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Biomedical subjects

G Zanetti

Publications and source records attributed to G Zanetti.

At least 127 records · Page 7Linked to original sources
PubMed1992

[Metastasis and markers].

Tumor markers are antigens which can be associated with certain malignancies. A variety of markers have been demonstrated in genitourinary tumors. The best known examples are human chorionic gonadotropin (bHCG) and alpha-fetoprotein (AFP) for testicular tumors, prostatic acid phosphatase (PAP) and prostatic specific antigen (PSA) for prostatic cancer. The plasma levels of these substances are influenced by the tumor mass and therefore by the tumor stage. Markedly elevated plasma levels can be demonstrated when metastases are present, although a few patients without metastases may elaborate abnormal amount of markers. The removal of the primary tumor leads to a fall to normal levels: a still increased level indicates residual primary tumor or the presence of metastases. Measurements of markers are also of value in estimating the effects of medical treatment and in detecting local or distant recurrences.

Acid Phosphatase↗
PubMed1992

[Use of ultrasound-guided percutaneous nephrostomy before and after ESWL: 4 years of experience].

We evaluated the usefulness of percutaneous nephrostomy in 1700 patients treated for reno-ureteral stones by extracorporeal shock wave lithotripsy (SWL). Out of this group 81 patients (5.8%) underwent echo-guided percutaneous nephrostomy (EPCN): the procedure has been performed in local anesthesia in 38% of the cases (31 pts) before SWL and in 62% (50 pts) after. The majority of EPCN were carried out for the presence of acute or chronic ureteral obstruction with echographic evaluable dilation of pyelocaliceal system when retrograde ureteral manipulations failed or were considered unsuitable. EPCN before SWL was performed because of ureteral stone and uncomplicated pyelocalyceal dilation (19 pts); ureteral stone, pyelocaliceal dilation and fever > 38 degrees C (3 pts); ureteral stone, pyelocalyceal dilation and functional IVP exclusion (5 pts); pyelic stone in solitary kidney (1 pts); ureteral stones in pregnancy (2 pts). EPCN after SWL was performed because of uncomplicated, persistent pile-up (31 pts); ureteral pile-up complicated by fever and colics (9 pts); ureteral obstructing fragments (2 pts); double J obstruction by stone dust (3 pts); persistent ureteral pile-up around double J (3 pts); anuria in solitary kidney (1 pt). Out of the patients who underwent EPCN before SWL 13% were stone free and without drainage at discharge, 77% had passable stone fragments at discharge and drainage has been taken out at 15-30 days check up, 10% had unbroken stone and underwent with drainage to ureterolithotripsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1992

[Postoperative impotence].

Increasing interest has developed in recent years about the preservation of sexual function after urological surgery. The pelvic plexus which is formed by parasympathetic visceral efferent preganglionic fibers that arise from the sacral center provides autonomic innervation to the corpora cavernosa. The cavernous nerves emerge from the pelvic plexus and then travel along the posterolateral portion of the seminal vesicle and prostate and then along the membranous urethra. The preservation of the nerve supply of the corpora during urological and pelvic procedures is of vital importance to preserve potency.

Erectile Dysfunction↗
PubMed1991

Mechanistic studies on Azospirillum brasilense glutamate synthase.

The reaction mechanism of Azospirillum brasilense glutamate synthase has been investigated by several approaches. 15N nuclear magnetic resonance studies demonstrate that the amide nitrogen of glutamine is reductively transferred to 2-oxoglutarate in an irreversible manner with no release of the transferred ammonia group into the medium. Identical results were obtained using thio-NADPH and acetylpyridine-NADPH, which are shown to be less efficient substrates of the enzyme than NADPH. Similarly, no exchange of the ammonia group being transferred with exogenous ammonium ion was observed during catalysis. The glutamate formed as the product of the iminoglutarate reduction was determined to be in the L configuration. The enzyme was also found to catalyze, under anaerobic conditions, the exchange of the 4proS H of NADPH with solvent both in the absence and in the presence of 2-oxoglutarate and glutamine. The reductive half-reaction is therefore a reversible segment of the overall irreversible amidotransferase reaction. 15N NMR studies also showed that the enzyme does not catalyze glutamate dehydrogenase/oxidase reactions or any observable glutaminase activity under neutral (pH 7.5) conditions. Glutaminase activity was also not observable with the reduced enzyme alone or in the presence of D-glutamate (a competitive inhibitor of glutamate synthase with respect to 2-oxoglutarate, with a Ki of about 11 microM) or with the oxidized enzyme in the presence of 2-oxoglutarate, D-glutamate, or NADP+. These data confirm species-dependent differences of A. brasilense glutamate synthase with respect to the enzyme from other sources.

Ammonia↗
PubMed1991

The kinetic mechanism of the reactions catalyzed by the glutamate synthase from Azospirillum brasilense.

The reactions catalyzed by glutamate synthase from Azospirillum brasilense have been investigated by a combination of absorption spectroscopy, steady-state kinetic measurements and experiments with stereospecifically labelled substrate. The data show that both L-glutamine-dependent and ammonia-dependent reactions of the glutamate synthase from A. brasilense follow an identical two-site uni-uni bi-bi kinetic mechanism, in which the enzyme is alternately reduced by NADPH and oxidized by the iminoglutarate formed on addition of ammonia to the C2 of 2-oxoglutarate. The spectroscopic experiments support the involvement of the enzyme chromophores (flavins and iron-sulfur centers) in both reactions. Finally, using stereospecifically labelled NADPH, we showed that the enzyme from Azospirillum is specific for the transfer of the 4S hydrogen of NADPH. During the catalysis of both L-glutamine-dependent and ammonia-dependent reactions, this hydrogen atom equilibrates with the solvent. The data obtained with glutamate synthase from A. brasilense, a diazotroph, differ significantly from those regarding the ammonia-dependent reaction of other glutamate synthases. The ammonia-dependent activity of glutamate synthase from Azospirillum is not physiologically significant, representing only a segment of the overall physiological L-glutamine-dependent activity and requiring the enzyme flavins and iron-sulfur centers. Finally, the data are not consistent with the hypothesis [Geary, L. E. & Meister, A. (1977) J. Biol. Chem. 252, 3501-3508] that the small subunit of glutamate synthase is endowed with a glutamate-dehydrogenase-like activity.

Ammonia↗
PubMed1991

Probing the role of lysine 116 and lysine 244 in the spinach ferredoxin-NADP+ reductase by site-directed mutagenesis.

Two mutants of the spinach ferredoxin-NADP+ reductase (FNR) were constructed, expressed by using a heterologous expression system previously described (Aliverti, A., Jansen, T., Zanetti, G., Ronchi, S., Herrmann, R. G., and Curti, B. (1990) Eur. J. Biochem. 191, 551-555), and purified to homogeneity. The mutant enzymes FNR-Lys116Gln and FNR-Lys244Gln were similar to the wild-type enzyme in the physicochemical properties measured; however, both enzymes showed a lower activity. Steady-state kinetic analyses and NADP+ binding measurements of the mutant proteins have revealed that the Lys116Gln enzyme had a catalytic efficiency (kcat/KmNADPH) 500-fold lower than that of the wild-type enzyme, and its interaction with NADP+ was greatly impaired. The Lys244Gln enzyme instead had almost the same kcat in the ferricyanide reductase reaction as the wild-type enzyme, while higher values of KmNADPH and Kd for NADP+ were observed. Thus, protein engineering has enabled us to define the role of Lys-116 and Lys-244 in ferredoxin-NADP+ reductase; whereas Lys-244 contributes to the stabilization of the Michaelis complex, the Lys-116 side chain plays an important role also in the further steps of the catalytic cycle, because both Km and kcat are highly affected by the mutation.

Binding Sites↗
PubMed1991

Identification of Lys116 as the target of N-ethylmaleimide inactivation of ferredoxin:NADP+ oxidoreductase.

Oxidized ferredoxin:NADP+ oxidoreductase (FNR) was slowly and irreversibly inactivated by N-ethylmaleimide. Complete protection against inactivation was afforded by saturating concentrations of NADP+. In the presence of NADPH, a rapid inhibition of the enzyme ensued; however, this inhibition was found to be reversible. In the tryptic map of the flavoprotein, modified with N-ethyl[2,3-14C]maleimide in oxidizing conditions, a unique radioactive peptide was found. Its sequence comprised residues 110-117 of the enzyme: Lys116 was shown to be the residue alkylated by N-ethylmaleimide. It is noteworthy that the same residue of FNR was found to be modified by 5-dimethylaminoaphthalene-1-sulfonyl(dansyl) chloride at the putative NADP(H)-binding site [Cidaria, D., Biondi, P. A., Zanetti, G. & Ronchi, S. (1985) Eur. J. Biochem. 146, 295-299]. Furthermore, the data reported here demonstrate that the sulfhydryl groups of FNR are not involved in enzyme inactivation by N-ethylmaleimide.

Amino Acids↗
PubMed1991

An unusual case of hepatic tumor.

A case is reported of a large hepatic tumor in a patient aged 71. Preoperative diagnostic techniques, including echography, CT and angiography, did not provide sufficient criteria for a precise diagnosis. The mass was removed with an extended right hepatectomy with no particular physiopathological consequences. Histological analysis revealed that this was a metastasis from a melonoma of the choroid, operated on 17 years previously.

Aged↗
PubMed1991

[Treatment of ureteral calculi with extracorporeal lithotripsy. Comparison between the original Dornier HM3 and the modified lithotriptor].

From January 1985 till June 1989, 222 patients with ureteral stones, underwent ESWL treatment. 109 patients were treated with the original Dornier HM3 under general or epidural anaesthesia and 113 patients were treated with the modified Dornier HM3 under anglosedation. 156 stones were in the upper ureter, 15 in the middle ureter, 51 in the lower ureter. We performed a total of 269 ESWL treatments. Out of 109 patients treated with the original HM3 and 113 patients treated by the modified HM3 12 (11%) and 28 (24.7%) needed, respectively, two or more ESWL sessions. In 89.9% and 88.5% of the patients, respectively, has been performed an ureteral manipulation before the treatment to push up or to localize the stone. The treatment was unsuccessful in 10 patients of whom 3 underwent anterograde lithotripsy by percutaneous access, 4 transureteral lithotripsy and 3 surgery. At three months the percentage of patients stone free was as follows: original HM3 patients 88% modified HM3 patients 92.9%. The extracorporeal lithotripsy is now-day the treatment of choice for the ureteral stone without any limitation, due to the stone localisation. The clinical use of modified HM3 on ureteral stones didn't low our success rate, but increased the shock wave out of session.

Humans↗
PubMed1990

Expression in Escherichia coli of ferredoxin:NADP+ reductase from spinach. Bacterial synthesis of the holoflavoprotein and of an active enzyme form lacking the first 28 amino acid residues of the sequence.

A cDNA clone for the preprotein of spinach ferredoxin:NADP+ reductase has been modified to allow the expression in Escherichia coli of the mature flavoprotein form the lacks the transit peptide. An expression vector, pFNR1, was constructed by subcloning the fragment into the plasmid pDS12/RBSII, SphI. In the crude extracts of transformed cells after induction, two active holoproteins of 35 kDa and 32 kDa, respectively, were found. The 32-kDa protein, purified by immunoaffinity chromatography, was found to lack the first 28 residues of the spinach protein sequence and to have a methionine as the N-terminal residue instead of Val29. A new expression plasmid, pFNR2, was obtained by in vitro mutagenesis of the codon GTG for Val29 to the synonymous GTT; in this case, only the 35-kDa protein was expressed by transformed cells. Both the 35-kDa and 32-kDa enzymes were purified and characterized. All the properties analyzed of the cloned 35-kDa enzyme were very similar to those of the spinach flavoprotein. The 32-kDa form showed the same catalytic efficiency of the spinach enzyme as a diaphorase but its interaction with oxidized ferredoxin was partially impaired.

Amino Acid Sequence↗
PubMed1990

Structure-function relationship in spinach ferredoxin-NADP+ reductase as studied by limited proteolysis.

Studies of limited proteolysis on purified ferredoxin-NADP+ reductase with various proteases were performed in the presence and absence of the flavoprotein ligands. Both the diaphorase and the ferredoxin-dependent activities of the enzyme were followed as well as the proteolytic pattern in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with further characterization of the polypeptides produced. These experiments revealed that only two regions of the flavoprotein are susceptible to the attack of the proteases used: (a) the N-terminal chain which can be cleaved only up to Lys35 and (b) the sequence segment 235-250. It can be inferred that these regions are on the surface of the protein molecule and presumably have a very flexible conformation adaptable to the protease active site. The deletion of the N-terminal region up to Thr36 of the native reductase (Mr 35,000) produced a truncated form (Mr about 31,000) which had full diaphorase activity but lost the capacity to catalyze the ferredoxin-dependent reaction. Proteolytic cleavage at the 235-250 segment of the sequence yielded a nicked protein (Mr about 30,000 by gel filtration; 23,000 plus 7,000 in denaturing electrophoresis) devoid of both activities. Protection by the flavoprotein ligands implies that the 23-35 region of the sequence is part of the binding site for ferredoxin and the 235-250 polypeptide segment is in the NADP(+)-binding site.

Amino Acid Sequence↗
PubMed1990

Structural studies on the subunits of glutamate synthase from Azospirillum brasilense.

The amino acid composition and the N-terminal sequences of the two dissimilar subunits of glutamate synthase from Azospirillum brasilense have been determined along with the sequences of selected CNBr peptides. Comparison of our data with those available for Escherichia coli glutamate synthase revealed an overall good homology between the enzymes from the two sources. This is more evident for the heavy subunits where the highly conserved N-terminal sequence containing Cys-1, suggests that this region may be involved in catalysis. However, it appears that the light subunits are different with respect to both their amino acid composition and their N-terminal region, suggesting that the latter may not be part of the enzyme active site. Finally, an extinction coefficient at 444 nm of 62.66 +/- 4.61 mM-1.cm-1 was determined.

Amino Acid Sequence↗
PubMed1990

Urinary NAG excretion after anesthesia-free extracorporeal lithotripsy of renal stones: a marker of early tubular damage.

Second generation lithotripters require a higher number of shocks per session as well as an increased rate of secondary treatments for complete stone disintegration compared to the original spark gap lithotripter. The clinical relevance of biological side effects caused by such treatment are less known. We evaluated urinary excretion of N-acetyl-glucosaminidase (NAG) before and after lithotripsy in 50 patients treated with a low pressure spark gap lithotripter (Dornier HM3) and in 36 patients treated with a piezoelectric lithotripter (Wolf Piezolith 2200) in an attempt to evaluate their side effects on renal tissue. The urinary excretion of NAG increased after both spark gap lithotripsy using the modified HM3 and piezoelectric lithotripsy. These changes may be associated with slight tubular damage that would occur after anesthesia-free lithotripsy in patients subjected both to a high number of shocks and to secondary treatments.

Acetylglucosaminidase↗
PubMed1990

Cytokeratin-immunoreactive cells of human lymph nodes and spleen in normal and pathological conditions. An immunocytochemical study.

The occurrence and the distribution of cytokeratin (CK)-immunoreactive reticulum cells in a series of normal and pathological human lymph nodes and spleens are documented. The immunoreactive cells exhibit morphological and immunophenotypic features of so-called fibroblastic reticulum cells, with or without myoid differentiation. They invariably co-express vimentin and, to a lesser extent, desmin and muscle-specific actin isoforms. These CK-immunoreactive cells are apparently a normal subpopulation of reticulum cells, being detectable from the early stages of spleen and lymph node development. They are distributed mainly in the paracortical and medullary regions of the lymph nodes and at the periphery of the white pulp in the spleen. Their number and distribution are highly variable in different neoplastic and non-neoplastic pathological conditions but the changes are not disease specific. CK-immunoreactive reticulum cells are easily identifiable in both frozen and fixed lymphoid tissue and in cytological smears of fine-needle aspirates, provided that monoclonal antibodies whose spectrum of reactivity includes cytokeratins 8 and 18 are used. The awareness of the occurrence of CK-immunoreactive cells in normal lymphoid tissues is of particular relevance in the search for micrometastatic foci using anti-CK antibodies.

Adult↗