bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Solid Friction on Polymer Relaxation in Gel Electrophoresis
Authors: Burlatsky Sergei , Deutch John
Published: October 2006

Solid friction between a charged polymer and fixed gel points can dramatically affect polymer mobility in gel electrophoresis. The effect is present when a polymer chain is entangled over many gel points along a portion of its length, leading to significantly different behavior than predicted by conventional theory: the mobility of the chain decreases and exhibits a stronger length dependence, which separates long linear charged polymers of different molecular weights.
Stratospheric Meteorological Conditions in the Arctic Polar Vortex, 1991 to 1992
Authors: Newman P. , Lait L. R. , Schoeberl M. , Nash E. R. , Kelly K. , Fahey D. W. , Nagatani R. , Toohey D. , Avallone L. , Anderson J.
Published: October 2006

Stratospheric meteorological conditions during the Airborne Arctic Stratospheric Expedition II (AASE II) presented excellent observational opportunities from Bangor, Maine, because the polar vortex was located over southeastern Canada for significant periods during the 1991-1992 winter. Temperature analyses showed that nitric acid trihydrates (NAT temperatures below 195 k) should have formed over small regions in early December. The temperatures in the polar vortex warmed beyond NAT temperatures by late January (earlier than normal). Perturbed chemistry was found to be associated with these cold temperatures.
Images of Excited H
3
+
at the Foot of the Io Flux Tube in Jupiter's Atmosphere
Authors: Connerney J. E. P. , Baron R. , Satoh T. , Owen T.
Published: October 2006

The electrodynamic interaction between Io and the Jovian magnetosphere drives currents to and from the planet's ionosphere, where H
3
+
emission is excited. Direct images of this phenomenon were obtained with the ProtoCAM infrared camera at the National Aeronautics and Space Administration's 3-m Infrared Telescope Facility. The emissions are localized to the instantaneous foot of the Io flux tube, ≈8° equatorward of the more intense auroral H
3
+
emission associated with higher magnetic latitudes. The foot of the Io flux tube leads that of (undisturbed) model magnetic field lines passing through Io by 15° to 20° in longitude and is less visible in the northern hemisphere at longitudes where the surface magnetic field strength is greatest. These data favor the unipolar inductor model of the Io interaction and provide insight into the source location and generation of Jovian decameter radio emission.
Lineage-Specific Requirement of c-
abl
Function in Normal Hematopoiesis
Authors: Caracciolo Daniele , Valtieri Mauro , Venturelli Donatella , Peschle Cesare , Gewirtz Alan M. , Calabretta Bruno
Published: October 2006

Structural abnormalities of the c-
abl
proto-oncogene are found in hematopoietic cells of more than 90 percent of individuals with chronic myelogenous leukemia. Therefore c-
abl
may be important in normal as well as malignant hematopoiesis. Normal human hematopoietic progenitor cells were exposed to three different c-
abl
sense or antisense oligodeoxynucleotides, and the effects on myeloid and erythroid colony formation were examined. The c-
abl
antisense oligodeoxynucleotides inhibited myeloid, but not erythroid, colony formation. The c-
abl
sense oligodeoxynucleotides and
bcr
sense and antisense oligodeoxynucleotides were not inhibitory in this assay. These data show that c-
abl
is critical in normal myelopoiesis and may explain the relatively selective expansion of leukocytes in patients with chronic myelogenous leukemia.
Dispersed Polaron Simulations of Electron Transfer in Photosynthetic Reaction Centers
Authors: Warshel A. , Chu Z. T. , Parson W. W.
Published: October 2006

A microscopic method for simulating quantum mechanical, nuclear tunneling effects in biological electron transfer reactions is presented and applied to several electron transfer steps in photosynthetic bacterial reaction centers. In this "dispersed polaron" method the fluctuations of the protein and the electron carriers are projected as effective normal modes onto an appropriate reaction coordinate and used to evaluate the quantum mechanical rate constant. The simulations, based on the crystallographic structure of the reaction center from
Rhodopseudomonas viridis
, focus on electron transfer from a bacteriopheophytin to a quinone and the subsequent back-reaction. The rates of both of these reactions are almost independent of temperature or even increase with decreasing temperature. The simulations reproduce this unusual temperature dependence in a qualitative way, without the use of adjustable parameters for the protein's Franck-Condon factors. The observed dependence of the back-reaction on the free energy of the reaction also is reproduced, including the special behavior in the "inverted region."
Endothelial Interleukin-8: A Novel Inhibitor of Leukocyte-Endothelial Interactions
Authors: Gimbrone M. A. , Obin M. S. , Brock A. F. , Luis E. A.. , Hass P. E. , Hébert C. A. , Yip Y. K. , Leung D. W. , Lowe D. G. , Kohr W. J. , Darbonne W. C. , Bechtol K. B. , Baker J. B.
Published: October 2006

Certain inflammatory stimuli render cultured human vascular endothelial cells hyperadhesive for neutrophils. This state is transient and reversible, in part because activated endothelial cells secrete a leukocyte adhesion inhibitor (LAI). LAI was identified as endothelial interleukin-8 (IL-8), the predominant species of which is an extended amino-terminal IL-8 variant. At nanomolar concentrations, purified endothelial IL-8 and recombinant human IL-8 inhibit neutrophil adhesion to cytokine-activated endothelial monolayers and protect these monolayers from neutrophil-mediated damage. These findings suggest that endothelial-derived IL-8 may function to attenuate inflammatory events at the interface between vessel wall and blood.
A General Method for the Chromosomal Amplification of Genes in Yeast
Authors: Boeke Jef D. , Xu Hua , Fink Gerald R.
Published: October 2006

The yeast retrotransposon Ty can be used to insert multiple copies of a gene at new sites in the genome. The gene of interest is inserted into a
GAL1
-Ty fusion construct; the entire "amplification cassette" is then introduced into yeast on a high copy number plasmid vector. Transposition of the Ty element carrying the gene occurs at multiple sites in the genome. Two genes, a bacterial neomycin phosphotransferase gene and the yeast
TRP1
gene, were amplified in this way. Although the amplified genes were about 1 kilobase in length, they were amplified to about the same extent as a 40-base pair segment. The benefit of this "shotgun" approach is that amplification can be achieved in one set of manipulations.
A Newly Defined Property of Somatotropin: Priming of Macrophages for Production of Superoxide Anion
Authors: Edwards Carl K. , Ghiasuddin Syed M. , Schepper Jeanette M. , Yunger Libby M. , Kelley Keith W.
Published: October 2006

Macrophages can be activated to produce reactive oxygen intermediates, such as superoxide anion (O
2
-
), which are responsible for intracellular killing of pathogenic microbes. Treatment with either native or recombinant somatotropin augmented the production of O
2
-
by both peripheral blood-derived and alveolar macrophages stimulated with opsonized zymosan in vitro. This effect was abolished by prior treatment with an antibody specific for somatotropin. When either native or recombinant porcine somatotropin or native rat somatotropin was administered to hypophysectomized rats in vivo, activation of peritoneal macrophages, as measured by release of O
2
-
in response to opsonized zymosan, was equivalent to that of macrophages from rats primed with the macrophage-activating factor interferon-γ. Priming of macrophages in vivo was observed at physiologically relevant doses of somatotropin that caused a 10 to 40 percent increase in growth rate. Priming of mononuclear phagocytes for augmented production of reactive oxygen metabolites is a newly defined property of somatotropin.
Steroid Binding at σ Receptors Suggests a Link Between Endocrine, Nervous, and Immune Systems
Authors: Su Tsung-Ping , London Edythe D. , Jaffe Jerome H.
Published: October 2006

Specific σ binding sites have been identified in the mammalian brain and lymphoid tissue. In this study, certain gonadal and adrenal steroids, particularly progesterone, were found to inhibit σ receptor binding in homogenates of brain and spleen. The findings suggest that steroids are naturally occurring ligands for σ receptors and raise the possibility that these sites mediate some aspects of steroid-induced mental disturbances and alterations in immune functions.
Regulation of Interprotein Electron Transfer by Residue 82 of Yeast Cytochrome c
Authors: Liang Nong , Mauk A. Grant , Pielak Gary J. , Johnson Jeanette A. , Smith Michael , Hoffman Brian M.
Published: October 2006

Yeast iso-1-cytochrome c (Cc) mutants have been constructed with Phe, Tyr, Gly, Ser, Leu, and Ile at position 82, each with Thr substituted for Cys at position 102. Their long-range electron transfer with zinc-substituted cytochrome c peroxidase (ZnCcP) has been studied by two kinetic techniques. The charge-separated complex, [(ZnCcP)
+
,Fe
II
Cc] converts to [ZnCcP,Fe
III
Cc] by a single, intracomplex electron transfer step that is not governed by "gating" through possible rapid dissociation of the complex or isomerization (for example, heme-ligand) by Fe
II
Cc subsequent to its formation from Fe
III
Cc. In every variant with an aliphatic residue at position 82 of Cc, the rate of this electron transfer process is ∼10
4
slower at ∼0°C than for the two variants with aromatic residues.
Calpain II Involvement in Mitosis
Authors: Schollmeyer Judith E.
Published: October 2006

Mitotic spindle disassembly requires major structural alterations in the associated cytoskeletal proteins and mitosis is known to be associated with Ca
2+
-sequestering phenomena and calcium transients. To examine the possible involvement of a ubiquitous Ca
2+
-activated protease, calpain II, in the mitotic process, synchronized PtK
1
cells were monitored by immunofluorescence for the relocation of calpain II. The plasma membrane was the predominant location of calpain II in interphase. However, as mitosis progressed, calpain II relocated to (i) an association with mitotic chromosomes, (ii) a perinuclear location in anaphase, and (iii) a mid-body location in telophase. Microinjection of calpain II near the nucleus of a PtK
1
cell promoted the onset of metaphase. Injection of calpain II at late metaphase promoted a precocious disassembly of the mitotic spindle and the onset of anaphase. These data suggest that calpain II is involved in mitosis.
Regulation of a Heart Potassium Channel by Protein Kinase A and C
Authors: Walsh Kenneth B. , Kass Robert S.
Published: October 2006

The enzymes adenosine 3′,5′-monophosphate (cAMP)-dependent protein kinase (protein kinase A) and protein kinase C regulate the activity of a diverse group of cellular proteins including membrane ion channel proteins. When protein kinase A was stimulated in cardiac ventricular myocytes with the membrane-soluble cAMP analog 8-chlorphenylthio cAMP (8-CPT cAMP), the amplitude of the delayed-rectifier potassium current (
I
K
) doubled when recorded at 32°C but was not affected at 22°C. In contrast, modulation of the calcium current (
I
Ca
) by 8-CPT cAMP was independent of temperature with similar increases in
I
Ca
occurring at both temperatures. Stimulation of protein kinase C by phorbol 12,13-dibutyrate also enhanced
I
K
in a temperature-dependent manner but failed to increase
I
Ca
at either temperature. Thus, cardiac delayed-rectifier potassium but not calcium channels are regulated by two distinct protein kinases in a similar temperature-dependent fashion.
A Pseudoautosomal Gene in Man
Authors: Goodfellow Paul J. , Darling Susan M. , Thomas Nicholas S. , Goodfellow Peter N.
Published: October 2006

The X/Y homologous gene
MIC2
was shown to exchange between the sex chromosomes, thus demonstrating that it is a pseudoautosomal gene in man.
MIC2
recombines with the sex-determining gene(s)
TDF
at a frequency of 2 to 3 percent. It is the most proximal pseudoautosomal locus thus far described and as such is an important marker for use in studies directed towards the isolation of
TDF
.
The
tat
Gene of Human T-Lymphotropic Virus Type 1 Induces Mesenchymal Tumors in Transgenic Mice
Authors: Nerenberg Michael , Hinrichs Steven H. , Reynolds R. Kay , Khoury George , Jay Gilbert
Published: October 2006

Human T-lymphotropic virus type 1 (HTLV-1) is a suspected causative agent of adult T-cell leukemia. One of the viral genes encodes a protein (tat) that not only results in transactivation of viral gene expression but may also regulate the expression of certain cellular genes that are important for cell growth. Transgenic mice that expressed the authentic tat protein under the control of the HTLV-1 long terminal repeat were generated, and cell types that are permissive for the viral promoter and the effects of the
tat
gene on these cells were studied. Three of eight founder mice with high levels of expression of the transgene in muscle were bred and then analyzed. All developed soft tissue tumors at multiple sites between 13 to 17 weeks of age. This phenotype was transmitted to nine of nine offspring that inherited the
tat
gene and were available for analysis. The remaining five founders expressed the transgene in the thymus, as well as in muscle. This second group of mice all exhibited extensive thymic depletion and growth retardation; in all of these mice, death occurred between 3 to 6 weeks of age before tumors became macroscopically visible. The
tat
gene under the control of the HTLV-1 regulatory region showed tissue-specific expression and the tat protein efficiently induced mesenchymal tumors. The data establish tat as an oncogenic protein and HTLV-1 as a transforming virus.
Muscarinic Modulation of Cardiac Rate at Low Acetylcholine Concentrations
Authors: DiFrancesco Dario , Ducouret Pierre , Robinson Richard B.
Published: October 2006

Slowing of cardiac pacemaking induced by cholinergic input is thought to arise from the opening of potassium channels caused by muscarinic receptor stimulation. In mammalian sinoatrial node cells, however, muscarinic stimulation also inhibits the hyperpolarization-activated current (
I
f
), which is involved in the generation of pacemaker activity and its acceleration by catecholamines. Acetylcholine at nanomolar concentrations inhibits
I
f
and slows spontaneous rate, whereas 20 times higher concentrations are required to activate the acetylcholine-dependent potassium current (
I
K,Ach
). Thus, modulation of
I
f
, rather than
I
K,Ach
, is the mechanism underlying the muscarinic control of cardiac pacing at low (nanomolar) acetylcholine concentrations.
The EGF Receptor Kinase Substrate p35 in the Floor Plate of the Embryonic Rat CNS
Authors: McKanna James A. , Cohen Stanley
Published: October 2006

P35 is a calcium- and phospholipid-binding protein that was originally isolated as a substrate for the epidermal growth factor (EGF) receptor tyrosine kinase and later was found to be related to lipocortin I. Immunohistochemistry was used to localize p35 to a raphe of primitive glial ependymal cells in the median one-third of the floor plate in the central nervous system (CNS) of rat embryos. The p35 appears by embryonic day 12 before the arrival of pioneering ventral commissural axons. The unexpected, discrete distribution of this protein during development opens the question of its role in neural morphogenesis.
A Portable Signal Causing Faithful DNA Methylation de Novo in
Neurospora crassa
Authors: Selker Eric U. , Jensen Bryan C. , Richardson Gladys A.
Published: October 2006

Methylation of cytosine residues in eukaryotic DNA is common, but poorly understood. Typically several percent of the cytosines are methylated; however, it is unclear what governs which sequences eventually become modified.
Neurospora crassa
DNA containing the "zeta-eta" (ζ-η) region, which is a region of unusually heavy methylation, was tested for its ability to direct DNA methylation de novo. DNA stripped of its methylation by propagation in
Escherichia coli
was reintroduced into
Neurospora crassa
by transformation. The ζ-η region reproducibly became "properly" methylated whether inserted at its native chromosomal position or at ectopic sites. Adjacent
Neurospora
and bacterial sequences in the transforming DNA rarely became methylated. A model is presented that accounts for position-independent faithful methylation as observed in the ζ-η region, as well as position-dependent methylation, as occasionally observed, especially with sequences not native to
Neurospora
.
Vaccinia Virus Recombinants: Expression of VSV Genes and Protective Immunization of Mice and Cattle
Authors: Mackett M. , Yilma T. , Rose J. K. , Moss B.
Published: October 2006

Vesicular stomatitis virus (VSV) causes a contagious disease of horses, cattle, and pigs. When DNA copies of messenger RNA's for the G or N proteins of VSV were linked to a vaccinia virus promoter and inserted into the vaccinia genome, the recombinants retained infectivity and synthesized VSV polypeptides. After intradermal vaccination with live recombinant virus expressing the G protein, mice produced VSV-neutralizing antibodies and were protected against lethal encephalitis upon intravenous challenge with VSV. In cattle, the degree of protection against intradermalingually injected VSV was correlated with the level of neutralizing antibody produced following vaccination.
Equine Infectious Anemia Virus
gag
and
pol
Genes: Relatedness to Visna and AIDS Virus
Authors: Stephens Robert M. , Casey James W. , Rice Nancy R.
Published: October 2006

Comparison of HTLV-III, the putative AIDS virus, with other related viruses, may help to reveal more about the origin of AIDS in humans. In this study, the nucleotide sequence of the
gag
and
pol
genes of an equine infectious anemia virus (EIAV) proviral DNA clone was determined. The sequence was compared with that of HTLV-III and of visna, a pathogenic lentivirus of sheep. The results show that these viruses constitute a family clearly distinct from that of the type C viruses or the BLV-HTLV-I and -II group. Within the family, EIAV, HTLV-III, and visna appear to be equally divergent from a common evolutionary ancestor.
The NOD Mouse: Recessive Diabetogenic Gene in the Major Histocompatibility Complex
Authors: Hattori M. , Buse J. B. , Jackson R. A. , Glimcher L. , Dorf M. E. , Minami M. , Makino S. , Moriwaki K. , Kuzuya H. , Imura H. , Strauss W. M. , Seidman J. G. , Eisenbarth G. S.
Published: October 2006

Examination of the histocompatibility region of the nonobese diabetic (NOD) mouse with antibodies against class II glycoproteins (products of immune response genes of the major histocompatibility complex I-A and I-E), hybrid T-cell clones, and mixed-lymphocyte cultures and analysis of restriction fragment length polymorphisms indicate that the NOD mouse has a unique class II major histocompatibility complex with no expression of surface I-E, no messenger RNA for I-E
α
, and an I-A not recognized by any monoclonal antibodies or hybrid T-cell clones studied. In crosses of NOD mice with control C3H mice, the development of diabetes was dependent on homozygosity for the NOD mouse's unique major histocompatibility region.
Effects of Pulse Shaping in Laser Spectroscopy and Nuclear Magnetic Resonance
Authors: Warren Warren S.
Published: October 2006

Pulsed excitation fields are routinely used in most laser and nuclear magnetic resonance (NMR) experiments. In the NMR case, constant amplitude (rectangular) pulses have traditionally been used; in laser spectroscopy the exact pulse shape is often unknown or changes from shot to shot. This article is an overview of the effects of radio-frequency and laser pulse shapes and the instrumental requirements for pulse shaping. NMR applications to selective excitation, solvent suppression, elimination of phase roll, and reduced power dissipation are discussed, as are optical applications to soliton generation, velocity selective excitation, and quantitative population transfer.
Human Insulin-Degrading Enzyme Shares Structural and Functional Homologies with
E. coli
Protease III
Authors: Affholter Joseph A. , Fried Victor A. , Roth Richard A.
Published: October 2006

A proteinase with high affinity for insulin has been proposed to play a role in the cellular processing of this hormone. A complementary DNA (cDNA) coding for this enzyme has been isolated and sequenced. The deduced amino acid sequence of the enzyme contained the sequences of 13 peptides derived from the isolated protein. The cDNA could be transcribed in vitro to yield a synthetic RNA that in cell-free translations produced a protein that coelectrophoresed with the native proteinase and could be immunoprecipitated with monoclonal antibodies to this enzyme. The deduced sequence of this proteinase did not contain the consensus sequences for any of the known classes of proteinases (that is, metallo, cysteine, aspartic, or serine), but it did show homology to an
Escherichia coli
proteinase (called protease III), which also cleaves insulin and is present in the periplasmic space. Thus, these two proteins may be members of a family of proteases that are involved in intercellular peptide signaling.
Studies on Environmental Chemical Carcinogenesis in Japan
Authors: Sugimura Takashi
Published: October 2006

The historical background of studies in Japan on chemical carcinogenesis from environmental sources is described from personal experience.
Elevated Levels of Glucose Transport and Transporter Messenger RNA Are Induced by
ras
or
src
Oncogenes
Authors: Flier Jeffrey S. , Mueckler Michael M. , Usher Patricia , Lodish Harvey F.
Published: October 2006

An accelerated rate of glucose transport is among the most characteristic biochemical markers of cellular transformation. To study the molecular mechanism by which transporter activity is altered, cultured rodent fibroblasts transfected with activated
myc
,
ras
, or
src
oncogenes were used. In
myc
-transfected cells, the rate of 2-deoxy-D-glucose uptake was unchanged. However, in cells transfected with activated
ras
and
src
oncogenes, the rate of glucose uptake was markedly increased. The increased transport rate in
ras
- and
src
-transfected cells was paralleled by a marked increase in the amount of glucose transporter protein, as assessed by immunoblots, as well as by a markedly increased abundance of glucose transporter messenger RNA. Exposure of control cells to the tumor-promoting phorbol ester 12-
O
-tetradecanoyl phorbol-13-acetate (TPA) for 18 hours had a similar effect of increasing the rate of glucose transport and the abundance of transporter messenger RNA. For
ras
,
src
, and TPA, the predominant mechanism responsible for activation of the transport system is increased expression of the structural gene encoding the glucose transport protein.
Eye Movements Initiate Visual-Motor Development in the Cat
Authors: Hein Alan , Vital-Durand François , Salinger Walter , Diamond Rhea
Published: October 2006

Visually naive kittens turn their eyes toward visual targets but lack other visual-motor coordinations. Light-reared animals were able to mediate guided behaviors with an immobilized eye, but animals with the eye immobilized before initial exposure to a lighted environment were not. Eye movement is implied to play an essential role in visual-motor development.
Welfare Dependence Within and Across Generations
Authors: Duncan Greg J. , Hill Martha S. , Hoffman Saul D.
Published: October 2006

A central question in the debate about the effects of welfare programs is whether their intended positive results—providing needed resources to recipients and their children—outweigh any unintended negative results—for example, the breaking up of families, reduction in work effort, or the fostering of a welfare "culture" that is passed on from parent to child. Recent research shows that although work effort is affected adversely by the generosity of welfare programs, effects on family structure appear quite weak, most welfare experiences are relatively short, and the majority of women who grew up in homes heavily dependent on welfare do not rely on those programs when they are young adults.
Site-Directed Mutagenesis of Two Trans-Regulatory Genes (
tat
-III,
trs
) of HIV-1
Authors: Sadaie M. Reza , Benter Thomas , Wong-Staal Flossie
Published: October 2006

Point mutations were introduced into the overlapping trans-regulatory genes (
tat
-III and
trs
) of human immunodeficiency virus type 1 (HIV-1), and the mutants were evaluated for virus expression. The results showed that
tat
-III has a positive transacting role and is required for transcriptional activation. A chain terminating mutation early in the
trs
gene resulted in an increase in transcription of viral messenger RNA as measured by nuclear transcription experiments, but only one major species of viral messenger RNA (1.8 kilobases) was detected, and little or no viral structural proteins were made. Thus, the
trs
gene product is essential for expression of virus structural proteins but, at the same time, may have a negative trans-regulatory role in transcription. Cotransfection of the point mutant proviruses defective in
tat
or
trs
with each other or with a complementary DNA clone containing
tat
and
trs
sequences restored the normal transcription pattern and subsequent virus production.
Peroxisomal Membrane Ghosts in Zellweger Syndrome—Aberrant Organelle Assembly
Authors: Santos M. J. , Imanaka T. , Shio H. , Small G. M. , Lazarow P. B.
Published: October 2006

Peroxisomes are apparently missing in Zellweger syndrome; nevertheless, some of the integral membrane proteins of the organelle are present. Their distribution was studied by immunofluorescence microscopy. In control fibroblasts, peroxisomes appeared as small dots. In Zellweger fibroblasts, the peroxisomal membrane proteins were located in unusual empty membrane structures of larger size. These results suggest that the primary defect in this disease may be in the mechanism for import of matrix proteins.
Atomic Force Microscopy of an Organic Monolayer
Authors: Marti O. , Ribi H. O. , Drake B. , Albrecht T. R. , Quate C. F. , Hansma P. K.
Published: October 2006

Atomic force microscope images of polymerized monolayers of
n
-(2-aminoethyl)-10,12-tricosadiynamide revealed parallel rows of molecules with a side-by-side spacing of ≈0.5 nanometer. Forces used for imaging (10
-8
newton) had no observable effect on the polymer strands. These results demonstrate that atomic force microscope images can be obtained for an organic system.
DNA Amplification for Direct Detection of HIV-1 in DNA of Peripheral Blood Mononuclear Cells
Authors: Ou Chin-Yih , Kwok Shirley , Mitchell Sheila W. , Mack David H. , Sninsky John J. , Krebs John W. , Feorino Paul , Warfield Donna , Schochetman Gerald
Published: October 2006

By means of a selective DNA amplification technique called polymerase chain reaction, proviral sequences of the human immunodeficiency virus (HIV-1) were identified directly in DNA isolated from peripheral blood mononuclear cells (PBMCs) of persons seropositive but not in DNA isolated from PBMCs of persons seronegative for the virus. Primer pairs from multiple regions of the HIV-1 genome were used to achieve maximum sensitivity of provirus detection. HIV-1 sequences were detected in 100% of DNA specimens from seropositive, homosexual men from whom the virus was isolated by coculture, but in none of the DNA specimens from a control group of seronegative, virus culture-negative persons. However, HIV-1 sequences were detected in 64% of DNA specimens from seropositive, virus culture-negative homosexual men. This method of DNA amplification made it possible to obtain results within 3 days, whereas virus isolation takes up to 3 to 4 weeks. The method may therefore be used to complement or replace virus isolation as a routine means of determining HIV-1 infection.
Genomic Amplification with Transcript Sequencing
Authors: Stoflet E. S. , Koeberl D. D. , Sarkar G. , Sommer S. S.
Published: October 2006

A sequencing method called genomic amplification with transcript sequencing (GAWTS) is described that is based on amplification with the polymerase chain reaction (PCR). GAWTS bypasses cloning and increases the rate of sequence acquisition by at least fivefold. The method involves the attachment of a phage promoter onto at least one of the PCR primers. The segments amplified by PCR are transcribed to further increase the signal and to provide an abundance of single-stranded template for reverse transcriptase-mediated dideoxy sequencing. An end-labeled reverse transcriptase primer complementary to the desired sequence generates the additional specificity required to generate unambiguous sequence data. GAWTS can be performed on as little as a nanogram of genomic DNA. The rate of GAWTS can be increased by coamplification and cotranscription of multiple regions as illustrated by two regions of the factor IX gene. Since GAWTS lends itself well to automation, further increases in the rate of sequence acquisition can be expected.
Synaptic Rearrangement During Postembryonic Development in the Cricket
Authors: Chiba A. , Shepherd D. , Murphey R. K.
Published: October 2006

Synaptic rearrangement during development is a characteristic of the vertebrate nervous system and was thought to distinguish vertebrates from the invertebrates. However, examination of the wind-sensitive cercal sensory system of the cricket demonstrates that some identified synaptic connections systematically decrease in strength as an animal matures, while others increase in strength over the same period. Moreover, a single sensory neuron could increase the strength of its synaptic connection with one interneuron while decreasing the strength of its connection with another interneuron. Thus, rather than being a hallmark of the vertebrate nervous system, synaptic rearrangement is probably characteristic of the development of many if not all nervous systems.
Expression and Characterization of the
Trans
-Activator of HTLV-III/LAV Virus
Authors: Wright Connie M. , Felber Barbara K. , Paskalis Harry , Pavlakis George N.
Published: October 2006

The human T-lymphotropic retrovirus HTLV-III/LAV encodes a
trans
-activator that increases viral gene expression. We expressed this
trans
-activator in animal cells and studied its structural and functional characteristics. The putative
trans
-activator protein was immunoprecipitated from overproducing stable cell lines and shown to migrate as a 14-kilodalton polypeptide on sodium dodecyl sulfate-polyacrylamide gels. S1 nuclease mapping experiments showed that the
trans
-activator increases the levels of steady-state messenger RNA transcribed from the viral long terminal repeat promoter. Sequences within the R region of the HTLV-III/LAV long terminal repeat are essential for
trans
-activation. Quantitations of messenger RNA and protein showed that the protein increase was greater than the messenger RNA increase in CV1 and HeLa cells, indicating that more than one mechanism was responsible for the
trans
-activation and that cell type-specific factors may determine the final level of
trans
-activation.
CDC25
: a Component of the
RAS
-Adenylate Cyclase Pathway in
Saccharomyces cerevisiae
Authors: Robinson Lucy C. , Gibbs Jackson B. , Marshall Mark S. , Sigal Irving S. , Tatchell Kelly
Published: October 2006

The yeast
Saccharomyces cerevisiae
contains two functional homologues of the
ras
oncogene family,
RAS1
and
RAS2
. These genes are required for growth, and all evidence indicates that this essential function is the activation of adenylate cyclase. In contrast,
ras
in mammalian cells does not appear to influence adenylate cyclase activity. To clarify the relation between
ras
function in yeast and in higher eukaryotes, and the role played by yeast
ras
in growth control, it is necessary to identify functions acting upstream of
ras
in the adenylate cyclase pathway. The evidence presented here indicates that
CDC25
, identified by conditional cell cycle arrest mutations, encodes such an upstream function.
Lipoprotein Uptake by Neuronal Growth Cones in Vitro
Authors: Ignatius Michael J. , Shooter Eric M. , Pitas Robert E. , Mahley Robert W.
Published: October 2006

Macrophages that rapidly enter injured peripheral nerve synthesize and secrete large quantities of apolipoprotein E. This protein may be involved in the redistribution of lipid, including cholesterol released during degeneration, to the regenerating axons. To test this postulate, apolipoprotein E-associated lipid particles released from segments of injured rat sciatic nerve and apolipoprotein E-containing lipoproteins from plasma were used to determine whether sprouting neurites, specifically their growth cones, possessed lipoprotein receptors. Pheochromocytoma (PC12) cells, which can be stimulated to produce neurites in vitro, were used as a model system. Apolipoprotein E-containing lipid particles and lipoproteins, which had been labeled with fluorescent dye, were internalized by the neurites and their growth cones; the unmetabolized dye appeared to be localized to the lysosomes. The rapid rate of accumulation in the growth cones precludes the possibility of orthograde transport of the fluorescent particles from the PC12 cell bodies. Thus, receptor-mediated lipoprotein uptake is performed by the apolipoprotein B,E(LDL) (low density lipoprotein) receptors, and in the regenerating peripheral nerve apolipoprotein E may deliver lipids to the neurites and their growth cones for membrane biosynthesis.
Fluorescence Properties of Calmodulin-Binding Peptides Reflect Alpha-Helical Periodicity
Authors: O'Neil Karyn T. , Wolfe Henry R. , Erickson-Viitanen Susan , DeGrado William F.
Published: October 2006

A basic amphiphilic α-helix is a structural feature common to many calmodulin-binding peptides and proteins. A set of fluorescent analogues of a very tight binding inhibitor (dissociation constant of 200 picomolar) of calmodulin has been synthesized. The fluorescent amino acid tryptophan has been systematically moved throughout the sequence of this peptide. The fluorescence properties for the peptides repeat every three to four residues and are consistent with the periodicity observed for an α-helix.
Transient Morphological Features of Identified Ganglion Cells in Living Fetal and Neonatal Retina
Authors: Ramoa Ary S. , Campbell Gregor , Shatz Carla J.
Published: October 2006

The function and morphology of retinal ganglion cells in the adult mammalian visual system has been well studied, but little is known about how the adult state is achieved. To address this question, the morphological changes that retinal ganglion cells undergo during development were studied. Ganglion cells were first identified by retrograde labeling with rhodamine latex microspheres deposited in retinorecipient targets in fetal and early postnatal cats. The structure of ganglion cells was then revealed by intracellular injection of Lucifer yellow in living retinas removed and maintained in vitro. As early as 2 weeks before birth, a morphologically diverse assortment of ganglion cells is present, some of which resemble the α, β, and γ classes found in the adult. However, in contrast to the adult, developing ganglion cells exhibit several transient features, including excessive axonal and dendritic branching and exuberant somatic and dendritic spines. These morphological features indicate that there is a transient network of connectivity that could play an important role in the final determination of retinal ganglion cell form and function.
Sodium-Calcium Exchange in Heart: Membrane Currents and Changes in [Ca
2+
]
i
Authors: Barcenas-Ruiz L. , Beuckelmann D. J. , Wier W. G.
Published: October 2006

Recordings have been made of changes in intracellular calcium ion concentration ([Ca
2+
]
i
) that can be attributed to the operation of an electrogenic, voltage-dependent sodium-calcium (Na-Ca) exchanger in mammalian heart cells. Guinea pig ventricular myocytes under voltage clamp were perfused internally with fura-2, a fluorescent Ca
2+
-indicator, and changes in [Ca
2+
]
i
and membrane current that resulted from Na-Ca exchange were identified through the use of various organic channel blockers and impermeant ions. Depolarization of cells elicited slow increases in [Ca
2+
]
i
, with the maximum increase depending on internal [Na
+
], external [Ca
2+
], and membrane voltage. Repolarization was associated with net Ca
2+
efflux and a decline in the inward current that developed instantaneously upon repolarization. The relation between [Ca
2+
]
i
and current was linear, and the slope was made steeper by hyperpolarization.
Induction of Synaptic Potentiation in Hippocampus by Patterned Stimulation Involves Two Events
Authors: Larson John , Lynch Gary
Published: October 2006

Electrical stimulation of axons in the hippocampus with short high-frequency bursts that resemble in vivo activity patterns produces stable potentiation of postsynaptic responses when the bursts occur at intervals of 200 milliseconds but not 2 seconds. When a burst was applied to one input and a second burst applied to a different input to the same target neuron 200 milliseconds later, only the synapses activated by the second burst showed stable potentiation. This effect was observed even when the two inputs innervated completely different regions of the postsynaptic cells; but did not occur when the inputs were stimulated simultaneously or when the second burst was delayed by 2 seconds. Intracellular recordings indicated that the first burst extended the decay phase of excitatory postsynaptic potentials evoked 200 milliseconds later. These results suggest that a single burst of axonal stimulation produces a transient, spatially diffuse "priming" effect that prolongs responses to subsequent bursts, and that these altered responses trigger spatially restricted synaptic modifications. The similarity of the temporal parameters of the priming effect and the theta rhythm that dominates the hippocampal electroencephalogram (EEG) during learning episodes suggests that this priming may be involved in behaviorally induced synaptic plasticity.
Mechanism of the Rapid Effect of 17β-Estradiol on Medial Amygdala Neurons
Authors: Nabekura Junichi , Oomura Yutaka , Minami Taketsugu , Mizuno Yuji , Fukuda Atsuo
Published: October 2006

The mechanism by which sex steroids rapidly modulate the excitability of neurons was investigated by intracellular recording of neurons in rat medial amygdala brain slices. Brief hyperpolarization and increased potassium conductance were produced by 17β-estradiol. This effect persisted after elimination of synaptic input and after suppression of protein synthesis. Thus, 17β-estradiol directly changes the ionic conductance of the postsynaptic membrane of medial amygdala neurons. In addition, a greater proportion of the neurons from females than from males responded to 17β-estradiol.
The Generation of Insulin-Like Growth Factor-1—Sensitive Cells by Growth Hormone Action
Authors: Zezulak Kathleen M. , Green Howard
Published: October 2006

Insulin-like growth factor-1 (IGF-1), a mitogenic polypeptide, is usually considered the sole effector by means of which growth hormone increases tissue mass. However, growth hormone, but not IGF-1, directly promotes the differentiation of cultured preadipocytes to adipocytes. Adipocytes newly differentiated from precursor cells in response to growth hormone were shown to be much more sensitive to the mitogenic effect of IGF-1 than the precursor cells. The result of IGF-1 action is therefore a selective multiplication of young differentiated cells (clonal expansion). This supports the concept of a dual effector system in which the preferred target cells of IGF-1 action are created by the direct action of growth hormone.
Pituitary-Brain Vascular Relations: A New Paradigm
Authors: Bergland Richard M. , Page Robert B.
Published: October 2006

Vascular casts of the pituitary gland have demonstrated a paucity of veins extending from the adenohypophysis to the systemic circulation and have suggested that some adenohypophyseal venous blood returns to the neurohypophysis. The neurohypophyseal capillary bed may function as a vascular switch and in this article a series of 14 questions are proposed regarding the vascular dynamics of the pituitary. Together these questions raise the larger question, namely, whether pituitary hormones are transported directly to the brain to modify brain function?
Identifying Environmental Chemicals Causing Mutations and Cancer
Authors: Ames Bruce N.
Published: October 2006

Damage to DNA appears to be the major cause of most cancer and genetic birth defects and may contribute to aging and heart disease as well. The agents that cause this damage must be identified. Many of these agents are natural chemicals present in the human diet as complex mixtures. The tens of thousands of man-made chemicals that have been introduced into the environment in the last few decades must also be tested for their ability to damage DNA. Existing animal tests and human epidemiology alone are inadequate for this task because of time, expense, and the difficulty of dealing with complex mixtures, Newly developed short-term tests, most of them assaying for mutagenicity, are discussed as key tools in identifying environmental mutagens and carcinogens.
The Role of the c-
mos
Gene in the 8;21 Translocation in Human Acute Myeloblastic Leukemia
Authors: Diaz Manuel O. , Le Beau Michelle M. , Rowley Janet D. , Drabkin Harry A. , Patterson David
Published: October 2006

The human c-
mos
proto-oncogene is located on chromosome 8 at band q22, close to the breakpoint in the t(8;21) (q22;q22) chromosome rearrangement. This translocation is associated with acute myeloblastic leukemia, subgroup M2. The c-
myc
gene, another proto-oncogene, has been mapped to 8q24. The breakpoint at 8q22 separates these genes, as determined by in situ hybridization of c-
mos
and c-
myc
probes. The c-
mos
gene remains on the 8q- chromosome and the c-
myc
gene is translocated to the 21q+ chromosome. Southern blot analysis of DNA from bone marrow cells of four patients with this translocation showed no rearrangement of c-
mos
.
Distinct Monoamine Oxidase A and B Populations in Primate Brain
Authors: Westlund K. N. , Denney R. M. , Kochersperger L. M. , Rose R. M. , Abell C. W.
Published: October 2006

Monoclonal antibodies specific for monoamine oxidase (MAO) A and MAO B, respectively, were used to localize these enzymes in primate brain. The reagents recognized different populations of neurons: those that recognized MAO A were located in cell groups containing catecholamines, including the substantia nigra, nucleus locus coeruleus, nucleus subcoeruleus, and the periventricular region of the hypothalamus, whereas those that recognized MAO B were observed in serotonin regions, including the nucleus raphe dorsalis and nucleus centralis superior. These data illustrate the physiological independence of MAO A and B and show that neurons may be specialized for their degradative as well as their synthetic functions.
Modulation of the
sis
Gene Transcript During Endothelial Cell Differentiation in Vitro
Authors: Jaye Michael , McConathy Evelyn , Drohan William , Tong Benton , Deuel Thomas , Maciag Thomas
Published: October 2006

Endothelial cells, which line the interior walls of blood vessels, proliferate at the site of blood vessel injury. Knowledge of the factors that control the proliferation of these cells would help elucidate the role of endothelial cells in wound healing, tumor growth, and arteriosclerosis. In vitro, endothelial cells organize into viable, three-dimensional tubular structures in environments that limit cell proliferation. The process of endothelial cell organization was found to result in decreased levels of the sis messenger RNA transcript and increased levels of the messenger RNA transcript for fibronectin. This situation was reversed on transition from the organized structure to a proliferative monolayer. These results suggest a reciprocity for two biological response modifiers involved in the regulation of endothelial cell proliferation and differentiation in vitro.
Experimental Leprosy in Three Species of Monkeys
Authors: Wolf Robert H. , Gormus Bobby J. , Martin Louis N. , Baskin Gary B. , Walsh Gerald P. , Meyers Wayne M. , Binford Chapman H.
Published: October 2006

Eleven mangabey monkeys inoculated with
Mycobacterium leprae
developed lepromatous-type leprosy. Nine of the mangabeys were inoculated with
M. leprae
isolated from a mangabey with naturally acquired lepromatous leprosy. Immune function was depressed in some of these animals after dissemination of the disease. Two mangabeys developed lepromatous leprosy after inoculation with human
M. leprae
passaged in an armadillo. Three rhesus and three African green monkeys inoculated with mangabey-derived
M. leprae
also developed lepromatous leprosy. Mangabeys may be the first reported nonhuman primate model for the study of leprosy. Rhesus and African green monkeys may also prove to be reproducibly susceptible to the disease.
Infantile Experience with Suckling Odors Determines Adult Sexual Behavior in Male Rats
Authors: Fillion Thomas J. , Blass Elliott M.
Published: October 2006

Because infant rats learn about odors that elicit suckling, and because certain chemosensory cues that help elicit mating behavior in adults are similar to those that elicit suckling, an experiment was undertaken to assess the influence of suckling-associated odors experienced during infancy on adult sexual behavior. Rat pups lived with and suckled dams whose nipple and vaginal odors were altered with citral, a lemon scent. The rats were weaned and never exposed again, until testing, to citral or females. At about 100 days of age, the males were paired in mating tests with a normal sexually receptive female or with a sexually receptive female that had been treated perivaginally with citral immediately before testing. The males ejaculated readily when paired with citral-treated females but were slow to achieve ejaculation when paired with normal females. These findings implicate an infantile experience as a determinant of adult sexual behavior in a mammal.
Hyperacuity in Cat Retinal Ganglion Cells
Authors: Shapley Robert , Victor Jonathan
Published: October 2006

Cat X retinal ganglion cells that can resolve sine gratings of only 2.5 cycles per degree can nevertheless respond reliably to displacements of a grating of approximately 1 minute of arc. This is a form of hyperacuity comparable in magnitude to that seen in human vision. A theoretical analysis of this form of hyperacuity reveals it to be a result of the high gain and low noise of ganglion cells. The hyperacuity expected for the best retinal ganglion cells is substantially better than that observed in behavioral experiments. Thus the brain, rather than improving on the retinal signal-to-noise ratio by pooling signals from many ganglion cells, is unable to make use of all the hyperacuity information present in single ganglion cell responses.
Continued Expression of Neonatal Myosin Heavy Chain in Adult Dystrophic Skeletal Muscle
Authors: Bandman Everett
Published: October 2006

The expression of myosin heavy chain isoforms was examined in normal and dystrophic chicken muscle with a monoclonal antibody specific for neonatal myosin. Adult dystrophic muscle continued to contain neonatal myosin long after it disappeared from adult normal muscle. A new technique involving western blotting and peptide mapping demonstrated that the immunoreactive myosin in adult dystrophic muscle was identical to that found in neonatal normal muscle. Immunocytochemistry revealed that all fibers in the dystrophic muscle failed to repress neonatal myosin heavy chain. These studies suggest that muscular dystrophy inhibits the myosin gene switching that normally occurs during muscle maturation.