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Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 1,225 records · Page 68Linked to original sources
PubMed1994

[Influence exerted by environmental and physicochemical factors on the results of sex identification of human dental pulp by polymerase chain reaction].

Sex identification of human tooth is an important aspect of individual identification in forensic science practice. This study was designed to determine the effects of environmental and physicochemical factors (EPF) on the deoxyribonucleic acid (DNA) from dental pulp and PCR result. Extracted teeth were subjected to the following treatment varying pH (2, 7, 10) solution; 10% formalin, 75% ethanol; different temperature (-20 degrees C, 4 degrees C, 25 degrees C, 37 degrees C, boiling, burning); humidity (20%, 66%, water submergence); burying the teeth outdoors; and aging (teeth stored at room temperature for 1.5, 3.5 and 8 years). DNA was extracted from the tooth followed by agarose gel electrophoresis for the purpose of DNA assay and quantity determination. Amplification was carried out using a pairs of primer Y1.1 and Y1.2. The results of the study showed that, 154 bp fragment was obtained in all male teeth, whereas no 154 bp fragment was found in a female fresh tooth. 154 bp fragment bands were not observed in case of teeth subjected to burial outdoors for 10 weeks, submergence in water for 10 weeks, soak in pH 2 solution for 10 weeks, and combustion for 10 minutes; only faint bands were observed in case of teeth subjected to 66% humidity and pH 10 solution for 10 weeks and combustion for 5 minutes; obvious bands were observed in the rest cases. In addition, the quality of DNA from dental pulp affected PCR amplification result. The integrity of DNA isolated was categorized as being high-molecular-weight (HMW), HMW with partial degraded DNA, completely degraded DNA, completely degraded and not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1994

[Clinicopathologic and immunohistochemical studies of midline malignant reticulosis in palate].

Fourteen patients (10 males and 4 females) with midline malignant reticulosis (MMR) in palate were studied. The symptoms were most commonly swelling and ulceration. In some cases, the lesion involved nasal, maxillary sinus and facial skin, but no regional lymph nodes were involved. A necrotizing infiltration of atypical lymphoid cells (ALCs) mixed with inflammatory cells was confirmed as the histopathologic feature of MMR. In 2 of 14 cases, ALCs formed a continuous sheet in several high-power fields with a few inflammatory cells. This overlapping feature may be a transitional form between MMR and malignant lymphoma. Immunohistochemical staining results indicated that in 10 of 14 cases, ALCs were CD3 positive; in 7 of 14 cases, ALCs were UCHL1 positive; and in all 14 cases, ALCs were L26 negative. We deem MMR a T-cell lymphoma in substance, but it should be treated as a histopathologic entity distinct from malignant lymphoma.

Adult↗
PubMed1994

Intrasplenic transplantation of isolated periportal and perivenous hepatocytes as a long-term system for study of liver-specific gene expression.

Many hepatocyte-specific genes are expressed heterogeneously in the liver lobule depending on the location of the hepatocytes in relation to the inflow or outflow of portal blood (i.e., periportal or perivenous). For example, albumin is expressed in all hepatocytes but more so in the periportal zone, cytochrome P-450IIE1 is exclusively expressed in the perivenous zone and glutamine synthetase is limited to one or two cell layers next to the terminal hepatic venule. Additionally, hepatic damage caused by several xenobiotics, including carbon tetrachloride, is more severe in the perivenous zone. We have isolated highly enriched perivenous and periportal hepatocytes by means of a digitonin-collagenase perfusion method and transplanted them separately into the spleens of syngeneic rats. After transplantation, hepatocyte-specific gene expression in the transplanted perivenous and periportal cells was monitored for up to 13 mo with in situ hybridization to detect the specific gene transcripts (mRNAs). We also studied the effects of carbon tetrachloride administration on transplanted periportal cells by comparing them with intrasplenic transplanted periportal hepatocytes without carbon tetrachloride treatment. Our results showed that: (a) both transplanted perivenous and periportal hepatocytes could survive and proliferate in the splenic microenvironment for a prolonged period; (b) long-term-transplanted periportal hepatocytes in spleen could eventually express a high level of cytochrome P-450IIE1 mRNA in all transplanted hepatocytes and could express glutamine synthetase mRNA in only about 5% to 10% of them, specifically those hepatocytes located adjacent to splenic blood vessels. It is noteworthy that periportal hepatocytes in situ normally do not express the glutamine synthetase gene and express only a low level of cytochrome P-450IIE1 mRNA; and (c) carbon tetrachloride yielded different toxic effects on transplanted periportal hepatocytes at day 3 and mo 8. Necrosis was seen only when transplanted periportal hepatocytes expressed a high level of cytochrome P-450IIE1 mRNA by mo 8.

Albumins↗
PubMed1994

A case of demyelinating disease with clinical and radiological features mimicking cerebral tumor.

Demyelinating disease may present with clinical and radiological features mimicking brain tumor. A 43-year-old man was admitted because of progressive right hemiparesis, facial weakness and dysarthria. Computed tomographic scans revealed two expansive lesions in the left frontal lobe and midbrain, respectively. A brain tumor or metastatic lesion was suspected. The patient underwent left frontal craniotomy and the surgical biopsy revealed a demyelinating process. The patient, however, had a poor response to steroid treatment and died two months later. The possible nature of demyelinating disease in this case is discussed.

Adult↗
PubMed1994

Poor perinatal outcome associated with retained cerclage in patients with premature rupture of membranes.

OBJECTIVE: To evaluate the role of immediate cerclage removal versus retention in patients experiencing premature rupture of the membranes remote from term (PROM). METHODS: Thirty patients with prophylactic cerclage experiencing PROM at 24-32 weeks were managed expectantly after either immediate removal in 20 (67%) or retention of the cerclage in ten (33%). Thirty-three patients without cerclage and with PROM at the same gestational age were used as controls. RESULTS: More patients with retained cerclage (nine of ten, 90%) had delivery delayed for at least 48 hours after PROM compared to patients with immediate cerclage removal (ten of 20, 50%) (P < .05). Perinatal mortality was significantly higher for those with retained cerclage (seven of ten, 70%) than with immediate removal (two of 20, 10%) or in the control group (six of 33, 18%) (P < .001). Sepsis was responsible for most of the poor outcomes in the retained-cerclage group (71%). CONCLUSIONS: Although retaining the cerclage prolonged the latency period between PROM and delivery, that benefit was more than offset by a greatly increased perinatal mortality rate. Our study supports immediate cerclage removal regardless of gestational age in cases of PROM.

Adult↗
PubMed1994

The detection and analysis of ventricular late potentials.

This paper introduces a ventricular late potentials (VLP) detecting and analyzing system and discusses the technique of detecting reference point used to align the QRS and the method for calculating diagnostic parameters. The AMDF algorithm fasts the correlation process. In order to eliminate analytical error, bidirectional digital filter is adopted.

Algorithms↗
PubMed1994

Apolipoprotein B synthesis: a square lattice model.

We have formulated a random walk model for emerging apolipoprotein B interaction with its translocation channel on the surface of the rough endoplasmic reticulum based on the assumption that this interaction is a diffusion-mediated process. From this model, we found that a substantial proportion of mRNA-ribosome complexes was not bound to their translocation channels at any given moment of quasi-steady state. The duration of polypeptide chain elongation was an important determinant of the number of mRNA-ribosome complexes bound to their channels, but it had little net effect on the integrated rate of protein synthesis and translocation. The rates of protein synthesis and translocation for different secretory proteins that were cotranslationally translocated were very similar provided that they had similar mRNA concentration. We conclude that one of the control mechanisms regulating apolipoprotein B production may rely on the properties of translocation channels to determine the fate of newly synthesized apolipoprotein B molecules.

Animals↗
PubMed1994

Modulation of hematopoiesis by lymphocyte membrane-derived components.

Membrane bound erythroid burst-promoting activity (mBPA) is an integral membrane protein that is present on normal B-cells and some activated T-cells, that induces burst-forming units-erythroid (BFU-E) when cultured with human erythropoietin (rHuEpo). Plasma membranes and vesicles shed from the leukemic A-1 cell line express mBPA. This activity derived from both A-1 cells and normal B-cells can be immunoadsorbed by the D3A4 antibody raised against mBPA. In this study, we demonstrate that interferon-gamma (IFN-gamma) suppresses BFU-E proliferation when added directly to culture of normal human bone marrow cells and in the absence and presence of A-1 cells. However, FACS analysis reveals that IFN-gamma enhances the surface expression of mBPA on A-1 cells. The role of IFN-gamma in modulating erythropoiesis in vitro is discussed with respect to the role of shedding membrane-derived vesicles from the B-cell surface.

Cells, Cultured↗
PubMed1994

Ultrasonically-guided needle aspiration with preparation of cell blocks in the diagnosis of liver tumors.

To evaluate the diagnostic value of a method combining ultrasonically-guided Chiba needle aspiration and histological block preparation of aspiration specimen, 50 consecutive patients with histologically confirmed focal or diffuse lesion of the liver were studied. In addition to conventional aspiration cytology, the aspiration specimen was mixed 1:1 by volume with 95% alcohol and centrifuged. The precipitated specimen was then embedded in paraplast. Serial sections were obtained and stained with hematoxylin and eosin (H & E) technique. The diagnostic specificity and positive predictive value of the cell block technique in diagnosing hepatic malignancies were both 100%, as was those of aspiration cytology. The diagnostic sensitivity and overall accuracy of cell blocks were significantly better than those of aspiration cytology (89.5% vs. 63.2%, P < 0.01; and 92.0% vs. 72.0%, P < 0.01). The negative predictive value of cell blocks was also better than that of aspiration cytology, but the difference was not statistically significant (75.0% vs. 46.2%, P > 0.05). In terms of cellular differentiation, the accuracy of the diagnosis of cell blocks was 78.6% (22/28) in hepatoma; 80.0% (4/5) in metastatic adenocarcinoma and 100.0% (1/1) in small cell carcinoma. No complications were encountered in any of the patients. The results suggest that the preparation of cell blocks of the aspiration specimen is a reliable and accurate method for the diagnosis of hepatic malignancies. This method also elevates the diagnosis of the aspiration specimen from the cytological to the histopathological level.

Adult↗
PubMed1994

Gallbladder adenocarcinoma with gallstone and calcified ova of clonorchis sinensis--a case report.

A case of gallbladder adenocarcinoma with gallstone and calcified parasitic ova of Clonorchis sinensis was described. The patient, a 58-year-old Chinese woman, presented with general malaise and jaundice. The gallbladder contained 3 stones in addition to the cancerous lesion. Microscopically, we saw calcified parasitic ova of Clonorchis sinensis associated with the stones. The relationships between Clonorchis sinensis, stones and adenocarcinoma were discussed.

Adenocarcinoma↗
PubMed1994

Extension of synaptic extracellular matrix during nerve terminal sprouting in living frog neuromuscular junctions.

Remodeling of the synaptic extracellular matrix (ECM) and its dynamic relationship with nerve terminal plasticity have been demonstrated in normal frog neuromuscular junctions (NMJs) in vivo (Chen et al., 1991). Our previous work has led to a hypothesis that extension of synaptic ECM precedes nerve terminal growth during synaptic remodeling. To test this hypothesis, the present study examined the changes of synaptic ECM in frog NMJs that were primarily undergoing nerve terminal growth and sprouting. Frog sartorius muscles were double stained with a fluorescent nerve terminal dye (4-Di-2-Asp) and rhodamine-tagged peanut agglutinin (PNA), which recognizes synaptic ECM. The double-labeled NMJs were visualized in vivo with video-enhanced fluorescence microscopy. Nerve sprouting was then induced in the muscle by grafting segments of the contralateral sciatic nerve. The identified NMJs were restrained and reexamined 2-3 months later. Extensive sprouting was observed in 46% of 167 identified NMJs. At junctional regions that showed extension or formation of new branches, synaptic ECM was commonly seen to have the same shape and distribution as the nerve terminal. However, extension of synaptic ECM beyond the corresponding nerve terminals, often by tens of microns, was observed in 29% of these newly formed junctional regions. This lack of correlation might be transient, as growth of nerve terminals following extended, PNA-stained ECM was seen. Examination with histological staining not only confirmed a lack of nerve terminal at the extended synaptic ECM region but also indicated an absence of AChE and postsynaptic junctional folds. The absence of these postsynaptic specializations at the extended, PNA-stained ECM region makes it unlikely that this region was previously occupied by nerve terminals that had retracted. Thus, the present study provides further findings consistent with the hypothesis that synaptic ECM precedes nerve terminal outgrowth and that the extension of synaptic ECM may play a role in synaptic remodeling.

Animals↗
PubMed1993

Crystallization and preliminary X-ray analysis of (1,3)- and (1,3;1,4)-beta-D-glucanases from germinating barley.

(1,3)-beta-D-Glucanase isoenzyme GII and (1,3;1,4)-beta-D-glucanase isoenzyme EII from barley have been crystallized by the hanging drop method in the presence of ammonium sulphate. The crystals of the (1,3)-beta-D-glucanase, which diffract to about 1.8 A resolution, belong to the trigonal space group P3(1)2(1)2 (or P3(2)2(1)2) with cell constants a = b = 86.9 A, c = 156.0 A and contain two molecules in the asymmetric unit. The crystals of the (1,3;1,4)-beta-D-glucanase which diffract to better than 1.8 A resolution, belong to the tetragonal space group P4(3)2(1)2 (or P4(1)2(1)2) with cell constants a = b = 87.4 A, c = 109.5 A and contain one molecule in the asymmetric unit.

Crystallization↗
PubMed1993

Aerobic metabolism of carbon reserves by the "obligate anaerobe" Desulfovibrio gigas.

The sulfate-reducing bacterium, Desulfovibrio gigas, is shown by in vivo 31P-NMR to be capable of generating NTP from the utilization of internal carbon reserves both in anaerobic and in aerobic conditions. Acetate, glycerol and ethanol are the major end-products, but the production of alcohols decreases strongly when oxygen is present. When the glycolytic pathway is inhibited with fluoride, NTP levels decrease drastically but can be remarkably restored when an electron acceptor, such as oxygen, is provided. Our data are in favour of a NADH-linked electron transfer chain enabling transfer of reducing power derived from polyglucose to oxygen which provides this so-called "strict anaerobe" with the capability of surviving to oxic environments.

Acetates↗
PubMed1993

Purification and characterization of an NADH-rubredoxin oxidoreductase involved in the utilization of oxygen by Desulfovibrio gigas.

An NADH--rubredoxin oxidoreductase previously isolated from Desulfovibrio gigas [LeGall, J. (1968) Ann. Inst. Pasteur 114, 109-115] has now been fully purified and further characterized. It contains two subunits of 27 kDa and 32 kDa. With two mid-point redox potentials of -295 mV and -325 mV, this FMN- and FAD-containing protein can induce the specific reduction of D. gigas rubredoxin. In contrast, rubredoxins from the other Desulfovibrio species or desulforedoxin from D. gigas show very low reaction rates with the same enzyme. The phylogenetic significance of the narrow specificity of the enzyme toward the rubredoxin from the same organism is discussed. The purified enzyme has NADH oxidase activity with H2O2 as a final product of O2 reduction. The reaction is half-inhibited by 4.2 microM p-chloromercuribenzoate, whereas cyanide and azide are not significant inhibitors in this reaction. The role of this protein as a part of the enzymic equipment that allows the formation of ATP in the presence of oxygen from the degradation of carbon reserves is discussed.

Chloromercuribenzoates↗
PubMed1993

Cloning a plant amino acid transporter by functional complementation of a yeast amino acid transport mutant.

Amino acids are transported across the plasma membrane of plant cells by proton-amino acid symports. We report here the successful cloning of a neutral amino acid carrier by functional complementation. A histidine transport deletion mutant of Saccharomyces cerevisiae was transformed with an Arabidopsis thaliana cDNA library constructed in a yeast expression vector. Forty transformants, out of 10(5), allowed growth on a histidine-limiting medium. The acquired ability to grow on low histidine was shown to be strictly dependent on the protein encoded by the expression plasmid. Histidine and alanine transport activity were 10- to 20-fold greater in the transformants. The transport kinetics, inhibitor sensitivity, and substrate specificity match those of neutral system II, a neutral amino acid carrier we previously described in plasma membrane vesicles isolated from leaf tissue. The cDNA insert is 1.7 kb with an open reading frame that codes for a protein containing 486 amino acids with a calculated molecular mass of 52.9 kDa and three sites of potential N-linked glycosylation. Hydropathy analysis of the deduced amino acid sequence suggests this is an integral membrane protein with 10-12 membrane-spanning alpha-helices. Overall, the sequence of this amino acid carrier is not closely related to any other protein sequences in the GenBank data base. Interestingly, however, there are small regions of sequence that exhibit significant levels of similarity with at least seven other integral membrane proteins.

Alanine↗