bluuebunny/crossref_metadata_2025 huggingface dataset:
Gonadal Hormones Induce Dendritic Growth in the Adult Avian Brain
Authors: DeVoogd Timothy , Nottebohm Fernando
Published: October 2006

Ovariectomized adult female canaries were treated with physiological doses of testosterone, dihydrotestosterone, or estradiol. Singing, which is typical of males, occurred in the testosterone-treated birds but not in any of the other birds. The effect of these hormones was assessed on dendrites from a class of neurons in the nucleus robustus archistriatalis (RA), a forebrain nucleus for song control. The RA neurons of the testosterone-treated birds had dendritic trees resembling those of intact males. The RA neurons of the estradiol- and dihydrotestosterone-treated birds resembled those of intact females. All hormone-treated groups had dendrites that were significantly longer than those of untreated ovariectomized females. Thus gonadal hormones induce dendritic growth in the adult avian brain.
Modulation of Parallel Fiber Excitability by Postsynaptically Mediated Changes in Extracellular Potassium
Authors: Malenka Robert C. , Kocsis Jeffery D. , Ransom Bruce R. , Waxman Stephen G.
Published: October 2006

Field potentials and extracellular potassium concentration ([K
+
]
o
) were simultaneously monitored in the molecular layer of the rat cerebellar cortex during stimulation of the parallel fibers. The synaptic field potential elicited by stimulation was reduced by several methods. Reduction of synaptic field potentials was accompanied by a marked increase in the excitability of the parallel fibers. This change in excitability was related to the degree of extracellular K
+
accumulation associated with parallel fiber stimulation. These findings support the proposal that increases in [K
+
]
o
associated with activity in postsynaptic elements can modulate the excitability of presynaptic afferent fibers.
Slow-Wave Sleep: A Recovery Period After Exercise
Authors: Shapiro Colin M. , Bortz Ralph , Mitchell Duncan , Bartel Peter , Jooste Pieter
Published: October 2006

Sleep recordings were carried out on athletes on four successive nights after completing a 92-kilometer road race. Significant increases in total sleep time and slow-wave sleep were found after this metabolic stress. The results show a definite exercise effect on sleep and support sleep-restoration hypotheses.
Disappearance of Stabilized Chromatic Gratings
Authors: Kelly D. H.
Published: October 2006

When the image of a stationary, sinusoidal luminance grating is stabilized on the retina of a human subject, he becomes unable to detect this stimulus at contrasts that are readily visible in normal, unstabilized vision. At much higher contrasts, such stabilized gratings can still be seen over most of the normal range of spatial frequencies, although the threshold contrast may be increased by as much as 20 or 30 times. When the analogous experiment is performed with an isoluminance chromatic grating, however, there is no contrast that can restore the visibility of the stabilized grating; the threshold elevations for stabilized chromatic gratings are too great to measure. Saturated red/green gratings fade out and disappear at 100 percent contrast (even where this is 45 times the unstabilized threshold), and they do not reappear as long as stabilization is maintained. Without some kind of temporal variation of the proximal stimulus, the opponent-color pathways apparently do not respond to spatial patterns.
Disorders of Human Hemoglobin
Authors: Bank Arthur , Mears J. Gregory , Ramirez Francesco
Published: October 2006

Studies of the human hemoglobin system have provided new insights into the regulation of expression of a group of linked human genes, the γ-δ-β-globin gene complex in man. In particular, the thalassemia syndromes and related disorders of man are inherited anemias that provide mutations for the study of the regulation of globin gene expression. New methods, including restriction enzyme analysis and cloning of cellular DNA, have made it feasible to define more precisely the structure and organization of the globin genes in cellular DNA. Deletions of specific globin gene fragments have already been found in certain of these disorders and have been applied in prenatal diagnosis.
Temperature Sensitivity of Tone in the Rabbit Facial Vein: Myogenic Mechanism for Cranial Thermoregulation?
Authors: Winquist Raymond J. , Bevan John A.
Published: October 2006

Intrinsic myogenic tone in the buccal segment of the rabbit facial vein is exquisitely sensitive to small changes in temperature in the range 33° to 44°C. This particular venous segment also exhibits a preponderance of β-adrenergic receptors and receives a dense, medial sympathetic innervation. This area of the vein is proposed to act as a temperature-sensitive sphincter that distributes cooled nasal venous blood between superficial and deep venous drainage systems in the head and neck. Deviation of cool blood to deeper venous sinuses has been shown to be an important thermoregulatory mechanism.
Does Malnutrition Affect Fecundity? A Summary of Evidence
Authors: Bongaarts John
Published: October 2006

Moderate chronic malnutrition has only a minor effect on fecundity (reproductive capacity), and the resulting effect on fertility (actual reproduction) is very small. Among the fecundity components examined here in noncontracepting populations, age at menarche and the duration of lactational amenorrhea appear to be the ones most affected by malnutrition. But from neither of those effects can a difference in fertility of more than a few percent be expected between poorly and well-nourished women in developing countries.
Specific Locus Mutations Induced in Somatic Cells of Rats by Orally and Parenterally Administered Procarbazine
Authors: Maier P. , Zbinden G.
Published: October 2006

A new test, the granuloma pouch assay, was used in detecting specific locus mutations in somatic cells of rats in vivo after the animals were treated orally and parenterally with procarbazine hydrochloride, an agent used in cancer chemotherapy. The results indicate that stable intermediates are formed in the body and distributed as proximate mutagens.
Cerebral Regional Oxygen Consumption and Supply in Anesthetized Cat
Authors: Buckweitz Ellen , Sinha Arabinda K. , Weiss Harvey R.
Published: October 2006

The study involved quantitative measurement of arterial and venous oxygen saturation, oxygen extraction, blood flow, and oxygen consumption in specific areas of the brain. No regional differences in oxygen consumption were found in anesthetized cat brain, and the amount of oxygen available to all regions studied was more than 2.5 times the consumption throughout the brain.
Carcinogenic Activity of Particulate Nickel Compounds Is Proportional to Their Cellular Uptake
Authors: Costa Max , Mollenhauer Hilton H.
Published: October 2006

Particles (≤5 micrometers) of the potent carcinogen crystalline nickel subsulfide were actively phagocytized by cultures of Syrian hamster embryo cells and Chinese hamster ovary cells. Cells did not take up significant quantities of similar-sized particles of the noncarcinogen amorphous nickel monosulfide. The carcinogenic activity of this and other metal compounds appears to be proportional to their cellular uptake.
Environmental Influences on Body Weight and Behavior in Developing Rats After Neonatal 6-Hydroxydopamine
Authors: Pearson David E. , Teicher Martin H. , Shaywitz Bennett A. , Cohen Donald J. , Young J. Gerald , Anderson George M.
Published: October 2006

There is less hyperactive motor activity and better avoidance performance in rat pups treated with 6-hydroxydopamine as neonates and reared with vehicle-treated littermates than in pups reared in litters composed solely of other 6-hydroxydopamine-treated animals. Thus, in this experimental model of hyperactivity, an environmental manipulation provides an alternative to pharmacologic agents in reducing activity and improving learning performance.
Trophic Interactions Between Astroglial Cells and Hippocampal Neurons in Culture
Authors: Banker Gary A.
Published: October 2006

Astroglial cells in primary culture release factors into the medium that promote the growth and prolong the survival of rat hippocampal neurons in vitro.
Transporting Renal Epithelium: Culture in Hormonally Defined Serum-Free Medium
Authors: Jefferson Douglas M. , Cobb Melanie H. , Gennaro Joseph F. , Scott Walter N.
Published: October 2006

A hormonally defined medium was used to isolate a homogeneous epithelioid cell population from canine kidney. Monolayers of these cells form domes, an indication of active ion transport, and this process is inhibited by ouabain. This technique allows the isolation of primary cultures of renal epithelial cells, free of fibroblasts, for the characterization of biochemical and physiological properties related to renal function.
Developmental Equations for the Electroencephalogram
Authors: John E. R. , Ahn H. , Prichep L. , Trepetin M. , Brown D. , Kaye H.
Published: October 2006

Thirty-two linear regression equations predict the frequency composition of the electroencephalogram within four frequency bands, for four bilateral regions of the brain, as a function of age. Equations based on such data from large groups of healthy children in the United States and Sweden are closely similar. These equations describe the development of the electrical activity of the normal human brain, independent of cultural, ethnic, socioeconomic, or sex factors.
Geologic Storage of Radioactive Waste: Field Studies in Sweden
Authors: Witherspoon P. A. , Cook N. G. W. , Gale J. E.
Published: October 2006

Access to a granitic rock mass in an iron ore mine in Sweden provided a unique opportunity for underground experiments related to the geologic disposal of radioactive waste. These field tests demonstrated the importance of hydrogeology and the difficulties in predicting the thermomechanical behavior of fractured granitic rocks. To characterize a site fully, measurements made from the surface must be supplemented by extensive subsurface measurements and experiments. Much effort is needed at this stage to generate the technology required for the development of waste repositories.
Aspirin Prevention of Cholesterol Gallstone Formation in Prairie Dogs
Authors: Lee Sum P. , Carey Martin C. , LaMont J. Thomas
Published: October 2006

When prairie dogs (
Cynomys ludovicianus
) are fed a diet containing cholesterol, a marked increase in gallbladder mucin secretion parallels the evolution of cholesterol supersaturated bile. Gelation of mucin precedes the precipitation of cholesterol liquid and solid crystals and the development of gallstones. Aspirin given to prairie dogs inhibited mucin hypersecretion and gel accumulation and prevented gallstone formation without influencing the cholesterol content of supersaturated bile. This suggests that gallbladder mucin is a nucleation matrix for cholesterol gallstones.
Analysis of CD36 Binding Domains: Ligand Specificity Controlled by Dephosphorylation of an Ectodomain
Authors: Asch Adam S. , Liu Isaac , Briccetti Frederick M. , Barnwell John W. , Kwakye-Berko Frank , Dokun Ayotunde , Goldberger Jeffrey , Pernambuco Mona
Published: October 2006

The protein CD36 is a membrane receptor for thrombospondin (TSP), malaria-infected erythrocytes, and collagen. Three functional sequences were identified within a single disulfide loop of CD36: one that mediates TSP binding (amino acids 87 to 99) and two that support malarial cytoadhesion (amino acids 8 to 21 and 97 to 110). One of these peptides (p87-99) is a consensus protein kinase C (PKC) phosphorylation site. Dephosphorylation of constitutively phosphorylated CD36 in resting platelets and a megakaryocytic cell line led to the loss of collagen adhesion and platelet reactivity to collagen, with a reciprocal increase in TSP binding. PKC-mediated phosphorylation of this ectodomain resulted in a loss of TSP binding and the reciprocal acquisition of collagen binding. In site-directed mutagenesis studies, when the threonine phosphorylation site was changed to alanine, CD36 was expressed in a dephosphorylated state and bound to TSP constitutively.
Specific Association of Human Telomerase Activity with Immortal Cells and Cancer
Authors: Kim Nam W. , Piatyszek Mieczyslaw A. , Prowse Karen R. , Harley Calvin B. , West Michael D. , Ho Peter L. C. , Coviello Gina M. , Wright Woodring E. , Weinrich Scott L. , Shay Jerry W.
Published: October 2006

Synthesis of DNA at chromosome ends by telomerase may be necessary for indefinite proliferation of human cells. A highly sensitive assay for measuring telomerase activity was developed. In cultured cells representing 18 different human tissues, 98 of 100 immortal and none of 22 mortal populations were positive for telomerase. Similarly, 90 of 101 biopsies representing 12 human tumor types and none of 50 normal somatic tissues were positive. Normal ovaries and testes were positive, but benign tumors such as fibroids were negative. Thus, telomerase appears to be stringently repressed in normal human somatic tissues but reactivated in cancer, where immortal cells are likely required to maintain tumor growth.
An Osmosensing Signal Transduction Pathway in Yeast
Authors: Brewster Jay L. , de Valoir Tamsen , Dwyer Noelle D. , Winter Edward , Gustin Michael C.
Published: October 2006

Yeast genes were isolated that are required for restoring the osmotic gradient across the cell membrane in response to increased external osmolarity. Two of these genes,
HOG1
and
PBS2
, encode members of the mitogen-activated protein kinase (MAP kinase) and MAP kinase kinase gene families, respectively. MAP kinases are activated by extracellular ligands such as growth factors and function as intermediate kinases in protein phosphorylation cascades. A rapid,
PBS2
-dependent tyrosine phosphorylation of
HOG1
protein occurred in response to increases in extracellular osmolarity. These data define a signal transduction pathway that is activated by changes in the osmolarity of the extracellular environment.
Developmental Regulation of Neural Response to FGF-1 and FGF-2 by Heparan Sulfate Proteoglycan
Authors: Nurcombe Victor , Ford Miriam D. , Wildschut Jason A. , Bartlett Perry F.
Published: October 2006

Murine neural precursor cells and cell lines derived from them are stimulated by members of the heparin-binding fibroblast growth factor (FGF) family. The activity of FGF is regulated by heparan sulfate proteoglycans (HSPGs), and this interaction is an essential prerequisite for the binding of growth factor to the signal transducing receptors. Messenger RNA for FGF-2 was detectable in the neuroepithelium at embryonic day 9, and the HSPGs produced by these cells at this time preferentially bound FGF-2. However, at embryonic day 11, when messenger RNA for FGF-1 was first detectable, there was a switch in the binding specificity of the HSPG to FGF-1. Thus, a single species of HSPG undergoes a rapid, tightly controlled change in growth factor-binding specificity concomitant with the temporal expression of the FGFs.
Spatially Resolved Dynamics of cAMP and Protein Kinase A Subunits in
Aplysia
Sensory Neurons
Authors: Bacskai Brian J. , Hochner Binyamin , Mahaut-Smith Martyn , Adams Stephen R. , Kaang Bong-Kiun , Kandel Eric R. , Tsien Roger Y.
Published: October 2006

Cyclic adenosine monophosphate (cAMP)-dependent protein kinase, labeled with fluorescein and rhodamine on the catalytic and regulatory subunits, respectively, was injected into
Aplysia
sensory neurons either in culture or in intact cell clusters. Energy transfer between the subunits, a measure of cytosolic cAMP concentration ([cAMP]), and compartmentation of the dissociated subunits were monitored by confocal fluorescence microscopy. Bath application of serotonin produced a much greater elevation of [cAMP] in the processes than in the central bodies of the neurons. The resulting gradients must drive a sizable centripetal flux of cAMP because direct microinjection of cAMP showed that it diffused readily. Perinuclear increases in [cAMP] slowly caused the translocation of the freed catalytic subunit into the nucleus to an extent proportional to the percentage of its dissociation from the regulatory subunit.
Preferential Migration of Activated CD4
+
and CD8
+
T Cells in Response to MIP-1α and MIP-1β
Authors: Taub Dennis D. , Conlon Kevin , Lloyd Andrew R. , Oppenheim Joost J. , Kelvin David J.
Published: October 2006

Recombinant human macrophage inflammatory protein-1α (rhMIP-1α) and rhMIP-1β were potent chemoattractants of human T lymphocytes. These rhMIP-1 cytokines attracted only T cells activated by monoclonal antibody to CD3 and did not attract unstimulated lymphocytes. Phenotypic analysis revealed that CD4
+
T cells were capable of migrating in response to rhMIP-1β, whereas rhMIP-1α induced chemotaxis of predominantly CD8
+
T lymphocytes. Activated naive and memory T cells also migrated in response to rhMIP-1 cytokines. Furthermore, these cytokines enhanced the ability of T cells to bind to an endothelial cell monolayer. These results suggest that rhMIP-1 cytokines preferentially recruit specific T cell subsets during the evolution of the immune response.
Primers for Mitochondrial DNA Replication Generated by Endonuclease G
Authors: Côté Jacques , Ruiz-Carrillo Adolf
Published: October 2006

Endonuclease G (Endo G) is widely distributed among animals and cleaves DNA at double-stranded (dG)

n

⋅(dC)

n

and at single-stranded (dC)

n

tracts. Endo G is synthesized as a propeptide with an amino-terminal presequence that targets the nuclease to mitochondria. Endo G can also be detected in extranucleolar chromatin. In addition to deoxyribonuclease activities, Endo G also has ribonuclease (RNase) and RNase H activities and specifically cleaves mouse mitochondrial RNA and DNA-RNA substrates containing the origin of heavy-strand DNA replication (O
H
). The cleavage sites match those found in vivo, indicating that Endo G is capable of generating the RNA primers required by DNA polymerase γ to initiate replication of mitochondrial DNA.
A Receptor for the Malarial Parasite
Plasmodium vivax
: the Erythrocyte Chemokine Receptor
Authors: Horuk Richard , Chitnis Chetan E. , Darbonne Walter C. , Colby Timothy J. , Rybicki Anne , Hadley Terence J. , Miller Louis H.
Published: October 2006

Plasmodium vivax
and
P. falciparum
are the major causes of human malaria, except in sub-Saharan Africa where people lack the Duffy blood group antigen, the erythrocyte receptor for
P. vivax
. Duffy negative human erythrocytes are resistant to invasion by
P. vivax
and the related monkey malaria,
P. knowlesi
. Several lines of evidence in the present study indicate that the Duffy blood group antigen is the erythrocyte receptor for the chemokines interleukin-8 (IL-8) and melanoma growth stimulatory activity (MGSA). First, IL-8 binds minimally to Duffy negative erythrocytes. Second, a monoclonal antibody to the Duffy blood group antigen blocked binding of IL-8 and other chemokines to Duffy positive erythrocytes. Third, both MGSA and IL-8 blocked the binding of the parasite ligand and the invasion of human erythrocytes by
P. knowlesi
, suggesting the possibility of receptor blockade for anti-malarial therapy.
Prevention of Collagen-Induced Arthritis with an Antibody to gp39, the Ligand for CD40
Authors: Durie Fiona H. , Fava Roy A. , Foy Teresa M. , Aruffo Alejandro , Ledbetter Jeffrey A. , Noelle Randolph J.
Published: October 2006

The ligand for the CD40 antigen is a 39-kilodalton protein, gp39, expressed on the surface of activated CD4
+
T cells and is essential for thymus-dependent humoral immunity. The role of gp39-CD40 interactions in autoimmune disease was investigated in vivo with the use of an antibody that blocks their interactions (anti-gp39). Arthritis induced in mice by immunization with type II collagen was inhibited by anti-gp39. Anti-gp39 blocked the development of joint inflammation, serum antibody titers to collagen, the infiltration of inflammatory cells into the subsynovial tissue, and the erosion of cartilage and bone. Thus, interference with gp39-CD40 interactions may have therapeutic potential in the treatment of autoimmune disease.
Isolation of New Ribozymes from a Large Pool of Random Sequences
Authors: Bartel David P. , Szostak Jack W.
Published: October 2006

An iterative in vitro selection procedure was used to isolate a new class of catalytic RNAs (ribozymes) from a large pool of random-sequence RNA molecules. These ribozymes ligate two RNA molecules that are aligned on a template by catalyzing the attack of a 3′-hydroxyl on an adjacent 5′-triphosphate—a reaction similar to that employed by the familiar protein enzymes that synthesize RNA. The corresponding uncatalyzed reaction also yields a 3′,5′-phosphodiester bond. In vitro evolution of the population of new ribozymes led to improvement of the average ligation activity and the emergence of ribozymes with reaction rates 7 million times faster than the uncatalyzed reaction rate.
Estrogenic Activity of the Insecticide Kepone on the Chicken Oviduct
Authors: Palmiter Richard D. , Mulvihill Eileen R.
Published: October 2006

Kepone induces ovalbumin and conalbumin synthesis in explants of chick oviduct in vitro by acting as a weak estrogen. It binds to the nuclear estrogen receptor and is antagonized by the antiestrogen tamoxifen. Kepone also induces egg white protein synthesis in vivo by direct interaction with estrogen receptors and by indirectly increasing the concentration of progesterone in the serum.
Antibacterial Synergism: A Proposal for Chemotherapeutic Potentiation Between Trimethoprim and Sulfamethoxazole
Authors: Poe Martin
Published: October 2006

Sulfamethoxazole and other sulfa drugs are moderately potent inhibitors of Escherichia coli dihydrofolate reductase. They also significantly potentiate the inhibition of this enzyme by trimethoprim. The molecular basis for inhibition potentiation is the simultaneous binding of trimethoprim and sulfa by the enzyme. This potentiation may explain the synergism observed when these drugs are used in antibacterial chemotherapy.
Calcium and Secretion: Distinction Between Two Pools of Glucose-Sensitive Calcium in Pancreatic Islets
Authors: Hellman B. , Sehlin J. , Täljedal I.-B.
Published: October 2006

D-Glucose, but not L-glucose or 3-O-methyl-D-glucose, stimulates
45
Ca
2+
uptake by both lanthanum-displaceable and lanthanum-nondisplaceable pools in pancreatic islets. The nondisplaceable pool probably represents secretory granules, while the displaceable pool may be located in the β-cell membrane. Kinetic studies with isotopically labeled islets suggest that only the displaceable pool participates in the short-term coupling of the glucose stimulus with secretion.
Transmissible Mink Encephalopathy: Infectivity of Corneal Epithelium
Authors: Marsh Richard F. , Hanson Robert P.
Published: October 2006

Corneal epithelium from hamsters dying of transmissible mink encephalopathy contained a virus titer of 10
-4.8
times the 50 percent lethal dose (10
-4.8
LD
50
) per 0.05 milliliter when assayed as a cell suspension derived directly from the infected animal. After one passage in tissue culture, an equivalent concentration of cells contained only 10
-0.8
LD
50
per 0.05 milliliter. It is concluded that corneal tissues are infectious; the infectivity may be mainly associated with free nerve endings. However, the most important immediate inference is that corneas from human beings affected with Creutzfeldt-Jakob disease are likely to be lethal if transplanted to healthy recipients.
Dormancy of Inhibitory Interneurons in a Model of Temporal Lobe Epilepsy
Authors: Bekenstein Jonathan W. , Lothman Eric W.
Published: October 2006

In humans temporal lobe epilepsy (TLE) is characterized by recurrent seizures, neuronal hyperexcitability, and selective loss of certain neuronal populations in the hippocampus. Animal models of the condition indicate that a diminution of inhibition mediated by gamma-aminobutyric acid (GABA) accounts for the altered function, and it has been hypothesized that the diminution arises because GABAergic basket interneurons are "dormant" as a result of their being disconnected from excitatory inputs. In hippocampal slices, inhibitory postsynaptic potentials (IPSPs) were elicited in CA1 pyramidal cells by activation of basket cells; responses from an animal model of TLE were compared to those from control tissue. IPSPs evoked indirectly by activation of terminals that then excited basket cells were reduced in the epileptic tissue, whereas IPSPs evoked by direct activation of basket cells, when excitatory neurotransmission was blocked, were not different from controls. These results provide support for the "dormant basket cell" hypothesis and have implications for the pathophysiology and treatment of human TLE.
"Infectious" Transplantation Tolerance
Authors: Qin Shixin , Cobbold Stephen P. , Pope Heather , Elliott James , Kioussis Dimitris , Davies Joanna , Waldmann Herman
Published: October 2006

The maintenance of transplantation tolerance induced in adult mice after short-term treatment with nonlytic monoclonal antibodies to CD4 and CD8 was investigated. CD4
+
T cells from tolerant mice disabled naïve lymphocytes so that they too could not reject the graft. The naive lymphocytes that had been so disabled also became tolerant and, in turn, developed the capacity to specifically disable other naive lymphocytes. This process of "infectious" tolerance explains why no further immunosuppression was needed to maintain long-term transplantation tolerance.
Slow Axonal Transport of Neurofilament Proteins: Impairment of β,β′-Iminodipropionitrile Administration
Authors: Griffin John W. , Hoffman Paul N. , Clark Arthur W. , Carroll Patrick T. , Price Donald L.
Published: October 2006

β,β′-Iminodipropionitrile (IDPN) administration prevented normal slow axonal transport of [
35
S]methionine- or [
3
H]leucine-labeled proteins in rat sciatic motor axons. Ultrastructural and electrophoretic studies showed that the neurofilament triplet proteins in particular were retained within the initial 5 millimeters of the axons, resulting in neurofilament-filled axonal swellings. Fast anterograde and retrograde axonal transport were not affected. The IDPN thus selectively impaired slow axonal transport. The neurofibrillary pathology in this model is the result of the defective slow transport of neurofilaments.
Erythrocyte P Antigen: Cellular Receptor for B19 Parvovirus
Authors: Brown Kevin E. , Anderson Stacie M. , Young Neal S.
Published: October 2006

The pathogenic human parvovirus B19 replicates only in erythroid progenitor cells. This virus was shown to bind to blood-group P antigen, as measured by hemagglutination. Erythrocytes lacking P antigen were not agglutinated with B19. Purified P antigen (globoside) blocked the binding of the virus to erythroid cells and the infectivity of the virus in a hematopoietic colony assay. Target cells were protected from infection by preincubation with monoclonal antibody to globoside. Knowledge of a parvovirus receptor has implications for understanding the pathogenesis of parvovirus infections and for the use of parvoviruses in gene therapy.
Protein Ladder Sequencing
Authors: Chait Brian T. , Wang Rong , Beavis Ronald C. , Kent Stephen B. H.
Published: October 2006

A new approach to protein sequencing is described. It consists of two steps: (i) ladder-generating chemistry, the controlled generation from a polypeptide chain by wet chemistry of a family of sequence-defining peptide fragments, each differing from the next by one amino acid; and (ii) data readout, a one-step readout of the resulting protein sequencing ladder by matrix-assisted laser-desorption mass spectrometry. Each amino acid was identified from the mass difference between successive peaks, and the position in the data set defined the sequence of the original peptide chain. This method was used to directly locate a phosphoserine residue in a phosphopeptide. The protein ladder sequencing method lends itself to very high sample throughput at very low per cycle cost.
Thalamocortical Oscillations in the Sleeping and Aroused Brain
Authors: Steriade Mircea , McCormick David A. , Sejnowski Terrence J.
Published: October 2006

Sleep is characterized by synchronized events in billions of synaptically coupled neurons in thalamocortical systems. The activation of a series of neuromodulatory transmitter systems during awakening blocks low-frequency oscillations, induces fast rhythms, and allows the brain to recover full responsiveness. Analysis of cortical and thalamic networks at many levels, from molecules to single neurons to large neuronal assemblies, with a variety of techniques, ranging from intracellular recordings in vivo and in vitro to computer simulations, is beginning to yield insights into the mechanisms of the generation, modulation, and function of brain oscillations.
Gene Replacement in
Toxoplasma gondii
with Chloramphenicol Acetyltransferase as Selectable Marker
Authors: Kim Kami , Soldati Dominique , Boothroyd John C.
Published: October 2006

A system for stable transformation of
Toxoplasma gondii
tachyzoites was developed that exploited the susceptibility of
Toxoplasma
to chloramphenicol. Introduction of the chloramphenicol acetyltransferase (CAT) gene fused to
Toxoplasma
flanking sequences followed by chloramphenicol selection resulted in parasites stably expressing CAT. A construct incorporating the tandemly repeated gene,
B1
, targeted efficiently to its homologous chromosomal locus. Knockout of the single-copy gene,
ROP1
, was also successful. Stable transformation should permit the identification and analysis of
Toxoplasma
genes important in the interaction of this opportunistic parasite with its host.
Activating Factor for the Iron Protein of Nitrogenase from
Rhodospirillum rubrum
Authors: Ludden Paul W. , Burris R. H.
Published: October 2006

As isolated from
Rhodospirillum rubrum
, the iron protein of nitrogenase has little or no activity. It can be activated by incubating it with a trypsin-sensitive, oxygen-labile component (activating factor) plus adenosine triphosphate and a divalent metal ion. After activation, the iron protein retains its nitrogenase activity when the activating factor is removed.
The
Caenorhabditis elegans
unc-17
Gene: a Putative Vesicular Acetylcholine Transporter
Authors: Alfonso Aixa , Grundahl Kiely , Duerr Janet S. , Han He-Ping , Rand James B.
Published: October 2006

Mutations in the
unc-17
gene of the nematode
Caenorhabditis elegans
produce deficits in neuromuscular function. This gene was cloned and complementary DNAs were sequenced. On the basis of sequence similarity to mammalian vesicular transporters of biogenic amines and of localization to synaptic vesicles of cholinergic neurons in C. elegans,
unc-17
likely encodes the vesicular transporter of acetylcholine. Mutations that eliminated all
unc-17
gene function were lethal, suggesting that the acetylcholine transporter is essential. Molecular analysis of
unc-17
mutations will allow the correlation of specific parts of the gene (and the protein) with observed functional defects. The mutants will also be useful for the isolation of extragenic suppressors, which could identify genes encoding proteins that interact with UNC-17.
Amyotrophic Lateral Ssclerosis and Structural Defects in Cu,Zn Superoxide Dismutase
Authors: Deng Han-Xiang , Hentati Afif , Tainer John A. , Iqbal Zafar , Cayabyab Annarueber , Hung Wu-Yen , Getzoff Elizabeth D. , Hu Ping , Herzfeldt Brian , Roos Raymond P. , Warner Carolyn , Deng Gang , Soriano Edwin , Smyth Celestine , Parge Hans E. , Ahmed Aftab , Roses Allen D. , Hallewell Robert A. , Pericak-Vance Margaret A. , Siddique Teepu
Published: October 2006

Single-site mutants in the Cu,Zn superoxide dismutase (SOD) gene (
SOD1
) occur in patients with the fatal neurodegenerative disorder familial amyotrophic lateral sclerosis (FALS). Complete screening of the
SOD1
coding region revealed that the mutation Ala
4
to Val in exon 1 was the most frequent one; mutations were identified in exons 2, 4, and 5 but not in the active site region formed by exon 3. The 2.4 Å crystal structure of human SOD, along with two other SOD structures, established that all 12 observed FALS mutant sites alter conserved interactions critical to the β-barrel fold and dimer contact, rather than catalysis. Red cells from heterozygotes had less than 50 percent normal SOD activity, consistent with a structurally defective SOD dimer. Thus, defective SOD is linked to motor neuron death and carries implications for understanding and possible treatment of FALS.
Dynamics of the Hippocampal Ensemble Code for Space
Authors: Wilson Matthew A. , McNaughton Bruce L.
Published: October 2006

Ensemble recordings of 73 to 148 rat hippocampal neurons were used to predict accurately the animals' movement through their environment, which confirms that the hippocampus transmits an ensemble code for location. In a novel space, the ensemble code was initially less robust but improved rapidly with exploration. During this period, the activity of many inhibitory cells was suppressed, which suggests that new spatial information creates conditions in the hippocampal circuitry that are conducive to the synaptic modification presumed to be involved in learning. Development of a new population code for a novel environment did not substantially alter the code for a familiar one, which suggests that the interference between the two spatial representations was very small. The parallel recording methods outlined here make possible the study of the dynamics of neuronal interactions during unique behavioral events.
Differential Sensitivity for Smell: "Noise" at the Nose
Authors: Cain William S.
Published: October 2006

The ability of subjects to resolve differences in concentration of chemicals in the vapor phase by smell rivaled the optimum performance of chromatographs. In some instances, subjects resolved a difference in concentration of only 5 percent. The reported inability of olfaction to register fine differences in intensity seems to be largely a result of fluctuations in the stimulus.
Stimulation of Human Periaqueductal Gray for Pain Relief Increases Immunoreactive β-endorphin in Ventricular Fluid
Authors: Hosobuchi Yoshio , Rossier Jean , Bloom Floyd E. , Guillemin Roger
Published: October 2006

Immunoreactive β-endorphin was measured in the ventricular fluid of six patients with chronic pain. Stimulation of the periaqueductal gray matter in three patients with pain of peripheral origin resulted in significant increases (50 to 300 percent) in the concentration of ventricular immunoreactive β-endorphin. In three other patients suffering deafferentation dysesthesia, stimulation of the posterior limb of the internal capsule did not alter the concentration of this peptide. These results provide evidence of the release of human immunoreactive β-endorphin in vivo and suggest that naloxone-reversible pain relief achieved by stimulation of the periaqueductal gray matter may be in part mediated by the activation of β-endorphin-rich diencephalic areas.
Radioimmunoassay of the Insulin Receptor: A New Probe of Receptor Structure and Function
Authors: Harrison Len C. , Flier Jeffrey , Itin Ahuva , Kahn C. Ronald , Roth Jesse
Published: October 2006

A sensitive and specific radioimmunoassay for the insulin receptor has been developed employing receptor autoantibodies from the serum of a patient with insulin-resistant diabetes. The assay detects insulin binding sites at concentrations as low as 0.1 nanomolar; distinguishes between receptors originating from human placental membranes, human lymphoblastoid cells, and mouse liver membranes; and measures the receptor independently of its binding function. Down-regulation, or loss of binding after exposure to insulin, is associated with loss of immunoreactive receptor.
Phosphatidylinositol 3-Kinase Encoded by Yeast
VPS
34 Gene Essential for Protein Sorting
Authors: Schu Peter V. , Takegawa Kaoru , Fry Michael J. , Stack Jeffrey H. , Waterfield Michael D. , Emr Scott D.
Published: October 2006

The
VPS
34 gene product (Vps34p) is required for protein sorting to the lysosome-like vacuole of the yeast
Saccharomyces cerevisiae
. Vps34p shares significant sequence similarity with the catalytic subunit of bovine phosphatidylinositol (PI) 3-kinase [the 110-kilodalton (p110) subunit of PI 3-kinase], which is known to interact with activated cell surface receptor tyrosine kinases. Yeast strains deleted for the
VPS
34 gene or carrying
vps
34 point mutations lacked detectable PI 3-kinase activity and exhibited severe defects in vacuolar protein sorting. Overexpression of Vps34p resulted in an increase in PI 3-kinase activity, and this activity was specifically precipitated with antisera to Vps34p.
VPS
34 encodes a yeast PI 3-kinase, and this enzyme appears to regulate intracellular protein trafficking decisions.
Import of a Mitochondrial Presequence Into Protein-Free Phospholipid Vesicles
Authors: Maduke Merritt , Roise David
Published: October 2006

A synthetic mitochondrial presequence has been shown to translocate across pure phospholipid bilayers. The presequence was fluorescently labeled so that its association with membranes could be monitored spectroscopically. In the presence of large unilamellar vesicles, the presequence showed time- and potential-dependent protection from reaction with added trypsin and dithionite. The protection was rapidly reversed by treatment of the vesicles with detergent. If the vesicles contained trypsin, the added presequence became sensitive to digestion by the protease. The results show that a mitochondrial presequence can translocate across phospholipid bilayers that lack a hydrophilic translocation pore.
Enzyme Polymorphisms as Genetic Signatures in Human Cell Cultures
Authors: O'Brien Stephen J. , Kleiner Gail , Olson Russell , Shannon John E.
Published: October 2006

The electrophoretic resolution of seven relatively polymorphic human gene-enzyme systems expressed in tissue culture cells can be used as a sensitive genetic monitor for intraspecific cell contamination. An identical genotype at each of the same allozyme loci provides a 95 percent (or greater) confidence estimate of the identity of two cultured lines, on the basis of the allelic frequencies of the seven enzyme loci in natural populations and in populations of independently derived cultured cells. Of 27 commonly used human cell lines examined, only one of 351 pairwise comparisons proved genetically indistinguishable.
Identification of Retinoyl Complexes as the Autofluorescent Component of the Neuronal Storage Material in Batten Disease
Authors: Wolfe Leonhard S. , Ng Ying Kin N. M. K. , Baker R. Roy , Carpenter Stirling , Andermann Frederick
Published: October 2006

Cytosomes filled with intensely fluorescent material in the form of curvilinear bodies were isolated by density gradient centrifugation followed by pronase digestion from the cerebral cortex of a child who had died at age 7 from the late infantile form of Batten disease. Forty-three percent of the dry weight of the storage material was extracted by a mixture of chloroform and methanol, leaving a waterinsoluble amorphous fluorescent residue. Infrared spectroscopy, proton magnetic resonance spectroscopy, and mass spectrometry of this residue strongly suggested the presence of retinoyl polyenes linked to a small peptide. Base hydrolysis and methanolysis yielded retinoic acid and methyl retinoate, respectively. Ozonolysis yielded a product derived from the substituted cyclohexenyl ring of vitamin A. The results indicate that the fluorescent component of the neuronal storage material is a retinoyl complex and is not derived from peroxidized polyunsaturated fatty acids as previously thought.
Perception of Impossible Limb Positions Induced by Tendon Vibration
Authors: Craske Brian
Published: October 2006

When the wrist flexor muscle is vibrated and the wrist is passively extended to a position close to its anatomical limit, the hand is felt to be bent to a position about 29° beyond its maximum operating range. The mechanism of position sense must in this case be operating on the basis of extrapolation. Ambiguity of sensed position can occur in this situation. Some subjects, when opposing the vibration-induced contraction of biceps, report experiencing multiple forearms.
Selective Perhydroxylation of Squalene: Taming the Arithmetic Demon
Authors: Crispino Gerard A. , Ho Pui Tong , Sharpless K. Barry
Published: October 2006

Osmium-catalyzed asymmetric dihydroxylation, which produces 1,2-diols of high enantiopurity from prochiral olefins, is an example of the synthetic catalysts that have been developed that rival enzymes in their efficiency and high enantioselectivity. Although the asymmetric dihydroxylation catalyst lacks an enzyme's ability to effectively distinguish among the subtly different olefinic sites in a polyolefin such as squalene, this very inability permits it to bring about the "exhaustive" polyhydroxylation of squalene to give a dodecahydroxy derivative. Twelve chemical and stereochemical events proceed in tandem with a remarkable average yield of 98 percent per step, giving 1 out of the 36 possible stereoisomers in (0.98)
12
= 78.9 percent overall yield.
Mediation by G Proteins of Signals That Cause Collapse of Growth Cones
Authors: Igarashi Michihiro , Strittmatter Stephen M. , Vartanian Timothy , Fishman Mark C.
Published: October 2006

During development, motion of nerve growth cones ceases on contact with particular targets. The signaling mechanism is unknown. In culture, growth cone collapse can be caused by solubilized embryonic brain membranes, central nervous system myelin, a 35-kilodalton protein isolated from myelin, and mastoparan. Collapse induced by each of these is blocked by pertussis toxin. Thus, collapse of growth cones is mediated by G protein-coupled receptors, which may be activated by proteins associated with the cell surface as well as by soluble ligands.
Role of Intracellular Calcium in NI-35-Evoked Collapse of Neuronal Growth Cones
Authors: Bandtlow Christine E. , Schmidt Marc F. , Hassinger Tim D. , Schwab Martin E. , Kater S. B.
Published: October 2006

A myelin-associated protein from the central nervous system, the neurite growth inhibitor NI-35, inhibits regeneration of lesioned neuronal fiber tracts in vivo and growth of neurites in vitro. Growth cones of cultured rat dorsal root ganglion neurons arrested their growth and collapsed when exposed to liposomes containing NI-35. Before morphological changes, the concentration of free intracellular calcium ([Ca
2+
]
i
) showed a rapid and large increase in growth cones exposed to liposomes containing NI-35. Neither an increase in [Ca
2+
]
i
nor collapse of growth cones was detected in the presence of antibodies to NI-35. Dantrolene, an inhibitor of calcium release from caffeine-sensitive intracellular calcium stores, protected growth cones from collapse evoked by NI-35. Depletion of these caffeine-sensitive intracellular calcium stores prevented the increase in [Ca
2+
]
i
evoked by NI-35. The NI-35-evoked cascade of intracellular messengers that mediates collapse of growth cones includes the crucial step of calcium release from intracellular stores.
Synaptic Vesicle Phosphoproteins and Regulation of Synaptic Function
Authors: Greengard Paul , Valtorta Flavia , Czernik Andrew J. , Benfenati Fabio
Published: October 2006

Complex brain functions, such as learning and memory, are believed to involve changes in the efficiency of communication between nerve cells. Therefore, the elucidation of the molecular mechanisms that regulate synaptic transmission, the process of intercellular communication, is an essential step toward understanding nervous system function. Several proteins associated with synaptic vesicles, the organelles that store neurotransmitters, are targets for protein phosphorylation and dephosphorylation. One of these phosphoproteins, synapsin I, by means of changes in its state of phosphorylation, appears to control the fraction of synaptic vesicles available for release and thereby to regulate the efficiency of neurotransmitter release. This article describes current understanding of the mechanism by which synapsin I modulates communication between nerve cells and reviews the properties and putative functions of other phosphoproteins associated with synaptic vesicles.
Multiple Defects of Immune Cell Function in Mice with Disrupted Interferon-γ Genes
Authors: Dalton Dyana K. , Pitts-Meek Sharon , Keshav Satish , Figari Irene S. , Bradley Allan , Stewart Timothy A.
Published: October 2006

Interferon-γ (IFN-γ) is a pleiotrophic cytokine with immunomodulatory effects on a variety of immune cells. Mice with a targeted disruption of the IFN-γ gene were generated. These mice developed normally and were healthy in the absence of pathogens. However, mice deficient in IFN-γ had impaired production of macrophage antimicrobial products and reduced expression of macrophage major histocompatibility complex class II antigens. IFN-γ-deficient mice were killed by a sublethal dose of the intracellular pathogen
Mycobacterium bovis
. Splenocytes exhibited uncontrolled proliferation in response to mitogen and alloantigen. After a mixed lymphocyte reaction, T cell cytolytic activity was enhanced against allogeneic target cells. Resting splenic natural killer cell activity was reduced in IFN-γ-deficient mice. Thus, IFN-γ is essential for the function of several cell types of the murine immune system.
The Need for a New Medical Model: A Challenge for Biomedicine
Authors: Engel George L.
Published: October 2006

The dominant model of disease today is biomedical, and it leaves no room within its framework for the social, psychological, and behavioral dimensions of illness. A biopsychosocial model is proposed that provides a blueprint for research, a framework for teaching, and a design for action in the real world of health care.
Regulation of TCR Signaling by CD45 Lacking Transmembrane and Extracellular Domains
Authors: Volarević Siniša , Niklinska Barbara B. , Burns Christopher M. , June Carl H. , Weissman Allan M. , Ashwell Jonathan D.
Published: October 2006

The CD45 protein is a transmembrane tyrosine phosphatase that is required for normal T cell receptor (TCR)-mediated signaling. A chimeric complementary DNA encoding the intracellular enzymatically active portion of murine CD45 preceded by a short amino-terminal sequence from p60

c-
src

was transfected into CD45- T cells. Expression of this chimeric protein corrected most of the TCR signaling abnormalities observed in the absence of CD45, including TCR-mediated enhancement of tyrosine kinase activity and Ca
2+
flux. Thus, the enzymatically active intracellular portion of CD45 is sufficient to allow TCR transmembrane signaling.
Rapid Assessment of Drug Susceptibilities of
Mycobacterium tuberculosis
by Means of Luciferase Reporter Phages
Authors: Jacobs William R. , Barletta Raúl G. , Udani Rupa , Chan John , Kalkut Gary , Sosne Gabriel , Kieser Tobias , Sarkis Gary J. , Hatfull Graham F. , Bloom Barry R.
Published: October 2006

Effective chemotherapy of tuberculosis requires rapid assessment of drug sensitivity because of the emergence of multidrug-resistant
Mycobacterium tuberculosis
. Drug susceptibility was assessed by a simple method based on the efficient production of photons by viable mycobacteria infected with specific reporter phages expressing the firefly luciferase gene. Light production was dependent on phage infection, expression of the luciferase gene, and the level of cellular adenosine triphosphate. Signals could be detected within minutes after infection of virulent
M. tuberculosis
with reporter phages. Culture of conventional strains with antituberculosis drugs, including isoniazid or rifampicin, resulted in extinction of light production. In contrast, light signals after luciferase reporter phage infection of drug-resistant strains continued to be produced. Luciferase reporter phages may help to reduce the time required for establishing antibiotic sensitivity of
M. tuberculosis
strains from weeks to days and to accelerate screening for new antituberculosis drugs.