scholarly journals POLARIZED LIGHT OBSERVATIONS ON STRIATED MUSCLE CONTRACTION IN A MITE

1967 ◽  
Vol 32 (1) ◽  
pp. 169-179 ◽  
Author(s):  
John F. Aronson
Keyword(s):  
Light Microscopy ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Polarized Light ◽  
Rate Of Change ◽  
Filament Length ◽  
Relative Movement ◽  
Significant Difference ◽  
Average Slope ◽  
Region Length

Contraction of individual sarcomeres within the living mite Tarsonemus sp. was observed by polarized light microscopy. In unflattened animals the usual range of contraction was such that the minimum sarcomere length approximated the length of the A region, and the maximum sarcomere length was about twice the length of the A region. The central sarcomeres of the dorsal metapodosomal muscles were observed in detail. The A band length increased slightly with increasing sarcomere length since the regression of I region length on sarcomere length had an average slope of 0.91. When the A band length in a sarcomere which was shortening was compared with the length when the same sarcomere lengthened, no significant difference was seen. The A band of each sarcomere seemed to act as a not too rigid limit to further shortening; this agreed with the reversible shortening of a muscle in which the A band had been experimentally shortened. An H region was visible at long sarcomere lengths and was not visible at short sarcomere lengths, even when the muscle was actively shortening. The rate of change of H region length with sarcomere length suggested that I filament length may increase as sarcomere length increases. Despite this effect and the small increase in A length with sarcomere length, the results are considered to be consistent with a model in which shortening occurs by the relative movement of A and I filaments, with little or no change in length of either set of filaments. Sarcomere shortening was clearly associated with an increase in the retardation of the A region.

scholarly journals Performance of Laser Fluorescence for Residual Caries Detection in Primary Teeth

2008 ◽  
Vol 02 (03) ◽  
pp. 176-184 ◽  
Author(s):  
Taskin Gurbuz ◽  
Yucel Yilmaz ◽  
Fatih Sengul
Keyword(s):  
Light Microscopy ◽  
Gold Standard ◽  
Primary Teeth ◽  
Polarized Light ◽  
Laser Fluorescence ◽  
Caries Detection ◽  
Sem Images ◽  
Significant Difference ◽  
Residual Caries ◽  
Cavity Floor

ABSTRACTObjectives: The aim of this study was to evaluate the performance of a visual-tactile examination and a laser fluorescence device for detecting residual dentinal caries after carious dentin removal with bur excavation, hand excavation and chemomechanical excavation (Carisolv™].Methods: Thirty extracted coronal caries primary second molars were used. The caries infected dentin has been removed. A blinded examiner checked all cavities for residual caries using a visualtactile examination and laser fluorescence. Then the teeth were sectioned through the prepared cavities andthe two halves of each tooth were processed for light microscopy and Scanning Electron Microscopy (SEM). The presence or absence of residual caries was verified using polarized light microscopy as the gold standard. The cavity floor dentin after removing carious dentin was examined using SEM.Results: In among all groups a significant difference is determined between visual-tactile examination and laser fluorescence (P<.05). There was an agreement between laser fluorescence or visual-tactile examination and histological gold standard (P>.05). In addition, SEM images of the surfaces with the caries removed have shown that a vast majority of the tubule openings is observed to be open in the samples of the Carisolv group in opposition to the other groups.Conclusions: The laser fluorescence system could be effective in checking the removal by other methods, such as bur or Carisolv and avoid excessive removal of the sound dentin. (Eur J Dent 2008;2:176-184)

scholarly journals ULTRASTRUCTURE OF THE RESTING AND CONTRACTED STRIATED MUSCLE FIBER AT DIFFERENT DEGREES OF STRETCH

1961 ◽  
Vol 11 (1) ◽  
pp. 95-117 ◽  
Author(s):  
F. Carlsen ◽  
G. G. Knappeis ◽  
F. Buchthal
Keyword(s):  
Isometric Contraction ◽  
Sarcomere Length ◽  
Striated Muscle ◽  
Fiber Diameter ◽  
Filament Length ◽  
Filament Diameter ◽  
Cent Increase ◽  
Passive Stretch ◽  
Tetanic Tension ◽  
Striated Muscle Fiber

Passive stretch, isometric contraction, and shortening were studied in electron micrographs of striated, non-glycerinated frog muscle fibers. The artifacts due to the different steps of preparation were evaluated by comparing sarcomere length and fiber diameter before, during, and after fixation and after sectioning. Tension and length were recorded in the resting and contracted fiber before and during fixation. The I filaments could be traced to enter the A band between the A filaments on both sides of the I band, creating a zone of overlap which decreased linearly with stretch and increased with shortening. This is consistent with a sliding filament model. The decrease in the length of the A and I filaments during isometric contraction and the finding that fibers stretched to a sarcomere length of 3.7 µ still developed 30 per cent of the maximum tetanic tension could not be explained in terms of the sliding filament model. Shortening of the sarcomeres near the myotendinous junctions which still have overlap could account for only one-sixth of this tension, indicating that even those sarcomeres stretched to such a degree that there is a gap between A and I filaments are activated during isometric contraction (increase in stiffness). Shortening, too, was associated with changes in filament length. The diameter of A filaments remained unaltered with stretch and with isometric contraction. Shortening of 50 per cent was associated with a 13 per cent increase in A filament diameter. The area occupied by the fibrils and by the interfibrillar space increased with shortening, indicating a 20 per cent reduction in the volume of the fibrils when shortening amounted to 40 per cent.

scholarly journals Erosion Potential of Tooth Whitening Regimens as Evaluated with Polarized Light Microscopy

2015 ◽  
Vol 16 (11) ◽  
pp. 921-925 ◽  
Author(s):  
So Ran Kwon ◽  
Fang Qian ◽  
Patrick Brambert
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Negative Control Group ◽  
Negative Control ◽  
Polarized Light Microscopy ◽  
Control Group ◽  
Tooth Whitening ◽  
Significant Difference ◽  
Enamel Erosion ◽  
Recommended Guidelines

ABSTRACT Aims Tooth whitening is a widely utilized esthetic treatment in dentistry. With increased access to over-the-counter (OTC) systems concerns have been raised as to potential adverse effects associated with overuse of whitening materials. Therefore, this study aimed to evaluate enamel erosion due to different whitening regimens when used in excess of recommended guidelines. Materials and methods Extracted human teeth (n = 66) were randomly divided into 11 groups (n = 6/group). Specimens were exposed to OTC products: Crest Whitestrips and 5-minute natural white and a do-it-yourself (DIY) strawberry whitening recipe. Within each regimen, groups were further divided per exposure time: specimens receiving the recommended product dosage; 5 times the recommended dosage; and 10 times the recommended dosage. Negative and positive controls were treated with grade 3 water and 1.0% citric acid, respectively. Specimens were nail-varnished to limit application to a 1 × 4 mm window. Following treatment, specimens were sectioned and erosion (drop in μm) measured using polarized light microscopy. Two-sample t-test was used to detect difference in amount of enamel erosion between negative and positive groups, while one-way analysis of variance (ANOVA), followed by post hoc Dunnett's test was used to detect difference between set of treatment groups and negative control groups or among all experimental groups. Results There was significant difference in mean amount of enamel erosion (p < 0.0001). Mean enamel erosion for positive control group was significantly greater than that for negative control group (23.50 vs 2.65 μm). There was significant effect for type of treatments on enamel erosion [F(9,50) = 25.19; p < 0.0001]. There was no significant difference between the negative control and each of treatment groups (p > 0.05 for all instances), except for Natural White_10 times treatment group (p < 0.0001) that was significantly greater than the negative control group (14.82 vs 2.65 μm). Conclusion Caution is advised when using certain over-thecounter products beyond recommended guidelines as there is potential for enamel erosion. Clinical significance Enamel erosion due to the overuse of whitening products varies for different modalities and products. Therefore, caution is advised when using certain over-thecounter products beyond recommended guidelines, as there is potential for enamel erosion. How to cite this article Brambert P, Qian F, Kwon SR. Erosion Potential of Tooth Whitening Regimens as Evaluated with Polarized Light Microscopy. J Contemp Dent Pract 2015;16(11):921-925.

scholarly journals Obesity alters the collagen organization and mechanical properties of murine cartilage

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Amber T. Collins ◽  
Guoli Hu ◽  
Hunter Newman ◽  
Michael H. Reinsvold ◽  
Monique R. Goldsmith ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Light Microscopy ◽  
High Fat Diet ◽  
Polarized Light ◽  
Polarized Light Microscopy ◽  
Indentation Modulus ◽  
Knee Cartilage ◽  
High Fat ◽  
Collagen Organization ◽  
Significant Difference

AbstractOsteoarthritis is a debilitating disease characterized by cartilage degradation and altered cartilage mechanical properties. Furthermore, it is well established that obesity is a primary risk factor for osteoarthritis. The purpose of this study was to investigate the influence of obesity on the mechanical properties of murine knee cartilage. Two-month old wild type mice were fed either a normal diet or a high fat diet for 16 weeks. Atomic force microscopy-based nanoindentation was used to quantify the effective indentation modulus of medial femoral condyle cartilage. Osteoarthritis progression was graded using the OARSI system. Additionally, collagen organization was evaluated with picrosirius red staining imaged using polarized light microscopy. Significant differences between diet groups were assessed using t tests with p < 0.05. Following 16 weeks of a high fat diet, no significant differences in OARSI scoring were detected. However, we detected a significant difference in the effective indentation modulus between diet groups. The reduction in cartilage stiffness is likely the result of disrupted collagen organization in the superficial zone, as indicated by altered birefringence on polarized light microscopy. Collectively, these results suggest obesity is associated with changes in knee cartilage mechanical properties, which may be an early indicator of disease progression.

scholarly journals A comparative analysis of the zona pellucida birefringence of fresh and frozen–thawed human embryos

Reproduction ◽  
2010 ◽  
Vol 139 (1) ◽  
pp. 121-127 ◽  
Author(s):  
Yi-Fan Gu ◽  
Chang-Fu Lu ◽  
Ge Lin ◽  
Guang-Xiu Lu
Keyword(s):  
Comparative Analysis ◽  
Light Microscopy ◽  
Embryo Transfer ◽  
Zona Pellucida ◽  
Polarized Light ◽  
Clinical Pregnancy ◽  
Human Embryos ◽  
Significant Difference ◽  
Before And After ◽  
Implantation Rates

The cryopreservation of human embryos is thought to induce alteration in the glycoprotein matrix and lead to zona change. However, this assumption has been full of controversies till now. The objective of this study was to evaluate the effect of cryopreservation on zona pellucida of human embryos. Fresh (n=106, from 40 patients) and frozen–thawed embryos (n=123, from 40 patients) were obtained from consenting patients who received conventional IVF and ICSI treatment. The birefringence of zona pellucida in human fresh and frozen–thawed embryos was imaged and quantitatively analyzed using polarized light microscopy before embryo transfer. There was no significant difference in retardance and thickness of the zona pellucida multilaminar structure between the two groups. Pregnancy and implantation rates of transferred fresh and frozen–thawed embryos were also compared. No significant difference was found in the rates of clinical pregnancy (47.5 vs 37.5%) and implantation (24.5 vs 23.2%) between the two groups. This study suggests that there is no significant change in the zona pellucida birefringence of human embryos before and after cryopreservation.

Light microscopy of ceramics

1993 ◽  
Vol 51 ◽  
pp. 908-909
Author(s):  
Walter C. McCrone
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Light Microscope ◽  
Polarized Light ◽  
Refractive Indices ◽  
Complete Coverage ◽  
The Subject ◽  
Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

Ferroelastic domains and phase transitions in organic–inorganic hybrid perovskite CH3NH3PbBr3

2021 ◽  
Author(s):  
Maryam Bari ◽  
Alexei A. Bokov ◽  
Zuo-Guang Ye
Keyword(s):  
Phase Transitions ◽  
Electric Field ◽  
Light Microscopy ◽  
Domain Structure ◽  
Polarized Light ◽  
External Stress ◽  
Polarized Light Microscopy ◽  
Inorganic Hybrid ◽  
Hybrid Perovskite ◽  
Ferroelastic Domains

Polarized light microscopy reveals twin domains and symmetry of the phases in CH3NH3PbBr3 crystal; domain structure remains unresponsive to electric field but changes under external stress, confirming ferroelasticity while ruling out ferroelectricity.

scholarly journals Exploiting the Binocular Head in Polarized Light Microscopy

1994 ◽  
Vol 2 (4) ◽  
pp. 16-16
Author(s):  
Walter C. McCrone
Keyword(s):  
Light Microscopy ◽  
Polarized Light ◽  
Polarized Light Microscopy ◽  
The Other ◽  
Monocular Viewing ◽  
Area Of Interest

Having been brought up on monocular microscopes I find the omnipresent binocular systems a luxury. To support this viewpoint I'd like to suggest some benefits you may not have considered.Because I'm used to monocular viewing I sometimes use two different oculars, say 10X and 25X, in order to scan quickly to find an area of interest and then to examine the detail with higher magnification. Occasionally I use both oculars simultaneously and “concentrate” on either image to the exclusion of the other. A better way is to set the interocular distance at the extreme setting most different from your own interocular distance. By moving your head about a centimeter either way you can use either ocular.

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