bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic Membrane Changes in Animal Cells: Transformed Cells Permanently Display a Surface Architecture Detected in Normal Cells Only during Mitosis
Authors: Fox Thomas O. , Sheppard John R. , Burger Max M. 
Published: May 2006

A membrane site exposed only during mitosis in normal 3T3 cells, but exposed in all polyomavirus transformed 3T3 (Py3T3) cells, has been detected The site was identified by the specific binding of a wheat-germ agglutinin conjugated with fluorescein isothiocyanate.
The receptor site has been studied previously. It binds wheat-germ agglutinin, causing the selective agglutination of Py3T3 cells, but not normal 3T3 cells. A short treatment with low concentrations of trypsin exposes cryptic sites in 3T3 cell membranes; this permits agglutination of these cells. The experiments reported here indicate that these sites normally are exposed during a brief period of the cell cycle for 3T3 cells. Specific hapten inhibitors of agglutination also inhibit the binding of the conjugated agglutinin and prevent fluorescence.
Glycolipid Synthesis in Normal and Virus-Transformed Hamster Cell Lines
Authors: Sakiyama Hisako , Gross Sonja K. , Robbins Phillips W. 
Published: May 2006

Studies have been continued on the synthesis of glycolipids by the NIL 2 line of hamster cells. Several clones were isolated from this line. These clones vary in morphology, saturation density, and glycolipid composition. Contrary to expectation there was no correlation between saturation density and complexity of the glycolipid pattern. In fact, the clone with the highest saturation density was the only one to show the complete set of glycolipids found previously in NIL 2 cells.
All untransformed NIL clones show an increase in the level of “higher” (more than two saccharides/ceramide) glycolipids as the cells approach confluence. In the line containing all three “higher” neutral glycolipids, all three increased as cells approached saturation density. In the line containing only hematoside, this compound increased at confluence. Cells transformed by hamster sarcoma virus or polyoma virus showed no density-dependent glycolipid synthesis.
Oxidation-Reduction Potentials of Bound Iron-Sulfur Proteins of Photosystem I
Authors: Ke Bacon , Hansen Raymond E. , Beinert Helmut 
Published: May 2006

Digitonin - fractionated photosystem - I subchloroplasts were titrated potentiometrically between -450 and -610 mV at pH 10. Examination of the titrated subchloroplasts by low-temperature (13°K) electron paramagnetic resonance spectroscopy revealed resonances centered at values of 2.05, 1.94, 1.92, 1.89, and 1.86 on the
g
-factor scale. The peak heights depended on the potentials at which the chloroplasts were poised. The resonances of at least three iron-sulfur centers can be recognized: one with lines at
g
= 2.05 and 1.94; one with lines at
g
= 2.05, 1.92, and 1.89; and one for which only a line at
g
= 1.86 has been resolved. The midpoint potentials of the iron-sulfur species fall into two distinctly separate regions: the titration profile of the
g
= 1.94 signal, the first segment of the
g
= 2.05 plot, and the rise phase of the
g
= 1.86 signal had a value of -530 ± 5 mV; the upper segment of the
g
= 2.05 plot, the decrease phase of the
g
= 1.86 signal, and the
g
= 1.89 profile had a midpoint potential estimated to be [unk] -580 mV. The oxidation-reduction reaction of each of the bound iron-sulfur species, as represented by the changes of the electron paramagnetic resonance spectra, was reversible and apparently involved a two-electron change.

Titration at pH 9 could only be carried to -560 mV, and essentially only the first half of the titration behavior as found at pH 10 was seen. At any given potential more positive than -560 mV, the part of the iron-sulfur protein that was not reduced electrochemically could be reduced photochemically, but only to the maximum extent reduced electrochemically at -560 mV. Whereas, chloroplasts illuminated at room temperature and then frozen while still being illuminated developed a signal similar to that produced by electrochemical reduction at -610 mV, illumination at 77°K did not bring about photoreduction beyond that accomplished electrochemically at about -560 mV.
Dithionite alone in the dark and under anaerobic conditions brought about a partial reduction to the extent of the first electrochemical reduction step. Dithionite plus illumination at room temperature or dithionite plus methyl viologen in the dark produced the maximum signal. Electron paramagnetic resonance spectra due to either light or electrochemically reduced iron-sulfur proteins showed no detectable decay for at least 3 days when samples were stored in the dark at 77°K.
Effect of Near-Ultraviolet and Visible Light on Mammalian Cells in Culture II. Formation of Toxic Photoproducts in Tissue Culture Medium by Blacklight
Authors: Stoien James D. , Wang Richard J. 
Published: May 2006

Near-ultraviolet radiation was found to be lethal for mammalian cells in Dulbecco's modified Eagle's medium without serum or phenol red. Irradiation of the cells with near-ultraviolet light while the cells were in phosphate-buffered-saline abolished the lethal effect. When only the medium was irradiated followed by the addition of unirradiated cells and serum, the cells were still killed. The photoactive components of the medium for this effect were riboflavin, tryptophan, and tyrosine. When riboflavin was deleted from the medium being irradiated and added later, almost no killing was detected. Irradiation of salt solution of riboflavin and tryptophan or riboflavin and tyrosine, resulted in cell killing. Little or no killing resulted when riboflavin, tryptophan, or tyrosine was irradiated singly.
The formation of photoproducts toxic for mammalian cells appears to involve photodynamic action. Experiments utilizing Dulbecco's or similar media without proper controls may produce anomalous results from light illuminating the laboratory.
Dissection of Chromosome Structure with Trypsin and Nucleases
Authors: Weintraub Harold , Lente Frederick Van 
Published: May 2006

Exhaustive digestion of chromatin with trypsin leads to the cleavage of only 20-30 amino acids from each of histones III (f3), IV (f2a1), IIb2 (f2b), and IIb1 (f2a1), the remainder of these chains being resistant. This resistance is not altered by removing the histones from the DNA with 2 M NaCl, but is dramatically reduced in 6 M urea. Histones III, IV, IIb2, and possibly IIb1 are cleaved at their N-termini. Histones I and V and the nonhistone proteins are the first to be attacked by trypsin and have no detectable trypsin-resistant fragments. The arginine rich histones, III and IV, are then cleaved as a pair, followed by most of IIb2 and IIb1, also as a pair. This data is consistent with a model in which basic N-terminal “arms” extend from a trypsin-resistant histone complex. The structural arrangement of these arms relative to the trypsin-resistant histone complex may define the spatial coordinates of DNA binding sites and, consequently, the folding of the DNA fiber in the chromosome.
Accompanying the tryptic digestion of the N-terminals of histones III, IV, IIb2, and possibly IIb1, is an increased sensitivity of chromatin to staphylococcal nuclease. As analyzed by electrophoresis, untrypsinized chromatin is digested into eight discrete limit-digest fragments by nuclease. Trypsinization results in the nuclease digestion of some, but not all, of these DNA bands. Together with the information on the way trypsin cleaves histones in chromatin, the analysis of the resistant DNA suggests that histone N-terminals are associated with some DNA bands and histone C-terminals with other DNA bands. We propose that histones fold the chromosome by crosslinking the DNA corresponding to these bands.
Immune Lysis of Liposomes and Erythrocyte Ghosts Loaded with Spin Label
Authors: Humphries Gillian Kitch , McConnell Harden M. 
Published: May 2006

It is shown that the paramagnetic resonance of spin labels offers a convenient technique for monitoring the complement-mediated immune lysis of erythrocyte ghosts, and sensitized phospholipid liposomes. The ghosts or liposomes are loaded with a concentrated solution of a water-soluble, membrane-impermeable spin label, so that there is a strong exchange broadening of the paramagnetic resonance signal due to labels enclosed within the liposomes or ghosts. Complement-mediated lysis releases the labels into a dilute solution, where a relatively sharp and intense paramagnetic resonance signal is detected.
An unanticipated result is also reported: this is the augmentation of release of spin label from loaded ghosts sensitized with egg albumin, in the presence of antibody against egg albumin, complement, and egg albumin in solution, over and above the release in the absence of egg albumin in solution. Comparison with complement fixation suggests that the augmentation of lysis is effected by crosslinking of immune complexes with the cell membrane.
Redox titration of fluorescence yield of photosystem II
Authors: Ke Bacon , Hawkridge Fred. M. , Sahu Saura 
Published: May 2006

The variable fluorescence yield of photosystem II is dependent on the redox state of the fluorescence quencher molecule or the primary electron acceptor of the system. We have carried out redox titrations of fluorescence yield of a photochemically active photosystem-II reaction-center particle and have measured the redox potential of the photosystem-II primary acceptor.
During reductive titrations using dithionite as the reductant, only a single quenching transition was observed. For instance, at pH 7.0, the midpoint potential of the fluorescence transition is -325 mV, and those at a pH between 6.0 and 7.5 are consistent with a pH dependence of about 60 mV/pH unit. At a given pH, the midpoint potential of the transition closely corresponds to that of the most negative transition previously measured in unfractionated chloroplasts (both by chemical reductive titration). Oxidative titrations using ferricyanide as the oxidant yielded hysteresis in the titration curves.
Similar changes in fluorescence yield were observed in redox titrations by electrochemical reduction or oxidation. Electrochemical reductive and oxidative titrations yielded reversible transitions, contrary to the hysteresis observed during chemical oxidative titration. From coulometric-titration data, we have estimated that most likely one electron is involved in the redox transition of the fluorescence-quencher or primary-electron-acceptor molecule of photosystem II. These findings are consistent with the current proposal that a membrane-bound plastoquinone functions as the primary acceptor of photosystem II.
Stability in dynamical astronomy
Authors: Szebehely Victor 
Published: May 2006

Hill's concept of stability is generalized and its relation to bifurcation theory is shown. A quantitative measure of stability is introduced that allows the comparison of the stability of different astronomical systems. Theoretical stability limits for triple stellar systems, for planetary systems, and for satellite systems are established. The measure of stability is evaluated for several known triple stellar systems as well as for the planets and for the natural satellites of the solar system. The model of the restricted problem of three bodies and values of the Jacobian constant are used to study planetary and satellite systems. The model of the general problem of three bodies is used to establish criteria for triple stellar systems.
In general, the results show a hierarchy of stability: the existing triple systems are more stable than the planetary orbits of the solar system. The satellites of the solar system are least stable; in fact, some of the satellites are close to the line of instability (the Earth's Moon) and some are actually unstable (the four outermost satellites of Jupiter).
Anopheles gambiae P450 reductase is highly expressed in oenocytes and in vivo knockdown increases permethrin susceptibility
Authors: Lycett G. J. , McLaughlin L. A. , Ranson H. , Hemingway J. , Kafatos F. C. , Loukeris T. G. , Paine M. J. I. 
Published: May 2006

AbstractWe describe an in vivo model for investigation of detoxification mechanisms of the mosquito Anopheles gambiae, important for the development of malaria control programmes. Cytochrome P450s are involved in metabolic insecticide resistance and require NADPH cytochrome P450 reductase (CPR) to function. Here we demonstrate that the major sites of adult mosquito CPR expression are oenocytes, mid‐gut epithelia and head appendages. High CPR expression was also evident in Drosophila oenocytes indicating a general functional role in these insect cells. RNAi mediated knockdown drastically reduced CPR expression in oenocytes, and to a lesser extent in mid‐gut epithelia; the head was unaffected. These flies showed enhanced sensitivity to permethrin, demonstrating a key role for abdominal/mid‐gut P450s in pyrethroid metabolism, aiding the development of insecticides.
The determination of phenylalanine content of foods suitable for phenylketonuria
Authors: Weetch E. , MacDonald A. 
Published: May 2006

AbstractBackground  A low phenylalanine diet for people with phenylketonuria (PKU) is very restrictive. Natural foods allowed are based chiefly on fruits and vegetables but there is limited analysis on the phenylalanine content of newer and exotic fruit and vegetables. The assumption that 1 g protein yields 50 mg phenylalanine does not apply to fruits and vegetables.Methods  The National Society for Phenylketonuria Medical Advisory Panel commissioned the phenylalanine analysis of 172 foods, which emphasis on fruit and vegetables. The foods were purchased from retail outlets and analysed by LGC Limited (67 foods) and the LFI (105 foods).Results  There was a strong correlation between this phenylalanine and UK analyses published in 1980, but previous analysis included only a limited range of fruits and vegetables (r = 0.8746; P < 0.0001). There was also correlation between phenylalanine and UK protein analyses (r = 0.7976; P < 0.0001).Conclusion  This new phenylalanine data have enabled a wider range of fruits and vegetables to be safely incorporated into the diet of people with PKU.
Somatic Hypermutation of Ig Genes is Affected Differently by Failures in Apoptosis Caused by Disruption of Fas (lpr Mutation) or by Overexpression of Bcl‐2
Authors: Mastache E. F. , Lindroth K. , Fernández C. , González‐Fernández Á. 
Published: May 2006

AbstractThe effects of the two main apoptotic pathways on the somatic hypermutation process were analysed. Transgenic mice carrying the VκOx1‐Jκ5 rat transgene were crossed with Fas‐deficient lpr mice or with mice overexpressing the Bcl‐2 protein. The transgenic VκOx1 segment and the endogenous JH4‐Cµ Ig intron from Peyer's patches germinal centre B cells were sequenced to study the intrinsic somatic hypermutation process without the skewing effects of specific antigen selection. The lpr/ox mice displayed, in both regions, a high level of mutations with a normal pattern of substitutions. On the contrary, the bcl‐2/ox mice displayed a lower level of mutations with an altered pattern, showing a decreased mutational rate in the intrinsic hotspots of the VκOx1 gene. Our results suggest that the lpr mutation does not have a direct effect on the somatic hypermutation process, but rather on the negative selection of B cells in the germinal centres, leading to the accumulation of recurrent mutations. In contrast, Bcl‐2 overexpression might influence the somatic hypermutational process either by altering the incorporation of mutations or by enhancing the repair mechanism(s). The present work supports the hypothesis that both apoptotic pathways, Fas and Bcl‐2, play distinct roles in the germinal centre reactions.
Blood groups and transfusions in pigs
Authors: Smith Douglas M. , Newhouse Michael , Naziruddin Bashoo , Kresie Lesley 
Published: May 2006

Smith DM, Newhouse M, Naziruddin B, Kresie L. Blood groups and transfusions in pigs. Xenotransplantation 2006; 13: 186–194. © Blackwell Munksgaard, 2006Abstract:  The blood groups of pigs are important to transplantation research because some are also important transplantation antigens and because pigs undergoing organ or hematopoietic transplantation may require transfusion support. There is considerable literature on the subject but much of it is not in transplant related journals. We will review this literature and also give some practical advice on transfusion support.
Increased serum level of vascular endothelial growth factor in Mycobacterium avium complex infection
Authors: NISHIGAKI Yutaka , FUJIUCHI Satoru , FUJITA Yuka , YAMAZAKI Yasuhiro , SATO Maki , YAMAMOTO Yasushi , TAKEDA Akinori , FUJIKANE Toshiaki , SHIMIZU Tetsuo , KIKUCHI Kenjiro 
Published: May 2006

Objective:  Pulmonary infection caused by Mycobacterium avium complex (MAC) is one of the granulomatous diseases which are associated with the expression of vascular endothelial growth factor (VEGF). The aim of the present study was to clarify the association of VEGF with the pathogenesis of MAC infection.Methodology:  The serum VEGF levels in 46 patients with pulmonary MAC infection were compared with those in 16 normal control subjects. Pulmonary lesions were evaluated using chest CT. In 20 patients, after treatment, serum VEGF levels were measured and chest CT performed again to evaluate pulmonary response to treatment.Results:  Infected patients had higher serum VEGF levels than controls (435.2 ± 29.1 vs. 167.0 ± 10.6 pg/mL, P < 0.0001), and serum VEGF level correlated with the extent of disease. The serum VEGF levels in 14 patients who underwent treatment and exhibited an improvement in their pulmonary lesions decreased significantly compared with the results pretreatment (509.0 ± 60.7 vs. 303.6 ± 65.3 pg/mL, P = 0.0092). In infected patients, alveolar macrophages, epithelioid cells and multinucleated giant cells exhibited VEGF overexpression on immunohistochemical staining.Conclusions:  This study suggests that VEGF may be associated with the pathogenesis of pulmonary MAC infection. Additionally, serum VEGF levels may be a useful surrogate marker for evaluating the extent of disease and of the response to treatment.
[125I]Iodomethyllycaconitine binds to α7 nicotinic acetylcholine receptors in monkey brain
Authors: Kulak Jennifer M. , Ivy Carroll F. , Schneider Jay S. 
Published: May 2006

AbstractWe examined the binding of the novel nicotinic acetylcholine receptor (nAChR) ligand [125I]iodomethyllycaconitine (iodoMLA) in the brains ofM. cynomologous(macaque) monkeys. [125I]iodoMLA bound throughout the brain with the greatest density in the thalamus and moderate intensity in the basal ganglia and cortical regions. The Kd and Bmax in whole brain tissue were similar whether 1 mmnicotine (Kd 33.25 ± 15.17 nm, Bmax 5.80 ± 1.06 fmol/mg) or 2 µmof the α7‐selective antagonist α‐bungarotoxin (Kd 46.12 ± 18.45 nm, Bmax 6.30 ± 1.06 fmol/mg) was used for nonspecific binding. The subtype‐selectivity of this ligand was further studied with competition binding studies using nicotine, α‐bungarotoxin and noniodinated MLA. Each ligand completely inhibited [125I]iodoMLA binding throughout the monkey brain, with Ki values of 2.23 ± 0.85 µmfor nicotine, 2.72 ± 1.71 nmfor α‐bungarotoxin and 1.83 ± 0.35 nmMLA in the caudate and 2.03 ± 1.14 µm, 2.65 ± 0.86 nmand 3.32 ± 0.71 nm, respectively, in the putamen. The α3β2/α6*‐selective antagonist α‐conotoxin MII failed to inhibit [125I]iodoMLA binding in any brain region. In monkeys with cognitive deficits resulting from 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine administration, [125I]iodoMLA binding was significantly increased in the striatum, similar to results previously observed for [125I]α‐bungarotoxin. These results suggest that, under the present experimental conditions, [125I]iodoMLA was selective for α7‐containing nAChRs and did not bind to α6‐containing nAChRs. This radioligand may be a useful tool for selectively imaging α7‐containing nAChRsin vivo.
Effect of Environmental Factors and Gender on the Heritability of Bone Mineral Density and Bone Size
Authors: Ng M. Y. M. , Sham P. C. , Paterson A. D. , Chan V. , Kung A. W. C. 
Published: May 2006

SummaryBone mineral density (BMD), a risk factor for osteoporosis, is believed to be under genetic control. The effect of environmental factors and gender on the heritability of BMD and bone size is ill‐defined. In this study, heritability estimates (h2) were determined in 3,320 southern Chinese subjects from 1,019 families using the variance components model. The h2 for age, weight and height‐adjusted BMD was 0.63–0.71 for females, and 0.74–0.79 for males; and for bone size, 0.44–0.64 for females and 0.32–0.86 for males. Adjustment for lifestyle factors including calcium and phytoestrogen intake, exercise, smoking and alcohol consumption altered the h2 differently in males and females. The proportion of variance in BMD and bone size explained by all covariates varied between skeletal sites, but was consistently greater in females than males. A significant gender difference was observed in the genetic variance of BMD and bone size at the hip but not the spine. In conclusion, a gender difference was observed in the degree of heritability of BMD and bone size at specific skeletal sites. Environmental influences contributed variably at different sites in the two sexes.
Central Administration of an Opiate Antagonist Decreases Oral Ethanol Self‐Administration in Rats
Authors: Heyser Charles J. , Roberts Amanda J. , Schulteis Gery , Koob George F. 
Published: May 2006

Background: Opioid peptides have been implicated in various behavioral actions of alcohol, including its reinforcing effects; however, the role of specific brain sites for these actions remains to be explored. The present study examined the effects of intracerebroventricular (ICV) or intracerebral injections of an opiate antagonist (methylnaloxonium) on ethanol self‐administration. The nucleus accumbens and amygdala were selected as intracerebral sites because these regions have been implicated in the reinforcing effects of drugs of abuse.Methods: Male Wistar rats were trained in a limited‐access paradigm (30 min/day) to respond for ethanol (10% w/v) or water in a two‐lever free‐choice condition using a saccharin fading procedure. After the establishment of stable baseline responding for ethanol, animals were implanted stereotaxically with a guide cannula above the lateral ventricle or with bilateral guide cannulae either above the nucleus accumbens or amygdala. After postoperative recovery of stable baseline responding, the rats were tested 15 min after ICV or intracerebral microinjections of methylnaloxonium (0‐2000 ng).Results: Injections of methylnaloxonium into the amygdala significantly reduced responding for ethanol at doses of 250–500 ng. Injections of methylnaloxonium into the nucleus accumbens significantly reduced responding for ethanol at doses of 500–1000 ng, whereas higher doses were needed ICV.Conclusions: These results provide evidence that opioid receptors located in the amygdala and nucleus accumbens may be involved in the regulation of ethanol self‐administration.