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Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 253 records · Page 14Linked to original sources
PubMed1998

Mechanisms of insulin resistance in experimental hyperinsulinemic dogs.

This study was undertaken to characterize the insulin resistance and the mechanism thereof caused by chronic hyperinsulinemia produced in dogs by surgically diverting the veins of the pancreas from the portal vein to the vena cava. Pancreatic venous diversion (PVD, n = 8) caused a sustained increase in arterial insulin and decrease in portal insulin concentration compared with the control group (n = 6). Hyperinsulinemic euglycemic clamps were conducted 4 wk after surgery. The increase in the glucose disposal rate (GDR) was significantly less in the PVD group (39.0+/-5.0 vs. 27.9+/-3.2 micromol/kg/min, P < 0.01) compared with the control group, but the suppression of hepatic glucose production by insulin was similar for both groups. Muscle insulin receptor tyrosine kinase activity (IR-TKA) increased from 6.2+/-0.4 to 20.3+/-2.7 in the control group, but from 5.8+/-0.5 to only 12.7+/-1.7 fmol P/fmol IR in the PVD group (P < 0.01). With respect to the periphery, the time to half-maximum response (t1/2a) for arterial insulin was the same for both groups, whereas the t1/2a for lymph insulin (30+/-3 vs. 40+/-4 min, P < 0.05) and GDR (29+/-3 vs. 66+/-10 min, P < 0.01) were greater for the PVD group. Chronic hyperinsulinemia led to marked peripheral insulin resistance characterized by decreased insulin-stimulated GDR, and impaired activation of GDR kinetics due, in part, to reduced IR-TKA. Transendothelial insulin transport was impeded and was responsible for one third of the kinetic defect in insulin-resistant animals, while slower intracellular mechanisms of GDR were responsible for the remaining two thirds.

Animals↗
PubMed1998

Fas (CD95)-transduced signal preferentially stimulates lupus peripheral T lymphocytes.

Fas (CD95) is a cell surface receptor whose biological function in circulating peripheral T cells is not well understood. To address the question of abnormal T cell sensitivity to Fas stimulation in systemic lupus erythematosus (SLE), we studied Fas-transduced stimulation and apoptosis in peripheral blood T cells from patients with SLE and normal control. Immobilized anti-Fas monoclonal antibodies (mAb) (imCH-11; IgM type) significantly stimulated SLE T cell proliferation compared to T cells from normal donors and patients with rheumatoid arthritis (p < 0.003 and p < 0.005, respectively). The soluble form of CH-11 and other immobilized anti-Fas mAb (UB-2, ZB-4; IgG type) failed to stimulate lupus T cells while immobilized human Fas ligand did. Furthermore, imCH-11 induced IL-2 and IL-6 mRNA expression. However, imCH-11 activation failed to induce expression of the T cell activation surface molecules CD25 and CD69. Addition of exogenous ceramide, a second messenger for Fas-mediated apoptosis signaling, also induced T cell proliferation in SLE and normal controls. Moreover, fumonisin B1, a specific ceramide synthase inhibitor, and caspase inhibitors markedly suppressed imCH-11 induced T cell proliferation, suggesting that the ceramide pathway may be involved in Fas-transduced stimulation signals in SLE T cells. These results show that SLE T cells have an alteration in the Fas signal transduction pathway leading to cell proliferation. This defect may be important in Fas-mediated peripheral immune homeostasis.

Adult↗
PubMed1998

High-Resolution Infrared Spectrum of H3SiI in the nu1/nu4 Region near 2200 cm-1

The Fourier transform infrared spectrum of H3SiI has been recorded in the nu1/nu4 region from 2075 to 2315 cm-1 at an optical resolution of 2.3 x 10(-3) cm-1. The nu1/nu4 fundamental bands and the (nu1 + nu3) - nu3/(nu4 + nu3) - nu3 hot bands have been rotationally investigated. Numerous local perturbations have been observed in the nu1 and nu4 bands and in the hot bands. Without the lines involved in perturbations, more than 2900 transitions of the nu1/nu4 bands were used to determine the band origins and the vibration-rotation parameters of the nu1 = 1 and nuv4 = 1 states. A least-squares fit of 766 apparently unperturbed transitions of the hot bands gave the parameters of the nu1 = nu3 = 1 and nu4 = nu3 = 1 states. The l(2, 2) resonance in nu4 and the A1-E Coriolis coupling between nu1 and nu4 have been investigated. Most of the local perturbations have been studied individually using a simple model by which the main perturber for each resonance was identified. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Intracellular transport of basement membrane-type heparan sulphate proteoglycan in adenoid cystic carcinoma cells of salivary gland origin: an immunoelectron microscopic study.

ACC3, a human adenoid cystic carcinoma cell system of salivary gland origin, is able to synthesize and secrete a large amount of basement membrane molecules in vitro. To define the ultrastructural secreting pathway of these molecules, we immunolocalized heparan sulphate proteoglycan (HSPG) in ACC3 for 7 days of culture. In the early stage of culture, the main compartments immunolabelled were rough endoplasmic reticulum (rER) and small secretory vesicles. From days 3 to 4 after plating, it was noticed that HSPG was localized in partially dilated spaces of the perinuclear, rER and Golgi cisternae and in lysosomes or those fused with multivesicular bodies and endosomes. On and after day 5, almost every Golgi apparatus showed marked dilatation of the cisternae and HSPG was immunolocalized in these dilated spaces. In the later stage of culture, autophagic vacuoles or secondary lysosomes, which were simultaneously labelled for HSPG and cathepsin D, were accumulated in the cytoplasm. HSPG deposition in the intercellular space was clearly demonstrated from day 1 and increased during the culture. The results indicate that ACC3 cells have an enhanced turnover cycle for HSPG: not only its biosynthesis but also degradation of both endogenous or exogenous HSPG. Such intracellular events may be reflected in the characteristic histology and biological behaviour of adenoid cystic carcinomas.

Biological Transport↗
PubMed1998

Neuronal excitatory properties of human immunodeficiency virus type 1 Tat protein.

Neuronal dysfunction and cell death in patients with human immunodeficiency virus type-1 (HIV-1) infection may be mediated by HIV-1 proteins and products released from infected cells. Two HIV-1 proteins, the envelope glycoprotein gp120 and nonstructural protein Tat, are neurotoxic. We have determined the neuroexcitatory properties of HIV-1 tat protein using patch-clamp recording techniques. When fmoles of Tat were applied extracellularly, it elicited dose-dependent depolarizations of human fetal neurons in culture and rat CA1 neurons in slices, both in the absence and presence of tetrodotoxin. These responses were voltage-dependent, reversed at approximately 0 mV, and were significantly increased by repetitive applications with no evidence of desensitization. That these responses to Tat were due to direct actions on neurons was supported by observations that Tat dose-dependently depolarized outside-out patches excised from cultured human neurons. Removal of extracellular Ca2+ decreased the responses both in neurons and membrane patches. This is the first demonstration that an HIV-1 protein can, in the absence of accessory cells, directly excite neurons and leads us to speculate that Tat may be a causative agent in HIV-1 neurotoxicity.

Animals↗
PubMed1998

Adenosquamous carcinoma of the tongue: report of a case with histochemical, immunohistochemical, and ultrastructural study and review of the literature.

A rare case of oral adenosquamous carcinoma in a 78-year-old woman is reported. The tumor occurred in her tongue and metastasized to the submandibular and cervical lymph nodes. Histologically, the tumor showed invasive growth involving the submucosal and muscle layers. Its solid carcinomatous nests exhibited ductal differentiation in the deeper aspects and squamous differentiation toward the surface. Histochemical examination revealed an accumulation of acid mucopolysaccharide in the ductal lumina, and the ductal cells were immunohistochemically positive for carcinoembryonic antigen, epithelial membrane antigen, cancer antigen 15-3 and Ulex europaeus agglutinin I. Ultrastructurally, tonofibrils, desmosomes and numerous cytoplasmic processes were common features of the tumor cells. In addition, true glandular structures and pseudocysts were seen in areas. Clinical features of 13 adenosquamous carcinomas in the literature were analyzed.

Aged↗
PubMed1998

Preparation and hybridization analysis of DNA/RNA from E. coli on microfabricated bioelectronic chips.

Escherichia coli were separated from a mixture containing human blood cells by means of dielectrophoresis and then subjected to electronic lysis followed by proteolytic digestion on a single microfabricated bioelectronic chip. An alternating current electric field was used to direct the bacteria to 25 microlocations above individually addressable platinum microelectrodes. The platinum electrodes were 80 microns in diameter and had center-to-center spacings of 200 microns. After the isolation, the bacteria were lysed by a series of high-voltage pulses. The lysate contained a spectrum of nucleic acids including RNA, plasmid DNA, and genomic DNA. The lysate was further examined by electronically enhanced hybridization on separate bioelectronic chips. Dielectrophoretic separation of cells followed by electronic lysis and digestion on an electronically active chip may have potential as a sample preparation process for chip-based hybridization assays in an integrated DNA/RNA analysis system.

Biosensing Techniques↗
PubMed1998

Quantitative cardiac SPECT in three dimensions: validation by experimental phantom studies.

A mathematical framework for quantitative SPECT (single photon emission computed tomography) reconstruction of the heart is presented. An efficient simultaneous compensation approach to the reconstruction task is described. The implementation of the approach on a digital computer is delineated. The approach was validated by experimental data acquired from chest phantoms. The phantoms consisted of a cylindrical elliptical tank of Plexiglass, a cardiac insert made of Plexiglass, a spine insert of packed bone meal and lung inserts made of styrofoam beads alone. Water bags were added to simulate different body characteristics. Comparison between the quantitative reconstruction and the conventional FBP (filtered backprojection) method was performed. The FBP reconstruction had a poor quantitative accuracy and varied for different body configurations. Significant improvement in reconstruction accuracy by the quantitative approach was demonstrated with a moderate computing time on a currently available desktop computer. Furthermore, the quantitative reconstruction was robust for different body characteristics. Therefore, the quantitative approach has the potential for clinical use.

Body Composition↗
PubMed1998

A cepstral method for analysis of acoustic transmission characteristics of respiratory system.

The generation and transmission process of transmitted sound signals (TSS) is analyzed and a mathematical model of TSS is established in this paper. The power cepstral characteristics of TSS are studied based on the mathematical model and a new analysis method of acoustic transmission of respiratory system using homomorphic processing technique is proposed. The experimental results show that the normal respiratory system has only one formant, while the abnormal respiratory system presenting lung consolidation has two formants and the second formant plays important role in that system. This new method is a simple and effective one.

Adult↗
PubMed1998

Electroanatomical mapping and ablation of the substrate supporting intraatrial reentrant tachycardia after palliation for complex congenital heart disease.

In patients with congenital heart disease who have undergone palliative surgical interventions postoperative arrhythmias frequently complicate the clinical course. Intraatrial reentrant tachycardias (IARTs) are one of the most common forms of postoperative arrhythmias in these patients and can lead to significant morbidity and even mortality. Drug therapy and/or antitachycardia pacing have been disappointing. Ablative therapy with radiofrequency energy offers a potential for cure for these patients but the conventional approach using multielectrode recordings and fluoroscopic guidance is technically difficult and provides limited success. Recent development of a novel nonfluoroscopic technology with electroanatomical mapping using the CARTO mapping/ablation system has shown promising results in defining the arrhythmia circuit, facilitating diagnosis, and guiding ablative therapy. Based on our preliminary experience, a systematic approach to postoperative IART using electroanatomical mapping is described. Further studies are needed to fully evaluate the impact of this new technology on the management and therapy of IART.

Adult↗
PubMed1998

Spindle cell carcinoma of the gingiva: report of an autopsy case.

An autopsied case of an 80-year-old man with spindle cell carcinoma of the gingiva is reported. The tumor was polypoid and mostly composed of a sarcomatous proliferation of spindle cells with a small focus of squamous cell carcinoma at the stalk portion. The carcinoma metastasized to a cervical lymph node, lungs and pleura with extension to the diaphragm. In the metastatic lymph node, the squamous cell component was more prominent than the spindle cell one, while only anaplastic pleomorphic carcinoma cells were found in the lungs. The spindle or anaplastic cells were immunohistochemically positive for vimentin and carcinoembryonic antigen (CEA) but not for other epithelial antigens. We have concluded that the sarcomatoid component arose from the oral squamous cell carcinoma by a metaplastic process. This is the first case report of an oral spindle cell carcinoma examined by autopsy.

Aged↗
PubMed1998

Regional differences in the cellular immune response to experimental cutaneous or visceral infection with Leishmania donovani.

Infection with the protozoan Leishmania donovani can cause serious visceral disease or subclinical infection in humans. To better understand the pathogenesis of this dichotomy, we have investigated the host cellular immune response to cutaneous or visceral infection in a murine model. Mice infected in the skin developed no detectable visceral parasitism, whereas intravenous inoculation resulted in hepatosplenomegaly and an increasing visceral parasite burden. Spleen cells from mice with locally controlled cutaneous infection showed strong parasite-specific proliferative and gamma interferon (IFN-gamma) responses, but spleen cells from systemically infected mice were unresponsive to parasite antigens. The in situ expression of IFN-gamma, interleukin-4 (IL-4), IL-10, IL-12, and inducible nitric oxide synthase (iNOS) mRNAs was determined in the spleen, draining lymph node (LN), and cutaneous site of inoculation. There was considerably greater expression of IFN-gamma and IL-12 p40 mRNAs in the LN draining a locally controlled cutaneous infection than in the spleen following systemic infection. Similarly, there was a high level of IFN-gamma production by LN cells following subcutaneous infection but no IFN-gamma production by spleen cells following systemic infection. Splenic IL-4 expression was transiently increased early after systemic infection, but splenic IL-10 transcripts increased throughout the course of visceral infection. IL-4 and IL-10 mRNAs were also increased in the LN following cutaneous infection. iNOS mRNA was detected earlier in the LN draining a cutaneous site of infection compared to the spleen following systemic challenge. Thus, locally controlled cutaneous infection was associated with antigen-specific spleen cell responsiveness and markedly increased levels of IFN-gamma, IL-12, and iNOS mRNA in the draining LN. Progressive splenic parasitism was associated with an early IL-4 response, markedly increased IL-10 but minimal IL-12 expression, and delayed expression of iNOS.

Animals↗
PubMed1998

BIMAAPC3, a component of the Aspergillus anaphase promoting complex/cyclosome, is required for a G2 checkpoint blocking entry into mitosis in the absence of NIMA function.

Temperature sensitive (ts) nimA mutants of Aspergillus nidulans arrest at a unique point in G2 which is post activation of CDC2. Here we show that this G2 arrest is due to loss of nimA function and that it is dependent on BIMAAPC3, a component of the anaphase promoting complex/cyclosome (APC/C). Whereas nimA single mutants arrested in G2 with decondensed chromatin and interphase microtubule arrays, nimA, bimAAPC3 double mutants arrested growth with condensed chromatin and aster-like microtubule arrays. nimA, bimAAPC3 double mutants entered mitosis with kinetics similar to bimAAPC3 single mutants and wild-type cells, indicating a checkpoint-like role for BIMAAPC3 in G2. Even cells which had been depleted for NIMA protein and which contained insignificant levels of NIMA kinase activity entered mitosis on inactivation of bimAAPC3. BIMAAPC3 was present in a >25S complex containing BIMEAPC1, and bimAAPC3 mutants were sensitive to elevated CYCLIN B expression, consistent with BIMAAPC3 being a component of the APC/C. Inactivation of bimAAPC3 had little affect on the steady state levels of the B-type cyclin, NIMECyclin B. Our results indicate that BIMAAPC3, and most likely the APC/C itself, is activated in G2 in nimA mutants. We propose that APC/C activation is part of a novel, late G2 checkpoint, which responds to a defective process or structure in nimA mutants, and which prevents inappropriate entry into mitosis.

Alleles↗
PubMed1998

cDNA cloning and expression of a novel family of enzymes with calcium-independent phospholipase A2 and lysophospholipase activities.

Previous studies have suggested that activation of calcium-independent PLA2 (CaIPLA2) is an early event in cell death after hypoxic injury in proximal tubule cells. An approximately 28-kD CaIPLA2 with preferential activity toward plasmalogen phospholipids has been recently purified from rabbit kidney cortex (D. Portilla and G. Dai, J Biol Chem 271, 15,451-15,457, 1996). Their report describes the cloning of a full-length rat cDNA encoding CaIPLA2, using sequences derived from the purified rabbit kidney cortex enzyme. In addition, cDNA from rabbit kidney that encode the rabbit homologue of the enzyme and a closely related isoform were isolated. The rat cDNA is predicted to encode an approximately 24-kD protein, and each cDNA contains the sequence G-F-S-Q-G, which fits the active site consensus sequence G-X-S-X-G of carboxylesterases. Several lines of evidence (DNA sequence comparison, Southern blot analysis, and examination of the expressed sequence tag database) show that CaIPLA2 enzymes are encoded by a multigene family in rats, mice, rabbits, and humans. Northern analysis of various tissues from the rat indicated that the CaIPLA2 gene is ubiquitously expressed, with highest mRNA abundance observed in the kidney and small intestine. The rat CaIPLA2 cDNA, when expressed in a baculovirus expression system, and the purified rabbit kidney cortex protein exhibit both CaIPLA2 and lysophospholipase activities. The cloned CaIPLA2 cDNA are expected to aid in understanding the role of CaIPLA2 in cell death after hypoxic/ischemic cell injury.

Amino Acid Sequence↗
PubMed1998

Influence of dietary lysine on the utilization of zinc from zinc sulfate and a zinc-lysine complex by young pigs.

We conducted two trials (n = 144 and 96) to evaluate the response of feeding either ZnSO4 x H2O or a zinc-lysine complex (ZnLys) in combination with various lysine levels on growth performance, liver, kidney, and 10th rib Zn concentration, serum Zn humoral immune response and absorption of Zn (chromic oxide method) of young pigs. The following treatments were started after a 7-d postweaning adjustment during which all pigs were fed a common diet adequate in zinc. Diets were as follows: 1) basal 1 (B1), .8% dietary lysine without added Zn (basal contained 32 ppm Zn); 2) B1 plus 100 ppm Zn from ZnSO4; 3) B1 plus 100 ppm Zn from ZnLys, 4) basal 2 (B2), 1.1% lysine without added Zn; 5) B2 plus 100 ppm Zn from ZnSO4; 6) B2 plus 100 ppm Zn from ZnLys. In Trial 1 only, 100 ppm Zn from ZnSO4 (diet 7) or ZnLys (diet 8) was added to a .95% lysine basal diet. The basal 20% CP diet contained 9.0% corn gluten meal to lower the total lysine level. Within lysine level, all diets were made isolysinic by using crystalline lysine. Zinc sulfate, ZnLys, or lysine replaced dextrose in the basal diet. After 4 wk on test, one barrow in each pen was killed; liver, kidney, left 10th rib, and contents of the stomach, small intestine, and lower colon were removed for Zn analyses. Performance (ADG and ADFI) was only improved (P < .05) in one of the two trials when either zinc source was added to the basal diets, but performance was higher (P < .01) for pigs fed 1.1% lysine diets compared with .8% lysine diets in both trials. Serum Zn concentrations were lower (P < .001) for pigs fed both dietary lysine basal diets without added Zn. The humoral response to sheep red blood cells and ovalbumin was not influenced (P > .20) by lysine level, or Zn level and source. Pigs fed diets without added Zn had lower (P < .001) liver, kidney, and rib Zn concentrations than pigs fed diets with added Zn regardless of Zn source. Dietary lysine did not influence liver Zn, but kidney (P < .01) and rib (P < .001) Zn concentrations were lower for pigs fed the higher lysine level. Digestibility coefficients of Zn were lower in the stomach for pigs fed diets without added Zn, similar among Zn levels and sources in the small intestine, and higher in the lower colon for pigs fed the basal diets without added Zn. Lysine level and Zn source did not influence Zn absorption. The ZnSO4 and a zinc lysine complex seemed to be equally effective in promoting growth performance, zinc absorption, and tissue stores of young pigs when diets contained deficient, adequate, or slightly more than adequate levels of lysine.

Animal Nutritional Physiological Phenomena↗
PubMed1998

[A new method to repair artery injuries in extremities by phleboplasty of branched vein graft].

In order to develope a new method to overcome the difficulties in anastomosis of blood vessels with different diameter, phleboplasty was utilized at the join-point to expand the diameter of branched vein graft, with a funnel-shaped stoma formed consequently. After successfully experimented in fresh blood vessels in vitro, the method was practised clinically to repair injured arteries in extremities, with the outcome that phleboplasty of branched vein graft could enlarge the diameter by 1-1.25 times, and with satisfied effects in 3 clinic cases. So, the conclusion was that: phleboplasty of branched vein graft was a new effective and convinient method to repair injured arteries with different diameters.

Adult↗
PubMed1998

[Effects of selenium polysaccharide and sodium selenite on blood selenium concentration and liver cytochrome P450 monooxygenase system in rat].

The effects of selenium polysaccharide and sodium selenite administered by single or repetitive intraperitoneal injection (i.p.) on blood selenium concentration, the activities of liver cytochrome P450, b5 as well as NAD(P)H cytochrome C reductase, glutathione S-transferase and glutathione were studied in rats. The biological effects of selenium polysaccharide and sodium selenite were also compared. The results indicated that the blood selenium concentration was increased rapidly and reached the peak in 2 hours followed by gradual decline after selenium polysaccharide and sodium selenite were i.p. injected at a dose of Se 0.6 mg/kg. The absorption and eliminating rates of Se from sodium selenite were faster than that from selenium polysaccharide. Administration of selenium polysaccharide and sodium selenite at a dose of 0.2 mg/kg by i.p. increased the blood selenium concentration to 2.6 and 2.1 times of those of control group, respectively, and the blood selenium concentration of selenium polysaccharide group was significantly higher than that of sodium selenite group (P < 0.05). The activities of liver cytochrome P450, b5 and GST were inhibited by selenium polysaccharide and sodium selenium in vivo and in vitro experiments. Those proteins were decreased to 57%, 70% and 62% of the control, respectively, by selenium polysaccharide which has particularly stronger effects on cytochrome P-450 monooxygenase system (P < 0.05). The two selenium compounds did not appear to affect the activity of NAD(P)H cytochrome C reductase. Both of the selenium polysaccharide and sodium selenite could enhance the activity of glutathion peroxidase significantly (P < 0.05).

Animals↗