Effects in skeletal muscle of supraphysiological growth hormone stimulation.
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Animals↗
Biomedical subjects
E Jennische
Publications and source records attributed to E Jennische.
Arterial smooth muscle cells express nitric oxide synthase in response to endothelial injury.
Endothelial cells regulate vascular tone by secreting paracrine mediators that control the contractility of arterial smooth muscle cells. Nitric oxide (NO) is an important vasodilating agent that is generated from L-arginine by the enzyme nitric oxide synthase (NOS), which is expressed constitutively by the endothelium. NO also inhibits platelet aggregation, contributing to the antithrombotic properties of the endothelial surface. It would therefore be expected that loss of the endothelium during arterial injury would lead to vasospasm and thrombosis but instead, the neointima formed after injury has a nonthrombogenic surface and a maintained vascular patency. We report here that arterial smooth muscle cells in the neointima formed after a deendothelializing balloon injury to the rat carotid artery express the cytokine-inducible isoform of NOS. Expression was detectable by reverse transcription-polymerase chain reaction from day 1-14 after injury and in situ hybridization showed expression of NOS mRNA by neointimal smooth muscle cells, particularly at the surface of the lesion. This was associated with systemically detectable NO production as revealed by electron paramagnetic resonance spectroscopic analysis of nitrosylated red cell hemoglobin. Local NO production by intimal smooth muscle cells after endothelial injury could represent an important mechanism for the maintenance of arterial patency and nonthrombogenicity in the injured artery.
Amino Acid Oxidoreductases↗
Increase in insulin-like growth factor I in hypertrophying smooth muscle.
The present study focuses on the role of the insulin-like growth factor (IGF) system in the development of smooth muscle hypertrophy. Hypertrophy was initiated by partial ligation of portal vein or urethra in female Sprague-Dawley rats weighing approximately 220 g. Levels of mRNA were analyzed by solution hybridization. Seven days after ligation, the wet weight of the portal vein was increased about threefold and the concentration of IGF-I mRNA was increased fourfold. The bladder wet weight was increased twofold 3 days after ligation and fourfold 10 days after ligation. IGF-I mRNA in the bladder was elevated 3-fold after 3 days and 2.5-fold after 10 days, whereas IGF binding protein 2 mRNA was increased approximately 2-fold after 3 days and 5-fold after 10 days. IGF-I receptor mRNA in the hypertrophying bladder remained unchanged. Increased levels of IGF-I were demonstrated with immunohistochemistry in both hypertrophying portal vein and urinary bladder. The results show a specific increase in IGF-I mRNA as well as an increased IGF-I immunoreactivity during hypertrophy of smooth muscle, which suggests that the local IGF-system may play a role in smooth muscle hypertrophy.
Animals↗
Evans blue permeation of intestinal mucosa in the rat.
The azo dye Evans blue (EB; molecular weight, 960.83) is widely used as an indicator of increased capillary permeability. In the present study, however, rat gut absorption of EB was investigated after dye instillation in either the small or large intestine. During a brief period of ether anaesthesia, EB was injected either into jejunal loops with a challenge period of 30 or 60 min or into a proximal and a distal colon loop with a challenge period of 30, 60, or 120 min. After the rats had been killed the intestinal specimens were washed with 6 mM acetylcysteine dissolved in phosphate-buffered saline, which efficiently cleared the tissues of mucus, and thus of EB trapped in mucus. Only EB absorbed by the gut wall remained to be estimated, and this absorption was found to be both dose- and time-dependent in the jejunum and the colon. After instillation in the colon, but not in jejunum, EB could be detected in the blood. EB absorption from the jejunum remained unaffected by the addition of either ouabain (1 mM) or lidocaine (0.38 mM). Either of these compounds inhibited EB uptake in the proximal part of the colon, while enhancing it in the distal part. Fluorescence microscopy showed penetration into the intestinal wall to be a prerequisite for EB to become fluorescent, and EB fluorescence increased with time. It is proposed that EB is transported over the mucosa by the paracellular route and that the amount of absorbed EB reflects epithelial permeability differently in different parts of the gastrointestinal tract.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Antisecretory factor enhances in vivo internalization of cholera toxin and of horseradish peroxidase into rat enterocytes.
The in vivo effect of antisecretory factor (ASF, derived from pig plasma) on the ability of cholera toxin (CT) and of horseradish peroxidase (HRP) to bind to and penetrate into epithelial cells of the rat small intestine was evaluated in the absence of anesthetics. The potency of intravenously administrated ASF was demonstrated by some 70% inhibition of CT-induced secretion in ligated small intestinal loops. Using immunohistochemical methods for visualization, we found ASF to enhance internalization of both CT and HRP after 30 to 60 min of challenge, without interfering with the initial binding to the enterocyte brush border region. The internalization process started in the upper 2/3 of the villus region. After 5 h, no CT or HRP could be seen bound to the enterocytes. The results suggest that ASF might enhance small intestinal absorption.
Animals↗
Expression of hepatocyte growth factor in growing and regenerating rat skeletal muscle.
The expression of hepatocyte growth factor (HGF) was studied in rat skeletal muscle during postnatal growth and during regeneration after ischemic injury. By Northern blot analysis two RNA transcripts with estimated sizes of 6.0 and 3.1 kb, respectively, could be detected in immature skeletal muscle at 2, 4, and 10 days after birth, whereas no signal could be detected in adult skeletal muscle. In regenerating muscle, HGF mRNA was reexpressed, and a distinct signal was evident during the first days after the injury. One week after the injury only a weak signal was obtained. By in situ hybridization staining, HGF mRNA could be demonstrated in the immature muscle tissue of newborn rats but not in adult skeletal muscle. In regenerating muscle, the staining for HGF mRNA could be demonstrated in the regenerating muscle cells during the early phase of the regeneration. One week after the injury, only faint staining for HGF mRNA persisted in the regenerated fibers. It is concluded that HGF expression is developmentally regulated in skeletal muscle and that HGF is reexpressed in a transient manner during postischemic muscle regeneration.
Animals↗
Expression of insulin-like growth factor I messenger ribonucleic acid in regenerating bone after fracture: influence of indomethacin.
Expression of insulin-like growth factor I (IGF-I) was studied during time in the callus formed after tibial fracture in rats. Levels of IGF-I mRNA in callus peaked on the day 8 postfracture, showing a 10- to 15-fold induction compared to control bone. Levels of IGF-I mRNA tended also to be increased in the fracture-adjacent musculus tibialis anterior. IGF-I immunoreactivity was found in cartilaginous cells, osteoblasts, and myocytes 6 and 8 days after fracture. No obvious differences were found between hypophysectomized animals and control animals with regard to IGF-I immunoreactivity. Administration of the antiinflammatory drug indomethacin decreased the IGF-I mRNA expression in the tibial fracture model. Previous findings have shown that IGF-I is activated during in vivo muscle regeneration, and also in this model indomethacin administration reduces the expression of IGF-I. The finding that indomethacin administration reduces IGF-I expression could indicate that an inflammatory response may be important for activation of IGF-I during tissue regeneration.
Animals↗
Distribution of IGF-I mRNA and IGF-I binding sites in the rat kidney.
In the present study we have investigated the distribution of IGF-I mRNA and IGF-I binding sites in the rat kidney. The distribution of IGF-I mRNA was investigated using a simple and sensitive non-radioactive in situ hybridisation technique based on probe labelling with digoxigenin labelled-UTP followed by detection with conventional immunocytochemical techniques. IGF-I mRNA was found predominantly in medullary collecting ducts and sparsely in cortical collecting duct cells. In addition IGF-I mRNA was expressed in scattered proximal tubular cells in the cortex and in cells confined to the glomerular tuft. IGF-I binding sites were studied using radiolabelled IGF-I and conventional autoradiographical techniques on tissue sections. It was found that IGF-I binding sites were widely distributed throughout the entire kidney and that the specific binding was highest in the inner medulla. These findings add further complexity to the understanding of IGF-I production and action on renal structures.
Animals↗
IGF-I binding and IGF-I mRNA expression in the post-ischemic regenerating rat kidney.
The localization of IGF-I peptide and IGF-I mRNA was investigated in the post-ischemic regenerating rat kidney using immunohistochemistry and non-radioactive in situ hybridization techniques. In addition, the distribution and relative quantity of IGF-I binding sites were studied by autoradiographic ligand-binding techniques. Two and three days after the injury, morphological signs of an intense regenerative activity was evident. By this time a substantial number of the regenerating cells were stained with a monoclonal antibody against the M1 subunit of ribonucleotide reductase, a proliferative marker used. Low proliferative tubular cells, replacing those that had been injured, were seen lining the tubular basement membrane. By seven days, the morphology in the cortex was quite normalized, while cells of the S3 segments in the outer medulla remained dedifferentiated. The regenerative cells expressed IGF-I peptide and IGF-I mRNA in a transient manner and this was found to correlate better to cell differentiation than cell division. In addition, non-tubular cells, predominantly macrophages, expressed both the IGF-I peptide and the mRNA. The IGF-I binding was significantly increased in the regenerative zone at all times studied and began to decline at day seven. The binding characteristics were found to be compatible with binding to the IGF-I receptor. Altogether, these findings provide circumstantial evidence that IGF-I is of trophic importance in the regeneration of renal tubular cells. The data are compatible with a local production and action of IGF-I, suggesting an autocrine and/or paracrine mode of action during the regenerative process.
Animals↗
Local infusion of IGF-I into the kidney of pituitary intact rats induces renal growth.
To determine whether insulin-like growth factor I (IGF-I) exerts growth-promoting actions on the kidneys of pituitary-intact animals IGF-I was infused into the kidney via two different routes using osmotic pumps. In a first set of experiments IGF-I was infused directly into the tissue by the use of an implanted catheter traversing the kidney. It was found that a dosage of 50 micrograms IGF-I wk-1 but not 20 micrograms wk-1 caused a gain in weight of the kidney. The growth was accompanied with morphological alterations among the cortical distal tubules. As a marker for hyperplasia, a monoclonal antibody directed against the M1 subunit of ribonucleotide reductase (RR) was used. The altered cells stained with RR, as also did the tubule cells of the medullary thick ascending limb (mTAL). No RR staining was found in the bulk of renal mass, i.e. the proximal tubules, indicating that possible growth in these cells did not involve cell division. In a second set of experiments IGF-I at 50, 100 and 300 micrograms wk-1 was infused into the renal circulation via a side branch of the renal artery, the suprarenal artery. In these experiments, no growth response or morphological alterations of the tissue were found. These findings demonstrate that IGF-I, when administered directly into the parenchyma, causes growth of the kidney in normal animals. The data are compatible with a causative role for IGF-I in the course of renal growth.
Animals↗
IGF-I binding and IGF-I expression in regenerating muscle of normal and hypophysectomized rats.
Binding of iodinated IGF-I to tissue sections from regenerating muscle was studied by autoradiography in normal and in hypophysectomized rats. Binding of IGF-I was low in control muscle in both groups of animals, but increased transiently about 10-fold during regeneration after injury. Maximal binding occurred later in hypophysectomized rats than in control rats, and there was also a slower regeneration process in these animals. IGF-I, as demonstrated by immunohistochemistry, and IGF-I mRNA, as demonstrated by in situ hybridization, were expressed by the regenerating muscle cells in both groups of animals. It is concluded that locally produced IGF-I is the most likely ligand for IGF-I receptors during muscle regeneration.
Animals↗
Left ventricular insulin-like growth factor I increases in early renal hypertension.
Increasing interest has been directed toward the possible role of trophically acting molecules as modulators or initiators, or both, of myocardial hypertrophy. The aim of the present study was to investigate the possible role of one such molecule, namely, insulin-like growth factor I, in myocardial hypertrophy developed in response to renal artery stenosis. Two-kidney, one clip Goldblatt hypertension was induced in Wistar rats weighing 180 g, and sham-operated animals were used as controls. Blood pressure was increased as early as 2 days after clipping (133 +/- 4 versus 116 +/- 4 mm Hg, p less than 0.05), and the increase persisted 4 and 7 days after clipping (148 +/- 6 versus 129 +/- 3 mm Hg, p less than 0.01 and 171 +/- 5 versus 139 +/- 3 mm Hg, p less than 0.01, respectively). Left ventricular weight followed a similar pattern (373 +/- 7 versus 350 +/- 8 mg, NS, 415 +/- 11 versus 386 +/- 9 mg, p less than 0.01, and 466 +/- 11 versus 391 +/- 10 mg, p less than 0.01 at 2, 4, and 7 days after clipping, respectively), but no changes in body weight between the groups were observed. Insulin-like growth factor I messenger RNA (mRNA) was quantified using a solution hybridization assay. After 4 days of renal hypertension, there was a significant increase in left ventricular insulin-like growth factor I mRNA (2.0 x 10(-18) +/- 0.48 x 10(-18) versus 0.4 x 10(-18) +/- 0.07 x 10(-18) mol.microgram DNA-1), which was no longer detectable 7 days after clipping.(ABSTRACT TRUNCATED AT 250 WORDS)
Actins↗
Activation of insulin-like growth factor II expression during skeletal muscle regeneration in the rat: correlation with myotube formation.
Insulin-like growth factors (IGFs) are important stimulators of proliferation and differentiation of cultured myoblasts. It has previously been shown that IGF-I is induced during muscle regeneration in rodents, however, little is known about the expression of IGF-II. Therefore, two in vivo models were used to analyze IGF-II mRNA expression during skeletal muscle regeneration in the rat: injection of the snake venom notexin and induction of ischemia. During the regeneration process the levels of both IGF-I and IGF-II mRNA were transiently induced, as analyzed by solution hybridization. Both IGF-I-like immunoreactivity and IGF-II-like immunoreactivity were found to be present during muscle regeneration. In a time course study, induction of IGF-II was preceded by IGF-I, both at the mRNA and protein levels. Using alpha- and beta-actin as markers for different stages of skeletal muscle differentiation, together with the immunohistochemistry data, it is concluded that the expression of IGF-I and IGF-II occurs at different differentiation stages, and that IGF-II appears concomitant to the formation of myotubes. These results suggest that each IGF has a distinct role during the differentiation of muscle cells.
Animals↗
Clostridium difficile toxin A induces a specific antisecretory factor which protects against intestinal mucosal damage.
Peroral challenge with toxin A from Clostridium difficile induced the formation of antisecretory factor in rats. The animals were given 100 micrograms of the toxin, which was followed by a pronounced diarrhoea and by the appearance of antisecretory factor in the pituitary gland. In electrofocusing, the induced antisecretory factor separated in two peaks (pI 5.4 and 5.0); both fractions showed a lectin-like binding to agarose. The pI 5.4 fraction inhibited cholera toxin as well as toxin A induced fluid secretion, while pI 5.0 inhibited toxin A induced secretion only. Immunohistochemistry showed that an antisecretory factor of pI 5.0 protected the mucosa from the cytotoxic effect of toxin A, but did not affect the binding of toxin A to the intestinal epithelium. Sodium dodecyl-sulphate-polyacrylamide gel electrophoresis of the pI 5.0 protein showed two major fractions to be present, one of molecular weight 60 kDa, the other of 30 kDa, the latter probably being a degradation product of the former.
Animals↗
Expression of GH receptor mRNA in regenerating skeletal muscle of normal and hypophysectomized rats. An in situ hybridization study.
Expression of growth hormone receptor mRNA was investigated by in situ hybridization in skeletal muscle from normal and hypophysectomized rats during the first seven days of regeneration after ischemic injury. A digoxigenin-labelled RNA probe directed against the extracellular part of the rat GH receptor was used. In both normal and hypophysectomized rats distinct expression of GH receptor mRNA could be demonstrated in the regenerating muscle cells at the myoblast/myotube stage. The GH receptor expression appeared to decline with increasing maturation of the regenerated muscle fibres. In hypophysectomized rats, the regeneration process and the expression of GH receptor mRNA was delayed compared with that in normal animals. It is concluded that growth hormone may affect also the early phase of muscle regeneration in normal animals. To what extent lack of growth hormone contributes to the delayed regeneration observed in the hypophysectomized rats remains to be elucidated.
Animals↗
Outbreak of spontaneous staphylococcal arthritis and osteitis in mice.
Staphylococcus aureus is the most common bacterial species found in association with nongonococcal bacterial arthritis in humans. We present here the first description of spontaneous bacterial arthritis and osteitis in mice. Clinically, the most obvious findings were swelling and/or ankylosis of hindpaws and nodose changes of the tail. The prevalence of arthritis and osteitis ranged from 0% to greater than 50% of the mice studied, depending on the mouse strain. The most prominent histopathologic feature of the arthritis was hypertrophy of the synovial tissue and destruction of cartilage and underlying bone. Most of the S aureus-infected mice displayed an identical phage type, which was also the only S aureus phage type found in skin isolates from clinically healthy mice. However, a few S aureus isolates were not typeable, indicating that an additional strain(s) might cause bacterial arthritis in mice.
Animals↗
Ultrastructural localization of IGF-I in the rat kidney; an immunocytochemical study.
We have shown recently by light microscopy that insulin-like growth factor I (IGF-I) immunoreactivity is localized in cells in the collecting ducts and in the thin loop of Henle in the normal rat kidney. In the present study, we have investigated the ultrastructural localisation of IGF-I using preembedding immunocytochemistry. The light microscopical findings were confirmed at the electronmicroscopical level. In collecting ducts as well as in the thin limb of Henle's loop a focal expression of IGF-I immunoreactivity was evident, i.e. distinctly IGF-I positive cells were intermingled with cells lacking IGF-I immunoreactivity. IGF-I immunoreactivity was found to have a diffuse cytoplasmatic distribution in both cell types. No specific association to organelles was found.
Animals↗
Neurophysiological evidence for and characterization of the post-ganglionic innervation of the adrenal gland in the rat.
The aim of this study was to examine and characterize the post-ganglionic innervation of the adrenal gland, using a neurophysiological nerve recording technique. Adrenal multifibre nerve activity was recorded in chloralose-anaesthetized Wistar rats. To test for post-ganglionic nerve activity, trimethaphan, a ganglionic blocker, was given intravenously. About 60% of the adrenal nerve preparations tested responded with a marked decrease in nerve activity (to 52 +/- 11% of pre-trimethaphan activity, P less than 0.01), while other nerves responded with an increase in activity (to 152 +/- 29% of pre-trimethaphan activity, P less than 0.01). Based on these responses, the nerves were considered to contain predominantly post- or preganglionic fibres respectively, and the difference in response to an intravenous injection of trimethaphan between the two groups was significant (P less than 0.01). It was also demonstrated that the post-ganglionic adrenal nerve activity had a greater variability in firing pattern than preganglionic adrenal nerve activity. We also examined whether there was any cardiac rhythmicity in the investigated nerves. There was a weak cardiac rhythmicity in six out of 12 post-ganglionic adrenal nerves, but there was no cardiac rhythmicity in the remaining six post-ganglionic nerves, and we observed no cardiac rhythmicity in preganglionic nerves. In contrast, renal sympathetic nerves showed a profound cardiac rhythmicity. Our results might explain recent histological findings of a direct post-ganglionic innervation of the adrenal cortex. We speculate that this nerve population is involved in steroid synthesis indirectly via regulation of the cortical blood flow or directly via a direct innervation of parenchymal cells in the adrenal cortex.
Adrenal Glands↗