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PubMed2002

Wet oxidative regeneration of activated carbon loaded with reactive dye.

Wet Oxidative Regeneration (WOR) of powdered activated carbon (PAC) and granular activated carbon (GAC) loaded with the reactive dyes, namely chemictive brilliant blue R and cibacron turquoise blue G, was studied. Attempts were made to regenerate the loaded carbons designated now as spent carbon. A slurry (10% w/v) of spent carbon in distilled water was oxidized by wet oxidation in the temperature range of 150-250 degrees C using oxygen partial pressures between 0.69-1.38 MPa in an 1 1 SS 316 autoclave. The percent regeneration was determined from a ratio, X(RC)/X(VC), corresponding to an equilibrium adsorption capacity of regenerated carbon/equilibrium adsorption capacity of virgin carbon from an initial adsorption period of 3 h. It was observed that the regeneration mainly occurred due to the oxidation of the adsorbates taking place on the surface of carbon. It was possible to regenerate the spent GAC and PAC to the extent of more than 98% (approximately X(RC)/X(VC) > 0.98) by wet oxidation. After four consecutive cycles of adsorption and regeneration using the same stocks of GAC, carbon weight loss observed at 200 degrees C was about 40%. SEM studies of the regenerated carbon showed widening of the pores and loss of structure between the adjacent pores as compared with the virgin carbon. PAC was found to be more suitable as compared with GAC for the adsorption and wet oxidative regeneration processes to treat the aqueous solution containing lower concentration of unhydrolyzed reactive dye. The suitability of wet oxidative regeneration is demonstrated at a bench scale to treat the synthetic reactive dye solution.

Adsorption↗
PubMed2000

Regeneration pattern of precursor-B-cells in bone marrow of acute lymphoblastic leukemia patients depends on the type of preceding chemotherapy.

Immunofluorescence stainings for the CD10 antigen and terminal deoxynucleotidyl transferase (TdT) can be used for the detection of leukemic blasts in CD10+ precursor-B-acute lymphoblastic leukemia (precursor-B-ALL) patients, but can also provide insight into the regeneration of normal precursor-B-cells in bone marrow (BM). Over a period of 15 years, we studied the regeneration of CD10+, TdT+, and CD10+/TdT+ cells in BM of children with (CD10+) precursor-B-ALL during and after treatment according to three different treatment protocols of the Dutch Childhood Leukemia Study Group (DCLSG) which differed both in medication and time schedule. This study included a total of 634 BM samples from 46 patients who remained in continuous complete remission (CCR) after treatment according to DCLSG protocols VI (1984-1988; n = 8), VII (1988-1991; n = 10) and VIII (1991-1997; n = 28). After the cytomorphologically defined state of complete remission with CD10+ and CD10+/TdT+ frequencies generally below 1% of total BM cells, a 10-fold increase in precursor-B-cells was observed in protocol VII and protocol VIII, but not in protocol VI. At first sight this precursor-B-cell regeneration during treatment resembled the massive regeneration of the precursor-B-cell compartment after maintenance treatment, and appeared to be related to the post-induction or post-central nervous system (CNS) therapy stops in protocols VII and VIII. However, careful evaluation of the distribution between the 'more mature' (CD10+/TdT-) and the 'immature' (CD10+/TdT+) precursor-B-cells revealed major differences between the post-induction/post-re-induction precursor-B-cell regeneration (low 'mature/immature' ratio: generally <1.0), the post-CNS treatment regeneration (moderate 'mature/immature' ratio: 1.2-2.8), and the post-maintenance regeneration (high 'mature/ immature' ratio: 5.7-7.6). We conclude that a therapy stop of approximately 2 weeks is already sufficient to induce significant precursor-B-cell regeneration even from aplastic BM after induction treatment. Moreover, differences in precursor-B-cell regeneration patterns are related to the intensity of the preceding treatment block, with lower 'mature/immature' ratios after the highly intensive treatment blocks. This information is essential for a correct interpretation of flow cytometric immunophenotyping results of BM samples during follow-up of leukemia patients. Particularly in precursor-B-ALL patients, regeneration of normal precursor-B-cells should not be mistaken for a relapse.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2002

Molding of the regenerate in mandibular distraction: Part 1: Laboratory study.

Distraction osteogenesis has evolved as a mainstream surgical technique for lengthening and augmentation of the hypoplastic mandible. As clinical experience accumulated, there developed the need to "mold" the bony regenerate to avoid the development of postdistraction malocclusion and to achieve the desired craniofacial form. Although the potential to mold the regenerate has important clinical implications, the safety and efficacy of such an acute manipulation of the bony regenerate form have not yet been investigated in the laboratory. The purpose of this study was to determine if the distraction regenerate could be molded and result in a bony union. Four adult female dogs underwent bilateral mandibular distraction with an external multiplanar device (Stryker, Osteonics). After a latency period of 5 days, the mandibles underwent linear (anteroposterior) and angular (superoinferior) distraction to produce an anterior open bite of approximately 30 degrees. At the conclusion of the distraction procedure, the distraction sites were molded to close the open bite. In two dogs, the maneuver was performed over 3 days by changing the angulation of the devices (gradual molding), and in the other two dogs, molding was achieved with a single movement (acute molding). In the latter, the distraction devices were adjusted and reapplied to allow for anatomical fixation during the consolidation period of 49 days. According to the research protocol, the mandibles were assessed serially by cephalograms and computed tomography (CT) scans. All dogs survived the study without complications. The bony regenerate was easily molded in both groups to close the surgically created open bite. After molding, all the regenerates showed CT scan evidence of solid bone (consolidation), which was classified as "extended" on the Hamanishi scale. After the dogs were killed and soft tissue was removed, the regenerate seemed to be robust on gross examination without any evidence of fibrous nonunion. In addition, histological study of the regenerate confirmed the bony union. The study demonstrates that the mandible can be successfully molded into a desired anatomical position immediately after distraction without producing a fibrous union. Furthermore, it has been demonstrated that the bony regenerate is sufficiently malleable before consolidation to undergo either acute or gradual angular molding without disturbing osteogenic potential. The ability to mold the regenerate without the fear of creating a fibrous union or destroying bony potential provides the surgeon the capability to optimize the dental occlusion and mandibular form as part of the distraction treatment process.

Animals↗
PubMedDate not supplied

A combination of ion exchange and electrochemical reduction for nitrate removal from drinking water. Part I: nitrate removal using a selective anion exchanger in the bicarbonate form with reuse of the regenerant solution.

The process of selective nitrate removal from drinking water by means of ion exchange was studied. A commercial strong base anion exchanger with triethylammonium (-N+Et3) functional groups was used in the bicarbonate (HCO3-) and carbonate (CO3(2-)) form. The aim of this study was to optimize ion-exchanger regeneration in view of the subsequent electrochemical reduction of nitrates in the spent regenerant solution. The effects of ion-exchanger form, concentration of regenerant solution, and presence of nitrates, chlorides, and sulphates in the regenerant solution were studied. The strong base anion exchanger in HCO3- form that was investigated was able to treat 270 bed volumes of model water solution containing 124 mg dm(-3) nitrates. To achieve adequate regeneration of the saturated anion exchanger, it is necessary to use approximately 30 bed volumes of fresh 1-M sodium bicarbonate (NaHCO3) regenerant solution. The presence of residual 50-mg dm(-3) nitrates in the regenerant solution, treated by electrolysis, resulted in an increase in the dose of regenerant solution to 35 bed volumes and a decrease in the subsequent sorption run of approximately 13%. The volume of applied regenerant solution was high, but the consumption of NaHCO3 for regeneration was low.

Anions↗
PubMed1978

Re-regeneration of lower jaws and the dental lamina in adult urodeles.

Transverse amputations were carried out through one-third fully regenerated jaw segments and through normal tissue of the mandible on the same and opposite sides of the jaw in adults of Notophthalmus viridescens. Collectively the results suggest that, in adult urodeles, the mandible and the dental lamina can be replaced in an identical manner more than one time. Although the major histological events are the same in jaw regeneration and re-regeneration, regrowth is more rapid in re-regeneration. It appears that recently differentiated tissues of the regenerate have a higher capacity for regeneration than normal tissues amputated for the first time. Re-regeneration of the jaw occurs by growth of the original regenerate cartilage which has undergone reorganization. In re-regeneration, the skeletal elements exhibit no polarity and regrowth occurs in both directions, while the dental lamina possesses an anterior-posterior polarity and can regrow in an anterior direction only. Information concerning the mechanisms involved in the regenerative events remain to be determined.

Animals↗
PubMed2005

Review: peripheral nerve regeneration using non-tubular alginate gel crosslinked with covalent bonds.

We have developed a nerve regeneration material consisting of alginate gel crosslinked with covalent bonds. in the first part of this study, we attempted to analyze nerve regeneration through alginate gel in the early stages within 2 weeks. in the second part, we tried to regenerate cat peripheral nerve by using alginate tubular or non-tubular nerve regeneration devices, and compared their efficacies. Four days after surgery, regenerating axons grew without Schwann cell investment through the partially degraded alginate gel, being in direct contact with the alginate without a basal lamina covering. One to 2 weeks after surgery, regenerating axons were surrounded by common Schwann cells, forming small bundles, with some axons at the periphery being partly in direct contact with alginate. At the distal stump, numerous Schwann cells had migrated into the alginate 8-14 days after surgery. Remarkable restorations of the 50-mm gap in cat sciatic nerve were obtained after a long term by using tubular or non-tubular nerve regeneration material consisting mainly of alginate gel. However, there was no significant difference between both groups at electrophysiological and morphological evaluation. Although, nowadays, nerve regeneration materials being marketed mostly have a tubular structure, our results suggest that the tubular structure is not indispensable for peripheral nerve regeneration.

Alginates↗
PubMed1985

Physiological properties and pattern of innervation of regenerated muscles in the rat.

The regeneration of fast and slow muscles was compared following "mincing" and replacement into their own or alien muscle bed. At intervals varying from 2 to 9 weeks the tension developed by the regenerated muscles was assessed and compared to that developed by the muscles from the contralateral unoperated side. This parameter was then taken as an indication of recovery. The regenerated muscles never developed more than half of the tension of the control muscles. Muscles regenerated in the bed of extensor digitorum longus became fast-twitch muscles and muscles regenerated in the bed of soleus became slow-twitch muscles, no matter whether they originated from an extensor digitorum longus or soleus "mince". The regeneration of the muscle tissue in the place of extensor digitorum longus developed better than in the place of soleus. The pattern of innervation of the regenerated muscles was analysed using a combined cholinesterase silver stain. Many of the regenerated fibres had more than one end plate and some end plates more than one axon terminal. These results show that in adult animals muscle redevelopment can occur, but only to a limited extent. Moreover, on reinnervation of regenerated muscle fibres the axons do not assume their original pattern of innervation.

Animals↗
PubMed2003

The effect of enamel matrix proteins on periodontal regeneration as determined by histological analyses.

BACKGROUND: Therapeutic approaches to periodontal regeneration in the past have utilized bone replacement grafts, growth factors, barrier membranes, or combinations of these approaches. More recently, enamel extracellular matrix proteins have been introduced to stimulate periodontal regeneration. One factor thought to have an impact on the outcome of the regenerative process is the initial size of the periodontal defect. This is particularly the case when using proteins to stimulate regeneration, because the concepts of guided tissue regeneration emphasize the need for space maintenance to allow for selected cell repopulation. The goal of this study was to evaluate periodontal regeneration in intrabony defects of various sizes treated with enamel matrix proteins. METHODS: Periodontal defects ranging in size from 1 to 6 mm were created bilaterally around 3 teeth in the mandibles of baboons. Plaque was allowed to accumulate around ligatures placed into the defects. After 2 months, the ligatures were removed, the teeth were scaled and root planed, and a notch was placed at the base of the defect. On one side of the mandible, neutral ethylene diamine tetracetic acid and enamel matrix proteins were used to treat the defects. The other side served as a control, with neutral ethylene diamine tetracetic acid treatment alone after scaling and root planing. Flaps were sutured and the animals were allowed to heal without oral hygiene procedures. After 5 months, the animals were sacrificed and the teeth were processed for histological evaluation. RESULTS: Periodontal regeneration occurred in all sizes of the periodontal defects. Qualitatively, new cementum, periodontal ligament with Sharpey's fibers, and new bone tissue were observed. In general, enamel matrix protein treatment resulted in greater tissue formation than controls. In many instances, dramatic tissue formation occurred far coronal to the base of the defects. In addition, horizontal bone fill occurred in defects that were initially 4 or 6 mm wide. The resultant width of the periodontal ligament was similar in all defects regardless of the original defect width. The cementum width was slightly greater in the wider (4 and 6 mm) defects compared to the more narrow (1 and 2 mm) defects. When evaluating the combined 1 and 2 mm defects, the height of new cementum with enamel matrix protein treatment was 45% greater than the control, with 31% greater new bone height versus the control. In the combined wider defects (4 and 6 mm), new tissue height was more similar between enamel matrix protein-treated defects and control defects. The results from the wider defects must be interpreted cautiously, because the interproximal bone heights were resorbed more adjacent to the wider defects during the plaque accumulation period and likely limited the potential for regeneration. CONCLUSIONS: The treatment of various sized periodontal defects with enamel matrix proteins stimulated substantial periodontal regeneration. In many cases, dramatic amounts of new cementum, Sharpey's fibers, periodontal ligament, and bone tissue were formed far coronal to the notch at the base of the defect, especially considering the width of the original defects. This periodontal regeneration occurred in the absence of exogenous growth factors, bone replacement grafts, barrier membranes, or their combination.

Alveolar Bone Loss↗
PubMed1994

Clinical implications of cellular biologic advances in periodontal regeneration.

It is known that periodontal tissues retain the ability to regenerate; however, current therapies fail in achieving predictable and consistent regeneration. Cell and molecular biology research in periodontal regeneration hold great promise in providing improved understanding of this complex phenomenon and direct us towards new possibilities of future clinical application. This paper reviews both the cells and extracellular matrix of the periodontal ligament in addition to the cell-to-matrix and cell-to-cell interaction involved in periodontal regeneration. Results of recent studies have suggested that periodontal regeneration recapitulates the process of morphogenesis, histogenesis, and cytodifferentiation, as well as cell field migration that occurs during development of the periodontium. A small population of purported periodontal stem cells is believed to be responsible for maintaining homeostasis in the periodontal ligament. This cell, which may have its origin in late periodontal mesenchyme of the dental papilla, is advocated as a tripotential cell capable of differentiating into cementoblast, osteoblast, and periodontal fibroblast. The clinical implication of advances made in cell and molecular biology research in periodontal regeneration may include future use of biomolecules in periodontal regeneration may include future use of biomolecules to improve the regenerative healing process and use of bioactive degradable membrane barriers in guided tissue regeneration as well as seeding of periodontal stem cells into periodontal defects. If the current trend continues, clinicians can look forward to seeing periodontal wound healing being substantially enhanced to achieve predictable periodontal regeneration.

Cell Communication↗
PubMedDate not supplied

Treatment of peri-implantitis using guided bone regeneration and bone grafts, alone or in combination, in beagle dogs. Part 2: Histologic findings.

The aim of this study was to histologically evaluate and compare the treatment of ligature-induced peri-implantitis using guided bone regeneration, two bone grafts alone, or guided bone regeneration combined with one of the two bone graft materials. Mandibular premolars and first molars in seven beagle dogs were extracted. After placement of Brånemark implants and connection of abutments, experimental peri-implantitis was induced. Flap surgery was performed, abutments were removed, and implant surfaces were treated with an air-powder abrasive unit. Bony defects were randomly treated with either (1) debridement only; (2) debridement plus resorbable hydroxyapatite; (3) debridement plus canine demineralized freeze-dried bone; (4) debridement plus guided bone regeneration; (5) debridement plus resorbable hydroxyapatite and guided bone regeneration; or (6) debridement plus canine demineralized freeze-dried bone and guided bone regeneration. Four months after surgery, a flap was elevated and the barriers were removed. One month later, the animals were sacrificed, and the implants with their supporting peri-implant tissues were processed for histologic evaluation. Guided bone regeneration procedures resulted in the greatest amount of new bone formation, followed by bone grafts alone, and flap debridement. There was no significant difference between guided bone regeneration and both guided bone regeneration/graft combinations in terms of bone regeneration; however, the guided bone regeneration/graft combinations resulted in a greater amount of "reosseointegration" than all of the other treatments. Therefore, the combination of guided bone regeneration with either demineralized freeze-dried bone or resorbable hydroxyapatite appears to be the treatment of choice for plaque-induced peri-implant defects.

Animals↗
PubMedDate not supplied

Effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in supra-alveolar peri-implant defects in dogs.

This randomized, split-mouth design study evaluated the adjunctive effect of allogeneic, freeze-dried, demineralized bone matrix on guided bone regeneration in a critical-size, supra-alveolar, peri-implant defect model. Contralateral supra-alveolar peri-implant defects, 5 mm in height, each including two titanium implants, were surgically created in five beagle dogs. Demineralized bone matrix in autologous blood was placed over the implants in one randomly selected mandibular jaw quadrant. A space-making expanded-polytetrafluoroethylene membrane was used to provide guided bone regeneration bilaterally. Following a 16-week healing interval, tissue blocks were harvested and prepared for histometric analysis. Differences between experimental conditions (guided bone regeneration sites with and without demineralized bone) were evaluated using paired t tests (n = 4). Demineralized bone particles were discernible, with limited signs of resorption. The bone matrix particles appeared to be solidified within a dense connective tissue matrix and in close contact with the implants. Limited matrix remineralization was apparent adjacent to the alveolar crest. No statistically significant differences were found between experimental conditions for any parameter examined. Peri-implant defect height averaged 5.0 +/- 0.2 mm and 4.9 +/- 0.4 mm, vertical bone regeneration 1.5 +/- 0.9 mm and 1.1 +/- 0.4 mm, osseointegration within the extent of the defect 10.0 +/- 3.9% and 15.3 +/- 5.3%, osseointegration within the extent of regenerated bone 30.4 +/- 13.7% and 52.1 +/- 17.9%, and osseointegration within the alveolar base 68.8 +/- 13.1% and 74.4 +/- 7.1% for guided bone sites with and without demineralized bone, respectively (P > .05). The results suggest that freeze-dried demineralized bone has no adjunctive effect on guided bone regeneration in supra-alveolar peri-implant defects, that guided bone regeneration has a limited potential to enhance alveolar regeneration in this defect model, and that a 16-week healing interval appears insufficient for turnover and maturation of demineralized bone under provisions for guided bone regeneration.

Alveolar Bone Loss↗
PubMed1997

Optic nerve regenerates but does not restore topographic projections in the lizard Ctenophorus ornatus.

In adult fish and amphibians, the severed optic nerve regenerates and visual behaviour is restored. By contrast, optic axons do not regenerate in the more recently evolved birds and mammals. Here we have investigated optic nerve regeneration in a member of the class Reptilia, phylogenetically intermediate between the fish and amphibians and the birds and mammals. We assessed visual recovery anatomically and behaviourally one year after unilateral optic nerve crush in the adult ornate dragon lizard. Ctenophorus ornatus. Ganglion cell densities and numbers of axons in the optic nerve on either side of the crush site indicated that two-thirds of ganglion cells survived axotomy and regrew their axons. However, myelination fell from a mean of 21% in normals to 5.5% and 3%, proximal and distal to the crush, respectively. Anterograde labelling of the entire optic nerve showed that axons regenerated along essentially normal pathways and that the major projection, as in normals, was to the superficial one-third of the contralateral optic tectum. However, localised retinal injections indicated that regenerated projections lacked retinotopic order. Any one retinal region projected to the entire tectum. This feature presumably explains why the experimental lizards consistently appeared blind to stimuli via the regenerated nerve. Our findings indicate that although axons regenerate along essentially normal pathways in adult lizards, conditions within the visual centres do not allow regenerating optic axons to select appropriate central connections. In a wider context, the result suggests that the ability for regenerating central axons to form topographic maps may also have been lost in the more recently evolved vertebrate classes.

Animals↗
PubMed1999

Expression of growth regulatory genes in a SCID mouse-human model of intestinal epithelial regeneration.

Analysis of human intestinal epithelial regeneration has been limited. This study has used a novel SCID mouse-human model to test the hypothesis that distinct stages of human intestinal epithelial regeneration are accompanied by differential expression of growth regulatory genes. Disaggregated epithelium, which included crypt cell aggregates, was isolated from human fetal small intestine and transplanted subcutaneously in SCID mice. This method induced a coordinated regeneration response and enabled temporal separation of cell populations at different stages of histogenesis and cytodifferentiation. Graft epithelium was identified using a specific anti-human monoclonal antibody (MAb 5D3) against cytokeratins 8 and 18. Functional epithelial lineages were identified by appropriate markers. Growth regulatory genes relevant to proliferation and apoptosis, including Bcl-2, p53 and Ki67, were assayed at different stages of regeneration. During early regeneration, Bcl-2, p53, and Ki67 were expressed throughout the epithelial compartment. On completion of regeneration, these genes were expressed only in crypt epithelium and were absent from villi. This study has established a novel SCID mouse-human model of intestinal epithelial regeneration. During early regeneration, increased Bcl-2 and Ki67 expression may indicate suppression of apoptosis and enhanced proliferation respectively, consistent with expansion of the stem cell fraction. The p53 gene may influence pathways of differentiation during regeneration, analogous to its role during development.

Animals↗
PubMed1999

Axon regeneration in organotypic slice cultures from the mammalian auditory system is topographic and functional.

In vitro models have frequently been employed to investigate the specificity of the formation of axonal projections during both development and regeneration. Such studies demonstrated pathway, target, and laminar specificity, yet they did not tackle the problem of topography. Here, we addressed the issue of regeneration of spatial specificity at the topographic level by lesioning a precisely organized projection from the auditory system of neonatal rats in organotypic slice culture and by analyzing regeneration capacity. Lesioning had no effect on the survival of axotomized neurons or the structure of the auditory nuclei. Anterograde and retrograde biocytin tracing demonstrated that the projection regenerated topographically at the supracellular level. Whole-cell patch-clamp recordings revealed that the regenerated projection was functional. Topographic regeneration was not impaired by blocking spike activity with tetrodotoxin or glycinergic transmission with strychnine. However, if lesioning was performed after the slices had been incubated for 1 week, regeneration capacity was lost despite good survival of neurons. The loss of the regeneration capacity in vitro occurs at a developmental stage that corresponds to the age when the capacity for axonal reorganization is lost in vivo. We conclude that the developmental processes occurring in vivo and in vitro are comparable in this system, which is why we think that essential aspects of the loss of regeneration capacity may be addressed with our culture model in the future.

Animals↗
PubMed1996

Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian Dugesia tigrina.

We recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. We report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 microT. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 microV/m. The addition of either 51.1 or 78.4 microT DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas our previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling. These results together with those reported previously point to two distinct physiological effects produced in regenerating planaria by exposure to weak extremely-low-frequency (ELF) magnetic fields. They further suggest that the planarian, which has recently been identified elsewhere as an excellent system for use in teratogenic investigations involving chemical teratogens, might be used similarly in teratogenic investigations involving ELF magnetic fields.

Abnormalities, Radiation-Induced↗
PubMed1995

Re-programming of expression of the KGFR and bek variants of fibroblast growth factor receptor 2 during limb regeneration in newts (Notophthalmus viridescens).

We have previously shown, by in situ hybridization, that fibroblast growth factor receptor 2 (FGFR2) is present in the basal layer of wound epithelium during limb regeneration in newts (Notophthalmus viridescens). In contrast, FGFR1 expression is observed throughout the blastema mesenchyme but is distinctly absent from the wound epithelium (Poulin et al. [1993] Development 119:353-361). Sequence analysis revealed that we have isolated both the KGFR and bek variants of FGFR2. These two variants differ only in the second half of the last of their three (or two) Ig-like domains. In this report, we show the expression patterns of FGFR2 variants during limb regeneration by in situ hybridization. During the pre-blastema stages of regeneration, FGFR2 expression was observed in the basal layer of the wound epithelium and in the cells of the periosteum. The wound epithelial hybridization was observed when the KGFR-specific probe was used while the bek-specific probe hybridized to mRNA in the cells of the periosteum. As regeneration progresses to the blastema stages, KGFR expression continued to be observed in the basal layer of the wound epithelium with additional hybridization seen in the blastema mesenchyme closely associated with the bisected bones. The bek-specific hybridization pattern observed at this stage corresponds specifically to the mesenchymal hybridization. In the differentiation stages of regeneration, the mesenchymal expression of FGFR2 becomes restricted to the cells of the condensing cartilage and later to the perichondrium. Interestingly, there appears to be a dorsoventral gradient of the expression of both KGFR and bek variants of FGFR2, which are opposite each other at the later stages of regeneration. Thus, re-programming of expression of the two FGFR2 variants is required during the initial wound closure of limb regeneration. Remarkably, the expression patterns of KGFR and bek mimic those observed in the mouse limb bud during early embryonic development (Orr-Urtreger et al. [1993] Dev. Biol. 18:475-486). Moreover, our results suggest that the two FGFR2 variants have distinct roles in limb regeneration. Further investigation regarding the potential sources of the FGF ligands will help establish the roles that FGFs and FGFRs play in limb regeneration.

Amino Acid Sequence↗
PubMed1991

Regeneration of skeletal muscle in streptozotocin-induced diabetic rats.

The present study analyzes the regeneration of skeletal muscle in diabetic rats. Intravenous injection of streptozotocin (STZ) was used to induce diabetes. Six weeks later the extensor digitorum longus (EDL) muscles from diabetic rats were either transplanted into diabetic or normal hosts to initiate regeneration. Normal EDL muscle transplants in normal and diabetic hosts were also performed for comparison. One, 2, 4, and 12 weeks after transplantation, the EDL regenerates were morphologically analyzed. Regeneration and formation of neuromuscular junctions were observed in all transplants, including diabetic regenerates in diabetic hosts. The overall mass and myofiber size of the diabetic EDL regenerate in the diabetic host was significantly reduced in spite of complete regeneration. Recovery of the diabetic muscle mass and the myofiber size was observed after transplantation into normal hosts. A reduction in mass and myofiber size was observed in normal EDL muscles transplanted into diabetic hosts. It is concluded that poor recovery of diabetic muscle is related to metabolic and structural alterations in the diabetic host, rather than to innate capacity of the muscle to per se undergo regeneration and reinnervation. The observed enhancement in recovery of diabetic muscle after transplantation in a normal host and deterioration of normal muscle after transplantation in a diabetic host shows that the host environment determines the success of muscle regeneration.

Animals↗
PubMed1995

Regeneration in denervated toad (Bufo viridis) gastrocnemius muscle and the promotion of the process by low energy laser irradiation.

BACKGROUND: It is known that while denervated skeletal muscles have the ability to regenerate, maturation of regenerated myofibres does not take place under these conditions. Denervation also causes elevation of "invasive" and satellite cells, but the role of these cells in the regeneration process after injury to the denervated muscle is still unknown. Low energy lasers have recently been found to modulate and accelerate physiological processes in cells. The aim of the present study was to compare regeneration in denervated and innervated amphibian muscles and to investigate whether this process in denervated muscles can be stimulated by low energy laser irradiation prior to injury in these muscles. METHODS: Denervated gastrocnemius muscles of toads were irradiated with He-Ne laser (6.0 mW, 31.2 J/cm2) 7 days postdenervation (control muscle received red light irradiation at the same wavelength). Nine days after denervation cold injury was performed on the site of irradiation of both groups of muscles. At 14 days postinjury all muscles were removed and processed for histology and histomorphometric analysis of mononucleated cells, myotubes, and young myofibres in the regenerated zone. RESULTS: The volume fraction (percent of total injured zone) of the various histological structures in the injured zones 14 days after cold injury in the denervated (9 days prior to injury) muscles did not differ from innervated injured muscles at the same time interval postinjury. The mononucleated cells and myotubes in the laser irradiated muscles comprised 49 +/- 4% and 6 +/- 1% of the injured area, respectively, which was significantly lower than their volume fraction (67 +/- 2% and 11 +/- 2%, respectively) in the control muscles. The young myofibres populated 34 +/- 4% of the total injured area in the denervated and laser irradiated muscles which was significantly higher than their volume fraction (12 +/- 2%) in control denervated muscles. CONCLUSIONS: It is concluded that initial stages of regeneration can also take place in skeletal denervated and injured muscles of amphibians. The kinetics of the regeneration process are identical in denervated and innervated muscles. The process of regeneration in denervated muscles can be markedly enhanced if the muscle is irradiated by low energy laser prior to injury, probably by activation (stimulation of proliferation and/or differentiation) cells in the muscles that are "recruited" and participate in the process of regeneration.

Animals↗