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Biomedical subjects

E Fugassa

Publications and source records attributed to E Fugassa.

At least 55 records · Page 3Linked to original sources
PubMed1988

Effects of insulin and dexamethasone on adenine nucleotide levels in cultured hepatocytes from adult rat.

Insulin and dexamethasone, usually added to culture media, play an important role in maintaining the survival of functional hepatocytes. Adenine nucleotide concentrations and energy charge values of cultured hepatocytes were determined to investigate the relationship between the beneficial effects of these hormones and the energy status of the cells. The results indicate that insulin and dexamethasone are essential in maintaining the metabolic competence of cultured hepatocytes and that this correlates with the absolute concentration of ATP rather than with the energy charge.

Adenine Nucleotides↗
PubMed1988

Nuclear triiodothyronine receptors in rat Sertoli cells.

The existence of specific triiodothyronine (T3) receptors in cultured rat Sertoli cells was investigated by evaluating the affinity and capacity of nuclear binding for T3. The results demonstrate the presence of high affinity (Ka = 0.15 +/- 0.02 X 10(10) M-1), low capacity (1.35 +/- 0.07 pmol T3/mg DNA) binding sites for T3 in rat Sertoli cell nuclei. It is demonstrated that, within the developing testis, the major localization of nuclear T3 receptors is in Sertoli cells.

Animals↗
PubMed1988

Effects of ethanol on protein metabolism in hepatocyte primary cultures from adult rat.

The effect of ethanol on protein synthesis and degradation in cultured hepatocytes from adult rat has been studied. The presence of 100 mM ethanol in the culture medium significantly decreased protein synthesis without affecting protein degradation rate. The depressing effect of ethanol on protein synthesis did not appear directly correlated with the changes in ATP level. However, an inhibition of sodium-dependent and energy-requiring systems of the plasma membrane following exposure to ethanol was observed.

Adenine Nucleotides↗
PubMed1987

Triiodothyronine decreases the production of androgen binding protein by rat Sertoli cells.

Triiodothyronine (T3) effects on cultured Sertoli cells from immature rats were investigated by evaluating the production of androgen binding protein (ABP) a biochemical marker of Sertoli cell function. The results demonstrate that T3 administration to the rat as well as T3 addition to the culture medium specifically decreases ABP production by Sertoli cells, suggesting a direct regulatory role of thyroid hormone on male reproductive function.

Androgen-Binding Protein↗
PubMed1987

Effect of tri-iodothyronine on protein turnover in rat hepatocyte primary cultures.

The effect of tri-iodothyronine (T3) on protein turnover was studied using primary cultures of rat hepatocytes. Protein synthesis was significantly stimulated in cells cultured for 6 days in the presence of T3 (1 mumol/l). Protein secretion into the culture medium was not affected by the hormone. Breakdown of long-lived proteins, the bulk of cellular proteins which are preferentially degraded through the autophagic lysosomal pathway, was significantly stimulated by the hormone. It is concluded that T3 elicits a general stimulation of protein turnover in cultured hepatocytes.

Animals↗
PubMed1985

Triiodothyronine-stimulated RNA synthesis in primary cultures of adult rat hepatocytes.

We have studied the effect of triiodothyronine (T3) on RNA synthesis by primary cultures of rat hepatocytes in order to ascertain whether hepatocyte transcriptional activity is directly stimulated by this hormone. The results demonstrate that T3 stimulates RNA synthesis as measured by [3H]orotic acid incorporation into RNA and by RNA polymerase activity. The responsiveness of cultured hepatocytes to T3 becomes evident only after a fairly long latency period required for the recovery of T3 nuclear binding sites. The response of RNA synthesis to T3 was absent unless the hepatocytes were simultaneously exposed to insulin and dexamethasone, indicating a permissive role of these factors in the action of T3 on RNA synthesis.

Animals↗
PubMed1985

Triiodothyronine receptor sites in serum-free cultured hepatocytes from adult rat liver.

Nuclear T3 specific binding sites were characterized by Scatchard analyses of L-125I-T3 binding to nuclei extracted from freshly isolated and 1, 2 and 6 day-cultured hepatocytes. The results demonstrate a marked decrease in T3 binding capacity of nuclei extracted from 1 day-cultured cells followed by an almost complete recovery within 6 days. The affinity constant value of nuclear receptor sites is significantly decreased in 1 day-cultured cells with a subsequent partial recovery. The affinity and capacity pattern of nuclear T3 binding sites appears to be in line with the delayed responses of hepatocyte primary cultures to T3.

Animals↗
PubMed1984

Collagenase perfusion of rat liver induces DNA damage and DNA repair in hepatocytes.

Evidence is presented that the collagenase perfusion of adult rat liver results in significant damage to nuclear DNA as evaluated by the alkaline elution technique. The extent of the damage is related to the perfusion time as well as to the clostridial enzyme preparation used. The DNA structure of isolated cells is almost completely repaired within 12 h of their culture in chemically defined medium.

Animals↗
PubMed1983

RNA synthesis in primary cultures of adult rat hepatocytes.

The ability of hepatocyte monolayers to synthesize RNA was investigated by measuring [3H]orotic acid incorporation into RNA and the total nuclear RNA polymerase activity as a function of the time in culture. The results demonstrate that primary cultures of hepatocytes maintained in a chemically defined serum- and hormone-free medium are able to synthesize RNA actively. This ability increases within the first 2 d of culture, despite the concomitant decrease in [3H]orotic acid uptake, and decreases only after 3 d. Factors such as serum, insulin, and dexamethasone, known to improve maintenance of functional hepatocytes, markedly stimulate the uptake of labeled precursor without apparently affecting the rate of RNA synthesis by cultured cells. It is suggested that the culture of adult rat hepatocytes provides a useful experimental model for the studies of hormonal regulation of transcription in liver.

Animals↗
PubMed1983

Hormonal stimulation of 3H-orotic acid incorporation into RNA by serum-free cultured hepatocytes.

Insulin and dexamethasone greatly stimulate the incorporation of 3H-orotic acid into RNA. Such a stimulation is associated to an increase in the uptake of the labelled precursor into the acid soluble fraction as well as in the the specific radioactivity of the nucleoside plus nucleotide pool suggesting that hormone supplementation does not affect RNA synthesis by cultured cells. The lack of effect of insulin and dexamethasone on the level of total RNA polymerase activity in nuclei isolated from cultured hepatocytes is in line with this assumption. The hormone stimulated uptake of orotic acid is dependent on protein synthesis since it is completely abolished by cycloheximide.

Animals↗
PubMed1980

[Uptake and incorporation of 3H-orotic acid in isolated perfused rat liver].

3H-orotic acid incorporation into RNA and the level of RNA polymerase activity in isolated rat liver perfused for 5 hrs were investigated. In spite of a dramatic decrease in 3H-orotic acid uptake by liver cells during perfusion, a constant rate of RNA synthesis was observed. Moreover, RNA polymerase I and II activities were not affected by a 5-hr perfusion. It is suggested that isolated perfused rat liver can be used to study direct effects of hormones and drugs on RNA synthesis.

Animals↗
PubMed1980

[Characteristics of synthesized RNA in the isolated and perfused rat liver].

The incorporation of 3H-orotic acid into nuclear and microsomal RNA from isolated perfused rat liver has been studied. The specific radioactivity of nuclear RNA indicates that the efficiency for RNA synthesis in the perfused liver is similar to that of the liver 'in vivo'. In contrast, the microsomal RNA specific radioactivity is well below that observed 'in vivo'. This may indicate a slower transport of the labelled RNA from the nucleus to the cytoplasm. Labelling pattern of total nuclear RNA, nuclear poly(A) containing RNA and microsomal RNA appear to be in line with these assumptions.

Animals↗
PubMed1977

Increased activity of rat liver nucleolar protein kinase following triiodothyronine administration.

Triiodothyronine (T3) administration to thyroidectomized rats induces a significant increase in the nucleolus-associated protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) activity. The general properties of the protein kinase solubilized from liver nucleoli have been investigated. Mg2+ (20 mM) is essential for the reaction and an appropriate concentration of NaCl (100 mM) is required to achieve maximal phosphorylation rates. The optimal pH for casein phosphorylation is 7.6. The kinase phosphorylates casein more efficiently than phosvitin and displays an almost undetectable activity towards histones and protamine. No significant stimulation of the kinase activity by cyclic AMP has been detected. The apparent Km values for casein and ATP are 1.5 mg/ml and 1.5-10(-5) M, respectively, and are not affected by the hormone administration.

Animals↗
PubMed1977

Increased RNA polymerase activity in isolated liver nucleoli from thyroidectomized rats treated with triiodothyronine.

In isolated liver nucleoli from thyroidectomized rats the activity of the two RNA polymerase I populations, one of which is active and the other inactive towards the endogenous chromatin template, is greatly enhanced 10 and 24h after a single ip injection triiodothyronine (T3). When the nucleolar enzyme is solubilized and assayed with exogenous DNA as template, it retains, after T3 treatment, the same increase in activity as observed in intact nucleoli. On the contrary, the template availability, as judged by the binding capacity of isolated nucleoli for [3H]actinomycin D, does not appear to be modified by the hormone. These observations support the conclusion that the enhanced nucleolar RNA synthesis following T3 administration is due to an increased activity of the RNA polymerase I itself rather than to a greater availability of ribosomal RNA cistrons. The hormonal stimulation of both nucleolar RNA polymerase activities depends on continuous protein synthesis since it is almost completely abolished by the administration of cycloheximide.

Animals↗