Biomedical subjects

T Shibasaki

Publications and source records attributed to T Shibasaki.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Genetic abnormalities of regulatory mechanism of appetite].

Recently, leptin was cloned and characterized as a sateity factor which acts through the hypothalamus. alpha-melanocyte-stimulating hormone derived from pro-opiomelanocortin(POMC) and melanocortin receptor-4(MC4-R) have been reported to be involved in the downstream of the effect of leptin. In this paper, we summarized the clinical characteristics and the mechanisms of obesity caused by genetic abnormalities involved in the regulatory mechanism of appetite such as leptin, leptin receptor, POMC, MC4-R and prohormone convertase 1.

Animals↗

PubMed2001

[Ruptured cerebral aneurysm in childhood--report of two cases].

We report two pediatric patients with rupture of cerebral aneurysm developing subarachnoid hemorrhage. These two patients complained of headache and vomiting. Patient 1 was a 15-year-old girl. Cranial computed tomography (CT) showed a high density area in the left sylvian fissure, suggesting subarachnoid hemorrhage. Left carotid arteriography revealed an aneurysm at the left internal carotid artery bifurcation. Surgical pathology showed a saccular type aneurysm with disappearance of internal elastic membrane. Patient 2 was a 14-year-old girl. Cranial CT exhibited a high density area in the basal cistern and hematoma in the right frontal lobe, penetrating to the right lateral ventricle. Right carotid arteriography showed a right anterior cerebral aneurysm in the right anterior cerebral artery. Both patients underwent craniotomy and trapping successfully, and their subsequent clinical courses were uneventful.

Adolescent↗

PubMed2000

Response of leptin mRNA to 24-h food deprivation and refeeding is influenced by age in rats.

To obtain an insight into the influence of aging on leptin gene expression, the responses of leptin mRNA in retroperitoneal and epididymal adipose tissues and plasma leptin concentrations to 24-h food deprivation and refeeding were examined in 2-, 10- and 24-month-old normal rats. The basal level of leptin gene expression in retroperitoneal adipose tissue was significantly higher in 10- and 24-month-old rats than that in 2-month-old rats, while the level in epididymal adipose tissue was highest in 10-month-old rats for all three age groups. The basal concentrations of plasma leptin was significantly higher in 10- and 24-month-old rats than those in 2-month-old rats. The 24-h food deprivation was followed by a significant reduction in leptin mRNA expression in both retorperitoneal and epididymal adipose tissues for all three age groups. The leptin gene expression was restored to control levels 24 h following refeeding in the 2- and 10-month-old rats, but failed to be restored in the 24-month-old rats. In addition, the time course of recovery for leptin mRNA expression by refeeding to the control levels differed between the retroperitoneal and the epididymal adipose tissue in 2- and 10-month-old rats. The concentrations of plasma leptin 24 h following refeeding were compatible with the leptin mRNA levels in adipose tissues in three age groups. These results suggest that the expression of the leptin gene in response to food-deprivation and refeeding is influenced by an animal's age and that this expression is different for different regions of white adipose tissue.

Adipose Tissue↗

PubMed2000

Urocortin in the ventromedial hypothalamic nucleus acts as an inhibitor of feeding behavior in rats.

Urocortin (UCN), a member of the corticotropin-releasing factor (CRF) family, inhibits food intake when it is injected intracerebroventricularly in rats. To explore the site of action of UCN in feeding behavior, we examined the effects of injection of UCN into various hypothalamic nuclei on food and water intake in 24-h fasted rats. Injection of UCN into the ventromedial hypothalamic nucleus (VMH) significantly inhibited food and water intake over 3 h without sedative effect, but no significant effect was observed following injection either into the lateral hypothalamic area, or the paraventricular nucleus of the hypothalamus. To further explore the physiological significance of endogenous UCN of the VMH in feeding behavior, the effect of immunoneutralization of hypothalamic UCN on food intake was examined. Injection of anti-rat UCN rabbit gamma-globulin into the bilateral VMH in freely fed rats significantly potentiated food and water intake compared with rats that received normal rabbit gamma-globulin. These results suggest that endogenous UCN in the VMH exert inhibitory control on ingestive behavior.

Animals↗

PubMed2000

A 6-day intracerebroventricular infusion of the growth hormone-releasing peptide KP-102 stimulates food intake in both non-stressed and intermittently-stressed rats.

The effects of a 6-day intracerebroventricular (i.c.v.) infusion of KP-102, a growth hormone-releasing peptide (GHRP), on food intake and body weight gain were observed in free-feeding rats that were or were not subjected to intermittent electric footshock stress during the 6 days. Food intake and body weight were significantly lower in rats exposed to a 60-min period of footshock twice a day for 6 days compared to non-stressed rats. A 6-day, i.c.v. infusion of KP-102 significantly and steadily increased food intake and body weight in free-feeding non-stressed rats compared to control rats receiving saline i.c.v. In rats exposed to intermittent footshock stress during the 6-day infusion, KP-102 treatment stimulated feeding behavior and resulted in significantly higher body weight compared to stressed rats that received i.c.v. infusion of saline. These results indicate that during a 6-day continuous i.c.v. infusion of GHRP, KP-102, food intake and body weight steadily increased without attenuation of the GHRP effect in both non-stressed rats and those subjected to intermittent stress.

Animals↗

PubMed2000

Construction of a novel hydroxyproline-producing recombinant Escherichia coli by introducing a proline 4-hydroxylase gene.

An Escherichia coli recombinant strain producing trans-4-hydroxy-L-proline (Hyp) was constructed by introducing a proline 4-hydroxylase gene into an L-proline-producing E. coli. Plasmid pPF1, which contains a gene encoding feedback resistant gamma-glutamyl kinase (proB74), was constructed and introduced into E. coli W1485 putA. The recombinant E. coli W1485 putA/pPF1 strain produced L-proline (1.2 g/l). The proline production by W1485 putA/pPF1 was converted to Hyp production by introducing pWFH1 which contains a proline 4-hydroxylase gene. E. coli W1485 putA which harbors pWFP1 carrying the proline 4-hydroxylase gene, proB74, and proA produced 25 g/l of Hyp in 96 h. A novel biosynthetic pathway of Hyp, which has not previously been produced in E. coli, was constructed in E. coli.

Journal Article↗

PubMed2000

cAMP-GEFII is a direct target of cAMP in regulated exocytosis.

Although cAMP is well known to regulate exocytosis in many secretory cells, its direct target in the exocytotic machinery is not known. Here we show that cAMP-GEFII, a cAMP sensor, binds to Rim (Rab3-interacting molecule, Rab3 being a small G protein) and to a new isoform, Rim2, both of which are putative regulators of fusion of vesicles to the plasma membrane. We also show that cAMP-GEFII, through its interaction with Rim2, mediates cAMP-induced, Ca2+-dependent secretion that is not blocked by an inhibitor of cAMP-dependent protein kinase (PKA). Accordingly, cAMP-GEFII is a direct target of cAMP in regulated exocytosis and is responsible for cAMP-dependent, PKA-independent exocytosis.

Animals↗

PubMed2000

Selective corticotropin-releasing factor type 1 receptor antagonist blocks conditioned fear-induced release of noradrenaline in the hypothalamic paraventricular nucleus of rats.

The effects of conditioned fear on the release of noradrenaline in the hypothalamic paraventricular nucleus (PVN) and the involvement of corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) in conditioned fear-induced changes in noradrenaline release were examined by intracerebral microdialysis in rats. Conditioned fear was produced by placing animals into a box where they had previously been exposed to a 5-min period of electric footshock, 135 min prior to the start of experiment. Conditioned fear for 20 min produced a significant increase in the release of noradrenaline in the PVN. Intraperitoneal preadministration of a selective nonpeptidic CRFR1 antagonist, CRA1000, completely blocked the conditioned fear-induced release of noradrenaline. These results suggest that CRFR1 is involved in the release of noradrenaline in the hypothalamic PVN induced by conditioned fear.

Animals↗

PubMed2000

The relationship between bone turnover and body weight, serum insulin-like growth factor (IGF) I, and serum IGF-binding protein levels in patients with anorexia nervosa.

Malnutrition is one of the risk factors for bone loss in patients with anorexia nervosa (AN). To clarify the effects of nutritional status on bone metabolism, we examined the relationship between serum levels of nutritional indicators [insulin-like growth factor I (IGF-I), IGF-binding protein-2 (IGFBP-2), and IGFBP-3] and markers for bone metabolism [serum osteocalcin and urinary excretion of C-terminal telopeptide of collagen type I (CrossLaps)] in 45 AN out-patients, including 8 severely malnourished patients who required hospitalization and iv hyperalimentation (IVH). Compared to healthy subjects, serum IGF-I and IGFBP-3 were lower, whereas IGFBP-2 was higher in out-patients who had a body mass index (BMI) less than 16.5 kg/m2. In these patients, urinary excretion of CrossLaps, a marker of bone resorption, was higher, whereas serum osteocalcin, a marker of bone formation, was lower than those in control subjects. All of these parameters were normal in patients whose BMI ranged from 16.5-18.5 kg/m2. Serum levels of osteocalcin correlated positively with BMI (r = 0.512; P<0.0001), IGF-I (r = 0.558; P<0.0001), and IGFBP-3 (r = 0.369; P<0.001) in AN out-patients. In the 8 severely malnourished AN patients, serum levels of IGF-I and osteocalcin significantly increased 3 and 7 days, respectively, after the start of a 5-week IVH therapy regimen and reached normal levels within 5 weeks, accompanied by still elevated urinary excretion of CrossLaps. The present study demonstrates that an improvement in nutritional status in AN patients during IVH therapy rapidly increases the serum IGF-I levels, followed by a progressive increase in osteocalcin, suggesting immediate start of bone formation. However, increased bone resorption appears to continue for at least 5 weeks.

Adolescent↗

PubMed2000

Enzymatic production of trans-4-hydroxy-L-proline by regio- and stereospecific hydroxylation of L-proline.

A proline 4-hydroxylase gene, which was cloned from Dactylosporangium sp. RH1, was overexpressed in Escherichia coli W1485 on a plasmid under a tryptophan tandem promoter after the codon usage of the 5' end of the gene was optimized. The proline 4-hydroxylase activity was l600-fold higher than that in Dactylosporangium sp. RH1. trans-4-Hydroxy-L-proline(Hyp) was produced and accumulated to 41 g/L (87% yield from L-proline) in 100 h when the recombinant E. coli was cultivated in a medium containing L-proline and glucose. 2-Oxoglutarate, which is necessary for the hydroxylation of L-proline by proline 4-hydroxylase, was apparently supplied from glucose through the cellular metabolic pathway. The putA mutant of W1485, which is not able to degrade L-proline, has allowed the quantitative conversion of L-proline to Hyp. The formation of other isomers of hydroxyproline was not observed. Productivity of Hyp was almost the same in a larger-scale culture. The method of manufacturing Hyp from L-proline was established.

Amino Acid Sequence↗

PubMed2000

RGS domain in the amino-terminus of G protein-coupled receptor kinase 2 inhibits Gq-mediated signaling.

We have previously shown that not only G protein-coupled receptor kinase (GRK) 2, but also a catalytically inactive Lys220Trp GRK2 decreases endothelin (ET)-1-induced inositol 1,4,5-trisphosphate (IP3) formation, and demonstrated the presence of phosphorylation-independent desensitization mechanism. To clarify the role of GRK2 other than that as a kinase, we characterized an RGS (regulator of G protein signaling)-like domain in the amino-terminus of GRK2. Both GRK2(1-181) and GRK2(54-174) suppressed Ca2+ responses induced by angiotensin II (Ang II) and ET-1, and bound directly with Galphaq but not Galphas nor Galphai3 in the presence of GDP and AlF4-. These results demonstrate that GRK2 regulates Gq-mediated signaling negatively by direct interaction between its RGS domain and the transitional state of Galphaq, as well as through phosphorylation of activated receptors by its kinase domain.

Aluminum Compounds↗

PubMed2000

Navigation system for neurosurgery with PC platform.

This paper presents a navigation system for a surgical microscope and an endoscope which can be used for neurosurgery. In this system, a wireframe model of a target tumor and other significant anatomical landmarks are superimposed in real-time onto live video images taken from the microscope and the endoscope. The wireframe model is generated from a CT/MRI slice images. Overlaid images are simultaneously displayed in the same monitor using the picture-in-picture function so that the surgeon can concentrate on the single monitor during the surgery. The system measures the position and orientation of the patient using specially designed non-contact sensing devices mounted on the microscope and the endoscope. Based on this real-time measurement, the system displays other useful information about the navigation as well as the rendered wireframe. The accuracy of registration between the wireframe model and the actual live view is less than 2 mm. We tested this system in actual surgery several times, and verified its performance and effectiveness.

Equipment Design↗

PubMed1999

Psychological stress increased corticotropin-releasing hormone mRNA and content in the central nucleus of the amygdala but not in the hypothalamic paraventricular nucleus in the rat.

The central administration of corticotropin-releasing hormone (CRH) to experimental animals sets into motion a coordinated series of physiological and behavioral events that promote survival during threatening situation. A large body of evidence suggest that CRH in the central nucleus of the amygdala (CEA) induces fear-related behaviors and is essential to fear conditioning; however, evidence of CRH-mediated activation of the amygdala under physiological situation is still limited. We report here a study of the impact of a psychological stressor on hypothalamic and amygdala CRH systems in the rat. Non-footshocked rats placed in a floored compartment surrounded by footshocked rats were defined as the psychological stress group. Rats were exposed to psychological stress for 15 min, and then sacrificed 1.5 and 3 h after cessation of stress. We found that our psychological stressor induced an increase in both CRH mRNA levels, as assessed by in situ hybridization histochemistry, and CRH content, as assessed by micropunch RIA, in the CEA. Exposure to the psychological stressor also caused a significant increase in CRH mRNA levels with a trend for an increase in CRH content in the dorsolateral subdivision of the bed nucleus of the stria terminalis (BNST) which is anatomically associated with the CEA. In contrast, psychological stress induced a small, but significant increase in type-1 CRH receptor (CRHR-1) mRNA in the hypothalamic paraventricular nucleus (PVN), while it failed to elevate either PVN CRH mRNA levels or content, CRH content in the median eminence (ME), or levels of plasma ACTH or corticosterone (CORT). Thus, in the context of a psychological stressor, the activation of the amygdala CRH system can occur without robust activation of the hypothalamic CRH system. In the light of previous data that the psychological stress-induced loss of sleep was reversed by the central administration of a CRH antagonist, these data suggest that CRH in the CEA may contribute to the psychological stress-evoked fear-related behavior such as hyperarousal. These data also indicate that in response to a psychological stressor, the amygdala CRH system is much more sensitive than is the CRH system emanating from the PVN.

Adrenocorticotropic Hormone↗

PubMed1999

Effect of insulin-like growth factor-I on growth hormone-releasing factor receptor expression in primary rat anterior pituitary cell culture.

We examined the effect of insulin-like growth factor-I (IGF-I) on GH-releasing factor (GRF) receptor expression in the primary rat anterior pituitary cell culture. The levels of GRF receptor mRNA were dose-dependently reduced by IGF-I treatment for 24 h. To clarify whether altered levels of GRF receptor mRNA contribute to GRF receptor concentrations, we examined the GH response to GRF in vitro. There was no difference in basal GH secretion between control and IGF-I pretreated cells, while GRF-stimulated GH secretion in cells pretreated with IGF-I for 24 h was significantly lower than that in control cells. Moreover, specific [125I] Tyr10-human GRF binding to pituitary cells was reduced significantly by IGF-I treatment. These results suggest that IGF-I acts directly on the pituitary and participates in the regulation of GRF receptor expression.

Animals↗

PubMed1999

Corticotropin-releasing factor receptor type 1 mediates emotional stress-induced inhibition of food intake and behavioral changes in rats.

We investigated whether corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) is involved in emotional stress-induced inhibition of food intake and behavioral changes in rats. The inhibition of food intake and increase in locomotor activity induced by emotional stress using a communication box were reversed by both intracerebroventricular injection of alpha-helical CRF (9-41), a non-selective CRF receptor antagonist, and intraperitoneal injection of a selective non-peptidic CRFR1 antagonist. These results suggest that CRFR1 mediates at least in part the emotional stress-induced inhibition of feeding behavior and increase in locomotor activity.

Animals↗

PubMed1999

The effects of prenatal stress on the development of hypothalamic paraventricular neurons in fetal rats.

The present experiments focused on the influence of prenatal stress on the development of neurons of the hypothalamic paraventricular nucleus in the fetal rat, including corticotropin-releasing factor-containing neurons. Prenatal stress was administered by restraining pregnant rats in a small cage for either 30 (30-min stress group) or 240 min (240-min stress group) daily for three days from embryonic day 15 to 17, and the fetal brains were taken on embryonic day 18 for later analysis. Golgi-impregnated neurons of the paraventricular nucleus in the 240-min stress group revealed that the total length of the processes was significantly shorter than in the control (unstressed) and 30-min stress groups. In addition, the 240-min stress group showed an increase in the number of apoptotic cells in the fetal paraventricular nucleus. On the other hand, Golgi-impregnated neurons of the paraventricular nucleus in the 30-min stress group had a greater degree of cell differentiation as manifested by an increase in both the number of branch points and the total length of the processes from the cell body. Furthermore, the fetal paraventricular nucleus in the 30-min stress group showed enhanced corticotropin-releasing factor messenger RNA expression, while the varicosities of corticotropin-releasing factor-containing axons at the median eminence revealed more matured morphology such as shorter intervals between the varicosities. These findings suggest the duration-dependent effects of prenatal stress on the development of fetal hypothalamic paraventricular nucleus neurons, including corticotropin-releasing factor-containing neurons: long-lasting stress causes neurotoxic changes of fetal paraventricular nucleus neurons, whereas short-lasting stress facilitates the development of these fetal brain neurons. These morphological changes induced by prenatal stress may contribute to behavioral changes of the offspring after birth.

Animals↗

PubMed1999

Characterization of the carboxyl terminal-truncated endothelin B receptor coexpressed with G protein-coupled receptor kinase 2.

The role of phosphorylation of the C-terminal tail of endothelin B receptor (ETBR) in agonist-induced desensitization was investigated, using a mutant lacking C-terminal 40 amino acids (delta 40 ETBR). In cells expressing the wild type or delta 40 ETBR, ET-1 caused rapid desensitization of calcium responses. The wild type ETBR was phosphorylated by biotinylated ET-1, and the phosphorylation was markedly enhanced by coexpression with G protein-coupled receptor kinase 2 (GRK2). However, delta 40 ETBR was not phosphorylated regardless of coexpression with GRK2. On the other hand, ET-1-induced IP3 formation in these cells was decreased by coexpression with GRK2 or catalytically inactive Lys220Arg GRK2 to the similar extent. The present study demonstrates the presence of phosphorylation-independent desensitization mechanism in delta 40 ETBR and suggests that GRK2 might play a role other than that as a kinase.

Animals↗

PubMed1999

Microbial proline 4-hydroxylase screening and gene cloning.

Microbial proline 4-hydroxylases, which hydroxylate free L-proline to trans-4-hydroxy-L-proline, were screened in order to establish an industrial system for biotransformation of L-proline to trans-4-hydroxy-L-proline. Enzyme activities were detected in eight strains, including strains of Dactylosporangium spp. and Amycolatopsis spp. The Dactylosporangium sp. strain RH1 enzyme was partially purified 3,300-fold and was estimated to be a monomer polypeptide with an apparent molecular mass of 31 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Degenerate primers based on the N-terminal amino acid sequence of the 31-kDa polypeptide were synthesized in order to amplify the corresponding 71-bp DNA fragment. A 5.5-kbp DNA fragment was isolated by using the 71-bp fragment labeled with digoxigenin as a probe for a genomic library of Dactylosporangium sp. strain RH1 constructed in Escherichia coli. One of the open reading frames found in the cloned DNA, which encoded a 272-amino-acid polypeptide (molecular mass, 29, 715 daltons), was thought to be a proline 4-hydroxylase gene. The gene was expressed in E. coli as a fused protein with the N-terminal 34 amino acids of the beta-galactosidase alpha-fragment. The E. coli recombinant exhibited proline 4-hydroxylase activity that was 13. 6-fold higher than the activity in the original strain, Dactylosporangium sp. strain RH1. No homology was detected with other 2-oxoglutarate-dependent dioxygenases when databases were searched; however, the histidine motif conserved in 2-oxoglutarate-dependent dioxygenases was found in the gene.

Actinomycetales↗