bluuebunny/crossref_metadata_2025 huggingface dataset:
Hummingbirds See Near Ultraviolet Light
Authors: Goldsmith Timothy H.
Published: October 2006

Three species of hummingbird (
Archilochus alexandri
,
Lampornis clemenciae
, and
Eugenes fulgens
) were trained to make visual discriminations between lights of different spectral content. On the basis of initial choices of feeders following a period of conditioning, birds of all three species were able to distinguish near ultraviolet (370 nanometers, 20-nanometer half bandwidth) from darkness (unilluminated viewing screen) or from the small amount of far red light that leaked through the ultraviolet-transmitting glass filter. A human observer was unable to make either discrimination. The birds were also able to distinguish white lights lacking wavelengths shorter than 400 nanometers from the full spectrum of the quartz-halogen bulbs. One can infer that the cone oil droplets, which have been lost from the retinas of most mammals, provide a potentially more flexible system for restricting the short wavelength end of the visible spectrum than does the filtering action of lens and macula that serves this function in the human eye.
High-Frequency Sensitivity in Infants
Authors: Schneider Bruce , Trehub Sandra E. , Bull Dale
Published: October 2006

Auditory thresholds were determined for infants and adults to half-octave bands of noise centered at 10,000 and 19,000 hertz. Adults were significantly more sensitive than infants at 10,000 hertz, but at 19,000 hertz, adults and infants had comparable thresholds.
Absence of Cross-Tolerance to Heroin in Morphine-Tolerant Mice
Authors: Lange D. G. , Roerig S. C. , Fujimoto J. M. , Wang R. I. H.
Published: October 2006

Mice implanted with morphine pellets demonstrated a 30-fold increase in tolerance to subcutaneously administered morphine but showed no cross-tolerance to subcutaneously administered heroin. When given morphine intracerebroventricularly, the mice showed no tolerance to morphine or cross-tolerance to heroin. These observations depended on the presence of the morphine pellet. If the pellets were removed prior to determinations of potency, the expected responses—tolerance to morphine and cross-tolerance to heroin—were obtained. The blood-brain barrier may be a prime site for the expression of morphine tolerance in mice.
Hydralazine-Pyrimidine Interactions May Explain Hydralazine-Induced Lupus Erythematosus
Authors: Dubroff Lewis M. , Reid Robert J.
Published: October 2006

Hydralazine, the prototypic drug that induces systemic lupus erythematosus, reacts with thymidine and deoxycytidine. Analysis of a reaction mixture of therapeutic concentrations of hydralazine with labeled thymidine reveals at least four labeled products. At higher concentrations, hydralazine reacts with labeled deoxycytidine to form at least three labeled products. Formation of these products is markedly enhanced by exposure to ultraviolet light. The reaction of hydralazine with thymidine and deoxycytidine may be in part responsible for initiating drug-induced systemic lupus erythematosus.
Calcium Regulation During Stimulus-Secretion Coupling: Continuous Measurement of Intracellular Calcium Activities
Authors: O'Doherty J. , Youmans S. J. , Armstrong W. McD. , Stark R. J.
Published: October 2006

Accurate measurements of intracellular calcium activities in salivary gland epithelial cells of the insect
Phormia regina
were obtained with microelectrodes in which
N
,
N
′-di(11-ethoxycarbonyl)undecyl-
N
,
N
′-4,5-tetramethyl-3,6-dioxaoctane diacid diamide wsa incorporated in a liquid membrane system. When calibrated in solutions approximating the ionic concentration of the cell interior, these microelectrodes gave rapid stable responses that were linear functions of the logarithm of calcium activities and were not affected by potassium, sodium, and magnesium. Continuous monitoring of calcium activities during serotonin-induced saliva release provided direct evidence of hormonal influence on transmembrane calcium movement and spontaneous regulation of intracellular calcium by stimulated cells.
Sodium-Calcium Exchange in Rabbit Heart Muscle Cells: Direct Measurement of Sarcoplasmic Ca
2+
Activity
Authors: Lee Chin O. , Uhm Dae Y , Dresdner Karl
Published: October 2006

Calcium ion-selective microelectrodes made with Simon's neutral carrier were used to measure simultaneously sarcoplasmic Ca
2+
activity (
a
i
Ca
) and resting tension (
T
r
) of rabbit ventricular muscle during reduction and restoration of external sodium ion concentration, [Na]
0
. Under the same experimental conditions the change in contractile tension (
T
a
) also was measured. In resting muscle the
a
i
Ca
was 38 ± 17 nanomolar (mean ± standard deviation;
N
= 10). The reduction of [Na]
0
from 153 to 20 millimolar led to about a threefold increase in
a
i
Ca
with parallel increases in
T
r
and
T
a
. The time course of the change in
a
i
Ca
was similar to that of the changes in
T
r
and
T
a
. The results are consistent with an important role of the sodium-calcium exchange system for regulating sarcoplasmic Ca
2+
activity.
Tumor Promoter TPA Mimics Irradiation Effects on the Cell Cycle of HeLa Cells
Authors: Kinzel Volker , Richards James , Stöhr Michael
Published: October 2006

When asynchronous and synchronous HeLa cells were incubated with small doses (10
-7
M
) of tumor promoter 12-
O
-tetradecanoylphorbol-13-acetate (TPA), a variety of transient alterations in the replication cycle were detected within 24 hours by the use of independent methods. Especially, a delayed passage through the S phase and influences on the G2 phase resemble x-ray irradiation effects on cell cultures. None of these alterations was observed with the hyperplasiogenic but nonpromoting 4-
O
-methyl-TPA.
Neural Organization Predicts Stimulus Specificity for a Retained Associative Behavioral Change
Authors: Farley Joseph , Alkon Daniel L.
Published: October 2006

Paired, but not random, presentations of light and rotation produced long-term changes in
Hermissenda
's response to light. The nature of this change depended on the orientation of the animals with respect to the center of rotation and was predicted by known organizational features of
Hermissenda
's nervous system. When rotation that excited caudal hair cells was paired with light, a significant increase in response latency to test lights resulted. Rotation exciting cephalic hair cells when paired with light decreased the response latencies compared with latencies produced by random presentation of light and rotation.
Dye Coupling and Possible Electrotonic Coupling in the Guinea Pig Neocortical Slice
Authors: Gutnick Michael J. , Prince David A.
Published: October 2006

Iontophoretic injection of the fluorescent dye Lucifer Yellow CH into single neurons of guinea pig neocortical slices resulted in the staining of more than one cell. Dye-coupled neuronal aggregates were found only in the superficial cortical layers and were often organized in vertical columns. Antidromic stimuli evoked all-or-none, subthreshold depolarizations in some superficial cells. These potentials were not eliminated by manganese and did not collide with spikes originating in the soma, suggesting that they arose from electrotonic interaction between superficial cortical neurons.
Immunophagocytic Properties of Retinal Pigment Epithelium Cells
Authors: Elner Victor M. , Schaffner Thomas , Taylor Katherine , Glagov Seymour
Published: October 2006

Retinal pigment cells were dislodged from normal monkey eyes and incubated in glass-slide chambers. All viable pigment cells adhered strongly to glass. They demonstrated surface receptors for the Fc portion of immunoglobulin G and for the third component of complement by selectively binding and phagocytizing antibody or complement-coated erythrocytes. These phagocytic cells with receptors were identified as retinal pigment cells by characteristic ultrastructural features. Thus, retinal pigment cells, which are generally believed to be derived from neural tissue, are not only scavengers of photoreceptor cell debris, but also have surface receptors and phagocytic functions that may be important in ocular defense.
Chemical Defense Mechanisms on the Great Barrier Reef, Australia
Authors: Bakus Gerald J.
Published: October 2006

Seventy-three percent of all exposed common coral reef invertebrates, from four phyla (42 species) tested, are toxic to fish. This represents the first evidence of the high incidence of toxicity in the marine tropics among several phyletic groups comprising dominant species. Most of the remaining exposed species have structural defense mechanisms against predation by fish. Of cryptic invertebrates, 25 percent are toxic to fish. The relation between toxicity, fish feeding behavior, community structure, and evolutionary theory is discussed.
Virus in a Parasitoid Wasp: Suppression of the Cellular Immune Response in the Parasitoid's Host
Authors: Edson Kathryn M. , Vinson S. Bradleigh , Stoltz Donald B. , Summers Max D.
Published: October 2006

A virus that replicates in the ovary of a parasitoid wasp is injected into the parasitoid's host during oviposition. Successful development of the parasitoid egg within the host depends on the presence of the virus, which acts to suppress the host's immune response (encapsulation) toward the egg. This is an example of obligatory mutualism between a virus and a eukaryotic organism.
Entorhinal and Septal Inputs Differentially Control Sensory-Evoked Responses in the Rat Dentate Gyrus
Authors: Deadwyler Sam A. , West Mark O. , Robinson John H.
Published: October 2006

Averaged sensory-evoked potentials were recorded from the outer molecular layer of the dentate gyrus in naive rats and in rats conditioned to respond in the presence of an auditory stimulus. Two components (negative peaks) of the potentials were functionally distinguished in terms of responsiveness to unique or conditioned auditory stimuli. Each component was independently generated by a separate input pathway to the dentate gyrus: The perforant path provided an "insignificance" or "unexpected" feature of the sensory stimulus when appropriate, and the septum controlled the development of a second component as a function of the behavioral significance of the stimulus during the acquisition of auditory discrimination behavior. A reciprocal relationship between the peak amplitudes of both components of the average evoked potentials dependent on the relative behavioral significance of the sensory stimulus was observed in all animals during extinction and reconditioning of the sensory discrimination task. The findings indicate that the entorhinal and septal projections to the dentate granule cells are activated differentially by sensory stimuli as a function of their acquired behavioral significance to the animal.
Cholestyramine: Use as a New Therapeutic Approach for Chlordecone (Kepone) Poisoning
Authors: Boylan James J. , Egle John L. , Guzelian Philip S.
Published: October 2006

In rats, as reported in humans, chlordecone (Kepone) is excreted predominantly in the feces. Cholestyramine, an anion exchange resin, binds chlordecone in rat intestine, increases its excretion into the feces, and decreases its content in the tissues. The resin appears to offer a practical method for treating chronic poisoning with this and possibly with other lipophilic toxins.
Reducing Epileptic Seizures Through Operant Conditioning of Central Nervous System Activity: Procedural Variables
Authors: Cott Arthur , Pavloski Raymond P. , Black Abraham H.
Published: October 2006

Operant conditioning of the sensorimotor rhythm of the human electroencephalogram with time-outs contingent on epileptiform activity reduces epileptic seizure rates in patients whose seizures are not well controlled by medication. A comparison of this procedure with time-out training alone demonstrates that operant conditioning of the sensorimotor rhythm is neither necessary nor sufficient for seizure reduction.
Tumor Rejection After Direct Costimulation of CD8
+
T Cells by B7-Transfected Melanoma Cells
Authors: Townsend Sarah E. , Allison James P.
Published: October 2006

A variety of tumors are potentially immunogenic but do not stimulate an effective anti-tumor immune response in vivo. Tumors may be capable of delivering antigen-specific signals to T cells, but may not deliver the costimulatory signals necessary for full activation of T cells. Expression of the costimulatory ligand B7 on melanoma cells was found to induce the rejection of a murine melanoma in vivo. This rejection was mediated by CD8
+
T cells; CD4
+
T cells were not required. These results suggest that B7 expression renders tumor cells capable of effective antigen presentation, leading to their eradication in vivo.
Forward Plasma Membrane Flow in Growing Nerve Processes
Authors: Popov Sergey , Brown Abraham , Poo Mu-ming
Published: October 2006

Nerve growth requires addition of new plasma membrane material, which is generally believed to occur at the growth cone. Local incorporation of a fluorescent lipid analog into the plasma membrane of fast-growing
Xenopus
neurites revealed an anterograde bulk membrane flow that correlated with neurite elongation. The rate of membrane flow depended on the position of the labeled membrane segment along the neurite, increasing with distance from the soma. This result suggests that new membrane in growing
Xenopus
neurites is added not at the growth cone but at the cell body and along the neurite.
Identification of the SH3 Domain of GAP as an Essential Sequence for Ras-GAP-Mediated Signaling
Authors: Duchesne Marc , Schweighoffer Fabien , Parker Fabienne , Clerc François , Frobert Yveline , Thang Ming Nguy , Tocqué Bruno
Published: October 2006

Guanosine triphosphatase activating protein (GAP) is an essential component of Ras signaling pathways. GAP functions in different cell types as a deactivator and a transmitter of cellular Ras signals. A domain (amino acids 275 to 351) encompassing the Src homology region 3 (SH3) of GAP was found to be essential for GAP signaling. A monoclonal antibody was used to block germinal vesicle breakdown (GVBD) induced by the oncogenic protein Ha-ras Lys
12
in
Xenopus
oocytes. The monoclonal antibody, which was found to recognize the peptide containing amino acids 275 to 351 within the amino-terminal domain of GAP, did not modify the stimulation of the Ha-Ras-GTPase by GAP. Injection of peptides corresponding to amino acids 275 to 351 and 317 to 326 blocked GVBD induced by insulin or by Ha-Ras Lys
12
but not that induced by progesterone. These findings confirm that GAP is an effector for Ras in
Xenopus
oocytes and that the SH3 domain is essential for signal transduction.
Mechanotransduction Across the Cell Surface and Through the Cytoskeleton
Authors: Wang Ning , Butler James P. , Ingber Donald E.
Published: October 2006

Mechanical stresses were applied directly to cell surface receptors with a magnetic twisting device. The extracellular matrix receptor, integrin β
1
, induced focal adhesion formation and supported a force-dependent stiffening response, whereas nonadhesion receptors did not. The cytoskeletal stiffness (ratio of stress to strain) increased in direct proportion to the applied stress and required intact microtubules and intermediate filaments as well as microfilaments. Tensegrity models that incorporate mechanically interdependent struts and strings that reorient globally in response to a localized stress mimicked this response. These results suggest that integrins act as mechanoreceptors and transmit mechanical signals to the cytoskeleton. Mechanotransduction, in turn, may be mediated simultaneously at multiple locations inside the cell through force-induced rearrangements within a tensionally integrated cytoskeleton.
Antisense Gene Inhibition by Oligonucleotides Containing C-5 Propyne Pyrimidines
Authors: Wagner Richard W. , Matteucci Mark D. , Lewis Jason G. , Gutierrez Arnold J. , Moulds Courtney , Froehler Brian C.
Published: October 2006

Phosphorothioate oligodeoxynucleotides containing the C-5 propyne analogs of uridine and cytidine bind RNA with high affinity and are potent antisense inhibitors of gene expression. In a cellular assay, gene-specific antisense inhibition occurred at nanomolar concentrations of oligonucleotide, was dose-dependent and exquisitely sensitive to sequence mismatches, and was correlated with the melting temperature and length of oligonucleotide. Activity was independent of RNA target site and cell type but was detectable only when the oligonucleotides were microinjected or delivered with cell-permeabilizing agents. These oligonucleotides may have important applications in therapy and in studies of gene function.
Interleukin-7: a Cofactor For V(D)J Rearrangement of the T Cell Receptor β Gene
Authors: Muegge K. , Vila M. P. , Durum S. K.
Published: October 2006

The diversity of the T cell receptor repertoire is generated by rearrangement of gene elements in immature thymocytes. To identify a thymic signal that induces this rearrangement, a variety of agents were tested for their ability to induce rearrangement of the T cell receptor β gene in suspensions of thymocytes from mouse embryos at day 14 of gestation. Of 16 agents tested, only interleukin-7 (IL-7) induced V(D)J gene rearrangement and sustained expression of the
RAG-1
and
RAG-2
genes, which are known to control rearrangement. These data implicate IL-7, a cytokine that is abundantly expressed in embryonic thymus, in driving gene rearrangement during early T cell development.
Insulin-Dependent Diabetes: A Disease of Autoaggression
Authors: Huang Shih-Wen , Maclaren Noel Keith
Published: October 2006

Lymphocytes from patients with insulin-dependent diabetes demonstrated significant cytoadherence and cytotoxicity against human insulinoma cells in vitro as compared to lymphocytes from normals. Complement was not involved in insulinoma cell destruction. The findings suggest that insulin-dependent diabetes may be a disease of autoaggression.
Structure-Function Analysis of the Ion Channel Selectivity Filter in Human Annexin V
Authors: Berendes Robert , Voges Dieter , Demange Pascal , Huber Robert , Burger Alexander
Published: October 2006

Electrophysiology and structural studies were performed on an annexin V variant containing a mutation of glutamic acid-95 to serine in the center of the pore region. The mutation resulted in a lower single channel conductance for calcium and a strongly increased conductance for sodium and potassium, indicating that glutamic acid-95 is a crucial constituent of the ion selectivity filter. There were only minor differences in the crystal structures of mutant and wild-type annexin V around the mutation site; however, the mutant showed structural differences elsewhere, including the presence of a calcium binding site in domain III unrelated to the mutation. Analysis of the membrane-bound form of annexin V by electron microscopy revealed no differences between the wild type and mutant.
Functional Stoichiometry of Shaker Potassium Channel Inactivation
Authors: MacKinnon Roderick , Aldrich Richard W. , Lee Alice W.
Published: October 2006

Shaker potassium channels from
Drosophila
are composed of four identical subunits. The contribution of a single subunit to the inactivation gating transition was investigated. Channels carrying a specific mutation in a single subunit can be labeled in a heterogeneous population and studied quantitatively with scorpion toxin sensitivity as a selection tag. Linkage within a single subunit of a mutation that removes the inactivation gate to a second mutation that affects scorpion toxin sensitivity demonstrates that only a single gate is necessary to produce inactivation. The inactivation rate constant for channels with a single gate was one-fourth that of channels with four gates. In contrast, the rate of recovery from inactivation was independent of the number of gates. It appears that each of the four open inactivation gates in a Shaker potassium channel is independent, but only one of the four gates closes in a mutually exclusive manner.
Isoniazid and Iproniazid: Activation of Metabolites to Toxic Intermediates in Man and Rat
Authors: Nelson S. D. , Mitchell J. R. , Timbrell J. A. , Snodgrass W. R. , Corcoran G. B.
Published: October 2006

Acetylhydrazine, a metabolite of isoniazid, a widely used antituberculosis drug, and isopropylhydrazine, a metabolite of iproniazid, an antidepressant removed from clinical use because of high incidence of liver injury, were oxidized by cytochrome P-450 enzymes in human and rat liver microsomes to highly reactive acylating and alkylating agents. Covalent binding of these metabolites to liver macromolecules paralleled hepatic cellular necrosis. The metabolites formed from these and probably other monosubstituted hydrazines are reactive electrophiles.
BRCA1
Mutations in Primary Breast and Ovarian Carcinomas
Authors: Futreal P. Andrew , Liu Qingyun , Shattuck-Eidens Donna , Cochran Charles , Harshman Keith , Tavtigian Sean , Bennett L. Michelle , Haugen-Strano Astrid , Swensen Jeff , Miki Yoshio , Eddington Ken , McClure Melody , Frye Cheryl , Weaver-Feldhaus Jane , Ding Wei , Gholami Zahra , Söderkvist Peter , Terry Lori , Jhanwar Suresh , Berchuck Andrew , Iglehart J. Dirk , Marks Jeff , Ballinger Dennis G. , Barrett J. Carl , Skolnick Mark H. , Kamb Alexander , Wiseman Roger
Published: October 2006

Loss of heterozygosity data from familial tumors suggest that
BRCA1
, a gene that confers susceptibility to ovarian and early-onset breast cancer, encodes a tumor suppressor. The
BRCA1
region is also subject to allelic loss in sporadic breast and ovarian cancers, an indication that
BRCA1
mutations may occur somatically in these tumors. The
BRCA1
coding region was examined for mutations in primary breast and ovarian tumors that show allele loss at the
BRCA1
locus. Mutations were detected in 3 of 32 breast and 1 of 12 ovarian carcinomas; all four mutations were germline alterations and occurred in early-onset cancers. These results suggest that mutation of
BRCA1
may not be critical in the development of the majority of breast and ovarian cancers that arise in the absence of a mutant germline allele.
Interaction Between PRP11 and SPP91 Yeast Splicing Factors and Characterization of a PRP9-PRP11-SPP91 Complex
Authors: Legrain Pierre , Chapon Christine
Published: October 2006

Several proteins are involved in the early steps of the spliceosome assembly pathway. Protein-protein interactions have been identified between two
Saccharomyces cerevisiae
yeast splicing factors, PRP9 and SPP91. Here it is demonstrated that protein-protein interactions occur between SPP91 and PRP11. The combination of the
prp9-1
mutant and a truncated
prp11
mutant exhibits a synthetic lethal phenotype, suggestive of a common biochemical defect. The PRP9 and PRP11 proteins do not interact directly, but the PRP9 and PRP11 molecules can simultaneously bind SPP91 to form a three-molecule complex. Structurally and functionally related proteins are found in mammalian cells and are associated in a single biochemical fraction. This strongly suggests that the PRP9-SPP91-PRP11 complex is a key element of the splicing machinery.
Dependence of Calmodulin Localization in the Retina on the NINAC Unconventional Myosin
Authors: Porter Jeffery A. , Yu Mujun , Doberstein Stephen K. , Pollard Thomas D. , Montell Craig
Published: October 2006

Calmodulin is a highly conserved regulatory protein found in all eukaryotic organisms which mediates a variety of calcium ion-dependent signaling pathways. In the
Drosophila
retina, calmodulin was concentrated in the photoreceptor cell microvillar structure, the rhabdomere, and was found in lower amounts in the sub-rhabdomeral cytoplasm. This calmodulin localization was dependent on the NINAC (neither inactivation nor afterpotential C) unconventional myosins. Mutant flies lacking the rhabdomere-specific p174 NINAC protein did not concentrate calmodulin in the rhabdomere, whereas flies lacking the sub-rhabdomeral p132 isoform had no detectable cytoplasmic calmodulin. Furthermore, a defect in vision resulted when calmodulin was not concentrated in the rhabdomeres, suggesting a role for calmodulin in the regulation of fly phototransduction. A general function of unconventional myosins may be to control the subcellular distribution of calmodulin.
Formation and Hydrolysis of Cyclic ADP-Ribose Catalyzed by Lymphocyte Antigen CD38
Authors: Howard Maureen , Grimaldi J. Christopher , Bazan J. Fernando , Lund Frances E. , Santos-Argumedo Leopoldo , Parkhouse R. M. E. , Walseth Timothy F. , Lee Hon Cheung
Published: October 2006

CD38 is a 42-kilodalton glycoprotein expressed extensively on B and T lymphocytes. CD38 exhibits a structural homology to
Aplysia
adenosine diphosphate (ADP)-ribosyl cyclase. This enzyme catalyzes the synthesis of cyclic ADP-ribose (cADPR), a metabolite of nicotinamide adenine dinucleotide (NAD
+
) with calcium-mobilizing activity. A complementary DNA encoding the extracellular domain of murine CD38 was constructed and expressed, and the resultant recombinant soluble CD38 was purified to homogeneity. Soluble CD38 catalyzed the formation and hydrolysis of cADPR when added to NAD
+
. Purified cADPR augmented the proliferative response of activated murine B cells, potentially implicating the enzymatic activity of CD38 in lymphocyte function.
A Link Between Cyclin A Expression and Adhesion-Dependent Cell Cycle Progression
Authors: Guadagno Thomas M. , Ohtsubo Motoaki , Roberts James M. , Assoian Richard K.
Published: October 2006

Cell adhesion has an essential role in regulating proliferation during the G
1
phase of the cell cycle, and loss of this adhesion requirement is a classic feature of oncogenic transformation. The appearance of cyclin A messenger RNA and protein in late G
1
was dependent on cell adhesion in both NRK and NIH 3T3 fibroblasts. In contrast, the expression of Cdc2, Cdk2, cyclin D1, and cyclin E was independent of adhesion in both cell lines. Transfection of NRK cells with a cyclin A complementary DNA resulted in adhesion-independent accumulation of cyclin A protein and cyclin A-associated kinase activity. These transfected cells also entered S phase and complete multiple rounds of cell division in the absence of cell adhesion. Thus, cyclin A is a target of the adhesion-dependent signals that control cell proliferation.
Initiation at Closely Spaced Replication Origins in a Yeast Chromosome
Authors: Brewer Bonita J. , Fangman Walton L.
Published: October 2006

Replication of eukaryotic chromosomes involves initiation at origins spaced an average of 50 to 100 kilobase pairs. In yeast, potential origins can be recognized as autonomous replication sequences (ARSs) that allow maintenance of plasmids. However, there are more ARS elements than active chromosomal origins. The possibility was examined that close spacing of ARSs can lead to inactive origins. Two ARSs located 6.5 kilobase pairs apart can indeed interfere with each other. Replication is initiated from one or the other ARS with equal probability, but rarely (< 5%) from both ARSs on the same DNA molecule.
Elements of the Yeast Pheromone Response Pathway Required for Filamentous Growth of Diploids
Authors: Liu Haoping , Styles Cora Ann , Fink Gerald R.
Published: October 2006

Transmission of an external signal from receptors to downstream targets is often mediated by a conserved set of protein kinases that act in sequence (a kinase cascade). In haploid strains of
Saccharomyces cerevisiae
, a signal initiated by peptide pheromones is transmitted through this kinase cascade to a transcription factor STE12, which is required for the expression of many mating-specific genes. Here it was shown that in diploids some of the same kinases and STE12 are required for filamentous growth, but the pheromone receptors and guanosine triphosphate-binding protein are not required for filament formation. Thus, a similar kinase cascade is activated by different signals in haploids and diploids and mediates different developmental outcomes in the two cell types.
Perceived Lightness Depends on Perceived Spatial Arrangement
Authors: Gilchrist Alan L.
Published: October 2006

The perceived shade of gray depends primarily on the luminance relationship between surfaces perceived to lie in the same plane and not between surfaces that are merely adjacent in the retinal image. This result implies that depth perception must precede lightness perception and that lateral inhibition cannot explain lightness constancy.
Natural Selection for Juvenile Lizards Mimicking Noxious Beetles
Authors: Huey Raymond B. , Pianka Eric R.
Published: October 2006

Adult
Eremias lugubris
in southern Africa are concealingly colored and move with a typical lizard gait, but the jet-black and white juveniles are conspicuous and forage actively with arched backs. In color, gait, and size, juveniles mimic "oogpister" beetles (Carabidae:
Anthia
) that spray an acidic, pungent fluid when molested. This unique mimicry, which is believed to be the first reported case of a terrestrial vertebrate mimicking an invertebrate, seems to reduce predation on juvenile lizards.
Evolution in a Time-Varying Environment
Authors: Armstrong Robert A. , Gilpin Michael E.
Published: October 2006

A simple model of competition in a time-varying environment was developed and used to discuss the evolution of life-history strategies.
Deficiency in Rhabdomyosarcomas of a Factor Required for MyoD Activity and Myogenesis
Authors: Tapscott Stephen J. , Thayer Mathew J. , Weintraub Harold
Published: October 2006

Rhabdomyosarcoma cells express the myogenic helix-loop-helix proteins of the MyoD family but do not differentiate into skeletal muscle cells. Gel shift and transient transfection assays revealed that MyoD in the rhabdomyosarcoma cells was capable of binding DNA but was relatively nonfunctional as a transcriptional activator. Heterokaryon formation with fibroblasts resulted in the restoration of transcriptional activation by MyoD and the differentiation of the rhabdomyosarcoma cells into skeletal muscle cells. These results suggest that rhabdomyosarcomas are deficient in a factor required for MyoD activity.
Structure and Functional Expression of a Member of the Low Voltage-Activated Calcium Channel Family
Authors: Soong Tuck Wah , Stea Anthony , Hodson Connie D. , Dubel Stefan J. , Vincent Steven R. , Snutch Terry P.
Published: October 2006

Oscillatory firing patterns are an intrinsic property of some neurons and have an important function in information processing. In some cells, low voltage-activated calcium channels have been proposed to underlie a depolarizing potential that regulates bursting. The sequence of a rat brain calcium channel α
1
subunit (rbE-II) was deduced. Although it is structurally related to high voltage-activated calcium channels, the rbE-II channel transiently activated at negative membrane potentials, required a strong hyperpolarization to deinactivate, and was highly sensitive to block by nickel. In situ hybridization showed that rbE-II messenger RNA is expressed in regions throughout the central nervous system. The electrophysiological properties of the rbE-II current are consistent with a type of low voltage-activated calcium channel that requires membrane hyperpolarization for maximal activity, which suggests that rbE-II may be involved in the modulation of firing patterns.
Cloning of a Type I TGF-β Receptor and Its Effect on TGF-β Binding to the Type II Receptor
Authors: Ebner Reinhard , Chen Ruey-Hwa , Shum Lillian , Lawler Sean , Zioncheck Thomas F. , Lee Angela , Lopez Alfredo R. , Derynck Rik
Published: October 2006

Transforming growth factor-β (TGF-β) affects cellular proliferation, differentiation, and interaction with the extracellular matrix primarily through interaction with the type I and type II TGF-β receptors. The type II receptors for TGF-β and activin contain putative serine-threonine kinase domains. A murine serine-threonine kinase receptor, Tsk 7L, was cloned that shared a conserved extracellular domain with the type II TGF-β receptor. Overexpression of Tsk 7L alone did not increase cell surface binding of TGF-β, but coexpression with the type II TGF-β receptor caused TGF-β to bind to Tsk 7L, which had the size of the type I TGF-β receptor. Overexpression of Tsk 7L inhibited binding of TGF-β to the type II receptor in a dominant negative fashion. Combinatorial interactions and stoichiometric ratios between the type I and II receptors may therefore determine the extent of TGF-β binding and the resulting biological activities.
Weaver Ants: Social Establishment and Maintenance of Territory
Authors: Hölldobler Bert , Wilson Edward O.
Published: October 2006

Workers of the African weaver ant
Oecophylla longinoda
recruit nestmates to previously unoccupied space by means of odor trails laid from the rectal gland, a hitherto unrecognized musculated organ located at the rear of the rectal sac. When enemy ants and other intruders are encountered on the territory, the
Oecophylla
assemble nestmates into small resting clusters by dispensing an attractant-arrestant pheromone from the sternal gland, a second newly discovered organ located on the last abdominal sternite. Under prolonged stress, additional forces are recruited to the combat area with the aid of the rectal-gland trail substance.
Species Identification in the North American Cowbird: Appropriate Responses to Abnormal Song
Authors: King Andrew P. , West Meredith J.
Published: October 2006

Female cowbirds raised in auditory isolation from males responded to the songs of male cowbirds with copulatory postures. The songs of males reared in isolation were more effective in eliciting the posture than the songs of normally reared males. The females did not respond to the songs of other species. These results indicate one mechanism of species identification for this parasitic species.
Release of Excess Amyloid β Protein from a Mutant Amyloid β Protein Precursor
Authors: Cai Xiao-Dan , Golde Todd E. , Younkin Steven G.
Published: October 2006

The 4-kilodalton amyloid βprotein (Aβ), which forms fibrillar deposits in Alzheimer's disease (AD), is derived from a large protein referred to as the amyloid β protein precursor (βAPP). Human neuroblastoma (M17) cells transfected with constructs expressing wild-type βAPP or a mutant, βAPP
ΔNL
, recently linked to familial AD were compared. After continuous metabolic labeling for 8 hours, cells expressing β APP
ΔNL
had five times more of an Aβ-bearing, carboxyl terminal, βAPP derivative than cells expressing wild-type βAPP and they released six times more Aβ into the medium. Thus this mutant βAPP may cause AD because its processing is altered in a way that releases increased amounts of Aβ.
Regulation by Heme of Mitochondrial Protein Transport Through a Conserved Amino Acid Motif
Authors: Lathrop Julia Tait , Timko Michael P.
Published: October 2006

A conserved motif, termed the heme regulatory motif (HRM), was identified in the presequences of the erythroid δ-aminolevulinate synthase precursors and was shown to be involved in hemin inhibition of transport of these proteins into mouse mitochondria in vitro. When the HRM was inserted into the presequence of the ornithine transcarbamoylase precursor, a normally unregulated mitochondrial protein, it conferred hemin inhibition on the transport of the chimeric protein. The conserved cysteine within the HRM was shown by site-directed mutagenesis to be required for hemin inhibition.
Probing the Structure and Mechanism of Ras Protein with an Expanded Genetic Code
Authors: Chung Hyun-Ho , Benson David R. , Schultz Peter G.
Published: October 2006

Mutations in Ras protein at positions Gly
12
and Gly
13
(phosphate-binding loop L1) and at positions Ala
59
, Gly
60
, and Gln
61
(loop L4) are commonly associated with oncogenic activation. The structural and catalytic roles of these residues were probed with a series of unnatural amino acids that have unusual main chain conformations, hydrogen bonding abilities, and steric features. The properties of wild-type and transforming Ras proteins previously thought to be uniquely associated with the structure of a single amino acid at these positions were retained by mutants that contained a variety of unnatural amino acids. This expanded set of functional mutants provides new insight into the role of loop L4 residues in switch function and suggests that loop L1 may participate in the activation of Ras protein by effector molecules.
Role of the Acylated Amino Terminus of Recoverin in Ca
2+
-Dependent Membrane Interaction
Authors: Dizhoor Alexander M. , Chen Ching-Kang , Olshevskaya Elena , Sinelnikova Valeria V. , Phillipov Pavel , Hurley James B.
Published: October 2006

Recoverin, a calcium ion (Ca
2+
)-binding protein of vertebrate photoreceptors, binds to photoreceptor membranes when the Ca
2+
concentration is greater than 1 micromolar. This interaction requires a fatty acyl residue covalently linked to the recoverin amino (NH
2
)-terminus. Removal of the acyl residue, either by proteolytic cleavage of the NH
2
-terminus or by production of nonacylated recoverin, prevented recoverin from binding to membranes. The acylated recoverin NH
2
-terminus could be cleaved by trypsin only when Ca
2+
was bound to recoverin. These results suggest that the hydrophobic NH
2
-terminus is constrained in Ca
2+
-free recoverin and liberated by Ca
2+
binding. The hydrophobic acyl moiety of recoverin may interact with the membrane only when recoverin binds Ca
2+
.
Molecular Matchmakers
Authors: Sancar Aziz , Hearst John E.
Published: October 2006

Molecular matchmakers are a class of proteins that use the energy released from the hydrolysis of adenosine triphosphate to cause a conformational change in one or both components of a DNA binding protein pair to promote formation of a metastable DNA-protein complex. After matchmaking the matchmaker dissociates from the complex, permitting the matched protein to engage in other protein-protein interactions to bring about the effector function. Matchmaking is most commonly used under circumstances that require targeted, high-avidity DNA binding without relying solely on sequence specificity. Molecular matchmaking is an extensively used mechanism in repair, replication, and transcription and most likely in recombination and transposition reactions, too.
Impairment of V(D)J Recombination in Double-Strand Break Repair Mutants
Authors: Taccioli Guillermo E. , Rathbun Gary , Oltz Eugene , Stamato Thomas , Jeggo Penny A. , Alt Frederick W.
Published: October 2006

Cells maintain the integrity of their genome through an intricate network of repair systems that recognize and remove lesions from DNA. The only known site-directed recombination process in vertebrates is the V(D)J recombination of lymphocyte antigen receptor genes. A large panel of cell lines deficient in DNA repair were tested for the ability to perform V(D)J recombination after introduction of the
RAG-1
and
RAG-2
genes. Two mutants failed to generate normal V(D)J recombination, and further analysis provided evidence for two distinct nonlymphoid-specific genes that encode factors involved in both DNA repair and V(D)J recombination.
Neoplastic and Possibly Related Skin Lesions in Neotenic Tiger Salamanders from a Sewage Lagoon
Authors: Rose Francis L. , Harshbarger John C.
Published: October 2006

Tiger salamanders (
Ambystoma tigrinum
) inhabiting a sewage sedimentation lagoon become neotenic, and approximately one-third develop neoplastic skin lesions including cancer. Circumstances suggest a chemical etiology for the neoplasms.
Retinoic Acid Stimulates Regeneration of Mammalian Auditory Hair Cells
Authors: Lefebvre Philippe P. , Malgrange Brigitte , Staecker Hinrich , Moonen Gustave , Van De Water Thomas R.
Published: October 2006

Sensorineural hearing loss resulting from the loss of auditory hair cells is thought to be irreversible in mammals. This study provides evidence that retinoic acid can stimulate the regeneration in vitro of mammalian auditory hair cells in ototoxic-poisoned organ of Corti explants in the rat. In contrast, treatment with retinoic acid does not stimulate the formation of extra hair cells in control cultures of Corti's organ. Retinoic acid-stimulated hair cell regeneration can be blocked by cytosine arabinoside, which suggests that a period of mitosis is required for the regeneration of auditory hair cells in this system. These results provide hope for a recovery of hearing function in mammals after auditory hair cell damage.
Internal Calcium Changes in a Bursting Pacemaker Neuron Measured with Arsenazo III
Authors: Thomas M. V. , Gorman A. L. F.
Published: October 2006

Arsenazo III was used to measure changes in the free intracellular calcium ion concentration during spontaneous bursting pacemaker activity in the
Aplysia
R15 neuron. Intracellular calcium increased during the burst, and this increase was sufficient to cause the hyperpolarization that followed. The results suggest that the interval between bursts is determined by the rate of subsequent decline of free intracellular calcium.
Partial Denervation Affects Both Denervated and Innervated Fibers in the Mammalian Skeletal Muscle
Authors: Cangiano A. , Lutzemberger L.
Published: October 2006

Partial denervation of the rat extensor digitorum longus muscle was performed by sectioning only one of the sciatic nerve roots. Measurements of spike resistance to tetrodotoxin in individual muscle fibers revealed denervation changes not only in the denervated fibers but also in the adjacent innervated ones. The results support the concept that products of nerve degeneration play a role in the origin of muscle changes induced by denervation.
Classical Conditioning with Auditory Discrimination of the Eye Blink in Decerebrate Cats
Authors: Norman R. J. , Buchwald J. S. , Villablanca J. R.
Published: October 2006

Cats were subjected to complete lower brainstem transection, and were then tested for learning ability according to a classical conditioning paradigm. An auditory stimulus was systematically paired with a brief shock to the eyelid. Within a few weeks after the operation, the decerebrate cats could learn the conditioned response with a tone frequency discrimination and then a discrimination reversal. Our results support the notion that the brainstem reticular formation can support a conditioned response which is behaviorally similar to that obtained in the intact animal.
Multistranded Helix in Xanthan Polysaccharide
Authors: Holzwarth G. , Prestridge E. B.
Published: October 2006

The extracellular polysaccharide xanthan is shown by electron microscopy to be an unbranched, probably double-stranded fiber 4 nanometers wide and 2 to 10 micrometers long when native. Denaturation yields a single strand only 2 nanometers wide and 0.3 to 1.8 micrometers long. Renatured xanthan shows short unraveled regions with two or three strands arranged in a right-handed twist.
Testing the Commitment Theory of Cellular Aging
Authors: Holliday R. , Huschtscha L. I. , Tarrant G. M. , Kirkwood T. B. L.
Published: October 2006

The commitment theory may explain both the finite lifespan of diploid fibroblasts and the apparent immortality of transformed lines. Potentially immortal cells are assumed on division to generate with some fixed probability cells committed to senesce after a specific number of divisions. During the period between commitment and senescence, cells are assumed to maintain normal growth so that the uncommitted cells are diluted by committed ones and may ultimately be lost in subculturing. A number of predictions of this model are described and experiments strongly supporting the theory are reported. We conclude that the limited growth of diploid fibroblasts is, in effect, an artifact of normal culturing procedures.
A Phantom-Motion Aftereffect
Authors: Weisstein Naomi , Maguire William , Berbaum Kevin
Published: October 2006

Motion aftereffects, typically found to result only from localized retinal stimulation, were obtained within regions of the visual field that had not been stimulated by moving contours. "Phantom" stripes are seen moving through a physically homogeneous (empty) region of the visual field when vertical stripes move above and below that region. Immediately afterward, stationary stripes in the previously empty region appear to move in the opposite direction. This phantom-motion aftereffect provides a novel instance of the way global structure affects processes that have been assumed to be influenced only by simpler local spatial and temporal variables.
Fascioliasis: Role of Proline in Bile Duct Hyperplasia
Authors: Isseroff Hadar , Sawma Joseph T. , Reino David
Published: October 2006

In animals with fascioliasis, extensive hyperplasia of the main bile duct occurs that often results in enlargement of the duct to more than 20 times the normal. We report that proline infused into the abdominal cavity of rats caused hyperplasia of the bile duct resembling that produced in the early stages of the disease. We suggest that
Fasciola hepatica
, which synthesizes and releases large amounts of proline, induces enlargement of the bile duct by a similar mechanism.
Measurement of the Human Magnetic Heart Vector
Authors: Barry William H. , Fairbank William M. , Harrison Donald C. , Lehrman Kenneth L. , Malmivuo Jaakko A. V. , Wikswo John P.
Published: October 2006

A unipositional lead system has been developed to record the human magnetic heart vector and to permit comparison with the electric heart vector recorded with a conventional Frank lead system. Recordings made in five normal subjects showed a remarkably consistent relation between the electric and magnetic heart vectors. However, the angle between electric heart vector
R
and
T
waves was markedly different from the magnetic heart vector
R
-
T
angle. In addition, recordings made in two patients with bundle branch block showed a different relation between the electric and magnetic heart vectors compared to normal subjects. These data support the hypothesis that magnetic measurements have a different sensitivity to some components of cardiac activation compared with body surface potential measurements.
Time-Resolved Spectroscopy of Hemoglobin and Its Complexes with Subpicosecond Optical Pulsess
Authors: Shank C. V. , Ippen E. P. , Bersohn R.
Published: October 2006

Subpicosecond optical pulses have been used to study the photolysis of hemoglobin complexes. Photodissociation of carboxyhemoglobin is found to occur in less than 0.5 picosecond. In hemoglobin and oxyhemoglobin a nondissociative excited state recovery in 2.5 picoseconds is observed.
Elevated Plasma Zinc: A Heritable Anomaly
Authors: Smith J. Cecil , Zeller Jack A. , Brown Ellen D. , Ong S. C.
Published: October 2006

An extremely high concentration of zinc in the plasma (hyperzincemia) was found in five out of seven members of one family and in two out of three second-generation individuals, an indication that the condition is heritable. The excess zinc in the plasma appears to be bound to serum proteins, with no apparent clinical symptoms or abnormalities.
A Multistable Movement Display: Evidence for Two Separate Motion Systems in Human Vision
Authors: Pantle Allan , Picciano Lucinda
Published: October 2006

Two competing sensations of apparent movement were produced by the rapid alternation of two multielement stimulus frames. Either sensation could be made dominant by appropriate manipulations of the stimulus display. The results suggest that there are two systems capable of generating movement signals in man. One system depends on preliminary processing of form, and the second system does not.
Genetic Composition of a High-Yielding Influenza A Virus Recombinant: A Vaccine Strain Against "Swine" Influenza
Authors: Palese Peter , Ritchey Mary B. , Schulman Jerome L. , Kilbourne Edwin D.
Published: October 2006

Analysis of the RNA migration pattern of a high-yielding influenza virus recombinant, X-53, used in vaccine production, reveals that only the two genes coding for hemagglutinin and neuraminidase antigens were derived from the "swine" influenza virus parent. A/New Jersey/11/76, while six were acquired from the A/PR/8/34 (H0N1) parent, donor of the high yield characteristic.