bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Arbovirus Infections Worldwide
Authors: GUBLER DUANE J.
Published: July 2010

Abstract: Viral diseases transmitted by blood‐feeding arthropods (arboviral diseases) are among the most important of the emerging infectious disease public health problems facing the world at the beginning of the third millennium. There are over 534 viruses listed in the arbovirus catalogue, approximately 134 of which have been shown to cause disease in humans. These are transmitted principally by mosquitoes and ticks. In the last two decades of the twentieth century, a few new arboviral diseases have been recognized. More important, however, is the dramatic resurgence and geographic spread of a number of old diseases that were once effectively controlled. Global demographic and societal changes, and modern transportation have provided the mechanisms for the viruses to break out of their natural ecology and become established in new geographic locations where susceptible arthropod vectors and hosts provide permissive conditions for them to cause major epidemics. West Nile virus is just the the latest example of this type of invasion by exotic viruses. This paper will provide an overview of the medically important arboviruses and discuss several in more detail as case studies to illustrate our tenuous position as we begin the twenty‐first century.
“Neon Needles” in a Haystack
Authors: EIDSON MILLICENT
Published: July 2010

Abstract: Passive surveillance is usually viewed as less efficient for case ascertainment than active surveillance. However, for diseases with nonhuman animal reservoirs, active surveillance can be like looking for a needle in a haystack and may be prohibitively expensive. Fortunately for surveillance of West Nile virus (WNV) in the northeast US, the dead crows have served as “neon needles in a haystack”—indicators of viral activity that call attention to themselves. In 2000, laboratory testing of dead birds, including all species, birds found singly, with signs of trauma, or no compatible pathology, provided the first confirmation of viral activity in most areas. The surveillance factor most closely associated with the number of human cases was the dead crow density. In 2001, dead crow densities will be used as an additional index for monitoring human risk and need for prevention and control activities. If there are few crows in an area, if their case‐fatality rate is reduced, or if there is public complacency about reporting dead crow sightings, this passive surveillance indicator may not be helpful in identifying areas likely to have occasional human cases or an outbreak.
West Nile Fever in Israel 1999‐2000
Authors: BIN H. , GROSSMAN Z. , POKAMUNSKI S. , MALKINSON M. , WEISS L. , DUVDEVANI P. , BANET C. , WEISMAN Y. , ANNIS E. , GANDAKU D. , YAHALOM V. , HINDYIEH M. , SHULMAN L. , MENDELSON E.
Published: July 2010

Abstract: West Nile virus (WNV) caused disease outbreaks in Israel in the 1950s and the late 1970s. In 1998 an outbreak of WNV in goose farms and evidence of infection in dead migratory birds were reported. Consequently, human diagnostic services for WNV were resumed, including virus isolation, serology, and RT‐PCR. Risk factors for infection were assessed by a serological survey in 1999, which revealed a seroprevalence of (a) 86% in people who had close contact with sick geese, (b) 28% in people in areas along bird migration routes, and (c) 27% in the general population. Following two fatal cases in Tel Aviv in September 1999 and one encephalitis case in the southern Eilot region, a regional serological survey was initiated there. The survey revealed two more WNV‐associated acute encephalitis cases, an IgG seroprevalence of 51%, and an IgM seroprevalence of 22%. In the summer of 2000, acute cases of WN disease were identified in the central and northern parts of Israel, involving 439 people. The outbreak started in mid‐August, peaked in September, and declined in October, with 29 fatal cases, primarily in the elderly. During the outbreak, diagnosis was based on IgM detection. Four virus isolates were subsequently obtained from preseroconverted frozen sera. Sequence and phylogenetic analysis of 1662 bases covering the PreM, M, and part of the E genes revealed two lineages. One lineage was closely related to a 1999 Israeli bird (gull) isolate and to a 1999 New York bird (flamingo) isolate, and the other lineage was closely related to a 1997 Romanian mosquito isolate and to a 1999 Russian human brain isolate.
The Ecology of West Nile Virus in South Africa and the Occurrence of Outbreaks in Humans
Authors: JUPP PETER G.
Published: July 2010

Abstract: This paper reviews studies done on West Nile virus (WNV) in South Africa, mainly between 1962 and 1980 on the temperate inland plateau (Highveld and Karoo). The virus is maintained in an enzootic transmission cycle between feral birds and the ornithophilic mosquito Culex univittatus. About 30 avian species have been shown to be involved without mortality. Humans, and other mammals, although they may have antibodies, are considered blind‐alleys in the transmission cycle except perhaps some dogs. Cx. univittatus also transfers infection to humans, almost invariably causing only a mild illness. Its usually low anthropophilism may explain why annual human infection on the Highveld is limited to sporadic cases. Besides multiple isolations from field collections of Cx. univittatus, this mosquito is both highly susceptible to the virus and an efficient transmitter. Culex theileri is a minor vector. In the summer of 1974 there was a large epidemic in the dry Karoo after unusual rains: there were many human cases, the infection rate in Cx. univittatus was 39.0/1000, and postepidemic immune rates in humans and birds were high. In 1984 there was an epizootic in Gauteng Province in the Highveld with an infection rate in Cx. univittatus reaching 9.6/1000 and more human infections than usual. The much lower immune rates in the KwaZulu‐Natal coastal lowlands than on the plateau and the single isolation from Cx. neavei, which replaces Cx. univittatus in the lowlands, are explained by the low susceptibility of Cx. neavei to the virus. Genetic relatedness of isolates from different countries showed two lineages, with one lineage comprising only African isolates, including 25 South African strains, which had a sequence homology of 86.3‐100%. This suggests that the viral enzooticity does not depend on annual importation of virus in migrant birds.
Variations in Biological Features of West Nile Viruses
Authors: DEUBEL V. , FIETTE L. , GOUNON P. , DROUET M. T. , KHUN H. , HUERRE M. , BANET C. , MALKINSON M. , DESPRÈS P.
Published: July 2010

Abstract: Pathological findings in humans, horses, and birds with West Nile (WN) encephalitis show neuronal degeneration and necrosis in the central nervous system (CNS), with diffuse inflammation. The mechanisms of WN viral penetration of the CNS and pathophysiology of the encephalitis remain largely unknown. Since 1996, several epizootics involving hundreds of humans, horses, and thousands of wild and domestic bird cases of encephalitis and mortality have been reported in Europe, North Africa, the Middle East, Russia, and the USA (see specific chapters in this issue). However, biological and molecular markers of virus virulence should be characterized to assess whether novel strains with increased virulence are responsible for this recent proliferation of outbreaks.
Host Factors Involved in West Nile Virus Replication
Authors: BRINTON MARGO A.
Published: July 2010

Abstract: Viruses use cell proteins during many stages of their replication cycles, including attachment, entry, translation, transcription/replication, and assembly. Mutations in the cell proteins involved can cause disruptions of these critical host‐virus interactions, which in turn can affect the efficiency of virus replication. These host‐virus interactions also represent novel targets for the development of new antiviral agents. The different alleles of the murine Flv gene confer resistance or susceptibility to flavivirus‐induced disease and provide a natural mutant system for the study of a host protein that can alter the outcome of a flavivirus infection. Since flaviviruses, such as West Nile virus, replicate in mosquitoes, mammals, and birds during their natural transmission cycles, it is expected that the critical cell proteins used by these viruses will be ones that are highly conserved between divergent host species. Our laboratory has focused on the identification and characterization of the flavivirus resistance gene product and of cell proteins that interact with the 3′ terminal regions of the West Nile virus genomic and antigenomic RNAs. The 3′ terminal regions of the viral RNAs function as promotors for viral RNA replication. Cell proteins that bind to the viral 3′ RNAs were detected by gel shift and UV‐induced cross‐linking assays. Individual proteins were then purified and partially sequenced. Mutation of a mapped, protein‐binding site within the 3′ terminal region of the viral RNA in an infectious West Nile virus clone was used to demonstrate the functional importance of one of the cell proteins for efficient West Nile virus replication. Data from additional studies suggested possible roles for this viral RNA‐cell protein interaction during the flavivirus replication cycle.
Current Status of Flavivirus Vaccines
Authors: BARRETT ALAN D.T.
Published: July 2010

Abstract: Although there are approximately 68 flaviviruses recognized, vaccines have been developed to control very few human flavivirus diseases. Licensed live attenuated vaccines have been developed for yellow fever (strain 17D) and Japanese encephalitis (strain SA14‐14‐2) viruses, and inactivated vaccines have been developed for Japanese encephalitis and tick‐borne encephalitis viruses. The yellow fever live attenuated 17D vaccine is one of the most efficacious and safe vaccines developed to date and has been used to immunize more than 300 million people. A number of experimental vaccines are being developed, most notably for dengue. Candidate tetravalent live attenuated dengue vaccines are undergoing clinical trials. Other vaccines are being developed using reverse genetics, DNA vaccines, and recombinant immunogens. In addition, the yellow fever 17D vaccine has been used as a backbone to generate chimeric viruses containing the premembrane and envelope protein genes from other flaviviruses. The “Chimerivax” platform has been used to construct chimeric Japanese encephalitis and dengue viruses that are in different phases of development. Similar strategies are being used by other laboratories.
Genetic Instability in Epithelial Tissues at Risk for Cancer
Authors: HITTELMAN WALTER N.
Published: July 2010

Epithelial tumors develop through a multistep process driven by genomic instability frequently associated with etiologic agents such as prolonged tobacco smoke exposure or human papilloma virus (HPV) infection. The purpose of the studies reported here was to examine the nature of genomic instability in epithelial tissues at cancer risk in order to identify tissue genetic biomarkers that might be used to assess an individual's cancer risk and response to chemopreventive intervention. As part of several chemoprevention trials, biopsies were obtained from risk tissues (i.e., bronchial biopsies from chronic smokers, oral or laryngeal biopsies from individuals with premalignancy) and examined for chromosome instability using in situ hybridization. Nearly all biopsy specimens show evidence for chromosome instability throughout the exposed tissue. Increased chromosome instability was observed with histologic progression in the normal to tumor transition of head and neck squamous cell carcinomas. Chromosome instability was also seen in premalignant head and neck lesions, and high levels were associated with subsequent tumor development. In bronchial biopsies of current smokers, the level of ongoing chromosome instability correlated with smoking intensity (e.g., packs/day), whereas the chromosome index (average number of chromosome copies per cell) correlated with cumulative tobacco exposure (i.e., pack‐years). Spatial chromosome analyses of the epithelium demonstrated multifocal clonal outgrowths. In former smokers, random chromosome instability was reduced; however, clonal populations appeared to persist for many years, perhaps accounting for continued lung cancer risk following smoking cessation.
Mechanisms of Hormonal Prevention of Breast Cancer
Authors: MEDINA DANIEL , SIVARAMAN LAKSHMI , HILSENBECK SUSAN G. , CONNEELY ORLA , GINGER MELANIE , ROSEN JEFFREY , O'MALLEY BERT W.
Published: July 2010

Reproductive history is a consistent risk factor for human breast cancer. Epidemiological studies have repeatedly demonstrated that early age of first pregnancy is a strong protective factor against breast cancer and provides a physiologically operative model to achieve a practical mode of prevention. In rodents, the effects of full‐term pregnancy can be mimicked by a three‐week exposure to low doses of estrogen and progesterone. Neither hormone alone is sufficient to induce protection. The cellular and molecular mechanisms that underlie hormone‐induced refractoriness are largely unresolved. Our recent studies have demonstrated that an early cellular response that is altered in hormone‐treated mammary cells is the initial proliferative burst induced by the chemical carcinogen methylnitrosourea. The decrease in proliferation is also accompanied by a decrease in the ability of estrogen receptor‐positive cells to proliferate. RNA expression of several mammary cell‐cycle‐related genes is not altered in hormone‐treated mice; however, immunohistochemical assays demonstrate that the protein level and nuclear compartmentalization of the p53 tumor suppressor gene are markedly upregulated as a consequence of hormone treatment. These results support the hypothesis that hormone stimulation, at a critical period in mammary development, results in cells with persistent changes in the intracellular regulatory loops governing proliferation and response to DNA damage. A corollary to this hypothesis is that the genes affected by estrogen and progesterone are independent of alveolar differentiation‐specific genes. Suppressive subtractive hybridization‐PCR methods have identified several genes that are differentially expressed as a consequence of prior estrogen and progesterone treatment. Future experiments are aimed at determining the mechanisms of hormone‐induced upregulation of p53 protein expression as part of the overall goal of identifying and functionally characterizing the genes responsible for the refractory phenotype.
Beyond Tamoxifen
Authors: FABIAN CAROL J. , KIMLER BRUCE F.
Published: July 2010

Although tamoxifen appears to markedly reduce breast cancer risk in women with a prior diagnosis of atypical hyperplasia orin situcarcinoma, it is not clear what other groups of women receive substantial benefit. Major breast chemoprevention priorities are to (1) develop new agents that (a) have fewer side effects, (b) are effective in ER− as well as tamoxifen‐resistant precancerous tissue, and (c) are compatible with hormone therapy; and (2) develop efficient clinical strategies including prognostic and predictive morphologic and molecular biomarkers. Breast tissue may be repeatedly sampled for evidence of intraepithelial neoplasia by fine needle aspiration, ductal lavage, or needle biopsy to select candidates at highest short‐term risk as well as to monitor response in small proof of principle studies prior to a large cancer incidence trial. Molecular marker expression may also be used to select a cohort most likely to respond to a particular agent. A large number of new agents are attractive as potential prevention agents and some are already in clinical prevention testing. Compounds which should be effective in ER+ precancerous tissue but may have a better side‐effect profile include new selective estrogen receptor modulators which lack uterine estrogen agonist activity, isoflavones, aromatase inactivators/inhibitors for postmenopausal women, and gonadotropin‐releasing hormone regimens for premenopausal women. Retinoids, rexinoids, and deltanoids may be efficacious in ER+ tissue resistant to tamoxifen. Agents which should theoretically have activity in ER− or ER+ precancerous tissue include polyamine synthesis inhibitors, tyrosine kinase inhibitors, combined demethylating agents and histone deacetylase inhibitors, as well as metalloprotease and angiogenesis inhibitors. Sample Phase I and Phase II clinical trial designs are reviewed using modulation of molecular markers and breast intraepithelial neoplasia as the major endpoints.
Chemoprevention with Antiestrogens: The Beginning of the End for Breast Cancer
Authors: JORDAN V. CRAIG
Published: July 2010

In the 1960s, compounds known as nonsteroidal antiestrogens were identified as potential contraceptives, but the drugs caused the induction of ovulation in subfertile women. Tamoxifen and clomiphene were marketed for this indication. However, tamoxifen was advanced for the treatment of breast cancer in the 1970s through a close cooperation between the laboratory and the clinical trials community. The extensive use of long‐term adjuvant tamoxifen has resulted in saving the lives of 400,000 women with breast cancer. Tamoxifen is a selective estrogen receptor modulator (SERM) that produces antiestrogenic actions in the breast but estrogen‐like actions in bone and lowers serum cholesterol. These properties not only allowed the application of tamoxifen as the first chemopreventive in high‐risk pre‐ and postmenopausal women but also the development of raloxifene to prevent osteoporosis with the potential to prevent breast cancer in postmenopausal women. The future development of SERMs holds the promise of preventing osteoporosis and coronary heart disease as well as breast and endometrial cancer.
Cellular Mechanisms of Calcium and Vitamin D in the Inhibition of Colorectal Carcinogenesis
Authors: LAMPRECHT SERGIO A. , LIPKIN MARTIN
Published: July 2010

Convincing evidence is available showing that dietary calcium and vitamin D impede the development of colonic carcinogenesis. The major cellular modes of action of calcium and vitamin D which can contribute to the inhibition of colonic neoplasia are reviewed in this article. These consist of complex series of signaling events induced by the chemopreventive agents acting at various tiers of colonic cell organization.
The Future of Colon Cancer Prevention
Authors: UMAR ASAD , VINER JAYE L. , HAWK ERNEST T.
Published: July 2010

Chemoprevention science is in flux owing to rapid advances in postgenomic technology. We have witnessed enormous advances in the areas of early detection and molecular profiling of colorectal carcinogenesis; however, unique interpretive and technologic challenges persist. Neoplastic hallmarks must be iteratively tested and validated as markers of risk, targets for intervention, and/or markers of response in order to expedite the development of preventive interventions. In this review, we highlight several of the technologies that are revolutionizing our understanding of carcinogenesis and our approach to colorectal cancer prevention.
Inhibition of Cyclooxygenase‐2
Authors: DANNENBERG ANDREW J. , ALTORKI NASSER K. , BOYLE JAY O. , LIN DERRICK T. , SUBBARAMAIAH KOTHA
Published: July 2010

Multiple lines of evidence suggest that cyclooxygenase‐2 (COX‐2), an inducible form of COX, represents a potential pharmacologic target to prevent cancer. Key data suggesting a causal relationship between increased COX‐2 activity and carcinogenesis and possible mechanisms of action of COX‐2 in this context will be discussed. The possibility that COX‐2 represents a pharmacological target for preventing upper aerodigestive cancers (head and neck, lung) will be emphasized. Importantly, clinical trials have been initiated to assess the chemopreventive properties of selective COX‐2 inhibitors.
Diet and Breast Cancer Surveillance Behaviors among Harlem Women
Authors: GORIN SHERRI SHEINFELD , JACOBSON JUDITH
Published: July 2010

The consumption of green, yellow, and other vegetables, fruits and fruit juices may be protective against breast cancer, and, alongside regular breast cancer screening, may contribute to ethnic and racial differences in breast cancer rates. The purpose of this study is to assess the dietary and sociodemographic predictors of surveillance among Harlem women, using a population‐based household survey. One half of the Harlem women in this sample consumed no or one fruit or vegetable per day. Logistic regression analyses revealed that women who consumed more fruits and vegetables had received more recent mammography, and that women who were unemployed were less likely to receive recent breast cancer screening than were those who worked full‐ or part‐time. The high response rate and the representativeness of the sample are study strengths. Owing to the small sample size for women between 40‐65, the ages for which screening mammography and clinical breast exam are recommended, subgroup analyses were limited. Therefore, additional study of age‐adjusted dietary patterns and screening among African American women is suggested.
Chemopreventive Agents Inhibit Aberrant Proliferation of the Aneuploid Phenotype in a Colon Epithelial Cell Line Established from Apc 1638N [+/−] Mouse
Authors: KATDARE MEENA , KOPELOVICH LEVY , TELANG NITIN
Published: July 2010

Loss of function of the adenomatous polyposis coli (APC) tumor suppressor gene predisposes for familial adenomatous polyposis (FAP) syndrome. The Apc gene knockout mice exhibit accelerated intestinal carcinogensis modifiable by diverse pharmacological agents. Present experiments utilized the Apc[+/−] 1638N COL colon epithelial cell line (origin: histologically normal colon) as the model. Retinoid receptor modulator 9‐cis‐retinoic acid (9‐cis‐RA), ornithine decarboxylase inhibitor difluoromethyl ornithine (DFMO), and nonselective cyclooxygenase inhibitor sulindac (SUL) represented the chemopreventive test compounds. Population doubling, cell cycle progression, and anchorage‐independent growth provided mechanistic end points for chemopreventive efficacy. Treatment of 1638N COL cells with 9‐cis‐RA, DFMO and SUL produced a dose‐dependent cytostatic growth arrest by decreasing the number of population doublings and altering aneuploid G0/G1: S+G2/M ratio. The clonally expanded 1638N‐Cl1 cells selected for anchorage‐independent growth exhibited decreased anchorage‐independent colony formation in response to treatment with the three test compounds. Susceptibility of preneoplastic 1638N COL cells to mechanistically distinct chemopreventive agents validates a unique epithelial cell culture model for FAP syndrome, and facilitates investigations on Apc regulated colon carcinogenesis and cancer prevention.
The Effect of High Doses of Folic Acid on the Overexpression of Ornithine Decarboxylase and S‐Adenosylmethionine Content in Human Colon Adenomatous Polyps
Authors: BUKIN YU. V. , DRAUDIN‐KRYLENKO V. A. , LEVCHUK A. A. , PODDUBNIY B. K. , MAZUROV S. T.
Published: July 2010

It was shown that the 3‐month supplementation of patients having colon polyps with folic acid (5 mg/day) led to a 35% decrease in abnormally high ornithine decarboxylase activity in polyps that was accompanied by a 43% increase of S‐adenosylmethionine content in polyps.
Origins of Epidemiology
Authors: SUSSER EZRA , BRESNAHAN MICHAELINE
Published: July 2010

Abstract:In this paper we trace the history of epidemiology from 1800 to the present time. The history is highly selective because our purpose is to illuminate the evolving relationship of epidemiology with demography. We first describe the common “prehistory” of these two disciplines in the early nineteenth century, and then describe their divergence during three successive eras of epidemiology up to the end of the twentieth century. In the final section, we draw attention to exceptional individuals who bridged the two disciplines despite the historical trend in the other direction, and express our hope that recent signs of convergence in the face of globalization and the AIDS pandemic will be borne out during the coming decades.
Success and Future of Demography
Authors: MORGAN S. PHILIP , LYNCH SCOTT M.
Published: July 2010

Abstract: Demography typifies paradigmatic success; that is, cumulative scientific work that has provided useful perspectives on a set of important questions. This success can be traced partly to the core subject matter of demography, which is relatively conducive to quantitative, observational science. The development of demography was further aided by extrinsic factors, such as the import of its data for government administration, for business purposes, and the import of demographic questions for social problems and public policy. These observations make suspect any simple projection of demography's success into the future or the transport of its experience to other disciplines.
Theory and Practice in Epidemiology
Authors: WEED DOUGLAS L.
Published: July 2010

Abstract: Scientific and ethical theories are examined in terms of the practice of epidemiology, the study of the determinants and distributions of disease, and the application of the knowledge gained to prevent disease and improve the health of populations. Scientific theories provide explanations and predictions for epidemiologic studies of disease etiology and prevention. Causal theory is the key example for epidemiologic science, although theories of selection processes, theories of health, and theories of probability and statistics are also core. Theories of ethics provide principles, warrants, and methods for acting upon the knowledge gained in the scientific pursuits of epidemiology and for obtaining that knowledge appropriately. Ethical theories guide practitioners in making justified decisions about when and under what conditions public health interventions should be undertaken and how research participants should be treated. Theories of midlevel bioethical principles have received the most attention in epidemiology, but other theories, such as virtue theory and communitarian theory, are also relevant. Many theories matter to the practice of epidemiology: theories of biology, aging, evolution, and medicine; theories of history, religion, law, economics, and politics, as well as the theories of the physical, behavioral, and social sciences. These theories matter because epidemiologists study many different biological and social phenomena, and preventive interventions occur at many different levels of explanation. Development of theory is not a high priority in contemporary epidemiology. Identifying the responsibilities of the discipline to be public health intervention and rigorous science is a first step toward developing and applying theory in epidemiology.
Advocacy in Epidemiology and Demography
Authors: STOTO MICHAEL A. , HERMALIN ALBERT I. , LI ROSE , MARTIN LINDA , WALLACE ROBERT B. , WEED DOUGLAS L.
Published: July 2010

Abstract:This paper is a summary of a panel discussion at the Conference on Epidemiology and Demography held at Georgetown University, in Washington D.C. on February 8‐9, 2001. The participants were Al Hermalin, Linda Martin, Mike Stoto, Robert Wallace, Douglas Weed, and Rose Li (who chaired the session). A list of questions similar to the section headings in this paper was prepared in advance of the conference, and each of the participants was asked to address specific issues, although the presentations typically covered a range of topics. This summary also includes comments from the floor.
Social Environment Effects on Health and Aging
Authors: SEEMAN TERESA E. , CRIMMINS EILEEN
Published: July 2010

Abstract:This paper provides an overview of epidemiological and demographic research linking social characteristics of both individuals and communities to differences in both morbidity and mortality risks. Evidence is presented linking three broad aspects of the social environment to health—the network of personal social relationships within which most of us live our lives, individual socioeconomic status (SES), and community‐level social characteristics. Large and consistent bodies of literature from both epidemiology and demography provide clear evidence for the generally health‐promoting effects of personal social relationships and SES. The bulk of the evidence relates to mortality although both fields have begun to examine other health outcomes, including aspects of physical and cognitive functioning as well as disease outcomes. A smaller but growing body of community‐level data, reflecting both the socioeconomic/resource characteristics of these broader communities and, more specifically, social features of these environments, also point to health impacts from these more macro level social environment characteristics. Much remains to be elucidated, however, concerning the actual mechanisms through which something as complex and multifaceted as SES “gets under the skin.” This necessarily includes consideration of external characteristics of the environments (both physical and sociocultural) where people live and work, and individual characteristics, as well as possible interactions between these in producing the observed SES gradients in health and mortality. These questions concerning links between social environment conditions and health may be a particularly fruitful area of future collaboration, drawing on the shared interest of demographers and epidemiologists in understanding how different social conditions promote variation in distributions of better versus worse health outcomes within a population.
Crystal Structure Studies on Fibrinogen and Fibrin
Authors: DOOLITTLE RUSSELL F. , YANG ZHE , MOCHALKIN IGOR
Published: July 2010

Abstract: X‐ray crystallography studies on fragments D and double‐D from human fibrinogen and fibrin have revealed the details of knob‐hole interactions between fibrin units, as well as the nature of the association at their ends. More recently, a lower‐resolution structure of native chicken fibrinogen has provided details about the structure of the central domain, and particularly the arrangement of disulfide bonds. Parts of the fibrinogen molecule are so flexible that they have not been visualized in electron density maps. The elusive regions include the αC domain, the amino‐terminal segments of the α and β chains, and the carboxyl‐terminal segments of the γ chains. Nonetheless, when all the structural data are considered together, it is possible to construct a realistic model not only of a fibrinogen molecule but also of a fibrin protofibril.
A Database for Human Fibrinogen Variants
Authors: HANSS M. , BIOT F.
Published: July 2010

Abstract: Identifying and studying abnormal human fibrinogens is a source of much information, and helps in taking care of the affected patients. To permit exhaustive numbering and easy updates, an extensive register has been compiled and made available on the internet. Known molecular abnormalities are mentioned with the essential clinical features.
Structural and Functional Role of the β‐Strand Insert (γ381–390) in the Fibrinogen γ‐Module
Authors: YAKOVLEV SERGEI , LOUKINOV DMITRY , MEDVED LEONID
Published: July 2010

Abstract: Study of the folding status of the fibrinogen γ‐module (residues γ148–411) revealed that its COOH‐terminal β‐strand (residues γ381–390), that is normally inserted into its central domain, can be removed without destroying its compact structure. Based on this and other observations we propose a “pull out” hypothesis that suggests a mechanism for the formation of transverse γ‐γ crosslinks in fibrin.
Fibrinogen Longmont
Authors: LOUNES KARIM C. , LEFKOWITZ JERRY B. , COATES ANDREW I. , HANTGAN ROY R. , HENSCHEN‐EDMAN AGNES , LORD SUSAN T.
Published: July 2010

Abstract: BβArg166 to Cys substitution was identified in an abnormal fibrinogen named fibrinogen Longmont. The proband, a young woman, and her mother were heterozygous; both experienced episodes of severe hemorrhage at childbirth. The neo‐Cys residues were found to be disulfide‐bridged to either an isolated Cys amino acid or to the corresponding Cys residue of another abnormal fibrinogen molecule, forming dimers. Thrombin and batroxobin induced fibrin polymerization were impaired, despite normal release of fibrinopeptides A and B. Moreover, the polymerization defect was not corrected by removing the dimeric species or adding calcium. Fibrinogen Longmont had normal polymerization site a, as evidenced by normal GPRP‐peptide binding. Thus, the sites A and a can interact to form protofibrils, as evidenced by dynamic light scattering measurements. These protofibrils, however, do not associate laterally in a normal manner, leading to an abnormal clot formation.
Early Events in the Polymerization of Fibrin
Authors: ROCCO MATTIA , BERNOCCO SIMONETTA , TURCI MARCO , PROFUMO ALDO , CUNIBERTI CARLA , FERRI FABIO
Published: July 2010

Abstract: The early events in the thrombin‐induced formation of fibrin have been studied by the use of stopped‐flow multiangle laser light scattering (SF‐MALLS). This technological advancement has allowed the recovering, as a function of time with a resolution of about 0.5 sec, of the mean square radius of gyration and of the molecular weight Mw, and to place an upper bound to the values of the mass/unit length ML. The ionic strength, pH and salt type conditions investigated were all close to physiological, starting with a 50 mM Tris, 104 mM NaCl, pH 7.4 buffer (TBS), to which either 1 mM EDTA‐Na2 or 2.5 mM CaCl2 were also added. Fibrinogen was 0.2–0.3 mg/ml and rate‐limiting concentrations of thrombin were used (0.05–0.25 NIH units/mg fibrinogen). By plotting and ML versus Mw on log‐log scales, runs proceeding at different velocities and under different solvent conditions could be compared and confronted with model curves. It was found that: (1) within this thrombin range, the mechanism of association does not depend on its concentration, nor on the buffers employed; (2) the versus Mw curves could all be reasonably fitted with a bifunctional polycondensation scheme involving semiflexible worm‐like, double‐stranded, half‐staggered polymers with persistence length between 200–600 nm, provided that a ratio Q= 16 between the rate of release of the two fibrinopeptides A was employed; (3) the ML versus Mw data seemed more compatible with lower Q values (4 < Q < 8), but their uncertainty prevented a better assessment of this issue; the formation of fibrinogen‐fibrin monomer complexes may also play a role in the polymer distributions; (4) in the very early stages (e.g., when Mw < 7 × 105), the versus Mw data were fitted well only in TBS and at the lowest thrombin concentration, suggesting that a transient, either sequential or concurrent fast second mechanism, involving longer and thinner polymers, may be at work.
Polymerization Site a Function Dependence on Structural Integrity of Its Nearby Calcium Binding Site
Authors: LOUNES KARIM C. , OKUMURA NOBUO , HOGAN KELLY A. , PING LIFANG , LORD SUSAN T.
Published: July 2010

Abstract: To explore the functional relationship between the polymerization site a and the nearby high affinity calcium binding site, we analyzed four variant fibrinogens with substitutions at these sites: γD364A in the a site and γD318A, γD320A, and γD318 +γD320A in the Ca2+ site. In all cases fibrinopeptide A release was normal and thrombin catalyzed polymerization was markedly impaired (unpublished observations). We examined the functional connection between the Ca2+ site and the a site by testing for plasmin protection in the presence of Ca2+ or the a site peptide ligand GPRP. SDS‐PAGE analysis of the products showed that γD364A fibrinogen was protected from plasmin cleavage by Ca2+ but not by the GPRP peptide. In contrast, neither Ca2+ nor the GPRP peptide protected γD318A, γD320A, or γD318 +γD320A fibrinogens from complete plasmin cleavage. These results suggest that the structural integrity of the calcium binding site is required for expression of the a site. In contrast, the structural integrity of the a site has no functional consequence on Ca2+ binding to this high affinity site.
Fibrin Formation and Proteolysis during Ancrod Treatment
Authors: DEMPFLE CARL‐ERIK , ARGIRIOU SOTIRIA , ALESCI SONJA , KUCHER KLAUS , MÜLLER‐PELTZER H. , RÜBSAMEN KLAUS , HEENE DIETER L.
Published: July 2010

Abstract: Ancrod is a purified fraction of venom from the Malayan pit viper Calloselasma rhodostoma, containing a serine protease that cleaves fibrinopeptides A from fibrinogen. We report on a study that involved intravenous and subcutaneous application of ancrod in healthy subjects in which it was shown that ancrod induces the formation of desAA‐fibrin complexes that are partially crosslinked by factor XIII proenzyme, and act as cofactor in tPA induced plasminogen activation. The plasmin generated degrades fibrin, as well as fibrinogen, leading to the appearance of large amounts of fibrinogen and fibrin degradation products in the circulation, including fragment D‐dimer. At low concentrations of ancrod, formation of desAA‐fibrin is preceded by production of desA‐profibrin, lacking only one fibrinopeptide A.
Characterization of Crosslinking Sites in Fibrinogen for Plasminogen Activator Inhibitor 2 (PAI‐2)
Authors: RITCHIE HELEN , LAWRIE LAURA C. , MOSESSON MICHAEL W. , BOOTH NUALA A.
Published: July 2010

Abstract: PAI‐2 is a serpin that can be crosslinked to fibrin(ogen) via the Gln‐Gln‐Ile‐Gln sequence (residues 83–86). We have characterized the lysine residues in fibrinogen to which PAI‐2 is crosslinked by tissue transglutaminase and factor XIIIa. There was no competition with the crosslinking of α2‐antiplasmin, another inhibitor of fibrinolysis, which was specific for Lys 303 in the Aα chain. PAI‐2 was crosslinked to several lysine residues, all in the Aα chain, 148, 176, 183, 230, 413, and 457, but not to Lys 303. The contrast with α2‐antiplasmin was clear from studies with truncated fibrinogens and competition by peptides. This was confirmed and extended by mass spectrometry of peptides after protease digestion of crosslinked products, which identified the lysine residues to which the inhibitors were crosslinked. PAI‐2 remained active after cross‐linking and inhibited fibrin breakdown, even by two‐chain t‐PA. Thus, a second inhibitor of fibrinolysis, in addition to α2‐antiplasmin, is crosslinked to fibrin and protects it from lysis.
Elements of the Fibrinolytic System
Authors: LIJNEN H.R.
Published: July 2010

Abstract: The blood fibrinolytic system comprises an inactive proenzyme, plasminogen, that can be converted to the active enzyme, plasmin. Plasmin degrades fibrin into soluble fibrin degradation products, by two physiological plasminogen activators (PA), the tissue type PA (t‐PA) and the urokinase type PA (u‐PA). t‐PA mediated plasminogen activation is mainly involved in the dissolution of fibrin in the circulation. u‐PA binds to a specific cellular receptor (u‐PAR), resulting in enhanced activation of cell bound plasminogen. Inhibition of the fibrinolytic system may occur either at the level of the PA, by specific plasminogen activator inhibitors (PAI), or at the level of plasmin, mainly by α2‐antiplasmin. Several molecular interactions have been observed between the fibrinolytic and the matrix metalloproteinase (MMP) system; both systems may cooperate in generating proteolytic activity. Thus, stromelysin‐1 (MMP‐3) cleaves a 55‐kDa kringle 1–4 fragment, containing the lysine binding site(s) involved in cellular binding, from plasminogen and removes a 17‐kDa NH2‐terminal fragment, containing the cellular receptor binding site, from urokinase (u‐PA). Thereby, MMP‐3 may downregulate cell associated plasmin activity by decreasing the amount of activatible plasminogen, without affecting cell bound u‐PA activity.
Modulation of Fibrin Cofactor Activity in Plasminogen Activation
Authors: NESHEIM MICHAEL , WALKER JOHN , WANG WEI , BOFFA MICHAEL , HORREVOETS ANTON , BAJZAR LASZLO
Published: July 2010

Abstract: Fibrin is a cofactor for the formation of plasmin from plasminogen as catalyzed by tissue plasminogen activator. Initial cleavages of fibrin by plasmin upregulates the cofactor activity of fibrin by exposing carboxyl terminal lysine residues. This effect is eliminated by a carboxypeptidase B‐like enzyme generated from the precursor, thrombin activatable fibrinolysis inhibitor (TAFI) that is generated by thrombin during the formation of fibrin. Thus, TAFI and its activation to TAFIa create a link between the coagulation and fibrinolytic cascade, such that activation of the former suppresses the latter. Complete solubilization of fibrin results in a family of very large fibrin degradation products. These also have very substantial tissue plasminogen activator cofactor activity that is very highly downregulated by TAFIa.
Fibrinogen αC Domains Contain Cryptic Plasminogen and tPA Binding Sites
Authors: TSURUPA GALINA , MEDVED LEONID
Published: July 2010

Abstract: Surface plasmon resonance and ELISA experiments revealed that recombinant fibrinogen αC fragment (residues Aα221–610) corresponding to the αC domain binds tPA and plasminogen with high affinity. This binding was found to be Lys‐dependent and occurred via independent binding sites. Study with truncated variants of the αC fragment located these sites in its COOH‐terminal half. Binding of tPA and plasminogen to these sites stimulated activation of the latter whereas proteolytic degradation of the αC fragment reduced this effect substantially, suggesting the importance of the αC domains in regulation of fibrinolysis.
Clot Lysis of Variant Recombinant Fibrinogens Confirms that Fiber Diameter is a Major Determinant of Lysis Rate
Authors: MULLIN JENNIFER L. , NORFOLK SUSAN E. , WEISEL JOHN W. , LORD SUSAN T.
Published: July 2010

Abstract: Previous studies have suggested that clots with thinner fiber diameter lyse at slower rates than clots with thicker fiber diameter. We examined lysis of fibrin clots formed from three variant fibrinogens, each with substitutions in the N‐terminal region of the Bβ chain. When we measured lysis as the rate of decrease in turbidity at 350 nm, we found that the rate of lysis was slower than normal for clots with thinner fibers. We noted, however, that the time to complete lysis was the same for all clots. Thus, when the data were considered as the percent of lysis with time, we found that the curves were the same as normal. We suggest that a complete and accurate characterization of clot dissolution requires comparison of normalized lysis rates.
Crosslinking of α2‐Antiplasmin to Fibrin
Authors: LEE KYUNG N. , LEE CHUNG S. , TAE WEON‐CHAN , JACKSON KENNETH W. , CHRISTIANSEN VICTORIA J. , MCKEE PATRICK A.
Published: July 2010

Abstract: Human α2‐antiplasmin (α2AP) is the primary inhibitor of plasmin‐mediated fibrinolysis and is an efficient substrate of activated factor XIII (FXI‐IIa). Among 452 amino acid residues in α2AP, Gln2 is believed to be the sole FXI‐IIa‐reactive site that participates in crosslinking α2AP to fibrin. We studied the effect of mutating Gln2 on the ability of FXIIIa to catalyze crosslinking of α2AP to fibrin. By FXIIIa catalysis, [14C]methylamine was incorporated into a Q2A‐α2AP mutant in which Gln2 (Q) was replaced by Ala (A), thereby indicating that wildtype α2AP has more than one FXIIIa‐reactive site. To identify the FXIIIa‐reactive sites in α2AP, wildtype α2AP and Q2A‐α2AP were labeled with 5‐(biotinamido)pentylamine by FXIIIa. Each labeled α2AP was digested with trypsin and applied to an avidin affinity column to capture labeled peptides. Edman sequencing and mass analysis of each labeled peptide showed that out of 35 Gln residues in wildtype α2AP, four were labeled with the following order of efficiency: Gln2 > Gln21 > Gln419 > Gln447. Q2A‐α2AP was also labeled at the three minor sites, Gln21 > Gln419 > Gln447. Q2A‐α2AP became crosslinked to fibirin(ogen) by FXIIIa catalysis at approximately one‐tenth the rate of wt‐α2AP. These results demonstrate that α2AP has one primary (Gln2) and three minor substrate sites for FXIIIa and that the three minor sites identified in this study can also participate in crosslink formation between α2AP and fibrin, but at a much lower efficiency than the Gln2 site.
Platelet‐Fibrinogen Interactions
Authors: BENNETT JOEL S.
Published: July 2010

Abstract: Binding of fibrinogen to GPIIb‐IIIa on agonist‐stimulated platelets results in platelet aggregation, presumably by crosslinking adjacent activated platelets. Although unactivated platelets express numerous copies of GPIIb‐IIIa on their surface, spontaneous, and potentially deleterious, platelet aggregation is prevented by tightly regulating the fibrinogen binding activity of GPIIb‐IIIa. Preliminary evidence suggests that it is the submembranous actin or actin‐associated proteins that constrains GPIIb‐IIIa in a low affinity state and that relief of this constraint by initiating actin filament turnover enables GPIIb‐IIIa to bind fibrinogen. Two regions of the fibrinogen α chain that contain an RGD motif, as well as the carboxyl‐terminus of the fibrinogen γ chain, represent potential binding sites for GPIIb‐IIIa in the fibrinogen molecule. However, ultrastructural studies using purified fibrinogen and GPIIb‐IIIa, and studies using recombinant fibrinogen in which the RGD and relevant γ chain motifs were mutated indicate that sequences located at the carboxyl‐terminal end of the γ chain mediates fibrinogen binding to GPIIb‐IIIa. There is evidence that fibrinogen itself binds to regions in the amino terminal portions of both GPIIb and GPIIIa and that the sites interacting with the fibrinogen γ chain and with RGD‐containing peptides are spatially distinct. Nonetheless, there appears to be allosteric linkage between these sites, accounting for the ability of RGD‐containing peptides to inhibit platelet aggregation and arterial thrombosis.
Identification and Characterization of Five New Fibrinogen Gene Polymorphisms
Authors: FELLOWES ANDREW P. , BRENNAN STEPHEN O. , GEORGE PETER M.
Published: July 2010

Abstract: It is clear that plasma fibrinogen levels are strongly influenced by genetic factors. To date 14 polymorphic sites have been identified within the fibrinogen gene cluster, mainly by restriction fragment length polymorphism (RFLP) and single‐stranded conformation polymorphism (SSCP) analyses. Since elevated plasma fibrinogen is an independent risk factor for cardiovascular disease, these and other polymorphisms are of practical interest in defining haplotypes that correlate with fibrinogen levels. Here, DNA sequencing of fibrinogen genes from four patients led to the identification of 17 variations from the published sequence. Nine of these occurred in all chromosomes sequenced and were considered to be errors in the published data. Of the remaining eight, five represented novel variations, three having been previously described. The population frequency of the five novel variations, together with six known polymorphisms, was estimated by genotyping 50 normal individuals at each locus. The five new variations were all found at polymorphic frequencies in this group. Two of these new polymorphisms, Bβ intron 2 and Bβ codon 159, belong to the Bβ linkage group defined by Behague et al.,1 since their rare alleles occurred in complete concordance with the rare alleles of BβMnl I and BβBcl I. Calculation of pairwise linkage disequilibrium coefficients showed that the three remaining novel polymorphisms, AαDde I, BβHinf I, and γ intron 9 exhibited linkage equilibrium with respect to all other loci examined, including nearby polymorphisms that are themselves in strong linkage disequilibrium. This data indicates that these polymorphisms occur randomly with respect to background haplotype, and suggests that they are mutational hot spots.