A multilevel account of hippocampal function in spatial and concept learning: Bridging models of behavior and neural assemblies

A complete neuroscience requires multilevel theories that address phenomena ranging from higher-level cognitive behaviors to activities within a cell. We propose an extension to the level of mechanism approach where a computational model of cognition sits in between behavior and brain: It explains the higher-level behavior and can be decomposed into lower-level component mechanisms to provide a richer understanding of the system than any level alone. Toward this end, we decomposed a cognitive model into neuron-like units using a neural flocking approach that parallels recurrent hippocampal activity. Neural flocking coordinates units that collectively form higher-level mental constructs. The decomposed model suggested how brain-scale neural populations coordinate to form assemblies encoding concept and spatial representations and why so many neurons are needed for robust performance at the cognitive level. This multilevel explanation provides a way to understand how cognition and symbol-like representations are supported by coordinated neural populations (assemblies) formed through learning

Superfund: An Assessment of Superfund Site Remedy Selectioin and Implementation

Since its inception in 1980, the U.S. Environmental Protection Agency’s (EPA) Superfund Program has served as the primary mechanism for coordinating the remediation of sites contaminated with hazardous substances. Although the program has successfully overseen cleanup at hundreds of sites, experts have identified a number of weaknesses in the remedy selection and implementation processes. Our study focuses on two weaknesses that have been identified at individual Superfund sites in the previous literature: Remedy Selection: • Selection of non-permanent remedies over permanent remedies Remedy Implementation: • Inconsistency and non-transparency shown in the documentation of cleanup objectives, site cleanup progress, and problems during remedy implementation Although these weaknesses were well documented in previous literature, our group found little evidence that the underlying cause of these weaknesses had been addressed. Our study adds to the current understanding of these weaknesses by investigating their origins using established policy and engineering systems analysis techniques. We have based our analysis on three Superfund site case studies. We offer several recommendations that address the observed weaknesses in site remedy selection and implementation. Lastly, we include suggestions for areas in which further inquiry may be useful

In vivo model for microbial invasion of tooth root dentinal tubules

ABSTRACT Objective Bacterial penetration of dentinal tubules via exposed dentine can lead to root caries and promote infections of the pulp and root canal system. The aim of this work was to develop a new experimental model for studying bacterial invasion of dentinal tubules within the human oral cavity. Material and Methods Sections of human root dentine were mounted into lower oral appliances that were worn by four human subjects for 15 d. Roots were then fixed, sectioned, stained and examined microscopically for evidence of bacterial invasion. Levels of invasion were expressed as Tubule Invasion Factor (TIF). DNA was extracted from root samples, subjected to polymerase chain reaction amplification of 16S rRNA genes, and invading bacteria were identified by comparison of sequences with GenBank database. Results All root dentine samples with patent tubules showed evidence of bacterial cell invasion (TIF value range from 5.7 to 9.0) to depths of 200 mm or more. A spectrum of Gram-positive and Gram-negative cell morphotypes were visualized, and molecular typing identified species of Granulicatella, Streptococcus, Klebsiella, Enterobacter, Acinetobacter, and Pseudomonas as dentinal tubule residents. Conclusion A novel in vivo model is described, which provides for human root dentine to be efficiently infected by oral microorganisms. A range of bacteria were able to initially invade dentinal tubules within exposed dentine. The model will be useful for testing the effectiveness of antiseptics, irrigants, and potential tubule occluding agents in preventing bacterial invasion of dentine

Inflammatory cell expression of Toll-like receptor-2 (TLR2) within refractory periapical granuloma. [version 1; referees: 2 approved]

Background: Toll-like receptor-2 (TLR2) is highly important within the immune system. Characterization of the expression of TLR2 within inflammatory cells in periapical lesions could help in diagnosis and management of refractory cases. The aim of the study is identification of Toll-like receptor (TLR2) through immunohistochemical and immunofluroscence expression in inflammatory cells within refractory periapical granuloma cases. Methods: Eight cases of refractory periapical granuloma were selected out of 772 cases. Histological examination and immunohistochemical staining with polyclonal rabbit antihuman TLR2, monoclonal mouse antihuman CD38, CD68 and CD83 primary antibodies, as well as immunofluorescence staining with goat anti-rabbit TLR2, donkey anti-mouse CD38, CD68 and CD83 primary antibodies was conducted. Positive controls, negative controls and experimental sections with no primary antibody were included in the study. Qualitative analysis and double immunofluorescence technique was used to characterize the TLR+ cells. Results: In periapical granuloma, lymphocytes (CD38 cells) expressed the most amount of TLR reactivity followed by macrophages (CD68 cells), and odontogenic epithelial cells. Neutrophils, red blood cells (RBCs) and collagen ground substance were negative to TLR2.  Conclusion: TLR2 was highly expressed by lymphocytes and plasma cells indicative of their major role in the inflammatory process and antigen recognition in refractory periapical granuloma. Dendritic cells expressing TLR2 were low in number suggesting a minor role in sustaining these lesions

Preserved Grasshopper Fauna Of Knife Point Glacier, Fremont County, Wyoming, U.S.A.

In 1987 and 1988, samples of preserved insects were extracted from the ice of Knife Point Glacier, Fremont County, Wyoming. The glacier lies at an altitude of 3500 m a.s.l. in the Shoshone National Forest, Wind River Range, and is known to contain preserved insects. Although the glacier has undergone extensive recession in the last 50 yr, some insect deposits are still embedded at 20 to 25 cm below the surface and perhaps much deeper. The frozen deposits appear to consist entirely of grasshoppers. A few, virtually intact, specimens and body parts were in a state of preservation that allowed their identification as Spharagemon campestris McNeill and Melanoplus spretus (Walsh) or M. sanguinipes (F.). The majority of the deposits consisted of partial bodies and isolated parts, including, in order of frequency: mandibles, tibiae, tentoria, femora, wings (primarily tegmina), and cingulae/epiphalli. Deposits from various depths and locations on the glacier were radiocarbon dated at 205 + 65 to 450 + 80 yr BP. Although access to the glacier is quite difficult, the insects are better preserved than any glacial deposit documented in recent history. Thus, the state of preservation and age of the frozen deposits would suggest that additional, intensive sampling may be valuable in obtain- ing information on the ecology of grasshoppers prior to European settlement of North America

Preserved Grasshopper Fauna Of Knife Point Glacier, Fremont County, Wyoming, U.S.A.

In 1987 and 1988, samples of preserved insects were extracted from the ice of Knife Point Glacier, Fremont County, Wyoming. The glacier lies at an altitude of 3500 m a.s.l. in the Shoshone National Forest, Wind River Range, and is known to contain preserved insects. Although the glacier has undergone extensive recession in the last 50 yr, some insect deposits are still embedded at 20 to 25 cm below the surface and perhaps much deeper. The frozen deposits appear to consist entirely of grasshoppers. A few, virtually intact, specimens and body parts were in a state of preservation that allowed their identification as Spharagemon campestris McNeill and Melanoplus spretus (Walsh) or M. sanguinipes (F.). The majority of the deposits consisted of partial bodies and isolated parts, including, in order of frequency: mandibles, tibiae, tentoria, femora, wings (primarily tegmina), and cingulae/epiphalli. Deposits from various depths and locations on the glacier were radiocarbon dated at 205 + 65 to 450 + 80 yr BP. Although access to the glacier is quite difficult, the insects are better preserved than any glacial deposit documented in recent history. Thus, the state of preservation and age of the frozen deposits would suggest that additional, intensive sampling may be valuable in obtain- ing information on the ecology of grasshoppers prior to European settlement of North America

In vivo model for microbial invasion of tooth root dentinal tubules

Objective Bacterial penetration of dentinal tubules via exposed dentine can lead to root caries and promote infections of the pulp and root canal system. The aim of this work was to develop a new experimental model for studying bacterial invasion of dentinal tubules within the human oral cavity. Material and Methods Sections of human root dentine were mounted into lower oral appliances that were worn by four human subjects for 15 d. Roots were then fixed, sectioned, stained and examined microscopically for evidence of bacterial invasion. Levels of invasion were expressed as Tubule Invasion Factor (TIF). DNA was extracted from root samples, subjected to polymerase chain reaction amplification of 16S rRNA genes, and invading bacteria were identified by comparison of sequences with GenBank database. Results All root dentine samples with patent tubules showed evidence of bacterial cell invasion (TIF value range from 5.7 to 9.0) to depths of 200 mm or more. A spectrum of Gram-positive and Gram-negative cell morphotypes were visualized, and molecular typing identified species of Granulicatella, Streptococcus, Klebsiella, Enterobacter, Acinetobacter, and Pseudomonas as dentinal tubule residents. Conclusion A novel in vivo model is described, which provides for human root dentine to be efficiently infected by oral microorganisms. A range of bacteria were able to initially invade dentinal tubules within exposed dentine. The model will be useful for testing the effectiveness of antiseptics, irrigants, and potential tubule occluding agents in preventing bacterial invasion of dentine