Substitution at the F-ring N-imide of the indolocarbazole antitumor drug NB-506 increases the cytotoxicity, DNA binding, and topoisomerase I inhibition activities.

The antitumor drug NB-506, which is currently undergoing phase I/II clinical trials, contains a DNA-intercalating indolocarbazole chromophore substituted with a glucose residue. In addition to interacting with DNA, the drug stabilizes the topoisomerase I-DNA covalent complex. To reinforce the DNA binding and anti-topoisomerase I activities of NB-506, an analogue containing a new substituent on the naphthalimide ring F was synthesized. The N-formylamino group of NB-506 has been replaced with a more hydrophilic group, N-bis(hydroxymethyl)methylamino. In this study we show that the incorporation of a longer substituent on the N6 position effectively reinforces both the interaction with DNA and the capacity of the drug to maintain the integrity of the topoisomerase I-DNA covalent complexes. The strength and the mode of binding of the drugs to DNA were studied by complementary biophysical techniques including absorption, fluorescence, and circular and linear dichroism. Various biochemical procedures were applied to investigate the effects on human topoisomerase I using plasmid DNA as well as restriction fragments. The drug binding sites and the positions of the topoisomerase I-mediated cleavage sites were mapped with nucleotide resolution using footprinting and sequencing techniques. Cytotoxicity measurements performed with various human cancer cell lines (HCT-116, DLD-1, MKN-45) indicate that the newly designed drug is 3 to 4 times more toxic to colon and gastric cancer cells than NB-506. Therefore, the results suggest that the antitumor activity of indolocarbazole-based drugs can be enhanced by incorporating DNA and/or topoisomerase I reactive groups. They also support the hypothesis that the substituent on the imide nitrogen on the F ring of NB-506 has direct interaction with the molecular target. The study helps to define the structure-activity relationships in the indolocarbazole series of antitumor agents targeting topoisomerase I.     

Anti-pressor effect of a Chinese-Japanese herbal medicine, saiko-ka-ryukotsu-borei-to on hemodynamics in rabbits

Saiko-ka-ryukotsu-borei-to (TJ-12) is a traditional Chinese-Japanese medicinal mixture clinically used for the treatment of hypertension and/or atherosclerosis concurrent with neurotic disorders. Study on the effect of TJ-12 on the vasoconstriction of cutaneous arterioles induced by nor-adrenaline (NA) was carried out using a rabbit ear chamber (REC) under conscious conditions. Before and after oral administration of TJ-12 everyday for 2 weeks, the same position of an arteriole within a REC was analyzed using an image shearing monitor every minute up to 15 min after varying doses (0.3, 1.0, 3.0 and 10.0 micrograms/kg i.v.) of NA. The changes of mean arteriolar diameter and vasomotion amplitude, before and after feeding of TJ-12 (1% w/w) supplemented diet were compared in the same position. Consequently, the pretreatment with TJ-12 significantly attenuated the changes of mean diameter of NA-induced vasoconstriction and also shortened its duration. In addition, concurrent with its cutaneous microcirculatory response, the pretreatment with TJ-12 systemically suppressed the increase of blood pressure under NA-induced vasoconstriction. These results suggest that the anti-pressor effect of TJ-12 might be apparently attributable to the inhibition of NA-induced vasoconstriction.     

Repair of a ruptured aortic arch aneurysm complicated by postoperative paraplegia: Report of a case

We report herein the rare case of a 79-year-old man who suffered permanent paraplegia after undergoing an otherwise successful total arch replacement for a ruptured aortic arch aneurysm. During cardiopulmonary bypass, perfusion to the distal aorta was maintained from the femoral artery, and postoperative aortography showed intact tributaries from the aorta including the intercostal arteries. Postoperative paraplegia is an extremely rare complication of operations on the aortic arch; however, we speculate that the paraplegia in this patient could be attributed either to a steal phenomenon involving the radicular artery, or to the anatomical particularity of the spinal cord artery described by Cole and Gutelius as the segmental system.     

Penetration of etoposide into human malignant brain tumors after intravenous and oral administration

Summary Penetration of etoposide into the cerebrospinal fluid, brain tumor, and brain tissue after intravenous administration was investigated in patients presenting with malignant brain tumors. A relatively low dose (55–65 mg/m²) was used to compare intravenous with oral administration. High-performance liquid chromatography with fluorescence detection was used to evaluate drug levels. Plasma and cerebrospinal fluid levels of etoposide after oral administration (50–150 mg/day) were also studied so as to determine the adequate oral dose for the treatment of malignant brain tumors. The peak plasma concentration after intravenous administration ranged from 7.01 to 10.47 g/ml, varying in proportion to the injected dose, whereas that after oral administration was lower, namely, 1.44–4.99 g/ml, and was unstable when the oral dose was 150 mg daily. The peak cerebrospinal fluid level following either intravenous or oral administration was much lower than the plasma concentration and was influenced by the peak plasma level and the sampling site. The etoposide concentration in cerebrospinal fluid taken from the subarachnoid space and ventricle of patients displaying no tumor invasion and of those presenting with meningeal carcinomatosis and in cerebrospinal fluid taken from the dead space after tumor resection was 0.7%±0.5%, 3.4%±1.0%, and 7.2% ± 8.5%, respectively, of the plasma concentration. Serial oral administration did not result in the accumulation of etoposide in cerebrospinal fluid. The tumor concentration (1.04–4.80 g/g) was 14.0%±2.9% of the plasma level after intravenous administration, was related to the injected dose, and was approximately twice the concentration detected in the brain tissue. Therefore, a relatively low dose of etoposide injected intravenously penetrates the brain tumor at an efficacious concentration. Our results indicate than an oral dose of 100 mg etoposide be given for malignant brain tumors, as limited penetration of the drug into the intracranial region was observed.     

Brain lesion in congenital myotonic dystrophy

Congenital myotonic dystrophy (CMyD) affects the brain, causing mental changes and psychomotor retardation. However, the pathophysiology of the brain dysfunctions in CMyD remain to be clarified. We described two cases of CMyD with brain abnormalities. Case 1 was diagnosed as having ventricular dilation at 17 days after birth, and died at 3 years and 6 months. Case 2 was diagnosed as having ventricular dilation at birth, and died at 1 year and 3 months. Pathologically, both cases showed remote hypoxic ischemic brain damage and leptomeningeal glioneuronal heterotopia (LGH). In our patients, the white matter changes may have been caused by perinatal asphyxia, and LGH by embryological abnormalities. Taken our data and those of previous reports together, it is suggested that cerebral abnormalities in CMyD are ascribed to both hypoxic ischemic changes and histogenetic abnormalities.     

Histological findings after angioplasty using conventional balloon, radiofrequency thermal balloon, and stent for experimental aortic coarctation

Abstract Background : Use of balloon angioplasty or stent implantation has been reported to be effective in relieving coarctation of the aorta. However, restenosis frequently occurs after balloon angioplasty for native aortic coarctation in small infants, and sometimes develops after stent implantation because of vessel growth. The causes of restenosis remain uncertain. The purpose of this study was to assess the histologic differences in vascular responses to angioplasty using conventional balloon, radiofrequency thermal balloon (RFTB), or stent for experimental aortic coarctation. Methods : The authors surgically created an aortic coarctation model using 14 puppies. Angioplasty using conventional balloon, RFTB, or stent was performed 1 month after the initial operation. At the acute or chronic phase after angioplasty, the animals were killed and histologic studies were performed. Results : More vascular injuries were noted in the specimens from animals undergoing conventional angioplasty than in those with RFTB or stent. However, neointimal hyperplasia was seen more often after RFTB or stent because of the proliferation of smooth muscle cells from the tunica media, caused by secretion of growth factors. Apoptosis reached a peak 1?2 weeks after angioplasty, regardless of the type of intervention. Conclusions : The authors conclude that angioplasty with RFTB or stent can provide relatively small injuries in the vessel wall for aortic coarctation, but care must be taken to prevent restenosis caused by intimal hyperplasia, because neointima hyperplasia is more frequent after RFTB or stent.     

Laterality of vestibular evoked myogenic potentials

To clarify the laterality of acoustically evoked vestibulocollic reflexes with a short latency (vestibular evoked myogenic potentials, VEMPs), responses on the bilateral sternocleidomastoid muscles (SCMs) to unilateral acoustic stimulation were studied. Twenty-one healthy volunteers were enrolled. Surface electrodes were placed on the upper half of each SCM (active) and on the lateral end of the upper sternum (reference). Clicks and 500-Hz tone-bursts (95 dB nHL) were used. All subjects showed positive-negative biphasic responses on the ipsilateral SCM by clicks and tone-bursts. Click-stimulation of 41 of the 42 ears did not evoke any response on the contralateral SCM. However, in one ear, positive-negative biphasic responses were evoked on the contralateral SCM. Recordings on the contralateral SCM by tonebursts showed no response in 32 ears, small positive-nega-tive biphasic responses in four ears, and small negative-positive biphasic responses in six ears. These findings show that VEMPs are ipsilateral-dominant, basically consistent with the hypothesis that they are of saccular origin.