bluuebunny/crossref_metadata_2025 huggingface dataset:
Engineering Enzyme Specificity by "Substrate-Assisted Catalysis"
Authors: Carter Paul , Wells James A.
Published: October 2006

A novel approach to engineering enzyme specificity is presented in which a catalytic group from an enzyme is first removed by site-directed mutagenesis causing inactivation. Activity is then partially restored by substrates containing the missing catalytic functional group. Replacement of the catalytic His
64
with Ala in the
Bacillus amyloliquefaciens
subtilisin gene (the mutant is designated His64Ala) by site-directed mutagenesis reduces the catalytic efficiency (
k
cat
/
K
m
) by a factor of a million when assayed with
N
-succinyl-L-Phe-L-Ala-L-Ala-L-Phe-
p
-nitroanilide (sFAAF-pNA). Model building studies showed that a His side chain at the P2 position of a substrate bound at the active site of subtilisin could be virtually superimposed on the catalytic His side chain of this serine protease. Accordingly, the His64Ala mutant hydrolyzes a His P2 substrate (sFAHF-pNA) up to 400 times faster than a homologous Ala P2 or Gln P2 substrate (sFAAF-pNA or sFAQF-pNA) at
p
H 8.0. In contrast, the wild-type enzyme hydrolyzes these three substrates with similar catalytic efficiencies. Additional data from substrate-dependent
p
H profiles and hydrolysis of large polypeptides indicate that the His64Ala mutant enzyme can recover partially the function of the lost catalytic histidine from a His P2 side chain on the substrate. Such "substrate-assisted catalysis" provides a new basis for engineering enzymes with very narrow and potentially useful substrate specificities. These studies also suggest a possible functional intermediate in the evolution of the catalytic triad of serine proteases.
Computer-Aided Molecular Design
Authors: McCammon J. Andrew
Published: October 2006

Theoretical chemistry, as implemented on fast computers, is beginning to yield accurate predictions of the thermodynamic and kinetic properties of large molecular assemblies. In addition to providing detailed insights into the origins of molecular activity, theoretical calculations can be used to design new molecules with specific properties. This article describes two types of calculations that show special promise as design tools, the thermodynamic cycle-perturbation method and the Brownian reactive dynamics method. These methods can be applied to calculate equilibrium and rate constants that describe many aspects of molecular recognition, stability, and reactivity.
Cytokine-Induced Expression of HIV-1 in a Chronically Infected Promonocyte Cell Line
Authors: Folks Thomas M. , Justement Jesse , Kinter Audrey , Dinarello Charles A. , Fauci Anthony S.
Published: October 2006

A model system for cytokine-induced up-regulation of human immunodeficiency virus type 1 (HIV-1) expression in chronically infected promonocyte clones was established. The parent promonocyte cell line U937 was chronically infected with HIV-1 and from this line a clone, U1, was derived. U1 showed minimal constitutive expression of HIV-1, but virus expression was markedly up-regulated by a phytohemagglutinin-induced supernatant containing multiple cytokines and by recombinant granulocyte/macrophage colony-stimulating factor alone. Recombinant interleukin-1 (IL-1), IL-2, interferon-γ, and tumor necrosis factor-α did not up-regulate virus expression. Concomitant with the cytokine-induced up-regulation of HIV-1, expression of membrane-bound IL-1β was selectively induced in U1 in the absence of induction of other surface membrane proteins. This cytokine up-regulation of IL-1β was not seen in the uninfected parent U937 cell line. These studies have implications for the understanding of the mechanism of progression from a latent or low-level HIV-1 infection to a productive infection with resulting immunosuppression. In addition, this model can be used to delineate the potential mechanisms whereby HIV-1 infection regulates cellular gene expression.
Effect of Neonatal Handling on Age-Related Impairments Associated with the Hippocampus
Authors: Meaney Michael J. , Aitken David H. , van Berkel Chayann , Bhatnagar Seema , Sapolsky Robert M.
Published: October 2006

In rats, an environmental manipulation occurring early in life resulted in changes in the adrenocortical axis that persisted throughout the entire life of the animals and attenuated certain deficits associated with aging. Rats handled during infancy had a permanent increase in concentrations of receptors for glucocorticoids in the hippocampus, a critical region in the negative-feedback inhibition of adrenocortical activity. Increased receptor concentrations led to greater hippocampal sensitivity to glucocorticoids and enhanced negative-feedback efficacy in the handled rats. Thus, at all ages tested, rats that were not handled secreted more glucocorticoids in response to stress than did handled rats. At later ages, nonhandled rats also showed elevated basal glucocorticoid levels, with the result that there was a greater cumulative exposure to glucocorticoids in nonhandled rats. Increased exposure to adrenal glucocorticoids can accelerate hippocampal neuron loss and cognitive impairments in aging. Hippocampal cell loss and pronounced spatial memory deficits emerged with age in the nonhandled rats, but were almost absent in the handled rats. Previous work showed that glucocorticoid hypersecretion, hippocampal neuron death, and cognitive impairments form a complex degenerative cascade of aging in the rat. The present study shows that a subtle manipulation early in life can retard the emergence of this cascade.
Tertiary Structure Is a Principal Determinant to Protein Deamidation
Authors: Kossiakoff A. A.
Published: October 2006

The protein deamidation process involves the conversion of the amide side-chain moieties of asparagine and glutamine residues to carboxyl groups. This conversion is an unusual form of protein modification in that it requires catalysis by an intramolecular reaction where both the substrate (asparagine and glutamine side chains) and "catalytic site" (the peptide nitrogen of the succeeding residue) are constituents of several consecutive residues along the polypeptide chain. The stereochemical factors governing this process were studied with a data base derived from the neutron crystallographic structure of trypsin from which amide groups and oxygen can be unambiguously differentiated because of their different neutron scattering properties. The neutron structure allowed for the direct determination of those residues that were deamidated; 3 of 13 asparagine residues were found to be modified. These modified residues were clearly distinguished by a distinct local conformation and hydrogen-bonding structure in contrast to those observed for the other asparagine residues. No correlation was found between preference to deamidate and the chemical character of residues flanking the site, as had been proposed from previous peptide studies.
Phosphorylation of Isocitrate Dehydrogenase of
Escherichia coli
Authors: Garnak Margit , Reeves Henry C.
Published: October 2006

Addition of acetate to a stationary phase culture of
Escherichia coli
in glycerol mineral salts medium containing phosphorus-32-labeled orthophosphate results in rapid loss of isocitrate dehydrogenase activity and concomitant incorporation of phosphorus-32 into the enzyme. This is the first example of protein phosphorylation in a bacterium in which the endogenous substrate for the protein kinase has been identified.
Amplification and Rearrangement of Hu-
ets
-1 in Leukemia and Lymphoma with Involvement of 11q23
Authors: Rovigatti Ugo , Watson Dennis K. , Yunis Jorge J.
Published: October 2006

The Hu-
ets
-1 oncogene was found to be rearranged and amplified 30-fold in one case of acute myelomonocytic leukemia in which a homogeneously staining region occurred on 11q23; the oncogene was rearranged and amplified approximately tenfold in a case of small lymphocytic cell lymphoma with an inverted insertion that also involved band 11q23. This work suggests that Hu-
ets
-1 is an unusual oncogene that can help explain the common involvement of chromosome band 11q23 in various subtypes of hematopoietic malignancies.
Specific Immunosuppression by Immunotoxins Containing Daunomycin
Authors: Diener E. , Diner U. E. , Sinha A. , Xie S. , Vergidis R.
Published: October 2006

Daunomycin, when conjugated with a targeting antigen by an acid-sensitive spacer, remains inactive at the intravascular
p
H of 7 but becomes active after cleavage within the acidic lysosomal environment of the target cell. This observation made it possible to construct cytocidal compounds that caused antigen-specific suppression of murine lymphocyte function. When daunomycin was coupled to the hapten conjugate of ovalbumin by an acid-sensitive
cis
-aconityl group, it caused hapten-specific impairment of immunocompetence in murine B lymphocytes in vitro and in vivo. Furthermore, the response by T lymphocytes to concanavalin A in vitro was selectively eliminated by a conjugate between daunomycin plus the acid-sensitive spacer and a monoclonal antibody specific for T cells.
A New Approach to the Adoptive Immunotherapy of Cancer with Tumor-Infiltrating Lymphocytes
Authors: Rosenberg Steven A. , Spiess Paul , Lafreniere Rene
Published: October 2006

The adoptive transfer of tumor-infiltrating lymphocytes (TIL) expanded in interleukin-2 (IL-2) to mice bearing micrometastases from various types of tumors showed that TIL are 50 to 100 times more effective in their therapeutic potency than are lymphokine-activated killer (LAK) cells. Therefore the use of TIL was explored for the treatment of mice with large pulmonary and hepatic metastatic tumors that do not respond to LAK cell therapy. Although treatment of animals with TIL alone or cyclophosphamide alone had little impact, these two modalities together mediated the elimination of large metastatic cancer deposits in the liver and lung. The combination of TIL and cyclophosphamide was further potentiated by the simultaneous administration of IL-2. With the combination of cyclophosphamide, TIL, and IL-2, 100% of mice (
n
= 12) bearing the MC-38 colon adenocarcinoma were cured of advanced hepatic metastases, and up to 50% of mice were cured of advanced pulmonary metastases. Techniques have been developed to isolate TIL from human tumors. These experiments provide a rationale for the use of TIL in the treatment of humans with advanced cancer.
Epithelial Wound Healing Enhanced by Transforming Growth Factor-α and Vaccinia Growth Factor
Authors: Schultz Gregory S. , White Michael , Mitchell Robert , Brown Gregory , Lynch Jenny , Twardzik Daniel R. , Todaro George J.
Published: October 2006

Epidermal regeneration following middermal injuries to skin requires both proliferation and migration of keratinocytes. Epidermal growth factor (EGF) stimulates the proliferation of keratinocytes in culture, and topical administration of EGF accelerates epidermal regeneration of partial thickness burns or split-thickness incisions in vivo. Transforming growth factor-alpha (TGF-α) and vaccinia growth factor (VGF) have substantial sequence homology with EGF, and all appear to bind to the same receptor protein. Whether TGF-α or VGF can affect epidermal wound healing in vivo is not known. The present studies show that topical administration of TGF-α or VGF in antibiotic cream to partial thickness burns (second degree) accelerated epidermal regeneration in comparison with untreated or vehicle-treated burns. Low levels of both TGF-α and VGF (0.1 microgram per milliliter) appeared to be more effective than EGF in stimulating epidermal regeneration. Regenerated epithelium from burns treated with TGF-α or VGF appeared normal histologically. This finding suggests that topical application of selected growth factors may be useful in accelerating healing of partial thickness injuries.
Perception of Risk
Authors: Slovic Paul
Published: October 2006

Studies of risk perception examine the judgments people make when they are asked to characterize and evaluate hazardous activities and technologies. This research aims to aid risk analysis and policy-making by (i) providing a basis for understanding and anticipating public responses to hazards and (ii) improving the communication of risk information among lay people, technical experts, and decision-makers. This work assumes that those who promote and regulate health and safety need to understand how people think about and respond to risk. Without such understanding, well-intended policies may be ineffective.
Vein-Cutting Behavior: Insect Counterploy to the Latex Defense of Plants
Authors: Dussourd David E. , Eisner Thomas
Published: October 2006

Many mandibulate insects that feed on milkweeds, or other latex-producing plants, cut leaf veins before feeding distal to the cuts. Vein cutting blocks latex flow to intended feeding sites and can be viewed as an insect counteradaptation to the plant's defensive secretion. Experimental vein severance renders milkweed leaves edible to generalist herbivores that do not show vein-cutting behaviors and ordinarily ignore milkweeds in nature.
Human Melanoma Proteoglycan: Expression in Hybrids Controlled by Intrinsic and Extrinsic Signals
Authors: Rettig Wolfgang J. , Real Francisco X. , Spengler Barbara A. , Biedler June L. , Old Lloyd J.
Published: October 2006

Human malignant melanoma cells express specific chondroitin sulfate proteoglycans (mel-CSPG) on the surface, both in vivo and in vitro. Melanocytes in normal skin show no detectable mel-CSPG but can be induced to express the antigen when cultured in the presence of cholera toxin and the tumor promoter 12-
O
-tetradecanoylphorbol-13-acetate. Most other cell types do not express mel-CSPG either in vivo or in vitro. A study was designed to examine regulatory signals controlling mel-CSPG expression. The gene encoding mel-CSPG was mapped to human chromosome 15, and this chromosome was introduced into rodent cells derived from distinct differentiation lineages. Three types of mel-CSPG-expressing hybrids were found: (i) hybrids derived from human melanomas; (ii) hybrids derived from human cells that do not express mel-CSPG; and (iii) hybrids derived from human cells expressing mel-CSPG that are antigen-negative but that are induced to express mel-CSPG when cultured on extracellular matrix instead of plastic surfaces. Thus, mel-CSPG expression can be controlled both through intrinsic signals, provided by the differentiation program of the rodent fusion partner, and through extrinsic signals, provided by specific cell-matrix interactions.
Immunochemical Proof That a Novel Rearranging Gene Encodes the T Cell Receptor δ Subunit
Authors: Band Hamid , Hochstenbach Frans , McLean Joanne , Hata Shingo , Krangel Michael S. , Brenner Michael B.
Published: October 2006

The T cell receptor (TCR) δ protein is expressed as part of a heterodimer with TCR γ, in association with the CD3 polypeptides on a subset of functional peripheral blood T lymphocytes, thymocytes, and certain leukemic T cell lines. A monoclonal antibody directed against TCR δ was produced that binds specifically to the surface of several TCR γδ cell lines and immunoprecipitates the TCR γδ as a heterodimer from Triton X-100 detergent lysates and also immunoprecipitates the TCR δ subunit alone after chain separation. A candidate human TCR δ complementary DNA clone (IDP2 O-240/38), reported in a companion paper, was isolated by the subtractive library approach from a TCR γδ cell line. This complementary DNA clone was used to direct the synthesis of a polypeptide that is specifically recognized by the monoclonal antibody to TCR δ. This complementary DNA clone thus corresponds to the gene that encodes the TCR δ subunit.
Dynamics of Automatic and Controlled Visual Attention
Authors: Weichselgartner Erich , Sperling George
Published: October 2006

The time course of attention was experimentally observed using two kinds of stimuli: a cue to begin attending or to shift attention, and a stimulus to be attended. Precise measurements of the time course of attention show that it consists of two partially concurrent processes: a fast, effortless, automatic process that records the cue and its neighboring events; and a slower, effortful, controlled process that records the stimulus to be attended and its neighboring events.
Environmental Correlates of Food Chain Length
Authors: Briand Frédéric , Cohen Joel E.
Published: October 2006

In 113 community food webs from natural communities, the average and maximal lengths of food chains are independent of primary productivity, contrary to the hypothesis that longer food chains should arise when more energy is available at their base. Environmental variability alone also does not appear to constrain average or maximal chain length. Environments that are three dimensional or solid, however, such as a forest canopy or the water column of the open ocean, have distinctly longer food chains than environments that are two dimensional or flat, such as a grassland or lake bottom.
Separation of Drug Stereoisomers by the Formation of β-Cyclodextrin Inclusion Complexes
Authors: Armstrong Daniel W. , Ward Timothy J. , Armstrong R. Douglas , Beesley Thomas E.
Published: October 2006

For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized β-cyclodextrin was investigated. Chiral recognition and racemic resolution were observed with a number of compounds from such clinically useful classes as β-blockers, calcium-channel blockers, sedative hypnotics, antihistamines, anticonvulsants, diuretics, and synthetic opiates. Separation of the diastereomers of the cardioactive and antimalarial cinchona alkaloids and of two antiestrogens was demonstrated as well. Three dimensional projections of β-cyclodextrin complexes of propanolol, which is resolved by this technique, and warfarin, which is not, are compared. These studies have improved the understanding and application of the chiral interactions of β-cyclodextrin, and they have demonstrated a means to measure optical purity and to isolate or produce pure enantiomers of drugs. In addition, this highly specific technique could also be used in the pharmacological evaluation of enantiomeric drugs.
Near-Total Glutathione Depletion and Age-Specific Cataracts Induced by Buthionine Sulfoximine in Mice
Authors: Calvin Harold I. , Medvedovsky Cecily , Worgul Basil V.
Published: October 2006

The specific inhibitor of glutathione biosynthesis, L-buthionine sulfoximine (L-BSO), although relatively nontoxic in adult mice, induces severe glutathione depletion and age-specific pathological changes when repeatedly administered to male suckling mice. Dense cataracts developed when mice aged 9 to 12 days were given a series of injections of L-BSO, despite excellent survival and the absence of other significant long-term effects. By contrast, similar treatment of mice aged 14 to 17 days, although slightly less effective in reducing glutathione levels, resulted frequently in death, hind-leg paralysis, or impaired spermatogenesis, but did not produce cataracts. Administration of L-BSO to preweanling mice provides a novel model system for the induction of cataracts by depletion of lens glutathione and may enable the study of critical functions of glutathione in the lens and other growing tissues during early postnatal development.
Cell Recognition by Neuronal Growth Cones in a Simple Vertebrate Embryo
Authors: Kuwada John Y.
Published: October 2006

The mechanism that guides neuronal growth cones to their targets in vertebrate embryos has been difficult to study primarily because of the complexity and large number of neurons found in many vertebrate nervous systems. The spinal cord of a simple vertebrate, the fish embryo, is used to analyze pathfinding mechanisms. The early embryonic spinal cord consists of a relatively small number of identifiable neurons. From the beginning of axonal outgrowth the growth cones of these identified neurons extend along stereotyped and precise pathways in the spinal cord. Laser ablation experiments (i) support the hypothesis that early growth cones that pioneer specific spinal tracts appear to recognize cues on subsets of longitudinally arrayed neuroepithelial cells and (ii) demonstrate that later growth cones that selectively fasciculate in these spinal tracts appear to recognize cues on specific subsets of axons.
Multiple Conformational States of Proteins: A Molecular Dynamics Analysis of Myoglobin
Authors: Elber R. , Karplus M.
Published: October 2006

A molecular dynamics simulation of myoglobin provides the first direct demonstration that the potential energy surface of a protein is characterized by a large number of thermally accessible minima in the neighborhood of the native structure (for example, approximately 2000 minima were sampled in a 300-picosecond trajectory). This is expected to have important consequences for the interpretation of the activity of transport proteins and enzymes. Different minima correspond to changes in the relative orientation of the helices coupled with side-chain rearrangements that preserve the close packing of the protein interior. The conformational space sampled by the simulation is similar to that found in the evolutionary development of the globins. Glasslike behavior is expected at low temperatures. The minima obtained from the trajectory do not satisfy certain criteria for ultrametricity.
Avian v-
myc
Replaces Chromosomal Translocation in Murine Plasmacytomagenesis
Authors: Potter Michael , Mushinski J. Frederic , Mushinski Elizabeth B. , Brust Susan , Wax Judith S. , Wiener Francis , Babonits Magda , Rapp Ulf R. , Morse Herbert C.
Published: October 2006

Deregulation of c-
myc
expression in association with chromosomal translocations occurs in over 95% of murine plasmacytomas, rat immunocytomas, and human Burkitt lymphomas. Infection with a murine retrovirus (J-3) containing an avian v-
myc
rapidly induced plasmacytomas in pristane-primed BALB/cAn mice. Only 17% of the induced plasmacytomas that were karyotyped showed the characteristic chromosomal translocations involving the c-
myc
locus. Instead, all of the translocation-negative tumors demonstrated characteristic J-3 virus integration sites that were actively transcribed. Thus, the high levels of v-
myc
expression have replaced the requirement for chromosomal translocation in plasmacytomagenesis and accelerated the process of transformation.
Interactions Between the Gonadal Steroids and the Immune System
Authors: Grossman Charles J.
Published: October 2006

The immune system is regulated by the gonadal steroids estrogen, androgen, and progesterone, but the circulating levels of these steroids can also be affected by immune system function. Such interactions appear to be mediated through the hypothalamic-pituitary-gonadal-thymic axis and depend on pituitary luteinizing hormone released by thymic factors under the control of the gonadal steroids.
Spontaneous Diabetes Mellitus: Reversal and Prevention in the BB/W Rat with Antiserum to Rat Lymphocytes
Authors: Like Arthur A. , Rossini Aldo A. , Guberski Dennis L. , Appel Michael C. , Williams R. Michael
Published: October 2006

Injections of rabbit antiserum to rat lymphocytes reversed hyperglycemia in 36 percent of spontaneously diabetic rats (Bio Breeding/Worcester) and prevented diabetes in susceptible nondiabetic controls. These findings strengthen the hypothesis that cell-mediated autoimmunity plays a role in the pathogenesis of diabetes in this animal model that mimics many morphologic and physiologic characteristics of human insulin-dependent diabetes mellitus.
Oxidation of Persistent Environmental Pollutants by a White Rot Fungus
Authors: Bumpus John A. , Tien Ming , Wright David , Aust Steven D.
Published: October 2006

The white rot fungus
Phanerochaete chrysosporium
degraded DDT [1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane], 3,4,3′,4′-tetrachlorobiphenyl, 2,4,5,2′,-4′,5′-hexachlorobiphenyl, 2,3,7,8-tetrachlorodibenzo-p-dioxin, lindane (1,2,3,4,5,6-hexachlorocyclohexane), and benzo[
a
]pyrene to carbon dioxide. Model studies, based on the use of DDT, suggest that the ability of
Phanerochaete chrysosporium
to metabolize these compounds is dependent on the extracellular lignin-degrading enzyme system of this fungus.
Rescue of the
Drosophila
Phototransduction Mutation
trp
by Germline Transformation
Authors: Montell Craig , Jones Kevin , Hafen Ernst , Rubin Gerald
Published: October 2006

Phototransduction is the process by which light-stimulated photoreceptor cells of the visual system send electrical signals to the nervous system. Many of the steps that follow the initial event in phototransduction, absorption of light by rhodopsin, are ill-defined. The fruitfly,
Drosophila melanogaster
, provides a means to dissect phototransduction genetically. Mutations such as transient receptor potential (
trp
) affect intermediate steps in phototransduction. In order to facilitate molecular studies of phototransduction, the
trp
gene was isolated and its identity was confirmed by complementing the mutant
trp
CM
allele of the
trp
gene by P-element mediated germline transformation of a 7.1-kilobase DNA fragment. Expression of the
trp
gene begins late in pupal development and appears to be limited to the eyes and ocelli.
Asymmetric Illumination Contrast: A Method of Image Formation for Video Light Microscopy
Authors: Kachar Bechara
Published: October 2006

Images with high resolution and exceptionally broad gray scale can be obtained by the application of video contrast enhancement to an optimized procedure for imaging transparent objects with oblique rays of illumination. This technique is simple to set up. A conventional microscope with a light source whose position can be adjusted and a video camera with controls for gain and black level are the only essential components. Features such as high resolution, optical sectioning, control of contrast, and operation under low light intensity make this technique preferable, in several instances, to currently used video microscopy techniques.
Comparative Toxinology of
Loxosceles reclusa
and
Corynebacterium pseudotuberculosis
Authors: Bernheimer Alan W. , Campbell Benedict J. , Forrester Lawrence J.
Published: October 2006

In contrast to other kinds of phospholipases, phospholipases D that are toxic for humans and animals are not commonly encountered as constituents of venoms or as products of pathogenic microorganisms. Toxic phospholipases D are present, however, in the venom of the brown recluse spider (
Loxosceles reclusa
) and in supernatants or filtrates of cultures of
Corynebacterium pseudotuberculosis
. Although the two enzyme toxins are derived from phylogenetically disparate entities, they are similar in molecular weight, charge, substrate specificity, and in several biological activities. They are immunologically distinguishable.
Model Structure for the Inflammatory Protein C5a
Authors: Greer Jonathan
Published: October 2006

The complement cleavage product C5a is a potent stimulant of inflammatory processes; thus, inhibition of C5a activity is of therapeutic interest. The three-dimensional structure of the major portion of C5a was modeled from the homologous C3a crystal structure by comparative modeling techniques. The model shows that core residues of C5a are completely conserved, while external residues differ from C3a. Even though the amino-terminal 12 residues of C3a are disordered in the crystal, this sequence in C5a may form an amphipathic helix. The distribution of species sequence differences in the complete C5a structure suggests a possible receptor binding site.
Filamentous Fusion Phage: Novel Expression Vectors That Display Cloned Antigens on the Virion Surface
Authors: Smith George P.
Published: October 2006

Foreign DNA fragments can be inserted into filamentous phage gene III to create a fusion protein with the foreign sequence in the middle. The fusion protein is incorporated into the virion, which retains infectivity and displays the foreign amino acids in immunologically accessible form. These "fusion phage" can be enriched more than 1000-fold over ordinary phage by affinity for antibody directed against the foreign sequence. Fusion phage may provide a simple way of cloning a gene when an antibody against the product of that gene is available.
[2 + 2] Photocycloadditions in the Synthesis of Chiral Molecules
Authors: Schreiber Stuart L.
Published: October 2006

A strategy for the synthesis of chiral molecules that receives growing popularity among organic chemists employs the photochemically mediated [2 + 2] cycloaddition reaction. These reactions can be performed on a multigram scale and often proceed with high yield and with stereocontrol. These features, in combination with the useful properties of the four-membered ring photoproducts in subsequent chemical transformations, make them attractive options in the early stage of a synthesis design. Various combinations of unsaturated functional groups can participate in this reaction process. Accordingly, these chemical reactions can be economical solutions to problems relating to the synthesis of a variety of target molecules.
Circulating Autoantibodies to the 200,000-Dalton Protein of Neurofilaments in the Serum of Healthy Individuals
Authors: Stefansson Kari , Marton Linda S. , Dieperink Michael E. , Molnar Gabor K. , Schlaepfer William W. , Helgason Cathy M.
Published: October 2006

There is substantial evidence that human serum contains antibodies to many autoantigens. For example, all healthy people have autoantibodies (immunoglobulin M) to some undefined brain antigens. In this study immunoblots and immunohistochemical staining were used to detect antibodies to neural tissues in serum samples from 200 healthy people and 200 patients with various neurological diseases. Ninety-nine percent of the 400 subjects had serum immunoglobulin M and 95 percent had immunoglobulin G that bound to a 200-kilodalton protein in homogenates of neural tissues. In most cases there were no antibodies to anything else in the homogenates. The 200-kilodalton protein was the heaviest of the neurofilament triplet proteins. These observations do not support a role for antibodies to the 200-kilodalton protein of neurofilaments in the pathogenesis of neurological diseases.
Immunoassay by Differential Pulse Polarography
Authors: Heineman William R. , Anderson C. William , Halsall H. Brian
Published: October 2006

An immunological method based on labeling an antigen with an electroactive group detectable by differential pulse polarography has been demonstrated. Estriol labeled with mercuric acetate is electroactive, giving a reduction wave at -300 millivolts versus a standard calomel electrode. Addition of estriol antibody to 4-mercuric acetate estriol diminishes the peak current as a result of the antigen-antibody binding reaction. Separation of free-labeled estriol from antibody-bound-labeled antigen is unnecessary. The method is potentially useful as an analytical immunological technique.
GABA Receptor Control of Parasympathetic Outflow to Heart: Characterization and Brainstem Localization
Authors: DiMicco Joseph A. , Gale Karen , Hamilton Betty , Gillis Richard A.
Published: October 2006

Blockade of γ-aminobutyric acid (GABA) receptor function by direct microinjection of the GABA receptor antagonist bicuculline into the nucleus ambiguus of the brainstem produced a marked, dose-related depression of heart rate and blood pressure which was mediated by the vagus nerve. This effect was not obtained in other regions of the brainstem and was reversed by the GABA receptor agonist muscimol. These data indicate that the nucleus ambiguus may be the site of a GABA receptor-mediated inhibition of vagal outflow.
Superstitious Bar Pressing in Hippocampal and Septal Rats
Authors: Devenport L. D.
Published: October 2006

Unlike normal animals or those with sham lesions, rats with hippocampal and septal lesions behaved in an operant chamber as if a dependency existed between pellet delivery and their behavior, despite the fact that reinforcement was based on time, not behavior, and was therefore free. This superstitious behavior did not result from a general inability to inhibit responding, as responding rapidly ceased when the pellets were discontinued. These findings suggest that the hippocampus integrates information regarding response-reinforcer relations, which in the normal rat permits superfluous operant behavior to be eliminated.
Molecular Microanalysis of Pathological Specimens in Situ with a Laser-Raman Microprobe
Authors: Abraham Jerrold L. , Etz Edgar S.
Published: October 2006

A laser-Raman microprobe has been used to identify microscopic inclusions of silicone polymer in standard paraffin sections of lymph node. This example of organic chemical microanalysis in situ in pathological tissue represents an extension of microanalytical capabilities from elemental analysis, performed with electron and ion microprobes, to compound-specific molecular microanalysis.
Tumor Location Detected with Radioactively Labeled Monoclonal Antibody and External Scintigraphy
Authors: Ballou Byron , Levine Geoffrey , Hakala Thomas R. , Solter Davor
Published: October 2006

Murine teratocarcmomas were located in mice by external γ-ray scintigraphy with a
131
I-labeled monoclonal antibody specific to the tumors. The specificity of the method was increased by subtracting the radiation produced by a
123
I-labeled indifferent monoclonal antibody of the same immunoglobulin class as the tumor-specific antibody.
Diazepam Maintenance of Alcohol Preference During Alcohol Withdrawal
Authors: Deutsch J. A. , Walton Nancy Y.
Published: October 2006

After forced intragastric intubation of alcohol, rats will show a greatly increased tendency to self-administer alcohol in a free-choice situation. Diazepam (Valium) dosage (5 milligrams per kilogram of body weight) during the period of withdrawal serves to maintain undiminished such alcohol self-administration. Without such diazepam dosage the tendency to self-administer alcohol returns to control levels.
Chemotactic Responses of Tumor Cells to Products of Resorbing Bone
Authors: Orr William , Varani James , Gondek Monica D. , Ward Peter A. , Mundy Gregory R.
Published: October 2006

To explore possible mechanisms for the metastasis of malignant cells to bone, a model of tumor cell migration was developed, using Walker carcinosarcoma or malignant lymphoma cells. It was found that bone contains a factor that is strongly chemotactic for tumor cells. This factor is released by a variety of agents that induce resorption of bone.
Accessory Optic Projections Upon Oculomotor Nuclei and Vestibulocerebellum
Authors: Brecha Nicholas , Karten H. J.
Published: October 2006

Displaced retinal ganglion cells in birds are the sole source of the retinal projection onto the nucleus of the basal optic root, the main component of the accessory optic system. This nucleus has direct bilateral axonal projections onto the oculomotor nuclear complex, the trochlear nucleus, and folia IXc,d and paraflocculus of the vestibulocerebellum. The cerebellar projection terminates within a superficial band of the granule cell layer adjacent to the Purkinje cell layer as a mossy fiber system. This bisynaptic projection onto oculomotor neurons and the cerebellum may play a functionally distinct and specific role in oculomotor reflexes.
Dr. Guthrie and
Felis fomesticus
Or: Tripping Over the Cat
Authors: Moore Bruce R. , Stuttard Susan
Published: October 2006

The principal reactions described in Guthrie and Horton's classic learning monograph appear to have been caused by the mere presence of the experimenters. Neither escape nor food reinforcement is necessary for the establishment of such responses. They are species-typical "greeting" reactions, readily elicited by the sight of human observers.
Adriamycin-Induced DNA Damage Mediated by Mammalian DNA Topoisomerase II
Authors: Tewey K. M. , Rowe T. C. , Yang L. , Halligan B. D. , Liu L. F.
Published: October 2006

Adriamycin (doxorubicin), a potent antitumor drug in clinical use, interacts with nucleic acids and cell membranes, but the molecular basis for its antitumor activity is unknown. Similar to a number of intercalative antitumor drugs and nonintercalative epipodophyllotoxins (VP-16 and VM-26), adriamycin has been shown to induce single- and double-strand breaks in DNA. These strand breaks are unusual because a covalently bound protein appears to be associated with each broken phosphodiester bond. In studies in vitro, mammalian DNA topoisomerase II mediates DNA damage by adriamycin and other related antitumor drugs.
Dynorphin Is a Specific Endogenous Ligand of the κ Opioid Receptor
Authors: Chavkin Charles , James Iain F. , Goldstein Avram
Published: October 2006

In the guinea pig ileum myenteric plexus—longitudinal muscle preparation, dynorphin-(1—13) and the prototypical κ agonist ethylketocyclazocine had equally poor sensitivity to naloxone antagonism and showed selective cross protection in receptor inactivation experiments with the alkylating antagonist β-chlornaltrexamine. In binding assays with membranes from guinea pig brain, ethylketocyclazocine and dynorphin-(1—13) amide were more potent in displacing tritium-labeled ethylketocyclazocine than in displacing typical μ and δ opioid receptor ligands. In the two preparations studied, the dynorphin receptor appears to be the same as the κ opioid receptor.
Lethal Effect of Phenothiazine Neuroleptics on the Pathogenic Protozoan
Leishmania donovani
Authors: Pearson Richard D. , Manian Albert A. , Harcus Jane L. , Hall Dennis , Hewlett Erik L.
Published: October 2006

Phenothiazine drugs, which are widely used for their antipsychotic, antianxiety, and antiemetic effects, have been found to have protozoacidal effects on the human pathogen
Leishmania donovani
. These compounds are lethal to both the extracellular stage of the organism, which is inoculated into humans by the sand fly, and the intracellular stage, which is found solely in human macrophages during established infection.
Cell Surface P-Glycoprotein Associated with Multidrug Resistance in Mammalian Cell Lines
Authors: Kartner Norbert , Riordan John R. , Ling Victor
Published: October 2006

The plasma membranes of hamster, mouse, and human tumor cell lines that display multiple resistance to drugs were examined by gel electrophoresis and immunoblotting. In every case, increased expression of a 170,000-dalton surface antigen was found to be correlated with multidrug resistance. This membrane component is of identical molecular size and shares some immunogenic homology with the previously characterized P-glycoprotein of colchicine-resistant Chinese hamster ovary cells. This finding may have application to cancer therapy.
At Least Three Human Type α Interferons: Structure of α2
Authors: Streuli Michel , Nagata Shigekazu , Weissmann Charles
Published: October 2006

The sequence of a human leukocyte-derived complementary DNA (cDNA), Hif-2h, which directs the formation in
Escherichia coli
of a polypeptide, IFN-α1, with interferon (IFN) activity has been described. A second IFN cDNA, Hif-SN206, which also elicits synthesis of a biologically active IFN, IFN-α2, is described in this article. Whereas IFN-α2 is twice as active on human as on bovine cells, IFN-α1 is 10 to 20 times more active on bovine than on human cells. As deduced from the cDNA's, the messenger RNA's for the two IFN's differ in length and in 20 percent of the nucleotides; the mature IFN polypeptides differ in 17 percent of the amino acids. Both IFN-α1 and IFN-α2 differ from the lymphoblastoid IFN described by others. Therefore, at least three different IFN-α genes are expressed in man; studies on genomic DNA reveal the presence of at least eight IFN-related genes.
Cell Lineage Analysis by Intracellular Injection of Fluorescent Tracers
Authors: Weisblat David A. , Zackson Saul L. , Blair Seth S. , Young Janis D.
Published: October 2006

Cell lineages during development of the leech are revealed by injection of a fluorescent peptide, rhodamine-D-peptide, into identified embryonic cells. Use of this peptide together with a nuclear stain showed a stereotypic cleavage pattern of stem cells and their progeny. Combined injection of rhodamine-D-peptide and pronase demonstrated the arrest of stem cell production in the pronase-injected teloblast.
Epidermis of Human Skin: Pyroelectric and Piezoelectric Sensor Layer
Authors: Athenstaedt Herbert , Claussen Helge , Schaper Daniel
Published: October 2006

The epidermis of live human skin has a permanent electric dipole moment perpendicular to its surface. Voltage responses to a rapid change of temperature are pyroelectric, while voltage responses to pressure pulses are piezoelectric in nature. The time course of the responses depends on
dX
/
dt
(
X
, temperature or pressure). The epidermal surface can react to all physical environmental influences to which nonbiological pyroelectric materials are known to respond. Epidermal voltage signals can be perceived through the intraepidermal and the superficial dermal nervous network. The pyroelectric and piezoelectric properties are also measurable on dead, dry skin samples.
Angiogenesis Induced by "Normal" Human Breast Tissue: A Probable Marker for Precancer
Authors: Jensen Hanne M. , Chen Ibsen , DeVault Martin R. , Lewis Alvin E.
Published: October 2006

Normal human breast lobules, freshly isolated by precision microdissection of tissue stained with methylene blue chloride, were assayed for their ability to induce neovascularization (angiogenesis) in rabbit irises. Histologically, normal lobules from cancerous breasts induced angiogenesis twice as often as lobules from noncancerous breasts, suggesting that preneoplastic transformation is diffuse.
Suppressor T Lymphocytes Control the Development of Primary Skin Cancers in Ultraviolet-Irradiated Mice
Authors: Fisher Michael S. , Kripke Margaret L.
Published: October 2006

Exposure of mice to ultraviolet radiation results in the development of suppressor T lymphocytes in lymphoid organs, followed by the appearance of primary skin cancers. The presence or absence of these suppressor lymphocytes determines whether or not primary cancers will develop in the ultraviolet-irradiated skin. This demonstrates the importance of immunological regulatory pathways in carcinogenesis and provides an example of immunological surveillance.
Heparan Sulfate Degradation: Relation to Tumor Invasive and Metastatic Properties of Mouse B16 Melanoma Sublines
Authors: Nakajima Motowo , Irimura Tatsuro , Di Ferrante Daniela , Di Ferrante Nicola , Nicolson Garth L.
Published: October 2006

After transport in the blood and implantation in the microcirculation, metastatic tumor cells must invade the vascular endothelium and underlying basal lamina. Mouse B16 melanoma sublines were used to determine the relation between metastatic properties and the ability of the sublines to degrade enzymatically the sulfated glycosaminoglycans present in the extracellular matrix of cultured vascular endothelial cells. Highly invasive and metastatic B16 sublines degraded matrix glycosaminoglycans faster than did sublines of lower metastatic potential. The main products of this matrix degradation were heparan sulfate fragments. Intact B16 cells (or their cell-free homogenates) with a high potential for lung colonization degraded purified heparan sulfate from bovine lung at higher rates than did B16 cells with a poor potential for lung colonization. Analysis of the degradation fragments indicated that B16 cells have a heparan sulfate endoglycosidase. Thus the abilities of B16 melanoma cells to extravasate and successfully colonize the lung may be related to their capacities to degrade heparan sulfate in the walls of pulmonary blood vessels.
Lichen Myxedematosus Serum Stimulates Human Skin Fibroblast Proliferation
Authors: Harper Robert A. , Rispler Jacob
Published: October 2006

Serum from patients with lichen myxedematosus, when added to exponentially growing normal human skin fibroblasts, stimulates DNA synthesis and cell proliferation. The degree of response in vitro is correlated with the extent of the disease in vivo and is specific for fibroblasts. The results suggest that there is a systemic factor (or factors) which may play a role in the etiology of diseases affecting the connective tissue.
Gene Expression in Eukaryotes
Authors: Brown Donald D.
Published: October 2006

Gene expression in eukaryotes is influenced by a wide variety of mechanisms including the loss, amplification, and rearrangement of genes. Genes are differentially transcribed, and the RNA transcripts are variably utilized. Multigene families regulate the amount, the diversity, and the timing of gene expression. The present level of understanding of gene expression in eukaryotes is attributable mainly to biochemical methods rather than to traditional genetics. The new techniques that permit analysis and modification of purified genes of known function will identify both the control regions in eukaryotic genes as well as the molecules within cells that influence gene expression.
Electrotonic Coupling Between Pyramidal Cells: A Direct Demonstration in Rat Hippocampal Slices
Authors: MacVicar Brian A. , Dudek F. Edward
Published: October 2006

Intracellular recordings from pairs of neurons in slices of rat hippocampus directly demonstrated electrotonic coupling between CA3 pyramidal cells. When two neurons were impaled simultaneously (as verified by subsequent double staining with horseradish peroxidase), current pulses injected into one cell caused voltage changes in other cells. These interactions were bidirectional. Fast prepotentials, historically thought to represent spike activity in dendrites, resulted from action potentials in other electrotonically coupled pyramidal cells. These data directly demonstrate electrotonic coupling between neurons in the mammalian brain and indicate that some fast prepotentials are coupling potentials. Coupling between pyramidal cells could mediate synchronization of normal rhythmic activity and of burst discharges during seizures.
Growth Arrest and Morphological Change of Human Breast Cancer Cells by Dibutyryl Cyclic AMP and L-Arginine
Authors: Cho-Chung Yoon Sang , Clair Timothy , Bodwin Jeffrey S. , Berghoffer Bela
Published: October 2006

The growth in vitro of human breast cancer cells, line MCF-7, was inhibited by a daily supplement of L-arginine (1 milligram per milliliter). Arginine acted synergistically with dibutyryl adenosine 3′,5′-monophosphate (cyclic AMP) (10
-6
molar) to enhance the growth inhibitory effect: the cell replication ceased completely within 2 days after treatment. The growth arrest accompanied a change in cell morphology and was preceded by increases in the cellular concentration of cyclic AMP, adenylate cyclase, and type II cyclic AMP-dependent protein kinase activities as well as a decrease of estrogen binding activity. The results suggest that growth of human breast cancer cells is subject to cyclic AMP-mediated regulation and that arginine may play a specific role in this process.
Eumelanins and Pheomelanins: Characterization by Electron Spin Resonance Spectroscopy
Authors: Sealy Roger C. , Hyde James S. , Felix Christopher C. , Menon I. A. , Prota Guiseppe
Published: October 2006

Synthetic dopa melanin and cysteinyldopa melanin have different electron spin resonance spectra. Data are reported for mixtures of these melanins and for dopa-cysteinyldopa copolymers, which are spectroscopically similar. A simple parameterization of the spectra allows estimation of the relative amounts of (i) dopa melanin and cysteinyldopa melanin in mixtures and of (ii) dopa and cysteinyldopa incorporated into copolymers. Several natural eumelanins and pheomelanins have been characterized and shown to be copolymers.