Biomedical subjects

H M Liu

Publications and source records attributed to H M Liu.

At least 55 records · Page 3Linked to original sources

PubMed2000

Constituents and their sweetness of food additive enzymatically modified licorice extract.

Enzymatically modified licorice extract (EMLE) is a natural sweetener, which is prepared with cyclodextrin glucanotransferase. It is used because of its unique properties such as higher solubility and better taste than those of licorice extract. In the present paper, the structures of six major constituents isolated from EMLE were determined, and their sweetness was studied. The isolated compounds were glycyrrhizin (1), 3-O-[beta-D-glucuronopyranosyl-(1-->2)-beta-D-glucuronopyranosyl]liquiritic acid (2), and their derivatives glucosylated at the C-4 position of the terminal glucuronopyranose with additional one (3 and 4, respectively) and two (5 and 6, respectively) glucose moieties. Compounds 1 and 2 are the major and minor sweet constituents in licorice extract, respectively. Compounds 3-6 are new compounds isolated for the first time. Compound 2 was sweeter than compound 1. Interestingly, compound 3, which is a monoglucosylated derivative of compound 1, was sweeter than compound 4. The sweetness of both compounds was lower than that of the parent compounds, while the lingering sweet aftertaste was markedly improved. Compounds 5 and 6, which have two additional glucose moieties, showed only slight sweetness.

Food Additives↗

PubMed2000

Experience in surgical management of tumours involving the cavernous sinus.

Potential injury to the neurovascular structures within the cavernous sinus often prohibits aggressive removal of tumours involving it, however, fully understanding the anatomy and selecting an appropriate surgical approach can often resolve this problem with acceptable morbidity. Moreover, a tumour may originate from different anatomical structures of the cavernous sinus which will influence the difficulty and outcome of the surgery. In general, tumours in this region can be classified as intradural, intracavernous and invasive types. The strategy of surgical treatment varies among these different anatomical types. Therefore, preoperative evaluation of tumours in the cavernous sinus is critical for the selection of an appropriate microsurgical approach. During the past 5 years, 12 tumours involving the cavernous sinus have been operated upon which included four neuromas, three meningiomas, three cavernous haemangiomas, one plasmacytoma and one chondroma. Nine of these twelve tumours were totally resected after one or two operations. There was no surgical mortality and the most common morbidity was transient cranial nerve palsy. At 2 months after surgery there was no additional postoperative cranial nerve deficit in all the patients; however, one patient developed a postoperative middle cerebral artery infarct due to accidental injury to the internal carotid artery during surgery. The respectability of the tumour mostly depends on its consistency and the involvement of the adjacent anatomy. The pathoanatomical features of the tumours and the clinicoradiological findings, as well as the selection of the microsurgical approach, are discussed.

Adolescent↗

PubMed2000

Molecular evolution of a type 1 wild-vaccine poliovirus recombinant during widespread circulation in China.

Type 1 wild-vaccine recombinant polioviruses were isolated from poliomyelitis patients in China from 1991 to 1993. We compared the sequences of 34 recombinant isolates over the 1,353-nucleotide (nt) genomic interval (nt 2480 to 3832) encoding the major capsid protein, VP1, and the protease, 2A. All recombinants had a 367-nt block of sequence (nt 3271 to 3637) derived from the Sabin 1 oral poliovirus vaccine strain spanning the 3'-terminal sequences of VP1 (115 nt) and the 5' half of 2A (252 nt). The remaining VP1 sequences were closely (up to 99.5%) related to those of a major genotype of wild type 1 poliovirus endemic to China up to 1994. In contrast, the non-vaccine-derived sequences at the 3' half of 2A were more distantly related (<90% nucleotide sequence match) to those of other contemporary wild polioviruses from China. The vaccine-derived sequences of the earliest (April 1991) isolates completely matched those of Sabin 1. Later isolates diverged from the early isolates primarily by accumulation of synonymous base substitutions (at a rate of approximately 3.7 x 10(-2) substitutions per synonymous site per year) over the entire VP1-2A interval. Distinct evolutionary lineages were found in different Chinese provinces. From the combined epidemiologic and evolutionary analyses, we propose that the recombinant virus arose during mixed infection of a single individual in northern China in early 1991 and that its progeny spread by multiple independent chains of transmission into some of the most populous areas of China within a year of the initiating infection.

Base Sequence↗

PubMed2000

Carotid and transcranial color-coded duplex sonography in different types of carotid-cavernous fistula.

BACKGROUND AND PURPOSE: Patients with carotid-cavernous fistula (CCF) may undergo direct or indirect shunting. Ultrasonography has value that is complementary to angiography in the assessment and follow-up of these patients. The aim of this study was to characterize findings provided by carotid duplex sonography (CDS) and transcranial color-coded duplex sonography (TCCD) in patients with different types of CCF. METHODS: CDS and TCCD were independently performed by technologists and neurologists. Digital subtraction or MR angiography was interpreted by a neuroradiologist. Ultrasonographic studies were categorized into 4 types: I, direct shunting only; II, direct shunting with a carotid aneurysm; III, indirect shunting only; and IV, mixed (direct and indirect) shunting. In addition to carotid and intracranial flow velocities, volume, and pulsatility, other direct and indirect ultrasound signs of shunting were evaluated. The direct sign of CCF was a mosaic flash detected by TCCD. Alteration of hemodynamic parameters on CDS and demonstration of draining veins with the use of TCCD were considered indirect signs. RESULTS: Fifteen patients (8 men, 7 women) were included in the study. According to angiographic results, patients in ultrasonographic classification types I (n=7) and II (n=3) corresponded to type A of Barrow's classification. Patients with type III (n=8) were Barrow's type C. Type IV (n=1) had a combination of Barrow's types A and C. On ultrasound, both direct and indirect signs were seen in types I, II, and IV CCF. The presence of a 2-colored oval mass divided by a zone of separation without turbulence differentiated type I from type II CCF. All patients with type III CCF had indirect signs, and only 1 patient had direct signs on TCCD. Abnormal TCCD findings were most commonly seen through the transorbital window (100%), followed by the transtemporal window (63%) and transforaminal window (40%). CONCLUSIONS: If only indirect ultrasonographic signs of CCF are present, TCCD can be used to predict an indirect CCF type on the basis of the origin of the fistula. With direct communication between carotid artery and cavernous sinus, both direct and indirect ultrasonographic signs can be found. The combination of CDS/TCCD may provide a noninvasive and reliable way to classify patients with CCF.

Adult↗

PubMed2000

A new diterpene glycoside from Rabdosia rubescens.

A new ent-kaurene beta-D-glucoside was isolated from Rabdosia rubescens, together with the known compounds oridonin, ponicidin, and pedalitin. The structure of new compound was determined, on the basis of spectral data and X-ray crystallographic analysis, to be ent-7 beta,20-epoxy-kaur-16-ene-1 beta,6 alpha,7 alpha,14 alpha,15 alpha-pentanol 1-O-beta-D-glucopyranoside.

Crystallography, X-Ray↗

PubMed2000

The preoperative and postoperative cerebral blood flow and vasoreactivity in childhood moyamoya disease.

PURPOSE: To report the hemodynamic pattern in childhood moyamoya disease before and after vascular reconstruction. METHODS: We performed the xenon cerebral blood flow (CBF) study in 10 cases of moyamoya disease in last 3 year. In 6 of them, study before and after operation was obtained for comparison. Preoperative study was obtained in 2 cases and postoperative study was obtained in 2 cases. They were 5 males and 5 females with age ranging from 1 to 12 years old. We studied their regional CBF before and after acetazolamide (CCBF) using stable xenon computed tomography. The angiography study was obtained for comparison. RESULT: In the routine study, the CBF and CCBF were poor in the ACA and MCA territory and well correlated to the angiography finding. However, in case of basal ganglion and posterior cerebral artery involvement, xenon CBF study was more sensitive than the angiography. On the postoperative cases, the CBF could increase to a level beyond the level of CCBF shown on the preoperative study. CONCLUSION: Hemodynamic study using stable xenon computed tomography can provide an objective reference for the treatment of moyamoya disease especially in case that surgical management is considered. It is a better modality for the evaluation of surgical outcome than the conventional contrast angiography study.

Acetazolamide↗

PubMed2000

Embolization of cerebral arteriovenous malformations with n-butyl-2-cyanoacrylate.

PURPOSE: To determine the safety and effectiveness of arteriovenous malformation (AVM) embolization using liquid adhesives in a series of 103 patients with cerebral AVMs who underwent embolization with n-butyl-2-cyanoacrylate (NBCA). METHODS: All embolization procedures were performed using NBCA and a lipiodol mixture delivered by a flow-directed and/or guide-wire directed microcatheter. RESULTS: Using the Spetzler-Martin grading system, there were two cases of grade I AVM, 23 of grade II AVM, 31 of grade III AVM, 37 of grade IV AVM, and 10 of grade V AVM. Eleven patients underwent embolization only; these patients either had evidence of morphologic cure on follow-up angiogram, or showed evidence of a stable condition at 2-years follow-up. Seven patients were not treated owing to technical problems or a positive functional test. All other patients underwent preoperative embolization; 75%-99% obliteration was noted in 39 of these patients, 50%-74% obliteration in 33, and less than 50% obliteration in 13. Embolization-related complications occurred in nine patients, and two patients died as a result of the procedure. Severe neurologic complications occurred in two patients and five patients developed mild or transient neurologic deficit. CONCLUSIONS: Endovascular treatment of brain AVMs with an NBCA mixture has a lower complication rate than shown in previous studies using other materials. The percentage of obliteration of the nidus is increased because NBCA penetrates AVMs better than polyvinyl alcohol particles. NBCA can be used at a lower concentration than other acrylates, and therefore causes almost no catheter gluing. The embolic mass formed by NBCA is more biocompatable than that formed by other acrylates.

Adolescent↗

PubMed1999

Quantitative analysis of manganese, chromium and molybdenum by ion-pair reversed-phase high-performance liquid chromatography with pre-column derivatization and UV-visible detection.

An ion-pair reversed-phase high-performance liquid chromatographic method with UV-visible spectrophotometric detection is proposed for the simultaneous determination of manganese, chromium and molybdenum. By using a C18-bonded silica column, 4-(2-pyridylazo)resorcinol (PAR) chelates of Mn(II), Cr(VI) and Mo(VI) were successfully separated and accurately determined at 480 nm. Tetrabutylammonium bromide (TBAB) was used as the ion-pair reagent. Effects of pH, the buffer system, the concentration of buffer, the color developing time, the concentration of chelating reagent and the ion-pair reagent on the resolution were investigated. PAR chelates were eluted within 20 min at a flow-rate of 1.0 ml min(-1) with a methanol aqueous mobile phase, CH3OH-water (20:80, v/v), containing 1.0 x 10(-3) mol l(-1) acetate buffer (pH 6.5), 1.8 x 10(-2) mol l(-1) TBAB and 2.0 x 10(-4) mol l(-1) PAR. The feasibility of the proposed method was verified with the standard reference materials of nickel-based alloys. The nickel-based alloys were analyzed chromatographically after ammonium pretreatment. Under the optimum conditions, the detection limits for the chelates of Mn(II), Cr(VI) and Mo(VI) were 0.31, 4.2 and 4.6 ng with 100 microl injection, respectively. The accuracy of the proposed chromatographic method was verified by good agreement between the values obtained by this method and certified values.

Chromatography, High Pressure Liquid↗

PubMed1999

Prenatal diagnosis of glycogen storage disease type IV using PCR-based DNA mutation analysis.

Deficiency of glycogen branching enzyme activity causes glycogen storage disease type IV (GSD-IV). Clinically, GSD-IV has variable clinical presentations ranging from a fatal neonatal neuromuscular disease, to a progressive liver cirrhosis form, and to a milder liver disease without progression. Current methods for prenatal and postnatal diagnosis are based on an indirect method of measuring the enzyme activity, which has a limited sensitivity and cannot be used to distinguish patients with these variable clinical phenotypes. In this study, a GSD-IV family with a non-progressive hepatic form of the disease requested prenatal diagnosis. Determination of the branching enzyme activity in cultivated amniocytes showed 20 per cent residual activity overlapping with the level detected in the heterozygotes. Mutation analysis revealed that the fetus carried two mutant alleles, L224P and Y329S, the same as the proband of this family. The fetus was predicted to be affected and postnatally his clinical presentation is consistent with the diagnosis. We conclude that DNA mutation analysis should be used in the prenatal diagnosis of GSD-IV, especially in the situation of high residual enzyme activity.

Child, Preschool↗

PubMed1999

3-D power Doppler cerebral angiography in neonates and young infants: comparison with 2-D power Doppler angiography.

The aims of this study were to evaluate the ability of 3-dimensional (3-D) power Doppler angiography (3DPDA) to depict the intracranial vasculature in infants, to compare with 2-D power Doppler ultrasonography (2DPDU), and to explore the potential clinical applications of this procedure in young infants with brain disorders. We performed 3DPDA in 27 infants. 2DPDU were completed in both sagittal and coronal directions in 12 of these patients. In the other 15, only right sagittal plane images were available for comparison. Using a grading system and with only vessels with more than half of the length demonstrated included for comparison, we compared the Doppler signals of major vessels. 3DPDA could have good visualization in more than 60% of the internal carotid artery, ophthalmic artery, pericallosal artery, callosomarginal artery, internal cerebral vein, vein of Galen, and straight sinus in the sagittal plane. 3DPDA also could have good demonstration in about 50% of basilar artery in coronal plane, and posterior communicating artery, posterior cerebral artery, and lenticulostriate artery in sagittal plane. 3DPDA was better than 2DPDU in demonstrating all the major intracranial vessels in different planes, except the anterior communicating artery. In the anterior communicating artery, neither can demonstrate more than 30%.

Brain Diseases↗

PubMed1999

p-Coumaroyltriacetic acid synthase, a new homologue of chalcone synthase, from Hydrangea macrophylla var. thunbergii.

Chalcone synthase and stilbene synthase are plant-specific polyketide synthases. They catalyze three common consecutive decarboxylative condensations and specific cyclization reactions. They are highly homologous to each other, and are likely to fall into a family of polyketide synthases along with acridone synthase and bibenzyl synthase. Two cDNA clones (named HmC and HmS), both of which show high homology to the known chalcone synthases, were obtained from leaves of Hydrangea macrophylla var. thunbergii. They were expressed in Escherichia coli in order to determine their enzyme functions. Detection of chalcone formation clearly indicated that HmC encoded chalcone synthase, while HmS protein catalyzed the formation of neither chalcone nor stilbene. However, a novel pyrone, a lactonization product of a linear tetraketide was detected in reaction products of HmS protein. This proves that HmS encodes a novel polyketide synthase that catalyzes only chain elongation without cyclization.

Acyltransferases↗

PubMed1998

Immunostimulatory CpG oligodeoxynucleotides enhance the immune response to vaccine strategies involving granulocyte-macrophage colony-stimulating factor.

Immunostimulatory oligodeoxynucleotides containing the CpG motif (CpG ODN) can activate various immune cell subsets and induce production of a number of cytokines. Prior studies have demonstrated that both CpG ODN and granulocyte-macrophage colony-stimulating factor (GM-CSF) can serve as potent vaccine adjuvants. We used the 38C13 murine lymphoma system to evaluate the immune response to a combination of these two adjuvants. Immunization using antigen, CpG ODN, and soluble GM-CSF enhanced production of antigen-specific antibody and shifted production towards the IgG2a isotype, suggesting an enhanced TH1 response. This effect was most pronounced after repeat immunizations with CpG ODN and antigen/GM-CSF fusion protein. A single immunization with CpG ODN and antigen/GM-CSF fusion protein 3 days before tumor inoculation prevented tumor growth. CpG ODN enhanced the production of interleukin-12 by bone marrow-derived dendritic cells and increased expression of major histocompatibility complex class I and class II molecules, particularly when cells were pulsed with antigen/GM-CSF fusion protein. We conclude that the use of CpG ODN in combination with strategies involving GM-CSF enhances the immune response to antigen and shifts the response towards a TH1 response and that this approach deserves further evaluation in tumor immunization approaches and other conditions in which an antigen-specific TH1 response is desirable.

Adjuvants, Immunologic↗

PubMed1998

Prenatal diagnosis and carrier detection for glycogen storage disease type III using polymorphic DNA markers.

Deficiency of glycogen debranching enzyme gene (AGL) causes glycogen storage disease type III (GSD-III), an autosomal recessive disease. Prenatal diagnosis and carrier detection using enzymatic methods are technically difficult and have limited ability to distinguish a carrier from an affected patient. Mutations in the AGL gene can be used for these purposes. However, the mutations identified thus far account for less than half of the total mutant alleles, and no common mutations have been detected except in North African Jews and in a rare subtype of the disease (GSD-IIIb). Our recent identification of three highly informative DNA polymorphic markers in the AGL gene allowed us to perform prenatal diagnosis and carrier detection in two GSD-III families with unknown mutations, using the polymerase chain reaction (PCR) and restriction analysis. In one family, a fetus was diagnosed to be a GSD-III carrier and his carrier status was confirmed postnatally. A newborn in the second family was postnatally diagnosed with the disease.

Adolescent↗

PubMed1998

Intracranial arachnoid cysts in children: related signs and associated anomalies.

Intracranial arachnoid cysts are benign development anomalies that may be clinically asymptomatic. The authors describe 30 children with intracranial arachnoid cysts in terms of clinical manifestations and relations to the associated brain anomalies or lesions. The mean age at onset of clinical manifestations was 4 years, 7 months (range 1 day to 14 years). The mean age at diagnosis was 6 years, 2 months (range 10 days to 16 years). Most patients with nonprogressive symptoms, such as seizures and headache, had focal epileptiform discharges on electroencephalogram, and they benefited from antiepileptic drugs. Surgery resulted in only partial reduction in both cyst size and seizure frequency in patients with intractable seizures, and it also failed to improve some neurologic signs, such as sexual precocity or cranial neuropathy resulting from long-term compression of arachnoid cysts. We conclude that the only absolute indication for surgery is the presence of progressive hydrocephalus or intracranial hypertension. The associated anomalies or lesions include brain tumors, giant nevocellular nevi, achondroplasia, microphthalmia, intracystic hemorrhage, dysgenesis of the corpus callosum, and heterotopia.

Adolescent↗

PubMed1998

Nasopharyngeal angiofibroma: a reappraisal of clinical features and treatment at National Taiwan University Hospital.

Nasopharyngeal angiofibroma (NAF), occurring mostly in young men, is a histologically benign tumor with aggressive clinical behavior that includes repeated epistaxis and intractable nasal obstruction. This paper reviews our recent experience at National Taiwan University Hospital (NTUH), and compares the results with those of a previous study (1955-1980) at NTUH to highlight the developments in the treatment of NAF. Fifteen patients with a diagnosis of NAF from 1984 to 1997 were included, and their clinical presentations, radiographic studies, treatments, and outcomes were retrospectively analyzed. The results showed that the clinical and demographic features were similar in the two studies. The average number of patients decreased from 2.1 patients in the previous study to 1.1 patients in this study. The duration of symptoms in the current study (8 months) was shorter than that of the previous study (16 months). Previously, the treatment consisted of radiation followed by surgery if there was residual tumor. The current treatment modality is preoperative transarterial embolization followed by surgery. The estimated intraoperative blood loss was reduced from 750 mL in the first study to 400 mL in this study. The recurrence rate decreased from 11% to 7% and the absolute relapse-free rate rose from 56% to 73%. Owing to the development of modern imaging techniques, the advent of preoperative arterial embolization, and advances in surgical techniques, successful removal of highly vascular tumors has become more feasible. Preoperative selective embolization followed by excision is an effective treatment modality. This strategy, an alternative to radiotherapy, not only avoids the long-term complications induced by radiation, but also reduces the tumor recurrence rate.

Adolescent↗

PubMed1997

Immunostimulatory oligodeoxynucleotides containing the CpG motif are effective as immune adjuvants in tumor antigen immunization.

Recent advances in our understanding of the immune response are allowing for the logical design of new approaches to cancer immunization. One area of interest is the development of new immune adjuvants. Immunostimulatory oligodeoxynucleotides containing the CpG motif (CpG ODN) can induce production of a wide variety of cytokines and activate B cells, monocytes, dendritic cells, and NK cells. Using the 38C13 B cell lymphoma model, we assessed whether CpG ODN can function as immune adjuvants in tumor antigen immunization. The idiotype served as the tumor antigen. Select CpG ODN were as effective as complete Freund's adjuvant at inducing an antigen-specific antibody response but were associated with less toxicity. These CpG ODN induced a higher titer of antigen-specific IgG2a than did complete Freund's adjuvant, suggesting an enhanced TH1 response. Mice immunized with CpG ODN as an adjuvant were protected from tumor challenge to a degree similar to that seen in mice immunized with complete Freund's adjuvant. We conclude that CpG ODN are effective as immune adjuvants and are attractive as part of a tumor immunization strategy.

Adjuvants, Immunologic↗

PubMed1997

Cerebral oxygen transport and metabolism during graded isovolemic hemodilution in experimental global ischemia.

To verify the optimal hematocrit (Hct) level in the treatment of cerebral ischemia, cerebral oxygen transport (CTO2) and cerebral oxygen metabolism (CMRO2) in graded isovolemic hemodilution were evaluated during cerebral ischemia. Isovolemic hemodilution with low molecular weight dextran to stepwise lower Hct from 43% to 36%, 31%, and 26% was carried out in 13 splenectomized dogs, 6 h after global cerebral ischemia. Global ischemia of the animals was produced by multiple intra- and extracranial ligations of cerebral arteries. Cerebral blood flow (CBF) was measured with radioisotope labeled microspheres. CTO2, CMRO2, and oxygen extraction fraction (OEF) were calculated from CBF, arterial oxygen content (CaO2), and venous oxygen content (CvO2). In dogs with global cerebral ischemia, CBF increased with graded isovolemic hemodilution (r=-0.73, P<0.05). CTO2 reached its highest value at a Hct level of 31.3%. CTO2 at Hct of 36.1% and 31.3% was statistically different from the value measured at a Hct of 43.3%, and there was a decrease when Hct was lowered to 25.9%. CMRO2 was the highest when Hct was at 31.3% and differed significantly from the value measured at a Hct of 43.3%. There was a 10% increase of OEF when Hct was at 25.9%; however this change was not statistically significant compared with the OEF at Hct of 36.1% and 31.3%, respectively. These findings indicate that CTO2 and CMRO2 were the highest when Hct was reduced to 31% in hemodilution. Hct at 31% is the optimum for cerebral metabolism in ischemic status. Uncoupling of CTO2, CMRO2 with CaO2 was also observed in this study. This phenomenon suggests that hemodilution to augment cerebral circulation may be at least partially attributed to the beneficial effects of hemorheologic improvement in the microcirculation of the ischemic brain.

Animals↗

PubMed1997

Combined encephalo-arterio-synangiosis and encephalo-myo-synangiosis in the treatment of moyamoya disease.

From January 1990 to December 1995, a total of nine cases of Moyamoya disease were treated at the National Taiwan University Hospital with combined encephalo-arterio-synangiosis (EAS) and encephalo-myo-synangiosis (EMS). There were five males and four females and their ages ranged from 6 months to 31 years. Of these, two cases had their first symptom as intracranial hemorrhage and the rest of the cases had ischemic manifestations. Surgical treatment with combined EAS and EMS was performed on 16 hemispheres of the nine cases. The superficial temporal artery with its anterior and posterior branches was isolated and fixed to the pial surface. Then, the muscle pedicle from the bivalved temporal muscle was used as a dural graft to cover the artery. All the cases showed good neovascularization on follow-up angiography performed at 2-3 months after surgery. These two patients with hemorrhagic symptoms were followed for 52 and 61 months, respectively. Neither of these two cases showed recurrent bleeding. For patients with ischemic symptoms, the follow-up period ranged from 8 to 73 months (mean 41.7 months). All the patients showed improvement in their clinical symptoms.

Adolescent↗