Identification and characterization of chemoattractants for epidermal cells

We have detected and partially characterized factors that promote the directed migration of mouse epidermal cells in a modified Boyden chamber assay. Smooth muscle cells grown in culture were found to secrete a potent chemoattractant for epidermal cells. This activity was further characterized and compared to the chemotactic activities found in wound fluid and conditioned medium from 3T3 L1 cells and with interleukin 1. The migration of epidermal cells during wound healing in vivo might be regulated by such factors.

Isolation and purification of an antibody to 67-KD calcimedin

The 67-KD calcimedin is a calcium-binding protein isolated from several muscle tissues. The protein shows apparent Mr of 67,000 by SDS-polyacrylamide gel electrophoresis. An antibody has been prepared by immunizing sheep with the protein purified from chicken gizzard smooth muscle. This antibody recognizes 67-KD calcimedin but not calmodulin, bovine serum albumin, transferrin, or brain p68 calelectrin. The presence of 67-KD calcimedin is demonstrated in the smooth muscle cell lines A10 and DDT1MF-2 as well as in primary cultures of chicken breast and heart muscle, by immunoprecipitation and immunofluorescence. The 67-KD calcimedin, being responsive to calcium, may play a role in calcium-mediated cell regulation. This report identifies several cells that may be useful for further delineation of the cellular role of 67-KD calcimedin.

Density of myosin filaments in the rat anococcygeus muscle, at rest and in contraction. II

Rat anococcygeus muscles were fixed at rest or in contraction by conventional methods and prepared for electron microscopy. Myosin filaments were counted on cross sections and their density expressed per unit cytoplasmic area. In contracted muscles, the mean density increased from 86 to 168 filaments per micron 2 (1.95 times), while the density of intermediate (10 nm) filaments increased by 1.25 times. Cell cross sections from the same muscles were measured. Contraction produced a shrinkage which explains the apparent increased density of the 10 nm filaments; however an excess of 61 myosin filaments per micron 2 cannot be explained in this way. These findings provide the structural basis which quantitatively explains the birefringence changes observed in living contracted muscle (Godfraind-De Becker & Gillis, 1988). Our optical and electron optical results provide evidence for a reversible formation of myosin filaments during contraction of the rat anococcygeus muscle.

The heavy-chain stoichiometry of smooth muscle myosin is a characteristic of smooth muscle tissues

The stoichiometry of the two heavy chains of myosin in smooth muscle was determined by electrophoresing extracts of native myosin and of dissociated myosin on sodium dodecyl sulfate (SDS) 4%-polyacrylamide gels. The slower migrating heavy chain was 3.6 times more abundant in toad stomach, 2.3 in rabbit myometrium, 2.0 in rat femoral artery, 1.3 in guinea pig ileum, 0.93 in pig trachea and 0.69 in human bronchus, than the more rapidly migrating chain. Both heavy chains were identified as smooth muscle myosin by immunoblotting using antibodies to smooth muscle and non-muscle myosin. The unequal proportion of heavy chains suggested the possibility of native isoforms of myosin comprised of heavy-chain homodimers. To test this, native myosin extracts wer electrophoresed on non-dissociating (pyrophosphate) gels. When each band was individually analysed on SDS-polyacrylamide gel the slowest was found to be filamin and the other bands were myosin in which the relative proportion of the heavy chains was unchanged from that found in the original tissue extracts. Since this is incompatible with either a heterodimeric or a homodimeric arrangement it suggests that pyrophosphate gel electrophoresis is incapable of separating putative isoforms of native myosin.

Beta-actinin isoforms in various types of muscle and non-muscle tissues

We found that beta-actinin isoforms are present in various types of tissues in adult chicken by using immunoblotting after two dimensional gel electrophoresis; for this purpose, an antibody was raised against beta-actinin purified from adult chicken breast muscle (pectoralis major). One of the beta-actinin subunits, beta I, was present in all tissues we examined, i.e. skeletal (pectoralis major, semitendinosus, and anterior latissimus dorsi), cardiac, and smooth (gizzard) muscles, non-muscle (brain, liver, and kidney) tissues and blood, whereas another subunit, beta II, was present only in muscle tissues. A new subunit (designated beta III) that was found in the embryonic stages of skeletal muscle (Asami, Funatsu & Ishiwata (1988) J. Biochem. 103, 72-75) was present instead of beta II in non-muscle tissues and blood. In cardiac and smooth muscles, beta III coexisted with beta I and beta II. The antibody of beta-actinin did not cross-react to cytoplasmic beta-actinin (molecular weight, 80,000 daltons) found in kidney. It was suggested that the combination of beta I and beta III present in non-muscle tissues and blood is identical to the barbed end capping protein isolated from brain by Killiman and Isenberg (EMBO J. 1, 889-894 (1982)). It is likely that beta-actinin forms a genetic family whose constituents have an ability to cap either the pointed or barbed end of actin filaments.

Wide variation of myoglobin contents in gizzard smooth muscles of various avian species

We determined myoglobin contents of gizzards (muscular stomach) and breast muscles in 34 avian species by a modification of Reynafarje's spectrophotometric procedure. The birds were apparently differentiated into two groups in respect of the gizzard, one with a high myoglobin content (7.74 +/- 1.81 mg/g muscle) and the other with a low (1.54 +/- 0.41 mg/g). In the former group of 15 species all but one were herbivorous, and all but one were carnivorous or else omnivorous in the latter group of 19 species. The myoglobin level was considered to closely correlate with mechanical performance and therefore oxygen demands of the gizzards. It might also be relevant to a circulatory situation during the tonic contractions of this organs.

Generation of multiple troponin T isoforms is a common feature of the muscles in various chordate animals

1. Troponin T (TNT) expressed in various vertebrate skeletal and ascidian smooth muscles was examined by two-dimensional electrophoresis in combination with immunoblotting. 2. A monoclonal anti-TNT antibody, NT-302, exhibited binding ability to various TNT variants in the vertebrate and protochordate animals. 3. TNT isoform pattern differed among the animals, but the existence of multiple TNT isoforms in a single muscle tissue was the general feature of all the animals examined.

Autoradiographic visualization of muscarinic receptors in pulmonary nerves and ganglia

We investigated autoradiographically the distribution of muscarinic receptors in bovine airways using (-)-[3H]quinuclidinyl benzilate as radioligand. The autoradiographs demonstrated the presence of muscarinic receptors in smooth muscle as well as neuronal muscarinic receptors in pulmonary nerves and ganglia. It is reasonable to believe that the neuronal muscarinic receptors participate in the regulation of neurotransmitter release at the peripheral nerve terminals innervating the bronchial smooth muscle.

Dystrophin: the protein product of the Duchenne muscular dystrophy locus

The protein product of the human Duchenne muscular dystrophy locus (DMD) and its mouse homolog (mDMD) have been identified by using polyclonal antibodies directed against fusion proteins containing two distinct regions of the mDMD cDNA. The DMD protein is shown to be approximately 400 kd and to represent approximately 0.002% of total striated muscle protein. This protein is also detected in smooth muscle (stomach). Muscle tissue isolated from both DMD-affected boys and mdx mice contained no detectable DMD protein, suggesting that these genetic disorders are homologous. Since mdx mice present no obvious clinical abnormalities, the identification of the mdx mouse as an animal model for DMD has important implications with regard to the etiology of the lethal DMD phenotype. We have named the protein dystrophin because of its identification via the isolation of the Duchenne muscular dystrophy locus.

Purification of two smooth muscle glycoproteins related to integrin. Distribution in cultured chicken embryo fibroblasts

We have purified two membrane glycoproteins from chicken gizzard smooth muscle. In the presence of reducing agents, these proteins have molecular weights on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 165,000 and 130,000, but they migrate at 165,000 and 110,000 without reduction. The two proteins can also be isolated as a complex in buffers containing physiologic salt concentrations. This complex has physical properties similar to two proteins of the integrin family of receptors for extracellular matrix proteins, the cell substratum attachment antigen from chicken embryos, and the glycoprotein IIb IIIa complex from mammalian platelets. When the smooth muscle complex is visualized by electron microscopy, it has a striking resemblance to both avian integrin and the glycoprotein IIb IIIa complex. Smooth muscle is a good source of the 165,000 and 130,000 proteins, and purification of both the individual subunits and the complex is achieved using conventional biochemical techniques. Antibodies directed against the 130,000 protein cross-react with integrin but do not cross-react with the 165,000 protein. Immunofluorescence microscopy using these antibodies reveals staining of fibroblast focal contacts and fibrillar streaks which coalign with fibronectin. Whereas monoclonal antibodies against integrin label the periphery of the focal contact more intensely than the center, the anti-130,000-protein serum stains the entire focal contact. Antibodies directed against the 165,000 protein also stain focal contacts and fibrillar streaks of fibroblasts in tissue culture. On the basis of similar physical properties, biochemical characteristics, and immunological cross-reactivity we conclude that the 165,000/130,000 complex is a smooth muscle integrin.

Extracellular matrix-cytoskeletal connections at the surface of the specialized contractile fibroblast (myofibroblast) in Dupuytren disease

The cellular basis of contracture of the palmar fascia in patients who have Dupuytren disease involves the generation of intracellular force and the transmission of this force to the surrounding tissue. A specialized cell, the myofibroblast, supposedly generates this intracellular force. Recently published studies from our laboratory demonstrated that the cytoskeleton of the myofibroblast contains non-muscle myosin and not smooth-muscle myosin, suggesting that it utilizes a non-muscle contractile system. In addition, these studies identified the extracellular glycoprotein fibronectin, not the basal-lamina-specific glycoprotein laminin, at the surface of myofibroblasts, suggesting that the transmission of the intracellular force to the surrounding tissue also occurs by a non-muscle mechanism. Because of the lack of proteins that are specific to smooth muscle in the specialized cell in Dupuytren disease, we prefer the term specialized contractile fibroblast to describe this type of cell. To determine the mechanism by which the intracellular force may be transmitted to the surrounding tissue, we examined the ultrastructure of the connection of the cytoskeleton of the specialized contractile fibroblast to the surrounding extracellular matrix. By electron microscopy, extracellular filamentous material was identified at the surface of the specialized contractile fibroblast. These extracellular fibrils were found to be in close association with intracellular bundles of actin microfilaments, resulting in specialized transmembranous associations at the surface of the specialized contractile fibroblast. Bundles of filamentous extracellular material were found to extend from the surface of the specialized contractile fibroblast, connecting it with the surrounding matrix and also with adjacent specialized contractile fibroblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokeratins in certain endothelial and smooth muscle cells of two taxonomically distant vertebrate species, Xenopus laevis and man

Using immunolocalization techniques, electron microscopy, and gel electrophoresis combined with immunoblotting, we have noted remarkable interspecies differences in the expression of cytokeratins in certain nonepithelial cells. In the present study we describe, in two taxonomically distant vertebrate species, the African clawed toad Xenopus laevis and man, endothelial and smooth muscle cells which express cytokeratin intermediate filaments (IFs), in addition to vimentin and/or desmin IFs. In Xenopus, all endothelia seem to produce both vimentin and cytokeratin IFs. As well, certain smooth muscle bundles located in the periphery of the walls of the esophagus and the urinary bladder produce small amounts of cytokeratin IFs in addition to IFs containing vimentin or desmin or both. The amphibian equivalents of human cytokeratins 8 and 18 have been identified in these nonepithelial tissues. In human endothelial cells, immunocytochemical reactions with certain cytokeratin antibodies are restricted to a rare subset of blood vessels. Vessels of this type were first noted in synovial and submucosal tissues, but also occur in some other locations. Cytokeratins have also been detected in certain groups of smooth muscles, such as those present in the walls of some blood vessels in synovial tissue and umbilical cord. Here, the synthesis of low levels of cytokeratins 8 and 18, sometimes with traces of cytokeratin 19, has been demonstrated in smooth muscle cells by colocalization with myogenic marker proteins, such as desmin and/or the smooth-muscle-specific isoform of alpha-actin. Possible reasons for the differences in cytokeratin expression between adjacent endothelia in man, and smooth-muscle structures in both species, as well as biologic and histodiagnostic implications of these findings, are discussed.

3H-neurokinin A labels a specific tachykinin-binding site in the rat duodenal smooth muscle

3H-Neurokinin A (3H-NKA) with high specific activity (75 Ci/mmol) was synthesized to study NKA (NK-2)-binding sites on membrane preparations of various tissues in the rat, including brain, spinal cord, duodenum, vas deferens, and ileum. The binding capacity of 3H-NKA (0.9 nM) was very low in membrane preparations of different central nervous system regions and the ileum smooth muscle (0.2-2 fmol/mg of protein). In contrast, relatively high specific binding was found in membrane suspensions of the rat duodenal smooth muscle (18 fmol/mg of protein) and the vas deferens (8 fmol/mg of protein). 3H-NKA-binding sites were further characterized on the rat duodenal smooth muscle. The specific binding of 3H-NKA was shown to be temperature dependent, saturable, reversible, and increased in parallel with the protein concentration. Scatchard analyses and Hill plots of equilibrium binding studies in the concentration range of 0.40-30 nM revealed that 3H-NKA bound to a single class of noninteracting binding sites (Bmax = 270 fmol/mg of protein, KD = 13.3 nM). Displacement of 3H-NKA with different tachykinin-related peptides gave the following rank order of potencies: NKA greater than NKA (4-10) greater than kassinin greater than eledoisin greater than NKB much greater than substance P greater than physalaemin, which suggests that the binding site labeled by 3H-NKA is different from substance P (NK-1)-and NKB (NK-3)-binding sites. The biological activities of tachykinins and related peptides were tested by measuring their contractile effects on the rat duodenum and rabbit pulmonary artery, two tissues known to be sensitive for NKA. Ki values were correlated with the EC50 obtained in biological assays. The results revealed a significant correlation (r = 0.86, p less than 0.01) between Ki and EC50 values obtained in the isolated rabbit pulmonary artery, whereas there was no significant correlation between binding affinities and biological responses on the rat duodenum (r = 0.62, p greater than 0.05).

Alpha- and beta-adrenergic receptors in the horse ureter

The presence of both alpha and beta adrenergic receptors in the caudal third ureter of the horse were studied in vitro under isometric conditions using adrenergic agonist and antagonist drugs. Isoprenaline and the beta 2- stimulating agent, salbutamol, elicited relaxation of the ureter smooth muscle strips. The responses were not affected by the beta 1- blocking agent, practolol, but were totally abolished by propranolol and the beta 2- blocking agent, butoxamine. The stimulation of alpha-adrenergic receptors with noradrenaline and phenylephrine evoked a contractile effect which was totally inhibited by phenoxybenzamine and the alpha 1- blocking agent, prazosin. It is concluded that in the horse ureter the alpha receptors are dominant and belong to alpha 1 subtype while the beta receptors are recessive and belong to beta 2- adrenoceptor subtype.

Polymerization of vertebrate non-muscle and smooth muscle myosins

We investigated how light chain phosphorylation controls the stability of filaments of vertebrate non-muscle myosins (from bovine thymocytes and chicken intestine epithelial brush border cells) and smooth muscle myosin (from chicken gizzard) in vitro. Using a sedimentation assay, the solubilities of the myosins were determined by measuring the amounts of myosin monomers (Cm) and filaments (Cp) present under a given set of conditions as a function of the total myosin concentration (Ct). Below 200 mM-NaCl, each myosin displayed distinct "critical monomer concentrations" (Cc) for polymerization, which were dependent on the salt concentration, the state of light chain phosphorylation and the presence of MgATP. At 150 mM-NaCl, MgATP increased the Cc of non-phosphorylated brush border myosin approximately five to tenfold, thymus myosin approximately 10 to 15-fold, and gizzard myosin approximately 25 to 50-fold. When these myosins were phosphorylated, MgATP had little effect on their solubilities, and their Cc values remained low. Analytical ultracentrifugation and electron microscopy demonstrated that the myosins were present in three different conformational states under the conditions used in the sedimentation assays, i.e. filaments, extended monomer (6 S) and folded monomer (10 S). Since at equilibrium only filaments and monomers were observed, we suggest that the polymerization pathway for these myosins can be analysed in terms of a dynamic monomer-polymer equilibrium (polymer in equilibrium 6 S monomer in equilibrium 10 S monomer). At roughly physiological ionic strength, light chain dephosphorylation (in the presence of MgATP) promotes the folded state (10 S), whereas phosphorylation promotes the extended state (6 S), and thereby favours filament assembly. The relevance of the monomer-polymer equilibrium to the state of organization of the myosin in vivo is discussed.

Complete primary structure of vertebrate smooth muscle myosin heavy chain deduced from its complementary DNA sequence. Implications on topography and function of myosin

The 1979 amino acid sequence of embryonic chicken gizzard smooth muscle myosin heavy chain (MHC) have been determined by cloning and sequencing its cDNA. Genomic Southern analysis and Northern analysis with the cDNA sequence show that gizzard MHC is encoded by a single-copy gene, and this gene is expressed in the gizzard and aorta. The encoded protein has a calculated Mr of 229 X 10(3), and can be divided into a long alpha-helical rod and a globular head. Only 32 to 33% of the amino acid residues in the rod and 48 to 49% in the head are conserved when compared with nematode or vertebrate sarcomeric MHC sequences. However, the seven residue hydrophobic periodicity, together with the 28 and 196 residue repeat of charge distribution previously described in nematode myosin rod, are all present in the gizzard myosin rod. Two of the trypsin-sensitive sites in gizzard light meromyosin have been mapped by partial peptide sequencing to 99 nm and 60 nm from the tip of the myosin tail, where these sites coincide with the two "hinges" for the 6 S/10 S transition. In the head sequence, several polypeptide segments, including the regions around the putative ATP-binding site and the reactive thiol groups, are highly conserved. These areas presumably reflect conserved structural elements important for the function of myosin. A multi-domain folding model of myosin head is proposed on the basis of the conserved sequences, information on the topography of myosin in the literature, and the predicted secondary structures. In this model, Mg2+ ATP is bound to a pocket between two opposing alpha/beta domains, while actin undergoes electrostatic interactions with lysine-rich surface loops on two other domains. The actin-myosin interactions are thought to be modulated through relative movements of the domains induced by the binding of ATP.

Identification of muscarinic M2 receptors on single muscle cells of the human and guinea pig intestine

Muscle cells were isolated from the longitudinal muscle layer of guinea pig and human jejunum and used to identify the muscarinic receptor subtype (M1 or M2) that mediates contraction. Single muscle cells were anchored to the ceiling of a minichamber and their contraction was measured in response to acetylcholine, alone and in combination with three muscarinic antagonists: atropine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), and pirenzepine. Estimates of the inhibitory dissociation constants (Ki) were closely similar in human and guinea pig muscle cells (atropine 2.5-5 X 10(-11) M, 4-DAMP 1.9-2.9 X 10(10) M, and pirenzepine 8.2-9.5 X 10(-8) M). Thus, pirenzepine, a preferential M1 antagonist, was 1900-3280 times less potent than atropine and 279-500 times less potent than 4-DAMP. Comparative measurements on longitudinal muscle strips from guinea pig jejunum confirmed the greater potency of atropine and 4-DAMP relative to pirenzepine. Inactivation of muscarinic receptors on single muscle cells with dibenamine showed that only a small fraction of receptors was responsible for the response to acetylcholine. It was concluded that intestinal muscle cells contain a large reservoir of muscarinic M2 receptors that exhibit considerable spareness and heterogeneity.

Characteristics of beta-adrenoceptors in tracheal smooth muscle of guinea pig sensitized by egg albumin

The effect of pretreatment with egg albumin was examined on the beta-adrenoceptors in guinea pig isolated trachea. Befunolol and carteolol acted as partial agonists and their pA2 values were significantly larger than their corresponding pD2 values in tracheae from both untreated guinea pigs and those treated with egg albumin, suggesting that the beta-adrenoceptors contain two different affinity sites. The Scatchard plot of specific [3H]befunolol binding showed two affinity sites of the receptor (high and low affinity sites) in tracheae from both untreated animals and those treated with egg albumin. The pKD values of befunolol for both low and high affinity sites were in agreement with their respective pD2 and pA2 values. The intrinsic activities of befunolol and carteolol and the pD2 values of the test drugs were decreased by the treatment with egg albumin. The treatment with egg albumin also decreased the total amount of the two affinity sites of the receptor without any change in affinity. The present results support the partial blockade of beta-adrenoceptors in asthma proposed by Szentivanyi.

A common myosin light chain is expressed in chicken embryonic skeletal, cardiac, and smooth muscles and in brain continuously from embryo to adult

We have isolated cDNA clones of the mRNA for chick embryonic myosin light chain (MLC), L23, by cross-hybridization with chicken skeletal muscle MLC1 cDNA. The identification of the isolated cDNAs was carried out by in vitro translation of hybrid-selected mRNA. Sequence analysis of the cloned cDNAs revealed that the cDNA insert contained 832 nucleotides and predicted a polypeptide of 185 amino acids with a calculated molecular weight of 20,687. The deduced amino acid sequence for L23 showed high sequence similarities to those of adult alkali type MLCs from various tissues, indicating that L23 belongs to the alkali MLC group. Using the cloned cDNA as a hybridization probe, we have revealed by RNA blot analysis that the expression of L23 mRNA was regulated in temporal and tissue-specific manners. The L23 mRNA of 1.1 kilobases is transiently expressed in embryonic skeletal, cardiac, and smooth muscles of chickens. It is also found in the brain of chickens during all stages of development so far investigated. Only a single gene for L23 was detected by Southern blot of chick genomic DNA. We therefore suggest that L23 is expressed from a single gene in both embryonic muscles and brain.

Characterization of stromal cells with myoid features in lymph nodes and spleen in normal and pathologic conditions

Stromal cells with myoid features were identified in rat or human lymph nodes and spleen in normal and pathologic conditions, using antibodies to desmin, alpha-smooth muscle actin, and smooth muscle myosin. In normal lymph nodes, myoid cells (MCs) were present in the superficial and deep paracortex as well as in the medulla, and absent in lymphoid follicles. In the spleen, they were numerous in the red pulp, less abundant in periarteriolar lymphocyte sheaths of the white pulp, and absent in lymphoid follicles. On double immunostaining, alpha-smooth muscle actin and smooth muscle myosin were coexpressed with desmin only in the deep paracortex and parafollicular areas of the lymph nodes, as well as in the MCs of the periarteriolar lymphocyte sheaths and marginal zone of the spleen; the remaining MCs expressed only desmin. When examined by means of electron microscopy, MCs showed a dendritic shape and cytoplasmic bundles of microfilaments with dense bodies scattered between them. When compared with normal conditions, MCs showed changes of distribution and number in several pathologic situations. Additional findings were 1) staining of pericytes surrounding high endothelium venules of lymph nodes with alpha-smooth muscle actin antibodies in man and rat and with desmin antibodies in rats; 2) staining of endothelial cells in these venules with desmin antibodies in rats. It is concluded that a subset of reticular cells in lymph nodes and spleen, as well as pericytes and endothelial cells in high endothelium venules display cytoskeletal features suggesting a myoid differentiation and function.

Photobleaching of fura-2 and its effect on determination of calcium concentrations

This study was performed to determine the effect of photobleaching on the spectral properties of the calcium-sensitive fluorescent dye fura-2. Fura-2, whether in cells or in calibrating solutions, was found to be bleached when exposed to excitation light. In contrast to the widely held belief, photobleaching altered the spectral properties of the dye. Decomposition of the excitation spectra of partially bleached fura-2 solutions revealed an intermediate that is still fluorescent and is not sensitive to calcium over the same range as fura-2, but which can bind calcium in the millimolar range. The presence of this intermediate violates one of the assumptions on which the ratio method of calibration is based; that is, that the only fluorescent species present are the calcium-bound and the free anion forms of fura-2. Thus, if photobleaching occurs, the ratio method will not give accurate calcium concentration values. We calculate that as little as an 8% loss of total fluorescence intensity is sufficient to produce a large error. Photobleaching of fura-2-loaded cells and fura-2 containing calibrating solutions can be minimized by reducing the oxygen concentration and by reducing the excitation light intensity. Strategies are presented to help maintain a high signal-to-noise ratio in fura-2 fluorescence detection systems, despite a lower excitation intensity so that photobleaching, and the resulting inaccuracies in calculated [Ca2+], can be largely avoided.

Elastin in a neonatal rat smooth muscle cell culture has greatly decreased susceptibility to proteolysis by human neutrophil elastase. An in vitro model of elastolytic injury

A neonatal rat aorta smooth muscle cell culture system with a unique elastin-rich extracellular matrix was used as a model substrate for elastases. To study the susceptibility to solubilization of insoluble elastin, cultures were incubated in the presence of human neutrophil elastase (HNE) or porcine pancreatic elastase (PPE) and in the absence of serum for periods up to 45 min. Both the incubation media and cell layers were then assessed for elastin and collagen markers, total protein, and lactate dehydrogenase (LDH). Although HNE and PPE exhibited comparable activity against elastin purified from the cell layer, HNE exhibited a 6.7- to 25-fold reduction in its elastin solubilizing activity using intact cell layers as compared with the purified elastin, whereas PPE exhibited only a 1.5- to 2.5-fold reduction. This effect could not satisfactorily be explained as preferential inhibition of HNE activity in the culture system, because the amount of protein solubilized by HNE was 59% that of PPE. The mean elastin content of PPE-solubilized protein was 110% that of the elastin content of the corresponding cell layer; the value for HNE-solubilized protein was only 16%. Thus, the amount of elastin per microgram of solubilized protein for HNE was 15% that for PPE. Possible explanations for the greatly diminished elastolytic activity of HNE in the culture system include the preference of HNE for other substrates in the cell layer, the inability of HNE to penetrate sufficiently into the cell layer, and the presence of sulfated glycosaminoglycans in the vicinity of the elastin that act in an inhibitory fashion. Although there was extensive proteolytic damage to the extracellular matrix, LDH and DNA measurements indicated that little loss of cells or cell viability occurred. The observed differences in elastolytic activity of HNE and PPE in the culture system parallel the relative emphysema-inducing potency of the elastases in the hamster model of elastase-induced emphysema.

Interaction of monoclonal antibodies with a neurite outgrowth factor from chicken gizzard extract

A neurite outgrowth factor (NOF), which promotes neurite outgrowth of cultured peripheral neurons, was purified to homogeneity from chicken gizzard extract and used as an immunogen for generating monoclonal antibodies. From 603 hybridoma clones, 55 positive hybridoma cell lines were detected. Four of them (IgG1 (kappa-chain) producers designated as 5-10A, M1-2G, 4-2C and 1-4D) were selected for further characterization. These antibodies immunoprecipitated 125I-labelled gizzard NOF molecules, whereas they did not inhibit the biological activity of NOF (or NOF-like molecules) derived from the tissues tested. The subcellular distribution of NOF in chick embryonal tissues was investigated using monoclonal antibody 4-2C. Both ciliary ganglionic (CG) neurons and gizzard muscle tissues were stained. The NOF content of embryonic CG, measured by an immunoblot assay, increased about 20-fold during embryogenesis from 6 to 15 days, whereas the sensitivity of neurons to NOF reciprocally decreased. At least two different sizes of NOFs (700 and 800 kDa) were found in CG of various ages, with the 800/700 kDa ratio gradually increasing with age. A mixture of these 4 monoclonal antibodies was used for immunoaffinity purification of NOF from chicken gizzard muscles.

Widespread codistribution of glycoprotein gp 115 and elastin in chick eye and other tissues

Frozen sections of chick tissues were exposed to affinity-purified monoclonal antibodies raised against chick gp 115 and to affinity-purified antibodies raised against chick tropoelastin to study the distribution pattern of the corresponding antigens by the avidin-biotin immunoperoxidase technique. Laminin and fibronectin antibodies were used for comparison. Gp 115 and tropoelastin antibodies localized to the same structure in several of the tissues examined. The endothelial membrane of the cornea and Bruch's membrane in the choroid were positive, while the corneal epithelial membrane was negative. Both antibodies displayed a peculiar punctate reactivity in the corneal stroma and a very fine fibrillar pattern in the conjunctiva and at the corneal-scleral junction. Liver, heart and large vessels, striated muscle and skin showed a similar pattern both for tropoelastin and gp 115 antibodies. Few differences were seen in the distribution of the reactivity: the pericellular matrix of intestinal smooth muscle cells was stained by gp 115 but not by tropoelastin antibodies. However, the reactivity of gp 115 and tropoelastin antibodies was similarly distributed in the lung smooth muscle cell clusters. The peritubular matrix in the kidney did also not react with tropoelastin antibodies as did the brain intraparenchymal vessels; whereas gp 115 antibody reactivity was present in both sites. We interpret these lack of apparent codistribution in some tissues as a variation in the relative availability of the target antigen for the reaction with the antibody and not as a consequence of a qualitative difference in the distribution of gp 115 and tropoelastin. By the use of anti gp 115 monoclonal antibodies that do not cross-react, and presumably recognize different epitopes, it was shown that some but not all antibodies, react with brain intraparenchymal blood vessels; whereas the pattern of distribution in other tissues was the same. This suggests that in vessels with an undetectable level of elastin, certain epitopes of gp 115 molecule might not be recognized as a result of being masked by other components or by a different conformation of the molecule.