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Biomedical subjects

L Lumeng

Publications and source records attributed to L Lumeng.

At least 109 records · Page 6Linked to original sources
PubMed1993

Greater abundance of serotonin1A receptor in some brain areas of alcohol-preferring (P) rats compared to nonpreferring (NP) rats.

Saturable [3H]8-OHDPAT binding to recognition sites of 5-HT1A receptors was shown to be higher in cortical membranes of alcohol-preferring (P) than in membranes of alcohol-nonpreferring (NP) rats. Neither the P nor the NP lines had been previously exposed to ethanol. The increase in binding was mainly due to 40-56% higher density or maximum of binding sites (Bmax) without significant change in affinity or dissociation constant (Kd) for the radioligand. Although Bmax values were also consistently higher in membranes isolated from other brain areas of P rats, including hypothalamus, striatum, and hippocampus, the differences did not reach statistical significance. Similar to the previously reported lack of difference in [3H]ketanserin binding to 5-HT2 receptors in cortical membranes from P and NP rats, there were also no significant differences in saturable binding of [3H]mesulergine and [3H]LY278584 to recognition sites of 5-HT1C and 5-HT3 receptors, respectively. Thus, an upregulation of 5-HT1A receptors in cerebral cortex and possibly in other brain areas of ethanol-naive P rats appears to have occurred as a consequence of the lower 5-HT innervation in this selected line of rats (13,15,27,28).

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Serotonin-2 receptors in the CNS of alcohol-preferring and -nonpreferring rats.

The densities of serotonin-2 (5-HT2) receptors, labelled with [3H]ketanserin (Ket), were examined in the CNS of alcohol-naive, adult, male alcohol-preferring (P) and -nonpreferring (NP) rats using quantitative autoradiography. The densities of binding sites labelled with 2.0 nM [3H]Ket were 15-25% lower (p < 0.05) in layer IV of the medial prefrontal, frontal, cingulate, parietal, and temporal cortices of the P line compared with the NP line. [3H]Ket binding in the P rats was also 40-50% lower (p < 0.05) in the medial and lateral nucleus accumbens, olfactory tubercle, and caudate-putamen, and 20% lower (p < 0.05) in the claustrum, compared with the NP line. No differences in 2.0 nM [3H]Ket binding were observed between the lines in the piriform cortex, hypothalamus, amygdala, hippocampus, ventral tegmental area, substantia nigra, central gray, and interpenduncular nucleus. Scatchard analysis of [3H]Ket binding (0.5-0.6 nM, determined in layer IV of the frontal and parietal cortex and in the lateral nucleus accumbens, indicated lower Bmax values without a change in Kd for the P compared to the NP rats. The results of this study indicate that there are fewer 5-HT2 receptors in certain CNS regions of the P relative to the NP rats.

Alcohol Drinking↗
PubMed1993

Housing conditions alter GABAA receptor of alcohol-preferring and -nonpreferring rats.

The effects of housing conditions on some functional properties of the GABAA benzodiazepine (BZD) receptor in the cerebral cortex were examined in the selectively bred alcohol-preferring (P) and -nonpreferring (NP) lines of rats. Compared to rats housed in pairs (P with P and NP with NP), P and NP rats housed individually had 44% (p < 0.005) and 32% (p < 0.01) lower values, respectively, for GABA-stimulated 36Cl- influx into cortical microsacs. The maximal effect (Vmax) of flunitrazepam (FNZ) to enhance GABA-stimulated 36Cl- uptake was 44% higher in individually housed P rats than pair-housed P rats (p < 0.05) and 51% higher than individually housed NP rats (p < 0.05). There was no difference between single and pair-housed NP rats for Vmax values of FNZ enhancement of GABA-stimulated 36Cl- influx. The results show housing conditions can alter some of the functional properties of the GABAA/BZD receptor in the P and NP lines of rats. The differential effect of housing conditions on FNZ enhancement of 36Cl- influx, observed between the lines, may be a result of higher levels of anxiety being produced by brief isolation in the P rat.

Alcohol Drinking↗
PubMed1993

Alcohol-preferring and nonpreferring rats display different levels of neurofilament proteins in the ventral tegmental area.

Previously, different levels of neurofilaments (NF) in the ventral tegmental area (VTA) have been identified in Sprague-Dawley rats treated chronically with morphine or cocaine and in drug-naive Lewis and Fischer 344, inbred strains that differ behaviorally in several ways, including alcohol, opiate, and cocaine preferences. These findings led us to examine whether rat lines that have been selectively bred for a difference in alcohol preference, the alcohol-preferring (P) and nonpreferring (NP) rats, also express different levels of NFs in the VTA. We found by use of back phosphorylation and immunolabeling procedures that the VTA of the P rat contains 20-50% lower levels of the three major types of NF proteins--NF-200, NF-160, and NF-68--compared with the VTA of the NP rat. No strain difference in NF levels was seen in the substantia nigra (which like the VTA is a major dopaminergic nucleus in brain), locus coeruleus (which is a major noradrenergic nucleus in brain), or spinal cord (which is enriched in NF proteins). In contrast to NFs, no P-NP line differences were found in VTA levels of tyrosine hydroxylase, which is also regulated by chronic morphine and cocaine treatments in Sprague-Dawley rats and shows prominent Lewis-Fischer strain differences, specifically in this brain region. The results provide additional support for the possibility that levels of NFs in the VTA may be related to preference for alcohol and other drugs of abuse.

Alcoholism↗
PubMed1993

Measurement of hemoglobin-acetaldehyde adduct in alcoholic patients.

A sensitive and specific test for chronic alcohol abuse is useful in the diagnosis and management of alcoholic patients. Herein, we report the measurement of hemoglobin-acetaldehyde adducts (Hb-AA) in alcoholic patients by a sandwich ELISA using different antibodies. Keyhole limpet hemocyanin (KLH), a peptide consists of eight amino acid residues (8-pep, V1 to K8) at the N-terminus of beta-chain of human sickle-cell Hb and a segment of HbA beta-chain consists of 11 amino acids rich in lysine or K (11-pep, G56-K66) were incubated with acetaldehyde and NaCNBH3 to form protein-AAs. 8-Pep-AA and 11-pep-AA were individually conjugated to unmodified KLH as the carrier. Anti-protein-AA IgGs were raised in rabbits using these three protein-AA immunogens. When anti-KLH-AA IgG was used in ELISA, optical densities for alcoholic patients and controls were 0.311 +/- 0.124 and 0.147 +/- 0.042 (means +/- SD, n = 40/group, p < 0.001), respectively. Using mean value +/- 2 SD of controls as the cut-off, sensitivities to detect alcoholic patients were 78, 75, and 43%, respectively, when anti-KLH-AA, anti-11-pep-AA, and anti-8-pep-AA were used. Correlation among optical densities obtained from the first two IgGs was excellent (R2 = 0.905). We conclude that: (1) Hb-AA has the potential of being a good marker for alcohol abuse, and (2) the site of Hb that is modified by acetaldehyde in vivo is primarily located in a surface-accessible domain near the center of the beta-chain of HbA where several lysine residues are clustered.

Acetaldehyde↗
PubMed1993

Production of antibodies that recognize the heterogeneity of immunoreactive sites in human hemoglobin chemically modified by acetaldehyde.

Human hemoglobin (Hgb) was incubated with acetaldehyde under two different conditions: (a) in the presence of 250 mM acetaldehyde for 1 hr then reduced with 100 mM NaCNBH3 for an additional 4 hr at room temperature; and (b) in the presence of 500 mM acetaldehyde for 10 days at room temperature and then reduced with 1 mM NaBH4 for 1 hr. It was found that 44% and 27% of free amino groups in Hgb-acetaldehyde adduct (AA) remained unmodified when Hgb was treated under conditions (a) and (b), respectively. SDS-PAGE analysis revealed that the molecular weight of Hgb-AA(a) [Hgb modified under condition (a)] was slightly greater than that of unmodified Hgb and extensive protein cross-linking had occurred in Hgb-AA(b) [Hgb modified under condition (b)]. Electrophoresis on agarose gel showed the order of negative charge was Hgb-AA(b) > Hgb-AA(a) > unmodified Hgb. Polyclonal antibody raised in rabbits using keyhole limpet hemocyanin as the carrier protein modified by acetaldehyde under condition (a) [i.e., KLH-AA(a)] preferentially recognized Hgb-AA(a), whereas antibody raised using KLH-AA(b) as the immunogen recognized only Hgb-AA(b). In conclusion, antibodies raised with protein-AA antigens produced under different conditions recognize different epitopes.

Acetaldehyde↗
PubMed1993

An experimental approach to understanding the genetic and neurobiological basis of alcoholism.

The development and characterization of an animal model to study mechanisms underlying abnormal alcohol-seeking behavior have been described. Raised by genetic means, it demonstrates the importance of genetic factors in this behavior. It has allowed the elucidation of neural pathways and neurotransmitter systems that subserve alcohol-seeking behavior. It offers the potential for screening new medications for the treatment of alcoholism, based upon these kinds of newly discovered knowledge.

Alcohol Drinking↗
PubMed1993

CNS mechanisms of alcohol self-administration.

Neurochemical and neuropharmacological studies were undertaken to examine the possible involvement of the ventral tegmental area (VTA) dopamine (DA) system and the dorsal raphe nucleus (DRN) serotonin (5-HT) system in regulating oral alcohol self-administration. In vivo microdialysis studies demonstrated that either i.p. ethanol administration (1.0-2.0 g/kg) or local perfusion with ethanol (100 mM) could enhance the extracellular concentrations of both DA and 5-HT in the nucleus accumbens (ACB). Furthermore, the effects of local perfusion with ethanol on DA release in the ACB could be blocked by co-perfusion with a 5-HT3 antagonist. In the selectively-bred alcohol preferring P line of rats, there appears to be abnormal 5-HT and/or DA systems in certain limbic structures, i.e., ACB, olfactory tubercles (OTU) and medial prefrontal cortex (MPF). This is indicated by (a) lower contents of DA and 5-HT; (b) fewer 5-HT immunostained fibers; (c) lower densities of 5-HT1B, 5-HT2 and D2 receptors; and (d) higher densities of 5-HT1A receptors in the CNS of P rats compared to the alcohol-nonpreferring NP line of rats. Neuropharmacological studies demonstrated that local microinfusion of the D2 antagonist, sulpiride, or, at low doses, the DA releaser, d-amphetamine, could increase alcohol drinking by P rats. Intracranial self-administration (ICSA) studies showed that the P line of rats, but not the NP line, will self-administer 50-150 mg% ethanol directly into the VTA. Overall, these results suggest an innate abnormal functioning of the VTA DA and DRN 5-HT systems may be key factors facilitating the rewarding actions of ethanol in the CNS of P rats.

Alcohol Drinking↗
PubMed1992

Diagnosis of chronic hepatitis C after liver transplantation by the detection of viral sequences with polymerase chain reaction.

Chronic hepatitis frequently occurs after liver transplantation. The role of hepatitis C virus infection in patients after liver transplantation is unknown, although antibodies to HCV are detected in some of these cases. The use of polymerase chain reaction techniques for the detection of hepatitis C virus RNA should improve sensitivity and specificity, particularly in these immunosuppressed patients. Our goal was to further clarify the role of hepatitis C virus infection in chronic hepatitis occurring after liver transplantation. Patients with chronic hepatitis of uncertain origin after transplantation were identified. Serum samples taken at the time of the most recent liver biopsy that showed chronic hepatitis were tested for anti-hepatitis C virus using enzyme-linked immunoassay and supplemented by recombinant immunoblot assay (recombinant immunoblot assay I and recombinant immunoblot assay II). The samples were also tested for the presence of hepatitis C virus RNA using polymerase chain reaction. Of the 25 patients with chronic hepatitis, 15 (60%) had hepatitis C virus RNA present. Only seven (47%) of these 15 patients had anti-hepatitis C virus detected. Hepatitis C virus is a major cause of chronic hepatitis occurring after liver transplantation. The magnitude of hepatitis C virus infection will be underestimated if only currently available assays for anti-hepatitis C virus are used.

Base Sequence↗
PubMed1992

Hepatitis C virus does not cause nonalcoholic steatohepatitis.

The pathogenesis of nonalcoholic steatohepatitis (NASH) remains poorly understood. Since inflammation and fatty changes are associated with hepatitis C (HCV) infection, we have tested the role of HCV in the genesis of NASH. Five consecutive cases of classic NASH were tested by Abbott anti-c100-3 EIA and polymerase chain reaction (PCR) to detect HCV-RNA. All serum specimens were negative for anti-c100-3 (or anti-HCV EIA) and HCV PCR. Based on this study, we conclude that HCV does not play a causative or contributing role in the pathogenesis of NASH.

Adult↗
PubMed1992

Corticotropin releasing factor (CRF): studies in alcohol preferring and non-preferring rats.

Electroencephalographic (EEG) responses to corticotropin releasing factor (CRF) as well as CRF concentrations in several brain regions were measured in two lines of rats which have been genetically selected for alcohol preferring (P) or non-preferring (NP) behaviors. Fifteen rats were implanted with chronic electrodes and EEG spectra were evaluated following intracerebroventricular (ICV) administration of CRF (0.15 nmol) or saline. P rats demonstrated a significantly increased EEG response to CRF in the theta frequency range (ANOVA: PREF x DRUG 4-6 Hz, P less than 0.03; 6-8 Hz, P less than 0.05) in frontal cortex. A significantly lower concentration of CRF was found in the P rats in hypothalamus (P less than 0.02), amygdala (P less than 0.003), prefrontal cortex (P less than 0.01), and cingulate cortex (P less than 0.02). The finding that P rats had an increased response to exogenously administered CRF, taken together with decreased CRF concentrations, suggests that CRF receptors may be up-regulated in these animals. Differences in the regulation of CRF neurons may contribute to the expression of behavioral preference for ethanol consumption in these rat lines.

Alcohol Drinking↗
PubMed1992

A reproducible rat liver cancer model for experimental therapy: introducing a technique of intrahepatic tumor implantation.

To investigate therapeutic strategies for hepatoma, it is necessary to have a reproducible animal model with a tumor growth pattern allowing accurate assessment of results. Many techniques of intrahepatic tumor implantation (IHTI) have been devised for intrahepatic tumor models. Most of them, however, have the disadvantage of high rates of artificial tumor dissemination during tumor implantation, which interferes with the evaluation of therapy. To overcome this problem, we have developed a technique of IHTI in which a piece of Gelfoam is placed into a small incision in the liver for the purpose of both hemostasis and formation of a tension-free pocket to accept the tumor implant. In 583 ACI rats receiving IHTI with Morris hepatoma 3924A, the tumor take rate was 100%. Resembling the natural course of human hepatoma, the implanted tumor grows locally early in the course of disease and eventually invades the surrounding organs causing ascites and also metastasizes to the lung. Liver microangiography demonstrated that the tumor received blood supply mainly from the hepatic artery. This IHTI technique was also compared to two other methods of IHTI: insertion of fragments without using Gelfoam and implantation with a tumor cell suspension. A significantly lower rate of early lung metastases was achieved with our technique (0%) in comparison with other two techniques (41 and 80%). We conclude that this rat liver cancer model is reproducible and allows efficient evaluation of treatment modalities for liver cancer without interference from tumor at undesirable sites.

Animals↗
PubMed1992

Distribution of alcohol dehydrogenase and the low Km form of aldehyde dehydrogenase in isolated perivenous and periportal hepatocytes in rats.

UNLABELLED: Hepatic damage induced by chronic alcohol abuse starts in the perivenous (PV) zone of the hepatic lobule. To explain this vulnerability in the PV zone, periportal (PP) and PV hepatocytes were isolated by digitonin-collagenase perfusion and the distributions of class I alcohol dehydrogenase (ADH) and the low-Km mitochondrial aldehyde dehydrogenase (ALDH) were studied. ADH was measured by three approaches i.e., specific activity, immunoreactive enzyme content and ADH mRNA level. ALDH was determined by specific activity and immunoreactive enzyme content. When compared with PV hepatocytes, isolated PP cells exhibited higher lactate dehydrogenase (PP/PV = 1.3-1.5), higher alanine aminotransferase (PP/PV = 1.7-1.9), but lower glutamine synthase (PP/PV less than 0.01). By prelabeling the PP zone with acridine orange before digitonin-collagenase digestion, flow cytometry indicated that mainly the isolated PP hepatocytes exhibited fluorescence. ADH activities and ADH mRNA levels did not differ in PP and PV cells. With a polyclonal antibody directed specifically against class I ADH, ADH immunoreactive protein also did not differ in PP vs PV cells. By activity assay, the low Km ALDH activities were found to be lower in the PV hepatocytes (PP/PV = 1.3). This was confirmed by immunotransblot with anti-ALDH IgG (PP/PV = 1.6). IN CONCLUSION: the preferential damage of the PV zone produced by ethanol is not caused by differences of ADH distribution in liver but could be related partly to a decrease in the low-Km ALDH in the PV zone.

Alcohol Dehydrogenase↗
PubMed1992

Alcohol self-administration in a nonrestricted access situation with alcohol-preferring (P) rats.

Genetic variables have been implicated as contributing factors in the development of alcoholic behavior. Rats bred selectively for alcohol preference have been used in laboratory studies to investigate the role of such variables. In the present study, rats from the alcohol preferring (P) line were placed in operant chambers in which food pellets, water, and 10% ethanol (v/v) were available continuously for 23 hr/day. Food pellets (45 mg) were presented on an FR 1 schedule of reinforcement, while ethanol was presented in a 0.1 ml dipper on an FR 4 schedule of reinforcement. Water was available in a drinking tube with licks monitored by a drinkometer. Data were analyzed in terms of both total daily intakes and computer defined bouts. The P rats showed greater daily ethanol intakes compared with Long-Evans (LE) animals previously studied under similar access conditions. The major difference in intake was a result of the P rats having a greater number of daily ethanol drinking bouts, while having only a slight increase in individual bout size. These data indicate that genetic selection for ethanol preference may result in the regulation of ethanol intake by means of changes in the frequency of ethanol drinking bouts but not by changes in bout size.

Alcohol Drinking↗
PubMed1992

Ethanol enhances the release of dopamine and serotonin in the nucleus accumbens of HAD and LAD lines of rats.

The effects of intraperitoneal administration of ethanol, 0.5, 1.0, and 2.0 g/kg body weight, on the extracellular concentrations of dopamine (DA), serotonin (5-HT), and their major metabolites were studied in the nucleus accumbens (ACC) of alcohol-naive, selectively bred high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) lines of rats using the technique of microdialysis. In both lines, the extracellular levels of DA were increased following the injection of 1.0 and 2.0 g of ethanol/kg body weight while only the 2.0-g/kg dose elevated the concentration of 5-HT. None of the ethanol doses altered the extracellular levels of the major metabolites of DA and 5-HT. Dose-response curves for DA and 5-HT release indicated no marked difference in the sensitivity to ethanol between the lines. Local perfusion with 60 mM K+ through the microdialysis probe markedly enhanced the release of DA and 5-HT in the ACC of both lines; there was a small difference between the lines in the amounts of DA, but not 5-HT, released by K(+)-stimulation. Overall, the results indicate that (1) the ACC DA system is more sensitive than the ACC 5-HT system to intraperitoneal ethanol administration in both lines and (2) there is no evidence for a relationship between alcohol preference and sensitivity of the ACC DA and 5-HT systems to acute intraperitoneal ethanol administration.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Localization of protein-acetaldehyde adducts on cell surface of hepatocytes by flow cytometry.

Acetaldehyde, a highly reactive intermediate of ethanol metabolism, has been shown to form adducts with liver proteins (e.g., a cytosolic 37 kDa protein and the microsomal cytP450IIE1) in rats fed alcohol chronically. In this study, flow cytometry was utilized to test for the presence of protein-acetaldehyde adducts (-AAs) on the surface of hepatocytes and immunotransblot was used to detect for the 37 kDa protein-AA in cytosol as was previously described. For flow cytometric analysis, rabbit anti-hemocyanin-AA IgG and fluorescein isothiocyanate-conjugated goat anti-rabbit serum IgG were used as the primary and secondary antibodies to label surface protein-AAs on hepatocytes at 0 degrees to 4 degrees C. After labeling and washing, hepatocytes were fixed with paraformaldehyde-cacodylate and analyzed with a flow cytometer. In an experiment wherein hepatocytes isolated from rats pair-fed liquid diets with and without ethanol were treated by adding both the primary and secondary IgGs, some hepatocytes from both alcohol-fed and control rats exhibited positive fluorescence but no significant difference in fluorescence intensity was noted. In another experiment, hepatocytes were isolated from rats pair-fed cyanamide (a selective aldehyde dehydrogenase inhibitor) with and without ethanol. The number of hepatocytes showing positive fluorescence in the presence of both primary and secondary IgGs was significantly higher in rats fed cyanamide plus ethanol than in rats fed cyanamide only. Of note, the 37 kDa protein-AA could be detected by immunotransblot in liver cytosol of alcohol-fed rats but not in the controls of both experiments with and without cyanamide supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1992

Effects of alcohol feeding on synthesis and secretion of apolipoproteins by regenerating rat sciatic nerve.

The amounts of apolipoprotein (apo) E and A1 released into the culture medium were examined in the regenerating nerves distal to a crush site following chronic alcohol feeding. Cultured minced segments of regenerating nerves taken from rats fed an alcohol-containing liquid diet for 5 weeks released only 50% of apoE but nearly 200% of apoA1 when compared with rats pair-fed with a control diet. The extent of decrease in medium apoE corresponded to the decrease of apoE mRNA in the nerve. Thus, chronic alcohol ingestion affects apoE synthesis of regenerating nerves by changing its mRNA level. On the other hand, apoA1 mRNA remained undetectable in regenerating and intact nerves whether the rats were fed alcohol or not. Furthermore, the amount of apoA1 released by the regenerating nerve into the culture medium was not significantly larger than that present in the nerve tissue prior to incubation. Therefore, it is most likely that apoA1 released by the injured nerve originated from the bloodstream and the increase in apoA1 content seen in the crushed nerve of alcohol-fed rats is due to an enhanced permeability of the nerve-blood barrier. Since the burst of apolipoproteins in the injured nerve is likely to play a role in nerve regeneration, the perturbation of apolipoprotein contents in regenerating nerves by chronic alcohol consumption may contribute to the pathogenesis of alcoholic neuropathy.

Alcoholism↗