Biomedical subjects

Thomas Quentin

Publications and source records attributed to Thomas Quentin.

11 recordsLinked to original sources

PubMed2006

Interactions of buprenorphine and dipotassium clorazepate on anxiety and memory functions in the mouse.

Buprenorphine, a partial mu-receptor agonist widely substituted for heroin in the treatment of addiction, is often misused in combination with benzodiazepines. Improved hedonic properties may result, but only at the cost of increased buprenorphine toxicity. In order to elucidate the appeal of the benzodiazepine-buprenorphine combination, the present study looked at its neuropsycho-pharmacological effects on various emotional and cognitive parameters in the mouse. On the basis of previous dose-response studies, the regimen used was buprenorphine 0.3mg/kg, s.c. plus dipotassium clorazepate 1, 4 and 16 mg/kg, i.p. Anxiety-like behaviour was assessed using the black and white test box, and memory processes were examined via the spontaneous alternation paradigm in the Y-maze, and passive avoidance tests. Spontaneous locomotor activity was also evaluated. High doses of clorazepate impaired buprenorphine-induced hyperactivity and anxiogenic-like effects. They also increased buprenorphine-induced spontaneous alternation impairment, but did not modify its impact on long-term memory processes. These results suggest that the positive reinforcement experienced with the buprenorphine-benzodiazepine combination may be attributable, at least in part, to an increase in buprenorphine's sedative effect associated with a decrease in anxiogenicity.

Animals↗

PubMed2006

Gene expression of the Na-Ca2+ exchanger, SERCA2a and calsequestrin after myocardial ischemia in the neonatal rabbit heart.

BACKGROUND: Neonatal hearts are less susceptible to developing myocardial dysfunction after hypoxia and/or ischemia than adult hearts. Differences in intracellular calcium homeostasis may be responsible for reduced calcium overload of the immature myocardium leading to the observed protection against ischemia. OBJECTIVE: To assess differences in baseline and post-ischemic gene expression of calcium handling proteins after ischemia in neonatal and adult rabbit hearts. METHODS: We used isolated antegrade perfused rabbit hearts (age 2 days, 28 days, n = 32), which were exposed to ischemia and hypothermia simulating myocardial stunning comparable to neonatal asphyxia. Gene and protein expression of the sodium-calcium exchanger (NCX), the sarco-endoplasmatic reticulum Ca2+-ATPase 2a (SERCA) and calsequestrin (CSQ) were measured using quantitative real-time PCR and Western blotting. RESULTS: After ischemia and reperfusion in neonatal and adult hearts, a significant decrease in myocardial performance was recorded. At the mRNA level, significant differences in the baseline expression of NCX, SERCA and CSQ between neonatal and adult hearts were observed. In neonatal post-ischemic hearts, NCX and CSQ expression were significantly higher at the mRNA level than in controls. In contrast, SERCA expression remained unchanged in neonatal hearts and decreased in adult hearts compared to the non-ischemic controls. CONCLUSION: These findings suggest that changes in gene expression of calcium handling proteins may be involved in the different susceptibility of neonatal compared to adult hearts to developing myocardial dysfunction after ischemia.

Animals↗

PubMed2006

Competitive displacement binding assay on rat brain sections and using a beta-imager: application to mu-opioid ligands.

A new approach of competitive displacement binding assay using brain sections and a beta-imager is presented to estimate binding parameters such as affinity and selectivity of new compounds or to characterize receptor families or subtypes of receptors in small brain regions. This method includes a preliminary saturation assay intended to define the optimal concentration of displaceable radio-labeled ligand followed by the determination of displacement constants (IC(50) and K(i)) in cerebral regions rich in studied receptor. The technique application was demonstrated in seven rat brain structures, using displacement of the selective tritiated mu-opioid ligand [(3)H]-DAMGO by six opioid ligands: a specific agonist (DAMGO), less specific agonists (morphine, remifentanil), a non-specific antagonist with good affinity for mu receptors (naloxone) and ligands specific of other opioid subtypes (naltrindole, U50.488). Radioactivity counts were collected during 48 h. The assay-validation was performed by measuring intra- and inter-assay variation on determinations and by comparing presently obtained K(i) values with data from recognised methodologies. Both prove the accuracy of the proposed method.

Analgesics, Opioid↗

PubMed2005

Clorazepate affects cell surface regulation of delta and kappa opioid receptors, thereby altering buprenorphine-induced adaptation in the rat brain.

Concomitant abuse of buprenorphine (BPN) and benzodiazepines (BZD) may relate to a pharmacodynamic interaction between the two. The objective of the present work was to investigate the acute and chronic effects of clorazepate (CRZ) alone or in combination with BPN on selective kappa opiate tritiated ligand [3H]-U69 593 and delta opiate radioligand [3H]-deltorphine II binding in the rat brain. Bmax (maximal receptor density) and Kd (the dissociation constant) were directly determined at different brain regions of interest (ROI) selected for high densities of kappa and/or delta receptors in rats treated with BPN and/or CRZ. The agents were administered either once or for 21 consecutive days. Differences in Bmax and Kd (for both specific ligands) were related to drug treatment and receptor location. Globally, single BPN administration induced no changes in kappa or delta opiate receptor binding, whereas repeated BPN administration up-regulated kappa receptor density and decreased delta affinity. At the kappa receptor level, repeated administration of CRZ acted only on Kd, whereas the delta receptor was up-regulated. Repeated addition of CRZ to BPN had no effect on kappa receptor Bmax versus chronic controls. By significantly decreasing Bmax, CRZ nullified the effect of chronic BPN on the kappa receptor. The modifications were strongest in the nucleus accumbens, where both types of receptor occur. Treatments had region-selective effects in some brain areas, such as the amygdala, periaqueductal gray matter, hypothalamus and caudate putamen. Increased mu and delta receptor densities would be expected to provide reinforcement by enhancing reward, and impairment of kappa receptor availability would be expected to decrease aversion. The effects described are likely to influence addictive behavior among people abusing BZD and BPN.

Adaptation, Physiological↗

PubMed2005

Acute and chronic administration of clorazepate modifies the cell surface regulation of mu opioid receptors induced by buprenorphine in specific regions of the rat brain.

The aim of the present study was to investigate the acute and chronic effects of clorazepate (CRZ) alone or in combination with buprenorphine (BPN) on binding of the selective mu opiate tritiated ligand [3H]-DAMGO in the rat brain. Using 0.1 to 5 nM [3H]-DAMGO concentrations and a beta-imager, Bmax (maximal receptor density) and K(D) (the dissociation constant) were directly determined at different regions of interest (ROI) in the brains of rats treated with BPN and/or CRZ administered either once or over 21 consecutive days. Differences in Bmax and K(D) were related to both treatment and location. Acute BPN induced a down-regulation (62% mean decrease in Bmax observed on the whole brain) of mu opiate receptors. CRZ induced a mean 39% decrease in Bmax associated with substantially decreased affinity, particularly after acute administration (136% mean K(D) increase). Addition of CRZ to BPN [mean Bmax decreases of 34% (acute) and 29% (chronic)] induced significantly less down-regulation than did BPN alone, while altering affinity. These changes were maximal in the amygdaloid nucleus. Significant and persistent decreases in Bmax and affinity were also detected in the hippocampus, hypothalamus and thalamus. In the thalamus, an opposite regulation of Bmax was observed that was maximal with the combination. As the regions where changes were greatest have been specifically implicated in memory and socio-emotional functions and/or vegetative and endocrine adaptations, there is reason to suspect that the addition of CRZ to BPN may have clinical consequences. On the one hand, it may have some impact on drug abuse and misuse behaviors towards treatments including heroin substitute and BZD, and on the other, amplify the BPN effect-particularly hedonic or toxic-mainly after sporadic BPN-BZD abuses. These pharmacodynamic findings may explain, at least in part, the well-established preference of patients for the BPN-benzodiazepine combination and the toxicity with which it is associated.

Animals↗

PubMed2005

Changes in expression levels of genes involved in fatty acid metabolism: upregulation of all three members of the PPAR family (alpha, gamma, delta) and the newly described adiponectin receptor 2, but not adiponectin receptor 1 during neonatal cardiac development of the rat.

UNLABELLED: During neonatal cardiac development, the heart changes its substrate preference from glucose to fatty acids. The aim of this study was to investigate the changes in mRNA expression levels of genes involved in the control of cardiac fatty acid metabolism in the transition from neonatal to adult life. METHODS: mRNA expression levels for peroxisome proliferator activated receptor (PPAR) alpha, gamma and delta, PPARgamma co-factor 1 alpha and beta (PGC-1 alpha and beta), 9-cis retinoc-acid-activated receptor alpha, beta and gamma (RXR alpha, beta, gamma), 5'-AMP activated protein kinase (AMPK) alpha1 and alpha2, adiponectin receptor 1 and 2 (AR 1 and AR 2) were measured in heart tissue of neonatal 0-day, 7-day and 21- day old rats. RESULTS: mRNA expression of all three members of the PPAR family were upregulated significantly from day 0 to day 21 (alpha +117%, gamma +133%, delta +203%). In addition, m-RNA expression of all RXR isoforms increased from day 0 to day 7 (alpha +125%, beta +69%; gamma +41%). AR 2 exhibited a small but significant increase in mRNA expression (+ 46%). CONCLUSIONS: We were able to demonstrate for the first time that in addition to PPARalpha, also PPARgamma and delta, as well as all RXR isoforms and AR 2 are upregulated in the heart during neonatal development.

Animals↗

PubMed2004

Down-regulation of Ku 70 and Ku 80 mRNA expression in transitional cell carcinomas of the urinary bladder related to tumor progression.

DNA-dependent protein kinase (DNA-PK) containing the regulatory subunits Ku 70 and Ku 80 plays a prominent role in the repair of double-stranded DNA breaks by a nonhomologous end-joining pathway maintaining genomic stability. In an attempt to elucidate the significance of the DNA-PK complex for human urothelial carcinogenesis, the expression of Ku 70 and Ku 80 was studied in 71 transitional cell carcinomas (TCC) of the urinary bladder of various grades and stages, and in relation to lifestyle and occupational bladder cancer risk factors. To analyse the mRNA expression of Ku 70 and Ku 80, real-time quantitative reverse transcription-polymerase chain reaction was used and the protein expression assessed by immunohistochemistry. Advanced high-grade, high-stage TCC expressed the mRNA of Ku 70 and Ku 80 at a lower level than superficial low-grade, low-stage carcinomas, suggesting down-regulation of the Ku system to be associated with progression of bladder cancer from a low to a high malignant potential. The protein expression of Ku 70 and Ku 80 was closely related and decreased consistently with increasing grades and stages, paralleling the expression of the mRNA. Among hazardous environmental bladder cancer risk factors, heavy consumption of coffee was associated with a twofold decreased Ku 70 and Ku 80 mRNA expression, whereas tobacco smoke did not substantially affect the activity of the Ku system, except for a trend towards a dose-response relationship in the expression of Ku 70 mRNA. There is some evidence that exposure to polycyclic hydrocarbons, paints and lacquer, and stone dust may modify the expression of Ku 70 mRNA. Although the underlying molecular genetic pathways are not yet clearly understood, our data indicate that down-regulation of the Ku system promotes progression of urothelial carcinogenesis to a more malignant and aggressive clinical behavior, presumably as a result of an impaired capacity for DNA repair.

Antigens, Nuclear↗

PubMed2004

Alteration of the MDM2-p73-P14ARF pathway related to tumour progression during urinary bladder carcinogenesis.

Transitional cell carcinomas (TCC) of the urinary bladder develop by a multistep process characterized by various stages of transformation differing in their grade of malignancy and biological behaviour. Since the prospective clinical outcome cannot be reliably predicted on histopathological grounds, we analysed the mRNA expression of the MDM2-p73-P14ARF tumour surveillance pathway in an attempt to detect alterations of gene activity, allowing a better understanding of the mechanisms responsible for conversion of low to high malignant TCC. Expression of the mRNA was determined in 71 TCC of various grades and stages using the real-time quantitative reverse transcription-polymerase chain reaction. The MDM2-p73-P14ARF pathway was dominated by the MDM2 gene, the mRNA expression of which proved to be significantly (5-fold) lower in advanced high-grade, high-stage than in superficial low-grade, low-stage TCC. Conversely, the expression of p73 mRNA increased with increasing tumour grades and stages, while the activity of the P14ARF gene was not substantially altered during early and late phases of urothelial carcinogenesis. Analysing the expression of spliced variants of MDM2 mRNA, we found a heterogeneous pattern including a novel splicing transcript coding for an abnormal protein. Promoter hypermethylation of P14ARF occurred in 10% of the TCC with an under-expression of mRNA. An analysis of the effects of lifestyle and occupational bladder cancer risk factors revealed that TCC of smokers showed a 2-fold elevated expression of MDM2 mRNA and an approximately 2-fold lower expression of P14ARF mRNA, whereas the activity of the p73 gene was unchanged. Heavy coffee consumption was associated with a 2-fold decreased expression level of P14ARF mRNA. Exposure to certain occupational hazards (plastic products, paints and lacquer, polycyclic hydrocarbons, chemical solvents) was observed to modulate the activity of the genes analysed. Our findings suggest that an alteration in the MDM2-p73-P14ARF pathway is involved in the progression of bladder cancer to a more malignant and aggressive form.

Base Sequence↗

PubMed2003

Abundant expression of spliced HDM2 in Hodgkin lymphoma cells does not interfere with p14(ARF) and p53 binding.

Recently, comparative genomic hybridization (CGH)- and fluorescence in situ hybridization (FISH)-analyses of native Hodgkin and Reed-Sternberg (H&RS) cells extracted from Hodgkin lymphoma (HL) revealed a recurrent amplification of the HDM2 locus on chromosome 12. HDM2 is known to target, inactivate and to degrade p53. Wild type (wt) p53 protein is detected in high levels in HL. Simultaneously, stabilized wt p53 and spliced hdm2 transcripts have been observed in different tumors. Therefore, we examined the expression and structure of HDM2 in HL cell lines and possible effects on components of the p53 pathway. DNA integrity and induction potential of p53 was verified by DNA sequencing and detection of potential effector proteins (p21(WAF/CIP), HDM2) using immunofluorescence, respectively. All HL cell lines show an overexpression of HDM2 protein. Furthermore, several different spliced hdm2 transcripts (mdm-sv) including five new variants lacking a functional p53 binding site were characterized. If expressed, corresponding proteins were shown to be not restricted to the nucleus. Co-localization of the potential binding partners HDM2/p14(ARF) and HDM2/p53 was found in HL cell lines. We suggest that HDM2-sv have no significant disturbing influence on the interaction of these proteins.

Alternative Splicing↗

PubMedDate not supplied

Altered mRNA expression of the Rb and p16 tumor suppressor genes and of CDK4 in transitional cell carcinomas of the urinary bladder associated with tumor progression.

Based on the concept that tumor suppressor genes are involved in the pathogenesis of urinary bladder carcinogenesis, we analysed the mRNA expression of the retinoblastoma (Rb) and p16 (CDKN2, INK4A, MTS1) genes as well as of the proto-oncogene cyclin D-dependent kinase 4 (CDK4) in 71 transitional cell carcinomas (TCC) of the urinary bladder in relation to the tumor grades and stages, and with reference to certain lifestyle and occupational risk factors. Using real-time quantitative reverse transcription-polymerase chain reaction, high-stage muscle invasive TCC expressed the Rb, p16 and CDK4 mRNA at lower levels than low-stage superficial cancers, indicating down-regulation to be linked with tumor progression. The drop of the expression in the group of grade 2 TCC when invading the muscle layer compared to grade 2 carcinomas with a superficial pattern of growth is considered to represent a key event in promoting urothelial carcinogenesis in this subset of carcinomas. The protein expression of the Rb gene evaluated by immunohistochemistry proved to be closely related to the tumor grades and stages as well as to the mRNA expression, high-grade and high-stage TCC disclosing a lower rate of positive immunoreactivity than low-grade and low-stage carcinomas. The p16 protein product was expressed at a lower level in grade 3 than in grade 1 TCC, but there was no correlation with the tumor stages or the mRNA expression. TCC with loss of heterozygosity (LOH) at the INK4A region showed a decreased expression of p16 mRNA compared to those without an allelic loss. Tobacco smoke was not identified to substantially modulate the Rb/p16/CDK4 pathways, except for a ten-fold elevated mRNA expression of the p16 gene in TCC of light compared to heavy smokers. Heavy coffee consumption was associated with a reduced expression of CDK4 mRNA. Among occupational exposures, TCC of patients in contact with stone dust, paints and lacquer, plastics, wood and wood preservers and chemical solvents and adhesives displayed altered partly elevated, partly reduced levels of Rb, p16 and CDK4 mRNA compared to non-exposed subjects. Although the underlying molecular-genetic pathways are not yet fully understood, the current results suggest functional reduction of the tumor suppressor genes Rb and p16 to be associated with progression of bladder cancer to a more malignant and aggressive behaviour.

Adult↗

PubMedDate not supplied

Alteration of the vascular endothelial growth factor and angiopoietins-1 and -2 pathways in transitional cell carcinomas of the urinary bladder associated with tumor progression.

Neoangiogenesis is assumed to play an important role in the progression, metastasis and prognosis of a wide variety of tumors. To get insights into the molecular-genetic pathways and the biological role of angiogenesis in urothelial carcinogenesis, we analyzed comparatively the expression of the mRNA of the vascular endothelial growth factor (VEGF) and of the angiopoietins-1 and -2 (Ang-1 and Ang-2) in 71 transitional cell carcinomas (TCC) of the urinary bladder in relation to the tumor grades and stages, and referring to epidemiological risk factors. Using real-time quantitative reverse transcription-polymerase chain reaction, low-stage superficial TCC expressed VEGF and Ang-2 mRNA at a significantly higher level than high-stage muscle invasive carcinomas, and low-grade TCC at an insignificantly higher level than high-grade tumors. The activity of both angiogenic factors was found to be significantly correlated. Conversely, Ang-1 mRNA was expressed at a 3-fold significantly lower level in low-grade, low-stage compared to high-grade, high-stage TCC. A significantly 3- and 2-fold respectively, drop of the VEGF and Ang-2 mRNA expression in conjunction with a 2-fold significantly higher expression of Ang-1 mRNA in the group of grade 2 TCC when infiltrating the muscle layer may represent a crucial event during urothelial carcinogenesis, and possibly indicates an important step in promoting the conversion of bladder cancer from a low to a high malignancy in this subset of carcinomas. By immunhistochemistry, high-grade, high-stage carcinomas less frequently displayed areas with a strong reactivity for the VEGF protein ('hot spots") than low-grade, low-stage TCC, paralleling the expression of the mRNA. The expression patterns observed are compatible with a reduced vascular destabilization and decreased formation of new blood vessels in advanced TCC, suggesting a balance between vessel regression and vascular growth, with a less pronounced vascular remodeling during late phases of urothelial carcinogenesis. Analyzing the effect of life-style bladder cancer risk factors, habitual smoking and coffee consumption was not observed to substantially alter the expression of the angiogenic mediators, except for weakly elevated levels of VEGF and Ang-2 mRNA in TCC of strong smokers and a borderline significantly decreased VEGF mRNA expression associated with heavy coffee consumption. Certain hazardous occupational exposures (polycyclic hydrocarbons, paints and lacquer, stone dust) may play a role in modulating tumor angiogenesis. The current data indicate that the signaling molecular-genetic pathways underlying vascular remodeling are involved in the progression of urinary bladder cancer to a more malignant and aggressive behaviour.

Angiopoietin-1↗