Biomedical subjects

Low-Tone Ho

Publications and source records attributed to Low-Tone Ho.

At least 55 records · Page 3Linked to original sources

PubMed2004

Neuronal correlates of consistency and frequency effects on Chinese character naming: an event-related fMRI study.

This event-related functional magnetic resonance imaging (efMRI) study aims to investigate the central representations of Chinese orthography-to-phonology transformation (OPT) by simultaneously manipulating character frequency and consistency. Bilateral inferior frontal cortices (including Broca's area and insula), the left temporoparietal region (superior parietal gyrus and supramarginal gyrus), and the left temporal-occipital junction showed greater activation, especially in low-frequency conditions, when naming inconsistent characters as compared to consistent ones. These findings suggest that these regions are involved in the sublexical conversion of orthographic input into phonological codes in naming Chinese. The similar activation pattern found in these three regions suggests a distributed process, rather than separate neural routes, for lexical and sublexical OPT. In addition, the regions involved in Chinese OPT are congruent with the findings for reading alphabetic scripts and indicate that the neuronal mechanisms for orthography-to-phonology transformation is domain universal across different writing systems.

Adult↗

PubMed2004

Serum and adipocyte resistin in polycystic ovary syndrome with insulin resistance.

BACKGROUND: The aim of this study was to investigate the relationship between resistin and insulin resistance in patients with polycystic ovary syndrome (PCOS). METHODS: We compared serum resistin levels in 17 PCOS women and 10 lean, healthy, age-matched non-PCOS women and also compared levels of insulin receptor (IR), phosphatidylinositol-3 kinase (PI3-kinase), glucose transporter 4 (GLUT4) protein and resistin mRNA in adipocytes isolated from the omental adipose tissue of five of the PCOS patients and five age- and weight-matched, non-PCOS controls, to look for local defects in insulin action in PCOS. RESULTS: The PCOS group was hyperinsulinaemic and displayed an impaired insulin response in a 75 g oral glucose tolerance test and an abnormal homeostasis model insulin resistance index. Serum resistin levels were similar in PCOS patients and controls; however, resistin mRNA levels were 2-fold higher in adipocytes from PCOS patients. No correlation was found between serum resistin levels and either the BMI or testosterone levels. Western blot analysis showed that adipocyte levels of insulin receptor, PI3-kinase, and GLUT4 were respectively decreased by 56, 39.4 and 54% in PCOS patients compared with controls. CONCLUSIONS: These results suggest that overexpression of the resistin gene in adipocytes may be a local determinant factor in the pathogenesis of PCOS.

Adipocytes↗

PubMed2004

Intestinal absorption and biliary secretion of zinc in rats with chronic renal failure.

BACKGROUND/AIMS: In chronic renal failure (CRF), zinc deficiency is partially attributed to decreased intestinal zinc absorption, but the mechanism of this decrease in intestinal zinc absorption is obscure. Therefore, the objective of this study was to investigate the cause of decreased intestinal zinc absorption in a uremic rat model using an in vivo perfusion technique as well as to evaluate the effect of intestinal zinc perfusion on the secretion of biliary zinc in normal and CRF rats. METHODS: CRF was induced by five-sixths nephrectomy (Nx). During zinc sulfate perfusion, absorption of zinc in the small intestine and the response of plasma zinc level were measured. After intestinal zinc perfusion for 80 min, the concentrations of zinc and metallothionein (MT) in the intestinal mucosal and liver tissue were assayed. The secretion of biliary zinc and the excretion of urinary zinc were also determined before and after zinc sulfate perfusion. The results were compared with those obtained from 10 sham-operated normal rats. RESULTS: The CRF rats showed a significant decrease in the rate of intestinal zinc absorption and in the response of plasma zinc levels during intestinal zinc perfusion. They also had significantly higher levels of mucosal zinc and MT than sham-operated normal rats, but their contents of liver zinc were significantly lower than those of sham-operated normal rats after zinc sulfate perfusion. CRF rats showed a low plasma zinc level and a high urinary zinc excretion in baseline levels, but had similar output of basal biliary zinc as compared with sham-operated normal rats. Zinc sulfate perfusion in the small intestinal was not found to increase the secretion of biliary zinc and the excretion of urinary zinc, either in normal or CRF rats. CONCLUSION: In the CRF rat, the reduction of intestinal zinc absorption may result from reduced mucosal zinc efflux from the basolateral membrane into plasma. These data also suggest that the absorbed zinc from the gastrointestinal tract is mostly taken up by the liver or other tissues, and is less excreted in bile juice and urine.

Animals↗

PubMed2004

Biethnic comparisons of autosomal genomic scan for loci linked to plasma adiponectin in populations of Chinese and Japanese origin.

Adiponectin is secreted by adipocytes and is thought to have insulin-sensitizing and antiatherogenic effects. Two previous genome scans for plasma adiponectin have identified different regions for European and Pima Indian populations. We here present multipoint linkage analysis of adiponectin levels using a variance-components model for 1007 siblings (from 360 nuclear families) of Chinese origin and 352 siblings (from 147 nuclear families) of Japanese origin. We found heritability for adiponectin concentrations was 0.70 for Chinese and 0.48 for Japanese. Autosomal genome scan was performed using microsatellite markers span at an interval of approximately 10 cM. Suggestive linkage of adiponectin, after adjusting for age and sex, was found on chromosome 15 at 39 cM (maximal LOD score = 3.19, P = 6.3 x 10(-5)) for Chinese; and on chromosome 18 at 28 cM (maximal LOD score = 2.40, P = 4.4 x 10(-4)) for Japanese. There were tentative loci of weak linkage on chromosomes 3, 18, and 20 in Japanese. We provide novel loci on chromosomes 15, 18, and 20 and confirm a region on chromosome 3 as reported in Pima Indians, which may influence differentially on circulating adiponectin concentrations in Chinese and Japanese populations. Further fine mapping of these regions will help to identify the gene(s) that might affect adiponectin levels.

Adiponectin↗

PubMed2004

A longitudinal study of growth patterns in school children in Taipei area I: growth curve and height velocity curve.

BACKGROUND: It has been pointed out that longitudinal rather than cross-sectional growth standards should be used to assess individual linear growth. The purpose of this study is to investigate the growth characteristics of school boys and girls living in Shih-Pai district in Taipei. METHODS: A defined group of 1,139 healthy school children (570 boys and 569 girls) from the Shih-Pai district of Taipei city were followed longitudinally for 3 to 4 years. Anthropometric measurement of height and weight and physical development in each child were obtained. The annual increments were calculated every 6 months to map the peak height velocity (PHV), height velocity curve (HVC), peak weight velocity (PWV) and weight velocity curve (WVC). RESULTS: The age at peak velocity was taken as 12.5 years for boys and 10.5 years for girls, and the whole year PHV as 8.0 cm/yr in boys and 7.0 cm/yr in girls. The mean PHV was less than 1 cm in boys and girls of about 17 years and 15 years, respectively, with mean heights of 170.8 cm and 158.7 cm, respectively. CONCLUSIONS: Our preliminary results were actually calculated from the combination of longitudinal data and cross-sectional data pools. Since this is only a pilot study design, we expect that a longer follow-up period of the same cohorts would give more exact growth characteristics.

Adolescent↗

PubMed2003

Production and characterization of bioactive recombinant resistin in Escherichia coli.

Type 2 diabetes, characterized by peripheral target tissue resistance to insulin, is epidemic in industrialized countries and is strongly associated with obesity. The protein hormone, resistin, secreted specifically by the adipose tissues, is found to antagonize insulin action upon glucose uptake and may serve as an important role between human obesity and insulin resistance. Here, we report the production of bioactive recombinant resistin in Escherichia coli. cDNA of resistin was obtained by RT-PCR from mRNA of mouse differentiated NIH/3T3-L1 cells. The cDNA of mature resistin was inserted in the pQE-31 vector and the recombinant plasmid was transferred into E. coli JM109. After IPTG induction, the rec. resistin found in the inclusion body was dissolved in 6 M guanidine-HCl in the presence of 10 mM beta-mercaptoethanol. The His-tag containing protein was purified by Ni-NTA column to 95% homogeneity. After a quasi-static-like refolding process, the secondary structure of the rec. resistin was elucidated by circular dichroism which indicated that the protein was composed of 34.3% alpha-helix, 8.9% beta-sheet, 23.4% beta-turn, and 31.2% unordered structure. No disulfide-linked homodimers were formed in SDS-PAGE analysis under non-reducing conditions. The rec. resistin showed a dose-dependent antagonizing action against insulin in [3H]-2-deoxy-glucose transport in a broad range from 1 ng ml(-1) to 10 microg ml(-1) of resistin. A suppression of 85% of transport was achieved at the dosage of 10 microg ml(-1). This result may indicate that the rec. resistin does not need to form homodimers to establish its bioactivity. The rec. resistin will be useful for exploring the biological functions of this newly discovered hormone.

Animals↗

PubMed2003

Healthy-side dominance of cortical neuromagnetic responses in sudden hearing loss.

Previous brain imaging and mapping studies have reported findings indicating functional reorganization in the central auditory pathways of patients with profound unilateral hearing loss. This study reports for the first time to our knowledge, using a whole-head neuromagnetometer with monaural stimulation of both intact and affected ears, a pattern of healthy-side dominance for cortical neuromagnetic responses in adult patients in the early stage of idiopathic sudden sensorineural hearing loss, and a pattern of contralateral dominance is verified in controls.

Adult↗

PubMed2003

ICA-based spatiotemporal approach for single-trial analysis of postmovement MEG beta synchronization.

The extraction of event-related oscillatory neuromagnetic activities from single-trial measurement is challenging due to the non-phase-locked nature and variability from trial to trial. The present study presents a method based on independent component analysis (ICA) and the use of a template-based correlation approach to extract Rolandic beta rhythm from magnetoencephalographic (MEG) measurements of right finger lifting. A single trial recording was decomposed into a set of coupled temporal independent components and corresponding spatial maps using ICA and the reactive beta frequency band for each trial identified using a two-spectrum comparison between the postmovement interval and a reference period. Task-related components survived dual criteria of high correlation with both the temporal and the spatial templates with an acceptance rate of about 80%. Phase and amplitude information for noise-free MEG beta activities were preserved not only for optimal calculation of beta rebound (event-related synchronization) but also for profound penetration into subtle dynamics across trials. Given the high signal-to-noise ratio (SNR) of this method, various methods of source estimation were used on reconstructed single-trial data and the source loci coherently anchored in the vicinity of the primary motor area. This method promises the possibility of a window into the intricate brain dynamics of motor control mechanisms and the cortical pathophysiology of movement disorder on a trial-by-trial basis.

Adult↗

PubMed2003

Acarbose improves glycemic control in insulin-treated Asian type 2 diabetic patients: results from a multinational, placebo-controlled study.

The purpose of the study was to determine the efficacy and tolerability of acarbose in Asian type 2 diabetic patients insufficiently controlled by insulin. Asian type 2 diabetic patients on stable insulin dosages were enrolled into a multinational, double-blind, placebo-controlled parallel arm study. After a 2-week screening phase, patients were randomly assigned to 50 mg acarbose t.i.d. or matching placebo for 6 weeks, followed by 100 mg acarbose t.i.d. or placebo for 12 weeks. The primary efficacy parameter was change from baseline in HbA(1c); secondary variables included the changes in fasting and postprandial blood glucose. After 18 weeks of treatment there was a difference in HbA(1c) levels between the two treatment groups (-0.69%, 95% CI (-1.18; -0.2), P=0.008) in favour of acarbose. Reductions in 1-h postprandial glucose levels from baseline to endpoint were observed with acarbose treatment (P=0.029). There were no differences in fasting blood glucose, total triglyceride and cholesterol between the two groups. Safety profiles were similar for both treatment arms except for the higher incidence of flatulence in the acarbose group (28.6% vs. 16.4% for placebo). Adjunctive acarbose therapy offers an efficacious and safe means for improvement of glycemic control in Asian type 2 diabetic patients insufficiently controlled by insulin.

Acarbose↗

PubMed2003

Frequency effects of Chinese character processing in the brain: an event-related fMRI study.

Knowing how the brain processes Chinese characters of different frequencies of occurrence may shed light on the extent to which orthographic variations of different languages can influence reading processes in the brain. In the present study, event-related fMRI was used to investigate frequency effects on Chinese character processing. Reading low-frequency characters invoked higher activation in several brain regions including the left premotor/inferior frontal gyrus, supplementary motor area, left anterior insula, left posterior inferior temporal gyrus, left superior parietal cortex, and lingual cortex, while reading high-frequency characters resulted in higher activation in the left supramarginal/angular gyrus and left precuneus. The activation pattern of reading infrequently encountered characters reflects a more demanding processing procedure of retrieving, formulating, and coordinating the phonological output. Access to the lexical route may benefit the reading of high-frequency characters. By uncovering the differential brain responses in reading Chinese characters of different occurrence frequencies, not only has a substantial overlap between functional neuroanatomy of reading Chinese and alphabetical languages been demonstrated, but also features permitting the separation of language-specific content from universal mechanisms.

Adult↗

PubMed2003

Differential effects of stimulus intensity on peripheral and neuromagnetic cortical responses to median nerve stimulation.

To study the differential effects of tactile stimulus intensity on cortical and peripheral responses, we measured neuromagnetic cortical responses, compound muscle action potentials (CMAP), sensory nerve action potentials (SNAP), and the subjective estimation of tactile magnitude to electric median nerve stimulation at the wrist in 13 male healthy adults. The sensory perception threshold (ST) for electric pulses at wrist skin was determined and then various levels of stimulus intensity (1 approximately 6 ST) were given to each subject. At 1 ST, only the P50m components of the primary somatosensory (SI) cortical responses were recorded. The second somatosensory (SII) cortical responses were saturated at 2 ST, while the SI responses reached maximum at 3 ST equivalent to the subjective threshold intensity for "strong" tactility. The CMAP and SNAP were maximum at 4-5 ST. At 2 ST, >70% of maximum SI responses were produced, whereas only <40% of maximum CMAP or SNAP responses were obtained. We concluded that the stimulus intensities for activating or saturating somatosensory cortical responses were lower than those for CMAP and SNAP. The differential intensity effects on cortical and peripheral responses suggest a polysynaptic organization underlying the central amplification for somatosensory cortical activation. The optimal intensity levels for producing maximum SI and SII responses were 3 and 2 ST, respectively. Compared with the SII, the SI plays a crucial role in the coding of the tactile stimulus intensity.

Action Potentials↗

PubMed2003

Hypoxic preconditioning prevents cortical infarction by transient focal ischemia-reperfusion.

One of the proposed pathologic actions underlying brain infarction is excess free radicals resulting from reoxygenation. In this paper we report an investigation of the neuroprotective effect of hypoxic preconditioning on transient focal ischemia-reperfusion injuries in rat brain. Female Wistar rats were subjected to 380 mmHg in an altitude chamber for 15 hours/day. Our ex vivo studies showed that auto-oxidation and iron-induced lipid peroxidation of brain homogenates of the four-week hypoxia-preconditioned rats were significantly lower than those of the normoxic rats. A focal infarction in the cerebral cortex of normoxic rats was consistently observed 24 hours after a 60-minute transient ischemic occlusion of the right middle cerebral artery and bilateral common carotid arteries. Hypoxic preconditioning in fact attenuated cortical infarction in a duration-dependent manner. Induction of the neuroprotection required two weeks of hypoxic preconditioning. Four weeks of hypoxic preconditioning significantly reduced the cortical infarcted area, the elevated lipid peroxidation, and resulted in an acute increase in cytosolic cytochrome c in the infarcted cortex of normoxic rats. The protective effect of four weeks of hypoxic preconditioning lasted seven days under a renormoxic condition. Our data suggest that oxidative stress may result in apoptosis in the transient focal ischemia-reperfusion injuries. Furthermore, hypoxic preconditioning attenuated cortical infarction in the rat brain. Although supplementation of antioxidants may encounter difficulty at the blood-brain barrier, hypoxic preconditioning is very likely to protect CNS targets from oxidative injuries without any barrier.

Animals↗

PubMed2003

Different central manifestations in response to electroacupuncture at analgesic and nonanalgesic acupoints in rats: a manganese-enhanced functional magnetic resonance imaging study.

Acupuncture analgesia is an important issue in veterinary medicine. This study was designed to elucidate central modulation effects in response to electroacupuncture (EA) at different acupoints. Manganese-enhanced functional magnetic resonance imaging was performed in Sprague-Dawley rats after sham acupuncture, sham EA, or true EA at somatic acupoints. The acupoints were divided into 3 groups: group 1, analgesic acupoints commonly used for pain relief, such as Hegu (LI 4); group 2, nonanalgesic acupoints rarely used for analgesic effect such as Neiguan (PC 6); and group 3, acupoints occasionally used for analgesia, such as Zusanli (ST 36). Image acquisition was performed on a 1.5-T superconductive clinical scanner with a circular polarized extremity coil. The results showed that there was no neural activation caused by EA at a true acupoint with shallow needling and no electric current (sham acupuncture). When EA at a true acupoint was applied with true needling but no electric current (sham EA), there was only a slight increase in brain activity at the hypothalamus; when EA was applied at a true acupoint with true needling and an electric current (true EA), the primary response at the hypothalamus was enhanced. Also, there was a tendency for the early activation of pain-modulation areas to be prominent after EA at analgesic acupoints as compared with nonanalgesic acupoints. In conclusion, understanding the linkage between peripheral acupoint stimulation and central neural pathways provides not only an evidence-based approach for veterinary acupuncture but also a useful guide for clinical applications of acupuncture.

Acupuncture Analgesia↗

PubMed2002

Loss of interhemispheric inhibition on the ipsilateral primary sensorimotor cortex in patients with brachial plexus injury: fMRI study.

This functional magnetic resonance imaging study verified an antagonistic pattern in which a concomitant deactivation of ipsilateral primary sensorimotor (SM1) was coupled to the contralateral SM1 activation in healthy controls during unimanual hand grasping. Of note, dramatic reduction of ipsilateral SM1 deactivation (loss of antagonistic pattern) was observed during movement of intact hands by patients with unilateral brachial plexus injury. We propose that the disappearance of the antagonistic pattern of SM1 activities in the patients with brachial plexus injury reflects a reduction of interhemispheric inhibition, which may mirror an adaptive mechanism to functional status.

Adult↗

PubMed2002

Portable electrochemical blood uric acid meter.

We describe a new portable uric acid (UA) meter, called the UASure (Apex Biotechnology Corp., Hsinchu, Taiwan). The UASure is an electrochemical blood UA meter designed for fast monitoring of UA concentrations in one drop of capillary blood using an electrochemical test strip. We compared the UASure with the standard method, the Hitachi 7600 modular system (Hitachi, Tokyo, Japan), in 146 volunteers (average age 62.5 +/- 12.8 years). Of these, 65 were known hyperuricemic subjects, 17 of whom received medical therapy. The patients donated their capillary and venous blood samples in random order. Capillary blood and one drop of venous blood were tested immediately by the UASure. The venous blood in the test tube was sent to the central laboratory for serum UA measurement by the Hitachi 7600. The intra-assay coefficients of variation (CVs) of the UASure were 4.79%, 5.77%, and 3.08% at UA levels of 5.8, 7.1, and 13.5 mg/dl, respectively. The UA concentrations tested by the UASure correlated well with those by the Hitachi 7600 (r = 0.87 in venous sampling and r = 0.78 in capillary sampling, P < 0.001). The intraclass correlation was good for venous samples by the UASure (rI = 0.84, 95% CI 0.82-0.90), somewhat below the meaningful criterion for capillary samples by the UASure (rI = 0.77, 95% CI 0.69-0.83). UASure with venous sampling is interchangeable with the standard method for UA measurement.

Aged↗

PubMed2002

Event-related functional MRI study on central representation of acute muscle pain induced by electrical stimulation.

Although pathological muscle pain involves a significantly larger population than any other pain condition, the central mechanisms are less explored than those of cutaneous pain. The aims of the study were to establish the pain matrix for muscle pain in the full head volume and, further, to explore the possibility of a functional segregation to nonpainful and painful stimuli within the area of the parasylvian cortex corresponding to the secondary somatosensory area. Additionally, we speculate that a randomization of nonpainful and painful stimuli may target specific structures related to stimulus salience. We used event-related functional magnetic resonance imaging (MRI) and the high sensitivity of the 3-T MRI scanner to study the central processing of acute muscle pain induced by intramuscular electrostimulation. Brief nonpainful and painful stimuli (1-ms duration, interstimulus interval = 12 s) were randomly applied to the left abductor pollicis brevis of 10 subjects. The data disclose a pain matrix for muscle pain similar to that for cutaneous pain. Individual analysis suggests separate representations within the area bounded by the upper bank of the Sylvian fissure (SF) and the circular sulcus of insula (CSI). Nonpainful stimulation activated the superficial parietal operculum adjoining the SF, while the painful condition additionally targeted the deeper parietal operculum bordering the CSI. Randomization of stimuli of different intensities likely introduces cognitive components that engage neural substrates servicing the appreciation of stimulus salience in the context of affect-laden pain imposition.

Acute Disease↗

PubMed2002

Local carboxyfullerene protects cortical infarction in rat brain.

The neuroprotective effect of carboxyfullerene, a water-soluble derivative of fullerene, on the transient focal ischemia-reperfusion injury was investigated in rat brain. A focal infarction in the cerebral cortex was consistently observed 24 h after a 60-min transient ischemia by occlusion of the right middle cerebral artery and bilateral common carotid arteries. The fluorescent end products of lipid peroxidation were increased in the infarcted cortical area. Furthermore, the GSH level was decreased in the infarcted cortex. Carboxyfullerene was either intravenously (6 mg/kg) or intracerebroventricularly (0.1, 0.3 mg per rat) infused to the chloral hydrate-anesthetized Sprague-Dawley rats 30 min prior to transient ischemia-reperfusion. No protection of cortical infarction was observed after intravenous administration of carboxyfullerene. In contrast, intracerebroventricular infusion of carboxyfullerene not only attenuated cortical infarction but also prevented both the elevated lipid peroxidation and the depleted GSH level induced by transient ischemia-reperfusion. Adverse behavioral changes were simultaneously observed in rats receiving intracerebroventricular infusion of carboxyfullerene (0.3 mg per rat), including writhing accompanied by trunk stretch and even death. Our data suggest that intracerebroventricular infusion of carboxyfullerene may attenuate oxidative injuries by transient ischemia-reperfusion. Nevertheless, undesired side effects may limit the usefulness of carboxyfullerene in biological organisms.

Animals↗

PubMed2002

Clustering and heritability of insulin resistance in Chinese and Japanese hypertensive families: a Stanford-Asian Pacific Program in Hypertension and Insulin Resistance sibling study.

The clustering between hypertension and other metabolic abnormalities related to insulin resistance syndrome (IRS) has been investigated in cross-sectional and prospective studies. Offspring studies have revealed that the clustering characteristics of IRS have familial components. However, it is not known whether the clustering also occurs in siblings (sibs) with different levels of blood pressure (BP). In addition, the genetic susceptibility accounting for the clustering in hypertensive families has not been determined. Siblings with Japanese or Chinese ancestry and having either similar BP levels (concordant sibs) or different BP levels (discordant sibs) were recruited. The delta method and variance component model were applied to analyze the differences in metabolic variables between hypertension (HTN) and low BP (LBP) sibs, and to compute the polygenic heritabilities for these metabolic variables and insulin sensitivity. After adjustment for age, gender and body mass index (BMI), HTN (n=393) sibs had higher levels of triglyceride (p < 0.0001), VLDL-cholesterol (p<0.0001), fasting insulin (p < 0.05), and homeostasis model assessment of insulin resistance (HOMAir) (p < 0.05) than LBP sibs (n = 389), but there were no differences in fasting glucose or high density lipoprotein (HDL)-cholesterol. The HTN sibs also had higher plasma glucose and insulin levels at 2 h after 75 g oral glucose loading (p<0.001 and p<0.01, respectively). The heritability estimates for fasting glucose, fasting insulin and HOMAir were 0.58, 0.43 and 0.46, respectively; for triglyceride, HDL-cholesterol, and BMI they were 0.60, 0.63 and 0.54, respectively. In hypertensive families, sibs with extreme levels of BP have significant differences in IRS-associated metabolic variables. The clustering characteristics and the significance of heritability estimation for these metabolic variables indicate that IRS is familial in nature and heritable in Chinese and Japanese hypertensive families.

Adult↗