Biomedical subjects

J S Yun

Publications and source records attributed to J S Yun.

At least 19 recordsLinked to original sources

PubMed2005

Expression and relationship of the insulin-like growth factor system with posthatch growth in the Korean Native Ogol chicken.

Insulin-like growth factors (IGF) act as regulators that modulate proliferation and differentiation of various cells. Also, IGF are involved in metabolism and body growth by regulating the synthesis and degradation of glycogen and proteins in animals. However, the effect of IGF system on body growth in poultry including Korean Native Ogol chickens (KNOC) has not been thoroughly studied. Therefore, this study was performed to investigate the expressions of IGF system and the relationship of IGF with body growth during posthatch growth in KNOC. Sera and organs were collected at hatch and at 1, 3, 5, and 7 wk. The mRNA expressions of IGF, IGF-I receptor, and IGF binding protein (IGFBP)-2 were quantitatively analyzed by reverse transcription (RT)-PCR. The IGF concentrations were measured by heterologous RIA, and the expression of IGFBP-2 was detected by Western ligand blotting. The body weight of KNOC rapidly increased during the experimental period, and increase in breast muscle weight was 5-fold from 1 to 3 wk. Although the circulating IGF-I concentration gradually increased, the level of IGF-I in breast muscle rapidly declined during growth period. The IGF-II expression was not similar to IGFBP-2 during postnatal growth. Moreover, the breast muscle IGF-II concentration was mainly correlated with body growth at 7 wk and breast muscle IGF-I at 1 and 5 wk. Taken together, the present study suggested that the endocrine manner of IGF-I was more important than auto/paracrine actions in body growth of KNOC and that expression of IGF-II was involved in body growth and IGF-I during posthatch growth of KNOC.

Animals↗

PubMed2001

Simultaneous determination of delta-aminolevulinic acid, porphobilinogen, levulinic acid and glycine in culture broth by capillary electrophoresis.

Capillary electrophoretic simultaneous determination of a mixture containing delta-aminolevulinic acid, porphobilinogen, levulinic acid and glycine was investigated. With increases in the sodium tetraborate buffer concentration (5-70 mM), resolution of the four components was improved, but the migration time was increased. Alternatively, with increases in the applied voltage (5-22.5 kV), a shortened migration time was seen but this adversely affected resolution. The components were separated with high resolution by using a fused-silica capillary column (75 cm x 75 microm I.D.) filled with 30 mM sodium tetraborate buffer (pH 9.3-9.4) under the applied voltage of 20 kV (constant voltage mode). When the established method was applied to the culture broth of Rhodopseudomonas sphaeroides, a photosynthetic bacterium, the four components mentioned above were separated with good resolution. Furthermore, the use of this method would provide a fast, sensitive and specific method for monitoring the administration of delta-aminolevulinic acid in photodynamic cancer therapy, for the measurement of delta-aminolevulinic acid dehydratase activity in erythrocytes, and for testing the delta-aminolevulinic acid assay and for impurities in drug formulation.

Aminolevulinic Acid↗

PubMed2001

The use of transgenic mice to analyze the role of accessory factor two in the regulation of phosphoenolpyruvate carboxykinase (GTP) gene transcription during diabetes.

The regulation of transcription of the gene for the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) (PEPCK-C) (4.1.1.32) during diabetes is a complex process that involves a number of regulatory elements in the PEPCK-C gene promoter. The accessory factor 2 (AF2)-binding region that is contained within the glucocorticoid regulatory unit of the PEPCK-C gene promoter (-451 to -353) has been implicated in the action of both insulin and glucocorticoids on PEPCK-C gene transcription. To determine the role of AF2 in these processes, we have generated a mouse model bearing a transgene that contains the PEPCK-C gene promoter with a mutation in the AF2-binding region. This promoter is linked to the structural gene for human growth hormone that is biologically inactive (AF2-2000/hGx). In the absence of the AF2 regulatory element, the transcription of the transgene in the liver is not induced by diabetes but is inhibited by the administration of insulin. There is also a marked reduction in the response of the AF2-2000/hGx gene in the kidney to the administration of glucocorticoids. The AF2-2000/hGx gene in the liver responds normally to a high carbohydrate diet with a marked decrease in gene transcription. This suggests that insulin is not exerting its usual negative effect on the PEPCK-C gene promoter through the AF2 site. In contrast, the response of this transgene to a high fat/carbohydrate-free diet is severely blunted. Our results support a role for the AF2 site in the PEPCK-C gene promoter in the effect of glucocorticoids, but not insulin, on PEPCK-C gene transcription in the liver.

Animals↗

PubMed2001

Clinical predictors of mental disorders among medical outpatients.

BACKGROUND: Mental disorders are common among primary care patients and often not detected by primary care physicians. We report on clinical cues that may allow physicians to target patients for psychiatric screening. METHODS: Two hundred fifty consecutive adults presenting to a walk-in clinic completed previsit surveys assessing demographics, symptom characteristics, recent stress, functional status (Medical Outcomes Study Short Form-6), and mental disorders (Primary Care Evaluation of Mental Disorders [PRIME-MD]). Patients with positive findings for a mental disorder on the PRIME-MD underwent a semistructured interview. Immediately after the visit, physicians completed the Difficult Doctor Patient Relationship Questionnaire. RESULTS: Patients averaged 50.5 years of age (range, 18-92 years). Little more than half were women (53%); 43%, white; 44%, African American; 8%, Hispanic; and 6%, other. Twenty-six percent had an underlying mental disorder; 11% had more than 1 mental disorder. Sixteen percent had a depressive disorder; 6%, major depression; 11%, an anxiety disorder; 2%, panic disorder; and 9%, a somatoform disorder. Independent correlates of a mental disorder included reporting recent stress (odds ratio [OR], 6.7; 95% confidence interval [CI], 3.3-13.6), having 5 or more physical symptoms (OR, 4.0; 95% CI, 2.1-7.9), or reporting health to be less than very good (OR, 2.2; 95% CI, 1.1-4.3). There was a stepwise increase in the likelihood of having a mental disorder and number of correlates present. Among patients with no predictors, only 2% had an underlying mental disorder, compared with 72% among patients with all 3 clinical predictors. CONCLUSIONS: Patients who report recent stress, 5 or more physical symptoms, or poor health are more likely to have an underlying mental disorder. These clinical cues may allow clinicians to select patients in whom formal screening for mental disorders would be particularly fruitful.

Adolescent↗

PubMed2001

Inhibition of baclofen on morphine-induced hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity.

The effects of baclofen on the development of reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine were examined in mice. A single administration of morphine induced hyperactivity and the morphine-induced hyperactivity was inhibited dose dependently by the administration of a GABA(B)receptor agonist, baclofen (1.25, 2.5 and 5 mg kg(-1), i.p.). Daily repeated administration of morphine developed reverse tolerance to the hyperactivity of morphine. The concomitant administration of baclofen inhibited the morphine-induced hyperactivity and the baclofen administration prior to and during the chronic administration of morphine in mice inhibited the development of reverse tolerance to the hyperactivity of morphine (10 mg kg(-1), s.c.). Postsynaptic dopamine receptor supersensitivity was also developed in reverse-tolerant mice that had received the same morphine. The development of postsynaptic dopamine receptor supersensitivity was evidenced by the enhanced ambulatory activity of apomorphine (2 mg kg(-1), s.c.). Baclofen also inhibited the development of postsynaptic dopamine receptor supersensitivity induced by the chronic administration of morphine. These results suggest that the hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine may be modulated via the activation of GABA(B)receptors induced by baclofen.

Animals↗

PubMed2001

Inhibitory effects of MK-801 on contextual sensitization to climbing behavior and on development of tolerance to hypothermia induced by a single high dose of apomorphine.

A single high dose of apomorphine (10 mg x kg(-1)) produced not only contextual sensitization to and conditioning of climbing behavior, but also context-independent tolerance to hypothermia. MK-801 (0.15 and 0.3 mg x kg(-1)) inhibited contextual sensitization to and conditioning of climbing behavior. Development of tolerance to hypothermia was also inhibited by MK-801. Dopamine D1 antagonist, SCH23390 (0.5 mg x kg(-1)), but not D2 antagonist, sulpiride, inhibited sensitization to and conditioning of climbing behavior. D2 antagonist, sulpiride (50 mg x kg(-1)), but not D1 antagonist, SCH23390, inhibited development of tolerance to hypothermia. These results suggest that MK-801 inhibited contextual sensitization to climbing behavior and development of tolerance to hypothermia through glutamatergic modulation of dopaminergic functions at dopamine receptors.

Animals↗

PubMed2001

Mechanisms and kinetics of high-temperature cadmium sorption by packed bed of calcined kaolin.

Sorption experiments by passing CdCl2-carrying flue gas through the packed bed of calcined macro-porous kaolin particles were performed over a temperature range of 973-1173K and a CdCl2 partial pressure range of 8-16.1 Pa. The observed structural change of the sorbent mineral at the stage of sorption and the results of desorption tests revealed the characteristics of an irreversible chemical reaction as a major cadmium capturing mechanism. In the fully saturated kaolin sorbent, CdO x Al2O x 2SiO2 is present as a sorption reaction product together with a smaller amount of 2CdO x Al2O x 2SiO2. The increase in sorbent bed temperature resulted in an increase in the rate of sorption, but it had no effect on maximum cadmium uptake. The gas-phase CdCl2 diffusion into the macro pores of calcined kaolin had a negligible effect on the overall sorption rate. The reaction between gaseous CdCl2 and solid Al2O3 x 2SiO2 is very sensitive to the concentration of CdCl2 but relatively insensitive to the temperature of the sorbent bed. The order of reaction with respect to the CdCl2 vapor concentration was determined to be 3.26. The activation energy, Ea, was estimated as 5.56 kcal/mol according to the Arrhenius relationship.

Adsorption↗

PubMed2000

Determinants of the cardiomyopathic phenotype in chimeric mice overexpressing cardiac Gsalpha.

Mice with overexpressed cardiac Gsalpha develop cardiomyopathy, characterized by myocyte hypertrophy and extensive myocardial fibrosis. The cardiomyopathy likely involves chronically enhanced beta-adrenergic signaling, because it can be blocked with long-term propranolol treatment. It remains unknown whether the genotype of the myocyte is solely responsible for the progressive pathological changes. A chimeric population in the heart should answer this question. Accordingly, we developed a chimeric animal, which combined cells from a transgenic overexpressed Gsalpha parent and a Rosa mouse containing the LacZ reporter gene, facilitating identification of the non-Gsalpha cells, which express a blue color with exposure to beta-galactosidase. We studied these animals at 14 to 17 months of age (when cardiomyopathy should have been present), with the proportion of Gsalpha cells in the myocardium ranging from 5% to 88%. beta-Galactosidase staining of the hearts demonstrated Gsalpha and Rosa cells, exhibiting a mosaic pattern. The fibrosis and hypertrophy, characteristic of the cardiomyopathy, were not distributed randomly. There was a direct correlation (r=0.85) between the extent of myocyte hypertrophy (determined by computer imaging) and the quantity of Gsalpha cells. The fibrosis, determined by picric acid Sirius red, was also more prominent in areas with the greatest Gsalpha cell density, with a correlation of r=0.88. Thus, the overexpressed Gsalpha can exert its action over the life of the animal, resulting in a local picture of cardiomyopathic damage in discrete regions of the heart, where clusters of the overexpressed Gsalpha cells reside, sparing the clusters of normal cells derived from the normal Rosa parent.

Animals↗

PubMed1999

Bioconversion of fumarate to succinate using glycerol as a carbon source.

In this study, a facultative bacterium that converts fumarate to succinate at a high yield was isolated. The yield of bioconversion was enhanced about 1.2 times by addition of glucose into culture medium at an initial concentration of 6 g/L. When the initial cell density was high (2 g/L), the succinate produced at pH 7.0 for initial fumarate concentrations of 30, 50, 80, and 100 g/L were 29.3, 40.9, 63.6, and 82.5 g/L, respectively, showing an increase with the initial fumarate concentration. The high yield of 96.8%/mole of fumarate in just 4 h was obtained at the initial fumarate concentration of 30 g/L. Comparing these values to those obtained with low cell culture (0.2 g/L), we found that the amount of succinate produced was similar, but the production rate in the high cell culture was about three times higher than was the case in the low cell culture. This strain converted fumarate to succinate at a rate of 3.5 g/L.h under the sparge of CO2.

Biodegradation, Environmental↗

PubMed1998

Differential in vivo activities of bovine growth hormone analogues.

In rodents, bovine (b) growth hormone (GH) binds only to GH receptors, while human (h) GH binds to both GH and PRL receptors. The phenotypic consequences of expression of bGH and hGH in transgenic mice are different and, in some cases, opposite. In the present study, site-directed in vitro mutagenesis of the bGH gene was used systematically to eliminate its differences from hGH at one, two, three or four suspected of conferring lactogenic activity: D11, H18, S57 and T60, respectively (corresponding to sites 12, 19, 57 and 60 of the bGH molecule). The resulting bGH analogues were expressed in cell lines and in transgenic mice. All of the seven bGH analogues produced retained their ability to bind to GH receptors and exhibited somatogenic activity in vitro and in vivo. However, none of them were able to bind to PRL receptors or to elicit detectable lactogenic response in vitro. Transgenic animals expressing any of the generated analogues were characterized by gigantism and splanchnomegaly. The effects of expression of each of the double, triple or quadruple mutants on the seminal vesicle weight resembled the effects of wild-type hGH and differed from the effects of expression of wild-type bGH. There were differences between the effects of the expression of different bGH analogues on plasma PRL levels and on the PRL response to pharmacological blockade of catecholamine synthesis. Plasma LH levels in ovariectomized females were suppressed by several of the analogues tested, an effect not seen in animals expressing wild-type bGH or hGH. Dopamine turnover in the median eminence of male mice was also altered in animals expressing different bGH analogues but not in those expressing wild-type bGH or hGH. In ovariectomized females, the effects of different bGH analogs on the turnover of dopamine and norepinephrine in the median eminence included changes resembling those detected in animals expressing hGH, as well as alterations differing from the effects of both bGH and hGH. The results indicate that biological actions of these bGH analogues cannot be characterized simply in terms of enhanced or reduced somatogenic or lactogenic activity and raise a possibility that different sites, domains or features of tri-dimensional structure of GH are involved in its actions on different cellular targets.

Animals↗

PubMed1997

Phosphoenolpyruvate carboxykinase (GTP) gene transcription and hyperglycemia are regulated by glucocorticoids in genetically obese db/db transgenic mice.

The molecular mechanisms underlying increased hepatic phosphoenolpyruvate carboxykinase (PEPCK) gene transcription and gluconeogenesis in type II diabetes are largely unknown. To examine the involvement of glucocorticoids and the cis-acting insulin response sequence (IRS, -416/-407) in the genetically obese db/db mouse model, we generated crosses between C57BL/KsJ-db/+ mice and transgenic mice that express -460 or -2000 base pairs of the rat PEPCK gene promoter containing an intact or mutated IRS, linked to a reporter gene. Transgenic mice expressing the intact PEPCK(460)-CRP (C-reactive protein) transgene bred to near homozygosity at the db locus were obese, hyperinsulinemic, and developed fasting hyperglycemia (389 +/- 26 mg/100 ml) between 4 and 10 weeks of age. Levels of CRP reporter gene expression were increased 2-fold despite severe hyperinsulinemia compared with non-diabetic non-obese transgenic mice. Reporter gene expression was also increased 2-fold in transgenic obese diabetic db/db mice bearing a mutation in the IRS, -2000(IRS)-hGx, compared with non-obese non-diabetic transgenic 2000(IRS)-hGx mice. Treatment of obese diabetic db/db transgenic mice with the glucocorticoid receptor blocker RU 486 decreased plasma glucose by 50% and reduced PEPCK, GLUT2, glucose-6-phosphatase, tyrosine aminotransferase, CRP, and hGx reporter gene expression to levels similar to those of non-obese normoglycemic transgenic mice. Taken together, these results establish that -460 bp of 5'-flanking sequence is sufficient to mediate the induction of PEPCK gene transcription in genetically obese db/db mice during the development of hyperglycemia. The results further demonstrate that the mechanism underlying increased expression of gluconeogenic enzymes in the db/db mouse requires the action of glucocorticoids and occurs independently of factors acting through the PEPCK IRS (-416/-407) promoter binding site.

Animals↗

PubMed1995

Remodeling of mouse milk glycoconjugates by transgenic expression of a human glycosyltransferase.

The mammary gland is a unique biosynthetic tissue that produces a variety of species-specific glycoconjugates, but the factors regulating the production of specific glycoconjugates are not well understood. To explore the underlying regulation, a fusion gene containing a cDNA encoding the human alpha 1,2-fucosyltransferase (alpha 1,2FT), which generates the H-blood group antigen, flanked by the murine whey acidic protein promoter and a polyadenylation signal, was introduced into mice. Milk samples from transgenic animals contained soluble forms of the alpha 1,2FT, as revealed by Western blots of milk samples using an anti-alpha 1,2FT antiserum and by the demonstration of alpha 1,2FT enzyme activity. Milk from transgenic animals also contained large quantities of 2'-fucosyllactose (Fuc alpha 1-2Gal beta 1-4Glc) and modified glycoproteins containing the H-antigen, whereas milk from control animals lacked these glycoconjugates. Expression levels of 2'-fucosyllactose were high in most animals and represented 1/3 to nearly 1/2 of the total milk oligosaccharides. These results demonstrate that heterologous transgenic expression of a glycosyltransferase can result in the expression of both the transgene and its secondary gene products and that the structures of milk oligosaccharides can be remodeled depending on expression of the appropriate enzyme. Furthermore, these results suggest that the lactating mammary gland may be a unique biosynthetic reactor for the production of biologically active oligosaccharides and glycoconjugates.

ABO Blood-Group System↗

PubMed1995

Expression of rabbit C-reactive protein in transgenic mice.

C-reactive protein (CRP) is a prototypic acute phase reactant in humans and rabbits whose serum concentration can increase up to 1000-fold following an acute inflammatory stimulus. CRP binds to many phosphate ester-containing compounds including phosphorylcholine, nucleotides, chromatin and snRNP. To examine the in vivo function of this protein, we produced transgenic mice capable of significant CRP synthesis. In contrast to most other vertebrates, mice synthesize CRP in only trace amounts. The transgenic animals express rabbit CRP from either the phosphoenolpyruvate carboxykinase promoter (PEPCK-CRP) or the mouse metallothionein I promoter (MT-CRP). Manipulating the diet in one of the PEPCK-CRP lines led to a rise in serum CRP levels from < 5 mu g/mL to 100-200 mu g/mL over a period of 2 days. The two MT-CRP lines examined expressed CRP constitutively which could be further elevated 2-4-fold following an inflammatory stimulus. Transgenic CRP bound phosphorylcholine was pentameric, had a circulating half-life of 30-60 min and was capable of activating mouse complement when bound to a ligand. We conclude that these transgenic lines express CRP with many of the properties of authentic rabbit CRP, and that the expression of CRP can be controlled to be dependent or independent of the acute phase response.

Acute-Phase Reaction↗

PubMed1994

An analysis of regulatory elements in the phosphoenolpyruvate carboxykinase (GTP) gene which are responsible for its tissue-specific expression and metabolic control in transgenic mice.

Sequences in the gene for P-enolpyruvate carboxykinase (PEPCK) which are responsible for its complex pattern of transcriptional control were determined using transgenic mice containing a chimeric PEPCK-bovine growth hormone (bGH) gene consisting of a segment of the PEPCK promoter from -460 to +73, with mutations in specific regulatory domains. A mutation in the cAMP response element (CRE) (-87 to -74), which binds CCATT/enhancer-binding protein beta (C/EBP beta) and/or cAMP response element-binding protein (CREB), resulted in a 4- and 20-fold elevation in the level of bGH mRNA in the liver and kidney of transgenic mice, respectively. Expression of the PEPCK-bGH gene in the liver was reduced 60% by a mutation in the P3 (I) region (-248 to -230), whereas expression in the kidney was increased 10-fold by the same mutation. A mutation in the P2 region (-200 to -164) greatly reduced expression of the PEPCK-bGH gene in the kidney but not in the liver. Induction of hepatic PEPCK-bGH gene expression by Bt2cAMP was eliminated by mutations in the CRE, P1, P3(I), or by a double mutation of the CRE and P3(I). Mutations in the CRE or P3(I) regions of the PEPCK promoter did not interfere with the expected induction of the PEPCK-bGH gene in the liver at birth. None of the mutations in the PEPCK promoter interfered with the induction of transcription of the PEPCK-bGH gene in the liver when mice were fed a carbohydrate-free diet or the deinduction of transcription from the PEPCK promoter caused by a diet high in carbohydrate, whereas a mutation in P2 (an HNF-1 binding domain) eliminated dietary regulation of transcription of the transgene in the kidney. A model to explain the role of the various elements in the PEPCK promoter on the control of PEPCK gene transcription in the liver and kidney is presented.

Animals↗

PubMed1994

Development of neuroepithelial tumors of the adrenal medulla in transgenic mice expressing a mouse hypothalamic growth hormone-releasing hormone promoter-simian virus-40 T-antigen fusion gene.

Expression of the mouse GH-releasing hormone (GRH) gene is restricted to neurons within the hypothalamus and to placenta. In an attempt to generate immortalized mouse hypothalamic neurons expressing GRH, the proximal 872-nucleotide segment of the 5'-flanking region of the hypothalamic mouse GRH gene was cloned by polymerase chain reaction and ligated to a 2.7-kilobase DNA sequence encoding the simian virus-40 (SV40) T-antigen, so that regulation of SV40 T-antigen expression was dependent on sequences within the mGRH 5'-flanking region. This region contains both TATA and CAAT boxes. The mouse GRH/SV40 T-antigen fusion gene was injected into 1-cell mouse embryos, and SV40 T-antigen incorporation in the mouse genome was found in 11 of 77 live births (3 males and 8 females). Although no evidence of hypothalamic tumors was found, all mice that expressed the transgene also developed tumors originating in the adrenal medulla. Gene copy number varied from 1-20 and was inversely proportional to survival, which ranged from 7-16 weeks. Corticosterone levels were normal. The male transgenic mice were fertile, and their progeny expressed the transgene and developed similar tumors. Microscopic examination of the tumors revealed a primitive neuroectodermal neoplasm that exhibited hematogenous and lymph node metastases and contained 100 ng norepinephrine, 2.85 ng epinephrine, and 1.1 ng dopamine/mg tumor tissue. Primary culture of dispersed tumor cells released norepinephrine into the medium (180 pg/ml.24 h). Cell lines from 2 tumors were established and exhibited characteristics similar to those of mixed neuroblastoma or primitive neuroectodermal tumors. In conclusion, the proximal 872 nucleotides of the hypothalamic mouse GRH promoter contain elements directing tissue-specific expression limited to early adrenal neuroectodermal cells. Other GRH DNA sequences appear to be required for restricted expression of mouse GRH within the hypothalamus.

Adrenal Gland Neoplasms↗

PubMed1993

Glucocorticoids regulate the induction of phosphoenolpyruvate carboxykinase (GTP) gene transcription during diabetes.

The hormonal regulation of transcription of the phosphoenolpyruvate carboxykinase (GTP) (4.1.1.32) (PEPCK) gene during diabetes was studied using transgenic mice containing a chimeric gene consisting of segments of the PEPCK promoter (-2000/+73, -460/+73, -355/+73) linked to bovine growth hormone (bGH) reporter gene. The effect of diabetes and insulin on transgenic mice containing a mutation in cAMP regulatory sequences at -90/-82 and -250/-234 was also studied. In addition, we analyzed the transcriptional response of the PEPCK gene to adrenalectomy, the administration of glucocorticoids, and alterations in dietary protein and carbohydrate. Our results indicate that deletion of the insulin regulatory sequence of the PEPCK promoter did not affect dietary control of PEPCK gene expression. However, glucocorticoids and the glucocorticoid regulatory unit appear to be essential for induction of PEPCK gene transcription by diabetes. By contrast, mutation of cAMP regulatory elements of the PEPCK promoter did not limit induction of PEPCK transcription by diabetes, nor did it affect negative regulation of transcription by insulin. These results provide evidence for the interaction of insulin and glucocorticoid regulatory elements in the control of PEPCK gene transcription and suggest an important role of glucocorticoids as a gluconeogenic activator during diabetes.

Adrenalectomy↗

PubMed1993

Gonadotropin secretion, synthesis, and gene expression in two types of bovine growth hormone transgenic mice.

Expression of the mouse metallothionein-I (MT) promoter/bovine growth hormone (bGH) or the phosphoenolpyruvate carboxykinase (Pepck) promoter/bGH fusion genes in male transgenic mice is associated with alternations in adenohypophyseal function and fertility. To determine the effects of these gene constructs on gonadotropin synthesis and secretion, we have examined basal and GnRH-stimulated LH and FSH release in vitro using static incubations and perifusions of the pituitary; we have also examined pituitary content of LH, FSH, LH beta mRNA, and FSH beta mRNA in MT/bGH and Pepck/bGH transgenic mice as well as in normal mice. In addition, we have measured LH and FSH release from normal pituitaries transplanted under the kidney capsules of Pepck/bGH transgenic or normal mice. We found that in Pepck/bGH transgenic mice, pituitary contents of FSH and FSH beta mRNA were reduced, while FSH release in vitro in pituitary incubations and perifusions was increased. Steady-state levels of LH beta mRNA as well as LH responses to GnRH in perifusions were reduced; LH release in incubations and pituitary LH content were not changed; and basal LH secretion in perifusions was increased. In MT/bGH transgenic mice, in which peripheral bGH levels are much lower than in Pepck/bGH mice, similar trends were observed, but most of the apparent differences between transgenic and normal animals were not statistically significant. When normal pituitaries were transplanted under the kidney capsules of Pepck/bGH transgenic mice, the expected decrease in LH and FSH secretion was attenuated and the response to GnRH stimulation was lost.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Glucose metabolism in transgenic mice containing a chimeric P-enolpyruvate carboxykinase/bovine growth hormone gene.

Transgenic mice, containing the chimeric gene obtained by linking the promoter-regulatory region of P-enolpyruvate carboxykinase (PEPCK) gene to the bovine growth hormone structural gene (bGH), were used to investigate the long-term effects of bGH on glucose metabolism. Expression of the PEPCK/bGH gene was markedly enhanced by feeding a diet high in protein and inhibited by a high carbohydrate diet. All transgenic mice had normal levels of blood glucose but were hyperinsulinemic, indicating that they were insulin resistant. The glycogen synthase activity ratios in the muscle and liver of transgenic mice were lower than noted for control animals, and remained unchanged in liver after feeding a standard high carbohydrate or a high protein diet. Similar effects were detected in the activity of glycogen phosphorylase, except that a high carbohydrate diet activated this enzyme in the liver. The activation of glycogen phosphorylase in both muscle and liver correlated with the expression of their genes. These animals had a significant content of glycogen and glucose 6-phosphate, which was related to the levels of glucokinase mRNA in the liver. The concentration of fructose 2,6-bisphosphate in the liver of all fed transgenic mice was lower than noted in livers from fed animals. In addition, a decrease in the hepatic expression of the endogenous genes for PEPCK, tyrosine aminotransferase (TAT), and the glucose transporter GLUT-2 was observed and directly correlated with the expression of bGH. Thus, bGH can control glucose metabolism in vivo, at least in part, by modifying the expression of several genes coding for proteins of importance in carbohydrate metabolism. Taken together, these results indicate a state of insulin resistance caused by chronic exposure of the animals to an elevated concentration of bGH.

Animals↗