Avian tropomyosin gene expression

Sequence analysis of overlapping fragments from a quail genomic library has revealed a tropomyosin gene consisting of 13 exons spaced over about 18 kilobase pairs of DNA. Skeletal muscle and smooth muscle transcripts share the same 5' untranslated sequence and may initiate from the same promoter. However, the regions encoding amino acids 39-80 and 258-284 are specific to each muscle type. The two sets of exons encoding these regions undergo mutually exclusive alternative splicing in a tissue-specific manner as determined by Northern blots and S1-nuclease protection. Similarly, the 3' ends of the transcripts are different in skeletal muscle and smooth muscle, and each contains two polyadenylation signals which appear to be utilized in vivo. The avian alpha-tropomyosin gene is not expressed in cardiac muscle. The sequence of the gene shows great homology with other muscle-specific tropomyosins and includes a region homologous to the amino terminus of nonmuscle tropomyosins.

[Experimental studies on urinary incontinence. II. Function and distribution of alpha 1- and alpha 2-adrenoceptors in male and female rabbit urethral smooth muscle]

The effects of various alpha-adrenergic agonists and antagonists on the contractile properties of the isolated urethra of male and female rabbits were examined and the population of alpha 1- and alpha 2-adrenoceptors, using radioligand receptor binding techniques, was also quantified to define the functional role of postsynaptic alpha-adrenoceptors in urethral smooth muscle. Norepinephrine, epinephrine (non-specific alpha-adrenergic agonists) and phenylephrine (alpha 1-adrenergic agonists) induced increases in contractile force in both the male and female urethra. Clonidine (alpha 2-adrenergic agonist) caused a relatively large contractile response in the female urethra but only a small contractile response in the male urethra. Receptor binding studies indicated that the male urethra contains almost equal amounts of alpha 1- and alpha 2-adrenoceptors (32 vs. 34 fmol/mg protein, respectively) whereas the female urethra contains a significantly greater density of alpha 2- than alpha 1-adrenoceptors (122 vs. 34 fmol/mg protein, respectively). Our studies have indicated that: (1) both alpha 1-and alpha 2-adrenoceptors cause contractile responses in male and female rabbit urethra; (2) the greater response to alpha 2-agonist in female than male urethra is correlated with a higher density of alpha 2-adrenoceptors in this tissue.

[Experimental studies on urinary incontinence. I. Effects of beta-adrenoceptor agonists on the contractile activities and intracellular cAMP levels of rabbit, canine and human urinary bladder smooth muscle]

Beta-adrenoceptor subtypes in detrusor and trigonal muscle of rabbit, canine and human urinary bladder were studied by in vitro techniques recording contractile force and by measuring intracellular cAMP content. The results of contractile studies were correlated with the intracellular cAMP levels. In the rabbit bladder, only beta 2-receptors were found in the detrusor though both beta 1- and beta 2-receptors were found in the trigonal muscle. In contrast, both beta 1 and beta 2-receptors were present in both detrusor and trigonal muscle of canine bladder. Human detrusor had only beta 2-receptors. Thus there are species differences in beta-adrenoceptor subtypes in urinary bladder smooth muscle.

Alpha-smooth muscle actin, a differentiation marker of smooth muscle cells, is present in microfilamentous bundles of pericytes

alpha-Smooth muscle (alpha-sm) actin, an isoform typical of smooth muscle cells (SMC) and present in high amounts in vascular SMC, was demonstrated in the cytoplasm of pericytes of various rat and human organs by means of immunocytochemistry at the electron microscopic level. In SMC and pericytes, alpha-sm actin was localized in microfilament bundles, strengthening the assumption that it is the functional isoform in these cell types and supporting the assumption that pericytes exert contractile functions.

Myofibroblasts from diverse pathologic settings are heterogeneous in their content of actin isoforms and intermediate filament proteins

We examined by immunofluorescence the distribution of vimentin, desmin, alpha-smooth muscle actin and alpha-sarcomeric actin in normal human soft tissues and in pathologic tissues containing myofibroblasts, including normally healing granulation tissue, hypertrophic scar, and fibromatosis. The pattern of actin isoforms was also documented biochemically by two-dimensional gel electrophoresis. Fibroblastic and/or myofibroblastic cells in each setting always expressed vimentin and never alpha-sarcomeric actin. Moreover, these cells showed an heterogeneous cytoskeletal composition which defined four phenotypes: (a) cells expressing only vimentin; (b) cells expressing vimentin, alpha-smooth muscle actin and desmin; (c) cells expressing vimentin and alpha-smooth muscle actin; and (d) cells expressing vimentin and desmin. Given this, two groups of lesions are distinguished: the first contains only vimentin cells and consists of normally healing granulation tissue, eschars and normally healed scars; the second contains vimentin cells admixed with variable proportions of vimentin, alpha-smooth muscle actin and desmin, vimentin and alpha-smooth muscle actin, and vimentin and desmin cells and consists of hypertrophic scars and fibromatoses. Immunogold electron microscopy showed that alpha-smooth muscle actin was present in a proportion of cells with ultrastructural features of myofibroblasts. Our findings suggest that contrary to myofibroblasts of normally healing granulation tissue and normally healed scars, myofibroblasts of pathologic conditions characterized by chronic retraction express always immunochemical features indicative of smooth muscle differentiation.

A histochemical and immunohistochemical study of the autonomic innervation of the lower urinary tract of the female pig. Is the pig a good model for the human bladder and urethra?

The detrusor muscle, bladder neck, proximal, middle and distal regions of the urethra of the female pig were studied by histochemical and immunohistochemical methods to localize catecholamine-containing, acetylcholinesterase-positive and peptide-containing nerves. The peptides examined included: vasoactive intestinal polypeptide, substance P, somatostatin, [Met]enkephalin, bombesin and gastrin. The greatest density of nerves was found in the smooth muscle of the distal urethra, followed by the bladder neck, middle urethra, and proximal urethra, with the least in the detrusor muscle. The greatest number of nerve fibres stained for acetylcholinesterase, followed by vasoactive intestinal polypeptide- and catecholamine-containing fibres. Substance P-immunoreactive nerve fibres were confined to the bladder neck and distal urethral regions. [Met]enkephalin-and gastrin-immunoreactive nerves were most dense in the distal urethra but absent in detrusor muscle, while somatostatin-immunoreactive nerve fibres were sparsely distributed throughout the lower urinary tract. No nerve fibres showing immunoreactivity to bombesin were found. Catecholamine-containing, acetylcholinesterase-positive, vasoactive intestinal polypeptide-, substance P-, [Met]enkephalin- and gastrin-immunoreactive nerves were also found on the adventitial-medial border of blood vessels in the pig urinary tract. In the intrinsic external urethral sphincter, located in the distal urethra, vasoactive intestinal polypeptide- and gastrin-immunoreactive nerve fibres were found bordering a small number of individual striated muscle fibres, while catecholamine-containing nerves were found predominantly in the connective tissue surrounding the striated muscle fibres. Dense populations of acetylcholinesterase-positive nerve fibres were found associated with the striated muscle fibres, with end plates on some of them. Intramural ganglia, composed of two to 30 neurones, were found in the bladder neck and middle and distal regions of the urethra. In the smooth muscle, and in the vicinity of the striated muscle regions of the intrinsic external urethral sphincter, there were small ganglia, containing two to three neurones, which were vasoactive intestinal polypeptide-, [Met]enkephalin- and somatostatin-immunoreactive. The results are compared to the autonomic innervation of the human bladder and urethra as previously described and it is concluded that the lower urinary tract of the pig is a good model for some features of the lower urinary tract of man, but a poor model for others.

Three-dimensional molecular distribution in single cells analysed using the digital imaging microscope

Cellular changes in molecular distribution are believed to underly a wide range of cell functions. In order to investigate changes in molecular distribution in single cells utilizing fluorescent probes we have developed a digital imaging microscope. The system, consisting of both hardware and software, automatically acquires 3-D data sets consisting of optical sections and then processes such data to facilitate the analysis of molecular distribution in single cells. The first major step in processing reverses distortion introduced principally by the optics of the fluorescent microscope. Various procedures for accomplishing this task are compared and a method based on regularization theory is shown to give superior results for several different 3-D images. Following this step features of interest are automatically extracted from 3-D images utilizing an artificial 3-D visual system. This artificial visual system utilize a system of spatial filters to identify regional characteristics of images, the information obtained from these filters being used to identify and characterize clusters of molecules within the image. This information is then utilized to construct a 3-D graphical model of molecular distribution in single cells. Such models are displayed in 3-D and may further analysed utilizing interactive 3-D computer graphics. These methods are illustrated by results obtained regarding alpha-actinin distribution in single smooth muscle cells.

Myosin heavy-chain isoforms in human smooth muscle

The myosin heavy-chain composition of human smooth muscle has been investigated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, enzyme immunoassay, and enzyme-immunoblotting procedures. A polyclonal and a monoclonal antibody specific for smooth muscle myosin heavy chains were used in this study. The two antibodies were unreactive with sarcomeric myosin heavy chains and with platelet myosin heavy chain on enzyme immunoassay and immunoblots, and stained smooth muscle cells but not non-muscle cells in cryosections and cultures processed for indirect immunofluorescence. Two myosin heavy-chain isoforms, designated MHC-1 and MHC-2 (205 kDa and 200 kDa, respectively) were reactive with both antibodies on immunoblots of pyrophosphate extracts from different smooth muscles (arteries, veins, intestinal wall, myometrium) electrophoresed in 4% polyacrylamide gels. In the pulmonary artery, a third myosin heavy-chain isoform (MHC-3, 190 kDa) electrophoretically and antigenically distinguishable from human platelet myosin heavy chain, was specifically recognized by the monoclonal antibody. Analysis of muscle samples, directly solubilized in a sodium dodecyl sulfate solution, and degradation experiments performed on pyrophosphate extracts ruled out the possibility that MHC-3 is a proteolytic artefact. Polypeptides of identical electrophoretic mobility were also present in the other smooth muscle preparations, but were unreactive with this antibody. The presence of three myosin heavy-chain isoforms in the pulmonary artery may be related to the unique physiological properties displayed by the smooth muscle of this artery.

Immunochemical identification of desmin in Torpedo postsynaptic membranes and at the rat neuromuscular junction

Preparations of acetylcholine receptor-rich (AChR-rich) postsynaptic membranes from electric tissue of electric rays often contain an Mr 55,000 protein (55kD protein) that has not been previously characterized. Using a monoclonal antibody (MAb 1403) against the 55kD protein from Torpedo californica and a pan-specific, anti-intermediate filament antibody (Pruss et al., 1981; Cell 27:419-428), we show that the 55kD protein has the properties expected of Torpedo desmin. By the electron microscope immunogold method applied to perfusion-fixed electric tissue, MAb 1403 labeled only cytoplasmic filaments in the electroplax. These filaments were neither more concentrated nor arranged detectably differently in postsynaptic regions relative to nonpostsynaptic regions. The 55kD protein could also be fractionated away from isolated postsynaptic membranes by gradient centrifugation. The protein is thus a minor component of the postsynaptic membrane in situ and after isolation. On semithin cryosections of rat skeletal muscle, on the other hand, MAb 1403, which recognizes rat desmin but not rat vimentin, gave strong fluorescent labeling of the postsynaptic region, weaker labeling of the Z-line, and still weaker labeling of the cell surface immediately surrounding extra-junctional nuclei. The pattern of postsynaptic labeling suggests that desmin, presumably in the form of intermediate filaments, occurs near the AChR-rich crests of the junctional folds, but is particularly concentrated among and around the ends of the folds. Similar results were obtained with a second monoclonal antibody raised against authentic desmin. These results suggest that desmin intermediate filaments may have an important role in organization of the postsynaptic cytoplasm in rat muscle.

Characterization of autonomic receptors in neonatal urinary tract smooth muscle

In the 1-day-old rabbit there are a large number of alpha-2- (labeled with [3H]yohimbine) than alpha-1- (labeled with [3H]prazosin) adrenergic receptors in the various parts of urinary tract smooth muscle, but the alpha-1 receptors are functionally more responsive to agonists than are the alpha-2 receptors. Unlike the findings in the adult rabbit, the neonatal bladder dome is functionally more sensitive to alpha-adrenergic agonists than the neonatal bladder base. The rank order of beta-adrenergic receptor densities (labeled with [3H]dihydroalprenolol) in various urinary tract smooth muscles correlates with the magnitude of the relaxant response to isoproterenol. There is a high number of functional muscarinic receptors (labeled with [3H]quinuclidinyl benzylate) in the neonatal urinary tract. The data demonstrate the existence of functional autonomic receptors in neonatal urinary tract smooth muscle.

Alpha smooth muscle actin (alpha-SM actin) in normal human ovaries, in ovarian stromal hyperplasia and in ovarian neoplasms

An immunohistochemical investigation of alpha-smooth muscle actin (alpha-SM actin) using the monoclonal anti-alpha-SM-1 antibody was carried out in 15 normal ovaries, in three ovaries with stromal hyperplasia and in 27 neoplastic ovaries. In selected cases the pattern of actin isoforms was examined by means of 2 D-gel electrophoresis. In addition, the tissues were stained for vimentin and desmin. In normal ovaries alpha-SM actin was found in the inner cortex and in the theca externa. In ovarian stromal hyperplasia expression of alpha-SM actin was minimal or absent. In primary and metastatic epithelial tumors there was positive stromal staining for alpha-SM actin, especially in the vicinity of epithelial elements. This tended to be more widespread in malignant neoplasms. Thecomas did not express alpha-SM-actin and could thus be differentiated from leiomyomas which stained intensely for alpha-SM actin. Only focal stromal staining of alpha-SM actin was observed in granulosa and germ cell tumors. In all the tissues studied blood vessels were strongly positive for alpha-SM actin. Desmin, although present in the stroma of most of the specimens, was less abundant than alpha-SM actin. We concluded that alpha-SM actin is a component of the normal human ovary where it may contribute to the contractility of its stroma. Its absence in the normal outer cortex and theca interna, and in stromal hyperplasia and thecoma implies that sex hormones do not constitute a stimulus for alpha-SM actin production in the ovary. Among neoplasms it is most widely represented in the stroma of epithelial tumors in which it may reflect stromal stimulation mediated by neoplastic epithelium.

Nonuniform behavior of multiple isoactins in the same cell is a cell-dependent phenomenon

The functional significance of multiple isoactins in the same cell is still not understood. To address this question, we examined the response of smooth muscle and cardiac muscle alpha-isoactins to a serial extraction procedure applied to both muscle and nonmuscle cell types. We compared these extraction results with results obtained with the beta- and gamma-nonmuscle actin isoforms from the same cells. In differentiated BC3H1 nonfusing muscle cells (smooth muscle alpha-isoactin), in human rhabdomyosarcoma cells (cardiac alpha-isoactin), and in chick skeletal muscle cells (cardiac alpha-isoactin), different fractions were found selectively enriched in either the nonmuscle or the muscle-specific actin isoforms compared with their relative abundance in whole cell extracts. Conversely, when these same isoactins were examined either in undifferentiated BC3H1 cells or in mouse nonmuscle cells stably transfected with a cardiac alpha-isoactin gene, no enrichment of these isoforms above their relative abundance in whole cell extracts was observed. These results indicate that within the muscle or muscle-like cells examined, the different actin isoforms were either selectively utilized or localized. These results further show that isoactin-specific responses observed were apparently related to the cell type in which they were found and not to differences in inherent physical properties such as solubility of the different isoactins examined.

Effect of progesterone on the stimulation of phosphatidylinositol turnover by epinephrine in guinea pig ductus deferens

Progesterone enhanced the contractile effect of epinephrine on the ductus deferens of the guinea pig in vitro. In relation to this mechanical phenomenon, we examined the phosphatidylinositol metabolism. In the 3H-myoinositol labeled ductus deferens, radioactivity in phosphatidylinositol bisphosphate was about 2.6 times as high as that in phosphatidylinositol. Phosphatidylinositol and phosphatidylinositol phosphate were not changed by epinephrine (100 microM), but phosphatidylinositol bisphosphate was increased at 10 sec and 1 min after the administration of epinephrine (100 microM). Progesterone (100 microM) added 5 min before the administration of epinephrine increased the stimulatory effect of epinephrine on the phosphatidylinositol bisphosphate metabolism, but had no effect on the phosphatidylinositol and phosphatidylinositol phosphate metabolism. These studies suggest that progesterone expresses its activity not through the cytoplasmic progesterone receptor but through the epinephrine mediated smooth-muscle contractile mechanism.

A comparative study of chicken ventricular and slow skeletal myosin light chains

1. Comparison of ventricular and slow skeletal myosin light chains was performed using high performance liquid chromatography (HPLC), peptide mapping of electrophoretically purified proteins and immunoblots. 2. Both in rabbit and in chicken ventricular and slow skeletal myosin light chain composition was identical.

Culture behavior of healthy bovine gallbladder muscularis smooth muscle cells

In contrast to the extensive experience culturing vascular smooth muscle cells, little is known about the culture behavior of gastrointestinal smooth muscle cells. In this work, we have studied smooth muscle cells from bovine gallbladder muscularis in culture. Properties reflecting their state of differentiation, including cellular morphology, multicellular arrangements, intermediate filament protein expression, and content of contractile proteins, were studied after dispersed cell preparations were placed into short- and long-term culture on a variety of substrates. Immunocytochemical analysis of intact healthy gallbladder wall demonstrated that the muscularis smooth muscle cells express actin and the intermediate filament protein desmin, while being vimentin-negative. In this tissue they are, however, surrounded by sheets of vimentin-positive fibroblasts. Optimal microdissection of mucosa and serosa from the muscularis therefore still produced a combination of smooth muscle cells and fibroblasts; however, multiple strategies for enriching the yield and purity of muscularis smooth muscle cells for culture were partially successful. Like vascular smooth muscle cells in culture, these visceral smooth muscle cells rapidly underwent morphological dedifferentiation, losing their contactile phenotype. By 5 days in culture, the desmin-positive muscle cells took on a spread, fibroblast-like morphology, likely representing modulation to a proliferative, dedifferentiated state. After long-term culture, the muscle cells were observed to regain some markers of differentiation, but they were never observed to attain complete morphological and functional redifferentiation.

Lanthanide chelates as new fluorochrome labels for cytochemistry

Anti-rabbit IgG labeled with a new fluorescent europium chelate was used to localize rabbit IgG to human smooth muscle myosin in a histological section. The antibody labeled with the europium chelate could be viewed with a conventional fluorescence microscope with a steady-state light source. This result encourages the development of a time-resolved fluorescence microscope, because a significant improvement in the signal-to-noise ratio can be anticipated.

An EPR study of the rotational dynamics of actins from striated and smooth muscle and their complexes with heavy meromyosin

The rotational motions of the actin from rabbit skeletal muscle and from chicken gizzard smooth muscle were measured by conventional and saturation transfer electron paramagnetic resonance (EPR) spectroscopy using maleimide spin-label rigidly bound at Cys-374. The conventional EPR spectra indicate a slight difference in the polarity of the environment of the label and in the rotational mobility of the monomeric gizzard actin compared to its skeletal muscle counterpart. These differences disappear upon polymerization. The EPR spectra of the two actins in their F form and in their complexes with heavy meromyosin (HMM) did not reveal any difference in the rotational dynamic properties that might be correlated with the known differences in the activation of myosin ATPase activity by smooth and skeletal muscle actin. Our results agree with earlier EPR studies on skeletal muscle actin in showing that polymerization stops the nanosecond rotational motion of actin monomers and that F-actin undergoes rotational motion having an effective correlation time of the order of 0.1 ms. However, our measurements show that complete elimination of the nanosecond motions requires prolonged incubation of F-actin, suggesting that the slow formation of interfilamental cross-links in concentrated F-actin solutions contributes to this process. We have also used the EPR spectroscopy to study the interaction between HMM and actin in the F and G form. Our results show that in the absence of salt one HMM molecule can cooperatively interact with eight monomers to produce a polymer which closely resembles F-actin in its rotational mobility but differs from the complex of F-actin with HMM. The results indicate that salt is necessary for further slowing down, in a cooperative manner, the sub-millisecond internal motion in actin polymer and for a non-cooperative change in the intramonomer conformation around Cys-374 on the binding of HMM.

Localization of phospholamban in smooth muscle using immunogold electron microscopy

Phospholamban, the putative regulator of the Ca2+-ATPase in cardiac sarcoplasmic reticulum, was immunolocalized in canine visceral and vascular smooth muscle. Gently disrupted tissues were labeled with an affinity-purified phospholamban polyclonal antibody and indirect immunogold, using preembedding techniques. The sarcoplasmic reticulum of smooth muscle cells was specifically labeled with patches of immunogold distributed in a nonuniform fashion, while the sarcolemma did not appear to contain any phospholamban. The outer nuclear envelopes were also observed to be heavily labeled with the affinity-purified phospholamban polyclonal antibody. These findings suggest that phospholamban may play a role in the regulation of cytoplasmic and intranuclear calcium levels in smooth muscle cells.

Immunolocalization of meta-vinculin in human smooth and cardiac muscles

Meta-vinculin, a vinculin-related protein, has been isolated from human uterus smooth muscle. Specific antibodies to meta-vinculin, which distinguish between meta-vinculin and vinculin, were prepared by absorption of anti-meta-vinculin serum on vinculin coupled to nitrocellulose. Meta-vinculin specific antibody demonstrates only smooth and cardiac muscle specificity and is able to cross-react with a small 21-kD fragment of the meta-vinculin polypeptide chain. This antibody does not interact with protease resistant 95-kD core shared by vinculin and meta-vinculin. Meta-vinculin specific antibody was used for the localization of meta-vinculin in smooth and cardiac muscles by the indirect immunofluorescence method. At the light microscopy resolution level it was found that meta-vinculin and vinculin are localized in the same cellular adhesive structures. Meta-vinculin is present in membrane-associated microfilament-bound plaques of smooth muscle, in intercalated discs and costameres of cardiac muscle. In primary culture of smooth muscle cells from human aorta, meta-vinculin and vinculin were found to be present in focal contacts of the cells. During the cultivation of smooth muscle cells, the quantity of meta-vinculin decreased progressively and finally meta-vinculin completely disappeared from the focal contacts. The data show that in smooth and cardiac muscles meta-vinculin could be a structural component of microfilament-membrane attachment sites, defined earlier by the localization of vinculin.

Molecular cloning and sequencing of the chicken smooth muscle myosin regulatory light chain

A cDNA probe was constructed from a chicken skeletal muscle regulatory light chain cDNA and was used to screen a chicken gizzard cDNA library. A clone containing the entire coding region of the chicken gizzard regulatory light chain was isolated and sequenced. The deduced protein sequence is identical to the most recently reported chemical sequence of the chicken smooth muscle regulatory light chain, and has homologies with other troponin C-like calcium-binding proteins.

Bulk isolation of the 20,000-Da light chain of smooth muscle myosin: separation of the unphosphorylated and phosphorylated species

The procedure of W. T. Perrie and S. V. Perry (1970, Biochem. J. 119, 31-38) has been improved and extended to allow a convenient large-scale isolation of the 20,000-Da light chain of vertebrate smooth muscle myosin. The method utilizes as source material tropomyosin-free actomyosin or myosin. The relatively pure light chain isolated from this material could be obtained in pure form by a single gel-filtration step. Separation of the unphosphorylated and phosphorylated light chain species was achieved by subsequent chromatography on a DEAE column. The solubility properties of this light chain, relevant to its use in myosin light chain kinase assays, were also established.

AFDX-116 discriminates between muscarinic M2 receptors of the heart and the iris smooth muscle

Studies with the atypical muscarinic antagonist pirenzepine provide convincing evidence for the classification of muscarinic acetylcholine receptors (mAChRs) into two subtypes, M1 and M2. The present study examines the heterogeneity of the M2 subtype employing the newly developed competitive muscarinic antagonist, AFDX-116. Comparison of the binding affinities of pirenzepine, atropine, and AFDX-116 to mAChRs in microsomes from the rabbit cerebral cortex, heart, and iris smooth muscle shows that iris mAChRs, which are pharmacologically of the M2 subtype, can be distinguished from M2 cardiac receptors based on their affinity for AFDX-116. These results are consistent with the hypothesis that the M2 receptor subtype consists of a heterogeneous population of receptors.

Cell and fiber-type distribution of dystrophin

Duchenne muscular dystrophy is the result of dystrophin deficiency. We have determined the cell types likely to express the pathogenic effects of this neuromuscular disease by determining the pattern of dystrophin expression in normal cells. We find that all physiological types of muscle cells express dystrophin at similar levels, and that the dystrophin content of various tissues correlates with the myogenic cell population of each tissue. The dystrophin content of brain and spinal cord, however, is found not to correlate with any type of muscle cell, and it is suggested that neurons express dystrophin. The potential involvement of striated muscle fibers, the vasculature, and the nervous system in the etiology of Duchenne muscular dystrophy makes it likely that the disease is a complex disorder of combined pathogenesis. We also find that the dystrophic chicken does not represent an animal model for dystrophin deficiency.

[Changes in the cyclic nucleotide levels during the contraction of smooth muscles exposed to muscarinic cholinomimetics]

Intracellular levels of cyclic nucleotides AMP and GMP were measured in isolated preparations of the guinea pig ileum, taenia coli, bladder and vas deferens. The cAMP level was about ten-fold as high as the cGMP level. During cholinergic stimulation for 5-10 sec contractile response preceded the cGMP rise. Muscarinic cholinomimetics obviously increased the cGMP levels especially in vas deferens, whereas no significant changes occurred in the cAMP levels. Changes in the cGMP levels were only found during phasic tension of muscles.

Monoclonal antibodies for the different chains of chick type VI collagen

Avian type VI collagen is composed of three subunits of Mr 140,000, 150,000 and 260,000. Monoclonal antibodies were raised against type VI collagen isolated from chick embryo gizzard, and these antibodies were used to immunoprecipitate type VI collagen from metabolically labeled embryo cells. Several antibodies appeared to react with epitopes independent of glycosylation and hydroxylation processes. The antibody-binding sites were identified on the different chains by immunoblotting of total cell extracts. In addition, antibodies that recognized different epitopes on the Mr 260,000 subunit could be grouped in at least three different clusters by competitive inhibition radioimmunobinding assays.