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Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 19 recordsLinked to original sources
PubMed2003

Prediction of response to incision using the mutual information of electroencephalograms during anaesthesia.

This paper presents a new approach to predict response during isoflurane anaesthesia by using mutual information (MI) time series of electroencephalograms (EEGs) and their complexity analysis. The MI between four lead electrodes was first computed using the EEG time series. The Lempel-Ziv complexity measures, C(n)s, were extracted from the MI time series. Prediction was made by means of artificial neural network (ANN). From 98 consenting patient experiments, 98 distinct EEG recordings were collected prior to incision during isoflurane anaesthesia of different levels. During and after skin incision, each patient was observed carefully for 2 min to detect subsequent responses (purposeful movement, changes in hemodynamic parameters and respiratory pattern) and then the EEG was labelled as 0.0 for responder or as 1.0 for non-responder. Training and testing the ANN used the 'drop-one-patient' method. The prediction was tested by monitoring the response to incision and the result given by the ANN. The system was able to correctly classify purposeful response in average accuracy of 91.84% of the cases. The results showed that the method has a better performance than other methods, such as spectral edge frequency, median frequency, and bispectral analysis. This method is computationally fast and acceptable real-time clinical performance was obtained.

Adult↗
PubMed2003

Hepatocyte growth factor and c-Met (HGF/c-Met) in adenoid cystic carcinoma of the human salivary gland.

BACKGROUND: Hepatocyte growth factor (HGF) enhances cell growth, morphogenesis, and scattering of various epithelial cells. The aim of this study was to evaluate the hypothesis that HGF/c-Met plays a biological role in the invasive growth of adenoid cystic carcinoma (ACC). METHODS: Immunohistochemically, expression of HGF and its receptor c-Met was examined in 15 cases of ACC. To examine the direct effects of HGF on ACC, cell line derived from of ACC (ACC3) was used. The expression of HGF and c-met in ACC3 was investigated by RT-PCR. Analysis of mechanisms of invasion was done by performing scattering assay and matrigel invasion chamber assay. RESULTS: Positive staining of HGF was found in all cases, and that of c-Met was 67%. In ACC3, c-met was expressed, but not HGF. Stimulation of ACC3 by rhHGF induced scattering and promoted invasion. CONCLUSION: The present results suggest that HGF/c-Met increases tumor cell scattering and may play a part in invasiveness of ACC.

Carcinoma, Adenoid Cystic↗
PubMed2003

Restricted neuronal expression of ubiquitous mitochondrial creatine kinase: changing patterns in development and with increased activity.

Whereas ATP consumption increases with neural activity and is buffered by phosphocreatine (PCr), it is not known whether PCr synthesis by ubiquitous mitochondrial creatine kinase (uMtCK) supports energy metabolism in all neurons. To explore the possibility that uMtCK expression in neurons is modulated by activity and during development, we used immunocytochemistry to detect uMtCK-containing mitochondria. In the adult brain, subsets of neurons including layer Va pyramidal cells, most thalamic nuclei, cerebellar Purkinje cells, olfactory mitral cells and hippocampal interneurons strongly express uMtCK. uMtCK is transiently expressed by a larger group of neurons at birth. Neurons in all cortical layers express uMtCK at birth (P0), but uMtCK is restricted to layer Va by P12. uMtCK is detected in cerebellar Purkinje cells at birth, but localization to dendrites is only observed after P5 and is maximal on P14. Hippocampal CA1 and CA3 pyramidal neurons contain uMtCK-positive mitochondria at birth, but this pattern becomes progressively restricted to interneurons. Seizures induced uMtCK expression in cortical layers II-III and CA1 pyramidal neurons. In the cortex, but not in CA1, blockade of seizures prevented the induction of uMtCK. These findings support the concept that uMtCK expression in neurons is (1) developmentally regulated in post-natal life, (2) constitutively restricted in the adult brain, and (3) regulated by activity in the cortex and hippocampus. This implies that mitochondrial synthesis of PCr is restricted to those neurons that express uMtCK and may contribute to protect these cells during periods of increased energy demands.

Adenosine Triphosphate↗
PubMed2002

Laparoscopic radiofrequency ablation and hepatic artery infusion pump placement in the evolving treatment of colorectal hepatic metastases.

BACKGROUND: Laparoscopic radiofrequency ablation (LRFA) and laparoscopic hepatic artery infusion pump (LHAIP) placement are new treatment options for patients with colorectal liver metastases. This study investigates the selection criteria, safety, efficacy, and preliminary outcomes of patients treated with LRFA and LHAIP placement. METHODS: Fourty five patients with colorectal metastases confined to the liver, 37 of whom had failed systemic chemotherapy, were treated with LRFA and/or LHAIP between September 1996 and December 2001. Treatment selection was individualized, based on each patient's general health, liver function, and tumor size, number, location, and distribution. RESULTS: Twenty patients (44%) had LRFA alone, 10 (22%) had LHAIP placement alone, and 15 (33%) patients had combined LRFA and LHAIP therapy. The LRFA group had a significantly shorter mean operative time and blood loss (p <0.05), but hospital stays were similar when compared to patients receiving LRFA + LHAIP or LHAIP alone. Tumor characteristics were worse in both LHAIP groups, with a higher incidence of tumors >or=4 cm, major vascular involvement, diffuse tumor pattern, bilobar distribution, and involvement of more than three segments. During a mean follow-up period of 11.5 +/- 7.8 months (range, 1-38), the actuarial survival was 70%, 67%, and 50% for LRFA, LRFA + LHAIP, and LHAIP, respectively. LHAIP only patients had the shortest estimated mean survival time of the three groups by Kaplan-Meier survival curves (p = 0.001). CONCLUSION: LRFA and/or LHAIP placement are safe and feasible treatment options for the treatment of colorectal hepatic metastases. The choice of treatment for patients should be based primarily on tumor characteristics. Long-term studies, which will elucidate the role of these evolving treatments, are now under way.

Adult↗
PubMed2002

Differential distribution of interneurons in the neural networks that control walking in the mudpuppy (Necturus maculatus) spinal cord.

Locomotor behavior is believed to be produced by interneuronal networks that are intrinsically organized to generate the underlying complex spatiotemporal patterns. In order to study the temporal correlation between the firing of individual interneurons and the pattern of locomotion, we utilized the spinal cord-forelimb preparation from the mudpuppy, in which electrophysiological recordings of neuronal activity were achieved during walking-like movement of the forelimb induced by bath application of N-methyl- D-aspartate (NMDA). Intra- and extracellular recordings were made in the C2 and C3 segments of the spinal cord. These segments contain independent flexor and extensor centers for the forelimb movement about the elbow joint during walking. Among the 289 cells recorded in the intermediate gray matter (an area between the ventral and dorsal horns) of the C2 and C3 segments, approximately 40% of the cells fired rhythmically during "walking." The firing rates were 6.4+/-0.4 impulses/s (mean +/- SE). These rhythmically active cells were classified into four types based on their phase of activity during a normalized step cycle. About half the rhythmic cells fired in phase with either the flexor (F) or extensor (E) motoneurons. The rest fired in the transitions between the two phases (F-->E and E-->F). Longitudinal distributions of the four types of interneurons along the spinal cord were in agreement with observations that revealed distinct but overlapping flexor and extensor centers for walking. Some cells triggered short-latency responses in the elbow flexor or extensor muscles and may be last-order interneurons. These observations suggest that there is a differential distribution of phase-specific interneurons in the central pattern generator of the mudpuppy spinal cord for walking.

Action Potentials↗
PubMed2002

Initial study of using a laminar fluid diffusion interface for sample preparation in high-performance liquid chromatography.

This report describes a new microfluidic device called the H Filter for sample preparation prior to HPLC. The H Filters make possible a diffusional transfer of an analyte from a sample stream into a stream of a "receiver" fluid. Existing mathematical models can be used for optimizing experimental conditions. The authors have selected the extraction of the antibiotic cephradine from blood to demonstrate the utility of the new device. The extracts of blood samples spiked with cephradine levels between 0.2 and 100 microg/ml were analyzed using a C8 reversed-phase column and UV detection at 260 nm. The HPLC results were in good agreement with theory. The recovery of 32.2+/-2.8% was uniform over the entire range of cephradine concentrations. The new method completely avoids the use of centrifuges, that is otherwise typical for most current methodologies for the preparation of blood samples prior to HPLC analysis.

Cephradine↗
PubMed2002

Body surface Laplacian mapping of atrial depolarization in healthy human subjects.

In the present study, we report body surface Laplacian mapping of atrial depolarization under sinus rhythm in 8 healthy male subjects. For each subject, 95 unipolar disk electrodes with inter-electrode distance of 2 cm were used to record simultaneously potential ECGs over the anterior chest. The Laplacian ECG was then estimated during the P wave using a novel spline Laplacian technique. The body surface potential map (BSPM) and body surface Laplacian map (BSLM) at different time instants or time intervals of the P wave were constructed and compared. The present results showed that the BSPMs during the P wave were characterized by the rotation of a pair of positive/negative potential distribution from right to left around the anterior torso. On the other hand, the corresponding BSLMs revealed more spatial details, including two positive activities (denoted as P1 and P2, appeared in all 8 subjects), and three negative activities (denoted as N1, N2, and N3, appeared in 7, 7, and 4 subjects, respectively). The separation of these activities and their evolving patterns were also compared and confirmed by computer simulation using a realistic geometry heart-torso model. The above findings may be directly related to the underlying activation sequence during atrial depolarization in healthy subjects, suggesting the potential clinical applications of the Laplacian ECG technique.

Adult↗
PubMed2002

Kindling induces the mRNA expression of methyl DNA-binding factors in the adult rat hippocampus.

We have investigated the gene expression responses of a family of methyl CpG-binding domain-containing factors (MeCP2, MBD1, MBD2, and MBD3) in the hippocampus of electrically kindled rats. Expression was examined in both amygdala- and partial perforant-pathway-kindled subjects, 24 h and 28 days following the final stimulation. In general, the responses of MBDs 2 and 3 paralleled each another, both temporally and spatially. The expression of both genes was significantly elevated in all hippocampal subfields at 24 h following either the fifth stage 5 seizure (amygdala kindling) or the 15th stimulation of the perforant pathway. This induced expression was transient, however, as the expression of both genes returned to control levels by 28 days. This pattern of response contrasted to that observed for MeCP2 and MBD1. MeCP2 displayed no change in expression either 24 h or 28 days after amygdala kindling, but did display a late-developing, significant increase in expression in the dentate gyrus at 28 days following perforant-pathway kindling. The expression of MBD1 was unchanged by partial perforant-pathway kindling, but was induced in the dentate gyrus 28 days after amygdala kindling. These results demonstrate that electrical kindling alters the hippocampal expression of methyl DNA-binding factors, but does not affect each factor equivalently. The responsive patterns observed suggest that this family of transcriptional regulators can be differentially altered in the hippocampus by seizure activity.

Amygdala↗
PubMed2002

Promotion of xenogeneic hematopoietic chimerism in rodents by mononuclear phagocyte depletion.

The successful establishment of tolerance toward pig tissues in primates through hematopoietic progenitor cell engraftment is restricted by the rapid disappearance of these cells in the recipient following infusion. We developed and tested the hypothesis that phagocytes of the reticuloendothelial system are responsible for the rapid clearance of infused pig hematopoietic cells using a mouse model. Mice received non-myeloablative conditioning and, on various days, were injected with medronate-encapsulated liposomes (M-L) or control blank liposomes, followed by the intravenous infusion of miniature swine hematopoietic cells. M-L were well-tolerated in mice (n=100) at levels that deplete mononuclear phagocytes. Depletion of mononuclear phagocytes in normal Balb/c mice as well as in severe combined immune deficient mice increased the accumulation of pig hematopoietic cells in the bone marrow (BM) by 10-fold when measured 24 h after the infusion of the cells. Colony-forming unit analysis showed an increased accumulation of pig hematopoietic progenitors in the BM of mice that were infused with medronate-liposomes. We conclude that depletion of mononuclear phagocytes by M-L has the potential to lower the barrier to the establishment of mixed chimerism and tolerance induction in xenotransplantation.

Animals↗
PubMed2001

A targeted dominant negative mutation of the thyroid hormone alpha 1 receptor causes increased mortality, infertility, and dwarfism in mice.

Mutations in the thyroid hormone receptor beta (TRbeta) gene result in resistance to thyroid hormone. However, it is unknown whether mutations in the TRalpha gene could lead to a similar disease. To address this question, we prepared mutant mice by targeting mutant thyroid hormone receptor kindred PV (PV) mutation to the TRalpha gene locus by means of homologous recombination (TRalpha1PV mice). The PV mutation was derived from a patient with severe resistance to thyroid hormone that has a frameshift of the C-terminal 14 aa of TRbeta1. We knocked in the same PV mutation to the corresponding TRalpha gene locus to compare the phenotypes of TRalpha1(PV/+) mice with those of TRbeta(PV/+) mice. TRalpha1(PV/+) mice were viable, indicating that the mutation of the TRalpha gene is not embryonic lethal. In drastic contrast to the TRbeta(PV/+) mice, which do not exhibit a growth abnormality, TRalpha1(PV/+) mice were dwarfs. These dwarfs exhibited increased mortality and reduced fertility. In contrast to TRbeta(PV/+) mice, which have a hyperactive thyroid, TRalpha1(PV/+) mice exhibited mild thyroid failure. The in vivo pattern of abnormal regulation of T3 target genes in TRalpha1(PV/+) mice was unique from those of TRbeta(PV/+) mice. The distinct phenotypes exhibited by TRalpha1(PV/+) and TRbeta(PV/+) mice indicate that the in vivo functions of TR mutants are isoform-dependent. The TRalpha1(PV/+) mice may be used as a tool to uncover human diseases associated with mutations in the TRalpha gene and, furthermore, to understand the molecular mechanisms by which TR isoforms exert their biological activities.

Animals↗