supplemental Cu. Serum total cholesterol concentrations were reduced (P < 0.05) on d 84 and 112 in steers supplemented with Cu. Serum norepinephrine (P < 0.14) and NEFA concentrations following feed withdrawal tended (P < 0.12) to be higher in Cu-supplemented steers. Postfeeding norepinephrine concentrations tended to be higher (P < 0.14) in Cu-supplemented steers. Nonesterifled fatty acid concentrations were lower (P < 0.10) in Cu-supplemented steers after norepinephrine administration. Backfat depth was decreased (P < 0.10) and longissimus muscle polyunsaturated fatty acid percentages were increased (P < 0.10) in steers receiving supplemental Cu. These results indicate that Cu addition to a finishing diet containing 5 mg Cu/kg DM alters lipid metabolism. The reduction in backfat depth may be due to copper altering catecholamine metabolism in steers.

Adipose Tissue↗
PubMed1999

Impact of maternal lifestyle factors on newborn HPRT mutant frequencies and molecular spectrum--initial results from the Prenatal Exposures and Preeclampsia Prevention (PEPP) Study.

Epidemiological studies have demonstrated associations between maternal tobacco smoke exposure and consumption of alcohol during pregnancy and increased risk of pediatric malignancies, particularly infant leukemias. Molecular evidence also suggests that somatic mutational events occurring during fetal hematopoiesis in utero can contribute to this process. As part of an ongoing multi-endpoint biomarker study of 2000 mothers and newborns, the HPRT T-lymphocyte cloning assay was used to determine mutant frequencies (Mf) in umbilical cord blood samples from an initial group of 60 neonates born to a sociodemographically diverse cohort of mothers characterized with respect to age, ethnicity, socioeconomic status, and cigarette smoke and alcohol exposure. Non-zero Mf (N = 47) ranged from 0.19 to 5.62 x 10(-6), median 0.70 x 10(-6), mean +/- SD 0.98 +/- 0.95 x 10(-6). No significant difference in Mf was observed between female and male newborns. Multivariable Poisson regression analysis revealed that increased HPRT Mf were significantly associated with maternal consumption of alcohol at the beginning [Relative Rate (RR) = 1.84, 95% CI = 0.99-3.40, P = 0.052) and during pregnancy (RR = 2.99, 95% CI = 1.14-7.84, P = 0.026). No independent effect of self-reported active maternal cigarette smoking, either at the beginning or throughout pregnancy, nor maternal passive exposure to cigarette smoke was observed. Although based on limited initial data, this is the first report of a positive association between maternal alcohol consumption during pregnancy and HPRT Mf in human newborns. In addition, the spectrum of mutations at the HPRT locus was determined in 33 mutant clones derived from 19 newborns of mothers with no self-reported exposure to tobacco smoke and 14 newborns of mothers exposed passively or actively to cigarette smoke. In the unexposed group, alterations leading to specific exon 2-3 deletions, presumably as a result of illegitimate V(D)J recombinase activity, were found in five of the 19 mutants (26.3%); in the passively exposed group, two exon 2-3 deletions were present among the seven mutants (28.6%); and in the actively exposed group, six of the seven mutants (85.7%) were exon 2-3 deletions. Although no overall increase in HPRT Mf was observed and the number of mutant clones examined was small, these initial results point to an increase in V(D)J recombinase-associated HPRT gene exon 2-3 deletions in cord blood T-lymphocytes in newborns of actively smoking mothers relative to unexposed mothers (P = 0.011). Together, these results add to growing molecular evidence that in utero exposures to genotoxicants result in detectable transplacental mutagenic effects in human newborns.

Alcohol Drinking↗
PubMed1999

Quantification of illegitimate V(D)J recombinase-mediated mutations in lymphocytes of newborns and adults.

We used a direct polymerase chain reaction (PCR) method for quantification of HPRT exons 2 + 3 deletions and t(14;18) translocations as a measure of illegitimate V(D)J recombination. We determined the baseline frequencies of these two mutations in mononuclear leukocyte DNA from the umbilical cord blood of newborns and from the peripheral blood of adults. In an initial group of 21 newborns, no t(14;18) translocations were detected (< 0.049 x 10(-7)). The frequency of HPRT exons 2 + 3 deletions was 0.10 x 10(-7) per mononuclear leukocyte, lower than expected based on the T-cell proportion of this cell fraction (55%-70%) and previous results using the T-cell cloning assay (approximately 2-3 x 10(-7) per clonable T-cell). Phytohemagglutinin (PHA), as used in the T-cell cloning assay, was examined for its effect on the frequencies of these mutation events in mononuclear leukocytes from an additional 11 newborns and from 12 adults. There was no significant effect of PHA on t(14;18) translocations which were rare among the newborns (1 detected among 2.7 x 10(8) leukocytes analyzed), and which occurred at frequencies from < 1 x 10(-7) (undetected) to 1.6 x 10(-4) among the adults. The extremely high frequencies of t(14;18)-bearing cells in three adults were due mainly to in vivo expansion of two to six clones. However, PHA appeared to stimulate a modest (although not significant) increase in the frequency of HPRT exons 2 + 3 deletions in the leukocytes of the newborns, from 0.07 x 10(-7) to 0.23 x 10(-7). We show that both the direct PCR assay and the T-cell cloning assay detect similar frequencies of HPRT exons 2 + 3 deletions when calculations are normalized to blood volume, indicating that the apparent discrepancy is probably due to the different population of cells used in the assays. This direct PCR assay may have utility in characterizing the effects of environmental genotoxic agents on this clinically important recombination mechanism.

Adult↗