Retention deficit for avoidance training in hypophysectomized rats: Time-dependent enhancement of retention performance with post-training ACTH injections

These experiments examined the effects of hypophysectomy on retention of avoidance training. In addition, the experiments examined the effects, on retention, of post-training ACTH injections administered to hypophysectomized rats. Rats were trained in a visual discriminated avoidance Y maze. Each rat received six training trials followed by six retraining trials the next day. Retention was measured by the number of correct choices during the retraining trials. When trained with a low-footshock intensity (0.8 mA), hypophysectomized rats showed retention performance which was significantly poorer than that of intact animals. There was no significant difference in performance when the animals were trained with a higher footshock intensity (1.4 mA), in part because of poorer retention performance of intact animals under these training conditions. Under both footshock conditions, a single post-training injection of ACTH enhanced later retention performance of hypophysectomized rats. This effect on memory was timedependent; injections delayed 2 or 6 hr after training did not significantly enhance retention. These findings are consistent with the view that hormonal responses to training may modulate later retention of the training experience.     

The therapeutic potential of blocking the activin signalling pathway

Members of the transforming growth factor β (TGF-β) family regulate fundamental physiological process, such as cell growth, differentiation and apoptosis. As a result, defects in this pathway have been linked to uncontrolled proliferation and cancer progression. Here we explore the signal transduction mechanism of TGF-β focusing on therapeutic intervention in human diseases. Like TGF-β, another member of the TGF-β superfamily, activin has been proven to play an important role in maintenance of tissue homeostasis and dysregulation leads to disease. Several studies showed elevated levels of activin are responsible for the development of gonadal tumours and a cachexia-like weight loss syndrome. Discussing the recent advances in approaches developed to antagonise the activin pathway and the encouraging results obtained in animal models, this review presents a therapeutic rationale for targeting the activin pathway in conditions such as cachexia, neuromuscular and/or musculoskeletal disorders.     

Levels of the Mahogunin Ring Finger 1 E3 Ubiquitin Ligase Do Not Influence Prion Disease

Prion diseases are rare but invariably fatal neurodegenerative disorders. They are associated with spongiform encephalopathy, a histopathology characterized by the presence of large, membrane-bound vacuolar structures in the neuropil of the brain. While the primary cause is recognized as conversion of the normal form of prion protein (PrP^C) to a conformationally distinct, pathogenic form (PrP^Sc), the cellular pathways and mechanisms that lead to spongiform change, neuronal dysfunction and death are not known. Mice lacking the Mahogunin Ring Finger 1 (MGRN1) E3 ubiquitin ligase develop spongiform encephalopathy by 9 months of age but do not become ill. In cell culture, PrP aberrantly present in the cytosol was reported to interact with and sequester MGRN1. This caused endo-lysosomal trafficking defects similar to those observed when Mgrn1 expression is knocked down, implicating disrupted MGRN1-dependent trafficking in the pathogenesis of prion disease. As these defects were rescued by over-expression of MGRN1, we investigated whether reduced or elevated Mgrn1 expression influences the onset, progression or pathology of disease in mice inoculated with PrP^Sc. No differences were observed, indicating that disruption of MGRN1-dependent pathways does not play a significant role in the pathogenesis of transmissible spongiform encephalopathy.     

Optimization of recombinant human nerve growth factor production in the psychrophilic Pseudoalteromonas haloplanktis

The optimization of production strategy is a very useful tool to attain high level of recombinant protein at a low cost. A promising biotechnological application of psychrophilic bacteria is their use as non-conventional host for the recombinant production of useful proteins. The lowering of the expression temperature can in fact facilitate the correct folding of heterologous proteins that accumulate in insoluble form as inclusion bodies when produced in Escherichia coli. An example of such "difficult" proteins is the human nerve growth factor (hNGF). The gene encoding the mature form of hNGF was expressed in the Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 at 4 degrees C. Western blotting experiments demonstrated that the protein was produced in soluble form and translocated in the periplasmic space. Furthermore, an analytical gel filtration chromatography confirmed that the recombinant protein was largely in dimeric form. For a more efficient recombinant rhNGF production, the influence of cultivation operational strategies and growth conditions (medium composition, temperature, specific growth rate) on biomass yield and recombinant protein production was investigated in batch and chemostat cultivations. The highest product yield of soluble rhNGF (7.5mg(NGF)g(dryweight)(-1)) has been achieved in batch culture at 4 degrees C on Schatz medium with addition of tryptone and vitamins.     

No effects of pulsed radio frequency electromagnetic fields on melatonin, cortisol, and selected markers of the immune system in man

There is growing public concern that radio frequency electromagnetic fields may have adverse biological effects. In the present study eight healthy male students were tested to see whether or not radio frequency electromagnetic fields as used in modern digital wireless telecommunication (GSM standard) have noticeable effects on salivary melatonin, cortisol, neopterin, and immunoglobulin A (sIgA) levels during and several hours after exposure. In a specifically designed, shielded experimental chamber, the circularly polarized electromagnetic field applied was transmitted by an antenna positioned 10 cm behind the head of upright sitting test persons. The carrier frequency of 900 MHz was pulsed with 217 Hz (average power flux density 1 W/m2). In double blind trials, each test person underwent a total of 20 randomly allotted 4 hour periods of exposure and sham exposure, equally distributed at day and night. The results obtained show that the salivary concentrations of melatonin, cortisol, neopterin and sIgA did not differ significantly between exposure and sham exposure.     

Molecular dynamics simulations show how the FMRP Ile304Asn mutation destabilizes the KH2 domain structure and affects its function

Mutations or deletions of FMRP, involved in the regulation of mRNA metabolism in brain, lead to the Fragile X syndrome (FXS), the most frequent form of inherited intellectual disability. A severe manifestation of the disease has been associated with the Ile304Asn mutation, located on the KH2 domain of the protein. Several hypotheses have been proposed to explain the possible molecular mechanism responsible for the drastic effect of this mutation in humans. Here, we performed a molecular dynamics simulation and show that the Ile304Asn mutation destabilizes the hydrophobic core producing a partial unfolding of two α-helices and a displacement of a third one. The affected regions show increased residue flexibility and motion. Molecular docking analysis revealed strongly reduced binding to a model single-stranded nucleic acid in agreement with known data that the two partially unfolded helices form the RNA-binding surface. The third helix, which we show here to be also affected, is involved in the PAK1 protein interaction. These two functional binding sites on the KH2 domain do not overlap spatially, and therefore, they can simultaneously bind their targets. Since the Ile304Asn mutation affects both binding sites, this may justify the severe clinical manifestation observed in the patient in which both mRNA metabolism activity and cytoskeleton remodeling would be affected.     

Partition kinetics of ribulose-1,5-bisphosphate carboxylase from Rhodospirillum rubrum

When the enzymatically generated intermediate 2-carboxy-3-keto-D-arabinitol-1,5-bisphosphate (II) was used as a substrate with fresh enzyme, 70% reacted to produce 3-phosphoglycerate (3PGA). When a reaction mixture of enzyme plus [1-32P]ribulose 1,5-bisphosphate (RuBP) was quenched in the steady state with the tightly bound inhibitor 2-carboxyarabinitol-1,5-bisphosphate, 30% of the enzyme-bound species was released as 3PGA and 70% as RuBP. The major source for this partition was the ternary substrates Michaelis complex. The level of carboxylated intermediate in the steady state was determined to be 8% of active sites under the conditions of substrate saturation. No burst was seen in the appearance of product when 6.5 eq of [1-32P]RuBP was mixed with enzyme plus saturating CO2 and the reaction followed in the steady state. From these data plus the steady-state Vmax and Km of RuBP it is possible to derive the five bulk rate constants represented in the scheme ECO2 + RuBP in equilibrium ERuBPCO2 in equilibrium E X II----E + 2(3PGA).     

Monte Carlo simulations of the peptide recognition at the consensus binding site of the constant fragment of human immunoglobulin G: the energy landscape analysis of a hot spot at the intermolecular interface

Monte Carlo simulations of molecular recognition at the consensus binding site of the constant fragment (Fc) of human immunoglobulin G (Ig) protein have been performed to analyze structural and thermodynamic aspects of binding for the 13-residue cyclic peptide DCAWHLGELVWCT. The energy landscape analysis of a hot spot at the intermolecular interface using alanine scanning and equilibrium-simulated tempering dynamics with the simplified, knowledge-based energy function has enabled the role of the protein hot spot residues in providing the thermodynamic stability of the native structure to be determined. We have found that hydrophobic interactions between the peptide and the Met-252, Ile-253, His-433, and His-435 protein residues are critical to guarantee the thermodynamic stability of the crystallographic binding mode of the complex. Binding free energy calculations, using a molecular mechanics force field and a solvation energy model, combined with alanine scanning have been conducted to determine the energetic contribution of the protein hot spot residues in binding affinity. The conserved Asn-434, Ser-254, and Tyr-436 protein residues contribute significantly to the binding affinity of the peptide-protein complex, serving as an energetic hot spot at the intermolecular interface. The results suggest that evolutionary conserved hot spot protein residues at the intermolecular interface may be partitioned in fulfilling thermodynamic stability of the native binding mode and contributing to the binding affinity of the complex.     

Exceptional diversity of mouse lemurs (Microcebus spp.) in the Makira region with the description of one new species

Although the number of described lemur species has increased considerably over the last 20 years, detailed biogeographic data are still lacking from many geographic regions, in particular in the eastern part of Madagascar. This study investigated mouse lemur species diversity in a previously unstudied Inter-River-System in the eastern Makira region. Three sites were visited and 26 individuals were sampled and characterized with 13 external morphometric measurements. Standard phylogenetic analyses were performed on the basis of sequences of three mitochondrial loci by including representatives of all other published mouse lemur species for comparison. The analyses revealed the presence of three mouse lemur species in one study site, two of which were previously undescribed. The two new species are genetically distinct and belong to the larger-bodied mouse lemur species on the island, whereas the third species, Microcebus mittermeieri, belongs to the smaller-bodied mouse lemur species. The study fully describes one of the new species. This study and other lemur inventories suggest that the Makira region is particularly rich in lemur species and the lack of any protected zone in this area should now attract the urgent attention of conservation stakeholders.