Biomedical subjects

X P Zhu

Publications and source records attributed to X P Zhu.

At least 19 recordsLinked to original sources

PubMed2006

Robust analysis of short echo time (1)H MRSI of human brain.

Short echo time proton MR Spectroscopic Imaging (MRSI) suffers from low signal-to-noise ratio (SNR), limiting accuracy to estimate metabolite intensities. A method to coherently sum spectra in a region of interest of the human brain by appropriate peak alignment was developed to yield a mean spectrum with increased SNR. Furthermore, principal component (PC) spectra were calculated to estimate the variance of the mean spectrum. The mean or alternatively the first PC (PC(1)) spectrum from the same region can be used for quantitation of peak areas of metabolites in the human brain at increased SNR. Monte Carlo simulations showed that both mean and PC(1) spectra were more accurate in estimating regional metabolite concentrations than solutions that regress individual spectra against the tissue compositions of MRSI voxels. Back-to-back MRSI studies on 10 healthy volunteers showed that mean spectra markedly improved reliability of brain metabolite measurements, most notably for myo-inositol, as compared to regression methods.

Adult↗

PubMed2005

A stage-specific open reading frame from three-day old adult worms of Trichinella spiralis encodes zinc-finger motifs.

The aim of the study was to isolate genes coding for stage-specific antigens of T. spiralis. Such antigens may then be associated with local and systemic immune responses against adult T. spiralis. Recombinant clones were obtained with an adult stage specific probe from a cDNA library of three-day old adult T. spiralis. Several cDNA clones encoding the same peptide were identified and their stage specificity was confirmed by northern blot analysis. Three independent clones were fully sequenced, and the resulting sequence found to code for a 487 amino acid peptide with a deduced molecular weight of approximately 55 kDa. Sequence analysis showed that the 55 kDa peptide contained putative DNA binding motifs, suggesting that this protein may be involved in transcriptional regulation during the early development of the parasite.

Amino Acid Sequence↗

PubMed2004

Higher atrophy rate of entorhinal cortex than hippocampus in AD.

OBJECTIVES: To determine if atrophy rates were higher for entorhinal cortex (ERC) than for hippocampus in Alzheimer disease (AD), to determine the relationship between hippocampal atrophy rate and memory impairment, and to compare atrophy rates of ERC and hippocampus in differentiating between patients with AD and cognitively normal (CN) controls. METHODS: Twenty patients with AD and 25 CN subjects had MRI scans and clinical evaluations twice approximately 1.9 years apart. ERC volumes were measured manually and hippocampal volumes were measured semiautomatically on volumetric T1-weighted MR images. RESULTS: In AD, the atrophy rate of ERC (7.1 +/- 3.2%/year) was higher (p < 0.02) than that of hippocampus (5.9 +/- 2.4%/year). Furthermore, memory deficit in mild AD, measured with the Delayed List Verbal Recall test, correlated significantly with atrophy rates of both ERC (r = -0.61) and hippocampus (r = -0.59). Atrophy rates of ERC and hippocampus were comparable in differentiating between AD and CN. Using atrophy rates of ERC or hippocampus to detect a 20% treatment effect with 90% power (p < 0.05) would require about 100 completed patients per arm in a 2-year study. CONCLUSION: The finding in AD that the atrophy rate in the entorhinal cortex is higher than in the hippocampus is consistent with the view that AD pathology begins in the entorhinal cortex.

Aged↗

PubMed2003

Atrophy rates of entorhinal cortex in AD and normal aging.

OBJECTIVES: To explore the atrophy rate of entorhinal cortex (ERC) in AD and normal aging and assess the value of rate measurement of ERC atrophy for classifying subjects with AD from cognitively normal (CN) control subjects. METHODS: Twenty-one AD patients and 23 CN subjects had MRI scans and clinical evaluations twice within 1.8 +/- 0.6 years. ERC volumes were manually measured on volumetric T1-weighted MR images. RESULTS: Patients with AD had a greater annual percentage volume change of ERC than CN subjects on both sides (left: 6.8 +/- 4.3%/year for AD vs 1.4 +/- 2.5%/year for CN [F(1,42) = 25.6, p < 0.001]; right: 6.3 +/- 3.3%/year for AD vs 1.4 +/- 2.3%/year for CN [F(1,42) = 25.6, p < 0.001]). Furthermore, increased ERC atrophy rate was correlated (r = -0.56, p = 0.01) with decreased memory performance in AD. CN subjects had on average annual ERC atrophy rates greater than zero (p < 0.01). Baseline volume of ERC predicted atrophy rate of ERC (left: r = -0.53, p < 0.01; right: r = -0.42, p < 0.05) in CN subjects but not in AD subjects. Using ERC baseline volumes alone resulted in 77% overall correct classification (p < 0.01) between AD and CN subjects, with 76% sensitivity and 78% specificity and an area under receiver operator characteristic (ROC) curve of 0.83. Adding annual atrophy rate of ERC to the model accounted for most of the variance (p < 0.01), diminishing contributions from baseline volume and yielding 82% overall classification, with 76% sensitivity and 86% specificity and an area under the ROC curve of 0.93. CONCLUSION: ERC volume loss over time may be a better indicator for AD than cross-sectional measurements.

Aged↗

PubMed2003

Simultaneous mapping of blood volume and endothelial permeability surface area product in gliomas using iterative analysis of first-pass dynamic contrast enhanced MRI data.

We describe a novel method for the calculation of endothelial permeability surface area product from dynamic contrast enhanced MRI. The technique uses iterative estimation to automatically decompose tissue residue function into intravascular and extravascular components, which are subsequently used to generate tumour blood volume, which is equal to relative cerebral blood volume calculated from T(1) weighted images and corrected for contamination by contrast agent leakage (rCBV(T1)(corrected), and endothelial permeability (k(fp)) maps. The technique was assessed in patients with cerebral glioma (n=5) by examining the reproducibility of endothelial permeability and rCBV(T1)(corrected) between two separate examinations conducted with a 2-day interval. The technique produces maps of endothelial permeability that appear to be free of any contribution from intravascular contrast agent. Maps of rCBV(T1)(corrected) show close correlation with maps of blood volume calculated from independently acquired dynamic susceptibility weighted MRI examinations, with no evidence of residual permeability effects. The results were highly reproducible with strong intra-class correlation between the two examinations for mean values and for 97.5 percentiles of endothelial permeability and rCBV(T1)(corrected). The excellent reproducibility of this technique and the ability to calculate endothelial permeability and rCBV(T1)(corrected) values from rapidly acquired data sets offer considerable advantages over conventional approaches and support the use of this methodology for therapeutic monitoring or trials of novel therapeutic agents.

Aged↗

PubMed2003

Reproducibility of quantitative dynamic contrast-enhanced MRI in newly presenting glioma.

We have investigated the reproducibility of dynamic contrast enhanced imaging techniques in nine patients with cerebral glioma. Patients were imaged twice with a 2 day interval between scans. Maps were produced of the time taken to achieve 90% enhancement (T90), the maximal intensity change per time interval ratio (MITR), the volume transfer coefficient between plasma and the extravascular extracellular space (K(trans)) and the extravascular extracellular contrast distribution volume, v(e). Measurements of K(trans) greater than 1.2 min(-1) were used to exclude pixels where first pass perfusion effects dominated the measurement. Measures of the test-retest coefficient of variation (CoV) and intraclass correlation coefficients were used to assess reproducibility for measurements from a volume of interest containing enhancing tissue from the whole tumour. MITR showed poor reproducibility (mean CoV 17.9%, 95% confidence limits for group comparisons 20.2%). T90 showed good reproducibility (mean CoV 7.1%, 95% confidence limits for group comparisons 5.2%). Calculated values of K(trans) and v(e) also showed good reproducibility (mean CoV 7.7% and 6.2% respectively, 95% confidence limits for group comparisons 6.2% and 4.8%, respectively). We conclude that the measurements of K(trans) and v(e) derived from pharmacokinetic analysis are sufficiently reproducible to support their use as a biological markers in therapeutic trials.

Aged↗

PubMed2002

Effects of subcortical ischemic vascular dementia and AD on entorhinal cortex and hippocampus.

OBJECTIVE: To determine the effects of subcortical ischemic vascular dementia (SIVD) and AD on entorhinal cortex (ERC) and hippocampus. METHODS: Thirty-eight cognitively normal subjects, 18 patients with SIVD, and 22 patients with AD were included. Volumes of ERC and hippocampus were manually measured based on MRI. Global cerebral changes of cortical gray matter, subcortical gray matter, white matter, sulcal CSF, ventricular CSF (vCSF), and white matter signal hyperintensities (WMSH) were assessed. RESULTS: Patients with SIVD had 21.7% (p < 0.01) smaller ERC and 18.2% (p < 0.01) smaller hippocampi than cognitively normal subjects and 24.4% (p < 0.01) larger ERC and 11.1% (p < 0.05) larger hippocampi than patients with AD. In addition, patients with SIVD had less cortical gray matter and white matter and more vCSF and WMSH (all p < 0.01) than cognitively normal subjects and more vCSF and WMSH (p < 0.01) than patients with AD. The volumes of ERC and hippocampus were positively correlated to similar extents (p < 0.01) in SIVD and AD. Cortical gray matter loss was positively correlated (p < 0.01) with hippocampal atrophy, but not with ERC atrophy, in SIVD and AD. Hippocampal volume alone could classify 82% of patients with SIVD from cognitively normal subjects and 63% of patients with SIVD from subjects with AD. Adding global cerebral changes to hippocampus substantially improved the classification to 96% between patients with SIVD and cognitively normal subjects and 83% between subjects with SIVD and those with AD, whereas adding ERC change to hippocampus did not significantly improve the discrimination. CONCLUSIONS: The entorhinal cortex and hippocampus are less affected by subcortical ischemic vascular dementia than by AD.

Aged↗

PubMed2002

Breath-hold perfusion and permeability mapping of hepatic malignancies using magnetic resonance imaging and a first-pass leakage profile model.

We have applied a novel pharmacokinetic model of the distribution of contrast media to dynamic contrast-enhanced MRI data from patients with hepatic neoplasms. The model uses data collected during the passage of a bolus of contrast medium and allows breath-hold image acquisition. The aims of the study were to investigate the feasibility of permeability mapping using the first pass technique and breath-hold acquisitions, and to examine the reproducibility of the technique and the effect of the liver's dual vascular supply on the assumptions of the model. Imaging was performed in 14 patients with hepatic neoplasms. Dynamic data clearly demonstrated differences in the timing and shape of the contrast medium concentration-time course curve in the systemic arterial and portal venous systems. Mapping of the arrival time (T(0)) of contrast medium allowed identification of tissue supplied by the hepatic arteries and portal vein. Hepatic tumours all showed typical hepatic arterial enhancement. Repeated measurements of endothelial permeability surface area product (k(fp)) and relative blood volume (rBV), performed in five patients, showed excellent reproducibility with variance ratios (V(r)) of 0.134 and 0.113, respectively. Measurement of enhancing tumour volume was also highly reproducible (V(r) = 0.096) and this was further improved by the use of T(0) maps to identify pixels supplied by the hepatic artery (V(r) = 0.026). Estimates of k(fp) and rBV in normal hepatic tissue supplied by the portal vein were highly inaccurate and these pixels were identified by use of the T(0) parameter and excluded from the analysis. In conclusion, dynamic MRI contrast enhancement combined with a pharmacokinetic model of the distribution of contrast media in the first pass allows us to produce highly reproducible parametric maps of k(fp) and rBV from hepatic tumours that are supplied by the hepatic arterial system using breath-hold acquisitions.

Adenocarcinoma↗

PubMed2001

[Establishment of rabbit model for peritoneal dialysis related peritonits].

OBJECTIVE: To establish a rabbit model corresponding with clinical characteristics of peritoneal dialysis related peritonitis. METHODS: Twelve New Zealand rabbits were randomly divided into peritonitis group and control group. They were infused standard living Staphylococcus aureus 3 x 10(9) colony forming unit (cfu) (peritonitis group) or 0.9% NaCl 1 ml (control group). After 48 hours, Laboratory rabbits in acute uremic model underwent regular dialysis for 6 hours. At different points of time, the concentration of glucose in dialysate and the dialysate/plasma (D/P) ratio of the concentration creatinine (Cr), total protein(TP), album(Alb) and IgG, the counts of leukocyte in dialysate and water ultrafiltrate were determined. RESULTS: D/D0 were significantly lower in the peritonitis group than that in the control group (P < 0.05). The counts of leukocyte and D/P ratio of Cr, TP, Alb and IgG were significantly increased in the peritonitis group (all P < 0.05). The drained volume was lower in the peritonitis group than that in the control group (but P > 0.05). CONCLUSION: In the rabbit model infused intraperoneally staphylococcus aureus, (1) transport peritoneum of low and large molecular weight solutes is increased, (2) the volume of ultrafiltrate is decreased, (3) the counts of leukocyte in dialysate is increased. These change in this model is basic all correspond with the clinical feature of patients of peritoneal dialysis related peritonitis. So this rabbit model of peritoneal dialysis related peritonitis is a successful experimental infection model.

Animals↗

PubMed2001

[Changes of renal blood flow and serum NO2-/NO3- in rabbits treated with mannitol at different dosages].

To observe the changes of renal blood flow and serum NO2-/NO3- in rabbits administrated with mannitol at different dosages, and investigate the mechanism of acute renal failure (ARF) induced by massive mannitol. Eighteen healthy male Zealand rabbits were randomly divided into 3 groups: minor mannitol group(n = 6, 8 g.kg-1 within 2 hours), control group (n = 6, saline of the same volume), massive mannitol group with free water taking(n = 6, mannitol 40-60 g.kg-1 with 3 days). The changes of renal function, renal blood flow and NO2-/NO3- in serum and urine were observed. The results showed that: no significant change in creatinine clearance (Ccr), renal blood flow (RBF) and serum NO2-/NO3- was found between minor mannitol group and control group. In massive mannitol group with free water taking, Ccr and RBF significantly decreased and serum NO2-/NO3- significantly increased (P > 0.05). The results suggest that ARF induced by massive mannitol is associated with a significant decline of RBF, on the other hand, endothelium-derived relaxing factor(EDRF) maybe compensatively increase.

Acute Kidney Injury↗

PubMed2001

[Clinical observation of combined therapeutic effect of prostaglandin E1 and mecobalamin on diabetic peripheral neuropathy].

OBJECTIVE: To observe the clinical effect of combined treatment of prostaglandin E1 and mecobalamin on diabetic peripheral neuropathy(DPN). METHODS: Seventy two patients of DPN were divided into 3 groups, they were given the drug of prostaglandin E1 (PGE1), mecobalamin, PGE1 plus mecobalamin (combined therapeutic group) and compared the therapeutic effects respectively. RESULTS: The improvement of DPN symptoms and nerve conducting speeds of combined therapeutic group was obviously better than that of the single PGE1 group or mecobalamin group(P < 0.01). CONCLUSION: Combined therapy of PGE1 and mecobalamin is better than each of single drug for improvement of DPN symptoms.

Adult↗

PubMed2001

[Variability of female peak bone mineral density at different skeletal regions and its effect on diagnosis of osteoporosis].

OBJECTIVE: To evaluate the changes in variability (V) of female peak bone mineral density (PBMD) at different skeletal regions and its effects on diagnosis of osteoporosis. METHODS: Using a Hologic QDR 4500A fan beam X-ray bone densitometer to measure the BMD at different skeletal regions (anteroposterior and supine lateral spine, hip, and forearm) in 1,810 women between the ages of 15-96 from Changsha city (Hunan province) in the People's Republic of China, the population grouped in every 5 years of age, then to get PBMD and its variability. RESULTS: According to every 5 years of age, the analysis showed that PBMD occurred varied in the age of 20-44, the variability ranged 6.0% to 17.0%, in an average of (11.4 +/- 3.1)%, the maximal value (17%) of V is at Ward's triangle, the minimal value of V is at distal one-third site of forearm (6%). The incidence of osteoporosis changed with V of PBMD at different skeletal regions. With different diagnostic standards, the incidences of OP also differed. CONCLUSION: Changes in PBMD and its V at different skeletal regions and the different diagnostic standard obviously affects the incidence of OP.

Adolescent↗

PubMed2001

Reproducibility of T2* blood volume and vascular tortuosity maps in cerebral gliomas.

The development of anti-angiogenic therapies for tumors has led to a demand for imaging-based surrogate markers of the angiogenic process. The utility of such markers is highly dependent on their test-retest reproducibility. This paper presents a formal assessment of the reproducibility of measurements of relative blood volume (rBV), normalized rBV (rBVnorm), and vascular tortuosity as estimated by measurement of relative recirculation (rR). The study was conducted in 11 patients with glioma who were scanned on two occasions 36-56 hours apart. The observed reliability estimates were used to calculate 95% confidence limits for detection of differences between groups and for changes in individual cases. The results show that measurement of rBV or rBVnorm in consecutive studies is statistically capable of reliably detecting changes in excess of 15% in between group studies and 25% in individual patients. Measurement of vascular tortuosity using is less reproducible but is able to confidently identify changes in excess of 30% in group studies and 35% in individuals.

Blood Volume↗

PubMed2001

Biological and genetic characteristics of two Trichinella isolates in China; comparison with European species.

The most recent taxonomic revision in Trichinella genus included 10 taxa. Trichinella spiralis (Ts) is a thoroughly studied species but most of the isolates came from the Europe or American continents. Few information is available from China about the Trichinella isolates and their diversity. In this report two Chinese isolates were characterized and compared with European strains. The in vitro release of newborn larvae (NBL) was determined for the two species. NBL is observed in supernatant of cell culture after adults purification on day 4 post infection (pi) with Ts, and on day 5 pi with Trichinella nativa (Tna). A new parameter was thus proposed to characterize Trichinella strains. Restriction fragment length polymorphism (RFLP) of genomic DNA and random amplified polymorphic cDNA (RAPD) were used to define genetic variability among different isolates. Species specific pattern could be obtained with RAPD but it was far more difficult to get geographical markers for Trichinella using these methods. A low genetic variability in Trichinella species (i.e. a strong "clonality") is suggested.

Animals↗

PubMed2001

Free radicals in hypoxic rat diaphragm contractility: no role for xanthine oxidase.

Recent evidence indicates that hypoxia enhances the generation of oxidants. Little is known about the role of free radicals in contractility of the rat diaphragm during hypoxia. We hypothesized that antioxidants improve contractility of the hypoxic rat diaphragm and that xanthine oxidase (XO) is an important source of free radicals in the hypoxic diaphragm. The effects of N-acetylcysteine (NAC; 18 mM), Tiron (10 mM), and the XO inhibitor allopurinol (250 microM) were studied on isometric and isotonic force generation during hypoxia (PO(2) approximately 7 kPa). NAC and Tiron decreased maximal force generation, slowed the shortening velocity, and decreased the power output. Fatigue rate was decreased in the presence of either NAC or Tiron. Allopurinol did not alter the contractility or fatigability of the diaphragm. During hyperoxia (PO(2) approximately 85 kPa), neither NAC nor allopurinol affected the contractility or fatigability of the diaphragm. Thus free radicals play a significant role in diaphragm contractility during hypoxia. Whether antioxidants exert a beneficial or harmful effect on muscle performance depends on the contraction pattern of the muscle. Free radicals generated by XO do not play a role in diaphragm contractility during either hypoxia or hyperoxia.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗

PubMed2001

[Screening and sequence analysis of the adult stage-specific gene of Trichinella spiralis].

OBJECTIVE: To obtain the sequence of the adult stage-specific gene of Trichinella spiralis. METHODS: An adult T. spiralis cDNA library was screened using an adult T. spiralis stage-specific probe. The gene sequence was analyzed by DNAstar software and GenBank database. RESULTS: A cDNA clone of 1,629 bp was obtained by screening the library with an adult stage-specific probe. The clone contained one open reading frame composed of 1,464 bp encoding 487 amino acids. GenBank searching revealed that no identical cDNA was found. Two zinc fingers located at the positions within amino acids 207-270. Some possible antigen epitopes were predicted within the amino acids 52-64, 108-116, 137-163 and 226-260. CONCLUSION: A novel stage-specific gene of adult T. spiralis encoding the protein containing certain predicted antigen epitopes was obtained.

Amino Acid Sequence↗

PubMed2001

[Genotypes of merozoite surface protein 2 of Plasmodium falciparum in different malaria endemic areas].

OBJECTIVE: To determine the genotypes and distribution of MSP2 of Plasmodium falciparum isolates in Yunnan and Hainan provinces, China. METHODS: The central polymorphic region of MSP2 allele was amplified by the nested PCR for genotyping of P. falciparum. RESULTS: The higher degree of polymorphism of MSP2 of P. falciparum was observed in Yunnan and Hainan. Distribution and allele frequencies differed in both provinces, indicating considerable geographical heterogeneity of parasite populations. The mixed infection of different allele-type and multiplicity of infection was more frequent in Hainan than in Yunnan. CONCLUSION: There were obvious differences in the distribution and frequencies of MSP2 alleles between Yunnan and Hainan endemic areas. MSP2 is suitable to be used as a marker gene for the genotyping of P. falciparum infection.

Alleles↗

PubMed2000

[Effects on simvastatin in continuous ambulatory peritoneal dialysis patients with hyperlipidemia].

The therapeutic effects of simvastatin on hyperlipidemia and its protective effects on residual renal function (RRF) in continuous ambulatory peritoneal dialysis (CAPD) patients with hyperlipidemia were observed. Forty-seven CAPD patients were randomly divided into two groups, the treatment group and control group. The treatments of two groups were the same except that the treatment group patients were additionally given simvastatin 20 mg.d-1. The results were that, after 12-week treatment, the total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), and apoprotein B100 (ApoB100) in the treatment group significantly decreased, but high density lipoprotein (HDL) and apoprotein A1 (ApoA1) significantly increased compared with the control group (all P < 0.05); one year later, RRF of patients of both groups all decreased but there was no significant difference between them. The results suggest that simvastatin can effectively normalize lipidemia, but has no protective effect on RRF in CAPD patients.

Adult↗