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Biomedical subjects

G R Martin

Publications and source records attributed to G R Martin.

At least 307 records · Page 17Linked to original sources
PubMed1983

Interactions of basement membrane components.

The binding of laminin, type IV collagen, and heparan sulfate proteoglycan to each other was assessed. Laminin binds preferentially to native type IV (basement membrane) collagen over other collagens. A fragment of laminin (Mr 600 000) containing the three short chains (Mr 200 000) but lacking the long chain (Mr 400 000) showed the same affinity for type IV collagen as the intact protein. The heparan sulfate proteoglycan binds well to laminin and to type IV collagen. These studies show that laminin, type IV collagen and heparan sulfate proteoglycan interact with each other. Such interactions in situ may determine the structure of basement membranes.

Animals↗
PubMed1983

Formation of a supramolecular complex is involved in the reconstitution of basement membrane components.

Basement membrane macromolecules, including type IV collagen, laminin, and heparan sulfate proteoglycan, do not aggregate when incubated alone. Rather, precipitation occurs in the presence of equimolar amounts of laminin and type IV collagen but variable amounts of heparan sulfate proteoglycan. This interaction requires native laminin and type IV collagen. Heparan sulfate proteoglycan increases the precipitation of laminin particularly in the presence of type IV collagen. Fibronectin does not cause type IV collagen to precipitate. These studies show that the components of basement membrane interact in a highly specific manner and suggest that such interactions may be involved in the deposition of basement membrane in situ.

Animals↗
PubMed1983

Reduced synthesis of basement membrane heparan sulfate proteoglycan in streptozotocin-induced diabetic mice.

In diabetes, certain basement membranes become thicker yet more porous than normal. To identify possible changes in the basement membrane, we have grown the Engelbreth-Holm-Swarm tumor, a tissue that produces quantities of basement membrane in normal mice and in streptozotocin-treated, insulin-deficient, diabetic mice. The level of laminin, a basement membrane-specific glycoprotein, and the level of total protein were slightly elevated in the diabetic tissue. In contrast, the level of the basement membrane specific heparan sulfate proteoglycan was only 20% of control. The synthesis of this proteoglycan was also reduced in the diabetic animals, while the synthesis of other proteoglycans by tissues such as cartilage was normal. The synthesis of the heparan sulfate proteoglycan in diabetic animals was inversely related to plasma glucose levels showing an abrupt decrease above the normal range of plasma glucose. Insulin restored synthesis to normal but this required doses of insulin that maintained plasma glucose at normal levels for several hours. Since the heparan sulfate proteoglycan in the basement membrane restricts passage of proteins, its absence could account for the increased porosity of basement membrane in diabetes. A compensatory synthesis of other components could lead to their increased deposition and the accumulation of basement membrane in diabetes.

Animals↗
PubMed1983

Interactions of asymmetric forms of acetylcholinesterase with basement membrane components.

Previous studies have indicated that the asymmetric form of acetylcholinesterase is localized in the basement membrane zone of the neuromuscular junction. We find that the collagenous subunit of the enzyme is required for interactions with basement membrane components. Acetylcholinesterase (the A12 form) binds best to the basement membrane heparan sulfate proteoglycan and type V collagen, to a lesser extent to laminin, fibronectin, and type I collagen, but not to type IV collagen. In addition, the purified A12 enzyme as prepared from electric eel is associated with a heparan sulfate-like component which appears to be responsible for the aggregation of the enzyme at low ionic strength. We observed that the purified form of the enzyme reacted with antibodies to type V collagen, and to a lesser extent with anti-type I collagen antibody, but not with anti-type IV collagen antibody. These data suggest that the collagenous subunit of the enzyme may have some similarity to type V collagen and that the interaction of the collagenous subunit with a heparan sulfate proteoglycan may be involved in its binding to basement membrane in the neuromuscular junction.

Acetylcholinesterase↗
PubMed1983

Light microscopic immunolocalization of type IV collagen, laminin, heparan sulfate proteoglycan, and fibronectin in the basement membranes of a variety of rat organs.

Immunohistochemical methods were used to determine whether type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan were present in diverse basement membranes. Antisera or antibodies against each substance were prepared, tested by enzyme-linked immunosorbent assay, and exposed to frozen sections of duodenum, trachea, kidney, spinal cord, cerebrum, and incisor tooth from rats aged 20 days to 34 months. Bound antibodies were then localized by indirect or direct peroxidase methods for examination in the light microscope. Immunostaining for type IV collagen, laminin, fibronectin, and heparan sulfate proteoglycan was observed in all of the basement membranes encountered. Fibronectin was also found in connective tissue. In general, the intensity of immunostaining was strong for type IV collagen and laminin, moderate for heparan sulfate proteoglycan, and weak for fibronectin. The pattern was similar in the age groups under study. Very recently the sulfated glycoprotein, entactin, was also detected in the basement membranes of the listed tissues in 20-day-old rats. It is accordingly proposed that, at least in the organs examined, type IV collagen, laminin, fibronectin, heparan sulfate proteoglycan, and entactin are present together in basement membranes.

Animals↗
PubMed1983

The adhesive glycoprotein laminin is an agglutinin.

The glycoprotein laminin appears to function in the attachment of various epithelial cells to basement membranes. We examined whether its putative cell-adhesive activity could be analyzed in a simple, one-component model system--the agglutination of erythrocytes. Laminin is a potent agglutinin of aldehyde-fixed sheep and human erythrocytes, with half-maximal agglutination at 0.8 micrograms/ml in a standard hemagglutination assay. Inhibitors of this hemagglutinating activity include gangliosides and certain charged phospholipids. The spectrum of molecules is similar but not identical to inhibitors of the hemagglutinating activity of the adhesive glycoprotein fibronectin. Laminin is much less biologically active in three other assays for fibronectin biological activity involving cell spreading on tissue culture substrates, attachment of fibroblastic cells to type I collagen, and restoration of normal morphology to transformed fibroblasts. The adhesive glycoproteins laminin and fibronectin therefore differ markedly in biological activities in several specific adhesion assays; however, they resemble one another in binding to heparin, collagen, and cell surfaces and in their agglutinin activity.

Animals↗
PubMed1983

Tunicamycin reversibly inhibits the terminal differentiation of teratocarcinoma stem cells to endoderm.

The differentiation of aggregates of certain teratocarcinoma stem cell lines begins with the formation of an outer layer of primary endoderm cells characterized by the production of plasminogen activator and the absence of histochemically detectable alkaline phosphatase activity. After several days of culture these outer cells develop into a mixture of two types of terminally differentiated endoderm: parietal endoderm which produces a thick layer of underlying basement membrane and visceral endoderm which produces alpha-fetoprotein (AFP). We report here that in the presence of tunicamycin, a drug that inhibits glycosylation of N-asparagine linked glycoproteins, a primary endoderm-like cell is formed which is alkaline phosphatase negative and plasminogen activator positive. However, terminal differentiation of these cells is inhibited as manifested by the lack of accumulation of a thick basement membrane and the absence of immunologically detected AFP. Such inhibition is reversible following removal of the tunicamycin. Terminal differentiation of endoderm depends, therefore, upon N-asparagine linked glycoproteins.

Alkaline Phosphatase↗
PubMed1983

The retinal binocular field of the pigeon (Columba livia: English racing homer).

An ophthalmoscopic reflex technique has shown that in sedated pigeons maximum retinal binocular field width occurs approximately 20 degrees above the bill. The binocular field has a maximum width of 27 degrees and extends vertically by 130 degrees (90 degrees above the bill, 40 degrees below it). Both the bill and cere intrude into the binocular field. Maximum optical binocularity also occurs approximately 20 degrees above the bill. The plane containing the optic axes of each eye coincides with the bill.

Animals↗
PubMed1983

Teratocarcinoma stem cell adhesion: the role of divalent cations and a cell surface lectin.

We describe two additive systems of intercellular adhesion in teratocarcinoma stem cells (Nulli cell line). One component is divalent cation-dependent (Ca++ or Mg++) and the other involves a cell surface fucan/mannan-specific lectin, previously identified on stem cells by an erythrocyte rosetting assay. The existence of these two systems is inferred from the observation that reaggregation of stem cells was partially inhibited by the removal of divalent cations or by the presence of lectin inhibitors such as fucoidan, but reaggregation was completely blocked when the two conditions were combined. Our results are related to recent work describing a calcium-dependent system of intercellular adhesion in teratocarcinoma stem cells.

Animals↗
PubMed1983

Automated reading of a microtitre plate: preliminary evaluation in antimicrobial susceptibility tests and Enterobacteriaceae identification.

An automated microELISA Reader was evaluated for its ability to read and interpret microtitre plates. A total of 309 microtitre plates were investigated by automated and visual methods. There was disagreement between the methods in one hundred and twelve (0.6%) wells. However agreements between the two methods for susceptibility tests and Enterobacteriaceae identification were respectively 98.8% and 89.3%.

Anti-Bacterial Agents↗
PubMed1983

Cultured tumor cells produce chemotactic factors specific for endothelial cells: a possible mechanism for tumor-induced angiogenesis.

The production of stimulants of endothelial cell motility by cultured tumor cells was studied. Spontaneously transformed murine fibroblasts in culture produced activity that stimulated migration of endothelial cells, while this kind of activity was not detected in media from cultures of the normal counterparts of the transformed cells. Furthermore, a line of murine tumor cells (HB4), known to induce vasoformative sarcomas in vivo, was found to produce in culture a strong chemoattractant specific for endothelial cells. Since the tumor-derived material also caused vessel ingrowth when implanted in the rabbit eye, these results suggest that the angiogenesis observed during tumor growth may involve chemoattractants for endothelial cells produced by tumor cells.

Animals↗
PubMed1983

Loss of heparan sulfate proteoglycan from glomerular basement membrane of nephrotic rats.

Three basement membrane components, heparan sulfate proteoglycan, laminin, and type IV collagen, were localized in renal glomeruli using light and electron microscopic immunohistochemistry in normal and aminonucleoside-treated nephrotic rats. In normal rats, type IV collagen was found in both laminae rarae and in lamina densa; laminin and heparan sulfate were found in the three layers of the basement membrane with more intense staining in both laminae rarae. In nephrotic rats laminin and type IV collagen had the same localization and distribution as in normal rats. This was in contrast to heparan sulfate proteoglycan which was lost to a considerable extent in nephrotic animals. These results support the concept that heparan sulfate proteoglycan is a major charge determinant in normal glomerular basement membrane and suggest a crucial role for this proteoglycan in the pathogenesis of the nephrotic syndrome.

Animals↗
PubMed1983

Structure, function, and pathology of basement membranes.

Basement membranes support epithelial and endothelial cells, prevent the passage of proteins, and generate histologically distinct compartments in the body. Basement membranes contain a number of components, only some of which have been isolated and characterized. These include type IV collagen, heparan sulfate proteoglycan, laminin, entactin, and fibronectin. Some components, such as bullous pemphigoid antigen and Goodpasture antigen, are present only in specific tissues, such as the skin or the kidneys. Alterations in basement membranes are associated with various diseases. For example, metastatic cells are able to attach to basement membranes and to degrade them. Such interactions with basement membranes underlie the ability of these cells to penetrate tissues and to spread in the body. In diabetes, basement membranes are thickened but are more porous, which is possibly due to a decreased amount of heparan sulfate proteoglycan. Basement membranes are also the site of immunopathologic disorders.

Autoimmune Diseases↗
PubMed1983

Developmental potential of teratocarcinoma stem cells in utero following aggregation with cleavage-stage mouse embryos.

Embryonal carcinoma cells were aggregated with cleavage stage mouse embryos, cultured briefly, and transferred as morulae to the uteri of pseudopregnant females. When midgestation foetuses were examined, many were morphologically abnormal. The severity of this abnormal development was correlated with the extent of contribution by embryonal carcinoma cells to the foetuses as indicated by GPI (glucose phosphate isomerase) analysis. This was true for all three of the cell lines studied, NG-2, PSA-1, and LT1-2D. The clear correlation between increasingly abnormal development and more extensive participation by the embryonal carcinoma cells was not observed in control experiments in which embryos of different stages of development were aggregated together. The data therefore suggest that the embryonal carcinoma cells studied here are unable to support normal development in the absence of a substantial number of host embryonic cells. It remains unclear whether this is a consequence of the karyotypic abnormalities of the cells tested, or whether it reflects a characteristic limitation in the ability of embryonal carcinoma cells to independently direct normal development. When aggregates were allowed to develop to term and the extent of chimaerism was examined in the live-born animals, it was found to be sporadic and limited. This is consistent with the results indicating that large contributions by embryonal carcinoma cells are not compatible with normal development at midgestation. The chimaerism observed in the live-born animals was comparable in both frequency and in tissue distribution to that generally obtained in other studies using either the aggregation or blastocyst injection techniques.

Animals↗
PubMed1982

Isolation and characterization of type IV procollagen, laminin, and heparan sulfate proteoglycan from the EHS sarcoma.

We have studied the extractability of type IV collagen, laminin, and heparan sulfate proteoglycan from EHS tumor tissue growth in normal and lathyritic animals. Laminin and heparan sulfate proteoglycan were readily extracted with chaotropic solvents from both normal and lathyritic tissue. The collagenous component was only solubilized from lathyritic tissue in the presence of a reducing agent. These results indicate that lysine-derived cross-links and disulfide bonds stabilize the collagenous component in the matrix but not the laminin or the heparan sulfate proteoglycan. The majority of the collagen present in the extracts had a native triple helix based upon the pattern of peptides resistant to pepsin digestion and visualization in the electron microscope by the rotary shadow technique. This protein was composed of chains (Mr 185000 and 170000) identical in migration to the chains of newly synthesized type IV procollagen. This finding confirms earlier work that indicates that the biosynthetic form, type IV procollagen, is incorporated as such in the basement membrane matrix. Material with smaller chains (Mr 160000 and 140000) appeared on storage in acetic acid solutions. These results indicate that the lower molecular weight collagen in acid extracts of basement membrane arises artifactually due to an endogenous acid-active protease.

Animals↗
PubMed1982

Antibodies to laminin in Chagas' disease.

We have found that sera from humans with Chagas' disease and Rhesus monkeys infected with Trypanosoma cruzi contain IgM and IgG antibodies, which react with structures in a variety of connective tissues. These antibodies react with laminin but not with various other purified connective tissue components like collagen types I, III, IV, and V, fibronectin, heparan sulfate (BM-1) proteoglycan, or chondronectin. The tissue-reacting antibodies were isolated by absorption to a laminin-Sepharose column. The bound fraction contained all the tissue-reacting antibodies. These antibodies strongly stained trypomastigotes and amastigotes, but weakly stained epimastigotes. These studies show that sera from T. cruzi-infected primates contain antilaminin antibodies, which may be produced by those host in response to a laminin-like molecule present in the parasite.

Adolescent↗
PubMed1982

The isolation and partial characterization of chondronectin, an attachment factor for chondrocytes.

We have previously demonstrated that the adhesion of embryonic chick sternal chondrocytes to a type II-collagen substrate is not mediated by fibronectin but rather by a distinct attachment factor which we have named chondronectin. Here we describe the isolation, properties, and biological activity of chondronectin prepared from chicken serum. Chondronectin is shown to be a glycoprotein with an estimated Mr = 180,000. After reduction, it migrates as subunits of Mr = 70,000. Antibodies directed against chondronectin inhibited the attachment of chondrocytes to type II collagen. Chondronectin is immunologically distinct from either fibronectin or laminin. Immunofluorescence studies on frozen sections of embryonic chick sternal cartilage and of cultured sternal chondrocytes showed that chondronectin is cell-associated rather than a major matrix component.

Animals↗