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Biomedical subjects

N Toyoda

Publications and source records attributed to N Toyoda.

At least 109 records · Page 6Linked to original sources
PubMed1990

Synergistic effect of thyroid hormone and thyrotropin on iodothyronine 5'-deiodinase in FRTL-5 rat thyroid cells.

The effects of T3 and T4 on the iodothyronine 5'-deiodinase (5'-D) activity in FRTL-5 rat thyroid cells were investigated. T3 and T4 stimulated the 5'-D activity in a dose-dependent manner. Kinetic studies showed that the stimulation of the 5'-D by T3 was associated with an increase in maximum velocity (Vmax) in [11.9 +/- 0.2 (mean +/- SE) and 25.4 +/- 0.9 pmol I-released/mg protein.min, respectively, in control and cultured with 10(-9) M T3 for four days] but without a change in apparent Michaelis-Menten constant (Km) (94.8 +/- 5.3 nM and 105.4 +/- 12.1 nM, respectively). Furthermore, cycloheximide (5 microM) completely abolished the stimulatory effect of T3 on the 5'-D activity. T3 and T4 also enhanced the 5'-D activity stimulated by TSH in a dose-dependent manner. Kinetic studies showed that the stimulatory effect of T3 on the 5'-D stimulated by TSH was again associated with an increase in Vmax (86.0 +/- 4.0 and 166.5 +/- 1.9 pmol I- released/mg protein.min, respectively, cultured with 0.3 U/liter TSH and cultured with TSH plus 10(-9) M T3 for four days) without a change in apparent Km (114.0 +/- 7.4 nM and 111.6 +/- 12.5 nM, respectively). Cycloheximide (5 microM) completely abolished the stimulatory effect of TSH plus T3 on the 5'-D activity. There were no significant differences observed between cells cultured with TSH and with TSH plus T3 in either the intra- or extracellular cAMP contents. Furthermore, T3 enhanced the 5'-D activity stimulated by (Bu)2 cAMP. These results strongly suggest that T3 or T4 was synergistic with TSH in stimulating the 5'-D activity in FRTL-5 cells, and that cAMP production would be an important component of the synergism.

Animals↗
PubMed1990

Graves' immunoglobulin G stimulates iodothyronine 5'-deiodinating activity in FRTL-5 rat thyroid cells.

To elucidate the effect of Graves' immunoglobulin G (IgG) on iodothyronine deiodination in the thyroid, we examined the characteristics of iodothyronine 5'-deiodinating (I-5'-D) activity in FRTL-5 rat thyroid cells and the effect of Graves' IgG on its activity. FRTL-5 cells were sonicated and incubated with 0.5 mumol/L rT3 with a tracer amount of [125I]rT3 in 0.1 mol/L phosphate buffer containing 1 mmol/L EDTA and 0.5 mmol/L dithiothreitol. The released 125I- was separated by Dowex-50WX2 column and counted. The amount of I- released was tissue, incubation time, temperature, and pH dependent, strongly suggesting that the reaction is enzymatic. The activity was completely inhibited by propylthiouracil. The Km value for rT3 was approximately 0.32 microM when analyzed by Lineweaver-Burk plot. TSH, dibutyl cAMP, and Graves' IgG induced I-5'-D activity in a dose-dependent manner. However, cycloheximide (5 mumol/L) abolished the stimulating effects of these agents on I-5'-D activity. These results suggest that TSH, dibutyl cAMP, and Graves' IgG induced I-5'-D activity through the synthesis of new enzyme protein. A significant positive correlation between thyroid-stimulating antibody activity assayed by measuring cAMP production using FRTL-5 cells and I-5'-D activity induced by the Graves' IgG in 10 patients with untreated Graves' disease was observed (r = 0.79; P less than 0.01). The present findings suggest that type I iodothyronine 5'-deiodinase exists in FRTL-5 rat thyroid cells and that Graves' IgG as well as TSH stimulate the activity at least in part by activating adenylate cyclase.

Animals↗
PubMed1990

Human chorionic gonadotropin promotes thyroid growth via thyrotropin receptors in FRTL-5 cells.

To ascertain the presence of thyroid growth-promoting activity (TGA) in the sera of pregnant women, we measured TGA in the sera of pregnant women by means of a bioassay based on [3H]-thymidine [( 3H]Tdr) incorporation in cultured rat FRTL-5 thyroid cells. Furthermore, to elucidate the mechanisms of human chorionic gonadotropin (hCG) in promoting the thyroid growth, we evaluated the effects of blocking type TSH receptor antibody (blocking IgGs) from patients with primary hypothyroidism on the activity of hCG. After the PEG-pretreated serum or the serum plus blocking IgGs was incubated for 72 h at 37 degrees C with FRTL-5 cells and [3H] Tdr, [3H] Tdr incorporated in the cells was counted. Although 9 normal pregnant women had normal TGA, two patients with hydatidiform mole, whose hCG levels were 966,500 and 497,100 IU/L, had positive TGA, but the activity showed normal when analyzed with the addition of a blocking IgG. hCG also showed a dose-dependent increase in [3H]Tdr incorporation, and it was inhibited by the addition of blocking IgGs. Furthermore, the inhibition of hCG-induced [3H]Tdr incorporation by 16 blocking IgGs correlated with their TBII and the inhibition activity of hCG-induced cAMP accumulation. Analysis by the Lineweaver-Burk plots of dose response curves of TSH- and hCG-induced [3H]Tdr incorporation showed the same inhibition pattern as with the addition of the same blocking IgGs. In conclusion, 1) hCG-related TGA exists in the sera of some patients with hydatidiform mole; and 2) hCG and the sera of some patients with hydatidiform mole promote thyroid growth, at least in a part, via TSH-receptors in FRTL-5 cells.

Adolescent↗
PubMed1989

Cord transferrin and ferritin values for erythropoiesis in newborn infants of diabetic mothers.

Neonatal polycythemia is a perinatal complication in infants of diabetic mothers. The cord CBC (complete blood counts), serum iron, transferrin and ferritin concentrations were studied in newborn infants of 9 GDM (gestational diabetes), 21 NIDDM (noninsulin-dependent diabetes mellitus), and 8 IDDM (insulin-dependent diabetes mellitus) mothers. The RBC (red blood cell) count, Hb (hemoglobin) and Hct (hematocrit) of these infants were higher than control infants. There was no difference between the serum iron concentration of the infants of each group diabetic mothers and the infants in the control group, but the transferrin concentration was significantly higher and the ferritin was significantly lower in the infants of diabetic mothers than in those of control mothers. There was a significant negative correlation between transferrin and ferritin (r = -0.491 p less than 0.001). Erythropoiesis is considered to be enhanced in the fetuses of diabetic mothers, and the iron needed for erythropoiesis is reportedly transported from the mother to the fetus according to the demands of the fetus, but the iron storage was shown to be reduced in the fetuses of diabetic mothers.

Adult↗
PubMed1989

Bilateral diffuse nephroblastomatosis, pancortical type. A case report with immunohistochemical investigations.

A variation of Perlman's syndrome of the pancortical type is reported in a male neonate whose parents were cousins. The patient was the product of a 35-week pregnancy, the Apgar score was 3, and the patient died of respiratory failure one hour and 12 minutes after delivery. Autopsy revealed bilateral diffuse nephroblastomatosis, pancortical type, associated with malformations (usually facial), congenital anomalies of the heart, hepatosplenomegaly, pancreatic islet cell hyperplasia, bilateral cryptorchidism, and hyperflexibility of the left knee joint. Renal immunohistochemical investigations revealed positive bindings with peanut and soybean agglutinins and epithelial membrane antigen along the luminal surface of the epithelium in the moderately differentiated tubules, but not in blastoma or primitive epithelium.

Abnormalities, Multiple↗
PubMed1987

Reassessment of insulin effects on the Vmax and Km values of hexose transport in isolated rat epididymal adipocytes.

Effects of insulin on the kinetic parameters of hexose transport in rat epididymal adipocytes were re-examined. The transport activity was assessed by measuring the rate of uptake of 3-O-[3H]methyl-D-glucose (MeGlc) under equilibrium exchange and zero-trans conditions. The incubation was carried out at 37 degrees C in an infant incubator. During the incubation, the cell suspension (25%, v/v, in a total volume of 48 microliter) was mechanically swirled at a rate of 600 rpm (r = 2 mm). The swirling facilitated the rapid uptake of MeGlc without stimulating the basal transport activity by "mechanical agitation". The basal and insulin-treated cells were incubated under identical conditions, except for the length of the incubation period. The incubation was terminated by the addition of 350 microliters of 1 mM phloretin, which inhibited transport in approximately 0.06 s. The time course of MeGlc uptake was consistent with the view that the process was a multiple-phase reaction. The initial phase of the reaction was completed when the intracellular distribution space of MeGlc was approximately 1% of the total cell volume. Insulin (10 nM) increased the Vmax value of MeGlc uptake 16-fold in equilibrium exchange experiments and 18-fold in zero-trans experiments. At the same time, the hormone decreased the Km value of MeGlc uptake from 11.7 to 5.4 mM in equilibrium exchange experiments and from 9.7 to 4.8 mM in zero-trans experiments. It is concluded that the major effect of insulin on MeGlc uptake is to increase the Vmax value, but the hormone has the additional effect of lowering the apparent Km value.

3-O-Methylglucose↗
PubMed1987

LiCl treatment releases a nickase implicated in genetic transformation of Streptococcus pneumoniae.

When cells competent for genetic transformation of Streptococcus pneumoniae which could bind and enable entry of extracellular DNA molecules were treated with LiCl, they released a nickase that introduced nicks into a double-stranded DNA in the presence of EDTA. The nickase was specific for competent cells and coupled with DNA-binding activity. Furthermore, when noncompetent cells were treated with LiCl, they released the putative receptors for the competence activator.

Chlorides↗
PubMed1986

Apparent translocation of glucose transport activity in rat epididymal adipocytes by insulin-like effects of high pH or hyperosmolarity.

The basal and plus insulin states of glucose transport activity in adipocytes are known to show different responses to changes in the pH or osmolarity of the incubation mixture. When the pH was raised from 7 to 8, the basal glucose transport activity (assessed from the rate of 3-O-methyl-D-glucose uptake) was increased approximately 3-fold while the plus insulin activity remained virtually unaffected. Likewise, when cells were exposed to 300 mM sorbitol, the basal glucose transport activity, but not the plus insulin activity, was considerably increased. In both cases, the change in the transport activity was ATP-dependent and was completed in approximately 60 min. The increase in the cellular glucose transport activity was accompanied, in both cases, by an increase in the glucose transport activity in the plasma membrane fraction and a decrease in the activity in the high-speed pellet fraction. The transport activity in the subcellular fractions was determined after reconstitution into egg lecithin liposomes. Both isotonic buffer at pH 8.0 and hypertonic buffer at pH 7.4 significantly stimulated membrane-bound cAMP phosphodiesterase in adipocytes. It is concluded that the above two experimental conditions may induce insulin-like effects in fat cells and may facilitate translocation of the glucose transport activity from an intracellular site to the plasma membrane.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1986

[Studies on somatomedin C in diabetic pregnancies].

Somatomedins have been shown to have potent mitogenic activities in cultured cells and also promote individual growth. We studied the concentrations of somatomedin C in diabetic pregnant women and rats. Serum and liver somatomedin C were measured by RIA double antibody method, after extraction with an ODS silica column. Serum somatomedin C concentrations were 20.45 +/- 5.14 nM/l (mean +/- S.D.) in nonpregnant normal women. In nonpregnant diabetic women, these were 16.96 +/- 4.37 nM/l, which were significantly lower than those of normal nonpregnant women. The concentrations of pregnant normal and diabetic women were similar to those of nonpregnant normal women. Maternal concentrations of somatomedin C significantly correlated with infant weight (r = 0.41, p less than 0.05, n = 41). Serum somatomedin C concentrations in the normal infants were 6.45 +/- 1.97 nM/l, which were considerably lower than those of their mothers. In the infants from diabetic mothers, these were 9.17 +/- 3.28 nM/l, which were significantly higher than those of normal infants. Rat serum somatomedin C concentrations which were 15.86 +/- 2.37 nM/l in nonpregnant normal rats, tended to increase during pregnancy. The mother's concentration significantly correlated with fetus weight (r = 0.491). Liver somatomedin C levels decreased in diabetic and pregnant states. Fetal rats had lower hepatic somatomedin C, which was about 10% of the mother's levels. These were higher in the fetuses from diabetic mothers. These finding suggested that the mother's somatomedins might contribute to fetal growth.

Animals↗
PubMed1985

Carcinoma of the pancreas with endocrine component in childhood. A case report.

A case of pancreatic tumor in a six-year-old girl is presented. The tumor had histologic characteristics of acinar cell carcinoma with endocrine component. Grossly, it was encapsulated and attached to the tail of the pancreas, measuring 8 cm in the greatest diameter. Histologically, the tumor was composed of medium-sized tumor cells, with mild pleomorphism showing mainly acinar structures. Many of these tumor cell contained fine granules that were periodic acid-Schiff positive, diastase resistant, and positive with dimethylaminobenzaldehyde nitrite strain for tryptophan, and some contained granules that were positive with Grimelius stain and positive with peroxidase-antiperoxidase technic for gastrin. Electron microscopy revealed two types of membrane-bound granules in the tumor cells. The larger granules measured 400-700 nm in diameter and appeared to be zymogen granules, while the smaller ones measured 100-200 nm in diameter and appeared to be neuroendocrine granules. Some cells contained both granules. The postoperative course of the patient was excellent, and she was alive and well 13 years after operation. This may be the second reported case of acinar-endocrine cell tumor of the pancreas.

Carcinoma↗
PubMed1985

Insulin binding, glucose oxidation, and methylglucose transport in isolated adipocytes from pregnant rats near term.

To elucidate the mechanism of insulin resistance during late pregnancy, we studied [125I]iodoinsulin binding, [1-14C]glucose oxidation, and 3-O-[methyl-14C]glucose transport in adipocytes isolated from pregnant rats on day 19 or 20 of gestation. Neither the affinity or number of insulin receptors on pregnant rat adipocytes differed from those on age-matched nonpregnant female rats. Insulin-stimulated glucose oxidation was reduced in the pregnant rat adipocytes. The maximum velocity of insulin-stimulated methylglucose transport was also significantly reduced in the pregnant rat adipocytes. These results suggest that insulin resistance in isolated adipocytes from pregnant rats near term is caused by some postreceptor changes, one of which is a reduction in the number and/or mobility of insulin-stimulated hexose transporters.

3-O-Methylglucose↗
PubMed1985

[Assessment of self monitoring of blood glucose (SMBG) and continuous subcutaneous insulin infusion (CSII) in diabetic pregnant women].

We instructed pregnant women with insulin dependent diabetes mellitus (IDDM) or noninsulin dependent diabetes mellitus (NIDDM) how to monitor their own blood glucose concentrations and evaluated the efficiency and feasibility of continuous subcutaneous insulin infusion (CSII) therapy. Self-monitored glucose concentrations with a reflectance meter correlated with those of hospital laboratory measurements (hexokinase method) with a coefficient of more than 0.9. Glycosylated hemoglobin (HbA1) levels of the patients were normalized with insulin treatment based on the self-monitored glucose concentrations. In pregnant women with NIDDM who monitored their blood glucose concentrations before breakfast, the fasting glucose concentrations could be lowered by insulin administration and the duration of hospitalization could be shortened compared to non-monitored patients. Although diurnal variations were prominent in pregnant women with IDDM and precise control of their blood glucose concentrations was difficult with conventional insulin administration, even if the patients had monitored their glucose concentrations 7 times a day, the mean glucose concentrations and M values could be kept in the optimum range in patients treated with CSII. These methods have contributed to the improvement in maternal and infant complications.

Blood Glucose↗
PubMed1984

A case of hereditary elliptocytosis associated with constitutional indocyanine green excretory defect.

A 24-year-old woman was diagnosed as having hereditary elliptocytosis and post-transfusion hepatitis. On admission, a marked delay in indocyanine green (ICG) plasma clearance was noted while bromsulphalein excretion was almost normal. Even when her levels of serum bilirubin and transaminases were decreased to the normal ranges and a liver biopsy revealed no evidence of any liver cirrhosis or active hepatitis, ICG excretion still remained abnormal. These findings were compatible to those of constitutional ICG excretory defect.

Adult↗