Biomedical subjects

Edwin K Jackson

Publications and source records attributed to Edwin K Jackson.

At least 37 records · Page 2Linked to original sources

PubMed2005

Murine orthostatic response during prolonged vertical studies: effect on cerebral blood flow measured by arterial spin-labeled MRI.

High-field MRI scanners are, in principle, well suited for mouse studies; however, many high-field magnets employ a vertical design that may influence the physiological state of the rodent. The purpose of this study was to investigate the orthostatic response of cerebral blood flow (CBF) in mice during a prolonged MR experiment in the vertical position. Arterial spin-labeled (ASL) MRI was performed at 4.7-Tesla with a 15-cm gradient insert that allowed horizontal and vertical CBF measurements to be obtained with the same scanner. For mice in the head-up (HU) vertical position, CBF decreased by approximately 40% compared to the horizontal position, although blood pressure did not differ. Furthermore, CBF values for vertically positioned mice treated with phenylephrine remained constant while blood pressure increased. These results support the conclusion that cerebral autoregulation was intact, albeit at a lower level. Since CBF recovers to near horizontal values by volume loading with saline, it appears that a decrease in central venous pressure (CVP) leading to an increase in sympathetic tone may be a contributing mechanism for lowered CBF. This suggests that using an HU vertical position for MRI in mice may have broader implications, especially for studies that rely on CBF (such as BOLD and fMRI).

Adaptation, Physiological↗

PubMed2005

Extracellular cyclic AMP-adenosine pathway in isolated adipocytes and adipose tissue.

OBJECTIVE: Our goal was to evaluate the presence and lipolytic impact of the extracellular cyclic adenosine monophosphate (AMP)-adenosine pathway in adipose tissue. RESEARCH METHODS AND PROCEDURES: Sixteen miniature Yucatan swine (Sus scrofa) were used for these in vitro and in situ experiments. Four microdialysis probes were implanted into subcutaneous adipose tissue and perfused at 2 microL/min with Ringer's solution containing no addition, varying levels of cyclic AMP, 10 microM isoproterenol, or 10 microM isoproterenol plus 1 mM alpha,beta-methylene adenosine 5'-diphosphate (AMPCP), a 5'-nucleotidase inhibitor. Dialysate was assayed for AMP, adenosine, inosine, hypoxanthine, and glycerol. Freshly isolated adipocytes were incubated with buffer, 1 microM isoproterenol, or 1 microM isoproterenol plus 0.1 mM AMPCP, and extracellular levels of AMP, adenosine, inosine, hypoxanthine, and glycerol were measured. RESULTS: Perfusion of adipose tissue with exogenous cyclic AMP caused a significant increase in AMP and adenosine appearance. Perfusion with AMPCP, in the presence or absence of isoproterenol, significantly increased the levels of AMP and glycerol, whereas it significantly reduced the level of adenosine and its metabolites. However, the AMPCP-provoked increase in lipolysis observed in situ and in vitro was not temporally associated with a decrease in adenosine. DISCUSSION: These data suggest the existence of a cyclic AMP-adenosine pathway in adipocytes and adipose tissue. The role of this pathway in the regulation of lipolysis remains to be clarified.

Adenosine↗

PubMed2005

Characterization of the effects of adenosine receptor agonists on cerebral blood flow in uninjured and traumatically injured rat brain using continuous arterial spin-labeled magnetic resonance imaging.

Hypoperfusion after traumatic brain injury may exacerbate damage. Adenosine, a vasodilator, regulates cerebral blood flow (CBF). Treatment with adenosine receptor agonists has shown benefit in experimental CNS trauma; however, their effects on CBF after injury remain undefined. We used magnetic resonance imaging to assess CBF in uninjured rats both early and at 24 h after intrahippocampal administration of either the nonselective adenosine receptor agonist 2-chloroadenosine (2-CA, 12 nmol) or the A(2A)-receptor agonist 2-p-(2-carboxyethyl)-phenethylamino-5'-N-ethylcarbox-amidoadenosine (CGS 21680, 6 nmol). We also assessed the effects of these agents on cerebral metabolic rate for glucose (CMRglu). We then assessed the effect of 2-CA on CBF at 3.5 to 5 h after controlled cortical impact (CCI). Injection of 2-CA into uninjured rat brain produced marked increases in CBF in ipsilateral hippocampus and cortex versus vehicle (P<0.05); CBF increases persisted even at 24 h. Measurement of hippocampal levels of 2-CA showed persistent increases to 24 h. CGS 21680 produced even more marked global increases in CBF than seen with 2-CA (2-6-fold versus vehicle, P<0.05 in 10/12 regions of interest (ROIs)). Neither agonist altered CMRglu versus vehicle. After CCI, 2-CA increased CBF in ipsilateral hippocampal and hemispheric ROIs (P<0.05 versus vehicle), but the response was attenuated at severe injury levels. We report marked increases in CBF after injection of adenosine receptor agonists into uninjured rat brain despite unaltered CMRglu. 2-Chloroadenosine produced enduring increases in CBF in uninjured brain and attenuated posttraumatic hypoperfusion. Future studies of adenosine-related therapies in CNS injury should address the role of CBF.

2-Chloroadenosine↗

PubMed2005

Enhanced activation of RhoA by angiotensin II in SHR preglomerular microvascular smooth muscle cells.

Angiotensin II causes a greater renal vasoconstriction in spontaneously hypertensive rats (SHR) than in normotensive Wistar Kyoto rats (WKY), and alpha2-adrenoceptor agonists potentiate angiotensin II-induced renal vasoconstriction more in SHR. Because angiotensin II activates RhoA, and RhoA contributes to vasoconstriction, we tested the hypothesis that the ability of angiotensin II to stimulate RhoA in preglomerular vascular smooth muscle cells and the ability of alpha2-adrenoceptor activation to potentiate this response are augmented in cells from SHR. In SHR preglomerular vascular smooth muscle cells, angiotensin II (1 micromol/L) greatly stimulated RhoA activity, and this effect was markedly potentiated by UK 14,304 (1 micromol/L; alpha2-adrenoceptor agonist) (fold increase from vehicle-treated cells: 9.0 +/- 2, 0.8 +/- 0.2, and 13.6 +/- 3.2 in cells treated with angiotensin II, UK 14,304, and angiotensin II + UK 14,304, respectively). In contrast, in WKY cells, angiotensin II only mildly activated RhoA (2.0 +/- 0.50), and this response was not enhanced by UK 14,304. The expression of Galpha12 and Galpha13, G-proteins thought to link G-protein-coupled receptors to RhoA, was not increased in SHR cells. We conclude that angiotensin II-induced activation of RhoA is much more robust in the preglomerular microcirculation of SHR compared with WKY and that this may contribute to the etiology of genetic hypertension.

Angiotensin II↗

PubMed2005

Estradiol metabolites attenuate renal and cardiovascular injury induced by chronic nitric oxide synthase inhibition.

Our previous studies in rodent models of nephropathy demonstrate that 2-hydroxyestradiol (2HE), an estradiol metabolite with little estrogenic activity, exerts renoprotective effects. In vivo, 2HE is readily converted to 2-methoxyestradiol (2ME), a major estradiol metabolite with no estrogenic activity. The goal of this study was to determine whether 2ME has renal and cardiovascular protective effects in vivo. First, the acute (90 minutes) and chronic (14 days) effects of 2ME (10 microg/kg/h) on blood pressure and renal function were examined in normotensive and spontaneously hypertensive rats (SHR). Second, a rat model of cardiovascular and renal injury induced by chronic nitric oxide synthase inhibition (N-nitro-L-arginine; 40 mg/kg/d; LNNA group) was used to examine the protective effects of estradiol metabolites. Subsets of LNNA-treated rats were administered either 2HE or 2ME (10 microg/kg/h via osmotic minipump; LNNA+2ME and LNNA+2HE groups, respectively. 2-Methoxyestradiol had no acute or chronic effects on blood pressure or renal function in normotensive animals or on hypertension in SHR. Prolonged, 5-week NOS inhibition induced severe cardiovascular and renal disease and high mortality (75%, LNNA group). 2ME, but not 2HE, significantly decreased elevated blood pressure and attenuated the reduction in GFR. 2HE delayed the onset of proteinuria, whereas no proteinuria was detected in the 2-ME group. 2HE and 2ME reduced mortality rate by 66% and 83%, respectively (P < 0.001). In the kidney, 2HE and 2ME abolished LNNA-induced interstitial and glomerular inflammation, attenuated glomerular collagen IV synthesis, and inhibited glomerular and tubular cell proliferation. In the heart, 2HE and 2ME markedly reduced vascular and interstitial inflammation and reduced collagen synthesis and vascular/interstitial cell proliferation. This study provides the first evidence that, in a model of severe cardiovascular and renal injury, 2-methoxyestradiol (a major nonestrogenic estradiol metabolite) exerts renal and cardiovascular protective effects and reduces mortality.

2-Methoxyestradiol↗

PubMed2005

Estradiol metabolites attenuate monocrotaline-induced pulmonary hypertension in rats.

Pulmonary arterial hypertension (PH) is a deadly disease characterized by pulmonary arterial vasoconstriction and hypertension, pulmonary vasculature remodeling, and right ventricular hypertrophy. Our previous in vivo studies, performed in several models of cardiac, vascular, and/or renal injury, suggest that the metabolites of 17beta-estradiol may inhibit vascular and cardiac remodeling. The goal of this study was to determine whether 2-methoxyestradiol (2ME), major non-estrogenic estradiol metabolite, prevents the development and/or retards the progression of monocrotaline (MCT)-induced PH. First, a total of 27 male Sprague Dawley rats were injected with distillated water (Cont, n=6) or monocrotaline (MCT; 60 mg/kg, i.p.; n=21). Subsets of MCT animals (n=7 per group) received 2ME or its metabolic precursor 2-hydroxyestradiol (2HE; 10 microg/kg/h via osmotic minipumps) for 21 days. Next, an additional set (n=24) of control and MCT rats was monitored for 28 days, before right ventricular peak systolic pressure (RVPSP) was measured. Some pulmonary hypertensive animals (n=8) were treated with 2ME (10 microg/kg/h) beginning from day 14 after MCT administration. MCT caused pulmonary hypertension (ie, increased right ventricle/left ventricle+septum [RV/LV+S] ratio and wall thickness of small-sized pulmonary arteries, and elevated RVPSP) and produced high and late (days 22 to 27) mortality. Pulmonary hypertension was associated with strong proliferative response (PCNA staining) and marked inflammation (ED1+cells) in lungs. Both metabolites significantly attenuated the RV/LV+S ratio and pulmonary arteries media hypertrophy and reduced proliferative and inflammatory responses in the lungs. Furthermore, in diseased animals, 2ME (given from day 14 to 28) significantly decreased RVPSP, RV/LV+S ratio and wall thickness, and reduced mortality by 80% (mortality rate: 62.5% vs. 12.5%, MCT vs. MCT+2ME day 14 to 28). This study provides the first evidence that 2ME, a major non-estrogenic, non-carcinogenic metabolite of estradiol, prevents the development and retards the progression of monocrotaline-induced pulmonary hypertension. Further evaluation of 2ME for management of pulmonary arterial hypertension is warranted.

2-Methoxyestradiol↗

PubMed2004

AT2 receptors cross talk with AT1 receptors through a nitric oxide- and RhoA-dependent mechanism resulting in decreased phospholipase D activity.

ANG II activation of phospholipase D (PLD) is required for ERK and NAD(P)H oxidase activation, both of which are involved in hypertension. Previous findings demonstrate that ANG II stimulates PLD activity through AT(1) receptors in a RhoA-dependent mechanism. Additionally, endogenous AT(2) receptors in preglomerular smooth muscle cells attenuate ANG II-mediated PLD activity. In the present study, we examined the signal transduction mechanisms used by endogenous AT(2) receptors to modulate ANG II-induced PLD activity through either PLA(2) generation of lysophosphatidylethanolamine or Galpha(i)-mediated generation of nitric oxide (NO) and interaction with RhoA. Blockade of AT(2) receptors, Galpha(i) and NO synthase, but not PLA(2), enhanced ANG II-mediated PLD activity in cells rich in, but not poor in, AT(2) receptors. Moreover, NO donors, a direct activator of guanylyl cyclase and a cGMP analog, but not lysophosphatidylethanolamine, inhibited ANG II-mediated PLD activity, whereas an inhibitor of guanylyl cyclase augmented ANG II-induced PLD activity. AT(2) receptor- and NO-mediated attenuation of ANG II-induced PLD activity was completely lost in cells transfected with S188A RhoA, which cannot be phosphorylated on serine 188. Therefore, our data indicate that AT(2) receptors activate Galpha(i), subsequently stimulating NO synthase and leading to increased soluble guanylyl cyclase activity, generation of cGMP, and activation of a protein kinase, resulting in phosphorylation of RhoA on serine 188. Furthermore, because AT(2) receptors inhibit AT(1) receptor signaling to PLD via modulating RhoA activity, AT(2) receptor signaling can potentially regulate multiple vasoconstrictive signaling systems through inactivating RhoA.

Animals↗

PubMed2004

Cytochromes 1A1/1B1- and catechol-O-methyltransferase-derived metabolites mediate estradiol-induced antimitogenesis in human cardiac fibroblast.

We investigated the role of specific cytochrome P450s (CYP450s) and catechol-O-methyltransferase (COMT) in the growth inhibitory effects of estradiol in cardiac fibroblasts (CFs) expressing functional estrogen receptors. 3-Methylcholantherene, phenobarbital (broad-spectrum CYP450 inducers), and beta-naphthoflavone (CYP1A1/1A2 inducer) augmented, and 1-aminobenzotriazole (broad-spectrum CYP450 inhibitor) blocked, the inhibitory effects of estradiol on serum-induced CF growth (DNA synthesis, cell number, and collagen synthesis). Neither ketoconazole (3A4 inhibitor) nor furafylline (selective 1A2 inhibitor) altered the antimitogenic effects of estradiol on CF growth. In contrast, ellipticine (selective 1A1 inhibitor), pyrene (selective 1B1 inhibitor), and alpha-naphthoflavone (1A1>1A2 inhibitor) abrogated the antimitogenic effects of estradiol on CF growth. OR486 (COMT inhibitor) also blocked the antimitogenic effects of estradiol in both the presence and absence of the CYP450 inducers. ICI182780 (estrogen receptor antagonist) attenuated the growth inhibitory effects of estradiol, but only at concentrations that inhibit the metabolism of estradiol to hydroxyestradiols (precursors of methoxyestradiols). CFs expressed CYP1A1 and CYP1B1, isozymes that convert estradiol to hydroxyestradiols. Moreover, CFs metabolized estradiol to hydroxyestradiol, and 2-hydroxyestradiol to 2-methoxyestradiol. OR486 and quercetin (COMT inhibitor) blocked the conversion of 2-hydroxyestradiol to 2-methoxyestradiol in CFs. We conclude that the antimitogenic effects of estradiol on CF growth are mediated in part by conversion to hydroxyestradiols via CYP1A1 and CYP1B1, followed by metabolism of hydroxyestradiols to methoxyestradiols by COMT.

Aryl Hydrocarbon Hydroxylases↗

PubMed2004

Hormone replacement therapy and cardiovascular disease: what went wrong and where do we go from here?

Observational studies in humans and experimental studies in animals and isolated cells supported the widely held belief that hormone replacement therapy protects the cardiovascular system from disease. To nearly everyone's astonishment, the Women's Health Initiative Study and the Heart and Estrogen/Progestin Replacement Study overturned the conclusion that hormone replacement therapy protects the cardiovascular system and, in fact, supported the opposite view that such therapy may actually increase the risk of cardiovascular disease. This review addresses 2 questions: what went wrong and where do we go from here?

Animals↗

PubMed2004

Increased expression of the sodium transporter BSC-1 in spontaneously hypertensive rats.

The purpose of this study was to compare the expression of BSC-1 (bumetanide-sensitive Na+-K+-2Cl- cotransporter) in kidneys of spontaneously hypertensive rats (SHR) versus Wistar-Kyoto (WKY) rats by immunoblotting and reverse transcription-polymerase chain reaction. To determine the specificity of any observed changes in BSC-1 expression, we also compared expression of the thiazide sensitive Na+-Cl- cotransporter (TSC), the type-3 Na+-H+ exchanger (NHE-3), Na+-K+-ATPase-alpha1, the inwardly rectifying K+ channel (ROMK-1), the type-1 Na+-HCO3- cotransporter (NBC-1), aquaporin-1, and aquaporin-2. Analyses were performed on outer cortex, outer medulla, and inner medulla. BSC-1 protein was detected in outer medulla and was markedly (6-fold) higher in SHR. TSC protein was detected in the cortex and was not overexpressed in SHR. Aquaporin-1 protein was detected in all three regions and was not overexpressed in SHR. Aquaporin-2 and ROMK-1 proteins were detected in all three regions, but were moderately elevated (2-fold) only in the SHR inner medulla. Na+-K+-ATPase and NHE-3 proteins were detected in all three regions. Na+-K+-ATPase-alpha1 was modestly (25%) increased in SHR outer and inner medulla, whereas NHE-3 was moderately (2-fold) increased in the SHR cortex and inner medulla. NBC-1 protein was detected only in the cortex and was higher (2-fold) in SHR. mRNA levels of BSC-1, aquaporin-2, and ROMK-1 were not elevated in SHR, indicating a post-translational mechanism of protein overexpression. High-dose furosemide increased fractional sodium excretion more in SHR than WKY (3-fold). We conclude that increased expression of BSC-1, and to a lesser extent, aquaporin-2, ROMK-1, NHE-3, and NBC-1 may contribute to the pathogenesis of hypertension in the SHR.

Animals↗

PubMed2004

Modulation of cyclic AMP production by signal transduction pathways in preglomerular microvessels and microvascular smooth muscle cells.

Cyclic AMP affects microvascular smooth muscle contraction and growth. Therefore, it is important to elucidate mechanisms regulating cyclic AMP production in microvascular smooth muscle. In this study, we determined whether several signal transduction pathways regulate receptor-induced cyclic AMP in isolated preglomerular microvessels and microvascular smooth muscle cells. Preglomerular microvessels were incubated with isoproterenol (beta-adrenoceptor agonist) and with and without U73122 (phospholipase C inhibitor), GF109203X (protein kinase C inhibitor), 1-butanol (phospholipase D inhibitor), CGP77675 (c-src inhibitor), HA1077 (Rho kinase inhibitor), Y27632 (Rho kinase inhibitor), LY294002 (phosphatidylinositol-3-kinase inhibitor), dipenyleneiodonium (NADPH oxidase inhibitor), or Tempol (superoxide dismutase mimetic). Cultured preglomerular microvascular smooth muscle cells were incubated with isoproterenol or forskolin (direct activator of adenylyl cyclase) and with or without U73122, C(2)-ceramide (phospholipase D inhibitor), or PP1 [src family inhibitor, 1-(1,1-dimethylethyl)-1-(4-methylphenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine]. All studies were conducted with 3-isobutyl-1-methylxanthine (broad-spectrum phosphodiesterase inhibitor) to eliminate changes in cyclic AMP degradation. In microvessels isoproterenol-induced cyclic AMP was not affected by Y27632, HA1007, LY294002, dipenylene-iodonium, or Tempol; was increased by U73122 and GF109203X; and was decreased by 1-butanol and CGP77675. In cells, U73122 increased and C(2)-ceramide and PP1 decreased isoproterenol-induced cyclic AMP. Forskolin-induced cyclic AMP was not altered. These results indicate that receptor-mediated activation of adenylyl cyclase is 1) not modulated by Rho kinase, phosphatidylinositol-3-kinase, NADPH oxidase, or superoxide; 2) is attenuated by phospholipase C and protein kinase C; and 3) is augmented by phospholipase D and src. Phospholipase C, phospholipase D, and src modulate receptor-induced cyclic AMP by affecting beta-adrenoreceptor/G protein/adenylyl cyclase coupling rather than by directly affecting adenylyl cyclase activity.

Adenylyl Cyclases↗

PubMed2004

2-hydroxyestradiol is a prodrug of 2-methoxyestradiol.

Previous in vivo studies indicate that 2-hydroxyestradiol (2OHE) attenuates cardiovascular and renal diseases. In vitro studies suggest that the biological effects of 2OHE are mediated by 2-methoxyestradiol (2MEOE) after methylation of 2OHE by catechol-O-methyltransferase (COMT). This study tested the hypothesis that in vivo 2OHE is a prodrug of 2MEOE. We administered to male rats i.v. boluses of either 2OHE or 2MEOE and measured plasma levels of 2OHE and 2MEOE by gas chromatography-mass spectrometry at various time points after drug administration. After administration of 2OHE, plasma levels of 2OHE declined extremely rapidly [t(1/2(1)) = 0.94 min and t(1/2(2)) = 10.2 min] becoming undetectable after 45 min. Concomitant with the disappearance of 2OHE, 2MEOE occurred and then declined [t(1/2(1)) = 7.9 min and t(1/2(2)) = 24.9 min]. The peak concentration and total exposure (area under the curve) for 2OHE were much lower than for 2MEOE. 2OHE had a much higher plasma clearance (CL) and volume of distribution (V(d)) compared with 2MEOE (2OHE: CL = 1215 ml min(-1) kg(-1) and V(d) = 17,875 ml/kg; 2MEOE: CL = 50 ml min(-1) kg(-1) and V(d) = 1760 ml/kg). After administration of 2MEOE, plasma levels of 2MEOE declined [t(1/2(1)) = 2.5 min and t(1/2(2)) = 20.2 min] with a plasma CL of 50 ml min(-1) kg(-1) and a V(d) of 1500 ml/kg. We could not detect 2OHE in plasma from rats receiving 2MEOE. We conclude that the conversion of 2OHE to 2MEOE is so efficient that in terms of 2MEOE exposure, administration of 2OHE is bioequivalent to administration of 2MEOE itself.

2-Methoxyestradiol↗

PubMed2004

AT2 receptors attenuate AT1 receptor-induced phospholipase D activation in vascular smooth muscle cells.

Previous studies indicate that angiotensin (AT)(1) receptor-induced activation of phospholipase D (PLD) may importantly contribute to vascular hypertrophy, injury, and contraction. However, the role of AT(2) receptors in regulating AT(1) receptor-induced PLD activation is unknown. In this study, we identified angiotensin II receptors on cultured preglomerular vascular smooth muscle cells (PGSMCs) from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) by reverse transcription-polymerase chain reaction (RT-PCR) and binding assays and examined their functional effects on angiotensin II-mediated PLD activity. Both RT-PCR and binding indicated that cultured SHR and WKY PGSMCs expressed AT(1) and AT(2) receptors, and the combined total of AT(1) and AT(2) receptors was similar between the strains. However, the number of AT(1) and AT(2) receptors differed between SHR and WKY PGSMCs in so much as the ratio of AT(1) to AT(2) receptors was approximately 1 to 1 and 3 to 1 in WKY and SHR PGSMCs, respectively. As previously reported, angiotensin II more potently activated PLD in SHR PGSMCs (SHR EC(50) = 4 nM; WKY EC(50) = 47 nM). Addition of an AT(2) receptor-specific antagonist or agonist shifted the angiotensin II-mediated PLD concentration-response curve of WKY PGSMCs in a manner consistent with AT(2) receptors producing an inhibitory signal. In contrast, in SHR little change was observed. Our findings indicate that the ratio of AT(1) to AT(2) receptors in vascular smooth muscle cells may be a determinant of the net effects of angiotensin II on PLD activity due to AT(2)-dependent inhibition of AT(1)-mediated PLD activity. Furthermore, cultured WKY PGSMCs provide an excellent model system to study endogenous AT(2) receptor signal transduction.

Angiotensin II↗

PubMed2004

Intraperitoneal administration of adenosine inhibits formation of abdominal adhesions.

PURPOSE: Previously we demonstrated that peritoneal lavage with high concentrations of adenosine (1 mM) provides pharmacologic levels of adenosine in the intestines without elevating adenosine levels in the systemic circulation and without causing systemic hemodynamic effects (Alimentary Pharmacology & Therapeutics 2000; 14:1371-80). Because adenosine can be safely administered into the peritoneal cavity, and because it inhibits fibroblast proliferation and collagen production and inflammation and enhances angiogenesis, we tested the hypothesis that adenosine applied into the abdominal cavity safely and effectively reduces formation of abdominal adhesions. METHODS: To test this hypothesis, in Sprague-Dawley rats, a window of right parietal peritoneum was removed and the cecum was brushed and placed next to the damaged peritoneum. After injury, rats received in the abdominal cavity either 20 ml of saline (n = 12, Saline Group) or 20 ml of 1 mM adenosine (n = 12, Adenosine 1X Group; and n = 12, Adenosine 4X Group). At 24, 48, and 72 hours after surgery, rats received by intraperitoneal injection either 10 ml of saline (Saline Group and Adenosine 1X Group) or 10 ml of 1 mM adenosine (Adenosine 4X Group). RESULTS: After 14 days, the degree of adhesion formation was scored (0 to 4) by a blinded observer. Animals tolerated the adenosine treatments without signs of discomfort or distress. The adhesion scores were 2.6 +/- 0.34, 1.7 +/- 0.40, and 0.74 +/- 0.29 in the Saline, Adenosine 1X, and Adenosine 4X groups, respectively (P = 0.0035, Kruskal-Wallis analysis of variance). CONCLUSION: Peritoneal administration of 1 mM adenosine safely and effectively reduces adhesion formation.

Adenosine↗

PubMed2004

A gas chromatography/mass spectrometry assay to measure estradiol, catecholestradiols, and methoxyestradiols in plasma.

We have developed a gas chromatography/mass spectrometry (GC/MS) assay to measure 17beta-estradiol (E) and its biologically active metabolites 2-hydroxyestradiol (2OHE) and 4-hydroxyestradiol (4OHE), and 2-methoxyestradiol (2MEOE) and 4-methoxyestradiol (4MEOE) in rat plasma. All analytes are well separated and show a linear relationship between concentration (0.25-5 pg/microl) and signal, and coefficients of variation (CVs) are low. Intra-assay CV for the lowest quality control samples (QCs) (0.375 pg/microl) were on average for 17beta-estradiol 20.5%, for 2-hydroxyestradiol 15.6%, for 4-hydroxyestradiol 16.5%, for 2-methoxyestradiol 16.5%, and for 4-methoxyestradiol 11.5%. The inter-assay CVs for the lowest QCs were for 17beta-estradiol 12.1%, for 2-hydroxyestradiol 7.1%, for 4-hydroxyestradiol 15.5%, for 2-methoxyestradiol 16.7%, and for 4-methoxyestradiol 9.7%. The highest sensitivity for this assay was observed for hydroxyestradiols followed by the methoxyestradiols and 17beta-estradiol. In summary, we describe a convenient, sensitive, and specific assay to measure 17beta-estradiol and its biologically active metabolites.

Animals↗

PubMed2004

Continuous versus intermittent cerebrospinal fluid drainage after severe traumatic brain injury in children: effect on biochemical markers.

Drainage of cerebrospinal fluid (CSF) is routinely used in the treatment of severe traumatic brain injury (TBI), either continuously or intermittently in response to increases in intracranial pressure (ICP). There has been little study of the effect of CSF drainage method on the biochemistry, pathophysiology or outcome of TBI in adults or children. Having previously reported that a variety of markers of injury or repair increase in CSF after severe TBI, we chose to evaluate directly the effect of CSF drainage method on the biochemistry and volume of CSF drained as well as ICP. We hypothesized that concentrations of these markers would be similar in CSF drained continuously vs intermittently. We compared CSF levels of markers of neuronal injury (neuron specific enolase, [NSE]), glial injury (s100B), inflammation (interleukin-6 [IL-6]), and regeneration (vascular endothelial growth factor [VEGF]) (measured by ELISA) in 80 CSF samples from 19 severely injured children whose CSF was drained continuously (n = 13) versus intermittently (n = 6) as part of standard care in two institutions. Compared to continuous CSF drainage, intermittent drainage of CSF was associated with twofold greater CSF concentrations of NSE, s100B, IL-6 and VEGF (p < 0.05) and with about half the volume of CSF removal than continuous drainage (p = 0.002). The resulting elimination (concentration x volume) of these biochemicals, however, was not influenced by drainage method. Patients treated with continuous drainage had lower mean ICPs than those with intermittent drainage (13.6 +/- 0.69 vs. 21.8 +/- 0.95 mm Hg, p < 0.0001). We conclude that the method of CSF drainage greatly affects concentrations of CSF markers after TBI and may influence ICP. The influence of method on CSF marker concentration must be kept in mind when interpreting studies of CSF biomarkers. The striking difference in biomarker concentration, CSF volume drained, and ICP suggests the need for a randomized trial directly comparing these two approaches in infants and children with severe TBI.

Adolescent↗

PubMed2004

The extracellular cyclic AMP-adenosine pathway in renal physiology.

Many cell types in the kidney express adenosine receptors, and adenosine has multiple effects on renal function. Although adenosine is produced within the kidney by several biochemical reactions, recent studies support a novel mechanism for renal adenosine production, the extracellular cAMP-adenosine pathway. This extracellular cAMP-adenosine pathway is initiated by efflux of cAMP from cells following activation of adenylyl cyclase. Extracellular cAMP is then converted to adenosine by the serial actions of ecto-phosphodiesterase and ecto-5'-nucleotidase. When extracellular cAMP is converted to adenosine near the biophase of cAMP production and efflux, this local extracellular cAMP-adenosine pathway permits tight coupling of the site of adenosine production to the site of adenosine receptors. cAMP in renal compartments may also be formed by tissues/organs remote from the kidney. For example, stimulation of hepatic adenylyl cyclase by the pancreatic hormone glucagon increases circulating cAMP, which is filtered at the glomerulus and concentrated in the tubular lumen as water is extracted from the ultrafiltrate. Conversion of hepatic-derived cAMP to adenosine in the kidney completes a pancreatohepatorenal cAMP-adenosine pathway that may serve as an endocrine link between the pancreas, liver, and kidney.

Adenosine↗

PubMed2004

Differential regulation of estrogen receptor subtypes alpha and beta in human aortic smooth muscle cells by oligonucleotides and estradiol.

We investigated the mechanisms regulating estrogen receptor (ER) expression in human aortic smooth muscle cells (HASMCs) and the mechanisms by which estradiol inhibits HASMC growth. The autologous down-regulation pathway involves binding of liganded ER to the ER gene, thus suppressing transcription. Blockade of this pathway with sense and AS-OLIGOs to ERs up-regulated the expression of ERalpha but not ERbeta. Activation of the autologous down-regulation pathway with ER agonists down-regulated the expression of ERalpha but not ERbeta. The proteasomal degradation pathway entails ubiquination of liganded ER, followed by proteasome-mediated degradation. Blockade of the proteasomal degradation pathway increased the expression of ERbeta. Up-regulation of ERalpha by AS-OLIGOs did not increase the antimitogenic effects of estradiol on HASMCs; the estradiol metabolites 2-hydroxyestradiol and 2-methoxyestradiol were more potent inhibitors of HASMC growth, compared with estradiol; and blockade of metabolism of estradiol to hydroxyestradiols and methoxyestradiols abrogated the inhibitory effects of estradiol on HASMC growth. We conclude that, in HASMCs: 1) the expression of ERalpha is regulated by the autologous downregulation pathway; 2) the expression of ERbeta is governed by the proteasomal degradation pathway; and 3) the antigrowth effects of estradiol are not mediated by ERalpha, but rather by metabolism of estradiol to methoxyestradiols.

Aorta↗