bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal structure of a murine α‐class glutathione S‐transferase involved in cellular defense against oxidative stress
Authors: Krengel Ute , Schröter Klaus-Hasso , Hoier Helga , Arkema Anita , Kalk Kor H , Zimniak Piotr , Dijkstra Bauke W
Published: July 2002

Glutathione S‐transferases (GSTs) are ubiquitous multifunctional enzymes which play a key role in cellular detoxification. The enzymes protect the cells against toxicants by conjugating them to glutathione. Recently, a novel subgroup of α‐class GSTs has been identified with altered substrate specificity which is particularly important for cellular defense against oxidative stress. Here, we report the crystal structure of murine GSTA4‐4, which is the first structure of a prototypical member of this subgroup. The structure was solved by molecular replacement and refined to 2.9 Å resolution. It resembles the structure of other members of the GST superfamily, but reveals a distinct substrate binding site.
A 1H NMR comparative study of human adult and fetal hemoglobins
Authors: Yamamoto Yasuhiko , Nagaoka Tomomi
Published: July 2002

The affinities of the individual subunits in human adult and fetal hemoglobins to azide ion have been determined from the combined analysis of NMR and optical titration data. Structural and functional non‐equivalence of the constituent subunits, i.e. α and β subunits in human adult hemoglobin and α and γ subunits in human fetal hemoglobin, has been confirmed. The function of the α subunits, which are common to both hemoglobins, is essentially identical in these hemoglobins and, in spite of the substitutions of 39 amino acid residues between β and γ subunits, they exhibit similar azide ion affinities. The present study also demonstrates that the NMR spectral comparison between the two proteins provides signal assignments to the individual subunits in intact tetramer.
Papain proteolysis releases a soluble NADPH dependent diaphorase activity from bovine neutrophil membranes
Authors: Li Jianrong , Kon Leanne M , Guillory Richard John
Published: July 2002

An NADPH dependent cytochrome c reductase has been purified from resting bovine neutrophil membranes. A high degree of purification, approaching homogeneity, is indicated by the presence of a single 75 kDa protein band on silver stained SDS‐PAGE (10%). The purified protein catalyzes as well an NADPH dependent reduction of iodonitrotetrazolium violet (INT). Limited papain digestion of the purified preparation produces a 65 kDa product which retains both enzymatic activities. In a similar fashion papain digestion of the plasma membrane bound protein generates a fully active soluble NADPH dependent INT and cytochrome c reductase preparation (65 kDa). Proteolytic cleavage would appear to occur at a protein‐membrane anchor remote from the proteins catalytic site. The cytochrome c reductase acts independently of the O−
2 generating cytochrome b
558, a leukocyte plasma membrane protein which also catalyzes an NADPH dependent INT reduction.
Endogenous tumour necrosis factor‐alpha sensitise melanoma cells to glucosaminylmuramyl dipeptide
Authors: Valyakina Tatyana I , Komaleva Ravilya L , Petrova Elena E , Malakhov Alexander A , Shamborant Ol'ga G , Andronova Tatyana M , Nesmeyanov Vladimir A
Published: July 2002

Flow cytometry was used to demonstrate that cultured human melanoma BRO cells expressed membrane‐bound tumour necrosis factor‐alpha (TNF‐α) and were able to release TNF‐α upon treatment with glucosaminylmuramyl dipeptide (GMDP). The released TNF‐α was shown to prime melanoma cells, previously unable to respond to GMDP by increasing expression of melanoma‐associated antigens, making them sensitive to GMDP treatment.
Chemiluminescence determination of hydroperoxides following radiolysis and photolysis of free amino acids
Authors: Robinson Stephen , Bevan Ruth , Lunec Joseph , Griffiths Helen
Published: July 2002

Hydroperoxides were determined in selected amino acids using three free radical generating systems by a sensitive (50 pmol limit of detection) and specific high performance liquid chromatography (HPLC)/chemiluminescence method. UVB and gamma radiation produced significant hydroperoxide formation, particularly in the aromatic amino acids tyrosine and tryptophan. Hydroperoxide yield was found to be dependent on both amino acid and irradiation source. Generation of hydrogen peroxide as a by‐product of irradiation caused interference with chemiluminescence detection demonstrating the need for catalase addition. Hydroperoxides were not detectable following metal‐catalysed H2O2 breakdown. We suggest that metal ions could interfere with the detection of hydroperoxides by causing preferential decomposition.
Inferences about the catalytic domain of P‐type ATPases from the tertiary structures of enzymes that catalyze the same elementary reaction
Authors: Smirnova Irina N , Kasho Vladimir N , Faller Larry D
Published: July 2002

The machinery to catalyze elementary reactions is conserved, and the number of solved enzyme structures is increasing exponentially. Therefore, structures of enzymes that catalyze phosphate transfer are reviewed, and a supersecondary structure connecting the Walker A sequence to another sequence containing functional amino acids is proposed as an additional signature for the active site. The new signature is used to infer the identity of the P‐loop in P‐type biological pumps and may be useful in predicting targets for site‐directed mutagenesis in other enzymes of unknown structure like the AAA family and ABC transporters.
Properties of the Ca2+ influx reveal the duality of events underlying the activation by vanadate and fluoride of the Gárdos effect in human red blood cells
Authors: Varečka Ĺudovı́t , Peterajová Elena , Pı́šová Erika
Published: July 2002

The properties of the 45Ca2+ influx by human red blood cells (RBC) induced by NaVO3 or NaF were compared. The NaVO3‐induced 45Ca2+ influx was slower and less extensive than that induced by NaF. Both processes were saturable with Ca2+. Substitution of Na+ by K+ inhibited the 45Ca2+ influx induced by NaVO3 but stimulated that by NaF. The NaVO3‐induced Ca2+ influx was sensitive to nifedipine (IC50=50 mol/l), Cu2+ (IC50=9 mol/l), DTNB (5,5′‐dithiobis‐(dinitrobenzoic acid)) (IC50=12 mol/l) (maximal inhibition 16%, 18%, and 28%, respectively, if NaF was used as inducer). On the other hand, tetrodotoxin (TTX) and cyclosporin A inhibited only the NaF‐induced 45Ca2+ influx (IC50=21 mol/l and 28 mol/l, respectively). Pig RBC, known not to display the NaVO3‐induced Ca2+ influx, exhibited Ca2+ influx induced by NaF. The results show that NaVO3 activates the Ca2+ influx via a pathway homologous to the L‐type Ca2+ channel while the NaF‐induced Ca2+ influx is mediated via the TTX‐sensitive Na+ channel in the presence of NaF with possible participation of calcineurin or cyclophilin. Thus, the Gárdos effect induced by NaVO3 and NaF represents two phenomena activated by different mechanisms present in the cryptic state in the RBC membrane.
Characterization of mutations located in exon 18 of the CFTR gene
Authors: Vankeerberghen Anne , Wei Lin , Teng Hui , Jaspers Martine , Cassiman Jean-Jacques , Nilius Bernd , Cuppens Harry
Published: July 2002

In order to get a better insight into the function of amino acid residues located in the second transmembrane domain of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, all exon 18 mutations found in cystic fibrosis (CF) patients were characterized at the protein and at the electrophysiological level. Of the different mutations present in transmembrane helix 12 (M1137V, M1137R, I1139V and ΔM1140), and the intracytoplasmic loop connecting TM12 and NBD2 (D1152H and D1154G), only M1137R interfered with the proper maturation of the protein. Permeability studies performed after injection of the different wild‐type and mutant cRNAs in Xenopus laevis oocytes indicated that the mutations did not alter the permeability sequence of the CFTR channels. The whole cell cAMP activated chloride currents, however, were significantly reduced for M1137V, I1139V, D1152H and D1154G and close to zero for ΔM1140, indicating that these mutations interfere with the proper gating of the chloride channels.
Modifications outside the proteinase binding loop in Cucurbita maxima trypsin inhibitor III (CMTI‐III) analogues change the binding energy with bovine β‐trypsin
Authors: Jaśkiewicz Anna , Lis Katarzyna , Różycki Jan , Kupryszewski Gotfryd , Rolka Krzysztof , Ragnarsson Ulf , Zbyryt Tomasz , Wilusz Tadeusz
Published: July 2002

Five 26‐peptide analogues of the trypsin inhibitor [Pro18]CMTI‐III containing Leu or Tyr in position 7 and Val or Tyr in position 27: 1 (Leu7, Tyr27), 2 (Tyr7, Val27), 3 (Tyr7, Tyr27), 4 (Leu7, Val27) and 5 (Leu7, Ala18, Tyr27) were synthesized by the solid‐phase method. Analogues 1–4 displayed K
a with bovine β‐trypsin of the same order of magnitude as the wild CMTI‐III inhibitor, whereas for analogue 5, this value was lower by about 3 orders of magnitude. This indicated that for the analogues with Pro (but not with Ala) in position 18, the side‐chain interactions between positions 7 and 27 did not play a critical role for the stabilization of the active structure. In addition, these results also suggest that Tyr7 is involved in an additional aromatic interaction with position 41 of the enzyme.
CTAB‐mediated enrichment for active forms of novel dimeric maxizymes
Authors: Nakayama Aya , Kuwabara Tomoko , Warashina Masaki , Taira Kazunari
Published: July 2002

We demonstrated previously that shortened forms of (stem II‐deleted) hammerhead ribozymes with low intrinsic activity form very active dimers with a common stem II (very active short ribozymes capable of forming dimers were designated maxizymes). As a result of such a dimeric structure, heterodimeric maxizymes are potentially capable of cleaving a substrate at two different sites simultaneously. In this case, active heterodimers are in equilibrium with inactive homodimers. Longer forms of common stem II can lead to enrichment of the active heterodimers in vitro. In this study, we investigated whether the cationic detergent CTAB, which is known to enhance strand displacement of nucleic acids, might inhibit the dimerization of maxizymes. Significantly, under all conditions examined, CTAB instead enhanced the activity of a variety of maxizymes, with the extent of enhancement depending on the conditions. The activity of our least stable, least active maxizyme was enhanced 100‐fold by CTAB. The strand displacement activity of CTAB thus appears to enhance the conversion of alternative conformations of inactive maxizymes, with intra‐ and inter‐molecular hydrogen bonds, to active forms. Thus, our smallest maxizyme can also be considered a potential candidate for a gene‐inactivating agent in vivo, in view of the fact that various facilitators of strand displacement reactions are known to exist in vivo (indeed, a separate experiment in cell culture supported the conclusion that our smallest maxizyme is a good gene‐inactivating agent). Although activities of ribozymes in vitro do not necessarily reflect their activities in vivo, our findings suggest that the activity of ribozymes in vivo can be better estimated by running ribozyme kinetics in the presence of CTAB in vitro.
Inhibition of poly(ADP‐ribose)polymerase binding to DNA by thymidine dimer
Authors: Yang Wan Seok , Kim Jin Woo , Lee Joon-Hwa , Choi Byong-Seok , Joe Cheol O.
Published: July 2002

The ability of poly(ADP‐ribose)polymerase to bind damaged DNA was assessed by electrophoretic mobility shift assay. DNA binding domain of poly(ADP‐ribose)polymerase (PARPDBD) binds to synthetic deoxyribonucleotide duplex 10‐mer. However, the synthetic deoxyribonucleotide duplex containing cys‐syn thymidine dimer which produces the unwinding of DNA helix structure lost its affinity to PARPDBD. It was shown that the binding of PARPDBD to the synthetic deoxyribonucleotide duplex was not affected by O6‐Me‐dG which causes only minor distortion of DNA helix structure. This study suggests that the stabilized DNA helix structure is important for poly(ADP‐ribose)polymerase binding to DNA breaks, which are known to stimulate catalytic activity of poly(ADP‐ribose)polymerase.
Human growth hormone site 2 lactogenic activity requires a distant tyrosine164
Authors: Duda Karen M. , Brooks Charles L.
Published: July 2002

Comparison of crystallographic structures of human growth hormone, either bound to the prolactin receptor or free of receptors, reveals that human growth hormone binding to the prolactin receptor at site 1 is associated with a structural change in human growth hormone that influences the organization of residues which constitute site 2. We have identified Tyr164 as a residue that is critical for the propagation of this structural rearrangement. Tyr164 is a structural epitope for site 1 and is distal to site 2. Mutation of Tyr164 to glutamic acid (Y164E) does not affect the somatotrophic activity, absorption or fluorescence spectra or binding to the human prolactin receptor when compared to wild‐type human growth hormone, indicating the subtle effects of the mutation. Lactogenic assays using extended concentrations of Y164E human growth hormone produce dose‐response curves that are characterized by a right‐shifted agonist phase and an unchanged antagonist phase when compared to wild‐type human growth hormone. These results indicate that Tyr164 is required for the lactogenic activity of human growth hormone and that mutation to glutamic acid disrupts the lactogenic function of site 2.
Gene for a protein capable of enhancing lateral root formation
Authors: Mikami Yoji , Horiike Goh , Kuroyanagi Masanori , Noguchi Hiroshi , Shimizu Masanori , Niwa Yasuo , Kobayashi Hirokazu
Published: July 2002

Analysis of genes preferentially expressed in hairy roots caused by infection with Agrobacterium rhizogenes has provided insights into the regulation of lateral root formation. A hairy root preferential cDNA, HR7, has been cloned from hairy roots of Hyoscyamus niger. HR7 encodes a novel protein partially homologous to a metallocarboxypeptidase inhibitor and is expressed exclusively in the primordium and base of lateral roots in hairy roots. Overexpression of HR7 in transgenic roots of H. niger dramatically enhances the frequency of lateral root formation. The results of this study indicate that expression of HR7 plays a critical role in initiating lateral root formation.
In vitro production of cytokines is influenced by sulfatide and its precursor galactosylceramide
Authors: Bovin Lone Frier , Fredman Pam , Månsson Jan-Eric , Buschard Karsten , Bendtzen Klaus
Published: July 2002

Effects of sulfatide and its precursor galactosylceramide (gal‐cer) on the kinetics of production of cytokines were studied. In human mononuclear leucocytes, gal‐cer but not sulfatide induced significantly increased amounts of interleukin (IL)‐1β, IL‐6 and tumor necrosis factor (TNF) mRNA. In phytohemagglutinin‐stimulated cultures, gal‐cer increased the levels of IL‐1β and IL‐6 mRNA and secreted IL‐1β and IL‐6, while sulfatide decreased the amounts of IL‐6 mRNA and secreted IL‐6. Gal‐cer also increased TNF secretion. In lipopolysaccharide‐stimulated cells, sulfatide but not gal‐cer decreased the secretion of IL‐1β and IL‐10, a potent suppressor of production of many cytokines. Thus, sulfatide and gal‐cer affect cytokine production differently, most likely at the level of gene expression. This may have implications in diseases where inflammatory cytokines play a pathogenic role.
Transactivation of the WT1 antisense promoter is unique to the WT1[+/−] isoform
Authors: Moorwood Kim , Salpekar Ashreena , Ivins Sarah M. , Hall Julie , Powlesland Rachel M. , Brown Keith W. , Malik Karim
Published: July 2002

The Wilms’ tumour suppressor gene, WT1, encodes a zinc finger transcription factor that has been shown to repress a variety of cellular promoters via binding to cognate DNA elements. Our earlier work identified an antisense WT1 promoter that contains WT1 consensus sites, but is transcriptionally activated by WT1. In this study, we demonstrate that, unlike previous reports of transcriptional regulation by WT1, transactivation of the antisense promoter is unique to a single isoform of WT1. Of the four alternatively spliced isoforms in which exon 5 (at splice I) or amino acid residues KTS (at splice II) are inserted or omitted, only the WT1 isoform containing splice I and omitting splice II (WT1[+/−]) displays transactivation. We demonstrate that transregulation variations observed with WT1 isoforms are not solely attributable to differential DNA binding by [+KTS] or [−KTS] isoforms. Thus, the transactivation of the antisense promoter displays an absolute requirement for exon 5, suggesting that interaction between WT1 and other cellular factors is necessary for this regulatory function.
Cloning, tissue distribution, subcellular localization and overexpression of murine histidine‐rich Ca2+ binding protein
Authors: Ridgeway Alan G. , Petropoulos Helen , Siu Aaron , Ball Judy K. , Skerjanc Ilona S.
Published: July 2002

The histidine‐rich Ca2+ binding protein (HRC) resides in the sarcoplasmic reticulum of muscle and binds Ca2+. Since Ca2+ concentrations can regulate gene expression via calcineurin, the mouse homologue of HRC (mHRC) was isolated and characterized. mHRC was detected in muscle progenitor cells, in primary clonal thymic tumors and a tumor cell line, suggesting a broader role for mHRC than in Ca2+ storage during muscle contraction. mHRC was present in the perinuclear region of myoblasts. To examine if it can regulate gene expression, mHRC was overexpressed in cells differentiating into cardiac and skeletal muscle. mHRC had no effect on cardiogenesis or myogenesis. Therefore, if mHRC plays a role in the regulation of gene expression during cellular differentiation, it does not appear to be either rate‐limiting or inhibitory.
Positive regulation of Bacillus subtilis sigD by C‐terminal truncated LacR at translational level
Authors: Ogura Mitsuo , Hirao Shigeharu , Ohshiro Yasuhiro , Tanaka Teruo
Published: July 2002

DegR is a positive regulator for degradative enzyme synthesis in Bacillus subtilis. The degR gene is transcribed by RNA polymerase containing σD, and the level of its expression is low in a mecA‐deficient mutant. In a search for suppressors of the mecA effect through mini‐Tn10 transposon mutagenesis, a lacR mutation designated lacR288 was discovered. The B. subtilis lacR gene encodes the repressor for lacA which specifies β‐galactosidase, and therefore, inactivation of the lacR gene results in overproduction of the enzyme. In the lacR288 mutant, however, the expression of lacA was at a negligible level, indicating that the repressor activity was not destroyed by the mutation. The putative gene product of the lacR288‐containing gene is a 288‐amino acid protein lacking the C‐terminal 42 amino acids of intact LacR and carries no extra amino acids derived from the transposon sequence. The suppression by lacR288 of the decreased degR expression in the mecA background was found to be caused by an increase in the σD level as shown by Western blot analysis. Furthermore, the increase was due to post‐transcriptional regulation of sigD, the gene encoding σD, as revealed by using both transcriptional and translational sigD‐lacZ fusions. The lacR288 mutation had no effect on the stability of the σD protein. Based on these results we conclude that the lacR288 mutation stimulates sigD expression at the translational level.
NEM modification prevents high‐affinity ATP binding to the first nucleotide binding fold of the sulphonylurea receptor, SUR1
Authors: Matsuo Michinori , Tucker Stephen J. , Ashcroft Frances M. , Amachi Teruo , Ueda Kazumitsu
Published: July 2002

Pancreatic β‐cell ATP‐sensitive potassium channels, composed of SUR1 and Kir6.2 subunits, serve as a sensor for intracellular nucleotides and regulate glucose‐induced insulin secretion. To learn more about the interaction of SUR1 with nucleotides, we examined the effect of N‐ethylmaleimide (NEM) modification. Photoaffinity labeling of SUR1 with 5 μM 8‐azido‐[α‐32P]ATP or 8‐azido‐[γ‐32P]ATP was inhibited by NEM with K
i of 1.8 μM and 2.4 μM, and Hill coefficients of 0.94 and 1.1, respectively. However, when the cysteine residue in the Walker A motif of the first nucleotide binding fold (NBF1) of SUR1 was replaced with serine (C717S), photoaffinity labeling was not inhibited by 100 μM NEM. These results suggest that NBF1 of SUR1 has a NEM‐sensitive structure similar to that of NBF1 of MDR1, a multidrug transporter, and confirm NBF1 as the high‐affinity ATP binding site on SUR1.
Expression of canine interferon‐β by a recombinant vaccinia virus
Authors: Nishikawa Yoshifumi , Iwata Akira , Xuan Xuenan , Nagasawa Hideyuki , Fujisaki Kozo , Otsuka Haruki , Mikami Takeshi
Published: July 2002

A recombinant vaccinia virus expressing canine interferon (IFN)‐β was constructed (vv/cIFN‐β). In rabbit kidney (RK13) and canine A72 cells infected with vv/cIFN‐β, the recombinant canine IFN‐β was detected in both cell extracts and supernatants, and the IFN activities of the culture supernatants were also detected. Inhibition of N‐linked glycosylation by tunicamycin treatment indicated that the recombinant canine IFN‐β was modified by N‐linked glycosylation in a different way between RK13 and A72 cells, and that N‐linked glycosylation is essential for its secretion. The growth of vv/cIFN‐β at a low multiplicity of infection was inhibited by antiviral activity of canine IFN‐β, indicating that this recombinant virus could be used as a suicide viral vector.
Functional association between the nef gene product and gag‐pol region of HIV‐1
Authors: Ono Takeshi , Iwatani Yasumasa , Nishimura Akiko , Ishimoto Akinori , Sakai Hiroyuki
Published: July 2002

Nef gene function is diverse among virus isolates of primate immunodeficiency viruses. We found differential effects of nef mutation on the virus replication between two HIV‐1 clones, NL432 and LAI. The nef mutation in NL432 affected the infectivity more severely compared with that in LAI, although the Nef functions of both clones were comparable. Analysis with a series of chimeric viruses between NL432 and LAI revealed that the gag‐pol region was responsible for the differential effect of nef mutation. The functional association between Nef and gag‐pol suggested that one of the potential targets of Nef was located within the gag‐pol region.
A community based study on the change of practice of female genital mutilation in a Sudanese village
Authors: Almroth L. , Almroth‐Berggren V. , Hassanein O.M. , El Hadi N. , Al‐Said S.S.E. , Hasan S.S.A. , Lithell U.‐B. , Bergström S.
Published: July 2002

Objective: To investigate the practice of female genital mutilation (FGM), among young and old parents. Methods: One hundred and twenty young parents and grandparents in a rural area in central Sudan were randomly selected for interviews carried out according to structured questionnaires with open answer possibilities. Results: All female respondents had undergone FGM. Of the young respondents, 44% had decided not to let their daughters undergo FGM. Young fathers were more involved in the decision process than previously known, especially when decisions were taken not to perform FGM. Tradition and social pressure were the main motives for performing FGM. Sexuality was an important aspect, mentioned both as motives for and against FGM. Religious belief and education level significantly affected to what extent FGM was practiced. Conclusion: This is the first community based study of FGM indicating a significant shift in practice between generations, young parents starting to question the value of FGM.
The soluble mammalian sperm factor protein that triggers Ca2+ oscillations in eggs: Evidence for expression of mRNA(s) coding for sperm factor protein(s) in spermatogenic cells
Authors: Parrington John , Lai F. Anthony , Swann Karl
Published: July 2002

At fertilisation in mammals the sperm initiates a series of Ca2+ oscillations that activate development. One theory of signalling at fertilisation suggests that the sperm contains a soluble protein factor that causes these Ca2+ oscillations by entering the egg after sperm‐egg membrane fusion. This theory is supported by the finding that, in some species, injection of sperm protein extracts into eggs triggers a pattern of Ca2+ oscillations similar to those seen at fertilisation. So far, all the direct evidence for a sperm factor has been based upon the injection of soluble proteins from mature sperm. Here, we demonstrate that injection of mRNA extracted from hamster spermatogenic cells also leads to generation of prolonged Ca2+ oscillations in mouse eggs. The ability of spermatogenic cell mRNA to induce Ca2+ oscillations is dependent upon translation into protein and also appears to be specific to spermatogenic cells since injection of mRNA isolated from somatic tissues into eggs was ineffective. These data support the hypothesis that sperm contain a soluble, cytosolic protein factor that induces Ca2+ oscillations in eggs at fertilisation. These data are discussed in the light of our recent findings that suggest that the sperm factor possesses a phospholipase C activity.
Oligodendrocyte development in the spinal cord and telencephalon: common themes and new perspectives
Authors: Woodruff Rachel H. , Tekki‐Kessaris Nicoletta , Stiles Charles D. , Rowitch David H. , Richardson William D.
Published: July 2002

There are clear parallels between oligodendrocyte development in the spinal cord and forebrain. However, there is new evidence that in both of these regions oligodendrocyte lineage development may be more complex than we earlier thought. This stems from the recent identification of three new transcription factor genes, Olig1, Olig2 and Sox10, that are expressed from the early stages of oligodendrocyte lineage development. In this article, we highlight the common themes underlying specification and early development of oligodendrocytes in the spinal cord and telencephalon. Then, we discuss recent studies of Sox10 and the Olig genes and their implications for oligodendrocyte specification. We conclude that although the mechanisms of oligodendrogenesis appear to be fundamentally similar at different rostro‐caudal levels of the neuraxis, there are still many unanswered questions about the details of oligodendrocyte specification.
Mitogen‐activated protein kinase signalling in oligodendrocytes: a comparison of primary cultures and CG‐4
Authors: Stariha Rochelle L. , Kim Seung U.
Published: July 2002

Oligodendrocytes play a significant role in the central nervous system, as these cells are responsible for myelinating axons and allowing for the efficient conduction of nerve impulses. Therefore, any understanding we can gain about the functional biology of oligodendrocytes will give us important insights into demyelinating diseases such as multiple sclerosis, where oligodendrocytes and myelin are damaged or destroyed. Currently, much attention has focussed on the role of a family of mitogen‐activated protein kinases in OL. This kinase family includes the extracellular signal‐regulated protein kinases (ERKs), the stress‐activated c‐Jun N‐terminal kinase (JNK), and the 38 kDa high osmolarity glycerol response kinase (p38). The actions of mitogen‐activated protein kinases in oligodendrocytes appear to range from proliferation and cell survival to differentiation and cell death. In the past, studies on oligodendrocytes have been hampered by the difficulties inherent in producing large enough quantities of these cells for experimentation. This problem arises in large part due to the post‐mitotic nature of mature oligodendrocytes. Over the years, a cell line known as Central Glia‐4 (CG‐4) has become a popular oligodendrocyte model due to its potentially unlimited capacity for self‐renewal. In this review, we will look at the suitability of the Central Glia‐4 cell line as an oligodendrocyte model, specifically in respect to studies on mitogen‐activated protein kinase signalling in oligodendrocytes.
Implantation of cultured human leptomeningeal cells into rat brain
Authors: DeGiorgio Lorraine A. , Bernstein Jerald J. , Blass John P.
Published: July 2002

Since previous studies have shown that cells cultured from human leptomeninges can express neuronal and glial antigens under appropriate culture conditions [DeGiorgio L. A. et al. (1994) J. Neurol. Sci.124, 141–148; Bernstein J. J. et al. (1996) Int. J. Devl Neurosci.14(5), 681–687], we have studied the developmental characteristics of these cells further by grafting them into young adult rat brains. Cells were labeled in culture with Fast Blue and were identified unequivocally by hybridization with nick‐translated human DNA. Intensely Fast Blue positive human leptomeningeal cells were concentrated in the implant pocket and adjacent rat leptomeninges at one and two weeks postimplant. Human and rat leptomeningeal cells were similar morphologically and were equally immunopositive for vimentin and fibronectin. Implanted human cells did not express the neuronal and glial proteins they had in vitro. Cells which hybridized with human DNA corresponded to the intensely Fast Blue positive cells. Small groups of human DNA hybridizing cells were also observed in the choroid plexus. Less intensely Fast Blue positive neurons and glia were found in the brain, but these hybridized with rat DNA. A minority of human leptomeningeal cells implanted into rat brain are subsequently found in host leptomeninges where they demonstrate properties characteristic of leptomeningeal fibroblasts. Small numbers of implanted cells can survive for two weeks.
Development of serotoninergic chick retinal neurons
Authors: Ríos H. , Brusco A. , Saavedra J.Pecci
Published: July 2002

Numerous neurotransmitters have been studied in detail in the developing retina. Almost all known neurotransmitters and neuromodulators were demonstrated in vertebrate retinas using formaldehyde‐induced fluorescence, uptake autoradiography or immunohistochemistry procedures. Serotoninergic (5HT) amacrine neurons were described in the inner nuclear layer (INL) of the retina with their dendrites spreading within the inner plexiform layer (IPL). The present work describes the morphological pattern of development of serotoninergic amacrine neurons with a stratified dendritic branching pattern in the chick retina from embryonic day 12 to postnatal day 7. Serotoninergic‐bipolar neurons are also described. 5HT‐amacrine neurons have round or pear‐shaped somata and primary dendritic trees oriented toward the IPL that runs through the INL, showing several varicosities. Secondary dendrites then go through the INL, without any collateral branch. At the outer and inner margin of the IPL the primary and secondary dendrites originate an outer and an inner serotoninergic network, respectively. When the primary dendritic tree reaches the IPL it deflects laterally in sublayer 1—the outer serotoninergic network. Tertiary branches then arise from the secondary dendrite and deflect in the innermost sublayer of the IPL— the inner serotoninergic network. The final pattern of branching of 5HT amacrine cells was present at embryonic day 14 and was completely developed at hatching. Serotoninergic (5HT) bipolar neurons were also present in the INL at hatching. They are weakly immunoreactive and are probably a subset of bipolar cells that accumulate serotonin from the intersynaptic cleft and are not “true” 5HT neurons.
Eradication of cerebellar granular cells alters thedevelopmental expression of TRK receptors in the ratinferior olive
Authors: Riva‐depaty Isabelle , Dubreuil Yolande Lemaigre , Mariani Jean , Delhaye‐bouchaud Nicole
Published: July 2002

Granule cells which relay the mossy fibre afferent system to the cerebellar cortex aregenerated postnatally in mammals. In their absence, the climbing fibres, i.e. the second afferentsystem to the cerebellum originating in the inferior olivary nucleus, remain in an immature stage,and substantial elimination of redundant synapses they establish on the Purkinje cells does notoccur in the rat between day five (P5) and day fifteen (P15). It is generally assumed that synapseelimination is partly regulated by electrical activity which modulates the competition amongafferent fibres for the uptake of a limited amount of trophic factors released by the target. Theneurotrophins, whose expression is developmentally regulated in the cerebellum, especially ingranule cells, could be this retrograde signal. Using RT‐PCR, we studied the expression of theirtrk receptors in the inferior olivary nucleus of developing and adult rats, and its alteration aftereradication of the granule cell precursors by X‐irradiation on P5. From P0 to P90, the amount oftrkA mRNA is low and remains stable in control rats ; the high levels of trkB and C mRNAsdetected at P0 markedly decrease in parallel from P5 and reach their minimal values at P15,when the process of synapse elimination is completed in the cerebellum. X‐irradiation of thecerebellum decreases the level of expression of the three trks, but a transient upregulation of trkCoccurs at P10. The downregulation of trkB and C expression in the inferior olivary nucleus,contemporary with the altered expression of neurotrophins in the cerebellum, suggest that NT‐3and/or BDNF/NT‐4/5 could be involved in the remodelling of olivocerebellar relationshipsduring development. In addition, the transient overexpression of trkC after granule cellseradication is consistent with a paracrin effect exerted on the olivary cells by granule cells releaseof NT‐3, at the time when the climbing fibres invest the growing Purkinje cell dendrites in themolecular layer.
Falling behavior and control effect on temperature rise under heating condition concerning water film flow on steel shutter surface
Authors: Ohmiya Yoshifumi , Tange Manabu , Nakamura Kohji , Miyazawa Yuya
Published: July 2020

A series of experiments were carried out on water film flow formed by a water discharge system on the surface of steel shutters. The experiments used three types of steel shutters for fire protection. The rates for water Ws supplied to the steel shutter from the slit of the water discharge system was changed. First, the water film flow that formed on the convex surfaces of the main curved parts of connected shutter slats was observed under non‐heating conditions. Then, the velocity of water film flow on the surface of steel shutter was analyzed by direct cross‐correlation method using PIV system. Next, the temperature distribution and other parameters of the water film flow were investigated under heating conditions using a radiation panel. The heating condition was changed by adjusting the separation distance between the radiation panel and the test specimen. To measure the temperatures on the non‐heated side of the test specimen, K‐type thermocouples were used. Fundamental knowledge was obtained about the behavior of water film flow on steel shutter surfaces under non‐heating conditions as well as the thermal insulation and other effects of the water film under heating conditions.
Fabricating 3D Metastructures by Simultaneous Modulation of Flexible Resist Stencils and Basal Molds
Authors: Cai Hongbing , Meng Qiushi , Chen Qiang , Ding Huaiyi , Dai Yanmeng , Li Sijia , Chen Disheng , Tan Qinghai , Pan Nan , Zeng Changgan , Qi Zeming , Liu Gang , Tian Yangchao , Gao Weibo , Wang Xiaoping
Published: July 2020

Metamaterials have gained much attention thanks to their extraordinary and intriguing optical properties beyond natural materials. However, universal high‐resolution fabrications of 3D micro/nanometastructures with high‐resolution remain a challenge. Here, a novel approach to fabricate sophisticated 3D micro/nanostructures with excellent robustness and precise controllability is demonstrated by simultaneously modulating of flexible resist stencils and basal molds. This method allows arbitrary manipulations of morphology, size, and orientation, as well as contact angles of the objects. Combined with a new alignment strategy of high‐resolution, previously inaccessible architectures are fabricated with ultrahigh precision, leading to an excellent spectra response from the fabricated metastructures. This method provides a new possibility to realize true 3D metamaterial fabrications featuring high‐resolution and direct‐compatibility with broad planar lithography platforms.
Single‐Crystal SnSe Thermoelectric Fibers via Laser‐Induced Directional Crystallization: From 1D Fibers to Multidimensional Fabrics
Authors: Zhang Jing , Zhang Ting , Zhang Hang , Wang Zhixun , Li Chen , Wang Zhe , Li Kaiwei , Huang Xingming , Chen Ming , Chen Zhe , Tian Zhiting , Chen Haisheng , Zhao Li‐Dong , Wei Lei
Published: July 2020

Single‐crystal tin selenide (SnSe), a record holder of high‐performance thermoelectric materials, enables high‐efficient interconversion between heat and electricity for power generation or refrigeration. However, the rigid bulky SnSe cannot satisfy the applications for flexible and wearable devices. Here, a method is demonstrated to achieve ultralong single‐crystal SnSe wire with rock‐salt structure and high thermoelectric performance with diameters from micro‐ to nanoscale. This method starts from thermally drawing SnSe into a flexible fiber‐like substrate, which is polycrystalline, highly flexible, ultralong, and mechanically stable. Then a CO2 laser is employed to recrystallize the SnSe core to single‐crystal over the entire fiber. Both theoretical and experimental studies demonstrate that the single‐crystal rock‐salt SnSe fibers possess high thermoelectric properties, significantly enhancing the ZT value to 2 at 862 K. This simple and low‐cost approach offers a promising path to engage the fiber‐shaped single‐crystal materials in applications from 1D fiber devices to multidimensional wearable fabrics.
Rational Design of Transparent Nanowire Architectures with Tunable Geometries for Preventing Marine Fouling
Authors: Wang Jing , Lee Sudarat , Bielinski Ashley R. , Meyer Kevin A. , Dhyani Abhishek , Ortiz‐Ortiz Alondra M. , Tuteja Anish , Dasgupta Neil P.
Published: July 2020

Marine biofouling is a sticky global problem that hinders maritime industries. Various microscale surface structures inspired by marine biological species have been explored for their anti‐fouling properties. However, systematic studies of anti‐marine‐fouling performance on surface architectures with characteristic length‐scales spanning from below 100 nm to greater than 10 µm are generally lacking. Herein, a study on the rational design and fabrication of ZnO/Al2O3 core–shell nanowire architectures with tunable geometries (length, spacing, and branching) and surface chemistry is presented. The ability of the nanowires to significantly delay or prevent marine biofouling is demonstrated. Compared to planar surfaces, hydrophilic nanowires can reduce fouling coverage by up to ≈60% after 20 days. The fouling reduction mechanism is mainly due to two geometric effects: reduced effective settlement area and mechanical cell penetration. Additionally, superhydrophobic nanowires can completely prevent marine biofouling for up to 22 days. The nanowire surfaces are transparent across the visible spectrum, making them applicable to windows and oceanographic sensors. Through the rational control of surface nano‐architectures, the coupled relationships between wettability, transparency, and anti‐biofouling performance are identified. It is envisioned that the insights gained from the work can be used to systematically design surfaces that reduce marine biofouling in various industrial settings.
Coupling 3D Printing and Novel Replica Molding for In House Fabrication of Skeletal Muscle Tissue Engineering Devices
Authors: Iuliano Alessandro , van der Wal Erik , Ruijmbeek Claudine W. B. , in ‘t Groen Stijn L. M. , Pijnappel W. W. M. Pim , de Greef Jessica C. , Saggiomo Vittorio
Published: July 2020

The transition from 2D to 3D engineered tissue cultures is changing the way biologists can perform in vitro functional studies. However, there has been a paucity in the establishment of methods required for the generation of microdevices and cost‐effective scaling up. To date, approaches including multistep photolithography, milling and 3D printing have been used that involve specialized and expensive equipment or time‐consuming steps with variable success. Here, a fabrication pipeline is presented based on affordable off‐the‐shelf 3D printers and novel replica molding strategies for rapid and easy in‐house production of hundreds of 3D culture devices per day, with customizable size and geometry. This pipeline is applied to generate tissue engineered skeletal muscles in vitro using human induced pluripotent stem cell‐derived myogenic progenitors. These production methods can be employed in any standard biomedical laboratory.
Enhanced Fractional Acoustic Vortices by an Annulus Acoustic Metasurface with Multi‐Layered Rings
Authors: Luo Yanchun , Jia Yurou , Yao Jie , Wu Dajian , Liu Xiaojun
Published: July 2020

An annulus acoustic metasurface (AAM) with multi‐layered rings is proposed to achieve the enhanced fractional acoustic vortices (FAVs). It is found that the enhancement of the transmitted FAV through the AAM is sensitive to the radial interval between adjacent ring‐structures. A greatly enhanced FAV is theoretically obtained by the optimized AAM. Then finite element models based on composite labyrinthine structures are established and the generation of the enhanced FAV is confirmed by simulations. Furthermore, the optimized AAM samples are fabricated and experimentally generate the enhanced FAV with topological charge of 1.5. The FAV generated by the optimized AAM with three‐rings is ≈5.4 times stronger than that generated by the classical AAM with one‐ring. Finally, experimental results show that the greatly enhanced FAV can capture micro‐particles and rotate a sound absorbing disk easily. The greatly enhanced FAV by the AAM may be more efficient for the micro‐particle manipulation, edge‐detection image, and acoustic communication.
Ultralow Broadband Reflectivity in Black Silicon via Synergy between Hierarchical Texture and Specific‐Size Au Nanoparticles
Authors: Zhang Zengxing , Martinsen Thomas , Liu Guohua , Tayyib Muhammad , Cui Danfeng , de Boer Meint J. , Karlsen Frank , Jakobsen Henrik , Xue Chenyang , Wang Kaiying
Published: July 2020

Antireflectivity is one of the critical factors defining the performance of black silicon in optical, photothermal, photochemical, and optoelectronic applications. The photonic applications under visible light illumination are commonly tuned through surface texturing; however, their promising performance under longer wavelength (>1100 nm) requires either intrinsic lattice modifications or additional substance enhancement. Recent advances in microfabrication and material engineering have enabled in‐depth exploration into the synergy between surface texturing and material reinforcement. In this study, black silicon with novel chimney‐like hierarchical micro/nanostructures is fabricated via two‐step reactive ion etching, and subsequently gold nanoparticles (Au NPs) are loaded on the black silicon by magnetron sputtering deposition. The micro/nanostructures result in synergy effect with the Au NPs on suppression of light reflection. An ultralow broadband reflection (<1%, wavelength 220–2600 nm) is achieved from the Au‐loaded black silicon substrates. The impact of Au NPs and structural design such as size, spacing, shape, and etching duration on antireflectivity of black silicon is investigated. This study opens up new avenue for high‐efficiency applications of black silicon in the fields of sustainable energy and photonics/microelectronics.
High‐Throughput Nanofabrication of Metasurfaces with Polarization‐Dependent Response
Authors: Matricardi Cristiano , Garcia‐Pomar Juan Luis , Molet Pau , Pérez Luis Alberto , Alonso Maria Isabel , Campoy‐Quiles Mariano , Mihi Agustín
Published: July 2020

Metal nanostructures offer exciting ways to manage light at the nanoscale exploited in fields such as imaging, sensing, energy conversion, and information processing. The optical response of the metallic architectures can be engineered to exhibit photonic properties that span from plasmon resonances to more complex phenomena such as negative refractive index, optical chirality, artificial magnetism, and more. However, the latter optical properties are only observed in intricate architectures, which are highly demanding in terms of nanofabrication and hence less scalable and far away from device implementation. Here, a series of metasurfaces covering centimeter areas and operating in the visible spectrum are presented, which are produced from the combination of nanoimprinting lithography and oblique angle metal evaporation. The potential of this scalable approach is illustrated by easily fabricating metasurfaces engineered to exhibit artificial optical magnetism, tunable linear polarization dependent response, chirality with g‐factor of 0.2, and photoluminescence enhancement of 20 times over a 9 mm2 area.
Ultrabroadband, Fast, and Flexible Photodetector Based on HfTe5 Crystal
Authors: Niu Yingying , Wang Yingxin , Wu Weidong , Wang Pengfei , Sun Jialin , Wen Jianguo , Lu Xiaowei , Jiang Peng , Zhang Sijie , Wang Nanlin , Wu Dong , Zhao Ziran
Published: July 2020

Ultrabroad spectrum detection has a wide range of photonic and optoelectronic applications, such as spectroscopy, optical communication, imaging, and sensing. 3D topological insulator candidates are promising materials for fast high‐performance photodetectors owing to their linear dispersion band structure and high carrier mobility. In this study, an ultrabroadband photothermoelectric (PTE) self‐powered detector based on the topological insulator candidate HfTe5 is reported for the first time. The photosensitive properties are characterized in an ultrabroadband range from the ultraviolet (375 nm) to terahertz (118.8 µm) wavelengths, and the responsivities at all examined wavelengths are found to be greater than 1 V W−1 at room temperature. Owing to the Dirac band dispersion of HfTe5, the response time (τ) of the proposed detector is as short as ≈1 ms, which is 1–3 orders of magnitude faster than that of recently reported PTE detectors based on millimeter‐scale graphene, 3D graphene, EuBiSe3 single crystal, and SrTiO3 crystal. Furthermore, the sensitivity of the HfTe5 detector to the light intensity and direction of linearly‐polarized light is demonstrated. Thus, the proposed device demonstrates outstanding flexibility, air stability, and long‐term photostability as well, displaying high potential for practical applications in wearable optoelectronics.
Chemical Artificial Internalizing Receptors for Primary T Cells
Authors: Monge Pere , Tvilum Anne , Søgaard Ane Bretschneider , Løvschall Kaja Borup , Jarlstad Olesen Morten T. , Zelikin Alexander N.
Published: July 2020

The newest generation of cell‐based technologies relies heavily on methods to communicate to the engineered cells using artificial receptors, specifically to deactivate the cells administered to a patient in the event of adverse effects. Herein, artificial synthetic internalizing receptors are engineered that function in mammalian cells in 2D and in 3D and afford targeted, specific intracellular drug delivery with nanomolar potency in the most challenging cell type, namely primary, donor‐derived T cells. Receptor design comprises a lipid bilayer anchor for receptor integration into cell membrane and a small xenobiotic molecule as a recognition ligand. Artificial receptors are successfully targeted by the corresponding antibody–drug conjugate (ADC) and exhibit efficient cargo cell entry with ensuing intracellular effects. Receptor integration into cells is fast and robust and affords targeted cell entry in under 2 h. Through a combination of the receptor design and the use of ADC, combined benefits previously made available by chimeric artificial receptors (performance in T cells) and the chemical counterpart (robustness and simplicity) in a single functional platform is achieved. Artificial synthetic receptors are poised to facilitate the maturation of engineered cells as tools of biotechnology and biomedicine.