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Biomedical subjects

H M Liu

Publications and source records attributed to H M Liu.

At least 37 records · Page 2Linked to original sources
PubMed2001

A novel glycoside lactone derivative with a 2-C-unsaturated diester substituent.

The title 4,6-O-benzylidene-alpha-D-glucopyranoside (systematic name: methyl 4-methoxy-2-oxo-8-phenyl-1,2,5a,6,9a,9b-hexahydro-4H,8H-7,9-dioxacyclopenta[c]chromene-3-carboxylate), C(18)H(18)O(8), has been synthesized from the reaction of methyl 4,6-O-benzylidene-alpha-D-2-ketoglucopyranoside with diethyl or dimethyl malonate. The compound adopts a chair-chair conformation. The newly formed five-membered ring is fused to the glucopyranoside ring along the C(2)--C(3) bond and is planar with an r.m.s. deviation of 0.0091 A.

Crystallography, X-Ray↗
PubMed2001

Stereoselective synthesis of methyl 4,6-O-benzylidene-2-C-methoxycarbonylmethyl-alpha-D-ribo-hexopyranosid-3-ulose, and its X-ray crystallographic analysis.

Methyl 4,6-O-benzylidene-2-C-methoxycarbonylmethyl-alpha-D-ribo-hexopyranosid-3-ulose has been stereoselectively synthesized in 65% yield by reaction of methyl 4,6-O-benzylidene-alpha-D-arabino-hexopyranosid-2-ulose with diethyl malonate. X-ray crystallographic structure analysis reveals that the chain-branch and the OH group are bonded to C-2 in axial and equatorial positions, respectively. The molecules in the crystal lattice are stacked along a one-dimensional chain, with intermolecular hydrogen bonds between O-8 of one molecule and 2-OH of the next as well as intramolecular hydrogen bonds between O-3 and 2-OH. All phenyl groups are parallel as well as the planes of sugar rings in the molecular columnar stacking.

Carbohydrate Conformation↗
PubMed2001

Metabolic changes following subthalamotomy for advanced Parkinson's disease.

We studied 6 advanced-stage Parkinson's disease patients with [18F] fluorodeoxyglucose/positron emission tomography before and 3 months after unilateral ablation of the subthalamic nucleus performed with microelectrode mapping. Operative changes in glucose metabolism were assessed by comparing baseline and postoperative scans. We also quantified operative changes in the activity of an abnormal Parkinson's disease-related metabolic network that we had identified in previous [18F] fluorodeoxyglucose/positron emission tomography studies. Following unilateral subthalamic nucleus ablation, a highly significant reduction in glucose utilization was present in the midbrain ipsilateral to the lesion site, most pronounced in the vicinity of the substantia nigra pars reticularis. Significant metabolic reductions were also present in the ipsilateral internal globus pallidus, ventral thalamus, and pons. Operative changes in Parkinson's disease network activity differed significantly for the lesioned and unlesioned hemispheres. In the lesioned hemisphere, network activity declined significantly following surgery, but was unaltered in the contralateral, unlesioned hemisphere. These results suggest that subthalamotomy reduces basal ganglia output through internal globus pallidus/substantia nigra pars reticularis and also influences downstream neural activity in the pons and ventral thalamus. This procedure also reduces the activity of abnormal Parkinson's disease-related metabolic brain networks, suggesting a widespread modulation of motor circuitry.

Adult↗
PubMed2001

Posterior cranial fossa arteriovenous fistula with presenting as caroticocavernous fistula.

We report cases of posterior cranial fossa arteriovenous fistula (AVF) with presenting with exophthalmos, chemosis and tinnitus in 26- and 66-year-old men. The final diagnoses was vertebral artery AVF and AVF of the marginal sinus, respectively. The dominant venous drainage was the cause of the unusual presentation: both drained from the jugular bulb or marginal sinus, via the inferior petrosal and cavernous sinuses and superior ophthalmic vein. We used endovascular techniques, with coils and liquid adhesives to occlude the fistulae, with resolution of the symptoms and signs.

Adult↗
PubMed2001

MRI in a case of adult-onset citrullinemia.

A 42-year-old man presented with a history of repeated episodes of consciousness disturbance for 5 years. The MRI showed abnormally high signal intensities on T2-weighted images at bilateral cingulate gyri, temporal lobes and insular regions, mimicking the finding of herpes simplex encephalitis. Hyperammonemia was disclosed. Serial work-up led to the diagnosis of adult-onset citrullinemia, deficiency of argininosuccinate synthetase. The clinical symptoms improved after diet control and medication. Follow-up MRI showed resolution of the abnormal signal intensities. The MRI findings of citrullinemia and other urea-cycle defects might be attributed to hyperammonemic encephalopathy, but the manifestations were varied. Similar distribution of the abnormalities in the MRI could be found in some reported cases and indicates probably vulnerable sites of hyperammonemic brain injury.

Adult↗
PubMed2001

Long-term clinical outcome of spontaneous carotid cavernous sinus fistulae supplied by dural branches of the internal carotid artery.

We report the long-term clinical outcome of spontaneous carotid cavernous sinus fistulae (CCF) originally supplied by branches arising from the internal carotid artery (Barrow's type B), or type-D lesion that became type B after particulate embolization. A total of 55 patients was included in this study. Their angiography revealed that cortical drainage was absent, and that the arteries supplying the fistulae originated in the dural branches of the internal carotid artery. Thirty-two patients had type-D lesions, which became type-B lesions after obliteration of the external carotid supply by endovascular treatment. The other 23 patients had type-B lesions documented by angiography, and had no embolization. The follow-up period ranged from 8 to 144.5 months. Clinical cure was achieved in 39 patients (70.9%), improvement in eight patients (14.5%), the lesion remained stable in four patients (7.3%), and was aggravated in four patients (7.3%). The number of drainage veins is the only radiographic factor that could predict the outcome. Those patients with single draining veins had a better chance of complete remission. The outcome between the group with original type D lesions after embolization and the group with original type B revealed no statistically significant difference. The time-course to complete cure was significantly shorter in the group with embolization of the external carotid supply. In the four patients whose symptoms were aggravated, embolization was performed, and the result was excellent. The clinical outcome of type-B CCF, or type D converted to type B, is good. Previous external carotid artery embolization can significantly shorten the time to complete cure. Aggressive treatment should be reserved for those who have aggravated symptoms.

Adult↗
PubMed2001

Measurement of high dose rates by photon activation of indium foils.

Photon activation of indium foils is proposed as a dosimetry technique for high dose rate measurements in a 60Co irradiation facility. The irradiated indium nuclei may be raised to its metastable isomers of 113mIn and 115mIn. The isomer 115mIn, with appreciable induced radioactivity, was selected for dose-rate measurements. Based on the photon flux distribution and the derived dose rates, which were simulated by the MCNP code, the dependence of dose rate measurement sensitivity of indium foils with respect to photon energy at various irradiation distances is described. For practical uses, the radioactivity of 115mIn was linearly related to the dose rate response at the specified irradiation positions. By comparing with a calibrated dosimetry system, the measurement deviation of the indium dosimeter, over dose rates ranging from 10 to 10(4) Gy/h, was evaluated and exhibited an uncertainty of +/- 7%. Other related characteristics including measurement sensitivity and range, linearity with respect to the variation of dose rate, and limitations of the indium dosimeter were evaluated to justify it as an alternative for monitoring dose rate in an irradiation field.

Journal Article↗
PubMed2001

Isolated vagus nerve palsy probably associated with herpes simplex virus infection.

Vagus nerve palsy caused by herpes simplex virus (HSV) infection is rare. Here, we present a 29-year-old man with acute onset of right side otalgia and sore throat, followed by dysphonia, dysphagia and some vesicles seen on the deep soft palate. Laryngoscopy revealed right vocal cord palsy. Neck to chest CT did not reveal local lesion. Three months later, his serum HSV IgG antibody titer was eight times elevation and a throat swab culture for virus isolation yielded HSV type I. T2-weighted images of neck MRI showed abnormally high signal intensity on the right sub-glottis region with Gadolinium enhancement that was compatible with local infection. Thereafter, one course of acyclovir; was given. Three months after finishing the acyclovir, his symptoms were almost gone and neck MRI did not show the aforementioned lesions. HSV infection should be considered as a differential diagnosis for patients with idiopathic dysphonia and dysphagia.

Acyclovir↗
PubMed2001

Gamma dose measurement in a water phantom irradiated with the BNCT facility at THOR.

It has been proposed that a LiF thermoluminescence dosemeter (TLD) is used as a gamma dosemeter in a water phantom irradiated with the BNCT facility at THOR. Based on the TLD neutron sensitivity and neutron fluxes in the water phantom, which were simulated by the MCNP code, TLD-700 was chosen as a gamma dosemeter in this report. For the correction of the neutron influence on TLD-700, the thermal neutron sensitivity to TLD-700 was investigated with MCNP simulation and the thermal neutron flux was measured with gold foils using the cadmium difference technique. The correction to the neutron influence on the TLD was established on the TLD thermal neutron sensitivity. the thermal neutron flux, and the conversion factor from energy deposition in the TLD to the TLD response. By comparing the experimental data with the thermal neutron influence correction, these data are in very good agreement with the MCNP predictions.

Boron Neutron Capture Therapy↗
PubMed2001

Measurement of the size and orientation of human masseter and medial pterygoid muscles.

To gain a better understanding of biting and chewing performance, the size and orientation of the masseter and medial pterygoid muscles in living humans were studied. Twenty-seven young males having complete dentition, class I dental occlusion and normal muscle and jaw function were examined using magnetic resonance images of the head between the zygomatic arch and hyoid bone. The sections were parallel to the palatal plane, and the thickness was 3 mm without a gap. A computer software program (Medical Dental Image, MDI) was developed to identify and calculate the area of each cross section of the muscle, and the volume of the muscle was then estimated. The axis of the muscle was determined by connecting the centroids of the sections in the lower and upper 1/3 of the whole muscle. The effective muscle cross section area was then calculated by resectioning the muscle perpendicularly to the muscle axis. It was found that the mean masseter muscle volume was around 31 cm3, and that the mean medial pterygoid muscle volume was 11 cm3. Their mean effective cross section areas were around 6.2 cm2 and 3.5 cm2, respectively. The axis of the masseter muscle was more perpendicular to the palatal plane and parallel to the sagittal plane than was the medial pterygoid muscle. The results suggest that the use of magnetic resonance images (MRI) is an effective noninvasive measurement technique for determining the size and orientation of masseter and medial pterygoid muscles. This technique can be employed in future studies on human bite force evaluation and masticatory function.

Adolescent↗
PubMed2001

Thickened pituitary stalk with central diabetes insipidus: report of three cases.

Diabetes insipidus of central origin usually results from lesions in the hypothalamic neurohypophyseal system. Lymphocytic infundibuloneurohypophysitis is an uncommon cause. Cases of lymphocytic infundibuloneurohypophysitis with thickening of the pituitary stalk and enlargement of the neurohypophysis with no hyperintense signal in the posterior pituitary have been reported. Reported cases presenting with isolated thickening of the pituitary stalk are very rare. We report three such cases, one in a nulliparous woman and the other two in men. Magnetic resonance (MR) imaging in these patients revealed isolated thickening of the pituitary stalk, loss of the hyperintense signal of the posterior pituitary, and an adenohypophysis of normal size. All cases had abnormal nodular infundibular enlargement. One male patient had hypogonadism; the other patients showed no sign of adenohypophyseal deficiency on stimulation test. Serial follow-up MR imaging revealed that all three patients had persistent thickening of the pituitary stalk. Diabetes insipidus was controlled by the administration of desmopressin acetate in all patients.

Adult↗
PubMed2001

Language/culture/mind/brain. Progress at the margins between disciplines.

At the forefront of research on language are new data demonstrating infants' strategies in the early acquisition of language. The data show that infants perceptually "map" critical aspects of ambient language in the first year of life before they can speak. Statistical and abstract properties of speech are picked up through exposure to ambient language. Moreover, linguistic experience alters infants' perception of speech, warping perception in a way that enhances native-language speech processing. Infants' strategies are unexpected and unpredicted by historical views. At the same time, research in three additional disciplines is contributing to our understanding of language and its acquisition by children. Cultural anthropologists are demonstrating the universality of adult speech behavior when addressing infants and children across cultures, and this is creating a new view of the role adult speakers play in bringing about language in the child. Neuroscientists, using the techniques of modern brain imaging, are revealing the temporal and structural aspects of language processing by the brain and suggesting new views of the critical period for language. Computer scientists, modeling the computational aspects of childrens' language acquisition, are meeting success using biologically inspired neural networks. Although a consilient view cannot yet be offered, the cross-disciplinary interaction now seen among scientists pursuing one of humans' greatest achievements, language, is quite promising.

Artificial Intelligence↗
PubMed2001

Surgical treatment of spinal arteriovenous malformations: vascular anatomy and surgical outcome.

BACKGROUND AND PURPOSE: Spinal arteriovenous malformations (AVMs) are rare but debilitating lesions of the central nervous system. This study evaluated the outcome in patients with spinal AVMs treated surgically, and the relationship between outcome and the vascular anatomy of the lesions. METHODS: These AVMs were classified into four types: dural AVM (type I), glomus AVM (type II), juvenile AVM (type III), and intradural direct arteriovenous fistula (type IV). Either interruption of the feeding vessels or excision of the AVMs was performed in all patients. RESULTS: Intradural AVMs manifested as subarachnoid or intramedullary hemorrhages, whereas dural AVM manifested as epidural hemorrhage in two patients, and as an episode of subarachnoid hemorrhage in one patient. The nidus in five of the six dural AVMs was below the mid-thoracic level. In six of the seven patients with intradural AVMs, the nidus was located in the cervical region. The prognosis of patients with dural AVMs was generally good, but in patients with intradural AVMs, motor recovery was worse and resection was more difficult. CONCLUSIONS: Correct diagnosis and classification of spinal AVMs are the key prerequisites for successful treatment. The surgical outcome is closely related to the vascular anatomy of the lesion. For dural AVMs, only surgical interruption of the arteriovenous shunting at the dural sleeve of the nerve is required and good surgical results are often obtained. Intradural direct arteriovenous fistula responded well to surgery, whereas combined endovascular and microsurgical techniques can minimize the chance of rebleeding in intramedullary AVMs.

Adolescent↗
PubMed2001

[Quantitative analysis of sparfloxacin injection by high performance liquid chromatography].

Analytical method of the quantitative determination of sparfloxacin injection by HPLC is described. The analytical conditions were as follows. A Waters Symmetry C18(5 microns, 150 mm x 3.9 mm i.d.) column was used as the analytical column. The detection wavelength was UV-298.8 nm. The column temperature was 30 degrees C. The mobile phase was 0.2% KH2PO4 buffer (pH 3.2)-CH3CN-CH3OH (80:15:5, volume ratio) and the flow-rate was 1.0 mL/min. The injection volume was 10 microL. The linear range (the peak area vs. the mass concentration of sparfloxacin) was from 39.94 mg/L to 199.68 mg/L, and the correlation coefficient was 0.9999. The average recovery of sparfloxacin was 100.1% (n = 5), and its RSD was 0.72%. The RSDs of continuous injections, within day injections per 2 hours and between day injections in three days were 0.19%, 0.14% and 0.13% respectively. The above analytical results show that this method has good precision and stability. It is a rapid, sensitive and accurate method for the analysis of sparfloxacin.

Antitubercular Agents↗
PubMed2001

[Analysis of fatty acids in rat liver peroxisomes].

Peroxisomes of rat liver from normal and di (2-ethylhexyl) phthalate (DEHP)-treated animals were isolated by density gradient centrifuge method. The fatty acids in the liver peroxisomes were extracted with chloroform and methanol, and were esterified with boron trifluoride and methanol. The fatty acids methyl esters were separated on SPB-1 (similar to SE-30, OV-101) capillary column, and were determined using heptadecanoic acid (C17:0) as an internal standard for the eleven fatty acids (C10:0-C22:6) in these peroxisomes by gas chromatography. The ratio of unsaturated fatty acids to total fatty acids in the control was significantly less than that in DEHP-treated animals (P < 0.05), but there was no difference between the control and DEHP-treated animals for the content of total fatty acids and the ratio of long chain fatty acids to total fatty acids. The results show that DEHP-treatment can alter the fatty acid composition of peroxisome. The membrane structure of the treated peroxisome was different to that of the control.

Animals↗
PubMed2000

Genotype-phenotype correlation in two frequent mutations and mutation update in type III glycogen storage disease.

Deficiency of glycogen debranching enzyme (AGL) activity causes glycogen storage disease type III (GSD-III). Generalized loss of AGL activity results in GSD-IIIa, and muscle-specific retention of AGL activity results in GSD-IIIb. To date, no common mutation has been described among GSD-III patients, except for three alleles; two linked specifically with GSD-IIIb, and the third found only in North African Jews with GSD-IIIa. Here we report two frequent mutations, each of which was found in the homozygous state in multiple patients, and each of which was associated with a subset of clinical phenotype in those patients with that mutation. A novel point mutation of a single T deletion at cDNA position 3964 (3964delT) was first detected in an African American patient, who has a severe phenotype and early onset of clinical symptoms. The second mutation was an A to G transition at position -12 upstream of the 3' splice site of intron 32 (IVS32-12A > G). This lesion, previously implicated as a IIIb mutation in a Japanese patient, was identified in a confirmed GSD-IIIa Caucasian patient presenting with mild clinical symptoms. These two mutations together account for more than 12% of the molecular defects in the GSD-III patients tested. Our molecular and clinical data suggest a genotype-phenotype correlation for each of these mutations. Furthermore, this current study, coupled with our previous reports, describes the molecular tools necessary for the development of a DNA-based diagnostic test for GSD-III.

Adult↗
PubMed2000

Transarterial embolisation of complex cavernous sinus dural arteriovenous fistulae with low-concentration cyanoacrylate.

We report the effectiveness of low-concentration n-butyl-2-cyanoacrylate (NBCA)-Lipiodol-tungsten mixture (10-15 %) in the management of patients with aggressive or recurrent complex cavernous dural arteriovenous fistulae (CSDAVF). We treated five patients with complex CSDAVF with a low concentration of an NBCA-Lipiodol-tungsten mixture after catheterisation of the feeding arteries arising from the external carotid artery. Three had a recurrent CSDAVF after transarterial particulate embolisation. Three refused transvenous treatment or could not be treated in this way; two patients had also feeding dural branches of the internal carotid artery. All patients had complete resolution of symptoms and signs within a month of the procedure. No definite neurological complication was found during follow-up ranging from 12 to 36 months. Transarterial embolisation with low-concentration cyanoacrylate appears to be an effective alternative management of aggressive or recurrent CSDAVF.

Arteriovenous Fistula↗