The dual dopamine‐glutamate phenotype of growing mesencephalic neurons regresses in mature rat brain

Coexpression of tyrosine hydroxylase (TH) and vesicular glutamate transporter 2 (VGLUT2) mRNAs in the ventral tegmental area (VTA) and colocalization of these proteins in axon terminals of the nucleus accumbens (nAcb) have recently been demonstrated in immature (15‐day‐old) rat. After neonatal 6‐hydroxydopamine (6‐OHDA) lesion, the proportion of VTA neurons expressing both mRNAs and of nAcb terminals displaying the two proteins was enhanced. To determine the fate of this dual phenotype in adults, double in situ hybridization and dual immunolabeling for TH and VGLUT2 were performed in 90‐day‐old rats subjected or not to the neonatal 6‐OHDA lesion. Very few neurons expressed both mRNAs in the VTA and substantia nigra (SN) of P90 rats, even after neonatal 6‐OHDA. Dually immunolabeled terminals were no longer found in the nAcb of normal P90 rats and were exceedingly rare in the nAcb of 6‐OHDA‐lesioned rats, although they had represented 28% and 37% of all TH terminals at P15. Similarly, 17% of all TH terminals in normal neostriatum and 46% in the dopamine neoinnervation of SN in 6‐OHDA‐lesioned rats were also immunoreactive for VGLUT2 at P15, but none at P90. In these three regions, all dually labeled terminals made synapse, in contradistinction to those immunolabeled for only TH or VGLUT2 at P15. These results suggest a regression of the VGLUT2 phenotype of dopamine neurons with age, following normal development, lesion, or sprouting after injury, and a role for glutamate in the establishment of synapses by these neurons. J. Comp. Neurol. 517:873–891, 2009. © 2009 Wiley‐Liss, Inc.     

Genotoxic and endocrine activities of bis(hydroxyphenyl)methane (bisphenol F) and its derivatives in the HepG2 cell line

Human can be exposed to bis(hydroxyphenyl)methane (bisphenol F or BPF) and its derivatives as environment and food's contaminants. This study was investigated to identify and to compare toxic potency of BPF, BFDGE, and two of BPF metabolites using in vitro methods. BPF did not induce any genic mutation in bacteria when the Ames test was performed according to the OECD guideline. In contrast, using Human cell lines and Comet assay, we demonstrated that BPF and Bisphenol F Diglycidyl Ether (BFDGE) were effective on HepG2 cell DNA fragmentation at non-cytotoxic concentrations. DHB was also positive but at higher concentrations, near its limit of solubility. Neither BPF, nor DHB induced a positive response in the micronucleus assay. The increase of micronuclei observed when cells were exposed to BFDGE was mostly due to a cytotoxic effect. Concerning endocrine activities, BPF increased the luciferase activity in HepG2 cells transiently transfected with a concentration dependant pattern, DHB also induced a positive response but at highest concentrations. Estrogenic responses in the HepG2 cells differed with the estrogen receptor (ER) involved. Using MDA-kb2 cell line stably transfected with pMMTV-neo-Luc, only BPF was anti-androgenic at the highest concentration (10(-5)M). Then, we demonstrated using human cell lines, especially HepG2, BPF was the most toxic compound in term of genotoxicity and endocrine activities compared to DHB and BPF-OH, the free metabolites identified in rat urine when BPF was administrated to rats.     

Sodium signals in cerebellar Purkinje neurons and Bergmann glial cells evoked by glutamatergic synaptic transmission

Glial cells express specific high-affinity transporters for glutamate that play a central role in glutamate clearance at excitatory synapses in the brain. These transporters are electrogenic and are mainly energized by the electrochemical gradient for sodium. In the present study, we combined somatic whole-cell patch-clamp recordings with quantitative Na+ imaging in fine cellular branches of cerebellar Bergmann glial cells and in dendrites of Purkinje neurons to analyze intracellular Na+ signals close to activated synapses. We demonstrate that pressure application of glutamate and glutamate agonists causes local Na+ signals in the mM range. Furthermore, we analyzed the pharmacological profile, as well as the time course and spatial distribution of Na+ signals following short synaptic burst stimulation of parallel or climbing fibers. While parallel fibers stimulation resulted in local sodium transients that were largest in processes close to the stimulation pipette, climbing fibers stimulation elicited global sodium transients throughout the entire cell. Glial sodium signals amounted to several mM, were mainly caused by sodium influx following inward transport of glutamate and persisted for tens of seconds. Sodium transients in dendrites of Purkinje neurons, in contrast, were mainly caused by activation of AMPA receptors and had much faster kinetics. By reducing the driving force for sodium-dependent glutamate uptake, intracellular sodium accumulation in glial cells upon repetitive activity might provide a negative feedback mechanism, promoting the diffusion of glutamate and the activation of extrasynaptic glutamate receptors at active synapses in the cerebellum.     

Intrinsic resistance to apoptosis of colon epithelial cells is a potential determining factor in the susceptibility of the A/J mouse strain to dimethylhydrazine-induced colon tumorigenesis

Alterations in the delicate balance between cell proliferation and cell death disrupt colon homeostasis and serve as determining factors in colon tumorigenesis. The two mouse strains, AKR/J (resistant) and A/J (susceptible), have been widely used as models for dimethylhydrazine-induced colon tumorigenesis. This study examined whether the differential susceptibilities of the two mouse strains to the tumorigenic effect of dimethylhydrazine were associated with intrinsic differences in the apoptotic machinery of the colon epithelial cells. While acute exposure to dimethylhydrazine caused massive apoptosis of colon epithelial cells in AKR/J mice, the effect was considerably less in A/J mice. Apoptosis in AKR/J mice occurred not only in the luminal side of the mucosa but also deep in the colonic crypts. In addition, this apoptosis appeared to involve caspase-3. The increased sensitivity of AKR/J to dimethylhydrazine was associated with a persistent expression of tumor necrosis factor (TNF) but not of its receptors. After establishing a new method for isolating primary colon epithelial cells, we determined that cells derived from A/J mice were substantially more resistant to apoptosis in response to dimethylhydrazine or to a combination of TNF, cyclohexamide, and butyrate compared to cells from AKR/J mice. These results strongly suggest that a higher intrinsic resistance to apoptosis of colon epithelial cells may be an important determinant of predisposition to colon tumorigenesis in the A/J mouse strain.     

Spinal anesthesia for endoscopic urological surgery--low dose vs. varying doses of hyperbaric bupivacaine

BACKGROUND AND OBJECTIVE: The aim of this study is to compare the efficiency of low dose vs. varying doses of hyperbaric bupivacaine in spinal anesthesia for endoscopic urological procedures. METHODS: Sixty consecutive patients were studied in a randomized prospective manner. They received either of 5 (Gr I), 7.5 (Gr II) or 10 mg (Gr III) of hyperbaric bupivacaine 0.5% combined with 25 microg of fentanyl, through a 25-gauge W hitacre spinal needle placed in the L3-L4 interspace. Characteristics of sensory and motor block, dose of ephedrine required, secondary effects, the patients, and the surgeons satisfaction, were noted. RESULTS: The maximum number of blocked segments was 14 +/- 1 (Gr I), 15 +/- 2 (Gr II) and 16 +/- 2 (Gr III). Time to T12 regression was significantly shorter for Gr I (53 +/- 13 min) than for Gr II (69 +/- 20 min) or Gr III (94 +/- 14 min). Bromage 3 block was not found in Gr I compared to 4 patients in Gr II and 15 patients in Gr III. The duration of motor block was shorter in Gr 1(51 +/- 18 min) than in Gr II (86 +/- 19 min) and in Gr III (138 +/- 21 min). Ephedrine was used for 16 patients in Gr III (9.8 +/- 12.2 mg), 5 patients in Gr II (3.7 +/- 7.8 mg) and 2 patients in Gr I (0.5 +/- 1.5 mg). The difference is statistically significant between Gr III and the other groups. CONCLUSIONS: These results suggest that the use of a low dose of bupivacaine (5 mg) added to fentanyl (25 microg) for endoscopic urological surgery, resulted in short-acting sensory block, without motor block and a lower incidence of cardiovascular side effects, as compared to either of 7.5 or 10 mg bupivacaine with 25 microg fentanyl.     

Mefloquine pharmacokinetics in healthy subjects and in peptic ulcer patients after cimetidine administration.

The pharmacokinetics of orally administered mefloquine were determined in six healthy male subjects and in six ulcer patients before and after a 3-day course of cimetidine (400 mg morning and evening). Peak plasma concentrations Cmax and AUC0-infinity were similarly and significantly (P < 0.05) increased after cimetidine pretreatement in both healthy subjects and peptic ulcer patients Cmax was increased by 42.4% and 20.5% while AUC0-infinity was increased by 37.5% in healthy and peptic ulcer subjects respectively. The values of t1/2ab absorption and t1/2 beta elimination, total crearance CLT/F and volume of distribution were altered to varying levels after cimetidine treatment but the changes were not statistically significant in both healthy and peptic ulcer subjects. The established long t1/2 beta and this apparent interaction between mefloquine and cimetidine which resulted in increased mefloquine plasma concentration might be of clinical significant in patients with neurological/psychiatric history.     

The effect of magnesium sulfate on large cerebral artery blood flow in preeclampsia.

OBJECTIVES: To determine the effect of a 6 gram intravenous bolus of magnesium sulfate on maternal cerebral blood flow in women with preeclampsia. STUDY DESIGN: Velocity-encoded phase-contrast magnetic resonance imaging studies were performed on twelve preeclamptic women prior to and immediately after infusion of a 6 gram magnesium sulfate loading dose. Cerebral blood flow was determined at the bilateral proximal middle and posterior cerebral arteries. Study participants returned 6 weeks postpartum for a non-pregnant measurement of cerebral blood flow. The Wilcoxon paired-sample test was used with statistical significance defined as p<0.05. RESULTS: There was no significant difference in cerebral vessel diameter nor blood flow for any of the examined arteries between the pre- and post magnesium sulfate therapy states. CONCLUSIONS: The absence of a significant difference in cerebral blood flow of the middle and posterior cerebral arteries before and after infusion of a 6 gram loading dose of magnesium sulfate in women with preeclampsia could suggest the absence of vasoconstriction of the large cerebral arteries in preeclampsia and question the role of magnesium sulfate as a vasodilator of these arteries.