Testicular steroidogenesis after human chorionic gonadotropin desensitization in rats.

When a single injection of 500 I.U. of human chorionic gonadotropin (hCG) is given to rats there is an initial acute rise of plasma testosterone and of testicular content for both cyclic AMP and testosterone. This response correlates with an increase in both lyase and 17 alpha-hydroxylase activities. Thereafter both plasma and testicular testosterone decline and do not increase after a second injection of hCG. During this period of desensitization, isolated Leydig cells were insensitive to the steroidogenic stimulatory effect of both hCG and dibutyryl cyclic AMP. The post-cyclic AMP block is not due to an alteration of the cyclic AMP-dependent protein kinase but it is correlated with a decrease in both lyase and 17 alpha-hydroxylase activities of the Leydig cell's microsomes. This decrease is not caused by the absence of the recently described cytosol activator of this enzyme because its addition did not restore the enzymatic activity. Within 60 to 96 h after hCG injection there was a spontaneous increase of both plasma and testicular testosterone and this parallels the recovery of lyase and 17 alpha-hydroxylase activities. These results suggest that both enzymatic activities are regulated, directly or indirectly, by hCG, and that this is partly responsible for the hCG-induced steroidogenic refractoriness of Leydig cells.     

Ultrastructural changes in hepatocytes in the dynamics of the development of esperimental liver cirrhosis in rats]

Both hepatocyte necrosis and organ fibrosis and intracellular reparative regeneration of the injured cells took place in the posttoxic cirrhosis development. The outcome of cirrhosis is supposed to be determined by the prevalence of one of the processes--either the irreversible destruction, restoration or the hypertrophy of the parenchymal cells. The progress of cirrhosis evidently depended on the overstraining and progressive exhaustion of the intracellular compensatory adaptive mechanisms.     

Change in morphometric parameters in silver-stained nucleoli from hepatocytes of rats with liver cirrhosis and during rehabilitation from it]

Silver-stained nucleoli of rat hepatocytes were studied in norm, in liver cirrhosis produced by CCl4 poisoning and after cessation of the poisoning. Morphometric parameters of nucleoli were measured using a Videotest computer image analyser. Under cirrhosis the mean number of nucleoli per nucleus was determined to exceed their normal number by 1.27 times. The total volume of nucleoli in the nucleus also exceeded the normal level (by 1.15 times). 3 months after the end of CCl4-poisoning, these parameters decreased almost to normal values. A statistically significant correlation was revealed between the number of nucleoli and their total volume (0.881). Changes of the parameters also correlated with the total protein content in the hepatocytes. Possible reasons for this correlation are discussed. The ratio of the number of chromosomal NORs to the mean number of nucleoli in the nucleus is proposed to be used as a feature for comparative analysis of functional status of nucleoli in the nuclei of different ploidy and in cells of different animal species.     

Ovarian reaction and estrus manifestation in delayed puberty gilts after treatment with equine chorionic gonadotropin

Background

Placental characters vary among Xenarthra, one of four supraordinal clades of Eutheria. Armadillos are known for villous, haemochorial placentas similar to humans. Only the nine-banded armadillo has been well studied so far.

Methods

Placentas of three species of armadillos were investigated by means of histology, immunohistochemistry including proliferation marker, and transmission and scanning electron microscopy.

Results

The gross anatomy differed: Euphractus sexcinctus and Chaetophractus villosus had extended, zonary placentas, whereas Chaetophractus vellerosus had a disk. All taxa had complex villous areas within the maternal blood sinuses of the endometrium. Immunohistochemistry indicated the validity of former interpretations that the endothelium of the sinuses was largely intact. Tips of the villi and the columns entering the maternal tissue possessed trophoblast cell clusters with proliferation activity. Elsewhere, the feto-maternal barrier was syncytial haemochorial with fetal vessels near the surface.

Conclusions

Differences among armadillos occurred in regard to the extension of the placenta, whereas the fine structure was similar. Parallels to the human suggest that armadillos are likely to be useful animal models for human placentation.     

Prostaglandin synthesizing enzyme activities of hepatocytes and non-hepatocytes in rat liver as a function of age

The developmental profile of prostaglandin (PG)-synthesizing enzymes in liver was investigated in rats from the fetus to 2 years old. In the neonatal period, the activities of PGD2-(2.7 nmol/min/mg protein) and PGE2-(2.2 nmol/min/mg protein) synthesizing enzymes were predominant, whereas PGE2-synthesizing enzyme alone further increased in activity during adult to old ages (5.2-6.1 nmol/min/mg protein). In order to determine the sites of PGs production in rat liver, we prepared hepatocytes and non-hepatocytes by a collagenase digestion method. Regardless of the ages we examined, the major PG produced in the hepatocytes was proved to be PGE2, on the other hand, PGD2 was almost exclusively produced in the non-hepatocytes. These results suggest that each PG may have individual roles in the development of rat liver.     

Autoradiographic analysis of follicle-stimulating hormone and human chorionic gonadotropin receptors in the ovary of immature rats treated with equine chorionic gonadotropin.

The gonadotropin-primed immature rat has become the most common model for the study of follicular development and ovulation. In this study, prepubertal female rats, 23 and 24 days old, were injected s. c. with 5 IU eCG, and ovaries were collected for topical autoradiography of FSH and hCG receptors at 48 or 24 h post-eCG, respectively (i.e., Day 25). In a baseline group, on Day 25 (before eCG), even the smallest preantral follicles with 1 layer of granulosa cells (GCs; primary follicles) possessed FSH receptors, but hCG receptors were found only on the theca of follicles with 2 or more layers of GCs. Human CG receptors were especially prominent in the interstitium that intimately surrounds preantral follicles without any distinction between theca and interstitial cells. There was a discrete theca surrounding antral follicles. Occasionally antral follicles had hCG receptors in the interstitium, but the adjacent theca was negative, suggesting that these follicles might be destined for atresia. By 24 h post-eCG, a now-discrete theca layer with hCG receptors surrounded all preantral follicles except for the primary follicles, which never responded to eCG. The interstitium was hypertrophied and epithelioid, as was the theca surrounding nonatretic preantral and antral follicles. Increased mitotic activity characterized the growing preantral follicle, and for the first time, FSH binding in GCs of antral follicles was greater than in the preantral population. By 48 h post-eCG, the primary follicles were still unresponsive to eCG. FSH receptors were even more pronounced in the GCs of large antral follicles, although hCG receptors were present in the GCs of only one third of the antral follicles, reflecting the small dose of eCG administered. By 48 h post-eCG, receptors in the interstitium were barely detectable. Using this model, the following study considers the functional in vitro changes in steroidogenesis in follicles from the smallest preantral follicles to the largest antral follicles.     

Response of dairy heifers to Prostaglandin F2alpha after treatment with human chorionic gonadotropin

After the observation of estrus following administration of Prostaglandin F(2alpha) (PGF(2alpha)), 79 dairy heifers were randomly either injected with 2500 IU of human chorionic gonadotropin (hCG) 48 h postestrus or maintained as controls with no injection at that time. Five to 9 d later, after a blood sample for progesterone determination was taken, all heifers were injected with 25 mg of PGF(2alpha). Heifers observed in estrus within the next 5 d were inseminated about 12 h after initial observation and were palpated for pregnancy 45 to 60 d postinsemination. Heifers treated with hCG had higher progesterone concentrations, reduced and delayed estrual responses, and lower insemination fertility rates when compared with control heifers.     

Glycogen phosphorylase hyperactive foci of altered hepatocytes in aged rats

In untreated 12- to 24-month-old rats, the enzyme histochemical pattern of 45 focal hepatic lesions was investigated in serial sections. In addition to previously characterized glycogen storage foci, a new type of enzymatically altered hepatic focus was found. The outstanding feature of this was an increased glycogen phosphorylase activity. The frequent appearance of glycogen phosphorylase hyperactive foci simultaneously exhibiting excessive glycogen storage suggests a close relationship to the well known glycogen storage foci representing an early stage in the sequence of cellular changes which lead to hepatic tumors.     

Biomechanics and functionality of hepatocytes in liver cirrhosis

Cirrhosis is a life-threatening condition that is generally attributed to overproduction of collagen fibers in the extracellular matrix that mechanically stiffens the liver. Chronic liver injury due to causes including viral hepatitis, inherited and metabolic liver diseases and external factors such as alcohol abuse can result in the development of cirrhosis. Progression of cirrhosis leads to hepatocellular dysfunction. While extensive studies to understand the complexity underlying liver fibrosis have led to potential application of anti-fibrotic drugs, no such FDA-approved drugs are currently available. Additional studies of hepatic fibrogenesis and cirrhosis primarily have focused on the extracellular matrix, while hepatocyte biomechanics has received limited attention. The role of hepatocyte biomechanics in liver cirrhosis remains elusive, and how the cell stiffness is correlated with biological functions of hepatocytes is also unknown. In this study, we demonstrate that the biomechanical properties of hepatocytes are correlated with their functions (e.g., glucose metabolism), and that hepatic dysfunction can be restored through modulation of the cellular biomechanics. Furthermore, our results indicate the hepatocyte functionality appears to be regulated through a crosstalk between the Rho and Akt signaling. These novel findings may lead to biomechanical intervention of hepatocytes and the development of innovative tissue engineering for clinical treatment to target liver cells rather than exclusively focusing on the extracellular matrix alone in liver cirrhosis.     

The function of the liver mitochondria in rats with experimental cirrhosis undergoing an organ-preserving operation on the spleen]

The effect of splenectomy and of spleen-preserving operation with suture ligation of the left gastric artery on the functional status of liver mitochondria was studied by using 102 white male-rats of mixed population with experimental cirrhosis. The obtained data made it evident that in the immediate postoperative period (from 1 to 3 weeks after the procedure) in the animals of both the first and the second series, the disorder of energetic regulation of mitochondria hepatocytes respiration and the decrease in phosphorylation efficiency had the same tendency, which were seemingly caused by stress-action of the operative trauma. The data accumulated in the more distant postoperative period (8 weeks after the procedure) indicated that the resection of the lower splenic pole in combination with supplementary liver arterialization improved essentially the functional status of mitochondria hepatocytes and was more beneficial in contradistinction to splenectomy.     

Metabolic heterogeneity of glycogen in hepatocytes of patients with liver cirrhosis

Concentrations of the total glycogen (TG) and of its labile and stable fractions (LF and SF, respectively) were determined in hepatocytes of portal and central zones of the normal human liver and in the liver of patients with cirrhosis of viral and alcohol etiology. Using the PAS reaction, TG and its LF and SF were revealed in histological sections of the material obtained by liver punction biopsies. Concentrations of TG and its fractions were measured by television cytophotometry. In liver cirrhosis, concentrations of TG, LF, and SF in both zones of the hepatic lobule were much higher than in the normal liver. The ratio between hepatocyte TG concentration in the portal zone and that in the central zone (P/C ratio), both in norm and in viral cirrhosis, exceeds 1.0 to reach, respectively, 1.26 +/- 0.02 and 1.03 +/- 0.01. The glycogen fraction composition in cells of both liver lobule zones in viral cirrhosis does not significantly differ from that in norm. On the contrary, in the liver of patients with alcoholic cirrhosis, the P/C ratio falls to 0.82 +/- 0.02 to be accompanied by qualitative changes in glycogen composition.     

Effects of IGF-I treatment on osteopenia in rats with advanced liver cirrhosis

IGF-I is an anabolic hormone which has been reported to increase bone formation in several conditions of undernutrition. Advanced liver cirrhosis is associated with osteopenia and also with low serum levels of IGF-I. Previous results showed that low doses of IGF-I increase osteoblastic activity and decrease bone reabsorption in early liver cirrhosis. The aim of this study was to evaluate whether IGF-I-treatment also induces beneficial effect on osteopenia associated with advanced cirrhosis. Rats with ascitic cirrhosis were divided into two groups: group CI (n=10) which received saline and group CI+IGF (n=10) which were treated with IGF-I (2 microg/100 g bw x day, sc, during 21 days). Healthy controls which received saline were studied in parallel (CO n=10). On the 22nd day, the animals were sacrificed, and bone parameters were analyzed in femur. Posterior-anterior diameter was similar in all groups. No significant differences were observed in bone content of calcium, total proteins, collagen and hydroxyapatite in cirrhotic rats as compared with controls. However, CI rats showed significant reductions in total bone density (-13.5%, p<0.001) assessed by densitometry and radiological study. In CI+IGF rat bone density (assessed by densitometry) improved significantly as compared with CI animals. In summary, osteopenia characterized by loss of bone mass and preserved bone composition was found in rats with advanced cirrhosis induced by CCl4 and phenobarbital in drinking water. This bone disorder is partially restored by treatment with low doses of IGF-I during only three weeks. Thus, IGF-I could be considered as a possible therapy for osteopenia associated with advanced liver cirrhosis.     

Glycogen synthesis from glucose and fructose in hepatocytes from diabetic rats

In rat hepatocytes, the basal glycogen synthase activation state is decreased in the fed and diabetic states, whereas glycogen phosphorylase a activity decreases only in diabetes. Diabetes practically abolishes the time- and dose-dependent activation of glycogen synthase to glucose especially in the fed state. Fructose, however, is still able to activate this enzyme. Glycogen phosphorylase response to both sugars is operative in all cases. Cell incubation with the combination of 20 mM glucose plus 3 mM fructose produces a great activation of glycogen synthase and a potentiated glycogen deposition in both normal and diabetic conditions. Using radiolabeled sugars, we demonstrate that this enhanced glycogen synthesis is achieved from both glucose and fructose even in the diabetic state. Therefore, the presence of fructose plays a permissive role in glycogen synthesis from glucose in diabetic animals. Glucose and fructose increase the intracellular concentration of glucose 6-phosphate and fructose reduces the concentration of ATP. There is a close correlation between the ratio of the intracellular concentrations of glucose 6-phosphate and ATP (G6-P/ATP) and the activation state of glycogen synthase in hepatocytes from both normal and diabetic animals. However, for any given value of the G6-P/ATP ratio, the activation state of glycogen synthase in diabetic animals is always lower than that of normal animals. This suggests that the system that activates glycogen synthase (synthase phosphatase activity) is impaired in the diabetic state. The permissive effect of fructose is probably exerted through its capacity to increase the G6-P/ATP ratio which may partially increase synthase phosphatase activity, rendering glycogen synthase active.     

Adenine nucleotide content of liver mitochondria increases after glucagon treatment of rats or isolated hepatocytes

Glucagon injected into rats via tail vein or incubated with isolated hepatocytes in vitro caused a 22–35% increase in the intramitochondrial ATP+ADP+AMP content. There was no statistically significant change in state 3 or uncoupled respiratory rates in these mitochondria. Similar glucagon effects were noted irrespective of the medium used or time required for isolation of mitochondria. There has been recent controversy over possible artifacts in assessing the effects of glucagon on mitochondrial function. The present results suggest that the glucagon-induced increase in the matrix adenine nucleotide content is a reproducible phenomenon with probable physiological significance.