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PubMedDate not supplied

An in vivo model for evaluating wound repair and regeneration microenvironments.

BACKGROUND: Factors differentially regulating regeneration and repair as contrasting resolutions to injury are unknown. We adapted a common wound healing model to further characterize mammalian wound repair and regeneration microenvironments. METHODS: Polyvinyl alcohol sponges, sponges containing minced muscle, or blocks of minced muscle were implanted onto the backs of Fischer rats. Vascularization was assessed by infusion with india ink and progress of regeneration was evaluated histologically. RESULTS: Regeneration occurring within sponges was histologically similar to that of free muscle blocks; but, was initiated more slowly. Vascularization of minced muscle implanted in sponges was delayed slightly compared to implanted free muscle blocks. CONCLUSIONS: Regeneration of minced muscle in sponges parallels normal regeneration of free minced muscle. Incorporation into a wound repair model provides access to interstitial fluids conditioned by regenerating muscle and will lead to more detailed comparisons of the content and properties of repair and regeneration microenvironments.

Animals↗
PubMed1996

[Axonal regeneration of retinal ganglion cells].

We have developed retinal culture system of adult mammals to investigate neural regeneration from adult retinal ganglion cells (RGC). In this culture system, neurites were regenerated from RGCs of adult retinal explants. Investigation of neurotrophic effects on the neural regeneration showed that some interleukins and neurotrophins enhanced neurite regeneration from adult rat RGCs. We also found that the adult human retina had the ability of neural regeneration and that neurotrophins enhanced this ability. A novel neurotrophic factor secreted by adult rat hepatocytes also enhanced neurite regeneration not only in adult mice but also in aged RGCs. This result indicated the novel hepatocyte secreted factor is an activator which enhances neural regeneration of the aged retina. We concluded that even adult aged RGCs had the ability of axonal regeneration after injury and that neurotrophic factors might enhanced these abilities. Therefore neurotrophic factors might have practicable applications in drug treatments for intractable disease of the neural retina and optic nerve. Future progress of neuroscience is expected to rescue the retina from various diseases, and to render possible the transplantation of the retina and optic nerve.

Adult↗
PubMed1996

[Effect of vitamin E on the endothelial function of the regenerated aorta in rats following direct arterial injury].

Fibromuscular intimal injury is frequent after coronary or peripheral angioplasty. Peroxidation of circulating and membrane lipids have been implicated in intimal hyperplasia and endothelial dysfunction following direct arterial trauma. The aim of this study was to evaluate the effects of natural membrane antioxidant, vitamin E (VE), on the vascular reactivity of the regenerated endothelium. A first group of rats (n = 10) was pretreated with VE 100 IU/kg/day for a week before undergoing aortic (thoracic) endothelial denudation with a Fogarty catheter. Rats were then fed with the same VE supplemented diet for a 2-month period. A second group (n = 10), was similarly denudated and fed with soya oil (SO), VE vehicle, for the same period. A third group (n = 10) was denuded and used as control (CL). Endothelial-dependent and independent relaxations were assessed in organ chambers with acetylcholine (ACH), adenosine diphosphate (ADP), histamine (HIS), 5-hydroxytryptamine (5-HT) and sodium nitroprusside (SNP). Endothelial regeneration was evaluated with Evans blue staining. Vascular relaxation to SNP was not affected either by the regeneration process or the VE supplementation. However, endothelial-dependent relaxation to ACH and HIS were significantly impeded in the regenerated endothelium compared to control but was not influenced by the VE or the SO supplementation. Vascular contraction to 5-HT was significantly decreased in VE group compared to the other groups. Morphometric studies with Evans blue staining showed over 95% regeneration of the endothelial surface of the denuded aortas. Our results suggest that in spite of a complete anatomical regeneration, endothelial cells did not resume predenudation function. Endothelial-independent relaxation was preserved in all groups indicating that smooth muscle function was not altered by the regenerating process. The presence of dietary supplement of VE (up to 20 fold the daily requirement) did not prevent the endothelial dysfunction to ACH and HIS but attenuated the vaso-contraction to 5-HT and then could contribute to decreased vascular tone in endothelium-regenerated vessels.

Animals↗
PubMed1997

Changes of insulin and somatostatin and their relationship to liver regeneration in experimental obstructive jaundice.

The liver is a parenchymal organ that has a substantial capacity to regenerate after damage. Obstructive jaundice is a common surgical disease and potentially risky. A successful outcome of operations depends upon the hepatic regeneration reserve. Insulin is one of factors responsible for hepatotrophic regeneration and somatostatin has a reversal suppressive action. Experimental obstructive jaundice was introduced and relieved. In addition, serum insulin and somatostatin concentrations were measured. We used immuno-histochemical study of pancreatic tissue by immunogold to express the tissue relative insulin and somatostatin concentrations. Nucleolar organizer regions (NORs) were used to predict the nucleolar activity of liver cells. In our studies, we observed the serum concentrations of insulin and somatostatin were similar to the relative tissue concentration in pancreatic tissues. The relative tissue gold-particle score of insulin in group A (rats with common bile duct tied), was CONT: T4: T7: T14 = 100%: 90.5%: 68.3%: 46.2%; of somatostatin was 100%: 120%: 118.2%: 115.5% respectively. In group B (common bile duct tied for 4 days then relieved), the gold-particle score of insulin was T4: T4R4: T4R7: T4R14 = 90.5%: 62.8%: 72.2%: 95.4%; of somatostatin was 120.2%: 114.3%: 108.1%: 106.2% respectively. In group C (common bile duct tied for 7 days then relieved), the gold-particle score of insulin was T7: T7R4: T7R7: T7R14 = 68.3%: 53.3%: 73.5%; of somatostain was 118.2%: 109.4%: 104.6%: 102.1% respectively. The mean numbers of AgNORs in group A revealed CONT: T4: T7: T14 = 2.24 +/- 0.24: 3.02 +/- 0.96: 3.26 +/- 1.02:3.08 +/- 0.84, group B was T4: T4R4: T4R7: T4R14 = 3.02 +/- 0.96: 3.03 +/- 0.73: 3.36 +/- 1.12: 3.72 +/- 1.46, and group C showed T7: T7R4:T7R7: T7R14 = 3.26 +/- 1.02: 3.26 +/- 0.84: 3.31 +/- 1.24: 3.54 +/- 1.24. In conclusion, our studies suggested: (1) liver regeneration appeared promptly after obstructive jaundice developed, but prolonged cholestasis inhibited this process. (2) Insulin levels gradually fell during the process of obstructive jaundice. Those levels elevated when cholestasis was improved. Nevertheless, both insulin and hepatic regeneration power could not reflect the initial improvement of cholestasis simultaneously. It took a longer time for the improvement of cholestasis and the recovery of the liver function. (3) Patho-physiologically, somatostatin had a weak influence on hepatic regeneration during obstructive jaundice. (4) Our studies provided clues that early biliary drainage might improve hepatic regeneration capacity. Supplement of insulin during the obstructive jaundice might be helpful for the improvement of hepatic regeneration power.

Animals↗
PubMed1995

[Development of metabolic parameters in the early phases of liver regeneration].

Liver regeneration means the ability of the liver to restore the initial cellular mass after damage of various etiology. The primary mechanism of liver regeneration is not clearly defined yet. According to the recent knowledge the liver regeneration is directed by co-acting of many factors and events, among which the metabolic changes in regenerating liver tissue play important role. The aim of this study is to summarize the most important metabolic changes in the early steps of liver regeneration. The study presents the changes, which are taking place in the liver and in the other tissues and organs during liver regeneration, particularly after partial hepatectomy, but also in other types of liver damage. In the beginning the short overview of genetic changes, which enable the development of metabolic changes, is presented. After that the attention is drawn to the carbohydrate, lipid and protein metabolism. In the part, discussing the lipids, the results of experiments, in which the authors followed the influencing of liver regeneration in the rat after partial hepatectomy by means of parenteral and enteral application of various types of lipids and lipids combined with carnitine, is presented. In the next part the study discusses the metabolism of protein kinases and/or ions and trace elements. The energy metabolism as the necessary part of metabolic events is mentioned after that. In the last part the study draws attention to enzymatic retrodifferentiation in regenerating liver.

Animals↗
PubMed1998

Characterization of neuronal regeneration in the abdominal ganglion of Aplysia californica.

The ability of neurons in the abdominal ganglion of Aplysia to regenerate their axons following branchial nerve crush was studied using retrograde staining and intracellular dye injection. The duration of the gill withdrawal reflex (GWR) was measured prior to and following nerve crush. Three days after crushing the nerve, the duration of the gill withdrawal reflex was reduced to 20% of control levels. There was rapid recovery 19 days after crushing the branchial nerve. The GWR duration returned to control levels by postlesion days 25-27. Some of the behavioral recovery can be attributed to axonal regeneration. Regeneration, as evidenced by retrograde staining, was first observed by postlesion day 15. The number of stained neurons in ganglia with crushes increased until postlesion day 33. The number of stained neurons in experimental animals was always less than that of controls (67+/-9% at postlesion day 56). More axonal regeneration was seen in the hemiganglion ipsilateral to the branchial nerve. Regeneration after 32 days postlesion was 60+/-5% of controls in the ipsilateral hemiganglion, as opposed to 29+/-6% in the contralateral hemiganglion. Regeneration of individual neurons was also demonstrated. Identified neuron R2 was shown by intracellular dye injection and electrical stimulation of antidromic action potentials to have an axon in the branchial nerve in all ganglia allowed to regenerate for longer than 32 days. These results indicate that in Aplysia, despite behavioral recovery, complete axonal regeneration does not occur in a large segment of the neurons in the adult central nervous system.

Abdomen↗
PubMed1976

Target discrimination in regenerating insect sensory nerve.

The paired abdominal cerci of the cricket Acheta domesticus are mechanosensory appendages which regenerate readily when amputated during larval life. Their peripherally-located sense cells form axons which project centrally as a purely sensory nerve to the terminal abdominal ganglion. In an attempt to analyze some of the factors which guide a regenerating sensory nerve to correct central terminations, implants of homologous, supernumerary terminal ganglia were made in cricket larvae and the host cerci amputated. The possibility that implants with multiple nerve stumps might release an attracting substance was considered. Surgical procedures used were (1) implant in posterior abdomen; (2) implant in posterior abdomen, ipsilateral to chronic cercal deprivation; (3) implant in mesothoracic leg socket, adjacent to heterotopically-transplanted regenerated cercus; (4) implant in posterior abdomen, ipsilateral host cercal motor nerve sectioned; (5) implant in posterior abdomen, ipsilateral margin of host terminal ganglion wounded. Results were determined after the adult molt, by conventional histology or by cobalt chloride filling of regenerated cercal nerves. In all procedures except (3) and (4), the regenerated afferent nerve bypassed the implant and terminated in the host terminal ganglion. In (3), the regenerated fibers from cercal grafts bypassed the implant; terminations were not found. In (4), some regenerated cercal axons connected with the implant and the majority terminated in the host ganglion. It is suggested that regenerating cercal afferents may depend in a facultative way on the cercal motor nerve as a pathway guide but there is as yet no clear evidence for a trophic influence from the central nervous system.

Animals↗
PubMed1999

Periodontal repair in dogs: histologic observations of guided tissue regeneration with a prostaglandin E1 analog/methacrylate composite.

This report describes observations of healing following guided tissue regeneration (GTR) including surgical implantation of the prostaglandin E1 analog misoprostol with calcium-layered methacrylate particles. Critical size, supra-alveolar periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in 4 beagle dogs. Wound management included soaking with a 24 microg/ml misoprostol solution and implantation of the misoprostol/methacrylate composite. One jaw quadrant per animal was prepared for GTR using expanded polytetrafluoroethylene membranes. The gingival flaps were coronally advanced and sutured to submerge the teeth. The tissues covering the surgical sites daily received topical misoprostol in an oral adhesive over the 4-week healing interval. Upon euthanasia, tissue blocks were prepared for histometric analysis of regeneration of alveolar bone and cementum, root resorption and ankylosis. The defect area underneath the membrane and the density of methacrylate particles were recorded for the GTR defects. The methacrylate particles appeared encapsulated in a dense connective tissue without signs of an inflammatory reaction, some in contact to newly formed bone. Alveolar bone regeneration height averaged (+/-SD) 1.2+/-1.0 and 1.0+/-0.6 mm for GTR and non-GTR defects, respectively. Corresponding values for bone regeneration area were 1.3+/-1.0 and 0.7+/-0.5 mm2. Cementum regeneration was confined to the apical aspect of the defects. Small areas of root resorption and ankylosis were observed for all teeth. Bone regeneration area correlated positively to the defect area and negatively to the density of methacrylate particles in the GTR defects. The histologic observations suggest that the methacrylate composite has marginal potential to promote bone and cementum regeneration under provisions for GTR.

Alveolar Bone Loss↗
PubMed1998

Periodontal repair in dogs: effect of recombinant human transforming growth factor-beta1 on guided tissue regeneration.

This study evaluated alveolar bone and cementum regeneration following surgical implantation of recombinant human transforming growth factor-beta1 (rhTGF-beta1) in conjunction with guided tissue regeneration (GTR). Supraalveolar, critical size, periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in right and left jaw quadrants in 5 beagle dogs. Alternate jaw quadrants in consecutive animals received rhTGF-beta1, in a CaCO3/hydroxyethyl starch carrier with GTR, or carrier with GTR alone (control). 20 microg of rhTGF-beta1 in buffer solution was incorporated into approximately 0.8 ml of carrier for each defect scheduled to receive rhTGF-beta1. Animals were sacrificed at week 4 postsurgery and tissue blocks were harvested and processed for histometric analysis. Clinical healing was generally uneventful. Minor membrane exposures were observed. Defects with membrane exposure displayed an inflammatory infiltrate underneath the membrane. Bone regeneration of trabecular nature, apparent in all animals, was generally limited to the very apical aspect of the defects. Cementum regeneration was limited without obvious differences between experimental conditions. Comparing rhTGF-beta1, to control defects, statistically significant differences were found for area (1.8+/-0.4 and 1.3+/-0.6 mm2, respectively; p<0.05) and density (0.3+/-0.1 and 0.2+/-0.03, respectively; p<0.05) of alveolar bone regeneration. Observed differences are small and represent a clinically insignificant potential for enhanced regeneration in this preclinical model. Within the limitations of study, it may be concluded that rhTGF-beta1 has a restricted potential to enhance alveolar bone regeneration in conjunction with GTR.

Alveolar Bone Loss↗
PubMed1998

Periodontal repair in dogs: effect of allogenic freeze-dried demineralized bone matrix implants on alveolar bone and cementum regeneration.

The objective of this study was to evaluate alveolar bone and cementum regeneration following surgical placement of an allogenic, freeze-dried, demineralized bone matrix (DBM) cortical strip implant. Critical size, supraalveolar periodontal defects were surgically created around the second, third, and fourth mandibular premolar teeth in eight mongrel dogs. Contralateral jaw quadrants in six animals were randomly assigned to receive the DBM implant, or serve as surgical control. Two additional animals received bilateral DBM implants. Flaps were coronally advanced to submerge teeth and implants, and sutured. Three animals were exited from the study due to extensive early wound failure. Remaining animals were sacrificed at 8 weeks postsurgery. Histometric recordings included defect height, bone regeneration/DBM implant height, cementum regeneration height, root resorption, and ankylosis. Large areas of unresorbed DBM exhibiting fragmentation and empty osteocyte lacunae were observed adjacent to new bone formation, or bone formation was observed adjacent to or within the implant, often exhibiting ankylosis. Cementum regeneration appeared enhanced in shelter of the DBM implant. Histometric recordings (mean+/-SD) for DBM and control defects, respectively, were: defect height, 4.8+/-0.2 mm and 4.4+/-0.2 mm; bone regeneration/DBM implant height, 4.0+/-1.3 mm and 1.2+/-0.6 mm; cementum regeneration height, 1.4+/-0.4 mm and 0.7+/-0.2 mm; root resorption, 0.5+/-0.3 mm and 1.2+/-0.3 mm; and ankylosis, 0.5+/-0.2 mm and 0.1+/-0.1 mm without statistically significant differences between experimental conditions (N=3). Within the limitations of this study, the histologic observations suggest that surgical implantation of allogenic, freeze-dried DBM cortical strip implants may have a potential to support cementum regeneration, possibly by providing conditions for guided tissue regeneration, however, alveolar regeneration appears unpredictable.

Alveolar Bone Loss↗
PubMed1998

Effects of regenerator geometry on pulse tube refrigerator performance.

This paper gives results of the cooling performance of a double-inlet pulse tube refrigerator using various regenerators. The same pulse tube was used for all the experiments and measured 4.76 mm in diameter and 46.2 mm in length. A commercial linear compressor with a swept volume of 4 cm3 was used in these experiments. The operating conditions were held constant at a mean pressure of 2.0 MPa and a frequency of 54 Hz. Using finite difference software called REGEN3.1, developed at NIST, and recent experiment results, we optimized a series of regenerators based on dimensions, materials and screen packing. The values used for calculating the thermal conduction through stacked screens by REGEN3.1 were based on recent experimental results from NIST. The regenerator tubes were designed using 316 stainless steel and titanium materials. The regenerator matrices investigated were 400-mesh and 500-mesh stainless steel screen. The valve settings for both orifices were adjusted to minimize the no-load temperature for all regenerators. A cooling capacity curve from 0 to 3 W was also determined. The performance of the pulse tube refrigerator using the different regenerators is discussed. The experimental results from the various regenerators are evaluated and compared with their corresponding numerically calculated coefficient of performance (COP) and regenerator design as determined by REGEN3.1.

Equipment Design↗
PubMed2006

Physical and chemical regeneration of zeolitic adsorbents for dye removal in wastewater treatment.

Natural zeolite and synthetic zeolite, MCM-22, were employed as effective adsorbents for a basic dye, methylene blue, removal from wastewater. Two methods, Fenton oxidation and high temperature combustion, have been used for regeneration of used materials. It is found that MCM-22 exhibits equilibrium adsorption at 1.7 x 10(-4) mol g(-1), much higher than the adsorption of natural zeolite (5 x 10(-5) mol g(-1)) at initial dye concentration of 2.7 x 10(-5)M and 30 degrees C. Solution pH will affect the adsorption behaviour of MCM-22. Higher solution pH results in higher adsorption capacity. The regenerated adsorbents show different capacity depending on regeneration technique. Physical regeneration by high temperature combustion will be better than chemical regeneration using Fenton oxidation in producing effective adsorbents. Regeneration of MCM-22 by high temperature treatment can make the adsorbent exhibit comparable or superior adsorption capacity as compared to the fresh sample depending on the temperature and time. The optimal temperature and time will be 540 degrees C and 1h. The Fenton oxidation will recover 60% adsorption capacity. For natural zeolite, regeneration can not fully recover the adsorption capacity with the two techniques and the regenerated natural zeolites by the two techniques are similar, showing 60% adsorption capacity of fresh sample. Kinetic studies indicate that the adsorption follows pseudo-second-order kinetics.

Adsorption↗
PubMed2001

Regeneration of surfactant-modified zeolite after saturation with chromate and perchloroethylene.

Surfactant-modified zeolites (SMZ) have drawn recent attention as sorbents due to their removal of multiple types of contaminants and low material cost. However, like most sorbents, SMZ has a finite sorption capacity for different contaminants. The potential applications, economics, and efficiency of SMZ as a sorbent are related to the ability to regenerate the material. This paper reports several methods to regenerate chromate- and perchloroethylene-saturated SMZ. Regeneration of chromate-saturated SMZ was achieved by flushing with a sodium carbonate/sodium hydroxide solution. However, this high-pH solution increased the counterion competition for chromate sorption sites and decreased the chromate sorption capacity of the regenerated SMZ. As an alternative regeneration method, chromate sorbed to SMZ was reduced to Cr(III) in situ using sodium dithionite solution. Although reduction with dithionite restored the chromate sorption maximum, the chromate sorption intensity was lowered, possibly due to the competition by sulfate (generated from oxidation of dithionite) for chromate sorption sites. Carbonate-regenerated SMZ showed no loss of sorption affinity for perchloroethylene (PCE) compared to virgin SMZ. Air sparging of PCE-saturated SMZ fully regenerated the SMZ. The results show that it is possible to regenerate and re-use SMZ following saturation with anionic or nonpolar organic contaminants.

Chromates↗
PubMed1999

Identification and optimization of regeneration conditions for affinity-based biosensor assays. A multivariate cocktail approach.

A general regeneration, identification, and optimization (RO) protocol for Biacore systems was developed. The RO protocol uses six multi-ingredient stock solutions that represent the six most common chemical properties employed as regeneration agents. The regeneration effect of different regeneration cocktails of these six stock solutions were tested iteratively until a satisfactory result was obtained. The RO protocol was designed with an ease-of-use and multivariate approach. The RO protocol was tested on 13 different antibody-antigen systems. For 10 of these, only the first screening session was tested. For 9 of the 13 systems, the RO-protocol screening session identified cocktails that removed more than 90% of the bound analyte in a 30 s pulse. For 5 systems, the RO protocol identified cocktails that regenerated the surface completely and that were more gentle than previously used regeneration conditions. Furthermore, the regeneration optimization results can be interpreted as a characterization of the interacting molecules. The relevance of testing cocktails was justified by the fact that at least one cocktail was significantly better than all diluted stock solutions for all tested model systems. By using the multivariate approach, the risk of missing relevant combinations of stock solutions was minimized. This resulted in an unexpected discovery of excellent properties of EDTA as an additive in regeneration cocktails containing chaotropic agents and ions in high concentration.

Biosensing Techniques↗
PubMed1998

Regeneration of three-disulfide mutants of bovine pancreatic ribonuclease A missing the 65-72 disulfide bond: characterization of a minor folding pathway of ribonuclease A and kinetic roles of Cys65 and Cys72.

The oxidative regeneration pathways of two three-disulfide mutants of bovine pancreatic ribonuclease A (RNase A) missing the 65-72 disulfide bond, [C65S,C72S] and [C65A,C72A], have been studied by using oxidized dithiothreitol (DTTox) as an oxidizing agent and 2-aminoethylmethanethiosulfonate (AEMTS) as a thiol-blocking agent at 25 degrees C and pH 8.0. These mutants are analogues of the des-[65-72] intermediate, which is one of the two major three-disulfide intermediates that follow after the transition states in the regeneration pathways of wild-type RNase A [Rothwarf, D. M., Li, Y.-J., and Scheraga, H. A. (1998) Biochemistry 37, 3760-3766, 3767-3776.]. Both mutants folded through the same pathway but at a rate lower than that of the wild-type protein. The major rate-determining step in the regeneration of these mutants was determined to be the oxidation from the two-disulfide intermediates (2S) to the post-transition-state three-disulfide intermediate (3S*), suggesting the existence of a minor oxidation pathway (2S --> 3S*, where 3S* is des-[65-72]) in the regeneration of the wild-type protein, in addition to one of the two major disulfide-rearrangement pathways (3S --> des-[65-72]). The regeneration intermediates of these mutants (R, 1S, 2S, and 3S) participate in a steady state with a kinetic behavior resembling that of the wild-type protein. However, the apparent equilibrium constants () in the steady state, averaged with statistical factors for these mutants, are significantly smaller than those for the wild-type protein, indicating that the intermediates in the regeneration of the mutants are relatively less stable by 0.32 kcal/mol. This difference is due to the decrease in the average rate constants for intramolecular disulfide-bond formation () for the mutant proteins. Loop entropy calculations indicate that the increase in the average length of all possible disulfide loops of the mutants due to the replacement of Cys65 and Cys72 is not sufficient to account for the observed reduction of the values of for the mutants. Therefore, it is the removal of energetic factors (arising from the loss of the 65-72 disulfide loop) that leads to deceleration of the regeneration of the mutant proteins. The formation of the 65-72 disulfide loop in the regeneration of wild-type RNase A appears to facilitate the subsequent folding events.

Animals↗
PubMed1993

The relative rate of aequorin regeneration from apoaequorin and coelenterazine analogues.

The regeneration of an active semi-synthetic aequorin, from apoaequorin produced in cells and a coelenterazine analogue, is a key step in measuring Ca2+ in the cells. The relative rates of the regeneration of semi-synthetic aequorins from apoaequorin and 28 synthetic coelenterazine analogues were compared. The results indicated that the rate is strongly influenced by the analogues used. The regeneration of ordinary aequorin with normal coelenterazine was relatively fast (50% regeneration in 22 min), whereas the rates of regenerating semi-synthetic aequorins with coelenterazine analogues varied widely, and all were slower than that of regenerating ordinary aequorin, except for e-type coelenterazines (containing an extra ethano group). The regeneration with e-type coelenterazines was significantly faster, indicating the possible superiority of e-type analogues in the intracellular regeneration of aequorin, especially when an increased sensitivity to Ca2+ is needed.

Aequorin↗
PubMed2003

Regeneration of peroxiredoxins during recovery after oxidative stress: only some overoxidized peroxiredoxins can be reduced during recovery after oxidative stress.

Peroxiredoxins (prx) are redox enzymes using an activated cysteine as their active site. This activated cysteine can be easily overoxidized to cysteine sulfinic acid or cysteine sulfonic acid, especially under oxidative stress conditions. The regeneration of peroxiredoxins after a short, intense oxidative stress was studied, using a proteomics approach. Important differences in regeneration speed were found, prx2 being the fastest regenerated protein, followed by prx1, whereas prx3 and prx6 were regenerated very slowly. Further study of the mechanism of this regeneration by pulse-chase experiments using stable isotope labeling and cycloheximide demonstrated that the fast-regenerating peroxiredoxins are regenerated at least in part by a retroreduction mechanism. This demonstrates that the overoxidation can be reversible under certain conditions. The pathway of this retroreduction and the reasons explaining the various regeneration speeds of the peroxiredoxins remain to be elucidated.

Binding Sites↗
PubMed2001

Return of potassium ion channels in regenerated hair cells: possible pathways and the role of intracellular calcium signaling.

Recent electrophysiological studies in pigeon have demonstrated that potassium channels are completely functional in regenerated type II hair cells at 21 days post-treatment (PT) with ototoxic doses of streptomycin. The currents return in the order they appear during development. The mixture of ionic currents in a regenerated type II hair cell in a particular region of the neuroepithelium is the same as in its ancestor in that region. The return of currents in regenerated type I hair cells is more complicated. The dominant conductance gKI is not present until after 70 days PT. Before 70 days, the ionic currents in type I hair cells resemble those of regenerated type II hair cells, suggesting that the ionic currents in type II hair cells might be precursors of the ionic currents in regenerated type I hair cells. New data show that at one year PT, the kinetics and drug sensitivity of the dominant K+ conductance in type I hair cells are identical to gKI. Supporting cells, believed to be the precursors of regenerated type II hair cells, have effectively no voltage-gated outward potassium channels, suggesting that regenerated type II hair cells must develop these channels de novo. The next step is to understand the mechanisms by which the potassium channel protein is synthesized, migrates through the cytosol, and is inserted into the plasmalemma of regenerating hair cells. These mechanisms are unknown. We propose that intracellular calcium is involved in this process, as well as in the differentiation, proliferation, and gene regulation of precursor cells fated to become hair cells.

Animals↗