Light microscopic and fine structural changes in the brown adipose tissue from torpid and aroused pigmy mice (Baiomys taylori)

Abstract

Changes in the composition and morphology of interscapular brown adipose tissue (BAT) are described for the adult pigmy mouse, Baiomys taylori, in its short-term, cold-torpor cycle. The study includes an analysis of tissues from, (1) room temperature (RT) controls, (2) RT, 24 hour starvation animals, ( 3 ) mice exposed on 1 5°C for six hours, (4) torpid animals (24, 48, and 72 hours at 15"C), and (5) mice allowed to arouse from torpor at RT for 1, 2, 5, 9, 24, and 288 hours. Control brown fat is composed predominately of lipid vacuoles, glycogen particles, and mitochondria with lamellaelike cristae. Starvation at RT has no marked effect on either the BAT energy stores, or the mitochondria1 morphometry. Short exposure to 15°C brings about a pronounced depletion in the lipid and glycogen content, and a significant swelling in the mitochondria. Brown fat from torpid mice is deplete of lipid and glycogen. Mitochondria remain enlarged, and have parallel, closely-packed cristae. The lipid and glycogen reappear in the early hours of arousal. The multilocular character of the control BAT is reached in five to nine hours after initiation of arousal. Throughout the arousal the mitochondria retain their cold-induced morphological a1 terations. Pinocytotic microvesicles in the capillary endothelium and in the brown adipocytes are observed in different degrees, i n all experimental groups. With the histological changes in evidence, the participation of pigmy mouse brown fat i n non-shivering thermogenesis in situations of cold exposure, and arousal from torpor, is discussed.

Brown Adipose Tissue Blood Flow and Mass in Obesity: A Contrast Ultrasound Study in Mice

“…The difference in vascularization between BAT and its neighboring tissues has been underlined in several anatomic studies. 9,37,38 Moreover, the difference in blood flow is considerably increased by sympathetic nervous system activation (in the present study by NE infusion), which augments BAT perfusion 15-fold to 20-fold (in the present study and in Foster and Frydman 15 and Foster 39 ) but does not change the white adipose tissue blood flow. 15 …”

Brown Adipose Tissue: Function and Physiological Significance

“…During deep hibernation, brown adipose tissue is inactive, as witnessed by, e.g., masked [ 3 H]GDP binding (353,454,486,587) and altered mitochondrial ultrastructure (285,360). This inactivity is probably mainly coincidental and does not require a specific regulatory mechanism.…”