Intermediate pressure-normalized principal wall strain values are associated with increased abdominal aortic aneurysmal growth rates.

Introduction: Current abdominal aortic aneurysm (AAA) assessment relies on analysis of AAA diameter and growth rate. However, evidence demonstrates that AAA pathology varies among patients and morphometric analysis alone is insufficient to precisely predict individual rupture risk. Biomechanical parameters, such as pressure-normalized AAA principal wall strain (ερ+¯/PP, %/mmHg), can provide useful information for AAA assessment. Therefore, this study utilized a previously validated ultrasound elastography (USE) technique to correlate ερ+¯/PP with the current AAA assessment methods of maximal diameter and growth rate. Methods: Our USE algorithm utilizes a finite element mesh, overlaid a 2D cross-sectional view of the user-defined AAA wall, at the location of maximum diameter, to track two-dimensional, frame-to-frame displacements over a full cardiac cycle, using a custom image registration algorithm to produce ερ+¯/PP. This metric was compared between patients with healthy aortas and AAAs (≥3 cm) and compared between small and large AAAs (≥5 cm). AAAs were then separated into terciles based on ερ+¯/PP values to further assess differences in our metric across maximal diameter and prospective growth rate. Non-parametric tests of hypotheses were used to assess statistical significance as appropriate. Results: USE analysis was conducted on 129 patients, 16 healthy aortas and 113 AAAs, of which 86 were classified as small AAAs and 27 as large. Non-aneurysmal aortas showed higher ερ+¯/PP compared to AAAs (0.044 ± 0.015 vs. 0.034 ± 0.017%/mmHg, p = 0.01) indicating AAA walls to be stiffer. Small and large AAAs showed no difference in ερ+¯/PP. When divided into terciles based on ερ+¯/PP cutoffs of 0.0251 and 0.038%/mmHg, there was no difference in AAA diameter. There was a statistically significant difference in prospective growth rate between the intermediate tercile and the outer two terciles (1.46 ± 2.48 vs. 3.59 ± 3.83 vs. 1.78 ± 1.64 mm/yr, p = 0.014). Discussion: There was no correlation between AAA diameter and ερ+¯/PP, indicating biomechanical markers of AAA pathology are likely independent of diameter. AAAs in the intermediate tercile of ερ+¯/PP values were found to have nearly double the growth rates than the highest or lowest tercile, indicating an intermediate range of ερ+¯/PP values for which patients are at risk for increased AAA expansion, likely necessitating more frequent imaging follow-up.

A Mixed-Methods Study to Evaluate the Feasibility and Acceptability of Implementing an Electronic Health Record Social Determinants of Health Screening Instrument into Routine Clinical Oncology Practice.

BACKGROUND: Routine screening for social determinants of health (SDOH) in the outpatient oncology setting is uncommon. The primary goal of this study was to prospectively evaluate the feasibility and acceptability of implementing an electronic health record (EHR) SDOH screening instrument into routine, clinical, oncology practice. METHODS: Adult patients with newly diagnosed gastrointestinal cancer presenting to a regional cancer center (November 2020 to July 2021) were eligible. Based on the consolidated framework for implementation research, feasibility measures included screening completion, median clinic visit time, and acceptability by the inter-professional care team and patients as measured by semistructured, qualitative interviews and surveys. Secondary outcomes included SDOH needs identified. RESULTS: Of 137 eligible patients, 112 (81.8%) were screened for SDOH. Demographics of the cohort included: 41.1% black (n = 46), 48.2% rural (n = 54), 4.5% uninsured (n = 5), and 6.3% Medicaid-insured (n = 7) patients. Median visit time was 97 min (95% CI 70-107 min) before and 100 min after implementation (95% CI 75-119 min; p = 0.95). In total, 95.5% (n = 107) reported at least one SDOH need. Clinicians (7/10) reported that SDOH screening was not disruptive and were supportive of ongoing use. Patients (10/10) found the screening acceptable. Screening staff (5/5) reported workflow barriers. Patients and staff also recommended revision of specific instrument questions. CONCLUSIONS: Routine collection of SDOH in an outpatient oncology setting using an EHR instrument is feasible and does not result in increased visit time for patients or clinicians. However, staff perceptions of clinic workflow disruption were reported. Further investigation to determine whether standardized SDOH assessment can improve cancer care delivery and outcomes is ongoing.

Opportunity Costs of Surgical Resection and Perioperative Chemotherapy for Locoregional Pancreatic Adenocarcinoma.

PURPOSE: Given the perioperative morbidity and intensity of multimodality treatment, patients with resected pancreatic ductal adenocarcinoma (PDAC) spend a substantial amount of time in clinical care. The primary aim was to determine total time spent in multimodality care for patients with locoregional PDAC. METHODS: A cohort study of all patients who underwent curative-intent resection for PDAC at a single-institution, tertiary care center was performed (2015-2019). Exact times for all relevant visits were abstracted from the primary medical record, and travel time was calculated. Care time was divided into preoperative, surgical, radiation, and systemic therapy phases of care. Primary outcome measures were the percentage of total survival time (TST) and percentage of overall survival (OS) days spent in receipt of care. RESULTS: One hundred seven patients were included. Patients spent a median of 5.0% (interquartile range [IQR] 2.4%-10.1%) of TST and 11.0% (IQR, 5.7%-20.4%) of OS days in receipt of clinical care. Preoperative, surgical, radiation, and systemic therapy phases of care comprised a median of 0.9% (IQR, 0.4%-2.2%), 3.0% (IQR, 1.9%-6.8%), 4.4% (IQR, 3.6%-6.3%), and 10.0% (IQR, 6.2%-14.1%) of OS days. The median per-visit travel time was 60 minutes (IQR, 32-120), and the median cumulative travel time was 22.0 hours (IQR, 12.0-51.5). 12.1% (n = 13) and 7.8% (n = 4) of patients spent > 10% of TST in receipt of surgical and systemic therapy care, respectively. CONCLUSION: Patients with locoregional pancreatic cancer spend a considerable percentage of their survival time in receipt of oncologic care. Further research to determine predictors of increased time burden is warranted to better inform shared decision making.

Changes in the Proportion of Patients Presenting With Early Stage Colon Cancer Over Time Among Medicaid Expansion and Nonexpansion States: A Cross-sectional Study.

BACKGROUND: The 2010 Patient Protection and Affordable Care Act mandated preventive screening coverage and provided support to participating states for Medicaid coverage. The association of Medicaid expansion with colon cancer stage at diagnosis is unknown. OBJECTIVE: This study aimed to determine whether the proportion of patients diagnosed with early stage colon cancer changed over time within states that expanded Medicaid compared with nonexpansion states. DESIGN: This is a cross-sectional cohort study. SETTING: This study evaluated multicenter registry data from the National Cancer Database (2006-2016). PATIENTS: There were 25,462 uninsured or Medicaid-insured patients with newly diagnosed colon cancer who resided in 2014 Medicaid expansion or nonexpansion states. MAIN OUTCOME MEASURES: This study assessed the annual proportion of patients with early stage (I-II) versus late stage (III-IV) colon cancer. RESULTS: A total of 10,289 patients were identified in expansion states and 15,173 patients in nonexpansion states. Cohorts were similar in age (median 55 years) and sex (46.7% female). A greater proportion of patients in nonexpansion states were Black (33.4% vs 24.0%) and resided in a zip code with median income <$38,000 (39.7% vs 28.2%) and lower educational status (37.4% vs 28.1%). In 2006, the proportions of patients with early stage colon cancer in expansion and nonexpansion cohorts were similar (33.2% vs 32.5%). The proportion of patients with early stage colon cancer within nonexpansion states declined by 0.8% per year after 2014, whereas the proportion within expansion states increased by 0.9% per year after 2014 ( p < 0.05). By 2016, the absolute difference in the propensity-adjusted proportion of early stage colon cancer was 8.8% (39.7% vs 30.9%, p < 0.001). LIMITATIONS: National Cancer Database data are obtained only from Commission on Cancer-accredited sites and are not population based. CONCLUSIONS: After Medicaid expansion in 2014, the proportion of patients diagnosed and treated at Commission on Cancer-accredited facilities with early stage colon cancer increased within expansion states and decreased in nonexpansion states. Increase in insurance coverage may have facilitated earlier diagnosis among patients in expansion states. See Video Abstract at http://links.lww.com/DCR/B804 . CAMBIOS EN LA PROPORCIN DE PACIENTES QUE PRESENTAN CNCER DE COLON EN ESTADIO TEMPRANA A LO LARGO DEL TIEMPO ENTRE LOS ESTADOS DE EXPANSIN Y NO EXPANSIN DE MEDICAID UN ESTUDIO TRANSVERSAL: ANTECEDENTES:La Ley del Cuidado de Salud a Bajo Precio del 2010 ordenó la cobertura de exámenes preventivos y brindó apoyo a los estados participantes para la cobertura de Medicaid. Se desconoce la asociación de la expansión de Medicaid con el estadio del cáncer de colon en el momento del diagnóstico.OBJETIVO:Determinar si la proporción de pacientes diagnosticados con cáncer de colon en estadio temprano cambió con el tiempo dentro de los estados que expandieron Medicaid en comparación con los estados sin expansión.DISEÑO:Estudio de cohorte transversal.ENTORNO CLINICO:Datos de registro multicéntrico de la Base de datos nacional de cáncer (2006-2016).PACIENTES:Había 25,462 pacientes sin seguro o asegurados por Medicaid con cáncer de colon recién diagnosticado. Exposición: Residencia en estados de expansión o no expansión de Medicaid en el 2014.PRINCIPALES MEDIDAS DE RESULTADO:Proporción anual de pacientes con cáncer de colon en estadio temprano (I-II) versus tardío (III-IV).RESULTADOS:Se identificaron un total de 10.289 pacientes en estados de expansión y 15.173 pacientes en estados de no expansión. Las cohortes fueron similares en edad (mediana de 55 años) y sexo (46,7% mujeres). Una mayor proporción de pacientes en estados sin expansión eran de raza negra (33,4% vs 24,0%) y residían en un código postal con ingresos medios <$38 000 (39,7% vs 28,2%) y un nivel educativo más bajo (37,4% vs 28,1%). En el 2006, las proporciones de pacientes con cáncer de colon en estadio temprano en cohortes en expansión y sin expansión fueron similares (33,2% vs 32,5%). La proporción de pacientes con estadio temprano dentro de los estados sin expansión disminuyó en un 0,8% por año después del 2014, mientras que la proporción dentro de los estados de expansión aumentó en un 0,9% por año después del 2014 (p <0,05). Para el 2016, la diferencia absoluta en la proporción ajustada por propensión de cáncer de colon en estadio temprano fue de 8.8% (39.7% vs 30.9%, p <0.001).LIMITACIONES:Los datos de la Base de datos nacional de cáncer se obtienen únicamente de los sitios acreditados por la Comisión de cáncer y no se basan en la población.CONCLUSIONES:Después de la expansión de Medicaid en el 2014, la proporción de pacientes diagnosticados y tratados en instalaciones acreditadas por la Comisión de Cáncer en pacientes con cáncer de colon en estadio temprano aumentó dentro de los estados de expansión y disminuyó en los estados de no expansión. El aumento de la cobertura del seguro puede haber facilitado un diagnóstico más temprano entre los pacientes en estados de expansión. Consulte Video Resumen en http://links.lww.com/DCR/B804 . (Traducción- Dr. Francisco M. Abarca-Rendon ).

Pseudoaneurysm of the Pancreaticoduodenal Artery Associated with Duodenal Diverticulitis.

BACKGROUND: Duodenal diverticula tend to be asymptomatic; however, patients may develop duodenal diverticulitis. CASE PRESENTATION: A 66-year-old Caucasian man presented to our emergency room with a two-day history of right-sided abdominal pain, chills, tachycardia, nausea, and emesis. His WBC, lactic acid, and bilirubin were elevated. CT-scan revealed an inflammatory process involving the gallbladder, the duodenum and ascending colon, a mesenteric soft tissue mass, and a diverticulum of the second portion of the duodenum. He was admitted, antibiotics were started, and he improved clinically over the next 36 hours. Repeat triple contrast CT-scan showed a two cm pseudoaneurysm (PA) of the pancreaticoduodenal artery causing a mesenteric hematoma. The inflammatory changes had significantly improved, and WBC and CRP were normalizing. Repeat CT-scan three days later demonstrated an interval increase in size of the PA. Angiography through celiac access and gastroduodenal artery demonstrated predominant inflow to the PA from the inferior pancreaticoduodenal artery. The superior mesenteric artery was accessed showing a replaced right hepatic artery hindering access to the branch feeding the PA. The patient was transferred to a specialized facility where ultimately occlusion of the PA inflow was obtained. The patient recovered without any complication from this rare condition. CONCLUSION: This seems to be the first reported case of duodenal diverticulitis causing a PA of the pancreaticoduodenal artery. Antibiotic therapy together with percutaneous embolization of the bleeding source resulted in a good outcome.

Signal Integration at Elongation Factor 2 Kinase: THE ROLES OF CALCIUM, CALMODULIN, AND SER-500 PHOSPHORYLATION.

Eukaryotic elongation factor 2 kinase (eEF-2K), the only calmodulin (CaM)-dependent member of the unique α-kinase family, impedes protein synthesis by phosphorylating eEF-2. We recently identified Thr-348 and Ser-500 as two key autophosphorylation sites within eEF-2K that regulate its activity. eEF-2K is regulated by Ca2+ ions and multiple upstream signaling pathways, but how it integrates these signals into a coherent output, i.e. phosphorylation of eEF-2, is unclear. This study focuses on understanding how the post-translational phosphorylation of Ser-500 integrates with Ca2+ and CaM to regulate eEF-2K. CaM is shown to be absolutely necessary for efficient activity of eEF-2K, and Ca2+ is shown to enhance the affinity of CaM toward eEF-2K. Ser-500 is found to undergo autophosphorylation in cells treated with ionomycin and is likely also targeted by PKA. In vitro, autophosphorylation of Ser-500 is found to require Ca2+ and CaM and is inhibited by mutations that compromise binding of phosphorylated Thr-348 to an allosteric binding pocket on the kinase domain. A phosphomimetic Ser-500 to aspartic acid mutation (eEF-2K S500D) enhances the rate of activation (Thr-348 autophosphorylation) by 6-fold and lowers the EC50 for Ca2+/CaM binding to activated eEF-2K (Thr-348 phosphorylated) by 20-fold. This is predicted to result in an elevation of the cellular fraction of active eEF-2K. In support of this mechanism, eEF-2K knock-out MCF10A cells reconstituted with eEF-2K S500D display relatively high levels of phospho-eEF-2 under basal conditions. This study reports how phosphorylation of a regulatory site (Ser-500) integrates with Ca2+ and CaM to influence eEF-2K activity.

Two Obese Patients with Presumptive Diagnosis of Anaphylactoid Syndrome of Pregnancy Presenting at a Community Hospital.

BACKGROUND: Anaphylactoid syndrome of pregnancy (ASP) is a rare but extremely serious complication, with an estimated incidence in North America of 1 in 15 200 deliveries. Despite its rarity, ASP is responsible for approximately 10% of all childbirth-associated deaths in the United States. At present, there is no validated biomarker or specific set of risk factors sufficiently predictive of ASP risk to incorporate into clinical practice. Toward the goal of developing a methodology predictive of an impending ASP event for use by obstetricians, anesthesiologists, and other practitioners participating in infant deliveries, physicians encountering an ASP event have been encouraged to report the occurrence of a case and its biologically plausible risk factors. CASE REPORT: Herein, we report on 2 patients who presented with a presumptive diagnosis of ASP to the delivery unit of a community hospital. Patient One was a 21-year-old, obese (5'11" tall, 250 lbs., BMI 34.9) white female, 1 pregnancy, no live births (G1P0), estimated gestational age (EGA) 40.2 weeks. Patient Two was a 29-year-old, obese (5'7" tall, 307 lbs., BMI 48.1) Hispanic female, second pregnancy, with 1 previous live birth via C-section (G2P1-0-0-1). Her pregnancy was at gestational age 38 weeks plus 2 days. CONCLUSIONS: Patient One had 2 possible risk factors: administration of Pitocin to induce labor and post-coital spotting from recent intercourse. Patient Two suffered premature rupture of the placental membranes. Both Patient One and Patient Two had very high body mass indices (BMIs), at the 97th and 99th percentiles, respectively. In the relatively few cases of anaphylactoid syndrome of pregnancy described to date, this is the first report of a possible association with high BMI.

DLK1/PREF1 regulates nutrient metabolism and protects from steatosis.

Nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance and obesity, as well as progressive liver dysfunction. Recent animal studies have underscored the importance of hepatic growth hormone (GH) signaling in the development of NAFLD. The imprinted Delta-like homolog 1 (Dlk1)/preadipocyte factor 1 (Pref1) gene encodes a complex protein producing both circulating and membrane-tethered isoforms whose expression dosage is functionally important because even modest elevation during embryogenesis causes lethality. DLK1 is up-regulated during embryogenesis, during suckling, and in the mother during pregnancy. We investigated the normal role for elevated DLK1 dosage by overexpressing Dlk1 from endogenous control elements. This increased DLK1 dosage caused improved glucose tolerance with no primary defect in adipose tissue expansion even under extreme metabolic stress. Rather, Dlk1 overexpression caused reduced fat stores, pituitary insulin-like growth factor 1 (IGF1) resistance, and a defect in feedback regulation of GH. Increased circulatory GH culminated in a switch in whole body fuel metabolism and a reduction in hepatic steatosis. We propose that the function of DLK1 is to shift the metabolic mode of the organism toward peripheral lipid oxidation and away from lipid storage, thus mediating important physiological adaptations associated with early life and with implications for metabolic disease resistance.

The molecular mechanism of eukaryotic elongation factor 2 kinase activation.

Calmodulin (CaM)-dependent eukaryotic elongation factor 2 kinase (eEF-2K) impedes protein synthesis through phosphorylation of eukaryotic elongation factor 2 (eEF-2). It is subject to complex regulation by multiple upstream signaling pathways, through poorly described mechanisms. Precise integration of these signals is critical for eEF-2K to appropriately regulate protein translation rates. Here, an allosteric mechanism comprising two sequential conformations is described for eEF-2K activation. First, Ca(2+)/CaM binds eEF-2K with high affinity (Kd(CaM)(app) = 24 ± 5 nm) to enhance its ability to autophosphorylate Thr-348 in the regulatory loop (R-loop) by > 10(4)-fold (k(auto) = 2.6 ± 0.3 s(-1)). Subsequent binding of phospho-Thr-348 to a conserved basic pocket in the kinase domain potentially drives a conformational transition of the R-loop, which is essential for efficient substrate phosphorylation. Ca(2+)/CaM binding activates autophosphorylated eEF-2K by allosterically enhancing k(cat)(app) for peptide substrate phosphorylation by 10(3)-fold. Thr-348 autophosphorylation results in a 25-fold increase in the specificity constant (k(cat)(app)/K(m)(Pep-S) (app)), with equal contributions from k(cat)(app) and K(m)(Pep-S)(app), suggesting that peptide substrate binding is partly impeded in the unphosphorylated enzyme. In cells, Thr-348 autophosphorylation appears to control the catalytic output of active eEF-2K, contributing more than 5-fold to its ability to promote eEF-2 phosphorylation. Fundamentally, eEF-2K activation appears to be analogous to an amplifier, where output volume may be controlled by either toggling the power switch (switching on the kinase) or altering the volume control (modulating stability of the active R-loop conformation). Because upstream signaling events have the potential to modulate either allosteric step, this mechanism allows for exquisite control of eEF-2K output.

BRAF inhibitors suppress apoptosis through off-target inhibition of JNK signaling.

Vemurafenib and dabrafenib selectively inhibit the v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) kinase, resulting in high response rates and increased survival in melanoma. Approximately 22% of individuals treated with vemurafenib develop cutaneous squamous cell carcinoma (cSCC) during therapy. The prevailing explanation for this is drug-induced paradoxical ERK activation, resulting in hyperproliferation. Here we show an unexpected and novel effect of vemurafenib/PLX4720 in suppressing apoptosis through the inhibition of multiple off-target kinases upstream of c-Jun N-terminal kinase (JNK), principally ZAK. JNK signaling is suppressed in multiple contexts, including in cSCC of vemurafenib-treated patients, as well as in mice. Expression of a mutant ZAK that cannot be inhibited reverses the suppression of JNK activation and apoptosis. Our results implicate suppression of JNK-dependent apoptosis as a significant, independent mechanism that cooperates with paradoxical ERK activation to induce cSCC, suggesting broad implications for understanding toxicities associated with BRAF inhibitors and for their use in combination therapies. DOI: http://dx.doi.org/10.7554/eLife.00969.001.

Calcium/calmodulin stimulates the autophosphorylation of elongation factor 2 kinase on Thr-348 and Ser-500 to regulate its activity and calcium dependence.

Eukaryotic elongation factor 2 kinase (eEF-2K) is an atypical protein kinase regulated by Ca(2+) and calmodulin (CaM). Its only known substrate is eukaryotic elongation factor 2 (eEF-2), whose phosphorylation by eEF-2K impedes global protein synthesis. To date, the mechanism of eEF-2K autophosphorylation has not been fully elucidated. To investigate the mechanism of autophosphorylation, human eEF-2K was coexpressed with λ-phosphatase and purified from bacteria in a three-step protocol using a CaM affinity column. Purified eEF-2K was induced to autophosphorylate by incubation with Ca(2+)/CaM in the presence of MgATP. Analyzing tryptic or chymotryptic peptides by mass spectrometry monitored the autophosphorylation over 0-180 min. The following five major autophosphorylation sites were identified: Thr-348, Thr-353, Ser-445, Ser-474, and Ser-500. In the presence of Ca(2+)/CaM, robust phosphorylation of Thr-348 occurs within seconds of addition of MgATP. Mutagenesis studies suggest that phosphorylation of Thr-348 is required for substrate (eEF-2 or a peptide substrate) phosphorylation, but not self-phosphorylation. Phosphorylation of Ser-500 lags behind the phosphorylation of Thr-348 and is associated with the Ca(2+)-independent activity of eEF-2K. Mutation of Ser-500 to Asp, but not Ala, renders eEF-2K Ca(2+)-independent. Surprisingly, this Ca(2+)-independent activity requires the presence of CaM.

Novel control by the CA3 region of the hippocampus on neurogenesis in the dentate gyrus of the adult rat.

The dentate gyrus is a site of continued neurogenesis in the adult brain. The CA3 region of the hippocampus is the major projection area from the dentate gyrus. CA3 sends reciprocal projections back to the dentate gyrus. Does this imply that CA3 exerts some control over neurogenesis? We studied the effects of lesions of CA3 on neurogenesis in the dentate gyrus, and on the ability of fluoxetine to stimulate mitotic activity in the progenitor cells. Unilateral ibotenic-acid generated lesions were made in CA3. Four days later there was no change on the number of either BrdU or Ki67-positive progenitor cells in the dentate gyrus. However, after 15 or 28 days, there was a marked reduction in surviving BrdU-labelled cells on the lesioned side (but no change in Ki-67+ cells). pCREB or Wnt3a did not co-localise with Ki-67 but with NeuN, a marker of mature neurons. Lesions had no effect on the basal expression of either pCREB or Wnt3a. Subcutaneous fluoxetine (10 mg/kg/day) for 14 days increased the number of Ki67+ cells as expected on the control (non-lesioned) side but not on that with a CA3 lesion. Nevertheless, the expected increase in BDNF, pCREB and Wnt3a still occurred on the lesioned side following fluoxetine treatment. Fluoxetine has been reported to decrease the number of "mature" calbindin-positive cells in the dentate gyrus; we found this still occurred on the side of a CA3 lesion. We then showed that the expression GAP-43 was reduced in the dentate gyrus on the lesioned side, confirming the existence of a synaptic connection between CA3 and the dentate gyrus. These results show that CA3 has a hitherto unsuspected role in regulating neurogenesis in the dentate gyrus of the adult rat.

The roles of BDNF, pCREB and Wnt3a in the latent period preceding activation of progenitor cell mitosis in the adult dentate gyrus by fluoxetine.

The formation of new neurons continues into adult life in the dentate gyrus of the rat hippocampus, as in many other species. Neurogenesis itself turns out to be highly labile, and is regulated by a number of factors. One of these is the serotoninergic system: treatment with drugs (such as the SSRI fluoxetine) markedly stimulates mitosis in the progenitor cells of the dentate gyrus. But this process has one remarkable feature: it takes at least 14 days of continuous treatment to be effective. This is despite the fact that the pharmacological action of fluoxetine occurs within an hour or so of first administration. This paper explores the role of BDNF in this process, using the effect of a Trk antagonist (K252a) on the labelling of progenitor cells with the mitosis marker Ki67 and the associated expression of pCREB and Wnt3a. These experiments show that (i) Fluoxetine increased Ki67 counts, as well as pCREB and Wnt3a expression in the dentate gyrus. The action of fluoxetine on the progenitor cells and on pCREB (but not Wnt3a) depends upon Trk receptor activation, since it was prevented by icv infusion of K252a. (ii) These receptors are required for both the first 7 days of fluoxetine action, during which no apparent change in progenitor mitosis occurs, as well as the second 7 days. Increased pCREB was always associated with progenitor cell mitosis, but Wnt3a expression may be necessary but not sufficient for increased progenitor cell proliferation. These results shed new light on the action of fluoxetine on neurogenesis in the adult dentate gyrus, and have both clinical and experimental interest.

Brain-derived neurotropic factor and neurogenesis in the adult rat dentate gyrus: interactions with corticosterone.

Flattening the diurnal corticosterone rhythm prevented the stimulating action of L-NAME (a nitric oxide synthase, NOS, inhibitor) on progenitor cell proliferation in the dentate gyrus in Lister-Hooded adult male rats. The increased expression of brain-derived neurotrophic factor (BDNF) and trkB mRNA in the dentate gyrus which otherwise occurred after L-NAME was also prevented by clamping the corticoid rhythm in adrenalectomized rats, but was restored by daily additional injections of corticosterone (which replicates the diurnal rhythm). Unilateral infusions of BDNF into the lateral ventricle increased proliferation in the dentate gyrus on the side of the infusion, but this was not observed following implantation of subcutaneous corticosterone, which flattened the diurnal corticosterone rhythm. 5HT1A mRNA in the dentate gyrus was increased on both sides of the brain by unilateral BDNF infusions, but this was also prevented by subcutaneous corticosterone pellets. These results show that the diurnal rhythm of corticosterone regulates the stimulating action of NOS inhibitors on BDNF as well as on neurogenesis in the dentate gyrus, and that BDNF becomes ineffective on both proliferation rates and 5HT1A expression in the absence of a rhythm in corticosterone. This, together with our previous findings, suggests that corticoid rhythms permit both serotonin and NO access to BDNF, and the latter to regulate progenitor cell activity.

Hypothalamic gene expression following ghrelin therapy to gastrectomized rodents.

We investigated whether ghrelin depletion (by gastrectomy surgery) and/or treatment/replacement with the gastric hormone ghrelin alters the expression of key hypothalamic genes involved in energy balance, in a manner consistent with ghrelin's pro-obesity effects. At 2 weeks after surgery mice were treated with ghrelin (12 nmol/mouse/day, sc) or vehicle for 8 weeks. Gastrectomy had little effect on the expression of these genes, with the exception of NPY mRNA in the arcuate nucleus that was increased. Ghrelin treatment (to gastrectomized and sham mice) increased the mRNA expression of orexigenic peptides NPY and AgRP while decreasing mRNA expression of the anorexigenic peptide POMC. Two weeks gavage treatment with the ghrelin mimetic, MK-0677, to rats increased NPY and POMC mRNA in the arcuate nucleus and MCH mRNA in the lateral hypothalamus. Thus, while predicted pro-obesity ghrelin signalling pathways were activated by ghrelin and ghrelin mimetics, these were largely unaffected by gastrectomy.

Interactions between nitric oxide and corticosterone in the regulation of progenitor cell proliferation in the dentate gyrus of the adult rat.

It is well established that L-NAME, a generic NOS inhibitor, stimulates neurogenesis in the dentate gyrus of the adult rat and corticosterone reduces it. These experiments explore the interaction between L-NAME and corticosterone. L-NAME (50 mg/kg), as expected, increased proliferation, but also lowered plasma corticosterone levels. However, the stimulating action of L-NAME depends on the presence of rhythmic changes in plasma corticosterone, as it is abolished in rats treated with a subcutaneous implant of corticosterone, which flattens the diurnal rhythm. Adrenalectomized rats implanted with corticosterone also failed to respond to L-NAME. Giving them a single daily injection of corticosterone (2 mg/kg) in an attempt to replicate the diurnal rhythm restored the sensitivity of the progenitor cells to L-NAME. The mechanism for this result remains to be investigated. Excess corticosterone given by daily injection (40/mg/kg) reduced proliferation but did not alter the response to L-NAME, even though this occurred from a lower baseline. nNOS was demonstrable only in the inner (proliferative) layer of the dentate gyrus in control rats, and did not alter following excess corticosterone treatment. iNOS was detectable at low levels in control rats, but was increased markedly following corticosterone. eNOS was evident throughout the dentate gyrus, and also increased after corticosterone (particularly in the hilus). Aminoguanidine (100 mg/kg/day; an iNOS antagonist) significantly increased proliferation in corticosterone-treated rats (40 mg/kg/day) but not in controls without additional corticosterone, confirming that iNOS plays a role in corticosterone-regulated neurogenesis. Corticosterone may thus act on progenitor cells in part at least through increased nitric oxide (NO) formation. The effects of reduced NO on neurogenesis may rely on a dual mechanism: corresponding reductions in plasma corticosterone and increased induction of iNOS (and/or eNOS) within the dentate gyrus. The possibility that NO acts downstream of glucocorticoids in the dentate gyrus is suggested.

The relation of cool flames and auto-ignition phenomena to process safety at elevated pressure and temperature.

The cool-flame phenomenon can occur in fuel-oxygen (air) mixtures within the flammable range and outside the flammable range, at fuel-rich compositions, at temperatures below the auto-ignition temperature (AIT). It is caused by chemical reactions occurring spontaneously at relatively low temperatures and is favoured by elevated pressure. The hazards that cool flames generate are described. These vary from spoiling a product specification through contamination and explosive decomposition of condensed peroxides to the appearance of unexpected normal (hot) flame (two-stage ignition).

The self-preserving size distribution theory. II. Comparison with experimental results for Si and Si3N4 aerosols.

The gas to particle synthesis route is a relatively clean and efficient manner for the production of high-quality ceramic powders. These powders can be subsequently sintered in any wanted shape. The modeling of these production systems is difficult because several mechanisms occur in parallel. From theoretical considerations it can be determined, however, that coagulation and sintering are dominant mechanisms as far as shape and size of the particles are considered. In part I of this article an extensive theoretical analysis was given on the self-preserving size distribution theory for power law particles. In this second part, cumulative particle size distributions of silicon and silicon nitride agglomerates, produced in a laser reactor, were determined from TEM pictures and compared to the distributions calculated from this self-preserving theory for power law particles. The calculated distributions were in fair agreement with the measured results, especially at the high end of the distributions. Calculated and measured particle growth rates were also in fair agreement. Using the self-preserving theory an analysis was made on the distribution of annealed silicon agglomerates, of interest in applications to nanoparticle technology.