bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Temperature XAS Study of Fe
2
SiO
4
Liquid: Reduced Coordination of Ferrous Iron
Authors: Jackson W. E. , de Leon J. Mustre , Brown G. E. , Waychunas G. A. , Conradson S. D. , Combes J. -M.
Published: October 2006

X-ray absorption spectroscopy (XAS) of Fe
2+
in Fe
2
SiO
4
liquid at 1575 kelvin and 10
-4
gigapascal (1 bar) shows that the Fe
2+
-O bond length is 1.98 ± 0.02 angstroms compared with ≈2.22 angstroms in crystalline Fe
2
SiO
4
(fayalite) at the melting point (1478 kelvin), which indicates a decrease in average Fe
2+
coordination number from six in fayalite to four in the liquid. Anharmonicity in the liquid was accounted for using a data analysis procedure. This reduction in coordination number is similar to that observed on the melting of certain ionic salts. These results are used to develop a model of the medium-range structural environment of Fe
2+
in olivine-composition melts, which helps explain some of the properties of Fe
2
SiO
4
liquid, including density, viscosity, and the partitioning of iron and nickel between silicate melts and crystalline olivines. Some of the implications of this model for silicate melts in the Earth's crust and mantle are discussed.
Production of Perfluoroalkylated Nanospheres from Buckminsterfullerene
Authors: Fagan Paul J. , Krusic Paul J. , McEwen C. N. , Lazar J. , Parkert Deborah Holmes , Herron N. , Wasserman E.
Published: October 2006

Perfluoroalkylated nanospheres have been prepared by reaction of fullerenes with a variety of fluoroalkyl radicals. The latter are generated by thermal or photochemical decomposition of fluoroalkyl iodides or fluorodiacyl peroxides. Up to 16 radicals add to C
60
to afford easily isolable fluoroalkylated derivatives. The monosubstituted radical adducts were detected by electron spin resonance in the early stages of the fluoroalkylation reactions. These spheroidal molecules are thermally quite stable, soluble in fluoroorganic solvents, chemically resistant to corrosive aqueous solutions, and more volatile than the parent fullerenes. Films of the sublimed material display properties typical for a perfluoroalkylated material.
Growth of High Aspect Ratio Nanometer-Scale Magnets with Chemical Vapor Deposition and Scanning Tunneling Microscopy
Authors: Kent Andrew D. , Shaw Thomas M. , von Molnár Stephan , Awschalom David D.
Published: October 2006

A combination of chemical vapor deposition and scanning tunneling microscopy techniques have been used to produce nanometer-scale, iron-containing deposits with high aspect ratios from an iron pentacarbonyl precursor both on a substrate and on the tunneling tip itself. The structure and composition of the resulting nanodeposits were determined by transmission electron microscopy and high spatial resolution Auger electron spectroscopy. Either polycrystalline, relatively pure, body-centered-cubic iron or disordered carbon-rich material can be deposited, depending on the bias conditions of the tip sample junction and the precursor pressure. Two mechanisms of decomposition are inferred from the growth phenomenology.
Photon Emission at Molecular Resolution Induced by a Scanning Tunneling Microscope
Authors: Berndt R. , Gaisch R. , Gimzewski J. K. , Reihl B. , Schlittler R. R. , Schneider W. D. , Tschudy M.
Published: October 2006

The tip-surface region of a scanning tunneling microscope (STM) emits light when the energy of the tunneling electrons is sufficient to excite luminescent processes. These processes provide access to dynamic aspects of the local electronic structure that are not directly amenable to conventional STM experiments. From monolayer films of carbon-60 fullerenes on gold(110) surfaces, intense emission is observed when the STM tip is placed above an individual molecule. The diameter of this emission spot associated with carbon-60 is approximately 4 angstroms. These results demonstrate the highest spatial resolution of light emission to date with a scanning probe technique.
A Binary Source Model for Extension-Related Magmatism in the Great Basin, Western North America
Authors: Leeman William P. , Harry Dennis L.
Published: October 2006

Models for extension-related magmatism based on decompression melting of asthenospheric mantle poorly simulate fluxes and bulk compositions of magmas produced during early stages of continental extension. For the Great Basin of western North America, it is proposed that magmatism proceeded in two stages, the first involving melting of lithospheric mantle sources between 40 and ∼5 million years ago (Ma), followed (since ∼5 Ma) by melting of upwelling asthenospheric mantle in areas where extension has exceeded about 100 percent. This transition in magma sources is diachronous, depending on initial variations in lithosphere thickness and on rates of lithospheric thinning.
The Location of DNA in RecA-DNA Helical Filaments
Authors: Egelman E. H. , Yu X.
Published: October 2006

The helical filament that the RecA protein of
Escherichia coli
forms around DNA is the active apparatus in protein-catalyzed homologous genetic recombination. The actual position of DNA within this complex has been unknown. Image analysis has been performed on electron micrographs of filaments of RecA on double-stranded DNA and on single-stranded DNA to visualize a difference that is consistent with one strand of the double-stranded DNA. This localization of the DNA gives additional information about the unusual structure of DNA in the complex with RecA protein.
Catalytic Antibodies with Lipase Activity and
R
or
S
Substrate Selectivity
Authors: Janda Kim D. , Benkovic Stephen J. , Lerner Richard A.
Published: October 2006

The specific hydrolysis of unactivated esters bearing an
R
or
S
enantiomeric alcohol has been achieved by two separate classes of catalytic antibodies induced to bind either the
R
or
S
substrates. The antibodies exhibit rate accelerations (10
3
) to 10
5
) above background hydrolysis that, coupled with their antipodal specificity, provide a novel set of reagents for use in synthesis.
Mechanics of Stimulated Neutrophils: Cell Stiffening Induces Retention in Capillaries
Authors: Worthen G. Scott , Schwab Bill , Elson Elliot L. , Downey Gregory P.
Published: October 2006

The effect of peptide chemoattractants on neutrophil mechanical properties was studied to test the hypothesis that stimulated neutrophils (diameter, 8 micrometers) are retained in pulmonary capillaries (5.5 micrometers) as a result of a decreased ability of the cell to deform within the capillary in response to the hydrodynamic forces of the bloodstream. Increased neutrophil stiffness, actin assembly, and retention in both 5-micrometer pores and the pulmonary vasculature were seen in response to
N
-formyl-methionyl-leucyl-phenylalanine. These changes were abolished in cells that had been incubated with 2 micromolar cytochalasin D, an agent that disrupts cellular actin organization. A monoclonal antibody directed at the CD11-CD18 adhesive glycoprotein complex did not inhibit the increase in stiffness or retention in pores. These data suggest that neutrophil stiffening may be both necessary and sufficient for the retention that is observed. Hence, neutrophil sequestration in lung and other capillaries in the acute inflammatory process may be the result of increased stiffness stimulated by chemoattractants.
A Single Amino Acid Interchange Yields Reciprocal CTL Specificities for HIV-1 gp160
Authors: Takahashi Hidemi , Merli Silvia , Putney Scott D. , Houghten Richard , Moss Bernard , Germain Ronald N. , Berzofsky Jay A.
Published: October 2006

For the IIIB isolate of human immunodeficiency virus type-1 (HIV-1), the immunodominant determinant of the envelope protein gp160 for cytotoxic T lymphocytes (CTLs) of H-2
d
mice is in a region of high sequence variability among HIV-1 isolates. The general requirements for CTL recognition of peptide antigens and the relation of recognition requirements to the natural variation in sequence of the HIV were investigated. For this purpose, a CTL line specific for the homologous segment of the envelope from the MN isolate of HIV-1 and restricted by the same class I major histocompatibility (MHC) molecule (D
d
) as the IIIB-specific CTLs was raised from mice immunized with MN-
env
-recombinant vaccinia virus. The IIIB-specific and MN-specific CTLs were completely non-cross-reactive. Reciprocal exchange of a single amino acid between the two peptide sequences, which differed in 6 of 15 residues, led to a complete reversal of the specificity of the peptides in sensitizing targets, such that the IIIB-specific CTLs lysed targets exposed to the singly substituted MN peptide and vice versa. These data indicate the importance of single residues in defining peptide epitopic specificity and have implications for both the effect of immune pressure on selection of viral mutants and the design of effective vaccines.
Mineralocorticoid Action: Target Tissue Specificity Is Enzyme, Not Receptor, Mediated
Authors: Funder John W. , Pearce Paul T. , Smith Robin , Smith A. Ian
Published: October 2006

Mineralocorticoid receptors, both when in tissue extracts and when recombinant-derived, have equal affinity for the physiological mineralocorticoid aldosterone and for the glucocorticoids cortisol and corticosterone, which circulate at much higher concentrations than aldosterone. Such receptors are found in physiological mineralocorticoid target tissues (kidney, parotid, and colon) and in nontarget tissues such as hippocampus and heart. In mineralocorticoid target tissues the receptors are selective for aldosterone in vivo because of the presence of the enzyme 11 β-hydroxy-steroid dehydrogenase, which converts cortisol and corticosterone, but not aldosterone, to their 11-keto analogs. These analogs cannot bind to mineralocorticoid receptors.
Translocation of Protein Kinase C Activity May Mediate Hippocampal Long-Term Potentiation
Authors: Akers Raymond F. , Lovinger David M. , Colley Patricia A. , Linden David J. , Routtenberg Aryeh
Published: October 2006

Protein kinase C activity in rat hippocampal membranes and cytosol was determined 1 minute and 1 hour after induction of the synaptic plasticity of long-term potentiation. At 1 hour after long-term potentiation, but not at 1 minute, protein kinase C activity was increased twofold in membranes and decreased proportionately in cytosol, suggesting translocation of the activity. This time-dependent redistribution of enzyme activity was directly related to the persistence of synaptic plasticity, suggesting a novel mechanism regulating the strength of synaptic transmission.
Perturbation of Red Cell Membrane Structure During Intracellular Maturation of
Plasmodium falciparum
Authors: Taraschi Theodore F. , Parashar Aruna , Hooks Mary , Rubin Harvey
Published: October 2006

An experimental approach, which in this study was applied to the malarial system, can be used to analyze the molecular structure and organization of individual phospholipids in a wide variety of biological membranes. Electron spin resonance spectroscopy was used to investigate the structural modifications of the major red cell phospholipids that occur in erythrocyte membranes infected with the human malarial parasite,
Plasmodium falciparum
. These modifications were correlated with the intracellular developmental stage of the parasite. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were increasingly disordered (fluidized) as infection progressed. This disordering occurred at different rates and to varying extents.
Infectious Mutants of HTLV-III with Changes in the 3′ Region and Markedly Reduced Cytopathic Effects
Authors: Fisher Amanda G. , Ratner Lee , Mitsuya Hiroaki , Marselle Lisa M. , Harper Mary E. , Broder Samuel , Gallo Robert C. , Wong-Staal Flossie
Published: October 2006

A variant of human T-lymphotropic virus type III (HTLV-III) is described that replicates but does not kill normal human T cells in vitro. This variant, designated X10-1, was derived from the genome of a cytopathic HTLV-III clone (pHXB2D) by excision of a 200-base pair segment in the 3′ region of the virus, spanning the
env
and 3′-
orf
genes. Comparable variants with 55 to 109 base pairs deleted exclusively in 3′-
orf
produced, in contrast, virus that was extremely cytopathic. On the basis of these findings it is concluded that the 3′-
orf
gene is not required for cytopathogenicity or replication of HTLV-III. In addition, the results suggest that virus replication and cytotoxicity are not intrinsically coupled. Furthermore, since clone X10-1 retains the ability to
trans
-activate genes linked to the viral long terminal repeats,
trans
-activation per se is not responsible for T-cell killing by HTLV-III. These results also raise the possibility that the carboxyl terminus of the envelope gene of HTLV-III has a direct role in T-cell killing by this virus.
Arteriosclerosis: Is Stress-Induced Immune Suppression a Risk Factor?
Authors: Lattime Edmund C. , Strausser Helen R.
Published: October 2006

Female Sprague-Dawley rats, purchased as retired breeders, developed arteriosclerosis that was accompanied by immune complex deposition in the arterial lesion and depressed immune responsiveness to T cell mitogens.
Mutant Trp Repressors with New DNA-Binding Specificities
Authors: Bass Steven , Sorrells Vincenza , Youderian Philip
Published: October 2006

Oligonucleotide-directed mutagenesis of the codons for glutamine-68 (Gln
68
), lysine-72 (Lys
72
), isoleucine-79 (Ile
79
), alanine-80 (Ala
80
), and threonine-81 (Thr
81
) of the
Escherichia coli
trpR
(tryptophan aporepressor) gene was used to make mutant repressors with each of 36 different amino acid changes. Mutant repressors were tested for binding to each member of a set of 28 different operators closely related to the consensus
trp
operator. Of the 36 mutant repressors, 11 bind a subset of the 28 operators; 5 of these have new binding specificities. These new specificities indicate that the hydroxyl group of Thr
81
makes a specific contact with one of the four critical base pairs in a
trp
operator half-site, and the methyl group of Thr
81
determines specificity at a second, critical base pair. The Trp repressor does not use the first two amino acids of its "recognition α-helix," Ile
79
and Ala
80
, to make sequence-specific DNA contacts, and interacts with its operator in vivo in a way fundamentally different from the way that phage lambda repressor, lambda Cro protein, and coliphage 434 repressor contact their respective binding sites.
Reversal of Experimental Allergic Encephalomyelitis with Monoclonal Antibody to a T-Cell Subset Marker
Authors: Waldor Matthew K. , Sriram Subramanian , Hardy Richard , Herzenberg Leonore A. , Herzenberg Leonard A. , Lanier Lewis , Lim Mae , Steinman Lawrence
Published: October 2006

Administration of a monoclonal antibody (GK1.5) that recognizes the L3T4 marker present on helper T cells prevented the development of experimental allergic encephalomyelitis (EAE) in mice. Furthermore, treatment with GK1.5 reversed EAE when the antibody was given to paralyzed animals. In vivo injection of GK1.5 selectively reduced the number of L3T4
+
cells in the spleen and the lymph nodes. These results suggest that manipulation of the human equivalent of the murine L3T4
+
T-cell subset with monoclonal antibodies may provide effective therapy for certain autoimmune diseases.
Ovothiol Replaces Glutathione Peroxidase as a Hydrogen Peroxide Scavenger in Sea Urchin Eggs
Authors: Turner Eric , Hager Lisa J. , Shapiro Bennett M.
Published: October 2006

Despite its potential toxicity, H
2
O
2
is used as an extracellular oxidant by
Strongylocentrotus purpuratus
eggs to cross-link their fertilization envelopes. These eggs contain 5 m
M
1-methyl-
N
α
,
N
α
-dimethyl-4-mercaptohistidine (ovothiol C), which reacts with H
2
O
2
. In consuming H
2
O
2
and being reduced by glutathione, ovothiol acts as a glutathione peroxidase and replaces the function of the enzyme in eggs. The ovothiol system is more effective than egg catalase in destroying H
2
O
2
at concentrations produced during fertilization and constitutes a principal mechanism for preventing oxidative damage at fertilization.
A 13-Kilodalton Maize Mitochondrial Protein in
E. coli
Confers Sensitivity to
Bipolaris maydis
Toxin
Authors: Dewey R. E. , Siedow J. N. , Timothy D. H. , Levings C. S.
Published: October 2006

The Texas male-sterile cytoplasm (
cms-T
) of maize carries the cytoplasmically inherited trait of male sterility. Mitochondria isolated from
cms-T
maize are specifically sensitive to a toxin (BmT-toxin) produced by the fungal pathogen
Bipolaris maydis
, race T, and the carbamate insecticide methomyl. A mitochondrial gene unique to
cms-T
maize, which produces a 13-kilodalton polypeptide associated with cytoplasmic male sterility, was expressed in
Escherichia coli
. After addition of BmT-toxin or methomyl, inhibition of whole cell respiration and swelling of spheroplasts were observed in
Escherichia coli
cultures producing the novel mitochondrial protein; these effects are similar to those observed with isolated
cms-T
mitochondria. The amino-terminal region of the 13-kilodalton polypeptide appears to be essential for proper interaction with the BmT-toxin and methomyl. These results implicate the 13-kilodalton polypeptide in conferring toxin sensitivity to mitochondria of
cms-T
maize.
A Fossil Reptile Embryo from the Middle Triassic of the Alps
Authors: Sander P. Martin
Published: October 2006

The first nothosaur (
Neusticosaurus
sp.) embryo, one of the very few fossil embryos known, provides a rare glimpse at reproduction in extinct reptiles. The specimen from the southern Alpine Middle Triassic (about 230 million years ago) was recognized as an embryo in comparison with an exceptionally large and well-understood sample of juvenile and sexed adult
Neusticosaurus
sp. The skeleton shows many embryonic features and may well be the smallest fossil reptile known (body length 51 millimeters). It reached only 22% of mean adult length whereas modern reptiles of this size do not hatch before they reach about 30% of mean adult length. The question of ovipary versus vivipary in pachypleurosaurs is discussed in light of the embryo.
A Molecular Basis for MHC Class II—Associated Autoimmunity
Authors: Todd John A. , Acha-Orbea Hans , Bell John I. , Chao Nelson , Fronek Zdenka , Jacob Chaim O. , McDermott Michael , Sinha Animesh A. , Timmerman Luika , Steinman Lawrence , McDevitt Hugh O.
Published: October 2006

Class II major histocompatibility (MHC) molecules have an immunoregulatory role. These cell-surface glycoproteins present fragments of protein antigens (or peptides) to thymus-derived lymphocytes (T cells). Nucleotide sequence polymorphism in the genes that encode the class II MHC products determines the specificity of the immune response and is correlated with the development of autoimmune diseases. This study identifies certain class II polymorphic amino acid residues that are strongly associated with susceptibility to insulin-dependent diabetes mellitus, rheumatoid arthritis, and pemphigus vulgaris. These findings implicate particular class II MHC isotypes in susceptibility to each disease and suggest new prophylactic and therapeutic strategies.
Hormone-Sensitive Lipase: Sequence, Expression, and Chromosomal Localization to 19 cent-q13.3
Authors: Holm Cecilia , Kirchgessner Todd G. , Svenson Karen L. , Fredrikson Gudrun , Nilsson Staffan , Miller Chad G. , Shively John E. , Heinzmann Camilla , Sparkes Robert S. , Mohandas Thuluvancheri , Lusis Aldons J. , Belfrage Per , Schotz Michael C.
Published: October 2006

Hormone-sensitive lipase, a key enzyme in fatty acid mobilization, overall energy homeostasis, and possibly steroidogenesis, is acutely controlled through reversible phosphorylation by catecholamines and insulin. The 757-amino acid sequence predicted from a cloned rat adipocyte complementary DNA showed no homology with any other known lipase or protein. The activity-controlling phosphorylation site was localized to Ser
563
in a markedly hydrophilic domain, and a lipid-binding consensus site was tentatively identified. One or several messenger RNA species (3.3, 3.5, or 3.9 kilobases) were expressed in adipose and steroidogenic tissues and heart and skeletal muscle. The human hormone-sensitive lipase gene mapped to chromosome 19 cent-q13.3.
A Novel Thyroid Hormone Receptor Encoded by a cDNA Clone from a Human Testis Library
Authors: Benbrook Doris , Pfahl Magnus
Published: October 2006

The c-
erb
A gene belongs to a multigene family that encodes transcriptional regulatory proteins including the v-
erb
A oncogene product, steroid hormone receptors, and the vitamin D3 receptor. A v-
erb
A DNA probe encoding the DNA-binding region of the v-
erb
A protein was used to screen a human complementary DNA testis library. One of the clones isolated,
erb
A-T-1, was found to encode a 490-amino acid protein (
erb
A-T). The
erb
A-T polypeptide shows high homology with the proteins encoded by both the chicken c-
erb
A and the human c-
erb
A-β genes but is most closely related to the chicken gene. The chicken c-
erb
A and the human c-
erb
A-β genes encode high-affinity receptors for thyroid hormone, and here it is shown that the
erb
A-T protein binds specifically to 3,5,3 ′-triiodo-L-thyronine with a dissociation constant of 3.8 ± 0.2 × 10
-10
M
. These data imply that more than one thyroid hormone receptor exists in humans and that these receptors might have different tissue- and gene-activating specificities.
Non-Watson-Crick G ⋅ C and A ⋅ T Base Pairs in a DNA-Antibiotic Complex
Authors: Quigley Gary J. , Ughetto Giovanni , van der Marel Gijs A. , van Boom Jacques H. , Wang Andrew H.-J. , Rich Alexander
Published: October 2006

The structure of a DNA octamer d(GCGTACGC) cocrystallized with the bisintercalator antibiotic triostin A has been solved. The DNA forms an unwound right-handed double helix. Four base pairs are of the Watson-Crick type while four are Hoogsteen base pairs, including two A ⋅ T and two G ⋅ C base pairs. This is the first observation in an oligonucleotide of Hoogsteen G ⋅ C base pairs where the cystosine is protonated. It is likely that these also occur in solutions of DNA complexed to this antibiotic.
Identification and Isolation of a Variant Surface Glycoprotein from
Trypanosoma vivax
Authors: Gardiner Peter R. , Pearson Terry W. , Clarke Michael W. , Mutharia Lucy M.
Published: October 2006

The protozoan
Trypanosoma vivax
is one of the most important agents of African trypanosomiasis, a disease that hinders the productive use of livestock in one-third of the African continent.
Trypanosoma vivax
is also present in the Caribbean and in South America, posing a threat to the livestock industries of the tropical and subtropical world. Much less is known of the biology of this trypanosome than of the better studied
T. brucei
and
T. congolense
. One of the variant surface glycoproteins (VSGs) of a West African stock of
T. vivax
was identified, purified, and partially characterized by the use of a combination of highly resolving techniques to maximize information from the relatively small amount of parasite material available. The molecular weight of the isolated protein (46,000) is smaller than that of VSGs from other species. As with
T. brucei
VSGs the protein from
T. vivax
is complexed with sugars and incorporates
3
H when living trypanosomes are incubated with [
3
H]myristic acid, but the
T. vivax
molecule is more hydrophobic than the
T. brucei
molecule. The small size of the
T. vivax
VSG may have a bearing on the functional and evolutionary relationships of variant antigens in trypanosomes.
Assignment of the Gene for Myelin Proteolipid Protein to the X Chromosome: Implications for X-Linked Myelin Disorders
Authors: Willard Huntington F. , Riordan John R.
Published: October 2006

Several inherited disorders in humans and in rodents result in myelin dysgenesis and a deficiency of the molecular constituents of myelin. A complementary DNA to one of the two major myelin proteins, myelin proteolipid protein (also known as lipophilin), has been used with Southern blot analysis of somatic cell hybrid DNA to map the human proteolipid protein gene to the middle of the long arm of the human X chromosome (bands Xq13-Xq22) and to assign the murine proteolipid protein gene to the mouse X chromosome. Comparison of the gene maps of the human and mouse X chromosomes suggests that myelin proteolipid protein may be involved in X-linked mutations at the mouse jimpy locus and has implications for Pelizaeus-Merzbacher disease, a human inherited X-linked myelin disorder.
Gene Transfer and Expression of Human Phenylalanine Hydroxylase
Authors: Ledley Fred D. , Grenett Hernan E. , DiLella Anthony G. , Kwok Simon C. M. , Woo Savio L. C.
Published: October 2006

Phenylketonuria (PKU) is caused by a genetic deficiency of the enzyme phenylalanine hydroxylase (PAH). A full-length complementary DNA clone of human PAH was inserted into a eukaryotic expression vector and transferred into mouse NIH3T3 cells which do not normally express PAH. The transformed mouse cells expressed PAH messenger RNA, immunoreactive protein, and enzymatic activity that are characteristic of the normal human liver products, demonstrating that a single gene contains all of the necessary genetic information to code for functional PAH. These results support the use of the human PAH probe in prenatal diagnosis and detection of carriers, to provide new opportunities for the biochemical characterization of normal and mutant enzymes, and in the investigation of alternative genetic therapies for PKU.
Isolation, Experimental Transmission, and Characterization of Causative Agent of Potomac Horse Fever
Authors: Holland Cynthia J. , Ristic Miodrag , Cole Adeyinka I. , Johnson Philip , Baker Gordon , Goetz Tom
Published: October 2006

Potomac horse fever, a disease characterized by fever, anorexia, leukopenia, and occasional diarrhea, is fatal in approximately 30 percent of affected animals. The seasonal occurrence of the disease (June to October) and evidence of antibodies to the rickettsia
Ehrlichia sennetsu
in the serum of convalescing horses suggested that a related rickettsia might be the causative agent. Such an agent was isolated in cultured blood monocytes from an experimentally infected pony. This intracytoplasmic organism was adapted to growth in primary cultures of canine blood monocytes. A healthy pony inoculated with these infected monocytes also developed the disease. The organism was reisolated from this animal which, at autopsy, had pathological manifestations typical of Potomac horse fever. Cross serologic reactions between the newly isolated agent and antisera to 15 rickettsiae revealed that it is related to certain members of the genus
Ehrlichia
, particularly to
Ehrlichia sennetsu
. Since the disease occurs in other parts of the United States as well as in the vicinity of the Potomac River, and since it has also been reported in Europe, the name equine monocytic ehrlichiosis is proposed as being more descriptive.
Adaptation of the Membrane Lipids of a Deep-Sea Bacterium to Changes in Hydrostatic Pressure
Authors: DeLong Edward F. , Yayanos A. Aristides
Published: October 2006

The fatty acid composition of the cell membrane of the barophilic marine bacterium CNPT3 was found to vary as a function of pressure. Greater amounts of unsaturated fatty acids were present in bacteria growing at higher pressures. The results suggest adaptations in the membrane lipids to environmentally relevant pressures. This response to pressure appears to be analogous to temperature-induced membrane adaptations observed in other organisms.
Fractal Surfaces of Proteins
Authors: Lewis Mitchell , Rees D. C.
Published: October 2006

Fractal surfaces can be used to characterize the roughness or irregularity of protein surfaces. The degree of irregularity of a surface may be described by the fractal dimension
D
. For protein surfaces defined with probes in the range of 1.0 to 3.5 angstroms in radius,
D
is approximately 2.4 or intermediate between the value for a completely smooth surface (
D
= 2) and that for a completely space-filling surface (
D
= 3). Individual regions of proteins show considerable variation in
D
. These variations may be related to structural features such as active sites and subunit interfaces, suggesting that surface texture may be a factor influencing molecular interactions.
Characterization of Bacterial Growth by Means of Flow Microfluorometry
Authors: Bailey James E. , Fazel-Makjlessi Jila , McQuitty Donald N. , Lee Y. N. , Allred J. C. , Oro James A.
Published: October 2006

By means of flow microfluorometry, the protein and nucleic acid contents of individual bacterial cells may be measured at the rate of several thousand cells per second. Accumulation of such information over a few minutes yields the composition distribution of the microbial population. These distributions have been determined at different times during batch growth of
Bacillus subtilis
, and the results indicate that the variance of cell composition decreases as the population passes through the exponential into the stationary phase. The relative abundance of endospores and vegetative cells as well as the protein distributions of these subpopulations may be readily determined from flow microfluorometry data. Experimental access to such details of microbial population dynamics should foster improved understanding of cell growth, spore germination, and spore formation kinetics.
The Psychophysical Function: Harmonizing Fechner and Stevens
Authors: Wasserman Gerald S. , Felsten Gene , Easland Gene S.
Published: October 2006

The methods of Fechner and Stevens for assessing sensation quantity usually yield different psychophysical functions even when all other factors are controlled. In this experiment, corresponding differences occurred when different features of the same sensory receptor signals were analyzed. In the visual system, the receptor potential saturated if the peak but not the area was measured; these results match visual psychophysical functions obtained with the methods of Fechner and Stevens, respectively. This result suggests that both methods are equally valid but that each method yields the particular psychophysical function appropriate for a particular kind of information processing. A novel factor in determining sensation quantity, namely the time used by the observer to make a judgment, is implicated by the data.
Siamese Cat: Altered Connections of Visual Cortex
Authors: Shatz Carla J. , LeVay Simon
Published: October 2006

In Siamese cats, each side of the brain receives a retinal input serving part of the ipsilateral visual field as well as the normal contralateral field representation. Both corticothalamic and cortico-cortical projections are systematically rearranged, but while one is retinotopically appropriate, the other fails to make a distinction between ipsilateral and contralateral fields. Different rules appear to govern the development of these two sets of connections.
Morphological Affinities of
Pan paniscus
Authors: Corruccini Robert S. , McHenry Henry M.
Published: October 2006

Although the pygmy chimpanzee (
Pan paniscus
) is more similar to man than is the common chimpanzee (
Pan troglodytes
) in some traits, the resemblance is due primarily to the smaller size and concomitant allometric generalization of the former. The two species of chimpanzees are equally good models for the common ancestry of African apes and man.
Visually Guided Locomotion: Psychophysical Evidence for a Neural Mechanism Sensitive to Flow Patterns
Authors: Regan D. , Beverley K. I.
Published: October 2006

Inspecting a radial flow pattern depressed visual sensitivity to changes in the size of a small test square, but only when the square was located near the focus of the flow pattern. This result suggests that precise visual judgments of one's direction of forward motion with respect to the outside world may be mediated by an already known neural organization sensitive to changes in the size of small objects.
Triglyceride Concentrations: The Disaccharide Effect
Authors: Thompson Robert G. , Hayford John T. , Hendrix James A.
Published: October 2006

The mean 24-hour or integrated concentration of triglyceride is significantly higher when dietary sucrose is provided rather than an equivalent amount of its component monosaccharides, glucose and fructose. In contrast, the plasma triglyceride concentration after a 12-hour fast is not significantly different.
Target Cells for 1,25-Dihydroxyvitamin D
3
in Intestinal Tract, Stomach, Kidney, Skin, Pituitary, and Parathyroid
Authors: Stumpf Walter E. , Sar Madhabananda , Reid Frederic A. , Tanaka Yoko , DeLuca Hector F.
Published: October 2006

After mature rats that had been fed on a vitamin D
3
-deficient diet were injected with tritium-labeled 1,25-dihydroxyvitamin D
3
, radioactivity became concentrated in nuclei of luminal and cryptal epithelium of the duodenum, jejunum, ileum, and colon; in nuclei of the epithelium of kidney distal tubules including the macula densa, and in podocytes of glomeruli; in nuclei of the epidermis including outer hairshafts and sebaceous glands; and in nuclei of certain cells of the stomach, anterior and posterior pituitary, and parathyroid. These results reveal cell types that contain receptors for 1,25-dihydroxyvitamin D
3
or metabolites of this compound both in known or hypothesized target tissues and in tissues that were previously unknown to participate in vitamin D
3
metabolism.
Vascular Smooth Muscle: Aerobic Glycolysis Linked to Sodium and Potassium Transport Processes
Authors: Paul Richard J. , Bauer Mary , Pease William
Published: October 2006

Under aerobic conditions, glucose is primarily catabolized by vascular smooth muscle to lactate, in spite of an adequate oxidative capacity. Although this is often considered to be indicative of some nonspecific metabolic insufficiency, there is evidence that aerobic glycolysis is specifically coupled to sodium and potassium transport processes, whereas oxidative metabolism is coupled to contractile energy requirements.
Rabies: Decimation of a Wolf Pack in Arctic Alaska
Authors: Chapman Richard C.
Published: October 2006

In a pack of ten wolves, one wolf behaved atypically and fought with several packmates. This wolf was shot when it approached the author. Within 4 weeks at least six other members of the pack were dead. Rabies was confirmed in the wolf that was shot and in two others that had not decomposed. Most of the wolves infected with rabies had sought or remained at familiar areas in the core area of their territory, which implies that they were not contacting neighboring packs. This was confirmed with an aerial survey. Arctic foxes, experiencing a regionwide rabies epizootic, were suspected vectors.
Hamster Refractoriness: The Role of Insensitivity of Pineal Target Tissues
Authors: Bittman Eric L.
Published: October 2006

Hamsters exposed to short days undergo gonadal collapse followed by recrudescence and insensitivity to the regressive effects of such photoperiods. This refractoriness may be due to exhaustion of the pineal gland or desensitization of its target. Hamsters whose gonads had spontaneously recrudesced were injected with melatonin (25 micrograms per injection) once daily (known to induce regression in intact hamsters) or thrice daily (reported to arrest reproduction in pinealectomized hamsters) for 7 weeks. In neither case did refractory hamsters respond to melatonin treatment. The gonads of intact hamsters treated with melatonin for 21 weeks regressed and spontaneously recrudesced along a normal time course. These results indicate that gonadal refractoriness is due to insensitivity of the target tissues of the pineal gland and imply that melatonin participates in photoperiodic regulation of reproduction in the golden hamster.
Oocyte-Follicle Cell Gap Junctions in
Xenopus laevis
and the Effects of Gonadotropin on Their Permeability
Authors: Browne Carole L. , Wiley H. Steven , Dumont James N.
Published: October 2006

Junctions between
Xenopus laevis
oocytes and follicle cells have been identified as gap junctions by the passage of microinjected fluorescent dye from oocytes to follicle cells. The opening or assembly of these junctions, or both, appears to be regulated by gonadotropins.
Early Chemical Evolution of Nucleic Acids: A Theoretical Model
Authors: Usher D. A.
Published: October 2006

Recent experimental work suggests a possible cyclical pathway for early prebiotic oligonucleotide formation that involves (i) dry-state (nontemplate) synthesis of random copolymers with mixed 2′,5′ and 3′,5′ bonds, (ii) passage of these oligomers into solution at low temperatures, and (iii) a preferential hydrolysis of the 2′,5′ bond in any short helices that have formed. This early system could have selected for complementary sequences that were largely 3′,5′-linked, but may not have selected efficiently for a single enantiomer of ribose.
Expression of the c-
fos
Gene and of an
fos
-Related Gene Is Stimulated by Platelet-Derived Growth Factor
Authors: Cochran Brent H. , Zullo John , Verma Inder M. , Stiles Charles D.
Published: October 2006

Complementary DNA clones of genes induced by platelet-derived growth factor (PDGF) in BALB/c-3T3 cells were isolated; one such clone contains a domain having nucleotide sequence homology with the third exon of c-
fos
. This nucleotide sequence homology is reflected in the predicted amino acid sequences of the gene products. Under low stringency conditions, the mouse v-
fos
gene cross-hybridizes with the PDGF-inducible complementary DNA clone. However, the messenger RNA transcripts of mouse c-
fos
and the new
fos
-related gene can be distinguished by gel electrophoresis and by S1 nuclease analysis. Expression of the authentic c-
fos
gene is induced by PDGF and superinduced by the combination of PDGF and cycloheximide.
Voltage-Dependent Calcium Channels in Glial Cells
Authors: MacVicar B. A.
Published: October 2006

The electrophysiological properties of glial cells were examined in primary culture in the presence of tetraethylammonium and Ba
2+
, a treatment that reduces K
+
permeability of the membrane and enhances currents through voltage-dependent Ca
2+
channels. Under these conditions, glial cells showed both spontaneous action potentials and action potentials evoked by the injections of current. These responses appear to represent entry of Ba
2+
through Ca
2+
channels because they were resistant to tetrodotoxin but were blocked by Mn
2+
or Cd2+.
Reorganization of the Axon Membrane in Demyelinated Peripheral Nerve Fibers: Morphological Evidence
Authors: Foster Robert E. , Whalen Christopher C. , Waxman Stephen G.
Published: October 2006

Cytochemical staining of demyelinated peripheral axons revealed two types of axon membrane organization, one of which suggests that the demyelinated axolemma acquires a high density of sodium channels. Ferric ion-ferrocyanide stain was confined to a restricted region of axon membrane at the beginning of a demyelinated segment or was distributed throughout the demyelinated segment of axon. The latter pattern represents one possible morphological correlate of continuous conduction through a demyelinated segment and suggests a reorganization of the axolemma after demyelination.
Systemic Lupus Erythematosus: Presence in Human Serum of an Unusual Acid-Labile Leukocyte Interferon
Authors: Preble Olivia T. , Black Roberta J. , Friedman Robert M. , Klippel John H. , Vilček Jan
Published: October 2006

A previously undescribed species of human leukocyte, or alpha, interferon is present in the serum of many patients with systemic lupus erythematosus. It was shown to be α-interferon by neutralization with specific antiserums, affinity column chromatography, and antiviral activity on bovine cells. However, 23 of 30 interferon samples tested were inactivated by incubation at
p
H 2, a characteristic of human "immune," or gamma, interferon. Multiple samples of interferon from the same patient had similar biological properties, but samples from different patients were not all identical, suggesting that several variants of this species of human α-interferon may exist.
The Proposed National Arboretum at Washington
Authors: Coville Frederick V.
Published: October 2006

Nature.
The proposed national arboretum at Washington would contain a permanent living collection of trees and other outdoor plants for purposes of scientific research and education. It would include the trees, shrubs, and perennials used in forestry and horticulture, and the wild relatives of these plants. It would be a bureau of standards for horticulture. It would contain a water garden and a wildrice preserve, and it would serve incidentally as a bird sanctuary.

Economic value.
The arboretum would make the work of the Department of Agriculture more valuable to the country in many ways, but especially through plant breeding. The development of faster-growing timber trees, improved fruits, and disease-resistant plants generally, through the facilities afforded by the arboretum, would increase profoundly the agricultural wealth and welfare of the United States.

Location.
The Mount Hamilton and Hickey Hill tracts in the District of Columbia, together with the Anacostia River flats above Benning Bridge, constitute an admirable site for the arboretum, convenient in location and with a great variety of soils.

Cost.
About 400 acres of the proposed site is already owned by the government. It consists of marsh land, about to be drained by army engineers. The Mount Hamilton and Hickey Hill area, 408 acres, privately owned, was reported by the assessor in January, 1925, to be valued at $343,048, distributed among thirty owners.

Maintenance.
If the purchase of the Mount Hamilton and Hickey Hill tracts in the fiscal year 1927 is authorized, it is estimated that the cost of maintenance of the arboretum for the first three years would be as follows:

1927. Nothing

1928. $25,000

1929. $50,000
Immunotoxins: A New Approach to Cancer Therapy
Authors: Vitetta Ellen S. , Krolick Keith A. , Miyama-Inaba Muneo , Cushley William , Uhr Jonathan W.
Published: October 2006

Conjugates of tumor-reactive antibody and toxins (immunotoxins) have been used to eradicate tumor cells in vitro and in vivo. Such immunotoxins are highly effective in killing murine leukemic cells in infiltrated bone marrow and should be useful in the bone marrow rescue approach for the treatment of cancer. Similar immunotoxins injected parentally can help to induce prolonged remissions in leukemic mice, and antigen-containing immunotoxins can induce immunologic unresponsiveness in vitro in normal murine splenocytes. Thus, long-range goals for the parental use of immunotoxins include the killing of cancer cells in vivo and the modulation of the immune response for therapeutic purposes.
Interaction of Critical Periods in the Visual Cortex of Kittens
Authors: Daw N. W. , Berman N. E. J. , Ariel M.
Published: October 2006

The critical period for modifying the preferred direction in cat cortical units occurs earlier than that for monocular deprivation. The independence of the effects of these two types of deprivation from each other was tested by rearing six kittens with both reverse suture and reversed directional deprivation. The kittens were placed in a drum rotating in one direction with one eye open at ages 2½ to 5 weeks; the drum rotation was reversed and the other eye opened when they were 5 to 12 weeks old. Recordings were then made in the visual cortex. The results were the sum of the effects of reverse suture and reversal of directional deprivation: most cells were driven by the eye that was open second, and most unidirectional cells preferred the direction to which the animals were exposed first. Consequently, many unidirectional cells preferred the first direction but were driven by the eye open second—a combination that the animal never saw during rearing. There was also an effect of ocular deprivation on directional properties and vice versa: reverse suture reduced the overall percentage of unidirectional cells, just as directional deprivation has been shown to affect the ocular dominance histogram. This result suggests that the same cells may be affected by both forms of deprivation.
Activation of Antitumor Agent Gilvocarcins by Visible Light
Authors: Elespuru R. K. , Gonda S. K.
Published: October 2006

Gilvocarcins that are antitumor agents are activated by low doses of visible light to induce bacteriophage lambda in
Escherichia coli
. This result is dependent on interaction with DNA. Gilvocarcin M, an analog without antitumor activity, failed to induce the prophage after light exposure, thus demonstrating a correlation between photosensitizing and antitumor activities. These results raise several possibilities regarding the mode of action of gilvocarcins as antitumor agents in vivo, involving light or enzymatic activating systems, which could be exploited in human cancer therapy.
Antibodies to Hepatitis B Surface Antigen Potentiate the Response of Human T Lymphocyte Clones to the Same Antigen
Authors: Celis Esteban , Chang Tse Wen
Published: October 2006

Human T-helper lymphocyte clones specific for hepatitis B virus surface antigen (HBsAg) proliferate on stimulation with HBsAg in vitro. Antibodies specific for HBsAg, but no other antibodies, augment this proliferative response. In the presence of antibodies to HBsAg, the maximum response could be achieved at HBsAg concentrations that were 1 percent of those required in the absence of the antibodies. These findings suggest that antigen-specific antibodies exert regulatory controls on T cells that recognize the same antigens.
Glutamine- and
N
-Acetylglutamate-Dependent Carbamoyl Phosphate Synthetase in Elasmobranchs
Authors: Anderson Paul M.
Published: October 2006

High levels of glutamine- and
N
-acetyl-L-glutamate-dependent carbamoyl phosphate synthetase activity are present in liver extracts of marine species of fish that retain high levels of urea in their tissues for the purpose of osmoregulation. The function of the synthetase in these species appears to be related to urea synthesis.
Centrifugal Fibers to the Eye in a Nonavian Vertebrate: Source Revealed by Horseradish Peroxidase Studies
Authors: Halpern Mimi , Wang Ruu Tong , Colman David R.
Published: October 2006

A source of efferent fibers to the eye of snakes of the genus
Thamnophis
has been identified by the use of the retrograde transport of horseradish peroxidase. Cell bodies of the contralateral nucleus of the ventral supraoptic decussation accumulate horseradish peroxidase after intraocular but not intraorbital injections. Intraocular injections also result in anterograde transport of horseradish peroxidase to retinofugal axon terminals. Intraorbital injections result in accumulation of horseradish peroxidase in the cell bodies of the cranial nerve nuclei of extraocular muscles.
Antibodies Reactive with Human T-Lymphotropic Retroviruses (HTLV-III) in the Serum of Patients with AIDS
Authors: Sarngadharan M. G. , Popovic Mikulas , Bruch Lilian , Schüpbach Jörg , Gallo Robert C.
Published: October 2006

In cats, infection with T-lymphotropic retroviruses can cause T-cell proliferation and leukemia or T-cell depletion and immunosuppression. In humans, some highly T4 tropic retroviruses called HTLV-I can cause T-cell proliferation and leukemia. The subgroup HTLV-II also induces T-cell proliferation in vitro, but its role in disease is unclear. Viruses of a third subgroup of human T-lymphotropic retroviruses, collectively designated HTLV-III, have been isolated from cultured cells of 48 patients with acquired immunodeficiency syndrome (AIDS). The biological properties of HTLV-III and immunological analyses of its proteins show that this virus is a member of the HTLV family, and that it is more closely related to HTLV-II than to HTLV-I. Serum samples from 88 percent of patients with AIDS and from 79 percent of homosexual men with signs and symptoms that frequently precede AIDS, but from less than 1 percent of heterosexual subjects, have antibodies reactive against antigens of HTLV-III. The major immune reactivity appears to be directed against p41, the presumed envelope antigen of the virus.