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PubMed2004

Cellular and molecular mechanisms of regeneration in Xenopus.

We have employed transgenic methods combined with embryonic grafting to analyse the mechanisms of regeneration in Xenopus tadpoles. The Xenopus tadpole tail contains a spinal cord, notochord and segmented muscles, and all tissues are replaced when the tail regenerates after amputation. We show that there is a refractory period of very low regenerative ability in the early tadpole stage. Tracing of cell lineage with the use of single tissue transgenic grafts labelled with green fluorescent protein (GFP) shows that there is no de-differentiation and no metaplasia during regeneration. The spinal cord, notochord and muscle all regenerate from the corresponding tissue in the stump; in the case of the muscle the satellite cells provide the material for regeneration. By using constitutive or dominant negative gene products, induced under the control of a heat shock promoter, we show that the bone morphogenetic protein (BMP) and Notch signalling pathways are both essential for regeneration. BMP is upstream of Notch and has an independent effect on regeneration of muscle. The Xenopus limb bud will regenerate completely at the early stages but regenerative ability falls during digit differentiation. We have developed a procedure for making tadpoles in which one hindlimb is transgenic and the remainder wild-type. This has been used to introduce various gene products expected to prolong the period of regenerative capacity, but none has so far been successful.

Animals↗
PubMed1989

Protoplast isolation and regeneration in Streptomyces clavuligerus.

The regeneration of streptomycete protoplasts is a major step following genetic manipulations such as fusion and DNA-mediated transformation. Reports of studies on the regeneration of protoplasts from Streptomyces clavuligerus are limited and for this reason the experiments described in this paper were carried out. An investigation of protoplast formation and cytology was made to gain further insight into the loss of protoplast viability in osmotically stabilized support media. Protoplasts with the highest regeneration frequency were isolated from mycelium, grown in a two-stage culture system (without glycine), using lysozyme dissolved in a sucrose osmoticum containing 1% bovine serum albumin. The latter promoted improved protoplast viability. A systematic survey was made of the components of regeneration medium R5, previously used for S. clavuligerus, and other potentially advantageous components and conditions, in an attempt to raise the regeneration frequency of the protoplasts. An improved regeneration medium (R6) and protocol which supported higher and more consistent levels of regeneration of S. clavuligerus protoplasts resulted from these experiments. These improved procedures for protoplast isolation and regeneration proved to be suitable for other streptomycete species.

Bacteriological Techniques↗
PubMed1982

The regeneration of the sympathetic catecholaminergic nerve fibers in the process of burn wound healing in guinea pigs.

In the present study, morphological alterations of cutaneous catecholaminergic nerve fibers in the process of burn wound healing have been investigated by using glyoxylic acid induced fluorescence histochemistry. The sympathetic denervation is detected within 48 hr after burns as well as in various excisions. The regenerating sympathetic fibers are observed on the 7th day after burns. These regenerating fluorescent fibers seem to develop in accordance with the regeneration of blood vessels in the wound margins at various stages of healing. Regenerating sympathetic fibers gradually increase in number and the maximum density of these fibers is found approximately at 2 weeks after burns. Thereafter, the density of the fibers gradually decreases to less than that of sympathetic innervation of intact skin. On the 14th day after burns, dense regenerating fibers are observed around the regenerated arterial vessels in the deep granulation tissue of the wound margins. These fibers may correlate with the degeneration of regenerated blood vessels in the center of the wound because of contracting the blood vessel of the wound margins. Moreover, dense collateral sprouting of regenerating fibers is observed around the degenerative blood vessel in the center of the wound on the 16 day after burns. This sprouting occurs not because of searching after a new target organ following the degeneration of the target organ but because of playing important roles in certain functions during wound healing.

Animals↗
PubMed1980

The influence of hormones and other substances on lens regeneration in vitro.

Culturing the dorsal iris epithelium of a newt with a pituitary gland in organ culture greatly enhances the ability of the iris epithelium to produce advanced lens regenerates in vitro. In an attempt to elucidate the mechanism by which the pituitary enhances lens regeneration irido-corneal complexes from adult newts were cultured in medium to which various substances had been added either singly or in numerous combinations. Prolactin, insulin, hydrocortisone, and thyroxine failed to enhance the production of advanced lens regenerates in any of the doses or combinations tested. Similarly, addition of 50 microgram/ml of sodium or calcium ascorbate had no effect on the progress of lens regeneration in vitro. Addition of dibutyryl cyclic-AMP caused an inhibition of depigmentation and regeneration at high doses. The results of these experiments show that the effects of the pituitary cannot be duplicated by hormones which other authors have asserted to be beneficial to limb or tail regenerates in vitro. The results with cyclic AMP suggest that prolonged exposure to high doses of cyclic AMP inhibit regeneration and indicate that further studies on the fluctations in cyclic AMP levels throughout the process of lens regeneration must be done.

Animals↗
PubMed1987

A test of the punctuated-cycling hypothesis in Ambystoma forelimb regenerates: the roles of animal size, limb innervation, and the aneurogenic condition.

The punctuated-cycling (PC) hypothesis [39] predicts that the proportion of actively cycling (AC) cells within the blastema influences the rate of limb regeneration in urodele amphibians. To test this, we compared the rate of regeneration and the parameters of the PC hypothesis in small and large Ambystoma mexicanum larvae and in aneurogenic limbs of Ambystoma maculatum. Aneurogenic limbs regenerated more slowly than limbs of small axolotls, but considerably faster than limbs of large axolotls. Regardless of regeneration rates, virtually all blastema cells were in the proliferative fraction (Pf) (ranging from 92.3% +/- 4.2% to 96.2% +/- 3.4%). As predicted, in the blastemata of more rapidly regenerating small axolotls, 86% of the proliferative fraction was actively cycling, but as regeneration slowed, the proportion of the proliferative fraction that was actively cycling decreased (the AC of aneurogenic limbs being 69.5%, and that of large axolotl limbs being 57.3%) and the proportion of transiently quiescent cells increased. The parameters of the PC hypothesis were also examined in small axolotls at two different times during regeneration. During dedifferentiation and initial blastema formation, 61% of the cells in the proliferative fraction were actively cycling and 34% were transiently quiescent. During the rapid-growth phase of the blastema, 88% of the cells in the proliferative fraction were actively cycling and only 7% of the cells were transiently quiescent. It therefore appears that dedifferentiated cells do not immediately begin active cycling and that the transiently quiescent population is relatively large; however, during the period of rapid growth the proportion of transiently quiescent cells is small. In amputated/denervated limbs of small axolotls, the size of the proliferative fraction decreased as the length of the denervation interval increased. Furthermore, with prolonged denervation the total proportion of actively cycling blastema cells also declined (to about 15%). The failure of denervated limbs to regenerate was correlated with an increased nonproliferative fraction and a reduced proportion of actively cycling cells.

Ambystoma↗
PubMed1991

Inhibition of glucose production during hepatic nerve stimulation in regenerating rat liver perfused in situ. Possible involvement of gap junctions in the action of sympathetic nerves.

To explore the possible role of gap junctions in neural regulation of hepatic glucose metabolism, the effects of hepatic nerve stimulation on metabolic and hemodynamic changes were examined in normal and regenerating rat liver which was perfused in situ at constant pressure via the portal vein with a medium containing 5 mM glucose, 2 mM lactate and 0.2 mM pyruvate. 1. The content of connexin 32, a major component of gap junctions in rat liver, decreased transiently to about 25% of the control level in regenerating liver 48-72 h after partial hepatectomy and recovered to normal by the 11th day after the operation. 2. In normal liver, electrical stimulation of the hepatic nerves (10 Hz, 20 V, 2 ms) and infusion of noradrenaline (1 microM) both increased glucose and lactate output and reduced perfusion flow. 3. In early stage of regenerating liver 48 h and 72 h after partial hepatectomy, the increase in glucose output in response to nerve stimulation was almost completely inhibited, whereas the change in lactate balance was partially suppressed and the reduction of flow rate was retained. The response of glucose output to nerve stimulation recovered by the 11th day after partial hepatectomy. In contrast, exogenous application of noradrenaline increased glucose output even in the early stage of regenerating liver. 4. The increase in noradrenaline overflow during hepatic nerve stimulation in the early stage of regenerating liver was approximately the same as in normal liver. Liver glycogen was sufficiently preserved in the early stage of regenerating liver. However, noradrenaline infusion could no more increase glucose output both in normal and in regenerating livers after 24 h of fasting that depleted liver glycogen. These results suggest that the impaired effects of sympathetic nerve stimulation on glucose metabolism observed in regenerating liver are derived neither from reduced release of noradrenaline nor from depletion of liver glycogen, but rather from transient reduction of gap junctions which assist signal propagation of the nerve action through intercellular communication in rat liver.

Animals↗
PubMed2004

Differential gene expression between the embryonic tail bud and regenerating larval tail in Xenopus laevis.

The regeneration of the amputated tail of Xenopus laevis larvae is an excellent model system for regeneration research. The wound left by the amputated tail is covered with epidermis within 24 h. Then, the cell number increases near the amputation plane at the notochord, spinal cord and muscle regions. An apparently complete tail with notochord, muscle and spinal cord is regenerated within two weeks. To reveal whether the molecular mechanism underlying the tail regeneration is the same as that in embryonic tail development, the gene expression patterns of the embryonic tail bud and the regenerating tail were compared by in situ hybridization and reverse transcription-polymerase chain reaction. Most genes analyzed were expressed at similar levels in both tissues, whereas two bone morphogenetic protein (BMP)-antagonists, chordin and noggin, were detected only in the embryonic tail bud. The regenerating tail also lacked expression of Xshh in the floor plate and expression of Xdelta-1 in the spinal cord and presomitic mesoderm. These results show that there are some differences in gene expression between the two processes. Furthermore, when the tail of Xenopus larvae is amputated, the regenerating tail has a gene expression pattern similar to the distal portion of the larval tail rather than the embryonic tail bud, suggesting that the cut larval tail does not make a new embryonic tail bud, but rather a new larval tail tip for regeneration.

Animals↗
PubMed1996

Accurate synapse regeneration despite ablation of the distal axon segment.

In each body ganglion of the leech Hirudo medicinalis there is a single S-cell. After an S-cell axon is severed, it regenerates along its surviving distal segment and reconnects with its synaptic target, the axon of the neighbouring S-cell. In approximately half the cases the regenerating axon forms a temporary electrical synapse specifically with the distal segment, which remains active and connected to the target, thereby functioning as a splice until regeneration is complete. To determine whether the distal axon segment is required for successful regeneration, distal segments of severed S-cell axons were ablated by intracellular injection of bacterial protease. Fifty-seven preparations were examined from 2 to 212 days after injection of the axon segment. The extent of S-cell axon regeneration was assessed electrophysiologically by intracellular and extracellular recording, and anatomically by intracellular injection of markers followed by light microscopy and electron microscopy. The S-cell axons regenerated successfully in almost 90% of animals examined after 2 weeks or more. In a further four animals the target S-cell was ablated in addition to the distal axon segment, permanently disrupting conduction along the S-cell pathway. Nevertheless, the regenerating axon grew along its usual pathway and there was no evidence that alternative connections were formed. It is concluded that, although the distal axon segment can provide a means for rapid functional repair, the segment is not required for reliable regeneration of the axon along its usual pathway and accurate formation of an electrical synapse.

Animals↗
PubMed2006

Effect of serotonin receptor 2 blockage on liver regeneration after partial hepatectomy in the rat liver.

UNLABELLED: The effect of serotonin receptor 2 blockade (5-HT(2)) on liver regeneration after 30-34% and 60-70% partial hepatectomy in the rat liver was investigated. MATERIALS AND METHODS: Male Wistar rats were subjected to 60-70% (group I) and 30-34% (group II) partial hepatectomy. Serotonin receptor 2 blockade was exerted by intraperitoneal administration of ketanserin at different doses and time points after partial hepatectomy. The rats of all groups were killed at different time points until 96 h after partial hepatectomy. The rate of liver regeneration was evaluated by the mitotic index in hematoxylin and eosin sections, the immunochemical detection of Ki67 and proliferating cell nuclear antigens, the rate of [(3)H]-thymidine incorporation into hepatic DNA and liver thymidine kinase enzymatic activity. RESULTS: Liver regeneration peaked at 24 and 32 h after partial hepatectomy in 60-70% hepatectomized rats. In 30-34% hepatectomized rats liver regeneration peaked at 60 h, whereas low rates of regenerative activity were observed between 24 and 72 h after partial hepatectomy. Ketanserin administration arrested liver regeneration only when administered at 16 h after 60-70% partial hepatectomy. Ketanserin also abrogated the observed peak of regenerative activity at 60 h in 30-34% hepatectomized rats when administered at 52 h after partial hepatectomy. All indices of liver regeneration were affected by ketanserin administration. CONCLUSIONS: Serotonin receptor 2 blockade can arrest liver regeneration only when administered close to G1/S transition point, and that while serotonin may be a cofactor for DNA synthesis, it does not play a role in initiation of liver regeneration.

Animals↗
PubMed2006

Growth-promoting activity of Hominis Placenta extract on regenerating sciatic nerve.

AIM: Extract of Hominis Placenta (HP) has been used in oriental medicine as an agent for improving physiological function. The present study was conducted to investigate whether HP treatment in an experimental sciatic nerve injury animal model produces growth-promoting effects on regenerating peripheral nerve fibers after injury. METHODS: After HP was injected into a sciatic nerve injury site, changes in protein levels were analyzed in the regenerating nerve area by Western blotting and immunofluorescence staining analyses. For quantitative assessment of axonal regeneration, a retrograde tracing technique was used to identify the neuronal cell bodies corresponding to regenerating axons, and the extent of neurite outgrowth in cultured dorsal root ganglia (DRG) sensory neurons prepared from animals that had experienced a sciatic nerve crush injury 7 d before neuron collection was analyzed. RESULTS: Induction levels of axonal growth-associated protein (GAP-43) in the injured sciatic nerves were elevated by HP treatment. HP treatment also upregulated cell division cycle 2 (Cdc2) protein levels in the distal stump of the injured sciatic nerve. Induced Cdc2 protein was detected in Schwann cells, suggesting that Cdc2 kinase activity may be involved in the growth-promoting activity of regenerating axons via Schwann cell proliferation. Cell body measurement by retrograde tracing indicated that HP treatment produced significant increases in regenerating motor axons. Finally, HP treatment of cultured DRG sensory neurons significantly increased neurite arborization and elongation. CONCLUSION: HP promotes the regeneration of injured sciatic axons by upregulating the synthesis of regeneration-related protein factors such as GAP-43 and Cdc2.

Animals↗
PubMed1967

Altered temperature and taste responses from cross-regenerated sensory nerves in the rat's tongue.

1. The chorda tympani nerve, which innervates the front of the rat tongue, was found to be much less responsive to tongue cooling than the IXth nerve, which innervates the back of the tongue. The two nerves also differed in their relative responsiveness to various taste chemicals.2. Through cross-union the IXth nerve was made to innervate the front of the tongue, and in other rats the chorda tympani nerve the back of the tongue.3. After an average of 15 post-operative weeks, electrophysiological recordings of whole nerve action potential discharges were made from normal, control regenerated, and cross-regenerated nerves. Cooling, and chemical and mechanical stimulation of the tongue demonstrated that the control regenerated and cross-regenerated nerves had established functional connexions.4. Neither the response to cooling nor the relative taste responses were altered by either of two types of control chorda tympani nerve regeneration.5. In contrast, the cross-regenerated chorda increased its responsiveness to tongue cooling and the cross-regenerated IXthe nerve lost much of its responsiveness to cooling.6. Cross-regeneration also caused the relative taste responses to change and appear quite similar to the responses obtained from the nerve which normally innervated that tongue region (e.g. the cross-regenerated IXth nerve responded like a chorda tympani nerve).7. It is suggested that the sensory response evoked in the chorda tympani and IXth nerves by tongue cooling or taste stimulation is at least partially dependent upon the character of the tongue tissue in which the nerve terminates-the epithelium at the front differs from that at the back of the rat tongue.8. These results rule out the following two hypotheses: (a) that the nerve ending itself functions as a taste receptor in direct contact with applied chemicals and yet is uninfluenced by the character of the tissue in which it terminates, (b) that assuming the taste bud cells are an integral part of the receptive process, the taste nerve ending determines the chemical specificity of the taste cell which it induces, without any previous modification of the nerve by the tissue in which it terminates.

Action Potentials↗
PubMed2004

Changes in contractile activation characteristics of rat fast and slow skeletal muscle fibres during regeneration.

Damaged skeletal muscle fibres are replaced with new contractile units via muscle regeneration. Regenerating muscle fibres synthesize functionally distinct isoforms of contractile and regulatory proteins but little is known of their functional properties during the regeneration process. An advantage of utilizing single muscle fibre preparations is that assessment of their function is based on the overall characteristics of the contractile apparatus and regulatory system and as such, these preparations are sensitive in revealing not only coarse, but also subtle functional differences between muscle fibres. We examined the Ca(2+)- and Sr(2+)-activated contractile characteristics of permeabilized fibres from rat fast-twitch (extensor digitorum longus) and slow-twitch (soleus) muscles at 7, 14 and 21 days following myotoxic injury, to test the hypothesis that fibres from regenerating fast and slow muscles have different functional characteristics to fibres from uninjured muscles. Regenerating muscle fibres had approximately 10% of the maximal force producing capacity (P(o)) of control (uninjured) fibres, and an altered sensitivity to Ca(2+) and Sr(2+) at 7 days post-injury. Increased force production and a shift in Ca(2+) sensitivity consistent with fibre maturation were observed during regeneration such that P(o) was restored to 36-45% of that in control fibres by 21 days, and sensitivity to Ca(2+) and Sr(2+) was similar to that of control (uninjured) fibres. The findings support the hypothesis that regenerating muscle fibres have different contractile activation characteristics compared with mature fibres, and that they adopt properties of mature fast- or slow-twitch muscle fibres in a progressive manner as the regeneration process is completed.

Animals↗
PubMed1992

Rapid induction in regenerating liver of RL/IF-1 (an I kappa B that inhibits NF-kappa B, RelB-p50, and c-Rel-p50) and PHF, a novel kappa B site-binding complex.

The liver is one of the few adult tissues that has the capacity to regenerate following hepatectomy or toxic damage. In examining the early growth response during hepatic regeneration, we found that a highly induced immediate-early gene in regenerating liver encodes RL/IF-1 (regenerating liver inhibitory factor) and is the rat homolog of human MAD-3 and probably of chicken pp40. RL/IF-1 has I kappa B activity of broad specificity in that it inhibits the binding of p50-p65 NF-kappa B, c-Rel-p50, and RelB-p50, but not p50 homodimeric NF-kappa B, to kappa B sites. Like RL/IF-1, several members of the NF-kappa B and rel family of transcription factors are immediate-early genes in regenerating liver and mitogen-treated cells. We examined changes in kappa B site binding activity during liver regeneration and discovered a rapidly induced novel kappa B site-binding complex designated PHF [posthepatectomy factor(s)]. PHF is induced over 1,000-fold within minutes posthepatectomy in a protein synthesis-independent manner, with peak activity at 30 min, and is not induced by sham operation. PHF is distinct from p50-p65 NF-kappa B, which is present only in the inactive form in liver posthepatectomy. Although early PHF complexes do not interact strongly with anti-p50 antibodies, PHF complexes present later (3 to 5 h) posthepatectomy react strongly, suggesting that they contain a p50 NF-kappa B subunit. Unlike p50-p65 NF-kappa B, c-Rel-p50, and RelB-p50 complexes, PHF binding to kappa B sites is not inhibited by RL/IF-1. One role of RL/IF-1 in liver regeneration may be to inhibit p50-p65 NF-kappa B activity present in hepatic cells, allowing for the preferential binding of PHF to kappa B sites. Because PHF is induced immediately posthepatectomy in the absence of de novo protein synthesis, PHF could have a role in the regulation of liver-specific immediate-early genes in regenerating liver.

Animals↗
PubMed2001

Influence of overload on phenotypic remodeling in regenerated skeletal muscle.

We studied the effects of 10 wk of functional overload on the expression of myosin heavy chain (MHC), sarcoplasmic reticulum Ca(2+)-ATPase isoforms (SERCA), and the activity of several metabolic enzymes in sham and regenerated plantaris muscles. Overload was accomplished by bilateral surgical ablation of its synergists 4 wk after right plantaris muscles regenerated after myotoxic infiltration. The overload-induced muscle enlargement was slightly less in regenerated than in sham muscles [28% (P < 0.005) and 43% (P < 0.001), respectively]. Overload led to an increase in type I MHC expression (P < 0.01) to a similar extent in sham and regenerated plantaris, while the expected shift from type IIb to type IIa MHC was less marked in regenerated than in sham plantaris. The overload-induced decrease in the expression of the fast SERCA isoform and in the activity of the M subunit of lactate dehydrogenase occurred to a similar extent in sham and regenerated plantaris [66% (P < 0.01) and 27% (P < 0.005), respectively]. In conclusion, the lesser responses of muscle mass and fast MHC composition of regenerated plantaris to mechanical overload suggest an alteration of the transcriptional, translational, and/or posttranslational control of gene expression in regenerated muscle.

Animals↗
PubMed2004

Nerve regeneration-induced recovery of quinine avoidance after complete gustatory deafferentation of the tongue.

The concentration-dependent decrease in quinine licking by rats is substantially attenuated by combined bilateral transection of the chorda tympani (CT) and glossopharyngeal (GL) nerves, but transection of either nerve alone produces marginal impairments at most. Here we tested whether regeneration of one or both of these nerves after combined transection would result in recovery of taste avoidance. Water-restricted rats were presented with a series of brief-access (5 s) taste trials (water and 0.003-3.0 mM quinine-HCl) in a 5-day test block of 40-min sessions both before nerve transection and starting 75-77 days after transection. Licking avoidance returned to presurgical levels when both nerves were allowed to regenerate. When only the GL was allowed to regenerate, performance did not differ from that of sham-transected animals. This suggests that even after considerable gustatory deafferentation, regeneration has the capacity to restore normal taste-guided behavior. Surprisingly, when only the CT was allowed to regenerate, avoidance behavior was severely impaired and was not different from that of rats in which regeneration of both nerves was prevented. Taking into account prior findings, it appears that the absence of the GL in the presence of an intact CT is fundamentally different from the absence of the GL in the presence of a regenerated CT with respect to some taste functions. This represents the first reported instance to our knowledge in which the capacity of a regenerated nerve to maintain taste-guided behavior was distinctly different from that of an intact nerve in a rodent model.

Algorithms↗
PubMed2006

Nitric oxide and prostaglandins potentiate the liver regeneration cascade.

The liver has the remarkable ability to regenerate following damage or surgical resection. Although this feature of the liver has been studied for over 100 years, the trigger of the liver regeneration cascade remains controversial. Recent experimental evidence supports the hypothesis that nitric oxide (NO) and prostaglandins (PGs), released secondary to an increase in the blood flow-to-liver mass ratio following two-thirds partial hepatectomy (PHx), work synergistically to trigger liver regeneration. To extend this research, the hypothesis that NO and PGs are potential therapeutic targets to potentiate the liver regeneration cascade is tested. The NO donor s-nitroso-n-acetylpenicillamine, the phosphodiesterase V antagonist zaprinast (ZAP) and PGI2 each potentiated c-fos messenger RNA expression, an index of initiation of the liver regeneration cascade, following PHx. Also, the triple combination of s-nitroso-n-acetylpenicillamine, ZAP and PGI2 potentiated c-fos messenger RNA expression. These results support the hypothesis that NO and PGs can potentiate initiation of the regeneration cascade. An additional index of liver weight restoration 48 h after PHx was also used to test the hypothesis, because this index encompasses the entire liver regeneration cascade. ZAP and 6-keto-PGF1alpha, a stable metabolite of PGI2, and the combination of ZAP and 6-keto-PGF1alpha, each potentiated liver weight restoration 48 h after PHx. These results also provide support for the hypothesis that NO and PGs are possible therapeutic targets to potentiate liver regeneration following surgical resection.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Delayed expression of calbindin D28k during regeneration of the periodontal Ruffini endings of the rat incisor following injury to the inferior alveolar nerve.

Expression of calbindin D28k (CB)-like immunoreactivity (-LI) was compared with that of protein gene product 9.5 (PGP 9.5), a general neuronal marker, in the periodontal ligament of the rat lower incisor following resection of the inferior alveolar nerve (IAN). In normal animals, the periodontal nerve fibers showing PGP 9.5-LI formed either Ruffini endings with expanded arborization or thin free nerve endings in the alveolar half of the ligament. Thick CB-like immunoreactive (-IR) nerve fibers terminated in a dendritic fashion in the same region, but thin CB-IR nerve fibers were rarely detected. During the 3 days following resection of the IAN, most of the PGP 9.5-IR and all CB-IR nerve fibers disappeared. Regenerated PGP 9.5-IR nerve fibers appeared around 7 days after resection, in contrast to the very small number of regenerated CB-IR nerve fibers. Around 21-28 days following resection, the number and terminal morphology of regenerated PGP 9.5-IR nerve fibers were comparable to those observed in normal animals, but the number of regenerated CB-IR nerve fibers was still smaller. The terminal morphologies of these regenerated CB-IR nerve fibers showed less expansion compared with normal animals at these post-injured periods. The number of regenerated CB-IR nerve fibers increased gradually to return to normal by 56 days following injury. The delayed expression of CB in the regenerated periodontal Ruffini endings suggests that the functional recovery of periodontal Ruffini endings occurred after the regeneration of periodontal Ruffini endings had been completed.

Animals↗
PubMedDate not supplied

Effects of cyclosporin and somatostatin on liver regeneration after partial hepatectomy in rats.

The major hepatic reaction which occurs in response to degeneration or partial loss of the liver is compensatory hyperplasia. After finding out that hemodynamic factors have no influence in hepatic regeneration, the investigations have been focused on some trophic factors which have been found in the blood and which have been believed to provide the basic control of regeneration. In our controlled experimental study we have tried to evaluate the effects on hepatic regeneration of cyclosporin and somatostatin which are known to act on the hepatic regeneration ability or which are thought to have effects on regeneration because of their mechanism of action. For the purpose of evaluating the regenerative response findings like the weight of the regenerated liver, mean Ag nuclear organizer region (AgNOR) number, the mitosis index, cells with double nuclei and hyperchromatic nucleus were taken into consideration. The results of the cyclosporin group were higher than of the controls, but there was no statistically significant difference between them. In the somatostatin group, an inhibition of regeneration related to the dose and to the duration at the beginning and a delayed augmentation of the regeneration rate due to the withdrawal of the drug were observed. Values of AgNOR were significantly higher compared to the control group on the 5th day postoperatively, while the liver weight was lower on the 1st day (p < or = 0.05).

Animals↗