Biomedical subjects

K Yang

Publications and source records attributed to K Yang.

At least 145 records · Page 8Linked to original sources

PubMed1998

Chronic hypoxemia selectively down-regulates 11beta-hydroxysteroid dehydrogenase type 2 gene expression in the fetal sheep kidney.

The present study was designed to examine the effects of chronic fetal placental embolization on the expression of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) types 1 and 2, the intracellular enzymes responsible for the metabolism of glucocorticoids. Twelve instrumented fetal sheep were randomly allocated on Day 110 (term = 147 days) to either a control (n = 6) or embolized (n = 6) group. Embolized fetuses received daily injections of nonradioactive microspheres into the abdominal aorta for 21 days to decrease arterial oxygen content by 40-50% of the pre-embolization values. At the end of the experiment, fetal liver and kidney tissues as well as placental cotyledons were collected, and tissue levels of 11beta-HSD mRNA and activity were determined by standard Northern blot analysis and radiometric conversion assay, respectively. There was a 44% reduction (p < 0.01) in the level of renal 11beta-HSD2 mRNA in the embolized group as compared with the control group. Moreover, this reduction in mRNA was carried through to 11beta-HSD2 protein, since there was a corresponding decrease in the level of 11beta-HSD2 activity (4.5+/-0.2 vs. 2.9+/-0.1 pmol/min per milligram protein, p < 0.01). In contrast, levels of both 11beta-HSD1 mRNA and activity in the fetal liver remained unchanged. Moreover, both 11beta-HSD types 1 and 2 mRNA and activity in the placenta were not altered by the fetal placental embolization. In conclusion, chronic hypoxemia selectively inhibits renal 11beta-HSD2 mRNA expression and enzyme activity in the ovine fetus, which may contribute, at least in part, to the mechanisms leading to fetal hypertension.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1998

Regulation of 11beta-hydroxysteroid dehydrogenase type 2 by progesterone, estrogen, and the cyclic adenosine 5'-monophosphate pathway in cultured human placental and chorionic trophoblasts.

Human placenta and fetal membranes contain two types of 11beta-hydroxysteroid dehydrogenase (11beta-HSD). 11Beta-HSD1 interconverts cortisol and cortisone and is the predominant isoform found in the fetal membranes. 11Beta-HSD2, which predominates in the placenta syncytiotrophoblast, converts cortisol to cortisone. It has been proposed that placental 11beta-HSD protects the fetus from high levels of maternal glucocorticoids. In this study, cultured term human placental and chorionic trophoblasts were used to examine the regulation of 11beta-HSD1 and 11beta-HSD2 activities and mRNA expression by progesterone, estrogen, and activators of adenylate cyclase (forskolin) and protein kinase C (phorbol 12-myristate 13-acetate, PMA). Placental trophoblast displayed mainly type 2 oxidase activities. 11Beta-HSD in the chorionic trophoblast was exclusively an 11beta-HSD1 reductase. Progesterone (0.001-1 microM) inhibited 11beta-HSD2 activity in a dose-dependent fashion. Inhibition of endogenous progesterone production with trilostane enhanced 11beta-HSD2 activity. The inhibitory effect of progesterone on 11beta-HSD2 activity was not reversed by the progesterone receptor antagonists RU-486 or onapristone. Progesterone (1 microM) also reduced levels of 11beta-HSD2 mRNA, an effect that was attenuated by both RU-486 and onapristone. Estradiol (1 microM) inhibited type 2 oxidase activity as well. Activation of adenylate cyclase by forskolin (100 microM) up-regulated both 11beta-HSD2 activity and mRNA expression; there was no effect of PMA (1 microM) on 11beta-HSD2. 11Beta-HSD1 reductase activity was unaffected by progesterone, estrogen, forskolin, or PMA in either the placental or chorionic trophoblasts. We conclude that both progesterone and estrogen are inhibitors of 11beta-HSD2 activity in term human placenta in vitro. Levels of 11beta-HSD2 activity and mRNA are increased by activation of the cAMP pathway. Progesterone also suppresses levels of 11beta-HSD2 mRNA.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1998

11beta-hydroxysteroid dehydrogenase type 2 is the predominant isozyme in the guinea pig placenta: decreases in messenger ribonucleic acid and activity at term.

The type 2 isozyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD2) is responsible for inactivating physiologically active glucocorticoids to their inert metabolites. This is the predominant 11beta-HSD isozyme in the human placenta, where it is believed to protect the fetus from high levels of maternal cortisol. Given the similarity in placental structure between the human and the guinea pig (hemomonochorial), we have evaluated the potential of utilizing the guinea pig as a model to study the function and regulation of placental 11beta-HSD2 in fetal development. In this study, we characterized the intrinsic properties of 11beta-HSD in the guinea pig placenta during late pregnancy. The 11beta-HSD activity in the placenta was characteristic of 11beta-HSD2 in that it possessed only dehydrogenase activity that was NAD-dependent and had a high affinity for cortisol (Km = 134 nM). Moreover, the level of the 11beta-HSD2-like activity decreased significantly at term. To verify the expression of 11beta-HSD2 gene and to determine whether corresponding changes in 11beta-HSD2 mRNA occur at term, we also cloned the cDNA encoding guinea pig placental 11beta-HSD2. The deduced guinea pig 11beta-HSD2 enzyme contains 395 amino acids and shares over 80% sequence identity with other mammalian 11beta-HSD2 proteins. Northern blot analyses demonstrated the presence of the mRNA for 11beta-HSD2 but not that for 11beta-HSD1. Moreover, the level of 11beta-HSD2 mRNA decreased significantly at term. The parallel decrease in levels of 11beta-HSD2 activity and mRNA at term is consistent with, and provides a plausible molecular basis for, the previously reported increase in the rate of placental transfer of cortisol between mother and fetus at that time. In conclusion, the present study demonstrates that the guinea pig resembles the human in that 11beta-HSD2 is the predominant, if not exclusive, isozyme expressed in the placenta. Therefore, the guinea pig appears to represent a suitable model in which to study the role of placental 11beta-HSD2 in human fetal development.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1998

International Study of Expert Judgement on Therapeutic Use of Benzodiazepines and Other Psychotherapeutic Medications: V. Treatment strategies in panic disorder, 1992-1997.

The objective of this study was to assemble expert clinical experience and judgment regarding the treatment of panic disorder in a systematic, quantitative manner, particularly with respect to changes during the past 5 years. A panel of 73 internationally recognized experts in the field of pharmacotherapy of anxiety and depression was constituted by multistage peer nomination. Sixty-six experts completed a questionnaire in 1992, and 51 of those completed a follow-up questionnaire in 1997. This report focuses on the experts' responses to questions about therapeutic options as they relate to a vignette describing a typical case of panic disorder. The preferred initial treatment strategy in 1992 (59%) and in 1997 (55%) was a combination of medication with cognitive behavioral therapy. The vast majority of the expert panel included a medication in their recommendations--91% in 1992 and 90% in 1997. Experts recommending a medication for panic in 1992 chose as first-line treatment a benzodiazepine (35%), a selective serotonin reuptake inhibitor (SSRI, 7%), an older antidepressant (33%), or a combination of medications (25%), principally a benzodiazepine plus an older antidepressant (19%). In 1997, fewer chose a benzodiazepine (15%) or an older antidepressant (11%) alone, whereas 33% chose an SSRI alone. More experts chose a combination of medications in 1997 (39%), and the increase was attributable mainly to the choice of a benzodiazepine plus an SSRI (17%). Overall, there was only a small decline in recommendations for benzodiazepines, whereas the increased choice of SSRIs came largely at the expense of the older antidepressants. As second-line medications for panic should their first-line choice fail, the experts in 1997 recommended a benzodiazepine (7%), an SSRI (15%), an older antidepressant (28%), or a combination of medications (50%), most often a benzodiazepine plus an older antidepressant (21%) or a benzodiazepine plus an SSRI (17%). (Experts were not asked to recommend second-line treatment in 1992). Thus, in case of unsatisfactory response, the experts' choices shifted from benzodiazepines and SSRIs alone toward the older antidepressants alone or combinations of an antidepressant plus a benzodiazepine. This report concluded that combined cognitive behavioral therapy plus medication was highly favored by the experts as the initial treatment strategy for panic disorder. Over the past 5 years, SSRIs displaced older antidepressants as the experts' choice for first-line pharmacotherapy of panic disorder. In case of an unsatisfactory response, the experts more often recommended an older antidepressant or a combination of an antidepressant plus a benzodiazepine. According to the experts' judgments, the benzodiazepines, especially combined with an antidepressant, remain mainstays of pharmacotherapy for panic disorder.

Adult↗

PubMed1998

The effect of estradiol on output of adrenocorticotropin and prolactin by fetal sheep anterior pituitary cells.

We examined the hypothesis that estradiol (E2) would affect fetal anterior pituitary corticotroph and lactotroph function in vitro, and that any effects would be influenced by gestational age. Anterior pituitary cells from fetal sheep at day 129 (n = 4) and at day 139 (n = 5) of gestation were cultured. After 96 h in culture, cells were treated for 18 h with E2 concentrations ranging from 0 to 1000 nM, in the presence or absence of 100 nM of corticotropin-releasing hormone (CRH), cortisol, arginine vasopressin (AVP), or CRH and cortisol, to examine their effects on corticotroph function. Cells were also treated with bromocriptine or increasing concentrations of E2 to study their effects on lactotroph function. Immunoreactive (ir) adrenocorticotropin (ACTH) and prolactin in the culture medium were measured by radioimmunoassay. Levels of cellular pro-opiomelanocortin (POMC) mRNA and prolactin mRNA were determined by in situ hybridization. Immunohistochemistry was used to determine the percentage of cells that were immunopositive for ACTH (corticotrophs) or prolactin (lactotrophs). ACTH output was stimulated by CRH treatment at day 139 but not at day 129 of gestation, and cortisol attenuated this response. ACTH output by cells cultured with 10 nM E2 and 100 nM CRH, at 139 days of gestation, was greater than with CRH alone (p < 0.05). E2 did not affect basal ACTH output or ACTH output with any other treatment or levels of POMC mRNA. Prolactin output was not affected by E2 treatment. Bromocriptine significantly decreased prolactin output but not levels of prolactin mRNA. We conclude that E2 may affect CRH-stimulated fetal sheep pituitary corticotroph function late in gestation, but only within a narrow, physiological range of concentration.

Adrenocorticotropic Hormone↗

PubMed1998

[Studies on the relationship between smoking and formation of DNA adducts in lung tissues].

OBJECTIVE: To explore the relationship between smoking and contents of DNA adducts in the lung tissues, and to study if there is any its difference between the patients with and without lung cancer and between males and females. METHODS: DNA was extracted from the normal lung tissues dissected from the concurrently hospitalized patients with and without lung cancer (19 and 18 each for males and females). Contents of DNA adducts in the lung tissues were determined by 32P-postlabelling assay. RESULTS: Smoking could cause increase in levels of DNA adducts in the lung tissues. There were no significant difference in DNA adduct levels between the lung tissues from men and women and from the patients with and without lung cancer, after the adjustment for smoking factor. CONCLUSION: More data should be accumulated to elucidate the relationship between DNA adduct levels in the human bodies and its biological effects.

DNA Adducts↗

PubMed1998

[Distribution of Mg2+ and Ca2+ in serum and lymphocyte of the patients with arrhythmia].

The distributions of Mg2+ and Ca2+ in serum and lymphocyte from 51 arrhythmic patients (15 cases of atrial premature beat, 12 cases of atrial fibrillation, 24 cases of ventricular premature beat) and 30 healthy subjects were detected by flame atomic absorption spectrophotometry. The results showed that the distribution of Mg2+ of the arrhythmia cases was significantly lower than that of the control group (P < 0.01) and the concentration of Ca2+ in lymphocytes of arrhythmia case group was significantly higher than that of the control group (P < 0.01). The above distribution of Mg2+ and Ca2+ was somewhat related to the degree of heart failure. It is suggested that the lower distribution of Mg2+ in lymphocytes may cause arrhythmias.

Arrhythmias, Cardiac↗

PubMed1998

[Applied anatomy of the vascularity in the ileocolic region and its clinical significance].

To understand the characteristics of the patterns of arteries and veins distributed over the ileocolic segment, 50 cadavers were studied by gross-anatomy. The arteries, veins and their paracolic anastomoses distributed over ileocecal region, ascending colon and transverse colon were observed. The results showed that the distribution pattern of venous vessel was far more constant than that of artery, that the arrangements of artery in the ileocolic segment were classified into 7 types, and there were no interruption of paracolic anastomoses between arteries. But in 3 specimens the paracolic anastemoses between the right colic vein and the middle colic vein were completely interrupted. These findings may be useful in guiding clinical practice and preventing postoperative complications in ileocolic replacement of esophagus.

Adult↗

PubMed1998

[Study on the antagonistic action of selenite on fluoride-induced lipid peroxidation and on the changes of trace elements in rats].

Five groups of SD male rats were provided with deionized drinking water containing 0 and 150 mg/L NaF, and containing both 150 mg/L NaF and 0.5, 2.0 or 4.0 mg/L Na2SeO3 respectively for 10 weeks, in order to find out the optimal level of selenite in drinking water against fluoride toxicity. The results showed that fluoride could cause significant increase of lipid peroxides (LPO) and metabolic disorder of trace elements in the serum and kidney of rats. The antagonistic effect of 2.0 mg/L Na2SeO3 drinking water on the lipid peroxidation induced by 150 mg/LNaF was the most evident, whereas those of 0.5 and 4.0 mg/L Na2SeO3 were not obvious. It is concluded that selenite possesses significant antagonistic effects on renal damages induced by fluoride and 2.0 mg/L Na2SeO3 is the optimal concentration for the antagonistic effect on renal impairments induced by 150 mg/L NaF in drinking water.

Animals↗

PubMed1998

[Co-existence of glutamate and substance P in electrophysiologically identified dorsal root ganglion neurons of rats].

Electrophysiological properties, reaction to substance P (SP) receptor agonist, and co-existence of glutamate (Glu) and SP in neurons of the spinal dorsal root ganglion (DRG) of the rat were investigated in vitro. The main results were: (1) According to the fiber conduction velocity, totally 135 intracellularly recorded DRG neurons were divided into A alpha/beta type (> 12 m/s) and C type (< 1.3 m/s). There were remarkable differences between the fast after hyperpolarization (fAHP) of action potential between the two types: fAHP of C type neurons had smaller amplititude and longer duration, whereas the fAHP of A alpha/beta type neurons had larger amplititude and shorter duration. (2) Among 22 DRG neurons of which overshoots of action potential appeared, specific SP receptor agonist Sar-SP induced depolorization in 42% (5/12) of the A alpha/beta type neurons and 80% (8/10) of the C type neurons. (3) Biocytin was intracellularly injected into the 22 Sar-SP administrated DRG neurons. After fixation and section, employing the immunofluorescent histochemical multi-staining technique for phosphate-activated glutaminase (PAG, a specific marker for glutamatergic neurons), SP and biocytin, 25% (3/12) of the A alpha/beta type neurons and 80% (8/10) of the C type neurons showed both PAG- and SP-like immunoreactivities. There was a great difference between the percentages of the PAG/SP co-existing A alpha/beta type neurons and C type neurons (P < 0.05). The present results indicated that there were some differences in chemicoanatomical and electrophysiological properties between A alpha/beta type and C type neurons, and SP might facilitate the discharge of DRG neurons through activating SP autoreceptors on their membrane.

Action Potentials↗

PubMed1998

[Peripheral substance P receptor mediating c-fos gene expression in the spinal dorsal horn induced by peripheral noxious stimulation].

Employing immunohistochemical staining for FOS protein, which is the expression product of c-fos proto-oncogene, the role of substance P receptor (SPR) in noxious information transmission at peripheral terminals of the dorsal root ganglion cells was investigated by means of a selective SPR antagonist L668, 169 and agonist Sar-SP. Unilateral injection of L668, 169 (10(-4) mol/L) into the plantar of hindpaw 10 min before injection of 4% formalin, the number of FOS-like immunoreactive (LI) neurons in the superficial laminae of dorsal horn was significantly decreased, but the changes were not obvious in the deeper laminae. Smaller doses of L668, 169 (10(-5), 10(-6) mol/L) were almost ineffective on FOS-LI neurons in both the superficial and the deeper laminae. However, Sar-SP (10(-4) mol/L) or formalin did result in the expression of c-fos gene in the superficial laminae of the dorsal horn. These results indicated that SP might contribute to the transmission of nociceptive information and induce noxious sensation, at least in part by activating SPR in peripheral terminals of the dorsal root ganglion cells.

Animals↗

PubMed1998

[Research on the regulation of glucoamylase gene(glaA) expression in A. niger. II. Analysis of the function of 5'-regulatory region of A. niger T21 and 3.795 glaA gene].

Two plasmid vectors pXH2 and pGH1 were constructed through the fusion of E. coli hph gene, the report gene and the 5' upstream regions of A. niger T21 and 3.795 respectively, as well as the terminator of A. nidulans trpC gene. The plasmid vectors were than used to transform A. niger T21 to functionally identify those different basic groups between the two 5' upstream regions responsible for high-level expression of the glaA gene. Southern analysis of two transformants XH2C and GH1C revealed that pXH2 and pGH1 were integrated respectively into the chromosome at same site with two copies in tandem array. The level resistant to HmB(3000 micrograms/ml) of XH2C was twice as high as that (1500 micrograms/ml) of GH1C, indicating that the changes of basic groups through mutation result in twice increase of functional level of region responsible for transcription and regulation of A. niger T21 glaA gene compared with that of 3.795.

Aspergillus niger↗

PubMed1997

Functional implications of disulfide bond, Cys45-Cys50, in recombinant prochymosin.

Bovine prochymosin (chymosin) contains three disulfide bonds: Cys45-Cys50, Cys206-Cys210 and Cys250-Cys283 (pepsin numbering). We have demonstrated that Cys250-Cys283 is not intimately involved in the catalytic mechanism of chymosin but is required for the correct refolding of prochymosin. To elucidate the functional implications of another disulfide bond of Cys45-Cys50, these two cysteine residues were replaced separately or simultaneously by site-directed mutagenesis. Like the wild-type prochymosin all the seven mutants generated (C45A, C50A, C45A/C50A, C45D, C50S, C45D/C50S, C45A/C50S) exhibit the activity of autocatalytic activation after refolding, indicating that Cys45-Cys50 is dispensable in prochymosin refolding. Spectroscopic analyses and urea-induced denaturation studies of prochymosin and four mutants tested (C45A, C50A, C45A/C50A, C45D/C50S) show that: (1) they share similar far-UV CD spectra and similar fluorescence emission spectra; (2) mutation results in a perturbance of tryptophan environment and somewhat destabilization of prochymosin conformation. However, quenching studies reveal that the only one tryptophan residue inaccessible to acrylamide is still buried in the mutated molecules. All these results suggest that the overall conformation of prochymosin is maintained after mutation. As for the enzymatic properties of pseudochymosin, the activation product of prochymosin, it has been found that elimination of Cys45-Cys50 causes a marked drop of thermostability and an alteration of substrate specificity.

Acrylamide↗

PubMed1997

Mutation in the mismatch repair gene Msh6 causes cancer susceptibility.

Mice carrying a null mutation in the mismatch repair gene Msh6 were generated by gene targeting. Cells that were homozygous for the mutation did not produce any detectable MSH6 protein, and extracts prepared from these cells were defective for repair of single nucleotide mismatches. Repair of 1, 2, and 4 nucleotide insertion/deletion mismatches was unaffected. Mice that were homozygous for the mutation had a reduced life span. The mice developed a spectrum of tumors, the most predominant of which were gastrointestinal tumors and B- as well as T-cell lymphomas. The tumors did not show any microsatellite instability. We conclude that MSH6 mutations, like those in some other members of the family of mismatch repair genes, lead to cancer susceptibility, and germline mutations in this gene may be associated with a cancer predisposition syndrome that does not show microsatellite instability.

Adenomatous Polyposis Coli Protein↗

PubMed1997

3-Methoxynaltrexone, a selective heroin/morphine-6beta-glucuronide antagonist.

Recent work has suggested that heroin and morphine-6beta-glucuronide (M6G) both act through a novel mu opioid receptor subtype distinct from those mediating morphine's actions. This very high affinity 3H-M6G site is selectively competed by 3-methoxynaltrexone. In vivo, 3-methoxynaltrexone (2.5 ng, i.c.v.) selectively antagonizes the analgesic actions of heroin and M6G without interfering with mu (morphine and [D-Ala2,MePhe4,Gly(ol)5]enkephalin), delta ([D-Pen2,D-Pen5]enkephalin), kappa1 (U50,488H) or kappa3 (naloxone benzoylhydrazone) analgesia. In dose-response studies, 3-methoxynaltrexone (2.5 ng, i.c.v.) significantly shifted the ED50 values for heroin and its active metabolite, 6-acetylmorphine, without affecting the morphine curve. These results indicate that 3-methoxynaltrexone selectively blocks a novel 3H-M6G binding site which is responsible for the analgesic actions of heroin and M6G. This ability to selectively antagonize heroin actions opens new possibilities in the development of therapeutics for the treatment of opioid abuse.

Analgesia↗

PubMed1997

DC-Chol liposome-mediated gene transfer in rat spinal cord.

We examined the potential of non-viral vector-mediated gene transfection in the rat spinal cord. Reporter gene (beta-gal) or brain-derived neurotrophic factor (BDNF) cDNA containing a pCMV promoter complexed with DC-Chol liposomes was injected into the intact rat spinal cord gray matter. RT-PCR confirmed the increased expression of BDNF mRNA in the injection areas. X-gal staining demonstrated the localized expression of beta-gal reporter genes. No overt tissue damage caused by DC-Chol liposome/DNA complex injections was detected. These results suggest that cationic liposome-mediated delivery can be a practical method for gene transfer in spinal cord.

Animals↗

PubMed1997

A mouse model of human familial adenomatous polyposis.

In an effort to generate a good mouse model for human colorectal cancer, we generated mice which carry a mutation in the adenomatous polyposis coli (Apc) gene. Mice which are heterozygous for the mutation, designated Apc1638, develop colonic polyps and tumors of the small intestine. Neoplasms were found in 96% of animals studied, and they included adenomas, adenocarcinomas, and polypoid hyperplasias. The mice developed an average of 3.3 tumors, with the highest number in duodenum, followed by jejunum, stomach, ileum, and colon. Focal areas of dysplasias were observed in the colonic mucosa in 50% of mice which were 10 months old or older. These results suggest that mice carrying the Apc1638 mutation can serve as a good model to study the initiation, progression, and inhibition of gastrointestinal tumors.

Adenomatous Polyposis Coli↗

PubMed1997

Probing the substrate specificity of an enzyme catalyzing inactivation of streptogramin B antibiotics using LC-MS and LC-MS/MS.

LC-MS and LC-MS/MS analyses indicated that an enzyme responsible for inactivating the antibiotic etamycin is specific for streptogramins and acts on both type B-I and B-II streptogramin subgroups. No enzymatic activity was detected for other cyclodepsipeptides such as surfactins and viscosin. It was demonstrated using analogs of etamycin that the picolinyl moiety is essential to obtain enzyme-generated ring-opened compounds. Because the picolinyl moiety is also essential for the biological activity of streptogramins, it is proposed that this residue is a distinctive topographic feature in the binding of this group of antibiotics to enzyme active sites.

Chromatography, Liquid↗