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Biomedical subjects

A F Michael

Publications and source records attributed to A F Michael.

At least 55 records · Page 3Linked to original sources
PubMed1989

Basement membrane collagen in the kidney: regional localization of novel chains related to collagen IV.

Variability in the collagen chain composition of renal basement membranes was demonstrated by immunofluorescent microscopy using polyclonal and monoclonal antibodies and correlating with imaging of the glomerular basement membrane by phase microscopy. Antibodies toward the globular domains of alpha 1(IV) and alpha 2(IV) collagen chains, triple helical and 7S domains of collagen IV bind within the glomerulus to mesangial matrix, along the subendothelial region of the glomerular capillary wall, and to all tubular and vascular basement membranes. The portion of glomerular basement membrane corresponding to the phase dense image is not reactive with these antibodies. A different binding pattern is seen with antibodies against two novel globular regions of basement membrane collagen chains which bind to the phase dense aspect of glomerular basement membrane and to Bowman's capsule. Human tubular basement membrane is not reactive, except along portions of the distal tubule, whereas bovine tubular basement membrane is diffusely reactive; mesangial matrix and extraglomerular vascular basement membranes are not reactive. Although a possible explanation for the regional distribution of basement membrane collagen antigens in the glomerulus may relate to antigen exposure, a more likely reason is that collagen chains are regionally expressed. The staining patterns suggest that the novel collagen chains have a selective tissue distribution compared with alpha 1(IV) and alpha 2(IV) chains and that the glomerular cells of origin of these collagen IV chains may differ.

Animals↗
PubMed1989

Identification of variant Alport phenotypes using an Alport-specific antibody probe.

An antibody, which recognizes an epitope(s) on a 26 kD peptide of the noncollagenous domain of type IV collagen and which fails to bind to basement membranes of individuals with Alport syndrome, was used to characterize members of families representing phenotypic variants of the disorder. Ten of 11 families with juvenile-onset renal failure and 4 of 5 families with adult-onset renal failure exhibited loss of the epitope(s) from epidermal and/or renal basement membranes by indirect immunofluorescence. Two families with typical Alport nephropathy but normal hearing exhibited the same abnormality. This study provides strong evidence that a defect in the main noncollagenous domain of type IV collagen is common to the various phenotypes of Alport syndrome.

Antibodies↗
PubMed1989

Lymphohaemopoietic antigens of cultured human glomerular epithelial cells.

Glomerular visceral epithelial cells (GVEC) from normal human glomeruli were grown in tissue culture. Cell surface markers were studied by immunofluorescence microscopy using antibodies against lymphohaemopoietic differentiation antigens which are known to be present early (BA-1, OKB2, BA-2) and late (J5, anti CR1) in renal ontogenesis. Like foetal human glomerular epithelium, the cultured cells reacted with BA-1 and OKB2 (identifying an antigen expressed on B cells and polymorphonuclear leucocytes), and BA-2 (leukaemia-associated antigen), but were consistently negative for CR1 (C3b receptor); J5 which identifies the common acute lymphoblastic leukaemia antigen (CALLA) stained variably. Reactivity with antimyosin or anti factor VIII were absent. The cells produced an extracellular matrix containing laminin, type IV collagen, and fibronectin. This study supports the notion that GVEC undergo dedifferentiation as shown by the acquisition of lymphohaemopoietic differentiation antigens present early in renal ontogeny. In addition, the production of extracellular matrix constituents in vitro may be useful for the investigation of human glomerular basement membranes.

Antibodies, Monoclonal↗
PubMed1989

Human tissue distribution of novel basement membrane collagen.

The authors have defined the specificity of monoclonal antibodies to collagen fragments of basement membrane (BM) and have used these highly specific antibodies to study the human tissue distribution of two novel 28 kd noncollagenous (NC1) peptides (M28 , M28+) compared with those derived from type IV collagen (alpha 1[26 kd] and alpha 2[24 kd] NC1). A limited distribution of the 28 kd peptides was observed in specialized BM of the kidney, eye, cochlea, lung, and brain, whereas type IV collagen is found in all human BM. These novel peptides, which colocalize with each other, are found in BM that also contain type IV collagen but do not, in all cases, colocalize with type IV collagen. The presence of the 28 kd peptides in the BM of the kidney, cochlea, and eye is in keeping with abnormalities involving these components in BM of patients with Alport familial nephritis (FN), who frequently have hearing loss, anterior lenticonus and retinal flecks in addition to renal disease. These 28 kd peptides are distinct, biochemically and immunochemically, from the alpha 1 and alpha 2 chain NC1 peptides of type IV collagen, and represent either peptide fragments of genetically distinct BM collagen molecules or additional molecules originating from the same gene family as type IV collagen.

Antibodies, Monoclonal↗
PubMed1989

Distribution of familial nephritis antigen in normal tissue and renal basement membranes of patients with homozygous and heterozygous Alport familial nephritis. Relationship of familial nephritis and Goodpasture antigens to novel collagen chains and type IV collagen.

The glomerular basement membranes (GBM) of Alport familial nephritis (FN) are laminated and split and fail to bind Goodpasture autoantibodies by indirect immunofluorescence. The Goodpasture antigen has been localized to multiple peptides of the noncollagenous C terminal (NC1) domain of type IV collagen. The principal target antigen is a 28-kDa peptide (M28) that coisolates with type IV collagen NC1 and which is derived from a larger collagenous molecule. We have shown that two novel 28-kDa peptides found in normal GBM (M28M28+) are absent from collagenase digests of X-linked dominant Alport FN GBM and that monoclonal antibodies specific for these collagen chains fail to bind to Alport GBM. In normal tissue these chains have a distribution restricted to specific basement membranes of kidney, eye, inner ear, lung, and brain, the former three of which are affected in Alport FN. Epitopes on a 26-kDa NC1 peptide identified by an antibody from a transplanted Alport patient (FN antibody) colocalized with the 28-kDa components in these tissues. The FN antibody did not bind to the GBM of homozygous Alport males. Antibodies to the 28-kDa peptides and the FN antibody colocalized in a segmental pattern in heterozygous Alport GBM by indirect immunofluorescence and were unrelated to the normal distribution of type IV collagen. Three of eight homozygous Alport FN tissues showed the presence of the 28-kDa components in Bowman's capsule in a focal distribution, and in four of eight tissues reactive antigen was present in the cytoplasm of some parietal and visceral epithelial cells. These observations support the hypothesis that the genetic abnormality in Alport FN is a defective parent chain of the 26-kDa peptide, which results in failure of normal 28-kDa collagen chain integration.

Antibodies, Monoclonal↗
PubMed1988

The glomerular mesangium.

The mesangium is more than simply a support structure for glomerular capillary circulation. Mesangial cells respond to various vasoactive mediators and probably contribute to the regulation of mesangial cell contractility and, consequently, glomerular perfusion. The surrounding extracellular matrix contains several glycoproteins and collagens that may affect the immune interactions of antigens and antibodies and may possibly influence the disposition of immune complexes. These properties may modulate the consequences of deposition of IgA-containing immune complexes in the mesangium in patients with IgA nephropathy and the consequent expression of clinical disease.

Animals↗
PubMed1988

Acute tubulointerstitial nephritis associated with aminonucleoside nephrosis.

The aminonucleoside of puromycin (PAN) induces nephrotic syndrome in rats. We studied the tubulointerstitial cellular (TIC) infiltrate previously unrecognized in this model. Rats received one i.p. injection of PAN (15 mg/100 g) and were sacrificed at 1, 3, 4, 5, 7, 14, 20 and 28 days. Frozen kidney sections and peripheral blood cells were stained with a panel of anti-rat monoclonal antibodies and quantitated by epifluorescence microscopy. An increase in Ia+ cells (60/1000 TIC) (P less than 0.001) and OX42+ macrophages (MO) (18/1000 TIC) (P less than 0.05) were observed on day 5. On day 7 the infiltrate consisted of OX19+ T-lymphocytes (29/1000 TIC) (P less than 0.001) and OX42+ MO (68/1000 TIC) (P less than 0.001). The majority of the lymphocytes expressed the OX8 cytotoxic T cell marker (23/1000 TIC) (P less than 0.001). The severe mixed cellular lesion present on day 14 was dominated by OX42+ MO (113/1000 TIC) (P less than 0.001). With resolution of proteinuria on days 20 and 28, the infiltrate decreased, although OX42+ MO persisted on day 28 (46/1000 TIC) (P less than 0.001). The severity of the cellular lesion correlated with the degree of albuminuria (r = 0.57 to 0.81 for the antibody panel). Expression of Ia antigens by proximal tubular epithelial cells markedly decreased during peak proteinuria but normalized by day 28. Increased deposition of C3 and IgG was not detected. Reversible tubulointerstitial nephritis develops in PAN-treated rats and may be a consequence of severe proteinuria.

Albuminuria↗
PubMed1988

Quantitative muscle testing in childhood dermatomyositis.

Sixteen children with dermatomyositis were followed longitudinally by quantitative muscle testing between 1972 and 1982. The time to achievement of normal muscle strength measured quantitatively was significantly delayed (p less than .001) compared to the time muscle strength was clinically assessed as normal by manual muscle testing. A significant difference was also found between the time normal muscle strength was measured and normal muscle enzymes were achieved (p less than .05). Quantitative muscle testing is a useful adjunct to clinical assessment of muscle strength and determination of muscle enzymes in the therapeutic management of patients with dermatomyositis.

Adolescent↗
PubMed1987

Cellular antigens in nephroblastoma: identification with monoclonal antibodies which recognize hemopoietic cells.

The correlation between expression of differentiation antigens and morphogenesis was examined in 11 human nephroblastomas using monoclonal antibodies which recognize both hemopoietic and renal cells. Analysis of frozen tissue sections by indirect immunofluorescence revealed that blastema cells and some tubules were recognized by BA-1 and OKB2, which identify unstimulated B cells and granulocytes. Stroma, some tubules, and focal blastema were recognized by BA-2, which identifies a 24-kDa antigen on leukemic cells and platelets. Mature epithelium in glomerular bodies was identified by C3bR and J5, which recognize CR1 and the common acute lymphoblastic leukemia antigen, respectively. Tissue sections from a clear cell sarcoma and a mesoblastic nephroma were notably reactive only with BA-2. These observations demonstrate that the relationship between antigen expression and morphology in nephroblastomas is similar to that observed in fetal kidney and suggest that expression of these cell surface antigens may have a role in morphogenesis.

Antibodies, Monoclonal↗
PubMed1987

Ultrastructural localization of the membrane attack complex of complement in human renal tissues.

Utilizing a monoclonal antibody (Poly C9-MA) to a neoantigen of the C9 portion of the membrane attack complex of complement (MAC), immunoelectron (IEM) and immunofluorescent (IF) microscopy were performed on kidney tissue from normal humans and patients with insulin-dependent diabetes mellitus (IDDM) and type II membrano-proliferative glomerulonephritis (MPGN II). Comparative studies were conducted using polyclonal antibodies to human C3, C5, IgG, IgA, and IgM. In normal human tissue, there was a close correlation between increasing chronologic age and the quantity of MAC deposited in the mesangial stalk, along the interstitial aspect of and within tubular basement membranes (TBMs) and in arteriolar walls. IF of kidney tissues from 12 patients with IDDM with varying degrees of mesangial expansion and glomerulosclerosis demonstrated a direct relationship between the degree of tissue damage and the amount of MAC deposited in the mesangium. IEM of three normal and four diabetic specimens revealed reaction product of Poly C9-MA on linear and circular membranous structures within the mesangium, TBMs, and vessel walls, and within the glomerular basement membranes (GBMs) in diabetic subjects. Evidence is presented that these structures, which have been previously described by routine electron microscopy, represent cellular debris in these loci on which Poly C9-MA has been deposited. In MPGN II, Poly C9-MA and C3 were distributed within subepithelial deposits, along either side of the dense deposits (DDs) within the GBMs and TBMs, and around circular masses of DDs within the mesangium.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Alport familial nephritis. Absence of 28 kilodalton non-collagenous monomers of type IV collagen in glomerular basement membrane.

Alport-type familial nephritis (FN), a genetic disorder, results in progressive renal insufficiency and sensorineural hearing loss. Immunochemical and biochemical analyses of the non-collagenous (NC1) domain of type IV collagen isolated from the glomerular basement membranes (GBM) of three males with this disease demonstrate absence of the normally occurring 28-kilodalton (kD) NC1 monomers, but persistence of the 26- and 24-kD monomeric subunits derived from alpha 1 and 2 (both type IV) collagen chains, respectively.

Basement Membrane↗
PubMed1987

Childhood dermatomyositis. Clinical course and long-term follow-up.

The presentation, clinical course, and long-term follow-up (3-22 years) of 39 children with dermatomyositis followed from 1962-1982 is presented. The medical course of these patients was complicated by respiratory diseases (20%), gastrointestinal diseases (24%), and calcinosis (30%). Patients presenting prior to 1972 received a wide variety of treatments. Since 1972, treatment has consisted of long-term prednisone, supplemented in some patients with azathioprine. Ten patients died (eight of whom were first seen before 1972) of complications after intestinal perforation (5) or aspiration pneumonia (5). Of 29 survivors, three have persistent calcinosis and/or contractures. Improved outcome since 1972 probably relates to better clinical assessment, management of complications, and regulation of drug therapy.

Adolescent↗
PubMed1986

Antibody specificity of human glomerular basement membrane type IV collagen NC1 subunits. Species variation in subunit composition.

NC1 subunits were purified from gel filtration pools of acid-extracted, collagenase-digested human glomerular basement membranes (hGBM). This methodology, which enriches 28-kDa monomers (M28) in the total digest, allowed purification of these monomers and 24-kDa (M24) and 26-kDa (M26) monomers free from dimers. Reactivity of these subunits with Goodpasture autoantibodies using immunoblotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional nonequilibrium pH gradient electrophoresis gels showed strong reactivity with the purified M28 subunits. Inhibition enzyme-linked immunosorbent assay, used to quantitate the reactivity of the purified NC1 subunits, indicated that M28 had a greater than 10-fold increase in ability to inhibit binding to NC1 than NC1 itself. Comparison of hGBM NC1 components were made with those obtained from collagenase digests of salt and acid-extracted bovine and sheep GBM and Englebreth-Holm-Swarm tumor similarly purified by gel filtration and reverse-phase high performance liquid chromatography. Two-dimensional gel analysis of these NC1 isolates revealed absence of the very cationic M28 monomers. Reactivity with antibodies eluted from diseased kidneys of sheep immunized with hGBM (Steblay nephritis) was compared with Goodpasture autoantibody reactivity by immunoblotting two-dimensional gels of hGBM NC1. We conclude that a very cationic M28 monomer (M28 ) found only in hGBM is the probable target in Goodpasture syndrome, that the epitope is present on most NC1 components from extracted and unextracted hGBM, and is exposed by urea denaturation which is enhanced by acid treatment. A weakly cationic M28 monomer (M28+) is present in GBM from other species and is the probable target in Steblay nephritis. Differential recognition of the two M28 components by these antibodies points to different genetic origins or possibly distinct post-translational modifications for these components. This is supported by their presence or absence in different species and tissues, as well as biochemical differences from the M24/26 monomers which presumably are derived from alpha 1(IV) and alpha 2(IV) collagen chains.

Amino Acids↗
PubMed1986

Comparison of non-collagenous type IV collagen components in the human glomerulus and EHS tumor.

A method for the isolation of the NC1 domain of type IV collagen has been developed using the EHS sarcoma, a basement membrane-producing mouse tumor. This NC1 domain has been compared to the NC1 of human glomerular basement membrane (hGBM) to assess its usefulness in the biochemical characterization of the Goodpasture antigen which is associated with NC1. Both NC1 isolates appeared to migrate by gel filtration as hexamers (Mr 160,000) and in SDS-polyacrylamide gel electrophoresis as dimers and monomers (Mr 54,000 and 26,000), and were shown to share biochemical identity by amino acid analysis. The hGBM NC1 showed greater complexity in the monomer region, and when compared by two-dimensional gel electrophoresis was found to contain more components in both regions than EHS NC1. Anti-GBM autoantibodies from patients with Goodpasture's syndrome reacted with the EHS NC1 by immunoblotting of two-dimensional gels. The EHS NC1 isolated by reverse phase HPLC partially inhibited the reactivity of the anti-GBM autoantibodies against hGBM NC1 by inhibition ELISA assay. Reverse phase HPLC elution of EHS and hGBM NC1 showed differences in subunit composition and interaction; complete dissociation of the EHS monomers and dimers in 0.1% trifluoroacetic acid was observed, whereas hGBM monomers and dimers eluted together. Rotary shadowing of hGBM NC1 domains revealed size heterogeneity of globular domains, compared with greater uniformity of EHS NC1 hexamers. We conclude that EHS NC1 contains an epitope(s) that is reactive with human autoantibodies to hGBM NC1. However, the immune response in Goodpasture's syndrome may involve antibodies directed against epitopes which are present in greater density and on a more complex array of peptides in the hGBM NC1 than in EHS NC1.

Amino Acids↗