The hepatocytes of the brown trout (<Emphasis Type="Italic">Salmo trutta</Emphasis> f. <Emphasis Type="Italic">fario</Emphasis>): a stereological study of their number and size during the breeding cycle

A firm knowledge of the normal structure is crucial for evaluating pathological processes and morphofunctional correlations. Stereological liver structure characterization had its debut for mammals in the 1960s, but only in the 1980s did it start to be used in fishes. Using stereology, our aim was to verify the hypothesis that in parallel with the well-known annual seasonal changes in the liver–body ratio of brown trout, hepatocytes would vary their number and/or size, and that gender differences likely exist. Three-year-old specimens were used. Five animals per gender were examined in May (endogenous vitellogenesis), September (exogenous vitellogenesis), and February (spawning season end). The liver was fixed by perfusion, and its total volume estimated. Systematically sampled material was embedded in epoxy or in metachrylate resins. Stereology was executed on light and electron microscopy images. Unbiased design-based techniques were applied, using physical disectors and differential point counting. Target parameters were the relative (per unit volume) and total number of hepatocytes, the mean cell and nuclear volumes, and the total volumes of hepatocytes and their nuclei. Data support that in both genders the number of hepatocytes and the volume of its nucleus change along the breeding cycle. The cell number increased from endogenous to exogenous vitellogenesis (accompanying relative liver size gains), later followed by a decline in the cell number, still detectable after the spawning season. The total liver volumes of the cell and nucleus also increased from May to September in females, despite that the mean hepatocyte nuclear volume showed a minimum in September. No statistical changes in the mean cell volume were detected, regardless of the tendency for lower mean values in September. Changes were more marked in females and showed a higher correlation with the gonad weight. It was firstly suggested that numerical (rather than cell size) changes govern the shifts of the relative liver weight seen during the brown trout annual breeding cycle, and eventually of other fishes. We hypothesized that there are seasonal cycles of hepatocyte mitosis (from after spawning to exogenous vitellogenesis) and of apoptosis (at spawning). These cycles would be regulated by sex steroids, being more striking in females.     

不同生殖期鳜肝脏超微结构变化的观察

应用透射电镜对生殖季节与非生殖季节鳜肝脏超微结构的变化进行了观察。鳜肝细胞含有单个卵圆形的核,核仁清楚;细胞质内含有粗面内质网、线粒体、糖原颗粒和脂滴等细胞器和内含物。胆小管由相邻的数个肝细胞质膜凹陷围成,而肝血窦则由内皮细胞的胞质构成。还发现了贮脂细胞、枯否氏细胞和成纤维细胞。胆小管腔和窦周隙内浸润许多由肝细胞发出的微绒毛结构。鳜肝细胞的超微结构在产卵前后呈现明显变化：产卵前的肝细胞内富含线粒体、糖原颗粒和脂滴,粗面内质网发达;而产卵后的肝细胞内核仁发生迁移,部分细胞核囊泡化,糖原颗粒和脂滴排空,少数肝细胞具双核结构。非生殖期多数肝细胞核含有双核仁结构,胞质内溶酶体数量增多。     

Histomorphological observations on the liver in some freshwater teleosts.

Histomorphology of liver is studied in six species of teleost viz., Heteropneustes fossilis, Clarias batrachus, Puntius ticto, Danio malabaricus, Nandus nandus, Chana punctatus. The liver is a bilobed structure usually reddish brown in colour. There are accessory liver lobes in H. fossolis and C. batrachus. The histological examination shows compact mass of oval or polygonel hepatocytes, blood sinusoids and reticuloendothelial cells. In addition several patches of pigmented hepatocytes are also noticed. After partial hepatectomy the changes in liver structure are shrunken nature of hepatocytes, enlarged blood vessels and accumulation of lymphocytes near the cut portion. After biliary obstruction with the help of ligation of bile duct hepatocytes become turgid in appearance within seven days. There is fibrosis of blood vessels as well as bile spaces. The turgidity of hepatocytes increases fifteen days after the ligation so much so that some of them show necrotic appearance. There are numerous bile thrombi noticed after biliary obstruction.     

Pathological effect of synthetic cereulide, an emetic toxin of Bacillus cereus, is reversible in mice

Cereulide is the causative toxin of the emetic type of food-borne illness caused by Bacillus cereus. This toxin was previously shown to be associated with fulminant liver failure in a human case. Mice were injected i.p. with synthetic cereulide and the development of histopathological changes was examined. Hepatocytes showed mitochondrial swelling with loss of cristae, and dose-dependent increase of small fatty droplets. These microsteatotic hepatocytes were distributed mainly in the pericentral area. At higher cereulide doses, massive degeneration of hepatocytes occurred. The serum values of hepatic enzymes were highest on days 2-3 after the inoculation of cereulide, and rapidly decreased thereafter. General recovery from the pathological changes and regeneration of hepatocytes was observed after 4 weeks.     

Leptin,ghrelin, and energy metabolism of the spawning burbot (Lota lota,L.)

The aim of this study was to investigate the energy metabolism of the burbot (Lota lota, n=38) before, during, and after spawning, which represents the greatest annual metabolic demand for the species. A decrease in body mass, relative weight of the livers, and glycogen concentration of the livers was observed toward the end of spawning. The prespawning period was characterized by high rates of liver glycogenolysis and lipid mobilization. Also, plasma triiodothyronine and sex steroid levels were high before reproduction. During spawning, liver lipolysis was reduced and muscle glycogenolysis stimulated. The levels of triiodothyronine and sex steroids decreased. After reproduction, liver glycogenolysis was suppressed and the rate of gluconeogenesis increased. Thyroid hormone levels were elevated after spawning. Leptin protein and a ghrelin-immunoreactive peptide were detected in burbot plasma. Their concentrations were relatively low before and during reproduction but increased after spawning. The functions of leptin and the ghrelin-immunoreactive peptide in the physiology of the burbot are not consistent with the models of their function in mammals.     

Liver Changes Related to Oocyte Growth in Roach,a Single Spawner Fish,and in Bleak and White Bream,Two Multiple Spawner Fish

The objectives of this study were to compare the seasonal hepatic activity and to evaluate whether this activity was related to the dynamics of oocyte recruitment in three cyprinids from the River Meuse (Belgium): the roach Rutilus rutilus as a single spawner, and the bleak Alburnus alburnus and the white bream Blicca bjoerkna as multiple spawners. In roach, hepatosomatic index (HSI) was low during exogenous vitellogenesis. However, the strong development of the rough endoplasmic reticulum (RER), the presence of large mitonchondria with many inner folds, and the depletion of glycogen, lipid droplets and phospholipids indicated intense hepatic activity during that period. Prior to spawning, hepatic activity decreased as indicated by a decrease of the HSI and in the hepatocytes a regression of the RER and the disappearance of the lipid droplets and glycogen. In bleak, the oocyte recruitment occurred continuously throughout the spawning season and the vitellogenic activity of the liver remained intense throughout that period as suggested by high HSI and the ultrastructure of the hepatocytes. In contrast in white bream the vitellogenic activity of the liver decreased during the spawning season as the completion of the vitellogenesis took place prior to spawnings. We concluded that the vitellogenic activity of the liver is strongly related to oogenesis.     

Dynamic expression of the cell adhesion molecule cell-CAM 105 in fetal and regenerating rat liver

Cell-CAM 105 is an integral cell surface glycoprotein that is involved in cell-cell adhesion of adult rat hepatocytes in vitro. In the present report we used a radio-immunoassay, a quantitative immunoblotting technique and immunofluorescence microscopy to investigate the expression of cell-CAM 105 in fetal and regenerating rat liver. In the fetal liver cell-CAM 105 did not appear until day 16 of the gestation, when it increased rapidly to reach the level found in adult liver, 3 weeks after birth. In liver regenerating after partial hepatectomy a transient decrease in the amount of cell-CAM 105 was observed in the plasma membranes of the hepatocytes. A significant decrease was observed as early as 12 h after partial hepatectomy, reaching a minimum by 3 days after the operation, corresponding to approx. 35% of the amount of cell-CAM 105 in normal liver. The amount then increased slowly and was back to the normal level by about 15 days after partial hepatectomy. The results indicate that cell-CAM 105 exerts its major function in terminally differentiated cells. An excellent correlation was seen between the kinetics of the expression of cell-CAM 105 and of reported changes of both enzymatic and organizational patterns of hepatocytes in regenerating and fetal liver. This suggests that cell-CAM 105 could be important for the development and maintenance of the cell-cell binding and organizational pattern characteristic of terminally differentiated hepatocytes.     

Liver regenerative potential of the lake frog Rana ridibunda after partial hepatectomy

A histomorphological study of the regenerating liver of Rana ridibunda, within 2 months after partial hepatectomy, shows that regenerative processes on the wound surface are slowly proceeding. Processes of reticular fiber reconstruction occurred in the composition of the basal membrane of liver sinusoids. A cytophotometric study shows that glandular cells in R. ridibunda liver are commonly tetraploid. The post-traumatic regeneration of the liver after partial hepatectomy involves activation of DNA synthesis in hepatocytes, leading to increase in their ploidy. Within the 1st month of regeneration, the mitotic index of hepatocytes substantially increased. Regeneration of glandular parenchyma of the liver is accompanied by a quantitative increase in binucleate hepatocytes, which is most highly expressed within 5-20 days after partial hepatectomy.     

Aneuploidy,polyploidy and ploidy reversal in the liver

Polyploidy has been described in the liver for over 100 years. The frequency of polyploid hepatocytes varies by age and species, but up to 90% of mouse hepatocytes and approximately 50% of human hepatocytes are polyploid. In addition to alterations in the entire complement of chromosomes, variations in chromosome copy number have been recently described. Aneuploidy in the liver is pervasive, affecting 60% of hepatocytes in mice and 30–90% of hepatocytes in humans. Polyploidy and aneuploidy in the liver are closely linked, and the ploidy conveyor model describes this relationship. Diploid hepatocytes undergo failed cytokinesis to generate polyploid cells. Proliferating polyploid hepatocytes, which form multipolar spindles during cell division, generate reduced ploidy progeny (e.g., diploid hepatocytes from tetraploids or octaploids) and/or aneuploid daughters. New evidence suggests that random hepatic aneuploidy can promote adaptation to liver injury. For instance, in response to chronic liver damage, subsets of aneuploid hepatocytes that are differentially resistant to the injury remain healthy, regenerate the liver and restore function. Future work is required to elucidate the mechanisms regulating dynamic chromosome changes in the liver and to understand how these processes impact normal and abnormal liver function.     

Development of the fetal rat liver: ultrastructural and stereological study of hepatocytes

Qualitative and quantitative changes in the liver tissue composition have been studied during prenatal development of the Wistar rat by electron microscopy and stereologic methods. The absolute volume of the fetal liver is multiplied by 84 between days 13 and 20 of gestation. In the meantime, the average hepatocyte volume is multiplied by 1.5 between days 12 and 20. The volumetric fraction of hepatocytes increases from 35% of the volumetric fraction of the liver on day 12 to 66% on day 20 of gestation. The non-hepatocyte cells decrease from 49% on day 12 to 25% on day 20. By days 12 and 13, the rough endoplasmic reticulum and the Golgi apparatus are well differentiated, indicating that young fetal hepatocytes are able to synthesize and export plasma proteins. The volumetric fraction of free ribosomes decreases from 38% of the hepatocytic cytoplasm on days 12 and 13 to 6% on day 20. The mitochondrial compartment occupies about 10% of the hepatocyte cytoplasm. The mitochondria, small and round on days 12, 13 and 14, become oblong from day 18 of gestation. The shape of hepatocytes changes during the prenatal development, from potato-like on days 12, 13, 14 to cubic on day 20, with an intermediate, more spheric, stage on day 18.     

Histomorphological study of mice inbred CBA liver under combined chronic influence of low dose gamma radiation and incorporated thorium nitrate

We studied histomorphology of the CBA line mice liver after 30 and 90 days of the low dose gamma-radiation influence combined with incorporated Th(NO3)4 in doses 0.03; 0.1; 0.3 grams per kilogram of the living mouse weight. Morphophysiological and morphometric changes were shown. The liver mass and index were significant by increased after 30 days influence. The same changes after 90 days influence were not shown. The morphometric parameters (dynamics of double-nucleus and polyploid hepatocytes, nucleoluses numbers) gave evidence of the liver energy disbalance.     

Dynamic changes in protein components of the tight junction during liver regeneration

The construction of the hepatocyte tight junction is one of the most important events during liver regeneration leading to the reorganization of the bile canaliculi and the repolarization of hepatocytes after cell division. To understand this event at the molecular level, we examined the expression of tight junction proteins by Western blot analysis and their cellular localization by immunofluorescence microscopy in regenerating rat liver after two-thirds hepatectomy. The levels of tight junction components such as claudin-3, ZO-1 and atypical protein kinase C (PKC)-specific interacting protein (ASIP) increased two- to three-fold over control levels in coordination with a peak 2-3 days after partial hepatectomy, whereas occludin levels remained unchanged. The bile canaliculi outlined by tight junction components and actin filaments reveal significant morphological changes from 2-3 days after partial hepatectomy. During this period, claudin-3/ZO-1 and ASIP/ZO-1 were nearly co-localized, whereas occludin was locally reduced or almost absent on the bile canaliculi outlined by ZO-1 staining. The uncoupled localization of F-actin and tight junction components was often observed. The function of hepatocytes, as revealed by the serum bile acids level, was distorted temporally at an early stage of regeneration but mostly restored 3 days after partial hepatectomy. These observations suggest that the de novo construction of tight junctions proceeds mainly 2-3 days after partial hepatectomy in parallel with the cell polarization required for hepatocyte function. However, the complete normalization of the composition of the tight junction components, such as occludin and the association with F-actin, requires additional time, which may support the regeneration of fully polarized normal hepatocytes.     

Isocaloric maternal low-protein diet alters IGF-I,IGFBPs, and hepatocyte proliferation in the fetal rat

We investigated the effect of an isocaloric maternal low-protein diet during pregnancy in rats on the proliferative capacity of cultured fetal hepatocytes. The potential roles of these changes on the IGF-IGF-binding protein (IGFBP) axis, and the role of insulin and glucocorticoids in liver growth retardation, were also evaluated. Pregnant Wistar rats were fed a control (C) diet (20% protein) or a low-protein (LP) diet (8%) throughout gestation. In primary culture, the DNA synthesis of hepatocytes derived from LP fetuses was decreased by approximately 30% compared with control hepatocytes (P < 0.05). In parallel, in vivo moderate protein restriction in the dam reduced the fetal liver weight and IGF-I level in fetal plasma (P < 0.01) and augmented the abundance of 29- to 32-kDa IGFBPs in fetal plasma (P < 0.01) and fetal liver (P < 0.01). By contrast, the abundance of IGF-II mRNA in liver of LP fetuses was unaffected by the LP diet. In vitro, the LP-derived hepatocytes produced less IGF-I (P < 0.01) and more 29- to 32-kDa IGFBPs (P < 0.01) than hepatocytes derived from control fetuses. These alterations still appeared after 3-4 days of culture, indicating some persistence in programming. Dexamethasone treatment of control-derived hepatocytes decreased cell proliferation (54 +/- 2.3%, P < 0.01) and stimulated 29- to 32-kDa IGFBPs, whereas insulin promoted fetal hepatocyte growth (127 +/- 5.5%, P < 0.01) and inhibited 29- to 32-kDa IGFBPs. These results show that liver growth and cell proliferation in association with IGF-I and IGFBP levels are affected in utero by fetal undernutrition. It also suggests that glucocorticoids and insulin may modulate these effects.     

Variations in the volumes of parenchyma and stroma of the liver and in the cytology of hepatocytes are associated with gonadal stages in female Ohrid trout (Salmo letnica)

Quantitative microscopic studies of season- and breeding-related changes in the liver of farm-raised fish are very scarce, and those of wild fish populations are virtually nonexistent. Moreover, none of the available studies investigated breeding-related changes in hepatic stroma, although it is already known that changes might exist in the parenchyma. To the best of our knowledge, ours is the first study using wild adult Ohrid trout females to evaluate quantitative influences of the breeding cycle on the volumes of the two liver compartments—parenchyma and stroma. Quantitative microscopy (stereology) using light microscopy was supplemented with semi-quantitative and quantitative analyses of hepatocyte cytology to express in numbers the seasonal changes in the extent of vacuolated versus basophilic cytoplasm. The liver volume and that of each compartment changed from that at the time of pre-vitellogenesis to the end of the spawning season. The changes in total volumes of parenchyma and stroma—increasing from pre-vitellogenesis to late vitellogenesis—followed the changes in total liver volume. Despite all the changes in total volumes, no differences existed in the relative proportions between the two major compartments. After spawning, the stromal volume continued to increase while that of the parenchyma reduced despite no detectable statistically significant impacts on the liver volume. Changes in both the liver and parenchyma volumes were correlated with the gonadosomatic index and plasma oestradiol levels. With this study, we first establish that fish liver remodelling might also occur in the stroma. When comparing Ohrid trout with other fish species, we noted interspecies similarities and differences with regard to the hepatocyte cytology during the breeding cycle. In our study, the semi-quantitative and stereological studies revealed that, from pre-vitellogenesis to post-spawning, although cytoplasmic vacuolation of the hepatocytes decreased, the basophilia increased. Overall, these cytological changes were only partially in agreement with the data from other trout studies. We believe that this is because of intrinsic interspecies differences in association with natural conditions. Thus, establishing normal patterns is crucial, at least for flagship species, namely to support interpretation of histopathological changes in biomonitoring.     

Sensitivity of liver cells formed after partial hepatectomy to glucagon, vasopressin and angiotensin II

During the active proliferation which follows partial hepatectomy, the sensitivity of liver cells to glucagon is markedly diminished. In hepatocytes obtained from rats partially hepatectomized 3 days before experiments were performed, the dose-response curves to glucagon were shifted to the right by about two orders of magnitude as compared to those of the control cells. Later on (7 days after surgery) the dose-response to glucagon was still shifted to the right but by only one order of magnitude. These data are consistent with the diminution in the number of glucagon receptors in liver plasma membrane during liver regeneration reported by other authors. No stimulation of glycogenolysis, gluconeogenesis or ureogenesis was produced by vasopressin or angiotensin II in hepatocytes from rats partially hepatectomized 3 days before experimentation. However, phosphatidylinositol labeling was stimulated in these cells to a similar extent as in the controls. The ionophore A23187 was also ineffective in stimulating glycogenolysis in these cells. Later, 7 days after surgery, the hepatic responsiveness to vasopressin and angiotensin II was restored. The data suggest that, during the initial stages of liver regeneration, the enzymatic machinery of the hepatocyte is not sensitive to calcium-signalling.     

The inter-spawning interval of the female Three-spined stickleback, Gasterosteus aculeatus

Female Three-spined sticklebacks spawn several times in a breeding season, at intervals of a few days. The changes that take place in females during the interval between successive spawnings were analysed. The average time between spawnings was 87.5 hours. Between spawnings females increased in weight by between 15 and 30%. The bulk of this weight increase was lost when the eggs were spawned. The increase in weight was because of an increase in weight of the ovaries, which showed an increase in both dry matter and water content. After spawning the ovaries formed 8 to 9% of the total body weight, and this increased to up to 24% just prior to the next spawning. The ovaries were maximally hydrated immediately after spawning. There were no significant changes in the calorific value of the ovaries, but the calorific value of the rest of the body was a minimum just after spawning. It was estimated that between spawnings females were making a net gain of energy at an average rate of 2 cal/hour. After spawning, courtship behaviour by the females waned, but recovered over the last half of the interval between spawnings. The inter-spawning interval of the Three-spined stickleback provides a useful situation in which physiological and nutritional aspects of reproduction in a teleost fish can be studied.     

Quantitative histological and histochemical studies on the occurrence and stages of controlled cell death (apoptosis) during regression of rat liver hyperplasia

Hyperplasia of the rat liver can be induced by cyproterone acetate (CPA). The fate of this hyperplasia after cessation of CPA treatment has been studied and the following findings were obtained: Liver DNA content decreased by about 25% within a few days after CPA withdrawal. In histological sections some hepatocytes showed degenerative changes. Among these, small membrane bounded bodies ("apoptotic bodies"; ABs) with or without chromatin were most numerous. Their incidence coincided with the phase of DNA elimination. Inflammatory reactions were not observed. Their small size and occurrence in clusters suggests that many of these ABs are formed by fragmentation of dying hepatocytes. Liver DNA was prelabelled with 3H-thymidine. Autoradiographic evaluation showed that many hepatocytes contained labelled nuclei, but unlabelled ABs. This finding strongly suggests that ABs, after the fragmentation stage, can be phagocytized by intact hepatocytes. About 80% of all ABs were found within hepatocytes. Extracellular ABs (early stage) contained no or very few active lysosomes. Intracellular ABs were sometimes surrounded by lysosomes, while others were in various stages of digestion. These observations suggest that the lysosomes of the phagocytizing hepatocytes degrade intracellular ABs, whereas intraapoptotic lysosomes seem to be inactive until the late stages of this degradation. Hepatocytes that did not replicate during CPA-induced liver growth appear to die off preferentially after CPA withdrawal. Retreatment with CPA greatly reduced the number of ABs within 4 h. Phenobarbital, another stimulus of liver growth, had the same effect. These findings suggest that the present type of cell death can be inhibited by growth stimuli and is therefore a controlled event serving to eliminate an excess of cells, rather than a manifestation of toxic injury to hepatocytes. The findings also suggest that this type of cell death and elimination is a rapid process completed within a few hours. It is concluded that cell death under the present experimental conditions probably occurs through apoptosis.     

Hepatocytes in heterokaryons can suppress entry into the S-period of fibroblast nuclei from murine NIH 3T3 cells

Mouse liver regeneration after partial hepatectomy can be considered as a spectacular example of controlled tissue increase. In this study serum-deprived (0.2%) resting and serum-stimulated (10%) proliferating NIH 3T3 mouse fibroblasts were fused with primary hepatocytes isolated from normal (intact) and regenerating adult mouse liver at different times after partial hepatectomy (1-15 days) to elucidate mechanisms of liver cell proliferation cessation at the regeneration end. DNA synthesis was investigated in the nuclei of heterokaryons and non-fused cells using radioautography. Hepatocytes isolated from regenerating liver within 1-12 days following operation did not retard the entry of stimulated fibroblast nuclei into the S-period. In contrast, hepatocytes isolated within 15 days after hepatectomy were found to have inhibitory effect on the entry of stimulated fibroblast nuclei into the S-period in heterokaryons. Preincubation of these hepatocytes with cyclocheximide for 2-4 h abolished their ability to suppress DNA synthesis in stimulated fibroblast nuclei in heterokaryons. Possible reasons of inhibitory effect of differentiated cells in heterokaryos are discussed. The data obtained enable us to conclude that the mechanism of proliferative process control in regenerating hepatocytes seems to be stopped being affected by the intracellular growth inhibitors, whose formation depends on protein synthesis.     

Age-dependent reversal of the lobular distribution of androgen-inducible alpha 2u globulin and androgen-repressible SMP-2 in rat liver.

Hepatocytes situated at pericentral and periportal zones of the liver lobule show differences in the expression of several liver-specific genes, such as androgen-inducible alpha 2u globulin and androgen-repressible senescence marker protein-2 (SMP-2). A marked temporal difference in the expression of these two androgen-regulated genes has also been observed. The liver of the pre-pubertal male rat is insensitive to androgen, and during this period hepatocytes synthesize only SMP-2. During young adult life (greater than 40 days), the liver becomes androgen sensitive and concomitant synthesis of alpha 2u globulin and repression of SMP-2 occur. In the senescent male rat (greater than 750 days), the liver again becomes androgen insensitive when the decline in alpha 2u globulin is accompanied by an increase in SMP-2 synthesis. In this article we present results to show a correlation between the temporal and spatial (intralobular) changes in the expression of the androgen-inducible alpha 2u globulin and the androgen-repressible SMP-2 in rat hepatocytes. Results indicate that the temporal changes in hepatic androgen sensitivity are dictated by the intralobular location of the hepatocytes. Hepatocytes located around the central vein (pericentral/perivenous) may benefit from a paracrine advantage for the expression of a subset of genes, including the gene for the androgen receptor.     

Ultrastructural changes in the liver of the sand lamprey,Lampetra reissneri,during sexual maturation

Ultrastructural changes of hepatocytes were examined in the sand lamprey,Lampetra reissneri, during various phases of the life cycle. In hepatocytes of ammocoetes, the rough endoplasmic reticulum was composed of short cisternae and the Golgi apparatus were scarcely developed, showing no sexual differences at this stage of life cycle. In hepatocytes of female lampreys at the metamorphic stages 4 to 5, the rough endoplasmic reticulum was developed to form long parallel cisternae and the Golgi apparatus were well-developed. The rough endoplasmic reticulum developed further to form stacks of long parallel cisternae extending over the cytoplasm in hepatocytes of females at the young adult stage, and became composed of both long parallel and vesicular cisternae in the cells of females at the adult stage. The Golgi apparatus were invariably welldeveloped in hepatocytes of young adult and adult females. No consipcuous development was observed in profiles of the rough endoplasmic reticulum and the Golgi apparatus in hepatocytes of males during and after metamorphosis. The ultrastructural changes of the rough endoplasmic reticulum and the Golgi apparatus observed in hepatocytes of female sand lampreys are considered to have an intimate relation to the activity of vitellogenin synthesis in the liver, and it is suggested that the hepatocytes begin to rapidly synthesize vitellogenin in the sand lamprey at the metamorphic stages 4 to 5.