Same-sex cohabitation under the effects of quinpirole induces a conditioned socio-sexual partner preference in males, but not in female rats

The effects of the dopamine D2-type receptor agonist quinpirole (QNP) were examined on the development of conditioned same-sex partner preference induced by cohabitation in rats. In Experiment 1, males received either saline or QNP (1.25 mg/kg) and cohabited during three trials with almond-scented stimulus males that were sexually naïve. In Experiment 2, males received six trials, and in Experiment 3 received three trials with sexually expert stimulus males. During a final drug-free preference test, males chose between the familiar or a novel male partner. In Experiments 1, 2 and 3 only QNP-treated males displayed a social preference for the familiar male, observed with more time spent together. In Experiment 3 males also displayed a sexual preference observed with more non-contact erections when were exposed to their male partner. In Experiment 4 we tested the effects on OVX, E+P primed females that received 1 systemic injection of either saline or QNP during three conditioning trials. In Experiment 5, females received 2 injections 12-h apart during each trial. Results indicated that both saline and QNP-treated females failed to develop partner preference. These data demonstrate that enhanced D2-type receptor activity during cohabitation facilitates the development of conditioned same-sex partner preference in males, but not in female rats. We discuss the implications for same-sex partner preferences.     

Monitoring follow up of two areas affected by the Prestige oil four years after the spillage

The sinking of the oil tanker Prestige in November 2002 resulted in the spill of more than 63,000 tonnes of crude oil, and polluted more than 1,000 km of coastline, especially affecting Galicia (northwestern Spain). Four years after the accident, a new biological monitoring study was undertaken of two Galician areas intensely affected by the spill, Lira and Ancoradoiro, previously evaluated in the months following the accident ( Laffon et al. 2006 ). The mussel Mytilus galloprovincialis was employed as bioindicator organism to determine both polycyclic aromatic hydrocarbons (PAH) levels and genotoxic effects. PAH were determined chromatographically in seawater samples and mussel tissues collected from November 2006 to January 2008. The results obtained showed that PAH pollution was still present in these areas, but bioaccumulation of these compounds in mussels was low, compared to reference mussels, and lower than in our previous study. DNA damage assessment was also performed in gills and hemolymph cells by means of the alkaline comet assay. DNA damage levels were higher in mussels from the exposed areas than in reference mussels. DNA damage decreased after a 7-d recovery period in the laboratory, but prolonging the recovery period up to 14 d did not contribute to less DNA damage in gill cells. Hemolymph cells were more sensitive than gill cells to the induction of DNA damage.     

Multiple stress signals activate mutant p53 in vivo

p53 levels are tightly regulated in normal cells, and thus, the wild-type p53 protein is nearly undetectable until stimulated through a variety of stresses. In response to stress, p53 is released from its negative regulators, mainly murine double minute 2 (Mdm2), allowing p53 to be stabilized to activate cell-cycle arrest, senescence, and apoptosis programs. Many of the upstream signals that regulate wild-type p53 are known; however, limited information for the regulation of mutant p53 exists. Previously, we showed that wild-type and mutant p53R172H are regulated in a similar manner in the absence of Mdm2 or p16. In addition, this stabilization of mutant p53 is responsible for the gain-of-function metastatic phenotype observed in the mouse. In this report, we examined the role of oncogenes, DNA damage, and reactive oxygen species, signals that stabilize wild-type p53, on the stabilization of mutant p53 in vivo and the consequences of this expression on tumor formation and survival. These factors stabilized mutant p53 protein which oftentimes contributed to exacerbated tumor phenotypes. These findings, coupled with the fact that patients carry p53 mutations without stabilization of p53, suggest that personalized therapeutic schemes may be needed for individual patients depending on their p53 status.     

Sequencing a mouse acute promyelocytic leukemia genome reveals genetic events relevant for disease progression

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML). It is characterized by the t(15;17)(q22;q11.2) chromosomal translocation that creates the promyelocytic leukemia-retinoic acid receptor α (PML-RARA) fusion oncogene. Although this fusion oncogene is known to initiate APL in mice, other cooperating mutations, as yet ill defined, are important for disease pathogenesis. To identify these, we used a mouse model of APL, whereby PML-RARA expressed in myeloid cells leads to a myeloproliferative disease that ultimately evolves into APL. Sequencing of a mouse APL genome revealed 3 somatic, nonsynonymous mutations relevant to APL pathogenesis, of which 1 (Jak1 V657F) was found to be recurrent in other affected mice. This mutation was identical to the JAK1 V658F mutation previously found in human APL and acute lymphoblastic leukemia samples. Further analysis showed that JAK1 V658F cooperated in vivo with PML-RARA, causing a rapidly fatal leukemia in mice. We also discovered a somatic 150-kb deletion involving the lysine (K)-specific demethylase 6A (Kdm6a, also known as Utx) gene, in the mouse APL genome. Similar deletions were observed in 3 out of 14 additional mouse APL samples and 1 out of 150 human AML samples. In conclusion, whole genome sequencing of mouse cancer genomes can provide an unbiased and comprehensive approach for discovering functionally relevant mutations that are also present in human leukemias.     

The use of polyacrylamide gels for mechanical calibration of cartilage--a combined nanoindentation and unconfined compression study

This study investigates polyacrylamide (PA) gel as a calibration material to measure the nanomechanical compressive modulus of cartilage using nanoindentation. Both nanoindentation and unconfined compression testing were performed on PA gel and porcine rib cartilage. The equilibrium moduli measured by the two methods were discernable. Nanoindentation has the advantage of distinguishing between spatially dependent constituent properties that affect tissue mechanical function in heterogeneous and hierarchically structured tissues such as cartilage. Both sets of measurements exhibited similar positive correlation with increasing gel crosslinker concentration. The compressive modulus measurements from compression in the PA gels ranged from 300 kPa–1.4 MPa, whereas those from nanoindentation ranged from 100 kPa–1.1MPa. Using this data, a method for relating nanoindentation measurements to conventional mechanical property measurements is presented for porcine rib cartilage. It is shown that based on this relationship, the local tissue modulus as measured from nanoindentation (1.1–1.4 MPa) was able to predict the overall global modulus of the same sample of rib cartilage (2.2 MPa), as confirmed by experimental measurements from unconfined compression. This study supports the use of nanoindentation for the local characterization of cartilage tissues and may be applied to other soft tissues and constructs.     

The Cavβ subunit prevents RFP2-mediated ubiquitination and proteasomal degradation of L-type channels

It is well established that the auxiliary Cavβ subunit regulates calcium channel density in the plasma membrane, but the cellular mechanism by which this occurs has remained unclear. We found that the Cavβ subunit increased membrane expression of Cav1.2 channels by preventing the entry of the channels into the endoplasmic reticulum-associated protein degradation (ERAD) complex. Without Cavβ, Cav1.2 channels underwent robust ubiquitination by the RFP2 ubiquitin ligase and interacted with the ERAD complex proteins derlin-1 and p97, culminating in targeting of the channels to the proteasome for degradation. On treatment with the proteasomal inhibitor MG132, Cavβ-free channels were rescued from degradation and trafficked to the plasma membrane. The coexpression of Cavβ interfered with ubiquitination and targeting of the channel to the ERAD complex, thereby facilitating export from the endoplasmic reticulum and promoting expression on the cell surface. Thus, Cavββ regulates the ubiquitination and stability of the calcium channel complex.     

Poly(ADP-ribose)polymerase inhibition counteracts renal hypertrophy and multiple manifestations of peripheral neuropathy in diabetic Akita mice

Poly(ADP-ribose) polymerase (PARP) activation has been implicated in the pathogenesis of diabetic complications, including nephropathy and peripheral neuropathy. This study aimed at evaluating the manifestations of both complications in diabetic Akita mice, a model of Type 1 (insulin-dependent) diabetes, and their amenability to treatment with the potent PARP inhibitor, 10-(4-methyl-piperazin-1-ylmethyl)-2H-7-oxa-1,2-diaza-benzo[de] anthracen-3-one (GPI-15427). Male non-diabetic C57Bl6/J and diabetic C57Bl/6-Ins2Akita/J (Akita) mice were maintained with or without treatment with GPI-15427, 30 mg/kg/day, for 4 weeks starting from 16 weeks of age. Sixteen week-old Akita mice displayed sensory nerve conduction velocity (SNCV) deficit, whereas the motor nerve conduction velocity (MNCV) tended to decrease, but the difference with controls did not achieve statistical significance. They also developed thermal and mechanical hypoalgesia and tactile allodynia. SNCV deficit, mechanical hypoalgesia, and tactile allodynia progressed with age whereas the severity of thermal hypoalgesia was similar in 16- and 20-week-old Akita mice. PARP inhibition alleviated, although it did not completely reverse, SNCV deficit, thermal and mechanical hypoalgesia and tactile allodynia. Sixteen-week-old Akita mice displayed MNCV deficit (41.3±2.5 vs. 51.0±1.2 m/sec in non-diabetic controls, P<0.01), axonal atrophy of myelinated fibers, kidney hypertrophy, and albuminuria. MNCV slowing, axonal atrophy, and kidney hypertrophy, but not albuminuria, were less severe in GPI-15427-treated age-matched Akita mice. Neuroprotective and nephroprotective effects of PARP inhibition were not due to alleviation of diabetic hyperglycemia, or peripheral nerve p38 mitogen-activated protein kinase activation. GPI-15427 did not affect any variables in control mice. In conclusion, the findings support an important role for PARP activation in diabetic peripheral neuropathy and kidney hypertrophy associated with Type 1 diabetes, and provide rationale for development and further studies of PARP inhibitors, for the prevention and treatment of these complications.     

Importance of inter-hemispheric prefrontal connection in the effects of non-competitive NMDA receptor antagonists

Previous studies have shown that systemic, but not unilateral intra-prefrontal cortex administration of non-competitive NMDA antagonists, increased prefrontal activity, the cortical efflux of serotonin, and induced stereotypies. In this work we used in-vivo microdialysis and immunohistochemistry to test the hypothesis as to whether MK-801 and ketamine need to act on both prefrontal cortices to reproduce these neurochemical and behavioural changes. Dialysis probes were implanted in the medial prefrontal cortex, and extracellular serotonin as well as behavioural stereotypies was measured after systemic administration of MK-801 and ketamine (1 mg/kg and 25 mg/kg, respectively), and unilateral and bilateral perfusion of both drugs (300 μm and 3 mm, respectively). Additionally, the prefrontal (glutamatergic) level of activity was measured using c-Fos immunohistochemistry. Systemic and bilateral (but not unilateral) prefrontal administration of MK-801 and ketamine increased serotonin efflux whereas only systemic administration of both drugs produced hyperlocomotion and stereotypies. The unilateral perfusion of 1 μm tetrodotoxin in the medial prefrontal cortex reduced increases of serotonin in both hemispheres, the expression of c-Fos in the contralateral side, and stereotypy scores after systemic NMDA antagonists. Our results support the hypothesis that a bilateral impairment of cortical inhibition in the medial prefrontal cortex is needed for non-competitive NMDA antagonists to induce the state of pyramidal cell hyperactivity and concurrent efflux of serotonin. Furthermore, hyperlocomotion and stereotypies produced by MK-801 and ketamine do not appear to result from changes in the activity of prefrontal cortex although this structure exerts some control over these behaviours.