[Show abstract][Hide abstract] ABSTRACT: Circadian secretion of melatonin was measured in melancholic depressed patients (n = 9) and age- and sex-matched healthy control patients (n = 9). The mean age of the depressed patients was 29 years, i.e. younger than in most earlier studies, and a drug-free interval of 3 weeks preceded the investigations. Melatonin secretion was similar in depressed patients and healthy subjects with no significant differences at any of the time points, thus not confirming earlier studies in which depressed patients were found to have lower melatonin levels than control patients. The discrepancy between our result and earlier studies may be explained by different patient characteristics such as age, duration of illness, previous treatment, and alcohol intake. It is conceivable that a diminution of nocturnal melatonin secretion in depressed patients might only occur during the long-term course of the depressive illness and/or its pharmacological treatment.
Full-text · Article · Sep 1997 · Psychiatry Research
[Show abstract][Hide abstract] ABSTRACT: Fragments from the amino end of the pα1(I) chain of sheep procollagen were isolated after digestion with cyanogen bromide (peptide CB 0.1) or collagenase (peptide Col 1). Peptide CB 0.1 contains the whole precursor-specific segment which consists mainly of a collagenous and a noncollagenous domain. It is primarily the noncollagenous portion which is retained in Col 1. Physical properties of these fragments were studied by circular dichroism and analytical ultracentrifugation. Peptide Col 1 showed no tendency to aggregate in solution whereas peptide CB 0.1 formed trimers at low temperature. This association occurred in the collagenous region and gave rise to a triple-helical structure. The noncollagenous portion in CB 0.1 had no or only little effect on the coil to triple-helix conversion. Peptide Col 1 showed a high frictional coefficient indicating an elongated shape. It resembled in its CD spectrum proteins containing aperiodic structural elements and β structure. Reduction of the five disulfide bridges in Col 1 caused unfolding of the fragment. Only small and reversible changes were induced in native Col 1 by guanidine hydrochloride, dodecyl sulfate, LiCl, elevated temperature, and extreme pH. High concentrations of trifluoroethanol produced a sharp transition from the native structure of Col 1 to a conformation with a considerable proportion of α helix. This type of conformational change was more readily achieved with reduced Col 1. A loss of native conformation was also obtained by tryptic cleavages of bonds in two disulfide loop regions of Col 1. Proteolytic removal of about 30% of the peptide sequences from the amino and carboxyl end of Col 1, however, produced little change in the CD spectrum, indicating the presence of randomly coiled structures in the terminal portions of the molecule.
[Show abstract][Hide abstract] ABSTRACT: A collagenous peptide T1X was isolated from a tryptic digest of the insoluble matrix of calf skin. The peptide consists of two identical polypeptide chains each with a length of 72 amino acid residues joined by a cross-link. Absorption spectra obtained from hydrazone and azine derivatives of T1X indicated that the peptide contains an aldol-type of cross-link (X). The sequence of 23 amino acid residues in the amino-terminal region was determined as Glx-Tyr-Glu-Ala-Tyr-Asp-Val-X-Ser-Gly-Val-Ala-Gly-Gly-Gly-Ile-Ala-Gly-Tyr-Hyp-Gly-Pro-Ala. This sequence overlaps the previously described amino-terminal sequence of alpha1 (III) chain obtained from pepsin treated, insoluble type III collagen. Thus, the present data demonstrate a nonhelical segment of 14 amino acid residues in type III collagen important for cross-linking.
No preview · Article · Jan 1977 · Hoppe-Seyler's Zeitschrift für physiologische Chemie
[Show abstract][Hide abstract] ABSTRACT: Antibodies to calf or sheep skin procollagen, to its consitituent pα1(I) and pα2 chain or to peptide fragments from the aminoterminal region in pα1(I) were studied by radioimmune assays using various 1250-labeled antigens. The highest antibody response was obtained against the globular region in pα1(I). The adjacent precursor-specific collagenous and non-helical domains may modulate the antigenicity of the globular determinants but are themselves only weak antigens. No antigenic determinants were detected in the pα2 chain. Antibodies to pα1(I) chain did not cross-react with pα2 or pα1(III) chains.Antisera against the globular procollagen peptide showed no difference between the peptide and procollagen indicating that the release of the globular region from pα1(I) by collagenase is not accompanied by large conformational alterations. Complete cross-reaction was observed between precursor-specific peptides obtained from calf or sheep procollagen. Reduction and S-carboxymethylation of the five disulfide bridges in the globular region largely destroyed antigenicity. However, a minor fraction of the antibodies against the native peptide could still react with the unfolded peptide.Determinants recognized in this reaction are apparently shared by the native and unfolded peptide and were stable towards trypsin. On the other hand, antibodies prepared against the reduced and alkylated procollagen peptide did not react with the native peptide.The data indicate that that globular regions in pα1(I) chain possesses both conformational and sequential determinants which differ considerably in their immunogenic capacity.
[Show abstract][Hide abstract] ABSTRACT: A cross-linked fragment (peptide T1X) with a molecular weight of 13,000 could be isolated from a tryptic digest of insoluble type III collagen of calf skin. Peptide T1X was conjugated on to bovine serum albumin by glutaraldehyde and used for immunization of rabbits. The antisera reacted in passive haemagglutination and radioimmune assay with peptide T1X, type III collagen and its constituent alpha1(III) chain. Little or no reaction was observed with type I collagen and alpha1(I) chain. While rabbit antisera to neutral salt-soluble type III Collagen also showed a strong binding for 125I-labelled peptide T1X much less reaction was observed with antisera to type I collagen. The antigenicity of type III collagen was largely destroyed by pepsin treatment suggesting that it resided in non-helical segments. A fragment of peptide T1X produced by digestion with collagenase retained antigenic activity. The data indicated that the aminoterminal region of type III collagen contains strong antigenic determinants located in a non-helical sequence of about sixteen amino acids. Antibodies to these antigenic determinants were purified and rendered specific for type III collagen by immunoadsorption. The antibodies stained in indirect immunofluorescence tests particularly those regions in various connective tissues which are rich in reticulin fibres. Different staining patterns were observed with antibodies to type I collagen.
[Show abstract][Hide abstract] ABSTRACT: A modified form of procollagen was extracted with 10 M urea from the skin of lambs with dermatosparaxis, a disease which is produced by a genetic defect in the conversion of procollagen to collagen. The extracts contained little if any alpha1 and alpha2 chains of normal type I collagen, and instead they contained the larger polypeptides palpha1 and palpha2 together with high polymers. palpha1 was purified by ion-exchange chromatography and gel filtration. The polypeptide was shown to be related to alpha1 by its chromatographic behavior, its amino acid composition, and the peptides obtained after cleavage with cyanogen bromide. The molecular weight of palpha1 by gel filtration was 112 300 +/- 6300. After digestion of palpha1 with bacterial collagenase, a fragment of about 100 amino acid residues was obtained which was similar in amino acid composition and antigenic activity to a comparable fragment previously obtained from the NH2-terminal region of palpha1 chains from dermatosparaxic cattle. However, after cleavage of palpha1 with cyanogen bromide, a larger NH2-terminal fragment of about 160 amino acid residues was obtained. The larger cyanogen bromide fragment contained 8 residues of hydroxyproline, 12 residues of proline, and 19 residues of glycine not found in the NH2-terminal fragment isolated after digestion with bacterial collagenase. The results indicated that, in addition to containing amino acid sequences similar to those found in globular proteins, the peptide extensions on the NH2-terminal end of the palpha1 chain of procollagen also contain amino acid sequences similar to those found in the triple-helical region of the collagen molecule. The molecular weight of palpha2 by gel filtration was 102 400 +/- 6800. No additional peptide fragment was recovered after digestion of palpha2 with bacterial collagenase.
[Show abstract][Hide abstract] ABSTRACT: Peptides derived from the aminoterminal portion of the palpha1(I)-chain of calf and sheep procollagen were labeled with iodine-125. Despite changes in electrophoretic homogeneity after labeling, reaction of the labeled peptide with antisera to unlabeled peptide was retained. Antisera to procollagen or the isolated procollagen peptide showed high titers for the native peptide, a much weaker binding with the reduced and alkylated peptide and little or no reaction with collagen. Antisera to collagen showed strong binding with collagen and a weaker but distinct reaction with the procollagen peptide. Evidence was obtained that a minor contaminant of procollagen peptide was present in the acid-extracted collagen and that there were no shared antigenic determinants. Bovine serum and amniotic fluid contained 1-10 mug/ml reactive antigen. These results indicate that the labeled peptides can be used as a specific, sensitive and accurate assay for the amino-terminal portion of procollagen in biological samples.
No preview · Article · Feb 1976 · Journal of Immunological Methods
[Show abstract][Hide abstract] ABSTRACT: Antibodies to bovine type I and type III collagen and their precursor form procollagen were produced in rabbits and rendered specific for the immunizing antigen by immunoadsorption. These purified antibodies showed distinct immunofluorescence staining on frozen sections of both bovine and human connective tissue at concentrations as low as 1–10 μg/ml. Antibodies to type III collagen and procollagen reacted with reticulin in liver and spleen, with fascicles around tendons and with the upper portion of the dermis. Antibodies to type I collagen and procollagen reacted with skin and fiber bundles in tendon but did not stain reticulin. No reaction was observed with cartilage collagen or with kidney glomerular basement membrane.
No preview · Article · Feb 1976 · Journal of Immunological Methods
[Show abstract][Hide abstract] ABSTRACT: Non-helical peptide fragments were isolated from rabbit skin collagen after cleavage of α chains with cyanogen bromide and proteases. Determination of their amino acid sequence indicated a length of 9, 16 and 25 amino acid residues for the non-helical sequences located in the N-terminal region of α2 and α1 chain and in the C-terminal region of α1 chain, respectively. The C-terminal sequence Tyr-Tyr hitherto considered as the genuine end of collagen α 1 chain is in part of rabbit collagen extended by two residues, alanine and arginine.
Rabbit collagen may differ considerably in its non-helical sequences from other vertebrate col-lagens, particularly in the C-terminal part. Some but not all of these differences are clustered in areas occupied by antigenic determinants which are recognized in the antibody response of rabbits to rat or calf collagen. On the other hand, a high homology to rabbit collagen, e.g. in the N-terminal region of rat collagen α1 chain or calf collagen α2 chain, probably prevents immunological recognition by the rabbit. The degree of foreignness alone, however, may not necessarily determine whether a particular non-helical area is able to express immunogenic activity.
Preview · Article · Jul 1975 · European Journal of Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Tryptic peptides from denatured insoluble collagen of calf skin revealed upon molecular sieve chromatography three additional peaks not observed in similar digests of collagen α chains or β components. Five different peptides with a relatively high tyrosine content and a size distribution between 87 and 142 amino acid residues could be purified from two of these peaks. Four peptides contained antigenic markers of the N terminal or C terminal nonhelical regions, usually associated with smaller sized tryptic peptides of the α1 chain. Determination of terminal amino acids suggested two or three chain structures for these peptides, indicating that these unique peptides are derived from crosslinking regions. The participation of a site located within helical sequences in the cross link formed was demonstrated for one of the peptides after additional cleavage with cyanogen bromide and isolation of the products. This particular cross link, between the C terminal peptide α1 CB6 and the helical peptide α1 CBS is compatible with the quarter stagger model for the packing of collagen molecules in a fibril. Involvement of helical sites of the collagen molecule in other peptides is suggested by their amino acid composition. The demonstration of different peptides having in common the same antigenic marker is interpreted as multiple combinations realized by a discrete cross link region with various sites on adjacent molecules.
No preview · Article · Jan 1975 · Hoppe-Seyler's Zeitschrift für physiologische Chemie