Overcrowding-mediated stress alters cell proliferation in key neuroendocrine areas during larval development in Rhinella arenarum.

Exposure to adverse environmental conditions can elicit a stress response, which results in an increase in endogenous corticosterone levels. In early life stages, it has been thoroughly demonstrated that amphibian larval growth and development is altered as a consequence of chronic stress by interfering with the metamorphic process, however, the underlying mechanisms involved have only been partially disentangled. We examined the effect of intraspecific competition on corticosterone levels during larval development of the toad Rhinella arenarum and its ultimate effects on cell proliferation in particular brain areas as well as the pituitary gland. While overcrowding altered the number of proliferating cells in the pituitary gland, hypothalamus, and third ventricle of the brain, no differences were observed in areas which are less associated with neuroendocrine processes, such as the first ventricle of the brain. Apoptosis was increased in hypothalamic regions but not in the pituitary. With regards to pituitary cell populations, thyrotrophs but not somatoatrophs and corticotrophs showed a decrease in the cell number in overcrowded larvae. Our study shows that alterations in growth and development, produced by stress, results from an imbalance in the neuroendocrine systems implicated in orchestrating the timing of metamorphosis.

Formation of synapses between dendritic cells and lymphocytes in skin lymph in an allogeneic reaction.

Skin is an important component of a composite tissue allograft and is considered among the most immunogenic of tissues. Because of the skin's high degree of immunogenicity, until recently it was widely assumed that the dosage of immunosuppressive drugs required to prevent rejection was too high to be used safely in the clinical setting. The mechanism of resistance of skin allografts to pharmacological immunosuppression remains unknown. We investigated this problem at the level of antigen presentation by graft dendritic cells to recipient lymphocytes. Cells obtained from lymph draining skin were used and formation of synapses, necessary for antigen presentation, in the presence of CsA or FK506 was studied. The study provided the following information: a) increased frequency of allogeneic compared to syngeneic DC-L synapses in culture, b) increased expression of CD49d on lymph allogeneic DC and L and of HLA DR on L forming synapses, c) lack of a downregulating effect of CsA on the allogeneic DC-L synapse formation rate, d) decreased formation rate of autologous and allogeneic DC-L synapses and lower expression of CD49d and HLA DR of cells treated with FK506. The suppressive effect of FK506 on DC-L synapses formation may explain the mechanism of effectiveness of this drug on skin allograft survival.

Skin allografts--lymph veiled (dendritic) cells are responsible for initiation of rejection in canine skin/SCID mouse chimera model.

Skin allografts are acutely rejected despite of intensive immunosuppressive therapy. Resistance of skin dendritic cells to immunosuppressive drugs and irradiation may be responsible for this phenomenon. Skin allograft is a site of interaction between the dendritic cells and lymphocytes of the donor and host origin and "direct" and "indirect" pathway of antigen presentation. Increasing evidence supports the significant role for the "indirect" allorecognition in graft rejection. To investigate a critical role of skin dendritic cells in the "indirect" allorecognition and graft destruction we have used a canine skin to severe-combined-immunodeficient (SCID)-mice transplantation model. At the time the skin grafts were deprived of own dendritic (Langerhans) cells, SCID mice were reconstituted with allogeneic canine whole lymph leukocytes, lymph lymphocytes, lymph veiled (dendritic) cells or peripheral blood mononuclear cells, and an early phase of skin rejection was evaluated in histopathological studies. We demonstrated that circulating canine allogeneic veiled cells facilitate recruitment of T lymphocytes into skin graft and promote an extensive graft destruction, compared to the less expressed effect of allogeneic peripheral lymph lymphocytes or blood mononuclear cells. These drug and radiation-resistant dendritic cells may be responsible for initiation of the difficult to control rejection process.

[Spontaneous splenic rupture as a complication of infectious mononucleosis]. / Samoistne pekniecie sledziony w przebiegu mononukleozy zakaznej.

Spontaneous splenic rupture as a complication of infectious mononucleosis in 17-years old man was described. Clinical manifestations of infectious mononucleosis were typical without any sign of the splenic rupture. At the end of third week of the disease sonographic investigation revealed subcapsular hematoma of the spleen without overt rupture. The patient was observed. Five days later in the next sonographic investigation the second hematoma of the spleen appeared. Patient was treated underwent splenectomy and he remain alive and well. Authors suggest that in cases with subcapsular hematoma of the spleen splenectomy remains the treatment of choice. Mononucleosis patients with significant enlarged spleen should be observed very carefully. Authors propose control sonographic investigation in 3rd or 4th week of the disease in those cases.