Biomedical subjects

T Okajima

Publications and source records attributed to T Okajima.

At least 55 records · Page 3Linked to original sources

PubMed1993

RNA priming coupled with DNA synthesis on natural template by calf thymus DNA polymerase alpha-primase.

A bovine genomic DNA library was surveyed with respect to the template activity for RNA-primed DNA synthesis by calf thymus DNA polymerase alpha-primase complex. About 7% of the single-stranded DNA clones contained distinct initiation sites consisting of pyrimidine clusters of pyrimidine-rich sequences. The initiation sites were located at or near the 3'-end of the pyrimidine clusters. One of these sequences, containing a 10-mer pyrimidine cluster with major initiation sites, was analyzed in detail. By the successive substitutions of pyrimidines in the cluster with oligodeoxydenylate [(dA)n] in the 5' to 3' direction, the minimum length of the initiation sequence was estimated to be as long as the 7-mer. In contrast, when one or three pyrimidines at the 3'-end of the cluster were replaced with (dA)n, the priming activity was largely lost, indicating that these pyrimidine residues were indispensable for priming. Furthermore, base substitutions of upstream or downstream sequences outside the pyrimidine cluster also decreased the total priming frequencies. Interestingly, the base substitutions inside or outside of the pyrimidine cluster sometimes caused a shift in the major priming sites. These results indicate that the minimum priming unit of the CTPPS1 template for RNA-primed DNA synthesis consists of a pyrimidine cluster (6-mer) with one purine at its 3'-border and that both the 3'-downstream 6-bases and the 5'-upstream 17-bases modulate the priming by enhancing the priming frequency and/or slightly shifting the sites of initiation of primer synthesis. It was also revealed that the lengths of the product RNA primers became shorter as the length of pyrimidine cluster was shortened by substitution with (dA)n. The gel retardation assay further showed that the complex formation between DNA polymerase alpha-primase and the DNA templates was strongly in competition with poly(dC), poly(dG), and poly(dT) but not with poly(dA). Furthermore, template activities as well as the pyrimidine contents of a series of base-substituted DNA correlated well with their affinities to the enzyme, as measured by both gel retardation assay and their Km values for the priming reaction. Apparently, DNA polymerase alpha-primase primarily recognizes the minimum priming unit consisting of a pyrimidine cluster with a purine at the 3'-boundary of purine, but the initiation of primer RNA synthesis can be modified by pyrimidine residues outside of the minimum priming unit.

Adenosine Triphosphate↗

PubMed1993

Site-directed mutagenesis of AMP-binding residues in adenylate kinase. Alteration of substrate specificity.

Adenylate kinase is highly specific for AMP as phosphoryl acceptor. We have found that the replacement of Thr39 by Ala in the chicken muscle enzyme, alone or together with the replacement of Leu66 by Ile, caused remarkable increases in CMP and UMP activities with a concomitant decrease in AMP activity; therefore, the resulting mutant enzymes show CMP and UMP activities/AMP activity ratios much higher than the wild-type enzyme. The mutant enzyme in which Ala is substituted for Thr39 has a Vmax value for CMP comparable to that of CMP-UMP kinase.

Adenosine Monophosphate↗

PubMed1993

Nonurea sodium dodecyl sulfate-polyacrylamide gel electrophoresis with high-molarity buffers for the separation of proteins and peptides.

A sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a discontinuous buffer system for separation of both peptides and proteins, which is a modification of the Laemmli system, is described. In the modified procedure, twofold higher concentrations of buffers in the separating gel and the running buffer solution allow superior resolution for peptides as small as M(r) 5000. The resolution of peptides was dependent on salt concentrations in the systems in which sodium chloride was partially substituted for Tris-HCl buffer and buffer concentrations were varied. In the stacking gel of the modified procedure, detection of peptides and SDS demonstrated a sharp stack of peptides at the trailing edge of the SDS stack. On the other hand, this SDS stack included peptides, forced them to diffuse, and produced a broad starting zone under Laemmli conditions. In addition, following expansion of the SDS stack impaired peptide resolution further in the separating gel. Accordingly, the different interaction with the SDS stack in the stacking process was found to produce different resolution of peptides in the electrophoretic procedures. The modified conditions have potential to provide a superior alternative to the Laemmli system for analysis of various proteins.

Buffers↗

PubMed1993

Site-directed random mutagenesis of AMP-binding residues in adenylate kinase.

Two highly conservative residues, Val67 and Gln101, in adenylate kinase are located in the hydrophobic region putatively involved in binding of the adenine ring of AMP. We have performed polymerase chain reaction-based random mutagenesis of the two residues using recombinant chicken muscle adenylate kinase cDNA as a template. The synthetic oligonucleotide primers contained A,G,C,T-mixed bases in the codons corresponding to those for Val67 and Gln101. The amplified fragments were ligated with the expression plasmid pKK223-3, and the mutant proteins expressed were identified by immunoblotting. Enzymatically active mutant proteins were selected on the basis of the growth at 45 degrees C of the temperature sensitive Escherichia coli mutant for adenylate kinase. At position 67, various amino acid residues other than Val have been found to restore the growth at 45 degrees C of the ts mutant. In contrast, only Gln, His, and Met could be present at position 101. These results are compatible with the proposal that Val67 contributes to the AMP binding through hydrophobic interactions and Gln101 by forming a hydrogen bond with the adenine ring. Indeed, several purified Val67 and Gln101 mutant enzymes exhibited markedly high Km values for AMP, whereas the Km values for MgATP were comparable to those of the wild-type enzyme. Substrate specificity for nucleoside monophosphates was changed significantly by the mutagenesis of the two residues.

Adenosine Monophosphate↗

PubMed1993

Transfection of the human insulin-like growth factor binding protein-3 gene into Balb/c fibroblasts inhibits cellular growth.

The insulin-like growth factors (IGFs) are potent mitogens with both endocrine and autocrine-paracrine effects on cell growth. The IGF binding proteins (IGFBPs) are found in many human biological fluids and in the conditioned media of many cell cultures. These molecules are ontogenically and hormonally regulated. Nevertheless, the biological role(s) of the IGFBPs remain controversial. Both inhibitory and stimulatory effects of IGFBPs on cell growth have been suggested. In order to evaluate the actions that endogenously produced IGFBPs have on cell growth, we constructed a mammalian expression vector containing the human IGFBP-3 cDNA and transfected the murine Balb/c cell line. While plasmid-transfected control Balb/c cells (Tx-P) produced only small amounts of a 28-kilodalton IGFBP, the IGFBP-3-transfected Balb/c cells (Tx-BP-3) additionally expressed readily detectable amounts of the characteristic 40- to 44-kilodalton human IGFBP-3 protein doublet and its mRNA. Growth of Tx-BP-3 in serum-containing media was significantly (2.5-fold) slower compared with Tx-P grown under identical conditions. Fully confluent Tx-BP-3 cells arrested their growth at a cell density that was 3-fold lower than did Tx-P cells. When nontransfected cells were grown in the presence of high concentrations of either IGF-I or insulin, growth was equally stimulated. However, when transfected cells were grown in insulin-containing media (5 micrograms/ml), growth rates of the IGFBP-3-transfected cells were not restored to those observed in plasmid-transfected control cells. These results suggest that in this model, the expression of endogenous IGFBP-3 has an inhibitory effect on cell growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Inhibitory effects of insulin-like growth factor (IGF)-binding proteins-1 and -3 on IGF-activated glucose consumption in mouse BALB/c 3T3 fibroblasts.

We have examined the biological effects of insulin-like growth factor-binding proteins (IGFBPs) on insulin-like growth factor (IGF)-activated glucose consumption in a BALB/c 3T3 subline. The method employed was a colorimetric measurement of glucose consumption, allowing the detection of changes from the initial glucose concentration in conditioned medium, following the addition of IGFs and IGFBPs. Human IGFBP-1, purified from amniotic fluid, inhibited IGF-activated glucose consumption, although it had no effect on insulin-activated glucose consumption. The median effective dose (ED50) of IGFBP-1 to cause inhibitory effects on IGF-activated glucose consumption was 100-200 micrograms/l and was similar for both IGF-I and IGF-II at a concentration of 1.0 microgram IGF/l. Therefore, at IGF concentrations of comparable activity, the inhibitory effects of IGFBP-1 were greater for IGF-I than for IGF-II, because of the higher activity of IGF-I in this assay. Recombinant human IGFBP-3 also inhibited IGF-activated glucose consumption, without affecting insulin-stimulated glucose consumption. The inhibitory effects of IGFBP-3 were greater for IGF-II than for IGF-I when IGFBP-3 was coincubated with either of the IGFs, at both IGF concentrations of comparable activity and equivalent molar concentrations. Thus, it became clear that the inhibitory effects of these IGFBPs on IGF biological action depended primarily upon their affinity for the specific IGF ligand and molar ratio of IGFBP/IGF peptide. Interestingly, when cells were pretreated with IGFBP-3, prior to the simultaneous addition of IGFs and IGFBP-3, the inhibitory effect was higher for IGF-I than for IGF-II. Either no effect or a minor inhibitory effect on IGF-activated glucose consumption was detected with IGFBP pretreatment alone. When the ED50 for inhibition of IGF action by IGFBPs in this in-vitro assay was compared with the physiological concentrations of IGFs and IGFBPs in normal human serum and in amniotic fluid, it was estimated that the IGFBP-1 concentration present in serum was not sufficient to modulate IGF action effectively while the concentration in amniotic fluid was enough for effective suppression. IGFBP-3 exhibited an ED50 low enough to suppress IGF-II and possibly IGF-I action when cells were pretreated with IGFBP-3. Thus, our data suggested that IGFBP-1 in amniotic fluid and IGFBP-3 in serum could be a potent inhibitor for IGF action. IGFBP-1 in serum, however, may not be able to function as a direct inhibitor under physiological conditions but, rather, may modulate IGF action together with other IGFBPs.

Animals↗

PubMed1993

Pure progressive autonomic failure presenting severe orthostatic hypotension.

A 59-year-old woman showed chronic progressive autonomic failure consisting of orthostatic hypotension and dyshidrosis. No signs of Parkinsonism, cerebellar or peripheral neuropathy were observed. Autonomic nervous function tests and findings of biopsied sural nerve suggested that this case had both sympathetic and parasympathetic dysfunctions, mainly postganglionic. A decrease in the total peripheral resistance and no increase in the heart rate on standing seemed to be the mechanism of orthostatic hypotension in this case. We conclude that pure PAF can be recognized as a distinct clinical syndrome of systematic degeneration of the autonomic nervous system.

Autonomic Nervous System Diseases↗

PubMed1993

Transfection of the human IGFBP-3 gene into Balb/c fibroblasts: a model for the cellular functions of IGFBPs.

The insulin-like growth factors (IGFs) are potent mitogens with both endocrine and autocrine-paracrine effects on cell growth. The insulin-like growth factor binding proteins (IGFBPs) are found in many human biological fluids and in the conditioned media of many cell cultures. These molecules are ontogenically and hormonally regulated. Nevertheless, the biological role(s) of the IGFBPs remain controversial. Both inhibitory and stimulatory effects of IGFBPs on cell growth have been suggested. In order to evaluate the actions of endogenously produced IGFBPs on cell growth, we have constructed a mammalian expression vector containing the hIGFBP-3 cDNA, and transfected the murine Balb/c cell line. The IGFBP-3 transfected Balb/c cells (Tx-BP-3) expressed readily detectable amounts of hIGFBP-3 protein and its mRNA. Growth of Tx-BP-3 in serum containing media was significantly slower, compared with control plasmid-transfected cells (Tx-P) grown under identical conditions. Fully confluent Tx-BP-3 cells arrested their growth at a cell density that was lower than did Tx-P cells. When transfected cells were grown in insulin-containing media, growth rates of the IGFBP-3 transfected cells were not restored to those observed in control plasmid-transfected cells. These results suggest that in this model, the expression of endogenous IGFBP-3 has an inhibitory effect on cell growth.

3T3 Cells↗

PubMed1993

[Myelopathy associated with HTLV-1: clinical electrophysiologic study].

Clinical and electrophysiological studies have been performed in 9 cases of HTLV-I associated myelopathy (7 female, 2 male). Spastic paraparesis and neurogenic bladder were present in 8; sensory disturbances were detected only in 4. The conduction velocities of the posterior tibial and sural nerves were reduced in 2 cases. Median nerve SSEP revealed a delay of N11, N13, N14, N20 peak latencies and an increase of N9-N20, N13-N14 and N13-N20 interpeak latencies. The electrophysiological studies are the most accurate indicators of the diffuse involvement not only of central motor and sensory pathways but also of the peripheral nervous system.

Adult↗

PubMed1993

[Inferior branch palsy of the oculomotor nerve following clipping of basilar apex aneurysm].

A 67-year-old woman experienced a severe headache and vomiting. A computed tomographic (CT) scan showed a mild subarachnoid hemorrhage. Cerebral angiography revealed a saccular aneurysm at the apex of the basilar artery. Several days later, she noticed mild hemiparesis of the left extremities. She underwent a clipping operation on the aneurysm by approaching from the right temporal love. Postoperatively, she developed diplopia and dilatation of the left pupil. Cerebral angiography revealed an occlusion of the left posterior cerebral artery. She was admitted to another hospital in order to continue rehabilitation. General physical examination was normal. Neurological examination revealed paralysis of the left medial and left inferior rectus muscles and palsy of the left inferior oblique muscle. The pupil of the left eye was dilated, measuring 5 mm in diameter, and it did not constrict to any stimuli. The left superior rectus and levator palpebrae superioris functioned normally. Visual acuity and visual fields were normal except for the influence of a senile cataract. She had a mild left hemiparesis, slight left ataxia and slurred speech. She had numbness of the left half of the body. A CT scan showed small low density areas in the right thalamus and left cerebellar hemisphere. Her ophthalmologic findings were compatible with the inferior branch palsy of the oculomotor nerve. The ophthalmoplegia of this case seems to be due to partial damage of the oculomotor nerve induced by ischemia of vascular supply. It is supposed to be caused by a vasospasm of the left posterior cerebral artery following a clipping operation of the basilar apex aneurysm.

Aged↗

PubMed1993

Studies on the relationship between hepatic and splenic density change in dynamic CT in the presence of a large splenorenal shunt in patients with liver cirrhosis.

Using dynamic computerized tomography (CT), we studied liver and spleen hemodynamics in one group of patients with a large splenorenal shunt and another group without a large shunt. Specifically, we measured the time-to-peak hepatic and splenic enhancement and the loss of enhancement, i.e., decay time. The time-to-peak liver enhancement (61 +/- 21 s vs. 81 +/- 14 s, p < 0.05) and the splenic decay time (24 +/- 16 s vs. 48 +/- 28 s, p < 0.05) were significantly shorter in patients with a large splenorenal shunt compared to those without. The groups had similar hepatic decay times and times to peak splenic enhancement. We found dynamic CT useful in assessing the effect of a large splenorenal shunt on portal and splenic hemodynamics.

Adult↗

PubMed1992

Evaluation of hepatic density change by dynamic CT in healthy humans and in patients with chronic liver diseases.

Dynamic computed tomography using 0.4 ml/kg of 65% meglumine diatrizoate was performed to estimate pharmacokinetics of contrast media in the liver in healthy controls (N = 11), in patients with chronic viral hepatitis (N = 17), posthepatic liver cirrhosis (N = 21), and alcoholic liver cirrhosis (N = 23). The time of peak enhancement (the time interval between peak aortic and liver enhancement) was significantly different between each group. Alcoholic liver cirrhosis was the most prolonged, followed by posthepatic liver cirrhosis, chronic viral hepatitis, and finally controls. A peak enhancement time of 28 sec had a diagnostic accuracy of 97% for chronic liver diseases. A time greater than 44 sec had a diagnostic accuracy for cirrhosis of 96%. The decay time (the time from peak enhancement of the liver to the curve's center of gravity) was also significantly different between each group. Again, alcoholic liver cirrhosis was the longest, followed by posthepatic liver cirrhosis, chronic viral hepatitis, and then the controls. Dynamic computed tomography has many potential applications in studying intrahepatic physiologic events and may contain diagnostic information for chronic liver diseases.

Adult↗

PubMed1992

Sensitive colorimetric bioassays for insulin-like growth factor (IGF) stimulation of cell proliferation and glucose consumption: use in studies of IGF analogs.

We have established two in vitro bioassay systems for quantification of insulin-like growth factor (IGF) bioactivity. The first assay was used to quantitate mitogenic activity and the second was used to quantitate metabolic activity. Both assays use BALB/c 3T3 fibroblasts grown under serum-free conditions; detection of bioactivity in assays was performed colorimetrically and did not require the use of radioisotopes. The mitogenic bioassay, which requires 48 h for detection, quantitates changes in cell number and provides an index for determining the mitogenic activity of growth factors. Changes in cell number were measured by the enzymatic reduction of exogenously added MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] to MTT-formazan by mitochondrial enzymes, which was directly correlated to cell number. The metabolic bioassay, which requires 22 h for detection, measures glucose consumption by detecting changes from the initial glucose concentration of conditioned medium after addition of various growth factors. When appropriate standards were established for these bioassays, they demonstrated a high level of reproducibility (coefficients of variation were 0.085-0.096 for the mitogenic bioassay and 0.120-0.191 for the metabolic bioassay). Both assays can be performed in 96-well microtiter plates, without the use of radioisotopes, or the limitations of conventional glucose, amino acid, or thymidine incorporation studies. In initial experiments for assay specificity, epidermal growth factor had no measurable effect in either assay. However, IGF-I, IGF-II, and insulin demonstrated effects on both metabolism and mitogenesis. In the case of the mitogenic bioassay, the maximum mitogenic activation by these growth factors was approximately 180% of control, and these factors demonstrated parallel sigmoidal dose-response curves, ranging from 0.02-2 ng/ml for IGF-I and from 2-200 ng/ml for both IGF-II and insulin. In the metabolic bioassay, in contrast to the mitogenic bioassay, insulin showed a dose-response curve whose shape was different from those of IGF-I and IGF-II. IGF-I and IGF-II stimulated glucose consumption in dose-dependent ranges of 0.02-3 ng/ml and 0.4-40 ng/ml, respectively. However, the dose-response effect of insulin was wider, ranging from 0.1-2000 ng/ml. When these assays were used to measure the bioactivity of IGF analogs, a des(1-3)-IGF-I, which has decreased affinity for IGF binding proteins, demonstrated activity equivalent to IGF-I, a [Leu27]IGF-II, which has markedly diminished affinity for the type 1 IGF receptor, exhibited approximately 0.07% of the potency of IGF-I and 1% of the potency of IGF-II.

3T3 Cells↗

PubMed1992

[A case of hyperparathyroid bone disease and the review of renal osteodystrophy].

We report here a typical case of hyperparathyroid bone disease associated with CRF on maintenance HD and review on Renal Osteodystrophy. A 39 year-old female patient was admitted because of polyarthralgia and pruritus. She had a history of HD due to CGN for about 13 years. Laboratory data showed an increase in serum PTH and Alkaline phosphatase level. The evidence of osteitis fibrosa was revealed by bone Xp and scintigraphy. Enlarged solid masses were found in her neck by echogram and parathyroid scintigraphy. She was diagnosed as hyperparathyroid bone disease and total parathyroidectomy c autoplantation was done. Shortly after the surgical treatment, subjective symptoms were relieved and PTH level was normalized. The bone Xp findings improved gradually.

Adult↗

PubMed1991

Role of leucine 66 in the asymmetric recognition of substrates in chicken muscle adenylate kinase.

Adenylate kinase has two distinct binding sites for nucleotide substrates, MgATP and AMP. To identify the location of the site that specifically interacts with the adenine ring of AMP, we have substituted Ala, Gly, Val, Gln, and Trp for Leu66 of the recombinant chicken muscle enzyme by site-directed mutagenesis. All the purified Leu66 mutant enzymes exhibited an essentially identical circular dichroism spectrum and had thermal stabilities similar to the wild-type enzyme. Steady state kinetic analysis showed that the Leu66 mutant enzymes have significantly decreased Vmax values and markedly large Km values only for AMP. These results show that the binding site for the adenine ring of AMP in adenylate kinase is presumably located close to Leu66, which is invariant in all the enzymes so far sequenced. Significant inhibition of activities of the mutant enzymes and quenching of the Trp66 fluorescence by substrates suggest that in some Leu66 mutant enzymes, MgATP also binds to the AMP-binding site. Thus, Leu66 of adenylate kinase might play a role in the asymmetric recognition of the adenine ring of AMP from that of MgATP. Furthermore, the hydrophobicity of the residue at position 66 appears to be important for the positive cooperativity of substrate binding.

Adenosine Monophosphate↗

PubMed1990

The role of Leu-190 in the function and stability of adenylate kinase.

To elucidate the role of C-terminal region of chicken adenylate kinase (a single polypeptide consisting of 193 amino acid residues) in the catalysis and stability of the enzyme, a series of mutant proteins truncated in the C-terminal region has been prepared by successive replacements of the sense codons by a termination codon via site-directed mutagenesis. Removal of the three C-terminal residues did not affect the apparent Michaelis constants (Km values) for AMP and ATP, although the Vmax values decreased gradually in parallel with the length of the polypeptide chain. A sudden increase in Km values for substrates, in particular for ATP, was observed on removal of one additional residue (Leu-190), the Vmax value also being less than one-half of that of the mutant enzyme with 3 residues shorter than the wild-type enzyme. These results suggest the importance of the highly conservative Leu-190. Therefore, we further prepared the mutant enzymes through replacement of Leu-190 by a variety of other amino acid residues. They all had substantially lower Vmax values and decreased thermostabilities. Their apparent Km values for ATP also changed, whereas those for AMP were affected to a lesser extent. The hydrophobicity of amino acid residues at position 190 was found to positively correlate with the specificity constants (kcat/Km values) for ATP and also with the thermostability of the enzyme. The fluorescence emission of the Trp-190 mutant enzyme was quenched by the addition of ATP. It is suggested that the C-terminal residues, particularly those around Leu-190, are present in a hydrophobic region which may be involved in binding of ATP.

Adenosine Monophosphate↗

PubMed1990

Chemical modification of tryptophan residues and stability changes in proteins.

The role of tryptophan residues in the stability of proteins was studied by ozone oxidation, which causes a small change in the tryptophan side chain. Trp 187 of the constant fragment of a type lambda immunoglobulin light chain, Trp 59 of ribonuclease T1, and Trp 62 of hen egg white lysozyme were oxidized specifically by ozone to N'-formylkynurenine or kynurenine. Judging from their circular dichroic and fluorescence spectra, these modified proteins were found to be the same as those of the respective intact proteins. However, even the slight modification of a single tryptophan residue produced a large decrease in the stability of these proteins to guanidine hydrochloride and heat. The smaller the extent of exposure of the tryptophan residue, the greater the effect of the modification on the stability. The formal kinetic mechanism of unfolding and refolding by guanidine hydrochloride of the CL fragment was not altered by tryptophan oxidation, but the rate constants for unfolding and refolding changed. The thermal unfolding transitions were analyzed to obtain the thermodynamic parameters. The enthalpy and entropy changes for the modified proteins were larger than the respective values for the intact proteins.

Animals↗

PubMed1990

[Non-specific esterase positive neutrophils in a case of refractory anemia with excess of blasts].

A 61-year-old woman was admitted with complaint of fever. The peripheral blood showed pancytopenia and bone marrow aspirate showed dysplasia in trilineage blood cells with increased blasts (18.2%). Bone marrow chromosome study revealed a karyotype of 46XX, -6, 3q-, +mar in 19 cells of 20 analyzed. She was diagnosed as refractory anemia with excess of blasts (RAEB). 95% of neutrophils in the bone marrow and 84% of that in the peripheral blood were stained with non-specific esterase using alpha-naphthyl acetate as substrate. On the other hand, the positivity of neutrophils for peroxidase. Sudan black B or chloroacetate esterase was markedly decreased. The phagocytotic activity of neutrophils was increased in comparison with normal control cells. Surface marker analysis of peripheral blood myeloid cells revealed increased expression of monocyte specific markers. These findings suggested that the patient's neutrophils, which were surely neutrophils in morphology, shared also monocyte-specific characters. After treatment with low dose Ara-C, pancytopenia was recovered and blasts in the bone marrow were reduced. Also was decreased non-specific esterase positive neutrophils, indicating that the neutrophils were derived from abnormal myeloid clone.

Anemia, Refractory, with Excess of Blasts↗