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Biomedical subjects

Karl G Sylvester

Publications and source records attributed to Karl G Sylvester.

9 recordsLinked to original sources
PubMed2006

Laparotomy versus peritoneal drainage for necrotizing enterocolitis and perforation.

BACKGROUND: Perforated necrotizing enterocolitis is a major cause of morbidity and mortality in premature infants, and the optimal treatment is uncertain. We designed this multicenter randomized trial to compare outcomes of primary peritoneal drainage with laparotomy and bowel resection in preterm infants with perforated necrotizing enterocolitis. METHODS: We randomly assigned 117 preterm infants (delivered before 34 weeks of gestation) with birth weights less than 1500 g and perforated necrotizing enterocolitis at 15 pediatric centers to undergo primary peritoneal drainage or laparotomy with bowel resection. Postoperative care was standardized. The primary outcome was survival at 90 days postoperatively. Secondary outcomes included dependence on parenteral nutrition 90 days postoperatively and length of hospital stay. RESULTS: At 90 days postoperatively, 19 of 55 infants assigned to primary peritoneal drainage had died (34.5 percent), as compared with 22 of 62 infants assigned to laparotomy (35.5 percent, P=0.92). The percentages of infants who depended on total parenteral nutrition were 17 of 36 (47.2 percent) in the peritoneal-drainage group and 16 of 40 (40.0 percent) in the laparotomy group (P=0.53). The mean (+/-SD) length of hospitalization for the 76 infants who were alive 90 days after operation was similar in the primary peritoneal-drainage and laparotomy groups (126+/-58 days and 116+/-56 days, respectively; P=0.43). Subgroup analyses stratified according to the presence or absence of radiographic evidence of extensive necrotizing enterocolitis (pneumatosis intestinalis), gestational age of less than 25 weeks, and serum pH less than 7.30 at presentation showed no significant advantage of either treatment in any group. CONCLUSIONS: The type of operation performed for perforated necrotizing enterocolitis does not influence survival or other clinically important early outcomes in preterm infants. (ClinicalTrials.gov number, NCT00252681.).

Birth Weight↗
PubMed2006

Absence of the p53 tumor suppressor gene promotes osteogenesis in mesenchymal stem cells.

OBJECTIVE: Osteosarcoma arises predominantly in the metaphyseal growth plate of children during the growth spurt years. These tumors develop during physiological growth from an expanding cell population, suggesting that the transformed cell is a bone-forming progenitor. An absence of the p53 oncogene has been implicated in the origin and progression of osteosarcoma, and because mesenchymal stem cells (MSCs) are the physiological osteogenic progenitor cell population, we hypothesized that a p53-/- mutation would enhance bone differentiation of MSC in a mouse model of in vitro osteogenesis. METHODS: Clonal MSC populations were derived from p53-/- mice. P53-/- and wild-type cells were placed in osteogenic culture and assessed via Alizarin Red quantification and alkaline phosphatase staining. The osteogenic marker genes Cbfa1, osteopontin, and osteocalcin were assessed by quantitative real time polymerase chain reaction during differentiation. RESULTS: Bone nodule formation and alkaline phosphatase staining was accelerated and enhanced in the p53-/- cells. The early and intermediate osteogenic markers, Cbfa1 and osteopontin, were upregulated in p53-/- MSCs compared with wild-type cells during osteogenesis. The terminal osteogenic marker gene osteocalcin was paradoxically lower in p53-/- MSCs indicating impaired terminal differentiation. CONCLUSION: The p53-/- mutation enhances and accelerates early osteogenesis in MSCs, but prevents terminal differentiation toward a mature osteocyte phenotype. These findings may have important implications for the regulation of the MSC compartment during the derivation of osteosarcoma in children.

Animals↗
PubMed2006

Stem cells: tissue regeneration and cancer.

Regenerative medicine is the promised paradigm of replacement and repair of damaged or senescent tissues. As the building blocks for organ development and tissue repair, stem cells have unique and wide-ranging capabilities, thus delineating their potential application to regenerative medicine. The recognition that consistent patterns of molecular mechanisms drive organ development and postnatal tissue regeneration has significant implications for a variety of pediatric diseases beyond replacement biology. The observation that organ-specific stem cells derive all of the differentiated cells within a given tissue has led to the acceptance of a stem cell hierarchy model for tissue development, maintenance, and repair. Extending the tissue stem cell hierarchical model to tissue carcinogenesis may revolutionize the manner in which we conceptualize cancer therapeutics. In this review, the clinical promise of these technologies and the emerging concept of "cancer stem cells" are examined. A basic understanding of stem cell biology is paramount to stay informed of this emerging technology and the accompanying research in this area with the potential for clinical application.

Animals↗
PubMed2004

Donor-derived, liver-specific protein expression after bone marrow transplantation.

BACKGROUND: Bone marrow transplantation (BMT) may represent a novel mechanism to deliver a functional gene to a deficient liver. Bone marrow-derived hepatocytes are rare and without a defined contribution to liver function. Consequently, the clinical significance of BMT to treat liver disease is unclear. We sought to quantify bone marrow-derived hepatocyte protein expression after BMT and determine whether the process is inducible with liver injury. METHODS: Mice transgenic for human alpha-1 antitrypsin (hAAT) under a hepatocyte-specific promoter were used as bone marrow donors. Adenoviral transduction of modified urokinase plasminogen activator (Ad-muPA) was used to induce liver injury. Eight weeks after lethal irradiation and BMT, recipients were stratified into two groups: BMT alone (n = 5) and BMT + Ad-muPA (n= 10). Both groups of animals were bled before (t = 0) and at 2, 4, 8, and 16 weeks after Ad-muPA administration, and the serum samples were assessed for hAAT by enzyme-linked immunosorbent assay. RESULTS: Transgenic donor mice expressed 5 to 10 mg/mL of hAAT. Recipients of BMT alone expressed less than 80 ng/mL of hAAT over all time periods. Animals receiving BMT + Ad-muPA showed sustained and stable hAAT expression of approximately 200 ng/mL. Differences were statistically significant at each time point. CONCLUSION: Serum protein levels from liver-specific transgene expression are detectable and persist after BMT. Expression is low, but inducible with liver injury. We are currently developing strategies to augment donor-derived, liver-specific protein expression after BMT.

Adenoviridae↗
PubMed2004

Stem cells: review and update.

Regenerative medicine and emerging biotechnologies stand to revolutionize the practice of medicine. Advancements in stem cell biology, including embryonic and postnatal somatic stem cells, have made the prospect of tissue regeneration a potential clinical reality. Short of reproductive cloning, these same technologies, properly used, could allow for the creation of replacement tissue for the deficient host. To provide a concise review for surgeons on the current science and biology of stem cells, we surveyed the scientific literature, MEDLINE, and relevant political headlines that illuminate the stem cell discussion; the issues are summarized in this review. Building on this conceptual framework, the related issues of clinical promise and the political debate enveloping this emerging technology are examined. A basic understanding of stem cell biology is paramount to stay informed of this emerging technology and the national debate.

Animals↗
PubMed2004

Congenital tuberculosis presenting as progressive liver dysfunction.

We report a case of congenital tuberculosis with an unusual presentation as progressive liver dysfunction, in the absence of respiratory symptoms. Several uncommon features were present, including petechiae, cutaneous lesions, ascites and positive peritoneal fluid culture.

Antitubercular Agents↗
PubMed2003

Tissue engineering and regenerative medicine.

Regenerative medicine is evolving toward a powerful new paradigm of functional restoration. With the ethical use of gene therapy or through the manipulation of autologous tissues, improved tissue replacements may soon be available. The promise of engineered whole organs, although fraught with technical hurdles, remains on the horizon. As these advances occur, physicians and surgeons of the twenty-first century will possess ever more powerful tools to restore form and function.

Genetic Therapy↗
PubMedDate not supplied

Repair and regeneration: opportunities for carcinogenesis from tissue stem cells.

This review will discuss the mechanisms of repair and regeneration in various tissue types and how dysregulation of these mechanisms may lead to cancer. Normal tissue homeostasis involves a careful balance between cell loss and cell renewal. Stem and progenitor cells perform these biologic processes as the functional units of regeneration during both tissue homeostasis and repair. The concept of tissue stem cells capable of giving rise to all differentiated cells within a given tissue led to the concept of a cellular hierarchy in tissues and in tumors. Thus, only a few cells may be necessary and sufficient for tissue repair or tumor regeneration. This is known as the hierarchical model of tumorigenesis. This report will compare this model with the stochastic model of tumorigenesis. Under normal circumstances, the processes of tissue regeneration or homeostasis are tightly regulated by several morphogen pathways to prevent excessive or inappropriate cell growth. This review presents the recent evidence that dysregulation of these processes may provide opportunities for carcinogenesis for the long-lived, highly proliferative tissue stem cell population. New findings of cancer initiating tissue stem cells identified in several solid and circulating cancers including breast, brain and hematopoietic tumors will also be reviewed. Finally, this report reviews the cellular biology of cancer and its relevance to the development of more effective cancer treatment protocols.

Animals↗