Identification of a Putative Binding Site for Negatively Charged Surfaces in the Fibronectin Type II Domain of Human Factor XII

Monoclonal antibodies directed against functional sites of proteins provide useful tools for structure-function studies. Here we describe a mAb, KOK5, directed against the heavy chain region of human coagulation factor XII (FXII), which inhibits kaolin-induced clotting activity by preventing the binding of FXII to kaolin. Furthermore, mAb KOK5 enhances FXII susceptibility for cleavage by kallikrein and supports FXII autoactivation. Hence, mAb KOK5 likely is directed against the binding site of FXII for negatively charged surfaces. Screening of two phage-displayed random peptide libraries with mAb KOK5 selected phages that could be grouped on the basis of two amino acid consensus sequences: A) FXFQTPXW and B) HQ/LCTHR/KKC. Sequence A contains two motifs: one shares homology with FXII amino acid residues 30-33 (FPFQ), the second one with residues 57-60 (TPNF); both amino acid stretches belonging to the fibronectin type II domain of FXII. Sequence B also reveals homology with part of the fibronectin type II domain, i.e. the stretch 40-47 (HKCTHKGR). A three-dimensional model of FXII residues 28-65, obtained by homology modeling, indicated that the three amino acid stretches 30-33, 40-47 and 57-60 are close to each other and accessible for the solvent, i.e. in a form available for interaction with the monoclonal antibody, suggesting that mAb KOK5 recognizes a discontinuous epitope on the fibronectin type II domain of FXII. Peptides corresponding to FXII sequences 29-37 (FXII29-37) or 39-47 (FXII39-47), were synthesized and tested for the capability to inhibit FXII binding to negatively charged surfaces. Peptide FXII39-47 inhibited the binding of labeled FXII to kaolin and effectively prevented both dextran sulfate-and kaolin-induced activation of the contact system in plasma. Hence, we suggest that the fibronectin type II domain of FXII, in particular residues 39 to 47, contribute to the binding site of FXII for negatively charged surfaces.

The Role of Cytokines in Activation of Coagulation and Fibrinolysis in Dengue Shock Syndrome

In a prospective clinical study of 50 patients with Dengue Shock Syndrome (DSS), we investigated the association of tumor necrosis factor-a (TNF-a), interleukin-1f3 (IL-1f3), IL-1 receptor antagonist (IL-1Ra), and IL-6 with activation markers of coagulation (F1+2 and TATc) and fibrinolysis (t-PA, PAPc, and D-dimer). We found that TNF-a, IL-1f3 and Il-1Ra, but not IL-6, concentrations were elevated in the circulation during the early stage of infection and at discharge from hospital. TNF-a was significantly associated with D-dimer, an activation marker of fibrinolysis (p < 0.003), but not with activation markers of coagulation. IL-1f3 was significantly associated with t-PA (p < 0.03). IL-1Ra was significantly associated with F1+2, TATc (p < 0.04 and p < 0.02, respectively), whereas IL-6 was significantly associated with both, activation markers of coagulation (F1+2; p < 0.03) and fibrinolysis (PAPc; p = 0.002). Our data are in line with studies in bacterial sepsis. In severe dengue virus infection the same cytokines are involved in the onset and regulation of hemostasis.

Interleukin 12 induces activation of fibrinolysis and coagulation in humans

Interleukin 12 (IL-12) has potential efficacy in malignant, infectious and allergic diseases. Its side-effects include activation of coagulation and fibrinolysis, as documented in chimpanzees. We assessed the coagulative and fibrinolytic response in 18 patients with renal cell carcinoma after subcutaneous injection of 0.5 microg/kg recombinant human IL-12. IL-12 induced a fibrinolytic response in 17 patients (94%): plasmin-alpha2-anti-plasmin complexes (PAPc) increased from 11.8 +/- 6.6 nmol/l (mean +/- SD) to a maximum of 18.8 +/- 7.4 nmol/l at 72 h. Baseline levels of tissue plasminogen activator (tPA) and plasminogen-activator inhibitor-I (PAI) were elevated in eight and 14 patients respectively. tPA increased from 12.6 +/- 5.2 ng/ml to a maximum of 19.0 +/- 6.7 ng/ml at 72 h. PAI decreased from 111 +/- 69 ng/ml to a minimum of 65 +/- 53 ng/ml at 8 h, thereafter remaining below baseline. Elevation of PAPc correlated with elevation of tPA and reduction of PAI. A coagulative response occurred in nine patients (50%): thrombin-anti-thrombin III complexes increased from 29 +/- 53 ng/ml to a maximum of 460 +/- 322 ng/ml at 12 h. Patients with and without a coagulative response had similar levels of recombinant human IL-12, interferon-gamma or tumour necrosis factor-alpha. We conclude that IL-12 can activate both fibrinolysis and coagulation in a significant proportion of patients with cancer. The time-frame and sequence of these activation processes differ from those known for other cytokines.

Prenatal cocaine and neonatal outcome: evaluation of dose-response relationship

OBJECTIVE

The aim of this study was to evaluate the hypothesis that prenatal cocaine exposure would negatively affect newborn behavior.

METHODS

A prospective observational study of term infants recruited from the low-risk nursery used a structured, standardized interview to obtain maternal data. Cocaine exposure was determined by radioimmunoassay of the infant's meconium stool. An examiner blinded to the infant's cocaine status administered the Brazelton Neonatal Behavioral Assessment Scales.

RESULTS

The sample was composed of 23 exposed and 29 nonexposed infants. On six of the seven Brazelton Neonatal Behavioral Assessment Scale clusters, cocaine-exposed infants performed less well than control infants, with significant differences observed for autonomic stability. In addition, a dose-response relationship was suggested. Significant negative, within-group relationships were evident in the exposed group, indicating poorer performance with increasing meconium cocaine concentration for orientation (r = -.40) and regulation of state (r = -.40). Regression model testing of the influence of meconium cocaine concentration on neurobehavioral outcomes, after controlling for significant confounders, identified a significant independent, negative effect of meconium cocaine concentration on two clusters-motor and regulation of state.

CONCLUSION

In otherwise healthy full-term infants, prenatal cocaine exposure identified by quantitative analysis of cocaine concentration in meconium had a significant, independent negative association with motor and regulation of state that remained after controlling for other significant confounders. A dose-response relationship was evident.

Nasal midazolam in children, plasma concentrations and the effect on respiration

Twenty ASA 1 children, one to six years old, weighing 10-20 kg, scheduled for a combination of general and caudal anaesthesia received at random midazolam 0.2, 0.4, or 0.6 mg.kg-1 or NaCl 0.9% (control group) intranasally. Drug or NaCl 0.9% were administered in one nostril, after inhalation induction of anaesthesia, intubation without relaxant and caudal anaesthesia. Spontaneous respiration was via a circle system and fresh gas flow of 6 l.min-1 (N2O/O2 = 2:1), PEEP 5 cm H2O, endtidal halothane 0.4%. Immediately before and 2, 5, 8, 12, 16, 20, 30, 60 and 120 min after application of the drug 2.5 ml blood was sampled for plasma levels of midazolam. Endtidal CO2, respiratory rate, and oxygen saturation were recorded as long as the children were intubated. Endtidal CO2 and respiratory rate showed no statistical difference between the groups at any time, however, in the group receiving 0.6 mg.kg-1, endtidal CO2 increased significantly from 5.3 kPa (41 mm Hg) at the start to 5.9 kPa (45.5 mm Hg) after 30 min. Plasma levels of midazolam were detected 2 min after application in 10 of 15 patients. Median peak levels were found between 12 and 16 min. Medians of peak plasma levels showed no statistical difference between the three groups (0.2 mg.kg-1:111 ng.ml-1, 0.4 mg.kg-1:136 ng.ml-1, 0.6 mg.kg-1:277 ng.ml-1). After 30, 60 and 120 min medians of midazolam plasma concentration were significantly higher in the group 0.6 mg.kg-1.

[Position and variations in the position of the canal system in the temporal bone. I. The canals of the pars petrosa between the margo superior and the meatus acusticus internus]

The canals of the temporal bone were measured on 103 objects at different levels. The distances (mean and extremes) were estimated as well as the width of the following: the facial canal, semicircular canals, vestibule, internal acoustic meatus, sigmoid sinus, superior bulb of the jugular vein, carotid canal, eustachian tube, perilymphatic and endolymphatic ducts and sac, glossopharyngeal nerve and mastoid cells.