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Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

At least 379 records · Page 21Linked to original sources
PubMed1995

Demonstration of kappa 3-opioid receptors in the SH-SY5Y human neuroblastoma cell line.

In addition to the mu- and delta-opioid receptors previously reported, the SH-SY5Y human neuroblastoma cell line has high levels of kappa 3 receptors, accounting for 40% of total opioid binding, as measured with [3H]-diprenorphine binding. Competition studies reveal binding profiles for all three receptor classes that are similar to those observed in brain membranes. Differentiation with retinoic acid increases the levels of opioid receptor binding in the cell line, with the largest elevations in kappa 3 binding. Fully 75% of the increased binding corresponds to kappa 3 sites, which represent 50% of total opioid receptor binding in differentiated cells. Morphine inhibits forskolin-stimulated cyclic AMP accumulation, and this effect is readily blocked by the mu antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP). Naloxone benzoylhydrazone, a kappa 3 agonist, inhibits forskolin-stimulated cyclic AMP accumulation more potently than morphine and is not reversed by CTAP. These studies indicate that SH-SY5Y cells contain high levels of functional kappa 3 receptors.

Binding Sites↗
PubMed1995

The basal keratin network of stratified squamous epithelia: defining K15 function in the absence of K14.

Keratin 5 and keratin 14 have been touted as the hallmarks of the basal keratin networks of all stratified squamous epithelia. Absence of K14 gives rise to epidermolysis bullosa simplex, a human blistering skin disorder involving cytolysis in the basal layer of epidermis. To address the puzzling question of why this disease is primarily manifested in skin rather than other stratified squamous epithelia, we ablated the K14 gene in mice and examined various tissues expressing this gene. We show that a key factor is the presence of another keratin, K15, which was hitherto unappreciated as a basal cell component. We show that the levels of K15 relative to K14 vary dramatically among stratified squamous epithelial tissues, and with neonatal development. In the absence of K14, K15 makes a bona fide, but ultrastructurally distinct, keratin filament network with K5. In the epidermis of neonatal mutant mice, K15 levels are low and do not compensate for the loss of K14. In contrast, the esophagus is unaffected in the neonatal mutant mice, but does appear to be fragile in the adult. Parallel to this phenomenon is that esophageal K14 is expressed at extremely low levels in the neonate, but rises in postnatal development. Finally, despite previous conclusions that the formation of suprabasal keratin filaments might depend upon K5/K14, we find that a wide variety of suprabasal networks composed of different keratins can form in the absence of K14 in the basal layer.

Amino Acid Sequence↗
PubMed1995

Magnetic field induced currents in a human head from use of portable appliances.

The induced currents in a model of the human head resulting from use of small hand-held appliances were computed. The source of the induced currents, i.e. the alternating (60 Hz) magnetic field was modelled as a magnetic dipole. The limits of applicability of this model are given. The model of the human head was obtained by translating MRI data into tissue conductivity data. Computations of the distribution of the induced currents were performed using the impedance method. The induced current density rapidly decreases with the distance from the appliance. The maximum, however, predictably is not at the surface, because of the geometry of the head. For typical appliances, the values of the maximum current densities are high as compared to those induced by a uniform magnetic field. Generalized graphs were obtained for the maximum induced current density normalized to the appliance magnetic moment, as a function of the distance from the appliance. These graphs are given for two representative locations of the appliance with respect to the head.

Electromagnetic Fields↗
PubMed1995

Metastable single-strand DNA conformational polymorphism analysis results in enhanced polymorphism detection.

Single-strand DNA conformational polymorphism (SSCP) makes use of sequence-dependent folding of single-stranded DNA (ssDNA), which alters the electrophoretic mobility of the fragments, to detect sequence differences between closely related molecules. In this study ssDNAs were purified by depletion of the complementary strand and PCR reactants on magnetic M-280-strepavidin beads. It was found that SSCP profiles created by purified ssDNAs differ from the profiles created by more usual SSCP methods. Under some conditions, SSCP profiles using whole PCR reaction products may result from the interaction between residual PCR primers and ssDNAs. We observed that the ratio of conformers revealed by band position and band intensity may vary between the assay techniques and misinterpretation of sequence variants may result. Another observation of this study was the formation of metastable conformational isomers with bead-purified ssDNAs by eliminating the thermal treatment used in conventional SSCP methods. The metastable SSCP (mSSCP) represents a novel and sensitive system for detection of sequence variation between closely related DNAs. The technique used here for the preparation of the purified ssDNAs is potentially useful for automated PCR-SSCP analysis using capillary electrophoresis or other methods.

Autoradiography↗
PubMed1995

Amplitude modulation of the soleus H reflex in the human during active and passive stepping movements.

1. It was hypothesized that passive movement of either the whole leg or its separate segments, in a manner mimicking human gait, leads to attenuation of the soleus H reflex. It was further hypothesized that this attenuation arises from presynaptic effects. Reflex amplitudes were observed in humans during natural bipedal and unipedal stepping on the spot, during passive stepping, during passive movement of the lower limb segments about the hip, knee, and ankle individually in a stepping fashion, and during passive movement with tonic contraction of the soleus muscle. 2. In natural stepping at a cadence of 54 steps/min, the reflex means were substantially depressed in the swing phase (P < 0.01). (Means, standing control 90.1%, unipedal 8.3%, bipedal 6.9%, of maximum M wave.) During the stance phase, reflex magnitudes were mildly and significantly elevated in four of six subjects, compared with standing controls (P < 0.05). 3. For passive stepping, subjects were dorsally tilted 20 and 90 degrees (lying supine) from the vertical position, to obtain quiet electromyograms (EMGs) in the postural muscles. Recorded during natural stepping, the right leg was manipulated to match the electrogoniometer traces of the three major joints. 4. At 20 degrees of tilt of the body, mean H reflexes were significantly lower, by 26.4%, compared with the supine position (P < 0.05). During passive stepping movement of the leg at 54 steps/min, the reflex was profoundly attenuated over the entire cycle (P < 0.01). The significantly attenuated reflexes during active stepping and during passive stepping movement of the whole leg were not significantly different at the point where the limb approached full flexion in the swing phase (P > 0.48). This was the case for measurements made at either body position, 20 degrees dorsal tilt or supine. 5. Passive flexion-extension, around either the hip or the knee, significantly inhibited the mean reflex magnitude close to full flexion, at either body position (P < 0.01). Such movement around the ankle resulted in significant inhibition of the reflex in two of the four subjects (P < 0.05). The numeric sum of the reflex depression arising from the flexion-extension of the individual joints was greater than that arising from movement of the whole limb. 6. With the ankle braced, the significant reflex attenuation remained when a tonic isometric contraction of the soleus muscle was introduced. This suggests premotoneuronal mechanisms for the inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1995

Transcription patterns of sequences on human chromosome 21.

The polymerase chain reaction (PCR) was used to screen embryonic, fetal and adult human cDNA libraries for transcription on chromosome 21q22.1-->q22.3. Seventy-three pairs of oligonucleotide primers on chromosome 21, used previously to screen a fetal brain cDNA library, were applied to analyze 41 different cDNA libraries. Only phage eluate (and therefore no DNA isolation) was required for this sensitive screening. Sixty primer pairs were positive with at least one cDNA library, indicating that the majority of primers were derived from transcribed sequences. Even with our most complex human fetal brain cDNA library, we detected only 57% (34/60) of transcribed sequences, illustrating the need to screen multiple human cDNA libraries to determine if transcription occurred. Since only 3/73 clones were present in only one cDNA library, the vast majority of transcribed sequences are present in more than one tissue.

Chromosomes, Human, Pair 21↗
PubMed1995

Time-frequency analysis of transient evoked otoacoustic emissions via smoothed pseudo Wigner distribution.

Transient evoked otoacoustic emissions (TEOAEs) can be processed by the smoothed pseudo Wigner distribution (SPWD). With this process, TEOAEs can be transformed into the time-frequency plane to give a three-dimensional pattern. The analyses of shape and localization of TEOAE patterns and the comparisons of pattern differences establish a method for describing otoacoustic emissions. A better understanding and interpretation of the characteristics of TEOAEs can be achieved as well. This method can be used as a powerful tool for monitoring the cochlear condition.

Acoustic Stimulation↗
PubMed1995

Inflammatory pseudocyst associated with trisomy 21 and Hirschsprung's disease.

A 15-month-old black male with trisomy 21 and Hirschsprung's disease developed an inflammatory abdominal pseudocyst 1 month after Swenson pull-through repair. Although abdominal pseudocyst associated with ventriculoperitoneal shunts, peritoneal dialysis catheters, meconium peritonitis, and pancreatitis have been reported, this is the first report of a pseudocyst developing 1 month after a surgical repair of Hirschsprung's disease.

Cysts↗
PubMed1995

Cloning and functional characterization through antisense mapping of a kappa 3-related opioid receptor.

We have identified a putative opioid receptor from mouse brain (KOR-3), belonging to the G protein-coupled receptor family, that is distinct from the previously cloned mu, delta, and kappa 1 receptors. Assignment of the clone to the opioid receptor family derives from both structural and functional studies. Its predicted amino acid sequence is highly homologous to that of the other opioid receptors, particularly in many of the transmembrane regions, where long stretches are identical to mu, delta, and kappa 1 receptors. Both cyclazocine and nalorphine inhibit cAMP accumulation in COS-7 cells stably expressing the clone. Northern analysis shows that the mRNA is present in brain but not in a number of other organs. Southern analysis suggests a single gene encoding the receptor. A highly selective monoclonal antibody directed against the native kappa 3 receptor recognizes, in Western analysis, the clone expressed in COS-7 cells. The in vitro translation product is also labeled by the antibody. Additional clones reveal the presence of several introns, including one in the second extracellular loop and another in the first transmembrane region. Antisense studies with an oligodeoxynucleotide directed against a region of the second extracellular loop reveal a selective blockade of kappa 3 analgesia in vivo that is not observed with a mismatch oligodeoxynucleotide based upon the antisense sequence. The mu, delta, and kappa 1 analgesia is unaffected by this antisense treatment. Antisense mapping of the clone downstream from the splice site in the first transmembrane region reveals that six different antisense oligodeoxynucleotides all block kappa 3 analgesia. In contrast, only one of an additional six different antisense oligodeoxynucleotides directed at regions upstream from this splice site is effective. This strong demarcation between the two regions raises the possibility of splice variants of the receptor. An additional clone reveals an insert in the 3' untranslated region. In conclusion, the antibody and antisense studies strongly associate KOR-3 with the kappa 3-opioid receptor, although it is not clear whether it is the kappa 3 receptor itself or a splice variant.

Amino Acid Sequence↗
PubMed1995

[Surgical treatment of gastric cardia cancer with fundoplication--a report of 193 cases].

From December 1987 to 1994, a total of 193 patients with carcinoma of the gastric cardia were surgically treated by partial esophagectomy, partial gastrectony and end-to-side esophagogastric anastomosis with fundoplication. When compared to those patients during the same time period similarly treated but with end-to-end esophagogastrostomy, the incidences of anastomotic leakage, anastomotic stricture and esophageal reflux were all significantly decreased (P < 0.01). It is a novel surgical treatment of choice for cancer of the gastric cardia.

Adult↗
PubMed1995

[Changes of amino acids release in rat's hippocampus during kainic acid induced epilepsy and acupuncture].

Changes of amino acids release in rat's hippocampus were studied by using push-pull perfusion and high performance liquid chromatography (HPLC) with fluorometric detection techniques during kainic acid (KA) induced epilepsy and acupuncture. The results indicated that the levels of glutamate, aspartate, glycine and GABA were statistically increased in hippocampus 40min after administration of KA. After EA treatment, there was marked elevation in the extracellular level of taurine. It's shown that the inhibitory effect of EA on epilepsy may be related to the increase of inhibitory amino acids's release in hippocampus.

Amino Acids↗
PubMed1994

Glycerol-enhanced separation of DNA fragments in entangled solution capillary electrophoresis.

(Hydroxyalkyl)methylcellulose additives to borate buffers have been used to create physically entangled solutions for fractionation of biological molecules by high-performance capillary electrophoresis, i.e., ESCE. We have observed that addition of glycerol to an entangled solution containing (hydroxypropyl)methylcellulose (HPMC) in Tris-borate buffer markedly improved the separation of double-strand DNA molecules ranging from less than 100 bp to about 1 kb by ESCE. This range of DNA fragment sizes is well suited to many PCR-based studies. We attribute the improved ESCE performance to the borate present in the buffer system. Borate can form dimeric 1:2 borate:didiol complexes with both glycerol and HPMC, acting as a central linkage to allow an entangled solution with different pore size to form chemically.

Ampholyte Mixtures↗
PubMed1994

The chromosomal tetracycline resistance locus of Bacillus subtilis encodes a Na+/H+ antiporter that is physiologically important at elevated pH.

The chromosomal tetB(L) gene of Bacillus subtilis encodes a transporter that catalyzes Na+/H+ antiport even more actively than tetracycline/H+ antiport, as shown by assays of membrane antiporter activity upon transformation of Na+/H+ antiporter-deficient Escherichia coli with the cloned gene; the transformation results in a substantial increase in Na+ resistance as well as detectable resistance to low tetracycline concentrations. Transpositional disruption of the chromosomal tetB(L) locus of B. subtilis led to reduced rates of electrogenic Na+ efflux and revealed a physiological role for this locus in Na+ resistance and Na(+)-dependent pH homeostasis at pH 8.5. The mutant phenotype was reversed by transformation with a plasmid expressing the cloned tetB(L) gene. Energy-dependent tetracycline efflux rates in the wild type were greater than in the transposition mutant but were not sufficient to confer resistance to the antibiotic. TetB(L) is also inferred to have a modest capacity for K+ efflux, since the transposition mutant is slightly impaired in K(+)-dependent pH homeostasis at pH 8.5 and grew better than the wild type at pH 7 on limiting K+ concentrations.

Bacillus subtilis↗
PubMed1994

Polymerase chain reaction heteroduplex polymorphism analysis by entangled solution capillary electrophoresis.

Heteroduplex DNA polymorphism analysis (HPA) makes use of conformational polymorphisms to alter electrophoretic mobility of fragments and can be used to detect non-restrictable loci. We have developed a novel application of entangled solution capillary electrophoresis (ESCE) to separate heteroduplex and homoduplex DNA molecules. The addition of ethidium bromide and glycerol to the free solution sieving buffer resulted in the improved peak resolution and good reproducibility. Reannealed polymerase chain reaction products could be used directly for mutation screening and with fully automated ESCE the entire HPA may be completed in less than 30 min including sample handling. This technology could provide a rapid and highly efficient way for screening rare mutations among large numbers of individuals.

Base Sequence↗
PubMed1994

Conversion of secretory proteins into membrane proteins by fusing with a glycosylphosphatidylinositol anchor signal of alkaline phosphatase.

Placental alkaline phosphatase (PLAP) is initially synthesized as a precursor (proPLAP) with a C-terminal extension. We constructed a recombinant cDNA which encodes a chimeric protein (alpha GL-PLAP) comprising rat alpha 2u-globulin (alpha GL) and the C-terminal extension of PLAP. Two molecular species (25 kDa and 22 kDa) were expressed in the COS-1 cell transfected with the cDNA for alpha GL-PLAP. Only the 22 kDa form was labelled with both [3H]stearic acid and [3H]ethanolamine. Upon digestion with phosphatidylinositol-specific phospholipase C the 22 kDa form was released into the medium, indicating that this form is anchored on the cell surface via glycosylphosphatidylinositol (GPI). A specific IgG raised against a C-terminal nonapeptide of proPLAP precipitated the 25 kDa form but not the 22 kDa form, suggesting that the 25 kDa form is a precursor retaining the C-terminal propeptide. When a mutant alpha GL-PLAP, in which the aspartic acid residue is replaced with tryptophan at a putative cleavage/attachment site, was expressed in COS-1 cells, the 25 kDa precursor was the only form found inside the cell and retained in the endoplasmic reticulum, as judged by immunofluorescence microscopy. In vitro translation programmed with mRNAs coding for the wild-type and mutant forms of alpha GL-PLAP demonstrated that the C-terminal propeptide was cleaved from the wild-type chimeric protein, but not from the mutant one. This gave rise to the 22 kDa form attached with a GPI anchor, suggesting that GPI is covalently linked to the aspartic acid residue (Asp159) of alpha GL-PLAP. Taken together, these results indicate that the C-terminal propeptide of PLAP functions as a signal to render alpha GL a GPI-linked membrane protein in vitro and in vivo in cultured cells, and that the chimeric protein constructed in this study may be useful for elucidating the mechanism underlying the cleavage of the propeptide and attachment of GPI, which occur in the endoplasmic reticulum.

Alkaline Phosphatase↗