Biomedical subjects

Bohuslav Dvorak

Publications and source records attributed to Bohuslav Dvorak.

22 records · Page 2Linked to original sources

PubMed2002

Epidermal growth factor reduces the development of necrotizing enterocolitis in a neonatal rat model.

Necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of prematurely born infants. Maternal milk plays an important protective role against NEC development and is the major source of epidermal growth factor (EGF) for neonates. The aim of this study was to examine the effect of orally administered EGF on the incidence of NEC in a neonatal rat model. Newborn rats were artificially fed either with growth factor-free rat milk substitute (RMS) or RMS supplemented with 500 ng/ml of EGF (RMS+EGF). Experimental NEC was induced by exposure to asphyxia and cold stress. Development of NEC was evaluated by gross and histological scoring of damage in the ileum. Ileal EGF receptor (EGF-R), EGF, and transforming growth factor-alpha mRNA expression was assessed by RT competitive-PCR, and the EGF-R was localized by immunohistochemistry. EGF supplementation of formula reduced the incidence and severity of NEC in rats (13/16 RMS vs. 4/13 RMS+EGF). Ileal EGF-R mRNA expression was markedly increased in the RMS group compared with RMS+EGF. Enhanced EGF-R expression in the RMS group was localized predominantly in the epithelial cells of injured ileum. These data suggest a new potential therapeutic approach for the prevention and treatment of NEC.

Animals↗

PubMed2002

Iron-deficient erythropoiesis in neonatal rats.

Anemia in premature infants is extremely common. Precise quantitation of iron status and determination of iron incorporation into erythrocytes are important in monitoring therapy for anemia in premature infants, especially when treating with recombinant human erythropoietin (rhEPO). However, the traditional indices of the iron status have limited usefulness in this population. The goal of the current work is to develop an experimental animal model system that addresses the clinical issue relating to quantitation of iron delivery to erythrocytes. We first determined normal hematological values for nontreated, dam-suckled Sprague-Dawley rats by measuring markers of erythropoiesis and iron status during the first 12 postnatal days (PND). The experimental group of rats were administered parenteral rhEpo (430 IU.kg(-1). day(-1)) for 8 days (from PND 4 until PND 12) in the absence (rhEpo(-Fe)) or presence (rhEpo(+Fe)) of oral iron supplementation (6 mg.kg(-1).day(-1)). Rat pups receiving oral iron only (control(+Fe)) and pups that were sham fed with the orogastric tube (control(-Fe)) were included as controls. Hematological parameters were measured in blood and bone marrow. In a pattern similar to that seen in premature infants during the first 2 months of life, the levels of these hematopoietic markers were dynamic and changed during the first 12 PND. After challenging experimental animals with subcutaneous rhEpo, evidence of iron-deficient erythropoiesis was seen in the rhEpo(-Fe) group. Red blood cell levels and absolute reticulocyte counts were higher in both groups receiving rhEpo as compared with the controls. However, the rhEpo(-Fe) group experienced a lower hemoglobin level, a lower mean red cell volume, a greater red cell distribution width, and a higher zinc protoporphyrin/heme (ratio than the rhEpo(+Fe) group. The neonatal rat is an excellent model of iron-deficient erythropoiesis and will be useful in designing future mechanistic studies examining the interplay between iron and erythropoiesis in the anemic, iron-challenged premature neonate.

Aging↗

PubMed2002

Erythropoietin stimulates vasculogenesis in neonatal rat mesenteric microvascular endothelial cells.

Human breast milk is a rich source of growth factors, including erythropoietin (Epo), the endogenous hormonal stimulant of erythropoiesis. Recombinant human Epo (rhEpo) has been shown to stimulate 1) angiogenesis, the process of new blood vessel growth from preexisting vessels; 2) vasculogenesis, tubule formation from single-cell suspensions; and 3) endothelial cell proliferation in immortalized endothelial cells and vessel explants. We hypothesized that Epo would induce mitogenesis and stimulate vasculogenesis in primary cultures of microvascular endothelial cells (MVECs) from neonatal rat mesentery. Isolation, purification, characterization, and culture of MVECs were performed. Cell proliferative effects of rhEpo were studied by 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay in cultured MVECs. Vasculogenic effects of rhEpo were examined on cultured MVECs plated on either hormone-rich Matrigel substratum or the extracellular matrix protein, type I collagen. Our findings show that MVECs are isolated and purified, and that rhEpo stimulates MVEC proliferation, with maximal proliferation seen with a concentration of 50 IU/mL rhEpo. Tubule formation assays reveal that an rhEpo concentration of 50 IU/mL produces maximal tubule formation after 12 h on both Matrigel and the simple substratum, type I collagen. Our study is the first to examine the effects of rhEpo on the endothelium of the neonatal gastrointestinal tract. These data suggest that Epo may have a trophic effect on the vasculature of the gastrointestinal tract early in development. Furthermore, as Epo has been measured in breast milk, and its receptor has been shown to exist on the mucosa and gastrointestinal vasculature, Epo may be an endogenous stimulant of vessel growth during neonatal gastrointestinal development.

Animals↗

PubMed2002

Up-regulation of IL-18 and IL-12 in the ileum of neonatal rats with necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease of premature infants. Because the proinflammatory cytokines IL-18, IL-12, and interferon (IFN)-gamma have been implicated in other diseases of the small intestine, we hypothesized that these cytokines would play an important role in NEC pathogenesis. NEC was induced in newborn rats via enteral feeding with rat milk substitute and asphyxia and cold stress (RMS). Dam-fed, asphyxia- and cold-stressed littermates were used as controls (DF). After 96 h, the distal ileum was removed from all animals and processed to determine expression and localization of IL-18, IL-12, and IFN-gamma using real-time reverse transcriptase PCR and immunohistology. IL-18 and IL-12 mRNA from the RMS group were increased (p < or = 0.05) compared with DF controls, and there was a correlation between increasing IL-18 and IL-12 mRNA levels and progression of tissue damage (r = 0.629 and 0.588, respectively; p < or = 0.05). Immunohistology revealed IL-18 in the cytoplasm of villi and crypt enterocytes and IL-12-positive monocytes/macrophages were increased with disease progression (r = 0.503, p < or = 0.05). No differences in the number of IFN-gamma-positive cells were observed between groups. These data demonstrate up-regulation of IL-18 and IL-12 in experimental NEC and a correlation between production of these proinflammatory cytokines and progression of tissue damage.

Animals↗