bluuebunny/crossref_metadata_2025_split huggingface dataset:
The sensor protein KdpD inserts into the Escherichia coli membrane independent of the Sec translocase and YidC
Authors: Facey Sandra J. , Kuhn Andreas 
Published: December 2004

KdpD is a sensor kinase protein in the inner membrane of Escherichia coli containing four transmembrane regions. The periplasmic loops connecting the transmembrane regions are intriguingly short and protease mapping allowed us to only follow the translocation of the second periplasmic loop. The results show that neither the Sec translocase nor the YidC protein are required for membrane insertion of the second loop of KdpD. To study the translocation of the first periplasmic loop a short HA epitope tag was genetically introduced into this region. The results show that also the first loop was translocated independently of YidC and the Sec translocase. We conclude that KdpD resembles a new class of membrane proteins that insert into the membrane without enzymatic assistance by the known translocases.When the second periplasmic loop was extended by an epitope tag to 27 amino acid residues, the membrane insertion of this loop of KdpD depended on SecE and YidC. To test whether the two periplasmic regions are translocated independently of each other, the KdpD protein was split between helix 2 and 3 into two approximately equal‐sized fragments. Both constructed fragments, which contained KdpD‐N (residues 1–448 of KdpD) and the KdpD‐C (residues 444–894 of KdpD), readily inserted into the membrane. Similar to the epitope‐tagged KdpD protein, only KdpD‐C depended on the presence of the Sec translocase and YidC. This confirms that the four transmembrane helices of KdpD are inserted pairwise, each translocation event involving two transmembrane helices and a periplasmic loop.
Solution structure of crotamine, a Na+ channel affecting toxin from Crotalus durissus terrificus venom
Authors: Nicastro Giuseppe , Franzoni Lorella , de Chiara Cesira , Mancin Adriana C. , Giglio Josè R. , Spisni Alberto 
Published: December 2004

Crotamine is a component of the venom of the snake Crotalus durissus terrificus and it belongs to the myotoxin protein family. It is a 42 amino acid toxin cross‐linked by three disulfide bridges and characterized by a mild toxicity (LD50 = 820 µg per 25 g body weight, i.p. injection) when compared to other members of the same family. Nonetheless, it possesses a wide spectrum of biological functions. In fact, besides being able to specifically modify voltage‐sensitive Na+ channel, it has been suggested to exhibit analgesic activity and to be myonecrotic. Here we report its solution structure determined by proton NMR spectroscopy. The secondary structure comprises a short N‐terminal α‐helix and a small antiparallel triple‐stranded β‐sheet arranged in an αβ1β2β3 topology never found among toxins active on ion channels. Interestingly, some scorpion toxins characterized by a biological activity on Na+ channels similar to the one reported for crotamine, exhibit an α/β fold, though with a β1αβ2β3 topology.In addition, as the antibacterial β‐defensins, crotamine interacts with lipid membranes. A comparison of crotamine with human β‐defensins shows a similar fold and a comparable net positive potential surface.To the best of our knowledge, this is the first report on the structure of a toxin from snake venom active on Na+ channel.
The Effects of Starvation on Crayfish Responses to Alarm Odor
Authors: Hazlett Brian A. 
Published: December 2004

AbstractThe effect of starvation on responses to alarm odor was tested with individuals of an invasive and a native species of crayfish. I predicted that chemical predator cues would inhibit feeding less in starving than well‐fed animals, and that this decrease would be stronger in a native compared with an invasive species. Individuals were exposed to food odor and then alarm odor after 3 and 10 d of starvation. The inhibition of food‐related behavior patterns was similar on the 2 d of testing for individuals of the invasive species, Orconectes rusticus. Individuals of O. virilis showed a significant reduction in the effects of alarm odor detection on day 10 compared with day 3 of starvation. The lack of a change in responses to alarm odors between days of testing by individuals of O. rusticus may be because they are more responsive to alarm odors than individuals of O. virilis. This behavioral difference could contribute to the successful range extension of O. rusticus.
Impact of blood testing on patient disposition from the emergency department
Authors: Knott Jonathan C , Meyer Alastair D McR 
Published: December 2004

AbstractObjective: To determine whether blood test results lead to a change in planned disposition of patients from the ED.Methods: A prospective review of the anticipated and actual disposition of patients from the ED before and after blood test results, including stratification by seniority of medical staff.Results: There were 256 patients enrolled, 53% had blood tests requested. Expected disposition was not altered by test results in 87% of patients having blood tests. Medical staff were poor at identifying those patients whose disposition would be altered by their blood results (sensitivity 44%, specificity 72%, negative predictive value 89%). Seniority of medical staff was not associated with an alteration in disposition due to the blood results (P = 0.37).Conclusions: Blood test results have minimal impact on expected patient disposition from the ED. Recognition of this may improve resource utilisation with earlier discharge planning.
Intravenous pamidronate in the treatment and prevention of osteoporosis
Authors: Chan S. S. Y. , Nery L. M. , McElduff A. , Wilmshurst E. G. , Fulcher G. R. , Robinson B. G. , StIel J. N. , Gunton J. E. , Clifton‐Bligh P. B. 
Published: December 2004

Abstract Background : Potent oral bisphosphonates are the mainstay of therapy for osteoporosis. However, there are patients who cannot have oral bisphosphonates (e.g. because of gastrointestinal side‐effects). Therefore, we wanted to examine the effects of intermittent i.v. pamidronate (APD) on bone mineral density (BMD) in patients who needed bisphosphonate therapy but could not have oral bisphosphonates.Aim : To assess BMD before and after intermittent i.v. APD in patients requiring a bisphosphonate either for the prevention of osteoporosis on concurrent steroid therapy or for the treatment of osteoporosis.Methods:  This was a retrospective audit of 84 consecutive patients at risk of fractures commencing APD between October 1997 and May 2000. Patients were treated with intermittent i.v. APD. BMD as measured by dual‐energy X‐ray absorptiometry before and after APD was the main outcome.Results:  The mean length of treatment and mean total APD dose were 16.8 ± 7.0 months and 186.1 ± 79.5 mg respectively. The reasons for using APD were failure to qualify for oral bisphosphonates on the pharmaceutical benefits scheme due to lack of documented minimal trauma fractures (58%), symptomatic gastro‐­oesophageal disease (20%), intolerance of oral bisphosphonates (18%) and lack of efficacy of calcitriol (4%). Mean baseline T‐score at lumbar (L) 2−4 spine and femoral neck were −1.54 ± 1.22 and − 2.87 ± 1.19, respectively.From baseline to after APD treatment, there was a significant increase in L2−4 BMD (0.883 ± 0.175 vs 0.912 ± 0.176 g/cm2, P < 0.001, mean increase +3.5%), in femoral neck BMD (0.667 ± 0.137 vs 0.680 ± 0.134 g/cm2, P= 0.001, mean increase +2.1%) and in trochanteric BMD (0.549 ± 0.129 vs 0.566 ± 0.132 g/cm2, P < 0.001, mean increase +3.1%). One‐third of the patients were on oral glucocorticoids at the time of the present study and they had a similar increase in BMD compared to patients not on gluco­corticoids. Mild side‐effects occurred in seven patients, none of whom discontinued treatment.Conclusion : Intermittent APD increases BMD and may be a suitable alternative for patients who cannot have oral bisphosphonates. (Intern Med J 2004; 34: 162−166)
Long‐term potentiation of mGluR1 activity by depolarization‐induced Homer1a in mouse cerebellar Purkinje neurons
Authors: Minami Itsunari , Kengaku Mineko , Smitt Peter Sillevis , Shigemoto Ryuichi , Hirano Tomoo 
Published: December 2004

AbstractMetabotropic glutamate receptor 1 (mGluR1) plays a crucial role in synaptic plasticity and motor learning in the cerebellum. We have studied activity‐dependent changes in mGluR1 function in mouse cultured Purkinje neurons. Depolarizing stimulation potentiated Ca2+ and current responses to an mGluR1 agonist for several hours in the cultured Purkinje neurons. It also blocked internalization of mGluR1 and increased the number of mGluR1s on the cell membrane. We found that depolarization simultaneously increased transcription of Homer1a in Purkinje neurons. Homer1a inhibited internalization and increased cell‐surface expression of mGluR1 when coexpressed in human embryonic kidney (HEK)‐293 cells. Depolarization‐induced Homer1a expression in Purkinje neurons was blocked by a mitogen‐activated protein kinase (MAPK) inhibitor. Changes in internalization and mGluR1‐mediated Ca2+ response were also blocked by inhibition of MAPK activity, suggesting that localization and activity of mGluR1 were regulated in the same signalling pathway as Homer1a expression. It is thus suggested that depolarization of the Purkinje neuron leads to the increment in mGluR1 responsiveness through MAPK activity and induction of Homer1a expression, which increases active mGluR1 on the cell surface by blocking internalization of mGluR1.
Does luminance‐contrast contribute to a saliency map for overt visual attention?
Authors: Einhäuser Wolfgang , König Peter 
Published: December 2004

AbstractIn natural environments, humans select a subset of visual stimuli by directing their gaze to locations attended. In previous studies it has been found that at fixation points luminance‐contrast is higher than average. This led to the hypothesis that luminance‐contrast makes a major contribution to a saliency map of visual overt attention, consistent with a computation of stimulus saliency in early visual cortical areas. We re‐evaluate this hypothesis by using natural and modified natural images to uncover the causal effects of luminance‐contrast to human overt visual attention and: (i) we confirm that when viewing natural images, contrasts are elevated at fixation points. This, however, only holds for low spatial frequencies and in a limited temporal window after stimulus onset; (ii) however, despite this correlation between overt attention and luminance‐contrast, moderate modifications of contrast in natural images do not measurably affect the selection of fixation points. Furthermore, strong local reductions of luminance‐contrast do not repel but attract fixation; (iii) neither contrast nor contrast modification is correlated to fixation duration; and (iv), even the moderate contrast modifications used fall into the physiologically relevant range, and subjects are well able to detect them in a forced choice paradigm. In summary, no causal contribution of luminance‐contrast to a saliency map of human overt attention is detectable. In conjunction with recent results on the relation of contrast sensitivity of neuronal activity to the level in the visual cortical hierarchy, the present study provides evidence that, for natural scenes, saliency is computed not early but late during processing.
Nucleus accumbens β‐endorphin levels are not elevated by brain stimulation reward but do increase with extinction
Authors: Zangen Abraham , Shalev Uri 
Published: December 2004

Abstractβ‐Endorphin is an endogenous opioid peptide implicated in reward processes, but the brain sites directly involved in its putative role in reward have not been identified. Here we used in vivo microdialysis in rats to study the effect of a potent reinforcer, lateral hypothalamus self‐stimulation (LHSS), on the extracellular levels of β‐endorphin in the nucleus accumbens (NAS). The NAS is involved in the reinforcing effects of natural and artificial rewards, has high density of opioid receptors and is innervated by arcuate nucleus β‐endorphin neurons. LHSS had no effect on extracellular levels of β‐endorphin in the NAS. Surprisingly, extinction of the self‐stimulation behaviour induced a rapid increase in NAS β‐endorphin levels. In a subsequent experiment in rats previously trained to self‐administer heroin for 10 days, β‐endorphin levels also were increased during a test for extinction of the heroin‐reinforced behaviour. Finally, the increase in extracellular β‐endorphin levels in the NAS was also observed during exposure to an aversive stimulus, intermittent footshock (20 min). These results indicate a possible role for increased levels of NAS β‐endorphin in the organism's adaptive response to stress and frustration.
Actions of neuropeptide Y and growth hormone secretagogues in the arcuate nucleus and ventromedial hypothalamic nucleus
Authors: Kumarnsit Ekkasit , Johnstone Louise E. , Leng Gareth 
Published: December 2004

AbstractSystemic or central administration of growth‐hormone secretagogues (GHS) induces dense Fos expression in the arcuate nucleus but little or no Fos expression in the ventromedial hypothalamic nucleus, although both sites show intense expression of mRNA for the GHS receptor. Here, we recorded the electrical activity of single neurons from the arcuate nucleus and from the ventromedial hypothalamic nucleus in a rat hypothalamic slice preparation, and compared responses of these two populations to GHS. At both sites, the predominant neuronal response to GHS was a long‐lasting excitation, indicating that GHS receptors at both sites are functional and similarly coupled to electrical excitation. We also tested neurons at both sites for their responses to neuropeptide Y and to somatostatin; at both sites the predominant response to each of these peptides was inhibitory. The arcuate cells that are activated by GHS include neuropeptide Y cells and growth hormone‐releasing hormone cells. It seems possible that neuropeptide Y released in the ventromedial hypothalamus from the terminals of arcuate neurons counteracts the activation of ventromedial hypothalamic neurons by GHS in vivo, or that somatostatin released following liberation of growth hormone may do so.
Glucocorticoid‐induced impairment of declarative memory retrieval is associated with reduced blood flow in the medial temporal lobe
Authors: De Quervain Dominique J.‐F. , Henke Katharina , Aerni Amanda , Treyer Valerie , McGaugh James L. , Berthold Thomas , Nitsch Roger M. , Buck Alfred , Roozendaal Benno , Hock Christoph 
Published: December 2004

AbstractPrevious work indicates that stress levels of circulating glucocorticoids can impair retrieval of declarative memory in human subjects. Several studies have reported that declarative memory retrieval relies on the medial temporal lobe. The present study used \mathrm{H}^{15}_{2}O‐positron emission tomography to investigate whether acutely elevated glucocorticoid levels affect regional cerebral blood flow in the medial temporal lobe, as well as in other brain regions, during declarative memory retrieval in healthy male human subjects. When measured over four different declarative memory retrieval tasks, a single, stress‐level dose of cortisone (25 mg) administered orally 1 h before retention testing, induced a large decrease in regional cerebral blood flow in the right posterior medial temporal lobe, the left visual cortex and the cerebellum. The decrease in the right posterior medial temporal lobe was maximal in the parahippocampal gyrus, a region associated with successful verbal memory retrieval. Cortisone administration also significantly impaired cued recall of word pairs learned 24 h earlier, while drug effects on performance in the other tasks (verbal recognition, semantic generation and categorization) were not significant. The present results provide further evidence that acutely elevated glucocorticoid levels can impair declarative memory retrieval processes and suggest that such impairments may be related to a disturbance of medial temporal lobe function.
Involvement of calcineurin in the neurotoxic effects induced by amyloid‐beta and prion peptides
Authors: Agostinho Paula , Oliveira Catarina Resende 
Published: December 2004

AbstractIt is usually accepted that prion and amyloid‐beta (Aβ) peptides induce apoptotic cell death. However, the mechanisms that trigger neuronal death, induced by these amyloidogenic peptides, remain to be clarified. In the present study we analysed the neurotoxic effects of the synthetic prion and Aβ peptides, PrP106‐126 and Aβ25−35, in primary cultures of rat brain cortical cells. PrP106‐126 and Aβ25−35 incubated at a concentration of 25 µm for 24 h, did not affect cell membrane integrity, but decreased the metabolic capacity of the cells. The intracellular free Ca2+ concentration and reactive oxygen species levels increased significantly after 24 h treatment with PrP106‐126 and Aβ25−35. Furthermore, these peptides (after 24 h exposure) also induced cytochrome c release from mitochondria and increased caspase‐3‐like activity. FK506, an inhibitor of the Ca2+/calmodulin‐dependent phosphatase, calcineurin, was able to prevent cytochrome c release, caspase‐3 activation and cell death induced by Aβ25−35 or PrP106‐126 peptides. Taken together these data suggest that calcineurin is involved in Aβ25−35 and PrP106‐126 neurotoxicity.
Inhibition of rostral basal forebrain neurons promotes wakefulness and induces FOS in orexin neurons
Authors: Satoh Shinsuke , Matsumura Hitoshi , Nakajima Tomoko , Nakahama Ken‐ichi , Kanbayashi Tuyoshi , Nishino Seiji , Yoneda Hiroshi , Shigeyoshi Yasufumi 
Published: December 2004

AbstractThe present study examined whether the activities of the rostral basal forebrain neurons alter the activities of the orexin (also known as hypocretin) neurons in the tuberal part of the hypothalamus in rats. We performed microdialysis perfusion of the ventromedial portion of the rostral basal forebrain with the GABAA receptor agonist muscimol to inhibit focally the neuronal activities in the rostral basal forebrain. Then, we monitored sleep/wake behaviour and investigated the pattern of activities of orexin neurons by examining the expression of FOS as an indicator of cellular activation. Bilateral perfusion with muscimol (5, 15, and 50 µm) produced a dose‐dependent decrease in the amount of sleep. This perfusion with muscimol at 50 µm produced FOS‐like immunoreactivity in 37% of the orexin neurons located in the tuberal part of the hypothalamus, whereas the FOS‐like immunoreactivity was sparse in orexin neurons of the sleeping control rats (P = 0.001 by Mann–Whitney U‐test). Unilateral perfusion with muscimol (50 µm) also suppressed sleep. In this case, FOS‐like immunoreactivity was seen in 40% of the orexin neurons on the side ipsilateral to the perfusion site but only in 10% of orexin neurons on the contralateral side (P = 0.018 by Wilcoxon signed rank test). These functional data suggested that a sleep‐generating element in the ventromedial part of the rostral basal forebrain provides an inhibitory influence on the activities of the orexin neurons in the tuberal part of the hypothalamus.
Periodic absence of nursing mothers phase‐shifts circadian rhythms of clock genes in the suprachiasmatic nucleus of rat pups
Authors: Ohta Hidenobu , Honma Sato , Abe Hiroshi , Honma Ken‐ichi 
Published: December 2004

AbstractEffects of absence of nursing mothers on the circadian pacemaker of their offspring were examined by measuring clock genes, the rat Per1 (rPer1) and rPer2 expression rhythms in the pup suprachiasmatic nuclei (SCN). Neonate rats born to mothers kept under a 12‐h light : 12‐h dark cycle (LD) were blinded immediately after birth and exposed to periodic maternal deprivation where pups were deprived of their mothers during the light phase of 12‐h for the first week of life. At postnatal day 6, the periodic maternal deprivation completely phase‐reversed the circadian rhythms in expression of the clock genes in the pup SCN and in spontaneous locomotor activity after the pups were weaned at postnatal day 21. The periodic maternal absence also altered the patterns of stress‐related gene expressions such as corticotropine‐releasing hormone, arginine vasopressin, and glucocorticoid receptor in particular brain areas of the mother‐deprived pups at P6. These findings indicate that periodic absence of the nursing mother in the first week of life produces a resetting effect on the neonatal circadian clock and induces stress responses in the hypothalamus–pituitary–adrenal axis.
Mineralocorticoid receptor expression and increased survival following neuronal injury
Authors: Macleod Malcolm R. , Johansson Inga‐Maj , Söderström Ingegerd , Lai Maggie , Gidö Gunilla , Wieloch Tadeusz , Seckl Jonathan R. , Olsson Tommy 
Published: December 2004

AbstractGlucocorticoids, acting via the mineralocorticoid receptor, are required for granule neuronal survival in the rat dentate gyrus. Whether this mineralocorticoid receptor‐mediated neuroprotective effect has more general applicability is unknown. Here we report increased mineralocorticoid receptor expression in rat hippocampal and cortical neurons exposed in vitro to low levels of staurosporine and in rat hippocampal pyramidal neurons exposed in vivo to hypothermic transient global ischaemia. In both the cell culture system and the in vivo system increased mineralocorticoid receptor expression is associated with increased neuronal survival, and this increase is reversed by mineralocorticoid receptor antagonism. Modulation of mineralocorticoid receptor gene expression may therefore be an important target for reduction of brain injury in conditions caused by cerebral ischaemia including brain damage following cardiac arrest and stroke.
Calcium‐dependent phosphorylation processes control brain aromatase in quail
Authors: Balthazart J. , Baillien M. , Charlier T. D. , Ball G. F. 
Published: December 2004

AbstractIncreased gene transcription activated by the binding of sex steroids to their cognate receptors is one important way in which oestrogen synthase (aromatase) activity is regulated in the brain. This control mechanism is relatively slow (hours to days) but recent data indicate that aromatase activity in quail preoptic‐hypothalamic homogenates is also rapidly (within minutes) affected by exposure to conditions that enhance Ca2+‐dependent protein phosphorylation. We demonstrate here that Ca2+‐dependent phosphorylations controlled by the activity of multiple protein kinases including PKC, and possibly also PKA and CAMK, can rapidly down‐regulate aromatase activity in brain homogenates. These phosphorylations directly affect the aromatase molecule itself. Western blotting experiments on aromatase purified by immunoprecipitation reveal the presence on the enzyme of phosphorylated serine, threonine and tyrosine residues in concentrations that are increased by phosphorylating conditions. Cloning and sequencing of the quail aromatase identified a 1541‐bp open reading frame that encodes a predicted 490‐amino‐acid protein containing all the functional domains that have been previously described in the mammalian and avian aromatase. Fifteen predicted consensus phosphorylation sites were identified in this sequence, but only two of these (threonine 455 and 486) match the consensus sequences corresponding to the protein kinases that were shown to affect aromatase activity during the pharmacological experiments (i.e. PKC and PKA). This suggests that the phosphorylation of one or both of these residues represents the mechanism underlying, at least in part, the rapid changes in aromatase activity.