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PubMed2000

The interaction and adhesive mechanisms between axon and Schwann cell during central and peripheral nerve regeneration.

It is well known that the injured mammalian PNS can successfully regenerate, while the CNS such as the optic nerve of adult mammals is incapable of regeneration. It is now generally accepted that the inability of CNS neurons to regenerate appears to be caused by the glial environment made up of astrocytes and oligodendrocytes. However, recent studies show that such CNS neurons have the intrinsic capacity to regenerate which is triggered by an experimental replacement of inhibitorial glial environment to peripheral nerve segment. Thus, the PNS environment is suitable not only for the regeneration of PNS itself, but also for the elicitation of CNS regeneration. Schwann cell is the major component of PNS, which plays a central role both in PNS and CNS regeneration by producing various kinds of functional substances. The contact of axons to Schwann cells based upon the structural and molecular linkages seems to be indispensable for stable and successful regeneration. In addition to cell adhesion molecules, Schwann cells utilize short focal tight junctions to provide morphological stabilization of the contact with the elongating axon, as well as small scale gap junctions to facilitate traffic of substances between them. Thus, nerve regeneration is not a simple phenomenon of axonal elongation on the part of the Schwann cell membrane, but is based on direct and dynamic communication between the axon and the neighboring Schwann cell, which may be partly associated with the mechanisms of neural regeneration.

Animals↗
PubMed1992

Sensory nerves in adult rats regenerate and restore sensory function to the skin independently of endogenous NGF.

We have investigated the possible roles of NGF, and of impulse activity, in the regeneration of sensory nerves. Unexpectedly, the ability of crushed axons to regrow and to restore functional recovery of three sensory modalities in adult rat skin (A alpha-mediated touch, A delta-mediated mechanonociception, and C-fiber-mediated heat nociception) was totally unaffected by anti-NGF treatment. This finding applied even when the anti-NGF dosage was almost eight times that which entirely blocked collateral sprouting of the undamaged axons of both classes of nociceptive nerves (the A alpha-axons do not sprout in adult animals). In the same anti-NGF-treated animal, regeneration would proceed normally on the one side, while collateral sprouting was prevented on the other. Light microscopic and EM examination revealed that in the denervated skin the regenerating axons utilized the same dermal perineurial pathways followed by collaterally sprouting axons. Regeneration within these antibody-accessible pathways progressed normally during anti-NGF treatment, extending 1-2 cm beyond the former field borders, that is, into territory whose invasion by collaterally sprouting axons was totally blocked. The blood-nerve barrier is absent within the degenerating peripheral nerve trunk, a putative NGF source for regenerating fibers but not for sprouting ones. The NGF-independent regeneration was also found to be unaffected when putative spinal cord sources of NGF were eliminated by dorsal root excision. Anti-NGF treatment also failed to block regeneration across 4 mm excision gaps in the nerve trunk. The daily anti-NGF regime continued to be effective for at least 8 weeks, at which time newly evoked collateral sprouting could still be blocked. Exogenous NGF, in doses that evoke collateral sprouting de novo in normal skin, failed to influence regeneration. Finally, an electrical stimulus regime, which markedly reduces the latency of collateral sprouting, failed to affect the time to arrival of regenerating axons at the skin, or the rate of their arborization in it. We conclude that, in striking contrast to their collateral sprouting, the regeneration of nociceptive axons occurs independently of endogenous NGF and is unaffected by impulse activity. These findings further support the proposal that these two growth behaviors have basically different biological functions in the organism.

Animals↗
PubMed2002

[To establish and observe the experimental lens regeneration model in rabbits].

PURPOSE: To establish the lens regeneration model in New Zealand rabbits, observe the lens regeneration process to investigate the mechanism of lens epithelial cell growth and lens regeneration. METHODS: Lens extraction by endocapsular phacoemulsification was performed on 8 experimental eyes in New Zealand albino rabbits weighing approximately 1.5 - 2.5 kg. To restore a relative intact capsule bag, a little needle tip was inserted through the limbal wound to perform a 2 mm-lined anterior capsulotomy, which just permitted the insertion of a 21G phacoemulsification tip. Phacoemulsification extraction was applied to remove all lens cortical material and then Healon was injected intracapsularly to distend the capsule bag. With slitlamp, the procedure of le ns regeneration were observed and taken photographs. A histologic study on regenerated lens were also performed. RESULTS: The relative 3 different results on experimental eyes according to the size of anterior capsulotomy in surgical procedure. In 4 eyes, when the size of anterior capsulotomy is approximately 2 mm and the capsule bag is relatively intact, lens regeneration occured and it has a relatively normal translucent cortex and central nuclear opacity. Among other 4 surgical eyes, the lower half part of lens regeneration was still observed in one eye though the upper half of anterior capsule was damaged, whereas in other 3, owing to the whole anterior capsule lack nearly, lens regrowth was not noted in areas of pupil under the slitlamp biomicroscopy observation and the posterior capsule appeared as gray-white membrane opacity. Histologic study showed that lens epithelial cells in equatorial zone proliferate and differentiate into lens fibers and continues to refill the whole capsule bag. Lens fiber alignment was regular in the periphery of regenerated lens, whereas in the center opacity nuclear, the bulk of the regenerated lens material consisted of an eosinophilic disorganized lens fibers. In addition, there were much of irregular cellular proliferation in capsule wrinkling. CONCLUSION: Capsule is the support material of lens epithelial cells regrowth. Lens regeneration occurred in rabbits after restoring lens capsular integrity following endocapsule phacoemulsification lens extraction, which was the result of the lens epithelial cells proliferation and differentiation. The cellular proliferation and differentiation was associated with the of capsule morphosis.

Animals↗
PubMed2005

[Optic nerve regeneration in Bcl-2 overexpressing mice].

OBJECTIVE: To determine whether overexpression of Bcl-2 is sufficient to support optic nerve regeneration in mouse in the early neonatal stage, when the brain environment remains permissive for axonal growth, and whether regenerating axons follow the guidance cues to reach the appropriate targets in the brain. METHODS: Optic nerve crush was performed in wild-type (C57BL/6J) and Bcl-2 transgenic mouse pups at 3 days after birth (P3). To assess optic nerve regeneration, mouse pups were allowed to survive for 1-4 days post-surgery. An anterograde tracer-cholera toxin B subunit (CTB) and anti-GAP-43 immunofluorescence were applied to reveal regenerating axons. RESULTS: In wild-type mice, severed optic nerves failed to regenerate, and most severed axons retracted within 24 hour post-surgery. In contrast, in all of the Bcl-2 transgenic mice examined, optic nerves regenerated robustly over long distances and reached their brain targets in 4 days after optic nerve crush. However, the majority of regenerating axons, appearing to follow the existing optic tract and visual pathways, entered the visual targets that were ipsilateral to the nerve injury. Much less number of regenerating axons innervated their contralateral visual targets. CONCLUSION: Overexpression of Bcl-2 is sufficient to support the intrinsic growth mechanisms of retinal ganglion cell axons and enables robust optic nerve regeneration over long distances in vivo if the injury is incurred at 3 days after birth. However, the regenerating axons appear to follow the existing CNS pathways and innervate uninjured brain areas.

Animals↗
PubMed1978

Lens regeneration from cornea of larval Xenopus laevis in the presence of the lens.

In Xenopus laevis tadpoles, wounding of the outer cornea failed to initiate lens regeneration. If both the outer and inner corneas were wounded or if the lens was dislocated, lens regeneration was initiated but failed to continue beyond stage III. However, lensectomy followed by re-implantation of the lens resulted in the regeneration of a fully differentiated lens in several cases, despite the presence of the re-implanted lens. Although some of the regenerates in these eyes were also arrested at stage III, those which attained full lens differentiation, i.e. stage V, developed normally and synthesized crystalline from the onset of stage IV as indicated by a positive immunofluorescence reaction. Histological examination of the dislocated and re-implanted lenses showed the majority of them to be normal in appearance. Cornea transplanted to the posterior chamber of the eye also regenerated a lens in the presence of the re-implanted lens. All these regenerates underwent lens fibre differentiation to give stage-V regenerates. These findings show that lens regeneration from the cornea can occur in the presence of lens. Results are discussed on the basis that contrary to earlier suggestions, an inhibitory lens factor does not exist in vivo, but rather that a factor for the initiation and maintenance of regeneration emanates from the eye cup and upon wounding of the inner cornea is able to reach the inner cell layer of the outer cornea and initiate lens regeneration.

Animals↗
PubMed1988

Meniscal regeneration and its effects on articular cartilage in rabbit knees.

The incidence and size of meniscal regeneration after medial meniscectomy on the right knee and lateral meniscectomy on the left knee of 44 rabbits was observed and correlated with development of degenerative arthritis. Complete meniscal regeneration was found in 23% of medial meniscectomy knees, partial regeneration in 68%, and no regeneration in 9%. Among 44 lateral meniscectomies, only 5% had complete meniscal regeneration, and 68% had no meniscal regeneration. The remaining 27% of knees had partial regeneration. Degenerative changes of articular cartilage in the tibiofemoral joints of all knees were inversely correlated with the size of the regenerated meniscus. These observations suggest that poor results following lateral meniscectomy may be due to a lower level of meniscal regeneration and relatively poor morphological regeneration of the lateral meniscus compared to the medial meniscus.

Animals↗
PubMed1983

Correlation of axonal regeneration and slow component B in two branches of a single axon.

We investigated the relationship between slow axonal transport and axonal regeneration in the rat dorsal root ganglion (DRG) cell. The DRG cell sends out a single axon which bifurcates within the ganglion; one axon proceeds centrally into the spinal cord and the other proceeds peripherally. The rate of axonal regeneration is approximately 2 times faster for the peripheral processes (4.6 +/- 0.9 mm/day) than for the central processes (2.1 +/- 0.5 mm/day). The peripheral and central processes regenerate through dissimilar environments (sciatic nerve and dorsal root, respectively); thus, environmental factors may account for the differences in regeneration rates. We tested this possibility by measuring the regeneration of motoneuron axons within the ventral root (histologically similar to the dorsal root). The motoneuron regeneration rate within the ventral root is similar to the motoneuron regeneration rate within the sciatic nerve, suggesting that factors within the DRG cell produce the differences in regeneration rate. Slow axonal transport is classified into two distinct components: slow component a (SCa), corresponding to the microtubule/neurofilament network of the axonal cytoskeleton, and slow component b (SCb), corresponding to the microfilament complex/axoplasmic matrix. The transport rate of SCa and SCb in the peripheral sensory axons is approximately 2 times faster than their counterparts in the central sensory axons. SCa moves at 1.0 to 3.0 mm/day in the peripheral processes and 0.5 to 1.0 mm/day in the central processes; SCb moves at 3.5 to 6.5 mm/day in the peripheral processes and 2.0 to 3.5 mm/day in the central processes. In each branch of the DRG cell, the rate of axonal regeneration is similar to the rate of SCb transport. These results support the hypothesis that SCb is a rate-limiting factor in axonal regeneration because of its role in providing the cytoskeletal elements which are directly involved in the motility of the growth cone and elongation of the axon.

Animals↗
PubMed1983

Axonal regeneration in lamprey spinal cord.

Spinal cords of sea lamprey larvae were transected at one of two levels: (a) rostral, at the last gill, or (b) caudal, at the cloaca. Following various recovery times, regeneration of the posteriorly projecting giant reticulospinal axons (RAs) was demonstrated by intra-axonal injection of horseradish peroxidase (HRP). Regeneration of axons of anteriorly projecting dorsal cells (DCs) and giant interneurons (GIs) was demonstrated by intrasomatic HRP injection into cells located just below the transection scar. After 40 days of recovery, 55% of proximally transected RAs (rostral cut) regenerated at least as far as the center of the scar, whereas only 15% of distally transected RAs (caudal cut) did so. Maximum distance of regeneration was 5.3 mm beyond the scar for proximally transected RAs but only 38 u for distally transected RAs. Proximally transected RAs also branched more profusely than distally transected ones. These data (when combined with others in the literature) suggest that the regenerative capacity of RAs may decrease with distance of axotomy from the cell body. Distance of regeneration and degree of branching of proximally transected RAs peaked between 40 and 100 days. Thereafter, there appeared to be a tendency toward neurite retraction. Of axotomized GIs, 76% regenerated anteriorly at least as far as the center of a caudal transection scar (GIs are located only in the caudal part of the cord). The maximum distance of regeneration was 1.3 mm beyond the scar. Of DC axons, 56% regenerated anteriorly at least as far as the transection site. The maximum distance was 1.1 mm beyond the scar. DCs located just below a caudal transection regenerated at least as well as those located below a rostral transection. Axonal regeneration was also demonstrated for a few lateral cells, edge cells, and crossed caudally projecting interneurons.

Animals↗
PubMed1980

Morphogenetic properties of the skin in axolotl limb regeneration.

A study has been made of the morphogenetic properties of anterior and posterior skin from the lower forelimb of the axolotl. The basic experiment consisted of a graft of a half cuff of skin from a donor to a host limb followed by a 2-week healing period, amputation through the graft, and a study of the resulting regenerate. Limbs with double posterior skin formed double posterior regenerates and, in contrast, limbs with double anterior skin formed normal or slightly hypomorphic regenerates. Posterior skin from post-metamorphic animals had a similar but weaker effect to that from ordinary axolotls. Immunological rejection of allografts could be completely avoided if the donor limb was transplanted to the flank of the host when both were at the stage of tail-bud embryos, and the skin graft was later carried out between the supernumerary limb and one of the host limbs. This technique was used to show that immunological rejection does not affect the formation of duplicates from the limbs with double posterior skin, and to facilitate the studies of the cellular provenance of the regenerate. The cellular composition of duplicate regenerates was studied by using both triploid donors and triploid hosts. It was shown that the posterior side of the duplications consisted wholly of host tissue and the anterior side consisted of mixed donor and host tissue. Formation of the duplicated regenerate therefore seems to involve positional reprogramming of both donor and host tissues together with metaplasia of the donor tissue. It was not possible to inhibit the duplication-inducing property of posterior skin by treatment with a variety of enzymes. A model based on the serial threshold theory of regeneration is advanced to explain the results. This model successfully accounts for the observed non-equivalence of anterior and posterior skin, and also explains the different regeneration behaviour of anterior and posterior half limbs, the limited regeneration of double anterior limbs, and the pattern expansion and contraction shown by regenerates from double posterior limbs.

Ambystoma↗
PubMed1982

Morphogenesis of regenerating fragments of Dugesia schubarti (Turbellaria tricladia).

An extensive study of regeneration processes from the point of view of the axial gradient theory and its corollary, the possibility of forming two heads from one fragment (the Janus head problem) was undertaken on the South American species Dugesia schubarti. Altogether 330 specimens were used, cut into 2,640 pieces and the regeneration of each of them was followed to the end result. Concerning the role of an axial gradient in the regeneration processes the results were not supportive. Anterior fragments often regenerated less completely (eyes and auricles without complete heads) than more posterior ones, although the differences were not sharp, due to individual variations of physiological nature. The Janus head regeneration, one of the postulates of the axial gradient theory, was analyzed both on preauricular (parts A) and postauricular fragments (part B). The regeneration of parts A was less perfect than that of parts B. ALthough a considerable number of the part A fragments regenerated normally, the majority of the cases remained incomplete for a long time and eventually disintegrated without completing the regeneration process. The only irregularity parts B proceeded more evenly and the death rate was also much lower. The only irregularity observed was a great number of cyclopic regenerates, i.e. heads with one single eye in the midline. Some of these cyclopic heads remained permanently in this condition but most of them later separated in two eyes but with a pigment between them, and in others the cyclopic eye separated in two normal eyes at the end of the regeneration. The Janus head phenomenon was never observed.

Animals↗
PubMed1995

Caudal fin regeneration in wild type and long-fin mutant zebrafish is affected by retinoic acid.

Zebrafish (Danio rerio) represents an ideal experimental model to tackle fundamental issues concerned with organogenesis during development and regeneration of complex body structures. We discuss here the development of the skeleton in zebrafish caudal fins, their regenerative ability in wild type and long-fin mutant adult fish, and how retinoic acid (RA), which induces duplications along the proximodistal axis in regenerating limbs, affects regeneration of the caudal fin. The dorsal and ventral lobes of zebrafish caudal fins are apparently symmetrical along the dorsoventral axis, but all of the skeletal elements and most of the soft tissues of both lobes originate from the ventral part of the embryo, as demonstrated by whole-mount staining of developing fish. Analysis of caudal fin regenerates in wild type adults does not reveal any difference in the regenerative ability of the two lobes, and in the length of the regenerate in comparison with the amputated part. In contrast, in the long-fin mutant the regenerated caudal fin is always somehow defective in that the original asymmetry in the length of the two lobes observed in this mutant is not reproduced in the regenerate. Furthermore, in the majority of the batches studied the regenerate is much smaller in size than the amputated part. This suggests that this mutant may be valuable to further our understanding of the mechanisms underlying growth control and patterning during regeneration. Finally, we show that the regenerating caudal fin is sensitive to RA-treatment, and clear teratogenic effects on the dorso-ventral axis are observed under many of the experimental conditions investigated both in wild type and long-fin mutants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Visual pigment assignments in regenerated retina.

Retinas of adult teleost fish can regenerate after injury. Two important issues regarding this phenomenon are the assembly of the regenerated retina and the neuronal images of the visual scene that the regenerated retina produces. Here we report experiments in which the visual pigment content of photoreceptors derived from native and regenerated sunfish retinas was determined by microspectrophotometry. In native retina, there is an apparently perfect correspondence between cone morphology and visual pigment content; all rods contain a middle-wavelength pigment, all single cones contain a different middle-wavelength pigment, and all double cone members contain a long-wavelength pigment. The visual pigments in regenerated rods and double cones were the same as in native retina; however, triple cones, a morphology never observed in native retina, contained the long-wavelength pigment. Moreover, although approximately 60% of regenerated single cones contained the expected middle-wavelength pigment, all other single cones contained the long-wavelength pigment. This mismatch between morphology of regenerated single cones and their visual pigment assignment indicated the following: (1) There is a degree of independence between the mechanisms that establish cone morphology and pigment content during regeneration, which suggests that cone photoreceptor regeneration is not a straightforward recapitulation of the normal cone photoreceptor developmental plan. (2) Although anomalous, the long-wavelength single cones may enable regenerated retina to restore the native spectral sampling of the visual scene.

Animals↗
PubMed1996

[Optic nerve regeneration by nerve transplantation].

The optic nerve fibers of adult mammals, once injured, can not regenerate spontaneously. However, from recent studies it has become clear that when their extracellular environment is replaced with that of the peripheral nervous system, namely surrounded with Schwann cells, they can regenerate their axons through the grafted nerve. Previous studies on the optic nerve regeneration by peripheral nerve transplantation have been done mostly in rats or hamsters. With an expectation of clinical application in future, we studied the optic nerve regeneration of adult cats because a great deal of knowledge on the optic nerve fibers and retinal ganglion cells had been accumulated. From recent series of studies we have obtained following results. 1. Retinal ganglion cells that regenerated axons constitute 2--4% of the total population, and among several types of ganglion cells, alpha cells have the greatest capacity for axonal regeneration. The ability of alpha cells for axonal regeneration is related to their relative resistance to axotomy. 2. Retinal ganglion cells with regenerated axons preserve their original dendritic fields, but their axons are thinner than normal, and mostly unmyelinated. 3. Single unit activities recorded from teased fibers of regenerated axons revealed that the units have mostly normal receptive field properties, enabling us to classify them into Y, X or W cells. 4. Amplitude reduction of pattern reversed electroretinogram (ERG) after the optic nerve section was slowed, to some extent, by the peripheral nerve transplantation. How we can reconnect these regenerated optic nerve fibers to the target neurons in the central visual system is a matter for future study.

Animals↗
PubMedDate not supplied

[Organ and tissue regeneration in lower vertebrate animals during space flight and after its completion].

The most important data obtained in studies of the influence of space flight factors on the limb and lens regeneration in the newt Pleurodeles waltlii have been summarized. Regeneration of these organs under the conditions of space flight and after its termination proceeded just as on the ground. However after the 7th, 13th and 16th days of space flight, a trend was shown toward acceleration of the limb and lens regenerates development according to the regeneration stages and synchronization of the achieved stages, which was accompanied in some cases by an increased proliferative activity of the regenerate cells. It was shown that in two groups of animals operated before the 16-day space flight (I) and just after its termination (II) accelerated development of the limb and lens regenerates was observed. In group II, at the large bud stage, the index of 3H-thymidine labeled blastema cells was more than twice that in the control. The size of regenerates in groups I and II exceeded reliably those in the control. These results suggest a prolonged effect of space flight factors on the limb and lens regeneration. It was also shown that the capacity of the muscle minced 14 days before the flight for regeneration was not suppressed, although somewhat decreased. An electron microscopic study showed degenerative-atrophic changes in the intact hind limb muscle after the 16-day space flight. We believe that the phenomenon of synchronization and accelerated regeneration of the limb and lens observed in the most experiments are due to the effect of microgravity on the animals.

Animals↗
PubMed1996

Regeneration of cat's optic nerve and its functional recovery.

The optic nerve of adult mammals can regenerate when a permissive environment is provided with a peripheral nerve (PN) graft. Using this method of PN transplantation, we have studied regeneration of the optic nerve in adult cats. Number of retinal ganglion cells (RGCs) which regenerated their axons through the PN graft corresponds to 3-4% of the total RGC population. The RGCs with regenerated axons distributed widely from central to peripheral retinas. Of the known cell types of cat's RGCs, alpha, beta, gamma and other cells, alpha cells revealed the greatest capacity to regenerate their axons. Dendritic field diameters of most RGCs with regenerated axons were preserved. These regenerated axons were, however, mostly unmyelinated when surveyed by electron microscopy at two months after the transplantation surgery. The regenerated axons revealed normal physiological properties in response to visual stimuli and were classifiable into Y, X or W cells. In accordance with morphological data, Y cells (morphological alpha cells) were more frequently sampled than in normal retinas, whereas the occurrences of X cells (morphological beta cells) and other cells were unchanged or decreased. These results suggest that RGCs retain their physiological function during axonal regeneration, and RGCs with large soma and large dendritic field (Y or alpha cells) have the greatest capacity to regenerate their axons.

Animals↗
PubMed2003

Periodontal regeneration with a combination of enamel matrix proteins and autogenous bone grafting.

BACKGROUND: Attempts to stimulate periodontal regeneration in the past have focused on either filling the defect with some type of material or providing a space for host cells to repopulate the site and elicit new tissue. In some cases, these approaches have been combined with the assumption that the filler material will help maintain the space necessary for the host cells to invade the area. Growth stimulating substances such as growth factors and other proteins have also been used to encourage periodontal tissue regeneration and histological evaluation supports the use of these substances. Thus, the role for and the necessity of a certain amount of space maintenance for periodontal regeneration is not exactly understood. In addition, it is not known if there is some critical size required for space maintenance or for exactly how long the space must be maintained in order for the host cells to stimulate new cementum, periodontal ligament, and bone. The goal of this study was to evaluate periodontal regeneration in intrabony defects of various sizes treated with a combination of enamel matrix proteins and autogenous bone graft. METHODS: Periodontal defects ranging in size from 1 to 6 mm were randomized and created bilaterally beside three teeth in the mandibles of baboons. Plaque was allowed to accumulate around wire ligatures placed into the defects. After 2 months, the wire ligatures were removed, the teeth and roots scaled and root planed, and a notch was placed with a chisel at the base of the defect. On one side of the mandible, neutral ethylene diamine tetracetic acid and enamel matrix derivative (EMD) were first used to treat the defect. Autogenous bone taken from the same surgical site was treated with enamel matrix derivative in a dampen dish and then added to the EMD-treated defects. The other side of the mandible served as control with neutral ethylene diamine tetracetic acid and 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: The results revealed new cementum, periodontal ligament with Sharpey's fibers, and new bone tissue similar to native periodontal tissues. Remnants of the autogenous bone chips were still present at this 5-month post-healing period. Thus periodontal regeneration occurred in all sizes of the periodontal defects. In general, EMD plus autogenous graft treatment resulted in greater tissue formation than controls. In fact, in many cases, very dramatic tissue formation occurred far coronal to the base of the defects in the EMD plus autogenous graft-treated lesions. In addition, horizontal bone fill occurred in the defects and was prominent in the 4 or 6 mm wide lesions. When evaluating the combined 1 and 2 mm defects, the height of new cementum with EMD plus graft was 3.88 mm versus 2.03 mm in the controls, a statistically significant (P < 0.005) difference. In the wider (4 and 6 mm) lesions, this difference was not significant and was much less between treated and control lesions with 2.78 and 2.57 mm of new cementum respectively. In the case of new bone height, in the smaller lesions EMD plus graft resulted in 4.00 mm new bone versus 2.22 mm in the controls, again a statistically significant (P < 0.005) difference. In the larger lesions, EMD plus autogenous bone graft had 3.24 mm new bone height compared to 2.71 mm in the controls, a difference that was not statistically significant. Additionally, in the smaller lesions, new cementum width at the level of the notch was twice as great (statistically significant, P < 0.015) in the EMD plus graft sites compared to control. The width of the periodontal ligament at the coronal aspect of the new bone tissue was similar in the smaller lesions between treated and control sites. The results from the wider defects must be interpreted cautiously as the interproximal bone heights were remodeled adjacent to the wider defects and likely limited the potential for regeneration. CONCLUSIONS: The combination of enamel matrix derivative plus autogenous bone graft stimulated statistically significant periodontal regeneration in the more narrow 1 and 2 mm lesions. No statistically significant difference was observed in the wider 4 and 6 mm lesions. In many cases, dramatic amounts of new cementum, Sharpey's fibers, periodontal ligament, and bone tissue were formed far above the notch placed at the base of the contaminated defects. This was especially significant considering the width of some of the defects and the fact that no oral hygiene was performed over the 5-month healing period. This periodontal regeneration occurred in the absence of exogenous growth factors or barrier membranes. In summary, the combination of enamel matrix derivative and autogenous bone represents a therapeutic combination that can be highly effective in stimulating significant amounts of periodontal regeneration.

Alveolar Bone Loss↗
PubMed1992

Extracellular glucose dependence of rhodopsin regeneration in the excised mouse eye.

To study the process of rhodopsin regeneration a superfused excised whole eye preparation of the albino mouse was developed. With this preparation, complete regeneration could be observed after each of the first two illuminations (bleaching 15-20%), and incomplete regeneration after a third illumination. Regeneration was minimal at extracellular glucose concentrations of 0 or 1 mM with improved regenerations at higher concentrations. Maximum regenerations were observed at glucose concentrations of 4-10 mM. First-bleach regenerations were as follows: 0 mM glucose, 20%; 1 mM, 8%; 2 mM, 45%; 3 mM, 82%; 4 mM, 115%; 5.1 mM, 121%; 7 mM, 120%; and 10 mM, 126%. The effects of reduced glucose were reversible. After an initial bleach with 0 or 1 mM extracellular glucose that exhibited minimal regeneration, the re-addition of glucose (5.1 mM) restored the ability of the eye to regenerate rhodopsin following a second bleach, but only to the level prior to that bleach. Mitochondrial substrates fumarate (10 mM) or pyruvate (10 mM) partly substituted for glucose, exhibiting first-bleach regenerations of 56 and 85%, respectively.

Animals↗
PubMed2007

Regeneration of granular activated carbon with adsorbed trichloroethylene using wet peroxide oxidation.

The objective of this study is to clarify the regeneration of granular activated carbon (GAC) adsorbed trichloroethylene (TCE) using wet peroxide oxidation (WPO). TCE and TOC concentrations decreased during WPO, whereas Cl(-) accumulated in water indicating that TCE was not only decomposed but was also mineralized to Cl(-) and CO(2) using WPO. Regeneration efficiencies (q/q(0)) of GAC regenerated at 150, 165 and 180 degrees C (initial pH 4) were 0.36, 0.45, 0.48, respectively. In addition, regeneration efficiencies of GAC regenerated in the solution of various initial pH (2.5, 3.0, 4.0) at 180 degrees C were 0.71, 0.60, 0.48, respectively. These results suggest that regeneration of GAC is more effective at higher reaction temperature and lower initial pH of the solution. In the repeated regeneration of GAC, the adsorption capacity of GAC for TCE gradually decreased and regeneration efficiency of the regenerated GAC at sixth step was 0.40. The adsorption capacity loss of regenerated GAC is probably due to oxidation of GAC during WPO.

Adsorption↗