Biomedical subjects

F Liu

Publications and source records attributed to F Liu.

At least 613 records · Page 34Linked to original sources

PubMed1994

Activation of protein kinase C alpha inhibits insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1.

Chinese hamster ovary (CHO) cells were transfected with a cDNA encoding protein kinase C alpha (PKC) and a cell line (CHO-PKC alpha) expressing approximately 7-fold greater amounts of PKC as the parental cells were isolated. Activation of PKC by 12-O-tetradecanoylphorbol-13-acetate in the CHO-PKC alpha cells inhibited by approximately 75% the: 1) insulin-stimulated increase in antiphosphotyrosine precipitable phosphatidylinositol 3-kinase activity in these cells; 2) insulin-stimulated increase in PI 3-kinase activity associated with insulin receptor substrate-1; and 3) tyrosine phosphorylation of the endogenous substrate, insulin receptor substrate-1. In contrast, 12-O-tetradecanoylphorbol-13-acetate treatment did not inhibit any of these responses in the parental CHO cells. These results indicate that excessive PKC activity can interfere in a very early step in insulin receptor signaling and are consistent with the hypothesis that excessive PKC activity may contribute to some states of insulin resistance.

Animals↗

PubMed1994

Oxygenation of the rat 9L gliosarcoma and the rat 13672 mammary carcinoma with various doses of a hemoglobin solution.

Tumor oxygen tensions were measured using a computer controlled pO2 microelectrode in two preclinical solid tumor models, the rat 9L gliosarcoma and the rat 13672 mammary carcinoma. Tumor oxygenation profiles were determined under four conditions: 1) normal air breathing, 2) carbogen (95% O2/5% CO2) breathing, 3) after intravenous administration of a solution of ultrapurified polymerized bovine hemoglobin with normal air breathing and 4) after intravenous administration of a solution of ultrapurified polymerized bovine hemoglobin with carbogen breathing. Both tumors had severely hypoxic regions under normal air breathing conditions. Although carbogen breathing increased the oxygenation of the better oxygenated portions of the tumor, it did not impact on the severely hypoxic tumor regions. Administration of the hemoglobin solution was effective in increasing the oxygenation throughout both tumors under normal air breathing conditions. The addition of carbogen breathing to administration of the hemoglobin solution eliminated severe hypoxia in the 9L gliosarcoma and markedly reduced the severely hypoxic regions of the 13672 mammary carcinoma.

Animals↗

PubMed1994

Oxygenation of human tumor xenografts in nude mice by a perfluorochemical emulsion and carbogen breathing.

Human solid tumors (prostate carcinomas PC-3 and DU-145, breast carcinoma MX-1, cervical carcinoma ME-180, small cell lung carcinoma SW2, and glioblastoma T98G) were grown as xenografts in nude mice. Using the Eppendorf pO2 histograph microelectrode system, the oxygen profiles of the tumors were determined while the animals breathed air or carbogen (95% O2/5% CO2), and after administration of the perfluorochemical emulsion Oxygent-CA (8 ml/kg) under air breathing and carbogen breathing conditions. Under normal air breathing with or without Oxygent-CA administration the mean oxygen tensions were between 4.9 and 9.3 mmHg and each tumor had severely hypoxic regions where the pO2 was less than 5 mmHg. The severely hypoxic regions comprised 41-71% of the oxygen tension measurements under normal air breathing conditions. Carbogen breathing alone increased the mean oxygen tensions to 10.9-23.9 mmHg. Administration of Oxygent-CA and carbogen breathing increased the mean oxygen tensions over the levels of carbogen breathing alone to varying degrees. The highest mean oxygen tensions were 40.8 mmHg in the T98G glioblastoma and 24.5 mmHg in the ME-180 cervical carcinoma. Investigation of the use of Oxygent-CA/carbogen to increase the oxygenation of clinical tumors is warranted.

Administration, Inhalation↗

PubMed1994

[Suppressive effects of adenosine on nonspecific and humoral immunities in mice].

Adenosine (Ade) 1.3, 13, 130 mg.kg-1 ip inhibited the ability of peripheral leukocytes and peritoneal macrophages in phagocytosing the Staphylococcus albus with [3H]TdR incorporation in mice, declined the hemolytic ability of plaque-forming cells and the production of antibody in mice immunized by sheep erythrocytes. Ade 13, 130 mg.kg-1 ip decreased the mouse serum muramidase (lysozyme) concentration. Dipyridamole (Dip) 10 mg.kg-1 ip attenuated the effects of Ade 130 mg.kg-1 on humoral immunity reaction, but the nonspecific immunity was not attenuated. These results showed that the uptake of Ade may play an important role in the effects of Ade on humoral immunity reaction. Aminophylline (Ami) 100 mg.kg-1 ip attenuated the effects of Ade 130 mg.kg-1 on hemolytic ability of plaque-forming cells and the ability of peripheral leukocytes in phagocytosing Staphylococcus albus. These results suggested that the effects of Ade on murine humoral and nonspecific immunity reaction were mediated by Ade A2 receptor (A2DR).

Adenosine↗

PubMed1994

[Study on evolutionary genetics of Drosophila auraria species complex--cladistic analysis and phenetic analysis].

In the present paper, seventeen geographic strains of D. auraria species complex and five geographic strains of other four species, which belong to the montium species subgroup were biochemically examined for the construction of phylogenetic tree based on phenetic and cladistic analysis. Eighteen isoenzymes were analyzed by isoelectric focusing polyacrylamide gel electrophoresis in the above twenty two geographic strains. The phenogram of the D. auraria species complex is supported by UPGMA program of phenetic analysis. It was found that: 1. D. auraria, D. triauraria and D. quadraria grouped as an type are more closely related to one another, and D. biauraria, D. subauraria are more closely related to each other, while the former three species are distantly related to the latter two species. 2. The genetic identity between two geographic strains of same species is higher than the genetic identity between different species, except the geographic strain T-KM of D. triauraria. 3. The geographic strain T-KM, one of the D. triauraria from the southeast isolated islands Kametoku [symbol: see text] of Japan is far more distantly related to the other geographic strains of it. We suggest that the new species or subspecies are diverged from D. triauraria will be due to the geographic speciation mechanisms. 4. The genetic differentiation among eight geographic strains of D. triauraria are much larger than those among three geographic strains of D. auraria, which may be related to their different inhabitation environment as well as their flying ability. On the other hand, a cladistic analysis of the D. auraria species complex are made in the present paper.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

A study of histology and enzymatic histochemistry on rabbit's retina in acute ocular hypertension.

The changes of activities of enzymes relating to energy metabolism in rabbit's retina in acute ocular hypertension were observed. The activities of succinate dehydrogenase and adenosine triphosphatase were found to be reduced, while the activities of the lactatic dehydrogenase and glucose-6-phosphatase increased. The results revealed the metabolic disturbance of energy in retina after acute ocular hypertension might be the underlying factors relating to the defects of the functions and structures of the retina.

Adenosine Triphosphate↗

PubMed1994

[Quantitative analysis of bencynonate in human plasma using a deuterated internal standard by GC-MS/SIM].

Bencynonate is a newly developed anticholinergic drug. After a dose (2 mg/person or 4 mg/person) of bencynonate, the circulating concentrations are so low that therapeutic drug monitoring studies have previously been impossible. Radioisotope assay and radioaccepter assay had been used in rat experiments, but the detections limits of these methods were not sensitive enough for the therapeutic drug monitoring. Further, the two methods were unsuitable in the human. For evaluation of the pharmacokinetics and the relative bioavailability of bencynonate in man, a gas chromatographic--mass spectrometric method for quantitative analysis of bencynonate in human plasma was developed. Deuterated bencynonate served as the internal standard and selected-ion monitoring of the fragments of bencynonate and internal standard permitted the quantitation of bencynonate down to 25 pg.ml-1 of plasma. The linearity was in the range from 25 pg.ml-1 to 3 ng.ml-1 of bencynonate plasma concentration. At 0.25 ng.ml-1 level the recovery and relative standard deviation of variation are 54.3% and 19.1%, respectively. Application of the method to clinical studies gave the results of pharmacokinetics and relative bioavailability of bencynonate in man.

Animals↗

PubMed1994

[Monitoring of dihydroetorphine hydrochloride in biological fluid].

A method for the monitoring of dihydroetorphine hydrochloride, a powerful anesthetic and analgesic drug, in biological fluid was developed by means of GC-MS with selected ion monitoring. Dihydroetorphine was extracted from human blood and urine with dichloromethane, and then was derivatized with N-heptafluorobutyrylimidazole after it was concentrated to dryness. A dihydroetorphine monoheptafluorobutyl derivative was formed, which showed good characteristics on GC-MS with electronic impact mode. Its M+ was m/z 609. Besides this, its main fragments included m/z 576, 534, 522 and 508. These main ions were all selected as the ions of identification due to their relative peak intensity and stability. The detection limit was 1 pg. The target drug was identified based on its retention time multiple ion monitoring and relative peak intensity. This method has been successfully used for detection of dihydroetorphine hydrochloride in blood and urine from dihydroetorphine addict and poisoned patient, respectively. Good results have been obtained.

Etorphine↗

PubMed1994

[Classification of hand and its significance].

Measurements of normal values in hand appearance and thumb movements were done in 102 male adult volunteers with no history of previous injury to their hands. The data showed some characteristics between the appearance and function of hand, for example, no case showed the distance of adduction of thumb was 0, but the normal function of hand was still acquired. Positive correlation appeared between the indexes of appearances of hand. Correlation analysis have been done for three pairs of indexes, that is, hand length and width, length of thumb and the distance of first web, adduction of thumb and thumb-opposition. The correlation charts and their formulae have been presented. Furthermore, hands of male chinese could be classified into five types according to the correlation chart or the formula. The significance of such classification i discussed as well.

Adult↗

PubMed1994

Determination of methaqualone and its metabolites in urine and blood by UV, GC/FID and GC/MS.

A systematic procedure for the determination of methaqualone and its metabolites in blood and urine by UV spectrophotometry, GC and GC/MS was developed. Urine and blood samples were from a suicidal patient who ingested 18 tablets of methaqualone. Both solid phase and liquid-liquid extractions were used in the extraction and clean-up of the samples. The total amount of methaqualone and its metabolites was measured by UV spectrophotometry. The amount of parent methaqualone was quantitated by GC/FID. Methaqualone and its 10 metabolites including two acetyl metabolites were found in urine and blood. This procedure is useful for monitoring drugs in emergency treatment.

Chromatography, Gas↗

PubMed1994

High density cultivation of genetically-engineered CHO cell lines with microcarrier culture systems.

Genetically-engineered CHO cell lines, r beta-13 and CLF-8B2, were cultivated with the MC-1 microcarrier culture system. The cell density could be enhanced by increasing the concentration of microcarrier. At a microcarrier concentration of 10 mg/ml, the cell density could reach 4 to 5 x 10(6) cells/ml. It was shown that these cell lines would spontaneously release from the microcarrier to attach to and proliferate on fresh microcarriers. We were thus able to scale up cultivation using a simple method, i.e. by adding fresh microcarriers and medium directly into the culture system to about 2, 4 or 8 times the original volume. Using a perfusion culture system, we have successfully cultivated CLF-8B2 cells in a 2 L bioreactor for several weeks at medium perfusion rates of 0.5 to 3 working volumes. Prourokinase was stably secreted.

Animals↗

PubMed1994

[Quality control of xiaoqinglong mixture].

TLC was used to detect ephedrine, paeoniflorin, glycyrrhizic acid, cinnamic aldehyde and xixin volatile oils in Xiaoqinglong mixture. Paeoniflorin was determined by HPLC. The average recovery is 99.42%, and RSD 0.23%.

Acrolein↗

PubMed1994

[Analysis of meperidine and its metabolites in urine of an addict by GC/FID and GC/MS].

Analytical methods of GC/FID and GC/MS for identification and determination of meperidine, an analgesic drug, and its metabolites were established. The determination of meperidine spiked in urine was shown to have a good linear relationship in the range of 0.1-8.0 micrograms/ml urine (Y = 0.4995X + 0.1201, r = 0.9996). The detection limit was 20 ng/ml urine. With the developed methods, meperidine and its metabolites in urine collected from a meperidine addict were identified and determined. Meperidine, normeperidine, meperidinic acid in free and conjugate forms, normeperidine acid in free and conjugate forms, and acetyl-normeperidine were detected. Among these metabolites, acetyl-normeperidine was reported for the first time.

Cholinesterase Inhibitors↗

PubMed1994

[Cross transposition of expanded scalp flaps for the treatment of postburn cicatricial alopecia].

When the area of alopecia is very large, the normal scalp is not sufficient to cover the defect resulting from excision of the alopecia. From August 1987 to December 1989, 8 cases with large defect of scalp are repaired by means of expanded cross scalp flaps with good result. Among 8 cases, 7 are male and 1 female, and the largest area of alopecia is 300 cm2 and the smallest 112 cm2, with a mean of 191 cm2. Two expanders are buried under the galea aponeurotica on both sides of alopecia, and the scalp is expanded. The central part of the expanded scalp is chosen to form the "major flap", the lateral part of the expanded scalp to form the "adjuvant flap". Two flaps are then crossed and the defect is repaired. The method of scalp expansion and "axial flap" is used in marginal alopecia. An expander is buried under the galea aponeurotica on each side of the alopecia. After the scalp is expanded, the central part of the expanded scalp is chosen to from "axial flap" with the pedicle consisting of superficial temporal artery or occipital artery and the lateral part of the expanded scalp to form the "adjuvant flap". Then two flaps are transposed and the defect is thus repaired.

Adolescent↗

PubMed1993

Liu et al. reply.

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Journal Article↗

PubMed1993

Genetic and biochemical analysis of an endonuclease encoded by the IncN plasmid pKM101.

The IncN plasmid pKM101 nuc gene encodes a periplasmically localized endonuclease. DNA sequence analysis indicates that this gene encodes a hydrophilic protein of about 19.5 kDa containing a hydrophobic signal sequence. nuc is homologous to a partially sequenced open reading frame adjacent to the sog gene of the plasmid CollB-P9, a plasmid known to encode an endonuclease similar to that of pKM101. A partially sequenced tra gene directly upstream of nuc is homologous to the virB11 gene of Agrobacterium tumefaciens. We have partially purified the pKM101 nuclease by osmotic shock and cation exchange chromatography, and used this enzyme preparation to sequence the protein's amino terminus. The first 13 amino acids of the mature protein match amino acids 23 to 35 of the predicted sequence, indicating that the protein is proteolytically processed to a molecular mass of approximately 17 kDa, probably during export to the periplasmic space. The enzyme was able to attack many sites along an end labelled duplex DNA substrate, but showed clearly preferred cleavage sites, and may cleave preferentially at purine-rich regions.

Amino Acid Sequence↗

PubMed1993

Human hepatoma cells synthesize and secrete insulin-like growth factor Ia prohormone under growth hormone control.

Nucleotide sequencing of cDNAs encoding human insulin-like growth factor I (IGF-I) predicts the existence of two different prohormone forms of IGF-I. The E peptide regions extend the carboxy-terminus of the 70 amino acid core IGF-I molecule (BCAD domains) by either an additional 35 (IGF-Ia) or 77 (IGF-Ib) amino acids. Employing antiserum directed against a peptide sequence unique to the E peptide region of IGF-Ia prohormone, we have identified EIa immunoreactive material (IR-EIa) in the conditioned medium of a human hepatoma cell line, HepG2. Human growth hormone (GH) had dose-dependent stimulatory effects on IR-EIa secretion; incubation of HepG2 cells with GH at maximal concentrations (1-5 micrograms/ml) increased specific IR-EIa in 24 h conditioned medium 3-fold. The addition of human placental lactogen, insulin, IGF-I, dexamethasone, beta-estradiol, or progesterone had no significant effect. Acid chromatography of HepG2 cell conditioned medium revealed a single elution peak of IR-EIa corresponding to M(r) = 12,000-20,000. There was no immunologically detectable 7500 M(r) IGF-I peptide in acid-chromatographed conditioned medium under either basal or stimulated conditions. Biosynthetic labelling of HepG2 cell products with [35S]Trans label and immunoprecipitation with antisera specific to the E or to the AD regions of the IGF-Ia molecule indicated a single species of approx. 14,000 M(r). These data indicate that the E peptide region of IGF-Ia is translated and released as part of the larger molecule in cultured HepG2 cells, and that the levels of this prohormone are regulated by GH.

Carcinoma, Hepatocellular↗

PubMed1993

An upstream promoter element of the Acanthamoeba castellanii TBP gene binds a DNA sequence specific transcription activating protein, TPBF.

We have characterized a positive-acting element in the upstream portion of the Acanthamoeba TBP gene promoter. The 27 bp element (TPE), located within the promoter between -97 and -70, stimulates transcription in an orientation independent fashion and tolerates modest changes in its distance from the TATA box. The TPE does not, however, function synergistically nor when positioned 3000 bp 5' or 260 base pairs 3' of the transcription start site. The TPE binds a DNA sequence-dependent factor, TPBF, which we have partly purified. TPBF was characterized using in vitro transcription, DNase I footprinting, methylation interference and electrophoretic mobility shift assays. TPBF does not have a counterpart in HeLa cells, but nonetheless strongly stimulates transcription of the Acanthamoeba TBP gene in mammalian extracts. Our results also suggest that there are additional positively and negatively acting elements within the TBP gene promoter, for which a model is presented.

Acanthamoeba↗