Three-dimensional spatial cognition in a benthic fish, Corydoras aeneus.

The way animals move through space is likely to affect the way they learn and remember spatial information. For example, a pelagic fish, Astyanax fasciatus, moves freely in vertical and horizontal space and encodes information from both dimensions with similar accuracy. Benthic fish can also move with six degrees of freedom, but spend much of their time travelling over the substrate; hence they might be expected to prioritise the horizontal dimension. To understand how benthic fish encode and deploy three-dimensional spatial information we used a fully rotational Y-maze to test whether Corydoras aeneus (i) encode space as an integrated three-dimensional unit or as separate elements, by testing whether they can decompose a three-dimensional trajectory into its vertical and horizontal components, and (ii) whether they prioritise vertical or horizontal information when the two conflict. In contradiction to the expectation generated by our hypothesis, our results suggest that C. aeneus are better at extracting vertical information than horizontal information from a three-dimensional trajectory, suggesting that the vertical axis is learned and remembered robustly. Our results also showed that C. aeneus prioritise vertical information when it conflicts with horizontal information. From these results, we infer that benthic fish attend preferentially to a cue unique to the vertical axis, and we suggest that this cue is hydrostatic pressure.

Insulin resistance impairs nigrostriatal dopamine function.

Clinical studies have indicated a link between Parkinson's disease (PD) and Type 2 Diabetes. Although preclinical studies have examined the effect of high-fat feeding on dopamine function in brain reward pathways, the effect of diet on neurotransmission in the nigrostriatal pathway, which is affected in PD and parkinsonism, is less clear. We hypothesized that a high-fat diet, which models early-stage Type 2 Diabetes, would disrupt nigrostriatal dopamine function in young adult Fischer 344 rats. Rats were fed a high fat diet (60% calories from fat) or a normal chow diet for 12 weeks. High fat-fed animals were insulin resistant compared to chow-fed controls. Potassium-evoked dopamine release and dopamine clearance were measured in the striatum using in vivo electrochemistry. Dopamine release was attenuated and dopamine clearance was diminished in the high-fat diet group compared to chow-fed rats. Magnetic resonance imaging indicated increased iron deposition in the substantia nigra of the high fat group. This finding was supported by alterations in the expression of several proteins involved in iron metabolism in the substantia nigra in this group compared to chow-fed animals. The diet-induced systemic and basal ganglia-specific changes may play a role in the observed impairment of nigrostriatal dopamine function.

Thermoelectric power of p-doped single-wall carbon nanotubes and the role of phonon drag.

We measured thermoelectric power S of bulk single-wall carbon nanotube materials p doped with acids. In contrast to oxygen-exposed or degassed samples, S is very small at the lowest temperatures, increases superlinearly above a characteristic and sample-dependent T, and then levels off. We attribute this unusual behavior to 1D phonon drag, in which the depression of the Fermi energy cuts off electron-phonon scattering at temperatures below a characteristic T0. This idea is supported by a model calculation in which the low temperature behavior of phonon drag is specifically related to the one-dimensional character of the electronic spectrum.

Cytokine pattern in aneurysmal and occlusive disease of the aorta.

BACKGROUND: Prominent inflammatory infiltrates of macrophages and T-lymphocytes are found in both aortic occlusive disease (AOD) and abdominal aortic aneurysms (AAA). These cells secrete different cytokines that might affect matrix turnover through modulation of matrix metalloproteinase expression. A different cytokine pattern might account for the evolution of AOD vs AAA. MATERIALS AND METHODS: Six different cytokines were examined to determine whether AOD and AAA could be characterized by unique cytokine patterns. AOD (n = 8) and AAA (n = 8) tissues were collected and serially treated with salt, dimethyl sulfoxide, and urea buffers to extract the soluble matrix or cell-bound cytokines. Levels of IL-1 beta, TNF-alpha, IL-10, IL-12, and IFN-gamma were measured by immunoenzymatic methods. Additionally, RNA levels of IL-12 and IFN-gamma were measured. RESULTS: AAA tissue contained higher levels of IL-10 compared to AOD tissue (P < 0.05). Higher levels of the proinflammatory cytokines IL-1 beta, TNF-alpha, and IL-6 were found in AOD (P < 0.05). mRNA levels of IL-12 and IFN-gamma did not differ between the diseases. Aortic tissues contained large amounts of matrix or cell-bound cytokines. CONCLUSIONS: AAA is characterized by greater levels of IL-10 while IL-1 beta, TNF-alpha, and IL-6 are higher in AOD. Targeted deletion of these cytokines in animal models might help in identifying their role in the progression of AAA.

Morphology of the normal human lens.

PURPOSE: To provide a quantitative, morphologic description of differentiated lens fiber cells in all regions of aged normal human lenses. METHODS: Transparent normal human lenses (age range, 44 to 71 years) were examined with correlative transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Vibratome sections allowed examination of internal structures, whereas dissected whole lenses revealed surface characteristics. Additionally, image analysis was used to measure cross-sectional areas of fiber cells. RESULTS: Approximate regional dimensions (percentage of diameter and thickness, respectively) were determined for whole lenses: cortex 16%, 17%; adult nucleus 24%, 21%; juvenile nucleus 12%, 9%; fetal nucleus 45%, 49%; and embryonic nucleus 3%, 4%. Cortical cells were irregularly hexagonal, and the average cross-sectional area measured 24 +/- 9 microns2. Adult nuclear cells were flattened with intricate membranous interdigitations and an area of 7 +/- 2 microns2. Juvenile nuclear cells had an area of 14 +/- 5 microns2. Fetal nuclear cells were rounded with an area of 35 +/- 22 microns2. Embryonic nuclear cells also were rounded and had a variable area of 80 +/- 68 microns2. Fiber cell cytoplasm in all lens regions appeared smooth in texture and homogeneous in staining density. CONCLUSIONS: Both TEM and SEM are necessary to obtain a complete description of fiber cells. Cross-sections of fibers give new insights into the lamellar organization of the lens, indicating that each region has characteristic cell shapes and sizes. Furthermore, average dimensions were used to demonstrate that the number of cells and approximate growth rates vary significantly between adjacent regions.

Localization of aortic disease is associated with intrinsic differences in aortic structure.

PURPOSE: While localization of atherosclerosis and aneurysms to the infrarenal aorta has been attributed, in part, to hemodynamic factors, anatomic differences between the proximal and the distal aorta may also be important. Our purpose was to determine the changes in content and organization of major structural proteins (elastin and collagen) throughout the normal human aorta. METHODS: Biochemical analysis for desmosine-isodesmosine (elastin) and hydroxyproline (collagen) content was done by HPLC on complete 1-cm transverse rings removed from the ascending and descending thoracic aorta and abdominal supraceliac, suprarenal, and midinfrarenal aorta. Elastin and collagen content was normalized to lumenal surface area and compared by ANOVA: Light microscopy and optical micrometry were used to determine changes in intimal, medial, and adventitial thickness and number of elastin lamellae at each level. RESULTS: Both collagen/cm2 and elastin/cm2 decrease from the proximal to distal aorta. Collagen content did not differ among the three abdominal segments, but there was a 58% decrease in elastin between the suprarenal and the infrarenal aorta. The proportion of elastin and collagen does not differ throughout the aorta except in the infrarenal aorta where there is decreased elastin relative to collagen. CONCLUSION: Collagen and elastin in the distal aorta bear an increased load as compared to the proximal aorta. The infrarenal aorta differs biochemically and histologically from the remainder of the aorta. A decrease in infrarenal elastin without a corresponding decrease in collagen may effect the compliance and integrity of the distal aorta. These anatomic differences may be important in predisposing the infrarenal aorta to atherosclerosis and aneurysm formation.

Elastin is increased in abdominal aortic aneurysms.

The decrease in elastin concentration in abdominal aortic aneurysm (AAA) has been ascribed to elastolysis. The discordant response of the elastin and collagen genes in AAA suggests a different explanation: dilution of elastin because of higher levels of synthesis of collagen and other matrix proteins. The purpose of this study was to determine circumferential content of elastin, collagen, and total protein in aneurysmal (AAA), atherosclerotic, and normal (NL) infrarenal aorta. Standard serial extraction techniques of complete 1-cm rings of midinfrarenal aortic tissue were used to remove soluble protein, calcium, and lipids. Hydroxyproline (collagen), desmosine/isodesmosine (elastin), and total amino acid (total protein) content were determined by amino acid analysis. Means values (+/- SEM) were compared by ANOVA. Circumferential content of desmosine/isodesmosine was increased 2.5-fold in AAA compared to NL (P < 0.05). Collagen and total protein were increased 5.7- and 4.7-fold, respectively (P < 0.05). There was a high degree of correlation between circumference and collagen content (r = 0.89). These data demonstrate that significant synthesis of matrix proteins accompanies aortic dilatation. While both elastin and collagen are increased, there is a much greater increase in circumferential collagen content than elastin content. These data do not preclude proteolysis as a factor in AAA but suggest that the decrease in elastin concentration results from dilution of elastin by a greater increase in the synthesis of other matrix proteins and that synthesis is an important factor in AAA formation.

Abdominal aortic aneurysms are associated with altered matrix proteins of the nonaneurysmal aortic segments.

PURPOSE: Abdominal aortic aneurysms (AAA) are associated with diffuse arteriomegaly and peripheral aneurysms, suggesting a generalized process. Elastin and collagen are the key structural proteins of the aorta, and their relative content is markedly altered in tissue from AAA. Our purpose was to investigate elastin and collagen content in the proximal, nonaneurysmal segments of aortas with infrarenal AAA. METHODS: After extraction of lipid, calcium, and soluble proteins, hydroxyproline (collagen) and desmosine-isodesmosine (elastin) contents were determined by high-performance liquid chromatography in the ascending and descending thoracic, supraceliac, and suprarenal aorta. By repeated measures of analysis of covariance, collagen was found to be increased throughout the aorta in AAA as compared with normal aorta or aorta with atherosclerotic occlusive disease. This difference remained significant when adjustments were made for group differences in age and degree of atherosclerosis. This increase in collagen content results in a dilutional decrease in elastin concentration. These data demonstrate that the same matrix protein alterations found in AAA tissue occur throughout the aorta, differing only in magnitude in the aneurysmal and nonaneurysmal segments. These data suggest that aneurysm formation may related to alterations in the regulation of elastin and collagen.