Evaluation of Adenosine Deaminase as a Diagnostic Marker in Tuberculous Pleural Effusion

Abstract:

Tuberculous pleural effusion (TPE) is a common medical condition more frequently encountered in poor countries. It is the second most common form of extra-pulmonary tuberculosis. The diagnosis of TPE is problematic because the clinical features are non-specific, and most laboratory tests are not diagnostic. An accurate diagnosis requires the detection of TB bacilli in the pleural fluid or tissue sample from the pleura, which is not an easy task due to the scarcity of bacilli in the pleural fluid and the need for invasive maneuvers to get pleural tissue for histopathological, bacteriological or molecular confirmation for the TB bacilli. Different markers in pleural fluid have been evaluated to aid in diagnosing TPE. Among those biomarkers, Adenosine deaminase (ADA) was the most studied marker. It is an enzyme predominantly produced by T-lymphocytes and catalyzes the conversion of adenosine to inosine and deoxyadenosine. It is a hallmark of active cellular immunity. A high level of ADA can be found in exudative effusion of different etiologies such as parapneumonic, tuberculous and malignant effusions. Although there is still a debate over the diagnostic accuracy of ADA as a marker for TPE, many studies recommend its use. A correct diagnosis is crucial for the start of treatment for TPE. Therefore, it is crucial to assess the diagnostic value of adenosine deaminase in diagnosing tuberculous pleural effusion. The ADA optimal cutoff value is still under investigation.

Utility of Lung Ultrasound in Decision making to prioritize hospital admission for COVID-19 patients: A Developing Country Perspective

BACKGROUND & AIMS

In healthcare settings with limited resources, it is crucial to make a plan to prioritize hospital admission for patients affected by COVID-19. So, we tried to develop a novel approach for triaging COVID-19 patients and deciding the priority for hospital admission using Lung Ultrasound. In this study, we aimed to evaluate the efficacy of lung ultrasound in triaging suspected COVID-19 patients and assessment of the severity of COVID-19 pneumonia and its comparison with CT chest as the gold standard.

METHOD

This was a multicenter cross-sectional study enrolled on 243 COVID-19 confirmed patients presented to the emergency department in three major University hospitals in Egypt. Lung ultrasound was done by an experienced emergency physician or chest physician according to the local protocol of each hospital. Demographic, clinical, and laboratory data were collected from each patient. Each patient was subjected to CT chest and lung ultrasound.

RESULTS

A total of 243 confirmed COVID-19 patients were enrolled in this study, with a mean age of 46.7+10.4 years. Ground glass opacity (GGO), subpleural consolidation, trans-lobar consolidation, and crazy paving were reported in chest CT scans of 54.3%, 15.2%, 11.1%, and 8.6% of patients, respectively. B-line artifacts were found in 81.1% of COVID-19 patients, which was of confluent pattern in 18.9% of patients. The lung ultrasound findings of 197 patients (81.1%) were completely coincident with those of CT with a Kappa agreement value of 0.77, and this offered a diagnostic sensitivity of 74 %, a diagnostic specificity of 97.9 %, positive predictive value (PPV) of 90.2% and negative predictive value (NPV) of 93.6 % for lung ultrasound in triaging COVID-19 patients. Adding O2 saturation to the findings of lung imaging, the accuracy of evaluation of lung ultrasound to differentiate between severe and non-severe lung diseases showed that ultrasound had 100% sensitivity and specificity.

CONCLUSION

Lung Ultrasound with Oxygen saturation is a very efficient tool for decision-making to prioritize hospital admission for patients affected by COVID-19 in healthcare settings with limited resources.

Serial ultrasonographic monitoring of diaphragmatic and mid-upper arm muscle thickness in mechanically ventilated respiratory patients: A single-center observational study

INTRODUCTION

Muscle monitoring during mechanical ventilation (MV) is gaining great interest nowadays; however, a proper monitoring tool is not well-established yet.

OBJECTIVES

To assess the role of ultrasound in muscle monitoring during MV in respiratory patients.

METHODS

Eligible 68 mechanically ventilated patients were consecutively enrolled. Serial ultrasound measurements of diaphragmatic thickness at the end of inspiration (Tdi) and mid-upper arm (MUA) muscle thickness were recorded every other day till weaning. Before discharge, functional status score (FSS) was assessed.

RESULTS

Tdi decreased in 72.1%, did not change in 13.2% and increased in 14.7% of the patients. MUA muscle thickness decreased in 47.17% and did not change in others. Significant correlation between Tdi and MUA muscle thickness change was found (r = 0.404, P = 0.001); however, MUA muscle thickness change could not predict Tdi change (B = 0.067, P = 0.059). Diaphragmatic and MUA thickness change showed significant negative correlation with ICU stay (r = -0.260, -0.647, P = 0.032, <0.001) and MV duration (r = -0.335, -0.596, P = 0.005, <0.001), respectively. Weaning failure was significantly higher among patients with decreased Tdi (64.28%) and FSS was significantly lower in those with decreased MUA muscle thickness. US measurements of Tdi and MUA muscle thickness showed excellent intra-observer (ICC = 0.996, 0.999, P < 0.001) and inter-observer agreement (ICC = 0.992, 0.998, P < 0.001), respectively.

CONCLUSION

Sonographic muscle monitoring during MV is promising. Changes in the diaphragmatic thickness during MV are common and weakly related to those of peripheral muscles. Early decreased muscle thickness heralds poor weaning and functional outcome.

Being Born Large for Gestational Age is Associated with Increased Global Placental DNA Methylation

Being born small (SGA) or large for gestational age (LGA) is associated with adverse birth outcomes and metabolic diseases in later life of the offspring. It is known that aberrations in growth during gestation are related to altered placental function. Placental function is regulated by epigenetic mechanisms such as DNA methylation. Several studies in recent years have demonstrated associations between altered patterns of DNA methylation and adverse birth outcomes. However, larger studies that reliably investigated global DNA methylation are lacking. The aim of this study was to characterize global placental DNA methylation in relationship to size for gestational age. Global DNA methylation was assessed in 1023 placental samples by LC-MS/MS. LGA offspring displayed significantly higher global placental DNA methylation compared to appropriate for gestational age (AGA; p < 0.001). ANCOVA analyses adjusted for known factors impacting on DNA methylation demonstrated an independent association between placental global DNA methylation and LGA births (p < 0.001). Tertile stratification according to global placental DNA methylation levels revealed a significantly higher frequency of LGA births in the third tertile. Furthermore, a multiple logistic regression analysis corrected for known factors influencing birth weight highlighted an independent positive association between global placental DNA methylation and the frequency of LGA births (p = 0.001).

B-lines: Transthoracic chest ultrasound signs useful in assessment of interstitial lung diseases

OBJECTIVE

This prospective study was conducted to evaluate the value of sonographic B-lines (previously called "comet tail artifacts"), which are long, vertical, well-defined, hyperechoic, dynamic lines originating from the pleural line in assessment of interstitial lung diseases (ILD) and compare them with the findings of chest high-resolution computed tomography (HRCT) and pulmonary function tests (PFTs).

MATERIALS AND METHODS

Sixty-one patients with ILD underwent transthoracic lung ultrasound for assessment of the presence of B-lines and the distance between them. These findings were compared with that of chest HRCT (ground glass, reticular, nodular or honey combing) and PFT as forced vital capacity (FVC), total lung capacity (TLC), diffusion capacity for carbon monoxide (DLCO) and partial arterial oxygen pressure (PaO2).

RESULTS

All patients had diffuse bilateral B-lines. The distance between each of the two adjacent B lines correlated with the severity of the disease on chest HRCT where B3 (the distance was 3 mm) correlated with ground glass opacity and B7 (the distance was 7 mm) correlated with extensive fibrosis and honey combing. Also, the distance between B-lines inversely correlated with FVC (r = -0.848, P < 0.001), TLC (r = -0.664, P < 0.001), DLCO (r = -0.817, P < 0.001) and PaO2 (r = -0.902, P < 0.001).

CONCLUSION

B-lines that are lung Ultrasound signs seem to be useful in the assessment of ILD.

Evaluation of different combined regimens in the treatment of cholinergic urticaria

BACKGROUND

: Cholinergic urticaria is uncommon and accounts for 10% of all young adults. To date, there is no effective therapy for cholinergic urticaria.

OBJECTIVE

: To determine the therapeutic efficacy of different drug combinations in the treatment of cholinergic urticaria.

PATIENTS AND METHODS

: The participants included in the study are in the age range of 16 to 29 years, with cholinergic urticaria of any duration as diagnosed by physicians. Patients were recruited from Asthma and Allergy Centers in Baghdad and Tikrit. The selected patients were divided randomly into 3 groups according to the treatment protocol. All patients completed screening before treatment.

RESULTS

: The study indicated that cholinergic urticaria was completely controlled in 30.4% of patients (group A) receiving 4 mg of chlorpheniramine maleate, half hour before the exercise, plus chlordiazopoxide (5 mg) and clindium bromide (2.5 mg) tablets, 3 times daily. However, cure rate was higher (83.1%) in patients (group B) receiving 4 mg of chlorpheniramine maleate (histadine), 3 times daily, plus 25 mg of maprotiline HCl (ludiomil), once daily at night. Furthermore, the complete cure rate was 85.4% in patients (group C) receiving 4 mg of chlorpheniramine maleate (histadine)3 times daily, plus 200 mg of cimetidine (tagadine), 3 times daily. The frequency of relapse was higher in group A (89%) as compared with group B (68.4%) and group C (23.5%) (P < 0.0001).

CONCLUSIONS

: Combination of H1 and H2 antagonists was more effective based on complete control of cholinergic urticaria with lower relapsing rate. However, a future placebo-controlled clinical trial taking in consideration higher H1 antagonists than we used is warranted.

Longevity of band and loop space maintainers using glass ionomer cement: a prospective study

AIM

This was to prospectively investigate the success and median survival rate of band and loop space maintainers using glass ionomer luting cement for attachment.

METHODS

A total of 40 children (22 females and 18 males) between the ages of 3.4 and 7.3 years participated in the study. Each patient received only one band and loop space maintainer. For each child, the same paediatric dentist carried out all diagnosis, band selection, and impression taking and appliance cementation. The same dental technician fabricated all appliances. The luting cement used was Ketac-Cem-Maxicap. Regular follow up appointments were scheduled at 4-6 months intervals. Variables, which might have affected the median survival time for the appliances were tested using Log-Rank and Chi-square tests.

RESULTS

40% of the band and loop space maintainers were successful and 57.5% failed during the study period (40 months). The most common cause of failure was decementation (82% of all failed cases). The overall median survival time was 19.9 months. Appliances fitted in the maxillary and mandibular left side of the mouth showed a statistically higher survival rate than those fitted in the right side (maxillary left quadrant = 35 months, mandibular left quadrant = 28 months, maxillary right quadrant = 14 months, mandibular right quadrant = 16 months) (p<0.008).

CONCLUSIONS

Although the overall median survival time was clinically acceptable (19.9 months), the failure rate of the band and loop space maintainers in general was high (57.5%). The main reason for failure was decementation of the band. Further studies are required to compare glass ionomer cements with more recent resin modified luting cements.

Anthropometric profiles of elite Asian female handball players

AIM

Handball has increased in status as a sport since its introduction in 1972 into the Summer Olympic Games. Whereas anthropometric profiles of female athletes have been reported for certain sports, data for elite handball players are limited. The current study was based on anthropometric measurements of 60 female Asian handball players competing in the continental championship, the aim being to identify any differences between countries and between playing positions.

METHODS

The setting was the 12(th) Asian Games in Hiroshima, Japan. Anthropometric data were obtained from 60 players including teams from China, Japan, Kazakhstan and South Korea. Measurements included height, mass, skinfold thicknesses: from these measures percent body fat and muscle mass were estimated. Profiles were compared between 4 nations and 4 positional roles by means of ANOVA.

RESULTS

Overall, mean (SD) values were 1.708 (0.068) m, 64.6 (7.7) kg, 20.8% (4.4%), 39.6% (5.2%) for stature, mass, percent body fat and percent muscle mass, respectively. There were small differences between players from different countries but no significant (P>0.05) influence of playing position. Players from Japan were shortest, lightest and lowest in adiposity. The Chinese players were tallest and had the greatest muscle mass.

CONCLUSION

These female international handball players differed in some respects in anthropometric characteristics according to their country of origin. The Asian players were found to be relatively homogeneous across the different positions.

Developing peptide inhibitors to thrombin activation of platelets from bradykinin analogs

Investigations identified peptide, platelet-selective thrombin inhibitors. Three peptides (MAP4-RPPGF, RGKWC and RGDWC) were relatively selective inhibitors of thrombin-induced platelet activation and calcium mobilization. MAP4-RPPGF at 35.5+/-0.03 microM inhibits gamma-thrombin-induced platelet aggregation 100% and alpha-thrombin-induced calcium mobilization in fibroblasts 84%. RGKWC at 800+/-400 microM inhibits gamma-thrombin-induced platelet aggregation 100% and calcium mobilization 63%. RGDWC at 140+/-100 microM inhibits gamma-thrombin-induced platelet aggregation 100% and calcium mobilization 32%. RGDWC also inhibits ADP-induced platelet aggregation, whereas MAP4-RPPGF and RGKWC do not. RGKWC prolongs the activated partial thromboplastin time (APTT) but not the prothrombin time (PT) or thrombin clotting time (TCT). RGKWC uniquely inhibits alpha-thrombin activation of human factor XI. Single amino acid substitutions in peptide pentamers result in differences in potency and mechanism(s) of inhibition of platelet and fibroblast activation by thrombin.

Decreased 13-S-hydroxyoctadecadienoic acid levels and 15-lipoxygenase-1 expression in human colon cancers

13-S-Hydroxyoctadecadienoic acid (13-S-HODE), the product of 15-lipoxygenase (15-LOX) metabolism of linoleic acid, enhances cellular mitogenic responses to certain growth factors. Other observations have questioned whether 13-S-HODE has tumorigenic effects. Our study evaluated the hypothesis that 15-LOX-1 is overexpressed in colon cancers resulting in an increase in intracellular 13-S-HODE. 15-LOX-1 and 13-S-HODE were quantified using western blots, ELISA and immunohistochemistry in 18 human colon cancers with paired normal colonic mucosa. Additionally, 15-LOX-1 expression was measured by western blots in three transformed colonic cell lines and in a human umbilical vein endothelial cell line. Next, we evaluated 13-S-HODE effects on cellular proliferation, cell cycle distribution and apoptosis in a transformed colonic cell line (RKO). Cell cycle distributions were measured by flow cytometry and apoptosis was assessed by phase contrast microscopy, electron microscopy, flow cytometry and DNA fragmentation assay. 15-LOX-1 immunohistochemistry staining scores were reduced in tumor tissues (P </= 0.0001) and 15-LOX-1 expression was absent in three transformed colonic cell lines. 13-S-HODE levels were also reduced in tumors tissues compared with normal controls by ELISA (median 3.3-fold, P = 0.02) and by immunohistochemistry (P </= 0.0001). In vitro 13-S-HODE inhibited RKO cell proliferation and induced cell cycle arrest and apoptosis. 13-S-HODE produced similar effects in HT-29 cells. Our observations indicate that: (i) human colon cancers are associated with a down-regulation in 15-LOX-1 expression and a reduction in 13-S-HODE intracellular levels; (ii) 13-S-HODE can suppress cell proliferation and induce apoptosis in transformed colonic epithelial cells.

Thrombostatin inhibits induced canine coronary thrombosis

Thrombostatin (RPPGF), an angiotensin converting enzyme metabolite of bradykinin, is an inhibitor of alpha-thrombin's ability to activate platelets. We examined the in vivo pharmacokinetics and pharmacodynamics of thrombostatin in rabbits and its ability to inhibit coronary thrombosis induced by electrolytic injury in dogs. Plasma half-life of thrombostatin had a t1/2alpha of 2.6 min and a t1/2beta of 24 min in rabbits. Ligating the renal arteries did not prolong clearance (t1/2alpha = 2.4 min; t1/2beta = 12 min). Thrombostatin produced a prolonged in vivo antiplatelet effect. At 30 min after a single intravenous administration in rabbits, thrombostatin's plasma concentration was <8.7 microM (5 microg/ml). However, ex vivo 20 and 40 nM gamma-thrombin-induced platelet aggregation of these rabbits' platelets was inhibited 40% for 2.75 and 1 h, respectively. In vitro, flow cytometry studies revealed that thrombostatin specifically bound to human platelets and washed human platelets treated with thrombostatin were less responsive to gamma-thrombin than control platelets. Using electrolytic injury to induce coronary artery thrombosis, dogs treated with thrombostatin, aspirin, or combined thrombostatin and aspirin occluded in 62+/-25 (mean +/- SD), 62+/-36, or 89+/-32 min versus untreated animals which occluded at 39+/-27 min, (p<0.01, p<0.01 and p<0.001, respectively). These studies show that thrombostatin binds to platelets and can delay coronary occlusion in vivo.

Factor XII does not initiate prekallikrein activation on endothelial cells

It is well known that on artificial surfaces, binding and autoactivation of factor XII (FXII) is the initiating event of plasma prekallikrein (PK) activation. We performed investigations to examine whether this mechanism was true for FXII activation on endothelial cells (HUVEC). Activation of PK on HUVEC required an optimal substrate and Zn2+ concentration, the latter of which varied with the buffer's carrier protein. Maximal PK activation required the addition of 250 microM or 10 microM Zn2+ to buffers containing bovine serum albumin (BSA) or gelatin, respectively. However, the actual free Zn2+ concentration in these buffers was the same at 8 microM. In both BSA- and gelatin-containing buffers and using two different chromogenic substrates for FXII, no autoactivation of FXII on HUVEC was seen when incubated for up to 60 min. Rather, initiation of FXII enzymatic activity required the presence of PK. FXII activation after PK activation contributed to the extent of measured enzymatic activity, but its role was secondary because treatment with corn trypsin inhibitor or a neutralizing antibody to FXIIa did not abolish the measured enzymatic activity. They also reduced the activity to the level seen with PK activation alone. Alternatively, soybean trypsin inhibitor abolished the proteolytic activity associated with PK and FXII activation on HUVEC. Further, only normal human and FXII-deficient plasmas, not PK-deficient plasma, had the ability to generate proteolytic activity when incubated over endothelial cells. In a purified system, maximal PK activation was measured after a 10-15 min incubation depending upon the concentration of reactants. When FXII was added with the PK, maximal activation occurred within 7.5-10 min. In normal human or FXII-deficient plasmas, but not in PK-deficient plasma, maximal activation was seen in 4 min. These data indicate that on HUVEC, unlike artificial surfaces, PK activation when bound to HK is the initiating activation event in this system. FXII activation is secondary to PK activation and contributes to the extent of measured enzymatic activity. These data challenge the accepted dogmas of "contact activation" and suggest that on biologic membranes a new notion as to how this system is activated needs to be considered.

Identification of cytokeratin 1 as a binding protein and presentation receptor for kininogens on endothelial cells

A kininogen binding protein(s), a putative receptor, was identified on endothelial cells. A 54-kDa protein was isolated by a biotin-high molecular mass kininogen (HK) affinity column that, on aminoterminal sequencing of tryptic digests, was identified as cytokeratin 1. Multiple antibodies directed to cytokeratin 1 reacted with a 54-kDa band on immunoblot of lysates of endothelial cells. On laser scanning confocal microscopy, cytokeratin 1 antigen was found on the surface of endothelial cells. Cytokeratin 1 antigen also was detected on endothelial cell membranes by flow cytometry. Moreover, an antipeptide antibody to a sequence unique to cytokeratin 1 also specifically bound to nonpermeabilized endothelial cells. Biotin-HK specifically bound to cytokeratin only in the presence of Zn2+, and cytokeratin blocked biotin-HK binding to endothelial cells. Further, HK and low molecular mass kininogen, but not factor XII, blocked biotin-HK binding to cytokeratin, and peptides of each cell binding region of HK on domains 3,4, and 5 blocked biotin-HK binding to cytokeratin. gC1qR and soluble urokinase-like plasminogen activator receptor also inhibited biotin-HK binding to cytokeratin. These investigations identify a new function for cytokeratin 1 as a kininogen binding protein. Cytokeratins, members of the family of intermediate filament proteins, may represent a new class of receptors.

High molecular weight kininogen regulates prekallikrein assembly and activation on endothelial cells: a novel mechanism for contact activation

The consequences of assembling the contact system of proteins on the surface of vascular cells has received little study. We asked whether assembly of these proteins on the surface of cultured human endothelial cells (HUVECs) results in the activation of prekallikrein (PK) and its dependent pathways. Biotinylated PK binds specifically and reversibly to HUVECs in the presence of high molecular weight kininogen (HK) (apparent Kd of 23 +/- 11 nmol/L, Bmax of 1.7 +/- 0.5 x 10(7) sites per cell [mean +/- SD, n = 5 experiments]). Cell-associated PK is rapidly converted to kallikrein. Surprisingly, the activation of cell-associated HK.PK complexes is entirely independent of exogenous factor XII (Km = 30 nmol/L, Vmax = 12 +/- 3 pmol/L/min in the absence v Km = 20 nmol/L, Vmax = 9.2 +/- 2.1 pmol/L/min in the presence of factor XII). Rather, kallikrein formation is mediated by an endothelial cell-associated, thiol protease. Cell-associated HK is proteolyzed during the course of prekallikrein activation, releasing kallikrein from the surface. Furthermore, activation of PK bound to HK on HUVECs promotes kallikrein-dependent activation of pro-urokinase, resulting in the formation of plasmin. These results indicate the existence of a previously undescribed, factor XII-independent pathway for contact factor activation on HUVECs that regulates the production of bradykinin and may contribute to cell-associated plasminogen activation in vivo.

Elemental iron does repress transferrin, haemopexin and haemoglobin receptor expression in Haemophilus influenzae

The iron repressible nature of Haemophilus influenzae transferrin binding proteins suggests a regulatory role for elemental iron in their expression. The existence of a Haemophilus ferric uptake repressor (Fur) binding motif identified in the promoter region of both tbpA and tbpB further supports this hypothesis. However, a recent study using brain heart infusion growth medium suggested that transferrin binding protein synthesis in H. influenzae was haem-rather than iron-regulated. The present study re-investigates this observation and using a chemically defined medium, we demonstrate that elemental iron haem or protoporphyrin IX can each regulate Haemophilus influenzae transferrin, haemopexin and haemoglobin receptor expression.

Conservation and antigenic cross-reactivity of the transferrin-binding proteins of Haemophilus influenzae, Actinobacillus pleuropneumoniae and Neisseria meningitidis

Haemophilus influenzae acquires iron from the iron-transporting glycoprotein transferrin via a receptor-mediated process. This involves two outer-membrane transferrin-binding proteins (Tbps) termed Tbp1 and Tbp2 which show considerable preference for the human form of transferrin. Since the Tbps are attracting considerable attention as potential vaccine components, we used transferrin affinity chromatography to examine their conservation amongst 28 H. influenzae type b strains belonging to different outer-membrane-protein subtypes as well as six non-typable strains. Whole cells of all type b and non-typable strains examined bound human transferrin; whilst most strains possessed a Tbp1 of approximately 105 kDa, the molecular mass of Tbp2 varied from 79 to 94 kDa. Antisera raised against affinity-purified native H. influenzae Tbp1/Tbp2 receptor complex cross-reacted on Western blots with the respective Tbps of all the Haemophilus strains examined. When used to probe Neisseria meningitidis Tbps, sera from each of four mice immunized with the Haemophilus Tbp1/2 complex recognized the 68 kDa Tbp2 of N. meningitidis strain B16B6 but not the 78 kDa Tbp2 of N. meningitidis strain 70942. Serum from one mouse also reacted weakly with Tbp1 of strain B16B6. Apart from a weak reaction with the Tbp2 of a serotype 5 strain, this mouse antiserum failed to recognize the Tbps of the porcine pathogen A. pleuropneumoniae. However, a monospecific polyclonal antiserum raised against the denatured Tbp2 of Neisseria meningitidis B16B6 recognized the Tbps of all Haemophilus and Actinobacillus strains examined. Since H. influenzae forms part of the natural flora of the upper respiratory tract, human sera were screened for the presence of antibodies to the Tbps. Sera from healthy adults contained antibodies which recognized both Tbp1 and Tbp2 from H. influenzae but not N. meningitidis. Convalescent sera from meningococcal meningitis patients contained antibodies which, on Western blots, recognized the Tbps2s of both pathogens. These data demonstrate the existence of shared epitopes on the Tbps of H. influenzae, N. meningitidis and A. pleuropneumoniae despite their transferrin species specificity.

Bradykinin and its metabolite, Arg-Pro-Pro-Gly-Phe, are selective inhibitors of alpha-thrombin-induced platelet activation

BACKGROUND

Plasma kininogens are selective inhibitors of alpha-thrombin activation of platelets and endothelial cells. In the present study, we localized the alpha-thrombin inhibitory sequence of kininogens and describe its mechanism of action.

METHODS AND RESULTS

Bradykinin and an analogue, MKRPPGFSPFRSSRIG, inhibited alpha-thrombin-induced platelet aggregation and secretion with an IC50 of 0.25 and 1 mmol/L and of 0.23 and 0.5 mmol/L, respectively. The minimal inhibitory peptide was RPPGF. Bradykinin and its analogues did not inhibit ADP-, collagen-, U46619-, or SFLLRN-induced platelet activation or the ability of alpha-thrombin to cleave chromogenic substrates, clot fibrinogen, or block alpha-thrombin binding to platelets. Bradykinin, MKRPPGFSPFRSSRIG, and RPPGF abolished alpha-thrombin-induced (1 nmol/L) calcium mobilization. On flow cytometry, bradykinin and MKRPPGFSPFRSSRIG blocked alpha-thrombin from removing the epitope of its cleavage site on the cloned thrombin receptor. Furthermore, peptide RPPGF or high-molecular-weight kininogen prevented alpha-thrombin from cleaving the thrombin receptor peptide, NATLDPRSFLLR, between arginine and serine.

CONCLUSIONS

These results indicate that bradykinin and its metabolites are selective antithrombins by preventing alpha-thrombin cleavage of the cloned thrombin receptor between arginine-41 and serine-42. These newly recognized antithrombin peptides, which are termed thrombostatins, contribute to the cardioprotective nature of kinins.

Conformational changes in low molecular weight kininogen alters its ability to bind to endothelial cells

The plasma kininogens, high (HK) and low (LK) molecular weight kininogens, are the parent proteins for bradykinin, a potent vasoactive peptide that locally influences vascular biology. Binding of both HK and LK to the endovascular wall contributes to bradykinin delivery. Recently, we found one preparation of LK (LKd) which had reduced inhibition of biotin-HK binding to endothelium. The functional defect in LKd was not merely due to bradykinin loss because two preparations of bradykinin-free LK blocked biotin-HK binding. However, using two different particular monoclonal antibodies to bradykinin, LKd, but no other preparation of LK, had its epitope to bradykinin exposed on non-reduced samples on immunoblot. These data suggested that LKd had an altered conformation which exposed the amino terminal arginine of bradykinin to antigenic detection. The altered conformation of LKd allowed it to be more susceptible to trypsin proteolysis. On circular dichroism, the percentage of alpha-helix was significantly increased, indicating an alteration in the protein. This alteration in LKd was not due to a loss of molecular mass of the protein. On laser desorption mass spectroscopy, the molecular mass of LKd was similar to the other preparations of LK. Investigations were performed to ascertain the mechanism by which LKd had altered ability to bind to cells. LKd was found to be proteolyzed by an unknown protease at the beginning of domain 2 between threonine119 and alanine120. Reduction of functional LK with dithiothreitol to expose its bradykinin epitope did not produce the LKd defect. Proteolysis of functional LK with plasma kallikrein, elastase followed by plasma kallikrein, chymotrypsin, or bromelain also did not produce the defect seen in LKd. These combined data indicated that LK maintains a particular conformation that allows the protein to orient itself such that it can bind to endothelial cells. Proteolysis in the surface exposed region between domains 1 and 2 probably allows for the protein to unfold and contributes to its lost ability to bind to endothelial cells.

Mapping the cell binding site on high molecular weight kininogen domain 5

Investigations mapped the region(s) on the light chain of high molecular weight kininogen (HK) that participates in cell binding. Sequential and overlapping peptides of domain 5 (D5H) were synthesized to determine its cell binding site(s). Three peptides from non-overlapping regions on D5H were found to inhibit biotin-HK binding to endothelial cells. Peptides GKE19 and HNL 21 weakly inhibited biotin-HK binding with IC50 of 792 and 215 microM, respectively. Peptide HKH20 inhibited biotin-HK binding with an IC50 of 0.2 microM. Two peptides, GGH18 and HVL24, which overlapped HKH20, also inhibited biotin-HK binding to endothelial cells with IC50 values of 108 and 0.8 microM, respectively. Biotinylated HKH20 directly bound to endothelial cells. HK and HKH20 bound at or near the same site on endothelial cells because HK inhibited biotin-HKH20 binding (IC50 = 0.2 microM). A polyclonal anti-HKH20 antibody also blocked biotin-HK binding. Peptides HKH20 and HVL24 and anti-HKH20 antibody also inhibited the procoagulant activity of plasma HK. These data indicated that the cell and artificial surface binding sites on D5H overlap. The orientation of HK on endothelial cells may be critical for the assembly and activation of contact system enzymes and the expression of kininogen's anti-thrombin activity.

Identification of an endothelial cell binding site on kininogen domain D3

High and low molecular mass kininogen, two multidomain plasma proteins, bind to endothelial cells, platelets, and neutrophils in the intravascular compartment. The specific cell attachment site on their common heavy chain is mediated by domain-3, a cystatin-like structure with inhibitory capacity for papain-like proteinases (Jiang, Y., Müller-Esterl, W., and Schmaier, A. H. (1992) J. Biol. Chem. 267, 3712-3717). In this report, the domain-3 cell binding site is determined by an antibody-directed strategy. The epitope of monoclonal antibody HKH15, which binds to domain-3 and blocks the binding of kininogens to platelets and endothelial cells, was mapped using seven synthetic peptides, which span the entire domain-3 sequence. One peptide, LDC27, specifically bound to HKH15. Fine mapping of the epitope of HKH15 revealed that a minimal 13-residue segment in LDC27, named CNA13, is the antibody binding site. LDC27 and CNA13 inhibited biotinylated high molecular mass kininogen binding to endothelial cells with apparent IC50 values of 60.3 +/- 12 and 113.3 +/- 63.7 microM, respectively. Carboxymethylated papain and affinity-purified anti-LDC27 polyclonal antibodies also inhibited the binding of biotinylated high molecular mass kininogen to endothelial cells with an apparent IC50 of 1.04 microM and 59 nM, respectively. Biotinylated LDC27 itself directly bound to endothelial cells, and domain-3 inhibited biotinylated LDC27 binding to human umbilical vein endothelial cells with an IC50 of 41 nM. Using the crystalline structure of cystatin to computer model domain-3, LDC27 and CNA13 were located in the second hairpin loop of the reactive site of cystatin-like proteins (Bode, W., Engh, R., Musil, D., Thiele, U. Huber, R., Karshikov, A., Brzin, J., Kos, J., and Turk, V. (1988) EMBO J. 7, 2593-2599). These results indicate that the major endothelial cell attachment site on kininogen domain-3 is located on its carboxyl-terminal portion and that it overlaps its cysteine protease inhibitory region.

High-molecular-weight kininogen is exclusively membrane bound on endothelial cells to influence activation of vascular endothelium

An important biologic function of high-molecular-weight kininogen (HK) is to deliver bradykinin (BK) to its cellular receptors. Internalization and degradation of HK may provide a mechanism by which endothelial cells modulate the production of BK and control its activities. Therefore, we investigated the binding and subsequent distribution of biotinylated-HK (biotin-HK) associated with human umbilical vein endothelial cells (HUVEC). HUVEC bound 3 to 4 times more HK and with greater avidity at 1 to 3 hours at 37 degrees C than at 4 degrees C (Bmax = 1.0 +/- 0.02 x 10(7) molecules/cell, kd = 7 +/- 3 nmol/L v Bmax = 2.6 +/- 0.2 x 10(6) molecules/cell, kd = 46 +/- 8 nmol/L). However, there was no evidence that the difference was caused by internalization of HK at the higher temperature. First, the same amount of biotin-HK was associated with nonpermeabilized and permeabilized HUVEC using buffers containing 20 to 50 mumol/L zinc ion in the absence or presence of 2 mmol/L calcium ion. Second, binding of biotin-HK to HUVEC was approximately 92% reversible at 1 hour when the cells were maintained at both 37 degrees C and 4 degrees C. Third, neither chloroquine nor primaquine altered the amount of biotin-HK bound to HUVEC. Fourth, biotin-HK bound to HUVEC was almost completely removed by pronase. Fifth, the nonpermeable dye, crystal violet, almost completely quenched the fluorescence signal emitted by HUVEC-associated fluorescein isothiocyanate (FITC) HK. Finally, the localization of HUVEC-bound FITC-HK was restricted to the membrane as shown by laser scanning confocal microscopy. The expression of HK binding sites had an absolute requirement for metabolic energy, but was not dependent on new protein synthesis. Membrane-bound HK contributed to the anticoagulant nature of endothelial cells by blocking human alpha-thrombin binding and its resultant induction of prostacyclin formation. These studies indicate that HK is not internalized by HUVEC, but remains primarily on cell surfaces to be accessible for BK liberation and to modulate the binding and actions of alpha-thrombin.

Factor IXa inhibition by protease nexin-2/amyloid beta-protein precursor on phospholipid vesicles and cell membranes

Protease nexin-2/amyloid beta-protein precursor (PN-2/A beta PP) is a Kunitz-type protease inhibitor which has been shown to be a tight-binding inhibitor of enzymes, factors XIa and IXa (FIXa), suggesting a role for this protein in hemostasis. Since coagulant reactions are modulated on biologic surfaces, we investigated how 25:75 (mol/mol) phosphatidylserine/phosphatidylcholine vesicles (PSPC), thrombin-activated platelets, or umbilical vein endothelial cells influence inactivation of FIXa by PN-2/A beta PP. The Km of human or porcine FIXa activation of human factor X in the presence of PSPC, activated platelets, or endothelial cells in the absence or presence of thrombin-activated factor VIII (FVIIIa) was similar, (0.05-0.39 microM). The presence of FVIIIa increased the catalytic efficiency (kcat/Km ratio) of human and porcine factor IXa's activation of factor X 4952-406-fold, respectively. In the presence of PSPC, the Ki of human and porcine FIXa inhibition by PN-2/A beta PP was Ki = 1.9 x 10(-9) M and 5.8 x 10(-9) M, respectively. After the addition of FVIIIa to the reaction, the Ki for both human and porcine FIXa inhibition by PN-2/A beta PP on PSPC increased 13- and 4-fold to Ki = 2.5 x 10(-8) M and 2.4 x 10(-8) M, respectively. These Ki for inhibition of human FIXa on phospholipid vesicles by PN-2/A beta PP were similar when factor X activation was measured by chromogenic or activation peptide release assays. FVIIIa reduced the inhibition of FIXa by PN-2/A beta PP only in the presence of PSPC.(ABSTRACT TRUNCATED AT 250 WORDS)

The carboxyl terminus of bradykinin and amino terminus of the light chain of kininogens comprise an endothelial cell binding domain

Bradykinin (BK), a potent vasoactive nonapeptide formed by proteolytic cleavage of kininogen, mediates its activity by binding to specific cell surface receptors. Delivery of BK to these receptors is limited by cell-bound and plasma kininases that degrade BK to inactive fragments. Binding of its parent compound, kininogen, to specific endothelial cell receptors may provide an environment in which the degradation of BK by kininases is restricted. The determinants that mediate kininogen binding to endothelial cells have not been fully elucidated. The present studies suggest that part of BK and the amino-terminal amino acids of kininogens' common light chain constitute part of this recognition sequence. Human umbilical vein endothelial cells (HUVEC) in culture at 37 degrees C express 2-3-fold more binding sites for biotinylated high molecular weight kininogen (biotin-HK) containing BK than for biotin-HK from which BK has been liberated by plasma kallikrein. Binding of BK-free biotin-HK was not restored by preincubating HUVEC with BK, arguing against the possibility that BK released from biotin-HK stimulated expression of additional HK receptors. The extent of biotin-HK binding to HUVEC at 37 degrees C directly correlated with the amount of BK retained within the protein. Four lines of evidence suggest that part of BK and the amino terminus of the light chain of kininogens are part of the sequence recognized by the endothelial cell kininogen receptor. First, monoclonal antibodies to the carboxyl terminus of BK (MBK3) and the common light chains of the kininogens (HKL6, HKL8) inhibited biotin-HK binding to HUVEC. Second, a synthetic, dimeric bradykinin receptor antagonist blocked biotin-HK (IC50 = 9 microM) binding to HUVEC as did two synthetic tissue kallikrein inhibitors modeled after the carboxyl-terminal sequence of BK. Third, synthetic peptides containing the carboxyl-terminal portion of BK and the amino terminus of kininogens' common light chain, MKRPPGFSPFRSSRIG and GFSPFRSSRIG, blocked binding of biotin-HK (IC50 = 2-3 mM), whereas an overlapping peptide, SPFRSSRIGEIKEETT, at 5 mM and a scrambled peptide, FSGPKRSPIMGRPSFR, did not. Fourth, biotinylated GMKRPPGFSPFRSSRIG specifically bound to HUVEC, and its binding was blocked by HK. Since the presence of the nonapeptide BK in HK contributes to maximal binding of HK to HUVEC, there is a novel type of BK receptor in which part of the nonapeptide is recognized within the context of its parent molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding of fibrin fragments to one-chain and two-chain tissue-type plasminogen activator

To explore whether fibrin fragments have binding affinity for the tissue-type plasminogen activator (t-PA) molecule, the interactions were studied of (DD)E complex and fragments DD, E1, and E3 with one-chain and two-chain t-PA. For this purpose, a solid-phase binding assay was developed using microtiter plates with nitrocellulose filters. It was found that (DD)E complex and fragments DD and E3 retained the t-PA binding function of the parent fibrin molecule, thus demonstrating that t-PA binds to both the D and E domains of fibrin. Unexpectedly, fragment E1 did not bind t-PA. Fibrin fragments had different binding properties for one-chain and two-chain t-PA. (DD)E complex had the highest and fragment E3 the lowest affinity for one-chain t-PA, both binding curves being consistent with one class of binding sites. However, binding of the fragments with two-chain t-PA was distinguished by more than one class of binding sites, with fragment E3 having the highest affinity for this form of the activator. epsilon-Aminocaproic acid, even at 50 mmol/L concentration, had only minimal effect on binding of (DD)E complex or fragment DD to either one-chain or two-chain t-PA. The potentiating effect of fibrin fragments on plasminogen activation by t-PA was measured by a chromogenic substrate assay. Fragment DD was the most effective stimulator of plasminogen activation by t-PA. In conclusion, (DD)E complex and fragment DD retained most of the regulatory functions of fibrin, which included t-PA binding and t-PA-mediated acceleration of plasminogen activation to plasmin.

Differences between binding of one-chain and two-chain tissue plasminogen activators to non-cross-linked and cross-linked fibrin clots

Interaction of tissue plasminogen activator (t-PA) with fibrin plays a key role in regulation of plasminogen activation and clot dissolution. Previous investigations of t-PA-fibrin interaction, using incorporation of t-PA into polymerizing fibrin clots, have suggested that no significant differences exist in the binding of one-chain or two-chain t-PA to non-cross-linked or cross-linked fibrin. In the present study, binding of 125I-labeled and affinity-purified one-chain and two-chain forms of t-PA to preformed non-cross-linked or cross-linked, sonicated suspension of fibrin was investigated. Interaction of one-chain t-PA with cross-linked fibrin involved a single type of binding site with dissociation constant (kd) of 0.58 mumol/L and a stoichiometry (n) of 1.5. Interaction of one-chain t-PA with non-cross-linked fibrin, however, involved two classes of binding sites with dissociation constants of 0.32 and 1.5 mumol/L and corresponding number of binding sites equal to 0.57 and 2.0, respectively. In contrast to the binding of one-chain t-PA to cross-linked fibrin by a limited number of sites, two-chain t-PA appeared to involve a considerably greater number of sites (minimum six) whose dissociation constant was 3.2 mumol/L. Interaction of two-chain t-PA with non-cross-linked fibrin also showed the presence of many binding sites (minimum seven) with approximate dissociation constant of 6.4 mumol/L, as well as a few (n = 0.012) high-affinity sites with a kd of 0.011 mumol/L epsilon-Aminocaproic acid did not completely reverse the binding of either one-chain t-PA or two-chain t-PA to fibrin. The present findings suggest that the fibrin-binding properties of t-PA undergo considerable changes on proteolytic conversion from one-chain to two-chain t-PA, catalyzed under physiologic conditions by plasmin. The cleavage of one-chain t-PA to two-chain t-PA allows to bind to a large number of low-affinity binding sites on fibrin. Cross-linking of fibrin by factor XIIIa results in masking of high-affinity binding sites that are present in non-cross-linked fibrin. We propose that both plasmin and factor XIIIa play an important regulatory role in dissolution of blood clots by modulating t-PA-fibrin interaction.

Ectopic pregnancy: a seven-year survey

Seventy-five patients with ectopic pregnancy were treated at Jordan University Hospital (JUH) during a 7-yr period from January 1976 to December 1982. The ratio of ectopic pregnancies to deliveries was 1 to 162. The most common symptoms were: abdominal pain, 96%; amenorrhea, 69.3%; vaginal bleeding, 60%. No patients with pelvic inflammatory disease were found. An intrauterine contraceptive device was present in 14.6% of the patients and 10.6% of the cases had previous pelvic surgery. Culdocentesis gave false negative results in 16.7% of the patients. The treatment of choice was salpingectomy. There were no maternal deaths in this series.

Management of premature rupture of the membranes

A 14-month prospective study of patients with premature rupture of the membranes was performed. The purpose of the study was to determine the effect of different therapeutic regimens for management of premature rupture of the membranes (PROM) on perinatal morbidity and mortality, as well as on maternal morbidity. Maternal and fetal risk factors and predictive factors in pregnancy outcome were prospectively defined. In patients with PROM whose gestational age was 34 weeks or more, induction within the first 12 hours of membrane rupture resulted in minimal maternal and fetal morbidity and mortality. Patients with gestational age of less than 34 weeks had an improved maternal and fetal outcome if left alone until spontaneous labor or 34 weeks' gestation was reached unless signs of sepsis developed. Respiratory distress syndrome (RDS) was the leading cause of morbidity and mortality in the infants of patients who delivered prematurely due to premature rupture of the membranes. Incidence of fetal infection was significantly less than that of RDS as a cause for fetal morbidity and mortality.