Regulation of RNA processing and transport by a nuclear guanine nucleotide release protein and members of the Ras superfamily

The RCC1 gene of mammals encodes a guanine nucleotide release protein (GNRP). RCC1 and a homolog in Saccharomyces cerevisiae (MTR1/PRP20/SRM1) have previously been implicated in control of mRNA metabolism and export from the nucleus. We here demonstrate that a temperature-sensitive fission yeast mutant which has a mutation in a homologous gene, and two of three additional (mtr1/prp20/srm1) mutants accumulate nuclear poly(A)+ RNA at 37 degrees C. In S.cerevisiae, maturation of rRNA and tRNA is also inhibited at 37 degrees C. Nevertheless, studies with the corresponding BHK-21 cell mutant indicate that protein import into the nucleus continues. MTR1 homologs regulate RNA processing at a point which is distinct from their regulation of chromosome condensation since: (i) poly(A)+ RNA accumulation in the fission yeast mutant precedes chromosome condensation, and (ii) unlike chromosome condensation, accumulation of nuclear poly(A)+ RNA does not require p34cdc28 kinase activation or protein synthesis. Moreover, experiments involving inhibition of DNA synthesis indicate that the S.cerevisiae homolog does not govern cell cycle checkpoint control. Since RCC1p acts as GNRP for Ran, a small nuclear GTPase of the ras superfamily, we have identified two homologs of Ran in S.cerevisiae (CNR1 and CNR2). Only CNR1 is essential, but both code for proteins extremely similar to Ran and can suppress mtr1 mutations in allele-specific fashion. Thus, MTR1 and its homologs appear to act as GNRPs for a family of conserved GTPases in controlling RNA metabolism and transport. Their role in governing checkpoint control appears to be restricted to higher eukaryotes.

Accelerated evolution of Trimeresurus flavoviridis venom gland phospholipase A2 isozymes

Six Trimeresurus flavoviridis (Habu snake) venom gland phospholipase A2 (PLA2) isozyme genes were found to consist of four exons and three introns and to encode proteins of 138 amino acid residues, including the signal sequence of 16 amino acid residues. Comparison of the nucleotide sequences showed that the introns are much more homologous than the protein-coding regions of exons except for the signal peptide-coding region of the first exon. The numbers of nucleotide substitutions per site (KN) for introns are approximately one-fourth of the numbers of nucleotide substitutions per synonymous site (KS) for the protein-coding regions, indicating that the introns are unusually conserved. The absence of an apparent functional role for the introns suggests that the protein-coding regions, except for the signal peptide-coding domains, have evolved at greater substitution rates than introns. The fact that the numbers of nucleotide substitutions per nonsynonymous site (KA) are close to or larger than KS values for relevant pairs of genes revealed that Darwinian-type accelerated substitutions have occurred in the protein-coding regions or exons. This is compatible with the presence of PLA2 species with diverse physiological activities in the venom.

Our technique of parathyroid autotransplantation in operation for papillary thyroid carcinoma

BACKGROUND

For papillary thyroid carcinoma, we have used our standard operative method consisting of total thyroidectomy, bilateral lymph node dissection, and parathyroid autotransplantation. Our special parathyroid transplantation method involves transplantation of the minced glands into the pectoralis major muscle. We investigated whether this method is useful for preserving parathyroid function.

METHODS

In 17 patients who underwent our standard operation for papillary thyroid carcinoma, the intact parathyroid hormone (PTH) and serum calcium levels were determined for 4 weeks after the operation.

RESULTS

In all cases the intact PTH levels fell below detectable limits immediately after operation and then recovered to the preoperative level about 2 weeks after the operation. The same recovery patterns were observed in two groups undergoing transplantation of two glands and three or four glands.

CONCLUSIONS

These recovery patterns of intact PTH levels seem to indicate that the glands were grafted successfully and recovered their function. Our method is thought to be useful for preserving parathyroid function after surgery.

Receptor-mediated specific biological activity of a beta-amyloid protein fragment for NK-1 substance P receptors

A beta-amyloid protein fragment AP21-35 (tetradeapeptide with amino acid residues 21-35) was found to be a highly selective agonist of substance P receptors (NK-1) among three tachykinin receptor subtypes. This peptide fragment contracted the smooth muscle preparations of guinea pig ileum in a dose dependent manner (EC50 = 22 microM). This activity was completely reversed by CP-96,345-1, a specific antagonist of NK-1 receptors, whereas atropine for NK-3 had no effect. The peptide was inactive in rat vas deferens which contains predominantly NK-2 receptors. These results indicated that AP21-35 is a highly selective agonist for NK-1 receptors. In the radio-ligand receptor binding assay using [125I]-Bolton-Hunter substance P to membranes from guinea pig ileum, the fragment exhibited a distinct dose-response curve (IC50 = 11 microM). All the present data strongly suggest that beta-amyloid protein function as a peptide ligand of substance P receptors with some pathophysiologic activities.

Enhancement of thrombin receptor activation by thrombin receptor-derived heptapeptide with para-fluorophenylalanine in place of phenylalanine

Thrombin receptor-derived peptide SFLLRNP (one-letter amino acid code) which corresponds to the N-terminal heptapeptide of tethered ligand is able to activate thrombin receptor and to stimulate the phosphoinositide (PI) turnover. The replacement of Phe-2 by Ala eliminated this activity completely, showing the crucial role of the Phe-phenyl group in receptor activation. It was found that substitution of para-fluorophenylalanine ((p-F)Phe) for Phe-2 enhanced several times the PI-turnover activity of SFLLRNP. This is the first example to date of a substitution with one order of magnitude greater increase in receptor activation. The Phe-2/Tyr substitution diminished the activity drastically (almost 2% of SFLLRNP), indicating the importance of hydrophobicity of Phe2-phenyl. The Phe-2/Leu substitution, however, diminished also the activity (less than 2% of SFLLRNP). These results suggested that highly specific hydrophobic interaction exists between Phe-2 of the tethered ligand and its binding site in thrombin receptor.

Chymotrypsin inhibitory conformation of dipeptides constructed by side chain-side chain hydrophobic interactions

A complete series of configurational isomers (L-L, L-D, D-L and D-D) of a dipeptide Leu-Phe benzyl ester have been synthesized and assayed for chymotrypsin. In the conformational analysis by 400 MHz 1H NMR, the L-D and D-L isomers, but not the L-L and D-D isomers, showed fairly large upfield shifts (0.2-0.4 ppm) of Leu-beta CH2 and gamma CH proton signals, indicating the presence of shielding effects from the benzene ring. In addition to distinct signal splitting of Phe-beta CH2, the NOE enhancement observed between Leu-delta CH3 and Phe-phenyl groups revealed that these groups are in close proximity. These data indicated that L-D and D-L isomers form a hydrophobic core between side chains of adjacent Leu and Phe residues. When the dipeptides were examined for inhibition of chymotrypsin using Ac-Tyr-OEt as a substrate, the L-L isomer showed no inhibition, itself becoming a substrate. However, the other three isomers inhibited chymotrypsin in a competitive manner, and the D-L isomer was strongest with Ki of 2.2 x 10(-5) M. It was found that the D-L isomer was only slowly hydrolysed but the L(or D)-D isomer was not. H-D-Phe-L-Leu-OBzl with the inverse sequence of H-D-Leu-L-Phe-OBzl inhibited chymotrypsin more strongly (Ki = 6.3 x 10(-6) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of antigenic determinants in thyroid peroxidase by synthesis of possible sequential peptides

One way to locate antigenic determinants in thyroid peroxidase (TPO) is to evaluate the binding of chemically synthesized peptides to autoantibodies. A major epitope of TPO involved in thyroid autoimmunity has been reported to be at residues 590 to 675. Therefore, we synthesized three peptides (P1, residues 603-610; P2, 615-630; and P3, 654-665) in the most antigenic part of this range, as judged by antigenicity analysis, and measured their antigenicity by enzyme-linked immunosorbent assay (ELISA). Amino groups protected with fluorenyl-methoxycarbonyl were used in the synthesis. Sera from 42 untreated patients with Hashimoto's disease and 30 untreated patients with Graves' disease were tested for binding with each peptide. In addition, 6 sera with antibodies against denatured and reduced microsomal antigen were tested. Sera obtained from 22 normal subjects were used as a control. Binding of sera from the patients with autoimmune thyroid disease to the synthetic peptides was weak, about 1% of binding to thyroid microsomes prepared from Graves' thyroid. However, the ELISA index of a mixture of P1, P2, and P3 was significantly higher in the patients with Hashimoto's disease than in the healthy subjects. For both P2 and P3, the ELISA index of the sera with antibodies against denatured and reduced TPO was higher than that of the sera from normal subjects. These results suggested 1) that the antigenic epitopes of TPO recognized by autoantibodies may be conformational and discontinuous, and 2) that antibodies against these linear portions of TPO may exist in patients with Hashimoto's disease.

Water-soluble chymotrypsin specific inhibitors containing arginine

In an attempt to develop water-soluble, potent inhibitors for chymotrypsin, structurally rigid dipeptides containing arginine were designed and synthesized. The dipeptide H-D-Arg-Phe-NHBzl inhibited chymotrypsin very strongly (Ki = 5.9 microM). The dipeptide with the inverse sequence, H-D-Phe-Arg-NHBzl, was also a moderate inhibitor for chymotrypsin with Ki of 240 microM. In spite of the presence of arginine in these dipeptides, they inhibited trypsin only weakly, indicating that they are highly specific for chymotrypsin. High resolution 1H-NMR (400-MHz) indicated that these dipeptides can make a strong intramolecular hydrophobic interaction between Arg-beta, gamma, delta-methylenes and Phe-phenyl, producing a rigid hydrophobic core which interacts with the chymotrypsin S2 site. Since these dipeptides are easily soluble in water, they are regarded as the sophisticated and effective inhibitors for chymotrypsin.

Working memory deficits following muscarinic blockade combined with depletion of brain somatostatin in rats

In a working memory task with three-panel runway paradigm, cysteamine, a depletor of somatostatin, at 100 or 200 mg/kg i.p. given 24 h before testing, had no effect on the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points). Cysteamine at 100 mg/kg caused a significant reduction in somatostatin-like immunoreactivity in the rat brain, including the hippocampus and cerebral cortex. Working memory errors were significantly increased by scopolamine, a muscarinic receptor antagonist, at 0.32 mg/kg i.p. given 20 min before testing, whereas errors were not affected by the 0.1 mg/kg dose. Combined administration of 100 mg/kg cysteamine and 0.1 mg/kg scopolamine significantly increased the number of working memory errors. However, cysteamine at 100 mg/kg and scopolamine at 0.1 mg/kg had no effect on reference memory errors, whether they were administered alone or in combination. These results suggest that depletion of brain somatostatin aggravates working memory deficits induced by blockade of muscarinic receptors.

Blockade of hippocampal nicotinic receptors impairs working memory but not reference memory in rats

In a three-panel runway task, intrahippocampal injection of the nicotinic receptor antagonist, mecamylamine (10 and 18 micrograms/side), significantly increased the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points) in a test of working memory. This increase in errors also occurred after rats were given IP mecamylamine (10 mg/kg). Mecamylamine did not affect the number of errors in a test of reference memory whether it was given at doses up to 18 micrograms/side intrahippocampally or up to 10 mg/kg IP. These results suggest that mechanisms mediated by hippocampal nicotinic receptors play a role in working memory but not in reference memory.

Purification and characterization of UDP-N-acetylglucosamine: alpha-6-D-mannoside beta 1-6N-acetylglucosaminyltransferase (N-acetylglucosaminyltransferase V) from a human lung cancer cell line

A beta 1-6N-acetylglucosaminyltransferase (GnT-V) [EC 2.4.1.155] which catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to alpha-D-6-mannoside has been purified up to 20,000-fold from the cultured supernatant of the QG small lung cancer cell line with a 37% yield. The isolation procedure included chromatography on phenyl-Sepharose, hydroxylapatite, UDP-hexanolamine Sepharose, and a biantennary sugar substrate (GnGn-bi-Asn) coupled to activated CH-Sepharose 4B. Sodium dodecyl sulfate gel electrophoresis under non-reducing conditions showed a single band of 73 kDa. Under reducing conditions, however, an additional component of 60 kDa was seen. Peptide mapping analysis indicated that both of these proteins were essentially identical, indicating that the 60-kDa component is probably a proteolytically cleaved form of the 73-kDa protein. Studies on the activity of the enzyme toward a variety of pyridylaminated sugars showed that the enzyme is most active toward triantennary (GnGnGn-tri-PA) and biantennary (GnGn-bi-PA) sugars. The Km values for GnGn-bi-PA and UDP-GlcNAc were 133 microM and 3.5 mM, respectively. These studies represent the first report of the enzymatic properties of a highly purified human GnT-V.

Carboxyl-terminal heparin-binding fragments of platelet factor 4 retain the blocking effect on the receptor binding of basic fibroblast growth factor

Platelet factor 4 (PF-4) blocks the binding of basic fibroblast growth factor (bFGF) to its receptor. In the present study, we constructed carboxyl-terminal fragments, which represent the heparin-binding region of the PF-4 molecule, and examined whether these synthetic peptides retain the blocking effects on the receptor binding of bFGF. Synthetic peptides inhibited the receptor binding of bFGF. Furthermore, they inhibited the migration and tube formation of bovine capillary endothelial cells in culture (these phenomena are dependent on endogenous bFGF).

Discriminative stimulus properties of NIK-247 and tetrahydroaminoacridine, centrally active cholinesterase inhibitors, in rats

The discriminative stimulus effect of the novel centrally active cholinesterase inhibitor, NIK-247, was investigated in rats and compared with that of tetrahydroaminoacridine (THA). Rats were trained to discriminate either 10 mg/kg NIK-247 or 1.8 mg/kg THA from saline in a two-lever food-reinforced procedure. The stimulus effect of NIK-247 was substituted for by the cholinesterase inhibitors, THA and physostigmine. The THA stimulus was substituted for by NIK-247 and physostigmine. The muscarinic receptor agonist arecoline substituted for the NIK-247 and THA stimuli. Both stimulus effects of NIK-247 and THA were blocked by the muscarinic antagonist scopolamine. The dopaminergic-activating drugs amantadine and lisuride substituted for the stimulus effects of NIK-247 and THA. However, neither the NIK-247 nor the THA stimulus was antagonized by the dopamine antagonists haloperidol, SCH 23390, and sulpiride. These results suggest that the discriminative stimulus effects of NIK-247 and THA are mediated by muscarinic receptors, and that the dopaminergic activity resulting from cholinergic activation may account for some part of both stimuli.

Working memory deficits induced by intrahippocampal administration of 8-OH-DPAT, a 5-HT1A receptor agonist, in the rat

In a test of working memory using a three-panel runway task, the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), at 1.0 mg/kg i.p. significantly increased the number of errors (attempts to pass through two incorrect panels of the three panel gates at four choice points), but it had no effect on errors in a test of reference memory. Intrahippocampal injection of 8-OH-DPAT at 10 micrograms/side also significantly increased the number of working memory errors, without affecting that of reference memory errors. The effect of intrahippocampal 8-OH-DPAT (10 micrograms/side) on working memory was blocked by the 5-HT1A receptor antagonist, (-)-propranolol, at 5 mg/kg i.p. These results suggest that activation of hippocampal 5-HT1A receptors impairs working memory, but does not affect retention of reference memory.

Thyrotropin receptor in non-thyroid tissues

Thyrotropin receptor (TSH-R), the main target for the autoantibody in Graves' disease, has been thought to be a thyroid-specific protein. However, we successfully obtained the cDNA fragments of TSH-R from rat retro-orbital tissues and adipose tissues by using polymerase chain reaction methods. Sequencing has revealed that the nucleotide sequence of the cDNAs from these non-thyroid tissues was identical to that from the thyroid. TSH-R peptide antibody, which recognizes rat TSH-R, stained a 104 kDa protein from the retro-orbital tissues and the adipose tissues. The band was not detected with the antibody preabsorbed with the peptide. These results suggest that the message is translated to make a TSH-R protein even in these non-thyroid tissues.

Proliferation of microglia/macrophages in the demyelinating CNS and PNS of twitcher mouse

In demyelinating lesions in the central and peripheral nervous systems of twitcher mouse, a murine model of globoid cell leukodystrophy, marked increases of [3H]thymidine-labeled elements including Mac-1 immunopositive (Mac-1+) microglia/macrophages was observed. Their proliferative activities were already pronounced at the postnatal day (P) 20, an early stage of demyelination, peaked at P30 and then declined at P45, at the terminal stage of the disease. Many of the [3H]thymidine-labeled Mac-1+ cells had morphological features of ramified microglia. Macrophage-like Mac-1+ cells were less frequently labeled. The results of this study showed that (1) microglia/macrophages proliferated in the genetic demyelinating lesions, (2) many dividing Mac-1+ cells had the shape of ramified microglia and (3) the rate of proliferation declined in later stages when reactive microglia/macrophages were abundant in the lesions. The temporal events of this study suggest that signal(s) from the degenerating myelin or myelin-forming cells stimulate(s) cellular proliferation and that ramified microglia were one of the principal-dividing elements in the lesion. The biological mechanisms underlying the decline of the proliferative activity of microglia require further studies.

Abnormal expression of intercellular adhesion molecule-1 on peripheral blood mononuclear cells from patients with systemic lupus erythematosus

The expression of intercellular adhesion molecule-1 (ICAM-1) on peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus was observed by flow cytometry. ICAM-1 expression on PBMC was increased in the patients with active disease, and was increased especially on CD5- or CD19+ lymphocytes and monocytes. Furthermore, when B cells were fractionated by Percoll-density gradients, ICAM-1 was more expressed on the low- and the intermediate-density B cells, which are thought to contain activated B cells, than on the high-density B cells, which are thought to contain resting B cells. This might be due to the polyclonal B-cell activation occurring in vivo. Together with the function of B cells and monocytes as antigen presenting cells, this enhanced expression of ICAM-1 on these cells might be associated with the mechanism to maintain the pathophysiology of this disease.

Interaction between pullulanase from Klebsiella pneumoniae and cyclodextrins

The interaction between pullulanase from Klebsiella pneumoniae and alpha-, beta-, and gamma-cyclodextrins and 6-O-alpha-glucosyl-alpha-cyclodextrin and 6-O-alpha-glucosyl-beta-cyclodextrin was examined by means of inhibition studies of the enzyme activity, UV difference spectroscopy, and flow calorimetry. All the above cyclodextrins were found to be competitive inhibitors, but beta-cyclodextrin and 6-O-alpha-glucosyl-beta-cyclodextrin showed strong inhibition, the inhibitor constants being two orders of magnitude less than those of alpha- and gamma-cyclodextrins. The difference spectra of beta-cyclodextrin were slightly but significantly different from those of the other cyclodextrins, showing blue shift of a few nanometers. Moreover, only beta-cyclodextrin has a positive entropy change upon binding with the enzyme; all the other cyclodextrins have negative values. These results show that the binding mode of beta-cyclodextrin is subtly different from those of alpha- and gamma-cyclodextrins.

Ameliorative effects of the centrally active cholinesterase inhibitor, NIK-247, on impairment of working memory in rats

Using a three-panel runway task, the effects of NIK-247 on impairment of working memory produced by scopolamine, hippocampal lesions, and cerebral ischemia were investigated in rats; these effects were compared with those of the well-known cholinesterase inhibitors, tetrahydroaminoacridine (THA) and physostigmine. Intraperitoneal injection of scopolamine (0.56 mg/kg) significantly increased the number of errors (pushes made on the two incorrect panels of the three-panel gates located at four choice points). NIK-247 (3.2-18 mg/kg PO), THA (1-10 mg/kg PO), and physostigmine (0.1 and 0.32 mg/kg IP) dose-dependently reduced the increase in errors induced by scopolamine. NIK-247 (32 mg/kg) was also effective in reducing the increase in errors produced by lesions of the dorsal hippocampus. A 5-min period of cerebral ischemia markedly increased the number of errors. NIK-247 (3.2 and 10 mg/kg), given immediately after blood flow recirculation and again 20 min before the runway test carried out 24 h after ischemia, significantly reduced the increase in errors expected to occur after ischemia. Tetrahydroaminoacridine (3.2 mg/kg) and physostigmine (0.1 mg/kg) similarly reversed the increased errors in ischemic rats. These results suggest that NIK-247 alleviates the impairment of working memory produced by scopolamine, hippocampal lesions, and cerebral ischemia, possibly through activation of the central cholinergic system.

Portal-systemic encephalopathy: report of a case with unusual MR findings

A case of subclinical portal-systemic encephalopathy with unusual MR findings is described. The basal ganglia and cerebral white matter were diffusely hyperintense on T1-weighted images. No similar cases have been previously described in the literature.

Olivary degeneration after cerebellar or brain stem haemorrhage: MRI

Magnetic resonance (MR) images of seven patients with olivary degeneration caused by cerebellar or brain stem haemorrhages were reviewed. In four patients with cerebellar haemorrhage, old haematomas were identified as being located in the dentate nucleus; the contralateral inferior olivary nuclei were hyperintense on proton-density- and T2-weighted images. In two patients with pontine haemorrhages, the old haematomas were in the tegmentum and the ipsilateral inferior olivary nuclei, which were hyperintense. In one case of midbrain haemorrhage, the inferior olivary nuclei were hyperintense bilaterally. The briefest interval from the ictus to MRI was 2 months. Hypertrophic olivary nuclei were observed only at least 4 months after the ictus. Olivary degeneration after cerebellar or brain stem haemorrhage should not be confused with ischaemic, neoplastic, or other primary pathological conditions of the medulla.