Uptake of lamivudine by rat renal brush border membrane vesicles

Uptake of lamivudine, a nucleoside analogue antiviral agent, by brush border membrane vesicles (BBMV) prepared from rat renal cortex was investigated. Initial uptake of lamivudine by BBMV was stimulated in the presence of an outward pH gradient. Determination of the kinetic parameters of the initial uptake yielded apparent Km and Vmax values of 2.28 mm and 1.56 nmol (mg protein)(-1) (20 s)(-1), respectively. The pH-driven uptake of lamivudine was inhibited by organic cations such as trimethoprim and cimetidine. The inhibitory effect of trimethoprim on lamivudine uptake was competitive, with an apparent Ki of 27.6 microM. The uptake of lamivudine was also inhibited by nitrobenzylthioinosine, a representative inhibitor of nucleoside transport, and by other nucleoside analogues, such as azidothymidine and dideoxycytidine, that are excreted by renal tubular secretion. These findings suggest that efflux of lamivudine at the brush border membrane of renal tubular epithelium is mediated by an H+/lamivudine antiport system, which may correspond to the H+/organic cation antiport system, and that this system is also involved in the renal secretion of other nucleoside analogues.     

Uptake of FH by two types of scavenger-like receptors in rat liver parenchymal cells in primary culture

Several anionic proteins that are known to be substrates of scavenger receptors documented in the literature were selected and tested for their effects on the uptake of fractionated heparin (FH), an anionic macromolecular drug. The tests were made in rat liver parenchymal cells to characterize scavenger-like receptors involved in FH uptake, probing into substrate recognition characteristics in comparison with those of scavenger receptors. Although the uptake of FH was completely inhibited by dextran sulfate, a typical substrate of scavenger receptors, suggesting that scavenger-like receptors that have affinity for some anionic macromolecules are responsible for the uptake, it was not inhibited by acetylated low density lipoprotein (Ac-LDL), another typical substrate. Thus, the scavenger-like receptors were suggested to be different from the major scavenger receptors of classes A and B that are known to be sensitive to Ac-LDL. The uptake of FH was only partially inhibited by maleylated bovine serum albumin (Mal-BSA), suggesting that the scavenger-like receptors can be classified into two types in terms of sensitivity to Mal-BSA. The Mal-BSA-sensitive receptor was also found to be sensitive to oxidized low density lipoprotein (Ox-LDL). Kinetic analysis revealed that the binding capacity (Bmax) of the Mal-BSA-insensitive receptor was significantly larger than that of the Mal-BSA-sensitive one, though their dissociation constants (Kd) and apparent internalization rate constants (kint,app) were comparable. Information obtained in this study should be helpful for understanding the disposition mechanism of FH and also of anionic macromolecules and for developing delivery strategies, although the physiological roles and molecular identity of each receptor need to be further clarified in the future.     

Impairment of reward-related learning by cholinergic cell ablation in the striatum

The striatum in the basal ganglia-thalamocortical circuitry is a key neural substrate that is implicated in motor balance and procedural learning. The projection neurons in the striatum are dynamically modulated by nigrostriatal dopaminergic input and intrastriatal cholinergic input. The role of intrastriatal acetylcholine (ACh) in learning behaviors, however, remains to be fully clarified. In this investigation, we examine the involvement of intrastriatal ACh in different categories of learning by selectively ablating the striatal cholinergic neurons with use of immunotoxin-mediated cell targeting. We show that selective ablation of cholinergic neurons in the striatum impairs procedural learning in the tone-cued T-maze memory task. Spatial delayed alternation in the T-maze learning test is also impaired by cholinergic cell elimination. In contrast, the deficit in striatal ACh transmission has no effect on motor learning in the rota-rod test or spatial learning in the Morris water-maze test or on contextual- and tone-cued conditioning fear responses. We also report that cholinergic cell elimination adaptively up-regulates nicotinic ACh receptors not only within the striatum but also in the cerebral cortex and substantia nigra. The present investigation indicates that cholinergic modulation in the local striatal circuit plays a pivotal role in regulation of neural circuitry involving reward-related procedural learning and working memory.     

Ischemic depolarization monitoring: evaluation of protein synthesis in the hippocampal CA1 after brief unilateral ischemia in a gerbil model

OBJECT: The authors investigate whether depolarization monitoring is an accurate index of ischemic damage in a gerbil model of unilateral ischemia and assess the effects of brief cerebral ischemia on protein synthesis in this model. METHODS: The authors evaluate the relationship between the duration of ischemic depolarization caused by unilateral carotid artery occlusion and ischemia-induced neuronal damage in the CA1 subregion 7 days after ischemia. When the depolarization period exceeded 210 seconds, some neuronal damage was detected, and almost complete neuronal damage was observed when the period exceeded 400 seconds. Uptake of [14C]valine was evaluated in ischemic and nonischemic CA1 subregions. Disturbances in protein synthesis were seen in all animals subjected to sublethal ischemia (< or = 210-second depolarization) after a 10-minute recirculation, and after 2 and 6 hours of recirculation in animals with 90 seconds or more of depolarization. Inhibition of protein synthesis was proportional to the length of the depolarization period. After 1 and 3 days of recirculation, protein synthesis returned to near normal, and some animals with depolarizations greater than 180 to 210 seconds showed an increase in protein synthesis. Protein synthesis in all animals returned to normal levels after 7 days of recirculation. CONCLUSIONS: In this study the authors demonstrate that monitoring of ischemic depolarization is a useful method to predict neuronal damage in the hippocampal CA1 in this model, and they identify subtle changes in protein synthesis after brief ischemia. Sublethal ischemia was divided into three categories by its depolarization period (< 90 seconds, 90-180 seconds, and > 180-210 seconds) with regard to changes in protein synthesis.     

Enhanced spontaneous and aflatoxin-induced liver tumorigenesis in xeroderma pigmentosum group A gene-deficient mice

Xeroderma pigmentosum (XP) is an autosomal recessive hereditary disease featuring defective nucleotide excision repair (NER). XP patients are highly sensitive to sunlight and develop skin cancer at an early age. While the fact that XP patients have a large increase in mortality from skin cancers has been extensively documented, the relation between XP and internal tumors has received little attention. We therefore analyzed development of spontaneous and aflatoxin B(1) (AFB(1))-induced liver tumors in XPA-deficient congenic mice, originally created by repeated back-crosses with inbred C3H/HeN mice. Spontaneous liver tumors were assessed at the age of 16 months in two separate experiments using F5 and F10 lines. The incidence of and average number of spontaneous tumors per mouse were significantly higher in XPA-/- than in XPA+/+ and +/- mice. Similarly, F10 XPA-/- mice receiving i.p. injection of 0.6 or 1.5 mg/kg b.w. AFB(1) at 7 days of age demonstrated more liver tumors than their heterozygous or homozygous positive counterparts when examined at month 11. These results demonstrate that XPA-deficient mice have increased susceptibility to both spontaneous liver tumor development and AFB(1)-induced hepatocarcinogenesis.     

Report based on fiscal 2000 diagnostic x-ray equipment questionnaire survey(conditions of radiography)

X-ray equipment has seen advances in inverters and the digitalization of reception systems. The X-ray Systems Study Group, in order to examine changes in the conditions of radiography, including pediatric radiography, variations in shortest irradiation time, and standardization of the conditions of radiography, carried out investigative research using a questionnaire survey that was sent to 400 facilities. The recovery rate was 33%. In terms of the reception system, half of the general radiography systems were using computed radiography (CR). Seventy percent of respondents used an intensifying screen and film(S EF)in stomach double-contrast radiography. About 80% used digital radiography (DR) and digital subtraction angiography (DSA) in aorta abdominalis angiography. At least 70% of high-voltage generators were of the inverter type. The conditions of radiography were not greatly influenced by changes in reception systems and X-ray equipment. Many pediatric radiographies were carried out by radiological technologists. We consider it useful to conduct such survey investigations.     

The retention indices of 201Tl-SPECT in brain tumors

OBJECTIVE: The aim of this study was to assess the utility of 201Tl SPECT in the differential diagnosis of intracranial tumors and to determine the relationship between 201Tl uptake and histological types. METHODS: Thirty-eight patients (19 males and 19 females) with thirty-eight brain tumors were evaluated with 201Tl-SPECT. The early and delayed 201Tl uptake ratio was calculated, and the retention index (RI) was applied as follows; RI = delayed uptake ratio/early uptake ratio. RESULTS: The RI of malignant tumors was higher (0.72 +/- 0.18) than that of benign tumors (0.50 +/- 0.16) and the difference was statistically significant (p = 0.00045). The difference between high-grade glioma (0.80 +/- 0.15) and metastatic tumors (0.64 +/- 0.19) was statistically significant (p = 0.039). CONCLUSION: 201Tl-SPECT may add useful biochemical information and could differentiate malignant brain tumors from benign lesions, but the RI of metastatic tumors varied depending on the organs with the primary lesion and histological types.     

Benefits of combined radioimmunotherapy and anti-angiogenic therapy in a liver metastasis model of human colon cancer cells

The combined use of anti-angiogenic therapy (AT) and radioimmunotherapy (RIT) may improve the therapeutic outcome in patients with cancer lesions. This hypothesis is based on the ability of AT to suppress tumour endothelial compartments and the direct action of RIT against tumour cells. We previously confirmed this hypothesis in an established subcutaneous xenograft model of colon cancer. The purpose of the current investigation was to determine the benefit of this combination within a liver metastasis model, which mimics treatment of minimal disease in an adjuvant setting. Liver metastases were established in nude mice by intrasplenic inoculation of LS180 colon cancer cells; following such inoculation, metastases of <1 mm in diameter can be observed at 1 week and these lesions can attain a size of several millimetres at 2 weeks. Daily AT with 2-methoxyoestradiol (2-ME), 75 mg/kg, was initiated at 1 week. RIT with 7 MBq of (131)I-A7, an IgG1 anti-colorectal monoclonal antibody, was conducted at 2 weeks. RIT employing an irrelevant IgG1, (131)I-HPMS-1, was implemented for comparison. The weight of liver metastases was measured 4 weeks after cell inoculation. The effect of AT on (131)I-A7 accumulation in metastases was also observed. Toxicity of treatment was monitored by blood cell counts. Monotherapy with 2-ME AT or (131)I-A7 RIT significantly suppressed metastasis growth ( P<0.0001): metastasis weight was 5.96+/-0.87 g in non-treated controls, 2.67+/-1.89 g in cases receiving AT and 0.85+/-0.68 g in those receiving (131)I-A7 RIT. Combination of AT and (131)I-A7 RIT more effectively suppressed the growth to 0.28+/-0.32 g ( P<0.05 vs RIT alone). The effect of (131)I-HPMS-1 RIT, which suppressed metastasis growth to 2.25+/-0.88 g, was significant in comparison with the control ( P<0.0001); however, the combination of AT and (131)I-HPMS-1 RIT (which suppressed growth to 1.41+/-0.68 g) was far less effective than the combination of AT and (131)I-A7 RIT. AT did not decrease (131)I-A7 accumulation in metastases. AT did not affect RIT myelotoxicity. The results of this study demonstrating the combined effects of AT and (131)I-A7 RIT in a small metastasis model indicate that such combination therapy may be suitable for the treatment of minimal disease.     

Prevalence of deep venous thrombosis in the lower limbs and the pelvis and pulmonary embolism in patients with positive antiphospholipid antibodies

BACKGROUND: Antiphospholipid antibodies (AA) are immunoglobulins that cross-react with phospholipid on cell membrane, and are therefore associated with a hypercoagulable state manifested by arterial/venous thromboses. We aimed to determine the prevalence of deep venous thrombosis in the lower limbs and the pelvic region (DVT) and pulmonary embolism (PE) in patients with positive AA. METHODS: Sixty-six patients (48 female, 18 male) with positive lupus anticoagulant (LA) and/or positive anticardiolipin antibody (aCL) underwent radionuclide (RN) venography with 370 MBq of 99mTc-MAA. Pulmonary perfusion scintigraphy was performed in 58 patients. Fifteen patients had positive LA and positive aCL (LA+/aCL+), 33 patients had positive LA only (LA+/ aCL-) and 18 patients had positive aCL only (LA-/aCL+). 43 patients were diagnosed with primary antiphospholipid syndrome (APS) and 19 were diagnosed with APS associated with SLE. RESULTS: DVT was detected in 21 of 66 patients (32%). Patients with LA+/aCL+ showed higher prevalence of DVT (53%) as compared to LA+/aCL- (27%) and LA-/aCL+ (22%). PE was found in 13 of 58 patients (22%). The prevalence of PE was higher in patients with positive aCL (33% in LA+/aCL+; 36% in LA-/aCL+) than in patients with negative aCL (10%). CONCLUSION: Because of the high prevalence of DVT and PE in patients with AA, RN scintigraphy must be recommended in screening for these clinical troubles. These results indicate that the prevalence of DVT and PE may vary in subgroups of AA.     

P16INK4Gene Mutations Are Relatively Frequent in Ampullary Carcinomas

A high incidence of gene mutations or deletions of P16INK4, a cell cycle regulator which inhibits the activity of cyclin-dependent kinase 4/cyclin D complex and blocks the Gl-to-S transition, has been reported in pancreato-biliary tract cancers. In order to investigate P16INK4 gene alterations in sporadic ampullary carcinomas, 17 sporadic ampullary carcinomas were examined. After histological diagnosis, DNA samples extracted separately from both cancerous and normal paraffin-embedded tissues were investigated. Loss of heterozygosity (LOH) was investigated utilizing 3 microsatellite markers on 9p21-22, and a mutationsl analysis was performed by cloning and sequencing. LOH was observed in 3 cases (17.6%) and somatic mutations with retention of heterozygosity were found in 7 cases (41.2%). Of note was that two mutations resulted in truncated incomplete proteins and one was a point mutation at the consensus site in the conserved ankyrin repeats, which would be crucial for function. Although two-hit inactivation was not evident in any of the mutation cases and further investigation would be needed to elucidate the role of altered p16INK4 , these results suggest that the pl6INK4 gene mutations are relatively frequent and its inactivation might be important in ampnllary carcinogenesis.