Pulp Region Research Articles

Tissue-specific autoregulation of the stat3 gene and its role in interleukin-6-induced survival signals in T cells.

Signal transducer and activator of transcription 3 (STAT3) mediates signals of various growth factors and cytokines, including interleukin-6 (IL-6). In certain IL-6-responsive cell lines, the stat3 gene is autoregulated by STAT3 through a composite IL-6 response element in its promoter that contains a STAT3-binding element (SBE) and a cyclic AMP-responsive element. To reveal the nature and roles of the stat3 autoregulation in vivo, we generated mice that harbor a mutation in the SBE (stat3(mSBE)). The intact SBE was crucial for IL-6-induced stat3 gene activation in the spleen, especially in the red pulp region, the kidney, and both mature and immature T lymphocytes. The SBE was not required, however, for IL-6-induced stat3 gene activation in hepatocytes. T lymphocytes from the stat3(mSBE/mSBE) mice were more susceptible to apoptosis despite the presence of IL-6 than those from wild-type mice. Consistent with this, IL-6-dependent activation of the Pim-1 and junB genes, direct target genes for STAT3, was attenuated in T lymphocytes of the stat3(mSBE/mSBE) mice. Thus, the tissue-specific autoregulation of the stat3 gene operates in vivo and plays a role in IL-6-induced antiapoptotic signaling in T cells.

Thioacetamide toxicity and the spleen: histological and biochemical analysis.

Exposure to thioacetamide is associated with the development of liver cirrhosis in experimental animals. In addition to liver, thioacetamide toxicity has been observed in other organs. In this study, the toxic effect of thioacetamide on the spleen was investigated at 0, 4, 8 and 12 weeks post-treatment durations. The level of tissue copper and selenium increased until the eighth week when a significant drop was observed. The zinc level was also increased but returned back to normal by week 8, thereafter it showed further increase. Calculation of the copper/zinc ratio showed an increase, but, recovered and returned to normal value by week 12. The level of manganese fluctuated until the eighth week. It then increased rapidly. Histological studies of the spleen tissue showed a significant increase in extramedullary haematopoiesis in the red pulp region and marked hyperplasia in the marginal zone and follicles. The results of this study, demonstrate an intimate association between trace element levels and spleen pathology, as observed in studies of other organs.

Histopathologic changes in the pulpal and periapical tissues after surgical removal of the coronal pulp chamber of rat lower molar

With the specific aim of the examination of tissue-damage and repair of surgically exposed pulp and periapical region in rat molar model, 14 female Sprague-Dawley rats were used. The coronal portion of lower first molars was surgically removed and the teeth remained untreated for 3 weeks prior to euthanasia of the animals. During this experimental period, all animals were injected with fluorochrome agents twice at the 12th and 19th days, in order to monitor formation of hard tissues in the exposed pulpal chamber and on the surfaces of cementum and alveolar bone. For histologic examination using microradiography and fluorescent and light microscopy, resin-embedded ground sections and serial decalcified sections were prepared. Observations revealed that: (1) over half of the surgically treated teeth gave rise to the formation of osteodentin so that the exposed pulp was partially covered; (2) the number of root canals filled with necrotic tissues was less than 25% of the total teeth examined, while the majority comprised vital granulation tissues and newly formed osteodentin, in certain cases with the appearance of odontoblastic cells aligning on the dentin wall; and (3) active deposition of cementum on the root apex and remodeling of alveolar bone were prominent in most of the treated teeth. The overall results support the contention that rat molar pulp has high potential activities for tissue-repair including hard tissue formation after pulpal exposure to the oral enviroment.

NK cell trafficking and cytokine expression in splenic compartments after IFN induction and viral infection.

Studies were undertaken to characterize mechanisms for NK cell cytokine delivery in vivo. Conditions of systemic IFN-beta expression elicited by polyinosinic-polycytidylic acid (poly(I:C)) treatment or IFN-alpha beta production during lymphocytic choriomeningitis virus or murine cytomegalovirus infections resulted in profound splenic histologic changes, with relocalization of nucleated cells from red to white pulp regions. Cell-trafficking experiments, with fluorescently labeled populations, showed that poly(I:C) induced T/B cell-dependent leukocyte migration into white pulp regions. Splenic leukocytes prepared from severe combined immunodeficient (SCID) and bone marrow cells prepared from SCID or normal C57BL/6 mice revealed a unique poly(I:C)-induced accumulation of non-T/non-B cells along splenic red and white pulp region borders characteristic of marginal zones. Lymphocytic choriomeningitis virus and murine cytomegalovirus infections also induced this trafficking pattern. Ab treatments of normal and SCID cell donor mice to eliminate specific cell subsets demonstrated that the unique migration of non-T/non-B cells was dependent upon cells with the NK phenotype, NK1.1+ AGM1+F4/80-. In situ hybridization showed that, at early times after infections, small proportions of cells along red and white pulp divisions expressed high levels of IFN-gamma mRNA, and that these cells were depleted by protocols eliminating NK cells. The results suggest an exciting model for induction of NK cell trafficking from bone marrow to secondary compartments. This migratory pattern may localize NK cells to receive additional activation signals and/or to precisely deliver NK cell-produced cytokines.

T helper cells in murine germinal centers are antigen-specific emigrants that downregulate Thy-1.

After immunization, activated splenic T cells proliferate in periarteriolar lymphoid sheaths (PALS) and subsequently migrate to the lymphoid follicle where they enter nascent germinal centers. Analysis of TCR V(D)J gene rearrangements indicates extensive emigration, frequently involving more than a single white pulp region. These migrants constitute a unique set of T helper cells that express antigen-specific alpha beta TCR, CD3, and CD4, but little or no Thy-1, a differentiation antigen present on the great majority of peripheral murine T lymphocytes. The origin of CD4+ Thy-1 follicular T cells appears to be the Thy+ population in the PALS, as both sets commonly share identical V(D)J rearrangements.

Immunolocalization of bone‐resorptive cytokines in rat pulp and periapical lesions following surgical pulp exposure

The bone-resorptive cytokines interleukin 1 (IL-1) and tumor necrosis factor (TNF) have been implicated in the pathogenesis of many chronic inflammatory diseases, including pulpitis and apical periodontitis.To further elucidate their role in these disorders, we have identified cells that express IL-1 alpha and TNF alpha in infected pulps and in developing rat periapical lesions after surgical pulp exposure. As detected by immunohistochemistry, IL-1 alpha- and TNF alpha-positive cells were present as early as 2 days after pulp exposure in both the pulp and periapical region. The numbers of cytokine-expressing cells increased up to day 4 in the pulp and up to day 30 in the periapex. In contrast, cells expressing IL-1 beta and TNF beta, the homologous forms of these mediators, were not found in pulp or periapical lesions during this period. Cells expressing IL-1 alpha and TNF alpha were identified primarily as macrophages and fibroblasts, with occasional staining of polymorphonuclear leukocytes. Osteoblasts and osteoclasts were also positive, whereas lymphocytes were negative. In general, cytokine-expressing cells were located proximal to abscesses and the root apex. These findings demonstrate that cells that express bone-resorptive cytokines IL-1 alpha and TNF alpha are present immediately after pulp exposure in this model, which supports the hypothesis that these mediators play a key role in pulpal and periapical pathogenesis, including the concomitant bone destruction. They also indicate that both resident connective tissue cells as well as infiltrating cells express bone-resorptive cytokines in response to infection in these lesions.

Neurovascular island pedicle flaps for terminal amputations and digital scars

Summary A volar island pedicle flap supplied by double neurovascular bundles is described in the treatment of terminal amputations and digital scars. Its use in selected cases is recommended including also elimination of anisthetic areas in the distal pulp region. Large flaps can be used for extensive digital tip defects and the method is applicable to multiple digital tip injuries.

THE INDUCTION OF GROWTH IN EXPLANTED TISSUE OF THE BANANA FRUIT

A method of obtaining proliferative growth of explanted fruit tissue from a number of cultivated varieties of bananas at different stages of development has been described.The explants weighing above 70 mg grow more rapidly than smaller pieces. Entire slices of the fruit, or only the axial part or pulp tissue have been cultured.A culture medium, as suggested by White, consisting of mineral salts, sucrose (2%), and vitamins, and solidified with 0.5% agar served as the basal nutrient medium. The chief supplements were various concentrations of casein hydrolysate; coconut milk; 2,4-D; benzothiazole-2-oxyacetic acid (BTOA); coumarin; 2,3,6-trichlorophenylacetic acid and other substituted phenylacetic acids; kinetin; adeninesulphate; and indoleacetic acid (IAA).The growth was recorded chiefly as the increment of fresh weight although dry weight and cell numbers were estimated in one experiment.Contrary to expectation the tissue from mature bananas responded better to the externally supplied growth substances than that from younger fruit. In fact the capacity for cell division did not decrease even in the pulp of the banana fruit as normally harvested for shipment. However, the tissue from postclimacteric fruit is incapable of any recrudescence of growth. Climacteric, therefore, seems to determine the point of no return beyond which the cells will not grow.Some growth occurred on the basal medium, but the best growth was obtained when 2,4-D; 2,3,6-TPA; or BTOA was added. Coconut milk increased the cell number but not markedly the fresh weight, depressed the effect of 2,4-D, but enhanced the response to 2,3,6-TPA. Among the numerous chloro-substituted phenylacetic acids tried, 2,3-; 2,6-; and 2,3,6-TPA were the most active. Adenine sulphate (in combination with IAA) enhanced the division of pulp cells.The ability to respond to the culture treatments is genetically controlled. Tissue from 'Lacatan' and 'Robusta'; 'T23' and 'T12' bananas of the same age and grown under identical conditions show a great deal of variation in their response to the different growth substances.It is the pulp region of the fruit which is most responsive to growth substances. A fluffy callus capable of being subcultured is produced from the pulp. Starch and other ergastic bodies are usually absent in the callus cells. No differentiation into organs has, however, been observed. The funiculi enlarge but do not form callus; the seeds are not affected.The utility of this technique for a further understanding of the problems of growth and senescence of fruits is discussed.When the explants were cultured in liquid media containing 2,4-D (with or without coconut milk) or 2,3,6-TPA in special glass tubes mounted on a wheel and slowly rotated around a horizontal shaft, a number of cells sloughed off into the bathing fluid. These were of diverse shapes and sizes. Aliquots of the liquid containing free cells have been successfully subcultured. However, under complete isolation and constant observation divisions in single cells were not observed.

The distribution of 91Y and the lesion by 91Y-beta-irradiation in spleen and liver of mouse

The rate of retention of Y/sup 91/ in spleen and liver after intravenous injection was about 20 times higher than after intraperitoneal injection, but the distribution pattern was similar, i.e., Y/sup 91/ was retained homogeneously in liver, but predominantly in the red pulp region in spleen. When mice were administered Y/sup 91/ intravenously at the rate of 3 mu c/g of body weight, the splenic weight was reduced exponentially with absorbed energy, and similarly, DNA content of spleen was decreased with tissue dose. These effects could be understood from consideration of disappearance of lymphocytes. RNA content of spleen was sensitively decreased. On the other hand, both the tissue weight and the nucleic acid content in liver showed scarcely any change. These studies indicate that liver and spleen result in different response against internal BETA radiation from Y/sup 91/, and thus, the general information that liver is radioresistant and spleen is radiosensitive can be fully accepted. (auth)

A developmental anomaly in the form of an occlusal tubercle with central canal which serves as the pathway of infection to the pulp and periapical region

A developmental anomaly in the form of an occlusal tubercle with central canal which serves as the pathway of infection to the pulp and periapical region