Production study of Fr, Ra and Ac radioactive ion beams at ISOLDE, CERN

The presented paper discusses the production of radioactive ion beams of francium, radium, and actinium from thick uranium carbide (UCx ) targets at ISOLDE, CERN. This study focuses on the release curves and extractable yields of francium, radium and actinium isotopes. The ion source temperature was varied in order to study the relative contributions of surface and laser ionization to the production of the actinium ion beams. The experimental results are presented in the form of release parameters. Representative extractable yields per μ C are presented for222 - 231 Ac, several Ra and Fr isotopes in the mass ranges 214 ≤ A ≤ 233 and 205 ≤ A ≤ 231 respectively. The release efficiency for several isotopes of each of the studied elements was calculated by comparing their yields to the estimated in-target production rates modeled by CERN-FLUKA. The maximal extraction efficiency of actinium was calculated to be 2.1(6)% for a combination of surface ionization using a Ta ion source and resonant laser ionization using the two-step 438.58 nm, and 424.69 nm scheme.

A coupled oscillator model for the origin of bimodality and multimodality

Perhaps because of the elegance of the central limit theorem, it is often assumed that distributions in nature will approach singly-peaked, unimodal shapes reminiscent of the Gaussian normal distribution. However, many systems behave differently, with variables following apparently bimodal or multimodal distributions. Here, we argue that multimodality may emerge naturally as a result of repulsive or inhibitory coupling dynamics, and we show rigorously how it emerges for a broad class of coupling functions in variants of the paradigmatic Kuramoto model.

Sox5 regulates beta-cell phenotype and is reduced in type 2 diabetes

Type 2 diabetes (T2D) is characterized by insulin resistance and impaired insulin secretion, but the mechanisms underlying insulin secretion failure are not completely understood. Here, we show that a set of co-expressed genes, which is enriched for genes with islet-selective open chromatin, is associated with T2D. These genes are perturbed in T2D and have a similar expression pattern to that of dedifferentiated islets. We identify Sox5 as a regulator of the module. Sox5 knockdown induces gene expression changes similar to those observed in T2D and diabetic animals and has profound effects on insulin secretion, including reduced depolarization-evoked Ca²⁺-influx and β-cell exocytosis. SOX5 overexpression reverses the expression perturbations observed in a mouse model of T2D, increases the expression of key β-cell genes and improves glucose-stimulated insulin secretion in human islets from donors with T2D. We suggest that human islets in T2D display changes reminiscent of dedifferentiation and highlight SOX5 as a regulator of β-cell phenotype and function.

Key Matrix Proteins Within the Pancreatic Islet Basement Membrane Are Differentially Digested During Human Islet Isolation

Clinical islet transplantation achieves insulin independence in selected patients, yet current methods for extracting islets from their surrounding pancreatic matrix are suboptimal. The islet basement membrane (BM) influences islet function and survival and is a critical marker of islet integrity following rodent islet isolation. No studies have investigated the impact of islet isolation on BM integrity in human islets, which have a unique duplex structure. To address this, samples were taken from 27 clinical human islet isolations (donor age 41-59, BMI 26-38, cold ischemic time < 10 h). Collagen IV, pan-laminin, perlecan and laminin-α5 in the islet BM were significantly digested by enzyme treatment. In isolated islets, laminin-α5 (found in both layers of the duplex BM) and perlecan were lost entirely, with no restoration evident during culture. Collagen IV and pan-laminin were present in the disorganized BM of isolated islets, yet a significant reduction in pan-laminin was seen during the initial 24 h culture period. Islet cytotoxicity increased during culture. Therefore, the human islet BM is substantially disrupted during the islet isolation procedure. Islet function and survival may be compromised as a consequence of an incomplete islet BM, which has implications for islet survival and transplanted graft longevity.

Islet cell research brings hope for a diabetes cure: meeting report from the 6(th) annual islet society meeting in Stellenbosch, South Africa

The International Diabetes Federation predicts that, over the next twenty years, the largest increase in the prevalence of diabetes will be in the Africa region. Recognizing an unmet need for more focus on Africa and engagement with African scholars, the Islet Society held its 6th annual meeting July 20-21, 2014 in Stellenbosch, South Africa. Here, we present a report that covers the presentations and discussion points from that meeting. Work was presented on a variety of topics and included presentations by a significant proportion of Africa diabetes researchers. Overall, it was an excellent conference, with many new international collaborations initiated. We hope that other groups will also respond to the need for more conferences in Africa and focused on Africa.

14-3-3 proteins are essential signalling hubs for beta cell survival

AIMS/HYPOTHESIS

Diabetes is characterised by pancreatic beta cell death and dysfunction, resulting from unbalanced pro-survival and pro-death signalling. The 14-3-3 proteins are molecular adaptors that integrate numerous signalling pathways, including the v-raf-leukaemia viral oncogene 1 (RAF1)/B cell leukaemia/lymphoma 2 (BCL-2)-associated agonist of cell death (BAD) pathway, which we have previously implicated in insulin-dependent beta cell survival. Nevertheless, the roles of 14-3-3 proteins in beta cell fate and function have not been investigated.

METHODS

We examined the abundance, localisation, modulation and roles of 14-3-3 proteins using quantitative RT-PCR, immunoblot or imaging. MIN6 cells or mouse islets cells were manipulated with inhibitors, short interfering RNA (siRNA) or plasmids overexpressing 14-3-3.

RESULTS

We first characterised the abundance and subcellular location of all seven 14-3-3 isoforms in mouse and human beta cells. Most isoforms were cytoplasmic, except 14-3-3σ, which appeared to be nuclear. Analysis of 14-3-3 abundance under stress conditions revealed distinct modulation in mouse islets and MIN6 cells. Generalised 14-3-3 inhibition promoted apoptosis and dysfunction, and siRNA-mediated knockdown revealed isoform-specific roles in caspase-3-dependent beta cell apoptosis, with a clear role for 14-3-3ζ. Overabundance of 14-3-3ζ sequestered BAD-BCL2-associated X protein (BAX) from mitochondria, attenuated Dp5 (also known as Hrk) and Puma (also known as Bbc3) induction, and increased survival in response to pro-inflammatory cytokines or thapsigargin. Anti-apoptotic insulin treatment increased the sequestration of BAD/BAX by 14-3-3ζ. BAD mutants that were unable to bind 14-3-3ζ localised to mitochondria and induced apoptosis.

CONCLUSIONS/INTERPRETATION

This first study of the 14-3-3 family in beta cells revealed specific regulation, localisation and anti-apoptotic roles among the isoforms. Focus on 14-3-3ζ revealed its importance in preventing BAD-BAX mitochondrial localisation and protecting beta cells from multiple stresses. Thus, some 14-3-3 proteins are pro-survival signalling hubs.

Meta-analytic review of P3 components in posttraumatic stress disorder and their clinical utility

Patients with posttraumatic stress disorder (PTSD) exhibiting disturbances in information processing, including trouble with attention, were studied. Event-related potentials (ERPs)-specifically, the P3 components (P3a, P3b, and P3 working memory {P3wm})-provide an objective, non-invasive, and cost-effective method for evaluating such disturbances. We evaluated the potential clinical utility of P3 components by examining the differences between PTSD and several control groups: normal participants, non-PTSD patients with trauma, and medicated patients with PTSD. We performed a meta-analysis of the ERP literature between 1990 and 2010 using a random effects model. P3a amplitude was larger in patients with PTSD compared to non-PTSD patients having trauma in the context of trauma-related distracters. P3b amplitude was also larger in patients with PTSD than in patients having trauma without PTSD, but in the context of trauma-related stimuli. P3b amplitude was smaller in patients with PTSD compared to normal controls in the context of neutral stimuli. P3wm signals were smaller with shorter latencies in patients with PTSD compared to normal controls or medicated patients with PTSD. The receiver-operator characteristic (ROC) analysis revealed that each P3 component had some potential to accurately classify patients, typically using amplitude for at least one lead. In conclusion, differences in P3 amplitude and latency between patients with PTSD and control patients confirm the results of Karl et al and extend our understanding of P3 as a neural correlate of working memory. These results further provide guidance on the potential design of future clinical trials supporting the development of P3 components as a PTSD diagnostic aid.

Ubiquitin C-terminal hydrolase L1 is required for pancreatic beta cell survival and function in lipotoxic conditions

AIMS/HYPOTHESIS

Ubiquitin C-terminal hydrolase L1 (UCHL1) is associated with neurodegenerative diseases and has been suggested to have roles in pancreatic beta cells. Our proteomic analysis revealed that UCHL1 was the most increased protein in MIN6 cells exposed to palmitate. The present study used a genetic loss-of-function model to test the hypothesis that UCHL1 is required for normal beta cell function and fate under lipotoxic conditions.

METHODS

Human islets, mouse islets and MIN6 cells were used to analyse UCHL1 protein levels and regulation of UCHL1 by palmitate. The levels of free mono-ubiquitin and poly-ubiquitinated proteins were assessed. Gracile axonal dystrophy (GAD) mutant mice lacking UCHL1 were fed a normal or lipotoxic high-fat diet. Glucose tolerance, insulin tolerance and insulin secretion were assessed in vivo. Beta cell death and proliferation were assessed by TUNEL and proliferating cell nuclear antigen (PCNA) staining. Insulin secretion, calcium signalling, endoplasmic reticulum (ER) stress, apoptosis and SNARE protein levels were assessed in vitro.

RESULTS

UCHL1 protein, which was highly specific to beta cells, was increased by palmitate at basal glucose, but not in the context of hyperglycaemia associated with frank diabetes. Although islet development and function were initially normal in Uchl1 (-/-) mice, a 4-week high-fat diet caused glucose intolerance and impaired insulin secretion. Uchl1 (-/-) mice had increased ER stress and beta cell apoptosis. The levels of SNARE proteins were dysregulated in Uchl1 (-/-) islets. Palmitate-stimulated vesicle-associated membrane protein 2 (VAMP2) ubiquitination was modulated by a chemical UCHL1 inhibitor.

CONCLUSIONS/INTERPRETATION

Together, these data suggest that UCHL1 has essential functional and anti-apoptotic roles in beta cells under stress conditions associated with lipotoxicity.

Musashi expression in β-cells coordinates insulin expression, apoptosis and proliferation in response to endoplasmic reticulum stress in diabetes

Diabetes is associated with the death and dysfunction of insulin-producing pancreatic β-cells. In other systems, Musashi genes regulate cell fate via Notch signaling, which we recently showed regulates β-cell survival. Here we show for the first time that human and mouse adult islet cells express mRNA and protein of both Musashi isoforms, as well Numb/Notch/Hes/neurogenin-3 pathway components. Musashi expression was observed in insulin/glucagon double-positive cells during human fetal development and increased during directed differentiation of human embryonic stem cells (hESCs) to the pancreatic lineage. De-differentiation of β-cells with activin A increased Msi1 expression. Endoplasmic reticulum (ER) stress increased Msi2 and Hes1, while it decreased Ins1 and Ins2 expression, revealing a molecular link between ER stress and β-cell dedifferentiation in type 2 diabetes. These effects were independent of changes in Numb protein levels and Notch activation. Overexpression of MSI1 was sufficient to increase Hes1, stimulate proliferation, inhibit apoptosis and reduce insulin expression, whereas Msi1 knockdown had the converse effects on proliferation and insulin expression. Overexpression of MSI2 resulted in a decrease in MSI1 expression. Taken together, these results demonstrate overlapping, but distinct roles for Musashi-1 and Musashi-2 in the control of insulin expression and β-cell proliferation. Our data also suggest that Musashi is a novel link between ER stress and the compensatory β-cell proliferation and the loss of β-cell gene expression seen in specific phases of the progression to type 2 diabetes.

Time-dependent mediators of HPA axis activation following live Escherichia coli

The hypothalamus-pituitary-adrenal (HPA) axis is activated during an immune challenge to liberate energy and modulate immune responses via feedback and regulatory mechanisms. Inflammatory cytokines and prostaglandins are known contributors to HPA activation; however, most previous studies only looked at specific time points following LPS administration. Since whole bacteria have different immune stimulatory properties compared with LPS, the aim of the present studies was to determine whether different immune products contribute to HPA activation at different times following live Escherichia coli challenge. Sprague-Dawley rats were injected intraperitoneally with E. coli (2.5 × 10(7) CFU) and a time course of circulating corticosterone, ACTH, inflammatory cytokines, and PGE(2) was developed. Plasma corticosterone peaked 0.5 h after E. coli and steadily returned to baseline by 4 h. Plasma PGE(2) correlated with the early rise in plasma corticosterone, whereas inflammatory cytokines were not detected until 2 h. Pretreatment with indomethacin, a nonselective cyclooxygenase inhibitor, completely blocked the early rise in plasma corticosterone, but not at 2 h, whereas pretreatment with IL-6 antibodies had no effect on the early rise in corticosterone but attenuated corticosterone at 2 h. Interestingly, indomethacin pretreatment did not completely block the early rise in corticosterone following a higher concentration of E. coli (2.5 × 10(8) CFU). Further studies revealed that only animals receiving indomethacin prior to E. coli displayed elevated plasma and liver cytokines at early time points (0.5 and 1 h), suggesting prostaglandins suppress early inflammatory cytokine production. Overall, these data indicate prostaglandins largely mediate the early rise in plasma corticosterone, while inflammatory cytokines contribute to maintaining levels of corticosterone at later time points.

Rat strain differences in restraint stress-induced brain cytokines

Induction of brain cytokines during times of stress has potent effects on altering behavior, mood, and cognitive functioning. Currently, it is unknown why exposure to some stressors such as tailshock and footshock elevate brain cytokines, while exposure to swim, predator odor, and restraint stress do not. Recent data indicate that brain noradrenergic signaling mediates brain cytokine production suggests magnitude of norepinephrine release during stress may be critical in initiating brain cytokine production. The aim of the current study was to investigate stress-induced brain cytokines between rat strains that differ in their magnitude of stress responsiveness as measured by brain norepinephrine and HPA responses. Sprague-Dawley and Fischer rats were placed in a restraint bag for 1 h or 2 h and sacrificed immediately following stressor termination. Exposure to restraint significantly elevated hypothalamic interleukin (IL)-1β and IL-1 receptor type (R) 2 mRNA after 1 h and IL-1β protein after 2 h in the high stress responsive Fischer rats, but not in Sprague-Dawley rats. IL-6, IL-1R1, Il-1 receptor antagonist (RA), and cyclooxygenase (Cox)-2 mRNA were not altered and neither there was expression of any cytokines in the hippocampus or circulating cytokines in either strain. Administration of desipramine (a norepinephrine reuptake inhibitor) to Sprague-Dawley rats was sufficient either alone or in combination with stress to increase IL-1β mRNA in the hypothalamus and desipramine combined with stress was sufficient to increase IL-1R2 mRNA in the hypothalamus. These data support our hypothesis that there is a critical threshold of brain norepinephrine necessary to stimulate brain cytokines, which may help to explain why severe stressors are more commonly reported to induce brain cytokines. These data also suggest an organisms' susceptibility to stress-induced brain cytokine production, depends on responsiveness and regulation of noradrenergic neurons.

Paracrine signalling loops in adult human and mouse pancreatic islets: netrins modulate beta cell apoptosis signalling via dependence receptors

AIMS/HYPOTHESIS

Adult pancreatic islets contain multiple cell types that produce and secrete well characterised hormones, including insulin, glucagon and somatostatin. Although it is increasingly apparent that islets release and respond to more secreted factors than previously thought, systematic analyses are lacking. We therefore sought to identify potential autocrine and/or paracrine islet growth factor loops, and to characterise the function of the netrin family of islet-secreted factors and their receptors, which have been previously unreported in adult islets.

METHODS

Gene expression databases, islet-specific tag sequencing libraries and microarray datasets of FACS purified beta cells were used to compile a list of secreted factors and receptors present in mouse or human islets. Netrins and their receptors were further assessed using RT-PCR, Western blot analysis and immunofluorescence staining. The roles of netrin-1 and netrin-4 in beta cell function, apoptosis and proliferation were also examined.

RESULTS

We identified 233 secreted factors and 234 secreted factor receptors in islets. The presence of netrins and their receptors was further confirmed. Downregulation of caspase-3 activation was observed when MIN6 cells were exposed to exogenous netrin-1 and netrin-4 under hyperglycaemic conditions. Reduction in caspase-3 cleavage was linked to the decrease in dependence receptors, neogenin and unc-5 homologue A, as well as the activation of Akt and extracellular signal-regulated protein kinase (ERK) signalling.

CONCLUSIONS/INTERPRETATION

Our results highlight the large number of potential islet growth factors and point to a context-dependent pro-survival role for netrins in adult beta cells. Since diabetes results from a deficiency in functional beta cell mass, these studies are important steps towards developing novel therapies to improve beta cell survival.

Reciprocal modulation of adult beta cell maturity by activin A and follistatin

AIMS/HYPOTHESIS

The functional maturity of pancreatic beta cells is impaired in diabetes mellitus. We sought to define factors that can influence adult beta cell maturation status and function.

METHODS

MIN6 cells labelled with a Pdx1 monomeric red fluorescent protein-Ins1 enhanced green fluorescent protein dual reporter lentivirus were used to screen candidate growth and/or differentiation factors using image-based approaches with confirmation by real-time RT-PCR and assays of beta cell function using primary mouse islets.

RESULTS

Activin A strikingly decreased the number of mature beta cells and increased the number of immature beta cells. While activins are critical for pancreatic morphogenesis, their role in adult beta cells remains controversial. In primary islets and MIN6 cells, activin A significantly decreased the expression of insulin and several genes associated with beta cell maturity (e.g. Pdx1, Mafa, Glut2 [also known as Slc2a2]). Genes found in immature beta cells (e.g. Mafb) tended to be upregulated by activin A. Insulin secretion was also reduced by activin A. In addition, activin A-treated MIN6 cells proliferated faster than non-treated cells. The effects of endogenous activin A on beta cells were completely reversed by exogenous follistatin.

CONCLUSIONS/INTERPRETATION

These results suggest that autocrine and/or paracrine activin A signalling exerts a suppressive effect on adult beta cell maturation and function. Thus, the maturation state of adult beta cells can be modulated by external factors in culture. Interventions inhibiting activin or its signalling pathways may improve beta cell function. Understanding of maturation and plasticity of adult pancreatic tissue has significant implications for islet regeneration and for in vitro generation of functional beta cells.

Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes

Although HDL-mediated cholesterol transport to the liver is well studied, cholesterol efflux from hepatocytes back to HDL is less well understood. Real-time imaging of efflux of 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino)-23,24-bisnor-5-cholen-3beta-ol (NBD-cholesterol), which is poorly esterified, and [(3)H]cholesterol, which is extensively esterified, from cultured primary hepatocytes of wild-type and sterol carrier protein-2 (SCP-2) gene-ablated mice showed that 1) NBD-cholesterol efflux was affected by the type of lipoprotein acceptor, i.e., HDL3 over HDL2; 2) NBD-cholesterol efflux was rapid (detected in 1-2 min) and resolved into fast [half time (t((1/2))) = 2.4 min, 6% of total] and slow (t((1/2)) = 26.5 min, 94% of total) pools, consistent with protein- and vesicle-mediated cholesterol transfer, respectively; 3) SCP-2 gene ablation increased efflux of NBD-cholesterol, as well as [(3)H]cholesterol, albeit less so due to competition by esterification of [(3)H]cholesterol, but not NBD-cholesterol; and 4) SCP-2 gene ablation increased initial rate (2.3-fold) and size (9.7-fold) of rapid effluxing sterol, suggesting an increased contribution of molecular cholesterol transfer. In addition, colocalization, double-immunolabeling fluorescence resonance energy transfer, and electron microscopy, as well as cross-linking coimmunoprecipitation, indicated that SCP-2 directly interacted with the HDL receptor, scavenger receptor class B type 1 (SRB1), in hepatocytes. Other membrane proteins in cholesterol efflux [SRB1 and ATP-binding cassettes (ABC) A-1, ABCG-1, ABCG-5, and ABCG-8] and several soluble/vesicle-associated proteins facilitating intracellular cholesterol trafficking (StARDs, NPCs, ORPs) were not upregulated. However, loss of SCP-2 elicited twofold upregulation of liver fatty acid-binding protein (L-FABP), a protein with lower affinity for cholesterol but higher cytosolic concentration than SCP-2. Ablation of SCP-2 and L-FABP decreased HDL-mediated NBD-cholesterol efflux. These results indicate that SCP-2 expression plays a significant role in HDL-mediated cholesterol efflux by regulating the size of rapid vs. slow cholesterol efflux pools and/or eliciting concomitant upregulation of L-FABP in cultured primary hepatocytes.

Endogenous extra-cellular heat shock protein 72: Releasing signal(s) and function

Exposure to acute physical and/or psychological stressors induces a cascade of physiological changes collectively termed the stress response. The stress response is demonstrable at the behavioural, neural, endocrine and cellular levels. Stimulation of the stress response functions to improve an organism's chance of survival during acute stressor challenge. The current review focuses on one ubiquitous cellular stress response, up-regulation of heat shock protein 72 (Hsp72). Although a great deal is known about the function of intra-cellular Hsp72 during exposure to acute stressors, little is understood about the potential function of endogenous extra-cellular Hsp72 (eHsp72). The current review will develop the hypothesis that eHsp72 release may be a previously unrecognized feature of the acute stress response and may function as an endogenous 'danger signal' for the immune system. Specifically, it is proposed that exposure to physical or psychological acute stressors stimulate the release of endogenous eHsp72 into the blood via an alpha1-adrenergic receptor-mediated mechanism and that elevated eHsp72 functions to facilitate innate immunity in the presence of bacterial challenge.

Overexpression of sterol carrier protein-2 differentially alters hepatic cholesterol accumulation in cholesterol-fed mice

Although in vitro studies suggest a role for sterol carrier protein-2 (SCP-2) in cholesterol trafficking and metabolism, the physiological significance of these observations remains unclear. This issue was addressed by examining the response of mice overexpressing physiologically relevant levels of SCP-2 to a cholesterol-rich diet. While neither SCP-2 overexpression nor cholesterol-rich diet altered food consumption, increased weight gain, hepatic lipid, and bile acid accumulation were observed in wild-type mice fed the cholesterol-rich diet. SCP-2 overexpression further exacerbated hepatic lipid accumulation in cholesterol-fed females (cholesterol/cholesteryl esters) and males (cholesterol/cholesteryl esters and triacyglycerol). Primarily in female mice, hepatic cholesterol accumulation induced by SCP-2 overexpression was associated with increased levels of LDL-receptor, HDL-receptor scavenger receptor-B1 (SR-B1) (as well as PDZK1 and/or membrane-associated protein 17 kDa), SCP-2, liver fatty acid binding protein (L-FABP), and 3alpha-hydroxysteroid dehydrogenase, without alteration of other proteins involved in cholesterol uptake (caveolin), esterification (ACAT2), efflux (ATP binding cassette A-1 receptor, ABCG5/8, and apolipoprotein A1), or oxidation/transport of bile salts (cholesterol 7alpha-hydroxylase, sterol 27alpha-hydroxylase, Na(+)/taurocholate cotransporter, Oatp1a1, and Oatp1a4). The effects of SCP-2 overexpression and cholesterol-rich diet was downregulation of proteins involved in cholesterol transport (L-FABP and SR-B1), cholesterol synthesis (related to sterol regulatory element binding protein 2 and HMG-CoA reductase), and bile acid oxidation/transport (via Oapt1a1, Oatp1a4, and SCP-x). Levels of serum and hepatic bile acids were decreased in cholesterol-fed SCP-2 overexpression mice, especially in females, while the total bile acid pool was minimally affected. Taken together, these findings support an important role for SCP-2 in hepatic cholesterol homeostasis.

Notch signalling suppresses apoptosis in adult human and mouse pancreatic islet cells

AIMS/HYPOTHESIS

The pathogenesis of diabetes and the success of islet transplantation depend on the control of pancreatic beta cell fate. The Notch signalling pathway is essential for normal prenatal pancreatic development, but the presence and function of this gene network in adult islets has received much less attention.

METHODS

The presence of Notch signalling components was assessed in vitro using RT-PCR, western blotting and immunofluorescence. The functional consequences of altering Notch signalling on insulin secretion and programmed cell death were examined.

RESULTS

Adult mouse islets, human islets and mouse insulinoma MIN6 cells possess key components of the Notch pathway. RT-PCR, western blotting and immunofluorescence indicated that the Notch target gene, neurogenin3 (Ngn3, also known as Neurog3), is also present in adult islet cells. Inhibiting Notch signalling with N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT) increased Ngn3 mRNA expression and protein levels in adult islets. The activated notch homologue 1 (NOTCH1) protein level was decreased upon serum withdrawal, as well as after treatment with a phosphatidylinositol 3-kinase inhibitor, or hydroxy-2-naphthalenylmethylphosphonic acid, an insulin receptor inhibitor. While islets cultured in DAPT did not exhibit defects in insulin secretion, indicating that differentiation is unaltered, inhibiting gamma-secretase-dependent Notch activation led to a dose-dependent increase in caspase-3-dependent apoptosis in both MIN6 cells and human islets. Conversely, gamma-secretase overactivity resulted in an accumulation of cleaved NOTCH1 and protection from apoptosis.

CONCLUSIONS/INTERPRETATION

Together these results show that the Notch/Ngn3 signalling network is intact and functional in adult islets. This pathway represents an attractive target for modulating beta cell fate in diabetes, islet transplantation and efforts to derive beta cell surrogates in vitro.

UC/MALDI-MS analysis of HDL; evidence for density-dependent post-translational modifications

The purpose of this study is to determine whether the nature of the post-translational modifications of the major apolipoproteins of HDL is different for density-distinct subclasses. These subclasses were separated by ultracentrifugation using a novel density-forming solute to yield a high-resolution separation. The serum of two subjects, a control with a normolipidemic profile and a subject with diagnosed cardiovascular disease, was studied. Aliquots of three HDL subclasses were analyzed by MALDI and considerable differences were seen when comparing density-distinct subclasses and also when comparing the two subjects. A detailed analysis of the post-translational modification pattern of apoA-1 shows evidence of considerable protease activity, particularly in the more dense fractions. We conclude that part of the heterogeneity of the population of HDL particles is due to density-dependent protease activity.

Islet microvasculature in islet hyperplasia and failure in a model of type 2 diabetes

Gene expression profiling of islets from pre-diabetic male Zucker diabetic fatty (ZDF) rats showed increased expression of hypoxia-related genes, prompting investigation of the vascular integrity of the islets. The islet microvasculature was increased approximately twofold in young male ZDF rats by both morphometric analysis and quantifying mRNA levels of endothelial markers. ZDF rats at 12 weeks of age showed a significant reduction in the number of endothelial cells, which was prevented by pretreatment with pioglitazone. Light and electron microscopy of normoglycemic 7-week-old ZDF rats showed thickened endothelial cells with loss of endothelial fenestrations. By 12 weeks of age, there was disruption of the endothelium and intra-islet hemorrhage. Islets from 7- and 12-week-old ZDF rats showed an approximate three- and twofold increase in vascular endothelial growth factor (VEGF)-A mRNA and VEGF protein secretion, respectively, compared with lean controls. Thrombospondin-1 mRNA increased in 7- and 12-week-old rats by 2- and 10-fold, respectively, and was reduced by 50% in 12-week-old rats pretreated with pioglitazone. Islets from young male control rats induced migration of endothelial cells in a collagen matrix only after pretreatment with matrix metalloproteinase (MMP)-9. Islets from 7-week-old ZDF rats showed a fivefold increase in migration score compared with wild-type controls, even without MMP-9 treatment. Islets from 15-week-old ZDF rats did not induce migration; rather, they caused a significant rounding up of the duct-derived cells, suggesting a toxic effect. These data suggest that in the ZDF rat model of type 2 diabetes, an inability of the islet to maintain vascular integrity may contribute to beta-cell failure.

Sexual dimorphism of the intracellular heat shock protein 72 response

The majority of previous work examining stress responses has been done in males. Recently, it has become clear that the impact of stressor exposure is modulated by sex. One stress response that may be affected by sex is the induction of intracellular heat shock protein (HSP) 72, which is a stress- responsive molecular chaperone that refolds denatured proteins and promotes cellular survival. The following study compared HSP72 in males and females and also examined whether the estrous cycle altered HSP72 induction in females. We hypothesized that females compared with males would have a constrained HSP72 response after an acute stressor and that the stress-induced HSP72 response in females would fluctuate with the estrous cycle. Male and female F344 rats were either left in their home cage or exposed to acute tail-shock stress (8–10/group). Immediately following stressor, trunk blood was collected and tissues were flash frozen. Vaginal smear and estrogen enzyme immunoassay were used to categorize the phase of estrous. Results show that female rats had a greater corticosterone response than males, that both males and females exhibit a stress-induced release of progesterone, and that males and females had equal levels of stress-induced circulating norepinephrine. Sexual dimorphism of the HSP72 (ELISA) response existed in pituitary gland, mesenteric lymph nodes, and liver such that female rats had an attenuated HSP72 response compared with males after stress. The adrenal glands, spleen, and heart did not exhibit sexual dimorphism of the HSP72 response. The estrous cycle did not have a significant effect on basal or stress-induced HSP72 in females.

The objective assessment of international collaboration between pathology laboratories

Collaboration between clinical laboratories in different countries is widespread but rarely subject to critical analysis. We developed a management tool for assessing the quality of an international pathology laboratory collaboration. Key areas of activity were identified and relevant performance indicators were established. There was no evidence of improved staff morale arising from the project but research, education, equipment, protocols and ethics activities all had demonstrable outputs. Identification of suboptimal performance in areas of the project allowed effective improvement planning. International collaboration may consume significant resources. Objective assessment should be used to measure performance and to enhance quality.

Multicenter experience with the Monarc transobturator sling system to treat stress urinary incontinence

This study was conducted to report on the safety and efficacy of a transobturator sling approach for treatment of urodynamic stress incontinence (USI). Women with urodynamic stress incontinence were offered a novel polypropylene mesh sling procedure, implanted beneath the lateral pubic rami rather than retropubically. Retrospective data were collected at three U.S. sites. Two hundred women with a mean age of 59 years (range 27-93) underwent the sling procedure. Mean follow-up was 21.5 weeks (range 3-43). Perioperative safety parameters are reported for all subjects and efficacy parameters for those who were followed up for 26 weeks or more. Among the subjects, 95.3% reported being continent or substantially continent (occasional leakage of small amounts, with protection not needed). Mean operative time was 13.8 min (range 7-34). Preoperatively, 75% wore pads, with 5.3% continuing to do so at 26 weeks. Pre-op urgency was reported by 62.7%, with 41.5% receiving medication. Urgency was reported postoperatively by 20.5% of patients, but only 13.6% were medicated for urgency. Urinary retention was identified in 0.9% at 26 weeks. Transobturator slings are highly effective for treatment of SUI, and may offer increased safety relative to traditional and tension-free retropubic slings.

Metal Ion Complexes of EDTA as Solutes for Density Gradient Ultracentrifugation: Influence of Metal Ions

In the study reported here, we study the nature of the metal ion complexes of EDTA as solute systems for analysis of lipoproteins by density gradient ultracentrifugation (DGU) by varying both the complexing metal ion and the counterion. Specifically, the sodium and cesium salts of complexes of Bi/EDTA, Pb/EDTA, Cd/EDTA, Fe/EDTA, and Cu/EDTA were chosen for this study. We show that useful gradients can be formed within a few hours beginning with a homogeneous solution. Data are presented that provide insight into the nature of how these gradients are formed from these complexes and how the selection of a specific complex can be used to enhance particular regions of the lipoprotein density profile for clinical studies. We also examine the use of equilibrium sedimentation theory to correlate the measured density profiles generated by these complexes with their molecular weight.

Catecholamines mediate stress-induced increases in peripheral and central inflammatory cytokines

Proinflammatory cytokines act at receptors in the CNS to alter physiological and behavioral responses. Exposure to stressors increases both peripheral and central proinflammatory cytokines, yet the mechanism(s) of induction remain unknown. Experiments here examined the role of catecholamines in the in vivo induction of proinflammatory cytokines following tailshock stress. Rats were pretreated i.p. with 2.0 mg/kg prazosin (alpha1-adrenoceptor antagonist), 10.0 mg/kg propranolol (beta-adrenoceptor antagonist), or 5.0 mg/kg labetalol (alpha1- and beta-adrenoceptor antagonist) 30 min prior to tailshock exposure and plasma interleukin-1beta (IL-1beta) and IL-6, along with tissue interleukin-1beta from the hypothalamus, hippocampus, and pituitary were measured immediately following stressor termination. Prazosin attenuated stress-induced plasma IL-1beta and IL-6, but had no effect on tissue IL-1beta levels, while propranolol attenuated plasma IL-6 and blocked tissue IL-1beta elevation, and labetalol, which cannot cross the blood-brain barrier, attenuated plasma IL-1beta and IL-6, blocked pituitary IL-1beta, but had no effect on central tissue IL-1beta levels. Furthermore, administration of 50.0 mg/kg N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride, a neurotoxin that lesions neural projections from the locus coeruleus, prevented stress-induced elevation in hippocampal IL-1beta, a region highly innervated by the locus coeruleus, but had no effect on hypothalamic IL-1beta, a region that receives few locus coeruleus projections. Finally, i.p. injection of 5.0 mg/kg isoproterenol (beta-adrenoceptor agonist) was sufficient to induce circulating IL-1 and IL-6, and tissue IL-1beta. These data suggest catecholamines play an important role in the induction of stress-induced proinflammatory cytokines and that beta-adrenoceptors are critical for tissue IL-1beta induction, while both alpha- and beta-adrenoceptors contribute to the induction of plasma cytokines.

Splenic norepinephrine depletion following acute stress suppresses in vivo antibody response

Exposure to an intense acute stressor immediately following immunization leads to a reduction in anti-KLH IgM, IgG, and IgG2a, but not IgG1. Stress also depletes splenic norepinephrine (NE) content. Immunization during pharmacological (alpha-methyl-p-tyrosine) or stress-induced splenic NE depletion results in antibody suppression similar to that found in rats immunized prior to stressor exposure. Prevention of splenic NE depletion during stress by tyrosine, but not pharmacological elevation (mirtazapine) of NE, resulted in normal antibody responses. These data support the hypothesis that splenic NE depletion is necessary and sufficient for stress-induced suppression of antibody to a T-cell dependent antigen.

Toxicology and carcinogenesis studies of microencapsulated trans-cinnamaldehyde in rats and mice

trans-Cinnamaldehyde is a widely used natural ingredient that is added to foods and cosmetics as a flavoring and fragrance agent. Male and female F344/N rats and B6C3F(1) mice were exposed to microencapsulated trans-cinnamaldehyde in the feed for three months or two years. All studies included untreated and vehicle control groups. In the three-month studies, rats and mice were given diets containing 4100, 8200, 16,500, or 33,000 ppm trans-cinnamaldehyde. In rats, feed consumption was reduced in all exposed groups. In mice, feed consumption was reduced in the highest dose groups. Body weights of all treated males were less than controls. Body weights were reduced in female rats exposed to 16,500 or 33,000 ppm and female mice exposed to 8200 ppm or greater. All rats survived to the end of the study but some male mice in the highest dose groups died due to inanition from unpalatability of the dosed feed. The incidence of squamous epithelial hyperplasia of the forestomach was significantly increased in rats exposed to 8200 ppm or greater and female mice exposed to 33,000 ppm. In mice, the incidence of olfactory epithelial degeneration of the nasal cavity was significantly increased in males and females exposed to 16,500 ppm and females exposed to 33,000 ppm. In the two-year studies, rats and mice were exposed to 1000, 2100, or 4100 ppm trans-cinnamaldehyde. Body weights were reduced in mice exposed to 2100 ppm and in rats and mice exposed to 4100 ppm. In rats, hippuric acid excretion was dose proportional indicating that absorption, metabolism, and excretion were not saturated. No neoplasms were attributed to trans-cinnamaldehyde in rats or mice. Squamous cell papillomas and carcinomas of the forestomach were observed in male and female mice but the incidences were within the NTP historical control range and were not considered to be related to trans-cinnamaldehyde exposure.

The role of IL-1β in stress-induced sensitization of proinflammatory cytokine and corticosterone responses

Proinflammatory cytokines often sensitize neuronal, hormonal, and behavioral responses to subsequent challenge. Recently, it was observed that exposure to inescapable tailshock enhances peripheral and central proinflammatory cytokine and corticosterone (CORT) responses to subsequent immune challenge up to 4 days later. Thus, we examined the role of central interleukin-1beta (IL-1beta) in stress-induced sensitization of proinflammatory cytokine and CORT responses to a subsequent immune challenge. Rats were administered IL-1 receptor antagonist (IL-1ra) or vehicle into the intra-cisterna magna 1 h prior to tailshock (100, 1.6 mA 5 s shocks) exposure. Twenty-four hours later, rats were challenged i.p. with 10 microg/kg lipopolysaccharide (LPS) and killed 1 h later. IL-1ra had no effect on basal proinflammatory cytokines, but completely blocked the stress-induced enhancement in central and pituitary IL-1beta and plasma IL-6 release following LPS challenge. IL-1ra had no effect on stress-induced enhancement in CORT responses following LPS challenge. Additional rats were administered i.c.v. hrIL-1beta or vehicle and returned to their home cage. Twenty-four hours later, rats were challenged i.p. with either saline or 10 microg/kg LPS and killed 1 h later. Central hrIL-1beta administration significantly elevated central IL-1beta levels and plasma CORT following LPS challenge compared with vehicle-injected controls. These data demonstrate that elevations in central IL-1beta, whether stress-induced or exogenously administered, are sufficient for sensitizing central IL-1beta and CORT responses to subsequent immune challenge. However, during times of stress, exogenous central IL-1ra administration only blocked sensitization of subsequent central IL-1beta responses, not CORT responses, suggesting other factors during the stress response can sensitize CORT responses.

Inescapable shock induces resistance to the effects of dexamethasone

Administration of bacterial endotoxin (lipopolysachharide; LPS) elevates proinflammatory cytokines, such as interleukin-1beta (IL-1beta) and IL-6, and activates the hypothalamic-pituitary-adrenal (HPA) axis. Corticosterone (CORT), the glucocorticoid (GC) effector hormone of the HPA axis in rats, inhibits both proinflammatory cytokine production/release and activity of the HPA axis itself. Exposure to chronic or repeated stressors often induces resistance to the effects of GCs. The following experiments were conducted to test the hypothesis that an acute stressor, inescapable tailshock (IS), alters responsivity of the HPA axis and proinflammatory cytokine system to dexamethasone (DEX), a synthetic GC. First, we examined the ability of various doses of DEX to suppress proinflammatory cytokine and HPA activity in response to LPS challenge 24 h after either home cage (HCC) or IS treatment. Upon finding resistance to DEX in IS animals, we examined the duration of the altered response to DEX by testing animals 1, 4 and 21 days after IS. To test whether IS animals were selectively resistant to the suppressive effects of DEX on the response to LPS, the ability of DEX to suppress HPA activity in response to a non-inflammatory stressor, exposure to an elevated "pedestal", was assessed. Again, DEX resistance was observed in IS animals. Finally, we examined whether changes in the responsivity to DEX were dependent upon the controllability of the stressor. The induction of DEX resistance was independent of the degree of behavioral control that the animal had over the stressor. Thus, a single session of IS induces DEX resistance of both HPA axis and cytokine responses measured in vivo.

Toxicology and carcinogenesis studies of microencapsulated citral in rats and mice

Citral, a widely used natural ingredient, is added to foods and cosmetics as a flavoring and fragrance agent. Male and female F344/N rats and B6C3F1 mice were exposed to microencapsulated citral in the feed for 14 weeks or two years. All studies included untreated and vehicle control groups. In the 14-week studies, rats and mice were given diets containing 3,900, 7,800, 15,600, or 31,300 ppm citral. In rats, food consumption was reduced in the two highest dose groups. In mice an apparent increase in food consumption was observed, but was due to mice scattering the feed. Body weights of all treated animals were less than controls. All rats and four male mice were killed moribund in the high dose groups. In rats, forestomach and kidney lesions were observed. At the higher doses, lesions observed in the bone marrow, testes, and thymus in rats and in the ovary in mice were considered related to inanition and resultant moribundity. In the two-year studies, rats were exposed to 1,000, 2,000, or 4,000 ppm citral. Body weights were reduced in the 4,000 ppm rats. Mice were exposed to 500, 1,000, or 2,000 ppm citral. Body weights in the 1,000 and 2,000 ppm groups were reduced. No neoplasms were attributed to citral in rats or mice. Malignant lymphoma occurred with a positive trend and was significantly greater than controls in female mice in the 2,000 ppm group. However, the incidences were within the NTP historical control range and could not be clearly related to citral administration.

A gonadotropin-releasing hormone insensitive, thapsigargin-sensitive Ca2+ store reduces basal gonadotropin exocytosis and gene expression: comparison with agonist-sensitive Ca2+ stores

We examined whether distinct Ca2+ stores differentially control basal and gonadotropin (GTH-II)-releasing hormone (GnRH)-evoked GTH-II release, long-term GTH-II secretion and contents, and GTH-II-beta mRNA expression in goldfish. Thapsigargin (Tg)-sensitive Ca2+ stores mediated neither caffeine-evoked GTH-II release, nor salmon (s)GnRH- and chicken (c)GnRH-II-stimulated secretion; the latter responses were previously shown to involve ryanodine (Ry)-sensitive Ca2+ stores. Surprisingly, Tg decreased basal GTH-II release. This response was attenuated by prior exposure to sGnRH and caffeine, but was insensitive to the phosphatase inhibitor okadaic acid, the inhibitor of constitutive release brefeldin A and cGnRH-II. GTH-II-beta mRNA expression was decreased at 24 h by 2 microm Tg, and by inhibiting (10 microm Ry) and stimulating (1 nm Ry) Ry receptors. Transient increases in GTH-II-beta mRNA were observed at 2 h and 12 h following 10 microm and 1 nm Ry treatment, respectively. Effects of Tg, Ry and GnRH on long-term GTH-II secretion, contents and apparent production differed from one another, and these changes were not well correlated with changes in GTH-II-beta mRNA expression. Our data show that GTH-II secretion, storage and transcription can be independently controlled by distinct Ca2+ stores.

Hyperinsulinism induced by targeted suppression of beta cell KATP channels

ATP-sensitive K+ (K(ATP)) channels couple cell metabolism to electrical activity. To probe the role of K(ATP) in glucose-induced insulin secretion, we have generated transgenic mice expressing a dominant-negative, GFP-tagged K(ATP) channel subunit in which residues 132-134 (Gly-Tyr-Gly) in the selectivity filter were replaced by Ala-Ala-Ala, under control of the insulin promoter. Transgene expression was confirmed by both beta cell-specific green fluorescence and complete suppression of channel activity in those cells ( approximately 70%) that did fluoresce. Transgenic mice developed normally with no increased mortality and displayed normal body weight, blood glucose levels, and islet architecture. However, hyperinsulinism was evident in adult mice as (i) a disproportionately high level of circulating serum insulin for a given glucose concentration ( approximately 2-fold increase in blood insulin), (ii) enhanced glucose-induced insulin release from isolated islets, and (iii) mild yet significant enhancement in glucose tolerance. Enhanced glucose-induced insulin secretion results from both increased glucose sensitivity and increased release at saturating glucose concentration. The results suggest that incomplete suppression of K(ATP) channel activity can give rise to a maintained hyperinsulinism.

Agonist-specific and sexual stage-dependent inhibition of gonadotropin-releasing hormone-stimulated gonadotropin and growth hormone release by ryanodine: relationship to sexual stage-dependent caffeine-sensitive hormone release

Differential utilization of intracellular Ca2+ stores with specific functional characteristics could be a potential mechanism for coupling various stimuli to specific cellular responses. In the goldfish pituitary, both gonadotropes and somatotropes possess multiple intracellular Ca2+ stores that are differentially coupled to agonist-evoked exocytosis. We investigated the role of ryanodine receptor/Ca2+-release channels (RyR) in basal and gonadotropin-releasing hormone (GnRH)-evoked hormone secretion from cultured gonadotropes and somatotropes using radioimmunoassay for gonadotropin (GTH-II) and growth hormone (GH). As is the case in vivo, the basal and evoked secretion of both hormones varied with seasonal reproductive status. GnRH-stimulated hormone release was three-fold higher in cells from sexually mature animals compared to those in a sexually regressed state. Nanomolar doses of ryanodine evoked significant GTH-II and GH secretion, suggesting that ryanodine-sensitive Ca2+ stores can couple to exocytosis in both cell types. In gonadotropes, 10 microM ryanodine abolished cGnRH-II-evoked GTH-II release in both sexually mature and sexually regressed fish, while sGnRH signalling was mediated by ryanodine-sensitive Ca2+ stores in cells from sexually regressed fish only. Ryanodine-sensitive Ca2+ stores in somatotropes were only involved in cGnRH-II-stimulated GH release during gonadal regression. In contrast, sGnRH-stimulated, but not cGnRH-II-stimulated, GH release was significantly reduced by 1 microM xestospongin C. Although hormone release stimulated by mobilizing caffeine-sensitive Ca2+ pools was also markedly seasonal, it was largely independent of ryanodine-sensitive Ca2+ stores. Ryanodine-sensitive Ca2+ stores in both cell types are not active downstream of ionomycin, BayK 8644, protein kinase C or cyclic adenosine monophosphate signalling pathways, suggesting difference from a classical Ca2+-induced Ca2+ release system. Ours study is the first to suggest that RyR2 may be involved in the seasonal plasticity of pituitary function, which may be related to cyclic changes observed in reproduction and growth.

Calculation of a deuterium double shock Hugoniot from ab initio simulations

We calculate the equation of state of dense deuterium with two ab initio simulation techniques, path integral Monte Carlo and density functional theory molecular dynamics, in the density range of 0.67 < or = rho < or = 1.60 g cm(-3). We derive the double shock Hugoniot and compare with the recent laser-driven double shock wave experiments by Mostovych et al. [Phys. Rev. Lett. 85, 3870 (2000)]. We find excellent agreement between the two types of microscopic simulations, but a significant discrepancy with the laser-driven shock measurements.

Modulation of gonadotropin II release by K+ channel blockers in goldfish gonadotropes: a novel stimulatory action of 4-aminopyridine

The effects of K+ channel blockers on basal gonadotropin II (GTH-II) release were examined in cultured goldfish gonadotropes. Tetraethylammonium (TEA) inhibited basal GTH-II release, whereas 4-aminopyridine (4-AP) increased basal release, although both K+ channel blockers generated increases in [Ca2+]i. Other K+ channel blockers had no significant effect on GTH-II release. We examined whether Ca2+ entry that arises from blockade of K+ channels by 4-AP mediates the secretory response. Secretion evoked by 4-AP was slightly reduced by TEA but was unaffected by reducing Ca2+ entry using either an inhibitor of Ca2+ channels, verapamil, or nominally Ca2+-free medium. In contrast, the Ca2+ signal evoked by 4-AP was largely blocked by Ca2+-free medium, as predicted by its inhibitory action on K+ channels. Together, these data suggest that the hormone release response to 4-AP is independent of entry of extracellular Ca2+. Finally, the mechanism of hormone release evoked by 4-AP appeared to be independent of mechanism(s) evoked by caffeine since 4-AP did not affect caffeine-evoked release and caffeine did not affect 4-AP evoked release. That both 4-AP and TEA generated Ca2+ signals but affected hormone release in either an extracellular Ca2+ independent (4-AP) or inhibitory (TEA) manner suggests that Ca2+ entry is linked to GTH-II secretion in a highly nonlinear fashion.

With great expectations, can two "wrongs" prime a "right"?

The proportion of related prime-target pairs (relatedness proportion, RP) and prime-target stimulus onset asynchrony (SOA) was varied to determine the involvement of strategic priming mechanisms in the reduction in semantic priming that occurs when a target follows an unmasked prime that itself receives immediate repetition priming from a masked prime. At 300-ms and 1,200-ms SOAs, (a) strategic semantic priming was operating, in that priming from a nonrepeated prime increased as RP increased from .25 to .75, and (b) for both RPs, prime repetition reduced semantic priming. At a 167-ms SOA, (a) priming from a nonrepeated prime was unaffected by RP, suggesting that strategic priming was not operating, and (b) for both RPs, prime repetition did not reduce semantic priming. Because prime repetition did not reduce priming at the 167-ms SOA (when only spreading activation should have been mediating semantic priming), the reduction in semantic priming produced by prime repetition is not evidence against spreading activation automaticity. Possible mechanisms through which prime repetition reduces semantic priming are discussed.

Diffuse lamellar keratitis: incidence, associations, outcomes, and a new classification system

PURPOSE

To evaluate the incidence, associations, and visual outcomes in patients with diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK).

SETTING

University-based refractive surgery center, Boston, Massachusetts, USA.

METHODS

This retrospective review comprised 2711 eyes that had LASIK between September 1996 and September 1999. All eyes that developed DLK after LASIK were included. They were divided into type I DLK (center sparing) or type II DLK (center involved) and then subdivided into A (sporadic-DLK not diagnosed in other patients treated on the same day) or B (cluster-other patients identified with DLK). Type IA corresponded to center sparing, sporadic; type IB, center sparing, cluster; type IIA, center involved, sporadic; and type IIB, center involved, cluster. The main outcome measures were incidence of DLK after LASIK, time to diagnosis, time to resolution, and changes in best spectacle-corrected visual acuity (BSCVA). Unpaired t tests were used for statistical analyses.

RESULTS

Thirty-six eyes (1.3%) developed DLK. Type I occurred in 58.3% of cases (type IA, n = 18; type IB, n = 3) and type II, in 41.7% (type IIA, n = 10; type IIB, n = 5). The mean time to diagnosis was not statistically significantly different between type I (1.8 days) and type II (1.1 days). Fourteen eyes (38.9%) developed DLK after an epithelial defect, representing an odds ratio of 13 times. The association with an epithelial defect was statistically significantly greater with type I (11/21 eyes, 52.4%) than with type II (3/15 eyes, 20.0%; P =.05). The mean time to resolution was 3.5 days in type I (type IA = 3.6 days; type IB = 2.7 days). This was significantly shorter than in type II, which had a mean time to resolution of 12.1 days (type IIA = 9.3 days; type IIB = 10.2 days) (P =.001). Loss of 2 or more lines of BSCVA occurred in 2 of 5 patients with type IIB and in no patients with types IA, IB, or IIA.

CONCLUSIONS

Epithelial defects after LASIK increased the risk of DLK occurrence, especially type I. Type II DLK was associated with a prolonged time to resolution and carried a significantly higher risk of BSCVA loss than type I.

Different orders for acquisition of apoptotic characteristics by leukocytes

Apoptotic leukocytes undergo cellular changes that are used as markers for "early" versus "late" stages of apoptosis. To ascertain if the order for acquisition of these changes is unique to specific hematopoietic cell types, we compared four leukocyte cell types and the following five apoptotic characteristics: MC540 incorporation, annexin V-FITC binding, propidium iodide (PI) labeling of hypodiploid nuclei, DNA fragmentation by a colorimetric assay, and cell membrane permeability to PI. The order for acquisition of these apoptotic characteristics was significantly different for each of the leukocyte cell types and for the mode of induction of apoptosis. It is interesting that the nuclear changes but not the membrane changes studied in mouse spleen cells required caspase activity. In summary, the acquisition of these apoptotic characteristics occurs through caspase-dependent and caspase-independent mechanisms, and importantly, the order for acquisition of the characteristics is specific for the cell type and for the mode of induction of apoptosis.

Cross-Reactivity studies of gutta-percha, gutta-balata, and natural rubber latex (Hevea brasiliensis)

Gutta-percha and gutta-balata are derived from the Paliquium gutta and Mimusops globsa trees, respectively, that are in the same botanical family as the rubber tree Hevea brasiliensis. For this reason the potential for immunological cross-reactivity between the gutta-percha and gutta-balata used in endodontics and natural rubber latex (NRL) has been the subject of some controversy, because these products may be used in latex-allergic individuals. The objective of this study was to investigate the potential cross-reactivity between gutta-percha, gutta-balata, and NRL. Physiological extracts of seven commercially available gutta-percha products, raw gutta-percha, raw gutta-balata, and synthetic transpolyisoprene were each analyzed for cross-reactivity with NRL in a competitive radioallergosorbent test inhibition assay. No detectable cross-reactivity was observed with any of the raw or clinically used gutta-percha products. In contrast the raw gutta-balata released proteins that were cross-reactive with Hevea latex. We conclude that the absence of gutta-percha proteins that can react with Hevea latex-specific IgE antibody supports the minimal potential for commercially available gutta-percha to induce allergic symptoms in individuals sensitized to NRL. Because gutta-balata is sometimes added to commercial gutta-percha products caution should be exercised if products containing gutta-balata are used in endodontic care of latex-allergic individuals.

Attentional capture by irrelevant color singletons

Four experiments investigated attentional capture by a color singleton in visual search for a nonsingleton target. B. S. Gibson and E. M. Kelsey (1998) found that a color singleton in a precuing array facilitated target discrimination at that location if the same color also signaled the target array onset. The authors found similar cuing effects regardless of whether the singleton color matched the target array and regardless of whether subjects could anticipate the singleton or target-array color. In Experiment 4, a color singleton captured attention when it appeared in the precuing array but not when it appeared in the target array. The results indicate that attentional control settings for displaywide attributes are imprecise: Although subjects may anticipate a specific color, they cannot avoid attentional capture by other irrelevant colors. In addition, the effect of irrelevant singletons depends on whether a target is simultaneously present in the array.

Surgically induced topographical abnormalities after LASIK: management of central islands, corneal ectasia, decentration, and irregular astigmatism

Proper preoperative evaluation is critical for avoiding many postoperative complications associated with laser in-situ keratomileusis (LASIK). Proper nonsurgical management includes careful monitoring of patients during the recovery period using various testing procedures, including corneal topography. When surgical intervention is required, a stepwise approach often is used as a conservative treatment, allowing further treatment if necessary. Many complications after LASIK are amenable to further treatment. However, it often is advisable to monitor patients until improved instrumentation is developed. The authors review the etiology and management of several complications after LASIK by reviewing the literature and relaying their own clinical experiences.

Attentional capture by irrelevant color singletons

Four experiments investigated attentional capture by a color singleton in visual search for a nonsingleton target. B. S. Gibson and E. M. Kelsey (1998) found that a color singleton in a precuing array facilitated target discrimination at that location if the same color also signaled the target array onset. The authors found similar cuing effects regardless of whether the singleton color matched the target array and regardless of whether subjects could anticipate the singleton or target-array color. In Experiment 4, a color singleton captured attention when it appeared in the precuing array but not when it appeared in the target array. The results indicate that attentional control settings for displaywide attributes are imprecise: Although subjects may anticipate a specific color, they cannot avoid attentional capture by other irrelevant colors. In addition, the effect of irrelevant singletons depends on whether a target is simultaneously present in the array.

Philosophies and practices regarding the management of the endodontic smear layer: results from two surveys

The purpose of this investigation was to ascertain the prevailing attitudes within the endodontic community regarding smear layer removal. The first survey asked the philosophies and techniques currently being taught to predoctoral dental students and postdoctoral endodontic residents in the United States, whereas the second surveyed some of the members of the American Association of Endodontists currently practicing in the United States. Findings from these surveys revealed that more than three-fourths of the dental students and nearly two-thirds of the endodontic residents are not being taught routine smear layer removal. Slightly more than one-half of endodontists responded they practice smear layer removal. These surveys indicate that there is no clear consensus in the endodontic community, either academically or clinically, as to whether the smear layer should be removed or be allowed to remain before obturation of the root canal space.

Analysis of pFQ12, a 22.4-kb Frankia plasmid

Frankia are gram-positive, filamentous bacteria capable of fixing atmospheric dinitrogen in symbiosis with a wide variety of woody plants and shrubs. Some isolates of Frankia harbor plasmids of 8.5 (pFQ11) and 22.4 kb (pFQ12) that have no known function but are transmitted through many generations in culture. We have sequenced the 22,437-bp pFQ12 plasmid that is present in isolates CpI1 and ArI3. This sequence, with 76% G+C, is almost totally unrelated to that of pFQ11 found in the same cells. However, four regions of identity, 40-90 bp each, are dispersed around the plasmids. The 22.4-kb plasmid has >50 open reading frames (ORFs) that encode putative proteins of more than 100 amino acids, with the largest being 2226 amino acids. Twenty of these ORFs are likely to encode proteins based on their codon bias as determined by two different algorithms. Transcripts from nine of these regions have been identified by reverse transcriptase-polymerase chain reaction (RT-PCR) or filter hybridization. The two Frankia plasmids each encode a protein similar to the korSA protein that regulates transmission of pSAM2 in Streptomyces. The origin of replication (ORI) region of pFQ12 was localized by intrastrand AT and GC equivalence switch. It includes a 40-bp, intergenic, A+T-rich region that has a strong identity in pFQ11.

Pacap stimulation of gonadotropin-II secretion in goldfish pituitary cells: mechanisms of action and interaction with gonadotropin releasing hormone signalling

Pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been shown to be a hypophysiotropic factor in the goldfish. In this study, we examined the mechanisms of PACAP action on goldfish maturational gonadotropin (GTH-II) release using primary cultures of pituitary cells. The GTH-II response to mammalian PACAP1-38 (mPACAP) was inhibited by a PACAP receptor antagonist suggesting a receptor-mediated action. Addition of either an adenylate cyclase inhibitor or a protein kinase A (PKA) inhibitor reduced the mPACAP-induced GTH-II release. In addition, when GTH-II release was already stimulated by either forskolin or 8-bromo-cAMP (8Br-cAMP), mPACAP did not further increase GTH-II secretion. These results strongly implicated the involvement of an adenylate cyclase/cAMP/PKA pathway in PACAP-stimulated GTH-II release. Although mPACAP induced a rise in intracellular Ca2+ level in identified gonadotropes, results with voltage-sensitive Ca2+ channel inhibitors indicated that the GTH-II responses to mPACAP, forskolin and 8Br-cAMP did not depend upon Ca2+ entry through these channels. Two protein kinase C (PKC) inhibitors did not affect mPACAP-elicited GTH-II release, and mPACAP further increased GTH-II secretion in the presence of PKC activators. These results indicate that PKC-dependent elements are not essential for the stimulatory action of mPACAP in gonadotropes. Interestingly, while GTH-II responses to a stimulatory concentration of mPACAP were additive to responses elicited by maximal effective concentrations of two endogenous gonadotropin releasing hormones (GnRHs), a subthreshold concentration of mPACAP potentiated GnRH and PKC activator stimulation of GTH-II secretion. Similarly, submaximal concentrations of forskolin potentiated the GTH-II response to the PKC activator, tetradecanoyl phorbol acetate. These data suggest that PACAP and its cAMP-dependent signalling mechanisms provide an alternate stimulatory input to goldfish gonadotropes and may influence the effectiveness of the major neuroendocrine control exerted by the PKC-dependent GnRH signalling pathway.

Modifying Mg2+ binding and exchange with the N-terminal of calmodulin

To follow Mg2+ binding to the N-terminal of calmodulin (CaM), we substituted Phe in position 19, which immediately precedes the first Ca2+/Mg2+ binding loop, with Trp, thus making F19WCaM (W-Z). W-Z has four acidic residues in chelating positions, two of which form a native Z-acid pair. We then generated seven additional N-terminal CaM mutants to examine the role of chelating acidic residues in Mg2+ binding and exchange with the first EF-hand of CaM. A CaM mutant with acidic residues in all of the chelating positions exhibited Mg2+ affinity similar to that of W-Z. Only CaM mutants that had a Z-acid pair were able to bind Mg2+ with physiologically relevant affinities. Removal of the Z-acid pair from the first EF-hand produced a dramatic 58-fold decrease in its Mg2+ affinity. Additionally, removal of the Z-acid pair led to a 1.8-fold increase in the rate of Mg2+ dissociation. Addition of an X- or Y-acid pair could not restore the high Mg2+ binding lost with removal of the Z-acid pair. Therefore, the Z-acid pair in the first EF-hand of CaM supports high Mg2+ binding primarily by increasing the rate of Mg2+ association.

Activation of Trp3 by inositol 1,4,5-trisphosphate receptors through displacement of inhibitory calmodulin from a common binding domain

Mammalian homologues of Drosophila Trp form plasma membrane channels that mediate Ca(2+) influx in response to activation of phospholipase C and internal Ca(2+) store depletion. Previous studies showed that human Trp3 is activated by inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) and identified interacting domains, one on Trp and two on IP(3)R. We now find that Trp3 binds Ca(2+)-calmodulin (Ca(2+)/CaM) at a site that overlaps with the IP(3)R binding domain. Using patch-clamp recordings from inside-out patches, we further show that Trp3 has a high intrinsic activity that is suppressed by Ca(2+)/CaM under resting conditions, and that Trp3 is activated by the following: a Trp-binding peptide from IP(3)R that displaces CaM from Trp3, a myosin light chain kinase Ca(2+)/CaM binding peptide that prevents CaM from binding to Trp3, and calmidazolium, an inactivator of Ca(2+)/CaM. We conclude that inhibition of the inhibitory action of CaM is a key step of Trp3 channel activation by IP(3)Rs.