Fractal analysis of pyramidal cells in the visual cortex of the galago (Otolemur garnetti): Regional variation in dendritic branching patterns between visual areas

Previously it has been shown that the branching pattern of pyramidal cells varies markedly between different cortical areas in simian primates. These differences are thought to influence the functional complexity of the cells. In particular, there is a progressive increase in the fractal dimension of pyramidal cells with anterior progression through cortical areas in the occipitotemporal (OT) visual stream, including the primary visual area (V1), the second visual area (V2), the dorsolateral area (DL, corresponding to the fourth visual area) and inferotemporal cortex (IT). However, there are as yet no data on the fractal dimension of these neurons in prosimian primates. Here we focused on the nocturnal prosimian galago (Otolemur garnetti). The fractal dimension (D), and aspect ratio (a measure of branching symmetry), was determined for I I I layer III pyramidal cells in V1, V2, DL and IT. We found, as in simian primates, that the fractal dimension of neurons increased with anterior progression from V1 through V2, DL, and IT. Two important conclusions can be drawn from these results: (1) the trend for increasing branching complexity with anterior progression through OT areas was likely to be present in a common primate ancestor, and (2) specialization in neuron structure more likely facilitates object recognition than spectral processing.

Intrinsic regional differences in androgen receptors and dihydrotestosterone metabolism in human preadipocytes

Androgens play an important role in regulating the central obesity that is a strong risk factor for cardiovascular disease and insulin resistance. This study confirms that androgen receptors are present in subcultured human preadipocytes, with androgen receptor gene expression and saturable specific dihydrotestosterone binding, dissociation constant 1.02 - 2.56 nM and maximal binding capacity 30.8 - 55.7 fmol/mg protein. There was an intrinsic regional difference in androgen receptor complement, with more androgen receptors in visceral than in subcutaneous preadipocytes. Dihydrotestosterone was metabolised by human preadipocytes, with more androstanediol produced by subcutaneous than visceral preadipocytes. While dihydrotestosterone metabolism was insufficient to explain the regional variation in androgen binding, both of these differences would reduce the androgen responsiveness of the subcutaneous preadipocytes compared with visceral preadipocytes. There were no gender differences in androgen binding or metabolism. While the direct effects of androgens on human PAS remain uncertain, these regional differences suggest that AR-mediated regulation of certain PA functions influences adipose tissue distribution.

The pyramidal neuron in occipital, temporal and prefrontal cortex of the owl monkey (Aotus trivirgatus): regional specialization in cell structure

Recent studies have revealed marked regional variation in pyramidal cell morphology in primate cortex. In particular, pyramidal cells in human and macaque prefrontal cortex (PFC) are considerably more spinous than those in other cortical regions. PFC pyramidal cells in the New World marmoset monkey, however, are less spinous than those in man and macaques. Taken together, these data suggest that the pyramidal cell has become more branched and more spinous during the evolution of PFC in only some primate lineages. This specialization may be of fundamental importance in determining the cognitive styles of the different species. However, these data are preliminary, with only one New World and two Old World species having been studied. Moreover, the marmoset data were obtained from different cases. In the present study we investigated PFC pyramidal cells in another New World monkey, the owl monkey, to extend the basis for comparison. As in the New World marmoset monkey, prefrontal pyramidal cells in owl monkeys have relatively few spines. These species differences appear to reflect variation in the extent to which PFC circuitry has become specialized during evolution. Highly complex pyramidal cells in PFC appear not to have been a feature of a common prosimian ancestor, but have evolved with the dramatic expansion of PFC in some anthropoid lineages.

Regional morphology of the transversus abdominis and obliquus internus and externus abdominis muscles

Background. The mechanisms by which the abdominal muscles move and control the lumbosacral spine are not clearly understood. Descriptions of abdominal morphology are also conflicting and the regional anatomy of these muscles has not been comprehensively examined. The aim of this study was to investigate the morphology of regions of transversus abdominis and obliquus internus and externus abdominis. Methods. Anterior and posterolateral abdominal walls were dissected bilaterally in 26 embalmed human cadavers. The orientation, thickness and length of the upper, middle and lower fascicles of transversus abdominis and obliquus internus abdominis, and the upper and middle fascicles of obliquus externus abdominis were measured. Findings. Differences in fascicle orientation, thickness and length were documented between the abdominal muscles and between regions of each muscle. The fascicles of transversus abdominis were horizontal in the upper region, with increasing inferomedial orientation in the middle and lower regions. The upper and middle fascicles of obliquus internus abdominis were oriented superomedially and the lower fascicles inferomedially. The mean vertical dimension of transversus abdominis that attaches to the lumbar spine via the thoracolumbar fascia was 5.2 (SD 2.1) cm. Intramuscular septa were observed between regions of transversus abdominis, and obliquus internus abdominis could be separated into two distinct layers in the lower and middle regions. Interpretation. This study provides quantitative data of morphological differences between regions of the abdominal muscles, which suggest variation in function between muscle regions. Precise understanding of abdominal muscle anatomy is required for incorporation of these muscles into biomechanical models. Furthermore, regional variation in their morphology may reflect differences in function. (C) 2004 Elsevier Ltd. All rights reserved.

Regional patterns of agricultural land use and deforestation in Colombia

An expanding human population and associated demands for goods and services continues to exert an increasing pressure on ecological systems. Although the rate of expansion of agricultural lands has slowed since 1960, rapid deforestation still occurs in many tropical countries, including Colombia. However, the location and extent of deforestation and associated ecological impacts within tropical countries is often not well known. The primary aim of this study was to obtain an understanding of the spatial patterns of forest conversion for agricultural land uses in Colombia. We modeled native forest conversion in Colombia at regional and national-levels using logistic regression and classification trees. We investigated the impact of ignoring the regional variability of model parameters, and identified biophysical and socioeconomic factors that best explain the current spatial pattern and inter-regional variation in forest cover. We validated our predictions for the Amazon region using MODIS satellite imagery. The regional-level classification tree that accounted for regional heterogeneity had the greatest discrimination ability. Factors related to accessibility (distance to roads and towns) were related to the presence of forest cover, although this relationship varied regionally. In order to identify areas with a high risk of deforestation, we used predictions from the best model, refined by areas with rural population growth rates of > 2%. We ranked forest ecosystem types in terms of levels of threat of conversion. Our results provide useful inputs to planning for biodiversity conservation in Colombia, by identifying areas and ecosystem types that are vulnerable to deforestation. Several of the predicted deforestation hotspots coincide with areas that are outstanding in terms of biodiversity value.

Overview, critical assessment, and conservation implications of koala distribution and abundance

Regional and national surveys provide a broadscale description of the koala's present distribution in Australia. A detailed understanding of its distribution is precluded, however, by past and continuing land clearing across large parts of the koala's range. Koala population density increased in some regions during the late 1800s and then declined dramatically in the early 1900s. The decline was associated with habitat loss, hunting, disease, fire, and drought. Declines are continuing in Queensland and New South Wales. In contrast, dense koala populations in habitat isolates in Victoria and South Australia are managed to reduce population size and browse damage. Current understanding of koala distribution and abundance suggests that the species does not meet Australian criteria as endangered or vulnerable fauna. Its conservation status needs to be reviewed, however, in light of the extensive land clearing in New South Wales and Queensland since the last (1980s) broadscale surveys. Consequently, we recommend that broadacre clearing by curtailed in New South Wales and Queensland and that regular, comprehensive, standardized, national koala surveys be undertaken. Given the fragmentation of koala habitat and regional differences in the status of the koala, we recommended that studies on regional variation in the koala be intensified and that koala ecology in fragmented and naturally restricted habitats be developed. More generally, the National Koala Conservation Strategy should be implemented.

Development of a fully quantitative approach to the interpretation of stress echocardiography using radial and longitudinal myocardial velocities

Background: Tissue Doppler may be used to quantify regional left ventricular function but is limited by segmental variation of longitudinal velocity from base to apex and free to septal walls. We sought to overcome this by developing a composite of longitudinal and radial velocities. Methods and Results. We examined 82 unselected patients undergoing a standard dobutamine echocardiogram. Longitudinal velocity was obtained in the basal and mid segments of each wall using tissue Doppler in the apical views. Radial velocities were derived in the same segments using an automated border detection system and centerline method with regional chords grouped according to segment location and temporally averaged. In 25 patients at low probability of coronary disease, the pattern of regional variation in longitudinal velocity (higher in the septum) was the opposite of radial velocity (higher in the free wall) and the combination was homogenous. In 57 patients undergoing angiography, velocity in abnormal segments was less than normal segments using longitudinal (6.0 +/- 3.6 vs 9.0 +/- 2.2 cm/s, P = .01) and radial velocity (6.0 +/- 4.0 vs 8.0 +/- 3.9 cm/s, P = .02). However, the composite velocity permitted better separation of abnormal and normal segments (13.3 +/- 5.6 vs 17.5 +/- 4.2 cm/s, P = .001). There was no significant difference between the accuracy of this quantitative approach and expert visual wall motion analysis (81% vs 84%, P = .56). Conclusion: Regional variation of uni-dimensional myocardial velocities necessitates site-specific normal ranges, probably because of different fiber directions. Combined analysis of longitudinal and radial velocities allows the derivation of a composite velocity, which is homogenous in all segments and may allow better separation of normal and abnormal myocardium.

Parvalbumin-, calbindin-, and calretinin-immunoreactive neurons in the prefrontal cortex of the owl monkey (Aotus trivirgatus): A standardized quantitative comparison with sensory and motor areas

Recent studies have revealed regional variation in the density and distribution of inhibitory neurons in different cortical areas, which are thought to reflect area-specific specializations in cortical circuitry. However, there are as yet few standardized quantitative data regarding how the inhibitory circuitry in prefrontal cortex (PFC), which is thought to be involved in executive functions such as cognition, emotion and decision making, compares to that in other cortical areas. Here we used immunohistochemical techniques to determine the density and distribution of parvalbumin (PV)-, calbindin (CB)-, and calretinin (CR)-immunoreactive (ir) neurons and axon terminals in the dorsolateral and orbital PFC of the owl monkey (Aotus trivirgatus), and compared them directly with data obtained using the same techniques in 11 different visual, somatosensory and motor areas. We found marked differences in the density of PV-ir, CB-ir, and CR-ir interneurons in several cortical areas. One hundred and twenty eight of all 234 possible between-area pairwise comparisons were significantly different. The density of specific subpopulations of these cells also varied among cortical areas, as did the density of axon terminals. Comparison of PFC with other cortical areas revealed that 40 of all 66 possible statistical comparisons of the density of PV-ir, CB-ir, and CR-ir cells were significantly different. We also found evidence for heterogeneity in the pattern of labeling of PV-ir, CB-ir, and CR-ir cells and axon terminals between the dorsolateral and orbital subdivisions of PFC. These data are likely to reflect basic differences in interneuron circuitry, which are likely to influence inhibitory function in the cortex. Copyright (C) 2003 S. Karger AG, Basel.

Dendritic branching of pyramidal cells in the visual cortex of the nocturnal owl monkey: A fractal analysis

The branching structure of neurones is thought to influence patterns of connectivity and how inputs are integrated within the arbor. Recent studies have revealed a remarkable degree of variation in the branching structure of pyramidal cells in the cerebral cortex of diurnal primates, suggesting regional specialization in neuronal function. Such specialization in pyramidal cell structure may be important for various aspects of visual function, such as object recognition and color processing. To better understand the functional role of regional variation in the pyramidal cell phenotype in visual processing, we determined the complexity of the dendritic branching pattern of pyramidal cells in visual cortex of the nocturnal New World owl monkey. We used the fractal dilation method to quantify the branching structure of pyramidal cells in the primary visual area (V1), the second visual area (V2) and the caudal and rostral subdivisions of inferotemporal cortex (ITc and ITr, respectively), which are often associated with color processing. We found that, as in diurnal monkeys, there was a trend for cells of increasing fractal dimension with progression through these cortical areas. The increasing complexity paralleled a trend for increasing symmetry. That we found a similar trend in both diurnal and nocturnal monkeys suggests that it was a feature of a common anthropoid ancestor.

The evaluation of the spatial and temporal stability of sugarcane farm performance based on yield and commercial cane sugar

In broader catchment scale investigations, there is a need to understand and ultimately exploit the spatial variation of agricultural crops for an improved economic return. In many instances, this spatial variation is temporally unstable and may be different for various crop attributes and crop species. In the Australian sugar industry, the opportunity arose to evaluate the performance of 231 farms in the Tully Mill area in far north Queensland using production information on cane yield (t/ha) and CCS ( a fresh weight measure of sucrose content in the cane) accumulated over a 12-year period. Such an arrangement of data can be expressed as a 3-way array where a farm x attribute x year matrix can be evaluated and interactions considered. Two multivariate techniques, the 3-way mixture method of clustering and the 3-mode principal component analysis, were employed to identify meaningful relationships between farms that performed similarly for both cane yield and CCS. In this context, farm has a spatial component and the aim of this analysis was to determine if systematic patterns in farm performance expressed by cane yield and CCS persisted over time. There was no spatial relationship between cane yield and CCS. However, the analysis revealed that the relationship between farms was remarkably stable from one year to the next for both attributes and there was some spatial aggregation of farm performance in parts of the mill area. This finding is important, since temporally consistent spatial variation may be exploited to improve regional production. Alternatively, the putative causes of the spatial variation may be explored to enhance the understanding of sugarcane production in the wet tropics of Australia.

Potassium channels and membrane potential in the modulation of intracellular calcium in vascular endothelial cells

K+ Channels and Membrane Potential in Endothelial Cells. The endothelium plays a vital role in the control of vascular functions, including modulation of tone; permeability and barrier properties; platelet adhesion and aggregation; and secretion of paracrine factors. Critical signaling events in many of these functions involve an increase in intracellular free Ca2+ concentration ([Ca2+](i)). This rise in [Ca2+](i) occurs via an interplay between several mechanisms, including release from intracellular stores, entry from the extracellular space through store depletion and second messenger-mediated processes, and the establishment of a favorable electrochemical gradient. The focus of this review centers on the role of potassium channels and membrane potential in the creation of a favorable electrochemical gradient for Ca2+ entry. In addition, evidence is examined for the existence of various classes of potassium channels and the possible influence of regional variation in expression and experimental conditions.