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Biomedical subjects

G Mezzetti

Publications and source records attributed to G Mezzetti.

At least 19 recordsLinked to original sources
PubMed2006

[Intraoperative quick parathyroid hormone assay in thyroid surgery: preliminary experience on 36 cases].

Through the analysis of our preliminary experience on 36 consecutive cases of thyroid surgery, we assessed the feasibility of the rapid intraoperative assay of the intact parathyroid hormone (iPTH) as predictive risk factor of hypocalcemia versus seric calcium level on the first post-operative day to select the patients eligible to an early discharge. Furthermore, we managed to determine if iPTH level during thyroid surgery could point out the cases in which parathyroid autotransplantation is necessary, as the macroscopic evaluation of the parathyroid gland's viability is inadequate.

Adult↗
PubMed2006

[The actual role of bilateral neck exploration in the treatment of primary hyperparathyroidism].

Surgery is the only curative treatment for primary hyperparathyroidism (pHPT). Surgical exploration is recommended for all patients with biochemically documented pHPT and signs or symptoms of the disease. Some patients are asymptomatic, others have subtle symptoms that disappear after parathyroid surgery. Felix Mandl successfully performed the first parathyroidectomy in 1925, using a bilateral neck exploration (BNE) with examination of all four glands and this remained the procedure of choice for pHPT into the 1990s. As over 80% of pHPT cases are due to a single parathyroid adenoma, many authors have questioned the need of BNE and have proposed directed unilateral approaches, termed "mini-invasive parathyroidectomies". The aim of this report is to define which is the actual role of the conventional surgical approach to pHPT.

Diagnostic Techniques, Surgical↗
PubMed2000

[Pseudosarcoma of the urinary bladder. Report of a case].

A case of myofibroblastic pseudosarcomatous tumor of the bladder occurred in a patient previously submitted to TURB is reported. Aim of this investigation is to demonstrate, on the basis of the literature, the importance of histopathology in the diagnosis of bladder pseudosarcoma, since endoscopical and radiological methods can erroneously show a neoplasm. A 65-year-old male patient with hematuria, submitted to ultrasonography and cystoscopy, revealed a bladder superficial papillary formation. A TURB was performed and the histological study showed a superficial bladder cancer (T1-G1-2). After a second hematuria episode with stranguria a new bladder formation was diagnosed and resected; the histological study revealed a bladder pseudosarcoma. The absolute benignity of the lesion and the slight difference in the symptomatology between urothelial carcinoma and pseudosarcoma are underlined. Furthermore, the importance of histopathology to obtain an accurate diagnosis is stressed. The difficulty of a preoperative diagnosis without histopathological examination is pointed out.

Aged↗
PubMed1988

Polyamines and the catalytic domain of protein kinase C.

The effect of polyamines on the catalytic domain of protein kinase C from rat brain was investigated. It was found that the addition of spermine strongly inhibited phosphorylation activity toward histone H1 as substrate. This tetramine, at millimolar concentrations, was most potently effective while triamines and diamines were almost uneffective, therefore the inhibitory action appeared to be structural specific. Data shown here suggest that polyamine by interacting with the catalytic domain of the enzyme may contribute to its regulation.

Animals↗
PubMed1988

1,25-Dihydroxycholecalciferol-dependent calcium uptake by mouse mammary gland in culture.

Mammary explants from pregnant mice cultured in the presence of lactogenic hormones express their differentiated function by producing milk components in vitro. In the present paper radioactive calcium uptake was studied in the mammary gland during terminal differentiation, when lactogenesis was initiated. Under these conditions a relevant accumulation of calcium in the tissue was clearly demonstrable. We have characterized the calcium uptake by the tissue as a saturable and energy dependent process. When 1,25-dihydroxycholecalciferol [1,25-(OH)2D3], the major calcium regulator hormone, was added to the incubation medium the secosteroid strongly stimulated this process by increasing the maximal velocity without significantly altering the Michaelis Menten constant (Km). Detectable increases in calcium uptake could be measured after the explants were cultured with 1,25-(OH)2D3 for 30 min, with the response continuing to increase sharply over time and reaching a plateau at 3 h. The increase was not affected by the presence of actinomycin D or cycloheximide suggesting that the 1,25-(OH)2D3 stimulation of calcium uptake may be independent of de novo protein synthesis. These results provide evidence for early and direct action of the hormonal form of vitamin D in affecting calcium transport across membranes of functionally differentiated epithelial cells of the mammary gland.

Animals↗
PubMed1987

Inhibitory action of polyamines on protein kinase C association to membranes.

Physiological activation of protein kinase C requires the interaction of this enzyme with cellular membranes [Nishizuka (1986) Science 233, 305-312]. In the present work a reconstituted system of protein kinase C and human inside-out erythrocyte vesicles was utilized to study the effect in vitro of naturally occurring polyamines on the activation process of protein kinase C. The active membrane-associated complex was conveniently determined by its ability to bind radioactive phorbol ester with an exact 1:1 stoichiometry. The association reaction of the enzyme to membrane was rapid, being complete within 1 min at 25 degrees C. The addition of polyamines, particularly spermine, greatly decreased in a dose-dependent manner the amount of protein kinase C bound to membranes (i.e. in the activated form). The effect observed was quite specific, since it was dependent on the chemical structure of the polyamine and it was manifest at micromolar concentrations of the polycation; the order of potency was spermine greater than spermidine greater than putrescine. A characterization of this effect is presented and possible physiological implications are discussed.

Binding Sites↗
PubMed1987

Phorbol esters, but not the hormonal form of vitamin D, induce changes in protein kinase C during differentiation of human histiocytic lymphoma cell line (U-937).

Human histiocytic lymphoma cells (U-937) undergo similar differentiation when incubated with the phorbol ester 12-0-tetradecanoyl phorbol-13-acetate (TPA) and 1,25-dihydroxycholecalciferol. In this action, TPA somehow implicates calcium-sensitive and phospholipid-dependent protein kinase (protein kinase C), which is rapidly and significantly affected by this inducer. On the contrary, 1,25-dihydroxycholecalciferol in its differentiating action does not involve protein kinase C thus suggesting that the secosteroid induces monocytic differentiation possible through a different mechanism of that of phorbol ester.

Antibodies, Monoclonal↗
PubMed1987

1,25-Dihydroxycholecalciferol receptor regulation in hormonally induced differentiation of mouse mammary gland in culture.

Mammary explants from pregnant mouse cultured in the presence of insulin, cortisol, and PRL express their differentiated function by producing milk proteins such as casein. Sucrose density gradient analysis of high salt extract of cultured explants showed the presence of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3 specific binding activity sedimenting at 3.3 S. Specific 1,25-(OH)2D3 binding activity in mammary explants varied as a function of the hormonal milieu in culture. The highest activity was found in explants cultured in the presence of insulin, cortisol, and PRL, whereas only a marginal activity was present in explants cultured with insulin. The comparison of 1,25-(OH)2D3 binding activity in explants cultured with insulin and with the three hormone combination by Scatchard plot analysis indicated that the synergistic actions of insulin, cortisol, and PRL increased the number of 1,25-(OH)2D3 specific binding proteins as much as 6-fold; however, the affinity constant of the binding protein was relatively constant in the two systems. Time course studies showed that the increase in 1,25-(OH)2D3 binding activity was detectable as early as 12 h after the addition of cortisol and PRL to insulin-primed explants. The increase was inhibited by the presence of actinomycin D and cycloheximide, suggesting that the hormonal stimulation of 1,25-(OH)2D3 binding activity involves both transcriptional and translational process. These results indicate that insulin, cortisol, and PRL stimulate the specific 1,25-(OH)2D3 binding activity during the induction of mammary functional differentiation when milk protein synthesis takes place.

Animals↗
PubMed1986

Modulation of cyclic nucleotide-independent protein kinase from chick intestine by naturally occurring polyamines and mucopolysaccharides.

Chick duodenal mucosa contains an endogenous factor which is capable to inhibit selectively a homologous polyamine-sensitive protein kinase. The inhibitor was partially purified and characterized, and it was found to contain typical mucopolysaccharidic components. Glycosidases digestion studies, selective degradation analysis and spectrophotometric titrations with metachromatic dyes indicated that the inhibitor preparation contained two major moieties identified as heparin-like and heparan sulfate-like structures. In chick intestine the inhibitor was specific for polyamine-sensitive protein kinase since selectively interacted with it and was inert towards other cAMP-independent and cAMP-dependent protein kinases. The inhibitory effect of the endogenous factor was counteracted by naturally occurring polyamines such as spermine. The order of potency of various polyamines was: spermine greater than thermine much greater than spermidine much greater than diamines. The release of inhibition by addition of physiological concentrations of spermine was also apparent when using cytosolic proteins as endogenous phosphate acceptors. These results suggest that a possible role of polyamine in the regulation of polyamine-sensitive protein kinase in the intestine is to protect the enzyme from the inhibitory action of endogenous heparinoids.

Animals↗
PubMed1986

Loss of plasma-generated vitamin D-binding protein in explants of mouse mammary gland in culture.

Selective removal of 6S plasma-generated vitamin D-binding protein from mouse mammary gland was achieved by a simple tissue culture technique. This binder was totally diluted out from the mammary explant in a time-dependent manner within 2 days of tissue culture, allowing conditions most suitable for 1,25-dihydroxyvitamin D3-receptor studies. In comparison with other methods to eliminate 6S plasma-generated vitamin D-binding protein the present technique is easy, simple and does not require the use of other vitamin D metabolites to study differential displacement of 1,25-dihydroxyvitamin D3 binding to the heterogeneous binding sites.

Animals↗
PubMed1985

Polyamine-sensitive protein kinase from chick intestinal mucosa.

A cyclic nucleotide-independent protein kinase which phosphorylates preferentially acidic proteins such as casein or phosvitin was isolated from cytosol of chick duodenal mucosa. The enzyme was purified more than 633 fold to apparent homogeneity by ammonium sulfate fractionation, column chromatography on DEAE-cellulose, phosphocellulose, hydroxylapatite and by sucrose density gradient centrifugation. The native enzyme has a molecular weight of 131 000 as measured by gel filtration. The enzyme is a complex protein containing three polypeptides of molecular weight of 39 000, 36 000 and 27 000. It behaves as a complex throughout its purification and gel filtration but its components are readily separated by electrophoresis in denaturing buffer. The 27 000 molecular weight band was selectively autophosphorylated when the enzyme was incubated in the presence of [gamma-32P]ATP. When casein was used as substrate, physiological concentrations of naturally occurring polyamines such as spermine and spermidine markedly stimulated enzyme activity. However with phosvitin as substrate polyamines were strong inhibitors of the enzyme activity. This contrasting effect on intestinal kinase activity was also apparent using cytoplasmic proteins as endogenous phosphate acceptors. A characterization of this differential effect is presented and some possible physiological implications are discussed.

Animals↗
PubMed1984

1 alpha, 25-dihydroxycholecalciferol and human histiocytic lymphoma cell line (U-937): the presence of receptor and inhibition of proliferation.

Human histiocytic lymphoma cells (U-937) contain high affinity binding protein for 1 alpha, 25-dihydroxycholecalciferol. The Kd (0.2 nM) and sedimentation coefficient on sucrose gradients (3.7 S) are similar to those reported for 1 alpha, 25-dihydroxycholecalciferol receptor in other tissues. This secosteroid added to the culture was able to inhibit cell proliferation in a dose dependent manner. Differentiation-associated properties such as phagocytic ability, C3 rosette formation, positive reaction for alpha- naphtyl acetate esterase as well as electron microscopy examination indicate that 1 alpha, 25-dihydroxycholecalciferol induces in vitro monocyte-macrophage differentiation in this monoblast-like cell line.

Calcitriol↗
PubMed1984

Peptide-chain initiation in duodenal mucosa of rachitic chicks after 1 alpha-,25-dihydroxycholecalciferol administration.

The post-ribosomal fraction of chick duodenal mucosa contains Met-tRNAMetf-binding protein(s) that behaves like the eukaryotic initiation factor (eIF-2) in protein synthesis. The binding activity of cytosol protein can be measured by retention of the radioactive complex formed on a nitrocellulose membrane. Complex-formation requires Met-tRNAMetf and GTP or guanosine [beta, gamma-methylene] triphosphate, and is inhibited by aurintricarboxylic acid. The ternary initiation complex thus formed can bind to ribosomal particles from chick intestine. By sucrose-density-gradient centrifugation, [35S]Met-tRNAMetf was found to bind exclusively to 40S and not to 60S ribosomal subunit particles. In the duodenal mucosa of rachitic chicks the ability of the cytosol proteins to promote the binding of Met-tRNAMetf to ribosomal particles via ternary-complex formation is detectably increased by 3 h after injection of 1 alpha,25-dihydroxycholecalciferol, the active form of vitamin D. Cholecalciferol and ergocalciferol under the same experimental conditions failed to stimulate Met-tRNAMetf-binding activity.

Animals↗
PubMed1983

Peptide chain initiation and analysis of in vitro translation products in rat heart undergoing hypertrophic growth.

The cytosol fraction of rat heart contains an initiation factor-like protein component that behaves like the eukaryotic factor (eIF-2) in binding [35S]-Met-tRNAf in the presence of GTP. The ternary initiator complex thus formed is able to bind to heart ribosomes. In the left ventricle of rat heart undergoing hypertrophic growth upon constriction of the descending aorta, the [35S]-Met-tRNAf binding activity of the cytosol protein(s) gradually increases after the operation from 40%, at 48 h, to 90%, at 10 days; slightly lower activation is seen in the [35S]-Met-tRNAf binding to ribosomes. Polysomal RNA is extracted from sham operated and hypertrophic rat hearts and translated in a reticulocyte cell free system. The translation products are analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis: no clearcut qualitative difference is observed in the pattern obtained from sham operated and hypertrophic animals.

Animals↗
PubMed1982

Spermine-binding protein and polyamine metabolism in duodenal mucosa of chick embryo.

The spermine-binding activity of a cytosolic protein from chick intestine increases during embryogenesis and in the first week of life. Ornithine and S-adenosylmethionine decarboxylase activities assayed under the same experimental conditions increase showing a maximum at day 18 and 20 respectively. The behaviour of either enzyme activity is reflected in the pattern of duodenal polyamine concentration measured during the same period. The possibility that duodenal spermine-binding protein may be correlated with spermine accumulation in the tissue is discussed.

Adenosylmethionine Decarboxylase↗