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Biomedical subjects

H Seo

Publications and source records attributed to H Seo.

305 records · Page 17Linked to original sources
PubMed1978

Early in vitro induction of rat pituitary GH mRNA by T31.

Previous work has shown that thyroid hormone stimulates rat pituitary GH synthesis and GH mRNA activity and concentration. However, the earliest demonstration of increase in GH mRNA activity was 24 hours following T3 addition whereas stimulation of GH synthesis has been observed 2 hours after treatment with T3. Thus, it is unknown whether increase in pituitary GH mRNA is a prerequisite for the stimulation of GH synthesis. In the present investigation in vitro addition of 1.5 x 10(-10) M T3 to pituitaries isolated from hypothyroid rats resulted in a slight but significant increase of GH mRNA activity within 2 hours. Further stimulation of GH mRNA activity was observed over the period of 12 hours. No increase of GH mRNA activity occurred in the absence of T3, and T3 had no effect on the PRL mRNA activity. These findings suggest that increase in GH mRNA may be responsible for the observed induction of GH synthesis, and that at least one of the primary actions of thyroid hormone is at the nuclear level.

Animals↗
PubMed1977

Triiodothyronine stimulates specifically growth hormone mRNA in rat pituitary tumor cells.

In a cell-free protein-synthesizing system from a rabbit reticulocyte lysate, total RNA extracted from cultured rat pituitary tumor (GH3) cells directed, in a dose-related manner, the synthesis of proteins that were precipitated by antisera specific to rat growth hormone (somatotropin) and rat prolactin. A marked decrease in growth hormone secretion and growth hormone mRNA activity was observed when cells were grown in a medium deficient in thyroid hormone. Addition of triiodothyronine in physiologic amounts both prevented and completely reversed this effect within 48 hr. Thyroid hormone had no effect on prolactin secretion or prolactin mRNA activity. These data suggest that thyroid hormone may stimulate synthesis of growth hormone through induction of transcriptional activity. The possibility of an additional effect at the posttranscriptional level has not been excluded. Although thyroid hormone is believed to have a general effect on a variety of metabolic processes, some effects, at the molecular level, may be quite selective, as indicated by the observed changes in growth hormone but not prolactin mRNA activity. The GH3 cell model is useful in the study of triiodothyronine action because of independence from secondary hormonal effects caused by hypothyroidism and because simultaneous measurement of prolactin mRNA activity serves as a unique internal control.

Cell Line↗
PubMed1977

Induction of hypothyroidism and hypoprolactinemia by growth hormone producing rat pituitary tumors.

The GH3 rat pituitary tumor cell line which secretes both growth hormone (GH) and prolactin (PRL) stopped releasing PRL when transplanted to animals; furthermore, it suppressed PRL production by the hosts' pituitary glands. When the same tumor was transferred back to cell culture, PRL production resumed. The PRL to GH ratio in cell culture medium and cells ranged from 5 to 1 while in the tumor and serum of the host animals it averaged 0.09 and 0.001, respectively. To investigate further this phenomenon, female rats were transplanted with GH3 tumors (T) and compared to intact normal (N) and to thyroidectomized (Tx) rats. T animals were larger and had splanchnomegaly but smaller pituitaries and thyroids. Serum PRL concentrations in the basal state were decreased, as were levels of triiodothyronine (T3), thyroxine (T4), and free T4 index. Despite reduced serum thyroid hormone concentrations, and in contrast to Tx animals, the serum thyrotropin (TSH) level in T rats was not elevated and they did not show a supranormal TSH response to thyrotropin-releasing hormone (TRH) administration. The PRL response to TRH in T animals was completely abolished while all N and Tx animals responded by a significant increase in serum PRL. Serum corticosteroids and estrogens were normal in T rats. Pituitary content of PRL was decreased and that of TSH increased in T rats. Tx animals, however, had a reduced pituitary content of PRL, TSH, and GH. When GH3 cells were grown in cell culture media containing serum from T animals, there was a reduction of PRL content in cells and released in the medium. Addition of T3 to the T serum did not alter its suppressive effect on PRL nor did rat GH added to N serum alter PRL production and release in vitro. In a preliminary experiment, rats injected ip with 50 mug hGH in two divided doses for eighteen days, suppressed serum T4 and T3 concentrations; pituitary content of TSH was significantly increased and that of PRL slightly decreased. Injection with 250 mug oPRL or saline, on the same schedule and for the same length of time, had no significant effect on the levels of serum thyroid hormones. Thus, GH, but also possibly other substance(s) secreted by GH3 tumors in vivo a) suppress the production of tumor and pituitary PRL; b) suppress the release of TSH, causing mild hypothyroidism; c) inhibit the PRL and TSH responses to TRH; and d) decrease the production of PRL in tissue culture. Although no simple and unifying theory could explain these findings, an hypothesis implicating somatomedin is presented.

Adrenal Cortex Hormones↗
PubMed1977

[Pharmacological studies on expectorants (author's transl)].

Perry and Boyd's method described in 1941 appears to be the most suitable for evaluating the efficacy of expectorants. In this method, changes in volume of respiratory tract fluid (RTF) collected by postural drainage from animals breathing air kept at a constant temperature and humidity are used as criteria. We attempted to improve on the method and to establish the optimum experimental conditions for rabbits. Accordingly, an air conditioning apparatus and tracheal cannula were re-designed and basic experimental conditions essential for quantitative collection of RTF were studied. Using this method, the effects of drugs on the volume of respiratory tract fluid (VRTF) were determined. Bromhexine and emetine as expectorants increased VRTF, and the former showed far more remarkable effects. Codeine and dextromethorphan as antitussives, isoproterenol, clorprenaline and C-78 as bronchodilators decreased VTRF. On the other hand, fominoben and eprazinone as antitussives increased VRTF. Our findings with application of this new approach indicate that this method is applicable for evaluating not only the efficacy of expectorants which increase VRTF but also that of other drugs which decrease VRTF.

Animals↗
PubMedDate not supplied

Macrophage activation with multi-porous beads prepared from partially deacetylated chitin.

The effect of multi-porous beads prepared from 80% deacetylated chitin on the activation of mouse peritoneal macrophages was examined. Deacetylated chitin bead (DAC-bead) preparations were shown to activate macrophages for tumoricidal activity depending on the increasing concentration of acetic acid used for the pretreatment of beads. The large DAC-bead was more susceptible to treatment with acetic acid than small DAC-bead, and showed more potent capacity for the activation of macrophages under the same pretreatment conditions with acetic acid. Deacetylated bead preparations, on the other hand, showed less activities. In addition, DAC-bead pretreated with acetic acid stimulated macrophages to produce interleukin 1. The possibilities of multi-porous beads as cancer chemotherapeutic-carrier were examined by the method of column chromatography and of in vitro antitumor experiment. Forty-four percent of adriamycin adsorbed on the surface of and in bead was released within the first 60 min. of elution, and then adriamycin was released more slowly in proportion to the elution time. Antitumor activity of adriamycin-adsorbed bead was less effective than that of free adriamycin if they were compared on the basis of total content of adriamycin.

Animals↗
PubMedDate not supplied

Thyrotropin-releasing hormone-like material in human retina.

Thyrotropin-releasing hormone (TRH)-like material was found in human retina obtained at autopsy from eyes used for corneal grafts. The TRH-like material was extracted with methanol and was found to be indistinguishable from synthetic TRH in its immunoreactivity and bioreactivity and in its proteolytic degradation by fresh human serum. The TRH concentration in human retina was similar to that reported in human cerebral cortex. These data are in keeping with the notion that the retina is an extension of the central nervous system. The physiological function of human retinal TRH in unknown: probably it acts as a neurotransmitter.

Adult↗
PubMedDate not supplied

Poly (adenosine diphosphate-ribose) synthesis in the anterior pituitary of the female rat throughout the estrous cycle: study of possible relation to cell proliferation and prolactin gene expression.

To investigate whether cell proliferation and PRL gene expression in female rat pituitary during estrous cycle were mediated by the poly (ADP)-ribosylation of chromatin proteins, anterior pituitaries at different estrous cycle were obtained from female Wistar rats, and poly (ADP-ribose) synthesis, DNA synthesis, PRL and GH messenger RNAs and PRL content in the pituitary, and serum concentrations of PRL and estradiol were analyzed. From diestrus to proestrus, poly (ADP-ribose) synthesis, the contents of PRL messenger RNA and PRL in the pituitary increased significantly, and decreased at estrus. However, DNA synthesis and serum concentration of PRL showed a significant increase from proestrus to estrus. Serum estradiol concentration increased from diestrus to proestrus. No significant change was observed in the pituitary GH messenger RNA content during estrous cycle. The increase of PRL messenger RNA from diestrus to proestrus was abolished completely by the administration of nicotinamide, an inhibitor of poly (ADP-ribose) synthesis, to rats at diestrus. These results indicate that poly (ADP)-ribosylation of chromatin proteins may play some role in cell proliferation and transcription of PRL gene during rat estrous cycle.

Animals↗
PubMedDate not supplied

Expression of human placenta alkaline phosphatase in placenta during pregnancy.

To clarify the expression of PLAP during the course of pregnancy, the amount of PLAP mRNA and its activity in normal placental villi were measured. Both PLAP and its mRNA were found in placentae of as early as 7 weeks of gestation, and they continued to increase throughout pregnancy. But they showed different patterns of increase. The amount of PLAP mRNA began to increase dramatically around 13th week and probably continued to increase gradually until term. PLAP activity per gram of villi showed a gradual increase from around 13th week and a marked increase was observed after about 20th week. PLAP levels in sera from pregnant women were also measured, and they showed a pattern of increase imilar to that of PLAP activity per gram of villi. The continuous increase in the expression of PLAP throughout pregnancy suggests that PLAP may play a role in feto-maternal metabolism and placental differentiation.

Alkaline Phosphatase↗
PubMedDate not supplied

An evaluation of a new radiographic technique utilizing a concave table.

In conventional radiography systems, it is apparent that only the area immediately around the central x-ray beam can be evaluated accurately. Consequently in some instances, spinal radiography for example, several exposures are needed at various points along the body to create an accurate image for diagnosis. However, if the film and body part are in a concave shape such that the radius of the curve is equal to the film focal distance, the x-ray beam will penetrate the body and strike the film at two-dimensionally right angles in all areas. Using the spine as an example we found the curved technique had three major advantages over the traditional flat technique: lack of distortion, more uniform beam intensity due to a constant focal film distance, and improved resolution at the periphery of the radiograph because of lack of a cross over effect. It was concluded that an accurate evaluation of larger body parts can be made with minimal distortion utilizing the principles of a curved table technique.

Animals↗
PubMedDate not supplied

Combination therapy with podophyllin and vidarabine for human papillomavirus positive cervical intraepithelial neoplasia.

Our aim was to establish an effective non-surgical treatment for cervical intraepithelial neoplasia (CIN) through inactivation of human papillomavirus (HPV), the major etiological agent for this disease. We show that vidarabine, a DNA polymerase inhibitor, suppressed growth and HPV gene expression in human cervical keratinocytes immortalized by HPV or in cervical cancer cell lines. Expression of HPV-16 E6 and E7 proteins in normal cervical keratinocytes sensitized cells to apoptosis in the presence of podophyllin or vidarabine. We applied vidarabine ointment and/or podophyllin to cervical epithelium in 28 cases of CIN I-II to evaluate the therapeutic effectiveness of these agents. Co-application of vidarabine and podophyllin in six treatments caused regression of lesions cytologically and histologically, and disappearance of HPV-16 or -18 DNA in 17 of 21 (81%) women. Our results suggest that the combination of vidarabine and podophyllin therapy is an effective non-surgical treatment for HPV-positive CIN.

Adult↗
PubMedDate not supplied

Quantitative evaluation of pulmonary ventilation dynamics using MR imaging: comparison of smokers and non-smokers.

PURPOSE: This quantitative study was conducted to evaluate lobar ventilation dynamics in non-smokers and smokers using MR imaging. METHODS: Ten non-smoker males and ten smoker males underwent MR imaging in the supine position without breath-holding. The volume rates and fluctuation rates were calculated for each lobe from MR images. TVRCs were constructed and analyzed. RESULTS: In non-smokers, the mean volume rates for each lung and lobe arranged in order of diminishing values were RL (54.8%), LL (45.2%), RLL (25.9%), LUL (24.2%), LLL (21.0%), RUL (18.5%), and RML (10.3%). In smokers, the mean volume rates for each lung and lobe arranged in order of diminishing values were RL (55.7%), LL (44.3%), RLL (25.1%), LUL (24.0%), RUL (21.0%), LLL (19.9%), and RML (9.5%). In both groups, there was a tendency for the fluctuation rates of the lower lobes to be higher than those of the upper and middle lobes. Although TVRCs for the right and left lung were nearly parallel, with no time lag, the peaks of TVRCs for the upper and middle lobes appeared slightly earlier than those for the lower lobes. CONCLUSION: The evaluation of pulmonary ventilation dynamics using MR may be a useful non-invasive technique by which to assess lung lobar ventilation.

Adult↗