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Biomedical subjects

K W Cheng

Publications and source records attributed to K W Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2000

Expression and regulation of P2U-purinergic receptor in human granulosa-luteal cells.

The P2U purinoceptor (P2UR) has been identified pharmacologically in the ovary. However, the expression and regulation of the P2UR messenger RNA (mRNA) in human ovarian cells are still poorly characterized. The present study was designed to examine the expression and regulation of the P2UR in human granulosa-luteal cells (hGLCs) by RT-PCR and Northern blot analysis. A PCR product corresponding to the expected 599-bp P2UR complementary DNA was obtained from hGLCs. Molecular cloning and sequencing of the PCR product revealed an identical sequence to the reported P2UR complementary DNA. Two mRNA transcripts of 2.0 kb and 4.6 kb were identified in hGLCs using Northern blot analysis. The expression of the P2UR mRNA was down-regulated by human CG in a dose- and time-dependent manner. Treatment with 8-bromo-cAMP and forskolin also attenuated P2UR mRNA levels. Calcium signaling following the activation of the P2UR in single hGLCs was studied using microspectrofluorimetry. It revealed that, like ATP, uridine triphosphate (UTP) also induced cytosolic calcium mobilization in a dose-dependent manner. These results demonstrate for the first time that the P2UR mRNA is expressed in hGLCs and that P2UR mRNA is regulated by human CG, cAMP, and forskolin. The P2UR expressed in hGLCs functional because activation of the P2UR by ATP or UTP resulted in rapid and transient mobilization of cytosolic calcium at the single cell level. These findings further support a potential role of this neurotransmitter receptor in the human ovary.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Autocrine role of gonadotropin-releasing hormone and its receptor in ovarian cancer cell growth.

We have recently proposed an autocrine role of gonadotropin-releasing hormone (GnRH) and its receptor (GnRH-R) in human ovarian surface epithelium. In the present study, we examine the presence and role of a GnRH/GnRH-R loop in epithelial ovarian cancer cells, OVCAR-3. A dose-dependent biphasic response in GnRH and GnRH-R mRNA levels were observed after treating with GnRH agonist [GnRHa, (D-Ala6)-GnRH], for 24 h. High concentrations of GnRHa (10(-9) M and 10(-7)) decreased the GnRH and GnRH-R mRNA levels, whereas a low concentration (10(-11) M) resulted in an upregulation of GnRH and GnRH-R genes expression. Cotretment with the competitive antagonist, antide, prevented the biphasic effect induced by GnRHa, confirming the specificity of the response. In addition, GnRHa treatment resulted in a time- and dose-dependent inhibition on OVCAR-3 cells growth. A significant inhibition of proliferation was detected as early as the d 2 of treatment. Treatment with 10(-7) M GnRHa induced DNA fragmentation in OVCAR-3 cells, suggesting that the GnRHa-induced antiproliferation in OVCAR-3 cells was mediated by apoptosis. Again, this effect was prevented by cotreatment of antide. Taken together, our findings strongly support the notion that GnRH acts as an autocrine/paracrine regulator of ovarian cancer cell proliferation.

Apoptosis↗
PubMed2000

Anesthesia for patients with aortic aneurysm for non-aneurysmal surgery--a retrospective study.

BACKGROUND: Most anesthesiologists at one time or other saw the anesthetic management of patients with aortic aneurysm who underwent surgical procedures other than correction of aneurysm with or without prior knowledge of the existence of the aneurysm. The risk of intraoperate rupture of aneurysm depends on its size, type, severity, and presentation of symptoms; stress and unstable hemodynamics have been usually held responsible for the aggravation and even rupture of aneurysm. There are numerous other factors that affect the hemodynamic force during anesthesia and surgery, the increase of which would be very dangerous to the surgical patients with aortic aneurysm whether they receive anesthesia for a radical correction of the disease per se or for a surgical procedure unrelated to its correction. Therefore the anesthetic management of a patient with aortic aneurysm is a great challenge which the anesthesiologist must accept. Here, we present eleven cases of aortic aneurysm, who underwent non-corrective surgery during 1992-1998. METHODS: There were eight cases of thoracoaortic dissecting aneurysm and three cases of abdominoaortic aneurysm. All underwent laparotomy under general anesthesia without the aneurysm being corrected. We reviewed the anesthetic management of these patients retrospectively. RESULTS: Our review showed that no aneurysm rupture was noted in these eleven cases. Seven of the eleven patients are still alive at the time of this report. CONCLUSIONS: We are of the opinion that under close monitoring and with prompt treatment, the allowance of a slow climb of arterial pulse pressure is acceptable and would not increase the risk of aneurysm rupture.

Aged↗
PubMed2000

The expression, regulation and signal transduction pathways of the mammalian gonadotropin-releasing hormone receptor.

Normal mammalian sexual maturation and reproductive functions require the integration and precise coordination of hormones at the hypothalamic, pituitary, and gonadal levels. Hypothalamic gonadotropin-releasing hormone (GnRH) is a key regulator in this system; after binding to its receptor (GnRHR), it stimulates de novo synthesis and release of gonadotropins in anterior pituitary gonadotropes. Since the isolation of the GnRHR cDNA, the expression of GnRHR mRNA has been detected not only in the pituitary, but also in extrapituitary tissues, including the ovary and placenta. It has been shown that change in GnRHR mRNA is one of the mechanisms for regulating the expression of the GnRHR. To help understand the molecular mechanism(s) involved in transcriptional regulation of the GnRHR gene, the 5' flanking region of the GnRHR gene has recently been isolated. Initial characterization studies have identified several DNA regions in the GnRHR 5' flanking region which are responsible for both basal expression and GnRH-mediated homologous regulation of this gene in pituitary cells. The mammalian GnRHR lacks a C-terminus and possesses a relatively short third intracellular loop; both features are important in desensitization of many others G-protein coupled receptors (GPCRs), Homologous desensitization of GnRHR has been shown to be regulated by various serine-threonine protein kinases including protein kinase A (PKA) and protein kinase C (PKC), as well as by G-protein coupled receptor kinases (GRKs). Furthermore, GnRHR was demonstrated to couple with multiple G proteins (Gq/11, Gs, and Gi), and to activate cascades that involved the PKC, PKA, and mitogen-activator protein kinases. These results suggest the diversity of GnRHR-G protein coupling and signal transduction systems. The identification of second form of GnRH (GnRH-II) in mammals adds to the complexity of the GnRH-GnRHR system. This review summaries our recent progress in understanding the regulation of GnRHR gene expression and the GnRHR signal transduction pathways.

Animals↗
PubMed1998

Thin slice CNS explants maintained on collagen-coated culture dishes.

We have developed a simple and inexpensive procedure for explant culture termed 'thin slice culture' that relies on the use of thin sections of CNS tissue ( < or = 150 microm) which adhere directly to the bottom of collagen-coated culture dishes (or glass coverslips within culture dishes). Microscopic visualization and tissue oxygenation are enhanced due to the reduced slice thickness, and the reduced volumes of incubation media required lessen the amount of expensive agents used (e.g. growth factors). We show that thin slice cultures of spinal cord, brainstem and hippocampus remain viable for at least several weeks and are suitable for many experimental approaches including time-dependent studies, immunocytochemistry and electrophysiology.

Animals↗
PubMed1998

Expression of the messenger RNA for gonadotropin-releasing hormone and its receptor in human cancer cell lines.

The presence of gonadotropin-releasing hormone (GnRH) binding sites in biopsy samples of human epithelial ovarian cancer and ovarian tumor cell lines as well as the demonstration of the inhibitory effects of GnRH analogues on the growth of these cells raised the possibility that GnRH is produced locally by ovarian cancer cells. In order to investigate an autocrine/paracrine regulatory mechanism in human carcinomas, we have studied the expression of GnRH and GnRHR mRNA in human ovarian epithelial cell lines (OVCAR-3 and SKOV-3), human choriocarcinoma cell line (JEG-3) and human hepatocarcinoma cell line (HepG 2). Using primers corresponding to published human GnRH and GnRHR cDNA sequences, predicted PCR products were obtained from these cell lines by reverse transcription-polymerase chain reaction (RT-PCR) and confirmed by Southern hybridization. Sequencing analysis of GnRH PCR products showed that their sequences have 100% identity to the published human GnRH cDNA sequence. These results indicated that GnRH and GnRHR genes are expressed in all the cell lines tested in the present study, and strengthen the concept that GnRH may act as an autocrine regulator on the growth of cancer cells.

Blotting, Southern↗
PubMed1997

Sequence of a cDNA clone encoding a novel somatolactin in goldfish, Carassius auratus.

As a first step towards the development of a sensitive ribonuclease protection assay to study the regulation of somatolactin (SL) mRNA expression in pituitary cells of goldfish, we have isolated a complementary DNA (cDNA) clone encoding precursor sequence of SL from a cDNA library prepared from goldfish pituitary poly(A)+ RNA. The 843-bp goldfish SL (gfSL) cDNA has an open reading frame of 693 nucleotides with two possible start codons of AUG. Amino acid sequence alignment revealed that gfSL has the characteristics of four conserved domains (A, B, C and D) common to all SLs with the domain B being the most conserved region among all the characterized SLs. Similar to other teleost SLs, this gfSL is similarly related but clearly distinct from growth hormone and prolactin of goldfish and other teleosts. However, unlike most other known teleost SLs which have more than 70% amino acid sequence identity to each other, the overall amino acid sequence identity of this novel gfSL with other previously characterized SLs ranges from only 36% to 51%. Moreover, this gfSL contains only six cysteine residues, rather than seven in most other SLs, in conserved positions. Northern blot analysis revealed a single gfSL mRNA transcript of approximately 1 kb in the pituitaries of both sexually regressed and maturing male and female goldfish.

Amino Acid Sequence↗
PubMed1996

Identification of two prolactin cDNA sequences from a goldfish pituitary cDNA library.

We have identified two different cDNA clones encoding for goldfish prolactin (gfPRL) from a pituitary cDNA library. The coding regions of these clones are predicted to encode for an identical amino acid (aa) sequence with four silent mutations. The 3'-untranslated regions (UTRs) of these clones show only 72% nucleotide (nt) sequence identity. The two genes each encoding gfPRL might have derived from recent gene duplication before the divergence of goldfish from other Cypriniforms. Genomic Southern blot analysis of goldfish DNA also demonstrated that there is a small family of two genes for prolactin in the genome of goldfish.

Amino Acid Sequence↗
PubMed1996

Isolation and characterization of two distinct growth hormone cDNAs from the goldfish, Carassius auratus.

As a first step toward the development of a ribonuclease protection assay for studying the regulation of growth hormone (GH) gene expression in pituitary cells of the goldfish, Carassius auratus, we report the isolation of two cDNA clones encoding goldfish GH from a cDNA library prepared from pituitary poly(A)+ RNA. The complete nucleotide sequences of these two GH cDNA clones have been determined and both of them were predicted to encode a polypeptide of 210 amino acids (aa) including a putative signal peptide of 22 aa. One of the GH cDNAs encodes a polypeptide (gfGHI) with five cysteine residues (similar to other carp Ms), whereas another encodes a polypeptide (gfGHII) with four cysteine residues (similar to most teleostean GHs). Because these two GH cDNAs have distinct nucleotide sequences at their coding and 3' untranslated regions, they are likely to be encoded by two different genes.

Amino Acid Sequence↗
PubMed1996

Evidence for estrogen receptor-mediated regulation of human gonadotropin-releasing hormone promoter activity in human placental cells.

Two fragments of the human gonadotropin-releasing hormone (GnRH) promoter, one containing 0.6 kb of the downstream promoter sequence (H-1) and another 1.8 kb fragment (H-2) containing the upstream promoter region with a deletion of the downstream promoter sequence, were fused to a promoterless luciferase (Luc) reporter construct and transfected into the human placental (JEG) cells. JEG cells transfected with both constructs showed insignificant changes in luciferase activity in response to estradiol. However, cotransfection of H-2-Luc construct with a vector expressing a human estrogen receptor (ER) cDNA results in dose-dependent decreases in luciferase activity in response to estradiol. This ER mediated down-regulation of promoter activity was retained in constructs with the GnRH promoter deleted to position 548 bp 5' to the upstream transcription start site. Further deletion of upstream promoter sequence to 169 bp reversed the estrogen responsiveness from inhibitory to stimulatory. Thus, this study demonstrated that the upstream GnRH promoter region can be regulated by estrogen in transfected JEG cells.

Dose-Response Relationship, Drug↗
PubMed1994

Comparison of the incidence of postpartum low back pain in natural childbirth and cesarean section with spinal anesthesia.

BACKGROUND: Many parturients and their obstetricians believe that spinal anesthesia will cause low back pain (LBP). MATERIALS & METHODS: We studied prospectively a total of 160 parturients; 80 of them had cesarean section (CS) with spinal anesthesia and another 80 who had natural childbirth. Incidence of LBP was investigated and compared in these patients before pregnancy, during pregnancy and postpartum. RESULTS: Our result showed that before pregnancy, about one third (33.1%) of the parturients already had LBP and the incidence of LBP seemed to increase during pregnancy. The incidence of LBP decreased gradually postpartum. There was no difference in the incidence of postpartum LBP between the CS with spinal anesthesia group and the natural childbirth group. CONCLUSIONS: We concluded that postpartum LBP could be related to changes during pregnancy and not related to spinal anesthesia.

Adult↗
PubMed1994

Outcome of surgery and anesthesia in patients 80 years of age and older.

We studied retrospectively the outcome of surgery and anesthesia in 294 patients aged 80 and older who underwent 362 surgical procedures. Of these, 52 cases (14.4%) were admitted to intensive care unit (ICU) post-operatively. The 48-hour, 48-hour-to-30-day and overall mortality rates were 0.8%, 3.8% and 5.2% respectively. ICU. admission and mortality rate were closely associated with the ASA physical status classification. The overall mortality rates were 1.3%, 5.7% and 27% in class II, III and IV respectively. The respective ICU admission rates were 3%, 20% and 56%. ICU admission rate and mortality rate were 42.5% and 13.8% in emergency surgery vs. 5.8% and 2.5% in elective surgery. Patients with 3 or more co-existing diseases had the mortality rate of 23% and the rates of ICU admission and mortality for those with 3 or more peri-operative complications were 22% and 16% respectively vs. 11% and 4% for those with 2 or less peri-operative complications. General surgery was associated with the highest mortality rate (15%) than other type of procedures. 22 of 74 cases who underwent intra-abdominal surgery required controlled ventilation for more than 24 hours post-operatively. 59% (13 cases) of such cases could not weaned successfully from ventilators and died subsequently. Only 2.5% (7 cases) of cases who underwent extra-pleural and extra-peritoneal procedures required controlled ventilation for more than 24 hours post-operatively. Of these, 2 died subsequently. For comparison, the study were artificially divided into two phases, each of three years long: they were the period from 1986-1988 and the period from 1989-1992.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Developmental transition by spinal cord plasma membranes of embryonic chick from permissive to restrictive substrates for the morphological differentiation of neuroblastoma x glioma hybrid NG108-15 cell.

Recent studies of spinal cord development and plasticity, in chick, have demonstrated a loss of regenerative ability correlating to embryonic day (E) 13 of the 21-day developmental period. Here we describe membrane fractions from embryonic chick spinal cords as permissive or restrictive substrates for the neuron-like differentiation of neuroblastoma x glioma hybrid NG108-15 cells, in vitro. Plasma membranes were purified from the thoracic spinal cord of embryos at a series of developmental stages (E10-E18). Micro-well plates were coated with the fractions and NG108-15 cells cultured thereon. Cells adhered to the E10-coated wells and began to differentiate after 2 h, becoming highly differentiated, with neurites 2-3 times longer than the diameter of the cell body after 24 h in in culture. In contrast, cells cultured in E18-coated wells remained as clusters of undifferentiated cells of rounded morphology, even after 48 h in culture. As well, the permissive and restrictive plasma membranes were assessed semiquantitatively as the number of adhering cells after 20 h of culture. Adhesion of cells to the substrate decreased as the embryonic age of the plasma membrane substrate increased. Examination of the plasma membrane fractions, using SDS-PAGE, revealed several proteins in the 40-60 kDa range that varied substantially between E12, E14 and E18. Results of this study provide in vitro confirmation of previous in vivo findings; namely, that early embryonic spinal cord is initially permissive for neuritic outgrowth becoming restrictive around E13.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A study on women's practice of breast self-examination in Taiwan.

METHODS: A questionnaire interview was conducted on a sample of 3,040 women ages 30-59 years in the Taipei area through multistage sampling with probability proportional to size. Excluding mistakes in household registration, there were 2,311 qualified subjects, 1,749 of whom (75.7%) completed the interview. The study framework was set up according to Green's PRECEDE model. RESULTS: In the results of this study only 8.4% of the subjects performed breast self-examinations monthly, and no single step of the breast self-examination procedure had a correct rate above 30%. The most remarkable associative factor for the correctness of breast self-examination was "source of instruction," a variable of "enabling factors"; other variables with strong associations were "newspaper contact" (contact with health reports in newspapers), which also belongs to the enabling factors category and "knowledge of breast cancer," a "predisposing factor." Demographic factors such as "educational level" and "urbanizational level" were only indirectly related. CONCLUSION: The authors suggested using all possible routes of health education, such as mass media, hospitals and clinics, and distribution of information in the workplace, to instruct and encourage breast self-examination, especially among women from rural communities and those with less education.

Adult↗
PubMed1992

A heparin-binding protein in porcine seminal plasma stimulates neurite outgrowth on neuroblastoma cells in culture.

A protein of neurite outgrowth activity has been identified in porcine seminal plasma after ammonium sulfate precipitation and affinity chromatography on heparin-Sepharose. Upon SDS-PAGE, the polypeptide is shown to have a M(r) of 16,000-18,000. Biologically by induction of neuritic processes on neuroblastoma cells, and immunologically by cross-reaction with specific antisera, this seminal plasma protein differs from acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF) and nerve growth factor (NGF). The neurite outgrowth activity is relatively stable at pH 3-7 and under denaturing conditions of 8 M urea and beta-mercaptoethanol, but is inactivated by treatment of trypsin. This appears to be a novel protein, enhancing morphological differentiation of neuroblastoma cells in culture.

Animals↗
PubMed1990

Identification and characterization of the beta-adrenergic receptor on neuroblastoma x glioma hybrid NG108-15 cells.

1. Using [3H]DHA and unlabeled L-alprenolol, a substantial amount of over 64% specific binding of beta-adrenergic receptor has been identified on the neuroblastoma x glioma hybrid NG108-15 cell, which has been proven to display numerous functional characteristics of intact neurons. 2. Beta-adrenergic receptor binding on intact NG108-15 cells does not change significantly upon morphological differentiation, induced by 1 mM dibutyryl cyclic AMP (dBcAMP). 3. The [3H]DHA binding on intact NG108-15 cells is rapid, saturable, and reversible, having a t1/2 of 1.0 min for association and 3.5 min for dissociation. 4. The affinity constant (Kd) and maximum binding capacity (Bmax) for binding of [3H]DHA to beta-adrenergic receptors on NG108-15 cells have been estimated by Scatchard plot analysis to be 2.5 and 0.23 nM, respectively. Further analysis indicates a single class of receptors for [3HDHA binding on NG108-15 cells. 5. Studies on kinetic properties have revealed on-rate (K + 1) and off-rate (K - 1) constants of 0.7 X 10(-9) M min-1 and 0.19 min-1, respectively. Further, the IC50 value and inhibition constant (Ki) for unlabeled L-alprenolol to inhibit [3HDHA binding on NG108-15 cells have been estimated to be 10(-5) and 8.9 X 10(-6) M, respectively. 6. The rank-order potency of catecholamine agonists, (-)ISO greater than (+)ISO greater than EPI greater than NE, reveals the presence of type 2 receptor for the beta-adrenergic binding on both differentiated and undifferentiated NG108-15 cells. 7. The present study indicates that the clonal neuroblastoma x glioma hybrid NG108-15 cell line possesses substantial amounts of beta-adrenergic receptors with characteristics similar to those on neuronal cells.

Alprenolol↗
PubMed1990

The effect of volume of epidural morphine on postoperative analgesia in patients undergoing cesarean section.

Ninety paturients undergoing elective cesarean section were included in this randomized study to compare the influence of the injected volume of epidural morphine (EM) on postoperative analgesia. Three similar groups of patients (n = 30 each) received 2 mg EM in 2 ml, 10 ml, and 20 ml saline respectively one hour after the last dose of 2% lidocaine. Pain scores (0-10) at rest (including uterine contraction pain) at the 2nd, 4th, 8th, 12th, 18th, and 24th h were compared among the three groups. There were no statistically significant differences of pain score among the three groups although lower pain score was present in the 20 ml group since the 8th h and thereafter. Regarding the number of patients who requested additional meperidine for pain relief 3 in 2 ml group, 2 in 10 ml group and 1 in 20 ml group respectively. The result may suggest that the influence of the injected volume of EM on postcesarean analgesia is not obvious.

Adult↗