Search PubMed⌕ Search

Biomedical subjects

C Y Cheng

Publications and source records attributed to C Y Cheng.

At least 73 records · Page 4Linked to original sources
PubMed1998

Synthesis of 2,3,4a,11b-tetrahydro-oxazino[2,3-c]benzopyran-9-carbonitriles as ATP-sensitive potassium channel openers.

A series of optically active tetrahydro-oxazino[2,3-c]benzopyran derivatives have been synthesized and evaluated for potassium channel opening activity. (4aR,11bR)-1-Benzoyl- 5,5-dimethyl-2,3,4a,11b-tetrahydro-oxazino[2,3-c]benzopyran-9-carb onitrile ((-)-11e) was identified as a bladder-selective potassium channel opener (IC50, bladder = 8.15 microM, IC50, portal vein = 34.5 microM).

Adenosine Triphosphate↗
PubMed1998

Human sperm endothelial nitric oxide synthase expression: correlation with sperm motility.

OBJECTIVE: To characterize the pattern of endothelial nitric oxide synthase (eNOS) expression on human spermatozoa and to determine whether sperm eNOS expression correlates with sperm function. DESIGN: Prospective, observational study. SETTING: University infertility clinic. PATIENT(S): Twelve nonazoospermic infertile men. INTERVENTION(S): Semen samples (n=12) obtained from nonazoospermic infertile men were fractionated on discontinuous Percoll gradients. Endothelial nitric oxide synthase staining on spermatozoa was correlated with sperm motility in Percoll gradient-fractionated spermatozoa. Endothelial nitric oxide synthase protein was detected with the use of a previously characterized monoclonal antibody. Control slides were incubated with preabsorbed antibody or mouse immunoglobulin G. MAIN OUTCOME MEASURE(S): Localization of eNOS on human spermatozoa and correlation between the pattern of sperm eNOS expression and sperm motility. RESULT(S): Morphologically normal spermatozoa exhibited postacrosomal and equatorial eNOS immunostaining. However, abnormally shaped spermatozoa often exhibited aberrant staining (in the midpiece and/or head region). A significant negative correlation was observed between the percentage of sperm with aberrant eNOS immunostaining and the percentage of motile sperm (r=-.46). CONCLUSION(S): The specific localization of eNOS to human spermatozoa suggests that nitric oxide may be involved in normal sperm physiology. However, aberrant patterns of sperm eNOS expression are associated with decreased sperm motility, possibly through the generation of excessive cytotoxic oxidants.

Humans↗
PubMed1998

Lysergic acid diethylamide (LSD) is a partial agonist of D2 dopaminergic receptors and it potentiates dopamine-mediated prolactin secretion in lactotrophs in vitro.

The hallucinogenic effects of lysergic acid diethylamide (LSD) have mainly been attributed to the interaction of this drug with the serotoninergic system, but it seems more likely that they are the result of the complex interactions of the drug with both the serotoninergic and dopaminergic systems. The aim of the present study was to investigate the functional actions of LSD at dopaminergic receptors using prolactin secretion by primary cultures of rat pituitary cells as a model. LSD produced a dose-dependent inhibition of prolactin secretion in vitro with an IC50 at 1.7x10(-9) M. This action was antagonized by spiperone but not by SKF83566 or cyproheptadine, which indicates that LSD has a specific effect on D2 dopaminergic receptors. The maximum inhibition of prolactin secretion achieved by LSD was lower than that by dopamine (60% versus 80%). Moreover, the fact that LSD at 10(-8)-10(-6) M antagonized the inhibitory effect of dopamine (10(-7) M) and bromocriptine (10(-11) M) suggests that LSD acts as a partial agonist at D2 receptors on lactotrophs in vitro. Interestingly, LSD at 10(-13)-10(-10) M, the concentrations which are 10-1000-fold lower than those required to induce direct inhibition on pituitary prolactin secretion, potentiated the dopamine (10(-10)-2.5x10(-9) M)-mediated prolactin secretion by pituitary cells in vitro. These results suggest that LSD not only interacts with dopaminergic receptors but also has a unique capacity for modulating dopaminergic transmission. These findings may offer new insights into the hallucinogenic effect of LSD.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1998

Enhanced antinociception of clonidine in spontaneously hypertensive rats involves a presynaptic noradrenergic mechanism.

We and others previously reported that the antinociceptive effect of clonidine, measured by the hot plate method, was greater in spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto rats (WKYs). In the present study, we found that the difference in clonidine-induced analgesia between these two strains was abolished after lesioning the presynaptic noradrenergic neurons with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). Previous studies indicated that clonidine increases tissue norepinephrine (NE) content by inhibiting NE release. We found that the basal NE concentration in locus coeruleus (LC), as measured by HPLC-ECD, was not different between WKYs and SHRs. Systemic application of clonidine (0.69 mg/kg, I.P.) significantly increased the tissue content of NE in the SHRs, but not in WKYs. Using pressure microinjection and high-speed chronoamperometric recording techniques, we found that local application of KCl to the LC brain slices increased extracellular NE levels in both strains. Perfusion of slices with clonidine (1 microM) selectively attenuated KCl-evoked NE release in SHRs, suggesting that clonidine-induced presynapitc inhibition is more effective in SHRs than in WKYs. In conclusion, our data indicate that SHRs possess augmented sensitivity to clonidine to inhibit presynaptic NE release, which may be responsible for the enhanced antinociceptive effect of clonidine in this strain.

Adrenergic Agents↗
PubMed1998

Blockade of the development of morphine tolerance by U-50,488, an AVP antagonist or MK-801 in the rat hippocampal slice.

1. In this study, we investigated the effects of different drugs (a kappa-opioid receptor agonist U-50,488, a vasopressin receptor antagonist dPTyr(Me)AVP or an N-methyl-D-aspartate (NMDA) receptor antagonist MK-801) on the development of morphine tolerance in rat hippocampal slices. 2. Hippocampal slices (450 microm) of Sprague-Dawley rats (250-300 g) were used. Slices were continuously superfused with artificial CSF or drugs at 1 ml min(-1). Nichrome wire electrodes were placed in the Schaffer-collateral pathway and used to deliver biphasic 0.2 ms pulses of 5-30 V (0.033 Hz). A glass microelectrode was placed in the CA1 area to record population spikes. 3. When the slices were superfused with 10 microM morphine, the amplitude of population spikes increased 2-3 fold in 30-40 min. However, this effect of morphine decreased, i.e. tolerance developed after continuous superfusion of morphine for 2-6 h. 4. When either U-50,488 (200 nM) or dPTyr(Me) AVP (500 pM) or MK-801 (500 pM) was co-superfused with morphine (10 microM), it significantly blocked the development of morphine tolerance. Nor-BNI (a kappa-opioid receptor antagonist, 200 nM) significantly reversed the inhibitory effect of U-50,488 but not those of dPTyr(Me)AVP or MK-801 on the development of morphine tolerance. 5. These data indicate that kappa-opioid receptors, AVP receptors and NMDA receptors are all involved in the development of morphine tolerance. The suppression of kappa-opioid receptor activity after chronic morphine may occur before the activation of AVP receptors or NMDA receptors during the development of morphine tolerance.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1998

Quantification of prostaglandin D synthetase in cerebrospinal fluid: a potential marker for brain tumor.

Prostaglandin D synthetase (PGD-S; prostaglandin-H2 D-isomerase, EC 5,3,99,2), a 30 kDa glycoprotein also known as beta-trace protein that catalyzes the formation of prostaglandin D2 (PGD2) from PGH2, was purified to apparent homogeneity from human cerebrospinal fluid (CSF) using a two-step procedure involving HPLC on a Vydac C8 reversed-phase column and high performance electrophoresis chromatography (HPEC) using a 10% T SDS-polyacrylamide gel. The purity of PGD-S isolated from CSF was confirmed by silver stained SDS-polyacrylamide gel and direct protein microsequencing (NH2-APEAQVSVQPNFQ). A highly specific polyclonal antibody was prepared against this protein for immunoassay development. Using an ELISA, it was found that the concentration of PGD-S in CSF did not alter significantly in different pathological conditions of the central nervous system (CNS). These include dementia (n = 9), hydrocephalus (n = 4), neuropathy (n = 11), optic neuritis (n = 4), multiple sclerosis (n = 11), and demyelinating syndrome (n = 11), when compared to normal individuals (n = 12); however, the level of PGD-S in the CSF obtained from patients with brain tumor (n = 11), was reduced by as much as 2-fold when compared to control samples (n = 12) illustrating PGD-S is a potentially useful marker for brain tumor.

Amino Acid Sequence↗
PubMed1998

Regulation of alpha2-macroglobulin expression in rat Sertoli cells and hepatocytes by germ cells in vitro.

Germ cells isolated from rat testes by trypsinization have been shown to yield unwanted artifacts in biological assays, since conditioned media derived from these germ cells (germ cell-conditioned media [GCCM]) can modulate Sertoli cell secretory function because of the presence of residual trypsin. To determine whether germ cells themselves can modulate Sertoli cell function, we isolated germ cells from tubules by a mechanical procedure and assessed the effect of these cells on Sertoli cell alpha2-macroglobulin (alpha2-MG) steady-state mRNA level. It was found that germ cells indeed could stimulate Sertoli cell alpha2-MG expression. This effect is probably mediated by a soluble factor(s) released from germ cells, since GCCM fractionated by HPLC contained multiple fractions that can stimulate Sertoli cell alpha2-MG expression dose-dependently. These results illustrate that germ cells play a role in regulating testicular alpha2-MG expression. Since Sertoli cells synthesize and secrete many of the serum proteins behind the blood-testis barrier that are also produced by hepatocytes, we sought to ascertain whether germ cells can affect hepatic alpha2-MG expression. When germ cells were cocultured with hepatocytes isolated from adult rats, the hepatocyte alpha2-MG steady-state mRNA level was shown to be stimulated by germ cells dose-dependently. Using different pools of fractions derived from GCCM after their fractionation by a preparative anion-exchange HPLC column, GCCM was found to contain a factor(s) that stimulated hepatocyte alpha2-MG expression dose-dependently. More importantly, the fractions that stimulated hepatocyte alpha2-MG expression had a retention time different from that of the factor(s) that affected Sertoli cell alpha2-MG expression. These data illustrate that germ cells secrete multiple biological factors capable of regulating alpha2-MG expression in the testis and the liver. In summary, this study reveals a possible physiological link between the testis and the liver in that germ cells may release a factor(s) capable of modulating alpha2-MG expression in both organs.

Aging↗
PubMed1998

Rat testicular extracellular superoxide dismutase: its purification, cellular distribution, and regulation.

Using multiple HPLC steps, we have identified and purified a 68-kDa polypeptide (as estimated by gel permeation HPLC) to apparent homogeneity, from primary Sertoli cell-enriched culture medium, that consisted of two monomers of 35 (alpha chain) and 33 kDa (ss chain) on SDS-polyacrylamide gel running under reducing conditions. Partial N-terminal amino acid sequence analysis of these two monomers revealed sequences of NH2-DXGESGVDLADRL (SODEX-alpha) and NH2-XXDTGESGVDLADXL (SODEX-ss), which are identical to rat extracellular superoxide dismutase (SODEX) with the exceptions that SODEX-alpha and SODEX-ss are missing, respectively, four (Trp-Thr-Met-Ser) and two (Trp-Thr) amino acids from their N-termini, compared to rat SODEX, suggesting that the cleavage sites of the SODEX gene in the testis are different from that of other organs. Studies by sequential use of reverse transcription and polymerase chain reaction (PCR) using two SODEX primers have demonstrated the expression of SODEX in the heart, brain, lung, kidney, epididymis, testis, Sertoli, and germ cells, with low expression in the liver and ovary and no expression in the uterus, spleen, or thymus. Nucleotide sequence analysis of this 447-base pair PCR product from Sertoli cells revealed that its sequence is equivalent to the sequence of previously published rat SODEX. During testicular maturation, the SODEX steady-state mRNA level increased significantly from 20 to 60 days of age and then declined at 90 days of age. Such an increase in the testicular SODEX expression during maturation is not likely a result of an up-regulation by germ cells, since germ cells isolated from either 20- or 60-day-old rats when cocultured with Sertoli cells failed to elicit an increase in SODEX expression in the cocultures. Using primary Sertoli cell cultures in vitro, it was found that Sertoli cell SODEX expression was stimulated by interleukin-1alpha but not by either interferon-gamma or basic fibroblast growth factor. These results illustrate that Sertoli cells as well as germ cells synthesize and/or secrete a testicular variant of SODEX that may provide essential clues to understanding superoxide radical-mediated damage in the gonad.

Animals↗
PubMed1998

Rat prostaglandin D2 synthetase: its tissue distribution, changes during maturation, and regulation in the testis and epididymis.

The changes in glutathione-independent prostaglandin D2 synthetase (PGD-S) during maturation in the rat were determined in selected organs by an RIA using PGD-S purified from rat cerebrospinal fluid and a monospecific anti-rat PGD-S polyclonal antibody. In a survey of its tissue distribution in various organ extracts and biological fluids, it was found that the concentration of PGD-S was highest in the epididymis-about 6- and 80-fold greater than that in the brain and testis, respectively. During maturation, PGD-S concentration increased steadily in the testis and epididymis; this is in contrast to the pattern of changes in the brain and liver, which showed a general trend of decline. Reverse transcription-polymerase chain reaction and Southern blotting were used to demonstrate the presence of PGD-S mRNA transcript in the testis and in Sertoli and germ cells. In the epididymis, the steady-state PGD-S mRNA level was highest in the caput, followed by the cauda and corpus. Orchiectomy induced a drastic reduction of PGD-S concentration in all three epididymal compartments. Administration of dihydrotestosterone (DHT) failed to restore the reduced epididymal PGD-S level except in the caput epididymis, where 4 days after DHT treatment the level of PGD-S was restored to about 50% of the pre-orchiectomized level; this suggests that the epididymal PGD-S level is not entirely regulated by androgen and that another yet to be identified testicular factor(s) is likely to be involved in its regulation. Germ cell-conditioned medium was also shown to stimulate PGD-S expression in the Sertoli cell. These results illustrate that PGD-S is an important molecule in testicular and epididymal function and that it is likely involved in spermatogenesis and sperm maturation.

Animals↗
PubMed1998

Rat testicular N-cadherin: its complementary deoxyribonucleic acid cloning and regulation.

Using primer sets specific for mouse N-cadherin and rat testicular RNA for RT-PCR, a full-length complementary DNA (cDNA) coding for rat testicular N-cadherin was isolated. The deduced amino acid sequence of rat N-cadherin yielded a 883-amino acid polypeptide that displayed a 98.6% identity with the mouse homolog. N-Cadherin was found to be expressed by Sertoli and germ cells in the rat testis by RT-PCR. Using Sertoli-germ cell cocultures, it was found that the N-cadherin expression increased with time in culture. To assess whether this is due to a soluble factor(s) released from germ cells that affects Sertoli cell N-cadherin expression, germ cell-conditioned media (GCCM) were fractionated by preparative anion-exchange HPLC, and the resulting fractions were divided into 14 pools. Pool 4 was found to contain a factor(s) that induced a dose-dependent stimulation on Sertoli cell N-cadherin expression with a maximal stimulation at 2 microg protein/dish/4.5 x 10(6) Sertoli cells. At higher doses between 12 and 32 microg protein/dish, this pool relinquished its effect on Sertoli cell N-cadherin expression suggestive of a biphasic effect. This biphasic effect was confirmed using increasing doses of crude GCCM on Sertoli cell cultures. Since nonviable germ cells failed to stimulate Sertoli cell N-cadherin expression, it illustrates the observed stimulatory effect by GCCM is likely to be mediated via a soluble factor(s) releasing from viable germ cells. These results reveal the presence of a stimulatory factor(s) in GCCM that can modulate Sertoli cell N-cadherin expression in vitro. Since N-cadherin plays a crucial role in facilitating invasive capacity of metastatic tumor cells, the observation of germ cell-released factor(s) in affecting Sertoli cell N-cadherin expression may suggest its possible role in facilitating germ cell migration during spermatogenesis.

Amino Acid Sequence↗
PubMed1998

Paraspinal muscle abscess after Chinese Kong Fu practitioner manipulation--a case report.

Paraspinal infection is a rare condition. Modes of infection include transcutaneous infection of the deep tissue by needles or catheters, surgery, blunt trauma, and hematogenous spread from distant sites. Chiropractic manipulation is a noninvasive procedure but is sometimes associated with vascular or neurologic insults resulting in hematoma or cerebrovascular accidents. We report a paraspinal muscle abscess in a healthy young man 7 days after Chinese Kong Fu practitioner manipulation for back pain without definite infection sources. The local paraspinal tenderness as demonstrated by the patient should be considered to be a sign of infection. Paraspinal infection often subjects to delayed diagnosis and this delay may be disastrous. In the management of low back pain or treating spinal disorders, physicians should be aware of the possibility of such a condition particularly in patients whose back pain has been managed with chiropractic manipulation to avoid misdiagnosis.

Abscess↗
PubMed1997

Effects of 3,3-dipyridylmethyl-1-phenyl-2-indolinone on gamma-aminobutyric acid elicited chloride current of snail central neuron.

The effects of (1) gamma-aminobutyric acid (GABA) on the excitable membrane and (2) DPMPI (3,3-dipyridylmethyl-1-phenyl-2-indolinone) on the microperfused GABA elicited currents were investigated on central LP5 neuron of giant African snail, Achatina fulica Ferussac, with conventional voltage-clamp technique. GABA elicited an inward current of LP5 neuron by a concentration and voltage dependent manner. Muscimol, GABAA receptor agonist, did, while baclofen, GABAB receptor agonist, did not, elicit the membrane current on the neuron. The GABA elicited currents in LP5 neuron were blocked by picrotoxin, a GABAA receptor ion channel complex antagonist while the currents were not blocked by phaclofen, a GABAB receptor antagonist. The results suggested that the GABA elicited current in LP5 neuron was mainly due to activation of GABAA receptor. DPMPI increased the frequency of the spontaneously generated action potential of the neuron. In the voltage clamped neuron, DPMPI decreased the GABA elicited responses by a concentration dependent manner. DPMPI altered neither the reversal potential of GABA elicited current, nor the membrane resistance of the excitable membrane of central LP5 neuron. The results concluded that DPMPI altered the GABAA activated receptor ionic channel complex of the LP5 neuron.

Action Potentials↗
PubMed1997

Polymorphisms and intron sequences flanking the alternatively spliced 8-amino-acid exon of gamma2 subunit gene for GABAA receptors.

Gamma-amminobutyric acid (GABA) is a major inhibitory neurotransmitter. Two alternatively spliced forms of the gamma2 subunit of GABAA receptor (gamma2L and gamma2S), which differ by an exon of eight amino acids, show different sensitivities to modulatory effects of ethanol on receptor activities. A 2.7 kb DNA fragment and an 1.7 kb DNA fragment covering respectively the introns upstream and downstream from the 8-amino-acid exon were obtained through PCR-amplification of human genomic DNA using primers derived from cDNA sequences. Total sequencing of these fragments showed a composite 4.2 kb segment containing the 8-amino-acid exon and consensus sequences for RNA splice junctions. Restriction fragment length polymorphisms (RFLP) based on NciI restriction digestion were found among Chinese in Taiwan. This RFLP provides a useful DNA marker for allelic association or linkage analyses of the role of GABAA receptors in predisposition to alcoholism or other neuropsychiatric disorders.

Alternative Splicing↗
PubMed1997

Astrocytes cultured in vitro produce estradiol-17beta and express aromatase cytochrome P-450 (P-450 AROM) mRNA.

Aromatase cytochrome P-450 (P-450AROM) is an enzyme that catalyzes the conversion of androgen to estrogen. Estrogen plays an important role in the neuronal function by promoting the formation of dendrites and may be involved in protecting the neurons in the cerebral cortex against specific pathological conditions such as Alzheimer's disease. However, the cellular origin of estrogen in the brain is not known. The present study demonstrated for the first time the production of estradiol-17beta and expression of P-450AROM mRNA in astrocytes isolated from the cerebral cortex of neonatal rats. Immunocytochemical studies using a monospecific antibody against rat P-450AROM has shown that this enzyme was localized in the cytoplasm of astrocytes. Interleukin-1 (IL-1) has been shown to stimulate the proliferation and differentiation of astrocytes and to affect the aromatase activity in non-neuronal cells such as Sertoli, Leydig, and placental cells. Treatment of astrocytes with IL-1beta induced a dose-dependent inhibition of estradiol production. This inhibitory action of IL-1beta can be reversed by the addition of anti-IL-1beta antibody. Since astrocytes are involved in the synaptic reorganization in the brain by removing cellular debris and by providing the necessary biological factors for neuronal growth, the ability of astrocytes to produce estradiol-17beta and express P-450AROM mRNA in vitro suggests a new role for these cells in protecting and supporting neurons.

Animals↗
PubMed1997

Testin is tightly associated with testicular cell membrane upon its secretion by sertoli cells whose steady-state mRNA level in the testis correlates with the turnover and integrity of inter-testicular cell junctions.

Testin, a Sertoli cell secretory protein whose mRNA is predominantly expressed in the testis, was shown to become tightly associated with Sertoli cell membrane upon its secretion whose solubilization requires the use of a detergent such as SDS. In the in vitro studies using Sertoli cells cultured at high cell density, where specialized junctions were being formed, the concentration of "soluble" testin in the spent media was greatly reduced versus monolayer cultures at low cell density, where specialized junctions were absent. Conversely, the concentration of "membrane-bound" testin from detergent-solubilized Sertoli cell membrane extract was positively correlated to the existence of specialized junctions in these cultures. In normal rat testes, the level of radioimmunoassayable soluble testin in the cytosol was low. However, when the inter-testicular cell junctions were disrupted either by a drug treatment such as lonidamine in vivo or by a physical treatment in vitro such as exposing Sertoli-germ cell co-cultures where specialized junctions were formed to a hypotonic treatment, a drastic surge in the testin gene expression was noted. Thus, testin can become tightly associated with Sertoli cell membrane upon its secretion when intercellular junctions are formed. It is also a marker to monitor the integrity of inter-testicular cell junctions.

Animals↗
PubMed1997

Effect of clozapine on dopamine-induced inhibition of prolactin release from cultured rat pituitary cells.

Although the atypical antipsychotic agent clozapine has little propensity to induce hyperprolactinemia in humans it increases serum prolactin levels in the rat. In this study, the effects of clozapine and of some typical antipsychotic drugs on basal and dopamine-mediated prolactin secretion from cultured rat pituitary cells were compared. Despite being less potent than the other antipsychotic agents tested, clozapine reverted the effect of dopamine on prolactin secretion in vitro. This finding suggests that clozapine interferes with dopamine receptors in the pituitary gland.

Animals↗
PubMed1997

The role of vasopressin on the effect of U-50,488 to block the development of morphine tolerance and physical dependence.

U-50,488, a selective kappa-opioid receptor agonist, has been reported to inhibit the development of antinociceptive tolerance to morphine in mice, rats and guinea pigs, but the mechanism involved in this action remains unknown. Since U-50,488 has been reported to suppress the plasma vasopressin level, we investigated the role of vasopressin with U-50,488 in the male Sprague Dawley rat in this study. Animals (230-270 g) were chronically treated with morphine (10 mg/kg, i.p.) twice a day for 6 days in order to induce tolerance to antinociceptive effect measured by tail-flick test. Withdrawal symptoms were precipitated by naloxone (10 mg/kg, i.p.) on day 7. U-50,488 (i.p.) or AVP (i.p. or i.c.v.) or U-50,488 and AVP was (were) coadministered with chronic morphine to investigate their effects on morphine tolerance and dependence. We found that coadministration of 8 mg/kg U-50,488 (i.p.) with morphine almost completely block morphine tolerance and partially block withdrawal symptoms. In contrast, coadministration of AVP (0.3 microgram/kg, i.p., or 0.01 microgram, i.c.v.) with morphine and U-50,488, the effects of U-50,488 to block morphine tolerance and dependence were reversed. In addition, treatment of AVP antagonist (dPTyr(Me)AVP, 0.5 microgram/kg, i.p. or 0.5 microgram, i.c.v.) has the similar effect as U-50,488 to block morphine tolerance. In summary, the effect of U-50,488 to block morphine tolerance and dependence may relate to its inhibitory effect on AVP release.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗