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G Zanetti

Publications and source records attributed to G Zanetti.

At least 181 records · Page 10Linked to original sources
PubMed1983

FAD analogues as mechanistic and 'binding-domain' probes of spinach ferredoxin-NADP+ reductase.

The native flavin, FAD, of spinach ferredoxin--NADP+ reductase, has been replaced by a number of FAD analogues with modifications of the isoalloxazine ring system. The apoenzyme binds 8-mercapto-FAD in its thiolate anion form and 6-hydroxy-FAD in its neutral form. These results are consistent with classification of this enzyme as a dehydrogenase/electron transferase, an ascription originally made on the basis of its physiological function and in common with other properties of this class, e.g. stabilization of the neutral flavin semiquinone. The chemical reactivity toward methylmethanethiolsulfonate of the 8-mercapto-FAD . enzyme clearly shows that the flavin 8-position is exposed to solvent. On the other hand, the lack of reactivity with the 2-thio-FAD . enzyme indicates that the pyrimidine subnucleus of the flavin is buried within the protein molecule. The seven modified flavins examined all support NADPH--ferricyanide reductase activity, the catalytic velocity being directly proportional to the redox potential of the flavin. No such linear free energy relationship was found between redox potential and activity with ferredoxin or iodonitrotetrazolium as acceptor.

Catalysis↗
PubMed1982

Preparation of apoprotein from spinach ferredoxin-NADP+ reductase. Studies on the resolution process and characterization of the FAD reconstituted holoenzyme.

1. Ferredoxin-NADP+ reductase resolved into apoprotein and flavin by incubation with 2.5 M CaCl2 at pH 7.5 and 2 degrees C. Essential factors to recover a reconstitutable apoprotein are dithiothreitol, glycerol and guanidine/HCl. The apoprotein is stable for at least a week at -20 degrees C. 2. The release of the prosthetic group from the protein by the Ca2+ ions is a multi-step process. Three different effects of these ions are identifiable: (a) a rapid 20-25% inhibition of catalytic activity, probably caused by an increase in the ionic strength of the medium; other cations can produce it as well; (b) a slower induction of a conformational change in the protein which causes complete loss of activity and exposure to solvent of the flavin moiety; the FAD is finally released from the protein; (c) complete conversion of FAD to FMN, which blocks reconstitution to holoenzyme, caused by the well-known hydrolytic action of Ca2+ ions on the pyrophosphate bridge of FAD. 3. Binding of FAD by the apoferredoxin-NADP+ reductase is very rapid and it is complete in a few minutes even at 0 degrees C. A Kd of 3.4 X 10(-9) M has been determined by fluorescence titration. The reconstituted holoenzyme has catalytic activity, spectral and fluorescence properties nearly identical to the native enzyme. The gel electrophoresis and isoelectrofocusing patterns of the two enzymes are very similar. Removal of factors from the apoprotein solution such as dithiothreitol and glycerol promotes the appearance of protein aggregates.

Apoenzymes↗
PubMed1981

Brunner's gland hamartoma with incipient ductal malignancy. Report of a case.

A duodenal tumor mainly composed of Brunner's glands was surgically resected in a 54-year-old man complaining of hematemesis and melena. Histologic examination of the specimen revealed a lobular pattern of either ducts or glandular acini, with Paneth cells; smooth muscle fibers, fat tissue and well formed vascular channels were seen in the stroma. These aspects are more suggestive of a hamartomatous rather than an adenomatous lesion. Moreover, the epithelium in some ducts showed early malignant transformation, which is a feature never observed in previous reports.

Brunner Glands↗
PubMed1981

Sarcomatous variant of Wilms' tumor. A light and immunohistochemical study of four cases.

Four cases of infantile sarcomatous renal tumors are reported. Rhabdomyoblastic differentiation was investigated in these tumors by the immunoperoxidase method using antimyoglobin sera. Rhabdomyoblastic cells were found in 2 cases and in a metastasis of one case in which the primary tumor was composed by undifferentiated cells negative for myoglobin stain. The histogenesis of these neoplasias is discussed, and it is suggested that they are a sarcomatous variant of Wilms' tumor.

Child, Preschool↗
PubMed1980

Familial study on the "double pre-beta lipoproteinemia" and on a polymorphic pattern of apolipoprotein E (EIV "variant" pattern) from human very low density lipoproteins (VLDL).

The familial aggregation of the "double pre-beta lipoproteinemia" (double-PBL) and of a "variant" pattern of the apolipoprotein E (EIV) from human very low density lipoproteins (VLDL) was investigated. Although double-PBL does not discriminate between blood relatives (BR) and controls (C), the former can be clearly distinguished from the latter as they have significantly higher VLDL-TG/TG and Apo-E/C-peptide ratios, implying that the proportion of "remnant" particles is significantly higher in the BR than in the C. Family subjects carrying apolipoprotein E enriched particles as the BR with the double-PBL phenomenon, exhibit significantly higher serum and LDL cholesterol levels as compared to C subjects with "single pre-beta lipoproteinemia" (single-PBL). The familial distribution of the apo-EIV "variant" pattern suggests an autosomal dominant transmission. The significantly higher prevalence of the double-PBL phenomenon in the group of EIV positive (+) as compared to the EIV negative (-) subjects suggests, but does not prove, that these two factors are possibly causally related. The clinical importance of such a finding, which seems to be substantiated in the light of recent experimental observations, is discussed.

Adult↗
PubMed1980

Serum lipids, "double pre-beta lipoproteinemia," and distribution of the apo-very-low density (VLDL) lipoprotein peptides in hypothyroid patients before and after substitution therapy.

Thirty-six hypothyroid patients had total thyroidectomy for cancer. Thirty of them were studied before and during hormone replacement therapy, 1-1 .1 microgram/kg triiodothyronine (T3) per day. Mean treatment period was 90 days. During treatment mean serum total cholesterol (TC), triglycerides (TG), the ratio of TC to TG in very-low-density lipoprotein and the prevalence of the "double pre-beta VLDL lipoproteinemia" (Double-PBL) were significantly reduced as compared to the pretreatment values. The VLDL peptides were separated bysoelectric focusing (IEF) in polyacrylamide gel. The relative content of apolipoprotein E (arginine-rich apoprotein) and the E/C-peptides ratio were significantly reduced after T3 therapy. On the contrary, the content of C11 peptide was significantly increased. Apoprotein E was positively correlated with serum TC. The proportion of the intermediate density lipoprotein fraction, evaluated by agarose gel electrophoresis, consistently decreased after treatment. The results of our study suggest that thyroid hormones affect the metabolism of remnant lipoproteins.

Adult↗
PubMed1980

[Precursors of atherosclerosis in childhood: Pordenone study. Transverse and longitudinal study of arterial blood pressure (BP) in a group of boys and adolescents (author's transl)].

Mean systolic BP values gradually and significantly increase from the infancy to the adolescence. On the contrary, diastolic BP does not change significantly. No sex differences were found for mean values of both systolic and diastolic BP. The results of the longitudinal study (two years follow-up) have shown, for the two sexes, a significant increase in the systolic BP values, which parallels the ponderal growth. In particular, the greatest increment of the values was observed in the triennium 12-14 year, that is around the puberty.

Adolescent↗
PubMed1980

[Study of the precursors of atherosclerosis in childhood: the Pordenone study. Longitudinal behaviour of total cholesterol and serum triglycerides in school children (author's transl)].

In a total number of approximately 500 school-children, belonging to a suburban area around Pordenone (Northern Italy), aged 6-9-12-15, we have performed a two years follow-up on serum TC and TG. As for serum TC, a progressive decrease of mean TC levels at the two rescreenings was observed. We cannot explain such trend, unless we admit that some dietary modification has been introduced in the families, although no dietary advices were given. However the observed decrease of the TC levels, makes clear that a single serum TC determination is not sufficient in order to define the lipid profile of a given subject. Unlike TC, serum TG tend to increase with the age. The "longitudinal" behavior of TC and TG is similar for both males and females.

Adolescent↗
PubMed1979

Modification of arginyl residues in ferredoxin-NADP+ reductase from spinach leaves.

Reaction of spinach leaves ferredoxin-NADP+ reductase (NADPH:ferredoxin oxidoreductase, EC 1.6.7.1) with alpha-dicarbonyl compounds results in a biphasic loss of activity. The rapid phase yields modified enzyme with about 30% of the original activity, but no change in the Km for NADPH. Only partial protection against inactivation is provided by NADP+, NADPH and their analogs, whereas ferredoxin affords complete protection. The reductase inactivated to 30% of original activity shows a loss of about two arginyl residues, whereas only one residue is lost in the NADP+-protected enzymes. The data suggest that the integrity of at least two arginyl residues are requested for maximal activity of ferredoxin-NADP+ reductase: one residue being located near the NADP+-binding site, the other presumably situated in the ferredoxin-binding domain.

Aldehydes↗
PubMed1979

Lipid--lipoprotein composition in hypercholesterolemic children and their parents.

In 13 hypercholesterolemic children, re-screened for serum cholesterol after a 1-year interval, hypercholesterolemia was confirmed in only 61.5% of the cases. A tentative explanation seems to be the statistical principle of regression towards the mean. The lipid--lipoprotein analysis showed that serum and LDL cholesterol concentrations in the 13 hypercholesterolemic children and their parents were significantly higher compared to controls (children and parents). At re-screening, hyper-LDL cholesterolemia was present in only 8 of the 13 children (61.5%); 4 cases exhibited hyper-HDL cholesterolemia (30.7%). The high prevalence of the parents repeating the lipoprotein abnormality and the electrophoretic pattern found in the propositi (children) confirms the familial aggregation of the hypercholesterolemic states (hyper-LDL and hyper-HDL cholesterolemia). In conclusion the results of our study stress the importance of determining the lipid--lipoprotein composition, rather then merely evaluating total serum cholesterol in order to make a correct diagnosis of the hypercholesterolemic state. It should also be emphasized that the lipoprotein disturbances and their familial aggregation may be detected early in childhood, suggesting that the familial screening for risk factors of atherosclerosis should be done at pediatric age.

Adolescent↗