Biomedical subjects

C L Lu

Publications and source records attributed to C L Lu.

At least 37 records · Page 2Linked to original sources

PubMed2000

Preparation of recombinant human GDNF by baculovirus expression system and analysis of its biological activities.

Recombinant human glial cell line-derived neurotrophic factor (GDNF) has been expressed at high levels and produced in large quantities in baculovirus-infected Trichoplusia ni cells (Tn-5B1-4). The glycosylated protein was purified using immunoaffinity chromatography and gel filtration. Pure, recombinant human GDNF promoted the survival and morphological differentiation of embryonic dopaminergic neurons and enhanced axonal regeneration after sciatic nerve transection. Because recombinant bioactive human GDNF can be obtained in large quantities, and purified to near homogeneity, they are suitable for evaluation in animal models.

Animals↗

PubMed2000

Leu-enkephalin induced by IL-2 administration mediates analgesic effect of IL-2.

Interleukin-2 (IL-2) was found to have an analgesic effect in both central and peripheral nervous systems. This effect is related to opioid receptors and mediated mainly by IL-2 directly binding to opioid receptors. Using radioimmunoassay, the content of Leu-enkephalin (LEK) in some nuclei were measured at intervals after the injection of IL-2 into the lateral ventricle of rats. Levels of LEK increased in both paraventricular hypothalamic nucleus (PVN) and locus ceruleus (LOC) after IL-2 administration, suggesting that the analgesic effect of IL-2 is also related to the change of LEK in PVN and LOC induced by IL-2 administration.

Analgesics↗

PubMed2000

Human glial cell-line-derived neurotrophic factor: a structure-function analysis.

Glial cell-line-derived neurotrophic factor (GDNF) is a protein known to enhance the survival of dopaminergic and motor neurons. It has been shown to have therapeutic potential in the treatment of Parkinson's disease and other neurodegenerative diseases. GDNF gene was modified by deletion and insertion mutagenesis using PCR methods. The various mutants were all highly expressed in Escherichia coli. The recombinant proteins were purified and their survival-promoting activities were determined by motor neurons. The result showed that the C-terminus was critical for structure stability of GDNF, and the alpha-helix, finger1 and finger2 regions were involved in receptor binding, while the N-terminus was not essential for the biological functions of GDNF.

Animals↗

PubMed2000

Distal stomach appears essential in the regulation of gastrointestinal transit.

Stomach and small bowel both influence gastrointestinal motility. We studied which portion of the stomach was essential for the regulation of gastrointestinal movement and determined the role of vasoactive intestinal polypeptide in this regulation. The study subjects consisted of 45 controls, 46 patients after subtotal gastrectomy, and 13 patients after total gastrectomy for stomach cancer. Orocecal transit time was measured, using the hydrogen breath test, to represent gastrointestinal movement, while plasma vasoactive intestinal polypeptide level was simultaneously assessed. The orocecal transit times in the study groups were (means +/- SD) 91.1 +/- 45.0, 57.1 +/- 34.3, and 60.8 +/- 34.8 min, respectively (P < 0.01). In the subtotal gastrectomy patients, age showed a negative correlation with orocecal transit time (r = -0.388; P < 0.01). In the total gastrectomy patients, no particular demographic factor influenced orocecal transit. Plasma vasoactive intestinal polypeptide levels in the three groups were 20.7 +/- 10.8, 22.7 +/- 10.9, and 20.6 +/- 9.1 pg/ml, respectively (NS). We conclude that both types of gastrectomies enhanced gastrointestinal movement, showing a similar effect, and that the distal stomach plus pylorus are most likely to exert an important inhibitory mechanism in the regulation of this movement. Vasoactive intestinal polypeptide is not a major peptide mediating this regulation.

Aged↗

PubMed2000

Analgesic effect of interferon-alpha via mu opioid receptor in the rat.

Using the tail-flick induced by electro-stimulation as a pain marker, it was found that pain threshold (PT) was significantly increased after injecting interferon-alpha (IFN alpha) into the lateral ventricle of rats. This effect was dosage-dependent and abolished by monoclonal antibody (McAb) to IFN alpha. Naloxone could inhibit the analgesic effect of IFN alpha, suggesting that the analgesic effect of IFN alpha be related to the opioid receptors. Beta-funaltrexamine (beta-FNA), the mu specific receptor antagonist could completely block the analgesic effect of IFN alpha. The selective delta-opioid receptor antagonist, ICI174,864 and the kappa-opioid receptor antagonist, nor-BNI both failed to prevent the analgesic effect of IFN alpha. IFN alpha could significantly inhibit the production of the cAMP stimulated by forskolin in SK-N-SH cells expressing the mu-opioid receptor, not in NG108-15 cells expressing the delta-opioid receptor uniformly. The results obtained provide further evidence for opioid activity of IFN alpha and suggest that this effect is mediated by central opioid receptors of the mu subtype. The evidence is consistent with the hypothesis that multiple actions of cytokines, such as immunoregulatory and neuroregulatory effects, might be mediated by distinct domains of cytokines interacting with different receptors.

Analgesia↗

PubMed2000

Promotion of neurite outgrowth by protein kinase inhibitors and ganglioside GM1 in neuroblastoma cells involves MAP kinase ERK1/2.

To investigate mechanisms of neurite outgrowth, murine Neuro-2a neuroblastoma cells were exposed to ganglioside GM1 in the presence or absence of specific protein kinase inhibitors. Isoquinolinesulfonamide (H-89), an inhibitor of cyclic AMP dependent protein kinase A (PKA), and bisindolylmaleimide I (BIM), which inhibits protein kinase C, each stimulated neurite outgrowth in a dose-dependent manner in the absence of exogenous GM1. Minimally effective (threshold) concentrations of H-89 or BIM potentiated outgrowth when they were used in combination with GM1. To search for a shared component in the mechanisms of GM1, H-89 and BIM, phosphorylation of ERK1/2 was examined. Inhibition of the activation of extracellular signal regulated kinases (ERK1/2) by U0126, prevented neuritogenesis of Neuro-2a by all the three agents. Pretreatment of serum-depleted Neuro-2a cultures with GM1 or BIM enhanced ERK1/2 phosphorylation when the serum level was restored to 10%. In contrast, H-89 did not alter the serum-mediated response. In cells exposed to GM1 or BIM without additional serum, a transitory decrease in ERK phosphorylation occurred. These data suggest that GM1 influences two neuritogenic pathways, one modulated by PKC and the other regulated by PKA. Therefore, GM1 may have the potential to stimulate alternate pathways resulting in outgrowth.

Animals↗

PubMed2000

Effect of a calcium channel blocker and antispasmodic in diarrhoea-predominant irritable bowel syndrome.

BACKGROUND: Irritable bowel syndrome (IBS) is a colonic function disorder. Both pinaverlum bromide (a selective calcium channel blocker) and mebeverine (an antispasmodic) are reported to be effective in the long-term (12-16 weeks) treatment of IBS patients. Their efficacy in the short-term treatment of IBS patients and colonic transit time is unclear. Furthermore, substance P and neuropeptide Y have either excitatory or inhibitory effects on colonic motility. Whether the efficacy of both drugs is mediated through these neuropeptides remains unknown. METHODS AND RESULTS: A clinical trial was conducted with 91 patients with diarrhoea-predominant IBS. After basal measurement of the total colonic transit time, IBS patients were randomized to receive either pinaverlum bromide (50 mg, t.i.d.) or mebeverine (100 mg, t.i.d.) for 2 weeks. The symptomatic scores regarding defaecation, total colonic transit time and serum levels of substance P and neuropeptide Y were measured before and after treatments. The daily defaecation frequency was markedly decreased after treatment (pinaverlum bromide, 2.9+/-1.2 vs 2.0+/-1.0, P< 0.05; mebeverine, 2.7+/-1.1 vs 2.1+/-1.0, P< 0.05). The stool consistency became well formed after both treatments (P< 0.05). Both drugs similarly improved the global well-being in these IBS patients (pinaverlum bromide vs mebeverine 73.4 vs 71.8%, P> 0.05). The total colonic transit time was significantly prolonged only after pinaverlum bromide treatment (21.4+/-15.5 vs 30.8+/-14.8 h, P< 0.01). Neither substance P nor neuropeptide Y serum level was significantly changed after either treatments. CONCLUSION: Pinaverlum bromide and mebeverine have similar therapeutic efficacies on diarrhoea-predominant IBS patients. Prolonged colonic transit time may be one of the factors responsible for the efficacy of pinaverlum bromide on the IBS patients. Substance P and neuropeptideY appear less important in the pathogenesis of diarrhoea-predominant IBS.

Calcium Channel Blockers↗

PubMed2000

Effects of caffeine on gastrointestinal myoelectric activity and colonic spike activity in dogs.

BACKGROUND: Caffeine is known to produce various effects on the gastrointestinal tract. Few studies have, however, investigated the effects of caffeine on gastrointestinal myoelectric activity under physiologic conditions. The aims of this study were to investigate the effects of caffeine on colonic motility (spike activity) and gastric and jejunal slow waves in conscious dogs. METHODS: The study was performed in eight healthy female hound dogs (15-20 kg) in which one pair of electrodes was implanted on the serosa of the stomach, one pair on the proximal jejunum, and another pair on the ascending colon. The protocol consisted of a 60-min recording as base line and a 90-min recording after intravenous injection of saline, a low dose of caffeine (125 mg), or a high dose of caffeine (250 mg). RESULTS: In the colon there was a significant increase in the number of spike bursts per minute after the injection of both the low (6.69+/-1.27 versus 8.22+/-1.31, P < 0.05) and the high dose (4.38+/-1.23 versus 6.92+/-0.98, P < 0.05) of caffeine. The increase in the total energy of spikes per minute after the injection of the high dose of caffeine was significantly higher than that after the low dose of caffeine (41.2+/-14.6 versus 133.4+/-39.2, P < 0.05). The characteristics of the gastric and jejunal slow waves were, however, not affected by caffeine. CONCLUSION: Caffeine increases spike activity in the colon, and its effect may be dose-dependent. Gastric and jejunal slow waves are not affected by caffeine.

Animals↗

PubMed2000

The impact of chronic hepatitis B viral infection on gastrointestinal motility.

OBJECTIVES: Disturbed gastrointestinal (GI) motility probably exists in alcoholic cirrhotic patients; however, the influence of chronic hepatitis B virus (HBV) infection on GI motility remains unknown. The purpose of this prospective study was to determine the impact of chronic HBV infection on human GI transit, and to explore the possible patient factors modulating GI motility. METHODS: We used a non-invasive hydrogen breath test measuring the oro-caecal transit time (OCTT) to assess the GI motility in 45 asymptomatic HBV carriers, 26 patients with chronic hepatitis B, 23 patients with HBV-related liver cirrhosis, and 45 age- and sex-matched healthy volunteers. Their clinical symptoms and various blood parameters, such as platelet count, prothrombin time, etc. were recorded. Plasma substance P, nitrate/nitrite and endothelin-1 levels were also measured. RESULTS: The OCTTs in controls, HBV carriers, chronic hepatitis B and liver cirrhosis patients were (mean +/- SEM) 78.4 +/- 5.8, 80.9 +/- 4.2, 93.9 +/- 8.8 and 106.5 +/- 12.4 min, respectively. The OCTT was delayed in patients with HBV-related liver cirrhosis compared to that of controls (P=0.039). Among the cirrhotic patients, presentation with ascites delayed OCTT (145.7 +/- 27.2 versus 91.3 +/- 11.9 min, P=0.039). Neither Child- Pugh grade, portal hypertension, various blood parameters, plasma substance P, nitrate/nitrite or endothelin-1 levels had any influence on OCTT. CONCLUSIONS: HBV infection alone does not alter GI motility, whereas the patients with liver cirrhosis may have delayed GI motility. Ascites is most likely a factor responsible for the delayed GI transit among chronic HBV-infected subjects.

Aged↗

PubMed2000

Enhanced postprandial gastric myoelectrical activity after moderate-intensity exercise.

OBJECTIVE: The aim of this study was to investigate the change of postprandial gastric myoelectrical activity and its relation with vagal activity after exercise. METHODS: Nine subjects were studied in two sessions. In the control session, gastric myoelectrical activity was recorded using electrogastrography (EGG) for 30 min in the fasting state and 60 min after a test meal. In the exercise session, after the baseline recording of both the EGG and electrocardiogram (ECG), the subject was put on a cycle ergometer for exercise until reaching 50% of the maximum age-predicted heart rate for 10 min. The test meal was then given and the recording was resumed for 60 more minutes. Spectral analyses were performed on both the EGG and the heart rate variability derived from the ECG. RESULTS: The postprandial increment of the dominant power (p<0.05) and the percentage of the 2-4 cpm slow waves (p = 0.01) were significantly higher with exercise. The standard deviation of the postprandial dominant frequency was significantly decreased (more stable slow waves) with exercise (p<0.04). While cardiac vagal activity was significantly decreased after the meal, exercise did not significantly affect the postprandial change. CONCLUSIONS: Gastric slow waves become more regular, more stable, and of higher amplitude after exercise, and this enhancement is probably not mediated via the vagal pathway.

Eating↗

PubMed2000

Delayed liquid gastric emptying in patients with hepatocellular carcinoma.

OBJECTIVE: Liver cirrhotic patients sometimes have disturbed gastric emptying (GE). Apparently there is no study addressing the issue of whether patients with hepatocellular carcinoma (HCC) have similarly impaired GE. Using impedance tomography to measure liquid GE, we attempted to assess the characteristics of GE in HCC patients. METHODS: We enrolled 34 healthy controls and 45 HCC patients in the current study, and compared their GE according to certain defined criteria. After each subject drank 500 ml of water, 12 electrodes were placed in a circular array around the subject's upper abdomen. One pair of electrodes was applied with electrical current, and the remaining 10 electrodes recorded signals consecutively in a rotating order. Based on tomographic calculation, serial changes in the averaged signals of altered resistivities were constructed to display liquid GE. Meanwhile, the demographic and clinical data, various blood parameters, and gut peptide levels of the patients were recorded. RESULTS: The half-emptying times in controls and HCC patients were 15.14 +/- 1.56 and 21.38 +/- 1.84 min, respectively (p < 0.05), whereas the areas under the emptying curve were 1732.2 +/- 106.4 and 2246.6 +/- 109.8 arbitrary units, respectively (p < 0.05). Delayed GE was observed in the HCC patients, as demonstrated by vomiting and anorexia. The cirrhotic component in HCC patients only resulted in a shorter period needed for full distention of the stomach after drinking (4.33 +/- 1.02 vs 8.78 +/- 2.1 min; p < 0.05). Other characteristics, including demographics, clinical state, tumor size, ascites, blood parameters, and gut peptides, had no influence on GE. CONCLUSIONS: Liquid GE is inhibited in HCC patients, particularly in those mainly showing symptoms of vomiting and anorexia. Other demographic and tumor characteristics are not responsible for delayed liquid GE; however, the cirrhotic component may promote stomach distention.

Carcinoma, Hepatocellular↗

PubMed2000

Interleukin-2: structural and biological relatedness to opioid peptides.

Interleukin (IL)-2 is not only an immunoregulatory factor, but also an analgesic molecule. There are distinct domains of immune and analgesic functions in the IL-2 molecule. The analgesic domain is located around the 45th Tyr residue of human IL-2 in tertiary structure. Antiopioid (beta-endorphin, Leu-enkephalin, Met-enkephalin and dynorphin A1-13) sera partially neutralized the analgesic activity of IL-2. Monoclonal antibody against the IL-2 receptor alpha subunit (Tac) could not block the analgesic activity of IL-2. There existed cross-reactivity between IL-2 and antiopioid sera by indirect ELISA. These studies show strong structural and biological similarities between IL-2 and opioid peptides. The tertiary structure around the 45th residue of IL-2 composes the analgesic domain that is similar to that of endogenous opioids. These results are consistent with the hypothesis that multiple domains of cytokines serve as the structural bases for the immunoregulatory and neuroregulatory effects of cytokines.

Analgesics↗

PubMed2000

Clinical, virologic and pathologic significance of elevated serum gamma-glutamyl transpeptidase in patients with chronic hepatitis C.

BACKGROUND: Elevated serum gamma-glutamyl transpeptidase (GGT) is often seen in patients with chronic hepatitis C virus (HCV) infection and is associated with a poor response to interferon treatment. The pathogenesis of these phenomena is unclear. Therefore, we assessed the prevalence of elevated serum GGT in Chinese patients with chronic hepatitis C and evaluated the clinical, biochemical, virologic and histologic features of this phenomenon. METHODS: One hundred and twelve patients with biopsy-proven chronic hepatitis C were enrolled. Patients who were habitual alcohol drinkers, alcoholics or had diabetes mellitus were excluded. RESULTS: Forty-three (38.4%) of 112 patients had elevated serum GGT (> 60 U/l). Patients with elevated serum GGT had significantly higher serum levels of alanine and aspartate aminotransferases, alkaline phosphatase and total bilirubin, significantly higher histologic scores of liver lobular necro-inflammation and fibrosis when compared to patients with normal serum GGT. Elevated serum GGT was not correlated to serum HCV RNA titer or HCV genotype. Multivariate logistic regression analysis showed that a histologic fibrotic score > or = 2 was the only significantly independent predictor associated with elevated serum GGT. Fifty-seven of 112 patients completed a six-month course of interferon treatment. Patients with elevated serum GGT had a significantly lower sustained response rate to interferon when compared to patients with normal serum GGT (8% vs 30%, p = 0.042). CONCLUSIONS: Elevated serum GGT in chronic hepatitis C patients was frequently associated with more severe hepatic fibrosis or cirrhosis and may, in part, account for poor response to interferon therapy.

Adult↗

PubMed2000

[Expression of human GDNF in methyltrophic yeast Pichia pastoris and silkworm larvae].

The cDNA encoding glial cell derived neurotrophic factor (GDNF) was cloned into the Pichia expression vector pPIC9K and then transformed into his4 mutant yeast GS115 by electroporation. Multicopy transformants were screened by various G418 concentrations and induced by methanol. The human GDNF gene was cloned into the baculovirus transfer vector pBacPAK8. The recombinant transfer vector pBacPAK-GDNF was coinfected with linear Bm-BacPAK6 DNA into BmN cells. The recombinant virus was screened and plaque-purified. The silkworm larvae were infected with the recombinant virus and collected 5 days later. SDS-PAGE and Western blot confirmed that GDNF was expressed in Pichia culture medium and silkworm larvae hemolymph. The GDNF protein expressed in Pichia and silkworm larvae could significantly promote the survival and neurite outgrowth of dopaminergic neurons.

Animals↗

PubMed2000

[Pituitary adenylate cyclase activating polypeptide ameliorates the damage and inhibits the increase of intracellular calcium concentration in cultured hippocampal neurons induced by glutamate].

Hippocampal neurons cultured from 7 to 9 d in vitro were used to observe the effect of glutamate. Treatment of glutamate for 24 h greatly decreased neuronal survival and pretreatment with pituitary adenylate cyclase activating polypeptide (PACAP) significantly attenuated hippocampal neuron death induced by glutamate. Moreover, glutamate dose-dependently increased the intracellular calcium concentration in cultured hippocampal neurons, while PACAP inhibited the increase of intracellular calcium concentration induced by glutamate. PACAP 6-38, a specific PACAP type I receptor antagonist, completely inhibited the amelioration of glutamate induced death and the decrease of intracellular calcium concentration induced by PACAP in cultured hippocampal neurons. The data suggest that PACAP has a neuroprotective effect on the hippocampal neuronal damage induced by glutamate, which is related to an inhibition of glutamate-induced increase of intracellular calcium concentration and mediated by PACAP type I receptor.

Animals↗

PubMed2000

[Protective effect of exogenous glial cell line derived neurotrophic factor on neurons after sciatic nerve injury in rats].

The aim of the study was to investigate the effect of exogenous glial cell line derived neurotrophic factor (GDNF) on spinal cord neurons after sciatic nerve axotomy. Upon silicone tubulization of transected sciatic nerve in the adult rat, either 0.9% saline or GDNF solution was injected into the silicone chamber. It was observed by Nissl and enzyme histochemistry staining that exogenous GDNF decreased lesion induced motor neuron death in lateral nucleus of spinal anterior horn and the changes in activity of cholinesterase and acid phosphatase in spinal cord and sensory ganglions. These results suggest that exogenous GDNF is capable of protecting motor neurons from death induced by peripheral nerve injury.

Animals↗

PubMed2000

[Distinct structural bases of the immunoregulatory and central analgesic effects of IFNalpha].

Interferon-alpha (IFNalpha), a cytokine, is also an analgesic molecule. There is significant cross reactivity between IFNalpha and anti-opioid sera, suggesting a strong antigenic relatedness between human IFNalpha molecules and opioid peptides. Different structural basis of the immunoactivity and analgesic effect of IFNalpha can be demonstrated by different reactivities of the two reactions towards different mutants of IFNalpha obtained by using the site-directed mutagenesis. When the 129th Tyr residue of human IFNalpha was mutated to Ser, the immunoactivity of the mutant almost disappeared, while the strong analgesic activity still persisted, which could be blocked by naloxone. These results indicate that there exist distinct domains in the IFNalpha molecule, which mediate immune and analgesic effects differentially, and that the receptor mechanism underlying immune and analgesic effects of IFNalpha may be different.

Adjuvants, Immunologic↗

PubMed2000

[Effects of GDNF on primary culture of spinal cord neurons].

The effect of GDNF on long-term cultured spinal cord neurons was studied. GDNF could promote spinal cord neurons survival after 7 d or 14 d culture by MTT assay. The effect of GDNF on growth cones, neuron soma magnitude, neurite length and spines formulation of spinal cord neurons in cell culture was observed by phase microscopy, Nissl stain and NSE immunocytochemistry stain. The results indicated that GDNF had significant trophic effects on long-term cultured spinal cord neurons.

Animals↗