Network analysis of rat spatial cognition: behaviorally-established symmetry in a physically asymmetrical environment

Background

We set out to solve two inherent problems in the study of animal spatial cognition (i) What is a “place”?; and (ii) whether behaviors that are not revealed as differing by one methodology could be revealed as different when analyzed using a different approach.

Methodology

We applied network analysis to scrutinize spatial behavior of rats tested in either a symmetrical or asymmetrical layout of 4, 8, or 12 objects placed along the perimeter of a round arena. We considered locations as the units of the network (nodes), and passes between locations as the links within the network.

Principal Findings

While there were only minor activity differences between rats tested in the symmetrical or asymmetrical object layouts, network analysis revealed substantial differences. Viewing ‘location’ as a cluster of stopping coordinates, the key locations (large clusters of stopping coordinates) were at the objects in both layouts with 4 objects. However, in the asymmetrical layout with 4 objects, additional key locations were spaced by the rats between the objects, forming symmetry among the key locations. It was as if the rats had behaviorally imposed symmetry on the physically asymmetrical environment. Based on a previous finding that wayfinding is easier in symmetrical environments, we suggest that when the physical attributes of the environment were not symmetrical, the rats established a symmetric layout of key locations, thereby acquiring a more legible environment despite its complex physical structure.

Conclusions and Significance

The present study adds a behavioral definition for “location”, a term that so far has been mostly discussed according to its physical attributes or neurobiological correlates (e.g. - place and grid neurons). Moreover, network analysis enabled the assessment of the importance of a location, even when that location did not display any distinctive physical properties.     

Silencing of the ADNP-family member, ADNP2, results in changes in cellular viability under oxidative stress

Activity-dependent neuroprotective protein (ADNP) 2 (KIAA0863; ZNF508) gene, a homeobox-profile containing gene, was identified in a screen for homologous proteins to ADNP. The human ADNP2 contains 1131 amino acid residues with a molecular weight of 122.8 KDa. In silico analysis indicated that ortholgs to ADNP2 exist in different phyla, suggesting that ADNP2 might be evolutionary conserved. Here, we began to explore the molecular and functional characterization of ADNP2. Results showed that the mouse ADNP2 mRNA is ubiquitously expressed in distinct normal tissues with increased expression in the brain, particularly in the cerebral cortex. During development, a relatively high level of ADNP2 gene expression was found in the embryonic mouse brain and was sustained throughout embryogenesis and adulthood. An increase in the mRNA was detected in differentiated P19 neuronal/glial-like cells as compared with the non-differentiated cells. To gain insight into ADNP2 function, ADNP2-deficient cell lines were established by the RNA silencing (small interfering RNA) technology. ADNP2 deficiency significantly changed the toxicity induced by hydrogen peroxide in P19 embryonic carcinoma cells, similar to what would be predicted for ADNP deficiency. These findings represent an initial characterization of ADNP2 and suggest that this gene product may have an important function in brain by playing a role in cellular survival pathways.     

Ethical Considerations of Triage Following Natural Disasters: The IDF Experience in Haiti as a Case Study

Natural disasters in populated areas may result in massive casualties and extensive destruction of infrastructure. Humanitarian aid delegations may have to cope with the complicated issue of patient prioritization under conditions of severe resource scarcity. A triage model, consisting of five principles, is proposed for the prioritization of patients, and it is argued that rational and reasonable agents would agree upon them. The Israel Defense Force's humanitarian mission to Haiti following the 2010 earthquake serves as a case study for the various considerations taken into account when designing the ethical‐clinical policy of field hospitals. The discussion focuses on three applications: the decision to include an intensive care unit, the decision to include obstetrics and neonatal units, and the treatment policy for compound fractures.     

Hospitalized dogs recovery from naturally occurring heatstroke; does serum heat shock protein 72 can provide prognostic biomarker?

Heatstroke is a serious illness in dogs characterized by core temperatures above 41 °C with central nervous system dysfunction. Experimental heatstroke models have tried to correlate biomarker levels with the severity of the syndrome. Serum heat shock protein (eHSP70) levels were recently evaluated as a biomarker of heat tolerance and acclimation, their role as a marker of heatstroke is inconclusive. Here, we monitored eHSP70 levels in correlation with systemic biomarkers in 30 naturally occurring canine heatstroke cases. Thirty dogs diagnosed with environmental (33 %) or exertional (66 %) heatstroke admitted to hospital (0–14 h post-injury) were tested for biomarkers of organ damage and coagulation parameters. eHSP70 levels were measured upon admission and 4, 12, and 24 h later (T1, T2, and T3, respectively). No differences were found between exertional and environmental heatstroke cases. The eHSP profile demonstrated an inverted bell shape, with the lowest levels at the 12 h time point. A positive correlation between eHSP70, lactate, and aPPT was also noted at T2 in all the dogs in the study. Twenty-four h after presentation, eHSP70 levels returned to those measured upon admission, this change was only significant in the survivors. The obtained results suggest that eHSP72 level profile may be predictive of survival.     

Point-like protrusion as a prestalk intermediate in membrane fusion pathway

The widely accepted pathway of membrane fusion begins with the fusion stalk representing the initial intermediate of hemifusion. The lipid structures preceding hemifusion and their possible influence on fusion kinetics were not addressed. Here, we suggest the point-like protrusion as a prestalk fusion intermediate, which has energy lower than that of stalk and, therefore, does not limit the fusion rate. We demonstrate that by calculating the energy of the point-like protrusion, which depends on the lipid monolayer elastic parameters and the strength of the intermembrane hydration repulsion. The point-like protrusion completes the fusion-through-hemifusion model of membrane merger.     

Predominant Ashkenazi BRCA1/2 mutations in families with pancreatic cancer

The present study aimed to identify pancreatic cancer patients who harbor a mutation in BRCA1/2 genes within hereditary breast-ovarian cancer families. History of cancer in 1014 families that attended our breast-ovarian oncogenetic clinic was evaluated. Twenty-three families with pancreatic cancer were studied. In nine families wherein the probands themselves presented with pancreatic cancer, two (22%) carried a BRCA mutation (185delAG in BRCA1 in one case and 6174delT in BRCA2 in the other). In 14 families, only a family history of pancreatic cancer was elicited. Of these, seven families segregated either the 185delAG (three families) or the 6174delT (three families) mutation; one family segregated both mutations, but the parental status was not studied. Pedigree analysis shows that four of the seven pancreatic cancer cases were obligatory carriers. In summary, from among 23 families with pancreatic cancer, 6 (26%) informative BRCA1/2 mutation carriers were identified, equally cosegregating the 185delAG or the 6174delT mutation. Yet, it is not fully elucidated whether the risk for pancreatic cancer attributed to BRCA1 is similar to the high risk conferred by BRCA2. In Ashkenazi Jews, mutations in BRCA1/2 may constitute a major cause for pancreatic cancer.     

Consumption of aphids by spiders and the effect of additional prey: evidence from microcosm experiments

Spiders are common generalist predators in agroecosystems and have been suggested to lower herbivore abundance in crops. It is not clear, however, if spiders can effectively suppress pest populations, and if so, by what mechanisms. In a microcosm experiment, we examined the consumption of the bird cherry-oat aphid, Rhopalosiphum padi L. (Homoptera: Aphididae), a pest species in wheat fields, by three spider species that differ in their hunting methods. We then tested the effect of additional prey type on the ability of erigonid spiders to reduce aphids. In a 48-h experiment Mermessus denticulatus (Banks) (Araneae: Linyphiidae; Erigoninae) consumed more aphids than did Enoplognatha gemina Bosmans and Van Keer (Araneae: Theridiidae) and Bathyphantes cf. extricatus (O·P.-Cambridge) (Araneae: Linyphiidae; Linyphiinae). This difference may be due to the ability of erigonids to forage actively on the vegetation in addition to using their webs to catch prey. In a 7-week experiment, we provided springtails (Collembola) in high and low densities as additional prey to mated erigonids, prior to aphid introduction. Spiders in the low-density springtail treatment built more webs on the vegetation, and caused a 50% reduction in aphid populations. There were significantly fewer aphids in the low-density springtail treatment, but not in the high-density treatment, in comparison to the control (high-density springtails without spiders). The results suggest that additional prey density affects predatory interactions between M. denticulatus and R. padi and that erigonids, which occur in high densities in wheat fields in the Negev desert, may be involved in aphid suppression in these agroecosystems.