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PubMed1998

Utrophin is a regeneration-associated protein transiently present at the sarcolemma of regenerating skeletal muscle fibers in dystrophin-deficient hypertrophic feline muscular dystrophy.

Utrophin, an autosomal homologue of dystrophin, has been suggested as a possible therapeutic replacement of dystrophin in Duchenne or Becker muscular dystrophies (DMD/BMD). We have undertaken this study to examine the expression of utrophin in the skeletal muscle of dystrophin-deficient cats, a spontaneous animal model for dystrophinopathy. Dystrophin was normal in size, but very low in quantity by immunohistochemistry and Western blot. Utrophin was heterogeneously overexpressed at extrajunctional sarcolemma of regenerating muscle fibers, as defined by overexpression of the myogenic markers: vimentin, desmin, and developmental isoform of myosin heavy chain (MHCd). Muscle regeneration occurred in 6 stages as assessed by fiber size, and immunolabeling of desmin, vimentin, and MHCd. Differential developmental patterns of utrophin, alpha-sarcoglycan, and beta-dystroglycan expression were seen with an increase followed by a decrease and with changes in their respective location. These results suggest that utrophin is a regeneration-associated protein. It can functionally replace dystrophin in anchoring dystrophin-associated proteins (DAPs). However, the expression of utrophin and its anchored DAPs is restricted to the period of muscle regeneration and tends to decrease in late stages. This study therefore suggests a novel role of utrophin during skeletal muscle regeneration.

Animals↗
PubMed1981

Post-irradiation thymocyte regeneration after bone marrow transplantation. I. Regeneration and quantification of thymocyte progenitor cells in the bone marrow.

Growth kinetics of the donor-type thymus cell population after transplantation of bone marrow into irradiated syngeneic recipient mice is biphasic. During the first rapid phase of regeneration, lasting until day 19 after transplantation, the rate of development of the donor cells is independent of the number of bone marrow cells inoculated. The second slow phase is observed only when low numbers of bone marrow cells (2.5 x 10(4)) are transplanted. The decrease in the rate of development is attributed to an efflux of donor cells from the thymus because, at the same time, the first immunologically competent cells are found in spleen. After bone marrow transplantation the regeneration of thymocyte progenitor cells in the marrow is delayed when compared to regeneration of CFUs. Therefore, regenerating marrow has a greatly reduced capacity to restore the thymus cell population. One week after transplantation of 3 x 10(6) cells, 1% of normal capacity of bone marrow is found. It is concluded that the regenerating thymus cells population after bone marrow transplantation is composed of the direct progeny of precursor cells in the inoculum.

Animals↗
PubMed1995

FGF-1 in normal and regenerating kidney: expression in mononuclear, interstitial, and regenerating epithelial cells.

The proximal tubule epithelium regenerates following nephrotoxic damage. To determine the role of fibroblast growth factors (FGFs) in the regeneration of rat proximal tubule epithelial (RPTE) cells, we investigated proliferation, differentiation, and FGF-1 expression in vivo in rat kidney before and after nephrotoxic damage to the proximal tubule epithelium caused by S-(1,1,2,2-tetrafluoroethyl)-L-cysteine administration. In undamaged kidneys, FGF-1 was expressed in distal tubule elements, including cortical and medullary collecting ducts, as well as in blood vessels and glomeruli, but was absent in RPTE. One day after damage, there was an increase in proliferation of surviving proximal tubule epithelial cells and a coincident increase in FGF-1 expression in invading mononuclear cells. After this initial burst of proliferation, FGF-1 expression increased in poorly differentiated vimentin-positive regenerative epithelial cells, indicating that autocrine FGF-1 expression in the regenerative epithelium is a later event in the regeneration process. FGF-1 staining persisted in foci of macrophages, interstitial cells, and nephropathic tubules within areas of interstitial expansion 2 wk after damage. We concluded that transient paracrine and autocrine expression of FGF-1 could play mitogenic and/or morphogenic roles during tubular regeneration. Persistent expression in macrophages, fibroblasts, and nephropathic tubules may be associated with tubular degeneration. FGF-1 expression may be an important contributor to both tubular regeneration and degenerative disease following toxicant exposure.

Animals↗
PubMed1979

Kinetics of the regeneration of sea-urchin cilia. II. Regeneration of animalized cilia.

The kinetics of the regeneration of cilia of Arbacia punctulata animalized by treatment with trypsin have been examined. The cilia regenerate with biphasic kinetics: an initial linear phase which changes abruptly to a second, slower linear rate. Inhibition of protein synthesis with 10 microM emetine has little effect on the first phase but totally abolishes the second, suggesting that the first phase represents the utilization of a pre-existing precursor pool while the second reflects de novo protein synthesis. However, cilia will regenerate again following a second deciliation in the presence of emetine, to half the plateau value of the first regeneration, indicating that only a fraction of the pool of the limiting precursor can be assembled into the regenerating cilium. It is proposed that a residual pool of this precursor is required to maintain the assembly-disassembly equilibrium in favour of the assembled organelle.

Animals↗
PubMed1983

Nerve regeneration and Schwann cell basal lamina: observations of the long-term regeneration.

Nerve segments approximately 6-7 mm long were excised from the predegenerated sciatic nerves of mice, and treated 5 times by repetitive freezing and thawing to kill the Schwann cells. Such treated nerve segments were grafted into the original place, being in contact with the proximal stump of the sciatic nerve. The animals were sacrificed 2, 3, 5, 7 and 10 days, 2, 3, 5 and 8 weeks after the grafting. The grafts were examined at the middle level, i.e., about 3-4 mm distal to the proximal end of the graft, by light and electron microscopy. Within 2-3 days after the grafting, the dead Schwann cells were disintegrated into fragments and gradually phagocytized by macrophages. However, the basal laminae of the Schwann cells remained as empty tubes (basal lamina scaffolds). The notable finding was that the regenerating axons always grew through these basal lamina scaffolds. New Schwann cells seemed to migrate along these axons from the proximal stumps. The number of axons growing through the basal lamina scaffolds gradually increased with time. These axons were surrounded in a bundle by Schwann cells. About 1 week after the grafting, axons began to be segregated into smaller bundles by Schwann cells. Axons with a relatively large diameter (about 2 microns) tended to be sorted out and surrounded by their own Schwann cells. The myelination began about 2 weeks after the grafting on such large diameter axons. The basal lamina scaffolds, through which the regenerating axons had grown, were gradually disintegrated into fragments by the expansive forces due to the increase in number and volume of the regenerating axons and Schwann cells. Groups of axons, which had been derived from the same basal lamina scaffolds, were enclosed with the cells resembling perineurial epithelial cells. These perineurial epithelial cells proliferated and further separated groups of axons into smaller ones or even into single axons. The number of myelinated axons increased with the advancement of regeneration. These results show that the basal lamina scaffolds of Schwann cells serve as efficient conduits for the elongation, maintenance and maturation of regenerating axons.

Animals↗
PubMed2005

[Effect of FK506 on axonal regeneration of rat sciatic nerve in regeneration chamber: an experimental study].

OBJECTIVE: To evaluate the effect of FK506 on expediting nerve regeneration of rat Sciatic Nerve in regeneration chamber and to look for a proper way of its administration to treat peripheral nerve injuries. METHODS: Sixty adult male SD rats which were randamizely divided into 3 groups received a neurotomy to bilateral sciatic nerves, then we reconnected the broken nerves with silicon tube to make regeneration chambers. The regeneration chambers were filled with either normal saline (group A and group B) or 1 microg/ml FK506 (group C). The rats of group B also received daily injection of FK506 (1 mg/kg) at the back of the neck for 14 days. Local immunoreaction, weight of fresh gastrocnemius muscles, histological changes and electrophysiology were observed at designate time after neurotomy. RESULTS: At 6 weeks postoperation the extent of local lymphocytes infiltration in group B and C were less than that in group A, all results in group B were much better than that of group A. Results of group C were better than that of group A without significance. CONCLUSIONS: (1) Systemic administration of FK506 (1 mg/kg) showed neuroprotective and neurotrophic effect, which can facilitate nerve regeneration and promote functional recovery. (2) Local administration of FK506 (1 microg/ml) showed some extent of neuroprotective effect at early period of nerve injury, but the neurotrophic function is uncertain and still needs to be studied further.

Animals↗
PubMed1998

Nerve regeneration over a 20-mm gap through a nerve conduit containing blood vessels in rats: the influence of interstump distance on nerve regeneration.

BACKGROUND: The present study was conducted in rats to investigate whether a tube with additional intrachamber vascularization could permit axons to extend over a distance greater than 10 mm, which appears to be the maximum axon regeneration distance for rat sciatic nerve axons through a normal empty tube. METHODS: A sural vessel-containing tube (VCT) was designed and interposed between transected sciatic nerve stumps in the thigh, leaving a 20-mm interneural gap. RESULTS: Twelve weeks after tubulation, six out of nine rats showed successful nerve regeneration and re-innervation of the soleus muscle using the VCT. At 24 weeks, intrachamber nerve regeneration and re-innervation of the soleus and pedal adductor muscles were electrophysiologically and histologically confirmed in all rats. However, no neural tissue was observed within any ligated sural vessel-containing tube (LVCT) or empty unmodified tube (ET) with a 20-mm interneural gap. When nerves regenerated in the VCT with a 20-mm gap were compared with those regenerated in a VCT with a 10-mm gap 12 and 24 weeks after surgery, the results produced by the VCT with a 20-mm gap were inferior to those after use of the VCT with a 10-mm gap, except for motor nerve conduction velocity at 24 weeks. CONCLUSIONS: The value recovered to almost identical levels (about 50-60% normal) in both groups.

Animals↗
PubMed1993

Regeneration of bovine pancreatic ribonuclease A. 4. Temperature dependence of the regeneration rate.

The rate of regeneration of bovine pancreatic ribonuclease A with oxidized and reduced dithiothreitol (DTTox and DTTred, respectively) decreases by a factor of 10 when the temperature is increased from 25 to 37 degrees C. The rate of regeneration of RNase A with oxidized and reduced glutathione increases slightly over that same range of temperature. This suggests that the regeneration processes with the two types of redox reagents proceed through different pathways. There is a significant change in the distribution of three-disulfide intermediates populated during regeneration with DTTox/DTTred over the range of temperature 15-37 degrees C that suggests that the three-disulfide species populated at 15 degrees C are directly involved in the major regeneration pathway observed at 25 degrees C.

Animals↗
PubMed1998

Morphology of peri-implant regenerated bone, in sheep's tibia, by means of guided tissue regeneration.

BACKGROUND: No data on the resistance to functional loads of bone regenerated by means of guided tissue regeneration, can be found. In this paper the new-formed bone is analyzed, in cases that see the surgical creation of defects in testing animals. The morphological aspects of perimplant bone, regenerated by means of bone substitutes or not, were evaluated. METHODS: A coronal defect was created by means of a counter-sink bur. The following step provided for osseointegrated fixtures, with a machined or blasted (TiOblast) surface, to be installed. Some bone defects were filled with Bio-Oss, and covered with resorbable membrane (Vycril), others were left unfilled. The animals were sacrificed after different periods of time (24 and 45 days). Some thick sections (200 microns) underwent then microradiography and were examined with a microscope, under transmitted and polarized light. Other sections, thin (5 microns), were coloured with toluidine blue, Gomori's Stain and Solochrome Cyanine/Congo red. RESULTS: Data confirm the excellent behaviour of bovine bone and of TiO blasted fixtures. The experimental results bring into evidence that, in cases of Guided Bone Regeneration (GBR) by means of membrane, the use of fixtures with a blasted surface (TiOblast), and of Bio-Oss as bone substitute, made osseointegration easier. CONCLUSIONS: Results, moreover, suggest that in case of implant surgery with GBR, in order to allow the maturation of regenerated bone, it's healing time must be prolonged.

Animals↗
PubMed1983

Regeneration and the immune system. I. In vitro and in vivo activation of lymphocytes by liver regeneration and the role of Kupffer cells in stimulation.

When syngeneic lymphocytes and mitomycin C-treated regenerating liver cells, prepared from partially hepatectomized mice, are cultured together, the in vitro DNA synthesis is activated (sMLHLR: syngeneic mixed hepatectomized-liver cell-lymphocyte culture). The Ia+ Kupffer cells play an important role as stimulators in the response, since the stimulating activity of regenerating liver cells is lost either by the pretreatment with anti-Ia monoclonal antibody plus complement or by the removing Kupffer cells from them. The lymphocytes are also activated in vivo during liver regeneration following partial hepatectomy. When lymphocytes, prepared from hepatectomized mice, are cultured with regenerating liver cells, the lymphocytes are stimulated to accelerate their DNA synthesis in a manner typical of the secondary immune responses (secondary sMLHLR). In primary sMLHLR, the responder cells are mainly Lyt-1+, whereas, in secondary sMLHLR, they are mainly Lyt-2+. The mechanism of changing the Lyt phenotype of major responder cells from Lyt-1 to Lyt-2 during sMLHLR is discussed.

Animals↗
PubMed1993

Genetic analysis of developmental mechanisms in hydra. XXI. Enhancement of regeneration in a regeneration-deficient mutant strain by the elimination of the interstitial cell lineage.

The interstitial cell lineage, including interstitial stem cells, nerve cells, and nematocytes, was eliminated from a regeneration-deficient mutant strain (reg-16) of Hydra magnipapillata. The resultant interstitial cell lineage-free (or "epithelial") reg-16 animals showed a marked enhancement in the ability to regenerate head structures. The epithelial reg-16 polyps regenerated nearly the same number of tentacles as was originally present within 8 days after head removal, while interstitial cell lineage-containing (or "complete") reg-16 polyps restored less than one-third of their original tentacle number under the same conditions. Lateral tissue transplantation was used to examine the head activation and inhibition potentials. The gradients of the two potentials along the body axis of intact epithelial 105 (a wild-type strain) and intact epithelial reg-16 polyps were nearly identical to the gradients in their complete counterparts. The changes of the two potentials occurring after head removal in the epithelial 105 animals were also similar to those in the complete 105 animals. However, the postdecapitation changes in the epithelial reg-16 polyps were different from those in complete reg-16 polyps. The changes in the epithelial reg-16 animals were similar to those observed in wild-type hydra while those of complete reg-16 polyps were highly abnormal. These observations suggest that the phenotypic expression of the genetic defect present in the reg-16 mutant strain is attenuated when the interstitial cell lineage is eliminated from its tissue. The role of the interstitial cell lineage in head regeneration and the nature of the defect present in the reg-16 strain are discussed based on the observations made in this and previous related studies.

Animals↗
PubMed1989

Cerebral endothelial regeneration following experimental brain injury. Variation in the regeneration process according to the severity of injury.

It is still unknown when and in which area endothelial regeneration occurs after brain injury, and to what extent such changes depend on the severity of the injury. We have, therefore, studied bromodeoxyuridine (BrdU) uptake by regenerating endothelial cells in two different groups of rats given cold lesions using immunohistochemistry employing anti-BrdU monoclonal antibody, anti-factor VIII-related antigen antibody and anti-glial fibrillary acidic protein antibody. The earliest evidence for the presence of BrdU-positive endothelial cells (BrdU + end) was observed at 2 days after injury, the injured endothelial cells regenerating from the edge toward the center of the lesion in both groups. We considered that edema fluid could act as an important factor, since at 2 days post-injury BrdU + end were not in contact with macrophages and were always found in Evans blue-stained areas. Study of endothelial cell kinetics also confirmed that the repair of injured endothelial cells was intimately involved in the reconstruction of the blood-brain barrier, since the time of disappearance of BrdU + end coincided with the disappearance of Evans blue-stained areas. The difference in the process of endothelial regeneration was first apparent on the 3rd day, there being no difference at 2 days.

Animals↗
PubMedDate not supplied

A subtractive cDNA library from an identified regenerating neuron is enriched in sequences up-regulated during nerve regeneration.

We have constructed a subtractive cDNA library from regenerating Retzius cells of the leech, Hirudo medicinalis. It is highly enriched in sequences up-regulated during nerve regeneration. Sequence analysis of selected recombinants has identified both novel sequences and sequences homologous to molecules characterised in other species. Homologies include alpha-tubulin, a calmodulin-like protein, CAAT/enhancer-binding protein (C/EBP), protein 4.1 and synapsin. These types of proteins are exactly those predicted to be associated with axonal growth and their identification confirms the quality of the library. Most interesting, however, is the isolation of 5 previously uncharacterised cDNAs which appear to be up-regulated during regeneration. Their analysis is likely to provide new information on the molecular mechanisms of neuronal regeneration.

Amino Acid Sequence↗
PubMed1993

A new method to study motoneuron regeneration using electromyograms shows that regeneration slows with age in rat sciatic nerve.

We developed a novel method for measuring motoneuron regeneration using transcutaneous electrical nerve stimulation to evoke electromyograms (EMGs). Using this technique we found that functional regeneration of the motoneurons of the rat sciatic nerve was significantly slower in 9-10-month-old rats (10 mo) than in 10-12 week old rats (3 mo). All rats received crush injuries of the sciatic nerve and were analyzed for reinnervation of the muscles in the foot by the novel EMG method on days 25, 29 and 33 post-surgery. There were significantly fewer test sites reinnervated in the foot of the older group. Fifty percent of the sites in the foot were reinnervated 27.2 days post-surgery in the 3 mo group in contrast to 33.7 days post-surgery in the 10 mo group, indicative of a 24% longer recovery period in the older animals. Rats were also assessed behaviourally with a behavioural test score (BTS). The BTS results correlated with the EMG findings demonstrating that our novel method measuring rate of recovery of EMGs is behaviourally relevant. We discuss the need to use animals older than 3 months for the study of 'adult' regeneration phenomena since 3-month-old rats may be somewhat immature. We applied this age principle and the novel EMG method in our accompanying paper which shows the acceleration of nerve regeneration by weak DC electric fields.

Aging↗
PubMed1986

Essential role of polyamine metabolism in hepatic regeneration. Inhibition of deoxyribonucleic acid and protein synthesis and tissue regeneration by difluoromethylornithine in the rat.

We studied liver regeneration after partial hepatectomy and the effects of inhibition of ornithine decarboxylase (ODC) and putrescine administration. The specific ODC inhibitor, alpha-difluoromethylornithine was given as a 3% oral solution (5.4 g/kg X day intake) to hepatectomized rats as well as sham-operated controls. alpha-Difluoromethylornithine had no effect other than inhibition of the low basal levels of ODC in sham-operated rats, but it markedly inhibited increases in ODC by 85% in hepatectomized rats. alpha-Difluoromethylornithine reduced hepatic deoxyribonucleic acid synthesis by 61%, protein synthesis by 46%, and liver weight increased by 83%, showing that alpha-difluoromethylornithine inhibition of ODC inhibits liver regeneration. Putrescine (2 mmol/kg X day) was then given intraperitoneally to hepatectomized rats and controls. Putrescine had no effect in rats not given alpha-difluoromethylornithine. In rats given alpha-difluoromethylornithine, putrescine markedly reversed the inhibitory effect of alpha-difluoromethylornithine on ODC (83%), deoxyribonucleic acid synthesis (94%), protein synthesis (95%), and liver regeneration (85%). These results document that the increases in ODC are important in hepatic regeneration and that polyamine metabolism plays an important role in the increased deoxyribonucleic acid and protein synthesis in this hepatic proliferative response.

Animals↗
PubMed2000

Axonal regeneration, but not myelination, is partially dependent on local cholesterol reutilization in regenerating nerve.

A recycling pathway in peripheral nerve permits cholesterol from degenerating myelin to be salvaged by macrophages and resupplied to myelinating Schwann cells by locally produced lipoproteins. A similar reutilization of cholesterol by regenerating axons has been proposed but not demonstrated. Neurites in culture, however, do take up cholesterol and cholesterol-containing lipoproteins, where these molecules are found to promote neurite extension. To test the requirement for cholesterol reutilization in axon regeneration and myelination, we examined 2 models of blocked intracellular cholesterol transport: 1) bone marrow transplants from Niemann-Pick C mice into wild-type recipient mice, and 2) imipramine treatment. Following nerve crush in these models, we found that unusually large, debris-filled macrophages appeared and persisted for many weeks. A morphometric analysis of regenerating nerves revealed that myelination proceeded at a normal rate (normal g-ratios), but that axon growth was retarded (decreased fiber numbers and diameters) in these animals. Cholesterol synthesis was elevated in these nerves, indicating that Schwann cells compensated for the decreased exogenous supply of cholesterol by up-regulating de novo synthesis to support myelination. These data indicate that Schwann cells are not dependent on cholesterol reutilization to support myelination, but that optimal axonal regeneration is dependent on a local supply of cholesterol.

Adrenergic Uptake Inhibitors↗
PubMed1985

Regenerating fish optic nerves and a regeneration-like response in injured optic nerves of adult rabbits.

Regeneration of fish optic nerve (representing regenerative central nervous system) was accompanied by increased activity of regeneration-triggering factors produced by nonneuronal cells. A graft of regenerating fish optic nerve, or a "wrap-around" implant containing medium conditioned by it, induced a response associated with regeneration in injured optic nerves of adult rabbits (representing a nonregenerative central nervous system). This response was manifested by an increase of general protein synthesis and of selective polypeptides in the retinas and by the ability of the retina to sprout in culture.

Animals↗
PubMed1998

[Pathophysiology in muscle fiber necrosis and regeneration with a particular reference to regenerating process].

It is well known that muscle fiber is capable of regeneration after myonecrosis even in a case of muscular dystrophies. We first examined how and when the regulatory genes for myogenesis, MyoD and myogenin were expressed in experimentally induced myonecrosis. MyoD, a responsible gene for myoblast proliferation began to express at 18 hours and reached to the maximum level 48 hours after necrosis. Myogenin known to play a role for myotube formation was most extensively expressed 72 hours after myonecrosis when the newly formed myotubes were recognizable, confirming that both genes were necessary for regenerating process. The MyoD and myogenin were also expressed in regenerating fibers in muscular dystrophies including dy mouse with progressive muscle weakness and mdx mouse with no apparent muscle symptom. The genes were more extensively expressed in mdx mouse, than dy mouse simply reflecting their respective regenerating activity.

Animals↗