Basement membrane collagen of renal glomerulus

Biochemistry of fusion mass consolidation in the sheep spine

We report here the biochemistry of fusion mass consolidation in sheep spines during a 1-year period following autogenous cortical-cancellous bone grafting and stabilization with Harrington distraction rods. Biochemical analysis of vertebral fusion mass included determination of wet weight and dry weight and quantification of glycosaminoglycan, collagen, calcium, and phosphate following extraction with neutral EDTA and proteolytic hydrolysis with papain. Our results showed that at 1 week after surgery, the fusion mass consisted of original cortical and cancellous bone graft material. The cortical bone graft was partially resistant to EDTA-papain treatment, resulting in a residue containing hydroxyproline and mineral. At 12 weeks after surgery, the fusion mass had become a homogeneous material, which, like cancellous bone graft, was completely susceptible to treatment by EDTA-papain. Collagen content of consolidating fusion mass was highest at 16 weeks after surgery when normalized to dry weight; glycosaminoglycan content was highest within 6 weeks after surgery. Mineral content was lowest at the 6-week stage but by 12 weeks after surgery, it was comparable with original bone grafting material. At 24 and 52 weeks after surgery, fusion mass consolidation was characterized by an increase in the proportion of organic and mineral components resistant to EDTA-papain. The appearance of the EDTA-papain-resistant material in the fusion mass coincided with formation of lamellar bone and successful consolidation.

Changes in type V collagen in the kidneys of DOCA-NaCl treated rats

Type V collagen was extracted and quantitated in the kidneys of unilaterally nephrectomized rats exposed to desoxycorticosteron acetate (DOCA-NaCl) treatment. A highly elevated content of collagen type V was found in these kidneys compared with controls. A higher content of collagen type V was present both in the pepsin digest of the total kidney and in the isolated glomerular basement membranes. It was previously reported that one of the factors involved in the growth of the remaining kidney in unilaterally nephrectomized DOCA-NaCl treated rats is the increase of collagen type IV, the effect being more prominent in rats nephrectomized at a younger age. The present study documents that the increase of type V collagen follows the same pattern.

The staining of type V collagen obtained from FBJ virus-induced osteosarcoma with concanavalin A

Type V collagen from FBJ virus-induced osteosarcoma of mice has a high content of saccharide as has been noted for type V collagens from different sources. In the present study, this collagen was found to contain significant amounts of mannose and hexosamine. Three alpha chains of this collagen were electrophoretically separated and cleaved by cyanogen bromide. The cyanogen bromide peptides, following their separation by SDS-polyacrylamide gel electrophoresis, were transferred onto nitrocellulose paper and stained with concanavalin A. Several bands derived only from alpha 3(V) stained positively, but this was inhibited by the presence of alpha-methylmannoside. Thus, at least one of these three chains appears to have an asparagine-linked oligosaccharide.

Collagens of the retinal microvascular basement membrane and of retinal microvascular cells in vitro

We have analysed the collagens present in vascular basement membranes isolated from bovine retinal and cerebral microvessels and bovine renal glomeruli, and from the non-vascular basement membrane of bovine lens capsule. These are compared with the collagens produced by cultured bovine retinal microvascular pericytes and lens epithelial cells, and by canine retinal microvascular endothelial cells, in vitro. Biochemical and immunocytochemical analyses indicate that all of the vascular basement membrane preparations have an identical collagenous composition, consisting of the same polypeptides present in lens capsule (primarily type IV collagen), together with other polypeptides that are identified as type I, and a small amount of type III collagen. Identification of the latter is based on two-dimensional gel electrophoresis in the presence and absence of a reducing agent. Immunocytochemical studies, however, demonstrate type I, type IV and some type V collagen in the basement membranes of the isolated microvessels. The cultured microvascular cells produce predominantly type I collagen molecules, but they also produce other collagen peptides that appear to be type IV, and, at least in some experiments, small amounts of type III collagen. The biochemical identification of collagens type I and IV is confirmed by immunocytochemistry. However, results with anti-type I collagen and procollagen antibodies in cultured pericytes vary with antibodies from different sources. The quantities of the type IV peptides produced by the cultured cells also vary in different experiments.

An electron microscopic examination of age-related changes in the rat kidney: the influence of diet

The changes with age in the ultrastructure of the kidneys were explored in ad libitum fed rats with restricted food intake started soon after weaning or started in young adult life or limited to early life and in rats restricted in protein but not caloric intake. Many ultrastructural changes occurred with age both in the glomeruli and the tubules. Food restriction started soon after weaning or in adult life modulated most of these age changes. By providing detailed information on basement membrane and tubular cell structure, these findings complement previous light microscopic and functional studies in regard to the effects of food restriction on progressive kidney disease in the rat. Food restriction limited to early life and protein restriction without caloric restriction were less effective in modulating these age changes in kidney ultrastructure than food restriction initiated at 6 weeks or 6 months of age and continued for the rest of the life span.

Functionality of muscle proteins in gelation mechanisms of structured meat products

Recent advances in muscle biology concerning the discoveries of a large variety of proteins have been described in this review. The existence of polymorphism in several muscle proteins is now well established. Various isoforms of myosin not only account for the difference in physiological functions and biochemical activity of different fiber types or muscles, but also seem to differ in functional properties in food systems. The functionality of various muscle proteins, especially myosin and actin in the gelation process in modal systems which simulate structured meat products, is discussed at length. Besides, the role of different subunits and subfragments of myosin molecule in the gelation mechanism, and the various factors affecting heat-induced gelation of actomyosin in modal systems are also highlighted. Finally, the areas which need further investigation in this discipline have been suggested.

Differential solubility of subcomponents of rat glomerular basement membrane

Marked differences were found in the electrophoretic profiles and amino-acid compositions of components prepared from rat glomerular basement membrane (GBM) by a number of different solubilization procedures. Treatment with reducing agent resulted in a simplified electrophoretic pattern which was characterized by the presence of a major collagenous component with a mol.wt. of 150 000. In contrast, detergent solubilized mainly lower-mol.-wt. material which had a more polar amino-acid composition. When both reagents were used together the majority of the basement-membrane material was solubilized within 2 h and components with mol.wts. of 170 000 and 135 000 were predominant in the pro-alpha region of the gel. Treatment for a further 16 h was required to solubilize higher-mol.-wt. material and to achieve maximum solubility of components in the pro-alpha region with mol.wts. of 185 000 and 150 000. These methods provide a means of separating subcomponents of rat GBM while avoiding the problems of degradation inherent in enzymatic procedures.

Nephrotic syndrome and collagenizing glomerulopathy in PVG/c rats treated with the alpha-mannosidase inhibitor "swainsonine"

Weanling PVG/c rats treated with the alpha-mannosidase inhibitor swainsonine developed increasing proteinuria which terminated as a severe nephrotic syndrome after 35 to 45 days. This was associated with a glomerulopathy characterized by the production of collagen fibrils adjacent to endothelial and mesangial cells, foot process expansion, subepithelial projections of the basement membrane, and splitting of the lamina densa. The swainsonine-induced glomerulopathy appeared to be an exacerbation of a spontaneous abnormality in this strain of rat.

Comparison of cartilage destruction between infectious and adjuvant arthritis

The timing and molecular profile of cartilage destruction in Escherichia coli and Staphylococcus aureus infectious arthritis and killed Mycobacterium butyricum adjuvant arthritis are presented. Infectious arthritis was studied for 3 weeks; cartilage samples were analyzed at 2, 10, and 21 days. At 48 h postinfection, glycosaminoglycan content was reduced by 20% (p less than 0.05) in E. coli infected knees and by 42% (p less than 0.05) in tibial plateau cartilage of S. aureus infected knees. By the 3rd week of infection, glycosaminoglycan losses amounted to as much as 73% (p less than 0.005). In comparison, collagen losses were not significant prior to the 3rd week of infection, at which time 42% (p less than 0.05) was lost. Adjuvant arthritic tibial plateau cartilage was examined at 1, 3 and 12 weeks. Glycosaminoglycans decreased by 42% the 1st week, plateauing at 62% by the 3rd and 12th weeks. Collagen degradation began at 3 weeks (28% loss, p less than 0.10) and by the 12th week was reduced by 49% (p less than 0.005). Analysis of the individual species of glycosaminoglycan showed a parallel loss of chondroitin sulfate and keratan sulfate. Fractionation of glycosaminoglycans with respect to size produced no evidence of shortened chains in cartilage from infected joints. Hyaluronic acid losses were greatest when collagen was significantly decreased. The pattern by which chondroitin and keratan sulfates are lost demonstrates that a prominent feature of infectious and noninfectious inflammatory arthritis is a rapid loss of proteoglycan subunits that precedes collagen loss.

Experimental pyelonephritis in the cat: 3. Collagen alterations in renal fibrosis

Chronic pyelonephritis was induced in young adult cats by the intravenous injection of a human or a feline strain of Escherichia coli after ligation of one ureter for 24 or 48 h. In the 3 cats infected with the feline strain, scarred kidneys from the obstructed side were removed at necropsy 3, 4 and 5 months later. Collagen was extracted from pyelonephritic and normal kidney tissue with dilute acetic acid and limited proteolysis with pepsin. Scarred kidneys gave higher yields of both acid-soluble collagen (normal = 0.57 +/- 0.12 mg per g tissue; scarred = 0.88 +/- 0.10 mg per g tissue) and pepsin-solubilized collagen (normal = 9.69 +/- 1.79 mg per g tissue; scarred = 20.02 +/- 2.84 mg per g tissue). There was no significant increase in the collagen yield from the kidneys of the 2 cats in which mild focal lesions were found 14 and 16 months after infection with the human strain of E. coli. Pepsin released collagens were separated by fractional salt precipitation and identified by agarose gel chromatography and polyacrylamide gel electrophoresis. Normal kidney was shown to contain collagen of Types I, IV and V (AB). The Type IV collagen extracted consisted of a mixture of 4 major pepsin-resistant chains of apparent molecular weights of 150 000, 115 000, 85 000 and 60 000. The collagen extracted from scarred kidneys was predominantly Type I, only trace amounts of Type IV and V components being present. These findings suggest that basement membrane collagens of the kidney are selectively degraded during the atrophy and scarring of chronic feline pyelonephritis and are preferentially replaced by interstitial Type I collagen.

Structural and immunological characterization of type IV collagen isolated from chicken tissues

Previously, a type IV collagen fraction was isolated from chicken gizzard and further fractionated into three components called F1, F2 and F3 [Mayne, R. and Zettergren, J.G. (1980) Biochemistry, 19, 4065-4072]. F1 and F2 were consistently isolated in a 2:1 proportion, and the existence of a small native fragment of structure (F1)2F2 was proposed. In the present series of experiments, a type IV collagen fraction was isolated from the chicken kidney and shown to consist almost entirely of F1 and F2 which were again present in a 2:1 proportion. Identical one-dimensional peptide maps for F1 and F2 from both sources were obtained by polyacrylamide gel electrophoresis of peptides obtained after cleavage with cyanogen bromide or Staphylococcus aureus V8 protease. The denaturation temperature of a preparation containing F1 and F2 in native form was determined by optical rotatory dispersion and a single melting curve was observed with a melting temperature of 33 degrees C. This result provides further supportive evidence that F1 and F2 exist as a native fragment (F1)2F2. Antibodies were prepared in rabbits against a type IV collagen fraction isolated from chicken gizzard, and immunofluorescent staining of a wide variety of basement membranes was demonstrated. Experiments were performed in which various type IV collagen fractions were observed in the electron microscope after rotary shadowing. The lengths of (F1)2F2 and F3 were 147 nm and 174 nm respectively, the sum of these lengths (321 nm) corresponding closely to the length of the major triple-helical domain of type IV collagen (326-328 nm). A specific cleavage site was located at a distance of 215 nm from the 7-S domain which, together with the length of (F1)2F2, gives a total length of 362 nm. This value corresponds closely to the maximum length of the arms which originate from the 7-S domain (355 nm) when type IV collagen was solubilized with a low concentration of pepsin. The results suggest that (a) type IV collagen isolated from the chicken gizzard is closely related, if not identical, to type IV collagen isolated from other tissues; (b) there is a single type IV collagen molecule of chain organization[alpha 1(IV)]2 alpha2(IV); (c) the order of the pepsin-resistant fragments within a type IV molecule is 7S-F3-(F1)2F2.

Purification and characterization of a collagenous protein secreted by a murine teratocarcinoma-derived cell line

A collagenous protein could be precipitated by (NH4)2SO4 from the culture medium of a murine teratocarcinoma-derived cell line (Ko, C.Y., Johnson, L.D. and Priest, R.E. (1979) Biochim. Biophys. Acta 581, 252-259). Further purification of this protein was achieved by combining DEAE-cellulose chromatography with either CM-cellulose or molecular sieve chromatography. The collagenous polypeptides had subunit molecular weights of 160 000, if determined by molecular sieve chromatography, or 190 000, if determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and they are not linked by disulphide bridges. Amino acid composition of this collagen is similar to that of a murine type IV collagen isolated from EHS sarcoma (Timpl et al. (1978) Eur. J. Biochem. 84, 43-52). The most prominent peptides resulting from cleavage of the protein by CNBr had estimated molecular weights of 25 000, 23 000, 11 700 and 9400. Pepsin treatment of this collagen under non-denaturing conditions produced three major fragments having molecular weights of 70 000, 45 000 and 43 000. We conclude that the collagen secreted by the murine teratocarcinoma-derived cell culture is a type IV basement membrane collagen. Therefore, this culture system should provide a continuous source of type IV collagen, which may be used to study the interaction of this collagen with other basement membrane components.

In vitro cartilage degradation by Escherichia coli and Staphylococcus aureus

Effects of Escherichia coli and Staphylococcus aureus on cartilage and chondrocytes in culture are reported. Under these conditions, bacterial effects on cartilage degradation and cell viability are measured in the absence of inflammation. E coli causes a 28% loss and S aureus an 83% loss of cartilage glycosaminoglycan within 48 hours. Collagen content is unchanged. Both bacterial species induce chondrocyte death in explants and in monolayers within 48 hours. Bacterial effects on glycosaminoglycans and cell viability do not result from depletion of nutrients from the culture medium. Serum in the culture media inhibits the bacterial effects on cartilage degradation but does not prevent cell death.

Age-related changes in rat glomerular basement membrane

1. The yield of GBM from rat kidney increased with rat age and the membrane became more collagen-like, as judged by the glycine, hydroxyproline, hydroxylysine content and the degree of glycosylation. 2. GBM became progressively less soluble in sodium dodecyl sulphate (SDS) and 2-mercaptoethanol with age. An increase in the lower molecular weight subunits of membranes prepared from older rats was demonstrated by polyacrylamide gel electrophoresis.

Non-collagen protein and proteoglycan in renal glomerular basement membrane

Extraction of rat glomerular basement membrane, purified by osmotic lysis and sequential detergent treatment, with 8 M urea containing protease inhibitors solubilizes protein that is devoid of hydroxyproline and hydroxylysine. This material represents 8-12% of total membrane protein, elutes mainly as two high molecular weight peaks on agarose gel filtration, and is associated with glycosaminoglycans. Isolated rat renal glomeruli incorporate [35S]sulfate into basement membrane from which this non-collagenous 35S-labeled fraction can be subsequently solubilized. The radioactivity incorporated into urea-soluble glomerular basement membrane eluted primarily with the higher molecular weight peak (Mr greater than 250 000). Cellulose acetate electrophoresis after pronase digestion of the urea-soluble fraction revealed glycosaminoglycan that was resistant to digestion with Streptomyces hyaluronidase and chondroitinase ABC, sensitive to nitrous acid treatment, and contained [35S]sulfate. The findings indicate that one of the non-collagenous components of glomerular basement membrane is a proteoglycan containing heparan sulfate.

Basement membrane collagen from bovine lung: its chain associations as observed by two-dimensional electrophoresis

A basement membrane collagen has been isolated from limited pepsin digests of bovine lung alveolar tissue by differential salt fractionation and DEAE-cellulose chromatography. Fractionation and characterization of the peptide chain fragments of the collagen have revealed the presence of two classes of collagen chains: one is 160K-1, 100K-1, and 80K-1 and the other is 100K-2 and 80K-2. Apparent isoelectric points of these chain fragments were 8.4, 8.6, 8.35-8.45, 8.9-9.0 and 8.9-9.0, respectively. Electrophoretic analysis on temperature dependent reductions of the collagen and its denaturation products has revealed the presence of disulfide bonds between collagen chain fragments of 160K-1-80K-2 and possibly 160K-1-160K-1 which require elevated temperatures for reduction and the bonds within 100K-2 fragments (80K-2-small fragments such as 10K-20K) and possibly between 80K-2-80K-2 which are reducible without elevated temperatures.

Pepsin fragments of human placental basement-membrane collagens showing interrupted triple-helical amino acid sequences

The pepsin digestion of human placental type IV collagen was studied in order to gain insight into the relationships between the fragments alpha 1(IV)95 000 and alpha 2(IV)70 000 which have previously been described. (For nomenclature see Crouch, E., Sage, H. & Bornstein, P. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 745-749.) Seven smaller pepsin fragments with apparent molecular weights in the range of Mr = 5 000 to 50 000 were also isolated and characterized. The amino-terminal amino acid sequences of alpha 1 (IV)95 000, alpha 2(IV) 70 000 and the smaller pepsin fragments are presented. Kinetic data on the pepsin solubilization provided evidence for the presence of at least two different collagen triple helices within basement membranes and sequence data demonstrated the presence of a number of short non-collagen-like sequences which interrupt the triple helical regions of the alpha chains.

Biosynthesis of type IV and V (alpha A-alpha B) collagens by human placenta

The collagenous proteins synthesized by placenta in organ culture were characterized. Types I and III collagen accounted for about two-thirds of the collagenous protein produced by the tissue while type IV procollagen comprised around 10%. Type IV collagen contained two chains of 185,000 and 175,000 daltons which are genetically distinct from one another as determined by a peptide mapping procedure. The type IV procollagen was identical to that produced by other tissues based on ratios of 3- to 4-hydroxyproline and hydroxyproline to proline, and on the pattern produced upon polyacrylamide gel electrophoresis before and after peptide mapping procedures. About 20% of the collagen resembled type V collagen in the proportions of 3- and 4-hydroxyproline to proline and of hydroxylysine to lysine, in solubility, and in peptide maps. However, it contained disulfide linked chains larger than those found in the type V collagen solubilized by pepsin. Following pepsin treatment, the disulfide bonds were removed and the mobility of the chains of the labeled protein resembled those in type V collagen. It is likely that the disulfide linked protein represents the intact type V collagen molecule.

Type IV collagen contains two distinct chains in separate molecules

Type IV collagen from the EHS sarcoma, a basement membrane producing tumor, was characterized. Acid extracts of tumor grown in lathyritic animals contain proteins with two predominant collagen chains of apparent molecular weights of 160,000 and 140,000 daltons, designated alpha 1(IV) and alpha 2(IV). In addition, dimers and larger polymers formed by covalent crosslinking of the alpha 1(IV) and alpha 2 (IV) chains are also present. These two chains were found to be distinct from one another in amino acid composition and in the peptide patterns obtained following treatment with cyanogen bromide and S. aureus V8 protease. Precipitation of native collagen from acid solutions by the stepwise addition of NaCl yielded mixtures of the two chains with varying ratios suggesting that the two chains reside in different macromolecules.

Modification of the glomerular basement membrane in sucrose-fed and streptozotocin-diabetic rats

Rats were fed on diets containing either sucrose or starch as the carbohydrate component (55%) for eight months. Diabetes was induced in animals of both groups by injecting streptozotocin (50 mg/kg body weight). Diabetic rats failed to gain weight, had enlarged kidneys, polyuria and elevated blood glucose levels. Starch and sucrose fed rats gained weight normally and had normal blood glucose levels. Sucrose fed rats had enlarged kidneys. Regional thickening of the glomerular basement membrane was present in sucrose-fed and diabetic rats but not in starch-fed controls. Glomerular basement membrane isolated from pooled kidney cortices from rats in the different experimental groups were analysed for amino acid, disaccharide and hexosamine content. Hydroxylysine (9 to 20%), hydroxyproline (21 to 24%), disaccharide (27%) and hexosamine (26%) were increased in membranes insolated from the three experimental groups, compared with starch-fed non-diabetic controls. An increase in low molecular weight components of the glomerular basement membrane of sucrose-fed and diabetic rats was observed using electrophoresis in sodium dodecyl sulphate. Significantly higher (p < 0.001) glucosyltransferase activity was present in kidney supernatants prepared from sucrose-fed (1050 +/- 60 nmol/2h/kidney) compared to starch-fed rats (510 +/- 40 nmol/2h/kidney). Sucrose feeding induces changes similar to those found in diabetes and the induction of diabetes made little difference over the feeding of sucrose alone.

Type IV collagen from chicken muscular tissues. Isolation and characterization of the pepsin-resistant fragments

Type IV collagen has been isolated from adult chicken gizzard after limited pepsin digestion and subsequent differential salt fractionation in acidic and neutral conditions. After denaturation, three fragments (called F1, F2, and F3) were isolated by agarose gel filtration and carboxymethylcellulose chromatography. F1 and F2 possessed apparent molecular weights of 53 000 and 50 000, respectively, and were consistently isolated in a 2:1 proportion. F3 was larger and after reduction of disulfide bonds gave rise to three fragments (called F3A, F3B, and F3C) of apparent molecular weights 68 000, 40 000, and 29 000. No alpha-chain-sized components of Type IV collagen were observed. A native fraction containing F1 and F2, but no F3, was isolated after extraction using less pepsin and an additional salt fractionation in acidic conditions. F1 and F2 in the native form were not separated by carboxymethylcellulose or diethylaminoethylcellulose chromatography performed in nondenaturating conditions or by differential salt precipitation in acidic or neutral conditions; these results suggest that F1 and F2 arise as a single native component of structure (F1)2F2. The fraction containing F1 and F2 also gave rise to a single segment long spacing crystallite pattern and to a circular dichroism spectrum which was typical for a native collagen. F1 and F2 were also isolated from chicken heart, blood vessels, and skeletal muscle, whereas from bovine aorta, using the same isolation procedures, two alpha-chain-sized components were obtained, which appeared to be similar to the two Type IV chains recently described by other groups. The data suggest that (i) pepsin fragmentation of type IV collagen from chicken tissues occurs in a different manner compared to Type IV collagen from mammalian tissues and (ii) for the chicken there must be at least two Type IV chains which are assembled into a single native molecule.

7-S collagen: characterization of an unusual basement membrane structure

A new type of collageneous structure, tentatively named 7-S collagen, was isolated from a mouse tumor basement membrane, mouse and human placenta, bovine lens capsule and human kidney. The protein was solubilized from the tissues by limited digestion with pepsin or trypsin and could easily be separated from other collageneous protein because of its resistance towards further degradation by bacterial collagenase at 20 degrees C. 7-S collagen showed an amino acid composition typical of basement membrane collagen and contained 22% carbohydrate mainly as glucosyl-galactosyl bound to hydroxylysine but also some mannose and glucosamine. Ultracentrifugal analysis demonstrated that the proteins were homogeneous with a sedimentation coefficient of about 7.2 S and with a molecular weight of about 360,000 both in phosphate buffer pH 7 and 6 M guanidine. The peptide was triple helical as shown by circular dichroism and exhibited a biphasic melting profile indicating two conformationally distinct domains with tm = 48 degrees C and 70 degrees C. The more stable domain could be isolated as an homogeneous fragment (Mr = 225,000) after a second digestion with collagenase at 37 degrees C. This fragment contained all the disulfide bonds (42 Cys/1,000 residues) of the original molecule. Electron microscopy showed a rod-like structure in agreement with the hydrodynamic properties of 7-S collagen. The dimensions of these peptides were 3 X 95 nm (long form) and 2.4 X 40-50 nm (short form). Complete reduction of 7-S collagen under denaturing conditions produced several polypeptide chains in the molecular weight range of 27,000-153,000 which differ from each other by Mr increments 25,000-27,000. Separation of the chains on agarose did not reveal any simple stoichiometric relationship indicating that some chains are either cross-linked or represent fragments produced during proteolytic treatments. Complete reduction of 7-S collagen under non-denaturing conditions lowered the thermal transiton of the triple helix to 48 degrees C but did not change its molecular weight except when exposed to dissociating solvents. 7-S collagens were potent immunogens and could be characterized by radioimmunoassays. Antigenicity was slightly reduced by reduction and denaturation while collagenase at 37 degrees C produced a larger decrease. Proteins obtained from various sources showed distinct immunological relationships although interspecies differences in affinity exist. No or only little cross-reaction was observed with type IV and V collagens and some further fragments of basement membrane collagen. The data indicate that 7-S collagen is a unique component of basement membranes which shows a more compact and stable structure than other collageneous proteins.

Type-IV collagens. Isolation and characterization of two structurally distinct collagen chains from bovine kidney cortices

Two sets of structurally distinct collagen components resembling type IV collagen have been isolated and purified from the pepsin digest of kidney cortex homogenates. C and D chains with the size of alpha chains were separated from disulfide-linked material on molecular sieves and were further purified by ion-exchange chromatography. The molecular gel filtration of the starting material also gave two high-molecular-weight collageneous fractions. The reduction of these fractions with dithiothreitol followed by carboxymethyl-cellulose chromatography resulted in the separation of two major peaks, one corresponding to C-1 and the second peak corresponding to D-1 and a 75 000-Mr components. These latter two components were further separated from each other by molecular sieve chromatography. In addition some smaller peptides (two 50 000-Mr and one 15 000-Mr peptides) were purified and analkyzed. By amino acid composition, chromatographic properties and cyanogen bromide peptide patterns on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, the C-1 and C chains and one of the 50 000-Mr components appear to be derived from the same chain by pepsin cleavage at different sites. Similarly, the D1 and D chains, and the 75 000-Mr, the second 50 000-Mr and the 15 000-Mr components are related to each other but are structurally distinct from the C-1 and C components. The presented data are consistent with the presence of two structurally distinct chains in basement membrane collageneous molecules.

The dynamics of calcium phosphate precipitation studied with a new polyacrylamide steady state matrix-model: influence of pyrophosphate collagen and chondroitin sulfate

A novel steady-state gel-matrix model system is described which facilitates the quantitative kinetic study of the influence of media and matrix composition on a precipitation process. The potentialities of the system are illustrated in experiments in which the precipitation of calcium phosphate in a polyacrylamide film is studied as a function of the calcium and phosphate concentration in the solutions flowing along opposite sides of the film. Addition of pyrophosphate to the reactant solutions was found to diminish the (calcium) x (phosphate) millimolar product at which precipitation starts, indicating a positive effect on nucleation. The slope of the curve was found to decrease, which points to a negative influence of pyrophosphate on the crystal growth process. Incorporation of collagen in the matrix did not change the curve, but incorporation of chondroitin sulfate decreased the formation product since the intercept of the curve was reduced. The usefulness of the system compared with test-tube and non-steady state gel experiments for calcium phosphate precipitation studies and its significance for the study of in vitro and in vivo precipitation processes in general, are discussed.

Isolation and characterization of hydroxyproline-containing proteins secreted by a murine carcinoma cell culture

A collagenous protein was isolated from a murine carcinoma cell culture, which has been shown to synthesize basement membrane. The molecular weight of this protein was estimated to be 155 000. It eluted from carboxymethyl-cellulose in the region near the alpha 1 and beta 11 components of calf skin collagen. 63--69% of the peptide-bound prolines were hydroxylated, and the 4-/3-hydroxyproline ratios ranged from 12 : 1 to 14 : 1. About 95% of the hydroxylysines in the peptide were glycosylated, and almost all of them were in the glucosylgalactosyl dissacharide form. Judging from the posttranslational characteristics, this collagenous protein is probably of basement membrane type.

Anomalous reactions in the haemagglutination assay for anti-collagen antibodies: studies on patients with rheumatoid arthritis or chronic low back pain

Sera from 23 patients with chronic low back pain, 20 rheumatoid patients and 16 normal controls were tested for antibodies to collagen types I, II and III, both native and denatured, by haemagglutination. Weak reactions against denatured collagen types I and II were found in 30-40% of the sera. Sera from individuals with rheumatoid arthritis or chronic low back pain behaved similarly, while only one normal serum showed any positive reaction. Reactions to denatured collagen type III and to native collagen of all 3 types were largely negative. Non-antibody serum components were thought to be responsible for these haemagglutination reactions since weakly positive reactions were abolished by cryoprecipitation and could not be confirmed by a solid-phase fluorimetric assay. Using the latter technique sera from 62 rheumatoid patients were screened for antibodies to type II collagen (native and denatured) and only one positive serum found. We conclude that haemagglutination is subject to false positive reactions and that the incidence of anticollagen antibodies in sera from patients with rheumatoid arthritis or chronic low back pain is low.

Immunofluorescence demonstration of type IV collagen and a noncollagenous glycoprotein in thickened vascular basal membranes in protoporphyria

Specific rabbit antibodies to type IV collagen isolated from a basement membrane producing mouse tumor were used in indirect immunofluorescence tests to study the thickened vascular basement membrane in skin biopsies from patients with erythropoietic porphyria (EPP) and from protoporphyric mice. In addition, rabbit antibodies to a noncollagenous, basement membrane specific glycoprotein also derived from the mouse tumor were tested. It was shown that normal as well as altered vascular basement membranes in both the human and the murine skin specimens react with the anti-type IV collagen and the antiglycoprotein antibodies. A particular strong reaction in the diseases skin indicated that formation of new vascular basement membrane layers involved deposition of the major structural proteins which also constitute normal basement membrane matrices.