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Biomedical subjects

S E Ross

Publications and source records attributed to S E Ross.

At least 19 recordsLinked to original sources
PubMed2001

p300 coactivates the adipogenic transcription factor CCAAT/enhancer-binding protein alpha.

Despite the knowledge that CCAAT/enhancer-binding protein alpha (C/EBPalpha) plays an important role in preadipocyte differentiation, our understanding of how C/EBPalpha interacts with nuclear proteins to regulate transcription is limited. Based on the hypothesis that evolutionarily conserved regions are functionally important and likely to interact with coactivators, we compared the amino acid sequence of C/EBPalpha from different species (frog to human) and identified four highly conserved regions (CR1-CR4) within the transactivation domain. A series of amino-terminal truncations and internal deletion constructs were made creating forms of C/EBPalpha which lack single or multiple conserved regions. To determine which regions of the C/EBPalpha transactivation domain are important in its ability to induce spontaneous differentiation of 3T3-L1 preadipocytes, we infected preadipocytes with expression vectors encoding the C/EBPalpha conserved region mutants and observed their ability to induce differentiation. We found that CR2 fused to the DNA binding domain is able to induce spontaneous differentiation independent of the other conserved regions. However, CR2 was not necessary for the adipogenic action of C/EBPalpha because a combination of CR1 and CR3 can also induce adipogenesis. Because the transcriptional coactivator p300 participates in the signaling of many transcription factors to the basal transcriptional apparatus, we examined whether functional interaction exists between C/EBPalpha and p300. Cotransfection of p300 with p42C/EBPalpha results in a synergistic increase in leptin promoter activity, indicating that p300 acts as a transcriptional coactivator of C/EBPalpha. Analyses using C/EBPalpha conserved region mutants suggest that multiple regions (CR2 and CR3) of the C/EBPalpha transactivation domain functionally interact with p300.

3T3 Cells↗
PubMed2001

Growth hormone regulates phosphorylation and function of CCAAT/enhancer-binding protein beta by modulating Akt and glycogen synthase kinase-3.

Growth hormone (GH) regulates transcription factors associated with c-fos, including C/EBPbeta. Two forms of C/EBPbeta, liver-activating protein (LAP) and liver inhibitory protein (LIP), are dephosphorylated in GH-treated 3T3-F442A fibroblasts. GH-induced dephosphorylation of LAP and LIP is reduced when cells are preincubated with phosphatidylinositol 3'-kinase (PI3K) inhibitors. GH activates Akt and inhibits glycogen synthase kinase-3 (GSK-3). Lithium, a GSK-3 inhibitor, increases GH-dependent dephosphorylation of LAP and LIP. Both are in vitro substrates of GSK-3, suggesting that GSK-3 inactivation contributes to GH-promoted dephosphorylation of C/EBPbeta. Alkaline phosphatase increases binding of LAP homodimers and decreases binding of LIP homodimers to c-fos, suggesting that dephosphorylation of C/EBPbeta modifies their ability to bind DNA. Both alkaline phosphatase- and GH-mediated dephosphorylation comparably increase binding of endogenous LAP in 3T3-F442A cells. In cells overexpressing LAP and GSK-3, LAP binding decreases, suggesting that GSK-3-mediated phosphorylation interferes with LAP binding. Expression of constitutively active GSK-3 reduced GH-stimulated c-fos promoter activity. These studies indicate that PI3K/Akt/GSK-3 mediates signaling between GH receptor and the nucleus, promoting dephosphorylation of C/EBPbeta. Dephosphorylation increases binding of LAP complexes to the c-fos promoter and may contribute to the participation of C/EBPbeta in GH-stimulated c-fos expression.

3T3 Cells↗
PubMed2001

Stapled versus sutured gastrointestinal anastomoses in the trauma patient: a multicenter trial.

BACKGROUND: Construction of gastrointestinal anastomoses utilizing stapling devices has become a familiar procedure. In elective surgery, studies have shown no significant differences in complications between stapled and sutured anastomoses. Controversy has recently arisen regarding the accurate incidence of complications associated with anastomoses in the trauma patient. The objective of this multi-institutional study was to determine whether the incidence of postoperative complications differs between stapled and sutured anastomoses following the emergent repair of traumatic bowel injuries. METHODS: Using a retrospective cohort design, all trauma registry records from five Level I trauma centers over a period of 4 years were reviewed. RESULTS: A total of 199 patients with 289 anastomoses were identified. A surgical stapling device was used to create 175 separate anastomoses, while a hand-sutured method was employed in 114 anastomoses. A complication was defined as an anastomotic leak verified at reoperation, an intra-abdominal abscess, or an enterocutaneous fistula. The mean abdominal Abbreviated Injury Scale score and Injury Severity Score were similar in the two cohort groups. Stapling and suturing techniques were evenly distributed in both small and large bowel repairs. Seven of the total 175 stapled anastomoses and none of the 114 hand-sewn anastomoses resulted in a clinically significant leak requiring reoperation (RR = undefined, 95% CI 1.08-infinity, p = 0.04). Each anastomotic leak occurred in a separate individual. Nineteen stapled anastomoses and four sutured anastomoses were associated with an intra-abdominal abscess (RR = 2.7, 95% CI 0.96-7.57, p = 0.04). Enterocutaneous fistula formation was not statistically associated with either type of anastomoses (stapled cohort = 3 of 175 and sutured cohort = 2 of 114). Overall, 22 (13%) stapled anastomoses and 6 (5%) sutured anastomoses were associated with an intra-abdominal complication (RR = 2.08, 95% CI 0.89-4.86, p = 0.076). CONCLUSION: Anastomotic leaks and intra-abdominal abscesses appear to be more likely with stapled bowel repairs compared with sutured anastomoses in the injured patient. Caution should be exercised in deciding to staple a bowel anastomosis in the trauma patient.

Adolescent↗
PubMed2000

Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 9. Incorporation of planar waveguide technology.

Incorporation of planar waveguide technology into a spectroelectrochemical sensor is described. In this sensor design, a potassium ion-exchanged BK7 glass waveguide was over-coated with a thin film of indium tin oxide (ITO) that served as an optically transparent electrode. A chemically selective film was spin-coated on top of the ITO film. The sensor supported five optical modes at 442 nm and three at 633 nm. Investigations on the impact of the ITO film on the optical properties of the waveguide and on the spectroelectrochemical performance of the sensor are reported. Sensing was based on the change in attenuation of light propagated through the waveguide resulting from an optically absorbing analyte. By applying either a triangular or square wave excitation potential waveform, electromodulation of the optical signal has been demonstrated with Fe(CN)6(3-/4-) as a model electroactive couple that partitions into a PDMDAAC-SiO2 film [where PDMDAAC = poly(dimethyldiallylammonium chloride)] and absorbs at 442 nm.

Journal Article↗
PubMed2000

Inhibition of adipogenesis by Wnt signaling.

Wnts are secreted signaling proteins that regulate developmental processes. Here we show that Wnt signaling, likely mediated by Wnt-10b, is a molecular switch that governs adipogenesis. Wnt signaling maintains preadipocytes in an undifferentiated state through inhibition of the adipogenic transcription factors CCAAT/enhancer binding protein alpha (C/EBPalpha) and peroxisome proliferator- activated receptor gamma (PPARgamma). When Wnt signaling in preadipocytes is prevented by overexpression of Axin or dominant-negative TCF4, these cells differentiate into adipocytes. Disruption of Wnt signaling also causes transdifferentiation of myoblasts into adipocytes in vitro, highlighting the importance of this pathway not only in adipocyte differentiation but also in mesodermal cell fate determination.

3T3 Cells↗
PubMed2000

Predictors of operative outcome in patients with human immunodeficiency virus infection and acquired immunodeficiency syndrome.

BACKGROUND: Plasma viral load has recently been associated with clinical outcome in patients with human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS). We hypothetized that, in addition to CD4 lymphocytes, plasma HIV-1 RNA counts are predictive of postoperative outcome. METHODS: HIV-infected and AIDS patients admitted to a major teaching hospital requiring invasive or surgical procedures were retrospectively analyzed for postoperative outcome. Preoperative and postoperative immune cell counts including plasma HIV-1 RNA counts were recorded. Chi-square analysis, Fisher's exact test, and multivariate regression were performed with statistical significance P </=0.05. RESULTS: Fifty-five consecutive patients between 14 and 62 years of age were admitted in a 1-year period and underwent 64 diagnostic and therapeutic procedures. Fourteen (22%) postoperative infections and 18 (28%) complications other than infection, with an overall mortality of 11%, were documented. Total preoperative white blood cell count ([WBC] P <0.01), preoperative percent lymphocyte count (P <0.01), absolute postoperative CD4 lymphocyte count (P <0.01), and postoperative plasma viral load (P <0.0001) are associated with mortality. Multivariate regression indicated that postoperative percent CD4 lymphocyte count is an independent predictor of both postoperative infection and other complications (P <0.05, R = 0.848, power = 0.9911), while the decrement in percent CD4 lymphocyte count is an independent predictor of postoperative complications other than infection (P <0.05, R = 0.596, power = 0.7838). CONCLUSIONS: In accordance with the medical literature for clinical outcome in HIV-infected and AIDS patients, both immune cell counts and HIV-1 RNA counts were found to associate with postoperative mortality. However, the postoperative and decrement in percent CD4 lymphocyte proved to be the independent predictors of postoperative complications.

Acquired Immunodeficiency Syndrome↗
PubMed1999

CCAAT/enhancer-binding protein beta (C/EBPbeta) and C/EBPdelta contribute to growth hormone-regulated transcription of c-fos.

Using the c-fos enhancer as a model to analyze growth hormone (GH)-promoted gene expression, the roles of CCAAT/enhancer-binding proteins (C/EBPs) in GH-regulated transcription were investigated. In 3T3-F442A fibroblasts stably expressing the c-fos promoter mutated at the C/EBP binding site upstream of luciferase, c-fos promoter activity is stimulated by GH 6-7-fold; wild type c-fos promoter shows only a 2-fold induction by GH. This suggests that C/EBP restrains GH-stimulated expression of c-fos. Electrophoretic mobility shift assays with nuclear extracts from 3T3-F442A cells indicate that GH rapidly (2-5 min) increases binding of C/EBPbeta and C/EBPdelta, to the c-fos C/EBP binding site. Both liver activating protein (LAP) and liver inhibitory protein (LIP), forms of C/EBPbeta, are detected in 3T3-F442A cells by immunoblotting. GH increases the binding of LAP/LAP and LAP/LIP dimers. Overexpression of LIP interferes with GH-promoted reporter expression in CHO cells expressing GH receptors, consistent with the possibility that LIP restrains GH-stimulated c-fos expression. Overexpression of LAP elevates basal luciferase activity but does not influence promoter activation by GH, while overexpressed C/EBPdelta elevates basal promoter activity and enhances the stimulation by GH. GH stimulates the expression of mRNA for C/EBPbeta and -delta and increases levels of C/EBPdelta. Although C/EBPbeta is not detectably altered, GH induces a shift to more rapidly migrating forms of LIP and LAP upon immunoblotting. Treatment of extracts from GH-treated cells with alkaline phosphatase causes a shift of the slower migrating form to the rapidly migrating form, consistent with GH promoting dephosphorylation of LIP and LAP. These studies implicate C/EBPbeta and -delta in GH-regulated gene expression. They also indicate that GH stimulates the binding of C/EBPbeta and -delta to the c-fos promoter and promotes the dephosphorylation of LIP and LAP. These events may contribute to the ability of C/EBPbeta and -delta to regulate GH-stimulated expression of c-fos.

3T3 Cells↗
PubMed1999

Biochemical characterization of alpha-ketooxadiazole inhibitors of elastases.

A series of alpha-ketooxadiazole compounds was prepared and evaluated in vitro as potential inhibitors of human neutrophil elastase (HNE), proteinase-3 (PR-3), and porcine pancreatic elastase (PPE). Several compounds have been found to be very potent, fast, reversible, and selective inhibitors of HNE with Ki values below 100 pM. The highest kon value exceeded 10(7) M(-1) s(-1). Some alpha-ketooxadiazoles were also very effective against PR-3 and PPE with Ki values in the range of 5(-10) nM and 0.1(-2) nM, respectively. The two rings, 1,2,4- and 1,3,4-oxadiazole, are amenable to substitutions, extending the P' side of the inhibitor and allowing additional binding interactions at S' subsites of the enzyme. Nonpeptidic HNE inhibitors containing the oxadiazole heterocycle displayed promising oral bioavailability.

Cathepsin G↗
PubMed1999

Carboxyhemoglobin elevation in trauma victims.

BACKGROUND: Products of the hemeoxygenase enzyme include carboxyhemoglobin (COH) and bilirubin, which have protective effects in stressed states. Hemeoxygenase-1 enzyme up-regulates in states of oxidative stress. We hypothesized that COH is elevated in septic trauma patients compared with nonseptic patients. METHODS: A prospective study was carried out at a Level I trauma center involving all patients admitted to the trauma intensive care unit. During a 3.5-month period, 45 patients were enrolled, with 76 samples being drawn on admission and at later time points. The samples were classified as septic (Bone's criteria), stressed (based on expired gas analysis), or nonstressed nonseptic. Correlations with Acute Physiology and Chronic Health Evaluation III score, white blood cell count, temperature, partial pressure of oxygen, and percentage of inspired oxygen were evaluated. RESULTS: COH levels in samples drawn from patients presenting in shock (systolic blood pressure < or =90 mm Hg) were significantly higher than levels in samples from patients not in shock (systolic blood pressure >90 mm Hg) (3.27+/-1.09 vs. 2.75+/-0.64; p = 0.013). Samples from septic patients with infection were associated with significantly higher Injury Severity Scores (34.1+/-11.2 vs. 21.8+/-18.3; p< or =0.05) and a lower percentage of inspired oxygen (41.6+/-10.3 vs. 61.0+/-26.3; p< or =0.05). CONCLUSION: COH was significantly elevated in samples drawn during stress, sepsis, and shock states. There was overlap between sepsis and stress COH sample values, limiting the clinical usefulness of the assays in predicting sepsis. Further studies focusing on hemeoxygenase-1 expression and the role of its by-products in the outcomes of trauma patients are warranted.

APACHE↗
PubMed1999

Glycogen synthase kinase 3 is an insulin-regulated C/EBPalpha kinase.

CCAAT/enhancer binding protein alpha (C/EBPalpha) is a transcription factor involved in creating and maintaining the adipocyte phenotype. We have shown previously that insulin stimulates dephosphorylation of C/EBPalpha in 3T3-L1 adipocytes. Studies to identify the insulin-sensitive sites of phosphorylation reveal that a C/EBPalpha peptide (amino acids H215 to K250) is phosphorylated on T222, T226, and S230 in vivo. The context of these phosphoamino acids implicates glycogen synthase kinase 3 (GSK3), whose activity is known to be repressed in response to insulin, as a potential kinase for phosphorylation of T222 and T226. Accordingly, GSK3 phosphorylates the predicted region of C/EBPalpha on threonine in vitro, and GSK3 uses C/EBPalpha as a substrate in vivo. In addition, the effect of pharmacological agents on GSK3 activity correlates with regulation of C/EBPalpha phosphorylation. Treatment of 3T3-L1 adipocytes with the phosphatidylinositol 3-kinase inhibitor wortmannin results in phosphorylation of C/EBPalpha, whereas treatment with the GSK3 inhibitor lithium results in dephosphorylation of C/EBPalpha. Collectively, these data indicate that insulin stimulates dephosphorylation of C/EBPalpha on T222 and T226 through inactivation of GSK3. Since dephosphorylation of C/EBPalpha in response to lithium is blocked by okadaic acid, strong candidates for the T222 and T226 phosphatase are protein phosphatases 1 and 2a. Treatment of adipocytes with insulin alters the protease accessibility of widespread sites within the N terminus of C/EBPalpha, consistent with phosphorylation causing profound conformational changes. Finally, phosphorylation of C/EBPalpha and other substrates by GSK3 may be required for adipogenesis, since treatment of differentiating preadipocytes with lithium inhibits their conversion to adipocytes.

3T3 Cells↗
PubMed1999

An introductory therapeutic modality for restoring implants and natural teeth using conus crowns: a 5-year case report.

The advent of cylindric titanium implants and the prevalence of periodontal disease have necessitated a restoration that facilitates the performance of oral physiotherapy. The use of the conical crown as a metallic covering over natural teeth and implants--with a suprastructure that is retained through a specific degree of convergence without cement or screws--allows access for enhanced oral hygiene practices, while providing for esthetic and functional goals.

Crowns↗
PubMed1999

Central nervous system metabolic and physiologic effects of laparoscopy.

We set out to determine whether the increases in intracranial pressure (ICP) associated with CO2 insufflation had any metabolic effect on the central nervous system in a head injury when compared with gasless laparoscopy (GL). To test this hypothesis, we looked at both the ICP and jugular bulb venous saturation (JVS), with and without a coexisting cerebral mass lesion. Twenty-five kilogram male pigs had tracheostomy, epidural balloon, pulmonary arterial catheter, arterial line, and jugular bulb catheter placed. Intravenous Pentobarbital was used for anesthesia. Either CO2 laparoscopy (CL; n=7) or GL (n=7) were performed both with and without an epidural balloon inflated to a baseline ICP of 25. Data were analyzed using the Student's t test with a P value <0.05 being significant. Cerebral perfusion pressure and most hemodynamic values did not differ. Both central venous pressure and peak inspiratory pressure were significantly elevated whenever CO2 insufflation took place, reflecting an increased intrathoracic pressure. When comparing both study groups, the partial pressure of CO2 did not differ. CL increases ICP significantly above the gasless group in our head injury model. This is most likely secondary to increased intrathoracic pressure. The question still remains whether these changes are clinically significant. We could not demonstrate significant metabolic effects secondary to laparoscopy. In patients suffering head injury, GL rather than CL might be safer to avoid ICP elevation. Additional studies looking at central nervous system metabolic and objective histopathologic effects should be undertaken with larger numbers of study animals.

Animals↗
PubMed1998

A role for the p38 mitogen-activated protein kinase/Hsp 27 pathway in cholecystokinin-induced changes in the actin cytoskeleton in rat pancreatic acini.

Cholecystokinin (CCK) and other pancreatic secretagogues have recently been shown to activate signaling kinase cascades in pancreatic acinar cells, leading to the activation of extracellular signal-regulated kinases and Jun N-terminal kinases. We now show the presence of a third kinase cascade activating p38 mitogen-activated protein (MAP) kinase in isolated rat pancreatic acini. CCK and osmotic stress induced by sorbitol activated p38 MAP kinase within minutes; their effects were dose-dependent, with maximal activation of 2.8- and 4.4-fold, respectively. The effects of carbachol and bombesin on p38 MAP kinase activity were similar to those of CCK, whereas phorbol ester, epidermal growth factor, and vasoactive intestinal polypeptide stimulated p38 MAP kinase by 2-fold or less. Both CCK and sorbitol also increased the tyrosyl phosphorylation of p38 MAP kinase. Using the specific inhibitor of p38 MAP kinase, SB 203580, we found that p38 MAP kinase activity was required for MAP kinase-activated protein kinase-2 activation in pancreatic acini. SB 203580 reduced the level of basal phosphorylation and blocked the increased phosphorylation of Hsp 27 after stimulation with either CCK or sorbitol. CCK treatment induced an initial rapid decrease in total F-actin content of acini, followed by an increase after 40 min. Preincubation with SB 203580 significantly inhibited these changes in F-actin content. Staining of the actin cytoskeleton with rhodamine-conjugated phalloidin and analysis by confocal fluorescence microscopy showed disruption of the actin cytoskeleton after 10 and 40 min of CCK stimulation. Pretreatment with SB 203580 reduced these changes. These findings demonstrate that the activation of p38 MAP kinase is involved not only in response to stress, but also in physiological signaling by gastrointestinal hormones such as CCK, where activation of Gq-coupled receptors stimulates a cascade in which p38 MAP kinase activates MAP kinase-activated protein kinase-2, resulting in Hsp 27 phosphorylation. Activation of p38 MAP kinase, most likely through phosphorylation of Hsp 27, plays a role in the organization of the actin cytoskeleton in pancreatic acini.

Actins↗
PubMed1998

Regulation of CCAAT/enhancer binding protein alpha (C/EBP alpha) gene expression by thiazolidinediones in 3T3-L1 adipocytes.

Thiazolidinediones are a class of antidiabetic drugs that induce preadipocyte differentiation by binding and activating peroxisome proliferator-activated receptor gamma 2. Although thiazolidinediones are commonly thought of as insulin-sensitizing agents, these drugs have opposing and antagonistic effects to that of insulin on CCAAT/enhancer binding protein alpha (C/EBP alpha) gene expression in fully differentiated 3T3-L1 adipocytes. Thiazolidinediones induce expression of C/EBP alpha mRNA and protein, while insulin stimulates a rapid decline in C/EBP alpha mRNA and protein. When added in combination, thiazolidinediones block the suppression of C/EBP alpha mRNA by insulin; however, thiazolidinediones do not block the insulin-induced decline in GLUT4 mRNA, indicating that repression of C/EBP alpha mRNA is not required for insulin to suppress expression of a C/EBP alpha-responsive gene such as GLUT4. Instead, insulin may regulate GLUT4 mRNA by inactivating C/EBP alpha through dephosphorylation as well as by inducing the expression of the dominant-negative form of C/EBP beta (liver inhibitory protein), since both of these processes occur in the presence of thiazolidinediones.

3T3 Cells↗
PubMed1998

Therapeutic actions of cyclosporine and anti-tumor necrosis factor alpha in collagen-induced arthritis and the effect of combination therapy.

OBJECTIVE: To define the mechanisms of action of 2 novel drugs, cyclosporine and anti-tumor necrosis factor alpha (TNFalpha), in collagen-induced arthritis and to determine the effect of combination therapy. METHODS: Type II collagen-immunized DBA/1 mice with established arthritis were treated with cyclosporine alone, anti-TNFalpha alone, cyclosporine plus anti-TNFalpha, or saline. RESULTS: Cyclosporine was found to ameliorate arthritis, suppress interferon-gamma (IFNgamma) production by CD4+ T cells, and reduce TNFalpha expression in arthritic joints. However, cyclosporine did not directly inhibit TNFalpha production by macrophages, indicating that the decrease in TNFalpha expression observed in vivo was probably an indirect consequence of the reduction in type 1 T helper cell activity. Anti-TNFalpha also reduced IFNgamma production by T cells, indicating that TNFalpha is involved in the cellular immune response to collagen. Combined treatment with cyclosporine plus anti-TNFalpha had an additive therapeutic effect. CONCLUSION: Although cyclosporine and anti-TNFalpha target different points in the inflammatory pathway, there is an overlap in the consequences of their actions in vivo.

Animals↗