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Biomedical subjects

B Liu

Publications and source records attributed to B Liu.

At least 703 records · Page 39Linked to original sources
PubMed1991

Lipoxygenase metabolites of arachidonic and linoleic acids modulate the adhesion of tumor cells to endothelium via regulation of protein kinase C.

12(S)-hydroxyeicosatetraenoic acid (12[S]-HETE) and 13(S)-hydroxyoctadecadienoic acid (13[S]-HODE), lipoxygenase metabolites of arachidonic acid and linoleic acid, respectively, previously have been suggested to regulate tumor cell adhesion to endothelium during metastasis. Adhesion of rat Walker carcinosarcoma (W256) cells to a rat endothelial cell monolayer was enhanced after treatment with 12(S)-HETE and this 12(S)-HETE enhanced adhesion was blocked by 13(S)-HODE. Protein kinase inhibitors, staurosporine, calphostin C, and 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine, inhibited the 12(S)-HETE enhanced W256 cell adhesion. Depleting W256 cells of protein kinase C (PKC) with phorbol 12-myristate-13-acetate abolished their ability to respond to 12(S)-HETE. Treatment of W256 cells with 12(S)-HETE induced a 100% increase in membrane-associated PKC activity whereas 13(S)-HODE inhibited the effect of 12(S)-HETE on PKC translocation. High-performance liquid chromatographic analysis revealed that in W256 cells 12-HETE and 13-HODE were two of the major lipoxygenase metabilites of arachidonic acid and linoleic acid, respectively. Therefore, these two metabolites may provide an alternative signaling pathway for the regulation of PKC. Further, these findings suggest that the regulation of tumor cell adhesion to endothelium by 12(S)-HETE and 13(S)-HODE may be a PKC-dependent process.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1991

A cis-acting element in the major immediate-early (IE) promoter of human cytomegalovirus is required for negative regulation by IE2.

The major immediate-early promoter (MIEP) of human cytomegalovirus (CMV) contains a number of different enhancer elements in both repetitive and nonrepetitive sequences that influence the level of downstream transcription. This report describes a cis-acting element in the MIEP that responds to negative regulation by the IE2 gene product. Deletion analysis demonstrated that the cis-acting repressor element is located between the TATA box and the transcription initiation site from -13 to -1. The DNA sequence of the repressor element is 5'-CGTTTAGTGAACC-3'. The sequence is found in both the human and simian CMV MIEPs but not the murine CMV MIEP or in several other enhancer-containing promoters. The repressor element was isolated in a DNA fragment from -13 to +3 and was found to be functional in either orientation. It could be transferred to a heterologous enhancer-containing promoter and was functional when placed between the TATA box and the transcription initiation site. The element did not function when placed downstream of the transcription initiation site. Therefore, the cis-acting repressor element is position dependent. The role of the repressor element and the IE2 gene product in human CMV productive or latent infection is discussed.

Base Sequence↗
PubMed1991

Cardiac mechanical restitution in active and hibernating Richardson's ground squirrel.

The cardiac mechanical restitution was compared in papillary muscles between the active and the hibernating Richardson's ground squirrels at 0.1, 2.8, and 5 mM external Ca2+ concentration [( Ca2+]o). The amplitude of the restitution was significantly higher in hibernating animals between 37 and 7 degrees C at all [Ca2+]o. The first postrest contraction (F1) was highest at 20 degrees C and lower at 37 and 7 degrees C in both groups. The pause duration for maximum F1 was 30 s in active but 10 s in hibernating animals at 37 degrees C and increased to 100 s in both groups at 7 degrees C. The postrest potentiation was eliminated by 10(-6) M ryanodine at 20 degrees C in both groups, and this inhibitory effect was more pronounced in the hibernating group. Together, our results suggest that the activator Ca2+ for excitation-contraction coupling is mainly derived from the sarcoplasmic reticulum (SR) pool in both active and hibernating ground squirrel, and the dependence on SR Ca2+ release via ryanodine-sensitive Ca2+ channels is more marked in the hibernating state. Furthermore, there is no significant difference in sensitivity of the cardiac mechanical restitution to [Ca2+]o between the active and the hibernating condition.

Activity Cycles↗
PubMed1991

The hypothalamus is not the origin of vasopressin and oxytocin in the rat pineal gland.

Immunoreactive levels of vasopressin (VP) and oxytocin (OT) were quantitated in the rat pineal gland in the middle of August, when nonapeptide levels have been reported to peak annually. The pineal levels of both VP and OT were found to be substantially elevated when sampled in August, compared to sampling in July and September. mRNA levels for OT and VP in hypothalamic nuclei (supraoptic, paraventricular, and suprachiasmatic nuclei) showed no such increases during August. A lesioning of the paraventricular nuclei did not suppress pineal VP and OT levels. Finally, the injection of colchicine into the third ventricle caused pineal VP and OT levels to increase substantially. Together, these results affirm the occurrence of a summertime rise in pineal VP and OT levels and suggest that such increases do not derive from sites of VP and OT cell bodies in the hypothalamus. Rather, they indicate that the source of these pineal nonapeptides may be the pineal itself.

Animals↗
PubMed1991

[Study of VLDL- and HDL-receptor on isolated parenchymal and non-parenchymal cells from rat liver].

Saturable high-affinity VLDL and HDL receptor on parenchymal cells (PC), and non-parenchymal cells (NPC) freshly isolated from rat liver were studied. The VLDL- and HDL-receptor could mediate liver PC and NPC to bind, uptake, and degrade 125I-labeled human VLDL and apoE-deficient HDL3, and the activities of these two receptors (expressed as ng/mg cell protein) on NPC were about 10- and 4-fold higher than those on PC, respectively. VLDL receptor on NPC with kd 15.0-34.2 micrograms/ml and Bmax 2170-2607 ng/mg cell protein could be inhibited by EDTA, and down-regulated by cell cholesterol content. HDL receptor on NPC with kd 10.1-17.7 micrograms/ml and Bmax 1004-2738 ng/mg cell protein could not be inhibited by EDTA, but could be up-regulated by cell cholesterol content. Competitive inhibition assay showed that VLDL receptor could not only bind VLDL and LDL, but also bind HDL3 to some extent. Unlabeled purified apolipoprotein CIII-1, but apoAI, CI, CII, could effectively inhibit 125I-labeled VLDL binding to NPC. These results suggest that liver NPC may be more active than PC in clearing VLDL and HDL from circulation, and apolipoprotein CIII play an important inhibitory role in these receptor-mediated processes.

Animals↗
PubMed1991

[Effects of apolipoproteins AI, CI, CII, CIII and E on the binding of 125I-labeled apoE-deficient HDL3 to rat liver plasma membranes].

Effects of purified human apolipoproteins AI, CI, CII, CIII-1, Cs and E on the binding of 125I-labeled apo E-deficient HDL3 to isolated rat liver plasma membranes were investigated. Unlabeled apo AI, CI, CII, CIII-1 and apo Cs, but not apo E, could effectively inhibit 125I-labeled HDL3 binding to liver membranes, apoCIII-1, was the strongest among the apoC subclasses and the inhibition curve of apoCIII-1 was similar to that of apo AI. This result indicates that apo C, especially apo CIII, may be another specific ligand of HDL receptor, and it plays an important role in regulation of HDL receptor activity in liver.

Animals↗
PubMed1991

[The analgesic effect of red nucleus and strengthening effect thereof to the acupuncture analgesia].

The modulation of red nucleus (RN) to pain sense was researched with the latent period of radiant-heat tail flick of rats as standard of the pain threshold. The pain threshold of tail flick reflex was raised significantly by bilateral injection of glutamic acid into RN. Simultaneous injecting glutamic acid into RN and lidocaine into nucleus raphe magnus (NRM) could attenuate the raising effect of pain threshold of RN. This showed that the activated RN has analgesic effect and the NRM plays an important role in the descending inhibitory pathway of RN. The discharges of neurons in caudal part of nucleus spinalis tract nervi trigemini (cNST) evoked by stimulating nerve alveolaris inferior (nAI) with strong pulse were recorded with microelectrode. The nAI-evoked discharges might be inhibited by stimulating contralateral or ipsilateral RN. The RN inhibitory time course on nAI-evoked discharges were shortened after injecting lidocaine into NRM. This demonstrated that the inhibitory effect of RN on neurons in cNST is mediated by NRM. The electrical stimulation of acupoint "Jiache" could inhibit the pain-evoked discharges of neurons in cNST. The inhibitory time course of electrical acupuncture were prolonged by stimulating RN. This result revealed that the activated RN can strengthen the analgesic effect of acupuncture.

Acupuncture Analgesia↗
PubMed1991

High-dose aprotinin (trasylol) in reducing bleeding and protecting lung function in potential bleeders undergoing cardiopulmonary bypass.

Intraoperative high-dose aprotinin during cardiopulmonary bypass was used to investigate if high-risk bleeders could be changed to bleed normally or less as well as see if aprotinin could preserve lung function. Eleven matched controls were compared with eleven aprotinin patients taking warfarin or aspirin preoperatively. The mean (+/- SEM) 12-h and 24-h postoperative amount of bleeding, volume of blood product transfusion and hemoglobin reduction in the aprotinin group were 328 +/- 45 ml, 418 +/- 63 ml, 341 +/- 99 ml and 1.8 +/- 0.5 g% respectively, which were significantly lower than the respective values of 716 +/- 86 ml (P less than 0.01), 1,029 +/- 115 ml (P less than 0.01), 985 +/- 294 ml (P less than 0.05) and 4.1 +/- 0.4 g% (P less than 0.02) in the controls. There was a 65% blood-saving effect by aprotinin in this study. The hypercapnea rate was 45% in the treated patients, and 82% (P less than 0.05) in the controls reflecting better preservation of pulmonary diffusion function which is clinically important following major surgery.

Aged↗
PubMed1991

[The distribution of apolipoproteins AI, CII and CIII mRNA in rat tissues].

It was demonstrated that apo AI, CII and CIII mRNA were distributed in rat (Sprague Dawley) liver, intestine, brain and kidney by RNA-dot blot analysis with apoAI, CII and CIII cDNA probes. The relative abundances of apoAI in liver, intestine, brain and kidney tissues are 100%, 212%, 170% and 224%, respectively, those of apoCII are 100%, 61%, 163% and 214%; and those of apoCIII 100%, 65%, 70% and 73%, respectively. The experiment was repeated for three times. The results were discussed in this paper.

Adult↗
PubMed1991

[Synthesis of delta virus cDNA of China Sichuan strain].

delta virus cDNA of China Sichuan strain, 1.2 kb in length, was synthesized by extraction of RNA from liver tissue in a patient with subacute severe hepatitis, followed by reverse transcription and polymerase chain reaction (RT-PCR). The result was confirmed by Southern blot hybridization using 32P and biotin labelled delta virus cDNA (HN88, cloned in USA) probes respectively.

Blotting, Southern↗
PubMed1991

[Effect of bile salt in duodenum on gastric myoelectric activity and motility of mouse with a preliminary study of its neuromechanism].

Changes of gastric myoelectric fast wave, slow wave and gastric motility were studied after intraduodenal infusion of sodium taurocholate (ST) in an attempt to search the concerned neuromechanism. Frequency and total amplitude of the fast wave and slow wave of gastric myoelectric activity and of gastric contractile wave were recorded every five minutes before and after intraduodenal infusion of ST under the background action of various drugs. The frequency and amplitude were expressed in percentage change of the respective premedication value. After intraduodenal infusion of ST (n = 10) the frequency and the amplitude of fast wave and gastric contractile wave were suppressed. Blocking anesthesia of celiac plexus, reserpinization and intravenous infusion of carbachol could eliminate the inhibition induced by ST, which could be partly eliminated by intravenous infusion of propranolol but not affected by phentolamine at all. The results demonstrate that intraduodenal infusion of bile salt suppresses the fast wave of gastric myoelectric activity and gastric motility, most probably controlled by efferent sympathetic adrenergic fibres through beta-receptor.

Animals↗
PubMed1991

[Apolipoproteins AI, B100, CII, CIII and E in human cerebrospinal fluid].

Apolipoproteins AI, B100, CII, CIII and E contents were measured by radial immunodiffusion assay kits developed by our Research Unit. The apolipoprotein in 10 human cerebrospinal fluid samples was determined. Results show that there are no apo B100, CII or trace apo CIII in human cerebrospinal fluid, the levels of apo AI in cerebrospinal fluid are 1.00 +/- 0.54 mg/dl with a range of 0.35-2.00 mg/dl and the apo E content is 0.69 +/- 0.16 mg/dl with a range of 0.51-0.99 mg/dl. The results are discussed.

Apolipoprotein A-I↗
PubMed1991

[Effects of liuwei dihuang decoction and its compositions on blood sugar and glycogen in mice].

We have studied the effects of liuwei dihuang decoction (LDD) and its compositions on blood sugar and glycogen in mice, and found that sanbu, shanzhuyu-danpi and shanyao-fuling matched pairs can reduce the level of blood sugar, while LDD, sanbu, shudi-zexie and shanzhuyu-danpi matched pairs can increase the content of glycogen in liver. The present study is only a preliminary research on the effects of LDD and its compositions on the metabolism of sugar in the body.

Animals↗
PubMed1991

[Purification and immunological behavior of beta-lactamase from Bacteroides fragilis].

The beta-lactamase crude extract of Bacteroides fragilis 55 was chromatographed with DEAE-sepharose CL-6B and sephadex G-100. The partial purified enzyme proteins was further purified by cutting the band on PAGE in which the beta-lactamase was distinguishable from other proteins by our method of fluorescent staining. Using purified preparations to be mixed with liposome-CPS-K, prepared specific antisera against the purified beta-lactamase. Serological reactions were carried out by IgG-ELISA together with western blotting. The results revealed that Bacteroides fragilis beta-lactamase possessed its species-specificity.

Bacteroides fragilis↗
PubMed1990

Crystallization and preliminary X-ray diffraction studies of the engrailed homeodomain and of an engrailed homeodomain/DNA complex.

The homeodomain from the engrailed protein of Drosophila has been crystallized from ammonium phosphate at pH 6.8. The crystals form in space group P6(1)22 (or P6(5)22), with cell dimensions a = b = 44.8 A and c = 118.2 A. These crystals diffract to 1.8 A resolution. A complex containing the engrailed homeodomain and a duplex DNA site also has been crystallized. The cocrystals form in space group C2 with a = 131.2 A, b = 45.5 A, c = 72.9 A and beta = 119.0 degrees. These crystals diffract to 2.6 A resolution.

Animals↗
PubMed1990

Effects of low temperature on contraction in papillary muscles from rabbit, rat, and hedgehog.

During hibernation the body temperature may fall to only a few degrees above 0 degree C. The heart of the hedgehog continues to function whereas the hearts of nonhibernating mammals stop beating. The present study was performed to investigate and compare the mechanical responses to hypothermia in rabbits, rats, and hedgehogs. Isometric force was recorded from papillary muscles mounted in an organ bath and effects of hypothermia on the mechanical restitution curve were also compared. A reduction of bath temperature from 35 degrees C caused an increase in peak developed force. Maximum force was seen at 20 degrees C in the rabbit, 15 degrees C in the rat, and 10 degrees C in the hedgehog preparations. In all the species there was a similar prolongation of time to peak force and of time from peak to half-relaxation as temperature was lowered. An increase in resting force and after-contractions were recorded in the rabbit and rat muscles at temperatures below 15 and 10 degrees C, respectively. The rabbit and rat preparations became inexcitable at temperatures below 10 and 5 degrees C, respectively. The hedgehog papillary muscle, on the other hand, still contracted at 0 degree C and did not show increased resting force nor after-contractions. The results are consistent with the hypothesis that there is a calcium overload in cardiac cells from rabbit and rat at low temperatures but there is no calcium overload in the hedgehog muscle during hypothermia.

Animals↗
PubMed1990

Mechanical restitution at different temperatures in papillary muscles from rabbit, rat, and hedgehog.

Mechanical restitution curves, i.e., peak isometric force as a function of the duration of the preceding test interval, were investigated in papillary muscles from rabbit, rat, and hedgehog. Peak force of rabbit papillary muscle increased with prolongation of the test interval from about 0.3 s to about 1.0 s and for longer intervals peak force declined (called type I mechanical restitution). On the other hand, in rat and hedgehog, papillary muscles' force reached a maximum value at intervals of 30-120 s (called type II mechanical restitution). When temperature was decreased from 35 to 15 degrees C, maximum force of type I mechanical restitution shifted from 1.0 to 10 s, whereas maximum force of type II restitution did not change significantly. Type II mechanical restitution consisted of two different phases, designated phase A and phase B, respectively. As temperature was decreased from 35 to 0 degree C in the hedgehog preparation, the two phases became even more separated. At 35 degrees C, the rising part of mechanical restitution in the rabbit muscle could not be distinguished from phase A of the hedgehog preparation and was also very similar to phase A of the rat muscle. Phase A is thus present in both type I and type II mechanical restitution, but phase B is a special feature of type II mechanical restitution. Phase A and phase B might be a manifestation of activator calcium originating from two different sources, e.g., the sarcoplasmic reticulum and the sarcolemma.

Animals↗