bluuebunny/crossref_metadata_2025 huggingface dataset:
Antigenic relationships between measles and canine distemper viruses: comparison of immune response in animals and humans to individual virus-specific polypeptides.
Authors: Stephenson J R , ter Meulen V
Published: May 2006

Precipitation with hyperimmune rabbit sera, sera from patients convalescing from measles, and sera from patients with subacute sclerosing panencephalitis, followed by electrophoresis, enabled antigenic relationships between the individual polypeptides of measles and canine distemper viruses to be examined. Virus isolates from patients with acute measles or subacute sclerosing panencephalitis showed no antigenic differences. With rabbit hyperimmune sera, antigenic crossreactivity was present between all polypeptides of measles and canine distemper viruses except H. The N polypeptides showed the highest degree of crossreactivity and were interpreted as group-specific antigens. Both convalescent measles sera and sera from subacute sclerosing panencephalitis showed high antibody titers to all measles polypeptides except L and M. However, these sera contained only low activities to the N and F1 polypeptides from canine distemper virus.
Defect in 3'-phosphoadenosine 5'-phosphosulfate formation in brachymorphic mice.
Authors: Sugahara K , Schwartz N B
Published: May 2006

Incorporation of 35SO42- into adenosine 5'-phosphosulfate (APS), 3'-phosphoadenosine 5'-phosphosulfate (PAPS), and chondroitin sulfate was simultaneously assessed with extracts prepared from epiphyseal cartilage of neonatal normal or homozygous brachymorphic mice. Radioactivity measured in APS, PAPS, and chondroitin sulfate of extracts from brachymorphic cartilage was approximately 300%, 9%, and 13% of the normal levels, respectively. Even though more APS accumulated in the mutant cartilage extracts, APS actually synthesized (total 35SO42- incorporated into APS, PAPS, and macromolecular products) was only 17% of that in the normal. However, of the amount synthesized, 90% and 55% of newly synthesized APS were converted to PAPS by cartilage extracts of normal and brachymorphic mice, respectively. Specific assays for ATP sulfurylase (sulfate adenylyltransferase; ATP:sulfate adenylyltransferase, EC 2.7.7.4) and APS kinase (adenylylsulfate kinase; ATP:adenylylsulfate 3'-phosphotransferase, EC 2.7.1.25) showed that the sulfurylase enzyme activity is reduced to approximately 1/2 and the kinase to approxomately 1/14 in brachymorphic mice. These results suggest that the production of an undersulfated proteoglycan in brachymorphic cartilage results from a defective conversion of APS to PAPS.
Acetylcholine and local anesthetic binding to Torpedo nicotinic postsynaptic membranes after removal of nonreceptor peptides.
Authors: Neubig R R , Krodel E K , Boyd N D , Cohen J B
Published: May 2006

After alkaline extraction, purified subsynaptic fragments isolated from Torpedo electric tissue exhibit on sodium dodecyl sulfate/polyacrylamide gel electrophoresis predominant peptides of apparent Mr 41,000, 50,000, and 65,000 (i.e., the peptides characteristic of the nicotinic receptor purified and isolated in detergent solutions). The peptide of Mr 43,000 that is also found in the isolated postsynaptic membranes is recovered in the supernatant after alkaline extraction. The alkaline-extracted membranes were functionally intact, as demonstrated by the following criteria. The kinetics of binding of [3H]acetylcholine in the presence and absence of 30 micron carbamoylcholine to occupy acetylcholine binding sites, [14C]-meproadifen [2-(diethylmethylaminoethyl)-2,2-diphenylvalerate iodide ] was bound with a dissociation constant, KD, of 0.3 +/- 0.1 micron to 0.3 +/- 0.1 site per [3H]alpha-toxin site. This binding was displaced by perhydrohistrionicotoxin. The carbamoylcholine-stimulated efflux of 22Na+ from the Torpedo vesicles were preserved after alkaline extraction. It is concluded that not only the acetylcholine binding site, but also the local anesthetic binding site, must be associated with the peptides of the cholinergic receptor itself and not that of Mr 43,000. Those peptides remaining after alkaline extraction are also sufficient for permeability control.
Contribution of negative cooperativity to the thyrotropin-receptor interaction in normal human thyroid: kinetic evaluation.
Authors: Powell-Jones C H , Thomas C G , Nayfeh S N
Published: May 2006

The kinetics of 125I-labeled thyrotropin (125I-TSH) binding to human thyroid receptors are presented. At pH 6.0, binding was maximal (30--35%) and there was one class of binding sites [Kd = 6.8 X 10(-9) M; binding capacity (Ro) = 57 pmol/mg of protein]. At pH 7.4, Scatchard plots of binding were nonlinear, indicating either a single class of negatively cooperative sites (Kd = 3.7 X 10(-9) M; Ro = 26 pmol/mg of protein) or, alternatively, independent high- (Kd = 5.0 X 10(-10) M; Ro = 3 pmol/mg of protein) and low-affinity (Kd = 1.7 X 10(-8) M; Ro = 26 pmol/mg of protein) binding sites. The role of negative cooperativity was evaluated from the rates of association and dissociation at pH 7.4. The kinetically determined binding constants (Kd = 1.7 X 10(-11) M; Ro = 2 pmol/mg of protein) were more similar to those determined for the high-affinity component than to those predicted from the negative cooperativity model. Dissociation of bound TSH was independent of initial site occupancy over a 40-fold range, corresponding to a 100-fold range of free TSH concentration. The dissociation rate of 125I-TSH was enhanced by unlabeled TSH to a similar degree, irrespective of initial binding site occupancy. Because the negative cooperativity model does not accommodate these data, it is concluded that TSH receptors in human thyroid behave kinetically and at equilibrium as a single class of high-affinity sites up to TSH concentrations well above the physiological range.
A protein that preferentially binds Drosophila satellite DNA.
Authors: Hsieh T , Brutlag D L
Published: May 2006

Using a nitrocellulose filter binding assay, we have detected and partially purified a protein from embryos of Drosophila melanogaster that preferentially binds to a highly repeated satellite DNA of the same species. Formation of the satellite DNA-protein complex requires physiological conditions of salt and temperature, but once formed, the complex is stable in high salt (1 M NaCl) or at low temperature. Optimal formation of the specific complex also requires the satellite DNA to be in a supertwisted conformation. The protein interacts with a limited region within the 359-base-pair repeated sequence of the satellite DNA.
Immunological evidence for two common precursors to corticotropins, endorphins, and melanotropin in the neurointermediate lobe of the toad pituitary.
Authors: Loh Y P
Published: May 2006

The biosynthesis of corticotropin (ACTH1--39), beta-endorphin [beta(61--91)-lipotropin] and alpha-melanotropin in the toad intermediate lobe was studied by using immunoprecipitation procedures with antisera specific for these peptides. Intermediate lobes were pulse-incubated with [3H]phenylalanine and then chase-incubated for varying periods; the radioactive proteins were immunoprecipitated. Immunoprecipitates were separated by acidic urea or sodium dodecyl sulfate polyacrylamide gel electrophoresis. Evidence from the pulse-chase and sequential immunoprecipitation studies using antisera to ACTH and beta-endorphin suggests that the toad intermediate lobe synthesizes two common precursors (apparent Mr 32,000 and 29,500) containing both the ACTH and beta-endorphin sequences. These precursors are processed to yield several forms of immunoreactive corticotropin (apparent Mr 23,000, 21,000, 13,000, and 4300), immunoreactive endorphin (apparent Mr 11,700 and 3500), and immunoreactive alpha-melanotropin. The 4300 Mr form of corticotropin and the 11,700 and 3500 Mr forms of endorphins were found to comigrate with synthetic ACTH1--39, beta-lipotropin and beta-endorphin, respectively, on both acidic urea and sodium dodecyl sulfate gels.
Change in nuclear potassium electrochemical activity and puffing of potassium-sensitive salivary chromosome regions during Chironomus development.
Authors: Wuhrmann P , Ineichen H , Riesen-Willi U , Lezzi M
Published: May 2006

Changes in nuclear K+ electrochemical activity and total nuclear K+ content in salivary glands of Chironomus tentans were measured with ion-selective microelectrodes based on valinomycin and with flameless atomic absorption spectrometry, respectively. The K+ activity increased by a factor of 2.6 and the total K+, by a factor of 1.5 as oligopausing larvae developed into prepupae. The extent of decondensation (puffing) of K+-sensitive regions in the polytene chromosomes underwent a parallel increase during this developmental event. In vitro culture of glands from oligopausing larvae resulted in similar changes with respect to nuclear K+ activity and puffing.
Phosphorylation of subunit proteins of intermediate filaments from chicken muscle and nonmuscle cells
Authors: O'Connor Clare M. , Balzer David R. , Lazarides Elias
Published: May 2006

The phosphorylation of the subunit proteins of intermediate (10-nm) filaments has been investigated in chicken muscle and nonmuscle cells by using a two-dimensional gel electrophoresis system. Desmin, the 50,000-dalton subunit protein of the intermediate filaments of muscle, had previously been shown to exist as two major isoelectric variants—α and β—in smooth, skeletal, and cardiac chicken muscle. Incubation of skeletal and smooth muscle tissue with
32
PO
4
3-
reveals that the acidic variant, α-desmin, and three other desmin variants are phosphorylated
in vivo
and
in vitro
. Under the same conditions, minor components of α- and β-tropomyosin from skeletal muscle, but not smooth muscle, are also phosphorylated. Both the phosphorylated desmin variants and the nonphosphorylated β-desmin variant remain insoluble under conditions that solubilize actin and myosin filaments, but leave Z-discs and intermediate filaments insoluble. Primary cultures of embryonic chicken muscle labeled with
32
PO
4
3-
possess, in addition to the desmin variants described above, a major nonphosphorylated and multiple phosphorylated variants of the 52,000-dalton, fibroblast-type intermediate filament protein (IFP). Filamentous cytoskeletons, prepared from primary myogenic cultures by Triton X-100 extraction, contain actin and all of the phosphorylated and nonphosphorylated variants of both desmin and the IFP. Similarly, these proteins are the major components of the caps of aggregated 10-nm filaments isolated from the same cell cultures previously exposed to Colcemid. These results demonstrate that a nonphosphorylated and several phosphorylated variants of desmin and IFP are present in assembled structures in muscle and nonmuscle cells.
Purine excretion by mouse peritoneal macrophages lacking adenosine deaminase activity.
Authors: Chan T S
Published: May 2006

Deoxyadenosine, a cytotoxic purine nucleoside, is excreted in large amounts by patients with severe combined immunodeficiency disease associated with deficiency of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4). To identify the source of the purine nucleoside, purine excretion by macrophages was studied by using mouse peritoneal macrophages as an experimental model system. Normally, macrophages excrete a large quantity of uric acid into the culture medium. However, in the presence of deoxycoformycin, a potent inhibitor of adenosine deaminase, these macrophages also excreted deoxyadenosine. Furthermore, phagocytosis of nucleated erythrocytes augmented the excretion of deoxyadenosine. Macrophages are involved in the phagocytosis of nuclei that are extruded from normoblasts during erythropoiesis and also of senescent cells in lymphoid organs. A hypothesis is proposed that macrophages of the reticuloendothelial system are a source of deoxyadenosine, which is one of the two cytotoxic purine nucleosides (the other is adenosine) apparently responsible for the suppression of immune functions in patients with adenosine deaminase deficiency.
Nonlinear systems analysis: comparison of white noise and sum of sinusoids in a biological system.
Authors: Victor J D
Published: May 2006

The Gaussian white noise and the sum-of-sinusoids methods of systems analysis provide equivalent descriptions of nearly linear and strongly nonlinear transductions in the cat retina. Smoothness in the frequency domain is a common characteristic of biological transductions. This permits a substantial improvement in the signal-to-noise ratio by using the sum-of-sinusoids method, as is demonstrated for the transductions of the cat retina.
Interaction of Escherichia coli ribosomal protein S1 with ribosomes.
Authors: Draper D E , von Hippel P H
Published: May 2006

The binding affinity of Escherichia coli ribosomal protein S1 for 30S ribosomal particles has been determined by a sucrose gradient band sedimentation technique; the association constant (K) for the binding of one S1 protein per active 30S ribosomal subunit is approximately 2 X 10(8) M-1. The involvement of the two polynucleotide binding sites of S1 protein (site I binding single-stranded DNA or RNA, and site II binding single-stranded RNA only) in the S1--ribosomal interaction have been examined by competition experiments with polynucleotides of known affinity for the two sites. We find that site I does not contribute to the interaction; site II binding appears to provide a major part of the binding free energy, presumably by interaction of S1 with the 16S rRNA of the 30S particle. The remaining binding free energy is probably derived from the interaction of S1 protein with other proteins of the 30S subunit. The affinity of S1 for 70S ribosomes is about the same as that for the 30S subunit; the affinity of S1 for 50S subunits is much less. Binding affinities and stoichiometries of S1 protein with "inactive" 30S ribosomal subunits have also been examined.
Structure of the A2m(1) allotype of human IgA—a recombinant molecule
Authors: Tsuzukida Yasuharu , Wang Chi-Chin , Putnam Frank W.
Published: May 2006

The complete amino-acid sequence of the constant (C) region of the α2 heavy chain of a human IgA2 protein of the A2m(1) allotype has been determined. Excluding the hinge region and the carbohydrate content, this α2 allotype differs from the α1 chain in only 14 amino-acid positions; all of these are identical to the A2m(2) allotype of the α2 chain and confer subclass (or isotypic) character on the α2 chains. However, the A2m(2) allotype differs in six positions where A2m(1) and α1 are identical; the first two are just before the hinge and the other four are in the last (C
H
3) domain. The A2m allotypic character of α2 chains is attributed to several conformational factors in the sequence at positions 211-221, just before the hinge. The isoallotypic determinant shared by α1 chains and the A2m(1) allotype of α2 resides in the identity of their C
H
3 domains. Thus, the A2m(1) allotype appears to be a hybrid chain that is identical with α1 in the C
H
3 domain and identical with the A2m(2) α2 chain in the C
H
1 and C
H
2 domains and in the hinge, except for the allotypic determinants arising from four structural differences from residues 211-221. The genetic origin of isotypes, allotypes, and isoallotypes of the α chain has involved several events of homologous crossing over and neutral point mutations accumulated late in the evolutionary development of IgA immunoglobulins. Since the crossing over appears to occur between C
H
2 and C
H
3, heavy chain domains may be coded for by independent units in embryonic DNA that are analogous to the variable (V) and C segments of light-chain genes.
Adenylate cyclase and acetylcholine release regulated by separate serotonin receptors of somatic cell hybrids.
Authors: MacDermot J , Higashida H , Wilson S P , Matsuzawa H , Minna J , Nirenberg M
Published: May 2006

Serotonin activates adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] of NCB-20 neuroblastoma--brain hybrid cells with an activation constant of 530 nM, but has little or no effect on cellular cyclic AMP or cyclic GMP content of NIE-115 neuroblastoma or NG108-15 hybrid cells. In homogenates of NCB-20 hybrid cells, lysergic acid diethylamide stimulates adenylate cyclase activity (Kact = 12 nM) and partially inhibits (Ki = 10 nM) the stimulation of adenylate cyclase activity by serotonin. No desensitization was detected of serotonin receptors coupled to adenylate cyclase. Serotonin also depolarizes NCB-20, NG108-15, and NIE-115 cells and increases acetylcholine release. Serotonin receptors mediating depolarizing responses desensitize rapidly and reversibly, and the depolarizing effects of serotonin are neither mimicked nor inhibited by lysergic acid diethylamide. These results indicate that (i) NCB-20 cells possess at least two species of serotonin receptors, which independently regulate cellular functions, (ii) activation of adenylate cyclase does not directly affect membrane potential or acetylcholine release, and (iii) serotonin-dependent cell depolarization does not affect cyclic AMP or cyclic GMP synthesis in the cell lines tested.
Models of fibrin.
Authors: Hermans J
Published: May 2006

High-symmetry models of the fibrin fiber are proposed that reproduce the experimentally observed high specific volume of the fiber. The models meet the following criteria: fibrin monomers have the three-domain Hall and Slayter structure; the monomers are arranged lengthwise into strands (protofibrils) in which successive monomers half overlap; the monomers' alignment is nearly parallel to the fiber axis; and the monomers make adequate longitudinal and lateral contacts, as required by observed fiber properties and the high affinity of monomers for one another. All the models contain helical protofibrils related to each other by rotation axes parallel to the fiber axis; as a consequence the protofibrils are in register in the fiber direction. The protofibrils may contain two, three, or four monomers per helical turn and can be packed in four different symmetries (space groups). A large specific volume is achieved only if the D-domain (which are presumed to contain the lateral polymerization sites) are somewhat displaced from the helical axes of the protofibrils. This displacement may involve either a lateral shift of the monomers away from the helix axis or a tilt of the monomers, which swings the D-domains away from the helix axis. It is shown that the fiber containing tilted monomers is more highly interconnected; the two D-domains of each tilted monomer form lateral contacts with different adjacent protofibrils, whereas the two D-domains of each nontilted monomer contact the same adjacent protofibril(s).
Glycosylation of human chorionic gonadotropin in mRNA-dependent cell-free extracts: Post-translational processing of an asparagine-linked mannose-rich oligosaccharide
Authors: Bielinska Malgorzata , Boime Irving
Published: May 2006

Placental RNA has previously been shown to direct the synthesis of an asparagine-linked mannose-rich glycosylated form of the α subunit of human chorionic gonadotropin (hCG-α) in lysates derived from mouse ascites tumor cells. Glycosylation was dependent on the presence of homologous microsomal membranes, and the glycosylated protein was sequestered into the microsomal vesicles. Here we show that when Triton X-100 is added after 60 min of translation and the incubation is continued, there is a shift of this glycosylated form to new discrete lower molecular weight proteins. The formation of these new proteins was not the apparent result of proteolysis because (
i
) treatment of the fully glycosylated protein or the proteins formed in the presence of Triton with endoglycosidase H resulted in the formation of a single protein migrating at the same rate on sodium dodecyl sulfate gels; (
ii
) the migration of nonglycosylated hCG-α synthesized in the presence of membranes isolated from tunicamycin-pretreated ascites tumor cells was not changed upon Triton addition; and (
iii
) the Triton-induced change was inhibited by mannonolactone, yeast mannan, and purified mannose oligosaccharides. It was also shown that little processing of the mannose-rich glycoprotein occurred in the presence of microsomal membranes alone. However, addition of the ribosome-free supernatant fraction to the glycoprotein resulted in processing. These data suggest that processing of the oligosaccharide core is a compartmentalized process in which removal of sugar, presumably mannose, requires a transfer of the glycoprotein from the endoplasmic reticulum to another component of the secretory cascade.
Large electrical currents traverse developing Ceropia follicles
Authors: Jaffe Linoel F. , Woodruff Richard I.
Published: May 2006

An intense (up to 20 μA/cm
2
) steady electrical current enters the anterior or nurse cell end of the growing follicle (or oocyte—nurse cell complex) of the Cecropia moth and is balanced by a more diffuse current leaving elsewhere. In late growth stages, the total transfollicular current is about 100 nA. Moreover, a separate small current, of about 1 nA, seems to leave the furrow between the oocyte and the nurse cells. After the nurse cells collapse, but before shell formation, the transfollicular current is redistributed so that a second relatively localized inward current appears at the posterior pole of the follicle. Thus, at this later stage currents enter both poles of the follicle and leave its sides. Previous measurements, with intracellular microelectrodes, seem to imply a very large (order of 1000 nA) back current across the cytoplasmic bridge between the oocyte and nurse cells. A simple model is presented that attributes the apparent bridge current, and the more directly measured transfollicular and furrow currents, to the action of an ion pump lying within the nurse cell face of the furrow membrane.
Mutations in nine chloroplast loci of Chlamydomonas affecting different photosynthetic functions.
Authors: Shepherd H S , Boynton J E , Gillham N W
Published: May 2006

Chloroplast components known to be coded by chloroplast DNA include chloroplast rRNAs, tRNAs, and the large subunit of ribulose-bisphosphate carboxylase. Because these components comprise less than 3% of the estimated coding capacity of the chloroplast genome, most chloroplast gene functions have yet to be identified. One approach to this problem is the isolation and characterization of mutations in the chloroplast genome affecting specific photosynthetic functions. Recently we have found that such mutations can be preferentially recovered by using arsenate selection on cells previously grown in 5-fluorodeoxyuridine. Sixteen mutants thus isolated have been localized into nine chloroplast loci, based on their ability to recombine and produce photosynthetically competent progeny. Mutants at two loci show the characteristic syndrome of photosynthetic defects that results from a deficiency in chloroplast protein synthesis. These have been found to lack chloroplast ribosome monomers. Mutants at three loci are missing chlorophyll-protein complex I in their thylakoid membranes. Mutants at three other loci are deficient in membrane polypeptides known to be associated with the chloroplast coupling factor.
Immunological tolerance to allergenic protein determinants: a therapeutic approach for selective inhibition of IgE antibody production.
Authors: Liu F T , Katz D H
Published: May 2006

Administration of stable conjugates prepared by coupling protein antigens such as ovalbumin or antigen E of ragweed extract to the synthetic random copolymer of D-glutamic acid and D-lysine (D-GL) is effective in inducing a state of long-lasting, antigen-specific immunological tolerance in experimental animals. A striking aspect of the tolerance induced by protein-D-GL conjugates is the remarkable selectivity of the tolerance for antibody responses of the IgE class. Protein-D-GL conjugates of either type were capable of inducing such tolerance both in unsensitized and in previously sensitized animals when administered in appropriate doses. Comparable doses of unconjugated proteins were likewise capable of suppressing IgE antibody production, although the duration of suppression in these cases was significantly less than that observed with protein-D-GL conjugates. If such conjugates act in man as they do in experimental animals, they could be of great value as therapeutic agents in selectively diminishing IgE antibody production while sparing antibody production in the IgG class.
In vitro transformation of mouse bone marrow cells by the polycythemic strain of Friend leukemia virus.
Authors: Revoltella R , Bertolini L , Friend C
Published: May 2006

Strains of Friend leukemia virus (FLV) that are associated with polycythemia contain the defective spleen focus-forming virus (SFFV). To determine whether the transforming ability of FLV was affected by the presence of this second agent, DBA/2J mouse bone marrow cells were infected in vitro. Criteria for transformation were the establishment of permanent lines, growth on semisolid agarose, and the production of tumors at the site of inoculation in syngeneic hosts. Two lines of immature hematopoietic cells that grow in suspension originated from the infected cultures. Each has an almost diploid karyotype (38-39 chromosomes) and 3-4 metacentric chromosomes. These transformed cells express gp71 viral envelope glycoprotein and p30 viral core protein antigens. Virus production was measured by reverse transcriptase (RNA-dependent DNA polymerase) activity of the virions released into the medium. The virus, assayed in vivo for infectivity, has SFFV activity but is attenuated for leukemogenicity. The stimulation of hemoglobin synthesis in the cells grown in medium supplemented with dimethyl sulfoxide or hexamethylene bisacetamide indicates that the cells are erythroid in origin. SFFV may have a function analogous to erythropoietin in influencing the process of transformation by FLV.
Blow-up of solutions of nonlinear wave equations in three space dimensions
Authors: John Fritz
Published: May 2006

Solutions
u(x, t)
of the inequality □
u
≥
A
|
u
|

p

for
x
ε R
3
,
t
≥ 0 are considered, where □ is the d'Alembertian, and
A,p
are constants with
A
> 0, 1 <
p
< 1 + √2. It is shown that the support of
u
is compact and contained in the cone 0 ≤
t
≤
t
0
-|
x - x
0
|, if the “initial data”
u(x
, 0),

u
t
(x

, 0) have their support in the ball|
x - x
0
| ≤
t
0
. In particular, “global” solutions of □
u = A
|
u
|

p

with initial data of compact support vanish identically. On the other hand, for
A
> 0,
p
> 1 + √2, global solutions of □
u = A
|
u
|

p

exist, if the initial data are of compact support and “sufficiently” small.
Evolution of olfactory receptor in oriental fruit fly
Dacus dorsalis
Authors: Metcalf Robert L. , Metcalf Esther R. , Mitchell W. C. , Lee Lena W. Y.
Published: May 2006

Male oriental fruit flies (
Dacus dorsalis
) from colonies in Taiwan and Hawaii were evaluated for limit of response to various analogues of methyl eugenol. The results are interpreted in terms of the geometry and allosteric requirements of the antennal receptor that triggers the characteristic methyl eugenol reflex. This receptor has evolved for complementarity to all portions of the methyl eugenol molecule and responds only to
ortho
-substituted benzenes with adjacent oxygen atoms or isoelectronic equivalents. Substantial differences in responses of Taiwan and Hawaiian
D. dorsalis
suggest that perceptible evolution of the receptor protein has occurred during the past 50 years. A plausible scheme for the coevolution of dacini flies with plants containing phenylpropionoid essential oils is outlined.
Protection and reactivation of oxidative phosphorylation in mitochondria by a stable free-radical prostaglandin polymer (PGBx).
Authors: Polis B D , Polis E , Kwong S
Published: May 2006

A stable free-radical polymeric derivative of prostaglandin B1 (PGBx) has been synthesized that exhibits regenerative effects on oxidative phosphorylation in aged mitochondria. The molecular weights of the most active preparations fall between 2000 and 2600. PGBx is characterized by a single-line electron spin resonance spectrum that is stable at room temperature. PGBx restores phosphorylating ability and net ATP synthesis in isolated mitochondria aged for 4 days at 0 degrees C and protects against further degradation of phosphorylating activity when such aged mitochondria are preincubated at 28 degrees C in the absence of adenine nucleotide phosphate acceptors. This compound has been reported to exert beneficial effects in vivo in experimental pathological conditions, such as regional ischemia, in which the mitochondria of the ischemic region may have been damaged.
Purified Escherichia coli recA protein catalyzes homologous pairing of superhelical DNA and single-stranded fragments.
Authors: Shibata T , DasGupta C , Cunningham R P , Radding C M
Published: May 2006

Purified Escherichia coli recA protein catalyzed ATP-dependent pairing of superhelical DNA and homologous single-stranded fragments. The product of the reaction: (i) was retained by nitrocellulose filters in 1.5 M NaCl/0.15 M Na citrate at pH 7, (ii) was dissociated at pH 12.3 but was not dissociated by heating at 55 degrees C for 4 min or by treatment with 0.2% sodium dodecyl sulfate and proteinase K, (iii) contained covalently closed circular double-stranded DNA (form I DNA), (iv) contained single-stranded fragments associated with replicative form (RF) DNA, and (v) contained a significant fraction of D-loops as judged by electron microscopy. Linear and nicked circular double-stranded DNA did not substitute well for superhelical DNA; intact circular single-stranded DNA did not substitute well for single-stranded fragments. Homologous combinations of single-stranded fragments and superhelical DNA from phages phiX174 and fd reacted, whereas heterologous combinations did not. The reaction required high concentrations of protein and MgCl2. The ATPase activity of purified recA protein was more than 98% dependent on the addition of single-stranded DNA. In 1 mM MgCl2, the ability of superhelical DNA to support the ATPase activity was two-thirds as good as that of single-stranded DNA.
Presence of chondroitin sulfate in the neuronal cytoplasm.
Authors: Margolis R K , Thomas M D , Crockett C P , Margolis R U
Published: May 2006

The distribution of glycosaminoglycans and glycoproteins has been studied in cytoplasmic and particulate fractions of neurons isolated in bulk from rat cerebrum. Lysis of the neurons in 25 mM sodium phosphate buffer at pH 7.5 released 20% of the protein and over 90% of the lactate dehydrogenase in a soluble form. Eighty-two percent of the chondroitin sulfate was also released, together with 55% of the heparan sulfate and 24-25% of the hyaluronic acid and glycoproteins. The chondroitin sulfate remaining in the membranes was completely depolymerized to disaccharides after treatment with chondroitinase ABC, and treatment of the neuronal membranes with 0.1% trypsin removed 55-63% of the chondroitin sulfate and heparan sulfate but only 25% of the sulfated glycoproteins. The results reported here support our previous conclusion that the soluble chondroitin sulfate proteoglycan of brain is largely a cytoplasmic constitutent of neurons (and astrocytes) and is not primarily present in nervous tissue as an extracellular ground substance.
Interactions of a photosensitive analog of cholesterol with hydroxymethylglutaryl-CoA reductase (NADPH) and acyl-CoA:cholesterol acyltransferase
Authors: Heller Renu A. , Klotzbücher Rainer , Stoffel Wilhelm
Published: May 2006

25-Azido[25-
3
H]norcholesten-3β-ol, a radioactive photosensitive analog of cholesterol, was synthesized as a probe to study lipid-protein interactions [Stoffel, W. & Klotzbücher, R. (1978)
Hoppe-Seyler's Z. Physiol Chem.
359, 199-209]. Upon UV irradiation a reactive nitrene is generated which can insert into carbon-hydrogen bonds of proteins to form covalent linkages. The compound has properties similar to those of cholesterol. When administered intravenously to rats it was transported to the liver, and within 4 hr it was found in all of the subcellular fractions, accounting for 8% of the microsomal sterol content. Concomitantly, it altered the activities of two membrane-bound enzymes. 3-Hydroxy-3-methylglutaryl (HMG)-CoA (NADPH) reductase [mevalonate:NADP
+
oxidoreductase (CoA-acylating), EC 1.1.1.34] activity was reduced to 20% of control values, and acyl-CoA:cholesterol acyltransferase (ACAT; acyl-CoA:cholesterol
O
-acyltransferase, EC 2.3.1.26) was stimulated at least 2-fold. Esterified products of the analog were found in both blood and liver, and no evidence was obtained for production of any hydroxylated or polar derivatives. UV irradiation of microsomes increased the radioactivity bound to the protein fraction and decreased it in the total lipid extract; in parallel a sharp decline in ACAT activity but unaltered HMG-CoA reductase activity was observed. These results are interpreted as a possible consequence of crosslinking of the sterol to the enzyme proteins and discussed in view of the evidence that HMG-CoA reductase is an extrinsic and ACAT an intrinsic membrane protein.
Positive control of
lac
operon expression in
vitro
by guanosine 5′-diphosphate 3′-diphosphate
Authors: Primakoff Paul , Artz Stanley W.
Published: May 2006

Maximal expression of the
Escherichia coli
lactose operon in a coupled
in vitro
transcription-translation system from a
Salmonella typhimurium relA
mutant was strongly dependent upon addition of guanosine 5′-diphosphate 3′-diphosphate (ppGpp). Without added ppGpp, at saturating 3′,5′-cyclic AMP (cAMP) concentrations, synthesis of β-galactosidase (β-D-galactoside galactohydrolase, EC 3.2.1.23) was reproducibly only 5-7% of that which can be obtained with 0.5-0.8 mM ppGpp. Experiments in which transcription was uncoupled from translation indicated that this 14- to 20-fold stimulation by ppGpp occurred at the level of transcription. When coupled β-galactosidase synthesis was primed with a template containing a well-characterized mutant
lac
promoter (
lacP
r
L8UV5), the dependence on ppGpp was greatly reduced. This result provides an important experimental control previously unavailable for verifying the significance of ppGpp effects on gene regulation
in vitro
; it indicates that activation of
lacP
+
expression by ppGpp is specifically an effect of increased transcription initiations. Furthermore, the large ppGpp stimulation of
lacP
+
DNA enabled the level of expression of this template to approach that of
lacP
r
L8UV5 DNA, an observation expected from results
in vivo
but not obtained with other transcription-translation systems
in vitro
. The importance of these results is considered with respect to previous ideas on the physiological role of ppGpp as a supercontrol molecule in bacterial regulation.
Ultrasonic absorption evidence of structural fluctuations in viral capsids.
Authors: Cerf R , Michels B , Schulz J A , Witz J , Pfeiffer P , Hirth L
Published: May 2006

When the coat protein of the small icosahedral virus, brome mosaic virus, reassembles into capsids, the ultrasonic absorption of the solution greatly increases. Submitting the solution to an ultrasonic field thus appears to reveal spontaneous molecular motions within a protein assembly. Confirmatory evidence of a dynamics of a protein shell comes from measurements on brome mosaic virus at various degrees of swelling and on tomato bushy stunt virus treated with the crosslinking agent glutaraldehyde. The detected fluctuations may be related either with cooperative deformational motion in the capsid or with more localized structural changes. Such structural changes may help liberate the RNA at an early stage of viral infection.
Construction of an artificial blood vessel wall from cultured endothelial and smooth muscle cells.
Authors: Jones P A
Published: May 2006

Cloned bovine endothelial cells were grown on a preformed layer of cultured rat smooth muscle cells that contained large amounts of connective tissue proteins. The successful growth of the endothelial cells was dependent upon the addition of more than 2.5 x 10(4) cells per cm2, and the final density reached was approximately 2.5 times higher than that obtained for the same cells growing on plastic. The endothelial cells anchored more firmly to the smooth muscle cells than to plastic, and electron microscopy showed the existence of an irregular, dense, basal lamina-like structure between the two cell types. Biochemical analysis of the lamina produced by the endothelial cells in isolation demonstrated the presence of collagen and two fucosylated glycoproteins. The structure produced, which has some of the characteristics of a blood vessel wall, was stable for several months in culture and has many potential applications.
Vaccinia virus replication requires active participation of the host cell transcriptional apparatus.
Authors: Hruby D E , Lynn D L , Kates J R
Published: May 2006

The ability of vaccinia virus to replicate in BSC-40 monkey cells whose nuclei have been functionally inactivated was examined. Exposure of cell monolayers to ultraviolet radiation at doses that did not alter the cells' capacity to support a subsequent infection by a cytoplasmic virus (vesicular stomatitis virus) caused a reduction to less than 10% in the observed yield of infectious progeny from vaccinia virus and herpes simplex virus (type 1) infections. Similarly, replication of vaccinia virus was reduced to 5% by treatment of BCS-40 cells with alpha-amanitin (10 microgram/ml), a potent inhibitor of nuclear mRNA synthesis. In both situations, ultraviolet irradiation and alpha-amanitin treatment, early and late vaccinia viral genes were expressed at high levels, but the newly synthesized virion components were not assembled into mature infectious particles. Taken together, these data suggest that the active involvement of the host cell nuclear transcriptive system is obligatory in the vaccinia virus replicative cycle.
Inhibitory spectrum of alpha 2-plasmin inhibitor.
Authors: Saito H , Goldsmith G H , Moroi M , Aoki N
Published: May 2006

alpha 2-Plasmin inhibitor (alpha 2PI) has been recently characterized as a fast-reacting inhibitor of plasmin in human plasma and appears to play an important role in the regulation of fibrinolysis in vivo. We have studied the effect of purified alpha 2PI upon various proteases participating in human blood coagulation and kinin generation. At physiological concentration (50 microgram/ml), alpha 2PI inhibited the clot-promoting and prekallikrein-activating activity of Hageman factor fragments, the amidolytic, kininogenase, and clot-promoting activities of plasma kallikrein, and the clot-promoting properties of activated plasma thromboplastin antecedent (PTA, Factor XIa) and thrombin. alpha 2PI had minimal inhibitory effect on surface-bound activated PTA and activated Stuart factor (Factor Xa). alpha 2PI did not inhibit the activity of activated Christmas factor (Factor IXa) or urinary kallikrein. Heparin (1.5-2.0 units/ml) did not enhance the inhibitory function of alpha 2PI. These results suggest that, like other plasma protease inhibitors, alpha 2PI possesses a broad in vitro spectrum of inhibitory properties.
Measles and subacute sclerosing panencephalitis virus proteins: lack of antibodies to the M protein in patients with subacute sclerosing panencephalitis.
Authors: Hall W W , Lamb R A , Choppin P W
Published: May 2006

Studies on the immunoprecipitation of the proteins of several different measles and subacute sclerosing panencephalitis (SSPE) virus strains from lysates of infected cells have revealed a relative lack of antibodies to the nonglycosylated viral membrane protein (M) in the sera of patients with SSPE, in contrast to a high level of antibodies to other viral proteins. No evidence was found for the existence of a large number of antigenically unique M proteins. In contrast to SSPE sera, other hyperimmune human or rabbit sera precipitated M protein as well as the other viral proteins. The results suggest that in patients with SSPE there is either diminished synthesis of M, or it is not recognized normally by the immune system, and that an abnormality in M protein is involved in the pathogenesis of SSPE. Although differences in electrophoretic mobility of the M proteins and several other viral proteins were observed among different SSPE and measles strains, there was no pattern characteristic of SSPE strains, nor could these strains be distinguished by peptide mapping.
Release of catecholamines from perfused cat adrenal gland by veratridine.
Authors: Kirpekar S M , Prat J C
Published: May 2006

Experiments were undertaken to verify the existence of fast sodium channels in the adrenal chromaffin cell membrane and to assess their contribution to the physiological release of catecholamines. We have used veratridine to activate sodium channels. Veratridine causes secretion of catecholamines from perfused cat adrenal gland. Secretory response to veratridine is calcium dependent and abolished by tetrodotoxin. Secretion of catecholamines by acetylcholine is only partially blocked by tetrodotoxin. It is concluded that the adrenal chromaffin cell membrane contains fast sodium channels directly comparable to those of impulse-propagating neurons, but they do not appear to be essential in the secretory response to acetylcholine or splanchnic nerve stimulation.
Codon-anticodon interaction at the ribosomal P (peptidyl-tRNA) site
Authors: Wurmbach Peter , Nierhaus Knud H.
Published: May 2006

A method for binding tRNA to ribosomes, introduced by Watanabe [Watanabe, S. (1972)
J. Mol. Biol.
67, 443-457], permits nonenzymatic binding of
N
-acetyl-Phe-tRNA
Phe
to either the ribosomal aminoacyl-tRNA (A) or peptidyl-tRNA (P) site with almost 100% specificity. We used this method to analyze a possible codon-anticodon interaction at the P site for NH
2
-blocked aminoacyl-tRNA and deacylated tRNA.
N
-Acetyl-Phe-tRNA
Phe
bound only to the P site of poly(U)-programmed 70S ribosomes, not to poly(A)-programmed ribosomes. The reverse mRNA dependence was found for
N
-acetyl-Lys-tRNA
Lys
. A series of purified deacylated tRNAs was analyzed in the poly(U) and poly(A) system for abilities to block P-site binding of
N
-acetyl-aminoacyl-tRNA and to direct the
N
-acetyl-aminoacyl-tRNA to the A site. Only the cognate tRNA was as effective as the bulk tRNA at a concentration of less than 1/20th that of bulk tRNA. tRNAs whose corresponding codons are identical or similar (same base character) in the first two codon positions showed a low but significant effect. The other noncognate tRNAs were unable to direct the NH
2
-blocked aminoacyl-tRNAs to the A site. Chlortetracycline interfered neither with the P-site binding of NH
2
-blocked aminoacyl-tRNA nor with the effects of deacylated tRNAs. Furthermore, the translocation blocker viomycin affected neither the binding to the A site nor that to the P site. These effects of both antibiotics indicate that both kinds of tRNA do not bind transiently in the A site before filling the P site and that codon-anticodon interaction takes place at the P site.
Structure-independent nucleotide sequence analysis.
Authors: Mills D R , Kramer F R
Published: May 2006

Substitution of inosine for granosine in the nucleic acid fragments synthesized for the sequencing of RNA effectively prevents the formation of secondary structures during electrophoretic analysis. Consequently, the mobility of each fragment in the sequencing gel is a strict function of its molecular weight. Inosine substitution should markedly improve the resolution that can be obtained in the sequencing of DNA as well as RNA.
Macrophage response to concanavalin A: effect of surface crosslinking on the electrophoretic mobility distribution.
Authors: Petty H R , Ware B R
Published: May 2006

Electrophoretic light scattering (laser Doppler electrophoresis) has been employed to study the effects of concanavalin A (Con A) and succinyl-Con A on the electrophoretic mobility distribution of resident guinea pig peritoneal macrophages. Con A, a tetrameric lectin, decreases slightly the mean mobility and increases by approximately 3-fold the width of the electrophoretic mobility distribution of resident macrophages. This effect can be abolished by alpha-methyl-D-mannoside, a hapten sugar of Con A. These effects were present in both low (0.010 M) and high (physiological, 0.15 M) ionic-strength media. Since lower ionic strengths correspond to a larger Debye screening distance, these data suggest that the alterations in the electrophoretic mobility distribution are not restricted to the outer portion of the glycocalyx. Succinyl-Con A, a dimeric derivative, was found to have no effect on the mobility distribution. However, the mean mobility decreased and the width increased over 4-fold when succinyl-Con A-treated macrophages were exposed to anti-Con A. These observations indicate that cross-linking of Con A receptors is an important process in the electrokinetic alterations of the macrophage surface. These results may have important consequences for the elucidation of the details of the endocytic mechanism.
Tabanomyces milkoi
(Dudka and Koval) emended,
genus novum
, a fungal pathogen of horseflies
Authors: Couch J. N. , Andreeva R. V. , Laird M. , Nolan R. A.
Published: May 2006

A fungus originally described as a new species of
Coelomomyces
(
C. milkoi
) from larval Tabanidae in the Ukraine, USSR, is transferred to a new genus,
Tabanomyces
, and described in detail. The zygospores germinate to form a linear four-celled conidiophore, each cell producing a spherical conidium ejected as in
Conidiobolus
, thus confirming that the organism belongs in the Entomophthorales. The resemblance between the conidiophore of
Tabanomyces milkoi
and the basidium of the rusts supports the old concept that the rust fungi may be related to the Entomophthorales.
Interaction of the cheC and cheZ gene products is required for chemotactic behavior in Escherichia coli.
Authors: Parkinson J S , Parker S R
Published: May 2006

Previous work has shown that the cheC gene product of Escherichia coli plays a key role in regulating the direction of flagellar rotation during chemotactic responses. An attempt was made to identify other stimulus transduction elements that interact with the cheC component by examining cheC revertants for functional suppressors. Approximately two-thirds of the revertants studied appeared to be due to back mutation or to second-site mutations near or within the cheC structural gene. The remainder of the revertants carried suppressor mutations that mapped at the cheZ locus. Half of these suppressors impaired chemotaxis in a cheC+ background and were shown by complementation analysis to be defective in cheZ function. These suppressors corrected cheC defects in an allele-specific pattern, suggesting that the cheC and cheZ proteins are in direct contact and are mutually corrective due to protein-protein interaction. Observation of swimming patterns and flagellar rotation in cheC cheZ mutants demonstrated that the interaction of these two gene products influences both the spontaneous frequency of flagellar reversals and the ability of the rotational machinery to respond to chemotactic stimuli. A model of this interaction and its possible role in chemotaxis are discussed.