74 research outputs found
Improved methods for detection of β-galactosidase (lacZ) activity in hard tissue
The ß-galactosidase gene (lacZ) of Escherichia coli is widely used as a reporter gene. The expression of lacZ can be detected by enzyme-based histochemical staining using chromogenic substrates such as 5-bromo-4-chloro-3-indolyl-ß-D: -galactoside (X-gal). Because the enzymatic activity of lacZ is vulnerable to high temperatures and acid treatment for demineralization, detection of lacZ on paraffinized sections is difficult, especially for hard tissues, which require demineralization before sectioning in paraffin. To circumvent this problem, whole-mount X-gal staining before sectioning is performed. However, detection of lacZ activity in the center of larger portions of hard whole adult tissues is challenging. In this study, focusing on fixation procedures, we determined the conditions conducive to improved detection of lacZ activity in deeper areas of whole tissues. We used an annexin a5 (Anxa5)-lacZ reporter mouse model in which the Anxa5 expression in hard tissue is indicated by lacZ activity. We found that lacZ activity could be detected throughout the periodontal ligament of adult mice when fixed in 100% acetone, whereas it was not detected in the periodontal ligament around the root apex fixed in glutaraldehyde and paraformaldehyde. This staining could not be detected in wild-type mice. Acetone maintains the lacZ activity within 48 h of fixation at both 4°C and at room temperature. In conclusion, acetone is the optimal fixative to improve permeability for staining of lacZ activity in large volumes of adult hard tissues
Natural and synthetic biodegradable polymers: different scaffolds for cell expansion and tissue formation
The formation of tissue produced by implanted cells is influenced greatly by the scaffold onto which
they are seeded. In the long term it is often preferable to use a biodegradable material scaffold so
that all the implanted materials will disappear, leaving behind only the generated tissue. Research in
this area has identified several natural biodegradable materials. Among them, hydrogels are receiv-ing increasing attention due to their ability to retain a great quantity of water, their good biocom-patibility, their low interfacial tension, and the minimal mechanical and frictional irritation that they
cause. Biocompatibility is not an intrinsic property of materials; rather it depends on the biological
environment and the tolerability that exists with respect to specific polymer-tissue interactions. The
most often utilized biodegradable synthetic polymers for 3D scaffolds in tissue engineering are satu-rated poly-a-hydroxy esters, including poly(lactic acid) (PLA) and poly(glycolic acid) (PGA), as well
as poly(lactic-co-lycolide) (PLGA) copolymers. Hard materials provide compressive and torsional
strength; hydrogels and other soft composites more effectively promote cell expansion and tissue
formation. This review focuses on the future potential for understanding the characteristics of the
biomaterials considered evaluated for clinical use in order to repair or to replace a sizable defect by
only harvesting a small tissue sample
Fine structure of the fungiform papilla in a ranid frog (rana esculenta).
The freetop of the fungiform papilla shows a sensorial area about 100 micron in diameter, surrounded by a ring of ciliated cells. Externally to the ciliated cells, i.e., in the lateral wall, numerous large goblet cells can be seen devoid of their mucous content. The sensorial area is composed by three types of cells: mucous, supporting, and neuroepithelial cells. Mucous cells form the most superficial layer, while the cell bodies of the other two are deep, and from them basal and apical processes arise. The above mentioned cells are connected by desmosomes preferentially located between the mucous and the supporting cells, rather than between the supporting and the neuroepithelial cells. The lateral wall of the papilla is made up of a multilayered epithelium that comprises two types of cells: the first type contains electron-dense granules and an abundant rough endoplasmic reticulum, the others are ciliated cells. In the connective axis of the papilla, numerous fenestrated capillaries with endothelial vesiculated cells and nerve fibers are found
Morphology of epiphyseal apparatus of a ranid frog (Rana Esculenta)
Morphological, histochemical and
ultrastructural investigations on epiphyseal apparatus
of Rana Esculenta were made. The most important
findings were the following: 1) metaphyseal cartilage is
localized inside proximal diaphyseal compact bone as
a plug; 2) metaphyseal cartilage do not reduce in
thickness during ageing; 3) metaphyseal cartilage do
not show vascular invasion and do not mineralize in
degenerative zone; 4) trabecular bone was not at al1
evident in this animal; 5) externa1 periosteum is well
vascularized and proliferates in correspondence to
marginal epiphyseal end of the diaphyseal.
From these results the hypothesis that the ranid
frog bone growth is not due to metaphyseal
metabolism (as in avian and mammals) but to bone
periosteal marginal mineralization is reached
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