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PubMedDate not supplied

The effects of dopamine synthesis inhibitors and dopamine antagonists on regeneration in the hydra Hydra attenuata.

The effects of catecholamine synthesis inhibitors (alpha-methyltyrosine, 3-iodotyrosine, and alpha-methyl-DOPA) and dopamine receptor blockers (haloperidol and spiperone) on the regeneration of apical, gastral, and basal fragments of the hydra Hydra attenuata were studied. These experiments showed that alpha-methyltyrosine and 3-iodotyrosine significantly inhibited regeneration but did not produce morphological anomalies. Alpha-Methyl-DOPA produce less inhibition of regeneration, but induced ectopic tentacles and outgrowths in gastral regenerates. Haloperidol and spiperone had no significant effect on the rate of regeneration but induced significant numbers of morphogenetic anomalies in gastral regenerates. Apical and basal regenerates, which retained their natural organizers (the head and base respectively) never yielded morphogenetic anomalies in the presence of either dopamine receptor blockers or dopamine synthesis inhibitors. The possible role of neurotransmitters. particularly dopamine, in morphogenesis in hydras is discussed.

Animals↗
PubMed2003

Transplantation of olfactory ensheathing cells fails to promote significant axonal regeneration from dorsal roots into the rat cervical cord.

The olfactory ensheathing cell (OEC) is a class of glial cell that has been reported to support regeneration in the central nervous system after various types of lesions, including rhizotomy of spinal dorsal roots at thoracic, lumbar and sacral levels. We have therefore carried out a detailed anatomical analysis to assess the efficacy of dorsal horn OEC transplants at promoting regeneration of primary afferents across the dorsal root entry zone (DREZ) at the cervical level in the adult rat. OECs were cultured from adult rat olfactory bulb and immunopurified (90% purity). Regeneration by large diameter afferents and by both peptidergic and non-peptidergic small diameter afferents was assessed using respectively cholera toxin B (CTB) labelling and immunocytochemistry for calcitonin gene-related peptide (CGRP) and the purinoceptor P2X3. Following an extensive (C3-T3) rhizotomy, CGRP and P2X3 immunoreactive axons regenerated across the rhizotomy site as far as the DREZ but there was no evidence of regeneration across the DREZ, except through sites where the OEC transplant was directly grafted into the DREZ. No evidence of regeneration into the dorsal horn by CTB-labelled axons was obtained. In addition, there was little sign of sprouting by intact axons in the vicinity of OEC transplant sites. In contrast to these results in vivo, cocultures of OECs and adult dorsal root ganglion cells showed that OECs stimulate extensive neurite outgrowth. The failure of the OECs to promote regeneration in vivo following cervical rhizotomy is therefore most likely due to factors in the environment of the graft site and/or the method of transplantation.

Animals↗
PubMed1977

Metabolism of 7,12,-dimethylbenz(a)anthracene by normal and regenerating rat livers.

The in vitro metabolisms of [14C]7,12-dimethylbenz(a)anthracene (DMBA) by post-mitochondrial supernates and microsomes from intact and regenerating rat livers were compared. Both cell fractions from regenerating livers at 48, 72, and 96 h after partial hepatectomy metabolized less [14C]DMBA than similar fractions from intact livers. Prior in vivo treatment with DMBA enhanced metabolism by the cell fractions from both groups, but specific activities of cell fractions from regenerating livers were always about 60% or less of those from intact livers. Thin-layer chromatographic analysis of metabolites formed in incubations using either cell fraction failed to reveal distinct differences between ether-soluble or water-soluble products of similar fractions from intact and regenerating livers. However, highly reproducible differences were found between chromatograms of water-soluble metabolites formed by microsomes and post-mitochondrial supernates in both intact and regenerating livers. Extrapolations from these studies indicate large differences in the metabolic capacity of intact and regenerating livers when expressed on a whole-liver basis, but it is suggested that there may be additional factors contributing to the increased retention of DMBA by regenerating livers.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2006

Mechanisms of Disease: what factors limit the success of peripheral nerve regeneration in humans?

Functional recovery after repair of peripheral nerve injury in humans is often suboptimal. Over the past quarter of a century, there have been significant advances in human nerve repair, but most of the developments have been in the optimization of surgical techniques. Despite extensive research, there are no current therapies directed at the molecular mechanisms of nerve regeneration. Multiple interventions have been shown to improve nerve regeneration in small animal models, but have not yet translated into clinical therapies for human nerve injuries. In many rodent models, regeneration occurs over relatively short distances, so the duration of denervation is short. By contrast, in humans, nerves often have to regrow over long distances, and the distal portion of the nerve progressively loses its ability to support regeneration during this process. This can be largely attributed to atrophy of Schwann cells and loss of a Schwann cell basal lamina tube, which results in an extracellular environment that is inhibitory to nerve regeneration. To develop successful molecular therapies for nerve regeneration, we need to generate animal models that can be used to address the following issues: improving the intrinsic ability of neurons to regenerate to increase the speed of axonal outgrowth; preventing loss of basal lamina and chronic denervation changes in the denervated Schwann cells; and overcoming inhibitory cues in the extracellular matrix.

Animals↗
PubMed2026

Establishment of an in vitro culture and regeneration protocol for the native Chilean grass Polypogon australis Brong.

Polypogon australis Brong. is a native Chilean grass frequently found colonizing metal-rich mine tailings, yet it lacks an established in vitro regeneration system to support controlled physiological and biotechnological studies. Here, we report a reproducible protocol for seed germination, callus induction, and plant regeneration using coleoptile-mesocotyl explants. Surface-sterilized seeds were germinated on Murashige and Skoog (MS) medium supplemented with sucrose, achieving a cumulative germination percentage of 47.67 ± 3.15% after 15 days. The coleoptile-mesocotyl explant proved highly responsive to culture on callus induction medium (CIM) supplemented with dicamba, resulting in a callus induction frequency of 30.55 ± 11.96% after 3-5 weeks. Induced calli were predominantly embryogenic, with embryogenic calli representing 65.42 ± 8.61% of the total callus population. Embryogenic calli regenerated complete plantlets with a regeneration efficiency of 45.0 ± 23.3%. Organogenic structures, including primary shoots and roots, developed directly from embryogenic calli maintained on callus induction medium (CIM) supplemented with dicamba, without transfer to a specialized regeneration medium containing organogenesis-promoting growth regulators. After the initiation of organogenesis, cultures were exposed to a 16 h light/8 h dark photoperiod while remaining on CIM, and regenerated plantlets were subsequently transferred to MS+10 S medium for further growth and elongation. This study establishes the first complete in vitro regeneration system for P. australis, providing a practical framework for future physiological studies, large-scale propagation, genetic transformation, and genome engineering applications in this ecologically relevant native Chilean grass.

Regeneration↗
PubMed1982

Transcriptional control of ribosome production in regenerating rat liver.

Kinetic experiments of labelling in vivo with [14C]orotate of cellular free UMP and/or UTP, nucleolar, nucleoplasmic and cytoplasmic rRNA in normal and 12 h-regenerating rat liver were performed. The specific-radioactivity curves obtained were analysed by computer and the rates of synthesis of precursor rRNA (45S pre-rRNA) and cytoplasmic 28S and 18S rRNA calculated. (a) The rates of synthesis of 45S pre-rRNA in normal and regenerating rat liver are 1400 and 3700 molecules/min per nucleus respectively; (b) the average rates of formation of mature 28S and 18S rRNA are identical with the rates of synthesis of 45S pre-rRNA in both normal and regenerating rat liver. Thus the synthesis of rRNA in 12h-regenerating rat liver is activated 2.7-fold. The analysis of rRNA synthesis in isolated nucleoli also shows a 2.7-fold stimulation of transcription in regenerating liver. It is concluded that all the 45S pre-rRNA molecules synthesized are processed and transferred as 28S and 18S rRNA in the cytoplasm, i.e. degradation (wastage) of newly synthesized ribosomes in the nucleus does not occur in both normal and regenerating rat liver. Thus the enhanced production of ribosomes in regenerating rat liver is regulated only at the transcriptional level.

Animals↗
PubMed1998

Neuro-regeneration: plasticity for repair and adaptation.

Specificity of connectivity is essential to nervous system function. It is determined by intrinsic programmes of gene expression that define neuronal phenotypes, and by activity-dependent mechanisms. Neuro-regeneration in the adult may involve re-activation of growth programmes within the constraints of neuron-type specific phenotypes. Lesion-induced re-induction of an axonal growth mode in adult neurons correlates with a vigorous cell body reaction that can also lead to apoptotic cell death. Directing the cell body reaction towards regeneration is a major goal towards improving regeneration. Extrinsic factors that prevent axonal regeneration in the adult CNS of higher vertebrates include inhibitory components on the surface of oligodendrocytes and CNS myelin, and proteoglycans associated with scar material; grafts of certain glial cells can promote regeneration. Local nerve sprouting and synaptic plasticity can produce dramatic functional adaptation to lesions in the adult and greatly enhance the impact of the partial regeneration of lesioned axons; nerve sprouting is promoted by diffusible and contact-mediated extrinsic mechanisms, and by intrinsic neuronal components. As a result of recent discoveries, significant progress in promoting axonal regeneration and recovery of function in the adult can be anticipated.

Adaptation, Physiological↗
PubMed2001

Liver regeneration after major hepatectomy for biliary cancer.

BACKGROUND: The aim of this study was to evaluate serial changes in liver volume after major hepatectomy for biliary cancer and to elucidate clinical factors influencing liver regeneration. METHODS: Serial changes in liver volume were determined, using computed tomography, in 81 patients with biliary cancer who underwent right hepatic lobectomy or more extensive liver resection with or without portal vein resection and/or pancreatoduodenectomy. Possible factors influencing liver regeneration were evaluated by univariate and multivariate analyses. RESULTS: The remnant mean(s.d.) liver volume was 41(8) per cent straight after hepatectomy. This increased rapidly to 59(9) per cent within 2 weeks, then increased more slowly, finally reaching a plateau at 74(12) per cent about 1 year after hepatectomy. The regeneration rate within the first 2 weeks was 16(8) cm3/day and was not related to the extent of posthepatectomy liver dysfunction. On multivariate analysis, the extent of liver resection (P < 0.001), body surface area (P = 0.02), combined portal vein resection (P = 0.024) and preoperative portal vein embolization (P = 0.047) were significantly associated with the liver regeneration rate within the first 2 weeks. In addition, body surface area (P < 0.001) and liver function expressed as plasma clearance rate of indocyanine green (P = 0.01) were significant determinants of final liver volume 1 year after hepatectomy. CONCLUSION: The liver regenerates rapidly in the first 2 weeks after major hepatectomy for biliary cancer. This early regeneration is influenced by four clinical factors. Thereafter, liver regeneration progresses slowly and stops when the liver is three-quarters of its original volume, approximately 6 months to 1 year after hepatectomy.

Adult↗
PubMed1997

Myosin heavy chain composition of regenerated soleus muscles during hindlimb suspension.

The aim of this study was to determine the MHC profile of regenerated soleus muscles in control (C, n = 8) and hindlimb suspended rats (HS, n = 8). After muscle degeneration was induced by injection of snake venom containing notexin, male rats were either tail suspended for 21 days or submitted to normal weight-bearing activity. Separation and detection of MHCs by sodium dodecyl sulphate-polyarcylamide gel electrophoresis (SDS-PAGE) showed that regenerated soleus muscles from C rats contained only type I and type IIa MHCs. The relative amount of type I MHC was higher in regenerated (93.9 +/- 1.7%) than in untreated muscles (86.5 +/- 2.3%)(P < 0.01). In the HS group, the immunohistochemical analysis showed that the majority of regenerated myofibres reacted positively with the antibody against fast MHCs. SDS-PAGE analysis demonstrated that HS resulted in a shift toward faster MHCs in both intact and regenerated myofibres. Regenerated soleus muscle from HS rats contained approximately 34% type IIa MHC, approximately 37% type IIx/d MHC and approximately 18% type IIb MHC, when type I MHC contributed to only approximately 12% of total myosin. The proportions of fast MHC isoforms in regenerated muscles were higher than those recorded in untreated muscles. Collectively, these results suggest that the shift in the MHC profile associated with hindlimb unweighting in adult undamaged soleus muscles is also related to the heterogeneity of early myoblasts.

Animals↗
PubMed1999

Changes in myosin heavy chain profile of mature regenerated muscle with endurance training in rat.

The objective of the present study was to examine the response of fast-twitch muscle to endurance training long after the muscle had regenerated from toxin injury. Seventeen male Wistar rats were randomly assigned to a sedentary (S, n = 10) or a trained group (T, n = 7). Endurance training by treadmill running (5 days week(-1), 30 m min(-1), 7% grade, 2 h day(-1) for 5 weeks) was initiated 5 weeks after myofibre degeneration was induced in the right extensor digitorum longus muscle (EDL) by two injections of 0.2 mL of the unfractionated venom from Naja nigricollis snake. Gel electrophoresis analyses showed that training alone resulted in a 140% increase in type IIX myosin heavy chain (MHC) (P < 0.01) and a slight decrease in type IIB MHC (-14% P < 0.05). Regeneration alone induced an increase in both type IIA and IIX MHC expression (103%, P < 0.05, and 131%, P < 0.01, respectively), and a concomitant decrease in the percentage of type IIB MHC (P < 0.05). The shift from type IIB toward type IIA MHC composition observed in regenerated muscles of T rats resulted not only from an additive, but from a cumulative effect of training and regeneration. Immunohistochemical analysis of MHC content in individual fibres showed similar changes. These data suggest that the impact of endurance training on fast-type MHCs was more marked in mature regenerated muscles than in regenerating ones, and provide evidence of the heightened plasticity of fully regenerated muscles to repeated exercise.

Animals↗
PubMed1999

Effects of anabolic/androgenic steroids on regenerating skeletal muscles in the rat.

We have examined the effect of male sexual hormones on the regeneration of skeletal muscles. Degeneration/regeneration of the left soleus and extensor digitorum longus muscles (EDL) of Wistar male rats was induced by an injection of snake venom (2 microg, Notechis scutatus scutatus). During the muscle regeneration (25 days), rats were treated with either oil (CON), nandrolone (NAN), NAN combined with exercise (NAN + EXE) or were castrated (CAS). Muscle growth and myosin heavy chain (MyHC) isoform content of regenerating muscles were studied. Castration altered the concentrations of MyHC in venom-treated EDL (P < 0.01) and soleus (P < 0.05). NAN increased the mass (P < 0.01) of regenerating soleus and decreased the relative amount of fast MyHC protein (% of total, P < 0.05). The effect of NAN + EXE on the fast MyHC proteins of venom-treated soleus was opposite (P < 0.05). NAN and NAN + EXE were without effect on the regenerating EDL (P > 0.05). In conclusion, it is possible that male sexual hormones play a role in the growth (synthesis of contractile proteins) of regenerating muscles in rat. In addition, contrary to NAN + EXE, NAN could be beneficial to soleus regeneration.

Anabolic Agents↗
PubMed1994

Effects of 3-nitrobenzothiazolo[3,2-a]quinolinium chloride (NBQ) and doxorubicin on lens regeneration in the adult newt: a morphological study.

The antitumor drug 3-nitrobenzothiazolo [3,2-a] quinolinium chloride (NBQ) stimulates the in vivo lens regeneration in the adult newt Notophthalmus viridescens and induces a differentiated state in HL-60 leukemia cells. Because the cytotoxic drug doxorubicin (Adriamycin) induces differentiation of HL-60 cells in vitro we decided to compare the effect(s) of doxorubicin with NBQ on lens regeneration in vivo. Both drugs were injected intraperitoneally at six different schedules. Morphological criteria of the different regeneration stages were used in the analysis of the regenerates. NBQ stimulated lens regeneration independently of the time intervals and the stage of regeneration at which the drug was administered. There was an increase in the mean number of mitoses suggesting that NBQ stimulated cell proliferation. Doxorubicin administered for five days did not modify the regenerative process. On the other hand, doxorubicin given for periods of nine or more days after lentectomy, strongly inhibited the formation of a new lens. Thus, the inhibitory effect of doxorubicin is dependent on the continuous long term contact with the tissue. Although NBQ and doxorubicin are both DNA intercalators, they induced the effects on lens regeneration through different mechanisms.

Animals↗
PubMed1999

Pax-6 and Prox 1 expression during lens regeneration from Cynops iris and Xenopus cornea: evidence for a genetic program common to embryonic lens development.

Lens regeneration from non-lens ocular tissues has been well documented in amphibians, from the dorsal iris in the newt and from the outer cornea in Xenopus. To understand the early molecular events which govern lens regeneration, we examined the expression of two early marker genes of normal lens development, Pax-6 and Prox 1. In both Cynops (newt) iris and Xenopus cornea, Pax-6 is expressed soon after lentectomy in a region broader than that giving rise to the regenerating lens, indicative of an important role for Pax-6 in determination of the regeneration potential. Then Prox 1 expression begins within the Pax-6-expressing tissue, and these Prox 1-expressing cells give rise to the regenerating lens. This sequence of events also takes place in the lens placode of the embryo, indicating that the presence of the same genetic program operates in both embryonic lens development and lens regeneration, at least partly. In the Cynops iris, Pax-6 expression occurs initially in the entire marginal region of the iris after lentectomy but then becomes restricted to the dorsal region. Further studies are expected to elucidate the mechanism of this long-standing problem of the dorsal-restriction of lens regeneration from the newt iris.

Amino Acid Sequence↗
PubMedDate not supplied

Fibroblast growth factor receptors regulate the ability for hindlimb regeneration in Xenopus laevis.

During outgrowth of the developing limb, signals from the apical ectodermal ridge, such as fibroblast growth factors, are paramount for limb patterning. Similarly, fibroblast growth factor molecules and their receptors are synthesized in the wound epithelium of the regenerating limb blastema, implicating an analogous function to limb development. To address this issue further and to understand the role of fibroblast growth factor receptor signaling in limb regeneration, we have examined the expression patterns of x-fibroblast growth factor receptors-1, -2, -3, -4a, and -4b in Xenopus laevis. This amphibian model provides a system in which both regenerating (premetamorphic; tadpole or larva stage) and nonregenerating (postmetamorphic; froglet stage) hindlimbs can be studied. In premetamorphic hindlimbs (stage 53), all of the receptors were expressed in the wound epithelium and the underlying mesenchyme. In postmetamorphic limbs (stage 61), however, transcripts for x-fibroblast growth factor receptors-1 and -2 were absent from the wound epithelium. The expression results for x-fibroblast growth factor receptors-1 and -2 were corroborated at the protein level by employing specific antibodies. Thus, it appears that expression of both fibroblast growth factor receptors-1 and -2 is associated with the ability for limb regeneration. The role of these receptors in regeneration was further investigated by using specific inhibitors to fibroblast growth factor receptors during premetamorphic hindlimb regeneration. These compounds inhibited the normal limb outgrowth and resulted, in the majority of the cases, in outgrowths of cones or spikes reminiscent of growth that is seen in amputated postmetamorphic limbs. Thus, fibroblast growth factor receptors-1 and -2 expression and function should be regarded as paramount for the ability of limb regeneration in Xenopus.

Amputation, Surgical↗
PubMed2001

Stimulation of corticospinal tract regeneration in the chronically injured spinal cord.

Acute spinal cord injury models have proved popular in studies aimed at identifying factors capable of influencing axonal regeneration within the central nervous system. In these models, the test factors (e.g. graft tissues or cells, antibodies, growth factors, etc.) are typically administered at the time of spinal cord injury. In this study, we use a rat chronic spinal cord injury model to identify possible factors which can stimulate regeneration of the chronically lesioned corticospinal tract axons. We demonstrate that surgical grafting of segments of autologous, preligated sural nerve, into the syrinx, stimulates sprouting and regeneration of the corticospinal tract as evidenced by the presence of anterograde labelled corticospinal tract processes within the cavity walls two or more weeks after treatment. Regrowing corticospinal processes were not observed within control animals. The anterogradely labelled corticospinal tract axons were found exclusively within the central grey tissue comprising the cavity walls with no regrowing corticospinal process observed within the white matter. A similar pattern of regeneration was observed following injection into the cavity of a suspension of minced autologous preligated sural nerve. Evidence of corticospinal tract regeneration was seen when either wheat germ agglutinin--horseradish peroxidase or biotinylated--dextran was used as an anterograde tracer. These data demonstrate that the chronically injured cortical motor neurons retain the capacity to regenerate for extended periods and that regeneration can be stimulated using grafts of minced, preligated autologous peripheral nerve tissue.

Animals↗
PubMed2002

A dose-dependent facilitation and inhibition of peripheral nerve regeneration by brain-derived neurotrophic factor.

The time-dependent decline in the ability of motoneurons to regenerate their axons after axotomy is one of the principle contributing factors to poor functional recovery after peripheral nerve injury. A decline in neurotrophic support may be partially responsible for this effect. The up-regulation of BDNF after injury, both in denervated Schwann cells and in axotomized motoneurons, suggests its importance in motor axonal regeneration. In adult female Sprague-Dawley rats, we counted the number of freshly injured or chronically axotomized tibial motoneurons that had regenerated their axons 1 month after surgical suture to a freshly denervated common peroneal distal nerve stump. Motor axonal regeneration was evaluated by applying fluorescent retrograde neurotracers to the common peroneal nerve 20 mm distal to the injury site and counting the number of fluorescently labelled motoneurons in the T11-L1 region of the spinal cord. We report that low doses of BDNF (0.5-2 microg/day for 28 days) had no detectable effect on axonal regeneration after immediate nerve repair, but promoted axonal regeneration of motoneurons whose regenerative capacity was reduced by chronic axotomy 2 months prior to nerve resuture, completely reversing the negative effects of delayed nerve repair. In contrast, high doses of BDNF (12-20 microg/day for 28 days) significantly inhibited motor axonal regeneration, after both immediate nerve repair and nerve repair after chronic axotomy. The inhibitory actions of high dose BDNF could be reversed by functional blockade of p75 receptors, thus implicating these receptors as mediators of the inhibitory effects of high dose exogenous BDNF.

Animals↗
PubMedDate not supplied

Regeneration as an evolutionary variable.

Regeneration poses a distinctive set of problems for evolutionary biologists, but there has been little substantive progress since these issues were clearly outlined in the monograph of T. H. Morgan (1901). The champions at regeneration among vertebrates are the urodele amphibians such as the newt, and we tend to regard urodele regeneration as an exceptional attribute. The ability to regenerate large sections of the body plan is widespread in metazoan phylogeny, although it is not universal. It is striking that in phylogenetic contexts where regeneration occurs, closely related species are observed which do not possess this ability. It is a challenge to reconcile such variation between species with a conventional selective interpretation of regeneration. The critical hypothesis from phylogenetic analysis is that regeneration is a basic, primordial attribute of metazoans rather than a mechanism which has evolved independently in a variety of contexts. In order to explain its absence in closely related species, it is postulated to be lost secondarily for reasons which are not understood. Our approach to this question is to compare a differentiated newt cell with its mammalian counterpart in respect of the plasticity of differentiation.

Adaptation, Physiological↗
PubMed1994

Tyrosination state of alpha-tubulin in regenerating peripheral nerve.

Certain modifications of the neuronal cytoskeleton that are associated with development also occur during regeneration of adult mammalian peripheral nerve. The aim of the present study was to examine one such modification, the tyrosination of alpha-tubulin. Adult rats were anaesthetized and the left or right sciatic nerve randomly selected and crushed to induce regeneration. In certain instances nerves were crushed then ligatured about the crush, to prevent regeneration. Five days later the rats were killed and the regenerating (or ligatured) and the contralateral (control) nerves were removed. Quantitative immunoblotting of nerve homogenates with antibodies that recognize tyrosinated alpha-tubulin and total alpha-tubulin revealed a significant increase (p < 0.01) in the proportion of alpha-tubulin that was tyrosinated in nerve pieces distal (peripheral) to a nerve crush and to uncrushed nerve. No such difference occurred in ligatured (crushed but nonregenerating) nerve, implying that the increase was related to the presence of regenerating fibres; nor was there any gradient in tyrosination of alpha-tubulin in control nerves. This effect was confirmed by cytofluorimetric scanning and fluorescence confocal laser scanning microscopy of fixed sections of control and regenerating nerve, stained with antibodies directed against tyrosinated alpha-tubulin. When nerves were separated into fractions containing assembled and nonassembled tubulin, a significant (p < 0.01) increase was found in the proportion of tyrosinated alpha-tubulin in the nonassembled tubulin fraction in nerve pieces containing regenerating fibres. This occurred in the absence of a change in the proportion of assembled and nonassembled tubulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗