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T Yoshimi

Publications and source records attributed to T Yoshimi.

At least 55 records · Page 3Linked to original sources
PubMed1996

The change in 123I-uptake between 3- and 24-hours is useful in predicting early response to methimazole in patients with Graves' disease.

Some patients with Graves' disease respond well to anti-thyroid drug treatment but others do not. Factors determining the patient's responsiveness to the medical treatment are unclear, but the intrathyroidal iodine pool is believed one of the important factors. In this study, we found that delta radioactive iodine uptake (RAIU) (RAIU at 24 h-RAIU at 3 h) is useful in predicting early response to treatment with methimazole (MMI). Among 32 patients with Graves' disease, who were given 30 mg MMI as an initial dose, 11 patients responded quickly to MMI-treatment. Within one month, serum free T4 levels decreased to below the normal range in 6 patients (< 10.3 pmol/L) or decreased from beyond the highest level of the assay (> 125 pmol/L) to the normal range in 5 patients. When these rapid responders (group A) were compared with the remaining 21 patients who showed a more gradual response to MMI-treatment (group B), a different pattern of 123I-thyroid uptake was noted. RAIU at 3 h was significantly higher in group A than in group B, while RAIU at 24 h was similar in the two groups. As a result, rapid responders had a significantly lower delta RAIU value than gradual responders (-0.7 +/- 8.4% in group A, 14.2 +/- 8.2 in group B, P < 0.01). No significant difference was found between the two groups in various pre-treatment parameters such as severity and duration of thyrotoxicosis, the titer of TSH receptor antibodies (TRAb), frequency of positive antithyroglobulin antibodies (TGHA), urinary excretion of iodine and thyroid volume. The incidence of positive antithyroid microsomal antibodies (MCHA) was higher in group A than in group B, and thyroid ultrasonography showed a tendency to low echogenicity in group A. delta RAIU was negatively correlated with the reduction in the serum free T4 level during the first two weeks after MMI-treatment was initiated (r = -0.60, P < 0.01). Moreover, delta RAIU correlated positively with the biological half-life of the intrathyroidal iodine, calculated in a different series of 24 patients with Graves' disease who received radioisotope treatment (r = 0.54, P < 0.01). The low delta RAIU value is considered to reflect the rapid turnover of the intrathyroidal iodine, and may be related to the small intrathyroidal iodine pool. delta RAIU is useful in predicting early responsiveness of patients with Graves' disease to MMI-treatment.

Adult↗
PubMed1996

Introducing a point mutation identified in a patient with pituitary resistance to thyroid hormone (Arg 338 to Trp) into other mutant thyroid hormone receptors weakens their dominant negative activities.

Clinical resistance to thyroid hormone (RTH) has been classified into generalized resistance to thyroid hormone (GRTH) and pituitary resistance to thyroid hormone (PRTH) types. Since similar mutations have been identified in tri-iodothyronine (T3) receptor (TR) beta gene in GRTH and PRTH, and since considerable overlap has been seen in the clinical manifestations in patients with GRTH and PRTH, two subtypes of RTH are now considered to be a continuous spectrum with the same genetic defect. A point mutation at amino acid Arg 338 to Trp (R338W) which we identified in a patient with PRTH is very interesting, since R338W has been found in several other patients with PRTH, raising the possibility that this mutation may tend to associate with a phenotype of PRTH. In our previous study, we found that R338W had relatively less impaired transcriptional potency, weaker dominant negative activity on various T3 response elements and poor homodimer formation, as compared with another GRTH mutant. In this study, to investigate the functional properties of R338W further, especially in terms of the relation between transcriptional activity and dimer formations, we introduced the R338W mutation into the mutant receptors, K443E and F451X, constructing the double mutants, R338W/K443E and R338W/ F451X. Both R338W/K443E and R338W/F451X showed negligible T3 binding and transcriptional activities. The dominant negative activities of K443E and F451X were, however, significantly weakened by introducing the R338W mutation. As a control, a double mutant G345R/K443E was constructed by introducing a point mutation, G345R, located in the same exon 9 as R338W, into the K443E mutant. Dominant negative activity did not differ between G345R/K443E and K443E. Homodimer formation was significantly reduced in the double mutants containing R338W, but not G345R. In summary, introducing the R338W mutation, but not G345R, into the mutant TR significantly weakened the dominant negative activity, despite further impairment of the T3 binding and transcriptional activities.

Cells, Cultured↗
PubMed1996

A rare case of ectopic antidiuretic hormone-producing pancreatic adenocarcinoma: new diagnostic approach.

We describe a 73-year old man with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) due to an ectopic ADH-producing pancreatic adenocarcinoma. His laboratory findings showed marked hyponatremia, and the water load test showed uncontrolled ADH secretion. The imaging studies revealed pancreatic body cancer. Histological examination revealed an adenocarcinoma of the pancreas, which was positive for ADH immuno-staining. The ADH in the tumor extract was 53.3 pg/g wet weight. In attempt to diagnose ADH-production from the tumor, the ADH in his pancreatic juice was measured and found to be 2.1 pg/ml. We conclude that it is valid to measure the ADH in pancreatic juice to diagnose ectopic ADH production by tumors.

Adenocarcinoma↗
PubMed1995

Daily variation of serum lipids in relation to the circadian rhythm of platelet aggregation in healthy male persons.

The circadian rhythm of platelet aggregation was compared with that of serum lipids in seven healthy male persons. Daily variations of remnant lipoprotein-cholesterol and of remnant lipoprotein-triglycerides were related to those of arachidonic acid-, ADP (adenosine diphosphate)-, and collagen-induced aggregation in platelet-rich plasma and to ADP-induced aggregation in whole blood, respectively. Statistical analyses indicate that the time course of remnant-cholesterol was correlated to that of ADP-induced aggregation in platelet-rich plasma and the time courses of blood cholesterol and triglyceride were correlated to arachidonic acid- and serotonin-induced platelet aggregation in platelet-rich plasma, respectively. In whole blood, the time course of remnant lipoprotein-triglyceride was correlated only to ADP-induced platelet aggregation. In contrast, the daily variation of HDL (high density lipoprotein)-cholesterol did not influence either that of platelet aggregation in platelet-rich plasma or that in whole blood. Our findings are of clinical interest regarding the development of atherosclerosis and thrombotic events in persons with an elevated level of serum lipids.

Adolescent↗
PubMed1995

[The changes in natriuretic peptide receptors (NP-R) in the lung and kidney in DOCA-salt hypertensive rats].

To elucidate the pathophysiological significance and the regulation of natriuretic peptide receptors (NP-R) in hypertension, we investigated the changes of NP-R in the lung, renal cortex and medulla using radioreceptor assay. We also examined the concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in the atria and ventricles and plasma ANP concentration by specific radioimmunoassays. Elevated plasma ANP level, decreased atrial ANP concentration and increased ventricular ANP and BNP contents were observed in the DOCA-salt group when compared with the control group (p < 0.01). The ratio of BNP/ANP in the ventricle of the DOCA-salt rats was 50% of the control rats. The elevated plasma ANP secreted from the heart seems to reflect a defensive compensatory mechanism to counteract hypertension, and that ANP is the major natriuretic peptide secreted from the cardiac ventricle in DOCA-salt hypertensive rats. Scatchard plot analysis revealed that the maximal binding capacities (Bmax) of NP-R of the lung and renal cortex in DOCA-salt rats were significantly decreased from 71.0 +/- 10.4 to 38.4 +/- 5.9 (p < 0.05) and from 32.7 +/- 1.8 to 21.7 +/- 0.4 (fmol/mg. protein) (p < 0.01) compared with those in the control rats. The values of Bmax of the renal medulla between the two groups were not different. There was no significant change in the apparent dissociation constant (Kd) in the lung, renal cortex and medulla between the two groups. A competitive binding study using 125I- alpha-rANP1-28 and C-ANF4-23, a biologically silent clearance receptor (C-receptor) specific ligand, revealed that C-receptors are abundantly present in the renal cortex, while a relatively small quantity of C-receptor was detected in the renal medulla. In the lung, a substantial amount of C-receptor was detected. In the DOCA-salt treated rats, C-receptors were decreased in the lung and renal cortex compared with the control rats. These results indicate that the down-regulation of NP-R, especially C-receptor, was induced in the lung and renal cortex when plasma ANP levels were elevated in DOCA-salt hypertensive rats. In conclusion, our results suggest that down-regulation of C-receptor in the lung and kidney contributes to maintaining higher plasma ANP levels and maybe responsible for the counter-regulatory role of endogenous ANP in DOCA-salt rats. Our results show that the down-regulation of NP-R in the lung was larger than that in the kidney, suggesting that the lung may play a dominant role in the regulation of the clearance of ANP through C-receptors in vivo.

Animals↗
PubMed1995

Immunoelectron microscopic analysis of chondroitin sulfates during calcification in the rat growth plate cartilage.

The proximal growth plate cartilage of rat tibia was fixed in the presence of ruthenium hexamine trichloride (RHT) in order to preserve proteoglycans in the tissue. Quantitative changes of chondroitin sulfates during endochondral calcification were investigated by immunoelectron microscopy using mouse monoclonal antibodies 1-B-5, 2-B-6, and 3-B-3, which recognize unsulfated, 4-sulfated, and 6-sulfated chondroitin sulfates, respectively. The content of chondroitin-4-sulfate in the cartilage matrix increased from the proliferative zone to the calcifying zone, while that of unsulfated chondroitin sulfate decreased. Chondroitin-6-sulfate remained constant from the proliferative zone to the upper hypertrophic zone, then decreased in the calcifying zone. The immunoreaction to each antibody increased conspicuously in the cartilagenous core of metaphysial bone trabeculae. The changes of sulfation in chondroitin sulfate chains of proteoglycans may play an important role in inducing and/or promoting calcification in growth plate cartilage.

Animals↗
PubMed1995

Expression of several muscle-specific genes during differentiation of cultured quail pineal body cells under artificial (high NaCl) conditions.

A change in cell differentiation of pineal body cells to cells with myogenic features can be induced when such cells are cultured with stepwise increases in the NaCl concentration up to a 125 mM NaCl excess. Further differentiation can be achieved by changing the culture medium to Cosmedium (serum-free) with the same high NaCl concentration. This system is a good candidate as an in vitro model for the commitment of pre-myoblastic cells to myogenic cells, and for studies on early phases of myogenic differentiation, since the myogenic fate is not selected under conventional isotonic culture conditions. Our first step was to analyze the expression schedule of an intermediate filament protein, desmin, as an early stage marker of muscle differentiation. Desmin expression was detected at a low level in mononucleated cells during early differentiation stages (two days in medium with a 50 mM excess of NaCl), and a higher order of expression was observed in later stages in 20-40% of cells corresponding to myotubes. Expression of qmf1 and qmf2 mRNA, quail counterparts of MyoD and myogenin, respectively, was detected in two different stages: in the pineal body of 9-day-old embryos and in myogenically differentiated pineal cells, by Northern blotting and RT-PCR analysis. When pineal cells were transferred to the culture system, qmf1 and qmf2 expression was not present in isotonic medium and no myogenic differentiation occurred under these conditions. However, they reappeared and increased during the final stages of myogenic differentiation in the high NaCl medium. Furthermore, by use of muscle-specific domain (MSD)-specific antibodies we found the expression of a muscle-specific neural cell adhesion molecule (NCAM) species at the late stages of differentiation. These results show that the gene expression and mRNA splicing patterns of the cells changed from pineal body-specific to muscle-specific. On the basis of these results, we conclude that this system is appropriate for studying the differentiation of non-muscle cells to muscle cells.

Animals↗
PubMed1995

The role of sodium in mediating adrenocorticotropin secretion by perifused rat anterior pituitary cells.

We studied the role of sodium ions in mediating basal and stimulated ACTH release from perifused rat anterior pituitary cells by exposing the cells to the sodium channel opener veratridine or the Na+/K(+)-adenosine triphosphatase inhibitor ouabain to increase the intracellular Na+ concentration or, conversely, by omitting Na+ from the perifusion medium or blocking Na+ entry into the cell with tetrodotoxin, a voltage-dependent sodium channel blocker, to decrease the intracellular Na+ concentration. Neither tetrodotoxin nor Na(+)-free medium had a significant effect on 100 nM arginine vasopressin (AVP) or 10 nM ovine corticotropin-releasing hormone (CRH)-induced ACTH secretion. Veratridine increased basal ACTH secretion by 122% (41.3 +/- 2.9 vs. 18.6 +/- 0.4 pg/min; P < 0.001), the initial spike phase of the response to AVP by 65% (0.28 +/- 0.01 vs. 0.17 +/- 0.03 ng/3 min; P < 0.005), the subsequent sustained phase to AVP by 129% (0.16 +/- 0.01 vs. 0.07 +/- 0.01 ng/7 min; P < 0.005), and the total response to CRH by 70% (0.39 +/- 0.01 vs. 0.23 +/- 0.04 ng/10 min; P < 0.05). Ouabain increased basal ACTH secretion by 39% (45.7 +/- 2.8 vs. 32.9 +/- 2.1 pg/min; P < 0.05), the initial spike phase of the response to AVP by 88% (0.32 +/- 0.02 vs. 0.17 +/- 0.01 ng/3 min; P < 0.005), the sustained phase response to AVP by 67% (0.10 +/- 0.01 vs. 0.06 +/- 0.01 ng/7 min; P < 0.05), and the total integrated response to CRH by 49% (0.88 +/- 0.09 vs. 0.59 +/- 0.03 ng/10 min; P < 0.05). However, the effects of both veratridine and ouabain on basal ACTH secretion were significantly attenuated in Ca(2+)-free EGTA-containing medium, suggesting that this effect was indirect, due to membrane depolarization and consequent influx of extracellular Ca2+. Dexamethasone (100 nM) had no effect on the ACTH response to either veratridine or ouabain. We conclude that changes in the intracellular Na+ concentration and sodium channel activity are not directly involved in AVP- or CRH-induced ACTH secretion.

Adrenocorticotropic Hormone↗
PubMed1995

Molecular cloning and expression of multiple isoforms of human prostaglandin E receptor EP3 subtype generated by alternative messenger RNA splicing: multiple second messenger systems and tissue-specific distributions.

Five distinct cDNA clones encoding four different isoforms of human prostaglandin (PG) E receptor EP3 subtype were isolated from a human kidney cDNA library. Two cDNA clones differed only in their 3'-untranslated regions. The four isoforms, tentatively named EP3-I, EP3-II, EP3-III, and EP3-IV, which were generated by alternative mRNA splicing, had identical amino acid sequences except for their different carboxyl-terminal tails. Transfection experiments revealed that all the four isoforms show high binding affinities to PGE2, PGE1, and M&B28767, an EP3-specific agonist, whereas their downstream signaling pathways are divergent. M&B28767 increased cAMP concentrations in cells expressing EP3-II and EP3-IV, whereas it inhibited forskolin-induced cAMP accumulations in cells expressing all EP3 isoforms. M&B28767 also stimulated phosphoinositide turnover in cells expressing EP3-I and EP3-II. Northern blot analysis revealed that the EP3 gene is expressed in a wide variety of human tissues. The human EP3 mRNA was present most abundantly in the kidney, pancreas, and uterus. A substantial expression was also detected in the heart, liver, skeletal muscle, small intestine, colon, prostate, ovary, and testis. Furthermore, reverse transcription-polymerase chain reaction analysis demonstrated tissue-specific expressions of the five different EP3 mRNA species. The present study suggests the presence of the multiple systems of PGE2/EP3 isoforms and leads to the better understanding of its physiological and pathophysiological implications in humans.

Alternative Splicing↗
PubMed1995

[Progesterone].

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Female↗
PubMed1994

Daily variations of platelet aggregation in relation to blood and plasma serotonin in diabetes.

The circadian rhythms of platelet aggregation in the whole blood and platelet rich plasma-PRP and plasma serotonin were studied in healthy volunteers (n = 10) and diabetic patients (type II diabetes mellitus n = 12). Platelet aggregation in the whole blood induced by collagen (2 micrograms/ml), ADP (10 microM), arachidonic acid (0.5 mM) and epinephrine (10 microM), and in PRP induced by collagen (2 micrograms/ml), ADP (5 microM), arachidonic acid (250 microM), epinephrine (10 microM) and serotonin-5-HT (1 microM) was measured at 7:30, 11:30, 17:00, 23:00, 4:00 and 7:00. In healthy subjects collagen- and ADP-induced platelet aggregation in the whole blood was significantly lower at 23:00 and 4:00 when compared to values at 7:30. In PRP normal and diabetic platelet response was the lowest during the night. Diabetic platelets exhibited an enhanced response to 5-HT starting from 17:00 until 4:00 when compared to 7:30. 5-HT-induced platelet aggregation was found to be significantly higher throughout the study in DM patients over controls in parallel to plasma 5-HT. In healthy volunteers plasma 5-HT was higher at 17:00 when compared to baseline values, whereas in DM patients plasma 5-HT was elevated starting from 17:00 until 4:00. An enhanced response of diabetic platelets to 5-HT together with elevated plasma 5-HT levels may contribute, at least partly, to the pathogenesis of diabetic vasculopathy and 5HT2 receptor blockers may be of value in DM patients.

Adenosine Diphosphate↗
PubMed1994

[The mechanism of thyroid hormone abnormalities in patients with diabetes mellitus].

In order to clarify the mechanism of impaired thyroid hormone levels in patients with diabetes mellitus, thyroid hormone, thyroid hormone binding inhibitor (THBI), inhibitor of extrathyroidal conversion of T4 to T3 (IEC) and free fatty acid (FFA) were examined. In addition, TRH test was performed on 9 diabetic patients showing poor control of plasma glucose before and after glycemic control. Before glycemic control, fasting plasma glucose and HbA1c were significantly higher than after glycemic control (P < 0.05). T3 and the T3/T4 ratio significantly increased and rT3 significantly decreased after glycemic control (P < 0.05). THBI index and plasma FFA level significantly decreased and %T3 production (IEC) significantly increased after glycemic control (P < 0.05). The response of TSH to TRH significantly increased after glycemic control. In conclusion, (1) the presence of THBI, (2) the presence of IEC, and (3) dysfunction of the hypothalamo-hypophysial-thyroid axis are considered to be involved in abnormal thyroid function in diabetic patients.

Blood Glucose↗
PubMed1994

Mutations in the glucokinase gene are not a major cause of late-onset type 2 (non-insulin-dependent) diabetes mellitus in Japanese subjects.

The role of the glucokinase gene in the development of diabetes in a group of 349 Japanese subjects with late-onset Type 2 diabetes was examined. These diabetic subjects and 197 non-diabetic controls were typed at two simple tandem repeat DNA polymorphisms in the glucokinase gene termed GCK2 and GCK3. Six and five alleles were evident in Japanese subjects at GCK2 and GCK3, respectively. There were no significant differences in allele, genotype or haplotype frequencies between diabetic and normal groups. In addition, the glucokinase gene of 340 diabetic and 170 non-diabetic Japanese subjects was screened for mutations using single strand conformation polymorphism analysis. Four nucleotide substitutions were identified: a silent substitution in exon 4 in the codon for proline 145 (CCC-->CCG), and A-->T, C-->G, and C-->A substitutions in introns 1b, 3, and 5, respectively. There were no significant differences in the frequencies of these nucleotide substitutions between diabetic and non-diabetic groups. These results suggest that glucokinase gene defects are not a major cause of late-onset Type 2 diabetes in Japanese subjects.

Amino Acid Sequence↗
PubMed1994

Rare case with metastatic involvement of hypothalamo-pituitary and pineal body presenting as hypopituitarism and diabetes insipidus.

An unusual case with metastatic spread of a small oat cell lung carcinoma to the hypothalamo-pituitary region and pineal body presenting as pituitary insufficiency is reported. Computed tomographic scan revealed an isodense mass in the hypothalamo-pituitary region and pineal body that was strongly enhanced by contrast medium. Magnetic resonance imaging demonstrated a downward displacement of the posterior lobe of the pituitary by the hypothalamo-pituitary mass. Dynamic assessment of hypothalamo-pituitary function showed hypopituitarism and diabetes insipidus; partial recovery was observed with the improvement in the carcinoma by chemotherapy. The brain was subsequently irradiated. The patient survived 10 months.

Aged↗
PubMed1994

Regulation of glucokinase gene expression in cultured rat islet cells: the inhibitory effects of T3 and glucagon, and the stimulatory effect of glibenclamide.

Hormonal and non-hormonal regulation of glucokinase gene expression was investigsted in cultured rat islet cells. To measure glucokinase mRNA in pancreatic islet cells, the competitive PCR method was adopted. With this method, GKmRNA levels can be measured using only 0.1-1.0 microgram of total RNA isolated from cultured rat islet cells. Following 24 h preculture with 5.5 mM glucose, islet cells were cultured for 24 or 8 h with hormonal or non-hormonal factors. Glucokinase mRNA levels tended to increase, but not significantly, at 16.7 mM glucose compared to those at 5.5 mM glucose. Treatment with either 1 microM T3 or 1 microM glucagon resulted in a decrease in the glucokinase mRNA level with 16.7 mM glucose, whereas 1 microM insulin had no effect on glucokinase mRNA. Five mM dibutyryl cyclic AMP decreased the glucokinase mRNA level with 16.7 mM glucose, but cycloheximide did not block this inhibitory effect, suggesting that the effect of glucagon may be mediated by cyclic AMP and that protein synthesis is not involved in the response. Furthermore, the islet glucokinase mRNA level increased in response to 1 microM glibenclamide with 5.5 mM glucose and the response was abolished by cycloheximide, which indicates the involvement of protein synthesis in the glibenclamide-induced mRNA change. An 8-bromo-cyclic GMP (1 microM) and vanadate (1 microM) did not affect the islet GKmRNA level. These findings suggested that thyroid hormone and glucagon-cyclic AMP suppress, and glibenclamide increases the GKmRNA level in cultured rat islet cells, and that insulin, cyclic GMP and vanadate differentially affect glucokinase gene expression in pancreatic islet cells and in the liver.

Animals↗