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R H Liu

Publications and source records attributed to R H Liu.

At least 19 recordsLinked to original sources
PubMed2002

Early events involved in the development of insulin resistance in Zucker fatty rat.

AIM: To clarify the mechanism by which insulin resistance develops in obesity, Zucker fatty rats (ZFR) and lean litter mates (ZLR) were temporally subjected to oral glucose tolerance tests (OGTT) at 6 and 15 weeks of age. METHOD: As candidates for causative factors of insulin resistance, plasma leptin, free fatty acids (FFA) and tumor necrosis factor (TNF)-alpha levels were evaluated. RESULTS: There was no difference in the body weight between the two groups at 6 weeks of age, but ZFR were significantly heavier than ZLR at 15 weeks of age. At 6 weeks of age, blood glucose levels and area under the curve of glucose (AUCg) during OGTT were not significantly different between the two groups, while plasma insulin levels and area under the curve of insulin (AUCi) in the ZFR group were significantly higher than those in the ZLR group. At 15 weeks of age, the blood glucose levels and AUCg as well as plasma insulin levels and AUCi in the ZFR group during OGTT were significantly higher than those in the ZLR group. The ratio of fasting insulin to glucose in the ZFR group was significantly higher than that in the ZLR group at 6 and 15 weeks of age. Peripheral and portal plasma leptin and FFA levels were significantly higher in ZFR than ZLR both at 6 weeks and 15 weeks of age. Meanwhile, at 6 weeks, plasma TNF-alpha levels and expression of TNF-alpha protein in subcutaneous and visceral fat tissues were similar in both groups; however at 15 weeks, these were significantly higher in the ZFR group than the ZLR group. CONCLUSION: These results suggest that FFA rather than TNF-alpha may play an important role in early events involved in the development of insulin resistance and TNF-alpha accelerates insulin resistance together with FFA in the later stage.

Adipose Tissue↗
PubMed2002

The enrichment of a ruminal bacterium (Megasphaera elsdenii YJ-4) that produces the trans-10, cis-12 isomer of conjugated linoleic acid.

AIMS: To isolate predominant ruminal bacteria that produce trans-10, cis-12 conjugated linoleic acid (CLA) from linoleic acid (LA). METHODS AND RESULTS: Mixed bacteria from ruminal contents of a cow fed grain were enriched with DL-lactate and trypticase. They produced more trans-10, cis-12 CLA than those that were not enriched (7 vs 2 microg mg protein(-1), P < 0.05). Enrichments had an abundance of large cocci that produced trans-10, cis-12 CLA from LA. Strain YJ-4 produced the most trans-10, cis-12 CLA (approx. 7 microg mg protein(-1)) and 16S rDNA sequencing indicated that YJ-4 was a strain of Megasphaera elsdenii. Megasphaera elsdenii T81 produced approx. 4 microg trans-10, cis-12 CLA mg protein(-1) while strains B159, AW106 and JL1 produced < 0.5 microg mg protein(-1). The trans-10, cis-12 CLA production of YJ-4 was first order with respect to cell concentration (0-800 microg protein ml(-1)), but kinetics were not first order with respect to substrate concentration. CONCLUSIONS: Some M. elsdenii strains produce significant amounts of trans-10, cis-12 CLA. SIGNIFICANCE AND IMPACT OF THE STUDY: Trans-10, cis-12 CLA appears to cause milk fat depression in cattle fed diets supplemented with grain and polyunsaturated fatty acids, but predominant ruminal bacteria that produced trans-10, cis-12 CLA from LA had not previously been isolated.

Animals↗
PubMed2001

Isotopic analogs as internal standards for quantitative analyses by GC/MS--evaluation of cross-contribution to ions designated for the analyte and the isotopic internal standard.

Isotopic analogs of the analytes are currently preferred internal standards (IS) for quantitative analyses of drugs and their metabolites in biological matrices by GC/MS procedures. Contributions of the analyte and the IS to the intensities of ions designated for the IS and the analyte, respectively--an undesirable phenomenon termed "cross-contribution"--greatly weakens the effectiveness of this approach. The cross-contribution phenomenon has been, in the past, evaluated by a "direct measurement" approach, in which intensities of interested ions were measured in two separate experiments using equal quantities of the analyte and the IS. Alternate procedures that may generate improved results are hereby studied. For the "improved direct measurement" approach, ion intensity data derived from the previously reported direct measurement procedure are first normalized before being used to calculate the extent of cross-contribution. An "internal standard" approach is also developed, in which a set amount of a third compound is incorporated into these two separate experiments, thus allowing corrections of ion intensity data that are imbedded with variations inherent to separate experiments. Finally, a "standard addition" approach, involving a series "addition" of "standards", generates multiple data points; thus, providing a mechanism to validate the resulting cross-contribution data. Secobarbital/(2)H(5)-secobarbital and secobarbital/(13)C(4)-secobarbital pairs are adapted as the exemplar systems for this study.

Gas Chromatography-Mass Spectrometry↗
PubMed2001

Spectra interference between diquat and paraquat by second derivative spectrophotometry.

A rapid and accurate method, combining solid-phase extraction and second-order derivative spectrophotomety approaches, is developed for the simultaneous determination of diquat (DQ) and paraquat (PQ) in blood, tissue and urine samples. Supernatant resulting from the precipitation of protein (with trichloroacetic acid) in plasma and tissue or Amberlite IRA-401 resin treated urine are passed through a mini-column packed with Wakogel gel (Silica gel). Analytes are then eluted with a non-organic solvent, 0.2mol/l HCl solution containing 2mol/l NH(4)Cl. UV spectrum of the eluent in 220-350nm range provides effective screen to detect the presence of DQ and/or PQ. In the presence of DQ or PQ alone, the analyte present is quantitated by conventional zero- or second-order derivative spectrophotometry. The calibration curve in the 0.1-5.0mg/l range for either analyte obeys Beer's law. When both DQ and PQ are present, their concentrations are determined by the peak amplitudes of their respective second-derivative spectra after the addition of alkaline dithionite reagent. Interference is negligible when the DQ/PQ concentration ratio is within the 5.0-0.2 range. Using a 2-ml of sample size, the detection limits for DQ and PQ in plasma are 0.02 and 0.005mg/l. The corresponding detection limits for urine samples (10ml sample size) are 0.004 and 0.001mg/l. Recoveries of DQ and PQ in triplicate plasma and urine samples spiked with 0.5mg/l of analytes are 93 and 85%. The precision of the proposed method resulting from triplicate study of spiked urine samples varies from 3.2 to 4.6% at 0.5mg/l of DQ and PQ, respectively.

Diquat↗
PubMed2001

Oral nicotine administration decreases tumor necrosis factor-alpha expression in fat tissues in obese rats.

To investigate the effect of oral nicotine administration on insulin resistance and insulin secretion in an animal model of obesity, Zucker fatty rats were administered nicotine tartrate dihydrate orally through tap water (4.6 mg/kg/d, N group). Plasma nicotine concentrations in N group were 33.67 +/- 10.49 ng/mL. The control (C) group consisted of pair-fed control rats. After 8 weeks of nicotine administration, both groups of rats were administered glucose (2 g/kg) orally in an anesthetized state, and blood was collected for glucose and plasma insulin measurements. The pancreases were isolated and perfused in vitro under pentobarbital anesthesia 1 week after glucose administration. The fat tissues were excised. The levels of tumor necrosis factor (TNF)-alpha protein were assessed using enzyme-linked immunosorbent assay (ELISA) or Western blot analysis. Serum leptin levels were measured using radioimmunoassay (RIA). Blood glucose levels in N group were significantly lower than in C group before and 120 minutes after glucose administration. The insulin secretion from the isolated perfused pancreases of N group appeared to be decreased compared with C group, but there was no significant difference. Histologic examination showed that the mean size of the pancreatic islets in N group was significantly smaller than in C group. The composition ratios of alpha and beta cell mass of the pancreatic islets and fibroelastic tissues were not altered by nicotine administration. Portal TNF-alpha levels were comparable to peripheral levels in both groups. There were no significant differences in peripheral serum levels of TNF-alpha, free fatty acids (FFA), or leptin levels between N and C group. The TNF-alpha levels in visceral fat tissues in N group were significantly lower than those in C group. These results suggest that oral nicotine administration reduces insulin resistance in obese diabetic rats by decreasing production of TNF-alpha in the visceral fat tissues. Decreased islet size may be a secondary phenomenon induced by ameliorated insulin resistance, because the cellularity and fibroelastic tissues were not affected by the nicotine.

Adipocytes↗
PubMed2001

Isotopic analogues as internal standards for quantitative analyses of drugs and metabolites by GC-MS--nonlinear calibration approaches.

In order to achieve accurate quantitation of drugs and metabolites (analytes) in complex matrices, 2H- (and less commonly 13C-) labeled analogues of the analytes are now routinely adapted as the internal standards (IS) using linear calibration models to fit data generated by selected ion monitoring gas chromatography-mass spectrometry (GC-MS) protocols. In this study, the effects of cross-contribution (contribution of the IS to the intensity of the ion designated for the analyte and vice versa) on the linearity of the calibration data are examined. Nonlinear approaches that may address this problem are also studied. Two ion pairs (one with least and one with significant cross-contribution) from each of the following analyte/IS pairs are used as the exemplar systems for this study: butalbital/13C4-butalbital, butalbital/2H5-butalbital, secobarbital/13C4-secobarbital, and secobarbital/2H5-secobarbital. Analyte/IS ion intensity ratios of a series of standard solutions are correlated with the analyte/IS concentration ratios using one-point, multiple-point (unweighted and weighted) linear, and hyperbolic functions. The one-point calibration approach produces excellent calibration results in treating data derived from ion pairs with no significant cross contribution. In cases where significant cross-contribution exists, results derived from the one-point approach show, as expected, significant deviations at both ends of the concentration range. With the cross-contribution phenomenon accounted for, the hyperbolic calibration model is clearly more effective in fitting calibration data at both the lower and higher analyte concentration ends, thus significantly lowering the detection limit and extending the calibration range to a higher level. However, the calibration range cannot be extended indefinitely. At the low concentration end, noise-to-signal ratio and the cross-contribution of the IS to the intensity of the ion designated for the analyte, however insignificant, will incrementally reduce the quality of the observed ion intensity and intensity ratio data. At the high concentration end, detection saturation and the cross-contribution of the analyte to the intensity of the ion designated for the IS, however insignificant, will incrementally decrease the "slope" of the calibration curve. Thus, acceptable sensitivity (increase in analyte/IS ion-pair intensity ratio per unit increase in analyte concentration) of the calibration curve will become the limiting factor.

Algorithms↗
PubMed2001

Animal experiment and clinical study of effect of gamma-interferon on hepatic fibrosis.

AIM: To evaluate the antifibrotic effect of different doses of recombinant human Gamma-Interferon (IFN-gamma) in two rat models of hepatic fibrosis, and to observe its effect on moderate chronic hepatitis B virus fibrosis. METHODS: Hepatic fibrosis was successfully induced in 150 and 196 rats by subcutaneous injection of carbon tetrachloride (CCl4) and intraperitoneal injection of dimethylnitrosamine (DMN), respectively. Each of the two model groups was divided into: (1) fibrotic model group; (2) colchicine treatment group (0.1 mg/kg/day, gastrogavage for 8 weeks); (3) high-dose IFN-gamma group (15 MU/kg per day, i.m. for 8 weeks); (4) medium-dose IFN-gamma group (5 MU/kg daily, i.m. for 8 weeks); and (5) Y low-dose IFN-gamma group (1.67 MU/kg daily, i.m. for 8 weeks). Another group of 10 rats without any treatment was used as normal controls. At the end of the experiment, semi-quantitative histopathological scores of inflammation and fibrosis, liver alpha smooth muscle actin (alpha-SMA) expression level, liver hydroxyl proline content and serum hyaluronic acid levels were compared. And 47 medium chronic hepatitis B viral fibrosis patients were studied. They were given IFN-gamma treatment, 100 MU/day i.m. for the first three months and 100 MU qod i.m. for the next six months. Semi-quantitative pathological scores of inflammation and fibrosis and serum hepatic fibrosis indices were compared within the 9 months. RESULTS: In animal experiment, the pathological fibrosis scores and liver hydroxyl proline content were found to be significantly lower in rats treated with different doses of IFN-gamma as compared with rats in fibrotic model group induced by either CCl4 or DMN, in a dose-dependent manner. For CCl4-induced model, pathological fibrosis scores in high, medium and low doses IFN-gamma groups were 5.10 +/- 2.88, 7.70 +/- 3.53 and 8.00 +/- 3.30, respectively, but the score was 14.60 +/- 7.82 in fibrotic model group. Hydroxyl proline contents were 2.83 +/- 1.18, 3.59 +/- 1.22 and 4.80 +/- 1.62, in the three IFN-gamma groups, and 10.01 +/- 3.23 in fibrotic model group. The difference was statistically significant (P<0.01). Similar results were found in DMN-induced model. Pathological fibrosis scores were 6.30 +/- 0.48, 8.10 +/- 2.72 and 8.30 +/- 2.58, in high, medium and low doses IFN-gamma groups, and 12.60 +/- 3.57 in fibrotic model group. Hydroxyl proline contents were 2.72 +/- 0.58, 3.14 +/- 0.71 and 3.62 +/- 1.02, in the three IFN-gamma groups, and 12.79 +/- 1.54 in fibrotic model group. The difference was statistically significant (P<0.01). Serum hepatic fibrosis indices decreased significantly in the 47 patients after IFN-gamma treatment (HA: 433.38 +/- 373.00 vs 281.57 +/- 220.48; LN: 161.22 +/- 41.02 vs 146 +/- 35 +/- 44. 67; PC III: 192.59 +/- 89.95 vs 156.98 +/- 49.22; C-I: 156.30 +/- 44.01 vs 139.14 +/- 34.47) and the differences between the four indices were significant (P <0.05). Thirty-three patients received two liver biopsies, one before and one after IFN-gamma treatment. In thirty of 33 patients IFN-gamma had better effects according to semi-quantitative pathological scores (8.40 +/- 5.83 vs 5.30 +/- 4.05, P<0.05). CONCLUSION: All the three doses of IFN-gamma are effective in treating rat liver fibrosis induced by either CCl4 or DMN, the higher the dose, the better the effect. And IFN-gamma is effective for patients with moderate chronic hepatitis B viral fibrosis.

Animals↗
PubMed2001

[Studies on synthesis and degradation of collagen at transcription level in liver fibrosis of rabbits with schistosomiasis japonica].

OBJECTIVE: To study the synthesis and degradation of collagen at the transcription level during liver fibrosis in rabbits with schistosomiasis japonica. METHODS: New Zealand rabbits infected with Schistosoma japonicum cercariae were served as animal models of liver fibrosis. The liver specimens were collected through operations at 4, 6, 8, 10, 12, 16, 20, 24 and 28 weeks after infection. Type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels of liver tissue were detected by RT-PCR plus dot blotting, and the size of egg granulomas and the degree of liver fibrosis were measured by histopathological examinations. RESULTS: Type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels increased simultaneously in the early stage after the infection, mostly reaching their peaks at 10 weeks after infection. Compared with normal controls, type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels increased by 12.0-, 11.0-, 6.6-, 10.0- and 11.0-fold, respectively, coinciding with the changes of egg granulomas. Thereafter, both collagen and collagenase mRNA levels decreased. Types I, III and IV collagen mRNA levels declined to 2-fold to 3-fold compared with normal controls (P < 0.05), while MMP-1 and MMP-9 mRNA levels declined to normal level (P > 0.05) at 28 weeks. This study showed that the synthesis and degradation of collagen remained dynamic balance in the early stage of schistosomiasis, while in the later stage the metabolism of collagen synthesis was higher than that of collagen degradation. CONCLUSION: It was confirmed at the transcription level that when the metabolism of collagen synthesis was higher than that of collagen degradation in rabbits with schistosomiasis japonica, liver fibrosis might be produced.

Animals↗
PubMed2000

Microfluidic tectonics: a comprehensive construction platform for microfluidic systems.

A microfluidic platform for the construction of microscale components and autonomous systems is presented. The platform combines liquid-phase photopolymerization, lithography, and laminar flow to allow the creation of complex and autonomous microfluidic systems. The fabrication of channels, actuators, valves, sensors, and systems is demonstrated. Construction times can be as short as 10 min, providing ultrarapid prototyping of microfluidic systems.

Journal Article↗
PubMed2000

[Effects on ang II receptor antagonist on experimental glomerulosclerosis].

OBJECTIVE: To observe the effects of angiotensin II receptor antagonist losartan in experimental glomerulosclerosis. METHODS: The 5/6 nephrectomized rats were randomly divided into losartan treatment group and control group, the rats with sham operation served as normal control. Urine proteins were measured in the 2nd, 4th and 6th week after operation, and serum BUN, creatinine, total protein and albumin were measured in the 6th week following operation. Renal pathologic changes were evaluated in the 6th week. RESULTS: Losartan not only reduced urine protein, serum creatinine and BUN(P < 0.01), but also significantly ameliorated glomerular mesangial proliferation and glomerular sclerosis. CONCLUSION: The results suggest that losartan can retard progression of glomerulosclerosis in 5/6 nephrectomized rats.

Angiotensin Receptor Antagonists↗
PubMed2000

trans-10,cis-12-conjugated linoleic acid isomer exhibits stronger oxyradical scavenging capacity than cis-9,trans-11-conjugated linoleic acid isomer.

Although studies have been performed to test whether conjugated linoleic acid (CLA) acts as an antioxidant, the results were not conclusive. In addition, the CLA widely used in previous research contains 43% cis-9,trans-11 isomer, 45% trans-10,cis-12 isomer, and 10 other minor isomers. The objective of this study was to investigate the antioxidant activity of cis-9,trans-11- and trans-10, cis-12-CLA isomers using high-purity CLA isomers (>98%) by total oxyradical scavenging capacity assay (Winston, G. W.; Regoli, F.; Dugas, Jr., A. J.; Fong, J. H.; Blanchard, K. A. Free Radical Biol. Med. 1998, 24, 480-493). At all concentrations (2-200 microM), t10, c12-CLA performed as an antioxidant with a 15-min lag phase, which was more effective than c9,t11-CLA and alpha-tocopherol at lower concentrations (2 and 20 microM). On the other hand, c9,t11-CLA possessed weak antioxidant activity at 2 and 20 microM, whereas at 200 microM it acted as a strong pro-oxidant, which suggests that discrepancies of the results of the previous studies on the antioxidant properties of CLA may be due to the balance of the antioxidant properties of t10,c12-CLA and the pro-oxidant properties of c9,t11-CLA in different oxidation conditions.

Antioxidants↗
PubMed2000

Nephrotoxicity of high- and low-osmolar contrast media. The protective role of amlodipine in a rat model.

PURPOSE: To evaluate the nephrotoxicity of high- and low-osmolar contrast media (HOCM, LOCM) on kidneys in Sprague-Dawley rats. The protective role of amlodipine was studied. MATERIAL AND METHODS: Forty rats of both sexes were randomly divided into 5 groups (n=8/group) and glycerine for inducing renal failure was given to all rats except controls. RESULTS: In diatrizoate-injected rats, blood urea nitrogen (BUN) and serum creatinine (SCr) were increased; levels of phospholipase A2 (PLA2), lipid peroxide (LPO) and calcium were also increased in renal tissues. There was no significant difference between LOCM (iohexol) animals and glycerol controls either in the renal levels of PLA2, LPO and calcium or in the levels of BUN and SCr. The histologic changes were milder in the LOCM animals than in the HOCM animals. In the group pretreated with amlodipine, no increase in the levels of BUN or SCr was discovered and the renal content of PLA2, LPO and calcium were significantly lower than in the HOCM group; the renal injuries induced by diatrizoate were alleviated. CONCLUSION: The HOCM, diatrizoate, was more toxic to rat kidneys than the LOCM iohexol; PLA2, LPO and calcium load played a role in producing renal function impairment induced by diatrizoate meglumine; amlodipine protected the renal tissue from nephrotoxicity induced by diatrizoate.

Acute Kidney Injury↗
PubMed2000

Effect of linoleic acid concentration on conjugated linoleic acid production by Butyrivibrio fibrisolvens A38.

Butyrivibrio fibrisolvens A38 inocula were inhibited by as little as 15 microM linoleic acid (LA), but growing cultures tolerated 10-fold more LA before growth was inhibited. Growing cultures did not produce significant amounts of cis-9, trans-11 conjugated linoleic acid (CLA) until the LA concentration was high enough to inhibit biohydrogenation, growth was inhibited, and lysis was enhanced. Washed-cell suspensions that were incubated anaerobically with 350 microM LA converted most of the LA to hydrogenated products, and little CLA was detected. When the washed-cell suspensions were incubated aerobically, biohydrogenation was inhibited, CLA production was at least twofold greater, and CLA persisted. The LA isomerase reaction was very rapid, but the LA isomerase did not recycle like a normal enzyme to catalyze more substrate. Cells that were preincubated with CLA lost their ability to produce more CLA from LA, and the CLA accumulation was directly proportional (r(2) = 0.98) to the initial cell density. Growing cells were as sensitive to CLA as LA, the LA isomerase and reductases of biohydrogenation were linked, and free CLA was not released. Because growing cultures of B. fibrisolvens A38 did not produce significant amounts of CLA until the LA concentration was high, biohydrogenation was arrested, and the cell density had declined, the flow of CLA from the rumen may be due to LA-dependent bacterial inactivation, death, or lysis.

Animals↗
PubMed2000

[Modulation of prolactin (PRL) secretion in human uterine decidual cells at early pregnancy].

Decidualization is essential for implantation of embryo and maintenance of pregnancy in human. The mechanism of decidualization was investigated in this study by regulation of prolactin (PRL) release in cultured human decidual cells during first trimester of gestation. Progesterone significantly stimulated PRL secretion, but the effect of estrogen depended on its concentration, which was ineffective at the physiological level (10( 9) mol/L) but suppressed the stimulatory effect of progesterone at higher levels. Thus adequate proportion of estrogen and progesterone is important for the decidualization. Furthermore, RU486 dramatically inhibited PRL release, suggesting that the effect of progesterone was mediated, at least in part, through its receptor. cAMP at concentration higher than 10( 5) mol/L significantly increased PRL secretion, suggesting that the cAMP signal pathway might be involved in decidualization.

Cells, Cultured↗
PubMed1999

Mitogen and substrate differentially affect the lineage restriction of adult rat subventricular zone neural precursor cell populations.

The effects of specific mitogens and substrates on the proliferative capacity and the differentiated phenotypic plasticity of neural precursor cell populations isolated from the adult rat subventricular zone (SVZ) were examined. SVZ cells were grown on uncoated tissue culture plastic, extracellular matrix, or poly-D-ornithine with either laminin or fibronectin. SVZ neural precursor cells could not be generated with platelet-derived growth factor (PDGF), granulocyte macrophage colony stimulating factor, stem cell factor, heparin-binding epidermal growth factor (HB-EGF), granulocyte colony stimulating factor, or ciliary neurotrophic factor (CNTF), but could be with EGF, fibroblast growth factor 2 (FGF2), and FGF2 plus heparin. Varying combinations of substrate and mitogen resulted in very different expansion rates and/or lineage potential. Neurons, oligodendrocytes, and astrocytes differentiated from all cultures, but EGF-generated neural precursor cells were more restricted to an astrocytic lineage and FGF2-generated neural precursor cells had a greater capacity for neuronal differentiation. In both EGF- and FGF2-generated cell populations, CNTF increased the number of differentiated astrocytes, triiodothyronine oligodendrocytes, PDGF neurons, and brain-derived neurotrophic factor neurons only from EGF cells. Electrophysiological analysis of differentiated cells showed three distinct phenotypes, glial, neuronal, and presumed precursor cells, although the neuronal properties were immature. Collectively, these data indicate that CNS neural precursor cell populations isolated with different mitogens and substrates are intrinsically different and their characteristics cannot be directly compared.

Animals↗
PubMed1999

Naloxone reduces the amplitude of IPSPs evoked in lumbar motoneurons by reticular stimulation during carbachol-induced motor inhibition.

During active sleep or carbachol-induced motor inhibition, electrical stimulation of the medullary nucleus reticularis gigantocellularis (NRGc) evoked large amplitude, glycinergic inhibitory postsynaptic potentials (IPSPs) in cat motoneurons. The present study was directed to determine whether these IPSPs, that are specific to the state of active sleep, are modulated by opioid peptides. Accordingly, intracellular recordings were obtained from lumbar motoneurons of acute decerebrate cats during carbachol-induced motor inhibition while an opiate receptor antagonist, naloxone, was microiontophoretically released next to the recorded cells. Naloxone reversibly reduced by 26% the mean amplitude of NRGc-evoked IPSPs (1.9+/-0.2 mV (S.E.M.) vs. 1.4+/-0.2 mV; n=11, control and naloxone, respectively, p<0.05), but had no effect on the other waveform parameters of these IPSPs (e.g., latency-to-onset, latency-to-peak, duration, etc.). The mean resting membrane potential, input resistance and membrane time constant of motoneurons following naloxone ejection were not statistically different from those of the control. These data indicate that opioid peptides have a modulatory effect on NRGc-evoked IPSPs during carbachol-induced motor inhibition. We therefore suggest that endogenous opioid peptides may act as neuromodulators to regulate inhibitory glycinergic synaptic transmission at motoneurons during active sleep.

Animals↗
PubMed1999

Electrophysiological properties of mitogen-expanded adult rat spinal cord and subventricular zone neural precursor cells.

Growth factor-expanded neural precursor cells isolated from the mammalian central nervous system can differentiate into neurons and glia. Although the morphological and neurochemical development of these neural precursor cells has been investigated, little attention has been paid to their electrophysiology. This study examined the electrophysiological properties of neurons and glia derived from neural precursor cells isolated from the adult rat spinal cord (SC) and subventricular zone (SVZ). Cells were cultured in medium containing epidermal growth factor and/or fibroblast growth factor-2. After at least two passages, spheres of neural precursor cells were plated on coated coverslips and maintained in culture for up to 6 weeks. Whole-cell patch recordings were made using standard current clamp techniques. Immature action potentials were observed within hours of plating for both SC and SVZ cells. Input resistance and time constants decreased over the first week after plating and no further changes were found at later times. At similar times following plating, however, SVZ cells had a lower input resistance and shorter time constant compared to SC cells. SVZ cells also had higher resting membrane potentials and smaller after hyperpolarizations than those of SC cells, despite no significant difference in the amplitude of action potentials. Neither the SC nor the SVZ cells were capable of eliciting more than a single action potential in response to injected current. While all SC cells tested were depolarized by glutamate, the response of SVZ cells to glutamate varied considerably. This study revealed that neural precursor cells from SC and SVZ differ in both active and passive membrane properties. It appears also that the electrophysiological development of SC and SVZ precursor-derived neurons is incomplete under the conditions used. These observations suggest that the neural precursor cells from different anatomical locations may be physiologically diverse and may exhibit some differences in commitment toward neuronal or glial phenotypes.

Animals↗