PubMed Health⌕ Search

Biomedical subjects

H Y Liu

Publications and source records attributed to H Y Liu.

At least 55 records · Page 3Linked to original sources
PubMed1998

Novel cytotoxic diterpenes, excavatolides A-E, isolated from the Formosan gorgonian Briareum excavatum.

The chemistry of Briareum excavatum, a Formosan gorgonian coral, was investigated. This study has led to the isolation of five novel marine natural products, excavatolides A-E (1-5), together with brianolide (6). The structures of the above compounds were established by spectral and chemical methods. The relative configuration of excavatolide B (2) was further confirmed by a single-crystal X-ray structure analysis. Cytotoxicity of these compounds toward various cancer cell lines also is described.

Animals↗
PubMed1998

Gene transfer via pollen-tube pathway for anti-fusarium wilt in watermelon.

In order to obtain transgenic fusarium wilt resistant watermelon plants, squash DNA was introduced into the ovaries of watermelon plants via the pollen-tube pathway. The introduction of foreign genes into ovaries was accomplished using co-transformation with the CaMV35S-GUS as a marker. Transformed watermelon plants contained integrated copies of the GUS activity and the seeds of transformed progeny produced a blue color when stained with 5-bromo-4-chloro-3-indolyl glucuronide, whereas seeds from untransformed control plants did not. Of 200 transformed seedlings, ten were wilt resistant. The presence of the GUS activity in the genome of stable transgenic seedlings was confirmed by Southern blot analysis. Furthermore, the generation of random amplified polymorphic DNA (RAPD) fingerprints using primers with embedded restriction sites showed amplification products unique to these transgenic plants. Primers OPA-1 and OPA-9 gave distinct band patterns of genomic DNA using the polymerase chain reaction.

DNA, Plant↗
PubMed1997

DBF2, a cell cycle-regulated protein kinase, is physically and functionally associated with the CCR4 transcriptional regulatory complex.

CCR4, a general transcriptional regulator affecting the expression of a number of genes in yeast, forms a multi-subunit complex in vivo. Using the yeast two-hybrid screen, we have identified DBF2, a cell cycle-regulated protein kinase, as a CCR4-associated protein. DBF2 is required for cell cycle progression at the telophase to G1 cell cycle transition. DBF2 co-immunoprecipitated with CCR4 and CAF1/POP2, a CCR4-associated factor, and co-purified with the CCR4 complex. Moreover, a dbf2 disruption resulted in phenotypes and transcriptional defects similar to those observed in strains deficient for CCR4 or CAF1. ccr4 and caf1 mutations, on the other hand, were found to affect cell cycle progression in a manner similar to that observed for dbf2 defects. These data indicate that DBF2 is involved in the control of gene expression and suggest that the CCR4 complex regulates transcription during the late mitotic part of the cell cycle.

Cell Cycle↗
PubMed1996

Cardiovascular effects of nitric oxide in the brain stem nuclei of rats.

Nitric oxide, synthesized from the semiessential amino acid L-arginine by nitric oxide synthase, is a remarkable regulatory molecule and plays an important role in physiological functions. However, the physiological role of nitric oxide in cardiovascular regulation by the central nervous system is not well understood. In this study we investigated the cardiovascular effects of nitric oxide in the lateral ventricle, nucleus tractus solitarii, area postrema, and rostral ventrolateral medulla in urethane-anesthetized male Sprague-Dawley rats. Microinjection of NG-monomethyl-L-arginine, a nitric oxide synthase inhibitor, into the cerebral ventricle of rats elicited a dose-dependent increase in blood pressure and heart rate. This suggests that nitric oxide may be involved in central cardiovascular regulation. Unilateral microinjection (60 nL) of L-arginine (1 to 100 nmol) into the nucleus tractus solitarii and rostral ventrolateral medulla produced prominent dose-related depressor and bradycardic effects and reduced renal sympathetic nerve activity. However, L-arginine had no significant cardiovascular effects in the area postrema. In addition, 4 to 6 hours after intravenous injection of bacterial endotoxin-lipopolysaccharide (10 mg/kg), there was a time-related potentiation of the L-arginine-induced depressor and bradycardic effects in the nucleus tractus solitarii. These results indicate that nitric oxide is involved in central cardiovascular regulation. The depressor effect of nitric oxide in the nucleus tractus solitarii and rostral ventrolateral medulla may be through inhibition of renal sympathetic nerve activity.

Animals↗
PubMed1995

Detection of tryptase TL2 and CD26 antigen in brain-derived cells non-permissive to T-cell line-tropic human immunodeficiency virus type 1.

Tryptase TL2 purified from MOLT-4 human T cells binds to the envelope protein of human immunodeficiency virus type 1 (HIV-1). Tryptase TL2 and CD26 antigen are supposed to play roles in HIV-1 entry into cells. Although CD4 is a principal receptor for HIV-1, brain cells expressing the CD4 antigen are not permissive to HIV-1 strains infectious to monocyte or T-cell lines. We examined whether the non-permissiveness of the brain-derived cells to standard HIV-1 strains could be explained by a lack of tryptase TL2 or CD26. Western blots showed that the amounts of tryptase TL2 expressed in cell lysates prepared from the brain-derived cells were similar to those prepared from various cells susceptible to HIV-1 strains. Furthermore, flow cytometry revealed the presence of the CD26 antigen on the cell surface of many types of cells. The resistance of the brain-derived cells to standard HIV-1 strains is not due to a lack of tryptase TL2 or CD26.

Brain↗
PubMed1995

Predictive equations for basal metabolic rate in Chinese adults: a cross-validation study.

OBJECTIVE: To develop predictive equations for basal metabolic rate (BMR) in healthy Chinese adults and to evaluate factors that may influence BMR. DESIGN: Measuring the BMR of Chinese adults by indirect calorimetry. Selected subjects were randomly assigned to a validation sample and a cross-validation sample. The validation sample was used to develop predictive equations that were cross-validated using the other sample. SUBJECTS: Two hundred twenty-three healthy Chinese adults (102 men and 121 women) participated in the study. Their ages ranged from 20 to 78 years old (mean = 43.8 +/- 14.3 years). MEASURES: BMR was measured by indirect calorimetry. Body composition was assessed by skinfold fat thicknesses, bioelectrical impedance analysis, and urinary creatinine excretion. STATISTICAL ANALYSES PERFORMED: Student's t test, Pearson correlation coefficients, linear regression analyses, and the best subset were used for statistical analyses. RESULTS: The better-fitting equation for predicting BMR in Chinese adults is BMR = 13.88 x weight (kg) + 4.16 x height (cm) - 3.43 x age (years) - 112.40 x sex (men = 0; women = 1) +54.34. Men had higher BMR values than women because men had greater fat-free mass, body cell mass, and muscle mass. BMR correlated best with body composition, which correlated highly with anthropometric measurements. Therefore, accurate determination of body weight and body height are beneficial in predicting a person's BMR. All of the currently available predictive equations overestimated BMR (P = .0001) for healthy Chinese adults. The equations developed in this study predict BMR more accurately for Chinese adults. APPLICATIONS: The equations developed in this study are recommended for clinical use in healthy Chinese adults who are within normal limits for body weight.

Adult↗
PubMed1995

Identification of Leishmania species by a specific DNA probe that is conserved only in the maxicircle DNA of human-infective Leishmania parasites.

An A + T-rich repeated DNA sequence cloned from maxicircle DNA of Leishmania mexicana amazonensis was found to be conserved in the maxicircles of human-infective Leishmania species but totally absent from non-human-infective ones. Differences in the pattern of distribution of this repeated sequence in the maxicircles of each human-infective Leishmania species potentially allow the development of a sensitive probe to differentiate among these species.

Animals↗
PubMed1994

Specific A+T-rich repetitive DNA sequences in maxicircles from wildtype Leishmania mexicana amazonensis and variants with DNA amplification.

To explain the low cross-hybridization between kinetoplast DNA maxicircles of Leishmania parasites that show DNA amplification and those of parasites without DNA amplification, we isolated and cloned two maxicircle fragments, one specific to each group of parasites. The cloned fragment from wildtype L. m. amazonensis (MbpW94) and that from an arsenite-resistant variant with DNA amplification (MpbA29) hybridized only to maxicircles from parasites of the group from which the fragment was originally derived. Both fragments were A+T-rich, tandemly repeated, and lacked long conserved open reading frames and transcriptional products. MpbW94 (685 bp) was harbored in a segment of roughly 12 kb in maxicircles of wildtype parasites and of an arsenite-resistant variant without DNA amplification, while MbpA29 (1121 bp) occupied a 6- to 7-kb segment of maxicircle DNA in arsenite- and tunicamycin-resistant variants with DNA amplification. These maxicircle DNA segments appear to resemble previously described maxicircle divergent regions of other kinetoplastids. The presence of these specific sequences allows differentiation between maxicircles of drug-resistant L. m. amazonensis with DNA amplification and those of parasites without DNA amplification and helps explain the low cross-hybridization between maxicircles of the two parasite groups. Furthermore, these sequences allow the study of the kinetics of the changeover of A+T-rich regions of maxicircles during the transition period from one maxicircle type to the other.

Animals↗
PubMed1994

Cytosolic acetylation of sulfamethazine decreases hepatic release of ketone bodies in vivo in fasting rats.

The effect of sulfamethazine (SMZ) on ketogenesis was studied in this report. SMZ, a sulfonamide metabolized by cytosolic acetylation in liver, was intraperitoneally injected (2 mmol/kg) to ketamine-anesthetized, overnight-fasted rats. Ketogenesis was measured by the Fick principle from the transhepatic (A-V) gradients of acetoacetate (AcAc) and D-beta-hydroxybutyrate (beta-OHB). Prior to SMZ injection, A-V gradient of ketone bodies (KB) (AcAc + beta-OHB) was -1.38 mM, indicating release from the liver. After SMZ injection, the release of KB decreased rapidly, maintaining at a level approximately 50% less than controls throughout the 2-h experimental period. Plasma concentrations of AcAc and beta-OHB also decreased. In contrast, plasma concentrations and trans-hepatic gradients of free fatty acids (FFA) were not significantly affected. Our results thus indicate that SMZ acetylation in liver mobilizes acetyl CoA from mitochondria. Decreased hepatic ketogenesis limits the availability of KB and may thus affect energy metabolism in the extrahepatic tissues. The incomplete inhibition on ketogenesis may indicate compartmentation of acetyl CoA in liver mitochondria.

3-Hydroxybutyric Acid↗
PubMed1994

Clinical outcome and management of prenatally diagnosed primary megaureters.

The objective of this study was to evaluate the clinical outcome of infants diagnosed perinatally with primary obstructive megaureter, and to determine which anatomical and physiological indexes best predict such outcome. A total of 67 megaureters thought to be due to primary vesicoureteral junction obstruction was detected in 53 newborns as a result of prenatally diagnosed hydronephrosis or hydroureteronephrosis. These patients were followed nonoperatively using periodic ultrasound and 99mtechnetium-diethylenetriaminepentaacetic acid (Tc-DTPA) renal scans. After a mean followup period of 3.1 years 23 dilated ureters (34%) spontaneously resolved while 33 (49%) persisted. Repair was performed on 11 megaureters (17%) because of breakthrough urinary infections in 3 and deteriorating renal function in 8. Postoperatively, all renal units showed improved drainage on 99mTc-DTPA renal scan, while half of those with decreased renal function regained the lost function. None had further deterioration in renal function. Of the clinical indexes studied ultrasonographic ureteral diameter (less than 6 mm. good, greater than 10 mm. poor prognosis) and drainage on 99mTc-DTPA renal scan correlated best with outcome. We conclude that the majority of primary megaureters detected in the perinatal period can be followed conservatively using periodic ultrasound and 99mTc-DTPA renal scans. Relatively few cases required surgical intervention and those at risk were identifiable by a diameter greater than 10 mm. and poor drainage on 99mTc-DTPA renal scan.

Dilatation, Pathologic↗
PubMed1994

The yeast CCR4 protein is neither regulated by nor associated with the SPT6 and SPT10 proteins and forms a functionally distinct complex from that of the SNF/SWI transcription factors.

The CCR4 protein is specifically required for the increased transcription at the ADH2 locus resulting from mutations in the SPT10 (CRE1) and SPT6 (CRE2) genes and is also required for the expression of ADH2 and other genes under non-fermentative growth conditions. The mechanism by which mutations in CCR4 suppress defects in SPT10 and SPT6 was examined. The SPT10 and SPT6 genes were shown not to control CCR4 mRNA or protein expression nor did SPT10 and SPT6 proteins co-immuneprecipitate with CCR4. CCR4 association with two other proteins, 195 and 185 kDa in size, was unaffected by either spt10 or spt6 mutations. Also, the ability of CCR4 to activate transcription when fused to the LexA DNA binding domain was not specifically enhanced by defects in either SPT10 or SPT6. These results suggest that SPT10 and SPT6, in negatively regulating transcription at ADH2, act through a factor that requires CCR4 function, but do not regulate CCR4 expression, control its activity, physically interact with it, or affect its binding to other factors. The relationship of CCR4 to the group of general transcription factors, SNF2, SNF5, SNF6 and SWI1 and SWI3, which comprise a multisubunit complex required for ADH2 and other genes' expression, was also examined. CCR4 protein expression was not controlled by these factors nor did they co-immuneprecipitate or associate with CCR4. In addition, a ccr4 mutation had little effect on an ADH2 promoter alteration in contrast to the large effects displayed by mutations in SNF2 and SNF5. These data suggest that CCR4 acts by a separate mechanism from that used by the SNF/SWI general transcription factors in affecting gene expression.

Alcohol Dehydrogenase↗
PubMed1994

Selection for arsenite resistance causes reversible changes in minicircle composition and kinetoplast organization in Leishmania mexicana.

Certain minor minicircle sequence classes in the kinetoplast DNA (kDNA) networks of arsenite- or tunicamycin-resistant Leishmania mexicana amazonensis variants whose nuclear DNA is amplified appear to be preferentially selected to replicate (S. T. Lee, C. Tarn, and K. P. Chang, Mol. Biochem. Parasitol. 58:187-204, 1993). These sequences replace the predominant wild-type minicircle sequences to become dominant species in the kDNA network. The switch from wild-type-specific to variant-specific minicircles takes place rapidly within the same network, the period of minicircle dominance changes being defined as the transition period. To investigate the structural organization of the kDNA networks during this transition period, we analyzed kDNA from whole arsenite-resistant Leishmania parasites by dot hybridization with sequence-specific DNA probes and by electron-microscopic examination of isolated kDNA networks in vitro. Both analyses concluded that during the switch of dominance the predominant wild-type minicircle class was rapidly lost and that selective replication of variant-specific minicircles subsequently filled the network step by step. There was a time during the transition when few wild-type- or variant-specific minicircles were present, leaving the network almost empty and exposing a species of thick, long, fibrous DNA which seemed to form a skeleton for the network. Both minicircles and maxicircles were found to attach to these long DNA fibrils. The nature of the long DNA fibrils is not clear, but they may be important in providing a framework for the network structure and a support for the replication of minicircles and maxicircles.

Animals↗
PubMed1994

CCR4 is a glucose-regulated transcription factor whose leucine-rich repeat binds several proteins important for placing CCR4 in its proper promoter context.

The yeast CCR4 protein is required for the expression of a number of genes involved in nonfermentative growth, including glucose-repressible ADH2, and is the only known suppressor of mutations in the SPT6 and SPT10 genes, two genes which are believed to be involved in chromatin maintenance. We show here that although CCR4 did not bind DNA under the conditions tested, it was able to activate transcription when fused to a heterologous DNA-binding domain. The transcriptional activation ability of CCR4, in contrast to that of many other activators, was glucose regulated. Two activation domains one of which was glucose responsive and encompassed a glutamine-proline-rich region similar to that found in other eukaryotic transcriptional factors were identified. The two transactivation regions, when separated from the leucine-rich repeat and the C terminus of CCR4, were unable to complement a defective ccr4 allele, suggesting that the leucine-rich repeat and the C terminus make contacts that link the activation regions to the proper gene context. Native immunoprecipitation of CCR4 revealed that CCR4 was complexed with at least four other proteins. The leucine-rich repeat of CCR4 was both necessary and sufficient for interaction with at least two of these factors. We propose that the leucine-rich repeat links CCR4 through its associated factors to its promoter context at ADH2 and other loci where it is required for proper transcriptional regulation.

Alcohol Dehydrogenase↗
PubMed1994

Splenosis presenting as a left renal mass: a report of two cases.

The development of splenosis is a recognized consequence of splenic trauma. We present 2 cases of splenosis that were initially diagnosed as left renal cell carcinomas. The diagnosis of splenosis was made by technetium sulfur colloid scans. The clinical presentation and diagnosis of these 2 cases of splenosis masquerading as renal cell carcinoma are reviewed.

Adult↗
PubMed1994

[Neuropsychiatric disturbances and neuro-electrophysiological examination in patients with arsenic poisoning].

Neuropsychiatric disturbances caused by arsenic poisoning in 28 patients were reported. The incidence was 32.2% of all the arsenic poisoning patients. The patients were classified into three types according to their clinical symptoms. The neurologic type constituted 46.4%, mental type 21.4% and mixed type 32.1% of the patient respectively. Various abnormalities were found in EEG, EMG, EP and EKG examination. EMG and EP were still abnormal in most of the patients after treatment for three months. The results showed that arsenic poisoning may cause neuropsychiatric disturbances. The symptoms in these patients are serious and the recovery is quite slow.

Adolescent↗
PubMed1994

[Chronological characteristics of retinoic acid-induced HL-60 cell differentiation].

HL-60 cells can be induced to differentiate into mature granulocytic cells in a continuous exposure to all-trans retinoic acid (RA) for at least 96 h. In this study, RA was removed after being exposed to HL-60 cells for 12-96h. Then the cells were reincubated in a fresh medium without drug for additional 48-144h and their differentiation markers such as NBT reduction, morphological changes and cytokinetic characteristics were studied. The results demonstrated that once exposed continuously to 1.0 mumol/L RA for at least 48h, the HL-60 cells would proceed to terminal differentiation: about 60-90 percent of the cells became NBT positive, 40-80 percent of cells exhibited decreased nucleus/cytoplasm ratio and marked reduction in the number of nucleoli and displayed matured granulocytic morphology. Cytokinetic studies demonstrated 48-85 percent of cells arrested in G1 phase, which is typical for differentiated cells. However, if the cells were exposed to RA for less than 48h, they would not show differentiation phenotype. These results indicate that 48h exposure is critical for HL-60 cell differentiation induced by RA, and the cell differentiation induced by RA is irreversible and RA-independent.

Cell Differentiation↗
PubMed1994

Role of transesophageal echocardiography in pre- and post-percutaneous balloon mitral valvuloplasty.

Transesophageal echocardiogram (TEE) was performed in 33 consecutive patients with both rheumatic mitral stenosis and chronic atrial fibrillation to evaluate the usefulness of this technique for the detection of left atrial thrombi, mitral regurgitation before percutaneous balloon mitral valvuloplasty and iatrogenic atrial septal defect after the procedure. TEE correctly identified thrombi in 10 (30%) patients and significant mitral regurgitation in 5 patients who underwent surgical intervention. The remaining 18 patients underwent percutaneous balloon mitral valvuloplasty without evidence of systemic embolic event and obtained adequate outcome. Transesophageal color doppler echocardiography demonstrated left-to-right shunting flow through atrial septum in 5 of 7(71%) patients 3 days after the procedure and repeated TEE in 2 of these 5 patients showed no shunting after 6 months. In conclusion, TEE plays a definite role in the selection of patients for balloon mitral valvuloplasty and assessment of iatrogenic atrial septal defect.

Adult↗