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F Ortolani

Publications and source records attributed to F Ortolani.

At least 37 records · Page 2Linked to original sources
PubMed1993

Glutaraldehyde-induced D-band pattern of type II collagen fibrils as revealed by negative staining.

A study was carried out on the negative staining band patterns (1% phosphotungstic acid (PTA) in phosphate buffer, 0.1 M, pH 7.4) exhibited by type II collagen fibrils after treatment with glutaraldehyde (5% in phosphate buffer 0.1 M, pH 7.4) and a comparison was made with the negative staining patterns of glutaraldehyde-fixed type I collagen fibrils. A characteristic D-band pattern was observed for type II collagen fibrils. The gap/overlap ratio was unusually low, with a 0.40 long gap zone and a 0.60 D overlap zone. This banding displayed eleven major light bands instead of the fifteen bands per period observed in the type I collagen patterns. On comparing the two types of microdensitograms, seven negative peaks (light bands) coincided and among them were the peaks corresponding to the N-terminal and C-terminal telopeptide regions. Although less numerous, the negative peaks of type II fibril traces were broader and more marked than those of type I microdensitograms and this feature accounts for the greater stain exclusion capacity of the type II fibrils. This is consistent with the larger quantity of hydroxylysines in type II collagen and, perhaps, with the more abundant hydroxyprolines.

Animals↗
PubMed1993

Correlation between amino acid composition and ultrastructural features of type I and type II native collagen fibrils.

The D-band patterns of native collagen fibrils negatively stained with phosphotungstic acid (PTA) of type II (bovine cartilaginous nasal septum) and type I (bovine reticular dermis) were compared in order to find differences and correlate these with the different amino acid composition of these two collagen types. By analyzing the averaged microdensitograms of the two types of D-banding, differences in type II fibrils were observed: a) the overlap zone was more electron-transparent on average; b) there was a different hierarchy of positive peaks (intraperiod dark bands) b1, b2 and c1; c) a more marked negative peak (intraperiod light band X3) corresponded to the C-terminal extrahelical region; d) there was a different D-location of one negative peak (intraperiod light band Y3). At the same time, different values were calculated for type I and type II tropocollagen molecule total amino acid "bulkiness" (molecular volume/length ratio) and "hydrophobicity", on the basis of literature-reported data. Consistency was found between these values and the differences of the two types of D-banding. The assumption of a correlation between the above two amino acid parameters and negative staining band patterns was supported.

Amino Acids↗
PubMed1993

"GA-banding": a new terminology and a study of the glutaraldehyde-induced band pattern of type I collagen fibrils.

The negative staining D-band patterns of glutaraldehyde-reacted collagen fibrils were compared to those of fresh collagen fibrils. Negative staining was obtained by using 1% phosphotungstic acid (PTA) diluted in phosphate buffer 0.1 M, pH 7.4. The stain was dripped onto grids where native type I collagen fibrils, isolated from bovine dermis, were collected. Ultrastructural pictures were digitized to form microdensitometric traces. The glutaraldehyde-induced patterns showed fifteen light bands (micrographs) or negative peaks (microdensitograms), whose D-locations were constant and characteristic. In order to make this ultrastructural feature a precise reference parameter, these bands were called "GA-bands" and numbered. When comparing this averaged microdensitogram with that of negatively stained fresh fibrils, peak "GA1" and peak "GA7" were observed to correspond to peak "X2" (known as N-terminal telopeptide region) and peak "X3" (known as C-terminal telopeptide region) respectively, while there was no correspondence between the other peaks of the two traces. It means that the regions where preexistent crosslinks exist are unaffected by interaction with glutaraldehyde, while in the other regions, where new glutaraldehyde-crosslinks occur, the band pattern modifies. The unchanged D-location of peaks "GA1" and "GA7" leads to the conclusion that the D-shortening induced by glutaraldehyde is not due to shifting of tropocollagen molecules but to changes in their orientation with respect to fibril long axis or in secondary-tertiary structure of collagen.

Animals↗
PubMed1991

Negative staining and genesis of D-periodicity in native collagen fibrils.

An investigation was carried out on the mechanism which gives rise to the banding exhibited by collagen fibrils after negative staining. The negative staining (phosphotungstic acid) band patterns of native collagen fibrils (type I), isolated from calf reticular dermis, were compared with computer-drawn band patterns. The stimulations were based on the primary structure of bovine type I collagen, the "quarter stagger" molecular packing and different conformations of telopeptides. The results suggest that in negative staining, the stain exclusion effect depends on both spatial factors and water repelling factors being the "bulkiness" (molecular volume/length ratio) as well as the hydrophobicity of the amino acids of alpha 1 (I) and alpha 2 (I) chains directly involved. No final conclusion could be drawn about the contribution of positive staining to negative staining. Improvements in the simulations were achieved when the telopeptides were shaped according to particular conformational models.

Animals↗
PubMed1990

Histological examination of gastric mucosal lesions induced by isolation in saline and cimetidine treated rat.

It has been recently pointed out that the most reliable method of assessment of gastric mucosal injury is the microscopic examination of the tissue. The purpose of the present paper was, therefore, to study the histological features of gastric lesions induced by a six week isolation in rats. It has also been investigated whether a two week treatment, beginning four weeks after isolation, with cimetidine 80 and 160 mg kg-1 p.o. daily could protect the gastric mucosa. In saline treated rats, histological examination of haemorrhagic areas showed that both surface epithelium and gastric pits were damaged or even completely absent with a consequent surfacing of subepithelial vessels. Damage extended deeply into the gastric glands with evidence of necrotic cells in the corpus and fundus. Simultaneous occurrence of the process of restitution was evident. Cimetidine partially lessened the severity of damage and appeared to favour the restitution processes.

Animals↗
PubMed1989

Collagen fibril surface structures: freeze-etching data and computer modelling.

In order to investigate the correlation between primary structure and surface profile of collagen, freeze-fractured and deep-etched (dehydrated) collagen fibrils have been compared with a fibril model built directly from the amino acid sequence. The model appeared to be almost identical to the freeze-etched collagen fibril with respect to the most relevant features, such as the gap-overlap ratio and the location of the two main intraperiod ridges (X3 and X2). However, it did not show the minor ridges observed in the gap zone (X1 and Y1), thus suggesting that these structures, although consistently present in collagen fibrils, may in fact be due to post-translational modifications or to non-collagenic material adhering to the fibril.

Amino Acid Sequence↗
PubMed1988

Localization of different alcian blue-proteoglycan particles in the intervertebral disc.

A histochemical investigation was carried out on proteoglycans of bovine intervertebral disc. Samples obtained from the "annulus fibrosus" (A.F.) and "nucleus pulposus" (N.P.) were treated with Alcian blue (AB) diluted in solutions of MgCl2 at critical electrolyte concentrations (CEC); some samples were incubated in testicular hyaluronidase before AB treatment. At least four types of elongated AB-proteoglycan particles were recognized: a) in A.F. lamellae and N.P., 1 nm rod-like particles were arranged orthogonally to the collagen fibrils and spaced at a distance equivalent to the fibril D-period (Figs. 1-5); b) within the A.F. lamellae, other 16-20 nm particles formed a close network among the collagen fibrils (Figs. 1,2,3,5); c) in the A.F. interlamellar crevices, 30-50 nm leaf-like particles were present (Fig. 6); d) in the N.P.Z., 20-30 nm leaf-like particles formed a wide-mesh (Fig. 4). The alcianophylic particle sizes suggest they may correspond to proteoglycan monomers in the A.F. lamellae and mostly proteoglycan aggregates in A.F. interlamellar crevices and N.P.. Both alcianophylia degrees at MgCl2 CEC solutions and enzymatic susceptibility indicate the presence of chondroitin sulphate and keratan sulphate and that the large particles in the A.F. interlamellar crevices are the keratan sulphate richest proteoglycans. The features of the observed AB-proteoglycan particles are consistent with previous morphological data reported for other tissues as well as some biochemical data for the intervertebral disc and may be correlated to the composite mechanical properties of this tissue.

Alcian Blue↗