N-methyl-d-aspartate receptor dysfunction in the prefrontal cortex of stroke-prone spontaneously hypertensive rat/Ezo as a rat model of attention deficit/hyperactivity disorder.

AIM: We previously reported that stroke-prone spontaneously hypertensive rat/Ezo (SHRSP/Ezo) has high validity as an attention deficit/hyperactivity disorder (AD/HD) animal model, based on its behavioral phenotypes, such as inattention, hyperactivity, and impulsivity. Fronto-cortical dysfunction is implicated in the pathogenesis of AD/HD. In this study, we investigated prefrontal cortex (PFC) function in SHRSP/Ezo rats by electrophysiological methods and radioreceptor assay. METHODS: We recorded excitatory postsynaptic potential in layer V pyramidal neurons in the PFC by intracellular recording method to assess synaptic plasticity in the form of long-term potentiation (LTP). We also performed N-methyl-d-aspartate acid (NMDA) receptor binding assay in the PFC and hippocampus using radiolabeled NMDA receptor antagonist [3 H]MK-801. RESULTS: Theta-burst stimulation induced LTP in the PFC of genetic control, WKY/Ezo, whereas failed to induce LTP in that of SHRSP/Ezo. The Kd value of [3 H]MK-801 binding for NMDA receptors in the PFC of SHRSP/Ezo was higher than in the WKY/Ezo. Neither the Bmax nor Kd of [3 H]MK-801 binding in the SHRSP/Ezo hippocampus was significantly different to WKY/Ezo. CONCLUSION: These results suggest that the AD/HD animal model SHRSP/Ezo has NMDA receptor dysfunction in the PFC.

111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibits higher tumor accumulation and lower renal radioactivity than 111In-DTPA-d-Phe1-octreotide.

INTRODUCTION: 111In-DTPA-d-Phe1-octreotide scintigraphy is an important method of detecting neuroendocrine tumors. We previously reported that a new derivative of 111In-DTPA-d-Phe1-octreotide, 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide, accomplished the reduction of prolonged renal accumulation of radioactivity. The aim of this study was to evaluate the tumor accumulation of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide in vitro and in vivo by comparing it with 111In-DTPA-d-Phe1-octreotide. METHODS: The tumor accumulation of this octreotide derivative was determined by measuring its uptake using cultured AR42J cells in vitro and biodistribution studies in vivo. The distribution of the radiotracer and the extent of somatostatin receptor-specific uptake in the tumor were estimated by a counting method using AR42J tumor-bearing mice. The radioactive metabolite species in the tumor and kidney were identified by HPLC analyses at 3 and 24h post-injection of the 111In-DTPA-conjugated peptide. RESULTS: In both cases, in vitro and in vivo, the tumor radioactivity levels of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide were approximately 2-4 times higher than those of 111In-DTPA-d-Phe1-octreotide. On in vitro cellular uptake inhibition and radioreceptor assay, 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibited a binding affinity to somatostatin receptor highly similar to that of 111In-DTPA-d-Phe1-octreotide. As the additional cellular uptake of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide was significantly lower at low temperature than at 37°C, it was considered that a cellular uptake pathway is involved in energy-dependent endocytotic processes. In the radiometabolite analysis of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide, 111In-DTPA-d-Phe-Asp-OH was a major metabolite in the tumor at 24h post-injection. CONCLUSION: 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibited higher tumor accumulation and persistence of tumor radioactivity than 111In-DTPA-d-Phe1-octreotide. We reasoned that this higher tumor accumulation would not be based on the receptor affinity but on a receptor-mediated endocytotic process involved in temperature-dependent cellular uptake. The present study demonstrated the great potential of the pharmaceutical development of a new radiolabeled peptide with high tumor accumulation and low renal radioactivity by the chemical modification of 111In-DTPA-d-Phe1-octreotide.

Redesign of negatively charged 111In-DTPA-octreotide derivative to reduce renal radioactivity.

INTRODUCTION: Radiolabeled octreotide derivatives have been studied as diagnostic and therapeutic agents for somatostatin receptor-positive tumors. To prevent unnecessary radiation exposure during their clinical application, the present study aimed to develop radiolabeled peptides which could reduce radioactivity levels in the kidney at both early and late post-injection time points by introducing a negative charge with an acidic amino acid such as L-aspartic acid (Asp) at a suitable position in 111In-DTPA-conjugated octreotide derivatives. METHODS: Biodistribution of the radioactivity was evaluated in normal mice after administration of a novel radiolabeled peptide by a counting method. The radiolabeled species remaining in the kidney were identified by comparing their HPLC data with those obtained by alternative synthesis. RESULTS: The designed and synthesized radiolabeled peptide 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibited significantly lower renal radioactivity levels than those of the known 111In-DTPA-d-Phe1-octreotide at 3 and 24h post-injection. The radiolabeled species in the kidney at 24h after the injection of new octreotide derivative represented 111In-DTPA-d-Phe-OH and 111In-DTPA-d-Phe-Asp-OH as the metabolites. Their radiometabolites and intact 111In-DTPA-conjugated octreotide derivative were observed in urine within 24h post-injection. CONCLUSION: The present study provided a new example of an 111In-DTPA-conjugated octreotide derivative having the characteristics of both reduced renal uptake and shortened residence time of radioactivity in the kidney. It is considered that this kinetic control was achieved by introducing a negative charge on the octreotide derivative thereby suppressing the reabsorption in the renal tubules and affording the radiometabolites with appropriate lipophilicity.

Design, synthesis and biological evaluation of negatively charged ¹¹¹In-DTPA-octreotide derivatives.

Our previous studies indicated that (111)In-diethylenetriaminepentaacetic acid ((111)In-DTPA)-octreotide derivatives with an additional negative charge by replacing N-terminal d-phenylalanine (d-Phe) with an acidic amino acid such as l-aspartic acid (Asp) or its derivative exhibited low renal radioactivity levels when compared with (111)In-DTPA-D-Phe(1)-octreotide. On the basis of the findings, we designed, synthesized and evaluated two Asp-modified (111)In-DTPA-conjugated octreotide derivatives, (111)In-DTPA-Asp(1)-octreotide and (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide. While (111)In-DTPA-Asp(1)-octreotide showed negligible AR42J cell uptake, (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide exhibited AR42J cell uptake similar to that of (111)In-DTPA-D-Phe(1)-octreotide. When administered to AR42J tumor-bearing mice, (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide exhibited renal radioactivity levels significantly lower than did (111)In-DTPA-D-Phe(1)-octreotide at 1 and 3 h post-injection. No significant differences were observed in tumor accumulation between (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide and (111)In-DTPA-D-Phe(1)-octreotide after 1 and 3h injection. The findings in this study suggested that an interposition of an Asp at an appropriate position in (111)In-DTPA-D-Phe(1)-octreotide would constitute a useful strategy to develop (111)In-DTPA-D-Phe(1)-octreotide derivatives of low renal radioactivity levels while preserving tumor accumulation.

Doctor's delay in endobronchial tuberculosis.

OBJECTIVE: The aim of this study was to investigate the current status of doctor's delay in diagnosing endobronchial tuberculosis (EBTB) and to elucidate the risk factors contributing to the delay. METHODS: Retrospective clinicopathological analysis. PATIENTS: Sixty-two patients with EBTB were admitted at our hospital between 1999 and 2010. Their backgrounds, symptoms, diagnoses at initial consultation, delay in diagnosis, and clinical examination results were analyzed. RESULTS: Of the 62 patients, 59 had acid-fast, bacillipositive sputum smear test results at admission. Among the 40 patients with total diagnostic delay of more than 2 months, only 11 experienced long patient's delay exceeding 2 months. However, 22 patients experienced long doctor's delay of more than 2 months (28% vs. 55%, respectively, p < 0.05), suggesting that doctor's delay contributes more to total delay than patient's delay. Fever was less frequent in patients with long doctor's delays than in those without (0% vs. 18%, respectively), at the initial consultation. In addition, radiographs showed that patients with long doctor's delays more frequently presented with shadows in the lower lung field (50% vs. 23%, p < 0.05), and most of these patients had noncavitary shadows on admission. All 7 patients diagnosed with bronchial asthma at the initial consultation had long doctor's delays. CONCLUSION: These findings demonstrate that long doctor's delays in diagnosing EBTB remain an issue. The clinical features of EBTB with long doctor's delays were confirmed to be quite different from those of pulmonary tuberculosis.