bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutral Evolution of Multiple Quantitative Characters: A Genealogical Approach
Authors: Griswold Cortland K , Logsdon Benjamin , Gomulkiewicz Richard
Published: March 2007

The G matrix measures the components of phenotypic variation that are genetically heritable. The structure of G, that is, its principal components and their associated variances, determines, in part, the direction and speed of multivariate trait evolution. In this article we present a framework and results that give the structure of G under the assumption of neutrality. We suggest that a neutral expectation of the structure of G is important because it gives a null expectation for the structure of G from which the unique consequences of selection can be determined. We demonstrate how the processes of mutation, recombination, and drift shape the structure of G. Furthermore, we demonstrate how shared common ancestry between segregating alleles shapes the structure of G. Our results show that shared common ancestry, which manifests itself in the form of a gene genealogy, causes the structure of G to be nonuniform in that the variances associated with the principal components of G decline at an approximately exponential rate. Furthermore we show that the extent of the nonuniformity in the structure of G is enhanced with declines in mutation rates, recombination rates, and numbers of loci and is dependent on the pattern and modality of mutation.
Genetic Positioning of Centromeres Using Half-Tetrad Analysis in a 4x–2xCross Population of Potato
Authors: Park Tae-Ho , Kim Jong-Bo , Hutten Ronald C B , van Eck Herman J , Jacobsen Evert , Visser Richard G F
Published: March 2007

From biological and genetic standpoints, centromeres play an important role in the delivery of the chromosome complement to the daughter cells at cell division. The positions of the centromeres of potato were determined by half-tetrad analysis in a 4x–2x population where the male parent produced 2n pollen by first-division restitution (FDR). The genetic linkage groups and locations of 95 male parent-derived amplified fragment length polymorphism markers could be determined by comparing their position on a 2x–2x highly saturated linkage map of potato. Ten centromere positions were identified by 100% heterozygosity transmitted from the 2n heterozygous gametes of the paternal parent into the tetraploid offspring. The position of these centromeric marker loci was in accordance with those predicted by the saturated 2x–2x map using the level of marker clustering as a criterion. Two remaining centromere positions could be determined by extrapolation. The frequent observation of transmission of 100% heterozygosity proves that the meiotic restitution mechanism is exclusively based on FDR. Additional investigations on the position of recombination events of three chromosomes with sufficient numbers of markers showed that only one crossover occurred per chromosome arm, proving strong interference of recombination between centromere and telomere.
Phylogenetic and Genomewide Analyses Suggest a Functional Relationship Betweenkayak, the Drosophila Fos Homolog, andfig, a Predicted Protein Phosphatase 2C Nested Within akayakIntron
Authors: Hudson Stephanie G , Garrett Matthew J , Carlson Joseph W , Micklem Gos , Celniker Susan E , Goldstein Elliott S , Newfeld Stuart J
Published: March 2007

A gene located within the intron of a larger gene is an uncommon arrangement in any species. Few of these nested gene arrangements have been explored from an evolutionary perspective. Here we report a phylogenetic analysis of kayak (kay) and fos intron gene (fig), a divergently transcribed gene located in a kay intron, utilizing 12 Drosophila species. The evolutionary relationship between these genes is of interest because kay is the homolog of the proto-oncogene c-fos whose function is modulated by serine/threonine phosphorylation and fig is a predicted PP2C phosphatase specific for serine/threonine residues. We found that, despite an extraordinary level of diversification in the intron–exon structure of kay (11 inversions and six independent exon losses), the nested arrangement of kay and fig is conserved in all species. A genomewide analysis of protein-coding nested gene pairs revealed that ∼20% of nested pairs in D. melanogaster are also nested in D. pseudoobscura and D. virilis. A phylogenetic examination of fig revealed that there are three subfamilies of PP2C phosphatases in all 12 species of Drosophila. Overall, our phylogenetic and genomewide analyses suggest that the nested arrangement of kay and fig may be due to a functional relationship between them.
Neuromotor Outcome at 2 Years of Very Preterm Infants Who Were Treated With High-Frequency Oscillatory Ventilation or Conventional Ventilation for Neonatal Respiratory Distress Syndrome
Authors: Truffert Patrick , Paris-Llado Josefa , Escande Benoît , Magny Jean-François , Cambonie Gilles , Saliba Elie , Thiriez Gérard , Zupan-Simunek Véronique , Blanc Thierry , Rozé Jean-Christophe , Bréart Gérard , Moriette Guy
Published: March 2007

OBJECTIVE. In a previous multicenter, randomized trial, elective use of high-frequency oscillatory ventilation was compared with the use of conventional ventilation in the management of respiratory distress syndrome in preterm infants <30 weeks. No difference in terms of respiratory outcome was observed, but concerns were raised about an increased rate of severe intraventricular hemorrhage in the high-frequency ventilation group. To evaluate outcome, a follow-up study was conducted until a corrected age of 2 years. We report the results concerning neuromotor outcome.

METHODS. Outcome was able to be evaluated in 192 of the 212 infants who survived until discharge from the neonatal unit: 97 of 105 infants of the high-frequency group and 95 of 104 infants of the conventional ventilation group.

RESULTS. In the infants reviewed, mean birth weight and gestational age were similar in the 2 ventilation groups. As in the overall study population, the following differences were observed between the high-frequency ventilation group and the conventional ventilation group: lower 5-minute Apgar score, fewer surfactant instillations, and a higher incidence of severe intraventricular hemorrhage. At a corrected age of 2 years, 93 of the 97 infants of the high-frequency group and 79 of the 95 infants of the conventional ventilation group did not present any neuromotor disability, whereas 4 infants of the high-frequency group and 16 infants of the conventional ventilation group had cerebral palsy.

CONCLUSIONS. Contrary to our initial concern about the increased rate of severe intraventricular hemorrhage in the high-frequency ventilation group, these data suggest that early use of high-frequency ventilation, compared with conventional ventilation, may be associated with a better neuromotor outcome. Because of the small number of patients studied and the absence of any explanation for this finding, we can conclude only that high-frequency oscillatory ventilation is not associated with a poorer neuromotor outcome.
Substitution of Marijuana for Alcohol: The Role of Perceived Access and Harm
Authors: Alter Randi J. , Lohrmann David K. , Greene Robert
Published: March 2007

Research has shown significant declines in gateway drug use among participants in a school/community substance abuse prevention intervention in a midwestern, suburban school district (Lohrmann, Alter, Greene, & Younoszai, 2005). Though still at or below national levels, student marijuana use was not impacted as positively. The current study investigated the possibility that efforts to prevent alcohol use resulted in an unintentional substitution effect thereby increasing marijuana use. Factors including perceived access to alcohol and marijuana, along with perceived harm associated with alcohol and marijuana use, were examined to determine their role in marijuana use. Findings revealed a relationship between perceived access to and perceptions of harm associated with marijuana and its use that depended on the level of perceived access to and harm associated with alcohol.
The Life Space: A Framework and Method to Describe the Individual's External Traits
Authors: Brackett Marc A. , Mayer John D.
Published: March 2007

A revised measure of the Life Space with a large sample ( N = 1021) of university undergraduates was developed. The Life Space divides the external environment into four domains, which broadly encompass a person's bio-logical foundations, owned possessions, daily interactions and activities, and group memberships. Factor analysis of over 1000 items divided among each domain resulted in 96 factor-based scales that provided a rich description of college students' personal surroundings and everyday behavior. A 2nd-order factor analysis of the primary scales resulted in seven global dimensions that replicate and expand upon prior research in the area: Positive and Social Orientation, Sports Orientation, Drug Culture Environment, Music and Arts Achievement, Media Consumer, Negative and Unhealthy Lifestyle, and Intellectual Pursuits. The Life Space scales also were examined for gender differences and associations with social desirability response bias. The discussion focuses on the value of a more detailed and comprehensive approach to studying personality within the context of the external systems that surround the person.
Insane, Poetic, Lovable: Creativity and Endorsement of the “Mad Genius” Stereotype
Authors: Kaufman James C. , Bromley Melanie L. , Cole Jason C.
Published: March 2007

The nature and extent to which creativity and mental illness are actually connected is a contentious matter that has been frequently debated. Yet regardless of whether the connection is real or romanticized, the idea of the mad genius has been prevalent in the research literature and in popular culture. This study examined how people's opinions about the “mad genius” stereotype were associated with their own creativity, as measured by the Creative Personality Scale (CPS) and the Remote Associates Test (RAT). Both high-endorsers and low-endorsers rated themselves as more creative than did those with a neutral opinion. On the RAT, those with higher creativity were more likely to endorse the stereotype. Reasons and implications are then discussed.
The Identity Theory and Refutation of Searle's Major Objections
Authors: Brooks Eugene M.
Published: March 2007

I present a version of a nonrestricted identity theory as well as refutations of Searle's objections to the theory. The objections countered are: 1) the theory violates Leibnitz' Law and 2) that consciousness is not reducible to neurons. Searle's arguments are refuted on the basis of the first-personal nature of consciousness. It does not violate Leibnitz' law when regarded from the subjective view of the individual under observation and it appears to be irreducible because it cannot be observed from a third-person perspective. In the discussion I point out why consciousness mistakenly appears to be immaterial instead of physicochemical and I suggest a method by which consciousness might be studied empirically.
A Preliminary Investigation of the Components of a Curriculum for the Preparation of Master's-Level Addiction Counselors
Authors: Whittinghill David
Published: March 2007

This study identified the preliminary curriculum components for the preparation of graduate-level addiction counselors. A review of the related literature revealed no agreed upon standards for post baccalaureate instruction of addiction counseling. The Delphi method was used to establish curriculum items from a list of 198 previously identified work behaviors associated with graduate-level addiction counseling. A panel of 28 addiction counseling experts responded to three administrations of an evolving questionnaire and reached consensus on a final list of 89 curriculum items. Consensus of expert judgments was corroborated by a post hoc multivariate of analysis of variance (MANOVA) that revealed no significant differences in ratings of importance among panelist subgroups.
Capillary blood pressure in syngeneic rat islets transplanted under the renal capsule is similar to that of the implantation organ.
Authors: Carlsson P O , Jansson L , Andersson A , Källskog O
Published: March 2007

The aim of the present study was to measure capillary blood pressure and interstitial pressure in transplanted pancreatic islets and to correlate these measurements to capillary and tubular pressures in the adjacent kidney. For this purpose, 250 syngeneic islets were implanted under the renal capsule of WF rats and studied 1, 2, or 6 months after transplantation. Some of the animals studied after 1 and 2 months were streptozotocin (STZ)-induced diabetic. Measurements were performed during basal conditions or after an acute glucose-stimulation of insulin release. The hydrostatic pressures were determined in vivo by direct micropuncture. The islet transplant capillary pressure in normoglycemic animals was 6.9 +/- 0.4 mmHg (n = 9), 10.0 +/- 0.8 mmHg (n = 7), and 12.4 +/- 0.8 mmHg (n = 7) when measured 1, 2, and 6 months after implantation, respectively. Previous data from our laboratory showed that the normal capillary pressure of native rat pancreatic islets is approximately 3 mmHg. The blood pressure in kidney peritubular capillaries was 10-12 mmHg in both transplanted and control animals. Islet transplant interstitial pressures were 4-6 mmHg in the normoglycemic recipients at 1, 2, and 6 months after transplantation. Acute glucose stimulation had no effect on islet transplant interstitial pressure or peritubular or transplant capillary blood pressures. Capillary pressures in the islet grafts were slightly increased 1 month after transplantation in STZ-induced diabetic rats, and this was associated with an increased blood perfusion of the transplants. However, 2 months after transplantation there were no differences in transplant capillary blood pressure between diabetic and normoglycemic animals. The graft interstitial pressure was, on the contrary, decreased in the diabetic animals 2 months after transplantation. We concluded that the capillary blood pressure in islets implanted under the renal capsule was similar to that of the implantation organ, which was three to four times higher than that normally found in native islets.
HLA-DR binding analysis of peptides from islet antigens in IDDM.
Authors: Geluk A , van Meijgaarden K E , Schloot N C , Drijfhout J W , Ottenhoff T H , Roep B O
Published: March 2007

HLA molecules are essential for thymic education and HLA restriction of T-cell responses. We therefore analyzed the HLA-DR binding affinities of synthetic peptides covering the entire sequences of GAD65, islet cell antigen 69 (ICA69), and (pro)insulin, which are candidate antigens in the autoimmune process of T-cell-mediated destruction of the pancreatic beta-cells. Subsequently, peptide HLA-DR binding was correlated to peptide antigenicity by comparing known T-cell epitopes with their HLA-binding affinities defined in this study. The results demonstrate the following. 1) (Pro)insulin peptides display a strong binding affinity for HLA-DR2, which is associated with negative genetic predisposition to IDDM, whereas poor binding was observed for HLA-DR molecules neutrally or positively associated with IDDM. This suggests that the absence of insulin-reactive T-cells in DR2+ individuals may be explained by negative selection on high-affinity DR2 binding insulin peptides. 2) Most autoantigenic peptides display promiscuous HLA-DR binding patterns. This promiscuity in itself is not sufficient to explain the genetic association of HLA-DR with development of IDDM. 3) HLA-DR3 binding of autoantigenic GAD65 peptides is relatively weak compared with that of other known T-cell epitopes. 4) All peptide epitopes recognized by HLA-DR-restricted T-cells from either IDDM patients or GAD65-immunized HLA-DR transgenic mice bind with high affinity to their HLA-DR restriction molecule (P < 0.0006). In contrast, T-cell epitopes recognized by nondiabetic controls bind DR molecules with weak or undetectable affinity. These results thus indicate a strong correlation between antigenicity and HLA-DR binding affinity of GAD65 peptides in IDDM. Furthermore, negative thymic selection of insulin peptides in low-risk (HLA-DR2 expressing) subjects may explain the lack of autoreactivity to insulin in such individuals.
Tyrosine phosphatase inhibitors, vanadate and pervanadate, stimulate glucose transport and GLUT translocation in muscle cells by a mechanism independent of phosphatidylinositol 3-kinase and protein kinase C.
Authors: Tsiani E , Bogdanovic E , Sorisky A , Nagy L , Fantus I G
Published: March 2007

Vanadate and pervanadate (pV) are protein tyrosine phosphatase (PTP) inhibitors that mimic insulin to stimulate glucose transport. To determine whether phosphatidylinositol (PI) 3-kinase is required for vanadate and pV, as it is for insulin, cultured L6 myotubes were treated with vanadate and pV. The two compounds stimulated glucose transport to levels similar to those stimulated by insulin; however, while PI 3-kinase activity and the increase in the lipid products PI 3,4-bisphosphate and PI 3,4,5-trisphosphate were inhibited by wortmannin after stimulation by all three agents--insulin, vanadate, and pV--wortmannin blocked glucose transport stimulated by insulin but not vanadate or pV. Vanadate and pV stimulated the translocation of GLUTs from an intracellular compartment to the plasma membrane; this stimulation was not blocked by wortmannin, but insulin-induced GLUT translocation was inhibited. Similar results were obtained in cultured H9c2 cardiac muscle cells in which wortmannin did not inhibit glucose transport or the vanadate-induced translocation of GLUT4 in c-myc-GLUT4 transfected cells. The ser/thr kinase PKB (Akt/PKB/RAC-PK) is activated by insulin, lies downstream of PI 3-kinase, and has been implicated in signaling of glucose transport. Insulin and pV stimulated PKB activity, and both were inhibited by wortmannin. In contrast, vanadate, at concentrations that maximally stimulated glucose transport, did not significantly increase PKB activity. To determine the potential role of protein kinase C (PKC), L6 cells were incubated chronically with phorbol myristate acetate (PMA) or acutely with the PKC inhibitors calphostin C and bisindolylmaleimide. There was no inhibition of glucose transport stimulation by insulin, vanadate, or pV, and a combination of wortmannin and PKC inhibitors also failed to block the effect of vanadate and pV. In contrast, disassembly of the actin network with cytochalasin D blocked the stimulation of glucose transport by all three agents. In conclusion, vanadate and pV are able to stimulate glucose transport and GLUT translocation by a mechanism independent of PI 3-kinase and PKC. Similar to that by insulin, glucose transport stimulation by vanadate and pV requires the presence of an intact actin network.
Functional interactions between melanin-concentrating hormone, neuropeptide Y, and anorectic neuropeptides in the rat hypothalamus.
Authors: Tritos N A , Vicent D , Gillette J , Ludwig D S , Flier E S , Maratos-Flier E
Published: March 2007

A growing body of evidence indicates that a number of peptides expressed in the mammalian hypothalamus are involved in the regulation of food intake and energy balance. Among these, melanin-concentrating hormone (MCH) and neuropeptide Y (NPY) are potent appetite stimulants, whereas alpha-melanocyte-stimulating hormone (alpha-MSH), neurotensin, and glucagon-like peptide (GLP)-1(7-36) amide have appetite-suppressing properties. However, the functional interactions between pathways involving these neuropeptides remain incompletely understood. In the current study, we describe the functional interactions between orexigenic (appetite-stimulating: MCH and NPY) and anorectic (appetite-suppressing: alpha-MSH, neurotensin, and GLP-1) peptides after intracerebroventricular (i.c.v.) administration in the rat. The i.c.v. administration of GLP-1 completely prevents the orexigenic effects of both MCH and NPY. However, i.c.v. administration of alpha-MSH prevents only the orexigenic effect of MCH, as we have previously shown, but does not prevent the effect of NPY on food intake. Similarly, i.c.v. administration of neurotensin prevents only the orexigenic effect of MCH, but does not prevent the appetite-stimulating effect of NPY. Thus, our study suggests that the functional interactions between these neuropeptides are specific, although the underlying mechanisms are as yet unexplored.
Sulfonylureas enhance exocytosis from pancreatic beta-cells by a mechanism that does not involve direct activation of protein kinase C.
Authors: Tian Y A , Johnson G , Ashcroft S J
Published: March 2007

Hypoglycemic sulfonylureas stimulate insulin release by binding to a regulatory subunit of plasma membrane ATP-sensitive K+ (K(ATP)) channels. The consequent closure of K(ATP) channels leads to depolarization, opening of voltage-dependent Ca2+ channels, Ca2+ influx, and a rise in intracellular [Ca2+]. Recently, however, it has been suggested that sulfonylureas may have an additional action on secretion, independent of changes in intracellular [Ca2+] but dependent on the activity of protein kinase C (PKC). We have investigated the mechanisms involved in the PKC-dependent effect of sulfonylureas on the secretion machinery in beta-cells. In MIN6 beta-cells permeabilized by streptolysin O, insulin release was stimulated by elevation of [Ca2+] from 10(-8) to 10(-5) mol/l. At a [Ca2+] of 10(-8) mol/l, insulin release from permeabilized beta-cells was stimulated by addition of GTP-gamma-S, or by addition of a phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). TPA, but not GTP-gamma-S, also increased insulin release when [Ca2+] was 10(-5) mol/l. Insulin release from permeabilized beta-cells was stimulated by tolbutamide (0.1-1 mmol/l) at 10(-8) but not at 10(-5) mol/l Ca2+. The effect of tolbutamide was blocked either by inhibition of PKC or when phorbol ester-sensitive PKC isoforms were maximally stimulated by TPA. Meglitinide and glibenclamide also stimulated insulin release from permeabilized beta-cells. To assess the possibility that direct activation of PKC mediates the exocytotic response to sulfonylureas, we studied the effect of tolbutamide and glibenclamide on PKC activity. Purified brain PKC was not activated by tolbutamide or glibenclamide, whether tested in the absence or presence of phosphatidylserine or TPA, or at low or high [Ca2+]; nor was the total PKC activity in extracts of MIN6 beta-cells affected by tolbutamide. Neither tolbutamide nor glibenclamide elicited translocation of any isoform of PKC in intact or permeabilized beta-cells under conditions in which TPA evoked a marked redistribution of PKC alpha- and epsilon-isoforms. We conclude that although the plasma membrane K(ATP) channel-independent stimulation of exocytosis by sulfonylureas may require functional PKC, the mechanism does not involve a direct activation of the enzyme.
Microalbuminuria and coronary heart disease in NIDDM: an incidence study.
Authors: Mattock M B , Barnes D J , Viberti G , Keen H , Burt D , Hughes J M , Fitzgerald A P , Sandhu B , Jackson P G
Published: March 2007

In most survival studies in NIDDM, microalbuminuria (urinary albumin excretion rate 20-200 microg/min) predicts early mortality; in cross-sectional studies, it is associated with coronary heart disease (CHD) morbidity. It is unclear, however, whether microalbuminuria is a risk factor for the development of CHD or the result of it, and little is known of the factors that predispose to the development of microalbuminuria in NIDDM. We examined these issues in a 7-year prospective study of a hospital-based cohort comprising 146 white NIDDM patients without clinical albuminuria. Microalbuminuria was a significant risk factor for both all-cause mortality (relative risk 3.94, 95% CI 2.04-7.62) and CHD mortality (relative risk 7.40, 95% CI 2.94-18.7) when adjusted for age only. Its independent predictive power did not persist, however, in age-adjusted multivariable survival analysis that allowed for the other significant risk factors: male sex, preexisting CHD, high levels of glycated hemoglobin, and high serum cholesterol. Among men free of CHD at baseline, the independent risk factors for CHD morbidity and mortality were microalbuminuria, current smoking, high diastolic blood pressure, and high serum cholesterol (all P < 0.05). For the 100 NIDDM patients with normoalbuminuria at baseline, the incidence of microalbuminuria was 29% over the 7-year period. In that group, fasting plasma glucose, current smoking, preexisting CHD, and high initial urinary albumin excretion rate were risk factors for the development of microalbuminuria (all P < 0.05). When men and women were analyzed separately, preexisting CHD was a significant risk factor in men only. These results demonstrate that microalbuminuria predicts incident clinical CHD in men with NIDDM. Preexisting CHD is also a risk factor for incident microalbuminuria in men, however, suggesting that microalbuminuria and CHD are not causally related but rather reflect common determinants.
Alpha-interferon inhibits the development of diabetes in NOD mice.
Authors: Sobel D O , Ahvazi B
Published: March 2007

The NOD mouse is a model of human IDDM, which is characterized by a cell-mediated autoimmune process resulting in spontaneous diabetes. Alpha-interferon (IFN-alpha) is thought to play a pathogenic role in this autoimmune process. We report that recombinant alpha-interferon (rIFN-alpha) administration decreases the development of spontaneous diabetes and the passive transfer of diabetes in NOD mice. Spontaneous diabetes was inhibited by IFN-alpha in a dose-dependent fashion. A dose of as little as 20 x 10(3) U inhibited diabetes development, while a dose of 100 x 10(3) U potently prevented diabetes (14% incidence vs. 70% incidence in control mice). Even at the termination of the experiment, nondiabetic mice administered rIFN-alpha maintained normal glucose tolerance. Islet inflammation was 65% lower in the pancreases of rIFN-alpha mice. rIFN-alpha administration decreased anti-islet effector cell bioactivity of spleen cells without inducing generalized immunosuppression. Passive transfer experiments demonstrated that the decreased anti-islet effector cell activity was not a direct action of rIFN-alpha on these cells. In conclusion, rIFN-alpha potently and paradoxically prevents diabetes by indirectly decreasing anti-islet effector cell activity and in turn the development of insulitis without inducing generalized immunosuppression. This work, which goes against our current understanding of the role of rIFN-alpha in autoimmunity, may have significant implications to further our understanding of the pathogenesis of IDDM and to further the development of novel modes to prevent the disease.
Contribution of Na/Ca exchange to Ca2+ outflow and entry in the rat pancreatic beta-cell: studies with antisense oligonucleotides.
Authors: Van Eylen F , Lebeau C , Albuquerque-Silva J , Herchuelz A
Published: March 2007

To characterize the role played by Na/Ca exchange in the pancreatic beta-cell, phosphorothioated antisense oligonucleotides (AS-oligos) were used to knock down the exchanger in rat pancreatic beta-cells. Na/Ca exchange activity was evaluated by measuring cytosolic free Ca2+ concentration ([Ca2+]i) in single cells using fura-2. Exposure of beta-cells to 500 nmol/l of the AS-oligos for 24 h inhibited Na/Ca exchange activity by approximately 77%. In contrast, control oligonucleotides (scrambled and mismatched) did not affect Na/Ca exchange activity. In AS-oligo-treated cells, the increase in [Ca2+]i induced by membrane depolarization (K+ or the hypoglycemic sulfonylurea, tolbutamide) was reduced by 28 or 40%, respectively. Likewise, the rate of [Ca2+]i decrease after K+ or tolbutamide removal was reduced by 72 or 40%, respectively. AS-oligos treatment also abolished the nifedipine-resistant increase in [Ca2+]i induced by K+ and profoundly altered the oscillatory or sustained increases in [Ca2+]i induced by 11.1 mmol/l glucose. The present study shows that AS-oligos may specifically inhibit Na/Ca exchange in rat pancreatic beta-cells. In those cells, Na/Ca exchange appears to mediate Ca2+ entry in response to membrane depolarization and to be responsible for up to 70% of Ca2+ removal from the cytoplasm upon membrane repolarization.
In vivo evidence for increased apolipoprotein A-I catabolism in subjects with impaired glucose tolerance.
Authors: Pietzsch J , Julius U , Nitzsche S , Hanefeld M
Published: March 2007

The in vivo kinetics of the HDL apolipoproteins (apo) A-I and A-II were studied in six subjects with impaired glucose tolerance (IGT) and six control subjects with normal glucose tolerance (NGT), using a stable isotope approach. During a 12-h primed constant infusion of L-[ring-13C6]-phenylalanine, tracer enrichment was determined in apoA-I and apoA-II from ultracentrifugally isolated HDL. The rates of HDL apoA-I and apoA-II production and catabolism were estimated using a one-compartment model-based analysis. Triglycerides were higher in IGT subjects (1.33 +/- 0.21 vs. 0.84 +/- 0.27 mmol/l, P < 0.05), but were within the normal range. HDL cholesterol and apoA-I levels were significantly lower in subjects with IGT (1.07 +/- 0.15 vs. 1.36 +/- 0.14 mmol/l, P < 0.05; 0.94 +/- 0.10 vs. 1.34 +/- 0.07 g/l, P < 0.01). In IGT subjects, HDL composition was significantly altered, characterized by an increase in HDL triglycerides (4.9 +/- 1.9 vs. 3.2 +/- 1.0%, P < 0.05) and HDL phospholipids (34.7 +/- 2.6 vs. 27.5 +/- 5.8%, P < 0.05) and a decrease in HDL cholesteryl esters (10.1 +/- 2.0 vs. 12.7 +/- 2.9%, P < 0.05) and HDL apoA-I (31.5 +/- 4.4 vs. 43.2 +/- 2.4%, P < 0.05). The mean fractional catabolic rate (FCR) of HDL apoA-I was significantly higher in IGT subjects (0.34 +/- 0.05 vs. 0.26 +/- 0.03 day(-1), P < 0.01), while the HDL apoA-I production rate (PR), as well as the PR and FCR of HDL apoA-II, showed no differences between the two groups. There were significant correlations between HDL apoA-I FCR and the following parameters: HDL apoA-I (r = -0.902, P < 0.001), HDL cholesterol (r = -0.797, P = 0.001), plasma triglycerides (r = 0.743, P < 0.01), HDL triglycerides (r = 0.696, P < 0.01), and cholesterol ester transfer protein activity (r = 0.646, P < 0.01). We observed a strong positive association between increased apoA-I catabolism and insulin (r = 0.765, P < 0.01) and proinsulin (r = 0.797, P < 0.01) concentrations. These data support the hypothesis that the decrease in HDL cholesterol and apoA-I levels in IGT is principally the result of an enhanced apoA-I catabolism. The latter seems to be an early metabolic finding in IGT even when other lipid parameters, especially plasma triglycerides, still appear to be not or only weakly affected.
Teratogenicity of 3-deoxyglucosone and diabetic embryopathy.
Authors: Eriksson U J , Wentzel P , Minhas H S , Thornalley P J
Published: March 2007

The increased rate of embryonic dysmorphogenesis in diabetic pregnancy is correlated with the severity and duration of the concurrent hyperglycemia during early gestation. Whole embryo culture was used to investigate a possible association of hyperglycemia-induced disturbances of embryo development with tissue levels of the three alpha-oxoaldehydes: glyoxal, methylglyoxal, and 3-deoxyglucosone (3-DG). Rat embryos exposed to high glucose levels in vitro showed severe dysmorphogenesis and a 17-fold increased concentration of 3-DG compared with control embryos cultured in a low glucose concentration. Exogenous 3-DG (100 micromol/l) added to the medium of control cultures yielded an increased embryonic malformation rate and a 3-DG concentration similar to that of embryos cultured in high glucose. Addition of superoxide dismutase (SOD) to the culture medium decreased the malformation rates of embryos exposed to either high glucose or high 3-DG levels, but it did not decrease the high embryonic 3-DG concentrations caused by either agent. Our results implicate the potent glycating agent 3-DG as a teratogenic factor in diabetic embryopathy. In addition, the anti-teratogenic effect of SOD administration appears to occur downstream of 3-DG formation, suggesting that 3-DG accumulation leads to superoxide-mediated embryopathy.
Effects of streptozotocin-induced diabetes and of insulin treatment on homocysteine metabolism in the rat.
Authors: Jacobs R L , House J D , Brosnan M E , Brosnan J T
Published: March 2007

An elevation in the concentration of total plasma homocysteine is known to be an independent risk factor for the development of vascular disease. Alterations in homocysteine metabolism have also been observed clinically in diabetic patients. Patients with either type 1 or type 2 diabetes who have signs of renal dysfunction tend to exhibit elevated total plasma homocysteine levels, whereas type 1 diabetic patients who have no clinical signs of renal dysfunction have lower than normal plasma homocysteine levels. The purpose of this study was to investigate homocysteine metabolism in a type 1 diabetic animal model and to examine whether insulin plays a role in its regulation. Diabetes was induced by intravenous administration of 100 mg/kg streptozotocin to Sprague-Dawley rats. We observed a 30% reduction in plasma homocysteine in the untreated diabetic rat. This decrease in homocysteine was prevented when diabetic rats received insulin. Transsulfuration and remethylation enzymes were measured in both the liver and the kidney. We observed an increase in the activities of the hepatic transsulfuration enzymes (cystathionine beta-synthase and cystathionine gamma-lyase) in the untreated diabetic rat. Insulin treatment normalized the activities of these enzymes. The renal activities of these enzymes were unchanged. These results suggest that insulin is involved in the regulation of plasma homocysteine concentrations by affecting the hepatic transsulfuration pathway, which is involved in the catabolism of homocysteine.
Sorting human beta-cells consequent to targeted expression of green fluorescent protein.
Authors: Meyer K , Irminger J C , Moss L G , de Vargas L M , Oberholzer J , Bosco D , Morel P , Halban P A
Published: March 2007

Pancreatic islets of Langerhans are composed of four major endocrine cell types with a smaller number of nonendocrine cells. To study the molecular constituents and function of just one subpopulation of islet cells, it is necessary to sort them from the other cell types. While rat beta-cells can be sorted by autofluorescence-activated flow cytometry, this has not proved possible on a routine and reproducible basis for human beta-cells. In the present study, we have selectively labeled human beta-cells with green fluorescent protein (GFP), allowing for their sorting by flow cytometry. Human islet cells were infected with replication-defective (attenuated) recombinant adenovirus expressing GFP driven by the rat insulin I promoter (Ad-RIP-GFP) for targeted expression in beta-cells, or beta-galactosidase driven by the promiscuous cytomegalovirus (CMV) promoter (Ad-CMV-beta-gal) as control. Whereas the majority of islet cells can be infected by adenovirus, as shown by control infection with Ad-CMV-beta-gal, increased fluorescence after infection with Ad-RIP-GFP was limited to insulin-containing beta-cells. Infection of islet cells with Ad-RIP-GFP resulted reproducibly in the appearance of a population of intensely fluorescent cells, when analyzed by flow cytometry. These cells were sorted using a fluorescence-activated cell sorter (FACS) and shown by immunofluorescence to consist of >95% beta-cells. The targeted expression of GFP thus allows for preparation of human beta-cells purified close to homogeneity. This method should be readily applicable in any laboratory with FACS capability.
Transplantation of allogeneic islets of Langerhans in the rat liver: effects of macrophage depletion on graft survival and microenvironment activation.
Authors: Bottino R , Fernandez L A , Ricordi C , Lehmann R , Tsan M F , Oliver R , Inverardi L
Published: March 2007

Early impairment of islet function and graft loss limit the success of allogeneic islet transplantation. Nonspecific inflammatory events occurring at the transplant site immediately after grafting, involving the production of cytokines and free radicals and sinusoidal endothelial cell (SEC) activation, may contribute to islet cell damage. To evaluate whether Kupffer cell inactivation would result in prolonged allograft survival in a model system of intrahepatic islet transplantation in rats, we systemically administered either gadolinium chloride (GdCl3) or dichloromethylene diphosphonate (Cl2MDP) to assess the effects of macrophage inactivation on rejection and on the release of proinflammatory molecules, as well as to assess the functional profile of SEC. The results obtained were compared with those observed in untreated, sham-injected animals and in rats receiving intraportal infusions of microbeads. Transient macrophage inhibition, particularly in hepatic Kupffer cells, is associated with significant prolongation of graft survival after intraportal islet allotransplantation (ITx) in rats: 7.2 days in the control group versus 11.9 days in the GdCl3 group (P < 0.01) and 15.6 days in the Cl2MDP group (P < 0.0006), respectively. Although systemic release of inflammatory mediators was observed only when islet transplantations were performed and it could be inhibited by macrophage-targeting treatments, perturbation of the functional profile of endothelial cells was also observed when microembolization was induced by the use of microbeads and could not be prevented by macrophage inhibition. These experiments provide evidence to support the concept that macrophages play a key role in early inflammatory events known to adversely affect islet engraftment and suggest that manipulation of nonspecific immune activation by inhibition of macrophage function may facilitate hepatic engraftment of islet allografts. The mechanisms mediating this effect are likely to include prevention of release of tumor necrosis factor-alpha, interleukin-1beta, and NO and interference with the rate of immune response to the islets.
Successful islet autotransplantation in humans: functional insulin secretory reserve as an estimate of surviving islet cell mass.
Authors: Teuscher A U , Kendall D M , Smets Y F , Leone J P , Sutherland D E , Robertson R P
Published: March 2007

Islet autotransplantation for treatment of chronic painful pancreatitis in nondiabetic patients reliably establishes normoglycemia and phasic insulin secretion and can achieve prolonged insulin independence. Whether functional transplanted beta-cell reserve is normal after intrahepatic islet transplantation is not known, nor is it known whether conventional measures of insulin secretion accurately reflect the functional beta-cell mass. To determine insulin secretory reserve after islet transplant, we performed studies of glucose potentiation of arginine-induced insulin secretion (GPAIS) in eight recipients of intrahepatic islet autotransplants. All eight subjects (and matched, healthy controls) were studied cross-sectionally 49 +/- 12 months posttransplant, and four subjects were studied pre- and posttransplant. Subjects had received a mean +/- SE of 479,000 +/- 79,000 islets, and all were insulin independent and normoglycemic at the time of study. Acute insulin responses to arginine, glucose, and GPAIS were significantly reduced after islet transplantation in both study groups. Importantly, the magnitudes of these three responses were highly correlated to the mass of islets transplanted (response to glucose: r = 0.84, P < 0.01; response to arginine: r = 0.69, P < 0.05; response to GPAIS = 0.81, P < 0.01). Data from hemipancreatectomized and normal control subjects generally agreed with the regression lines. These findings demonstrate that despite normoglycemia and insulin independence, recipients of intrahepatic islet transplantation have significantly reduced functional beta-secretory reserve and that after islet transplantation, functional beta-cell mass can be estimated by measurements of glucose and arginine-induced insulin responses. Thus, these measurements can be used to estimate the mass and functional capacity of islets surviving intrahepatic transplantation in humans.
Independent genetic regulation of T-cell and antigen-presenting cell participation in autoimmune islet inflammation.
Authors: Fox C J , Danska J S
Published: March 2007

Genetic susceptibility to type 1 diabetes in the nonobese diabetic (NOD) mouse involves at least 17 Idd loci. Idd1 has been mapped to a class II gene in the major histocompatibility complex (MHC), whereas the products and functions of the remaining Idd loci are unresolved. To investigate how non-MHC Idd genes regulate islet inflammation and IDDM progression, NOD mice were compared with the nonobese diabetes-resistant (NOR) mouse, a related MHC-identical strain that possesses a subset of the NOD-derived alleles at the Idd loci. Using quantitative reverse transcriptase-polymerase chain reaction amplification and immunohistochemistry, we observed that disease resistance in NOR mice is reflected by a protracted block at the earliest stage of insulitis. In NOD islets, early antigen-presenting cell (APC) recruitment to islet lesions was temporally coincident with progressive T-cell infiltration. In striking contrast, islet infiltrates in NOR mice were composed of APCs with minimal contribution from T-cells and T-cell-derived inflammatory cytokines, conferring apparent resistance to invasive insulitis and beta-cell destruction. This is the first evidence that a subset of Idd susceptibility loci independently regulate T-cell and APC participation in insulitis progression. As progress is made toward identification of the Idd gene products, it will be crucial to determine how they regulate diabetogenesis. Our data define distinct cellular stages of IDDM pathogenesis in which the impact of Idd genes can be readily analyzed.
Unselective inhibition of endothelin receptors reduces renal dysfunction in experimental diabetes.
Authors: Benigni A , Colosio V , Brena C , Bruzzi I , Bertani T , Remuzzi G
Published: March 2007

Chronic nephropathies are associated with enhanced renal synthesis of endothelin (ET)-1. A recent study demonstrated that an ET(A) receptor antagonist given to diabetic rats at the moment of disease induction prevented the development of renal injury. Here we investigated whether an unselective ET(A)/ET(B) receptor antagonist, PD 142,893, was renoprotective when given to streptozotocin diabetic rats when animals were already proteinuric. The effect of PD 142,893 was compared with that of an ACE inhibitor, lisinopril, known to retard progressive renal disease in experimental and human diabetes. PD 142,893 normalized systemic blood pressure, reduced urinary protein and albumin excretion, and ameliorated renal blood flow in diabetic rats, but it did not affect such parameters in control rats. Lisinopril had a renoprotective effect comparable to PD 142,893, although lisinopril controlled systemic blood pressure better. Northern blot analysis of ET-1 mRNA revealed upregulation of ET-1 gene in the diabetic kidney. Similar results were obtained by in situ hybridization in glomeruli and tubuli of diabetic rats. Both treatments remarkably attenuated exaggerated renal ET-1 gene expression. These data suggest that ET-1 is a contributory mediator of kidney damage in diabetes and indicate that ET receptor antagonists may represent a new therapeutic mean for treatment of progressive diabetic nephropathy.
Evidence for involvement of the proteasome complex (26S) and NFkappaB in IL-1beta-induced nitric oxide and prostaglandin production by rat islets and RINm5F cells.
Authors: Kwon G , Corbett J A , Hauser S , Hill J R , Turk J , McDaniel M L
Published: March 2007

Interleukin-1beta (IL-1beta) has been implicated as an effector molecule of beta-cell destruction in autoimmune diabetes. IL-1beta inhibits insulin secretion from pancreatic beta-cells by stimulating the expression of inducible nitric oxide synthase (iNOS) that generates the free radical nitric oxide. IL-1beta also induces the coexpression of the inducible isoform of cyclooxygenase (COX-2) that results in the overproduction of proinflammatory prostaglandins. The current studies were designed to characterize the involvement of protease(s) in the signaling pathway of IL-1beta-induced iNOS and COX-2 expression by rat islets and transformed rat pancreatic beta-cells. Because of the limitations of cell numbers of purified primary beta-cells obtained from rat islets, biochemical and molecular studies were performed using the rat insulinoma beta-cell line RINm5F. A serine protease inhibitor, Nalpha-P-tosyl-L-lysine chloromethyl ketone (TLCK), and a proteasome complex (26S) inhibitor, MG 132, inhibited IL-1beta-induced nitrite formation, an oxidation product of nitric oxide produced by iNOS, in a concentration-dependent manner, with complete inhibition observed at 100 micromol/l and 10 micromol/l, respectively. Both TLCK and MG 132 also inhibited iNOS gene expression at the level of mRNA and protein. In an analogous manner, TLCK (100 micromol/l) and MG 132 (10 micromol/l) inhibited IL-1beta-induced COX-2 enzyme activity (PGE2 formation) and COX-2 gene expression at the level of mRNA and protein. In human islets, the proteasome inhibitor MG 132 also inhibited the formation of the products of iNOS and COX-2 enzyme activity, nitrite, and PGE2, respectively. These findings suggest that the inhibitory action of TLCK and MG 132 on iNOS and COX-2 expression precedes transcription. The transcription factor NFkappaB is essential for activation of a number of cytokine-inducible enzymes and was evaluated as a possible site of protease action necessary for IL-1beta-induced coexpression of iNOS and COX-2. TLCK and MG 132 inhibited both IL-1beta-induced activation of NFkappaB and degradation of IkappaBalpha by islets and RINm5F cells. These results implicate protease activation as an early signaling event in IL-1beta-induced inhibition of beta-cell function. This study also suggests that IL-1beta-induced iNOS and COX-2 coexpression by pancreatic beta-cells share a common signaling pathway in utilizing the proteasome complex (26S) and the transcription factor NFkappaB, and it identifies sites of intervention to prevent the overproduction of their inflammatory products.