Current treatments of schizophrenia are compromised by their inability to treat all symptoms of the disease and their sideeffects. Whilst existing antipsychotic drugs are effective against positive symptoms, they have negligible efficacy against the prefrontal cortex (PFC)-associated cognitive deficits and negative symptoms. New models that reproduce core pathophysiological features of schizophrenia are more likely to have improved predictive validity in identifying new treatments. We have developed a NMDA receptor antagonist model that reproduces core PFC deficits of schizophrenia and discuss this in relation to pathophysiology and treatments. Subchronic and chronic intermittent PCP (2.6 mg/kg i.p.) was administered to rats. PFC activity was assessed by 2-deoxyglucose imaging, parvalbumin and Kv3.1 mRNA expression, and the attentional set-shifting test (ASST) of executive function. Affymetrix gene array technology was employed to examine gene expression profile patterns. PCP treatment reduced glucose utilization in the PFC (hypofrontality). This was accompanied by a reduction in markers of GABAergic interneurones (parvalbumin and Kv3.1 mRNA expression) and deficits in the extradimensional shift dimension of the ASST. Consistent with their clinical profile, the hypofrontality was not reversed by clozapine or haloperidol. Transcriptional analysis revealed patterns of change consistent with current neurobiological theories of schizophrenia. This model mirrors core neurobiological deficits of schizophrenia; hypofrontality, altered markers of GABAergic interneurone activity and deficits in executive function. As such it is likely to be a valuable translational model for understanding the neurobiological mechanisms underlying hypofrontality and for identifying and validating novel drug targets that may restore PFC deficits in schizophrenia.
Abstract:The thalamus has recently received renewed interest in systems-neuroscience and schizophrenia (ScZ) research because of emerging evidence highlighting its important role in coordinating functional interactions in cortical-subcortical circuits. Moreover, higher cognitive functions, such as working memory and attention, have been related to thalamo-cortical interactions, providing a novel perspective for the understanding of the neural substrate of cognition. The current review will support this perspective by summarizing evidence on the crucial role of neural oscillations in facilitating thalamo-cortical (TC) interactions during normal brain functioning and its potential impairment in ScZ.Specifically, we will focus on the relationship between NMDA-R mediated (glutamatergic) neurotransmission in TC-interactions. To this end, we will first review the functional anatomy and neurotransmitters in thalamic circuits, followed by a review of the oscillatory signatures and cognitive processes supported by TC-circuits. In the second part of the paper, data from preclinical research as well as human studies will be summarized that have implicated TC-interactions as a crucial target for NMDA-receptor hypofunctioning. Finally, we will compare these neural signatures with current evidence from ScZ-research, suggesting a potential overlap between alterations in TC-circuits as the result of NMDA-R deficits and stage-specific alterations in large-scale networks in ScZ.
The nesting requirements of the yellow-tailed black-cockatoo (Calyptorhynchus funereus) were studied at 68 sites in Eucalyptus regnans forest in the Strzelecki Ranges, South Gippsland, Victoria. Nest trees were located and their characteristics related to forest stand variables. Eighteen nest hollows were found. Nest trees had a mean diameter at breast height of 2.5 m, a mean estimated age of 221 years, a mean height of 58 m and for live nest trees a mean crown diameter of 22 m. The currently proposed rotation time for silvicultural systems of 80-150 years will reduce the number of hollow-bearing trees suitable for nesting yellow-tailed black-cockatoos. Adequate numbers of trees must be retained in logged areas and wildlife corridors and reserves, and protected to ensure a continual supply for yellow-tailed black-cockatoos and other hollow-dependent species. If agonistic behaviour is operating between female yellow-tailed black-cockatoos, nesting potential may be enhanced if trees retained on coupes are evenly distributed rather than clumped. Silvicultural systems that facilitate the protection of trees retained on coupes would benefit the conservation of the yellow-tailed black-cockatoo.
In a study of the genetic basis of essential hypertension (HT), we tested four variants in three candidate genes not previously investigated in HT. These encoded the endothelin receptor type A (EDNRA), which transduces most of the vasoconstrictive properties of endothelin-1, protein kinase lysine deficient 4 (WNK4) whose gene resides in a HT linkage region on chromosome 17, and FK506-binding protein 1B (FKBP1B), which can reduce blood pressure by increasing nitric oxide. The variants were: for EDNRA, a G-->A in the 5'-UTR and C-->T in exon 8; for WNK4, a tetranucleotide repeat in intron 10; and for FKBP1B, a T-->C in exon 4. Subjects were Anglo-Celtic white Australians and included 155 HTs with two HT parents and 245 normotensives (NTs) whose parents were both NT. For EDNRA, we found a weak association of the exon 8 variant with HT (p = 0.019) and association of the 5'-UTR variant with elevation in systolic and diastolic blood pressure (BP) (p = 0.038 and 0.0031, respectively). The WNK4 intron 10 variant and the FKP1B exon 4 variant showed no association with HT, but tracking with BP was seen for the latter (p = 0.015 and 0.0011 for systolic and diastolic BP, respectively). Our study thus suggests possible involvement of EDNRA in essential HT.
A polymerase chain reaction (PCR) procedure capable of amplifying specific DNA sequences by up to a millionfold was developed for detection of infection by human papillomaviruses (HPVs) of low (HPV6, HPV11) or high (HPV16, HPV18, HPV33) oncogenic potential. For high-risk HPVs the region chosen was within the E6 open reading frame, which can become integrated into genomic DNA. A region corresponding to this was chosen for low-risk HPVs. After repeated cycles of specific oligonucleotide-primed extension of viral DNA with Klenow or thermophilic DNA polymerase, the type of HPV present was then determined on the basis of the size of the ethidium-bromide-stained band visible after polyacrylamide gel electrophoresis: for HPV6 or 11 the band was approximately 120 bp, for HPV 16 or 33 it was approximately 200 bp, and for HPV18 it was approximately 100 bp. Specific hybridization to the relevant band was seen using radioactive or nonradioactive (alkaline-phosphatase-linked) target oligonucleotide probes. Using the PCR method, we have determined, within as little as a few hours, the infection status of a variety of clinical specimens, including cervical scrapes and lavages, anal scrapes, and anogenital biopsies. The PCR steps can be automated, adding to the potential of PCR for widespread use in the detection of HPV, which is becoming increasingly popular in cervical screening.
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