Areas Of High Cell Density Research Articles

Peranan Sekuen Diffusion Weighted Imaging (DWI) Pada Pemeriksaan MRI Soft Tissue Leher Kasus Kanker Nasofaring (Studi Literatur)

The aim of this research is to determine the role of the Diffusion Weighted Imaging (DWI) sequence in Soft Tissue MRI examinations of the neck in cases of nasopharyngeal cancer and to determine the advantages of using the Diffusion Weighted Imaging (DWI) sequence in MRI Soft Tissue examinations of the neck in cases of nasopharyngeal cancer. The research method used was a descriptive qualitative research method with a literature study method. The results of the literature review research showed: 1) Nasopharyngeal cancer, especially squamous cell carcinoma, can be treated with radiation therapy where treatment failure is still a serious problem, especially in advanced cases. DWI and ADC are imaging methods that utilize the movement of water inside. DWI provides additional information regarding response to treatment in hard-to-reach cases of nasopharyngeal cancer. plays an important role in detection, evaluation of response to treatment, and early monitoring of chemoradiotherapy therapy. DWI also provides information that helps distinguish between tissue experiencing post-RTH fibrosis and areas that may contain active cancer cells. DWI and ADC are also useful in tumor staging, delineation of target volumes, and detection of tumor recurrence. Elevated ADC may be indicative of a favorable response to therapy, whereas low pretreatment ADC values ​​may predict a favorable response. In the diagnosis of nasopharyngeal cancer, DWI and ADC also help differentiate squamous cell carcinoma subtypes, predict response to chemoradiation therapy, and determine the appropriate time for alternative treatment regimens. 2) DWI and ADC provide advantages in the diagnosis and monitoring of nasopharyngeal cancer. DWI can image restrictions on water diffusion within tissue, helping to detect areas of high cell density associated with tumors. Its advantages include sensitivity to microenvironmental changes and the ability to early identify recurrence or secondary cancer post-radiation therapy.

Abstract 4322: AI assisted detection and characterization of tertiary lymphoid structures in patients with colorectal cancer

Abstract Tertiary Lymphoid Structures (TLSs) are ectopic immune cell aggregates that form in response to abnormal physiology and inflammation. TLS presence in the tumor environment has been associated with positive clinical outcomes and response to immune checkpoint inhibition therapy. Using a fluorescent multiplex panel consisting of Pan-cytokeratin (PanCK), Programmed Death Ligand-1 (PD-L1), cluster of differentiation (CD) 8, CD3, and CD68 we developed a HALO-based artificial intelligence (AI) classifier to detect TLSs in colorectal cancer (CRC) tissue. In conjunction with cell-type and spatial analyses, we used the AI TLS classifier to characterize several features of the TLS and peri-TLS environment. We trained the AI classifier using 51 examples of TLSs from 8 patients, and applied it to images of 21 CRC patient tissues. TLSs were detected in 9/21 patient samples. We then used cellular detection and spatial analysis to characterize features of the TLS, including the germinal center (GC), T cell zone and peri-TLS area. We detected a higher cell density (Mean=12250 ±2039 SD; cells/mm2) within the interior of AI-detected GCs relative to the 1st 200 μm outside of the AI-defined GC border (8005±1870). In addition, we examined the spatial distribution of CD3+ and CD8+ T cells relative to the TLS GC. We found elevated CD3+ cell density in the interior of the GC (5784±1649) and within 200 μm of the GC border (5126±2239) which decreased at distances >200 μm from the GC border. We found CD8+ density to be elevated within the 1st 200 μm of the GC border (1903±1182) and declined 400 μm away from the GC border (963±828). The spatial distribution of T cells surrounding an area of high cell density is indicative of a T cell zone surrounding germinal center. Further analysis of the AI-detected TLS GCs indicated that PD-L1+ cell density was highest within the germinal center (355± 534;9) relative to the exterior of the germinal center (1st 150μm outside germinal center:276± 441). We created an AI classifier that can detect TLS(s) within patient tissue in the absence of a B-cell marker and confirmed that our AI classifier was detecting TLSs by characterizing canonical features of TLSs. Further exploration of the TLS and peri-TLS area may offer insights into immune-tumor interaction within the tumor microenvironment, and paired detection of TLSs in a clinical cohort with outcome data may predict patient response to immune checkpoint inhibitor therapy. Citation Format: Samantha Burg, Nathaniel Hart, Astin Powers, Wenjun Zhang. AI assisted detection and characterization of tertiary lymphoid structures in patients with colorectal cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4322.

Learn-Morph-Infer: A new way of solving the inverse problem for brain tumor modeling.

Current treatment planning of patients diagnosed with a brain tumor, such as glioma, could significantly benefit by accessing the spatial distribution of tumor cell concentration. Existing diagnostic modalities, e.g. magnetic resonance imaging (MRI), contrast sufficiently well areas of high cell density. In gliomas, however, they do not portray areas of low cell concentration, which can often serve as a source for the secondary appearance of the tumor after treatment. To estimate tumor cell densities beyond the visible boundaries of the lesion, numerical simulations of tumor growth could complement imaging information by providing estimates of full spatial distributions of tumor cells. Over recent years a corpus of literature on medical image-based tumor modeling was published. It includes different mathematical formalisms describing the forward tumor growth model. Alongside, various parametric inference schemes were developed to perform an efficient tumor model personalization, i.e. solving the inverse problem. However, the unifying drawback of all existing approaches is the time complexity of the model personalization which prohibits a potential integration of the modeling into clinical settings. In this work, we introduce a deep learning based methodology for inferring the patient-specific spatial distribution of brain tumors from T1Gd and FLAIR MRI medical scans. Coined as Learn-Morph-Infer, the method achieves real-time performance in the order of minutes on widely available hardware and the compute time is stable across tumor models of different complexity, such as reaction-diffusion and reaction-advection-diffusion models. We believe the proposed inverse solution approach not only bridges the way for clinical translation of brain tumor personalization but can also be adopted to other scientific and engineering domains.

Comparative retinal histomorphometry and visual acuity of three bat species of the genus Artibeus (Phyllostomidae: Stenodermatinae)

ABSTRACT: This study performed a histomorphometric analysis of the retina and estimated the visual acuity of three fruit-eating bats of the genus Artibeus, including Artibeus lituratus, Artibeus planirostris and Artibeus obscurus. In total, 13 animals were used for this study, in which the retinas were hemidisected, fixed, cut, and stained. The visual acuity was determined by the density of ganglion cells in the retina and the retinal layers were also measured from histological sections. The retinas of these bats are avascular, do not present tapetum lucidum in any quadrant, and have the 10 retinal layers common in mammals. Moreover, it was observed that the thickness of the retina in the central region was significantly higher in all measured parameters (p<0.001), except for the outer plexiform layer (OPL) which was significantly higher in the peripheral region (p<0.001). The retinas of the three species showed a horizontal visual streak with a higher concentration of retinal ganglion cells (RGCs) at the inferotemporal region. In addition, the species A. lituratus exhibited extras areas of high cell density in the retina. Thus, A. lituratus showed the highest visual acuity (1.92 cycles/degree), while A. planirostris showed a visual acuity of (1.77 cycles/degree) and A. obscurus exhibited the lowest visual acuity (1.50 cycles/degree). All these characteristics are related to the echolocation system and the eating habits of each species. Therefore, it can be concluded that bats of the genus Artibeus have a high visual acuity value compared to other echolocating bats and all these differences might be directly linked to the phylogeny of the genus.

3D printed oxidized alginate-gelatin bioink provides guidance for C2C12 muscle precursor cell orientation and differentiation via shear stress during bioprinting

Biofabrication can be a tool to three-dimensionally (3D) print muscle cells embedded inside hydrogel biomaterials, ultimately aiming to mimic the complexity of the native muscle tissue and to create in-vitro muscle analogues for advanced repair therapies and drug testing. However, to 3D print muscle analogues of high cell alignment and synchronous contraction, the effect of biofabrication process parameters on myoblast growth has to be understood. A suitable biomaterial matrix is required to provide 3D printability as well as matrix degradation to create space for cell proliferation, matrix remodelling capacity, and cell differentiation. We demonstrate that by the proper selection of nozzle size and extrusion pressure, the shear stress during extrusion-bioprinting of mouse myoblast cells (C2C12) can achieve cell orientation when using oxidized alginate-gelatin (ADA-GEL) hydrogel bionk. The cells grow in the direction of printing, migrate to the hydrogel surface over time, and differentiate into ordered myotube segments in areas of high cell density. Together, our results show that ADA-GEL hydrogel can be a simple and cost-efficient biodegradable bioink that allows the successful 3D bioprinting and cultivation of C2C12 cells in-vitro to study muscle engineering.

Cationic osteogenic peptide P15-CSP coatings promote 3-D osteogenesis in poly(epsilon-caprolactone) scaffolds of distinct pore size.

P15-CSP is a biomimetic cationic fusion peptide that stimulates osteogenesis and inhibits bacterial biofilm formation when coated on 2-D surfaces. This study tested the hypothesis that P15-CSP coatings enhance 3-D osteogenesis in a porous but otherwise hydrophobic poly-(ɛ-caprolactone) (PCL) scaffold. Scaffolds of 84 µm and 141 µm average pore size were coated or not with Layer-by-Layer polyelectrolytes followed by P15-CSP, seeded with adult primary human mesenchymal stem cells (MSCs), and cultured 10 days in proliferation medium, then 21 days in osteogenic medium. Atomic analyses showed that P15-CSP was successfully captured by LbL. After 2 days of culture, MSCs adhered and spread more on P15-CSP coated pores than PCL-only. At day 10, all constructs contained nonmineralized tissue. At day 31, all constructs became enveloped in a "skin" of tissue that, like 2-D cultures, underwent sporadic mineralization in areas of high cell density that extended into some 141 µm edge pores. By quantitative histomorphometry, 2.5-fold more tissue and biomineral accumulated in edge pores versus inner pores. P15-CSP specifically promoted tissue-scaffold integration, fourfold higher overall biomineralization, and more mineral deposits in the outer 84 µm and inner 141 µm pores than PCL-only (p < 0.05). 3-D Micro-CT revealed asymmetric mineral deposition consistent with histological calcium staining. This study provides proof-of-concept that P15-CSP coatings are osteoconductive in PCL pore surfaces with 3-D topography. Biomineralization deeper than 150 µm from the scaffold edge was optimally attained with the larger 141 µm peptide-coated pores. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2171-2181, 2017.

Comparison of the methods for measuring the Ki-67 labeling index in adrenocortical carcinoma: manual versus digital image analysis

Adrenocortical carcinoma (ACC) is a rare, highly malignant neoplasm harboring marked histologic heterogeneity. The Ki-67 labeling index (LI) is one of the most effective diagnostic and prognostic markers in ACC. However, its assessment has by no means been standardized. Therefore, in this study, we analyzed the Ki-67 LI in 18 ACC cases both by seven pathologists using microscopes (MA; manual analysis) and with digital image analysis (DIA) and also compared the Ki-67 LI obtained by selecting "hot spots" and formulating the "average" reading of the whole tumor specimen. In addition, we performed statistical analysis of the association between Ki-67 LI and the clinical and pathologic features of individual cases. The DIA was significantly correlated with MA in hot spots but not in the average fields. The Ki-67 LI in hot spots was significantly and consistently higher than that in average areas by both MA and DIA, indicating intratumoral heterogeneity. The Ki-67 LI was significantly correlated with the Weiss criteria (eosinophilic cytoplasm, nuclear atypia, atypical mitoses, and sinusoidal invasion) by any mode of evaluation. The clinical outcome was significantly better in the patients with a Ki-67 < 10% than in those with a Ki-67 > 10% by MA in hot spots. The Ki-67 LI in hot spots measured by MA best reflected the clinical and pathologic features of ACC. Employment of DIA to obtain the Ki-67 LI in ACC requires further improvement, including correction of its overestimation of the value by counting non-tumorous cells and nuclear segmentation in areas of high cell density.

Ocular morphology, topography of ganglion cell distribution and visual resolution of the pilot whale (Globicephala melas)

The ocular morphology, morphological characteristics and topography of ganglion cell distribution were studied in four eyes of Globicephala melas to estimate the retinal resolution. The ganglion cell layer was composed of a single row of ganglion cells with a primarily round shape and a cell size which varied from 10 to 75 µm (mean 33.5 µm) in diameter. The typical feature was that 65 % of ganglion cells had a diameter larger than 25 µm, with a similar average size in all regions of the retina. The total number of ganglion cells (183,000–218,000; mean 203,000) was distributed in several isodensity lines with two definite areas of high cell density: one area was located in the temporal retinal area, and the other one in the nasal retina, at 65° ± 5° from the optic disk. A surprising result was the presence of a third cell density peak in the dorsal region of one retina. The mean peak cell densities of three retinas were 268 and 267 cells/mm2 in the nasal and temporal areas, respectively, and 287 cells/mm2 in the third peak of the dorsal region. Finally, the underwater retinal resolution, calculated from posterior nodal distance and the peak cell density, was 10.9′ (2.8 cycles/degree) in both nasal and temporal retinal areas, whereas the aerial resolution was 14.5′ (2.1 cycles/degree). These data suggest that G. melas has a visual acuity similar to other cetaceans investigated so far.

A Novel Mechanism by Which Tissue Transglutaminase Activates Signaling Events That Promote Cell Survival

Tissue transglutaminase (tTG) functions as a GTPase and an acyl transferase that catalyzes the formation of protein cross-links. tTG expression is frequently up-regulated in human cancer, where it has been implicated in various aspects of cancer progression, including cell survival and chemo-resistance. However, the extent to which tTG cooperates with other proteins within the context of a cancer cell, versus its intrinsic ability to confer transformed characteristics to cells, is poorly understood. To address this question, we asked what effect the ectopic expression of tTG in a non-transformed cellular background would have on the behavior of the cells. Using NIH3T3 fibroblasts stably expressing a Myc-tagged form of tTG, we found that tTG strongly protected these cells from serum starvation-induced apoptosis and triggered the activation of the PI3-kinase/mTOR Complex 1 (mTORC1)/p70 S6-kinase pathway. We determined that tTG forms a complex with the non-receptor tyrosine kinase c-Src and PI3-kinase, and that treating cells with inhibitors to block tTG function (monodansylcadaverine; MDC) or c-Src kinase activity (PP2) disrupted the formation of this complex, and prevented tTG from activating the PI3-kinase pathway. Moreover, treatment of fibroblasts over-expressing tTG with PP2, or with inhibitors that inactivate components of the PI3-kinase pathway, including PI3-kinase (LY294002) and mTORC1 (rapamycin), ablated the tTG-promoted survival of the cells. These findings demonstrate that tTG has an intrinsic capability to stimulate cell survival through a novel mechanism that activates PI3-kinase signaling events, thus highlighting tTG as a potential target for the treatment of human cancer.

Visual Eyes: A Quantitative Analysis of the Photoreceptor Layer in Deep-Sea Sharks

The marine environment presents unique visual challenges for a range of organisms, particularly those dwelling at great depths, where sunlight may either be absent or drop to very low levels. Under these environmental conditions, the visual system must maximise light absorption in order to enhance the detection of prey, predators and potential mates. Using stereological analysis of retinal wholemounts, the distribution and number of photoreceptors (rods) was determined for 5 deep-sea shark species from a range of depths (46-1,500 m). All species possessed areas of increased photoreceptor density (with peaks between 41,000 and 82,000 rods/mm²) within discrete regions of the retina. The total number of rods in the photoreceptor layer also varied between 17 × 10⁶ and 63 × 10⁶. It is evident that increasing sensitivity of the retina is an important adaptation to life in the deep sea. The location of discrete areas of high cell density within the photoreceptor layer of the retina corresponds to discrete areas of the visual field that are sampled at a higher intensity, hence increasing sensitivity. The location of these areas of increased sensitivity differed between the species of this study. The disparity of areas of increased sensitivity seen between species is thought to reflect distinctive predator avoidance and prey capture strategies. This study reveals that the visual demands of deep-sea sharks vary interspecifically and that sampling of each species' visual field is not solely determined by its habitat.

Retinal Ganglion Cell Topography of Five Species of Ground-Foraging Birds

Birds that forage on the ground have been studied extensively in relation to behavioral trade-offs between foraging and scanning for predators; however, we know little about the topography of their retinas, which can influence how they gather visual information. We characterized the density of retinal ganglion cells across the retina and estimated visual acuity of four Passeriformes (European starling Sturnus vulgaris, brown-headed cowbird Molothrus ater, house sparrow Passer domesticus, house finch Carpodacus mexicanus) and one Columbiforme (mourning dove Zenaida macroura) that forage on the ground. We used cresyl violet to stain retinal ganglion cells and estimated visual acuity based on cell density and eye size. All species contained a single area centralis, where cell densities were >20,000 cells/mm². The proportion of the retina that fell in each of five cell density ranges varied between species. European starlings and house finches had the largest area of high cell density, mourning doves had the smallest. The largest proportion of the retina (>35%) of brown-headed cowbird and house sparrow was in the second-lowest cell density range. Considering the 25th percentile of highest cell densities, house finches and European starlings showed the highest cell densities and mourning doves the lowest. Estimated visual acuity increased from house finch, house sparrow, brown-headed cowbird, European starling to mourning dove, and was associated with both retinal area and cell density. Our findings suggest that these ground foragers do not have highly specialized retinas in relation to other types of foragers (e.g. tree foragers), probably because foraging on seeds and insects from the ground is not as visually demanding; however, the studied species showed variability in retinal topography that may be related to foraging techniques, eye size constraints, and size of the area centralis.

Topographical distribution of visual cell nuclei in the retina in relation to the habitat of five species of Decapodiformes (Cephalopoda)

Studies of retinal histology of fish have established that the position of an area of high cell density reflects both the habitat and feeding behaviour. Here, we discuss potential relationships between biology, specifically behaviour and ecology, and visual axes (estimated from density of visual cell nuclei) in five species of Decapodiformes. In all species, the posterior retina had the highest cell density. In coastal species, the region of highest density was dorsal to the midline of the body, meaning that the visual axis was likely directed downwards and forwards, suitable for focusing on the sea bottom. In oceanic species, the highest density region was ventral to the midline, meaning that the visual axis was directed upwards and forwards. This may be advantageous for detecting prey silhouetted against light from above in the open ocean.

Activation of the tgfΒ/activin signaling pathway in intimal hyperplasia and atherosclerosis

Intimal hyperplasia and atherosclerosis are the Achilles' heels of vascular interventions. Many cytokines and growth factors have been shown to mediate these pathological processes. There are conflicting data concerning the expression of transforming growth factor-β1 (TGFβ1) antigen in human intimal hyperplasia and atherosclerotic lesions and conflicting views about whether TGFβ1 is pro- or anti-atherogenic. The presence of TGFβ1 is not sufficient to infer activation of its signaling pathway because TGFβ1 may be present in inactive complexes. A sensitive immuno-fluorescence assay (cyanine-3 tyramide signal amplification system) was used on human coronary artery and aorta sections with early or advanced stage lesions to detect TGFβ1, activin, Smad2-P, a marker of the activated TGFβ1/activin pathway and components of latent TGFβ complexes. All antigens were readily detected in the media and neointima of early stage lesions. The levels were either reduced or undetectable in the media of advanced lesions but were increased in the neointima in areas of high cell density. In marked contrast to activin, TGFβ1 and LAP1 expression levels were closely correlated with Smad2-P throughout the artery wall. Discrepancies in previous data for TGFβ1 expression are probably due to assay sensitivity. TGFβ1, but not activin, expression is consistently correlated with Smad pathway activation in the artery wall. The pattern of Smad2 activation supports a model in which TGFβ/activin signaling is anti-atherogenic in the media of normal artery walls but is equally compatible with an anti-atherogenic or pro-atherogenic response to TGFβ/activin in the neointima of lesions.

Topography of retinal photoreceptor cells in the Jungle Crow (Corvus macrorhynchos) with emphasis on the distribution of oil droplets

Previously, we analyzed the regional specialization of ganglion cells in the retina of the Jungle Crow (Corvus macrorhynchos). The present study extends this analysis by determining the numbers and regional distribution of photoreceptor cells and the different colored oil droplets. The numbers of the different colored oil droplets were counted using color microphotographs of fresh retinas. Estimation of the numbers of photoreceptor cells was made using Nissl-stained retinal whole mounts. The estimated total number of photoreceptor cells in the whole mount retina was approximately 17,933,788 (N=4). The peak density of photoreceptor cells was 92,109/mm2 in the central area of the retina, followed by temporal and nasal areas, respectively. Four types of oil droplet were identified on the basis of their color: red, orange, green and translucent. The central retina had a significantly higher population of oil droplets, with a density of 91,202/mm2; this sharply declined at the peripheral retina. The lowest observed density was 13,192/mm2 in the dorsal retina. The densities and sizes of the different colored oil droplets were inversely correlated across the retina. The average sizes of red, orange, green and translucent oil droplets had 6 μm2, 4 μm2, 7 μm2 and 4 μm2, respectively. At the periphery of the retina, the oil droplets were significantly larger than in the central area. The sizes of the different colored oil droplets also varied within the same area. Orange colored oil droplets (33%) were the most common type in the central area, whereas green colored oil droplets were the most frequent in other areas. The results of the present study show that photoreceptor cells and oil droplets are differentially distributed in the retina. From these results, we conclude that the area of high cell density, matched by high neuron densities of the ganglion cell layer, corresponds to the site of acute color vision in the crow retina.

Human osteoblast response to silicon‐substituted hydroxyapatite

Human osteoblasts were cultured on hydroxyapatite (HA), 0.8 wt % silicon substituted hydroxyapatite (Si-HA) and 1.5 wt % Si-HA discs. The influence of these substrates on cell behaviour in vitro was assessed by measuring total protein in the cell lysate and the production of several phenotypic markers: collagen type I (COL I), alkaline phosphatase (ALP), osteocalcin (OC), and the formation of bone mineral. After 7 days, beta-glycerophosphate and physiological levels of hydrocortisone were added to the culture medium to stimulate cell differentiation and mineral production. There was a significantly higher production of ALP on 1.5 wt % Si-HA at day 7 following which, the addition of hydrocortisone promoted the differentiation of cells on the other two substrates. Hydrocortisone addition also decreased the production of OC. During the period, when hydrocortisone was present, no significant difference in behavior was seen between cells on Si-HA and HA; however, following removal of hydrocortisone, cells responded to 0.8 wt % Si-HA with a significant increase in protein production. Using fluorescence microscopy, nodular structures labeled with tetracycline were observed on the surface of all substrates after 21 days. These structures were deposited on areas of high cell density but were not related to the presence or level of silicon in the substrate. These results indicate that human osteoblasts are affected by the presence of silicon in the HA substrate and that the timing of these effects may be dependent upon the level of silicon substitution.

Simultaneous fermentation of glucose and xylose by pure and mixed cultures of Saccharomyces cerevisiae and Candida shehatae immobilized in a two-chambered bioreactor

Varying amounts of viable Saccharomyces cerevisiae and Candida shehatae cells were coimmobilized in a composite structure consisting of a flat agar layer encompassed between two microporous membrane filters. This immobilized cell system was placed between the two halves of a two-chambered bioreactor and tested for ethanol production from a glucose-xylose mixture. One chamber of the bioreactor was filled with the sugar mixture whereas the second compartment received an equal volume of a substrate-free mineral medium. Batch incubation of the immobilized cell structure was performed at 30°C under two different oxygenation conditions: limited aerobiosis in both bioreactor chambers (symmetrical aeration) and asymmetrical oxygen supply obtained by continuous gas bubbling in the two bioreactor compartments, i.e., anaerobiosis in the substrate chamber (N 2 bubbling) and microaerobiosis in the buffer chamber (bubbling of a O 2 N 2 mixture at low O 2 content). Pure cultures and cocultures of S. cerevisiae and C. shehatae were able to simultaneously consume glucose and xylose, producing ethanol and xylitol. The fermentation efficiency of immobilized cell mixtures was no higher than that of pure cultures, however. Asymmetrical oxygenation conditions affected the fermentation performance of immobilized cultures. Coimmobilized S. cerevisiae and C. shehatae both displayed growth inside the composite structure. Biofilm-like gel areas of high cell density appeared behind the microporous membrane filters during incubation of immobilized organisms. The cell number and repartition of the two yeasts in the gel layer depended on their relative proportions in the initial cell loading and the oxygenation conditions of the structure.

Compartmental distribution of ventral striatal neurons projecting to the mesencephalon in the rat

The ventral striatum is characterized by an intricate neurochemical compartmentation that is reflected in the distribution of most of its afferent fiber systems. In the present study, the compartmental relationships of ventral striatal neurons projecting to the mesencephalon were studied by combining tract tracing with the immunohistochemical localization of leu-enkephalin. Injections of the retrograde tracer cholera toxin subunit B were placed at various sites in the ventral mesencephalon. The anterograde tracer Phaseolus vulgaris leucoagglutinin was injected in single compartments in the rostrolateral part of the nucleus accumbens. The projections from the ventral striatum to the dopaminergic cell groups in the ventral mesencephalon and those to the substantia nigra pars reticulata originate from distinct subpopulations of ventral striatal neurons that respect neurochemically defined compartmental boundaries. In the "shell" of the nucleus accumbens, neurons that project to the dopaminergic cell groups are located outside areas of high cell density and weak enkephalin immunoreactivity (ENK-IR). Rostrolaterally in the "core" of the nucleus accumbens, neurons inside large areas of strong ENK-IR surrounding the anterior commissure project to the dorsomedial part of the substantia nigra pars reticulata, whereas neurons outside these areas innervate the ventral tegmental area and/or the medial part of the substantia nigra pars compacta. By contrast, more caudally in the dorsal part of the nucleus accumbens and in the ventral part of the caudate-putamen, the relationships are reversed: neurons in- or outside small patches of strong ENK-IR project respectively to the pars compacta or the pars reticulata of the substantia nigra. Since the thalamic and cortical afferents of the ventral striatum are compartmentally ordered as well, the present results imply that through the ventral striatal compartments information from disparate combinations of cortical and thalamic sources may be conveyed to distinct mesencephalic targets. The component of the ventral striatomesencephalic system reaching the dopaminergic cell groups A10, A9, and A8 may modulate the dopaminergic input to virtually the entire striatum. The other component can, by way of the pars reticulata of the substantia nigra, participate in nigrothalamic and nigrotectal output pathways of the basal ganglia.

Topographical organization and relationship with ventral striatal compartments of prefrontal corticostriatal projections in the rat.

The anterograde tracer Phaseolus vulgaris-leucoagglutinin was used to examine the topographical organization of the projections to the striatum arising from the various cytoarchitectonic subdivisions of the prefrontal cortex in the rat. The relationship of the prefrontal cortical fibres with the compartmental organization of the ventral striatum was assessed by combining PHA-L tracing and enkephalin-immunohistochemistry. The prefrontal cortex projects bilaterally with an ipsilateral predominance to the striatum, sparing only the lateral part of the caudate-putamen complex. Each of the cytoarchitectonic subfields of the prefrontal cortex has a longitudinally oriented striatal terminal field that overlaps slightly with those of adjacent prefrontal areas. The projections of the medial subdivision of the prefrontal cortex distribute to rostral and medial parts of the striatum, whereas the lateral prefrontal subdivision projects to more caudal and lateral striatal areas. The terminal fields of the orbital prefrontal areas involve midventral and ventromedial parts of the caudate-putamen complex. The projection of the ventral orbital area overlaps with that of the prelimbic area in the ventromedial part of the caudate-putamen. In the "shell" region of the nucleus accumbens, fibres arising from the prelimbic area concentrate in areas of high cell density that are weakly enkephalin-immunoreactive, whereas fibres from the infralimbic area avoid such areas. Rostrolaterally in the "core" region of the nucleus accumbens, fibres from deep layer V and layer VI of the dorsal part of the prelimbic area avoid the enkephalin-positive areas surrounding the anterior commissure and distribute in an inhomogeneous way over the intervening moderately enkephalin-immunoreactive compartment. The other prefrontal afferents show only a preference for, but are not restricted to, the latter compartment. In the border region between the nucleus accumbens and the ventromedial part of the caudate-putamen complex, patches of strong enkephalin immunoreactivity receive prefrontal cortical input from deep layer V and layer VI, whereas fibres from more superficial cortical layers project to the surrounding matrix. Individual cytoarchitectonic subfields of the prefrontal cortex thus have circumscribed terminal domains in the striatum. In combination with data on the organization of the midline and intralaminar thalamostriatal and thalamoprefrontal projections, the present results establish that the projections of the prefrontal cortical subfields converge in the striatum with those of their midline and intralaminar afferent nuclei. The present findings further demonstrate that the relationship of the prefrontal corticostriatal fibres with the neurochemical compartments of the ventral striatum can be influenced by both the areal and the laminar origin of the cortical afferents, depending on the particular ventral striatal region under consideration.

Pericytes derived from the retinal microvasculature undergo calcification in vitro

Pericytes isolated from the bovine retinal microvasculature retain characteristic features of their in vivo counterparts, such as the presence of glycogen deposits, long filamentous processes, prominent microfilament bundles and the ability to display two distinct and reversible phenotypes. Time-lapse video-microscopy demonstrated that pericytes tend to overlap and aggregate, even in sparse cultures. After reaching confluence, they form multilayered areas that retract away from each other, resulting in the formation of multicellular nodules. These nodules increase in size and cellularity by going through repeated 5- to 6-h cycles of anchoring, spreading, cell proliferation and retraction. Alkaline phosphatase was not detected in pericytes at subconfluent or confluent densities, but this enzyme was expressed in areas of high cell density, such as multilayers and nodules. Pericytes synthesise and deposit an extracellular matrix at all stages of their in vitro development, including nodule formation. The matrix within the nodules contains cross-striated collagen fibres and matrix vesicles. Needle-like crystals of hydroxyapatite appear to be deposited within the matrix, thus leading to massive calcification of the nodule. Calcification, as assessed by electron microscopy, histochemical staining and X-ray microprobe analysis, occurred on plastic and collagen substrate in the absence of disodium-beta-glycerophosphate. The addition of this compound at 5 or 10 mM or the use of a collagen substratum (rather than plastic), brought forward the process of nodule formation and calcification by 3-6 days. Our results suggest that retinal pericytes may differentiate in vitro along the osteogenic pathway.

Organization of the thalamostriatal projections in the rat, with special emphasis on the ventral striatum

The organization of the thalamic projections to the ventral striatum in the rat was studied by placing injections of the retrograde tracer cholera toxin subunit B in the ventral striatum and small deposits of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) in individual midline and intralaminar thalamic nuclei. In order to provide a complete map of the midline and intralaminar thalamostriatal projections, PHA-L injections were also made in those parts of the intralaminar nuclei that project to the dorsal striatum. The relationship of thalamic afferent fibres with the compartmental organization of the ventral striatum was assessed by combining PHA-L tracing and enkephalin immunohistochemistry. The various midline and intralaminar thalamic nuclei project to longitudinally oriented striatal sectors. The paraventricular thalamic nucleus sends most of its fibres to medial parts of the nucleus accumbens and the olfactory tubercle, whereas smaller contingents of fibres terminate in the lateral part of the nucleus accumbens and the most ventral, medial, and caudal parts of the caudate-putamen complex. The projections of the parataenial nucleus are directed towards central and ventral parts of the nucleus accumbens and intermediate mediolateral parts of the olfactory tubercle. The intermediodorsal nucleus projects to lateral parts of the nucleus accumbens and the olfactory tubercle and to ventral parts of the caudate-putamen. The projection of the rhomboid nucleus is restricted to the rostrolateral extreme of the striatum. A diffuse projection to the ventral striatum arises from neurons ventral and caudal to the nucleus reuniens rather than from cells inside the nucleus. Fibres from the central medial nucleus terminate centrally and dorsolaterally in the rostral part of the nucleus accumbens and medially in the caudate-putamen. Successively more lateral positions in the caudate-putamen are occupied by fibres from the paracentral and central lateral nuclei, respectively. The lateral part of the parafascicular nucleus projects to the most lateral part of the caudate-putamen, whereas projections from the medial part of this nucleus terminate in the medial part of the caudate-putamen and in the dorsolateral part of the nucleus accumbens. Furthermore, a rostral to caudal gradient in a midline or intralaminar nucleus corresponds to a dorsal to ventral and rostral to caudal gradient in the striatum. In the ventral striatum, thalamic afferent fibres in the "shell" region of the nucleus accumbens avoid areas of high cell density and weak enkephalin immunoreactivity.(ABSTRACT TRUNCATED AT 400 WORDS)