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Biomedical subjects

Lin Zhang

Publications and source records attributed to Lin Zhang.

At least 235 records · Page 13Linked to original sources
PubMed2004

On-line concentration of neutral and charged species in capillary electrochromatography with a methacrylate-based monolithic stationary phase.

A method involving self-concentration, on-column enrichment and field-amplified sample stacking for on-line concentration in capillary electrochromatography with a polymer monolithic column is presented. Since monolithic columns eliminate the frit fabrication and the problems associated with frits, the experimental conditions could be more flexibly adjusted to obtain higher concentration factor in comparison with conventional particulate packed columns. With self-concentration effect, the detection sensitivity of benzene and hexylbenzene is improved by a factor of 4 and 8, respectively. With on-column enrichment and ultralong injection, improvement as high as 22,000 times in detection sensitivity of benzoin is achieved. Furthermore, a combination of the three above-mentioned methods yields up to a 24,000-fold improvement in detection sensitivity for caffeine, a charged compound. Parameters affecting the efficiency of on-line concentration are investigated systematically. In addition, equations describing on-line concentration process are deduced.

Benzene↗
PubMed2004

Selective detection of monohydroxy metabolites of polycyclic aromatic hydrocarbons in urine using liquid chromatography/triple quadrupole tandem mass spectrometry.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously present in the environment and associated with a variety of adverse health effects. Monohydroxylated PAHs (OH-PAHs), metabolites of PAHs, have been employed as biomarkers for human exposure assessment of PAHs. This manuscript describes new, selective detection methods for OH-PAHs using liquid chromatography and tandem mass spectrometry (LC/MS/MS). Electrospray ionization was operated in the negative ion mode to detect the deprotonated PAH metabolites ([M-H](-)). Hydroxylated metabolites of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, benzo[c]phenanthrene, chrysene, benzo[a]anthracene, and benzo[a]pyrene were selected for the method development. Based on the collision-induced dissociation MS/MS spectra of the selected OH-PAHs, a characteristic ion fragmentation, loss of 28 Da from the [M--H](-) ion, was identified for all of these OH-PAHs. This characteristic fragmentation was exploited for selective screening for OH-PAHs in human urine by incorporating a constant neutral loss (CNL) scan with data-dependent scanning, using a triple quadruple mass spectrometer. Selected reaction monitoring (SRM) was also used to tentatively identify isomers of the target OH-PAHs in human urine. The excellent linearity (3-4 orders of magnitude) and signal-to-noise performance provided by the SRM method allowed development of a sensitive LC/MS/MS method for measuring OH-PAHs in urine samples. The limits of detection of the SRM method ranged from approximately 0.1-5 pg on column for a suite of OH-PAHs tested in the study. The LC-SRM method was applied, following enzymatic deconjugation and solid-phase extraction of the urine, to preliminarily determine the OH-PAH concentrations in urine specimens from six Chinese non-occupationally exposed workers and seven Chinese coke oven workers.

Chromatography, Liquid↗
PubMed2004

Air concentrations of VOCs in portable and traditional classrooms: results of a pilot study in Los Angeles County.

Recent state and federal public school class-size reduction initiatives, increased elementary and pre-K enrollment driven by population growth and immigration, and limited resources for capital projects, modernization, and maintenance at aging schools have increased the prevalence of prefabricated, portable classrooms (portables). At present, approximately one of three California students are taught in portables, whose use is especially prevalent in more populated counties such as Los Angeles, home to the nation's second largest school district. Limited data existed on chemical compound air concentrations, and thus exposures, inside American public schools. Measurements have been limited, usually performed in complaint schools, and varied in sampling protocols and analysis methods. To address a school environment and children's health issue of present concern, an assessment of public school portables was conducted in Los Angeles County. Seven schools in two school districts were recruited, from which 20 classrooms--13 portables, seven in main buildings--were randomly selected. We report indoor air concentrations of 21 target toxic and odorous volatile organic compounds (VOCs), including formaldehyde and acetaldehyde, measured with passive samplers (DNSH PAKS and 3M OVM 3500) in the cooling and heating seasons between June 2000 and June 2001. None of the measured indoor air formaldehyde concentrations exceeded the existing California Air Resources Board guideline (50 ppb, or 60 microg/m(3)). The main sources of aldehydes in classrooms, especially portables, were likely interior finish materials and furnishings made of particleboard without lamination. Indoor air VOC concentrations were generally low in this pilot study. The four most prevalent VOCs measured were toluene, m-/p-xylene, alpha-pinene, and delta-limonene; likely indoor sources were personal, teaching, and cleaning products. Future schools research should attempt larger samples over larger geographical areas.

Acetaldehyde↗
PubMed2004

Glycogen in the brain of Drosophila melanogaster: diurnal rhythm and the effect of rest deprivation.

One function of sleep is thought to be the restoration of energy stores in the brain depleted during wakefulness. One such energy store found in mammalian brains is glycogen. Many of the genes involved in glycogen regulation in mammals have also been found in Drosophila melanogaster and rest behavior in Drosophila has recently been shown to have the characteristics of sleep. We therefore examined, in the fly, variation in the glycogen contents of the brain, the whole head and the body throughout the rest/activity cycle and after rest deprivation. Glycogen in the brain varies significantly throughout the day (p=0.001) and is highest during rest and lowest while flies are active. Glycogen levels in the whole head and body do not show diurnal variation. Brain glycogen drops significantly when flies are rest deprived for 3 h (p=0.034) but no significant differences are observed after 6 h of rest deprivation. In contrast, glycogen is significantly depleted in the body after both 3 and 6 h of rest deprivation (p<0.0001 and p<0.0001, respectively). Glycogen in the fly brain changes in relationship to rest and activity and demonstrates a biphasic response to rest deprivation similar to that observed in mammalian astrocytes in culture.

Animals↗
PubMed2004

Apoptosis in human cancer cells.

PURPOSE OF REVIEW: Apoptosis, or programmed cell death, is a vital physiologic process to eliminate damaged or unwanted cells. Defects in apoptosis promote tumor formation and make cancer cells resistant to therapy. This review provides an overview of recent advances in the understanding of apoptosis in human cancer cells. RECENT FINDINGS: Recent studies revealed that the apoptotic machinery in humans consists of a molecular network of a large number of proteins. These proteins regulate a cascade of events in signaling, commitment and execution stages of apoptosis through multiple parallel pathways. Delineation of the basic mechanisms of apoptosis has shed light on how apoptosis is deregulated in human cancer cells. Therapeutic strategies based on apoptosis have also been designed to selectively target tumor cells. SUMMARY: Understanding the basic mechanisms of apoptosis and determining how cancer cells evade apoptosis will afford discoveries of new molecular targets and better cancer therapies.

Apoptosis↗
PubMed2004

Direct and repeat uses of tissue sections as templates for liquid-phase polymerase chain reaction amplification: applications and implications.

The liquid-phase polymerase chain reaction (PCR) technique is the most commonly used method for the amplification of genetic materials, although it requires the lysis of cells for DNA or RNA extraction, making it impossible to visualize the distribution and subcellular localization of the biomolecules. This study intended to assess whether tissue sections may be directly and repeatedly used as templates for liquid-phase PCR amplifications. Consecutive paraffin sections of breast tissues were placed on gamma-methacryloxypropyltrimethoxysilane-coated microscopic cover glasses perforated with a diamond knife into strips. After hematoxylin and eosin or immuno-staining, the strip of interest was inserted into a PCR tube for amplifications, and the adjacent strip with the same tissue was subject to microdissection, DNA extraction, and PCR amplifications. To use the strip repeatedly, it was transferred into a new PCR tube and amplified with a new primer set, after an initial amplification for 5 to 7 cycles. Then, initially amplified samples were amplified to a total of 40 cycles. An equal volume of PCR products from the strip and DNA extract were loaded side by side for electrophoresis and detection. The strip and DNA extract from the same tissue yielded a very comparable quality and quantity of PCR products with the same primer sets. The strip, however, could be repeatedly used for PCR amplifications with substantially more primer sets. In addition, the strip could be used for immunohistochemical or other molecular assays after PCR amplifications. Further studies with the same protocol on strips containing chromosomal spreads generated similar results.

DNA↗
PubMed2004

[Further study on heterogeneic basis of complement C8 beta deficiency].

OBJECTIVE: In Caucasian population, the most common molecular basis for C8 beta deficiency s a single C to T transition in exon 9 of C8 beta gene resulting in a stop codon. In previous family studies, two individuals were identified with C8 beta complete deficiency and were found to be only heterozygous for this mutation. This study was conducted by the present authors in search of other possible causes for these two C8 beta deficient individuals. METHODS: Using direct DNA sequence analysis of all exon-specific PCR products of the C8 beta gene from these two C8 beta deficient patients and their descendants. RESULTS: Two other C to T transitions at base 298 and 388 in exon 3 were detected, which could also create a termination codon. The descendants from one of the deficient patients were also analysed for the mutations, and it could be demonstrated that the two C to T mutations in exons 9 and 3 are segregating independently. CONCLUSION: These two mutations, which create a termination codon, are sufficient to explain the complete C8 beta deficiency in both patients.

Codon, Nonsense↗
PubMed2004

[Polymorphisms of five short tandem repeat systems in Chinese Zang population in Kangba area].

OBJECTIVE: To get preliminary genotype and allele frequency distributions of D1S549, D3S1754, D12S391, D12S375 and D18S865 loci in Chinese Zang (Tibetan) population in Kangba area and to validate more short tandam repeat (STR) systems for forensic application. METHODS: Fresh samples of venous blood from 100 unrelated individuals of Chinese Zang population in Kangba area were dropped on the filter paper. After they dried up, DNA were extracted by chelex-100 method and amplified by the polymerase chain reaction (PCR). The PCR products were analyzed by PAG vertical electrophoresis and silver staining. RESULTS: Seven alleles were found at D1S549 locus, six alleles at D3S1754 locus, ten alleles at D12S391 locus, six alleles at D12S375 and six alleles at D18S865 locus. No deviations from Hardy-Weinberg equilibrium were observed. The heterozygosities observed were 0.86, 0.77, 0.81, 0.69, 0.80 for D1S549, D3S1754, D12S391, D12S375 and D18S865 respectively. The calculated values of the Power of Exclusion were 0.715, 0.545, 0.618, 0.413 and 0.599, and the values of the Power of Discrimination were 0.929, 0.838, 0.934, 0.886 and 0.890, respectively. CONCLUSION: All of the five loci in this study were useful for individual identification and paternity test, as well as for research purposes in genetics.

Alleles↗
PubMed2004

[Expression of vascular endothelial growth factor C in laryngeal squamous carcinoma and its role in lymphatic metastasis].

OBJECTIVE: To study the expression of vascular endothelial growth factor C (VEGF-C) in laryngeal squamous carcinoma (LSC) and its relationship to lymph node metastasis. METHODS: Paraffin-embedded specimens of primary laryngeal carcinomas from 60 patients subjected to operation were studied. VEGF-C expression was investigated using immunohistochemical staining. RESULTS: Positive immunohistochemical staining for VEGF-C protein was observed in some laryngeal squamous carcinoma cells (45/60), the VEGF-C antigen was identified in the cytoplasm of cancer cells. Furthermore, the expression of VEGF-C in laryngeal squamous carcinoma cells was significantly higher in lymph-node-positive groups than in node-negative groups, and the expression was significantly higher in poorly differentiated LSC tissues than in moderately and well differentiated LSC tissues. CONCLUSION: The above findings indicate a close correlation between VEGF-C expression and lymph node metastasis in laryngeal squamous carcinoma.

Adult↗
PubMed2004

[Plasma endothelin levels in patients with multiple organ dysfunction syndrome caused by fish gall bladder poisoning].

OBJECTIVE: To investigate the correlation between the change of plasma endothelin (ET) and the occurrence and progress of multiple organ dysfunction syndrome (MODS) caused by fish gall bladder poisoning. METHODS: Plasma ET was measured in 85 patients with fish gall bladder poisoning and 30 healthy controls and comparison of the levels of plasma ET was carried out between patients groups with different severity of fish gall bladder poisoning. The relationship between plasma ET levels and enzymology as well as some biochemistry indexes in patients with fish gall bladder poisoning was then analyzed. RESULTS: Plasma ET in patients with fish gall bladder poisoning (150.5 +/- 90.5) ng/L was much higher than that in controls (52.8 +/- 9.3) ng/L. The concentration of plasma ET in slight poisoning group (61.2 +/- 13.6) ng/L increased a little, but it was not significantly different with that in controls (P > 0.05). The concentration of plasma ET was significantly higher in moderate poisoning group and severe poisoning group (162.3 +/- 82.3) ng/L and (232.6 +/- 92.7) ng/L as compared with that in the controls (P < 0.01), with the severe poisoning group much higher than the moderate poisoning group and the latter much higher than the normal. At the same time, plasma ET in MODS group and non-MODS group (210.2 +/- 98.7) ng/L and (126.3 +/- 68.3) ng/L were both notably higher than that in the controls. Furthermore plasma ET in the MODS group was much higher than that in the non-MODS (P < 0.01). It was also found that a positive correlation existed between plasma ET and creatine kinase-MB, cardiac troponin I, lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen and serum creatinine (P < 0.01) and a negative correlation between plasma ET and endogenous creatinine clearance rate (P < 0.01). CONCLUSION: Plasma ET may be involved in the process of fish gall ladder poisoning and later in the progress of MODS. It was shown that the higher the level of plasma ET, the severer the degree of poisoning and the higher the fatality rate. So monitoring plasma ET level dynamically may be an important clinical index in judging the patients condition and their prognosis in fish gall bladder poisoning. Simultaneously it is useful for earlier diagnosis of fish gall bladder poisoning and alertness of MODS caused by it as well as for proper management with antagonist and inhibitor against plasma ET for prevention and cure of fish gall bladder poisoning.

Adult↗
PubMed2004

[Study on the genetic polymorphisms of D8S1132 locus in Chinese Han, Mongolian and Thai populations].

OBJECTIVE: The aim of the present study was to obtain the population genetic data of short tandem repeat (STR) locus D8S1132 and study the difference of allelic frequency distributions among different populations. METHODS: A sample of 380 unrelated individuals from 3 populations (Han, Mongolian, Thai) were studied using single PCR followed by polyacrylamide gel electrophoresis and silver staining. RESULTS: Eleven allels and 42 genotypes were observed. The observed heterozygosity and the discrimination power were 85.0%-89.5% and 94.1%-95.5%, respectively. The genotype distributions of D8S1132 locus in 3 populations were in accordance with Hardy-Weinberg equilibrium and the difference of allelic frequency distributions among 3 populations was obvious. CONCLUSION: The methods established are easy-to-perform and sensitive. The discrimination power and exclusion chances of this locus are desirable for forensic analysis.

Alleles↗
PubMed2004

[Sequence polymorphisms of the mitochondrial DNA control region in 100 Chengdu Hans in China].

OBJECTIVE: To study the genetic polymorphisms of the mitochondrial DNA (mtDNA) control region in Chengdu Han population. METHODS: Sequence polymorphisms of the mtDNA control region, hypervariable regions I and II from 100 unrelated Chinese Hans were determined by PCR and direct sequencing. RESULTS: Sequences of 404 nucleotides for hypervariable region I and 379 nucleotides for region II were obtained. Ninety-two and fifty variable sites were revealed in region I and region II respectively as compared to the reference sequence, and a total of 97 different genetic patterns from both the regions I and II were determined. The probability of identity was estimated at 1.84% for region I, 1.94% for region II, and 1.18% for both the regions. CONCLUSION: These results suggest that sequence polymorphism of mtDNA control region would be very useful in forensic practice as a marker for individual identification.

Base Sequence↗
PubMed2004

[A population study of three Y-STR loci by multiplexing in Han population in Chengdu, China].

OBJECTIVE: To establish a better method determining three Y-STR loci. METHODS: A multiplex of Y-STRs and amplify simultaneously three Y-STRs loci. RESULTS: Establish successfully a multiplexing system of three Y-STR loci (DYS390, DYS391 and DYS393) followed by a population genetic study of Han population in Chengdu, China. CONCLUSION: The diversity of haplotype is 0.8965, the value of discrimination and the chance of exclusion chance is 0.8965 with the standard error 0.0081. This established system is one of the good tools in personnel identification and genetic study.

China↗
PubMed2004

[The effect of postoperative chemotherapy after esophagectomy on the survival rate to patients with original squamous cell carcinoma of esophagus].

OBJECTIVE: To study the prognostic factors affecting the survival rate after extended radical esophagectomy with three-field lymph node dissection for squamous cell carcinoma and the effect of postoperative chemotherapy. METHODS: Out of 126 patients with original squamous cell carcinoma of esophagus who accepted extended radical esophagectomy with three-field lymph node dissection from 1987 - 1992 in a hospital, 97 of them were included in this study. Data on the clinical/pathological characters and post surgery survival records of the subjects' were collected. Survival analysis methods included Kaplan-Meier, Log-rank test and Cox multivariable model and the effects of postoperative chemotherapy were analyzed for patients in early and late stages. RESULTS: There was no significant difference in clinical and pathological character between those patients only undergone surgery and patients accepting postoperative chemotherapy. The size of tumor, grade of differentiation of the tumor cells, infiltration deepness, with or without lymph node metastasis, expression of nm23 and EGFR and treatment after surgery etc. were correlated with the survival rate. For patients in early tumor stage, postoperative chemotherapy with cisplatin and 5-FU after surgery seemed to be a risk factor. For patients in late stage, postoperative chemotherapy with cisplatin and 5-FU after surgery did not seem to improve survival rate. CONCLUSION: It is imperative to study on the effect of adjuvant postoperative chemotherapy to patients, especially those at early stage with squamous cell carcinoma of esophagus. Doctors must be scrupulous when making decisions.

Adult↗
PubMed2004

[Clinicopathological significance of homeobox gene BP1 mRNA expression in human breast cancer].

BACKGROUND & OBJECTIVE: Beta protein 1 (BP1) gene, a novel member of DLX homeobox gene family, is located in 17q21-22 region and overexpressed in both acute myeloid leukemia and acute T cell lymphocytic leukemia. However, the reports on the function of BP1 in solid tumors are rare. The study was designed to determine the expression of BP1 gene in breast cancer and to analyze its relationship with various clinicopathological factors. METHODS: With beta-actin gene as a reference, BP1 mRNA expression was detected in 82 breast cancer tissues and 12 near adjacent tissues and 10 far adjacent tissues using reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: The expression rates of BP1 in near and far adjacent tissues were 16.67% (2/12) and 0% (0/10), respectively; while the expression rate in breast cancer group was 64.63% (53/82). There were statistically significant differences among the three groups (P< 0.05). Overexpression of BP1 in breast cancer was correlated with histological grade (P< 0.05). Nevertheless, no correlation was found between BP1 expression and other clinicopathological factors, including tumor size, lymph nodal metastasis, family history, pathological type, menarcheal age, primiparous age, number of pregnancy, menopausal status, ER status and PR status (P >0.05). CONCLUSION: BP1 gene is of upregulated expression in breast tumors and could be regarded as a new and vital biomarker in breast cancer research.

Adult↗