Biomedical subjects

D H Yu

Publications and source records attributed to D H Yu.

35 records · Page 2Linked to original sources

PubMed1995

[Methodological study on the determination of naftopidil concentration in biological samples by HPLC].

A method was developed for the determination of the novel antihypertensive drug naftopidil in biological samples by HPLC. Metoprolol was used as the internal standard. The analytical column was a stainless steel column filled with 10 micron C18 packing. The mobile phase was a mixture of methanol-acetonitrile-water-0.2 mol.L-1 HAc-0.2 mol.L-1 NaAc (50:45:5:0.9:0.1). Detection was performed at UV 232 nm. Biological samples can be well purified after two extractions with ether. The lowest detection limit was 5 ng.ml-1. The precision and accuracy within-day and day-to-day ranged from 3.17 to 10.88%. The mean recoveries were 79.35% to 95.72%. The results showed that this method was simple, sensitive and good enough to be used in pharmacokinetic study of naftopidil.

Animals↗

PubMed1994

[Methodological study on the determination of oxiracetam concentration in serum and urine by HPLC].

A method was developed for the determination of oxiracetam concentration in serum and urine by HPLC. Acyclovir was used as an internal standard. The analytical column was a stainless-steel column (30 mm x 4.6 mm ID) filled with 10 microns Bondapak NH2. A mixture of acetonitrile and water (80: 20) as mobile phase was used at a flow rate of 1 ml.min-1. Detection was performed at 210 nm. The retention times were 6.3 min for oxiracetam and 8.1 min for the internal standard. The lower detection limits were 1 microgram.ml-1 for serum and 20 micrograms.ml-1 for urine. The precision and accuracy within-day and day-to-day for both serum and urine samples ranged from 5.0 to 10.7%. The mean recoveries were 99.7 +/- 5.9% and 99.0 +/- 5.6% for human serum and urine, respectively. The results showed that the method is simple, rapid, sensitive, reliable and good enough to be used in studying the clinical pharmacokinetics of oxiracetam.

Chromatography, High Pressure Liquid↗

PubMed1992

Molecular cloning and characterization of v-mos-activated transformation-associated proteins.

Using monoclonal antibodies we previously detected two forms of transformation-associated proteins, a 64-kDa protein and a 68-kDa protein, in temperature-sensitive 110-Moloney murine sarcoma virus-mutant-transformed rat kidney 6m2 cells. The identity and functions of the transformation-associated proteins were previously unknown. By molecular cloning techniques and immunoscreening, we have isolated two cDNA clones (34A and 79B3) that were found by Western blot analysis to code for a monoclonal anti-transformation-associated protein antibody-reactive polypeptide of approximately 58 kDa. Limited restriction enzyme mapping indicated 34A and 79B3 are two different cDNA clones. The nucleotide sequence of 34A cDNA was determined, and a search of GenBank revealed that it is identical to that of rat transin-2. The deduced amino acid sequence of 34A shares 71% sequence identity with rat transin and 41-76% identity with six human metalloproteinases. The limited restriction enzyme mapping and partial nucleotide sequencing data indicated that 79B3 may be the rat transin gene. When either 34A cDNA or 79B3 cDNA was used as a probe in Northern blot analysis, one mRNA band of approximately 1.9 kilobases was detected in 6m2 cells grown at the permissive temperature of 33 degrees C, at which the cells exhibited transformation properties, and a much lower level in 6m2 cells grown at the nonpermissive temperature of 39 degrees C, at which the cells reverted to normal phenotypes. These results suggest that at 39 degrees C, these two genes were not transcribed at the same level as at 33 degrees C. Zymogram and Western blot analysis of 6m2 cells further confirmed that the 64- and 68-kDa proteins have metalloproteinase activities and that the synthesis of metalloproteinases was also temperature-sensitive. Apparently, the two proteins we formerly designated transformation-associated proteins are members of the rat transin gene family. Therefore, within v-mos transformed 6m2 cells, the absence of transformation-associated protein (metalloproteinase) synthesis at the nonpermissive temperature was due to the absence of transcription of two rat transin genes.

Amino Acid Sequence↗

PubMed1991

Adenovirus type 5 E1A gene products act as transformation suppressors of the neu oncogene.

The adenovirus type 5 early region 1A (E1A) gene was introduced into neu-transformed B104-1-1 cells. Cells that expressed E1A possessed reduced transforming activity in vitro and reduced tumorigenicity in nude mice. These results demonstrate that the E1A gene products can act negatively to suppress the transformed phenotype in neu-transformed cells.

Adenovirus Early Proteins↗

PubMed1991

Expression of activated rat neu oncogene is sufficient to induce experimental metastasis in 3T3 cells.

Amplification or overexpression of the human neu oncogene has been shown to correlate with the number of lymph node metastases in breast cancer patients, suggesting that expression of the neu oncogene may be associated with increased metastatic potential. However, there has been no systematic study on the role of the neu oncogene in metastasis to support this correlation. In our study, mouse embryo fibroblast 3T3 cells transformed by the mutation-activated rat neu oncogene exhibited metastatic properties both in vitro and in vivo, while parental 3T3 cells did not. Monoclonal antibodies capable of inducing down-regulation of the neu-encoded p185 protein reduced the metastatic potential induced by neu. These data provide strong experimental evidence that neu oncogene expression is sufficient for the induction of metastasis in the 3T3 cell system and supply a molecular basis supporting the correlations found in clinical observation. The results also suggest that neu-specific monoclonal antibodies may have preventative or therapeutic potential for neu-induced metastasis.

Animals↗

PubMed1990

Pancreatic receptors for cholecystokinin: evidence for three receptor classes.

For inhibition of binding of 125I-Bolton-Hunter-labeled cholecystokinin octapeptide (125I-BH-CCK-8) to guinea pig pancreatic acini, the potencies for agonists were CCK-8 greater than desulfated [des(SO3)] CCK-8 greater than gastrin-17-I greater than pentagastrin greater than CCK-4 and for the antagonists L 364718 greater than proglumide analogue 10 greater than CBZ-CCK-(27-32)-NH2. For all non-sulfated agonists, the curves were biphasic with 20% of the tracer bound to sites with high affinity for these agonists with the following relative potencies: gastrin-17-I greater than pentagastrin greater than des(SO3)CCK-8 much greater than CCK-4; whereas 80% was bound to low-affinity sites with the following potencies: des(SO3)CCK-8 greater than gastrin-17-I = pentagastrin much greater than CCK-4. For L 364718 and proglumide analogue 10, 80% of 125I-BH-CCK-8 was bound to sites with high affinity for these antagonists and 20% to sites with low affinity. Analysis of the dose-inhibition curve for CCK-8 demonstrated two binding sites; however, comparison with the analysis in the presence of 0.1 microM gastrin-17-I suggested three binding sites. The gastrin-17-I dose-inhibition curve was significantly better fit by a three-site model than by a two-site model. The affinities of the various agonists and antagonists for the three sites were compared with their abilities to inhibit binding of 125I-gastrin-I and either stimulate or inhibit CCK-8-stimulated amylase release. These results demonstrate that 125I-BH-CCK-8 binds to three classes of receptors, not two as reported previously. Two classes are CCK-preferring, bind 83% of 125I-BH-CCK-8 at tracer concentrations, and comprise high- and low-affinity CCK-preferring sites that can be distinguished by all agonists but have equally high affinity for L 364718 and proglumide 10. A third class binds 17% of the tracer, cannot be differentiated from high-affinity CCK-preferring receptors by CCK-8, and has low affinities for L 364718 and proglumide 10. Future studies relating binding of 125I-BH-CCK-8 to biological activity or characterization of the CCK receptor by using radiolabeled agonists should consider CCK interaction with three receptors, not two as was done in the past.

Animals↗

PubMed1989

[Puborectalis syndrome: a cause of obstinate constipation].

Two patients with severe chronic constipation caused by spasmodic hypertrophy of puborectalis underwent partial resection of the muscle. Pre-operative anorectal manometry showed increased length of the anal canal. Concentric electromyography showed that the puborectalis muscle failed to relax during attempted defecation and patients were unable to expel a water-filled balloon from the rectum. After surgery they have a regular defecation without difficulty. We consider that partial resection of the puborectalis muscle is a useful procedure for the puborectalis syndrome.

Aged↗

PubMed1987

Characterization of gastrin receptors on guinea pig pancreatic acini.

Recent studies have demonstrated gastrin receptors in some pancreatic tumors and that gastrin is a potent stimulant of pancreatic Na+-H+ exchange. In the present study we used 125I-labeled gastrin (125I-gastrin) to characterize gastrin receptors on guinea pig pancreatic acini. Binding of 125I-gastrin was temperature dependent, saturable, and specific for gastrin-related peptides. Analysis demonstrated a single class of receptors with high affinity for gastrin (Kd = 1.5 nM) and a binding capacity of 1 fmol/mg protein. Binding of 125I-gastrin was inhibited with the following relative potencies (Kd): cholecystokinin octapeptide (CCK-8) (0.35 nM) greater than gastrin-17-I = gastrin-34-I (1.5 nM) greater than pentagastrin (7 nM) greater than desulfated [des(SO3)]CCK-8 (28 nM) greater than CCK-4 (508 nM) and by the receptor antagonists CBZ-CCK-27-32-NH2 (3.5 microM) greater than proglumide analogue 10 (30 microM) greater than asperlicin (265 microM) greater than Bt2-guanosine 3',5'-cyclic monophosphate (828 micron). In contrast, for both stimulation of enzyme secretion and inhibition of binding of 125I-CCK-8 the relative potencies were CCK-8 much greater than des(SO3)CCK-8 greater than gastrin-17-I = gastrin-34-I greater than pentagastrin greater than CCK-4. For each receptor antagonist the dose-inhibition curve for gastrin-stimulated amylase release was superimpossible with that for CCK-8-stimulated amylase release. Gastrin-17-I at concentrations less than 0.1 microM did not potentiate carbachol or vasoactive intestinal peptide-stimulated amylase secretion and did not affect basal or stimulated adenosine 3',5'-cyclic monophosphate or 45Ca outflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗

PubMed1987

Increased alpha 1- and decreased alpha 2-adrenoceptor sensitivities upon chronic treatment with imipramine in mediating cardiovascular responses in pithed rats.

After chronic treatment with imipramine (20 mg/kg, i.p., twice daily for 14 days) the pressor dose-response curves to phenylephrine, methoxamine and cirazoline (alpha 1-adrenoceptor agonists) significantly shifted to the left with decreased PD50 values in pithed rats; however, the dose-response curve to Sgd 101/75, a selective alpha 1-adrenoceptor agonist was not affected. On the other hand, the alpha 2-adrenoceptor agonists such as B-HT 920, xylazine and clonidine produced a rightward shift for both the pressor (increased PD50) and cardioinhibition (increased ID50) dose-response curves in these rats. These results required treatment with imipramine over 2 weeks. Chronic treatment with imipramine has reduced the antagonism by prazosin of the pressor effect of phenylephrine when compared with the dose-ratios between the 2 groups. On the contrary, the antagonism by piperoxan of the cardioinhibitory effect of B-HT 920 was rather enhanced by the treatment, but that of the pressor effect of B-HT 920 was little changed. In cerebrocortical membrane fractions obtained from rats pretreated with imipramine, Ki of phenylephrine to displace [3H]prazosin was decreased, whereas that of clonidine and yohimbine to displace [3H]yohimbine was increased. In conclusion, it is demonstrated that after chronic imipramine treatment the peripheral alpha 2-adrenoceptors (both presynaptic and postsynaptic sites) as well as central alpha 2-adrenoceptors respond with a decreased sensitivity to the alpha 2-adrenoceptor agonists, and moreover, this treatment produces an increased sensitivity of the central and peripheral alpha 1-adrenoceptors to the alpha 1-adrenoceptor full agonists.

Adrenergic alpha-Antagonists↗

PubMed1986