bluuebunny/crossref_metadata_2025 huggingface dataset:
Silver-Intensified Gold and Peroxidase as Dual Ultrastructural Immunolabels for Pre- and Postsynaptic Neurotransmitters
Authors: van den Pol Anthony N.
Published: October 2006

An ultrastructural immunostaining method that uses silver-intensified gold was combined with another procedure that uses biotin peroxidase conjugates to allow simultaneous identification of two neurotransmitter-related antigens in the central nervous system. Tyrosine hydroxylase-immunoreactive neurons labeled with silver-intensified gold could be differentiated at both light and electron microscopic levels from glutamate decarboxylase-immunoreactive neurons labeled with peroxidase. Cross reactivity of the second group of immunoreagents with the first group was reduced by the heavy metal silver shell formed around the colloidal gold immunoglobulin complex. With this dual pre-embedding method, peroxidase-stained axons containing the inhibitory neurotransmitter γ-aminobutyric acid were found to synapse directly on silver-stained dopamine neurons in the rat dorsomedial hypothalamus. This approach can be used in combination with a post-embedding immunocytochemical colloidal gold procedure, allowing ultrastructural identification of three neurotransmitter-related antigens in the same tissue section.
Gonadotroph-Specific Expression of Metallothionein Fusion Genes in Pituitaries of Transgenic Mice
Authors: Low Malcolm J. , Lechan Ronald M. , Hammer Robert E. , Brinster Ralph L. , Habener Joel F. , Mandel Gail , Goodman Richard H.
Published: October 2006

Transgenic mice expressing a metallothionein-somatostatin fusion gene contain high concentrations of somatostatin in the anterior pituitary gland, a tissue that does not normally produce somatostatin. Immunoreactive somatostatin within the anterior pituitaries was found exclusively within gonadotrophs. Similarly, a metallothionein-human growth-hormone fusion gene was also expressed selectively in gonadotrophs. It is proposed that sequences common to the two fusion genes are responsible for the gonadotroph-specific expression.
Long-Term Neuropathological and Neurochemical Effects of Nucleus Basalis Lesions in the Rat
Authors: Arendash Gary W. , Millard William J. , Dunn Adrian J. , Meyer Edwin M.
Published: October 2006

The long-term effects of excitotoxic lesions in the nucleus basalis magnocellularis of the rat were found to mimic several neuropathological and chemical changes associated with Alzheimer's disease. Neuritic plaque-like structures, neurofibrillary changes, and neuronal atrophy or loss were observed in the frontoparietal cortex, hippocampus, amygdala, and entorhinal cortex 14 months after the lesions were made. Cholinergic markers in neocortex were reduced, while catecholamine and indoleamine metabolism was largely unaffected at this time. Bilateral lesions of the nucleus basalis magnocellularis increased somatostatin and neuropeptide Y in the cortex of the rat by at least 138 and 284 percent, respectively, suggesting a functional interaction between cholinergic and peptidergic neurons that may differ from that in Alzheimer's disease.
Induction of Suppressor Cells Specific for AChR in Experimental Autoimmune Myasthenia Gravis
Authors: McIntosh Kevin R. , Drachman Daniel B.
Published: October 2006

Suppressor cells specific for acetylcholine receptor (AChR) were induced in a population of lymphocytes previously sensitized to AChR, obtained from rats with experimental autoimmune myasthenia gravis (EAMG). The lymphocytes were cultured with the immunosuppressive drug cyclosporin A plus purified AChR for 7 days. These cells, when mixed with lymphocytes from rats with EAMG in vitro, strongly suppressed the antibody response to AChR. They did not inhibit antibody responses to an unrelated antigen, an indication that suppression was specific for AChR. This approach should be a useful way to induce specific suppressor cells from sensitized populations of lymphocytes and may be applicable in the treatment of autoimmune diseases such as myasthenia gravis.
A Subset of Yeast snRNA's Contains Functional Binding Sites for the Highly Conserved Sm Antigen
Authors: Riedel Nora , Wolin Sandra , Guthrie Christine
Published: October 2006

Autoimmune sera of the Sm specificity react with the major class of small nuclear RNA (snRNA)-containing ribonucleoprotein particles (snRNP's) from organisms as evolutionarily divergent as insects and dinoflagellates but have been reported not to recognize snRNP's from yeast. The Sm antigen is thought to bind to a conserved snRNA motif that includes the sequence A(U
3-6
)G. The hypothesis was tested that yeast also contains functional analogs of Sm snRNA's, but that the Sm binding site in the RNA is more strictly conserved than the Sm antigenic determinant. After microinjection of labeled yeast snRNA's into
Xenopus
eggs or oocytes, two snRNA's from
Saccharomyces cerevisiae
become strongly immunoprecipitable with human auto-antibodies known as anti-Sm. These each contain the sequence A(U
5-6
)G, are essential for viability, and are constituents of the spliceosome. At least six other yeast snRNA's do not become immunoprecipitable and lack this sequence; these non-Sm snRNA's are all dispensable.
Direct Evidence for DNA Bending at the Lambda Replication Origin
Authors: Zahn Kenneth , Blattner Frederick R.
Published: October 2006

Replication initiation in bacteriophage lambda appears to require wrapping of origin DNA on an approximately 50 angstrom radius in or around the complex with the initiator protein O. Since short lengths of DNA are not that flexible, it may be that runs of coherently spaced deoxyadenylate residues constitute bend sites in the ori sequence that facilitate the process. Earlier data showed that ori DNA has electrophoretic anomalies characteristic of bend sites and that these are augmented by initiator protein binding. Here origin bending is examined by direct measurement of the ability of polymerized ori sequences to form small circles. The smallest circles observed (84 residues) are compatible with the required radius of curvature. Bend sites within the O protein binding sites, bend sites in the spacers between them, plus the inherent flexibility of non-bent DNA in the origin may all contribute to origin bending. The data also show that a bend site is required for O protein binding to DNA.
Location of the c-
yes
Gene on the Human Chromosome and Its Expression in Various Tissues
Authors: Semba Kentaro , Yamanashi Yuji , Nishizawa Makoto , Sukegawa Jun , Yoshida Michihiro , Sasaki Motomichi , Yamamoto Tadashi , Toyoshima Kumao
Published: October 2006

Analysis of DNA from human embryo fibroblasts showed that ten Eco RI fragments were hybridizable with the Yamaguchi sarcoma virus oncogene (v-
yes
). Four of the Eco RI fragments were assigned to chromosome 18 and one to chromosome 6. There was evidence for multiple copies of
yes
-related genes in the human genome; however, only a single RNA species, 4.8 kilobases in length, was related to
yes
in various cells.
In Vivo Competition Between a Metallothionein Regulatory Element and the SV40 Enhancer
Authors: Scholer Hans , Haslinger Alois , Heguy Adriana , Holtgreve Heidi , Karin Michael
Published: October 2006

The human metallothionein-II
A
(hMT-II
A
) gene contains an enhancer element within its 5′ regulatory region. This enhancer element can compete with the SV40 enhancer for one or more cellular factors in vivo. The competition between the two elements is modulated by cadmium, an inducer of hMT-II
A
transcription. The data presented are consistent with a model in which heavy metal ions control the ability of the hMT-II
A
enhancer to bind a positive factor, leading to increased transcription. The same factor is required for maximal activity of the SV40 enhancer, which suggests that viruses utilize factors that have a normal role in cellular gene expression to control their own genes.
Receptor-Associated Resistance to Growth Hormone-Releasing Factor in Dwarf "Little" Mice
Authors: Jansson John-Olov , Downs Thomas R. , Beamer Wesley G. , Frohman Lawrence A.
Published: October 2006

Anterior pituitaries from the dwarf mouse strain "little" did not release growth hormone or accumulate adenosine 3′,5′-monophosphate (cyclic AMP) in response to human and rat growth hormone-releasing factor (GRF). Dibutyryl cyclic AMP, as well as the adenylate cyclase stimulators forskolin and cholera toxin, markedly stimulated growth hormone (GH) release. The basis of the GH deficiency in the little mouse may therefore be a defect in an early stage of GRF-stimulated GH release related either to receptor binding or to the function of the hormone-receptor complex.
Physiological Variation in α-Adrenoceptor-Mediated Arterial Sensitivity: Relation to Agonist Affinity
Authors: Bevan John A. , Oriowo M. A. , Bevan Rosemary D.
Published: October 2006

Vascular smooth muscle from different arteries of the rabbit varies in sensitivity to norepinephrine, even when factors known to contribute to this variation are excluded. Sensitivity to norepinephrine mediated through the α-adrenoceptor is linearly related to the agonist dissociation constant, but is not significantly related to receptor reserve. These results suggest that agonist affinity is the primary determinant of sensitivity to norepinephrine, at least in these arteries, and that this is a locally regulated characteristic which may account for regional sensitivity changes.
T-Cell Tumor Elimination as a Result of T-Cell Receptor-Mediated Activation
Authors: Ashwell Jonathan D. , Longo Dan L. , Bridges Sandra H.
Published: October 2006

It has recently been shown that activation of murine T-cell hybridomas with antigen inhibits their growth in vitro. The "suicide" of these neoplastic T cells upon stimulation with antigen suggested the possibility that activation via the antigen-specific receptor could also inhibit the growth of neoplastic T cells in vivo. To test this, mice were subcutaneously inoculated with antigen-specific T-cell hybridomas and then treated intraperitoneally with antigen. Administration of the appropriate antigen immediately after inoculation with the T-cell hybridoma abrogated tumor formation; antigen administered after tumors had become established decreased the tumor burden and, in a substantial fraction of animals, led to long-term survival. The efficacy of antigen therapy was due to both a direct inhibitory effect on tumor growth and the induction of host immunity. These studies demonstrate the utility of cellular activation as a means of inhibiting neoplastic T-cell growth in vivo and provide a rationale for studying the use of less selective reagents that can mimic the activating properties of antigen, such as monoclonal antibodies, in the treatment of T-cell neoplasms of unknown antigen specificity.
Functional Interaction and Partial Homology Between Human Immunodeficiency Virus and Neuroleukin
Authors: Lee Mark R. , Ho David D. , Gurney Mark E.
Published: October 2006

Dementia is common in patients with AIDS, but the mechanism by which the human immunodeficiency virus type 1 (HIV-1) causes the neurological impairment is unknown. In this study the possibility that an antigen of HIV-1 suppresses neuronal responses to neurotrophic factors was examined. Both HIV-1 and a related retrovirus, simian immunodeficiency virus (SIV), inhibited the growth of sensory neurons from chick dorsal root ganglia in medium containing neuroleukin (NLK) but not in medium containing nerve growth factor. An unrelated type D retrovirus, simian acquired immunodeficiency syndrome virus, did not affect the growth of neurons in the presence of either neurotrophic factor. The inhibition by HIV-1 of neuron growth in the presence of NLK was found to be due to the gp120 envelope glycoprotein. Regions of sequence homology between gp120 and NLK may account for this inhibitory property of gp120 and functional interactions between gp120 and NLK may be important in the pathogenesis of the AIDS dementia complex.
How Do Enzymes Work?
Authors: Kraut Joseph
Published: October 2006

The principle of transition-state stabilization asserts that the occurrence of enzymic catalysis is equivalent to saying that an enzyme binds the transition state much more strongly than it binds the ground-state reactants. An outline of the origin and gradual acceptance of this idea is presented, and elementary transition-state theory is reviewed. It is pointed out that a misconception about the theory has led to oversimplification of the accepted expression relating catalysis and binding, and an amended expression is given. Some implications of the transition-state binding principle are then explored. The amended expression suggests that internal molecular dynamics may also play a role in enzymic catalysis. Although such effects probably do not make a major contribution, their magnitude is completely unknown. Two examples of recent advances due to application of the transition-state binding principle are reviewed, one pertaining to the zinc protease mechanism and the other to the generation of catalytic antibodies.
Acute Myelogenous Leukemia: A Human Cell Line Responsive to Colony-Stimulating Activity
Authors: Koeffler H. Phillip , Golde David W.
Published: October 2006

A permanent human cell line that maintains the granulocytic characteristics of acute myelogenous leukemia cells has been established. The cells of this line form myeloid colonies in soft gel culture in the presence of human colony-stimulating activity. The cell line may be useful for studying human acute myelogenous leukemia and the mechanism of response to colony-stimulating activity.
Inhibin-Mediated Feedback Control of Follicle-Stimulating Hormone Secretion in the Female Rat
Authors: Rivier Catherine , Rivier Jean , Vale Wylie
Published: October 2006

The secretion of follicle-stimulating hormone (FSH) by the anterior pituitary gland is regulated by the interaction of hypothalamic and gonadal hormones. Recently, proteins termed inhibins that selectively suppress FSH secretion have been purified and characterized from the gonadal fluids of several species. Antibodies to a synthetic peptide encompassing the amino terminal 25 residues of the recently characterized porcine inhibin were used to develop a specific radioimmunoassay (RIA) for inhibin and to neutralize endogenous inhibin during the estrous cycle of the rat. The administration of 20 international units of pregnant mare serum gonadotropin (PMSG) stimulated the secretion of inhibin in intact immature female rats, whereas ovariectomy caused an abrupt decrease in plasma inhibin concentrations that were not prevented by the injection of PMSG. The infusion of a polyclonal antiserum to inhibin, from 12 noon on proestrus to 1 a.m. on the morning of estrus, as well as its acute intravenous injection during diestrus I or II, caused an increase in plasma FSH (but not luteinizing hormone) concentrations. These results support the hypothesis of a feedback loop between the release of ovarian inhibin and FSH in the female rat.
Thyroid Hormone Induction of an Autocrine Growth Factor Secreted by Pituitary Tumor Cells
Authors: Hinkle P. M. , Kinsella P. A.
Published: October 2006

Thyroid hormones stimulate the rate of cell division by poorly understood mechanisms. The possibility that thyroid hormones increase cell growth by stimulating secretion of a growth factor was investigated. Thyroid hormones are nearly an absolute requirement for the division of GH
4
C
1
rat pituitary tumor cells plated at low density. Conditioned media from cells grown with or without L-triiodothyronine (T3) were treated with an ion exchange resin to remove T3 and were tested for ability to stimulate the division of GH
4
C
1
cells. Conditioned medium from T3-treated cells was as active as thyroid hormone at promoting GH
4
C
1
cell growth but did not elicit other thyroid hormone responses, induction of growth hormone, and down-regulation of thyrotropin-releasing hormone receptors, as effectively as T3 did. A substance or substances associated with T3-induced growth stimulatory activity migrated at high molecular weight at neutral
p
H and was different from known growth-promoting hormones induced by T3. The results demonstrate that thyroid hormones stimulate the division of GH
4
C
1
pituitary cells by stimulating the secretion of an autocrine growth factor.
Regulation in Vitro of Metallothionein Gene Binding Factors
Authors: Seguin Carl , Hamer Dean H.
Published: October 2006

Mouse nuclear factors that bind to an upstream metal regulatory element of the mouse metallothionein-I gene have been identified by DNA footprinting and oligonucleotide band shift assays. The formation of complexes at this site can be activated 20- to 40-fold by the in vitro addition of ionic cadmium. The activation reaction is rapid, reversible by a metal chelator, and may involve multiple proteins. These results suggest that the initial step in cadmium detoxification is an interaction between the metal and nuclear DNA-binding factors leading to an increase in metallothionein gene transcription. The ability to observe metal activation in vitro makes this a powerful system to study the biochemistry of eukaryotic gene regulation.
Common Pathogenetic Mechanism for Three Tumor Types in Bilateral Acoustic Neurofibromatosis
Authors: Seizinger Bernd R. , Rouleau Guy , Ozelius Laurie J. , Lane Andrew H. , St George-Hyslop Peter , Huson Susan , Gusella James F. , Martuza Robert L.
Published: October 2006

Bilateral acoustic neurofibromatosis (BANF) is a genetic defect associated with multiple tumors of neural crest origin. Specific loss of alleles from chromosome 22 was detected with polymorphic DNA markers in two acoustic neuromas, two neurofibromas, and one meningioma from BANF patients. This indicates a common pathogenetic mechanism for all three tumor types. The two neurofibromas were among three taken from the same patient, and both showed loss of identical alleles demonstrating that the same chromosome suffered deletion in both tumors. The third neurofibroma from this patient showed no detectable loss of heterozygosity, which suggests the possibility of a more subtle mutational event that affects chromosome 22. In the two acoustic neuromas, only a portion of chromosome 22 was deleted, narrowing the possible chromosomal location of the gene that causes BANF to the region distal to the D22S9 locus in band 22q11. The identification of progressively smaller deletions on chromosome 22 in these tumor types may well provide a means to clone and characterize the defect.
Tertiary Structure of Plant RuBisCO: Domains and Their Contacts
Authors: Chapman Michael S. , Suh Se Won , Curmi Paul M. G. , Cascio Duilio , Smith Ward W. , Eisenberg David S.
Published: October 2006

The three-dimensional structure of ribulose-1,5-biphosphate carboxylase-oxygenase (RuBisCO), has been determined at 2.6 Å resolution. This enzyme initiates photosynthesis by combining carbon dioxide with ribulose bisphosphate to form two molecules of 3-phosphoglycerate. In plants, RuBisCO is built from eight large (L) and eight small (S) polypeptide chains, or subunits. Both S chains and the NH
2
-terminal domain (N) of L are antiparallel β, "open-face-sandwich" domains with four-stranded β sheets and flanking α helices. The main domain (B) of L is an α/β barrel containing most of the catalytic residues. The active site is in a pocket at the opening of the barrel that is partly covered by the N domain of a neighboring L chain. The domain contacts of the molecule and its conserved residues are discussed in terms of this structure.
A DNA Binding Protein Regulated by IL-4 and by Differentiation in B Cells
Authors: Boothby Mark , Gravallese Ellen , Liou Hsiou-Chi , Glimcher Laurie H.
Published: October 2006

The class II (Ia) major histocompatibility complex antigens are a family of integral membrane proteins whose expression is limited to certain cell types, predominantly B lymphocytes, macrophages, and thymic epithelial cells. In B cells, Ia expression is both developmentally regulated and responsive to external stimuli. The differentiation of early B stem cells to mature B lymphocytes is accompanied by the appearance of cell surface Ia antigens; the transition to plasma cells results in loss of class II gene expression. In Ia-expressing B cells, the T cell-derived lymphokine interleukin-4 (IL-4) increases such expression by an as yet undefined mechanism. Chloramphenicol acetyltransferase gene expression was cis-activated by a region of the Ia Aα
k
gene in a B lymphoma line, but not in a myeloma line. A nuclear protein that bound to two sites within this region, upstream from previously described transcription elements, was found in normal spleen cells. This binding activity was also found in spleen extracts from athymic mice, which lack T lymphocytes, and in Ia-positive B lymphocyte tumor cell lines, demonstrating that it is a B cell protein. Further analysis showed the activity to be undetectable in an Ia-negative pre-B cell line and in three plasmacytoma cell lines that are Ia negative. IL-4 treatment of normal and athymic mouse spleen cells greatly increased the binding of this nuclear protein to these two sites, concomitant with increased MHC class II gene transcription. Thus, B cells contain a sequence-specific DNA-binding activity whose level is influenced both by IL-4 and by differentiation signals.
Thermosensitivity of a DNA Recognition Site: Activity of a Truncated
nut
L Antiterminator of Coliphage Lambda
Authors: Peltz Stuart W. , Brown Alexandra L. , Hasan Noaman , Podhajska Anna J. , Szybalski Waclaw
Published: October 2006

Antitermination is an important transcriptional control. In bacteriophage lambda, the presence of the
nut
antiterminators between the promoters and terminators results in relatively unhindered transcription when the lambda
N
gene product and necessary host factors are supplied. This antitermination system has been rendered thermosensitive by modification of the
nut
site. A fragment of λ DNA [74 base pairs (bp) in length] that contained the 17-bp
nut
L core sequence, but lacked the 8-bp
box
A sequence, was cloned in a
p
p
-
N
-
t
L1
-
galK
plasmid between the
p
p
promoter and gene
N
. This fragment mediated antitermination of transcription at 30°C, as measured by assaying
galK
gene expression in
Escherichia coli
. At 42°C, however, antitermination at the λ
t
L1
terminator was abolished. Antitermination at 42°C was restored by replacing the 74-bp
nut
L fragment with longer sequences containing both
nut
L and
box
A or by cloning a synthetic
box
A sequence ahead of the 74-bp
nut
L fragment. Thus, efficient antitermination required both
box
A and the 17-bp
nut
L core, with the latter becoming conditionally defective when the
box
A sequence was deleted.
Benzo(
a
)pyrene-7,8-dihydrodiol 9,10-Oxide Adenosine and Deoxyadenosine Adducts: Structure and Stereochemistry
Authors: Jeffrey A. M. , Grzeskowiak K. , Weinstein I. B. , Nakanishi K. , Roller P. , Harvey R. G.
Published: October 2006

The structure and absolute stereoconfigurations of four adenosine adducts with (±)-7 α,8 β-dihydroxy-9 β, 10 β-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (BPDE) and their deoxyadenosine analogs have been determined. They result from both
cis
and
trans
addition of the N
6
amino group of adenine to the 10 position of both enantiomers of BDPE. This was determined from studies of the nuclear magnetic resonance spectra, mass spectra, and circular dichroism spectra, as well as from their pK
a
values and chemical reactivities.
Translation of Unspliced Transcripts After Heat Shock
Authors: Yost H. Joseph , Lindquist Susan
Published: October 2006

Severe heat shocks block the splicing of intervening sequences from messenger RNA precursors. The RNA's that accumulate after a severe heat shock have normal transcription start sites and are uncut at both their 5' and 3' splice junctions. Some of these unspliced transcripts leave the nucleus and enter the pool of cytoplasmic messenger RNA. Translation of these RNA's proceeds into their intervening sequences, resulting in the production of abnormal proteins. Thus, the repression of normal transcription, which usually accompanies the heat shock response, may protect the cell from the large-scale synthesis of abnormal RNA's and aberrant proteins.
Extensive Junctional Diversity of Rearranged Human T Cell Receptor δ Genes
Authors: Hata Shingo , Satyanarayana Karuturi , Devlin Peter , Band Hamid , McLean Joanne , Strominger Jack L. , Brenner Michael B. , Krangel Michael S.
Published: October 2006

The human T cell receptor δ (TCR δ) gene encodes one component of the TCR γδ-CD3 complex found on subsets of peripheral blood and thymic T cells. Human TCR δ diversity was estimated by characterizing rearrangements in TCR γδ cell lines and determining the structures of complementary DNA clones representing functional and nonfunctional transcripts in these cell lines. One Vδ segment and one Jδ segment were identified in all functional transcripts, although a distinct Jδ segment was identified in a truncated transcript. Further, one Dδ element was identified, and evidence for the use of an additional Dδ element was obtained. Thus human TCR δ genes appear to use a limited number of germline elements. However, the apparent use of two Dδ elements in tandem coupled with imprecise joining and extensive incorporation of N nucleotides generates unprecedented variability in the junctional region.
Prevention of Type I Diabetes in Nonobese Diabetic Mice by Virus Infection
Authors: Oldstone Michael B. A.
Published: October 2006

The nonobese diabetic (NOD) mouse is an animal model of type I diabetes and develops a characteristic autoimmune lesion in the islets of Langerhans with lymphocytic infiltration and destruction of pancreatic β cells. The result is hypoinsulinemia, hyperglycemia, ketoacidosis, and death. Diabetes usually begins by the sixth month of age but can occur earlier when young NOD mice are infused with lymphocytes from older NOD donors. When newborn or adult NOD mice were infected with a lymphotropic virus they did not become diabetic. The interaction between viruses and lymphocytes is pivotal in aborting diabetes, as established by experiments in which lymphocytes from virus-infected donors failed to transfer diabetes. In contrast, lymphocytes from age- and sex-matched uninfected donors caused disease. Therefore, viruses and, presumably, their products can be developed to be beneficial and may have potential as a component for treatment of human diseases. Further, these results point to the utility of viruses as probes for dissecting the pathogenesis of a nonviral disease.
Research on Bacteria in the Mainstream of Biology
Authors: Magasanik Boris
Published: October 2006

The study of the genetics, biochemistry, and physiology of bacteria during the last 40 years has provided the concepts and methods for the study of cells of all types at the molecular level. Although much is already known about the mechanisms bacteria use to regulate the expression of their genes, a great deal more remains to be discovered that will have relevance to both prokaryotic and eukaryotic cells. Similarly, the study in bacteria of the transactions of DNA, of the synthesis and function of the cell membrane, of differentiation, and of the interaction with eukaryotic cells will undoubtedly produce results of general importance. The advantages of using bacteria for these studies include their simple noncompartmented structure, the accessibility of their genetic material, and the possibility of correlating the expression of a gene in the intact cell with its expression in a system composed of highly purified components. Finally, the comparative study of a wide variety of microorganisms may result in a better understanding of the evolution of prokaryotes and eukaryotes and lead to a comprehensive theory of cell biology.
The Chicken B Cell Compartment
Authors: Weill Jean-Claude , Reynaud Claude-Agnès
Published: October 2006

A very unusual molecular mechanism is involved in generating the preimmune repertoire in the chicken bursa of Fabricius. A unique rearranged V gene is diversified through a program of segmental gene conversion with a pool of noncoding pseudogenes being used as donors. A specifically committed progenitor that originates in the embryonic bursa is responsible for long-term maintenance of the B cell population. Both these properties and the characteristics of the peripheral B cell compartment are discussed in terms of the evolution of the T and B immune systems.
Phagocytosis of
Candida albicans
Enhances Malignant Behavior of Murine Tumor Cells
Authors: Ginsburg Isaac , Fligiel Suzanne E. G. , Kunkel Robin G. , Riser Bruce L. , Varani James
Published: October 2006

Murine tumor cells were induced to phagocytize either
Candida albicans
or group A streptococcal cells. The presence of microbial particles within the tumor cell cytoplasm had no effect on in vitro tumor cell growth. However, when
Candida albicans
-infected tumor cells were injected into syngeneic mice, they formed tumors that grew faster, invaded the surrounding normal tissue more rapidly and metastasized more rapidly than control tumor cells. Tumor cells infected with group A streptococcal particles did not grow faster or show increased malignant behavior. These data indicate that the in vivo behavior of malignant tumor cells can be modulated by microbial particles, which are often present in the microenvironment of the growing tumor.
Gonadotropin-Releasing Hormone in Milk
Authors: Baram Tallie , Koch Yitzhak , Hazum Eli , Fridkin Mati
Published: October 2006

The hypothalamic hormone gonadotropin-releasing hormone (GnRH) has been found in milk of man, cow, and rat. Radioimmunoassays of acidified milk indicate concentrations of GnRH ranging between 0.1 and 3 nanograms per milliliter. Multistep extractions, followed by electrophoresis, reveal gonadotropin-releasing activity in the fraction that comigrates with the GnRH-marker. A second hypothalamic hormone, thyrotropin-releasing hormone, is present in milk at a much lower concentration. "Milk-GnRH" may influence the secretion of the gonadotropic hormones in neonates.
Molecular Basis for the Influence of Muscle Length on Myocardial Performance
Authors: Babu Árvind , Sonnenblick Edmund , Gulati Jagdish
Published: October 2006

According to Starling's law of the heart, the force of contraction during the ejection of blood is a function of the end-diastolic volume. To seek the molecular explanation of this effect, a study was made of the effects of length on Ca2
+
sensitivity during tension development by isolated demembranated cardiac muscle in which the cardiac form of troponin C was substituted with skeletal troponin C. The results of troponin C exchange were compared at sarcomere lengths of 1.9 and 2.4 micrometers. Enhancement of the myocardial performance at the stretched length was greatly suppressed with the skeletal troponin C compared with the cardiac troponin C. Thus the troponin C subunit of the troponin complex that regulates the activation of actin filaments has intrinsic molecular properties that influence the length-induced autoregulation of myocardial performance and may be a basis for Starling's law of the heart.
Scanning Tunneling Microscopy of recA-DNA Complexes Coated with a Conducting Film
Authors: Amrein M. , Stasiak A. , Gross H. , Stoll E. , Travaglini G.
Published: October 2006

A link between scanning tunneling microscopy (STM) and conventional transmission electron microscopy has been established for biological material by applying STM on freeze-dried recA-DNA complexes coated with a conducting film. The topography of the complexes observed by means of STM revealed a right-handed single helix composed of about six recA monomers per helical turn.
Dopamine-Accumulating Retinal Neurons Revealed by in Vitro Fluorescence Display a Unique Morphology
Authors: Dacey Dennis M.
Published: October 2006

Dopamine is the principal catecholamine neurotransmitter in the vertebrate retina. The shape of retinal neurons that accumulate dopamine has been demonstrated in an in vitro preparation of cat retina. This was achieved by the discovery that the combined uptake of dopamine and the indoleaminergic transmitter analog 5,7-dihydroxytryptamine leads to an intense, catecholamine-like fluorescence in the cell bodies and processes of presumed dopaminergic amacrine cells in the living retina. This fluorescence served as an in vitro marker for these cells, and their detailed morphology was analyzed after intracellular injection of horseradish peroxidase under direct microscopic control. The horseradish peroxidase-filled cells show an unprecedented neuronal morphology: each cell gives rise to multiple, axon-like processes that arise from, and extend for millimeters beyond, the dendritic tree. The unique structure of this type of amacrine cell suggests a function for dopamine in long-range lateral interactions in the inner plexiform layer.
Isolation and Characterization of a Novel Protein (X-ORF Product) from SIV and HIV-2
Authors: Henderson L. E. , Sowder R. C. , Copeland T. D. , Benveniste R. E. , Oroszlan S.
Published: October 2006

A protein designated p14 was purified from a simian immunodeficiency virus (SIV
Mne
) and was shown by amino acid sequence analysis to be nearly identical to the predicted translational product of a unique open reading frame (X-ORF) in the nucleotide sequences of SIV
mac
and human immunodeficiency virus type 2 (HIV-2). Thus the X-ORF is proven to be a new retroviral gene. The p14 is present in SIV
Mne
in molar amounts equivalent to those of the
gag
proteins. This is the first example of a retrovirus that contains a substantial quantity of a viral protein that is not a product of the
gag
,
pro
,
pol
, or
env
genes. SIV p14 and its homolog in HIV-2 may function as nucleic acid binding proteins since purified p14 binds to single-stranded nucleic acids in vitro. Antisera to the purified protein detected p14 in SIV
Mne
, SIV
mac
, and a homologous protein (16 kilodaltons) in HIV-2 but did not react with HIV-1. Diagnostic procedures based on this novel protein will distinguish between HIV-1 and HIV-2.
Type-Restricted Neutralization of Molecular Clones of Human Immunodeficiency Virus
Authors: Looney David J. , Fisher Amanda G. , Putney Scott D. , Rusche James R. , Redfield Robert R. , Burke Donald S. , Gallo Robert C. , Wong-Staal F.
Published: October 2006

In a study of the immunologic significance of the genetic diversity present within single isolates of human immunodeficiency virus type 1 (HIV-1), the neutralization of viruses derived from molecular clones of the HIV-1 strain HTLV-III
B
by an extensive panel of sera was compared. Sera from HIV-1-infected patients and from goats immunized with polyacrylamide gel-purified HIV-1 envelope glycoprotein (gp120), native gp120, or gp120-derived recombinant peptides, showed marked heterogeneity in neutralizing activity against these closely related viruses. The change of a single amino acid residue in gp120 may account for such "clonal restriction" of neutralizing activity.
Molecular Characterization of a Functional cDNA Encoding the Serotonin 1c Receptor
Authors: Julius David , MacDermott Amy B. , Axel Richard , Jessell Thomas M.
Published: October 2006

Neurons that release serotonin as a neurotransmitter project to most regions of the central and peripheral nervous system and mediate diverse neural functions. The physiological effects of serotonin are initiated by the activation of multiple, distinct receptor subtypes. Cloning in RNA expression vectors was combined with a sensitive electrophysiological assay in
Xenopus
oocytes in order to isolate a functional cDNA clone encoding the 5HTlc serotonin receptor. Injection of RNA transcribed in vitro from this clone into
Xenopus
oocytes elicits serotonin sensitivity. Mouse fibroblasts transformed with this clone bind serotonin agonists and antagonists and exhibit an increase in intracellular Ca
2+
concentrations in response to serotonin. The sequence of the 5HTlc receptor reveals that it belongs to the family of G protein-coupled receptors, which are thought to traverse the cytoplasmic membrane seven times. Moreover, in situ hybridization and RNA blot analysis indicate that the 5HTlc receptor is expressed in neurons in many regions of the central nervous system and suggest that this subclass of receptor may mediate many of the central actions of serotonin.
Induction of an Antibody That Catalyzes the Hydrolysis of an Amide Bond
Authors: Janda Kim D. , Schloeder Diane , Benkovic Stephen J. , Lerner Richard A.
Published: October 2006

Catalysis of amide bond hydrolysis is of singular importance in enzymology. An antibody was induced to an analog of a high-energy intermediate anticipated along the reaction coordinate of amide hydrolysis. This antibody is an amidase with high specificity and a large rate enhancement (250,000) relative to the uncatalyzed reaction. This reaction represents the kinetically most difficult hydrolysis reaction yet catalyzed by an antibody.
Accelerated Electron Transfer Between Metal Complexes Mediated by DNA
Authors: Purugganan Michael D. , Kumar Challa V. , Turro Nicholas J. , Barton Jacqueline K.
Published: October 2006

DNA-mediated long-range electron transfer from photoexcited 1,10-phenanthroline complexes of ruthenium, Ru(phen)
3
2+
, to isostructural complexes of cobalt(III), rhodium(III), and chromium(III) bound along the helical strand. The efficiency of transfer depended upon binding mode and driving force. For a given donor-acceptor pair, surface-bound complexes showed greater rate enhancements than those that were intercalatively bound. Even in rigid glycerol at 253 K, the rates for donor-acceptor pairs bound to DNA remained enhanced. For the series of acceptors, the greatest enhancement in electron-transfer rate was found with chromium, the acceptor of intermediate driving force. The DNA polymer appears to provide an efficient intervening medium to couple donor and acceptor metal complexes for electron transfer.
Climbing Adaptations in the Early Eocene Mammal
Chriacus
and the Origin of Artiodactyla
Authors: Rose Kenneth D.
Published: October 2006

A virtually complete articulated skeleton of the arctocyonid
Chriacus
, recently found in northern Wyoming, is one of the most intact early Eocene mammal skeletons ever found. It exhibits numerous adaptations characteristic of mammals that climb, including strong bony crests and processes (reflecting powerful musculature), ability for considerable forearm supination, a highly mobile ankle joint, plantigrade feet, curved and transversely compressed claws, and a long, possibly semiprehensile tail. These features contrast sharply with those of the oldest artiodactyls and indicate that
Chriacus
or a similar arctocyonid was not ancestral to the Artiodactyla, as has been proposed.
Ethanol: Modifications of Acute Intoxication by Divalent Cations
Authors: Erickson Carlton K. , Tyler Thomas D. , Harris R. Adron
Published: October 2006

Calcium, other divalent cations, and calcium antagonists were tested for their ability to alter ethanol-induced sleeping time, hypothermia, and behavioral intoxication in mice and rats. Calcium given intraventricularly significantly enhanced sleeping time and behavioral intoxication in a dose-related manner. The ionophores X537A and A23187 accentuated the effect of a low dose of calcium, whereas the calcium chelators EDTA and EGTA decreased sleeping time. Calcium also enhanced tertiary butanol- and chloral hydrate-induced sleeping time. The effects of cations on ethanol-induced hypothermia were less significant. The results suggest the existence of a central calcium pool that is involved in ethanol intoxication in rodents.
Myosin: Immunofluorescent Localization in Neuronal and Glial Cultures
Authors: Roisen Fred , Inczédy-Marcsek Margit , Hsu Linda , Yorke Wanda
Published: October 2006

The distribution of intracellular myosin was studied by the double antibody immunofluorescence method in primary organotypic neuronal cultures and two established neuronal and glial cell lines. An array of parallel filaments aligned with the major cellular axis and a three-dimensional subsurface network were shown to react with two different myosin antibodies. The presence of myosin-rich filaments in regions known to contain actin filaments suggests that these proteins interact to generate the motive force in nonmuscle contractile systems.
Pertussis Toxin-Sensitive Pathway in the Stimulation of c-
myc
Expression and DNA Synthesis by Bombesin
Authors: Letterio John J. , Coughlin Shaun R. , Williams Lewis T.
Published: October 2006

The bombesin-like peptides are potent mitogens for Swiss 3T3 fibroblasts, human bronchial epithelial cells, and cells isolated from small cell carcinoma of the lung. The mechanism of signal transduction in the proliferative response to bombesin was investigated by studying the effect of
Bordetella pertussis
toxin on bombesin-stimulated mitogenesis. At nanomolar concentrations, bombesin increased levels of c-
myc
messenger RNA and stimulated DNA synthesis in Swiss 3T3 cells. Treatment of the cells with pertussis toxin (5 nanograms per milliliter) completely blocked bombesin-enhanced c-
myc
expression and eliminated bombesin-stimulated DNA synthesis. This treatment had essentially no effect on the mitogenic responses to either platelet-derived growth factor or phorbol 12,13-dibutyrate. These results suggest that the mitogenic actions of bombesin-like growth factors are mediated through a pertussis toxin-sensitive guanine nucleotide-binding protein. Furthermore they indicate that bombesin-like growth factors act through pathways that are different from those activated by platelet-derived growth factor.
Alloantigen Recognition Is Preceded by Nonspecific Adhesion of Cytotoxic T Cells and Target Cells
Authors: Spits Hergen , van Schooten Wim , Keizer Hiskias , van Seventer Gys , van de Rijn Matthijs , Terhorst Cox , de Vries Jan E.
Published: October 2006

T-cell receptors bind antigens only when the antigens are exposed on the cell surface. This can be studied best in the interaction of cytolytic T lymphocytes (CTL) with target cells because the recognition and binding event can be separated from the lytic phase. Studies with CTL clones specific for HLA-A2 and HLA-B7 demonstrated that conjugates of CTL's and target cells can be formed in the absence of specific-antigen recognition. Furthermore, T-cell receptor and target antigen cannot interact unless there is conjugate formation. This indicates that nonspecific conjugate formation between CTL's and target cells precedes the recognition of specific antigen by the T-cell receptor.
A Mutant of Yeast Defective in Cellular Morphogenesis
Authors: Sloat Barbara F. , Pringle John R.
Published: October 2006

In the budding yeast
Saccharomyces cerevisiae
, each bud appears within a ring of chitin formed in the cell wall of the mother cell. Temperature-sensitive mutants defective in gene
cdc24
synthesize chitin at restrictive temperatures, but do not organize it into the discrete rings found in normal cells, nor do they form buds. The chitin ring or an annular precursor structure may play an essential role in reinforcing the region of the cell wall involved in budding.
A Sea Urchin Gene Encodes a Polypeptide Homologous to Epidermal Growth Factor
Authors: Hursh Deborah A. , Andrews Mary E. , Raff Rudolf A.
Published: October 2006

A sea urchin DNA clone complementary to an embryonic messenger RNA whose protein product bears striking homology to the epidermal growth factor family of proteins has been identified and characterized. The structure of the protein is similar to that of previously identified regulatory genes in
Drosophila
and
Caenorhabditis
. RNA gel blot hybridization showed a unique temporal pattern of expression of this gene during embryogenesis and transcript enrichment in the embryonic ectoderm. These results suggest that this member of the epidermal growth factor gene family plays a role in early development decisions in sea urchin embryos.
Regulation by Growth Hormone of Number of Chondrocytes Containing IGF-I in Rat Growth Plate
Authors: Nilsson Anders , Isgaard Jörgen , Lindahl Anders , Dahlström Annica , Skottner Anna , Isaksson Olle G. P.
Published: October 2006

Whether growth hormone stimulates longitudinal bone growth by a direct effect at the site of the growth plate or indirectly by increasing the concentration of circulating somatomedins (insulin-like growth factors) has been the subject of controversy. Immunohistochemical methods were used to explore the localization and distribution of insulin-like growth factor I (IGF-I) immunoreactivity in the epiphyseal growth plate of the proximal tibia of male rats. Cells in the proliferative zone of the growth plate of normal rats exhibited a bright immunofluorescence, whereas cells in the germinal and hypertrophic zones stained only weakly. In rats subjected to hypophysectomy, the number of fluorescent cells was markedly reduced. When the hypophysectomized rats were treated with growth hormone, either systemically or at the site of the growth plate, the number of IGF-I-immunoreactive cells in the proliferative zone was increased. The results show that IGF-I is produced in proliferative chondrocytes in the growth plate and that the number of IGF-I-containing cells is directly regulated by growth hormone. These findings suggest that IGF-I has a specific role in the clonal expansion of differentiated chondrocytes and exerts its function locally through autocrine or paracrine mechanisms.
Electron Tunneling Paths in Proteins
Authors: Kuki Atsuo , Wolynes Peter G.
Published: October 2006

One of the crucial issues in biological electron transfer is the determination of the role of spatially intermediate amino acid residues in controlling or directing the electronic tunneling interaction between redox sites. A quantum path integral Monte Carlo method is developed for the analysis of electronic tunneling pathways in a highly structured environment. This path integral method is applied to intramolecular electron transfer in a ruthenium-modified myoglobin that contains a tryptophan in the "line-of-flight." A principal result is the identification of the relevant cylindrical zone swept out by the tunneling electron.
Molecular Biology of the H-2 Histocompatibility Complex
Authors: Flavell Richard A. , Allen Hamish , Burkly Linda C. , Sherman David H. , Waneck Gerald L. , Widera Georg
Published: October 2006

The H-2 histocompatibility complex of the mouse is a multigene family, some members of which are essential for the immune response to foreign antigens. The structure and organization of these genes have been established by molecular cloning, and their regulation and function is being defined by expression of the cloned genes.
A Relationship Between DNA Helix Stability and Recognition Sites for RNA Polymerase
Authors: Vollenweider H. J. , Fiandt M. , Szybalski W.
Published: October 2006

The RNA polymerase binding sites on the DNA of (i) the
aroE-trkA-spc
segment of the
Escherichia coli
genome, (ii) transposon Tn3, (iii) plasmid ColE1, and (iv) coliphage λ were mapped by electron microscopy, with the use of the BAC technique; these maps were compared with the maps of the early-melting regions for the same genomes. The results indicate that in all these cases the binding sites for the
E. coli
RNA polymerase lie preferentially in the early melting regions of DNA. These data indicate that helix stability may be an important feature of the multipartite nature of the promoter structure.