bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective Sparing of a Class of Striatal Neurons in Huntington's Disease
Authors: Ferrante R. J. , Kowall N. W. , Beal M. F. , Richardson E. P. , Bird E. D. , Martin J. B.
Published: October 2006

A distinct subpopulation of striatal aspiny neurons, containing the enzyme nicotinamide adenine dinucleotide phosphate diaphorase, is preserved in the caudate nucleus in Huntington's disease. Biochemical assays confirmed a significant increase in the activity of this enzyme in both the caudate nucleus and putamen in postmortem brain tissue from patients with this disease. The resistance of these neurons suggests that the gene defect in Huntington's disease may be modifiable by the local biochemical environment. This finding may provide insight into the nature of the genetically programmed cell death that is a characteristic of the disease.
Organ-Resident, Nonlymphoid Cells Suppress Proliferation of Autoimmune T-Helper Lymphocytes
Authors: Caspi Rachel R. , Roberge Francois G. , Nussenblatt Robert B.
Published: October 2006

Local presentation of autoantigen by organ-resident cells inappropriately expressing Ia determinants has been implicated in organ-specific autoimmunity. Experimental autoimmune uveoretinitis, induced in rats by immunization with retinal soluble antigen, is used as a model of organ-specific autoimmunity. In an in vitro system derived from this model, uveitogenic rat T-helper lymphocytes specific to the retinal soluble antigen, or control T-helper lymphocytes reactive to the purified protein derivative of tuberculin, were cocultured with Ia-expressing syngeneic retinal glial cells (Müller cells) in the presence of specific antigen. Antigen presentation was not apparent under ordinary culture conditions, and the Müller cells profoundly suppressed the proliferative response of primed T-helper lymphocytes to antigen presented on conventional antigen-presenting cells, as well as their subsequent interleukin-2 (IL-2)-dependent expansion. Suppression of proliferation was accompanied by inhibition of IL-2 production in response to antigen, as well as by reduction in high-affinity IL-2 receptor expression, and proceeded via a contact-dependent mechanism. These results suggest a role for locally acting suppression mechanisms in immune regulation and maintenance of tissue homeostasis.
The Human Laminin Receptor Is a Member of the Integrin Family of Cell Adhesion Receptors
Authors: Gehlsen Kurt R. , Dillner Lena , Engvall Eva , Ruoslahti Erkki
Published: October 2006

A receptor for the adhesive basement membrane protein, laminin, was isolated from human glioblastoma cells by affinity chromatography on laminin. This receptor has a heterodimeric structure similar to that of receptors for other extracellular matrix proteins such as fibronectin and vitronectin. Incorporation of the laminin receptor into liposomal membranes makes it possible for liposomes to attach to surfaces coated with laminin. The receptor liposomes also attached to some extent to surfaces coated with fibronectin, but not with other matrix proteins. These properties identify the laminin receptor as a member of the integrin family of cell adhesion receptors.
An Early Hierarchic Role of U1 Small Nuclear Ribonucleoprotein in Spliceosome Assembly
Authors: Ruby Stephanie W. , Abelson John
Published: October 2006

Splicing of nuclear precursor messenger RNA (pre-mRNA) occurs on a large ribonucleoprotein complex, the spliceosome. Several small nuclear ribonucleoproteins (snRNP's) are subunits of this complex that assembles on the pre-mRNA. Although the U1 snRNP is known to recognize the 5′ splice site, its roles in spliceosome formation and splice site alignment have been unclear. A new affinity purification method for the spliceosome is described which has provided insight into the very early stages of spliceosome formation in a yeast in vitro splicing system. Surprisingly, the U1 snRNP initially recognizes sequences at or near both splice junctions in the intron. This interaction must occur before the other snRNP's (U2, U4, U5, and U6) can join the complex. The results suggest that interaction of the two splice site regions occurs at an early stage of spliceosome formation and is probably mediated by U1 snRNP and perhaps other factors.
Distinct Hepatic Receptors for Low Density Lipoprotein and Apolipoprotein E in Humans
Authors: Hoeg Jeffrey M. , Demosky Stephen J. , Gregg Richard E. , Schaefer Ernst J. , Brewer H. Bryan
Published: October 2006

Since the liver is a central organ for lipid and lipoprotein synthesis and catabolism, hepatic receptors for specific apolipoproteins on plasma lipoproteins would be expected to modulate lipid and lipoprotein metabolism. The role of hepatic receptors for low density lipoproteins and apolipoprotein E-containing lipoproteins was evaluated in patients with complementary disorders in lipoprotein metabolism: abetalipoproteinemia and homozygous familial hypercholesterolemia. In addition, hepatic membranes from a patient with familial hypercholesterolemia were studied and compared before and after portacaval shunt surgery. The results establish that the human liver has receptors for apolipoproteins B and E. Furthermore, in the human, hepatic receptors for low density lipoproteins and apolipoprotein E are genetically distinct and can undergo independent control.
Evidence for Exposure to HTLV-III in Uganda Before 1973
Authors: Saxinger W. Carl , Levine Paul H. , Dean A. G. , de Thé Guy , Lange-Wantzin Gunhild , Moghissi Jasmine , Laurent Francine , Hoh Mei , Sarngadharan M. G. , Gallo Robert C.
Published: October 2006

Fifty of 75 serum samples collected in the West Nile district of Uganda between August 1972 and July 1973 contained antibodies reactive with human T-cell leukemia (lymphotropic) virus type 3 (HTLV-III; mean titer, 601), while 12 of 75 samples were positive in a similar test for HTLV type 1 (HTLV-I) antibodies (mean titer, 236). The samples were screened by enzyme-linked immunosorbent assay and positive results were confirmed by a newly developed unlabeled antibody-peroxidase procedure with enhanced sensitivity for detection of antibody binding to immunoblots of HTLV-III antigen, demonstrating antibodies to proteins with molecular weights of 24,000, 41,000, and 76,000 in nearly all positive samples. Analysis of titration data indicated enhanced titers of antibody against HTLV-III and HTLV-I when coinfection occurred. The high prevalence and relatively low titers [compared to serum from patients with acquired immune deficiency syndrome (AIDS)] of antibodies recognizing HTLV-III proteins in sera from this population at a time that may predate or coincide with the appearance or spread of the AIDS agent (HTLV-III) suggest that the virus detected may have been a predecessor of HTLV-III or is HTLV-III itself but existing in a population acclimated to its presence. It further suggests an African origin of HTLV-III.
Antiviral Chemotherapy and Chemoprophylaxis
Authors: Dolin Raphael
Published: October 2006

Antiviral compounds have been developed for use in chemoprophylaxis and chemotherapy of a variety of infections in humans, including those caused by influenza viruses, respiratory syncytial virus, and herpesviruses. The efficacy of several of these compounds has been demonstrated in rigorously controlled trials. Advances in molecular virology have led to the identification of biochemically defined, virus-specific functions that serve as appropriate targets for the future development of antiviral compounds. Clinical investigators and practicing physicians are now confronting questions previously raised with the use of antibacterial antibiotics. These questions concern appropriate routes of administration for antiviral compounds, optimal dosage regimens, risks of long-term prophylaxis, and the emergence of resistant organisms.
Biochemical Modeling of an Autonomously Oscillatory Circadian Clock in
Euglena
Authors: Goto Ken , Laval-Martin Danielle L. , Edmunds Leland N.
Published: October 2006

Eukaryotic microorganisms, as well as higher animals and plants, display many autonomous physiological and biochemical rhythmicities having periods approximating 24 hours. In an attempt to determine the nature of the timing mechanisms that are responsible for these circadian periodicities, two primary operational assumptions were postulated. Both the perturbation of a putative element of a circadian clock within its normal oscillatory range and the direct activation as well as the inhibition of such an element should yield a phase shift of an overt rhythm generated by the underlying oscillator. Results of experiments conducted in the flagellate Euglena suggest that nicotinamide adenine dinucleotide (NAD
+
), the mitochondrial Ca
2+
-transport system, Ca
2+
, calmodulin, NAD
+
kinase, and NADP
+
phosphatase represent clock "gears" that, in ensemble, might constitute a self-sustained circadian oscillating loop in this and other organisms.
Infection of the Basal Ganglia by a Murine Coronavirus
Authors: Fishman Paul S. , Gass Jennifer S. , Swoveland Peggy T. , Lavi Ehud , Highkin Maureen K. , Weiss Susan R.
Published: October 2006

The coronavirus, mouse hepatitis virus strain A59 (MHV-A59), causes mild encephalitis and chronic demyelination. Immunohistochemical techniques showed that MHV-A59-infected C57BL/6 mice contained dense deposits of viral antigen in the subthalamic nucleus and substantia nigra, with fewer signs of infection in other regions of the brain. The animals showed extra- and intracellular vacuolation, neuronal loss, and gliosis in the subthalamic-nigral region. Such localization is unprecedented among known viral encephalitides of humans and other species. This infection by a member of a viral class capable of causing both encephalitis and persistent infection in several species may be related to postencephalitic parkinsonism.
Gonadotropin-Releasing Hormone Binding Sites in Human Breast Carcinoma
Authors: Eidne Karin A. , Flanagan Colleen A. , Millar Robert P.
Published: October 2006

Gonadotropin-releasing hormone analogs can cause regression of hormone-dependent breast carcinomas. These effects are thought to be mediated through the inhibition of gonadotropic and steroid hormones. These analogs may also act directly on the tumor because they are effective in treating breast cancer in some postmenopausal women. The presence of specific binding sites for gonadotropin-releasing hormone was demonstrated in human breast carcinomas by means of a novel approach of ligand immunoblotting. The results indicate a possible mechanism by which the peptide has direct effects on this tissue. These binding proteins were not detectable in non-neoplastic breast tissue.
Molecular Cloning of a Complementary DNA Encoding Human Macrophage-Specific Colony-Stimulating Factor (CSF-1)
Authors: Kawasaki Ernest S. , Ladner Martha B. , Wang Alice M. , Van Arsdell Janelle , Warren M. Kim , Coyne Mazie Y. , Schweickart Vicki L. , Lee Mei-Ting , Wilson Kenneth J. , Boosman Albert , Stanley E. Richard , Ralph Peter , Mark David F.
Published: October 2006

Complementary DNA (cDNA) clones encoding human macrophage-specific colony-stimulating factor (CSF-1) were isolated. One cDNA clone codes for a mature polypeptide of 224 amino acids and a putative leader of 32 amino acids. This cDNA, which was cloned in the Okayama-Berg expression vector, specifies the synthesis of biologically active CSF-1 in COS cells, as determined by a specific radioreceptor assay, macrophage bone marrow colony formation, and antibody neutralization. Most of the cDNA isolates contain part of an intron sequence that changes the reading frame, resulting in an abrupt termination of translation; these cDNA's were inactive in COS cells. The CSF-1 appears to be encoded by a single-copy gene, but its expression results in the synthesis of several messenger RNA species, ranging in size from about 1.5 to 4.5 kilobases.
The Action of Oncogenes in the Cytoplasm and Nucleus
Authors: Weinberg Robert A.
Published: October 2006

As many as 40 distinct oncogenes of viral and cellular origin have been identified to date. Many of these genes can be grouped into functional classes on the basis of their effects on cellular phenotype. These groupings suggest a small number of mechanisms of action of the oncogene-encoded proteins. Some data suggest that, in the cytoplasm, these proteins may regulate levels of critical second messenger molecules; in the nucleus, these proteins may modulate the activity of the cell's transcriptional machinery. Many of the gene products can also be related to a signaling pathway that determines the cell's response to growth-stimulating factors. Because some of these genes are expressed in nongrowing, differentiated cells, the encoded proteins may in certain tissues mediate functions that are unrelated to cellular growth control.
Association of Crossover Points with Topoisomerase I Cleavage Sites: A Model for Nonhomologous Recombination
Authors: Bullock Peter , Champoux James J. , Botchan Michael
Published: October 2006

Nonhomologous DNA recombination is frequently observed in somatic cells upon the introduction of DNA into cells or in chromosomal events involving sequences already stably carried by the genome. In this report, the DNA sequences at the crossover points for excision of SV40 from chromosomes were shown to be associated with eukaryotic topoisomerase I cleavage sites in vitro. The precise location of the cleavage sites relative to the crossover points has suggested a general model for nonhomologous recombination mediated by topoisomerase I.
α
2
-Adrenergic Mechanisms in Prefrontal Cortex Associated with Cognitive Decline in Aged Nonhuman Primates
Authors: Arnsten Amy F. T. , Goldman-Rakic Patricia S.
Published: October 2006

This study provides evidence that the α
2
-adrenergic receptor agonist clonidine ameliorates the cognitive deficits exhibited by aged nonhuman primates through drug actions at α
2
receptors. Furthermore, pharmacological profiles in animals with lesions restricted to the dorsolateral prefrontal cortex indicate that this area may be the site of action for some of clonidine's beneficial effects. These results demonstrate that α-adrenergic systems contribute to cognitive function and suggest a new strategy for treating memory disorders in aged humans.
Ras
-Transformed Cells: Altered Levels of Phosphatidylinositol-4,5-Bisphosphate and Catabolites
Authors: Fleischman Laurie F. , Chahwala Suresh B. , Cantley Lewis
Published: October 2006

Steady-state cellular levels of phosphatidylinositol-4,5-bisphosphate (PIP
2
), 1,2-diacylglycerol (DAG), and inositol phosphates have been measured in two different fibroblast cell lines (NIH 3T3 and NRK cells) before and after transformation with three different
ras
genes. At high cell density the ratio of DAG to PIP
2
was 2.5- to 3-fold higher in the
ras
-transformed cells than in their untransformed counterparts. The sum of the water-soluble breakdown products of the polyphosphoinositides, inositol-1,4-bisphosphate and inositol-1,4,5-trisphosphate, was also elevated in
ras
-transformed NRK cells compared with nontransformed NRK cells. These findings suggest that the
ras
(p21) protein may act by affecting these levels, possibly as a regulatory element in the PIP2 breakdown pathway.
Stress-Induced Inhibition of Reproductive Functions: Role of Endogenous Corticotropin-Releasing Factor
Authors: Rivier Catherine , Rivier Jean , Vale Wylie
Published: October 2006

In the adult castrated male rat, exposure to inescapable, intermittent electroshocks inhibited the pulsatile pattern of luteinizing hormone release and markedly lowered its plasma concentrations. The central administration of the corticotropin-releasing factor (CRF) antagonist α-helical ovine CRF residues 9 to 41 reversed the inhibitory action of stress. Neither its peripheral injection, nor the intraventricular injection of the inactive CRF analog des-Glu
17
to Arg
35
ovine CRF was effective. These results suggest that endogenous CRF may mediate some deleterious effects of noxious stimuli on reproduction.
New Human T-Lymphotropic Retrovirus Related to Simian T-Lymphotropic Virus Type III (STLV-III
AGM
)
Authors: Kanki Phyllis J. , Barin Francis , M'Boup Souleyman , Allan Jonathan S. , Romet-Lemonne Jean Loup , Marlink Richard , McLane Mary Frances , Lee Tun-Hou , Arbeille Brigitte , Denis Francois , Essex M.
Published: October 2006

This report describes serologic evidence for a virus similar to that known as simian T-lymphotropic virus type III of African Green monkeys (STLV-III
AGM
) infecting apparently healthy people in Senegal, West Africa, and the isolation of virus from these individuals. Serum samples from selected healthy West African people showed unusual serologic profiles when tested with antigens of HTLV-III/LAV, the etiologic agent of AIDS, and of STLV-III
AGM
. The samples reacted strongly with all of the major viral antigens of STLV-III
AGM
but showed variable or no reactivity with the major viral antigens of HTLV-III/LAV by radioimmunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A new human T-lymphotropic virus (HTLV-IV) isolated from these people was grown in vitro and shown to have retroviral type particles, growth characteristics, and major viral proteins similar to those of the STLV-III and HTLV-III/LAV group of retroviruses. The gp120/160, gp32, p64, p55, p53, p24, and p15 proteins precipitated were the same size as and reactive with STLV-III
AGM
proteins. The serologic data suggest that this virus shares more common epitopes with STLV-III
AGM
than with the prototype HTLV-III/LAV that infects people in the United States and Europe. Further study of this virus and of the origin of the HTLV-III/LAV group of viruses may expand our understanding of the human AIDS virus.
HTLV-III Legend Correction
Authors: Gilden Raymond V. , Gonda Matthew A. , Sarngadharan M. G. , Popovic Mikulas , Gallo Robert C.
Published: October 2006

We recently reexamined the electron micrographs used in our publications in
Science
(4 May 1984) and discovered that in the composite micrograph of Schüpbach
et al.
(figure 4) the panel labeled HTLV-III was inadvertently composed from photographs of a HUT-78 culture transiently infected with a sample of LAV
1
provided by L. Montagnier's laboratory.

The LAV
1
preparation was used to transiently infect T cells in one of our laboratories to confirm that it was indeed a retrovirus. In the several months preceding preparation of the composite in question, electron micrographs of cultures infected with our HTLV-III isolates were available from specimens obtained from known ARC and AIDS patients. One appeared in Gao
et al.
; others were used in Popovic
et al.
and Shaw
et al.
(4).

The figure legend in Schupbach
et al.
was prepared with the intent that particles from patient J.S. shown in Galo
et al.
(figure 2) were to be used. Thus, this correction relates only to the choice of photographs used in the one communication and not to the content of that paper or any of the other papers.
Calcium Modulation Activates Epstein-Barr Virus Genome in Latently Infected Cells
Authors: Faggioni Alberto , Zompetta Claudia , Grimaldi Settimio , Barile Giuseppe , Frati Luigi , Lazdins Janis
Published: October 2006

In many viral infections the host cell carries the viral genome without producing viral particles, a phenomenon known as viral latency. The cellular mechanisms by which viral latency is maintained or viral replication is induced are not known. The modulation of intracellular calcium concentrations by calcium ionophores induced Epstein-Barr viral antigens in lymphoblastoid cell lines that carry the virus. When calcium ionophores were used in conjunction with direct activators of protein kinase C (12-
O
-tetradecanoyl phorbol-13-acetate and a synthetic diacylglycerol), a greater induction of viral antigens was observed than with either agent alone. Activation of protein kinase C may be required for the expression of the viral genome.
Human Prion Protein cDNA: Molecular Cloning, Chromosomal Mapping, and Biological Implications
Authors: Liao Yu-Cheng , Lebo Roger V. , Clawson Gary A. , Smuckler Edward A.
Published: October 2006

A human complementary DNA whose protein product is considered to be the major component of scrapie-associated fibrils in Creutzfeldt-Jakob disease, kuru, and Gerstmann-Straussler syndrome has been identified and characterized. The extensive homology of this gene sequence to the hamster PrP 27- to 30-kilodalton prion protein complementary DNA clone, and its existence as a single copy in the human genome, leads to the conclusion that this is the human prion gene. This human prion gene has been mapped to human chromosome 20, negating a direct link between the prion protein and Down's syndrome or the amyloid of Alzheimer's disease.
Long-Range Electron Transfer in Heme Proteins
Authors: Mayo Stephen L. , Ellis Walther R. , Crutchley Robert J. , Gray Harry B.
Published: October 2006

Kinetic experiments have conclusively shown that electron transfer can take place over large distances (greater than 10 angstroms) through protein interiors. Current research focuses on the elucidation of the factors that determine the rates of long-range electron-transfer reactions in modified proteins and protein complexes. Factors receiving experimental and theoretical attention include the donor-acceptor distance, changes in geometry of the donor and acceptor upon electron transfer, and the thermodynamic driving force. Recent experimental work on heme proteins indicates that the electron-transfer rate falls off exponentially with donor-acceptor distance at long range. The rate is greatly enhanced in proteins in which the structural changes accompanying electron transfer are very small.
Human Monoclonals from Antigen-Specific Selection of B Lymphocytes and Transformation by EBV
Authors: Casali Paolo , Inghirami Giorgio , Nakamura Minoru , Davies Terry F. , Notkins Abner Louis
Published: October 2006

Hybridoma technology has made it possible to prepare monoclonal antibodies with the use of murine lymphocytes. Attempts to extend this technology to the human level, however, have met with difficulties. A method has been developed for making human monoclonal antibodies of predetermined specificity. Biotinylated antigens (human thyroglobulin or tetanus toxoid) were incubated with human B lymphocytes from peripheral blood. The lymphocytes to which the antigens bound were selected by fluorescence-activated cell sorting. Positively selected (high fluorescence) and negatively selected (low fluorescence) cells were then transformed with Epstein-Barr virus (EBV) and grown in microculture wells. All wells from the positively selected fraction produced antigen-specific antibody (95 to 1800 nanogram-equivalents per milliliter), whereas fewer than 6% of the wells from negatively selected fraction made any detectable antibody (less than 10 nanogram-equivalents per milliliter). When the positively selected EBV-transformed cells were cultured in limiting dilution, clones were obtained that made antigen-specific monoclonal antibodies. By this method, monoclonal antibodies to both foreign antigens and autoantigens can be prepared from the normal human B-cell repertoire.
Variable Number of Tandem Repeat (VNTR) Markers for Human Gene Mapping
Authors: Nakamura Yusuke , Leppert Mark , O'Connell Peter , Wolff Roger , Holm Tom , Culver Melanie , Martin Cindy , Fujimoto Esther , Hoff Mark , Kumlin Erika , White Ray
Published: October 2006

A large collection of good genetic markers is needed to map the genes that cause human genetic diseases. Although nearly 400 polymorphic DNA markers for human chromosomes have been described, the majority have only two alleles and are thus uninformative for analysis of genetic linkage in many families. A few known marker systems, however, detect loci that respond to restriction enzyme cleavage by producing a fragment that can have many different lengths. This polymorphism is due to variation in the number of tandem repeats of a short DNA sequence. Because most individuals will be heterozygous at such loci, these markers will provide linkage information in almost all families. Ten oligomeric sequences derived from the tandem repeat regions of the myoglobin gene, the zeta-globin pseudogene, the insulin gene, and the X-gene region of hepatitis B virus, were used to develop a series of single-copy probes. These probes revealed new, highly polymorphic genetic loci whose allele sizes reflected variation in the number of tandem repeats.
Rapid Identification of Nonessential Genes of Herpes Simplex Virus Type 1 by Tn5 Mutagenesis
Authors: Weber Peter C. , Levine Myron , Glorioso Joseph C.
Published: October 2006

The large genome of herpes simplex virus type 1 (HSV-1) encodes at least 80 polypeptides, the majority of which have no recognized function. A subgroup of these gene products appears to be nonessential for virus replication in cell culture, but contributes to the complex life cycle of the virus in the host. To identify such functions, a simple insertional mutagenesis method has been used for selective inactivation of individual HSV-1 genes. The bacterial transposon Tn5 was allowed to insert randomly into cloned restriction fragments representing the entire short unique (U
S
) region of the HSV-1 genome. Of the 12 open reading frames that were mutagenized with Tn5, mutant derivatives of US2, US4, and US5 were recombined into the virus. These three genes proved to be nonessential for HSV-1 replication in Vero (African Green monkey kidney) cells and the US4 gene appeared to be involved in viral pathogenesis in the central nervous system of mice. This rapid mutagenesis procedure should prove useful in exploring the entire HSV-1 genome as well as the genomes of other complex animal viruses.
Mapping Patterns of c-
fos
Expression in the Central Nervous System After Seizure
Authors: Morgan James I. , Cohen Donna R. , Hempstead James L. , Curran Tom
Published: October 2006

A dramatic and specific induction of c-
fos
was observed in identifiable neuronal populations in vivo after administration of the convulsant Metrazole. This effect was time- and dose-dependent and was abolished by prior treatment with the anticonvulsant drugs diazepam or pentobarbital. About 60 minutes after administration of Metrazole, c-
fos
messenger RNA reached a maximum and declined to basal levels after 180 minutes. A further decrease below that in normal brain was observed before a return to basal levels after 16 hours. While Metrazole still elicited seizures during this period, reinduction of c-
fos
was largely refractory. At 90 minutes, c-
fos
protein was observed in the nuclei of neurons in the dentate gyrus, and in the pyriform and cingulate cortices. Subsequently, c-
fos
protein appeared throughout the cortex, hippocampus, and limbic system. Thus, seizure activity results in increased c-
fos
gene expression in particular subsets of neurons.
Wound Macrophages Express TGF-α and Other Growth Factors in Vivo: Analysis by mRNA Phenotyping
Authors: Rappolee Daniel A. , Mark David , Banda Michael J. , Werb Zena
Published: October 2006

The presence of macrophages is required for the regeneration of many cell types during wound healing. Macrophages have been reported to express a wide range of mitogenic factors and cytokines, but none of these factors has been shown in vivo to sustain all the wound-healing processes. It has been suggested that transforming growth factor-α (TGF-α) may mediate angiogenesis, epidermal regrowth, and formation of granulation tissue in vivo. Macrophages isolated from a wound site, and not exposed to cell culture conditions, expressed messenger RNA transcripts for TGF-α, TGF-β, platelet-derived growth factor A-chain, and insulin-like growth factor-1. The expression of these transcripts was determined by a novel method for RNA analysis in which low numbers of mouse macrophages were isolated from wound cylinders, their RNA was purified and reverse-transcribed, and the complementary DNA was amplified in a polymerase chain reaction primed with growth factor sequence-specific primers. This single-cell RNA phenotyping procedure is rapid and has the potential for quantification, and mRNA transcripts from a single cell or a few cells can be unambiguously demonstrated, with the simultaneous analysis of several mRNA species. Macrophages from wounds expressed TGF-α antigen, and wound fluids contained TGF-α. Elicited macrophages in culture also expressed TGF-α transcripts and polypeptide in a time-dependent manner after stimulation with modified low-density lipoproteins and lipopolysaccharide endotoxin, which are characteristic of the activators found in injured tissues.
Signal Transduction and Transcriptional Regulation by Glucocorticoid Receptor-LexA Fusion Proteins
Authors: Godowski Paul J. , Picard Didier , Yamamoto Keith R.
Published: October 2006

The glucocorticoid receptor regulates transcriptional initiation upon binding to its cognate hormone. A series of fusion genes was constructed to examine the mechanism of hormone-regulated transcriptional enhancement. The DNA binding domain of the bacterial LexA repressor was fused to receptor derivatives lacking the region that is necessary and sufficient for specific DNA binding and transcriptional enhancement at glucocorticoid response elements (GRE's). The resultant hybrid proteins activated transcription from promoters linked to the lex operator. Enhancement still required hormone binding by the hybrid receptor regardless of the exact positioning of the LexA binding domain within the protein. Thus, the unliganded hormone binding domain of the receptor acts as a strong but reversible inhibitor of receptor activity in a manner that is independent of the means by which the receptor recognizes DNA. The results also show directly that the receptor contains at least one "enhancement domain" other than that overlapping the GRE binding region; the second domain, enh2, occupies a region near the receptor amino terminus.
Characterization of a Helical Protein Designed from First Principles
Authors: Regan Lynne , DeGrado William F.
Published: October 2006

The question of how the primary amino acid sequence of a protein determines its three-dimensional structure is still unanswered. One approach to this problem involves the de novo design of model peptides and proteins that should adopt desired three-dimensional structures. A systematic approach was aimed at the design of a four-helix bundle protein. The gene encoding the designed protein was synthesized and the protein was expressed in
Escherichia coli
and purified to homogeneity. The protein was shown to be monomeric, highly helical, and very stable to denaturation by guanidine hydrochloride (GuHCl). Thus a globular protein has been designed that is capable of adopting a stable, folded structure in aqueous solution.
Biomaterials and Biomedical Devices
Authors: Hanker Jacob S. , Giammara Beverly L.
Published: October 2006

This review discusses the factors important in the incorporation or integration of biomaterials and devices by tissue. Methods for surface modification and surface-sensitive techniques for analysis are cited. In vitro methods to evaluate the biocompatibility or efficacy of certain biomaterials and devices are presented. Present and future directions in neural prostheses, cardiovascular materials, blood or bone substitutes, controlled drug delivery, orthopedic prostheses, dental materials, artificial organs, plasma- and cytapheresis, and dialysis are discussed.
Distinct Regions of Sp1 Modulate DNA Binding and Transcriptional Activation
Authors: Kadonaga James T. , Courey Albert J. , Ladika Joseph , Tjian Robert
Published: October 2006

Sp1 is a sequence-specific DNA binding protein that activates RNA polymerase II transcription from promoters that contain properly positioned GC boxes. A series of deletion mutants of Sp1 were expressed in
Escherichia coli
and used to identify separate regions of the protein that are important for three different biochemical activities. The sequence-specificity of DNA binding was conferred by Zn(II) fingers, whereas a different region of Sp1 appeared to regulate the affinity of DNA binding. The
E. coli
-synthesized Sp1 was able to stimulate initiation of RNA synthesis in vitro, and at least two distinct segments of the protein contributed to its transcriptional activity.
Human T-Cell γ Chain Genes: Organization, Diversity, and Rearrangement
Authors: Quertermous Thomas , Murre Cornelis , Dialynas Deno , Duby Allan D. , Strominger Jack L. , Waldman Thomas A. , Seidman J. G.
Published: October 2006

The human T-cell γ chain genes have been characterized in an attempt to better understand their role in immune response. These immunoglobulin-like genes are encoded in the genome in variable, joining, and constant segments. The human γ genes include at least six variable region genes, two joining segments, and two constant-region genes in germline DNA. Variable and joining segments recombine during the development of T cells to form rearranged genes. The diversity of human γ genes produced by this recombinational mechanism is greater than that produced by the murine genome but is more limited than that of other immunoglobulin-like genes.
Age-Dependent Changes in Proteins of
Drosophila melanogaster
Authors: Fleming J. E. , Quattrocki E. , Latter G. , Miquel J. , Marcuson R. , Zuckerkandl E. , Bensch K. G.
Published: October 2006

Several molecular theories of aging postulate that there are age-dependent changes in gene expression and that these changes contribute to the reduction in the viability of senescent cells. High-resolution, semiautomated, quantitative two-dimensional gel electrophoresis of many soluble proteins was used to test this hypothesis in
Drosophila
. Two-dimensional protein gel patterns were analyzed for each of three age groups of [
35
S]methionine-labeled adult male
Drosophila melanogaster
, which, except for their spermatocytes, consist entirely of fixed postmitotic cells. Seven relatively abundant polypeptides expressed in middle-aged (28-day-old) flies were absent in both young (10-day-old) and old (44-day-old) flies. Quantitative analyses of an additional 100 polypeptides were carried out by computer-assisted microdensitometry of fluorograms of the gel preparations. These analyses revealed a significant age-related heterogeneity in the quantitative distribution of radiolabel in these proteins. The data indicate that the qualitative pattern of gene expression is identical in young and old flies, but that profound quantitative changes occur in the expression of proteins during the
Drosophila
life-span.
A Neuronal Antigen in the Brains of Alzheimer Patients
Authors: Wolozin Benjamin L. , Pruchnicki Alex , Dickson Dennis W. , Davies Peter
Published: October 2006

A monoclonal antibody was prepared against pooled homogenates of brain tissue from patients with Alzheimer's disease. This antibody recognizes an antigen present in much higher concentration in certain brain regions of Alzheimer patients than in normal brain. The antigen appears to be a protein present in neurons involved in the formation of neuritic plaques and neurofibrillary tangles, and in some morphologically normal neurons in sections from Alzheimer brains. Partial purification and Western blot analysis revealed the antigen from Alzheimer brain to be a single protein with a molecular weight of 68,000. Application of the same purification procedure to normal brain tissue results in the detection of small amounts of a protein of lower molecular weight.
CNS and Hypoderm Regulatory Elements of the
Drosophila melanogaster
Dopa Decarboxylase Gene
Authors: Scholnick Steven B. , Bray Sarah J. , Morgan Bruce A. , McCormick Carol Ann , Hirsh Jay
Published: October 2006

Expression of the dopa decarboxylase gene (
Ddc
) is regulated in a tissue- and developmental stage-specific manner throughout the life cycle of the fruit fly,
Drosophila melanogaster
. Essential
Ddc
regulatory elements lie within 208 base pairs upstream from the RNA start point. Functional elements within this 5′ flanking region were mapped by deletion analysis, which assayed expression in vivo after germline integration via P element vectors. One of the elements is essential for expression in both the larval and adult central nervous system, and at least two other elements are necessary for quantitatively normal expression in the hypoderm. Within each of the intervals that have regulatory effects are found sequence elements conserved between the
Ddc
genes of two distantly related species of flies. On the basis of this correlation, regulatory functions for these sequence elements can be postulated.
Diurnal Expression of Transducin mRNA and Translocation of Transducin in Rods of Rat Retina
Authors: Brann Mark R. , Cohen Leslie V.
Published: October 2006

The messenger RNA (mRNA) that encodes α subunit of the guanosine triphosphate-binding protein transducin (T
α
) and T
α
immunoreactivity were localized and measured in the rat retina during the light-dark cycle with in situ hybridization and immunohistochemistry. Both T
α
mRNA and T
α
immunoreactivity were observed only in photoreceptors. Within the photoreceptor T
α
mRNA was present primarily in the inner segments and to a lesser extent in the outer nuclear layer at all times during the day and night. However, the distribution of T
α
immunoreactivity varied profoundly with the light-dark cycle; during the day, T
α
immunoreactivity was highest in the inner segments, and at night the outer segments were more immunoreactive. The amounts of T
α
mRNA and T
α
immunoreactivity also depended on the light-dark cycle. Levels of T
α
mRNA were high immediately before and after lights on; levels were low for the rest of the light-dark cycle. During the day, T
α
immunoreactivity increased in the inner segments following the increase in T
α
mRNA. After the lights were turned off, T
α
immunoreactivity decreased in the inner segments and increased in the outer segments. Thus, it appears that T
α
is synthesized in the inner segments after a morning increase in T
α
mRNA. Newly synthesized T
α
remains in the inner segments until it is transported to the outer segments at night, where it may be involved in the increase in the sensitivity of photoreceptor rods at night.
Promotion of Tubulin Assembly by Aluminum Ion in Vitro
Authors: MacDonald Timothy L. , Humphreys W. Griffith , Martin R. Bruce
Published: October 2006

It has been proposed that aluminum ion is a contributing factor in a variety of neurological diseases. In many of these diseases, aberrations in the cytoskeleton have been noted. The effects of aluminum ion on the in vitro assembly of tubulin into microtubules has been examined by determining the association constants for the metal ion-guanosine triphosphate-tubulin ternary complex required for polymerization. The association constant for aluminum ion was approximately 10
7
times that of magnesium ion, the physiological mediator of microtubule assembly. In addition, aluminum ion at 4.0 × 10
-10
mole per liter competed effectively with magnesium ion for support of tubulin polymerization when magnesium ion falls below 1.0 millimole per liter. The microtubules produced by aluminum ion were indistinguishable from those produced by magnesium ion when viewed by electron microscopy, and they showed identical critical tubulin concentrations for assembly and sensitivities to cold-induced depolymerization. However, the rate of guanosine triphosphate hydrolysis and the sensitivity to calcium ion-induced depolymerization, critical regulatory processes of microtubules in vivo, were markedly lower for aluminum ion microtubules than for magnesium ion microtubules.
X-Ray Absorption Edge Fine Structure of Potassium Ions in Various Environments: Application to Frog Blood Cells
Authors: Huang H. W. , Hunter S. H. , Warburton W. K. , Moss S. C.
Published: October 2006

The edge spectrum is a sensitive probe of local chemistry. Edge spectra of potassium in various chemical environments were measured, and each environment gives a unique edge spectrum. Hydrated potassium has a unique spectrum that is insensitive to counterions. Comparison of the spectra shows that the chemical state of potassium in cells differs appreciably from that in aqueous solutions.
Similarity of Cruzin, an Inhibitor of
Trypanosoma cruzi
Neuraminidase, to High-Density Lipoprotein
Authors: Prioli R. P. , Ordovas J. M. , Rosenberg I. , Schaefer E. J. , Pereira M. E. A.
Published: October 2006

A specific inhibitor of the neuraminidase of the protozoan parasite
Trypanosoma cruzi
was isolated recently and named cruzin. It is now shown that cruzin is similar to high-density lipoprotein by amino acid homology, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, by immunoblot analysis, and by isoelectric focusing. Cruzin purified by ion exchange chromatography and high-density lipoprotein isolated by density gradient ultracentrifugation inhibited
Trypanosoma cruzi
neuraminidase to the same extent. Cruzin or high-density lipoprotein restores to normal the decreased multiplication rate of
Trypanosoma cruzi
epimastigotes grown in a medium depleted of lipoproteins, suggesting that it may be important for survival of the parasite in nature.
Insights into Enzyme Function from Studies on Mutants of Dihydrofolate Reductase
Authors: Benkovic S. J. , Fierke C. A. , Naylor A. M.
Published: October 2006

Kinetic analysis and protein mutagenesis allow the importance of individual amino acids in ligand binding and catalysis to be assessed. A kinetic analysis has shown that the reaction catalyzed by dihydrofolate reductase is optimized with respect to product flux, which in turn is predetermined by the active-site hydrophobic surface. Protein mutagenesis has revealed that specific hydrophobic residues contribute 2 to 5 kilocalories per mole to ligand binding and catalysis. The extent to which perturbations within this active-site ensemble may affect catalysis is discussed in terms of the constraints imposed by the energy surface for the reaction.
Mitotic Recombination Within the Centromere of a Yeast Chromosome
Authors: Liebman Susan W. , Symington Lorraine S. , Petes Thomas D.
Published: October 2006

Centromeres are the structural elements of eukaryotic chromosomes that hold sister chromatids together and to which spindle tubules connect during cell division. Centromeres have been shown to suppress meiotic recombination in some systems. In this study yeast strains genetically marked within and flanking a centromere, were used to demonstrate that gene conversion (nonreciprocal recombination) tracts in mitosis can enter into and extend through the centromere.
Antiproliferative Activity of a Hybrid Protein Between Interferon-γ and Tumor Necrosis Factor-β
Authors: Feng Gen-Sheng , Gray Patrick W. , Shepard H. Michael , Taylor Milton W.
Published: October 2006

A hybrid protein between interferon-γ and tumor necrosis factor-β was made by ligating the respective genes and expressing the fused genes under the control of the
trp
promoter in
Escherichia coli
. The antiproliferative activity of the hybrid protein in vitro was greatly increased compared with either interferon-γ or tumor necrosis factor-β alone, and both antiviral activity and cytotoxic effect were retained in the hybrid protein. The hybrid protein may have potential clinical application.
Microtubule-Associated Protein MAP2 Shares a Microtubule Binding Motif with Tau Protein
Authors: Lewis Sally A. , Wang Dashou H. , Cowan Nicholas J.
Published: October 2006

The microtubule-associated protein MAP2 is a prominent large-sized component of purified brain microtubules that, like the 36- to 38-kilodalton tau proteins, bears antigenic determinants found in association with the neurofibrillary tangles of Alzheimer's disease. The complete sequence of mouse brain MAP2 was determined from a series of overlapping cloned complementary DNAs. The sequence of the carboxyl-terminal 185 amino acids is very similar (67 percent) to a corresponding region of tau protein, and includes a series of three imperfect repeats, each 18 amino acids long and separated by 13 or 14 amino acids. A subcloned fragment spanning the first two of the 18-amino acid repeats was expressed as a polypeptide by translation in vitro. This polypeptide copurified with microtubules through two successive cycles of polymerization and depolymerization, whereas a control polypeptide derived from the amino-terminal region of MAP2 completely failed to copurify. These data imply that the carboxyl-terminal domain containing the 18-amino acid repeats constitutes the microtubule binding site in MAP2. The occurrence of these repeats in tau protein suggests that these may be a general feature of microtubule binding proteins.
Newly Identified Brain Potassium Channels Gated by the Guanine Nucleotide Binding Protein G
o
Authors: VanDongen A. M. J. , Codina J. , Olate J. , Mattera R. , Joho R. , Birnbaumer L. , Brown A. M.
Published: October 2006

Potassium channels in neurons are linked by guanine nucleotide binding (G) proteins to numerous neurotransmitter receptors. The ability of G
o
, the predominant G protein in the brain, to stimulate potassium channels was tested in cell-free membrane patches of hippocampal pyramidal neurons. Four distinct types of potassium channels, which were otherwise quiescent, were activated by both isolated brain G
o
and recombinant G
o
α. Hence brain G
o
can couple diverse brain potassium channels to neurotransmitter receptors.
Developmental Expression of PDGF, TGF-α, and TGF-β Genes in Preimplantation Mouse Embryos
Authors: Rappolee Daniel A. , Brenner Carol A. , Schultz Richard , Mark David , Werb Zena
Published: October 2006

Control of growth and differentiation during mammalian embryogenesis may be regulated by growth factors from embryonic or maternal sources. With the use of single-cell messenger RNA phenotyping, the simultaneous expression of growth factor transcripts in single or small numbers of preimplantation mouse embryos was examined. Transcripts for platelet-derived growth factor A chain (PDGF-A), transforming growth factor (TGF)-α, and TGF-β1, but not for four other growth factors, were found in whole blastocysts. TGF-α, TGF-β1, and PDGF antigens were detected in blastocysts by immunocytochemistry. Both PDGF-A and TGF-α were detected as maternal transcripts in the unfertilized ovulated oocyte, and again in blastocysts. TGF-β1 transcripts appeared only after fertilization. The expression of a subset of growth factors in mouse blastocysts suggests a role for these factors in the growth and differentiation of early mammalian embryos.
Perceived Risk, Real Risk: Social Science and the Art of Probabilistic Risk Assessment
Authors: Freudenburg William R.
Published: October 2006

Risk assessment is commonly seen as the domain of physical and biological sciences, with social scientists focusing instead on risk management and communication. This division is unnecessary, and it may lead to errors in risk assessments. Social science input is needed for more accurate calculations of risk consequences and probabilities and for identifying potential biases created by certain risk assessment procedures, as well as in analyzing and explaining public responses to risk. Findings, moreover, suggest that the dichotomy between "real" and "perceived" risk is less "real" than is often assumed, particularly in cases involving controversial technologies.
A Graph-Dynamic Model of the Power Law of Practice and the Problem-Solving Fan-Effect
Authors: Shrager Jeff , Hogg Tad , Huberman Bernardo A.
Published: October 2006

Numerous human learning phenomena have been observed and captured by individual laws, but no unified theory of learning has succeeded in accounting for these observations. A theory and model are proposed that account for two of these phenomena: the power law of practice and the problem-solving fan-effect. The power law of practice states that the speed of performance of a task will improve as a power of the number of times that the task is performed. The power law resulting from two sorts of problem-solving changes, addition of operators to the problem-space graph and alterations in the decision procedure used to decide which operator to apply at a particular state, is empirically demonstrated. The model provides an analytic account for both of these sources of the power law. The model also predicts a problem-solving fan-effect, slowdown during practice caused by an increase in the difficulty of making useful decisions between possible paths, which is also found empirically.