Synaptic vesicle dynamics in the mossy fiber-CA3 presynaptic terminals of mouse hippocampus

The mossy fiber (MF)-CA3 synapse in the hippocampus is unique in the CNS because of its wide dynamic range of transmitter release during short- and long-term plasticity. The presynaptic mechanisms underlying the fidelity of transmission were investigated for the MF-CA3 synapses. The relative size of readily releasable pool (RRP) of vesicles was estimated by counting the number of docked vesicles at an active zone (AZ) on the transmission electron microscopy (TEM) image. The size of the releasable pool and the exo-endocytosis kinetics were directly measured from individual large MF boutons in hippocampal slices of transgenic mice that selectively express synaptopHluorin (SpH), a pH-sensitive GFP fused to the lumenal aspect of one of the vesicular membrane proteins, VAMP-2, in these boutons. Here we found (1) there are distinct two vesicle pools, the resting pool which is resistant to exocytosis, and the releasable pool, (2) the initially docked vesicles are easily depleted and the RRP is maintained by refilling from the reserve subpopulation of releasable pool ("reserve" releasable pool), and (3) the contribution of rapid reuse of recycled vesicles is relatively small. Therefore, the fidelity of transmission is suggested to be ensured by the rapid refilling rate of RRP.     

Effects of streptozotocin-induced diabetes on circulating levels of vitamin D metabolites

In order to investigate vitamin D metabolism in insulin-deficient diabetic rats, plasma vitamin D metabolites were measured at various periods after induction of diabetes by iv administration of 60 mg/kg streptozotocin (STZ). After STZ injection, plasma insulin was significantly decreased and plasma urea nitrogen increased with the duration of diabetes, while plasma creatinine remained unchanged. Plasma calcium, 25-dihydroxyvitamin D (25(OH)D), and 24,25-dihydroxyvitamin D (24,25(OH)2D) progressively decreased. On the other hand, plasma 1,25-dihydroxyvitamin D (1,25(OH)2D) did not change at any period, but the ratio of 1,25(OH)2D to 25(OH)D became high in proportion to the severity of hypocalcaemia. Since significantly lower 25(OH)D and 24,25(OH)2D levels were observed at the later stage of diabetes, it is suggested that the altered vitamin D metabolism in diabetes is secondary to the disturbances in metabolic homeostasis derived form the insulin deficiency.     

Antibody-producing cells: virus-induced alteration of response to antigen.

Spleen antibody-forming cells of mice yield a 3- to 10-fold increase in their response to sheep erythrocyte antigen if they are acutely infected by lactate dehydrogenase-elevating virus. This early stimulation is replaced by a long-term inhibition of the antibody-forming cells as the viremia goes into its persisting chronic stage. These contrasting immunological phenomena are examined as contributing factors responsible for the enhancement by this virus of asparaginase (EC 3.5.1.1; L-asparagine amidolydrolase) therapy against leukemia in mice, and for the alteration of the susceptibility of mice to various neoplastic processes.     

Cell surface phenotyping of megakaryoblasts

Surface phenotypic characterization of megakaryoblasts, identified by platelet peroxidase activity, was investigated in four patients who showed increased proliferation of megakaryoblasts: one patient with typical features of acute leukemia, one presenting with acute myelofibrosis, and two with Down's syndrome in whom blasts disappeared spontaneously (transient abnormal myelopoiesis, TAM). MY10 and/or MY9 antigens were expressed on the surface of some megakaryoblasts, but MY7, and MY4, antigens specific to granulocytic or monocytic cells, were not. Some megakaryoblasts were positive for only anti-HLA-DR antibodies. It was speculated that, during the differentiation of the megakaryocytic lineage, MY9 antigen appears transiently on the surface of megakaryoblasts that have lost HLA-DR antigens and have gained the glycoprotein IIb/IIIa antigen. This study also demonstrated that the proliferating blasts in some patients with TAM were mainly megakaryoblasts and suggested that the target cells in TAM are CFU-GEMM.     

Echocardiographic characteristics predicting efficacy of drug therapy in patients with hypertrophic obstructive cardiomyopathy

BACKGROUND: The efficacy of long-term drug therapy for patients with hypertrophic obstructive cardiomyopathy (HOCM) remains unclear. This study was performed to characterize the echocardiographic findings of patients responsive to drug therapy. METHODS: Left ventricular outflow tract (LVOT) gradient and morphologic characteristics of the septum, posterior wall, and mitral valve were measured echocardiographically in 35 Japanese patients. The mean follow-up time was 41+/-22 months. RESULTS: Long-term drug therapy was effective in 14 patients and ineffective in 21 patients. Five of the refractory patients required mitral valve replacement to become free of symptoms. Only 5 of 21 patients whose LVOT gradient was 100 mm Hg were responsive to drug therapy, whereas 9 of 14 patients whose LVOT gradient was <100 mm Hg were responsive to drug therapy. Seven of eight patients with an asymmetric septal hypertrophy (ASH) ratio >==1.3 and LVOT gradient <100 mm Hg were responsive to drug therapy. Only 3 of 16 patients with an ASH ratio <1.3 were responsive to drug therapy. There was no correlation between the efficacy of drug therapy and the morphology of the mitral valve or the width of the LVOT. CONCLUSION: Our results demonstrate that drug therapy effectively reduces the LVOT gradient in patients with asymmetric septal hypertrophy and a less severe LVOT gradient.     

Relevance of abdominal gas analysis and transit study after colorectal cancer surgery

BACKGROUND: Colon gas volume analysis using abdominal radiographs is an objective and reproducible method for evaluating functional bowel disorders. The aim of this study was to clarify the relevance of colon gas distribution and transit time in rectosigmoid cancer patients after surgery. METHODS: Segmental colon gas volume score was calculated using plain abdominal radiography and evaluated in 40 patients who had undergone sphincter-saving resection. Segmental colonic transit time was analysed using radiopaque markers in the same patients. RESULTS: Transit times in the right colon (RCT) were 15.3 +/- 1.1 h and in the left colon (LCT) 11.2 +/- 1.1 h. Gas volume scores in the RCS and LCS were 1.10 +/- 0.13% and 1.06 +/- 0.14%, respectively. Neither colonic transit time nor colon gas volume score correlated with the operation methods for rectosigmoid colon cancer. A positive correlation of RCS and a negative correlation of LCS/RCS with ageing were noted in male patients but not in female patients. There was no correlation between RCT and RCS (r = 0.028); however, LCT correlated with LCS (r = 0.318, P < 0.05). The ratio of colonic transit time (LCT/RCT) was 0.84 +/- 0.10, while that of colon gas volume score (LCS/RCS) was 1.29 +/- 0.21. There was a significant correlation between LCT/RCT and LCS/RCS (r = 0.541, P < 0.001). CONCLUSIONS: Analysis of colon gas volume is useful for evaluating colonic transit time in rectosigmoid cancer patients after sphincter-saving surgery.     

Fas/Fas ligand expression and characteristics of primed CD45RO+ T cells in the inflamed mucosa of ulcerative colitis

BACKGROUND: Chronic immune activation in the colon is characteristic of ulcerative colitis (UC). Fas/Fas ligand (FasL) system is a mechanism responsible for activation-induced cell death (AICD), which maintains homeostasis within the immune system. Thus, Fas/FasL expression on activated colonic T cells of UC patients, as well as the susceptibility of such T cells to AICD was investigated in order to determine the role of activated colonic T cells in the long lasting inflammation in UC. METHODS: Fas, FasL, and CD45RO expression on peripheral blood and colonic T cells of UC patients were assayed by flow cytometry. Apoptosis of colonic T cells induced by anti Fas antibody was assessed using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. RESULTS: The majority of colonic T cells expressed both CD45RO and Fas in the colonic mucosa, a situation that was quite different from that in the peripheral blood. The number of CD45RO+CD8+ and Fas+CD8+ T cells was significantly lower in UC patients than the controls, unlike the number of Fas+CD4+ T cells. In contrast, the number of both CD45RO+CD4+ and CD45RO+CD8+ T cells in UC mucosa expressing FasL was significantly higher than in the controls. While Fas mediated apoptosis of CD45RO+CD8+ T cells was higher in UC patients than the controls, the number of apoptotic CD45RO+CD4+ T cells from UC mucosa was not. CONCLUSIONS: In UC patients, CD45RO+CD4+ T cells are less sensitive to apoptotic signals mediated by Fas. These phenomena may contribute to the pathogenesis of UC.     

Genetic variant of the renin-angiotensin system and prevalence of type 2 diabetes mellitus: a modest but significant effect of aldosterone synthase

Recent genome-wide association studies have identified multiple variants that confer risk of type 2 diabetes mellitus (DM). However, established associations explain only a part of the heritability. Thus, even at the genome-wide association studies era, candidate gene approach should be still useful. Recent interventional studies against the renin-angiotensin system (RAS) showed reduction in new onset of DM, implying the system is involved in the onset. We substantiated the hypothesis that genetic variants of RAS have significant association with prevalence of DM. We enrolled to the study consecutive 782 subjects who had consulted our hospitals for mainly lifestyle related diseases. They consisted of 282 (36.1 %) diabetes cases. Genotypes were assayed with genomic DNA for conventional four genes of the RAS, i.e., angiotensin converting enzyme (ACE) insertion/deletion variant, angiotensinogen (AGT) M235T variant, angiotensin II type I receptor (AT1) A1166C variant, and aldosterone synthase (CYP11B2) C-344T variant. Association between the genetic variants of the RAS and prevalence of type 2 DM was tested. A significant association of DM and CYP11B2 genotype was obtained. There was no significant association between DM and ACE, AGT and AT1 variants. A multivariate logistic regression showed that age, gender, and CYP11B2 genotype were independent factors for association to diabetes, the DM risk of CC/CT to TT being 1.40 (95 % CI 1.04–1.90, p = 0.029). Thus, it is concluded that a genetic variant of the RAS should have a modest but significant impact on the onset of type 2 diabetes mellitus.