A three-dimensional structure model of the complex of glutamyl-tRNA synthetase and its cognate tRNA

A docking model of glutamyl-tRNA synthetase (GluRS) and tRNAGlu was constructed, on the basis of the distinguished similarity between the X-ray crystallographic three-dimensional structures of the N-terminal halves of the Thermus thermophilus GluRS in the free state and the Escherichia coli glutaminyl-tRNA synthetase in a complex with tRNAGln. The modeled structure is energetically favorable and is also well consistent with the results of site-directed mutagenesis studies. The model indicates that the GluRS-specific insertions 2 and 3 fit and bind to the acceptor stem and the D arm, respectively, of the cognate tRNA without affecting other contacts. In particular, insertion 3 strongly interacts with the two D-stem base pairs that are essential for the tRNA-GluRS recognition.

Involvement of a cellular surface factor(s) in lipid-free apolipoprotein-mediated cellular cholesterol efflux

Involvement of cellular surface factors in cellular lipid efflux mediated by lipid-free apolipoprotein has been investigated. Lipid-free human apolipoprotein (apo) A-I generated net efflux of cholesterol and phospholipid from mouse peritoneal macrophages and rat aorta smooth muscle cells. Ratio of cholesterol to phospholipid was much lower in the lipid released by this mechanism from the smooth muscle cells than that from the macrophages, in agreement with our previous observation (Li, Q., Komaba, A. and Yokoyama, S. (1993) Biochemistry 32, 4597-4603). On the other hand, free apoA-I did not cause any lipid efflux from human erythrocytes. In contrast, apparent efflux of cellular cholesterol to HDL was similarly observed from all of these three cellular membranes. Trypsin treatment of the cultured macrophages completely inhibited apoA-I-mediated efflux of cholesterol and phospholipid. Smooth muscle cells also showed complete inhibition of the apoA-I-mediated cellular lipid efflux by trypsin treatment except that it required longer incubation with the enzyme. The same cellular treatment with trypsin even by prolonged incubation had only a limited effect on apparent cellular cholesterol efflux to HDL and apolipoprotein-free lipid microemulsions. Thus, free apolipoprotein-mediated cellular lipid efflux seems to depend on a trypsin-susceptible cellular surface factor(s) that erythrocytes may lack, being distinct from physicochemical cholesterol exchange reaction between cell and lipoprotein.

Synthesis of N-acetylglucosaminyl asparagine-substituted puromycin analogues

As part of our project aimed to introduce specifically glycosylated amino acids into proteins, new glycosylated puromycin analogues were chemically synthesized. Introduction of a free N-acetylglucosaminyl asparaginyl side chain abolished the activity of puromycin completely, but when the sugar OH groups were rendered increasingly hydrophobic by acetylation or benzylation, up to 8% of the activity was recovered. The results of our preliminary inhibition tests suggest that the interaction of puromycin analogues and therefore also of glycosylated aminoacyl tRNA, with the ribosomal A site increase with hydrophobicity of the modifying protecting groups.

[Surgical treatment of congenital atypical coarctation of the aorta and postoperative management for hypertension]

A 10-year-old boy was admitted to our hospital with severe hypertension due to unusual aortic coarctation at the level of the diaphragm without renal artery stenosis. We made left interior thoracotomy and left para-rectal incision through extraperitoneal approach, and extra-anatomic bypass was established with a 16 mm knitted Dacron graft from the descending aorta to the infrarenal abdominal aorta, under a circulatory assist. Postoperatively, he complained of abdominal pain with residual hypertension and required an intensive anti-hypertensive treatment to avoid intestinal necrosis. Pressure gradient between upper and lower extremities disappeared 3 weeks after repair. High level of plasma renin activity still continued 4.5 months after surgery in spite of oral administration of beta blockade and ACE inhibitor.

Independent regulation of cholesterol incorporation into free apolipoprotein-mediated cellular lipid efflux in rat vascular smooth muscle cells

Cholesterol was poorly available to free apolipoprotein (apo)A-I-mediated cellular lipid efflux from cholesterol-loaded rat vascular smooth muscle cells generating cholesterol-poorer pre-beta-HDL particles than those generated from macrophages by the same reaction (Li, Q., Komaba, A., and Yokoyama, S. (1993) Biochemistry 32, 4597-4603). The factors known to induce transformation of the smooth muscle cells into a macrophage-like stage were used in order to modulate this reaction, such as human platelet-derived growth factor, macrophage colony-stimulating factor, and phorbol 12-myristate-13-acetate (PMA). When the cells were stimulated by PMA following the pretreatment with platelet-derived growth factor plus macrophage colony-stimulating factor, cholesterol efflux mediated by free apoA-I increased 3-fold without changing phospholipid efflux, resulting in generation of pre-beta-HDL particles more rich in cholesterol. This treatment had only a little or no effect on apparent cellular cholesterol efflux to HDL or lipid microemulsion, respectively. Overall cellular free cholesterol pool size was unaffected by the treatment, and probing by extracellular cholesterol oxidase did not detect gross change in the cellular surface cholesterol. This specific enrichment of cholesterol in the apoA-I-mediated cellular lipid efflux was reversed by protein kinase C inhibitors. Measurement of intracellular cholesterol esterification suggested that PMA induced translocation of intracellular cholesterol to a specific pool for apoA-I-mediated efflux, and a protein kinase C inhibitor reversed this effect.

Relationship between cell proliferation activity and morphological characteristics of papillary microcarcinoma in the thyroid of Graves' disease

Three hundred and seven lesions of papillary microcarcinoma of the thyroid (PMT), found in 6830 cases of Graves' disease, were reviewed to evaluate the morphological characteristics. The prevalence rate and incidence of multiplicity of PMT in Graves' disease were higher (P < 0.05 and P < 0.005, respectively) in females (4.03% and 0.73%, respectively) than in males (2.68% and 0.12%, respectively). All lesions of PMT were classified histologically into three types: sclerosing non-encapsulated (SNE), non-sclerosing encapsulated (NSE) and non-sclerosing non-encapsulated (NSNE). Comparison of the three types of PMT revealed that the mean age and tumor size of NSNE were less than those of NSE and SNE (P < 0.001 and P < 0.005, respectively), and 13 of 19 lesions less than 1 mm belonged to NSNE. In addition, cell proliferation and expression of estrogen and progesterone receptors were examined immunohistochemically in 257 lesions of PMT. The Ki-67 labeling index of NSE was lower than that of NSNE and SNE (P < 0.005). None of the cases of PMT was positive for estrogen or progesterone receptors. The present study indicated that NSNE may be an early stage in tumor progression, and that fibrous encapsulation has the potential to modify neoplastic cell proliferation.

Microheterogeneity in heteromultimeric assemblies formed by Shaker (Kv1) and Shaw (Kv3) subfamilies of voltage-gated K+ channels

Single K+ channels were recorded in Xenopus oocytes injected with a 1:1 mixture of mRNAs coding for NGK1 (Kv1.2) and NGK2 (Kv3.1a) voltage-dependent K+ channels. A new class of channels of 18 pS conductance was observed, and was designated as NGK1,2 channels. According to their properties of activation voltages and open life times, four types of NGK1,2 channels with microheterogeneity were detected. The results suggest that voltage-dependent NGK1 Shaker and NGK2 Shaw K+ channels, from different subfamilies, assemble to form heteromultimeric K+ channels, giving rise to a mosaic of characteristics inherited from two parental channels.

Slow inactivation conserved in heteromultimeric voltage-dependent K+ channels between Shaker (Kv1) and Shaw (Kv3) subfamilies

Single K+ channels were recorded under the cell-attached mode in Xenopus oocytes injected with an equal amount of mRNAs coding for NGK1 (Kv1.2) and NGK2 (Kv3.1a) voltage-dependent K+ channels. A new class of channels of 20 pS in conductance with three degrees of inactivation was observed. The results suggest that voltage-dependent NGK1 Shaker and NGK2 Shaw K+ channels, from different subfamilies, assemble to form heteromultimeric K+ channels in Xenopus oocytes and show characteristics inherited from two parental channels.

Whole-cell analysis of NGK2 (mKv3.1a) K+ channels stably expressed in mouse fibroblast cells

NGK2 (mKv3.1a) K+ channel cDNA was introduced into mouse B82 fibroblast cells to express in a mammalian system. The NGK2 current in the stably transformed fibroblast cells exhibited a high threshold for activation and slow decay with two components. The data suggest that the NGK2 channel may contribute to slowly inactivating K+ currents observed in excitable and inexcitable cells.

Appendiceal intussusception due to an appendiceal malignant polyp--an association in a patient with Peutz-Jeghers syndrome: report of a case

A 40-year-old woman with Peutz-Jeghers syndrome and an appendiceal intussusception is reported. In this patient, the lead point was a large sessile, appendiceal polyp. The invaginated and inverted portion of the appendix resembled the long stalk of a pedunculated polyp on roentgenography and endoscopic examination. Histologically, the appendiceal polyp was a villous adenoma with mild to severe atypia and focal carcinoma in situ. In patients with Peutz-Jeghers syndrome, hamartomatous polyps and colorectal adenomatous polyps with highly malignant potential can coexist and must be managed appropriately. Therefore, when evaluating a polypoid or a pedunculated lesion in the cecal lumen, the possibility of an appendiceal intussusception should also be investigated.

Cell-free synthesis and amino acid-selective stable isotope labeling of proteins for NMR analysis

For the application of multidimensional NMR spectroscopy to larger proteins, it would be useful to perform selective labeling of one of the 20 amino acids. For some amino acids, however, amino acid metabolism drastically reduces the efficiency and selectivity of labeling in in vivo expression systems. In the present study, a cell-free protein synthesis system was optimized, so that highly efficient and selective stable isotope labeling of proteins can be achieved in the absence of amino acid metabolism. The productivity of the E. coli cell-free coupled transcription-translation system was first improved, by about fivefold, by using the T7 RNA polymerase for transcription and also by improving the translation conditions. Thus, about 0.1 mg protein per 1 ml reaction mixture was synthesized. Then, this improved cell-free system was used for Asp- or Ser-selective 15N-labeling of the human c-Ha-Ras protein. With a 15 ml cell-free reaction, using less than 1 mg of 15N-labeled amino acid, 1 mg of the Ras protein was obtained. 1H-15N HSQC experiments confirmed that the Ras protein was efficiently labeled with high selectivity. These results indicate that this cell-free protein synthesis system is useful for NMR studies.

[A case of pulmonary blastoma composed of histological features of both pulmonary blastoma and pulmonary endodermal tumor resembling fetal lung]

A case of pulmonary blastoma in a 71-year-old male was reported. Chest X-ray and CT scan showed a well demarcated mass lesion in the apical segment of the right lung. A polypoid tumor was detected in the apical branch of the right bronchus by bronchoscopy. The biopsy confirmed the diagnosis of pulmonary blastoma. The patient underwent a right upper lobectomy with lymph nodes dissection on Jan. 26, 1990. The resected tumor was really composed of two parts: a main tumor in the lung parenchyma and polypoid one protruding into the bronchus from the main tumor. The polypoid tumor exhibited typical features of pulmonary blastoma with both carcinomatous and sarcomatous components. The histology of the main tumor was identical to pulmonary endodermal tumor resembling fetal lung (PET). The metastases in the excised lymph nodes consisted entirely of carcinomatous elements. The patient died of brain stem metastasis a year after his operation. The present case, with typical pulmonary blastoma and PET present in the same tumor, supports the idea that pulmonary blastoma and PET belong to the same group neoplasma.

Morule with biotin-containing intranuclear inclusions in thyroid carcinoma

One thousand and sixty cases of thyroid carcinoma were reviewed to compare morules with squamous metaplasia clinicopathologically and immunohistochemically. Morules and squamous metaplasia were found in five (0.47%) and 32 cases (3.0%) respectively. The five patients with morules were all female (age 20-36 years) including four with papillary carcinoma and one with follicular carcinoma. The 32 patients with squamous metaplasia consisted of 30 females and 2 males (age 14-78 years), all of whom had papillary carcinoma except for one follicular carcinoma. The morules demonstrated characteristic 'optically clear nuclei' (OCN), which ultrastructurally showed filamentous structures in the nuclei. The OCN were immunohistochemically demonstrated to contain intranuclear biotin. Furthermore, the morule often accompanied with the OCN was positive for Ulex Europaeus agglutinin l (UEA-l) but negative for bovine muzzle epidermal keratin (EK). On the contrary, squamous metaplasia unaccompanied with the OCN was negative for UEA-l, but positive for EK. Follow-up information revealed that one of the five patients with morules had died of the disease, one was alive with pulmonary metastasis, and three were disease-free. Eight of 32 patients with squamous metaplasia had died of the disease; of the others who were alive, four patients have had recurrence.

Aneurysm of the distal anterior inferior cerebellar artery--case report

A 38-year-old female presented with vertigo, right hearing disturbance, and slight headache which were treated medically. However, she suddenly developed severe headache with vomiting and vertigo. Computed tomography revealed subarachnoid hemorrhage, and right vertebral angiography disclosed a rare aneurysm at the distal portion of the anterior inferior cerebellar artery. She underwent a right suboccipital craniectomy in the lateral position. The aneurysm could not be clipped because the aneurysm was tightly adhered to the brainstem, so it was trapped. Postoperatively, she showed slight VIIIth to Xth cranial nerve disturbances. Three months postoperatively, the IXth and Xth cranial nerve disturbances had disappeared, but the tinnitus and right hearing disturbance were still present. The initial symptoms were probably caused by minor bleeding from the aneurysm.

Initial mutational steps toward loss of opsin gene function in cavefish

The river-dwelling fishes of Astyanax fasciatus and their derivatives from Pachon and Micos caves in Mexico were collected. By comparing red (r007) and green (g103) opsin gene sequences from the three populations, we found a high frequency of C-->T changes in r007 and g103 of the eyed Micos fishes presumably due to spontaneous cytosine methylation or enzymatic deamination of the CG dinucleotide, and a deletion of 12 consecutive nucleotides in g101 of the blind Pachon fishes. Thus, high rates of nucleotide substitution and C-->T transitions, usually found for pseudogenes, may occur even before they become nonfunctional.

Expression of erythroid-specific genes in acute megakaryoblastic leukaemia and transient myeloproliferative disorder in Down's syndrome

Acute megakaryoblastic leukaemia (M7) and transient myeloproliferative disorder in Down's syndrome (TMD) are characterized by rapid growth of abnormal blast cells which express megakaryocytic markers. To clarify properties of the blast cells in M7 and TMD cases, we examined erythroid markers expression in blasts from six cases with M7 and seven cases with TMD in this study. Erythroid-specific mRNAs encoding gamma-globin and erythroid delta-aminolevulinate synthase were found to be expressed in blasts from most of these cases, indicating that majorities of the blasts in M7 and TMD cases have erythroid and megakaryocytic phenotypes. We also found that mRNAs encoding GATA-1 and GATA-2 are expressed in all these cases. These results suggest that M7 blasts and TMD blasts correspond to the erythroid/megakaryocytic bipotential progenitor cells.

[A surgical case report of isolated congenital tricuspid valve insufficiency]

A 17-year-old boy observed as a case with Ebstein's anomaly. Echocardiogram and ventriculogram revealed enlargement of the tricuspid valve ring, dysplasia of anterior and posterior leaflet of tricuspid valve, but the anatomy of the septal leaflet was almost normal. According to these findings, the diagnosis of this patient was isolated congenital tricuspid regurgitation. Tricuspid annuloplasty of DeVaga's method and Reed's method were done. Post-operative residual regurgitation was mild. These procedures were resulting in a successful course. Isolated congenital tricuspid valve insufficiency was extremely rare. Only 7 cases of isolated congenital tricuspid insufficiency successfully operated in Japan were collected.

Phosphorothioate oligonucleotides block reverse transcription by the Rnase H activity associated with the HIV-1 polymerase

We demonstrate the degradation of RNA bound to an antisense oligonucleotide by a reverse transcriptase enzyme-associated RNase H activity. We found that phosphorothioate oligonucleotides inhibit the RNase H activity by binding to AMV RT, rather than to the template RNA, whereas the RNase H activity of HIV-1 RT is not affected by the antisense phosphorothioate oligonucleotide. Selective inhibition of HIV-1 gene expression involves the degradation of the template RNA bound to the antisense phosphorothioate oligonucleotide by the RNase H activity associated with the HIV-1 polymerase.

The zinc-binding site of Escherichia coli glutamyl-tRNA synthetase is located in the acceptor-binding domain. Studies by extended x-ray absorption fine structure, molecular modeling, and site-directed mutagenesis

The zinc contents of fragments of Escherichia coli glutamyl-tRNA synthetase, as well as the conservation of the CYC sequence only in zinc-containing glutamyl-tRNA synthetases, suggested that the 98CYCX24-CRHSHEHHADDEPC138 includes some or all residues involved in binding its zinc atom (Liu, J., Lin, S.-X., Blochet, J.-E., Pézolet, M., and Lapointe, J. (1993) Biochemistry 32, 11390-11396). Extended x-ray absorption fine structure (EXAFS) shows that this zinc atom has a four-coordinate non-planar coordination environment with 3 sulfur and 1 nitrogen atoms with bond lengths, respectively, 2.37 +/- 0.02 A and 2.01 +/- 0.02 A, presumably belonging to 3 cysteine residues and 1 histidine residue. Conservative replacement of each histidine and cysteine residue of the 98C-138C segment, respectively, with glutamine (Q) and serine (S), yields variants H129Q, H131Q, H132Q, and C138S (which sustain the growth at 42 degrees C of E. coli JP1449, whose glutamyl-tRNA synthetase is thermosensitive) and C98S, C100S, C125S, and H127Q (which do not). The amount of this enzyme in these mutants is at least 1 order of magnitude larger than that in a wild type strain; however, no glutamyl-tRNA synthetase activity is detectable in extracts of the variants C100S and C125S, whereas its specific activity in those of C98S and H127Q is about 10-fold lower than in cells overproducing the wild type enzyme or the variants H129Q, H131Q, H132Q, and C138S. These results indicate that the zinc atom present in E. coli glutamyl-tRNA synthetase is bound by the 2 evolutionarily conserved cysteines at positions 98 and 100, and by Cys125 and His127. Molecular modeling of the N-terminal half of this enzyme, using the known structure of E. coli glutaminyl-tRNA synthetase, supports this conclusion and suggests that the 98C-127H segment does not have the characteristics of the classical zinc fingers.

Effect of magnesium on secretion of platelet-derived growth factor by cultured human umbilical arterial endothelial cells

Conditioned media were prepared by incubating human cultured umbilical arterial endothelial cells for 48 h in magnesium (Mg) sufficient (900 microM) and deficient (100 microM) conditions. Minimum essential media (MEM) are designated as [900]- and [100]-MEM, respectively. After the incubation, a portion of the [100]-MEM media was adjusted from 100 to 900 microM magnesium ([100-900]-MEM). Smooth muscle cells were incubated with the three media and their growth rates were determined by [3H]-thymidine incorporation and cell counting. The growth rate in [100-900]-MEM was significantly higher than in [900]- or [100]-MEM. When platelet-derived growth factor (PDGF) was neutralized by the addition of a mixture of anti-PDGF-AA and -BB, [3H]-thymidine incorporation in [100-900]-MEM decreased by 12.5 per cent, but only by 4.9 per cent in [900]-MEM. These results indicate that magnesium deficiency increases the secretion of PDGF by endothelial cells. This is also supported by the results of the radioimmunoassay for PDGF-BB; the quantity of PDGF in the magnesium-deficient media was greater than in the magnesium-sufficient media.

Paralogous origin of the rhodopsinlike opsin genes in lizards

Rhodopsinlike opsins constitute a distinct phylogenetic group (Yokoyama 1994, Mol. Biol. Evol. 11:32-39). This RH2 group includes the green-sensitive opsins in chicken and goldfish and the blue-sensitive opsin in a nocturnal lizard gecko. In the present study, we isolated and sequenced the genomic DNA clones for the RH2 opsin gene, rh2Ac, of the diurnal lizard Anolis carolinensis. This single-copy gene spans 18.3 kb from start to stop codons, making it the longest opsin gene known in vertebrates. Phylogenetic analysis strongly suggests that rh2Ac is more closely related to the chicken green opsin gene than to the gecko blue opsin gene. This gene tree differs from the organismal tree, where the two lizard species should be most closely related, implying that rh2Ac and the gecko blue-sensitive opsin genes have been derived from duplicate ancestral genes.

[Local chemotherapy for malignant brain tumors using methotrexate-containing fibrin glue]

Fibrin glue (FG) is an agent developed for achieving hemostasis and the adhesion of living tissue during surgical operations. Incorporation of a drug into FG may be expected to have a sustained local release. In the present study, methotrexate (MTX) included in FG (FG-MTX) was used. The release of MTX into human plasma and cerebrospinal fluid was studied by in vitro study to confirm the sustained release effect of this preparation, by in vivo study, in which the antitumor effect of FG-MTX was assessed in rats bearing 9L-gliosarcoma subcutaneously; and clinically, FG-MTX therapy was attempted in patients with malignant brain tumors. The in vitro study showed that MTX levels rapidly decreased over 1 to 3 days, but was still detected on days 7 and 14. The results showed the sustained release effect of MTX. The in vivo study showed that in the FG-MTX group, all tumors began to decrease soon after administration and disappeared in four out of five animals (80%) on about day 10. In the clinical study, sustained release for more than one week was found, and tumor decrease occurred in the case of a malignant brain tumor. Thus, FG-MTX appears to provide an effective local chemotherapy.