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Biomedical subjects

G T Liu

Publications and source records attributed to G T Liu.

At least 19 recordsLinked to original sources
PubMed2006

Magnocellular and parvocellular visual pathways have different blood oxygen level-dependent signal time courses in human primary visual cortex.

PURPOSE: The magnocellular and parvocellular pathways (M and P pathways) are the major pathways of the visual system, with distinct histologic and physiologic properties that may also have different metabolic characteristics. We hypothesize that the differences of the 2 visual pathways would also manifest as differences in the signal time course of blood oxygen level-dependent functional MR imaging (BOLD fMRI). The differences in BOLD signal time course may provide insight into the metabolic requirements of the 2 pathways. METHODS: Eleven fMRI sessions on 6 subjects were performed using stimuli that preferentially activated the 2 pathways. Regions commonly activated by both the M and P stimuli in the primary visual cortex (V1) were determined, and the contrast elicited by the stimulus, time-to-peak (TTP), and the full width at half maximum (FWHM) of the BOLD signal time course were measured. RESULTS: The functional stimuli activated cortical regions described previously in the literature, such as V1, V4, and V5. Within V1, the TTP of the signal time course of the 2 stimuli were statistically different, with the P stimulus generating TTPs that were on average 12% faster than the M stimulus (P = .0037). CONCLUSION: We have demonstrated the ability to functionally differentiate the M and P stimuli in a commonly activated anatomic region. Because the BOLD response is dependent on the ratio of oxyhemoglobin and deoxyhemoglobin in the blood, the difference in the BOLD time course between the 2 stimuli suggests that the oxygen demand of the 2 pathways may be different.

Brain Mapping↗
PubMed2004

Metamagnetic transition in Na 0.85 CoO2 single crystals.

We report the magnetization, specific heat, and transport measurements of a high quality Na(0.85)CoO2 single crystal in applied magnetic fields up to 14 T. At high temperatures, the system is in a paramagnetic phase. It undergoes a magnetic phase transition below approximately 20 K. For the field H||c, the measurement data of magnetization, specific heat, and magnetoresistance reveal a metamagnetic transition from an antiferromagnetic state to a quasiferromagnetic state at about 8 T at low temperatures. However, no transition is observed in the magnetization measurements up to 14 T for H perpendicular c. The low temperature magnetic phase diagram of Na(0.85)CoO2 is determined.

Journal Article↗
PubMed2002

Effect of PYCNOGENOL on the toxicity of heart, bone marrow and immune organs as induced by antitumor drugs.

PYCNOGENOL is a mixture of water-soluble bioflavonoids extracted from the bark of pine trees growing in the southwest coastal region of France. In the present paper the effects of PYCNOGENOL (Pyc) on the toxicity of bone marrow, heart and immune organs induced by anticancer drugs were investigated, in mice. The following results were obtained: 1. Pyc at the orally-administered dose of 200 and 150 mg/kg body wt. markedly prevented the elevation of serum creatine phosphokinase (CPK) activity and the decrease of heart rate in mice treated with doxorubicin (Dox); 2. Pyc at 100 and 150 mg/kg body wt. significantly antagonized the inhibition of DNA synthesis in thymus induced by subcutaneous injection of cyclophosphamide (Cyc); 3. Pyc at 150 and 200 mg/kg body wt. markedly induced increase of erythrocytes and hemoglobin, but had no effect on leukopenia, in Cyc-treated mice; and 4. Pyc has no antagonizing effect on the anticancer activity of Dox and Cyc. All the results suggest that Pyc possesses a protective effect on the cardiotoxicity of Dox and the inhibition of thymus DNA synthesis induced by Cyc in mice.

Animals↗
PubMed2001

Oculomotor synkinesis following a midbrain stroke.

A 33-year-old man developed a complete third nerve palsy in the setting of acute bacterial endocarditis. MRI revealed an ischemic stroke in the cerebral peduncle involving the third nerve fascicle. Subsequently, he was observed to have paradoxic elevation of the eyelid on adduction and downgaze. To the authors' knowledge, this is the first demonstration of oculomotor synkinesis after an acquired, ischemic CNS lesion.

Adult↗
PubMed2001

Cerebral air embolism complicating cardiac ablation procedures.

Two patients with similar courses of neurologic impairment and subsequent recovery after cerebral air embolism complicating cardiac ablation procedures are described. Hyperbaric oxygen therapy, combined with aggressive resuscitative efforts, appears to have contributed to each patient's recovery.

Adult↗
PubMed2001

Horner syndrome associated with implantation of a vagus nerve stimulator.

PURPOSE: To report a case of Horner syndrome that occurred after implantation of a vagus nerve stimulator. METHODS: Case report. RESULTS: A 6-year-old female with cerebral dysgenesis and intractable partial seizures presented with Horner syndrome after vagus nerve stimulator implantation. CONCLUSION: Horner syndrome can occur as a result of the vagus nerve stimulator implant procedure and should be included as one of its possible surgical complications.

Blepharoptosis↗
PubMed2001

Visual loss in children with neurofibromatosis type 1 and optic pathway gliomas: relation to tumor location by magnetic resonance imaging.

PURPOSE: To examine the potential for visual acuity loss, and its relation to extent and location of optic pathway gliomas in a cohort of children with neurofibromatosis type 1 studied with magnetic resonance imaging. METHODS: We reviewed the neuro-ophthalmologic records and brain/orbital magnetic resonance imaging scans for 43 consecutive pediatric patients with neurofibromatosis type 1 and optic pathway gliomas who were followed at the Children's Hospital of Philadelphia. The presence of visual loss, defined as abnormal visual acuity for age in one or both eyes, was determined. Optic pathway gliomas were classified by tumor extent and location according to involvement of the optic nerves, chiasm, and postchiasmal structures by magnetic resonance imaging. RESULTS: Involvement of the optic tracts and other postchiasmal structures at tumor diagnosis was associated with a significantly higher probability of visual acuity loss (P =.048, chi-square test). Visual loss was noted in 20 of 43 patients (47%) at a median age of 4 years; however, three patients developed visual acuity loss for the first time during adolescence. CONCLUSIONS: In pediatric patients with neurofibromatosis type 1 and optic pathway gliomas, the likelihood of visual loss is dependent on the extent and location of the tumor by magnetic resonance imaging and is particularly associated with involvement of postchiasmal structures. Furthermore, older age during childhood (adolescence) does not preclude the occurrence of visual loss. Close follow-up beyond the early childhood years, particularly for those with postchiasmal tumor, is recommended.

Adolescent↗
PubMed2001

Current neuro-ophthalmic therapies.

The clinical characteristics, differential diagnosis, and treatment options are presented for five different categories of neuro-ophthalmic disease. Nystagmus, optic neuritis, diplopia, pseudotumor cerebri, and temporal arteritis, are frequently encountered in neuro-ophthalmic practice. This article focuses on current therapies for these neuro-ophthalmic disorders. Potential differences in approach to pediatric versus adult patients are emphasized.

Adult↗
PubMed2001

Ocular dominance in anterior visual cortex in a child demonstrated by the use of fMRI.

Negative signal changes in the visual cortex have been observed during visual stimulation when performing functional magnetic resonance imaging (fMRI) in children. This report investigated whether the ocular dominance, which has been demonstrated in the contralateral anterior visual cortex in adults, could be observed in a child by the use of fMRI. A 5-year-old child was studied using fMRI at 1.5 T during alternating monocular visual stimulation under sedation with morphine and pentobarbital. The functional images were motion corrected, and statistical parametric maps were made by contrasting the left or right eye stimulation conditions vs the right or left eye stimulation conditions, respectively, at each voxel. Areas with negative signal changes were found on the left anterior visual cortex during monocular visual stimulation of the right eye and vice versa. There was no area with negative or positive signal change on the ipsilateral visual cortex to the stimulated eye and no area with positive signal change on the contralateral visual cortex. Contralateral ocular dominance of anterior visual cortex similar to that of adults was demonstrated in this child with a negative correlation with the visual stimulus. This finding suggests that peripheral visual fields are represented in the anterior visual cortex of 5-year-old children.

Child, Preschool↗
PubMed2001

Olfactory responses of Ips duplicatus from inner Mongolia, China to nonhost leaf and bark volatiles.

Leaf and bark volatiles from nonhost angiosperm trees were tested on Ips duplicatus by gas chromatographic-electroantennographic detection (GC-EAD) and by pheromone-baited traps in Sweden and Inner Mongolia, China, respectively. GC-EAD analysis of the headspace volatiles from fresh bark chips of Betula pubescens revealed trans-conophthorin, two green leaf volatiles (GLVs): 1-hexanol and (Z)-3-hexen-1-ol, and two C8 alcohols: 3-octanol and 1-octen-3-ol, that consistently elicited antennal responses by I. duplicatus. The identification of these EAD-active compounds was confirmed in further GC-EAD recordings with synthetic mixtures. Antennal responses were also found to synthetic (E)-2-hexen-1-ol and linalool, which have been identified from the leaves of nonhost birch and aspen species. No antennal responses of I. duplicatus were found to hexanal, (E)-2-hexenal, and (Z)-3-hexyl acetates. In field trapping experiments, blends of EAD-active green leaf alcohols or C8 alcohols, or transconophthorin alone resulted in significant reductions (27-60%) in the number of I. duplicatus captured compared with pheromone-baited traps. The unsuitable host compound, verbenone (Vn), also significantly reduced trap catches by up to 60% in both experiments. The strongest disruptive effect resulted from the addition of the combination of green leaf alcohols, C8 alcohols, and verbenone to the pheromone trap, which caused an 84% reduction in trap catch. The blend of two green leaf aldehydes plus the acetate increased the trap catches in 1998 and had no negative or positive effects in 1999. Our results suggest that these nonhost volatiles (NHVs) are important olfactory signals used by I. duplicatus in host selection. They may have great significance in developing semiochemical-based management programs for I. duplicatus by reducing or stopping attacks on suitable hosts.

Animals↗
PubMed2001

Visual activation in functional magnetic resonance imaging at very high field (4 Tesla).

OBJECTIVES: Functional magnetic resonance imaging (fMRI) at very high field strengths provides functional brain mapping with the enhanced signal to noise ratio and the larger blood oxygenation level-dependent (BOLD) effect. We report activated areas in the standard space detected by fMRI at 4 Tesla (T) during simple visual stimulation. MATERIALS AND METHODS: Twelve healthy young subjects were scanned using a 4 T scanner during binocular flashing visual stimulation. Functional images were realigned to the first scan and then spatially normalized. Individual and group data analyses were performed to identify areas of visual activation. RESULTS: Activation of the bilateral primary visual cortex (V1/V2) was observed along the entire calcarine fissure in all subjects. The activated area extended to the extrastriate cortex in all subjects. Activation of the bilateral lateral geniculate nucleus (LGN) was detected in all subjects. The group data showed activation of the bilateral primary visual cortex and the bilateral lateral geniculate nucleus. CONCLUSIONS: Robust activation of the vision-related areas was successfully obtained in all subjects using a 4 T magnetic resonance scanner. These results suggest that fMRI at very high field strengths may be effective in showing visual system physiology, and that it can be a promising method to assess visual function of human subjects.

Adult↗
PubMed2001

Functional magnetic resonance imaging of the visual system.

Functional magnetic resonance imaging (fMRI), which is a technique useful for non-invasive mapping of brain function, is well suited for studying the visual system. This review highlights current clinical applications and research studies involving patients with visual deficits. Relevant reports regarding the investigation of the brain's role in visual processing and some newer fMRI techniques are also reviewed. Functional magnetic resonance imaging has been used for presurgical mapping of visual cortex in patients with brain lesions and for studying patients with amblyopia, optic neuritis, and residual vision in homonymous hemianopia. Retinotopic borders, motion processing, and visual attention have been the topics of several fMRI studies. These reports suggest that fMRI can be useful in clinical and research studies in patients with visual deficits.

Amblyopia↗
PubMed2001

Antioxidative activity of natural isorhapontigenin.

Isorhapontigenin (ISOR), isolated from Belamcanda chinensis, is a derivative of stilbene. Its chemical structure is very similar to that of resveratrol, with a potent antioxidative effect. In the present study, we investigated the antioxidative activity of ISOR in vitro. Oxidative damage of rat liver microsomes, brain mitochondria and synaptosomes was induced by Fe2+-Cys, VitC-ADP-Fe2+ and H2O2, respectively. The formation of malondialdehyde (MDA), decrease of reduced glutathione (GSH) and increase of ultra-weak chemiluminescence during the lipid peroxidation process were determined. In addition, the characteristic ultra-weak chemiluminescence of oxidative DNA damage induced by CuSO4-Phen-VitC-H2O2 system was studied. The results showed that ISOR significantly inhibited MDA formation in liver microsomes, brain mitochondria and synaptosomes induced by Fe2+-Cys. Also, ISOR markedly prevented the decrease of GSH in mitochondria and synaptosomes induced by H2O2 and the increase of ultra-weak chemiluminescence during lipid peroxidation induced by VitC-ADP-Fe2+ as well as oxidative DNA damage induced by CuSO4-Phen-VitC-H2O2. The effects of ISOR at 10(-5) and 10(-6) mol/L on the MDA formation and decrease of GSH were similar to that of the classical antioxidant vitamin E (10(-4) mol/L). It may be concluded that ISOR possessed potent antioxidative activity and was much more potent than vitamin E.

Animals↗
PubMed2001

The neuro-ophthalmologic examination (including coma).

Ophthalmologic practice requires a solid foundation in the principles and interpretation of the neuro-ophthalmologic examination. This article reviews the techniques used in the neuro-ophthalmologic examination to assess visual acuity, ocular motility, visual fields, the pupils, the eyelids, and the fundus. The neuro-ophthalmological examination in comatose patients is also reviewed. Neuro-ophthalmic techniques are paramount in the assessment of comatose patients, especially with regard to brainstem localization and diagnosis.

Color Perception↗
PubMed2001

[Application of molecular markers-assisted selection of wx genes in breeding the waxy wheat].

Chinese Spring and its null-tetrasomic lines were used to identify the specific bands of STS-marker and microsatellites (SSR) marker of wx genes. Twelve varieties and five waxy wheat lines were screened with these two markers, and the results are in agreement with those from Wx subunits SDS-PAGE. A F2 segregating population from cross Jiangsu Baihuomai x Kanto 107 was also detected by molecular markers, not only eight wx genotypes were developed while three genotypes did not exist in the nature, but also the first batch of waxy wheat lines were bred. The Jiangsu Bainuomai improvement population was screened, and six 7D momosomic plants with wx-D1b were obtained, which could provide materials for waxy wheat breeding. Application molecular markers of wx genes will improve the selection procedure for the waxy wheat and good noodle-quality wheat.

Breeding↗
PubMed2001

[Effect of bicyclol on acetaminophen-induced hepatotoxicity: energetic metabolism and mitochondrial injury in acetaminophen-intoxicated mice].

AIM: To investigate the mechanism of the protective effect of bicyclol on acetaminophen-induced hepatotoxicity in mice. METHODS: 31P-MRS spectra in vivo were determined by using surface coil technique. The membrane fluidity of mitochondria and the activity of mitochondrial ATPase were also determined by spectrofluorophogometry and spectrophotometry methods. RESULTS: The hepatotoxicity of acetaminophen is related to the lipid peroxidation and covalent binding to macromolecules, which leads to damage of mitochondrial function. Our results showed that the decrease of ATP/Pi and the elevation of PME/ATP in acetaminophen-intoxicated mice were significantly inhibited by two doses of bicyclol (100, 200 mg.kg-1) pretreatment, which indicate that bicyclol has significant protective effect on the decrease of liver ATP content induced by acetaminophen. Acetaminophen significantly inhibited the activity of mitochondrial ATPase by its cytotoxic metabolite NAPQI [N-acetyl-p-benzoquinone], which has the potential to react with sulfhydryl groups or through sulfhydryl group oxidation. Our results showed that the reduction of mitochondrial fluidity as well as the inhibitory effect of mitochondrial ATPase induced by acetaminophen were also reduced by bicyclol. CONCLUSION: The effect of bicyclol on acetaminophen-induced liver injury maybe partly due to its protective effects on hepatic energy metabolism and mitochondria function.

Acetaminophen↗