bluuebunny/crossref_metadata_2025 huggingface dataset:
Kaposi's Sarcoma Cells: Long-Term Culture with Growth Factor from Retrovirus-Infected CD4
+
T Cells
Authors: Nakamura Shuji , Salahuddin S. Zaki , Biberfeld Peter , Ensoli Barbara , Markham Phillip D. , Wong-Staal Flossie , Gallo Robert C.
Published: October 2006

Studies of the biology and pathogenesis of Kaposi's sarcoma (KS) have been hampered by the inability to maintain long-term cultures of KS cells in vitro. In this study AIDS-KS-derived cells with characteristic spindle-like morphology were cultured with a growth factor (or factors) released by CD4
+
T lymphocytes infected with human T-lymphotropic virus type I or II (HTLV-I or HTLV-II) or with human immunodeficiency virus type 1 or 2 (HIV-1 or HIV-2). Medium conditioned by HTLV-II-infected, transformed lines of T cells (HTLV-II CM) contained large amounts of this growth activity and also supported the temporary growth of normal vascular endothelial cells, but not fibroblasts. Interleukin-1 and tumor necrosis factor-α stimulated the growth of the KS-derived cells, but the growth was only transient and these factors could be distinguished from that in HTLV-II CM. Other known endothelial cell growth promoting factors, such as acidic and basic fibroblast growth factors and epidermal growth factor, did not support the long-term growth of the AIDS-KS cells. The factor released by CD4
+
T cells infected with human retroviruses should prove useful in studies of the pathogenesis of KS.
Computers in Molecular Biology: Current Applications and Emerging Trends
Authors: DeLisi Charles
Published: October 2006

The rate of generation of molecular sequence data is forcing the use of computers as a central tool in molecular biology. Current use of computers is limited largely to data management and sequence comparisons, but rapid growth in the volume of data is generating pressure for the development of high-speed analytical methods for deciphering the codes connecting nucleotide sequence with protein structure and function.
Assembly of a Functional Immunoglobulin F
v
Fragment in
Escherichia coli
Authors: Skerra Arne , Plückthun Andreas
Published: October 2006

An expression system was developed that allows the production of a completely functional antigen-binding fragment of an antibody in
Escherichia coli
. The variable domains of the phosphorylcholine-binding antibody McPC603 were secreted together into the periplasmic space, where protein folding as well as heterodimer association occurred correctly. Thus, the assembly pathway for the F
v
fragment in
E. coli
is similar to that of a whole antibody in the eukaryotic cell. The F
v
fragment of McPC603 was purified to homogeneity with an antigen-affinity column in a single step. The correct processing of both signal sequences was confirmed by amino-terminal protein sequencing. The functionality of the recombinant F
v
fragment was demonstrated by equilibrium dialysis. These experiments showed that the affinity constant of the F
v
fragment is identical to that of the native antibody McPC603, that there is one binding site for phosphorylcholine in the F
v
fragment, and that there is no inactive protein in the preparation. This expression system should facilitate future protein engineering experiments on antibodies.
Aspects of a Cognitive Neuroscience of Mental Imagery
Authors: Kosslyn Stephen M.
Published: October 2006

Although objects in visual mental images may seem to appear all of a piece, when the time to form images is measured this introspection is revealed to be incorrect; objects in images are constructed a part at a time. Studies with split-brain patients and normal subjects reveal that two classes of processes are used to form images—ones that activate stored memories of the appearances of parts and ones that arrange parts into the proper configuration. Some of the processes used to arrange parts are more effective in the left cerebral hemisphere and some are more effective in the right cerebral hemisphere; the notion that mental images are the product of right hemisphere activity is an oversimplification.
Development and Testing of AIDS Vaccines
Authors: Koff Waynce C. , Hoth Daniel F.
Published: October 2006

Recent advances in delineating the molecular biology of human immunodeficiency virus type 1 (HIV-1) have led to innovative approaches to development of a vaccine for acquired immunodeficiency syndrome (AIDS). However, the lack of understanding of mechanisms of protective immunity against HIV-1, the magnitude of genetic variation of the virus, and the lack of effective animal models for HIV-1 infection and AIDS have impeded progress. The testing of AIDS vaccines also presents challenges. These include liability concerns over vaccine-related injuries; identification of suitable populations for phase 3 efficacy studies; balancing the ethical obligation to counsel research subjects to avoid high-risk behavior with the necessity to obtain vaccine efficacy data; and the effect of vaccine-induced seroconversion on the recruiting and welfare of trial volunteers. Several candidate AIDS vaccines are nevertheless currently under development, and some are undergoing phase 1 clinical trials. Rapid progress will depend on continued scientific advancement in conjunction with maximum use of resources, open information and reagent exchange, and a spirit of international collaboration.
Fish Oil Prevents Insulin Resistance Induced by High-Fat Feeding in Rats
Authors: Storlien Leonard H. , Kraegen Edward W. , Chisholm Donald J. , Ford Glenn L. , Bruce David G. , Pascoe Wendy S.
Published: October 2006

Non-insulin-dependent diabetes mellitus is an increasingly prevalent disease in Western and developing societies. A major metabolic abnormality of non-insulin-dependent diabetes is impaired insulin action (insulin resistance). Diets high in fat from vegetable and nonaquatic animal sources (rich in linoleic acid, an ω-6 fatty acid, and saturated fats) lead to insulin resistance. In rats fed high-fat diets, replacement of only 6 percent of the linoleic ω-6 fatty acids from safflower oil with long-chain polyunsaturated ω-3 fatty acids from fish oil prevented the development of insulin resistance. The effect was most pronounced in the liver and skeletal muscle, which have important roles in glucose supply and demand. The results may be important for therapy or prevention of non-insulin-dependent diabetes mellitus.
Efflux of Chloroquine from
Plasmodium falciparum
: Mechanism of Chloroquine Resistance
Authors: Krogstad Donald J. , Gluzman Ilya Y. , Kyle Dennis E. , Oduola Ayoade M. J. , Martin Samuel K. , Milhous Wilbur K. , Schlesinger Paul H.
Published: October 2006

Chloroquine-resistant
Plasmodium falciparum
accumulate significantly less chloroquine than susceptible parasites, and this is thought to be the basis of their resistance. However, the reason for the lower accumulation of chloroquine was unknown. The resistant parasite has now been found to release chloroquine 40 to 50 times more rapidly than the susceptible parasite, although their initial rates of chloroquine accumulation are the same. Verapamil and two other calcium channel blockers, as well as vinblastine and daunomycin, each slowed the release and increased the accumulation of chloroquine by resistant (but not susceptible)
Plasmodium falciparum
. These results suggest that a higher rate of chloroquine release explains the lower chloroquine accumulation, and thus the resistance observed in resistant
Plasmodium falciparum
.
The Approaching Era of the Tumor Suppressor Genes
Authors: Klein George
Published: October 2006

Genes that can inhibit the expression of the tumorigenic phenotype have been detected by the fusion of normal and malignant cells, the phenotypic reversion of in vitro transformants, the induction of terminal differentiation of malignant cell lineages, the loss of "recessive cancer genes," the discovery of regulatory sequences in the immediate vicinity of certain oncogenes, and the inhibition of tumor growth by normal cell products. Such tumor suppressor genes will probably turn out to be as, if not more, diversified as the oncogenes. Consideration of both kinds of genes may reveal common or interrelated functional properties.
Methylphenidate in Hyperkinetic Children: Differences in Dose Effects on Learning and Social Behavior
Authors: Sprague Robert L. , Sleator Esther K.
Published: October 2006

Methylphenidate (Ritalin) is widely prescribed for hyperkinetic children. This study showed a peak enhancement of learning in children after being given a dose of 0.3 milligram per kilogram of body weight, and a decrement in learning in those given larger doses; social behavior showed the most improvement in children given 1.0 milligram per kilogram. These results had been hypothesized from theoretical dose-response curves which indicate different target behaviors would improve at different doses.
Diffusion of Small Solutes in Polymer-Containing Solutions
Authors: Yam Kit L. , Anderson Donald K. , Buxbaum Robert E.
Published: October 2006

Diffusion processes involving polymers are common in scientific and engineering separations and are a major component of biological functions. Analyses of these systems are usually based on versions of the Stokes-Einstein equation, although order of magnitude deviations have been observed. Presented here is a theoretical correction to the Stokes-Einstein equation containing a "local viscosity" function that combines diffusional hydrodynamics with Maxwell's treatment of electrical resistance in inhomogeneous regions. The resulting equation accurately predicts experimental diffusion data within tight bounds for polymer concentrations from 0 to 9 percent. It requires knowledge only of thermodynamics and of pure solvent and solution viscosities.
Brain Enolases as Specific Markers of Neuronal and Glial Cells
Authors: Schmechel Donald , Marangos Paul J. , Zis Athanasios P. , Brightman Milton , Goodwin Frederick K.
Published: October 2006

There are three distinct enolase isoenzymes in brain; neuron-specific enolase (NSE), formerly referred to as neuron-specific protein, which is specifically localized in neurons, a nonneuronal enolase (NNE), and a third hybrid form. Light microscopy with immunocytochemical techniques has permitted localization of non-neuronal enolase. The NNE is located in glial cells with no staining of endothelial cells or neurons. Thus, NSE and NNE can be used as specific metabolic markers for neurons and glial cells, respectively.
Dextroamphetamine: Cognitive and Behavioral Effects in Normal Prepubertal Boys
Authors: Rapoport Judith L. , Buchsbaum Monte S. , Zahn Theodore P. , Weingartner Herbert , Ludlow Christy , Mikkelsen Edwin J.
Published: October 2006

The behavioral, cognitive, and electrophysiological effects of a single dose of dextroamphetamine (0.5 milligram per kilogram of body weight) or placebo was examined in 14 normal prepubertal boys (mean age, 10 years 11 months) in a double-blind study. When amphetamine was given, the group showed a marked decrease in motor activity and reaction time and improved performance on cognitive tests. The similarity of the response observed in normal children to that reported in children with "hyperactivity" or minimal brain dysfunction casts doubt on pathophysiological models of minimal brain dysfunction which assume that children with this syndrome have a clinically specific or "paradoxical" response to stimulants.
Developmental Regulation of Two 5
S
Ribosomal RNA Genes
Authors: Wolffe Alan P. , Brown Donald D.
Published: October 2006

The developmental regulation of two kinds of
Xenopus
5
S
RNA genes (oocyte and somatic types) can be explained by differences in the stability of protein-protein and protein-DNA interactions in a transcription complex that directs transcription initiation by RNA polymerase III. Dissociation of transcription factors from oocyte 5
S
RNA genes during development allows them to be repressed by chromatin assembly. In the same cells, somatic 5
S
RNA genes remain active because their transcription complexes are stable.
Pinealocyte Projections into the Mammalian Brain Revealed with S-Antigen Antiserum
Authors: Korf H.-W. , Oksche A. , Ekström P. , Gery I. , Zigler J. S. , Klein D. C.
Published: October 2006

Neural processes from mammalian pinealocytes have been discovered in several brain areas. These processes were visualized immunocytochemically in the Djungarian hamster,
Phodopus sungorus
, with an antiserum against bovine retinal S-antigen and traced as far as the region of the posterior commissure and habenular nuclei. This result indicates that pineal-to-brain connections exist in the mammal, and that the mammalian pineal gland, currently thought of only as a neuroendocrine organ, may communicate directly with select brain regions by way of these projections. The existence of mammalian pinealocyte projections is consistent with the view that these cells are not of glial origin but are derivatives of photoreceptor cells of the pineal complex of lower vertebrates that transmit signals to the brain by neural projections.
Diverse Gene Expression for Isotypes of Murine Serum Amyloid A Protein During Acute Phase Reaction
Authors: Yamamoto Ken-Ichi , Shiroo Masahiro , Migita Shunsuke
Published: October 2006

Serum amyloid A protein (SAA) is a precursor for a major component of amyloid fibrils, which, upon deposition, cause secondary amyloidosis in diseases such as rheumatoid arthritis. In mice, SAA is encoded by at least three genes, which show diverse expression during inflammation. Furthermore, in amyloidosis-resistant SJL mice, the gene expression for one SAA isotype, SAA2, is defective, although SAA2 gene expression is normal in amyloidosis-susceptible BALB/c mice. Because only SAA2-derived products deposit in mouse amyloid tissues, the resistance of SJL mice to amyloidosis seems to be due to defective SAA2 gene expression. Thus, the study emphasizes the importance of SAA gene structure in determining susceptibility to amyloidosis.
Fine Structure Genetic Analysis of a β-Globin Promoter
Authors: Myers Richard M. , Tilly Kit , Maniatis Tom
Published: October 2006

A novel procedure for saturation mutagenesis of cloned DNA was used to obtain more than 100 single base substitutions within the promoter of the mouse β-major globin gene. The effects of these promoter substitutions on transcription were determined by transfecting the cloned mutant genes into HeLa cells on plasmids containing an SV40 transcription enhancer, and measuring the levels of correctly initiated β-globin transcripts after 2 days. Mutations in three regions of the promoter resulted in a significant decrease in the level of transcription: (i) the CACCC box, located between -87 and -95, (ii) the CCAAT box, located between -72 and -77, and (iii) the TATA box, located between -26 and -30 relative to the start site of transcription. In contrast, two different mutations in nucleotides immediately upstream from the CCAAT box resulted in a 3- to 3.5-fold increase in transcription. With two minor exceptions, single base substitutions in all other regions of the promoter had no effect on transcription. These results precisely delineate the
cis
-acting sequences required for accurate and efficient initiation of β-globin transcription, and they establish a general approach for the fine structure genetic analysis of eukaryotic regulatory sequences.
Reversible Inhibition of Mammary Gland Growth by Transforming Growth Factor-β
Authors: Silberstein Gary B. , Daniel Charles W.
Published: October 2006

Transforming growth factor-β (TGF-β) can stimulate or inhibit growth of cells in vitro, as well as induce the transformed phenotype. Although widely distributed in animal tissue, the effects of TGF-β in vivo are largely unknown, and a physiological role for the peptide hormone has not been demonstrated. The effect of TGF-β on developing epithelial tissue in situ was studied by using slow-release plastic pellets containing TGF-β to treat developing mouse mammary gland. Powerful inhibition of mammary growth and morphogenesis was observed. This growth-inhibited mammary tissue was histologically normal, and the inhibitory effect was fully reversible. Under the conditions of these experiments, TGF-β displayed many of the characteristics expected of a physiologically active growth-regulatory molecule.
Morton's Ranking of Races by Cranial Capacity
Authors: Gould Stephen Jay
Published: October 2006

Samuel George Morton, self-styled objective empiricist, amassed the world's largest pre-Darwinian collection of human skulls. He measured their capacity and produced the results anticipated in an age when few Caucasians doubted their innate superiority: whites above Indians, blacks at the bottom. Morton published all his raw data, and it is shown here that his summary tables are based on a patchwork of apparently unconscious finagling. When his data are properly reinterpreted, all races have approximately equal capacities. Unconscious or dimly perceived finagling is probably endemic in science, since scientists are human beings rooted in cultural contexts, not automatons directed toward external truth.
Both Photons and Fluoride Ions Excite
Limulus
Ventral Photoreceptors
Authors: Fein Alan , Corson D. Wesleu
Published: October 2006

Illuminating
Limulus
ventral photoreceptors with dim light results in a response composed of discrete waves. In the dark, adding 10 m
M
sodium fluoride to the artificial seawater that bathes the photoreceptor includes discrete waves. The fluoride-induced waves are similar to those evoked by light. These findings suggest that fluoride induces a process similar or identical to visual excitation of the photoreceptor.
The Fos Protein Complex Is Associated with DNA in Isolated Nuclei and Binds to DNA Cellulose
Authors: Sambucetti Lidia C. , Curran Tom
Published: October 2006

The properties of the viral and cellular
fos
proteins (Fos) were investigated as a first step toward understanding the function of the
fos
gene. Treatment of nuclei with salt and nonionic detergents solubilized a complex that contained Fos together with several other cellular proteins. The majority of the Fos protein complex was released from isolated nuclei incubated in the presence of deoxyribonuclease I or micrococcal nuclease but not with ribonuclease A, suggesting that Fos is associated with chromatin. This hypothesis is supported by the finding that Fos protein from native or denatured nuclear extracts exhibited DNA-binding activity in vitro. These results suggest that Fos is involved in the regulation of gene expression.
Regulation of
bcl-2
Proto-Oncogene Expression During Normal Human Lymphocyte Proliferation
Authors: Reed John C. , Tsujimoto Yoshihide , Alpers James D. , Croce Carlo M. , Nowell Peter C.
Published: October 2006

The
bcl
-2 and c-
myc
proto-oncogenes are brought into juxtaposition with the immunoglobulin heavy chain locus in particular B-cell lymphomas, resulting in high levels of constitutive accumulation of their messenger RNAs. Precisely how the products of the
bcl
-2 and c-
myc
genes contribute to tumorigenesis is unknown, but observations that c-
myc
expression is rapidly induced in nonneoplastic lymphocytes upon stimulation of proliferation raise the possibility that this proto-oncogene is involved in the control of normal cellular growth. In addition to c-
myc
, the
bcl
-2 proto-oncogene also was expressed in normal human B and T lymphocytes after stimulation with appropriate mitogens. Comparison of the regulation of the expression of these proto-oncogenes demonstrated marked differences and provided evidence that, in contrast to c-
myc
, levels of
bcl
-2 messenger RNA are regulated primarily through transcriptional mechanisms.
Viremia in Experimental Creutzfeldt-Jakob Disease
Authors: Manuelidis Elias E. , Gorgacs Edward J. , Manuelidis Laura
Published: October 2006

Inoculation of the buffy coat of blood from guinea pigs infected with Creutzfeldt-Jakob disease resulted in passage of this disease to recipient animals. This demonstrates that there is a viremia in experimental Creutzfeldt-Jakob disease. These findings suggest that the hematogenous route may be implicated in the human infection and that the disease may possibly be transmitted by blood transfusions.
Three-Dimensional Structure of Interleukin-2
Authors: Brandhuber Barbara J. , Boone Tom , Kenney William C. , McKay David B.
Published: October 2006

Interleukin-2 is an effector protein that participates in modulating the immune response; it has become a focal point for the study of lymphokine structure and function. The three-dimensional structure of the interleukin molecule has been solved to 3.0 angstrom resolution. Interleukin-2 has a novel alpha-helical tertiary structure that suggests one portion of the molecule forms a structural scaffold, which underlies the receptor binding facets of the molecule.
Biosynthesis of the
Torpedo californica
Acetylcholine Receptor α Subunit in Yeast
Authors: Fujita Norihisa , Nelson Nathan , Fox Thomas D. , Claudio Toni , Lindstrom Jon , Riezman Howard , Hess George P.
Published: October 2006

Yeast cells were transformed with a plasmid containing complementary DNA encoding the α subunit of the
Torpedo californica
acetylcholine receptor. These cells synthesized a protein that had the expected molecular weight, antigenic specificity, and ligand-binding properties of the α subunit. The subunit was inserted into the yeast plasma membrane, demonstrating that yeast has the apparatus to express a membrane-bound receptor protein and to insert such a foreign protein into its plasma membrane. The α subunit constituted approximately 1 percent of the total yeast membrane proteins, and its density was about the same in the plasma membrane of yeast and in the receptor-rich electric organ of
Electrophorus electricus
. In view of the available technology for obtaining large quantities of yeast proteins, it may now be possible to obtain amplified amounts of interesting membrane-bound proteins for physical and biochemical studies.
Adherence of Group A Streptococci to Pharyngeal Cells: A Role In The Pathogenesis of Rheumatic Fever
Authors: Selinger Daniel S. , Julie Neil , Reed William P. , Williams Ralph C.
Published: October 2006

We used an assay in vitro to investigate the possible role of streptococcal adherence to human pharyngeal cells in the pathogenesis of acute rheumatic fever. There was no difference in adherence of rheumatic fever-associated and non-associated strains of group A streptococci to pooled pharyngeal cells of normal people. Likewise, streptococci not associated with rheumatic fever adhered equally well to cells taken from normal people and from patients with rheumatic heart disease. However, the pharyngeal cells of all nine rheumatic heart disease patients tested had increased avidity for adherence for a rheumatic fever-associated strain of streptococcus compared to the pharyngeal cells obtained from age- and sex-matched controls. Increased streptococcal adherence to pharyngeal cells of rheumatic fever-prone patients may play a role in the pathogenesis of rheumatic fever.
Bone Marrow Origin of Hepatic Macrophages (Kupffer Cells) in Humans
Authors: Gale Robert Peter , Sparkes Robert S. , Golde David W.
Published: October 2006

Hepatic macrophages (Kupffer cells) from two male recipients of bone marrow transplants from females were studied for fluorescent Y body staining and sex chromatin (Barr body). After the transplant, macrophages had the sex karyotype of the donor, indicating that human hepatic macrophages originate in bone marrow.
Answering Autobiographical Questions: The Impact of Memory and Inference on Surveys
Authors: Bradburn Norman M. , Rips Lance J. , Shevell Steven K.
Published: October 2006

Survey questions often probe respondents for quantitative facts about events in their past: "During the last 2 weeks, on days when you drank liquor, about how many drinks did you have?" "During the past 12 months, how many visits did you make to a dentist?" "When did you last work at a full-time job?" are all examples from national surveys. Although questions like these make an implicit demand to remember and enumerate specific autobiographical episodes, respondents frequently have trouble complying because of limits on their ability to recall. In these situations, respondents resort to inferences that use partial information from memory to construct a numeric answer. Results from cognitive psychology can be useful in understanding and investigating these phenomena. In particular, cognitive research can help in identifying situations that inhibit or facilitate recall and can reveal inferences that affect the accuracy of respondents' answers.
Risk Assessment in Environmental Policy-Making
Authors: Russell Milton , Gruber Michael
Published: October 2006

Environmental policy-making has become more dependent on formal, quantitative risk assessment because of increasing attention to the prevention of human health damage from toxic chemicals. Risk assessment helps set priorities for regulation of the very large numbers of chemicals that are of potential concern and helps direct limited social and government resources against the most significant risks. Although the scientific basis for risk assessment is often uncertain and the public and its representatives have often been confused by its use in regulatory decisions, the U.S. Environmental Protection Agency currently uses a variety of risk assessment techniques to set priorities, tailor regulations, and make decisions at particular sites. The Environmental Protection Agency also attempts to make the practice of risk assessment more consistent throughout the agency and to improve public understanding of the meaning of risk assessment and risk management.
Gene Flow and the Geographic Structure of Natural Populations
Authors: Slatkin Montgomery
Published: October 2006

There is abundant geographic variation in both morphology and gene frequency in most species. The extent of geographic variation results from a balance of forces tending to produce local genetic differentiation and forces tending to produce genetic homogeneity. Mutation, genetic drift due to finite population size, and natural selection favoring adaptations to local environmental conditions will all lead to the genetic differentiation of local populations, and the movement of gametes, individuals, and even entire populations—collectively called gene flow—will oppose that differentiation. Gene flow may either constrain evolution by preventing adaptation to local conditions or promote evolution by spreading new genes and combinations of genes throughout a species' range. Several methods are available for estimating the amount of gene flow. Direct methods monitor ongoing gene flow, and indirect methods use spatial distributions of gene frequencies to infer past gene flow. Applications of these methods show that species differ widely in the gene flow that they experience. Of particular interest are those species for which direct methods indicate little current gene flow but indirect methods indicate much higher levels of gene flow in the recent past. Such species probably have undergone large-scale demographic changes relatively frequently.
Disruption of the
Dictyostelium
Myosin Heavy Chain Gene by Homologous Recombination
Authors: De Lozanne Arturo , Spudich James A.
Published: October 2006

The phenomenon of homologous recombination, which allows specific gene conversion and gene insertion, can be a powerful system for the study of eukaryotic cell biology. Data are presented demonstrating that integration of a transfected plasmid by homologous recombination occurs in the motile eukaryotic cell
Dictyostelium discoideum
. A plasmid carrying a G418 resistance gene and the amino terminal half of the myosin heavy chain gene was used to transfect
Dictyostelium
. A large fraction of the resultant G418-resistant cells had the plasmid integrated into the single genomic copy of the heavy chain gene. These cells, which fail to express the native myosin but express the myosin fragment, are defective in cytokinesis and become large and multinucleate. In spite of the absence of native myosin, these cells, termed
hmm
cells, exhibit many forms of cell movement, including membrane ruffling, phagocytosis, and chemotaxis. The
hmm
cells can aggregate but are blocked at a later stage in the
Dictyostelium
developmental cycle. The
hmm
cells revert to the wild-type phenotype. Reversion of the
hmm
phenotype is due to excision and loss of the transforming plasmid. The revertant cells express native myosin, are G418 sensitive, and have a normal developmental cycle. These results constitute genetic proof that the intact myosin molecule is required for cytokinesis and not for karyokinesis.
The Inversion of Sensory Processing by Feedback Pathways: A Model of Visual Cognitive Functions
Authors: Harth E. , Unnikrishnan K. P. , Pandya A. S.
Published: October 2006

The mammalian visual system has a hierarchic structure with extensive reciprocal connections. A model is proposed in which the feedback pathways serve to modify afferent sensory stimuli in ways that enhance and complete sensory input patterns, suppress irrelevant features, and generate quasi-sensory patterns when afferent stimulation is weak or absent. Such inversion of sensory coding and feature extraction can be achieved by optimization processes in which scalar responses derived from high-level neural analyzers are used as cost functions to modify the filter properties of more peripheral sensory relays. An optimization algorithm, Alopex, which is used in the model, is readily implemented with known neural circuitry. The functioning of the system is investigated by computer simulations.
Isolation of a T-Lymphotropic Virus from Domestic Cats with an Immunodeficiency-Like Syndrome
Authors: Pedersen Niels C. , Ho Esther W. , Brown Marlo L. , Yamamoto Janet K.
Published: October 2006

A highly T-lymphotropic virus was isolated from cats in a cattery in which all the animals were seronegative for feline leukemia virus. A number of cats in one pen had died and several had an immunodeficiency-like syndrome. Only 1 of 18 normal cats in the cattery showed serologic evidence of infection with this new virus, whereas 10 of 25 cats with signs of ill health were seropositive for the virus. Tentatively designated feline T-lymphotropic lentivirus, this new feline retrovirus appears to be antigenically distinct from human immunodeficiency virus. There is no evidence for cat-to-human transmission of the agent. Kittens experimentally infected by way of blood or plasma from naturally infected animals developed generalized lymphadenopathy several weeks later, became transiently febrile and leukopenic, and continued to show a generalized lymphadenopathy 5 months after infection.
Cellular Applications of
31
P and
13
C Nuclear Magnetic Resonance
Authors: Shulman R. G. , Brown T. R. , Ugurbil K. , Ogawa S. , Cohen S. M. , den Hollander J. A.
Published: October 2006

High-resolution nuclear magnetic resonance (NMR) studies of cells and purified mitochondria are discussed to show the kind of information that can be obtained in vivo. In suspensions of
Escherichia coli
both phosphorus-31 and carbon-13 NMR studies of glycolysis and bioenergetics are presented. In rat liver cells the pathways of gluconeogenesis from carbon-13-labeled glycerol are followed by carbon-13 NMR. In the intact liver cells cytosolic and mitochondrial
p
H's were separately measured by phosphorus-31 NMR. In purified mitochondria the internal and external concentrations of inorganic phosphate, adenosine diphosphate, and adenosine triphosphate were determined by phosphorus-31 NMR while the
p
H difference across the membrane was measured simultaneously.
Chitin Synthetase Distribution on the Yeast Plasma Membrane
Authors: Duran Angel , Cabib Enrico , Bowers Blair
Published: October 2006

Purified, intact yeast plasma membranes were allowed to synthesize chitin, and the nascent chains of polysaccharide were observed either by the fluorescence produced with a brightener or by autoradiography. By both methods, it was concluded that the newly formed chitin emerged at many sites on each membrane. Thus, the synthetase that catalyzes chitin formation has a similar distribution. Since chitin synthetase is found mainly in a zymogen form, these results confirm the hypothesis that initiation of the chitinous primary septum of
Saccharomyces
occurs by localized activation of the uniformly distributed zymogen.
Purification and Properties of
Drosophila
Heat Shock Activator Protein
Authors: Wu Carl , Wilson Susan , Walker Barbara , Dawid Igor , Paisley Thomas , Zimarino Vincenzo , Ueda Hitoshi
Published: October 2006

Drosophila
heat shock activator protein, a rare transacting factor which is induced upon heat shock to bind specifically to the heat shock regulatory sequence in vivo, has been purified from shocked cells to more than 95 percent homogeneity by sequence-specific duplex oligonucleotide affinity chromatography. The purified protein has a relative molecular mass of 110 kilodaltons, binds to the regulatory sequence with great affinity and specificity, and strongly stimulates transcription of the
Drosophila
hsp70
gene. Studies with this regulatory protein should lead to an understanding of the biochemical pathway underlying the heat shock phenomenon.
A Distinct Endothelial Cell Recognition System That Controls Lymphocyte Traffic into Inflamed Synovium
Authors: Jalkanen S. , Steere A. C. , Fox R. I. , Butcher E. C.
Published: October 2006

Lymphocytes are essential mediators of normal tissue inflammatory reactions and of pathologic tissue damage in, for example, rheumatoid arthritis and other autoimmune diseases. In a study of the mechanisms controlling lymphocyte entry into sites of inflammation from the blood, the function and specificity of lymphocyte-endothelial interactions were examined in inflamed joint tissue (synovium) from patients with rheumatoid arthritis. Synovial high endothelial venules (HEV) supported the binding of normal peripheral blood lymphocytes in vitro. The characteristics of this binding, which were similar to those of lymphocyte-HEV interactions controlling lymphocyte migration into organized lymphoid tissues, included a requirement for calcium ions, a dependence on metabolic activity, and a preferential adherence of circulating lymphocytes as opposed to immature thymocytes. However, the binding of lymphocytes to synovial HEV was not inhibited by a monoclonal antibody to lymphocyte receptors for lymph node HEV, and synovial HEV failed to bind either lymph node HEV-specific or mucosal HEV-specific B lymphoblastoid cells. The results suggest that a lymphocyte-endothelial cell recognition system that is distinct from such systems in organized lymphoid tissues directs the extravasation of normal lymphocytes as well as pathologically important effector cells into inflamed synovium.
Split Genes and RNA Splicing
Authors: Crick Francis
Published: October 2006

A number of genes in higher organisms and in their viruses appear to be split. That is, they have "nonsense" stretches of DNA interspersed within the sense DNA. The cell produces a full RNA transcript of this DNA, nonsense and all, and then appears to splice out the nonsense sequences before sending the RNA to the cytoplasm. In this article what is known about these intervening sequences and about the processing of the RNA is outlined. Also discussed is their possible use and how they might have arisen in evolution.
Chromosome Y-Specific DNA Is Transferred to the Short Arm of X Chromosome in Human XX Males
Authors: Andersson Mea , Page David C. , de la Chapelle Albert
Published: October 2006

Y-chromosomal DNA is present in the genomes of most human XX males. In these cases, maleness is probably due to the presence of the Y-encoded testis-determining factor (TDF). By means of in situ hybridization of a probe (pDP105) detecting Y-specific DNA to metaphases from three XX males, it was demonstrated that the Y DNA is located on the tip of the short arm of an X chromosome. This finding supports the hypothesis that XX maleness is frequently the result of transfer of Y DNA, including TDF, to a paternally derived X chromosome.
Correspondence Matching in Apparent Motion: Evidence for Three-Dimensional Spatial Representation
Authors: Green Marc , Odom J. Vernon
Published: October 2006

The path of an object in apparent motion depends on correspondence matching, the decision that images seen at different places and at different times represent the same object. One determinant of correspondence is proximity. Still debated, however, is whether proximity is defined in a two- or three-dimensional spatial representation. Observers judged the motion path taken by an object with two neighbors of different apparent depth. Given similar two-dimensional distances, objects moved toward the neighbor of the same apparent depth. This is evidence that correspondence operates in a three-dimensional spatial representation.
Leucosulfakinin, a Sulfated Insect Neuropeptide with Homology to Gastrin and Cholecystokinin
Authors: Nachman Ronald J. , Holman G. Mark , Haddon William F. , Ling Nicholas
Published: October 2006

A sulfated, myotropic neuropeptide termed leucosulfakinin (Glu-Gln-Phe-Glu-Asp-Tyr(SO
3
H)-Gly-His-Met-Arg-Phe-NH
2
) was isolated from head extracts of the cockroach
Leucophaea maderae
. The peptide exhibits sequence homology with the hormonally active portion of the vertebrate hormones human gastrin II and cholecystokinin, suggesting that these peptides are evolutionarily related. Six of the 11 amino acid residues (55 percent) are identical to those in gastrin II. In addition, the intestinal myotropic action of leucosulfakinin is analogous to that of gastrin.
Stimulation of Neuronal Acetylcholine Receptors Induces Rapid Gene Transcription
Authors: Greenberg Michael E. , Ziff Edward B. , Greene Lloyd A.
Published: October 2006

Cholinergic agonists rapidly and transiently induced transcription of the c-
fos
protooncogene and one or more actin genes in neuronally differentiated PC12 cells. Transcription was activated within minutes after stimulation of the nicotinic acetylcholine receptor and required an influx of extracellular Ca
2+
ions through voltage-sensitive calcium channels. Nicotine activation proceeded by a different pathway from activation by nerve growth factor, whose stimulation of these genes is independent of extracellular Ca
2+
ions. These findings suggest that neurotransmitters may rapidly activate specific gene transcription in nondividing neuronally differentiated cells. They also suggest a functional role for neurotransmitter induction of c-
fos
and actin expression in the nervous system.
Activation of Smooth Muscle Contraction: Relation Between Myosin Phosphorylation and Stiffness
Authors: Kamm Kristine E. , Stull James T.
Published: October 2006

Contraction and myosin light-chain phosphorylation were measured in electrically stimulated tracheal smooth muscle. Latencies for the onset of force, stiffness, and light-chain phosphorylation were 500 milliseconds. Myosin light chain was phosphorylated from 0.04 to 0.80 mole of phosphate per mole of light chain with a pseudo-first-order rate of 1.1 per second with no evidence of an ordered or negatively cooperative process. Following the period of latency, stiffness increased with phosphorylation and both increased more rapidly than isometric force. The linear relation between stiffness and phosphorylation during activation suggests independent attachment of each myosin head upon phosphorylation.
Cultivation of
Rhinosporidium seeberi
in Vitro: Interaction with Epithelial Cells
Authors: Levy Michael G. , Meuten Donald J. , Breitschwerdt Edward B.
Published: October 2006

Rhinosporidium seeberi
, a fungus that is associated with polyp-like tumors in animals and man, was successfully cultivated. This organism stimulated proliferation of epithelial cells in vitro, producing polyp-like structures. Spores produced in culture required a period of aging or development, or both, before they were capable of reinitiating the growth cycle.
Permeability of the Cell-to-Cell Membrane Channels in Mammalian Cell Junction
Authors: Flagg-Newton Jean , Simpson Ian , Loewenstein Werner R.
Published: October 2006

The channels in the junctions of various mammalian cell types—primary cultures and lines—were probed with a series of linear fluorescent amino acid and peptide molecules of different size and charge. Permeability is limited by probe size and electronegativity, these two factors apparently being related reciprocally. In respect to both factors, mammalian junctional channels are more restrictive than insect channels; hence the mammalian channels are narrower, more polar, or both. The channels of the various mammalian cell types differed slightly from each other; in some types the serum of the culture medium affected the channel permeability.
Induction of Luteolysis in the Human with a Long-Acting Analog of Luteinizing Hormone-Releasing Factor
Authors: Casper R. F. , Yen S. S. C.
Published: October 2006

Subcutaneous injection of 50 micrograms of a long-acting analog of luteinizing hormone-releasing factor on each of two successive days during midluteal phase in normally cycling women induced a short luteal phase and premature menstruation. These events were associated with luteolysis, as evidenced by the consistent and parallel premature decline of progesterone and estradiol levels compared with those in control cycles. This finding may prove to be useful in the prevention or interception of implantation.
Heparin Neutralization of PGI
2
: Effects Upon Platelets
Authors: Saba Hussain I. , Saba Sabiha R. , Blackburn Cynthia A. , Hartmann Robert C. , Mason Reginald G.
Published: October 2006

Heparin neutralizes the inhibitory effect of prostacyclin (PGI
2
) on platelet aggregation. The PGI
2
-induced enhancement of platelet cyclic adenosine monophosphate levels is also inhibited. The mechanism appears to involve a direct interaction in which heparin neutralizes the inhibitory effects of PGI
2
on platelet aggregation but, at the same time, does not lose its own anticoagulant activity. These findings may explain instances in which heparin infusions have been reported to produce hyperaggregation of platelets, thrombotic episodes, and thrombocytopenia in patients.
The Glucocorticoid Receptor Protein Binds to Transfer RNA
Authors: Ali Masarrat , Vedeckis Wayne V.
Published: October 2006

The glucocorticoid receptor from mouse AtT-20 cells exists in three forms: (i) the untransformed receptor (9.1
S
;
M
r
of 319,000), a large oligomeric molecule that does not bind to DNA; (ii) the transformed receptor (4
S
;
M
r
of 96,000), which is formed by dissociation of untransformed receptor after steroid binding and which binds to DNA to modulate gene expression; and (iii) an intermediate size receptor (6
S
;
M
r
of 132,000), which also binds to DNA and contains a bound small RNA molecule. This RNA species has now been purified and identified as transfer RNA (tRNA). The three tRNA's for the basic amino acids accounted for about 78% of the total amino acid-accepting activity [arginine (52%), lysine (17%), and histidine (9%)], while the remaining 22% was represented by six other tRNA species. This tRNA-binding activity of the glucocorticoid receptor may reflect post-transcriptional mechanisms of regulating gene expression, such as alterations in the translational efficiency of or the modulation of the stability of hormone-induced proteins.
Genetic Effects of Impure and Pure Saccharin in Yeast
Authors: Moore Carol W. , Schmick Ann
Published: October 2006

Yeast cells were grown in media containing impure or purified saccharin preparations. Dose-dependent increases in frequencies of cells possessing aberrant cell morphologies were revealed by light microscopy. At each test dose, cells grown in impure saccharin exhibited up to sevenfold higher frequencies of mitotic crossing-over or gene conversion in three of four assays for genetic recombination than cells grown in purified saccharin from the same lot. With one exception, the sweetener produced by the Maumee process caused larger increases in recombination and gene reversion than the sweetener produced by the Remsen-Fahlberg process. The several test markers did not respond equally to any test saccharin. Cells grown in liquid media containing no saccharin or two of three test concentrations of saccharin produced cell titers that were approximately equivalent.
Computer-Assisted Analysis in Organic Synthesis
Authors: Corey E. J. , Long Alan K. , Rubenstein Stewart D.
Published: October 2006

The planning of alternative routes for the synthesis of complex organic molecules has been facilitated by the formulation of guiding strategies that can be applied to a broad range of problems. Analysis of organic synthesis can be carried out in the retrosynthetic direction, opposite to the actual process of chemical synthesis, or bidirectionally, that is, as a combined retrosynthetic and synthetic search. An interactive computer program is described which utilizes the general strategies of retrosynthetic analysis and an appropriate database to generate pathways of chemical intermediates for chemical synthesis of a particular target structure. Computer graphics and standard chemical structures are used for man-machine communication.
Insertion Mutagenesis of Embryonal Carcinoma Cells by Retroviruses
Authors: King Walter , Patel Mayuri D. , Lobel Leslie I. , Goff Stephen P. , Nguyen-Huu M. Chi
Published: October 2006

Mutagenesis was studied in cultured F9 embryonal carcinoma cells infected with a variant of Moloney murine leukemia virus. Proviral insertion induced the inactivation of the hypoxanthine phosphoribosyltransferase locus, and the virus was used to isolate the mutated genes rapidly. Mutagenesis by these methods may be useful for the genetic dissection of the various mammalian cell phenotypes.
Antibodies to Histones and Histone-Histone Complexes: Immunochemical Evidence for Secondary Structure in Histone 1
Authors: Mihalakis Nicholas , Miller Orlando J. , Erlanger Bernard F.
Published: October 2006

Highly specific antibodies were raised to histone 1 (H1) and the histone complexes H3
2
-H4
2
and H2A-H2B, isolated by salt extraction. Antibody to H1 could detect irreversible conformational changes in acid- or urea-treated H1. The antibodies showed different reactivities with chromosomes as compared to antibodies in acid-extracted histones and should be useful in studies of native chromatin and chromosome structure.
Antibodies to Sporozoites: Their Frequent Occurrence in Individuals Living in an Area of Hyperendemic Malaria
Authors: Nardin Elizabeth Higgins , Nussenzweig Ruth S. , McGregor Ian A. , Bryan Joan H.
Published: October 2006

Serum samples from 158 West Africans were tested for antibodies against sporozoites, the vector stage of the malaria parasite. Antibodies specific for
Plasmodium falciparum
sporozoites were detected by means of the circumsporozoite precipitation assay and indirect immunofluorescence. More than 90 percent of the serum samples from adults gave positive immunofluorescent reactions against falciparum sporozoites, whereas most of the samples from children gave low or negative reactions.