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Biomedical subjects

I Ohsawa

Publications and source records attributed to I Ohsawa.

At least 19 recordsLinked to original sources
PubMed1998

Novel domain-specific actions of amyloid precursor protein on developing synapses.

The effect of the secretory form of amyloid precursor protein (sAPP) on synaptic transmission was examined by using developing neuromuscular synapses in Xenopus cell cultures. The frequency of spontaneous postsynaptic currents (SSCs) was reduced by the addition of sAPP, whereas the amplitude of impulse-evoked postsynaptic currents (ESCs) was increased by sAPP. These opposing effects on spontaneous versus evoked release were separated by using the specific domain of APP. The C-terminal fragment of sAPP (CAPP) only reduced SSC frequency and did not affect ESCs. By contrast, the N-terminal fragment of sAPP (NAPP) did not affect SSC frequency but did increase ESC amplitude. The reduction of SSC frequency by sAPP appears to be mediated by activation of potassium channels through a cGMP-dependent pathway, whereas the increase of ESC amplitude is mediated by a different pathway involving activation of protein kinase(s). These results suggest the potential role of sAPP as a modulator of synaptic activity by two specific domains.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1998

Involvement of amyloid precursor protein in functional synapse formation in cultured hippocampal neurons.

Amyloid precursor protein (APP) is known to be widely expressed in neuronal cells, and enriched in the central and peripheral synaptic sites. Although it has been proposed that APP functions in synaptogenesis, no direct evidence has yet been reported. In this study we investigated the involvement of APP in functional synapse formation by monitoring spontaneous oscillations of intracellular Ca2+ concentration ([Ca2+]i) in cultured hippocampal neurons. As more and more neurons form synapses with each other during the culture period, increasing numbers of neuronal cells show synchronized spontaneous oscillations of [Ca2+]i. The number of neurons that showed synchronized spontaneous oscillations of [Ca2+]i was significantly lower when cultured in the presence of monoclonal antibody 22C11 against the N-terminal portion of APP. Moreover, incubation with excess amounts of the secretory form of APP or the N-terminal fragment of APP also inhibited the increase in number of neurons with synchronized spontaneous oscillations of [Ca2+]i. The addition of monoclonal antibody 22C11 or secretory form of APP did not, however, affect MAP-2-positive neurite outgrowth. These findings suggest that APP play a role in functional synapse formation during CNS development.

Amyloid beta-Protein Precursor↗
PubMed1998

Secreted form of beta-amyloid precursor protein activates protein kinase C and phospholipase Cgamma1 in cultured embryonic rat neocortical cells.

The secreted form of beta-amyloid precursor protein (sAPP) has been reported to exert various biological activities in cultured neurons. The signal transduction mechanisms underlying these physiological functions of sAPP remain unclear. We now report that treatment of neural cells with the secreted form of APP695 (sAPP695) leads to dose- and time-dependent increase in phosphorylation of the endogenous substrates with a molecular mass of 80, 57 and 43 kDa. Pretreatment of cells with protein kinase C (PKC) inhibitor H-7 reduced phosphorylation of the 80- and 43-kDa proteins in a dose-dependent manner. The effect of sAPP695 on the phosphorylation is mimicked by phorbol 12-myristate-13-acetate (PMA). Downregulation of PKC by prolonged treatment of cells with PMA abolished sAPP695-enhanced phosphorylation of the 80- and 43-kDa proteins, indicating PKC is involved in the sAPP695-enhanced phosphorylation of these proteins in the cells. We also suggest that the 80- and 43-kDa proteins phosphorylated by sAPP695-stimulation are the major PKC substrates myristoylated alanine-rich C-kinase substrate and growth-associated protein-43. Furthermore, we demonstrate that tyrosine phosphorylation of phospholipase Cgamma1 and formation of inositol 1,4,5-trisphosphate were increased by sAPP695-stimulation. These observations suggest that sAPP695 induces the activation of the signaling pathways through a stimulation of phosphoinositide-PKC cascade.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

The effect of a secreted form of beta-amyloid-precursor protein on intracellular Ca2+ increase in rat cultured hippocampal neurones.

1. The effects of secreted forms of beta-amyloid-precursor proteins (APP(S)s) on the intracellular Ca2+ concentration ([Ca2+]i) were investigated in rat cultured hippocampal neurones. APP695S, a secretory form of APP695, attenuated the increase in [Ca2+]i evoked by glutamate. In addition, APP695S itself evoked an increase in [Ca2+]i in 1 or 2 day-cultured hippocampal cells, but not in 7 to 13 day-cultured cells. 2. Eighty-one percent of neurones which were immunocytochemically positive for microtubule-associated protein 2 responded to APP695S with an increase in [Ca2+]i. 3. APP695S induced a transient rise in [Ca2+]i even in the absence of extracellular Ca2+ and produced an elevation in inositol-1,4,5-trisphosphate (IP3) in a concentration-dependent manner from 100 to 500 ng ml(-1). In the presence of extracellular Ca2+, APP695S caused a transient rise in [Ca2+]i followed by a sustained phase at high [Ca2+]i, suggesting Ca2+ entry from the extracellular space. 4. The [Ca2+]i elevation was mimicked by amino terminal peptides of APPs, but not by carboxy terminal peptides. 5. These results taken together suggest that APP695S induces an increase in [Ca2+]i in hippocampal neurones through an IP3-dependent mechanism that changes according to the stage of development.

Amyloid beta-Protein Precursor↗
PubMed1998

Effect of insulin on intramuscular 3-hydroxybutyrate levels in diabetic rats.

It has been shown that inhibition of lipolysis and ketogenesis by insulin is more sensitive than suppression of hepatic glucose production and stimulation of tissue glucose uptake. Clinically, on the other hand, blood glucose concentrations fall much more quickly than blood ketone concentrations. Therefore, during continuous insulin infusion at a rate of 3.0 mU/kg B.W./min over a period of 150 min we monitored blood glucose and 3-hydroxybutyrate (3-OHBA) concentrations and muscle 3-OHBA levels using the microdialysis technique in streptozotocin-induced diabetic rats. Blood glucose concentrations decreased rapidly after insulin infusion. However, significant reduction in blood-3-OHBA concentration was found for the last 30 min. In muscle dialysate 3-OHBA concentrations and muscle local blood flow there was no significant change throughout the study. These results suggest that one possible mechanism of delayed improvement in ketonemia is a reduction in muscle removal capacity.

3-Hydroxybutyric Acid↗
PubMed1998

Glomerular deposition of mannose-binding lectin (MBL) indicates a novel mechanism of complement activation in IgA nephropathy.

BACKGROUND: IgA nephropathy (IgA-N) is considered the most common glomerular disease in the world and leads to renal failure in a substantial number of patients. Although many studies have looked at the pathogenesis of the disease, many points need to be clarified, including the mechanism of complement activation. Recent studies have shown that mannose-binding lectin (MBL or mannose binding protein, MBP) initiates activation of the complement cascade (lectin pathway) utilizing two types of MBP-associated serine protease, namely MASP-1 and MASP-2. The present study was undertaken to elucidate whether the lectin pathway was involved in the pathogenic mechanism of IgA-N. METHODS: Forty-five renal biopsy cases with IgA-N, 35 cases with other forms of glomerulonephritis (GN), and normal kidney tissues were collected and an immunohistochemical study was performed using monoclonal antibodies against MBL and MASP-1. Furthermore, clinicopathological and serological features were also analysed in the patients with IgA-N. RESULTS: Glomerular deposition of MBL, which was accompanied by MASP-1, was detected in 11 of 45 (24.4%) cases with IgA-N, while it was detected in only one case with other forms of GN. The deposited MBL/MASP-1 was observed to associate with C3b/C3c and C5b-9 but not with IgG, IgM, C1q, C4c, or properdin. Compared with MBL/MASP-1 negative cases with IgA-N, the positive cases with IgA-N were young and the renal biopsies had been performed at an early stage of the disease. No significant correlation was found between glomerular deposition of MBL/MASP-1 and proteinuria, haematuria, creatinine clearance, and serum levels of IgA, C3, or C4 at the time of renal biopsy. There were also no significant differences between MBL/MASP-1 positive cases and negative cases in the plasma levels of circulating immune complexes or soluble C5b-9. CONCLUSION: The lectin pathway of complement activation, which is initiated by the MBL/MASPs complex, evidently contributes to the development of glomerular injury in a significant number of cases with IgA-N. In addition, these findings will add insight to the pathogenesis of IgA-N, including its relation to infection, since MBL plays a crucial role in the host defense against various pathogens.

Adolescent↗
PubMed1998

The association of physical activity level characteristics and other lifestyles with obesity in Nagoya University alumni, Japan.

Improving daily-life habits is considered to be effective in treating obesity. We have examined obesity in regular physical examinations in university students since 1974. In this study, the subjects were 199 students regarded as obese (Broca's index: more than 120%) and 326 non-obese students randomly selected (525 subjects in total) among students who underwent regular physical examinations at Nagoya University, Japan, between 1974 and 1978. Here we report our follow-up survey of obese university students and non-obese individuals who were students of the same university during the same period. This study was carried out for the purpose of clarifying the relationship between changes in lifestyle and body weight 20 years after graduation. Concerning eating behavior, a higher proportion of subjects cared about diet intake in the current non-obese group than in the current obese group (P<0.05). The meal-time in the obese was shorter than that in the non-obese group (P<0.01). Ten percent of subjects in the obese group and 24.4% of subjects in the non-obese group selected class II (moderate) or higher as indicative of the intensity of their daily physical activity. There was a significant difference in distribution between the groups (P<0.05). In the group showing improvement in obesity over time, a higher proportion of subjects cared about diet intake than in the group with continued obesity (P<0.05). Concerning intensity of physical activity, 11.8% of subjects in the group with continued obesity selected class II (moderate) or higher, while 45.5% of subjects in the group showing improvement in obesity chose class II (moderate) or higher. A significant difference in distribution existed between the groups (P<0.01). These findings suggest that the eating behavior of ending meals before feeling satiety and a lifestyle change to enhance the intensity of daily physical activity including walking, even if not having any special sports habits, are effective in decreasing body weight.

Adult↗
PubMed1998

Appearance of nephrotic syndrome following interferon-alpha therapy in a patient with hepatitis B virus and hepatitis C virus coinfection.

A 59-year-old woman with hepatitis B surface antigen (HBsAg) and hepatitis C viral (HCV) antibody presented with proteinuria and hematuria. The patient was treated with interferon-alpha (INF-alpha) because plasma aminotransferase levels had been elevated and a liver biopsy had showed chronic active hepatitis. Her urinary protein excretion decreased as liver function normalized and her serum HCV-RNA was negative during treatment. Eleven weeks after completion of INF-alpha treatment, she suddenly presented with nephrotic-range proteinuria, although an improvement in the hepatic function was maintained. Renal pathologic findings were consistent with membranous glomerulonephritis (MGN), and HBsAg was detected in the glomeruli but not HCV. After treatment with prednisolone, her 24-hour protein excretion was below 0.7 g/day. To our knowledge this is the first report on hepatitis B virus MGN with nephrotic syndrome following IFN-alpha therapy for HCV. This suggests that treatment with INF-alpha might affect the immune processes and may be associated with the pathogenic mechanism in this patient.

Anti-Inflammatory Agents↗
PubMed1998

Intramuscular 3-hydroxybutyrate levels after 60 tetani/min contraction in diabetic and non-diabetic rats.

Post-exercise hyperketonemia in poorly-controlled diabetic patients is a well recognized phenomenon, but because studies concerning changes in ketone body metabolism in muscle during and/or after exercise are scarce, we measured the intramuscular 3-hydroxybutyrate (3-OHBA) and lactate concentrations in 12 diabetic (streptozotocin-induced; 60 mg/kg, ip) and 13 non-diabetic control rats before and after a 1-h muscle contraction. One thigh tetanic contraction was elicited at a tetanic frequency of 60 tetani/min and the other thigh was kept resting. We used a microdialysis technique in both quadriceps muscles, vastus lateralis, and the right jugular vein. Blood flow in both femoral muscles was also monitored before and after contraction. Dialysate 3-OHBA and lactate levels in contracting and non-contracting muscles and in blood showed a significant increase after contraction (P<0.05) in diabetic rats. In control rats there was no significant change in dialysate 3-OHBA or the lactate concentration in contracting and non-contracting muscles or in blood before and after contraction. A significant increase in contracting muscle blood flow was observed only for the first 5 min after contraction in diabetic and control rats. These results suggest that 3-OHBA uptake in contracting muscle is reduced, and that this phenomenon may play a role in post-exercise ketosis in diabetes.

3-Hydroxybutyric Acid↗
PubMed1998

[Beneficial effect of salazosulfapyridine (SASP) in a patient with secondary renal amyloidosis].

A 55-year old female with rheumatoid arthritis (RA) had presented with proteinuria since July 1996. She was referred to us for persistent edema on her face and legs in November 1996. On admission, her 24-hour urinary protein excretion was 4.4 g/day, total serum protein level was 5.3 g/dl, and serum level of amyloid A protein (SAA) was elevated to 45.8 mg/ml. A percutaneous renal biopsy was performed, and light microscopy revealed varying degrees of amyloid deposits in the mesangial areas and arteriolar walls. The diagnosis of secondary amyloidosis (AA amyloidosis) was based on immunohistochemical staining for amyloid A protein using monoclonal antibody against SAA. Four weeks after treatment with salazosulfapyridine (SASP) and dipyridamole, proteinuria began to decrease and the edema had disappeared. Finally she recovered from nephrotic syndrome. AA amyloidosis has been thought to have a poor prognosis, with progression to renal failure. Since there is no specific effective therapy for the disease, it is very important to reduce the activity of the underlying cause. In our patient with renal amyloidosis following RA, SASP was evidently effective for arthritis and improvement of renal function. SASP might have a beneficial effect on AA amyloidosis by suppressing inflammatory cytokines.

Amyloidosis↗
PubMed1998

Level of red blood cells in the urinary sediment reflects the degree of renal activity in Wegener's granulomatosis.

Symptoms due to renal lesions often disappear and smolder by successful treatment during the first episode of Wegener's granulomatosis (WG). It is indispensable to recognize an increase in disease activity and provide adequate treatment to inhibit the progression of renal dysfunction as well as regulate disease activity in patients with WG. We gave attention to red blood cells in urinary sediment (U-RBC), a criterion in the diagnosis of WG, to more exactly determine the degree of renal activity. Comparison of level of U-RBC with other laboratory data and renal histology was performed in the clinical course of six cases. The level of U-RBC altered reversibly during the period studied and correlated with the C-reactive protein level and erythrocyte sedimentation rate which reflect disease activity in cases with microhematuria before treatment. When U-RBC disappeared within eight weeks after treatment, glomerular histological change remained small. The reported cases revealed that the alteration in U-RBC was more sensitive and more specific for renal involvement than the other disease markers. In conclusion, the level of U-RBC reflects the degree of renal activity in WG. We propose that the quantitation of U-RBC is extremely useful in following patients with WG.

Adult↗
PubMed1997

The amino-terminal region of amyloid precursor protein is responsible for neurite outgrowth in rat neocortical explant culture.

We have previously shown that secreted forms of beta-amyloid precursor protein (APP(s)s) promote neurite outgrowth in embryonic rat neocortical explant culture. To determine the region of APP(s) responsible for its biological activity, we produced both amino- and carboxyl-terminal regions of APP(s) using a yeast expression system. The purified fragment corresponding to the amino-terminal region (NAPP) enhanced neurite outgrowth of neocortical explants, but the carboxyl-terminal region fragment did not. The neurite-promoting activity of full length APP(s) and NAPP was blocked by the antibody, 22C11, specific for the amino-terminal region, and the 16-mer peptide of epitope for 22C11 also enhanced neurite outgrowth. However, the 17-mer peptide which contains RERMS sequence did not enhance the neurite outgrowth, but promoted the survival of neocortical neurons in dissociated culture. These findings suggested that the amino-terminal region is responsible for the neurite-promoting activity of APP(s)s.

Amyloid beta-Protein Precursor↗
PubMed1997

Specific inhibitor for prolyl endopeptidase suppresses the generation of amyloid beta protein in NG108-15 cells.

A potent and specific prolyl endopeptidase inhibitor, JTP-4819, was used to investigate the role of prolyl endopeptidase in the generation of amyloid beta protein (A beta) from APP by NG108-15 cells. Synthetic substrates, 7-(succinyl-Ile-Ala)-4-methylcoumarinamide and Z(Val-Lys-Met)-4-methylcoumarinamide, respectively, corresponding to the C-terminal and N-terminal portions of A beta, were cleaved by NG108-15 cell lysates. Cleavage of the C-terminal portion, but not the N-terminal, was inhibited by JTP-4819 (IC50 = 0.6 nM). Western blot analysis showed that the A beta level in the culture medium of NG108-15 cells was increased by serum deprivation. JTP-4819 caused concentration (>10(-9) M)- and time-dependent inhibition of this serum deprivation-induced increase of A beta without having any effect on the level of the secretory form of APP. Using both specific anti-A beta (1-40) and anti-A beta (1-42) antisera, the A beta that increased with serum deprivation was confirmed to be A beta (1-40), suggesting that it might be produced by conversion of A beta (1-42) to A beta (1-40). These findings indicate that prolyl endopeptidase may be a key enzyme in the production of A beta by NG108-15 cells and that A beta secretion can be modulated by a prolyl endopeptidase inhibitor.

Amyloid beta-Peptides↗
PubMed1996

Effect of C-peptide administration on whole body glucose utilization in STZ-induced diabetic rats.

Recent studies suggest that C-peptide stimulates glucose transport in isolated skeletal muscle. In order to determine the effect of C-peptide on whole body glucose utilization, streptozotocin (60 mg kg-1) (STZ)-induced diabetic and normal rats were studied using the euglycaemic clamp procedure and continuous infusion of somatostatin (1.0 micrograms kg-1 min-1) in pentobarbital-anaesthetized rats. Plasma insulin levels during the 6.0- and 30.0-mU kg-1 min-1 insulin infusions rose to 70-90 microU mL-1 and 500-700 microU mL-1, respectively. Blood glucose concentrations were clamped at 7.5-7.9 mmol L-1 in the diabetic rats and at basal levels or 7.7 mmol L-1 in the non-diabetic (normal) rats. Biosynthetic human C-peptide (0.5 nmol kg-1 min-1) was infused in 12 diabetic and 11 normal rats, resulting in concentrations of 26-41 nmol L-1. The metabolic clearance rate of glucose (MCR) for the diabetic rats receiving C-peptide (12.0 +/- 1.0 mL kg-1 min-1) was significantly (P < 0.01) higher than that in the diabetic rats given saline (6.3 +/- 0.7 mL kg-1 min-1) or a randomly scrambled C-peptide (7.8 +/- 1.3 mL kg-1 min-1) at low-dose insulin infusion but not at the high-dose insulin infusion. In normal rats C-peptide did not significantly increase the MCR for glucose. These results thus demonstrate that C-peptide has the capacity to increase glucose utilization in STZ-induced diabetic rats.

Animals↗
PubMed1996

Exercise training prevents maturation-induced decrease in insulin sensitivity.

We examined the effects of exercise training initiated before maturation or after maturation on insulin sensitivity and glucose transporter GLUT-4 content in membrane fractions of skeletal muscle. Female Wistar rats (4 wk of age) were divided into sedentary and exercise-trained groups. At 12 wk of age, a subset of the trained animals (Tr) was killed along with a subset of sedentary controls (Sed). One-half of the remaining sedentary animals remained sedentary (Sed-Sed) while the other half began exercise training (Sed-Tr). The remaining rats in the original trained group continued to train (Tr-Tr). Euglycemic clamp (insulin infusion rate at 6 mU.kg body wt-1. min-1) was performed at 4, 12, and 27 wk. After euglycemic clamp in all animals except the 4-wk-old, hindlimb (gastrocnemius and part of quadriceps) muscles were removed for preparation of membrane fractions. In sedentary rats, glucose infusion rate (GIR) during euglycemic clamp was decreased from 15.9 mg.kg-1.min-1 at 4 wk of age to 9.8 mg.kg-1.min-1 at 12 wk of age and 9.1 mg.kg-1.min-1 at 27 wk of age. In exercise-trained rats, the GIR was not significantly decreased by maturation (at 12 wk) and further aging (at 27 wk). Initiation of exercise after maturation restored the GIR at 27 wk of age to the same levels as these for the corresponding exercise-trained rats. GLUT-4 content in plasma and intracellular membrane fractions of hindlimb muscle obtained just after euglycemic clamp showed the same trend as the results of GIR. These results suggest that exercise training prevented the maturation-induced decrease in insulin sensitivity. Improvement of insulin sensitivity caused by exercise training was attributed, at least in part, to the increase in insulin-sensitive GLUT-4 on the plasma membrane in skeletal muscle.

Age Factors↗
PubMed1996

Elevation of plasma thrombomodulin level in primary glomerulonephritis with heavy proteinuria.

Thrombomodulin (TM) is a thrombin receptor found on endothelial cells. TM acts as a cofactor for the thrombin-catabolized activation of protein C and protects these cells from the formation of thrombi. We hypothesized that the soluble form of TM which reflects the damage of the endothelial cells and that simultaneously, soluble TM will be affected by renal excretion because a significant positive correlation has been found between soluble TM and serum creatinine (sCr) in the renal failure state. However, there have been no reports on the relationship between plasma TM and clinical parameters except for sCr in primary glomerulonephritis (PGN). Plasma TM (pTM) and urinary TM (uTM) were measured in 107 patients with PGN using a one-step sandwich enzyme immunoassay. These values were assessed together with other laboratory and histological findings. We were able to divide all subjects into two groups: an sCr-dependent group whose sCr level was over 1.2 mg/dl and an sCr-independent group whose sCr level was under 1.2 mg/dl. In the sCr-independent group, patients who suffered from nephrotic syndrome (NS) had a much higher pTM level than patients who did not suffer from NS. Histological findings and other parameters were not correlated with pTM or uTM. Therefore, the two patients who suffered from NS with very high pTM levels and normal sCr level at the time of admission exhibited a decrease in their pTM value as their condition improved. We concluded that in our patients, pTM was affected not only by renal excretion of TM, but also by renal damage with heavy proteinuria and may have been associated with an ongoing disease process in PGN.

Adolescent↗
PubMed1995

Expression, purification, and neurotrophic activity of amyloid precursor protein-secreted forms produced by yeast.

The secreted form of amyloid precursor protein (APPs) including most of the extracellular domain of APP is released from the cell surface, suggesting physiological significance of APPs in vivo. We used the methylotrophic yeast Pichia pastoris as a host system for the production of recombinant APPs (rAPPs). Two rAPPss derived from isoforms of APP (APP695 and APP770) were secreted into the culture medium from the yeast, which carried cDNA encoding the N-terminal portion of APP under the control of a P. pastoris alcohol oxidase promoter. Like APPss produced by the transfected COS-1 cells, the purified rAPPss from yeast were shown to be biologically active in terms of neurite outgrowth of embryonic rat neocortical explants. These rAPPss could be valuable tools for investigating the biological functions of APPss.

Amino Acid Sequence↗