Sex-dependent structural asymmetry of the medial habenular nucleus of the chicken brain

Summary An investigation of structural asymmetry in the avian brain was conducted on the epithalamic medial habenular nucleus of the chicken. Twelve male and ten female two-day-old chickens were used for a morphometric evaluation of asymmetry. The medial habenular nucleus was measured from paraffin-wax-embedded, 8 m-thick sections by use of a semiautomatic image analyser. The volumes of the right and left medial habenula of each animal were statistically analysed (within animal experimental design). The right medial habenula in males showed significant group asymmetry. In contrast, females failed to demonstrate group bias in favour of either hemisphere. However, individual females were lateralised, with either a larger right or left medial habenula. Although individuals of both sexes were lateralised, there was no significant sex difference in volume in either the right or left medial habenula.We propose that sex-linked structural asymmetry may be influenced by steroid hormonal effects in the central nervous system, and that such asymmetry could be more prevalent in the non-mammalian vertebrate brain than previously considered.     

Probing the ATP-induced conformational flexibility of the PcrA helicase protein using molecular dynamics simulation

Helicases are enzymes that unwind double-stranded DNA (dsDNA) into its single-stranded components. It is important to understand the binding and unbinding of ATP from the active sites of helicases, as this knowledge can be used to elucidate the functionality of helicases during the unwinding of dsDNA. In this work, we investigated the unbinding of ATP and its effect on the active-site residues of the helicase PcrA using molecular dynamic simulations. To mimic the unbinding process of ATP from the active site of the helicase, we simulated the application of an external force that pulls ATP from the active site and computed the free-energy change during this process. We estimated an energy cost of ~85 kJ/mol for the transformation of the helicase from the ATP-bound state (1QHH) to the ATP-free state (1PJR). Unbinding led to conformational changes in the residues of the protein at the active site. Some of the residues at the ATP-binding site were significantly reoriented when the ATP was pulled. We observed a clear competition between reorientation of the residues and energy stabilization by hydrogen bonds between the ATP and active-site residues. We also checked the flexibility of the PcrA protein using a principal component analysis of domain motion. We found that the ATP-free state of the helicase is more flexible than the ATP-bound state.     

Methyl Anthranilate, an Inhibitor for the Germination of Spores of Aerobic Bacilli

Methylanthranilate inhibited the germination of spores of aerobic bacilli without affecting growth and sporulation. The inhibition of germination could not be reversed by removal of methylanthranilate.     

Relationship Between [3H]Mazindol Binding to Dopamine Uptake Sites and [3H]Dopamine Uptake in Rat Striatum During Aging

Certain drugs exhibit a remarkable correlation between their ability to inhibit synaptosomal uptake of dopamine and the binding of [3H]mazindol to striatal membranes. To investigate the role of mazindol binding sites in the dopamine uptake process and the fate of these sites (labeling dopaminergic neurons) during aging, we have examined the properties of mazindol binding and dopamine uptake in individual young and old rats. There was a 48% decrease (p = 0.0001) in the Bmax of mazindol binding and a 23% decrease (p = 0.0166) in the Vmax of dopamine uptake with no apparent change in their affinities with age. Regression analysis of the relationship between Bmax and Vmax exhibited a significant correlation in old (p = 0.0156) but not young rats (p = 0.1398). These data suggest that the number of mazindol binding sites decreases with age and that the number of sites on the dopamine transporter complex far exceeds the number required to elicit maximal dopamine uptake.     

Characterization and subcellular distribution of specific thyrotropin-releasing hormone binding sites in rat cerebellum

The specific binding of thyrotropin-releasing hormone (TRH) by 30,000g pellet fraction was ubiquitously distributed throughout various rat brain regions including cerebellum. Although the cerebellum had the lowest apparent density of specific TRH binding sites found in any of the brain regions studied, it represented a single class of high afinity receptor (K _D=37.73±4.88 nM,B _max=156.0±5.7 fmol/mg protein,n=4). Furthermore, the cerebellar synaptic plasma membrane fractions were richly endowed with TRH-binding, two other membrane fractions (light-synaptic plasma membrane and microsomal) exhibited high TRH-binding whereas nuclear, mitochondrial or myelin fractions were devoid of significant binding activity. These data show for the first time the existence of specific TRH-binding in cerebellum, and thus suggest that TRH may modulate cerebellar synaptic functions by acting through a specific high affinity-receptor.     

Chronic Alcohol Consumption Increases Cyclo (His-Pro)-Like Immunoreactivity in the Rat Brain

Abstract: Administration of histidyl-proline diketopiperazine (cyclo (HisPro)) to rats attenuates ethanol-induced sleep. To understand the role played by cyclo (His-Pro) in the pathophysiology of prolonged alcohol consumption, we have measured the distribution of this peptide in brains of control and alcohol-treated rats. The data show that prolonged alcohol consumption increases the concentration of cyclo (His-Pro) in hypothalamic as well as extrahypothalamic brain. These changes may reflect a physiologic adaptation of the brain during alcohol consumption.     

Asymmetric μ2-1,1-azido bridged copper(II) complex: Synthesis, X-ray structure, magnetic study and DFT calculations

A new rare variety asymmetric μ₂-1,1-azido bridged copper(II) complex has been synthesized and characterized structurally and magnetically. The complex [Cu₂L₂(μ₂-1,1-N₃)₂] · H₂O · CH₃OH (L = 1-(N-ortho-hydroxyacetophenimine)-2-aminoethane) (1), crystallizes in monoclinic space group, P2₁/n, with a = 9.469(4) Å, b = 12.526(8) Å, c = 12.899(10) Å, β = 105.79(6)°, V = 1472.2(16) Å³. X-ray study reveals that he Cu-N(azide)-Cu angles in this complex is 90.4°. This is unusually low in comparison to that of the same angle in other end-on azido-bridged binuclear complexes. Though a strong ferromagnetic interaction between the metal centers is expected in the complex, the coupling has actually been found to be antiferromagnetic (J = −4.2 cm⁻¹), instead. To rationalize this paradoxical magnetic behavior, DFT calculation of this and other four complexes with very similar structure have been performed within broken symmetry framework. The calculated magnetic coupling constants (J) are in excellent agreement, both in sign and in the magnitude of the exchange interaction, with the experimental data, and the spin density map is correctly reproduced.