Biomedical subjects

M Igarashi

Publications and source records attributed to M Igarashi.

At least 19 recordsLinked to original sources

PubMed1992

Actin-binding proteins in the growth cone particles (GCP) from fetal rat brain: a 44 kDa actin-binding protein is enriched in the fetal GCP fraction.

Neuronal growth cones, the motile tips of growing neurites, are thought to play a significant role in nerve growth. To study the role of actin in their motility, we examined actin-binding proteins in growth cone particles (GCP) isolated from fetal rat brain, using a blot-overlay method with biotinylated actin. Among the more than ten species of actin-binding proteins in the GCP, a 44 kDa protein was found specifically in growth cones and was enriched in the cytoskeletal and the membrane skeletal subfractions from the GCP. This protein binds to actin in a Ca(2+)- and Mg(2+)-dependent manner, and ATP enhances its binding to actin. The protein was predominantly present in the fetal GCP, but it is expressed at a much lower level in the neonatal GCP and not detected in adult synaptosomes. The protein also bound to a deoxyribonuclease I column and was eluted by EGTA-containing buffer. The 44 kDa protein appears to be a novel actin-binding protein, since none of the known actin-binding proteins exhibit this combination of properties. Our results suggest that the protein may be involved with the early stages of neurite extension.

Animals↗

PubMed1992

Structural organization of the gene for prostaglandin D synthase in the rat brain.

A 3-kilobase-pair gene for rat brain prostaglandin D synthase [(5Z,13E)-(15S)-9 alpha,11 alpha-epidoxy-15-hydroxyprosta-5,13- dienoate D-isomerase, EC 5.3.99.2], which belongs to the lipocalin family, was isolated from a rat genomic DNA library by plaque hybridization with the cDNA for the enzyme. The gene contains seven exons, and all the splice donor and acceptor sites conform to the GT/AG rule. Transcription initiates at a guanine residue 39 base pairs upstream of the translation initiation codon, as determined by primer-extension analysis of rat brain mRNA. The 5'-flanking region of the gene lacks typical transcriptional regulatory sequences, such as TATA and CAAT boxes, but contains several sets of inverted repeats, direct repeats, and sequences resembling the transcriptional factor Sp1-binding site. The gene structure of prostaglandin D synthase is remarkably analogous to those of other lipocalins, such as beta-lactoglobulin, alpha 2-urinary globulin, placental protein 14, and alpha 1-microglobulin, in terms of number and sizes of exons and phase of splicing of introns. Furthermore, in a multiple alignment of the deduced amino acid sequences, positions of exon/intron junction of the prostaglandin D synthase gene are highly conserved and located around the positions of those of the genes for other lipocalins despite a weak homology.

Amino Acid Sequence↗

PubMed1992

Specific induction by glucocorticoids of steroid esterase in rat hepatic microsomes and its release into serum.

Steroid esterase hydrolysing methylprednisolone 21-hemisuccinate was induced specifically and markedly in hepatic microsomes and serum of rats by various glucocorticoids. Among the glucocorticoids examined, dexamethasone and betamethasone showed the highest potency to induce the hepatic steroid esterase, the induction ratio being 32 and 33 times higher than the basal level (about 160 mU/g liver), respectively. Steroid esterase in the serum was induced greatly by fluocinolone acetonide and betamethasone to 92 and 79 times of the basal level of about 16 mU/mL, respectively, followed by dexamethasone and methylprednisolone. When dexamethasone was given to rats, the enzyme in other tissues except for duodenum and small intestine (of which activity was lowered to 50% of the basal level) was also elevated, but the induction ratio was much lower than that in the liver and serum. The induction of the steroid esterase is probably due to stimulation of de novo synthesis of the enzyme by glucocorticoids, because the elevation of esterase activity was inhibited by treatment with cycloheximide (a translation inhibitor) and actinomycin D (a transcription inhibitor), and about 4- and 10-hr lag time was observed before the elevation of esterase activity in liver and serum, respectively. Coupled with these observations the following results indicate that the steroid esterase in serum is probably synthesized in the liver and subsequently released into the blood via the Golgi apparatus: (1) when the liver of rats treated with dexamethasone was subjected to perfusion with a recycling system, significant amounts of steroid esterase were released into the perfusate; (2) anti-hepatic esterase antibody inhibited the steroid esterase activity not only in the liver but also in serum; and (3) monensin, which prevents the secretion of various kinds of secretory proteins by disrupting the function of the Golgi apparatus, inhibited the elevation of the steroid esterase activity in serum by dexamethasone but did not affect the induction in liver.

Animals↗

PubMed1992

Purification and characterization of glucocorticoid-inducible steroid esterase in rat hepatic microsomes.

A steroid esterase hydrolysing methylprednisolone 21-hemisuccinate was purified from the hepatic microsomes of rats treated with dexamethasone, a potent inducer of the esterase. The enzyme was solubilized by Lubrol WX and purified up to 30-fold over the microsomal fraction by ammonium sulfate fractionation and successive chromatographies with gel permeation, DEAE-cellulose and hydroxylapatite. The steroid esterase thus purified showed a single band and a molecular mass of 58 kDa on SDS-polyacrylamide gel electrophoregram. The enzyme appears likely to exist as two interconvertible forms, which can be distinguished by pI values, pI 4.9 and 5.1. The enzyme was completely inhibited by organic phosphates, indicating that it can be classed as a carboxylesterase (EC 3.1.1.1). Both negatively charged and uncharged esters of several steroids (methylprednisolone, hydrocortisone, deoxycorticosterone and dehydrotestosterone) as well as various non-steroidal esters including 4-nitrophenyl esters were hydrolysed by the enzyme, but none of the amides were substrates. The enzyme showed higher activity with increasing lipophilicity of the substrates. It is noticeable that the optimum pH for charged esters was 5.5, whereas the highest activity was observed around pH 7-8 for uncharged esters. When methylprednisolone 21-hemisuccinate (one of the charged esters) was used as substrate, the Km value was 2.8 mM and Vmax was 59.3 mumol/mg protein for 1 min at the optimum pH of 5.5. Regarding the methyl ester of methylprednisolone 21-hemisuccinate, Km and Vmax values were 1.8 mM and 193 mumol/mg protein/min, respectively, at the optimum pH of 7.0. On the basis of these results, the enzyme is most likely a carboxylesterase.

Amino Acids↗

PubMed1992

Biochemical characterization of nerve growth cones isolated from both fetal and neonatal rat forebrains: the growth cone particle fraction mainly consists of axonal growth cones in both stages.

Nerve growth cones are responsible for the exact pathway finding, and for the establishment of neurocytoarchitecture. To elucidate the developmental changes of biochemical characteristics of nerve growth cones, growth cone particle (GCP) fractions were isolated biochemically from embryonal day 17 (E17) rat forebrain and from postnatal day 5 (P5). There were no significant differences in protein phosphorylation pattern in a Ca(2+)-dependent manner between E17-GCP fraction and that of P5. As for the membrane lipid composition, molar ratios of cholesterol to total phospholipids were well conserved during these ages. The immunoreactivity to anti-synaptophysin monoclonal antibody as a marker of mature synaptic elements could not be detected either in E17-GCP or P5-GCP fractions. To exclude the possibility of the contamination of dendritic elements, RNA contents and immunoreactivity to anti-high molecular weight microtubule-associated protein 2 (MAP2) monoclonal antibody were examined. RNA contents of the GCP fractions were extremely low compared to those of other subcellular fractions both in E17 and P5. No immunoreactivities to anti-MAP2 antibody were observed in either GCP fraction. Our results suggest that the GCP fractions, isolated from forebrains of E17 to P5 rat, are free from the contamination of the synaptic elements, and that the GCP fractions are mainly composed of axonal growth cones.

Aging↗

PubMed1992

[Mini review on inhibins and activins].

Recent researches on inhibin and activin were reviewed. This mini review contains brief history of researches on inhibins and activins, criteria, chemistry, the site of production of these two hormones, assay method (bio- and radioimmunoassay), changes of serum inhibin levels in normal physiologic states and in various pathologic states of men and women, actions of inhibins and activins upon FSH and LH secretion from the pituitary, upon other pituitary functions, upon brain functions, erythropoiesis, erythroleukemia, bone and bone marrow, immunology, other organs such as liver, pancreas, adrenals, placenta, Xenopus oocyte and general cell proliferation, paracrine and autocrine actions of these hormones inside the ovary and the testis, activin receptor, inhibin receptor, follistatin, effects of exogenous administration of recombinant inhibin and activin, and TGF-beta super gene family.

Activins↗

PubMed1992

An immunodominant haptenic epitope of carbamazepine detected in serum from patients given long-term treatment with carbamazepine without allergic reaction.

An anticarbamazepine antibody was detected in the serum of a patient with severe carbamazepine-induced serum sickness. We found that the patient's T cells and IgG antibody recognized an epitope which appeared in subjects showing an allergic reaction, as well as that in subjects who showed no allergic reaction, after long-term carbamazepine therapy. These results show that an anti-carbamazepine immune response does not occur in the majority of subjects who undergo long-term carbamazepine therapy without developing allergic symptoms, although the immunodominant haptenic epitope of carbamazepine is present in their sera.

Carbamazepine↗

PubMed1992

Differences in glucagon-like peptide-1 and GIP responses following sucrose ingestion.

To investigate the mechanism of oral carbohydrate-stimulated secretion of the two most potent incretin candidates, gastric inhibitory polypeptide (GIP) and truncated glucagon-like peptide-1 (tGLP-1), we studied the changes in the plasma levels of these peptides in five healthy men after sucrose ingestion with or without pretreatment with an alpha-D-glucosidase inhibitor (AO-128). After sucrose ingestion, plasma levels of GIP peaked at 15 min and remained high up to 120 min. Plasma levels of GLP-1 NT measured with antiserum R1043 (N-terminal specific) tended to decrease gradually and those of GLP-1 CT measured with antiserum R2337 (C-terminal specific) increased. Therefore, estimated plasma levels of tGLP-1 increased markedly within 30 min, then declined slightly over the next 60 min. After treatment with AO-128 (0.6 mg/day) for 1 week, increases in plasma glucose and insulin levels were attenuated and the increase in plasma GIP levels was diminished, while the increase in tGLP-1 levels was sustained much longer. It is concluded that GIP secretion is stimulated by glucose absorption and tGLP-1 secretion by the presence of sucrose in the gut.

Adult↗

PubMed1992

Sepsis inhibits insulin-stimulated glucose transport in isolated rat adipocytes.

To assess the mechanism of insulin resistance in sepsis, we investigated insulin receptor binding and glucose uptake in isolated rat epididymal adipocytes. Male Sprague-Dawley (SD) rats weighing 200-220 g were submitted to cecal ligation under chloral hydrate anesthesia, followed by double punctures with 18-G needle into the ligated portion to produce peritonitis. Age-matched SD rats without operation were used as the controls. After starvation for 16 h, blood samples were taken from the inferior vena cava for bacterial culture and assayed for plasma glucose and IRI levels, and then adipocytes were isolated from the dissected epididymal fat tissues. Plasma levels of both glucose and IRI in septic rats were higher than those in the controls. The [125I]-insulin binding rate of the adipocytes in septic rats was similar to that of the controls. However, [3H]-2-deoxy-D-glucose uptake by adipocytes was markedly decreased in the septic group (approximately 45% of the control group at the plateau). In conclusion, this study suggests that insulin resistance in the septic state results, at least partly, from impairment in the post-binding level of the insulin receptor.

Adipose Tissue↗

PubMed1992

Insulin antibody does not cause insulin resistance during glucose clamping in rats.

Although it has often been stated that insulin antibodies cause insulin resistance, this concept is still controversial. The effect of insulin antibody GP30, commonly used in insulin radioimmunoassay, on insulin action was investigated in Wistar rats in vivo by the euglycemic glucose clamp technique. As a preliminary experiment, the equilibrium time required for insulin antibody to bind with endogenous insulin was examined. One hundred microliters/kg insulin antibody took 60 min or more to attain equilibrium, but 10 microliters/kg insulin antibody almost immediately equilibrated with endogenous insulin. During a 60-min glucose clamp study, 2 mU/kg/min porcine insulin was infused with 100 microliters/kg insulin antibody. At steady state, during the last 20-min period, the mean glucose infusion rate was 2.10 +/- 0.85 mg/kg/min (n = 5, mean +/- SD), significantly lower than the 5.77 +/- 1.61 mg/kg/min of the control, indicating insulin resistance before equilibrium was reached. However, the glucose infusion rates during the clamp with 10 microliters/kg insulin antibody and 100 microliters/kg insulin antibody infused 75 min before the insulin were 6.10 +/- 1.44 and 7.12 +/- 1.19 mg/kg/min, respectively, no different from the control. In these instances, free insulin levels measured by radioimmunoassay using the polyethyleneglycol method were 43.8 +/- 20.4 and 15.4 +/- 6.1 microU/ml, respectively, lower than the control (77.0 +/- 16.1 microM/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Pharmacologic treatment of childhood migraine.

This review of pharmacologic treatment of childhood migraine shows that no agent for abortive treatment has been proved effective in controlled studies and that most commonly used prophylactic agents (e.g., propranolol and cyproheptadine) lack proof of their effectiveness. Flunarizine seems to be the only agent with positive results in controlled studies. This drug, although well tolerated, is slow to act. For the treatment of an acute attack, aspirin or acetaminophen may be chosen. Two of us currently use propranolol as the first-choice prophylactic agent because of its tolerance and cost, and on the assumption of its effectiveness reported by the adult studies. For children with a history of asthma, metoprolol may be chosen because of its selective blocking of the beta 1-adrenoreceptor. One of us (W.N.M.) prefers cyproheptadine as the drug of choice. Behavioral therapy may be a good alternative to pharmacotherapy in the management of childhood migraine.

Child↗

PubMed1992

Congenital muscular dystrophy presenting with respiratory failure.

Respiratory failure is an unusual initial manifestation of congenital muscular dystrophy. The authors describe a case of congenital muscular dystrophy in a patient presenting with rhabdomyolysis at birth. Despite an initially poor prognosis, aggressive respiratory therapy during the neonatal period permitted normal subsequent development. The muscular dystrophy predominantly involved the respiratory muscles.

Biopsy↗

PubMed1992

Further observations on serial serum immunoreactive inhibin levels in the luteal phase and early gestation after ovarian stimulation for in vitro fertilization and embryo transfer.

Serum immunoreactive inhibin of the luteal phase was measured by radioimmunoassay in 71 patients in vitro fertilization and embryo transfer (IVF-ET). The correlation between the pregnancy outcome and the serial inhibin pattern from the luteal phase to early gestation was studied. In nonconception cycles (n = 35), serum inhibin concentration rose and reached a peak level around 5 or 6 days after oocyte pick-up (OPU), then fell to the level of the early follicular phase. In conception cycles (n = 22), serum inhibin levels rose again 10-15 days after OPU. Serum inhibin levels were significantly higher from 10 days after OPU in multiple pregnancy (n = 5) than in single pregnancy (n = 17). In viable single pregnancy (n = 17), serum inhibin levels were significantly higher than in non-viable pregnancy (n = 14) from 15 days after OPU. Serum inhibin levels in early gestation correlated well with the pregnancy outcome of IVF-ET. These data suggest that inhibin is an important factor for the diagnosis of pregnancy outcome.

Abortion, Spontaneous↗

PubMed1992

Development of the endolymphatic sac in chick embryos, with reference to the degradation of otoconia.

The endolymphatic sac of chick embryos (from embryonic day 7 to 1-day-old chicks) was studied light- and electron-microscopically. At stage 30-31 (embryonic day 7-7.5), the epithelial cells of the endolymphatic sac were cuboidal to columnar in shape. Microvilli were relatively well developed. The intercellular space was wide. In the endolymphatic space of the endolymphatic sac, varying shapes and sizes of otoconia-like bodies were often observed. Intracytoplasmic phagosomes containing these bodies were rarely found. After stage 37 (embryonic day 11), otoconia-like bodies in the endolymphatic sac decreased in number and size. They were almost the same as the otoconia in the macular organs, ultrastructurally. These findings indicate that the endolymphatic sac of the chick embryos may possess the function of otoconial degradation and removal of calcium from otoconia.

Animals↗

PubMed1992

In vivo action of activin-A on pituitary-gonadal system.

Activin, a dimer of the beta-subunits of inhibin, has been found to stimulate FSH secretion from the cultured pituitary cells. However, in vivo action of activin is poorly elucidated. Daily sc injections of 40 micrograms activin-A over a period of 1-3 days to intact immature female rats caused a significant increase in serum FSH, inhibin, estradiol, uterine weight, and ovarian FSH receptors. Daily sc injections of 5 micrograms or 20 micrograms activin-A for 6 days caused a marked increase in ovarian weight and the development of large ovarian follicles. However, daily sc injections of 20 micrograms activin-A to hypophysectomized immature female rats for 3 days induced no significant changes in ovarian and uterine weight, serum inhibin, estradiol, and progesterone levels. Simultaneous injections of both activin-A and 5 IU PMSG induced a significant increase in ovarian and uterine weight, serum inhibin, and estradiol levels, compared to simultaneous injections of both vehicle and PMSG in the hypophysectomized immature female rats. These results demonstrate that activin-A induces not only an increase of FSH secretion from the pituitary but also a direct autocrine or paracrine ovarian stimulation resulting in an increase of the number of ovarian FSH receptors and ovarian and uterine weight, as well as an increase in the level of inhibin and estradiol secretion from the ovary.

Activins↗

PubMed1992

Purification and characterization of high molecular weight forms of inhibin from bovine follicular fluid.

High molecular mass forms [95 kilodaltons (kDa)] of bovine inhibin-A as well as the known forms of intermediate (55 kDa) and low (32 kDa) mass were purified from bovine follicular fluid by ion exchange chromatography on DEAE-Sepharose, immunoaffinity chromatography using a monoclonal antibody directed against bovine 32-kDa inhibin-A, gel permeation HPLC on TSK-gel, and reverse phase HPLC. The 95-kDa inhibin-A had similar suppressive activity on FSH secretion from cultured rat anterior pituitary cells as the 55- and 32-kDa inhibins. There is, however, a possibility that the inhibin activity detected with larger forms may be due to that of the 32-kDa form that results from proteolytic processing during incubation with rat pituitary cells. Both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting analysis using monoclonal antibodies specific for 32-kDa inhibin alpha- or beta A-subunits revealed that the 95-kDa inhibin preparation contained two forms of inhibin (105 and 95 kDa), which were composed of either a 50- or a 40-kDa alpha-subunit linked by a disulfide bond(s) to a 55-kDa beta A-subunit. Amino-terminal sequence analysis showed that the 50-kDa alpha-subunit and the 55-kDa beta A-subunit were generated by removal of a signal peptide from each corresponding primary translation product [the first NH2-terminal 17 residues of the inhibin alpha-subunit (residues 1-360) and the first 20 residues of the inhibin beta A-subunit (residues 1-425)] and suggested that the 40-kDa alpha-subunit was formed by proteolytic processing of the 50-kDa alpha-subunit. On the basis of our findings, we propose that in bovine follicular fluid, the larger 105-kDa form of inhibin is processed successively to form the lowest molecular mass form, 32 kDa inhibin, through the smaller 95- and 55-kDa forms.

Amino Acid Sequence↗

PubMed1992

Plasma lidocaine concentrations during epidural blockade with isoflurane or halothane anesthesia.

Because isoflurane maintains hepatic blood flow at higher flows than halothane, we proposed that the elimination of lidocaine would be different between these two volatile anesthetics. The plasma lidocaine concentrations were determined in 14 female patients undergoing epidural blockade plus isoflurane anesthesia and compared with those obtained during halothane anesthesia for lower abdominal surgery. General anesthesia was maintained with isoflurane (0.46% +/- 0.04% [mean +/- SE] inspired, n = 7) or halothane (0.48% +/- 0.05% inspired, n = 7) and 67% nitrous oxide in oxygen. All patients received 2% lidocaine solution, 10 mL as a bolus dose and continuous administration at a rate of 10 mL/h, through the epidural catheter. The plasma lidocaine concentrations over 180 min after the epidural injection in patients receiving isoflurane were similar to those in patients receiving halothane. The results suggest that low inspired concentrations of isoflurane do not reduce plasma lidocaine concentrations in patients during epidural blockade, compared with halothane.

Adult↗

PubMed1992

[Effects of tiropramide hydrochloride on the isolated detrusor and intravesical pressure of the bladder in situ in rats].

The effects of tiropramide on the isolated detrusor and intravesical pressure of the bladder in situ in rats were compared with those of flavoxate, oxybutynin and terodiline. The IC50 values (x 10(-5) M) of tiropramide for carbachol (CCh)-, K+ (60 mM)-, Ba2+ (10 mM)-, and electrical stimulation-induced contractions were 3.6, 4.2, 5.8, and 2.9, respectively. The four antispasmodics used (2 and 4 mg/kg, i.v., each) abolished the rhythmic bladder contractions in situ in anesthesized rats. Of the four compounds, oxybutynin was most potent and no significant differences were observed between the inhibitory effects of tiropramide, flavoxate and terodiline. The administration of flavoxate (30 and 60 mg/kg) into the duodenum little influenced the rhythmic bladder contractions. Tiropramide, flavoxate, oxybutynin and terodiline (8 and 12 mg/kg, i.v., each) dose-dependently prolonged the time to the volume-evoked micturition reflex, and the activity of tiropramide was not statistically different from those of the other three antispasmodics. Under unilateral pelvic and bilateral hypogastric nerve transection, both of the contractions induced by electrical stimulation of the peripheral and central cut ends of the pelvic nerve were dose-dependently inhibited to the same extent by tiropramide and terodiline. These results suggest that the effects of tiropramide on the function of urinary bladder in rats may be mainly due to direct actions on the smooth muscle, and that tiropramide is more potent than flavoxate and less potent than oxybutynin and terodiline.

Animals↗