Human P301L-Mutant Tau Expression in Mouse Entorhinal-Hippocampal Network Causes Tau Aggregation and Presynaptic Pathology but No Cognitive Deficits

Accumulation of hyperphosphorylated tau in the entorhinal cortex (EC) is one of the earliest pathological hallmarks in patients with Alzheimer’s disease (AD). It can occur before significant Aβ deposition and appears to “spread” into anatomically connected brain regions. To determine whether this early-stage pathology is sufficient to cause disease progression and cognitive decline in experimental models, we overexpressed mutant human tau (hTauP301L) predominantly in layer II/III neurons of the mouse EC. Cognitive functions remained normal in mice at 4, 8, 12 and 16 months of age, despite early and extensive tau accumulation in the EC. Perforant path (PP) axon terminals within the dentate gyrus (DG) contained abnormal conformations of tau even in young EC-hTau mice, and phosphorylated tau increased with age in both the EC and PP. In old mice, ultrastructural alterations in presynaptic terminals were observed at PP-to-granule cell synapses. Phosphorylated tau was more abundant in presynaptic than postsynaptic elements. Human and pathological tau was also detected within hippocampal neurons of this mouse model. Thus, hTauP301L accumulation predominantly in the EC and related presynaptic pathology in hippocampal circuits was not sufficient to cause robust cognitive deficits within the age range analyzed here.     

Inhibition of leukocyte adhesion by the in vivo and in vitro administration of cannabinoids

Cannabinoids have been shown to affect various aspects of arachidonic acid metabolism both in vivo and in vitro. Eicosanoid metabolites of arachidonate and related octadecanoate are believed to be involved in cell adhesion processes as agonists in some instances and as antagonists in other cases. This report shows data in which cannabinoids exhibit marked inhibitory effects on the adhesion of mouse peritoneal cells to polystyrene culture dishes. The effects could be seen by in vivo administration of the drugs as well as by direct exposure of the cells in vitro. The data suggest that this inhibition of adhesion is mediated by one or more products generated by stimulation of a lipoxygenase pathway.     

The ras-like protein p25rab3A is partially cytosolic and is expressed only in neural tissue.

An antipeptide antiserum has been developed against a sequence near the C terminus of the small guanine nucleotide-binding protein p25rab3A. This protein is the product of one of a large number of genes that show homology to the ras proto-oncogenes. Immunoblotting with the antiserum specifically detected a 25-kilodalton protein in brain membranes. This protein coeluted from a MonoQ high-resolution ion-exchange column with a 25-kilodalton GTP-binding protein at a salt concentration similar to that known to elute purified p25rab3A. Unlike p21ras, which is exclusively membrane bound, p25rab3A is present in both the cytosol and membrane fractions of rat brain. It was not detected in other tissues, although a band of slightly lower molecular weight was observed with skeletal muscle. Western blot (immunoblot) analysis of five regions of the rat brain indicated that p25rab3A is most abundant in the hypothalamus and hippocampus.     

Intrinsic potential for high fetal hemoglobin production in a Druze family with β-thalassemia is due to an unlinked genetic determinant

Summary The mechanism for elevated production of fetal hemoglobin (Hb F) in a Druze patient with °-thalassemia intermedia was investigated. Heterozygous family members exhibited normal Hb F levels, suggesting that the increase in -gene expression in the propositus may be partly due to anemic stress. Erythroid progenitors of these family members cultured in vitro [burst forming units (erythroid); (BFUe)] showed elevated synthesis of Hb F, indicating the existence of a genetically determined intrinsic capacity for high Hb F production in this family. The propositus was found to be homozygous for a IVS2-position 1 mutation, on the background of Mediterranean haplotype I, which is not known to be linked to high Hb F production. Moreover, extensive molecular studies of the -globin gene cluster, including sequence analysis of the promoter regions of the -globin genes, did not reveal any cisacting mechanism that could account for the high Hb F production in the propositus. A young niece of the propositus with °-thalassemia major was recently discovered, who was homozygous for the same -globin allele and haplotype as the propositus. However, unlike her uncle, she does not have a high Hb F level and presents with a severe clinical course. Her inability to produce high Hb F suggests that the genetic determinant for increased -gene expression in the propositus is unlinked to the -globin gene cluster.     

Translocation of cytosolic acetylcholine into synaptic vesicles and demonstration of vesicular release

The rate of translocation of newly synthesized acetylcholine (ACh) from the presynaptic cytosol of Torpedo electric organ nerve terminals into synaptic vesicles and the extent to which ACh release from these neurons is mediated by a vesicular mechanism were investigated. For this purpose the compound 2(4-phenylpiperidino)cyclohexanol (AH5183), which inhibits the active transport of ACh into isolated cholinergic synaptic vesicles, was employed. Preincubation of purified Torpedo nerve terminals (synaptosomes) with AH5183 does not affect the intraterminal synthesis of [3H]ACh but results in a marked inhibition (85%) of its Ca2+-dependent K+-evoked release. By contrast, the evoked release of the endogenous nonlabeled ACh is not affected by this compound. When AH5183 is added during radiolabeling, it causes a progressively smaller inhibition of [3H]ACh release which is completely abolished if the drug is added after the preparation has been labeled. These findings suggest that most of the newly synthesized synaptosomal [3H]ACh (85%) is released by a vesicular mechanism and that some [3H]ACh (15%) may be released by a different process. The translocation of cytosolic [3H]ACh into the synaptic vesicles was monitored by determining the time course of the loss of susceptibility of [3H]ACh release to AH5183. It was found not to be coupled kinetically to [3H]ACh synthesis and to lag behind it. The nature of the intraterminal processes underlying this lag is discussed.     

The oral assimilation of radiomanganese by the mouse

The metabolism of orally administered radiomanganese was studied in mice. Assimilation of absorbed manganese (Mn) was determined using whole body counting techniques. When⁵⁴MnCl₂ was administered, 2.7% of the dose was retained after 10 d compared with 1.2% from the⁵⁴Mn-nitrilotriacetate (NTA) complex. However, this difference was accounted for by the rapid and persistent adsorption of the Mn onto the teeth of the lower jaw when fed as the ionic salt at pH 2.0 compared with the NTA-chelate fed at pH 9.0. Once corrected for the amount adsorbed onto the teeth, the biodistribution and relative specific activity of the assimilated radiomanganese into a variety of tissues were similar for both forms of the metal.     

Partial amino acid sequence of porcine elastase II. Active site and the activation peptide regions

The partial amino acid sequence of porcine elastase II, isolated from crude trypsin Type II, was determined. The enzyme consists of two polypeptide chains, a light chain composed of 11 residues, and a heavy chain (Mr = 23 500) with four intrachain disulfide bridges; the two chains are held together by one interchain disulfide bond. Elastase II was fragmented into several peptides by chemical cleavages with CNBr at the two methionine residues, 99 and 180 (chymotrypsinogen numbering), and with hydroxylamine at the peptide bond following DIP-Ser195. About 50% of the sequence was determined and the positions of 120 amino acids were located, including the light chain residues and most of the active site residues. The partial sequence shows 64% difference between porcine elastase II and elastase I and only 26% difference between porcine elastase II and bovine chymotrypsin B.