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Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 235 records · Page 13Linked to original sources
PubMed1999

[Knowing from experience of surgical treatment to 27 cases of facial nerve injures].

OBJECTIVE: In order to investigate the elements which affect operative treatment effect to patients with facial nerve injuries. METHOD: 27 postoperative cases with facial nerve injures were analyzed. RESULT: The results showed that the effect of treatments was more satisfactory when age was younger, the timing of operation was earlier, operative approach was right, facial nerve injury was mild, or lesion position was lower. The effect of postoperation reached House I-II degree in 21 patients (21/27), House III-IV degree in 6 patients. CONCLUSION: According to different causes of facial nerve injuries, the keys to efficient treatment are confirming of injury range, selecting of operative approach, probing into damages completely in case of missing lesion.

Adolescent↗
PubMed1999

[Image displacement elimination method in tomosynthesis].

Computerized Tomography needs projected images from all directions, tomosynthesis doesn't need the information from all directions, but its reconstruction image is indistinct. In this paper, we introduce Frequency Domain Deconvolution Imaging(FDDI) which proposed recently. FDDI overcomes shortcoming of tomosynthesis, but FDDI's calculation is large, and its zero frequency will lose. We propose a new method-image displacement elimination method(IDEM), it overcome shortcomings of FDDI and can solve convolution equation set in space domain quickly.

Algorithms↗
PubMed1999

[New parameter of liver ulitasonic tissue characterization--multi-fractal spectrum].

Based on the previous research about the feature of liver ultrasonic images, this paper presents a new analysis method of multifractal spectrum alpha-f(alpha). Using a series of partition Hausdorff dimension f(q) this paper describes the sophisticated fractal characteristics of the ultrasonic images in the different section of the growing process and the multi-fractal spectrum alpha-f(alpha) acts as the new parameter of the ultrasonic issue characterization. Using the neural network it has catalogued and recognized the tissue diseases, caring out ultrasonic tissue characterization. Apparently, this method has practical significance.

Algorithms↗
PubMed1999

[Determination of potassium, calcium, manganese, chromium and cadmium in 10 kinds of (tobacco) cigarettes by flame atomic absorption spectrophotometer].

We used the flame atomic absorption spectrophometer to determine the contents of potassium,calcium,manganese, chromium and cadmium in 10 kinds of (tobacco) cigarettes. The results showed that there were different contents of five kinds of metals in different cigarettes, providing useful data for plant and dryness of tobacco as well as the reduction of harm of smoking to human body.

Cadmium↗
PubMed1999

[Determination of 11 metal elements in niuhuang jiangya wan by atomic absorption spectrophotometer].

Eleven metal elements in niuhuang jiangya wan, including sodium, calcium, magnesium, potassium, iron, chromium, manganese, nickel, cadmium, copper and zinc, were determined by flame atomic absorption spectrophotometer. The results showed that there are rich metal elements in niuhuang jiangya wan and provided useful data for discussing the relation between trace elemtnts in niuhuang jiangya wan and cure for high blood pressure.

Drugs, Chinese Herbal↗
PubMed1998

Electrogenic antiport activities of the Gram-positive Tet proteins include a Na+(K+)/K+ mode that mediates net K+ uptake.

Two Gram-positive Tet proteins, TetA(L) from Bacillus subtilis and TetK from a Staphylococcus aureus plasmid, have previously been suggested to have multiple catalytic modes and roles. These include: tetracycline (Tc)-metal/H+ antiport for both proteins (Yamaguchi, A., Shiina, Y., Fujihira, E., Sawai, T., Noguchi, N., and Sasatsu, M. (1995) FEBS Lett. 365, 193-197; Cheng, J. Guffanti, A. A., Wang, W., Krulwich, T. A., and Bechhofer, D. H. (1996) J. Bacteriol. 178, 2853-2860); Na+(K+)/H+ antiport for both proteins (Cheng et al. (1996)); and an electrical potential-dependent K+ leak mode for TetK and highly truncated segments thereof that can facilitate net K+ uptake (Guay, G. G., Tuckman, M., McNicholas, P., and Rothstein, D. M. (1993) J. Bacteriol. 175, 4927-4929). Studies of membrane vesicles from Escherichia coli expressing low levels of complete and 3'-truncated versions of tetA(L) or tetK, now show that the full-length versions of both transporters catalyze electrogenic antiport and that demonstration of electrogenicity depends upon use of a low chloride buffer for the assay. The K+ uptake mode, assayed via 86Rb+ uptake, was also catalyzed by both full-length TetA(L) and TetK. This mode does not represent a potential-dependent leak. Such a leak was not demonstrable in energized membrane vesicles. Rather, Rb+ uptake occurred in right-side-out vesicles when the intravesicular space contained either Na+ or K+ but not choline. If an outwardly directed gradient of Na+ or K+ was present, Rb+ uptake occurred without energization in vesicles from cells transformed with a plasmid containing tetA(L) or tetK but not a control plasmid. Experiments in which a comparable exchange was carried out in low chloride buffers to which oxonol was added confirmed that the exchange was electrogenic. Thus, the K+ uptake mode is proposed to be a mode of the electrogenic monovalent cation/H+ antiport activity of TetA(L) and TetK in which K+ takes the place of the external protons. Truncated TetK and TetA(L) failed to catalyze either Tc-metal/H+ or Na+/H+ antiport in energized everted vesicles. Truncated TetK, but not TetA(L), did, however, exhibit modest, electrogenic Na+(K+)/Rb+ exchange as well as a small, potential-dependent leak of Rb+. The C-terminal halves of the TetA(L) and TetK proteins are thus required both for proton-coupled active transport activities of the multifunctional transporter and, perhaps, for minimizing cation leakiness.

Antiporters↗
PubMed1998

Octamer formation and coupling of cardiac sarcomeric mitochondrial creatine kinase are mediated by charged N-terminal residues.

Mitochondrial creatine kinases form octameric structures composed of four active and stable dimers. Octamer formation has been postulated to occur via interaction of the charged amino acids in the N-terminal peptide of the mature enzyme. We altered codons for charged amino acids in the N-terminal region of mature sarcomeric mitochondrial creatine kinase (sMtCK) to those encoding neutral amino acids. Transfection of normal sMtCK cDNA or those with the mutations R42G, E43G/H45G, and K46G into rat neonatal cardiomyocytes resulted in enzymatically active sMtCK expression in all. After hypoosmotic treatment of isolated mitochondria, mitochondrial inner membrane-associated and soluble sMtCK from the intermembranous space were measured. The R42G and E43G/H45G double mutation caused destabilization of the octameric structure of sMtCK and a profound reduction in binding of sMtCK to the inner mitochondrial membrane. The other mutant sMtCK proteins had modest reductions in binding. Creatine-stimulated respiration was markedly reduced in mitochondria isolated from cells transfected with the R42G mutant cDNA as compared with those transfected with normal sMtCK cDNA. We conclude that neutralization of charges in N-terminal peptide resulted in destabilization of octamer structure of sMtCK. Thus, charged amino acids at the N-terminal moiety of mature sMtCK are essential for octamer formation, binding of sMtCK with inner mitochondrial membrane, and coupling of sMtCK to oxidative phosphorylation.

Amino Acids, Diamino↗
PubMed1998

Movement-induced modulation of soleus H reflexes with altered length of biarticular muscles.

Passive pedaling movements of the leg results in the phasic modulation of the soleus H reflex of that leg. In contrast, the H reflex of the contralateral leg is attenuated tonically. The phasic modulation of the reflex ipsilaterally can be attributed to the afferent discharge associated with the cyclic lengthening of the extensor muscles. We hypothesized that the tonic attenuation of the contralateral reflex could be explained if the afferent feedback arising from the lengthening of the biarticular muscles had an increased importance in regulating the amplitude of the contralateral reflex. To test this, the passive pedaling movements were reduced to those about either the knee or hip alone. Despite the alteration in the pattern of stretching of the biarticular muscles, the contralateral soleus H reflex was tonically attenuated during both forms of single joint movements. We suggest that the same phasic afferent discharge responsible for the modulation of the ipsilateral soleus H reflex initiates the tonic attenuation contralaterally, but that the signal undergoes a complex transformation in crossing the cord. These results do not rule out the possibility that the stretching of the biarticular muscles contributes to the attenuation of the ipsilateral soleus H reflex, which is subsequently masked by a powerful influence from the stretching of the uniarticular extensor muscles. To test this possibility, a second experiment manipulated the lengths of the muscles of the leg by altering the positions of the static joints during isolated rotation of either the knee or hip and measuring the amplitude of the ipsilateral soleus H reflex. From the results, it was clear that stretching the uniarticular extensor muscles produced the most dramatic effects. However, the stretch of the biarticular muscles yielded mild inhibitory influences if these muscles were near their maximal lengths.

Adult↗
PubMed1998

Isolation of cultured cervical carcinoma cells mixed with peripheral blood cells on a bioelectronic chip.

The separation and subsequent isolation of the metastatic human cervical carcinoma cell line (HeLa cells) from normal human peripheral blood cells has been achieved by exploiting their differential dielectric properties. The isolation process is carried out on a silicon chip containing a five-by-five array of microlocations. These microlocations contain underlying circular platinum electrodes with 80-micron diameters and center-to-center spacing of 200 microns. The surfaces of the electrodes and nonmetallized areas have been coated with a permeation layer to prevent the direct contact of cells with the electrode and also to minimize the nonspecific adhesion of the cells to the chip surface. An inhomogenous ac field is applied to the electrodes to create the conditions for dielectrophoretic separation of cells. Cell separation using dielectrophoresis as well as electronic lysis on a silicon chip would provide essential sample-processing steps which may be combined with a later multiplex electronic hybridization step in an integrated assay system.

Blood Cells↗
PubMed1998

Identification, localization, and modulation of neural networks for walking in the mudpuppy (Necturus maculatus) spinal cord.

We tested the hypothesis that the neural networks for walking in the mudpuppy can be divided into a flexor and an extensor center, each of which contains collections of interneurons localized in the vicinity of their motoneuron pools. Combining a battery of techniques, we identified and localized the elbow flexor center and its motoneuron pool in the C2 segment and the elbow extensor center and its motoneuron pool in the C3 segment. Rhythmic flexion or extension of the limb in isolation could be induced by continuous trains of current pulses of the C2 or C3 segments, respectively. Independent activation could also occur after application of glutamate receptor agonist NMDA. Part of segment C2 in isolation generated rhythmic elbow flexor bursts, whereas part of segment C3 in isolation generated rhythmic elbow extensor bursts. An isolated region spanning the C3 roots generated both flexor and extensor bursts. The step cycle was modulated in a phase-dependent manner by stimulation of the dorsal roots, the ventral roots, or either of the two centers. The effects of ventral root stimulation were removed by deafferentation to block reafferent input attributable to muscle contraction induced by the stimulation. We conclude that the neural networks for walking contain at least a flexor and an extensor generator that are localized in close apposition to the motoneuron pools, that the two centers can work independently despite the fact that there are reciprocal inhibitory interconnections between them, and that sensory input interacts with the spinal neural networks to reset the ongoing walking rhythm in a phase-dependent manner.

Animals↗
PubMed1998

Autocrine and paracrine apoptosis are mediated by differential regulation of Fas ligand activity in two distinct Jurkat T cell populations.

Fas ligand (FasL) produced by activated T cells mediates autocrine-induced apoptosis to limit T cell expansion. To investigate the regulation of FasL activity, Jurkat cells were stably transfected with a 2.3-kb fragment of human FasL promoter that controlled the expression of a GFP reporter gene. Two populations of Jurkat cells with different levels of GFP expression were obtained. One population constitutively expressed high levels of GFP (GFP+), while the other population expressed low levels of GFP (GFP-). The level of GFP expression in the two populations correlated with their levels of FasL transcription and its functional activity. Autocrine regulation of apoptosis was demonstrated by increased FasL activity after stimulation of GFP- cells with anti-CD3, phorbyl myristyl acetate plus ionomycin, or Con A. Paracrine regulation of apoptosis was suggested by the induction of apoptosis of GFP- cells after coculture with unstimulated GFP+ cells. GFP+ cells exhibited a decreased sensitivity to FasL-mediated apoptosis compared with GFP- cells. Furthermore, the cell surface expression of Fas and CD4 was lower on GFP+ cells than GFP- cells, whereas the expression of CD45RO was higher. A decreased level of IL-2 was produced by GFP+ cells after phorbyl myristyl acetate and ionomycin stimulation. Our results indicate that a subpopulation of T cells that express low levels of FasL and IL-2, which are responsive to up-regulation of these molecules after activation, can undergo apoptosis either by suicide after activation or by a paracrine pathway mediated by T cells that constitutively express higher levels of FasL.

Apoptosis↗
PubMed1998

Acceleration of typical atrial flutter due to double-wave reentry induced by programmed electrical stimulation.

BACKGROUND: Acceleration of reentrant tachycardia induced by programmed electrical stimulation is a well-documented phenomenon, but the mechanisms remain poorly understood. METHODS AND RESULTS: Twelve patients with typical atrial flutter were studied. Activation sequence of the underlying reentrant circuit was recorded by multiple multipolar electrodes placed in the right atrium. In five patients, 27 episodes of atrial flutter acceleration were induced by single extrastimuli delivered in the isthmus between the tricuspid annulus and eustachian ridge (TA-ER isthmus) and one by rapid overdrive atrial pacing. Analyses of the activation sequences, intracardiac electrograms, and 12-lead surface ECG P-wave morphology indicated that the acceleration was caused by two successive activation wave fronts circulating in the same direction along the same reentrant circuit (double-wave reentry, DWR). DWR was induced only within a narrow range of coupling interval, from 2 to 45 ms beyond the effective refractory period, and was associated with unidirectional antidromic block of the paced impulse. Patients with DWR had a shorter effective refractory period (138.8+/-13.4 versus 163.8+/-12.2 ms, P<.015) and larger excitable gap (124.0+/-22.6 versus 83.2+/-13.2 ms, P<.009) compared with patients without inducible DWR. All of the DWR episodes were transient. Most (78.6%) terminated after one of the double wave fronts was blocked in the TA-ER isthmus. CONCLUSIONS: DWR is one of the mechanisms responsible for programmed electrical stimulation-induced atrial flutter acceleration in human subjects. Its induction requires a sufficient excitable gap and antidromic unidirectional block of the paced impulse in the TA-ER isthmus. In addition, the TA-ER isthmus is the usual site of DWR termination.

Adult↗
PubMed1998

Determination of the amino acid neurotransmitters in the dorsal root ganglion of the rat by capillary electrophoresis with a laser-induced fluorescence-charge coupled device.

A sensitive, rapid and accurate analysis of the amino acid neurotransmitters in dorsal root ganglion (DRG) of rat was accomplished by capillary electrophoresis with a laser-induced fluorescence-charged coupled device (LIF-CCD) and fluorescein isothiocyanate (FITC) derivatization. Since the CCD is an image detector with a matrix array of photoelements, the photogenerated charge generated from single photoelements was summed up by on-chip charge binning, and used to improve the detection sensitivity. A self-compiled data processing program was used to calculate digitally the summation of the multiwavelength data and transform three-dimensional electropherograms into two-dimensional electropherograms. Use of this program improved the detection sensitivity, the extraction of useful statistical data and the performance of the quantitative analysis. Owing to its excellent detectability and the unique characteristic of its two-dimensional format, which allows to perform analog and digital summation, high detection sensitivity with detection limits ranging from 1.2 to 17.2 nM was obtained for the amino acid neurotransmitters by LIF-CCD. This method was demonstrated to be a powerful tool for analyzing the complex biological samples through quantitative determination of the six amino acid neurotransmitters in the DRG of rat.

Animals↗
PubMed1998

Multiple hemopoietic defects and lymphoid hyperplasia in mice lacking the transcriptional activation domain of the c-Rel protein.

The c-rel protooncogene encodes a member of the Rel/nuclear factor (NF)-kappaB family of transcriptional factors. To assess the role of the transcriptional activation domain of c-Rel in vivo, we generated mice expressing a truncated c-Rel (Deltac-Rel) that lacks the COOH-terminal region, but retains a functional Rel homology domain. Mice with an homozygous mutation in the c-rel region encoding the COOH terminus of c-Rel (c-relDeltaCT/DeltaCT) display marked defects in proliferative and immune functions. c-relDeltaCT/DeltaCT animals present histopathological alterations of hemopoietic tissues, such as an enlarged spleen due to lymphoid hyperplasia, extramedullary hematopoiesis, and bone marrow hypoplasia. In older c-relDeltaCT/DeltaCT mice, lymphoid hyperplasia was also detected in lymph nodes, liver, lung, and stomach. These animals present a more severe phenotype than mice lacking the entire c-Rel protein. Thus, in c-relDeltaCT/DeltaCT mice, the lack of c-Rel activity is less efficiently compensated by other NF-kappaB proteins.

Animals↗
PubMed1998

Integrated cell isolation and polymerase chain reaction analysis using silicon microfilter chambers.

White blood cells are isolated from whole blood in silicon-glass 4.5-microliter microchips containing a series of 3.5-micron feature-sized 'weir-type' filters, formed by an etched silicon dam spanning the flow chamber. Genomic DNA targets, e.g., dystrophin gene, can be directly amplified using the polymerase chain reaction (PCR) from the white cells isolated on the filters. This dual function microchip provides a means to simplify nucleic acid analyses by integrating in a single device two key steps in the analytical procedure, namely, cell isolation and PCR.

Cell Separation↗
PubMed1998

Degenerate oligonucleotide primed-polymerase chain reaction and capillary electrophoretic analysis of human DNA on microchip-based devices.

Random amplification of the human genome using the degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR) was performed in a silicon-glass chip. An aliquot of the DOP-PCR amplified genomic DNA was then introduced into another silicon-glass chip for a locus-specific, multiplex PCR of the dystrophin gene exons in order to detect deletions causing Duchenne/Becker muscular dystrophy. Amplicons were analyzed by both conventional capillary electrophoresis and microchip electrophoresis and results were compared to those obtained using standard non-chip-based PCR assays. Results from microchip electrophoresis were consistent with those from conventional capillary electrophoresis. Whole genome amplification products obtained by DOP-PCR proved to be a suitable template for multiplex PCR as long as amplicon size was < 250 bp. Successful detection and resolution of all PCR products from the multiplex PCR clearly shows the feasibility of performing complex PCR assays using microfabricated devices.

DNA↗
PubMed1998

Crossed inhibition of the soleus H reflex during passive pedalling movement.

We hypothesized that sensory input from the moving leg induces presynaptic inhibition of the soleus H reflex pathway in the contralateral stationary leg. The results showed a crossed inhibition during passive pedalling movement of the leg, which was not removed by low levels of tonic contraction of soleus in the stationary leg. The inhibition was correlated exponentially to the rate of the movement (R2 = 0.934, P < 0.05) and was not dependent on the quadrants through which the moving leg was passing. Static flexion of the stationary leg caused ipsilateral inhibition of the reflexes (t = 5.590, P < 0.05), independent of the orientations of the other leg. We concluded that sensory inflow from the moving leg induces presynaptic inhibition in the stationary leg, that a complex transformation of the sensory input in the spinal cord or brain underlies the tonic crossed inhibition and phasic ipsilateral inhibition, and that descending motor commands exert a powerful control over these sensorimotor modulatory mechanisms.

Adult↗