[Effect of antiserum to regenerating bone tissue on the mineral and protein metabolism of this tissue in the process of post-traumatic regeneration].
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Animals↗
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[Relation of degree of regeneration to wound site in skin regeneration in rats].
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Animals↗
[A dialysis system with regeneration and recirculation of the dialyzing fluid. In vitro tests of the regeneration of the dialyzing fluid of the artificial kidney and the peritoneal dialysis].
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Carbon↗
Regenerative capacities of normal and cirrhotic livers following 70% hepatectomy in rats and the effect of alpha-tocopherol on cirrhotic regeneration.
BACKGROUND: The regeneration of normal and cirrhotic liver has been very well demonstrated after partial hepatectomy; although the tissue regenerated by cirrhotic liver is also cirrhotic. The structural differences of the regenerated tissues between normal and cirrhotic livers may also indicate different regeneration capacities. The objective of this study was to compare the regeneration capacities of normal and cirrhotic livers by bromodeoxyuridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) labeling indices in replicating nuclei and mitotic figures in cells in partially hepatectomized normal and cirrhotic rats and to study the effect of alpha-tocopherol on cirrhotic liver regeneration. METHODS: Five groups of adult Wistar rats comprised normal livers, cirrhotic livers, regenerated normal livers, regenerated cirrhotic livers, and alpha-tocopherol-treated regenerated cirrhotic livers. Cirrhosis was induced by intragastric administration of carbon tetrachloride and phenobarbital in the drinking water of the rats. Liver regeneration capacities in normal and cirrhotic rats and following partial hepatectomy in normal and cirrhotic rats and cirrhotic rats that were administered alpha-tocopherol were evaluated through BrdU incorporation, PCNA labeling, and mitotic indices. RESULTS: BrdU and PCNA labeling and mitotic indices were zero for normal rats and 4.3 +/- 3.5, 6.5 +/- 5, and 2.5 +/- 1.5 for cirrhotic rats, respectively. The values after partial hepatectomy in normal and cirrhotic rats were 46.2 +/- 8.7 and 27.8 +/- 7.5 for BrdU labeling, 83.7 +/- 6.5 and 51.3 +/- 6.8 for PCNA labeling, and 31.8 +/- 4.2 and 18.6 +/- 3.4 for mitotic index, respectively. For the fifth group comprising cirrhotic rats that were administered alpha-tocopherol and had undergone partial hepatectomy, BrdU incorporation, PCNA labeling, and mitotic indices were 37.5 +/- 6.3, 76.5 +/- 6.2, and 27.2 +/- 4.2, respectively. When the cirrhotic liver regeneration group was compared with the normal liver regeneration group, rates of liver regeneration in the cirrhotic group were significantly depressed (P < 0.01). Although the BrdU incorporation and PCNA labeling indices of the alpha-tocopherol-administered cirrhotic liver regeneration group indicated significantly lower rates of liver regeneration when compared with the normal liver regeneration group (P < 0.05), the liver regeneration rates of the alpha-tocopherol-administered cirrhotic group were also significantly higher than those of the cirrhotic liver regeneration group that was not administered alpha-tocopherol (P < 0.01). CONCLUSIONS: Cirrhotic livers revealed a significantly depressed capacity for regeneration following partial hepatectomy. alpha-Tocopherol administration seemed to improve the rates of regeneration in cirrhotic rats with respect to the BrdU incorporation, PCNA labeling, and mitotic indices.
Animals↗
Regeneration of spinal neurons in inframammalian vertebrates: morphological and developmental aspects.
This review discusses regeneration of spinal neurons in inframammalian vertebrates. In contrast to the limited regeneration of nerve fibers in mammalian spinal cord, relatively complete regeneration of spinal cord, including the formation of new neurons, occurs in cyclostomes, selachians, teleosts, and urodele amphibians. The various experimental techniques which have been used to accelerate or enhance regeneration of spinal cord, such as implantation of peripheral nerve bridges, application of growth factors or chemical agents, and the application of exogenous electrical fields, are discussed. Processes involved in regeneration of other systems, e.g., the trophic effect of nerve fibers, the effect of certain hormones, and the effects of the blastema, are discussed as they may relate to regeneration in the spinal cord. Recent work on the factors which influence nerve outgrowth is discussed. Factors such as diffusible chemical gradients, contact with other cells, pre-formed channels for nerve growth, and differences in adhesivity of neurites for the substratum may act to control the direction of axon outgrowth in regeneration as well as normal embryonic development. This article next reviews work from our laboratory on regeneration of spinal neurons in the teleost, Sternarchus albifrons. We have used Sternarchus as a model system for the study of regeneration and remyelination since: 1. spinal cord readily regenerates after amputation of the tail, 2. new nerve cell bodies are formed during this regeneration, and 3. Sternarchus contains large neurogenic electric organs which also regenerate after tail amputation. The axons of the electric organ arise from spinal neurons and have a highly specific and complex morphology which is recapitulated after regeneration. Studies on Sternarchus indicate that new nerve cell bodies are produced during regeneration from the enlarged ependymal cells. Initially, many more of the electromotor neurons are produced in regenerated spinal cord than are present normally. Cell death subsequently occurs in some of these asynaptic cells, reducing the number of electrocytes in older regenerated cord to a more normal condition. The spinal electromotor neurons in Sternarchus have also been used to demonstrate that section of the axon in an asynaptic neuron will produce a typical "axon reaction" in the cell body. It is interesting that cell death during regeneration and the retrograde axon reaction both appear to occur without loss of synaptic elements in these normally asynaptic cells. Neurites grow through regenerating Sternarchus spinal cord in small bundles, in close contact with adjacent ependymal cell processes. Longitudinal channels, filled with neurites, are seen extending through many stages of regenerating Sternarchus cord, usually near the periphery of the cord. There are numerous invaginations of the peripheral edge of regenerating cord and its associated external lamina. These infoldings may be involved in the generation of the neurite filled channels.(ABSTRACT TRUNCATED AT 400 WORDS)
Aging↗
Ethylene influences green plant regeneration from barley callus.
The plant hormone ethylene is involved in numerous plant processes including in vitro growth and regeneration. Manipulating ethylene in vitro may be useful for increasing plant regeneration from cultured cells. As part of ongoing efforts to improve plant regeneration from barley (Hordeum vulgare L.), we investigated ethylene emanation using our improved system and investigated methods of manipulating ethylene to increase regeneration. In vitro assays of regeneration from six cultivars, involving 10 weeks of callus initiation and proliferation followed by 8 weeks of plant regeneration, showed a correlation between regeneration and ethylene production: ethylene production was highest from 'Golden Promise', the best regenerator, and lowest from 'Morex' and 'DH-20', the poorest regenerators. Increasing ethylene production by addition of 1-aminocyclopropane 1-carboxylic acid (ACC) during weeks 8-10 increased regeneration from Morex. In contrast, adding ACC to Golden Promise cultures during any of the tissue culture steps reduced regeneration, suggesting that Golden Promise may produce more ethylene than needed for maximum regeneration rates. Blocking ethylene action with silver nitrate during weeks 5-10 almost doubled the regeneration from Morex and increased the Golden Promise regeneration 1.5-fold. Silver nitrate treatment of Golden Promise cultures during weeks 8-14 more than doubled the green plant regeneration. These results indicate that differential ethylene production is related to regeneration in the improved barley tissue culture system. Specific manipulations of ethylene were identified that can be used to increase the green plant regeneration from barley cultivars. The timing of ethylene action appears to be critical for maximum regeneration.
2,4-Dichlorophenoxyacetic Acid↗
Axonal sprouting and frank regeneration in the lizard tail spinal cord: correlation between changes in synaptic circuitry and axonal growth.
In our previous studies, we found that the number of supraspinal neurons projecting to the level of tail spinal cord increases by 74% during tail regeneration and that the number of local spinal neurons with descending projections increases 233%. However, only a small fraction of the supraspinal axons (less than 4%) and half of the local spinal axons actually enter the regenerated spinal cord. We suggested that this may be the result of "synaptic capture" in which regrowing axons make synapses on denervated targets rostral to the transection, aborting further regeneration. To examine this hypothesis, morphometric analysis of electron microscope (EM) photomontages was used to test for changes in synaptic distribution on ventral horn neurons rostral to regenerating tail spinal cord. In addition, 3H-thymidine and retrograde markers were used to determine whether the regenerate axons arose from cut axons, neurogenesis, or sprouting from uninjured neurons. 3H-thymidine injections during regeneration, combined with retrograde HRP pathway tracing, did not reveal the production of new neurons in the tail spinal cord. To test whether cut axons regenerate, fluorescein isothiocyanate conjugated latex beads were applied to the exposed end of the tail spinal cord. After tail regeneration, HRP was applied to the new spinal cord in the regenerated tail. Examination of local spinal neurons (the primary source of axons that enter the regenerated tail spinal cord) revealed that 28% of the neurons contained both labels. This indicated that cut axons successfully regrew into the new tail spinal cord. The regenerated axons that fail to enter the new tail spinal cord can be found in the normal spinal cord immediately rostral to the regenerated tail. To determine whether these axons were making synaptic contacts, lamina IX ventral horn neurons were examined. EM photomontages of the spinal cord rostral to the regenerate tail revealed the following properties: (1) neurons rostral to regenerated tails are larger in area compare to non-regenerates (mean increase = 112%); (2) axosomatic contacts cover a greater percentage of the neuronal soma following regeneration compared to normal (mean increase = 23%); and (3) this increased innervation is the result of an increase in the number of synaptic boutons rather than larger boutons. The number of synaptic contacts in regenerated lizards returned to normal following lumbar transection, indicating that supraspinal and/or long descending propriospinal afferents were the major source of the increased synaptic contacts.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Heat shock protein 40 enhances axon regeneration in a mouse model of traumatic optic neuropathy.
Retinal ganglion cell death occurs following injury to the optic nerve either by trauma or in disease such as glaucoma, leading to severe vision loss. Recent innovations have demonstrated that optic nerve regeneration is feasible; however, the regeneration is limited. The aim of the present study is to identify genomic elements enhancing axon regeneration. We have taken a forward genetics approach using the BXD recombinant mouse strains to identify a gene that increases the extent of optic nerve regeneration. Axon regeneration was induced by knocking down Pten in retinal ganglion cells using adeno-associated virus to deliver an shRNA followed by an intravitreal injection of Zymosan with CPT-cAMP that produced a mild inflammatory response. Retinal ganglion cell axons were damaged by optic nerve crush. Following a 12-day survival period, regenerating axons were labeled by intravitreal injection of Cholera Toxin B conjugated with Alexa Fluor 647. Two days later, labeled axons within the optic nerve were examined to determine the number of regenerating axons and the distance they traveled down the optic nerve. The analysis revealed a surprising difference in the amount of axonal regeneration across all 33 BXD strains. There was a 7.5-fold difference in the number of regenerating axons and a 4-fold difference in the distance traveled by regenerating axons. These data were used to generate an interval map defining genomic loci that modulate enhanced axonal regeneration. A quantitative trait locus modulating axon regeneration was identified on Chromosome 14 (115 to 119 Mb). Within this locus were 16 annotated genes. Subsequent testing revealed that one candidate gene, Dnajc3, modulated axonal regeneration. Dnajc3 encodes heat shock protein 40 (HSP40), a molecular chaperone. Knocking down Dnajc3 in the high regenerative strain (BXD90) led to a decreased regeneration response, whereas, overexpression of Dnajc3 in a low regenerative strain (BXD34) resulted in an increased regeneration response. These findings reveal that Dnajc3 not only increases the number of regenerating axons, but also increases the distance that axons travel. The enhanced regeneration will prove to be critical for functional recovery in humans, where the distance axons travel to their targets is considerably longer than that of mice.
axon regeneration↗
Effects of oxidized regenerated cellulose on the expression of extracellular matrix and transforming growth factor-beta1 in human peritoneal fibroblasts and mesothelial cells.
OBJECTIVE: The purpose of this study was to evaluate the potential biologic effects of oxidized regenerated cellulose, which has been shown in multiple human in vivo studies to reduce postoperative adhesion development, on the messenger RNA levels of transforming growth factor-beta1, type I collagen, type III collagen, and fibronectin. STUDY DESIGN: The oxidized regenerated cellulose was dissolved in saline solution and added to confluent, monolayer cultures of human normal fibroblasts and mesothelial cells. Control cells were maintained in media alone at the same pH. After 24 hours of treatment, total RNA was extracted from all cells. Real-time reverse transcription-polymerase chain reaction was performed to determine the relative change in messenger RNA levels of type I, type HI collagen, fibronectin, transforming growth factor-beta1, and beta-actin (housekeeping gene) in response to the oxidized regenerated cellulose treatment (n=4 cultures). Student t tests were performed for each cell type, which compared oxidized regenerated cellulose-treated cells to control cells. Calculated power for the statistically significant findings ranged from 65% to 100%. RESULTS: Transforming growth factor-beta1 messenger RNA was elevated by the oxidized regenerated cellulose treatment in the mesothelial cells by 13% (control cells, 0.562+/-0.022; oxidized regenerated cellulose-treated cells, 0.636+/-0.014; P=.03). In normal fibroblasts, transforming growth factor-beta1 messenger RNA was slightly, but not significantly, decreased in oxidized regenerated cellulose-exposed normal fibroblasts compared with controls (control cells, 0.622+/-0.062; oxidized regenerated cellulose-treated cells, 0.609+/-0.006; P=.85). Type I collagen was found to be increased by exposure to oxidized regenerated cellulose in both mesothelial cells and normal peritoneal fibroblasts. Type I collagen was increased by 23% in mesothelial cells (control cells [0.587+/-0.018] vs oxidized regenerated cellulose-treated cells [0.722+/-0.010], P=.002), and 27% in normal fibroblasts (control cells, 0.522+/-0.018, oxidized regenerated cellulose-treated cells, 0.665+/-0.009; P=.001). However, messenger RNA levels of type III collagen and fibronectin (other representative molecules of the extracellular matrix) were not altered significantly by oxidized regenerated cellulose application in vitro. CONCLUSION: Oxidized regenerated cellulose influences the expression of factors that are accepted commonly to be associated with adhesiogenesis. Oxidized regenerated cellulose increased the expression of transforming growth factor-beta1 in mesothelial cells and type I collagen in mesothelial cells and normal peritoneal fibroblasts. Minimization of these oxidized regenerated cellulose-induced molecular changes, if they occur in vivo, may improve the ability of oxidized regenerated cellulose to reduce postoperative adhesion development.
Cells, Cultured↗
Abnormal limb regeneration in the short-toes mutant of the axolotl, Ambystoma mexicanum: studies of age, level of amputation, and extracellular matrix.
Limb regeneration in the short-toes axolotl is impaired. Our goal was to characterize the regeneration process in this mutant by histological and immunocytochemical methods. Previous research indicates that age and a defective basement membrane may be instrumental factors in short-toes axolotl regeneration (Del Rio-Tsonis et al. [1992] Proc. Natl. Acad. Sci. U.S.A., 89:5502-5506). The present results show that limb regeneration can occur even in older (1-2-year-old) short-toes axolotls. The process was always significantly delayed, but the time required for complete regeneration varied. Even so, the basement membrane of short-toes regenerates showed no differences in thickness or shape compared with wild-type regenerates. Distally amputated short-toes limbs gave rise to more digits in the regenerate, indicating that regeneration may be somewhat dependent on the level of amputation. Since extracellular matrix (ECM) remodeling occurs extensively during regeneration, we compared the ECM of the short-toes and wild-type regenerates using monoclonal antibodies (mAbs) MT2 and ST1 (Tassava et al. [1996] Wound Rep. Reg., 4:75-81). The short-toes regenerates showed decreased reactivity to mAb MT2, which identifies type XII collagen, an ECM protein that is normally unregulated during regeneration, and increased reactivity to mAb ST1, which identifies a limb ECM component that typically undergoes breakdown in the distal stump. Thus, impaired regeneration in the short-toes axolotl is correlated with impaired ECM remodeling in the distal limb stump. This supports the view that ECM remodeling plays an important role in regeneration.
Aging↗
Heavy metals inhibit limb regeneration in horseshoe crab larvae
We studied the effects of heavy metals on the regeneration of walking legs in horseshoe crabs (Limulus polyphemus). The second walking leg was amputated in embryos (stage 20 and 21) and first instar (trilobite) larvae, and the length and morphology of the regenerated appendage was observed after molting to the second instar stage. Regeneration following continuous exposure to TBT (0. 001-100 mg/L), mercury (0.001-100 mg/L), cadmium (0.01-100 mg/L), chromium (0.1-100 mg/L), lead (0.1-100 mg/L), and copper (1-100 mg/L) was measured relative to regeneration in seawater. Although regeneration was incomplete in controls, treatment with heavy metals led to smaller and/or malformed legs. The impacts of heavy metals on survival, molting, and regeneration of horseshoe crab larvae were ranked as follows: organotin > Hg > Cd > Cr > Zn > Pb >== Cu. Cu and Pb did not inhibit regeneration, even at 100 mg/L. TBT, Hg, Cd, Cr, and Zn inhibited the regeneration of appendages, although first instar larvae successfully molted into second instars even after treatment. Regeneration was comparable to seawater controls in less than 2.5 mg/L Zn. In 5.0 and 10.0 mg/L Zn, regeneration was inhibited and the length of regenerated appendages remained shorter in all second instars. Larvae treated with 10 mg/L Zn for 1-week intervals during the molt cycle showed similar patterns of regeneration. The regeneration of claws was not all or none, and formation of the claw was proportional to the length of regenerated appendages. Limb regeneration in horseshoe crab larvae may be a useful model system for the study of pollutant impacts.
Journal Article↗
Nerve growth factor facilitates regeneration across nerve gaps: morphological and behavioral studies in rat sciatic nerve.
The rat sciatic nerve does not possess a high potential for regeneration through silastic tubes when the interstump nerve gap is greater than 10 mm. In this study, the effect of NGF treatment on regeneration of the rat sciatic nerve in 10- and 15-mm silastic chambers was compared. In addition, regeneration in 15-mm silastic chambers was compared to regeneration in 15-mm semipermeable chambers. Sections of tubing were implanted and filled with NGF or a control solution of cytochrome C (Cyt. C). Tube implants were removed at various postoperative times and regeneration was assessed histologically and behaviorally. NGF treatment promoted regeneration success rate. It enhanced the initial outgrowth of nonneuronal cells and neuronal fibers into the chamber producing more cellular, organized regenerates. At 2 weeks, in 10-mm chambers, NGF-treated regenerates had fourfold more unmyelinated fibers than controls. At 3 weeks, NGF-treated regenerates possessed threefold more myelinated fibers than controls. After 4 weeks all regenerates had similar numbers of myelinated nerves at the chamber's midpoint. This initial "head start" was sustained peripherally as indicated by the earlier return of sensory function (response to a noxious temperature stimulus) in NGF-treated animals. Finally, regeneration success rate in 15-mm semipermeable tubes is greater than that in 15-mm silastic chambers (NGF and Cyt. C). However, regenerates in silastic chambers possessed twofold more myelinated fibers than regenerates in semipermeable chambers. The positive effects of NGF on neural regeneration and recovery of sensory function provide support for the potential use of NGF in treating peripheral nerve injuries.
Animals↗
Chronic Schwann cell denervation and the presence of a sensory nerve reduce motor axonal regeneration.
Motor axonal regeneration is compromised by chronic distal nerve stump denervation, induced by delayed repair or prolonged regeneration distance, suggesting that the pathway for regeneration is progressively impaired with time and/or distance. In the present experiments, we tested the impacts of (i) chronic distal sensory nerve stump denervation on axonal regeneration and (ii) sensory or motor innervation of a nerve graft on the ability of motoneurons to regenerate their axons from the opposite end of the graft. Using the motor and sensory branches of rat femoral nerve and application of neuroanatomical tracers, we evaluated the numbers of regenerated femoral motoneurons and nerve fibers when motoneurons regenerated (i) into freshly cut and 2-month chronically denervated distal sensory nerve stump, (ii) alone into a 4-cm-long distally ligated sensory autograft (MGL) and, (iii) concurrently as sensory (MGS) or motor (MGM) nerves regenerated into the same autograft from the opposite end. We found that all (315 +/- 24: mean +/- SE) the femoral motoneurons regenerated into a freshly cut distal sensory nerve stump as compared to 254 +/- 20 after 2 months of chronic denervation. Under the MGL condition, 151 +/- 5 motoneurons regenerated, which was not significantly different from the MGM group (134 +/- 13) but was significantly reduced to 99 +/- 2 in the MGS group (P < 0.05). The number of regenerated nerve fibers was 1522 +/- 81 in the MGL group, 888 +/- 18 in the MGM group, and 516 +/- 44 in the MGS group, although the high number of nerve fibers in the MGL group was due partly to the elaboration of multiple sprouts. Nerve fiber number and myelination were reduced in the MGS group and increased in the MGM group. These results demonstrate that both chronic denervation and the presence of sensory nerve axons reduced desired motor axonal regeneration into sensory pathways. A common mechanism may involve reduced responsiveness of sensory Schwann cells within the nerve graft or chronically denervated distal nerve stump to regenerating motor axons. The findings confirm that motor regeneration is optimized by avoiding even short-term denervation. They also imply that repairing pure motor nerves (without their cutaneous sensory components) to distal nerve stumps should be considered clinically when motor recovery is the main desired outcome.
Animals↗
Sciatic nerve regeneration after autologous sural nerve transplantation in the rat.
The present study is concerned with the question as to whether the size of a nerve used as a transplant to bridge a gap between the stumps of transected nerves has a bearing on the number of axons and the cytological structure of the regenerate. The paradigm is rat sciatic nerve transection with 8 mm of nerve removed with the stumps placed in a silicone tube and two strands of the smaller sural nerve used as bridging transplants. The comparisons are with previously published results where the transplant, which is the removed piece of sciatic nerve, is exactly matched in size and with no transplant in the same regeneration paradigm. One surprising finding is that the size of the transplant does not seem to determine the size of the regenerated nerve. The cytological structure of the regenerated nerve is related to the size of the transplant, however, in that the proportion of axons that regenerate inside and outside the transplanted perineurial tubes differs in relation to the size of the transplant. In addition, although there is an increase in the number of blood vessels in all of these paradigms, the greatest increase is with the sural nerve transplants. The key finding in the study, however, is the similarity in numbers of regenerated axons in the gap, distal stump and tributary nerves when regeneration after sciatic nerve transplantation is compared with regeneration after sural nerve transplantation. Thus, notwithstanding the cytologic differences of the two types of regenerate, regenerated axon numbers are approximately the same. The conclusion is that the size of the transplant determines neither the size of the regenerate nor the numbers of regenerated axons in this paradigm. On the assumption that regeneration is better when axonal numbers are closer to normal, the non-matched sural nerve transplant is approximately equal to the matched sciatic nerve transplant and both are superior to the regeneration that takes place in the absence of a transplant in this paradigm.
Animals↗
The effect of retinoic acid on positional memory in the dorsoventral axis of regenerating axolotl limbs.
We investigated the effect of retinoic acid (RA) on pattern regulation in the dorsoventral (DV) axis of regenerating axolotl limbs. Half and double half dorsal and ventral zeugopodia (lower arms or legs) were amputated through their distal ends, and 4 days later the animals were injected intraperitoneally with 50 (large animals) or 100 (small animals) micrograms RA/g body wt. Half and double half dorsal and ventral zeugopodia of uninjected axolotls, and sham-operated zeugopodia of untreated and RA-treated limbs served as controls. Skeletal patterns and the DV muscle patterns of control and experimental regenerates were then analyzed. Sham-operated zeugopodia of uninjected animals regenerated normally. Sham-operated, RA-treated zeugopodia regenerated normally with proximodistal duplications. Sixty percent of uninjected control dorsal half zeugopodia, 80% of control ventral half zeugopodia, and 100% of control double dorsal and double ventral zeugopodia regenerated distally, but the regenerates did not reconstitute the muscle pattern of the missing half. Thirty-eight percent of RA-treated ventral half zeugopodia and 78% of RA-treated double ventral zeugopodia failed to regenerate distally. Of those cases that did regenerate distally, none regenerated the muscle pattern of the missing half. By contrast, 100% of RA-treated dorsal half zeugopodia regenerated distally and all completed the normal DV muscle pattern. Forty-one percent of RA-treated double dorsal zeugopodia failed to regenerate, but of the remainder that did regenerate, 50% completed the normal DV muscle pattern. These represented eight cases, six of which regenerated single limbs, and two of which regenerated twin limbs, each with a normal DV muscle pattern. We interpret these data to mean that RA ventralizes the positional memory of blastema cells in the DV axis.
Ambystoma↗
Tracer coupling among regenerated amacrine cells in the retina of the goldfish.
This study sought to characterize the tracer coupling of regenerated amacrine cells in the retina of the goldfish and assess the integration of regenerated neurons into existing retinal circuits. Regeneration of new neurons from injury-induced progenitors was stimulated by surgically excising a small rectangular piece of retina. Several months after regeneration was complete, intracellular injections of Neurobiotin, a gap junction-permeant tracer, were made into single regenerated amacrine cells or nonregenerated (extant) amacrine cells lying outside the regenerated patch. Two groups of amacrine cells were injected: those that in normal retina are tracer coupled and a single type (the radiate amacrine cell) that is not. The data show that regenerated amacrine cells are tracer coupled to each other and to their homologous counterparts outside the patch of regenerated retina. Regenerated radiate cells possess morphologically abnormal dendrites, but these processes can extend out of regenerated retina into surrounding normal retina. Similarly, the dendrites of extant radiate cells, severed by the original lesion, can regenerate into the patch of regenerated retina. These results indicate that in the goldfish retina the cell-specific junctional circuitry present in normal retina is re-created in the regenerated retina, and suggest that regenerated neurons are functionally integrated into the existing retina.
Animals↗
Efficient regeneration of fertile barley plants from callus cultures of several Nordic cultivars.
The regeneration potential of three major Estonian barley cultivars was tested and compared to that of the Finnish cultivar Kymppi. Two different regeneration systems were used. The first was characterized by the high maltose concentration (60 g l(-1)) and by the use of 2,4D together with two different combinations of amino acids in the callus induction medium followed by the regeneration medium containing BAP (2 mg l(-1)) and 2,4D (0.2 mg l(-1)). The second exploited callus induction medium that contained Dicamba, lower concentrations of maltose (30 g l(-1)) and higher concentrations of myo-inositol and thiamine and different set of amino acids and regeneration medium that contained higher concentrations of Cu2+ and inorganic nitrogen accompanied by lower concentrations of NH4+ and BAP, when compared to the first regeneration system. The second regeneration system used produced significantly higher rates of callus induction, callus growth and regeneration of plantlets. However, it yielded also many albino plants (up to 51%), whereas the first regeneration system used did not produce practically any albino plants. No major genotype-dependent differences were observed in comparison between two regeneration systems - in both systems higher regeneration potential of Anni, Elo and Kymppi contradicted to the low regeneration potential of Teele. It is concluded that the continuous somatic embryogenesis on the regeneration medium allows the regeneration of many plants from the same callus over long periods of time and makes available highly efficient regeneration protocols for Estonian and Finnish barley cultivars.
2,4-Dichlorophenoxyacetic Acid↗
Hedgehog signaling controls dorsoventral patterning, blastema cell proliferation and cartilage induction during axolotl tail regeneration.
Tail regeneration in urodeles requires the coordinated growth and patterning of the regenerating tissues types, including the spinal cord, cartilage and muscle. The dorsoventral (DV) orientation of the spinal cord at the amputation plane determines the DV patterning of the regenerating spinal cord as well as the patterning of surrounding tissues such as cartilage. We investigated this phenomenon on a molecular level. Both the mature and regenerating axolotl spinal cord express molecular markers of DV progenitor cell domains found during embryonic neural tube development, including Pax6, Pax7 and Msx1. Furthermore, the expression of Sonic hedgehog (Shh) is localized to the ventral floor plate domain in both mature and regenerating spinal cord. Patched1 receptor expression indicated that hedgehog signaling occurs not only within the spinal cord but is also transmitted to the surrounding blastema. Cyclopamine treatment revealed that hedgehog signaling is not only required for DV patterning of the regenerating spinal cord but also had profound effects on the regeneration of surrounding, mesodermal tissues. Proliferation of tail blastema cells was severely impaired, resulting in an overall cessation of tail regeneration, and blastema cells no longer expressed the early cartilage marker Sox9. Spinal cord removal experiments revealed that hedgehog signaling, while required for blastema growth is not sufficient for tail regeneration in the absence of the spinal cord. By contrast to the cyclopamine effect on tail regeneration, cyclopamine-treated regenerating limbs achieve a normal length and contain cartilage. This study represents the first molecular localization of DV patterning information in mature tissue that controls regeneration. Interestingly, although tail regeneration does not occur through the formation of somites, the Shh-dependent pathways that control embryonic somite patterning and proliferation may be utilized within the blastema, albeit with a different topography to mediate growth and patterning of tail tissues during regeneration.
Ambystoma↗