Reticular fiber

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Reticular fibers or reticulin is a histochemical term used to describe a type of structural fibers in some connective tissues which is formed fine meshwork(reticulim) of glycosylated collagen III and other components which show up in certain histochemical meothods. The term reticulin was coined in the article Siegfried, M. Habilitationaachrift. Leipzig: F.A. Brockhaus (1892) according to a 1953 Science article by Glegg et al^[1]. During pre-molecular biological era, for a long time there were confusion in the use of the term 'reticulin' to describe the argyrophilic (silver stained) fibrous structures present as basement membrane in the parenchymatous organs and also to describe fibres which are histologically similar but are present in developing connective tissue^[2].

1 Locations
2 Structure
3 History of Silver staining method for reticular fibers
4 External links
5 References

[edit] Locations

Networks of these fibers make up stroma of lymphatic and hemopoietic tissues such as the thymus, lymph nodes, spleen, bone marrow and adipose tissue, and also parenchyma of liver, testis and lung.

[edit] Structure

Reticular fiber one or more types of very thin and delicately woven strands of type III collagen, these strands build a highly ordered cellular network and provide a supporting network. Many of these types of collagen have been combined with carbohydrate. Thus, they react with silver stains and with periodic acid-Schiff reagent but are not demonstrated with ordinary histological stains such as those using hematoxylin. The 1953 science article mentioned above concluded that the reticular and regular collagenous materials contained the same four sugars - galactose, glucose, mannose and fucose - but in a much greater concentration in the reticular than the collagenous material.

In a 1993 paper ^[3] the reticular fibers of the capillary sheath and splenic cord were studied and compared in the pig spleen by transmission electron microscopy. This paper attempted to reveal their components and the presence of sialic acid in the amorphous ground substance. Collagen fibrils, elastic fibers, microfibrils, nerve fibers and smooth muscle cells were observed in the reticular fibers of the splenic cord. On the other hand, only microfibrils were recognized in the reticular fibers of the capillary sheath. The binding of LFA lectin to the splenic cord was stronger than the capillary sheath. These findings suggested that the reticular fibers of the splenic cord included multiple functional elements and might perform an important role during contraction or dilation of the spleen. On the other hand, the reticular fiber of the capillary sheath resembled the basement membrane of the capillary in its components.

[edit] History of Silver staining method for reticular fibers

The history of the "reticulin(silver) stain is reviewed in a 1978 Histochemistry paper ^[4] whose abstract says:

Maresch (1905) introduced Bielschowsky's silver impregnation technic for neurofibrils as a stain for reticulum fibers, but emphasized the nonspecificity of such procedures. This lack of specificity has been confirmed repeatedly. Yet, since the 1920's the definition of "reticulin" and studies of its distribution were based solely on silver impregnation technics. The chemical mechanism and specificity of this group of stains is obscure. Application of Gomori's and Wilder's methods to human tissues showed variations of staining patterns with the fixatives and technics employed. Besides reticulum fibers, various other tissue structures, e.g. I bands of striated muscle, fibers in nervous tissues, and model substances, e.g. polysaccharides, egg white, gliadin, were also stained. Deposition of silver compounds on reticulum fibers was limited to an easily removable substance; the remaining collagen component did not bind silver. These histochemical studies indicate that silver impregnation technics for reticulum fibers have no chemical significance and cannot be considered as histochemical technics for "reticulin" or type III collagen.

[edit] External links

[edit] References

^ Glegg, RE, Edinger D, Leblond CP, Some carbohydrate components of Reticular Fibers. Science, New series, vol 118, No 3073 (Nov 20, 1953), pp. 614-616 http://www.jstor.org/view/00368075/ap993073/99a00040/0
^ JACKSON, D.S. and G. WILLIAMS, Nature of reticulin, 178(4539), 915, 1956. http://www.nature.com/nature/journal/v178/n4539/abs/178915b0.html
^ Miyata, H., M. Abe, K. Takehana, K. Iwasa and T. Hiraga, Electron microscopic studies on reticular fibers in the pig sheathed artery and splenic cords, J Vet Med Sci, 55(5), 821, 1993.
^ Puchtler, H. and F.W. Waldrop, Silver impregnation methods for reticulum fibers and reticulin: A re-investigation of their origins and specificity, Histochemistry, 57(3), 177, 1978.