Cryptanalysis of the RCES/RSES image encryption scheme

Recently, a chaos-based image encryption scheme called RCES (also called RSES) was proposed. This paper analyses the security of RCES, and points out that it is insecure against the known/chosen-plaintext attacks: the number of required known/chosen plain-images is only one or two to succeed an attack. In addition, the security of RCES against the brute-force attack was overestimated. Both theoretical and experimental analyses are given to show the performance of the suggested known/chosen-plaintext attacks. The insecurity of RCES is due to its special design, which makes it a typical example of insecure image encryption schemes. A number of lessons are drawn from the reported cryptanalysis of RCES, consequently suggesting some common principles for ensuring a high level of security of an image encryption scheme.     

Discovery of the ammonium substrate site on glutamine synthetase, a third cation binding site

Glutamine synthetase (GS) catalyzes the ATP-dependent condensation of ammonia and glutamate to yield glutamine, ADP, and inorganic phosphate in the presence of divalent cations. Bacterial GS is an enzyme of 12 identical subunits, arranged in two rings of 6, with the active site between each pair of subunits in a ring. In earlier work, we have reported the locations within the funnel-shaped active site of the substrates glutamate and ATP and of the two divalent cations, but the site for ammonia (or ammonium) has remained elusive. Here we report the discovery by X-ray crystallography of a binding site on GS for monovalent cations, Tl+ and Cs+, which is probably the binding site for the substrate ammonium ion. Fourier difference maps show the following. (1) Tl+ and Cs+ bind at essentially the same site, with ligands being Glu 212, Tyr 179, Asp 50', Ser 53' of the adjacent subunit, and the substrate glutamate. From its position adjacent to the substrate glutamate and the cofactor ADP, we propose that this monovalent cation site is the substrate ammonium ion binding site. This proposal is supported by enzyme kinetics. Our kinetic measurements show that Tl+, Cs+, and NH4+ are competitive inhibitors to NH2OH in the gamma-glutamyl transfer reaction. (2) GS is a trimetallic enzyme containing two divalent cation sites (n1, n2) and one monovalent cation site per subunit. These three closely spaced ions are all at the active site: the distance between n1 and n2 is 6 A, between n1 and Tl+ is 4 A, and between n2 and Tl+ is 7 A. Glu 212 and the substrate glutamate are bridging ligands for the n1 ion and Tl+. (3) The presence of a monovalent cation in this site may enhance the structural stability of GS, because of its effect of balancing the negative charges of the substrate glutamate and its ligands and because of strengthening the "side-to-side" intersubunit interaction through the cation-protein bonding. (4) The presence of the cofactor ADP increases the Tl+ binding to GS because ADP binding induces movement of Asp 50' toward this monovalent cation site, essentially forming the site. This observation supports a two-step mechanism with ordered substrate binding: ATP first binds to GS, then Glu binds and attacks ATP to form gamma-glutamyl phosphate and ADP, which complete the ammonium binding site. The third substrate, an ammonium ion, then binds to GS, and then loses a proton to form the more active species ammonia, which attacks the gamma-glutamyl phosphate to yield Gln. (5) Because the products (Glu or Gln) of the reactions catalyzed by GS are determined by the molecule (water or ammonium) attacking the intermediate gamma-glutamyl phosphate, this negatively charged ammonium binding pocket has been designed naturally for high affinity of ammonium to GS, permitting glutamine synthesis to proceed in aqueous solution.     

On measuring network robustness for weighted networks

Knowledge and Information Systems - Network robustness measures how well network structure is strong and healthy when it is under attack, such as vertices joining and leaving. It has been widely...     

Hyperprolactinemia in end‐stage renal disease and effects of frequent hemodialysis

Introduction: End‐stage renal disease is associated with elevations in circulating prolactin concentrations, but the association of prolactin concentrations with intermediate health outcomes and the effects of hemodialysis frequency on changes in serum prolactin have not been examined. Methods: The FHN Daily and Nocturnal Dialysis Trials compared the effects of conventional thrice weekly hemodialysis with in‐center daily hemodialysis (6 days/week) and nocturnal home hemodialysis (6 nights/week) over 12 months and obtained measures of health‐related quality of life, self‐reported physical function, mental health and cognition. Serum prolactin concentrations were measured at baseline and 12‐month follow‐up in 70% of the FHN Trial cohort to examine the associations among serum prolactin concentrations and physical, mental and cognitive function and the effects of hemodialysis frequency on serum prolactin. Findings: Among 177 Daily Trial and 60 Nocturnal Trial participants with baseline serum prolactin measurements, the median serum prolactin concentration was 65 ng/mL (25th–75th percentile 48–195 ng/mL) and 81% had serum prolactin concentrations >30 ng/mL. While serum prolactin was associated with sex (higher in women), we observed no association between baseline serum prolactin and age, dialysis vintage, and baseline measures of physical, mental and cognitive function. Furthermore, there was no significant effect of hemodialysis frequency on serum prolactin in either of the two trials. Discussion: Serum prolactin concentrations were elevated in the large majority of patients with ESRD, but were not associated with several measures of health status. Circulating prolactin levels also do not appear to decrease in response to more frequent hemodialysis over a one‐year period.     

Localization of atrial natriuretic peptide receptors in the rat tongue and hard palate

The effect of a naturally occurring plant phenolic constituent (the acylphloroglucinol derivative, jensenone, derived from Eucalyptus jensenii) on the food intake of two folivorous marsupials, the common ringtail (Pseudocheirus peregrinus) and the common brushtail possum (Trichosurus vulpecula) was studied. When fed diets containing varying concentrations of jensenone, both species regulated their intake of jensenone so as not to exceed a ceiling intake. This ceiling was about twice as high for common ringtails as for common brushtails from northern Australia. Southern populations of common ringtails showed greatly reduced capacities to tolerate jensenone. When common brushtails were injected (0.5 mg.kg-0.75 body mass) with ondansetron (a selective antagonist of serotonin 5HT3 receptors), they ate significantly more jensenone than animals injected with physiological saline. The same pattern was observed when common ringtails were fed diets containing both jensenone and ondansetron (0.0035 mg.g-1 wet mass of diet). Ondansetron injection had no effect on food intake when the food did not contain jensenone while the addition of higher doses of ondansetron to diets of common ringtails very slightly reduced food intakes of a non-jensenone diet. When common brushtails were given 50 mg of jensenone by gastric lavage, their average subsequent intake of dietary jensenone matched the difference between the daily threshold and the dose given, although the response of individuals was highly variable. Lavage with water alone had no effect on subsequent jensenone intake compared with the pre-dose period. We interpret these results as evidence that the antifeedant effects of jensenone and related compounds are partly mediated by serotonin action on 5HT3 receptors most likely via "nausea" to condition a food aversion.     

Solution structure of glutathione bound to human glutathione transferase P1-1: comparison of NMR measurements with the crystal structure

The conformation of the bound glutathione (GSH) in the active site of the human glutathione transferase P1-1 (EC 2.5.1.18) has been studied by transferred NOE measurements and compared with those obtained by X-ray diffraction data. Two-dimensional TRNOESY and TRROESY experiments have been performed under fast-exchange conditions. The family of GSH conformers, compatible with TRNOE distance constraints, shows a backbone structure very similar to the crystal model. Interesting differences have been found in the side chain regions. After restrained energy minimization of a representative NMR conformer in the active site, the sulfur atom is not found in hydrogen-bonding distance of the hydroxyl group of Tyr 7. This situation is similar to the one observed in an "atypical" crystal complex grown at low pH and low temperature. The NMR conformers display also a poorly defined structure of the glutamyl moiety, and the presence of an unexpected intermolecular NOE could indicate a different interaction of this substrate portion with the G-site. The NMR data seem to provide a snapshot of GSH in a precomplex where the GSH glutamyl end is bound in a different fashion. The existence of this precomplex is supported by pre-steady-state kinetic experiments [Caccuri, A. M., Lo Bello, M., Nuccetelli, M., Nicotra, M., Rossi, P., Antonini, G., Federici, G., and Ricci, G. (1998) Biochemistry 37, 3028-3034] and preliminary time-resolved fluorescence data.     

Infective endocarditis complicated with rapidly progressive glomerulonephritis: a case report

Despite a general national decline in criminal activities in the 1990s, juvenile criminal offenses continue to increase, (including violent, property, and delinquency acts). In addition increased numbers of children are being held in juvenile jails. It is all but impossible for pediatric health providers to think that "their patients" and "their practices" are immune from the epidemic of crime that affects and is caused by "just kids."     

Rerouting of the intratemporal facial nerve: an analysis of the literature

Anterior rerouting of the intratemporal facial nerve in the infratemporal fossa approach is employed to access to the jugular bulb, hypotympanum, and lateral skull base, whereas posterior rerouting of the facial nerve, as employed in the transcochlear craniotomy, is most frequently used for surgery of the posterior fossa, cerebellopontine angle, prepontine region, and petrous apex. Facial nerve rerouting may lead to facial paresis or paralysis. This review of the literature is intended to define the physiologic "cost" of these procedures, so that the neurotologic surgeon can determine if the morbidity incurred in these techniques is worth the resultant exposure. Inconsistencies in reporting facial function places into question the validity of some of the cumulative data reported. Postoperatively, grades I-II facial nerve function was seen in 91% of patients undergoing short anterior rerouting, 74% of patients undergoing long anterior rerouting, and 26% of patients undergoing posterior complete rerouting. Although facial nerve rerouting allows unhindered exposure to previously inaccessible regions, it is achieved at the cost of facial nerve function. Facial nerve dysfunction increases with the length of facial nerve rerouted.