Assay interference leading to erroneous pregnancy-associated plasma protein-A results

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Exploring attitudes and knowledge of climate change and sustainability in a dental practice: A feasibility study into resource management

Objective To understand the attitudes and behaviour of staff in dental practice towards adopting a reduce, reuse, recycle approach to resource management.Design A qualitative interview study.Setting The site for the study was a mixed NHS/private dental practice in North Devon.Subjects All disciplines from one dental practice.Methods (1) A practice scoping exercise - provided context and identified an interview sample. (2) Qualitative interviews with practice staff - explored knowledge and attitudes about sustainability and identified opportunities and limitations for the sustainable management of resources.Results The main issue raised by staff was the amount of waste generated. There was a strong desire to implement changes, but deep concerns were expressed about the impact of challenging current guidance on infection control.Conclusions Primary care dentistry provides both surgical and non-surgical care to more than half the UK population. Therefore, lessons learned from general dental practice can encourage positive change. More research is needed across dental practice in order to generalise these findings.

Comparison of utility weighted DMFT with patient-reported oral well-being

This study investigated a method of measuring oral health, as opposed to measuring disease. The objective was to compare DMF score and whole mouth utility scores to a patient-reported outcome measure (PROM). Disutility values for lost and restored teeth were used to weight the decayed, missing and filled teeths(DMFTs) of 10 adult patients. This gave two whole mouth utility scores (WMU). These scores were then compared with a patient-reported oral health outcome measure recorded by the use of a visual analogue scale (VAS). The anchors for the VAS were 'my mouth could not be worse' and 'my mouth could not be better'. There was a positive correlation (r = 0.6457) between WMU1 and the patient-reported outcome measure (P < 0.05) and a negative correlation (r = -0.8383) between WMU1 and DMFT which was significant at the P < 0.01 level. There was a statistically significant positive correlation of r = 0.7926 between WMU2 and the patient-reported outcome measure (P < 0.01) and a negative correlation (r = -0.9393) between WMU2 and DMFT (P < 0.01). The Pearson's correlation between DMFT and the patient-reported outcome measure was -0.8757, which was significant at the 0.01 level. Patient reports of their perceived level of health correlate well with DMFT scores. Weighting DMFT scores according to the differential values assigned to missing, or missing and filled, teeth does not increase the degree of correlation between the measure and the patients' personal quantification of their oral health. Decayed, missing and filled teeth therefore seems to adequately capture the patient's sense of well-being.

Neural control of the lower urinary tract: peripheral and spinal mechanisms

This review deals with individual components regulating the neural control of the urinary bladder. This article will focus on factors and processes involved in the two modes of operation of the bladder: storage and elimination. Topics included in this review include: (1) The urothelium and its roles in sensor and transducer functions including interactions with other cell types within the bladder wall ("sensory web"), (2) The location and properties of bladder afferents including factors involved in regulating afferent sensitization, (3) The neural control of the pelvic floor muscle and pharmacology of urethral and anal sphincters (focusing on monoamine pathways), (4) Efferent pathways to the urinary bladder, and (5) Abnormalities in bladder function including mechanisms underlying comorbid disorders associated with bladder pain syndrome and incontinence.

Impaired transforming growth factor beta signalling in Barrett's carcinogenesis due to frequent SMAD4 inactivation

BACKGROUND AND AIMS

Transforming growth factor beta (TGF-beta) is frequently involved in gastrointestinal carcinogenesis although its contribution to oesophageal adenocarcinoma (AC) and its precursor Barrett's oesophageal epithelium (BE) metaplasia are unclear.

METHODS

Expression of TGF-beta signalling components was assessed by reverse transcription-polymerase chain reaction (PCR), western blot, and immunohistochemistry in oesophageal endoscopic biopsies and cell lines. Genomic alterations in SMAD4 were characterised by fluorescence in situ hybridisation, methylation specific PCR, and sequencing. Functional integrity of TGF-beta signalling was assessed by characterisation of p21 and proliferation status. Smad4 negative BIC-1 cells were transiently transfected with smad4 and TGF-beta responsiveness evaluated.

RESULTS

smad4 mRNA expression was progressively reduced in the metaplasia-dysplasia-adenocarcinoma sequence (p<0.01). A quarter of AC samples displayed an abnormal Smad4 protein isoform, with no corresponding changes in gene sequence or organisation. Methylation of smad4 has not been described previously but we found promoter methylation in 70% of primary AC samples. In 6/8 oesophageal cell lines, chromosomal rearrangements affected the smad4 locus. Lack of smad4 expression in BIC-1 cells occurred secondary to loss of one copy and extensive deletion of the second allele's promoter region. TGF-beta dependent induction of p21 and downregulation of minichromosome maintenance protein 2 was lost in >80% of BE and AC. TGF-beta failed to inhibit proliferation in 5/8 oesophageal cell lines. In BIC-1, the antiproliferative response was restored following transient transfection of smad4 cDNA.

CONCLUSIONS

In BE carcinogenesis, downregulation of Smad4 occurs due to several different mechanisms, including methylation, deletion, and protein modification. Frequent alterations in TGF-beta signalling lead to a functionally significant impairment of TGF-beta mediated growth suppression.

Extracellular signal-regulated kinases 1 and 2 activation in endothelial cells exposed to cyclic strain

The aim of this study was to determine whether extracellular signal-regulated kinases 1/2 (ERK1/ERK2) are activated and might play a role in enhanced proliferation and morphological change induced by strain. Bovine aortic endothelial cells (BAEC) were subjected to an average of 6 or 10% strain at a rate of 60 cycles/min for up to 4 h. Cyclic strain caused strain- and time-dependent phosphorylation and activation of ERK1/ERK2. Peak phosphorylation and activation of ERK1/ERK2 induced by 10% strain were at 10 min. A specific ERK1/ERK2 kinase inhibitor, PD-98059, inhibited phosphorylation and activation of ERK1/ERK2 but did not inhibit the increased cell proliferation and cell alignment induced by strain. Treatment of BAEC with 2,5-di-tert-butyl-1, 4-benzohydroquinone, to deplete inositol trisphosphate-sensitive calcium storage, and gadolinium chloride, a Ca2+ channel blocker, did not inhibit the activation of ERK1/ERK2. Strain-induced ERK1/ERK2 activation was partly inhibited by the protein kinase C inhibitor calphostin C and completely inhibited by the tyrosine kinase inhibitor genistein. These data suggest that 1) ERK1/ERK2 are not critically involved in the strain-induced cell proliferation and orientation, 2) strain-dependent activation of ERK1/ERK2 is independent of intracellular and extracellular calcium mobilization, and 3) protein kinase C activation and tyrosine kinase regulate strain-induced activation of ERK1/ERK2.

Antiproliferative effect of elevated glucose in human microvascular endothelial cells

Diabetic microangiopathy has been implicated as a fundamental feature of the pathological complications of diabetes including retinopathy, neuropathy, and diabetic foot ulceration. However, previous studies devoted to examining the deleterious effects of elevated glucose on the endothelium have been performed largely in primary cultured cells of macrovessel origin. Difficulty in the harvesting and maintenance of microvascular endothelial cells in culture have hindered the study of this relevant population. Therefore, the objective of this study was to characterize the effect of elevated glucose on the proliferation and involved signaling pathways of an immortalized human dermal microvascular endothelial cell line (HMEC-1) that possess similar characteristics to their in vivo counterparts. Human dermal microvascular endothelial cells (HMEC-1) were grown in the presence of normal (5 mM) or high D-glucose (20 mM) for 14 days. The proliferative response of HMEC-1 was compared under these conditions as well as the cAMP and PKC pathways by in vitro assays. Elevated glucose significantly inhibited (P < 0.05) HMEC-1 proliferation after 7, 10, and 14 days. This effect was not mimicked by 20 mM mannitol. The antiproliferative effect was more pronounced with longer exposure (1-14 days) to elevated glucose and was irreversible 4 days after a 10-day exposure. The antiproliferative effect was partially reversed in the presence of a PKA inhibitor, Rp-cAMP (10-50 microM), and/or a PKC inhibitor, Calphostin C (10 nM). HMEC-1 exposed to elevated glucose (20 mM) for 14 days caused an increase in cyclic AMP accumulation, PKA, and PKC activity but was not associated with the activation of downstream events such as CRE and AP-1 binding activity. These data support the hypothesis that HMEC-1 is a suitable model to study the deleterious effects of elevated glucose on microvascular endothelial cells. Continued studies with HMEC-1 may prove advantageous in delineation of the molecular pathophysiology associated with diabetic microangiopathy.

Molecular basis for tissue expansion: clinical implications for the surgeon

A wide variety of tissue expansion techniques have been used for breast reconstruction, craniofacial surgery, and burn care in plastic reconstructive surgery. However, the basic mechanism by which skin and surrounding tissue respond to mechanical expansion remains unclear. Recent studies have revealed the biomechanical aspects of cells subjected to strain and various factors involved in the stretch-induced signal transduction pathway. In this regard, we have reported previously that mechanical force increases keratinocyte growth and protein synthesis and alters cell morphology. The mechanism by which strain causes an enhancement of cellular growth appears to be a network of several integrated cascades, implicating growth factors, cytoskeleton, and the protein kinase family. Recently, additional evidence has accumulated that mechanical strain stimulates signal transduction pathways that could trigger a series of cascades eventually leading to a new skin production. For example, we have evidence suggesting a key role for protein kinase C (PKC) in mechanosignaling as PKC is activated and translocated in keratinocytes subjected to strain in an isoform-specific manner. In this report, molecular mechanisms leading to enhancement of skin surface area are reviewed, and possible future applications are discussed.

Calcium-independent activation of extracellular signal-regulated kinases 1 and 2 by cyclic strain

We have previously demonstrated that cyclic strain induces extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation in endothelial cells (EC). The aim of this study was to investigate the effect of Ca2+ on the activation of ERK1/2. Bovine aortic EC were pretreated with a chelator of extracellular Ca2+, ethylaneglycol-bis(aminoethylether)-tetra-acetate (EGTA), a depleter of Ca2+ pools, 2,5-Di-(tert-butyl)-1,4-benzohydroquinone (BHQ), or a Ca2+ channel blocker, GdCl3, and subjected to an average 10 % strain at a rate of 60 cycles/min for 10 min. BHQ and GdCl3 did not inhibit the strain-induced ERK1/2 activation. Chelation of normal extracellular Ca2+ (1.8 mM) medium with EGTA (3 mM) acutely stimulated baseline phosphorylation and activation of ERK1/2, thereby obscuring any strain-induced activation of ERK1/2. However, in EC preincubated for 24 hours in Ca2+-free medium, elevated baseline phosphorylation was minimally activated by EGTA (200 microM) such that cyclic strain stimulated ERK1/2 in the presence or absence of BHQ. These results suggest a Ca2+ independence of the ERK1/2 signaling pathway by cyclic strain.

Induction of interleukin (IL)-1 alpha and beta gene expression in human keratinocytes exposed to repetitive strain: their role in strain-induced keratinocyte proliferation and morphological change

Recent studies in our laboratory have demonstrated that mechanical strain alters many facets of keratinocyte biology including proliferation, protein synthesis, and morphology. IL-1 is known to play an important role in the autocrine regulation of these basic cellular properties under basal and stimulated conditions. However, it is not known whether IL-1 plays a role in strain-induced alteration of keratinocyte biology. Thus, the objective of this study was to test the hypothesis that cyclic strain stimulates IL-1 expression and that strain-induced changes in keratinocyte function is regulated by IL-1. To test this hypothesis, we examined the effect of cyclic strain (10% average deformation) on keratinocyte IL-1 gene expression and the effect of neutralizing antibodies of IL-1 alpha and IL-1 beta on strain-induced changes in keratinocyte proliferation, morphology, and orientation. Northern blot analyses demonstrated that steady state levels of IL-1 alpha and beta mRNA were elevated by 4 h, peaked at 1 2 h of cyclic strain (IL-1 alpha, 304+/-14.2%; IL-1 beta, 212+/-5.6% increase vs. static controls) and decreased gradually by 24 h. IL-1 antibodies (IL-1 alpha, 0.01 microg/ml; IL-1 beta, 0.01 microg/ml) significantly blocked strain-induced keratinocyte proliferation as well as the basal rate of proliferation. In contrast, IL-1 antibodies (IL-1 alpha, 0.01 microg/ml; IL-1 beta, 0.1 microg/ml) had no effect on strain-induced morphological changes such as elongation and alignment. We conclude that mechanical strain induces IL-1 mRNA expression in keratinocytes. The role of IL-1 in mediating strain-induced changes in keratinocyte biology remains to be determined but appears to be independent of morphological changes.

Cyclic strain stimulates isoform-specific PKC activation and translocation in cultured human keratinocytes

Previous studies have demonstrated that cyclic strain induces keratinocyte proliferative and morphological changes. Since protein kinase C (PKC) is known to play an important role in the regulation of keratinocyte growth and differentiation, the objective of this study was to determine the role of the PKC signaling pathway as a mediator of strain modulation of the keratinocyte phenotype. In particular, we tested the following specific hypotheses: (1) cyclic strain stimulates PKC activity and translocation, (2) cyclic strain activates PKC in an isoform-specific manner, and (3) PKC mediates the strain activated proliferative and morphological response in cultured human keratinocytes. To test these hypotheses, keratinocytes were subjected to vacuum-generated cyclic strain (10% average strain), followed by measurement of PKC activity, PKC isoform distribution by Western blot analysis and confocal microscopy, and examination of the effect of PKC inhibitors (calphostin C and staurosporine) on strain induced proliferative and morphological changes. We observed stimulation of PKC activity (62.3 +/- 5.1% increase) coupled with translocation of PKC from the cytosolic to the membrane fraction in keratinocytes subjected to acute cyclic strain. Cyclic strain also caused translocation of PKC alpha and delta, but not zeta isoforms, from the cytosolic to the membrane fraction as demonstrated by both Western blot analysis and confocal microscopy. PKC beta was not detected in these cells. PKC inhibitors, calphostin C (10 nM), and staurosporine (5 nM), inhibited strain-induced PKC activation and keratinocyte proliferation, but did not block the effects of strain on cellular morphology or alignment. We conclude that these data support our hypothesis that cyclic strain stimulates PKC activity and translocation in an isoform-specific manner in cultured human keratinocytes. Moreover, our studies with PKC inhibitors support the hypothesis that strain-induced changes in the keratinocyte phenotype may be selectively modulated by PKC.

Recruiting general practitioners to rural areas: one community's experience

The rural community of Dalwallinu found itself without a medical practitioner early in 1995. Believing recruitment of a replacement practitioner would be relatively straightforward, the Shire and the Hospital Board combined for this process. Little did we realise that there would be many factors that would impinge upon our ability to recruit a general practitioner (GP) other than the availability of a suitably qualified practitioner. Locum availability, providing a furnished house, a motor car, becoming the employer of the locum practitioner, community reactions, government regulations on recruiting doctors trained overseas, Health Department restructures and the arbitrary regulations of professions all had a significant impact, not to mention the cost to the local council to provide a community service.

Effect of strain on human keratinocytes in vitro

Tissue expansion, a technique to enlarge the skin surface area with an expandable balloon, has been widely used in reconstructive surgery. Although the effect of tissue expansion on in vivo skin physiology and histology has been well documented, it remains unclear whether keratinocytes or other cell types are responsible for these changes. Therefore, we investigated the in vitro effect of cyclic (10 cycles/min, 150 mmHg) or constant (continuous, 150 mmHg) strain on human keratinocyte phenotype and relevant mechanosignaling pathways. Our results demonstrate that keratinocytes subjected to cyclic strain exhibit a significant (P < 0.05) increase in cell proliferation (49.2+/-15.8%), DNA synthesis (37.7+/-4.5%), elongation (20.3+/-2.7%), and protein synthesis (17.9+/-6.6% increase) as compared with stationary controls. In contrast, keratinocytes subjected to constant strain were unaffected aside from a modest transitory increase in the proliferative rate. Keratinocytes subjected to cyclic strain aligned perpendicular to the force vector (24.2+/-1.6 degrees) as compared with stationary controls (40.4+/-2.2 degrees; the smaller degree indicates better alignment). We also report strain-induced reduction in the levels of cyclic adenosine mono phosphate (cAMP), protein kinase A (PKA), and prostaglandin E2 (PGE2) as compared with stationary controls (cAMP, 30+/-7.5%; PKA, 45+/-17%; PGE2, 58+/-4.3%; percent decrease vs. that of control). We conclude that direct application of cyclic strain on human keratinocytes modulates cell phenotype and cAMP-mediated signaling pathways in an inverse manner. Moreover, keratinocytes may play an important role in previously observed alterations in skin properties associated with tissue expansion and other strain-induced responses.

Effect of strain on human keratinocytes in vitro

Tissue expansion, a technique to enlarge the skin surface area with an expandable balloon, has been widely used in reconstructive surgery. Although the effect of tissue expansion on in vivo skin physiology and histology has been well documented, it remains unclear whether keratinocytes or other cell types are responsible for these changes. Therefore, we investigated the in vitro effect of cyclic (10 cycles/min, 150 mmHg) or constant (continuous, 150 mmHg) strain on human keratinocyte phenotype and relevant mechanosignaling pathways. Our results demonstrate that keratinocytes subjected to cyclic strain exhibit a significant (P < 0.05) increase in cell proliferation (49.2+/-15.8%), DNA synthesis (37.7+/-4.5%), elongation (20.3+/-2.7%), and protein synthesis (17.9+/-6.6% increase) as compared with stationary controls. In contrast, keratinocytes subjected to constant strain were unaffected aside from a modest transitory increase in the proliferative rate. Keratinocytes subjected to cyclic strain aligned perpendicular to the force vector (24.2+/-1.6 degrees) as compared with stationary controls (40.4+/-2.2 degrees; the smaller degree indicates better alignment). We also report strain-induced reduction in the levels of cyclic adenosine mono phosphate (cAMP), protein kinase A (PKA), and prostaglandin E2 (PGE2) as compared with stationary controls (cAMP, 30+/-7.5%; PKA, 45+/-17%; PGE2, 58+/-4.3%; percent decrease vs. that of control). We conclude that direct application of cyclic strain on human keratinocytes modulates cell phenotype and cAMP-mediated signaling pathways in an inverse manner. Moreover, keratinocytes may play an important role in previously observed alterations in skin properties associated with tissue expansion and other strain-induced responses.

Cyclic strain is a weak inducer of prostacyclin synthase expression in bovine aortic endothelial cells

Recent studies indicate that hemodynamic forces such as cyclic strain and shear stress can increase prostacyclin (PGI2) secretion by endothelial cells (EC) but the effect of these forces on prostacyclin synthase (PGIS) gene expression remains unclear and is the focus of this study. Bovine aortic EC were seeded onto type I collagen coated flexible membranes and grown to confluence. The membranes and attached EC were subjected to 10% average strain at 60 cpm (0.5 sec deformation alternating with 0.5 sec relaxation) for up to 5 days. PGIS gene expression was determined by Northern blot analysis and protein level by Western blot analysis. The effect of cyclic strain on the PGIS promoter was determined by the transfection of a 1-kb human PGIS gene promoter construct coupled to a luciferase reporter gene into EC, followed by determination of luciferase activity. PGIS gene expression increased 1.7-fold in EC subjected to cyclic strain for 24 hr. Likewise, EC transfected with a pGL3B-PGIS (-1070/-10) construct showed an approximate 1.3-fold elevation in luciferase activity in EC subjected to cyclic strain for 3, 4, 8, and 12 hr. The weak stimulation of PGIS gene expression by cyclic strain was reflected in an inability to detect alterations in PGIS protein levels in EC subjected to cyclic strain for as long as 5 days. These data suggest that strain-induced stimulation of PGIS gene expression plays only a minor role in the ability of cyclic strain to stimulate PGI2 release in EC. These findings coupled with our earlier demonstration of a requisite addition of exogenous arachidonate in order to observe strain-induced PGI2 release, implicates a mechanism that more likely involves strain-induced stimulation of PGIS activity.

Strain activation of bovine aortic smooth muscle cell proliferation and alignment: study of strain dependency and the role of protein kinase A and C signaling pathways

Smooth muscle cell (SMC) phenotype can be altered by physical forces as demonstrated by cyclic strain-induced changes in proliferation, orientation, and secretion of macromolecules. However, the magnitude of strain required and the intracellular coupling pathways remain ill defined. To examine the strain requirements for SMC proliferation, we selectively seeded bovine aortic SMC either on the center or periphery of silastic membranes which were deformed with 150 mm Hg vacuum (0-7% center; 7-24% periphery). SMC located in either the center or peripheral regions showed enhanced proliferation compared to cells grown under the absence of cyclic strain. Moreover, SMC located in the center region demonstrated significantly (P < 0.005) greater proliferation as compared to those in the periphery. In contrast, SMC exposed to high strain (7-24%) demonstrated alignment perpendicular to the strain gradient, whereas SMC in the center (0-7%) remained aligned randomly. To determine the mechanisms of these phenomena, we examined the effect of cyclic strain on bovine aortic SMC signaling pathways. We observed strain-induced stimulation of the cyclic AMP pathway including adenylate cyclase activity and cyclic AMP accumulation. In addition, exposure of SMC to cyclic strain caused a significant increase in protein kinase C (PKC) activity and enzyme translocation from the cytosol to a particulate fraction. Further study was conducted to examine the effect of strain magnitude on signaling, particularly protein kinase A (PKA) activity as well as cAMP response element (CRE) binding protein levels. We observed significantly (P < 0.05) greater PKA activity and CRE binding protein levels in SMC located in the center as compared to the peripheral region. However, inhibition of PKA (with 10 microM Rp-cAMP) or PKC (with 5-20 ng/ml staurosporine) failed to alter either the strain-induced increase in SMC proliferation or alignment. These data characterize the strain determinants for activation of SMC proliferation and alignment. Although strain activated both the AC/cAMP/PKA and the PKC pathways in SMC, singular inhibition of PKA and PKC failed to prevent strain-induced alignment and proliferation, suggesting either their lack of involvement or the multifactorial nature of these responses.

Activation of the adenylyl cyclase/cyclic AMP/protein kinase A pathway in endothelial cells exposed to cyclic strain

The aim of this study was to assess the involvement of the adenylyl cyclase/cyclic AMP/protein kinase A pathway (AC) in endothelial cells (EC) exposed to different levels of mechanical strain. Bovine aortic EC were seeded to confluence on flexible membrane-bottom wells. The membranes were deformed with either 150 mm Hg (average 10% strain) or 37.5 mm Hg (average 6% strain) vacuum at 60 cycles per minute (0.5 s strain; 0.5 s relaxation) for 0-60 min. The results demonstrate that at 10% average strain (but not 6% average strain) there was a 1.5- to 2.2-fold increase in AC, cAMP, and PKA activity by 15 min when compared to unstretched controls. Further studies revealed an increase in cAMP response element binding protein in EC subjected to the 10% average strain (but not 6% average strain). These data support the hypothesis that cyclic strain activates the AC/cAMP/PKA signal transduction pathway in EC which may occur by exceeding a strain threshold and suggest that cyclic strain may stimulate the expression of genes containing cAMP-responsive promoter elements.

Gene regulation by mechanical forces

Endothelial cells are subjected to various mechanical forces in vivo from the flow of blood across the luminal surface of the blood vessel. The purpose of this review was to examine the data available on how these mechanical forces, in particular cyclic strain, affect the expression and regulation of endothelial cell function. Studies from various investigators using models of cyclic strain in vitro have shown that various vasoactive mediators such as nitric oxide and prostacyclin are induced by the effect of mechanical deformation, and that the expression of these mediators may be regulated at the transcription level by mechanical forces. There also seems to be emerging evidence that endothelial cells may also act as mechanotransducers, whereby the transmission of external forces induces various cytoskeletal changes and second messenger cascades. Furthermore, it seems these forces may act on specific response elements of promoter genes.

Protein phosphatase 2A in stretch-induced endothelial cell proliferation

We previously proposed that activation of protein kinase C is a key mechanism for control of cell growth enhanced by cyclic strain [Rosales and Sumpio (1992): Surgery 112:459-466]. Here we examined protein phosphatase 1 and 2A activity in bovine aortic endothelial cells exposed to cyclic stain. Protein phosphatase 2A activity in the cytosol was decreased by 36.1% in response to cyclic strain for 60 min, whereas the activity in the membrane did not change. Treatment with low concentration (0.1 nM) of okadaic acid enhanced proliferation of both static and stretched endothelial cells in 10% fetal bovine serum. These data suggest that protein phosphatase 2A acts as a growth suppressor and cyclic strain may enhance cellular proliferation by inhibiting protein phosphatase 2A as well as stimulating protein kinase C.

Cyclic strain causes heterogeneous induction of transcription factors, AP-1, CRE binding protein and NF-kB, in endothelial cells: species and vascular bed diversity

Recent studies demonstrate that cyclic strain stimulates protein kinase C in bovine aortic endothelial cells (BAEC) as well as the induction of immediate early genes and the transcription factor activator protein-1 (AP-1) in human umbilical vein endothelial cells (HUVEC). The objective of this study was to determine whether transcriptional factor induction in endothelial cells (EC) exposed to strain is the same with regard to the species and vascular bed they are derived from. Evidence for a heterogeneous response for growth, orientation and prostacyclin secretion has been obtained for a variety of EC exposed to cyclic strain. In this study, we investigated cyclic strain mediated induction of transcription factors, AP-1, cAMP response element binding protein (CRE) and nuclear factor kB (NF-kB) in cultured EC from HUVEC, human aorta (HAEC), and BAEC. EC were exposed to 10% average strain at 60 cpm for up to 24 h. At varying time points, nuclear protein was extracted and analyzed for production of AP-1, CRE and NF-kB by electromobility shift assay. The results demonstrate that EC exposure to cyclic strain leads to a significant induction of AP-1, CRE and NF-kB in HAEC and HUVEC, but not in BAEC. Furthermore, these findings are in marked contrast to the previously described shear stress induced activation of AP-1 and NF-kB in BAEC. There was also a temporal difference in their response such that stretch-induced activation of AP-1 and NF-kB peaked at 4 h, whereas CRE increased in a biphasic manner at 15 min and 24 h. These results may partially explain the divergent effects of cyclic strain on EC gene expression and phenotype in EC from different vascular beds and species and underscore the difference in EC response to cyclic strain and shear stress.

Cyclic strain stimulates dephosphorylation of the 20kDa regulatory myosin light chain in vascular smooth muscle cells

The role of cyclic strain in the regulation of 20 kDa myosin light chain phosphorylation (MLC20) in cultured smooth muscle cells (SMC) is unknown. The objective of this study was to determine whether cyclic strain stimulates the dephosphorylation of MLC20 in serum-fed SMC displaying a high basal level of phosphorylation. Confluent bovine aortic SMC were subjected to 10% average strain at 60 cycles per minute for 30 and 60 minutes. Basal MLC20 phosphorylation (N = non,M = mono,D = di) of serum-fed SMC was as follows: N = 34%:M = 27%:D = 39%. After 60 min of cyclic strain, both mono and diphosphorylated MLC20 were decreased to 21 and 15% respectively. The strain-induced dephosphorylation of MLC20 was partially inhibited by the protein phosphatase 1/2A inhibitor, calyculin A (5 nM). However, phosphorylase a phosphatase activities in Triton-soluble and insoluble fractions of SMC were unaffected by cyclic strain. The data suggest that cyclic strain causes dephosphorylation of MLC20 in SMC which may be partially due to activation of MLC20 phosphatase and/or inhibition of MLC20 phosphorylation.

Induced mood, phobic responding and the return of fear

The link between depression and phobic responding is poorly understood. Forty-eight spider phobics were exposed to videotaped spider sequences whilst in relatively depressed or relatively elated moods, then presented the same stimuli whilst in a neutral mood. Results indicated that depressed mood increased initial responding, and was associated with greater return of fear during the second (non-mood) sequence. The return of fear was not attributable solely to differential habituation rates during the first sequence, suggesting that the differences observed may have been due to cognitive effects.

Adaptive responses of coronary circulation and myocardium to chronic reduction in perfusion pressure and flow

We tested the hypothesis that chronic reduction in perfusion pressure and flow in the coronary circulation induces a state of myocardial "hibernation" characterized not only by a steady-state reduction in myocardial O2 consumption (MVO2) but also by evidence of persistent dilator reserve of the distal vasculature. Biochemical and morphological changes in the coronary vasculature were also assessed. Experiments were conducted in swine with an extraluminal coronary stenosis placed 4-32 wk before study. Stenosis reduced lumen diameter by approximately 80% at the time of final experimentation. Baseline, regional myocardial blood flow distal to the stenosis in both endocardial and epicardial layers was reduced vs. that of the normal zone. Vasodilator reserve persisted in both endocardial and epicardial layers of the stenosis zone. Flow increased in each layer in response to adenosine plus phenylephrine and failed to decline despite a marked reduction in perfusion pressure in response to adenosine alone. Regional MVO2 at baseline was reduced vs. historical controls without coronary stenosis. Protein synthesis rate in coronary vessels of the stenosis zone was reduced vs. that of the normal zone. Morphological responses of stenosis zone vessel walls were heterogeneous. Smaller microvessels exhibited mild hypertrophy of their walls, whereas walls of larger microvessels tended to atrophy. Thus chronic reduction in perfusion pressure and flow induces a state of myocardial hibernation characterized by a steady-state reduction in MVO2 in association with persistent dilator capacity. Biochemical and morphological changes occur in microvessel walls and may contribute to observed physiological responses.

Chronic cyclic strain reduces adenylate cyclase activity and stimulatory G protein subunit levels in coronary smooth muscle cells

Previous studies from this laboratory have demonstrated that acute cyclic strain causes a reduction in adenylate cyclase activity in cultured coronary vascular smooth muscle cells. The objective of this study was to test the hypothesis that chronic cyclic strain of coronary vascular smooth muscle cells also causes inhibition of adenylate cyclase activity and that this may be related to changes in G protein steady-state levels. Cultured smooth muscle cells obtained from porcine coronary artery were subjected to 24 h of cyclic strain of 20 kPa (24% maximum strain) at 60 cycles/min. Unstretched cells served as controls. Basal, Gpp(NH)p, and forskolin plus Mn(2+)-stimulated adenylate cyclase activities were inhibited significantly in stretched versus unstretched vascular smooth muscle cells. The reduction in adenylate cyclase activity observed after 24 h of cyclic strain was associated with a significant (P < 0.05 vs controls) reduction in steady-state levels of Gs alpha 45, whereas Gi alpha 1,2 and G beta levels remained unchanged. The data support the hypothesis that adenylate cyclase activity and G protein steady-state levels in coronary smooth muscle are sensitive to chronic cyclic strain. It suggests that the G protein adenylate cyclase effector pathway may play an important role in the subacute adaptation of the coronary circulation to changes in intravascular pressure.

Phospholipase C: a putative mechanotransducer for endothelial cell response to acute hemodynamic changes

Endothelial cells (EC) in vivo are exposed to a multitude of physical forces with each pulse of the cardiac cycle. Ongoing studies support the concept that EC respond to these forces through specific signal transduction pathways. Previous investigations in our laboratory have shown that EC respond to the initiation of cyclic strain or to an acute increase in cyclic strain frequency with the production of inositol 1,4,5-trisphosphate (IP3). This study demonstrates that EC also respond to an acute decrease in cyclic stretch frequency with a transient increase in IP3 production. Thus, EC detect both increases and decreases in cyclic stretch frequency with phospholipase C (PLC) activation leading to IP3 generation.

Intracellular cyclic AMP levels in endothelial cells subjected to cyclic strain in vitro

Human saphenous vein endothelial cells (EC) were grown to confluence in fibronectin-coated culture plates with flexible membrane bottoms and maintained in M-199 supplemented with substrates. One hour prior to experimentation 5 mM IBMX, a phosphodiesterase inhibitor, was added. Vacuum was used to deform the membrane bottoms to 24% strain at 60 cycles/min (0.5 sec elongation alternating with 0.5 sec relaxation). After 10-60 min of cyclic strain, or upon exposure of EC to 100 microM forskolin or 0.1 microM galanin, intracellular cyclic AMP (cAMP) was measured by radioimmunoassay. In parallel experiments, tissue plasminogen activator (tPA) secretion was determined after 24 hr of cyclic strain in the absence or presence of forskolin or galanin. The results demonstrate that exposure of EC to cyclic strain led to no change in cAMP levels and confirmed our previous observation that tPA secretion was enhanced with cyclic strain. Addition of forskolin, which led to an almost 10-fold increase in cAMP levels, or galanin, which led to a 34% decrease in cAMP levels, did not significantly alter the rise in tPA induced by cyclic strain.

Mechanosensitive adenylate cyclase activity in coronary vascular smooth muscle cells

The purpose of the present study was to test the hypothesis that adenylate cyclase activity of porcine coronary artery smooth muscle cells is sensitive to mechanical stretch. Cultured vascular smooth muscle cells were stretched at 24% maximal strain at 60 cycles/min for 30 minutes. Both basal and maximal catalytic activity of adenylate cyclase (as assessed by stimulation by 100 microM forskolin with 5 mM manganese chloride) were reduced by 30% (P less than 0.05) in membranes obtained from stretch versus unstretched cells. The magnitude of the stretch-induced reduction in Gpp(NH)p was identical over the entire time course studied (5-30 minutes). Furthermore, basal adenylate cyclase activity was inversely related to the magnitude of stretch. Thus, cyclic stretch can influence adenylate cyclase activity in coronary vascular smooth muscle cells. These data provide important information concerning potential biochemical mechanisms involved in the myogenic response of vascular smooth muscle and also suggest a potential mechanism by which the coronary circulation may adapt to chronically reduced perfusion pressure.

Cultured vascular smooth muscle cells from porcine coronary artery possess A1 and A2 adenosine receptor activity

This study tested the hypothesis that an A1 adenosine receptor capable of inhibiting adenylate cyclase activity is present in porcine coronary vascular smooth muscle cells. In the absence of blockade of the A2 adenosine receptor, the A1 adenosine receptor agonists phenylisopropyladenosine (PIA) and cyclopentyladenosine (CPA) (10(-9) M) failed to inhibit Gpp(NH)p stimulated adenylate cyclase activity. However, after blockade of the A2 adenosine receptor with 30 nM CGS 15943A, cyclopentyladenosine (10(-9) M) inhibited Gpp(NH)p stimulated adenylate cyclase activity by 27 +/- 3% (4.3 +/- 0.7, Mean +/- SEM; pmoles/min/mg vs 5.9 +/- 0.8, P less than .05). The data demonstrate that both A1 and A2 adenosine receptors are present in coronary vascular smooth muscle. The results indicate that adenosine may mediate both vasodilation and vasoconstriction in the coronary circulation via A2 and A1 adenosine receptors, respectively.

The role of symmetrical and asymmetrical social conflict in cognitive change

We asked whether dyads consisting of nonconservers of liquid would be more likely than solo controls to change to a conservation answer when each child gave symmetrically conflicting answers from different perspectives ("more" versus "less" from different viewpoints). We also asked whether nonconservers are more likely than conservers to abandon their answers in conserver + nonconserver dyads. In order to stimulate the perspectival conflicts in the nonconserver + nonconserver dyads, the partners experienced artificial displays in which the two possible answers were afforded by different views of the apparatus. We found no evidence that social conflict of the kind engineered in the nonconserver + nonconserver dyads stimulates cognitive change. Our evidence that nonconservers tend to adopt the conservation answer of their partners was less strong than that collected in previous studies, but this may have been due to the fact that, contrary to previous studies, the children's social dominance relations were affecting the outcome. We concluded that the ineffectiveness of symmetrical social conflict is consistent with Piaget's conception of nonconservers as children insensitive to the perspective-relative nature of their judgments.

Effect of thyroid status on catecholamine stimulation of thyroxine 5'-deiodinase in brown adipocytes

We examined type II 5'-iodothyronine deiodinase activation by adrenergic agonists in dispersed brown adipocytes from euthyroid and hypothyroid rats. In euthyroid cells, basal deiodinase activity was 30-100 fmol I-.h-1.10(6) cells-1 and increased four- to fivefold during exposure to norepinephrine, an effect that was enhanced by alprenolol. In cells from hypothyroid rats, norepinephrine caused a three- to fourfold greater deiodinase stimulation than occurred in euthyroid cells but alprenolol inhibited the response. In euthyroid cells, phenylephrine caused greater stimulation than did norepinephrine, but this was inhibited by alprenolol. Isoproterenol and 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) inhibited the phenylephrine response but were modestly stimulatory alone. Although both alpha 1- and beta-adrenergic agonists increased deiodinase activity modestly in hypothyroid cells, in combination they caused a marked synergistic stimulation. This synergism was induced by 8-BrcAMP and forskolin, as well as by isoproterenol. The stimulation of deiodinase in both cell types was due to an increase in Vmax without an alteration in the Km and required mRNA synthesis. The markedly greater deiodinase response of the hypothyroid brown adipocyte to catecholamines may serve to enhance the impaired thermogenic response of this tissue to cold exposure.

Phorbol esters, protein kinase C, and thyroxine 5'-deiodinase in brown adipocytes

Protein kinase C activity has been identified in the rat brown adipocyte. About 60% of this activity is found in the cytosolic fraction under basal conditions, and 12-O-tetradecanoylphorbol 13-acetate (TPA) causes a rapid shift from the cytosol to the particulate fraction. Norepinephrine and phenylephrine cause a similar redistribution that can be blocked by prazosin but not by alprenolol. alpha 1-Adrenergic agonists cause three- to fivefold stimulation of type 2 iodothyronine 5'-deiodinase activity in brown adipocytes. TPA has no effect on basal deiodinase activity and reduces the response of the enzyme to alpha 1-adrenergic agonists. These results suggest that the translocation of protein kinase C from cytosol to particulate fraction is not sufficient to increase deiodinase activity but can modulate the alpha 1-adrenergic agonist-mediated responses in these cells.

Catecholamine stimulation of iodothyronine 5'-deiodinase activity in rat dispersed brown adipocytes

We describe an in vitro system for evaluating the direct effects of catecholamines on the activity of the type II iodothyronine 5'-deiodinase in dispersed rat brown adipocytes. Incubation with norepinephrine or phenylephrine for 3-4 h causes up to a 5-fold increase in deiodinase activity in these cells. As found in vivo studies, the norepinephrine stimulation is blocked by coincubation with the alpha 1-adrenergic antagonist prazosin. The beta-adrenergic antagonist alprenolol either has no effect or increases stimulation by norepinephrine. These results suggest that beta-adrenergic agonists inhibit the activation or synthesis of the deiodinase in these cells.

Insulin stimulation of iodothyronine 5'-deiodinase in rat brown adipocytes

Insulin (100-3333 microU/ml) stimulates iodothyronine 5'-deiodinase 3 to 4 fold in dispersed rat brown adipocytes. Deiodinase activity increased steadily from 1 to 4 hours. Insulin increased enzyme activity via an increase in the Vmax while the Km remained unchanged. Omission of glucose from the medium did not affect the insulin response. Studies with alpha-amanitin suggested that the increase in deiodinase activity was not due to an increase in the rate of transcription. The insulin effect was not additive to that of alpha 1-catecholamines, suggesting the two stimulators might have one or more common elements.

Pertussis toxin effects on adenylate cyclase activity, cyclic AMP accumulation and lipolysis in adipocytes from hypothyroid, euthyroid and hyperthyroid rats

Adipocytes from hypothyroid rats have a decreased responsiveness to agents that activate adenylate cyclase, whereas cells from hyperthyroid rats have an increased responsiveness as compared to the controls. This is reflected in cyclic AMP accumulation as well as lipolysis. Administration of pertussis toxin to rats or its in vitro addition to adipocytes increased basal lipolysis and cyclic AMP accumulation as well as the response to norepinephrine or forskolin. The effects of thyroid status was not abolished by toxin treatment. Pertussis toxin-catalyzed ADP ribosylation of Ni was increased in adipocyte membranes from hypothyroid rats as compared to those from euthyroid rats. However, no change in sensitivity to N6-(phenylisopropyl)adenosine was observed. The data suggest that the amount of Ni might not be rate-limiting for the inhibitory action of adenosine. A consistent decrease in maximal lipolysis was observed in freshly isolated adipocytes from hypothyroid animals as compared to those from the controls. Such defective maximal lipolysis was not corrected by adenosine deaminase or in vivo administration of pertussis toxin. The relationship between cyclic AMP levels and lipolysis suggests that in fat cells from hypothyroid rats either the cyclic AMP-dependent protein kinase or the lipase activity itself may limit maximal lipolysis. There appears to be multiple effects of thyroid status on lipolysis involving factors other than those affecting adenylate cyclase activation.

Pertussis toxin reversal of the antilipolytic action of insulin in rat adipocytes in the presence of forskolin does not involve cyclic AMP

Insulin inhibition of lipolysis in the presence of forskolin was reversed by a four hour exposure of adipocytes to pertussis toxin. In contrast, the antilipolytic action of insulin against lipolysis due to theophylline was unaffected by pertussis toxin as was the ability of insulin to lower cyclic AMP in the presence of either forskolin or theophylline. The stimulation of adenylate cyclase by norepinephrine in crude plasma membranes obtained from rat adipocytes was inhibited by N6-(Phenylisopropyl)adenosine (PIA) and abolished by pretreating rat adipocytes with pertussis toxin. The stimulation of glucose metabolism by insulin was not altered by pertussis toxin pretreatment of rat adipocytes. These findings suggest that pertussis toxin selectively abolishes the antilipolytic effect of insulin in the presence of forskolin through a cyclic AMP independent mechanism.

A comparison of the mechanisms of alpha-adrenergic inhibition of thyrotropin-stimulated adenosine 3',5'-monophosphate in cat, rat, mouse, hamster, beef, and pig tissues with the stimulatory effect of epinephrine on beef thyroid iodination: evidence for multiple, species-specific adrenergic mechanisms

Epinephrine was shown to inhibit TSH-stimulated cAMP formation in cat and pig thyroid slices and isolated rat and hamster thyroid lobes. In contrast, no such inhibitory action could be demonstrated in sheep or beef thyroid slices or mouse thyroid-trachea preparations. The inhibitory effect of epinephrine on TSH-stimulated cAMP formation in pig thyroid slices was blocked by 10 microM yohimbine, but not by 10 microM prazosin, suggestive of mediation through an alpha 2-catecholamine receptor mechanism. In cat thyroid slices, the inhibitory effect of epinephrine was blocked by both yohimbine and prazosin, suggestive of a mixed alpha-adrenoceptor mechanism. Meclofenamate and indomethacin attenuated the epinephrine response in cat, but not pig, thyroid slices, but other prostaglandin inhibitors were ineffective. Beef thyroid slices responded to epinephrine with an increase in iodide organification that is mediated through an alpha-adrenergic mechanism not blocked by propranolol. This stimulatory effect of epinephrine was abolished by both 10 microM prazosin and 10 microM yohimbine. In contrast to the inhibitory effect of the catecholamines on TSH-stimulated cAMP formation in cats, the stimulatory response of beef iodide organification to epinephrine was not modified by meclofenamate, indomethacin, or verapamil. These findings suggest that the receptor mechanisms mediating the inhibitory effect of catecholamines on cat thyroid and the stimulatory effect of catecholamines in beef thyroid slices may well be mediated by separate and as yet undefined receptor mechanisms. In contrast, the inhibitory effect of epinephrine on TSH-stimulated cAMP formation in pigs is most likely mediated through an alpha 2-adrenoceptor mechanism. These findings further document the multiplicity of catecholamine actions on thyroid function as well as the diversity observed among various species.

Thyroid-catecholamine interactions in isolated rat brown adipocytes

The effects of hyperthyroidism and hypothyroidism on the metabolism of adipocytes isolated from rat brown adipose tissue were as follows: The yield of brown adipocytes was 65% less in the hypothyroid as compared to the control rats. No change in cell recovery was observed in the hyperthyroid group as compared to controls but there was a 65% increase in cell volume. The stimulation of respiration by isoproterenol and forskolin was markedly greater in cells from hyperthyroid as compared to euthyroid rats. In the adipocytes from hypothyroid rats, respiration and lipolysis were reduced but there was no defect in stimulation of adenylate cyclase by forskolin or isoproterenol as compared to euthyroid controls. The effects of different thyroid states on respiration did not correlate with changes in adenosine 3':5'-cyclic phosphate (cyclic AMP) or lipolysis. Phenylephrine in the presence of alprenolol or octanoate were as potent stimulators of respiration as 10 mumol/L isoproterenol in adipocytes from hypothyroid rats. In cells from hyperthyroid rats phenylephrine was twice, octanoate three times, and isoproterenol 16 times more effective in stimulating respiration than in cells from hypothyroid rats. These data indicate that thyroid status regulates beta-catecholamine and forskolin stimulation of respiration in brown adipocytes.

Forskolin inhibition of glucose metabolism in rat adipocytes independent of adenosine 3',5'-monophosphate accumulation and lipolysis

Addition of forskolin (1 microM) to rat adipocytes incubated with insulin and 0.2 mM glucose inhibited glucose metabolism in the absence of any significant stimulation of either cAMP accumulation or lipolysis. The action of forskolin was in contrast to that of isoproterenol, since forskolin inhibited [1-14C]glucose conversion to total lipid, whereas isoproterenol had the opposite effect. Elevation of the medium glucose concentration to 10 mM reversed the inhibitory effects of forskolin on glucose metabolism. The ability of forskolin to inhibit glucose metabolism was observed whether glucose was labeled in the 1 or the 6 position. The results of the present study suggest that forskolin affects glucose metabolism independently of adenylate cyclase activation.

Activation of lipolysis and cyclic AMP accumulation in rabbit adipocytes by isoproterenol in the presence of forskolin or pertussis toxin

Adipocytes from rabbits are relatively insensitive to catecholamines or forskolin. However, the combination of catecholamines plus forskolin increased cyclic AMP accumulation and lipolysis much more than either agent alone. Pertussis toxin treatment also restored sensitivity to catecholamines. No defect in activation by catecholamines of adenylate cyclase was seen in isolated membranes incubated in the presence of GTP. Rabbit adipocytes appear to have an excess of the inhibitory guanine nucleotide binding protein (Ni). However, in plasma membranes this protein appeared to be relatively inactive as there was an activation of adenylate cyclase activity by catecholamines in the presence of GTP. These data suggest that in intact rabbit adipocytes catecholamines and forskolin are ineffective as stimulators of adenylate cyclase due to an excess of inhibitory guanine nucleotide binding proteins.