The typical abnormalities observed in the brain of Alzheimer's disease (AD) patients include synaptic alterations, neuronal death, brain inflammation, and the accumulation of protein aggregates in the form of amyloid plaques and neurofibrillary tangles. Despite the development of many animal and in vitro models for AD, there is a lack of an experimental approach that fully recapitulates essential aspects of the disease in human cells. Here, we report the generation of a new model to study AD, consisting of cerebral organoids (COs) produced from human-induced pluripotent stem cells (iPSCs). Under our experimental conditions, COs grow to form three-dimensional (3D) structures containing neural areas with cortical-like organization. Analysis of COs by histological and biochemical methods revealed that organoids produced from iPSCs derived from patients affected by familial AD or Down syndrome (DS) spontaneously develop over time pathological features of AD, including accumulation of structures highly reminiscent to amyloid plaques and neurofibrillary tangles. These pathological abnormalities were not observed in COs generated from various controls, including human iPSCs from healthy individuals, human iPSCs from patients affected by Creutzfeldt-Jakob disease, mouse embryonic stem cells (ESCs), or mouse iPSCs. These findings enable modeling genetic AD in a human cellular context in a 3D cortical-like tissue developed in vitro from patient-specific stem cells. This system provides a more relevant disease model compared to pre-existing methods and offers a new platform for discovery of novel targets and screening of drugs for therapeutic intervention.

Protein misfolding and aggregation into fibrillar deposits is a common feature of a large group of degenerative diseases affecting the central nervous system or peripheral organs, termed protein misfolding disorders (PMDs). Despite their established toxic nature, clinical trials aiming to reduce misfolded aggregates have been unsuccessful in treating or curing PMDs. An interesting possibility for disease intervention is the regular intake of natural food or herbal extracts, which contain active molecules that inhibit aggregation or induce the disassembly of misfolded aggregates. Among natural compounds, phenolic molecules are of particular interest, since most have dual activity as amyloid aggregation inhibitors and antioxidants. In this article, we review many phenolic natural compounds which have been reported in diverse model systems to have the potential to delay or prevent the development of various PMDs, including Alzheimer's and Parkinson's diseases, prion diseases, amyotrophic lateral sclerosis, systemic amyloidosis, and type 2 diabetes. The lower toxicity of natural compounds compared to synthetic chemical molecules suggest that they could serve as a good starting point to discover protein misfolding inhibitors that might be useful for the treatment of various incurable diseases.

The symptoms of prion infection can take years or decades to manifest following the initial exposure. Molecular markers of prion disease include accumulation of the misfolded prion protein (PrP Sc ), which is derived from its cellular precursor (PrP C ), as well as downregulation of the PrP-like Shadoo (Sho) glycoprotein. Given the overlapping cellular environments for PrP C and Sho, we inferred that PrP C levels might also be altered as part of a host response during prion infection. Using rodent models, we found that, in addition to changes in PrP C glycosylation and proteolytic processing, net reductions in PrP C occur in a wide range of prion diseases, including sheep scrapie, human Creutzfeldt-Jakob disease, and cervid chronic wasting disease. The reduction in PrP C results in decreased prion replication, as measured by the protein misfolding cyclic amplification technique for generating PrP Sc in vitro. While PrP C downregulation is not discernible in animals with unusually short incubation periods and high PrP C expression, slowly evolving prion infections exhibit downregulation of the PrP C substrate required for new PrP Sc synthesis and as a receptor for pathogenic signaling. Our data reveal PrP C downregulation as a previously unappreciated element of disease pathogenesis that defines the extensive, presymptomatic period for many prion strains.

The cellular prion protein (PrPC) comprises a natively unstructured N-terminal domain, including a metal-binding octarepeat region (OR) and a linker, followed by a C-terminal domain that misfolds to form PrPSc in Creutzfeldt-Jakob disease. PrPC β-endoproteolysis to the C2 fragment allows PrPSc formation, while α-endoproteolysis blocks production. To examine the OR, we used structure-directed design to make novel alleles, ‘S1’ and ‘S3’, locking this region in extended or compact conformations, respectively. S1 and S3 PrP resembled WT PrP in supporting peripheral nerve myelination. Prion-infected S1 and S3 transgenic mice both accumulated similar low levels of PrPSc and infectious prion particles, but differed in their clinical presentation. Unexpectedly, S3 PrP overproduced C2 fragment in the brain by a mechanism distinct from metal-catalysed hydrolysis reported previously. OR flexibility is concluded to impact diverse biological endpoints; it is a salient variable in infectious disease paradigms and modulates how the levels of PrPSc and infectivity can either uncouple or engage to drive the onset of clinical disease.

A tag-recapture study of the Ozark Hellbender salamander, Cryptobranc/ws a. bishopi, was made on the North Fork of the White River, Ozark Co., Missouri. During the summers of 1969 and 1970, animals were tagged along a 2.67-km stretch of stream bed. Population estimates were 428 with 95% C.L. of 341-573 hellbenders/km of stream bed. Biomass estimates were 156 kg/km with 95% C.L. of 124.5-210 kg/km of stream bed. Density estimate in "prime habitat" was one/8-10 m2 with 95% C.L. of one/6-7 mz_one/13-16 m 2 . Recaptures indicated little movement. Ozark Hellbenders are one of the dominant organisms in this stream system.