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Background: Acute psychological stress can provoke mental stress-induced myocardial ischemia (MSIMI) in coronary artery disease (CAD). Stromal cell-derived factor 1 (SDF1) is released in response to hypoxia, and higher levels of SDF1 are associated with adverse outcomes. We examined whether an increase in SDF1 level in response to mental stress predicts adverse outcomes in CAD patients. Methods: A total of 554 patients with stable CAD (mean age 63 years; 76% male; 26% Black) underwent standardized mental stress testing. Plasma SDF1 levels were measured at rest and 90 minutes after mental stress, and MSIMI was evaluated by 99mTc-sestamibi perfusion imaging. Participants were followed for 5 years for the primary endpoint of composite of death and myocardial infarction (MI) and the secondary endpoint of composite of death, MI, and heart failure hospitalization. Cox hazard models were used to assess the association between SDF1 change and incident adverse events. Results: Mean (standard deviation) SDF1 change with mental stress was +56.0 (230) pg/mL. During follow-up, a rise of 1 standard deviation in SDF1 with mental stress was associated with a 32% higher risk for the primary endpoint of death and MI (95% confidence interval, 6%-64%), independent of the resting SDF1 level, demographic and clinical risk factors, and presence of ischemia. A rise of 1 standard deviation in SDF1 was associated with a 33% (95% confidence interval, 11%-59%) increase in the risk for the secondary endpoint, independent of the resting SDF1 level, demographic, and clinical risk factors and presence of ischemia. Conclusions: An increase in SDF1 level in response to mental stress is associated with a higher risk of adverse events in stable CAD, independent of MSIMI. Résumé: Contexte: Un stress psychologique aigu peut provoquer une ischémie myocardique induite par le stress mental chez les patients atteints d’une coronaropathie. Le facteur dérivé des cellules stromales de type 1 (SDF1) est libéré en réponse à une hypoxie, et des taux accrus de SDF1 sont associés à des résultats défavorables. Nous avons examiné si une élévation des taux de SDF1 en réponse à un stress mental permettait de prévoir la survenue de résultats défavorables chez des patients atteints d’une coronaropathie. Méthodologie: Au total, 554 patients présentant une coronaropathie stable (âge moyen de 63 ans; 76 % d’hommes; 26 % de patients de race noire) ont subi une évaluation standardisée du stress mental. Les taux plasmatiques de SDF1 ont été mesurés au repos et 90 minutes après un stress mental, et l’ischémie myocardique induite par le stress mental a été évaluée par imagerie avec injection de Tc-99m sestamibi. Les participants ont fait l’objet d’un suivi pendant cinq ans afin de surveiller la survenue des événements constituant le paramètre d’évaluation principal composé (décès et infarctus du myocarde [IM]) et le paramètre d’évaluation secondaire composé (décès, IM et hospitalisation en raison d’une insuffisance cardiaque). Des modèles de Cox ont été utilisés pour évaluer le lien entre la modification des taux de SDF1 et les événements indésirables susceptibles de survenir. Résultats: La variation moyenne du taux de SDF1 (écart-type) associée au stress mental a été de +56,0 (230) pg/ml. Pendant le suivi, une augmentation de 1 écart-type du taux de SDF1 en raison du stress mental a été associée à un risque 32 % plus élevé de survenue de l’un des événements constituant le paramètre d’évaluation principal (décès et IM) [intervalle de confiance [IC] à 95 % : 6 % à 64 %], indépendamment du taux de SDF1 au repos, des caractéristiques démographiques, des facteurs de risque clinique et de la présence d’une ischémie. Une augmentation de 1 écart-type du taux de SDF1 a été associée à un risque 33 % plus élevé (IC à 95 % : 11 % à 59 %) de survenue de l’un des événements constituant le paramètre d’évaluation secondaire, indépendamment du taux de SDF1 au repos, des caractéristiques démographiques, des facteurs de risque clinique et de la présence d’une ischémie. Conclusions: Une augmentation du taux de SDF1 en réponse à un stress mental est associée à une augmentation du risque d’événements indésirables chez les patients atteints d’une coronaropathie stable, indépendamment de la présence d’une ischémie myocardique induite par le stress mental.

Background: Adverse mental health conditions including depression, posttraumatic stress disorder (PTSD), and anxiety are prevalent among patients who survive myocardial infarctions (MI) and are associated with adverse outcomes. The mechanisms underlying these associations, however, are not well understood. Inflammatory pathways may mediate the cardiovascular outcomes of patients with mental health disorders. We examined the bidirectional association between PTSD symptoms and inflammatory biomarkers in a young/middle-aged post MI population. We further examined how this association may differ between women and men as well as between Black and non-Black individuals. Methods: Participants included individuals with early onset MI between the ages 25 and 60. Mental health scores for depression, PTSD, perceived stress, and anxiety as well as inflammatory biomarkers, interleukin-6 (IL-6) and high sensitivity C-reactive protein (hsCRP), were collected at baseline and at six-month follow up. We examined the bidirectional changes in mental health symptoms and inflammatory biomarkers between baseline and follow-up. Results: Among 244 patients in the study (mean age: 50.8, 48.4% female, 64.3% Black), the geometric means for IL-6 level and hsCRP at rest were 1.7 pg/mL and 2.76 mg/L, respectively. Mental health scores at baseline did not consistently predict changes in inflammatory biomarkers at follow-up. However, baseline levels of both IL-6 and hsCRP were robustly associated with an increase in re-experiencing PTSD symptoms at 6 months: in adjusted linear mixed models, there was a 1.58-point increase in re-experiencing PTSD symptoms per unit of baseline hsCRP (p = 0.01) and 2.59-point increase per unit of baseline IL-6 (p = 0.02). Once the analysis was stratified by race, the association was only noted in Black individuals. Baseline inflammation was not associated with change in any of the other mental health symptom scores. Conclusion: Markers of inflammation are associated with an increase in post-event PTSD symptoms in younger or middle-aged patients who experienced an MI, especially Black patients. These results suggest a mechanistic link between inflammation and the development of PTSD among individuals with cardiovascular disease.

Background: Traumatic stress can have lasting effects on neurobiology and result in psychiatric conditions such as posttraumatic stress disorder (PTSD). We hypothesize that non-invasive cervical vagal nerve stimulation (nVNS) may alleviate trauma symptoms by reducing stress sympathetic reactivity. This study examined how nVNS alters neural responses to personalized traumatic scripts. Methods: Nineteen participants who had experienced trauma but did not have the diagnosis of PTSD completed this double-blind sham-controlled study. In three sequential time blocks, personalized traumatic scripts were presented to participants immediately followed by either sham stimulation (n = 8; 0–14 V, 0.2 Hz, pulse width = 5s) or active nVNS (n = 11; 0–30 V, 25 Hz, pulse width = 40 ms). Brain activity during traumatic scripts was assessed using High Resolution Positron Emission Tomography (HR-PET) with radiolabeled water to measure brain blood flow. Results: Traumatic scripts resulted in significant activations within the bilateral medial and orbital prefrontal cortex, premotor cortex, anterior cingulate, thalamus, insula, hippocampus, right amygdala, and right putamen. Greater activation was observed during sham stimulation compared to nVNS within the bilateral prefrontal and orbitofrontal cortex, premotor cortex, temporal lobe, parahippocampal gyrus, insula, and left anterior cingulate. During the first exposure to the trauma scripts, greater activations were found in the motor cortices and ventral visual stream whereas prefrontal cortex and anterior cingulate activations were more predominant with later script presentations for those subjects receiving sham stimulation. Conclusion: nVNS decreases neural reactivity to an emotional stressor in limbic and other brain areas involved in stress, with changes over repeated exposures suggesting a shift from scene appraisal to cognitively processing the emotional event.

Background: Posttraumatic stress disorder (PTSD) is a highly disabling condition associated with alterations in multiple neurobiological systems, including increases in inflammatory and sympathetic function, responsible for maintenance of symptoms. Treatment options including medications and psychotherapies have limitations. We previously showed that transcutaneous Vagus Nerve Stimulation (tcVNS) blocks inflammatory (interleukin (IL)-6) responses to stress in PTSD. The purpose of this study was to assess the effects of tcVNS on PTSD symptoms and inflammatory responses to stress. Methods: Twenty patients with PTSD were randomized to double blind active tcVNS (N=9) or sham (N=11) stimulation in conjunction with exposure to personalized traumatic scripts immediately followed by active or sham tcVNS and measurement of IL-6 and other biomarkers of inflammation. Patients then self administered active or sham tcVNS twice daily for three months. PTSD symptoms were measured with the PTSD Checklist (PCL) and the Clinician Administered PTSD Scale (CAPS), clinical improvement with the Clinical Global Index (CGI) and anxiety with the Hamilton Anxiety Scale (Ham-A) at baseline and one-month intervals followed by a repeat of measurement of biomarkers with traumatic scripts. After three months patients self treated with twice daily open label active tcVNS for another three months followed by assessment with the CGI. Results: Traumatic scripts increased IL-6 in PTSD patients, an effect that was blocked by tcVNS (p

Schizophrenia (SCZ) is an etiologically heterogeneous disease with genetic and environmental risk factors (e.g., Toxoplasma gondii infection) differing among affected individuals. Distinguishing such risk factors may point to differences in pathophysiological pathways and facilitate the discovery of individualized treatments. Toxoplasma gondii (TOXO) has been implicated in increasing the risk of schizophrenia. To determine whether TOXO-positive individuals with SCZ have a different polygenic risk burden than uninfected people, we applied the SCZ polygenic risk score (SCZ-PRS) derived from the Psychiatric GWAS Consortium separately to the TOXO-positive and TOXO-negative subjects with the diagnosis of SCZ as the outcome variable. The SCZ-PRS does not include variants in the major histocompatibility complex.Of 790 subjects assessed for TOXO, the 662 TOXO-negative subjects (50.8% with SCZ) reached a Bonferroni corrected significant association (p = 0.00017, R2 = 0.023). In contrast, the 128 TOXO-positive individuals (53.1% with SCZ) showed no significant association (p = 0.354) for SCZ-PRS and had a much lower R2 (R2 = 0.007). To account for Type-2 error in the TOXO-positive dataset, we performed a random sampling of the TOXO-negative subpopulation (n = 130, repeated 100 times) to simulate equivalent power between groups: the p-value was 0.354.We found intriguing evidence that the SCZ-PRS predicts SCZ in TOXO-negative subjects, as expected, but not in the TOXO-positive individuals. This result highlights the importance of considering environmental risk factors to distinguish a subgroup with independent or different genetic components involved in the development of SCZ.

Posttraumatic stress disorder (PTSD) is a highly disabling condition associated with alterations in multiple neurobiological systems, including increases in inflammatory function. Vagus nerve stimulation (VNS) decreases inflammation, however few studies have examined the effects of non-invasive VNS on physiology in human subjects, and no studies in patients with PTSD. The purpose of this study was to assess the effects of transcutaneous cervical VNS (tcVNS) on inflammatory responses to stress. Thirty subjects with a history of exposure to traumatic stress with (N ​= ​10) and without (N ​= ​20) PTSD underwent exposure to stressful tasks immediately followed by active or sham tcVNS and measurement of multiple biomarkers of inflammation (interleukin-(IL)-6, IL-2, IL-1β, Tumor Necrosis Factor alpha (TNFα) and Interferon gamma (IFNγ) over multiple time points. Stressful tasks included exposure to personalized scripts of traumatic events on day 1, and public speech and mental arithmetic (Mental Stress) tasks on days 2 and 3. Traumatic scripts were associated with a pattern of subjective anger measured with Visual Analogue Scales and increased IL-6 and IFNγ in PTSD patients that was blocked by tcVNS (p ​

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide that plays a key role in the neurobiology of the stress response, and prior studies suggest that its function is dysregulated in post-traumatic stress disorder (PTSD). Transcutaneous cervical vagus nerve stimulation (tcVNS) acts through PACAP and other neurobiological systems to modulate stress responses and/or symptoms of PTSD. In this pilot study, we examined the effects of tcVNS on PACAP in a three day chronic stress laboratory paradigm involving serial traumatic and mental stress exposures in healthy individuals with a history of exposure to psychological trauma (n ​= ​18) and patients with PTSD (n ​= ​12). Methods: A total of 30 subjects with a history of exposure to psychological trauma experience were recruited (12 with PTSD diagnosis) for a three-day randomized double-blinded study of tcVNS or sham stimulation. Subjects underwent a protocol that included both personalized trauma recall and non-personalized mental stressors (public speaking, mental arithmetic) paired to tcVNS or sham stimulation over three days. Blood was collected at baseline and multiple time points after exposure to stressors. Linear mixed-effects models were used to assess changes in PACAP over time (in response to stressors) and its relation to active tcVNS or sham stimulation. Results: PACAP blood levels increased over the course of three days for both active tcVNS and sham groups. This increase was statistically-significant in the sham group at the end of the second (Cohen’s drm ​= ​0.35, p ​= ​0.04), and third days (drm ​= ​0.41, p ​= ​0.04), but not in the active tcVNS group (drm ​= ​0.21, drm ​= ​0.18, and p ​> ​0.20). Conclusion: These pilot findings suggest tcVNS may attenuate this neurobiological stress-response. Larger studies are needed to investigate gender and interaction effects.

Objective: Exacerbated autonomic responses to acute stress are prevalent in posttraumatic stress disorder (PTSD). The purpose of this study was to assess the effects of transcutaneous cervical VNS (tcVNS) on autonomic responses to acute stress in patients with PTSD. The authors hypothesized tcVNS would reduce the sympathetic response to stress compared to a sham device. Methods: Using a randomized double-blind approach, we studied the effects of tcVNS on physiological responses to stress in patients with PTSD (n = 25) using noninvasive sensing modalities. Participants received either sham (n = 12) or active tcVNS (n = 13) after exposure to acute personalized traumatic script stress and mental stress (public speech, mental arithmetic) over a three-day protocol. Physiological parameters related to sympathetic responses to stress were investigated. Results: Relative to sham, tcVNS paired to traumatic script stress decreased sympathetic function as measured by: decreased heart rate (adjusted β = −5.7%; 95% CI: ±3.6%, effect size d = 0.43, p

While adult neurogenesis has been demonstrated in the hippocampal dentate gyrus of several mammalian species, including humans, the impact of viral infections has not been well studied. To examine this question we used a model in which neonatal rats are infected with lymphocytic choriomeningitis virus (LCMV) leading to a gradual loss of dentate granule cells (DGCs), which becomes fully evident in adulthood. Stereological cell counts performed 8 months after infection revealed that the loss of mature DGCs was accompanied by an 84.2% reduction in proliferation of DGCs as measured by BrdU uptake. Moreover, there was a severe loss of Mash1-labeled neuronal progenitor cells (87 and 83% decrease in the granule cell layer and hilus, respectively). Thus, neurogenesis is impaired in this model of chronic DGC loss, perhaps due to a virus-induced impoverishment of DGC neuronal progenitors. The LCMV model could be exploited to examine pathophysiological mechanisms of neurodegeneration and to test pharmacological strategies aimed at increasing neurogenesis or rescuing multipotent progenitors.

Glucocorticoid induced leucine zipper protein (GILZ) is an aldosterone-regulated protein that controls sodium transport in cultured kidney epithelial cells. Mice lacking GILZ have been reported previously to have electrolyte abnormalities. However, the mechanistic basis has not been explored. Here we provide evidence supporting a role for GILZ in modulating the balance of renal sodium and potassium excretion by regulating the sodium-chloride cotransporter (NCC) activity in the distal nephron. Gilz -/- mice have a higher plasma potassium concentration and lower fractional excretion of potassium than wild type mice. Furthermore, knockout mice are more sensitive to NCC inhibition by thiazides than are the wild type mice, and their phosphorylated NCC expression is higher. Despite increased NCC activity, knockout mice do not have higher blood pressure than wild type mice. However, during sodium deprivation, knockout mice come into sodium balance more quickly, than do the wild type, without a significant increase in plasma renin activity. Upon prolonged sodium restriction, knockout mice develop frank hyperkalemia. Finally, in HEK293T cells, exogenous GILZ inhibits NCC activity at least in part by inhibiting SPAK phosphorylation. Thus, GILZ promotes potassium secretion by inhibiting NCC and enhancing distal sodium delivery to the epithelial sodium channel. Additionally, Gilz -/- mice have features resembling familial hyperkalemic hypertension, a human disorder that manifests with hyperkalemia associated variably with hypertension., (Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Although contamination of the marine ecosystems by plastics is becoming recognised as a serious pollution problem, there are few studies that demonstrate the contribution made by freshwater catchments. Over a three month period from September to December 2012, at seven localities in the upper Thames estuary, 8490 submerged plastic items were intercepted in eel fyke nets anchored to the river bed. Whilst there were significant differences in the numbers of items at these locations, the majority were some type of plastic. Additionally in excess of 20% of the litter items were components of sanitary products. The most contaminated sites were in the vicinity of sewage treatment works. While floating litter is visible, this study also demonstrates that a large unseen volume of submerged plastic is flowing into the marine environment. It is therefore important that this sub-surface component is considered when assessing plastic pollution input into the sea., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objectives: We investigated the accuracy of reduction of intramedullary nailed femoral shaft fractures in human cadavers, comparing conventional and computer navigation techniques., Methods: Twenty femoral shaft fractures were created in human cadavers, with segmental defects ranging from 9 to 53 mm in length (Winquist 3-4, AO 32C2). All fractures were fixed with antegrade 9 mm diameter femoral nails on a radiolucent operating table. Five fractures ("Fluoro" group) were fixed with conventional techniques and fifteen fractures ("Nav 1" and "Nav 2" groups) with computer navigation, using fluoroscopic images of the normal femur to correct for length and rotation. Postoperative CT scans compared femoral length and rotation with the normal leg., Results: Mean leg length discrepancy in the computer navigation groups was smaller, namely, 3.6 mm for Nav 1 (95% CI: 1.072 to 6.128) and 4.2 mm for Nav 2 (95% CI: 0.63 to 7.75) vs. 9.8 mm for Fluoro (95% CI: 6.225 to 13.37) (p<0.023). Mean rotational discrepancies were 8.7° for Nav 1 (95% CI: 4.282 to 13.12) and 5.6° for Nav 2 (95% CI: -0.65 to 11.85) vs. 9.0° for Fluoro (95% CI: 2.752 to 15.25) (p=0.650)., Conclusions: Computer navigation significantly improves the accuracy of femoral shaft fracture fixation with regard to leg length, but not rotational deformity., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Insulin and growth factors activate the phosphatidylinositide-3-kinase pathway, leading to stimulation of several kinases including serum- and glucocorticoid-inducible kinase isoform SGK3, a transport regulating kinase. Here, we explored the contribution of SGK3 to the regulation of renal tubular phosphate transport. Coexpression of SGK3 and sodium-phosphate cotransporter IIa significantly enhanced the phosphate-induced current in Xenopus oocytes. In sgk3 knockout and wild-type mice on a standard diet, fluid intake, glomerular filtration and urine flow rates, and urinary calcium ion excretion were similar. However, fractional urinary phosphate excretion was slightly but significantly larger in the knockout than in wild-type mice. Plasma calcium ion, phosphate concentration, and plasma parathyroid hormone levels were not significantly different between the two genotypes, but plasma calcitriol and fibroblast growth factor 23 concentrations were significantly lower in the knockout than in wild-type mice. Moreover, bone density was significantly lower in the knockouts than in wild-type mice. Histological analysis of the femur did not show any differences in cortical bone but there was slightly less prominent trabecular bone in sgk3 knockout mice. Thus, SGK3 has a subtle but significant role in the regulation of renal tubular phosphate transport and bone density.

Study Objectives: The objectives of this study were to determine the prevalence of morphometric vertebral fractures in a large cohort of adult cystic fibrosis (CF) patients, and to examine the association between fractures and bone mineral density (BMD)., Design: Cross-sectional retrospective study., Setting: A tertiary care academic hospital., Patients: Adult CF patients who had undergone BMD testing and chest radiography within 1 month of each other., Measurements and Results: BMD was measured by dual-energy x-ray absorptiometry (DXA) at the lumbar spine (LS) and femoral neck (FN). Vertebral fractures were diagnosed using lateral chest radiographs. Several clinical and biochemical variables were assessed as correlates. Sixty subjects (36%) had z scores between -1.0 and -2.5, and 15 subjects (9%) had z scores of < -2.5. Twelve patients (7.2%) had 19 morphometric fractures. The mean BMD at the LS was 1.266 g/cm(2) in the fracture group and 1.112 g/cm(2) in the nonfracture group (p = 0.0002). The mean BMD at the FN was 1.129 g/cm(2) in the fracture group and 0.987 g/cm(2) in the nonfracture group (p = 0.0006). Both FEV(1) and body mass index were significantly associated with BMD at both the LS and the FN., Conclusion: Seven percent of adult patients with CF had vertebral fractures as determined by morphometry. Subjects in the fracture group had both clinically and statistically higher BMD as measured by DXA. Our findings raise the intriguing possibility that BMD may not be useful in identifying CF patients with fractures.

The surface composition of four industrial spray-dried dairy powders (skim milk powder, whole milk powder, cream powder and whey protein concentrate) was estimated by electron spectroscopy for chemical analysis (ESCA), and its influence on powder flowability was studied. It was found that skim milk powder flows well compared to the other powders because the surface is made of lactose and protein with a small amount of fat, whereas the high surface fat composition inhibits the flow of whole milk, cream and whey protein powders. However, the poor flowability of the powders with high surface fat coverage was drastically improved by removal of fat present on the surface through a brief wash with petroleum ether. The results obtained indicate that, although there are several parameters including particle size, which influence the flowability of powders, the flowability of powders is strongly influenced by the surface composition of powders, particularly for fat-containing powders.

The melting characteristics of the fat present on the surface (surface free-fat) of two industrial spray-dried dairy powders (cream powder and whole milk powder) were investigated in comparison with those of other milk fat fractions present in the powder, such as free-fat from the interior of the powder particle (inner free-fat) and encapsulated fat. The melting characteristics of the milk fat fractions were studied by fatty acid composition, melting profile and solid fat content profile. The results indicated that all milk fat fractions including surface free-fat contained various triglycerides with melting points ranging from -40 to +40 degrees C. However, some fractionation was observed among the different milk fat fractions. The free-fat fractions (surface free-fat and inner free-fat) had a greater proportion of high-melting triglyceride species than the encapsulated fat. Furthermore, the high-melting triglyceride species present in the free-fat fractions were slightly accumulated at the surface of powder. This phenomenon was observed in both cream powder and whole milk powder and its effect on wetting time was established. This indicates that manipulation of the surface fat content during drying operation may hold the key to functionality improvement.

The aldosterone-induced increase in sodium reabsorption across tight epithelia can be divided schematically into two functional phases: an early regulatory phase starting after a lag period of 20 to 60 minutes, during which the pre-existing transport machinery is activated, and a late phase (>2.5 h), which can be viewed as an anabolic action leading to a further amplification/differentiation of the Na+ transport machinery. At the transcriptional level, both early and late responses are initiated during the lag period, but the functional impact of newly synthesized regulatory proteins is faster than that of the structural ones. K-Ras2 and SGK were identified as the first early aldosterone-induced regulatory proteins in A6 epithelia. Their mRNAs also were shown to be regulated in vivo by aldosterone, and their expression (constitutively active K-Ras2 and wild-type SGK) was shown to increase the function of ENaC coexpressed in Xenopus oocytes. Recently, aldosterone was also shown to act on transcription factors in A6 epithelia: It down-regulates the mRNAs of the proliferation-promoting c-Myc, c-Jun, and c-Fos by a post-transcriptional mechanism, whereas it up-regulates that of Fra-2 (c-Fos antagonist) at the transcriptional level. Together, these new data illustrate the complexity of the regulatory network controlled by aldosterone and support the view that its early action is mediated by the induction of key regulatory proteins such as K-Ras2 and SGK. These early induced proteins are sites of convergence for different regulatory inputs, and thus, their aldosterone-regulated expression level tunes the impact of other regulatory cascades on sodium transport. This suggests mechanisms for the escape from aldosterone action.

Mineralocorticoids stimulate electrogenic Na+ transport in tight epithelia by altering the transcription of specific genes. Although the earliest mineralocorticoid effect is to increase the activity of the epithelial sodium channel (ENaC), ENaC mRNA and protein levels do not change. Instead, physiologic observations suggest that a mineralocorticoid target gene(s) encodes an ENaC regulator(s). To begin to identify and characterize mineralocorticoid-regulated target genes, we used suppression-subtractive hybridization to generate a cDNA library from A6 cells, a stable cell line of Xenopus laevis of distal nephron origin. A serine-threonine kinase, SGK, was identified from this screen. Sequence comparison revealed that frog, rat, and human SGK are 92% identical and 96% similar at the amino acid level. SGK mRNA was confirmed by Northern blot to be strongly and rapidly corticosteroid stimulated in A6 cells. In situ hybridization revealed that SGK was strongly stimulated by aldosterone in rat collecting duct but not proximal tubule cells. Low levels of SGK were present in rat glomeruli, but SGK was unregulated in this structure. Finally, SGK stimulated ENaC activity approximately sevenfold when coexpressed in Xenopus laevis oocytes. These data suggest that SGK is an important mediator of aldosterone effects on Na+ transport in tight epithelia. In view of the existence of SGK homologues in invertebrates, it is interesting to speculate that SGK is an ancient kinase that was adapted to the control of epithelial Na+ transport by early vertebrates as they made the transition from a marine to a freshwater environment.

The mineralocorticoid and glucocorticoid receptors (MR and GR, respectively) are closely related members of the nuclear receptor superfamily. Despite marked functional similarities and a high degree of sequence conservation between MR and GR, the mineralocorticoid and glucocorticoid hormones elicit markedly different physiological effects, even in cells expressing both receptors. Hormone specificity is, in part, determined by the actions of 11 beta-hydroxysteroid dehydrogenase. However, other mechanisms must obtain in cells that express both receptors and respond differentially to the two classes of hormone. Indeed, MR and GR, while functionally redundant in some contexts, in others display distinct transcriptional specificities. In particular, in the presence of members of the AP1 family of regulatory factors, cJun and cFos, a composite response element, plfG, is GR-specific. Transcription from a plfG-linked gene is stimulated by GR in the presence of cJun and repressed by GR in the presence of cJun and cFos. MR neither stimulates nor represses transcription in the same contexts, thus indicating that receptor transcriptional specificities can be distinguished by differential interactions with nonreceptor factors at a composite response element. The implications of these findings for mineralocorticoid and glucocorticoid hormone specificity in various tissues are discussed.