Different pathways of molecular pathophysiology underlie cognitive and motor tauopathy phenotypes in transgenic models for Alzheimer's disease and frontotemporal lobar degeneration.

A poorly understood feature of the tauopathies is their very different clinical presentations. The frontotemporal lobar degeneration (FTLD) spectrum is dominated by motor and emotional/psychiatric abnormalities, whereas cognitive and memory deficits are prominent in the early stages of Alzheimer's disease (AD). We report two novel mouse models overexpressing different human tau protein constructs. One is a full-length tau carrying a double mutation [P301S/G335D; line 66 (L66)] and the second is a truncated 3-repeat tau fragment which constitutes the bulk of the PHF core in AD corresponding to residues 296-390 fused with a signal sequence targeting it to the endoplasmic reticulum membrane (line 1; L1). L66 has abundant tau pathology widely distributed throughout the brain, with particularly high counts of affected neurons in hippocampus and entorhinal cortex. The pathology is neuroanatomically static and declines with age. Behaviourally, the model is devoid of a higher cognitive phenotype but presents with sensorimotor impairments and motor learning phenotypes. L1 displays a much weaker histopathological phenotype, but shows evidence of neuroanatomical spread and amplification with age that resembles the Braak staging of AD. Behaviourally, the model has minimal motor deficits but shows severe cognitive impairments affecting particularly the rodent equivalent of episodic memory which progresses with advancing age. In both models, tau aggregation can be dissociated from abnormal phosphorylation. The two models make possible the demonstration of two distinct but nevertheless convergent pathways of tau molecular pathogenesis. L1 appears to be useful for modelling the cognitive impairment of AD, whereas L66 appears to be more useful for modelling the motor features of the FTLD spectrum. Differences in clinical presentation of AD-like and FTLD syndromes are therefore likely to be inherent to the respective underlying tauopathy, and are not dependent on presence or absence of concomitant APP pathology.

Conserved residues in RF-NH2 receptor models identify predicted contact sites in ligand-receptor binding.

Peptides in the RF-NH2 family are grouped together based on an amidated dipeptide C terminus and signal through G-protein coupled receptors (GPCRs) to influence diverse physiological functions. By determining the mechanisms underlying RF-NH2 signaling targets can be identified to modulate physiological activity; yet, how RF-NH2 peptides interact with GPCRs is relatively unexplored. We predicted conserved residues played a role in Drosophila melanogaster RF-NH2 ligand-receptor interactions. In this study D. melanogaster rhodopsin-like family A peptide GPCRs alignments identified eight conserved residues unique to RF-NH2 receptors. Three of these residues were in extra-cellular loops of modeled RF-NH2 receptors and four in transmembrane helices oriented into a ligand binding pocket to allow contact with a peptide. The eighth residue was unavailable for interaction; yet its conservation suggested it played another role. A novel hydrophobic region representative of RF-NH2 receptors was also discovered. The presence of rhodopsin-like family A GPCR structural motifs including a toggle switch indicated RF-NH2s signal classically; however, some features of the DMS receptors were distinct from other RF-NH2 GPCRs. Additionally, differences in RF-NH2 receptor structures which bind the same peptide explained ligand specificity. Our novel results predicted conserved residues as RF-NH2 ligand-receptor contact sites and identified unique and classic structural features. These discoveries will aid antagonist design to modulate RF-NH2 signaling.

Differential effect of opioid and cannabinoid receptor blockade on heroin-seeking reinstatement and cannabinoid substitution in heroin-abstinent rats.

BACKGROUND AND PURPOSE: Opioids and cannabinoids interact in drug addiction and relapse. We investigated the effect of the opioid receptor antagonist naloxone and/or the cannabinoid CB(1) receptor antagonist rimonabant on cannabinoid-induced reinstatement of heroin seeking and on cannabinoid substitution in heroin-abstinent rats. EXPERIMENTAL APPROACH Rats were trained to self-administer heroin (30 µg·kg(-1) per infusion) under a fixed-ratio 1 reinforcement schedule. After extinction of self-administration (SA) behaviour, we confirmed the effect of naloxone (0.1-1 mg·kg(-1)) and rimonabant (0.3-3 mg·kg(-1)) on the reinstatement of heroin seeking induced by priming with the CB(1) receptor agonist WIN55,212-2 (WIN, 0.15-0.3 mg·kg(-1)). Then, in a parallel set of heroin-trained rats, we evaluated whether WIN (12.5 µg·kg(-1) per infusion) SA substituted for heroin SA after different periods of extinction. In groups of rats in which substitution occurred, we studied the effect of both antagonists on cannabinoid intake. KEY RESULTS: Cannabinoid-induced reinstatement of heroin seeking was significantly attenuated by naloxone (1 mg·kg(-1)) and rimonabant (3 mg·kg(-1)) and fully blocked by co-administration of sub-threshold doses of the two antagonists. Moreover, contrary to immediate (1 day) or delayed (90 days) drug substitution, rats readily self-administered WIN when access was given after 7, 14 or 21 days of extinction from heroin, and showed a response rate that was positively correlated with the extinction period. In these animals, cannabinoid intake was increased by naloxone (1 mg·kg(-1)) and decreased by rimonabant (3 mg·kg(-1)). CONCLUSIONS AND IMPLICATIONS: Our findings extend previous research on the crosstalk between cannabinoid and opioid receptors in relapse mechanisms, which suggests a differential role in heroin-seeking reinstatement and cannabinoid substitution in heroin-abstinent rats.

The impact of StuI digestion in situ on FISH to human chromosomes with satellite DNA probes.

Human metaphase chromosomes were digested with StuI and subsequently hybridized in situ using chromosome 9 alphoid DNA and classical satellite III DNA as probes. The data obtained suggest that it is not possible to establish a general rule regarding the cytological effects induced by restriction enzymes in particular chromosome regions and that a number of factors, such as DNA sequences, DNA-protein interaction and enzyme structure, play a role in determining such effects.

Custom-tailored hemodilution with albumin and crystalloids in acute ischemic stroke.

BACKGROUND AND PURPOSE: Hemodilution in the acute phase of ischemic stroke is still controversial. Multicenter studies have failed to demonstrate any benefit. The present study focuses attention on analysis of circulation in stroke and on individual restabilization of circulation. METHODS: The Amsterdam Stroke Study is a prospective, single-center, randomized clinical trial (n = 300). Normovolemic hemodilution is accomplished in a customized procedure by administration of 20% albumin plus crystalloids under hemodynamic and rheological monitoring in the acute phase of stroke. All patients receive general intensive care treatment and monitoring with a pulmonary artery catheter. This custom-tailored fluid therapy is guided on the basis of a target pulmonary capillary wedge pressure (12 +/- 3 mm Hg) and hematocrit (0.32 +/- 0.02). The control group receives only customized rehydration by infusion of crystalloids. RESULTS: We obtained significant (p less than 0.05) reduction in mortality at 3 months (from 27% to 16%) and an increase in independence at home (from 35% to 48%) after viscosity reduction by means of hemodilution with albumin in the subgroup with a hematocrit less than 0.45 (n = 201) (specific viscosity effect). We also obtained a significant (p less than 0.005) reduction in mortality at 3 months (from 27% to 8%) and an increase in independence (from 35% to 59%) after only rehydration with crystalloids in the subgroup with overt dehydration (hematocrit greater than or equal to 0.45; n = 51) as compared with the normal-hematocrit group without signs of dehydration (hematocrit less than 0.45; n = 103) (specific rehydration effect). CONCLUSIONS: This study may provide an explanation for the failures in former hemodilution trials and may re-establish proper hemodilution and rehydration as a valuable therapy in the acute phase of stroke, thus reducing mortality and improving independence after 3 months.