Glutamate receptors modulate sodium-dependent and calcium-independent vitamin C bidirectional transport in cultured avian retinal cells

Vitamin C is transported in the brain by sodium vitamin C co‐transporter 2 (SVCT‐2) for ascorbate and glucose transporters for dehydroascorbate. Here we have studied the expression of SVCT‐2 and the uptake and release of [¹⁴C] ascorbate in chick retinal cells. SVCT‐2 immunoreactivity was detected in rat and chick retina, specially in amacrine cells and in cells in the ganglion cell layer. Accordingly, SVCT‐2 was expressed in cultured retinal neurons, but not in glial cells. [¹⁴C] ascorbate uptake was saturable and inhibited by sulfinpyrazone or sodium‐free medium, but not by treatments that inhibit dehydroascorbate transport. Glutamate‐stimulated vitamin C release was not inhibited by the glutamate transport inhibitor l ‐β‐threo‐benzylaspartate, indicating that vitamin C release was not mediated by glutamate uptake. Also, ascorbate had no effect on [³H] d ‐aspartate release, ruling out a glutamate/ascorbate exchange mechanism. 2‐Carboxy‐3‐carboxymethyl‐4‐isopropenylpyrrolidine (Kainate) or NMDA stimulated the release, effects blocked by their respective antagonists 6,7‐initroquinoxaline‐2,3‐dione (DNQX) or (5R,2S)‐(1)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo[a,d]cyclohepten‐5,10‐imine hydrogen maleate (MK‐801). However, DNQX, but not MK‐801 or 2‐amino‐5‐phosphonopentanoic acid (APV), blocked the stimulation by glutamate. Interestingly, DNQX prevented the stimulation by NMDA, suggesting that the effect of NMDA was mediated by glutamate release and stimulation of non‐NMDA receptors. The effect of glutamate was neither dependent on external calcium nor inhibited by 1,2‐bis (2‐aminophenoxy) ethane‐N′,N′,N′,N′,‐tetraacetic acid tetrakis (acetoxy‐methyl ester) (BAPTA‐AM), an internal calcium chelator, but was inhibited by sulfinpyrazone or by the absence of sodium. In conclusion, retinal cells take up and release vitamin C, probably through SVCT‐2, and the release can be stimulated by NMDA or non‐NMDA glutamate receptors.     

Sequence instability in the long terminal repeats of avian spleen necrosis virus and reticuloendotheliosis virus

Summary Sequence divergence between the 3 long terminal repeats (LTR) of avian reticuloendotheliosis virus (REV), deletion variant proviral clone 2-20-4, and spleen necrosis virus (SNV)—proviral clones 14-44, 60, and 70—was found to involve two classes of base substitutions: low-frequency interspersed and high-frequency clustered substitutions. Clones 2-20-4 and 14-44 have diverged 4.4% owing to low-frequency substitutions. In contrast, two high-frequency substitution segments have diverged by 30% and 29%, respectively. Clustered substitutions appear to be located either within or next to tandem repeats, suggesting their introduction concomitant with sequence deletions and duplications commonly associated with such repeats. A new 19-bp tandem repeat is found in clone 2-20-4. Its sequence could have evolved from the 26-bp repeats found in the SNV clones.     

Physical illness in patients with severe mental disorders. II. Barriers to care, monitoring and treatment guidelines, plus recommendations at the system and individual level

Physical disorders are, compared to the general population, more prevalentin people with severe mental illness (SMI). Although this excess morbidityand mortality is largely due to modifiable lifestyle risk factors, the screeningand assessment of physical health aspects remains poor, even in developedcountries. Moreover, specific patient, provider, treatment and system factorsact as barriers to the recognition and to the management of physical diseasesin people with SMI. Psychiatrists can play a pivotal role in the improvementof the physical health of these patients by expanding their task from clinicalpsychiatric care to the monitoring and treatment of crucial physical parameters.At a system level, actions are not easy to realize, especially for developingcountries. However, at an individual level, even simple and very basic monitoringand treatment actions, undertaken by the treating clinician, can already improvethe problem of suboptimal medical care in this population. Adhering to monitoringand treatment guidelines will result in a substantial enhancement of physicalhealth outcomes. Furthermore, psychiatrists can help educate and motivatepeople with SMI to address their suboptimal lifestyle, including smoking,unhealthy diet and lack of exercise. The adoption of the recommendations presentedin this paper across health care systems throughout the world will contributeto a significant improvement in the medical and related psychiatric healthoutcomes of patients with SMI.     

Cloning,expression and biochemical characterization of a GH1 β-glucosidase from Cellulosimicrobium cellulans

β-Glucosidase plays an important role in the degradation of cellulose. In this study, a novel β-glucosidase ccbgl1b gene for a glycosyl hydrolase (GH) family 1 enzyme was cloned from the genome of Cellulosimicrobium cellulans and expressed in Escherichia coli BL21 cells. The sequence contained an open reading frame of 1494?bp, encoded a polypeptide of 497?amino acid residues. The recombinant protein CcBgl1B was purified by Ni sepharose fastflow affinity chromatography and had a molecular weight of 57?kDa, as judged by SDS-PAGE. The optimum β-glucosidase activity was observed at 55?°C and pH 6.0. Recombinant CcBgl1B was found to be most active against aryl-glycosides p-nitrophenyl-β-D-glucopyranoside (pNPβGlc), followed by p-nitrophenyl-β-D-galactopyranoside (pNPβGal). Using disaccharides as substrates, the enzyme efficiently cleaved β-linked glucosyl-disaccharides, including sophorose (β-1,2-), laminaribiose (β-1,3-) and cellobiose (β-1,4-). In addition, a range of cello-oligosaccharides including cellotriose, cellotetraose and cellopentaose were hydrolysed by CcBgl1B to produce glucose. The interaction mode between the enzyme and the substrates driving the reaction was modelled using a molecular docking approach. Understanding how the GH1 enzyme CcBgl1B from C. cellulans works, particularly its activity against cello-oligosaccharides, would be potentially useful for biotechnological applications of cellulose degradation.     

In silico screening and identification of potential GSK3β inhibitors

Abstract

Glycogen synthase kinase-3β (GSK3β) has been reported for its impact on multitude biological processes from cell proliferation to apoptosis. The increase in the ratio of active/inactive GSK3β is the major factor associated in the etiology of several psychiatric diseases, diabetes, muscle hypertrophy, neurodegenerative diseases, and some cancers. These findings made GSK3β a promising therapeutic target, and the interest in the discovery, synthesis of novel drugs to effectively attenuate its function with probably no side effects has been increasing in the chronology of GSK3β drug discovery. In the present study, we applied a combination of computational tools on a chemical library for the virtual discovery of their potency to inhibit GSK3β. The chemical library was screened against a set of filters at different levels. Finally, five compounds in the chemical library were found to potentially inhibit GSK3β with no toxic effects. Furthermore, binding mode analysis revealed that all the compounds bound to the ATP site and most of the hydrogen bonding interactions are conserved as in GSK3β structures deposited in PDB.     

Eating, drinking and temperature responses to intracerebroventricular cholecystokinin in the chick

The central effect of cholecystokinin-octapeptide (CCK), SQ 19,844 or sincalide, on the intake of food and water and on colonic temperature (Tc) was investigated using the broiler cockerel. Four-week old chicks were maintained in a thermoneutral environment of 23-24 degrees C. After food was removed for a 24 hr interval, CCK was infused in a volume of 10.0 microliters into the lateral cerebral ventricle (ICV) in doses ranging from 10-150 ng. Although lower doses of CCK had no effect on food intake, 100 or 150 ng of CCK significantly reduced consumption of food in a dose-dependent manner; water drinking was significantly decreased by 100 ng of CCK. In addition, CCK at doses of 100 and 150 ng prevented the slow rise in Tc observed following infusions of control CSF. This latter effect appeared to be a result of feeding activity associated with caloric intake and the heat increment in the control birds rather than a specific thermoregulatory effect. Overall, our results suggest that CCK may comprise a part of the central mechanism underlying the neural control of short term satiety in an avian species similar to that proposed for the mammal.