Biomedical subjects

M Liu

Publications and source records attributed to M Liu.

At least 37 records · Page 2Linked to original sources

PubMed2006

Occurrence of proteolytic activity and N-acyl-homoserine lactone signals in the spoilage of aerobically chill-stored proteinaceous raw foods.

Proteolytic pseudomonads dominate the spoilage flora of aerobically chill-stored proteinaceous raw foods. Proteolysis during spoilage of these food systems affects both food quality and the dynamics of the bacterial community because it increases the availability of nutrients to the community as a whole. Quorum sensing, or cell-cell signaling, is associated closely with ecological interactions among bacteria in mixed communities. The potential role of quorum sensing in proteolytic food spoilage was examined, based on the evaluation of N-acyl-homoserine lactone (AHL) signal molecules. The occurrence of proteolytic activity and AHL signals was studied during spoilage of aerobically chill-stored ground beef, fish, chicken, and raw milk. Pseudomonads dominated the psychrotrophic flora, followed distantly by members of the Enterobacteriaceae. The growth of pseudomonads was correlated with the occurrence of proteolytic activity in all food systems. AHL concentration began increasing significantly only after the onset of proteolytic activity. Widely divergent AHL profiles were revealed by thin-layer chromatography analysis of the different food samples, and these profiles were likely determined by the undefined bacterial flora in these systems and by the characterized pseudomonads and Enterobacteriaceae. Although Hafnia alvei was a major component of the Enterobacteriaceae flora in all foods tested and a strong AHL producer, the signal molecules produced by H. alvei strain EB1 did not influence protease production by Pseudomonas fluorescens strain 395 in vitro. These results do not indicate any clear correlation between the overall detectable AHL signal molecules accumulated in the food samples and proteolytic activity.

4-Butyrolactone↗

PubMed2006

Effect of cold blood cardioplegia enriched with potassium-magnesium aspartate during coronary artery bypass grafting.

AIM: The aim of this investigation is to evaluate the effect of enriched with potassium-magnesium aspartate cold-blood cardioplegia on early reperfusion injury and postoperative arrhythmias in patients with ischemic heart disease undergoing coronary artery bypass grafting (CABG), using measurements of cardiac troponin I (CTnI), hemodynamic indexes and clinical parameters. METHODS: Forty patients with three-vessel coronary artery disease (CAD) and stable angina, receiving first-time elective CABG, were randomly divided into 2 groups: patients in control group (C group n=20) received routine institutional cold blood cardioplegia (4 degrees C) concentration of Mg2+4 mmol/L, Ca2+1.2 mmol/L and K+ 24mmol/L during myocardial arrest. Patients in P group (n=20) received modified cold blood cardioplegia enriched with potassium-magnesium aspartate and maintained concentration of Mg2+10 mmol/L, Ca2+1.2 mmol/L and K+20mmol/L in the final blood cardioplegia solution. Clinical outcomes were observed during operation and postoperatively. Serial venous blood samples for CTnI were obtained before induction, after cardiopulmonary bypass (CPB), and postoperative 6, 24, and 72 hours. Hemodynamic indexes were obtained before and after bypass by the radial catheter and Swan-Ganz catheter. RESULTS: In both groups, there were no differences regarding preoperative parameters. There were no cardiac related deaths in either group. The time required to achieve cardioplegic arrest after cardioplegia administration was significantly shorter in P group (47.5+/-16.3 s) than in C group (62.5+/-17.6 s) (P<0.01). The number of patients showing a return to spontaneous rhythm after clamp off was significantly greater in P group (n=20, 100%) than in C group (n=14, 70%) (P<0.01). Eight patients in C group had atrial fibrillation (AF) compared with two patients in P group (P<0.05) in the early of postoperative period. The level of CTnI increased 6 hours and 12 hours postoperatively, and there was a significant difference between groups (P<0.05). P group also shortened the time of postoperative mechanical ventilation (P<0.05) after surgery. CONCLUSIONS: Cold blood cardioplegia enriched with potassium-magnesium aspartate is beneficial on reducing reperfusion injury.

Aged↗

PubMed2005

Internal fiducial markers can assist dose escalation in treatment of prostate cancer: result of organ motion simulations.

Use of internal fiducial markers and electronic portal imaging (EPI) to realign patients has been shown to significantly reduce positioning uncertainties in prostate radiation treatment. This creates the possibility of improving the treatment by decreasing the planning target volume (PTV) margin added to the clinical target volume (CTV), which in turn may allow dose escalation. Conformal treatment plans for three prostate cancer patients were evaluated by using different PTV margins with dose prescription of 70 Gy/35 fr initially. Two beam arrangements, 4-field-box (4FB) and 4-field-oblique (4FO), were used. Then, two dose escalation schemes, 74 Gy and 78 Gy, with tighter PTV margins, were chosen from the first simulation and were tested. A Monte Carlo model was developed to simulate the daily geometric uncertainty and calculate the dose to each organ. After the whole treatment, dose-volume histograms were produced and tumour control probability, prostate equivalent uniform dose and the effective dose to critical organs were calculated. By comparing these radiobiological metrics, optimized dose escalation schemes were found. The results show that using internal fiducial markers and EPI, the prescription dose can be escalated to 78 Gy/39 fr with a 4 mm PTV margin. Based on the available dose-response data for intermediate risk prostate patients, this is estimated to result in a 20% increase of local control and significantly reduced rectal complications.

Algorithms↗

PubMed2005

Enhancement of the Gibberella zeae growth inhibitory lipopeptides from a Bacillus subtilis mutant by ion beam implantation.

Bacillus subtilis JA antagonized the growth of Gibberella zeae. In order to reduce growth of this fungi pathogen to a greater extent, low-energy ion beam implantation was applied in mutant breeding. We studied the effects of different energies and different doses of nitrogen ion implantation. The mutant strain designated as JA026 was obtained showing higher inhibition activity in the screening plate. Its inhibition zone against indicator organism increased by 14.3% compared to the original strain. The electrospray ionization mass spectrometry (ESI/MS) analysis indicated that the antifungal lipopeptides produced by the mutant were identical to those produced by the wild-type strain. The mutant strain exhibited favorable properties including the high yield of antifungal lipopeptides production and faster growth over the parent strain, which suggested that this strain would be a promising biocontrol candidate in agriculture.

Antifungal Agents↗

PubMed2005

Ginkgo biloba for acute ischaemic stroke.

BACKGROUND: Ginkgo biloba extract is widely used in the treatment of acute ischaemic stroke in China. We aimed to assess the evidence from randomised controlled trials and quasi-randomised controlled trials on the use of Ginkgo biloba extract in acute ischaemic stroke. OBJECTIVES: The primary objective was to determine whether Ginkgo biloba extract improves functional outcome without causing undue harm in patients with acute ischaemic stroke. Secondary objectives were to assess the effect of Ginkgo biloba extract on neurological impairment and quality of life. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register (last searched October 2004), the Trials Register of the Cochrane Complementary Medicine Field (last searched October 2004) and the Chinese Stroke Trials Register (last searched June 2004). In addition, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2004), MEDLINE (1966 to August 2004), EMBASE (1980 to June 2004), AMED (1985 to May 2002) and the China Biological Medicine Database (CBM-disc, 1979 to August 2004). We searched relevant clinical trials and research registers and contacted pharmaceutical companies and researchers in an effort to identify further published and unpublished studies. SELECTION CRITERIA: Randomised controlled trials or quasi-randomised controlled clinical trials comparing Ginkgo biloba extract with placebo or open control (no placebo) in patients with acute ischaemic stroke. DATA COLLECTION AND ANALYSIS: Two reviewers independently selected trials for inclusion, assessed trial quality and extracted the data. MAIN RESULTS: Fourteen trials were identified, of which 10 trials (792 patients) were included. Four trials are awaiting assessment. In the 10 included trials follow up was performed at 14 to 35 days after stroke. In all studies neurological outcome was assessed but none of them reported on disability (activities of daily living function) or quality of life. Only three trials reported adverse events. In nine trials, all of them assessed to be of inferior quality, significant improvement in neurological deficit at the end of the treatment was used as the outcome measure. When analysing these trials together, Ginkgo biloba extract was associated with a significant increase in the number of improved patients (Peto odds ratio (OR) 2.66; 95% confidence interval (CI) 1.79 to 3.94). One placebo-controlled trial, assessed to be of good quality, reported neurological outcome as a continuous variable. It failed to show an improvement of neurological deficit at the end of treatment (weighted mean difference (fixed) 0.81; 95% CI -8.9 to 10.52). No deaths or major adverse events were reported during the follow-up period. AUTHORS' CONCLUSIONS: There was no convincing evidence from trials of sufficient methodological quality to support the routine use of Ginkgo biloba extract to promote recovery after stroke. High-quality and large-scale randomised controlled trials are needed to test its efficacy.

Ginkgo biloba↗

PubMed2005

Interaction between the bone morphogenetic proteins and Ras/MAP-kinase signalling pathways in lung cancer.

Bone morphogenetic proteins (BMPs) are an integral component of the TGFbeta superfamily, responsible for regulation of cell proliferation, differentiation, migration and programmed cell death in a variety of cell types. The BMPs transduce their signals directly through the SMAD family of proteins but they also have been reported to interact with the MAPK and Erk pathways. Inactivation of the BMP pathway genes has been implicated as important in several cancers. Recent work has shown that BMP3b is epigenetically inactivated in cancer and suggests that BMP6 can be epigenetically inactivated. We investigated whether BMP6 is epigenetically inactivated in cell lines and whether BMP3b and BMP6 are epigenetically inactivated in non-small-cell lung cancer (NSCLC). We also studied the relationship between BMP methylation and k-ras mutation. Here, we demonstrate that the BMP3b and BMP6 genes are common targets of epigenetic inactivation in NSCLC, and that they are significantly more likely to be concurrently inactivated (P=0.009). Furthermore, this coinactivation of BMP3b and BMP6 is significantly associated with mutation of k-ras codon 12 in lung cancer (P=0.003); those with a k-ras mutation were six times more likely to have concurrent methylation of these BMP loci. Hence, these data suggest that concurrent inactivation of the BMP and activation of the Ras signalling pathways are important in lung carcinogenesis.

Bone Morphogenetic Protein 3↗

PubMed2005

The rationale behind a vaccine based on multiple HIV antigens.

The viral diversity of HIV-1 is likely to require a vaccine strategy that induces broad cellular and humoral anti-HIV-1 immunity. Our strategy is based on multiple HIV-1 DNA immunogens together with adjuvant recombinant granulocyte-macrophage stimulating factor. This article describes pre-clinical and clinical work preceding the initiation of clinical HIV-1 phase I/II trials.

AIDS Vaccines↗

PubMed2005

Intrapallidal lipopolysaccharide injection increases iron and ferritin levels in glia of the rat substantia nigra and induces locomotor deficits.

Increasing evidence suggests that abnormal iron handling may be involved in the pathogenesis of Parkinson's disease. The present study investigates the role of iron and the iron-storage protein ferritin in inflammation-induced degeneration of dopaminergic neurons of the substantia nigra pars compacta. Injection of lipopolysaccharide into the globus pallidus of young and middle-aged rats substantially decreased tyrosine hydroxylase immunostaining in substantia nigra pars compacta four weeks after injection. Loss of tyrosine hydroxylase expression was accompanied by increased iron and ferritin levels in glial cells of the substantia nigra pars reticulata. Despite greater increases in nigral iron levels, ferritin induction was less pronounced in older rats, suggesting the regulation of ferritin was compromised with age. Automated movement tracking analyses showed that young rats recovered from LPS-induced locomotor deficits within four weeks, yet older rats failed to improve on measures of speed and total distance moved. Intrapallidal lipopolysaccharide injection also increased expression of alpha-synuclein and ubiquitin in tyrosine hydroxylase-positive neurons of the substantia nigra pars compacta. These results suggest that pallidal inflammation significantly increases stress on dopamine-containing neurons in the substantia nigra pars compacta. Alterations in nigral iron levels and protein handing may increase the vulnerability of nigral neurons to degenerative processes.

Aging↗

PubMed2005

HCHs and DDTs in sediment-dwelling animals from the Yangtze Estuary, China.

HCHs and DDTs in sediment-dwelling animals including mollusks and crabs from the Yangtze Estuary were determined by GC-ECD. Levels of t-HCH were in the range of 1.2-5.5 ng g(-1) and averaged 3.5 ng g(-1) in mollusks, while t-DDT concentrations ranged from 26.0 to 68.8 ng g(-1), with a mean of 34.5 ng g(-1). In crabs t-HCH concentrations varied from 2.0 to 25.7 ng g(-1) and averaged 13.8 ng g(-1), whereas the concentrations of t-DDT were in the range of 1.5-24.8 ng g(-1) with a mean value of 5.9 ng g(-1). The HCHs and DDTs levels depend on geographical position and sources, showing the high levels at fresh water area in the estuary, such as XP, CM and LHK sites, and lower at brackish water area, such as FX site, and little difference between species. Results also indicate there was no significant relationship between t-HCH (t-DDT) concentrations and lipid contents both in mollusks and crabs because of non-equilibrium state under a specific estuarine dynamics; smaller individuals accumulated more HCHs and DDTs than larger individuals of mollusks at LHK site, showing different uptake rate for these pesticides; moreover, HCHs and DDTs levels were lower in female crab bodies than male crab bodies suggesting that the release of spawning. BSAFs (Biota- Sediment Accumulation Factors) from sediment-dwelling animals for HCHs and DDTs show a significant "one high with two low" and "one low with two high" effect in the Yangtze Estuary.

Animals↗

PubMed2005

HCHs and DDTs in salt marsh plants (Scirpus) from the Yangtze estuary and nearby coastal areas, China.

HCHs and DDTs in salt marsh plants taken from intertidal flats in the Yangtze estuary and coastal area in April and July 2002 were determined by GC-ECD. A significant seasonal effect was observed for HCHs and DDTs in sources and concentration levels in different sample types including above-ground tissues and roots as well as the whole plants and rhizospheric sediments. The results indicated that the concentration of t-HCH was higher in the above-ground tissues than in their roots in April; however, the partitioning of DDTs between contaminated sediments and the roots showed the higher concentrations of t-DDT in their roots. HCHs and DDTs concentration levels were higher in above-ground tissues than in roots in July. BCFs of HCHs and DDTs exhibited lower values with higher levels of contaminants in sediments, and higher values with lower levels in sediments.

China↗

PubMed2005

Identification of a differential gene HUMMLC2B between F1 hybrids Landrace x Yorkshire and their female parents Yorkshire.

In order to investigate heterosis on a molecular basis, suppression subtractive hybridization was used to analyze the differences in gene expression between porcine F1 hybrids Landrace x Yorkshire and their female parents Yorkshire. From two specific subtractive cDNA libraries, the clones screened out by reverse Northern high-density blots screening were chosen to clone full-length cDNA by RACE. An expression-upregulated gene for Yorkshire skeletal muscle, designated as HUMMLC2B, was identified. Porcine HUMMLC2B contains an open reading frame (ORF) encoding 169 amino acids residues with 59 and 115 nucleotides in the 5' and 3' untranslated regions (UTRs), respectively. In the porcine genome, it contains seven exons separated by six introns. High allelic variations and four SINEs were detected in it. Comparison of derived amino acid sequence of HUMMLC2B with database sequences revealed highly conserved 12 amino acid residues in a putative calcium-binding region. RT-PCR analysis showed a tissue-specific pattern of expression in skeletal muscle and a similar level of expression during skeletal muscle development. The possible role of HUMMLC2B and its relation to porcine heterosis are discussed.

Amino Acid Sequence↗

PubMed2005

Facilitatory effect of Ins(1,4,5)P3 on store-operated Ca2+-permeable cation channels in rabbit portal vein myocytes.

In rabbit portal vein smooth muscle cells, store-operated Ca2+-permeable cation channels (SOCs) display multi-modal gating mechanisms. SOCs are activated by depletion of intracellular Ca2+ stores but also may be stimulated in a store-independent manner by noradrenaline acting on alpha-adrenoceptors and by diacylglycerol (DAG) via protein kinase C (PKC). In the present study we have investigated whether inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) modulates SOC activity in freshly dispersed rabbit portal vein myocytes with patch pipette recording techniques. Inclusion of 1 mum Ins(1,4,5)P3 in the patch pipette solution increased whole-cell currents evoked by the Ca2+-ATPase inhibitor cyclopiazonic acid (CPA) by about 3-fold at -80 mV. In the cell-attached configuration the cell-permeable Ca2+ chelator BAPTA-AM stimulated SOC activity and after excision of an isolated inside-out patch bath application of 1 mum Ins(1,4,5)P3 increased open channel probability (NP(o)) by approximately 3-fold. Ins(1,4,5)P3 also produced a similar increase in NP(o) of SOCs stimulated by the phorbol ester, phorbol 12,13-dibutyrate (PDBu) in inside-out patches and these channel currents had a unitary conductance of about 2 pS. The equilibrium constant of Ins(1,4,5)P3 on increasing PDBu-evoked SOC activity was about 0.4 mum. The facilitatory effect of Ins(1,4,5)P3 was also manifest as markedly increasing the rate of activation of SOCs. The synergistic effect of Ins(1,4,5)P3 was mimicked by the metabolically stable analogue 3-fluoro-Ins(1,4,5)P3 and Ins(1,4)P2, a metabolite of Ins(1,4,5)P3, but was not inhibited by the classical Ins(1,4,5)P3 receptor antagonist heparin. Finally Ins(1,4,5)P3 also increased NP(o) of SOCs activated by a PKC catalytic subunit. It is concluded that Ins(1,4,5)P3 facilitates SOC opening via a heparin-insensitive mechanism at, or close to, the channel protein.

Animals↗

PubMed2005

Acupuncture for acute stroke.

BACKGROUND: Acupuncture-like sensory stimulation activates multiple efferent (nerve) pathways leading to altered activity in numerous neural systems. Acupuncture is widely accepted by Chinese people and it is increasingly requested by patients and their relatives in Western countries. OBJECTIVES: To assess the effectiveness and safety of acupuncture in patients with acute stroke. SEARCH STRATEGY: We searched the Cochrane Stroke Group trials register (last searched August 2003), the Chinese Stroke Trials Register (August 2003) and the Chinese Acupuncture Trials Register (August 2003). Electronic searches were performed in the Cochrane Controlled Trials Register (The Cochrane Library, Issue 3, 2003), MEDLINE (1966 to 2003), EMBASE (1980 to 2003), Alternative Medicine Database (1985 to 2003), CINAHL (1982 to 2003) and the Chinese Biological Medicine Database (1981 to 2003). Reference lists of systematic reviews and identified trials were handsearched. SELECTION CRITERIA: Randomised and quasi-randomised trials of acupuncture started within 30 days of stroke onset, compared with placebo/sham acupuncture or open control in patients with acute ischaemic and/or haemorrhagic stroke. Needling into skin was required for acupuncture. DATA COLLECTION AND ANALYSIS: Two reviewers selected trials for inclusion, assessed trial quality, and extracted the data independently. Authors of trials were contacted for missing data. MAIN RESULTS: Fourteen trials involving 1208 patients were included. Ten trials included patients with only ischaemic stroke. When acupuncture was compared with sham acupuncture or open control, there was a borderline significant trend towards fewer patients being dead or dependent (Odds ratio (OR) 0.66, 95% confidence interval (CI) 0.43 to 0.99), and significantly fewer being dead or needing institutional care (OR 0.58, 95% CI 0.35 to 0.96) in the acupuncture group after three months or more. There was also a significant difference favouring acupuncture in the mean change of global neurological deficit score during the treatment period (standardized mean difference (SMD) 1.17, 95% CI 0.30 to 2.04). Comparison of acupuncture with sham acupuncture only showed a statistically significant difference on death or requiring institutional care (OR 0.49, 95% CI 0.25 to 0.96), but not on death or dependency (OR 0.67, 95% CI 0.40 to 1.12), or change of global neurological deficit score (SMD 0.01, 95% CI -0.55 to 0.57). Severe adverse events with acupuncture (dizziness, intolerable pain and infection of acupoints) were rare (6/386, 1.55%). AUTHORS' CONCLUSIONS: Acupuncture appeared to be safe but without clear evidence of benefit. The number of patients is too small to be certain whether acupuncture is effective for treatment of acute ischaemic or haemorrhagic stroke. Larger, methodologically-sound trials are required.

Acupuncture Therapy↗

PubMed2005

The Rho family of small GTPases: crucial regulators of skeletal myogenesis.

The Rho family of small GTPases is involved in a diverse array of cellular processes, including regulation of the actin cytoskeleton, cell polarity, microtubule dynamics, membrane transport pathways and transcription factor activity. Recent findings have implicated the Rho proteins as key regulators of the skeletal myogenic program; however, much controversy presently exists as to the precise role of these proteins in this process. This review examines the present controversial findings pertaining to the Rho family's regulation of skeletal myogenesis and extrapolates from both other differentiation systems and recently published data the possible mechanisms by which these proteins function in the myogenic cascade.

Animals↗

PubMed2005

Persistent shedding of viable SARS-CoV in urine and stool of SARS patients during the convalescent phase.

In order to further the present knowledge of the emerging severe acute respiratory syndrome-associated coronavirus (SARS-CoV), 486 different specimens from 54 patients with a clinical diagnosis of SARS were investigated for the presence of viral RNA, and 314 plasma specimens of 73 patients were examined for IgM and IgG antibodies specific against SARS-CoV using an indirect ELISA. Viral RNA was detectable in 28 of the 54 patients tested. Cumulative data showed that 67 of the 73 SARS patients demonstrated seroconversion by week 5 of illness. In contrast, only 1 of 278 healthy subjects enrolled in the study was found to be positive for the IgG antibody. Coexistence of viral RNA in plasma and specific antibodies was simultaneously observed over three consecutive weeks in two critical cases. In three convalescent patients in particular, cultivable SARS-CoV was detected in stool or urine specimens for longer than 4 weeks (29-36 days). These findings suggest that SARS-CoV may remain viable in the excretions of convalescent patients.

Adult↗

PubMed2005

Candidemia in pediatric outpatients receiving home total parenteral nutrition.

This is a cohort study of pediatric outpatients receiving total parenteral nutrition (TPN) and follow-up care in a Tennessee hospital between January and June 1999. The study was conducted following an increase in the incidence of candidemia. Of 13 children receiving home TPN, five had candidemia; three were due to Candida parapsilosis. Case patients were more likely to have an underlying hematologic disease (P = 0.02) as well as previous history of fungemia (P = 0.02). Two case patients had successive candidemia episodes 3 months apart; karyotypes and RAPD profiles of each patient's successive C. parapsilosis isolates were similar. Candida spp. were frequently detected in hand cultures from cohort members (four of 10) and family member caregivers (nine of 11); C parapsilosis was isolated from five caregivers. Our findings underscore the challenges of maintaining stringent infection control practices in the home health care setting and suggest the need for more intensive follow-up and coordination of home TPN therapy among pediatric patients.

Adolescent↗

PubMed2005

Cyclization of several linear penta- and heptapeptides with different metal ions studied by CD spectroscopy.

A cyclic pentapeptide c(Tyr-Leu-Ala-Gly-Pro) (I), which was isolated and identified from Pseudostellaria heterophylla medicinal herbs, and two cyclic heptapeptides, c(Gly-Tyr-Gly-Gly-Pro-Phe-Pro) (II) and c(Gly-Ile-Pro-Tyr-Ile-Ala-Ala) (III), which were isolated and identified from Stellaria yunnanensis Franch (M), were synthesized by using 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3 H)-one (DEPBT) as a coupling reagent in solution, and mediated by different metal ions, from their linear peptide precursors H-Tyr-Leu-Ala-Gly-Pro-OH (I-1) and H-Ala-Gly-Pro-Tyr-Leu-OH (I-2), H-Gly-Tyr-Gly-Gly-Pro-Phe-Pro-OH (II-1) and H-Gly-Ile-Pro-Tyr-Ile-Ala-Ala-OH (III-1), respectively. The results show that alkali metal ions can improve the cyclization yields and/or the cyclization rates of linear peptide precursors, such as Na(+) ion is favorable for the cyclization of linear pentapeptides and Cs(+) ion is favorable for the cyclization of linear heptapeptides, while some bivalent and trivalent metal ions, such as Mg(2+), Ca(2+), Zn(2+), Fe(2+), Ni(2+) and Cr(3+) reduced/inhibited both the cyclization yields and the cyclization rates of the linear peptide precursors. The circular dichroism spectra of I-1, II-1 and III-1 with different metal ions were studied to elucidate the changes in their secondary structures. It is shown that Cs(+) can induce and stabilize the type I beta-turn conformation in the linear heptapeptide II-1 and the type II beta-turn conformation in the linear heptapeptide III-1.

Circular Dichroism↗

PubMed2005

Phospholipase C-beta1 mediates alpha1-adrenergic receptor-stimulated activation of the sodium-hydrogen exchanger in Chinese hamster lung fibroblasts (CCL39).

The activation of the Na+-H+ exchanger 1 (NHE1) and extracellular-signal regulated kinase (ERK) phosphorylation in Chinese hamster lung fibroblasts (CCL39) was characterized in response to the specific alpha1-adrenergic agonist, phenylephrine (PE). Addition of 100 micromol PE/L increased the steady-state intracellular pH (pHi) by 0.16 +/- 0.03 pH units, as well as increasing the phosphorylation of ERK. The response of NHE1 to PE in CCL39 cells was determined by the use of specific antagonists. Use of 2 specific chemical inhibitors of phosphoinositide-specific phospholipase C (PLC) reduced the ability of PE to activate either the exchanger or ERK. Studies were conducted in PLCbeta-deficient cell lines derived from parental CCL39 cells. NHE1 activity in both mutant cell lines was increased in response to phorbal esters or lysophosphatidic acid, whereas the addition of PE only caused a minimal change in either pHi or ERK phosphorylation. These results, combined with reconstitution experiments with exogenously expressed PLCbeta1, PLCbeta2, or PLCbeta3, revealed that stimulation of NHE1 activity by PE in CCL39 cells is a PLCbeta1-coupled event. Furthermore, the data indicate that alpha1-adrenergic signaling of PLCbeta is upstream of ERK activation. These data demonstrate that PLCbeta1 is primarily involved in the activation of NHE1 in CCL39 fibroblasts.

Adrenergic alpha-1 Receptor Agonists↗