bluuebunny/crossref_metadata_2025 huggingface dataset:
Primary reactions of sensory rhodopsins
Authors: Lutz I. , Sieg A. , Wegener A. A. , Engelhard M. , Boche I. , Otsuka M. , Oesterhelt D. , Wachtveitl J. , Zinth W.
Published: July 2012

The first steps in the photocycles of the archaeal photoreceptor
proteins sensory rhodopsin (SR) I and II from
Halobacterium
salinarum
and SRII from
Natronobacterium
pharaonis
have been studied by ultrafast pump/probe
spectroscopy and steady-state fluorescence spectroscopy. The data for
both species of the blue-light receptor SRII suggests that their
primary reactions are nearly analogous with a fast decay of the excited
electronic state in 300–400 fs and a transition between two
red-shifted product states in 4–5 ps. Thus SRII behaves similarly to
bacteriorhodopsin. In contrast for SRI at pH 6.0,
which absorbs in the orange part of the spectrum, a strongly increased
fluorescence quantum yield and a drastically slower and biexponential
decay of the excited electronic state occurring on the picosecond time
scale (5 ps and 33 ps) is observed. The results suggest that the
primary reactions are controlled by the charge distribution in the
vicinity of the Schiff base and demonstrate that there is no direct
connection between absorption properties and reaction dynamics for the
retinal protein family.
The origins of stability of spontaneous vesicles
Authors: Jung H. T. , Coldren B. , Zasadzinski J. A. , Iampietro D. J. , Kaler E. W.
Published: July 2012

Equilibrium unilamellar vesicles are stabilized by one of two
distinct mechanisms depending on the value of the bending constant.
Helfrich undulations ensure that the interbilayer potential is always
repulsive when the bending constant,
K
, is of order
k
B
T
. When
K
≫
k
B
T
, unilamellar
vesicles are stabilized by the spontaneous curvature that picks out a
particular vesicle radius; other radii are disfavored energetically. We
present measurements of the bilayer elastic constant and the
spontaneous curvature,
R
o
, for three
different systems of equilibrium vesicles by an analysis of the vesicle
size distribution determined by cryo-transmission electron microscopy
and small-angle neutron scattering. For cetyltrimethylammonium bromide
(CTAB)/sodium octyl sulfonate catanionic vesicles,
K
= .7
k
B
T
, suggesting that the
unilamellar vesicles are stabilized by Helfrich-undulation repulsions.
However, for CTAB and sodium perfluorooctanoate
(FC
7
) vesicles,
K
= 6
k
B
T
, suggesting stabilization
by the energetic costs of deviations from the spontaneous curvature.
Adding electrolyte to the sodium perfluorooctanoate/CTAB vesicles
leads to vesicles with two bilayers; the attractive interactions
between the bilayers can overcome the cost of small deviations from the
spontaneous curvature to form two-layer vesicles, but larger deviations
to form three and more layer vesicles are prohibited. Vesicles with a
discrete numbers of bilayers at equilibrium are possible only for
bilayers with a large bending modulus coupled with a spontaneous
curvature.
Role of transforming growth factor-α in von Hippel– Lindau (VHL)
−/−
clear cell renal carcinoma cell proliferation: A possible mechanism coupling VHL tumor suppressor inactivation and tumorigenesis
Authors: de Paulsen Natalie , Brychzy Alexander , Fournier Marie-Christine , Klausner Richard D. , Gnarra James R. , Pause Arnim , Lee Stephen
Published: July 2012

Mutations of the VHL tumor suppressor gene occur in patients with
VHL disease and in the majority of sporadic clear cell renal carcinomas
(VHL
−/−
RCC). Loss of VHL protein function is associated
with constitutive expression of mRNAs encoding hypoxia-inducible
proteins, such as vascular endothelial growth factor. Overproduction of
angiogenic factors might explain why VHL
−/−
RCC tumors
are so highly vascularized, but whether this overproduction is
sufficient for oncogenesis still remains unknown. In this report, we
examined the activity of transforming growth factor-α (TGF-α),
another VHL-regulated growth factor. We show that TGF-α mRNA and
protein are hypoxia-inducible in VHL
−/−
RCC cells
expressing reintroduced VHL. In addition to its overexpression by
VHL
−/−
RCC cells, TGF-α can also act as a specific
growth-stimulatory factor for VHL
−/−
RCC cells expressing
reintroduced wild-type VHL, as well as primary renal proximal tubule
epithelial cells, the likely site of origin of RCC. This role is in
contrast to those of other growth factors overexpressed by
VHL
−/−
RCC cells, such as vascular endothelial growth
factor and TGF-β1, which do not stimulate RCC cell proliferation. A
TGF-α-specific antisense oligodeoxynucleotide blocked TGF-α
production in VHL
−/−
RCC cells, which led to the
dependence of those cells on exogenous growth factors to sustain growth
in culture. Growth of VHL
−/−
RCC cells was also
significantly reduced by a drug that specifically inhibits the
epidermal growth factor receptor, the receptor through which TGF-α
stimulates proliferation. These results suggest that the generation of
a TGF-α autocrine loop as a consequence of VHL inactivation in renal
proximal tubule epithelial cells may provide the uncontrolled growth
stimulus necessary for the initiation of tumorigenesis.
Crystal structure of the Holliday junction migration motor protein RuvB from
Thermus thermophilus
HB8
Authors: Yamada Kazuhiro , Kunishima Naoki , Mayanagi Kouta , Ohnishi Takayuki , Nishino Tatsuya , Iwasaki Hiroshi , Shinagawa Hideo , Morikawa Kosuke
Published: July 2012

We report here the crystal structure of the RuvB motor protein from
Thermus thermophilus
HB8, which drives branch migration
of the Holliday junction during homologous recombination. RuvB has a
crescent-like architecture consisting of three consecutive domains, the
first two of which are involved in ATP binding and hydrolysis. DNA is
likely to interact with a large basic cleft, which encompasses the
ATP-binding pocket and domain boundaries, whereas the
junction-recognition protein RuvA may bind a flexible β-hairpin
protruding from the N-terminal domain. The structures of two subunits,
related by a noncrystallographic pseudo-2-fold axis, imply that
conformational changes of motor protein coupled with ATP hydrolysis may
reflect motility essential for its translocation around double-stranded
DNA.
Surface-localized glycine transporters 1 and 2 function as monomeric proteins in
Xenopus
oocytes
Authors: Horiuchi Masahisa , Nicke Annette , Gomeza Jesus , Aschrafi Armaz , Schmalzing Günther , Betz Heinrich
Published: July 2012

Na
+
/Cl
−
-dependent neurotransmitter
transporters form a superfamily of transmembrane proteins that share 12
membrane-spanning regions. To gain information about the quaternary
structure of these transporter proteins, we heterologously expressed
the glial glycine transporter GlyT1 and its neuronal homolog GlyT2 in
Xenopus
oocytes. By using metabolic labeling with
[
35
S]methionine or surface labeling with a plasma
membrane impermeable reagent followed by affinity purification, we
separately analyzed the total cellular pools of newly synthesized GlyTs
and its functional plasma membrane-bound fractions. Upon blue native
gel electrophoresis, the surface-localized transporter proteins were
found to exist exclusively in complex-glycosylated monomeric form,
whereas a significant fraction of the intracellular GlyT1 and GlyT2 was
core-glycosylated and oligomeric. In contrast, even after treatment
with the crosslinker glutaraldehyde, surface GlyTs failed to migrate as
oligomeric proteins. These results indicate that plasma membrane-bound
GlyT1 and GlyT2 are monomeric proteins. Thus,
Na
+
/Cl
−
-dependent neurotransmitter
transporters do not require oligomerization for substrate
translocation.
Mutagenesis of the regulatory domain of phenylalanine hydroxylase
Authors: Wang Guo-An , Gu Peide , Kaufman Seymour
Published: July 2012

The regulatory domain of phenylalanine hydroxylase (PAH, EC
1.14.16.1
) consists of more than 100 amino acids at the N terminus, the
removal of which significantly activates the enzyme. To study the
regulatory properties controlled by the N terminus, a series of
truncations and site-specific mutations were made in this region of rat
PAH. These enzymes were expressed highly in
Escherichia
coli
and purified through a pterin-conjugated Sepharose
affinity column. The removal of the first 26 amino acids of the N
terminus increased the activity by about 20-fold, but removal of the
first 15 amino acids increased the activity by only 2-fold.
Replacing serine-29 of rat PAH with cysteine from the same site of
human PAH increased the activity by more than 4-fold. Mutation of
serine to other amino acids with varying side chains: alanine,
methionine, leucine, aspartic acid, asparagine, and arginine also
resulted in significant activation, indicating a serine-specific
inhibitory effect. But these site-specific mutants showed 30–40%
lower activity when assayed with 6-methyl-5,6,7,8-tetrahydropterin.
Stimulation of hydroxylase activity by preincubation of the enzyme with
phenylalanine was inversely proportional to the activation state of all
these mutants. Combined with recent crystal structures of PAH [Kobe,
B.
et al.
(1999)
Nat. Struct. Biol.
6,
442–448; and Erlandsen, H., Bjorgo, E., Flatmark, T. & Stevens,
R. C. (2000)
Biochemistry
39, 2208–2217], these
data suggest that residues 16–26 have a controlling regulatory effect
on the activity by interaction with the dihydroxypropyl side chain of
(6R)-5,6,7,8-tetrahydrobiopterin. The serine/cysteine switch explains
the difference in regulatory properties between human and rat PAH. The
N terminus as a whole is important for maintaining rat PAH in an
optimum catalytic conformation.
Constitutively activated Stat3 protects fibroblasts from serum withdrawal and UV-induced apoptosis and antagonizes the proapoptotic effects of activated Stat1
Authors: Shen Yuhong , Devgan Geeta , Darnell James E. , Bromberg Jacqueline F.
Published: July 2012

Stats1 and 3 (signal transducers and activators of transcription) can be activated simultaneously, although not necessarily to the same degree or duration, by the interaction of cells with the same polypeptide ligand (EGF, PDGF, or high concentrations of IL-6, for example). However, these two Stat proteins can mediate opposing effects on cell growth and survival. Stat1 activation slows growth and promotes apoptosis. In contrast, activated Stat3 can protect cells from apoptosis. Furthermore, a constitutively active form of Stat3, Stat3-C (bridged by S-S linkages between cysteines instead of phosphotyrosines) can induce cellular transformation of fibroblasts. We have determined that fibroblasts transformed by Stat3-C are more resistant to proapoptotic stimuli than nontransformed cells. Also, to examine the potential opposing roles in apoptosis of Stat1 and Stat3, we studied the cervical carcinoma-derived cell line, Me180, which undergoes Stat1-dependent, IFNγ-induced apoptosis. Me180 cells that express Stat3-C are protected against IFNγ-mediated apoptosis.
Origin of nanomechanical cantilever motion generated from biomolecular interactions
Authors: Wu Guanghua , Ji Haifeng , Hansen Karolyn , Thundat Thomas , Datar Ram , Cote Richard , Hagan Michael F. , Chakraborty Arup K. , Majumdar Arunava
Published: July 2012

Generation of nanomechanical cantilever motion from biomolecular
interactions can have wide applications, ranging from high-throughput
biomolecular detection to bioactuation. Although it has been suggested
that such motion is caused by changes in surface stress of a cantilever
beam, the origin of the surface-stress change has so far not been
elucidated. By using DNA hybridization experiments, we show that the
origin of motion lies in the interplay between changes in
configurational entropy and intermolecular energetics induced by
specific biomolecular interactions. By controlling entropy change
during DNA hybridization, the direction of cantilever motion can be
manipulated. These thermodynamic principles were also used to explain
the origin of motion generated from protein–ligand binding.
Bromination of deoxycytidine by eosinophil peroxidase: A mechanism for mutagenesis by oxidative damage of nucleotide precursors
Authors: Henderson Jeffrey P. , Byun Jaeman , Williams Michelle V. , McCormick Michael L. , Parks William C. , Ridnour Lisa A. , Heinecke Jay W.
Published: July 2012

Oxidants generated by eosinophils during chronic inflammation may lead to mutagenesis in adjacent epithelial cells. Eosinophil peroxidase, a heme enzyme released by eosinophils, generates hypobromous acid that damages tissue in inflammatory conditions. We show that human eosinophils use eosinophil peroxidase to produce 5-bromodeoxycytidine. Flow cytometric, immunohistochemical, and mass spectrometric analyses all demonstrated that 5-bromodeoxycytidine generated by eosinophil peroxidase was taken up by cultured cells and incorporated into genomic DNA as 5-bromodeoxyuridine. Although previous studies have focused on oxidation of chromosomal DNA, our observations suggest another mechanism for oxidative damage of DNA. In this scenario, peroxidase-catalyzed halogenation of nucleotide precursors yields products that subsequently can be incorporated into DNA. Because the thymine analog 5-BrUra mispairs with guanine in DNA, generation of brominated pyrimidines by eosinophils might constitute a mechanism for cytotoxicity and mutagenesis at sites of inflammation.
Negative genetic correlation for adult fitness between sexes reveals ontogenetic conflict in
Drosophila
Authors: Chippindale Adam K. , Gibson Jonathan R. , Rice William R.
Published: July 2012

Because of their distinctive roles in reproduction, females and
males are selected toward different optimal phenotypes. Ontogenetic
conflict between the sexes arises when homologous traits are selected
in different directions. The evolution of sexual dimorphism by
sex-limited gene expression alleviates this problem. However, because
the majority of genes are not sex-limited, the potential for
substantial conflict may remain. Here we assess the degree of
ontogenetic conflict in the fruit-fly,
Drosophila
melanogaster,
by cloning 40 haploid genomes and measuring their
Darwinian fitness in both sexes. The intersexual genetic correlations
for juvenile viability, adult reproductive success, and total fitness
were used to gauge potential conflict during development. First, as
juveniles, where the fitness objectives of the two sexes appear to be
similar, survival was strongly positively correlated across sexes.
Second, after adult maturation, where gender roles diverge, a
significant negative correlation for reproductive success was found.
Finally, because of counterbalancing correlations in the juvenile and
adult components, no intersexual correlation for total fitness was
found. Highly significant genotype-by-gender interaction variance was
measured for both adult and total fitness. These results demonstrate
strong intersexual discord during development because of the expression
of sexually antagonistic variation.
Eight novel families of miniature inverted repeat transposable elements in the African malaria mosquito,
Anopheles gambiae
Authors: Tu Zhijian
Published: July 2012

Eight novel families of miniature inverted repeat transposable
elements (MITEs) were discovered in the African malaria mosquito,
Anopheles gambiae
, by using new software designed to
rapidly identify MITE-like sequences based on their structural
characteristics. Divergent subfamilies have been found in two families.
Past mobility was demonstrated by evidence of MITE insertions that
resulted in the duplication of specific TA, TAA, or 8-bp targets. Some
of these MITEs share the same target duplications and similar terminal
sequences with MITEs and other DNA transposons in human and other
organisms. MITEs in
A. gambiae
range from 40 to 1340
copies per genome, much less abundant than MITEs in the yellow fever
mosquito,
Aedes aegypti
. Statistical analyses suggest
that most
A. gambiae
MITEs are in highly AT-rich
regions, many of which are closely associated with each other. The
analyses of these novel MITEs underscored interesting questions
regarding their diversity, origin, evolution, and relationships to the
host genomes. The discovery of diverse families of MITEs in
A.
gambiae
has important practical implications in light of
current efforts to control malaria by replacing vector mosquitoes with
genetically modified refractory mosquitoes. Finally, the systematic
approach to rapidly identify novel MITEs should have broad applications
for the analysis of the ever-growing sequence databases of a wide range
of organisms.
Anti-DNA antibodies are a major component of the intrathecal B cell response in multiple sclerosis
Authors: Williamson R. Anthony , Burgoon Mark P. , Owens Gregory P. , Ghausi Omar , Leclerc Estelle , Firme Louise , Carlson Sharon , Corboy John , Parren Paul W. H. I. , Sanna Pietro P. , Gilden Donald H. , Burton Dennis R.
Published: July 2012

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of unknown cause that afflicts the central nervous system. MS is typified by a highly clonally restricted antigen-driven antibody response that is confined largely to the central nervous system. The major antigenic targets of this response and the role of antibody in disease pathogenesis remain unclear. To help resolve these issues, we cloned the IgG repertoire directly from active plaque and periplaque regions in MS brain and from B cells recovered from the cerebrospinal fluid of a patient with MS with subacute disease. We found that high-affinity anti-DNA antibodies are a major component of the intrathecal IgG response in the patients with MS that we studied. Furthermore, we show DNA-specific monoclonal antibodies rescued from two subjects with MS as well as a DNA-specific antibody rescued from an individual suffering from systemic lupus erythematosus bound efficiently to the surface of neuronal cells and oligodendrocytes. For two of these antibodies, cell-surface recognition was DNA dependent. Our findings indicate that anti-DNA antibodies may promote important neuropathologic mechanisms in chronic inflammatory disorders, such as MS and systemic lupus erythematosus.
The Gln-Ala repeat transcriptional activator CA150 interacts with huntingtin: Neuropathologic and genetic evidence for a role in Huntington's disease pathogenesis
Authors: Holbert Sébastien , Denghien Isabelle , Kiechle Tamara , Rosenblatt Adam , Wellington Cheryll , Hayden Michael R. , Margolis Russell L. , Ross Christopher A. , Dausset Jean , Ferrante Robert J. , Néri Christian
Published: July 2012

Huntington's disease (HD) is a neurodegenerative disease caused by
polyglutamine expansion in the protein huntingtin (htt). Pathogenesis
in HD appears to involve the formation of ubiquitinated neuronal
intranuclear inclusions containing N-terminal mutated htt, abnormal
protein interactions, and the aggregate sequestration of a variety of
proteins (noticeably, transcription factors). To identify novel
htt-interacting proteins in a simple model system, we used a yeast
two-hybrid screen with a
Caenorhabditis
elegans
activation domain library. We found a predicted WW
domain protein (ZK1127.9) that interacts with N-terminal fragments of
htt in two-hybrid tests. A human homologue of ZK1127.9 is CA150, a
transcriptional coactivator with a N-terminal insertion that contains
an imperfect (Gln-Ala)
38
tract encoded by a polymorphic
repeat DNA. CA150 interacted
in vitro
with full-length
htt from lymphoblastoid cells. The expression of CA150, measured
immunohistochemically, was markedly increased in human HD brain tissue
compared with normal age-matched human brain tissue, and CA150 showed
aggregate formation with partial colocalization to ubiquitin-positive
aggregates. In 432 HD patients, the CA150 repeat length explains a
small, but statistically significant, amount of the variability in the
onset age. Our data suggest that abnormal expression of CA150, mediated
by interaction with polyglutamine-expanded htt, may alter transcription
and have a role in HD pathogenesis.
Inhibition of the visual cycle
in vivo
by 13
-cis
retinoic acid protects from light damage and provides a mechanism for night blindness in isotretinoin therapy
Authors: Sieving Paul A. , Chaudhry Prem , Kondo Mineo , Provenzano Matthew , Wu David , Carlson Thomas J. , Bush Ronald A. , Thompson Debra A.
Published: July 2012

Isotretinoin (13
-cis
retinoic acid) is
frequently prescribed for severe acne [Peck, G. L., Olsen,
T. G., Yoder, F. W., Strauss, J. S., Downing, D.
T., Pandya, M., Butkus, D. & Arnaud-Battandier, J. (1979)
N. Engl. J. Med.
300, 329–333] but can
impair night vision [Fraunfelder, F. T., LaBraico, J. M. &
Meyer, S. M. (1985)
Am. J. Ophthalmol.
100,
534–537] shortly after the beginning of therapy [Shulman, S. R.
(1989)
Am. J. Public Health
79, 1565–1568]. As rod
photoreceptors are responsible for night vision, we administered
isotretinoin to rats to learn whether night blindness resulted from rod
cell death or from rod functional impairment. High-dose isotretinoin
was given daily for 2 months and produced systemic toxicity, but this
caused no histological loss of rod photoreceptors, and rod-driven
electroretinogram amplitudes were normal after prolonged dark
adaptation. Additional studies showed, however, that even a single dose
of isotretinoin slowed the recovery of rod signaling after exposure to
an intense bleaching light, and that rhodopsin regeneration was
markedly slowed. When only a single dose was given, rod function
recovered to normal within several days. Rods and cones both showed
slow recovery from bleach after isotretinoin in rats and in mice. HPLC
analysis of ocular retinoids after isotretinoin and an intense bleach
showed decreased levels of rhodopsin chromophore, 11
-cis
retinal, and the accumulation of the biosynthetic intermediates,
11-
cis
and all
-trans
retinyl esters.
Isotretinoin was also found to protect rat photoreceptors from
light-induced damage, suggesting that strategies of altering retinoid
cycling may have therapeutic implications for some forms of retinal and
macular degeneration.
Mechanism for fetal globin gene expression: Role of the soluble guanylate cyclase–cGMP-dependent protein kinase pathway
Authors: Ikuta Tohru , Ausenda Sabrina , Cappellini Maria D.
Published: July 2012

Despite considerable concerns with pharmacological stimulation of
fetal hemoglobin (Hb F) as a therapeutic option for the β-globin
disorders, the molecular basis of action of Hb F-inducing agents
remains unclear. Here we show that an intracellular pathway including
soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase (PKG)
plays a role in induced expression of the γ-globin gene. sGC, an
obligate heterodimer of α- and β-subunits, participates in a
variety of physiological processes by converting GTP to cGMP. Northern
blot analyses with erythroid cell lines expressing different β-like
globin genes showed that, whereas the β-subunit is expressed at
similar levels, high-level expression of the α-subunit is
preferentially observed in erythroid cells expressing γ-globin but
not those expressing β-globin. Also, the levels of expression of the
γ-globin gene correlate to those of the α-subunit. sGC activators
or cGMP analogs increased expression of the γ-globin gene in
erythroleukemic cells as well as in primary erythroblasts from normal
subjects and patients with β-thalassemia. Nuclear run-off assays
showed that the sGC activator protoporphyrin IX stimulates
transcription of the γ-globin gene. Furthermore, increased expression
of the γ-globin gene by well known Hb F-inducers such as hemin and
butyrate was abolished by inhibiting sGC or PKG activity. Taken
together, these results strongly suggest that the sGC–PKG pathway
constitutes a mechanism that regulates expression of the γ-globin
gene. Further characterization of this pathway should permit us to
develop new therapeutics for the β-globin disorders.
Dynamics of subjective contour formation in the early visual cortex
Authors: Lee Tai Sing , Nguyen My
Published: July 2012

To elucidate the roles of visual areas V1 and V2 and their
interaction in early perceptual processing, we studied the responses of
V1 and V2 neurons to statically displayed Kanizsa figures. We found
evidence that V1 neurons respond to illusory contours of the Kanizsa
figures. The illusory contour signals in V1 are weaker than in V2, but
are significant, particularly in the superficial layers. The population
averaged response to illusory contours emerged 100 msec after stimulus
onset in the superficial layers of V1, and around 120–190 msec in the
deep layers. The illusory contour response in V2 began earlier,
occurring at 70 msec in the superficial layers and at 95 msec in the
deep layers. The temporal sequence of the events suggests that the
computation of illusory contours involves intercortical interaction,
and that early perceptual organization is likely to be an interactive
process.
The CYP88A cytochrome P450,
ent
-kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway
Authors: Helliwell Chris A. , Chandler Peter M. , Poole Andrew , Dennis Elizabeth S. , Peacock W. James
Published: July 2012

We have shown that
ent
-kaurenoic acid oxidase, a
member of the CYP88A subfamily of cytochrome P450 enzymes, catalyzes
the three steps of the gibberellin biosynthetic pathway from
ent
-kaurenoic acid to GA
12
. A
gibberellin-responsive barley mutant,
grd5
, accumulates
ent
-kaurenoic acid in developing grains. Three
independent
grd5
mutants contain mutations in a gene
encoding a member of the CYP88A subfamily of cytochrome P450 enzymes,
defined by the maize Dwarf3 protein. Mutation of the
Dwarf3
gene gives rise to a gibberellin-responsive dwarf
phenotype, but the lesion in the gibberellin biosynthesis pathway has
not been identified.
Arabidopsis thaliana
has two
CYP88A
genes, both of which are expressed. Yeast strains
expressing cDNAs encoding each of the two
Arabidopsis
and the barley CYP88A enzymes catalyze the three steps of the GA
biosynthesis pathway from
ent
-kaurenoic acid to
GA
12
. Sequence comparison suggests that the maize
Dwarf3
locus also encodes
ent
-kaurenoic
acid oxidase.
Galantamine: Effect on nicotinic receptor binding, acetylcholinesterase inhibition, and learning
Authors: Woodruff-Pak Diana S. , Vogel Richard W. , Wenk Gary L.
Published: July 2012

Classical eyeblink conditioning is a well-characterized model
paradigm that engages the septohippocampal cholinergic system. This
form of associative learning is impaired in normal aging and severely
disrupted in Alzheimer's disease (AD). Some nicotinic cholinergic
receptor subtypes are lost in AD, making the use of nicotinic
allosterically potentiating ligands a promising therapeutic strategy.
The allosterically potentiating ligand galantamine (Gal) modulates
nicotinic cholinergic receptors to increase acetylcholine release as
well as acting as an acetylcholinesterase (AChE) inhibitor. Gal was
tested in two preclinical experiments. In Experiment 1 with 16 young
and 16 older rabbits, Gal (3.0 mg/kg) was administered for 15 days
during conditioning, and the drug significantly improved learning,
reduced AChE levels, and increased nicotinic receptor binding. In
Experiment 2, 53 retired breeder rabbits were tested over a 15-wk
period in four conditions. Groups of rabbits received 0.0 (vehicle),
1.0, or 3.0 mg/kg Gal for the entire 15-wk period or 3.0 mg/kg Gal
for 15 days and vehicle for the remainder of the experiment. Fifteen
daily conditioning sessions and subsequent retention and relearning
assessments were spaced at 1-month intervals. The dose of 3.0 mg/kg
Gal ameliorated learning deficits significantly during acquisition and
retention in the group receiving 3.0 mg/kg Gal continuously.
Nicotinic receptor binding was significantly increased in rabbits
treated for 15 days with 3.0 mg/kg Gal, and all Gal-treated rabbits
had lower levels of brain AChE. The efficacy of Gal in a learning
paradigm severely impaired in AD is consistent with outcomes in
clinical studies.
ECM stiffness primes the TGFβ pathway to promote chondrocyte differentiation
Authors: Allen Jessica L. , Cooke Margaret E. , Alliston Tamara
Published: July 2012

Cells encounter physical cues such as extracellular matrix (ECM) stiffness in a microenvironment replete with biochemical cues. However, the mechanisms by which cells integrate physical and biochemical cues to guide cellular decision making are not well defined. Here we investigate mechanisms by which chondrocytes generate an integrated response to ECM stiffness and transforming growth factor β (TGFβ), a potent agonist of chondrocyte differentiation. Primary murine chondrocytes and ATDC5 cells grown on 0.5-MPa substrates deposit more proteoglycan and express more Sox9, Col2α1, and aggrecan mRNA relative to cells exposed to substrates of any other stiffness. The chondroinductive effect of this discrete stiffness, which falls within the range reported for articular cartilage, requires the stiffness-sensitive induction of TGFβ1. Smad3 phosphorylation, nuclear localization, and transcriptional activity are specifically increased in cells grown on 0.5-MPa substrates. ECM stiffness also primes cells for a synergistic response, such that the combination of ECM stiffness and exogenous TGFβ induces chondrocyte gene expression more robustly than either cue alone through a p38 mitogen-activated protein kinase–dependent mechanism. In this way, the ECM stiffness primes the TGFβ pathway to efficiently promote chondrocyte differentiation. This work reveals novel mechanisms by which cells integrate physical and biochemical cues to exert a coordinated response to their unique cellular microenvironment.
The Strategic Use of Private Quality Standards in Food Supply Chains
Authors: von Schlippenbach Vanessa , Teichmann Isabel
Published: July 2012

We explore the strategic role of private quality standards in food supply chains. Considering two symmetric retailers that are exclusively supplied by a finite number of producers and endogenizing the suppliers’ delivery choice, we show that there exist two asymmetric equilibria in the retailers’ quality requirements. Our results reveal that the retailers use private quality standards to improve their bargaining position in the intermediate goods market. This is associated with inefficiencies in the upstream production, which can be mitigated by enforcing a minimum quality standard.
How to Get the Most Out of Your GP Tutorials
Authors: Baishnab Elora
Published: July 2012

GP tutorials, together with General Practice Vocational Training Scheme teaching and on-the-job experience, form the bedrock of general practice training. All GPs in training working in GP practices experience regular one-to-one tutorials with a named GP trainer. These provide both educational and clinical supervision. However, one-to-one tutorials are a relatively new experience for many trainees used to larger group teaching based in hospitals. Moreover the proximity and longevity of the GP trainer-trainee relationship is unique within medicine. The one-to-one setting has its benefits and also disadvantages. This article aims to look closely at the pros and cons of the one-to-one tutorials, with a view to helping both trainees and trainers get the most out of them.
Evolution of signal multiplexing by 14-3-3-binding 2R-ohnologue protein families in the vertebrates
Authors: Tinti Michele , Johnson Catherine , Toth Rachel , Ferrier David E. K. , MacKintosh Carol
Published: July 2012

14-3-3 proteins regulate cellular responses to stimuli by docking onto pairs of phosphorylated residues on target proteins. The present study shows that the human 14-3-3-binding phosphoproteome is highly enriched in 2R-ohnologues, which are proteins in families of two to four members that were generated by two rounds of whole genome duplication at the origin of the vertebrates. We identify 2R-ohnologue families whose members share a ‘lynchpin’, defined as a 14-3-3-binding phosphosite that is conserved across members of a given family, and aligns with a Ser/Thr residue in pro-orthologues from the invertebrate chordates. For example, the human receptor expression enhancing protein (REEP) 1–4 family has the commonest type of lynchpin motif in current datasets, with a phosphorylatable serine in the –2 position relative to the 14-3-3-binding phosphosite. In contrast, the second 14-3-3-binding sites of REEPs 1–4 differ and are phosphorylated by different kinases, and hence the REEPs display different affinities for 14-3-3 dimers. We suggest a conceptual model for intracellular regulation involving protein families whose evolution into signal multiplexing systems was facilitated by 14-3-3 dimer binding to lynchpins, which gave freedom for other regulatory sites to evolve. While increased signalling complexity was needed for vertebrate life, these systems also generate vulnerability to genetic disorders.
A prospective study of learning, memory, and executive function in new MDMA users
Authors: Wagner Daniel , Becker Benjamin , Koester Philip , Gouzoulis‐Mayfrank Euphrosyne , Daumann Joerg
Published: July 2012

Aims

It is still unclear if cognitive abnormalities in human 3,4‐methylenedioxymeth‐amphetamine (MDMA) users existed before the beginning of use or if other confounders could explain the deficits. The present study was conducted in order to assess the relationship between beginning MDMA use and subsequent cognitive performance and to overcome previous methodological shortcomings.

Design

A prospective cohort study in new MDMA users between 2006 and 2009 with a follow‐up duration of 12 months.

Setting and Participants

Of the 149 almost MDMA‐naive subjects examined at the initial assessment, 109 subjects participated again after 1 year. During this period, 43 subjects did not use any other illicit substance apart from cannabis; 23 subjects used more than 10 pills MDMA (mean = 33.6). These groups then were compared by means of multivariate analyses of variance.

Measurements

Change scores between the initial examination and follow‐up on a neuropsychological test battery including measures of learning, memory, and frontal executive functions [Auditiv‐Verbaler Lerntest (AVLT), Lern‐ und Gedächtnistest (LGT) 3, digit span test, digit symbol test, Stroop task, Trail‐making test]. In addition, a comprehensive number of possibly relevant confounders including age, general intelligence, cannabis use, alcohol use, cigarette use, medical treatment, participation in sports, nutrition, sleep patterns and subjective wellbeing was assessed.

Findings

Groups did not differ in any of the potential confounders. However, significant effects of immediate and delayed recall of a visual paired associates learning task between MDMA users and controls were found (respectively, F
(1,64) = 11.43, P = 0.001, η2 = 0.136 and F
(1,64) = 11.08, P = 0.002, η2 = 0.144). No significant differences on the other neuropsychological tests were found.

Conclusions

MDMA appears to impair visual paired associates learning in new users, suggesting serotonergic dysfunction in hippocampal regions as a consequence of MDMA use.
DOSE‐RESPONSE RELATIONSHIPS IN TROPICAMIDE‐INDUCED MYDRIASIS AND CYCLOPLEGIA
Authors: SMITH S.E.
Published: July 2012

Mydriatic and cycloplegic effects of tropicamide in the normal and in the guanethidine‐treated human eye have been recorded following prolonged exposure of the eye to drug solutions.

Marked effects and satisfactory dose‐response relationships were observed at drug concentrations within the range 1.25–40 μg/ml, by comparison with concentrations of 5–10 mg/ml usually applied as eye‐drops.

The findings are discussed in relation to drug concentrations which produce cholinergic antagonism in vitro.
INTERACTION BETWEEN DEBRISOQUINE AND PHENYLEPHRINE IN MAN
Authors: ALLUM WENDY , AMINU J. , BLOOMFIELD T.H. , DAVIES CAROL , SCALES A.H. , VERE D.W.
Published: July 2012

The interaction between phenylephrine and debrisoquine was studied using normal and hypertensive human volunteers, measuring blood pressure, pulse rate and pupil diameter. Single doses of phenylephrine were given before, during and after a short course of debrisoquine treatment.

The circulatory effects of phenylephrine are potentiated by debrisoquine; in a few subjects this potentiation was marked and a potential hazard.

Limited deductions could be made about the effects of debrisoquine on baroceptor responses and adrenergic mechanisms.
INHIBITION OF PHENYTOIN METABOLISM BY SULTHIAME IN EPILEPTIC PATIENTS
Authors: HOUGHTON G.W. , RICHENS A.
Published: July 2012

Measurements have been made of steady state serum phenytoin concentration, serum half‐life of 14C‐labelled phenytoin, and the urinary ratio of the major metabolite of phenytoin to the unchanged drug (p‐HPPH: DPH ratio) in epileptic patients on and off sulthiame therapy.

Starting sulthiame treatment produced an increase in serum phenytoin concentration, a prolongation of the half‐life and an increase in the p‐HPPH: DPH ratio. The total urinary output of phenytoin plus p‐HPPH was unaltered by sulthiame.

The results indicate that sulthiame or one of its metabolites inhibits the parahydroxylation of phenytoin by hepatic enzymes.
EFFECTS OF FOOD AND EXERCISE ON THE ABSORPTION OF EFFERVESCENT ASPIRIN
Authors: VOLANS G.N.
Published: July 2012

The absorption of effervescent aspirin was studied in normal volunteers of both sexes under varied conditions of activity in both fasting and non‐fasting states.

Moderate activity resulted in no significant changes in absorption compared with that at rest.

In non‐fasting subjects the absorption was reduced but this reduction was attenuated with time until after 60 min the plasma levels were similar.

There was no interaction between the resting/non‐resting and fasting/non‐fasting absorption.
Ro 3–4787, A NEW β‐ADRENOCEPTOR BLOCKING AGENT: STUDIES IN NORMAL VOLUNTEERS
Authors: KILBORN J.R. , TURNER P.
Published: July 2012

A new β‐adrenoceptor blocking agent, Ro 3–4787, was administered orally to resting subjects. Peak levels of 106.2 ±15.5 ng/ml were reached after 20 mg given in the fasting state. After intravenous administration, an inverse rectilinear relationship was shown between the log dose (2 mg‐20 mg) and the heart rate during vigorous exercise on a bicycle ergometer.

A double‐blind study in five normal subjects using 0.03 mg/kg and 0.15 mg/kg showed that propranolol and Ro 3–4787 were equally effective in reducing the exercise heart rate. There was an inverse correlation between the log plasma level before exercise and the heart rate during exercise for both drugs over the range studied.
PHENYTOIN DOSE ADJUSTMENT IN EPILEPTIC PATIENTS
Authors: MAWER G.E. , MULLEN P.W. , RODGERS MARGARET , ROBINS A.J. , LUCAS S.B.
Published: July 2012

A preliminary survey showed that many outpatients with partially controlled epilepsy had serum concentrations of phenytoin below the recommended therapeutic range (10–20 μg/ml). A phenytoin tolerance test was devised with the intention of predicting a more adequate daily dose for such a patient.

Fifteen patients were each given an oral test dose of 600 mg phenytoin sodium and the serum concentration of phenytoin was measured at intervals over 48 h; the concentration rose during the first 4 h and decayed between 12–48 h as an almost linear function of time.

The serum concentration/time curves were fitted by an iterative computer program based on the Michaelis‐Menten equatioa The mean saturated rate of elimination of phenytoin was 435 mg/day and the serum concentration (Km) corresponding with 50% saturation was 3.8 μg/ml. The mean calculated dose of phenytoin sodium required for a steady state serum concentration of 10–20 μg/ml was 345–400 mg/day.

The Michaelis‐Menten principle was used to predict steady state serum phenytoin concentrations in individual patients receiving daily doses of phenytoin sodium adjusted by steps of 100 mg. The serum concentrations tended to be either too low or too high. The steep relationship between phenytoin concentration and dose indicates that when the concentration reaches 5–10 μg/ml it is then appropriate to adjust dose by small steps of about 25 mg.
EFFECT OF CAFFEINE ON SLEEP: EEG STUDY IN LATE MIDDLE AGE PEOPLE
Authors: BŘEZINOVÁ VLASTA
Published: July 2012

The effect of caffeine alkaloid base (300 mg) on whole night sleep was investigated by electrophysiological techniques in six late middle age subjects (mean age 56 years), comparison being made with decaffeinated coffee and with no drink prior to sleep, using each condition five times in a balanced order on non‐consecutive nights.

After caffeine the mean total sleep time decreased on average by 2 h, the mean sleep latency increased to 66 minutes. The number of awakenings increased and the mean total intervening wakefulness was more than doubled after caffeine.

In the first 3 h of sleep a decreased amount of stage 3 + 4 was observed, accompanied by an increased amount of stage 2 and of intervening wakefulness, without a significant change in the amount of rapid eye movement sleep.

The change in sleep pattern observed suggests an increased capability for arousal and decreased ability to develop or sustain deeper stages of non‐rapid eye movement sleep after caffeine.
CORRELATION BETWEEN PLASMA QUINIDINE AND CARDIAC EFFECT
Authors: EDWARDS I.R. , HANCOCK B.W. , SAYNOR R.
Published: July 2012

The relationship between serum quinidine levels and rate‐corrected QT (QTc) interval after administration of single identical doses of quinidine was assessed. Quinidine concentrations were determined by a modification of Hamfelt & Malers' (1963) method. The significance and clinical application of our findings is discussed.

Individual responses (both in quinidine concentration and QTc prolongation) were variable, though the variation was no greater with QTc prolongation response than with serum quinidine levels. A significant peak in QTc prolongation occurred after quinidine administration and this was not accompanied by a similar peak in quinidine levels. There was some correlation (r = 0.53) between serum quinidine levels and QTc interval but a better correlation was found between rate of rise of quinidine concentration and QTc prolongation (r = 0.87).

One individual showed marked QTc prolongation with slow rate of rise of quinidine levels. Red cell quinidine levels were lower in this individual and he may be showing increased myocardial sensitivity to quinidine.
COMPARISON OF THE THERAPEUTIC EFFECTIVENESS OF APRINDINE, PROCAINAMIDE AND QUINIDINE IN CHRONIC VENTRICULAR DYSRHYTHMIAS
Authors: VAN DURME J.P. , BOGAERT M.G. , ROSSEEL M.T.
Published: July 2012

A cross‐over study with aprindine (100 mg daily after a loading dose of 200 mg), procainamide (4 times 1000 mg daily) and quinidine bisulphate (2 times 750 mg daily), all given orally, was performed in seventeen patients with stable chronic premature ventricular contractions following healed myocardial infarction.

The effectiveness of the treatment was evaluated during three consecutive weeks by continuous ambulatory tape recording of the electrocardiogram and repeated determinations of plasma levels were done.

The results showed that aprindine was more effective than procainamide and quinidine.

For the three drugs the therapeutic plasma levels varied markedly from patient to patient, but for each patient taken individually, the therapeutic activity could be correlated with the plasma levels.
BIOAVAILABILITY OF DIFFERENT PREPARATIONS OF PARACETAMOL
Authors: RICHTER ANNA , SMITH S.E.
Published: July 2012

Plasma drug concentrations in eight volunteer subjects following oral administration of six preparations of paracetamol have been studied.

Significant interindividual differences in plasma paracetamol concentration were found within 1 h but there were no consistent differences between the different drug preparations. The results indicate that all the preparations have equivalent bioavailability.

In four subjects, tested with the same preparation on two occasions, the findings suggest that drug absorption may differ from one occasion to another.
ALTERED DISTRIBUTION OF DIGOXIN IN RENAL FAILURE—A CAUSE OF DIGOXIN TOXICITY?
Authors: ARONSON J.K. , GRAHAME‐SMITH D.G.
Published: July 2012

Three cases are described in which renal failure was accompanied by a lowered apparent volume of distribution of digoxin. In two cases this resulted in frank digoxin toxicity and in one equivocal toxicity. In all three cases digoxin plasma levels were greater than 2 ng/ml.

The possible causes of the abnormal distribution of digoxin in renal failure are discussed.

Recommendations are outlined for the use of digoxin in patients with renal failure aimed at circumventing the problem raised by a lowered apparent volume of distribution of the drug.
DRUG ADVERTISING IN MEDICAL JOURNALS
Authors: MORGAN A.H. , JEFFERS T.A. , PETRIE J.C. , WALKER W.
Published: July 2012

One hundred different drug advertisements from each of seven leading medical journals have been assessed.

Information about drug interactions, adverse reactions, mode of action, absorption, distribution, metabolism, excretion and cost was seldom provided in UK journals.

A requirement should exist that drug advertisements include such clinically important information. Only a few pharmaceutical companies are attempting to educate doctors through their marketing and promotional material in advertisements in medical journals.
CONTROLLED TRIAL OF FRUSEMIDE AS AN ANTIEPILEPTIC DRUG IN FOCAL EPILEPSY
Authors: AHMAD S. , CLARKE LESLEY , HEWETT A.J. , RICHENS A.
Published: July 2012

The antiepileptic activity of oral frusemide (120 mg daily) was compared with that of an identical placebo in a double‐blind crossover trial in fourteen patients with severe focal epilepsy who were receiving long‐term therapy with established antiepileptic drugs.

A statistically significant reduction in the frequency of focal fits was seen with the active drug.

Marked drowsiness occurred in three patients during frusemide therapy, causing their withdrawal from the trial.

A slight, but significant, rise in serum phenobarbitone concentrations was observed during frusemide therapy, but no change was seen in serum primidone or phenytoin concentrations.

Frusemide significantly lowered plasma sodium and potassium concentrations, and increased plasma bicarbonate.
A CONTROLLED STUDY ON THE ANTIHYPERTENSIVE EFFECT OF A NEW β‐ADRENERGIC RECEPTOR BLOCKING DRUG, METOPROLOL, IN COMBINATION WITH CHLORTHALIDONE
Authors: JÄÄTTELÄ A. , PYÖRÄLÄ K.
Published: July 2012

A double‐blind crossover evaluation of the antihypertensive effect of metoprolol v. placebo was carried out in a series of twenty‐three patients with mild or moderate essential hypertension who were receiving chlorthalidone (25 mg daily) as their basic treatment. An individually titrated metoprolol dosage (75–300 mg) was used. The double‐blind crossover study consisted of two 3‐month periods during which the patients received either metoprolol or placebo in addition to chlorthalidone.

Metoprolol, as compared with placebo, produced a statistically significant reduction of blood pressure, both in supine and standing positions. Normotension was achieved during metoprolol‐chlorthalidone treatment in twenty‐two of the twenty‐three patients, but during placebo‐chlorthalidone treatment in only twelve of the twenty‐three patients.

During the double‐blind crossover study mild side‐effects occurred during metoprololchlorthalidone treatment in fourteen patients during first month, in twelve patients during second month and seven patients during third month. During placebo‐chlorthalidone treatment side effects occurred in seven, six and seven patients, respectively.

In conclusion, metoprolol caused a significant fall in blood pressure when given to patients already receiving chlorthalidone. Metoprolol in combination with chlorthalidone appears to be an effective and well‐tolerated treatment for mild and moderate hypertension in those patients not responding to chlorthalidone alone.