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Biomedical subjects

H Kaji

Publications and source records attributed to H Kaji.

At least 199 records · Page 11Linked to original sources
PubMed1989

Alpha 2-adrenergic control of growth hormone (GH) secretion in conscious male rabbits: involvement of endogenous GH-releasing factor and somatostatin.

In an attempt to clarify the regulatory role in GH secretion of central alpha-adrenergic and dopaminergic mechanisms, the effects of iv administration of alpha 1- and alpha 2-adrenergic antagonists and dopaminergic antagonists were investigated in undisturbed conscious male rabbits. During a 6-h observation period (1030-1630 h), control animals demonstrated spontaneous pulsatile GH secretion with mean (+/- SEM) 6-h GH levels of 6.49 +/- 0.54 ng/ml (n = 16). Intravenous injection of yohimbine (YOM; an alpha 2-antagonist), chlorpromazine (CPZ), and haloperidol (HAL; dopamine and alpha-adrenergic antagonists) completely suppressed this pulsatile GH secretion (mean 6-h GH levels, 2.98 +/- 0.24, 3.48 +/- 0.24, and 2.91 +/- 0.29 ng/ml, respectively; P less than 0.001), whereas prazosin (an alpha 1-antagonist), pimozide (a selective dopamine antagonist), sulpiride, and YM-09151-2 (YM; D2-specific antagonists) failed to affect the GH secretory pattern (mean 6-h GH levels, 6.61 +/- 0.73, 6.71 +/- 0.56, 5.44 +/- 0.44, and 6.87 +/- 1.44 ng/ml, respectively). While an iv injection of 2 micrograms synthetic human GH-releasing factor-(1-44)-NH2 (hGRF) induced GH rises in prazosin-, HAL-, pimozide-, sulpiride-, and YM-treated rabbits as well as control rabbits, YOM and CPZ completely abolished these GH responses to hGRF injection. An iv injection of 10 ml antisomatostatin gamma-globulin caused a prompt and transient GH rise, followed by a sustained elevation of GH trough levels in normal control rabbits. YOM treatment completely abolished this highly oscillated GH release. However, suppression by YOM or CPZ of hGRF-induced GH rises was significantly reversed by iv administration of 10 ml antisomatostatin gamma-globulin. Therefore, the inhibitory effect of YOM and CPZ on both episodic GH release and hGRF-induced GH rises is due to the enhanced release of somatostatin, with a simultaneous suppression of endogenous GRF. On the other hand, HAL, possessing a weaker alpha-blocking action than CPZ, blunted pulsatile GH secretion, but only modestly suppressed hGRF-induced GH rises. These results suggest the following. 1) Central alpha 2-adrenergic mechanisms play a more important role in the regulation of GH secretion than alpha 1-adrenergic mechanisms in the rabbit as well as in other species. 2) The alpha 2-adrenergic blockade causes suppression of the release of hypothalamic GRF and enhanced release of endogenous somatostatin, thereby suppressing GH secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1988

Thyrotropin releasing hormone action in pituitary cells. Protein kinase C-mediated effects on the epidermal growth factor receptor.

Thyrotropin releasing hormone (TRH) causes phosphatidylinositol bisphosphate hydrolysis to form inositol trisphosphate and diacylglycerol. Since diacylglycerol activates protein kinase C (Ca2+/phospholipid-dependent enzyme), this enzyme may be involved in mediating the physiological response to TRH. Activation of protein kinase C leads to phosphorylation of receptors for epidermal growth factor (EGF) and decreased EGF affinity. The present study examined the effect of TRH on EGF binding to intact GH4C1 rat pituitary tumor cells to test whether TRH activates protein kinase C. Cells were incubated with TRH at 37 degrees C and specific 125I-EGF binding was then measured at 4 degrees C. 125I-EGF binding was decreased by a 10-min treatment with 0.1-100 nM TRH to 30-40% of control in a dose-dependent manner. 125I-EGF binding was not altered if cells were incubated at 4 degrees C, although TRH receptors were saturated or in a variant pituitary cell line without TRH receptors. TRH (10 min at 37 degrees C) decreased EGF receptor affinity but caused little change in receptor density, 125I-EGF internalization, or degradation. When cells were incubated continuously with TRH, there was a recovery of 125I-EGF binding after 24 h. Incubation with the protein kinase C activating phorbol ester TPA caused an immediate (less than 10 min) profound (greater than 85%) decrease in 125I-EGF binding followed by partial recovery at 24 h. Maximally effective doses of TRH and TPA decreased EGF receptor affinity with half-times of 3 min. EGF treatment (5 min) caused an increase in the tyrosine phosphate content of several proteins; prior incubation with TRH resulted in a small decline in the EGF response. GH4C1 cells were incubated with 500 nM TPA for 24 h in order to down-regulate protein kinase C. Protein kinase C depletion was confirmed by immunoblots and the effects of TRH and TPA on 125I-EGF binding were tested. TRH and TPA were both much less effective in cells pretreated with phorbol esters. TRH increased cytoplasmic pH measured with an intracellularly trapped pH sensitive dye after mild acidification with nigericin. This TRH response is presumed to be the result of protein kinase C-mediated activation of the amiloride-sensitive Na+/H+ exchanger and was blunted in protein kinase C-depleted cells. All of these results are consistent with the view that TRH acts rapidly in the intact cell to activate protein kinase C and that a consequence of this activation is EGF receptor phosphorylation and Na+/H+ exchanger activation.

Animals↗
PubMed1988

Oncogene transcription in normal human IMR-90 fibroblasts: induction by serum and tetradecanoyl phorbol acetate.

We report studies of oncogene transcription induced by the addition of serum to quiescent cultures of human IMR-90 fibroblasts. Oncogene messenger RNAs for c-myc, c-erbB and c-ras were increased in a specific temporal sequence after the addition of serum. Compounds that are proposed to exert their actions by the stimulation of cell growth were tested for their effect on oncogene transcription in IMR-90 fibroblasts. The tumor promoter tetradecanoyl phorbol acetate (TPA) was found to selectively induce the transcription of c-myc without observable effect on the transcription of the other oncogenes studied, and without inducing cell division. The inactive analog, phorbol didecanoate (PDD), and two complete carcinogens dimethylbenzanthracene (DMBA) and 4-nitro quinoline-1-oxide (4NQO) were without effect on the transcription of the genes studied. These results suggest that the complete ordered sequence of gene transcription is necessary to achieve the physiologic response of cell division, and that classical promoters and complete carcinogens achieve their effects through different pathways.

4-Nitroquinoline-1-oxide↗
PubMed1988

The effects of hydrocortisone on c-fos, c-myc and c-ras oncogene expression in IMR-90 fibroblasts.

The effects of hydrocortisone on oncogene expression in human IMR-90 fibroblasts was analyzed by Northern blotting of total RNA. In synchronized fibroblasts stimulated with serum alone, there were two time periods of increased c-fos expression during the G1 phase of the cell cycle. There was no significant difference between cells treated with serum plus hydrocortisone, and cells treated with serum alone with respect to c-fos expression. Quiescent cells showed no change in c-fos expression during the G1 phase of the cell cycle. Three peaks of c-fos expression occur when cells are treated with hydrocortisone alone, but hydrocortisone in the absence of serum is insufficient to initiate DNA synthesis. Hydrocortisone has no effect on c-myc or c-Ha-ras expression in the presence or absence of serum in synchronized fibroblasts. Therefore, the control of mRNA production of the nuclear oncogenes c-fos and c-myc, and the cytoplasmic oncogene c-ras are independent and hydrocortisone may enhance DNA synthesis by increasing c-fos expression.

Cells, Cultured↗
PubMed1988

Application of the sum peak method to determine the perturbed angular correlation parameters in biological specimens.

The counting rate of a sum peak formed by two gamma-ray emissions in radioactive decay of a nuclide depends on its integral attenuation factor G22. Therefore, in the "sum peak method", the G22 value for the specimen in question can be obtained merely from sum peak measurements using one radiation detector when the resolution time and the geometry are fixed. The procedure to determine the G22 values is described for specimens containing 111In, together with the detailed relationships between the sum peak counting rates and the values of G22.

Animals↗
PubMed1988

Chemical modifications of histidyl and tyrosyl residues of inorganic pyrophosphatase from Escherichia coli.

Chemical modifications by photooxidation in the presence of rose bengal (RB) and with tetranitromethane (TNM) were carried out to elucidate the amino acid residues involved in the active site of inorganic pyrophosphatase (pyrophosphate phosphohydrolase) [EC 3.6.1.1] from Escherichia coli Q13. The photooxidation caused almost complete inactivation, which followed pseudo-first-order kinetics depending on pH and concentration of RB. The presence of Mg2+ or complex between Mg2+ and substrate or substrate analogues, imidodiphosphate and sodium methylenediphosphate, gave partial protection against the photoinactivation, whereas the substrate alone showed no protective effect. The enzyme was almost completely inactivated by chemical modification with TNM, depending upon the concentration of TNM. The amino acid analyses and enzyme activity measurements revealed that 2 histidyl residues among 5 photooxidized residues and 2 tyrosyl residues per subunit were essential for the enzyme activity. The circular dichroism (CD) spectra in the far ultraviolet region showed no significant alteration during these two modifications, indicating that the polypeptide chain backbone of the enzyme remained unaltered. However, the modifications altered considerably the CD bands in the near ultraviolet region and the fluorescence spectra, indicating that subtle change in conformation had occurred in the vicinity of the active site in the enzyme molecule. These results strongly suggest that histidyl and tyrosyl residues may be involved in the active site or be located in the vicinity of the active site and seem to participate in the mechanism of stability against heat inactivation.

Binding Sites↗
PubMed1988

[A case of early gastric cancer accompanied by Recklinghausen's disease].

In September, 1980, a 57-year-old male, was admitted to hospital for precise examinations to determine if he had Recklinghausen's disease, pneumoconiosis, and a duodenal ulcer. Endoscopy revealed a redness and a shallow depression of the posterior wall of the antrum, and a biopsy of a specimen led to the diagnosis of early gastric cancer, Stage II c. After the examination, the patient did not return to our department again. In May, 1987, however, the man was readmitted to our hospital, suffering from pains in the right back. X-ray and endoscopic findings revealed a gastric cancer with a center depression and a peripheral elevation (II a + II c). Histological findings showed the gastric cancer to be a moderately differentiated tubular adenocarcinoma, with a submucosal invasion that was also seen. This case, uncovered 80 months earlier, represents a rare instance in which an early gastric cancer, accompanied by Recklinghausen's disease, expanded slowly.

Adenocarcinoma↗
PubMed1987

Random integration of SV40 in SV40-transformed, immortalized human fibroblasts.

We have studied the relationship between immortalization of SV40-transformed human embryonic fibroblasts and their SV40 integration sites. From several independently transformed cell pools, we have isolated clones which do not harbor unintegrated SV40 DNA. We have analysed whole-cell DNA from these clones, using the Southern blot method. Our results suggest that no specific integration sites in the cellular genome exist which are a prerequisite for the immortalization process. Although some integration sites were found to be predominant in pre-crisis clones, they could not be detected in the post-crisis clones. This suggests that none of these predominating sites is selected for during the crisis period.

Cell Line↗
PubMed1987

Sum peak method applied to the study of human platelet cells.

The sum peak method based on the phenomenon of perturbed angular correlation was applied to study the chemical environments of 111In in intact platelet cells. The sum peak appearing in the gamma-ray spectrum of 111In which emits two gamma-rays in cascade was observed for 111InCl3 solutions and 111In-labeled platelets. An increase in intensity ratios of the sum peak to its single peak was found when 111In incorporated into platelets from its aqueous solution. This fact was discussed in terms of physico-chemical environments of 111In together with an evaluation of sum peak analysis in the spectra.

Blood Platelets↗
PubMed1987

Epidermal growth factor decreases thyroid hormone receptors and attenuates thyroid hormone responses in GH4C1 cells.

The present study was undertaken to examine the effect of long term exposure to epidermal growth factor (EGF) on thyroid hormone responses as well as the concentration of specific nuclear thyroid hormone receptors in GH4C1 rat pituitary tumor cells. GH4C1 cells were first incubated for 48 h in medium with 5% fetal calf serum depleted of thyroid hormones by ion exchange resin. EGF had no effect on thyroid hormone receptors after 2 h, but decreased [125I]T3 binding to 56% of control values at 24 h and 68% at 48 h. L-T3 (0.5 nM) caused down-regulation of thyroid hormone receptors, and addition of EGF caused a further decrease. T3 alone (0.5 nM) caused a 2- to 3-fold induction of GH after 48 h, and GH induction was significantly inhibited by the addition of 10 nM EGF. Scatchard analysis of specific nuclear [125I]T3 binding showed that 48-h incubation with 10 nM EGF decreased T3 receptors from a Bmax of 2.35 to 1.26 pmol/mg DNA in thyroid hormone-depleted medium without affecting receptor affinity (Kd, 80 pM). The decrease in nuclear thyroid hormone receptors caused by EGF was dose dependent, with half-maximal inhibition at 0.10 nM EGF. EGF attenuated the GH response to T3 with similar dose-response characteristics. When cells were incubated for 48 h with different concentrations of T3, EGF (10 nM) decreased thyroid hormone receptors to 56-72% of control values regardless of the dose of T3, and EGF shifted the ED50 for T3 stimulation of GH from 0.1 to 1.2 nM. EGF also reduced from 5- to 1.8-fold the increase in cell number caused by thyroid hormone over 2 weeks. In contrast, EGF stimulation of PRL synthesis was changed only slightly by thyroid hormone at all times. In conclusion, we demonstrate that low concentrations of EGF decrease nuclear thyroid hormone receptors and thyroid hormone responses; this may be the mechanism by which EGF suppresses T3-induced GH production in GH4C1 cells.

Animals↗
PubMed1987

Regulation of thyroid hormone receptors and responses by thyrotropin-releasing hormone in GH4C1 cells.

The present study was undertaken to test the effects of TRH on thyroid hormone receptors and responses in GH4C1 rat pituitary tumor cells. TRH caused a loss of up to 32% of specific nuclear thyroid hormone binding sites with an ED50 of approximately 1 nM, and this loss was additive to the receptor down-regulation caused by T3 itself. Scatchard analysis of nuclear T3 binding revealed that 10 nM TRH decreased the concentration of T3 receptors from Bmax (femtomoles per mg protein) of 110 to 50 while receptor affinity in serum-free medium changed from dissociation constant (Kd) 110 to 50 pM with TRH. TRH lowered the GH response to 0.5 nM T3 from 215% to 127% of control. The concentrations of TRH required to decrease T3 receptors and T3 responses were similar and indicated that these TRH effects are mediated by the TRH receptor. In the absence of added thyroid hormone TRH had little effect on the rate of GH synthesis. TRH did not affect the binding of 0.5 nM [125I]T3 to receptors during the first 8 h but reduced T3 receptor occupancy up to 25-50% in different experiments after 24 h. TRH blocked the induction of GH by T3 only after 48 h or longer. When cells were incubated for 2 weeks with or without 2 nM T3 and 10 nM TRH, the stimulation of cell growth by T3 was decreased by TRH (2- vs. 5-fold increase in cell number) as was stimulation of GH by T3 (5- vs. 13-fold). As expected, T3 blunted the PRL response to TRH from 19- to 3-fold. The effects of TRH on the density of thyroid hormone receptors could be mimicked by the calcium channel agonist BAY K8644 plus a protein kinase C-activating phorbol ester which together caused a 53% reduction in thyroid hormone binding. The dose-response and temporal relationships suggest a causal relationship between the TRH-mediated decrease in thyroid hormone receptors and the decrease in thyroid hormone responses in GH4C1 cells. It has previously been shown that thyroid hormones decrease the concentration of TRH receptors and TRH responsivity in pituitary cells. The results shown here for GH4C1 cells suggest that TRH regulation of T3 responses may also be important in feedback control at the pituitary level.

Animals↗
PubMed1987

Urinary 3-methylthiopropionate excretion and the effect of D- or L-methionine ingestion studied in healthy subjects.

After overnight fasting, the urinary concentrations of 3-methylthiopropionate in 23 healthy male subjects aged from 17 to 72 were studied by gas chromatography and flame photometry. The urinary 3-methylthiopropionate concentrations after fasting showed an approximately normal distribution in the logarithmic scale (M +/- SD = 0.953 +/- 0.394): 10M = 8.97, 10M-SD = 3.62 and 10M + SD = 22.23 ng/mg Creatinine. In 6 volunteers, a 2g D- or L-methionine loading test was also performed. Following D-methionine ingestion, urinary 3-methylthiopropionate concentrations over a 1-hour period increased 22- to 95-fold above those of the pre- loading values and then decreased in an approximately linear manner on semilogarithmic graph paper during a further 2- or 3-hour observation period, after which the examination ended. The mean amount of 3-methylthiopropionate excreted in the urine 3 hrs after loading was 147.7 micrograms (n = 6). Following L-methionine ingestion, by contrast, the increases in 3-methylthiopropionate concentrations over a 1-hr period were 0.3- to 8.3-fold above those of the preloading values. The mean urinary excretion of 3-methylthiopropionate 3 hrs after loading was 3.58 micrograms (n = 4). Because of the simple and specific analytical procedure, quantitative determination of urinary 3-methylthiopropionate is useful in the study of human methionine metabolism.

Adolescent↗
PubMed1986

Regional distribution of gastrin-releasing peptide- and somatostatin-like immunoreactivity in the rabbit hypothalamus.

Regional distribution of gastrin-releasing peptide- (GRP) and somatostatin (SRIF)-like immunoreactivity in the discrete nuclei of the hypothalamus was examined in the rabbit according to Palkovits' microdissection method. GRP-like immunoreactivity (LI) was detected abundantly in the hypothalamus as compared with the cerebral cortex when measured by radioimmunoassay using the antiserum recognizing the C-terminal portion of synthetic porcine GRP. On gel-filtration chromatography of the hypothalamic extracts, two major peaks of GRP-LI were eluted; the peak with larger molecular size corresponded to synthetic porcine GRP1-27 and the smaller size to porcine GRP14-27. A concentration of GRP-LI was highest in the infundibular nuclei (IFN) as well as the ventromedial nuclei (VMN), and next high in the paraventricular nuclei (PVN), suprachiasmatic nuclei (SCN) and periventricular nuclei (PEV). The content of GRP-LI in the median eminence was not so much when compared with them. On the other hand, SRIF was localized in the highest concentration in the ME, followed by the VMN and IFN, as well as the PEV. The findings indicate that porcine GRP-LI exists in the hypothalamus of rabbits with characteristic regional distribution. Concurrent localization of GRP-LI and SRIF in some parts of the hypothalamus may suggest the interaction of both peptides in these areas under various physiological and pathological status.

Animals↗
PubMed1986

Increased erythrocyte catalase activity in patients with hyperthyroidism.

Levels of human erythrocyte catalase activity were determined in 38 patients with thyroidal dysfunction. In patients with hyperthyroidism, erythrocyte catalase activities were found to be higher than the levels of normal subjects (P less than 0.001). In hypothyroidism, erythrocyte catalase activities were of the same order as those of normal subjects. Significantly high positive correlation was found between erythrocytes catalase activity and the levels of thyroxine (r = 0.5794, n = 36, P less than 0.001), and slight positive correlation was detected between catalase activity and the levels of triiodothyronine (r = 0.3978, n = 33, P less than 0.05). A decreased erythrocyte catalase activity was observed when erythrocytes lysate was incubated with thyroid hormones. It was suggested that erythrocyte catalase activity had close relationship with thyroid state, however, direct effect of thyroid hormones were not observed on erythrocyte catalase assay system in vitro.

Adult↗
PubMed1986

Characterization of human IMR-90 fibroblasts as a model system for the study of chemical carcinogenesis in vitro.

The effects of chemical carcinogens on various aspects of cellular metabolism were measured in human IMR-90 fibroblasts. These studies were undertaken to assess the ability of IMR-90 cells to be used for the study of chemical carcinogenesis in vitro. It was found that chemical carcinogens inhibited DNA synthesis in synchronous cultures of IMR-90 fibroblasts; the effective concentrations of carcinogens showing effects in this system were lower than for other published in vitro cell assay systems; compounds that require metabolic activation to a carcinogenic form demonstrated the ability to inhibit DNA synthesis in IMR-90 fibroblasts; a fluorometric determination of aryl hydrocarbon hydroxylase (AHH) activity in IMR-90 cells revealed a low level of inducible AHH; IMR-90 cells can metabolize 7,12-dimethylbenzanthracene (DMBA) to compounds that are identified as metabolites of DMBA in vivo.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1986

Conformational changes of papain induced on interaction with thiol proteinase inhibitors from newborn rat epidermis.

The conformational changes of the papain molecular on interaction with two thiol proteinase inhibitors (TPI(1) and TPI(2] from newborn rat epidermis were studied by measuring circular dichroism (CD), the difference absorption spectrum, and the fluorescence spectrum due to tryptophan residues in papain. The far-ultraviolet CD band of papain between 210 and 230 nm was distinctly reduced on interaction with both inhibitors. Also, the near-ultraviolet CD spectrum of TPI(1)-bound papain changed between 285 and 320 nm as well as that of the TPI(2)-bound enzyme. The difference absorption spectrum for TPI(1)-bound papain exhibited two distinct peaks at 276.5 and 282 nm, indicating perturbation of aromatic amino acid residues. The fluorescence intensity of papain was significantly decreased on interaction with both inhibitors, which showed pH-dependency on an ionizable group, with pK values of 8.5 and 7.9 for TPI(1) and TPI(2), respectively. The complex formation of papain with both inhibitors caused a reduction of the susceptibility of a tryptophan residue, probably tryptophan-177, to chemical modification with N-bromosuccinimide. These results suggest that the active site involving histidine-159 in the papain molecule was much influenced by the alteration of the microenvironment of tryptophan-177 as a part of the interaction site for these two thiol proteinase inhibitors.

Animals↗