Quaternary and tertiary aldoxime antidotes for organophosphate exposure in a zebrafish model system.

The zebrafish is rapidly becoming an important model system for screening of new therapeutics. Here we evaluated the zebrafish as a potential pharmacological model for screening novel oxime antidotes to organophosphate (OP)-inhibited acetylcholinesterase (AChE). The ki values determined for chlorpyrifos oxon (CPO) and dichlorvos (DDVP) showed that CPO was a more potent inhibitor of both human and zebrafish AChE, but overall zebrafish AChE was less sensitive to OP inhibition.

Organophosphate pesticides induce morphological abnormalities and decrease locomotor activity and heart rate in Danio rerio and Xenopus laevis.

Organophosphate pesticides (OPs), a class of acetylcholinesterase inhibitors, are used widely in agriculture to reduce insect populations. Because of the conservation of acetylcholinesterase between invertebrates and vertebrates, OPs also can adversely affect nontarget species, such as aquatic and terrestrial animals. This study used uniform conditions to analyze the morphological and physiological effects caused by developmental exposure to 3 commonly used OPs-chlorpyrifos, dichlorvos, and diazinon-on 2 aquatic vertebrate species, Danio rerio (zebrafish) and Xenopus laevis.

The functional group on (E)-4,4'-disubstituted stilbenes influences toxicity and antioxidative activity in differentiated PC-12 cells.

This work probes the relationship between stilbene functional group and biological activity. The biological activity of synthesized stilbenes (E)-4,4'-dicyanostilbene, (E)-4,4'-diacetylstilbene, (E)-4,4'-diaminostilbene, a novel stilbene, 1,1'-(vinylenedi-p-phenylene)diethanol, and (E)-stilbene was assessed at biologically relevant nanomolar concentrations using the MTS cell viability assay in differentiated PC-12 cells under optimal culture conditions and conditions of oxidative stress. Under optimal culture conditions the synthesized stilbene derivatives were found to be non-toxic to cells at concentrations up to 10 μg/ml.

C-terminal tetrapeptides inhibit Aβ42-induced neurotoxicity primarily through specific interaction at the N-terminus of Aβ42.

Inhibition of amyloid β-protein (Aβ)-induced toxicity is a promising therapeutic strategy for Alzheimer's disease (AD). Previously, we reported that the C-terminal tetrapeptide Aβ(39-42) is a potent inhibitor of neurotoxicity caused by Aβ42, the form of Aβ most closely associated with AD. Here, initial structure-activity relationship studies identified key structural requirements, including chirality, side-chain structure, and a free N-terminus, which control Aβ(39-42) inhibitory activity.

Mechanistic investigation of the inhibition of Abeta42 assembly and neurotoxicity by Abeta42 C-terminal fragments.

Oligomeric forms of amyloid beta-protein (Abeta) are key neurotoxins in Alzheimer's disease (AD). Previously, we found that C-terminal fragments (CTFs) of Abeta42 interfered with assembly of full-length Abeta42 and inhibited Abeta42-induced toxicity. To decipher the mechanism(s) by which CTFs affect Abeta42 assembly and neurotoxicity, here, we investigated the interaction between Abeta42 and CTFs using photoinduced cross-linking and dynamic light scattering.

Biophysical characterization of Abeta42 C-terminal fragments: inhibitors of Abeta42 neurotoxicity.

A key event in Alzheimer's disease (AD) is age-dependent, brain accumulation of amyloid beta-protein (Abeta) leading to Abeta self-association into neurotoxic oligomers. Previously, we showed that Abeta oligomerization and neurotoxicity could be inhibited by C-terminal fragments (CTFs) of Abeta42. Because these CTFs are highly hydrophobic, we asked if they themselves aggregated and, if so, what parameters regulated their aggregation.

C-terminal peptides coassemble into Abeta42 oligomers and protect neurons against Abeta42-induced neurotoxicity.

Alzheimer's disease (AD) is an age-related disorder that threatens to become an epidemic as the world population ages. Neurotoxic oligomers of Abeta42 are believed to be the main cause of AD; therefore, disruption of Abeta oligomerization is a promising approach for developing therapeutics for AD. Formation of Abeta42 oligomers is mediated by intermolecular interactions in which the C terminus plays a central role.

Knocked down and out: PACAP in development, reproduction and feeding.

One approach to understanding the role of PACAP in vivo is to knockdown the translation of PACAP mRNA to protein or to knock out the PACAP gene by targeted disruption. In this paper, we review the effect of PACAP knockdown with morpholinos on early brain development in zebrafish. Also reviewed is the role of PACAP at several stages of reproduction as assessed in mice with a disrupted PACAP gene.

Role of two genes encoding PACAP in early brain development in zebrafish.

To study the role of pituitary adenylate cyclase-activating polypeptide (PACAP) in early brain development, we examined PACAP and its receptors for first expression and then separately knocked down the two forms of PACAP in zebrafish where development is rapid and observable. We injected morpholinos (antisense oligonucleotides) into fertilized eggs to block PACAP. Morphological changes in the brain were observed in embryos at 27 h post fertilization (hpf).

En route to early diagnosis of Alzheimer's disease--are we there yet?

As therapeutics for Alzheimer's disease (AD) become available, it will become increasingly important to develop accurate and reliable tools for its early diagnosis. A recent paper by Georganopoulou et al. suggests that nanobiotechnology could help to overcome the limitations with the current diagnostic methods.

Neurotoxic protein oligomers--what you see is not always what you get.

An increasing body of evidence suggests that soluble assemblies of amyloid proteins are the predominant neurotoxic species in many amyloid-related diseases. Consequently, the focus of research on pathologic mechanisms underlying amyloidoses has shifted from amyloid fibrils to oligomers. Biophysical characterization of oligomers is difficult due to their metastable nature.

Characterization of four receptor cDNAs: PAC1, VPAC1, a novel PAC1 and a partial GHRH in zebrafish.

To understand the role of growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclase-activating polypeptide (PACAP) and to examine the functional significance of the co-expression of GHRH and PACAP in fish, their receptors were characterized in zebrafish. Three cDNAs encoding the PAC(1) receptor, the VPAC(1) receptor, and the partial GHRH receptor were identified from zebrafish. Functional expression of the PAC(1) and VPAC(1) receptors revealed that both are potently coupled to the adenylyl cyclase pathway, but only the PAC(1) receptor is coupled to the phospholipase C pathway.

Developmental changes in the expression of growth hormone-releasing hormone and pituitary adenylate cyclase-activating polypeptide in zebrafish.

Growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclase-activating polypeptide (PACAP) are structurally and functionally related members of the glucagon superfamily, a group of hormones important in development, growth, and metabolism. Our objectives were to determine the developmental expression pattern of the ghrh-pacap1 gene using the zebrafish model. The temporal and spatial expression pattern of the ghrh-pacap1 gene was examined by RT-PCR and in situ hybridization.