A new family of tacrine (THA) analogues (7-9, 12), containing the azaheterocyclic pyrazolo[4,3-d]pyridine or pyrazolo[3,4-b][1,8]naphthyridine systems as isosteres of the quinoline ring of THA, has been synthesized. The compounds were tested in rat brain cholinesterases using Ellman's method, and all were fully efficacious in inhibiting the enzymes. Compounds 9 and 12b were the most potent against acetylcholinesterase (AChE), showing IC(50) of 6.0 and 6.4 microM, and were less active against rat brain butyrylcholinesterase, showing selectivity indexes of 5.3 and 20.9, respectively. Compounds 7-9 and 12 were also tested for their acute neurotoxicity in vitro, using cultured rat cortical cells. Compounds 7 and 8 were not significantly toxic; 9 was toxic at 500 microM, but not at 100 microM. The naphthyridine derivatives 12a and 12b showed a significant concentration-dependent neurotoxicity, being able to kill most cells at 500 microM. Molecular dynamic simulation using the X-ray crystal structure of AChE from Torpedo californica was used to explain the possible binding mode of these new THA isosteres.

Bone marrow mesenchymal stem cells (MSC) have been tested and proven effective in some neurodegenerative diseases, but their tracking after transplantation may be challenging. Our group has previously demonstrated the feasibility and biosafety of rat MSC labeling with iron oxide superparamagnetic nanoparticles (SPION). In this study, we investigated the therapeutic potential of SPION-labeled MSC in a rat model of Huntington's disease, a genetic degenerative disease with characteristic deletion of striatal GABAergic neurons. MSC labeled with SPION were injected into the striatum 1h after quinolinic acid injection. FJ-C analysis demonstrated that MSC transplantation significantly decreased the number of degenerating neurons in the damaged striatum 7 days after lesion. In this period, MSC transplantation enhanced the striatal expression of FGF-2 but did not affect subventricular zone proliferation, as demonstrated by Ki67 proliferation assay. In addition, MSC transplantation significantly reduced the ventriculomegaly in the lesioned brain. MRI and histological techniques detected the presence of the SPION-labeled cells at the lesion site. SPION-labeled MSC produced magnetic resonance imaging (MRI) signals that were visible for at least 60 days after transplantation. Our data highlight the potential of adult MSC to reduce brain damage under neurodegenerative diseases and indicate the use of nanoparticles in cell tracking, supporting their potential as valuable tools for cell therapy.

We investigated the role of retinotectal projections on the distribution of nitric oxide synthase (NOS) in the retinoceptive layers of the rat superior colliculus (SC) using histochemical methods. Rats enucleated at birth showed no alteration in the temporal pattern of NOS expression. There was, however, a dramatic change in the NADPH-diaphorase staining pattern of NOS-positive cells. NOS was absent from the distal portions of the dendritic trees of the deafferented SC. Nevertheless, staining the dendritic trees of these cells with Lucifer yellow showed that they were not morphologically different from those of the ipsilateral SC of monoenucleated animals. The same results were obtained when enucleation was performed in adult rats. We conclude that NOS intracellular distribution in the SC cells can be regulated by retinotectal projections in both developing and adult animals.

The natural alkaloid (-)PHY is a reversible anticholinesterase carbamate, but in contrast, its optical isomer (+)PHY, is a very weak anticholinesterase. We have shown that treatment of rats with atropine and (-)PHY prior to injections of a lethal dose of the irreversible organophosphate sarin (0.13 mg/kg) not only protected 100% of the animals from lethality but also reduced the size of the subneural lesions of the nicotinic synapses of skeletal muscle. Similar protection against lethality is provided by pretreatment with (+)PHY. At the concentration used (0.3 mg/kg), there was no detectable inhibition of AChE activity. We have examined the protection afforded by (+)PHY or (-)PHY against lethality and myopathy due to organophosphate agents such as sarin. The major alterations in the soleus motor endplates 1 hr after drug treatment were as follows: (1) A single sublethal dose of sarin (0.08 mg/kg) produced enlarged, blistered, and severely disrupted subjunctional regions, with muscle damage extending beyond the endplate to include myofiber necrosis and subsequent phagocytosis; (2) (+)PHY (0.3 mg/kg) produced no obvious damage in the postjunctional region; (3) (-)PHY (0.1 mg/kg) had a selective effect in inducing irregularities of the subjunctional sarcomere band patterns without any gross vacuolization; (4) light microscopic data indicated that the combination of atropine and (+)PHY, or of atropine and (-)PHY (0.1 mg/kg), 30 min prior to a lethal dose of sarin, offered dramatic reduction in the average dimension of lesions. Lesions were detectable in most endplates but recognizable changes were markedly less severe than those seen in sarin myopathy. Few instances of extensive muscle damage and myofiber necrosis were visible.(ABSTRACT TRUNCATED AT 250 WORDS)

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Global cerebral ischemia (GCI) results in death of the pyramidal neurons in the CA1 layer of the hippocampus. In this study we used the four-vessel occlusion (4VO) model of GCI to investigate a potential neuroprotective role of bone-marrow mononuclear cells (BMMCs) transplantation. BMMCs (3×10(7)) were injected through the carotid artery, 1 or 3 days after ischemia (DAI), and the number of cells undergoing degeneration was investigated in brains at 7 DAI. A significant decrease in the number of dying cells was observed in the treated group, compared to animals treated with saline. Biodistribution of the injected cells (1 or 3 DAI) was investigated by (99m)Technetium labeling of the BMMCs and subsequent image analysis 2h after transplantation. In addition, the presence of CellTrace(™)-labeled BMMCs was investigated in tissue sections of the hippocampal area of these transplanted animals. BMMCs treatment significantly reduced the number of FJ-C positive cells in the hippocampal CA1 layer at 7 DAI. We also observed a decrease in the number of activated microglia/macrophage (ED1-positive cells) in the BMMCs-treated group compared with the untreated group. Our data show that BMMCs are able to modulate the microglial response and reduce neurodegeneration in the CA1 layer.