Correlation in inflammatory fibroblasts between the number of glucocorticoid receptors and PGE2 release

The anti-inflammatory effects of glucocorticoids are mediated through steroid receptor occupancy and there is a significant correlation between the extent of receptor saturation and the extent of the biological effects. In a previously published study, we found that the number of these receptors was higher in inflammatory fibroblasts than in quiescent ones. PGE2 release, measured at the same time as the number of steroid receptors, was higher when the cells were from inflammatory tissue. Our aim, in the present study, was to determine whether the PGE2 released by cells during inflammatory processes could participate in increasing the number of steroid receptors. Fibroblasts obtained from rat quiescent subcutaneous connective tissue and granulomas were subcultured in monolayers. The specific binding of [3H]dexamethasone was assessed and analyzed by a method described by Kalimi et al. After a freeze-thaw cycle, we observed a decrease in the number of receptors in inflammatory fibroblasts. When the frozen and thawed fibroblasts were subcultured in the presence of PGE2 (10(-8) M), the number of receptors was enhanced in fibroblasts from inflammatory tissue. Cycloheximide (3 X 10(-7) M) prevented this increase. The release of PGE2 decreased after freezing and then increased simultaneously with the number of receptors in inflammatory cells. These findings suggest that PGE2 may play a role in regulating steroid effects on fibroblast function.     

D-2 dopamine receptors in the frontal cortex of rat and human

D-2 dopamine receptors and serotonin receptors in the frontal cortex of rat and human were labelled with 3H-spiroperidol. The D-2 receptors were then distinguished in 4 ways. Dissociation of spiroperidol was biphasic, indicating two populations of sites. Cinanserin in competition with 3H-spiroperidol exhibited high (75%) and low (25%) affinity sites. Dopamine and LY 141865 in competition with 1.25 nM 3H-spiroperidol exhibited high (20-25%) and low (80-75%) affinity sites in the absence of cinanserin, while in the presence of 300 nM cinanserin only the high affinity sites remained. Lesioning of the dopaminergic meso-cortical pathway increased the number of cinanserin-resistant sites by 26%. Thus 3H-spiroperidol binding in the presence of cinanserin can be used to selectively label D-2 receptors in the frontal cortex.     

5-HT1B Autoreceptors limit the effects of selective serotonin re-uptake inhibitors in mouse hippocampus and frontal cortex

We used knockout mice and receptor antagonist strategies to investigate the contribution of the serotonin (5-hydroxytryptamine, 5-HT) 1B receptor subtype in mediating the effects of selective serotonin re-uptake inhibitors (SSRIs). Using in vivo intracerebral microdialysis in awake mice, we show that a single systemic administration of paroxetine (1 or 5 mg/kg, i.p.) increased extracellular serotonin levels [5-HT]ext in the ventral hippocampus and frontal cortex of wild-type and mutant mice. However, in the ventral hippocampus, paroxetine at the two doses studied induced a larger increase in [5-HT]ext in knockout than in wild-type mice. In the frontal cortex, the effect of paroxetine was larger in mutants than in wild-type mice at the 1 mg/kg, but not at 5 mg/kg. In addition, either the absence of the 5-HT1B receptor or its blockade with the mixed 5-HT1B/1D receptor antagonist, GR 127935, potentiated the effect of a single administration of paroxetine on extracellular 5-HT levels more in the ventral hippocampus than in the frontal cortex. These data suggest that 5-HT1B autoreceptors limit the effects of SSRIs on dialysate 5-HT levels at serotonergic nerve terminals.     

Correlation between the number of centrioles and ploidy of mouse liver hepatocytes

Using the electron microscope it was shown that in interphase hepatocytes with ploidies equal to 2n, 2n.2, 4n, 4n.2 and 8n, the number of centrioles per cell exactly corresponded to the ploidy of the cell. Both in mononuclear and binuclear cells all the centrioles are accumulated in one complex in which each pair of centrioles forms a diplosome. In binuclear cells, the complex of diplosomes is situated at equal distances from each nucleus, thus making the cell centre. The involvement of the supernumerous centrioles in polyploid metaphase cells was detected for the regenerating liver of old mice. It was found that each mitotic pole had at least four centrioles. In the pole, a pair of centrioles forms diplosomes tightly connected to each other. It is suggested that the initially tetraploid cell might divide in this manner. In addition, a question is discussed on how the existence of centrioles can be associated with the mechanism of polyploidization.     

Increased uptake sites for serotonin and dopamine with decreased S2 serotonin receptors in microencephalic rat brain

Methylazoxymethanol (MAM)-induced cerebral hypoplasia resulted in a significant increase in densities of both serotonin uptake sites in frontal cortex and dopamine uptake sites in striatum, suggesting serotonergic and dopaminergic axon terminals were compressed in the smaller brain volumes. The density of S2 serotonin receptors in MAM-lesioned frontal cortex was decreased probably due to down-regulation, while densities of D1 and D2 dopamine receptors in striatum were identical between MAM-lesioned rats and control rats.     

Differential up- and down-regulation of type I and type II receptors for adrenocorticosteroid hormones in mouse brain

Adult female mice were adrenalectomized and ovariectomized and the concentration of Type I and Type II receptors in whole brain, kidney, and liver cytosol determined at various time thereafter by incubation with [3H]aldosterone (+ RU 26988 to prevent binding to Type II receptors) or [3H]dexamethasone, respectively. Type I receptor binding in brain was found to undergo a dramatic biphasic up-regulation, with levels six times that of intact levels by 24 h post-surgery and a doubling again by 4-8 days post-surgery. By 16 days, however, Type I specific binding had returned to intact levels. Similar, but less dramatic fluctuations were seen in kidney and liver, whereas much smaller fluctuations were seen for Type II receptors in all three tissues. In a follow-up study with Scatchard analyses we observed a similar transient up- and down-regulation in maximal binding for Type I, and to a lesser extent Type II receptors in all three tissues. As expected, the apparent binding affinity for both receptors increased after surgical removal of competing endogenous steroids. Radioimmunoassays revealed that plasma concentrations of corticosterone were reduced to near undetectable levels by 24 h post-surgery. A direct comparison of male and female mice revealed no sex-related differences in Type I receptor binding capacity fluctuations in brain cytosol after adrenalectomy-gonadectomy. Lastly, treatment with exogenous aldosterone or corticosterone was found to prevent adrenalectomy-gonadectomy-induced up-regulation of Type I and, to a lesser extent, Type II receptors in brain. Somewhat surprisingly, the potency of these two adrenocorticosteroids appeared to be very similar for both receptor types.     

Novel DNA polymorphism in the mouse tumor necrosis factor receptors type 1 and type 2

The introduction of the polymerase chain reaction (PCR) provides an entirely new means of analyzing DNA polymorphism and makes practical the analysis of length variation in simple-sequence tandem repeats of dinucleotides. In the process of cloning and sequencing the mouse genomic DNA for tumor necrosis factor (TNF) receptors type 1 and type 2, we identified two simple dinucleotide repeats within the noncoding regions of TNF receptor type 1 and three such sequences within TNF receptor type 2. PCR analysis of these sequences, using genomic DNA from 21 different inbred and wild mouse strains, as demonstrated by running the amplified products on sequencing gels, showed that the repeats are highly polymorphic. We identified seven alleles of TNF receptor type 2 and five alleles of TNF receptor type 1. Using these polymorphic markers in two sets of recombinant inbred strains of mice, the chromosomal localization of Tnfr-1 was mapped to mouse chromosome 6 and Tnfr-2 was located to the distal portion of mouse chromosome 4.     

Correlation of evoked potentials in the frontal cortex and hippocampus of cats in emotional stress

Averaged auditory evoked potentials (AEPs) were recorded in symmetric points of the frontal cortex and dorsal hippocampus of cats performing acquired conditioned food-procuring reaction reinforced in 100% cases, urgent transition to 30%-reinforcement, and return to 100%-reinforcement. Emotional stress estimated by a heart rate rise developed during increased food motivation of a cat as well as during change in ordinary food-procuring stereotype. The emotional stress was accompanied by a high positive correlation of cortical and hippocampal AEPs. Decrease in the stress level led to a drop between AEP correlations and appearance of their negative values. In emotional stress, the interactions between the frontal cortex and dorsal hippocampus were asymmetric: right-side correlations were higher.     

Opposite changes in imidazoline I2 receptors and alpha2-adrenoceptors density in rat frontal cortex after induced gliosis

Opposite age-dependent changes in alpha2-adrenoceptor and imidazoline I2 receptor (I2-IRs) density have been related to brain gliosis development with aging. To check this hypothesis we applied in rats a model of reactive gliosis induced by heat. The specific binding of [3H]idazoxan (0.5-20 nM) in the presence of (-)adrenaline (5 x 10(-6) M) to membranes from rat brain cortex showed that the density of I(2)-IRs was significantly higher in membranes of injured cortex (Bmax=60+/-6 fmol/mg protein; n=9) than in control (Bmax=38+/-3 fmol/mg protein; n=9; p=0.0053). Conversely, the density of alpha2-adrenoceptors, measured by [3H]clonidine (0.25-16 nM), in the injured cortex (Bmax=75+/-4 fmol/mg protein; n=9) was significantly lower than in sham membranes (Bmax=103+/-7 fmol/mg protein; n=9; p=0.0035). No significant differences in receptor's affinity were observed between both groups. These results support the hypothesis that gliosis induces opposite changes in alpha2-adrenoceptor and I2-IR density.     

Correlation between release of free arachidonic acid and prostaglandin formation in brain cortex and cerebellum

Levels of free arachidonic acid and of prostaglandin F_2α and E₂ have been measured in both brain cortex and cerebellum of rats killed by focussed microwave irradiation, and after decapitation followed by ischemia. The same parameters were studied during incubation assays. It was found that: a) after ischemia levels of both free arachidonic acid and of prostaglandins in cerebellum are lower than in brain cortex, b) formation of prostaglandins from endogenous precursor in incubated cortex is higher than in cerebellum, c) release of free arachidonic acid occurs mainly during the time interval between the sacrifice of the animals and the beginning of the incubation, whereas prostaglandins are formed mainly during the incubation assay. The correlation between release of free arachidonic acid and prostaglandin formation is discussed.     

Serotonin receptors in the frontal cortex of the rat. Influence of supralethal irradiation

The density of the frontal cortex serotonin-2 receptors was determined after a supralethal irradiation (20 Gy) in Wistar rat. Using spiperone as ligand, we observed an important decrease in the density of serotonin-2 receptor and an increase in the dissociation constant receptor-ligand, 3 days after exposure.     

Interactions between number and space in parietal cortex

Since the time of Pythagoras, numerical and spatial representations have been inextricably linked. We suggest that the relationship between the two is deeply rooted in the brain's organization for these capacities. Many behavioural and patient studies have shown that numerical-spatial interactions run far deeper than simply cultural constructions, and, instead, influence behaviour at several levels. By combining two previously independent lines of research, neuroimaging studies of numerical cognition in humans, and physiological studies of spatial cognition in monkeys, we propose that these numerical-spatial interactions arise from common parietal circuits for attention to external space and internal representations of numbers.     

Modulation of brain S2 serotonin receptors by lithium, sodium and potassium chloride

The effect of LiCl, NaCl, and KCl on serotonin competition for 3H-ketanserin binding to S2 serotonin receptors in homogenates of rat prefrontal cortex were investigated. LiCl was the most potent of the ionic modulators in lowering the apparent affinity of serotonin for the S2 serotonin receptor. A threshold effect was noted at 12 mM LiCl (a 60% change in IC50); at 120 mM LiCl a nine-fold shift in the serotonin IC50 was noted. 120 mM NaCl or KCl demonstrated similar effects as 12 mM LiCl in reducing serotonin's apparent affinity. These results indicated that monovalent cations modulate S2 serotonin receptor affinity for serotonin and that lithium ion is more potent than sodium or potassium.     

Correlation between the number of placental opioid receptors, mode of delivery, and maternal narcotic use

Human placental opioid receptors were assayed using the radioactive opioid agonist, etorphine, to determine the number of binding sites in villous tissue membrane preparations. Significant differences in receptor concentration per milligram of protein of tissue were found between placentas obtained following vaginal or abdominal delivery (P less than 0.002). Labor itself did not alter apparent receptor numbers. In patients with maternal narcotic abuse during pregnancy, no opioid binding could be detected regardless of the mode of delivery, suggesting possible receptor down-regulation.