bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein uptake by intestinal macrophages and eosinophilic granulocytes in trout: An in vivo study
Authors: Dorin Dominique , Martin Patrick , Sire Marie‐France , Smal Jean , Vernier Jean‐Marie
Published: August 2004

Summary— A homologous protein, recombinant trout somatotropin (rtST) and its heterologous counterpart, native bovine somatotropin (bST), were administered anally to juvenile rainbow trout (Oncorhynchus mykiss). Plasma levels of rtST, determioned by radio‐immunoassay, peaked between 15 and 60 min and remained high until 2 h after administration. Immunogold labelling was used to follow the routes of transfer of rtST and bST, and to observe potential interaction between the hormones and the cells constituting the first line of non‐specific defence, ie the macrophages infiltrated between epithelial cells, or dispersed in the subepithelial lamina propria, and eosinophilic granulocytes (EGCs) of the lamina propria, whose properties have been considered to be similar to mammalian mast cells. Macrophages were immunolabelled for the homologous and heterologous proteins. EGCs took up to the heterologous but not the homologous protein. This finding was confirmed using indirect immunofluorescence assay. EGCs could internalize foreign proteins transferred from the intestinal lumen to the lamina propria.
Ultrastructural and morphometrical analyses of the brown adipocyte nucleus in a hibernating dormouse
Authors: Zancanaro Carlo , Malatesta Manuela , Vogel Peter , Osculati Francesco , Fakan Stanislav
Published: August 2004

Summary— The fine morphology, size, and perichromatin granule frequency were analysed in brown adipocyte nuclei from hibernating, arousing, and euthermic dormice, Muscardinus avellanarius. Unusual nuclear structural constituents such as nuclear amorphous bodies, coiled body‐like constituents and bundles of nucleoplasmic filaments were described as typical of hibernating nuclei. Morphometrical findings showed significant difference in total nuclear and nucleolar size in the three physiological conditions investigated as well as decreasing frequency of perichromatin granules in nuclei of hibernating to euthermic animals. A possible involvement of these granules in the intranuclear transport or storage of pre‐mRNA is discussed in the context of other experimental evidence.
Identification and characterization of the tumor‐specific P1A gene product
Authors: Amar‐Costesec Alain , Godelaine Daniéle , Van den Eynde Benoit , Beaufay Henri
Published: August 2004

Summary— In murine mastocytoma P815, gene P1A directs the expression of antigens P815A and B which are the target of a T cell‐mediated rejection response in syngeneic animals. This gene is expressed at a high level in various tumors, but is silent in normal tissues except testis and placenta; its activation is thus possibly related to malignant transformation. An anti‐synthetic peptide rabbit antiserum reacted by immunoblotting with a cellular protein migrating near 40 kDa on SDS‐PAGE. The immunoreactive protein was detected only in lysates from cells which express antigen P815A: P1.HTR mastocytoma cells and, after transfection with cosmids carrying the P1A gene, the antigen‐loss variant PO.HTR cells and DAP‐3 H‐2L fibroblasts. The identity of this protein as the P1A gene product was confirmed by cell‐free transcription‐translation of the P1A cDNA, the product of which also migrated near 40 kDa in SDS‐PAGE and was captured by protein A‐Sepharose in the presence of the antiserum. Subcellular fractionation by differential and isopycnic centrifugation indicated that the P1A protein is associated with cytoplasmic membranes demonstrating a broad distribution with respect to size and density. Immunofluorescence microscopy also revealed a cytoplasmic signal, particularly intense in small vesicles, which coincides with that produced by an anti‐mouse type I collagen guinea pig antiserum except near the cell periphery where the P1A signal is weaker. We conclude that the P1A protein is bound to membranes of the secretory pathway, at a concentration which goes increasing from the endoplasmic reticulum to secretion vesicles. The N‐terminal portion of the protein was readily removed by proteolytic enzymes in the absence of detergent, suggesting a localization at the cytoplasmic surface. The P1A protein is renewed with a half‐life of 50 mm and is readily phosphorylated upon metabolic labeling of mastocytoma cells with [32P]‐orthophosphate. When immunoisolated from cells lysed with Nonidet P‐40, the P1A protein is accompanied by a 62‐kDa protein which also exists in a phosphorylated form. Thus, it is probably associated with another phosphoprotein, either as a stable functional unit, or as a dissociable complex.
Subcellular distribution of aster‐nucleated microtubule length: A more or less mitotic status of cytoplasmic areas during meiosis I of starfish oocytes
Authors: Barakat Hamid , Geneviere‐Garrigues Anne‐Marie , Schatt Philippe , Picard André
Published: August 2004

Summary— Shortening of aster‐nucleated microtubules is a mitotic feature, which is proportional to the M‐phase promoting factor kinase activity. We have taken advantage of this characteristic to appraise the mitotic status of cytoplasmic territories in polyspermic starfish oocytes. In early prometaphase, asters are small in the nuclear area, where cyclin B accumulated before GVBD, while in the remaining of the oocytes asters are large. In metaphase all asters are small. This coincides with a change in behaviour of cyclin B, whose association with microtubules increases in late prometaphase. We discuss the possibility that uneven distribution of cyclin B‐dependent kinase is a general feature of mitosis and that it allows the cell to build the convenient spindle at the right place.
Localization of rDNA transcription sites in nucleoli of human sertoli cells: An EM quantitative autoradiographic study using 3H‐uridine
Authors: Brechard Marie‐Pierre , Hartung Michéle , de Lanversin Anne , Cau Pierre , Stahl André
Published: August 2004

Summary— The sites of rDNA transcription within human Sertoli cell nucleoli have been localized using EM autoradiography after a 45‐min pulse of 3H‐uridine and an exposure time of 6 months. Two successive quantitative image analyses, one derived from the 50% probability circle method and the other from the cross‐fire method, allowed us to estimate the radioactivity incorporated within each nucleolus compartment. This study demonstrated that rDNA transcription occurred mainly at the border between fibrillar centers and dense fibrillar components and to a lesser extent within the dense fibrillar component. The other Sertoli cell nucleoli compartments did not incorporate 3H‐uridine and therefore were not involved in rDNA transcription.
Immuno‐electron microscopic localization of estradiol receptor in cells of male and female reproductive and non‐reproductive organs
Authors: Echeverría Olga M. , Maciel Angélica Gonzalez , Traish Abdulmaged M. , Wotiz Herbert H. , Ubaldo Ernestina , Vázquez‐Nin Gerardo H.
Published: August 2004

Summary— The localization of estradiol receptor (ER) in various tissues and their distribution in sub‐cellular compartments were studied by means of immunogold‐electron microscopic methods using a site‐directed polyclonal antibody developed against a peptide from the DNA binding site of ER. This method was used to determine the presence and localization of ER in tissues and cells of male and female reproductive and non‐reproductive organs. In the female reproductive tract, endometrial cells and the cells of the corpus luteum were found to contain ER. In non‐reproductive organs of both sexes the following cell types showed significant labeling: hepatocytes, epithelial duodenal cells, striated muscle fibers, cells of the proximal convoluted tubules of the kidney, lymphocytes, neurons, and adipose cells. Alveolar epithelial cells were studied only in female specimens and were labeled by the anti‐ER. Prostatic and epididymal epithelial cells were found to be labeled in the male reproductive organs. In all these cells a higher density of label was found in the nucleus, especially in the space between the clumps of compact chromatin, as was previously found in epithelial endometrial cells. These results suggest that estradiol exerts its effects through a common nuclear mechanism in cells of male and female reproductive and non‐reproductive organs.
Trypanosoma cruzi cDNA encodes a tandemly repeated domain structure characteristic of small stress proteins and glutathione S‐transferases
Authors: Schöneck Ralf , Plumas‐Marty Bétrice , Taibi Ali , Billaut‐Mulot Odile , Loyens Marc , Gras‐Masse Hélène , Capron André , Ouaissi Ali
Published: August 2004

The isolation, characterization, and expression of a novel cDNA encoding a Trypanosoma cruzi polypeptide (TcAc2), homologous to various small stress proteins and glutathione S‐transferases, are described. The deduced amino‐acid sequence revealed two domains sharing 27% identity and an additional 27% similarity to each other suggesting that the molecule may have evolved from a single domain by a process of gene duplication and fusion. The TcAc2 cDNA was subcloned into the pGEX‐2T vector for expression in E coli. In vitro translation products of epimastigote mRNA, immunoprecipitated with anti‐TXepi serum, showed a major radioactive band of 52 kDa. Immunoprecipitation of [35S] methionine labelled epimastigote and trypomastigote antigens after pulse chase experiments, using anti‐TcAc2 fusion protein antibodies, showed that the protein is released into the culture medium. Moreover, Western blot analysis revealed a single band of 52 kDa with epimastigote, trypomastigote and amastigote antigens. Primary structure homology searches revealed that each TcAc2 domain contained within its N‐terminus significant homology to Solanum tuberosum pathogenesis‐related protein PRI, soybean heat shock protein 26‐A, auxin regulated clone pCNT103 from Nicotiana tabacum and Drosophila melanogaster glutathione S‐transferase 27 (GST27). This finding was supported by a comparison of hydrophobicity profiles of TcAc2 and these proteins. Most of them play a central role in protection mechanisms against stress. Based on the homology between TcAc2, glutathione S‐transferases (GST) and small stress proteins, it is likely that the TcAc2 gene product may play a crucial role in parasite's adaptation to its microenvironment. These molecules could be considered as members of the GST superfamily, where the T cruzi protein may take a particular place because of its internal gene duplication.
Kurloff cell lysosomal arylsulphatases: Presence of both cationic and highly anionic isoforms of the sole B class
Authors: Taouji Saïd , Buat Marie‐Laure , Izard Jacques , Landemore Gerard
Published: August 2004

Following the previous ultrastructural demonstration of the presence of arylsulphatase (Asase) activities in Kurloff cells (KC) and of their quasi‐exclusive localization in the Kurloff body (KB), this work investigates their biochemical and zymographic properties after extraction from purified KC suspensions. Using the discriminative inhibitory conditions of both the Baum or LeeVaupel and Conzelmann methods, nitrocatechol sulphate hydrolyzing enzymes of the KC were assumed to belong to the B class of the type II Asase alone. After electrophoretic separation under non‐denaturing conditions in a 4–23% polyacrylamide gel, they were characterized by 55 kDa and 62 kDa zymographic bands. After isoelectric focusing, ‘classical’ cationic isoforms (pI 8.5) and two anionic isoforms (pI 4.4 and 4.6) were observed on zymograms. As expected for class B Asase, the different zymographic forms of KC Asase were only recovered in the unadsorbed fraction after anion‐exchange chromatography on DEAE‐cellulose column equilibrated with high ionic strength buffer. Their Km (2.1 mM), their optimum pH (5.8) and their inhibitions by sulfite, phosphate, sulphate and ascorbic acid as well as their slight stimulation by AgNO3 were also characteristic of this class of Asase. Finally, chondroitin4‐sulphate was shown to potentially be a physiological substrate for these lysosomal enzymes.
Statistical evidence for two major proteins in freeze‐fractured gastric parietal cell tubulovesicles and canaliculus
Authors: Maccario Jean , Péranzi Gabriel , Bayle Denis , Lewin Miguel JM , Thomas‐Soumarmon Annick
Published: August 2004

In a previous work, resting and acid‐secreting rabbit gastric mucosa were freeze‐fractured and shadowed at 45° with Pt‐C. The shadow widths of proteic particles of tubulovesicle and canaliculus membranes were measured and compared. It was concluded that the frequency distributions of widths are significantly different in resting and secreting membranes and that each distribution accounts for several subpopulations of homogenous particles. In the present study, an attempt is made to describe the experimental distributions as a mixture of those of two major proteins, say A and B and their aggregates (AA, AB and BB). The modelling, although simple, gave a very satisfactory statistical fit between observed and computed distributions. The comparison of parameters calculated from histamine and ranitidine experimental data further improves the fits and finally, component A accounts for 69% of the particles. Most replica of A particles are heart‐shaped and the median shadow widths are 6.1 and 6.8 nm in canaliculus and tubulovesicles respectively. The component B accounts for 31% of the particles. They mainly appear as small barrels and the median shadow widths are 8.8 and 10.3 nm in canaliculus and tubulovesicles respectively. According to calculated parameters and observed particle replica, the onset of secretion does not change the relative ratio of proteins but changes their shapes. Component A should be the (H+, K+)ATPase whereas debate on the identity of B is wide open.
Atomic force microscopy study of the collagen fibre structure
Authors: Revenko Irène , Sommer Françoise , Minh Duc Tran , Garrone Robert , Franc Jean‐Marie
Published: August 2004

Observations of intact reconstituted and native collagen fibres were performed with the atomic force microscope. The results are compared between the two types of fibres and with those obtained previously with the electron microscope on freeze‐etched or negative stained samples. Some of the findings presented here indicate that the specimens observed in air with the atomic force microscope were still in a hydrated state.
Immunohistochemical identification of the uncoupling protein in human hibernoma
Authors: Zancanaro Carlo , Pelosi Giuseppe , Accordini Cristina , Balercia Giancarlo , Sbabo Laura , Cinti Saverio
Published: August 2004

The expression of the uncoupling protein (UCP), a protein unique to brown adipocyte mitochondria, was studied in sections of a human hibernoma by means of immunohistochemistry. Multilocular, but not unilocular, adipocytes expressed the UCP in the tissue. Further, the immunostaining was not uniform in multilocular cells, because small adipocytes with finely multivacuolar or scanty lipid deposit showed more intense staining. This pattern is similar to that found in brown adipose tissue. Ultrastructural investigation confirmed that a majority of proliferating cells had the morphological characteristics of brown adipocyte. Results indicate that adipocytes in hibernoma may be very close to brown adipocytes both morphologically and immunocytochemically.
Structure of the polyglutamyl chain of tubulin: Occurrence of alpha and gamma linkages between glutamyl units revealed by monoreactive polyclonal antibodies
Authors: Wolff Annie , Houdayer Monique , Chillet Denise , de Néchaud Béatrice , Denoulet Philippe
Published: August 2004

Summary— Polyglutamylation, a posttranslational modification which consists of the sequential addition of one to six glutamyl units in the carboxy‐terminal domain of both tubulin subunits, is a major event in neurons. Its structure has been investigated by using monoreactive polyclonal antibodies directed against distinct glutamylation motifs, ie α‐ and γ‐linkages between glutamyl units. It is shown that, beside α‐linkages previously characterized, γ‐Linkages also occur in glutamyl chains of brain tubulin. The co‐existence of these two basic motifs leads to a conception of the polyglutamyl chain with a very sophisticated structure which could, through its complexity, help the microtubule to reach its structure and fulfil its functions.
The orientation of primary cilia during the wound response in 3Y1 cells
Authors: Katsumoto Tetsuo , Higaki Katsumi , Ohno Kousaku , Onodera Kazukiyo
Published: August 2004

Summary— The behavior of the primary cilia of 3Y1 cells in the interphase was investigated by indirect immunofluorescence microscopy and transmission electron microscopy, using an antibody for tubulin. At 4.5 h after scraping a part of a confluent cell sheet, the primary cilia of cells facing the wound were located predominantly forward of the nucleus on the wounded side, and were oriented in the direction of the leading lamellae. Cytoplasmic microtubules (MTs), emanating from around the base of the cilia, were well developed in the leading lamellae on the wounded side. On the other hand, in the cells of an unperturbed area away from the wounded edge, the primary cilia remained randomly distributed near the nucleus. The position and a certain well‐defined orientation of a pair of centrioles seem to play an important role for the development of cytoplasmic MTs, and consequently the orientation of the centrioles is controlled by the primary cilia.
Protein kinase C (PKC) level is increased in PC12 cells overexpressing transfected liver‐type phosphofructokinase
Authors: Elson Ari , Weiss Yael , Groner Yoram
Published: August 2004

Summary— PC12 cells which overexpress transfected liver‐type phosphofructokinase (PFKL) have previously been described as a model system for PFKL overexpression in Down's syndrome and have been shown to perform glycolysis at enhanced rates. Here we report that levels of protein kinase C (PKC) in PC 12‐PFKL cells were almost doubled, as estimated from in vitro activity and phorbol ester binding experiments and from an increase found in PKC‐alpha mRNA levels. Most of the added PKC was found to be associated with the cellular membrane while the cytoplasmic levels of PKC were barely increased. The steady‐state levels of 1,2‐sn‐diacylglycerol in PC12‐PFKL cells were found to be unaltered, suggesting that enhanced glycolysis in these cells did not influence PKC by altering the amounts of this compound. PFKL is one of several genes known to be overexpressed in Down's syndrome. Upregulation of PKC due to PFKL overexpression could result in widespread disturbances of gene expression and play a part in causing some of the many symptoms of the disease.
Nuclear matrix involvement in sperm head structural organization
Authors: Santi Spartaco , Rubbini Silvia , Cinti Caterina , Squarzoni Stefano , Matteucci Alessandro , Caramelli Elisabetta , Guidotti Lia , Maraldi Nadir M.
Published: August 2004

Summary— In the sperm nuclei the DNA is packaged into a highly condensed form and is not organized into nucleosome and solenoid but is bound and stabilized mainly by the protamines that arrange the DNA in an almost crystalline state. As demonstrated for somatic cells, the sperm DNA has been reported to be organized in loop domains attached to the nuclear matrix structures. However, the possible role of the sperm head matrix in maintaining the loop organization in absence of a typical nucleosomal structures has not been fully elucidated. By using in situ nick translation at confocal and electron microscope level, we analyzed the organization of the DNAprotamine complex and its association with the sperm nuclear matrix. The data obtained indicate that the chromatin organization in sperm nuclei is maintained during the sperm condensation by means of interactions with the nuclear matrix at fixed sites. The fine stucture of sperm nucleus and of sperm nuclear matrix, investigated on sections and replicas of freeze‐fractured specimens, suggests that the lamellar array, observed by freeze‐fracturing in the sperm nuclei, could depend on the inner matrix which presents a regular organization of globular structures possibly involved in the maintenance of chromatin domains in highly condensed sperm nuclei also.
Densitometric analysis of nuclear DNA content in lentil roots grown in space
Authors: Driss‐Ecole Dominique , Schoëvaërt Damien , Noin Michële , Perbal Gérald
Published: August 2004

Summary— Lentil seedlings were grown for 28 h in space, on board Spacelab (IML I Mission) and growth of the primary root was analysed. The length of cortical cells was less in near weightlessness than on the 1 g centrifuge (flight control) and mitotic index was lower but there was no apparent perturbation in the mitosis. To further investigate which phase of cell cycle was modified, densitometric analysis of nuclear DNA content in cortical cells was carried out by the mean of an image processing system (SAMBA). In microgravity there was a decrease in DNA synthesis and a promotion of the arrest in the G2 phase of cell cycle. These results, and other ones obtained elsewhere on a slowly rotating clinostat, led us to think that in microgravity the perturbation of the gravisensing cells and/or the absence of convection could account for the modification of cell growth registered in the primary root.
Microinjection of Cdc25 protein phosphatase into Xenopus prophase oocyte activates MPF and arrests meiosis at metaphase I
Authors: Rime Hélène , Huchon Denise , De Smedt Véronique , Thibier Catherine , Galaktionov Konstantin , Jessus Catherine , Ozon René
Published: August 2004

Summary— Microinjection of bacterially expressed human cdc25A protein into Xenopus prophase oocytes provokes the activation of p34cdc2 kinase and the tyrosine dephosphorylation of p34cdc2 in the presence or absence of protein synthesis. The level of p34cdc2 kinase activity then drops in parallel with the degradation of cyclin B2 and finally increases again to stabilize at a high level. Cdc25 microinjection induces the assembly of a metaphase I spindle which is abnormally located in the deep cytoplasm. Moreover, oocytes arrest at the metaphase I stage and do not reach metaphase II even 10 h after cdc25 microinjection. The extended metaphase I period observed in cdc25‐injected oocytes results from an equilibrium between degradation of cyclins and synthesis of new cyclins. This is in contrast with progesterone‐stimulated oocytes where cyclin degradation is turned off when oocytes enter metaphase II. During metaphase I, the reactivation of MPF activity can be disrupted in two different ways: 1) cycloheximide, an inhibitor of protein synthesis, by preventing the synthesis of new cyclins, provokes the disappearance of MPF kinase activity and the reformation of a nucleus; 2) when the cAMP level is increased during the metaphase I period in cdc25‐injected oocytes, MPF kinase activity drops following a rephosphorylation of tyrosine 15 of p34cdc2, while the cyclin turn‐over remains unaffected. Moreover, increasing the cAMP level in prophase oocytes totally prevents the action of cdc25. Our results indicate that in Xenopus oocytes, the PKA pathway negatively regulates the activation of MPF and the activity of p34cdc2/cyclin B complex through tyrosine phosphorylation of p34cdc2 during metaphase I.
Molecular and immunological characterization of a Trypanosoma cruzi protein homologous to mammalian elongation factor 1 gamma
Authors: Billaut‐Mulot Odile , Schöneck Ralf , Fernandez‐Gomez Rodolfo , Taibi Ali , Capron André , Pommier Valérie , Plumas‐Marty Beatrice , Loyens Marc , Ouaissi Ali
Published: August 2004

Summary— In previous studies, we reported the characterization of three Trypanosoma cruzi proteins with molecular masses of 45, 30 and 25 kDa eluted from a glutathione agarose column (these proteins were named TcGBP). Using antibodies against TcGBP native proteins we could isolate from a lambda ZAPII epimastigote cDNA library cDNA clones encoding the 30 and 25 kDa proteins. Comparison of the two sequences with amino acid sequences in several data banks revealed that both protein sequences were highly homologous to human and Artemia salina elongation factor 1β. Thus, the proteins were named TcEF‐1 β25 and TcEF‐1 β30. In the present study we used a double immunoscreening strategy that allowed us to isolate a cDNA clone corresponding to the 45 kDa protein. The protein sequence revealed 31% identity and 61% homology with human and Artemia salina EF1γ and therefore was named TcEF‐1γ. Moreover, three putative phosphorylation sites at position 51 (CSPC), at position 90 (RTPL) and at position 265 (PSPF) were found in the TcEF‐1γ sequence. These sites are compatible with the notion that TcEF‐1γ could be the target of phosphorylation by protein kinase(s). Random primed cDNA hybridized with a single 1.4 kb mRNA found in epimastigote, trypomastigote and amastigote forms. In addition, Southern blot analysis of genomic DNA suggested that the protein is encoded by a single gene. The TcEF‐1γ cDNA was subcloned into the pGEX‐4T‐3 vector for expression in Escherichia coli. Antibodies against the fusion peptide allowed us to identify the weight sizes of the native protein (48 kDa) and its major degradation product (24.4 kDa) which are in close agreement with those of EF1‐γ from Artemia salina and Schizosaccharomyces pombe. These antibodies reacted against macrophage cell line J774 extracts which indicates that EF‐1γ epitopes were conserved throughout evolution.
Effects of acidic pH on the formation of vinblastine‐induced paracrystals in Chinese hamster ovary cells
Authors: Takanari Hideki , Morita Joji , Yamanaka Hidetaka , Yada Kenichiro , Takahashi Asahiko , Izutsu Kosaku
Published: August 2004

Summary— The pH‐related change in morphology of vinblastine (VLB)‐induced paracrystals formed in Chinese hamster ovary (CHO) cells was examined immunohistochemically in order to determine both the mechanism of tubulin crystallization and the influence of acidic pHs on cytoskeletal microtubules. Lowering the extracellular pH (pHe) rapidly reduced the intracellular pH (pHi) in CHO cells. Lowering the pHi to near the neutral range significantly accelerated the growth of VLB‐induced paracrystals, compared to that of paracrystals formed at a physiological pHe. However, further cytoplasmic acidification caused by the addition of sodium azide into the culture medium induced the disappearance of typical paracrystals and the appearance of a highly organized meshwork of tubulin appearing as short, thick filaments at the light microscopic level. Treatments using different concentrations of VLB at different pHe's showed that low pHi's (6.7 and 6.3) suppressed paracrystal‐formation at lower concentrations of VLB (5×10−6 M and 10−5 M). At higher concentrations of VLB (5×10−5 M and 10−4 M), only short filaments were formed at pHi 6. 3. Electron microscopy revealed that the filaments had a ladder‐like structure probably consisting of a stacked series of fused rings. This indicates that paracrystals may be modified by extremely low pH. These results show that paracrystals are unstable in living cells and that their formation is regulated by environmental pH.
The unique fibrillar arrangement of the bullfrog pressure‐bearing tendon as an indicative of great functional deformability
Authors: de Carvalho Hernandes Faustino , Vidal Benedicto de Campos
Published: August 2004

Summary— The fiber distribution and ultrastructure in the plantaris longus pressure‐bearing tendon of the bullfrog were investigated. The tension region of the tendon showed a predominant parallel distribution of collagen fibers, but three main zones with different crimp parameters were identified with the use of the polarizing microscope. The compression region showed collagen fibers with aspects of disaggregation and were composed of disperse and undulating fibrils. These collagen fibers establish a three‐dimensional network but showed a preferential distribution in planes disposed perpendicularly to the tendon's main axis. It is assumed that the convoluted and disaggregated collagen fibers must be distended before exerting any reinforcement on the tissue and that this only occurs after a great deformation of the tendon. Groups of 5–6 fibrils not associated in fibers are also dispersed in the compression region. The tissue is assumed to have a highly viscous fluid nature allowing for the deformation needed for collagen fibrils to reinforce the tendon structure. The convoluted and crimped structure of collagen fibers would be especially useful when the tendon is submitted to the sudden and strong mechanical loading expected to occur during jumping and to provide the tendon with the capacity of great functional deformability necessary for the high amplitude of feet movements attained on jumping and swimming.
The peroxisomes of the hepatopancreas in marine gastropods
Authors: Lobo‐da‐Cunha Alexandre , Batista Carla , Oliveira Elsa
Published: August 2004

Summary— An ultrastructural study of the peroxisomes was performed in the hepatopancreas of six species of marine gastropods. Peroxisome morphology was described in the basophilic cells and digestive cells of each species. The identification of this organelle was supported by the cytochemical detection of catalase. Large peroxisomes, frequently with a diameter between 1.0 and 1.5 μm, possessing a prominent crystalline nucleoid with hexagonal section were observed in Gibbula umbilicalis and Monodonta lineata basophilic cells. In the digestive cells of the same two species, the peroxisomes usually do not exceed 0.5 μm in diameter and in some of them a small nucleoid was found. A diamond shaped nucleoid was observed in the digestive cell peroxisomes of Patella vulgata and Ocenebra erinacea. In the hepatopancreas of Siphonaria algesirae the peroxisomes also presented a diamond shaped nucleoid. On the other hand, nucleoids were not detected in the basophilic cell peroxisomes of P vulgata, O erinacea and Nucela lapillus. In the peroxisomes of N lapillus digestive cells, typical nucleoids were also not found, but in some of them a dense region attached to the peroxisomal membrane was observed. In general, digestive cell peroxisomes were associated with mitochondria and lipid droplets, while basophilic cell peroxisomes were close to endoplasmic reticulum cisternae, mitochondria, lipofuscin granules or secretion granules.
Transferrin receptor 1 mRNA is downregulated in placenta of hepcidin transgenic embryos
Authors: Martin Marie Elise , Nicolas Gaël , Hetet Gilles , Vaulont Sophie , Grandchamp Bernard , Beaumont Carole
Published: August 2004

We have previously shown that hepcidin transgenic embryos are severely anemic and die around birth. Here, we report that embryonic hepcidin transgene expression decreases transferrin receptor 1 (TfR1) mRNA level in placenta, as shown by cDNA microarray analysis and quantitative RT‐PCR, by a mechanism which is independent of placenta iron content and iron responsive element/iron regulatory protein (IRE/IRP) activity. On the contrary, iron injections into pregnant mothers result in increased placenta iron and ferritin content, and reduced IRE binding activity of IRP1 leading to decreased TfR1 mRNA level. Taken together, these results suggest that hepcidin action on placenta is mostly through transcriptional downregulation of the iron uptake machinery.
Binding of von Willebrand factor to the small proteoglycan decorin
Authors: Guidetti Gianni F. , Bartolini Barbara , Bernardi Bruno , Tira Maria E. , Berndt Michael C. , Balduini Cesare , Torti Mauro
Published: August 2004

The small proteoglycan decorin plays an important role in the organisation of the extracellular matrix by binding to several components, including collagen and fibronectin. In this work, we report the dose‐dependent and saturable interaction of decorin with the adhesive glycoprotein, von Willebrand factor (VWF). This interaction was mediated by the glycosaminoglycan side chain of decorin and was critically regulated by the degree of sulfation, but not by the amount of iduronic acid. Both chondroitin sulfate and dermatan sulfate, in addition to heparin, were found to bind VWF equally well. Although soluble decorin prevented VWF binding to heparin, purified VWF‐A1 domain failed to interact with the proteoglycan. These results identify VWF as a new partner for the small proteoglycan, decorin, in the structural organisation of the extracellular matrix.
A continuum of gravity waves in the Arecibo thermosphere?
Authors: Djuth F. T. , Sulzer M. P. , Gonzáles S. A. , Mathews J. D. , Elder J. H. , Walterscheid R. L.
Published: August 2004

Previous incoherent radar studies at Arecibo Observatory, Puerto Rico have demonstrated that ∼1–3% electron density “imprints” of internal gravity waves are routinely present in the Arecibo thermosphere (∼118–500 km). A special radar technique involving photoelectron‐enhanced plasma waves (PEPWs) was used for these observations. Recently, it was discovered that the trails of the gravity waves can be detected in standard incoherent scatter power profiles when properly filtered. This result was validated using simultaneous PEPW observations. This new development opens up the possibility of monitoring thermospheric gravity waves day and night. Preliminary studies indicate that gravity waves are continually propagating through the Arecibo thermosphere, and that “sets” of waves separated by approximately 20–60 min are typically present. With the aid of additional radar tests, it may be possible to unlock Arecibo power profiles recorded over the past 30 years for gravity wave studies. The precise origin of the waves is currently unknown.
Formation of the hematite‐bearing unit in Meridiani Planum: Evidence for deposition in standing water
Authors: Christensen Philip R. , Ruff Steven W.
Published: August 2004

The most plausible models for the origin and evolution of a unique geologic unit in Meridiani Planum, Mars, are low‐temperature precipitation of Fe oxides/oxyhydroxides from standing water, precipitation from circulating fluids of hydrothermal origin, or the thermal oxidation of magnetite‐rich ash. Analysis of Odyssey Thermal Emission Imaging System (THEMIS) infrared and visible images, together with MGS TES, MOLA, and MOC data, has provided additional insight into the Meridiani region. The hematite at Meridiani was most likely derived from a Fe oxyhydroxide precursor such as goethite, is mixed with basalt as the major component, occurs as a thin layer meters to <200 m thick, and is thermophysically distinct from units immediately above and below. Remnants of a hematite‐poor unit lie directly above the hematite layer, indicating that hematite formation was sharply confined vertically. The hematite unit appears to embay preexisting channels and occurs only as outliers within closed crater basins, suggesting that it was deposited in a gravity‐driven fluid, rather than as a dispersed air fall. The hematite unit lies within a topographic trough over ∼3/4 of its circumference, with the remaining perimeter <150 m lower in elevation. Oxidation of ash during emplacement is unlikely given a goethite precursor and basalt as the major component. Hydrothermal alteration does not account for the confined vertical extent of the hematite layer over large distances and across disconnected outliers. The preferred model is the deposition of hematite or precursor Fe oxyhydroxides in water‐filled basins, followed by dehydroxylation to hematite in low‐temperature diagenesis. This model accounts for (1) the uniform deposition of a thin hematite‐bearing unit over an area ∼150,000 km2 in size; (2) the transition from hematite‐rich to hematite‐poor units over less than ∼10 m vertical distance; (3) the distinct differences from the underlying layers; (4) goethite as the precursor to hematite; (5) the embayment relationships; (6) the occurrence of remnants of the hematite‐bearing unit in isolated craters surrounding the main deposit; (7) the lack of other hydrothermal minerals; and (8) the presence of coarse‐grained, low‐albedo basalt, rather than ash, as the major component. The occurrence of unweathered olivine, pyroxene, and feldspar throughout the equatorial region provides strong evidence that extensive aqueous weathering has not occurred on Mars. Thus the presence of a small number of bodies of standing water appears to represent brief, localized phenomena set against the backdrop of a cold, frozen planet.
Restoring and flux adjustment in simulating variability of an idealized ocean
Authors: Simmons Harper L. , Polyakov Igor V.
Published: August 2004

Multi‐century model runs are used to investigate the impact of restoring and flux adjustment on the variability of an idealized Atlantic Ocean forced by net atmospheric heat flux possessing decadal and multi‐decadal variability. Restoring suppresses simulated modes of variability, causes phase shifts, and modifies nonlinear relations in the model. Flux adjustment has little effect on the water temperature variability, however it suppresses low‐frequency variability of the meridional overturning circulation and causes a phase shift of multi‐decadal mode of the meridional heat transport. An important effect of flux adjustment is that it may misrepresent physical mechanisms substituting, for example, dynamically‐driven meridional heat transport by equivalent amount of heat supplied locally, though surface heat fluxes. We conclude that restoring provides improper framework for simulation of climate variability. Flux adjustment is less damaging, however, it modulates internal modes of variability in ways not fully understood.
Regional climate effects of Arctic Haze
Authors: Rinke A. , Dethloff K. , Fortmann M.
Published: August 2004

The direct climate effect of aerosols has been studied within a regional atmospheric model of the Arctic. The mean springtime effect on the near surface temperature has been estimated and showed to be within ±1 K. However, the aerosol effect varies strongly regionally depending on the surface albedo, atmospheric humidity, and cloud condition of the region. The interannual variability of the aerosol effect is very pronounced (for the near surface temperature in the order of 2 K) and is connected with the strong varying year‐specific atmospheric conditions. Due to the high horizontal resolution of the model, it was possible to assess the influence both on the large‐scale as well as on the meso‐scale atmospheric circulation. Through the aerosol‐radiation‐circulation feedback, the scattering and absorption of radiation by aerosol cause pressure pattern changes which have the potential to modify Arctic teleconnection patterns like the Barents Sea Oscillation.
Radicals and reservoirs in the GMI chemistry and transport model: Comparison to measurements
Authors: Douglass Anne R. , Stolarski Richard S. , Strahan Susan E. , Connell Peter S.
Published: August 2004

We have used a three‐dimensional chemistry and transport model (CTM), developed under the Global Modeling Initiative (GMI), to carry out two simulations of the composition of the stratosphere under changing halogen loading for 1995 through 2030. The two simulations differ only in that one uses meteorological fields from a general circulation model while the other uses meteorological fields from a data assimilation system. A single year's winds and temperatures are repeated for each 36‐year simulation. We compare results from these two simulations with an extensive collection of data from satellite and ground‐based measurements for 1993–2000. Comparisons of simulated fields with observations of radical and reservoir species for some of the major ozone‐destroying compounds are of similar quality for both simulations. Differences in the upper stratosphere, caused by transport of total reactive nitrogen and methane, impact the balance among the ozone loss processes and the sensitivity of the two simulations to the change in composition.
Time of flight and direction of arrival of HF radio signals received over a path along the midlatitude trough: Theoretical considerations
Authors: Siddle D. R. , Zaalov N. Y. , Stocker A. J. , Warrington E. M.
Published: August 2004

Observations from an HF radio experiment on a subauroral path between Sweden and the UK near sunspot maximum in 2001 are compared with the position of the midlatitude trough according to a statistical model. Periods of off‐great circle propagation, occurring predominantly in winter and equinoctial nights at frequencies 7–11 MHz, show characteristics consistent with scattering from field‐aligned irregularities in the northern trough wall and/or auroral oval. Very little reflection and/or scattering was apparent from directions to the south of the great circle path. These results are in marked contrast with those from a similar experiment conducted near sunspot minimum in 1994 in Canada, during which both southerly and northerly deviations were observed in the 5–15 MHz range. The contrasting results were simulated using ray tracing through a model ionosphere incorporating a model of the trough and, optionally, precipitation. The observed off‐great circle propagation features on the European path could only be reproduced when precipitation within the northern trough wall/auroral zone was included, whereas features of the northerly and southerly deviations observed in the Canadian experiment could be simulated by the presence of the trough walls and without the need for precipitation.
Driven phase space holes and synchronized Bernstein, Greene, and Kruskal modes
Authors: Friedland L. , Peinetti F. , Bertsche W. , Fajans J. , Wurtele J.
Published: August 2004

The excitation of synchronized Bernstein, Greene, and Kruskal (BGK) modes in a pure electron plasma confined in Malmberg–Penning trap is studied. The modes are excited by controlling the frequency of an oscillating external potential. Initially, the drive resonates with, and phase-locks to, a group of axially bouncing electrons in the trap. These initially phase-locked electrons remain phase-locked (in “autoresonance”) during a subsequent downward chirp of the external potential’s oscillation frequency. Only a few new particles are added to the resonant group as the frequency, and, hence, the resonance, moves to lower velocities in phase space. Consequently, the downward chirp creates a charge density perturbation (a hole) in the electron phase space distribution. The hole oscillates in space, and its associated induced electric field constitutes a BGK mode synchronized with the drive. The size of the hole in phase space, and thus the amplitude of the mode, are largely controlled by only two external parameters: the driving frequency and amplitude. A simplified kinetic theory of this excitation process is developed. The dependence of the excited BGK mode amplitude on the driving frequency chirp rate and other plasma parameters is discussed and theoretical predictions are compared with recent experiments and computer simulations.
The AMBEGUJAS Phenomenon and Colour Constancy
Authors: Bergström Sten Sture
Published: August 2004

The AMBEGUJAS phenomenon is a reversible flat figure that is spontaneously shifting between two apparent 3-D shapes—‘tile’ and ‘roof. 2-D perceptions have very rarely been reported. Tied to the shifts between the tile and roof shapes are remarkable changes of perceived colour. In our example, the tile appears to have orange (top half) and blue–green (bottom half) surface colours in white light. The roof appears grey but in an orange illumination and with a blue–green shadow. This phenomenon appears whether a grey display is presented in two coloured illuminations, or a chromatic display with two surface colours (orange and blue–green) is presented in white light.

In the coloured illuminations the tile is an example of non-constancy, since its colours are non-veridical colour perceptions. The centre stripe of the display appears to have the same orange and blue–green colours as the lateral stripes but in a shadow. This seems like a colour constancy in a non-constancy situation. An alternative to the classical definition of colour constancy is discussed.
Visual Neuroscience before the Neuron
Authors: Wade Nicholas J
Published: August 2004

Visual neuroscience is considered to be a contemporary concern, based in large part on relating characteristics of neural functioning to visual experience. It presupposes a detailed knowledge of neural activity for which the neuron doctrine is a fundamental tenet. However, long before either the neuron doctrine had been advanced or the nerve cell had been described, attempts were made to estimate the dimensions of nerve fibres from measures of visual resolution. In the seventeenth century, the microscopes of Hooke and van Leeuwenhoek were unable to resolve structures as small as nerves adequately. However, it was not Hooke's microscope that led to an estimate of the dimensions of nerve fibres but his experiments on the limits of visual resolution. Hooke determined that a separation of one minute of arc was the minimum that could normally be seen. Descartes had earlier speculated that the retina consisted of the terminations of fibres of the optic nerve, and that their size defined the limits of what could be seen. Estimates of the diameters of nerve fibres were made on the basis of human visual acuity by Porterfield in 1738; he calculated the diameters of nerve fibres in the retina as one 7200th part of an inch (0.0035 mm), based on the resolution of one minute of arc as the minimum visible. In the same year, Jurin questioned the reliability of such estimates because of variations in visual resolution with different stimuli. The measurement of visual acuity was refined by Mayer in 1755, with dots, gratings, and grids used as stimuli. In the 1830s, Treviranus fused the microscopic and acuity approaches to determine the dimensions of nerve fibres. His indirect estimates of the dimensions of retinal fibres were close to those derived from microscopic observation. However, the suggestion that the retina consisted of terminations of nerve fibres influenced his detailed illustrations of its microscopic structure. Contrary to the situation that obtained after the microscopic structure of the retina had been established, a function of vision (acuity) was used to determine the dimensions of the structures (retinal elements) that were thought to mediate it.
Visual Synaesthesia in the Blind
Authors: Steven Megan S , Blakemore Colin
Published: August 2004

Synaesthesia is characterised by idiosyncratic ectopic sensations which commonly take the form of coloured visual impressions evoked by touch or hearing. We studied six late-blind individuals who have retained synaesthetic colour perception. Four of them had been without any form of genuine colour vision for more than 10 years. All perceived colours when they heard or thought about letters, numbers, and time-related words (days of the week and months of the year). One experienced synaesthetic colours for all words. Another saw Braille characters as coloured dots when he touched them. The aberrant experiences were compelling and reliable: detailed verbal descriptions of the colours were remarkably consistent in tests more than 2 months apart. The percepts predominantly took the form of coloured patches, localised in body-centred space for five of the subjects and in head-centred space for the sixth. This implies that the neural activity underlying synaesthesia occurs after the establishment of a visual representation independent of eye (or head) position. The synaesthetic colour depended only on phonetic cues in one case, but on semantic context in others. Although synaesthesia might be due to idiosyncratic, aberrant corticocortical connectivity established during early development, it can persist for very long periods with little or no natural experience in the referred modality and therefore does not depend solely on continuing associative learning.