bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymorphism of DNA sequence adjacent to human beta-globin structural gene: relationship to sickle mutation.
Authors: Kan Y W , Dozy A M
Published: May 2006

Restriction endonuclease mapping of the human globin genes revealed a genetic variation in a Hpa I recognition site about 5000 nucleotides from the 3' end of the beta-globin structural gene. Instead of a normal 7.6-kilobase (kb) fragment which contains the beta-globin structural gene, 7.0-kb and 13.0-kb variants were detected. Both variants were found in people of African origin and were not detected in Asians or Caucasians. The 13.0-kb variant is frequently associated with the sickle hemoglobin mutation and may be useful for the prediction of the sickle cell gene in prenatal diagnosis. Polymorphism in a restriction enzyme site could be considered as a new class of genetic marker and may offer a new approach to linkage analysis and anthropological studies.
Lymphoblastoid cell lines from patients with chronic lymphocytic leukemia: identification of tumor origin by idiotypic analysis.
Authors: Hurley J N , Fu S M , Kunkel H G , McKenna G , Scharff M D
Published: May 2006

Multiple lymphoblastoid cell lines have been derived from two patients with chronic lymphocytic leukemia with an associated monoclonal immunoglobulin (Ig) band. Idiotypic antisera raised against the monoclonal serum Ig bands were shown to be specific for the membrane Ig of the patients' leukemic cells. The idiotypic determinants in these patients thereby constitute tumor-specific antigens. Surface and intracellular immunofluorescence studies utilizing these idiotypic antisera were used to identify the cell lines of leukemic origin. These studies showed that certain cell lines from each patient were derived from the leukemic cells while other cell lines were derived from residual normal B lymphocytes. The leukemic cell lines were variable and contained different percentages of lymphoid cells with the idiotype-specific membrane Ig and, in addition, different percentages of plasma cells with intracellular Ig of the same specificity. Specific Ig synthesis was also demonstrated by hemagglutination-inhibition analysis of cell line supernatants. Aside from Ig specificity, no differences have been found between the leukemic cell lines and those derived from normal cells. One of the leukemic cell lines was cloned in soft agarose. All the clones were shown to be of leukemic origin.
Proton nuclear magnetic resonance characterization of heme disorder in hemoproteins.
Authors: La Mar G N , Budd D L , Viscio D B , Smith K M , Langry K C
Published: May 2006

A proton NMR method is described for determining the orientation of a porphyrin within the heme pocket of a hemoprotein. The pattern of the hyperfine-shifted heme methyl resonances in low-spin ferric model compounds is demonstrated to characteristically reflect the position of a localized low-symmetry perturbation on the pi system. The specific assignments via deuteration of the two interconvertible sets of methyl resonances observed for deuteroporphyrin-reconstituted sperm whale metmyoglobin cyanide lead to the conclusion that the low-symmetry perturbations on the heme due to the apo-protein contacts differ for the two protein components by a 180 degrees rotation about the alpha-gamma meso axis. Hence the heme in the reconstituted myoglobin is "disordered" in solution, and the altered functional properties of the reconstituted protein cannot be simply attributed to the local effect of the heme substituent. This NMR technique has applicability for determining the relative heme orientation in related hemoproteins, and may clarify the origin of doubling of heme resonances observed in several native hemoproteins.
Isolation and characterization of a tumor cell surface antigen from spontaneously transformed BALB/c mouse fibroblasts.
Authors: Kamm A R , Grimes W J
Published: May 2006

This work describes the detection, isolation, and partial characterization of a BALB/c mouse fibroblast cell surface antigen. This antigen migrates as a polypeptide of approximately 100,000 daltons in a discontinuous sodium dodecyl sulfate/polyacrylamide gel electrophoresis system, can be labeled by either lactoperoxidase-catalyzed cell surface 125I iodination or metabolic incorporation of [3H]glucosamine, and can be isolated by concanavalin A affinity chromatography. This cell surface glycoprotein is antigenic in BALB/c mice and has been correlated with the rejection of immunogenic tumor cells. Also, antiserum specific for Moloney leukemia virus precipitates the 100,000-dalton cell surface protein from viral and immunogenic spontaneous transformants. This virus-related antigen comigrates on sodium dodecyl sulfate gels with the major iodinated cell surface protein of these transformants. Rabbit antiserum to the purified antigen demonstrates a marked preference for the surfaces of immunogenic tumor cells as compared with normal cells and nonimmunogenic tumor cells.
Endogenous viral genes of the White Leghorn chicken: common site of residence and sites associated with specific phenotypes of viral gene expression.
Authors: Astrin S M
Published: May 2006

The DNAs from greater than 150 individual White Leghorn chickens were digested with restriction endonucleases BamHI, EcoRI, HindIII, and Sst I, fractionated by gel electrophoresis, denatured, and transferred to nitrocellulose filters. Fragments containing the endogenous viral genes were detected by hybridization with 70S Rous associated virus type 2[32P]RNA. Embryos of several different phenotypes with respect to production of the endogenous virus and expression of viral group-specific antigen and viral envelope protein were analyzed. DNA from birds of each phenotype produced a distinctive pattern of fragments containing viral genetic information. Individual fragments were seen to segregate as genetic loci in mating experiments. From the fragment patterns and the segregation data, the following conclusions were drawn with respect to the sites of residence in the chicken chromosome of the endogenous viral genes: (i) the DNA of all chickens contains viral genetic information in at least one site, and this site of residence appears to be the same in all chickens analyzed; (ii) four other sites have been identified, and the presence of viral information at each of these sites is always accompanied by a specific phenotype of endogenous viral gene expression; (iii) in addition to the above-mentioned five sites, a small number of other sites have been identified which are not associated with a known phenotype.
Interaction of bleomycin with DNA.
Authors: Takeshita M , Grollman A P , Ohtsubo E , Ohtsubo H
Published: May 2006

The sequence of oligonucleotides produced by the action of bleomycin and ferrous ion on double- and single-stranded DNA has been determined. In the presence of ferrous ion, bleomycin promotes cleavage at G-T and G-C sequences, while high concentrations of ferrous ion alone result in strand scission that is not base specific. In the presence of bleomycin and ferrous ion, pyrimidine bases located to the 3' side of guanosine are released preferentially and a low molecular weight product that forms a chromophore with thiobarbituric acid is produced from the deoxyribose moiety. Oligonucleotides produced by the action of bleomycin differ slightly in electrophoretic mobility from those produced by chemical or enzymatic cleavage. A model is proposed to explain the interactions of bleomycin with DNA.
In vitro mutagenesis of a circular DNA molecule by using synthetic restriction sites.
Authors: Heffron F , So M , McCarthy B J
Published: May 2006

A method for mutagenizing circular DNA molecules has been developed that uses synthetic oligodeoxynucleotide restriction sites as mutagens. A single synthetic restriction site is introduced at random by cleaving circular DNA with a nonspecific double-strand endonuclease. The restriction site is then ligated to the ends and the molecule is subsequently recircularized. These small additions to the genome are mapped by digestion with the appropriate restriction enzyme. Rearrangements such as duplications and deletions can be engineered at will by using the added restriction sites. This technique has been used to produce a fine-structure map of RSF1050, a ColE1 derivative, 60% of which is a transposable DNA sequence encoding the TEM beta-lactamase (Tn3). A subset of the mutations, mapping within a narrow region of Tn3, result in an increased frequency of Tn3 transposition; mutations in other regions abolish transposition entirely.
Demonstration of an ecdysteroid receptor in a cultured cell line of Drosophila melanogaster.
Authors: Maroy P , Dennis R , Beckers C , Sage B A , O'Connor J D
Published: May 2006

Incubation of the high-speed supernatant from the Kc cell line of Drosophila melanogaster with [3H]ponasterone A results in significant binding of the ligand as determined by gel filtration and dextran-coated charcoal binding assays. In vivo exposure of the Kc line to [3H]ponasterone A for 30 min results in a marked binding of the ligand by a KCl-soluble nuclear extract. With both the cytosol and nuclear preparations the binding has specificity and a low dissociation constant (3 X 10(-9) M). In addition the labeling of the nuclear preparation exhibits a saturation at approximately 7 X 10(-10) M which probably reflects the molar concentration of cytoplasmic receptors.
Adipose conversion of 3T3 cells depends on a serum factor.
Authors: Kuri-Harcuch W , Green H
Published: May 2006

The adipose conversion of 3T3-F442A cells depends on an adipogenic factor in serum. In the presence of this factor, cells grown to confluence become spherical, greatly increase the activity of their lipogenic enzymes, and accumulate triglyceride. In the absence of the adipogenic factor, the cells grow normally, but when they reach confluence they do not become spherical, do not accumulate triglyceride, and do not undergo any increase in activity of lipogenic enzymes. In cattle there is a great deal more of the adipogenic factor in the serum before birth than in the serum of grown animals. The nature of the adipogenic factor suggests that it may play an important role in the development of adipose tissue.
Linear arrays of intramembranous particles in pulmonary tubular myelin.
Authors: Chi E Y , Lagunoff D
Published: May 2006

Freeze-fracture preparations of tubular myelin in edematous rat lungs reveal the presence of linear arrays of intramembranous particles. The lines of particles are approximately 50 nm apart and appear to correspond to the intersections of sheets of bilayer membranes. Particles are not seen in lamellar bodies but become evident first in membranes transitional between lamellar bodies and tubular myelin. It is proposed that the particles represent a hydrophobic protein that plays a significant role in the organization of tubular myelin.
Neonatal suprachiasmatic nucleus ablation: absence of functional and morphological plasticity.
Authors: Mosko S , Moore R Y
Published: May 2006

Neonatal ablation of the suprachiasmatic nucleus in the rat has two important consequences. First, the direct projection from the retina to the suprachiasmatic nucleus fails to develop and no other retinal projection to any hypothalamic nucleus is formed. Second, circadian rhythms in drinking and spontaneous locomotor activity to not appear in these rats when they are tested as adults, and the females exhibit constant vaginal estrus. These observations indicate that the central neural mechanisms responsible for the generation and entrainment of circadian rhythmicity in the rat are not capable of either the functional or morphological plasticity characteristic of other developing neural systems.
Biochemical evidence for presynaptic and postsynaptic alpha-adrenoceptors in rat heart membranes: positive homotropic cooperativity of presynaptic binding.
Authors: Guicheney P , Garay R P , Levy-Marchal C , Meyer P
Published: May 2006

In crude rat cardiac membrane preparations, [3H]dihydroergocryptine (3H-DHE) appears to bind to two classes of sites with limited capacity, differing in their specificities and their affinities. The first class of binding sites interacts preferentially with the postsynaptic alpha-adrenoceptor blocker ARC239, as can be expected for postsynaptic alpha-adrenoceptors. The binding of 3H-DHE to these receptors follows the law of mass action, with a high affinity for 3H-DHE (Kd 25 degrees C = 1.67 +/- 0.37 nM). Postsynaptic saturating levels of 3H-DHE are necessary to occupy the second class of binding sites. These sites exhibit a preferential affinity for presynaptic ligands such as clonidine and yohimbine, as would be expected for presynaptic alpha-adrenergic receptors. This presynaptic binding shows a markedly positive homotropic cooperativity (Hill n = 2.88) with initial and final apparent Kds of 23 and 0.83 nM, respectively. Free energy of interaction between sites is of the order of 2 kcal (8.36 kJ)/mol of sites. These characteristics provide a rational molecular basis for the functional role of presynaptic alpha-adrenoceptors that mediate the inhibition of norepinephrine release from nerve endings.
Ionic factors in release of 45Ca2+ from chicken cerebral tissue by electromagnetic fields.
Authors: Bawin S M , Adey W R , Sabbot I M
Published: May 2006

Electrical stimulation with radiofrequency fields amplitude-modulated at brain wave frequencies increased 45Ca2+ efflux from isolated chicken cerebral tissue. The response was not sensitive to variations of the calcium concentration (0-4.16 mM) in the bathing solution but was enhanced by addition of H+ (0.108 mM HCl) and inhibited in the absence of normal bicarbonate levels (2.4 mM). Addition of lanthanum to the bicarbonate-free solution restored electrical responsiveness, but the stimulus decreased instead of increasing 45Ca2+ efflux. It is suggested that low-frequency, weak, extracellular electric gradients may be transduced in a specific class of extracellular negative binding sites normally occupied by Ca2+ and susceptible to competitive H+ binding.
Dense plexus of substance P immunoreactive nerve terminals in eminentia medialis of the primate hypothalamus
Authors: Hökfelt T. , Pernow B. , Nilsson G. , Wetterberg L. , Goldstein M. , Jeffcoate S. L.
Published: May 2006

The indirect immunofluorescence technique of Coons and collaborators was used to study the distribution of substance P-like and luliberin (luteinizing hormone-releasing hormone)-like immunoreactivity in the eminentia mediana (eminentia medialis or infundibulum) of rats, monkeys, and human beings. In rats, abundant luliberin-positive fibers were present in the external layer (mainly lateral parts) whereas almost no substance P-immunoreactive nerves were observed in this region. In contrast, in the external layer of the primate eminentia medialis a dense plexus of substance P-positive nerve terminals was observed close to the blood vessels supplying the anterior pituitary gland. Luliberin-immunoreactive fibers were also present, but with a more even distribution all over the eminentia medialis and in lower numbers. The present findings indicate that substance P may play a role in the control of hormone secretion from the anterior pituitary, either by being released into the portal vessels, i.e., acting as a releasing or inhibitory hormone, or by an action as local regulator (modulator or transmitter) at the level of the eminentia medialis. Thus, in agreement with many earlier studies, substances other than the “classical” releasing and inhibitory hormones may be important for the regulation of the pituitary gland. Furthermore, there may exist marked species differences with regard to the type of substances involved in the central control of the pituitary.
Nucleotide sequence of an insertion element, IS1.
Authors: Ohtsubo H , Ohtsubo E
Published: May 2006

PSM2, PSM1, and PSM15 are small plasmids derived from R100 by spontaneous deletions at either end of the insertion sequence IS1. These plasmids were used to identify regions neighboring IS1 as well as the IS1 DNA itself, by cleavage with EcoR1, HindIII, Hae III, Hpa II, Hha I, Hinf, and AIu I. The nucleotide sequencing results demonstrate that IS1 contains 768 bases. About 30 bases at the ends of IS1 were found to be repeated in an inverted order. The deletions occurring at the ends of IS1 were found to be due to illegitimate recombination. The hypothesis that RNA polymerase could play an important role in such recombination phenomena is discussed based on the nucleotide sequences surrounding the recombinational hot spots.
Intervening sequence of DNA identified in the structural portion of a mouse beta-globin gene.
Authors: Tilghman S M , Tiemeier D C , Seidman J G , Peterlin B M , Sullivan M , Maizel J V , Leder P
Published: May 2006

The unusual electron microscopic appearance of a hybrid formed between 9S mouse beta-globin mRNA and its corresponding cloned gene segment is caused by at least one, and possibly two, intervening sequences of DNA that interrupt the mouse beta-globin gene. Such an interpretation is consistent with a paradoxical restriction site pattern previously noted in this gene and with the nucleotide sequence of that portion of the gene that spans both structural and intervening sequences. The large intervening sequence, approximately 550 base pairs in length, occurs in the structural globin sequence and immediately follows the beta-globin codon corresponding to amino acid 104. A smaller, putative intervening sequence is located close to the 5' end of the beta-globin-coding sequence but may reside beyond its initiation codon. The beta-globin gene thus appears to be encoded in two, and possibly three, discontinuous segments.
Oligosaccharide chains are trimmed during synthesis of the envelope glycoprotein of vesicular stomatitis virus.
Authors: Hunt L A , Etchison J R , Summers D F
Published: May 2006

The biosynthesis and maturation of the oligosaccharide moieties of the envelope glycoprotein of vesicular stomatitis virus were investigated in virus-infected HeLa and BHK21 cells after pulse labeling with [2-3H]mannose. Two major forms of the virus glycoprotein were detected by polyacrylamide gel electrophoresis, which appear to correspond to the viral glycoprotein with either "precursor" or "mature" oligosaccharide chains. The precursor chains in both HeLa and BHK21 cells infected with vesicular stomatitis virus obtained after a 30-min pulse were large oligomannose structures containing approximately 7--9 mannose residues as estimated by gel filtration analysis. The size of the oligomannose structures initially transferred to the protein may have been even larger. Mature, virus-size oligosaccharide chains, which could be detected after a 20- to 30-min delay, contained only three mannose residues and, in addition, contained branch structures terminating in sialic acid. A precursor--product relationship of these two forms of oligosaccharide chains was demonstrated by pulse--chase labeling of virus-infected HeLa cells. These studies indicated that the large oligomannosyl core structures initially added to the glycoprotein were being "trimmed" by the removal of mannose residues prior to (and/or during) the addition of the branch chains terminating in sialic acid.
EcoRI cleavage site variants of mitochondrial DNA molecules from rats.
Authors: Buzzo K , Fouts D L , Wolstenholme D R
Published: May 2006

The mitochondrial DNA (mtDNA) molecules of some rats obtained from the SASCO colony contain six EcoRI-sensitive sites while the mtDNA molecules of other rats obtained from the same source contain only four EcoRI sites. By mapping the positions of the EcoRI sites on the molecules relative to the D-loop it was determined that mtDNA molecules from all rats have four EcoRI sites in common, but all the mtDNA molecules of some rats have two extra EcoRI sites. EcoRI sensitivity of mtDNA molecules was shown to be maternally inherited. Construction of heteroduplex molecules failed to reveal evidence of gross nucleotide sequence changes associated with differences in EcoRI sensitivity.
Infection of mouse preimplantation embryos with simian virus 40 and polyoma virus
Authors: Abramczuk Jan , Vorbrodt Andrzej , Solter Davor , Koprowski Hilary
Published: May 2006

Mouse two-cell embryos, morulae, and blastocysts were killed when infected
in vitro
with simian virus 40 (SV40) at high multiplicities of infection. Polyoma virus was not deleterious for preimplantation embryos, even at a very high multiplicity of infection; however, the outgrowths of polyoma-infected blastocysts disintegrated after several days of culture. Indirect immunofluorescence tests revealed the presence of SV40 T and V antigens and polyoma virus V antigen in the nuclei of trophoblastic cells. Virus-specific antigens were not found in the nuclei of cells forming inner cell masses of blastocysts or in inner cell mass-derived cells in blastocyst out-growths. The appearance of SV40 T and V antigens in the nuclei was inhibited by αamanitin, a RNA polymerase II inhibitor. The amount of infectious virus recovered from cultures of morulae or blastocysts on subsequent days after infection with SV40 initially declined but later increased. These points of evidence indicate that some cells of early mouse embryos are permissive for the expression of early and late functions of SV40 genome and that susceptibility to infection with polyoma virus and/or permissiveness for the expression of polyoma virus late functions develop gradually between the two-cell and blastocyst stages. Electron microscope observations showed the presence of specific complexes of membranes and virions in the cytoplasm of trophoblastic cells. Single viral particles could be found in the nuclei and also in mitochondria.
Electrophilic and free radical nitration of benzene and toluene with various nitrating agents
Authors: Olah George A. , Lin Henry C. , Olah Judith A. , Narang Subhash C.
Published: May 2006

Electrophilic nitration of toluene and benzene was studied under various conditions with several nitrating systems. It was found that high
orthopara
regioselectivity is prevalent in all reactions and is independent of the reactivity of the nitrating agent. The methyl group of toluene is predominantly
ortho-para
directing under all reaction conditions. Steric factors are considered to be important but not the sole reason for the variation in the
ortho/para
ratio. The results reinforce our earlier views that, in electrophilic aromatic nitrations with reactive nitrating agents, substrate and positional selectivities are determined in two separate steps. The first step involves a π-aromatic-NO
2
+
ion complex or encounter pair, whereas the subsequent step is of arenium ion nature (separate for the
ortho, meta
, and
para
positions). The former determines substrate selectivity, whereas the latter determines regioselectivity. Thermal free radical nitration of benzene and toluene with tetranitromethane in sharp contrast gave nearly statistical product distributions.
Crystal structures of the α″-cerium phases
Authors: Zachariasen W. H.
Published: May 2006

Endo
et al.
[Endo, S., Sasaki, H. & Mitsui, T. (1972)
J. Phys. Soc. Jpn.
42, 882-885] have reported x-ray diffraction data for an unidentified phase of cerium metal observed in the 50- to 100-kbar range. It is shown that the unknown phase is a variant of the metastable monoclinic phase, α″-Ce, previously observed. The complete structure of the new form of α″-Ce is deduced.
Fluorescent photoaffinity labeling: Adenosine 3′,5′-cyclic monophosphate receptor sites
Authors: Dreyfuss Gideon , Schwartz Kenneth , Blout Elkan R. , Barrio Jorge R. , Liu Fu-Tong , Leonard Nelson J.
Published: May 2006

An approach to the study of protein receptor sites in protein mixtures or supramolecular assemblies by using fluorescence spectroscopy is described. This approach, fluorescent photoaffinity labeling, combines the merits of photoaffinity labeling to attain site-directed reactivity with the probing power of fluorescent ligands. A fluorescent photoaffinity label for cyclic AMP receptor sites of cyclic AMP-dependent protein kinases was synthesized in both unlabeled and radioactive forms. The probe, 8-azido-1,
N
6
-ethenoadenosine 3′,5′-cyclic monophosphate, mimics cyclic AMP in its ability to stimulate the phosphotransferase activity of the protein kinases and strongly competes with cyclic AMP for its binding sites in all preparations so far tested. Photolysis, after equilibration of protein kinase and 8-azido-1,
N
6
-ethenoadenosine 3′,5′-cyclic monophosphate in the dark, effects binding of the intermediate nitrene irreversibly and specifically to the cyclic AMP sites with the development of fluorescence. Excess reagent and low molecular weight photolytic products are removable by dialysis. Studies of a crude beef heart preparation containing cyclic AMP-dependent protein kinase suggest that the cyclic AMP binding sites are hydrophobic in nature and strongly immobilize the adenine moiety of the cyclic nucleotide.
Evidence for receptor-mediated binding of glycoproteins, glycoconjugates, and lysosomal glycosidases by alveolar macrophages.
Authors: Stahl P D , Rodman J S , Miller M J , Schlesinger P H
Published: May 2006

Alveolar macrophages have been shown to bind glycoproteins and synthetic glycoconjugates (neoglycorpoteins) that have mannose, N-acetylglucosamine, or glucose in the exposed, nonreducing position. Galactose-terminal glycoproteins are not bound. Binding of radiolabeled ligands to cells is nearly completely impaired by the presence of an excess of yeast mannan. Binding is temperature sensitive and proceeds optimally at pH 7.0. Prior treatment of the cells with trypsin severely decreases their capacity to bind ligands. An inhibition assay has been developed, using radioiodinated glucose-albumin conjugate, agalacto-orosomucoid, beta-glucuronidase, and RNase B as ligands. Various glycoproteins have been shown to be effective inhibitors of ligand binding including horseradish peroxidase, agalacto-orosomucoid, beta-glucuronidase, ovalbumin, agalacto-fetuin, and RNase B. RNase A and asialo-fetuin are ineffective as antagonists. The results suggest the presence of a cell surface receptor on alveolar macrophages that binds glycoproteins having terminal sugars with the mannose or glucose configuration.
Comparison of synchronization of circadian corticosteroid rhythms by photoperiod and food
Authors: Krieger Dorothy T. , Hauser Herbert
Published: May 2006

Under conditions of feeding at will and normal light-dark alternation, rats consume the major portion of their daily food intake during the dark period and the circadian peak of plasma corticosteroid concentrations and of body temperature levels occurs just prior to or subsequent to the time of light-dark transition. Both light-dark transition and time of food presentation have been implicated as “Zeitgebers” in determining the phase of these two circadian rhythms.

The present data indicate the following: (
i
) The time of food presentation appears to be a more potent synchronizer of the phase of plasma corticosteroid levels than is the light-dark cycle. This has been demonstrated in rats under conditions in which light-dark phase shift has been dissociated from a concomitant shift of time of eating. In contrast, under such conditions, the rhythm of body temperature appears to be more tightly coupled to the light-dark cycle. This illustrates that the time of food ingestion and the peak of body temperature rhythms can be uncoupled and that the phasing effects of restricted food ingestion on corticosteroid rhythms does not extend to body temperature rhythms. It also suggests the presence of different control mechanisms and/or pathways for corticosteroid and body temperature rhythms as well as the use of different pathways by different Zeitgebers. (
ii
) Rats maintained in constant dim light with free access to food exhibit aperiodic feeding behavior; plasma corticosteroid concentrations and body temperature levels are also aperiodic. Imposition of a restricted period of food access under such constant light conditions is associated with the appearance of a circadian periodicity of both plasma corticosteroid concentrations and body temperature levels, with peaks, respectively, just before and after the time of food presentation. This represents an additional example of food entrainment of previously aperiodic functions, similar to the food entrainment we have described in animals rendered aperiodic by lesions of the suprachiasmatic nucleus.
Protein deficiency and energy restriction in young cebus monkeys.
Authors: Samonds K W , Hegsted D M
Published: May 2006

Infant cebus monkeys (Cebus albifrons) were fed liquid formulas that were limited in protein, energy, or a combination of the two restrictions. Weight gain, food intake, hematological development, and plasma protein and cholesterol levels were monitored over a 20-week period. The animals restricted in protein developed the classical signs of protein deficiency--reductions in plasma albumin, a mild anemia, accumulation of fat in the liver, and, in a few cases, facial edema. These animals maintained a relatively high energy intake, and apparently wasted energy when compared to similarly non-growing energy-restricted animals. Energy-restricted animals did not exhibit these symptoms, even when their daily protein intake was reduced to match that of protein-restricted monkeys. It is concluded that an energy restriction superimposed upon a limited protein intake did not increase protein requirements or precipitate protein deficiency.
Cyclopenta[c,d]pyrene: a highly mutagenic polycyclic aromatic hydrocarbon.
Authors: Eisenstadt E , Gold A
Published: May 2006

A polycyclic aromatic hydrocarbon recently isolated from carbon black and identified as cyclopenta[c,d]pyrene (CPP) is highly mutagenic. By the criteria of the Salmonella/mammalian-microsome mutagenicity test, the mutagenic potency of CPP is equalled by only two other naturally occurring polycyclic aromatic hydrocarbons--benzo[a]pyrene and dibenz[a,c]anthracene. The potent mutagenicity of CPP is noteworthy for two reasons: (i) CPP is a mutagenic polycyclic aromatic hydrocarbon without a "bay-region" and (ii) there is evidence that it is distributed widely in the environment. On the basis of experimental observations and perturbational molecular orbital calculations we propose that a mutagenic metabolite of CPP will be the 3,4-oxide. The carbonium ion derived from opening of CPP 3,4-oxide is identical to that derived from opening of benzo[a]pyrene 7,8-diol-9,10-oxide, the metabolite now thought to be an ultimate mutagenic and carcinogenic species.
Isolation and characterization of the normal crossreacting antigen: homology of its NH2-terminal amino acid sequence with that of carcinoembryonic antigen.
Authors: Engvall E , Shively J E , Wrann M
Published: May 2006

The normal antigen, NCA, which crossreacts with the carcinoembryonic antigen, CEA, was purified from normal spleen tissue by an immunochemical purification method using insolubilized antibodies to either CEA or NCA. The highly purified NCA obtained was extensively characterized by immunological tests. The molecular weight of NCA determined by chromatography on Sephadex G-200 was approximately 100,000. The total amount of carbohydrate in NCA was 30%, compared to 60% in CEA. NCA and CEA also differed in sugar composition. The amino acid composition of NCA was nearly identical to that of CEA, except for the apparent presence of methionine in NCA but not in CEA. The sequence of the first 26 NH2-terminal amino acids in NCA was identical to that of CEA except at position 21, where alanine was found in NCA instead of valine in CEA.
Synthesis of phage M13 coat protein and its assembly into membranes in vitro.
Authors: Wickner W , Mandel G , Zwizinski C , Bates M , Killick T
Published: May 2006

The coat protein (gene 8 product) of coliphage M1O is an integral protein of the host cell membrane at all stages of virus infection. This protein, when made in a cell-free reaction, has been shown by others to have an additional NH2-terminal peptide region and is referred to as "procoat." It is initially not membrane-bound but, upon exposure to Escherichia coli membrane vesicles or to liposomes prepared from E. coli lipids, it assembles into the bilayer in an integral fashion. Much of this protein is shown to be exposed on the inner surface of the liposome. We suggest that refolding of procoat as it encounters the bilayer is sufficient to transport large segments of the peptide chain through the apolar hydrocarbon core.
Cytoplasmic microtubular images in glutaraldehyde-fixed tissue culture cells by electron microscopy and by immunofluorescence microscopy
Authors: Weber Klaus , Rathke Peter C. , Osborn Mary
Published: May 2006

Electron microscopy and indirect immunofluorescence microscopy using monospecific tubulin antibodies were performed in parallel on glutaraldehyde-fixed tissue culture cells without osmium fixation. In order to reduce the excess aldehyde groups of the strongly crosslinked cellular matrix, which normally interfere with subsequent immunofluorescence microscopy, a mild NaBH
4
treatment was introduced during or after the dehydration steps. Cells processed through the NaBH
4
step show, in transmission electron microscopy, normal cytoplasmic microtubules approximately 250 Å in diameter. When such cells are subjected to indirect immunofluorescence microscopy using monospecific tubulin antibody they reveal a complex system of unbroken, fine, fluorescent fibers traversing the cytoplasm between the perinuclear space and the plasma membrane. Thin sections of cells processed through the indirect immunofluorescence procedure show antibody-decorated microtubules with a diameter of approximately 600 Å. This decoration is not obtained when non-immune IgGs are used instead of monospecific antitubulin IgGs. Thus, a direct comparison of cytoplasmic microtubules in glutaraldehyde-fixed cells by both electron microscopy and immunofluorescence microscopy can be obtained.
Duality of hepatitis B e antigen in serum of persons infected with hepatitis B virus: evidence for the nonidentity of e antigen with immunoglobulins.
Authors: Takahashi K , Imai M , Miyakawa Y , Iwakiri S , Mayumi M
Published: May 2006

Hepatitis B e antigen (HBeAg) is detected in the serum of some persons infected with hepatitis B virus. Owing to a close correlation of HBeAg and hepatitis B virus in the serum, it has been used as a practical indicator of infectivity. Two entities of HBeAg activity physicochemically different from each other were demonstrated in the serum of persons infected with hepatitis B virus. One was associated with a molecule that precipitated in 1.33 M ammonium sulfate solution, was larger than IgG, and had an electrophoretic mobility in the beta- to gamma-globulin regions and an isoelectric point of approximately pH 5.7. In contrast, the other HBeAg activity was associated with a molecule that was soluble in 1.33 M ammonium sulfate solution, was smaller than IgG, and had an electrophoretic mobility in the alpha-globulin region and an isoelectric point at pH 4.8. In spite of their marked physicochemical differences, a line of antigenic identity was clearly observed for them when they were tested against antibody to HBeAg by a them when they were tested against antibody to HBeAg by a double immunodiffusion method. The HBeAg activity associated with the large molecule was completely removed by an affinity column of anti-IgG, whereas the activity of the small molecule was not. These results indicate that, in the serum, HBeAg exists as a molecule smaller than IgG and also in association with IgG.
Crossreacting determinants in variant-specific surface antigens of African trypanosomes.
Authors: Barbet A F , McGuire T C
Published: May 2006

A number of variant-specific surface antigens (VSSAs) were purified from clones of Trypanosoma brucei and T. congolense and tested for immunological crossreactivity. Anti-VSSA sera were clone-specific when tested by indirect immunofluorescence of living trypanosomes, but they were not clone-specific when tested by radioimmunoassay with purified 125I-labeled VSSAs. In this double-antibody radioimmunoassay every VSSA tested was precipitated by the homologous and all heterologous anti-VSSA sera. Any unlabeled VSSA could inhibit the heterologous precipitation reactions by 100%. The homologous precipitation reactions were effectively inhibited only by unlabeled homologous VSSA. Crossreactions between different VSSA molecules were also revealed by microcomplement fixation tests. The results confirm the presence, in VSSAs, of variable determinants specific to individual VSSAs and also show crossreacting determinants in all VSSAs tested, including those isolated from different species of trypanosomes. These results contrast with previous studies which failed to find evidence for immunological crossreactivity between different VSSA molecules. We suggest that the crossreacting determinants in VSSAs may represent common structural regions. The existence of such regions would have considerable implication for the development of theories and experiments concerning the mechanism of antigenic variation in African trypanosomes.
Prolyl hydroxylase half reaction: peptidyl prolyl-independent decarboxylation of alpha-ketoglutarate.
Authors: Counts D F , Cardinale G J , Udenfriend S
Published: May 2006

Prolyl hydroxylase (proline,2-oxoglutarate dioxygenase, EC 1.14.11.2) is a mixed-function oxygenase that hydroxylates peptidyl proline with the simultaneous and stoichiometric decarboxylation of alpha-ketoglutarate to succinate and CO2. It has been found that highly purified preparations of the enzyme can decarboxylate alpha-ketoglutarate in the absence of a peptidyl proline substrate. The uncoupled decarboxylation proceeds at only a fraction of the rate of the whole reaction and for study requires substrate quantities of the pure enzyme, as well as oxygen, ferrous ion, and ascorbate. No hydroxyproline is formed under these conditions. Immobilized antiserum to prolyl hydroxylase was found to remove both activities from enzyme preparations. However, addition of free antiserum during incubation inhibits only the complete reaction. Poly(L-proline), a specific inhibitor of prolyl hydroxylation, enhances the uncoupled decarboxylation of alpha-ketoglutarate without itself being hydroxylated. All of these findings prove that alpha-ketoglutarate can serve as substrate in the absence of peptidyl proline and is most likely the initial site of attack by oxygen. In the coupled reaction an oxidized form of the keto acid, perhaps a peroxy acid, then attacks prolyl residues in the unhydroxylated substrate.
Two fragments from fibrinolysin digests of ovine prolactin: characterization and recombination to generate full immunoreactivity.
Authors: Birk Y , Li C H
Published: May 2006

The action of fibrinolysin (plasmin; EC 3.4.21.7) on ovine prolactin has been investigated. It was found that the enzyme selectively cleaves the bond between Met-53 and Ala-54. The two fragments, PRL-(1-53) and PRL-(54-199), have been purified and characterized. A recombinant molecule has been obtained by noncovalent interaction of PRL-(1-53) and PRL-(54-199). The recombined protein behaves nearly identically to the parent hormone in circular dichroism spectra and exclusion chromatography. The recombinant possesses full immunoreactivity, as revealed by gel double-diffusion and complement fixation. However, the recombined protein exhibits low prolactin activity in the pigeon crop-sac test.
Local mutagenesis: a method for generating viral mutants with base substitutions in preselected regions of the viral genome.
Authors: Shortle D , Nathans D
Published: May 2006

DNA from simian virus 40 (SV40) was prepared for local mutagenesis by nicking the molecule at a specific site with a restriction endonuclease that recognizes one site in SV40 DNA and then extending the nick enzymatically to expose a short, single-stranded segment of DNA. The "gapped" DNA was treated with a single-strand-specific mutagen, sodium bisulfite, which converts cytosine to uracil. After mutagenesis, the gap was repaired with DNA polymerase, generating molecules resistant to the restriction enzyme used to make the initial nick. From cells infected with DNA thus modified, SV40 mutants were isolated that had enzyme-resistant genomes. In some cases, precise positions of G.C to A.T transitions could be inferred from the patterns of susceptibility of mutant DNA to other restriction endonucleases whose recognition sequences were altered by the mutagenesis procedure. One of the restriction endonuclease sites mutagenized (Bgl I) maps at the origin of SV40 DNA replication and near sequences corresponding to the 5' ends of viral mRNAs. Many of the resulting Bgl I-resistant mutants yielded small plaques, suggesting partial defectiveness in DNA replication or transcription.
Selective labeling of α-adrenergic receptors in caudate nucleus by [
3
H]dihydroergocryptine in the presence of spiperone-blocked dopamine receptors
Authors: Titeler M. , Seeman P.
Published: May 2006

Because it was known that [
3
H]dihydroergocryptine can label α-adrenergic receptors as well as dopamine receptors, this study was done to establish the conditions under which [
3
H]dihydroergocryptine would be a reliable ligand for selective labeling of α-adrenergic receptors. The calf caudate was chosen because it contains both dopamine and adrenergic receptors, and 5 nM spiperone (spiroperidol) was used to block the neuroleptic/dopamine receptors. Thus, in the presence of spiperone, [
3
H]dihydroergocryptine exhibited saturable binding with a
K
d
of 0.73 nM and a total number of sites of 150 fmol/mg of protein. The catechol neurotransmitters competed for [
3
H]dihydroergocryptine binding in the potencies order epinephrine > (-)-norepinephrine > dopamine, indicating that [
3
H]dihydroergocryptine (in the presence of 5 nM spiperone) was revealing α receptors. The α-adrenergic antagonists also competed for binding in the appropriate order: phentolamine > phenoxybenzamine > dibenamine. Finally, chlorpromazine was more potent than haloperidol in competing for [
3
H]dihydroergocryptine, also in accord with the properties of α receptors. These results with [
3
H]dihydroergocryptine as an α-adrenergic receptor ligand correlate well with those published by others for [
3
H]WB-4101.
Topography and kinetics of genetic recombination in
Escherichia coli
treated with psoralen and light
Authors: Sinden Richard R. , Cole Ronald S.
Published: May 2006

Genetic exchanges appear to be involved in repair of cross-linked DNA. Kinetics for completion of repair and strand rejoining controlled by the
recA
+
gene were examined in
Escherichia coli
treated with psoralen and light. The results suggest the following model for genetic recombination. After cross-linking treatment, cells in a population initiate repair in near synchrony. Removal of DNA cross-links, preparation of substrate for recombination, and initiation of the first
recA
-dependent event are completed in less than 1 min. Recombination events occur singly in each cell or chromosome, and require 2.3 ± 0.4 min at 32° for the
recA
+
-dependent step. After completion of the first event, subsequent recombination events occur in a sequential or progressive fashion around the chromosome or in clusters which may consist of one or more domains of the folded chromosome. The time required to proceed to successive sites is either a constant, independent of the distance on the chromosome, or is quite small compared to 2.3 min. DNA substrate for recombination decays with approximate first-order kinetics and the rate is dependent on the number of unrepaired sites. Cell survival can be expressed as a competition between completion of all repair events and the simultaneous decay of chromosomes to forms not reparable by recombination.

Equations relating kinetics for completion of repair, the size distribution of DNA molecules, and cell survival are derived for the above model, using as parameters only rate constants for recombination and decay of substrate, and number of events per chromosome. An excellent correlation is found between experimentally determined and theoretical values.
Inhibition of dual Ir gene-controlled T-lymphocyte proliferative response to poly (Glu56Lys35Phe9)n with anti-Ia antisera directed against products of either I-A or I-C subregion.
Authors: Schwartz R H , David C S , Dorf M E , Benacerraf B , Paul W E
Published: May 2006

Previous studies have demonstrated that both the antibody and T-lymphocyte proliferative immune responses to poly(Glu53Lys36Phe11)n (GLphi) are under the control of two major histocompatibility-linked immune response (Ir) genes. One gene, termed Ir-GL phi-alpha, has been mapped to the I-C or I-E subregion of the major histocompatibility complex, while the other, termed Ir-GL phi-beta, has been mapped to the I-A subregion. In this paper we examine the effect of anti-I-region-associated (Ia) antisera on the T-lyphocyte proliferative response to GL phi. Antibodies directed against Ia antigens coded for by genes in either the I-A or I-C subregion were found to inhibit the proliferative response to GLphi. These results suggest that a function mediated by two Ir gene products can be blocked by anit-Ia antisera directed against either one, and thus, that both products are expressed on the cell surface.
Heterogeneity of locomotion in human T cell subsets.
Authors: Parrott D M , Good R A , O'Neill G J , Gupta S
Published: May 2006

Locomotor activity of T cells with receptors for IgM and IgG, T cells without receptors for IgM or IgG, and T and non-T cells from human peripheral blood and human tonsils towards the chemoattractant casein was examined in modified Boyden chambers. T cells with receptors for IgG both from human tonsils and peripheral blood did not move in response to casein. T cells with receptors for IgM and those without receptors for IgM or IgG, on the other hand, moved very well toward casein and the distances were comparable to those achieved by T cells before separation. This difference in the locomotor activity of T cell subsets might explain their differential distribution in various lymphoid compartments. Separated T cells, cultured in medium supplemented with fetal calf serum, moved into the filters in response to casein. Prior culture of T cells in medium alone or in medium supplemented with human AB serum resulted in a reduction in the distance traveled in response to casein; however, the effect of AB serum was variable. Non-T cells from peripheral blood and B cells from tonsils responded poorly to casein.
Identification of an Abelson murine leukemia virus-encoded protein present in transformed fibroblast and lymphoid cells.
Authors: Witte O N , Rosenberg N , Paskind M , Shields A , Baltimore D
Published: May 2006

Extracts from lymphoid and fibroblast cell lines transformed by Abelson murine leukemia virus (A-MuLV) contain a protein of molecular weight 120,000 (P120). Immunoprecipitation with specific sera shows that P120 contains regions homologous to the 5'-terminal segment of the MULV gag gene complex--p15, p12, and at least part of p30--but lacks detectable determinants of p10, reverse transcriptase, and the envelope glycoprotein. P120 is phosphorylated and has an intracellular half-life of 3--6 hr. In vitro translation of virion RNA from A-MuLV, with Moloney MuLV as helper, yields a product of molecular weight 120,000 with serological reactivity similar to that of the cellular P120. Translation of the RNA from the helper gave no P120. P120 is expressed in all lymphoid and fibroblastic cell lines we have tested that were transformed by A-MuLV but is not detectable in a lymphoid line in which the A-MuLV genome was established by infection but was not responsible for the transformation. Expression of P120 is selectively retained in clones of A-MuLV-transformed lymphocytes that convert to a nonproducer state after loss of expression of helper MuLV intracellular precursors. These results suggest that the P120 product of the A-MuLV genome may be responsible for maintenance of the transformed phenotype of lymphoid and fibroblast cells transformed by the virus.