Ascorbic acid in the normal and regenerating tail of the house lizard, Hemidactylus flaviviridis

Development ◽  
1971 ◽  
Vol 26 (2) ◽  
pp. 285-293
Author(s):  
R. V. Shah ◽  
P. K. Hiradhar ◽  
D. K. Magon
Keyword(s):  
Wound Healing ◽  
Ascorbic Acid ◽  
Matrix Material ◽  
Growth Period ◽  
Tail Regeneration ◽  
The Matrix ◽  
Metabolic Activities ◽  
Vitamin Level ◽  
Hemidactylus Flaviviridis

The concentration of ascorbic acid (AA) and the histochemical distribution of the vitamin in the normal and regenerating tail of the gekkonid lizard, Hemidactylus flaviviridis, have been investigated. In the regenerating tail of the lizard the AA concentration almost doubles during wound healing and becomes fivefold during differentiation. However, it falls almost to the normal level during the blastema phase (i.e. period between wound healing and differentiation). Again, during the growth period (i.e. after differentiation) the AA concentration gradually becomes reduced, reaching the normal mark as the regenerate regains the full length of the original tail. Nevertheless, the vitamin level does not fall below the normal mark at any stage of regeneration. Increase of ascorbic acid during wound healing is thought to be mainly due to increased demand for the vitamin at the broken ends of the stump tissues, for their repair and formation of wound epithelium; the vitamin is known to help these processes. A fivefold increase of the vitamin during the differentiation period corresponds to an increased pace of laying down of the matrix material for the connective tissues, suggesting the role of ascorbic acid in the formation of collagen and mucopolysaccharides. Besides, the role of ascorbic acid in lipid and carbohydrate metabolism is also important during tail regeneration. Fluctuations in the vitamin level during different phases of tail regeneration are correlated with various states of metabolic activities of the corresponding phases.

scholarly journals Физико-химические процессы, сопровождающие локализацию пластической деформации при импульсном нагружении

2021 ◽  
Vol 91 (3) ◽  
pp. 450
Author(s):  
С.Н. Буравова ◽  
И.С. Гордополова ◽  
Е.В. Петров
Keyword(s):  
Mass Transfer ◽  
Phase Composition ◽  
Damage Zone ◽  
Matrix Material ◽  
Cold Deformation ◽  
Decisive Role ◽  
Wave Mode ◽  
Spall Damage ◽  
The Matrix

Investigation of the strains development under pulsed loading showed the decisive role of powerful ultrasonic sample vibrations in the standing wave mode. The effect of mass transfer of atoms and ultrafine hardening phase particles from the matrix material to the spall damage zone on the strain bands microstructure is determined. Rapid cooling of the metal inside the localization bands, the size of which does not exceed several tens of microns, indicates that changes in the phase composition occur as a result of cold deformation. Rapid the metal cooling inside the localization bands, the size of which does not exceed several tens of microns, indicates that changes in the phase composition occur as a result of cold deformation.

scholarly journals Parachlorophenylalanine retards tail regeneration in the gekkonid lizard Hemidactylus flaviviridis exposed to continuous light

1989 ◽  
Vol 143 (1) ◽  
pp. 235-243
Author(s):  
A. V. Ramachandran ◽  
P. I. Ndukuba
Keyword(s):  
Continuous Light ◽  
Control Group ◽  
High Dose ◽  
Daily Growth ◽  
Tail Regeneration ◽  
Total Percentage ◽  
Hemidactylus Flaviviridis ◽  
Caudal Autotomy ◽  
Dose Dependent

Parachlorophenylalanine (p-CPA) was used for chemical pinealectomy in a study of tail regeneration in the gekkonid lizard, Hemidactylus flaviviridis. Two doses of p-CPA (200 or 400 micrograms kg-1 body mass) were injected into two groups of lizards (5 days prior to and 30 days after caudal autotomy) exposed to continuous light of 2500 lx intensity during the summer season (March-May). Our observations show that the initiation of regeneration, the daily growth rate, the total length of new growth (regenerate) produced, and the total percentage replacement of the lost (autotomized) tails 30 days after autotomy were all significantly less with 400 micrograms kg-1 and insignificantly less with 200 micrograms kg-1 of p-CPA than in the control group of animals. The results may indicate that the effect of the drug p-CPA, an agent employed for chemical pinealectomy, on tail regeneration in H. flaviviridis is dose-dependent and that p-CPA at the high dose of 400 micrograms kg-1 has a similar retardation effect to that of complete pineal ablation. The role of the pineal in photoperiodic photoreception, and the effect of p-CPA on serotonin-melatonin biosynthesis and the consequent effects on tail regeneration, are discussed.

Computational micromechanical modelling of the material removal process in a carbon fibre composite under single-erodent particle impact

2020 ◽  
Vol 234 (10) ◽  
pp. 1605-1617
Author(s):  
Ajaz A Deliwala ◽  
Chandra S Yerramalli
Keyword(s):  
Carbon Fibre ◽  
Volume Fraction ◽  
Matrix Material ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Erosion Behaviour ◽  
The Matrix ◽  
Material Erosion ◽  
Erodent Particle

A multiscale model is developed to understand the material removal process in a unidirectional carbon fibre epoxy composite impacted by a single-erodent particle. The embedded cell approach is used to model the carbon fibre and epoxy at a microscale. The micromodel is embedded centrally in the macroscale lamina of the composite plate. The carbon fibre is considered to be elastic with orthotropic strain limits as the failure criteria. The epoxy matrix is modelled as an elastic--plastic material with multilinear isotropic hardening. The maximum equivalent plastic strain limit is used as the matrix material failure limit. Using this embedded micromechanics model, the role of matrix and the fibre in developing the composite material erosion behaviour has been clearly elucidated. The results from the simulation indicate the change in the matrix erosion behaviour as a function of the fibre volume fraction. For the current thermoset matrix, material erosion response changes from brittle behaviour to ductile behaviour with an increase in fibre volume fraction. The current study has been able to highlight the individual role of matrix and the fibre in developing the semi-ductile erosion response peculiar to a fibre-reinforced composite material.

Modeling Strain Localization Using a Plane Stress Two-Particle Model and the Influence of Grain Level Matrix Inhomogeneity

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Xiaohua Hu ◽  
David S. Wilkinson ◽  
Mukesh Jain ◽  
Raja K. Mishra
Keyword(s):  
Plane Stress ◽  
Strain Localization ◽  
Matrix Material ◽  
Interparticle Spacing ◽  
Particle Model ◽  
Element Analysis ◽  
Hard Particles ◽  
The Matrix ◽  
Particle Alignment

The role of dilute small particles on the development of strain localization under uniaxial tension has been studied by finite element analysis using a plane stress model with two small hard particles embedded in Al matrix. The influence of particle alignment and interparticle spacing in a homogeneous and inhomogeneous matrix are investigated. When the matrix material is a homogeneous continuum, there are small localization strains when close packed and aligned along the loading direction. In the case of an inhomogeneous matrix with grains of different strengths represented by their Taylor factors, the location of localization band is insensitive to the interparticle spacing, but mainly determined by grain-level inhomogeneity. This is because the particles are dilute and small compared with the matrix grains. The particles, however, can decrease the localization strains when they straddle the localization band.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

Application of cross correlation to HREM images of surfaces

1987 ◽  
Vol 45 ◽  
pp. 754-755
Author(s):  
D. E. Luzzi ◽  
L. D. Marks ◽  
M. I. Buckett
Keyword(s):  
Cross Correlation ◽  
A Priori ◽  
Matrix Material ◽  
Correlation Method ◽  
Accurate Knowledge ◽  
Complex Image ◽  
Fourier Filtering ◽  
The Matrix ◽  
Low Pass ◽  
Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

Extracellular matrix: the gatekeeper of tumor angiogenesis

2019 ◽  
Vol 47 (5) ◽  
pp. 1543-1555 ◽  
Author(s):  
Maurizio Mongiat ◽  
Simone Buraschi ◽  
Eva Andreuzzi ◽  
Thomas Neill ◽  
Renato V. Iozzo
Keyword(s):  
Extracellular Matrix ◽  
Tumor Angiogenesis ◽  
Signaling Cascades ◽  
Cancer Growth ◽  
Cell Behavior ◽  
Metastatic Progression ◽  
Surface Receptors ◽  
The Matrix ◽  
Multiple Signaling

Abstract The extracellular matrix is a network of secreted macromolecules that provides a harmonious meshwork for the growth and homeostatic development of organisms. It conveys multiple signaling cascades affecting specific surface receptors that impact cell behavior. During cancer growth, this bioactive meshwork is remodeled and enriched in newly formed blood vessels, which provide nutrients and oxygen to the growing tumor cells. Remodeling of the tumor microenvironment leads to the formation of bioactive fragments that may have a distinct function from their parent molecules, and the balance among these factors directly influence cell viability and metastatic progression. Indeed, the matrix acts as a gatekeeper by regulating the access of cancer cells to nutrients. Here, we will critically evaluate the role of selected matrix constituents in regulating tumor angiogenesis and provide up-to-date information concerning their primary mechanisms of action.

Experience of negative pressure wound therapy over sternal wound healing: A retrospective review

WCET Journal ◽  
2019 ◽  
Vol 39 (2) ◽  
pp. 9-18
Author(s):  
Wai Sze Ho ◽  
Wai Kuen Lee ◽  
Ka Kay Chan ◽  
Choi Ching Fong
Keyword(s):  
Wound Healing ◽  
Negative Pressure ◽  
Negative Pressure Wound Therapy ◽  
Assessment Tool ◽  
Wound Care ◽  
Wound Therapy ◽  
Treatment Pathways ◽  
Wound Assessment ◽  
One Year

Objectives The aim of this study was to retrospectively review the effectiveness of negative pressure wound therapy (NPWT) in sternal wound healing with the use of the validated Bates-Jensen Wound Assessment Tool (BWAT), and explore the role of NPWT over sternal wounds and future treatment pathways. Methods Data was gathered from patients' medical records and the institution's database clinical management system. Seventeen subjects, who had undergone cardiothoracic surgeries and subsequently consulted the wound care team in one year were reviewed. Fourteen of them were included in the analysis. Healing improvement of each sternal wound under continuous NPWT and continuous conventional dressings was studied. In total, 23 continuous NPWT and 13 conventional dressing episodes were analysed with the BWAT. Results Among conventional dressing episodes, sternal wound improvement was 2.5–3% over 10 days to 3.5 weeks, whereas 4–5% sternal healing was achieved in 5 days to 2 weeks with sternal wire presence. Better healing at 11% in 1 week by conventional dressing was attained after sternal wire removal. In NPWT episodes, 8–29%, 13–24%, and 15–46% of healing was observed in 2 weeks, 3.5 to 5 weeks and 6 to 7 weeks, respectively. Only 39% wound healing was acquired at the 13th week of NPWT in one subject. With sternal wire present, 6%–29% wound healing progress was achieved by NPWT in 1–4 weeks, and 16–23% wound improvement in 2 to 4.5 weeks by NWPT after further surgical debridement. After sternal wire removal, 6–34% sternal wound healing occurred by continuous NPWT for 1–2 weeks, and maximum healing at 46% after 2.5 weeks of NPWT were observed. Conclusions Better wound healing was achieved in the NPWT group in comparison to conventional dressings alone. However, suboptimal sternal wound healing by NPWT alone was observed. Removal of sternal wire may improve the effectiveness of NPWT. Successful tertiary closure after NPWT among subjects supports the important bridging role of NPWT in sternal wound healing. Factors causing stagnant sternal wound healing by NPWT alone are discussed.

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