bluuebunny/crossref_metadata_2025 huggingface dataset:
Load‐displacement properties of the human triceps surae aponeurosis and tendon in runners and non‐runners
Authors: Rosager S. , Aagaard P. , Dyhre‐Poulsen P. , Neergaard K. , Kjaer M. , Magnusson S. P.
Published: March 2003

The load‐displacement and stress–strain characteristics of the human triceps surae tendon and aponeurosis,in vivo, was examined during graded maximal voluntary plantarflexion efforts in runners who trained 80 km/ week or more and age‐matched non‐runners. Synchronous real‐time ultrasonography of triceps surae tendon and aponeurosis displacement, electromyography of the gastrocnemius, soleus and dorsiflexor muscles, and joint angular rotation were obtained. Tendon cross‐sectional area and ankle joint moment arm were obtained from magnetic resonance imaging. Tensile tendon force was calculated from the joint moments and tendon moment arm and stress was obtained by dividing force by cross‐sectional area. Strain was obtained from the displacements normalized to tendon length. Antagonist coactivation and small amounts of ankle joint rotation significantly affected tensile tendon force and aponeurosis and tendon displacement, respectively (P < 0.01). Plantarflexion moment was similar in runners (138 ± 27 Nm, mean ± SEM) and non‐runners (142 ± 17 Nm). Tendon moment arm was alike in non‐runner (58.3 ± 0.2 mm) and runners (55.1 ± 0.1 mm). Similarly, there was no difference in tendon tensile force between runners (2633 ± 465 N) and non‐runners (2556 ± 401 N). The cross‐sectional area of the Achilles tendon was larger in runners (95 ± 3 mm2) than non‐runners (73 ± 3 mm2) (P < 0.01). The load‐deformation data yielded similar stiffness (runners 306 ± 61 N/mm, non‐runners 319 ± 42 N/mm). The maximal strain and stress was 4.9 ± 0.8% and 38.2 ± 9.8 MPa in non‐runners and 4.1 ± 0.8% and 26.3 ± 5.1 MPa in runners. The larger tendon cross‐sectional area in trained runners suggests that chronic exposure to repetitive loading has resulted in a tissue adaptation.
Prevalence of stress incontinence in nulliparous elite trampolinists
Authors: Eliasson K. , Larsson T. , Mattsson E.
Published: March 2003

During trampoline jumping the pelvic floor is exposed to high forces. There has been a general belief that physically fit women have a strong pelvic floor as a result of their regular training, thus preventing urinary incontinence. The aim of this study was to survey the prevalence of stress urinary incontinence in female elite trampolinists. The prevalence of urinary incontinence was assessed by a questionnaire, sent to all 35 elite trampolinists (mean age 15, range 12–22 years) in Sweden. Eighty percent of the trampolinists reported involuntary urinary leakage, but only during trampoline training. The leakage started after 2.5 (range 1–4) years of training. Age (P < 0.001), duration of training (P = 0.04), and training frequency (P = 0.01) were significantly associated with leakage. All women above 15 years of age (n = 23) reported urinary leakage (P < 0.001). Eighteen incontinent women continued the study and their leakage was verified by a pad test. The leakage averaged 28 g during a jump session. The muscle strength was measured with perineometry in 10 women and showed good strength in the pelvic floor muscles.
Electron paramagnetic resonance: a new techniquein skin research
Authors: Mizushima Junichi , Kawasaki Yoshiaki , Sakamoto Kazutami , Kawashima Makoto , Cooke Roger , Maibach Howard I.
Published: March 2003

Background/aim:

Electron paramagnetic resonance (EPR) spectra of nitroxide spin probes have been used for studying biological membranes and chemical‐membrane interaction. We have investigated the influence of surfactants on the intercellular lipid structure of cadaver stratum corneum and the possibility of EPR spectral measurements on the stripped stratum corneum utilizing cyanoacrylate resin, which might reflect the actual skin lipid conditions.

Conclusion: EPR spectra are useful in evaluating the fluidity measurement of stratum corneum of cadaver skin and stripped stratum corneum.
Electron paramagnetic resonance study utilizing stripping method on normal human stratum corneum
Authors: Mizushima Junichi , Kawasaki Yoshiaki , Kitano Takeshi , Sakamoto Kazutami , Kawashima Makoto , Cooke Roger , Maibach Howard I.
Published: March 2003

Background/aim:

Electron paramagnetic resonance (EPR) spectra of nitroxide spin probes are useful for studying biological membranes, and chemical‐membrane interaction. The objective of this study was to assess the fluidity of stripped stratum corneum (SC) of normal human skin with EPR.

Methods: We quantified the fluidity of stripped SC (S‐SC) by a single stripping with cyanoacrylate onto quartz glass, cover glass or transparent film. Spectra were compared with those of the SC of cadaver skin (C‐SC).

Results: All S‐SC spectra were similar to those of C‐SC. There were no statistical differences in the order parameters S between C‐SC and those on quartz cell and cover glass, but those of transparent film were significantly higher. Spectra after a month storage at room temperature at 5°C and at −20°C were unchanged. The order parameter S had decreased after a 3‐month storage in all conditions.

Conclusion: This method is useful for the evaluation of the fluidity measurement utilizing EPR spectra of S‐SC.
Physical and physiological effects of stratum corneum tape stripping
Authors: Bashir Saqib J. , Chew Ai‐Lean , Anigbogu Angela , Dreher Frank , Maibach Howard I.
Published: March 2003

Background/aims: Tape stripping of human stratum corneum has been performed to measure stratum corneum mass, barrier function, drug reservoir and percutaneous penetration. However, the technique itself requires further development to facilitate interpretation.

Methods: In this study we quantified stratum corneum (SC) tape stripping and water kinetic parameters utilizing three types of adhesive tapes, in an in vivo randomized clinical trial. Stratum corneum was tape stripped, and the mass of SC removed by each tape was quantified utilizing a protein assay. Transepidermal water loss (TEWL) was measured and barrier disruption and SC water kinetics calculated. Three commonly utilized acrylate adhesive tapes were utilized and a comparison made between them.

Results: Each type of tape successfully stripped the stratum corneum, but the rayon tape did not induce SC barrier disruption. Neither the type of tape nor the site stripped significantly influenced the mass of SC removed. Water kinetic parameters did not differ significantly for the tapes that did induce barrier disruption. Individual variation in barrier disruption to water following tape stripping was demonstrated.

Conclusion: The tapes utilized removed a similar amount of SC. The tapes have a different propensity to cause barrier disruption. Some individuals do not demonstrate increased TEWL despite an equivalent mass of SC being removed compared to those who do show a response.
Pathways for Lipid Antigen Presentation by CD1 Molecules: Nowhere for Intracellular Pathogens to Hide
Authors: Sugita Masahiko , Peters Peter J. , Brenner Michael B.
Published: March 2003

A crucial feature of peptide antigen presentation by major histocompatibilty complex (MHC) class I and II molecules is their differential ability to sample cytosolic and extracellular antigens. Intracellular viral infections and bacteria that are taken up in phagosomes, but then escape from the endocytic compartment efficiently, enter the class I pathway via the cytosol. In contrast, phagosome‐resident bacteria yield protein antigens that are sampled deep in the endocytic compartment and presented in a vacuolar acidification‐dependent pathway mediated by MHC class II molecules. Despite this potential for antigen sampling, microbes have evolved a variety of evasive mechanisms that affect peptide transport in the MHC class I pathway or blockade of endosomal acidification and inhibition of phagosome–lysosome fusion that may compromise the MHC class II pathway of antigen presentation. Thus, besides MHC class I and II, a third lineage of antigen‐presenting molecules that bind lipid and glycolipid antigens rather than peptides exists and is mediated by the family of CD1 proteins. CD1 isoforms (CD1a, b, c, and d) differentially sample both recycling endosomes of the early endocytic system and late endosomes and lysosomes to which lipid antigens are differentially delivered. These CD1 pathways include vacuolar acidification‐independent pathways for lipid antigen presentation. These features of presenting lipid antigens, independently monitoring various antigen‐containing intracellular compartments and avoiding certain evasive techniques employed by microbes, enable CD1 molecules to provide distinct opportunities to function in host defense against the microbial world.
Biogenesis of the Sorting Endosome: The Role of Rab5
Authors: Woodman Philip G.
Published: March 2003

Rab5 is a regulatory guanosine triphosphatase that is associated with the sorting endosome and participates in endosomal membrane fusion reactions. Recent experiments have provided insights into Rab5 function by demonstrating direct links between Rab5‐interacting proteins and components of the membrane fusion apparatus. In addition, a realisation that Rab5 has additional functions in endosome biogenesis is emerging. These advances may be profoundly important in changing the way that we view the sorting endosome and in developing models that properly reflect the dynamic qualities of the endocytic pathway.
AP‐3 Adaptor Functions in Targeting P‐Selectin to Secretory Granules in Endothelial Cells
Authors: Daugherty Brandy L. , Straley Kimberly S. , Sanders John M. , Phillips J. William , Disdier Magali , McEver Rodger P. , Green Samuel A.
Published: March 2003

P‐selectin, a cell adhesion protein participating in the early stages of inflammation, contains multiple sorting signals that regulate its cell surface expression. Targeting to secretory granules regulates delivery of P‐selectin to the cell surface. Internalization followed by sorting from early to late endosomes mediates rapid removal of P‐selectin from the surface. We show here that the P‐selectin cytoplasmic domain bound AP‐2 and AP‐3 adaptor complexes in vitro. The amino acid substitution L768A, which abolishes endosomal sorting and impairs granule targeting of P‐selectin, reduced binding of AP‐3 adaptors but not AP‐2 adaptors. Turnover of P‐selectin was 2.4‐fold faster than turnover of transferrin receptor in AP‐3‐deficient mocha fibroblasts, similar to turnover of these two proteins in AP‐3‐competent cells, demonstrating that AP‐3 function is not required for endosomal sorting. However, sorting P‐selectin to secretory granules was defective in endothelial cells from AP‐3‐deficient pearl mice, demonstrating a role for AP‐3 adaptors in granule assembly in endothelial cells. P‐selectin sorting to platelet α‐granules was normal in pearl mice, consistent with earlier evidence that granule targeting of P‐selectin is mechanistically distinct in endothelial cells and platelets. These observations establish that AP‐3 adaptor functions in assembly of conventional secretory granules, in addition to lysosomes and the ‘lysosome‐like’ secretory granules of platelets and melanocytes.
Late Endosomes: Sorting and Partitioning in Multivesicular Bodies
Authors: Piper Robert C. , Luzio J. Paul
Published: March 2003

Late endosomes, which have the morphological characteristics of multivesicular bodies, have received relatively little attention in comparison with early endosomes and lysosomes. Recent work in mammalian and yeast cells has given insights into their structure and function, including the generation of their multivesicular morphology. Lipid partitioning to create microdomains enriched in specific lipids is observed in late endosomes, with some lumenal vesicles enriched in lysobisphosphatidic acid and others in phosphatidylinositol 3‐phosphate. Sorting of membrane proteins into the lumenal vesicles may occur because of the properties of their trans‐membrane domains, or as a result of tagging with ubiquitin. Yeast class E Vps proteins and their mammalian orthologs are the best candidates to make up the protein machinery that controls inward budding, a process that starts in early endosomes. Late endosomes are able to undergo homotypic fusion events and also heterotypic fusion with lysosomes, a process that delivers endocytosed macromolecules for proteolytic degradation.
Ubiquitin Sorts Proteins into the Intralumenal Degradative Compartment of the Late‐Endosome/Vacuole
Authors: Urbanowski Jennifer L. , Piper Robert C.
Published: March 2003

Many studies have demonstrated a role for ubiquitin (Ub) in the down‐regulation of cell surface proteins. In yeast, down‐regulation is marked by the internalization of proteins, followed by their delivery to the lumen of the vacuole where both the cytosolic and lumenal domains are degraded. It is generally believed that the regulatory step of this process is internalization from the plasma membrane and that protein delivery to the lysosome or vacuole is by default. By separating the process of internalization from degradation, we demonstrate that incorporation of proteins into intralumenal vesicles represents a distinct sorting step along the endocytic pathway that is controlled by recognition of ubiquitin. We show that attachment of a single ubiquitin can serve as a specific sorting signal for the degradative pathway by redirecting recycling Golgi proteins and resident vacuolar proteins into intralumenal vesicles of the yeast vacuole. This pathway is independent of PtdIns(3,5) P2 and does not rely on the specific composition of transmembrane domain segments. These data provide a physiological basis for how ubiquitination of cell surface proteins guides their degradation and removal from the recycling pathway.
To Find the Road Traveled to Tumor Immunity: The Trafficking Itineraries of Molecular Chaperones in Antigen‐Presenting Cells
Authors: Berwin B. , Nicchitta C. V.
Published: March 2003

Molecular chaperones, both endoplasmic reticulum and cytosol derived, have been identified as tumor rejection antigens; in animal models, they can elicit prophylactic and therapeutic immune responses against their tumor of origin. Chaperone immunogenic activity derives from three principal characteristics: they bind an array of immunogenic (poly)peptides, they can be efficiently internalized by professional antigen‐presenting cells, and once internalized, they traffic to a subcellular compartment(s) where peptide release can occur. Within the antigen‐presenting cell, chaperone‐derived peptides can be assembled onto major histocompatibility class I molecules for presentation at the antigen‐presenting cell surface, thereby yielding the requisite and specific CD8+ T‐cell responses that contribute to the process of tumor rejection. Though it is clear that chaperones, in particular GRP94 (gp96), calreticulin and Hsp70, can elicit cellular immune responses, the subcellular basis of chaperone processing by antigen‐presenting cells remains mysterious. In this review, we discuss recent reports describing the identification of a chaperone internalization receptor and the physiological release of chaperones from necrotic cells, and we present views on the trafficking pathways within antigen‐presenting cells that may function to deliver the chaperone‐associated peptides to subcellular organelles for their subsequent exchange onto major histocompatibility complex molecules.
Ubiquitin‐Related Modifier SUMO1 and Nucleocytoplasmic Transport
Authors: Pichler Andrea , Melchior Frauke
Published: March 2003

Small ubiquitin related modifier SUMO‐1 and its homologs can be conjugated to a large number of cellular proteins. This involves an enzymatic cascade that resembles ubiquitination, and the modification can be reverted by isopeptidases. SUMOylation does not lead to degradation but instead appears to regulate protein/protein interactions, intracellular localization and protects some modified targets from ubiquitin‐dependent degradation. Data collected for more than 30 different target proteins point to two cellular processes, nucleocytoplasmic transport and intranuclear targeting, in which SUMO plays an active role. Here we will focus on links between SUMO and nuclear transport.
Imaging Secretory Vesicles by Fluorescent Protein Insertion in Propeptide Rather Than Mature Secreted Peptide
Authors: Watkins Simon , Geng Xuehui , Li Lehong , Papworth Glenn , Robbins Paul D. , Drain Peter
Published: March 2003

We combined confocal and live‐cell imaging with a novel molecular strategy aimed at revealing mechanisms underlying glucose‐regulated insulin vesicle secretion. The ‘Ins‐C‐GFP’ reporter monitors secretory peptide targeting, trafficking, and exocytosis without directly tagging the mature secreted peptide. We trapped a green fluorescent protein (GFP) reporter in equimolar quantity within the secretory vesicle by fusing it within the C peptide of proinsulin which only after nascent vesicle sealing and acidification is cleaved from the mature secreted A and B chains of insulin. Ins‐C‐GFP expression in mouse islets without fail exhibited punctate distribution of green fluorescence by confocal microscopy. Ins‐C‐GFP colocalized GFP with insulin at vesicle dense cores by immuno‐electron microscopy. Glucose stimulation decreased vesicle fluorescence coordinately with enhanced secretion from islets of C‐GFP detected by anti‐GFP Western blots, and of insulin detected by anti‐insulin radioimmunoassay. An insulin secretagogue with a red fluorescent label, glibenclamide BODIPY®TR, was applied to islets expressing Ins‐C‐GFP. The stimulus response was imaged as a rise in red secretagogue leading to marked loss in green granules. Since neuropeptides as well as peptide hormones are processed from propeptides after sealing of secretory granules, vesicle trapping likely is widely applicable for studies on targeting, trafficking, and regulated release of secretory peptides.
Clathrin and Plant Endocytosis
Authors: Holstein Susanne E. H.
Published: March 2003

Endocytosis requires the coordinated interaction of a plethora of cytosolic and membrane proteins. In mammalian cells, clathrin plays a crucial role in this process as a scaffolding protein underlying the invaginating plasma membrane and surrounding the primary endocytic vesicle. Despite great similarities at the morphological level, the cargo of endocytic clathrin‐coated vesicles in plant cells remains to be elucidated. Thus, the role of endocytosis in the plant cell is difficult to ascertain. This review will present important discoveries on putative endosomal compartments and on the functions of plasma membrane‐derived plant clathrin‐coated vesicles, but will also emphasize the striking similarities of the clathrin‐, network‐ and vesicle fusion‐machineries between plant and animal cells.
Dental considerations for the paediatric AIDS/HIV patient
Authors: Ramos‐Gomez F
Published: March 2003

HIV infection and AIDS are spreading rapidly among the world's children, especially among African‐American and Hispanic children in the USA, and those in developing countries. Although recent research has identified several ways of preventing perinatal transmission of HIV, most of these methods are too expensive for widespread use in developing countries, where the epidemic is most severe. Oral manifestations are early and common clinical indicators of HIV infection and progression in children, as in adults, although the specific manifestations differ between adults and children. Oropharyngeal candidiasis is the most common sign of HIV infection in children and is significantly associated with markers of HIV disease progression. Other common oral manifestations in children include herpes simplex, linear gingival erythema, parotid enlargement and recurrent aphthous ulceration. Further research is needed on the ways in which oral manifestations can be used as predictors of disease progression; on the impact of the limited availability of health care for impoverished families who are disproportionately affected by HIV infection; and on supportive care and its impact on infected children's quality of life.
Saliva as a diagnostic fluid
Authors: Streckfus CF , Bigler LR
Published: March 2003

In the last 10 years, the use of saliva as a diagnostic fluid has become somewhat of a translational research success story. Technologies are now available enabling saliva to be used to diagnose disease and predict disease progression. This review describes some important recent advances in salivary diagnostics and barriers to application and advancement. This review will also stimulate future research activity.
Mobius syndrome: a dental hygiene case study and review of the literature
Authors: Sensat Michelle L.
Published: March 2003

Abstract: Mobius syndrome, a rare, non‐progressive, congenital neuromuscular disorder, presents with multiple dental and medical complications. Signs and symptoms of this condition include: congenital, bilateral or unilateral palsies of the facial and abducens cranial nerves (cardinal sign), and a broad scope of multisystem abnormalities, which may or may not include the following: opthalmoplegia externa, lingual palsy, clubfoot, branchial malformation, ptosis, mental retardation, and pectoralis muscle defect. From a dental standpoint, a number of anomalies may manifest, including: multiple congenitally missing teeth (both deciduous and permanent), micrognathia, paralysis and hypoplasia of the tongue, absence of facial expression and weakness of the palate. This article reviews the case study of a 40‐year‐old male client with Mobius syndrome, dental hygiene diagnosis (DHDx) and intervention, and the dental hygienists' responsibility and role in care.
Family Members' Preferences for Nutrition Interventions to Improve Nursing Home Residents' Oral Food and Fluid Intake
Authors: Simmons Sandra F. , Lam Helene Y. , Rao Geetha , Schnelle John F.
Published: March 2003

OBJECTIVES: To measure family members' preferences for nutrition interventions to improve the oral food and fluid intake of their relatives in a nursing home.

DESIGN: Cross‐sectional descriptive.

SETTING: Three skilled nursing facilities in Southern California.

PARTICIPANTS: One hundred five residents from the three skilled nursing facilities and their respective family members.

MEASUREMENTS: A mailed questionnaire to family members that consisted of 15 forced‐choice comparisons between six nutrition interventions. An assessment of oral food and fluid intake during mealtime for 3 days (nine meals) for each participant using direct observations and estimations of percentage consumed (0% to 100%) by trained research staff.

RESULTS: In order of most to least desirable, the family members preferred the following interventions to improve their relative's oral food and fluid intake: (1) improve quality of food; (2) improve quality and quantity of feeding assistance; (3) provide multiple small meals and snacks throughout the day; (4) place resident in preferred dining location; (5) provide an oral liquid nutritional supplement between meals; and (6) provide a medication to stimulate appetite. The average ± standard deviation total percentage intake for residents whose family members reported that they thought their relative had a problem with their intake was 50%± 16%.

CONCLUSIONS: Family members prefer that other nutrition interventions be attempted before the use of oral supplements or pharmacological approaches. Family members perceive a need for interventions when residents consume, on average, only half of the food and fluid items provided during mealtime.
Simulation of photon transport in a three‐dimensional leaf: implications for photosynthesis
Authors: Ustin S. L. , Jacquemoud S. , Govaerts Y.
Published: March 2003

A model to evaluate photon transport within leaves and the implications for photosynthesis are investigated. A ray tracing model, Raytran, was used to produce absorption profiles within a virtual dorsiventral plant leaf oriented in two positions (horizontal/vertical) and illuminated on one of its two faces (adaxial/abaxial). Together with chlorophyll profiles, these absorption profiles feed a simple photosynthesis model that calculates the gross photosynthetic rate as a function of the incident irradiance. The differences observed between the four conditions are consistent with the literature: horizontal‐adaxial leaves, which are commonly found in natural conditions, have the greatest light use efficiency. The absorption profile obtained with horizontal‐abaxial leaves lies below this, but above those obtained for vertical leaves. The latter present similar gross photosynthetic rates when irradiated on either the adaxial or abaxial surfaces. Vertical profiles of photosynthetic rates across the leaf confirm that carbon fixation occurs mainly in the palisade parenchyma, that the leaf anatomy is integral to its function and that leaves cannot be considered as a single homogeneous unit. Finally, the relationships between leaf structure, orientation and photosynthesis are discussed.
Soft‐tissue anatomy of the extant hominoids: a review and phylogenetic analysis
Authors: Gibbs S. , Collard M. , Wood B.
Published: March 2003

This paper reports the results of a literature search for information about the soft‐tissue anatomy of the extant non‐human hominoid genera,Pan,Gorilla,PongoandHylobates, together with the results of a phylogenetic analysis of these data plus comparable data forHomo. Information on the four extant non‐human hominoid genera was located for 240 out of the 1783 soft‐tissue structures listed in theNomina Anatomica. Numerically these data are biased so that information about some systems (e.g. muscles) and some regions (e.g. the forelimb) are over‐represented, whereas other systems and regions (e.g. the veins and the lymphatics of the vascular system, the head region) are either under‐represented or not represented at all. Screening to ensure that the data were suitable for use in a phylogenetic analysis reduced the number of eligible soft‐tissue structures to 171. These data, together with comparable data for modern humans, were converted into discontinuous character states suitable for phylogenetic analysis and then used to construct a taxon‐by‐character matrix. This matrix was used in two tests of the hypothesis that soft‐tissue characters can be relied upon to reconstruct hominoid phylogenetic relationships. In the first, parsimony analysis was used to identify cladograms requiring the smallest number of character state changes. In the second, the phylogenetic bootstrap was used to determine the confidence intervals of the most parsimonious clades. The parsimony analysis yielded a single most parsimonious cladogram that matched the molecular cladogram. Similarly the bootstrap analysis yielded clades that were compatible with the molecular cladogram; a (Homo,Pan) clade was supported by 95% of the replicates, and a (Gorilla,Pan,Homo) clade by 96%. These are the first hominoid morphological data to provide statistically significant support for the clades favoured by the molecular evidence.
Fibroblast growth factor‐2 induces astroglial and microglial reactivity in vivo
Authors: Goddard Diane R. , Berry Martin , Kirvell Sara L. , Butt Arthur M.
Published: March 2003

A role for fibroblast growth factor‐2 (FGF‐2) has been proposed in mediating the glial response to injury in the central nervous system (CNS). We have tested this possibility in vivo, by injecting FGF‐2 into the cerebrospinal fluid (CSF) of the brain ventricles of young rats and analysing glial cells in the anterior medullary velum (AMV), which partly roofs the IVth ventricle. FGF‐2 was administered at two different doses, low FGF‐2 (500 ng mL−1 CSF) and high FGF‐2 (10 µg mL−1 CSF), and saline vehicle was injected in controls. Injections were performed twice daily for three days, commencing at postnatal day (P) 6, and AMV were analysed at P9, using immunohistochemistry and Western blotting. Glial cells were unaffected by treatment with saline or low FGF‐2, whereas high FGF‐2 induced reactive changes in glial cell types: (1) there was increased GFAP expression in astrocytes, demonstrated by Western blot and immunohistochemistry, and astrocytes appeared hypertrophic, with increased process thickness and number; (2) the number of ED1 labelled microglia/macrophages was doubled, from 47 ± 6 to 114 ± 17 cells per field (0.75 mm2; values are mean ± SEM), and microglia appeared activated, with a multipolar and granular appearance; (3) NG2 positive glial cells appeared more fibrous and there was increased density of processes, although there was no significant increase in their number; (4) oligodendrocyte somata were enlarged and there was a loss of myelin sheaths. The results show that at high CSF titres of FGF‐2 induce glial reactivity in vivo and support a role for FGF‐2 in the pathology of CNS injury and EAE.
Mechanisms of changes to the liver pigmentary component during the annual cycle (activity and hibernation) of Rana esculenta L.
Authors: Barni Sergio , Vaccarone Rita , Bertone Vittorio , Fraschini Annunzia , Bernini Franco , Fenoglio Carla
Published: March 2003

The present study was performed to elucidate the mechanisms responsible for the changes of melanin content/distribution we had previously discovered in the liver parenchyma of Rana esculenta during natural hibernation. Melanomacrophagic component response was analysed using morphocytochemical methods. The results demonstrated that during the prehibernation period (October–November) the melanomacrophages reach the highest proliferative activity (BrdU, PCNA labelling) which is accompanied by an evident melanosynthesis (dopa‐oxidase activity). In contrast, after hibernation, the decrease of liver pigmentation was the consequence of a partial cell loss by apoptotic mechanisms (TUNEL labelling, pyknosis‐karyorhexis) accompanied by a decrease of melanosome content by autophagy and low melanosynthetic activity. On the basis of these findings, there is evidence that liver melanomacrophages represent a metabolically (melanin synthesis/degradation) and cytokinetically (proliferation/death) active cell population during the annual cycle of the frog. The results are also discussed in relation to the functional synergism between hepatocytes and pigment cells in the adaptation to environmental changes.
Stochastic population dynamics and time to extinction of a declining population of barn swallows
Authors: Engen Steinar , Sæther Bernt‐erik , Møller Anders Pape
Published: March 2003

Time to extinction was predicted for a declining population of barn swallowHirundo rusticain Denmark, using a model that includes demographic as well as environmental stochasticity and that takes the uncertainties in the parameter estimates into account.

We apply the concept of population prediction interval (PPI), which is a stochastic interval that includes the unknown variable that may be the extinction time or the population size at some future point of time, with a given probability (1 − α).

The lower bound of the upper one‐sided prediction interval for the extinction time for α = 0·10 was 22 years.

Ignoring uncertainties in the parameter estimates led to a 41% increase in this statistic.

Although the estimate of the demographic variance was small compared to other passerines (σd2 = 0·180), a sensitivity analysis showed that it strongly influenced the predicted time to extinction compared to the model ignoring demographic stochasticity. A similar effect on the prediction of the time to extinction was found for the environmental variance σe2. In addition, choosing σe2 = 0 strongly reduced the width of the prediction interval.

This demonstrates that reliable population projections require modelling of the environmental as well as the demographic stochasticity, and that the uncertainty in the estimates of the model parameters must be taken into account.
Disease persistence and apparent competition in a three‐host community: an empirical and analytical study of large‐scale, wild populations
Authors: Gilbert L. , Norman R. , Laurenson K. M. , Reid H. W. , Hudson P. J.
Published: March 2003

We investigated the effects of three types of host on the persistence of a tick‐borne virus, using the grouse–hare–deer–tick–louping ill virus system of upland Britain. Each host differed in its interaction with the vector and pathogen. Grouse amplify virus only, deer amplify vector only and hares amplify both. Grouse alone suffer high virus‐induced mortality.

 An analytical model of the system was parameterized using empirical data from two wild populations with different community structures. By changing relative host densities we examined the conditions under which the virus would persist and considered the possibility of parasite‐mediated competition between hosts.

 Although deer alone and grouse alone were unable to maintain louping ill virus, a deer–grouse community usually allowed virus persistence because grouse transmitted virus while deer maintained the tick population. Since virus reduces grouse populations this is a type of apparent competition, and is unusual because deer do not amplify the virus.

 At very high deer densities, the opposite effect could occur, whereby virus died out because of ‘wasted’ infected tick bites on deer, that do not transmit virus (the dilution effect).

 In a hare–grouse two‐host system virus usually persisted because hares amplified both the vector and virus (through non‐viraemic transmission). Thus, apparent competition may occur between mountain hares and grouse.

 The addition of a third host type increased the likelihood of disease persistence. Hares added to the deer–grouse system rendered the dilution effect unlikely because of additional virus amplifiers. Deer added to the hare–grouse system meant virus almost always persisted because they amplified the vector.
The geographical range structure of the holly leaf‐miner. I. Population density
Authors: Brewer Andrew M. , Gaston Kevin J.
Published: March 2003

The local population density structure of a phytophagous insect, the holly leaf‐miner Phytomyza ilicis Curtis, was examined across its natural geographical range in Europe.

The frequency distribution of the number of sample sites at which the leaf‐miner attained different densities per tree was strongly right‐skewed, with the species being absent from a large number of sites at which its host occurred, particularly in southern regions.

There was a decline in the spatial autocorrelation of leaf‐miner densities with increasing distance between sample sites, with negative autocorrelation at long lags resulting in part from high densities being attained at the north‐eastern range limits and low densities at the southern range limits.

Partial regression analysis was used to model leaf‐miner densities in terms of spatial position within the geographical range and the broad climate experienced at the sample localities. This accounted for between 40 and 65% of the variation in densities, dependent upon how the leaf‐miner’s geographical range was defined.

While overall these results are at odds with common and intuitively appealing assertions about the abundance structure of geographical ranges, they can readily be interpreted in terms of a simple modification of a general model of such structures.
Cross‐scale vegetation patterns of Flooding Pampa grasslands
Authors: Perelman S. B. , León R. J. C. , Oesterheld M.
Published: March 2003

The spatial pattern of vegetation heterogeneity across different scales may indicate the major environmental controls on vegetation structure, and thus guide strategies for the conservation of biodiversity.

 We analysed cross‐scale vegetation patterns in a 90 000‐km2area of natural grasslands in the Flooding Pampa, Argentina. We assessed the contribution of regional (latitudinal) and landscape (topographic) patterns of species turnover to overall heterogeneity using data from 749 censuses.

 A large proportion of the variation in species composition across the entire region was observed at very fine spatial scales (0.1–10 km2), associated with subtle topographic features and soil salinity gradients. Latitudinal variation played a secondary role.

 Species turnover among stands occupying different landscape positions at the same latitude was 50% greater than among inventories encompassing two degrees of latitude. The fine‐grain heterogeneity determined that an area of 10 km2was often sufficient to include 50% of all vascular plant species of the region.

 Although a large proportion (nearly 70%) of the vascular flora was composed of rare (satellite) species that occurred in less than 10% of the samples, few core species (i.e. those occurring in more than 90% of the samples) were seen at any scale of analysis.

 Latitude contributed most clearly to variation in species composition among the zonal communities located in well‐drained soils where differences in relative cover of C3and C4grasses were seen. However, photosynthetic pathways still varied more along salinity or topographic gradients than across regions. A latitudinal pattern in abundance of the differentPoaceaetribes was also consistent with their climatic classification.

 Alpha diversity showed a threefold variation among different stands within a landscape: it increased from low topographic positions and high soil salinity to high topographic positions and low salinity. However, it was constant among surveys within the region.

 Nearly 25% of the species were exotic, mostly European, whose invasion was promoted by livestock grazing. Compared with the native species, exotics were consistently enriched in annuals, particularly forbs, across latitude, and were less tightly associated with landscape heterogeneity than native species.
Periodic spotted patterns in semi‐arid vegetation explained by a propagation‐inhibition model
Authors: Couteron P. , Lejeune O.
Published: March 2003

Vegetation cover regularly punctuated by spots of bare soil is a frequent feature of certain semi‐arid African landscapes, which are also characterized by banded vegetation patterns (i.e. tiger bush).

 The propagation‐inhibition (PI) model suggests that a periodic pattern characterized by a dominant wavelength can theoretically establish itself through a Turing‐like spatial instability depending only on a trade‐off between facilitative and competitive interactions among plants. Under strictly isotropic conditions, spotted and banded patterns are distinct outcomes of a unique process, whereas anisotropy leads to a banded structure. The model predicts that spotted patterns will have a lower dominant wavelength than bands.

 We test some outcomes of the PI model against vegetation patterns observable in aerial photographs from West Africa. Two sites with rainfall ofc.500–600 mm year−1were studied: a 525‐ha plain in north‐west Burkina Faso and a 300‐ha plateau in southern Niger. Digitized photographs were subjected to spectral analysis by Fourier transform in order to quantify vegetation patterns in terms of dominant wavelengths and orientations.

 Spotted vegetation proved highly periodic. The characteristic range of dominant wavelengths (30–50 m) was similar at two sites more than 500 km apart. The PI model suggests that spots may occur as a hexagonal lattice but there is little evidence of such patterning in the field. A dominant wavelength was far quicker to establish in simulations (c. 102–103 years for annual grasses) than a hexagonal symmetry (c. 105 years), and observed patterns are therefore likely to be far from the asymptotic structure.

 Elongated and smudged spots that locally became flexuous bands have been observed in southern Niger. This pattern that had a dominant wavelength of 50 m but lacked any dominant orientation can be interpreted as a transition from spots to bands under fairly isotropic conditions.

 The PI model provides a framework for further investigation of patterns in semi‐arid vegetation and may be of a broader ecological application.
Effect of shrubs on tree seedling establishment in an abandoned tropical pasture
Authors: Holl Karen D.
Published: March 2003

The objective of this study was to evaluate whether early successional shrubs facilitate, tolerate or inhibit different stages of tree establishment in abandoned tropical pasture.

Seed rain, seed predation, seed germination and seedling survival of tropical forest trees in pasture grass, below small (< 25 m2) shrub patches and below large (> 40 m2) shrub patches, were compared in one abandoned pasture in Costa Rica over 2 years.

Seed rain of animal‐dispersed trees was higher below both large and small shrub patches than below grass. Seed rain of wind‐dispersed trees did not differ in the three patch types.

Predation of all animal‐dispersed seeds combined and of three individual species was significantly higher below large and small shrub patches compared with below grass; predation of five species did not differ significantly in the three patch types.

Germination did not differ significantly in the three patch types for any of the species.

Seedling survival was highest below large shrub patches for three of four species.

Computer simulations of probabilities of seeds arriving in the pasture and surviving to the seedling stage suggest that early successional shrubs have a net facilitative effect on the early stages of forest tree seedling establishment compared with areas without shrubs in the pasture studied, although variance was high. Shrubs may facilitate, inhibit and tolerate different stages of tree seedling establishment.
Fine‐scale spatial structure in a grassland community: quantifying the plant’s‐eye view
Authors: Purves D. W. , Law R.
Published: March 2003

The fine‐scale spatial patterns of Agrostis stolonifera, Holcus lanatus and Lolium perenne were recorded in an English lowland grassland as presence/absence maps from 400‐cell quadrats at two different scales (2 × 2 cm or 8 × 8 cm cells).

Local spatial structure in these patterns was quantified using spatial covariance functions. Distance‐ and direction‐dependent components were examined separately for both intra‐ and interspecific patterns. The significance of departures from randomness was determined using Monte Carlo techniques.

The smaller‐scale data showed that all three species were significantly aggregated, Agrostis to a greater distance (8 cm) than Holcus or Lolium(4 cm). The intensity of aggregation decreased in the order Lolium > Holcus > Agrostis. The larger‐scale data suggested that this aggregation extended to greater distances, and that it was most intense in Agrostis.

Despite the lack of visual directionality in the environment, Agrostis showed a directional pattern at both scales, with Lolium varying in the same direction at the larger scale.

Only Agrostis and Lolium showed a significant interspecific relationship (segregated to 2 cm at the small scale, but aggregated to 8 cm at the larger scale). There was no evidence of directionality in the interspecific components of pattern.

The nature of spatial structure appears to depend on the scale of observation, but the smaller‐scale data are more likely to provide a biologically interpretable measure of local spatial structure in this community.
A method for quantifying cell size from differential interference contrast images: validation and application to osmotically stressed chondrocytes
Authors: Alexopoulos L. G. , Erickson G. R. , Guilak F.
Published: March 2003

An automatic image analysis method was developed to determine the shape and size of spheroidal cells from a time series of differential interference contrast (DIC) images. The program incorporates an edge detection algorithm and dynamic programming for edge linking. To assess the accuracy and working range of the method, results from DIC images of different focal planes and resolutions were compared to confocal images in which the cell membrane was fluorescently labelled. The results indicate that a 1‐µm focal drift from the in‐focus plane can lead to an overestimation of cell volume up to 14.1%, mostly due to shadowing effects of DIC microscopy. DIC images allow for accurate measurements when the focal plane lies in a zone slightly above the centre of a spherical cell. In this range the method performs with 1.9% overall volume error without taking into account the error introduced by the representation of the cell as a sphere. As a test case, the method was applied to quantify volume changes due to acute changes of osmotic stress.
β‐Amyloid inhibits integrated mitochondrial respiration  and key enzyme activities
Authors: Casley C. S. , Canevari L. , Land J. M. , Clark J. B. , Sharpe M. A.
Published: March 2003

Disrupted energy metabolism, in particular reduced activity of cytochrome oxidase (EC 1.9.3.1), α‐ketoglutarate dehydrogenase (EC 1.2.4.2) and pyruvate dehydrogenase (EC 1.2.4.1) have been reported in post‐mortem Alzheimer's disease brain. β‐Amyloid is strongly implicated in Alzheimer's pathology and can be formed intracellularly in neurones. We have investigated the possibility that β‐amyloid itself disrupts mitochondrial function. Isolated rat brain mitochondria have been incubated with the β‐amyloid alone or together with nitric oxide, which is known to be elevated in Alzheimer's brain. Mitochondrial respiration, electron transport chain complex activities, α‐ketoglutarate dehydrogenase activity and pyruvate dehydrogenase activity have been measured. β‐Amyloid caused a significant reduction in state 3 and state 4 mitochondrial respiration that was further diminished by the addition of nitric oxide. Cytochrome oxidase, α‐ketoglutarate dehydrogenase and pyruvate dehydrogenase activities were inhibited by β‐amyloid. The Km of cytochrome oxidase for reduced cytochrome c was raised by β‐amyloid. We conclude that β‐amyloid can directly disrupt mitochondrial function, inhibits key enzymes and may contribute to the deficiency of energy metabolism seen in Alzheimer's disease.
Phosphate limited cultures of the cyanobacterium Synechococcus are capable of very rapid, opportunistic uptake of phosphate
Authors: Ritchie Raymond J. , Trautman Donelle A. , Larkum A. W. D.
Published: March 2003

Phosphate uptake rates were measured in Synechococcus R‐2 incubated in artificial secondary‐ and tertiary‐treated sewage.

Phosphate uptake was measured using chemical assay and 32P incorporation. Intracellular pH was measured using accumulation of 14C‐labelled weak acids and bases and membrane potentials using 86Rb+/valinomycin.

Synechococcus cells are capable of very rapid, opportunistic uptake of phosphate (10–30 nmol m−2 s−1) even though net uptake by growing cultures was < 0.5 nmol m−2 s−1. Km and Vmax in the light were not significantly different at pHo 7.5 and 10. The mean Km values were 1.91 ± 0.41 mmol m−3 and 0.304 ± 0.055 mmol m−3 for P‐sufficient (secondary‐treated sewage) and P‐deficient (tertiary‐treated sewage) cells, respectively. The transport systems probably recognize both H2PO4− and HPO42−. Intracellular inorganic phosphate is +28 to +56 kJ mol−1 from electrochemical equilibrium. In P‐sufficient cells uptake is very slow in the dark (c. 0.1 nmol m−2 s−1) but phosphate‐starved cells can opportunistically take up P about 100 times faster.

Two separate ATP‐driven phosphate uptake mechanisms (1 PO4 in per ATP) appear to be responsible for phosphate uptake by the cells. They have different Km values, different light/dark responses and electrical behaviour.