A polymorphism in the delta-aminolevulinic acid dehydratase gene may modify the pharmacokinetics and toxicity of lead

Associations between the presence of a constitutional variant of delta-aminolevulinic acid dehydratase (ALAD-2) and lead concentrations in blood and bone, as well as between this allele and indices of kidney function, were investigated among 691 members of a construction trade union. The average blood lead level in this group was 7.78 micrograms/dl. No significant difference was observed in blood lead concentration in ALAD-2 carriers compared to those homozygous for the more common ALAD-1 allele (7.78 +/- 3.62 micrograms Pb/dl vs. 7.73 ( +/- 3.48 micrograms Pb/dl, respectively; p = 0.73). Bone lead was measured in a subset of 122 of the study subjects. Patella minus tibia lead concentrations for each individual averaged 3.35 +/- 11.99 micrograms Pb/g bone mineral in ALAD-1 homozygotes and 8.62 +/- 9.47 micrograms Pb/g bone mineral in ALAD-2 carriers (p = 0.06). Comparisons of blood urea nitrogen (BUN) and uric acid by genotype indicated elevated levels among ALAD-2 individuals (p = 0.03 and 0.07, respectively). In logistic regression models accounting for other variables potentially associated with BUN and uric acid levels, BUN was significantly associated with blood lead levels (p = 0.01). Associations of BUN and uric acid levels with ALAD-2 were of borderline statistical significance in these models (p = 0.06 and 0.07). Taken together, these results suggest that the ALAD-2 genotype may influence the pharmacokinetic distribution and chronic renal toxicity of lead, perhaps due to differential binding of lead to the variant protein.

Bone lead measured by X-ray fluorescence: epidemiologic methods

In vivo X-ray fluorescence (XRF) measurement of bone lead concentration (XRF) has emerged as an important technique for future epidemiological studies of long-term toxicity. Several issues germane to epidemiologic methodology need to be addressed, however. First, sources of variability in measurements of bone lead need to be quantified, including imprecision related to the physical measurement itself and the variability of lead deposition over the two main compartments of bones (cortical vs. trabecular) and within each compartment. Imprecision related to the physical measurement can be estimated for each individual measurement based on the variability of the signal and background. Second, approaches to low-level data need to be debated. We argue for using the minimal detection limit (MDL) to compare instruments and interpret individual measurements; however, with regard to epidemiologic studies, we would abandon the MDL in favor of using all point estimates. In analyses using bone lead as an independent variable, statistical techniques can be used to adjust regression estimates based on estimates of measurement uncertainty and bone lead variability. Third, factors that can be expected to modify the relationship between bone lead and toxicity such as gravida history, endocrinological states, nutrition, and other important influences on bone metabolism, need to be identified and measured in epidemiologic studies. By addressing these issues, investigators will be able to maximize the utility of XRF measurements in environmental epidemiologic studies.

Bone lead measured by X-ray fluorescence: epidemiologic methods

In vivo X-ray fluorescence (XRF) measurement of bone lead concentration (XRF) has emerged as an important technique for future epidemiological studies of long-term toxicity. Several issues germane to epidemiologic methodology need to be addressed, however. First, sources of variability in measurements of bone lead need to be quantified, including imprecision related to the physical measurement itself and the variability of lead deposition over the two main compartments of bones (cortical vs. trabecular) and within each compartment. Imprecision related to the physical measurement can be estimated for each individual measurement based on the variability of the signal and background. Second, approaches to low-level data need to be debated. We argue for using the minimal detection limit (MDL) to compare instruments and interpret individual measurements; however, with regard to epidemiologic studies, we would abandon the MDL in favor of using all point estimates. In analyses using bone lead as an independent variable, statistical techniques can be used to adjust regression estimates based on estimates of measurement uncertainty and bone lead variability. Third, factors that can be expected to modify the relationship between bone lead and toxicity such as gravida history, endocrinological states, nutrition, and other important influences on bone metabolism, need to be identified and measured in epidemiologic studies. By addressing these issues, investigators will be able to maximize the utility of XRF measurements in environmental epidemiologic studies.

Validation of K-XRF bone lead measurement in young adults

K-X-ray fluorescence (K-XRF) is a useful tool for assessing environmental exposure to lead in occupationally exposed individuals and older adults. This study explores the possibility of using this technique on young adults with low environmental lead exposure. Twenty-three college students, aged 18-21 years, were recruited for 2 hr of bone lead measurement. Bone lead measurements were taken from the mid-shaft tibia for periods of 30 or 60 min. In the analysis, 30-min measurements were combined so that each subject had the equivalent of two 60-min measurements. The average concentration of two bone lead measurements in this population ranged from -1.5 to 8.2 micrograms Pb/g bone mineral, with a mean of 3.0 micrograms Pb/g bone mineral. In a one sample t-test, this mean was significantly different from 0 (p < 0.0001). A linear trend with age was detected despite the small age range of our population. By doubling the sampling time, the reported measurement uncertainty decreased by a factor of 1.5, resulting in uncertainty estimates below the mean bone lead estimates. Power calculations using the observed variance estimates suggest that with 80% power, differences in bone lead concentration of 2-3 micrograms Pb/g bone mineral can be identified in groups of 100 or smaller. Due to the large within-person variation in young adults, K-XRF may not yet be a useful diagnostic tool for individual subjects, but it may be of great use to environmental scientists trying to characterize long-term lead exposure and dose in the general population or specific subpopulations.

Prostate-specific antigen expression by various tumors

There is a growing body of evidence indicating that prostate-specific antigen (PSA) may be present in many steroid hormone-stimulated epithelial tissues other than that of the prostate. In particular, breast tumor cell lines treated with steroid hormone receptor agonists, breast tumors, and normal human breast have recently been found by our group to contain PSA. To investigate whether PSA may also be present in other human tumors, we employed a highly sensitive immunofluorometric assay technique to quantify PSA immunoreactivity in tumor extracts. Using a PSA-positivity cutoff value of 0.005 ng per mg of protein, 23 of 43 diverse tumors tested positive for PSA protein. Confirmatory analyses for PSA by a commercially available method (IMx) on six samples demonstrated a high degree of concordance between the two methods. To establish the molecular weight of the immunoreactive species, the most highly positive tumor extracts of each tumor type were fractionated by high performance liquid chromatography. Whereas the majority of tumors had immunoreactivity eluting at both 100 KDa and 33 KDa, corresponding to PSA bound to alpha 1-antichymotrypsin and free PSA, respectively, the colon and parotid tumors displayed immunoreactivity only at the 33 KDa fraction. We conclude that in addition to breast tumors and normal breast, colon, ovarian, liver, kidney, adrenal, and parotid tumors can also produce PSA. The physiological role of PSA in these tumors is currently under investigation.

Reduction of donor-specific cytotoxic T lymphocyte precursors in peripheral blood of allografted heart recipients

Tolerance to allografted hearts in human recipients has been observed both in clinical situations and in in vitro experiments. To elucidate whether a quantitative change of alloreactive CTL is one of the mechanisms accounting for this graft tolerance, CTL precursor (CTLp) frequencies in the peripheral blood of 10 heart recipients were measured against spleen cells from donors and HLA nonidentical third-party persons. In this longitudinal follow-up study, we showed that the rejection reaction(s) in the grafted heart correlated with CTLp frequencies in samples taken before transplantation against the donor spleen cells, but not with the CTLp frequencies against the spleen cells from the third-party persons. The CTLp frequencies against the spleen cells from donors decreased 4-6 months after transplantation, and remained at a low level afterward. However, the CTLp frequencies against spleen cells from third-party persons in blood samples obtained 1 year after transplantation were not significantly different from those before transplantation. Therefore, we conclude that donor-reactive CTLs are important in rejecting allografted heart. The decrease in donor-specific CTLp after transplantation could explain the donor-specific tolerance. The decrease may be due to homing of the specific CTLp to the graft, or by clonal deletion of the donor-reactive CTL caused by chronic alloantigen stimulation in the presence of immunosuppressive therapies.

Study of natural diamonds by dynamic nuclear polarization-enhanced 13C nuclear magnetic resonance spectroscopy

The results of a study of two types of natural-diamond crystals by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) are reported. The home-built DNP magic-angle spinning (MAS) 13C NMR spectrometer operates at 54 GHz for electrons and 20.2 MHz for carbons. The power of the microwave source was about 30 W and the highest DNP enhancement factor came near to 10(3). It was shown that in the MAS spectra the 13C NMR linewidths of the Ib-type diamond were broader than those of IaB3-type diamond. From the hyperfine structure of the DNP enhancement as a function of frequency, four kinds of nitrogen-centred and one kind of carbon-centred free radicals could be identified in the Ib-type diamond. The hyperfine structures of the DNP enhancement curve that originated from the anisotropic hyperfine interaction between electron and nuclei could be partially averaged out by MAS. The 13C polarization time of DNP was rather long, i.e. 1500 s, and the spin-lattice relaxation time (without microwave irradiation) was about 300 s, which was somewhat shorter than anticipated. Discussions on these experimental results have been made in this report.

Cytotoxic T lymphocytes infiltrating the human cardiac allograft show a restriction in T-cell receptor V beta gene usage: a study on serial biopsy and blood specimens

T lymphocytes were propagated in vitro from endomyocardial biopsy specimens that were obtained weekly from four patients during the first 2 to 3 months after heart transplantation. The culture was performed in the presence of recombinant interleukin-2 and interleukin-4, with or without mitogen, in which especially CD8+ donor-specific cytotoxic T cells expanded. These cells, presumably reflecting an in vivo activated population, could even be cultured from biopsy specimens without histopathologic signs of rejection. A preferential expression of T cell receptor V beta gene families was found in these T-cell lines. This finding is in contrast with the heterogenous expression in peripheral blood T cells of the same patient. The restriction in V beta gene family expression was substantiated in the evaluation of clones obtained from two cell lines. Among 17 donor-specific cytotoxic T-cell clones derived from one cell line, only four V beta gene families were expressed. All five clones from the other cell line used the V beta 8 family. Some clones expressing a distinct V beta gene family used the same V-D-J junction sequence, indicative of their origin from the same precursor. With the use of oligonucleotide probes complementary to clone-specific V-D-J junction sequences, four of five clones were detected not only in the parent T-cell line but also in T-cell lines derived from biopsy specimens with rejection reactions taken 1 week earlier and 2 weeks later and in blood cells taken before and 0.5, 3, and 6 months after transplantation; these clones were not detected in blood cells harvested 12 months after transplantation. This study showed a restricted usage of the V beta gene families by activated donor-specific cytotoxic T lymphocytes in the heart transplant.

Low-level lead exposure and renal function in the Normative Aging Study

Occupational and environmental lead exposure has been associated with significant impairment in renal function. The authors studied the cross-sectional relation between creatinine clearance and blood lead concentration in a population of 744 men participating in the Normative Aging Study of the Department of Veterans Affairs between July 1988 and April 1991. These men, aged 43-90 years, were recruited from communities in the Greater Boston, Massachusetts, area and were selected without regard to lead exposure. The mean values for blood lead concentration and creatinine clearance rate were 8.1 micrograms/dl (standard deviation, 3.9 micrograms/dl) and 88.2 ml/minute (standard deviation, 22.0 ml/minute), respectively. Independent relations of creatinine clearance to blood lead were assessed by multivariate linear regression analysis, with adjustment for various potential confounders. In multivariate linear regression models, the rate of creatinine clearance was significantly and negatively associated with increasing levels of blood lead, even after adjustment for age, body mass index, and use of diuretic and analgesic medications (the beta-coefficient for ln blood lead measured in microgram[microgram/dl]-1 was -0.030; standard error = 0.014, p = 0.037). A rise in ln blood lead of 10.0 micrograms/dl was associated with a decrease in the ln creatinine clearance rate of 10.4 ml/minute. These results support the hypothesis that exposure to low-level environmental lead correlates with a significant decrement in renal function.

Diagnosis of Chlamydia trachomatis infections in men and women by testing first-void urine by ligase chain reaction

From April to September 1993, 305 men and 447 women in Hamilton, Canada, consented to the collection of a urethral or cervical swab, respectively, for culture and 20 ml of first-void urine (FVU) for testing by the enzyme immunoassay Chlamydiazyme and by ligase chain reaction (LCR) in the form of a kit from Abbott Laboratories called LCx Chlamydia trachomatis. Evaluation of test performance with each specimen was calculated on the basis of an expanded "gold standard" of a patient found to be positive by culture or by a confirmed nonculture test. By using this expanded standard, the prevalence of infection was determined to be 6% (27/447) for the women and 18.4% (56/305) for the men. LCR testing of FVU in both studies was the most sensitive approach (96%). The performance of Chlamydiazyme was as follows: cervical swab, 78.3% sensitivity; female FVU, 37% sensitivity; and male FVU, 67.9% sensitivity. Culture was the least sensitive approach to diagnosis: female cervix, 55.6%; and male urethra, 37.5%. LCR testing of FVU from men or women diagnosed the greatest number of genitourinary tract infections with no false positives.

Correlates of bone and blood lead levels in carpenters

In the course of a health screening for construction carpenters, 127 subjects underwent blood lead testing, administration of detailed questionnaires, and in vivo measurement of bone lead levels with a 109Cd K-X-ray fluorescence (K-XRF) instrument. The mean age of subjects was 48.5 (SD = 9.8) years. Blood lead levels were low, with a mean of 8.2 (SD = 4.0) micrograms/dl. Bone lead levels had means of 9.8 (SD = 9.3) micrograms/g bone mineral for the tibia and 14.0 (SD = 13.8) micrograms/g bone mineral for the patella (which consist primarily of cortical bone and trabecular bone, respectively). In multivariate regression models, age was the dominant predictor of both tibia and patella bone lead, with years since last worked and welding/brazing contributing an additional small amount of influence over tibia bone lead, and carpet laying, paint stripping, and regular exercise contributing an additional small amount of influence over patella bone lead. Demolition, carpet laying, and alcohol ingestion were significant predictors of blood lead. We conclude that age is the most important predictor of bone lead levels among workers with intermittent exposures to lead; in addition, K-XRF is useful in generating hypotheses on additional factors that may influence lead burden.

Lipopolysaccharide-stimulated events in B cell activation

High concentrations of thymus-independent (TI) antigens are capable of inducing polyclonal B cell activation by their intrinsic mitogenic properties, irrespective of the specificity of the Ig receptors. Due to a genetic defect on the 4th chromosome, B cells from C3H/HeJ mice do not respond to lipopolysaccharide (LPS). In order to define at which step the mutation affects the signalling pathway, we compared B cells from C3H/HeJ and CBA mice with regard to changes of three events, namely cell size, and MHC class I and II antigen expression after LPS stimulation. We found that cell size and expression of MHC antigens increase in B cells from CBA mice after LPS stimulation, whereas B cells from C3H/HeJ mice do not respond at all. This suggests that the defect in C3H/HeJ mice interferes with early events in the signalling pathway, either due to the absence of a LPS receptor on B cell surface or the lack of an initial component necessary for effective signal transmission subsequent to LPS receptor binding. Our results also have shown that stimulation of anti-Ig antibodies and LPS differ in some signalling events and have different final effects on B cells, which suggests that they may function differently via distinct signalling pathways.

The effects of thermal injury on mitochondrial oxygen consumption and the glycerol phosphate shuttle

Since many of the physiologic adaptations to postburn hypermetabolism must be related to alterations in mitochondrial function, the effects of thermal injury on rat liver mitochondrial oxygen consumption were studied. A 60% full-thickness thermal injury was found to cause a significant increase in mitochondrial oxygen consumption, peaking at postburn day 12, without the loss of respiratory control. The same thermal injury was also found to cause a significant increase in glycerol-3-phosphate dehydrogenase (GPD) activity, which also peaks at postburn day 12. The increase in GPD activity and the resultant increase in the flow through the glycerol phosphate shuttle might be related to the increase of postburn mitochondrial oxygen consumption. It is also shown that although the loss of respiratory control could also be a contributing factor to postburn hypermetabolism at postburn days 15 and 18, this was not observed during the early days after thermal injury.

Localization of Boron in Cell Walls of Squash and Tobacco and Its Association with Pectin (Evidence for a Structural Role of Boron in the Cell Wall)

B deficiency results in a rapid inhibition of plant growth, and yet the form and function of B in plants remains unclear. In this paper we provide evidence that B is chemically localized and structurally important in the cell wall of plants. The localization and chemical fractionation of B was followed in squash plants (Curcurbita pepo L.) and cultured tobacco cells (Nicotiana tabacum) grown in B-replete or B-deficient medium. As squash plants and cultured tobacco cells became deficient, an increasingly large proportion of cellular B was found to be localized in the cell wall. Cytoplasmic B concentrations were reduced to essentially zero as plants became deficient, whereas cell wall B concentration remained at or above 10 [mu]g B/g cell wall dry weight in all experiments. Chemical and enzymic fractionation studies suggest that the majority of cell B is associated with pectins within the cell wall. Physical analysis of B-deficient tissue indicates that cell wall plastic extensibility is greatly reduced under B deficiency, and anatomical observations indicate that B deficiency impairs normal cell elongation in growing plant tissue. In plants in which B deficiency had inhibited all plant growth, tissues remained green and did not show any additional visible symptoms for at least 1 week with no additional B. This occurred even though cytoplasmic B had been reduced to extremely low levels (<0.2 [mu]g/g). This suggests that B in these species is largely associated with the cell wall and that any cytoplasmic role for B is satisfied by very low concentrations of B. The localization of B in the cell wall, its association with cell wall pectins, and the contingent effects of B on cell wall extensibility suggest that B plays a critical, although poorly defined, role in the cell wall structure of higher plants.

Full-load expansion technique and preliminary clinical application

For accelerating the inflation process of soft-tissue expansion, a continuous inflation protocol regarding pain as the criterion of overinflation, the full-load expansion technique, has been introduced. It is carried out by restricting persistently the pressure in the expander near the pain threshold in a state of dynamic equilibrium between the infusing rate and the skin expansion velocity with a simple and practical device. This inflation is neither at a uniform infusion rate nor at a constant filling pressure. Nineteen expanders in 13 patients were inflated following this protocol. Their inflations were fulfilled in 5 to 20 days, depending individually on their anatomic regions, total volumes of infusion, areas of the overlying skin, and patient susceptibilities.

Lead poisoning from mobilization of bone stores during thyrotoxicosis

We describe a case of thyrotoxicosis accompanied by markedly elevated blood lead levels (initially 53 micrograms/dl) in a 37-year-old woman. No current source of lead exposure was found; the woman gave a history indicative of lead exposure as a child and as an adult 7 years previously, however. In addition, she was found to have markedly elevated bone lead levels, as measured by K-x-ray fluorescence (154 +/- 5 in the mid-tibia and 253 +/- 6 micrograms/g bone mineral in the patella), and an increased serum osteocalcin level (2.76 nmol/l), reflecting the increased bone turnover that often accompanies hyperthyroidism. During treatment with propylthiouracil, serial observations demonstrated a decline in serum osteocalcin that paralleled a decline in blood lead levels. Bone lead levels did not change appreciably. The patient also continued to have lingering neuropsychological symptoms consistent with chronic lead effects. We suggest that increased bone turnover accompanying thyrotoxicosis led to clinically significant lead poisoning in this patient, due to mobilization of accumulated bone lead stores acquired many years earlier. This phenomenon raises the general issue of more subtle forms of lead exposure from increased bone turnover states (e.g., osteoporosis).

Attentional correlates of dentin and bone lead levels in adolescents

In an effort to determine whether specific aspects of attention are impaired by lead, the performance of 79 subjects (aged 19 and 20 y) on a neuropsychologically based battery of tests of attention was examined in relation to lead levels in deciduous teeth (dentin), current blood, and tibia and patella bones measured by K-X-ray fluorescence. Dentin lead levels averaged 14 micrograms/g. Most bone lead levels were less than 10 micrograms/g. Dentin lead levels were related inversely to scores on two of four attention factors: focus-execute (ability to select and respond to critical information) and shift (ability to shift focus adaptively). Few significant associations were observed between bone lead levels and performance. Five individuals with the ALA-D 1-2 isozyme phenotype tended to achieve more optimal scores. Executive and self-regulation functions may be among the cognitive skills targeted by lead.

Enhancement of hepatocarcinogenesis and induction of specific cytochrome P450-dependent monooxygenase activities by the barbiturates allobarbital, aprobarbital, pentobarbital, secobarbital and 5-phenyl- and 5-ethylbarbituric acids

To test predictions that barbiturates which are long-acting sedatives and/or strong inducers of CYP2B-mediated monooxygenase activities would be effective promoters of hepatocarcinogenesis, a series of clinically-useful barbiturates and structural analogs were tested for ability to promote hepatocellular carcinogenesis in male F344/NCr rats initiated with N-nitrosodiethylamine and for efficacy as inducers of CYP2B activity in non-initiated rats of the same sex and strain. The barbiturates were administered in the diet at concentrations equimolar to 500 p.p.m. of the known liver tumor promoter phenobarbital, which served as the positive control for this study. Phenobarbital, which has the longest duration of sedative action of this series of compounds, caused the greatest induction of CYP2B activity, and displayed strong liver tumor promoting effects. Allobarbital and aprobarbital, two intermediate-duration sedatives, were found to promote hepatocarcinogenesis, with allobarbital proving to be as effective as phenobarbital in this respect and aprobarbital being somewhat weaker as a promoter. These intermediate-duration sedatives were each relatively weak CYP2B-type inducers, causing approximately 25% of the induction displayed by phenobarbital. The nonsedatives, 5-phenyl- and 5-ethyl-barbituric acids, were essentially inactive as CYP2B-type inducers and were also found to be relatively inactive as promoters of hepatocarcinogenesis. Of the shorter-duration sedatives, pentobarbital was found to promote, and was relatively effective as a CYP2B-type inducer, while secobarbital showed little or no promoting activity and was less effective as an inducer of CYP2B activities. Pentobarbital thus proved an important exception to our hypothesis that only long-acting sedative barbiturates would promote hepatocarcinogenesis. Although both the durations of sedative action and the degrees of CYP2B-type induction exhibited by these compounds correlate with a quantitative parameter for liver tumor-promoting activity (relative promotion index), neither parameter appears to be sufficient, by itself, as a predictor of promoting activity for rat liver.

[Observation on parasite density in the early stage of vivax malaria]

Thirty-eight cases were artificially infected with local Plasmodium vivax sporozoites and experienced onsets of acute attacks after a short incubation period. The parasite densities upon the patent of malaria parasites in the peripheral blood and the primary clinical onset were 0.2-1.6 and 0.6-4 040/microliters, respectively. Such significant difference in parasitaemia level seems to be closely related to the interval between the initial parasitaemia and the first onset, as indicated by the fact that for the majority of cases, the earlier the appearance of clinical attack after sporozoite inoculation, the lower the parasite density at the beginning of the patent period, while primary onsets of later occurrence, in those with higher initial parasitemia. The biological and epidemiological significance of the evidence was discussed.