Enhanced optical magnetoelectric effect in a patterned polar ferrimagnet

A simple method to dramatically enhance the optical magnetoelectric (ME) effect, i.e., nonreciprocal directional birefringence, is proposed and demonstrated for a polar ferrimagnet GaFeO3 as a typical example. We patterned a simple grating with a period of 4 microm on a surface of GaFeO3 crystal and used the diffracted light as a probe. The optical ME modulation signal for the Bragg spot of the order n=1 becomes gigantic in the photon energy 1-4 eV and reaches 1-2% of the bare diffracted light intensity in a magnetic field of 500 Oe. This is amplified by more than 3 orders of magnitude compared to that for the reflection of bulk GaFeO3. Fabricating a photonic crystal will make it possible to lead the way for the practical use of the optical ME effect.

Dynamical identification of a threshold instability in Si-doped heterofullerenes

We rationalize the origins of a threshold instability and the mechanism of finite temperature fragmentation in highly Si-doped C(60-m)Si(m) heterofullerenes via a first-principles approach. Cage disruption is driven by enhanced fluctuations of the most internal Si atoms. These are located within fully segregated Si regions neighboring the C-populated part of the cage. The predominance of inner Si atoms over those involved in Si-C bonds marks the transition from thermally stable to unstable C(60-m)Si(m) systems at m = 20.

Positron emission tomography and magnetic resonance imaging in spinocerebellar ataxia type 2: a study of symptomatic and asymptomatic individuals

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder characterized as an expanded CAG trinucleotide repeats in SCA2 gene resulting in abnormal polyglutamine sequence. We used positron emission tomography (PET) and magnetic resonance imaging (MRI) to clarify metabolic and atrophic changes of the brain in two symptomatic and three asymptomatic individuals who were genetically confirmed for SCA2. PET revealed decreased glucose metabolism in both patients and two of the three asymptomatic carriers in the cerebellum, pons, or both. No PET abnormality was found in the remaining one carrier who had only a very mildly expanded CAG repeat. MRI showed cerebellar and/or pontine atrophic changes in both patients and one of three carriers. The present study suggest that hypometabolism and atrophy of the cerebellum and pons may occur years before the clinical onset of SCA2. PET and MRI may be useful in the early detection of subclinical brain changes associated with SCA2.

A case of gain-of-function mutation in calcium-sensing receptor: supplemental hydration is required for renal protection

AIMS

The calcium-sensing receptor (CaSR) regulates the extracellular calcium level, mainly by controlling parathyroid hormon secretion and renal calcium reabsorption. In gain-of-function CaSR mutations, the genetic abnormalities increase CaSR activity leading to the development of such clinical manifestations as hypercalciuric hypocalcemia and hypoparathyroidism. We report a Japanese case of CaSR gain-of-function mutation and represent a therapeutic intervention based on the functional characteristics of CaSR in renal tubule.

METHODS AND RESULTS (CASE)

DNA sequence analysis revealed a heterozygous G to T mutation identified in a 12-year-old Japanese girl presenting with sporadic onset of hypercalciuric hypocalcemia and hypoparathyroidism. The mutation is located in the N-terminal extracellular domain of the CaSR gene, one of the most important parts for the three-dimensional construction of the receptor, resulting in the substitution of phenylalanine for cysteine at amino acid 131 (C131F) in exon 3. Based on the diagnosis of the gain-of-function mutation in the CaSR, oral hydrochlorothiazide administration and supplemental hydration were started in addition to calcium supplementation. The combination therapy of thiazide and supplemental hydration markedly reduced both renal calcium excretion and urinary calcium concentration from 0.4-0.7 to less than 0.1 mg/mg (urinary calcium/creatinine ratio) and from 10-15 to 3-5 mg/dl (urinary calcium concentration), respectively. This therapy stopped the progression of renal calcification during the follow-up period.

CONCLUSION

Supplemental hydration should be considered essential for the following reasons: (1) calcium supplementation activates the CaSR in the kidney and suppresses renal urinary concentrating ability, (2) the thiazide has a diuretic effect, (3) as calcium supplementation increases renal calcium excretion, the supplemental hydration decreases urinary calcium concentration by increasing urinary volume, thereby diminishing the risk of intratubular crystallization of calcium ion.

Modeling the pressure inactivation dynamics of Escherichia coli

Escherichia coli, as a model microorganism, was treated in phosphate-buffered saline under high hydrostatic pressure between 100 and 300 MPa, and the inactivation dynamics was investigated from the viewpoint of predictive microbiology. Inactivation data were curve fitted by typical predictive models: logistic, Gompertz and Weibull functions. Weibull function described the inactivation curve the best. Two parameters of Weibull function were calculated for each holding pressure and their dependence on holding pressure was obtained by interpolation. With the interpolated parameters, inactivation curves were simulated and compared with the experimental data sets.

Effects of olopatadine hydrochloride, an antihistamine drug, on skin inflammation induced by repeated topical application of oxazolone in mice

BACKGROUND

Olopatadine hydrochloride (olopatadine) is one of the second-generation antihistamines, which is prescribed for allergic disorders such as rhinitis, urticaria and eczema dermatitis.

OBJECTIVES

To investigate the possible anti-inflammatory effect of olopatadine on the chronic contact hypersensitivity response to repeated topical application of oxazolone in mice.

METHODS

The preventive and therapeutic effects of oral olopatadine were quantified by measurements of ear swelling, cytokine protein and mRNA expression in the ear lesion, and were compared with those of topical betamethasone 17-valerate (betamethasone).

RESULTS

The ear receiving repeated applications of oxazolone exhibited erythema, oedema and abrasion. Both preventive and therapeutic administration of olopatadine (10 mg kg(-1) day(-1)) significantly inhibited the ear swelling and the increased production of interleukin (IL)-4, IL-1beta, granulocyte-macrophage colony-stimulating factor (GM-CSF) and nerve growth factor. In the histopathological analysis, olopatadine ameliorated epidermal hyperplasia and infiltration of inflammatory cells. Consistent with these results, olopatadine significantly reduced the increased expression of interferon-gamma and IL-4 mRNA. Although betamethasone (0.012 mg ear(-1) day(-1)) showed similar activities to olopatadine against these responses, it caused atrophy of the ear skin.

CONCLUSIONS

These results indicate that olopatadine is an antihistamine agent having inhibitory activities against chronic inflammatory dermatitis, possibly resulting from its diminishing effect on elevated cytokines.

Olopatadine hydrochloride suppresses the rebound phenomenon after discontinuation of treatment with a topical steroid in mice with chronic contact hypersensitivity

BACKGROUND

Olopatadine hydrochloride (olopatadine; Allelock) is one of the second-generation antihistamines that are treated for allergic disorders such as rhinitis, urticaria and eczema dermatitis. Olopatadine has recently been shown to have inhibitory effects on the chronic contact hypersensitivity induced by repeated application of oxazolone in mice. Although topical steroids have widely been prescribed for atopic dermatitis, a relapse often occurs within several days after discontinuation of their prolonged use.

OBJECTIVES

We investigated the possible efficacy of olopatadine against the relapse after discontinuation of prolonged use of topical prednisolone in the Balb/c mice with oxazolone-induced chronic contact hypersensitivity.

METHODS

Mice with the chronic contact hypersensitivity induced by repeated application of oxazolone were treated with olopatadine as a sequential therapeutic agent. The effects of olopatadine were quantified by measurements of ear-swelling, and levels of cytokines and histamine in the lesioned ear. Results Topical prednisolone (0.05 mg/ear/day) significantly inhibited the increases in ear swelling and production of IL-1beta, IL-4, IL-18, granulocyte-macrophage colony-stimulating factor (GM-CSF) and histamine. However, after discontinuation of the treatment with topical prednisolone, the inflammation relapsed and the IL-4 level exceeded the control one. The sequential treatment with olopatadine (10 mg/kg/day) after discontinuation of the treatment with topical prednisolone alone, or topical prednisolone with olopatadine, significantly inhibited the increases in ear swelling and levels of IL-1beta, IL-4, IL-18, GM-CSF, nerve growth factor and histamine.

CONCLUSIONS

These results indicate that olopatadine is an antihistamine agent having inhibitory activities against the rebound phenomenon following the discontinuation of topical steroid therapy. Olopatadine is thus expected to be a sequential therapeutic agent after discontinuation of the chronic treatment with a topical steroid.

Bonding behavior and thermal stability of C54Si6: A first-principles molecular dynamics study

By using a self-consistent plane-waves density functional approach we study the bonding behavior and the thermal properties of C(54)Si(6) heterofullerenes. Calculations are carried out by employing a generalized gradient approximation. Our investigation improves upon previous findings on the same system obtained via the local density approximation approach. This is due to a much larger search in configurational space and the explicit account of temperature effects. Overall, isomers can be classified in two groups. In the first, nearest-neighboring Si atoms form a subnetwork, while in the second the Si atoms are farther apart on the cage. In addition to structural optimization, we carried out first-principles molecular dynamics for temperatures up to T=3000 K on a time interval of 12 ps. These simulations show that Si-Si bond variations with temperature are less important when all Si atoms are found on a hexagon. Therefore, this structural arrangement is the most likely to be observed experimentally. Analysis of charge topology reveals that the amount of charge on each atom depends on the number of heterogeneous bonds, due to a significant charge transfer from the Si to the neighboring C atoms.

Optical magnetoelectric effect in the polar GaFeO3 ferrimagnet

The optical magnetoelectric (ME) effect, i.e., the change of optical absorption upon the reversal of the light propagation direction, has been investigated for a polar ferrimagnet GaFeO3. For dipole- and spin-forbidden d-d transition bands located at 1.2-2.3 eV, a clear signal of the optical ME effect (Deltaalphat approximately 3x10(-3)) is observed with an applied magnetic field as low as 500 Oe and a sample thickness (t) of 50 microm. The observation of a large ME effect in the present compound suggests a possible route to magnification of this novel phenomenon for application.

Cerebral alterations in a MPTP-mouse model of Parkinson's disease--an immunocytochemical study

We investigated the immunohistochemical alterations of neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS), tyrosine hydroxylase (TH), microtubule-associated protein 2a,b (MAP 2), glial fibrillary acidic protein (GFAP), parvalbumin (PV), and dopamine transporter (DAT) in the striatum and substantia nigra following the application of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice. TH-, MAP 2- and DAT-immunoreactive cells were decreased gradually in the striatum and substantia nigra from 1 day up to 7 days after MPTP treatment, as well as the reduction of the striatal dopamine, DOPAC and HVA content. The number of GFAP-immunoreactive astrocytes increased gradually in the striatum and substantia nigra from 1 day up to 7 days after MPTP treatment. Striatal nNOS-immunoreactive cells were unchanged in MPTP-treated mice. In the substantia nigra, intense immunoreactivity of nNOS-positive cells increased 5 hr after MPTP treatment. Thereafter, the immunoreactivity of nNOS-positive cells decreased gradually from 1 day up to 7 days after MPTP treatment. eNOS-immunopositive cells were unchanged in the striatum and substantia nigra. These results demonstrate that nNOS may play a key role in the development of MPTP neurotoxicity. Our findings also indicate that MPTP can cause the functional damage of interneurons in the substantia nigra, but not in the striatum.

[Leaflet extension technique in a congenital aortic valve regurgitation]

A 17-year-old boy who was diagnosed as congenital aortic valve regurgitation underwent the leaflet extension technique in 3 aortic leaflets using glutaraldehyde-preserved autologous pericardium. Intraoperative transesophageal echocardiography and postoperative cardiac catheter revealed grade I regurgitation and the patient has been doing well for more than 4 months after the surgery. The leaflet extension technique is considered to be an acceptable surgical treatment for aortic valve disease especially in young patients to whom valve replacement or Ross procedure might not be suitable. A careful long-term follow-up will be necessary to evaluate the durability of the leaflet extension technique with autologous pericardium.

Increased incidence of acute graft-versus-host disease with the continuous infusion of cyclosporine A compared to twice-daily infusion

We retrospectively compared the incidence of acute graft-versus-host disease (GVHD) before and after September 1999, when we changed the mode of cyclosporine A (CsA) administration from twice-daily infusions (TD) (n=58) to continuous infusion (CIF) (n=71). The incidence of grade II-IV acute GVHD in the CIF group (56%) was significantly higher than that in the TD group (27%, P=0.00022). Multivariate analysis identified only two independent significant risk factors for the development of grade II-IV acute GVHD; CIF of CsA (relative risk 2.59, 95% CI 1.46-4.60, P=0.0011) and the presence of HLA mismatch (2.01, 95% CI 1.15-3.53, P=0.014). The incidence of relapse was significantly lower in the CIF group when adjusted for disease status before transplantation (0.41, 95% CI 0.18-0.95, P=0.038), which resulted in better disease-free survival in high-risk patients (43 vs 16% at 2 years, P=0.039), but not in standard-risk patients (72 vs 80%, P=0.45). CIF of CsA with a target level of 250-400 ng/ml may not be appropriate for GVHD prophylaxis in standard-risk patients.

Factors which affect the progression of osteoarthritis after rotational acetabular osteotomy

We have investigated the factors which affect the progression of osteoarthritis after rotational acetabular osteotomy (RAO). Between 1984 and 1998, we treated 60 dysplastic hips by RAO. The mean age at surgery was 31.6 years (13 to 51) and the mean period of follow-up was 4.6 years (2 to 9.5). The thickness of the articular cartilage on the weight-bearing area, pre- and postoperative acetabular cover, and the sphericity of the femoral head were used for radiological assessment. The osteoarthritis did not progress in 39 hips. Significant factors which affected the radiological grade included sphericity of the femoral head and the postoperative acetabular cover. The surgical approach and preoperative acetabular cover did not affect the progression of osteoarthritis. Patients were divided into two groups according to the surgical approach used, either conventional (23 hips) or modified (37 hips). Significant factors included the postoperative acetabular cover in the modified approach, and the sphericity of the femoral head in the conventional approach. It is critical that the postoperative cover is sufficient, especially when RAO is carried out using our modified technique.

[Management of mediastinitis after pediatric cardiac surgery with continuous closed irrigation method]

Two cases are presented as a successful management for mediastinitis with the continuous closed irrigation method after pediatric cardiac surgery. The continuous closed irrigation method has significant advantages over conventional open irrigation method or muscle flap in pediatric cases, because the system is simple to handle and easy to wash out any infectious tissue debris without additional invasive intervention. However, adequate duration of the irrigation and subsequent antibiotic regimen is still unclear. We conclude that the continuous closed irrigation method is an effective management which is applicable to most of mediastinitis cases after pediatric cardiac surgery.

Role of dopamine transporter against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in mice

We investigated the alterations of dopamine transporter (DAT)-immunopositive cells against MPTP neurotoxicity, in comparison with tyrosine hydroxylase (TH)-immunopositive neurons and glial fibrillary acidic protein (GFAP)-immunopositive cells. This study showed that DAT and TH immunoreactivity was decreased gradually in the striatum and substantia nigra of mice after MPTP treatment. The patterns of the intense TH-immunoreactive fibers and cell bodies were similar to those of DAT-immunoreactive fibers and cell bodies in the striatum and substantia nigra of mice after MPTP treatment. In contrast, GFAP immunoreactivity was increased gradually in the striatum and substantia nigra after MPTP treatment. In our double-labeled immunostaining with anti-DAT and anti-GFAP antibodies, DAT immunoreactivity was observed only in the nigral dopaminergic neurons, but not in the reactive astrocytes. The present results provide further evidence that the functional damage of DAT may precede dopaminergic neuronal death after MPTP treatment, although the decrease in the number of TH-immunopositive neurons was more pronounced than that in the number of DAT-immunopositive neurons. Furthermore, our findings demonstrate that MPTP can selectively injure the dopaminergic neurons which DAT proteins are predominantly distributed on the striatum and substantia nigra. The results provide beneficial information for MPTP-induced neurodegeneration of the nigrostriatal dopaminergic neuronal pathway.

Pose estimation of artificial hip joint using a single radiographic projection

Total hip joint arthroplasty is commonly used in cases of osteoarthritis and rheumatoid arthritis. A hip joint prosthesis consists of a cup and a stem. The relative pose (position and orientation) of the prosthesis, when the patient is standing naturally, is planned pre-operatively; however, there is no guarantee that the pre-operatively planned pose will be accurate. Prosthesis component malposition, which is inadequate positioning of the acetabular or femoral component, results in limited joint movement and a large prosthetic joint contact area, and this can cause dislocation of the femoral head from the cap. Because the range of motion after total hip joint arthroplasty is determined by the relative pose of the cup and the stem, it is important to know the relative pose after hip arthroplasty. Several pose estimation methods using single-plane fluoroscopy or conventional roentgenography have been proposed. Because a conventional radiograph system is commonly used at small cost, a method using conventional radiograms is desirable for use in a clinical setting. In this study, a pose estimation method using conventional radiography is proposed, and an in vitro experiment is performed to evaluate its accuracy. The rotational errors of the relative pose of the cup with respect to the stem were smaller than 2.3 degrees.

Role of nitric oxide synthase against MPTP neurotoxicity in mice

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes nigrostriatal dopaminergic pathway injury similar to that observed in Parkinson's disease. Many hypotheses have been proposed to explain the mechanisms underlying MPTP neurotoxicity. Previous work showed that the inhibitor of neuronal nitric oxide synthase (nNOS) might produce protection against MPTP-induced dopaminergic toxicity. To exactly test the role of NO in MPTP neurotoxicity, we examined the effect of nNOS inhibitor 7-nitroindazole, in comparison with that of nonselective NOS inhibitor (L-NAME), immunosuppressant (FK-506), monoamine oxidase (MAO) inhibitors (clorgyline and pargyline), N-methyl-D-aspartate receptor antagonist (MK-801) and Ca2+ antagonist (amlodipine). Among seven compounds, 7-nitroindazole produced dose-dependent protection against MPTP-induced depletion of striatal dopamine and its metabolite 3,4-dihydroxyphenyl acetic acid (DOPAC) in mice. Clorgyline and pargyline also showed a significant effect on MPTP-induced dopamine depletion in the mouse striatum. However, both compounds did not protect against MPTP-induced depletion of striatal DOPAC Our immunohistological study with tyrosine hydroxylase (TH) and microtuble-associated protein 2 (MAP 2) showed that 7-nitroindazole or pargyline can protect against MPTP-induced depletion of TH and MAP 2 immunostained neurons in the substantia nigra. Furthermore, these compounds reduced a marked increase in GFAP-positive astrocytes of the mouse striatum after MPTP treatments. The present study demonstrates that nNOS inhibitor 7-nitroindazole as well as MAO inhibitors clorgyline and pargyline can produce dose-dependent neuroprotection against the dopaminergic neurotoxicity of MPTP. However, nonselective NOS inhibitor L-NAME, immunosuppressant FK-506, NMDA receptor antagonist MK-801 and Ca2+ antagonist amlodipine did not show a beneficial effect on MPTP neurotoxicity.

Therapeutic effect of neuronal nitric oxide synthase inhibitor (7-nitroindazole) against MPTP neurotoxicity in mice

Effects of neuronal nitric oxide synthase (nNOS) inhibitor (7-nitroindazole), nonselective NOS inhibitor (N(G)-nitro-L-arginine methyl ester; L-NAME), and monoamine oxidase inhibitor (pargyline) were studied on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. The mice received four intraperitoneal injections of MPTP at 1-h intervals. A significant depletion in dopamine and DOPAC concentration was observed in the striatum from 1 day after MPTP treatment. The pretreatment of 7-nitroindazole and pargyline, but not L-NAME, dose-dependently protected against MPTP-induced depletion in dopamine content 3 days after MPTP treatment. Our histochemical study also showed that 7-nitroindazole and pargyline can prevent a marked decrease in the nigral cells and a marked increase in astrocytes in striatum 7 days after MPTP treatment. The protective effect of 7-nitroindazole against MPTP-induced dopamine and DOPAC depletion in the striatum was not attenuated by intraperitoneal pretreatment with L-arginine. Furthermore, the posttreatment of 7-nitroindazole or pargyline protected against MPTP-induced depletion of dopamine content. These results demonstrate that the protective mechanism by which 7-nitroindazole counteracts MPTP neurotoxicity in mice may be due not only to inhibition of nNOS, but also to MAO-B inhibition. Furthermore, our study suggests that the posttreatment of 7-nitroindazole and pargyline can prevent a significant decrease in dopamine levels in the striatum of MPTP-treated mice. These findings have important implications for the therapeutic time window and choice of nNOS or MAO inhibitors in patients with Parkinson's disease.

Postnatal changes in ghrelin mRNA expression and in ghrelin-producing cells in the rat stomach

Ghrelin was recently isolated from the rat stomach as an endogenous ligand for the GH secretagogue receptor. Although it is well known that a large amount of ghrelin is produced in the gastrointestinal tract, developmental changes in ghrelin mRNA expression and differentiation of ghrelin-immunopositive (ghrelin-ip) and mRNA-expressing (ghrelin-ex) cells in the stomach have not been elucidated. In this study, we therefore investigated the changes in ghrelin mRNA expression levels and in the numbers of ghrelin-ip and -ex cells in the stomachs of 1- to 8-week-old male and female rats by Northern blot analysis, immunohistochemistry and in situ hybridization. Northern blot analysis showed that the level of weak ghrelin mRNA expression was low in the postnatal period but then increased in a dimorphic pattern, i.e. transient stagnation at 4 weeks in the male rats and at 5 weeks in the female rats. The number of ghrelin-ip and ghrelin-ex cells also increased after birth, and more numerous ghrelin cells were found in female rats than in male rats, and this finding was confirmed by Northern blot analysis. Ghrelin-ip and -ex cells first appeared in the glandular base of the fundic gland and then they were found in the glandular base and the glandular neck at 3 weeks of age, suggesting that the distribution of ghrelin cells is extended from the glandular base to the glandular neck during the postneonatal development period. This is the first report on detailed changes in postneonatal ghrelin expression level and in the number of ghrelin cells in the rat stomach. The sexual dimorphism of ghrelin expression and ghrelin cell differentiation suggest that ghrelin plays an important physiological role in the stomach.

Elevated serum leptin concentrations in women with components of multiple risk factor clustering syndrome

This cross sectional study was undertaken to determine whether serum leptin levels were associated with multiple risk factor (MRF) clustering syndrome. We examined the relationship between serum leptin concentrations and blood pressure (BP), serum lipids levels, calculated insulin resistance (HOMA-ratio) and adiposity among 581 Japanese adult women. The serum leptin was increased in female subjects with systolic (> or =160 mmHg) and diastolic > or =90 mmHg) hypertension compared with the normotensive females (mean+/-SE; 9.3+/-0.5 vs 7.7+/-0.3; 10.2+/-0.6 vs 7.1+/-0.3 ng/ml, both p<0.001). Serum leptin was elevated in those with hyper-cholesterolemia (C; > or =220 mg/dl) and triglyceridemia (TG; > or =150 mg/dl) compared with the normolipidemia (9.4+/-0.4 vs 7.8+/-0.3; 11.7+/-0.6 vs 7.5+/-0.2 ng/ml, both p <0.001). Serum leptin was also elevated in those with adiposity (BMI > or =26.4 kg/m2) and insulin resistance (HOMA-ratio > or =2.5) compared with the normal females (14.8+/-0.7 vs 5.2+/-0.2; 11.3+/-1.1 vs 7.1+/-0.4ng/ml, both p<0.001). Even after adjusting for BMI or percent body fat mass (BFM), leptin levels remained to be elevated significantly in all these diseases. There was a positive correlation between serum leptin and systolic, diastolic BP, TC, TG, BMI, BFM, IRI and HOMA-ratio (r=0.12, p=0.005; r=0.24, p<0.0001; r=0.19, p<0.0001; r=0.35, p<0.0001; r=0.72, p<0.0001; r=0.73, p<0.0001; r=0.47, p< 0.0001; r=0.44, p<0.0001), and a negative correlation with HDL-C levels (r= -0.20, p< 0.0001). These correlations were also observed in leptin levels after adjusting for the BMI or BFM. Multiple regression analysis showed that BFM, HOMA-ratio and TG were significant determinants of leptin concentration before (t=12.6, p<0.0001; t=3.33, p=0.001; t=3.22, p=0.001) and after adjusting for BMI or BFM. These results suggest that because serum leptin levels were elevated in components of MRF clustering syndrome, leptin may have a pathophysiological role in MRF clustering syndrome.

Regulational effect of ghrelin on growth hormone secretion from perifused rat anterior pituitary cells

Ghrelin, a novel growth hormone (GH)-releasing peptide, was recently isolated from the rat stomach as an endogenous ligand to growth hormone secretagogue receptor (GHS-R). Ghrelin specifically stimulates the release of GH from the rat anterior pituitary gland, but the regulational effect of ghrelin on GH secretion has not yet been clarified. We used a perifusion system to examine the single effect and combined effects of ghrelin with growth hormone-releasing hormone (GHRH) and somatostatin on GH secretion from rat anterior pituitary cells. The increase in GH concentration due to ghrelin stimulation showed a transitory peak that was almost the same as that previously reported for GHS, but apparently distinct from that of GHRH. Ghrelin (10(-10) M to 10(-8) M) stimulated GH secretion from the rat anterior pituitary cells in a dose-dependent manner. Serial ghrelin stimulation of the dispersed cells at 1-h intervals decreased the GH response, but the response recovered with stimulation at 3-h intervals, indicating that ghrelin strongly desensitized cells. Costimulation with ghrelin and GHRH elicited neither a synergistic nor an additive GH response from the rat pituitary cells. Furthermore, pretreatment to anterior pituitary cells with somatostatin strongly abolished ghrelin- and/or GHRH-stimulated GH secretion. In this study, we demonstrated that ghrelin caused weaker GH secretion than that caused by GHRH, and we also showed that costimulation with GHRH had no additive or synergistic effect on GH secretion, suggesting that ghrelin indirectly affects coordinated GH release from pituitary gland, as found in vivo.

Gamma-aminobutyric acidA and benzodiazepine receptor alterations in the rat brain after unilateral 6-hydroxydopamine lesions of the medial forebrain bundle

Gamma-aminobutyric acidA (GABA(A)) and benzodiazepine (BZ) receptors and dopamine uptake sites in 6-hydroxydopamine-treated rat brains were studied by receptor autoradiography using [3H]muscimol, [3H]flunitrazepam and [3H]mazindol binding, respectively. The rats were unilaterally lesioned in the medial forebrain bundle and the brains were analyzed at 1, 2, 4 and 8 weeks post-lesion. Degeneration of the nigrostriatal pathway after 6-hydroxydopamine treatment caused a significant loss of dopamine uptake sites in the ipsilateral striatum and substantia nigra (SN) in the lesioned animals. In the contralateral side, however, dopamine uptake sites showed no significant changes in the brain throughout the experiments. On the other hand, no significant changes in GABA(A) receptors were observed in the brain of both the ipsilateral and contralateral sides during post-lesion. In contrast, BZ receptors were observed significantly increased in the ventromedial part of striatum of the ipsilateral side from 2 to 4 weeks post-lesion. Furthermore, a transient increase in BZ receptors was found in the ipsilateral SN only at 2 weeks post-lesion. In contralateral side, most regions examined showed no significant changes in BZ receptors throughout the experiments except for a transient increase in the SN at 1 week post-lesion. These results demonstrate that 6-hydroxydopamine can cause severe functional damage in dopamine uptake sites in the nigrostriatal pathway. Our results also suggest that the change in BZ receptors is more pronounced than that in GABA(A) receptors in the brain after 6-hydroxydopamine treatment. Furthermore, our findings suggest that the increase in BZ receptors in the brain of 6-hydroxydopamine-treated model may be due to the additional disruption of the nigrostriatal dopamine system. Thus, investigations into possible changes in neurotransmitter receptors other than dopaminergic receptors appear to be important for the elucidation of pathogenesis of Parkinsons disease.

Aldosterone synthase gene (CYP11B2) C-334T polymorphism, ambulatory blood pressure and nocturnal decline in blood pressure in the general Japanese population: the Ohasama Study

OBJECTIVE

The C-344T polymorphism in the 5'-flanking region of the aldosterone synthase (CYP11B2) gene has been suggested to be associated with hypertension and disturbed circadian blood pressure (BP) rhythm through its effect on aldosterone synthesis. However, previous findings on this topic have been inconsistent.

DESIGN

A cross-sectional study.

SUBJECTS AND METHODS

We investigated the CYP11B2 C-344T genotype in 802 subjects, aged 40 and over, in a Japanese community, who gave written informed consent and were monitored for 24 h ambulatory BP.

RESULTS

The frequencies of the CC, CT, and TT genotypes in these Japanese subjects were 0.14, 0.44, and 0.42, showing a higher frequency of the T allele (0.64) than in Caucasians. Although there was no significant difference in 24 h ambulatory BP levels among the genotypes, the nocturnal decline in BP was significantly greater in the CC homozygous subjects than in other subjects (P = 0.0065 for systolic and P = 0.031 for diastolic decline in nocturnal BP). Detailed analyses demonstrated that this association was significant only in aged (60 years and over) or male subjects. The prevalence of previous cardiovascular disease was significantly less in these subjects with the CC genotype than in those with the TC and TT genotypes, although age, body mass index, male gender, smoking, use of alcohol and antihypertensive medication did not differ among the three genotypes. There was no significant difference among the three genotypes in biochemical and hormonal parameters.

CONCLUSION

Although the C-344 T polymorphism of CYP11B2 did not directly influence the level of 24 h BP, the CC genotype was associated with decreased nocturnal BP in elderly or male Japanese. Since prevalence of previous cardiovascular disease was significantly less in homozygous CC subjects, greater nocturnal BP decline in this genotype appears to be beneficial in the circadian BP rhythm.

Predictive values of automated blood pressure measurement: what can we learn from the Japanese population - the Ohasama study

BACKGROUND

Measurements of ambulatory blood pressure (ABP) and of home blood pressure (HBP) as an adjunct to casual/clinic blood pressure (CBP) measurements are currently widely used for the diagnosis and treatment of hypertension. We have monitored a rural cohort of people from the population of Ohasama, Japan, with respect to their prognosis and have previously reported that ABP and HBP are superior to CBP for the prediction of cardiovascular mortality. One reason that CBP is a poor predictor of prognosis is that it incorporates several biases, including the white-coat effect.

METHODS AND RESULTS

We examined the prognostic significance of white-coat hypertension for mortality and found that the relative hazard for the overall mortality of patients with white-coat hypertension was significantly lower than that for true hypertension. Short-term blood pressure variability has recently attracted attention as a cause of target-organ damage and cardiovascular complications. Our results confirmed that short-term blood pressure variability (as measured every 30 min) was independently associated with cardiovascular mortality. In addition, research has recently focused on isolated systolic hypertension and pulse pressure as independent risk factors for poor cardiovascular prognosis. The Ohasama study also clearly demonstrated that isolated systolic hypertension and increased pulse pressure, as assessed by HBP, were associated with an increase in the risk of cardiovascular mortality. Circadian blood pressure variation is characterized by a diurnal elevation and a nocturnal decline in blood pressure. We therefore compared morbidity from stroke between dippers (subjects who show an ordinal nocturnal dipping of blood pressure) and non-dippers (those with a diminished nocturnal dipping or nocturnal elevation of blood pressure [inverted dippers]) in the Ohasama study. The incidence of stroke increased with an increased length of observation in dippers using antihypertensive medication but not in non-dippers using antihypertensive medication. In contrast, the relative hazard for mortality increased in non-dippers and inverted dippers. These results suggest a cause-and-effect relationship for both dippers and non-dippers.

CONCLUSION

The Ohasama study showed that the level and variability of hypertension as assessed by ABP and HBP are independent predictors of cardiovascular mortality. It also demonstrated an independent association between the prognosis of hypertension and each component of ABP and HBP, indicating the prognostic significance of these blood pressure measurements.