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Biomedical subjects

G Zanetti

Publications and source records attributed to G Zanetti.

At least 163 records · Page 9Linked to original sources
PubMed1987

Interaction between photosystem I and ferredoxin. Identification by chemical cross-linking of the polypeptide which binds ferredoxin.

Ferredoxin has been effectively cross-linked to photosystem I complex by treatment of purified particles or thylakoids with N-ethyl-3-(3-dimethylaminopropyl)carbodiimide, a zero-length cross-linker which stabilizes protein-protein electrostatic interactions. Analysis of photosystem I polypeptide composition after such a treatment showed a specific decrease of the 20-kDa subunit and the appearance of a new component of about 42 kDa which was recognized by the anti-ferredoxin antibody. Cross-linking of ferredoxin to thylakoids allowed the membrane preparation to photoreduce cytochrome c without requiring exogenous ferredoxin, whereas photosystem I particles purified from treated thylakoids were inactivated in the NADP+ photoreduction activity. From these results, it can be inferred that the polypeptide of 20 kDa is the photosystem I subunit which interacts with ferredoxin during the photosynthetic electron transport.

Carbodiimides↗
PubMed1987

Acute and chronic effects of dextro-thyroxine on pituitary thyroid axis and on reverse triiodothyronine production in euthyroid subjects.

Serum levels of thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3) and TSH were measured in euthyroid subjects after a single dose of 4 mg D-thyroxine (DT4) or of 0.25 mg L-thyroxine (LT4). The same parameters and TSH response to TRH were also evaluated in 7 dyslipidemic patients before and after one month of treatment with 6 mg DT4. T4 levels increased about 165% at h 4 after DT4 and only 47% after LT4; T3 levels remained unchanged until h 10 both after DT4 and after LT4; rT3 levels increased almost 179% after DT4 and only 32% after LT4. TSH levels decreased about 30% after both DT4 and LT4. In the long term study similar variations of the same parameters were observed: basal TSH levels decreased and TSH response to TRH was inhibited in all patients but one; T4 levels increased 62%, T3 levels increased 35%, while rT3 levels increased 545%. Our results show that: both acute and long-term treatment with DT4 suppress TSH secretion; DT4 both in acute and in long-term administration, is preferentially dealogenated in the alaninic ring with production of rDT3, instead of in the phenolic ring with production of DT3. This may contribute to explain its lower metabolic activity.

Adult↗
PubMed1987

Apolipoprotein E polymorphism, serum lipids and occurrence of "double pre-betalipoproteinemia' (DPBL) in subjects from two different populations.

The association between apolipoprotein E phenotype and the presence of 2 electrophoretic populations of very low density (VLDL) lipoproteins from human sera, double pre-beta(VLDL)lipoproteinemia (DPBL), was studied in 2 groups of subjects, one from Italy and one from Finland. In both populations the prevalence of DPBL was significantly higher in subjects with E4/4 and E4/3 phenotypes than in the other phenotypes not containing the E4 isoprotein. This finding suggests that the presence of a structural variant of the apo E protein, the isoprotein E4, may be causally related to the appearance of DPBL phenomenon.

Adolescent↗
PubMed1986

Cystic nephroma in children. Report of a case.

A case of cystic nephroma is described in a 20-month-old female. The diagnosis of this rare renal pathologic lesion is essentially based on its pathologic features. The treatment consisted of nephrectomy followed by a brief course of chemotherapy. The literature is reviewed with regard to the pathologic features and treatment of this lesion, which has a favorable prognosis.

Female↗
PubMed1986

Properties of rabbit liver glutathione reductase reconstituted with FAD analogs.

The FAD binding site of rabbit liver glutathione reductase has been explored by reconstitution of the apoprotein with several FAD analogs modified in the isoalloxazine ring. The apoglutathione reductase binds the p-quinoid form of 8-mercapto-FAD, suggesting that the protein stabilizes a negative charge in the -N1-C2 = O position of the pyrimidine subnucleus. The main absorption peak in the visible spectrum of the 8-mercapto-FAD-enzyme is at 585 nm; treatment of the reconstituted protein with reducing agents of disulfide groups induces a reversible hypochromic shift of 20 nm of the peak. Thus, in 8-mercapto-FAD-glutathione reductase, the oxidation-reduction state of the active center disulfide can be monitored. The chemical reactivity toward methylmethanethiosulfonate and iodoacetamide of the 8-mercapto-FAD-enzyme shows that the flavin position 8 is freely accessible to solvent. However, position 2 is buried within the protein molecule as judged from the lack of reactivity of the 2-thio-FAD-enzyme with methylmethanethiosulfonate. Hydrogen peroxide reacts slowly with both 2-thio-FAD-enzyme and native glutathione reductase, yielding inactive enzyme with a modified spectrum; the prosthetic group is still protein bound. Differences in the active site of the rabbit liver enzyme compared to the human erythrocyte glutathione reductase are evidenced by use of FAD analogs: the peaks of reconstituted liver enzymes are shifted about 10 nm toward longer wavelengths.

Animals↗
PubMed1986

Epithelial inclusions and Tamm-Horsfall protein in paranephric lymph nodes. A light microscopy and immunocytochemical study.

An unusual histological pattern made up of tubular structures and clusters of apparently epithelial cells floating within sinusoidal deposits of Tamm-Horsfall (TH) protein was observed in several lymph nodes removed with renal tumours (3 Wilms' tumours, 1 cystic nephroma) and pathological but non neoplastic kidneys (2 cases of reflux nephropathy). Masses of TH protein, often containing desquamated tubular epithelial cells, were also found in tubules, interstitium and perivascular lymphatic vessels of the resected kidneys, but never in the tumour tissue. Lymph nodes draining renal tumours, although moderately enlarged because of reactive hyperplasia and TH protein deposits, did not contain metastases. Our findings suggest that these inclusions originate from renal tubular epithelium and are transported to paranephric lymph nodes along with TH protein.

Child↗
PubMed1986

Rhabdomyosarcoma of the diaphragm in a 4-year-old girl.

Rhabdomyosarcoma of the diaphragm is a very rare entity, especially in childhood. A case of a 4-year-old girl is reported. The mass extended completely into the abdominal cavity, causing problems in differential diagnosis with other abdominal masses. Dimensions, structure and limits of the mass had been outlined by several examinations (IVP, sonography, CT, angiography), but its actual nature could not be shown, so that a surgical exploration was needed. A pedunculated, well-capsulated mass, arising from the left diaphragmatic portion, was found. A complete excision could be performed and histologic findings were compatible with rhabdomyosarcoma of the diaphragm.

Abdominal Neoplasms↗
PubMed1985

The NADP+-binding site of ferredoxin-NADP+ reductase. Sequence of the peptide containing the essential lysine residue.

The flavoprotein ferredoxin-NADP+ reductase is inactivated and loses its ability to bind NADP+ during covalent modification of a lysine by 5-dimethylaminonaphthalene-1-sulfonyl chloride (dansyl chloride) [Zanetti, G. (1976) Biochim. Biophys. Acta 445, 14-24]. The substrate NADP+ gives almost complete protection against inactivation and modification. These observations are extended in this report by the characterization of an octapeptide containing the dansyl-lysine which was isolated by high-performance liquid chromatography from tryptic digests of protein modified with radiolabeled reagent. The amount of this peptide was severely reduced in protein modified in the presence of NADP+. The sequence of the dansyl-peptide, only partially obtained by Edman degradation, was completed by analysis of the fragments resulting from thermolysin digestion of the purified tryptic dansyl-peptide. Thus, the octapeptide containing the essential lysine residue has the following sequence: H2N-Ser-Val-Ser-Leu-Cys-Val-Lys-Arg-COOH. A comparison with corresponding sequences of other known NADP+-dependent dehydrogenases is attempted.

Amino Acid Sequence↗
PubMed1985

Degeneration of the corticospinal tract following portosystemic shunt associated with spinal cord infarction.

The clinicopathological aspects of a case of myelopathy that followed the creation of a surgical porto-caval shunt for hepatic cirrhosis and oesophageal varices are presented. Degeneration of the lateral corticospinal tracts associated with diffuse bilateral ischaemic changes of the spinal gray matter and proliferation of Alzheimer type 2 glia in the brain and brain stem were the most prominent findings. The association of corticospinal tract degeneration and ischaemic lesions of spinal gray matter in absence of any anatomical cause of spinal cord infarction suggests that a modification of the spinal blood flow caused by creation of portosystemic shunts might be the basic pathogenetic mechanism of this complication of severe liver disease.

Brain↗
PubMed1985

Purification and characterization of glutamate synthase from Azospirillum brasilense.

Growth conditions for Azospirillum brasilense Sp6 were devised for maximal expression of glutamate synthase. The enzyme levels were largely affected by the type and concentration of the nitrogen source. A 10-fold increase in the synthesis of the enzyme was observed at a limiting concentration of ammonia. The enzyme was purified to homogeneity by a procedure which was fairly rapid and allowed a good recovery of enzyme (30%). Azospirillum glutamate synthase is a complex iron-sulfur flavoprotein with a stoichiometry of 1 flavin adenine dinucleotide:1 flavin mononucleotide:8 Fe:8 S per protomer with a molecular weight of 185,000. The protomer is composed of two dissimilar subunits with molecular weights of 135,000 and 50,000. Kinetic parameters were determined. Km values for NADPH, 2-oxoglutarate, and L-glutamine were 6.25, 29, and 450 microM, respectively. The optimum pH was about 7.5. Complete reduction of the enzyme under anaerobic conditions was obtained either by NADPH (in the presence of a regenerating system) or dithionite or by photochemical reduction (in the presence of EDTA and 5-deazariboflavin). No stable long-wavelength intermediates were observed.

Amino Acids↗
PubMed1985

The double pre-beta very low density lipoprotein lipoproteinemia (DPBL): a new dyslipoproteinemic state.

A new dyslipoproteinemic state, characterized by two populations of very low density lipoprotein particles giving the electrophoretic appearance of two pre-beta bands, the double pre-beta lipoproteinemia, is described. Based upon the lipid and apoprotein composition, it can be inferred that the slow moving pre-beta component is probably made up of remnant very low density lipoprotein particles; the absence of apo B 48 in the very low density lipoprotein fraction in these subjects rules out the intestinal origin of this remnant. Clinical interest in the double pre-beta lipoproteinemia relates to its potential atherogenicity; in fact it seems to be causally associated with such pathological conditions as hypothyroidism, uremia and dialysis, which are frequently accompanied by clinical complications of atherosclerosis. Double pre-beta lipoproteinemia also shows familial aggregation. Six years follow-up in a large family kindred has demonstrated that the family members carrying the double pre-beta lipoproteinemia, develop an incidence of coronary and cerebrovascular events higher than that of family members without the double pre-beta lipoproteinemia.

Apolipoproteins B↗
PubMed1984

A cross-linked complex between ferredoxin and ferredoxin-NADP+ reductase.

The water-soluble carbodiimide, N-ethyl-3-(3-dimethylaminopropyl)carbodiimide was found to effectively cross-link ferredoxin to ferredoxin-NADP+ reductase. The covalent complex has a stoichiometry of 1 mol of ferredoxin per mol of the reductase. The flavoprotein moiety of the cross-linked complex maintains most of its diaphorase activity and more interestingly has gained the capacity to catalyze the NADPH-cytochrome c reaction without addition of free ferredoxin in the assay mixture. Furthermore, the cross-linked complex binds NADP+ with a Kd = 88 microM at an ionic strength of 0.02 M. These results show that a ternary complex among the reductase and its substrates can be formed, suggesting that the binding sites for ferredoxin and the pyridine nucleotides are distinct. The bound ferredoxin can interact with cytochrome c; the iron-sulfur cluster of the cross-linked complex is shown to be reduced under anaerobic conditions by NADPH and to be required for the catalysis of the NADPH-cytochrome c reductase reaction. The cross-linked complex, added to thylakoids inhibited by the antibody against the reductase, catalyzes the H2O-cytochrome c photoreduction, which suggests that the ferredoxin moiety of the complex can interact with its electron donor in the photosynthetic chain. Restoration of NADP+ photoreduction requires the addition of free ferredoxin.

Carbodiimides↗
PubMed1984

Effects of dextro-thyroxine, a preparation almost free of levo-thyroxine, on thyroid function, serum lipids and apolipoprotein A-I in "double pre-beta lipoproteinemia".

Eight subjects, belonging to a large family kindred repeatedly showing the electrophoretic pattern of the "double pre-beta lipoproteinemia", were studied. In seven of them thyroid function, serum lipids and apolipoprotein A-I were determined before and after treatment with dextro-thyroxine, preparation almost free of levo-thyroxine. In most of the patients, total-T4 levels and free-T4 Index were in the lower normal range, but basal TSH levels and the TSH response to TRH were normal. Dextro-thyroxine was effective in reducing both serum total cholesterol and triglycerides, but the percentage decrease in serum triglycerides was definitely greater than that of serum total cholesterol. This marked, unexpected hypotriglyceridemic effect is similar to that observed in a group of obese, hypertriglyceridemic hypothyroid patients treated with levo-thyroxine. Besides serum total cholesterol and triglycerides, the VLDL cholesterol/triglycerides ratio and the electrophoretic "slow moving" pre-beta component were also significantly reduced after treatment, suggesting that dextro-thyroxine can remove efficiently "remnant" VLDL particles from the plasma. Following dextro-thyroxine therapy, the relatively low pretreatment values of apolipoprotein A-I were significantly increased, being restored to normal.

Adult↗
PubMed1984

Chemical modification of histidine residues in rabbit liver glutathione reductase.

The role of histidine residues of glutathione reductase from rabbit liver was investigated by chemical modification with both ethoxyformic anhydride and dansyl chloride. At least four histidine residues were concomitantly modified by ethoxyformic anhydride at pH 6; both the GSSG reductase and the transhydrogenase activities were inhibited to the same extent. Dansyl chloride inactivated the enzyme showing pH-independence in the range 7-9. About 2.6 moles dansyl were incorporated in the protein 80% inactivated at pH 8, whereas at pH 7 a lower amount of labelling was found. Nearly complete reactivation of the inactivated enzyme could be obtained by incubation with hydroxylamine, which released all the acid-labile bound dansyl. Of the two histidine residues modified, only the slower reacting residue seems essential for activity. The modification with dansyl chloride will allow the identification of the histidine residues modified, in the sequence of the protein.

Animals↗