Comparison of three analytical methods for 1-hydroxypyrene glucuronide in urine after non-occupational exposure to polycyclic aromatic hydrocarbons

Urinary pyrene metabolites, 1-OHP and 1-OHPG, have been used as biomarkers for the assessment of occupational and environmental exposure to PAHs. This study compares the sensitivity and applicability of the different analytical methods of 1-OHPG for human biomonitoring of low level exposure to PAHs. Three analytical methods were compared: (1) HPLC method from that reported by Singh et al. (Singh, R., Tucek, M., Maxa, K., Tenglerova, J., Weyand, E.H., 1995. A rapid and simple method for the analysis of 1-hydroxypyrene glucuronide: a potential biomarker for polycyclic aromatic hydrocarbon exposure. Carcinogenesis 16, 2909-2915); (2) IAC-SFS method: the rapid and simple assay using IAC purification using monoclonal antibody specific for PAH-DNA adduct and PAH metabolites and SFS quantitation; and (3) IAC-HPLC method: IAC and HPLC separation and quantitation. The correlation between the IAC-SFS method, HPLC method, and the IAC-SFS method was determined in 20 first year-grade junior high school students (age 12-13) from Yochon, Korea who participated in a nationwide survey for the environmental disease surveillance projects in Korea. Chromatograms obtained by the IAC purification and HPLC quantitation method were clear with no interfering peaks adjacent to 1-OHPG, thus 1-OHPG could be easily quantitated. However, the HPLC method produced chromatogram profiles with many interfering peaks adjacent to 1-OHPG peak. The concentrations of 1-OHPG in 20 urine samples were similar when analyzed by all three analytical methods. The correlation coefficient between the IAC-HPLC and IAC-SFS methods was 0.915, and between the IAC-HPLC and HPLC methods was 0.844, and between the IAC-SFS and HPLC methods was 0.805. The analytical methods for 1-OHPG compared in this study showed a good correlation with one another. These results suggest that any of the methods can be applied to human biomonitoring of PAH exposure. However, SFS quantitation after IAC purification is rapid and simple because this method does not need HPLC separation of 1-OHPG.

Variations in urinary 1-hydroxypyrene glucuronide in relation to smoking and the modification effects of GSTM1 and GSTT1

The measurement of the pyrene metabolite, 1-hydroxypyrene, in human urine has been used to assess recent exposure to polycyclic aromatic hydrocarbons (PAH). The objective of this study was to see whether genetic polymorphisms in metabolic enzymes could explain some of the variation in urinary 1-hydroxypyrene glucuronide (1-OHPG) excretion in relation to smoking. Forty-seven male hospital workers, who were not occupationally exposed to PAH, participated in this study. The urine samples were analyzed for 1-OHPG utilizing immunoaffinity chromatography and synchronous fluorescence spectroscopy. The analysis of GSTM1 and GSTT1 polymorphism was performed by PCR. The 1-OHPG concentration in the urine of the hospital workers was 0.57 +/- 0.85 micromol/mol creatinine, and ranged from 0.02 to 5.04 mciromol/mol creatinine. Cigarette smoking was significantly correlated with urinary 1-OHPG (r = 0.3976, P = 0.0056). The 1-OHPG excretion in GSTM1-deficient smokers was higher than that in GSTM1-positive smokers. On the other hand, 1-OHPG excretion was higher in GSTT1-positive smokers than in GSTT1-deficient smokers. It is important to note the variability of individual PAH metabolite excretion due to different GSTM1 and GSTT1 genotypes.

Mitochondrial electron transport complex I is a potential source of oxygen free radicals in the failing myocardium

Oxidative stress in the myocardium may play an important role in the pathogenesis of congestive heart failure (HF). However, the cellular sources and mechanisms for the enhanced generation of reactive oxygen species (ROS) in the failing myocardium remain unknown. The amount of thiobarbituric acid reactive substances increased in the canine HF hearts subjected to rapid ventricular pacing for 4 weeks, and immunohistochemical staining of 4-hydroxy-2-nonenal ROS-induced lipid peroxides was detected in cardiac myocytes but not in interstitial cells of HF animals. The generation of superoxide anion was directly assessed in the submitochondrial fractions by use of electron spin resonance spectroscopy with spin trapping agent, 5, 5'-dimethyl-1-pyrroline-N-oxide, in the presence of NADH and succinate as a substrate for NADH-ubiquinone oxidoreductase (complex I) and succinate-ubiquinone oxidoreductase (complex II), respectively. Superoxide production was increased 2.8-fold (P<0.01) in HF, which was due to the functional block of electron transport at complex I. The enzymatic activity of complex I decreased in HF (274+/-13 versus 136+/-9 nmol. min(-1). mg(-1) protein, P<0.01), which may thus have caused the functional uncoupling of the respiratory chain and the deleterious ROS production in HF mitochondria. The present study provided direct evidence for the involvement of ROS in the mitochondrial origin of HF myocytes, which might be responsible for both contractile dysfunction and structural damage to the myocardium.

Anticlinic coupling between layers of an antiferroelectric liquid crystal

The anticlinic interlayer coupling coefficient U was evaluated as a function of temperature for a pitch-compensated liquid crystal by optical observation of the electric field-induced optic mode. U was found to exhibit an unusual "S-shaped" dependence on temperature, with values ranging between 0.4x10(4) and 2.2x10(4) erg cm(-3) over a 10 degrees C temperature range below the smectic-A-smectic-C(*)(A) phase-transition temperature. The results are in good agreement with estimates for U based upon the threshold field for the onset of solitary waves, and provide strong support in the low-field regime for the single Fourier component model proposed by Li et al. [Phys. Rev. B 52, R13 075 (1995)].

[Health-related quality of life in hypertensive patients]

OBJECTIVES

To explore the health-related quality of life (HRQOL) for hypertensive patients (HBP) and to provide reasonable evidence for evaluating the effectiveness of antihypertensive therapy in clinical practice.

METHODS

A cross-sectional study was used to survey 106 patients with HBP and 127 nomotensives using SF-36 short form of quality of life in the community. The cutoff point score of HRQOL was decided by receiver operating characteristic (ROC) Curve analysis. There were 60 patients with BP > or = 160/95 mm Hg who had been treated by antihypertensive drugs for 6 months. Before and after the treatment, their HRQOL was measured and evaluated, and the relationship between the change of HRQOL and antihypertensive effect was evaluated.

RESULTS

Apart from physical function and pain, other 7 domains were significantly lower in the hypertensive group than in the normotensive group, which included social function, role limitations attributed to both physical and emotional problems, mental health, activity or fatigue and overall evaluation of health (P < 0.05-0.001). A cutoff point of HRQOL was decided using ROC analysis in which the 290 score was the best one for diagnostic HRQOL with the sensitivity of 80% and a specificity of 70%. The target rate of the antihypertensive care and the improved rate of HRQOL for 60 patients with HBP were 63% and 75% separately for a 6-month treatment.

CONCLUSION

The HRQOL of these hypertensives was significantly lower than that in the normotensives in the study. The measurement of HRQOL was more useful to evaluate the antihypertensive effectiveness in clinical practice.

Mitochondrial DNA replication in human T lymphocytes is regulated primarily at the H-strand termination site

The most unique feature in the replication of mitochondrial DNA (mtDNA) is that most of the newly synthesized heavy strands (H-strands) terminate prematurely, resulting in the formation of displacement loop (D-loop) strands. Only the H-strand which proceeds past the termination site is a true nascent H-strand leading to the overall replication on a circular mtDNA molecule. The physiological significance of the D-loop formation has long been unclear. To examine the role of premature termination in mtDNA replication, we therefore developed a method for selectively measuring both the total amount of nascent H-strands and the amount of true nascent H-strands using ligation-mediated polymerase chain reaction, which, for the first time, enabled us to estimate the frequency of premature termination. The stimulation of cell proliferation with interleukin 2 and phytohemagglutinin in human peripheral T lymphocytes caused an increase in the net replication rate of mtDNA. In stimulated cells, in comparison to resting ones, the amount of true nascent H-strands increased approx. 2.6-fold while the total amount of nascent H-strands remained unchanged, indicating that premature termination decreased while the initiation of replication remained the same. Our findings thus demonstrate the first clear example that premature termination plays a primary role in the up-regulation of the net rate of mtDNA replication in human cells.

Evidence for functional conservation of a mammalian homologue of the light-responsive plant protein COP1

Identified in Arabidopsis as a repressor of light-regulated development, the COP1 (constitutively photomorphogenic 1) protein is characterized by a RING-finger motif and a WD40 repeat domain [1]. The subcellular localization of COP1 is light-dependent. COP1 acts within the nucleus to repress photomorphogenic development, but light inactivates COP1 and diminishes its nuclear abundance [2]. Here, we report the identification of a mammalian COP1 homologue that contains all the structural features present in Arabidopsis COP1 (AtCOP1). When expressed in plant cells, a fusion protein comprising mammalian COP1 and beta-glucuronidase (GUS) responded to light by changing its subcellular localization pattern in a manner similar to AtCOP1. Whereas the mammalian COP1 was unable to rescue the defects of Arabidopsis cop1 mutants, expression of the amino-terminal half of mammalian COP1 in Arabidopsis interfered with endogenous COP1 function, resulting in a hyperphotomorphogenic phenotype. Therefore, the regulatory modules in COP1 proteins that are responsible for the signal-dependent subcellular localization are functionally conserved between higher plants and mammals, suggesting that mammalian COP1 may share a common mode of action with its plant counterpart in regulating development and cellular signaling.

The Alzheimer-related gene presenilin 1 facilitates notch 1 in primary mammalian neurons

The normal functional neurobiology of the Alzheimer's disease (AD) related gene presenilin 1 (PS1) is unknown. One clue comes from a genetic screen of Caenorhabditis elegans, which reveals that the presenilin homologue sel-12 facilitates lin-12 function [D. Levitan, I. Greenwald, Facilitation of lin-12-mediated signalling by sel-12, a Caenorhabditis elegans S182 Alzheimer's disease gene, Nature 377 (1995) 351-355]. The mammalian homologue of lin-12, Notch1, is a transmembrane receptor that plays an important role in cell fate decisions during development, including neurogenesis, but does not have a known function in fully differentiated cells. To better understand the potential role of Notch1 in mammalian postmitotic neurons and to test the hypothesis that Notch and PS 1 interact, we studied the effect of Notch1 transfection on neurite outgrowth in primary cultures of hippocampal/cortical neurons. We demonstrate that Notch1 inhibits neurite extension, and thus has a function in postmitotic mature neurons in the mammalian CNS. Furthermore, we present evidence demonstrating that there is a functional interaction between PS1 and Notch1 in mammalian neurons, analogous to the sel-12/lin-12 interaction in vulval development in C. elegans [D. Levitan, T. Doyle, D. Brousseau, M. Lee, G. Thinakaran, H. Slunt, S. Sisodia, I. Greenwald, Assessment of normal and mutant human presenilin function in Caenorhabditis elegans, Proc. Natl. Acad. Sci. U.S.A. 93 (1996) 14940-14944; D. Levitan, I. Greenwald, Effect of Sel-12 presenilin on Lin-12 localization and function in Caenorhabditis elegans, Development, 125 (1998) 3599-3606]. The inhibitory effect of Notch1 on neurite outgrowth is markedly attenuated in neurons from PS1 knockout mice, and enhanced in neurons from transgenic mice overexpressing wild type PS1, but not mutant PS1. These data suggest that PS1 facilitates Notch1 function in mammalian neurons, and support the hypothesis that a functional interaction exists between PS1 and Notch1 in postmitotic mammalian neurons.

Expression and differential intracellular localization of two major forms of human 8-oxoguanine DNA glycosylase encoded by alternatively spliced OGG1 mRNAs

We identified seven alternatively spliced forms of human 8-oxoguanine DNA glycosylase (OGG1) mRNAs, classified into two types based on their last exons (type 1 with exon 7: 1a and 1b; type 2 with exon 8: 2a to 2e). Types 1a and 2a mRNAs are major in human tissues. Seven mRNAs are expected to encode different polypeptides (OGG1-1a to 2e) that share their N terminus with the common mitochondrial targeting signal, and each possesses a unique C terminus. A 36-kDa polypeptide, corresponding to OGG1-1a recognized only by antibodies against the region containing helix-hairpin-helix-PVD motif, was copurified from the nuclear extract with an activity introducing a nick into DNA containing 8-oxoguanine. A 40-kDa polypeptide corresponding to a processed form of OGG1-2a was detected in their mitochondria using antibodies against its C terminus. Electron microscopic immunocytochemistry and subfractionation of the mitochondria revealed that OGG1-2a locates on the inner membrane of mitochondria. Deletion mutant analyses revealed that the unique C terminus of OGG1-2a and its mitochondrial targeting signal are essential for mitochondrial localization and that nuclear localization of OGG1-1a depends on the NLS at its C terminus.

Large-scale optimization of neuron arbors

At the global as well as local scales, some of the geometry of types of neuron arbors-both dendrites and axons-appears to be self-organizing: Their morphogenesis behaves like flowing water, that is, fluid dynamically; waterflow in branching networks in turn acts like a tree composed of cords under tension, that is, vector mechanically. Branch diameters and angles and junction sites conform significantly to this model. The result is that such neuron tree samples globally minimize their total volume-rather than, for example, surface area or branch length. In addition, the arbors perform well at generating the cheapest topology interconnecting their terminals: their large-scale layouts are among the best of all such possible connecting patterns, approaching 5% of optimum. This model also applies comparably to arterial and river networks.

R-Loop in the replication origin of human mitochondrial DNA is resolved by RecG, a Holliday junction-specific helicase

Stable RNA-DNA hybrids (R-loops) prime the initiation of replication in Escherichia coli cells. The R-loops are resolved by Escherichia coli RecG protein, a Holliday junction specific helicase. A stable RNA-DNA hybrid formation in the mitochondrial D-loop region is also implicated in priming the replication of mitochondrial DNA. Consistent with this hypothesis, the 3' ends of the mitochondrial R-loop formed by in vitro transcription are located close to the initiation sites of the mitochondrial DNA replication. This mitochondrial R-loop is resolved by RecG in a dose-dependent manner. Since the resolution by RecG requires ATP, the resolution is dependent on the helicase activity of RecG. A linear RNA-DNA heteroduplex is not resolved by RecG, suggesting that RecG specifically recognizes the higher structure of the mitochondrial R-loop. This is the first example that R-loops of an eukaryotic origin is sensitive to a junction-specific helicase. The resolution of the mitochondrial R-loop by RecG suggests that the replication-priming R-loops have a common structural feature recognized by RecG.

[Estimation of healthy reference intervals for elderly people through the use of outpatient data]

It is important to determine transferable reference intervals as well as uniformity in measured values for inter-regional and inter-institutional availability of clinical test results. For that purpose, the National Committee for Clinical Laboratory Standards (NCCLS) issued forth guidelines in 1995. Some regional institutions in Japan are making efforts to determine normal reference intervals based on these guidelines. We, the Fukuoka Five Hospitals Group, have selected 3,375 healthy reference individuals and have determined the normal reference intervals for the age groups of 20-29, 30-39, 40-49, and 50-59 years old. The rapidly increasing percentage of elderly people gives rise to ever increasing health-care needs for the elderly, which requires normal reference intervals for older age groups. However, we were unable to collect the required number of the reference individuals above 60 years of age. To obtain reference intervals with adequate reliability and usefulness temporally, we made use of the laboratory data of outpatients at Kyushu University Hospital, and were then easily able to collect the required number of elderly individuals. By performing a very simple selection from among the outpatients, our outpatient group became virtually indistinguishable from the group of healthy reference individuals established by us, with regard to many clinical tests, thus enabling us to estimate reference intervals for older age groups. This approach could be adopted in other regions.

1-Methyl-4-phenylpyridinium ion (MPP+) selectively inhibits the replication of mitochondrial DNA

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine is known to cause Parkinsonism in its neurotoxic form, 1-methyl-4-phenylpyridinium ion (MPP+). We have previously reported that MPP+ decreases the content of mitochondrial DNA (mtDNA) independently of the inhibition of complex I in human cells [Miyako, K., Kai, Y., Irie, T., Takeshige, K., and Kang, D. (1997) J. Biol. Chem. 272, 9605-9608]. Here we study the mechanism causing the decrease in mtDNA. MPP+ inhibits the incorporation of 5-bromo-2'-deoxyuridine into mtDNA but not into nuclear DNA, indicating that MPP+ inhibits the replication of mtDNA but not that of the nuclear genome. The replication of mtDNA is initiated by the synthesis of the heavy strand switched from the transcription of the light strand. MPP+ decreases the nascent heavy strands per mtDNA and increases the transcript of the ND6 gene, encoded on light strand, per mtDNA. The amount of mitochondrial transcription factor A is not decreased. These data suggest that the transcription is not inhibited and therefore the transition from transcription to replication of mtDNA is lowered in the MPP+-treated cells. Electron microscopy shows that the number of mitochondria is not decreased in the MPP+-treated cells, suggesting that MPP+ does not affect the overall biogenesis of mitochondria. Thus, MPP+ selectively inhibits the replication of mtDNA.

Cotransduction of tyrosine hydroxylase and aromatic L-amino acid decarboxylase genes into cultured striatal cells using adeno-associated virus vectors

OBJECTIVE

To examine whether tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) genes can be cotransduced into the same target striatal cells using adeno-associated virus (AAV) vectors, and to determine whether the cotransduction would result in better biochemical change than the TH gene alone.

METHODS

TH and AADC genes were cotransduced into cultured striatal cells with separate AAV vectors. Expressions of TH and AADC were detected by immunocytochemistry; intracellular catecholamine levels were assayed by high-performance liquid chromatography (HPLC).

RESULTS

TH and AADC genes were efficiently cotransduced into the striatal cells. Specifically, the coexpression of TH and AADC resulted in more effective dopamine production compared with the TH gene alone.

CONCLUSION

Using AAV vectors, coexpression of TH and AADC in the striatal cells might be a useful approach to gene therapy for Parkinson's disease.

Excitatory amino acids in cerebrospinal fluid and their relations with clinical features and outcomes in acute head injury

OBJECTIVE

To determine the contents and dynamics of excitatory amino acids (EAAs), glutamate (GLU) and aspartate (ASP) in the cerebrospinal fluid (CSF) of patients with acute head injury and to clarify the relationship of EAAs with clinical features and outcomes.

METHODS

Forty-two adults with acute head injury were included. Glasgow coma scale (GCS) obtained at admission and Glasgow outcome scale (GOS) obtained three months post-injury were assessed. Samples of CSF were obtained via ventricular or lumbar puncture every 24 hours. GLU and ASP in CSF were analyzed by reversed-phase HPLC with a fluorescent detector. Nine control subjects were adults with lumbar anesthesia but without neurological diseases.

RESULTS

The peak concentration of GLU and ASP of head-injured group was significantly higher than that of the control group. Dynamic research on severely injured ones indicated that the peak value of GLU mostly appeared within 48 hours post-injury; it decreased with the improving or remaining of the neurological status, and increased with the deterioration, but was still higher than that of the control seven days post-injury. The peak value of EAAs of severely injured patients was conspicuously higher than that of mildly injured group. There was a significant negative correlation between the peak values of GCS and EAAs. The peak value of EAAs in patients with poor outcome was remarkably higher than that in patients with good outcome. GOS was closely correlated to the peak value of EAAs. When the concentration of GLU was over 7 mumol/L, the rate of poor-outcome increased markedly.

CONCLUSION

The content of EAAs in CSF increases following acute head injury and remains higher at least a week post-injury in severely injured patients. The more severe the trauma, the more obvious the excitotoxicity induced by EAAs; the more serious the secondary brain insult and the brain edema will be, the worse the outcome, naturally.

New sensitive method for the detection of the A3243G mutation of human mitochondrial deoxyribonucleic acid in diabetes mellitus patients by ligation-mediated polymerase chain reaction

An adenine-to-guanine mutation at nucleotide position (np) 3243 in the mitochondrial tRNALeu(UUR) gene is closely associated with various clinical phenotypes of diabetes mellitus. Because the mutation creates a new restriction site for the restriction enzyme ApaI, the mutation is usually detected and quantified by ApaI cleavage of the PCR products including np 3243. The sensitivity of the conventional method is, however, 5-10% heteroplasmy. The percentage of heteroplasmy of the mutation is usually highest in the affected tissues and is much lower in peripheral blood cells, which are used most frequently for the analysis. The sensitivity of the conventional method, however, is not sufficient to detect the mutation from peripheral blood cells. Utilizing ligation-mediated polymerase chain reaction, we have developed a feasible and sensitive method to detect 0.01% heteroplasmy of the 3243 mutation in peripheral leukocytes.

A peptidoglycan recognition protein in innate immunity conserved from insects to humans

Innate nonself recognition must rely on common structures of invading microbes. In a differential display screen for up-regulated immune genes in the moth Trichoplusia ni we have found mechanisms for recognition of bacterial cell wall fragments. One bacteria-induced gene encodes a protein that, after expression in the baculovirus system, was shown to be a peptidoglycan recognition protein (PGRP). It binds strongly to Gram-positive bacteria. We have also cloned the corresponding cDNA from mouse and human and shown this gene to be expressed in a variety of organs, notably organs of the immune system-i.e., bone marrow and spleen. In addition, purified recombinant murine PGRP was shown to possess peptidoglycan affinity. From our results and the sequence homology, we conclude that PGRP is a ubiquitous protein involved in innate immunity, conserved from insects to humans.

Female sex hormones and body mass in adolescent and postmenopausal Korean women

A cross-sectional study was conducted to evaluate the relationship between body mass and serum level of female sex hormones among 153 adolescent girls, and 153 postmenopausal women in Korea. Information on lifestyles, and both menstrual and reproductive factors was collected by personal interview. Serum total estradiol (E2), progesterone (Pg), and sex hormone binding globulin (SHBG) concentrations were measured by radioimmunoassay. Multiple linear regression analysis was used to determine whether the hormonal levels would be affected by the obesity indices. Body weight and body mass index (BMI) were inversely related to SHBG level in both premenopausal (p<0.005) and postmenopausal women (p<0.005) after adjusting for age. E2 levels during any phase in premenopausal girls were not related to BMI, whereas heavier girls had significantly higher levels of late luteal-phase Pg (p<0.05). Taller postmenopausal women had lower E2 levels (p<0.05). Results on the association between SHBG and BMI are consistent with previous results in Caucasian women, and might suggest the potential role of bioavailable estradiol in breast carcinogenesis in pre- and post-menopausal women. The finding that progesterone might be related to body mass in premenopausal women should be pursued in further studies.

Interaction of apolipoprotein E epsilon 4 with other genetic and non-genetic risk factors in late onset Alzheimer disease: problems facing the investigator

The Apolipoprotein E4 allele (Apo-epsilon4) is the major susceptibility gene for late onset Alzheimer Disease (AD) but epidemiological data suggest that the effect of this allele is modified in different individuals by genetic or environmental factors. Age and head injury are major non-genetic factors modifying the Apo-epsilon4 risk. There is conflicting data as to whether alleles of other chaperon proteins (such as alpha-1-antichymotrypsin (ACT)) or Apo-epsilon4 receptors (such as the VDRL receptor) modify the Apo-epsilon4 risk for AD. We analyze problems posed by genetic association studies including those of multiple comparisons and selection of controls, the latter problem exacerbated by the wide variations in Apolipoprotein E allele frequencies observed in different groups and localities.

Gene therapy targeting cord blood-derived CD34+ cells from HIV-exposed infants: preclinical studies

Hematopoietic CD34+ cells from placental and umbilical cord blood (PUCB) can be valuable vehicles for gene therapy of immunodeficiencies and genetic disorders. We have conducted preclinical studies towards the treatment of HIV-1-infected infants with genetically 'immunized' CD34+ cells derived from PUCB using anti-HIV-1 hairpin ribozyme genes. PUCB was collected from 10 newborns of HIV-1-positive mothers. CD34+ cells were enriched with a modified procedure using Dynal immunomagnetic beads and chymopapain, stimulated with stem cell factor (SCF), IL-3 and IL-6, and transduced using cell-free recombinant retroviral vector (MJT) expressing a ribozyme against the U5 region of HIV-1. No significant differences were observed in the growth pattern of CD34+ cells from normal infants, HIV-1 exposed infants or infants confirmed to be infected by HIV-1. The transduction efficiency of the CD34+ cells from all the infants was also comparable. MJT-transduced CD34+ cells from an HIV-1-infected infant were maintained in a liquid culture system for 4 weeks, and the progeny macrophage cells were challenged with the monocyte-tropic laboratory strain, HIV-Bal, or the HIV-1 isolate from the infant's mother. Significant inhibition of virus replication was observed in ribozyme-transduced cells. Thus, we have demonstrated efficient and stable gene transfer into progenitor cells from the cord blood of HIV-1-exposed or -infected infants and shown that protection from HIV-1 infection was conferred to the progeny cells produced by CD34+ cells transduced with the anti-HIV ribozyme gene construct.

Reversible ischemia increases levels of Alzheimer amyloid protein precursor without increasing levels of mRNA in the rabbit spinal cord

In a rabbit spinal cord ischemia model (RSCIM), the time courses of neuropathological damage of the spinal cord and neurological impairment of the motor functions are well established, demonstrating that the extent of neuropathological damage and the severity of neurological impairment are closely correlated. We used the RSCIM to elucidate the effects of reversible (15 min) and irreversible (60 min) ischemia on the endogenous levels of amyloid protein precursors (APPs) at both the mRNA and protein levels in the caudolumbar/sacral region of the spinal cord. We speculate that endogenous APPs are induced by ischemia as either trophic factors or stress-induced proteins in the RSCIM. A 15-min occlusion transiently increased the APP protein levels in neurons, which returned to the original levels by the end of 60 min occlusion. The increase in APP protein levels during 15-min ischemic insult does not appear to involve regulation at the mRNA level. The increased level of APPs, particularly of the soluble form, could support the possibility that APPs play a neuroprotective role in the RSCIM as stress-induced proteins. In contrast, failure to maintain the increased APP protein levels or to increase the mRNA, as seen in the 60-min ischemia samples, may be one of the causal factors that induce necrosis and neuronal cell death leading to irreversible neurological impairment.

p32 protein, a splicing factor 2-associated protein, is localized in mitochondrial matrix and is functionally important in maintaining oxidative phosphorylation

Human p32, originally cloned as a splicing factor 2-associated protein, has been reported to interact with a variety of molecules including human immunodeficiency virus Tat and complement 1q (C1q). p32 protein is supposed to be in the nucleus and on the plasma membrane for the association with human immunodeficiency virus Tat and C1q, respectively. None of the interactions, however, is proven to have a physiological role. To investigate the physiological function of p32, we determined the intracellular localization of p32. The fractionation of cells, fluorescent immunocytochemistry, and electron microscopic immunostaining show that p32 is exclusively localized in the mitochondrial matrix. We cloned a Saccharomyces cerevisiae homologue of human p32 gene, referred to yeast p30 gene. The yeast p30 protein is also localized in the mitochondrial matrix. The disruption of the p30 gene caused the growth retardation of yeast cells in a glycerol medium but not in a glucose medium, i.e. the impairment of the mitochondrial ATP synthesis. The growth impairment was restored by the introduction of the human p32 cDNA, indicating that p30 is a functional yeast counterpart of human p32. Taken together, both p32 and p30 reside in mitochondrial matrix and play an important role in maintaining mitochondrial oxidative phosphorylation.

Risk factors associated with uterine cervical cancer in Korea: a case-control study with special reference to sexual behavior

OBJECTIVE

A hospital-based case-control study was conducted to identify characteristics of women at high risk of developing cervical cancer with special reference to sexual behavior in Korea.

METHODS

Histologically confirmed cases of invasive cervical cancer were selected from the Department of Gynecology, Seoul National University Hospital between September 1992 to May 1995 (n = 203). Women with normal pap smear tests and women free of past history of any malignancies were regarded as controls (n = 827). Information on risk factors were collected by both a self-administered questionnaire and a direct interview.

RESULTS

Uterine cervical cancer risk was higher in women with a less educated spouse (Ptrend = 0.0003), women with a family history of cervical cancer (adjusted odds ratio [OR] = 2.20., 95% confidence interval [CI] 1.21-4.01), women of shorter height (Ptrend = 0.02), women with early age at first full term pregnancy (Ptrend = 0.0005), and women who have had multiple full term pregnancies (Ptrend = 0.006) by the multiple linear logistic analysis. Particularly noteworthy was a significant decreasing trend in the adjusted OR with the age at first sexual intercourse increasing (Ptrend = 0.002) after adjusting the number of sexual partners. The husband's indecent sexual history showed a borderline significance (Ptrend = 0.07).

CONCLUSIONS

This study confirmed that the risk factors of cervical cancer in Korea are similar with those found in other countries.

Proteolytic cleavage sites of band 3 protein in alkali-treated membranes: fidelity of hydropathy prediction for band 3 protein

To assess the fidelity of hydropathy prediction for band 3 protein, we determined the cleavage sites of the protein and the portions of the protein tightly bound to the membrane lipid bilayer by means of in situ proteolytic digestion. For the removal of all anticipated hydrophilic connector loops from membranes, we had to denature the band 3 protein molecule in situ by alkali treatment. When the alkali-treated membranes were digested with trypsin, chymotrypsin, and pepsin, the majority of the anticipated transmembrane portions remained in the membrane fraction. However, five anticipated transmembrane portions were released into the supernatant fraction. Thus, the first, second, third, sixth and tenth anticipated transmembrane portions, in accordance with the hydropathy prediction, were released into the supernatant with the proteolytic digestion method. This indicates that these anticipated transmembrane portions are not bound with the boundary lipids although the hydrophobicity of these portions is comparable to that of the portions experimentally remaining in the membrane fraction. It is conceivable that the membrane peptide portions of band 3 protein could be classified into at least two categories, i.e. one bound to the boundary lipids and the other free from the boundary lipids. Approximately 90% of the transmembrane domain of the band 3 protein are recovered in either the supernatant fraction or the membrane fraction. The fidelity of hydropathy prediction for polytopic membrane proteins and the nature of the membrane embedded peptide portions are discussed.

Coplanar PCBs and the relative contribution of coplanar PCBs, PCDDs, and PCDFs to the total 2,3,7,8-TCDD toxicity equivalents in human serum

Coplanar PCBs in human serum were measured by high-resolution gas chromatography/isotope-dilution high-resolution mess spectrometry in 46 pulp and paper mill workers and 16 community residents with no specific known source of PCB exposure. The relative contribution of coplanar PCBs, PCDDs, and PCDFs to the total 2,3,7,8-TCDD toxicity equivalents (TEQs) were compared using the toxic equivalency factors proposed by Safe [1] and the factors recently proposed by WHO [2]. The mean concentrations of PCB-126 and PCB-169 were higher in paper mill workers than in community residents. However, these differences were not statistically significant. Serum PCB-126, but not PCB-169, was correlated with body mass index (Spearman's r = 0.40, p = 0.002). Serum PCB-169, but not PCB-126, was correlated with age (Spearman's r = 0.54, p = 0.0001). Multiple linear regression analysis for log-transformed combined PCBs showed that age (p = 0.008), body mass index (p = 0.031), and eating locally caught fish (p = 0.019) were statistically significant predictors. The majority of the total TEQ in serum is due to PCDDs (63%), whereas PCDFs account for 21% and coplanar PCBs account for 15% when calculated using the TEFs proposed by Safe. The percent contributions from PCDDs, PCDFs, and coplanar PCBs were 66%, 24%, and 10% respectively when calculated based on the TEFs proposed by WHO. Age, body mass index, and consumption of locally caught fish are significant predictors for coplanar PCB levels in human serum. Serum PCDDs were the major contributors to the total 2,3,7,8-TCDD equivalent toxicity in this study.

In vivo determination of replication origins of human mitochondrial DNA by ligation-mediated polymerase chain reaction

A large part of replication is aborted in human mitochondria, the result being a D-loop. As few attempts have been made to distinguish free 5' ends of true replicate from those of abortive ones, we examined the 5' ends of true replicate of human mitochondrial DNA at one nucleotide resolution in vivo by making use of ligation-mediated polymerase chain reaction. The distribution and relative amounts of origins of the true replicate are exactly the same as those of total newly synthesized heavy strands, which means that the abortion of replication is independent of 5' ends. Treatment of DNA with RNase H frees 5' ends on both heavy and light strands. This is the first in vivo evidence for covalently attached primer RNA to nascent strand in human mitochondrial DNA.

Interactions between superoxide and nitric oxide: implications in DNA damage and mutagenesis

Chronic inflammation is known to be associated with enhanced production of both nitric oxide (NO) and reactive oxygen species such as superoxide (O2-) and hydrogen peroxide (H2O2). Patients with long-standing ulcerative colitis are also known to be at increased risk of developing colorectal cancer. Although NO and reactive oxygen intermediates alone have been known to damage DNA and to promote a wide array of mutagenic reactions, there is increasing evidence to suggest that the interaction between O2- and NO may dictate the type of mutagenic reactions produced at sites where both these free radicals are produced. In the absence of O2-, NO will engage in nitrosative chemistry to yield stable N-nitrosamine derivatives of secondary amines and promote nitrosative deamination of DNA bases. As the flux of O2- is increased, nitrosation reactions are suppressed and oxidative chemistry is enhanced. Thus, depending upon the fluxes of each radical either nitrosation or oxidation chemistry may predominate. The fundamental understanding between O2- and NO may provide new insight in the mechanisms responsible for inflammation-induced mutagenesis.

The content of intracellular mitochondrial DNA is decreased by 1-methyl-4-phenylpyridinium ion (MPP+)

1-Methyl-4-phenylpyridinium ion (MPP+), an oxidative metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is considered to be directly responsible for MPTP-induced Parkinson's disease-like symptoms by inhibiting NADH-ubiquinone oxidoreductase (complex I) in the mitochondrial respiratory chain. Here we demonstrate that 25 microM MPP+ decreases the content of mitochondrial DNA to about one-third in HeLa S3 cells. On the contrary, 0.1 microM rotenone, which inhibits complex I to the same extent as 25 microM MPP+ in the cells, increases the content of mitochondrial DNA about 2-fold. Hence, the effect of MPP+ on mitochondrial DNA is not mediated by the inhibition of complex I. To examine the replication state of mitochondrial DNA, we measured the amount of nascent strands of mitochondrial DNA. The amount is decreased by MPP+ but increased by rotenone, suggesting that the replication of mitochondrial DNA is inhibited by MPP+. Because the proper amount of mitochondrial DNA is essential to maintain components of the respiratory chain, the decrease of mitochondrial DNA may play a role in the progression of MPTP-induced Parkinson's disease-like symptoms caused by the mitochondrial respiratory failure.

Genetic evidence for the involvement of tau in progressive supranuclear palsy

A dinucleotide repeat polymorphism in a tau intron was identified and used in a case-control study to analyze the genetic association of tau with several neurodegenerative diseases with tau pathology. Subjects with the homozygous tau AO alleles were excessively represented in the progressive supranuclear palsy (PSP) group, compared with the age-matched healthy control group. Consequently, this allele is more frequently found in PSP than in a group of healthy subjects. This trend was not found in Alzheimer's disease or parkinsonism-dementia complex of Guam, both of which are accompanied by major tau pathology. The result suggests a possible involvement of tau in the pathogenesis of PSP.

Changes of energy metabolism induced by 1-methyl-4-phenylpyridinium (MPP+)-related compounds in rat pheochromocytoma PC12 cells

We examined effects of three structurally related pyridinium compounds, 1-methyl-4-phenylpyridinium (MPP+), paraquat, and 1-methyl-4-(4'-nitrophenyl) pyridinium (analog 1), on the energy metabolism in pheochromocytoma PC12 cells. MPP+ inhibited the intracellular NADH oxidation by the mitochondrial respiratory chain, judging from the decrease of the cytosolic NAD+/NADH ratio. Paraquat enhanced the oxidation of NADH and decreased intracellular ATP more than MPP+. The inhibition of the mitochondrial respiration by MPP+ was partially compensated by enhanced glycolysis, while paraquat inhibited glycolysis at the level of hexokinase probably due to the intracellular production of oxygen radicals. Analog 1 moderately enhanced glycolysis, moderately increased a cytosolic ratio of NAD+/NADH, and caused only a slight decline of intracellular ATP. Paraquat was the most cytotoxic of the three compounds. Thus, the three structurally related compounds, MPP+, paraquat, and analog 1, showed different effects on the mitochondrial respiratory chain and the glycolytic pathway in PC 12 cells. Their properties found in the cells well reflected those obtained by using bovine heart submitochondrial particles.

A dual effect of 1-methyl-4-phenylpyridinium (MPP+)-analogs on the respiratory chain of bovine heart mitochondria

We examined effects of several compounds, structurally related to 1-methyl-4-phenylpyridinium (MPP+), on the NADH-dependent respiration of bovine heart submitochondrial particles. 1-Methyl-4-(3 '-trimethylammoniophenyl)pyridinium (analog 8) as well as MPP+ completely inhibited O2 consumption, reduction of ubiquinone-10, and reduction of cytochrome b in a dose-dependent manner. The production of superoxide (O2-) induced by MPP+ or analog 8 was to the same extent as that by rotenone, an inhibitor of complex I of the mitochondrial respiratory chain. Rotenone had no additive effect on the maximal production of O2- induced by MPP+ or analog 8, suggesting that the production was mediated by the same way as rotenone. 1-Methyl-4-(4'-nitrophenyl) pyridinium (analog 1) induced about 20-fold more production of O2 than MPP+ and the production was additively increased by rotenone. Analog 1 only partially inhibited rotenone-sensitive O2 consumption. Paraquat induced the production of O2- as much as analog 1. Paraquat, however, did not inhibit rotenone-sensitive O2 consumption or reduction of cytochrome b. These results suggest that MPP+ and its analogs interact with the mitochondrial respiratory chain at two sites, the substrate side of the rotenone-binding site and the rotenone-binding site. The analogs may be reduced to produce O2- at the former site and inhibit the respiratory chain at the latter site.

Glial cells in Alzheimer's disease: preferential effect of APOE risk on scattered microglia

Reactive glial cells are consistently found in the brain tissue of Alzheimer's disease (AD) patients. Both clustered and scattered glial cells occur in AD brain. A number of clustered microglial cells, but not astrocytes, had a positive correlation with neurite plaque numbers, suggesting that clustered micro-glial cells are uniquely associated with plaques whereas clustered astrocytes may have functions outside the plaques as well. APOE epsilon 4, the major genetic risk factor for AD, had a dose-dependent effect to increase the numbers of scattered microglial cells whereas the APOE risk showed no correlation with any of the clustered glial cells or scattered astrocytes. These findings raise the possibility that the increased levels of scattered, but not clustered, microglial cells are the immediate response to APOE risk and might be primarily involved in AD pathogenesis.

Analysis of a lysozyme gene from the malaria vector mosquito, Anopheles gambiae

A genomic DNA sequence encoding a basic lysozyme was isolated from the malaria vector mosquito Anopheles gambiae by screening a library with a probe prepared by PCR of reverse transcribed adult RNA. The sequence consists of an upstream region of about 2 kb, a coding region containing three exons and two introns, and a short 3' untranslated region. The coding region indicates that this mosquito lysozyme consists of a signal peptide of 20 residues followed by an 120 aa mature protein which is very similar to other basic lysozymes. The two small introns, 67 and 76 bp, are located at evolutionarily conserved sites. RT-PCR indicated that this gene is expressed abundantly in sugar-fed adults, and at considerably lower levels when females have fed on blood. Although it remains to be seen whether this gene is induced by bacterial infection, the surrounding sequence contains six sequence motifs very similar to the consensus binding sites for a transcription factor similar to NF-kappa B that are found associated with most insect immune response genes. This lysozyme gene maps to division 27 on the left arm of polytene chromosome 2L. An ORF unrelated to any animal protein in current data bases was found at the 5' end of the clone.

Trichoplusia ni attacin A, a differentially displayed insect gene coding for an antibacterial protein

The mRNA differential display method was used to isolate antibacterial defense genes from Trichoplusia ni. The mRNA population in last-instar T. ni larvae injected with bacteria was compared to that of untreated larvae. Using a PCR amplified probe corresponding to an induced mRNA, we were able to clone an attacin homolog from a lambda cDNA library from vaccinated larvae. The corresponding protein showed 63% identity to Hyalophora cecropia acidic attacin. The induction kinetics of T. ni attacin A gave optimal mRNA levels at 20 h post-infection. Genomic analysis showed this to be a single-copy gene with two introns.

Polycyclic aromatic hydrocarbon metabolites in urine as biomarkers of exposure and effect

Humans are exposed to polycyclic aromatic hydrocarbons (PAHs) from various occupational, environmental, medicinal, and dietary sources. PAH metabolites in human urine can be used as biomarkers of internal dose to assess recent exposure to PAHs. PAH metabolites that have been detected in human urine include 1-hydroxypyrene (1-OHP), 1-hydroxypyrene-O-glucuronide (1-OHP-gluc), 3-hydroxybenzo[a]pyrene, 7,8,9,10-tetrahydroxy-7,8,9, 10-tetrahydrobenzo[a]pyrene, and a number of other hydroxylated PAHs. The most widely used of these is 1-OHP-gluc, the major form of 1-OHP in human urine, by virtue of its relatively high concentration and prevalence in urine and its ease of measurement. This metabolite of pyrene can be measured as 1-OHP after deconjugation of the glucuronide with beta-glucuronidase or directly as 1-OHP-gluc without deconjugation. Elevated levels of 1-OHP or 1-OHP-gluc have been demonstrated in smokers (versus nonsmokers), in patients receiving coal tar treatment (versus pretreatment), after workshifts in road pavers (versus before shifts or versus controls), after shifts in coke oven workers (versus before shift), and in subjects ingesting charbroiled meat (versus preingestion). More importantly, this metabolite is found (at low levels) in most human urine, even in persons without apparent occupational or smoking exposure. Although measurement of these metabolites is useful in assessing recent exposure to PAHs, their value as predictive markers of biological effect or health outcomes has not been rigorously tested and at present can only be inferred by association.

PCR differential display of immune gene expression in Trichoplusia ni

The immune state of insects is defined by a set of proteins that is absent in the naive state. To explore the immune system of Trichoplusia ni in more detail we have employed a PCR differential display technique to compare the mRNA population of untreated last instar larvae to that of immunized animals. In the primary display, more than one hundred bands seemed induced upon bacterial challenge. When they were used as probes in Northern blots, 35% of these probes detected inducible mRNA species. Such probes were used to screen a cDNA library from immunized larvae. We isolated clones for T. ni homologs of cecropin A, lysozyme and attacin. One differentially expressed band hybridized to clones for BJHSP1, a hemacy-anin-related protein which is hormonally up-regulated in last instar larvae; this induction is probably not related to the bacterial infection. Still other probes recognized inducible mRNAs of 1.6 and 1.0 kb. The corresponding cDNA clones did not show strong sequence homology to any known proteins. We have demonstrated the potential of this PCR technique to display both known and unknown genes specific for the immune state of whole insects against a background of genes involved in larval development.

A structural study of the carboxyl terminal region of the human erythrocyte band 3 protein

Two peptides derived from the carboxyl terminal region of the human erythrocyte band 3 protein were identified as fragments releasable from cell membranes on trypsin digestion. These peptides, Asn-880-Lys-892 and Ala-893-Val-911-COOH, however, were resistant to trypsin, unless the cell membranes had been treated with high concentrations of NaOH. This suggests that the carboxyl terminal region is located in situ within the native band 3 molecule. Unlike in the cases of other portions of the band 3 protein, such as Gly-647-Arg-656, Ser-731-Lys-743, and Tyr-818-Lys-826, the release of the carboxyl terminal region was not inhibited by pretreatment of erythrocytes with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), indicating that there is no major structural difference in the carboxyl terminal portion between the outward and inward facing forms. The carboxyl terminal region of the band 3 protein has a negative charge cluster. In the middle of the negative charge cluster, consensus sequences, Val-Asp-X-X-X-Leu-Asp-Ala-Asp-Asp and Thr-Phe-Asp-Glu (TFDE), were found in the carboxyl terminal regions of aquaporin CHIP and glucose transporter 1, respectively. The sequence, TFDE, exists in the highly amphipathic 11-residue sequence of glucose transporter 1, and this amphipathic sequence has been suggested to promote normal membrane insertion of polytopic membrane proteins such as glucose transporter 1 and serine chemoreceptor. The role of the carboxyl terminal region of the band 3 protein is discussed.

Quantitative contribution of the acid production to the intracellular acidification in human neutrophils stimulated by N-formyl-methionyl-leucyl-phenylalanine

A chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (fMLP), induced an acidification of cytosol by about 0.05 pH units in 30 sec followed by an alkalinization in human neutrophils. The quantitative contribution of acid production to the acidification was studied. The superoxide (O2-) production stimulated by fMLP was not involved in the acidification because the production of acids in neutrophils from patients with chronic granulomatous disease who do not produce O2-, was the same as that in normal neutrophils. The intracellular acidification was completely inhibited by deoxyglucose, suggesting that energy metabolism enhanced upon stimulation by fMLP might be the main source of the acidification. Although enhancement of the lactate formation by fMLP was 0.8 nmol/10(6) cells, which could lower intracellular pH by 0.08 pH units, the lactate production could not explain the initial acidification because the production of lactate started at 1 min after the stimulation while the intracellular acidification began immediately after the stimulation. Mitochondrial respiratory inhibitors such as KCN and rotenone had no effects on the fMLP-induced intracellular acidification. The fMLP-induced production of CO2 in 30 sec through the hexose monophosphate shunt was only 2.6 pmol/10(6) cells, which was calculated to decrease intracellular pH by only 0.0014. Thus, changes of energy metabolism induced by fMLP does not explain the acidification.

Metastatic pleural cancer in radionuclide angiocardiography. A pulmonary time-activity curve mimicking left-to-right cardiac shunt

A 55-year-old man, with a history of nephrectomy for renal cell carcinoma, was evaluated using radionuclide angiocardiography to exclude cardiac shunts as the cause of vascular bruits heard at auscultation. A pulmonary time-activity curve derived from the right lung showed a pattern typical of a large left-to-right shunt, whereas that from the left lung was normal. Increased systemic arterial flow to the lateral right chest was noted in early dynamic images. Subsequent studies revealed that this flow and the abnormal time-activity curve of the right lung were due to systemic arterial supply to metastatic pleural cancer, originating from the kidney. The authors conclude that special caution should be undertaken in the interpretation of the radionuclide angiocardiography for determining left-to-right cardiac shunts, especially in those showing a asymmetric pulmonary time-activity curve.

NACP, the precursor protein of the non-amyloid beta/A4 protein (A beta) component of Alzheimer disease amyloid, binds A beta and stimulates A beta aggregation

NACP, a 140-amino acid presynaptic protein, is the precursor of NAC [the non-amyloid beta/A4 protein (A beta) component of Alzheimer disease (AD) amyloid], a peptide isolated from and immunologically localized to brain amyloid of patients afflicted with AD. NACP produced in Escherichia coli bound to A beta peptides, the major component of AD amyloid. NACP bound to A beta 1-38 and A beta 25-35 immobilized on nitrocellulose but did not bind to A beta 1-28 on the filter under the same conditions. NACP binding to A beta 1-38 was abolished by addition of A beta 25-35 but not by A beta 1-28, suggesting that the hydrophobic region of the A beta peptide is critical to this binding. NACP-112, a shorter splice variant of NACP containing the NAC sequence, bound to A beta, but NACP delta, a deletion mutant of NACP lacking the NAC domain, did not bind A beta 1-38. Furthermore, binding between NACP-112 and A beta 1-38 was decreased by addition of peptide Y, a peptide that covers the last 15 residues of NAC. In an aqueous solution, A beta 1-38 aggregation was observed when NACP was also present in an incubation mixture at a ratio of 1:125 (NACP/A beta), whereas A beta 1-38 alone or NACP alone did not aggregate under the same conditions, suggesting that the formation of a complex between A beta and NACP may promote aggregation of A beta. Thus, NACP can bind A beta peptides through the specific sequence and can promote A beta aggregation, raising the possibility that NACP may play a role in the development of AD amyloid.

Association of exposure to polycyclic aromatic hydrocarbons (estimated from job category) with concentration of 1-hydroxypyrene glucuronide in urine from workers at a steel plant

OBJECTIVES

Increased risk of lung cancer has been associated with employment in the steel industry. This association is thought to be due in part to increased concentrations of polycyclic aromatic hydrocarbons (PAHs) in air found in this work environment. Measurement of PAH metabolites in human urine provides a means of assessing individual internal dose of PAHs. This study examined the relative contribution of occupation and smoking to urinary concentration of 1-hydroxypyrene glucuronide (1-OHPG) among a group of workers at a steel plant.

METHODS

Concentrations of 1-OHPG in urine from 44 workers with jobs associated with increased air concentrations of PAHs and 40 workers with jobs with low or no exposure to PAHs were measured. 20 workers in each group were not current smokers. Urinary 1-OHPG was measured by synchronous fluorescence spectroscopy after immunoaffinity chromatography specific for PAH metabolites.

RESULTS

Mean (SEM) urinary 1-OHPG concentration was 2.16 (0.42) pmol/ml urine among the 44 occupationally exposed workers compared with 0.38 (0.05) among the 40 workers with no or low exposure (P < 0.0001). Mean urinary 1-OHPG concentration was 1.82 (0.41) pmol/ml urine among the 44 current smokers compared with 0.75 (0.20) among the 40 non-smokers (P < 0.005). Mean 1-OHPG concentrations in non-smokers were 0.26 (n = 20), 0.70 (n = 15), and 2.84 pmol/ml urine (n = 5) for strata of exposure to PAHs (no or low, mid, and high) based on job category; the corresponding values in smokers were 0.55 (n = 20), 0.94 (n = 12), and 4.91 pmol/ml (n = 12), respectively. Multiple linear regression showed significant differences between subjects in different PAH exposure with increased concentrations of 1-OHPG in urine. Amounts of foods containing PAHs ingested by this group of workers were relatively low and did not contribute significantly to urinary 1-OHPG concentrations.

CONCLUSIONS

These results indicate that 1-OHPG is a common urinary metabolite in people with recent occupational exposure to PAHs and is associated with both job category and estimated stratum of PAH exposure.

Roles of histidine 752 and glutamate 699 in the pH dependence of mouse band 3 protein-mediated anion transport

In the accompanying paper we have shown that four different histidine residues are involved in the maintenance of mouse band 3 in a state in which it is able to execute its anion transport function. Here we focus on the functional significance of His 752 and demonstrate that this residue, together with Glu 699, plays a key role in the control of pH dependence of Cl- transport. Mouse band 3-encoding cRNA was expressed in Xenopus oocytes, and band 3-mediated Cl- transport was measured at zero membrane potential over the pH range 6.0-9.2. Transport decreased with increasing H+ concentration and was governed by a single pK of 5.8. After correction for temperature differences, this result agrees well with measurements in erythrocyte ghosts of Cl- flux by Funder and Wieth [Funder, J., & Wieth, J. O. (1976) J. Physiol. 262, 679-698] and our own determinations by 35Cl NMR spectroscopy of Cl- exchange between the substrate binding site and the medium. After mutation of either Glu 699 to Asp or of His 752 to Ser, the maximal rate of transport is reduced and the rate of anion exchange is now governed by a single pK of about 6.8-6.9. This suggests that the formation of a hydrogen bond between His 752 and Glu 699 is essential for the decrease of band 3-mediated Cl- transport at low pH. We suggest that in the wild type band 3 both the decrease of the chloride exchange between the medium and the substrate binding site and the inhibition of chloride translocation across the membrane are dominated by a common rate-limiting step and that this step involves hydrogen bond formation between Glu 699 and His 752.

Intracellular localization of 8-oxo-dGTPase in human cells, with special reference to the role of the enzyme in mitochondria

We examined the intracellular distribution of 8-oxo-dGTPase (8-oxo-7,8-dihydrodeoxyguanosine triphosphatase) encoded by the MTH1 gene, a human mutator homologue. The activity of 8-oxo-dGTPase mainly located in cytosolic and mitochondrial soluble fractions of Jurkat cells, a human T-cell leukemia line. Electron microscopic immunocytochemistry, using a specific antibody against MTH1 protein, showed localization of MTH1 protein in the mitochondrial matrix. Activity in the mitochondria accounted for about 4% of the total activity. The specific activity in the mitochondrial soluble fraction (8093 units/mg protein) was as high as that in the cytosolic fraction (8111 unit/mg protein). The 8-oxo-dGTPase activities in cytosolic and mitochondrial soluble fractions co-eluted with MTH1 protein by anion-exchange chromatography, and the molecular mass of the mitochondrial MTH1 protein was much the same as that of the cytosolic MTH1 protein (about 18 kDa). HeLa cells expressing MTH1 cDNA showed an increased cytoplasmic signal together with a weak signal in the nucleus in in situ immunostaining of MTH1 protein, and the overexpressed MTH1 protein was recovered from both cytosolic and mitochondrial fractions. Thus, the 8-oxo-dGTPase encoded by MTH1 gene is localized in mitochondrial and cytosol.