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Biomedical subjects

X Hu

Publications and source records attributed to X Hu.

At least 433 records · Page 24Linked to original sources
PubMed1994

A new T2 preparation technique for ultrafast gradient-echo sequence.

The T2 contrast in images obtained with driven equilibrium (90degreesx-180degreesx-90degreesx) prepared ultrafast gradient-echo sequence is compromised by the longitudinal magnetization build-up after the second 90degreesx pulse, which does not carry T2 information. This paper describes a new T2 contrast preparation technique for ultrafast gradient-echo sequence that suppresses the signal arising from the build-up. By dephasing in the preparation and rephasing in the acquisition of the gradient echoes, the new technique eliminates signals that are not dictated by the T2 contrast in a driven-equilibrium approach. Consequently, it generates an image that is essentially T2-weighted. Phantom and in vivo experiments were conducted to validate the technique and to demonstrate its clinical utility. These studies indicate that the technique works properly and can be used for in vivo studies.

Animals↗
PubMed1994

Potential pitfalls of functional MRI using conventional gradient-recalled echo techniques.

The conventional gradient-recalled echo technique, FLASH, has widely been used for functional MRI. FLASH results at 4 T with short TEs of 10-20 ms mimic those at 1.5 T with TEs of 25-50 ms or longer. Under these conditions, large venous vessels dominate the activated area; however, the use of longer TEs at 4 T reveals activation in gray matter areas as well as large vessels. Inflow effects of large vessels can be greatly reduced with centric-reordering of phase-encoding steps and inter-image delay. Finger and toe movement paradigms show that functional activation maps are consistent with classical somatotopic maps, and are specific to the tasks. Navigator-based motion correction generates functional maps with larger activation areas by reducing physiological noise.

Brain↗
PubMed1994

A new strategy for spectroscopic imaging.

This paper describes a new approach for reducing ringing artifacts in spectroscopic imaging (or chemical-shift imaging). The new method is aimed at reducing the signal contamination in areas of interest, due to ringing, that often arises from adjacent areas with high intensity, such as subcutaneous fat in the case of 1H spectroscopy and skeletal muscle in case of the 31P spectroscopy. The method is based on the fact that the high-intensity signals which are the major source of contamination can be captured with one or few acquisitions and the metabolite resonances in areas of interest require considerably more averaging in the data acquisition due to low signal-to-noise ratio. In order to reduce ringing and maintain adequate SNR for the metabolites, the data points in high k space are measured with one or few excitations while those in the low k space are sampled with many excitations. By virtue of this sampling scheme, the data contain more noise in the high-spatial-frequency region and direct Fourier transformation reconstruction generates a very noisy image. Therefore, a new reconstruction technique is developed for the reconstruction. This approach has been studied by simulations and its practical utility is demonstrated by an in vivo proton CSI experiment. Technical details and simulation and experimental results are presented. From these results, it is concluded that the technique is robust and can be used for in vivo applications.

Artifacts↗
PubMed1994

Spectroscopic imaging of circular voxels with a two-dimensional Fourier-series window technique.

Spatial localization with the spectroscopic imaging technique is normally implemented with the Fourier-transform approach, yielding rectangular voxels, with potentially significant cross-voxel contamination. Multidimensional Fourier-series window (FSW) is an alternate approach that generates single voxels of predetermined shape, with minimal out-of-voxel contamination. The spatial location of the voxel is shifted by means of postacquisition processing. A two-dimensional circular voxel is introduced, which for many in vivo applications is a good match of the region of interest. Phantom images illustrate the spatial distribution of signal intensity within the circular FSW voxels. Phantom spectroscopic studies show excellent spatial localization, with no detectable out-of-voxel contamination. The circular FSW voxel approach is implemented in human and animal model studies, demonstrating the technique's utility. This arbitrary shape approach can be extended to three dimensions, defining, for example, cylinders, spheres, or ellipsoids.

Adenosine Triphosphate↗
PubMed1994

Equilibrium dialysis of metal-serum albumin. I. Successive stability constants of Zn(II)-serum albumin and the Zn(2+)-induced cross-linking self-association.

The binding of Zn(II) to human serum albumin (HSA) and bovine serum albumin (BSA) was intensively studied by equilibrium dialysis. The successive stability constants were obtained by least-squares fitting. For both the Zn(II)-HSA and Zn(II)-BSA systems, the successive stability constants are basically similar, though such constants for the latter generally slightly larger than those for the former; the order of magnitude of K1 and K2 was found to be approximately 10(5) M-1. The twelve binding sites found for Zn(II)-HSA and fourteen binding sites for Zn(II)-BSA can be divided into three and two different sets, respectively, but in both systems, there exist approximately three identical strongest binding sites. The binding equilibrium of Zn(II)-HSA markedly depends on the concentration of HSA. The type of Scatchard plots indicates the existence of the Zn(2+)-induced cross-linking self-association of HSA, which was found from Wyman plots to be the strongest at a concentration of Zn2+ in the range (4-6) x 10(-6) M. The maximum of the apparent self-association constants k2 so obtained was approximately 2.6 x 10(4) M-1. Such a self-association mechanism and the order of magnitude of K1 and K2 both to some extent support the inference that the zinc group ions are bound to the cysteinyl sulphur atoms.

Animals↗
PubMed1994

Determination of trace amounts of urea by using flow injection with chemiluminescence detection.

Reaction between urea and hypobromite in alkaline solution was found to produce chemiluminescence with a maximum wavelength at 510 nm. A simple chemiluminescence detection method was used for the determination of urea in human urine and natural aqueous samples, which combined this chemiluminescence reaction with a flow injection analysis system. The relative standard deviation for 5 x 10(-7) mol dm-3 urea is 1.9% (n = 6), and the detection limit is 9.0 x 10(-8) mol dm-3 (3Sr). As this chemiluminescence reaction is very fast, a double concentric tube mixer connected directly to the chemiluminescence cell was used to mix urea solution and hypobromite solution. Alkylamines, carboxylic acids and most amino acids do not interfere in the determination. Ammonium ion interferes, but the sensitivity for ammonium ion is only 1% of that for urea. The interference from ammonium ion was removed sufficiently by using an on-line cation-exchange column.

Flow Injection Analysis↗
PubMed1994

Functional limitations and recovery in children with severe trauma: a one-year follow-up.

To examine functional limitations, recovery rates, and association with Injury Severity Scores (ISSs), we followed 92 children with severe trauma and 59 control subjects with appendicitis at 6 months and 1 year after discharge. Physical health status was assessed by the Rand Health Insurance Study instrument. Overall, 73% and 55% of trauma patients had one or more functional limitations at 6 months and 1 year, respectively, in contrast to 14% and 9% of the controls. Overall functional status of the trauma patients improved by 22% in the first 6 months and 24% in the second. Much higher recovery rates (73% and 46%) were noted for self care. Although ISS did not correlate with overall functional status, higher ISSs were related to impairment in patients whose principal injury was to the head or the face-chest-abdomen but not in those whose principal injury was to an extremity. This study shows that many children with severe trauma are left with disabilities. Recovery rates are not uniform but depend on type of limitation. Functional impairment and recovery are related more to the body parts involved than to ISS.

Activities of Daily Living↗
PubMed1994

Family-based intervention for schizophrenic patients in China. A randomised controlled trial.

BACKGROUND: We developed and evaluated a comprehensive, ongoing intervention for families of schizophrenic patients appropriate for China's complex family relationships and unique social environment. METHOD: Sixty-three DSM-III-R schizophrenic patients living with family members were enrolled when admitted to hospital and randomly assigned to receive standard care or a family-based intervention that included monthly 45-minute counselling sessions focused on the management of social and occupational problems, medication management, family education, family group meetings, and crisis intervention. RESULTS: At 6, 12, and 18-month follow-ups by blind evaluators, the proportion of subjects rehospitalised was lower, the duration of rehospitalisation was shorter, and the duration of employment was longer in the experimental group than in the control group; these differences were statistically significant at the 12 and 18-month follow-ups and were not explained by differences in drug compliance. Family intervention was associated with significantly lower levels of family burden. CONCLUSIONS: This intervention is less costly than standard treatment, is suitable for urban families of schizophrenic patients in China and feasible given the constraints of the Chinese mental health system.

Adolescent↗
PubMed1994

Acute and chronic respiratory effects of sodium borate particulate exposures.

This study examined work-related chronic abnormality in pulmonary function and work-related acute irritant symptoms associated with exposure to borate dust in mining and processing operations. Chronic effects were examined by pulmonary function at the beginning and end of a 7-year interval. Time-specific estimates of sodium borate particulate exposures were used to estimate cumulative exposure during the study interval. Change in pulmonary function over the 7 years was found unrelated to the estimate of cumulative exposure during that interval. Exposure-response associations also were examined with respect to short-term peak exposures and incidence of five symptoms of acute respiratory irritation. Hourly measures of health outcome and continuous measures of particulate exposure were made on each subject throughout the day. Whenever a subject reported one of the irritant symptoms, a symptom intensity score was also recorded along with the approximate time of onset. The findings indicated that exposure-response relationships were present for each of the specific symptoms at several symptom intensity levels. The associations were present when exposure was estimated by both day-long and short-term (15-min) time-weighted average exposures. Associations persisted after taking account of smoking, age, and the presence of a common cold. No significant difference in response rate was found between workers exposed to different types of sodium borate dusts.

Adult↗
PubMed1994

[A study of prostaglandine E(2) level in root canal fluid of patients with periapical lesions]

It has been reported that there is close relationship between prostaglandine E(PGE) and the pathogenesis of periapical lesions, In this study the root canal fluid(RCF) of 35 cases with acute,chronic and convalescent periradicular lesions were collected with assessed by the method of radioimmunoassay.The results showed:RCF-PGE(2) levels were increased with the severity of periapical lesion(P<0.01).The PGE level was highest in acute periradicular lesions,middle in chronic,and lowest in convalescent.RCF-PGE(2) levels were significantly different between either two groups of the three groups of patients(P<0.01-0.05).This study repeatedly proved that PGE(2) has certain effect in pathogenesis of periapical lesions and it is meaningful in guiding clinical therapy.It was also pointed out that RCF is one of worthwhile samples in the study of periradicular lesion.

Journal Article↗
PubMed1994

Studies on structural changes of collagen in silicosis.

In order to provide scientific information on the prevention and treatment of silicosis, studies about changes of silicotic collagen in lungs were carried out. In this paper, we present experiments about the structural changes of collagen in silicotic lungs of rats and patients. These included electron microscopy, circular dichroism and infrared spectroscopy studies of collagen fibers. The results indicated that fibers of silicotic collagen were shorter in length, smaller in diameter and decreased in alpha-helix content. The -Si-O-R- group and -OH group were found increased and -C-C- backbone shortened. The increase of -Si-O-R- group indicated that silica formed linking bridges between collagens which may be the cause of progressive enlargement of nodules.

Animals↗
PubMed1994

[Relation between histo-compatibility antigen immunogenetics and pregnancy induced hypertension].

Fourty cases with pregnancy induced hypertension (PIH) and 100 normal pregnant women were selected for this study. The distribution of histo-compatibility antigen D region (HLA-DR) frequency, the frequency of homozygosity and the HLA-DR antigens sharing between partners were investigated. The results showed that the frequency of HLA-DR4 was significantly higher in PIH than that in normal pregnancy (P < 0.001). There was a very high DR antigen sharing between partners in PIH as compared to normal pregnancy (P < 0.01), specially obvious in the frequency of DR4 antigen sharing in PIH (P < 0.0001). There was, however, no significant difference in the frequency of homozygosity or heterozygosity between HLA-DR and DR4 locus. This study suggested that HLA-DR4 may be related to the genetic susceptibility of PIH. This correlation is presumably due to a linkage imbalance of susceptible gene of PIH and DR4, but whether DR4 acts directly as an immunodeficient gene remains to be determined.

Adult↗
PubMed1994

Restoration of intracellular drug accumulation in MDR cell line K562r does not mean reversal of its drug resistance.

Our purpose was to test whether drug sensitivity and drug accumulation in MDR cell erythroleukemic K562r could be restored by incubating cells with 3 anthracycline antibiotics in combination. Drug sensitivities of cells were assessed with MTT assay, in which doxorubicin, epirubicin, daunorubicin, or the 3-drug mixture was applied with concentrations ranging from 1 to 3125 ng.ml-1. The IC50 of K562r cells were 1.0, 1.0, 0.1, and 0.2 microgram.ml-1, respectively, about 22, 16, 10, and 20 times higher than those of K562 cells. After cells were exposed to doxorubicin (2-32 micrograms.ml-1) for 1 h, the drug concentrations in K562r cells were all higher than those in K562 cells. Similar results were obtained for epirubicin or daunorubicin. After 1-h incubation of cells with the 3-drug mixture (3 to 192 micrograms.ml-1), there were no considerable differences of drug accumulation between K562r and K562 cells with only 3 exceptions in 21 groups. It is concluded that restoration of intracellular drug accumulation in MDR cell line K562r was not correlated with reversal of its drug resistances.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

[Association of polymorphism for HLA-DQA1 promotor region (QAP) with IDDM].

We have identified the DNA polymorphism for the HLA-DQA1 promotor region (QAP) in patients with early and late onset insulin-dependent diabetes mellitus (IDDM) by PCR direct sequencing. The result showed that single nucleotide substitution at position-92(C-->T-92) and -146 (T-->C-146) were detected in QAP for early and late onset IDDM respectively. These findings suggests that the mutation seems to alter the conformation of QAP so that these are likely to influence the aberrant expression of MHC-class II loci in beta-pancreatic islet cells.

Base Sequence↗
PubMed1994

[Chromosome 15 satellite enlargement and hereditary deafness].

The clinical and cytologic examinations in 6 deaf patients from 2 genealogical trees with chromosomal 15 satellite enlargement, karyotype 46, XY(X), PS++(15) are reported. A proband as well as his brother and sister suffered from phenotype with gradual hearing loss at the age of 12 to 13 and big satellite 15 existed in chromatinic karyotype. His father's phenotype was normal, but karyotype was the same as the 3 siblings of the proband, which suggested that the abnormal chromosome may originate from the father. The proband as well as his mother and uncle from family tree 2 may all suffer from dysaudia in both ears without any cause and with rapid exacerbation of the disease and deafness at last, 1 to 2 years after birth. Based on the fact that they had similar clinical phenotype and karyotype, their delayed deaf-mutism may be related to the structural abnormality of chromosome 15. An examination of the proband's grandparents showed that both phenotype and karyotype were normal. The abnormal chromosome from the proband's mother and uncle may originate from a new mutation. Obviously, the proband's abnormal chromosome originates from the mother. It is estimated that such chromosomal structural abnormality may be caused by some hearing genetic effects.

Adult↗
PubMed1994

Concepts of myocardial perfusion imaging in magnetic resonance imaging.

Based on the major innovations in ultrafast magnetic resonance (MR) imaging in recent years, myocardial perfusion imaging with MR has become the focus of many investigators. Two major approaches to myocardial perfusion imaging involve either exogenous or endogenous contrast agents. For the first category of perfusion experiments, we review the characteristics of the common contrast agents and MR techniques for experimental and clinical first-pass studies and in particular address the question of extracting quantitative estimates for myocardial blood flow (milliliters per minute per gram) and volume (milliliters per gram). We demonstrated quantitative perfusion analysis using intravascular relaxation agents and heavily T1-weighted ultrafast gradient echo sequences. Signal time curves need to be transformed to content time curves and the resulting residue functions were analyzed with a multiple-pathway, axially distributed perfusion model. These preliminary results suggest that quantitative assessment of myocardial perfusion is feasible, but additional studies should provide further confidence for this novel MR approach. The exact sensitivity and specificity of MR first-pass imaging in conjunction with extracellular contrast agents in patient studies and its diagnostic accuracy as judged against coronary angiography and scintigraphic perfusion imaging remain yet undefined. The second category of perfusion experiments does not require exogenous contrast agents and has not yet been tested in patient studies. Progress is reported on several MR perfusion-sensitive methods that use the tissue water as an endogenous contrast agent in combination with magnetization transfer techniques as well as paramagnetic deoxyhemoglobin for measuring tissue oxygenation using heavily T2*-weighted sequences for blood oxygen-level-dependent contrast. Possible future directions and developments toward further improvements for MR myocardial perfusion measurements and contraction-perfusion matching are also addressed.

Blood Volume↗
PubMed1994

A rating instrument for the evaluation of in-patient rehabilitation programmes in China. Results of reliability and validity testing.

To objectively evaluate in-patient rehabilitation programmes in China, we developed a new rating scale: the Inpatient Psychiatric Rehabilitation Outcome Scale (IPROS). The scale has five subscales: performance in occupational therapy, daily activities, socialisation, personal hygiene, and level of interest in external events. Evaluators (physicians or nurses) observe patients for one week before coding items on a five-point scale. Comparison of four independent evaluators' results for 32 schizophrenic patients assessed on two separate occasions indicated that the inter-rater and test-retest reliability for the overall IPROS score and for the five subscale scores was excellent (all ICC values > or = 0.973). Validity was evaluated by comparing IPROS results with those of five other independently assessed clinical measures for 101 chronic schizophrenic patients before and after a six-month rehabilitation programme; concurrent validity and longitudinal validity were satisfactory (correlation coefficients 0.37-0.81, all P values < 0.01).

Activities of Daily Living↗