Enkephalins-modulation of Plasmodium cynomolgi antigens-induced colony-stimulating factors elaboration by macrophages.

Methionine-enkephalin (M-Enk) and its analogue compound 82/205 (10(-5) and 10(-6) M) inhibited elaboration of Plasmodium cynomolgi total antigens soluble in culture medium (P.c.SA)-induced colony-stimulating factors (CSFs) by monkey blood monocyte-derived macrophages, in vitro. Paradoxically, lower concentrations (10(-7)-10(-9) M) of both the peptides greatly augmented CSFs elaboration; 82/205 appeared to be nearly 2.3-fold more potent. Naloxone (10(-5) M) pretreatment of macrophages inhibited only the M-Enk- and 82/205-induced enhanced CSFs elaboration, suggesting an opiate receptors-mediated mechanism of action. None of the peptides or naloxone (10(-5)-10(-9) M) had any direct effect on the CSF elaboration by unstimulated macrophages.     

Quantifying Significance of Topographical Similarities of Disease-Related Brain Metabolic Patterns

Multivariate analytical routines have become increasingly popular in the study of cerebral function in health and in disease states. Spatial covariance analysis of functional neuroimaging data has been used to identify and validate characteristic topographies associated with specific brain disorders. Voxel-wise correlations can be used to assess similarities and differences that exist between covariance topographies. While the magnitude of the resulting topographical correlations is critical, statistical significance can be difficult to determine in the setting of large data vectors (comprised of over 100,000 voxel weights) and substantial autocorrelation effects. Here, we propose a novel method to determine the p-value of such correlations using pseudo-random network simulations.     

Occurrence and bioassay responses of G

A growth regulator (G) occurs at high concentrations in adult leaves of E. grandis Maiden. Low concentrations of G are present in juvenile leaves of this species and also in adult leaves of some other Myrtaceae. Low concentrations of G (5×10^–6 and 10^–5 M) promote rooting in mung-bean cuttings and elongation in Avena coleoptile sections; high concentrations (5×10^–4 M) inhibit. These and other bioassay results indicate that G may have auxin-like activity.     

Smad4-dependent regulation of urokinase plasminogen activator secretion and RNA stability associated with invasiveness by autocrine and paracrine transforming growth factor-beta

Metastasis is a primary cause of mortality due to cancer. Early metastatic growth involves both a remodeling of the extracellular matrix surrounding tumors and invasion of tumors across the basement membrane. Up-regulation of extracellular matrix degrading proteases such as urokinase plasminogen activator (uPA) and matrix metalloproteinases has been reported to facilitate tumor cell invasion. Autocrine transforming growth factor-beta (TGF-beta) signaling may play an important role in cancer cell invasion and metastasis; however, the underlying mechanisms remain unclear. In the present study, we report that autocrine TGF-beta supports cancer cell invasion by maintaining uPA levels through protein secretion. Interestingly, treatment of paracrine/exogenous TGF-beta at higher concentrations than autocrine TGF-beta further enhanced uPA expression and cell invasion. The enhanced uPA expression by exogenous TGF-beta is a result of increased uPA mRNA expression due to RNA stabilization. We observed that both autocrine and paracrine TGF-beta-mediated regulation of uPA levels was lost upon depletion of Smad4 protein by RNA interference. Thus, through the Smad pathway, autocrine TGF-beta maintains uPA expression through facilitated protein secretion, thereby supporting tumor cell invasiveness, whereas exogenous TGF-beta further enhances uPA expression through mRNA stabilization leading to even greater invasiveness of the cancer cells.     

Expression of constitutive and inducible cytochrome P450 2E1 in rat brain

Studies initiated to investigate the expression of cytochrome P450 2E1 (CYP2E1) in rat brain demonstrated low but detectable protein and mRNA expression in control rat brain. Though mRNA and protein expression of CYP2E1 in brain was several fold lower as compared to liver, relatively high activity of N-nitrosodimethylamine demethylase (NDMA-d) was observed in control rat brain microsomes. Like liver, pretreatment with CYP2E1 inducers such as ethanol or pyrazole or acetone significantly increased the activity of brain microsomal NDMA-d. Kinetic studies also showed an increase in the Vmax and affinity (Km) of the substrate towards the brain enzyme due to increased expression of CYP2E1 in microsomes of brain isolated from ethanol pretreated rats. In vitrostudies using organic inhibitors, specific for CYP2E1 and anti-CYP2E1 significantly inhibited the brain NDMA-d activity indicating that like liver, NDMA-d activity in rat brain is catalyzed by CYP2E1. Olfactory lobes exhibited the highest CYP2E1 expression and catalytic activity in control rats. Furthermore, several fold increase in the mRNA expression and activity of CYP2E1 in cerebellum and hippocampus while a relatively small increase in the olfactory lobes and no significant change in other brain regions following ethanol pretreatment have indicated that CYP2E1 induction maybe involved in selective sensitivity of these brain areas to ethanol induced free radical damage and neuronal degeneration.     

Cytochrome P4503A: Evidence for mRNA expression and catalytic activity in rat brain

Studies initiated to investigate the presence of cytochrome P4503A (CYP3A) isoenzymes in brain revealed constitutive mRNA and protein expression of CYP3A1 in rat brain. Western blotting studies showed that pretreatment with CYP3A inducer such as pregnenolone-16α -carbonitrile (PCN) significantly increased the cross reactivity comigrating with hepatic CYP3A1 and CYP3A2 in rat brain microsomes. RT-PCR studies have also shown increase in mRNA expression of CYP3A1 following pretreatment of rats with PCN. The ability of rat brain microsomes to catalyze the demethylation of erythromycin, known to be mediated by CYP3A isoenzymes in liver and significant increase in the activity of erythromycin demethylase (EMD) following pretreatment with dexamethasone or PCN have indicated that CYP3A isoenzymes expressed in brain are functionally active. Kinetic studies revealed that increase in the enzyme activity following pretreatment with PCN resulted in increase in the apparent affinity (Km) and Vmax of the reaction. Similarities in the inhibition of the constitutive and inducible brain and liver EMD activity following in vitro addition of ketoconazole, a inhibitor specific for CYP3A catalysed reactions and anti-CYP3A have further indicated that like in liver, CYP3A isoenzymes catalyse the activity of EMD in rat brain. Data also revealed regional differences in the activity of EMD in the brain. Relatively higher constitutive as well as inducible mRNA expression of CYP3A1 in hypothalamus and hippocampus, the brain regions responsive to steroid hormones have suggested that CYP3A isoenzymes may not only be involved in the process of detoxication mechanism but also in the metabolism of endogenous substrates in brain.     

Protective Role of Lithium in Ameliorating the Aluminium-induced Oxidative Stress and Histological Changes in Rat Brain

This study was carried out to investigate the effects of lithium (Li) supplementation on aluminium (Al) induced changes in antioxidant defence system and histoarchitecture of cerebrum and cerebellum in rats. Al was administered in the form of aluminium chloride (100 mg/kg b.wt./day, orally) and Li was given in the form of Li carbonate through diet (1.1 g/kg diet, daily) for a period of 2 months. Al treatment significantly enhanced the levels of lipid peroxidation and reactive oxygen species in both the cerebrum and cerebellum, which however were decreased following Li supplementation. The enzyme activities of catalase, superoxide dismutase (SOD) and glutathione reductase (GR) were significantly increased in both the regions following Al treatment. Li administration to Al-fed rats decreased the SOD, catalase and GR enzyme activities in both the regions; however, in cerebellum the enzyme activities were decreased in comparison to normal controls also. Further, the specific activity of glutathione-s-transferase and the levels of total and oxidized glutathione were significantly decreased in cerebrum and cerebellum following Al treatment, which however showed elevation upon Li supplementation. The levels of reduced glutathione were significantly decreased in cerebrum but increased in cerebellum following Al treatment, which however were normalized upon Li supplementation but in cerebellum only. Apart from the biochemical changes, disorganization in the layers of cerebrum and vacuolar spaces were also observed following Al treatment indicating the structural damage. Similarly, the loss of purkinje cells was also evident in cerebellum. Li supplementation resulted in an appreciable improvement in the histoarchitecture of both the regions. Therefore, the study shows that Li has a potential to exhibit neuroprotective role in conditions of Al-induced oxidative stress and be explored further to be treated as a promising drug against neurotoxicity.