Sensorimotor recovery following spaceflight may be due to frequent square-wave saccadic intrusions

Square-wave jerks (SWJs) are small, involuntary saccades that disrupt steady fixation. We report the case of an astronaut (approximately 140 d on orbit) who showed frequent SWJs, especially postflight, but who showed no impairment of vision or decrement of postflight performance. These data support the view that SWJs do not impair vision because they are paired movements, consisting of a small saccade away from the fixation position followed, within 200 ms, by a corrective saccade that brings the eye back on target. Since many returning astronauts show a decrement of dynamic visual function during postflight locomotion, it seems possible that frequent SWJs improved this astronaut's visual function by providing postsaccadic enhancement of visual fixation, which aided postflight performance. Certainly, frequent SWJs did not impair performance in this astronaut, who had no other neurological disorder.     

Structural characterization and pharmacology of a potent (Cys101-Cys119, Cys110-Cys117) bicyclic agouti-related protein (AGRP) melanocortin receptor antagonist

Agouti-related protein (AGRP) is one of two known naturally occurring antagonists of G-protein coupled receptors. AGRP is synthesized in the brain and is an antagonist of the melanocortin-3 and -4 receptors (MC3R, MC4R). These three proteins are involved in the regulation of energy homeostasis and obesity in both mice and humans. The human AGRP protein is 132 amino acids and contains five disulfide bridges in the C-terminal domain. Previous reports of the NMR structures of hAGRP(87-132) and a truncated 34 amino acid form consisting of four disulfide bridges identified that AGRP contains an inhibitor cystine knot (ICK) structural fold, and that is the first mammalian example. Herein, we report a bicyclic hAGRP analogue that, when compared to hAGRP(87-132), possesses equal binding affinity but is 80-fold less potent at the mouse MC4R. Using NMR, computer assisted molecular modeling (CAMM), and cluster analysis, we have identified five structural families, two of which are highly populated, of this bicyclic hAGRP analogue. Computational docking experiments of this bicyclic hAGRP derivative, using a three-dimensional homology molecular model of the mouse MC4R, identified that three of the five structural families could be docked into the MC4R without problems from steric hindrance. Those three docked mMC4R-bicyclic hAGRP family structures were compared with putative hAGRP(87-132) ligand-receptor interactions previously reported (Wilczynski et al. J. Med. Chem. 2004, 47, 2194) in attempts to identify a "bioactive" conformation of the bicyclic hAGRP peptide and account for the 80-fold decreased ligand potency compared to hAGRP(87-132).     

Progesterone receptor ligand binding pocket flexibility: crystal structures of the norethindrone and mometasone furoate complexes

Although progesterone, the natural ligand of the progesterone receptor (PR), has a hydrogen atom at the 17alpha position, other potent steroid agonists such as norethindrone and mometasone furoate have larger substituents at this position that are accommodated by the PR ligand binding pocket. Crystallographic analysis of PR ligand binding domain complexes clearly demonstrated that these moieties were accommodated by local shifts of the protein main chain and by adoption of alternative side chain rotamer conformations of ligand-proximal amino acids. These conformational changes imparted a ligand-specific volume to the binding pocket, from 490 A3 in the metribolone complex to 520 A3 in the norethindrone complex, 565 A3 in the progesterone complex, and 730 A3 in the mometasone furoate complex. Despite these marked alterations in binding pocket volume, critical interactions essential for establishment of an active AF2 conformation were maintained.     

Quantitative assays of chemotaxis and chemokinesis for human neural cells

Cell migration is vital for many physiological processes, and its modulation is likely to be of therapeutic benefit. In this study we have developed fluorescence image-based chemokinesis and chemotaxis assays on the Cellomics (Pittsburgh, PA) ArrayScan platform, which would be suitable for industrial drug discovery in a variety of fields. Studying the migratory characteristics of neural stem cells is of interest for understanding the therapeutic potential of these cells, in terms of both cellular transplantation and the activation of endogenous populations of stem cells. Growth conditions were identified whereby human neural precursors could be maintained as neurospheres and plated out into microtitre plates for high-content assays. Chemokinesis was assessed using fluorescent bead-coated 96-well microtitre plates, whilst chemotaxis was assessed using BD Biosciences (Oxford, UK) Fluoroblok 24-well plates. Assays for both chemokinesis and chemotaxis were developed that were quantified automatically using the ArrayScan and appropriate algorithms. Using the two complementary techniques, foetal bovine serum was observed to have chemokinetic effects on the cells, whilst platelet-derived growth factor isoform AB was chemotactic. The two assays described here are suitable for screening for novel modulators of cell migration, or for performing more detailed mechanistic follow-up studies. These assays enable us to perform cell motility studies with minimal laboratory handling, in an automated manner, thereby allowing quantitative studies of cell behaviour to be incorporated in a routine drug discovery screening cascade.     

Reduced perception of urgency in treatment of overactive bladder with extended-release tolterodine

OBJECTIVE: To evaluate the effect of once-daily, extended-release tolterodine on urinary urgency in patients with overactive bladder. METHODS: Patients with urinary frequency (eight or more micturitions per 24 hours) and urge incontinence (five or more episodes per week) were randomized to oral treatment with tolterodine extended release 4 mg once daily (n=398) or placebo (n=374) for 12 weeks. Efficacy was assessed by use of patient perception evaluations. RESULTS: The results presented are a secondary analysis of this double-blind, placebo-controlled study. Of patients treated with tolterodine extended release, 44% reported improved urgency symptoms (compared with 32% for placebo), and 62% reported improved bladder symptoms (placebo, 48%) (both P<.001 compared with placebo). The odds of reducing urgency and improving bladder symptoms were 1.68 and 1.78 times greater, respectively, for patients in the tolterodine extended release group than for patients receiving placebo. In response to urgency, there was a more than six-fold increase in the proportion of patients able to finish a task before voiding in the tolterodine extended release group. The proportion of patients unable to hold urine upon experiencing urgency was also decreased by 58% with tolterodine, compared with 32% with placebo (P<.001). The proportion of patients reporting "much benefit" from treatment was greater for tolterodine extended release than for placebo (43% versus 24%; P<.001). The only adverse events with an incidence of greater than 5% were dry mouth, headache, and constipation, with only dry mouth markedly more frequent with tolterodine than with placebo. CONCLUSION: Tolterodine extended release has demonstrable efficacy in reducing the severity of urinary urgency and is associated with improvements in overactive bladder symptoms that are meaningful to patients.     

Palliative irradiation of the spleen

We analyzed the efficacy of splenic irradiation in a population of patients with hematologic diseases. The records of the Radiation Oncology Division, Naval Medical Center San Diego were retrospectively reviewed for all patients treated with splenic irradiation (SI) between January 1, 1990 and March 1, 2001. The charts of 17 patients were identified: 5 patients had chronic myelogenous leukemia, 4 had chronic lymphocytic leukemia, 4 had idiopathic myelofibrosis, 2 had polycythemia vera, and 1 patient each had idiopathic thrombocytopenic purpura and acute myelogenous leukemia. Patient ages ranged from 37 to 88 years. Sixteen of 17 suffered from symptomatic splenomegaly. Twenty-six courses of splenic irradiation were delivered to these 17 patients. Treatment courses generally consisted of two fractions of 50 cGy in the first week, two fractions of 75 cGy the second week, and two fractions of 100 cGy the third week. Blood counts were checked prior to each treatment. Seven of the 17 patients died 1 month or less after SI due to the terminal nature of their disease. Twenty-two of 25 treatment courses for splenomegaly resulted in decreased pain and symptoms. Five patients required two treatment courses for splenomegaly, and one patient required five treatment courses. Three of four patients treated for thrombocytopenia demonstrated improvement, but only one was evaluable for more than 2 weeks due to disease-related mortality. Three of five patients treated for leukocytosis had significant improvement. In general, patients suffered few significant complications from this palliative intervention. Splenic irradiation can effectively palliate symptomatic splenomegaly in patients for whom splenectomy is not an option. Retreatment is possible. Splenic irradiation is less effective in the treatment of thrombocytopenia or leukocytosis.     

Long-term neuronal effects and disposition of ectopic preproNGF gene transfer into the rat septum

Although NGF gene therapy has been proposed to treat age- or disease-related brain cholinergic decline, little is known about the ectopic expression or function of this trophic factor after transduction in the brain especially over long intervals. The neuron-targeting, recombinant adeno-associated virus serotype 2 (rAAV2) vector was used to express mouse NGF with C-terminal myc-tag in septum using a full-length preproNGF sequence. While the predominant form of endogenous NGF immunoreactivity in septum was 31 kd of proNGF, almost all of the ectopic NGF-immunoreactivity attributable to the rAAV2-mediated transduction in this region was recovered as mature NGF. Transgene expression was found in both cholinergic and GABAergic neurons, with the number of transduced neurons dependent on vector dose. To determine the long-term effects of this NGF-expression on neuron function, fimbria-fornix (FF) lesions were conducted 6 months after NGF gene transfer. NGF gene transfer attenuated the lesion-induced loss of septal cholinergic but not GABAergic neurons, indicating that long-term expression did not eliminate this response, which has been noted over short intervals. The effects and dose dependency of NGF gene delivery on neuroprotection and neurotrophism were also examined. NGF transduction increased cholinergic cell size in the septum, but required a higher vector dose than neuroprotection. These results reveal potential long-term benefits as well as concerns for genetically modifying septal NGF gene expression to preserve neuronal viability and function.