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S Forsgren

Publications and source records attributed to S Forsgren.

At least 91 records · Page 5Linked to original sources
PubMed1987

Immunohistochemical procedures for the demonstration of peptide- and tyrosine hydroxylase-containing nerve fibers in cryostat sections of unfixed rapidly frozen tissue stored for long periods of time. A study on heart tissue.

Traditional protocols for the immunohistochemical localization of peptides and tyrosine hydroxylase (TH) in nerve fibers in cryostat sections require the tissue to be thoroughly fixed and rinsed and to be processed for the cryostat sectioning and the immunohistochemical staining more or less directly after freezing. In the present study it was tested whether also unfixed, rapidly frozen tissue, conforming to guinea pig and bovine heart specimens, can be used for the visualization of neuropeptides [neuropeptide Y (NPY) and substance P (S P)] and TH in cryostat sections. The following observations were made: 1) NPY-immunoreactive (IR) and S P-IR nerve fibers could be clearly identified in both fixed and unfixed sections of this type of tissue. 2) TH-IR nerve fibers could be detected in unfixed tissue if the sections were post-fixed with aldehydes by the use of a two-step fixation process related to a sudden change of pH. However, the outlines of the nerve fibers were sometimes diffuse. 3) Storage of unfixed tissue for periods of up to 2.5 years at-80 degrees C did not lead to a decrease in immunoreactivity. 4) Somewhat higher concentrations of primary antibodies had to be used for sections of unfixed tissue than for sections of fixed tissue when the FITC method was used. This waste of antibodies was partly overcome by use of the biotin-streptavidin method. The glyoxylic acid induced catecholamine(CA)-fluorescence method for demonstration of sympathetic nerve fibers was also applied and was found to give optimal results after storage of tissue for up to 2.5 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Marked sympathetic innervation in the regions of the bundle branches shown by catecholamine histofluorescence.

The distribution of sympathetic nerve fibers in the regions of the bundle branches of bovine and rat hearts was examined by the glyoxylic acid-induced method for histofluorescence demonstration of catecholamines and by acetylcholinesterase (AChE) histochemistry. The studies on the bovine heart were concentrated on the nerve fascicles, the arteries and the ganglionic cells, and showed that (1) the AChE-positive nerve fascicles that occur just outside the bundle branches show a positive catecholamine-fluorescence reaction to varying degrees, the paraarterial nerve fascicles showing a uniform reaction; (2) the AChE-positive nerve fascicles within the bundle branches contain a few, mainly varicose, sympathetic nerve fibers; (3) extensive plexuses of sympathetic nerve fibers supply the arterial branches; and (4) sympathetic nerve fibers occur close to some of the ganglionic cells. The pattern of distribution of sympathetic nerve fibers in the region of the SA node was found to be essentially the same. The studies on the rat heart showed that (1) the septal arteries that occur in the proximity of the bundle branches are accompanied by the sympathetic component of innervation; and (2) there is a substantial number of varicose sympathetic nerve fibers within the bundle branches. These observations show that there is a pronounced sympathetic innervation in bundle branch regions and suggest that the paraarterial route is the most important for sympathetic nerve fibers to reach these regions.

Animals↗
PubMed1987

The role of I-A/E molecules in B-lymphocyte activation. II. Mechanism of inhibition of the responses to lipopolysaccharide by anti-I-A/E antibodies.

We have previously demonstrated that monoclonal anti-I-A/E antibodies inhibit B-cell responses to lipopolysaccharide (LPS). In the present report, the inhibitory effects were shown to be carried out directly on B cells, and to be totally independent of the LPS concentration used, thereby showing that antibodies do not mediate their effect through blocking of accessory cells or steric hindrance of LPS-receptors. Of the three different phases in B-cell activation/induction, proliferation, and maturation, induction was shown to be the most sensitive to inhibition by anti-I-A/E antibodies. Thus, kinetic studies showed that anti-I-A/E antibodies are only inhibitory for the first 16 h of LPS activation, after which B cells can no longer be inhibited by these antibodies. Class II MHC molecules appear, therefore, to be part of a membrane molecular complex which regulates delivery of activation signals to resting B cells. Since it was also shown that this time period corresponds approximately to the time required for B cells to express functional reactivity to growth factors, we suggest that anti-I-A/E antibodies act on resting B lymphocytes to inhibit mitogen-dependent induction of growth receptor expression.

Animals↗
PubMed1986

The role of immunoglobulin receptors in "cognate" T-B cell collaboration.

The functional effects of anti-Ig antibodies have been investigated, using an experimental system where B cell activation is brought about by direct and specific interactions with T helper (Th) cells without participation of surface Ig receptors on the responding B cell. We have used Th cell lines and clones directed to class II major histocompatibility complex antigens of the responding B cells, and titrated into cooperative cultures either purified rabbit anti-mouse mu, or monoclonal mouse anti-delta antibodies. Both types of antibodies greatly enhanced B lymphocyte responses to suboptimal concentrations of functionally efficient Th cells, while they had no effect in cultures containing optimal Th:B cell ratios. In contrast, helper activity by low efficiency Th was, at all Th:B cell ratios, enhanced by appropriate concentrations of anti-Ig antibodies. Anti-Ig effects were exclusively observed when B cells were the targets for "cognate" recognition by Th cells. We conclude that ligand binding to surface Ig receptors on resting B cells fails, in our experimental conditions, to overcome "linked" collaboration, but it greatly facilitates productive Th-B cell interactions. Whatever the mechanisms underlying this facilitation, the observations imply roles of surface Ig in Th-dependent B lymphocyte activation other than either passive "focusing" of antigen or activation into reactivity to soluble, unspecific factors.

Animals↗
PubMed1984

Reactions among IgM antibodies derived from normal, neonatal mice.

Attempting to obtain a representative sample of the "natural antibody" repertoire in the developing immune system, we have derived IgM-secreting hybridomas from 4 normal untreated BALB/c mice of the same litter on day 6 after birth. Partially purified IgM preparations obtained in the supernatants of 70 such clones were each screened in binding assays for reactivity with a panel of 9 IgM antibodies, randomly selected from the same collection. Five of these 9 IgM antibodies were found to react with a considerable number of other IgM in the collection, while the other 4 showed only sporadic reactivity. On the other hand, more than half of the 70 antibodies were found to bind specifically to at least one of these five. With a few exceptions, these reactions showed quantitative levels ranging from 5 to 20% of those observed between either of the two interacting IgM and monoclonal rat anti-mu antibodies. The selectivity of these reactions indicated V-region specificity, which was confirmed by analyzing in some detail the reaction between 2 IgM antibodies isolated from the same mouse.

Animals↗
PubMed1984

Idiotypic determinants of natural IgM antibodies that resemble self Ia antigens.

A collection of immunoglobulin-secreting B-cell hybridomas was derived from normal neonatal BALB/c spleen and searched for reactivity against a panel of monoclonal anti-H-2 antibodies. We describe here one IgM antibody which was found to react with the monoclonal anti-Ia.7 antibody 14-4-4S. The characterization of this clone (BA.N 4:4.57) revealed its anti-trinitrophenyl specificity and demonstrated specific binding to five different monoclonal anti-Ia.7 antibodies but not to other anti-H-2 antibodies. The variable region specificity of these interactions was shown by the use of pepsin Fab fragments of the IgM antibody. Anti-Ia.7 antibodies were shown to specifically inhibit plaque formation by the hybridoma cells, and dinitrophenylglycine was shown to inhibit the reaction between the IgM antibody and anti-Ia.7 molecules. We interpret these results as to indicate that BA.N 4:4.57 expresses an idiotope or idiotopes which mimic Ia.7 determinants. This idiotypic family is naturally expressed in both newborn and adult BALB/c mice, as shown by the presence in normal serum of IgM molecules that specifically react with the F(ab')2 fragment of the 14-4-4S antibody. We speculate on the importance of idiotypic mimicry with major histocompatibility complex determinants, for both the selection of natural antibody repertoires and the evolution of antibody genes.

Animals↗
PubMed1984

Functional and chemical characterization of B-cell growth factor produced by normal cloned T helper cells.

Media conditioned by clones of normal helper T cells exposed to appropriate antigen-presenting cells contain growth-promoting activity for B-cell blasts induced either by lipopolysaccharide or on direct interaction with competent helper cells. This B-cell growth factor (TH-BGAPet) is recovered on sodium doecyl sulphate polyacrylamide gel electrophoresis corresponding to mol. wt of 15,000-20,000 displays no mitogenicity for small, non-induced B lymphocytes and is completely devoid of the ability to activate immunoglobulin secretion in proliferating B cells. These results are ascribed to the activity derived from normal T cells, with the same characteristics as BSF-p1 previously obtained from lymphomas and hybridomas. Since hybridization of these T helper cells results in the constitutive production of BSF-p1 in the absence of macrophages, these experiments demonstrate that BSF-p1 is a normal T-cell product.

Animals↗
PubMed1984

T cell-dependent B cell activation.

T cell-dependent induction of small, resting B lymphocytes requires direct recognition of antigen and/or I-A/E molecules on the B cell surface by the inducing helper cell, and it does not require the participation of Ig receptors on the responding B cell. Triggering B cell receptors, therefore, are either the I-A/E molecules themselves, or other structures with complementarities on helper cell membranes that become available for productive interactions upon I-A/E recognition. It would appear that signal delivery by such triggering receptors can be regulated by a membrane complex of molecules, involving immunoglobulins, Class II MHC molecules and other classes of receptors, which in selective and distinct manners control the quantitative levels of expression and/or availability of the relevant structures. Classical in vivo observations and our in vitro experiments led us to conclude that induction of B cells does not occur upon binding of T cell-dependent antigens to Ig receptors and, consequently, that B lymphocyte activation by anti-receptor antibodies has no physiological counterpart. Induced B lymphocytes proliferate and mature to high rate secretion of antibodies under the influence of selective growth and maturation factors produced by helper cells which are MHC-unrelated, act polyclonally and have no influence in normal, resting cells. Specific ligand interactions with the membrane molecules participating of that functional complex may also regulate reactivity to either growth or maturation factors, and, thus, control clonal performances and the fate of activated cells.

Animals↗
PubMed1984

The role of I-A/E molecules in B lymphocyte activation. I. Inhibition of lipopolysaccharide-induced responses by monoclonal antibodies.

A panel of 22 different monoclonal antibodies, including specificities against various antigenic clusters of I-A and I-E molecules, were probed over a wide range of concentrations for their ability to inhibit lipopolysaccharide-induced B lymphocyte proliferation and maturation to immunoglobulin-secreting plaque-forming cells (PFC). Most antibodies were competent to inhibit up to 80 to 100% of the response of appropriate target cells, although having little or no effect on irrelevant spleen cell cultures. Mixtures of either anti-I-A or anti-I-E specificities were more efficient inhibitors than individual antibodies, as shown by the average concentrations required for 50% inhibition (30 and 300 ng/ml, respectively). The selective role of I-A/E molecules in B cell activation was demonstrated by the failure of anti-K antibodies of the same isotype, bound in comparable amounts to target cells, to modulate B cell responses in parallel cultures. Fc receptor-mediated inhibitory effects were further excluded by equivalent inhibition obtained with anti-I-A antibodies of the IgM class. Anti-I-A/E antibodies appear to inhibit the inductive phase of B cell responses, as suggested by limiting dilution experiments performed in the presence of 50% inhibitory concentrations of antibodies: 50% of the control number of reactive clones were found to respond, but those that escaped inhibition developed to control sizes of progenies producing PFC.

Animals↗
PubMed1983

Differentiation of the atrioventricular node, the atrioventricular bundle and the bundle branches in the bovine heart: an immunohistochemical and enzyme histochemical study.

The previous observations of differences between different cardiac regions (ventricular myocardium, atrial myocardium, Purkinje fibre system) with respect to the maturation of the M-line region and the establishment of mature metabolic characteristics, have been extended. It was found that M-line maturation proceeds differently also between different regions of the conduction system. The M-line proteins, myomesin and MM-creatine kinase, were detected earlier, by means of immunohistochemistry, in the AV bundle and bundle branch cells than in the AV node cells. Also, a difference was observed in large foetuses. Striations in the AV node were less evident than in the AV bundle and the bundle branches in sections incubated with antibodies against myomesin as well as against MM-creatine kinase. Using enzyme histochemistry it was observed that the differences in metabolic properties between the AV node, the AV bundle and the bundle branches on the one hand, and the ordinary myocardium on the other, of adult hearts, are not established at the early stages. No clear difference in activity of succinate dehydrogenase was seen between the conduction tissues and the ordinary myocardium in the foetal hearts, while the conduction tissues showed a lower activity in the adult hearts. Furthermore, the pattern of activity of mitochondrial glycerol-3-phosphate dehydrogenase between the conduction tissues and the atrial and ventricular myocardium was quite different in early foetal stages compared with the adult stage.

Animals↗
PubMed1982

The conduction system in the human heart at midgestation--immunohistochemical demonstration of the intermediate filament protein skeletin.

The intermediate filaments have during recent years increasingly attracted attention and new information on the distribution of the subunits of the filaments has become available by the use of specific antibodies. In the present study human fetal hearts at midgestation were studied with immunofluorescence microscopy for a demonstration of the intermediate filament subunit skeletin. In the ordinary ventricular and atrial myocytes the fluorescence was moderate, mainly concentrated to the Z disk levels. The proximal parts of the conduction system also showed a moderate fluorescence, while the fluorescence was intense in the cells in the peripheral parts. The shift from moderate to intense fluorescence occurred in the very proximal part of the left bundle branch and in the distal part of the intramural right bundle branch. We conclude that the conduction cells attain Purkinje fibre-like characteristics at these levels, as evidenced by the content of skeletin. Furthermore, the human fetal Purkinje fibres are more easily distinguished with the technique used herein than with conventional histological techniques. The observed differences in content of skeletin are discussed in terms of the cytoskeletal function of intermediate filaments and the embryology of the conduction system.

Cholinesterases↗
PubMed1982

Differentiation of Purkinje fibres and ordinary ventricular and atrial myocytes in the bovine heart: an immuno- and enzyme histochemical study.

The differentiation of Purkinje fibres and ordinary ventricular and atrial myocytes in bovine hearts was studied with specific antibodies against M-line proteins (MM-creatine kinase and myomesin) and with enzyme histochemistry (succinate dehydrogenase and mitochondrial glycerol-3-phosphate dehydrogenase). MM-creatine kinase was detected at an earlier stage in Purkinje fibres and atrial myocytes than in ordinary ventricular myocytes. The findings are in agreement with previous ultrastructural observations that an earlier appearance of a dense M-band occurs in Purkinje fibres than in ordinary ventricular myocytes. Myomesin was detected in all three cell types even at early foetal stages, in accordance with suggestions that it is an integral component of the myofibrillar structure. The activity of succinate dehydrogenase gradually increased in both ordinary ventricular and atrial myocytes, while the activity of mitochondrial glycerol-3-phosphate dehydrogenase was high at different stages of early foetal development in the two tissues, finally becoming low in the adult stage. The activity of succinate dehydrogenase and mitochondrial glycerol-3-phosphate dehydrogenase seemed to remain unchanged in the Purkinje fibres from early to late foetal stages. The present study shows that the Purkinje fibres are already different from ordinary ventricular myocytes at early foetal stages and that the two cell types differentiate in different ways. It is concluded that there are also developmental differences between ordinary ventricular and atrial myocytes.

Animals↗
PubMed1982

Myocardial cell heterogeneity in the human heart with respect to myosin ATPase activity.

The PH sensitivity of the Ca2+-activated myosin ATPase in atrial, ventricular and conduction tissue of human hearts has been established. Heterogeneity with respect to ATPase activity is shown not only to exist between the atrial, the ventricular myocardium and the conduction system but also within both the ordinary atrial and ventricular myocardium and within the conduction system. These observations are related to the polymorphism of the myosin molecule and suggest that fibre types with different contractile properties co-exist in the human heart.

Adenosine Triphosphatases↗
PubMed1981

The development of Purkinje fibres and ordinary myocytes in the bovine fetal heart. An ultrastructural study.

A comparative ultrastructural study of bovine Purkinje fibres and ordinary myocytes during fetal development has been undertaken. Differences between the two cell types with respect to the intercalated disc, amount of myofibrils, arrangement of mitochondria, amount of glycogen and formation of T-tubules became apparent gradually. In all stages studied an abundance of intermediate filaments was typical for the Purkinje fibres. Myofibrillar M-bands developed at an earlier stage in Purkinje fibres than in ordinary myocytes. Myofilament-polyribosome complexes typical of adult cow Purkinje fibres were not observed in the fetal hearts. Only in late fetal stages were leptofibrils observed in both cell types. We conclude that in the bovine heart Purkinje fibres develop along a different pathway from ordinary myocytes.

Animals↗
PubMed1980

The development of the Purkinje fibre system in the bovine fetal heart.

In the bovine fetal heart, subendocardial bundles of cells could be distinguished from the main myocardial mass. Their morphological characteristics suggest that they represent bundles of Purkinje fibres. An intense fluorescence after incubation in antisera against the intermediate filament protein skeletin also supports this suggestion. Further, the bundles exhibited different histochemical reaction from the main myocardial mass. During development the histochemical pattern changed. Bundle cells in mitosis were observed. With increasing fetal age, binucleate cells were seen progressively more frequently. Our observations indicate that the Purkinje fibres differentiate along a line separate from the ordinary myocardial cells and that they acquire their adult characteristics gradually.

Animals↗
PubMedDate not supplied

The distribution of sympathetic nerve fibres in the AV node and AV bundle of the bovine heart.

The sympathetic nervous system has important effects on the properties of the heart, including the conduction of the impulse. However, it is not known how this nervous system is distributed in the atrioventricular (AV) bundle, which together with the AV node constitutes the only conduction pathway between the atria and ventricles in normal hearts. Therefore, in the present study the adrenergic innervation in the bovine AV node/AV bundle was examined by use of the glyoxylic acid induced method for histofluorescence demonstration of catecholamines. Acetylcholinesterase (AChE) histochemistry was also used. It was found that the AChE-positive nerve fascicles in these regions partly contain sympathetic nerve fibres, that sympathetic nerve fibres occur in the proximity of some of the ganglionic cells that occur outside the AV node/AV bundle, that the arteries supplying AV bundle tissue as well as AV nodal tissue have perivascular plexuses of sympathetic nerve fibres, and that there is a substantial number of sympathetic nerve fibres outside Purkinje fibre bundle surfaces. The observations give new insight into the question of the distribution of the sympathetic nerves in the AV bundle in relation to the distribution of these nerves in the AV node. Possible functional implications of the observations are discussed.

Acetylcholinesterase↗
PubMedDate not supplied

From the mechanisms of lymphocyte activation to internal activity in the immune system.

The principles of lymphocyte activation were summarized for all three sets of immunocompetent cells: B cells, cytotoxic cells and helper T lymphocytes. They were then used to derive the basic mechanisms and specificities which drive internal activity in the normal immune system and which select available antibody repertoires. It was postulated that "natural antibodies" are induced by "natural helper cells" and are selected on the basis of their idiotypic profiles, which are complementary to available T-helper-cell repertoires. "Natural idiotypes" would then carry idiotopes similar to MHC epitopes, the predominant germ-line specificity of T-cell repertoires.

Animals↗