PubMed Health⌕ Search

Biomedical subjects

F Bertini

Publications and source records attributed to F Bertini.

At least 73 records · Page 4Linked to original sources
PubMed1967

The use of formaldehyde-treated 131-I-albumin in the study of digestive vacuoles and some properties of these particles from mouse liver.

The trichloroacetic acid-soluble radioactivity released during incubation of mouse liver particles containing intravenously injected formaldehyde-treated (131)I-albumin consisted almost entirely of (131)I-iodotyrosine. The material was shown to be excreted into the medium and was not due to disruption of the particles by acid. Triton X-100 or the absence of sucrose in the medium inhibited hydrolysis of the particle-associated labeled protein. This inhibition was due to disruption of the digestive vacuoles and dilution of the protein and cathepsins in the suspending medium. These results and other experimental evidence strongly suggest that the (131)I-albumin-containing liver particles are digestive vacuoles. The results also establish that (131)I-albumin may be used to study these vacuoles. High concentrations of sucrose (1 M) inhibited degradation of intraparticulate protein. However, 1 M salts inhibited only the rate of the digestion. Sucrose had an inhibitory effect on a crude cathepsin preparation, and salts stimulated the activity when (131)I-albumin was used as substrate. The effect of high sucrose concentrations as an inhibitor of protein hydrolysis within digestive vacuoles was, therefore, most likely due principally to an inhibition of cathepsin activity within the vacuoles. The effect of salt was probably caused by a stimulation of both intra- and extra-particulate cathepsin activities, although 0.5-1.0 M KCl appeared to protect the particles.

Albumins↗
PubMedDate not supplied

The origin of some acid hydrolases of the fluid of the rat cauda epididymidis.

The activity of N-acetyl-beta-D-glucosaminidase (NAG, 60.1 units/mg protein) and of acid phosphatase (57.7 units/mg protein) in fluid from the cauda epididymidis formed without any contribution from the testis (fluid obtained from a perfused and isolated cauda epididymidis or from an epididymis whose corresponding efferent ducts had been ligated for 40 days) was significantly higher than the activity of these enzymes in normal fluid (39.6 and 41.2 units/mg protein, respectively). Arylsulphatase activity of the locally formed fluid (11.2 units/mg protein) was lower than that of normal fluid (74.1 units/mg protein). The rete testis fluid was relatively rich in arylsulphatase since the ratio of arylsulphatase to acid phosphatase activity was 17 times higher in this fluid than in locally formed fluid. It is concluded that the activities of NAG and acid phosphatase in normal fluid from the epididymis originate in the epididymal tissue, while most of the arylsulphatase activity comes from the testis.

Acetylglucosaminidase↗
PubMedDate not supplied

High-affinity sites for beta-D-galactosidase on membrane-bound vesicles isolated from rat epididymal fluid.

Glycosidases in rat epididymal fluid are secreted under androgen stimulation and possess receptors on the sperm surface. One of these enzymes, beta-D-galactosidase (gal), was found in the epididymal fluid as a soluble enzyme and also in a heterogeneous population of membrane bound vesicles (mbv). beta-D-Galactosidase was specifically localized to a subpopulation of larger, electron-dense mbv. The aim of this study was to analyze the high-affinity sites for gal on the membrane of mbv using two different methods: classical fluorometric assay (used in previous papers) and colloidal gold (20 nm) conjugated to gal as a marker in ultrastructural studies. beta-D-Galactosidase bound to mbv with high-affinity (Kd in a nanomolar range) are in a saturable form. Furthermore, 25 mM fructose-1,6-diphosphate (f-1,6-dip), a sugar that competes for the binding site, showed 50% inhibition of the binding. The gold conjugates were mostly observed on the surface of the large, electron-dense mbv but not on the small, electron-lucent mbv. Gold particles were also observed on the larger vesicles, but less frequently in the presence of f-1.6-dip. Larger mbv possesses high-affinity sites for gal on their membrane.

Animals↗
PubMedDate not supplied

Incorporation and intracellular hydrolysis of 131 I-albumin injected in rat testis.

A method of cell separation by enzymatic attack and filtration was applied after injecting the testes. The results indicated that in the case of the interstitial injections, the fraction rich in interstitial cells captures from 30 to 50 times more RISA than that rich in germinal cells, and from 10 to 20 times more than that rich in Sertoli cells. Following the intratubular injection, radioactivity incorporation was greatly reduced and there were no differences in RISA (radioactivity/mg of protein) among the cell fractions. It was concluded that Sertoli cells do not have in its apical side a phagocytic activity comparable to that of the interstitial macrophages and possibly they incorporate only a small amount of tracer by a process of moderate pinocytosis.

Animals↗
PubMedDate not supplied

First observations on enzymatic activity and protein content of vesicles separated from rat epididymal fluid.

Fluid of rat cauda epididymidis was obtained by flushing the duct with 0.25 mol l-1 sucrose in 0.01 mol l-1 Tris-HCl buffer pH 7.4. The fluid was centrifuged at 600 x g for 15 min and the sperm free supernatant was centrifuged at 47,000 x g for 1 h. The sediments observed with the electron microscope consisted of a heterogeneous population of membrane-bound vesicles similar to those seen in the intact organ. In the sediment containing the vesicles the activity of beta-galactosidase was mostly unavailable for the substrate showing a high degree of latency: the activity became soluble after a treatment with 0.5% saponin. The activity of N-acetyl-galactosaminadase instead, was mainly available for the substrate and soluble in buffer containing 0.6 mol l-1 KCl. It was then inferred that beta-galactosidase is located inside vesicles with no or little affinity for the membrane, while N-acetylglucosaminadase is bound to the external surface of vesicles. Supernatants and precipitates from suspensions of vesicles in buffered 0.5% saponin were analysed for proteins by gel electrophoresis. The electrophoretic patterns of the sediments were very different from those of supernatants and showed a number of bands greater than that of the latter. The vesicles are believed to arise from the epididymal epithelium, but their physiological role is unknown.

Animals↗
PubMedDate not supplied

Vesicles in rat epididymal fluid. Existence of two populations differing in ultrastructure and enzymatic composition.

Glycosidase activity is very high in rat epididymal fluid as a consequence of the secretory capacity of the epithelium. The mechanism of this secretion is, so far, unknown. Membrane-bound vesicles with activity of beta-galactosidase and N-acetyl-beta-D-glucosaminidase were previously isolated by us from rat epididymal fluid. We report here the existence of two populations of epididymal vesicles separated by centrifugation in a sucrose gradient. They were found to differ in isopicnic equilibrium, size, ultrastructure, and enzymatic activity. Seven days after castration the protein content and specific activities of both enzymes were found decreased in the fractions containing the vesicles. A role in enzyme secretion by the epididymal epithelium is suggested for each vesicle population.

Acetylglucosaminidase↗
PubMedDate not supplied

Purification and characterization of beta-galactosidase from rat epididymal fluid.

Beta-galactosidase from rat epididymal fluid was purified by a combination of chromatographic techniques and precipitation with ammonium sulphate. Specific activity of the enzyme in the final precipitate was 18 times greater than in the original fluid, and it was practically free of N-acetyl-beta-D-glucosaminidase. A single major band was seen when the precipitate was analysed by sodium dodecylsulphate polyacrylamide gelectrophoresis (SDS-PAGE). The activity of the purified enzyme has an optimum at pH 4.5, and the temperature optimum is around 45 degrees C. The activity was inhibited by p-chloromercuribenzoic acid and ions such as Cd(II), Co(II), Cu(II) and Ag(I). Lactose does not appear to be a substrate for this enzyme.

Animals↗
PubMedDate not supplied

Affinity sites for beta-glucuronidase on the surface of human spermatozoa.

Glycosidases secreted by the epididymis become bound to the surface of spermatozoa during their transit through the epididymal duct. They are believed to play a role in mammalian fertilization. In the present report, we demonstrate that beta-glucuronidase binds to the surface of ejaculated human spermatozoa with high affinity and in a saturable manner. The binding is Ca(2+)-independent, inhibited by either mannose-6-phosphate, phosphomannan fragments from the yeast Hansenula holstii and alpha-mannosidase from the Dictyostelium discoideum, suggesting that phosphomannosyl receptors are involved in the recognition of the enzyme. The catalytic site of the enzyme is not involved in the binding. The localization of the beta-glucuronidase binding-sites is restricted to the surface of the sperm head. These results suggest that the spermatozoa could be the target for glycosidases present in the seminal plasma.

Alkaline Phosphatase↗