Hepatic glycogen patterns are described for rats adapted to a precisely controlled feeding schedule and ad libitum fed rats. Liver samples were processed for biochemical and histochemical glycogen analysis at precise intervals following a 22 hour fast and a 2 hour meal. Histochemical determination of glycogen (PAS) after freeze substitution showed lobular patterns of hepatic glycogen which correlate with chemically determined glycogen levels and nutritional states of the rats. After 22 hour fasting, hepatocytes from rats with low glycogen levels (< 0.09% ) exhibited no significant staining. In control fed rats, feeding caused glycogen deposition throughout the lobule but in greatest concentration centrilobularly throughout the early phases of glycogen accumulation. As glycogen deposition continued, periportal lobular patterns were observed in rats with high glycogen levels (> 5% ). Glycogen depletion reduced glycogen staining in cells throughout the lobule, but centrilobular patterns prevailed until late in depletion when periportal patterns appeared. Ad libitum-fed rats showed similar glycogen patterns except maximum deposition was characterized by centrilobular or even lobular distribution of glycogen, and periportal patterns of glycogen were seen only rarely in extreme fasted rats. Differences in lobular patterns between ad libitum and control fed rats is apparently related to lower maximum hepatic glycogen levels reached by ad libitum-fed animals.The mammalian liver is important in regulating blood glucose by storing and breaking down hepatic glycogen after appropriate stimulation. Many biochemical details of glycogenolysis and glycogenesis have been reported and much work has been directed toward elucidating the control mechanisms of these processes. (Scrutton and Utter, '68; Robison et al., '68; Villar-Palasi and Larner, '70; Ryman and Whelan, '71). A problem of considerable importance for studies of glycogen metabolism at the cellular level is an accurate description of glycogen patterns in the liver during deposition and depletion of the carbohydrate.In general, investigators have agreed that hepatic intralobular differences in glycogen distribution exist during a cycle of feeding and fasting, but the precise pattern was unclear. Bock and Hoffman (1872) reported that liver glycogen in rabbits was deposited initially around the central vein and only later in more peripheral regions. This finding was confirmed in studies of livers from a variety of species AM. J. ANAT., 140: 299-338.by several workers (Noel, '23; Kater, '33; Forsgren, '35; Eger and Ottensmeir, '52; Themann, '63; Corrin and Aterman, '68). In contrast to this, others claimed that glycogen deposition proceeded from the periphery of the lobule to more centrally situated hepatocytes (Smith, '31; Kater, '33; Edlund and Holmgren, '40; Deane, '44; Ekman and Holmgren, '49).Literature on glycogen patterns during depletion also presents conflicting results. Noel ('23) reported that hepatic glycogen patterns during glycogenolysis were the reve...

The fine structure of hepatocytes from rats maintained on a controlled feeding schedule are described. Liver samples were processed for electron microscopy, histochemistry and chemical determinations of glycogen at precise time-intervals following a 30-hour fast and a 2-hour meal. Hepatocytes from 30-hour-fasted rats with extremely low hepatic glycogen levels were devoid of glycogen particles. Centrilobular cells showed areas of the cytoplasm rich in vesicles of smooth endoplasmic reticulum (SER) while periportal hepatocytes contained less extensive regions of SER. Soon after feeding the fasted rats, glycogen particles appeared in regions of the cell rich in SER. Centrilobular hepatocytes contained numerous glycogen areas which were infiltrated with tubules of SER, while periportal cells showed dense glycogen deposits with SER restricted to the periphery of the masses of glycogen. Throughout glycogen deposition each glycogen particle was closely associated with membranes of SER until maximum glycogen deposition was achieved 12 hours after initiation of feeding. At this point SER was reduced to the lowest amounts of the time-periods studied. During stages of glycogen depletion SER proliferated and reached the highest concentration measured in this study. Tubules of SER were present throughout the glycogen masses of centrilobular hepatocytes, whereas in periportal cells the organelle was restricted to the periphery of the glycogen masses. It is concluded that SER is associated with glycogen particles in rat hepatocytes during both deposition and depletion of glycogen.

Male rats were maintained on a controlled feeding schedule and groups of animals sacrificed at 2, 15, 21, 36, 48 and 72 hours of fasting. Chemical determinations of glycogen showed that livers of rats fasted two hours contained 8.7% glycogen; 15 hours, 6.2%; 21 hours, 0.7%; 36 hours, 0.7%; 48 hours, 0.8% ; and 72 hours, 0.4%. After PA/S procedures, glycogen appeared in hepatocytes of rats fasted 2 and 15 hours as large masses intensely stained. At these time-periods, almost all cells contained significant quantities of glycogen but hepatocytes located toward portal tracts showed larger and more intensely stained masses of glycogen than found in cells near central veins. After longer periods of fasting, glycogen masses decreased in size, number, and staining intensity. The fine structure of hepatocytes from rats fasted 2 or 15 hours showed abundant a and P particles of glycogen in the form of large masses throughout the cytosome. These correlated in position and shape to the masses of glycogen seen in the light microscope. As glycogen depletion occurred (fasted 21 hours and longer) the number of glycogen particles decreased in hepatocytes. It is concluded from this study that a good correlation exists between chemical determinations of hepatic glycogen, cytochemistry of glycogen in hepatocytes, fine structure of liver cells, and the fasting state of the animal.The mammalian liver contributes to maintenance of appropriate blood-glucose levels by forming and storing glycogen when blood-glucose is high and degrading glycogen to release glucose when bloodglucose levels decline. Numerous studies, both biochemical (Dallner et al., '66a,b; Robison et al., '68 Lacking in these studies, however, were biochemical determinations of hepatic glycogen at time-intervals of fasting.In the present study rats were maintained on a controlled feeding schedule and groups of animals sacrificed at 2, 15, 21, 36, 48 and 72 hours of fasting. The glycogen content of the livers was determined biochemically, cytochemical methods employed for demonstration of glycogen, and the ultrastructure of hepatocytes for each specimen studied. In this paper we relate these findings to the physiological state of the liver. MATERIALS AND METHODSFifty-two male (100 gm) rats (SpragueDawley strain) were trained to the feeding schedule for five days. Three animals per cage were maintained under a controlled light (12 hours) -dark (12 hours) cycle at 24°C. Water was available at all times. At 4 : 00 PM the animals were transferred to a cage containing food (Purina Rat Chow; 56.4% carbohydrate, 23% protein, 4.3% fat, 16.3% other) and allowed to eat for three hours (until 7 : O O PM).

The course of development of the lateral oviducts ofDrosophila virilis was investigated in normal unoperated animals and subsequent to unilateral and bilateral larval ovariectomy. The development of the epithelial component of the oviducts can be divided into three phases, each characterized by different processes of growth. During the first two days following puparium formation, growth of the oviducts occurs through morphogenesis and mitotic activity. As the cell number increases, all the primordia characteristic of the imaginal reproductive system become recognizable. Early in this phase, a bifurcation of the oviducal rudiment becomes evident, thereby indicating distinct development of the lateral oviduct pair. With the cessation of cellular divisions by about 54 hours after puparium formation, a second phase of growth occurs through alterations in the arrangement of the cells and in their morphology. The third phase begins toward the end of pupal life. It is characterized by cellular enlargement and cytodifferentiation. These processes are not completed at the time of eclosion of the adult females and continue to occur during the first few days of imaginal life. Details of the histogenesis of oviducal epithelium and muscle are described. The course of development of free lateral oviducts obtained after either unilateral or bilateral ovariectomy was found to be indistinguishable from that of normal oviducts up to and even beyond the stage at which ovarian attachment normally occurs. In the latter part of pupal life, a collapsed configuration that may be the result of mechanical factors is observed in the free lateral oviduct. Differentiation of the epithelium and of oviducal muscle, however, proceed normally in such structures, at least until the time of eclosion. No evidence can be offered to support the previously reported view that outgrowth of lateral oviducts is dependent upon an induction by the ovaries.

The lateral oviducts ofDrosophila virilis were investigated in normal unoperated adult females, after unilateral and bilateral ovariectomy, and following the transplantation of genital discs. Subsequent to unilateral ovariectomy at larval stages of development, mature adult females exhibited reproductive systems with a free lateral oviduct which appeared somewhat shorter and less distended than a lateral oviduct normally attached to an ovary. Histological examination revealed that such free lateral oviducts have undergone considerable growth and differentiation in the absence of direct ovarian attachment, but exhibited a smaller lumen and more highly folded epithelium. They may be distinguished from attached lateral oviducts by conformational differences and by a possibly lesser size of the epithelial cells. Free lateral oviducts observed among bilaterally ovariectomized and sham-ovariectomized specimens were indistinguishable from those obtained after unilateral ovariectomy. The results are at variance with the previously accepted conclusion that oviduct growth inDrosophila is dependent upon inductive influences emanating from the ovary and directing the outgrowth of the oviducts. Differences in the developmental performance of the oviducts as a function of age at the time of ovariectomy were not evident in the study which included larvae ranging from the second instar to late in the third instar. Transplants of larval female genital discs to other larvae revealed a lesser development of the lateral oviducts than that exhibited by a genital disc developingin situ. A range of oviducal growth which lacked any relation to ovarian influences or to other internal organs of the hosts was obtained. In general, decreased amounts of oviducal muscle were found associated with the transplants.