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PubMedDate not supplied

[Inhibition of growth of B16 melanoma caused by liver regeneration].

Phenomenon of spontaneous regression of cancer indicates that recovery from malignant disease can happen without the application of any so far known therapeutic treatment. The most of the self-cured patients have undergone surgical operation which did not eliminate entire tumor or did not affect malignant tissue at all. Furthermore, regression or reversion of tumors (transformation of tumor cells into normal, nonmalignant cells) can be achieved in plants or amphibia after exposure of tumor cells to the influence of normal, regenerating tissue. Thus, it seems that during tissue regeneration certain local changes in tissue happen (synthesis of some regulatory growth factors) which induce dying of tumor cells or modify main features of malignant cells. Previously we have studied growth of murine malignant tumors in regenerating tissue of liver and skin. Obtained results indicated that under the influence of regenerating tissue anaplasia of fibrosarcoma decreases, as well as do pigmentation and the incidence of live cells in melanoma B16 tissue. Thus, it is obvious that mechanism of regenerating tissue growth control, which can also change characteristics of tumor cells, exists in mammalia, too. In order to analyse whether the same homeostatic mechanism is responsible for the phenomenon of spontaneous regression of human cancer, we have analysed the growth of melanoma B16 in back limb of nonoperated and sham or partially hepatectomized mice. Regeneration of skin and abdominal wall tissue in sham hepatectomized animals slowed down tumor growth, while liver regeneration completely inhibited tumor progression. Tumor growth inhibition was result of tumor tissue necrosis which developed around blood vessels. However, the structure and integrity of blood vessels themselves was normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Sodium channels in normal and regenerated feline ventral spinal roots.

Regenerated and remyelinated nerve fibers have shorter internodes and thus more nodes than normal mature fibers. This requires either a decrease in the number of sodium channels per node or an increase in the number of channels per fiber or both. The purpose of this investigation was to determine what happens to sodium channel number, as estimated by 3H-saxitonin (STX) binding, in regenerated fibers and to relate this to nodal number. Five adult cats underwent cryoaxotomy of ventral root levels L5, L6, L7, and S1 on the left side. After regeneration for 16-45 weeks, binding parameters were determined. On the right (control) side, binding was consistent with that in unoperated animals (b = 1.3, Bmax = 10.2 +/- 0.4 fmol/mg wet, Kd = 0.6 +/- 0.1 nM). However, the regenerated nerves showed a 3.5-fold increase in maximal binding (b = 1.3, Bmax = 36.1 +/- 0.5, Kd = 0.45 +/- 0.4). Computer-aided histologic analysis of the regenerated roots revealed a decrease in fiber size; a significant decrease in internodal length for fibers in a given size class; and a 1.35-fold increase in total fibers per root. These factors account for a 2.36-fold increase in nodes per milligram (wet). The number of STX binding sites per regenerated node was calculated to be 1.95 X 10(6) (1.31, 3.07, 95% confidence limits), whereas it was 1.26 X 10(6) (0.78, 2.02) for the control roots. The difference was not significant (p greater than 0.05). It is concluded that, in regeneration, the increase in nodal number is accompanied by an increase in sodium channels, so that the number of channels per node is normal or slightly increased. There is a marked increase in channels per fiber and an even greater increase in channels per anterior horn cell. The implications of these data for nodal reorganization in remyelination are discussed.

Animals↗
PubMed1989

Corneal nerve regeneration. Correlation between morphology and restoration of sensitivity.

Corneal nerve regeneration was determined in albino rabbits after deepithelialization of the cornea using heptanol. Regeneration was monitored up to 10 weeks by measuring corneal tactile sensitivity using an esthesiometer and by examining stromal and intraepithelial nerve patterns following gold chloride impregnation and acetylcholinesterase staining. Tactile sensitivity was much reduced, possibly absent, up to 2 weeks after wounding. From 2.5-4 weeks, sensitivity recovered rapidly to 60% of prewounding levels and remained unchanged thereafter. In control corneas, a distinct orientation of the basoepithelial leashes towards the nasal-most limbus was observed in the central two-thirds of the cornea. Three days after wounding, neurites that were oriented radially towards the wound center extended into the periphery of the wound area from just beyond the wound margin. At 1 week, regenerating axons were present as single neurites and in the form of modified leashes, mainly at the periphery of the wound area but also more towards the center. At 3 weeks, neurites, regenerated leashes and networks of terminals with terminal endings were found throughout the regenerated epithelium. Regional changes in the orientation of the regenerated leashes were observed also. No further change in the intraepithelial nerve pattern was detectable thereafter up to 10 weeks after wounding. It was concluded that partial restoration of tactile sensitivity following deepithelialization of the cornea is a function of the establishment of a near-normal nerve pattern in the regenerated epithelium and is correlated with the subnormal neural density observed in a previous study.

Acetylcholinesterase↗
PubMed1985

Regeneration of axons and synaptic connections by touch sensory neurons in the leech central nervous system.

In studies of axonal regeneration, it has been difficult to determine (a) whether growth along the normal pathway is important for restoration of connections with previous targets and (b) whether the new synapses resemble the old in strength and location. To address these problems at the level of individual nerve cells, we have studied touch (T) sensory neurons in the leech after their axons have been severed and we have confirmed that their axons regenerate electrical connections with some of their usual synaptic targets in the central nervous system. Injections of horseradish peroxidase and Lucifer Yellow dye into separate T cells in unoperated animals showed that T cell axons typically run close to one another within single ganglia or from ganglion to ganglion. Knowledge of one T cell's arborizations thus revealed the groundplan of others in the same ganglia and the sites of apparent contact with its synaptic targets. For regenerating axons, those sprouts that encountered the normal pathway (as marked by homologous axons) grew preferentially along it. Despite the striking coincidence of old and new pathways, regenerated branching patterns within the ganglionic neuropils were usually incomplete and sometimes had atypical branches. Synaptic connections with normal targets (other T cells as well as S and C cells) were abnormally weak physiologically. The numbers of apparent contacts seen with the light microscope were also lower than normal. In addition, the strength of the synaptic potentials, normalized to the number of contacts (calculated as microvolts per contact), was generally smaller in the regenerated connections than in the controls, and smallest at earliest times, during the first 6 weeks following injury. It thus appears to be characteristic of T cell regeneration that axon regrowth is aided by the recognition of specific pathways and that successful regeneration, as assayed anatomically and physiologically, occurs frequently but usually incompletely.

Animals↗
PubMed1988

A review of experimental methods measuring peripheral nerve regeneration in animals.

We have reviewed the morphologic, electrophysiologic, biochemical, and functional methods of evaluating PN regeneration in animal models. There are a large number of anatomic techniques that can provide clear insights into the processes of peripheral nerve regeneration. Since many of these are costly in terms of labor, careful selection of the technique appropriate for the question asked is important. Two of the more important questions are: 1) What are the neurotrophic factors produced by the distal segment that attract the growing axon tip? and 2) What are the components of the basal lamina that facilitate the directed growth of the axons? To answer these questions, whole mount preparations provide the means to economically evaluate the result of experimental manipulation of the environment. Automated nerve fiber counts will be increasingly used to help interpret electrophysiologic studies. Quantitative as well as descriptive ultrastructural analyses will continue to provide valuable data that will be needed in the interpretation of biochemical and histochemical studies. Immunohistochemical probes are sure to become more important as the range of their specificities broadens. With the diversity of anatomic methods available and their capacity to help us visualize the processes occurring during nerve regeneration they will remain a key tool in these studies. Electrophysiologic methods that integrate the CAP and correlate it with the number of functioning NF are most useful. Functional methods are beginning to become more objective and quantitative. The most precise measurements are muscle weight and the isometric response of muscle to tetanic contraction. Sensory function has now been measured objectively by Horch. Single methods of measuring PN regeneration give only limited data, but by combining methods a better understanding of PN regeneration is possible. While understanding the limitations of each method and technique, multi-parameter animal models may provide data most helpful clinically. However, because of great species variability in the reparative response, caution must be given not to extrapolate too much from animal studies. We urge investigators to use the most objective methods available to measure nerve regeneration. Recognizing these limitations, however, animal studies will continue to provide significant insights into PN regeneration and should point the way to improved clinical practice.

Animals↗
PubMed1986

Determinants of directional specificity in the regeneration of lamprey spinal axons.

The projection patterns of regenerating spinal axons in the larval sea lamprey (Petromyzon marinus) were determined by intracellular injection of HRP. Four hundred and eighty-six of 562 stained axons and axon-like neurites (87%) arising from Muller and Mauthner axons, giant interneurons, and dorsal cells terminated in an orientation similar to that of their counterpart control cells. Therefore, lamprey spinal axons regenerate selectively along their normal projection paths. During the first 4 weeks of recovery, i.e., before any had regenerated beyond the transection site, 91 of 114 axons and long neurites (80%) projected in the proper direction. Thus, the correctness of the final projection patterns did not result from selective retraction of randomly directed long neurites. When the cords were doubly transected 1 cm apart, orientation of regenerating neurites remained normal both within the 1 cm island and in the adjacent spinal cord. This suggests that the directional specificity of axonal regeneration was determined neither by the location of the scar nor by the availability of channels formed by the degenerating fibers. Finally, removing 1 cm of spinal cord eliminated potential synaptic targets for regenerating axons on either side of the lesion, but did not affect the direction of axonal growth. These findings are consistent with the hypothesis that the regeneration of lamprey spinal axons is guided by local chemical cues that persist long after the pathways are formed early in development.

Animals↗
PubMed1979

Effects of x-rays on nerve-dependent (limb) and nerve-independent (jaw) regeneration in the adult newt, Notophthalmus viridescens.

The newt limb requires nerves for successful regeneration, but the jaw appears to be nerve independent. Among the current hypotheses for the regeneration-inhibitory action of X-rays is one proposing inactivation of nerves as the main cause. We decided to test this hypothesis by comparing the irradiation levels necessary for inhibition of limb and jaw regeneration. Jaws and left front limbs were exposed locally to doses of ionizing X-irradiation ranging from 250 to 2000 R at least 6 weeks prior to amputation of the jaw and both front limbs. After 90 days post-amputation all surviving animals were examined grossly for signs of regeneration. In addition, some of the controls and most of those receiving 250, 500 and 1000 R were processed for histological examination. All unirradiated limbs and jaws supported regeneration. Those exposed to 250 R also regenerated, but a third of the jaws were hypomorphic. At 500 R and above, neither jaws nor limbs regenerated. Since both systems were affected by similar doses of X-rays, it appears that nerves are not the primary X-ray target in adult newts.

Animals↗
PubMed1981

Poly(adenosine diphosphoribose) polymerase activity and adenosine diphosphate ribosylation of proteins during pancreatic degeneration and regeneration.

The activity of poly(adenosine diphosphoribose) polymerase was measured in isolated rat pancreatic nuclei and was found to increase during pancreatic nuclei which follows an ethionine treatment, although a possible relationship of enzyme activity to the initial degenerative phase may also be considered. There is a 2-fold increase in the enzyme activity during the destruction process which remains high during the regeneration period. This increase of activity observed during regeneration is not related to a decrease of the polymer degradation. We have studied the adenosine diphosphate ribosylation of proteins during pancreatic regeneration, and we have found increases in the level of adenosine diphosphate ribosylations of these proteins just before regeneration and during the regeneration period. The in vivo adenosine diphosphate ribosylation of nuclear proteins does not correlate with synthetase activity measured in nuclei during the degeneration period but does correlate during the regeneration period and thereafter with the relative amount of enzymatic activity found in nuclei. Furthermore, as verified by autoradiography, labeling of the nuclei by polyadenosine diphosphoribose polymer shows a marked increase during regeneration.

Adenosine Diphosphate↗
PubMedDate not supplied

[Radioautographic study of nonhistone protein synthesis in the process of lens and retina regeneration in adult tritons].

The incorporation of 3H-tryptophane (3H-T) in the cell nuclei of pigment epithelium, retinal rudiment, iris and vitreous body has been studied during lens and retina regeneration in the adult smooth newts. A gradual increase (7 to 13-fold as compared with the control) of the intensity of labelling was found in the cell nuclei of pigment epithelium of the central part of fundus oculi. The cells of this zone are a source of regeneration. In the peripheral zones which do not participate in retina regeneration the intensity of 3H-T incorporation increased 2 to 4-fold only. The area of cell nuclei of pigment epithelium of the central part of fundus oculi increased, whereas that in the peripheral part suffered no changes. The cell nuclei of iris, retinal and lens rudiments incorporated 3H-T intensively. In the iris the most intensive labelling was shown in the inner layer of its dorsal zone which is a source of lens regeneration. The incorporation of 3H-T in the vitreous body was also found, thus suggesting both the secretion of vitreous body by the regenerating retina cells and the migration of some proteins secreted by the regenerating retina from its surface in the direction of a lens regenerating from the dorsal iris.

Animals↗
PubMed1981

Regeneration from duplicating fragments of the Drosophila wing disc.

It is a general rule that of two complementary Drosophila imaginal disc fragments, one regenerates and the other duplicates. This paper reports an investigation of an exception to this rule. Duplicating fragments from the periphery of the wing disc which lacked presumptive notum were found to regenerate notum structures during and after duplication. The propensity for this was greatest in fragments lying close to the presumptive notum, with the exception of a fragment confined to the posterior compartment, which did not regenerated notum. Structures were added sequentially, and regeneration stopped once most of the notum was present. These results are not easily explained by the polar coordinate model, which states that regeneration cannot occur from duplicating fragments. Since compartments appear to be involved in this type of regeneration as in others, it is suggested that a new type of model is required, one which permits simultaneous regeneration and duplication, and assigns a major role to compartments.

Animals↗
PubMed1980

Distal regeneration in proximal fragments of the wing disc of Drosophila.

The rules governing proximo-distal regeneration in the wing disc of Drosophila were investigated. It was found that proximal fragments confined to either anterior or posterior compartments could not regenerate distally, although many fragments having tissue from both compartments could do so even in the absence of circumferential regeneration. Fragments containing the ventral but not the dorsal end of the anterior-posterior border were able to regenerate distally. The use of a cuticular marker in the posterior compartment very close to the border permitted precise localization of the tissue required to cause anterio fragments to regenerate distally; in anterior fragments cut close to the border, there was an almost perfect correlation between possession of this marker and distal regeneration. It was found however, that distal regeneration was not an all-or-none phenomenon; its extent was dependent on the total amount of tissue present from both compartments.

Animals↗
PubMed1981

[Interrelation between protein synthesis and nucleo-cytoplasmic transport of messenger RNA in cells of rat livers in different stages of regeneration].

Synthesis of nonribosomal RNA was increased 2-2.5-fold in nuclei of rat liver cells at early steps of regeneration /2 days after partial hepatectomy/under conditions of protein synthesis inhibition by means of cycloheximide within 3 hrs. Amount of mRNA, transferred from nuclei into cytoplasm, was also 2-fold higher under these conditions as compared with control cells. The mRNA, transferred from nuclei into cytoplasm under the conditions of cycloheximide treatment of liver cells at early steps of regeneration, did penetrate the polyribosomes although the protein synthesis did not occur on the polyribosomes formed. At the later steps of regeneration /within 5 days after partial hepatectomy/ under the conditions of protein synthesis inhibition by cycloheximide within 3 hrs, formation of nonribosomal RNA was decreased by 40% in liver cell nuclei; amount of mRNA, transferred into cytoplasm, was also decreased by 40%. When the cycloheximide treatment was carried out during 1 hr, synthesis of nonribosomal RNA was increased 1.5-fold in liver cell nuclei at the later steps of regeneration although the amount of mRNA, transferred from nuclei into cytoplasm, was decreased by 30% as compared with the control cells. The data obtained suggest that during rat liver tissue regeneration a change occurred in the molecular mechanisms linking translation, biosynthesis and nuclear-cytoplasmic transport of mRNA of "tumoral" type/at early steps of regeneration/ or "normal type"/ at later steps of regeneration.

Animals↗
PubMedDate not supplied

Respiration during wound regeneration and healing in the planarian worm Dendrocoelum lacteum.

The intensity of respiration of the body fragments of the planarian after its division anteriorly and posteriorly to the pharynx was studied. After division anteriorly to the pharynx regeneration takes place. During regeneration of the anterior fragment respiration increases in the first day after the operation and at the differentiation stage. During regeneration of the posterior fragments the oxygen consumption is unchanged. Healing of the wound after division of the planarian posteriorly to the pharynx is accompanied by intensification of respiration during the first two days after the operation. Comparison of regeneration and healing of the wound in fragments of equal weight shows that in the initial stages the intensity of respiration was the same. A significant difference is found at the stage of differentiation of the regenerating worm, when the regenerating fragments have a higher intensity of respiration than fragments unable to regenerate.

Animals↗
PubMed1980

The effect of prolonged light and dark adaptation on lens regeneration in the adult newt Triturus viridescens.

Light intensity has been shown to affect lens regeneration in adult newts. Experiments were designed to study the effects of different light controlled environments on lens regeneration in the newt T, viridescens. Animals were preadapted to three light conditions: control, light from below and dark for ninety (90) days prior to lentectomy. The newts remained in the controlled environments post-lentectomy to test the effects of light preadaptation on lens regeneration. The results indicate that controlled light sources from below cannot stimulate the ventral iris to regenerate a new lens or inhibit the dorsal iris from normal lens regeneration. Lens regeneration in preadapted dark animals is similar in rate and amount to the control group indicating a totally dark environment does not always inhibit lens regeneration.

Adaptation, Ocular↗
PubMed1994

Tenascin expression in developing, adult and regenerating caudal spinal cord in the urodele amphibians.

Tenascin (Tn) protein and transcripts were analyzed in developing, adult and regenerating caudal spinal cord (SC) of Pleurodeles waltl. A polyclonal antibody (PAb) against Xenopus Tn and a newt Tn cDNA probe were used. In Western blots, anti-Tn PAb recognized Tn polypeptides of 200-220 kDa in tail regenerate extracts, but also the homolog of Tn/Cytotactin/J1 in brain and SC of adult newt. Immunofluorescence studies showed some reactivity around ependymoglial cells and strong labeling in the nervous tracts, in the developing as well as in the regenerating SC or adult SC. Immunogold electron microscopy revealed the presence of Tn throughout the ependymoglial cells, particularly near and along the plasma membrane of radial processes surrounding axons, especially growth cones. Tn could be more precisely found within rough endoplasmic reticulum and Golgi structures, or again in the surrounding extracellular space. This suggested that Tn was at least produced by radial glial profiles forming axonal compartments in which axons grew. Using the DNA probe for Tn, expression of Tn mRNA was also examined by Northern blot and RNAase protection analyses and by in situ hybridization, respectively. The levels of transcripts, barely detectable in adult tail, increased in regenerates from 3 days through 4-8 weeks post-amputation. In situ Tn mRNA were mainly localized in the mesenchyme, especially at the epithelial-mesenchymal interface, and in the developing cartilage, at the early regeneration stages, whereas high amounts of transcripts were seen not only at these stages, but also later, in the regenerating SC. Our main results supported the view that, in the caudal SC of newts, Tn, synthesized by radial ependymoglial cells, was similarly expressed during regeneration as well as larval development, and exhibited a sustained high accumulation level in the adult SC. On the basis of the multifunctional properties of Tn, the putative roles played by Tn as a substrate for neuronal pathfinding and boundary shaping were discussed.

Animals↗
PubMed1995

Coexpression of liver-specific and growth-induced genes in perinatal and regenerating liver: attainment and maintenance of the differentiated state during rapid proliferation.

The liver shows maximal cellular growth during fetal development and after partial hepatectomy. Exploring overlaps in gene expression patterns in these two types of hepatic growth may provide insight into common regulatory pathways. The expression of a large number of growth-induced and liver-specific genes induced in liver regeneration has been examined in the perinatal liver from several days prenatal to 4 weeks postnatal when the major growth phase of the liver ceases. As in liver regeneration, many growth-induced genes, such as PRL-1 and beta-actin, are expressed at a high level throughout the temporal course of liver development and correlate with the proliferative state. The level of fetal liver expression of these genes is similar to peak expression found in the regenerating liver, suggesting that common pathways of transcriptional regulation exist in the two types of proliferation. A subset of liver-restricted immediate-early genes including, IGFBP-1, CL-6, and glucose-6-phosphatase (G6Pase) are induced in regenerating liver and may be important in maintaining hepatic metabolism during regeneration. In developing liver, these genes are expressed primarily in the perinatal period but, unlike the regenerating liver, are not coinduced. For instance, at birth, G6Pase is induced, whereas CL-6 is downregulated. In situ analyses confirm that a proliferation associated gene PRL-1 is expressed in multiple cell types throughout the developing liver, whereas the expression of liver-specific genes is confined to hepatocytes. Taken together, these findings imply that significant similarities and differences in transcriptional regulation and hormonal milieu exist in liver during regeneration and development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[The effect of space flight factors on the cellular proliferative activity of different eye tissues during lens regeneration in the Spanish newt Pleurodeles waltlii].

The proliferative activity of the cells of various eye tissues was studied during lens regeneration in Pleurodeles waltlii under the influence of space-flight factors. After space-flight termination, the index of 3H-thymidine labelled nuclei increased reliably in the lens regenerate, in the ciliary zone of the iris, and in the growth zone of the retina, i.e., in the eye tissues that are not directly involved in formation of the regenerate cell population. The rate of increase in regenerate size was higher in the flight group than in the control. Enhancement of the proliferative activity of eye tissues, acceleration of lens regeneration, and the larger size of the regenerates are related to hormonal changes arising under the effect of space-flight factors. We propose that changes in calcium metabolism under the conditions of microgravity (in particular, increased prolactin production) accelerates the regeneration of both lens and limb in P. waltlii.

Animals↗
PubMed1995

Functional synaptic connections made by regenerated retinal ganglion cell axons in the superior colliculus of adult hamsters.

Regenerated synaptic connections in the damaged mammalian visual system were studied in adult hamsters in which retinal ganglion cells (RGCs) regrew their axons through autologous peripheral nerve grafts directed from the stump of the transected optic nerve to the superior colliculus (SC). Unitary responses to illumination of small areas of the visual field were recorded within the superficial laminae of the reinnervated SC 23 to 60 weeks after grafting. Each element of a typical bursting response to light consisted of a terminal potential (TP) (half width 164 +/- 25 microseconds, amplitude up to 171 microV) arising from a regenerated RGC axon terminal arborization, followed at a latency of 268 +/- 63 microseconds by a longer duration negative focal synaptic potential (FSP) (half width 938 +/- 396 msec, amplitude up to 188 microV) reflecting EPSPs in neurons within the terminal field of the regenerated RGC axon. The FSP but not the TP was attenuated in a dose-dependent manner by iontophoretic application of GABA. In some cases spikes arose from FSPs after the first two or three impulses of a train, presumably reflecting summation of EPSPs to threshold for excitation in SC neurons contacted by the regenerated RGC axon terminals. Up to one-third of the area of the SC can be infiltrated by arborizations of the regenerated RGC axons that enter the SC through a nerve graft inserted in the lateral aspect of the SC. These experiments indicate that terminal arborizations of individual regenerated RGC axons can synapse with multiple neurons in the SC and that convergence of inputs from regenerated RGC axons is not required for activation of SC neurons in response to light.

Animals↗