MATERIAL PROPERTIES OF ADULT RAT SKULL

2011 ◽  
Vol 11 (05) ◽  
pp. 1199-1212 ◽  
Author(s):  
HAOJIE MAO ◽  
CHRISTINA WAGNER ◽  
FENGJIAO GUAN ◽  
YENER N. YENI ◽  
KING H. YANG
Keyword(s):  
Elastic Modulus ◽  
Energy Density ◽  
Cross Sections ◽  
Material Properties ◽  
Soft Tissues ◽  
Beam Theory ◽  
Bending Stress ◽  
Adult Rats ◽  
Adult Rat ◽  
Young’S Moduli

Development of advanced computational rat head models requires accurate material properties of the rat brain, meninges, skull, and other soft tissues. This study investigated adult rat skull material properties, which are very limited in the current literature. A total of 20 skull specimens were harvested from 10 adult rats. High resolution (16 μm) microcomputed tomography scans were performed for each specimen to observe dimensional changes within each specimen and internal porosities through the cross sections. The specimens were tested in three-point bending at loading velocities of 0.02 and 200 mm/s. The elastic modulus, energy absorbed to failure, energy density, and bending stress were calculated using classical beam theory. Results demonstrated that bending velocity (strain rate) had significant effect on elastic modulus and bending stress, but not on energy and energy density. The Young's moduli of rat skull measured in this study were comparable to those measured from the adult human skull.

SEM analysis of fish scale cross sections: A technique study

1992 ◽  
Vol 50 (1) ◽  
pp. 744-745
Author(s):  
M.E. Lee ◽  
A. Moller ◽  
P.S.O. Fouche ◽  
I.G Gaigher
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cross Sections ◽  
Soft Tissues ◽  
Close Association ◽  
Sem Analysis ◽  
Fish Scale ◽  
Fish Scales ◽  
Micro Structures ◽  
Scanning Electron

Scanning electron microscopy of fish scales has facilitated the application of micro-structures to systematics. Electron microscopy studies have added more information on the structure of the scale and the associated cells, many problems still remain unsolved, because of our incomplete knowledge of the process of calcification. One of the main purposes of these studies has been to study the histology, histochemistry, and ultrastructure of both calcified and decalcified scales, and associated cells, and to obtain more information on the mechanism of calcification in the scales. The study of a calcified scale with the electron microscope is complicated by the difficulty in sectioning this material because of the close association of very hard tissue with very soft tissues. Sections often shatter and blemishes are difficult to avoid. Therefore the aim of this study is firstly to develop techniques for the preparation of cross sections of fish scales for scanning electron microscopy and secondly the application of these techniques for the determination of the structures and calcification of fish scales.

scholarly journals HOMOLOGOUS DISEASE IN THE ADULT RAT, A MODEL FOR AUTOIMMUNE DISEASE

1963 ◽  
Vol 118 (4) ◽  
pp. 635-648 ◽  
Author(s):  
Peter Stastny ◽  
Vernie A. Stembridge ◽  
Morris Ziff
Keyword(s):  
Autoimmune Disease ◽  
Lupus Erythematosus ◽  
Connective Tissue Diseases ◽  
Skin Lesions ◽  
Cutaneous Lesions ◽  
Adult Rats ◽  
Hydropic Degeneration ◽  
Skin Changes ◽  
Adult Rat ◽  
The One

The cutaneous lesions of adult rats with homologous disease are described, and evidence is presented to indicate that they have an immunologic basis. The skin changes included erythema, purpura, edema, and a variety of inflammatory lesions. In the more active lesions, dermal infiltration, hydropic degeneration, acanthosis, and atrophy of the epidermis with hyperkeratosis and follicular plugging were present. In some cases, ulceration and sloughing were also observed. More chronic lesions were characterized by atrophy of the epidermis and collagenization of the dermis with disappearance of the skin appendages. Rejection of autografts was observed simultaneously with acceptance of homografts. The histologic appearance of autografts undergoing rejection was similar to that of the spontaneous skin lesions, suggesting that the latter, too, had an immunologic basis. In favor of this, also, was the specificity of the dermatitis for the skin of the host, with sparing of neighboring homograft tissue. There was a histologic similarity between the spontaneous skin lesions of homologous disease and those of lupus erythematosus on the one hand, and scleroderma on the other, thus supporting the possibility that the cutaneous lesions of these connective tissue diseases of man may also have an immunologic basis. It was concluded that the adult rat with homologous disease may furnish a model for human autoimmune disease.

Hyperthyroid adult rat cardiomyocytes. I. Nucleotide content, beta- and alpha-adrenoreceptors, and cAMP production

1989 ◽  
Vol 257 (5) ◽  
pp. C948-C956 ◽  
Author(s):  
C. M. Hohl ◽  
S. Wetzel ◽  
R. H. Fertel ◽  
D. K. Wimsatt ◽  
G. P. Brierley ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Adenine Nucleotide ◽  
Phosphodiesterase Inhibitor ◽  
Cardiac Cells ◽  
Beta Agonist ◽  
Camp Production ◽  
Adult Rats ◽  
Rat Cardiomyocytes ◽  
Adult Rat ◽  
Half Maximal Effective Concentration

Ventricular myocytes isolated from the hypertrophied hearts of thyrotoxic adult rats have an increase in mean protein content per myocyte (6.3 +/- 0.2 vs. 4.4 +/- 0.2 ng) compared with euthyroid cells. Viability and adenine nucleotide profiles are similar in both populations, but NAD content of the hyperthyroid myocytes is depressed (4.9 +/- 0.2 vs. 5.5 +/- 0.2 nmol/mg for controls) and UTP is higher (1.2 +/- 0.09 vs. 0.9 +/- 0.04 nmol/mg). Binding of (-)-[125I]iodocyanopindolol to intact hyperthyroid myocytes is increased by 42% compared with controls, with no change in the dissociation constant (Kd). This elevation in beta-receptor number is correlated to enhanced beta-agonist-induced adenosine 3',5'-cyclic monophosphate (cAMP) production. The half-maximal effective concentration (EC50) for the euthyroid isoproterenol dose-response curve is 2.14 x 10(-7) M but is decreased to 2.51 x 10(-8) M in hyperthyroid cardiac cells. Basal adenylate cyclase activity is apparently not affected by thyroid hormones, since basal cAMP levels for both groups are identical (5 pmol/mg) and both rise roughly twofold in the presence of a phosphodiesterase inhibitor. Forskolin-induced cAMP production and cAMP-specific phosphodiesterase activity are similar as well. In contrast to beta-adrenergic response, there are no significant differences in alpha 1-antagonist [3H]prazosin binding parameters between hyperthyroid and euthyroid cardiomyocytes.

scholarly journals A Kollár and Pluzsik anisotropic composite beam theory for arbitrary multicelled cross sections

2016 ◽  
Vol 35 (23) ◽  
pp. 1696-1711 ◽  
Author(s):  
Danilo S Victorazzo ◽  
Andre De Jesus
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Composite Beam ◽  
Linear Equations ◽  
Beam Theory ◽  
Element Formulation ◽  
Compliance Matrix ◽  
Asymmetric System ◽  
Anisotropic Composite ◽  
Stiffness Matrices

In this paper we extend Kollár and Pluzsik’s thin-walled anisotropic composite beam theory to include multiple cells with open branches and booms, and present a finite element formulation utilizing the stiffness matrix obtained from this theory. To recover the 4 × 4 compliance matrix of a beam containing N closed cells, we solve an asymmetric system of 2N + 4 linear equations four times with unitary section loads and extract influence coefficients from the calculated strains. Finally, we compare 4 × 4 stiffness matrices of a multicelled beam using this method against matrices obtained using the finite element method to demonstrate accuracy. Similarly to its originating theory, the effects of shear deformation and restrained warping are assumed negligible.

scholarly journals Competition of glycerol with other oxidizable substrates in rat brain

1986 ◽  
Vol 237 (1) ◽  
pp. 47-51 ◽  
Author(s):  
M C McKenna ◽  
L I Bezold ◽  
S J Kimatian ◽  
J T Tildon
Keyword(s):  
Rat Brain ◽  
Glutamine Metabolism ◽  
Glycerol Oxidation ◽  
Adult Rats ◽  
Adult Rat ◽  
Rat Pups ◽  
Age Related ◽  
Adult Rat Brain ◽  
14Co2 Production ◽  
Age Related Changes

The rate of conversion of [1,3-14C]glycerol into 14CO2 was measured in the presence and absence of unlabelled alternative substrates in whole homogenates from the brains of young (4-6 and 18-20 days old) and adult rats. Unlabelled glucose decreased 14CO2 production from [1,3-14C]glycerol by about 40% at all ages studied. Unlabelled 3-hydroxybutyrate significantly decreased the 14CO2 production from both low (0.2 mM) and high (2.0 mM) concentrations of glycerol in 4-6- and 18-20-day-old rat pups. However, the addition of 3-hydroxybutyrate had no effect on the rate of 14CO2 production from 2.0 mM-glycerol in adult rats, suggesting that the interaction of 3-hydroxybutyrate with glycerol in adult rat brain is complex and may be related to the biphasic kinetics previously reported for glycerol oxidation. Unlabelled glutamine decreased the production of 14CO2 by brain homogenates from 18-20-day-old and adult rats, but not in 4-6-day-old rat pups. In the converse situation, the addition of unlabelled glycerol to whole brain homogenates had little effect on the rate of 14CO2 production from [6-14C]glucose, 3-hydroxy[3-14C]butyrate and [U-14C]glutamine, although some significant differences were noted. Collectively these results suggest that glycerol and these other substrates may be metabolized in separate subcellular compartments in brain such that the products of glucose, 3-hydroxybutyrate and glutamine metabolism can dilute the oxidation of glycerol, but the converse cannot occur. The data also demonstrate that there are complex age-related changes in the interaction of glycerol with 3-hydroxybutyrate and glutamine. The fact that glycerol oxidation was only partially suppressed by the addition of 1-5 mM-glucose, -3-hydroxybutyrate or -glutamine could also suggest that glycerol may be selectively utilized as an energy substrate in some discrete brain region.

Design with Nonhomogeneous Materials—Part I: Pure Bending of Prismatic Bars

1987 ◽  
Vol 109 (1) ◽  
pp. 82-86 ◽  
Author(s):  
V. K. Stokes
Keyword(s):  
Tensile Test ◽  
Material Properties ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Mechanical Design ◽  
Beam Theory ◽  
Pure Bending ◽  
Strongly Coupled ◽  
Point To Point ◽  
Nonhomogeneous Materials

Because material properties vary from point to point in nonhomogeneous materials, there is some question as to what “properties” are measured in tests such as the tensile test, and how such “properties” can be used in the mechanical design process. In this paper, the mechanical response of nonhomogeneous prismatic bars in pure bending has been shown to depend on parameters that are strongly coupled combinations of geometry and material properties. The purely geometry based inertia tensor in homogeneous beam theory is replaced in the nonhomogeneous case by the rigidity tensor, which combines geometry and material properties. Interpretations for the average elastic moduli, which would be determined by tests on nonhomogeneous materials, have been explored. Also discussed is the usefulness of such average moduli for predicting the mechanical response of nonhomogeneous bars.

Modeling the Inflation Response of C57BL/6 Mouse Sclera

2011 ◽  
Author(s):  
Kristin M. Myers ◽  
Thao D. Nguyen
Keyword(s):  
Material Properties ◽  
Soft Tissues ◽  
Ganglion Cells ◽  
The United States ◽  
Small Rodent ◽  
Tissue Samples ◽  
Tissue Microstructure ◽  
Material Parameters ◽  
Meaningful Material

Small rodent models have become increasingly useful to investigate how the mechanical properties of soft tissues may influence disease development. These animal models allow access to aged, diseased, or genetically-altered tissue samples, and through comparisons with wild-type or normal tissue it can be explored how each of these variables influence tissue function. The challenges to deriving meaningful material parameters for these small tissue samples include designing physiologically-relevant mechanical testing protocols and interpreting the experimental load-displacement data in an appropriate constitutive framework to quantify material parameters. This study was motivated by determining the possible role of scleral material properties in the development of glaucomatous damage to the retinal ganglion cells (RGC). Glaucoma is one of the leading causes of blindness in the United States and in the world with an estimate of 60 million people affected by this year [1]. Through exploring mouse models, the overall goal of our work is to determine the role of scleral material properties and scleral tissue microstructure in the pathogenesis of glaucoma.

Effects of hypophysectomy and subsequent FSH and testosterone treatment on inhibin production by adult rat testes

1985 ◽  
Vol 105 (1) ◽  
pp. 1-6 ◽  
Author(s):  
C. L. Au ◽  
D. M. Robertson ◽  
D. M. de Kretser
Keyword(s):  
Seminiferous Tubule ◽  
Hormonal Control ◽  
Human Chorionic Gonadotrophin ◽  
Experimental Conditions ◽  
Adult Rats ◽  
Adult Rat ◽  
Fluid Production ◽  
Tubule Fluid

ABSTRACT The hormonal control of inhibin production by adult rat testes was investigated using an in-vitro inhibin bioassay validated for the measurement of inhibin activity in charcoal-treated rat testicular extracts. The effect of hypophysectomy examined at 16 h, 3, 7 and 42 days after surgery showed a decrease in testicular inhibin content and seminiferous tubule fluid production by 7 days and a decrease in inhibin production by 42 days. Serum FSH and LH were suppressed 3 days after surgery. In 30-day chronically hypophysectomized adult rats treated for 3 days with twice daily s.c. injections of (a) human FSH (hFSH, 22 i.u./rat per day), (b) testosterone (5 mg/rat per day), (c) hFSH + testosterone (same doses as a and b), or (d) human chorionic gonadotrophin (hCG, 12 i.u./rat per day), hFSH or hFSH and testosterone stimulated an increase in testicular inhibin content but not in inhibin production or tubule fluid production. Testosterone and hCG had no effect on these parameters. It is concluded that in vivo, FSH alone stimulates an increase in testicular inhibin content. The failure to observe an increase in inhibin production in vivo is attributed to the suppression of seminiferous tubule fluid production under the same experimental conditions. J. Endocr. (1985) 105, 1–6

Selective Modulation of Tonic and Phasic Inhibitions in Dentate Gyrus Granule Cells

2002 ◽  
Vol 87 (5) ◽  
pp. 2624-2628 ◽  
Author(s):  
Zoltan Nusser ◽  
Istvan Mody
Keyword(s):  
Dentate Gyrus ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Hippocampal Slices ◽  
Tonic Inhibition ◽  
Adult Rats ◽  
Adult Rat ◽  
Phasic Inhibition ◽  
The Mean

In some nerve cells, activation of GABAA receptors by GABA results in phasic and tonic conductances. Transient activation of synaptic receptors generates phasic inhibition, whereas tonic inhibition originates from GABA acting on extrasynaptic receptors, like in cerebellar granule cells, where it is thought to result from the activation of extrasynaptic GABAA receptors with a specific subunit composition (α6βxδ). Here we show that in adult rat hippocampal slices, extracellular GABA levels are sufficiently high to generate a powerful tonic inhibition in δ subunit–expressing dentate gyrus granule cells. In these cells, the mean tonic current is approximately four times larger than that produced by spontaneous synaptic currents occurring at a frequency of ∼10 Hz. Antagonizing the GABA transporter GAT-1 with NO-711 (2.5 μM) selectively enhanced tonic inhibition by 330% without affecting the phasic component. In contrast, by prolonging the decay of inhibitory postsynaptic currents (IPSCs), the benzodiazepine agonist zolpidem (0.5 μM) augmented phasic inhibition by 66%, while leaving the mean tonic conductance unchanged. These results demonstrate that a tonic GABAA receptor–mediated conductance can be recorded from dentate gyrus granule cells of adult rats in in vitro slice preparations. Furthermore, we have identified distinct pharmacological tools to selectively modify tonic and phasic inhibitions, allowing future studies to investigate their specific roles in neuronal function.

scholarly journals Flexural Interpretation of Simply Supported Laminated Composite Beam

2020 ◽  
Vol 8 (5) ◽  
pp. 3559-3565
Keyword(s):  
Shear Deformation ◽  
Composite Beam ◽  
Laminated Composite ◽  
Beam Theory ◽  
Composite Beams ◽  
Shear Stresses ◽  
Bending Stress ◽  
Simply Supported ◽  
Laminated Composite Beam ◽  
Laminated Composite Beams

In this Paper, the analysis of simply supported laminated composite beam having uniformly distributed load is performed. The solutions obtained in the form of the displacements and stresses for different layered cross ply laminated composite simply supported beams subjected uniformly distributed to load. Different aspect ratio consider for different results in terms of displacement, bending stress and shear stresses. The shear stresses are calculated with the help of equilibrium equation and constitutive relationship. Using displacement field including trigonometric function of laminated composite beams are derived from virtual displacement principle. There are axial displacement, transverse displacement, bending stress and shear stresses. In addition, Euler-Bernoulli (ETB), First order shear deformation beam theory (FSDT), Higher order shear deformation beam theory (HSDT) and Hyperbolic shear deformation beam theory (HYSDT) solution have been made for comparison and better accuracy of solutions and results of static analyses of laminated composite beams for simply supported laminated composite beam.

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