Biomedical subjects
E D Israels
Publications and source records attributed to E D Israels.
Apoptosis.
Mechanisms in Hematology is a book with an accompanying interactive CD-ROM designed to assemble basic concepts that underlie clinical understanding and progress. It is presented as a concise text with a series of diagrams that distill diffuse information into a compact form. The interactive CD, in particular, brings many of the processes "to life" as details of the more complex pathways are conveyed in clear visual images. The text begins with the basic molecular biology that underlies hematological and oncological physiology/pathology-cell signaling, adhesion molecules, and apoptosis. This is followed by sections, among others, on hematopoiesis, iron, B12, and folate metabolism, neutrophil function, immunoproteins, chemotherapy, and coagulation. With the permission of the authors and publisher, Stem Cells has reproduced the section on apoptosis, which we think our readers will enjoy.
Apoptosis.
Mechanisms in Hematology is a book with an accompanying interactive CD-ROM designed to assemble basic concepts that underlie clinical understanding and progress. It is presented as a concise text with a series of diagrams that distill diffuse information into a compact form. The interactive CD, in particular, brings many of the processes "to life" as details of the more complex pathways are conveyed in clear visual images. The text begins with the basic molecular biology that underlies hematological and oncological physiology/pathology--cell signaling, adhesion molecules, and apoptosis. This is followed by sections, among others, on hematopoiesis, iron, B12, and folate metabolism, neutrophil function, immunoproteins, chemotherapy, and coagulation. With the permission of the authors and publisher. The Oncologist has reproduced the section on apoptosis, which we think our readers will enjoy.
A novel role for vitamin K1 in a tyrosine phosphorylation cascade during chick embryogenesis.
The development of the embryo is dependent upon a highly coordinated repertoire of cell division, differentiation, and migration. Protein-tyrosine phosphorylation plays a pivotal role in the regulation of these processes. Vitamin K-dependent gamma-carboxylated proteins have been identified as ligands for a unique family (Tyro 3 and 7) of receptor tyrosine kinases (RTKs) with transforming ability. The involvement of vitamin K metabolism and function in two well characterized birth defects, warfarin embryopathy and vitamin K epoxide reductase deficiency, suggests that developmental signals from K-dependent pathways may be required for normal embryogenesis. Using a chick embryogenesis model, we now demonstrate the existence of a vitamin K1-dependent protein-tyrosine phosphorylation cascade involving c-Eyk, a member of the Tyro 12 family, and key intracellular proteins, including focal adhesion kinase (pp125FAK), paxillin, and pp60src. This cascade is sensitive to alteration in levels or metabolism of vitamin K1. These findings provide a major clue as to why, in the mammalian (and human) fetus, the K-dependent proteins are maintained in an undercarboxylated state, even to the point of placing the newborn at hemorrhagic risk. The precise regulation of vitamin K1-dependent regulatory pathways would appear to be critical for orderly embryogenesis.
The riddle of vitamin K1 deficit in the newborn.
Vitamin K in the fetus and newborn is maintained at levels less than that necessary to achieve full gamma-carboxylation of the K-dependent proteins, including those required for hemostasis. As the infant matures and even into adulthood, there is no significant storage pool for this vitamin, and a K1-deficient state can be produced by placing an adult on a K-deficient diet for 7 to 10 days. Questions arise as to why the level of vitamin K is so rigidly controlled and why the placental gradient in humans and other mammals maintains the fetus in a K-"deficient" state. The evidence is reviewed that suggests that K-dependent proteins are ligands for receptor tyrosine kinases, which, in the rapidly proliferating cell milieu of the fetus, control growth regulation. Increased stimuli may result in growth dysregulation whereas conversely, the further depletion of vitamin K-dependent proteins, as in warfarin toxicity, depletes the required stimuli for normal embryogenesis. These findings argue for the need for tightly controlled levels of vitamin K consistent with normal embryogenesis.
Observations on vitamin K deficiency in the fetus and newborn: has nature made a mistake?
The microsomal mixed function oxidase system metabolizes xenobiotics (Phase I) to products that, if not activated and conjugated for excretion (Phase II), are capable of forming conjugates with cellular macromolecules, including DNA, resulting in toxic, mutagenic, or carcinogenic events. Benzo(a)pyrene (BP), a polycyclic aromatic hydrocarbon, is a model carcinogen for this system. Vitamin K1 (phylloquinone) is a regulator of BP metabolism. These studies demonstrate that K1 is capable of increasing Phase I metabolism and decreasing glutathione transferase activity (Phase II) in chick embryo liver; that deprivation of K1 reduces BP/DNA adducts in mouse liver and reduces tumor formation in mice given intraperitoneal BP; and that K1 supplementation increases BP induced tumor formation in mice. However, epidemiologic studies indicate that children of mothers who smoke during pregnancy may not be at increased risk of cancer. It is known that the placentas from these pregnancies exhibit markedly increased levels of arylhydrocarbon hydroxylase induced by the polycyclic aromatic hydrocarbons in tobacco smoke, but there is no corresponding increase in this enzyme activity in the fetus in such pregnancies. We suggest that the low vitamin K level is a secondary protective mechanism for xenobiotics, such as BP, that may escape the primary placental screen. The recently described role of vitamin K-dependent Gla protein as ligands for receptor tyrosine kinases, also establishes K as a link in cell growth and transformation. It is proposed that the small total body pool of K1 in the adult, which is sufficient only to meet continuing needs, and the even smaller pool in the fetus are protective. This protective effect of low K1 levels is particularly important in the presence of the high mitotic rates and rapid cell turnover in the avian embryo and mammalian fetus.
Development of antibodies to bovine and human factor V in two children after exposure to topical bovine thrombin.
PURPOSE: Acquired inhibitors to coagulation factors are rare in pediatric patients. Exposure to topical bovine thrombin is a risk factor for the development of inhibitors in adult cardiac surgery patients. We report two pediatric patients who developed inhibitors to bovine and human factor V after exposure to fibrin glue containing bovine thrombin. PATIENTS AND METHODS: The two patients, ages 3 1/2 years and 10 months, were studied after cardiac surgery. One patient had clinical bleeding. Coagulation factor assays and inhibitor studies were performed. RESULTS: The presence of a circulating inhibitor to bovine factor V was observed in both patients and to human factor V in one patient. The inhibition of bovine factor V interfered with standard assays for factor VIII activity using a commercial substrate fortified with bovine factor V resulting in spurious factor VIII deficiency. In one patient, an inhibitor of bovine thrombin was also identified. The inhibition of human factor V activity in one patient may have contributed to clinical bleeding. CONCLUSIONS: Pediatric patients exposed to topical bovine thrombin, particularly in the setting of cardiac surgery, are at risk for the development of antibodies to bovine thrombin and factor V. This may also result in apparent but spurious depletion of other coagulation factors. These antibodies may cross-react with human coagulation factors, particularly factor V, resulting in clinical bleeding.
Bleeding/bruising symptomatology in children with and without bleeding disorders.
A questionnaire, designed to assess bleeding/bruising tendencies, was administered to 251 otherwise healthy children undergoing a tonsillectomy and/or adenoidectomy. 23 children with excessive bleeding during or after the operation, with a long bleeding time or who reported taking aspirin recently were excluded, to give a population of 228 non-bleeders. For comparative purposes, 31 patients with bleeding disorders (von Willebrand's disease and/or platelet function defects) were studied. A considerable proportion of "non-bleeding" children reported easy bruising (24%), had bruises at least once a week (36%) and suffered from nosebleeds (39%). The respective frequencies (67%, 68% and 69%) for children with bleeding disorders were significantly higher. Occurrence of bruises usually on more than one part of the body, frequent large bruises or hematomas were rare in "non-bleeders" (4.9%, 3.5% and 2.7% respectively), but more common in "bleeders" (38.5%, 29.6% and 21.7% respectively).
Synergistic shortening of the bleeding time by desmopressin and ethamsylate in patients with various constitutional bleeding disorders.
Desmopressin and ethamsylate were evaluated for possible synergistic effects on the bleeding time. The drugs were administered individually and together to 12 patients with markedly prolonged bleeding times known to be relatively or absolutely unresponsive to desmopressin alone. The bleeding disorders studied included Glanzmann's thrombasthenia (one), other disorders of platelet function (four), pseudo-von Willebrand disease (one), and von Willebrand disease type I (three), type II (two), and type III (one). Desmopressin alone shortened the bleeding time from 23.9 +/- 1.5 to 19.5 +/- 2.3 min (p = 0.03). Ethamsylate alone was without effect. Desmopressin and ethamsylate together shortened the bleeding time to 11.2 +/- 1.4 min (p less than 0.01 compared to baseline, p = 0.02 compared to desmopressin alone). The combination was ineffective in three patients, with Glanzmann's thrombasthenia (one), and von Willebrand disease type I (one) and type III (one). Toxic effects of the drugs were not observed. Five patients received desmopressin and ethamsylate prior to dental work with mandibular block (one), heart surgery requiring cardiopulmonary bypass (two), and adenotonsillectomy surgery (two). Normal hemostasis was achieved in each case. A synergistic shortening of the bleeding time was observed with the combination of desmopressin and ethamsylate in a wide range of bleeding disorders.
Inherited platelet-storage pool deficiency associated with a high incidence of acute myeloid leukaemia.
A family with an inherited bleeding disorder extending over four generations, and multiple cases of myeloblastic and myelomonoblastic leukaemia was studied. Ten members of the family had, by history, a haemorrhagic diathesis. There were three documented cases of myeloblastic leukaemia, two documented cases of myelomonoblastic leukaemia and two more cases of leukaemia by history. In four of the cases the bleeding diathesis clearly antedated the leukaemia, in two by many years. The bleeding disorder is characterized by a long bleeding time, abnormal platelet aggregation, low platelet ADP and decreased numbers of platelet dense bodies consistent with a dense granule storage pool deficiency. The number of dense granules was decreased by immunofluorescence employing quinacrine or using an antibody to the dense granule membrane protein, granulophysin, confirming an absolute decrease in dense granule numbers rather than the presence of empty granule sacs. This congenital storage pool deficiency is associated with a high incidence of acute myeloid leukaemia in this family.
Studies in patients with bleeding disorders show that platelet-vessel interaction is important for thromboxane formation in bleeding time wounds.
The production of thomboxane B2, the primary metabolite of thromboxane A2, and 6-keto prostaglandin F1 alpha, the primary metabolite of prostacyclin, were measured in response to a standardized vascular injury, the bleeding time, in patients with von Willebrand's disease and in patients with platelet function defects. Compared to controls, thromboxane B2 levels in bleeding time blood were significantly lower in subjects with von Willebrand's disease. In patients with platelet function defects associated with a deficient response to thromboxane A2, thromboxane B2 production in bleeding time blood was similar to controls. In subjects with other platelet function defects, thromboxane production was significantly lower than normal. 6-keto PGF1 alpha production in bleeding time blood was not significantly different in patients compared to controls. The results suggest that bleeding time thromboxane production is influenced by the extent of platelet-vessel interaction.
A reassessment of the bleeding time: association of age, hematocrit, platelet function, von Willebrand factor, and bleeding time thromboxane B2 with the length of the bleeding time.
In order to provide an overview of the relative contribution of platelet, von Willebrand factor, and other abnormalities to patients with clinical bleeding difficulties, we performed a retrospective survey of coagulation studies on 569 individuals referred to the University of Manitoba coagulation laboratory because they, or a closely related family member, showed clinical evidence of a bleeding disorder. There was a highly significant (p less than 0.001) negative correlation between the bleeding time and each of the following parameters: the platelet count; the hematocrit; the percent aggregation to collagen, epinephrine, ADP, and arachidonic acid; and the logarithm of von Willebrand factor antigen and a measure of its activity (ristocetin cofactor). A significant and independent inverse relationship between the length of the bleeding time and the extent of platelet adhesion to glass beads, patient age, and prothrombin consumption were also observed. Multivariate analysis of the ability of all parameters to predict the bleeding time showed an r2 of only 0.33. Bleeding time thromboxane B2, in a second smaller study of 70 patients, showed a negative correlation with the length of the bleeding time (p = 0.0001), and, when used together with the above parameters, significantly enhanced the ability to predict the length of the bleeding time (r2 = 0.55). Defects in platelet function, as measured in vitro, and significant enough to have an effect on the bleeding time, occurred with greater frequency than defects in von Willebrand factor in the Manitoba patients evaluated.
Vitamin K1 increases sister chromatid exchange in vitro in human leukocytes and in vivo in fetal sheep cells: a possible role for "vitamin K deficiency" in the fetus.
The levels of the vitamin K-dependent clotting factors are markedly lower in the human fetus and newborn than in older infants and adults. Direct measurement of vitamin K1 in cord plasma records low or undetectable levels. This phenomenon, although the norm, is referred to as vitamin K deficiency and is a significant risk factor for hemorrhage in the fetus and newborn. Sister chromatid exchange (SCE), which may be used as an index of mutagenic activity, was assayed in cultured leukocytes of placental and adult blood following phytohemagglutinin stimulation. The mean number of SCEs per metaphase in human placental blood was 3.32 +/- SE 0.219 as compared with levels of 5.13 +/- SE 0.273 in young adults (p less than 0.01), and in the presence of added vitamin K1 at a concentration of 1 X 10(-6) M the SCE increased significantly in both adult and placental cells. In vitro SCE dose response curves to K1 in the blood of fetal and maternal sheep were obtained. When five fetal sheep were given 1 mg of K1 by catheter into the femoral vein the SCE increased from 3.94 +/- SE 0.15 preinjection to 5.38 +/- SE 0.23 at 24 h postinjection (p less than 0.01). In the pretreatment fetal sheep, serum vitamin K1 was below detectable levels in all seven animals in which it was assayed and reached levels as high as 0.3 X 10(-6) M 1 h post-K1 injection. The low level of K1 in the fetus may in fact confer some biological advantage by reducing the risk of mutagenic events during a period of rapid cell proliferation.
1-Desamino-8-D-arginine vasopressin (desmopressin) decreases operative blood loss in patients having Harrington rod spinal fusion surgery. A randomized, double-blinded, controlled trial.
To evaluate the effect of 1-desamino-8-D-arginine vasopressin (desmopressin) on blood loss in surgery, we conducted a randomized, double-blind trial of the drug in 35 patients with normal hemostatic function who were having spinal fusion with Harrington rod instrumentation. Seventeen patients were designated to receive 10 micrograms/m2 of desmopressin, and 18, to receive a placebo. Preoperative testing showed that desmopressin increased factor VIII coagulant activity, von Willebrand antigen concentrations, glass bead platelet retention, and prothrombin consumption and decreased the partial thromboplastin and bleeding times (p less than or equal to 0.0003). During surgery, desmopressin reduced blood loss by 32.5% (547 mL; 95% confidence interval [CI], 19 to 1075; p = 0.015) and reduced the need for concentrated erythrocyte transfusions by 25.6% (0.86 units; 95% CI, 0.08 to 1.65; p = 0.022). After surgery, desmopressin reduced the duration of treatment with analgesic agents by 13.1% (34.0 hours; 95% CI, -5.2 to 72.7; p = 0.105), presumably by decreasing bleeding in the surgical wound. When adjusted for the origin of the scoliosis by two-way analysis of variance, this effect was even more evident (p = 0.014). Multiple regression analysis showed that the best three predictors of blood loss in surgery and transfusion requirements were the bleeding time, glass bead platelet retention, and the use of desmopressin.
Absent factor VIII response to synthetic vasopressin analogue (DDAVP) in nephrogenic diabetes insipidus.
To study the effect of 1-deamino-8D-arginine vasopressin (DDAVP) on the factor VIII response in nephrogenic diabetes insipidus (NDI), 0.30 microgram/kg DDAVP was given to 2 unrelated NDI patients, 3 obligate carriers, and 20 controls. Factor VIII coagulant activity (FVIIIC) and factor VIII related antigen (FVIIIR:Ag) responses were absent in both NDI patients and were decreased by approximately 50% in the carriers by comparison with controls. These results show that the vasopressin receptor defect in NDI is not confined to the kidney but is equally expressed in other tissues including the vascular endothelium and hepatic sinusoids, the respective sites of FVIIIR:Ag and FVIIIC production. A decreased factor VIII response may help in identifying carriers in families at risk.
Vitamin K1 as a modulator of benzo(a)pyrene metabolism as measured by in vitro metabolite formation and in vivo DNA-adduct formation.
Vitamin K1 (2-methyl-3-phytyl-1,4-napthoquinone) increases the microsomal metabolism of benzo(a)pyrene in rat liver microsomes in vitro. The increase is most marked in the 9,10 diol, 4,5 diol and 3-OH metabolites. The effect is seen at an in vitro concentration of 25 microM and disappears at higher concentrations of K1. The production of BP metabolite-DNA adducts in liver in vivo in ICR/Ha mice is reduced in dietary induced vitamin K deficient mice and this effect is reversed by vitamin K1. These findings indicate a role for vitamin K1 in the regulation of the microsomal mixed function oxidase system and suggest a reason for the low intracellular content and minimal body stores of this vitamin.