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Biomedical subjects

Y P Pan

Publications and source records attributed to Y P Pan.

13 recordsLinked to original sources
PubMed2004

Persistent primitive trigeminal artery associated with aneurysm: report of two cases and review of the literature.

We present two cases of persistent primitive trigeminal artery (PPTA) associated with a giant aneurysm originating at the opening of the PPTA on the internal carotid artery (ICA). In one case, opening of the PPTA occurred 4 months after balloon occlusion of the ICA, when a giant aneurysm located at the cavernous segment of the ICA was being treated. The PPTA was occluded successfully using a Guglielmi detachable coil (GDC). A vertebral artery approach was taken. This is the first report of the opening of a PPTA associated with contrast filling of the aneurysm after balloon occlusion of the parent artery. The possibility of contrast filling of the aneurysm via potential PPTA should therefore be considered in the event of an ICA aneurysm with parent artery occlusion.

Balloon Occlusion↗
PubMed2003

Purification, characterization of two peptides from Buthus martensi Karch.

A new peptide named Martentoxin I and an analogue Martentoxin were purified and characterized from the venom of Buthus martensi Karch. Martentoxin I consisted of 36 amino acid residues with molecular mass as 3908.0 Da determined by matrix-assisted laser desorption ionization time-of-flight-MS. The amino acid sequence was determined as GLIDVKCFASSECWTACKKVTGSGQGKCQNNQCRCY by Edman degradation. Martentoxin consisted of 37 amino acid residues with a molecular mass as 4055.3 Da and it showed highly sequence identity to Martentoxin I as FGLIDVKCFASSECWTACKKVTGSGQGKCQNNQCRCY. Estimation from circular dichroism spectra indicated Martentoxin I owned 18.0% alpha-helix, 53.0% beta-sheet structure and 3.9% turn while Martentoxin contained 13.3% alpha-helix, 64.3% beta-sheet structure and 1.1% turn. The toxicity assay showed both peptides had no toxic effects on mice up to the dose of 10 mg/kg. Electrophysiological studies showed that Martentoxin I and Martentoxin at the concentration of 1 microm significantly inhibited voltage-dependent Na+ current (INa) and voltage-dependent delayed rectifier K+ current (IK) but had no effects on transient K+ current (IA). Both interactions with Na+ and K+ channels were irreversible.

Amino Acid Sequence↗
PubMed2001

Using flexible loop mimetics to extend phi-value analysis to secondary structure interactions.

Chemical synthesis allows the incorporation of nonnatural amino acids into proteins that may provide previously untried probes of their folding pathway and thermodynamic stability. We have used a flexible thioether linker as a loop mimetic in the human yes kinase-associated protein (YAP 65) WW domain, a three-stranded, 44-residue, beta-sheet protein. This linkage avoids problems of incorporating sequences that constrain loops to the extent that they significantly change the nature of the denatured state with concomitant effects on the folding kinetics. An NMR solution structure shows that the thioether linker had little effect on the global fold of the domain, although the loop is apparently more dynamic. The thioether variants are destabilized by up to 1.4 kcal/mol (1 cal = 4.18 J). Preliminary Phi-value analysis showed that the first loop is highly structured in the folding transition state, and the second loop is essentially unstructured. These data are consistent with results from simulated unfolding and detailed protein-engineering studies of structurally homologous WW domains. Previously, Phi-value analysis was limited to studying side-chain interactions. The linkers used here extend the protein engineering method directly to secondary-structure interactions.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Phenotypic and genotypic diversity of Streptococcus sanguis in infants.

Streptococcus sanguis comprises a heterogeneous group of oral streptococci indigenous to the oral cavity of humans. A total of 289 isolates from an infant population (n=37) were tentatively identified as S. sanguis on the basis of the distinctive colony morphology as shown on MM10-sucrose non-selective medium. These isolates were divided into four biovars of S. sanguis as determined by an extended panel of biochemical attributes. Chromosomal DNA was extracted from each isolate, and an AP-PCR fingerprint profile was obtained to allow study of the diversity within and among the infants. In this study, all four biovars of S. sanguis were detected in the infants. A wide genotypic diversity of S. sanguis was observed among these isolates; on average, each infant harbored 2.7 unique amplitypes as shown by the AP-PCR fingerprints. To explore the phylogenic relationship among these S. sanguis isolates, 20 strains representing the four biovars were selected at random for sequencing of their 16S rDNA and 16S-23S rDNA intergenic spacer chromosomal loci. Two major sequence patterns were identified within the 16S rDNA sequences. A phylogenic analysis showed that members from each of the four biovars of S. sanguis bore close relationship with the type-strain ATCC 10556 sequence, and that all of the isolates representing the four biovars could be clustered into two main phylotypes. The biovars were distributed throughout the phylotypes, indicating no correlation between the genetic and phenotypic groupings.

Bacterial Typing Techniques↗
PubMed2000

The effect of methyldopa on retinal artery circulation in pre-eclamptic gravidae.

OBJECTIVE: To evaluate the effect of methyldopa on retinal artery circulation in pre-eclamptic gravidae using color Doppler imaging and spectral analysis. METHODS: Fifty-three pre-eclamptic singleton gravidae of gestational age greater than 22 weeks were examined. Patients with sustained hypertension after 1-2 days hospital rest were treated with oral antihypertensive medication, 250-500 mg methyldopa, three to four times a day for a minimum of 5-7 days. The right central retinal arteries were insonated and Doppler waveform values were analysed before and after medication. RESULTS: The change of the maternal heart rate after methyldopa treatment was -3.96 +/- 7.88 beats per min (P = 0.0006). The change of fetal heart rate was not significantly altered. The change of the diastolic arterial blood pressure after treatment was -4.19 +/- 12.36 mmHg (P = 0.0169). In 36 gravidae, in whom hypotensive effects were noted after treatment with methyldopa, the increase in peak velocity, end-diastolic velocity and mean velocity of the retinal artery were 2.41 +/- 2.20 (P < 0.0001); 1.48 +/- 1.23 (P < 0.0001) and 1.70 +/- 1.42 (P < 0.0001), respectively. The decrease in pulsatility index of the retinal artery after treatment with methyldopa was -0.17 +/- 0.22 (P < 0.0001). In the remaining 17 gravidae, in whom no hypotensive effects were noted after treatment with methyldopa, the decrease in end-diastolic velocity and mean velocity were -1.50 +/- 1.70 (P = 0.0022) and -0.98 +/- 1.90 (P = 0.0488), respectively. The increase in pulsatility index was 0.34 +/- 0.30 (P = 0.0003). CONCLUSIONS: In pre-eclamptic gravidae in whom the hypotensive effects were noted after treatment with methyldopa, the mean velocity of the retinal arteries was significantly higher and the mean pulsatility index lower after treatment. We conclude that the hypotensive effect of methyldopa in pre-eclamptic gravidae is associated with a significant decrease in retinal artery vascular resistance.

Adult↗
PubMed1999

Color Doppler waveforms of maternal cervical internal carotid arteries in normotensive and preeclamptic gravidas.

The objective of this study was to investigate and determine fitted percentiles of blood flow resistance of cervical internal carotid arteries in normal pregnancies from gestational weeks 20 to 42 and to compare the resistance indices and mean velocities of the these arteries in normotensive and preeclamptic gravidas. A duplex color apparatus with pulsed Doppler ultrasound scanner (7.5 MHz) was used to determine the resistance index and mean velocity values of maternal cervical internal carotid arteries in 310 healthy singleton gravidas (group 1) and 74 singleton preeclamptic gravidas (group 2). The resistance index and mean velocity values of the maternal cervical internal carotid arteries decrease as the gestational age increases in normal gravidas, whereas in preeclamptic pregnancies these values are no different from those in normal gravidas during the second half of the gestational period.

Adult↗
PubMed1997

Color Doppler ultrasound, pregnancy-induced hypertension and small-for-gestational-age fetuses.

OBJECTIVE: The nomogram of blood velocity flow resistance of the spiral arteries was built at 13-25 gestational weeks. Thereafter, by using the nomogram we tried to assess the results of the color Doppler examination of the uteroplacental circulation at the second trimester to predict pregnancy-induced hypertension (PIH) and small-for-gestational-age (SGA). METHODS: Two groups of patients were studied. Group 1, for the establishment of the nomogram, included 175 uncomplicated pregnancies with gestational ages ranging from 13-25 weeks. The Doppler flow waveforms of the spiral arteries were measured once for each pregnancy in the studies. Group 2 consisted of 305 singletons selected consecutively for prospective study to confirm the occurrence of PIH or SGA. They were scanned twice for the measurements of the spiral artery waveforms at 13-19 and 20-25 weeks, respectively to test which gestational weeks interval in the nomogram is most sensitive in predicting PIH and SGA. RESULTS: The 5th, 50th and 95th percentiles of the pulsatility index (PI) values of the nomogram at the second trimester were used as the cut-off points to predict pregnancies complicated with SGA or PIH at delivery. Using the receiver operator curve, the 50th percentiles of the PI values of the nomograms were chosen as predictives for the development of PIH and SGA. At 13-19 gestational weeks, the specificities in predicting PIH and SGA were 50.71% and 49.82%, respectively, and the sensitivities were 52.00% and 50.00%, respectively. The calculated Cohen's Kappa statistics were 0.008 and 0.001, respectively in predicting PIH and SGA. At 20-25 gestational weeks, the specificities in predicting PIH and SGA were 49.64% and 49.46%, respectively, and the sensitivities were 56.00% and 57.14%, respectively. The calculated Cohen's Kappa statistics were 0.017 and 0.022, respectively in predicting PIH and SGA. CONCLUSION: The measurements of uteroplacental blood flow velocity waveforms at the second trimester are not sensitive enough to be an early screening tool for PIH and SGA in the low risk, non-selected pregnancy population. The fact suggests that in most gravidas complicated with PIH and SGA, the physiological process of trophoblastic invasion in the spiral artery was not prevented before the 25th gestational week.

Blood Flow Velocity↗
PubMed1997

Color Doppler ultrasound of spiral arteries in normal second-trimester pregnancies.

BACKGROUND: Blood flow resistance of the subplacental spiral arteries in second-trimester pregnancies has not been previously reported. A reference range of blood flow resistance of the subplacental spiral arteries at 13-25 gestational weeks was designed in the hope the reference data could provide a basis for Doppler studies of pathologic disorders in second-trimester pregnancies. METHODS: A cross-sectional study was performed in 175 uncomplicated pregnancies at 13-25 gestational weeks. Doppler flow examinations of the subplacental spiral arteries were done. RESULTS: In the 175 normal pregnancies, both the predicted systolic/diastolic ratios(S/ D) (Y = 1.96258-0.02061x gestational age (GA), adjusted R2 = 0.03773, p = 0.003) and resistance indices (RI) (Y = 0.52131-0.00871 x GA, adjusted R2 = 0.03797, p = 0.003) of the subplacental spiral arteries decreased progressively with advancing gestational age. The predicted S/D value of the subplacental spiral artery decreased from 1.695 at the 13th week's gestation (5th% = 1.221, 95th% = 2.169) to 1.468 at the 24th week's gestation (5th% = 1.057, 95th% = 1.878). The predicted RI value of the subplacental spiral artery also decreased from 0.408 at the 13th week's gestation (5th% = 0.193, 95th% = 0.623) to 0.312 at the 24th week's gestation (5th% = 0.148, 95th% = 0.477). CONCLUSIONS: Normal blood flow resistance of the subplacental spiral arteries at 13-25 gestational weeks decreases progressively with advancing gestational age. The fact suggests that trophoblastic invasion of the spiral arteries occurred continuously throughout normal second-trimester pregnancies.

Cross-Sectional Studies↗
PubMed1993

N-(1-arylpropionyl)-4-aryltetrahydropyridines, a new class of high-affinity selective sigma receptor ligands.

A series of N-(1-arylpropionyl)-4-aryl-1,2,3,6-tetrahydropyridines, prepared by simple Mannich condensations, have been found by radioligand binding assays to have moderate to high affinity (IC50 0.5-500 nM) for bovine cerebellar sigma receptor/binding sites and no measurable affinity (IC50 > 5000 nM) for bovine striatal D2 receptors. The most active of these compounds rival in potency the most active sigma ligands previously reported. Three of these sigma-active compounds were screened for pharmacological activity under the NIMH-NovaScreen program and showed moderate affinity only for D2 and 5-HT2 receptors among the 40 sites assayed. Since these N-(1-arylpropionyl)-4-aryltetrahydropyridines are structurally related to other potent sigma receptor ligands, in particular haloperidol and 4-phenylpiperidines, these data provide insights into the nature of the essential pharmacophore of the sigma receptor. The selective affinity of these materials for sigma receptors indicates they have potential as prototypes of novel psychotherapeutic medicinal agents, particularly as antipsychotic drugs which would be devoid of debilitating side effects associated with blockade of D2 receptors.

Animals↗
PubMed1991

Using ultrasonic measurement of cardiac size in predicting congenital heart defect.

A Duplex Color apparatus equipped with real-time imaging and Doppler sector scanner was used to scan fetal hearts, ranging from 17 to 41 weeks gestational age. A total of 323 normal fetuses were studied. The four-chamber view was obtained in a horizontal section just above the level of the fetal diaphragm. Five variables of the Chinese fetal heart in relation to the width of the right ventricle, width of the left ventricle, ratio of right ventricle/left ventricle (RV/LV), length of the fetal heart and the cardiac volume of a four-chamber view were set against gestational age in weeks and expressed in regression equations. The ratio of RV/LV is quite constant in relation to the gestational age. The mean ranges between 0.9916 for 17 weeks gestation and 1.0045 for a term fetus. In 10 abnormal cases with congenital cardiac defects, using the 5th and the 95th percentiles of this normal data as cutoff points, the RV/LV ratio had the highest sensitivity rate of 70% (7/10) in predicting fetal cardiac anomaly. The width of the left ventricle was the second most sensitive parameter with a sensitivity of 4/10 (40%). The RV/LV ratio of a four-chamber view is a simple, time-saving screening parameter for predicting congenital cardiac defects antenatally.

Female↗