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PubMed1983

[Experimental studies on regeneration of myoepithelial cells--the rat submandibular gland autografted in the tongue].

The regeneration process of myoepithelial cells in the injured salivary gland was studied. Fragments of the rat submandibular gland autografted in the tongue were examined from 12 hours to 14 days after implantation by means of the methods of autoradiography, histochemistry and electron microscopy. Two days after implantation, the central area of the fragments showed necrosis and parenchymal regeneration was, on the other hand, revealed at the remaining periphery. It was demonstrated by [3H] thymidine autoradiography that the regeneration of the intralobular parenchyma took place at the remaining intercalated and striated portions of the duct, but never did at the secretory endpieces. Initially, solid cell clusters were composed of regenerating uniformly immature polygonal epithelial cells. Four days after implantation, intracytoplasmic filaments running parallel to the plasma membrane of the cell, measured 50-70 A in diamter, were detected in some cells of the cluster. These filaments were accompanied by dense bodies characteristic of those of smooth muscle cells, and were thereby identified with myofilaments. Based on the findings, the regenerating cells with myofilaments were recognized as immature myoepithelial cells. Showing mosaic arrangement, they intermingled with the other kind of regenerating epithelial cells in the cluster. Each regenerating cell cluster formed gradually tubular structure with epithelial stratification. Ten days after implantation, most tubular structures were consisted of the single layer of columnar or cuboidal cells. Fourteen days after implantation, alkaline phosphatase activity characteristic of mature myoepithelial cells was observed in the spindle cells located between tubular epithelium and basal lamina. Ultrastructurally these spindle cells were identified with mature myoepithelial cells because of furnishing myofilaments with dense bodies. The results of this experiment suggest that, in case of tissue injury, the epithelial regeneration in the intralobular portion of the salivary gland is initiated at the intercalated and/or striated portions of the duct, and followed by myoepithelial differentiation of some of the regenerating epithelial cells.

Animals↗
PubMed1983

Pathways of Xenopus optic fibres regenerating from normal and compound eyes under various conditions.

We have used Horseradish peroxidase to investigate the pathways taken by Xenopus optic fibres regenerating from normal and electrophysiologically-confirmed compound eyes to the optic tectum. Optic fibres, when sectioned near the chiasma, regenerate up both sides of the diencephalon to both tecta. We have therefore been able, by using animals in which one eye had or had not been removed at early embryonic stages, to look at the behaviour of regenerating axons in three different situations: (1) regeneration to the contralateral tectum, previously innervated by the sectioned fibres; (2) regeneration to a "virgin' ipsilateral tectum, never before innervated by optic fibres; and (3) regeneration to an ipsilateral tectum already innervated by fibres from a normal eye. From the chiasma to the tectodiencephalic junction regenerating fibres behave similarly in all three situations, following roughly the course of the normal optic tract, but running in a rather disorganised way, with frequent crossing over of fibres. However fibres of nasal retinal origin (from an NN eye) spread to occupy a much larger area of the side of the diencephalon than those of temporal origin (from a TT eye). From the tectodiencephalic junction to the tectal termination of the fibres there are differences between the three situations investigated; fibres regenerating to a 'virgin' ipsilateral, or to a denervated contralateral tectum, tend to grow straight onto the tectum, instead of being channelled into lateral or medial brachium as uncut fibres tend to be. There is however, the remains of a brachial organisation, and of differential selection of these brachia by fibres from the different types of compound eye, this being well seen on "virgin' tecta. Fibres regenerating to an ipsilateral innervated tectum behave very differently. As they reach the tectodiencephalic junction they suddenly start to grow in a less disorganised way, and are channelled into well defined brachia. If from a compound eye, these fibres terminate on only that part of the tectum innervated by fibres from the corresponding part of the normal eye. Thus fibres from a VV eye and those from the ventral half of the normal eye all terminate on medial tectum; fibres from an NN eye, and those from the nasal half of the normal eye all terminate in caudal tectum; and temporal fibres from both normal and TT eyes terminate in rostral tectum.

Animals↗
PubMed1982

Determination of axial polarity in the urodele limb regeneration blastema.

The state of determination of the anterior-posterior, dorsal-ventral and proximal-distal axes of the undifferentiated limb regeneration blastema was evaluated by heterografting and autografting experiments in which these axes were reversed with respect to the limb stump. Species-specific size differences in skeletal elements were used as markers to trace the origin of regenerate tissues in the heterografting experiments, and differences in the skeletal patterns of hindlimbs and forelimbs were used as markers in the autografting experiments. The resulting primary regenerates fell into two categories, those composed wholly or partly of donor tissues, and those composed entirely of host tissues. Regenerate structures formed from donor tissues always maintained the handedness of origin, while regenerates formed from host tissues always displayed host-side handedness. These results demonstrate that the axes of the blastema are determined from the start of regeneration, and that previous claims of axial lability in reversal experiments are based on an illusion created by resorption of graft tissue, accompanied by regeneration from the host. Reversal of the transverse axes resulted in the formation of supernumerary limbs. Analysis of heterograft cases in which the anterior-posterior axis was reversed showed that 50% of the supernumeraries were constructed partly of donor blastema tissue whose axial polarity was reversed with respect to the adjacent primary regenerate. The vast majority of the primary regenerates in these cases possessed the normal number of digits. It is thus likely that the reprogrammed donor blastema cells used to construct the supernumeraries are derived by division of a thin band of cells at the edge of the graft adjacent to the supernumerary.

Ambystoma↗
PubMedDate not supplied

[Molecular-biological approaches to studying gene expression during regeneration].

This paper constitutes a review of the methodical approaches allowing analysis of the mechanisms underlying development and differentiation. Progress in investigation of the mechanisms underlying embryogenesis is related to the discovery of genic families in the Drosophila genome, which are responsible for different periods of embryogenesis. The true revolution in studies of developmental mechanisms began with the application of molecular-genetic methods for analysis of Drosophila mutant lines. The clarification and analysis of the genes controlling regeneration is one of the most effective paths toward an understanding of the mechanisms underlying regeneration. No mutations affecting regeneration are, and the development of alternative (i.e., not based on mutation analysis) methods of discovery of the genes controlling regeneration is necessary for investigation of the genetic mechanisms of regeneration. The advantages and drawbacks of the two main approaches for discovery of the genes controlling regeneration are considered. The first approach is based on the production of a bank of sequences expressed in the regenerating structures and subsequent screening of the bank by the known probes. This approach also involves analysis of the structure, function, and expression pattern of the obtained homologs. The second approach is based on subtractive hybridization, which allows identification of the genes specifically expressed in the regenerating structures. This approach was made it possible to identify, for the first time, new genes specifically expressed during lens and retina regeneration in amphibians.

Animals↗
PubMed1996

Urodele limb and tail regeneration in early biological thought: an essay on scientific controversy and social change.

Lazzaro Spallanzani (1729-1799) announced his discoveries of salamander tail and limb regeneration to Charles Bonnet (1729-1793) in the 1760's. The phenomenon soon became embroiled with the ongoing epigenesis/preformation controversy over the fundamental nature of generation. The concept of animal regeneration as a process linked to reproduction had emerged in 1740 with Abraham Trembley's (1710-1783) demonstration that a bisected hydra gives rise to two new, completely formed individuals. The discovery of urodele appendage regeneration revealed for the first time that a quadruped could regenerate and restore complex form, lizard tail regenerates having been recognized as only substitute structures. Moreover, regeneration of a quadruped appendage became problematic because it was not supposed to be possible and because it conflicted with prevailing opinion about the nature of higher organisms. Why animal regeneration in general engendered conflict transcends biological concerns and touches on personal philosophical commitments. Preformation had been adopted into orthodox theology as a validation of predestination and of the hierarchical structuring of man's relationships to nature and within society. Epigenetic interpretations of regeneration represented challenges to certain aspects of the extant social and political fabric in their extrapolation to ideas of what constituted natural order. Urodele regeneration as an integral part of the epigenesis/preformation debate therefore constituted a formative component of eighteenth century thought in a period of social and intellectual revolution.

Animals↗
PubMed1997

Recovery of neurofilament expression selectively in regenerating reticulospinal neurons.

During regeneration of lamprey spinal axons, growth cones lack filopodia and lamellipodia, contain little actin, and elongate much more slowly than do typical growth cones of embryonic neurons. Moreover, these regenerating growth cones are densely packed with neurofilaments (NFs). Therefore, after spinal hemisection the time course of changes in NF mRNA expression was correlated with the probability of regeneration for each of 18 identified pairs of reticulospinal neurons and 12 cytoarchitectonic groups of spinal projecting neurons. During the first 4 weeks after operation, NF message levels were reduced dramatically in all axotomized reticulospinal neurons, on the basis of semiquantitative in situ hybridization for the single lamprey NF subunit (NF-180). Thereafter, NF expression returned toward normal in neurons whose axons normally regenerate beyond the transection but remained depressed in poorly regenerating neurons. The recovery of NF expression in good regenerators was independent of axon growth across the lesion, because excision of a segment of spinal cord caudal to the transection site blocked regeneration but did not prevent the return of NF-180 mRNA. The early decrease in NF mRNA expression was not accompanied by a reduction in NF protein content. Thus the axotomy-induced loss of most of the axonal volume resulted in a reduced demand for NF rather than a reduction in volume-specific NF synthesis. We conclude that the secondary upregulation of NF message during axonal regeneration in the lamprey CNS may be part of an intrinsic growth program executed only in neurons with a strong propensity for regeneration.

Animals↗
PubMed1997

The role of Schwann cells during retinal ganglion cell regeneration induced by peripheral nerve transplantation.

PURPOSE: To investigate the key role of Schwann cells in retinal ganglion cell regeneration elicited by peripheral nerve autotransplantation. METHODS: Three kinds of autografts, Schwann-cell graft (intact sciatic nerve, consisting of living Schwann cells and their basal laminae). Schwann-cell-eliminated graft (consisting mainly of Schwann cell basal laminae) and partial Schwann-cell graft (consisting of basal laminae and diffusible factors secreted by Schwann cells) were prepared and autotransplanted to the adult rat optic nerve. The membrane specialization between regenerating axons and Schwann cells was observed by electron microscopy. The expression of cell adhesion molecules was demonstrated by Western blot analysis and immunohistochemistry. RESULTS: Retinal ganglion cell axons were observed to regenerate into the Schwann-cell graft in contact with Schwann cells but not into the Schwann-cell-eliminated graft. The regeneration was not observed in the empty basal laminae of the partial Schwann-cell graft. Most of regenerating axons contacted astrocytes in the optic nerve segment, and Schwann cells in the graft. At the interface of regenerating axon and Schwann cell, in addition to immunoreactivity of N-CAM and LI, short focal tight junctions were observed. CONCLUSIONS: These results suggested that viable Schwann cells are good substrate for retinal ganglion cell regeneration, the intimate contact with viable Schwann cell surface plays an important role in retinal ganglion cell regeneration, tight junctions, and cell adhesion molecules (LI, N-CAM) are observed between the regenerating axon and Schwann cell.

Animals↗
PubMed1998

A homeobox gene of the orthodenticle family is involved in antero-posterior patterning of regenerating planarians.

We studied the expression of DtOtx, a homeobox gene of the freshwater planarian Dugesia tigrina closely related to the Drosophila orthodenticle (otd) and vertebrate Otx genes, which are known to control head development in both fruit flies and vertebrates. DtOtx was not significantly expressed in adult planarians but it was activated within one hour in regenerating tissues with a clearly asymmetric pattern. Animals sectioned transversally, either between the head and the pharynx, or caudal to the pharynx, give rise to a head-containing fragment regenerating a tail region and to a tail-containing fragment regenerating a head region. DtOtx was found to be activated in both regeneration blastemas but its transcripts were much more abundant in the head-regenerating tissues than in the tail-regenerating tissues. The same asymmetric distribution of DtOtx transcripts was observed in central portions of the body regenerating both head and tail structures and in animals laterally regenerating after a longitudinal cut. These data suggest a role of this gene in patterning the body axis of these primitive bilateria, at least during regeneration.

Amino Acid Sequence↗
PubMed1975

Methods of regeneration.

This paper is concerned with methods of regeneration: morphallaxis, epimorphosis, and regeneration by induction. The last method was demonstrated by investigations to study the restoration of lost regenerative power of the cranial bones in adult dogs and in some other cases. During regeneration by induction an inducing agent, reactive or competent material, and the right conditions for induction must be present. It is emphasized that the method and mechanism of regeneration are one and the same thing. The methods of regeneration specified above differ not only in their formal and secondary features, but also in the essence of their fundamental processes: true reorganization, growth, and induction. Each method of regeneration can be found not only in the pure form, but also in combinations of varying degree and type. Besides regeneration, hypertrophy is also very important for the restoration of parenchymatous internal organs in mammals, but it is not identical with regenerations.

Animals↗
PubMed2002

Vertebrate limb regeneration and the origin of limb stem cells.

The existence of multipotent cells in the adult tissues and organs of those vertebrates that are capable of regeneration has been accepted for decades. Although studies of vertebrate limb regeneration have yet to identify many of the specific molecules involved in regeneration, numerous tissue grafting experiments and studies of cell lineage have contributed significantly to an understanding of the origin, activation, proliferation and cell-cell interactions of these progenitor cells. This has allowed the development of ideas about the regulation of pattern formation to restore the structure and function of lost tissues and organs. An understanding of the molecular mechanisms controlling these processes has lagged behind the dramatic advances achieved with other model organisms. However, given the intense, new research interest in stem cells over the past few years, there is good reason to be encouraged that insights about the biology of mammalian stem cells will accelerate progress in understanding the biology of regeneration in organisms that can regenerate. Advances in regeneration research will then feed back in terms of devising new strategies for therapies to induce regeneration in organisms such as humans that have traditionally been viewed as incapable of regeneration.

Animals↗
PubMed2005

Comparisons of food availability and group density of Japanese macaques in primary, naturally regenerated, and plantation forests.

We compared food availability and group density of Japanese macaques in Yakushima, southern Japan, among primary forest and two habitats that had been disturbed by logging and had different regeneration histories. The study was conducted in an undisturbed national park, forest that was logged 7-18 years ago and later naturally regenerated, and forest that was logged 19-27 years ago and later planted with Japanese cedar (Cryptomeria japonica) trees. The plantation forest was primarily composed of large Cryptomeria japonica trees at low stand density, while the naturally regenerated forest was composed of many small trees. The total basal area and number of trees in the primary forest were comparable to those in the plantation forest. Annual fruit production was greatest in the naturally regenerated forest, intermediate in the primary forest, and negligible in the plantation forest. Herb availability was high in the naturally regenerated forest, but low in the primary and plantation forests. The group density of Japanese macaques was high in the naturally regenerated forest, intermediate in the primary forest, and low in the plantation forest. Since group size in the naturally regenerated forest was small, individual density was almost the same as in the primary forest. These results suggest that the effects of regeneration on macaques vary between the two habitats. The plantation forest consisted mostly of Cryptomeria japonica, which supplies only flowers as food in a limited season, and had a lower density of macaques. On the other hand, in the naturally regenerated forest, fruit production and herb availability were high (probably because of the enhanced light conditions after logging), and the density of macaques was as high as in the primary forest.

Animals↗
PubMed2006

Genomic instability in phenotypically normal regenerants of medicinal plant Codonopsis lanceolata Benth. et Hook. f., as revealed by ISSR and RAPD markers.

Codonopsis lanceolata Benth. et Hook. f., commonly known as bonnet bellflower, is a high-valued herb medicine and vegetable. In this study, a large number of plants were regenerated via organogenesis from immature seed-derived calli in C. lanceolata by a simple and efficient method. Compared with the mother donor plant, the regenerated plants did not exhibit visible phenotypic variations in six major morphological traits examined at the stage of one-season-maturity under field conditions. To gain insight into the genomic stability of these regenerated plants, 63 individuals were randomly tagged among a population of more than 2,000 regenerants, and were compared with the single mother donor plant by two molecular markers, the inter-simple sequence repeats (ISSR) and randomly amplified polymorphic DNA (RAPD). Apparent genomic variation was detected in the 63 regenerants, whereas preexisting heterozygosiy in the donor plant was deemed minimal by testing 30 seedlings germinated from selfed seeds of the same donor plant. The percentages of polymorphic bands (PPB) in the ISSR and RAPD analysis were respectively 15.7 and 24.9% for the 63 regenerated plants. Cluster analysis indicates that the genetic similarity values calculated on the basis of RAPD and ISSR data among the 64 plants (63 regenerated and one donor) were respectively 0.894 and 0.933, which allow classification of the plants into distinct groups. Nineteen randomly isolated bands underlying the changed RAPD or ISSR patterns were sequenced, and three of them showed significant homology to known-function genes. Detailed pairwise sequence comparison at one locus between the donor plant and a regenerant revealed that insertion of two short (24 and 19 bp) stretches of nucleotides in the regenerated plant relative to the donor plant occurred in an apparently stochastic manner.

Base Sequence↗
PubMed2001

Changes in symplastic permeability during adventitious shoot regeneration in tobacco thin cell layers.

Thin cell layer (TCL) explants of tobacco (Nicotiana tabacum L.) were cultured in either a regeneration medium that resulted in formation of adventitious vegetative shoots or a non-regeneration (control) medium that maintained the TCLs but did not promote shoot formation. Microinjections were conducted on epidermal cells at 1- or 2-day intervals during the culture period (14 days) and also on meristematic regions as they appeared in regenerating TCLs. A fluorescein isothiocyanate-labelled peptide (F(Glu)3 MW 799) was used to assess the permeability of the symplast during adventitious shoot regeneration. A period of increased symplastic movement of F(Glu)3 was detected during day 2 of culture and was significantly greater in regenerating TCLs than in non-regenerating TCLs. This corresponded to the period of the first cell divisions and represents the re-initiation of a meristematic type of symplastic linkage between epidermal cells. A smaller increase in cell-to-cell movement within non-regenerating TCLs indicated a possible stress response as a factor in these changes. Movement of F(Glu)3 throughout the epidermal symplast of regenerating TCLs returned to pre-culture levels by the time of shoot primordia formation. F(Glu)3 movement was further down-regulated in non-regenerating TCLs, with a high degree of cell isolation observed. Within newly formed shoots, symplastic movement of F(Glu)3 cycled between high and low levels.

Biological Transport↗
PubMed2003

Fibroblast growth factor 2 in synovial fluid from an osteoarthritic knee with cartilage regeneration.

The levels of fibroblast growth factor 2 (FGF2) in synovial fluid of osteoarthritic knees were measured. The correlation between FGF2 and the severity of cartilage degeneration in varus-deformed knees with medial compartmental osteoarthritis or the articular cartilage regeneration that occurs after high tibial osteotomy (HTO) were investigated. Knees that underwent total knee arthroplasty (TKA) were categorized as either mildly or severely degenerated according to a modified Outerbridge's grading system for degeneration of articular cartilage. Regeneration of articular cartilage was observed in a biopsy specimen from the medial femoral condyle removed with the patient's consent during hardware removal approximately 2 years after HTO. The joint fluid FGF2 level was measured at that time using an enzyme-linked immunosorbent assay. Cartilage regeneration was classified as immature or mature according to the staging for regeneration of articular cartilage. The histological findings were analyzed using Pineda's evaluation method for cartilage regeneration. The mean concentration of FGF2 was 57.4 +/- 17.6 pg/ml in the joint fluid from knees with severely degenerated cartilage. This was higher than the FGF2 concentration found in the mildly degenerated group. Approximately 2 years after HTO the FGF2 level in synovial fluid was lower in knees with mature regenerated cartilage than in those with immature regeneration. Osteoarthritic knees at a more mature regeneration stage had a lower Pineda's histological score. This result suggested that the FGF2 concentration in knees with osteoarthritis was influenced by articular cartilage degeneration and regeneration, and it correlated with the histological evaluation.

Aged↗
PubMed2005

Impact of coenzyme regeneration on the performance of an enzyme-based optical biosensor: a computational study.

A mathematical model of a reagent-less optical sensing scheme composed of an enzymatic reaction coupled to light-controlled photochemical coenzyme regeneration is described. The model is based on previous experimental work describing the regeneration of NADPH from NADP(+) by excited state thionine coupled to the oxidation of isocitrate by isocitrate dehydrogenase. The system is capable of repeated isocitrate measurements without the addition of exogenous coenzyme. The model is simulated using numerical integration to determine the effect of regeneration on the sensor sensitivity, response time and maximum sample throughput rate. Prediction of these effects without a model is difficult due to activation and inhibition of the dehydrogenase by both forms of the coenzyme. The regeneration parameters, including thionine concentration and thionine excitation pattern, are varied to determine optimal sensor conditions to maximize performance. A periodic regeneration approach is found to be superior to a continuous regeneration approach as the former maximizes sensitivity and minimizes response time in most cases. In addition periodic regeneration results in a maximum sample throughput frequency that is achieved at a single optimal thionine level and is independent of the analyte concentration. In contrast the optimal thionine concentration during continuous regeneration varies with the sample analyte concentration. These findings highlight the importance of designing controllable regeneration for dehydrogenase-based optical biosensors.

Biosensing Techniques↗
PubMed1998

Differential rhodopsin regeneration in photoreceptor membranes is correlated with variations in membrane properties.

Rhodopsin, the major transmembrane protein in both the plasma membrane and the disk membranes of photoreceptor rod outer segments (ROS) forms the apo-protein opsin upon the absorption of light. In vivo the regeneration of rhodopsin is necessary for subsequent receptor activation and for adaptation, in vitro this regeneration can be followed after the addition of 11-cis retinal. In this study we investigated the ability of bleached rhodopsin to regenerate in the compositionally different membrane environments found in photoreceptor rod cells. When 11-cis retinal was added to bleached ROS plasma membrane preparations, rhodopsin did not regenerate within the same time course or to the same extent as bleached rhodopsin in disk membranes. Over 80% of the rhodopsin in newly formed disks regenerated within 90 minutes while only 40% regenerated in older disks. Since disk membrane cholesterol content increases as disks are displaced from the base to the apical tip of the outer segment, we looked at the affect of membrane cholesterol content on the regeneration process. Enrichment or depletion of disk membrane cholesterol did not alter the % rhodopsin that regenerated. Bulk membrane properties measured with a sterol analog, cholestatrienol and a fatty acid analog, cis parinaric acid, showed a more ordered, less "fluid", lipid environment within plasma membrane relative to the disks. Collectively these results show that the same membrane receptor, rhodopsin, functions differently as monitored by regeneration in the different lipid environments within photoreceptor rod cells. These differences may be due to the bulk properties of the various membranes.

Animals↗
PubMed1997

Somatostatin sst5 inhibition of receptor mediated regeneration of rat aortic vascular smooth muscle cells.

1. The aim of the present study was to determine the effect of somatostatin (SRIF) on mitogen-induced regeneration of rat aortic vascular smooth muscle cells (VSMC) and for comparison Chinese hamster ovary (CHO)-K1 cells expressing human recombinant sst5 receptors (CHOsst5), following partial denudation of a confluent cell monolayer. Regeneration was assessed by measuring areas of recovery into the denuded area and by counting total cell numbers. 2. In VSMC, SRIF (0.1 nM - 1 microM) had no effect on the basal levels of regeneration but caused a concentration-dependent inhibition (pIC50 8.0-8.6) of the stimulated regeneration induced by submaximal concentrations of basic fibroblast growth factor (bFGF, 10 ng ml[-1]), platelet-derived growth factor-BB (PDGF, 5 ng ml[-1]) or endothelin-1 (ET-1, 100 nM). SRIF (pIC50 8.8) also inhibited bFGF-induced regeneration of CHOsst5 cells. 3. In VSMC, the inhibitory action of SRIF on the regeneration induced by bFGF (10 ng ml[-1]) was due to an anti-proliferative effect, rather than an effect on cell migration, as SRIF (0.1 nM - 1 microM) abolished bFGF-induced increases in total cell numbers. The bFGF-induced increase in cell numbers was also abolished by actinomycin D (0.1 microg ml[-1]). 4. The sst5 receptor-selective agonist, L-362,855 (pIC50 10.5), was about 100 times more potent than SRIF at inhibiting bFGF-induced regeneration of both VSMC and CHOsst5 cells whilst the sst2 receptor-selective agonist, BIM-23027 (pIC50 6.8), was approximately 20 times weaker than SRIF. 5. The sst5 receptor antagonist, BIM-23056 (100 nM), antagonized SRIF-induced inhibition of bFGF-induced regeneration in both VSMC and CHOsst5 cells (estimated pKB values 8.8 and 8.3, respectively). 6. SRIF-induced inhibition of bFGF-induced regeneration of VSMC and CHOsst5 cells was abolished by pretreating cells with pertussis toxin (100 ng ml[-1]) for 20 h. 7. These findings suggest that SRIF-induced inhibition of the proliferation of rat aortic VSMC is mediated via activation of receptors which are similar to human sst5 receptors. Furthermore this inhibitory effect is transduced via pertussis toxin-sensitive Gi/Go proteins.

Animals↗
PubMed2002

Thermal regeneration of granular activated carbons using inert atmospheric conditions.

Thermal regeneration is increasingly being used for the recovery of field-spent granular activated carbons (GAC) generated by the water treatment industry. Despite its commercial success, conventional methods using oxidising conditions (usually steam) are known to damage the porosity of the regenerated carbons, thus reducing their adsorption capacity and economic value. This paper presents a comparative investigation into the benefits of using inert conditions for the regeneration of field-spent GAC. For the purpose of this work, a sample of spent carbon was regenerated in nitrogen and in steam to different degrees of burn off. The resulting samples were analysed for their porosity and surface area characteristics using nitrogen gas adsorption, and for their aqueous adsorption capacities using phenol and methylene blue. Experimental results showed that steam was sightly more effective than nitrogen at regenerating the total micropore volume and BET surface area of the carbons. However, these benefits were largely counteracted by greater losses in the carbon yield and damage to the narrow microporosity. Carbons regenerated in nitrogen exhibited greater adsorption capacities for the adsorption of small molecular size compounds (phenol) from solution, while carbons regenerated in steam adsorbed larger molecular size compounds (methylene blue) more effectively. However, when product yields were taken into consideration, inert regeneration was found to produce significantly better results than steam regeneration. An optimum process temperature was determined to be 950 degrees C.

Adsorption↗