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Biomedical subjects

S C Watkins

Publications and source records attributed to S C Watkins.

At least 37 records · Page 2Linked to original sources

Impaired gut contractility following hemorrhagic shock is accompaied by IL-6 and G-CSF production and neutrophil infiltration.

Recovery from hemorrhagic shock (HS) is frequently accompanied by bowel stasis. The aim of this study was to examine whether or not HS initiates an inflammatory response that includes production of cytokines, specifically G-CSF and interleukin-6 (IL-6), and recruitment of leukocytes within the intestinal muscularis which contribute to impaired muscle contractility. Sprague-Dawley rats were subjected to HS (MAP 40 mm Hg for 156 min) followed by resuscitation, and then they were killed at 4 hr. Shock animals demonstrated accumulation of PMNs in the jejunal muscularis and decreased spontaneous and bethanechol-stimulated muscle contractility. Semiquantitative RT-PCR demonstrated elevated levels of IL-6 and G-CSF mRNA in shock animals in full-thickness jejunum and in mucosa and muscularis layers compared to sham controls. Immunostaining demonstrated increased IL-6 protein production within the muscularis externa and submucosa. In situ hybridization studies localized G-CSF mRNA production to the submucosa. Gel shift assays revealed increased NF-kappaB and Stat3 activity in full-thickness jejunum and jejunal layers of shock animals. Activation of Stat3 also was demonstrated in normal muscularis tissue exposed to IL-6 and G-CSF in vitro. IL-6 and G-CSF are produced in the muscularis and mucosa layers of the gut in HS where they may contribute to PMN recruitment and smooth muscle dysfunction.

Animals↗

Dermal-resident CD14+ cells differentiate into Langerhans cells.

Epidermal Langerhans cells (LCs) show extraordinary immunostimulatory capacity and play a key role in the initiation and regulation of immune responses. Studies of LC biology are currently the focus of efforts to engineer immune responses and to better understand the immunopathology of cutaneous diseases. Here we identified and characterized a population of LC precursors that were resident in human skin. These immediate precursors expressed CD14, langerin and functional CCR6. When cultured with transforming growth factor-beta1 alone, they had the potential to differentiate into epidermal LCs; when cultured in the presence of granulocyte macrophage-colony-stimulating factor and interleukin 4 they differentiated into functionally mature dendritic cells. Identification and characterization of these LC precursors provided insight into LC biology and the mechanism(s) through which LCs repopulate the epidermis.

Antigens↗

Direct transfection and activation of human cutaneous dendritic cells.

Gene therapy techniques can be important tools for the induction and control of immune responses. Antigen delivery is a critical challenge in vaccine design, and DNA-based immunization offers an attractive method to deliver encoded transgenic protein antigens. In the present study, we used a gene gun to transfect human skin organ cultures with a particular goal of expressing transgenic antigens in resident cutaneous dendritic cells. Our studies demonstrate that when delivered to human skin, gold particles are observed primarily in the epidermis, even when high helium delivery pressures are used. We demonstrate that Langerhans cells resident in the basal epidermis can be transfected, and that biolistic gene delivery is sufficient to stimulate the activation and migration of skin dendritic cells. RT-PCR analysis of dendritic cells, which have migrated from transfected skin, demonstrates the presence of transgenic mRNA, indicating direct transfection of cutaneous dendritic cells. Importantly, transfected epidermal Langerhans cells can efficiently present a peptide derived from the transgenic melanoma antigen MART-1 to a MART-1-specific CTL. Taken together, our results demonstrate direct transfection, activation, and antigen-specific stimulatory function of in situ transduced human Langerhans cells.

Biolistics↗

Prostanoid production via COX-2 as a causative mechanism of rodent postoperative ileus.

BACKGROUND & AIMS: This study demonstrates a significant role for cyclooxygenase (COX)-2 and prostanoid production as mechanisms for surgically induced postoperative ileus. METHODS: Rats, COX-2+/+, and COX-2-/- mice underwent simple intestinal manipulation. Reverse-transcription polymerase chain reaction and immunohistochemistry were used to detect and localize COX-2 expression. Prostaglandin levels were measured from serum, peritoneal lavage fluid, and muscularis culture media. Jejunal circular muscle contractions were measured in an organ bath, and gastrointestinal transit was measured in vivo. RESULTS: The data show that intestinal manipulation induces COX-2 messenger RNA and protein within resident muscularis macrophages, a discrete subpopulation of myenteric neurons and recruited monocytes. The manipulation-induced increase in COX-2 expression resulted in significantly elevated prostaglandin levels within the circulation and peritoneal cavity. The source of these prostanoids could be directly attributed to their release from the inflamed muscularis externa. As a consequence of the molecular up-regulation of COX-2, we observed a decrease in in vitro jejunal circular muscle contractility and gastrointestinal transit, both of which could be alleviated pharmacologically with selective COX-2 inhibition. These studies were corroborated with the use of COX-2-/- mice. CONCLUSIONS: Prostaglandins, through the induction of COX-2, are major participants in rodent postoperative ileus induced by intestinal manipulation.

Animals↗

The fate of the poly-L-lactic acid interference screw after anterior cruciate ligament reconstruction.

We report the persistence of a poly-L-lactic acid (PLLA) interference screw 2.5 years after anterior cruciate ligament (ACL) reconstruction with Achilles tendon allograft. The arthroscopy was performed because the patient sustained a reinjury of the ACL graft, making ACL revision surgery necessary. At the time of arthroscopy, both PLLA screws were macroscopically still intact but could not be removed in 1 piece. No inflammation could be observed either macroscopically or in the histologic analysis. The biopsy specimen from the femoral insertion of the graft showed parts of the PLLA material surrounded by scar tissue. This case shows that biodegradation of PLLA material in the knee joint causes no irritation and can take several years, even if the material is in contact with the synovial fluid.

Absorbable Implants↗

Sinusoidal ultrastructure evaluated during the revascularization of regenerating rat liver.

Sinusoidal endothelial cell (SEC) porosities were compared between the periportal (zone 1) and pericentral (zone 3) regions of the rat liver during regeneration following partial hepatectomy (PHx). SEC porosities and fenestration diameters were measured in control livers, as well as at 5 minutes, 24, 48, 72, 96, 120 hours, and 14 days following PHx. Bimodal maximums in both porosity and fenestration diameters were observed in both zones at 5 minutes and 5 days following PHx. SEC porosities increased significantly in both zones 1 and 3 within 5 minutes following PHx, but the increase was maintained only in zone 1 at 24 hours after resection. Following the initial rise, both zones displayed a gradual decrease to less than half their porosity values at 72 hr post-PHx. After 72 hours, porosities increased to over control levels and remained elevated until 14 days after PHx. The decrease in porosity at 72 hr post-PHx is accompanied by ultrastructural changes within the sinusoid at this time. Vascular corrosion casting and transmission electron microscopy (TEM) show sinusoid compression resulting from increased hepatic plate widths due to hepatocyte proliferation in the absence of SEC proliferation. Also at this time, we observed many SEC completely enveloped by stellate cells. The zonal variations observed for porosities throughout regeneration did not correlate with changes in laminin, collagen I and IV, or fibronectin deposition within the space of Disse. Taken together, the data reveal that SEC are dynamic regulators of porosity that respond rapidly and locally to environmental zonal stimuli during liver regeneration.

Animals↗

Spatiotemporal expression of angiogenesis growth factor receptors during the revascularization of regenerating rat liver.

Regenerating liver was evaluated for the spatiotemporal expression of angiogenic growth factor receptors on endothelial cell (EC) membranes during revascularization resulting from 70% partial hepatectomy (PHx). Fractions enriched in EC membranes were examined by Western blot for angiogenic growth factor receptor expression from 1 to 14 days after PHx. Increases in vascular endothelial growth factor (VEGF) receptors Flt-1 and Flk-1/KDR, angiopoietin receptors Tie-1, Tie-2, and platelet-derived growth factor receptor beta (PDGF-Rbeta), modest increases in epidermal growth factor receptor (EGF-R), and no increase in hepatocyte growth factor receptor (c-Met) or fibroblast growth factor receptors (FGF-R) were observed in isolated membranes during EC proliferation. All receptors were tyrosine phosphorylated, and therefore activated, during peak expression. Immunofluorescence staining of regenerating liver identified populations with increased receptor expression, indicating cells receptive to ligand signaling. EGF-R was upregulated evenly throughout the sinusoidal membrane, whereas c-Met was observed on hepatocyte canaliculae, bile duct epithelium, and large vessel EC. Tie-2 and PDGF-Rbeta were increased on sinusoidal and large vessel EC, whereas Tie-1 was expressed in EC surrounding avascular hepatic islands. Flk-1/KDR was increased on large vessels with slight increases on sinusoidal EC, whereas Flt-1 was increased in arterioles, sinusoidal EC as well as in hepatocytes. Although Flt-1 was phosphorylated on isolated hepatocytes, vascular endothelial growth factor(165) (VEGF(165)) did not induce a proliferative or motogenic response. Proliferation assays on isolated EC indicated responsiveness to VEGF(165), but synergism among several growth factors including PDGF-BB was also observed. The data identify novel autocrine and paracrine interactions and indicate that each growth factor acts on a specific set of EC at specific times during revascularization of regenerating liver.

Animals↗

Intestinal cytokine gene expression in infants with acute necrotizing enterocolitis: interleukin-11 mRNA expression inversely correlates with extent of disease.

BACKGROUND/PURPOSE: The authors have shown previously that surgical specimens from infants with acute necrotizing enterocolitis (NEC) show upregulation of inducible nitric oxide (NO) synthase (iNOS) and interferon-gamma mRNA. However, the contribution of other inflammatory cytokines such as interleukin-8 (IL-8), IL-11, and IL-12 has not been defined. Likewise, the role of GTP-cyclohydrolase, the rate-limiting enzyme in tetrahydrobiopterin synthesis, and thus NO production by iNOS is unclear. In this study, the authors sought to further define the pattern of cytokine expression seen in infants with acute NEC. METHODS: The authors measured intestinal cytokine mRNA expression by semiquantitative reverse transcriptase polymerase chain reaction in 21 infants with histologically confirmed NEC, 18 with other inflammatory conditions, and in 9 patients without intestinal inflammation. Guanosine triphosphate-cyclohydrolase (GTP-CH) activity was measured by specific enzyme assay. Univariate exact logistic regression analysis was performed to identify predictors of outcome. RESULTS: IL-8 and IL-11 mRNA were upregulated in patients with acute NEC compared with those with other inflammatory conditions or those without disease; these levels returned to baseline at the time of stoma closure. Increased IL-11 mRNA decreased the likelihood of pan-necrosis (odds ratio, 0.93; P =.002). Increased IL-12 levels (but not IL-8) seemed to protect against pan-necrosis (odds ratio, 0.70; P =.06). CONCLUSIONS: Local upregulation of IL-11 may represent an adaptive response designed to limit the extent of intestinal damage in NEC. Decreased IL-12 levels may contribute to the pathogenesis of NEC by allowing bacteria to escape host defenses.

Acute Disease↗

Adenovirus-mediated gene transfer of human inducible nitric oxide synthase in porcine vein grafts inhibits intimal hyperplasia.

OBJECTIVE: The aim of this study is to determine whether adenoviral inducible nitric oxide synthase (iNOS) gene transfer could inhibit intimal hyperplasia (IH) in porcine internal jugular veins interposed into the carotid artery circulation. METHODS: Porcine internal jugular veins were transduced passively with 1 x 10(11) particles of an adenoviral vector carrying either the human iNOS (AdiNOS) or beta-galactosidase (AdlacZ) cDNA for 30 minutes and then interposed into the carotid artery circulation. Segments of each vein graft were maintained in an ex vivo organ culture to measure nitrite accumulation, a marker of nitric oxide synthesis. The grafts were analyzed immunohistochemically for the presence of neutrophils, macrophages, and leukocytes by staining for myeloperoxidase, ED1, and CD45, respectively, at 3 (n = 4) and 7 (n = 4) days. Morphometric analyses and cellular proliferation (Ki67 staining) were assessed at 3 (n = 4), 7 (n = 4), and 21 days (n = 8). RESULTS: AdlacZ-treated vein grafts demonstrated high levels of beta-galactosidase expression at 3 days with a gradual decline thereafter. Nitrite production from AdiNOS-treated vein grafts was approximately fivefold greater than AdlacZ-treated grafts (P =.00001). AdiNOS or AdlacZ treatment was associated with minimal graft inflammation. Cellular proliferation rates were significantly reduced in AdiNOS-treated grafts as compared with controls at both 3 (41%, P =.000004) and 7 days (32%, P =.0001) after bypass. This early antiproliferative effect was most pronounced at the distal anastomosis (65%, P =.0005). The iNOS gene transfer reduced the intimal/medial area ratio in vein grafts at 7 (36%, P =.009) and 21 days (30%, P =.007) versus controls. This inhibition of IH was again more prominent in the distal segments of the grafts (P =.01). CONCLUSION: Adenovirus-mediated iNOS gene transfer to porcine internal jugular vein grafts effectively reduced cellular proliferation and IH. Although iNOS gene transfer reduced IH throughout the entire vein graft, the most pronounced effect was measured at the distal anastomosis. These results suggest potential for iNOS-based genetic modification of vein grafts to prolong graft patency.

Adenoviridae↗

Detection of single- and double-strand DNA breaks after traumatic brain injury in rats: comparison of in situ labeling techniques using DNA polymerase I, the Klenow fragment of DNA polymerase I, and terminal deoxynucleotidyl transferase.

DNA damage is a common sequela of traumatic brain injury (TBI). Available techniques for the in situ identification of DNA damage include DNA polymerase I-mediated biotin-dATP nick-translation (PANT), the Klenow fragment of DNA polymerase I-mediated biotin-dATP nick-end labeling (Klenow), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). While TUNEL has been widely utilized to detect primarily double-strand DNA breaks, the use of PANT to detect primarily single-strand DNA breaks and Klenow to detect both single- and double-strand DNA breaks has not been reported after TBI. Accordingly, coronal brain sections from naive rats and rats at 0, 0.5, 1, 2, 6, 24, and 72 h (n = 3-5/group) after controlled cortical impact with imposed secondary insult were processed using the PANT, Klenow, and TUNEL methods. Cells with DNA breaks were detected by PANT in the ipsilateral hemisphere as early as 0.5 h after injury and were maximal at 6 h (cortex = 66.3+/-15.8, dentate gyrus 58.6+/-12.8, CA1 = 15.8+/-5.9, CA3 = 12.8+/-4.2 cells/x 400 field, mean +/- SEM, all p < 0.05 versus naive). Cells with DNA breaks were detected by Klenow as early as 30 min and were maximal at 24 h (cortex = 56.3+/-14.3, dentate gyrus 78.0+/-16.7, CA1 = 25.8+/-4.7, CA3 = 29.3+/-15.1 cells/x 400 field, all p < 0.05 versus naive). Cells with DNA breaks were not detected by TUNEL until 2 h and were maximal at 24 h (cortex = 47.7+/-21.4, dentate gyrus 63.0+/-11.9, CA1 = 5.6+/-5.4, CA3 = 6.9+/-3.7 cells/x 400 field, cortex and dentate gyrus p < 0.05 versus naive). Dual-label immunofluorescence revealed that PANT-positive cells were predominately neurons. These data demonstrate that TBI results in extensive DNA damage, which includes both single- and double-strand breaks in injured cortex and hippocampus. The presence of multiple types of DNA breaks implicate several pathways in the evolution of DNA damage after TBI.

Animals↗

Hsp70 molecular chaperone facilitates endoplasmic reticulum-associated protein degradation of cystic fibrosis transmembrane conductance regulator in yeast.

Membrane and secretory proteins fold in the endoplasmic reticulum (ER), and misfolded proteins may be retained and targeted for ER-associated protein degradation (ERAD). To elucidate the mechanism by which an integral membrane protein in the ER is degraded, we studied the fate of the cystic fibrosis transmembrane conductance regulator (CFTR) in the yeast Saccharomyces cerevisiae. Our data indicate that CFTR resides in the ER and is stabilized in strains defective for proteasome activity or deleted for the ubiquitin-conjugating enzymes Ubc6p and Ubc7p, thus demonstrating that CFTR is a bona fide ERAD substrate in yeast. We also found that heat shock protein 70 (Hsp70), although not required for the degradation of soluble lumenal ERAD substrates, is required to facilitate CFTR turnover. Conversely, calnexin and binding protein (BiP), which are required for the proteolysis of ER lumenal proteins in both yeast and mammals, are dispensable for the degradation of CFTR, suggesting unique mechanisms for the disposal of at least some soluble and integral membrane ERAD substrates in yeast.

Calcium-Binding Proteins↗

bcl-2 Antisense treatment prevents induction of tolerance to focal ischemia in the rat brain.

In the rat, 60 minutes of transient ischemia to the middle cerebral artery results in infarction of the caudate putamen. Ischemic preconditioning with 20 minutes of transient focal ischemia produced tolerance (attenuated infarction volume) to 60 minutes of subsequent focal ischemia administered three days, five days, or seven days later. Western blots from tolerant caudate putamen demonstrated increased bcl-2 expression, maximum at 3 days and persisting through 7 days. Immunocytochemical examination found that bcl-2 was expressed in cells with both neuronal and nonneuronal morphology in striatum after preconditioning ischemia. bcl-2 antisense oligodeoxynucleotides (ODNs), bcl-2 sense ODNs, or artificial cerebrospinal fluid (CSF, vehicle) was infused into the lateral ventricle for the 72 hours between the 20-minute ischemic preconditioning and the 60-minute period of ischemia. Antisense ODN treatment reduced expression of bcl-2 in the striatum and blocked the induction of tolerance by preconditioning ischemia. Sense and CSF treatments had no effect on either bcl-2 expression or tolerance. In this model of induced tolerance to focal ischemia, bcl-2 appears to be a major determinant.

Animals↗

Dendritic cells pulsed with apoptotic squamous cell carcinoma have anti-tumor effects when combined with interleukin-2.

OBJECTIVES: Dendritic cells, the most potent of the antigen-presenting cells, have been widely studied as a promising tool for antitumor immunotherapies. However, little has been determined about the efficacy of dendritic cell-based therapy for the treatment of squamous cell carcinoma (SCC) because there are no known SCC-specific antigens. Recent reports indicate that dendritic cells can acquire antigens in the form of apoptotic cells and induce cytotoxic T-lymphocyte responses. The aim of this study was to test the feasibility of adoptive dendritic cell immunotherapy against SCC by using apoptotic tumor cells as a source of tumor antigens. STUDY DESIGN: A poorly immunogenic SCC line KLN 205 was used to make subcutaneous tumors on the flank of DBA2/J syngeneic mice. Bone marrow-derived dendritic cells were pulsed with ultraviolet B-irradiated (apoptotic) KLN 205 cells in vitro and transferred to the opposite flank subcutaneously. Some of the animals received simultaneous intraperitoneal injections of low-dose interleukin-2. RESULTS: When combined with interleukin-2, adoptive transfers of dendritic cells that were pulsed with apoptotic SCC significantly suppressed the tumor growth (P <.001) without notable side effects. Splenic T cells of treated mice produced greater amounts of interferon-gamma when restimulated with the relevant tumor (P <.001) as compared with control groups, indicative of an effective T-cell-mediated systemic immune response. CONCLUSION: Adoptive transfer of dendritic cells pulsed with apoptotic tumor cells as a source of tumor antigens, can elicit effective antitumor responses in the poorly immunogenic SCC model when combined with interleukin-2.

Animals↗

The roles of iNOS in liver ischemia-reperfusion injury.

To determine the contribution of the inducible nitric oxide synthase (iNOS) to hepatic injury following warm ischemia-reperfusion, we developed a model of partial hepatic ischemia-reperfusion in mice and studied the injury response in iNOS knockout (KO) mice. Compared with wild types, iNOS KO animals exhibited lower plasma transaminase levels after 1 and 6 h of reperfusion following 1 h of ischemia. At the 3-h time point, enzyme levels were not different between the two groups. iNOS mRNA was not detectable in the ischemic hepatic lobes of wild-type mice until 3 h of reperfusion; however, perfusion studies identified a significant delay in reperfusion of the ischemic lobe in the iNOS KO mice at the 1-h time point with similar perfusion rates at 3 and 6 h compared with wild type. By way of comparison, mice deficient in the endothelial NOS (eNOS) were also assessed for the degree of hepatic damage 3 h post-reperfusion. Plasma transaminase levels were significantly increased in eNOS KO animals compared with wild-type controls. These data suggest that systemic as well as local sources of iNOS regulate reperfusion, and local iNOS contributes to hepatic injury, while eNOS is protective in warm hepatic ischemia-reperfusion.

Alanine Transaminase↗

Husband-wife survey responses in Malawi.

Previous efforts by demographers to describe and explain spousal differences in reporting about family planning behavior have focused on individual attributes that are assumed to be related to the practice of contraception. This study extends that research by documenting spousal disagreement on a range of issues--household items, livestock, children, and spousal communication about fertility, family planning, and AIDS. Using data from a 1998 study of 585 monogamous couples in rural Malawi, the analysis identifies a systematic gender component to reporting: For many of the survey questions considered, when spouses disagree, husbands are more likely to say "yes" and wives "no." The findings are interpreted in terms of gendered strategies in the interview process.

Acquired Immunodeficiency Syndrome↗

Disobedient distributors: street-level bureaucrats and would-be patrons in community-based family planning programs in rural Kenya.

The implementation of social welfare programs, including family planning programs, is strongly conditioned by the needs, desires, and agendas of those who carry them out, known as "street-level bureaucrats." In this study, the strategies of CBD agents in western Kenya are examined in order to understand how they use their job as a means to achieve their own personal goals. The concept of clientelism, borrowed from the field of political science, can help to explain what the CBD agents are trying to achieve for themselves in their communities, at the same time as they promote the use of contraceptive pills and injections. CBD agents are concerned with building up their own stocks of prestige and respect from their community members, while avoiding blame for any possible negative outcomes of family planning.

Community Health Services↗

Scavenging nitric oxide reduces hepatocellular injury after endotoxin challenge.

Sustained upregulation of inducible nitric oxide (NO) synthase in the liver after endotoxin [lipopolysaccharide (LPS)] challenge may result in hepatocellular injury. We hypothesized that administration of a NO scavenger, NOX, may attenuate LPS-induced hepatocellular injury. Sprague-Dawley rats received NOX or saline via subcutaneous osmotic pumps, followed 18 h later by LPS challenge. Hepatocellular injury was assessed using biochemical assays, light, and transmission electron microscopy (TEM). Interleukin (IL)-6 mRNA was measured by RT-PCR. Tumor necrosis factor (TNF)-alpha protein expression was determined by immunohistochemistry. NOX significantly reduced serum levels of ornithine carbamoyltransferase and aspartate aminotransferase. TNF-alpha and IL-6 expression were increased in the livers of saline-treated but not NOX-treated rats. Although there was no difference between groups by light microscopy, TEM revealed obliteration of the space of Disse in saline-treated but not in NOX-treated animals. Electron paramagnetic resonance showed the characteristic mononitrosyl complex in NOX-treated rats. We conclude that NOX reduces hepatocellular injury after endotoxemia. NOX may be useful in the management of hepatic dysfunction secondary to sepsis or other diseases associated with excessive NO production.

Animals↗

Effects of soluble TNF receptor treatment on lipopolysaccharide-induced myocardial cytokine expression.

Tumor necrosis factor (TNF)-alpha plays a key role in the pathogenesis of septic shock syndrome, and myocardial TNF-alpha expression may contribute to this pathophysiology. We examined the myocardial expression of TNF-alpha-related cytokines and chemokines in mice exposed to lipopolysaccharide (LPS) and tested the effects of anti-TNF therapy on myocardial cytokine expression. Cytokine mRNA levels were measured by RNase protection assay, and protein levels in the plasma and myocardium were assessed by enzyme-linked immunosorbent assays. LPS (4 microg/g body wt ip) induced marked cytokine expression, including TNF-alpha, interleukin (IL)-1beta, IL-6, and monocyte chemotactic protein (MCP)-1, in both the plasma and myocardium. Pretreatment with adenovirus-mediated TNF receptor fusion protein (AdTNFR1; 10(9) plaque-forming units iv) decreased plasma cytokine levels. In contrast, whereas myocardial IL-1beta expression was also suppressed, expression of IL-6 and MCP-1 was not inhibited by AdTNFR1. In summary, anti-TNF treatment differentially altered the cytokine expression in the plasma and myocardium during endotoxemia. Inability to block myocardial expression of IL-6 and MCP-1 suggests a possible mechanism for the failure of anti-TNF therapies in the treatment of endotoxin shock.

Adenoviridae↗