Effect of thirst challenge on ADH levels in patients with bilateral Menière's disease

The aim of the study was to investigate plasma ADH levels and plasma/urine osmolality in patients suffering from bilateral Menière's disease since a disturbance in the water household after thirst challenge is a suspected pathogenic factor in the development of this disease. In this study the plasma ADH levels and plasma/urine osmolality of bilateral Menière's disease patients under thirst challenge were investigated to show whether the water balance is affected. 9 patients with bilateral Menière's disease and 9 healthy controls skipped water intake for 12 h. Plasma ADH, plasma/urine osmolality, and electrolytes were measured after this thirst period as well as 8 h later after food and fluid intake. During food and fluid intake the patients demonstrated a slightly higher plasma ADH level and plasma osmolality than controls, whereas at the end of the thirst period patients and the controls showed no significant change. Instead the urine osmolality differed significantly (p<0.001): showing a high urine osmolality in controls and an almost stable urine osmolality in patients after thirst challenge. This indicates that the water balance in patients is likely different from that of controls. These observations point to ADH and its target aquaporine 2 as keyplayers in the pathophysiological events leading to the development of Menière's disease.     

Characteristics of differentiated CD8+ and CD4+ T cells present in the human brain

Immune surveillance of the central nervous system (CNS) by T cells is important to keep CNS-trophic viruses in a latent state, yet our knowledge of the characteristics of CNS-populating T cells is incomplete. We performed a comprehensive, multi-color flow-cytometric analysis of isolated T cells from paired corpus callosum (CC) and peripheral blood (PB) samples of 20 brain donors. Compared to PB, CC T cells, which were mostly located in the perivascular space and sporadically in the parenchyma, were enriched for cells expressing CD8. Both CD4⁺ and CD8⁺ T cells in the CC had a late-differentiated phenotype, as indicated by lack of expression of CD27 and CD28. The CC contained high numbers of T cells expressing chemokine receptor CX3CR1 and CXCR3 that allow for homing to inflamed endothelium and tissue, but hardly cells expressing the lymph node-homing receptor CCR7. Despite the late-differentiated phenotype, CC T cells had high expression of the IL-7 receptor α-chain CD127 and did not contain the neurotoxic cytolytic enzymes perforin, granzyme A, and granzyme B. We postulate that CNS T cells make up a population of tissue-adapted differentiated cells, which use CX3CR1 and CXCR3 to home into the perivascular space, use IL-7 for maintenance, and lack immediate cytolytic activity, thereby preventing immunopathology in response to low or non-specific stimuli. The presence of these cells in this tightly regulated environment likely enables a fast response to local threats. Our results will enable future detailed exploration of T-cell subsets in the brain involved in neurological diseases.     

Plasma levels of plasminogen activator inhibitor type 1, beta- thromboglobulin, and fibrinopeptide A before, during, and after treatment of acute myocardial infarction with alteplase

Plasma levels of plasminogen activator inhibitor type-1 (PAI-1), beta- thromboglobulin (beta TG), and fibrinopeptide A (FPA) were followed over 24 hours in 30 patients treated with alteplase for acute myocardial infarction. Samples were taken at baseline (T Oh), after 90 minutes (under alteplase, no heparin, T 1.5h), after 120 minutes (under alteplase and heparin, T 2h), 30 minutes after thrombolytic therapy (T 3.5h), as well as 12 hours (T 12h) and 24 hours (T 24h) after baseline. PAI-1 antigen levels (55 +/- 9 ng/mL at T Oh, mean +/- SEM) decreased to 35 +/- 5 (T 1.5h) and 40 +/- 6 (T 2h) ng/mL under alteplase, before increasing to 84 +/- 22 (T 3.5h), 130 +/- 30 (T 12h), and 64 +/- 7 (T 24h) ng/mL after therapy, P less than .001. A high baseline PAI-1 activity (18 +/- 3 ng/mL) decreased to 2.0 +/- 0.4 (T 1.5h) and 1.7 +/- 0.2 (T 2h) under alteplase and increased to 32 +/- 5 (T 12h) and 19 +/- 3 (T 24h) ng/mL after therapy (P less than .0001). beta TG levels (339 +/- 105 ng/mL at T Oh) decreased to 203 +/- 48 (T 2h), 154 +/- 51 (T 3.5h), 187 +/- 40 (T 12h), and 142 +/- 32 (T 24h) ng/mL under heparin (P less than .01). FPA levels (34 +/- 9 ng/mL at T Oh) increased to 85 +/- 15 ng/mL under alteplase alone (T 1.5h) and normalized under heparin (11 +/- 4, 6 +/- 2, 4 +/- 2, and 3 +/- 1 ng/mL at T 2h, T 3.5h, T 12h, and T 24h, respectively). A high level of FPA at T 3.5h correlated with reocclusion (33 +/- 12 ng/mL, n = 4 v 2.9 +/- 0.5 ng/mL, n = 21, P less than .005). We conclude that plasma levels of PAI- 1 antigen as well as activity markedly increase after alteplase therapy of acute myocardial infarction. The high activity of PAI-1 and decreasing beta TG levels suggest that platelets do not contribute significantly to this phenomenon. The marked increase of FPA levels under recombinant tissue-type plasminogen activator alone and its normalization under heparin emphasize the important role of concomitant anticoagulation in controlling further intravasal fibrin generation under alteplase.     

DLA-identical bone marrow grafts after low-dose total body irradiation: the effect of canine recombinant hematopoietic growth factors

Previous studies found that bone marrow (BM) allografts from DLA- identical littermates resulted in survival of two thirds of recipient dogs after otherwise lethal doses of 450 to 600 cGy of total body irradiation (TBI) because of successful allografts or autologous recovery after rejection of the allografts. The current study asked whether survival could be further improved by treating allograft recipients with recombinant canine granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), or G-CSF/SCF. Of 21 dogs, 14 (67%) receiving allografts but no growth factors survived, 10 with successful allografts (including 5 mixed chimeras) and 4 with autologous recovery; whereas 7 animals died, 5 from infections during BM aplasia and 2 from acute graft-versus-host disease. By comparison, 30 of 34 dogs (88%) receiving hematopoietic growth factors in addition to the BM graft survived, 17 with successful allografts (including 10 mixed chimeras) and 13 with autologous recovery; whereas 4 died, all with infection related to BM aplasia after rejection of the allograft. Survival was similar for recipients of G-CSF, SCF, or the combination of G-CSF and SCF. Logistic regression analyses, which accounted for possible effects of TBI dose, showed a trend for improved survival in dogs receiving growth factors (P = .09), no change in allogeneic engraftment (P = .74), and a slight increase in autologous recovery (P = .22). In agreement with previous data, we found that grafts of BM from DLA-identical littermates improved survival of recipient dogs exposed to low but otherwise lethal doses of TBI. A further improvement in survival could be achieved by additional treatment with G-CSF, SCF, or G-CSF/SCF. Results suggest that treatment by hematopoietic growth factors along with BM grafts should be considered for victims of radiation accidents.     

Association of impaired phosphatidylinositol 3-kinase activity in GLUT1-containing vesicles with malinsertion of glucose transporters into the plasma membrane of fibroblasts from a patient with severe insulin resistance and clinical features of Werner syndrome

The purpose of this study was to examine the molecular mechanism responsible for the defective insulin-stimulated glucose transport in cultured fibroblasts from a patient (VH) with clinical features of Werner syndrome and severe insulin resistance. Thus, in cells derived from VH, the subcellular distribution, structure, functional activity, as well as plasma membrane insertion of GLUT1 glucose transporters were analyzed. Furthermore, the insulin signal transduction pathway leading to activation of phosphatidylinositol (PI) 3-kinase as well as components of GLUT1-containing membrane vesicles were characterized. In fibroblasts derived from VH, GLUT1 glucose transporters were overexpressed by 8-fold in plasma membranes (PM) and by 5-fold in high density microsomes, respectively. Exofacial photolabeling revealed that only 14% of the overexpressed PM-GLUT1 transporters were properly inserted into the plasma membrane. The complementary DNA structure of the patient's insulin receptor and the GLUT1 glucose transporter, the intrinsic activity of plasma membrane glucose transporters, the tyrosine phosphorylation, as well as the protein expression of insulin receptor substrate-1/2 and p85 alpha/beta- and p110 alpha/beta-subunits of PI 3-kinase were normal. However, insulin-stimulated association of the p85 subunit of PI 3-kinase was defective in fibroblasts derived from VH compared to those from controls, and this defect was associated with a reduced IRS-1-dependent activation of PI 3-kinase by 50.2% and 63.6% after incubation for 5 and 10 min with 100 nmol/L insulin, respectively. Furthermore, immunodetection of small GTP-binding Rab proteins in subcellular membrane fractions indicated a decreased expression of Rab4 in total cellular homogenates as well as in high density microsomes by 70% and 58%, respectively. After preparation of GLUT1-containing vesicles, Rab4 was not detected to be a component of these vesicles. Analysis of the PI 3-kinase in GLUT1-containing membrane vesicles revealed insulin-dependent targeting of the p85 subunit to the vesicles immunoadsorbed from VH and control fibroblasts. Importantly, the association of the p85 subunit as well as the p85-immunoprecipitable PI 3-kinase activity were markedly reduced in GLUT1-vesicles derived from the patient. In conclusion, impaired PI 3-kinase activity in GLUT1-containing membrane vesicles derived from fibroblasts of VH is associated with a defective docking and/or fusion process of glucose transporters with the plasma membrane and thus might contribute to the molecular defect causing insulin resistance in this patient.