bluuebunny/crossref_metadata_2025 huggingface dataset:
Niemann–Pick Type C Mutations Cause Lipid Traffic Jam
Authors: Liscum Laura
Published: March 2003

The Niemann–Pick C protein (NPC1) is required for cholesterol transport from late endosomes and lysosomes to other cellular membranes. Mutations in NPC1 cause lysosomal lipid storage and progressive neurological degeneration. Cloning of the NPC1 gene has given us tools with which to investigate the function of this putative cholesterol transporter. Here, we discuss recent studies indicating that NPC1 is not a cholesterol‐specific transport molecule. Instead, NPC1 appears to be required for the vesicular shuttling of both lipids and fluid‐phase constituents from multivesicular late endosomes to destinations such as the trans‐Golgi network.
Garrotes, Springs, Ratchets, and Whips: Putting Dynamin Models to the Test
Authors: Sever Sanja , Damke Hanna , Schmid Sandra L.
Published: March 2003

The GTPase dynamin is essential for clathrin‐mediated endocytosis. Numerous new and exciting discoveries regarding dynamin function in vivo and in vitro have led to various models in which dynamin functions directly in membrane fission and the release of clathrin‐coated vesicles from the plasma membrane. This would make dynamin unique among GTPases in its ability to act as a mechanochemical enzyme. Here we review the various models and their supporting data. We then discuss new findings that raise doubts as to whether dynamin breaks the paradigm that governs regulatory GTPases.
Secretory Lysosome Biogenesis in Cytotoxic T Lymphocytes from Normal and Chediak Higashi Syndrome Patients
Authors: Stinchcombe Jane C. , Page Lesley J. , Griffiths Gillian M.
Published: March 2003

The lytic proteins mediating target cell killing are stored in the lysosomes of activated cytotoxic T lymphocytes (CTL) and are secreted upon recognition of a target cell. These secretory lysosomes cannot be detected in resting T lymphocytes. Interaction of a resting cell with a target cell activates de novo formation of secretory lysosomes. CTL clones in culture mimic this behaviour, and so provide an ideal system for studying secretory lysosome biogenesis and maturation. In the genetic disease, Chediak Higashi syndrome (CHS), all lysosomes in the cells are enlarged and reduced in number compared with wild‐type (WT) cells. We have used CTL from this disease to study secretory lysosome biogenesis and maturation. We show that at early stages after activation the secretory lysosomes are identical in WT and mutant cells, and that delivery of proteins to the secretory lysosome along the biosynthetic and endocytic pathways is normal in the mutant cells. With time, the lysosomes in the mutant cells aggregate, become larger and fewer in number and eventually form giant structures. Our results show that the initial steps of secretory lysosome formation are normal in CHS, but that the organelles subsequently fuse together during cell maturation to form the giant secretory lysosomes.
Greasing Membrane Fusion and Fission Machineries
Authors: Burger Koert N.J.
Published: March 2003

Biological membrane fusion is a local‐point event, extremely fast, and under strict control. Proteins are responsible for the mutual recognition of the fusion partners and for the initiation of biomembrane fusion, and thus determine where and when fusion occurs. However, the central event during membrane fusion is the merger of two membranes, which requires a transient reorganization of membrane lipids into highly curved fusion intermediates. This review focuses on the potential role of lipids in the generation of membrane curvature, and thus in the regulation of membrane fusion and fission.
Procathepsin L Self‐Association as a Mechanism for Selective Secretion
Authors: Yeyeodu Susan , Ahn Kyujeong , Madden Victoria , Chapman Richard , Song Linhua , Erickson Ann H.
Published: March 2003

The lysosomal cysteine pro‐protease procathepsin L was enriched in dense vesicles detectable when microsomes prepared from wild‐type or transformed mouse fibroblasts were resolved on sucrose gradients. These dense vesicles did not comigrate with proteins characteristic of the endoplasmic reticulum, Golgi, endosomes or lysosomes. When gradient fraction vesicles were lysed at acidic pH in the presence of excess mannose 6‐phosphate to prevent binding to mannose phosphate receptors, the majority of the procathepsin L was associated with the membrane, not the soluble, fraction. Immunogold labeling of procathepsin L in thin sections of cells or gradient fractions, using antibodies directed against the propeptide to avoid detection of the mature enzyme in dense lysosomes, revealed that the proenzyme was concentrated in dense cores localized in small vesicles near the plasma membrane and in multivesicular bodies. Consistent with the density of the gradient fraction and the electron density of the cores, yeast two‐hybrid assays indicated the proenzyme could bind itself but could not interact with the aspartic proprotease procathepsin D. The data suggest that in mouse fibroblasts procathepsin L may self‐associate into aggregates, initiating the formation of dense vesicles that could mediate the selective secretion of procathepsin L independent of mannose phosphate receptors.
The Use of Yeast Two‐Hybrid Screens in Studies of Protein:Protein Interactions Involved in Trafficking
Authors: Stephens David J. , Banting George
Published: March 2003

The yeast two‐hybrid system has provided a convenient means to both screen for proteins that interact with a protein of interest and to characterise the known interaction between two proteins. Several groups with an interest in the molecular mechanisms that underlie discrete steps along trafficking pathways have exploited the yeast two‐hybrid system. Here, we provide a brief background to the technology, attempt to point out some of the pitfalls and benefits of the different systems that can be employed, and mention some of the areas (within the trafficking field) where yeast two‐hybrid interaction assays have been particularly informative.
Nuclear Relocation of Normal Huntingtin
Authors: Tao Tao , Tartakoff Alan M.
Published: March 2003

In Huntington's Disease (HD), the huntingtin protein (Htt) includes an expanded polyglutamine domain. Since mutant Htt concentrates in the nucleus of affected neurons, we have inquired whether normal Htt (Q16−23) is also able to access the nucleus. We observe that a major pool of normal full‐length Htt of HeLa cells is anchored to endosomes and also detect RNase‐sensitive nuclear foci which include a 70‐kDa N‐terminal Htt fragment. Agents which damage DNA trigger caspase‐3‐dependent cleavage of Htt and dramatically relocate the 70 kDa fragment to the nucleoplasm. Considering that polyglutamine tracts stimulate caspase activation, mutant Htt is therefore poised to enter the nucleus. These considerations help rationalize the nuclear accumulation of Htt which is characteristic of HD and provide a first example of involvement of caspase cleavage in release of membrane‐bound proteins which subsequently enter the nucleus.
Antigen Loading of MHC Class I Molecules in the Endocytic Tract
Authors: Kleijmeer Monique J. , Escola Jean‐Michel , UytdeHaag Fons G.C.M. , Jakobson Eva , Griffith Janice M. , Osterhaus Albert D.M.E. , Stoorvogel Willem , Melief Cornelis J.M. , Rabouille Catherine , Geuze Hans J.
Published: March 2003

Major histocompatibility complex (MHC) class I molecules bind antigenic peptides that are translocated from the cytosol into the endoplasmic reticulum by the transporter associated with antigen processing. MHC class I loading independent of this transporter also exists and involves peptides derived from exogenously acquired antigens. Thus far, a detailed characterization of the intracellular compartments involved in this pathway is lacking. In the present study, we have used the model system in which peptides derived from measles virus protein F are presented to cytotoxic T cells by B‐lymphoblastoid cells that lack the peptide transporter. Inhibition of T cell activation by the lysosomotropic drug ammoniumchloride indicated that endocytic compartments were involved in the class I presentation of this antigen. Using immunoelectron microscopy, we demonstrate that class I molecules and virus protein F co‐localized in multivesicular endosomes and lysosomes. Surprisingly, these compartments expressed high levels of class II molecules, and further characterization identified them as MHC class II compartments. In addition, we show that class I molecules co‐localized with class II molecules on purified exosomes, the internal vesicles of multivesicular endosomes that are secreted upon fusion of these endosomes with the plasma membrane. Finally, dendritic cells, crucial for the induction of primary immune responses, also displayed class I in endosomes and on exosomes.
Endocytic Traffic in Polarized Epithelial Cells: Role of the Actin and Microtubule Cytoskeleton
Authors: Apodaca Gerard
Published: March 2003

The cytoskeleton is required for multiple cellular events including endocytosis and the transfer of cargo within the endocytic system. Polarized epithelial cells are capable of endocytosis at either of their distinct apical or basolateral plasma membrane domains. Actin plays a role in internalization at both cell surfaces. Microtubules and actin are required for efficient transcytosis and delivery of proteins to late endosomes and lysosomes. Microtubules are also important in apical recycling pathways and, in some polarized cell types, basolateral recycling requires actin. The microtubule motor proteins dynein and kinesin and the class I unconventional myosin motors play a role in many of these trafficking steps. This review examines the endocytic pathways of polarized epithelial cells and focuses on the emerging roles of the actin cytoskeleton in these processes.
Using Optics to Measure Biological Forces and Mechanics
Authors: Kuo Scot C.
Published: March 2003

Spanning all size levels, regulating biological forces and transport are fundamental life processes. Used by various investigators over the last dozen years, optical techniques offer unique advantages for studying biological forces. The most mature of these techniques, optical tweezers, or the single‐beam optical trap, is commercially available and is used by numerous investigators. Although technical innovations have improved the versatility of optical tweezers, simple optical tweezers continue to provide insights into cell biology. Two new, promising optical technologies, laser‐tracking microrheology and the optical stretcher, allow mechanical measurements that are not possible with optical tweezers. Here, I review these various optical technologies and their roles in understanding mechanical forces in cell biology.
Sorting Out Signals in Fly Endosomes
Authors: Krämer Helmut
Published: March 2003

Ligands and receptors that mediate cell–cell interactions during development are removed from the cell surface by endocytosis. Subsequently, many of these internalized proteins are detected in multivesicular bodies (MVBs). Recent work in different organisms has elucidated some aspects of MVB biogenesis and trafficking. This review discusses some intriguing links between these findings, the sorting of proteins in endocytic trafficking, and the regulation of signaling pathways in Drosophila.
An Alternate Targeting Pathway for Procathepsin L in Mouse Fibroblasts
Authors: Ahn Kyujeong , Yeyeodu Susan , Collette John , Madden Victoria , Arthur Joshua , Li Lian , Erickson Ann H.
Published: March 2003

In transformed mouse fibroblasts, a significant proportion of the lysosomal cysteine protease cathepsin L remains in cells as an inactive precursor which associates with membranes by a mannose phosphate‐independent interaction. When microsomes prepared from these cells were resolved on sucrose gradients, this procathepsin L was localized in dense vesicles distinct from those enriched for growth hormone, which is secreted constitutively when expressed in fibroblasts. Ultrastructural studies using antibodies directed against the propeptide to avoid detection of the mature enzyme in lysosomes revealed that the proenzyme was concentrated in dense cores within small vesicles and multivesicular endosomes which labeled with antibodies specific for CD63. Consistent with the resemblance of these cores to those of regulated secretory granules, secretion of procathepsin L from fibroblasts was modestly stimulated by phorbol, 12‐myristate, 13‐acetate. When protein synthesis was blocked with cycloheximide and lysosomal proteolysis inhibited with leupeptin, procathepsin L was found to gradually convert to the active single‐chain protease. The data suggest that when synthesis levels are high, a portion of the procathepsin L is packaged in dense cores within multivesicular endosomes localized near the plasma membrane. Gradual activation of this proenzyme achieves targeting of the proenzyme to lysosomes by a mannose phosphate receptor‐independent pathway.
The leaden Gene Product Is Required with Rab27a to Recruit Myosin Va to Melanosomes in Melanocytes
Authors: Hume Alistair N. , Collinson Lucy M. , Hopkins Colin R. , Strom Molly , Barral Duarte C. , Bossi Giovanna , Griffiths Gillian M. , Seabra Miguel C.
Published: March 2003

The function of lysosome‐related organelles such as melanosomes in melanocytes, and lytic granules in cytotoxic T lymphocytes is disrupted in Griscelli syndrome and related diseases. Griscelli syndrome results from loss of function mutations in either the RAB27A (type 1 Griscelli syndrome) or MYO5A (type 2 Griscelli syndrome) genes. Melanocytes from Griscelli syndrome patients and respective murine models ashen (Rab27a mutant), dilute (myosin Va mutant), and leaden exhibit perinuclear clustering of melanosomes. Recent work suggests that Rab27a is required to recruit myosin Va to melanosomes, thereby tethering melanosomes to the peripheral actin network and promoting melanosome retention at the tips of melanocytic dendrites. Here, we characterize the function of the leaden gene product. We show that Rab27a, but not myosin Va, can be localized to melanosomes in leaden melanocytes, suggesting that the leaden gene product acts downstream of, or in parallel to, Rab27a in melanocytes to promote recruitment of myosin Va to melanosomes. We also observed reduced levels of myosin Va protein in leaden and ashen melanocytes, suggesting that myosin Va stability is influenced by the leaden and ashen gene products. In leaden cytotoxic T lymphocytes, we observed that lytic granules polarize towards the immunological synapse and kill target cells normally. However, in contrast to melanocytes, we found that neither the leaden gene product (melanophilin) nor myosin Va was detectable in cytotoxic T lymphocytes. These results suggest that Rab27a interacts with different classes of effector proteins in melanocytes and cytotoxic T lymphocytes.
Ca2+ and Mg2+/ATP Independently Trigger Homotypic Membrane Fusion in Gastric Secretory Membranes
Authors: Duman Joseph G. , Singh Gaurav , Lee Ga Yi , Machen Terry E. , Forte John G.
Published: March 2003

Exocytic activation of gastric parietal cells represents a massive transformation. We studied a step in this process, homotypic fusion of H,K‐ATPase‐containing tubulovesicles, using R18 dequenching. Ca2+ and Mg2+/ATP each caused dramatic dequenching, reflecting a change in R18 distribution from 5% to 65–90% of the assay's membranes in 2.5 min. These stimuli also triggered fusion between tubulovesicles and liposomes. Independent confirmation that dequenching represented membrane fusion was established by separating tubulovesicle–liposome fusion products on density gradients. Only agents that trigger fusion allowed the transmembrane H,K‐ATPase to move to low‐density fractions along with R18. EC50 for Ca2+‐triggered fusion was 150 nm and for Mg2+/ATP‐triggered fusion 1 mm, the latter having a Hill coefficient of 2.5. ATP‐triggered fusion was specific for Mg2+/ATP, required ATP hydrolysis, and was insensitive to inhibition of NSF and/or H,K‐ATPase. Fusion initiated by either trigger caused tubulovesicles to become resistant to subsequent challenge by either trigger. Ca2+‐and Mg2+/ATP‐triggered fusion required protein component(s) in tubulovesicles, though this was required in only one of the fusing membranes since tubulovesicles fused well with liposomes containing no proteins. Our data suggest that exocytosis in parietal cells is triggered by separate but interacting pathways and is regulated by self‐inhibition.
Cargo Selection in Vesicular Transport: The Making and Breaking of a Coat
Authors: Aridor Meir , Traub Linton M.
Published: March 2003

Intracellular traffic is mediated by vesicular/tubular carriers. The carriers are formed by the activity of cytosolic coat proteins that are recruited to their target membranes and deform these membranes into buds and vesicles. Specific interactions between recruited coat subunits and short peptide sequences (transport motifs) on cargo proteins direct the incorporation of cargo into budded vesicles. Here, we focus on cargo selection reactions mediated by COPII and AP‐2/clathrin vesicle coat complexes to explore common mechanisms by which coat assembly support localized and selective cargo sorting. Recent findings suggest that multiple, low‐affinity interactions are employed in a cooperative manner to support coat assembly and enable cargo recognition. Thus low‐binding affinities between coat subunits and transport motifs are transiently transformed into high‐avidity, multivalent and selective interactions at vesicle bud sites. The temporal and regulated nature of the interactions provide the key to cargo selection.
Interferon‐Induced Mx Proteins: Dynamin‐Like GTPases with Antiviral Activity
Authors: Haller Otto , Kochs Georg
Published: March 2003

Mx proteins are interferon‐induced GTPases that belong to the dynamin superfamily of large GTPases. Similarities include a high molecular weight, a propensity to self‐assemble, a relatively low affinity for GTP, and a high intrinsic rate of GTP hydrolysis. A unique property of Mx GTPases is their antiviral activity against a wide range of RNA viruses, including bunya‐ and orthomyxoviruses. The human MxA GTPase accumulates in the cytoplasm of interferon‐treated cells, partly associating with the endoplasmic reticulum. In the case of bunyaviruses, MxA interferes with transport of the viral nucleocapsid protein (N) to the Golgi compartment, the site of virus assembly. In the case of Thogoto virus (an orthomyxovirus), MxA prevents the incoming viral nucleocapsids from being transported into the nucleus, the site of viral transcription and replication. In both cases, the GTP‐binding and carboxy‐terminal effector functions of MxA are required for target recognition. In general, Mx GTPases appear to detect viral infection by sensing nucleocapsid‐like structures. As a consequence, these viral components are trapped and sorted to locations where they become unavailable for the generation of new virus particles.
The Role of BEACH Proteins in Dictyostelium
Authors: De Lozanne Arturo
Published: March 2003

The BEACH family of proteins is a novel group of proteins with diverse roles in eukaryotic cells. The identifying feature of these proteins is the BEACH domain named after the founding members of this family, the mouse beige and the human Chediak–Higashi syndrome proteins. Although all BEACH proteins share a similar structural organization, they appear to have very distinct cellular roles, ranging from lysosomal traffic to apoptosis and cytokinesis. Very little is currently known about the function of most of these proteins, few binding‐partner proteins have been identified, and no molecular mechanism for any of these proteins has been discovered. Thus, it is important to establish good model systems for the study of these novel proteins. Dictyostelium contains six BEACH proteins that can be classified into four subclasses. Two of them, LvsA and LvsB, have clearly distinct roles in the cell. LvsA is localized on the contractile vacuole membrane and is essential for cytokinesis and osmoregulation. LvsB is most similar in sequence to the mammalian beige/Chediak–Higashi syndrome proteins and shares with them a common function in lysosomal trafficking. Structural and functional analysis of these proteins in Dictyostelium will help elucidate the function of this enigmatic novel family of proteins.
Oral status, cognitive and functional capacity versus oral treatment need in nursing home residents: a comparison between assessments by dental and ward staff
Authors: Nordenram G , Ljunggren G
Published: March 2003

OBJECTIVES: The aim of this study was to study the relationships between cognitive and functional capacity versus oral health and treatment need and to compare oral status assessments and oral treatment need, assessed by nurses and dental professionals, respectively.

DESIGN: Cross‐sectional survey.

SETTING: Nursing home.

SUBJECTS: One hundred and ninety‐two nursing home residents were examined in 1997.

MAIN OUTCOME MEASURES: Cognitive and functional capacity in different groups of residents regarding oral health and treatment need, measured by a comprehensive assessment with the Resident Assessment Instrument (RAI) and dental status in a separate examination protocol, recorded by a dentist.

RESULTS: There was a significant correlation between being dentate and having need of oral treatment. Those who were able to chew also had significantly better cognitive and functional capacity. Oral treatment need was identified most often by the dentist, intermediately by the RAI assessment and least frequently by the residents themselves.

CONCLUSIONS: Being dentate and having a loss of cognitive and functional capacity is predictive of oral treatment need among nursing home residents. Enhanced interaction between nurses and dental professionals needs to be promoted for better awareness of preventive measures and better regular oral care for frail and dependent elderly persons.
Minor recurrent aphthous stomatitis and smoking: an epidemiological study measuring plasma cotinine
Authors: Atkin PA , Xu X , Thornhill MH
Published: March 2003

OBJECTIVE: To compare blood cotinine levels between a group of patients with minor recurrent aphthous stomatitis (RAS) and a group representative of the general population, matched for age and gender.

SETTING:  Although smoking has been implicated as a protective factor in RAS, few studies have compared the prevalence of smoking in RAS patients with population controls. Cotinine is a smoking derivative with a long half‐life in the circulation. Measurement of plasma cotinine levels provides an accurate and objective measurement of an individual's cigarette consumption

METHODS: Blood samples were taken from 84 RAS patients and 81 controls. A microplate enzyme immunoassay (EIA) was used to detect plasma cotinine levels.

RESULTS: The number of RAS patients [2 (2.4%)] who were smokers (plasma cotinine >25 μg ml−1) was significantly lower than in the control group [12 (14.8%); P=0.00102]. Furthermore, the mean cotinine level amongst smokers in the RAS group was significantly lower than in smokers in the control group (P=0.0068).

CONCLUSION: This study shows that a group of RAS patients is significantly less likely to contain smokers than a matched control population, and among smokers the level of cigarette use was significantly lower in RAS patients than the control population. The perceived negative association between RAS and smoking was supported by this epidemiological study.
A histopathological and lectin‐histochemical study of the lining epithelium in postoperative maxillary cysts
Authors: Maruyama M , Onodera K , Ooya K
Published: March 2003

OBJECTIVE: Histopathological and lectin‐histochemical characteristics were studied in the lining epithelium of postoperative maxillary cysts (POMC).

MATERIALS AND METHODS: Histological (HE, PAS, AB), immunohistochemical (CD3 and L26) and lectin (wheat germ agglutinin, WGA; Ulex europaeus agglutinin I, UEA‐I; concanavalin A, ConA) stainings were performed in the 360 POMC specimens. The number of goblet cells and inflammatory cells was counted and statistically analyzed.

RESULTS: The lining epithelium was classified into three types based on histopathological characteristics; pseudostratified ciliated epithelium (pSCE), transitional epithelium (TE) and stratified squamous epithelium (SSE). Local infiltration of inflammatory cells into the cyst wall was associated with an increased number of goblet cells in the lining epithelium. The observed association between the infiltration of inflammatory cells and an increase in the number of goblet cells was statistically significant in groups with lining pSCE and TE. Glycoconjugate histochemical analysis revealed that the surfaces of the lining epithelium with squamous metaplasia showed an increased degree of staining reactivity with UEA‐I, whereas the staining reactivity with ConA was reduced. Goblet cells were able to be stained with WGA and UEA‐I, but showed extremely low reactivity with ConA.

CONCLUSION: Changes in the glycoconjugate expression of the metaplastic lining epithelium and goblet cell development play an important role in the local defense mechanisms against inflammatory factors in POMC.
Clinical applications of antimicrobial host proteins lactoperoxidase, lysozyme and lactoferrin in xerostomia: efficacy and safety
Authors: Tenovuo J
Published: March 2003

Innate human salivary defence proteins, lysozyme, lactoferrin and peroxidase, are known to exert a wide antimicrobial activity against a number of bacterial, viral and fungal pathogens in vitro. Therefore, these proteins, alone or in combinations, have been incorporated as preservatives in foods and pharmaceuticals as well as in oral health care products to restore salivas' own antimicrobial capacity in patients with dry mouth. These antimicrobials used in oral health care products, such as dentifrices, mouth‐rinses, moisturizing gels and chewing gums, have been purified from bovine colostrum. In this review I critically evaluate the clinical efficacy and safety of this kind of preventive approach against various oral diseases and symptoms.
Amelogenesis imperfecta: a classification and catalogue for the 21st century
Authors: Aldred MJ , Savarirayan R , Crawford PJM
Published: March 2003

Amelogenesis imperfecta (AI) is a collective term for a number of conditions with abnormal enamel formation. Many cases are inherited, either as an X‐linked, autosomal dominant or autosomal recessive trait. Several classifications have evolved since 1945, based primarily on phenotype with the mode of inheritance being used in some systems as a secondary factor in allocating a case into a particular category. The benefits and shortcomings of these systems are reviewed. As we move into an era of establishing the molecular basis of AI we propose a robust mechanism for classification and cataloguing of the disorder which parallels systems used in medical genetics. This system is applicable to individuals and families irrespective of current or future knowledge of the molecular defect involved. We argue that this system is of more benefit to these individuals and families than previous classifications.
Bone Loss Predicts Subsequent Cognitive Decline in Older Women: The Study of Osteoporotic Fractures
Authors: Lui Li‐Yung , Stone Katie , Cauley Jane A. , Hillier Teresa , Yaffe Kristine
Published: March 2003

OBJECTIVES: To determine whether the rate of bone loss predicts subsequent cognitive decline independently of baseline bone mass and whether apolipoprotein E (ApoE) genotype explains the association.

DESIGN: A prospective cohort study.

SETTING: Clinical centers in Baltimore, Maryland; Minneapolis, Minnesota; Pittsburgh, Pennsylvania; and Portland, Oregon.

PARTICIPANTS: Four thousand four hundred sixty‐two women aged 70 and older (mean = 75.8) participating in the Study of Osteoporotic Fractures.

MEASUREMENTS: Total hipbone mineral density (BMD) was measured 2 and 6 years after enrollment (mean follow‐up = 3.5 years), and expressed as annualized percentage rate of bone change. A modified Mini‐Mental State Examination (mMMSE) was administered at 6 and 10 years (mean follow‐up = 4.5 years) and defined cognitive decline as a decline of three or more points on repeat mMMSE score. ApoE genotype information was available on 883 women.

RESULTS: Cognitive decline occurred in 12% of the women with the least bone loss (by quartile), 14% in the second, 16% in the third, and 20% in those with the greatest bone loss. After adjustment for age, education, stroke, functional status, estrogen use, body mass index, and smoking, the results were similar. Those who lost the most BMD were almost 40% more likely than women in the lowest quartile to develop cognitive decline in the multivariate model (odds ratio (OR) = 1.4, 95% confidence interval (CI) = 1.1–1.8). A similar association between hipbone loss and cognitive decline was observed in the multivariate model further adjusting for ApoE e4 (OR = 1.5, 95% CI = 0.8–2.7).

CONCLUSIONS: Women with more rapid hipbone loss were more likely to develop cognitive decline than those who had lower rate of loss (or who gained bone mass). Differences in functional status, estrogen use, and ApoE did not explain this association. Further investigation is needed to determine the mechanisms that link osteoporosis and cognitive decline.
Erroneous incorporation of oxidized DNA precursors by Y‐family DNA polymerases
Authors: Shimizu Masatomi , Gruz Petr , Kamiya Hiroyuki , Kim Su‐Ryang , Pisani Francesca M , Masutani Chikahide , Kanke Yusuke , Harashima Hideyoshi , Hanaoka Fumio , Nohmi Takehiko
Published: March 2003

Deranged oxidative metabolism is a property of many tumour cells. Oxidation of the deoxynucleotide triphosphate (dNTP) pool, as well as DNA, is a major cause of genome instability. Here, we report that two Y‐family DNA polymerases of the archaeon Sulfolobus solfataricus strains P1 and P2 incorporate oxidized dNTPs into nascent DNA in an erroneous manner: the polymerases exclusively incorporate 8‐OH‐dGTP opposite adenine in the template, and incorporate 2‐OH‐dATP opposite guanine more efficiently than opposite thymine. The rate of extension of the nascent DNA chain following on from these incorporated analogues is only slightly reduced. These DNA polymerases have been shown to bypass a variety of DNA lesions. Thus, our results suggest that the Y‐family DNA polymerases promote mutagenesis through the erroneous incorporation of oxidized dNTPs during DNA synthesis, in addition to facilitating translesion DNA synthesis. We also report that human DNA polymerase η, a human Y‐family DNA polymerase, incorporates the oxidized dNTPs in a similar erroneous manner.
Late Simian virus 40 transcription factor is a target of the phosphoinositide 3-kinase/Akt pathway in anti-apoptotic Alzheimers amyloid precursor protein signalling
Authors: KASHOUR Tarek , BURTON Teralee , DIBROV Alexander , AMARA Francis M.
Published: March 2003

The association of familial Alzheimer's disease (FAD) with mutations in Alzheimer's amyloid precursor protein (APP) suggests important functions for APP in the central nervous system. Mutations in APP impair its function to confer resistance to apoptosis in cells under stress, and this may contribute to neurodegeneration in Alzheimer's disease (AD) brain, but the mechanisms involved are unknown. We examined the role of the late Simian virus 40 transcription factor (LSF), in anti-apoptotic APP pathways. We show that in APP-deficient B103 cells, expression of wild-type human APP (hAPPwt), but not of FAD-mutant APP, inhibited staurosporine (STS)-induced apoptosis. This inhibition was further enhanced by expression of LSFwt, although LSFwt alone was not sufficient to inhibit STS-induced apoptosis. In contrast, expression of dominant-negative LSF led to a marked increase in STS-induced cell death that was significantly blocked by hAPPwt. These effects of APP were accompanied by LSF nuclear translocation and dependent gene transcription. The activation of LSF is dependent on the expression of hAPPwt and is inhibited by the expression of dominant-negative forms of either phosphoinositide 3-kinase or Akt. These results demonstrate that LSF activation is required for the neuroprotective effects of APP via phosphoinositide 3-kinase/Akt signalling. Alterations in this pathway by aberrations in APP and/or LSF could promote neuronal loss in AD brain, due to secondary insults. Thus a link is established between APP and LSF and AD.
Distribution of Androgen Receptor mRNA Expression and Immunoreactivity in the Brain of the Green Anole Lizard
Authors: Rosen G. , O'Bryant E. , Matthews J. , Zacharewski T. , Wade J.
Published: March 2003

Male courtship and copulation are androgen dependent in the green anole lizard, and female receptivity can be facilitated by testosterone. However, only a few, and relatively large, regions in the brain have been implicated in the control of these behaviours. In situ hybridization and immunohistochemistry were therefore used to determine in detail where androgens are likely to act in the brains of breeding males and females. A 697‐bp fragment of the anole androgen receptor (AR) was cloned from total RNA isolated from the kidney, which contains the highly androgen‐sensitive renal sex segment. The cloned fragment spanned part of the C, the entire D, and part of the E domains, and shared a high degree of similarity with the AR of various species. 35S‐labelled antisense and sense probes were generated from the 697‐bp fragment for use in in situ hybridization, and the AR antibody PG‐21 was used for immunohistochemistry. Both sexes consistently had AR mRNA expression and immunoreactivity in areas associated with vertebrate reproductive behaviours and in motor areas of the brainstem. Interestingly, the PG‐21 antibody produced labelling in both the nucleus and cytoplasm, including neuronal processes. The distribution of mRNA and immunoreactivity were comparable in males and females, and the amount of labelling was generally similar, although slightly greater in females. The expression pattern of AR in this species supports the idea that distribution is highly conserved among vertebrates, but that it probably does not dictate behavioural differences between the sexes in anoles.
Melatonin Modulates [3H]Serotonin Release in the Rat Hippocampus: Effects of Circadian Rhythm
Authors: Monnet F. P.
Published: March 2003

Serotonin (5‐HT) participates as a neurotransmitter in the control of the circadian sleep/wake rhythm, feeding and sexual behaviours, and emotional and affective states. The present study investigated whether melatonin affects the circadian rhythm of 5‐HT neurotransmission in the hippocampus, a major target for serotoninergic antidepressants. The present results show a daytime dependency of [3H]5‐HT uptake insensitive to melatonin, with a peak from 14.00 h to 22.00 h and a trough from 02.00 h to 06.00 h. They also indicate that melatonin reduced the spontaneous efflux of [3H]5‐HT as well as KCl‐evoked release of [3H]5‐HT during the dark phase, while it increased the evoked release during the light phase. Both effects were concentration‐dependent; the facilitatory effect was maximum at high nanomolar concentrations of melatonin, whereas the inhibition preferentially occurred at low concentrations. Finally, nifedipine, an effective antagonist of l‐type voltage‐sensitive calcium channels, prevented the effects of melatonin on KCl‐evoked [3H]5‐HT release during the light but not the dark phase. Together, these data suggest the involvement of two distinct mechanisms by which melatonin might regulate both spontaneous efflux and evoked release of 5‐HT in the hippocampus.
Leaf age affects the seasonal pattern of photosynthetic capacityand net ecosystem exchange of carbon in a deciduous forest
Authors: Wilson K. B. , Baldocchi D. D. , Hanson P. J.
Published: March 2003

Temporal trends in photosynthetic capacity are a critical factorin determining the seasonality and magnitude of ecosystem carbonfluxes. At a mixed deciduous forest in the south‐eastern United States (Walker Branch Watershed, Oak Ridge, TN, USA), we independently measured seasonal trends in photosynthetic capacity (using single‐leaf gas exchange techniques) and the whole‐canopycarbon flux (using the eddy covariance method). Soil respiration was also measured using chambers and an eddy covariance system beneath the canopy. These independent chamber and eddy covariance measurements, along with a biophysical model (CANOAK), areused to examine how leaf age affects the seasonal pattern of carbon uptake during the growing season. When the measured seasonality in photosynthetic capacity is representedin the CANOAK simulations, there is good agreement with the eddy covariance data on the seasonal trends in carbon uptake. Removing the temporal trends in the simulations by using the early season maximum value of photosynthetic capacity over the entire growing season over estimates the annual carbon uptake by about 300 g C m−2 year−1– halfthe total estimated annual net ecosystem exchange. Alternatively, use of the mean value of photosynthetic capacity incorrectly simulates the seasonality in carbon uptake by the forest. In addition to changes related to leaf development and senescence, photosynthetic capacitydecreased in the middle and late summer, even when leaf nitrogenwas essentially constant. When only these middle and late summer reductions were neglected in the model simulations, CANOAK still overestimated the carbon uptake by an amount comparable to 25% ofthe total annual net ecosystem exchange.
Sub‐optimal morning temperature induces photoinhibition in dense outdoor cultures of the alga Monodus subterraneus (Eustigmatophyta)
Authors: Vonshak A. , Torzillo G. , Masojidek J. , Boussiba S.
Published: March 2003

Diel changes in photosynthetic oxygen evolution and several photochemical parameters measured by chlorophyll fluorescence quenching and induction were measured in outdoor dense cultures of the alga Monodus subterraneus (Eustigmatophyta). Cultures were maintained under two temperature regimes. In one, a rise in temperature was initiated in the morning by the increase in solar radiation up to the optimal temperature of 28 °C; in the other, a heating device was used to increase the rate of warming up in early morning.

Although the two cultures were maintained at the same temperature and light intensity for most of the day, cultures exposed for only a short time to suboptimal morning temperature showed a larger decrease in almost all the photosynthetic parameters. By comparing the diel changes in maximal photochemistry efficiency of photosystem II, the electron transport rate and the photochemical and non‐photochemical chlorophyll fluorescence quenching of the cultures, we concluded that even a relatively short exposure to suboptimal morning temperatures induced photoinhibitory damage. The higher photochemical activity of the heated culture was also reflected in a significant increase in productivity, which was 60% higher in the morning heated cultures than in the non‐heated cultures.
An experimental test of the link between foraging, habitat selection and thermoregulation in black rat snakes Elaphe obsoleta obsoleta
Authors: Blouin‐Demers Gabriel , Weatherhead Patrick J.
Published: March 2003

Most physiological processes are temperature‐dependent. Thus, for ectotherms, behavioural control of body temperatures directly affects their physiology. Ectotherms thermoregulate by adjusting habitat use and therefore thermoregulation is probably the single most important proximate factor influencing habitat use of terrestrial reptiles, at least in temperate climates.

Snakes have been shown to raise their body temperature following feeding in a laboratory thermal gradient, presumably to enhance digestion. This experiment was exported to the field to explore the link between feeding, habitat selection and thermoregulation in free‐ranging snakes.

Experimental feeding was conducted in the laboratory and in the field on black rat snakes (Elaphe obsoleta obsoleta) that had temperature‐sensitive radio‐transmitters surgically implanted.

Snakes had higher mean body temperatures following feeding than prior to feeding in a laboratory thermal gradient.

Some, but not all evidence, indicated that black rat snakes increased their mean body temperature following feeding in the field. Indices of thermoregulation indicated that the snakes thermoregulated more carefully and more effectively after they had eaten.

Forest edges provided the best opportunities for thermoregulation in the study area. Black rat snakes were less likely to move following feeding when fed in edges than when fed in the forest and were more likely to be found in edges following feeding, whether they had been fed in the forest or in an edge.

Results of this study and one previous study suggest that thermoregulatory behaviour of snakes following feeding in the laboratory is a reliable predictor of their behaviour in the field. A review of 13 studies of the thermoregulatory behaviour of snakes following feeding in the laboratory revealed that not all species behave similarly. However, the quality and number of studies currently available is not adequate for testing hypotheses about which species should change thermoregulatory behaviour in response to eating and which should not.
A long‐term study of reproductive performance in tree swallows: the influence of age and senescence on output
Authors: Robertson Raleigh J. , Rendell Wallace B.
Published: March 2003

We describe age‐related reproductive performance and recapture rates of tree swallows (Tachycineta bicolorVieillot) based on a 25‐year study of a nestbox population in south‐eastern Ontario, Canada (1975–99).

Performance improved from first‐time breeders to intermediate‐aged birds. Nest initiation advanced, and clutch size increased in both sexes. In females the number of hatchlings and fledglings increased, and the proportion of nests failing completely declined. Performance declined in females after ‘middle‐age’, in the number of young fledged, and the proportion of young fledged relative to initial clutch and brood size. Also, the proportion of nests that failed completely increased in the oldest birds. Males showed similar patterns.

An index of performance incorporating clutch size, hatching and fledging efficiency, and two measures of total nest failure increased to, then declined after, 4 years of age in females and 3 years in males. The relationship between this index and age was best predicted by quadratic regression.

We found no support for three of four hypotheses to explain improvement in performance with age. Recapture rates declined after age 4Y in males, but remained unchanged in females until age 7Y +, while output decreased in both sexes (Residual Reproductive Value). Birds breeding repeatedly did not perform better during their first attempt compared to birds that bred only once (Selection). Birds with varied breeding experience did not differ in their performance within age‐groups (Breeding Experience). We did find support for the Breeding Age hypothesis; in females with no breeding experience, there was a successive advance in laying and increase in clutch size from 2 to 4 years of age.

Improved performance may be due to skills acquired with age, such as those devoted to feeding and balancing energy demands, which are necessary to prepare and maintain individual condition prior to, and during, breeding. Senescence in performance after ‘middle‐age’ may result from accumulated costs of previous breeding effort which have been identified in this species based on research elsewhere.
Benefits of early arrival at breeding grounds vary between males
Authors: Forstmeier Wolfgang
Published: March 2003

It is often assumed that, in migratory birds, males of highest phenotypic quality are the first to arrive at breeding grounds, as only males in good body condition can afford the costs of early arrival. Here it is argued that variation in how much an individual can gain from being early may sometimes override these patterns of condition dependence. Benefits from early arrival will depend on how good the chances of an individual are of successfully occupying and defending a high‐quality territory. Other studies have shown that these chances depend on male resource‐holding power (RHP) and on value asymmetries (VA), as resulting from prior ownership.

 Patterns of spring arrival were studied in a polygynous population of the dusky warblerPhylloscopus fuscatusBlyth, a species with high breeding‐site tenacity. During the period of postnuptial moult, just before departure to winter quarters, about half of the males preoccupied and vigorously defended high‐quality territories. Apparently these males enhanced their success in competition over these territories in the following breeding season by taking advantage of having prior ownership.

 Males with good chances of obtaining a high‐quality territory (i.e. males that had occupied such territories before) were the first to arrive in spring, suggesting that high motivation drives early arrival. In contrast, there was no indication for male quality or body condition to affect arrival patterns.

 Interestingly, males of small body size, possibly reflecting low RHP, invested more in gaining prior ownership than did large males.

 The present study suggests that, in some species, individual variation in benefits rather than in costs resulting from early arrival determine which males are the first to arrive.
Effect of jasmonate‐induced plant responses on the natural enemies of herbivores
Authors: Thaler Jennifer S.
Published: March 2003

Plant traits can act as defences against herbivores both by reducing herbivore performance directly and by increasing the effectiveness of the natural enemies of herbivores. Natural enemy performance and rate of parasitism can be affected by plant traits and/or changes in herbivore quality.

Jasmonic acid is responsible for the induction of many changes in plant resistance that occur following herbivore attack. This study examines the effects of jasmonate‐induced defences on the abundance and performance of natural enemies, as well as the interaction between induced plant responses and parasitism in their ability to kill herbivores.

In a tomato field containing plants induced with jasmonic acid and control plants, the abundance of natural enemies was counted using several census techniques. Induced resistance affected the abundance of natural enemies of herbivores differently. One predator of aphids, syrphid flies, was negatively affected by the decrease in herbivore abundance on induced plants. One parasitoid of caterpillars, Hyposoter exiguae Viereck, was not affected by induced resistance in this study although it was positively affected in a previous study. Two other natural enemies, a parasitoid of aphids and ladybeetle predators, were not affected by induced resistance.

Induced resistance and parasitism both reduced the survivorship of herbivores. In a 2 × 2 factorial design with induced resistance crossed by parasitism, the interaction between the effects of induced resistance and parasitism on herbivore survival was tested. Two trials of this experiment were conducted; one where induced resistance affected both herbivore quantity and quality and one where induced resistance only affected herbivore quality (herbivore density was equalized).

Parasitoids were more effective at killing herbivores feeding on control plants than herbivores on induced plants. This difference was due to a difference in herbivore quality, not herbivore quantity. Herbivores feeding on induced plants have lower mass than herbivores on control plants and this appears to be a major factor reducing the performance of developing parasitic wasps.

Thus, jasmonate‐induced responses influence natural enemies species in differing ways, sometimes reducing the density of herbivores and sometimes reducing the quality of herbivores for natural enemies.