PubMed Health⌕ Search

Biomedical subjects

S C Robson

Publications and source records attributed to S C Robson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Transforming growth factor-beta expression in human placenta and placental bed in third trimester normal pregnancy, preeclampsia, and fetal growth restriction.

Normal human pregnancy depends on physiological transformation of spiral arteries by invasive trophoblasts. Preeclampsia (PE) and fetal growth restriction (FGR) are associated with impaired trophoblast invasion and spiral artery transformation. Recent studies have suggested that transforming growth factor (TGF)-beta3 is overexpressed in the placenta of PE patients and that this may be responsible for failed trophoblast invasion. There are, however, no studies on TGF-betas in the placenta in FGR or in the placental bed in PE or FGR. In this study we have used immunohistochemistry, Western blot analysis, and enzyme-linked immunosorbent assay to examine the expression of TGF-beta1, TGF-beta2, and TGF-beta3 in placenta and placental bed of pregnancies complicated by PE and FGR and matched control pregnancies. The results show that TGF-beta1, -beta2, and -beta3 are not expressed in villous trophoblasts but are present within the placenta. TGF-beta1, -beta2, and, to a much lesser extent, TGF-beta3 were present within the placental bed but only TGF-beta2 was present in extravillous trophoblast. No changes in expression of either isoform were found in placenta or placental bed in PE or FGR compared with normal pregnancy. These data are not consistent with overexpression of TGF-beta3 being responsible for failed trophoblast invasion in PE. Our findings suggest that the TGF-betas do not have a pathophysiological role in either PE or FGR.

Adult↗
PubMed2001

Human trophoblast invasion and spiral artery transformation: the role of PECAM-1 in normal pregnancy, preeclampsia, and fetal growth restriction.

During early human pregnancy extravillous cytotrophoblasts invade the uterus and spiral arteries transforming them into large vessels of low resistance. Failure of trophoblast invasion and spiral artery transformation occurs in preeclampsia and fetal growth restriction (FGR); these processes are not well understood. Recent studies have suggested that cytotrophoblasts that invade spiral arteries mimic the endothelial cells they replace and express PECAM-1. It was also reported that in preeclampsia, cytotrophoblasts fail to express PECAM-1 and that failure to express endothelial cell adhesion molecules may account for failed trophoblast invasion. Despite the possible importance of adhesion molecules in trophoblast invasion, no study has systematically investigated the expression of PECAM-1 in the placental bed throughout the period of invasion, particularly in the myometrial segments where the key failure occurs. There are no studies on PECAM-1 expression in the placental bed in FGR. We have examined the expression of PECAM-1 in placental bed biopsies and placentas from 8 to 19 weeks of gestation and in the placenta and placental bed in the third trimester in cases of preeclampsia, FGR, and control pregnancies. PECAM-1 was expressed on endothelium of vessels in the placenta and placental bed but not by villous or extravillous trophoblasts in normal or pathological samples. These findings do not support a role for PECAM-1 in normal invasion or in the pathophysiology of preeclampsia or FGR.

Adult↗
PubMed2001

Porcine hematopoietic cell xenotransplantation in nonhuman primates is complicated by thrombotic microangiopathy.

Thrombotic microangiopathy (TM) is a serious complication of bone marrow transplantation (BMT) that resembles thrombotic thrombocytopenic purpura (TTP). In attempting to achieve hematopoietic cell chimerism in the pig-to-baboon model, we have observed TM following infusion of high doses (>10(10) cells/kg) of porcine peripheral blood mobilized progenitor cells (PBPC) into baboons. We performed investigations to analyze the pathobiology of this TM and to test therapeutic interventions to ameliorate it. PBPC were obtained by leukapheresis of cytokine-stimulated swine. The initial observations were made in two baboons that underwent a non-myeloablative regimen (NMR) prior to PBPC transplantation (TX) (group 1). We then studied three experimental groups. Group 2 (n = 2) received NMR without PBPC TX. Group 3 (n = 2) received PBPC TX alone. Group 4 (n = 6) received NMR + PBPC TX combined with prostacyclin, low-dose heparin, methylprednisolone, and cyclosporine was replaced by anti-CD40L mAb in five cases. Baboons in groups 1 and 3 developed severe thrombocytopenia (<10,000/mm3), intravascular hemolysis with schistocytosis (>10/high powered field (hpf)), increase in plasma lactate dehydrogenase (LDH) (2500-9000 U/l), transient neurologic changes, renal insufficiency, and purpura. Autopsy on two baboons confirmed extensive platelet thrombi in the microcirculation, and, similar to clinical BMT-associated TM/TTP, no unusually large vWF multimers or changes in vWF protease activity were observed in the plasma of baboons with TM. In group 2, self-limited thrombocytopenia occurred for 10-15 days following NMR. Group 4 baboons developed thrombocytopenia (<20,000/mm3) rarely requiring platelet transfusion, minimal schistocytosis (<3/hpf), minor increase in LDH (<1000 U/l), with no clinical sequelae. We conclude that high-dose porcine PBPC infusion into baboons induces a microangiopathic state with vWF biochemical parameters resembling clinical BMT-associated TM/TTP and that administration of antithrombotic and anti-inflammatory agents can ameliorate this complication.

Animals↗
PubMed2001

The C-terminal cysteine-rich region dictates specific catalytic properties in chimeras of the ectonucleotidases NTPDase1 and NTPDase2.

Ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) comprise a novel family of ectonucleotidases that are important in the hydrolysis of extracellular nucleotides. The related NTPDase1 (ecto-apyrase) and NTPDase2 (ecto-ATPase) share a common membrane topography with a transmembrane domain at both the N- and C-terminus, an extensive extracellular loop with five 'apyrase conserved regions' (ACR1 to ACR5), and a cysteine-rich C-terminal region. Whereas NTPDase1 expressed in CHO cells hydrolyzes ATP and ADP equivalently, NTPDase2 has a high preference for the hydrolysis of ATP over ADP. In addition recombinant NTPDase1 hydrolyzes ATP to AMP with the formation of only minor amounts of free ADP. In contrast, ADP appears as the major free product when ATP is hydrolyzed by NTPDase2. In order to determine molecular domains responsible for these differences in catalytic properties, chimeric cDNAs were constructed in which N-terminal sequences of increasing length of NTPDase1 were substituted by the corresponding sequences of NTPDase2 and vice versa. The turnover points were contained within ACR1 to ACR5. Chimeric cDNAs were expressed in CHO cells and surface expression was verified by immunocytochemistry. ATP and ADP hydrolysis rates and ADP and AMP product formation were determined using HPLC. Amino-acid residues between ACR3 and ACR5 and in particular the cysteine-rich region between ACR4 and ACR5 conferred a phenotype to the chimeric enzymes that corresponded to the respective wild-type enzyme. Protein structure rather than the conserved ACRs may be of major relevance for determining differences in the catalytic properties between the related wild-type enzymes.

Adenosine Diphosphate↗
PubMed2001

Investigation of the epidemiology and prenatal diagnosis of holoprosencephaly in the North of England.

OBJECTIVE: This study was undertaken to provide epidemiologic data on the prevalence of holoprosencephaly and to assess the sensitivity of routine ultrasonographic screening in a low-risk population. STUDY DESIGN: A population-based register of congenital abnormalities was used to identify reported cases of holoprosencephaly between 1985 and 1998. Sources included fetal losses, termination for fetal anomaly, stillbirths, and live births. Prenatal diagnoses and pregnancy outcomes were determined. RESULTS: Sixty-eight cases of holoprosencephaly were found among 531,686 births. The total prevalence (including pregnancy terminations) was 1.2 cases/10,000 registered births, and the birth prevalence (affected live births and stillbirths at >24 weeks' gestation) was 0.49 cases/10,000 births. Prenatal diagnosis was achieved in 71% of cases, rising to 86% during the second half of the study period; the mean gestational age at diagnosis was 19.8 weeks' gestation. Chromosomal abnormalities (75% of which were trisomy 13) were present in 38% of cases in which a karyotype was established. All those with aneuploidy (80% diagnosed prenatally) had other nonfacial anomalies; additional anomalies were also common in the euploid group (61% diagnosed prenatally), with 90% having facial abnormalities and 70% having other abnormalities. CONCLUSION: The prevalence of holoprosencephaly in second-trimester pregnancies was about 1 in 8000. Prenatal detection reached 86% with a routine anomaly scanning program. The etiology could usually be determined, which has important implications for recurrence risks.

Aneuploidy↗
PubMed2001

Nitric oxide signaling mechanisms in the forearm vasculature of pregnant women.

During pregnancy, forearm blood flow and constrictor responses to nitric oxide synthase inhibition are enhanced. Responses to brachial artery infusion of N(G)-monomethyl-L -arginine in pregnant women who have normal resting forearm blood flow and in pregnant women who have norepinephrine-induced reduced forearm blood flow were no different. Mechanisms independent of acute flow effects may account for the enhanced vascular nitric oxide activity during pregnancy.

Blood Flow Velocity↗
PubMed2001

Targeting platelet aggregation: CD39 gene transfer augments nucleoside triphosphate diphosphohydrolase activity in injured rabbit arteries.

BACKGROUND: CD39, the major endothelial nucleoside triphosphate diphosphohydrolase (NTPDase), plays an important role in local thromboregulation. We hypothesized that balloon injury (BI) leads to an acute reduction in arterial NTPDase activity that could be restored by a targeted gene delivery strategy. METHODS: Recombinant adenoviral vectors containing human CD39 (Ad-CD39) or beta-galactosidase (Ad-LacZ) were used. Endothelial (ECs) and smooth muscle cells (SMCs) were infected in vitro and NTPDase activity measured. New Zealand white rabbits (N = 28) underwent bilateral iliofemoral artery balloon injury, followed by incubation with Ad-CD39, Ad-LacZ, or vehicle. Explanted vessels were analyzed for NTPDase activity and localization of CD39 expression by immunohistochemistry. Deposition of fluorescent-labeled platelets was studied 3 days after injury and vector treatment. RESULTS: In vitro, Ad-CD39 infection resulted in a greater than 40-fold increase in adenosine diphosphatase activity in ECs and a 3-fold increase in SMCs. In vivo, CD39 transgene expression localized to the luminal aspect of Ad-CD39--treated vessels. BI resulted in an acute reduction in vessel wall NTPDase activity (P <.05). Ad-CD39 augmented NTPDase activity when compared with vehicle or Ad-LacZ (P <.05). Platelet deposition on the injured arterial surface was modest and not different between Ad-CD39-- and Ad-LacZ--treated vessels. CONCLUSIONS: BI decreases native NTPDase activity, which can be augmented by adenovirus-mediated gene transfer of CD39. Further studies are required to determine whether targeted delivery of CD39 could convey thromboprotective properties to an injured vessel.

Acid Anhydride Hydrolases↗
PubMed2001

Heme oxygenase expression in human placenta and placental bed: reduced expression of placenta endothelial HO-2 in preeclampsia and fetal growth restriction.

In this study we tested the hypothesis that expression of heme oxygenases HO-1 and HO-2, which are responsible for the production of carbon monoxide, are reduced in the placenta and placental bed of pregnancies complicated by preeclampsia (PE) and fetal growth restriction (FGR) compared with control third-trimester pregnancies. Placental protein expression was determined by Western blotting (n=10 in each group) and immunohistochemistry (controls n=18, PE n=19, FGR n=10). Extravillous trophoblast expression was determined by immunohistochemistry of placental bed biopsy samples (controls n=17, PE n=19, FGR n=10). Western blot analysis of placental homogenates showed no overall differences in HO-2 among groups. However, immunohistochemical analysis showed a reduction in HO-2 expression in endothelial cells in both abnormal groups (PE P<0.01; FGR P<0.0005 vs. control group) but no differences in villous trophoblast staining. HO-1 was undetectable by Western blotting in control and abnormal pregnancies and immunoreactivity was very low, suggesting that there is little HO-1 in the placenta. Within the placental bed, HO-2 but not HO-1 was detected on all populations of extravillous trophoblast, but expression of HO-2 or HO-1 did not change in PE or FGR. The reduced expression of HO-2 on endothelial cells in PE and FGR may be responsible for reduced placental blood flow in these conditions. The data do not show changes in HO in the placental bed in PE or FGR.

Adult↗
PubMed2001

Renal function, sodium and water homeostasis in patients with idiopathic extrahepatic portal vein thrombosis compared with normal healthy controls.

OBJECTIVES: To determine whether portal hypertension in the absence of liver disease contributes to changes in renal function and renal sodium and water handling. METHODS: Nine patients with extrahepatic portal vein thrombosis (PVT) with normal liver function and histology were compared with 9 matched healthy control subjects. All underwent standard measurements of glomerular filtration rate and effective renal blood flow using inulin and paraaminohippuric acid (PAH) clearances, respectively. Sodium excretion and renin and aldosterone levels were studied before, during and after an intravenous saline infusion. RESULTS: At baseline there were no differences in inulin clearance, PAH clearance, fractional excretion of sodium and free water excretion. During and after the saline infusion both groups showed a significant increase in sodium excretion with a reduction in water excretion, while the PAH and inulin clearances remained unchanged. Although aldosterone and renin levels both fell after the infusion, aldosterone levels were significantly lower in the PVT group. There were no other significant differences between the PVT and control groups. CONCLUSION: Renal function and sodium and water handling were comparable in healthy controls and patients with PVT. It is unlikely that portal hypertension alone plays a significant role in the impaired ability to excrete sodium and water in patients with liver cirrhosis.

Adult↗
PubMed2001

Molecular incompatibilities in hemostasis between swine and men--impact on xenografting.

The rejection of xenografts is associated with vascular-based inflammation, thrombocytopenia and the consumption of coagulation factors that may evolve into disseminated intravascular coagulation. Natural regulators of coagulation in porcine xenografts have abnormal physiological interaction with human effectors. We have demonstrated the enhanced potential of porcine von Willebrand factor to associate with human platelet GPlb to be dependent upon the isolated AI domain of von Willebrand factor. The inability of porcine tissue factor pathway inhibitor (TFPI) to adequately neutralize human factor Xa (FXa), the aberrant activation of both human prothrombin and FXa by porcine EC and the failure of the porcine natural anticoagulant, thrombomodulin to bind human thrombin and hence activate human protein C may all be pathogenetic in the DIC following xenograft rejection. In this brief review, molecular incompatibilities of contributors in the physiologically fine tuned system of hemostasis are summarized and brought in context with the disordered thromboregulation, that seems to be invariably associated with delayed xenograft rejection. Possible therapeutic interventions are discussed.

Animals↗
PubMed2000

Coagulation and thrombotic disorders associated with pig organ and hematopoietic cell transplantation in nonhuman primates.

BACKGROUND: Efforts to achieve tolerance to transplanted pig organs in nonhuman primates by the induction of a state of mixed hematopoietic chimerism have been associated with disorders of coagulation and thrombosis. Activation of recipient vascular endothelium and platelets by porcine hematopoietic cells and/or activation of donor organ vascular endothelium and/or molecular differences between the species may play roles. Irradiation or drug therapy could possibly potentiate endothelial cell activation and/or injury. METHODS: We have investigated parameters of coagulation and platelet activation in nonhuman primates after (1) a regimen aimed at inducing mixed hematopoietic chimerism and tolerance (TIR that included total body irradiation, T cell depletion, and splenectomy; (2) pig bone marrow or pig peripheral blood mobilized progenitor cell transplantation (PCTx); and/or (3) pig organ transplantation (POTx). Five experimental groups were studied. Baboons were the recipient subjects in all groups except Group 1. Gp 1 Cynomolgus monkeys (n=6) underwent TIR + allotransplantation of hematopoietic cells and a kidney or heart or TIR + concordant xenotransplantation (using baboons as donors) of cells and a kidney; Gp 2 Baboons (n=4) underwent TIR with or without (+/-) autologous hematopoietic cell infusion; Gp 3 (n=12) PCTx+/-TIR; Gp 4 (n=5) POTx+/-TIR; Gp 5 (n=4) TIR + PCTx + POTx. Platelet counts, with plasma prothrombin time, partial thromboplastin time, fibrinogen levels, fibrin split products and/or D-dimer were measured. RESULTS: In the absence of a discordant (porcine) cellular or organ transplant (Groups 1 and 2), TIR resulted in transient thrombocytopenia only, in keeping with bone marrow depression from irradiation. PCTx alone (Group 3) was associated with the rapid development of a thrombotic thrombocytopenic (TTP)-like microangiopathic state, that persisted longer when PCTx was combined with TIR. POTx (+/-TIR) (Group 4) was associated with a gradual fall (over several days) in platelet counts and fibrinogen with disseminated intravascular coagulation (DIC); after graft excision, the DIC generally resolved. When TIR, PCTx and POTx were combined (Group 5), an initial TTP-like state was superseded by a consumptive picture of DIC within the first week, necessitating graft removal. CONCLUSIONS: Both PCTx and POTx lead to profound alterations in hemostasis and coagulation parameters that must be overcome if discordant xenotransplantation of hematopoietic cells and organs is to be fully successful. Disordered thromboregulation could exacerbate vascular damage and potentiate activation of coagulation pathways after exposure to xenogeneic cells or a vascularized xenograft.

Animals↗
PubMed2000

Recombinant adenoviral mediated CD39 gene transfer prolongs cardiac xenograft survival.

BACKGROUND: Extracellular ATP and ADP may be important mediators of vascular inflammation and thrombosis. Nucleoside triphosphate diphosphohydrolase (NTPDase or CD39) is a vascular ectoenzyme that hydrolyses ATP and ADP; however, this activity is lost during reperfusion injury. We show that the supplementation of NTPDase activity within xenograft vasculature using CD39 recombinant adenoviruses (AdCD39) has protective effects in vivo. METHODS: Recombinant adenoviruses containing human CD39 or beta-galactosidase (Adbeta-gal) encoding genes were constructed. Hartley guinea pig coronary arteries were perfused ex vivo with University of Wisconsin solution containing 10(9) plaque-forming units of the recombinant adenovirus. Infected grafts were then implanted in the abdomen of complement depleted Lewis rats. RESULTS: NTPDase activities decreased in all grafts within the first 24 hr and subsequently recovered only in those hearts infected with AdCD39. Immunohistological examination of AdCD39-infected grafts confirmed successful CD39 gene transfer into the endocardium and macrovasculature. Expression of CD39 modestly prolonged graft survival (90.2+/-5.4 hr, mean+/-SD, n=5) when compared with Adbeta-gal-infected grafts (67.4+/-5.4 hr, P<0.005) and perfusion controls (66.4+/-5.2 hr; P<0.005). CONCLUSIONS: Recombinant adenoviral infection can induce expression of CD39 within cardiac xenografts and provide survival benefits in vivo. Our data show that ex vivo infection by recombinant adenovirus vectors can result in vascular expression of a potential therapeutic agent.

Adenosine Triphosphatases↗
PubMed2000

Long-term survival of hamster hearts in presensitized rats.

We transplanted hamster hearts into rats that had been sensitized to hamster cardiac grafts 5 days earlier as a model for discordant xenotransplantation. Sensitized rats had high serum levels of elicited anti-donor IgM and IgG that caused hyperacute rejection. Transient complement inhibition with cobra venom factor (CVF) plus daily and continuing cyclosporin A (CyA) prevented hyperacute rejection. However, grafts underwent delayed xenograft rejection (DXR). DXR involved IgG and associated Ab-dependent cell-mediated rejection, because depletion of IgG or Ab-dependent cell-mediated rejection-associated effector cells prolonged graft survival and the serum-mediated Ab-dependent cell-mediated cytotoxicity in vitro. Blood exchange in combination with CVF/CyA treatment dramatically decreased the level of preexisting Abs, but DXR still occurred in association with the return of Abs. Splenectomy and cyclophosphamide acted synergistically to delay Ab return, and when combined with blood exchange/CVF/CyA facilitated long-term survival of grafts. These grafts survived in the presence of anti-donor IgM, IgG, and complement that precipitated rejection of naive hearts, indicating that accommodation (survival in the presence of anti-graft Abs and complement) had occurred. We attribute the long-term survival to the removal of preexisting anti-donor Abs and therapy that attenuated the rate of Ab return. Under such conditions, the surviving hearts showed expression in endothelial cells and smooth muscle cells of protective genes and an intragraft Th2 immune response. Th2 responses and protective genes are associated with resistance to IgM- and IgG-mediated, complement-dependent and -independent forms of rejection.

Animals↗
PubMed2000

CD39 modulates IL-1 release from activated endothelial cells.

The activation of endothelial cells (EC) and monocyte-macrophages (M&phi;) by lipopolysaccharide (LPS) is considered an important element of the vascular injury observed in endotoxemia. Interleukin-1 (IL-1) beta release from M&phi; in response to LPS, appears to be mediated by the autocrine/paracrine release of ATP via P2X7 receptor activation. In EC, similar nucleotide-mediated signaling pathways may be influenced by high levels of expression of CD39, the vascular nucleoside triphosphate diphosphohydrolase (NTPDase; ENTPD I). To determine whether CD39 modulates ATP-mediated release of IL-1 from EC, we stimulated human EC with LPS and measured levels of ATP secretion and IL-1 release. LPS triggered ATP secretion from EC that was soon followed by IL-1alpha release. Overexpression of CD39 following infection with recombinant CD39 adenoviral vectors (AdCD39) abrogated the initial phase of ATP secretion and inhibited IL-1alpha release; comparable results were obtained with soluble NTPDase. These data demonstrate that CD39/NTPDase modulates IL-1alpha release from LPS stimulated human EC.

Adenosine Triphosphatases↗
PubMed2000

The short stature homeobox gene SHOX is involved in skeletal abnormalities in Turner syndrome.

Turner syndrome is characterized by short stature and is frequently associated with a variable spectrum of somatic features including ovarian failure, heart and renal abnormalities, micrognathia, cubitus valgus, high-arched palate, short metacarpals and Madelung deformity. Madelung deformity is also a key feature of Leri-Weill syndrome. Defects of the pseudoautosomal homeobox gene SHOX were previously shown to lead to short stature and Leri-Weill syndrome, and haploinsufficiency of SHOX was implicated to cause the short stature phenotype in Turner syndrome. Despite exhaustive searches, no direct murine orthologue of SHOX is evident. SHOX is, however, closely related to the SHOX2 homeobox gene on 3q, which has a murine counterpart, Og12x. We analysed SHOX and SHOX2 expression during human embryonic development, and referenced the expression patterns against those of Og12x. The SHOX expression pattern in the limb and first and second pharyngeal arches not only explains SHOX -related short stature phenotypes, but also for the first time provides evidence for the involvement of this gene in the development of additional Turner stigmata. This is strongly supported by the presence of Turner-characteristic dysmorphic skeletal features in patients with SHOX nonsense mutations.

Adult↗