Ultrastructural evaluation of oocytes during atresia in rat ovarian follicles

Mammalian females are born with a finite number of ovarian oocytes, the vast majority of which ultimately undergo degeneration by atresia. The overall process of ovarian follicular atresia has been morphologically well described only in large antral follicles. Additionally, little attention has been focused on ultrastructural changes in the oocyte. Furthermore, most such morphological studies were performed prior to identification of apoptosis as a mechanism of physiological cell death. Therefore, the purpose of this study was to use electron microscopy to compare the process of atretic oocyte degradation in ovarian follicles of female Fischer 344 rats (38 days old) with ultrastructural characteristics of apoptosis. Examination of ovarian follicles revealed that nucleolar segregation, cytoplasmic or nuclear condensation, apoptotic body formation, and chromatin margination along the nuclear membrane are never observed in atretic oocytes during the degenerative process. Instead, early morphological changes in atretic oocytes include retraction of granulosa cell- and oocyte-derived microvilli and condensation of mitochondria and loss of cristae. These occurrences coincide with initiation of granulosa cell apoptosis. After most granulosa cells are lost, more severe changes occur, including segmentation of the oocyte and cytoplasmic vacuolization as atresia progresses. Thus, these results suggest that, during atresia, oocytes are removed by physiological oocyte cell death, a method that does not involve classically described apoptosis.

In vivo and electron microscopic observations of the responses of the hepatic sinusoid to interleukin-1

Interleukin-1 (IL-1), which is produced by Kupffer cells and sinusoidal endothelial cells, may play an important role in immunological and microvascular responses to a variety of stimuli in the liver. The responses of the hepatic microvasculature including phagocytic activity of sinusoidal lining cells to IL-1 alpha were examined in C57Bl/6 mice in vivo and using electron microscopy. One hour after recombinant mouse IL-1 alpha was injected at doses of 80 U, the low dose group, and 800 U, the high dose group, the phagocytic activity of sinusoidal lining cells showed significant differences between the two treated groups and between the two groups and the controls. In the low dose group, the numbers of sinusoids containing blood flow and of leukocytes adhering to the sinusoidal lining remained unchanged, but the former decreased and the latter increased significantly in the high dose group. Ultrastructurally, Kupffer cells that phagocytosed latex particles appeared to have decreased in number while the sinusoidal endothelial cells became phagocytic. A considerable number of leukocytes were seen adhering to the sinusoidal endothelium. These findings demonstrate that IL-1 alpha not only elicited sticking and plugging by leukocytes in sinusoids but also activated phagocytic functions in the hepatic sinusoidal endothelial cells. These endothelial responses are similar to those seen following FV3 virus infection, chronic administration of ethanol, or a combination of cocaine and ethanol, or during extracorporal perfusion, suggesting that IL-1 may participate in these responses.

Characterization of a reproducible rat model of hepatic veno-occlusive disease

Lack of a reproducible animal model has hampered progress in understanding hepatic veno-occlusive disease (HVOD). This article characterizes a reproducible model of HVOD. Rats gavaged with monocrotaline, 160 mg/kg, were killed between days 1 and 10. Sections were evaluated by light microscopy with a standardized scoring system, by immunoperoxidase staining with ED-1 (monocytes, macrophages) and ED-2 (Kupffer cells) antibodies, and by transmission (TEM) and scanning electron microscopy (SEM). On days 1 and 2, the earliest manifestations were progressive injury to the sinusoidal wall with loss of sinusoidal lining cells, sinusoidal hemorrhage, and mild damage to central vein (CV) endothelium. On days 3 through 5 ("early HVOD"), there was centrilobular coagulative necrosis, severe injury to sinusoids, severe sinusoidal hemorrhage, and severe CV endothelial damage; inflammation with ED-1-positive cells was most marked on these days. Days 6 and 7 ("late HVOD") were characterized by subendothelial and advential fibrosis of CVs, damage of the CV endothelium with subendothelial hemorrhage, and some restoration of the sinusoidal wall. Between days 8 and 10, sections showed interindividual variation ranging from mild, residual fibrosis to severe, late HVOD. From days 1 through 10, ED-2-positive cells were decreased in number, and the number of ED-1-positive cells was increased. Sinusoidal damage is the earliest change in HVOD. Coagulative necrosis follows sinusoidal injury and resolves with improvement in sinusoidal endothelial cell (SEC) morphology. Moderate-to-severe CV fibrosis occurs after reappearance of sinusoidal lining cells and resolution of hepatocyte necrosis. The inflammatory response within the lobule and CVs is a result of recruitment of monocytes, whereas Kupffer cells are decreased in number.

A bile acid-induced apoptosis assay for colon cancer risk and associated quality control studies

Bile acids are important in the etiology of colorectal cancer. Bile acids induce apoptosis in colonic goblet cells at concentrations comparable to those found in fecal water after high-fat meals. Preliminary evidence indicated that cells of the normal-appearing (nontumorous) portion of the colon epithelium of colon cancer patients are more resistant to bile salt-induced apoptosis than are cells from normal individuals. In the present study, 68 patients were examined, and biopsies were taken at 20 cm from the anal verge, cecum, and descending colon. The patients included 17 individuals with a history of colorectal cancer, 37 individuals with adenomas, and 14 individuals who were neoplasia free. The mean bile salt-induced apoptotic index among normal individuals was 57.6 +/- 3.47 (SE), which differed significantly (P < 0.05) from the mean value of 36.41 +/- 3.12 in individuals with a history of colon cancer. The correlation between independent observers was 0.89 (P < 0.001), indicating good interobserver reliability. Components of variance comparing interindividual versus intraindividual sources of variation suggested that site-to-site variability, both between regions of the colon and for adjacent biopsies, was larger than the interpatient variability for individuals with a history of neoplasia. Therefore, there was "patchiness" of the susceptibility of regions of the colon to bile acid-induced apoptosis in individuals with a history of neoplasia (a patchy field effect). There was no obvious correlation of low-apoptotic index regions with regions in which previous neoplasias had been found and removed. On the other hand, for normal, i.e., neoplasia-free, individuals, there was relatively less intraindividual variation compared to interindividual variation. Our assay shows an association between resistance to bile acid-induced apoptosis, measured at 20 cm from the anal verge, and colon cancer risk. Thus, this assay may prove useful as a biomarker of colon cancer risk.