Preparation and pharmaceutical evaluation for clinical application of high specific activity S-(-)[11C]CGP-12177, a radioligand for beta-adrenoreceptors.

BACKGROUND: Although S-(-)[C]CGP-12177 is a useful positron emission tomography (PET) ligand for beta-adrenoreceptors, the difficulty in radiolabelling the compound has prevented its extensive clinical application. Recently, we have developed a simple synthesis method for S-(-)[C]CGP-12177. In the present study, we attempted to prepare S-(-)[C]CGP-12177 with a high specific activity for intravenous injection which is feasible for the clinical evaluation of beta-adrenoreceptors. METHODS: The [C]methane produced during irradiation of a N2--H2 (95/5) mixture with an 18 MeV proton beam (20 microA, 30 min) was chlorinated using Cl2 to yield [C]carbon tetrachloride. S-(-)[C]CGP-12177 was synthesized by reacting the diamino precursor with [C]phosgene produced by oxidizing [C]carbon tetrachloride on a Fe--Fe2O3 column. The product was purified by using reversed phase, high-performance liquid chromatography (RP-HPLC) and the radioactive fraction containing S-(-)[C]CGP-12177 was collected and evaporated to dryness. S-(-)[C]CGP-12177 dissolved in physiological saline was sterilized through a 0.22 microm membrane filter. The radiochemical purity and the mass of the compound were determined with RP-HPLC. The residual organic solvents were determined with GC. Tests for sterility and the presence of bacterial endotoxins were also performed. RESULTS: S-(-)[C]CGP-12177 for intravenous injection was prepared in 25 min after the end of bombardment with a yield of 1.5+/-0.2 GBq. Specific activity was found to be 385.4+/-133.0 GBq/ micromol at the end of synthesis (EOS) (n=3). Radiochemical purity was found to be more than 99%. Toluene was not detected in the solution. The ethanol concentration was determined to be 60.3+/-52.5 ppm. Tests for sterility and bacterial endotoxins showed negative results. CONCLUSION: We successfully prepared S-(-)[C]CGP-12177 formulated for intravenous injection with high purity and high specific activity, which is feasible for the clinical evaluation of beta-adrenoreceptors.

Combination therapy of rat brain tumours using localized interstitial hyperthermia and intra-arterial chemotherapy.

Several investigators have reported that a high concentration of drugs in a tumour can be achieved using intra-arterial (IA) chemotherapy. This treatment was highly effective, especially in brain tumours, but the actual therapeutic advantage is still unknown. There are also indications that human malignant gliomas can effectively be treated using interstitial hyperthermia. Therefore, a combined treatment of IA chemotherapy and interstitial hyperthermia should be very promising and this has been studied in a tumour model. Wistar rats with isotransplanted C(6) gliomas in the brain were treated with adriamycin (ADR, 1.0 mg/kg body weight) either infused via the carotid artery (i.a.) or via the tail vein (i.v.), with or without interstitial hyperthermia. Hyperthermia of the tumours was applied using a homemade radiofrequency antenna (RF-heating) and a heating device that maintained the tumour temperature above 40 degrees C. Concentration of adriamycin in tumours after treatment was measured using HPLC. The effectiveness of treatment was determined by the survival time of the animals and histopathological examinations. The highest uptake of adriamycin in the rat C(6) glioma was obtained when the animals were treated with hyperthermia and i.a. ADR infusion (p <0.01). These animals also showed significantly longer overall survival time (SF50 =46 days) in comparison to the other treatments (p < 0.05). The histological studies demonstrated a necroti c tumour; however, the surrounding normal brain tissue remained intact. Thus, a combination of IA chemotherapy with adriamycin and localized interstitial hyperthermia enhances considerably the efficacy of adriamycin and has a greater antitumour effect for malignant brain tumours. This method is suitable for clinical use, and may be a new strategy for treating gliomas not successfully treated today.

Outcomes of radiotherapy for inoperable locally advanced (T4) esophageal cancer-retrospective analysis-.

To assess the treatment outcome after radiotherapy with or without chemotherapy for inoperable locally advanced (T4) esophageal cancer (EC), a retrospective analysis was performed. We enrolled 37 patients with T4 EC and analyzed 35 patients. A total of 28 patients were treated with radiotherapy and chemotherapy (median dose, 60 Gy) and seven patients were treated with radiation alone (median dose, 60 Gy). Many mainly received high-dose cisplatin (CDDP) and 5-fluorouracil (FU) or continuous infusion of low-dose CDDP and 5-FU. Among the 35 patients, there were eight survivors and 27 deaths. The median follow-up period was 15.5 months (3.5 to 74 months). The one-year, 3-year, and 5-year survival rates were 37.5%, 10.0%, and 10.0%, respectively, with a median survival time (MST) of 7.3 months. When the patients were divided into two groups, a complete response (CR) group and a non-CR group, MST was 16.5 and 6.2 months, respectively, showing significant differences between the two groups (p=0.0317). CR patients showed more satisfactory long-term outcomes than non-CR patients.

[A case of central retinal artery occlusion after anterior posterior fusion of the lumbar spine].

We report a case of central retinal artery occlusion after anterior-posterior fusion of the lumbar spine. The patient suddenly lost his vision of the right eye in the ICU just after the end of long procedure for anterior-posterior fusion of the lumbar spine. The patient was diagnosed as having central retinal artery occlusion, and treated successfully with treatments including immediate administration of urokinase and PGE1, stellate ganglion block, and hyperbaric oxygen therapy. The patient was discharged from the hospital on the 54th postoperative day with adequate vision to drive a car. Central retinal artery occlusion is a rare but very serious complication during and after supine surgery with prone position. It is very important for us to be aware of its possible occurrence. We have to diagnose and treat, as soon as possible, the vision loss after the spine surgery.

Effects of volatile and intravenous anesthetics on the uptake of GABA, glutamate and dopamine by their transporters heterologously expressed in COS cells and in rat brain synaptosomes.

Although the neurotransmitter uptake system is considered a possible target for the presynaptic action of anesthetic agents, observations are inconsistent concerning effects on the transporter and their clinical relevance. The present study examined the effects of volatile and intravenous anesthetics on the uptake of GABA, glutamate and dopamine in COS cells heterologously expressing the transporters for these neurotransmitters and in the rat brain synaptosomes. Halothane and isoflurane, but not thiamylal or thiopental, significantly inhibited uptake by COS cell systems of GABA, dopamine and glutamic acid in a concentration-dependent manner within clinically relevant ranges for anesthesia induced by these agents. Similarly, in synaptosomes halothane and isoflurane but not thiopental significantly suppressed the uptake of GABA and glutamic acid, respectively. These results do not support the hypothesis that volatile and intravenous anesthetics exert their action via specific inhibition of GABA uptake to enhance inhibitory GABAergic neuronal activity. Rather, they suggest that presynaptic uptake systems for various neurotransmitters including GABA may be the molecular targets for volatile anesthetic agents.

Comparison of (18)F-FDG, (131)I-Na, and (201)Tl in diagnosis of recurrent or metastatic thyroid carcinoma.

UNLABELLED: There are several reports about the usefulness of (18)F-FDG PET in thyroid cancer. However, few studies have compared FDG PET with (131)I and (201)Tl scintigraphy. The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from (131)I and (201)Tl scintigraphy. METHODS: Whole-body FDG PET was performed on 32 patients (10 men, 22 women; age range, 30-77 y; mean age, 54 y) with differentiated thyroid cancer (5 cases of follicular cancer and 27 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including cytology, thyroglobulin level, sonography, MRI, and CT, to allow a comparison with functional imaging results for each patient. Metastatic regions were divided into five areas: neck, lung, mediastinum, bone, and other. Multiple lesions in one area were defined as one lesion. The tumor-to-background ratio (TBR) was measured for the lesions that were positive for both (201)Tl uptake and FDG PET uptake. RESULTS: The number of lesions totaled 47. Forty-one (87%) were detected by all scintigraphic methods. FDG uptake was concordant with (131)I uptake in only 18 lesions (38%). FDG uptake was concordant with (201)Tl uptake in 44 lesions (94%). Only one lesion was negative for FDG uptake and positive for (201)Tl uptake, and two lesions were positive for FDG uptake and negative for (201)Tl uptake. A significant correlation was seen between the TBR of (201)Tl and that of FDG (r = 0.69; P<0.05). CONCLUSION: These data indicate that for detecting metastatic lesions, FDG PET and (131)I scintigraphy may provide complementary information, whereas FDG PET may provide results similar to those of (201)Tl scintigraphy. Thus, the combination of (131)I scintigraphy and FDG PET (or (201)Tl scintigraphy) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy.

Thalamic asymmetry on interictal SPECT in patients with frontal lobe epilepsy.

BACKGROUND: Interictal brain single photon emission computed tomography (SPECT) is useful for the detection of seizure focus. Recent reports indicate a hypoperfusion in the ipsilateral thalamus as a seizure focus on interictal SPECT in temporal lobe epilepsy. In frontal lobe epilepsy (FLE), however, the alteration of perfusion in the thalamus has not been well documented. This study aimed to assess whether perfusion analysis on the thalamus may add useful information for the detection of epileptic foci in patients with FLE. METHODS: Interictal brain SPECT was performed in 11 patients with FLE. The asymmetry index for the thalamus and frontal area in the SPECT image was calculated in order to compare the laterality of the seizure foci. RESULTS: Thalamic asymmetry was seen in seven patients (64%), while cortial asymmetry was seen in six patients (55%). The concordance with the lateralization of the seizure foci was 6/7 (86%) in the thalamus, and 4/6 (67%) in the frontal area. Four patients showed only thalamic asymmetry. Concordance with the lateralization of the seizure focus was found in all of them. CONCLUSION: These preliminary results suggest that hypoperfusion in the thalamus may have a complementary role to lateralize the epileptic foci in patients with FLE.

Possible inhibitory mechanism of FK506 (tacrolimus hydrate) ointment for atopic dermatitis based on animal models.

The effects of FK506 (tacrolimus hydrate) ointment on cutaneous allergic reactions in mice and rats were investigated. FK506 ointment showed significant suppressive effects on delayed allergic reactions in both species, and especially in rats, its inhibitory action was much stronger than that of alclometasone dipropionate, a so-called medium class steroid ointment. On the other hand, FK506 ointment did not inhibit the immediate allergic reaction in rats. FK506 ointment suppressed the delayed allergic reactions in locally passively sensitized mice to the same degree as that in actively sensitized mice. Accordingly, it is speculated that FK506 ointment inhibits the activation of sensitized T lymphocytes (Th1 cells) already accumulated in the dermis.

Chlorella accelerates dioxin excretion in rats.

We investigated the effects of Chlorella on fecal excretion of polychlorinated dibenzo-p-dioxin (PCDD) congeners and polychlorinated dibenzofuran (PCDF) congeners in Wistar rats administered the rice oil that caused Yusho disease, as a substitute for purified dioxin. The rats were fed 4 g of a control diet or a 10% Chlorella diet containing 0.2 mL of the rice oil once during the 5-d experimental period. The amounts of PCDD and PCDF congeners excreted in feces from d 1 to 5 in the group fed 10% Chlorella were 0.2-11.3 and 0.3-12.8 times greater (P < 0.05), respectively, than those of the control group. We then investigated the fecal excretion of PCDD and PCDF congeners from d 8 to 35 in rats administered 0.5 mL of the rice oil. Rats consumed the basal diet for 1 wk. After 1 wk, they consumed either the basal diet or the 10% Chorella diet. The fecal excretions of PCDD and PCDF congeners in the group fed 10% Chlorella were 0.3-3.4 and 0.5-2.5 times greater (most, P < 0.05), respectively, than those of the control group. Thus, the fecal excretions of PCDD and PCDF congeners were greater in rats fed Chlorella. These findings suggest that the administration of Chlorella may be useful in preventing gastrointestinal absorption and for promoting the excretion of dioxin already absorbed into tissues. Moreover, these findings suggest that Chlorella might be useful in the treatment of humans exposed to dioxin.

[Effect of protoporphyrin on digestive tract absorption of dioxins in rats].

This paper presents the fecal excretion of polychlorinated dibenzo-p-dioxin (PCDD) congeners, and polychlorinated dibenzofuran (PCDF) congeners in male rats fed a diet containing 0.5% disodiumprotoporphyrin (PPNa) or 0.5% hemin. The animals were administered 4 g of 0.5% PPNa or 0.5% hemin diet containing 0.5 ml of the causal rice-bran oil of Yusho that had occurred in the Southwest part of Japan in 1968 and kept on the same diet for five days. The fecal excretion of 2,3,7,8-T4CDD and 2,3,4,7,8-P5CDF in the group fed with 0.5% PPNa were 2.1 and 1.9 times higher, respectively, than that in the group fed with a control diet. Hemin did not show any significant effect on the inhibition of absorption of dioxins. Next, the rats were given a diet containing 0.5% PPNa or 0.5% Hemin for four weeks after a week interval from the day of the causal rice-bran oil administration. The fecal excretion of 2,3,7,8-T4CDD and 2,3,4,7,8-P5CDF in the group fed with 0.5% PPNa were stimulated 2.1 times higher, respectively, than that in the group fed with a control diet. Hemin did not show any significant effect on the inhibition of re-absorption of dioxins.

[Effect of green vegetable on digestive tract absorption of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in rats].

The effect green vegetable on fecal excretion of polychlorinated dibenzo-p-dioxin (PCDD) congeners and polychlorinated dibenzofuran (PCDF) congeners was examined in male rats. The rats were administered 10% vegetable diets or a basal diet containing 0.2 ml of the causal rice-bran oil of Yusho that had occurred in the Southwest part of Japan in 1968 and kept on the same diet for five days. The fecal excretion of 2,3,7,8-T4CDD and 2,3,4,7,8-P5CDF in the group fed with Komatsuna, Mitsuba, Spinach and Perilla were 7.6-11.6 and 6.5-9.4 times higher, respectively, than that in the group fed with a basal diet. The fecal excretion of 2,3,7,8-T4CDD and 2,3,4,7,8-P5CDF in the group fed with Kale, Chinese chive, Shungiku, Chingentsuai, Green lettus and Sweet pepper were 3.3-4.8 and 4.3-4.5 times higher, respectively, than that in the basal group. The fecal excretion of 2,3,7,8-T4CDD and 2,3,4,7,8-P5CDF in the group fed with Chinese cabbage, Broccoli, Onion, Welsh onion, Cabbage and Celery were 1.6-3.0 and 1.2-1.3 times higher, respectively, than that in the basal group. A correlation between Chllophyll consumption and fecal excretion of PCDD and PCDF congeners was highly significant (p < 0.01). Next, we investigated the fecal excretion of PCDD and PCDF congeners from day 8 to day 35 in rats administered with 0.5 ml of the rice oil. The fecal excretion of 2,3,7,8-T4CDD and 2,3,4,7,8-P5CDF in the group fed with Perilla, Kale and Spinach were 3.1-4.9 and 3.0-3.6 times higner, respectively, than that in the basal group. The presents results suggest that the green vegetables might be useful in treatment of humans exposed to PCDD and PCDF congeners.

Molecular cloning and hormonal regulation of PiT-1, a sodium-dependent phosphate cotransporter from rat parathyroid glands.

The extracellular concentration of inorganic phosphate (Pi) is an important determinant of parathyroid cell function. The effects of Pi may be mediated through specific molecules in the parathyroid cell membrane, one candidate molecule for which would be a Na+-dependent Pi cotransporter. A complementary DNA encoding a Na+-Pi cotransporter, termed rat PiT-1, has now been isolated from rat parathyroid. The 2890-bp complementary DNA encodes a protein of 681 amino acids that shows sequence identities of 97% and 93% with the type III Na+-Pi cotransporters mouse PiT-1 and human PiT-1, respectively. Expression of rat PiT-1 in Xenopus oocytes revealed that it possesses Na+-dependent Pi cotransport activity. PiT-1 messenger RNA (mRNA) is widely distributed in rat tissues and is most abundant in brain, bone, and small intestine. The amount of PiT-1 mRNA in the parathyroid of vitamin D-deficient rats was reduced compared with that in normal animals and increased markedly after administration of 1,25-dihydroxyvitamin D3. Furthermore, the abundance of PiT-1 mRNA in the parathyroid was much greater in rats fed a low-Pi diet than in those fed a high-Pi diet. Thus, rat PiT-1 may contribute to the effects of Pi and vitamin D on parathyroid function.

[SMANCS-TAE combined with PEI in the treatment for hepatocellular carcinoma].

From January 1996 to August 1997, 24 patients with advanced hepatocellular carcinoma (HCC) equal to or more than 2 cm (mean +/- SD; 4.1 +/- 3.0 cm) in main tumor diameter were treated by SMANCS-TAE (20 cases) or SMANCS-TAI (4 cases) combined with PEI. Six cases had solitary lesion, 16 cases had multiple lesions, and 2 cases had massive lesions. After this combination therapy, 21 of 24 cases had complete tumor necrosis. During 3 to 19 months follow up period, 12 cases had cancer-free survival (SMANCS-TAI; 3 cases), and 9 cases had tumor recurrences (3 cases were local recurrences and 6 cases involved new lesions). Two cases died of hepatic infarction and cancer death, however, the remaining 22 cases were surviving. SMANCS-TAE combined with PEI is useful treatment for advanced large or multiple HCC lesions in patients who are poor surgical risks.

The long term efficacy of combined transcatheter arterial embolization and percutaneous ethanol injection in the treatment of patients with large hepatocellular carcinoma and cirrhosis.

BACKGROUND: The long term efficacy of combination therapy with transcatheter arterial embolization (TAE) followed by percutaneous ethanol injection (PEI) was studied in patients with large primary hepatocellular carcinoma (HCC) tumors and cirrhosis. METHODS: The series included 83 patients with large unresectable HCC lesions, the largest of which was greater than 3 cm in largest dimension. Fifty-five had a solitary lesion and 28 had multiple (2 or 3) lesions. All patients were treated with both TAE and PEI and their survival rates were determined. RESULTS: The 3-, 5-, and 7-year calculated survival rates for the patients were be 68%, 35%, and 14%, respectively. The number of lesions (solitary vs. multiple), the stage of cirrhosis (Child's Class A vs. Class B or C), and the size of the largest lesion (3-5 cm in largest dimension compared with > 5 cm) significantly affected the survival rate (P < 0.05 to P < 0.01, log rank test). The 3-, 5-, and 7-year survival rates of the Child's Class A patients who had a 3-5 cm solitary lesion (n = 22) were 100%, 75%, and 27%, respectively. The Cox proportional hazards model showed the stage of cirrhosis and size of the largest lesion to be independently associated with survival. No serious complications occurred during or after treatment. CONCLUSIONS: Combination therapy with TAE and PEI is an effective and safe treatment that may improve the long term survival of patients with cirrhosis associated with large HCC lesions, and survival after this combination therapy may be comparable to that after surgery.

Gene structure and functional analysis of the human Na+/phosphate co-transporter.

Three lambda phage clones encompassing the Na+/phosphate co-transporter (NaPi-3) gene and its 5' flanking region were isolated from a human genomic DNA library. The gene comprises 13 exons and 12 introns and spans approx. 14 kb. All exon-intron junctions conform to the GT/AG rule. The major transcription-initiation site was determined by primer-extension analysis and is an adenosine residue 57 bp upstream of the 3' end of the first exon. There is a typical TATA box 28 bp upstream of the major transcription-initiation site and various cis-acting elements, including a cAMP-responsive element, AP-1, AP-2 and SP-1 sites in the 5' flanking region. This region also contains three direct-repeat-like sequences that resemble the consensus binding sequence for members of the steroid-thyroid hormone receptor superfamily, including vitamin D. Deletion analysis suggests that the region from nt-2409 to nt-1259 in the 5' flanking region may be involved in kidney-specific gene expression. Vitamin D responsiveness of the NaPi-3 promoter was also detected in COS-7 cells co-transfected with a human vitamin D receptor expression vector. The presence of the three vitamin D receptor- responsive elements in the NaPi-3 promoter may be important in mediating the enhanced expression of the gene by 1,25-dihydroxyvitamin D3.

[Effect of green tea (matcha) on gastrointestinal tract absorption of polychlorinated biphenyls, polychlorinated dibenzofurans and polychlorinated dibenzo-p-dioxins in rats].

This paper presents the liver distribution and fecal excretion of polychlorinated biphenyls (PCB), polychlorinated dibenzofurans (PCDF) congeners and polychlorinated dibenzo-p-dioxins (PCDD) congeners, in male rats fed with powdered green tea (matcha). The rats were given a treatment diet containing 10% matcha for the first five days. Then, the animals were administered 4 g of 10% matcha diet containing 0.5 ml of the casual rice-bran oil of Yusho that had occurred in the Southwest part of Japan in 1968 and kept on the same diet for another five days. The fecal excretion of PCB, PCDF and PCDD in the group fed with 10% matcha were 4.4, 2.4-9.1 and 2.5-4.7 times higher (p < 0.01), respectively, than that in the control group. The liver distribution of PCB, PCDF and PCDD in the same groups were 79%, 20-75% and 26-67% of the control group, respectively. These findings suggest that administration of matcha is useful as a treatment of Yusho patients exposed to PCB, PCDF and PCDD.

Prevention of reoxygenation injury in hypoxaemic immature hearts by priming the extracorporeal circuit with antioxidants.

This study tests the hypothesis that abrupt reoxygenation of cyanotic immature hearts when starting cardiopulmonary bypass produces an unintended reoxygenation injury that: (i) nullifies the cardioprotective effects of blood cardioplegia; and (ii) is avoidable by adding the antioxidants, N-(2-mercaptopropionyl)-glycine (MPG) plus catalase to the cardiopulmonary bypass prime. Twenty immature piglets (aged 2-3 weeks) underwent 30 min of blood cardioplegic arrest (BCP) with standard clinical blood cardioplegia (hypocalcaemic, alkalotic, hyperosmolar, substrate-enriched). Six piglets remained normoxaemic (BCP). Fourteen others were made hypoxic (PO2 20-30 mmHg) for up to 2 h by lowering ventilator FiO2 (5-7%) before undergoing reoxygenation on cardiopulmonary bypass at PO2 400 mmHg. In eight animals, the pump prime was not supplemented with antioxidants (Reox + BCP), whereas MPG (80 mg/kg) and catalase (CAT; 5 mg/kg) were added to the pump prime in the other six (MPG/CAT). Myocardial function (end-systolic elastance, conductance catheter), oxidant damage (myocardial conjugated diene production), oxygen consumption and antioxidant reserve capacity were evaluated. Blood cardioplegic arrest caused no functional or biochemical changes in controls without preceding hypoxia. In contrast, hypoxia and reoxygenation in animals undergoing the same blood cardioplegic protocol (Reox + BCP) caused profound myocardial dysfunction, as end-systolic elastance recovered only to 21(2)% (P < 0.05 versus control) of baseline values. Additionally, it reduced antioxidant reserve capacity (malondialdehyde, MDA at 4.0 mM of t-BHP: 1342(59) (P < 0.05 versus control) versus 788(53) mmol/g protein), and led to significantly greater production of conjugated dienes during warm induction (42(4.4) (P < 0.05 versus control) versus 3.3(1.4) A233 nm/100 g per min) and reperfusion (22(2.7) (P < 0.005 versus control) versus 2(0.6) A233 nm/100 g per min). Conversely, supplementation of MPG plus catalase to the pump prime reduced lipid peroxidation (conjugated diene production during warm induction: 22.3(7) A233 nm/100 g per min P < 0.05 versus Reox + BCP), restored antioxidant reserve capacity (MDA at 4.0 M of t-BHP: 975(139) mmol/g protein P < 0.05 versus Reox + BCP) and allowed almost complete functional recovery (80(8)%). Abrupt reoxygenation of hypoxaemic immature hearts on cardiopulmonary bypass causes oxidant damage, nullifies the cardioprotective effects of blood cardioplegia, and leads to reduced myocardial contractility. Antioxidant supplementation of the cardiopulmonary bypass prime avoids these detrimental effects, and results in improved biochemical and functional status.

Cloning, functional expression and dietary regulation of the mouse neutral and basic amino acid transporter (NBAT).

The Na+-independent dibasic and neutral amino acid transporter NBAT is among the least hydrophobic of mammalian amino acid transporters. The transporter contains one to four transmembrane domains and induces amino acid transport activity via a b0,+-like system when expressed in Xenopus oocytes. However, the physiological role of NBAT remains unclear. Complementary DNA clones encoding mouse NBAT have now been isolated. The expression of mouse NBAT in Xenopus oocytes also induced an obligatory amino acid exchange activity similar to that of the b0,+-like system. The amount of NBAT mRNA in mouse kidney increased during postnatal development, consistent with the increase in renal cystine and dibasic transport activity. Dietary aspartate induced a marked increase in cystine transport via the b0,+ system in mouse ileum. A high-aspartate diet also increased the amount of NBAT mRNA in mouse ileum. In the ileum of mice fed on the aspartate diet, the extent of cystine transport was further increased by preloading brush border membrane vesicles with lysine. Hybrid depletion of NBAT mRNA from ileal polyadenylated RNA revealed that the increase in cystine transport activity induced by the high-aspartate diet, as measured in Xenopus oocytes, was attributable to NBAT. These results demonstrate that mouse NBAT has an important role in cystine transport.

Degradation of topoisomerase IIalpha during adenovirus E1A-induced apoptosis is mediated by the activation of the ubiquitin proteolysis system.

The human epithermoid carcinoma-derived cell line MA1, established by introduction of the adenovirus E1A 12 S cDNA linked to the mouse mammary tumor virus long terminal repeat, elicits apoptosis after induction of E1A12S in response to dexamethasone. The level of topoisomerase IIalpha begins to decrease steeply within 36 h preceding the onset of DNA fragmentation, whereas its mRNA level is unchanged (Nakajima, T., Ohi, N., Arai, T., Nozaki, N., Kikuchi, A., and Oda, K. (1995) Oncogene 10, 651-662). Topoisomerase IIalpha prepared by immunoprecipitation or extraction of the nuclear matrix was degraded much more efficiently in the S10 extract prepared from MA1 cells treated with dexamethasone for 42 h (the 42-h extract) than in the extract from untreated MA1 cells (the 0-h extract) in an ATP- and ubiquitin-dependent manner. The proteolytic activity for degradation of topoisomerase IIalpha was suppressed specifically by inhibitors for the proteasome and was much reduced in the 42-h extract prepared from MA1-derivative cell lines expressing E1B19k or Bcl-2. The proteolytic activity was lost after fractionation of the 42-h S10 extract into the S70 and P70 fractions by centrifugation at 70,000 x g for 6 h but partially recovered when these fractions were combined. Polyubiquitinated forms of topoisomerase IIalpha could be detected by incubating it in the S70 or S100 extract, which lacks most of the proteasome activity. The ubiquitination activity in S70 prepared from the 42-h extract was 4- to 5-fold higher than that prepared from the 0-h extract. These results suggest that a component(s) in the ubiquitin proteolysis pathway, responsible for ubiquitination and degradation of topoisomerase IIalpha, is activated or induced during the latent phase of E1A-induced apoptosis.