Gerstmann–Sträussler–Scheinker syndrome (GSS) with the P102L mutation is a rare genetic prion disease caused by a pathogenic mutation at codon 102 in the prion protein gene. Cluster analysis encompassing data from 7 Czech patients and 87 published cases suggests the existence of 4 clinical phenotypes (typical GSS, GSS with areflexia and paresthesia, pure dementia GSS, and Creutzfeldt–Jakob disease–like GSS); GSS may be more common than previously estimated. In making a clinical diagnosis or progression estimates of GSS, magnetic resonance imaging and real‐time quaking‐induced conversion may be helpful, but the results should be evaluated with respect to the overall clinical context. ANN NEUROL 2019;86:643–652
Reduced beta cell mass in pancreatic islets (PI) of Goto-Kakizaki (GK) rats is frequently observed in this diabetic model, but knowledge on delta cells is scarce. Aiming to compare delta cell physiology/pathology of GK to Wistar rats, we found that delta cell number increased over time as did somatostatin mRNA and delta cells distribution in PI is different in GK rats. Subtle changes in 6-week-old GK rats were found. With maturation and aging of GK rats, disturbed cytoarchitecture occurred with irregular beta cells accompanied by delta cell hyperplasia and loss of pancreatic polypeptide (PPY) positivity. Unlike the constant glucose-stimulation index for insulin PI release in Wistar rats, this index declined with GK age, whereas for somatostatin it increased with age. A decrease of GK rat PPY serum levels was found. GK rat body weight decreased with increasing hyperglycemia. Somatostatin analog octreotide completely blocked insulin secretion, impaired proliferation at low autocrine insulin, and decreased PPY secretion and mitochondrial DNA in INS-1E cells. In conclusion, in GK rats PI, significant local delta cell hyperplasia and suspected paracrine effect of somatostatin diminish beta cell viability and contribute to the deterioration of beta cell mass. Altered PPY-secreting cells distribution amends another component of GK PI's pathophysiology.
The occurrence of phosphorylated proteins in ribosomes of Streptomyces coelicolor was investigated. Little is known about which biological functions these posttranslational modifications might fulfil. A protein kinase associated with ribosomes phosphorylated six ribosomal proteins of the small subunit (S3, S4, S12, S13, S14 and S18) and seven ribosomal proteins of the large subunit (L2, L3, L7/L12, L16, L17, L23 and L27). The ribosomal proteins were phosphorylated mainly on the Ser/Thr residues. Phosphorylation of the ribosomal proteins influences ribosomal subunits association. Ribosomes with phosphorylated proteins were used to examine poly (U) translation activity. Phosphorylation induced about 50% decrease in polyphenylalanine synthesis. After preincubation of ribosomes with alkaline phosphatase the activity of ribosomes was greatly restored. Small differences were observed between phosphorylated and unphosphorylated ribosomes in the kinetic parameters of the binding of Phe-tRNA to the A-site of poly (U) programmed ribosomes, suggesting that the initial binding of Phe-tRNA is not significantly affected by phosphorylation. On contrary, the rate of peptidyl transferase was about two-fold lower than that in unphosphorylated ribosomes. The data presented demonstrate that phosphorylation of ribosomal proteins affects critical steps of protein synthesis.
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