We tested the urine and saliva of 137 wild rats (Rattus norvegicus) from Vancouver, Canada, for the presence of Leptospira spp. Only one saliva sample was found positive and two were suspect, all from urine-positive rats (n=81), indicating that active shedding of leptospires in saliva is unlikely to occur.
Background: Certain phthalates can impair Leydig cell distribution and steroidogenesis in the fetal rat in utero, but it is unknown whether similar effects might occur in the human. Objectives: Our aim in this study was to investigate the effects of di(n-butyl) phthalate (DBP), or its metabolite monobutyl phthalate (MBP), on testosterone production and Leydig cell aggregation (LCA) in fetal testis explants from the rat and human, and to compare the results with in vivo findings for DBP-exposed rats. We also wanted to determine if DBP/MBP affects testosterone production in vivo in the neonatal male marmoset. Methods: Fetal testis explants obtained from the rat [gestation day (GD)19.5] and from the human (15-19 weeks of gestation) were cultured for 24-48 hr with or without human chorionic gonadotropin (hCG) or 22R-hydroxy-cholesterol (22R-OH), and with or without DBP/MBP. Pregnant rats and neonatal male marmosets were dosed with 500 mg/kg/day DBP or MBP. Results: Exposure of rats in utero to DBP (500 mg/kg/day) for 48 hr before GD21.5 induced major suppression of intratesticular testosterone levels and cytochrome P450 side chain cleavage enzyme (P450scc) expression; this short-term treatment induced LCA, but was less marked than longer term (GD13.5-20.5) DBP treatment. In vitro, MBP ( ) did not affect basal or 22R-OH-stimulated testosterone production by fetal rat testis explants but slightly attenuated hCG-stimulated steroidogenesis; MBP induced minor LCA in vitro. None of these parameters were affected in human fetal testis explants cultured with MBP for up to 48 hr. Because the in vivo effects of DBP/MBP were not reproduced in vitro in the rat, the absence of MBP effects in vitro on fetal human testes is inconclusive. In newborn (Day 2-7) marmosets, administration of a single dose of 500 mg/kg MBP significantly (p = 0.019) suppressed blood testosterone levels 5 hr later. Similar treatment of newborn co-twin male marmosets for 14 days resulted in increased Leydig cell volume per testis (p = 0.011), compared with co-twin controls; this is consistent with MBP-induced inhibition of steroidogenesis followed by compensatory Leydig cell hyperplasia/hypertrophy. Conclusions: These findings suggest that MBP/DBP suppresses steroidogenesis by fetal-type Leydig cells in primates as in rodents, but this cannot be studied in vitro.
N-(2,2-Dimethyl-3,4-dihydro-2H-1-benzopyran-4-yl)-4H-1,2,4-benzothiadiazine-3-carboxamides 1,1-dioxides were prepared and evaluated on rat uterus, rat aortic rings and rat pancreatic β-cells. Pharmacological studies conducted on rat uterus indicated that several of these original hybrid compounds displayed a strong myorelaxant activity. The most active compounds hold a bromine atom at the 6-position of the dihydrobenzopyran ring. Moreover, the compounds failed to display a marked inhibitory effect on insulin secretion and vascular myogenic activity. These features suggest that the 6-bromo compounds could be relatively selective towards the uterine smooth muscle. Strong myorelaxant activity on rat uterus, but not on rat aorta, was found with 6-bromo-substituted dihydrobenzopyran hybrid compounds. [Display omitted] ► Hybrid compounds between diazoxide and cromakalim, two potassium channel openers, were synthesized. ► They were evaluated on three KATP channel-expressing tissues (pancreatic β-cells, aorta, uterus). ► Strong myorelaxant activity on uterus, but not on rat aorta, was found with 6-bromo-substituted dihydrobenzopyran hybrid compounds. ► None of these compounds were found to exert any inhibitory activity on insulin release.
Missense mutations in the leucine-rich repeat kinase 2 (LRRK2) gene can cause late-onset Parkinson disease. Past studies have provided conflicting evidence for the protective effects of LRRK2 knockdown in models of Parkinson disease as well as other disorders. These discrepancies may be caused by uncertainty in the pathobiological mechanisms of LRRK2 action. Previously, we found that LRRK2 knockdown inhibited proinflammatory responses from cultured microglia cells. Here, we report LRRK2 knockout rats as resistant to dopaminergic neurodegeneration elicited by intracranial administration of LPS. Such resistance to dopaminergic neurodegeneration correlated with reduced proinflammatory myeloid cells recruited in the brain. Additionally, adeno-associated virus-mediated transduction of human α-synuclein also resulted in dopaminergic neurodegeneration in wild-type rats. In contrast, LRRK2 knockout animals had no significant loss of neurons and had reduced numbers of activated myeloid cells in the substantia nigra. Although LRRK2 expression in the wild-type rat midbrain remained undetected under nonpathological conditions, LRRK2 became highly expressed in inducible nitric oxide synthase (iNOS)-positive myeloid cells in the substantia nigra in response to α-synuclein overexpression or LPS exposures. Our data suggest that knocking down LRRK2 may protect from overt cell loss by inhibiting the recruitment of chronically activated proinflammatory myeloid cells. These results may provide value in the translation of LRRK2-targeting therapeutics to conditions where neuroinflammation may underlie aspects of neuronal dysfunction and degeneration.
Following ingestion of [2-14C](–)-epicatechin by rats, radioactivity in urine, feces, body fluids and tissues collected over a 72h period, was measured and 14C-metabolites were analyzed by HPLC-MS2 with a radioactivity monitor. In total 78% of the ingested radioactivity was absorbed from the gastrointestinal tract (GIT), and then rapidly eliminated from the circulatory system via renal excretion. A peak plasma concentration occurred 1h after intake corresponding to ~0.7% of intake. Low amounts of radioactivity, <2% of intake, appeared transiently in body tissues. Glucuronidation and methylation of (–)-epicatechin began in the duodenum but occurred more extensively in the jejunum/ileum. Radioactivity reaching the cecum after 6–12h was predominantly in the form of the ring fission metabolites 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone and 5-(3′,4′-dihydroxyphenyl)-γ-hydroxyvaleric acid along with smaller amounts of their phase II metabolites. Low levels of metabolites were detected in the colon. Of the ingested radioactivity, 19% was voided in feces principally as ring-fission metabolites. The main components in plasma were (–)-epicatechin-5-O-glucuronide and 3′-O-methyl-(–)-epicatechin-5-O-glucuronide with small amounts of (–)-epicatechin, 3′-O-methyl-(–)-epicatechin, 5-(3′-hydroxyphenyl)-γ-hydroxyvaleric acid-4′-glucuronide and hippuric acid also being detected. No oxidized products of (–)-epicatechin were detected. No compelling evidence was obtained for biliary recycling of metabolites. The findings demonstrate substantial differences in the metabolism of (–)-epicatechin by rats and humans. Caution should, therefore, be exercised when using animal models to draw conclusions about effects induced by (–)-epicatechin intake in humans. [Display omitted] •Ingested [2-14C]-epicatechin is metabolized extensively by rats.•19 radiolabeled metabolites and microbiota-derived catabolites were identified.•78% of the ingested radioactivity was excreted in urine and 19% in feces.•No oxidized metabolites of [2-14C]-epicatechin were detected.•Epicatechin metabolism in rats is very different to that occurring in humans.
In an attempt to reveal the mechanism of rats' resistance to Alzheimer's disease, we determined the structure of the metal-binding domain 1–16 of rat β-amyloid (rat Aβ(1–16)) in solution in the absence and presence of zinc ions. A zinc-induced dimerization of the domain was detected. The zinc coordination site was found to involve residues His-6 and His-14 of both peptide chains. We used experimental restraints obtained from analyses of NMR and isothermal titration calorimetry data to perform structure calculations. The calculations employed an explicit water environment and a simulated annealing molecular-dynamics protocol followed by quantum-mechanical/molecular-mechanical optimization. We found that the C-tails of the two polypeptide chains of the rat Aβ(1–16) dimer are oriented in opposite directions to each other, which hinders the assembly of rat Aβ dimers into oligomeric aggregates. Thus, the differences in the structure of zinc-binding sites of human and rat Aβ(1–16), their ability to form regular cross-monomer bonds, and the orientation of their hydrophobic C-tails could be responsible for the resistance of rats to Alzheimer's disease.
The blood-brain barrier is a formidable obstacle for glioma chemotherapy due to its compact structure and drug efflux ability. In this study, a dual-targeting drug delivery system involving Angiopep-2-conjugated biodegradable polymersomes loaded with doxorubicin (AngPS-DOX) was developed to exploit transport by the low-density lipoprotein receptor-related protein 1 (LRP1), which is overexpressed in both blood-brain barrier and glioma cells. The polymersomes (PS) were prepared using a thin-film hydration method. The PS were loaded with doxorubicin using the pH gradient method (Ang-PS-DOX). The resulting PS were uniformly spherical, with diameters of similar to 135 nm and with similar to 159.9 Angiopep-2 molecules on the surface of each PS. The drug-loading capacity and the encapsulation efficiency for doxorubicin were 7.94%+/- 0.17% and 95.0%+/- 1.6%, respectively. Permeability tests demonstrated that the proton diffusion coefficient across the PS membrane was far slower than that across the liposome membrane, and the common logarithm value was linearly dependent on the dioxane content in the external phase. Compared with PS-DOX, Ang-PS-DOX demonstrated significantly higher cellular uptake and stronger cytotoxicity in C6 cells. In vivo pharmacokinetics and brain distribution experiments revealed that Ang-PS-DOX achieved a more extensive distribution and more abundant accumulation in glioma cells than PS-DOX. Moreover, the survival time of glioma-bearing rats treated with Ang-PS-DOX was significantly prolonged compared with those treated with PS-DOX or a solution of free doxorubicin. These results suggested that AngPS-DOX can target glioma cells and enhance chemotherapeutic efficacy.
In an awake state, neurons in the cerebral cortex fire irregularly and electroencephalogram (EEG) recordings display low-amplitude, high-frequency fluctuations. During sleep, neurons oscillate between 'on' periods, when they fire as in an awake brain, and 'off' periods, when they stop firing altogether and the EEG displays high-amplitude slowwaves. However, what happens to neuronal firing after a long period of being awake is not known. Here we show that in freely behaving rats after a long period in an awake state, cortical neurons can go briefly 'offline' as in sleep, accompanied by slow waves in the local EEG. Neurons often go offline in one cortical area but not in another, and during these periods of 'local sleep', the incidence of which increases with the duration of the awake state, rats are active and display an 'awake' EEG. However, they are progressively impaired in a sugar pellet reaching task. Thus, although both the EEG and behaviour indicate wakefulness, local populations of neurons in the cortex may be falling asleep, with negative consequences for performance.