Dual role of SRC homology domain 2-containing inositol phosphatase 2 in the regulation of platelet-derived growth factor and insulin-like growth factor I signaling in rat vascular smooth muscle cells

Src homology domain 2 (SH2)-containing inositol phosphatase 2 (SHIP2) possesses 5-phosphatase activity and an SH2 domain. The role of SHIP2 in platelet-derived growth factor (PDGF) and IGF-I signaling was studied by expressing wild-type (WT-) and a catalytically defective (Delta IP-) SHIP2 into rat aortic smooth muscle cells by adenovirus-mediated gene transfer. PDGF- and IGF-I-induced tyrosine phosphorylation of their respective receptors and phosphatidylinositol 3-kinase (PI3-kinase) activity were not affected by the expression of either WT- or Delta IP-SHIP2. SHIP2 possessed 5'-phosphatase activity to hydrolyze the PI3-kinase product phosphatidylinositol 3,4,5-trisphosphate in vivo. Akt and glycogen synthase kinase 3beta are known to be downstream molecules of PI3-kinase, leading to the antiapoptotic effect. Overexpression of WT-SHIP2 inhibited PDGF- and IGF-I-induced phosphorylation of these molecules and the protective effect of poly(ADP-ribose) polymerase degradation, whereas these phosphorylations and the protective effect were enhanced by the expression of Delta IP-SHIP2, which functions in a dominant negative fashion. Regarding the Ras-MAPK pathway, PDGF- and IGF-I-induced tyrosine phosphorylation of Shc was not affected by the expression of either WT- or Delta IP-SHIP2, whereas both expressed SHIP2 associated with Shc. Importantly, PDGF and IGF-I stimulation of Shc/Grb2 binding, MAPK activation, and 5-bromo-2'-deoxyuridine incorporation were all decreased in both WT- and Delta IP-SHIP2 expression. These results indicate that SHIP2 plays a negative regulatory role in PDGF and IGF-I signaling in vascular smooth muscle cells. As the bifunctional role, our results suggest that SHIP2 regulates PDGF- and IGF-I-mediated signaling downstream of PI3-kinase, leading to the antiapoptotic effect via 5-phosphatase activity, and that SHIP2 regulates the growth factor-induced Ras-MAPK pathway mainly via the SH2 domain.     

A case of Japanese summer-type hypersensitivity pneumonitis: monitoring with serum KL-6 and examination of the phenotype of HLA]

A 55-year-old woman was admitted with a cough and fever in August. A diagnosis of Japanese summer-type hypersensitivity pneumonitis was made on the basis of radiological, serological and pathological findings, in addition to positive returning home provocation. Serum KL-6 was monitored during the clinical course. Although KL-6 fluctuated slowly in comparison with the clinical symptoms and HRCT findings, it was considered useful for confirming the effects of treatment. Serum anti-Trichosporon antibody and the phenotype of HLA were studied in both the patient and her asymptomatic roommate, with whom she had no blood relationship. Though both were sensitized immunologically, HLA-DQ 3, which was reported to be associated with Japanese summer-type hypersensitivity pneumonitis, was detected in the patient but not in her roommate. It was suggested that HLA plays a role in the development of this disease.     

Administration of atrial natriuretic peptide attenuates reperfusion phenomena and preserves left ventricular regional wall motion after direct coronary angioplasty for acute myocardial infarction.

To evaluate the effects of synthetic human atrial natriuretic peptide (hANP) on myocardial reperfusion injury and left ventricular remodeling, 19 patients within 12 h of a first attack of anterior myocardial infarction (AMI) underwent intracoronary injection of 25 microg of hANP immediately after coronary angioplasty, combined with intravenous infusion of 0.025 microg x kg(-1) x min(-1) of hANP initiated on admission for 1 week (hANP group); 18 similar patients had saline administered (control group). The incidences of premature ventricular contraction, ventricular tachycardia and/or fibrillation in the hANP group were significantly less than in the control group after coronary angioplasty. Left ventricular ejection fraction was significantly greater and left ventricular end-diastolic volume index was significantly smaller 6 months after coronary angioplasty. Left ventricular regional wall motion of the infarcted segments significantly increased. Thus, hANP remarkably suppressed reperfusion phenomena and preserved left ventricular function through improvement of regional wall motion of the infarcted segments after coronary angioplasty.     

Effects of dose rates on radiation-induced replenishment of intestinal stem cells determined by Lgr5 lineage tracing

An understanding of the dynamics of intestinal Lgr5⁺ stem cells is important for elucidating the mechanism of colonic cancer development. We previously established a method for evaluating Lgr5⁺ stem cells by tamoxifen-dependent Lgr5-lineage tracing and showed that high-dose-rate radiation stimulated replenishment of colonic stem cells. In this study, we evaluated the effects of low-dose-rate radiation on stem cell maintenance. Tamoxifen (4OHT)-injected Lgr5-EGFP-IRES-Cre^ERT2 × ROSA-LSL-LacZ mice were used, LacZ-labeled colonic crypts were enumerated, and the loss of LacZ⁺ crypts under low-dose-rate radiation was estimated. After 4OHT treatment, the number of LacZ-labeled Lgr5⁺ stem cells was higher in the colon of infant mice than in adult mice. The percentage of LacZ-labeled crypts in infant mice rapidly decreased after 4OHT treatment. However, the percentage of labeled crypts plateaued at ∼2% at 4 weeks post-treatment and remained unchanged for up to 7 months. Thus, it will be advantageous to evaluate the long-term effects of low-dose-rate radiation. Next, we determined the percentages of LacZ-labeled crypts irradiated with 1 Gy administered at different dose rates. As reported in our previous study, mice exposed to high-dose-rate radiation (30 Gy/h) showed a marked replenishment (P = 0.04). However, mice exposed to low-dose-rate radiation (0.003 Gy/h) did not exhibit accelerated stem-cell replenishment (P = 0.47). These findings suggest the percentage of labeled crypts can serve as a useful indicator of the effects of dose rate on the stem cell pool.     

Case of malignant hyperthermia in which treatment was carried out smoothly

We experienced a case of the abortive malignant hyperthermia (MH) that had developed during operation. The patient was a 14-year-old girl, and plastic surgery was scheduled under general anesthesia. Serum creatine kinase (CK) levels were high with 505 IU x l(-1) at the preoperative examination. General anesthesia was induced with propofol and vecuronium bromide, and maintained with sevoflurane. Suddenly, sinus tachycardia of an uncertain cause and a rapid rise of end-tidal carbon dioxide (Et(CO2)) concentration were noticed. Since we suspected MH, we did cooling and hyperventilation and administered dantrolene sodium 2 mg x kg(-1) for the patient. As a result, the highest temperature remained at 37.6 degrees C. Serum CK levels increased most postoperative 18 hours later and it is improved gradually. As sevoflurane, promotes the CICR (calcium-induced calcium release) mechanism, the trigger of this case is probably sevoflurane. As for the symptom that makes us doubt MH first, there is a maked rapid rises of Et(CO2). Therefore, it is important monitor and recognize the first symptom of MH.     

Experience in postoperative sedation with dexmedetomidine for mandibular osteotomy

BACKGROUND: Dexmedetomidine may be suitable for postoperative sedation of patients with mandibular osteotomy. METHODS: Twenty patients were sedated with dexmedetomidine (group D) employing loading infusion at 1.0 microg x kg(-) x hr(-1) and then continuous infusion at 0.7 mg x kg(-1) x hr(-1). Other twenty patients were sedated with midazolam 0.1 mg x kg(-1) (group C). Ramsay score was recorded at 3 hours and 12 hours after infusing sedative drugs. Then, we questioned patients, nurses and doctors. RESULTS: Ramsay score in the group D was higher than that in the group C (P < 0.01). Hypotension and respiratory depression did not occur. But bradycardia occurred in two cases. By adding propofol, group D showed more effective sedation. CONCLUSIONS: This study shows that sedation with dexmedetomidine is more suitable than that with midazolam.     

Activation of supraspinal NMDA receptors by both D-serine alone or in combination with morphine leads to the potentiation of antinociception in tail-flick test of rats

Although there is a variety of information concerning the effects of the N-methyl-D-aspartate (NMDA) receptor on opioid-induced antinociception at the spinal level, little is known about the effects at the supraspinal level. To clarify the role of the NMDA receptor on the morphine-induced antinociception at the supraspinal level, we investigated the effects of the intracerebroventricular (i.c.v.) administration of D-serine, a selective agonist for the glycine site of the NMDA receptors, alone or in combination with morphine using the tail-flick test. The i.c.v. administration of D-serine, but not L-serine, alone produced a dose-dependent antinociception in the tail-flick response. D-Serine also dose-dependently potentiated the antinociceptive effect induced by the i.c.v. administration of morphine and the simultaneous administration produced an additive effect. The potentiation of the antinociception produced by both D-serine alone or in combination with morphine was dose-dependently attenuated by the i.c.v. administration of L-701,324, a selective antagonist for the glycine site of the NMDA receptors. In addition, the potentiation of the D-serine-induced antinociception was antagonized by the i.c.v. administration of naloxone, a nonselective opioid receptor antagonist. These observations, together with the fact that D-serine is an endogenous and selective co-agonist for the glycine site of the NMDA receptors, strongly suggested that the activation of the supraspinal NMDA receptors by D-serine leads to the potentiation of the antinociception in the tail-flick test and that endogenous D-serine could modulate the mu-opioid receptor mediated antinociception via the glycine site of the NMDA receptors at the supraspinal level.     

Kinetic model to predict the absorption of nasally applied drugs from in vitro transcellular permeability of drugs

The purpose of this study is to propose a kinetic model to predict the absorption of nasally applied drugs from their permeability to the Caco-2 monolayer (P(Caco-2)). Since a drug applied to the nose in an in vivo physiologic condition is translocated to the gastrointestinal (GI) tract by coordinated beats of cilia (mucociliary clearance, MC), the drug undergoes absorption both from the nasal cavity and from the GI tract. The detailed MC of the rat was examined, using inulin as a marker of the applied solution. Inulin disappeared monoexponentially from the nasal cavity, indicating that the MC can be assumed to follow first-order kinetics. From the disappearance of inulin, the first order rate constant for MC (k(MC)) was calculated as 0.0145 min(-1). In the proposed kinetic model, the fractional absorption of the drug following nasal application is predicted as the sum of F(NC) (fractional absorption from the nasal cavity) and F(GI) (fractional absorption from the GI tract), both of which are estimated indirectly from P(Caco-2). F(NC) is calculated according to the equation, k(a)/(k(a)+k(MC)), where k(a) is the absorption rate constant. Nasal drug absorption is assumed to follow first order kinetics. The k(a) of four drugs was initially calculated from k(MC) and their F(NC); thereafter, the linear relationship between k(a) and P(Caco-2), from which k(a) is predicted, was determined. F(GI) is calculated as F(p.o.)(1-F(NC)), where F(p.o.) is fractional absorption after oral administration. F(p.o.) was predicted from the previously determined sigmoid curve between F(p.o.) and P(Caco-2). The proposed kinetic model is the first estimation system for nasal drug absorption based on drug disposition after nasal application and is useful for the development of nasal dosage forms.