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Biomedical subjects

H Hu

Publications and source records attributed to H Hu.

At least 163 records · Page 9Linked to original sources
PubMed1998

Determination of the total arsenic concentration in human urine by inductively coupled plasma mass spectrometry: a comparison of the accuracy of three analytical methods.

Measurement of arsenic (As) in biological samples such as urine has important clinical applications and is being undertaken more frequently in epidemiologic studies because of concern about the carcinogenicity of low to moderate levels of As exposure. The objective of this study was to evaluate and improve the accuracy of As determination in urine by inductively coupled plasma mass spectrometry (ICP-MS). Determination of As in biological samples by ICP-MS is difficult for two reasons: the formation of the molecular ion 40Ar35Cl, which overlaps with monoisotopic As at a mass-to-charge ratio (m/z) of 75 (causing spectral interference), and signal enhancement due to organic matrix (nonspectral interference). Available procedures were examined, including the application of different correction procedures using 40Ar37Cl and 16O35Cl molecular-ion formation; the addition of N2 into plasma or nebulizer gas flows; and the addition of organic molecules to the sample and to calibration standards to eliminate or correct for interference due to molecular-ion formation. The accuracy and precision of determination of As [m/z 75, ionization potential (IP) 9.81 eV] with use of an internal standard was also investigated. Three elements were studied as candidate internal standards: germanium (Ge: m/z 74, IP 7.90 eV), indium (In: m/z 115, IP 5.79 eV), and tellurium (Te: m/z 128, IP 9.01 eV). It was found that these three elements performed more or less equally well with Ar-N2 plasma; it was also found that accuracy was significantly improved when Te was used as the internal standard instead of Ge or In for ethanol-added samples. Our results indicate that accurate and precise measurement of As in urine by ICP-MS can be obtained by either of two methods (< 5% error, approximately 2% RSD, limit of detection 0.1 ng ml-1): (1) the addition of 1% N2 to plasma gas flow or 3% N2 to nebulizer gas flow, along with use of any of the internal standards tested, or (2) the addition of ethanol to the sample and to calibration standards, with use of Te as the internal standard. The most accurate results (< 1% error) for National Institute of Standard and Technology Standard Reference Material (NIST SRM) 2670 (toxic elements in urine) were obtained with Ar-N2 plasma with either Te or In as the internal standard.

Arsenic↗
PubMed1998

Non-responsiveness to mercury-induced autoimmunity in resistant DBA/2 mice is not due to immunosuppression or biased Th1-type response.

Mercury can induce systemic autoimmunity in susceptible mouse strains characterized by a T-cell-dependent polyclonal B-cell activation, increased serum levels of IgG1 and IgE antibodies, production of autoantibodies, and the formation of immune complexes in the kidneys. However, certain resistant mouse strains do not show any of the autoimmune manifestations after mercury injection. Th1/Th2 dichotomy has been proposed to be responsible for resistance and susceptibility, respectively. Immunosuppression has also been suggested in resistant animals after mercury injection. To test whether immunosuppression or a biased Th1-type response was induced by mercury in resistant DBA/2 mice, we injected DBA/2 mice with mercury for 1 or 3 weeks and then immunized the mice with horse red blood cells (HRBCs) to study whether the subsequent humoral response to HRBCs was inhibited or skewed to the production of antibodies of IgG2a isotype switched by Th1-type cytokines. We found that there was no reduction of the number of splenic antibody-producing cells in the subsequent response to HRBCs compared with saline-treated mice. By haemagglutination tests, the titers of HRBC-specific antibodies were the same after HRBCs injection in both mercury- and saline-treated DBA/2 mice. There was no increase in total serum IgG2a antibody. Sera of both mercury- and saline-treated mice immunized with HRBCs showed high titres of specific IgM, IgG1 and IgG2a anti-HRBCs antibodies. Surprisingly, 3-week treatment with mercury induced a reduction in the titres of specific IgG2a anti-HRBCs antibodies in DBA/2 mice after immunization with HRBCs. Our results demonstrated that mercury did not induce a general immunosuppression or a biased Th 1-type immune response in resistant DBA/2 mice. The nonresponsiveness in mice resistant to mercury-induced autoimmunity must be due to some other unknown mechanism(s).

Animals↗
PubMed1998

Feldkamp and circle-and-line cone-beam reconstruction for 3D micro-CT of vascular networks.

Detailed morphometric knowledge of the microvascular network is needed for studies relating structure to haemodynamic function in organs like the lung. Clinical volumetric CT is limited to millimetre-order spatial resolution. Since evidence suggests that small arterioles (50 to 300 micrometres) dominate pulmonary haemodynamics, we built a micro-CT scanner, capable of imaging excised lungs in 3D with 100 microm resolution, for basic physiology research. The scanner incorporates a micro-focal (3 microm) x-ray source, an xyz theta stage and a CCD-coupled image intensifier detector. We imaged phantoms and contrast-enhanced rat lungs, reconstructing the data with either the Feldkamp or the circle-and-line cone-beam reconstruction algorithm. We present reconstructions using 180 views over 360 degrees for the circular trajectory, augmented with views from a linear scan for the circle-and-line algorithm. Especially for platelike features perpendicular to the rotation axis and remote from the midplane, the circle-and-line algorithm produces superior reconstructions compared with Feldkamp's algorithm. We conclude that the use of nonplanar source trajectories to perform micro-CT on contrast-enhanced, excised lungs can provide data useful for morphometric analysis of vascular trees, currently down to the 130 microm level.

Algorithms↗
PubMed1998

Long-term health and employment outcomes of occupational asthma and their determinants.

Occupational asthma is common, yet little is known about long-term outcomes in the United States. A case series of 55 (of 72) occupational asthma patients were interviewed in follow-up 31 (+/- 15) months after removal from the cause to evaluate asthma severity and employment outcomes. Standard criteria were used to rate severity. At follow-up, 54 subjects (98%) had active asthma, of which 26 cases (47%) were "severe." Multivariate analysis showed increased risk of "severe" asthma for women (odds ratio [OR] = 13.8; 95% confidence interval [95% CI] = 1.3 to 151.7) and industrial sector workers (OR = 11.9; 95% CI = 1.3 to 109.8). Thirty-eight subjects (69%) were unemployed, risk being greater for those with "severe" asthma (OR = 20.9; 95% CI = 1.9 to 229.8) and for those without a college degree (OR = 7.3; 95% CI = 1.2 to 43.4). These results indicate that occupational asthma is disabling and probably irreversible for most patients referred to a specialty clinic, despite prolonged removal from causative agents. Women, industrial workers, and those with severe asthma or lack of a college degree appear to be at risk for worse outcomes. Greater efforts at primary and secondary prevention should lessen the burden of long-term illness and unemployment due to occupational asthma.

Adult↗
PubMed1998

Fitness for duty evaluations in hazardous materials firefighters.

We analyzed results from the medical examinations of 340 hazardous materials firefighters and applied various objective standards in simulated fitness for duty determinations. Ten percent had elevated blood pressures, 13% had far visual acuity worse than 20/30 in one or both eyes, and 38% had abnormal audiometry. The strictest standards for resting blood pressure and corrected visual acuity would have failed 2% and 1% of the cohort, respectively. For audiometry, 0%-5% of the cohort would have failed, depending on the hearing requirements set. The strictest hearing standard did not allow for corrective devices so that few failures would be reversible. Visual and audiometric testing and measurement of resting blood pressure all have significant clinical yields. Studies of simulated firefighting are needed to establish minimum hearing requirements and determine whether corrective devices can be worn safely during duty.

Adult↗
PubMed1998

Helical CT reconstruction with longitudinal filtration.

Each of the currently used helical reconstruction algorithms represents one tradeoff selection of the image noise or mA requirement and resultant artifacts versus the width of the section profile. For many applications, the performance tradeoffs different from those existed are desired. In this paper, we present a general framework of incorporating the longitudinal (z) filtration in helical CT reconstruction, which leads to a new class of helical reconstruction algorithms with tunable performance characteristics to suit various applications. The z-filtering algorithm enables us to derive the performance curve of image noise or mA requirement versus the width of the section profile, whereas the existing helical reconstruction algorithms only represent limited discrete samples of the curve. We demonstrate that using a new helical reconstruction algorithm derived from this general framework, a substantial reduction in image noise or mA requirement can be achieved with a slight increase of FWHM of the section profile. Thus for many applications requiring both compact section profile and low image noise or mA requirement, the new algorithm represents a better tradeoff than both the 180 degrees and 360 degrees interpolation algorithms. The new algorithm also offers the following potential clinical benefits: (1) longer x-ray tube life; (2) longer scan duration with less x-ray tube cooling delays--longer volume coverage and/or longer thin-slice scan; (3) less radiation to patient; (4) less image noise; and (5) less helical artifacts. Initial clinical results are also presented.

Abdomen↗
PubMed1998

Location-specific, unequal contribution of the N glycans in simian immunodeficiency virus gp120 to viral infectivity and removal of multiple glycans without disturbing infectivity.

One of the striking features of human immunodeficiency virus, simian immunodeficiency virus (SIV), and other lentiviruses is extensive N glycosylation of the envelope protein. To assess the requirement of each N glycan for viral infectivity, we individually silenced all 23 N glycosylation sites in the gp120 subunit of SIVmac239 envelope protein by mutagenizing the canonical Asn-Xaa-Thr/Ser N glycosylation motif in an infectious molecular clone, attempted to rescue viruses from the clones, and compared the replication capability of the rescued viruses in MT4 cells. The mutation resulted in either the recovery of a fully infectious virus (category I); recovery of a faster-replicating virus, compared with the parental virus (category II); or no virus recovery (category III). These categorically different sites were not distributed randomly but were clustered. The sites of category I were localized largely in the N-terminal half, whereas the sites of categories II and III were localized in the C-terminal region, including the CD4 binding site, and the central part, including the C loop, respectively. To learn how far SIV can tolerate the removal of glycans, multiplex mutagenesis was also attempted. When they were appreciably distant from one another in the primary sequence, up to five sites could be silenced in combination without disturbing infectivity. On the other hand, it was difficult to silence contiguous sites. Thus, it appeared that a certain degree of sugar chain density over the local region had to be preserved. We discuss the potential utility of these variously deglycosylated mutants for clarifying the role of N glycans in SIV replication in vivo, as well as in the host response, and for designing vaccines and the generation of glycoprotein crystals.

Base Sequence↗
PubMed1998

Production and characterization of improved adenovirus vectors with the E1, E2b, and E3 genes deleted.

Adenovirus (Ad)-based vectors have great potential for use in the gene therapy of multiple diseases, both genetic and nongenetic. While capable of transducing both dividing and quiescent cells efficiently, Ad vectors have been limited by a number of problems. Most Ad vectors are engineered such that a transgene replaces the Ad E1a, E1b, and E3 genes; subsequently the replication-defective vector can be propagated only in human 293 cells that supply the deleted E1 gene functions in trans. Unfortunately, the use of high titers of E1-deleted vectors has been repeatedly demonstrated to result in low-level expression of viral genes still resident in the vector. In addition, the generation of replication-competent Ad (RCA) by recombination events with the E1 sequences residing in 293 cells further limits the usefulness of E1-deleted Ad vectors. We addressed these problems by isolating new Ad vectors deleted for the E1, E3, and the E2b gene functions. The new vectors can be readily grown to high titers and have several improvements, including an increased carrying capacity and a theoretically decreased risk for generating RCA. We have also demonstrated that the further block to Ad vector replication afforded by the deletion of both the E1 and E2b genes significantly diminished Ad late gene expression in comparison to a conventional E1-deleted vector, without destabilization of the modified vector genome. The results suggested that these modified vectors may be very useful both for in vitro and in vivo gene therapy applications.

Adenoviridae↗
PubMed1998

The influence of bone and blood lead on plasma lead levels in environmentally exposed adults.

There is concern that previously accumulated bone lead stores may constitute an internal source of exposure, particularly during periods of increased bone mineral loss (e.g., pregnancy, lactation, and menopause). Furthermore, the contribution of lead mobilized from bone to plasma may not be adequately reflected by whole-blood lead levels. This possibility is especially alarming because plasma is the main circulatory compartment of lead that is available to cross cell membranes and deposit in soft tissues. We studied 26 residents of Mexico City who had no history of occupational lead exposure. Two samples of venous blood were collected from each individual. One sample was analyzed by inductively coupled plasma-magnetic sector mass spectrometry for whole-blood lead levels. The other sample was centrifuged to separate plasma, which was then isolated and analyzed for lead content by the same analytical technique. Bone lead levels in the tibia and patella were determined with a spot-source 109Cd K-X-ray fluorescence instrument. Mean lead concentrations were 0.54 microg/l in plasma, 119 microg/l in whole blood, and 23.27 and 11.71 microg/g bone mineral in the patella and tibia, respectively. The plasma-to-whole-blood lead concentration ratios ranged from 0.27% to 0.70%. Whole-blood lead level was highly correlated with plasma lead level and accounted for 95% of the variability of plasma lead concentrations. Patella and tibia lead levels were also highly correlated with plasma lead levels. The bivariate regression coefficients of patella and tibia on plasma lead were 0.034 (p<0. 001) and 0.053 (p<0.001), respectively. In a multivariate regression model of plasma lead levels that included whole-blood lead, patella lead level remained an independent predictor of plasma lead level (ss = 0.007, p<0.001). Our data suggest that although whole-blood lead levels are highly correlated with plasma lead levels, lead levels in bone (particularly trabecular bone) exert an additional independent influence on plasma lead levels. It will be important to determine whether the degree of this influence increases during times of heightened bone turnover (e.g., pregnancy and lactation).

Adult↗
PubMed1998

Bone lead as a biological marker in epidemiologic studies of chronic toxicity: conceptual paradigms.

The skeleton contains the majority of the body's lead burden in both children and adults. The half-life of lead in bone is in the range of years to decades, depending on bone type, metabolic state, and subject age, among other things. Measurement of skeletal lead has benefited greatly from the recent development of X-ray fluorescence (XRF) instruments that can make rapid, safe, accurate, and relatively precise measurements of lead in bone. Two types of XRF technologies exist, LXRF and KXRF; this paper focuses on KXRF, which has been the most widely validated and used. KXRF is proving to be a powerful analytical methodology for evaluating bone lead levels as a measure of time-integrated (i.e., cumulative) lead dose in epidemiologic studies of the effects of chronic lead exposure. However, insufficient attention has been given to conceptualizing the paradigms by which bone lead levels reflect lead exposure and by which the skeleton serves as an endogenous source of lead. Consideration of these paradigms, which rely on bone lead kinetics, is necessary for the proper development of a priori hypotheses involving bone lead accumulation and release, the selection of bone sites for measurement by KXRF, and the design of epidemiologic studies involving bone lead dynamics. We discuss and present supporting evidence for a conceptual model that distinguishes two major paradigms of skeletal lead, including 1) bone lead as an indicator of cumulative lead exposure (bone lead as repository), and 2) bone lead as a source of body lead burden that is mobilizable into the circulation (bone lead as source). These two roles are not mutually exclusive. Instead, they are components of the processes controlling lead accumulation into and release from bone over time. Developing successful strategies for distinguishing these two processes in epidemiologic studies will require separate measurements of lead in cortical and trabecular bone and additional measurement of specific markers of bone mineral turnover and resorption. It may also involve developing accurate methods for evaluating lead in labile compartments of the circulation, such as plasma, as a potentially useful and responsive measure of bone lead release, of the partitioning of circulatory lead, and of the toxicological significance of lead released from bone to other target organs.

Animals↗
PubMed1998

Bone lead as a new biologic marker of lead dose: recent findings and implications for public health.

Measurements of lead in bone have recently become the focus of research because a) bone lead levels serve as a cumulative dosimeter of lead exposure over many years (because of lead's long residence time in bone), and cumulative exposure may be more predictive of chronic toxicity than recent exposure, which is what blood lead levels mostly reflect; b) there is suspicion that heightened bone turnover (e.g. during pregnancy, lactation, and aging) may liberate enough stored lead to pose a significant threat of delayed toxicity; and c) although lead exposure has largely declined in the United States over the past 10 to 15 years, decades of heavy environmental pollution have resulted in significant accumulation of lead in bone among most members of the general U.S. population. Epidemiologic research on the impact of lead stored in bone is now possible with the development of 109Cd K-X-ray fluorescence (KXRF) instruments for the in vivo measurement of lead in bone. In this paper, the KXRF method will be briefly reviewed, followed by a summary of several Superfund-supported studies (and others) of blood lead and KXRF-measured bone lead in which these measures are compared as biologic markers of lead dose. Measurement of bone lead in epidemiologic studies has proved useful in exposure assessment studies, i.e., in identifying factors that contribute most to retained body lead burden, and in investigating cumulative lead exposure as a risk factor for poor health outcomes such as hypertension, kidney impairment, cognitive impairment, behavioral disturbances, and adverse reproductive outcomes.

Biomarkers↗
PubMed1998

Nutritional habits and serum lipid levels in a low-fat intake Chinese population sample.

The dietary intake of macronutrients and of specific minerals and vitamins was measured in a low-fat intake adult population living in a rural area in northwestern China. The total intake of fat amounted to +/- 12% of total energy. The P/S ratio was 2.5 and the U/S ratio 3.8. Carbohydrates provide about 75% of total energy. The mean total serum cholesterol was 148 mg/dl in men and 163 mg/dl in women. The mean HDL-cholesterol level was 38.6 mg/dl in men and 39.4 mg/dl in women, confirming the absence of a significant sex difference in HDL-cholesterol in low-fat consuming populations. Triglyceride levels were similar to those of Western populations. For both sexes taken together a positive correlation was found between the serum cholesterol level and saturated fat intake (p < 0.001) and a negative correlation with the P/S ratio (p < 0.05). Calcium intake was low: 346 mg/d in men and 245 mg/d in women.

Adult↗
PubMed1998

Cardiac protection by long-term treatment with captopril in patients with acute myocardial infarction.

OBJECTIVES: To assess the effects of long-term angiotensin-converting enzyme (ACE) inhibitor treatment with captopril on cardiac function in acute myocardial infarction (AMI). METHODS: One hundred and one patients with AMI who were admitted to hospital within 72 hours of the onset of symptoms with no cardiogenic shock were randomly allocated to captopril (n = 52; group I) and conventional treatment (n = 49; group II). Left ventricular (LV) systolic performance and diastolic transmitral flow velocity profiles were assessed by Doppler echocardiography at admission (1.2 +/- 1.1 days), before discharge (27 +/- 10 days) and during follow-up (363 +/- 31 days). RESULTS: At one year follow-up, in group I LV end-diastolic volume decreased, and ejection fraction increased due to a disproportionate decrease in end-systolic volume. The incidence of cardiac dilatation was reduced. LV early diastolic filling velocity (E) increased and late atrial filling velocity (A) decreased, resulting in an elevation of E/A ratio. However, the mean values of LV systolic and diastolic functional parameters were unchanged in group II. CONCLUSIONS: Long-term treatment with captopril exerts a beneficial effect on cardiac protection for patients with AMI.

Aged↗
PubMed1998

[Repair of large and complicated defect with multiple expanders].

OBJECTIVE: A method is introduced to obtain good aesthetic and functional results in repairing complicated defects on the face and neck, or total skin defects of the upper limb. METHODS: Two to four expanders are implanted in different areas where the color and texture of skin are similar to that of the defects, expanded simultaneously. During the second operation, several flaps corresponding to the defect areas are created and employed in one procedure. RESULTS: Six patients of 4-41 years old were treated with this technique. All of them have been followed up for 12-18 months with satisfactory results. CONCLUSION: Carefully planned, this maneuver shows better effects than the conventional method in repairing the skin defects of face, neck and upper limb.

Adolescent↗
PubMed1998

[A comparison of chromosome fragile sites in elderly and young people].

In this comparative study, the authors investigated the chromosome aberrations and expression of fragile sites in the lymphocytes which were collected from 45 elderly people and 29 young people and were cultured with FUDR for 24 hours. The results showed that the aberration rate was 24.75% for elderly people, but 4.22% for young people (P < 0.01): that the expression of fragile sites was 45.94% for elderly peoples, but 23.02% for young people (P < 0.01): and that the relation of aberrations with fragile sites was 79.98% for elderly people, and 92% for young people. These findings suggest that chromosome aberration is in close association with fragile site.

Adolescent↗
PubMed1998

[Study on the enantiomeric separation of adrenalines by capillary zone electrophoresis].

Capillary zone electrophoresis (CZE) has been used for the enantiomeric separation of the racemic isoprenaline, noradrenaline and adrenaline with bare fused silica capillary and employing beta-cyclodextrin(beta-CD) and beta-cyclodextrin derivatives as the chiral selectors. Both the complexion and enantiomeric resolution were influenced by the temperature, beta-CD type, CD concentration and pH of background electrolyte (BGE). The effects of the BGE types and concentrations on the enantiomeric separation were also investigated. The results showed that 2,6-di-O-carboxymethyl-beta-cyclodextrin (CM-beta-CD) has stronger recognition than that of beta-CD for the chiral separation of the basic drugs under study. The CD concentrations and pH of BGE have strong influence on the efficiency of chiral separation. The adsorption of the basic compound on the surface of bare fused silica capillary is a disadvantage to the chiral separation while the use of beta-CD as the chiral selector and the addition of an amphiphile, such as tetraethylammonium bromide (TEA+) or tetrabutylammonium bromide (TBA+) to the BGE could improve the resolution of the enantiomers due to the reduction of the adsorption of the basic compound on the silica surface by the strong electrostatic force between the positively charged amphiphile and the silica surface. It was also found that as CM-beta-CD was used as the chiral selector there was no influence on the chiral separation of the basic compound whether the amphiphile was added to BGE or not. Lower temperature was favorable to improve the efficiency of the chiral separation. CM-beta-CD gave a baseline enantiomeric separation for isoprenaline, while beta-CD, under the same experimental conditions, gave an incomplete chiral separation. Both CM-beta-CD and beta-CD could not give enantiomeric resolution for noradrenaline and adrenaline.

Electrophoresis, Capillary↗
PubMed1998

[Management of true extremity aneurysms: experience in 23 patients].

OBJECTIVE: To explore the etiologic feature and specificity of diagnosis and treatment in true aneurysms of the extremities. METHOD: 23 patients with true aneurysms of the extremities from January 1984 to September 1997 were retrospectively reviewed. RESULT: Of 30 true aneurysms of the extremities, multiple aneurysms were found in 7 patients (30.4%). The multiple aneurysms were diagnosed in the same time or in different time. 21 patients were treated by exclusion of aneurysm and replacement with autogenous saphenous vein or graft. CONCLUSION: Early diagnosis and treatment are recommended to prevent complications which can cause limb loss, and multiple aneurysms must be taken into account. Importance of arteriography should be stressed in the diagnosis of multiple aneurysms. Exclusion of aneurysm and autogenous saphenous vein reconstruction is the first choice of treatment, circulation of the operated extremities should be noticed and close follow-up is imperative to pay attention to the development of new aneurysms.

Adolescent↗