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Biomedical subjects

Y M Liu

Publications and source records attributed to Y M Liu.

At least 55 records · Page 3Linked to original sources
PubMed1997

Positive chronotropic actions of parathyroid hormone and parathyroid hormone-related peptide are associated with increases in the current, I(f), and the slope of the pacemaker potential.

BACKGROUND: The classic calciotropic hormone parathyroid hormone (PTH) and its paracrine factor parathyroid hormone-related protein (PTHrP) both increase heart rate. METHODS AND RESULTS: We used standard electrophysiological techniques to study the effects of PTH and PTHrP on isolated rabbit sinus node, isolated canine Purkinje fibers, and disaggregated rabbit sinus node myocytes. Sinus node maximum diastolic potential, activation voltage, and amplitude were unchanged by PTH or PTHrP (P>.05). However, the slope of phase 4 and the automatic rate were increased at PTH and PTHrP > or = 10 nmol/L (P<.05). Comparable results were seen in canine Purkinje fibers. We then used the perforated-patch technique to study the I(f) pacemaker current in sinus node. PTH 12.5 nmol/L and PTHrP 12.5 to 18 nmol/L increased I(f) at -65 mV by 68+/-41% (n=5) and 69+/-50% (n=5), respectively. Actions of both agents were reversible. The increase in I(f) appeared to result from a change in maximal conductance and not a shift in the voltage dependence of activation. CONCLUSIONS: These observations provide, for the first time, direct electrophysiological support for the chronotropic actions of PTH and PTHrP. They suggest that classic hormones and paracrine factors can have multiple functions and that in the case of PTH and PTHrP, a newly recognized action is to alter automaticity directly.

Action Potentials↗
PubMed1997

Uncoupling protein gene: quantification of expression levels in adipose tissues of obese and non-obese humans.

The mitochondrial uncoupling protein (UCP), which is exclusively expressed in brown adipose tissue, regulates energy expenditure in rodents but its importance in the energy homeostasis of adult humans is uncertain. To study associations of UCP gene expression with human obesity, we determined, by a competitive reverse transcription-polymerase chain reaction assay, UCP mRNA expression levels in intra- and extraperitoneal adipose tissues of 79 obese subjects and 17 lean controls. UCP mRNA and internal standard RNA were reverse transcribed and coamplified in one reaction in which the same primers were used. The signal intensities of UCP mRNA products were compared with the signal intensities of standard RNA products to quantify UCP mRNA abundance. UCP mRNA was detected in all intra- and extraperitoneal adipose tissues studied. In both obese and non-obese subjects, UCP mRNA abundance was higher in the intraperitoneal than in the extraperitoneal tissue (P < 0.001). Compared to lean controls, morbidly obese subjects showed a significantly lower age- and gender-adjusted UCP mRNA expression level in the intraperitoneal adipose tissue (3.467 +/- 2.483 vs. 6.917 +/- 4.292 amol/fmol beta-actin mRNA; mean +/- SD, P < 0.002), while UCP mRNA abundance in extraperitoneal adipose tissue did not differ between obese and nonobese subjects. These data are consistent with reduced energy expenditure in obesity, but it remains to be determined whether the association of decreased intraperitoneal UCP mRNA expression with obesity status reflects a causal contribution of brown adipose tissue function to the pathogenesis of obesity.

Adipose Tissue, Brown↗
PubMed1997

[Selection of location for transcutaneous bilirubinometry in light therapy].

64 jaundiced neonates were measured with transcutaneous bilirubinometer for the jaundice index on the forehead and superciliary narch where was covered during photo therapy respectively. The result showed that the jaundice index in the uncovered place decreased greatly after the therapy was over, but the index went up again 12 hours later. The index on the covered place did not show this change. It is suggested that the covered place is a better site for measuring jaundice index because it can avoid the effect of phototherapy on the measuring result and make the result more accurate.

Bilirubin↗
PubMed1997

Four types of late Na channel current in isolated ventricular myocytes with reference to their contribution to the lastingness of action potential plateau.

Patch clamp technique was employed to record single Na channel current in isolated guinea-pig ventricular myocytes. Four types of late Na channel currents were observed with whole cell and inside-out recording, which are (1) isolated brief openings, (2) scattered openings, (3) long openings and (4) bursts. The occurrence frequencies of the four types were different. Bursts appeared about 1 in every 2,000 depolarizations, with an open time constant longer than others. However, all the four types of late current openings, as well as the early openings occurring immediately upon depolarization, could be blocked by tetrodotoxin. It was also found that at a certain stimulation frequency, normal action potential duration (APD) was not invariable as supposed before, but varied from stimulation to stimulation. Special Na channel blocker, TTX, shortened the APD and refractory period and abolished the dispersion. The above results suggest that the activities of the various types of late Na channel play an important role in the formation of action potential plateau.

Action Potentials↗
PubMed1997

[Voltage dependence of late Na channel with burst mode in isolated cardiac myocytes].

Patch clamp technique was employed to record single Na channel currents in isolated guinea-pig ventricular myocytes. Burst mode could be elicited by step depolarization and terminates immediately after repolarization. The unitary current of burst mode was not only dependent on Na concentration in the pipettes but also on the test voltage. The open time constant increased as testing voltage becomes more positive. The results from stepwise-depolarization and ramp depolarization experiments showed that the more steps or the faster the upstroke velocity of depolarization used, the more the burst mode would occure.

Action Potentials↗
PubMed1996

Two-dimensional separations: capillary electrophoresis coupled to channel gel electrophoresis.

Two-dimensional separations provide extremely high peak capacities. Coupling capillary zone electrophoresis with ultrathin channel gel electrophoresis offers a convenient and efficient way to perform such two-dimensional microseparations. By means of in situ polymerization, high-concentration (up to 50%T) polyacrylamide gels are prepared in 75 mm long, 25 mm wide, and 40 microns thick rectangular channels. By moving the outlet end of the capillary electrophoresis capillary across the entrance of the channel, both separations are completely preserved. Mixtures of peptides labeled by fluorescein isothiocyanate (FITC) are well resolved in less than 15 min, with theoretical plate numbers in the range of 20,000-50,000 for each independent separation. Significant enhancement in separation efficiency and peak capacity over one-dimensional separations are demonstrated by this combination. The two-dimensional separations of a model mixture of peptides, a tryptic digest of trypsinogen, and < 0.05% of an individual B2 neuron from the marine mollusk Aplysia californica are presented.

Animals↗
PubMed1996

Channel electrophoresis for kinetic assays.

A rectangular channel electrophoresis system and a cylindrical sampling capillary combination allows chemical changes in nanoliter-volume samples to be monitored as a function of time. The electrophoretic microseparation is carried out in a rectangular channel with a 7 -cm-long, 40-microm x 2.5-cm geometry and is coupled to a 50-microm-i.d. cylindrical sample introduction capillary. The channel width dimension is used as a time axis by moving the outlet of the sampling capillary across the entrance of the separation channel. Detection of the separated analyte bands is achieved with laser-induced fluorescence and spatially resolved detection based on a charge-coupled device. The system is characterized with a series of fluorescein thiocarbamyl amino acid derivatives; limits of detection are < 10(-8) M for amino acids and 10(-9)M (425 zmol) for fluorescein. The ability to achieve a time-based dynamic microseparation is demonstrated by monitoring fluorescent product formation during the enzyme-catalyzed hydrolysis of fluorescein di-beta-D-galactopyranoside (FDG), a commonly used fluorescent substrate for enzymological studies.

Electrophoresis↗
PubMed1996

[Clinical research of the bushen tiaojing decotion in promoting ovulation].

A comparative study on effect of promoting ovulation between Bushen Tiaojing Decoction (BSTJD) and clomifene was conducted. Results showed that the ovulation rate of BSTJD group was 66.67%, as compared with that of clomifene group (61.54%), the difference was insignificant (P > 0.05), However, there was a significant difference (P < 0.05) between the two groups in effective rate of menoxenia treatment (82.14% versus 66.67%). No toxicity or side-effect appeared. These results suggested the BSTJD could definitely promote the ovulation, and has a good effect in treating menoxenia and improving the symptoms. The mechanism of BSTJD might be regulating the function of hypothalamus-pituitary-ovary system to promote ovulation.

Adult↗
PubMed1995

Gene for cytochrome c oxidase subunit II in the mitochondrial DNA of Culex quinquefasciatus and Aedes aegypti (Diptera: Culicidae).

The cytochrome c oxidase subunit II (COII) gene between transfer RNA for Leu and Lys in the mitochondrial DNA of Culex quinquefasciatus Say and Aedes aegypti (L.) was amplified by the polymerase chain reaction (PCR) technique. Both the gene order and direction of transcription were identical to Anopheles and Drosophila. Nucleotide sequences of the PCR-amplified COII genes in these two mosquitoes exhibited 88% homology, and the frequency of transition was very close to that of transversion. The homology of deduced amino acid sequences of COII between these two mosquitoes was 95%. Two highly conserved segments of COII proteins were found in mosquitoes, fruit flies, locust, and honeybee. These segments contain the major amino acid residues of cytochrome c oxidase involved in electron transport and ligand binding. The amino acid residues are located at the positions similar to those of the mammalian enzymes. Two sets of the phylogenetic trees of a similar pattern were generated by comparing the divergences of nucleotide and amino acid sequences of COII. The branch lengths of the trees estimated by amino acid and nucleotide sequences showed different evolution rates of Aedes and Culex from their common ancestor.

Aedes↗
PubMed1994

Effect of enteral versus parenteral feeding on leucine kinetics and fuel utilization in premature newborns.

To determine whether the route of nutrient delivery affects whole-body protein kinetics and fuel utilization, eight premature newborns were studied during both a 4-h period of enteral intake and a 4-h period of parenteral nutrition. The kinetics of the essential amino acid leucine were measured using a constant tracer infusion of 1-13C-leucine, and fuel utilization and energy expenditure were assessed by respiratory calorimetry. All leucine kinetic parameters were similar during enteral or parenteral nutrition (in mean +/- SD mumol/kg/h, flux = 233 +/- 51 enteral versus 258 +/- 42 parenteral, leucine from protein breakdown = 177 +/- 50 enteral versus 200 +/- 41 parenteral, leucine oxidation = 57 +/- 26 enteral versus 63 +/- 20 parenteral, and leucine used for protein synthesis = 176 +/- 63 enteral versus 196 +/- 50 parenteral). In addition, overall rates of energy expenditure (approximately 52 kcal/kg/d) and pattern of fuel utilization (approximately 70% carbohydrate, 13% fat, 17% protein) were unaltered by the route of feeding. Thus, as reflected by leucine kinetics, overall rates of protein turnover, synthesis, oxidation, and breakdown as well as energy expenditure and fuel utilization are similar when nutrition is provided to premature newborns by either the enteral or parenteral route. These results suggest that short-term provision of parenteral nutrition may be able to substitute appropriately for enteral intake, at least with regard to the utilization of one essential amino acid and the overall pattern of fuel utilization.

Amino Acids↗
PubMed1994

[Effects of alpha-adrenoreceptor excitation on the delayed after-depolarization of sheep cardiac Purkinje fibers].

By using acetyl strophanthidin (AS) 0.2 mumol/L, the delayed after-depolarization (DAD) was induced in sheep cardiac Purkinje fibers and recorded with intra-cellular microelectrode. When beta-adrenoceptor was blocked by propranolol 1.0 mumol/L, phenylephrine 1.0 mumol/L increased the amplitude of DAD from 8.1 +/- 2.2 mV to 9.5 +/- 2.8 mV, prolonged the duration of DAD from 240 +/- 47 ms to 273 +/- 47 ms (n = 13, P < 0.01) and increased the up rising velocity of DAD from 0.039 +/- 0.023 V/s to 0.051 +/- 0.026 V/s (n = 13, P < 0.05). The DAD occurred earlier for 30 +/- 47 ms to preceding action potential (n = 13, P < 0.05). When triggered action potentials were induced by norepinephrine 1.0 mumol/L on the basis of DAD, propranolol 1.0 mumol/L could suppress the triggered beats while phentolamine 1.8 mumol/L showed little effect. The above results indicate that excitation of alpha-receptor had only slight augmentation effect on DAD. However, for the triggered activity induced by DAD, the inhibitory effect of beta-blockers are stronger than that of alpha-blockers.

Action Potentials↗
PubMed1994

[Estimation of the effect of mitral valve correction].

From September 1958 to December 1992, 488 patients underwent mitral valve repair in Fuwai Hospital. Patients ages ranged from 49 days to 60.5 years (mean age 29.02 +/- 9.97 years). The cause of mitral valve disease was rheumatic in 415 patients (85.04%). 391 patients (80.12%) had isolated mitral valve disease and 97 patients (19.88%) had associated with aortic or tricuspid valve disease, or both. There were 167 patients (34.22%) with pure mitral stenosis, 106 patients (21.72%) with pure mitral regurgitation and 215 patients (44.06%) with both. 64.96% of the patients were in New York Heart Association (NYHA) III and IV before the operation. There were 433 patients (88.73%) with isolated mitral valve repair and 55 patients (11.27%) with mitral valve repair associated with other valve repair. The hospital mortality rate was 11.27% (7.00% after 1980). 7.39% of the patients were in NYHA III and IV after operation (P < 0.01). Follow-up was 92.38% complete and totaled 4824. 12 patient-years. The mean follow-up time was 12.3 +/- 8.83 years. The 5-year, 10-year and 20-year survival rates were 94.92%, 89.70% and 70.19%, respectively. The rate of reoperation was 4.16% (0.37%/pt-yr) and the one of thromboemboli was 5.54% (0.498%/pt-yr). The follow-up mortality and reoperation rate of rheumatic mitral valve disease were significantly higher than the other causes (P < 0.01). In hospital and follow-up results of the pure MI were better than the MS and MSI (P < 0.01). The better results were obtained in mitral annuloplasty with prosthetic valve ring.

Adolescent↗
PubMed1994

[Hysteroscopic resection of submucous myomas in 27 cases].

Hysteroscopic resection of submucous myomas was done in 27 patients with the Karl Storz equipment. Among them 20 were peduncular myomas, 5 of which dropped out of the external of cervix, 7 were sessile myomas. Under ultrasonography the largest sessile myoma was 5cm in diameter. The depth of the uterine cavity was less than 10cm in all cases. For the sessile submucous myomas, the surface vessels were electro-coagulated first, then the myomas were electro-resected chip-by-chip. Peduncular for the myomas, if the pedicle was larger than 1cm, it was electro-resected, if it was less than 1cm, the myoma was removed by grasping and twisting the pedicle. Hysteroscopic resection of submucous myomas under video camera monitor is safe, less traumatic and requires, shorter stay in hospital. There was no significant postoperative complications. Follow up for one to twenty-nine months showed satisfactory results.

Adult↗
PubMed1993

A comparative study on commercial samples of phellodendri cortex.

A total of 31 commercial samples of Phellodendri cortex (Rutaceous plant) which originated from PHELLODENDRON AMURENSE Ruprecht, P. CHINENSE Schneid, P. WILSONII Hayata et Kanehira, and P. AMURENSE Rupr. var. SACHALINENSE Fr. Schm., respectively, were collected from the Taiwan and Japan herbal markets. The contents of five quaternary alkaloids (berberine, palmatine, jatrorrhizine, phellodendrine and magnoflorine) in these samples were determined by capillary electrophoresis. It was found that P. WILSONII (4.10 +/- 0.78%) and P. AMURENSE var. SACHALINENSE (4.18 +/- 1.03%) were superior to P. AMURENSE (1.55 +/- 0.72%) and P. CHINENSE (1.54 +/- 0.60%). Berberine was the major alkaloid in almost all samples. In comprised about 80% of the total alkaloids in the first two of the four herbs named above, but only about 40% in the latter two. From the data on the chemical analysis of the herb's constituents, as well as the herb's texture and color, we can postulate the origin and quality of a herb drug.

Journal Article↗
PubMed1993

Dynamic in vivo observation of rat islet microcirculation.

In vivo fluorescent microscopy with direct observation of flow through the islet was used to investigate the islet microcirculation. In urethane-anesthetized rats (n = 18), the pancreas was exposed and an islet was identified under direct microscopy. The vertical illuminator for fluorescent microscopy was turned on and fluorescein-albumin conjugate or fluorescent microspheres were injected intravenously or intraarterially. Each study was videotaped; on slow motion playback, the flow of the conjugate or microspheres was followed through the islet, the islet capillaries, and then to venules exiting the islet. One islet in the head of the pancreas in 12 rats was studied. The arterioles first reached the surrounding mantle of the islet where they divided into capillaries that carried conjugate or microspheres to other portions of the mantle or the core of the islet. Flow of conjugate traversed the core and returned to different portions of the mantle. The fluorescent microsphere study permitted a more detailed study of the pathways followed, the individual microspheres being seen to travel through numerous tortuous pathways through the islet. The flow of microspheres was nonhomogeneous in that individual microspheres in one portion of the islet would stop, then move on, while other microspheres flowed freely. The capillaries joined two to six venules that carried the conjugate or microspheres out of the islet. One or two of the exiting microvessels entered the adjacent acinar microcirculation; the others entered larger collecting venules. In six tail islets studied, the microcirculation was similar to that of the islets in the head of the pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Increased fetal glucose concentration decreases ovine fetal leucine oxidation independent of insulin.

Fetal leucine oxidation rate is elevated during fasting of the ewe. Euglycemic hyperinsulinemia causes the leucine oxidation rate to decline. However, it is unclear whether this is a direct effect of insulin or is secondary to increased insulin-mediated glucose utilization. To better delineate the mechanism of decreased oxidation, we suppressed fetal insulin secretion by somatostatin infusion. Glucose was infused at a variable rate to achieve glucose concentrations 125 and 150% of basal. Leucine rate of appearance (Ra) was determined by infusion of [15N, 1-13C]leucine. Fraction of leucine appearance oxidized was determined by [1-14C]leucine infusion and determination of fetal 14CO2 excretion. Each fetus was studied during ad libitum maternal feeding and after a 5-day complete maternal fast. Changes were noted in fetal leucine oxidation, which declined from 8.4 +/- 1.2 to 5.0 +/- 0.8 mumol/min in the fed state during glucose infusion. Basal leucine oxidation was elevated during fasting (11 +/- 1.5 mumol/min, P < 0.05) and declined to 8.0 +/- 1.4 mumol/min during glucose infusion (P = 0.056). Leucine carbon Ra was unchanged by fasting and by glucose infusion; leucine nitrogen Ra declined in the fed state only. Leucine oxidation was inversely correlated with glucose concentration (oxidation = 12-0.26 x glucose concentration, r = 0.42, P = 0.004). Leucine oxidation was not correlated with insulin concentration (r = 0.2). Changes in fetal glucose concentration may alter the pattern of utilization of essential amino acids, independent of changes in insulin and insulin-mediated glucose utilization rate.

Amino Acids, Branched-Chain↗
PubMed1993

Intravenous glucose suppresses glucose production but not proteolysis in extremely premature newborns.

To ascertain whether the inability to suppress glucose production and increase glucose utilization in response to glucose infusion is an inherent characteristic of immature individuals, we determined glucose rate of appearance (R(a)) in minimally stressed, clinically stable, extremely premature infants (approximately 26-wk gestation) at two glucose infusion rates (6.2 +/- 0.4 and 9.5 +/- 0.5 mg/kg per min). We also assessed whether an increase in glucose delivery suppresses proteolysis by measuring the R(a) of phenylalanine and leucine. Glucose R(a) (and utilization) increased significantly at the higher glucose infusion rate (7.9 +/- 0.5 vs. 9.8 +/- 0.6 mg/kg per min). Glucose production persisted at the lower glucose infusion rate but was suppressed to nearly zero at the higher rate (1.7 +/- 0.5 vs. 0.3 +/- 0.1 mg/kg per min). Proteolysis was unaffected by the higher glucose infusion rate as reflected by no change in the rates of appearance of either phenylalanine (96 +/- 5 vs. 95 +/- 3 mumol/kg per h) or leucine (285 +/- 20 vs. 283 +/- 14 mumol/kg per h). Thus, clinically stable, extremely premature infants suppress glucose production and increase glucose utilization in response to increased glucose infusion, demonstrating no inherent immaturity of these processes. In contrast, increasing the rate of glucose delivery results in no change in whole body proteolysis in these infants. The regulation of proteolysis in this population remains to be defined.

Birth Weight↗