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Biomedical subjects

D Wu

Publications and source records attributed to D Wu.

At least 397 records · Page 22Linked to original sources
PubMed1996

Outward K+ current in epithelial cells isolated from intermediate portion of endolymphatic sac of guinea pigs.

Ion currents in epithelial cells isolated from the intermediate portion of endolymphatic sac (ES) in guinea pigs were investigated with the use of the whole cell patch-clamp technique. Depolarizing voltage steps from a holding potential of -60 mV induced a time- and voltage-dependent outward current, which is comparable to that of delayed rectifying K+ currents. The average resting membrane potential in the current-clamp mode was -54.8 +/- 11 mV (n = 45), which was similar to the value of zero current potential (-55.6 +/- 0.8 mV, n = 32) obtained from current-voltage (I-V) relationships of outward currents in voltage-clamp mode. The I-V relationship of the tail current exhibited a reversal potential (Erev) of -78.1 +/- 0.9 mV (n = 19) in standard external solution. The Erev of the outward current was linearly related to the logarithm of extracellular K+ concentrations. The slope was 48 mV per 10-fold change in extracellular K+ concentrations. The time constants of K+ current activation, inactivation, and K+ tail current deactivation were voltage dependent. The steady-state activation and inactivation of K+ current exhibited a sigmoidal relationship to voltage. The 50% maximal activation voltage and slope factor were -21 and 11 mV (n = 8), respectively. The 50% maximal inactivation voltage and slope factor were -45 and 13 mV (n = 7), respectively. The K+ current was blocked by externally applied 1 mM 4-aminopyridine (4-AP), 5 mM Ba2+ and 20 mM tetraethylammonium chloride (TEA). The sensitivity of the current to 4-AP and Ba2+ was higher than that to TEA. Elimination of external Ca2+ and increase of internal Ca2+ failed to significantly change the current, suggesting that the K+ current may be Ca2+ independent. The results show that epithelial cells in the intermediate portion of the ES possess a delayed-rectifier K+ current, which may be involved in membrane stability or in the ion balance between the cytosol and the extracellular environment.

Animals↗
PubMed1996

Pulmonary pseudosequestration receiving arterial supply from a coronary artery fistula. A case report.

A forty-eight-year-old man with a history of pulmonary tuberculosis and scarring of both hila and upper lobes was noted to have bilateral pulmonary pseudosequestration, in which the blood supply originated from a coronary artery fistulous vessel arising from the left circumflex artery and draining into the pulmonary artery. This is the first reported patient with the source of blood supply to the pulmonary pseudosequestration arising from a coronary artery fistula.

Bronchopulmonary Sequestration↗
PubMed1996

The proto-oncogene c-myb is expressed in sporadic bovine lymphoma, but not in enzootic bovine leukosis.

We examined bovine c-myb gene expression in six samples of sporadic bovine lymphomas (two calf, three thymic and one intermediate) and five of enzootic bovine leukosis. Tumor cells of the sporadic bovine lymphomas were of immature cell lineage (one B lymphoma and five T lymphomas). The c-myb mRNA was expressed in almost all the sporadic bovine lymphomas (except for one thymic form) including a BoCD8 single positive T lymphoma. On the contrary, c-myb was not expressed in mature B lymphomas of enzootic bovine leukosis. The results suggest that c-myb expression is closely associated with tumor cell differentiation of bovine lymphomas.

Animals↗
PubMed1996

The effects of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on intracellular adenosine 3',5'-monophosphate (cAMP) levels and GH secretion in ovine and rat somatotrophs.

The mechanism of action of GH-releasing peptide-6 (GHRP-6) and GHRP-2 on GH release was investigated in ovine and rat pituitary cells in vitro. In partially purified sheep somatotrophs, GHRP-2 and GH-releasing factor (GRF) increased intracellular cyclic AMP (cAMP) concentrations and caused GH release in a dose-dependent manner; GHRP-6 did not increase cAMP levels. An additive effect of maximal doses of GRF and GHRP-2 was observed in both cAMP and GH levels whereas combined GHRP-6 and GHRP-2 at maximal doses produced an additive effect on GH release only. Pretreatment of the cells with MDL 12,330A, an adenylyl cyclase inhibitor, prevented cAMP accumulation and the subsequent release of GH that was caused by either GHRP-2 or GRF. The cAMP antagonist, Rp-cAMP also blocked GH release in response to GHRP-2 and GRF. The cAMP antagonist did not prevent the effect of GHRP-6 on GH secretion whereas MDL 12,330A partially reduced the effect. An antagonist for the GRF receptor, [Ac-Tyr1,D-Arg2]-GRF 1-29, significantly diminished the effect of GHRP-2 and GRF on cAMP accumulation and GH release, but did not affect GH release induced by GHRP-6. Somatostatin prevented cAMP accumulation and GH release responses to GHRP-2, GRF and GHRP-6. Ca2+ channel blockade did not affect the cAMP increase in response to GHRP-2 or GRF but totally prevented GH release in response to GHRP-2, GRF and GHRP-6. These results indicated that GHRP-2 acts on ovine pituitary somatotrophs to increase cAMP concentration in a manner similar to that of GRF; this occurs even during the blockade of Ca2+ influx. GHRP-6 caused GH release without an increase in intracellular cAMP levels. GH release in response to all three secretagogues was reduced by somatostatin and was dependent upon the influx of extracellular Ca2+. The additive effect of GHRP-2 and GRF or GHRP-6 suggested that the three peptides may act on different receptors. In rat pituitary cell cultures, GHRP-6 had no effect on cAMP levels, but potentiated the effect of GRF on cAMP accumulation. The synergistic effect of GRF and GHRP-6 on cAMP accumulation did not occur in sheep somatotrophs. Whereas GHRP-2 caused cAMP accumulation in sheep somatotrophs, it did not do so in rat pituitary cells. These data indicate species differences in the response of pituitary somatotrophs to the GHRPs and this is probably due to different subtypes of GHRP receptor in rat or sheep.

Animals↗
PubMed1996

Pharmacokinetics and blood-brain barrier transport of [3H]-biotinylated phosphorothioate oligodeoxynucleotide conjugated to a vector-mediated drug delivery system.

Antisense phosphorothioate oligodeoxynucleotides (PS-ODNs) are potential neuropharmaceuticals should these agents be made transportable through the blood-brain barrier (BBB) in vivo. The present studies report on attempts to enhance brain uptake of systemically administered 3'-biotinylated PS-ODN (bio-PS-ODN) by conjugation to a complex of streptavidin (SA) and the OX26 monoclonal antibody to the rat transferrin receptor. This antibody undergoes receptor-mediated transcytosis through the BBB and the OX26/SA conjugate mediates BBB transport of biotinylated therapeutics. The brain uptake of unconjugated [3H]-bio-PS-ODN approximated that of [14C]sucrose, a plasma volume marker that is not significantly transported through the BBB. Conjugation of [3H]-bio-PS-ODN to the OX26/SA vector resulted in a marked increase in BBB transport and the permeability-surface area (PS) product of the conjugate was 4.0 microliters/min/g. However, when the bio-PS-ODN/OX26-SA conjugate was injected intravenously in anesthetized rats, the BBB PS product of the conjugate was reduced 23-fold to a value of 0.173 +/- 0.006 microliters/min/g. The marked inhibition of vector-mediated transport of the bio-PS-ODN after intravenous injection was due to avid plasma protein binding of PS-ODNs, as has been demonstrated with protein binding assays and internal carotid artery perfusion studies. In conclusion, although PS-ODNs have the advantage of increased metabolic stability and resistance to endonucleases in vivo, the BBB transport of antisense PS-ODN therapeutics conjugated to the brain drug delivery vector OX26/SA is markedly attenuated due to plasma protein-binding effects.

Animals↗
PubMed1996

Expression of cytochrome P4502E1 in rat fetal hepatocyte culture.

Cytochrome P450 (CYP) 2E1 is present at very low levels or cannot be detected in rat fetal liver. Experiments were carried out to develop an ex vivo model of CYP2E1 expression in fetal liver. Fetal hepatocytes were prepared from pregnant rats on gestation days ranging from 12 to 19 and placed into culture for 2 days. Expression of CYP2E1 was observed at all gestational periods as evident from immunoblots and oxidation of paranitrophenol and N,N-dimethylnitrosamine by fetal liver microsomes. Northern blot analysis indicated production of CYP2E1 mRNA by the fetal hepatocytes cultured for 2 days but not by freshly isolated fetal rat hepatocytes. The addition of ethanol to the hepatocyte cultures did not have a significant effect on CYP2E1 catalytic oxidation of substrates or CYP2E1 mRNA levels. The content of CYP2E1, CYP2E1 mRNA levels, and CYP2E1 catalytic activity was greater in the fetal cultures grown in the presence of 2.5% fetal calf serum than in that grown with 15% fetal calf serum, suggesting that factors present in the serum limit expression or stability of CYP2E1. CYP2E1 was not detectable in two human fetal livers; however, expression did occur when human fetal hepatocytes were placed into culture for 4 days. These results suggest that cultures of rat and human fetal hepatocytes may be a valuable model with which to study factors that regulate expression of CYP2E1 and the influence of ethanol and other inducers on expression and stabilization of CYP2E1.

Animals↗
PubMed1996

kappa-Opioid agonist, U50,488H, stimulates ovine fetal pituitary-adrenal function via hypothalamic arginine-vasopressin and corticotrophin-releasing factor.

The fetal hypothalamic-pituitary-adrenal axis is regulated by such factors as corticotrophin releasing factor, arginine vasopressin and the endogenous opioid peptides. The goal of this study was to determine whether activation of the kappa-opioid system can modulate ovine fetal pituitary-adrenal function. The highly selective kappa-opioid agonist, U50,488H ¿trans-(+/-)-3, 4-dichloro-N-methyl-[2-(1-pyrrolidinyl)-cyclohexy]benzeneacetamide ¿ (1 mg/kg, i.v.), was administered directly to the ovine fetus in utero and fetal plasma levels of immunoreactive adrenocorticotrophin (ir-ACTH) and cortisol (ir-cortisol) were measured via radioimmunoassay. U50,488H resulted in an immediate and highly significant (P = .00005) increase in ir-ACTH, with a concomitant, significant (P = .02) increase in ir-cortisol. The peak increase was 312.1 +/- 31.2 pg/ml and 17.9 +/- 5.4 ng/ml from predrug control values for ir-ACTH and ir-cortisol, respectively, at 60 min after administration of U50,488H. This stimulation was completely blocked by concurrent naloxone (12 mg/hr, i.v.) administration, indicating that U50,488H is acting at classical opioid receptors to elicit this effect. Pretreatment with antagonists of arginine vasopressin or corticotrophin releasing factor attenuated the U50,488H response and it was therefore concluded that U50,488H is most likely acting to modulate ir-ACTH and ir-cortisol levels through regulation of arginine vasopressin and corticotrophin releasing factor release via hypothalamic kappa-opioid receptors. The results of this study should aid in the design of obstetrical analgesics that will not alter the fetal stress response.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1996

Central nervous system pharmacologic effect in conscious rats after intravenous injection of a biotinylated vasoactive intestinal peptide analog coupled to a blood-brain barrier drug delivery system.

Previous studies showed that intracarotid artery perfusion of biotinylated vasoactive intestinal peptide analog (bio-VIPa) coupled to a blood-brain barrier (BBB) drug delivery vector, OX26/avidin, causes an increase in brain blood flow by 65% in N2O-anesthetized rats. OX26 is a murine monoclonal antibody to the rat transferrin receptor and undergoes receptor-mediated transport through the BBB in vivo. The present investigation examined the central nervous system effects of bio-VIPa after conventional i.v. injection to conscious rats. The VIPa was monobiotinylated (bio) with an-XX-noncleavable (amide) linker, and the bio-XX-VIPa conjugated to OX26/streptavidin (SA) maintained affinity for the VIP receptor in radioreceptor assays. Brain uptake of the bio-XX-VIPa coupled to the OX26/SA vector after i.v. injection was at least 10-fold higher than that of the free bio-XX-VIPa, because of both an increased plasma area under the concentration curve and BBB permeability-surface area product. Administration of the free bio-XX-VIPa increased salivary gland blood flow by 350%, but had no effect on brain blood flow. By contrast, bio-XX-VIPa/OX26-SA conjugate at equal doses (20 micrograms/kg) after i.v. injection increased brain blood flow by 60% in conscious rats, but had no effect on salivary gland blood flow. In summary, the use of the BBB peptide drug delivery system targeted the drug to the central nervous system, and optimized the therapeutic index of the VIPa by enhancing cerebral blood flow and by attenuating side effects in peripheral organs such as salivary gland.

Animals↗
PubMed1996

Effect of captopril on intracellular free calcium ([Ca2+]i) of thymocytes in spontaneously hypertensive rats.

Hypertension is associated with dysfunction of the immune system. Intracellular free calcium ([Ca2+]i) was reportedly increased in immune cells, such as lymphocytes and thymocytes, both in hypertensive patients and in animals. To evaluate if captopril has an effect on the immune system, [Ca2+]i in thymocytes was monitored during the development of hypertension from 4-24 weeks, and after treatment with captopril for 4 and 12 weeks in spontaneously hypertensive rats (SHR). SHR (n = 24) were treated with captopril at a dose of 20 mg/kg/day at 12 weeks of age after establishment of hypertension. Untreated SHR (n = 17) and normotensive Wistar Kyoto (WKY n = 14) served as control. [Ca2+]i of thymocytes was measured using Fura-2. It was found that [Ca2+]i of thymocytes decreased both in SHR and WKY from 4-12 weeks of age. From 12-24 weeks, [Ca2+]i in thymocytes remained at a constant level in WKY. However, [Ca2+]i in thymocytes increased significantly in SHR after 12 weeks. Captopril (CAP) treatment significantly lowered [Ca2+]i in thymocytes derived from SHR at 24 weeks. This treatment was associated with a moderate reduction in systolic blood pressure. Established hypertension in SHR is associated with increased [Ca2+]i in thymocytes. This may be indicative of immunological dysfunction. Captopril inhibits the increase in [Ca2+]i of thymocytes in SHR.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Retrograde atrio-His bundle dissociation as a sign indicative of retrograde accessory pathway conduction.

Electrophysiologic study and radiofrequency ablation therapy were performed in a 36-year-old male with Wolff-Parkinson-White syndrome and Ebstein's anomaly. The study disclosed the presence of a posteroseptal accessory pathway and dual atrioventricular (AV) nodal pathways. Retrograde atrio-His bundle (A-H) dissociation was noted during rapid ventricular pacing, in which the atria were activated by retrograde impulse from the accessory pathway with a fixed ventriculo-atrial (VA) interval while the retrograde His bundle potential was visible during the diastolic isoelectric period due to the occurrence of Wenckebach periodicity within the His-Purkinje system. This phenomenon is a useful sign for rapid recognition of the accessory pathway conduction.

Adult↗
PubMed1996

Oncogenic transformation of Syrian hamster embryo cells by 5.3-MeV alpha particles and a tumor promoter phorbol ester.

The primary Syrian hamster embryo (SHE) cells were used to study the oncogenic transformation by 238pu alpha particles or X-rays alone or in combination with a chemical promoter phorbol ester. Survival curves of SHE cells following exposure to alpha-particles or X-rays were fitted to single-or multi-target models, respectively. Model parameters were: Do = 0.55 Gy, n = 1 for alpha particles; Do = 1.44 Gy, Dq = 3.0 Gy, n = 7.7 for X-rays. Incidence of alpha particles or X-rays induced cell transformation was dose-dependent. alpha particles were more efficient in inducing cell transformation than that of X-rays. The enhancement of SHE cell transformation by phorbol 12-myristate 13-acetate (PMA) following exposure to alpha particles of 0.25-1.00 Gy was observed.

Animals↗
PubMed1996

DNA ploidy, expression of p53 protein and metastatic behaviour of gastric carcinoma.

DNA ploidy of 57 gastric carcinomas with metastases (12 liver, 1 adrenal, 4 ovary and 48 lymph node) were measured by flow cytometry. DNA anueploidy was significantly related to liver metastases: 9 out of 12 gastric carcinomas with liver metastases were anueploid (75%) as compared to 13 out of 45 (28.8%) of cases without liver metastases (P < 0.01); the one gastric carcinoma with adrenal metastasis was also anueploid. DNA ploidy was not related to ovarian or lymph node metastases. Another interesting finding was that all of 3 gastric carcinomas with liver metastases which showed a diploid DNA pattern, expressed p53 protein, while all of 3 carcinomas with liver metastases but no p53 protein expression were anueploid. The expression of p53 protein was not related to ovarian metastases. The results suggested that an anueploid DNA pattern and the expression of p53 protein are both objective markers valuable in predicting high risk potential of metastases to the liver, and that the combined detection of these markers can be a most useful method in the follow-up of patients with gastric carcinoma in detecting those at high risk of developing metastases following surgical resection. Also the poorer prognosis of patients with gastric carcinoma showing an anueploid DNA pattern may be related to the development of distant organ metastases through the blood vascular system. Furthermore, the clone of gastric carcinoma cells which accumulate p53 protein or show an anueploid DNA pattern may have a causative role in the development of liver (& adrenal) metastases.

Adenocarcinoma↗
PubMed1996

Partial deletion of p53 gene in alpha particle-induced transformant of Syrian hamster embryo cells.

The mutation of p53 gene was detected in Syrian hamster embryo (SHE) cells neoplastically initiated with alpha particles. The level of the p53 mRNA in transformant was obviously higher than that in non-irradiated counterpart, as measured by Northern blot analysis of total RNA. A pair of primers were designed based on p53 cDNA sequence to produce the whole length of coding sequence about 1.2 kilobase (Kb) by reverse transcription of mRNA followed by the polymerase chain reaction (RT-PCR), but the length of fragment amplified from transformant mRNA was about 0.3 Kb, remarkably shorter than that from normal SHE cells. Immunohistochemical analysis of p53 protein showed that no heavy staining was found on slice of tumor derived from transformant inoculated in nude mice with hamster specific p53 monocloned antibody HD200. The results implied that p53 gene had been mutated by deletion, which might lead to loss of p53 protein expression but the increased expression of p53 remained in alpha particle-induced SHE transformant.

Animals↗
PubMed1996

[Mechanism of inhibitory action of sodium ferulate on liver lipid peroxidation in mice].

The study has shown that sodium ferulate (SF) significantly inhibits the rise of liver lipid peroxides MDA content, alleviates the depletion of hepatic GSH pond, and reverses the decline of GST, GSH-Px levels in ethanol treated mice. The results indicate this inhibitory action of SF is related to diminishing the generation of oxygen free radicals by stabilizing GSH and related enzyme levels.

Animals↗
PubMed1996

[The study on changes of macular light sensitivity before and after photocoagulation for diabetic macular edema].

OBJECTIVE: The study was designed to determine whether laser photocoagulation could damage macular visual function in treatment of diabetic macular edema. METHODS: A prospective clinical trial was taken to determine the effects of argon green (514.5nm) laser photocoagulation on macular light sensitivity (MLS) by comparing the self MLS pairing data collected from a Humphrey automatic visual field analyzer before and after the procedure. Nineteen eyes of 15 patients with diabetic macular edema consistent with its diagnostic criteria were enrolled in this study, a follow-up period being 3 months. RESULTS: The mean MLS at the photocoagulation area, non-photocoagulation area, 5 degrees and 13 degrees eccentricity were significantly decreased within 1 week after the treatment, the drops of MLS were 1.85 dB, 1.05 dB, 0.99 dB, 1.66 dB respectively (P < 0.05). The mean reduction of MLS at the fovea within 1 week after the treatment has no statistical significance. The MLS gradually recovered at the 1st and 3rd month after photocoagulation, and the visual acuities in most of the cases were stable or increased. CONCLUSIONS: MLS is affected little by laser photocoagulation, and photocoagulation can reduce the risk of visual loss or increase visual acuity in an eye with diabetic macular edema.

Adult↗
PubMed1995

Identification of an active site arginine in rat choline acetyltransferase by alanine scanning mutagenesis.

Kinetic as well as chemical modification studies have implicated the presence of an active site arginine in choline acetyltransferase, whose function is to stabilize coenzyme binding by interacting with the 3'-phosphate of the coenzyme A substrate. In order to identify this residue seven conserved arginines in rat choline acetyltransferase were converted to alanine by site-directed mutagenesis, and the properties of these mutants were compared with the wild type enzyme. Substitution of arginine 452 with alanine resulted in a 7-12-fold increase in the Km for both CoA and acetylcholine as well as kcat, with little change in the Km for dephospho-CoA. Product inhibition studies showed choline to be a competitive inhibitor with respect to acetylcholine, indicating R452A follows the same Theorell-Chance kinetic mechanism as the wild type enzyme. Similar results were obtained with R452Q and R452E, with the latter showing the largest changes in kinetic parameters. These findings are consistent with Arg-452 mutations increasing the rate constant, k5, for dissociation of the coenzyme from the enzyme. Direct evidence that arginine 452 is involved in coenzyme A binding was obtained by showing a 5-10-fold decrease in affinity of the R452A mutant for coenzyme A as determined by the ability to protect against phenylglyoxal inactivation as well as thermal inactivation.

Alanine↗