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KMID : 0378019640070040088
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New Medical Journal
1964 Volume.7 No. 4 p.88 ~ p.99
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Anatomical Studies on the Brown Adipose Tissue of Rodents
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Abstract
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The macroscopic locations and regional distributions of the brown fat in rodents were mentioned in the previous report.
The amount of white fat depends upon the nutritional state, whereas the quantity, location and distribu-. tion of brown fat is relatively stable. These observations are based upon the study of histological sections of the interscapular brown fat and adjacent subcutaneous white fat of rodents.
The histological organization and histochemical reactions of brown adipose tissue in comparison with white adipose tissue are as follows:
1. Section reveals gland-like-lobulation, which is separated by a small amount of connective tissue.
2. Interlobular connective tissue consists of an abundant delicate network of collagenous fibeKs, less numerous reticulum fibers and elastic fibers. There are usually profuse capillary net-works, unlike that of white fat, and, this difference of vascularity may correlate with difference of physiological activity. The cells of brown adipose tissue are polygonal in shape and generally contain several small lipid droplets and abundant granular acidophilic cytoplasm, while in the white fat cells the cytoplasm is reduced to a thin membrane which surrounds the fat drop.
4. The nuclei are spherical and are not situated on periphery but eccentrically.
5. The glucocid was tested by Best´s Carmine stain, Bauer reaction and PAS reaction. A trace of glycogen was found occasionally in a few scattered cells of brown fat, while normal white adipose tissue was devoid of demonstrable: glycogen. No difference in quality of stainable glycogen was seen in either adipose tissue.
6. Each lobule shows two kinds of fat cells. Typical multillocular cells occupy the central portion of the lobule and unilocular cells are scattered in the periphery.
7. Two kinds of fat tissue were stained and compared, with the following methods(the differences were the most pronounced, as could be expected, during the histochemical studies):
a) Sudan III stain: The brown fat took an orange to orange-yellow color, and the white fat became deep red. These reactions suggest that white fat contains large amounts of neutral fat, but brown fat consists mostly of other lipids, such as cholesterol.
b) Schultz reaction: The brown fat cells stained light brown-green, and appeared to contain a trace of cholesterol, but, little or negative reactions were noted in white fat.
c) Nile blue sulfate reaction: The brown fat showed light blue to violet, and the white fat pink to violet on frozen section; suggesting that brown fat contains less neutral fat.
d) Osmic acid stain Erozen sections were exposed by osmic acid. The lipid droplets in the brown fat were gradully colored grey, while the adjacent white fat became black immediately. However, in secondary blackening, the lipid droplets in the brown fat were more grey-black.
e) Plasmal reaction: The plasmal reaction w,as studied in unfixed adiposd tissue. Brown fat presented a light pink color uniform throughout the lobule. White fat was more faintly stained than brown fat. This difference of coloration could be caused by the difference., in quantity of cytoplasmic tissue. F
f) Baker´s acid hematein, stain: The cytoplasm of the brown fat cells stained a deep blue: the lipid droplets were light blue, while the white fat stained light blue or colorless. After extraction with pyridine, it revealed no cytoplasmic staining. It was concluded that brown fat is. unusually rich in phospholipid.
8. Decisive differences were not observed when both adipose tissues were compared with Xanthoprotein reaction for protein.
9. Kurnidk´s method for nucleic acids was applied to two kinds of fat tissues. Nuclei of brown adipose tissue cells stained deep green, indicating that they contained large amounts of DNA, whereas,, cytoplasm remained colorless and seemed to lack of RNA.
10. Alkaline enzymatic activities were investigated, alkaline phosphatase appeared to be abundant in brown fat which shows blackbrown coloration, but the white fat remained colorless.
Summary
Brown fat, when compared with white, has marked gland like organization. Histochemicall
y, qualitative differences between brown and white fat were noted when studied for glucocid, lipid and protein. But
decisive qualitative differences were seen in alkaline phosphatase, phospholipid and neutral fat. Brown fat seems to contain less neutral fat, more glycogen, cholesterol, alkaline phosphatase and phospholipid.
41r, It seems reasonable to conclude that brown fat is functionally more active than white fat. However,., these findings failed to support earlier suggestions, that the brown fat is an endocrine gland, or, is an organ of hibernation.
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