Factor V Leiden and recurrent miscarriage-prospective outcome of untreated pregnancies

BACKGROUND

Some cases of recurrent miscarriage and later pregnancy complications have a thrombotic basis. Factor V Leiden is a common thrombophilic mutation.

METHODS

The prospective outcome of untreated pregnancies amongst 25 women heterozygous for the Factor V Leiden allele who had a history of either recurrent early miscarriages only (three or more miscarriages at <12 weeks gestation; n = 19) or of late miscarriage (>12 weeks gestation; n = 9) was studied. Control groups of women with a similar pregnancy history but who had a normal Factor V genotype were also studied.

RESULTS

The live birth rate was significantly lower amongst women with a history of recurrent early miscarriage who carried the Factor V Leiden allele (6/16; 37.5%) compared with that amongst those with a normal Factor V genotype (106/153; 69.3%; odds ratio 3.75, 95% confidence intervals 1.3-10.9). The live birth rate was 11.1% (1/9) amongst those with a history of late miscarriage carrying the Factor V Leiden allele and 48.9% (22/45) amongst those with a normal Factor V genotype.

CONCLUSIONS

Attention should be directed at screening women with recurrent miscarriage associated with placental thrombosis for Factor V Leiden and a policy of targeted thromboprophylaxis during future pregnancies should be assessed in the form of a randomized controlled trial.

In vitro intestinal permeability of factor Xa inhibitors: influence of chemical structure on passive transport and susceptibility to efflux

PURPOSE

To study the in vitro intestinal permeability of a number of newly synthesised factor Xa inhibitors to better understand the poor oral absorption of these compounds.

METHODS

The bidirectional transport of the fXa inhibitors was studied in the Caco-2 cell model and isolated rat ileal tissue. An attempt was made to characterize efflux mechanisms with the help of commonly used substrates and inhibitors of various transport proteins. In addition, the transport of the fXa inhibitors was studied in MDCK cells transfected with the human MDR1 gene and expressing large amounts of P-glycoprotein (Pgp).

RESULTS

The in vitro absorptive permeability was low for all but one of the fXa inhibitors. For compounds with non-substituted amidine, a charge (due to ionisation at neutral pH) may have resulted in poor membrane partitioning. Neutral compounds with substituted amidines were effluxed from the epithelial cells. The significance of the secretion process was illustrated by the results obtained for a neutral analogue showing high absorptive Caco-2 cell permeability that was not obviated by efflux. Transport inhibition studies in Caco-2 and permeability studies in the MDR1-transfected MDCK cells consistently showed that Pgp is not involved in the secretion of fXa inhibitors. Besides efflux, metabolic liability limited the permeation of the neutral lipophilic analogues with a carbamate ester.

CONCLUSIONS

Poor intestinal permeability may be an important factor in the incomplete oral absorption of the bisbenzimidazole-type fXa inhibitors. Poor permeability may be related to poor membrane partitioning for hydrophilic analogues, whereas susceptibility to efflux transports and gastro-intestinal enzymatic degradation may limit the permeability of some of the neutral less hydrophilic derivatives.

Metformin therapy in the management of polycystic ovary syndrome: endocrine, metabolic and reproductive effects

Polycystic ovary syndrome (PCOS) is a convergence of multisystem endocrine derangements. Impairment in insulin metabolism is a prominent feature of the syndrome and appears to play a key pathogenetic role precipitating the cascade of other disorders associated with PCOS. Recent studies report that insulin-sensitizing agents, such as metformin, reduce hyperinsulinemia, reverse the endocrinopathy of PCOS and normalize endocrine, metabolic and reproductive functions, leading to the resumption of menstrual cyclicity and ovulation. In this review, we report the most recent evidence regarding metformin usage in women with PCOS.

Optimization of a screening lead for factor VIIa/TF

The structure-based design and progression of a screening lead to a 3nM factor VIIa/TF inhibitor with improved selectivity versus related enzymes is described.

Development of serine protease inhibitors displaying a multicentered short (<2.3 A) hydrogen bond binding mode: inhibitors of urokinase-type plasminogen activator and factor Xa

Novel scaffolds that bind to serine proteases through a unique network of short hydrogen bonds to the catalytic Ser195 have been developed. The resulting potent serine protease inhibitors were designed from lead molecule 2-(2-hydroxyphenyl)1H-benzoimidazole-5-carboxamidine, 6b, which is known to display several modes of binding. For instance, 6b can recruit zinc and bind in a manner similar to that reported by bis(5-amidino-2-benzimidazolyl)methane (BABIM) (Nature 1998, 391, 608-612).(1) Alternatively, 6b can bind in the absence of zinc through a multicentered network of short (<2.3 A) hydrogen bonds. The lead structure was optimized in the zinc-independent binding mode toward a panel of six human serine proteases to yield optimized inhibitors such as 2-(3-bromo-2-hydroxy-5-methylphenyl)-1H-indole-5-carboxamidine, 22a, and 2-(2-hydroxybiphenyl-3-yl)-1H-indole-5-carboxamidine, 22f. Structure-activity relationships determined that, apart from the amidine function, an indole or benzimidazole and an ortho substituted phenol group were also essential components for optimal potency. The affinities (K(i)) of 22a and 22f, for example, bearing these groups ranged from 8 to 600 nM toward a panel of six human serine proteases. High-resolution crystal structures revealed that the binding mode of these molecules in several of the enzymes was identical to that of 6b and involved short (<2.3 A) hydrogen bonds among the inhibitor hydroxyl oxygen, Ser195, and a water molecule trapped in the oxyanion hole. In summation, novel and potent trypsin-like serine protease inhibitors possessing a unique mode of binding have been discovered.

Green fluorescent protein-Dal80p illuminates up to 16 distinct foci that colocalize with and exhibit the same behavior as chromosomal DNA proceeding through the cell cycle of Saccharomyces cerevisiae

Four GATA family DNA binding proteins mediate nitrogen catabolite repression-sensitive transcription in Saccharomyces cerevisiae. Gln3p and Gat1p are transcriptional activators, while Dal80p and Deh1p repress Gln3p- and Gat1p-mediated transcription by competing with these activators for binding to DNA. Strong Dal80p binding to DNA is thought to result from C-terminal leucine zipper-mediated dimerization. Many Dal80p binding site-homologous sequences are relatively evenly distributed across the S. cerevisiae genome, raising the possibility that Dal80p might be able to "stain" DNA. We demonstrate that cells containing enhanced green fluorescent protein-Dal80p (EGFP-Dal80p) exhibit up to 16 fluorescent foci that colocalize with DAPI (4',6'-diamidino-2-phenylindole)-positive material and follow DNA movement through the cell cycle, suggesting that EGFP-Dal80p may indeed be useful for monitoring yeast chromosomes in live cells and in real time.

Development of potent and selective factor Xa inhibitors

The development of potent and selective small molecule inhibitors of factor Xa is described.

Involvement of male genitalia in leprosy

Four hundred and sixty-seven male patients with leprosy were screened for genital involvement. Genital lesions were observed in 6.6% of all male cases of leprosy. They were seen most frequently in lepromatous leprosy (25.8%), followed by borderline lepromatous (13.3%) and borderline tuberculoid (1.4%) leprosy.

Factor V Leiden and acquired activated protein C resistance among 1000 women with recurrent miscarriage

Activated protein C (APC) resistance, both in its congenital form, due to the factor V Leiden mutation, and in its acquired form, are important risk factors for systemic venous thrombosis. In view of the suspected thrombotic aetiology of some cases of recurrent miscarriage, the prevalence of APC resistance was determined among 1111 consecutive Caucasian women with a history of either recurrent early miscarriage (three or more consecutive pregnancy losses at <12 weeks gestation; n = 904) or a history of at least one late miscarriage (>12 weeks gestation; n = 207). A control group of 150 parous Caucasian women with no previous history of adverse pregnancy outcome was also studied. Acquired APC resistance was significantly more common among both women with recurrent early miscarriage (8.8%: 80/904; P = 0.02) and those with late miscarriage (8.7%: 18/207; P = 0.04) compared with controls (3.3%: 5/150). In contrast, the frequency of the factor V Leiden allele was similar among (i) women with recurrent early miscarriage (3.3%:60/1808; 58 heterozygotes and one homozygote), (ii) those with late miscarriage (3.9%:16/414; 14 heterozygotes and one homozygote) and (iii) the control group (4.0%:12/300; 12 heterozygotes). Acquired but not congenital APC resistance (due to the factor V Leiden mutation) is associated with both early and late miscarriage.

A novel serine protease inhibition motif involving a multi-centered short hydrogen bonding network at the active site

We describe a new serine protease inhibition motif in which binding is mediated by a cluster of very short hydrogen bonds (<2.3 A) at the active site. This protease-inhibitor binding paradigm is observed at high resolution in a large set of crystal structures of trypsin, thrombin, and urokinase-type plasminogen activator (uPA) bound with a series of small molecule inhibitors (2-(2-phenol)indoles and 2-(2-phenol)benzimidazoles). In each complex there are eight enzyme-inhibitor or enzyme-water-inhibitor hydrogen bonds at the active site, three of which are very short. These short hydrogen bonds connect a triangle of oxygen atoms comprising O(gamma)(Ser195), a water molecule co-bound in the oxyanion hole (H(2)O(oxy)), and the phenolate oxygen atom of the inhibitor (O6'). Two of the other hydrogen bonds between the inhibitor and active site of the trypsin and uPA complexes become short in the thrombin counterparts, extending the three-centered short hydrogen-bonding array into a tetrahedral array of atoms (three oxygen and one nitrogen) involved in short hydrogen bonds. In the uPA complexes, the extensive hydrogen-bonding interactions at the active site prevent the inhibitor S1 amidine from forming direct hydrogen bonds with Asp189 because the S1 site is deeper in uPA than in trypsin or thrombin. Ionization equilibria at the active site associated with inhibitor binding are probed through determination and comparison of structures over a wide range of pH (3.5 to 11.4) of thrombin complexes and of trypsin complexes in three different crystal forms. The high-pH trypsin-inhibitor structures suggest that His57 is protonated at pH values as high as 9.5. The pH-dependent inhibition of trypsin, thrombin, uPA and factor Xa by 2-(2-phenol)benzimidazole analogs in which the pK(a) of the phenol group is modulated is shown to be consistent with a binding process involving ionization of both the inhibitor and the enzyme. These data further suggest that the pK(a) of His57 of each protease in the unbound state in solution is about the same, approximately 6.8. By comparing inhibition constants (K(i) values), inhibitor solubilities, inhibitor conformational energies and corresponding structures of short and normal hydrogen bond-mediated complexes, we have estimated the contribution of the short hydrogen bond networks to inhibitor affinity ( approximately 1.7 kcal/mol). The structures and K(i) values associated with the short hydrogen-bonding motif are compared with those corresponding to an alternate, Zn(2+)-mediated inhibition motif at the active site. Structural differences among apo-enzymes, enzyme-inhibitor and enzyme-inhibitor-Zn(2+) complexes are discussed in the context of affinity determinants, selectivity development, and structure-based inhibitor design.

Perspectives on factor Xa inhibition

Blood coagulation involves a complex cascade of enzymatic reactions, ultimately generating fibrin, the basis of all blood clots. This cascade is comprised of two arms, the intrinsic and extrinsic pathways which converge at factor Xa to form the common pathway. Factor Xa activates prothrombin to thrombin, which in turn catalyzes the conversion of fibrinogen to fibrin. Recently, both natural and synthetic factor Xa inhibitors have shown promising pharmacological effects in animal models of thrombosis. Accordingly, factor Xa has emerged as a compelling target for pharmacological intervention and much recent effort has focused on selective and potent inhibition of this key enzyme. Factor Xa and other enzymes in the coagulation cascade belong to the trypsin-like serine protease family, the various members of which are involved in numerous physiological functions in the body. Hence, to avoid toxicity and adverse side effects, it is important to selectively inhibit the target enzyme. Achieving the needed selectivity has proved challenging due to the high degree of structural homology around the active site of this class of enzymes. This article provides a brief review of the strategies currently being employed to develop oral anticoagulants and, more specifically, the structural features of protein-ligand binding that have been utilized to achieve potency and selectivity toward factor Xa. Additionally, selected lead molecules will be discussed to highlight binding motifs used to attain both potency and selectivity in drug candidates.

Childhood cutaneous tuberculosis: a study over 25 years from northern India

AIMS

We undertook this study to analyse the pattern of childhood cutaneous tuberculosis prevailing in northern India over the past 25 years and to highlight differences from and similarities to adult tuberculosis.

MATERIALS AND METHODS

Clinical records of children with cutaneous tuberculosis who attended the Nehru Hospital attached to the Postgraduate Institute of Medical Education and Research, Chandigarh, India, between January 1975 to December 1999 were analysed.

RESULTS

Four hundred and two patients with cutaneous tuberculosis were examined during the 25-year period of observation. These patients formed 0.1% of the total dermatology outpatients. Seventy-five (18.7%) of these 402 cases were children (</= 16 years). There were 32 (42.7%) boys and 43 (57.3%) girls with a boy : girl ratio of 0.74 : 1. The majority of the children, 41 (54.7%) were in the 10-14 years age group. There was no significant boy or girl preponderance in any group other than in scrofuloderma (SFD), where girls significantly outnumbered boys at all ages. Of the various patterns of cutaneous tuberculosis seen, 40 (53.3%) had SFD, 30 (40.0%) had lupus vulgaris (LV), 3 (4.0%) had tuberculosis verrucosa cutis (TVC), 1 (1.3%) child each had tuberculids and tubercular gumma. No child had a tubercular chancre or acute miliary cutaneous tuberculosis. The neck was the commonest site afflicted with SFD and the face was the commonest site affected with LV. No child had generalized lymphadenopathy. Eighteen (60.0%) of the 30 children with LV had regional lymphadenopathy of which 15 (83.3%) had localized disease and 3 (16.7%) had disseminated disease. Of the 16 children with systemic organ involvement, 12 (75.0%) had regional lymphadenopathy. Of the 62 children in whom the data regarding vaccination status was available, 31 (50.0%) had been vaccinated and 31 (50.0%) had not. Among the vaccinated group no child had disseminated disease. Three (9.7%) children in the nonvaccinated group had disseminated disease. Information regarding Mantoux reactivity was available in 71 (94.7%) children, 61 (86.0%) with localized disease and 10 (14.1%) with disseminated disease. Of the 61 children with localized disease, 56 (91.8%) were Mantoux positive and of the 10 children with disseminated disease, only 5 (50.0%) were Mantoux positive (> 10 mm). Histopathologic reports were available for evaluation in all 75 children. Out of 30 cases of LV, 24 (80%) showed classical tuberculous histology. In contrast, out of 40 cases with SFD, only 19 (47.5%) showed classical histology. Classical tuberculous histology was noted in all 3 (100%) cases of TVC and 1 (100%) case each with tuberculids and gumma. Tubercle bacilli could be demonstrated in 4/30 (13.3%) cases with LV and 9/40 (22.5%) cases with SFD. Systemic involvement was seen in 16 (21.3%) children, of whom 3 (18.8%) had LV and 13 (81.3%) SFD. The lungs were the most common organs involved in 8 (50.0%) children followed by bone(s) in 4 (25.0%), abdomen in 2 (12.5%), and both lung and bone in 1 (6.3%) child. In contrast to adults, girls outnumbered boys in the childhood series; SFD was a common form of presentation in contrast to LV and TVC, tuberculous gumma and tuberculids were noted less often. In both children and adults, Mantoux reactivity did not correlate with the extent of the disease; patients with disseminated disease were found to be less often vaccinated with BCG and regional lymphadenopathy was noted more often in patients with disseminated disease.

CONCLUSIONS

In the whole spectrum of cutaneous tuberculosis, there is a proportion of patients with dissemination (systemic involvement) who are of great epidemiological significance as they require a change in the standard therapeutic regimens recommended for cutaneous tuberculosis.

Stochastic resonance without an external periodic drive in a simple prey-predator model

We have investigated the effect of noise on a simple prey-predator model where the oscillations are triggered by the internal dynamics of the system without the aid of any external periodic drive. We report the occurrence of stochastic resonancelike behavior in this system, which does not have a threshold or a potential barrier, in the absence of an external drive.

The level of DAL80 expression down-regulates GATA factor-mediated transcription in Saccharomyces cerevisiae

Nitrogen-catabolic gene expression in Saccharomyces cerevisiae is regulated by the action of four GATA family transcription factors: Gln3p and Gat1p/Nil1p are transcriptional activators, and Dal80 and Deh1p/Gzf3p are repressors. In addition to the GATA sequences situated upstream of all nitrogen catabolite repression-sensitive genes that encode enzyme and transport proteins, the promoters of the GAT1, DAL80, and DEH1 genes all contain multiple GATA sequences as well. These GATA sequences are the binding sites of the GATA family transcription factors and are hypothesized to mediate their autogenous and cross regulation. Here we show, using DAL80 fused to the carbon-regulated GAL1,10 or copper-regulated CUP1 promoter, that GAT1 expression is inversely regulated by the level of DAL80 expression, i.e., as DAL80 expression increases, GAT1 expression decreases. The amount of DAL80 expression also dictates the level at which DAL3, a gene activated almost exclusively by Gln3p, is transcribed. Gat1p was found to partially substitute for Gln3p in transcription. These data support the contention that regulation of GATA-factor gene expression is tightly and dynamically coupled. Finally, we suggest that the complicated regulatory circuit in which the GATA family transcription factors participate is probably most beneficial as cells make the transition from excess to limited nitrogen availability.

High-throughput screening of enzyme inhibitors: simultaneous determination of tight-binding inhibition constants and enzyme concentration

Active site titration by a reversible tight-binding inhibitor normally depends on prior knowledge of the inhibition constant. Conversely, the determination of tight-binding inhibition constants normally requires prior knowledge of the active enzyme concentration. Often, neither of these quantities is known with sufficient accuracy. This paper describes experimental conditions under which both the enzyme active site concentration and the tight-binding inhibition constant can be determined simultaneously from a single dose-response curve. Representative experimental data are shown for the inhibition of human kallikrein.

Epidemiology and the medical causes of miscarriage

Human reproduction is extraordinarily wasteful. The reasons for this have taxed all of the contributors to this book. As we move into the 21st century it is sobering to reflect on the fact that we have failed to harness the power of the evolving revolution in molecular medical biology to answer the fundamental question: why is the fate of a fertilized egg so hazardous and so unsuccessful? The following account summarizes our limited knowledge of the epidemiology of miscarriage and then moves on to consider some of the medical causes of miscarriage. The contribution of genetic abnormalities to the problem of pregnancy wastage is discussed elsewhere in this volume.

Recurrent miscarriage--an aspirin a day?

Recurrent miscarriage and later pregnancy complications are in some cases associated with placental thrombosis and infarction. The aim of this study was to assess the value of low dose aspirin (75 mg daily) in improving the subsequent livebirth rate amongst women with either unexplained recurrent early miscarriage (<13 weeks gestation; n = 805) or unexplained late pregnancy loss (n = 250). Amongst women with recurrent early miscarriages, there was no significant difference in the livebirth rate between those who took aspirin (251/367; 68.4%) compared with those who did not take aspirin [278/438; 63.5%; odds ratio (OR) 1.24; 95% confidence interval (CI) 0.93-1.67]. This relationship was independent of the number of previous early miscarriages. In contrast, women with a previous late miscarriage who took aspirin had a significantly higher livebirth rate (122/189; 64.6%) compared with those who did not take aspirin (30/61; 49.2%: OR 1.88; 95% CI 1.04-3.37). The empirical use of low dose aspirin amongst women with unexplained recurrent early miscarriage is not justified. We are currently investigating the role of incremental doses of aspirin in the treatment of women both with early miscarriages associated with thrombophilic abnormalities and in those with late pregnancy losses.

Predicting early mortality following percutaneous stent insertion for malignant biliary obstruction: a multivariate risk factor analysis

BACKGROUND

Percutaneous stent placement is an accepted method of palliation in malignant biliary obstruction. Factors predicting early mortality after this procedure have not been identified.

METHODS

We performed a retrospective study of 141 patients with malignant biliary obstruction who underwent percutaneous stent placement for biliary decompression to identify the risk factors associated with early mortality (< or = 30 days).

RESULTS

Of 14 clinicopathological and laboratory variables analysed blood urea, albumin, haemoglobin and alkaline phosphatase were found to be significant on univariate analysis. The age and gender of the patient along with cancer type, level of obstruction, presence of pyrexia and bilirubin level had no influence on early mortality. Stepwise logistic regression identified the haemoglobin level and blood urea to be independently significant in predicting early mortality. Overall 30-day mortality was 20.5% (29/141). Patients with blood urea over 4.3 mmol/l and a haemoglobin less than 10.9 g/dl had a mortality rate of 52% (12/23) compared with 14% (17/118) in the remainder. Using these two variables a regression equation has been derived which allows calculation of the probability of survival at 30 days after the percutaneous procedure.

CONCLUSIONS

Laboratory variables in patients with malignant obstructive jaundice can be used to predict mortality following percutaneous stent insertion.

Obstetric management of antiphospholipid syndrome

The obstetric management of women with antiphospholipid (aPL) syndrome remains controversial. Despite recent advances, the controversies have been fueled by our limited understanding of the multi-factorial causes of aPL-associated pregnancy loss and the lack of data from randomized studies. We have escaped from the narrow confines of the concept of aPL pregnancy loss being purely thrombotic in aetiology and attention is now focused on the adverse effects of aPL on embryonic implantation and trophoblast invasion. Combined treatment with aspirin and heparin has been demonstrated in two randomized studies to lead to a high live birth rate in aPL pregnancies. However, successful pregnancies are characterized by a high rate of perinatal complications and some women are refractory to this treatment combination. In addition to addressing these issues, multi-centre studies, which should perhaps be internet based, are needed to identify those aPL that are causative of pregnancy complications and those that are not, the role of IVIG and the long-term follow-up of both mothers with aPL and their babies.