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Biomedical subjects

G Cecchini

Publications and source records attributed to G Cecchini.

At least 91 records · Page 5Linked to original sources
PubMed1979

Inhibition of liver protein degradation in vivo by intensive treatment with cycloheximide.

The AA in experiments performed on male rats treated with 0,5 mCi/kg of cycloheximide have observed an inhibition of liver protein degradation and have suggested two mechanism: 1) cycloheximide prevents the acute proteolytic response induced in fibroblast culture by exposure to serum-deficient media and in rat livers after perfusion probably by inhibiting the lysosomal - autophagic system, without modifications in total activity of lysosome proteinases. 2) It may be that protein degradation rate and level of lysosomal proteinases reinterrelated; the latter probably being a factor controlling the overall cell protein turnover rate.

Animals↗
PubMed1978

Reconstitution of neutral amino acid transport systems from Ehrlich ascites tumor cells.

Amino acid transport systems for alanine and leucine were reconstituted into artificial lipid vesicles. Purified plasma membrane vesicles from Ehrlich ascites cells were dissolved in 2% sodium cholate, 1mM dithiothreitol, and 0.5 mM EDTA a mixture that solubilized approximately 50% of the membrane protein. This solubilized protein fraction was further purified by a combination of ammonium sulfate precipitations, gel filtration, and DEAE-cellulose chromatography. A fraction containing approximately 15 Coomassie blue-staining bands on sodim dodecyl sulfate gels was obtained. This material was reconstituted into liposomes, and preliminary results demonstrated transport of alanine and leucine dependent on a sodium gradient. In addition, an electrogenic gradient mediated by valinomycin-induced potassium diffusion seemed to stimulate alanine uptake further.

Alanine↗
PubMed1978

Reconstitution of neutral amino acid transport system from Ehrlich ascites tumor cells.

Amino acid transport systems for alanine and leucine have been reconstituted into artificial lipid vesicles. Purified plasma membrane vesicles from Ehrlich ascites cells were dissolved in 2% sodium cholate, 1 mM dithiothreitol, 0.5 mM EDTA, a mixture which solubilized approximately 50% of the membrane protein. This solubilized protein fraction was further purified by a combination of ammonium sulfate precipitations, gel filtration, and DEAE-cellulose chromatography. A fraction containing approximately 15 Coomassie blue staining bands on sodium dodecyl sulfate gels was obtained. This material was reconstituted into liposomes, and preliminary results demonstrated transport of alanine and leucine dependent on a sodium gradient. In addition, an electrogenic gradient mediated by valinomycin-induced potassium diffusion seemed to stimulate alanine uptake further.

Alanine↗
PubMed1977

Biphasic effects of translational inhibitors on liver tyrosine aminotransferase.

Low doses of cycloheximide or emetine cause rat liver tyrosine aminotransferase activity to rise up to twice the control levels in 2 h. By contrast, in the same interval no changes, or only a slight decrease, are produced by either drug at high dosage. Adrenalectomised animals display the same pattern of response. High doses of either antibiotic virtually afford a complete inhibition of 14C-labelled amino acid incorporation into liver and plasma proteins, whereas no more than a 30% decrease is observed with low doses. When administered in the course of the induction by cortisol, high doses of inhibitor prevent any further change in tyrosine aminotransferase activity, stabilising it at the level already attained; low doses, while slightly affecting the synthetic phase evoked by cortisol, drastically interfere with the deinduction. Six hours after various doses of either inhibitor the tyrosine aminotransferase activity is markedly increased, this late effect being largely dependent on the presence of adrenals. The amino acid incorporating actitivy of the liver may exceed that of controls, as observed particularly after small doses of emetine.

Adrenalectomy↗
PubMed1977

Neutral amino acid transport systems of tissue culture cells.

We have studied the interactions among a varied group of neutral amino acids for uptake into two different animal tissue culture cell lines. 3T3 mouse cells and Chinese hamster ovary cells were used in these studies. The results showed that the affinities of the amino acids clustered into two groups, one including amino acids such as glycine, alanine, and alpha-aminoisobutyric acid and the other group included amino acids such as leucine and phenylalanine. The specificities and properties of these systems are similar to those described earlier for the Ehrlich ascites cell, System A (alanine-preferring) and System L (leucine-preferring). System A is highly concentrative, sensitive to sodium ion, and serves only poorly for exchange while System L is not very concentrative or sensitive to alkali metal ion, although it serves very well for exchange with endogenous amino acids. The kinetic parameters for several amino acids are reported and other properties of the transport systems are discussed.

Alanine↗
PubMed1977

Regulation of amino acid transport activity and growth rate of animal cells in culture.

Balb/3T3 mouse cells grown in cell culture contain the A and L systems for neutral amino acid transport. L-Alanine was used as a test amino acid for the A system and L-leucine for the L system. Transport activities for both transport systems are altered as the growth conditions for the cells are altered. When cell growth was arrested by allowing cells to approach confluency, or by the removal of serum or by the addition of protein synthesis inhibitors, System A transport activity decreased and System L activity increased significantly. The content of the cellular amino acids increased 2- to 3-fold whenever cell growth was arrested by the conditions stated above. Increased cellular amino acids, therefore, are associated with decreased transport activity of System A and increased activity of System L. Altering cellular amino acids by loading or depleting the cells produced the predicted responses for the rapidly exchanging L-system but System A was less responsive. It is possible that regulatory mechanisms operate for the A system other than the direct action of alterations in cellular amino acid levels. The implications of the amino acid transport activity changes observed here on various studies on the role of transport in cell growth regulation and malignant transformation are discussed.

Alanine↗
PubMed1977

Reconstitution of neutral amino acid transport from partially purified membrane components from Ehrlich ascites tumor cells.

Solubilized protein fractions have been obtained from plasma membranes of Ehrlich ascites cells either by extraction with 0.5% Triton X-100 or by extraction with 2% cholate. Partial purification of the solubilized protein fraction has been obtained by utilizing a combination of ammonium sulfate precipitation and column chromatography. Leucine-binding activity has been detected in the Triton X-100 solubilized membrane fraction. The leucine-binding activity was measured by equilibrium dialysis and was saturable with high levels of leucine or phenylalanine and is not strongly effected by alanine. These properties are similar to those previously identified as System L. In addition, the cholate extracted protein fraction was partially purified and reconstituted into liposomes. Sodium dependent uptake of alanine and leucine could be demonstrated in the reconstituted vesicles. Concentrative uptake was dependent upon a sodium gradient. A membrane potential produced by valinomycin mediated potassium diffusion in the presence of sodium also stimulated amino acid transport in reconstituted liposomes.

Alanine↗
PubMed1976

Transport of amino acids in intact 3T3 and SV3T3 cells. Binding activity for leucine in membrane preparations of ehrlich ascites tumor cells.

Transport of amino acids into 3T3 and SV3T3 (SV40 virus-transformed 3T3) cells was measured on glass cover slips. The 3T3 and SV3T3 cells contain both A (alanine preferring) and L (leucine prefferring) systems for neutral amino acid transport. Initial rates of uptake of amino acids are about twofold higher in SV3T3 than in 3T3 cells. Other parameters measured, however, do not indicate marked differences in the transport of amino acids by the two cell types. L-system amino acids, such as leucine, are subject to trans-stimulation in both cell lines, whereas A-system amino acids, such as alanine and glycine, are not. Leucine was transported to higher levels in confluent cells than in nonconfluent cells. Glycine, however, shows distinctly less transport activity as the cells become confluent. Ehrlich ascites cell plasma membranes were prepared and assayed for amino acid-binding activity. Leucine-binding activity was detected by equilibrium dialysis in Triton X-100-treated membrane preparations.

Animals↗
PubMed1976

Regulation of transport in mammalian cell culture.

The regulation of amino acid transport has been investigated in Balb/3T3 cells. Transport for neutral amino acids in animal tissues is carried out by two distinct systems. The transport activity of the A system (alanine preferring) is inhibited by high internal of substrate amino acids, a process termed trans-inhibition. In contrast, the L system transport activity is greatly stimulated by high internal levels of substrate, a phenomenon termed trans-stimulation. Regulation of amino acid transport in animal cells occurs by a repression-derepression mechanism or by a feedback inhibition or feedback stimulation process. The level of endogenous amino acids is shown to be important in the regulation of transport activity. Cells which are slow growing or quiescent have increased levels of endogenous amino acids, which in turn effect the transport activity. The A system transport activity is decreased in quiescent cells, whereas L system transport activity increases. Conditions which effect endogenous amino acid levels have an effect on transport activity. Feedback regulation of transport activity through the amino acid pool levels is another way animal cells can regulate transport activity.

Alanine↗
PubMed1975

Tryptophanase from Sphaerophorus funduliformis. Purification, molecular weight and subunit properties.

A crystalline tryptophanase can be obtained from extracts of Spaerophorus funduliformis using a heat treatment, hydroxyapatite chromatography and solubility in solutions of (NH4)2SO4 as a function of pH and temperature. The purified enzyme is homogeneous by several criteria. S. funduliformis tryptophanase has a specific activity of 11.5-13.5 and requires pyridoxal 5'-phosphate for enzymatic activity. Like other tryptophanases that have been studied, the S. funduliformis enzyme is a tetramer protein consisting of four apparently identical subunits. The native enzyme has a sedimentation coefficient of 11.2 S and a molecular weight of 244 000. In solutions of 5 M guanidine - HCl, 8 M urea, and sodium dodecylsulfate, at high pH or in the presence of thiols, the enzyme dissociates to 59 000 molecular weight species which are homogeneous by the criterion of weight. Peptide maps of the reduced holo-tryptophanase show one pyridoxal-containing peptide and, lacking agreement with the determined amino acid composition, suggest that the subunits of the enzyme contain a high degree of internal sequence homology.

Amino Acids↗
PubMed1975

Effect of uncouplers on "downhill" beta-galactoside transport in energy-depleted cells of Escherichia coli.

Galactoside permease-containing cells of Escherichia coli can be depleted of energy reserves so that the "downhill" cellular hydrolysis of o-nitrophenyl-beta-d-galactopyranoside (ONPG) no longer takes place. Treatment of such energy-depleted cells with proton-conducting agents such as carbonylcyanide m-chlorophenylhydrazone results in stimulation of ONPG transport. The same agents lower transport of non-energy-depleted cells towards the same levels that result from stimulation of the energy depleted cells. Of course, these agents prevent "uphill" accumulation against a concentration gradient under all conditions. Since uncouplers allow normal and energy-depleted cells to assume the same facilitated transport capability, these results lend support to the chemiosmotic hypothesis of Mitchell that comigration of charge is necessary for the transport of neutral galactosides. Our results imply that a potential favorable to transport is maintained by metabolism in non-energy-depleted cells, whereas an unfavorable potential is developed in the initial instant of time when energy-depleted cells are given ONPG.

Biological Transport, Active↗
PubMedDate not supplied

Urinary excretion of glycated albumin in insulin-dependent diabetic patients with normal urinary albumin excretion.

Glycation involves both circulating proteins, such as albumin, and structural proteins, such as the components of the glomerular basement membrane. A preferential excretion of glycated albumin (more anionic at physiological pH compared with unmodified plasma albumin) has been reported by some authors, but not by others. We therefore investigated the selectivity index (renal clearance of non-glycated albumin/clearance of glycated albumin) in 25 insulin-dependent diabetic patients with normal urinary albumin excretion and in 19 well-matched control subjects. The selectivity index was significantly higher in diabetic patients than in control subjects: 1.38 +/- 0.05 SEM vs 0.98 +/- 0.02, p less than 0.0001. This result is not consistent with a preferential urinary excretion of glycated albumin, at least in normoalbuminuric uncomplicated insulin-dependent diabetic patients.

Adult↗
PubMedDate not supplied

Factors associated with climacteric symptoms in women around menopause attending menopause clinics in Italy.

OBJECTIVE: To obtain data on correlates of climacteric symptoms in women around menopause attending menopause clinics in Italy. METHODS: Since 1997 a large cross sectional study has been conducted on the characteristics of women around menopause attending a network of first level menopause outpatient's clinics in Italy. A total of 66,501 (mean age 54.4 years) women are considered in the present paper. RESULTS: The odds ratios of moderate and severe hot flashes/night sweats were lower in more educated women and (for severe symptoms only) in women reporting regular physical activity. Depression, difficulty to sleep, forgetfulness and irritability tended to be less frequent in more educated women and (depression only) in women reporting regular physical activity. Parous women reported more frequently these symptoms. CONCLUSIONS: This large study confirms in Southern European population that low education, body mass index and low physical activity are associated with climacteric symptoms. Parous women are at greater risk of psychological symptoms.

Adult↗
PubMedDate not supplied

Local impairment of immunoreactivity in HIV-infected women with HPV-related squamous intraepithelial lesions of the cervix.

AIMS AND BACKGROUND: The aim of this study was to compare the local immune response in two groups of patients with high-grade cervical intraepithelial squamous lesions (SIL): one with HIV infection and the other with HPV infection alone. MATERIALS AND METHODS: 16 conization specimens (8 from HIV-infected and 8 from non-HIV-infected patients) of HPV-related, high-grade SIL were selected. The specimens from non-HIV patients were considered as controls. The total number of Langerhans cells, CD4 and CD8 cells present in 10 field areas (3.120 mm2) was recorded in each case. In HIV patients CD4 and CD8 peripheral counts were performed immediately before surgery. RESULTS: The CD4/CD8 ratio never exceeded 0.71, whereas the lowest ratio in controls was 0.81: this difference was statistically significant (P = 0.0009). The mean number of Langerhans cells was markedly reduced in the high-grade SILs in the HIV patients in comparison with controls (P = 0.001). The number of CD4 cells and the CD4/CD8 ratio correlated with the peripheral CD4 count (P = 0.001 and 0.02). CONCLUSIONS: In our study a marked local impairment of cervical immunoreactivity was observed, which may play a major role in the progression of these lesions in HIV-infected women.

Adult↗