FXII (46C→T) Polymorphism and In Vivo Generation of FXII Activity

Increased Factor XIIa concentrations have been found in association with coronary artery disease. Recently, a common 46 C to T point mutation in exon 1 of the factor XII gene has been described which is associated with lower FXII clotting activity and lower zymogen levels in relation to possession of the T allele. It is not known whether this polymorphism relates to the phenotypes of FXIIa in vivo or to coronary artery disease. The aim of the study was to investigate the interaction of this polymorphism with FXIIa plasma levels and to study the prevalence of the polymorphism in 266 patients with suspected coronary artery disease characterised by angiography and in 185 healthy controls. FXIIa levels were strongly associated with FXII genotype with lower levels with increasing numbers of T alleles (p <0.0001). There was no difference between the prevalence of this polymorphism in patients with MI compared to those without MI and controls and between all patients and controls (p ≥0.2, chi-square test). There was no association between extent of coronary artery disease (0, 1, 2, and 3 vessel disease) and FXII genotype. In conclusion, the common 46 C to T point mutation is strongly associated with FXIIa but the present study did not show an association with coronary artery disease. The role of this polymorphism in other thrombotic disorders such as ischemic stroke and venous thrombosis and its clinical significance in FXII deficient states remains to be investigated.

The activation peptide of coagulation factor XIII is vital for its expression and stability

BACKGROUND

The human activation peptide of factor XIII (AP-FXIII) comprises the first 37 amino acids of the N-terminus and holds the FXIII in an inactive state. FXIII is activated either proteolytically by cleavage of AP-FXIII by thrombin, or non-proteolytically by high calcium concentrations.

OBJECTIVE

To investigate the role of AP-FXIII in the expression and stability of FXIII.

METHODS

We cloned 13 FXIII variants with progressive truncations of AP-FXIII from the N-terminus (delN-FXIII-A), expressed them in mammalian cells, and measured their thermostability, activation, and transglutaminase activity. We also used in silico calculations to analyze the stability of hypothetical delN-FXIII dimers and to identify crucial motifs within AP-FXIII.

RESULTS

Variants with deletions longer than the first 10 amino acids and an R11Q point mutant were not expressed as proteins. In silico calculations indicated that the sequence (8) FGGR(12) R plays a substantial role in intersubunit interactions in FXIII-A2 homodimers. In agreement with this prediction, the temperature stability of delN-FXIII variants decreased with increasing length of deletion. These results may suggest a role of the N-terminus of AP-FXIII in dimer stability. Substantial sequence homology was found among activation peptides of vertebrate and even invertebrate (crustacean) FXIII-A orthologs, which further supports our conclusion.

CONCLUSIONS

We conclude that deletion of 11 or more N-terminal amino acids disrupts intersubunit interactions, which may prevent FXIII-A2 homodimer formation. Therefore, AP-FXIII plays an important role in the stability of the FXIII-A2 dimer.

New developments in the area of factor XIII

Coagulation factor (F)XIII is best known for its role in fibrin stabilization and cross-linking of antifibrinolytic proteins to the fibrin clot. From patients with congenital FXIII deficiency, it is known that FXIII also has important functions in wound healing and maintaining pregnancy. Over the last decade more and more research groups with different backgrounds have studied FXIII and have unveiled putative novel functions for FXIII. FXIII, with its unique role as a transglutaminase among the other serine protease coagulation factors, is now recognized as a multifunctional protein involved in regulatory mechanisms and construction and repair processes beyond hemostasis with possible implications in many areas of medicine. The aim of this review was to give an overview of exciting novel findings and to highlight the remarkable diversity of functions attributed to FXIII. Of course, more research into the underlying mechanisms and (patho-)physiological relevance of the many described functions of FXIII is needed. It will be exciting to observe future developments in this area and to see if and how these interesting findings may be translated into clinical practice in the future.

Sexual and marital trajectories and HIV infection among ever-married women in rural Malawi

Objective:

To explore how sexual and marital trajectories are associated with HIV infection among ever-married women in rural Malawi.

Methods:

Retrospective survey data and HIV biomarker data for 926 ever-married women interviewed in the Malawi Diffusion and Ideational Change Project were used. The associations between HIV infection and four key life course transitions considered individually (age at sexual debut, premarital sexual activity, entry into marriage and marital disruption by divorce or death) were examined. These transitions were then sequenced to construct trajectories that represent the variety of patterns in the data. The association between different trajectories and HIV prevalence was examined, controlling for potentially confounding factors such as age and region.

Results:

Although each life course transition taken in isolation may be associated with HIV infection, their combined effect appeared to be conditional on the sequence in which they occurred. Although early sexual debut, not marrying one’s first sexual partner and having a disrupted marriage each increased the likelihood of HIV infection, their risk was not additive. Women who both delayed sexual debut and did not marry their first partner are, once married, more likely to experience marital disruption and to be HIV-positive. Women who marry their first partner but who have sex at a young age, however, are also at considerable risk.

Conclusions:

These findings identify the potential of a life course perspective for understanding why some women become infected with HIV and others do not, as well as the differentials in HIV prevalence that originate from the sequence of sexual and marital transitions in one’s life. The analysis suggests, however, the need for further data collection to permit a better examination of the mechanisms that account for variations in life course trajectories and thus in lifetime probabilities of HIV infection.

Molecular characterization of five Italian families with inherited severe factor XIII deficiency

Factor XIII (FXIII) deficiency is a very rare (1:2 000 000) severe autosomal recessive bleeding disorder, mostly due to mutations in the coagulation FXIII A-subunit gene. We have studied the molecular basis of FXIII deficiency in five unrelated Italian families. The coding region, intron-exon boundaries and 5'- and 3'-untranslated regions of the FXIII gene encoding the A subunit were amplified and directly sequenced. Candidate mutations were identified in all the patients. Three novel mutations occurred in three patients. These include a novel homozygous deletion of two base pairs (bp) in exon 14 (c.2002-2003 DelCT). This deletion causes a frameshift from Leu667 and the formation of a stop codon at amino acid position 681. The second patient presents a novel homozygous (c.2126 G>A) transition in exon 15, predicting a Ser708Asn in Barrel 2 domain. The third patient is compound heterozygote for two missense mutations, a previously reported Arg260His substitution, and a novel transition in exon 4 (c.560 C>T) predicting a Pro186Leu in the core domain. The remaining two patients have two previously reported mutations: a 4-bp homozygous deletion in exon 11 (c.1392-1395 Del AATT), previously reported to occur in the Vicenza Area, and a homozygous nonsense mutation in exon 8 (c.979 C>T) predicting an Arg326X in the core domain. The novel mutations occurred at amino acid residues highly conserved among different species (pig, monkey, mouse and dog) and were not detected in 110 normal alleles. Structural analysis shows that Pro186Leu mutation leads to the replacement of the rigid proline pyrrolidine ring by the larger and more flexible leucine side chain and Ser708Asn may probably disrupt the hydrogen bond with Ala291.

Congenital factor XIII deficiency in Switzerland: from the worldwide first case in 1960 to its molecular characterisation in 2005

Coagulation factor XIII (FXIII) has a major role in the final stage of blood coagulation, is important for wound healing and maintaining pregnancy. Severe congenital FXIII deficiency is a rare disorder with 1 patient in 1-3 million. Untreated, it causes bleeding events, with intracranial haemorrhage being the major cause of death, impaired wound healing, and abortion. FXIII deficiency was traditionally diagnosed using the clot solubility test, but quantitative FXIII activity and antigen assays are preferred today. Treatment consists of replacement therapy with FXIII concentrates administered every 4-6 weeks. The molecular-genetic causes of FXIII deficiency are mutations in the genes coding for the FXIII A- and B-subunits. More than 60 mutations distributed throughout the FXIII A-subunit gene have been identified so far and 4 mutations in the FXIII B-subunit gene. The first case of congenital FXIII deficiency was reported in Switzerland in 1960. In Switzerland we observed a disproportionately high incidence, which can be explained in part by a founder effect. In this article, we summarise general facts on severe congenital FXIII deficiency, and we characterise all FXIII deficient patients living in Switzerland, including the first case described in 1960 who is a member of a large family originating from the canton of Uri.

Phenotype ? genotype correlation in eight Polish patients with inherited Factor XIII deficiency: identification of three novel mutations

Inherited factor XIII (FXIII) deficiency is known as one of the most rare blood coagulation disorder in humans. In the present study, phenotype and genotype of eight FXIII deficient Polish patients from five unrelated families were compared. The patients presented with a severe phenotype demonstrated by a high incidence of intracerebral haemorrhages (seven of eight patients), haemarthrosis (six patients) and bleeding due to trauma (five patients). Introduction of regular substitution with FXIII concentrate prevented spontaneous bleeding in seven patients. In all patients, mutations within the F13A gene have been identified revealing four missense mutations (Arg77Cys, Arg260Cys, Ala378Pro, Gly420Ser), one nonsense mutation (Arg661X), one splice site mutation (IVS5-1 G>A) and one small deletion (c.499-512del). One homozygous large deletion involving exon 15 was detected by failure of PCR product. The corresponding mutations resulted in severely reduced FXIII activity and FXIII A-subunit antigen concentration, while FXIII B-subunit antigen remained normal or mildly decreased. Structural analysis demonstrated that the novel Ala378Pro mutation may cause a disruption of the FXIII catalytic triad leading to a non-functional protein which presumably undergoes premature degradation. In conclusion, the severe phenotype with high incidence of intracranial bleeding and haemarthrosis was in accordance with laboratory findings on FXIII and with severe molecular defects of the F13A gene.

Congenital factor XIII deficiency in Switzerland: from the worldwide first case in 1960 to its molecular characterisation in 2005

Coagulation factor XIII (FXIII) has a major role in the final stage of blood coagulation, is important for wound healing and maintaining pregnancy. Severe congenital FXIII deficiency is a rare disorder with 1 patient in 1-3 million. Untreated, it causes bleeding events, with intracranial haemorrhage being the major cause of death, impaired wound healing, and abortion. FXIII deficiency was traditionally diagnosed using the clot solubility test, but quantitative FXIII activity and antigen assays are preferred today. Treatment consists of replacement therapy with FXIII concentrates administered every 4-6 weeks. The molecular-genetic causes of FXIII deficiency are mutations in the genes coding for the FXIII A- and B-subunits. More than 60 mutations distributed throughout the FXIII A-subunit gene have been identified so far and 4 mutations in the FXIII B-subunit gene. The first case of congenital FXIII deficiency was reported in Switzerland in 1960. In Switzerland we observed a disproportionately high incidence, which can be explained in part by a founder effect. In this article, we summarise general facts on severe congenital FXIII deficiency, and we characterise all FXIII deficient patients living in Switzerland, including the first case described in 1960 who is a member of a large family originating from the canton of Uri.

[When the tongue impairs breathing]

Ätiologisch ist im vorliegenden Fall ein Angioödem mit Mastzelldegranulation unwahrscheinlich. Einerseits wegen fehlendem Exanthem und Pruritus und andererseits fehlte ein suffizientes Ansprechen auf hochdosierte Steroidgabe oder Adrenalin. Der wiederholt normale Wert von C1-INH im Serum sowohl quantitativ und auch qualitativ spricht gegen das Vorliegen eines C1-Esteraseinhibitor-Mangel. Aufgrund der Anamnese und des klinischen Verlaufs bleibt als wahrscheinlichste Ursache für das Angioödem die bereits lange Jahre etablierte und in der Dosierung unveränderte ACE-Hemmer-Therapie, obwohl eine derartige Manifestation nach langjährigem ACE Hemmer Einsatz sehr selten ist.

[Acute chest pain--it's not always the heart! What additional laboratory and diagnostic imaging is needed]

Few diagnostic decisions in medicine have been more heavily researched and debated than the approach to patients with acute chest pain. In addition, the question is which patients with acute chest pain have a presentation benign enough to make discharge from the emergency department safe and appropriate despite the advances in diagnostic tests. There is always the possibility of missed diagnosis which may cause substantial morbidity and mortality. The use of algorithms or protocols is not always sufficient to avoid missed diagnosis and the individual physicians's diagnostic performance and clinical experience is as important as the best algorithm for atypical chest pain! Patients with atypical symptoms are most likely to be mistakenly discharged. This article does mainly focus on diagnostic tests including ECG and biomarkers such as troponin and D-dimer as well as the investigation by helical CT scan in patients with suspected pulmonary embolism. The article also discuss the importance of repeated assessments of biomarkers and the determination of the exact time interval between the first clinical symptoms and the presentation to the emergency department. This time interval can be very crucial for the diagnostic work-up of patients with acute chest pain.

[Poisoning and drug emergency in practice]

Intoxicated patients make up 5-10% of all patients seen at emergency departments. The management of these patients is not always simple. Many of them are seen after ingestions of relatively non-toxic substances that require minimal medical care, intentional poisoning however often requires the highest standards of medical and nursing care and therefore the admission to an emergency department is mandatory. At admission, the involved substances are often not known since some of the patients are comatose. In such cases, the information from relatives and friends can be very crucial but to get hold of these sometimes essential "hints" is not always easy. Knowledge of the specific toxic agent allows the physician to plan a rational approach to the definitive management of the intoxicated patient after the vital functions have been stabilised. In some cases, very rare intoxications but with typical clinical signs do occur (e.g scromboid fish poisoning, coprinus-syndrome), which needs special diagnostic and therapeutic steps and a great deal of clinical experience. In most cases it is preferable to contact the Poison Control Center for additional advice.

[Methods for the determination of factor XIII/XIIIa]

Activated factor XIII (FXIIIa) plays an important role in the final stage of the coagulation cascade by covalent crosslinking of fibrin strands. As a transglutaminase FXIIIa catalyses the generation of intermolecular amide bonds between lysine and glutamine residues resulting in a complex three-dimensional clot structure. Enhanced clot stability is supported by covalent binding of cytosceleton factors like actin and myosin. Moreover, the clot is protected against premature lysis by the incorporation of fibrinolysis inhibitors like alpha(2)-antiplasmin and thrombin activatable fibrinolysis inhibitor (TAFI). A covalent crosslinking of the fibrin strands with extra-cellular matrix proteins like fibronectin, vitronectin, collagen and von Willebrand factor (vWF) immobilizes the clot at the site of injury. Moreover FXIII supports the healing process of damaged tissue. In this review assays for determination of FXIIIa activity, FXIII concentration and identification of the FXIIIVal34Leu polymorphism are shown.

[Role of coagulation factor XIII in cardio- and cerebrovascular diseases]

In the final step of the clotting cascade coagulation factor XIII (FXIII) is activated by thrombin. The activated enzyme (FXIIIa) has an important role in the final stage of blood coagulation in cross-linking soluble fibrin to a stable insoluble clot. The role of FXIII in cardio- and cerebrovascular diseases has been investigated recently. The widespread Val34Leu polymorphism in the gene coding for the FXIII subunit A (FXIII Val34Leu) has been shown to protect against myocardial infarction and ischemic stroke, but is also associated with an increased risk for hemorrhagic stroke. Additionally, FXIII Val34Leu is supposed to be protective against pulmonary embolism and deep vein thrombosis. As possible mechanisms for the antithrombotic effect, premature depletion of the mutant protein from circulation and altered fibrin structures of clots cross-linked by the mutant FXIIIa are under discussion. The connection between FXIII and the insulin resistance syndrome also attracts attention, i.e. the interaction between a component of the coagulation cascade and thus a thrombotic risk factor and classical atheromatous risk factors. Therefore, FXIII must be considered as another coagulation factor contributing to complex interactions between genes and environment important for the pathogenesis of cardio- and cerebrovascular and thromboembolic diseases.

[Fever of unknown origin, head and muscle pain, hemoptysis, hepatosplenomegaly and icterus. 2 case reports]

Die Leptospirose kommt in der Schweiz aufgrund der klimatischen Verhältnisse selten vor, trotzdem wird die Inzidenz dieser Krankheit unterschätzt. Das klinische Bild ist vielfältig. Die Differentialdiagnose reicht von einer grippeähnlichen Erkrankung bis hin zur akut verlaufenden Systemerkrankung. Diese Tatsache erfordert aufgrund der therapeutischen Konsequenz, die Durchführung einer intensiven und häufig auch invasiven Diagnostik, welche letztlich oft unergiebig bleibt. Neue und vor allem schnellere diagnostische Möglichkeiten mittels PCR aus Blut, Liquor und Urin werden diskutiert, sind aber noch nicht etabliert. Eine antibiotische Therapie wird je nach Verlaufsform kontrovers beurteilt.

Methoden zur Bestimmung des Faktors XIII/XIIIa

Aktivierter Blutgerinnungsfaktor XIII (FXIIIa), eine Transglutaminase, quervernetzt in der letzten Phase der Sekundärhämostase die Fibrinpolymere durch Bildung intermolekularer Amidbindungen zwischen Glutaminund Lysinresten zu einem komplex strukturierten, dreidimensionalen Gerinnsel. Die dadurch gesteigerte Gerinnselfestigkeit wird durch den kovalenten Einbau von Zytoskelettbestandteilen wie Aktin und Myosin weiter erhöht. Darüber hinaus schützt der FXIIIa-abhängige Einbau antifibrinolytisch wirkender Faktoren wie α2-Antiplasmin und Thrombin-aktivierbarer Fibrinolyseinhibitor (TAFI) vor vorzeitiger Lyse des Gerinnsels. Die kovalente Vernetzung der Fibrinpolymere mit Adhäsionsproteinen der extrazellulären Matrix (z. B. Fibronektin, Kollagen, Vitronektin, von-Willebrand-Faktor) fixiert das Gerinnsel am Ort der Gefäßläsion und unterstützt den Regenerationsprozess des Gewebes. Diese vielfältigen Funktionen von FXIIIa zeigen seine zentrale Bedeutung in der Hämostase. Im vorliegenden Übersichtsartikel werden Tests zur Erfassung der funktionellen Aktivität, Konzentration und zur Identifizierung des FXIII-Val34Leu-Polymorphismus vorgestellt.

Influence of blood coagulation factor XIII and FXIII Val34Leu on plasma clot formation measured by thrombelastography

Blood coagulation factor XIII (FXIII) plays an important role in the final stage of the blood coagulation process. Thrombelastography (TEG) enables global assessment of the hemostatic function. The present study tested for the first time the specificity and sensitivity of the rotation thrombelastography (ROTEG: rotation thrombelastography) method for the influence of FXIII and the FXIIIVal34Leu polymorphism on thrombelastograms measured in citrated plasma. Three thrombelastographic parameters were determined in (a) citrated pool plasma, (b) FXIII-deficient plasma, (c) different mixtures of both, and (d) in 60 plasma samples genotyped for FXIIIVal34Leu. Thrombelastograms from FXIII-deficient plasma were significantly smaller than those from pool plasma (8 mm vs. 20.9 mm). Increasing amounts of pool plasma added to FXIII-deficient plasma led to an increase in maximum clot firmness (MCF). FXIIIVal34Leu showed an influence on clot formation time (CFT) values, which decreased with increasing number of Leu alleles. The difference between the wild type and the homozygote mutant genotype was statistically significant (median 185.3 vs. 86.0 s, P=.031). ROTEG is a simple but effective method for the investigation of FXIII function in plasma. The ROTEG method has shown to be not only specific for the FXIII influence, as effects exclusively dependent on FXIII could be observed, but also sensitive, as already smallest amounts of FXIII could be detected. Additionally, the impact of a common genetic polymorphism on ROTEG could be shown for the first time.

Biotransformation of various substituted aromatic compounds to chiral dihydrodihydroxy derivatives

The biotransformation of four different classes of aromatic compounds by the Escherichia coli strain DH5alpha(pTCB 144), which contained the chlorobenzene dioxygenase (CDO) from Pseudomonas sp. strain P51, was examined. CDO oxidized biphenyl as well as monochlorobiphenyls to the corresponding cis-2,3-dihydro-2,3-dihydroxy derivatives, whereby oxidation occurred on the unsubstituted ring. No higher substituted biphenyls were oxidized. The absolute configurations of several monosubstituted cis-benzene dihydrodiols formed by CDO were determined. All had an S configuration at the carbon atom in meta position to the substituent on the benzene nucleus. With one exception, the enantiomeric excess of several 1,4-disubstituted cis-benzene dihydrodiols formed by CDO was higher than that of the products formed by two toluene dioxygenases. Naphthalene was oxidized to enantiomerically pure (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene. All absolute configurations were identical to those of the products formed by toluene dioxygenases of Pseudomonas putida UV4 and P. putida F39/D. The formation rate of (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene was significantly higher (about 45 to 200%) than those of several monosubstituted cis-benzene dihydrodiols and more than four times higher than the formation rate of cis-benzene dihydrodiol. A new gas chromatographic method was developed to determine the enantiomeric excess of the oxidation products.

DF-analyses of heritability with double-entry twin data: asymptotic standard errors and efficient estimation

In this paper we establish the asymptotic distribution of DeFries Fulker (1985) regression estimates for heritability and shared environmental influences with double-entry twin data. A simple formula to estimate the covariance matrix of the coefficients in DF-regressions is provided, and applications to simulated data and Danish twin data show that this method can substantially increase the statistical power of the analyses. We also provide an 'efficient DF-analysis' that yields more precise estimates when additional covariates are included among the explanatory variables.

The density of social networks and fertility decisions: evidence from South Nyanza district, Kenya

Demographers have argued increasingly that social interaction is an important mechanism for understanding fertility behavior. Yet it is still quite uncertain whether social learning or social influence is the dominant mechanism through which social networks affect individuals' contraceptive decisions. In this paper we argue that these mechanisms can be distinguished by analyzing the density of the social network and its interaction with the proportion of contraceptive users among network partners. Our analyses indicate that social learning is most relevant with high market activity; in regions with only modest market activity, however, social influence is the dominant means by which social networks affect women's contraceptive use.

Behavior genetic modeling of human fertility: findings from a contemporary Danish Twin Study

Behavior genetic designs and analysis can be used to address issues of central importance to demography. We use this methodology to document genetic influence on human fertility. Our data come from Danish twin pairs born from 1953 to 1959, measured on age at first attempt to get pregnant (FirstTry) and number of children (NumCh). Behavior genetic models were fitted using structural equation modeling and DF analysis. A consistent medium-level additive genetic influence was found for NumCh, equal across genders; a stronger genetic influence was identified for FirstTry, greater for females than for males. A bivariate analysis indicated significant shared genetic variance between NumCh and FirstTry.

Variance effects in the Bongaarts-Feeney formula

Bongaarts and Feeney have recently proposed an adjusted total fertility rate to disentangle tempo effects from changes in the quantum of fertility. We propose an extension to the Bongaarts and Feeney formula that includes variance effects: that is, changes in the variance of the fertility schedule over time. If these variance effects are ignored, the mean age at birth and the adjusted total fertility rate are biased. We provide approximations for these biases, and we extend the TFR adjustment to fertility schedules with changing variance. We apply our method to the Swedish baby boom and bust, and show that variance effects are important for evaluating the relative contributions of tempo and quantum effects to the fertility change from 1985 to 1995.

Transcriptional organization and dynamic expression of the hbpCAD genes, which encode the first three enzymes for 2-hydroxybiphenyl degradation in Pseudomonas azelaica HBP1

Pseudomonas azelaica HBP1 degrades the toxic substance 2-hydroxybiphenyl (2-HBP) by means of three enzymes that are encoded by structural genes hbpC, hbpA, and hbpD. These three genes form a small noncontiguous cluster. Their expression is activated by the product of regulatory gene hbpR, which is located directly upstream of the hbpCAD genes. The HbpR protein is a transcription activator and belongs to the so-called XylR/DmpR subclass within the NtrC family of transcriptional activators. Transcriptional fusions between the different hbp intergenic regions and the luxAB genes of Vibrio harveyi in P. azelaica and in Escherichia coli revealed the existence of two HbpR-regulated promoters; one is located in front of hbpC, and the other one is located in front of hbpD. Northern analysis confirmed that the hbpC and hbpA genes are cotranscribed, whereas the hbpD gene is transcribed separately. No transcripts comprising the entire hbpCAD cluster were detected, indicating that transcription from P(hbpC) is terminated after the hbpA gene. E. coli mutant strains lacking the structural genes for the RNA polymerase sigma(54) subunit or for the integration host factor failed to express bioluminescence from P(hbpC)- and P(hbpD)-luxAB fusions when a functional hbpR gene was provided in trans. This pointed to the active role of sigma(54) and integration host factor in transcriptional activation from these promoters. Primer extension analysis revealed that both P(hbpC) and P(hbpD) contain the typical motifs at position -24 (GG) and -12 (GC) found in sigma(54)-dependent promoters. Analysis of changes in the synthesis of the hbp mRNAs, in activities of the 2-HBP pathway enzymes, and in concentrations of 2-HBP intermediates during the first 4 h after induction of continuously grown P. azelaica cells with 2-HBP demonstrated that the specific transcriptional organization of the hbp genes ensured smooth pathway expression.

Frailty modelling for adult and old age mortality: the application of a modified DeMoivre hazard function to sex differentials in mortality

Unobserved differences in individual's susceptibility to death are an important aspect in the analysis of contemporary mortality patterns. However, observed mortality rates at adult ages, which are usually well described by a Gompertz curve, are often perceived inconsistent with frailty models of mortality. The authors therefore propose a modified DeMoivre hazard function that is suitable for the application of frailty models to adult and old ages. The proposed hazard increases faster than exponential, and when combined with unobserved frailty it can capture a broad range of patterns encountered in the analysis of adult mortality. The authors' application to Bulgaria during 1992-93 suggests that the stronger selection process in the male population, caused by an overall higher level of mortality, may constitute a primary mechanism leading to the convergence of male and female mortality at higher ages. Hence, the convergence between male and female mortality is not necessarily caused by differential process of aging across sexes, but is merely a consequence of the different levels of mortality at adult ages.

Empirical assessments of social networks, fertility and family planning programs: nonlinearities and their implications

Empirical studies of the diffusion of modern methods of family planning have increasingly incorporated social interaction within nonlinear models such as logits. But they have not considered the full implications of these nonlinear specifications. This paper considers the implications of using nonlinear models in empirical analyses of the impact of family programs, modulated by social interaction, on reproductive behavior. Three implications of nonlinear models, in comparison with linear models, are developed. 1) With nonlinear models, there may be both low and high contraceptive-use equilibria (i.e., the ultimate level of use of modern family planning that a population can be expected to reach after the effects of a sustained change in a family planning program have worked through the population) rather than just one equilibrium as in linear models. If there are multiple equilibria, then one striking and important result is that a transitory large program effort may move a community from sustained low- to high-level contraceptive use. 2) With nonlinear models, the extent to which a social interaction multiplies program efforts depends on whether the community is at a low or high level of contraceptive use rather than being independent of the level of contraceptive use as in linear models. 3) With nonlinear models, intensified social interaction can retard or enhance the diffusion of family planning, in contrast to only enhancing diffusion as within linear models. To clarify these implications, for comparison a simple and more transparent linear model is also discussed. Illustrative estimates are presented of simple linear and nonlinear models for rural Kenya that demonstrate that some of these effects may be considerable.

alpha-fibrinogen Thr312Ala polymorphism and venous thromboembolism

The Aalpha-fibrinogen Thr312Ala polymorphism, which occurs in a region involved in factor XIII (FXIII)-dependent cross-linking processes, is associated with poststroke mortality in subjects with atrial fibrillation, suggesting an influence either on intraatrial clot formation or embolization. We have determined the association of Thr312Ala with deep vein thrombosis (DVT) and pulmonary embolism (PE) and have assessed the interaction of Thr312Ala with the FXIII Val34Leu polymorphism in 122 patients with DVT, 99 patients with PE, and 254 healthy control subjects. The genotype distribution of patients with PE (TT = 49%, TA = 36%, AA = 15%), but not DVT (TT = 50%, TA = 42%, AA = 8%), differed significantly from healthy control subjects (TT = 60%, TA = 34%, AA = 6%, P =.02). A significant interaction of Thr312Ala and Val34Leu was also identified (P =.01), indicating an inverse association between Leu34 and Ala312. These results support the hypothesis that Thr312Ala alters FXIII-dependent cross-linking, making formed fibrin clot more susceptible to embolization.

Fate of the herbicides mecoprop, dichlorprop, and 2,4-D in aerobic and anaerobic sewage sludge as determined by laboratory batch studies and enantiomer-specific analysis

Aerobic degradation experiments with the racemic mixtures of mecoprop and dichlorprop revealed that activated sludge collected from the aeration tank of a municipal waste water treatment plant degraded both enantiomers of mecoprop and dichlorprop within 7 days, albeit in an enantioselective manner; the (S) enantiomers were preferentially degraded. Mecoprop, dichlorprop, and 2,4-D were completely metabolized under aerobic conditions, as shown by the 86-98% elimination of dissolved organic carbon. Under anaerobic conditions, the concentration of 2,4-D decreased exponentially with a first-order reaction rate constant of 0.24 per day and without a lag-phase. After an incubation time of 17 days, 2,4-D was completely removed. 2,4-Dichlorophenol was the main metabolite of anaerobic 2,4-D degradation; only traces of 4-chlorophenol were detected. In contrast, the chiral phenoxypropionic acid herbicides mecoprop and dichlorprop persisted under anaerobic conditions during 49 days of incubation.

HbpR, a new member of the XylR/DmpR subclass within the NtrC family of bacterial transcriptional activators, regulates expression of 2-hydroxybiphenyl metabolism in Pseudomonas azelaica HBP1

The regulation of 2-hydroxybiphenyl and 2,2'-dihydroxybiphenyl degradation in Pseudomonas azelaica is mediated by the regulatory gene, hbpR. The hbpR gene encodes a 63-kDa protein belonging to the NtrC family of prokaryotic transcriptional activators and having the highest homology to members of the XylR/DmpR subclass. Disruption of the hbpR gene in P. azelaica and complementation in trans showed that the HbpR protein was the key regulator for 2-hydroxybiphenyl metabolism. Induction experiments with P. azelaica and Escherichia coli containing luxAB-based transcriptional fusions revealed that HbpR activates transcription from a promoter (P(hbpC)) in front of the first gene for 2-hydroxybiphenyl degradation, hbpC, and that 2-hydroxybiphenyl itself is the direct effector for HbpR-mediated activation. Of several compounds tested, only the pathway substrates 2-hydroxybiphenyl and 2,2'-dihydroxybiphenyl and structural analogs like 2-aminobiphenyl and 2-hydroxybiphenylmethane were effectors for HbpR activation. HbpR is therefore, to our knowledge, the first regulator of the XylR/DmpR class that recognizes biaromatic but not monoaromatic structures. Analysis of a spontaneously occurring mutant, P. azelaica HBP1 Prp, which can grow with the non-wild-type effector 2-propylphenol, revealed a single mutation in the hbpR gene (T613C) leading to a Trp-->Arg substitution at amino acid residue 205. P. azelaica HBP1 derivative strains without a functional hbpR gene constitutively expressed the genes for 2-hydroxybiphenyl degradation when complemented in trans with the hbpR-T613C gene. This suggests the importance of this residue, which is conserved among all members of the XylR/DmpR subclass, for interdomain repression.