Post-traumatic regeneration of the epithelium of the gastric and intestinal mucous membranes of dogs

The work was devoted to the study of the sources of reparative regeneration of the epithelium of the gastric and intestinal mucosa. A number of surgical interventions on the stomach and intestine of 1 dogs were performed for the solution of this problem. On the basis of the investigations carried out the leading role in the regeneration of the gastric and intestinal mucosa was found to be played by uninjured epithelium surrounding the area of the surgical intervention. This was confirmed by the fact that a mucosa-free intestinal pedicle graft implanted into the defect of the wall of the stomach was covered by gastric mucosa; a stomach graft devoid of own mucosa became covered with intestinal mucosa when displaced in the form of a cylindrical "insertion" into the intestinal tube; mucosa-free stomach pouch became obliterated; this could be reliably attributed to the absence of the main source of regeneration -- uninjured mucosal epithelium along the periphery of the defect. No regeneration of the epithelium of the gastric mucosa from the implanted cells was revealed; this served as an additional confirmation of the fact that regeneration under conditions of the mentioned experiments occurred on account of creeping of epithelial cells surrounding the area of the surgical intervention over the free surface of mucosa.     

Expression of the third component of complement, C3, in regenerating limb blastema cells of urodeles

In this study we have shown that complement component C3 is expressed in the regenerating tissue during urodele limb regeneration. C3 was expressed in the dedifferentiated regeneration blastema and in the redifferentiated limb tissues in the axolotl, Amblystoma mexicanum, and in Notophthalmus viridescens. This expression was verified by immunofluorescent staining using an Ab against axolotl C3 and by in situ hybridization with an axolotl C3 cDNA probe. In the early stages of regeneration C3 appeared to be equally present in all mesenchymal cells and in the wound epithelium, whereas in the later stages it was mainly expressed in the differentiating muscle cells. Since no expression was seen in the developing limb, it appears that the C3 expression was specific to the regeneration process. We then demonstrated by hybridization experiments that a blastema cell line of myogenic origin expresses C3. All these findings implicate C3 in the dedifferentiation process and may indicate a new role for this molecule in muscle differentiation.     

Cell sources, regulatory factors and gene expression in the regeneration of the crystalline lens and retina in vertebrate animals

Over the past century extensive experimental materials have been accumulated concerning cell sources of lens and retina regeneration, successive transformations of the cells, regulatory factors, and gene expression during restitution of these eye structures. The use of nuclear and cytoplasmic markers provided convincing evidence that the removed lens is restituted from the dorsal iris cells in vivo or from embryonic cells of the pigment epithelium and retina in vitro. The removed or destroyed retina is restituted as a result of transdifferentiation of the pigment epithelium cells in amphibians, fish, birds, and mammals during embryogenesis, in larvae of some anuran amphibians, and in adult newts. Cell precursors of rods are a cell source of retina regeneration in adult fish. A subpopulation of randomly distributed cells, which are a cell source of rod formation during the normal development of the eye was found in the external nuclear layer with the use of electron microscopy and nuclear and cytoplasmic markers. These cells are not only a source of regeneration of rods, but also of cones and cells of the internal nuclear layer after destruction of the corresponding retina layers. There is a peripheral growth area in the retina of vertebrates, where multi- and unipolar cells are localized, which provide for the retina growth during ontogenesis. A paradox of retina regeneration consists in that these little differentiated cells are not a source of complete restitution of the removed or destroyed retina. They make only a small contribution to its regeneration corresponding to the growth potential of cells of this eye region, while restitution of the retina proceeds only at the expense of cells of another type of differentiation. A factor controlling the differentiated state of the cell was found in the dorsal iris during studies of lens regeneration. Removal of this factor in the early stages of cell transformations leads to the initiation of lens regeneration. The factor is not specific and was identified in many cells of vertebrates, including the pigment epithelium and limb tissues, which, as is known, may be fully restituted. Studies of gene expression during lens and retina regeneration are now at the initial stage. The greatest advances were achieved on the model of transdifferentiation of the pigment epithelium cells of chick embryos into lentoids. Expression of genes MMP115 and pP344 was established in the pigment epithelium cells, which characterize the pigmented phenotype of the initial cells. Expression of the alpha-, beta-, and delta-crystallin genes was found in the lentoids, which characterize the phenotype of regenerating structures. The gene activity appears to be switched at an intermediate stage during cell dedifferentiation. Expression of the gamma-crystallin genes during lens regeneration in adult newts is initiated after completion of dedifferentiation and cell proliferation in the dorsal iris. The genes specifically expressed in the dorsal and ventral iris and in the retina rudiment have been identified by the method of gene subtraction. Expression of homeobox-containing genes from the family of PAX genes was found during lens regeneration in adult newts and retina regeneration in adult fish. The role of growth factors (FGF) as morphogenetic factors was proved, which are involved in a yet unknown way of altering the differentiation pathway of the initial cells during formation of the neuroepithelium rudiment in chick embryos, adult newts, and fish.     

Clinical and histologic observation of replacement of biphasic calcium phosphate by bone tissue in monkeys

Biphasic calcium phosphate, consisting of beta-tricalcium phosphate and hydroxyapatite, was implanted in wide and deep periodontal osseous defects of monkeys in combination with the guided tissue regeneration technique. After 12 weeks, sites treated with a combination of biphasic calcium phosphate and guided tissue regeneration maintained the shape of the ridge, but both guided tissue regeneration and control sites (untreated) showed extreme resorption. A histopathologic investigation revealed that numerous macrophages contained small particles of ceramic within their vesicles and the active bone replacement occurred from the surrounding bone. Biphasic calcium phosphate has osteoconductive potential and this potential may be related to degradation by macrophage phagocytosis.     

Ultrastructure of the granulomatous reaction against Descemet's membrane (author's transl)

Ultrastructural findings in regard to the so-called granulomatous reaction against Descemet's membrane indicate that the membrane is phagocytized in the form of small clumps. Basically epithelial cells and, to a lesser extent giant cells, participate in the phagocytosis. In addition to the connective tissue, the epithelium is fairly actively involved in the regeneration of the cornea.     

Rectal mucosal stripping: a technique for preservation of the rectum after total colectomy for chronic ulcerative colitis

Rectal mucosal stripping is a technique for removal of diseased tissue secondary to chronic ulcerative colitis. It is a technique for the preservation of a functional rectum following a total colectomy. Subsequent mucosal regeneration can allow ileorectal anastomosis without fear of recurrent disease and with maintenance of general health and acceptable gastrointestinal tract function.     

Application of a hybrid computational fluid dynamics and physiologically based inhalation model for interspecies dosimetry extrapolation of acidic vapors in the upper airways

This study provides a scientific basis for interspecies extrapolation of nasal olfactory irritants from rodents to humans. By using a series of short-term in vivo studies, in vitro studies with nasal explants, and computer modeling, regional nasal tissue dose estimates were made and comparisons of tissue doses between species were conducted. To make these comparisons, this study assumes that human and rodent olfactory epithelium have similar susceptibility to the cytotoxic effects of organic acids based on similar histological structure and common mode of action considerations. Interspecies differences in susceptibility to the toxic effects of acidic vapors are therefore assumed to be driven primarily by differences in nasal tissue concentrations that result from regional differences in nasal air flow patterns relative to the species-specific distribution of olfactory epithelium in the nasal cavity. The acute, subchronic, and in vitro studies have demonstrated that the nasal olfactory epithelium is the most sensitive tissue to the effects of inhalation exposure to organic acids and that the sustentacular cells are the most sensitive cell type of this epithelium. A hybrid computational fluid dynamics (CFD) and physiologically based pharmacokinetic (PBPK) dosimetry model was constructed to estimate the regional tissue dose of organic acids in the rodent and human nasal cavity. The CFD-PBPK model simulations indicate that the olfactory epithelium of the human nasal cavity is exposed to two- to threefold lower tissue concentrations of a representative inhaled organic acid vapor, acrylic acid, than the olfactory epithelium of the rodent nasal cavity when the exposure conditions are the same. The magnitude of this difference varies somewhat with the specific exposure scenario that is simulated. The increased olfactory tissue dose in rats relative to humans may be attributed to the large rodent olfactory surface area (greater than 50% of the nasal cavity) and its highly susceptible location (particularly, a projection of olfactory epithelium extending anteriorly in the dorsal meatus region). In contrast, human olfactory epithelium occupies a much smaller surface area (less than 5% of the nasal cavity), and it is in a much less accessible dorsal posterior location. In addition, CFD simulations indicate that human olfactory epithelium is poorly ventilated relative to rodent olfactory epithelium. These studies suggest that the human olfactory epithelium is protected from irritating acidic vapors significantly better than rat olfactory epithelium due to substantive differences in nasal anatomy and nasal air flow. Furthermore, the general structure of the hybrid CFD-PBPK model used for this study appears to be useful for target tissue dosimetry and interspecies dose comparisons for a wide range of inhaled vapors.     

A histological study on tissue responses to titanium implantation in rat maxilla: the process of epithelial regeneration and bone reaction

The present study aimed to establish a titanium implantation model using rat maxillae as well as demonstrate the chronological tissue responses to implantation. Pure titanium implants were inserted in the upper first molar extraction sites of Wistar rats 1 month after tooth extraction. The animals were sacrificed at 1 to 30 days postimplantation, and prepared tissue specimens were processed for light microscopy. The removal of implants from tissue blocks was done using 2 methods: mechanical removal or a cryofracture technique. In the early stages, peri-implant tissues showed severe damage to the oral epithelium and collagen bundles with significant inflammatory cell infiltration. The peri-implant epithelium grew apically along the implant by 10 days postimplantation, and regenerated to show a similar feature of junctional epithelium seen in normal rats at 15 days postimplantation, at which time no signs of inflammation were observed. The regenerated collagen bundles in the connective tissue were arranged circumferentially to the implants in the horizontal sections. New bone formation first appeared around the implants at 5 days postimplantation, covering the entire perimeter of implants by 30 days postimplantation. Scanning electron microscopic observations of the surface texture of the removed implants suggest the probability of an adhesive mechanism between the implants and the peri-implant epithelium and/or the alveolar bone. These findings indicate that this experimental model is useful for detailed analysis of peri-implant tissue because of its easy implantation procedure.     

Overview of ethical issues perceived by allied health professionals in the workplace

Intestinal lymphoid tissue has a complex interrelationship with the epithelium. The epithelia of intestinal crypts associated with lymphoid aggregates have an increased proliferation rate. In the present study, the authors tested the hypothesis that organized intestinal lymphoid tissue (Peyer's patches) enhances intestinal regeneration by studying this process with and without an adjacent Peyer's patch. Forty adult male Sprague-Dawley rats had full-thickness ileal defects patched with cecal serosa to allow regeneration of ileal mucosa. Control animals (group I) had the patch constructed adjacent to a Peyer's patch, whereas this Peyer's patch was excised in group II. Intestinal regeneration in both groups was evaluated on the third, fifth, seventh, and ninth days after operation. During the early phase of regeneration, both epithelial cell proliferation and migration were decreased in the patched defect after excision of the Peyer's patch. Crypt cell production rate in the adjacent normal mucosa also was decreased after excision of the Peyer's patch. Excision of the Peyer's patch resulted in less well-developed crypts and villi. Wound contraction, however, was greater in the intestinal defect adjacent to the Peyer's patch until day 7. In conclusion, Peyer's patches have a facilitative effect on the healing of intestinal wounds by promoting both epithelial cell migration on the defect and epithelial cell proliferation in the crypts adjacent to the wound and by decreasing the rate of wound contraction. These findings support a role for intestinal lymphoid tissue in the regulation of epithelial cell maintenance.     

Amelioration of virulent Babesia bovis infection in calves by administration of the nitric oxide synthase inhibitor aminoguanidine

The expression of synaptosomal-associated protein (SNAP-25), neural growth-associated protein (GAP-43) and neural cell adhesion molecule (NCAM) were studied in mouse olfactory cells and axons for 2 weeks following unilateral bulbectomy. The olfactory cells and axons in the control olfactory epithelium were positive for SNAP-25 but levels decreased in the atrophic olfactory epithelium 3 days after bulbectomy. There was no expression of SNAP-25 in the olfactory epithelium on the bulbectomy side 7 days after bulbectomy, indicating that this protein may be a good marker for the degeneration of olfactory cells. The expression of NCAM was still found in the atrophic olfactory epithelium at 7 days after bulbectomy, while the expression of NCAM in the olfactory epithelium of the bulbectomy side was stronger than that on the control side at 14 days after bulbectomy. The expression of GAP-43 in the olfactory axonal bundles of the bulbectomy side at 3 and 4 days after bulbectomy was stronger than that on the control side. These results suggest that upregulation of NCAM may be related to the regeneration of the olfactory cells, with upregulation of GAP-43 probably playing a role in axonal regeneration after bulbectomy.     

Study of the action of tamoxifen on the mammary gland epithelium of premenopausal patients by lysosome quantification

Tamoxifen is an antiestrogen drug widely utilized for the adjuvant hormonal treatment of breast carcinoma. Its use in the primary prophylaxis of this disease is currently being proposed. Although the drug has few side effects, its precise action on breast tissue that has not undergone neoplastic transformation has not been fully elucidated. This prospective, randomized study assessed the estrogen activity of tamoxifen on the mammary gland epithelium of premenopausal patients using a quantitative analysis of mammary epithelium lysosome identified by the cytochemical technique of GOMORI for acid phosphatase and by light microscopy. Tamoxifen significantly increased the number of lysosomes only during the secretory phase of the menstrual cycle. We concluded that the early effect of the drug on normal mammary tissue is synergistic with the effect of estrogen during the premenopausal period.     

Elucidation of the mechanism of retinal degeneration and regeneration and the prospects for its clinical application

In order to obtain the basic knowledge necessary to develop therapeutical intervention for blindness due to the damaged retina and optic nerve, the mechanism of retinal degeneration and regeneration in an amphibian model, Cynops pyrrhogaster, was studied. In the retinal degenerative process following enucleation and reimplantation of the eye ball, evidence was found for active cell death of neural retinal cells. As the degeneration proceeded, Musashi, an ribonucleic acid (RNA)-binding protein, started its expression in the daughter cells of proliferating retinal pigment epithelium (RPE) cells, messenger RNA (mRNA) expression of proneural genes with basic helix-loop-helix motif was then detected in the newly developing retina. These results suggest that transdifferentiation of RPE cells to neural retina involves at least partial cascade, if not entirely, of neural induction from uncommitted ectodermal tissue. Search for genes that are required for transdifferentiation of RPE cells to neural retinal cells, in addition to those mentioned above, will provide the basic knowledge for successful retinal transplantation and retinal regeneration in higher vertebrates.     

The induction of lipid peroxidation in the serum of patients with acute peritonitis

Wound-healing activity of 2% betamicil ointment in comparison with the traditional stimulants of corneal repair regeneration (methyluracyl and solcoseril) was studied in experiments. The rate of epithelialization of a standard trephination wound in rabbit cornea (28 animals), mitotic activity of the anterior corneal epithelium, and strength of the regenerated tissue were assessed after use of different stimulants and in control. A maximal positive effect of local betamicil (2% ointment) was observed: the wounds epithelialized 57% sooner than in control, but there was no reliable difference from solcoseril; the regenerate of linear corneal wound was 1.5 times stronger. Use of this ointment in ophthalmology is validated.     

The synthetic leu-enkephalin--dalargin--in the therapy of the irritable bowel syndrome and chronic noninfectious undefined colitis

The author proceeds from the belief that it is the dystrophic changes and disturbances in the regeneration of the intestinal epithelium that play a decisive role in the pathogenesis and morphogenesis of irritable intestinal syndrome and chronic non-infectious undefined colitis. The above alterations develop secondary to the action of harmful factors and disturbed trophic influences of neurohumoral systems of regulation during different stages of stress. At the same time the synthetic leu-enkefalin dalargin is endowed with a marked antistressor activity as well as ability to strikingly improve the regeneration of the epithelium. This was reason why therapeutic efficacy of dalargin has been given a trial in the above pathologies. Positive dynamics of symptoms of the conditions in question has been shown as well as of the histologic picture of colonic mucosa biopsies during the course of treatment of the above ailments with dalargin.     

Experience with allografts in the surgery of peripheral nerves (experimental study)

Peroneal nerve allografts four to seven cm in length were transplanted in 36 tissue typed beagle dogs, using a standard microsurgical technique. The influence of tissue typing on nerve regeneration through these grafts was studied with the help of electromyography and histology seven to nine months after nerve implantation. Better regeneration was found through the grafts with compatible than with noncompatible typing. The favourable effect of tissue compatibility became more evident when the length of the graft was longer than four cm. Tissue rejection reaction was much more marked and evident with longer grafts in noncompatible than in compatible groups. Radiation, with tissue typing, did not seem to confer any additional beneficial effect. Compatible tissue typed nerve allografts probably behave more like autografts.     

Regenerative periodontal therapy in mucogingival surgery for root coverage

This article illustrates the potential benefits of regenerative periodontal therapy in mucogingival surgery and esthetic dental treatment. Cases are described in which the treatment of soft-tissue recessions and root exposures are treated with surgical procedures where both clinical soft-tissue augmentation and the regeneration of periodontal attachment are obtained. Cases are also presented to illustrate the clinical application of guided tissue regeneration. Resorbable and nonresorbable barriers are placed over the root surface and bone and covered by the overlying flap, which allows the selective repopulation of the lesion by progenitor cells and the inhibition of a long junctional epithelium. Emphasis is placed on regenerative procedures in soft-tissue augmentation, particularly with respect to rationales, techniques, and indications.     

Cellular mechanisms of intestine regeneration in the sea cucumber, Holothuria glaberrima Selenka (Holothuroidea:Echinodermata)

Echinoderms are the deuterostome group with the most striking capacity to regenerate lost body parts. In particular, members of the class Holothuroidea are able to regenerate most of their internal organs following a typical evisceration process. Such formation of new viscera in an adult organism provides a unique model to study the process of organogenesis. We have studied this process in the sea cucumber Holothuria glabberrima by describing the spatial and temporal pattern of cellular events that occur during intestine regeneration following chemically induced evisceration. Regeneration begins as a thickening of the mesenteries that supported the autotomized organs to the body wall. The mesenterial thickening consists of tissues where most of the cellular populations found in the normal intestine are already present. However, the cell numbers differ, particularly those of hemocytes and amoebocytes, suggesting that some of these cells play an important role in the formation of the solid rod of hypertrophic mesentery that characterizes the intestinal primordia. The appearance of the luminal epithelium, together with the formation of the lumen, occurs during the second week of regeneration by proliferation and extensive migration of cells from the esophagus and cloacal ends into the thickenings. At this stage all tissue layers are present, but it takes an additional week for them to exhibit the proportions typical of the normal organ. Cell division, as determined by BrdU labeling, mainly occurs in the coelomic epithelia of the hypertrophic mesentery and in the regenerating luminal epithelium. Our study provides evidence that the process of new organ formation in holothurians can be described as an intermediate process showing characteristics of both epimorphic and morphallactic phenomena.     

The GTR technic within the framework of combined periodontal-orthodontic treatments. A case report

Periodontal defects in adolescents or young adults are often an incidental finding within the framework of orthodontic treatment. Often these patients are suffering from a special form of periodontal disease, juvenile periodontitis. Guided tissue regeneration (GTR) offers a technique for long-term therapy in such cases. In the case presented here, the periodontal problems were aggravated by malpositioning of the affected teeth. Orthodontic and periodontal treatment enabled the malpositioning to be corrected and the osseous defects to be largely regenerated. Controls on regular bases up to now revealed a stable status over 2 years.     

Membrane anchoring: an alternative technique

A technique for stabilizing membranes used in guided tissue regeneration is described. The technique does not require the purchase of new armamentaria or the acquisition of new skills.