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S K Durham

Publications and source records attributed to S K Durham.

At least 37 records · Page 2Linked to original sources
PubMed1998

The insulin-like growth factor axis and growth in children with chronic renal failure: a report of the Southwest Pediatric Nephrology Study Group.

Children with chronic renal failure (CRF) are often growth recarded despite normal serum levels of GH and insulin-like growth factors (IGFs). Recent studies suggest that excess IGF-binding proteins (IGFBPs) in the 35-kDa fractions of CRF serum contribute to CRF growth failure. This report characterizes the relationship between IGFBP-3 and IGF peptides in the serum of growth-retarded CRF children. Size-exclusion chromatography at pH 7.4 found IGFBP-3 and IGFs almost exclusively in the 150-kDa fractions of normal serum, where their molar stoichiometry was approximately 1:1. However, similar chromatography of CRF serum found a molar excess of IGFBP-3 over total IGFs in the 150-kDa fractions and large amounts of IGFs in the 35-kDa fractions. In the 150-kDa fractions of CRF serum, IGFBP-3 was present in normal amounts, but a greater than normal amount was in the form of a 29-kDa IGFBP-3 fragment. Treatment of these CRF children with recombinant human GH increased the molar excess of IGFBP-3 over total IGFs in the 150-kDa fractions, the amount of IGFBP-3 and total IGFs in the 150-kDa fractions, and the amount of IGFs, but not IGFBPs, in the 35-kDa fractions. These data suggest that in untreated CRF children, proteolysis of IGFBP-3 in the 150-kDa fractions releases IGFs to the excess IGFBPs in the 35-kDa fractions, but insufficient IGF is released to overcome the growth-inhibiting effects of these excess IGFBPs. Treatment with recombinant human GH increases levels of IGFs and IGFBP-3 in the 150-kDa fractions, and subsequent IGFBP-3 proteolysis releases sufficient IGF to overcome the growth inhibitory effects of excess IGFBPs in the 35-kDa fractions of CRF serum.

Child↗
PubMed1998

Captopril prevents nephropathy in HIV-transgenic mice.

Transgenic mice (T26) bearing the envelope, regulatory, and accessory genes of HIV- I develop renal disease resembling human HIV-associated nephropathy (HIVAN). Effects of vehicle (VEH) and the angiotensin-converting enzyme inhibitor captopril (CAP) were examined in wild-type (WT) or T26 mice treated from 7 to 100 d of age. Mortality was lower in CAP T26 mice (30 mg/kg: 8%; 100 mg/kg: 12%) than VEH T26 mice (52%). The urinary protein/creatinine ratio was increased in VEH T26 mice (19.5+/-7.60) versus WT mice (6.1+/-0.83), but not in low-dose (7.3+/-0.94) or high-dose (8.2+/-1.02) CAP T26 mice. Blood urea nitrogen was higher in VEH T26 mice (52+/-16.2 mg/dl) than VEH WT mice (24+/-0.8). Blood urea nitrogen was also elevated in CAP WT (high dose: 43+/-2.1 mg/dl) and T26 mice (high dose: 42+/-2.4 mg/dl). Glomerular injury was higher in VEH T26 mice (6.8+/-0.58) than VEH WT mice (0.2+/-0.08) or CAP T26 mice (low dose: 1.1+/-0.17; high dose: 0.7+/-0.13). Tubulointerstitial injury was also greater in VEH T26 mice (1.1+/-0.10) than VEH WT mice (0.2+/-0.08) or CAP T26 mice (low dose: 0.4+/-0.10; high dose: 0.3+/-0.10). These data validate recent nonrandomized studies of captopril in HIV-infected patients, and suggest that an angiotensin-converting enzyme substrate is an important mediator in HIVAN. A randomized placebo-controlled trial of captopril in HIVAN may be warranted.

AIDS-Associated Nephropathy↗
PubMed1997

p50-NF-kappaB complexes partially compensate for the absence of RelB: severely increased pathology in p50(-/-)relB(-/-) double-knockout mice.

RelB-deficient mice (relB(-/-)) have a complex phenotype including multiorgan inflammation and hematopoietic abnormalities. To examine whether other NF-kappaB/Rel family members are required for the development of this phenotype or have a compensatory role, we have initiated a program to generate double-mutant mice that are deficient in more than one family member. Here we report the phenotypic changes in relB(-/-) mice that also lack the p50 subunit of NF-kappaB (p50(-/-)). The inflammatory phenotype of p50(-/-)relB(-/-) double-mutant mice was markedly increased in both severity and extent of organ involvement, leading to premature death within three to four weeks after birth. Double-knockout mice also had strongly increased myeloid hyperplasia and thymic atrophy. Moreover, B cell development was impaired and, in contrast to relB(-/-) single knockouts, B cells were absent from inflammatory infiltrates. Both p50(-/-) and heterozygous relB(-/+) animals are disease-free. In the absence of the p50, however, relB(-/+) mice (p50(-/-)relB(-/+)) had a mild inflammatory phenotype and moderate myeloid hyperplasia. Neither elevated mRNA levels of other family members, nor increased kappaB-binding activities of NF-kappaB/Rel complexes could be detected in single- or double-mutant mice compared to control animals. These results indicate that the lack of RelB is, in part, compensated by other p50-containing complexes and that the "classical" p50-RelA-NF-kappaB activity is not required for the development of the inflammatory phenotype.

Abnormalities, Multiple↗
PubMed1997

Inhibition of cholesterol synthesis by squalene synthase inhibitors does not induce myotoxicity in vitro.

The cholesterol-lowering HMG CoA reductase inhibitors (HMGRI), pravastatin and lovastatin, have been associated with skeletal myopathy in humans and in rats. In a previous in vitro study, HMGRI-induced changes in neonatal rat skeletal muscle cells were characterized by reversible inhibition of protein synthesis and loss of differentiated myotubes at concentrations markedly lower than those inducing enzyme leakage. Myotoxicity was determined to be directly related to inhibition of HMG CoA reductase, since mevalonate, the immediate product of HMG CoA reductase metabolism, abrogated the drug-induced changes. Farnesol, geranylgeraniol, and squalene are metabolites of mevalonate. Squalene, formed from farnesol by squalene synthase, is the first metabolite solely committed to cholesterol synthesis. In contrast, geranylgeraniol, formed by the addition of an isoprene group to farnesol, is the first metabolite uncommitted to cholesterol synthesis. The objective of the present study was to determine the role of inhibition of cholesterol synthesis in HMGRI-induced in vitro myotoxicity. HMGRI-treated neonatal rat skeletal muscle cultures were supplemented with farnesol and geranylgeraniol, and in another study, muscle cultures were exposed to two squalene synthase inhibitors (SSI), BMS-187745 and its prodrug ester, BMS-188494. Endpoints evaluated for both studies included protein synthesis ([3H]leucine incorporation), total cellular protein (a measure of cell loss), intra- and extracellular lactate dehydrogenase activity (a measure of membrane integrity), cholesterol biosynthesis ([14C]acetate incorporation), and morphology. HMG CoA reductase inhibitor-induced morphologic changes and inhibition of protein synthesis were significantly ameliorated by supplementation with farnesol and geranylgeraniol. In contrast to HMGRI-induced in vitro myotoxicity, SSI induced an irreversible, minimal cytotoxicity at close to maximum soluble concentrations. These results indicate that depletion of metabolites of geranylgeranyl pyrophosphate, and not inhibition of cholesterol synthesis, is the primary cause of HMG CoA reductase-induced myotoxicity.

Analysis of Variance↗
PubMed1997

HMG CoA reductase inhibitor-induced myotoxicity: pravastatin and lovastatin inhibit the geranylgeranylation of low-molecular-weight proteins in neonatal rat muscle cell culture.

In previous studies, inhibition of cholesterol synthesis by HMG CoA reductase inhibitors (HMGRI) was associated with myotoxicity in cultures of neonatal rat skeletal myotubes, and rhabdomyolysis in rats, rabbits, and humans in vivo. In vitro myotoxicity was directly related to HMGRI-induced depletion of mevalonate, farnesol, and geranylgeraniol, since supplementation with these intermediate metabolites abrogated the toxicity. Both farnesol and geranylgeraniol are required for the posttranslational modification, or isoprenylation, of essential regulatory proteins in mammalian cells. The objective of the present study was to measure changes in protein isoprenylation in cultured neonatal rat skeletal muscle cells exposed for 24 hr to increasing concentrations of pravastatin or lovastatin. Proteins were labeled with [3H]mevalonate, [3H]farnesyl pyrophosphate (FPP), or [3H]geranylgeranyl pyrophosphate (GGPP), and then separated by SDS-PAGE and quantitated by scintillation counting and densitometry of autoradiographs. Mevalonate and FPP labeling of the majority of proteins increased in a concentration-dependent manner, even at concentrations greater than 2 microM lovastatin and 25 microM pravastatin that completely inhibited cholesterol synthesis. In contrast, mevalonate and FPP labeling of three protein bands with molecular weights of 26.6, 27.7, and 28.9 kDa was markedly inhibited at concentrations higher than 1 microM lovastatin and 400 microM pravastatin, which inhibited protein synthesis and disrupted myotube morphology after longer exposures in a previous study. In contrast, these proteins were equally well labeled by GGPP at all HMGRI concentrations tested, suggesting that isoprenylation of the 26.9-, 27.8-, and 28.9-kDa proteins requires geranylgeraniol. The results of this study indicate that HMGRI-induced myotoxicity is most likely related to reduced posttranslational modification of specific regulatory proteins by geranylgeraniol.

Animals↗
PubMed1997

Modulation of growth factors by growth hormone in children with chronic renal failure. The Southwest Pediatric Nephrology Study Group.

Anthropometric measurements and circulating growth factors were studied serially in 44 prepubertal children with growth failure and chronic renal failure (GFR = 10 to 40 ml/min/1.73 m2) who were randomized to receive either recombinant human growth hormone (rhGH; N = 30) or no treatment (N = 14). RhGH was given as Nutropin, 0.05 mg/kg/day, and the studies were carried out at baseline and after 3 and 12 months. At baseline, serum insulin-like growth factor binding protein (IGFBP)-1 and -2 levels were, while IGFBP-3 levels were not, higher than those of children with normal renal function. In addition, height SDS at baseline correlated inversely with serum IGFBP-2 levels (r = -0.461, P = 0.0016), but did not correlate significantly with any other factor. After 12 months of study, the 30 children receiving rhGH showed: (i) greater increase in height (9.1 +/- 2.8 vs. 5.5 +/- 1.9 cm, P < 0.0001); (ii) increases in serum levels of IGF-I, IGF-II, free IGF-I, IGFBP-3 and acid labile subunit (ALS); (iii) a greater decrease in serum IGFBP-1 levels; and (iv) no significant difference in serum IGFBP-2 levels, when compared to the 14 control patients. The change in height SDS after 12 months of rhGH (+0.8) in the 30 treated children correlated significantly and positively with serum ALS, IGFBP-3, total IGF, IGF-I, IGF-II and free IGF-I levels measured during treatment. These observations suggest that, in children with growth failure associated with chronic renal failure: (i) IGFBP-2, and not IGFBP-3, is likely to be a growth inhibitor; (ii) rhGH stimulates catch-up growth in part by increasing serum levels of IGF peptides; and (iii) linear growth is influenced by the balance between growth stimulating IGFs and growth inhibitory IGFBPs.

Age Determination by Skeleton↗
PubMed1997

Thymus dysfunction and chronic inflammatory disease in gp39 transgenic mice.

Expression of gp39 on activated T cells provides a co-stimulatory signal in peripheral lymphoid tissue that regulates humoral and cell-mediated immunity. The function of gp39 and its receptor CD40 in thymus remains uncertain. Here we report that overexpression of gp39 in transgenic mouse thymus caused a dose-dependent decline in thymocyte numbers (> 500 fold), loss of cortical epithelium and expansion of CD40+ medullary cells. Transplantation of transgenic bone marrow into normal mice indicated that gp39 significantly diminished thymocyte viability in the context of a 'normal' thymic environment. The peripheral tissues of transgenic mice also accumulated abnormalities in a transgene dose-dependent manner that involved inflammation and lymphoid tissue hypertrophy. Animals with the highest transgene copy numbers acquired a lethal inflammatory bowel disease marked by the infiltration of gp39+ T cells and CD40+ cells into diseased tissues. Examination of cells overexpressing gp39 suggested that these defects were caused, in part, by the saturation of a mechanism that sequesters gp39 inside non-activated cells and thus protects the immune system from inappropriate gp39-CD40 interaction. These results establish a regulatory role for gp39 in thymus function and a causal relationship in mediating chronic inflammatory disease.

Animals↗
PubMed1997

Hypoxia stimulates human preproendothelin-1 promoter activity in transgenic mice.

Significant elevations in endothelin (ET)-1 levels accompany many diseases, but the underlying regulatory mechanisms are unclear. To investigate the in vivo regulation of human preproendothelin-1 (PPET-1), we examined the activity of the PPET-1 promoter in transgenic mice exposed to hypoxia. Mice expressing one of three PPET-1 promoter-luciferase (PPET-1/LUC) reporter transgenes (approximately 2.5 kb, 138 bp, or none of the 5'-flanking sequences of the PPET-1 gene) were generated. LUC expression was reduced in mice with a truncated 138-bp PPET-1 promoter. Exposure of mice bearing the 2.5-kb PPET-1/LUC transgene to hypoxia (10% O2 for 24 h) increased LUC expression sixfold in pulmonary tissue but only twofold in other tissues. In situ hybridization revealed the strongest transgene expression in the pulmonary vasculature and bronchiolar epithelium. These data are consistent with the hypothesis that hypoxic induction of the PPET-1 gene leads to increased pulmonary production of ET-1 in diseases associated with low O2 tension.

Animals↗
PubMed1997

Bioactivity of a 29-kilodalton insulin-like growth factor binding protein-3 fragment present in excess in chronic renal failure serum.

Children with chronic renal failure (CRF) have normal or high serum levels of GH, IGF-I, and IGF-II. Despite this, the serum of CRF patients has low IGF bioactivity, which may contribute to CRF growth failure. Recent studies suggest that excess IGF binding proteins (IGFBPs) in the approximately 35-kD fractions of CRF serum contribute to this low IGF bioactivity. This report characterizes a 29-kD form of IGFBP-3, IGFBP-3(29), which accumulates in the approximately 35-kD fractions of CRF serum and peritoneal dialysate. Deglycosylation and [125I]IGF ligand blot studies show that IGFBP-3(29) is a glycosylated IGFBP-3 fragment with low affinity for IGF peptides. Using an IGFBP-3 antibody column, IGFBP-3(29) was purified to homogeneity from the approximately 35-kD fractions of peritoneal dialysate from children with CRF. Compared with native IGFBP-3, pure IGFBP-3(29) has a 4-10-fold lower affinity for IGF-II and a 200-fold lower affinity for IGF-I. Consistent with the binding data, IGFBP-3(29) inhibited IGF-II-stimulated thymidine incorporation in chondrosarcoma cells, but was a less potent inhibitor than native IGFBP-3; also, native IGFBP-3 clearly inhibited IGF-I-stimulated thymidine incorporation in chondrosarcoma cells and potentiated IGF-I-stimulated aminoisobutyric acid uptake in bovine fibroblasts, but higher concentrations of IGFBP-3(29) had no effect on these IGF-I actions. Thus, the 29-kD IGFBP-3 form that accumulates in CRF serum and extravascular spaces is an IGFBP-3 fragment that may modulate IGF-II, but not IGF-I, effects on target tissues. Whether IGFBP-3(29) plays any role in the growth failure of children with CRF remains to be determined.

Animals↗
PubMed1997

Hepatic nuclear factor 3 and high mobility group I/Y proteins bind the insulin response element of the insulin-like growth factor-binding protein-1 promoter.

The insulin response element (IRE) of the human insulin-like growth factor-binding protein-1 (IGFBP-1) promoter contains a palindrome of the T(A/G)TTT sequence crucial to hormonal regulation of many genes. In initial studies of how this IRE participates in hormonal regulation, the electromobility shift assay was used under a variety of conditions to identify IRE-binding proteins. An exhaustive search identified five proteins that specifically bind this IRE; purified proteins were used to show that all five are related to either the high mobility group I/Y (HMGI/Y) or hepatic nuclear factor 3 (HNF3) protein families. Further studies used purified HNF3 and HMGI proteins to show: 1) eah protects the IGFBP-1 IRE from deoxyribonuclease I (DNaseI) digestion; and 2) HNF3 but not HMGI/Y binds to the related phosphoenolpyruvate carboxykinase and Apo CIII IREs. A series of IRE mutants with variable responsiveness to insulin were used to show that the presence of a TGTTT sequence in the mutants did parallel, but HMGI/Y and HNF3 binding to the mutants did not parallel, the ability of the mutants to confer the inhibitory effect of insulin. In contrast, HNF3 binding to these IRE mutants roughly correlates with response of the mutants to glucocorticoids. The way by which HNF3 and/or other as yet unidentified IRE-binding proteins confer insulin inhibition to IGFBP-1 transcription and the role of HMGI/Y in IRE function have yet to be established.

Base Sequence↗
PubMed1997

Decreased hepatic insulin-like growth factor (IGF)-I and increased IGF binding protein-1 and -2 gene expression in experimental uremia.

The imbalance between normal insulin-like growth factor-I (IGF-I) and markedly increased IGF binding protein (IGFBP) plasma levels plays a pathogenic role for growth retardation and catabolism in children with chronic renal failure. To investigate the mechanism of these alterations, experiments were performed in an experimental model of uremia in rats (5/6 nephrectomy) and in pair-fed and ad libitum-fed sham-operated controls Using a specific solution hybridization/RNase protection assay, we observed a marked reduction of hepatic IGF-I messenger RNA (mRNA) abundance at steady state in uremic animals (37 +/- 5% of control) compared both with pair-fed (65 +/- 10%) and ad libitum-fed controls (100 +/- 11%) (P < 0.001). Reduced IGF-I gene expression was clearly organ-specific; it was most pronounced in liver (significant vs., pair-fed controls) and lung and muscle tissue (significant vs., ad libitum-fed controls); no change was observed in kidney and heart tissue. To determine a potential mechanism of reduced hepatic IGF-I gene expression in uremia, the hepatic GH receptor gene expression in the same experimental animals was analyzed by specific solution hybridization/RNase protection assay. Uremic animals had a 20-30% reduction of hepatic GH receptor mRNA abundance compared with controls. Hepatic GHBP expression in uremia was decreased in parallel. Despite the reduction of hepatic IGF-I mRNA abundance, plasma IGF-I levels in uremia were not different from ad libitum-fed controls. This discrepancy is explained by an increased concentration of IGFBPs in uremic plasma. By RIA, plasma IGFBP-1 levels in uremia were increased 4-fold; by Western immunoblot, plasma IGFBP-2 levels were increased 7-fold and plasma IGFBP-4 levels were increased 2-fold compared with both control groups. Intact IGFBP-3 (M(r), approximately 48 kDa) and low molecular IGFBP-3 fragments were not significantly different among the three groups. By Northern blot analysis, hepatic IGFBP-1 mRNA levels in uremia were 2-fold higher than in controls. IGFBP-2 mRNA abundance in liver tissue was increased 4-fold, whereas in kidney there was a significant reduction of IGFBP-2 mRNA (30% of control). IGFBP-4 mRNA was increased by 50% in kidney but not in liver. Plasma insulin and corticosterone levels were not different among the groups. Our study shows that hepatic IGF-I gene expression was specifically reduced in uremia, partially as the consequence of a reduced hepatic GH receptor gene expression. One of the mechanisms contributing to increased IGFBP levels in uremia is increased hepatic gene expression of IGFBP-1 and IGFBP-2. The imbalance between reduced hepatic IGF-I production and increased hepatic IGFBP-1 and 2 production is likely to play a pathogenic role for catabolism and growth failure in CRF.

Animal Nutritional Physiological Phenomena↗
PubMed1997

Kinetics of insulin-like growth factor (IGF) and IGF-binding protein responses to a single dose of growth hormone.

The in vivo physiological relationships among GH, the insulin-like growth factors (IGFs), and the IGF-binding proteins (IGFBPs) are not completely defined, and single random measurements of these serum proteins do not completely reveal their dynamic relationships. We report the kinetic responses of the IGFs and IGF-binding proteins to exogenous GH in 23 subjects with untreated GH deficiency [5 women and 18 men; age, 15.0 +/- 6.2 yr (+/- s.d.), height z-score = -4.4 +/- 2.2 (+/- s.d.); body mass index = 19.3 +/- 2.4 kg/m2]. After an overnight fast, subjects were given a sc dose of recombinant human GH (2.85 i.u./m2), and blood was sampled from an indwelling peripheral venous catheter 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, and 24 h after the injection. Subjects were then treated with recombinant human GH (2.85 i.u./m2.day); fasting samples were obtained at 3 months (n = 22), and timed sampling was repeated at 6 months (n = 21). Fasting levels of IGF-I, free IGF-I, IGF-II, IGFBP-3, and insulin increased significantly within 3 months of GH treatment, whereas IGFBP-1, IGFBP-2, and IGFBP-6 showed no change. In the timed sampling studies at 0 and 6 months, GH levels peaked 3 h after treatment; the degree of rise and the rate of decline were both greater at 6 months. IGF-I levels increased beginning at 4 h, continuing throughout the 24-h period at month 0, whereas a plateau was observed after 6-8 h during the 6-month study. Free IGF-I paralleled total IGF-I except during fasting, when it varied inversely with IGFBP-1. IGFBP-3 and IGF-II both showed late (> 20 h) responses to a dose of GH, whereas IGFBP-2 and IGFBP-6 showed minimal changes. IGFBP-1 varied inversely with insulin, which, in turn, varied with meal intake. Comparative studies in 2 subjects with GH receptor deficiency showed no response to exogenous GH. However, both IGFBP-1 and IGFBP-2 were several-fold elevated, and IGFBP-1 varied inversely with the low insulin levels. Our data are the first to examine multiple elements of the serum IGF system in response to GH in both GH-deficient and replete states. The relationships of the different response patterns provide insight into the physiology of this system and may guide future studies.

Adolescent↗
PubMed1997

Insulin-like growth factor-binding protein-6 levels are elevated in serum of children with chronic renal failure: a report of the Southwest Pediatric Nephrology Study Group.

Previous studies suggest that growth retardation in children with chronic renal failure (CRF) results in part from inhibition of insulin-like growth factor (IGF) action by excess serum IGF-binding proteins (IGFBPs). Excess IGFBPs in CRF serum include IGFBP-1, -2, and -3 and a diffuse approximately 24- to 28-kDa IGFBP band identified by [125I]IGF ligand blot. The present studies characterized this diffuse approximately 24- to 28-kDa band. Initial studies identified this band as IGFBP-6, because it was immunoprecipitated by antiserum raised against a synthetic peptide of human IGFBP-6 (hIGFBP-6). Additional [125I]IGF ligand blots found that the immunoprecipitated band was 1) recognized by [125I]IGF-II but not [125I]IGF-1, 2) more abundant in CRF than in normal serum, and 3) more abundant in serum from dialyzed than nondialyzed prepubertal CRF children. Using the hIGFBP-6 antiserum in a specific and sensitive RIA, we found that serum IGFBP-6 levels were 4.7 +/- 1.7 nmol/L in 10 normal prepubertal children, 21.4 +/- 6.1 nmol/L in 44 nondialyzed prepubertal CRF children, 73.5 +/- 14.4 nmol/L in 7 dialyzed prepubertal CRF children, and 94.6 +/- 26.2 nmol/L in 14 dialyzed pubertal CRF children. IGFBP-6 levels were also elevated in 71 nondialyzed European children with CRF. In nondialyzed CRF children, serum IGFBP-6 levels 1) correlated inversely with the glomerular filtration rate, 2) did not correlate with height SD score, and 3) were not altered by 12 months of daily recombinant hGH treatment. In summary, a specific antiserum and RIA were used to demonstrate elevated levels of intact IGF-II-binding IGFBP-6 in serum of CRF children. We postulate that the excess IGFBP-6 may modulate the action of IGF-II on target tissues.

Adolescent↗
PubMed1997

Glucokinase regulatory protein may interact with glucokinase in the hepatocyte nucleus.

Glucokinase (GK) plays a central role in the sensing of glucose in pancreatic beta-cells and parenchymal cells of the liver. Glucokinase regulatory protein is a physiological inhibitor of GK in the liver. To understand the role of the interaction of these two proteins in glucose sensing, we carried out a series of experiments to localize the protein in the liver cell. The regulatory protein was found to be present mainly in the nucleus of the cell under a variety of conditions that mimicked the glucose status of the fed and fasted state. GK was localized in the nucleus when the cells were exposed to low glucose concentrations. At higher glucose concentrations or in the presence of low concentrations of fructose, GK translocated to the cytoplasm. The effect of fructose was more robust and rapid than the effect of high glucose concentrations. Furthermore, the effect of fructose and high glucose on the translocation of GK from the nucleus could be partially reversed by glucagon. This unusual localization and behavior suggests a role for GK and its regulatory protein in hepatic energy metabolism that may be broader than glucose phosphorylation.

1-Methyl-3-isobutylxanthine↗
PubMed1996

Both multiorgan inflammation and myeloid hyperplasia in RelB-deficient mice are T cell dependent.

Mice with a targeted disruption of RelB, a member of the Rel/NF-kappaB family of transcription factors, have multifocal, mixed inflammatory cell infiltration in several organs, myeloid hyperplasia, and splenomegaly due to extramedullary hemopoiesis. To elucidate the cellular requirements for this complex phenotype, we have bred RelB-deficient (RelB(kappaO)) animals to two strains of immunodeficient mice, recombinase-activating gene-1-deficient (RAG-1(kappaO), lacking B and T cells), and Nur77/N10-transgenic mice (Nur77/N10(TG), lacking only T cells). We also generated mutant mice deficient in both RelB and the p50 subunit of NF-kappaB (p50(kappaO), multiple defects in B cell function). RelB(kappaO)RAG-1(kappaO) and RelB(kappaO)Nur77/N10(TG) mice are disease-free, while RelB(kappaO)p50(kappaO) double-mutant animals develop an even more severe phenotype despite the absence of B cells in the inflammatory infiltrates. Thus, both multiorgan inflammation and myeloid hyperplasia in RelB-deficient mice are T cell dependent, whereas B cells are not crucially involved.

Animals↗
PubMed1996

Neutrophil infiltration, glial reaction, and neurological disease in transgenic mice expressing the chemokine N51/KC in oligodendrocytes.

Chemokines (pro-inflammatory chemoattractant cytokines) are expressed in pathological conditions of the central nervous system (CNS). Previous studies suggested that the CNS is relatively resistant to leukocyte diapedesis after chemokine injection, leaving their functional role unresolved. The CNS function of N51/KC, a neutrophil-selective chemokine, was addressed by expressing N51/KC under control of the myelin basic protein (MBP) promoter in transgenic (tg) mice (MBP-N51/KC mice). CNS-specific N51/KC expression produced remarkable neutrophil infiltration into perivascular, meningeal, and parenchymal sites, demonstrating that this chemokine exerts the multiple functions in vivo required to recruit leukocytes into the CNS. MBP-N5 1/KC mice represent an incisive model for the molecular dissection of neutrophil entry into the CNS. Unexpectedly, MBP-N51/KC mice developed a neurological syndrome of pronounced postural instability and rigidity at high frequency beginning at 40 days of age, well after peak chemokine expression. 68/182 mice in one tg fine were found dead before one year of age, with prominent neurological symptoms premortem in 26 (38%). Florid microglial activation and blood-brain barrier disruption without dysmyelination were the major neuropathological alterations. Late-onset neurological symptoms in MBP-N51/KC mice may indicate unanticipated consequences of CNS chemokine expression.

Animals↗
PubMed1996

Expression of FosB during mouse development: normal development of FosB knockout mice.

FosB, one of the members of the Fos family, is rapidly induced in many cell types upon stimulation and has a stimulatory effect on the proliferation of cultured cells. To understand the tissue distribution of FosB, we have studied its expression pattern by immunohistochemistry in newborn and late embryonic stage mice. These results show that FosB is widely expressed with the highest levels of expression observed in both bony and cartilagenous regions of developing bone. FosB is also detected within whisker follicles, liver, and epidermal tissue. To study the role of FosB in mammalian development we generated embryonic stem (ES) cells, mice and mouse embryo fibroblasts (MEFs) that are deficient for FosB. FosB -/- mice are born at a normal frequency, are fertile and present no obvious phenotypic or histologic abnormalities. FosB-deficient ES cells and MEFs proliferate and enter the S phase normally and we do not find upregulation of other fos family genes to compensate for the lack of FosB. However, we do find that the induction of two AP-1 containing genes is reduced after stimulation of FosB-deficient cells, demonstrating that FosB does indeed play a functional role in transcriptional regulation.

Animals↗