bluuebunny/crossref_metadata_2025 huggingface dataset:
A novel clade of protistan parasites near the animal-fungal divergence.
Authors: Ragan M A , Goggin C L , Cawthorn R J , Cerenius L , Jamieson A V , Plourde S M , Rand T G , Söderhäll K , Gutell R R
Published: July 2002

Sequences of nuclear-encoded small-subunit rRNA genes have been determined for representatives of the enigmatic genera Dermocystidium, Ichthyophonus, and Psorospermium, protistan parasites of fish and crustaceans. The small-subunit rRNA genes from these parasites and from the "rosette agent" (also a parasite of fish) together form a novel, statistically supported clade. Phylogenetic analyses demonstrate this clade to diverge near the animal-fungal dichotomy, although more precise resolution is problematic. In the most parsimonious and maximally likely phylogenetic frameworks inferred from the most stably aligned sequence regions, the clade constitutes the most basal branch of the metazoa; but within a limited range of model parameters, and in some analyses that incorporate less well-aligned sequence regions, an alternative topology in which it diverges immediately before the animal-fungal dichotomy was recovered. Mitochondrial cristae of Dermocystidium spp. are flat, whereas those of Ichthyophonus hoferi appear tubulovesiculate. These results extend our understanding of the types of organisms from which metazoa and fungi may have evolved.
Modeling back propagating action potential in weakly excitable dendrites of neocortical pyramidal cells.
Authors: Rapp M , Yarom Y , Segev I
Published: July 2002

Simultaneous recordings from the soma and apical dendrite of layer V neocortical pyramidal cells of young rats show that, for any location of current input, an evoked action potential (AP) always starts at the axon and then propagates actively, but decrementally, backward into the dendrites. This back-propagating AP is supported by a low density (-gNa = approximately 4 mS/cm2) of rapidly inactivating voltage-dependent Na+ channels in the soma and the apical dendrite. Investigation of detailed, biophysically constrained, models of reconstructed pyramidal cells shows the following. (i) The initiation of the AP first in the axon cannot be explained solely by morphological considerations; the axon must be more excitable than the soma and dendrites. (ii) The minimal Na+ channel density in the axon that fully accounts for the experimental results is about 20-times that of the soma. If -gNa in the axon hillock and initial segment is the same as in the soma [as recently suggested by Colbert and Johnston [Colbert, C. M. & Johnston, D. (1995) Soc. Neurosci. Abstr. 21, 684.2]], then -gNa in the more distal axonal regions is required to be about 40-times that of the soma. (iii) A backward propagating AP in weakly excitable dendrites can be modulated in a graded manner by background synaptic activity. The functional role of weakly excitable dendrites and a more excitable axon for forward synaptic integration and for backward, global, communication between the axon and the dendrites is discussed.
Energy metabolism, enzymatic flux capacities, and metabolic flux rates in flying honeybees.
Authors: Suarez R K , Lighton J R , Joos B , Roberts S P , Harrison J F
Published: July 2002

Honeybees rely primarily on the oxidation of hexose sugars to provide the energy required for flight. Measurement of VCO2 (equal to VO2, because VCO2/VO2 = 1.0 during carbohydrate oxidation) during flight allowed estimation of steady-state flux rates through pathways of flight muscle energy metabolism. Comparison of Vmax values for flight muscle hexokinase, phosphofructokinase, citrate synthase, and cytochrome c oxidase with rates of carbon and O2 flux during flight reveal that these enzymes operate closer to Vmax in the flight muscles of flying honeybees than in other muscles previously studied. Possible mechanistic and evolutionary implications of these findings are discussed.
A novel heat-activated current in nociceptive neurons and its sensitization by bradykinin
Authors: Cesare Paolo , McNaughton Peter
Published: July 2002

Pain differs from other sensations in many respects. Primary
pain-sensitive neurons respond to a wide variety of noxious stimuli, in
contrast to the relatively specific responses characteristic of other
sensory systems, and the response is often observed to sensitize on
repeated presentation of a painful stimulus, while adaptation is
typically observed in other sensory systems. In most cases the cellular
mechanisms of transduction and sensitization in response to painful
stimuli are not understood. We report here that application of pulses
of noxious heat to a subpopulation of isolated primary sensory neurons
rapidly activates an inward current. The ion channel activated by heat
discriminates poorly among alkali cations. Calcium ions both carry
current and partially suppress the current carried by other ions. The
current is markedly increased by bradykinin, a potent algogenic
nonapeptide that is known to be released
in vivo
by
tissue damage. Phosphatase inhibitors prolong the sensitization caused
by bradykinin, and a similar sensitization is caused by activators of
protein kinase C. We conclude that bradykinin sensitizes the response
to heat by activating protein kinase C.
DNA damage enhances melanogenesis.
Authors: Eller M S , Ostrom K , Gilchrest B A
Published: July 2002

Although the ability of UV irradiation to induce pigmentation in vivo and in vitro is well documented, the intracellular signals that trigger this response are poorly understood. We have recently shown that increasing DNA repair after irradiation enhances UV-induced melanization. Moreover, addition of small DNA fragments, particularly thymine dinucleotides (pTpT), selected to mimic sequences excised during the repair of UV-induced DNA photoproducts, to unirradiated pigment cells in vitro or to guinea pig skin in vivo induces a pigment response indistinguishable from UV-induced tanning. Here we present further evidence that DNA damage and/or the repair of this damage increases melanization. (i) Treatment with the restriction enzyme Pvu II or the DNA-damaging chemical agents methyl methanesulfonate (MMS) or 4-nitroquinoline 1-oxide (4-NQO) produces a 4- to 10-fold increase in melanin content in Cloudman S91 murine melanoma cells and an up to 70% increase in normal human melanocytes, (ii) UV irradiation, MMS, and pTpT all upregulate the mRNA level for tyrosinase, the rate-limiting enzyme in melanin biosynthesis. (iii) Treatment with pTpT or MMS increases the response of S91 cells to melanocyte-stimulating hormone (MSH) and increases the binding of MSH to its cell surface receptor, as has been reported for UV irradiation. Together, these data suggest that UV-induced DNA damage and/or the repair of this damage is an important signal in the pigmentation response to UV irradiation. Because Pvu II acts exclusively on DNA and because MMS and 4-NQO, at the concentrations used, primarily interact with DNA, such a stimulus alone appears sufficient to induce melanogenesis. Of possible practical importance, the dinucleotide pTpT mimics most, if not all, of the effects of UV irradiation on pigmentation, tyrosinase mRNA regulation, and response to MSH without the requirement for antecedent DNA damage.
Immunohistochemical detection of 4-hydroxynonenal protein adducts in Parkinson disease.
Authors: Yoritaka A , Hattori N , Uchida K , Tanaka M , Stadtman E R , Mizuno Y
Published: July 2002

There is growing evidence that oxidative stress and mitochondrial respiratory failure with attendant decrease in energy output are implicated in nigral neuronal death in Parkinson disease (PD). It is not known, however, which cellular elements (neurons or glial cells) are major targets of oxygen-mediated damage. 4-Hydroxy-2-nonenal (HNE) was shown earlier to react with proteins to form stable adducts that can be used as markers of oxidative stress-induced cellular damage. We report here results of immunochemical studies using polyclonal antibodies directed against HNE-protein conjugates to label the site of oxidative damage in control subjects (ages 18-99 years) and seven patients that died of PD (ages 57-78 years). All the nigral melanized neurons in one of the midbrain sections were counted and classified into three groups according to the intensity of immunostaining for HNE-modified proteins--i.e., no staining, weak staining, and intensely positive staining. On average, 58% of nigral neurons were positively stained for HNE-modified proteins in PD; in contrast only 9% of nigral neurons were positive in the control subjects; the difference was statistically significant (Mann-Whitney U test; P < 0.01). In contrast to the substantia nigra, the oculomotor neurons in the same midbrain sections showed no or only weak staining for HNE-modified proteins in both PD and control subjects; young control subjects did not show any immunostaining; however, aged control subjects showed weak staining in the oculomotor nucleus, suggesting age-related accumulation of HNE-modified proteins in the neuron. Our results indicate the presence of oxidative stress within nigral neurons in PD, and this oxidative stress may contribute to nigral cell death.
Regulation of mitochondrial pyruvate dehydrogenase activity by tau protein kinase I/glycogen synthase kinase 3beta in brain.
Authors: Hoshi M , Takashima A , Noguchi K , Murayama M , Sato M , Kondo S , Saitoh Y , Ishiguro K , Hoshino T , Imahori K
Published: July 2002

According to the amyloid hypothesis for the pathogenesis of Alzheimer disease, beta-amyloid peptide (betaA) directly affects neurons, leading to neurodegeneration and tau phosphorylation. In rat hippocampal culture, betaA exposure activates tau protein kinase I/glycogen synthase kinase 3beta (TPKI/GSK-3beta), which phosphorylates tau protein into Alzheimer disease-like forms, resulting in neuronal death. To elucidate the mechanism of betaA-induced neuronal death, we searched for substrates of TPKI/GSK-3beta in a two-hybrid system and identified pyruvate dehydrogenase (PDH), which converts pyruvate to acetyl-CoA in mitochondria. PDH was phosphorylated and inactivated by TPKI/GSK-3beta in vitro and also in betaA-treated hippocampal cultures, resulting in mitochondrial dysfunction, which would contribute to neuronal death. In cholinergic neurons, betaA impaired acetylcholine synthesis without affecting choline acetyltransferase activity, which suggests that PDH is inactivated by betaA-induced TPKI/GSK-3beta. Thus, TPKI/GSK-3beta regulates PDH and participates in energy metabolism and acetylcholine synthesis. These results suggest that TPKI/GSK-3beta plays a key role in the pathogenesis of Alzheimer disease.
cDNA cloning and gene mapping of a candidate human cell cycle checkpoint protein.
Authors: Cimprich K A , Shin T B , Keith C T , Schreiber S L
Published: July 2002

A family of proteins involved in cell cycle progression, DNA recombination, and the detection of DNA damage has been recently identified. One of the members of this family, human ATM, is defective in the cells of patients with ataxia telangiectasia and is involved in detection and response of cells to damaged DNA. Other members include Mei-41 (Drosophila melanogaster), Mec1p (Saccharomyces cerevisiae), and Rad3 (Schizosaccharomyces pombe), which are required for the S and G2/M checkpoints, as well as FRAP (Homo sapiens) and Torl/2p (S. cerevisiae), which are involved in a rapamycin-sensitive pathway leading to G1 cell cycle progression. We report here the cloning of a human cDNA encoding a protein with significant homology to members of this family. Three overlapping clones isolated from a Jurkat T-cell cDNA library revealed a 7.9-kb open reading frame encoding a protein that we have named FRP1 (FRAP-related protein) with 2644 amino acids and a predicted molecular mass of 301 kDa. Using fluorescence in situ hybridization and a full-length cDNA FRP1 clone, the FRP1 gene has been mapped to the chromosomal locus 3q22-q24. FRP1 is most closely related to three of the PIK-related kinase family members involved in checkpoint function--Mei-41, Mec1p, and Rad3--and as such may be the functional human counterpart of these proteins.
The repetition of large-earthquake ruptures.
Authors: Sieh K
Published: July 2002

This survey of well-documented repeated fault rupture confirms that some faults have exhibited a "characteristic" behavior during repeated large earthquakes--that is, the magnitude, distribution, and style of slip on the fault has repeated during two or more consecutive events. In two cases faults exhibit slip functions that vary little from earthquake to earthquake. In one other well-documented case, however, fault lengths contrast markedly for two consecutive ruptures, but the amount of offset at individual sites was similar. Adjacent individual patches, 10 km or more in length, failed singly during one event and in tandem during the other. More complex cases of repetition may also represent the failure of several distinct patches. The faults of the 1992 Landers earthquake provide an instructive example of such complexity. Together, these examples suggest that large earthquakes commonly result from the failure of one or more patches, each characterized by a slip function that is roughly invariant through consecutive earthquake cycles. The persistence of these slip-patches through two or more large earthquakes indicates that some quasi-invariant physical property controls the pattern and magnitude of slip. These data seem incompatible with theoretical models that produce slip distributions that are highly variable in consecutive large events.
Movement of yeast cortical actin cytoskeleton visualized in vivo.
Authors: Doyle T , Botstein D
Published: July 2002

Fusion proteins between the green fluorescent protein (GFP) and the cytoskeleton proteins Act1p (actin), Sac6p (yeast fimbrin homolog), and Abp1p in budding yeast (Saccharomyces cerevisiae) localize to the cortical actin patches. The actin fusions could not function as the sole actin source in yeast, but fusions between the actin-binding proteins Abp1p and Sac6p complement fully the phenotypes associated with their gene deletions. Direct observation in vivo reveals that the actin cortical patches move. Movement of actin patches is constrained to the asymmetric distribution of the patches in growing cells, and this movement is greatly reduced when metabolic inhibitors such as sodium azide are added. Fusion protein-labeled patches are normally distributed during the yeast cell cycle and during mating. In vivo observation made possible the visualization of actin patches during sporulation as well.
Fragile X mental retardation protein is translated near synapses in response to neurotransmitter activation
Authors: Weiler Ivan Jeanne , Irwin Scott A. , Klintsova Anna Y. , Spencer Corinne M. , Brazelton Anthony D. , Miyashiro Kevin , Comery Thomas A. , Patel Bindu , Eberwine James , Greenough William T.
Published: July 2002

Local translation of proteins in distal dendrites is thought to support synaptic structural plasticity. We have previously shown that metabotropic glutamate receptor (mGluR1) stimulation initiates a phosphorylation cascade, triggering rapid association of some mRNAs with translation machinery near synapses, and leading to protein synthesis. To determine the identity of these mRNAs, a cDNA library produced from distal nerve processes was used to screen synaptic polyribosome-associated mRNA. We identified mRNA for the fragile X mental retardation protein (FMRP) in these processes by use of synaptic subcellular fractions, termed synaptoneurosomes. We found that this mRNA associates with translational complexes in synaptoneurosomes within 1–2 min after mGluR1 stimulation of this preparation, and we observed increased expression of FMRP after mGluR1 stimulation. In addition, we found that FMRP is associated with polyribosomal complexes in these fractions.In vivo, we observed FMRP immunoreactivity in spines, dendrites, and somata of the developing rat brain, but not in nuclei or axons. We suggest that rapid production of FMRP near synapses in response to activation may be important for normal maturation of synaptic connections.
The I/LWEQ module: a conserved sequence that signifies F-actin binding in functionally diverse proteins from yeast to mammals
Authors: McCann Richard O. , Craig Susan W.
Published: July 2002

Talin is an actin-binding protein involved in integrin-mediated cell adhesion and spreading. The C-terminal 197 amino acids of vertebrate talin are 45% similar to the C-terminal residues of Sla2, a yeast protein implicated in polarized assembly of the yeast actin cytoskeleton. Talin is also homologous in this region to nematode talin, cellular slime mold filopodin, and an Sla2 homolog from nematode. Analysis of the conserved C-terminal sequences of these five proteins with
block maker
reveals a series of four blocks, which we name the I/LWEQ module after the conserved initial residues in each block. Experiments presented here show that the conserved protein domain represented by the I/LWEQ module competes quantitatively with native talin for binding to F-actin
in vitro
. Furthermore, the corresponding domain of Sla2 binds to both yeast and vertebrate F-actin
in vitro
. Mutation of one of the conserved residues in the fourth conserved block abolishes the interaction of the Sla2 I/LWEQ module with F-actin. These results establish the location of an F-actin binding domain in native talin, demonstrate that direct interaction of Sla2 with actin is a possible basis for its effect on the actin cytoskeleton
in vivo
, and define the I/LWEQ consensus as a new actin-binding motif.
Characterization of the major histocompatibility complex class II binding site on LAG-3 protein
Authors: Huard Bertrand , Mastrangeli Renato , Prigent Philippe , Bruniquel Denis , Donini Silvia , El-Tayar Nabil , Maigret Bernard , Dréano Michel , Triebel Frédéric
Published: July 2002

The lymphocyte activation gene-3 (LAG-3), selectively transcribed in human activated T and NK cells, encodes a ligand for major histocompatibility complex (MHC) class II molecules. Like CD4, LAG-3 ectodomain is composed of four Ig-like domains (D1–D4). Nothing is known about the LAG-3 regions or residues required to form a stable MHC class II binding site. In contrast to CD4, soluble LAG-3 molecules stably interact with MHC class II molecules expressed on the cell surface. In addition, the first two N-terminal domains of soluble LAG-3 (D1 and D2) molecules, alone, are capable of binding MHC class II. From a LAG-3 model structure, we designed mutants and tested their ability to bind MHC class II molecules in an intercellular adhesion assay. We found residues on the membrane-distal, CDR1–2-containing top face of D1 that are essential for either binding or repulsing MHC class II proteins. Most of these residues are clustered at the base of a large extra-loop structure that is a hallmark of the LAG-3 D1 Ig-like domain. In addition, as for CD4, oligomerization of LAG-3 on the cell surface may be required to form a stable MHC binding site because mutation of three residues in the ABED β-strands containing side of D1 results in a dominant negative effect (i.e., binding inhibition of coexpressed wild-type LAG-3).
Neurotoxicity associated with dual actions of homocysteine at the
N
-methyl-
d
-aspartate receptor
Authors: Lipton Stuart A. , Kim Won-Ki , Choi Yun-Beom , Kumar Shanta , D’Emilia Danielle M. , Rayudu Posina V. , Arnelle Derrick R. , Stamler Jonathan S.
Published: July 2002

Severely elevated levels of total homocysteine (approximately millimolar) in the blood typify the childhood disease homocystinuria, whereas modest levels (tens of micromolar) are commonly found in adults who are at increased risk for vascular disease and stroke. Activation of the coagulation system and adverse effects of homocysteine on the endothelium and vessel wall are believed to underlie disease pathogenesis. Here we show that homocysteine acts as an agonist at the glutamate binding site of the
N
-methyl-
d
-aspartate receptor, but also as a partial antagonist of the glycine coagonist site. With physiological levels of glycine, neurotoxic concentrations of homocysteine are on the order of millimolar. However, under pathological conditions in which glycine levels in the nervous system are elevated, such as stroke and head trauma, homocysteine’s neurotoxic (agonist) attributes at 10–100 μM levels outweigh its neuroprotective (antagonist) activity. Under these conditions neuronal damage derives from excessive Ca
2+
influx and reactive oxygen generation. Accordingly, homocysteine neurotoxicity through overstimulation of
N
-methyl-
d
-aspartate receptors may contribute to the pathogenesis of both homocystinuria and modest hyperhomocysteinemia.
Serotonin and aggressive motivation in crustaceans: Altering the decision to retreat
Authors: Huber Robert , Smith Kalim , Delago Antonia , Isaksson Karin , Kravitz Edward A.
Published: July 2002

In crustaceans, as in most animal species, the amine serotonin has been suggested to serve important roles in aggression. Here we show that injection of serotonin into the hemolymph of subordinate, freely moving animals results in a renewed willingness of these animals to engage the dominants in further agonistic encounters. By multivariate statistical analysis, we demonstrate that this reversal results principally from a reduction in the likelihood of retreat and an increase in the duration of fighting. Serotonin infusion does not alter other aspects of fighting behavior, including which animal initiates an encounter, how quickly fighting escalates, or which animal eventually retreats. Preliminary studies suggest that serotonin uptake plays an important role in this behavioral reversal.
Complete nucleotide sequence of the chloroplast genome from the green algaChlorella vulgaris: The existence of genes possibly involved in chloroplast division
Authors: Wakasugi Tatsuya , Nagai Toshiyuki , Kapoor Meenu , Sugita Mamoru , Ito Mari , Ito Shiho , Tsudzuki Junko , Nakashima Keiko , Tsudzuki Takahiko , Suzuki Yasuhiko , Hamada Akira , Ohta Tutomu , Inamura Atsushi , Yoshinaga Koichi , Sugiura Masahiro
Published: July 2002

The complete nucleotide sequence of the chloroplast genome (150,613 bp) from the unicellular green algaChlorella vulgarisC-27 has been determined. The genome contains no large inverted repeat and has one copy of rRNA gene cluster consisting of 16S, 23S, and 5S rRNA genes. It contains 31 tRNA genes, of which the tRNALeu(GAG) gene has not been found in land plant chloroplast DNAs analyzed so far. Sixty-nine protein genes and eight ORFs conserved with those found in land plant chloroplasts have also been found. The most striking is the existence of two adjacent genes homologous to bacterial genes involved in cell division,minDandminE, which are arranged in the same order inEscherichia coli. This finding suggests that the mechanism of chloroplast division is similar to bacterial division. Other thanminDandminEhomologues, genes encoding ribosomal proteins L5, L12, L19, and S9 (rpl5,rpl12, rpl19, andrps9); a chlorophyll biosynthesis Mg chelating subunit (chlI); and elongation factor EF-Tu (tufA), which have not been reported from land plant chloroplast DNAs, are present in this genome. However, many of the new chloroplast genes recently found in red and brown algae have not been found inC. vulgaris.Furthermore, this algal species possesses two long ORFs related toycf1andycf2that are exclusively found in land plants. These observations suggest thatC. vulgarisis closer to land plants than to red and brown algae.
Glutamine synthetase protects against neuronal degeneration in injured retinal tissue
Authors: Gorovits Rena , Avidan Nili , Avisar Noa , Shaked Iftach , Vardimon Lily
Published: July 2002

The neurotransmitter glutamate is neurotoxic when it is accumulated in a massive amount in the extracellular fluid. Excessive release of glutamate has been shown to be a major cause of neuronal degeneration after central nervous system injury. Under normal conditions, accumulation of synaptically released glutamate is prevented, at least in part, by a glial uptake system in which the glia-specific enzyme glutamine synthetase (GS) plays a key role. We postulated that glial cells cannot cope with glutamate neurotoxicity because the level of GS is not high enough to catalyze the excessive amounts of glutamate released by damaged neurons. We examined whether elevation of GS expression in glial cells protects against neuronal degeneration in injured retinal tissue. Analysis of lactate dehydrogenase efflux, DNA fragmentation, and histological sections revealed that hormonal induction of the endogenous GS gene in retinal glial cells correlates with a decline in neuronal degeneration, whereas inhibition of GS activity by methionine sulfoximine leads to increased cell death. A supply of purified GS enzyme to the culture medium of retinal explants or directly to the embryo
in ovo
causes a dose-dependent decline in the extent of cell death. These results show that GS is a potent neuroprotectant and that elevation of GS expression in glial cells activates an endogenous mechanism whereby neurons are protected from the deleterious effects of excess glutamate in extracellular fluid after trauma or ischemia. Our results suggest new approaches to the clinical handling of neuronal degeneration.
Evolution by the birth-and-death process in multigene families of the vertebrate immune system
Authors: Nei Masatoshi , Gu Xun , Sitnikova Tatyana
Published: July 2002

Concerted evolution is often invoked to explain the diversity and evolution of the multigene families of major histocompatibility complex (MHC) genes and immunoglobulin (Ig) genes. However, this hypothesis has been controversial because the member genes of these families from the same species are not necessarily more closely related to one another than to the genes from different species. To resolve this controversy, we conducted phylogenetic analyses of several multigene families of the MHC and Ig systems. The results show that the evolutionary pattern of these families is quite different from that of concerted evolution but is in agreement with the birth-and-death model of evolution in which new genes are created by repeated gene duplication and some duplicate genes are maintained in the genome for a long time but others are deleted or become nonfunctional by deleterious mutations. We found little evidence that interlocus gene conversion plays an important role in the evolution of MHC and Ig multigene families.
Complete resolution of the solid-state NMR spectrum of a uniformly
15
N-labeled membrane protein in phospholipid bilayers
Authors: Marassi Francesca M. , Ramamoorthy A. , Opella Stanley J.
Published: July 2002

Complete resolution of the amide resonances in a three-dimensional solid-state NMR correlation spectrum of a uniformly
15
N-labeled membrane protein in oriented phospholipid bilayers is demonstrated. The three orientationally dependent frequencies,
1
H chemical shift,
1
H–
15
N dipolar coupling, and
15
N chemical shift, associated with each amide resonance are responsible for resolution among resonances and provide sufficient angular restrictions for protein structure determination. Because the protein is completely immobilized by the phospholipids on the relevant NMR time scales (10 kHz), the linewidths will not degrade in the spectra of larger proteins. Therefore, these results demonstrate that solid-state NMR experiments can overcome the correlation time problem and extend the range of proteins that can have their structures determined by NMR spectroscopy to include uniformly
15
N-labeled membrane proteins in phospholipid bilayers.
Ultraviolet plumage colors predict mate preferences in starlings
Authors: Bennett Andrew T. D. , Cuthill Innes C. , Partridge Julian C. , Lunau Klaus
Published: July 2002

Avian plumage has long been used to test theories of sexual selection, with humans assessing the colors. However, many birds see in the ultraviolet (<400 nm), to which humans are blind. Consequently, it is important to know whether natural variation in UV reflectance from plumage functions in sexual signaling. We show that female starlings rank males differently when UV wavelengths are present or absent. Principal component analysis of ≈1300 reflectance spectra (300–700 nm) taken from sexually dimorphic plumage regions of males predicted preference under the UV+ treatment. Under UV− conditions, females ranked males in a different and nonrandom order, but plumage reflectance in the human visible spectrum did not predict choice. Natural variation in UV reflectance is thus important in avian mate assessment, and the prevailing light environment can have profound effects on observed mating preferences.
Glutamate receptor-mediated toxicity in optic nerve oligodendrocytes
Authors: Matute Carlos , Sánchez-Gómez M. Victoria , Martínez-Millán Luis , Miledi Ricardo
Published: July 2002

In cultured oligodendrocytes isolated from perinatal rat optic nerves, we have analyzed the expression of ionotropic glutamate receptor subunits as well as the effect of the activation of these receptors on oligodendrocyte viability. Reverse transcription–PCR, in combination with immunocytochemistry, demonstrated that most oligodendrocytes differentiated
in vitro
express the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluR3 and GluR4 and the kainate receptor subunits GluR6, GluR7, KA1 and KA2. Acute and chronic exposure to kainate caused extensive oligodendrocyte death in culture. This effect was partially prevented by the AMPA receptor antagonist GYKI 52466 and was completely abolished by the non-
N
-methyl-
d
-aspartate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), suggesting that both AMPA and kainate receptors mediate the observed kainate toxicity. Furthermore, chronic application of kainate to optic nerves
in vivo
resulted in massive oligodendrocyte death which, as
in vitro
, could be prevented by coinfusion of the toxin with CNQX. These findings suggest that excessive activation of the ionotropic glutamate receptors expressed by oligodendrocytes may act as a negative regulator of the size of this cell population.
Targeted overexpression of protein kinase C β2 isoform in myocardium causes cardiomyopathy
Authors: Wakasaki Hisao , Koya Daisuke , Schoen Frederick J. , Jirousek Michael R. , Ways D. Kirk , Hoit Brian D. , Walsh Richard A. , King George L.
Published: July 2002

Increased cardiovascular mortality occurs in diabetic patients with or without coronary artery disease and is attributed to the presence of diabetic cardiomyopathy. One potential mechanism is hyperglycemia that has been reported to activate protein kinase C (PKC), preferentially the β isoform, which has been associated with the development of micro- and macrovascular pathologies in diabetes mellitus. To establish that the activation of the PKCβ isoform can cause cardiac dysfunctions, we have established lines of transgenic mice with the specific overexpression of PKCβ2 isoform in the myocardium. These mice overexpressed the PKCβ2 isoform transgene by 2- to 10-fold as measured by mRNA, and proteins exhibited left ventricular hypertrophy, cardiac myocyte necrosis, multifocal fibrosis, and decreased left ventricular performance without vascular lesions. The severity of the phenotypes exhibited gene dose-dependence. Up-regulation of mRNAs for fetal type myosin heavy chain, atrial natriuretic factor, c-
fos
, transforming growth factor, and collagens was also observed. Moreover, treatment with a PKCβ-specific inhibitor resulted in functional and histological improvement. These findings have firmly established that the activation of the PKCβ2 isoform can cause specific cardiac cellular and functional changes leading to cardiomyopathy of diabetic or nondiabetic etiology.
The N-terminal propiece of interleukin 1α is a transforming nuclear oncoprotein
Authors: Stevenson Frazier T. , Turck Johanna , Locksley Richard M. , Lovett David H.
Published: July 2002

Interleukin 1α (IL-1α) is a pleiotropic cytokine involved in the immune response, inflammatory processes, and hematopoiesis, and acts as a mitogen for several malignant cell types, including acute leukemia and Kaposi sarcoma cells. These diverse activities have been exclusively attributed to the plasma membrane receptor-binding, 17-kDa C-terminal component (mature IL-1α) that results from proteolytic processing of the 31- to 33-kDa precursor protein. No biologic function has been ascribed to the unusually large, 16-kDa N-terminal propiece formed as a result of proteolytic processing of IL-1α. We report that the IL-1α N-terminal propiece is concentrated by means of a nuclear localization sequence within the nuclei of both transfected and leukemic cell lines. Overexpression of this component in glomerular mesangial cells, a model perivascular myofibroblast cell type capable of IL-1α synthesis and processing, results in malignant transformation to a spindle cell-type tumor. The functionally bipartite nature of the IL-1α precursor represents a unique combination of the C-terminal, classical cytokine and an N-terminal nuclear oncoprotein. These findings suggest that nuclear transport of the IL-1α N-terminal component may represent a critical component in the transformation of IL-1α-producing cells in the bone marrow or the perivascular area to a malignant phenotype.
The neural code between neocortical pyramidal neurons depends on neurotransmitter release probability
Authors: Tsodyks Misha V. , Markram Henry
Published: July 2002

Although signaling between neurons is central to the functioning of the brain, we still do not understand how the code used in signaling depends on the properties of synaptic transmission. Theoretical analysis combined with patch clamp recordings from pairs of neocortical pyramidal neurons revealed that the rate of synaptic depression, which depends on the probability of neurotransmitter release, dictates the extent to which firing rate and temporal coherence of action potentials within a presynaptic population are signaled to the postsynaptic neuron. The postsynaptic response primarily reflects rates of firing when depression is slow and temporal coherence when depression is fast. A wide range of rates of synaptic depression between different pairs of pyramidal neurons was found, suggesting that the relative contribution of rate and temporal signals varies along a continuum. We conclude that by setting the rate of synaptic depression, release probability is an important factor in determining the neural code.
The macrophage/endothelial cell mannose receptor cDNA encodes a protein that binds oligosaccharides terminating with SO4-4-GalNAcβ1,4GlcNAcβ or Man at independent sites
Authors: Fiete Dorothy , Beranek Mary C. , Baenziger Jacques U.
Published: July 2002

Lutropin (LH) and other glycoproteins bearing oligosaccharides with the terminal sequence SO4-4-GalNAcβ1,4GlcNAcβ1,4Man- (S4GGnM) are rapidly removed from the circulation by an S4GGnM-specific receptor (S4GGnM-R) expressed at the surface of hepatic endothelial cells. The S4GGnM-R isolated from rat liver is closely related to the macrophage mannose-specific receptor (Man-R) isolated from rat lung both antigenically and structurally. The S4GGnM-R and Man-R isolated from these tissues nonetheless differ in their ability to bind ligands bearing terminal GalNAc-4-SO4or Man. In this paper, we have explored the structural relationship between the Man-R and the S4GGnM-R by examining the properties of the recombinant Man-R in the form of a transmembrane protein and a soluble chimeric fusion protein in which the transmembrane and cytosolic domains have been replaced by the Fc region of human IgG1. Like the S4GGnM-R isolated from liver, the chimeric fusion protein is able to bind ligands terminating with GalNAc-4-SO4and Man at independent sites. When expressed in CHO cells the recombinant Man-R is able to mediate the uptake of ligands bearing either terminal GalNAc-4-SO4or terminal Man. We propose that the Man-R be renamed the Man/S4GGnM receptor on the basis of its multiple and independent specificities.
Random locomotion and chemotaxis of human blood polymorphonuclear leukocytes (PMN) in the presence of EDTA: PMN in close quarters require neither leukocyte integrins nor external divalent cations
Authors: Malawista Stephen E. , Chevance Anne de Boisfleury
Published: July 2002

Divalent cations are thought essential for motile function of leukocytes in general, and for the function of critical adhesion molecules in particular. In the current study, under direct microscopic observation with concomitant time-lapse video recording, we examined the effects of 10 mM EDTA on locomotion of human blood polymorphonuclear leukocytes (PMN). In very thin slide preparations, EDTA did not impair either random locomotion or chemotaxis; motile behavior appeared to benefit from the close approximation of slide and coverslip (“chimneying”). In preparations twice as thick, PMN in EDTA first exhibited active deformability with little or no displacement, then rounded up and became motionless. However, on creation of a chemotactic gradient, the same cells were able to orient and make their way to the target, often, however, losing momentarily their purchase on the substrate. In either of these preparations without EDTA, specific antibodies to β2 integrins did not prevent random locomotion or chemotaxis, even when we added antibodies to β1 and αvβ3 integrins and to integrin-associated protein, and none of these antibodies added anything to the effects of EDTA. In the more turbulent environment of even more media, effects of anti-β2 integrins became evident: PMN still could locomote but adhered to substrate largely by their uropods and by uropod-associated filaments. We relate these findings to the reported independence from integrins of PMN in certain experimental and disease states. Moreover, we suggest that PMN locomotion in close quarters is not only integrin-independent, but independent of external divalent cations as well.
Long-term potentiation activates the GAP-43 promoter: Selective participation of hippocampal mossy cells
Authors: Namgung Uk , Matsuyama Shogo , Routtenberg Aryeh
Published: July 2002

Perforant path long-term potentiation (LTP) in intact mouse hippocampal dentate gyrus increased the neuron-specific, growth-associated protein GAP-43 mRNA in hilar cells 3 days after tetanus, but surprisingly not in granule cells, the perforant path target. This increase was positively correlated with level of enhancement and restricted to central hilar cells on the side of stimulation. Blockade of LTP by puffing
dl
-aminophosphonovalerate (APV), an
N
-methyl-
d
-aspartate (NMDA) receptor blocker into the molecular layer, eliminated LTP-induced GAP-43 mRNA elevation in hilar cells. To determine whether the mRNA elevation was mediated by transcription, LTP was studied in transgenic mice bearing a GAP-43 promoter-
lacZ
reporter gene.
P
romoter
a
ctivity as indexed by
T
ransgene
e
xpression (PATE) increased as indicated by blue staining of the
lacZ
gene product, β-galactosidase. Potentiation induced a blue band bilaterally in the inner molecular layer of the dentate gyrus along the entire septotemporal axis. Because mossy cells are the only neurons in the central hilar zone that project to the inner molecular layer bilaterally along the entire septotemporal axis and LTP-induced activation of PATE in this zone was confined to the side of stimulation, we concluded that mossy cells were unilaterally activated, increasing synthesis of β-galactosidase, which was transported bilaterally. Neither granule cells nor pyramidal cells demonstrated increased PATE or increased GAP-43 mRNA levels. These results and recent evidence indicating the necessity of hilar neurons for LTP point to previously unheralded mossy cells as potentially critical for perforant path LTP and the GAP-43 in these cells as important for LTP persistence lasting days.
The affected gene underlying the class K glycosylphosphatidylinositol (GPI) surface protein defect codes for the GPI transamidase
Authors: Yu Jianliang , Nagarajan Shanmugam , Knez Jansen J. , Udenfriend Sidney , Chen Rui , Medof M. Edward
Published: July 2002

The final step in glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins consists of a transamidation reaction in which preassembled GPI donors are substituted for C-terminal signal sequences in nascent polypeptides. In previous studies we described a human K562 cell mutant, termed class K, that accumulates fully assembled GPI units but is unable to transfer them to N-terminally processed proproteins. In further work we showed that, unlike wild-type microsomes, microsomes from these cells are unable to support C-terminal interaction of proproteins with the small nucleophiles hydrazine or hydroxylamine, and that the cells thus are defective in transamidation. In this study, using a modified recombinant vaccinia transient transfection system in conjunction with a composite cDNA prepared by 5′ extension of an existing GenBank sequence, we found that the genetic element affected in these cells corresponds to the human homolog ofyGPI8, a gene affected in a yeast mutant strain exhibiting similar accumulation of GPI donors without transfer.hGPI8gives rise to mRNAs of 1.6 and 1.9 kb, both encoding a protein of 395 amino acids that varies in cells with their ability to couple GPIs to proteins. The gene spans ≈25 kb of DNA on chromosome 1. Reconstitution of class K cells withhGPI8abolishes their accumulation of GPI precursors and restores C-terminal processing of GPI-anchored proteins. Also,hGPI8restores the ability of microsomes from the mutant cells to yield an active carbonyl in the presence of a proprotein which is considered to be an intermediate in catalysis by a transamidase.
The
zntA
gene of
Escherichia coli
encodes a Zn(II)-translocating P-type ATPase
Authors: Rensing Christopher , Mitra Bharati , Rosen Barry P.
Published: July 2002

The first Zn(II)-translocating P-type ATPase has been identified as the product of
o732
, a potential gene identified in the sequencing of the
Escherichia coli
genome. This gene, termed
zntA
, was disrupted by insertion of a kanamycin gene through homologous recombination. The mutant strain exhibited hypersensitivity to zinc and cadmium salts but not salts of other metals, suggesting a role in zinc homeostasis in
E. coli
. Everted membrane vesicles from a wild-type strain accumulated
65
Zn(II) and
109
Cd(II) by using ATP as an energy source. Transport was sensitive to vanadate, an inhibitor of P-type ATPases. Membrane vesicles from the
zntA
∷
kan
strain did not accumulate those metal ions. Both the sensitive phenotype and transport defect of the mutant were complemented by expression of
zntA
on a plasmid.
Oat–maize chromosome addition lines: A new system for mapping the maize genome
Authors: Ananiev Evgueni V. , Riera-Lizarazu Oscar , Rines Howard W. , Phillips Ronald L.
Published: July 2002

Novel plants with individual maize chromosomes added to a complete oat genome have been recovered via embryo rescue from oat (
Avena sativa
L., 2
n
= 6x = 42) × maize (
Zea mays
L., 2
n
= 20) crosses. An oat–maize disomic addition line possessing 21 pairs of oat chromosomes and one maize chromosome 9 pair was used to construct a cosmid library. A multiprobe (mixture of labeled fragments used as a probe) of highly repetitive maize-specific sequences was used to selectively isolate cosmid clones containing maize genomic DNA. Hybridization of individual maize cosmid clones or their subcloned fragments to maize and oat genomic DNA revealed that most high, middle, or low copy number DNA sequences are maize-specific. Such DNA markers allow the identification of maize genomic DNA in an oat genomic background. Chimeric cosmid clones were not found; apparently, significant exchanges of genetic material had not occurred between the maize-addition chromosome and the oat genome in these novel plants or in the cloning process. About 95% of clones selected at random from a maize genomic cosmid library could be detected by the multiprobe. The ability to selectively detect maize sequences in an oat background enables us to consider oat as a host for the cloning of specific maize chromosomes or maize chromosome segments. Introgressing maize chromosome segments into the oat genome via irradiation should allow the construction of a library of overlapping fragments for each maize chromosome to be used for developing a physical map of the maize genome.
Conservation of function between mammalian and plant steroid 5α-reductases
Authors: Li Jianming , Biswas Michael G. , Chao Alex , Russell David W. , Chory Joanne
Published: July 2002

Arabidopsis det2
mutants are small dark-green dwarfs displaying pleiotropic defects in light-regulated development during multiple stages of the plant life cycle. The
DET2
gene encodes a protein that shares ≈40% sequence identity with mammalian steroid 5α-reductases and is implicated in the synthesis of a class of plant steroids, the brassinosteroids. Here we show that the DET2 protein, when expressed in human embryonic kidney 293 cells, catalyzes the 5α-reduction of several animal steroid substrates and has similar kinetic properties to the mammalian steroid 5α-reductase enzymes. Moreover, human steroid 5α-reductases expressed in
det2
mutant plants can substitute for DET2 in brassinosteroid biosynthesis. These data indicate that DET2 is an ortholog of the mammalian steroid 5α-reductases and provide further evidence that brassinosteroids play an essential role in light-regulated plant development. The structural and functional conservation between DET2 and human steroid 5α-reductases raise interesting issues concerning the evolutionary origin of the steroid hormone signaling system.
Emotion, olfaction, and the human amygdala: Amygdala activation during aversive olfactory stimulation
Authors: Zald David H. , Pardo José V.
Published: July 2002

Electrophysiologic and lesion studies of animals increasingly implicate the amygdala in aspects of emotional processing. Yet, the functions of the human amygdala remain poorly understood. To examine the contributions of the amygdala and other limbic and paralimbic regions to emotional processing, we exposed healthy subjects to aversive olfactory stimuli while measuring regional cerebral blood flow (rCBF) with positron emission tomography. Exposure to a highly aversive odorant produced strong rCBF increases in both amygdalae and in the left orbitofrontal cortex. Exposure to less aversive odorants produced rCBF increases in the orbitofrontal cortex but not in the amygdala. Change of rCBF within the left amygdala and the left OFC was highly intercorrelated, indicating a strong functional interaction between these brain regions. Furthermore, the activity within the left amygdala was associated significantly with subjective ratings of perceived aversiveness. These findings provide evidence that the human amygdala participates in the hedonic or emotional processing of olfactory stimuli.
Cloning and characterization of a putative human serine/threonine protein kinase transcriptionally modified during anisotonic and isotonic alterations of cell volume
Authors: Waldegger Siegfried , Barth Petra , Raber Gertraud , Lang Florian
Published: July 2002

Hepatic metabolism and gene expression are among other regulatory mechanisms controlled by the cellular hydration state, which changes rapidly in response to anisotonicity, concentrative substrate uptake, oxidative stress, and under the influence of hormones such as insulin and glucagon. Differential screening for cell volume sensitive transcripts in a human hepatoma cell line revealed a gene for a putative serine/threonine kinase, h-sgk, which has 98% sequence identity to a serum- and glucocorticoid regulated kinase, sgk, cloned from a rat mammary tumor cell line. h-sgk transcript levels were strongly altered during anisotonic and isotonic cell volume changes. Within 30 min h-sgk RNA was, independent of
de novo
protein synthesis, induced upon cell shrinkage and, due to a complete stop in h-sgk transcription, reduced upon cell swelling. Comparable changes of sgk transcript levels were observed in a renal epithelial cell line. h-sgk mRNA was detected in all human tissues tested, with the highest levels in pancreas, liver, and heart. The putative serine/threonine protein kinase h-sgk may provide a functional link between the cellular hydration state and metabolic control.