bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallelverarbeitung mit Matlab – DC- und DP-Toolbox im Vergleich (Parallel Processing with Matlab – Comparison between DC- and DP-Toolbox)
Authors: Fink René , Pawletta Sven , Lampe Bernhard P. , Schultalbers Matthias , Pawletta Thorsten
Published: September 2006

Parallelverarbeitung in ingenieurtechnischen Anwendungen bietet die Möglichkeit, umfangreiche Berechnungen, wie z.B. Simulationsstudien oder Optimierungen in deutlich kürzerer Zeit durchzuführen und somit lange Wartezeiten, die besonders im Rahmen von Entwurfsprozessen sehr störend sind, erheblich zu reduzieren. Im Beitrag wird der bisherige Verlauf der Einführung von Parallelverarbeitung in Matlab und ähnlichen Systemen dargestellt. Anhand von zwei konkreten Toolboxen werden typische Architekturen der Middleware, relevante Programmiermodelle und erforderliche Systemvoraussetzungen diskutiert. Abschließend werden die Ergebnisse vergleichender Aufwands- und Leistungsuntersuchungen präsentiert, welche an einer realen Testanwendung aus dem Automotive-Bereich durchgeführt wurden.
Raster-Sonden-Mikroskopie mit Cantilever-Arrays (Scanning Probe Microscopy with Cantilever Arrays)
Authors: Rangelow Ivo W. , Ivanov Tzvetan , Volland Burkhard E. , Dontsov Denis , Sarov Yanko , Ivanova Katerina , Persaud Arun , Filenko Denis , Nikolov Nikolaj , Zier Michael , Schmidt Bernd , Gotszalk Teodor , Sulzback Thomas
Published: September 2006

Der Artikel beschreibt die Realisierung von piezoresistiven Cantilever-Arrays für die Raster-Kraft-Mikroskopie. Sensoren für die Raster-Sonden-Mikroskopie (RSM) sind aus physikalischer Sicht faszinierende Mikrosysteme, da sie durch geeignete Kombination von Physik und Technologie ein neues nanoskopisches Materialverständnis ermöglichen. Die Raster-Sonden-Mikroskopie führt nicht nur zur Eröffnung neuer Horizonte für die Grundlagenforschung, sondern bietet auch die Chance, durch die Entwicklung neuartiger Sensoren und Sensorarrays bisher ungenutzte Wirkmechanismen zu nutzen. Physikalische, biologische und chemische Größen und Wechselwirkungen können auf der Basis von Mikro-Biegebalken (sog. Cantilever) durch die Umwandlung in eine mechanische Reaktion (Verbiegung des Cantilevers) sehr effektiv erfasst und dann wiederum in elektronisch verwertbare Signale umgewandelt werden. In diesem Artikel werden die Grundideen zur Realisierung von selbstoszillierenden piezoresistiven Cantilever-Arrays als System vorgestellt, mit denen Bilder mit hoher Geschwindigkeit aufgenommen werden können.
Renal Outcome of Neonatal Renal Venous Thrombosis: Review of 28 Patients and Effectiveness of Fibrinolytics and Heparin in 10 Patients
Authors: Messinger Yoav , Sheaffer Jan Watterson , Mrozek Jeanne , Smith Clark M. , Sinaiko Alan R.
Published: September 2006

OBJECTIVES. Neonatal renal venous thrombosis is a rare disorder that can result in severe renal damage. To evaluate the experience over 10 years and review the effectiveness of fibrinolytic and/or heparin therapy, chart reviews were performed for newborns with renal venous thrombosis.

PATIENTS, INTERVENTIONS, AND OUTCOME MEASURES. Twenty-eight newborns with renal venous thrombosis were treated at Children's Hospitals and Clinics of Minnesota and Fairview University Medical Center from 1991 to 2001.

RESULTS. Unilateral involvement was noted in 25 neonates (89%) and bilateral involvement in 3 (11%). Unilateral renal venous thrombosis affected mostly term infants, whereas 2 of 3 infants with bilateral renal venous thrombosis were <32 weeks' gestational age (birth weight: 745–1505 g). One mother had antiphospholipid syndrome. Of 11 neonates evaluated for congenital thrombophilia, 1 had the factor V Leiden mutation. Ten neonates received either unfractionated or low molecular weight heparin for 3 days to 7 months. Three infants with unilateral renal venous thrombosis treated with heparin alone did not seem to benefit from such therapy. Seven neonates were treated with fibrinolytics and unfractionated heparin (4 neonates with unilateral renal venous thrombosis and 3 with bilateral renal venous thrombosis). Treatment with fibrinolytics did not result in restoration of renal function in the 4 neonates with unilateral renal venous thrombosis but was associated with return of almost normal function in the 2 neonates with bilateral renal venous thrombosis who received fibrinolytics immediately after renal venous thrombosis diagnosis. Two neonates treated with fibrinolytics suffered bleeding complications at the area of adrenal hemorrhage. Two neonates (not treated for renal venous thrombosis) died as a result of underlying disease.

CONCLUSIONS. Most neonatal renal venous thrombosis is unilateral and does not respond to fibrinolytic therapy and heparin. The use of fibrinolytics may prevent chronic renal failure in neonates with bilateral renal venous thrombosis if begun within 24 hours of diagnosis. Fibrinolytic therapy, however, is associated with a risk of bleeding, specifically if there is an associated adrenal hemorrhage.
Management and Outcomes of Double Aortic Arch in 81 Patients
Authors: Alsenaidi Khalfan , Gurofsky Rebecca , Karamlou Tara , Williams William G. , McCrindle Brian W.
Published: September 2006

OBJECTIVES. Double aortic arch is a common form of complete vascular ring, encircling both the trachea and esophagus, resulting in noncardiac morbidity. We sought to describe management and outcomes in a large single institution clinical series.

PATIENTS AND METHODS. We reviewed the medical charts of all of the patients diagnosed with double aortic arch at age <18 years. Data regarding clinical presentation, anatomy, management, and outcomes were abstracted.

RESULTS. We identified 81 patients (67% males) born between 1964 and 2005 and presenting at a median age of 5 months (range: birth to 10.3 years). Respiratory symptoms were present in 91%, including stridor in 77%. Gastrointestinal symptoms were present in 40%, with choking with feeds being most common. The dominant branch of the double aortic arch was right in 72%. Associated cardiac anomalies were present in 18%, with noncardiac anomalies in 7%. Repair was performed in 79 patients at a median age of 6 months. There were 2 deaths after surgical repair with no late deaths, with Kaplan-Meier survival estimates of 96% at 5 years. Postoperative complications included chylothorax in 9%. Only 1 patient required reoperation. The most common symptoms at most recent follow-up were respiratory (54%) followed by gastrointestinal symptoms (6%). Postoperative tracheal stenosis was documented in 14%, with tracheomalacia in 7%. There were no late reoperations and no evidence of aortic arch obstruction.

CONCLUSIONS. Outcomes are excellent after repair of double aortic arch, although persistent respiratory symptoms are frequent and probably associated with previous compression-related maldevelopment of the trachea and major airways.
Diffuse Pneumocephalus in Neonatal Citrobacter Meningitis
Authors: Alviedo Joseph N. , Sood Beena G. , Aranda Jacob V. , Becker Cristie
Published: September 2006

Pneumocephalus, intracranial air or gas collection, associated with neonatal meningitis is extremely rare. We report the first case in the United States and the second case in the world of intracranial gas accumulation in a neonate with Citrobacter koseri meningitis. The clinical presentation was acute with pneumocephalus demonstrated by cranial sonography and computed tomography. The clinical course was fatal despite the prompt administration of antibiotics.
Severe Hyperphosphatemia and Hypocalcemic Tetany After Oral Laxative Administration in a 3-Month-Old Infant
Authors: Domico Michele B. , Huynh Van , Anand Sudhir K. , Mink Richard
Published: September 2006

A 3-month-old infant presented to the pediatric emergency department with respiratory distress and tetany after ingestion of a phosphate-containing oral laxative. The initial phosphorus level was 38.3 mg/dL. With aggressive fluid resuscitation and intravenous calcium administration, the infant completely recovered. Although the risks of phosphate-containing enemas are well described, life-threatening hyperphosphatemia can also result from administration of phosphate-containing oral laxatives. Aggressive fluid hydration is the mainstay of treatment. Intravenous calcium administration may be necessary to avoid hemodynamic collapse despite the theoretical possibility of metastatic calcifications. Physicians should be alerted to the possibility of phosphate toxicity and hypocalcemic tetany in young children when treated with over-the-counter laxatives. Caregivers should be advised not to administer over-the-counter laxatives to infants without physician supervision.
The sarcoplasmic–endoplasmic reticulum Ca2+ ATPase 2b regulates the Ca2+ transients elicited by P2Y2 activation in PC Cl3 thyroid cells
Authors: Ulianich Luca , Elia Maria Giovanna , Treglia Antonella Sonia , Muscella Antonella , Di Jeso Bruno , Storelli Carlo , Marsigliante Santo
Published: September 2006

In PC Cl3 cells, a continuous, fully differentiated rat thyroid cell line, P2Y2 purinoceptor activation provoked a transient increase of [Ca2+]i, followed by a decreasing sustained phase. The α and β1 protein kinase C (PKC) inhibitor Gö6976 decreased the rate of decrement to the basal [Ca2+]i level and increased the peak of Ca2+ entry of the P2Y2-provoked Ca2+transients. These effects of Gö 6976 were not caused by an increased permeability of the plasma membrane, since the Mn2+ and Ba2+ uptake were not changed by Gö 6976. Similarly, the Na+/Ca2+ exchanger was not implicated, since the rate of decrement to the basal [Ca2+]i level was equally decreased in physiological and Na+-free buffers, in the presence of Gö 6976. On the contrary, the activity of the sarcoplasmic–endoplasmic reticulum Ca2+ATPase (SERCA) 2b was profoundly affected by Gö 6976 since the drug was able to completely inhibit the stimulation of the SERCA 2b activity elicited by P2-purinergic agonists. Finally, the PKC activator phorbol myristate acetate had effects opposite to Gö 6976, in that it markedly increased the rate of decrement to the basal [Ca2+]i level after P2Y2 stimulation and also increased the activity of SERCA 2b. These results suggest that SERCA 2b plays a role in regulating the sustained phase of Ca2+ transients caused by P2Y2 stimulation.
Islet neogenesis associated protein transgenic mice are resistant to hyperglycemia induced by streptozotocin
Authors: Taylor-Fishwick David A , Bowman Angela , Hamblet Natasha , Bernard Paul , Harlan David M , Vinik Aaron I
Published: September 2006

Islet neogenesis associated protein (INGAP) is a protein factor that can stimulate new islet mass from adult pancreatic progenitor cells. In models of islet neogenesis, INGAP expression is elevated in pancreatic acinar cells. Using a transgenic model to drive a sustained expression of INGAP in pancreatic acinar cells, we have identified a protection to chemical-induced hyperglycemia. A sustained expression of INGAP during development did not perturb islet development or basal blood glucose homeostasis, although β-cell mass and pancreatic insulin content were significantly increased in the INGAP transgenic mice. When challenged with a diabetogenic dose of streptozotocin (STZ), mice carrying the INGAP transgene did not become hyperglycemic. In contrast, wild-type mice became and remained hyperglycemic, blood glucose > 550 mg/dl. The serum insulin levels and islet morphology were preserved in the transgenic mice after STZ treatment. These data suggest that the sustained expression of INGAP in the acinar pancreas confers resistance to a diabetogenic insult. The INGAP transgenic mouse provides a new model to uncover factors that are protective to diabetes onset and biomarkers to track β-cell pathology.
Serotonin stimulates GnRH secretion through the c-Src-PLC γ1 pathway in GT1–7 hypothalamic cells
Authors: Kim Hyeon Soo , Yumkham Sanatombi , Choi Jang Hyun , Son Gi Hoon , Kim Kyungjin , Ryu Sung Ho , Suh Pann-Ghill
Published: September 2006

Serotonin is a neurotransmitter that alters the hypothalamic-pituitary-adrenal axis. To date, however, the molecular mechanisms underlying the role of serotonin in hormone secretion have remained largely unclear. In this study, we report that serotonin activates phospholipase C (PLC) γ1 in an Src-dependent manner in hypothalamic GT1–7 cells, and that pretreatment with either 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazole [3, 4-d] pyrimidine, an Src-kinase inhibitor, or U73122, a PLC inhibitor, attenuates the serotonin-induced increase in calcium levels. Also, PLC γ1 binds to c-Src through the Src-homology (SH) 223 domain upon serotonin treatment. Moreover, calcium increase is alleviated in the cells transientlyexpressing SH223 domain-deleted PLC γ1 or lipase inactive mutant PLC γ1, as compared with cells transfected with wild-type PLC γ1. Furthermore, the inhibition of the activities of either PLC or Src results in a significant diminution of the serotonin-induced release of gonadotropin-releasing hormone (GnRH). In addition, the results of our small-interfering RNA experiment confirm that endogenous PLC γ1 is a prerequisite for serotonin-mediated signaling pathways. Taken together, our findings demonstrate that serotonin stimulates the release of GnRH through the Src-PLC γ1 pathway, via the modulation of intracellular calcium levels.
Influence of porcine genotype on the abundance of thyroid hormones and leptin in sow milk and its impact on growth, metabolism and expression of key adipose tissue genes in offspring
Authors: Mostyn Alison , Sebert Sylvain , Litten Jennie C , Perkins Katharine S , Laws John , Symonds Michael E , Clarke Lynne
Published: September 2006

Neonatal mortality is greater in commercial porcine genotypes, compared with the ancient Meishan breed that rapidly lay down adipose tissue; this may be related to hormones, such as triiodothyronine (T3) or leptin. Leptin is present in maternal milk; however, the extent to which this supply provides the neonate with leptin is unknown, but may play a role in growth and development. We investigated whether thyroid hormones and leptin concentrations in maternal milk differed between genotypes; and whether this influenced piglet concentrations or expression of genes involved in adipose tissue regulation. Eight Meishan and six commercial sows were entered into the study and milk samples from the day of parturition to day 4 postpartum was taken daily. The median birth weight piglet in each litter had a daily venous blood sample taken and was euthanised on day 4. Gene expressions of IGF-I, IGF-binding protein 3 (IGFBP-3), peroxisome proliferators activated receptor (PPAR)γ and glucocorticoid receptor (GR) were measured in adipose tissue using real-time PCR. T3 was increased in Meishan milk, but not in piglet plasma. Milk thyroxine was similar between breeds but commercial piglet levels were significantly higher. Leptin was higher in commercial sow milk throughout the study. Milk leptin was strongly correlated to plasma leptin during the first postnatal days and also to organ and body weight in Meishan piglets that also had significantly higher expression of GR, but not IGF-I, IGFBP-3 or PPARγ. In conclusion, we have found a significant disparity in the provision of thyroid hormones in Meishan and commercial sow’s milk. These changes are not always translated to plasma concentrations of hormone in the piglet. Leptin appears to have a stronger role in growth and development in the Meishan genotype compared with commercial; along with the increased GR expression, this may also represent a potential mechanism behind the rapid accumulation of adipose tissue in Meishan piglets.
Identification of prostatic-secreted proteins in mice by mass spectrometric analysis and evaluation of lobe-specific and androgen-dependent mRNA expression
Authors: Fujimoto Nariaki , Akimoto Yukimi , Suzuki Tomoharu , Kitamura Shigeyuki , Ohta Shigeru
Published: September 2006

Rats and guinea pigs have frequently been used to study the development of the prostate and the mechanism of androgen action, but the mouse prostate has also become an attractive model for prostate research, because an enormous range of genetically altered mice is now available. However, the secretion of proteins in the mouse prostate has not yet been thoroughly investigated. In the present study, major secreted proteins from the ventral prostate (VP), dorso-lateral prostate (DLP), and anterior prostate (AP) of mice were identified by means of 2D-gel electrophoresis followed by MALDI-TOF mass spectrometric analysis. A quantitative reverse transcriptase-PCR method was further employed to examine the androgen-dependent transcriptional regulation of the identified proteins. Proteome analysis revealed that the VP secretes spermine-binding protein, serine protease inhibitor Kazal type-3, and a 91 kDa hypothetical scavenger receptor (AK035662). DLP and AP secrete a protein similar to immunoglobulin-binding protein, immunoglobulin-binding protein-like protein, and one of the experimental autoimmune prostatitis antigen proteins (EAPA2). Peroxiredoxin-6, glucose-regulated protein 78, zinc-α2-glycoprotein, and phospholipase Cα are also secreted. Castration of animals led to a decrease in the mRNAs of these secreted proteins, although the extents of changes varied greatlyamong different lobes. We present here an outlined view of mouse prostate secretion, which should contribute to an understanding of the biological functions of the prostate gland, as well as the androgen dependency of prostate secretion.
Involvement of calpain and synaptotagmin Ca2+ sensors in hormone secretion from excitable endocrine cells
Authors: Aganna Ebun , Burrin Jacky M , Hitman Graham A , Turner Mark D
Published: September 2006

The requirement for Ca2+ to regulate hormone secretion from endocrine cells is long established, but the precise function of Ca2+ sensors in stimulus–secretion coupling remains unclear. In the current study, we examined the expression of calpain and synaptotagmin in INS-1 pancreatic and GH3 and AtT20 pituitary cells, and investigated the sensitivity of hormone secretion from these cells to inhibition of the calpain family of cysteine proteases. Little difference in expression of μ-calpain was observed between the different endocrine cells. However, AtT20 cells did exhibit an extremely low abundance of both m-calpain and the 54 kDa isoform of calpain-10 relative to their expression in INS-1 and GH3 cells. Interestingly, secretagog-stimulated secretion from both INS-1 and GH3 cells was completely abolished following pre-incubation with the cysteine protease inhibitor E64, whereas stimulated secretion from AtT20 cells was modest and completely insensitive to E64 inhibition. These results are in stark contrast to synaptotagmin data. Synaptotagmin expression in AtT20 cells is abundant, whereas INS-1 cells express extremely low levels of this Ca2+ sensor, relative to the pituitary cells. We hypothesize that the expression pattern of calpain and synaptotagmin isoforms may reflect alternative mechanisms of stimulus–secretion coupling in excitable endocrine cells.
UbcH7 interacts with the glucocorticoid receptor and mediates receptor autoregulation
Authors: Garside Helen , Waters Charlotte , Berry Andy , Rice Lisa , Ardley Helen C , White Anne , Robinson Philip A , Ray David
Published: September 2006

Unlike other nuclear receptors, transactivation by the glucocorticoid receptor (GR) is increased by the inhibition of the ubiquitin/proteasome pathway. Here, we demonstrate that the ubiquitin-conjugating enzyme (E2), UbcH7, physically interacts with the GR and, when overexpressed, reduces the ability of the receptor to upregulate gene expression. Chemical inhibition of the 26S proteasome abolished the downregulation effect of overexpressed UbcH7, suggesting a role for the 26S proteasome, and GR protein stability in mediating the UbcH7 effect. Furthermore, a UbcH7 dominant negative mutant (C89S), unable to transfer ubiquitin, failed to repress GR transactivation. Indeed, overexpression of the mutant UbcH7 was sufficient to augment GR transactivation to levels achieved using the proteasome inhibitor MG132, but there was no further induction when MG132 and the UbcH7 mutant were used together. Expression of the dominant negative UbcH7 abolished ligand-dependent downregulation of GR protein, suggesting that the UbcH7 effect was mediated by regulation of GR protein concentration. Taken together, these data show that UbcH7 is a key regulator of GR turnover and glucocorticoid sensitivity.
Gastric estrogen directly induces ghrelin expression and production in the rat stomach
Authors: Sakata Ichiro , Tanaka Toru , Yamazaki Mami , Tanizaki Takashi , Zheng Zhao , Sakai Takafumi
Published: September 2006

Ghrelin, an endogenous ligand for the GH secretagogue receptor, is predominantly produced in the stomach. Little is known about the regulation mechanism of gastric ghrelin. Here, we report that estrogen synthesized in the stomach induces rat gastric ghrelin gene expression and production. We established a gastric ghrelin cell enrichment method using Percoll centrifugation and then studied the effect of estrogen and/or its antagonist on ghrelin expression and production. Treatment with estrogen for 8 h significantly increased the level of ghrelin expression, and ICI-182 780, an estrogen receptor (ER) antagonist, completely reversed this effect. Reverse transcriptase-PCR analysis clearly showed that ERα and aromatase are expressed in the female rat stomach. Moreover, treatment with an aromatase inhibitor, 4-hydro-xyandrostenedione (formestane), significantly decreased the level of ghrelin mRNA expression in minced stomach tissue. In vivo studies revealed that the ghrelin mRNA expression and production did not change in gonadectomized rat 3 weeks after surgery. These results strongly suggest that estrogen produced in the stomach directly induces ghrelin expression and production in both female and male rat stomachs.
Identification, characterization, and quantitative expression analysis of rainbow trout myostatin-1a and myostatin-1b genes
Authors: Garikipati Dilip K , Gahr Scott A , Rodgers Buel D
Published: September 2006

Myostatin is a potent negative regulator of skeletal muscle growth. Although several cDNA clones have been characterized in different vertebrates, the genomic organization and bioactivity of non-mammalian homologs have not. The intron/exon organization and promoter subsequence analysis of two rainbow trout myostatin genes, rtMSTN-1a and rtMSTN-1b (formerly 1 and 2 respectively), as well as a quantitative assessment of their embryonic, larval, and adult tissue expression profiles are reported herein. Each gene was similarly organized into three exons of 490, 368, and 1600 bp for MSTN-1a and 486, 386, and 1419 bp for MSTN-1b. Comparative mapping of coding regions from several vertebrate myostatin genes revealed a common organization between species, including conserved pre-mRNA splice sites; the first among the fishes and the second across all vertebrate species. In silico subsequence analysis of the promoter regions identified E-boxes and other putative myogenic response elements. However, the number and diversity of elements were considerably less than those found in mammalian promoters or in the recently characterized zebrafish MSTN-2 gene. A quantitative analysis of the embryonic expression profile for both genes indicates that rtMSTN-1a expression is consistently greater than that of rtMSTN-1b and neither gene is significantly expressed throughout gastrulation. Expression of both steadily increases fourfold during somitogenesis and subsides as this period ends. After eyeing, however, rtMSTN-1a mRNA levels ultimately rise 20-fold by day 49 and peak before hatching and yolk sac absorption (YSA). Levels of rtMSTN-1b rise similarly, but do not peak before YSA. An analysis of adult (2-year-old fish) tissue expression indicates that both transcripts are present in most tissues although levels are highest in brain, testes, eyes, muscle, and surprisingly spleen. These studies suggest that strong selective pressures have preserved the genomic organization of myostatin genes throughout evolution. However, the different expression profiles and putative promoter elements in fishes versus mammals suggests that limitations in myostatin function may have evolved recently.
GH in the dwarf dopaminergic D2 receptor knockout mouse: somatotrope population, GH release, and responsiveness to GH-releasing factors and somatostatin
Authors: García-Tornadú Isabel , Rubinstein Marcelo , Gaylinn Bruce D , Hill David , Arany Edith , Low Malcolm J , Díaz-Torga Graciela , Becu-Villalobos Damasia
Published: September 2006

Recently, the importance of the dopaminergic D2 receptor (D2R) subtype in normal body growth and neonatal GH secretion has been highlighted. Disruption of D2R alters the GHRH–GH–IGF-I axis and impairs body growth in adult male mice. The D2R knockout (KO) dwarf mouse has not been well characterized; we therefore sought to determine somatotrope function in the adult pituitary. Using immunohistochemistry and confocal microscopy, we found a significant decrease in the somatotrope population in pituitaries from KO mice (P=0.043), which was paralleled by a decreased GH output from pituitary cells cultured in vitro. In cells from adult mice the response amplitude to GHRH differed between genotypes (lower in KO), but this difference was less dramatic after taking into account the lower basal release and hormone content in the KO cells. Furthermore, there were no significant differences in cAMP generation in response to GHRH between genotypes. By Western blot, GHRH-receptor in pituitary membranes from KO mice was reduced to 46% of the level found in wildtype (WT) mice (P=0.016). Somatostatin induced a concentration-dependent decrease in GH and prolactin (PRL) secretion in both genotypes, and 1×10−7 M ghrelin released GH in cells from both genotypes (P=0.017) in a proportionate manner to basal levels. These results suggest that KO somatotropes maintain a regulated secretory function. Finally, we tested the direct effect of dopamine on GH and PRL secretion in cells from both genotypes at 20 days and 6 months of life. As expected, we found that dopamine could reduce PRL levels at both ages in WT mice but not in KO mice, but there was no consistent effect of the neurotransmitter on GH release in either genotype at the ages studied. The present study demonstrates that in the adult male D2R KO mouse, there is a reduction in pituitary GH content and secretory activity. Our results point to an involvement of D2R signaling at the hypothalamic level as dopamine did not release GH acting at the pituitary level either in 1-month-old or adult mice. The similarity of the pituitary defect in the D2R KO mouse to that of GHRH-deficient models suggests a probable mechanism. A loss of dopamine signaling via hypothalamic D2Rs at a critical age causes the reduced release of GHRH from hypophyseotropic neurons leading to inadequate clonal expansion of the somatotrope population. Our data also reveal that somatotrope cell number is much more sensitive to changes in neonatal GHRH input than their capacity to develop properly regulated GH-secretory function.
The involvement of epoxygenase metabolites of arachidonic acid in cAMP-stimulated steroidogenesis and steroidogenic acute regulatory protein gene expression
Authors: Wang XingJia , Shen Chwan-Li , Dyson Matthew T , Yin Xianling , Schiffer Randolph B , Grammas Paula , Stocco Douglas M
Published: September 2006

The essential role of arachidonic acid (AA) in steroidogenesis has been previously demonstrated. The present study continues the investigation into how AA regulates steroidogenesis by examining the effects of epoxygenase-derived AA metabolites on cAMP-stimulated steroidogenic acute regulatory (StAR) gene expression and steroid hormone production in MA-10 mouse Leydig cells. The HPLC analysis of cell extracts from MA-10 cells treated with the cAMP analog dibutyryl cAMP (dbcAMP) demonstrated an increase in three epoxygenase-generated AA metabolites: 5,6-epoxyeicosatrienoic acid (EET), 8,9-EET, and 11,12-EET. Incubating MA-10 cells with each of the EETs induced a dose–dependent increase in StAR protein expression and steroid hormone production in the presence of dbcAMP. These metabolites also significantly enhanced StAR gene transcription as determined by luciferase assays of StAR promoter activity and reverse transcriptase-PCR analysis of StAR mRNA levels. While the EETs enhanced steroidogenesis, inhibiting the activity of protein kinase A (PKA) abolished the stimulatory effects of these AA metabolites on StAR expression and steroid hormone production. This study suggests that cAMP stimulation of MA-10 cells increases epoxygenase-generated AA metabolites and the co-action of these metabolites with PKA significantly increases StAR gene expression and steroid hormone production.
Rosiglitazone Treatment Enhances Acute AMP-Activated Protein Kinase–Mediated Muscle and Adipose Tissue Glucose Uptake in High-Fat–Fed Rats
Authors: Ye Ji-Ming , Dzamko Nick , Hoy Andrew J. , Iglesias Miguel A. , Kemp Bruce , Kraegen Edward
Published: September 2006

AMP-activated protein kinase (AMPK) has been implicated in the insulin-sensitizing actions of thiazolidinediones (TZDs), but it is not known whether TZD treatment can enhance tissue glucose uptake in response to AMPK activation. The present study investigated the influence of the TZD rosiglitazone on glucose turnover induced by intravenous infusion of the AMPK activator 5-aminoimidazole 4-carboxamide riboside (AICAR) under euglycemic and iso-insulinemic conditions in insulin-resistant high-fat–fed rats. We found that rosiglitazone treatment significantly enhanced AICAR-stimulated whole-body glucose disposal by 27% in high-fat–fed rats, and a 44% greater glucose infusion rate (both P < 0.01 vs. vehicle control rats) was required to maintain euglycemia. Along with this, both AICAR-stimulated glucose uptake and glucose incorporation into glycogen in muscle and adipose tissue were enhanced (P < 0.05). The enhanced glucose uptake and glycogen synthesis in muscle were associated with increased activity of total AMPK and the AMPKα2 subunit. In comparison, these effects were not apparent in rats fed standard rodent diet. Thus, our findings suggest that in addition to ameliorating insulin resistance, TZDs may enhance AMPK-stimulated glucose clearance into peripheral tissues in insulin-resistant states.
Palmitate-Mediated Downregulation of Peroxisome Proliferator–Activated Receptor-γ Coactivator 1α in Skeletal Muscle Cells Involves MEK1/2 and Nuclear Factor-κB Activation
Authors: Coll Teresa , Jové Mireia , Rodríguez-Calvo Ricardo , Eyre Elena , Palomer Xavier , Sánchez Rosa M. , Merlos Manuel , Laguna Juan Carlos , Vázquez-Carrera Manuel
Published: September 2006

The mechanisms by which elevated levels of free fatty acids cause insulin resistance are not well understood. Previous studies have reported that insulin-resistant states are characterized by a reduction in the expression of peroxisome proliferator–activated receptor-γ coactivator (PGC)-1, a transcriptional activator that promotes oxidative capacity in skeletal muscle cells. However, little is known about the factors responsible for reduced PGC-1 expression. The expression of PGC-1 mRNA levels was assessed in C2C12 skeletal muscle cells exposed to palmitate either in the presence or in the absence of several inhibitors to study the biochemical pathways involved. We report that exposure of C2C12 skeletal muscle cells to 0.75 mmol/l palmitate, but not oleate, reduced PGC-1α mRNA levels (66%; P < 0.001), whereas PGC-1β expression was not affected. Palmitate led to mitogen-activated protein kinase (MAPK)–extracellular signal–related kinase (ERK) 1/2 (MEK1/2) activation. In addition, pharmacological inhibition of this pathway by coincubation of the palmitate-exposed cells with the MEK1/2 inhibitors PD98059 and U0126 prevented the downregulation of PGC-1α. Furthermore, nuclear factor-κB (NF-κB) activation was also involved in palmitate-mediated PGC-1α downregulation, since the NF-κB inhibitor parthenolide prevented a decrease in PGC-1α expression. These findings indicate that palmitate reduces PGC-1α expression in skeletal muscle cells through a mechanism involving MAPK-ERK and NF-κB activation.
Bradykinin Augments Insulin-Stimulated Glucose Transport in Rat Adipocytes via Endothelial Nitric Oxide Synthase–Mediated Inhibition of Jun NH2-Terminal Kinase
Authors: Beard Kristin M. , Lu Huogen , Ho Karen , Fantus I. George
Published: September 2006

An increase in bradykinin has been suggested to contribute to the enhanced insulin sensitivity observed in the presence of ACE inhibitors. To investigate a potential direct, nonvascular effect on an insulin target tissue, the effect of bradykinin on glucose uptake and insulin signaling was studied in primary rat adipocytes. Whereas basal glucose uptake was not altered, bradykinin augmented insulin-stimulated glucose uptake twofold, which was blocked by HOE-140, a bradykinin B2 receptor antagonist. The bradykinin effect on glucose uptake was nitric oxide (NO) dependent, mimicked by NO donors and absent in adipocytes from endothelial NO synthase−/− mice. Investigation of insulin signaling revealed that bradykinin enhanced insulin receptor substrate-1 (IRS-1) Tyr phosphorylation, Akt/protein kinase B phosphorylation, and GLUT4 translocation. In contrast, insulin-stimulated extracellular signal–regulated kinase1/2 and Jun NH2-terminal kinase (JNK) activation were decreased in the presence of bradykinin, accompanied by decreased IRS-1 Ser307 phosphorylation. Furthermore, bradykinin did not enhance insulin action in the presence of the JNK inhibitor, SP-600125, or in adipocytes from JNK1−/− mice. These data indicate that bradykinin enhances insulin sensitivity in adipocytes via an NO-dependent pathway that acts by modulating the feedback inhibition of insulin signaling at the level of IRS-1.
Altered Gene Expression Related to Glomerulogenesis and Podocyte Structure in Early Diabetic Nephropathy of db/db Mice and Its Restoration by Pioglitazone
Authors: Makino Hisashi , Miyamoto Yoshihiro , Sawai Kazutomo , Mori Kiyoshi , Mukoyama Masashi , Nakao Kazuwa , Yoshimasa Yasunao , Suga Shin-ichi
Published: September 2006

Glomerular injury plays a pivotal role in the development of diabetic nephropathy. To elucidate molecular mechanisms underlying diabetic glomerulopathy, we compared glomerular gene expression profiles of db/db mice with those of db/m control mice at a normoalbuminuric stage characterized by hyperglycemia and at an early stage of diabetic nephropathy with elevated albuminuria, using cDNA microarray. In db/db mice at the normoalbuminuric stage, hypoxia-inducible factor-1α (HIF-1α), ephrin B2, glomerular epithelial protein 1, and Pod-1, which play key roles in glomerulogenesis, were already upregulated in parallel with an alteration of genes related to glucose metabolism, lipid metabolism, and oxidative stress. Podocyte structure-related genes, actinin 4α and dystroglycan 1 (DG1), were also significantly upregulated at an early stage. The alteration in the expression of these genes was confirmed by quantitative RT-PCR. Through pioglitazone treatment, gene expression of ephrin B2, Pod-1, actinin 4α, and DG1, as well as that of oxidative stress and lipid metabolism, was restored concomitant with attenuation of albuminuria. In addition, HIF-1α protein expression was partially attenuated by pioglitazone. These results suggest that not only metabolic alteration and oxidative stress, but also the alteration of gene expression related to glomerulogenesis and podocyte structure, may be involved in the pathogenesis of early diabetic glomerulopathy in type 2 diabetes.
Lipin Expression Is Attenuated in Adipose Tissue of Insulin-Resistant Human Subjects and Increases With Peroxisome Proliferator–Activated Receptor γ Activation
Authors: Yao-Borengasser Aiwei , Rasouli Neda , Varma Vijayalakshmi , Miles Leslie M. , Phanavanh Bounleut , Starks Tasha N. , Phan Jack , Spencer Horace J. , McGehee Robert E. , Reue Karen , Kern Philip A.
Published: September 2006

Lipin-α and -β are the alternatively spliced gene products of the Lpin1 gene, whose product lipin is required for adipocyte differentiation. Lipin deficiency causes lipodystrophy, fatty liver, and insulin resistance in mice, whereas adipose tissue lipin overexpression results in increased adiposity but improved insulin sensitivity. To assess lipin expression and its relation to insulin resistance in humans, we examined lipin-α and -β mRNA levels in subjects with normal or impaired glucose tolerance. We found higher expression levels of both lipin isoforms in lean, insulin-sensitive subjects. When compared with normal glucose-tolerant subjects, individuals with impaired glucose tolerance were more insulin resistant, demonstrated higher levels of intramyocellular lipids (IMCLs), and expressed ∼50% lower levels of lipin-α and -β. In addition, there was a strong inverse correlation between adipose tissue lipin expression and muscle IMCLs but no evidence for an increase in muscle lipid oxidation. After treatment of the impaired glucose-tolerant subjects with insulin sensitizers for 10 weeks, pioglitazone (but not metformin) resulted in a 60% increase in the insulin sensitivity index (Si) and a 32% decrease in IMCLs (both P < 0.01), along with an increase in lipin-β (but not lipin-α) expression by 200% (P < 0.005). Lipin expression in skeletal muscle, however, was not related to obesity or insulin resistance. Hence, high adipose tissue lipin expression is found in insulin-sensitive subjects, and lipin-β expression increases following treatment with pioglitazone. These results suggest that increased adipogenesis and/or lipogenesis in subcutaneous fat, mediated by the LPIN1 gene, may prevent lipotoxicity in muscle, leading to improved insulin sensitivity.
Insulin Restores Metabolic Function in Cultured Cortical Neurons Subjected to Oxidative Stress
Authors: Duarte Ana I. , Proença Teresa , Oliveira Catarina R. , Santos Maria S. , Rego A. Cristina
Published: September 2006

We previously demonstrated that insulin has a neuroprotective role against oxidative stress, a deleterious condition associated with diabetes, ischemia, and age-related neurodegenerative diseases. In this study, we investigated the effect of insulin on neuronal glucose uptake and metabolism after oxidative stress in rat primary cortical neurons. On oxidative stress, insulin stimulates neuronal glucose uptake and subsequent metabolism into pyruvate, restoring intracellular ATP and phosphocreatine. Insulin also increases intracellular and decreases extracellular adenosine, counteracting the effect of oxidative stress. Insulin effects are apparently mediated by phosphatidylinositol 3-K and extracellular signal–regulated kinase signaling pathways. Extracellular adenosine under oxidative stress is largely inhibited after blockade of ecto-5′-nucleotidase, suggesting that extracellular adenosine results preferentially from ATP release and catabolism. Moreover, insulin appears to interfere with the ATP release induced by oxidative stress, regulating extracellular adenosine levels. In conclusion, insulin neuroprotection against oxidative stress–mediated damage involves 1) stimulation of glucose uptake and metabolism, increasing energy levels and intracellular adenosine and, ultimately, uric acid formation and 2) a decrease in extracellular adenosine, which may reduce the facilitatory activity of adenosine receptors.
Whole-Body Proteolysis Rate Is Elevated in HIV-Associated Insulin Resistance
Authors: Reeds Dominic N. , Cade W. Todd , Patterson Bruce W. , Powderly William G. , Klein Samuel , Yarasheski Kevin E.
Published: September 2006

Type 2 diabetes is characterized by impaired glucose tolerance (IGT) and insulin resistance with respect to glucose metabolism but not amino acid metabolism. We examined whether whole-body leucine and protein metabolism are dysregulated in HIV-infected individuals with IGT. Glucose and leucine kinetics were measured under fasting insulin conditions and during euglycemic hyperinsulinemia using primed-constant infusions of 2H2-glucose and 13C-leucine in 10 HIV-seronegative control subjects, 16 HIV+ subjects with normal glucose tolerance, and 21 HIV+IGT subjects. Glucose disposal rate during hyperinsulinemia was lower in HIV+IGT than the other two groups. Absolute plasma leucine levels and rate of appearance (whole-body proteolysis) were higher in HIV+IGT at all insulin levels but declined in response to hyperinsulinemia in parallel to those in the other two groups. HIV+IGT had greater visceral adiposity, fasting serum interleukin (IL)-8 and free fatty acid levels, and higher lipid oxidation rates during the clamp than the other two groups. These findings implicate several factors in the insulin signaling pathway, which may be further dysregulated in HIV+IGT, and support the notion that insulin signaling pathways for glucose and leucine metabolism may be disrupted by increased proinflammatory adipocytokines (IL-8) and increased lipid oxidation. Increased proteolysis may provide amino acids for gluconeogenesis, exacerbating hyperglycemia in HIV.
Central and Opposing Effects of IGF-I and IGF-Binding Protein-3 on Systemic Insulin Action
Authors: Muzumdar Radhika H. , Ma Xiaohui , Fishman Sigal , Yang Xiaoman , Atzmon Gil , Vuguin Patricia , Einstein Francine H. , Hwang David , Cohen Pinchas , Barzilai Nir
Published: September 2006

IGF-I is recognized as an insulin sensitizer at the liver and muscle, while recent evidence suggests that IGF-binding protein (IGFBP)-3 acts as an insulin antagonist. As there is a paucity of IGF-I receptors in the liver and as the IGF-IGFBP system in the central nervous system is emerging as physiologically relevant, we examined whether the effects of IGF-I and IGFBP-3 on insulin action are mediated through central mechanisms. Intracerebroventricular (ICV) infusion of IGF-I during the insulin clamp (3 mU · kg−1 · min−1) resulted in significant improvement in hepatic insulin action (50%, P < 0.05). In contrast, ICV infusion of IGFBP-3 significantly impaired insulin action at the liver (45% increase in hepatic glucose production, P < 0.01). While IGF-I marginally increased peripheral glucose uptake, IGFBP-3 significantly decreased peripheral glucose uptake (∼30%, P < 0.01). As the nuclear localization signal mutant IGFBP-3, which has a normal affinity to IGFs but binds other IGFBP-3 partners poorly and fails to normally internalize, has reduced central activity on metabolism, we conclude that the effects of IGFBP-3 on the hypothalamus involve activity mediated by interfacing with other molecules in addition to IGFs. Marked, opposing, and independent physiological effects of IGF-I and IGFBP-3 through central mechanisms may have implications on potential strategies in specific modulation of peripheral insulin action.
Bardet-Biedl Syndrome Gene Variants Are Associated With Both Childhood and Adult Common Obesity in French Caucasians
Authors: Benzinou Michael , Walley Andrew , Lobbens Stephan , Charles Marie-Aline , Jouret Béatrice , Fumeron Frédéric , Balkau Beverley , Meyre David , Froguel Philippe
Published: September 2006

Bardet-Biedl syndrome (BBS) is a rare developmental disorder with the cardinal features of abdominal obesity, retinopathy, polydactyly, cognitive impairment, renal and cardiac anomalies, hypertension, and diabetes. BBS is genetically heterogeneous, with nine genes identified to date and evidence for additional loci. In this study, we performed mutation analysis of the coding and conserved regions of BBS1, BBS2, BBS4, and BBS6 in 48 French Caucasian individuals. Among the 36 variants identified, 12 were selected and genotyped in 1,943 French-Caucasian case subjects and 1,299 French-Caucasian nonobese nondiabetic control subjects. Variants in BBS2, BBS4, and BBS6 showed evidence of association with common obesity in an age-dependent manner, the BBS2 single nucleotide polymorphism (SNP) being associated with common adult obesity (P = 0.0005) and the BBS4 and BBS6 SNPs being associated with common early-onset childhood obesity (P = 0.0003) and common adult morbid obesity (0.0003 < P < 0.007). The association of the BBS4 rs7178130 variant was found to be supported by transmission disequilibrium testing (P = 0.006). The BBS6 variants also showed nominal evidence of association with quantitative components of the metabolic syndrome (e.g., dyslipidemia, hyperglycemia), a complication previously described in BBS patients. In summary, our preliminary data suggest that variations at BBS genes are associated with risk of common obesity.
Leptin Deficiency Unmasks the Deleterious Effects of Impaired Peroxisome Proliferator–Activated Receptor γ Function (P465L PPARγ) in Mice
Authors: Gray Sarah L. , Nora Edoardo Dalla , Grosse Johannes , Manieri Monia , Stoeger Tobias , Medina-Gomez Gema , Burling Keith , Wattler Sigrid , Russ Andreas , Yeo Giles S.H. , Chatterjee V. Krishna , O’Rahilly Stephen , Voshol Peter J. , Cinti Saverio , Vidal-Puig Antonio
Published: September 2006

Peroxisome proliferator–activated receptor (PPAR)γ is a key transcription factor facilitating fat deposition in adipose tissue through its proadipogenic and lipogenic actions. Human patients with dominant-negative mutations in PPARγ display lipodystrophy and extreme insulin resistance. For this reason it was completely unexpected that mice harboring an equivalent mutation (P465L) in PPARγ developed normal amounts of adipose tissue and were insulin sensitive. This finding raised important doubts about the interspecies translatability of PPARγ-related findings, bringing into question the relevance of other PPARγ murine models. Here, we demonstrate that when expressed on a hyperphagic ob/ob background, the P465L PPARγ mutant grossly exacerbates the insulin resistance and metabolic disturbances associated with leptin deficiency, yet reduces whole-body adiposity and adipocyte size. In mouse, coexistence of the P465L PPARγ mutation and the leptin-deficient state creates a mismatch between insufficient adipose tissue expandability and excessive energy availability, unmasking the deleterious effects of PPARγ mutations on carbohydrate metabolism and replicating the characteristic clinical symptoms observed in human patients with dominant-negative PPARγ mutations. Thus, adipose tissue expandability is identified as an important factor for the development of insulin resistance in the context of positive energy balance.
Role of a Proline Insertion in the Insulin Promoter Factor 1 (IPF1) Gene in African Americans With Type 2 Diabetes
Authors: Elbein Steven C. , Wang Xiaoqin , Karim Mohammad A. , Freedman Barry I. , Bowden Donald W. , Shuldiner Alan R. , Brancati Frederick L. , Kao Wen Hong Linda
Published: September 2006

African Americans have twice the prevalence of type 2 diabetes as Caucasians and much greater genetic diversity. We identified an inframe insertion of a proline in the insulin promoter factor 1 (IPF1) gene (InsCCG243), which was relatively common (minor allele frequency ∼0.08) in African Americans and showed a trend to association with type 2 diabetes in preliminary studies. An earlier French study identified InsCCG243 as a cause of autosomal dominant diabetes. To determine the role of this variant in African Americans, we examined an additional population from North Carolina (n = 368) and a subset of African-American participants from the Atherosclerosis Risk in Communities (ARIC) study (n = 1,741). We also looked for segregation in 66 African-American families and for a role in insulin secretion in 112 nondiabetic subjects. InsCCG243 did not increase the risk of type 2 diabetes (P = 0.16 in North Carolina; P = 0.97 in the ARIC study) and did not segregate with type 2 diabetes in families. However, we found suggestive evidence for reduced insulin response to glucose (P = 0.05). Neither indirect measures of β-cell mass nor β-cell compensation were altered (P > 0.1). InsCCG243 does not act in a dominant, highly penetrant fashion in African Americans and is not a significant risk factor for type 2 diabetes in this population.