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Biomedical subjects

H Hu

Publications and source records attributed to H Hu.

At least 253 records · Page 14Linked to original sources
PubMed1994

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.

Adult↗
PubMed1994

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).

Adult↗
PubMed1994

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.

Adult↗
PubMed1994

Characterization and expression of C/EPB-like genes in the liver of Rana catesbeiana tadpoles during spontaneous and thyroid hormone-induced metamorphosis.

Tissue-specific changes in gene expression occur in the liver of Rana catesbeiana tadpoles undergoing metamorphosis. Many of these changes can be induced precociously by administration of thyroid hormone (TH) to a tadpole or to cultured tadpole liver. While the precise molecular means by which TH exerts a tissue-specific response is unknown, recent studies suggest that the expression of genes which are liver-specific and characteristic of the adult liver phenotype may rely on TH-induction of tissue-specific transcription factors, as well as the thyroid hormone receptor proteins. Guided by this notion, we screened our Rana catesbeiana liver cDNA library and isolated clones, RcC/EBP-1 and -2, encoding Rana homologues of a mammalian transcription factor, C/EBP (CCAAT/enhancer core binding protein), implicated in the expression of liver-specific genes and terminal differentiation of hepatocytes. Gel mobility shift assays demonstrate that the proteins synthesized from these cDNAs bind specifically to the consensus binding site for C/EBP-related proteins. Characterization of the amino acid sequence in the bZIP DNA-binding domains of these proteins suggests that RcC/EBP-1 and -2 encode Rana homologues of C/EBP alpha and delta, respectively. Hybridization analyses demonstrate that the amount of RcC/EBP-2 mRNAs in tadpole liver remains constant throughout metamorphosis, whereas RcC/EBP-1 mRNAs are up-regulated during both spontaneous and TH-induced metamorphosis. The TH-induced up-regulation of RcC/EBP-1 mRNAs precedes the up-regulation of liver-specific urea cycle enzyme mRNAs by 6 to 12 hours. These results, coupled with in situ hybridization studies, suggest that RcC/EBP-1 mRNAs encode a transcription factor which may play an early role(s) in the terminal differentiation and/or reprogramming of gene expression in this tadpole's liver cells during both spontaneous and TH-induced metamorphosis.

Amino Acid Sequence↗
PubMed1994

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.

Analysis of Variance↗
PubMed1994

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.

Diamond↗
PubMed1994

Improvements in the calibration of 109Cd K x-ray fluorescence systems for measuring bone lead in vivo.

A 109Cd K x-ray fluorescence (XRF) system using a point source in a back-scatter geometry is described. The suitability of plaster-of-Paris phantoms as targets for intercalibration standards was evaluated. When the phantom concentrations were measured by inductively-coupled-plasma mass spectrometry (ICPMs), the calculated phantom concentrations underestimated true concentrations by an average of 15%. Since calculated values are used to calibrate the K XRF system, in vivo bone-lead concentrations may be similarly underestimated. The difference between calculated and measured concentration is attributable to impurities in the plaster of Paris (e.g. calcium carbonate). The ICPMS-measured concentrations were used to calibrate the K XRF system. The same phantoms were also measured as 'unknowns' by a bone-lead measurement system (Abiomed, Danvers, MA, USA). The commercial system overestimated the lowest-concentration phantoms and underestimated the phantoms with concentrations above 15 microg Pb/g plaster of Paris. The commercial system and our system were compared by measurement of the new phantoms in air and in water. The K XRF system exhibited better precision in both situations. On the basis of this work, we recommend that plaster-of-Paris phantoms used to calibrate K XRF measurement systems be analysed first by ICPMS or another valid analytical technique.

Bone and Bones↗
PubMed1994

Oversampled filters for quantitative volumetric PET reconstruction.

Three-dimensional filtered backprojection uses filters generally specified in the Fourier domain. Implementing these filters by direct sampling in the Fourier domain produces an artifact in the reconstructed images consisting primarily of a DC shift. This artifact is caused by aliasing of the reconstruction filter. We have developed a filter construction technique using Fourier domain oversampling, which reduces the artifact. A method to construct the filter efficiently without the need to create and store the entire oversampled filter array is also presented. Quantitative accuracy in filtered backprojection is of particular importance in multiple-pass algorithms used to reconstruct data from cylindrical PET scanners. We are able to implement such algorithms without fitting the reprojected views to the scanner data.

Algorithms↗
PubMed1994

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.

Animals↗
PubMed1994

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.

Adult↗
PubMed1994

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.

Animals↗
PubMed1994

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.

Bacteriuria↗
PubMed1994

[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.

Animals↗
PubMed1993

Relation between blood lead and urinary biogenic amines in community-exposed men.

The cross-sectional relation between levels of urinary biogenic amines (dopamine, epinephrine, norepinephrine, and serotonin) and levels of blood lead was examined in a study of 645 male participants from a longitudinal study of aging. This stable population of men had initially been recruited from communities in and around Boston, Massachusetts, and had not been selected with regard to lead exposure. Blood lead samples and 24-hour and 2-hour urine specimens were collected during regularly scheduled clinic visits. In multivariate linear regression step-forward models, 24-hour epinephrine excretion was significantly and positively associated with blood lead (beta = 0.101 microgram(microgram/dl)-1 blood lead, SE (standard error) (beta) = 0.045, p = 0.026). Twenty-four-hour norepinephrine excretion was positively associated with blood lead (beta = 0.023 microgram(microgram/dl)-1 blood lead, SE(beta) = 0.029, p = 0.425), and both 24-hour dopamine (beta = -4.35 microgram(microgram/dl)-1 blood lead, SE(beta) = 6.90, p = 0.529) and 2-hour serotonin (beta = -0.348 microgram(microgram/dl)-1 blood lead, SE(beta) = 0.277, p = 0.210) excretion were negatively associated with blood lead; however, these relations did not achieve statistical significance. An increase of 10 micrograms/dl in blood lead was associated with an increase in epinephrine excretion of 11 micrograms/24 hours. These results support the hypothesis that epinephrine metabolism is influenced by low levels of lead exposure.

Adult↗
PubMed1993

Hapten-immune pulmonary interstitial fibrosis (HIPIF) in mice requires both CD4+ and CD8+ T lymphocytes.

We present a description and analysis of a mouse model for pulmonary interstitial fibrosis that is induced by a specific immune response to a small reactive chemical group called trinitrophenyl. We describe the model, and then we examine the cellular mechanism for the induction of the fibrosis. The specific increase in hydroxyproline reached a peak by day 7 and persisted through day 28 in all animals that were sensitized to and challenged with the hapten. Distinct patterns of fibrosis that were seen histologically correlated with antigenic pretreatment and were dependent on T lymphocytes. We also report that the inflammatory and fibrotic responses could be adoptively transferred with immune lymphocytes but not with immune serum. In vivo administration of anti-CD4 and anti-CD8 monoclonal antibodies to sensitized mice prevented the development of immune-mediated lung inflammation and was effective in reducing hydroxyproline deposition. We conclude that (activated) T lymphocytes contribute to the pathogenesis of pulmonary fibrotic diseases. The possibility arises that haptens in the environment may promote sensitization of individuals via their skin or lungs and cell-mediated immune responses to haptenated antigens within the lung may promote pulmonary fibrosis.

Animals↗
PubMed1993

A case-control study of oral cancer in Beijing, People's Republic of China. Associations with nutrient intakes, foods and food groups.

A case-control study of oral cancer was conducted in Beijing, People's Republic of China to examine the association between dietary nutrient intake and risk of oral cancer, both in terms of estimated intake of nutrients and micro-nutrients, and in terms of specific foods and food groups. The study was hospital-based and controls were hospital in-patients matched for age and sex with the cases. The response rate for cases and controls was 100% and 404 case/control pairs were interviewed. The results suggest that increased protein and fat intake are related to a decreased risk of oral cancer. Carbohydrate intake, however, showed a moderate increased risk for oral cancer. Total carotene intake and carotene intake from fruits and vegetables are inversely associated with risk of oral cancer. A similar pattern was observed for dietary vitamin C intake. Dietary fibre derived from fruits and vegetables showed a strong negative association with oral cancer risk, but fibre derived from other sources did not exhibit any protective effect. At the level of foods and food groups, increased consumption of fresh meat, chicken and liver was significantly associated with a reduction in oral cancer risk: the tests for trend were all statistically significant at the P < 0.01 level. Consumption of common carp, hairtail, shrimp and lobster were also associated with decreased risk. Risk was found to increase with increasing consumption of millet and corn bread (P < 0.01) but to decrease with increasing consumption of rice (P < 0.01). Increased consumption of grapes, bananas, oranges, tangerines, peaches and pears were associated with reduced risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Expression of T-cell receptor alpha and beta variable genes in normal and malignant human T cells.

A PCR method was developed to analyse each of 29 families of the T cell receptor V alpha gene and 20 families of the V beta gene at the mRNA level in heterogenous cell populations. All V alpha and V beta families were detectable in blood mononuclear cells from four of six healthy donors. In two donors only V alpha 22 was missing, and all other V alpha and V beta families were detected. V beta family expression was observed in T-leukaemic cell lines Jurkat, HSB, Molt-3 and Molt-4. In contrast, V alpha family expression was not detectable in any cell line except Jurkat cells. In T-cell malignancies (non-Hodgkin's lymphoma and mycosis fungoides), one or two V alpha and V beta families were detectable. Four of 10 cases investigated showed two V alpha transcripts and one V beta transcript. This fits with concepts in literature that allelic exclusion for the genes encoding alpha chains is not strictly required in the DNA rearrangement, or that this exclusion is a post-translational event. Using a limited series of antibodies to V beta gene family products, blood mononuclear cells from healthy donors were analysed by flow cytometry in a follow-up study. Two of four donors were rather stable in proportions of T cells expressing distinct V beta families, and two other donors showed variation in one or more families. When analysed on frozen tissue sections of normal lymph node and tonsil, there was no preferential location of lymphocytes expressing a distinct V beta gene family in different compartments (interfollicular area, follicle, or tonsillar epithelium).

Base Sequence↗