The identification of a selective dopamine D2 partial agonist,D3 antagonist displaying high levels of brain exposure

The identification of a highly selective D₂ partial agonist, D₃ antagonist tool molecule which demonstrates high levels of brain exposure and selectivity against an extensive range of dopamine, serotonin, adrenergic, histamine, and muscarinic receptors is described.     

Experimental chronic low‐frequency resistance training produces skeletal muscle hypertrophy in the absence of muscle damage and metabolic stress markers

Volitional animal resistance training constitutes an important approach to modeling human resistance training. However, the lack of standardization protocol poses a frequent impediment to the production of skeletal muscle hypertrophy and the study of related physiological variables (i.e., cellular damage/inflammation or metabolic stress). Therefore, the purposes of the present study were: (1) to test whether a long‐term and low frequency experimental resistance training program is capable of producing absolute increases in muscle mass; (2) to examine whether cellular damage/inflammation or metabolic stress is involved in the process of hypertrophy. In order to test this hypothesis, animals were assigned to a sedentary control (C, n = 8) or a resistance trained group (RT, n = 7). Trained rats performed 2 exercise sessions per week (16 repetitions per day) during 12 weeks. Our results demonstrated that the resistance training strategy employed was capable of producing absolute mass gain in both soleus and plantaris muscles (12%, p < 0.05). Furthermore, muscle tumor necrosis factor (TNF‐α) protein expression (soleus muscle) was reduced by 24% (p < 0.01) in trained group when compared to sedentary one. Finally, serum creatine kinase (CK) activity and serum lactate concentrations were not affected in either group. Such information may have practical applications if reproduced in situations where skeletal muscle hypertrophy is desired but high mechanical stimuli of skeletal muscle and inflammation are not. Copyright © 2010 John Wiley & Sons, Ltd.     

Localization of liver myofibroblasts and hepatic stellate cells in normal and diseased rat livers: distinct roles of (myo-)fibroblast subpopulations in hepatic tissue repair

Previous in vitro studies indicated that hepatic stellate cells (HSC) and rat liver myofibroblasts (rMF) have to be regarded as different cell populations of the myofibroblastic lineage with fibrogenic potential. Employing the discrimination features defined by these studies the localization of HSC and rMF was analyzed in diseased livers. Normal and acutely as well as chronically carbon tetrachloride-injured livers were analyzed by immunohistochemistry and by in situ hybridization. In normal livers HSC [desmin/glial fibrillary acid protein (GFAP)-positive cells] were distributed in the hepatic parenchyma, while rMF (desmin/smooth muscle alpha actin-positive, GFAP-negative cells colocalized with fibulin-2) were located in the portal field, the walls of central veins, and only occasionally in the parenchyma. Acute liver injury was characterized almost exclusively by an increase in the number of HSC, while the amount of rMF was nearly unchanged. In early stages of fibrosis, HSC and rMF were detected within the developing scars. In advanced stages of fibrosis, HSC were mainly present at the scar–parenchymal interface, while rMF accounted for the majority of the cells located within the scar. At every stage of fibrogenesis, rMF, in contrast to HSC, were only occasionally detected in the hepatic parenchyma. HSC and rMF are present in normal and diseased livers in distinct compartments and respond differentially to tissue injury. Acute liver injury is followed by an almost exclusive increase in the number of HSC, while in chronically injured livers not only HSC but also rMF are involved in scar formation. Accepted: 16 September 1999     

An architectural hypothesis for direction selectivity in the visual cortex: the role of spatially asymmetric intracortical inhibition

Within a linear field approach, an architectural model for simple cell direction selectivity in the visual cortex is proposed. The origin of direction selectivity is related to recurrent intracortical interactions with a spatially asymmetric character along the axis of stimulus motion. No explicit asymmetric temporal mechanisms are introduced or adopted. The analytical investigation of network behavior, carried out under the assumption of a linear superposition of geniculate and intracortical contributions, shows that motion sensitivity of the resulting receptive fields emerges as a dynamic property of the cortical network without any feed-forward direction selectivity bias. A detailed analysis of the effects of the architectural characteristics of the cortical network on directionality and velocity-response curves was conducted by systematically varying the model's parameters. Received: 8 May 1998 / Accepted in revised form: 10 November 1998     

Structural composition and differential anticoagulant activities of dermatan sulfates from the skin of four species of rays, Dasyatis americana, Dasyatis gutatta, Aetobatus narinari and Potamotrygon motoro

We compared the disaccharide composition of dermatan sulfate (DS) purified from the ventral skin of three species of rays from the Brazilian seacoast, Dasyatis americana, Dasyatis gutatta, Aetobatus narinari and of Potamotrygon motoro, a fresh water species that habits the Amazon River. DS obtained from the four species were composed of non-sulfated, mono-sulfated disaccharides bearing esterified sulfate groups at positions C-4 or C-6 of N-acetyl galactosamine (GalNAc), and disulfated disaccharides bearing esterified sulfate groups at positions C-2 of the uronic acid and at position C-4 or C-6 of GalNAc. However, DS from the skin of P. motoro presented a very low content of the disulfated disaccharides. The anticoagulant actions of ray skin DS, measured by both APTT clotting and HCII-mediated inhibition of thrombin assays, were compared to that of mammalian DS. DS from D. americana had both high APTT and HCII activities, whereas DS from D. gutatta showed activity profiles similar to those of mammalian DS. In contrast, DS from both A. narinari and P. motoro had no measurable activity in the APTT assay. Thus, the anticoagulant activity of ray skin DS is not merely a consequence of their charge density. We speculate that the differences among the anticoagulant activities of these three DS may be related to both different composition and arrangements of the disulfated disaccharide units within their polysaccharide chains.     

Computational, spectroscopic, and resonant mirror biosensor analysis of the interaction of adrenodoxin with native and tryptophan-modified NADPH-adrenodoxin reductase

In steroid hydroxylation system in adrenal cortex mitochondria, NADPH-adrenodoxin reductase (AR) and adrenodoxin (Adx) form a short electron-transport chain that transfers electrons from NADPH to cytochromes P-450 through FAD in AR and [2Fe-2S] cluster in Adx. The formation of [AR/Adx] complex is essential for the electron transfer mechanism in which previous studies suggested that AR tryptophan (Trp) residue(s) might be implicated. In this study, we modified AR Trps by N-bromosuccinimide (NBS) and studied AR binding to Adx by a resonant mirror biosensor. Chemical modification of tryptophans caused inhibition of electron transport. The modified protein (AR*) retained the native secondary structure but showed a lower affinity towards Adx with respect to AR. Activity measurements and fluorescence data indicated that one Trp residue of AR may be involved in the electron transferring activity of the protein. Computational analysis of AR and [AR/Adx] complex structures suggested that Trp193 and Trp420 are the residues with the highest probability to undergo NBS-modification. In particular, the modification of Trp420 hampers the correct reorientation of AR* molecule necessary to form the native [AR/Adx] complex that is catalytically essential for electron transfer from FAD in AR to [2Fe-2S] cluster in Adx. The data support an incorrect assembly of [AR*/Adx] complex as the cause of electron transport inhibition.     

Gastrointestinal helminth parasitism in fruit-eating bats (Chiroptera, Stenodermatinae) from western Amazonian Brazil

In this paper we report endoparasites from a sample of 50 stenodermatine bats collected mainly over lick sites at the Parque Nacional da Serra do Divisor, westernmost extremity of Amazonian Brazil. Four helminth species were recovered (Hasstilesia tricolor, Vampirolepis elongatus, Cheiropteronema globocephala. and Capillaria sp.), most of them from small intestines. Overall helminth prevalence achieved 26% (13/50) and the more prevalent species was H. tricolor (20%). Previously unknown in bats and reported for the first time in Brazil, this digenetic trematode was found in seven of the 18 bat species studied here. We argue that the drinking behaviour of stenodermatines at lick sites may be implicated in the dissemination of helminth infection among these bats.     

Effects induced by mono- and divalent cations on protein regions responsible for thermal adaptation in β-glycosidase from<Emphasis Type="Italic"> Sulfolobus solfataricus</Emphasis>

The perturbation induced by mono- and divalent cations on the thermophilicity and thermostability of Solfolobus solfataricus -glycosidase, a hyperthermophilic tetrameric enzyme, has been investigated by spectroscopic and computational simulation methods to ascertain the Hofmeister effects on two strategic protein regions identified previously. Specifically, (1) an extra segment (83–124), present only in the sequence of hyperthermophilic glycosidases and recognized as an important thermostability determinant for the enzyme structure; and (2) a restricted area of the subunit interface responsible for the quaternary structure maintenance. Mono- and divalent cations inhibit to a different extent the -glycosidase activity, whose kinetic constants show an apparent competitive inhibition of the catalytic process that reflects the Hofmeister order. The thermostability is also affected by the nature and charge of the cations, reaching maximal effects for the case of Mg²⁺. Fourier transform infrared spectroscopy has revealed very small changes in the protein secondary structure in the presence of the investigated cations at 20 °C, while large effects on the protein melting temperatures are observed. Computational analysis of the enzyme structure has identified negative patches on the accessible surface of the two identified regions. Following the Hofmeister series, cations weaken the existing electrostatic network that links the extra segment to the remaining protein matrix. In particular, the perturbing action of cations could involve the ionic pair interactions E107–R245 and E109–R185, thus leading to a local destructuring of the extra segment as a possible starting event for thermal destabilization. A detailed investigation of the electrostatic network at the A–C intermolecular interface of Sgly after energy minimization suggests that cations could cause a strong attenuation of the ion pair interactions E474–K72 and D473–R402, with consequent partial dissociation of the tetrameric structure.Abbreviations Amide I amide I band in a ²H₂O medium - EM energy minimization - ONPG o-nitrophenyl--d-galactopyranoside - Sgly Escherichia coli expressed Sulfolobus solfataricus -glycosidase