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J H Rand

Publications and source records attributed to J H Rand.

At least 37 records · Page 2Linked to original sources
PubMed1998

In vitro studies of the interactions between platelets and amniotic membranes: a potential treatment for preterm premature rupture of the membranes.

OBJECTIVE: Thus far there is no satisfactory treatment for preterm premature rupture of the amniotic membranes. To evaluate the use of platelets to seal the membranes, we investigated in vitro interactions between platelets and the membranes. STUDY DESIGN: Platelet aggregation in the presence of amnion, chorion, and amniotic fluid was quantified. Platelet adhesion to the fetal membranes was investigated by electron microscopy. In addition, a model system was designed to evaluate the capacity of platelets to seal a standardized puncture in the membranes. RESULTS: Platelets aggregated in response to amnion but not to chorion or amniotic fluid. Adhesion and activation occurred on connective tissues underlying amnion and chorion but not on the amniotic epithelium. Platelets sealed a puncture in fetal membranes, and the platelet plug was visualized by electron microscopy. CONCLUSIONS: Exposed connective tissue of amniotic membranes was demonstrated to trigger platelet adhesion, aggregation, and activation, and platelets were shown to seal a standardized puncture in fetal membranes. Our results indicate that platelets might be useful for treatment of ruptured membranes after needle puncture.

Amnion↗
PubMed1998

Antiphospholipid antibody syndrome: new insights on thrombogenic mechanisms.

The antiphospholipid antibody syndrome is a thrombophilic condition manifested by vascular thrombosis or recurrent pregnancy loss together with the presence of antibodies against anionic phospholipid protein complexes. These antibodies are detected by their reactivity to the anionic phospholipids (or protein phospholipid complexes) in solid-phase immunoassays or by their property of inhibiting phospholipid-dependent coagulation reactions (the "lupus anticoagulant" effect). The pathophysiologic mechanisms of this syndrome have remained obscure because of the apparent multiplicity of antigenic determinants recognized by the antibodies and also because of the many effects which have been described for them. This article reviews current concepts of the antiphospholipid disease process and evidence for the hypothesis that thrombosis in this syndrome is a result of the displacement of annexin-V, an anionic phospholipid-binding protein with potent anticoagulant activity, from phospholipid surfaces. The authors propose that under physiologic conditions, annexin-V plays a thromboregulatory role at the vascular-blood interface by shielding anionic phospholipids from complexation with coagulation proteins in circulating blood. Thrombosis in the antiphospholipid syndrome is due to disruption of the annexin shield by antiphospholipid (and cofactor) antibodies which results in the increased exposure of thrombogenic phospholipids. Accumulated data are consistent with the hypothesis that the disruption of annexin-V binding to anionic phospholipid surfaces plays an important thrombogenic role in the antiphospholipid syndrome.

Animals↗
PubMed1998

Fibrillin containing elastic microfibrils support platelet adhesion under dynamic shear conditions.

The vascular subendothelium contains macromolecular structures called microfibrils. Type VI collagen is one protein found in microfibrils that supports platelet adhesion and aggregation and we have previously evaluated the roles of platelet receptors and vWf involved in these processes under physiological shear conditions. Here we investigate the ability of fibrillin containing elastic microfibrils to support mural thrombus formation. Our results show that elastic microfibril surfaces support platelet adhesion under low shear conditions at a level similar to collagen VI tetramers. However, the degree of aggregation on the elastic microfibril surface is much higher. Both adhesion and aggregation were shown to be mediated by the GPIIb-IIIa platelet receptor. Elastic microfibrils do not support the formation of mural thrombi under high shear conditions. These results suggest roles for both collagen VI and fibrillin containing elastic microfibrils in modulating the platelet response to blood vessel injury.

Actin Cytoskeleton↗
PubMed1997

Pregnancy loss in the antiphospholipid-antibody syndrome--a possible thrombogenic mechanism.

BACKGROUND: The mechanisms of vascular thrombosis and pregnancy loss in the antiphospholipid-antibody syndrome are unknown. Levels of annexin V, a phospholipid-binding protein with potent anticoagulant activity, are markedly reduced on placental villi from women with this syndrome. Hypercoagulability in such women may therefore be due to the reduction of surface-bound annexin V by antiphospholipid antibodies. To test this idea, we studied how antiphospholipid antibodies affect levels of annexin V on cultured trophoblasts and human umbilical-vein endothelial cells and how they affect the procoagulant activity of these cells. METHODS: We isolated IgG fractions from three patients with the antiphospholipid-antibody syndrome and from normal controls. These antibodies were incubated with cultured BeWo cells (a placental-trophoblast cell line), primary cultured trophoblasts, and human umbilical-vein endothelial cells. Annexin V on the cell surfaces was measured by an enzyme-linked immunosorbent assay. The coagulation times of plasma overlaid on the cells were also determined. RESULTS: Trophoblasts and endothelial cells exposed to antiphospholipid-antibody IgG as compared with control IgG had reduced levels of annexin V (trophoblasts, 0.37 +/- 0.02 vs. 0.85 +/- 0.12 ng per well, P=0.02; endothelial cells, 1.6 +/- 0.04 vs. 2.1 +/- 0.05 ng per well, P=0.001). Also, trophoblasts and endothelial cells exposed to antiphospholipid-antibody IgG had faster mean (+/- SE) plasma coagulation times than cells exposed to control IgG (trophoblasts, 8.7 +/- 2.0 vs. 21.3 +/- 2.9 minutes, P=0.02; endothelial cells, 9.8 +/- 0.8 vs. 14.2 +/- 1.2 minutes, P=0.04). CONCLUSIONS: Antiphospholipid antibodies reduce the levels of annexin V and accelerate the coagulation of plasma on cultured trophoblasts and endothelial cells. The reduction of annexin V levels on vascular cells may be an important mechanism of thrombosis and pregnancy loss in the antiphospholipid-antibody syndrome.

Abortion, Spontaneous↗
PubMed1997

Anticardiolipin antibody-associated stroke after liver transplantation.

Stroke is uncommon after orthotopic liver transplantation. We offer the first report, to our knowledge, of two posttransplant patients with stroke associated with elevated anticardiolipin antibodies, and we discuss their management, including the use of immunosuppression and antithrombotic therapy. We suggest that anticoagulation is the treatment of choice for such patients.

Antibodies, Anticardiolipin↗
PubMed1997

Prothrombin activation fragment (F1.2) is increased in pregnant patients with antiphospholipid antibodies.

Recurrent fetal wastage has been attributed to thrombosis in the antiphospholipid antibody syndrome (APAS); however, this has not been proven. Assays of coagulation activation fragments which may provide evidence for a role for thrombosis, have not been previously reported in this setting. We therefore investigated whether F1.2 levels are altered in APAS pregnancies. F1.2 levels were performed on plasmas obtained from fifty-four APA patients with a history of persistent elevation of antiphospholipid antibodies and recurrent abortion who were studied during eighty-three consecutive visits. Results from these patients were compared to a control group of thirty-two healthy pregnant females. F1.2 levels were significantly higher in APAS patients than controls in the second trimester (6.5 nM +/- 4.3 nM vs. 1.2 nM +/- 0.9 nM, p < 0.0001), and in the third trimester of pregnancy (8.6 nM +/- 2.5 nM vs. 3.7 nM +/- 2.0 nM, p < 0.0001). The F1.2 levels in the APA group returned to baseline soon after delivery. No correlation was observed between F1.2 and APA values. This study shows that pregnant patients with a history of recurrent abortions and APA have significantly increased activation of prothrombin compared to healthy pregnant females. These data indicate that the potential value of activations peptide assays such as F1.2 in this setting should be tested in prospective clinical trials.

Adult↗
PubMed1997

Antiphospholipid immunoglobulin G antibodies reduce annexin-V levels on syncytiotrophoblast apical membranes and in culture media of placental villi.

OBJECTIVES: The mechanism by which antiphospholipid antibodies are associated with pregnancy loss and thromboembolism has not been established. We previously showed that annexin-V, a phospholipid-binding protein with potent anticoagulant activity, is present on the apical membranes of the syncytiotrophoblasts that line placental villi and that this protein is reduced, by immunohistochemistry, on placentas of patients with antiphospholipid antibodies. We therefore investigated whether annexin-V in apical membranes of placental villi is quantitatively reduced by antiphospholipid antibody immunoglobulin G. STUDY DESIGN: Placentas were obtained from an index patient with antiphospholipid syndrome with intrauterine growth restriction and from a patient with an uncomplicated pregnancy who were both delivered by cesarean section. Apical villous membranes were isolated and annexin-V levels were measured by enzyme-linked immunosorbent assay. We then studied the effects of antiphospholipid immunoglobulin G on placental villous apical annexin-V in vitro. Antiphospholipid immunoglobulin G was isolated from the sera of five different patients with antiphospholipid antibody syndrome along with five paired control immunoglobulin Gs. Short-term cultures were established from normal placental villi and were exposed to the antibodies, after which isolated apical membranes and culture media were immunoassayed for annexin-V levels. RESULTS: Measurements of apical membrane-associated annexin-V from the antiphospholipid placenta showed significantly less apical membrane-associated annexin-V than did the normal placenta (mean +/- SEM: 4.9 +/- 0.4 micrograms/gm villi for antiphospholipid placenta vs 10.2 +/- 0.6 micrograms/gm villi for control, p < 0.001, n = 4). Exposure of placental villous cultures to five different antiphospholipid immunoglobulin Gs for 24 hours resulted in significant reduction of the levels of apical membrane annexin-V (mean +/- SEM: 3.9 +/- 0.3 micrograms/gm villi) compared with paired controls (5.1 +/- 0.3 micrograms/gm villi, p = 0.02). Villi incubated with the different antiphospholipid immunoglobulin Gs had significantly less annexin-V in conditioned media (mean +/- SEM: 45.1 +/- 4.9 ng/gm villi) compared with the paired normal immunoglobulin G control levels (72.6 +/- 11.4 ng/gm villi, p = 0.03). CONCLUSIONS: Antiphospholipid immunoglobulin G reduces the levels of syncytiotrophoblast apical membrane-associated annexin-V in placental villi and the release of annexin-V into surrounding media. Reduction of this anticoagulant protein at the maternal-fetal interface may account for the pregnancy loss observed in patients with antiphospholipid syndrome. Short-term culture of placental villi may offer an in vitro model to further study the mechanism of this effect of antiphospholipid antibodies.

Adult↗
PubMed1997

The significance of subendothelial von Willebrand factor.

von Willebrand factor (vWf) serves to bridge between receptors on the platelet cytoplasmic membrane and the extracellular matrix. In addition to circulating in plasma, vWf is deposited into the extracellular matrix of the subendothelium where it is associated with type VI collagen microfibrils, but not with the elastin-associated microfibrils which are present in the deepest portion of the subendothelium at the zone of the internal elastic lamina. The reaction of platelets to type VI collagen in flow systems is qualitatively different from the shear rate dependent adhesion and aggregation response which is observed with fibrillar type I collagen, exhibiting a response only at low shear rates. The adhesion response to type VI collagen is dependent upon vWf, GP Ib and the GP IIb-IIIa complex. Platelets exposed to purified fibrillin-containing elastin-associated microfibrils adhere and aggregate at low shear rates; this response appears to involve GP IIb-IIIa but not GP Ib. The data are consistent with the hypothesis that type VI collagen is a physiologically relevant binding site for vWf in subendothelium.

Animals↗
PubMed1996

Morphological relationships of von Willebrand factor, type VI collagen, and fibrillin in human vascular subendothelium.

von Willebrand factor (vWF) plays an important role in the process of platelet adhesion after endothelial injury by serving as a bridge between constituents of the vascular subendothelium and platelet membrane receptors. We previously presented evidence that type VI collagen microfibrils serve as a binding site for vWF in human vascular subendothelium. However, others have proposed that vWF is not associated with type VI collagen but rather with the thicker elastin-associated microfibrils, which contain several proteins including fibrillin. We therefore investigated the relationships among vWF, type VI collagen, and fibrillin in human vascular subendothelium by immunoelectron microscopy using single- and double-labeling immunogold localization techniques. In addition, we observed the three-dimensional ultrastructure of vWF-microfibril complexes by stereo paired micrographs and stereo viewer. We found that vWF co-localizes only with the type VI collagen microfibrils in subendothelium but not with fibrillin microfibrils or striated collagen. The vWF is present in subendothelium in the form of electron-dense aggregates having diameters varying between 65 and 80 nm that are closely associated with, and enmesh, the type VI collagen microfibrils and have structural similarities to intracellular Weibel-Palade bodies. The occasional co-localization of type VI collagen and fibrillin adjacent to internal elastic lamina was observed. These results are consistent with the hypothesis that type VI collagen, but not fibrillin-containing microfibrils, serves as a physiologically relevant binding site for vWF in the vascular subendothelium, where the type VI collagen-vWF complex may play an important role modulating the hemostatic response to vascular injury.

Collagen↗
PubMed1995

Reduced thrombogenicity of type VI collagen as compared to type I collagen.

Type VI collagen has been recently identified as a major constituent of vascular subendothelium where it serves as a binding site for von Willebrand factor. The present study compares the functional characteristics of type VI collagen with those of type I collagen with respect to platelet aggregating and secretory activities. The differences between the two collagens in platelet aggregation and serotonin and beta-thromboglobulin release were found to be highly significant (p < 0.001, p < 0.0007, p < 0.005 respectively). Our results indicate that under in vitro conditions, type VI collagen stimulates a significantly lesser platelet activation and aggregation response than collagen I, suggesting that type VI collagen may play a role in vivo to limit the platelet thrombotic response following injury to the vascular subendothelium.

Collagen↗
PubMed1995

Platelet adhesion and aggregation on human type VI collagen surfaces under physiological flow conditions.

Type VI collagen is a subendothelial constituent that binds von Willebrand factor (vWF) and platelets. The interaction of platelets with type VI collagen and the roles of platelet glycoprotein (GP) receptors and vWF were studied under flow conditions using epi-fluorescent videomicroscopy coupled with digital image processing. We found that surface coverage was less than 6% on collagen VI at a relatively high-wall shear rate (1,000 s-1) and was approximately 60% at a low-wall shear rate (100 s-1). The molecular mechanisms involved in low-shear platelet binding were studied using monoclonal antibodies to platelet GPIb and GPIIb-IIIa, and polymeric aurin tricarboxylic acid. Anti-GPIIb-IIIa was the most effective in eliminating adhesion (surface coverage, 0.8%), followed by anti-GPIb (4.3%), and ATA (12.6%). Experiments with von Willebrand disease blood indicate that vWF is involved in platelet adhesion to collagen VI at 100 s-1. In the absence of vWF, there may be direct binding of platelet GPIIb-IIIa complexes to collagen VI. Adhesion and aggregation on collagen VI are different in shear rate dependence from collagen I. Our results suggest a possible role for collagen VI and vWF in platelet adhesion and aggregation in vascular regions with low shear rates.

Animals↗
PubMed1994

Reduction of annexin-V (placental anticoagulant protein-I) on placental villi of women with antiphospholipid antibodies and recurrent spontaneous abortion.

OBJECTIVE: The mechanism by which antiphospholipid antibodies are associated with pregnancy loss and thromboembolic conditions has yet to be elucidated. Annexin-V, an anticoagulant phospholipid-binding protein, is normally present in syncytiotrophoblasts lining the placental villi, where it may play a role in the maintenance of intervillous blood fluidity. We therefore investigated the distribution of annexin-V in placentas of patients with antiphospholipid antibodies in situ and then used short-term villous cultures to study the direct effect of antiphospholipid antibodies on the immunolocation of annexin-V. STUDY DESIGN: We performed a blinded study by means of computerized morphometric analysis of placental tissues that were stained for annexin-V with affinity-purified polyclonal antibody in an avidin-biotin peroxidase system. The distribution of villous surface annexin-V on cross sections of placentas of patients with antiphospholipid antibodies was compared with that of placentas from patients with uncomplicated pregnancies, elective abortions, and pregnancy losses not associated with antiphospholipid antibodies (n = 8 for each group). We quantitated villous surface annexin-V in cultured placental villi that were incubated with antiphospholipid antibodies immunoglobulin G compared with normal immunoglobulin G and measured annexin-V levels by enzyme-linked immunosorbent assay in conditioned media and in the villi. RESULTS: The mean villous surface annexin-V of the group with antiphospholipid antibodies was 26.2% +/- 17% (SD) versus 93.9% +/- 5.7% in the normal control group (p < 0.0001). Villi from patients undergoing elective abortions and with pregnancy losses that were not attributed to antiphospholipid antibodies also showed higher mean villous surface annexin-V levels (86.9% +/- 10.6% and 83.5% +/- 11.3%, respectively, p < 0.0001). Organ culture of normal placental villi with affinity-purified immunoglobulin G from patients with antiphospholipid antibodies showed a dose-dependent decrease of villous surface annexin-V over a concentration range of 1.5 micrograms/ml to 1.5 mg/ml. Annexin-V concentrations in conditioned media were significantly lower in the presence of antiphospholipid antibodies immunoglobulin G compared with normal immunoglobulin G (49.4 +/- 8.9 ng/gm wet weight vs 57.2 +/- 11.5 ng/gm, respectively, p < 0.05). In contrast, the mean level of annexin-V in placental villi incubated with antiphospholipid antibodies immunoglobulin G was greater than in villi incubated with normal immunoglobulin G, 1328 +/- 130 ng/gm wet weight versus 1183 +/- 165 ng/gm (p < 0.02). CONCLUSIONS: Patients with antiphospholipid antibodies and a history of previous pregnancy losses have a significant reduction in annexin-V immunostaining on placental villous surfaces, and antiphospholipid antibodies immunoglobulin G can directly decrease levels of villous surface annexin-V on cultured placental villi. Assays of annexin-V in the conditioned media and cell pellets of cultured placental villi suggest that the mechanism for antiphospholipid antibodies-mediated reduced annexin-V surface staining is an inhibition of annexin-V transport to the villous surface rather than displacement by antiphospholipid antibodies from the surface. This antiphospholipid antibodies-induced deficiency of placental surface annexin-V may contribute to the placental thrombosis observed in these patients.

Abortion, Habitual↗
PubMed1994

The expression of the placental anticoagulant protein, annexin V, by villous trophoblasts: immunolocalization and in vitro regulation.

We evaluated the histological and ultrastructural localization of the potent anticoagulant protein, annexin V, at the light and electron microscopic levels, using immunohistochemistry and an immunogold method. Annexin V was found to localize to the microvillar surface of the villous syncytiotrophoblasts. Isolated villous-derived trophoblasts were then utilized to evaluate the expression of annexin 1 protein mRNA in response to syncytialization in vitro, as well as to exposure to adenylate cyclase and protein kinase C agonists. Levels of immunoreactive annexin V released into the conditioned media and associated with cell protein were assessed by ELISA while levels of annexin V mRNA were evaluated by Northern analysis. No significant change in either media or cell-associated annexin V concentrations were detected over time in culture or in response to 1.5 mM 8-bromo-cyclic-adenosine-monophosphate (8-b-cAMP) or 0.15 nM phorbol ester myristic acid (PMA). These results indicate that annexin V is ideally positioned to inhibit intervillous thrombosis and maintain the fluidity of the intervillous circulation. Moreover, the absence of trophoblast annexin V regulation by intracellular second messenger regulators suggests that this crucial placental anticoagulant factor is constitutively produced.

Annexin A5↗
PubMed1994

The immunobiology and obstetrical consequences of antiphospholipid antibodies.

Two classes of antiphospholipid antibodies (APA) are associated with adverse pregnancy outcomes. Those APA identified by immunoassays using phospholipid-coated surfaces (e.g., anticardiolipin antibodies) seem to bind to the 57 kD anticoagulant protein, beta 2-glycoprotein-I, when complexed with anionic phospholipid bilayers. Such APA may or may not prolong phospholipid-dependent clotting assays. A second class of APA are identified by their interference with phospholipid-dependent clotting assays (i.e., lupus anticoagulants). The latter bind to phospholipids present in a unique hexagonal phase either alone or complexed with prothrombin or beta 2-glycoprotein-I. There is evidence that both classes of APA are directly responsible for adverse pregnancy outcomes including spontaneous abortions, stillbirths, fetal growth retardation, thrombosis, thrombocytopenia, and preeclampsia. Putative APA-mediated pathogenic mechanisms include intervillous thrombosis, intravillous infarctions and decidual vasculopathy. The thrombogenicity of APA may result from their interference with endothelial phospholipids required for antithrombin III and protein C and S anticoagulant activity and prostacyclin synthesis and/or increased endothelial expression of the procoagulants: tissue factor, von Willebrand factor, platelet-activating factor, and plasminogen activator inhibitor type-1. Other prothrombotic properties seem to include: increased platelet aggregation, and reduced beta 2-glycoprotein-1 and annexin V anticoagulant activity. Rigorous diagnostic criteria must be applied to the detection of both classes of APA because the prevention of adverse pregnancy outcomes requires potentially hazardous anticoagulant therapy.

Animals↗
PubMed1994

Abnormal coagulation profile in brain tumor patients during surgery.

Neurosurgical patients are at high risk for the development of thrombosis and thromboembolism. We compared the perioperative clotting factor and coagulation parameters of 20 patients undergoing elective craniotomy for brain tumors to those of 20 patients undergoing elective abdominal surgery. We also measured the levels of plasma arginine vasopressin to determine if changes in this hormone might be associated with changes in clotting factors, activated partial thromboplastin times, or bleeding times. The results demonstrated a significant reduction in partial thromboplastin times and bleeding times in the neurosurgery group, which began at the initiation of surgery and lasted to the end of the study (12 h postoperatively). Elevations in factor assays and plasma arginine vasopressin occurred in both groups during surgery, but there were no differences between the neurosurgical and abdominal surgical patients, except with Factor IX levels, which were elevated only in the neurosurgical patients. Serum osmolality and hemoglobin levels were significantly higher in the neurosurgical cohort. These results suggest that there are hemostatic differences between neurosurgical patients with brain tumors and abdominal surgery patients that cannot be explained solely by elevations in plasma arginine vasopressin or the clotting factors measured; these differences may be the consequence of perioperative variables such as dehydration and hyperosmolality.

Adult↗
PubMed1994

An association between refractory HELLP syndrome and antiphospholipid antibodies during pregnancy; a report of 2 cases.

The HELLP syndrome (hemolysis, elevated liver enzymes and low platelets) is a thrombotic microangiopathic vasculopathy that presents in pregnancy. HELLP syndrome usually resolves with delivery of the fetus without sequelae and is often managed successfully with conservative care. To our knowledge, there has been no prior report of an association between HELLP syndrome and elevated titers of antiphospholipid antibodies (aPL). We describe 2 patients who each presented with HELLP syndrome that was refractory despite delivery of the fetus, corticosteroids, and anticoagulation. Both patients had elevated levels of anticardiolipin antibodies. Examination of skin and placental pathology revealed diffuse deposition of fibrin with small vessel thrombi, without evidence of vasculitis. Coincident with plasmapheresis, HELLP resolved in both patients. We conclude that there may be an association between the presence of aPL and a protracted HELLP syndrome in pregnancy; this may be a new manifestation of the antiphospholipid syndrome. Plasmapheresis appears to benefit these patients. Further investigation into this association is warranted.

Adrenal Cortex Hormones↗