bluuebunny/crossref_metadata_2025 huggingface dataset:
Stem Cell Aging and Cancer
Authors: Fuller Jennifer
Published: June 2006

Stem cells are capable of self-renewal, differentiation into various lineages, and proliferation; thus, they play critical roles in the functioning and maintenance of many biological systems. However, these unique qualities of stem cells also make them more vulnerable to mutations as the organism ages. The biggest risk factor in cancer development is age, and most scientists believe that cancers partly result from a buildup of mutations in different cell types over time. This accumulation of mutations takes place over the course of a person's lifetime, during which repeated rounds of cell division result in editing errors in the DNA. Genetic alterations can cause changes in the signaling pathways controlling proliferation, differentiation, and apoptosis. In the case of stem cells, such mutations would be passed on to all of the stem cell's progeny, ultimately resulting in a pool of stem cells that feeds neoplastic formation. Studies aiming to identify and characterize these putative cancer stem cells and to understand how they arise will shed light on the process of stem cell aging and its role in cancer.
The Age of Skin Cancers
Authors: Desai Anu , Krathen Richard , Orengo Ida , Medrano Estela E.
Published: June 2006

Cancer affects two major cell types in the human skin: epithelial cells and melanocytes. Aging and a previous history of ultraviolet light exposure are major risk factors for skin cancers, including basal and squamous cell carcinomas and melanomas. However, melanomas, which are the most deadly of the skin tumors, display two intriguing characteristics: The incidence is increased and the prognosis is worse in males over 60 years as compared with females of the same age. This Perspective discusses possible reasons for age and gender as melanoma risk factors, as well as the need for studies aimed at unraveling the molecular mechanism of such puzzling events.
Aging at the Interface of Stem Cell Renewal, Apoptosis, Senescence, and Cancer
Authors: Nebel Almut , Schaffitzel Elke , Hertweck Maren
Published: June 2006

The aging-related research field has focused on the detection of genetic factors that affect the aging process, but more recently scientists have started to shift their attention to novel and more integrative ways of studying cellular and organismal function. Such approaches allow them to uncover and explore unexpected patterns and themes, resulting in a more comprehensive knowledge of the complex regulatory pathways and networks involved in aging and age-related diseases. Eventually, this knowledge will lead to a systems-level understanding of aging. The third "Functional Genomics of Aging" conference held in Palermo, Italy, in March/April 2006 highlighted some of the more exciting work in this area.
BRAF
and
MEK
Mutations Make a Late Entrance
Authors: Duesbery Nick , Vande Woude George
Published: June 2006

The small guanosine triphosphatase KRAS and the protein kinases BRAF, which is a mitogen-activated protein kinase kinase kinase (MAPKKK), and mitogen-activated protein kinase kinase 1 and 2 (MAPKK1/2, also known as MKK1/2 or MEK1/2) are signaling partners in the MAPK signal transduction pathway. They are involved in many biological processes and play crucial roles during embryonic development. When inappropriately expressed, KRAS, BRAF, and MEK1/2 are also frequently implicated in tumor progression. Hence, it might reasonably have been predicted that either loss- or gain-of-function germline mutations in the genes that encode them would cause embryonic death. However, in a surprising development, two articles report that germline mutations in the
KRAS
,
BRAF
, and
MEK1/2
genes are associated with cardio-facio-cutaneous (CFC) syndrome. This unexpected discovery demonstrates that mutations in
KRAS
,
BRAF
, and
MEK
can pass through the germline to cause specific developmental syndromes. This finding will undoubtedly stimulate further research into the function of these proteins in development and in both inherited and sporadic cancers.
Multiple Thermometers in Mammalian Cells: Why Do Cells from Homeothermic Organisms Need to Measure Temperature?
Authors: Sherman Michael Y. , Gabai Vladimir L.
Published: June 2006

Mammalian cells activate survival signaling pathways and other protective mechanisms or induce apoptotic cell death in response to heat stress at temperatures beyond the range of those that they would ever be expected to encounter in vivo. Recent work has demonstrated that heat shock directly activates the apoptotic proteins Bax and Bak, suggesting that these polypeptides function as cellular thermometers in the mitochondrial apoptotic pathway. Here we review this and other heat-activated signaling pathways and propose a model that postulates that these "cellular thermometers" are not designed to sense physiologically irrelevant temperatures but rather to detect a general buildup of abnormal proteins in the cytosol and other cellular compartments.
Shedding Light on the Distinct Functions of Proteoglycans
Authors: Selleck Scott B.
Published: June 2006

Heparan sulfate proteoglycans (HSPGs) are ubiquitous molecules that are critical for signaling mediated by many growth factors, including members of the Wnt, transforming growth factor–β, Hedgehog, and fibroblast growth factor families, and are essential for cell specification, axon guidance, and the establishment of morphogen gradients. Although the heparan sulfate modifications of HSPGs are critical, there is much to learn about how the protein cores contribute to the specific signaling functions of these cell-surface and matrix molecules. Recent work has demonstrated that glypican-1 and syndecan-1 expressed by tumor cells have specific roles in FGF2 signaling, affecting their responses to this mitogenic stimulus.
What’s Ub Chain Linkage Got to Do with It?
Authors: Kim Ikjin , Rao Hai
Published: June 2006

Ubiquitination—the covalent conjugation of ubiquitin (Ub) to other cellular proteins—regulates a wide range of cellular processes. Often, multiple Ub molecules are added to the substrate to form a Ub chain. Distinct outcomes have been observed for substrates modified with multi-Ub chains linked through particular lysine residues. However, recent studies suggest that Ub chain linkages may not be the key determinant for substrate fate. Here, we review evidence suggesting that Ub-binding proteins play a pivotal role in determining the outcome of substrate ubiquitination. In fulfilling their functions in proteasome-mediated proteolysis or signaling, Ub receptors link ubiquitinated proteins to downstream molecules through protein-protein interactions. Studies of Ub-binding factors may therefore hold the key to understanding the diverse functions of the Ub molecule.
Focus Issue: Peering into the Proteome
Authors: Adler Elizabeth M.
Published: June 2006

This week’s issues of
Science
and
Science
’s STKE focus on approaches to analyzing proteins and investigating their function in the proteomic era. Reviews in
Science
discuss the application of mass spectrometry to protein analysis and proteomics, probing protein dynamics with NMR, and the use of fluorescent probes to study proteins in living cells. A Protocol in STKE uses a photoreactive antagonist to inactivate cell surface receptors with electrophysiological recording to monitor trafficking of a specific type of glutamate receptor. An STKE Review discusses how to avoid problems in fluorescence resonance energy transfer (FRET) experiment interpretation through the use of FRET standards and by considering how changes in the stoichiometry and abundance of FRET donors and acceptors affect FRET analysis.
Rapid Photoinactivation of Native AMPA Receptors on Live Cells Using ANQX
Authors: England Pamela M.
Published: June 2006

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors, a major subtype of ionotropic glutamate receptors, mediate the majority of fast excitatory synaptic transmission in the mammalian brain. The constitutive and regulated trafficking of AMPA receptors into and out of excitatory synapses ensures rapid responses to synaptically released glutamate and provides a mechanism for synaptic plasticity. To permit the direct, quantitative, real-time measurement of native AMPA receptor trafficking in live neurons, we designed and utilized a membrane-impermeable, photoreactive AMPA receptor antagonist to rapidly and irreversibly inactivate surface receptors with ultraviolet (UV) light. The photoreactive antagonist, 6-azido-7-nitro-1,4-dihydroquinoxaline-2,3-dione (ANQX), is an aryl azide that, when irradiated with UV light, becomes a highly reactive nitrene that can covalently cross-link to and thus irreversibly antagonize bound AMPA receptors. Thus, ANQX provides a means of rapidly silencing surface-exposed AMPA receptors. Combined with a functional AMPA receptor assay, such as continuous recording of AMPA receptor–mediated ionic currents, ANQX provides a means of directly monitoring native AMPA receptor trafficking in real time.
Fanciful FRET
Authors: Vogel Steven S. , Thaler Christopher , Koushik Srinagesh V.
Published: June 2006

The validity of experiments based on Förster resonance energy transfer (FRET), an imaging technique widely used to measure protein-protein interactions in living cells, critically depends on the accurate and precise measurement of FRET efficiency. The use of FRET standards to determine FRET efficiency, and a consideration of such factors as how the abundance of FRET acceptors and the stoichiometry of donors and acceptors in a molecular complex can affect measured FRET efficiency, will enhance the usefulness with which FRET experiments can be interpreted.
Focus Issue: Reactive Oxygen Species—Friend or Foe?
Authors: Gough Nancy R.
Published: June 2006

Science
’s STKE focuses on the signaling pathways activated in response to pathological accumulation of reactive oxygen species (ROS), as well as on mechanisms by which cells have harnessed these reactive molecules as active participants in signaling that leads to a desirable cellular response. ROS are chemically reactive because they contain unpaired electrons and, depending on the location of their production and the molecules with which they interact, they can cause cellular damage or trigger specific signaling events. Indeed, kinases and phosphatases are now recognized as key molecules that can be modified by interaction with ROS, and the Protocol by Wu and Terada describes a method for detecting oxidatively modified protein tyrosine phosphatases. In a Perspective, Michel
et al
. discuss how susceptibility to elevated ROS contributes to death of specific neurons and in a Review, Storz discusses the signaling pathways activated to detoxify ROS and how mitochondrial ROS may contribute to aging.
Dopaminergic Neurons Reduced to Silence by Oxidative Stress: An Early Step in the Death Cascade in Parkinson’s Disease?
Authors: Michel Patrick P. , Ruberg Merle , Hirsch Etienne
Published: June 2006

Parkinson’s disease (PD) is a common neurodegenerative disorder that is most often sporadic, but in some cases it can be inherited as a simple Mendelian trait. The most important pathological feature of the disease is the death of brainstem dopaminergic neurons in the substantia nigra, which leads to characteristic motor symptoms. The etiology of PD remains unknown, but mitochondrial dysfunction and oxidative stress may contribute actively to the underlying pathomechanism. New studies suggest that K
ATP
channel activation may represent a downstream effector of these two cellular anomalies.
Oxidative Modification of Protein Tyrosine Phosphatases
Authors: Wu Ru Feng , Terada Lance S.
Published: June 2006

Our understanding of the biological effects of reactive oxidants has deepened considerably over the past decade. Less the indiscriminate loose cannons we previously imagined, both superoxide and hydrogen peroxide appear to target relatively specific molecular structures. Perhaps the most consequential of such targets within proteins is the reduced sulfhydryl of cysteine residues. Because protein tyrosine phosphatases (PTPs) all harbor an absolutely conserved catalytic cysteine residue, oxidation of this residue inactivates PTPs, rendering tyrosine kinase signaling pathways highly sensitive to the local redox environment. Therefore, tyrosine phosphorylation–dependent signaling involving receptor tyrosine kinases, mitogen-activated protein kinases, Abl, Src, and Pyk2 is known to be initiated or amplified by reactive oxidants. We describe a nonradioisotopic method that discriminates between reduced and oxidatively modified tyrosine phosphatases, thus facilitating studies that may mechanistically link oxidant activity with specific signaling pathways.
Reactive Oxygen Species–Mediated Mitochondria-to-Nucleus Signaling: A Key to Aging and Radical-Caused Diseases
Authors: Storz Peter
Published: June 2006

Mitochondria-generated reactive oxygen species have been implicated as a common feature that connects aging of organisms and age-related diseases. Efficient elimination of these radicals by antioxidants correlates with increased life span. Understanding how the mitochondrion signals to the nucleus to regulate antioxidant proteins might be a key to aging processes and treatment of human diseases.
Where Do You Think You Are Going? The NMDA-D1 Receptor Trap
Authors: Cepeda Carlos , Levine Michael S.
Published: June 2006

The number and outcomes of reciprocal interactions between dopamine (DA) D1 receptors and
N
-methyl-
D
-aspartate (NMDA)–type glutamate receptors continue to increase. Recent studies have demonstrated close physical interactions in which activation of one receptor affects the function of the other. In one physical interaction, the activation of NMDA receptors alters the topography and movement of D1 receptors by trapping them in dendritic spines and thus altering their distribution. In a second physical interaction, D1 and subunits of NMDA receptors form heterodimers, which are translocated from the cell interior to the surface. Finally, a third physical interaction posits that the C terminus of D1 receptors makes contact with subunits of the NMDA receptor. These physical interactions can attenuate or potentiate receptor function. In contrast, the more traditional interactions mediated by second messengers generally cause NMDA receptor function to be potentiated through the activation of D1 receptors and the cAMP–PKA–DARPP-32 [adenosine 3′,5′-monophosphate (cAMP)–protein kinase A–cAMP-regulated phosphoprotein of 32 kD] or PKC (protein kinase C) cascades. Together, these mechanisms provide a basis for understanding the increasing complexity of D1-NMDA receptor interactions and their importance in physiological and pathological processes.
Assembly and Organization of Macromolecular Complexes
Authors: Diversé-Pierluissi María
Published: June 2006

This Teaching Resource provides lecture notes and slides for a class covering the roles of scaffold proteins in signal transduction and is part of the course "Cell Signaling Systems: A Course for Graduate Students." The lecture includes an overview of scaffold proteins in signal integration and focuses on the following scaffold proteins: A-kinase anchoring proteins (AKAPs), WAVE-1, and proteins that contain PDZ domains.
Cell Culture as a Model System for Teaching: Using PC12 Cells
Authors: Adler Elizabeth M.
Published: June 2006

This Teaching Resource provides an introduction to the use of cultured cells as an experimental approach in undergraduate laboratory research and the study of neuronal differentiation in PC12 cells. In addition, a thought experiment with answers is provided that can be used to assess student understanding of (i) the scientific method, (ii) signaling processes involved in cellular differentiation, and (iii) the use of pharmacological agents to manipulate a cell culture system.
The Sherlock Holmes Lab: Investigations in Neurophysiology
Authors: Adler Elizabeth M. , Schwartz Paul J.
Published: June 2006

This Teaching Resource describes a research project that can be used in an advanced undergraduate course in neurobiology that covers basic electrophysiology and synaptic transmission. A thought experiment is provided that can be used to assess student understanding of (i) the scientific method, (ii) the process whereby nerve stimulation leads to muscle contraction, and (iii) the use of pharmacological agents to analyze a physiological system.
Focus Issue: Viruses—Miniature Machiavellis of the Signaling World?
Authors: Adler Elizabeth M.
Published: June 2006

This week’s issue of
Science
’s STKE, published in conjunction with a Special Issue of
Science
on virology, describes viral mechanisms for manipulating signaling pathways in the host cell to ensure their own replication and survival. Münter
et al
. focus on how viruses and other pathogens manipulate tyrosine kinase- and Rho guanosine triphosphatase-mediated pathways; Barry and Früh discuss how viruses manipulate cullin RING ubiquitin ligases to evade host defenses; and Hayward
et al
. compare mechanisms whereby Epstein-Barr virus (EBV) and Kaposi's sarcoma associated herpesviruses (KSHV) interact with the Wnt and Notch signaling pathways. In a Review in
Science
, García-Sastre and Biron discuss the interplay between virus offenses and host defenses, focusing on the role of the type I interferons.
Viral Modulators of Cullin RING Ubiquitin Ligases: Culling the Host Defense
Authors: Barry Michele , Früh Klaus
Published: June 2006

Cullin RING ubiquitin ligases (CRULs) are found in all eukaryotes and play an essential role in targeting proteins for ubiquitin-mediated destruction, thus regulating a plethora of cellular processes. Viruses manipulate CRULs by redirecting this destruction machinery to eliminate unwanted host cell proteins, thus allowing viruses to slip past host immune barriers. Depending on the host organism, virus-modified CRULs can perform an amazing range of tasks, including the elimination of crucial signal transduction molecules in the human interferon pathway and suppression of virus-induced gene silencing in plants. This Perspective summarizes recent advances in our understanding of how viral proteins manipulate the function of CRULs.
Notch and Wnt Signaling: Mimicry and Manipulation by Gamma Herpesviruses
Authors: Hayward S. Diane , Liu Jianyong , Fujimuro Masahiro
Published: June 2006

A small number of fundamental cell signaling pathways are key to the regulation of proliferation and differentiation responses during normal development. Two of these pathways, the Notch and Wnt pathways, have proven to be attractive targets for virus interaction and manipulation. In general, viral gene expression and replication are intimately linked to the differentiation state of the infected cell and, in the case of the gamma herpesviruses, establishment of a lifelong persistent infection in the host is also dependent on the proliferative expansion of an infected B cell population. This review examines the ways in which the gamma herpesviruses Epstein-Barr virus (EBV) and Kaposi’s sarcoma–associated herpesvirus (KSHV) have exploited the Notch and Wnt pathways to advance their own life cycles. The virus-pathway interactions are compared with the mechanisms and outcome of cellular Notch and Wnt signaling.
Signaling During Pathogen Infection
Authors: Münter Sylvia , Way Michael , Frischknecht Freddy
Published: June 2006

Over the millennia, pathogens have coevolved with their hosts and acquired the ability to intercept, disrupt, mimic, and usurp numerous signaling pathways of those hosts. The study of host/pathogen interactions thus not only teaches us about the intricate biology of these parasitic invaders but also provides interesting insights into basic cellular processes both at the level of the individual cell and more globally throughout the organism. Host/pathogen relationships also provide insights into the evolutionary forces that shape biological diversity. Here we review a few recent examples of how viruses, bacteria, and parasites manipulate tyrosine kinase–mediated and Rho guanosine triphosphatase–mediated signaling pathways of their hosts to achieve efficient entry, replication, and exit during their infectious cycles.
Second Messenger Pas de Deux: The Coordinated Dance Between Calcium and cAMP
Authors: Borodinsky Laura N. , Spitzer Nicholas C.
Published: June 2006

Dynamic calcium signaling is a well-established precept in biology. Different cell types exhibit spontaneous as well as stimulus-triggered transient changes in the concentration of intracellular calcium. Does this behavior extend to other second messengers? Optical dissection of various signal transduction pathways with fluorescent reporter molecules that enable visualization of changes in concentration of other second messengers is well under way. Recent research using technologically refined probes provides improved temporal and spatial resolution of adenosine 3′,5′-monophosphate (cAMP) dynamics to generate insights into the bidirectional interplay between intracellular fluctuations of cAMP and calcium. cAMP oscillations are generated in response to hormones, and cells can recognize and differentially respond to transient versus sustained changes in this second messenger. Second messenger reporters are now available to track multiple players and so provide a dynamic picture of signaling networks.
Food for Thought: Honeybee Foraging, Memory, and Acetylcholine
Authors: Weinberger Norman M.
Published: June 2006

Recent research implicates acetylcholine signaling through muscarinic receptors in structural changes that take place in the honeybee brain in response to foraging. These new findings are consistent with research from earlier studies implicating cholinergic signaling in associative learning as well as in the response to an enriched environment in mammals, which suggests that cholinergic signaling may play a critical role in learning and memory mechanisms across phyla.
Focus Issue: Turning the Corner in Cancer Therapy?
Authors: Adler Elizabeth M. , Gough Nancy R. , Ray L. Bryan
Published: June 2006

This week’s issues of
Science
and
Science
’s STKE are devoted to cancer research and to exploring how recent discoveries may impact our ability to diagnose and treat cancer.
Science
's STKE focuses on mechanisms by which growth factor–mediated stimulation of hypoxia-inducible factor signaling contributes to cancer progression and research that suggests a role as a tumor suppressor for a splicing variant of the c-H-ras oncogene.
p19

ras

Brings a New Twist to the Regulation of p73 by Mdm2
Authors: Harms Kelly Lynn , Chen Xinbin
Published: June 2006

p53
is the most commonly mutated gene in human cancer. It is now known that the p53 family proteins p63 and p73 play important roles in tumor suppression as well as in development. Because p63 and p73 are rarely mutated in human cancer, understanding the signaling pathways that activate p63 and p73 will not only shed light on the developmental processes regulated by p63 and p73 but may also yield insight into ways to harness p63 and p73 activity for cancer therapy. Recent research has shown that an alternative splice form of c-H-
ras
, called p19

ras

, is a positive regulator of p73β through a mechanism that involves the E3 ubiquitin ligase Mdm2. Implications for this previously unidentified means of regulation are discussed in light of tumor suppression and are extended to p53 and p63.
HIFing the Brakes: Therapeutic Opportunities for Treatment of Human Malignancies
Authors: Garcia Joseph A.
Published: June 2006

The unfortunate ability of tumor cells to survive and expand in an uncontrolled manner has captivated the attention of clinicians and basic scientists alike. The molecular mechanisms that tumor cells use to grow are the very same pathways used in normal cell growth and differentiation. One important pathway conferring a growth advantage on tumor cells is the epidermal growth factor receptor (EGFR) pathway. Signaling through the EGFR leads to activation of the phosphatidylinositol 3-kinase and Akt pathway and to increased activity of multiple effectors, including hypoxia-inducible factors (HIFs), which are cellular transcription factors involved in environmental stress response. The target genes that HIF members stimulate that are relevant to tumor growth include transcriptional activators and repressors and cytokines and growth factors, as well as their receptors. In this Perspective, findings from several recent studies are discussed in terms of their effect on the signal transducers, target genes, and tumor properties that are ultimately affected during EGFR-stimulated HIF signaling in cancer cells.
Differential Secretion of Cytokines
Authors: Moqbel Redwan , Coughlin Jason J.
Published: June 2006

Eosinophil granules store a vast array of cytokines and chemokines, many of which possess opposing activities. Specific stimuli can induce the release of entire granules or selective mediators through a process termed piecemeal degranulation. Until recently, the mechanisms that governed the decision to opt for either of these processes were unknown. Recent research has identified a mechanism through which differential secretion occurs during piecemeal degranulation. Eotaxin stimulation of eosinophils induces the selective mobilization of the granule-stored alpha chain of the interleukin-4 (IL-4) receptor into secretory vesicles. This process selectively recruits IL-4 to these vesicles and facilitates its differential secretion. There is also recent evidence for a mechanism of differential mobilization and membrane fusion of secretory vesicles versus granules. These two compartments possess a different set of SNARE and Rab molecules as vesicle fusion and transport-docking proteins, respectively. This presumably allows differential regulation of the processes of mobilization and plasma membrane fusion. These findings provide a model to explain the mechanism by which eosinophils, and likely many other cell types, differentially secrete cytokines and chemokines.
Cytokine Receptors and Jak-STAT Signaling
Authors: Schindler Christian
Published: June 2006

This Teaching Resource provides lecture notes and slides for a class covering interferons, their receptors, and Jak-STAT signaling and is part of the course "Cell Signaling Systems: A Course for Graduate Students." The lecture begins with a discussion of the different families of cytokines and their receptors and then proceeds to describe how cytokine receptor interactions lead to the activation of different members of the STAT family of transcription factors.
Innate Immune Defense Through RNA Interference
Authors: Fritz Jörg H. , Girardin Stephen E. , Philpott Dana J.
Published: June 2006

RNA interference (RNAi, also known as RNA silencing) has recently emerged as a fundamental and widespread regulator of gene expression. New developments in this field implicate RNAi in the innate immune response to infection in plants and animals. Evidence from plants, tissue culture cells, and
Caenorhabditis elegans
–based systems previously suggested that RNAi plays a role in the defense against viral infection, but definitive evidence using viruses and whole animals has been lacking. Two recent reports now show that both
Drosophila
embryos and adult flies mount a substantial innate immune response to insect viruses that requires the RNAi machinery. This innate response is distinct from known bacterial and fungal defense systems provided by the Toll and immune deficiency (Imd) pathways, thus defining a previously unrecognized strategy to fight viral infection. Whether RNAi, aside from its function in counteracting viruses, is also used to fight bacterial infection remained enigmatic. New evidence, however, now shows that in
Arabidopsis
, the bacterial component, flagellin, induces the expression of a specific microRNA, which in turn leads to the down-regulation of the signaling pathways that are implicated in disease susceptibility. This down-regulation then increases the plant's resistance to infection. Whether RNAi mechanisms also exist for combating bacterial diseases in animals remains an intriguing question for future studies.
"Bits" and Pieces
Authors: Yaffe Michael B.
Published: June 2006

Many protein-protein interactions involved in signal transduction occur through the interaction of modular protein domains in one molecule with short linear sequences of amino acids ("motifs") in another. Although protein domains are recognized by a variety of computational tools, bioinformatic approaches alone have not been successful in identifying the short sequence motifs to which domains bind. A new approach, applying motif-determining algorithms to smaller subproteomic collections of proteins that are already known to associate with each other in high-throughput protein-protein interaction screens, now appears to be capable of capturing a reasonably large number of low-affinity core motif sequences. Application of this approach to the genomes of yeast, fruit flies, nematodes, and humans has doubled the number of known or suspected protein-protein interaction motifs.
Accumulation of p27(kip1) is associated with cyclin D3 overexpression in the oxyphilic (Hurthle cell) variant of follicular thyroid carcinoma
Authors: Troncone G , Iaccarino A , Russo M , Palmieri E A , Volante M , Papotti M , Viglietto G , Palombini L
Published: June 2006

Background:The down regulation of protein p27kip1(p27) in most cases of thyroid cancer has relevant diagnostic and prognostic implications. However, the oxyphilic (Hurthle cell) variant of follicular thyroid carcinoma expresses more p27 than benign oxyphilic lesions do.

Aim:To evaluate the mechanism underlying this difference in expression of p27.

Methods:Because high levels of cyclin D3 lead to p27 accumulation in cell lines and clinical samples of thyroid cancer, the immunocytochemical pattern of cyclin D3 in oxyphilic (n = 47) and non-oxyphilic (n = 70) thyroid neoplasms was investigated.

Results:In the whole study sample, there was a significant correlation between p27 and cyclin D3 expression (Spearman’s r: 0.64; p<0.001). The expression of cyclin D3 and p27 was significantly higher in the oxyphilic variant of follicular carcinomas than in non-oxyphilic carcinomas (p<0.001). In the former, cyclin D3 overexpression and p27 accumulation were observed in a median of 75% and 55% of cells, respectively. In co-immunoprecipitation experiments, the level of p27-bound cyclin D3 was much higher in oxyphilic neoplasias than in normal thyroids and other thyroid tumours.

Conclusion:These results show that increased p27 expression in the oxyphilic (Hurthle cell) variant of follicular thyroid carcinoma results from cyclin D3 overexpression.
Our approach to follicular-patterned lesions of the thyroid
Authors: Baloch Zubair W , LiVolsi Virginia A
Published: June 2006

Follicular-patterned lesions of the thyroid are common; these include hyperplastic/adenomatoid nodules, follicular adenoma, follicular carcinoma and follicular variants of papillary carcinoma. Most of these lesions can be diagnosed with ease; however, there is a controversial subgroup. In this review, we present our diagnostic approach based on our experience with the histological diagnosis of these tumours, which can help in appropriate clinical management.
Fine-needle aspiration cytology of metaplastic carcinoma of the breast
Authors: Lui Philip C W , Tse Gary M K , Tan Puay Hoon , Jayaram Gita , Putti Thomas C , Chaiwun Benjaporn , Chan Norman H L , Lau Patrick P L , Mak Kong Ling , Khin Aye T
Published: June 2006

Background:Metaplastic carcinoma of the breast encompasses a heterogeneous group of tumours with variable components of sarcomatoid, squamous or poorly differentiated carcinomas.

Aim:To review a series of 19 cytological preparations of metaplastic carcinomas to assess diagnostic cytological features.

Methods:17 cases of fine-needle aspirates of histologically proven metaplastic carcinomas (4 monophasic spindle cell carcinomas, 4 squamous cell carcinomas and 11 biphasic tumours) were reviewed, with an emphasis on the presence of poorly differentiated carcinoma, squamous cell carcinoma, atypical spindle cells, benign stromal fragments and necrosis.

Results:All cases were diagnosed as malignant, with 68% of cases showing moderate to high cellularity, and 47% showing necrosis. If the tumours were analysed according to the constituting components histologically, 7, 15 and 8 cases, respectively, possess poorly differentiated carcinoma cells, sarcomatoid malignant cells and squamous carcinoma cells, whereas these components were cytologically identified in 11, 10 and 7 cases, respectively. Dual tumour populations were identified in only 5 of the 11 biphasic carcinomas in the cytological preparations; and the stromal material was cytologically identified in the only case with chondroid stroma.

Conclusions:Identification of metaplastic carcinoma in cytology remains problematic. There seems to be morphological overlap between various components. The identification of dual components, unequivocal squamous carcinoma cells and chondroid stroma is helpful for diagnosis, but it is uncommon. The presence of poorly differentiated carcinoma cells with a suggestion of focal spindle morphology is another clue to the suggestion of metaplastic carcinoma.
The impact of late career job loss on myocardial infarction and stroke: a 10 year follow up using the health and retirement survey
Authors: Gallo W T , Teng H M , Falba T A , Kasl S V , Krumholz H M , Bradley E H
Published: June 2006

Background:Involuntary job loss is a major life event associated with social, economic, behavioural, and health outcomes, for which older workers are at elevated risk.

Objective:To assess the 10 year risk of myocardial infarction (MI) and stroke associated with involuntary job loss among workers over 50 years of age.

Methods:Analysing data from the nationally representative US Health and Retirement Survey (HRS), Cox proportional hazards analysis was used to estimate whether workers who suffered involuntary job loss were at higher risk for subsequent MI and stroke than individuals who continued to work. The sample included 4301 individuals who were employed at the 1992 study baseline.

Results:Over the 10 year study frame, 582 individuals (13.5% of the sample) experienced involuntary job loss. After controlling for established predictors of the outcomes, displaced workers had a more than twofold increase in the risk of subsequent MI (hazard ratio (HR) = 2.48; 95% confidence interval (CI) = 1.49 to 4.14) and stroke (HR = 2.43; 95% CI = 1.18 to 4.98) relative to working persons.

Conclusion:Results suggest that the true costs of late career unemployment exceed financial deprivation, and include substantial health consequences. Physicians who treat individuals who lose jobs as they near retirement should consider the loss of employment a potential risk factor for adverse vascular health changes. Policy makers and programme planners should also be aware of the risks of job loss, so that programmatic interventions can be designed and implemented to ease the multiple burdens of joblessness.
Geochemistry and U–Pb protolith ages of eclogitic rocks of the Asís Lithodeme, Piaxtla Suite, Acatlán Complex, southern Mexico: tectonothermal activity along the southern margin of the Rheic Ocean
Authors: Murphy J. Brendan , Keppie J. Duncan , Nance R. Damian , Miller Brent V. , Dostal Jaroslav , Middleton Matt , Fernandez-Suárez Javier , Jeffries Teresa E. , Storey Craig D.
Published: June 2006

Recent data indicating that the Piaxtla Suite (Acatlán Complex, southern Mexico) underwent eclogite-facies metamorphism and exhumation during the Devono-Carboniferous suggest an origin within the Rheic Ocean rather than the Iapetus Ocean. The Asís Lithodeme (Piaxtla Suite) consists of polydeformed metasediments and eclogitic amphibolites that are intruded by megacrystic granitoid rocks. U–Pb (zircon) data indicate that the metasediments were deposited after
c
. 700 Ma and before intrusion of
c
. 470–420 Ma quartz-augen granite. The metasedimentary rocks contain abundant Mesoproterozoic detrital zircons (
c
. 1050–1250 Ma) and a few zircons in the range of
c
. 900–992 and
c
. 1330–1662 Ma. Their geochemical and Sm–Nd isotopic signature is typical of rift-related, passive margin sediments derived from an ancient cratonic source, which is interpreted to be the adjacent Mesoproterozoic Oaxacan Complex. Megacrystic granites were derived by partial melting of a
c
. 1 Ga crustal source, similar to the Oaxacan Complex. Amphibolitic layers exhibit a continental tholeiitic geochemistry, with a
c
. 0.8–1.1 Ga source (
T
DM
age), and are inferred to have originated in a rift-related environment by melting of lithospheric mantle in the Ordovician. This rifting may be related to the Early Ordovician drift of peri-Gondwanan terranes (e.g. Avalonia) from Gondwana and the origin of the Rheic Ocean.
Tectonostratigraphic evolution of a Mesozoic graben border system: the Chachil depocentre, southern Neuquén Basin, Argentina
Authors: Franzese J.R. , Veiga G.D. , Schwarz E. , Gómez-Pérez I.
Published: June 2006

The Chachil depocentre is one of a number of early Mesozoic extensional basins that form the early depocentres of the southern Neuquén Basin in Argentina. The synrift volcanic fill is composed of andesites, rhyolites and volcaniclastic deposits. Coarse-grained, non-marine facies dominate the sedimentary fill, mainly in the form of sediment gravity flow deposits. Stream flow deposits and minor non-marine carbonates are also locally present. The evolution of the graben border system was mainly controlled by subsidence along the main boundary fault (the Chihuido Bayo fault system) and recurrent volcanic activity. Marked changes in the thickness of the synrift megasequence indicate that episodic normal faulting in the hanging wall was also important. The integration of structural, magmatic and sedimentary data from the study area has led to the definition of three stages in the evolution of the synrift succession. The early rift stage is defined by the interplay between bimodal volcanism and gravity-driven sedimentation. The mid-rift stage is marked by the transition to acidic magmatism (rhyolitic and pyroclastic flows), also associated with coarse-grained non-marine deposition. The late-rift stage is dominated by fine-grained turbidites and pyroclastic falls related to the first marine sedimentation in the Neuquén Basin.
Pioglitazone increases secretion of high-molecular-weight adiponectin from adipocytes
Authors: Bodles Angela M. , Banga Anannya , Rasouli Neda , Ono Fumiyo , Kern Philip A. , Owens Randall J.
Published: June 2006

Adiponectin is an adipocyte-derived serum protein that plays important roles in energy homeostasis, obesity, and insulin sensitivity. Using sucrose gradients and Western blotting of nondenaturing gels, we examined the adiponectin isoforms secreted from human adipose tissue, human and mouse adipocytes, and cell lines in response to pioglitazone added in vitro. The predominant form secreted from adipose tissue in vitro was the high-molecular-weight (HMW) isoform, with small amounts of low-molecular-weight (LMW) forms present. The addition of pioglitazone (1–3 μM) in vitro increased the secretion of the HMW isoform, with no significant effect on the other isoforms. Human adipose tissue was also examined for changes in adiponectin mRNA levels upon pioglitazone treatment. No difference was detected, suggesting that the effect of pioglitazone is not at the transcriptional level but, rather, at a posttranscriptional phase of the secretory pathway. Additional experiments were conducted to determine whether adiponectin expression was mechanistically similar in other adipose cells. Examination of primary human adipocytes revealed an increase in intracellular HMW isoform with a decline in LMW forms following pioglitazone treatment, with a corresponding increase in the secreted HMW form. Similar results were observed with primary mouse adipocytes, 3T3-F422A cells, and SGBS human adipocyte cells, although differences in the distribution of HMW and LMW isoforms were apparent between cell types. Although there are differences in isoforms between species, in all cases pioglitazone served to increase the secretion of the HMW form of adiponectin.
Role of Akt2 in contraction-stimulated cell signaling and glucose uptake in skeletal muscle
Authors: Sakamoto Kei , Arnolds David E. , Fujii Nobuharu , Kramer Henning F. , Hirshman Michael F. , Goodyear Laurie J.
Published: June 2006

The serine/threonine kinase Akt/PKB plays diverse roles in cells, and genetic studies have indicated distinct roles for the three Akt isoforms expressed in mammalian cells and tissues. Akt2 is a key signaling intermediate for insulin-stimulated glucose uptake and glycogen synthesis in skeletal muscle. Akt2 has also been shown to be activated by exercise and muscle contraction in both rodents and humans. In this study, we used Akt2 knockout mice to explore the role of Akt2 in exercise-stimulated glucose uptake and glycogen synthesis as well as intracellular signaling pathways that regulate glycogen metabolism in skeletal muscle. We found that Akt2 deficiency does not affect basal or exercise-stimulated glucose uptake or intracellular glycogen content in the soleus muscle. In addition, lack of Akt2 did not result in alterations in basal Akt Thr308or basal and contraction-stimulated glycogen synthase kinase-3β (GSK-3β) Ser9phosphorylation, glycogen synthase phosphorylation, or glycogen synthase activity. In contrast, in situ contraction failed to elicit normal increases in Akt T-loop Thr308phosphorylation and GSK-3α Ser21phosphorylation in tibialis anterior muscles from Akt2-deficient animals. Our data establish a key role for Akt2 in the regulation of GSK-3α Ser21phosphorylation with contraction and add genetic evidence to support the separation of the intracellular pathways regulated by insulin and exercise that converge on glucose uptake and glycogen synthesis in skeletal muscle.
Rac1 mediates intestinal epithelial cell apoptosis via JNK
Authors: Jin Shi , Ray Ramesh M. , Johnson Leonard R.
Published: June 2006

Apoptosis plays a key role in the maintenance of a constant cell number and a low incidence of cancer in the mucosa of the intestine. Although the small GTPase Rac1 has been established as an important regulator of migration of intestinal epithelial cells, whether Rac1 is also involved in apoptosis is unclear. The present study tested the hypothesis that Rac1 mediates TNF-α-induced apoptosis in IEC-6 cells. Rac1 is activated during TNF-α-induced apoptosis as judged by the level of GTP-Rac1, the level of microsomal membrane-associated Rac1, and lamellipodia formation. Although expression of constitutively active Rac1 does not increase apoptosis in the basal condition, inhibition of Rac1 either by NSC-23766 (Rac1 inhibitor) or expression of dominant negative Rac1 protects cells from TNF-α-induced apoptosis by inhibiting caspase-3, -8, and -9 activities. Inhibition of Rac1 before the administration of apoptotic stimuli significantly prevents TNF-α-induced activation of JNK1/2, the key proapoptotic regulator in IEC-6 cells. Inhibition of Rac1 does not modulate TNF-α-induced ERK1/2 and Akt activation. Inhibition of ERK1/2 and Akt activity by U-0126 and LY-294002, respectively, increased TNF-α-induced apoptosis. However, inhibition of Rac1 significantly decreased apoptosis in the presence of ERK1/2 and Akt inhibitors, similar to the effect observed with NSC-23766 alone in response to TNF-α. Thus, Rac1 inhibition protects cells independently of ERK1/2 and Akt activation during TNF-α-induced apoptosis. Although p38 MAPK is activated in response to TNF-α, inhibition of p38 MAPK did not decrease apoptosis. Rac1 inhibition did not alter p38 MAPK activity. Thus, these results indicate that Rac1 mediates apoptosis via JNK and plays a key role in proapoptotic pathways in intestinal epithelial cells.
Role of enteric glia in intestinal physiology: effects of the gliotoxin fluorocitrate on motor and secretory function
Authors: Nasser Yasmin , Fernandez Ester , Keenan Catherine M. , Ho Winnie , Oland Lorraine D. , Tibbles Lee Anne , Schemann Michael , MacNaughton Wallace K. , Rühl Anne , Sharkey Keith A.
Published: June 2006

The role of enteric glia in gastrointestinal physiology remains largely unexplored. We examined the actions of the gliotoxin fluorocitrate (FC) on intestinal motility, secretion, and inflammation after assessing its efficacy and specificity in vitro. FC (100 μM) caused a significant decrease in the phosphorylation of the glucose analog 2-[ N-(7-nitrobenz-2-oxa-1,3-diaz-4-yl)amino]-2-deoxyglucose in enteric glial cultures and a reduction in glial uptake of the fluorescent dipeptide Ala-Lys-7-amino-4-methylcoumarin-3-acetic acid in both the ileum and colon. Dipeptide uptake by resident murine macrophages or guinea pig myenteric neurons was unaffected by FC. Incubation of isolated guinea pig ileal segments with FC caused a specific and significant increase in glial expression of the phosphorylated form of ERK-1/2. Disruption of enteric glial function with FC in mice reduced small intestinal motility in vitro, including a significant decrease in basal tone and the amplitude of contractility in response to electrical field stimulation. Mice treated with 10 or 20 μmol/kg FC twice daily for 7 days demonstrated a concentration-dependent decrease in small intestinal transit. In contrast, no changes in colonic transit or ion transport in vitro were observed. There were no changes in glial or neuronal morphology, any signs of inflammation in the FC-treated mice, or any change in the number of myenteric nitric oxide synthase-expressing neurons. We conclude that FC treatment causes enteric glial dysfunction, without causing intestinal inflammation. Our data suggest that enteric glia are involved in the modulation of enteric neural circuits underlying the regulation of intestinal motility.
Intestinal barrier failure during experimental necrotizing enterocolitis: protective effect of EGF treatment
Authors: Clark Jessica A. , Doelle Sarah M. , Halpern Melissa D. , Saunders Tara A. , Holubec Hana , Dvorak Katerina , Boitano Scott A. , Dvorak Bohuslav
Published: June 2006

Necrotizing enterocolitis (NEC) is the most common intestinal disease of premature infants. Although increased mucosal permeability and altered epithelial structure have been associated with many intestinal disorders, the role of intestinal barrier function in NEC pathogenesis is currently unknown. We investigated the structural and functional changes of the intestinal barrier in a rat model of NEC. In addition, the effect of EGF treatment on intestinal barrier function was evaluated. Premature rats were divided into three groups: dam fed (DF), formula fed (NEC), or fed with formula supplemented with 500 ng/ml EGF (NEC + EGF); all groups were exposed to asphyxia/cold stress to develop NEC. Intestinal permeability, goblet cell density, mucin production, and composition of tight junction (TJ) proteins were evaluated in the terminal ileum, the site of NEC injury, and compared with the proximal jejunum, which was unaffected by NEC. Animals with NEC had significantly increased intestinal paracellular permeability compared with DF pups. Ileal goblet cell morphology, mucin production, and TJ composition were altered in animals with NEC. EGF treatment significantly decreased intestinal paracellular permeability, increased goblet cell density and mucin production, and normalized expression of two major TJ proteins, occludin and claudin-3, in the ileum. In conclusion, experimental NEC is associated with disruption of the intestinal barrier. EGF treatment maintains intestinal integrity at the site of injury by accelerating goblet cell maturation and mucin production and normalizing expression of TJ proteins, leading to improved intestinal barrier function.