Retention of the differentiated state by larvalXenopus liver cells in primary culture (original) (raw)
Related papers
Differentiation, 1998
It is generally known that the anuran stomach begins to express pepsinogens (Pg) during metamorphosis. To clarify the mechanisms of differentiation of Pgproducing cells, we examined immunohistochemically the epithelial transformation from larval to adult form in Xenopus laevis stomach at the cellular level. At the beginning of metamorphic climax, concomitantly with the modification of the basement membrane, apoptotic cells labelled by TUNEL suddenly increased in number in the entire epithelium except for the primordia of adult epithelial cells in the basal region of larval glands. Subsequently, with the development of connective tissue, the adult epithelial cells actively proliferated and replaced the larval cells from the basal to the luminal region. Following the start of morphogenesis of adult glands, Pgproducing cells became differentiated in newly formed adult glands, but not in the adult surface epithelium. We then developed an organ culture system and examined effects of thyroid hormone (TH) on the differentiation of Pg-producing cells in X. laevis stomach in vitro. In the presence of TH, just as in spontaneous metamorphosis, Pg-producing cells differentiated from the adult epithelial primordia after the apoptosis of larval epithelial cells. In contrast, in the absence of TH, neither apoptotic larval cells no Pg-producing cells were detected. Therefore, we conclude that TH triggers organ-autonomously the entire process leading to the differentiation of Pgproducing cells in X. laevis stomach. In addition, the strict localization of Pg-producing cells in the adult glands both in vivo and in vitro suggests the correlation between the differentiation of Pg-producing cells and morphogenesis of the glands surrounded by the developed connective tissue.& b d y :
Molecular and Cellular Endocrinology, 1976
This report describes morphological and biochemical changes accompanying oestrogeninduced synthesis of the egg-yolk protein precursor, vitellogenin, in male Xenopus liver. Extensive proliferation of the rough and smooth endoplasmic reticulum and the Golgi apparatus occurs between 3 and 9 days after administration of oestradiol-17& Subcellular fractionation showed that microsomal fractions have an increased protein and RNA content after hormone treatment, whereas the level of the endoplasmic reticulum marker enzyme, glucosed-phosphatase. decreased. In addition to an increased number of ribosomes available for protein synthesis, hormone treatment enhances the in vitro protein synthetic capacity per unit of RNA, both in microsome and ribosome preparations. Polypeptides synthesized in vitro by ribosome preparations show an enrichment in serine content after hormone treatment and an increased proportion of ribosomes can be immunoprecipitated by antibodies directed against vitellogenin. Our data are consistent with the proposal that vitellogenin is synthesized on the ribosomes of the rough endoplasmic reticulum and processed and packaged for secretion in the smooth endoplasmic reticulum and Golgi apparatus. Response to hormonal induction of vitellogenin involves an early phase in which membrane proliferation occurs in order to increase the cellular capacity to synthesize, process and secrete large quantities of egg-yolk protein precursor.
Zeitschrift f�r Parasitenkunde, 1966
The egg production of the liver fluke in vitro is about 2 eggs per minute (BJSI~KMAN and THO~SnLL, 1963). The egg components, o v u m and vitelline cells, ars produced in the ovary and the vitelline glands respectively. The antecedents of the cells in the mentioned organs both contain numerous ribosomes (BJORKMAN and THORSELL, 1963, 1964; GR~SSON, 1964). This suggests a high protein synthesizing capacity. With histochemical technique GOVAERT (1960) has found Millon positive reaction in the ovary. This might be an indication of the presence of tyrosine. Paper chromatographic studies on hydrolysates from homogenates of vitelline glands have shown the occurrence of 13 amino acids, of which tyrosine, phenylalanine, and histidine are present in considerable quantities (SMYTH and CLEO¢, 1959). Eleven ormore amino acids are found in hydrolysates of protein from eggs, e.g. methionine and glycine (KRvAVICA, 1964).
Molecular and Cellular Endocrinology, 1975
The metamorphic tissue changes in liver ard tail muscle of Xeccprrs larvae have been followed with the aid of biochemical and morphcmetric characteristics. After induction cf metamorphosis by thyroxire the larval liver shows an increase and then a marked decrease in weight, but no change in water content. Coincident with this, there are similar, but differential fiuctuations in the an:ount of DNA, total RNA ar,d acid precipitable protein. The concentration of RNA and protein (per unit fresh weight) remains constant throughout metamorphosis, whereas that of DNA decreases during the growth period and increases during late n~etal~orphosis. In tail muscle, which undergoes involution at metamorphosis, there is no change in water content. The concentration of macromolecular constituents does not show any significant change, except for DNA the concentration of which increases during later stages of metamorphosis. The morphometric analysis of the liver tissue reveals that the initial growth response occurs without any significant change in the volume proportion between extrahepatocytic space and hepatocytes, and that liver atrophy during later stages of metamorphosis coincides with similar decreases in the fractional volumes of hepatocytes and their cytoplasmic constituents (mitochordria, ER, ground substance). It is deduced that the larval liver of Xe~opus-in contrast to tail muscle-responds to thyroid hormone by transient growth followed by a marked atrophy of the hepatocytes. Biochemical and morphometric data support the view that this response primarily involves cell mass, and possibly to some extent also cell number, but does not affect the volume proportions of cytoplasmic constituents of the hepatocytes.
Cloning and Thyroid Hormone Regulation of Albumin mRNA inRana catesbeianaTadpole Liver
Molecular Endocrinology, 1990
Thyroid hormones are responsible for the specific biochemical and structural changes that occur during amphibian metamorphosis. In this study we screened a series of cDNAs from a. library constructed from T 4-treated premetamorphic tadpole liver poly(A) + RNA in order to identify a clone that could be used to study the influence of T 3 on liverspecific gene expression during Rana catesbeiana metamorphosis. The cDNA from one clone exhibited a greater degree of hybridization to liver RNA from thyroid hormone-treated tadpoles than untreated tadpoles and no hybridization to RNA from tail fins of tadpoles of either group. On Northern blots, the mRNA to which the cDNA hybridized was 2.3 kilobases in size. The pattern of hybridization to genomic DNA digested by various restriction enzymes was consistent with the presence of a single gene. Using slot blot analysis we found that the mRNA levels first rose above basal levels only after 5 days of immersion of tadpoles in 12.5 M9/liter T 3. The mRNA levels increased approximately 10-fold after 7 and 9 days of treatment. Frog livers had mRNA levels that were intermediate between those in untreated tadpoles and tadpoles immersed in T 3 for 7 days. Sequence analysis revealed a significant degree of homology to serum albumin and a-fetoprotein. While it is known that serum albumin levels rise dramatically during metamorphosis in Rana species, presumably playing a critical role in maintaining water and electrolyte balance during the animals' terrestrial phase, the molecular basis of the induction has not been fully explained. (Molecular Endo
General and Comparative Endocrinology, 1984
The binding of the synthetic glucocorticoid dexamethasone (dex) to Rana catesbeiana tadpole liver, intestine, and tailfin cytosol during both spontaneous and triiodothyronine (T&induced metamorphosis has been examined. No change was observed in the dissociation constant (K,) in the liver or intestine during either spontaneous or T,-induced metamorphosis compared with liver and intestine cytosol from the frog. The binding capacity (N) in liver cytosol of premetamorphic tadpoles (14.33 x lo-l4 mol dexfmg protein) was not significantly different from that found during prometamorphosis (stage XVIII) (11 SO x lo-l4 mol dex/mg protein) and in the adult frog (19.24 x lo-l4 mol dex/mg protein). Following the onset of metamorphic climax, however, there were significant reductions in N in liver cytosol, reaching a nadir at stage XXIV (0.38 x lo-l4 mol dex/mg protein). Binding capacity in premetamorphic tadpole intestine (19.60 x lo-l4 mol dex/mg protein) was significantly reduced following premetamorphosis. Values did not return to premetamorphic values in the frog intestine (6.54 x lo-l4 mol dexlmg protein) as occurred in the frog liver, nor were values significantly reduced following the onset of metamorphic climax (10.43 x lo-l4 mol dexfmg protein) when compared with prometamorphosis (11.58 x lo-l4 mol dexl mg protein). The binding capacity in the tailfin cytosol did not deviate from premetamorphic tadpole values (11.61 x lo-l4 mol dex/mg protein) through stage XXI (9.68 x lo-l4 mol dex/mg protein), the last stage in which sufficient tissue was available for analysis.
Experimental Cell Research, 1972
Protein synthesis and aggregate diameters were measured in cultures of 'I-day embryonic chick liver cells reaggregating for 20 h in chemically-defined medium and in media supplemented with horse serum and with beef embryo extract. Statistically significant differences were found between defined and supplemented media in the rate of increase of mean aggregate diameters over a 20 h period. However, no statistically significant differences were detected in the rates of cellular protein synthesis in the different media. The results suggest that chemically-defined media are preferable to embryo extract and/or serum-supplemented media for short-term cell aggregation studies.