Neural progenitor cells do not differentiate prematurely in presenilin-1 null mutant mice

Mice with a null mutation of the presenilin-1 (PS1-/-) gene die during late intrauterine life or shortly after birth and exhibit defects in cortical development. A previous report suggested that neurons differentiate prematurely in PS1-/- brain [M. Handler, X. Yang, J. Shen, Presenilin-1 regulates neuronal differentiation during neurogenesis, Development 127 (2000) 2593-2606]. Here we reexamined the issue of whether premature neuronal differentiation occurs in PS1-/- brain using fresh cell suspensions from embryonic E11.5 and E13.5 telencephalon where individual cell phenotypes can be easily determined with cell type specific markers. Immunostaining with seven neuronal specific markers (MAP2, beta-III tubulin, GABA, reelin, GluR2/3, calbindin, and calretinin) failed to reveal any evidence of premature neuronal differentiation in PS1-/- telencephalon. We also determined the fraction of cells expressing the neural progenitor marker nestin and found no evidence for premature depletion of neural progenitor cells in PS1-/- telencephalon. Moreover, based on MAP2 staining of tissue sections from E12.5 embryos the topography of newly generated neurons also appeared to be undisturbed in the telencephalon of PS1-/- embryos. These studies thus argue that premature neuronal differentiation is unlikely to be a core pathophysiological feature underlying the aberrant cortical development that occurs in PS1-/- brain.     

Activation of mGluR5 modulates Ca2+ currents in retinal amacrine cells from the chick

In the inner plexiform layer, amacrine cells receive glutamatergic input from bipolar cells. Glutamate can depolarize amacrine cells by activation of ionotropic glutamate receptors or mediate potentially more diverse changes via activation of G protein-coupled metabotropic glutamate receptors (mGluR5). Here, we asked whether selective activation of metabotropic glutamate receptor 5 is linked to modulation of the voltage-gated Ca2+ channels expressed by cultured GABAergic amacrine cells. To address this, we performed whole-cell voltage clamp experiments, primarily in the perforated-patch configuration. We found that agonists selective for mGluR5, including (RS)-2-chloro-5-hydroxyphenylglycine (CHPG), enhanced the amplitude of the voltage-dependent Ca2+ current. The voltage-dependent Ca2+ current and CHPG-dependent current enhancement were blocked by nifedipine, indicating that L-type Ca2+ channels, specifically, were being modulated. We have previously shown that activation of mGluR5 produces Ca2+ elevations in cultured amacrine cells (Sosa et al., 2002). Loading the cells with 5 mM BAPTA inhibited the mGluR5-dependent enhancement, suggesting that the cytosolic Ca2+ elevations are required for modulation of the current. Although activation of mGluR5 is typically linked to activation of protein kinase C, we found that direct activation of this kinase leads to inhibition of the Ca2+ current, indicating that stimulation of this enzyme is not responsible for the mGluR5-dependent enhancement. Interestingly, direct stimulation of protein kinase A produced an enhancement of the Ca2+ current similar to that observed with activation of mGluR5. Thus, activation of mGluR5 may modulate the L-type voltage-gated Ca2+ current in these GABAergic amacrine cells via activation of protein kinase A, possibly via direct activation of a Ca2(+)-dependent adenylate cyclase.     

Iridoids as allelochemicals and DNA polymerase inhibitors

Growth inhibitory activities and nutritional indices of catalpol (1), 8-O-acetylharpagide (2), and harpagide (3) were determinated in larvae and adults of Tribolium castaneum, respectively. Compound 1 produced a series of allelochemical effects probably related with the DNA synthesis. This iridoid possessed the highest inhibitory activity against DNA polymerase. Molecular orbital calculations suggest that a pi-pi charge transfer recognition model could explain the action of iridioids toward nucleic acid synthesis.     

In vivo topical anti-inflammatory and in vitro antioxidant activities of two extracts of Thymus satureioides leaves

Four extracts at increasing polarity were prepared from the leaves of Thymus satureioides Coss. (Labiatae) and assayed for the in vivo topical anti-inflammatory effect using the croton oil ear test in mice, and for in vitro both antioxidant (DPPH degrees test) and anti-bacterial (broth microdilution method) activities. The chloroform extract showed a topical anti-inflammatory activity (ID50=282 microg cm(-2)), only three times lower than that of the reference drug indomethacin (ID50=93 microg cm(-2)) and its active components were identified as ursolic and oleanolic acids. The methanol extract, showing a significant radical-scavenging effect (SC50=14.54 microg), was characterized by the isolation and identification of some flavonoids. On the contrary, the extracts did not show any anti-bacterial effect against four standard aerobial bacteria strains.     

Percutaneous penetration and genotoxicity of 4,4'-methylenedianiline through rat and human skin in vitro

4,4'-Methylenedianiline (MDA) is a primary aromatic amine used in the plastics industry and is classified by the International Agency for Research on Cancer as an animal carcinogen and possible human carcinogen. In order to estimate human exposure it is useful to determine percutaneous penetration. Previous studies have suggested that both rat and human skin were permeable to MDA, with greater penetration being seen through human skin. In this study no significant difference was seen between the percutaneous penetration of MDA through human or rat skin for three different treatment levels: 0.01, 0.1 and 1mg per skin membrane (0.32 cm(2)). The apparent dermal flux was calculated as 0.7 +/- 0.3 and 10.1 +/- 2.0 microg/cm(2)/h for the 0.01 and 0.1mg treatments, respectively. The permeability constant K(p) was estimated at 1.8 x 10(-3) cm/h and the lag time at 3.5 +/- 0.5 h. MDA absorbed into the skin was found to be bioavailable. Experiments also showed that after application of 0.1mg MDA, 4% penetrated through latex and nitrile gloves, respectively. The potential genotoxicity of MDA in human skin was assessed by DNA (32)P-postlabelling; levels of DNA adducts were detected, following the treatment and penetration of 1mg MDA.     

Use of antidiabetes agents in pregnancy: current practice and controversy

Prior to the discovery of insulin, the combination of diabetes and pregnancy was considered potentially lethal. Advances in the care of diabetes, combined with advances in antepartum fetal testing, have reduced maternal and perinatal mortality outcomes to levels expected in nondiabetic pregnancies. As new oral antidiabetes medications are introduced, the safety and efficacy of using them during pregnancy are under investigation. This article describes the oral medications currently available to treat diabetes, reviews the body of research available on these agents, and discusses current recommendations and controversies.     

Effect of severe protein-calorie malnutrition on the penetration kinetics of trimethoprim and sulfamethoxazole to the deep tissues of Wistar rats

This study shows the effect that severe malnourishment has on the kinetics of antibiotic penetration in tissues. A total of 104 male Wistar rats, 21 days old, were randomly divided into eight groups. Five groups of experimental rats were severely malnourished (SM) and three further groups were considered well-nourished control groups (WN). A single dose of trimethoprim-sulfamethoxazole (TMP-SMX) was administered intraperitoneally. Blood samples were taken by heart puncture and five organs were extracted 0-24 h after the administration of the drug. HPLC was used to assess the amount of trimethoprim and sulfamethoxazole in fluids. The elimination half-life for trimethoprim from plasma was longer in SM rats with a median of 3.15 h; in WN rats, it was 0.390 h. Clearance was slower in SM rats: 646.72 mL microg(-1) h(-1) vs 3036.38 mL microg(-1) h(-1) in WN rats (P < 0.05). Tissue penetration was much higher for trimethoprim, with penetration indexes of 0.80-5.66 in WN rats, compared with 0.35-2.14 in SM rats. In the case of sulfamethoxazole, penetration indexes were 0.029-1.13 for WN and 0.075-0.657 for SM rats. Similarly, the penetration ratio to muscle and heart tissue was lower in SM rats. However, penetration to kidney, lung, liver and spleen was greater in SM rats. It is evident that severe SM decreases the capacity of trimethoprim more importantly than sulfamethoxazole biotransformation.