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Biomedical subjects

H Yu

Publications and source records attributed to H Yu.

At least 685 records · Page 38Linked to original sources
PubMed1993

cDNA cloning and expression of potato polyphenol oxidase.

Polyphenol oxidases (PPOs) of plants are copper metalloproteins which catalyze the oxidation of mono- and o-diphenols to o-diquinones. Although PPOs are believed to be primarily responsible for the deleterious browning of many fruit and vegetable crops and are thought to be involved in plant-pest interactions, direct evidence for these roles is lacking. We report the cloning of two PPO cDNAs from Solanum tuberosum leaves. These cDNAs exhibit 97% and 98% sequence similarity at the DNA and deduced amino acid levels, respectively. Putative copper-binding regions of both cDNAs are very similar to those of mammalian, bacterial and Neurospora tyrosinases. Both leaf PPO cDNAs appear to encode polypeptides which are processed to a mature molecular weight of 57,000. In potato leaves, petioles, roots, and flowers, PPO is encoded by ca. 2 kb transcripts. Leaf PPO mRNA is developmentally regulated and only detectable in young foliage. In contrast, the protein profile of immunologically detectable PPO remains constant from the apical node through the eleventh leaf node.

Amino Acid Sequence↗
PubMed1993

Phosphatase inhibition by calyculin A increases i(f) in canine Purkinje fibers and myocytes.

The actions of the phosphatase inhibitor calyculin A on the pacemaker current i(f) were studied in canine Purkinje fibers and myocytes. Calyculin A increased i(f) in response to hyperpolarizations toward the middle of the i(f) activation curve. A three pulse protocol indicated this increase was due to a positive shift of i(f) activation on the voltage axis. Taken together with our previous results (that kinase inhibition with H7 shifts i(f) activation in the negative direction on the voltage axis (2)), these results suggest that phosphorylation is an important regulator of the voltage dependence of i(f) activation.

Animals↗
PubMed1993

A paradoxical stimulatory effect of berberine on guinea-pig ileum contractility: possible involvement of acetylcholine release from the postganglionic parasympathetic nerve and cholinesterase inhibition.

The effects of berberine on guinea-pig ileum contractility were studied in both transmurally-stimulated and unstimulated preparations. Transmural stimulation (80 V, 0.5 ms, 0.05 Hz) of the guinea-pig ileal segments produced a twitch response. Berberine (10(-8)-10(-5) M) enhanced this response dose-dependently. Atropine (10(-7) M), but not mecamylamine (10(-5) M), abolished this response. Acetylcholine (3 x 10(-9) and 10(-8) M) also enhanced the response to transmural stimulation. Pretreatment with hemicholinium (3 x 10(-5) M) antagonized the effect of berberine but failed to change that of acetylcholine. Berberine (10(-5) M) also antagonized the alpha 2-adrenoceptor agonist xylazine (10(-8) and 10(-7) M)-induced inhibition of the twitch response to transmural stimulation. In unstimulated ileal preparations, berberine (10(-5) M) produced contractile responses. In these preparations, atropine (10(-6) M), but not mecamylamine (10(-4) M), abolished the response to berberine. Furthermore, berberine (10(-6)-10(-4) M) inhibited dose-dependently the cholinesterase activity of the guinea-pig blood. The results suggest that berberine increases ileal contractility by: 1) increasing acetylcholine release from the postganglionic parasympathetic nerve terminal, 2) increasing acetylcholine retention through an inhibition of cholinesterase activity, and 3) blocking alpha 2-adrenoceptors, possibly in the postganglionic parasympathetic nerve.

Acetylcholine↗
PubMed1993

Electron diffraction studies of molecular ordering and orientation in phospholipid monolayer domains.

The molecular order and orientation of phase separated domains in monolayers of DP(Me)PE and DP(Me)2PE were determined by electron diffraction. Dark and bright fluorescent domains at the air-water interface were observed by fluorescence microscopy. The monolayers were transferred to Formvar coated electron microscope grids for electron diffraction studies. The positions of domains on the marker grids were recorded in fluorescence micrographs, which were used as guide maps to locate these domains in the electron microscope. Selected area electron diffraction patterns were obtained from predetermined areas within and outside the dark domains. Sharp hexagonal diffraction patterns were recorded from dark domains, and diffuse diffraction rings from bright areas in between dark domains. The diffraction results indicated that the dark domains and bright areas were comprised of lipid molecules in solid and fluid states, respectively. The orientation of diffraction patterns from adjacent locations within a dark domains changed gradually, indicating a continuous bending of the molecular packing lattice vector within these domains. Orientation directors in U-shaped DP(Me)2PE domains followed the turn of the arm; no vortex nor branching was indicated by electron diffraction. Directors branching from the "stem" of highly invaginated DP(Me)PE domains usually occurred at twinning angles of n pi/3 from the stem director, which would minimize packing defects in the development of thinner branches. Electron diffraction from local areas of individual domains proved that dark fluorescent domains were solid ones, and that pseudo-long range order existed in these solid domains.

Biophysical Phenomena↗
PubMed1993

Comparison of cellular binding and uptake of antisense phosphodiester, phosphorothioate, and mixed phosphorothioate and methylphosphonate oligonucleotides.

The effects of phosphorothioate (S-oligonucleotide) or terminal phosphorothioate-phosphodiester (S-O-oligonucleotides) or methylphosphonate-phosphodiester (MP-O-oligonucleotides) modifications on mouse spleen cell surface binding, uptake, and degradation were studied using fluorescein (FITC)-conjugated oligonucleotides. S-oligonucleotides had the highest cell binding and uptake, followed by S-O-, O-, and MP-O-oligonucleotides. Competition studies indicated that S-oligonucleotides have an increased affinity for cell membrane oligonucleotide binding sites, because they could completely block O-oligonucleotide binding at a molar ratio of just 0.1. Uptake of all oligonucleotides was higher in B cells than T cells and was increased by stimulation with the B-cell mitogen, lipopolysaccharide. Although our cells had been purified using conventional techniques to eliminate dead cells, there remained about 5% of cells that were dead or dying, as determined by flow cytometry using propidium iodide staining. Of note, oligonucleotide association with dead cells was approximately 50-fold greater than that with living cells. Confocal microscopy confirmed that the oligonucleotides in living cells were intracellular, and indicated little nuclear uptake by 4 h. While extensive degradation of intracellular O-oligonucleotides was apparent by 4 h, there was no detectable degradation of S-, S-O, or MP-O-oligonucleotides.

Animals↗
PubMed1993

The role of activated vascular angiotensin II generation in vascular hypertrophy in one-kidney, one clip hypertensive rats.

OBJECTIVE: To investigate the role of vascular angiotensin II (Ang II) in the vascular thickening of one-kidney, one clip (1-K, 1C) hypertensive rats, which show normal plasma renin activity. METHODS: The type 1 Ang II receptor antagonist TCV-116 (1 mg/kg per day), the angiotensin converting enzyme (ACE) inhibitor delapril (20 mg/kg per day), hydralazine (20 mg/kg per day) or vehicle were administered to four groups of 1-K, 1C rats aged 6-10 weeks. Vehicle was also given to uninephrectomized rats. RESULTS: The aortae of 1-K, 1C rats contained significantly higher levels of Ang II than those of uninephrectomized rats and showed hypertrophy, but not hyperplasia of their medial smooth muscle cells. Hypertrophy was estimated by immunohistochemical staining of alpha-actin. Hyperplasia was estimated by DNA content and incorporation of 5-bromo-2'-deoxyuridine. The blood pressure of the 1-K, 1C rats was not affected by either TCV-116 or delapril, even at doses sufficient to induce depressor effects in spontaneously hypertensive rats. However, subdepressor doses of TCV-116 and delapril both significantly reduced the alpha-actin-stained area to 78 and 73%, respectively, of that in the 1-K, 1C rats, whereas a depressor dose of hydralazine did not affect the alpha-actin-stained area. The level of Ang II in the aorta, but not in plasma, was suppressed by delapril but not by hydralazine. CONCLUSIONS: These results suggest strongly that vascular Ang II plays a major role in the development of vascular hypertrophy, independently of plasma Ang II, bradykinin and ACE-independent pathways of Ang II generation, and in the regulation of blood pressure in this normoreninaemic hypertensive model.

Actins↗
PubMed1993

Effects of dietary sodium on central and peripheral ouabain-like activity in spontaneously hypertensive rats.

High dietary Na+ intake enhances pressor and sympathoexcitatory responses in spontaneously hypertensive rats (SHR) but not Wistar-Kyoto (WKY) rats. To evaluate the possible contribution of central ouabain-like activity (OLA), brain and peripheral OLA was assessed in SHR vs. WKY rats at 4 wk of age and after 2 and 4 wk of high vs. control Na+ intake started at 4 wk of age. In SHR, hypertension developed with maturation and was exacerbated by high Na+ intake. With control Na+ intake, SHR showed higher OLA at 4, 6, and 8 wk of age in the pituitary and hypothalamus and also by 8 wk in the adrenals and left ventricle but not in plasma. High Na+ intake increased OLA in all tissues examined in both WKY rats and SHR. After 2 wk on high Na+, only OLA in hypothalamus and pituitary was higher in SHR vs. WKY rats; after 4 wk on high Na+, peripheral (i.e., adrenals, left ventricle, and plasma) OLA was also higher. These results indicate that in SHR the development of hypertension is associated early on with increases in central OLA and in a later phase with increases in peripheral OLA as well. High Na+ intake increases OLA in both SHR and WKY rats, but the higher OLA may affect sympathetic activity and blood pressure only in SHR.

Animals↗
PubMed1993

Dietary sodium stimulates ouabainlike activity in adrenalectomized spontaneously hypertensive rats.

Both the adrenal glands and the hypothalamus have been proposed to produce compound(s) with ouabainlike activity (OLA). To evaluate the contribution of the adrenal glands, 4-wk-old spontaneously hypertensive rats (SHR) were sham operated or adrenalectomized. The adrenalectomized SHR were given daily injections of corticosterone and aldosterone. Subsequently, rats were randomized to control or high (8%) dietary Na+, and after 2.5 wk, blood pressure and OLA in plasma, hypothalamus, and pituitary were evaluated. Hypertension developed somewhat less in adrenalectomized vs. sham-operated SHR. On control Na+ intake, adrenalectomy caused only minor decreases in circulating and central OLA. Adrenalectomy did not prevent the 50-90% increases in plasma, hypothalamus, and pituitary OLA caused by high Na+ intake for 2.5 wk. These findings are consistent with the concept that, at least in SHR, the central nervous system may represent the major source of both central and peripheral OLA.

Adrenalectomy↗
PubMed1993

The effect of a tannin-fluoride mixture on human dental enamel.

In this study, the effect of a tannin-fluoride mixture (Ta-F, 0.5% tannic acid, 450 ppm fluoride, pH 5.9) on dental enamel has been investigated by using scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD), compared with the effect of acidulated phosphate fluoride (APF, 0.015 M phosphoric acid, 450 ppm fluoride, pH 5.3). Under the SEM, a large number of spherical globules (1-5 microns in diameter) were observed on the enamel surface treated with Ta-F. On a fractured cross section, these large globules showed a columnar appearance, measuring 2.5-5 microns each in height. They had a good range and formed a single coating layer on the enamel, whereas on the APF-treated enamel only very small spherical globules 0.1-0.5 micron in diameter were seen. Moreover, three types of connective patterns were observed between the basal ends of these columnar deposits and the enamel surface: (a) a pattern loosely attached to the enamel surface, (b) a pattern partially connected with the crystals of enamel, and (c) a pattern inserted into the pores of enamel. These columnar deposits also showed very strong resistance either to acid decalcification or to water washing. By EPMA and XRD examinations, a remarkable elevation of the fluoride profile accompanied by a high elevation of calcium was observed and CaF2 peaks were detected on the enamel surface. These results suggest that the columnar deposits might contain the CaF2-like substances and possess unique morphological and qualitative features which are quite different from the deposits found after APF or NaF treatment as described in previous studies.

Acid Etching, Dental↗
PubMed1993

Pacemaker current exists in ventricular myocytes.

I(f), the "cardiac pacemaker current," is a nonselective cation channel activated on hyperpolarization in primary and secondary pacemaker regions of the mammalian heart. The cardiac pacing rate can be modulated by shifting the activation of I(f) to more positive (faster pacing) or more negative (slower pacing) voltages. We report for the first time the presence of this pacemaker current in ventricular myocytes. The potential importance of this observation to the mechanism of differentiation of nonpacing regions in the heart is discussed.

Animals↗
PubMed1993

Hypertensive rats produced by in vivo introduction of the human renin gene.

We established an efficient and nontoxic in vivo gene transfer method mediated by the Sendai virus (hemagglutinating virus of Japan [HVJ]), liposomes, and nuclear protein. In this study, to produce a hypertensive model rat that is dependent on human renin, the human renin gene was introduced into adult rat liver by our efficient in vivo gene transfer method using HVJ and liposomes (HVJ-liposomes). The rats treated with HVJ-liposomes containing the human renin gene showed a significant elevation of blood pressure for 6 days compared with control rats, which received injections of HVJ-liposomes without the human renin gene. On day 5 after the transfer, human active renin as well as angiotensin II were found in the plasma of rats in which the human renin gene was introduced. Moreover, the blood pressure of these rats was significantly correlated with the plasma levels of human active renin and angiotensin II. To confirm that the elevated blood pressure was due to the expression of the human renin gene, we administered a newly developed specific human renin inhibitor, FK 906. The elevated blood pressure was normalized by the intravenous administration of this drug. These data indicate that this hypertensive rat was produced by the in vivo transfer of the human renin gene into rat liver and that the expressed human renin cleaved rat substrate (angiotensinogen). This hypertensive rat produced by in vivo gene transfer should be useful in further studies on hypertension.

Angiotensin II↗
PubMed1993

Ultrasensitive time-resolved immunofluorometric assay of prostate-specific antigen in serum and preliminary clinical studies.

We developed an ultrasensitive method for measuring prostate-specific antigen (PSA) in serum. The assay includes a capture monoclonal anti-PSA antibody coated to microtiter wells, a biotinylated rabbit polyclonal detection antibody, and alkaline phosphatase (ALP)-labeled streptavidin. The activity of ALP is measured with the substrate diflunisal phosphate; the released diflunisal forms highly fluorescent complexes with Tb(3+)-EDTA that are quantified with microsecond time-resolved fluorometry. The assay is precise and accurate and correlates well with the established Hybritech Tandem-PSA kit. Its distinguishing feature is extreme sensitivity (lowest limit of detection is 0.002 micrograms/L or 2 x 10(6) PSA molecules per assay). This is the most sensitive PSA assay reported thus far; we used it to quantify PSA in patients who had undergone radical prostatectomy. Many patients had < 0.01 micrograms/L PSA in their serum. This method could have important clinical applications in postsurgical early detection of relapse or residual prostate cancer, as recently suggested in the literature (Clin Chem 1992;38:1930-2).

Adolescent↗
PubMed1993

Total gastrectomy via thoracotomy for cancer of the cardia or fundus of the stomach (report of 90 cases).

From 1978 through 1990, 90 total gastrectomies with esophagojejunostomy via thoracotomy were performed for the treatment of cancer of the cardia or fundus of the stomach in our hospital. Eighty-five patients were in TNM-stage III and five in stage IV. The 30-day postresectional mortality was 1.1%, and the 5-year survival rate was 13.8%. 14CO2 breathing test and clinical evaluation of 34 postoperative patients (not included in the 90 patients) showed that total gastrectomy may decrease the incidence of positive residual cancer along the incision lines, and may help to avoid small stomach syndrome. There was no statistical difference in postoperative fat absorption between patients treated by ordinary proximal subtotal gastrectomy and those receiving total gastrectomy via thoracotomy.

Adult↗
PubMed1993

Developmental changes of protein kinase C and Gs alpha in hypertrophic cardiomyopathic hamster hearts.

Protein kinase C (PKC) and GTP-binding proteins (G-proteins) are known to be major determinants in the modulation of cardiac function. In this study, we examined the developmental changes of PKC and the alpha-subunit of the stimulatory guanosine triphosphate binding protein (Gs alpha) in hypertrophic cardiomyopathic Syrian hamster (BIO 14.6) hearts, before the onset of hypertrophy (30 days old) and at the peak of hypertrophy (6 months old) and compared these with age-matched control hamster (BIO RB) hearts. At 30 days, cardiac PKC activity was similar between BIO 14.6 and BIO RB both in the membrane (117.1 +/- 9.9 pmol/min/mg vs 131.2 +/- 12.7 pmol/min/mg in controls, n = 8) and in the cytosolic fractions (213.1 +/- 22.0 pmol/min/mg vs 186.6 +/- 23.9 pmol/min/mg in controls, n = 9). At 6 months, PKC activity was significantly higher in BIO 14.6 than in controls, both in the cardiac membrane (131.9 +/- 7.1 pmol/min/mg vs 40.7 +/- 4.7 pmol/min/mg in controls, n = 8, p < 0.00001) and cytosol (77.9 +/- 2.1 pmol/min/mg vs 54.6 +/- 3.3 pmol/min/mg in controls, n = 6, p < 0.0005). In BIO RB hearts, membrane and cytosolic PKC activities were significantly reduced at 6 months compared with those at 30 days of age (p < 0.001). However, the membrane PKC activity in 6-month-old BIO 14.6 was maintained at the level of the 30-day-old hearts. On the other hand, the relative immunoreactive amounts of Gs alpha were similar between BIO RB and BIO 14.6 hearts at 30 days and at 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Thymic carcinoid tumor--a report of 7 cases.

The thymic carcinoid tumor is a rare neoplasm which is often clinically misdiagnosed as thymoma. But the two differ in origin, biological behavior, accompanying syndromes, pathological features, and prognosis. The characteristics of the thymic carcinoid tumor are: difficulty in diagnosis, high malignancy, frequent recurrence and extrathoracic metastasis over a prolonged period postoperatively. Complete surgical resection of original and recurrent tumors is the important treatment. Microscopic, electron microscopic and immunohistochemical examinations may be required in making an accurate pathological diagnosis. This paper reports 7 cases of thymic carcinoid tumor.

Adult↗
PubMed1993

The efficacy of povidone-iodine pessaries in a short, low-dose treatment regime on candidal, trichomonal and non-specific vaginitis.

Povidone-iodine pessaries (Betadine vaginal pessaries) containing 200 mg of povidone-iodine (PVP-I) in a water soluble base, are a widely used gynaecological preparation for treatment of vaginitis. We conducted a study on PVP-I pessaries at the reduced dose of one pessary daily for 7 days to suit conditions in Macau where patients are eager for a simple, short treatment course with confirmed clinical efficacy benefiting their professional and household essential requirements. Thirty-eight cases were selected for this particular clinical trial. These consisted of housewives, factory workers and professional girls (a sexually high risk group) who were suffering from vaginitis and complaining of vaginal discharge and irritation due to trichomonas, candida or non-specific vaginitis. After routine examination, including the collection of samples for microbiology, patients were treated with PVP-I pessaries 200 mg once a day for 7 days. The second microbiology samples were collected after the 7 day treatment period. Among the 38 cases, we had 30 cases with a complete record to allow us to make a summary and analysis of the trial. There were 14 cases of vaginitis due to yeasts and fungi infection, 3 cases of protozoa (trichomonas), and 13 cases due to non-specific pathogenic infections. 73.3% of cases had a complete symptomatic and microbiological cure and a further 16.7% had a microbiological cure with a good improvement in symptoms. No complications or side effects were found in the 7 days consecutive treatment course and inflammation quickly subsided during the course of treatment. PVP-I pessaries, used once daily for 7 days, seem to be an ideal treatment for cases who are likely to be unable to follow a longer treatment course.

Candidiasis, Vulvovaginal↗
PubMed1993

Neuromedicinal chemistry of 5-HT1A-receptor agonists and antagonists.

Recent progress in a project aiming at developing selective 5-HT1A-receptor agonists and antagonists is reviewed. A large number of analogues of 8-OH-DPAT has been synthesized, and throughout, we have attempted to prepare enantiopure derivatives. Modifications have been concentrated to the N-alkyl substituents, and substitutions in the C1, C2 and C3-positions. The synthetic strategies and procedures are discussed. A number of interesting observations have been made. Affinity, efficacy and stereoselectivity are modified by the various substitutions. The results have been used to deduce a 3D-model for 5-HT1A-receptor agonists. Recently, Pd-catalyzed reactions have been utilized to prepare a number of pharmacologically interesting analogues of 8-OH-DPAT with various C8-substituents. We have also succeeded to convert the agonist 8-OH-DPAT into an antagonist by introduction of a C5-fluoro substituent, producing (S)-UH-301. The pharmacology of this selective 5-HT1A-receptor antagonist is discussed.

8-Hydroxy-2-(di-n-propylamino)tetralin↗