bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultraviolet irradiation of eggs and blastomere isolation experiments suggest that gastrulation in the direct developing ascidian, Molgula pacifica, requires localized cytoplasmic determinants in the egg and cell signaling beginning at the two‐cell stage
Authors: Bates William R.
Published: April 2004

Summary
Gastrulation in the maximum direct developing ascidian Molgula pacifica is highly modified compared with commonly studied “model” ascidians in that endoderm cells situated in the vegetal pole region do not undergo typical invagination and due to the absence of a typical blastopore the involution of mesoderm cells is highly modified. At the gastrula stage, embryos are comprised of a central cluster of large yolky cells that are surrounded by a single layer of ectoderm cells in which there is only a slight indication of an inward movement of cells at the vegetal pole. As a consequence, these embryos do not form an archenteron. In the present study, ultraviolet (UV) irradiation of fertilized eggs tested the possibility that cortical cytoplasmic factors are required for gastrulation, and blastomere isolation experiments tested the possibility that cell signaling beginning at the two‐cell stage may be required for the development of the gastrula. Irradiation of unoriented fertilized eggs with UV light resulted in late cleavage stage embryos that failed to undergo gastrulation. When blastomeres were isolated from two‐cell embryos, they developed into late cleavage stage embryos; however, they did not undergo gastrulation and subsequently develop into juveniles. These results suggest that cytoplasmic factors required for gastrulation are localized in the egg cortex, but in contrast to previously studied indirect developers, these factors are not exclusively localized in the vegetal pole region at the first stage of ooplasmic segregation. Furthermore, the inability of embryos derived from blastomeres isolated at the two‐cell stage to undergo gastrulation and develop into juveniles suggests that important cell signaling begins as early as the two‐cell stage in M. pacifica. These results are discussed in terms of the evolution of maximum direct development in ascidians.
Evolution of posterior lateral line development in fish and amphibians
Authors: Pichon Fabien , Ghysen Alain
Published: April 2004

Summary The lateral line is a sensory system present in fish and amphibians. It is composed of discrete sense organs, the neuromasts, arranged on the head and body in species‐specific patterns. The neuromasts are deposited by migrating primordia that originate from pre‐ and postotic placodes and follow defined pathways on the head and body. Here we examine the formation of the posterior lateral line (PLL), which extends rostrocaudally on the trunk and tail. In amphibians, the PLL neuromasts are deposited as a single wave from the head to the tip of the tail. In the zebrafish, however, the first wave of neuromast deposition forms but a rudimentary PLL, and several additional waves are needed to form the adult pattern. We show that the amphibian mode is also present in the sturgeon and therefore probably represents the primitive mode, whereas the zebrafish mode is highly conserved in several teleost species. A third mode is found in a subgroup of teleosts, the protacanthopterygians, and may represent a synapomorphy of this group. Altogether, the mode of formation of the embryonic PLL appears to have undergone remarkably few changes during the long history of anamniote evolution, even though large differences can be observed in the lateral line morphology of adult fishes.
Associations of Mass Media Exposure with Family Planning Attitudes and Practices in Uganda
Authors: Gupta Neeru , Katende Charles , Bessinger Ruth
Published: April 2004

This study examines the associations between multimedia behavior change communication (BCC) campaigns and women's and men's use of and intention to use modern contraceptive methods in target areas of Uganda. Data are drawn primarily from the 1997 and 1999 Delivery of Improved Services for Health (DISH) evaluation surveys, which collected information from representative samples of women and men of reproductive age in the districts served by the DISH project. Additional time‐trend analyses rely on data from the 1995 Uganda Demographic and Health Survey. Logistic regressions are used to assess the associations between BCC exposure and family planning attitudes and practices, controlling for individuals' background characteristics. To minimize the biases of self‐reported exposure, the analyses also explore cluster‐level indexes of the penetration of BCC messages in the community. Results indicate that exposure to BCC messages was associated with increased contraceptive use and intention to use. Some evidence of self‐reported bias is found, and the pathways to fertility‐related behavioral change appear different for women and men.
Inequality and Changes in Women's Use of Maternal Health‐care Services in Tajikistan
Authors: Falkingham Jane
Published: April 2004

Using recently available survey data for Tajikistan, this study explores changes in the pattern of maternal health care during the last decade and the extent to which inequalities in access to that care have emerged. In particular, the links between poverty and women's educational status and the use of maternal health‐care services are investigated. The survey findings demonstrate a significant decline in the use of maternal health‐care services in Tajikistan since the country gained independence from the Soviet Union in 1991. They show changes in the location of delivery and the person providing assistance, with a clear shift away from giving birth in a medical facility toward giving birth at home. More than two‐fifths of all women who gave birth in the year prior to the survey delivered their baby at home. Women from the poorest quintile are three times more likely than women from the richest quintile to undergo a home delivery without a trained assistant.
Age and Economic Asymmetries in the Sexual Relationships of Adolescent Girls in Sub‐Saharan Africa
Authors: Luke Nancy
Published: April 2004

This literature review assesses the extent of age mixing and economic transactions in the sexual relationships of adolescent girls in sub‐Saharan Africa and the behavioral dynamics of girls and men involved in these partnerships. The examination of more than 45 quantitative and qualitative studies finds that relationships with older partners and those that involve economic transactions are common and that these asymmetries are associated with unsafe sexual behaviors and increased risk of HIV infection. Although the reasons that adolescent girls engage in sexual relationships with older men are varied, receipt of financial benefits is a major motivation. The literature presents evidence that girls have considerable negotiating power over certain aspects of sexual relationships with older men, including partnership formation and continuation; however, they have little control over sexual practices within partnerships, including condom use and violence. The review discusses directions for further research and the implications of current knowledge for future interventions.
How Gender Roles Influence Sexual and Reproductive Health Among South African Adolescents
Authors: Varga Christine A.
Published: April 2004

Although the literature on Africa increasingly adopts a gendered approach to sexual and reproductive health issues, few studies have addressed adolescent pregnancy and parenthood in such a framework. This article examines links between gender ideology or gender roles and the social impact of adolescent childbearing in the lives of rural and urban adolescents in KwaZulu/Natal, South Africa. It employs a triangulated research methodology (focus‐group discussions, narrative role playing and discussions, and questionnaires and in‐depth interviews) to inform an analysis of adolescents' notions of male and female gender ideals. This analysis forms the basis for an exploration of the potential influence of adolescent childbearing on young peoples' lives and factors that shape their sexual and reproductive well‐being. Results indicate that gender ideals are grounded in traits that reinforce poor sexual negotiation dynamics and behavioral double standards and that place adolescents at risk for early pregnancy and other sexual and reproductive health complications. Overall, adolescent parenthood is viewed negatively by participants of both sexes because it compromises personal, professional, and financial aspirations. Compared with its effect on boys, parenthood has a disproportionate (and highly negative) impact on girls that is directly linked to gender‐based inequities. The article addresses the research and policy implications of these findings.
Factors Influencing Young Malians' Reluctance to Use Hormonal Contraceptives
Authors: Castle Sarah
Published: April 2004

During a qualitative evaluation of three peer‐education programs in urban Mali, young people stated that they were wary of using either the pill or injectable contraceptives because they believed that these methods would make them sterile. Unmarried women's contraceptive decisionmaking was not primarily driven by a current need to limit fertility, but rather by a future need to maximize it in order to gain status through childbearing in their marital households. Further interviews explored notions of conception, menstruation, and the perceived action of hormonal methods on the reproductive system. Findings revealed that menstrual disruption (in the form of amenorrhea or prolonged bleeding) appeared to have dire repercussions, including accusations of witchcraft and immoral behavior that could result in a woman's being divorced or in her husband's acquiring an additional wife. The social consequences of side effects were perceived to be more important than their biological manifestations, and together with the fear of sterility, resulted in a preference for the condom.
The “Softer Side” of Consulting to Business-Owning Families: Understanding Our Clients and Ourselves
Authors: Herz Brown Fredda
Published: April 2004

It is the responsibility of those who consult to business-owning families to have as much knowledge about themselves as they do about their clients. A framework is offered for the consultant to understand self and others. A case study and implications for consultative practice evolve from the framework described in this paper.
Revisiting the Study of Family Businesses: Methodological Challenges, Dilemmas, and Alternative Approaches
Authors: Winter Mary , Fitzgerald Margaret A. , Heck Ramona K. Z. , Haynes George W. , Danes Sharon M.
Published: April 2004

Family businesses are vital but understudied economic and social units. Previous family business research is limited relative to its definitions, sampling, and resulting empirical evidence. This paper presents an alternative methodological approach to the study of family businesses with the potential for allowing multiperspective and detailed analyses of the nature and internal dynamics of both the family and the business and the interaction between the two.
The Role of Going Public in Family Businesses' Long-Lasting Growth: A Study of Italian IPOs
Authors: Mazzola Pietro , Marchisio Gaia
Published: April 2004

This research note investigates how going public affects the capacity of companies to pursue growth and profitability in the long run. It combines the results of transversal and longitudinal analyses of two databases of fast-growing Italian companies and IPOs and compares the results with nonfamilyowned businesses that went public during the same period. Studies of companies' growth show two main reasons for growth: external causes due to evolution in progress in the competitive environment and internal causes brought about by management ambitions. In either case, growth provides companies with three main advantages: the ability to increase value, higher market shares, and increased productivity. Italian empirical research shows the great difficulties that both small and large companies have growing. It is estimated that most companies, especially small ones, are family owned. The literature shows that family-owned companies face particular obstacles and that the IPO appears to provide them with some advantages.
Enterprising Families Domain: Family-Influenced Ownership Groups in Pursuit of Transgenerational Wealth
Authors: Habbershon Timothy G. , Pistrui Joseph
Published: April 2004

The field of family business studies has not explicitly identified the entrepreneurial potential of the family ownership group or adequately delineated the strategic requirements for sustaining wealth creation across generations. To address such issues, this paper presents the parameters for family-influenced transgenerational wealth creation. It identifies the family ownership group as the appropriate unit of entrepreneurial analysis and delineates the entrepreneurial strategy methods and family-as-investor mind-set that create the enterprising families domain. In so doing, the paper creates a true nexus between the fields of entrepreneurial strategy and family business studies.
The Dynamics of Women's Roles as Family Business Managers
Authors: Curimbaba Florence
Published: April 2004

This study investigates the professional experiences of female heirs in a variety of family businesses located in three states of the Brazilian Southeast. The aim is to analyze both how the family and business structures affect the daughters' visibility in managerial positions and the resulting gender relations. Twelve open-ended, in-depth interviews were conducted. The responses were analyzed, and pathways were classified according to the Gersick, Davis, Hampton, and Lansberg (1997) three-dimensional development model of family businesses. Three groups were formed to describe the daughters' experiences: invisible, professional, and anchor.
Governance and Flexibility in Family-Owned SMEs
Authors: Gubitta Paolo , Gianecchini Martina
Published: April 2004

This article presents an empirical study that uses a sample of 83 small and medium-size enterprises (SMEs) based in Northeast Italy. The study analyzes the impact of nonfamily management on the corporate governance structure. We employ an original framework, based on the New Theory of Property Rights, to analyze corporate governance models in SMEs. Moreover, this article offers a definition of flexibility of the corporate governance model. We also analyze the correspondence between corporate governance systems and organizational structures.
Local and Systemic Antibody Responses in Mice Immunized Intranasally with Native and Detergent-Extracted Outer Membrane Vesicles fromNeisseria meningitidis
Authors: Guthrie Terry , Wong Simon Y. C. , Liang Bin , Hyland Lisa , Hou Sam , Høiby E. Arne , Andersen Svein Rune
Published: April 2004

The mouse humoral immune response toward native or detergent-extracted outer membrane vesicles (NOMVs and DOMVs, respectively) fromNeisseria meningitidiswas determined after intranasal immunization. Both preparations elicited high frequencies of NOMV-specific antibody-forming cells (AFCs) locally in the nasal associated lymphoid tissue (NALT) after three or four weekly doses. The diffuse NALT (D-NALT) contained ca. 10-fold more NOMV-specific AFCs than those observed in the mediastinal lymph node, spleen, and bone marrow. AFCs observed in the D-NALT were primarily immunoglobulin A positive (IgA+) and were maintained for at least 1 month. In contrast, the organized NALT (O-NALT) contained low numbers of AFCs, and the response was relatively short-lived. In other lymphoid tissues, AFCs producing various IgG subclasses and IgM were present with IgG2b-producing AFCs being dominant or codominant with IgA or IgG2a. In serum and in all of the tissues examined, with the exception of the NALT, NOMVs clearly induced a stronger antibody response and a broader range of antibody isotypes than DOMVs. The development of NOMV-specific AFCs in spleen and bone marrow after intranasal immunization was slow compared to intravenous immunization but, once established, the intranasally elicited responses increased steadily for at least 75 days. NOMV-specific antibodies induced via several routes of immunization had high bactericidal activities in serum. Our results indicated that intranasally administered OMVs induced strong local and systemic antibody responses in mice that were relatively long-lived.
Cloning and Characterization of the Gene Encoding the Major Cell-Associated Phospholipase A of
Legionella pneumophila
,
plaB
, Exhibiting Hemolytic Activity
Authors: Flieger Antje , Rydzewski Kerstin , Banerji Sangeeta , Broich Markus , Heuner Klaus
Published: April 2004

Legionella pneumophila
, the causative agent of Legionnaires' disease, is an intracellular pathogen of amoebae, macrophages, and epithelial cells. The pathology of
Legionella
infections involves alveolar cell destruction, and several proteins of
L. pneumophila
are known to contribute to this ability. By screening a genomic library of
L. pneumophila
, we found an additional
L. pneumophila
gene,
plaB
, which coded for a hemolytic activity and contained a lipase consensus motif in its deduced protein sequence. Moreover,
Escherichia coli
harboring the
L. pneumophila plaB
gene showed increased activity in releasing fatty acids predominantly from diacylphospho- and lysophospholipids, demonstrating that it encodes a phospholipase A. It has been reported that culture supernatants and cell lysates of
L. pneumophila
possess phospholipase A activity; however, only the major secreted lysophospholipase A PlaA has been investigated on the molecular level. We therefore generated isogenic
L. pneumophila plaB
mutants and tested those for hemolysis, lipolytic activities, and intracellular survival in amoebae and macrophages. Compared to wild-type
L. pneumophila
, the
plaB
mutant showed reduced hemolysis of human red blood cells and almost completely lost its cell-associated lipolytic activity. We conclude that
L. pneumophila plaB
is the gene encoding the major cell-associated phospholipase A, possibly contributing to bacterial cytotoxicity due to its hemolytic activity. On the other hand, in view of the fact that the
plaB
mutant multiplied like the wild type both in U937 macrophages and in
Acanthamoeba castellanii
amoebae,
plaB
is not essential for intracellular survival of the pathogen.
Pattern of Cytokine Responses to Gram-Positive and Gram-Negative Commensal Bacteria Is Profoundly Changed when Monocytes Differentiate into Dendritic Cells
Authors: Karlsson Helen , Larsson Pia , Wold Agnes E. , Rudin Anna
Published: April 2004

The normal gastrointestinal bacterial flora is crucial for the maturation of acquired immunity via effects on antigen-presenting cells (APCs). Here we investigated how two types of APCs, monocytes and dendritic cells (DCs), react to different bacterial strains typical of the commensal intestinal microflora. Purified human monocytes and monocyte-derived DCs were stimulated with UV-inactivated gram-positive (Lactobacillus plantarumandBifidobacterium adolescentis) and gram-negative (Escherichia coliandVeillonella parvula) bacterial strains. Monocytes produced higher levels of interleukin 12p70 (IL-12p70) and tumor necrosis factor (TNF), as detected by an enzyme-linked immunosorbent assay, in response toL. plantarumthan in response toE. coliandV. parvula. In contrast, DCs secreted large amounts of IL-12p70, TNF, IL-6, and IL-10 in response toE. coliandV. parvulabut were practically unresponsive toL. plantarumandB. adolescentis. The lack of a response to the gram-positive strains correlated with lower surface expression of Toll-like receptor 2 (TLR2) on DCs than on monocytes. The surface expression of TLR4 on DCs was undetectable when it was analyzed by flow cytometry, but blocking this receptor decreased the TNF production in response toV. parvula, indicating that TLR4 is expressed at a low density on DCs. Gamma interferon increased the expression of TLR4 on DCs and also potentiated the cytokine response to the gram-negative strains. Our results indicate that when monocytes differentiate into DCs, their ability to respond to different commensal bacteria dramatically changes, and they become unresponsive to probiotic gram-positive bacteria. These results may have important implications for the abilities of different groups of commensal bacteria to regulate mucosal and systemic immunity.
Engulfment ofNeisseria gonorrhoeae: Revealing Distinct Processes of Bacterial Entry by Individual Carcinoembryonic Antigen-Related Cellular Adhesion Molecule Family Receptors
Authors: McCaw Shannon E. , Liao Edward H. , Gray-Owen Scott D.
Published: April 2004

IndividualNeisseria gonorrhoeaecolony opacity-associated (Opa) protein variants can bind up to four different carcinoembryonic antigen-related cellular adhesion molecule (CEACAM) receptors. Most human cells encountered by gonococci express a combination of CEACAM receptors, thereby complicating the elucidation of intracellular signaling pathways triggered by individual receptors. Here, we compare the process of bacterial engulfment by a panel of stably transfected HeLa epithelial cell lines expressing each CEACAM receptor in isolation. CEACAM1 and CEACAM3 each contain proteinaceous transmembrane and cytoplasmic domains; however, the processes of neisserial uptake mediated by these receptors differ with respect to their susceptibilities to both tyrosine kinase inhibitors and the actin microfilament-disrupting agent cytochalasin D. Neisserial uptake mediated by glycosylphosphatidylinositol (GPI)-anchored CEACAM5 and CEACAM6 was not significantly affected by any of a broad spectrum of inhibitors tested. However, cleavage of the GPI anchor by phosphatidylinositol-specific phospholipase C reduced bacterial uptake by HeLa cells expressing CEACAM5, consistent with a single zipper-like mechanism of uptake mediated by this receptor. Regardless of the CEACAM receptor expressed, internalized gonococci were effectively killed by a microtubule-dependent process that required acidification of the bacterium-containing phagosome. Given the phase-variable nature of neisserial Opa proteins, these results indicate that the mechanism of bacterial engulfment and the cellular response to gonococcal infection depend on both the receptor specificities of the neisserial Opa protein variants expressed and the spectrum of CEACAM receptors present on target cells, each of which determines the combination of receptors ultimately engaged.
Proteolytic Processing of theMycoplasma hyopneumoniaeCilium Adhesin
Authors: Djordjevic Steven P. , Cordwell Stuart J. , Djordjevic Michael A. , Wilton Jody , Minion F. Chris
Published: April 2004

Mycoplasma hyopneumoniaeis an economically significant swine pathogen that colonizes the respiratory ciliated epithelial cells. Cilium adherence is mediated by P97, a surface protein containing a repeating element (R1) that is responsible for binding. Here, we show that the cilium adhesin is proteolytically processed on the surface. Proteomic analysis of strain J proteins identified cleavage products of 22, 28, 66, and 94 kDa. N-terminal sequencing showed that the 66- and 94-kDa proteins possessed identical N termini and that the 66-kDa variant was generated by cleavage of the 28-kDa product from the C terminus. The 22-kDa product represented the N-terminal 195 amino acids of the cilium adhesin preprotein, confirming that the hydrophobic leader signal sequence is not cleaved during translocation across the membrane. Comparative studies ofM. hyopneumoniaestrain 232 showed that the major cleavage products of the cilium adhesin are similar, although P22 and P28 appear to be processed further in strain 232. Immunoblotting studies using antisera raised against peptide sequences within P22 and P66/P94 indicate that processing is complex, with cleavage occurring at different frequencies within multiple sites, and is strain specific. Immunogold electron microscopy showed that fragments containing the cilium-binding site remained associated with the cell surface whereas cleavage products not containing the R1 element were located elsewhere. Not all secreted proteins undergo multiple cleavage, however, as evidenced by the analysis of the P102 gene product. The ability ofM. hyopneumoniaeto selectively cleave its secreted proteins provides this pathogen with a remarkable capacity to alter its surface architecture.
Importance of the Ornibactin and Pyochelin Siderophore Transport Systems in
Burkholderia cenocepacia
Lung Infections
Authors: Visser M. B. , Majumdar S. , Hani E. , Sokol P. A.
Published: April 2004

Previously,
orbA
, the gene encoding the outer membrane receptor for ferric-ornibactin, was identified in
Burkholderia cenocepacia
K56-2, a strain which produces ornibactin, salicylic acid, and negligible amounts of pyochelin. A K56-2
orbA
mutant was less virulent than the parent strain in a rat agar bead infection model. In this study, an
orbA
mutant of
B. cenocepacia
Pc715j which produces pyochelin in addition to ornibactin and salicylic acid was constructed. The gene encoding the outer membrane receptor for ferric-pyochelin (
fptA
) was also identified. An
fptA
mutant was constructed in Pc715j and shown to be deficient in [
59
Fe]pyochelin uptake. A 75-kDa iron-regulated protein was identified in outer membrane preparations of Pc715j that was absent in outer membrane preparations of Pc715j
fpt
A::tp. Pc715j
fptA
::tp and Pc715j
orbA
::tp produced smaller amounts of their corresponding siderophores. Both Pc715j
orbA
::tp and Pc715j
fptA
::tp were able to grow in iron starvation conditions in vitro. In the agar bead model, the Pc715j
orbA
::tp mutant was cleared from the lung, indicating that the pyochelin uptake system does not compensate for the absence of a functional ornibactin system. Pc715j
fptA
::tp persisted in rat lung infections in numbers similar to those of the parent strain, indicating that the ferric-ornibactin uptake system could compensate for the defect in ferric-pyochelin uptake in vivo. These studies suggest that the ornibactin uptake system is the most important siderophore-mediated iron transport system in
B. cenocepacia
lung infections.
Partial Analysis of the Genomes of Two Nontypeable
Haemophilus influenzae
Otitis Media Isolates
Authors: Munson Robert S. , Harrison Alistair , Gillaspy Allison , Ray William C. , Carson Matt , Armbruster David , Gipson Jenny , Gipson Mandy , Johnson Linda , Lewis Lisa , Dyer David W. , Bakaletz Lauren O.
Published: April 2004

In 1995, The Institute for Genomic Research completed the genomic sequence of a rough derivative of
Haemophilus influenzae
serotype d, strain KW20. This sequence, though extremely useful in understanding the basic biology of
H. influenzae
, has yet to provide significant insight into our understanding of disease caused by nontypeable
H. influenzae
(NTHI), because serotype d strains are not generally pathogens. In contrast, NTHI strains are frequently mucosal pathogens and are the primary pathogens of chronic otitis media as well as a significant cause of acute otitis media in children. Thus, it is of great importance to further understand their biology. We used a DNA-based microarray approach to identify genes present in a clinical isolate of NTHI that were absent from strain Rd. We also sequenced the genome of a second NTHI isolate from a child with chronic otitis media to threefold coverage and then used an array of bioinformatics tools to identify genes present in this NTHI strain but absent from strain Rd. These methods were complementary in approach and results. We identified, in both strains, homologues of
H. influenzae lav
, an autotransported protein of unknown function;
tnaA
, which encodes tryptophanase; as well as a homologue of
Pasteurella multocida tsaA
, which encodes an alkyl peroxidase that may play a role in protection against reactive oxygen species. We also identified a number of putative restriction-modification systems, bacteriophage genes and transposon-related genes. These data provide new insight that complements and extends our ongoing analysis of NTHI virulence determinants.
Cdc42 and the Actin-Related Protein/Neural Wiskott-Aldrich Syndrome Protein Network Mediate Cellular Invasion by
Cryptosporidium parvum
Authors: Chen Xian-Ming , Huang Bing Q. , Splinter Patrick L. , Orth James D. , Billadeau Daniel D. , McNiven Mark A. , LaRusso Nicholas F.
Published: April 2004

Cryptosporidium parvum
invasion of epithelial cells involves host cell membrane alterations which require a remodeling of the host cell actin cytoskeleton. In addition, an actin plaque, possibly associated with the dense-band region, forms within the host cytoplasm at the host-parasite interface. Here we show that Cdc42 and RhoA, but not Rac1, members of the Rho family of GTPases, are recruited to the host-parasite interface in an in vitro model of human biliary cryptosporidiosis. Interestingly, activation of Cdc42, but not RhoA, was detected in the infected cells. Neural Wiskott-Aldrich syndrome protein (N-WASP) and p34-Arc, actin-regulating downstream effectors of Cdc42, were also recruited to the host-parasite interface. Whereas cellular expression of a constitutively active mutant of Cdc42 promoted
C. parvum
invasion, overexpression of a dominant negative mutant of Cdc42, or depletion of Cdc42 mRNA by short interfering RNA-mediated gene silencing, inhibited
C. parvum
invasion. Expression of the WA fragment of N-WASP to block associated actin polymerization also inhibited
C. parvum
invasion. Moreover, inhibition of host cell Cdc42 activation by dominant negative mutation inhibited
C. parvum
-associated actin remodeling, membrane protrusion, and dense-band formation. In contrast, treatment of cells with a Rho inhibitor, exoenzyme C3, or cellular overexpression of dominant negative mutants of RhoA and Rac1 had no effect on
C. parvum
invasion. These data suggest that
C. parvum
invasion of target epithelia results from the organism's ability to activate a host cell Cdc42 GTPase signaling pathway to induce host cell actin remodeling at the attachment site.
Porcine Choroid Plexus Epithelial Cells InduceStreptococcus suisBacteriostasis In Vitro
Authors: Adam Rüdiger A. , Tenenbaum Tobias , Valentin-Weigand Peter , Laryea Maurice , Schwahn Bernd , Angelow Susanne , Galla Hans-Joachim , Däubener Walter , Schroten Horst
Published: April 2004

The involvement of the choroid plexus in host defense during bacterial meningitis is unclear. Aiming to elucidate possible antibacterial mechanisms, we stimulated primary porcine choroid plexus epithelial cells (pCPEC) with proinflammatory cytokines and challenged them with variousStreptococcus suisstrains. In the supernatant of gamma interferon (IFN-γ)-stimulated pCPEC, streptococcal growth was markedly suppressed. Costimulation with tumor necrosis factor alpha enhanced this bacteriostatic effect, while supplementation ofl-tryptophan completely eliminated it. We also demonstrate that an activation of indoleamine 2,3-dioxygenase in the pCPEC seems to be responsible for the IFN-γ-induced bacteriostasis. This supports the hypothesis of an active role of the choroid plexus in host defense against bacterial meningitis.
Restitution of defective glucose-stimulated insulin release of sulfonylurea type 1 receptor knockout mice by acetylcholine
Authors: Doliba Nicolai M. , Qin Wei , Vatamaniuk Marko Z. , Li Changhong , Zelent Dorothy , Najafi Habiba , Buettger Carol W. , Collins Heather W. , Carr Richard D. , Magnuson Mark A. , Matschinsky Franz M.
Published: April 2004

Inhibition of ATP-sensitive K+(KATP) channels by an increase in the ATP/ADP ratio and the resultant membrane depolarization are considered essential in the process leading to insulin release (IR) from pancreatic β-cells stimulated by glucose. It is therefore surprising that mice lacking the sulfonylurea type 1 receptor (SUR1−/−) in β-cells remain euglycemic even though the knockout is expected to cause hypoglycemia. To complicate matters, isolated islets of SUR1−/−mice secrete little insulin in response to high glucose, which extrapolates to hyperglycemia in the intact animal. It remains thus unexplained how euglycemia is maintained. In recognition of the essential role of neural and endocrine regulation of IR, we evaluated the effects of acetylcholine (ACh) and glucagon-like peptide-1 (GLP-1) on IR and free intracellular Ca2+concentration ([Ca2+]i) of freshly isolated or cultured islets of SUR1−/−mice and B6D2F1 controls (SUR1+/+). IBMX, a phosphodiesterase inhibitor, was also used to explore cAMP-dependent signaling in IR. Most striking, and in contrast to controls, SUR1−/−islets are hypersensitive to ACh and IBMX, as demonstrated by a marked increase of IR even in the absence of glucose. The hypersensitivity to ACh was reproduced in control islets by depolarization with the SUR1 inhibitor glyburide. Pretreatment of perifused SUR1−/−islets with ACh or IBMX restored glucose stimulation of IR, an effect expectedly insensitive to diazoxide. The calcium channel blocker verapamil reduced but did not abolish ACh-stimulated IR, supporting a role for intracellular Ca2+stores in stimulus-secretion coupling. The effect of ACh on IR was greatly potentiated by GLP-1 (10 nM). ACh caused a dose-dependent increase in [Ca2+]iat 0.1–1 μM or biphasic changes (an initial sharp increase in [Ca2+]ifollowed by a sustained phase of low [Ca2+]i) at 1–100 μM. The latter effects were observed in substrate-free medium or in the presence of 16.7 mM glucose. We conclude that SUR1 deletion depolarizes the β-cells and markedly elevates basal [Ca2+]i. Elevated [Ca2+]iin turn sensitizes the β-cells to the secretory effects of ACh and IBMX. Priming by the combination of high [Ca2+]i, ACh, and GLP-1 restores the defective glucose responsiveness, precluding the development of diabetes but not effectively enough to cause hyperinsulinemic hypoglycemia.
Novel regulation by Rac1 of glucose- and forskolin-induced insulin secretion in INS-1 β-cells
Authors: Li Jingsong , Luo Ruihua , Kowluru Anjaneyulu , Li GuoDong
Published: April 2004

Stimulation of insulin secretion by glucose and other secretagogues from pancreatic islet β-cells is mediated by multiple signaling pathways. Rac1 is a member of Rho family GTPases regulating cytoskeletal organization, and recent evidence also implicates Rac1 in exocytotic processes. Herein, we report that exposure of insulin-secreting (INS) cells to stimulatory glucose concentrations caused translocation of Rac1 from cytosol to the membrane fraction (including the plasmalemma), an indication of Rac1 activation. Furthermore, glucose stimulation increased Rac1 GTPase activity. Time course study indicates that such an effect is demonstrable only after 15 min stimulation with glucose. Expression of a dominant-negative Rac1 mutant (N17Rac1) abolished glucose-induced translocation of Rac1 and significantly inhibited insulin secretion stimulated by glucose and forskolin. This inhibitory effect on glucose-stimulated insulin secretion was more apparent in the late phase of secretion. However, N17Rac1 expression did not significantly affect insulin secretion induced by high K+. INS-1 cells expressing N17Rac1 also displayed significant morphological changes and disappearance of F-actin structures. Expression of wild-type Rac1 or a constitutively active Rac1 mutant (V12Rac1) did not significantly affect either the stimulated insulin secretion or basal release, suggesting that Rac1 activation is essential, but not sufficient, for evoking secretory process. These data suggest, for the first time, that Rac1 may be involved in glucose- and forskolin-stimulated insulin secretion, possibly at the level of recruitment of secretory granules through actin cytoskeletal network reorganization.
Sucrose-induced cardiomyocyte dysfunction is both preventable and reversible with clinically relevant treatments
Authors: Davidoff Amy J. , Mason Meredith M. , Davidson Michael B. , Carmody Marybeth W. , Hintz Kadon K. , Wold Loren E. , Podolin Deborah A. , Ren Jun
Published: April 2004

We recently identified cardiomyocyte dysfunction in the early stage of type 2 diabetes (i.e., diet-induced insulin resistance). The present investigation was designed to determine whether a variety of clinically relevant interventions are sufficient to prevent and reverse cardiomyocyte dysfunction in sucrose (SU)-fed insulin-resistant rats. Subsets of animals were allowed to exercise (free access to wheel attached to cage) or were treated with bezafibrate in drinking water to determine whether these interventions would prevent the adverse effects of SU feeding on cardiomyocyte function. After 6–8 wk on diet and treatment, animals were surgically prepared to assess whole body insulin sensitivity (intravenous glucose tolerance test), and isolated ventricular myocyte mechanics were evaluated (video edge recording). SU feeding produced hyperinsulinemia and hypertriglyceridemia, with euglycemia, and induced characteristic whole body insulin resistance. Both exercise and bezafibrate treatment prevented these metabolic abnormalities. Ventricular myocyte shortening and relengthening were slower in SU-fed rats (42–63%) compared with starch (ST)-fed controls, and exercise or bezafibrate completely prevented cardiomyocyte dysfunction in SU-fed rats. In separate cohorts of animals, after 5 wk of SU feeding, animals were either switched back to an ST diet or given menhaden oil for an additional 7–9 wk to determine whether the cardiomyocyte dysfunction was reversible. Both interventions have previously been shown to have favorable metabolic effects, and both improved myocyte mechanics, but only the ST diet reversed all indications of cardiomyocyte dysfunction induced by SU feeding. Thus phenotypic changes in cardiomyocyte mechanics associated with early stages of type 2 diabetes were found to be both preventable and reversible with clinically relevant treatments, suggesting that the cellular processes contributing to this dysfunction are modifiable.
Nonexercise activity thermogenesis (NEAT): environment and biology
Authors: Levine James A.
Published: April 2004

Nonexercise activity thermogenesis (NEAT) is the energy expended for everything that is not sleeping, eating, or sports-like exercise. It includes the energy expended walking to work, typing, performing yard work, undertaking agricultural tasks, and fidgeting. NEAT can be measured by one of two approaches. The first is to measure or estimate total NEAT. Here, total daily energy expenditure is measured, and from it “basal metabolic rate-plus-thermic effect of food” is subtracted. The second is the factoral approach, whereby the components of NEAT are quantified, and total NEAT is calculated by summing these components. The amount of NEAT that humans perform represents the product of the amount and types of physical activities and the thermogenic cost of each activity. The factors that impact a human's NEAT are readily divisible into environmental factors, such as occupation or dwelling within a “concrete jungle,” and biological factors such as weight, gender, and body composition. The combined impact of these factors explains the substantial variance in human NEAT. The variability in NEAT might be viewed as random, but human and animal data contradict this. It appears that changes in NEAT subtly accompany experimentally induced changes in energy balance and are important in the physiology of weight change. Inadequate modulation of NEAT plus a sedentary lifestyle may thus be important in obesity. It then becomes intriguing to dissect mechanistic studies that delineate how NEAT is regulated into neural, peripheral, and humoral factors. A scheme is described in this review in which NEAT corresponds to a carefully regulated “tank” of physical activity that is crucial for weight control.
Effects of modulation on Rayleigh‐Benard convection. Part I
Authors: Bhadauria B. S. , Debnath Lokenath
Published: April 2004

The linear stability of a horizontal layer of fluid heated from below and above is considered. In addition to a steady temperature difference between the walls of the fluid layer, a time‐dependent periodic perturbation is applied to the wall temperatures. Only infinitesimal disturbances are considered. Numerical results for the critical Rayleigh number are obtained at various Prandtl numbers and for various values of the frequency. Some comparisons have been made with the known results.
A discrete and finite approach to past physical reality
Authors: Orthuber Wolfgang
Published: April 2004

This paper is a synthesis of previously
published material on the topic. We show that an
adequate mathematical model for the physical (i.e., perceptible
and therefore past) reality must be finite. A finite
approach to past proper time is given. Proper time turns out to
be proportional to the sum of the return probabilities of a
Bernoulli random walk.
Minimax Mutual Information Approach for Independent Component Analysis
Authors: Erdogmus Deniz , Hild Kenneth E. , Rao Yadunandana N. , Príncipe José C.
Published: April 2004

Minimum output mutual information is regarded as a natural criterion for independent component analysis (ICA) and is used as the performance measure in many ICA algorithms. Two common approaches in information-theoretic ICA algorithms are minimum mutual information and maximum output entropy approaches. In the former approach, we substitute some form of probability density function (pdf) estimate into the mutual information expression, and in the latter we incorporate the source pdf assumption in the algorithm through the use of nonlinearities matched to the corresponding cumulative density functions (cdf). Alternative solutions to ICA use higher-order cumulant-based optimization criteria, which are related to either one of these approaches through truncated series approximations for densities. In this article, we propose a new ICA algorithm motivated by the maximum entropy principle (for estimating signal distributions). The optimality criterion is the minimum output mutual information, where the estimated pdfs are from the exponential family and are approximate solutions to a constrained entropy maximization problem. This approach yields an upper bound for the actual mutual information of the output signals—hence, the name minimax mutual information ICA algorithm. In addition, we demonstrate that for a specific selection of the constraint functions in the maximum entropy density estimation procedure, the algorithm relates strongly to ICA methods using higher-order cumulants.
A Modified Algorithm for Generalized Discriminant Analysis
Authors: Zheng Wenming , Zhao Li , Zou Cairong
Published: April 2004

Generalized discriminant analysis (GDA) is an extension of the classical linear discriminant analysis (LDA) from linear domain to a nonlinear domain via the kernel trick. However, in the previous algorithm of GDA, the solutions may suffer from the degenerate eigenvalue problem (i.e., several eigenvectors with the same eigenvalue), which makes them not optimal in terms of the discriminant ability. In this letter, we propose a modified algorithm for GDA (MGDA) to solve this problem. The MGDA method aims to remove the degeneracy of GDA and find the optimal discriminant solutions, which maximize the between-class scatter in the subspace spanned by the degenerate eigenvectors of GDA. Theoretical analysis and experimental results on the ORL face database show that the MGDA method achieves better performance than the GDA method.
Stability-Based Validation of Clustering Solutions
Authors: Lange Tilman , Roth Volker , Braun Mikio L. , Buhmann Joachim M.
Published: April 2004

Data clustering describes a set of frequently employed techniques in exploratory data analysis to extract “natural” group structure in data. Such groupings need to be validated to separate the signal in the data from spurious structure. In this context, finding an appropriate number of clusters is a particularly important model selection question. We introduce a measure of cluster stability to assess the validity of a cluster model. This stability measure quantifies the reproducibility of clustering solutions on a second sample, and it can be interpreted as a classification risk with regard to class labels produced by a clustering algorithm. The preferred number of clusters is determined by minimizing this classification risk as a function of the number of clusters. Convincing results are achieved on simulated as well as gene expression data sets. Comparisons to other methods demonstrate the competitive performance of our method and its suitability as a general validation tool for clustering solutions in real-world problems.
Intellectual Property Rights and Biodiversity Management: The Case of India
Authors: Cullet Philippe , Raja Jawahar
Published: April 2004

This article analyzes the impacts of the international legal framework for the promotion of intellectual property rights on India's legal regime concerning the control over biological resources and inventions derived from biological resources. It focuses in particular on the newly adopted Biodiversity Act and Plant Variety Act as well as on amendments to the Patents Act and their organic relationship within the overall domestic legal framework. It analyzes these enactments in the context of the move towards the control of biological resources and derived products through property rights fostered by existing international treaties, in particular the TRIPS agreement and the biodiversity convention. This has impacts not only for control over biological resources and derived products but also more generally on the management of agriculture in India and other developing countries and the realization of food security and the human right to food at the individual level.
Osteology and myology of the cephalic region and pectoral girdle of Schilbe mystus and comparison with other schilbids, with comments on the monophyly and phylogenetic relationships of the Schilbidae (Teleostei: Siluriformes)
Authors: Diogo Rui , Chardon Michel , Vandewalle Pierre
Published: April 2004

The cephalic and pectoral girdle structures of Schilbe mystus are described and compared with those of other schilbids, as well as several other non-schilbid catfishes, as the foundation for a discussion on the monophyly and the phylogenetic relationships of the Schilbidae. Our observations and comparisons suggest that the family Schilbidae is a monophyletic group, defined, at least, by three autapomorphies, namely: 1) the adductor mandibulae A2 is lateral to the A1-Ost; 2) the posterior margin of the horizontal portion of Meckel's cartilage is situated further beyond the coronoid process; 3) the adductor mandibulae Aω is visible in a lateral view of the cephalic region. With respect to the phylogenetic relationships of the Schilbidae, our observations and comparisons support a close relationship between this family and the Pangasiidae.
Fights among Adolescents from the Ethnic Majority and from Immigrant Groups
Authors: Bratt Christopher
Published: April 2004

Fighting among adolescents was tested for association with alcohol/drug use and out-of-home activities without adult control (such as ‘hanging out’ on the streets). A survey was used to collect data from the majority of 13 to 15-year-olds in a Norwegian town ( N> 1400). Structural equation modelling resulted in a high regression weight for the latent variable of participation in out-of-home activities (beta = 0.54), supporting routine activities theory, and only a moderate regression weight for the latent variable of alcohol consumption (beta = 0.19). An assumption that the two exogenous variables would demonstrate an interaction effect was not supported by the data. However, subgroup analyses suggested that routine activities theory should not be applied to the exclusion of subcultural theories. As one might expect, differences between boys’ and girls’ experience of fighting could only partially be explained by the variables investigated. More significant, however, was that participation in the out-of-home activities investigated appeared not to be associated with fighting among girls from non-Western immigrant groups – a finding that questions routine activities theory. The article concludes that routine activities theory has merits as far as the investigation of general tendencies in delinquent behaviour is concerned, but it should not replace investigations of subcultural differences.