A unique precipitating autoantibody against plasma thromboplastin antecedent associated with multiple apparent plasma clotting factor deficiencies in a patient with systemic lupus erythematosus

A 42-yr-old woman with systemic lupus erythematosus without bleeding diathesis developed a prolonged activated partial thromboplastin time that was not corrected by normal plasma. An inhibitor that acted rapidly and inactivated 0.5 U/ml plasma thromboplastin antecedent (PTA, factor XI) at a 1:200 plasma dilution was demonstrated. In addition to a low titer of PTA (less than 0.01 U/ml), plasma assayed at 20-fold dilution also showed low titers of Hageman (factor XII, 0.02 U/ml), Fletcher (plasma prekallikrein, 0.02 U/ml), and Fitzgerald (high molecular weight kininogen, less than 0.01 U/ml) factors. The titer of these factors, except PTA, returned to normal upon further plasma dilution or upon removal of the inhibitor by protein A adsorption. Thus, the inhibitor appeared to interfere with these clotting factor assays, possibly by inactivating PTA in the substrate plasmas in the test system. Its specificity was further confirmed. The inhibitor did not interfere with surface-induced proteolytic cleavage of Hageman factor. Surface-induced generation of plasma kallikrein activity (amidolysis of H-D-pro-phe-arg-pNa and cold-promoted factor VII activity enhancement) requires only Hageman, Fletcher, and Fitzgerald factors and was normal. Reactions requiring all 4 contact phase factors, including PTA, such as surface-induced generation of plasmin activity (amidolysis of H-D-val-leu-lys-pNa) and activated Christmas factor (factor IXa) activity, were defective. Furthermore, the inhibitor bound to agarose-protein A inactivated and removed PTA selectively from normal plasma. The inhibitor was an IgG-lambda autoantibody that precipitated PTA. The inactivated activated PTA (factor XIa) without the requirement for an additional cofactor. Furthermore, it inhibited surface-induced activation of PTA by interfering with its proteolytic cleavage upon glass surface exposure and with its binding onto the reactive surfaces.     

Studies on immunological assay of vitamin K dependent factors.

A radioimmunoassay (RIA) for factor VII was developed using 125I-factor VII, anti-factor VII rabbit serum and anti-rabbit IgG goat serum. The lower limit of sensitivity in normal reference plasma was 3 X 10(-3) units/ml. Although the level of factor VII antigen (VII:Ag) in normal plasma samples (n = 20) 0.944 +/- 0.176 units/ml, correlated with that of factor VII coagulant activity (r = 0.89), VII:Ag level in paired normal sera showed a higher value (1.469 +/- 0.376 units/ml). The level of antigen according to RIA of factor VIIa activated by factor Xa increased 2.5-fold compared with that of unactivated factor VII. It is suggested that the polyclonal anti-factor VII produced in a rabbit had higher affinity for factor VIIa than for factor VII. In two out of seven patients with congenital factor VII deficiency, VII:Ag was detectable (0.04, 0.31 units/ml, respectively) whereas VII:C was less than 0.01 units/ml. In 12 warfarin-treated individuals, VII:C showed a lower level (0.121 +/- 0.063 units/ml) that that of VII:Ag (0.518 +/- 0.186 units/ml). During 4 weeks observation after stopping warfarin, VII:C and VII:Ag reached normal levels in 1 week. However, VII:C did not reach equivalence with VII:Ag until 4 weeks had elapsed.     

Normal titer of functional and immunoreactive protein-C inhibitor in plasma of patients with congenital combined deficiency of factor V and factor VIII

Protein-C inhibitor (PCI) is a newly described plasma inhibitor directed against a vitamin-K-dependent serine protease, activated protein-C, which is involved in the inactivation of factor V and factor VIII. Marlar and Griffin have reported that PCI activity is absent in the plasma of patients with congenital combined factor V/VIII deficiency. We have measured the levels of PCI in the plasma of seven unrelated patients with this disorder using both functional and immunologic methods. The rate at which the amidolytic activity of activated protein-C was neutralized in the patients' plasma was essentially identical to that observed in normal plasma. The titer of PCI antigen, as measured by an electroimmunoassay using a monospecific anti-PCI serum, was 5.3 +/- 1.6 micrograms/ml in the patients' plasma and was not significantly different from that of normal plasma (5.3 +/- 2.7 micrograms/ml, n = 30). The levels of factor-V-related antigen, factor V coagulant antigen, and factor VIII coagulant antigen were low in all patient plasma and were in good agreement with their respective coagulant activity. Our results do not appear to support the hypothesis that combined factor V/VIII defect is due to a lack of PCI.     

Radioimmunoassay for 21-deoxycortisol: clinical applications

A radioimmunoassay for 21-deoxycortisol is described. The immunogen, 21-deoxycortisol-3-(0-carboxymethyl) oxime-bovine serum albumin, was prepared, the antisera raised against it were studied and the reliability of the assay was checked. The antiserum selected cross-reacted with 11-deoxycortisol (0.08%), corticosterone (0.25%), cortisol (0.6%) and 17-hydroxyprogesterone (1.6%). 21-deoxycortisol was separated by celite partition chromatography and eluted in the 70/30 (v/v) isooctane/ethyl acetate fraction together with 11-deoxycortisol and corticosterone. The radioimmunoassay was used to measure 21-deoxycortisol in the plasma of normal subjects and patients with androgen excess. In normal subjects, men (0.19 ng/ml +/- 0.08) and women (0.18 ng/ml +/- 0.09) had similar basal levels (mean +/- SD). One hour after ACTH stimulation, these levels were increased by a factor of 3.5. In 7 patients treated for classical congenital adrenal hyperplasia associated with 21-hydroxylase deficiency, basal values varied between 9.1 and 39.9 ng/ml (measured at 8 a.m.). In 7 untreated women with late-onset congenital adrenal hyperplasia (with 21-hydroxylase deficiency), ACTH-stimulated levels were increased to between 9 and 25.5 ng/ml. In 14 heterozygous carriers of 21-hydroxylase deficiency, diagnosed by HLA genotyping, all ACTH-stimulated levels were well above the highest corresponding levels in normal subjects, whereas 17-hydroxyprogesterone levels remained within the normal range in 9 of the cases.     

Fitzgerald factor (high molecular weight kininogen) clotting activity in human plasma in health and disease in various animal plasmas.

Fitzgerald factor (high molecular weight kininogen) is an agent in normal human plasma that corrects the impaired in vitro surface-mediated plasma reactions of blood coagulation, fibrinolysis, and kinin generation observed in Fitzgerald trait plasma. To assess the possible pathophysiologic role of Fitzgerald factor, its titer was measured by a functional clot-promoting assay. Mean +/- SD in 42 normal adults was 0.99+/-0.25 units/ml, one unit being the activity in 1 ml of normal pooled plasma. No difference in titer was noted between normal men and women, during pregnancy, or after physical exercise. Fitzgerald factor activity was significantly reduced in the plasmas of eight patients with advanced hepatic cirrhosis (0.40+/-0.09 units/ml) and of ten patients with disseminated intravascular coagulation (0.60+/-0.30 units/ml), but was normal in plasmas of patients with other congenital clotting factor deficiencies, nephrotic syndrome, rheumatoid arthritis, systemic lupus erythematosus, or sarcoidosis, or under treatment with warfarin. The plasmas of 21 mammalian species tested appeared to contain Fitzgerald factor activity, but those of two avian, two repitilian, and one amphibian species did not correct the coagulant defect in Fitzgerald trait plasmas.     

Acquired free protein S deficiency associated with multiple myeloma: A case report

Investigation of recurrent venous thromboembolic events in a 46-year-old man with progressive IgG kappa (total serum IgG, 74.3 mg/ml) multiple myeloma revealed profound reductions in free protein S (PS) antigen (<0.1 U/ml) and PS activity (0.33 U/ml). Total PS antigen, protein C, antithrombin III, and C4b-binding protein levels were within normal limits. The patient had no family history suggestive of a congenital PS deficiency and no history of thrombosis predating the diagnosis of his plasma cell dyscrasia. Patient IgG was isolated from serum using a protein A-sepharose affinity column and characterized. PS-dependent clotting assays (Staclot Protein S, Diagnostica Stago, Asnleres sur-Seine, France) performed on normal pooled plasma mixed with dilutions of patient IgG (0.0–33.0 mg/ml) revealed a dose-dependent neutralization of PS activity by 43%. Total and free PS antigen levels were measured using Laurell rocket electroimmunodiffusion (Assera-Plate Protein S, Diagnostica Stago), which revealed a similar dose-dependent reduction in free PS antigen but preserved normal total PS antigen. Free PS antigen was reduced by 77% to 0.23 U/ml using an IgG concentration (16.5 mg/ml) less than one-fourth of that of the patient at time of serum collection. Specific binding of the patient IgG to commercially available purified human PS was demonstrated by Western Immunoblot analysis. Whereas acquired free PS deficiency has been previously reported in association with nephrotic syndrome, inflammatory bowel disease, HIV infection, and varicella infection, this is the first reported case of a hypercoagulable syndrome associated with acquired free PS deficiency and multiple myeloma. © 1996 Wiley-Liss, Inc.     

Changes in the factor VIII complex in diabetic ketoacidosis: evidence of endothelial cell damage?

Summary Factor VIII-related antigen and von Willebrand factor are synthesised by and released from vascular endothelium. Acute increases in the plasma concentration of these proteins may reflect endothelial cell damage. We have thus measured the plasma concentration of factor VIII-related antigen and von Willebrand factor, together with procoagulant factor VIII, during the course of acute diabetic ketoacidosis in seven patients. In addition, evidence for qualitative changes in the factor VIII complex was sought. Plasma factor VIII-related antigen and von Willebrand factor were markedly increased (plasma factor VIII-related antigen at presentation, median 2.75 U/ml; von Willebrand factor 2.95 U/ml) and returned toward normal with clinical and biochemical resolution (plasma factor VIII-related antigen at clinical recovery, median 1.80 U/ml; von Willebrand factor 2.05 U/ml). Plasma procoagulant factor VIII followed a similar pattern, but levels were less elevated (plasma procoagulant factor VIII, at presentation, median 1.6U/ml; at clinical recovery, 1.2U/ml). Crossed immunoelectrophoresis and sodium dodecyl sulphate-acrylamide electrophoresis with autoradiographic identification of multimeric structure revealed no evidence of structurally abnormal factor VIII-related antigen in diabetic ketoacidosis. However, an extra peak on crossed immunoelectrophoresis (pre-peak) was a feature in the acute phase ketoacidotic plasma in six subjects, and may represent aggregated factor VIII. Changes in plasma factor VIII are a feature of diabetic ketoacidosis and, whilst not specific to this condition, may be the result of endothelial cell damage.     

Hereditary plasma thromboplastin antecedent (PTA,FXI)

A rare case of factor XI (PTA) deficiency was discovered in a Saudi family in the Riyadh area. Nine members of the family were studied. Two were found to have a severe PTA deficiency’ levels of factor XI clotting activity were 0.01 i.u./ml and 0.02 i.u./ml respectively. Both plasmas were markedly deficient in factor XI antigen and appeared to be negative for cross-reactive material (CRM-). The parents were first cousins and both were found to have a minor PTA deficiency. Factor XI levels were: mother 0.048 i.u./ml and father 0.33 i.u./ml. Another sibling was found to have a FXI level of 0.47 i.u./ml. Menorrhagia and bleeding for 1 day after tooth extraction were the main bleeding manifestations found in one member with severe PTA deficiency. Clinically this member presented with iron deficiency anaemia. Other family members had no significant history of bleeding tendency. This is the first report of a Saudi Arabian family with PTA deficiency.     

Superior sagittal sinus thrombosis occurring at high altitude associated with protein C deficiency.

A 42-year-old male presented with right-sided weakness, dysphasia and seizures while climbing the French Alps at an approximate altitude of 3,000 m. Imaging studies were consistent with superior sagittal sinus thrombosis with hemorrhage. Laboratory testing for thrombophilic states, 18 days after presentation at our hospital, showed a low protein C level (0.32 U/ml, normal 0.80-1.60 U/ml). A family member was also found to have protein C deficiency without a history of thrombosis. The patient gradually improved and was discharged on warfarin and valproic acid. This is the first reported case of cerebral venous thrombosis in a patient with congenital protein C deficiency who ascended to high altitude. We postulate that the ascent to high altitude represented an additional prothrombotic risk factor to the congenital protein C deficiency leading to cerebral thrombosis.     

Hereditary plasma thromboplastin antecedent (PTA, FXI) deficiency in a Saudi family

A rare case of factor XI (PTA) deficiency was discovered in a Saudi family in the Riyadh area. Nine members of the family were studied. Two were found to have a severe PTA deficiency; levels of factor XI clotting activity were 0.01 i.u./ml and 0.02 i.u./ml respectively. Both plasmas were markedly deficient in factor XI antigen and appeared to be negative for cross-reactive material (CRM-). The parents were first cousins and both were found to have a minor PTA deficiency. Factor XI levels were: mother 0.048 i.u./ml and father 0.33 i.u./ml. Another sibling was found to have a FXI level of 0.47 i.u./ml. Menorrhagia and bleeding for 1 day after tooth extraction were the main bleeding manifestations found in one member with severe PTA deficiency. Clinically this member presented with iron deficiency anaemia. Other family members had no significant history of bleeding tendency. This is the first report of a Saudi Arabian family with PTA deficiency.     

CRM+ severe Fletcher factor deficiency associated with Graves' disease

A 59-year-old male patient with Graves' disease and severe hereditary Fletcher factor deficiency is described. PKK clotting activity as well as the activity by a chromogenic substrate method (Chromozym PK) was less then 0.01 U/ml. In contrast to functional tests, the immunological assay (Laurell method) showed a PKK antigen concentration of 0.25 U/ml, indicating the presence of an abnormal nonfunctional PKK molecule (CRM+ variant). An inhibitor was excluded since the patient plasma did not inactivate partially purified PKK. Investigation of 11 family members revealed a reduction of the PKK clotting activity in 9 relatives of the patient. Since Graves' disease is considered an autoimmune disease, our case represents an example of an association of a severe hereditary deficiency of a contact factor and an autoimmune disease.     

Prognostic relevance of preoperative bilirubin-adjusted serum carbohydrate antigen 19-9 in a multicenter subset analysis of 179 patients with distal cholangiocarcinoma

BackgroundDistal cholangiocarcinoma (DCC) is a rare malignancy and validated prognostic markers remain scarce. We aimed to evaluate the role of serum CA19-9 as a potential biomarker in DCC.MethodsPatients operated for DCC at 6 high-volume surgical centers from 1994 to 2015 were identified from prospectively maintained databases. Patient baseline characteristics, surgical and histopathological parameters, as well as overall survival after resection were assessed for correlation with preoperative bilirubin-adjusted serum carbohydrate antigen 19-9 (CA19-9). Preoperative CA19-9 to bilirubin ratio (CA19-9/BR) was classified as elevated (≥ 25 U/ml/mg/dl) according to the upper serum normal values of CA19-9 (37 U/ml) and bilirubin (1.5 mg/dl) giving a cut-off at ≥ 25 U/ml/mg/dl.ResultsIn total 179 patients underwent resection for DCC during the study period. High preoperative CA19-9/BR was associated with advanced age and regional lymph node metastases. Median overall survival after resection was 27 months. Elevated preoperative serum CA19-9/bilirubin ratio (HR 1.6, p = 0.025), T3/4 stage (HR 1.8, p = 0.022), distant metastasis (HR 2.5, p = 0.007), tumor grade (HR 1.9, p = 0.001) and R status (HR 1.7, p = 0.023) were identified as independent negative prognostic factors following multivariable analysis.ConclusionElevated preoperative bilirubin-adjusted serum CA19-9 correlates with regional lymph node metastases and constitutes a negative independent prognostic factor after resection of DCC.     

PLASMA PREGNENOLONE, PROGESTERONE, 17-HYDROXYPROGESTERONE, TESTOSTERONE AND 5α-DIHYDROTESTOSTERONE IN DIFFERENT TYPES OF CONGENITAL ADRENAL HYPERPLASIA

Unconjugated pregnenolone, progesterone, 17-hydroxyprogesterone, testosterone and 5a-dihydrotestosterone were simultaneously measured by radioimmunoassay in plasma from children with congenital adrenal hyperplasia (CAH) due to a deficiency of 21-hydroxylase (21-OHase), 11 β-hydroxylase (11β-OHase) or 3β-hydroxysteroid dehydrogenase (3β-HSD). These steroids were also measured in a reference group of children of similar age. The following concentrations of these five steroids were observed in the prepubertal children aged 0-4-10-9 years: pregnenolone <0-2-0-85 ng/ml; progesterone 0-17-0-68 ng/ml; 17-hydroxyprogesterone 0-10-0-53 ng/ml; testosterone <0-05-0-14 ng/ml, and 5α-dihydrotestosterone <0-05 ng/ml (detection limit of the method). The concentrations were clearly elevated in the plasma of children with CAH. A very high plasma concentration of 17-hydroxyprogesterone differentiates a 21-OHase deficiency from the two other types: children with this defect had levels mostly in excess of 100-fold that of normal. Plasma progesterone concentrations in these patients were also high being in the range found during the luteal phase level in the adult. Their plasma testosterone concentrations showed a scatter from normal values to high adult male levels being mostly at the level of adult females. The concentrations of 5a-dihydrotestosterone were at or above those of adult males. A high plasma concentration of pregnenolone with at most slightly elevated progesterone and 17-hydroxyprogesterone levels differentiated the 3β-HSD defect from the other two forms of CAH. The plasma profile of the five steroids determined in a patient with an 11 β-OHase deficiency was close to normal, but slightly elevated pregnenolone, progesterone and 17-hydroxyprogesterone levels were found to be characteristic of this enzyme deficiency.     

Constitutional protein C deficiency in 57 patients from 22 non-related families

A congenital deficiency in protein C (physiological inhibitor of coagulation) was identified in 57 patients: the deficiency was quantitative (type I) in 20 families, qualitative (type II) in two families. The transmission was autosomal dominant in 21 families but was suspected to be recessive in one family: the 18 years old homozygous propositus has a severe deficiency (protein C = 16 p. 100): both parents are heterozygous (consanguinity was present) and 5 other family members with heterozygous deficiency are asymptomatic. In the 49 patients (25 women, 24 men) belonging to the 21 other families, 9 men and 4 women (27 p.100) are asymptomatic although precipitating factors had existed in 5 patients. In the remaining 36 symptomatic patients, a deep venous thrombosis was observed in 34, a pulmonary embolism in 18. Recurrent arterial thromboses were diagnosed in 3 patients. The first thrombotic episode was observed at the mean age of 27 +/- 11 years and a triggering factor was found in 26 patients (72 p. 100). Thrombosis was recurrent in 21 (60 p. 100). In the patients without oral anticoagulant treatment, mean protein C antigen concentrations were 47 +/- 9 p. 100 and mean protein C activity was 46 +/- 10 p. 100. In 4 patients with type II deficiency, protein C antigen levels were normal (113 +/- 15 p. 100), contrasting with decreased protein C activity (43 +/- 6 p. 100). Thirty-eight patients have been treated with oral anticoagulants and a skin necrosis developed in the homozygous patients only.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recombinant factor VIIa for the treatment of congenital factor VII deficiency

Factor VII deficiency is a rare autosomal bleeding disorder with a highly variable hemorrhagic predisposition. Severe bleeding, including hemarthroses, may be encountered when plasma factor VII levels are below 1%. Patients have prolonged prothrombin times, and the final diagnosis is established by quantitative factor VII assays. Some patients have true deficiencies, that is, very low factor VII activity and low factor VII antigen (cross-reacting material) levels (CRM-); others have normal antigen levels but low activity (CRM+). Still others have reduced antigen levels (CRMR). There is a rather poor correlation between clinical symptoms and factor VII activity levels in plasma. Treatment of these patients consists of fresh frozen plasma, prothrombin complex concentrates, or factor VII concentrates. Recombinant activated factor VII (rFVIIa) is a very useful alternative, and several patients have been treated successfully. Because of the short half-life of factor VIIa, repeated doses have to be administered, and continuous infusion may be even better. Antibodies to factor VII have been reported but seem to be rather rare. From the available data it appears that rFVIIa is a safe and effective treatment modality for patients with congenital factor VII deficiency.     

Coagulation Factors in the Human Fetus of about 20 Weeks of Gestational Age

S ummary In plasma samples of 11 fetuses of about 20 weeks of gestational age the following coagulation factors have been determined (mean values found are given in parentheses): fibrinogen (0·30 U/ml), prothrombin (±0·17 U/ml), factor V (0·28 U/ml), factor VII (0·21 U/ml), factor VIII coagulant activity (factor VIII:C) (0·12 U/ml), factor VIII-related antigen (factor VIIIR:Ag) (1·04 U/ml), coagulant factor VIII-related antigen (factor VIII:CAg) (0·19 U/ml), factor IX coagulant activity (0·05 U/ml), factor IX antigen (≤0·03 U/ml), factor X (0·19 U/ml) and antithrombin III (AT-III) (0·23 U/ml).
Our data support the evidence that prenatal diagnosis of haemophilia A is at present possible; less optimism is warranted where haemophilia B is concerned. The number of samples is sufficient to establish normal values for the age group.
Means of quality control of the sample—which is often difficult to obtain—are discussed.     

CA19-9显著升高的特发性肺纤维化一例--附文献复习

目的提高对CA19-9显著升高的特发性肺纤维化(IPF)的认识,评价CA19-9的升高与IPF进展的相关性.方法对1例79岁男性血清CA19-9显著升高IPF患者的临床资料进行分析,并复习相关的文献进行分析.结果本例患者血清CA19-9进行性升高,从最初的899U/ml升高至10个月后的3854U/ml,经过反复全面检查和10个月随访,未发现恶性肿瘤和其他疾病的证据, CA19-9的进行性升高与肺纤维化程度的进展正相关.通过检索Medline文献,发现日本有6例血清CA19-9升高>1000U/ml的类似病例报道,通过免疫组化分析发现重度纤维化区域CA19-9呈阳性反应.结论作为消化道恶性肿瘤标志物的CA19-9显著升高可见于IPF患者,可能提示肺纤维化的进展,但不提示疾病的活动性,是预后不良的标志.     

A female hemophilia A combined with hereditary coagulation factor XII deficiency: a case report.

A 2-year-old Japanese girl with easy bruising and arthropathy was demonstrated to have severe hemophilia A (Factor VIII activity: less than 0.01 U/ml). She had normal 46XX karyotype. Her brother also had hemophilia A, and her mother and grandmother seem to be hemophiliac carriers. Additionally, activated partial thromboplastin time (APTT) of the patient was disproportionately prolonged and there were reduced levels of coagulation factor XII in the patients and members of the maternal trait which are compatible with heterozygous factor XII deficiency. Her father had both normal factor VIII and factor XII levels. Southern blotting analysis of genomic DNA from the propositus and family members with factor VIII and factor XII DNA probes revealed no gross alterations. This patient represents a female hemophilia A combined with heterozygous factor XII deficiency. Nonrandom inactivation of a normal X-chromosome (extreme lyonization) may be the basis for the expression of hemophilia A in this female patient.     

Plasma and platelet von Willebrand factor defects in uremia

PURPOSE: Several mechanisms have been proposed to explain the prolonged bleeding times and clinical bleeding in chronic renal failure. Recent evidence has implicated an abnormality in the structure or function of the von Willebrand factor or in its interaction with uremic platelets. We investigated this factor in 11 patients with chronic renal failure. PATIENTS AND METHODS: Blood samples for cell counts, chemistries, and coagulation studies were obtained from 11 patients with chronic renal failure and prolonged bleeding times. Concentrations of von Willebrand factor antigen and ristocetin cofactor activity were determined in plasma and platelets. Multimeric analysis of von Willebrand factor in plasma and platelets was conducted. In eight cases, the platelets of uremic patients were purified, and the thrombin- and ristocetin-induced binding of normal von Willebrand factor to these platelets was examined. RESULTS: The mean plasma von Willebrand factor antigen and activity (ristocetin cofactor assay) were elevated 2.77 mu/ml and 1.88 mu/ml, respectively (normal, 1.01 mu/ml and 1.07 mu/ml, respectively). The ratio of activity to antigen in uremic plasma was 0.67 (normal, 1.05). The mean platelet von Willebrand factor antigen and activity in the uremic patients was decreased (0.26 and 0.50 mu/10(9) platelets, respectively) compared with normal patients (0.46 and 0.93 mu/10(9) platelets, respectively). The oligomeric structure of the uremic plasma von Willebrand factor lacked the largest multimers. Collection of the blood for analysis in several protease inhibitors and/or EDTA did not change the multimeric structure. The von Willebrand factor multimeric structure of platelets from uremic patients was normal. The ristocetin-induced platelet aggregation of the uremic platelet-rich plasma was decreased compared with normal plasma samples. Thrombin and ristocetin-induced binding of normal von Willebrand factor to uremic patients' platelets was indistinguishable from the binding to normal platelets. CONCLUSION: These data suggest that the uremic platelet-binding sites for von Willebrand factor are intact and that the defect in ristocetin-induced platelet aggregation is most likely plasmatic in nature. At least one plasmatic defect was the observed reduction or absence of the largest plasma von Willebrand factor multimer in uremic patients. The platelet von Willebrand content was significantly decreased. These defects may play a role in the prolonged bleeding time and the clinical bleeding observed in patients with uremia.     

Study on the mechanism of abnormal growth hormone (GH) secretion in anorexia nervosa: no evidence of involvement of a low somatomedin-C level in the abnormal GH secretion

The response of plasma growth hormone (GH) to an iv injection of synthetic human growth hormone-releasing factor (hGHRF-44) (2 micrograms/kg bw) was studied in 23 patients with anorexia nervosa. The basal plasma concentrations of somatomedin-C (Sm-C) in these patients were also measured. Basal plasma GH levels were above normal in 8 out of 23 patients and an exaggerated GH response to hGHRF-44 compared to that in age-matched normal females was found in 9 patients. Mean basal plasma Sm-C concentration in the patients was 0.41 +/- 0.04 U/ml (mean +/- SE), which was in the low normal limit. When 6 patients were reexamined after their weight gain of 4-18 kg as well as their normalization of basal plasma Sm-C levels, their elevation of basal plasma GH level was lowered and the responsiveness to hGHRF-44 improved. However, there was no significant correlation between the Sm-C concentration and basal plasma GH level as well as the integrated GH response to hGHRF-44 expressed as the area under the curve (OhGH). These findings, therefore, suggest that some factor(s) other than the lowered plasma Sm-C level are involved in the mechanism of abnormal GH secretion in patients with anorexia nervosa.