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Biomedical subjects

J Zhan

Publications and source records attributed to J Zhan.

At least 19 recordsLinked to original sources
PubMed2006

Hippocampal cerebrospinal fluid spaces on MR imaging: Relationship to aging and Alzheimer disease.

BACKGROUND AND PURPOSE: Perihippocampal fissures (PHFs) and hippocampal sulcus residual cavities (HSCs) are common findings in the MR imaging examination of the hippocampus in aging and Alzheimer disease (AD); however, little is known about how to distinguish them or their relative clinical relevance. We hypothesized that prominence of the HSC, unlike PHF, is not significantly influenced by the hippocampal atrophy related to aging or AD. METHODS: We studied and evaluated these hippocampal CSF spaces on MR imaging scans from 130 normal control (NC) subjects (20-90 years of age) and 27 AD patients. RESULTS: HSC is poorly correlated with age and is not related to the magnitude of hippocampal atrophy. There is no significant difference of HSCs between AD and age-matched NCs, but in the extremely high HSCs group (top 20%), 91% of cases are NC. PHFs, on the other hand, are strongly correlated with age and are valuable in the diagnosis of AD. Location and communication with ambient cistern is the key to distinguish HSC from PHF. CONCLUSION: Identifying hippocampal atrophy (enlarged PHF) may be particularly challenging in the presence of HSC. Distinguishing among the CSF spaces in hippocampus may help in the radiologic evaluation of hippocampal atrophy. Patients with extremely high HSCs (>8.4) can be excluded from AD risk with 93% specificity.

Adult↗
PubMed2005

Type II collagen and aggrecan mRNA expressions in rabbit condyle following disc displacement.

The aim of this investigation was to study the remodelling of cartilage in the mandibular condyle following disc displacement (DD) of the temporomandibular joint (TMJ). Forty adult Japanese white rabbits were used in this study. The right joints of 28 of the 40 rabbits had their discs surgically displaced. Four of the 28 were killed at 4 days or 1, 2, 4, 6, 8 and 12 weeks after surgery. The messenger RNA (mRNA) expression levels of aggrecan and type II collagen in cartilages were measured using in situ hybridization techniques. Results showed that aggrecan mRNA expression reduced in the first week after DD. The expression began to recover after 4 weeks and reached a normal level after 6 weeks. Type II collagen mRNA expression reduced from 4 weeks and the expression recovered after 8 weeks. This suggests that the chondrocyte reacting to the displacement of the TMJ disc, alters its matrix gene expression patterns and it is may be the cause of the shape changes of TMJ after DD.

Aggrecans↗
PubMed2005

Variation for neutral markers is correlated with variation for quantitative traits in the plant pathogenic fungus Mycosphaerella graminicola.

We compared genetic variation and population differentiation at RFLP marker loci with seven quantitative characters including fungicide resistance, temperature sensitivity, pycnidial size, pycnidial density, colony size, percentage of leaves covered by pycnidia (PLACP) and percentage of leaves covered by lesions (PLACL) in Mycosphaerella graminicola populations sampled from four regions. Wide variation in population differentiation was found across the quantitative traits assayed. Fungicide resistance, temperature sensitivity, and PLACP displayed a significantly higher Q(ST) than G(ST), consistent with selection for local adaptation, while pycnidial size, pycnidial density and colony size displayed a lower or significantly lower Q(ST) than G(ST), consistent with constraining selection. There was not a statistical difference between Q(ST) and G(ST) in PLACL. We also found a positive and significant correlation between genetic variation in molecular marker loci and quantitative traits at the multitrait scale, suggesting that estimates of overall genetic variation for quantitative traits in M. graminicola could be derived from analysis of the molecular genetic markers.

Ascomycota↗
PubMed2004

The interaction among evolutionary forces in the pathogenic fungus Mycosphaerella graminicola.

The population genetic dynamic of a species is driven by interactions among mutation, migration, drift, mating system, and selection, but it is rare to have sufficient empirical data to estimate values for all of these forces and to allow comparison of the relative magnitudes of these evolutionary forces. We combined data from a mark-release-recapture experiment, extensive population surveys, and computer simulations to evaluate interactions among these evolutionary forces in the pathogenic fungus Mycosphaerella graminicola. The results from these studies showed that, on average, the immigration rate was 0.027, the fraction of outcrossing individuals was 0.035, and the selection coefficient associated with immigrants was 0.106 each generation. We also estimated that effective population sizes for this fungus were larger than 24,000 and the mutation rate for the RFLP markers used in surveys and field experiments was approximately 4 x 10(-5). Computer simulations based on these estimates indicate that, on average, the global population of M. graminicola has reached equilibrium. Population genetic parameters including number of alleles, gene diversity, and population subdivision estimated from the computer simulations were surprisingly close to empirical estimates. Simulations also revealed that random drift is the major evolutionary force decreasing genetic variation in this fungus, followed by natural selection. The major force adding to genetic variation was mutation, followed by gene flow and sexual recombination. Gene flow played the leading role in decreasing population subdivision while natural selection was the major factor increasing population subdivision.

Ascomycota↗
PubMed2003

The global genetic structure of the wheat pathogen Mycosphaerella graminicola is characterized by high nuclear diversity, low mitochondrial diversity, regular recombination, and gene flow.

A total of 1673 Mycosphaerella graminicola strains were assayed for DNA fingerprints and restriction fragment length polymorphism (RFLP) markers in the nuclear and mitochondrial genomes. The isolates were collected from 17 wheat fields located in 11 countries on five continents over a six year period (1989-1995). Our results indicate that genetic diversity in the nuclear genome of this fungus was high for all but three of the field populations surveyed and that populations sampled from different continents had similar frequencies for the most common RFLP alleles. Hierarchical analysis revealed that more than 90% of global gene diversity was distributed within a wheat field, while approximately 5% of gene diversity was distributed among fields within regions and approximately 3% was distributed among regions on different continents. These findings suggest that gene flow has occurred on a global scale. On average, each leaf was colonized by a different nuclear genotype. In contrast, only seven mtDNA haplotypes were detected among the 1673 isolates and the two most common mtDNA haplotypes represented approximately 93% of the world population, consistent with a selective sweep. Analysis of multilocus associations indicated that all field populations were in gametic equilibrium, suggesting that sexual recombination is a regular occurrence globally.

Ascomycota↗
PubMed2002

Distribution of mating type alleles in the wheat pathogen Mycosphaerella graminicola over spatial scales from lesions to continents.

A total of 2035 Mycosphaerella graminicola strains collected from 16 geographic locations on four continents were assayed for the mating type locus. RFLP fingerprints were used to identify clones in each population. At the smallest spatial scale analyzed, both mating types were found among fungal strains sampled from different lesions of the same leaf as well as from different pycnidia in the same lesion. At larger spatial scales, the two mating types were found at equal frequencies across spatial scales ranging from several square meters to several thousand square kilometers. Though the absolute frequencies of the two mating types sometimes varied for different sampling units within the same spatial scale in the hierarchy (plots within a field, fields within a country, or different continents of the world), none of the differences were statistically significant from the null hypothesis of equal frequencies for the two mating types. The evolutionary forces likely to maintain the even distribution of the two mating types in this pathogen were discussed.

Alleles↗
PubMed2001

Mass transport characteristics and chromatographic behavior of preparative electrochromatography on hydroxyapatite.

Introducing an electric field into chromatography on hydroxyapatite (HAP) was attempted in order to enhance mass transfer and separation performance. A membrane spaced multicompartment electrolyzer was developed for electrochromatography on HAP. The high performance of liquid transport by electroosmotic flux was identified and described in terms of dynamic electroosmotic pressure. The application of the electric field resulted in an improved adsorption of bovine serum albumin as shown by the breakthrough curve as function of the electric field. An improved elution was also obtained in the presence of the electric field. The results show that electroosmosis is a powerful tool of liquid transport and dispersion in a packed bed of fine particles and has potential in the large-scale chromatography of biological molecules.

Adsorption↗
PubMed2001

[A study on the effects of CD3AK cells on the improvement of cellular immune function in burned patients].

OBJECTIVE: To explore new ways of correcting postburn immune suppression in severely burned patients. METHODS: CD3AK cells were cultured in serum-free medium and were employed to treat patients with major burns. Similar patients treated by routine treatment were set to be control group. The changes of cellular immunological indices were dynamically observed in the patients of two groups at different time points. RESULTS: Compared to those in control group, the ratio of CD4+ cell of T cell subgroup increased in patients treated by CD3AK, in concomitant with the decrease of the ratio of CD8+ cells and the increase of the ratio of CD4/CD8. Serum soluble IL-2R level decreased. T lymphocyte transforming activity increased and NK cell activity increased. CONCLUSION: CD3AK cells cultured in serum-free medium could improve and restore the decreased cellular immune function in burn patients.

Adult↗
PubMed2000

Determination of diclofenac sodium by capillary zone electrophoresis with electrochemical detection.

Capillary zone electrophoresis was employed for the determination of diclofenac sodium using an end-column amperometric detection with a carbon fiber microelectrode, at a constant potential of 0.83 V vs. saturated calomel electrode. The optimum conditions of separation and detection are 4.90 x 10(-3) mol/l Na2HPO4-3.10 x 10(-3) mol/l NaH2PO4 (pH 7.0) for the buffer solution, 10 kV for the separation voltage, 5 kV and 10 s for the injection voltage and the injection time, respectively. The limit of detection is 2.5 x 10(-6) mol/l or 5.2 fmol (S/N=2). The relative standard deviation is 0.8% for the migration time and 4.7% for the electrophoretic peak current. The method was applied to the determination of diclofenac sodium in human urine.

Diclofenac↗
PubMed2000

[Clinical analysis of 224 cases of small intestine disease].

OBJECTIVE: To increase the knowledge of small intestine disease, improve the diagnostic rate and discusses the examination methods. METHODS: 224 cases of small intestine disease were studied and their major symptoms, etiology, diagnostic methods were analyzed. RESULTS: The major symptoms of small intestine disease were abdominal pain (58%), abdominal mass (18%), fever (17%) and hematochezia (12%). The most common disease of small intestine was malignant tumor (32%), others were diverticulum (29%), leiomyomas (7%), hemorrhagic necrotizing enteritis (6%), Crohn's disease (4%). Double-contrast enteroclysis and laparotomy were still the major diagnostic methods. CONCLUSION: Malignant tumor was the most common disease of small intestine. More attention should be paid to the diagnosis of small intestine disease.

Adolescent↗
PubMed2000

[Analysis of clinical characteristic and tendency on inpatients with colorectal cancer in Shanxi Tumor hospital from 1989 - 1999].

OBJECTIVE: To understand the clinical characteristics and variable tendency on inpatients with colorectal cancer admitted to Shanxi Tumor Hospital from 1989 - 1999. METHODS: Statistical analysis on all cases from 1989 - 1999. RESULTS: Results showed that 3,050 cases with colorectal cancer were admitted during 11 years including 2,246 (73.64%) cases of surgical patients. The 1,168 cases males and 1,078 females were with ratio being 1.08/1.0 (M:F). There was no obvious change on the numbers of inpatient from 1991 to 1994, but the numbers was higher than that in 1989 and 1990. The numbers of inpatient rose from 1995 to 1999 year by year. In all the admitted inpatients during the 11 years, 1,348 cases were from countryside and 898 cases from city with the ratio being 1.5/1.0. When adjusted by the general population in 1992, the frequency of the admitted patients was higher in city (14.66/10(5)) than that in countryside (5.96/10(5)). Regarding the distribution of inpatients, it was found higher in Tiayuan city and Jinzhong area than that in else areas. The age of inpatients rose from 40 years and reached high peak in 51 - 70 years. Dukes stages showed that most of inpatients were middle or advanced stage and chief ill location was in rectal (82.36%). Most histological classification referred to adenocarcinoma (56.23%) and papilla adenocarcinoma (20.88%). CONCLUSION: Data suggested that it is very important to strenghen the knowledge of prevention and self-protection of colorectal cancer. Screening and early diagnosis and early treatment should be paid great attention to improve survival rate among high risk population.

ABO Blood-Group System↗
PubMed1999

Expression of RET proto-oncogene and GDNF deficit in Hirschsprung's disease.

PURPOSE: The aim of this study was to investigate GDNF (glial cell line-derived neurotrophic factor) protein expression and RNA expression level of the RET proto-oncogene in human aganglionic (AG) bowel in Hirschsprung's disease (HD) and to further understand the pathophysiology of HD. METHODS: To evaluate the possible implication of the RET gene and GDNF for the development of HD, mRNA expression level of the RETgene was examined by using the reverse transcription-polymerase chain reaction (RT-PCR) technique and protein expression level of the GDNF using an immunohistochemical technique in the bowel specimens of 15 HD patients. RESULTS: A significantly less intense signal for RETmRNA was found in the AG bowel compared with the ganglionic bowel. In different age groups of patients, the intensities of RET level had similar results. In the same patients, there was strong GDNF immunoreactivity in the myenteric plexuse in ganglionic bowel. In the myenteron in AG bowel, the number of GDNF immunoreactive neuron cells was reduced significantly compared with normal ganglionic bowel. CONCLUSIONS: From these preliminary data we conclude that the decreased RET expression in the AG bowel may suggest mal development of neural crest-derived cells in HD. The reduced level of GDNF in AG bowel may suggest a GDNF expression deficit interrupting the faithful signaling via RET, and both are implicated in the pathogenesis of HD.

Base Sequence↗
PubMed1998

Modification of ricin A chain, by addition of endoplasmic reticulum (KDEL) or Golgi (YQRL) retention sequences, enhances its cytotoxicity and translocation.

A pKK expression system in Escherichia coli was used to produce recombinant ricin A chain (rRTA) and rRTA modified by addition of organelle-specific amino acid retention sequences, including KDEL (an endoplasmic reticulum, ER, lumen retention signal), KKMP (an ER membrane retention signal), YQRL (a trans-Golgi network retention signal) and KFERQ (a lysosome-targeting signal) to the C terminus of rRTA. The toxicities of these RTA mutants were assessed in Jurkat cells following fluid-phase endocytosis. rRTA-KDEL and rRTA-YQRL were significantly more cytotoxic for Jurkat cells than rRTA, rRTA-KKMP or rRTA-KFERQ. This difference did not result from signal(KDEL or YQRL)-mediated binding of these RTA mutants to the cell surface. Reconstituted ER and Golgi vesicles have been employed to assess translocation of rRTA and mutant rRTA. RTA-KDEL and RTA-YQRL respectively exhibited 6.7-fold and 6.1-fold more protection against papain digestion in reconstituted ER vesicles and 2.2-fold and 1.8-fold more protection in reconstituted Golgi vesicles, than unmodified rRTA. These mutants were reassociated with ricin B chain to form holotoxins. The mutant RTA-KDEL and RTA-YQRL holotoxins were 3.8-fold and 1.5-fold more cytotoxic for target cells, respectively, than ricin produced using unmodified rRTA. Our results suggest that both ER and the trans-Golgi network may play important roles in the intracellular trafficking and translocation of ricin A chain.

Cytosol↗
PubMed1998

[Allograft of frozen nerve in repairing sensory nerve defect].

To observe the effect of allogenic transplantation of deep frozen nerve in repairing sensory nerve defect, 22 patients who had received this type of treatment were followed up for 0.5-5 years. There were 18 males and 4 females in this group, and the average age was 28 years old. Thirty-six nerve defects including the common volar digital nerve, proper volar digital nerve were repaired by allograft of nerves stored at deep frozen (-80 degrees C). The storation period was ranged from 9 days to 1 years. The length of the nerves were 2 cm-12 cm. After follow-up for 3 years (ranged from 7 months-5 years), 23 cases of nerve allograft obtained excellent and good results (63.9%), 10 cases were fair (27.7%) and 3 cases were poor (8.3%). It was concluded that (1) frozen nerve is one of nice materials for repairing the nerve defect (< 5 cm); (2) the immunity of allogenenic nerve is weak; (3) the deep frozen storation can reduce the immunity of nerve; (4) the dimethyl sulfoxide can prevent the nerve tissue from injury by deep frozen; (5) the best temperature and period for deep frozen storation should be studied further.

Adolescent↗
PubMed1997

Restoration of lectin activity to a non-glycosylated ricin B chain mutant by the introduction of a novel N-glycosylation site.

Ricin B chain (RTB) is an N-glycosylated, galactose-specific lectin. Removal of the two native N-glycosylation sites at Asn95 and Asn135 by site-directed mutagenesis generated a recombinant protein devoid of lectin activity. Two novel N-glycosylation sites were introduced into RTB at Asn42 and Asn123, either singly or in combination. Microinjection of pre-RTB transcripts into Xenopus oocytes showed that these novel sites became glycosylated in vivo. The single oligosaccharide site chain at Asn42 restored lectin activity to RTB, whereas glycosylation at Asn123 or simultaneous glycosylation at Asn42 and Asn123 failed to do so.

Animals↗
PubMed1997

Sensitive nonradioactive dot blot/ribonuclease protection assay for quantitative determination of mRNA.

We have developed a simple and sensitive method for the rapid quantitation of mRNA from cell cultures and small tissue samples. The method combines the high sensitivity and specificity of the ribonuclease protection assay with simple handling and rapid execution of dot blotting. The use of digoxygenin-labeled cRNA probes eliminates all problems associated with radioisotopes commonly used in the ribonuclease protection assay. The RNA preparation is dotted directly onto nylon membranes, and after hybridization the filters are treated with ribonuclease A, which removes the nonhybridized single-stranded RNA. The mRNA-hybrid is then visualized by the chemiluminescence technique using labeled anti-digoxigenin antibody, and the signal intensity is quantitated. Comparison with the Northern blotting ribonuclease protection assay revealed that this dot blot technique is almost ten times more sensitive and that its signals are linear over a wide range of RNA concentrations (0.01-10 micrograms/microL/dot). This method seems particularly valuable for simultaneous processing of large numbers of samples containing a wide range of RNA concentrations.

Animals↗