Use Of Polarized Light Microscopy Research Articles

Characterization and identification of surface crystals on smear-ripened cheese by polarized light microscopy

Surface crystallization and radial demineralization of Ca, P, and Mg occur in smear-ripened cheese. Furthermore, crystals of ikaite, struvite, calcite, and brushite have been identified in cheese smears by powder X-ray diffractometry (PXRD), and ikaite and struvite exist in smears as single crystals. Polarized light microscopy (PLM) is a simple, inexpensive, and well-established method in geology to detect and identify single crystals. However, use of PLM to identify cheese crystals has not been reported previously. The specific objectives of this research were (1) to identify crystals in cheese smears using selected PLM criteria; (2) to compare identification by PLM against PXRD; and (3) to develop and evaluate a novel treatment for smear material to improve crystal analyses by both PLM and PXRD. Duplicate wheels of 4 cheeses produced by different manufacturers were obtained from retail sources. Scrapings of surface smears were prepared and analyzed by PLM and PXRD by previously described methods. Crystals were categorized by PLM based on angle of extinction (AE), birefringence behavior under crossed polarizers and quartz filters, and size and shape (circularity) by image analysis. Crystals observed by PLM fell almost exclusively into 2 readily differentiated groups based on birefringence behavior and estimated angle of extinction. Group 1 (n = 18) were highly birefringent with AE = 88-92°, whereas group 2 (n = 28) had no birefringence with AE = 13-26°. Group 2 crystals were significantly larger and more circular than group 1 crystals. Group 1 and 2 were identified as struvite and ikaite, respectively, based on known birefringence and AE characteristics. Struvite was identified in all 4 cheeses by PLM but in only 3 cheeses by PXRD. Ikaite was identified in 3 cheeses by PLM but in only 2 cheeses by PXRD. These discrepancies occurred because the smear scrapings from 1 cheese contained excessive amorphous matter that caused extreme background noise, potentially obscuring diffractogram peaks that may have been present. To minimize noise, smear scrapings were dispersed in aqueous NaOH (pH 10) before analyses, which resulted in consistent results by PXRD and PLM. The method also rendered high-quality images by PLM. Data suggest that PLM may offer a simple and inexpensive means to identify struvite, ikaite, and possibly other single crystals in cheese smears.

Crystallization and enzymatic hydrolysis of PLA grade for orthopedics

AbstractPoly(lactic acid) (PLA) absorbable reinforcement ligaments that are used in orthopedics for the repair and reinforcement of articulation instabilities as well as PLA samples synthesized in the laboratory were studied with respect to their thermal properties, crystallization kinetics, mechanical properties, and enzymatic hydrolysis. For these purposes, thermogravimetric analysis, differential scanning calorimetry (DSC), step‐scan modulated temperature DSC, hot stage polarized light microscopy (PLM), scanning electron microscopy, tensile testing, and enzymatic hydrolysis experiments were performed on both cases of samples and findings were compared. The PLA ligament showed higher tensile properties and higher crystallization rates under both isothermal and nonisothermal conditions. Isothermal crystallization and cold crystallization kinetics were studied using various models. The effective energy barrier of nonisothermal crystallization was also evaluated using the isoconversional method of Friedman. The generated morphology in the case of isothermal crystallization was observed with the use of PLM, and the spherulite growth rates were calculated. Finally, both materials showed very slow enzymatic degradation rates, although in the case of the reinforcement ligament they were substantially higher compared to the laboratory PLA sample. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:280–299, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20194

Polarized Light Microscopy in Mammalian Oocytes

The meiotic spindle structure plays a key role in normal chromosome alignment and segregation during meiosis. Polarized light microscopy (PLM) allows non-invasive evaluation of the meiotic spindle of metaphase oocytes from different animal species. The purpose of this article is to review the use of PLM in animal reproduction, mainly in the assessment of the meiotic spindle in oocytes. A brief overview of the methods to assess the meiotic spindle is presented as well as the principles behind the PLM. The use of PLM to evaluate oocyte quality and spindle morphology is discussed and the results on the viability of the oocytes after being exposed to PLM are presented. Several researchers showed that PLM could be successfully implemented on cryopreservation, nuclear transfer and intracytoplasmic sperm injection procedures as a tool to improve the outcome of these procedures. In addition, PLM can be used to develop studies on oocyte maturation and spindle dynamics. However, the information on the practical use of this technology in farm animals is very limited and further studies are needed to assess the importance of PLM in animal reproduction.

Correlation between structural features and mechanical properties of boron nitride fibres derived from alkylaminoborazines

The microstructure and texture of a series of four boron nitride fibres prepared from three alkylaminoborazines 2,4,6-[(CH 3) 2N] 3B 3N 3H 3 ( 1), 2,4-[(CH 3) 2N] 2-6-(CH 3HN)B 3N 3H 3 ( 2) and 2-[(CH 3) 2N]-4,6-(CH 3HN) 2B 3N 3H 3 ( 3) have been studied by means of transmission electronic microscopy (TEM) and polarized light microscopy (PLM) on the basis of relevant X-ray diffraction (XRD) and Raman spectroscopy data. TEM results indicate that the general structure of the fibres consists in three concentric parts with a gradual increase in the crystallites size from the outer region to the core of the fibres. The grains appear to be randomly distributed in the fibre prepared from 1 whereas a pronounced orientation of crystallites is found in the fibres derived from 2 and 3. This local feature was extended to a larger scale by the use of PLM, which showed that the orientation of crystallites with respect to the fibre axis is improved within the fibres prepared, respectively, from 1, 2 and 3. The comparison of these results evidenced a correlation between microstructural and textural properties and the mechanical performances of the studied boron nitride fibres. Thus, this work exemplified that mechanical properties of BN fibres are closely associated with both a good crystallization state, e.g. large crystallites and a preferred mean alignment of BN crystallites following their (0 0 2) planes (i.e. planes of hexagons) in a direction parallel to the fibre axis.

Analytical technique for quantification of selected resorbable calcium phosphate bone void fillers with the use of polarized-light microscopy.

Synthetic calcium phosphate bone void fillers promote varying rates of bone formation and material resorption depending on chemistry, porosity, pore structure, and implant site. The objective of this study was to quantify the resorption of a novel ultraporous beta-tricalcium phosphate cancellous bone void filler with simultaneous quantification of bone formation in a canine humerus model. Potential measurement error involved in conventional histomorphometry using Von Kossa stains inspired the development of a new technique. This technique utilizes bright-field and polarized-light microscopy in conjunction with image analysis software, allowing more accurate histomorphometry. This technique was validated with two separate controlled experiments. Scanning electron microscopy further supported the results. The findings suggest that the use of polarized-light microscopy combined with image analysis software can be an effective tool in simultaneously quantifying calcium phosphate resorption and bone formation.

Use of polarized-light microscopy as an aid in the diagnosis of silicosis.

THE clinical diagnosis of silicosis is based on a detailed occupational history of significant exposure to silica and characteristic serial chest roentgenograms. However, there may be attendant dif...