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PubMed1995

Architecture of individual dendrites from intracellularly labeled thalamocortical projection neurons in the ventral posterolateral and ventral posteromedial nuclei of cat.

This study provides quantitative descriptions of individual dendrites from electrophysiologically characterized and intracellularly labeled thalamocortical projection (TCP) neurons of the cat ventrobasal complex. One hundred nine dendrites from six ventral posterolateral (VPL) neurons and six ventral posteromedial (VPM) neurons were examined. Measurement of several parameters showed that the individual dendrites were very similar to each other in overall architecture even though they varied greatly in total length and number of dendritic branches. The mean path distance (length from soma to a dendritic tip) was very similar for all dendrites in each group (VPL or VPM) regardless of the number of branches found along the path distance. However, VPL dendrites had a longer mean path distance (VPL = 206 +/- 36 microns; n = 51) than VPM dendrites (VPM = 182 +/- 29 microns; n = 58; P < 0.001). For all dendrites there was a strong correlation between the stem dendrite diameter and the dendritic length, which allows the estimation of dendritic length from dendrite diameter. Analysis of dendritic scaling shows that branches higher than first order do not follow Rall's 3/2 power rule, so these neurons cannot be modeled using the equivalent cylinder approximation. The data add to the qualitative descriptions of cat ventrobasal (VB) TCP dendrites currently available and provide a basis for future comparative, developmental, and plasticity studies. Analysis shows that many parameters of cat VB TCP dendrites fall within a narrow range, suggesting that, regardless of differences in length or superficial appearance, these dendrites share a stable underlying architecture.

Animals↗
PubMed1997

Lymphotoxin but not tumor necrosis factor functions to maintain splenic architecture and humoral responsiveness in adult mice.

To compare the function of the tumor necrosis factor (TNF) and lymphotoxin (LT)alpha/beta systems in the mature immune system, these two pathways were blocked with soluble receptor-immunoglobulin (R-Ig) fusion proteins in normal adult mice. Inhibition of LT alpha/beta signaling using LT betaR-Ig or a blocking monoclonal antibody against murine LT beta had profound effects. The spleen lacked discrete B cell follicles and the marginal zone was altered. Less marked changes were detected in lymph nodes. LT alpha/beta inhibition also prevented germinal center formation in the spleen and impaired Ig production in response to sheep red blood cells (SRBC) immunization. These results show that the LT alpha/beta system is required for the maintenance of splenic architecture and normal immune responses, and not simply for the development of peripheral immune organs during ontogeny. In contrast, inhibition of the TNF/LT alpha pathway with TNF-R55-Ig did not affect the splenic architecture or the anti-SRBC response. Splenic defects and impaired antibody responses are seen in TNF-deficient mice, suggesting that TNF is important during development. Therefore relative to TNF, the LT system has the dominant influence on splenic organization and anti-SRBC Ig formation in the adult mouse.

Animals↗
PubMed2001

Genetic lesions and perturbation of chromatin architecture: a road to cell transformation.

Differential gene expression is a rigorously precise procedure that defines the developmental program of cells, tissues, organs, and of the entire organism. The correct execution of this program requires the participation of multiple and complex groups of regulators. In addition to transcription factors, which are key tools in ontogenesis by providing sequential switch of different genes, the structure of the chromatin is a dominant determinant leading to gene expression. Through the novel and insightful work of several investigators, it appears that the architecture of the chromatin spanning the genes can and does influence the efficiency of RNA transcription, and therefore of gene expression. Several new enzymatic complexes have been identified that reversibly modify the chromatin architecture by methylation, phosphorylation, and acetylation of the nucleosomal core proteins. These enzymes are crucial for the proper balance and maintenance of gene expression, and are often the target of mutations and alterations in human cancer. Here, we review briefly the current models proposing how some of these enzymes normally modify the chromatin structure and how their functional disruption leads to inappropriate gene expression and cell transformation.

Acetylation↗
PubMed2006

Long-term serotonin administration leads to higher bone mineral density, affects bone architecture, and leads to higher femoral bone stiffness in rats.

New evidence suggests a control of bone mass by the central nervous system. We have previously shown that functional serotonin receptors are present in bone cells and that serotonin stimulates proliferation of osteoblast precursor cells in vitro. In the present study we investigated the effects of serotonin on bone tissue in vivo. Ten, 2-month-old female Sprague-Dawley rats were injected with serotonin subcutaneously (s.c.) (5 mg/kg) once daily for 3 months, controls received saline. Using microdialysis and HPLC, free circulating serotonin levels were measured. DXA scans were made after 3 months of serotonin administration. Bone architecture and mechanical properties were investigated by micro-computed tomography (microCT), histomorphometry, and mechanical testing. A long-lasting hyperserotoninemia with a >10-fold increase in serotonin appeared. Total body BMD was significantly higher (0.1976+/-0.0015 vs. 0.1913+/-0.0012 g/cm2) in rats receiving serotonin. Cortical thickness (Ct.Th) measured by microCT analysis was also higher, whereas trabecular bone volume (BV) was lower. Interestingly, the perimeter and cross-sectional moment of inertia (MOI), a proxy for geometrical bone strength, were the same in both groups. These data suggest that serotonin reduces resorption or/and increases apposition of endosteal bone. Mechanical testing showed that femoral stiffness was higher in serotonin-dosed animals. The energy absorption also seemed slightly, but not significantly higher. In conclusion, hyperserotoninemia led to a higher BMD, altered bone architecture and higher femural bone stiffness in growing rats, demonstrating that serotonin may have important effects on bone in vivo.

Animals↗
PubMed2007

Palladin regulates cell and extracellular matrix interaction through maintaining normal actin cytoskeleton architecture and stabilizing beta1-integrin.

Cell and extracellular matrix (ECM) interaction plays an important role in development and normal cellular function. Cell adhesion and cell spreading on ECM are two basic cellular behaviors related to cell-ECM interaction. Here we show that palladin, a novel actin cytoskeleton-associated protein, is actively involved in the regulation of cell-ECM interaction. It was found that palladin-deficient mouse embryonic fibroblasts (MEFs) display decreased cell adhesion and compromised cell spreading on various ECMs. Disorganized actin cytoskeleton architecture characterized by faint stress fibers, less lamellipodia and focal adhesions can account for the weakened cell-ECM interaction in palladin(-/-) MEFs. Furthermore, decreased polymerized filament actin and increased globular actin can be observed in palladin(-/-) MEFs, strongly suggesting that palladin is essential for the formation or stabilization of polymerized filament actin. Elevated phospho-cofilin level and proper responses in cofilin phosphorylation to either Rho signal agonist or antagonist in palladin(-/-) MEFs indicate that disrupted stress fibers in palladin(-/-) MEFs is not associated with cofilin phosphorylation. More interestingly, the protein level of ECM receptor beta1-integrin is dramatically decreased in MEFs lacking palladin. Down-regulation of beta1-integrin protein can be restored by proteasome inhibitor MG-132 treatment. All these data implicate that palladin is essential for cell-ECM interaction through maintaining normal actin cytoskeleton architecture and stabilizing beta1-integrin protein.

Actins↗
PubMed2007

Long-term fluoxetine administration does not result in major changes in bone architecture and strength in growing rats.

Many studies have indicated that serotonin and its transporter play a role in bone metabolism. In this study we investigated the effect of selective serotonin re-uptake inhibitor (SSRI), fluoxetine (Prozac) on bone architecture and quality in growing female rats. We therefore administrated rats with clinically relevant doses of fluoxetine for a period of 6 months. DXA scans were performed during the treatment period in order to follow parameters as body weight, fat percentage and BMD. After 6 months of treatment, femurs were used to analyze bone architecture and bone strength, by means of microCT scans and three-point bending assays, respectively. We found a slightly diminished bone quality, reflected in a lower bone tissue strength, which was compensated by changes in bone geometry. As leptin and adiponectin could be possible factors in the serotonergic regulation of bone metabolism, we also determined the levels of these factors in plasma samples of all animals. Leptin and adiponectin levels were not different between the control group and fluoxetine-treated group, indicating that these factors were not involved in the observed changes in bone geometry and quality.

Adiponectin↗
PubMed2002

Analysis of the three-dimensional lymphatic architecture of the periodontal tissue using a new 3D reconstruction method.

Few studies of lymphatic vessels have been reported because diacrisis of this vascular system is rare. A complete examination of diacrisis of venula is not yet possible even using recent enzyme-histochemical or immunohistochemical techniques. In this study, we examined a lymphatic vessel by serial sectioning from the afferent lymphatic of the lymph node to the periphery by three-dimensional observation using a three-dimensional reconstitution method. This method was conventional and accurate, and the time required for processing was markedly reduced by using a computer. Reconstitution of the vasculature became possible utilizing the entire section instead of a portion of a parenchymatous organ. We examined the lymphatic vessel architecture of various oral regions, including gingiva, tongue, and the floor of the mouth, using this method. In the future, using this method, we plan to investigate the alteration of lymphatic vessel architecture in a pathological region, and correlate these changes with the dynamics of lymphatic vessel absorption.

Animals↗
PubMed2003

Horse hooves and bird feathers: Two model systems for studying the structure and development of highly adapted integumentary accessory organs--the role of the dermo-epidermal interface for the micro-architecture of complex epidermal structures.

Accessory organs of the integument are locally modified parts of the potentially feather-bearing skin in birds (e.g., the rhamphotheca, claws, or scales), and of the potentially hairy skin in mammals (e.g., the rhinarium, nails, claws, or hooves). These special parts of the integument are characterised by a modified structure of their epidermal, dermal and subcutaneous layers. The developmental processes of these various integumentary structures in birds and mammals show both similarities and differences. For example, the development of the specialised epidermal structures of both feathers and the hoof capsule is influenced by the local three-dimensional configuration of the dermis. However, in feathers, in contrast to hooves, the arrangement of the corneous cells is only partially a direct result of the particular arrangement and shape of the dermal surface of the papillary body. Whereas the diameter of the feather papilla, as well as the number, length, and width of dermal ridges on the surface of the feather papilla influence the three-dimensional architecture of the feather rami, there is no apparent direct correlation between the dermo-epidermal interface and the development of the highly ordered architecture of the radii and hamuli in the feather vane. In order to elucidate this morphogenic problem and the problem of locally different processes of keratinisation and cornification, the structure and development of feathers in birds are compared to those of the hoof capsule in horses. The equine hoof is the most complex mammalian integumentary structure, which is determined directly by the dermal surface of the papillary body. Perspectives for further research on the development of modified integumentary structures, such as the role of the dermal microangioarchitecture and the selective adhesion and various differentiation pathways of epidermal cells, are discussed.

Animals↗
PubMed1984

Architectural and histochemical analysis of the semitendinosus muscle in mice, rats, guinea pigs, and rabbits.

The architectural and histochemical properties of the anatomically distinct compartments of the semitendinosus muscle (ST) of mice, rats, guinea pigs, and rabbits show that the ST is composed of two separate compartments aligned in series--a distal compartment (STd) and a proximal one (STp). The STp is further subdivided into a ventral head (STpv) and a dorsal head (STpd). The muscle fibers were arranged in parallel to the line of muscle pull within each compartment. The STd has the longest and the STpv the shortest fibers in all species. The physiological cross-sectional area and the estimated tetanic tension was greatest in the STd. Based on the staining pattern for myosin ATPase (alkaline preincubation) and an oxidative indicator (NADH or SDH), the STpv has the highest percentage of slow-oxidative (SO) or SO plus fast-oxidative-glycolytic (FOG) fibers of any portion of the muscle. The differences in fiber-type distributions and architectural designs of the separate compartments suggest a specialization of function of the individual compartments.

Animals↗
PubMed1989

Skeletal muscle architecture of the rabbit hindlimb: functional implications of muscle design.

The muscle-fiber architecture of 29 muscles from six rabbits (Oryctolagus cuniculus) was measured in order to describe the muscular properties of this cursorial animal, which possesses several specific skeletal adaptations. Several muscles were placed into one of four functional groups: hamstrings, quadriceps, dorsiflexors, or plantarflexors, for statistical comparison of properties between groups. Antagonistic groups (i.e., hamstrings vs. quadriceps or dorsiflexors vs. plantarflexors) demonstrated significant differences in fiber length, fiber length/muscle length ratio, muscle mass, pinnation angle, and number of sarcomeres in series (P less than .02). Discriminant analysis permitted characterization of the "typical" muscle belonging to one of the four groups. The quadriceps were characterized by their large pinnation angles and low fiber length/mass ratios, suggesting a design for force production. Conversely, the hamstrings, with small pinnation angles, appeared to be designed to permit large excursions. Similar differences were observed between plantarflexors and dorsiflexors, which have architectural features that suit them for force production and excursion respectively. Although these differences were not absolute, they represented clear morphological distinctions that have functional consequences.

Animals↗
PubMed1993

In-series fiber architecture in long human muscles.

The fiber architecture of adult human sartorius and gracilis muscles was examined using a combination of fiber microdissections and histological methods. Intact fibers were dissected from fascicles of muscle strips that were digested in nitric acid. All of these fibers terminate intrafascicularly by tapering to a fine strand at one or both ends. They measure 4-20 cm after correction for shrinkage. Systematic dissections of 1 cm long blocks sampled at intervals along the muscle length suggest that tapered fiber endings occur at all locations along the muscle but are most common centrally; here they accounted for up to 14% of dissected fibers in each block. Transverse sections of muscle confirm that fiber profiles with small diameters occur at all levels of the muscle but are especially common in sections more than 5 cm from its origin or insertion. The architectural arrangement demonstrated here suggests that long human muscles, like muscles in other species, are composed of relatively short, in-series fibers. This has many implications for the neural activation and force-developing behavior of these muscles that must be considered when paralyzed muscles are reanimated using electrical stimulation. Further, it may predispose long muscles to certain types of neuromuscular damage and dysfunction.

Adult↗
PubMed2001

T2 relaxation reveals spatial collagen architecture in articular cartilage: a comparative quantitative MRI and polarized light microscopic study.

It has been suggested that orientational changes in the collagen network of articular cartilage account for the depthwise T2 anisotropy of MRI through the magic angle effect. To investigate the relationship between laminar T2 appearance and collagen organization (anisotropy), bovine osteochondral plugs (N = 9) were T2 mapped at 9.4T with cartilage surface normal to the static magnetic field. Collagen fibril arrangement of the same samples was studied with polarized light microscopy, a quantitative technique for probing collagen organization by analyzing its ability to rotate plane polarized light, i.e., birefringence (BF). Depthwise variation of safranin O-stained proteoglycans was monitored with digital densitometry. The spatially varying cartilage T2 followed the architectural arrangement of the collagen fibril network: a linear positive correlation between T2 and the reciprocal of BF was established in each sample, with r = 0.91 +/- 0.02 (mean +/- SEM, N = 9). The current results reveal the close connection between the laminar T2 structure and the collagen architecture in histologic zones.

Animals↗
PubMed2004

Assessment of axonal fiber tract architecture in excised rat spinal cord by localized NMR q-space imaging: simulations and experimental studies.

NMR q-space imaging is a method designed to obtain information from porous materials where diffusion-diffraction phenomena were observed from which pore size was derived. Recently, the technique has been applied to the study of biological structures as well. Although diffusive diffraction has so far not been observed in multicellular systems, displacement profiles have been used with some success as a means to estimate structure size. However, there have been no quantitative correlations of the retrieved structure sizes with histology. Clearly, the complexity of tissue architecture poses significant challenges to the interpretation of q-space data. In this work, simulations were first performed on a two-compartment model to demonstrate the effects of interference of the diffraction patterns arising from intra and extra-axonal compartments and finite boundary permeability on q-space data. Second, q-space echo attenuation was simulated on the basis of histologic images of various rat spinal cord fiber tracts and the information obtained from the displacement profiles were compared with structural parameters computed from the histologic images. The results show that calculated mean displacements and kurtosis parallel mean axon size and axonal density. Finally, spatially localized q-space measurements were carried out at the locations where simulations had previously been performed, resulting in displacement data that support those obtained by simulation. The data suggest the NMR q-space approach has potential for nondestructive analysis of the axonal architecture in the mammalian spinal cord.

Animals↗
PubMed2005

Mapping complex tissue architecture with diffusion spectrum magnetic resonance imaging.

Methods are presented to map complex fiber architectures in tissues by imaging the 3D spectra of tissue water diffusion with MR. First, theoretical considerations show why and under what conditions diffusion contrast is positive. Using this result, spin displacement spectra that are conventionally phase-encoded can be accurately reconstructed by a Fourier transform of the measured signal's modulus. Second, studies of in vitro and in vivo samples demonstrate correspondence between the orientational maxima of the diffusion spectrum and those of the fiber orientation density at each location. In specimens with complex muscular tissue, such as the tongue, diffusion spectrum images show characteristic local heterogeneities of fiber architectures, including angular dispersion and intersection. Cerebral diffusion spectra acquired in normal human subjects resolve known white matter tracts and tract intersections. Finally, the relation between the presented model-free imaging technique and other available diffusion MRI schemes is discussed.

Algorithms↗
PubMed2006

Molecular architecture of the neuromuscular junction.

The neuromuscular junction (NMJ) is a complex structure that serves to efficiently communicate the electrical impulse from the motor neuron to the skeletal muscle to signal contraction. Over the last 200 years, technological advances in microscopy allowed visualization of the existence of a gap between the motor neuron and skeletal muscle that necessitated the existence of a messenger, which proved to be acetylcholine. Ultrastructural analysis identified vesicles in the presynaptic nerve terminal, which provided a beautiful structural correlate for the quantal nature of neuromuscular transmission, and the imaging of synaptic folds on the muscle surface demonstrated that specializations of the underlying protein scaffold were required. Molecular analysis in the last 20 years has confirmed the preferential expression of synaptic proteins, which is guided by a precise developmental program and maintained by signals from nerve. Although often overlooked, the Schwann cell that caps the NMJ and the basal lamina is proving to be critical in maintenance of the junction. Genetic and autoimmune disorders are known that compromise neuromuscular transmission and provide further insights into the complexities of NMJ function as well as the subtle differences that exist among NMJ that may underlie the differential susceptibility of muscle groups to neuromuscular transmission diseases. In this review we summarize the synaptic physiology, architecture, and variations in synaptic structure among muscle types. The important roles of specific signaling pathways involved in NMJ development and acetylcholine receptor (AChR) clustering are reviewed. Finally, genetic and autoimmune disorders and their effects on NMJ architecture and neuromuscular transmission are examined.

Animals↗
PubMed2004

Expression of acyl-CoA synthetase 5 reflects the state of villus architecture in human small intestine.

Several disorders of the small intestine are associated with disturbances in villus architecture. Thus, an understanding of the molecular mechanisms associated with the differentiation of villi represents an important step in the improvement of the understanding of small intestinal pathology. Screening of antibodies from a hybridoma library led to the identification of an acyl-CoA synthetase 5-specific monoclonal antibody. Protein synthesis, mRNA expression, and the enzyme activity of acyl-CoA synthetase 5 were studied by several methods in human small intestinal tissues with Crohn's disease or coeliac disease, respectively. Acyl-CoA synthetase 5 mRNA and protein levels were substantially reduced in injured small intestinal mucosa. Moreover, impaired synthesis of the acyl-CoA synthetase 5 protein was reflected by a decrease in intramucosal enzyme activity. Subtle changes of the acyl-CoA synthetase 5 pattern correlate with conversion of intestinal epithelial cells to a gastric phenotype. These results suggest that deranged acyl-CoA synthetase 5 expression, synthesis, and activity are closely related to the state of villus architecture and epithelial homeostasis in human small intestine.

Adult↗
PubMed2001

Fractal dimension of trabecular bone: comparison of three histomorphometric computed techniques for measuring the architectural two-dimensional complexity.

Trabecular bone has been reported as having two-dimensional (2-D) fractal characteristics at the histological level, a finding correlated with biomechanical properties. However, several fractal dimensions (D) are known and computational ways to obtain them vary considerably. This study compared three algorithms on the same series of bone biopsies, to obtain the Kolmogorov, Minkowski-Bouligand, and mass-radius fractal dimensions. The relationships with histomorphometric descriptors of the 2-D trabecular architecture were investigated. Bone biopsies were obtained from 148 osteoporotic male patients. Bone volume (BV/TV), trabecular characteristics (Tb.N, Tb.Sp, Tb.Th), strut analysis, star volumes (marrow spaces and trabeculae), inter-connectivity index, and Euler-Poincaré number were computed. The box-counting method was used to obtain the Kolmogorov dimension (D(k)), the dilatation method for the Minkowski-Bouligand dimension (D(MB)), and the sandbox for the mass-radius dimension (D(MR)) and lacunarity (L). Logarithmic relationships were observed between BV/TV and the fractal dimensions. The best correlation was obtained with D(MR) and the lowest with D(MB). Lacunarity was correlated with descriptors of the marrow cavities (ICI, star volume, Tb.Sp). Linear relationships were observed among the three fractal techniques which appeared highly correlated. A cluster analysis of all histomorphometric parameters provided a tree with three groups of descriptors: for trabeculae (Tb.Th, strut); for marrow cavities (Euler, ICI, Tb.Sp, star volume, L); and for the complexity of the network (Tb.N and the three D's). A sole fractal dimension cannot be used instead of the classic 2-D descriptors of architecture; D rather reflects the complexity of branching trabeculae. Computation time is also an important determinant when choosing one of these methods.

Cluster Analysis↗
PubMed1997

Architecture of helix bundle membrane proteins: an analysis of cytochrome c oxidase from bovine mitochondria.

We have analyzed the structure of mitochondrial cytochrome c oxidase in terms of general characteristics thought to be important for describing the architecture of helix bundle membrane proteins. Many aspects of the structure are similar to what has previously been found for the photosynthetic reaction center and bacteriorhodopsin. Our results lead to a considerably more precise general picture of membrane protein architecture than has hitherto been possible to obtain.

Amino Acids↗