Biomedical subjects

Y Y Lin

Publications and source records attributed to Y Y Lin.

At least 19 recordsLinked to original sources

PubMed2006

Light-enhanced electro-optic spectral tuning in annealed proton-exchanged periodically poled lithium niobate channel waveguides.

We report the observation of light-enhanced electro-optic spectral tuning in annealed proton-exchanged, asymmetric domain-duty-cycle periodically poled lithium niobate (PPLN) channel waveguides for second-harmonic generation. The spectral tuning rate was increased rapidly from 0.07 nm/(kV/mm) to a saturated value of 0.32 nm/(kV/mm) in a 30%/70% domain-duty-cycle PPLN waveguide when the fundamental pump power near 1534 nm was increased from 0.6 to 46 mW. The second-harmonic laser power at 767 nm was identified to be the source enhancing the spectral tuning.

Journal Article↗

PubMed2005

Enhanced terahertz-wave parametric generation and oscillation in lithium niobate waveguides at terahertz frequencies.

We observed parametric-generation efficiency of 1.61% from 1064 to 1071 nm and at 162 microm in a 0.5 mm thick, 45 mm long z-cut congruent lithium niobate waveguide with a pump energy of 2.2 mJ and a pump pulse width of 5.8 ns. We also measured an ultralow-threshold intensity of 70 MW/cm2 for a 1064 nm pumped parametric oscillator resonating at 1071 nm and emitting at 162 microm with a 1 mm thick, 45 mm long lithium niobate waveguide.

Journal Article↗

PubMed2005

Monolithic quasi-phase-matched nonlinear crystal for simultaneous laser Q switching and parametric oscillation in a Nd:YVO4 laser.

We report the performance of a periodically poled lithium niobate (PPLN) crystal inside a diode-pumped Nd:YVO4 laser for simultaneous laser Q switching and optical parametric oscillation. The monolithic PPLN crystal consists of two sections, a 1-cm-long 14-microm-period electrode-coated section and a 4-cm-long 30-microm-period section, functioning as a low-voltage Pockels cell and a quasi-phase-matched parametric gain medium, respectively. At a 150-V Q-switching voltage and a 6-kHz switching rate, we measured 25-microJ pulse energy and 4-kW peak power at 1.55 microm with 9-W absorbed diode power.

Journal Article↗

PubMed2005

Heat shock protein 70 and tumor necrosis factor alpha in Taiwanese patients with dementia.

This study was to determine whether polymorphisms of heat shock protein 70-1 (HSP70-1) and tumor necrosis factor alpha (TNF-alpha) are associated with the risk of Alzheimer's disease (AD) and vascular dementia (VaD). Using the criteria of the NINCDS-ADRDA and NINDS-AIREN, 125 AD patients, 57 VaD patients and 109 ethnically matched nondemented controls were enrolled. The HSP70-1 -110 A/C and TNF-alpha -1031 T/C, -863 C/A and -857 C/T polymorphisms were analyzed by means of genotype or haplotype association methods. None of the four genotypes examined showed a statistically significant difference in genotype distribution between the AD cases and controls. However, the HSP70-1 -110 CC genotype occurred more frequently among AD cases (p=0.0821; odds ratio: 2.08; 95% confidence interval, CI: 0.92-4.98). The overall genotype distribution among the VaD cases tended to be different at the HSP70-1 -110 and TNF-alpha -1031 sites (p=0.0604 and 0.0316, respectively). The HSP70-1 -110 CC genotype was more frequent (p=0.0459), and the association of the -110 CC genotype with VaD was evident (p=0.0207; odds ratio: 3.22; 95% CI: 1.20-8.87). The more frequent TNF-alpha -1031 TC genotype (p=0.0614) was also evidently associated with VaD (p=0.0209; odds ratio: 2.32; 95% CI: 1.14-4.78). Multivariate analysis demonstrated the synergistic effect of the HSP70-1 -110 CC and TNF-alpha -1031 TC/CC genotypes on VaD (p=0.0091; odds ratio: 10.09; 95% CI: 2.01-75.97). Haplotype analysis among TNF-alpha -1031, -863, -857 sites revealed that -1031C-857C may act as a risk haplotype among VaD cases (p=0.0132, odds ratio: 2.26; 95% CI: 1.19-4.33). Our results suggest a potential protective role for HSP70 in both VaD and AD, whereas TNF-alpha may act as a risk factor only for VaD, and not for AD.

Aged↗

PubMed2003

Video-assisted laparoscopic procedures in peritoneal dialysis.

BACKGROUND: Although laparoscopy is commonly adopted for the diagnosis and management of various medical or surgical problems, its use for patients with peritoneal dialysis has seldom been addressed. This retrospective study analyzes the indications and clinical effects of this procedure. METHODS: A retrospective chart was drawn up and a videotape review performed for 18 laparoscopic procedures involving 198 patients receiving peritoneal dialysis on a long-term basis at our dialysis unit from May 1992 to June 2002. The clinical and demographic parameters in this study included gender, age, underlying renal diseases, duration of peritoneal dialysis before laparoscopy, indications of laparoscopic intervention, laparoscopic findings, time of operation, laparoscopic procedures, postoperative complications, mortality, and catheter results. RESULTS: A total of 18 laparoscopic procedures were performed in 17 uremia patients, with indications including catheter malfunction in five cases, preimplantation evaluation of peritoneal space in three cases, evaluation of the etiology underlying intractable peritonitis in nine cases, and verification of the cause for dialysate leakage in one case. Four (80%) of the five catheter malfunctions were successfully corrected, including one case of catheter migration and three cases of omental wrapping, whereas correction failed in the remaining case because of severe bowel adhesion. New catheter placement after adhesiolysis was successful in all three cases of preimplantation peritoneal evaluation (100%). Of the nine patients whose peritonitis episodes were evaluated, two were found to have secondary peritonitis, two had fungal peritonitis; one had tuberculous peritonitis and four had bacterial peritonitis. In the case of persistent exit-site dialysate leakage, laparoscopy showed a penetrating injury of the abdominal wall, raising a strong suspicion of iatrogenic injury during the tunneling maneuvers in initial catheter placement. Two conversions to laparotomy were performed: one to repair the penetrating injury and the other to save the life of a patient threatened by severe fungal peritonitis with abdominal cocoon formation. The laparoscopic procedures lasted 20 to 150 min (average, 50 min). Despite one instance of postoperative hydrocele, there was no operative mortality. CONCLUSIONS: The analytical results of this study demonstrate that the current video-assisted laparoscopic technique is an effective means for managing several problems related to peritoneal dialysis such as catheter malfunction, preimplantation evaluation, location of the source of the dialysate leak, and assessment of the causes for peritonitis. Thus, this technique should always be considered when the these problems arise.

Adolescent↗

PubMed2003

MEG localization of rolandic spikes with respect to SI and SII cortices in benign rolandic epilepsy.

The purpose of this study was to study the relationship between interictal spike sources and somatosensory cortices in benign rolandic epilepsy of childhood (BREC) using a whole-scalp neuromagnetometer. We recorded spontaneous magnetoencephalography (MEG) and EEG signals and cortical somatosensory-evoked magnetic fields (SEFs) to electric stimulation of the median nerve in 9 children with BREC. Interictal rolandic discharges (RDs) and SEFs were analyzed by equivalent current dipole (ECD) modeling. Based on the orientation and locations of corresponding ECDs, we compared generators of RDs with primary (SI) and second somatosensory cortices (SII). Our results showed that RDs and SII responses had similar ECD orientation on the magnetic field maps. The ECDs of RDs were localized 15.3 +/- 1.9 and 12.2 +/- 2.8 mm anterior to SI and SII, respectively. The spatial distance on average from the location of RDs to SII (21.9 +/- 1.6 mm) cortex was significantly shorter than to SI cortex (29.7 +/- 1.7 mm) (P<0.01, Wilcoxon signed-rank test). In conclusion, the cortical generators for RDs in patients with BREC are localized in the precentral motor cortex, closer to hand SII than to SI cortex.

Child↗

PubMed2003

Magnetoencephalographic yield of interictal spikes in temporal lobe epilepsy. Comparison with scalp EEG recordings.

To compare magnetoencephalography (MEG) with scalp electroencephalography (EEG) in the detection of interictal spikes in temporal lobe epilepsy (TLE), we simultaneously recorded MEG and scalp EEG with a whole-scalp neuromagnetometer in 46 TLE patients. We visually searched interictal spikes on MEG and EEG channels and classified them into three types according to their presentation on MEG alone (M-spikes), EEG alone (E-spikes), or concomitantly on both modalities (M/E-spikes). The M-spikes and M/E-spikes were localized with MEG equivalent current dipole modeling. We analyzed the relative contribution of MEG and EEG in the overall yield of spike detection and also compared M-spikes with M/E-spikes in terms of dipole locations and strengths. During the 30- to 40-min MEG recordings, interictal spikes were obtained in 36 (78.3%) of the 46 patients. Among the 36 patients, most spikes were M/E-spikes (68.3%), some were M-spikes (22.1%), and some were E-spikes (9.7%). In comparison with EEG, MEG gave better spike yield in patients with lateral TLE. Sources of M/E- and M-spikes were situated in the same anatomical regions, whereas the average dipole strength was larger for M/E- than M-spikes. In conclusion, some interictal spikes appeared selectively on either MEG or EEG channels in TLE patients although more spikes were simultaneously identified on both modalities. Thus, simultaneous MEG and EEG recordings help to enhance spike detection. Identification of M-spikes would offer important localization of irritative foci, especially in patients with lateral TLE.

Adolescent↗

PubMed2002

Functional characterization of human second somatosensory cortex by magnetoencephalography.

Magnetoencephalographic (MEG) recordings allow noninvasive monitoring of simultaneously active brain areas with reasonable spatial and excellent temporal resolution. Whole-scalp neuromagnetic recordings show activation of contralateral primary (SI) and bilateral second (SII) somatosensory cortices to unilateral median nerve stimulation. Recent MEG studies on healthy and diseased human subjects have shown some functional characteristics of SII cortex. Besides tactile input, the SII cortex also responds to nociceptive afferents. The SII activation is differentially modulated by isometric muscle contraction of various body parts. Lesions in the SII cortex may disturb the self-perception of body scheme. Moreover, the SI and SII cortices may be sequentially activated within one hemisphere, but the SII cortex may also receive direct peripheral input on the ipsilateral side.

Animals↗

PubMed2001

Oscillatory interaction between human motor cortex and trunk muscles during isometric contraction.

We investigated oscillatory interaction between magnetoencephalographic signals of the human motor cortex and surface electromyogram from the paraspinal (PS) and abdominal (ABD) muscles. The results were compared with data obtained during contraction of the first dorsal interosseus (FDI) and tibialis anterior (TA) muscles. Significant coherence at 15-35 Hz was observed for both PS and ABD muscles in all subjects but the coherence was weak compared with that for FDI and TA. The cortical sources for both the PS and the ABD coherences were located in the motor cortex between the source areas for the FDI and TA coherences, thereby agreeing with the classical trunk area of the motor homunculus previously determined by invasive studies. The sources were strictly contralateral for PS but bilateral for ABD contractions. Our results indicate that during isometric contractions descending motor commands are modulated by cortical oscillations for both limb and trunk muscles, although the modulation is weaker and may be bilateral for trunk muscles.

Abdominal Muscles↗

PubMed2001

Reflections on sterol sidechain cleavage process catalyzed by cytochrome P450(scc).

The essay examines the evidence upon which the presently accepted version of the mechanism of the cytochrome P450(scc)-catalyzed-cleavage of the sidechain of cholesterol is based. This analysis indicates that the generally held view of the process (two consecutive hydroxylations, followed by cleavage of the resulting glycol) most likely does not describe the true mechanism. The available evidence can not be used to support this traditional notion. Two alternative hypotheses are proposed.

Animals↗

PubMed2001

Lateralizing value of early head turning and ictal dystonia in temporal lobe seizures: a video-EEG study.

To investigate early head turning, we retrospectively studied videotapes of 262 seizures from 82 patients who were seizure free after temporal lobectomy. Early head movements were arbitrarily classified into non-tonic turning, tonic turning, and absence of turning. Among the 222 seizures which showed early head turning, 168 (75.7%) had non-tonic turning and 54 (24.3%) had tonic turning. The direction of the first head turning was ipsilateral to the epileptogenic foci in 132 (78.6%) seizures with non-tonic turning and in 35 (64.8%) seizures showing tonic head turning. The proportion of seizures with turning towards the ipsilateral side in the presence of tonic and non-tonic head turning were significantly different (P= 0.04). Seventy-four seizures (28.2%) evolved to secondary generalization, more frequently found in seizures with early head turning (P= 0.0015) and especially those showing tonic turning (P< 0.0001). The direction of head turning immediately preceding secondary generalization was contralateral to the lesion side in 53 seizures (82.8%). Dystonic upper limb posturing occurred in 86 seizures (32.8%), exclusively contralateral to the seizure focus, whereas 65 (75.6%) were associated with initial head turning ipsilateral to the focus. In summary, temporal lobe seizures with tonic head turning tends to secondarily generalize and the direction of head turning before secondarily generalized was contralateral to the seizure foci. Earlier in the seizures the direction of non-tonic head turning tends to be towards the epileptogenic hemisphere. In addition, dystonic posturing of the extremities is a significant lateralizing sign to the contralateral hemisphere in temporal lobe seizures.

Adult↗

PubMed2001

Novel mutations of CYP3A4 in Chinese.

Human cytochrome P450 3A4 is a major P450 enzyme in the liver and gastrointestinal tract. It plays important roles in the metabolism of a wide variety of drugs, some endogenous steroids, and harmful environmental contaminants. CYP3A4 exhibits a remarkable interindividual activity variation as high as 20-fold. To investigate whether the interindividual variation in CYP3A4 levels can be partly explained by genetic polymorphism, we analyzed DNA samples from 102 Chinese subjects by polymerase chain reaction (PCR)-single-strand conformation polymorphism analysis for novel point mutation in the CYP3A4 coding sequence and promoter region. Using PCR and directed sequencing method to establish the complete intron sequence of CYP3A4 from leukocytes, the complete genomic sequence from exon 1 through 13 of CYP3A4 was determined and published in the GenBank database (accession no. AF209389). CYP3A4-specific primers were designed accordingly. After PCR-single-strand conformation polymorphism and restriction fragment length polymorphism screening, we found three novel mutations; two are point mutations and one is insertion. The first variant allele (CYP3A4*4), an Ile118Val change, was found in 3 of 102 Chinese subjects. The next allele (CYP3A4*5), which causes a Pro218Arg amino acid change, was found in 2 of 102 subjects. We found an insertion in A(17776), designated as CYP3A4*6, which causes frame shift and an early stop codon in exon 9, in one heterozygous subject. We also investigated the CYP3A4 activity in these mutant subjects by measuring the morning spot urinary 6beta-hydroxycortisol to free cortisol ratio with the enzyme-linked immunosorbent assay method. When compared with healthy Chinese population data, the 6beta-hydroxycortisol to free cortisol ratio data suggested that these alleles (CYP3A4*4, CYP3A4*5, and CYP3A4*6) may decrease the CYP3A4 activity. Incidences of these mutations in Chinese subjects are rare. The prevalence of these point mutations in other ethnic groups and its effect on the metabolic activity of CYP3A4 remain to be further evaluated.

Alleles↗

PubMed2001

Impact of parent death and an intervention on the adjustment of adolescents whose parents have HIV/AIDS.

The impact of parental death and the efficacy of a coping-skills intervention were examined on the adjustment of 211 adolescent children of parents with HIV/AIDS (PWH) over a 2-year period. During the follow-up period, 35% of the PWH died. Using longitudinal structural equation model, controlling for prior measures of adjustment at baseline, the authors found that children of deceased PWH reported significantly more emotional distress and problem behaviors 2 years later. Youth randomized with their parent to a coping-skills intervention reported significantly fewer problem behaviors and sexual partners 2 years later. Also, adolescents were better-adjusted 2 years later when their parents had reported less emotional distress and less severe physical health symptoms at baseline. Female adolescents reported more emotional distress at baseline and at 2 years than males; male adolescents reported more problem behaviors at baseline than the females.

Adjustment Disorders↗

PubMed2000

Resurrection of crushed magnetization and chaotic dynamics in solution NMR spectroscopy.

We show experimentally and theoretically that two readily observed effects in solution nuclear magnetic resonance (NMR)-radiation damping and the dipolar field-combine to generate bizarre spin dynamics (including chaotic evolution) even with extraordinarily simple sequences. For example, seemingly insignificant residual magnetization after a crusher gradient triggers exponential regrowth of the magnetization, followed by aperiodic turbulent spin motion. The estimated Lyapunov exponent suggests the onset of spatial-temporal chaos and the existence of chaotic attractors. This effect leads to highly irreproducible experimental decays that amplify minor nonuniformities such as temperature gradients. Imaging applications and consequences for other NMR studies are discussed.

Journal Article↗

PubMed2000

Differential effects of muscle contraction from various body parts on neuromagnetic somatosensory responses.

We studied eight healthy subjects with a whole-scalp 306-channel neuromagnetometer to explore the effect of motor activity from different body parts on somatosensory responses to left median nerve stimulation. The stimuli produced clear tactile sensation without any motor movement. In the rest condition, the subject had no task. During contraction conditions, the subject had to maintain submaximal isometric contraction in masseter, left deltoid, left thenar, or left tibialis muscles. Short-latency responses from the primary somatosensory cortex did not change during contraction. Responses from both the right (contralateral) and left second somatosensory cortices (SII) were significantly enhanced during contraction of the left thenar muscles. Responses from the left SII were significantly enhanced also during contraction of the left deltoid muscles, but they were decreased during contraction of the masseter and left tibialis anterior muscles. This study implies that SII activation is modulated by motor activity and that the effect depends on the topographical proximity of the stimulated and contracted body parts.

Adult↗

PubMed1999

Transient elevation in plasma prolactin level in rats with temporal lobe status epilepticus.

Microinjection of kainic acid into the CA3 subfield of hippocampus in anesthetized rats elicited seizure-like hippocampal EEG activity that persisted for more than 180 minutes. There was a concomitant rise in plasma prolactin level that peaked at 15 to 20 minutes but endured less than 60 minutes. We conclude that plasma prolactin exhibited only transient elevations during experimental temporal lobe status epilepticus in rats.

Animals↗

PubMed1999

Serum anti-p53 antibodies in gastric adenocarcinoma patients are associated with poor prognosis, lymph node metastasis and poorly differentiated nuclear grade.

Mutation of the p53 tumour suppressor gene often leads to the accumulation of mutant p53 protein in tumour cells. Many cancer patients develop antibodies that recognize the overexpressed p53 protein. The presence of these antibodies is, in some tumour types, associated with poor prognosis. Gastric cancer is a highly prevalent disease associated with a high rate of mortality, there is a need for improved clinical and biological markers for disease behaviour. To investigate the clinical relevance of serum anti-p53 antibodies in patients with gastric adenocarcinoma, we have examined the sera of 501 gastric cancer patients for the presence of serum antibodies against the p53 protein. By immunoblotting analysis using a cell lysate containing overexpressed p53 protein as well as affinity-purified recombinant p53 protein as antigens, we have detected anti-p53 antibodies in 11.2% (61 of 501) of gastric cancer patients, but in none of 46 cancer-free individuals. The presence of anti-p53 antibodies was tightly associated with tumours of higher nuclear grade and lymph node metastasis, and a negative association was found between the presence of anti-p53 antibodies and survival. These results suggest that a preoperative test of serum anti-p53 antibodies in gastric cancer patients can be useful to identify subset of patients who may need gastrectomy with lymph node dissection and post-operative adjuvant therapy.

Adenocarcinoma↗

PubMed1999

Evaluation of pre- and postdilutional on-line hemodiafiltration adequacy by partial dialysate quantification and on-line urea monitor.

On-line highflux hemodiafiltration (HDF) is a clinically interesting and effective mode of renal replacement therapy, which offers the possibility to obtain an increased removal of both small and large solutes. The fundamental role of urea kinetic monitoring to assess dialysis adequacy in conventional hemodialysis has been widely studied. Both direct measurement of the urea removed by the modified direct dialysate quantitation (mDDQ) based on partial dialysate collection (PDC) and dialysate-based urea kinetic modeling (DUKM) using urea monitor have been advocated. The validity of this assessment tool in the patients with on-line HDF remained unclear. The aims of this investigation were (1) to compare the delivered Kt/V, urea mass removal (UMR), solute removal index (SRI) and normalized protein catabolic rate (nPCR) between pre- and postdilutional high-flux HDF; (2) to verify and compare the efficiency of pre- and postdilutional HDF using DUKM with on-line dialysate urea sensor, and mDDQ with partial dialysate collection. During both mode of HDF, the paired analysis urea removed and Kt/V showed no significant difference. Using mDDQ, mean values for predilutional mode were as follows: Kt/V 1.53 +/- 0.01 UMR, 16.8 +/- 0.3 g/session; urea clearance 178 +/- 18 ml/min; SRI 75.5 +/- 7.7%; urea distribution volume (V) 28.3 +/- 1.2 liters; nPCR 1.34 +/- 0.18 g/kg/day; on the other hand, mean values for postdilutional mode were Kt/V 1.58 +/- 0.01; UMR 17.10 +/- 0.28 g/session; urea clearance 184 +/- 21 ml/min; SRI 77.2 +/- 3.5%; urea distribution volume, 27.8 +/- 1.5 liters; nPCR 1.34 +/- 0.19 g/kg/day. The mean value of urea generation rate was 5.82 +/- 1.12 mg/min during HDF. Our results showed that dialysis adequacy was achieved with both high-volume predilutional HDF and postdilutional HDF. These two modes of HDF provided similar and adequate small solute clearance. In addition, we found that on-line analysis of urea kinetics is a reliable tool for quantifying and assuring delivery of adequate dialysis.

Adult↗