THE INCORPORATION OF ISOTOPIC CARBON 14C INTO THE CEREBRAL GLYCOGEN OF NORMAL AND X-IRRADIATED RATS

Maximal incorporation of ¹⁴C from labelled glucose into cerebral glycogen of the rat occurred at 3-6 h following intravenous injection of the precursor. A reduction of the rate of glycogen breakdown is the most likely cause of the glycogen accumulation observed in rat brain following exposure to 10 krad of X-radiation.     

Imprints of multiple glacial refugia in the Pyrenees revealed by phylogeography and palaeodistribution modelling of an endemic spider

Mediterranean mountain ranges harbour highly endemic biota in islandlike habitats. Their topographic diversity offered the opportunity for mountain species to persist in refugial areas during episodes of major climatic change. We investigate the role of Quaternary climatic oscillations in shaping the demographic history and distribution ranges in the spider Harpactocrates ravastellus, endemic to the Pyrenees. Gene trees and multispecies coalescent analyses on mitochondrial and nuclear DNA sequences unveiled two distinct lineages with a hybrid zone around the northwestern area of the Catalan Pyrenees. The lineages were further supported by morphological differences. Climatic niche‐based species distribution models (SDMs) identified two lowland refugia at the western and eastern extremes of the mountain range, which would suggest secondary contact following postglacial expansion of populations from both refugia. Neutrality test and approximate Bayesian computation (ABC) analyses indicated that several local populations underwent severe bottlenecks followed by population expansions, which in combination with the deep population differentiation provided evidence for population survival during glacial periods in microrefugia across the mountain range, in addition to the main Atlantic and Mediterranean (western and eastern) refugia. This study sheds light on the complexities of Quaternary climatic oscillations in building up genetic diversity and local endemicity in the southern Europe mountain ranges.     

Systemic Administration of NMDA and AMPA Receptor Antagonists Reverses the Neurochemical Changes Induced by Nigrostriatal Denervation in Basal Ganglia

In Parkinson's disease, nigrostriatal denervation leads to an overactivity of the subthalamic nucleus and its target areas, which is responsible of the clinical manifestations of the disease. Because the subthalamic nucleus uses glutamate as neurotransmitter and is innervated by glutamatergic fibers, pharmacological blockade of glutamate transmission might be expected to restore the cascade of neurochemical changes induced by a dopaminergic denervation within the basal ganglia. To test this hypothesis, two types of glutamate antagonists, the NMDA receptor antagonist MK-801 and the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonist LY293558, were administered systemically, either alone or in combination with L-DOPA, in rats with a unilateral 6-hydroxydopamine lesion of the nigrostriatal dopamine pathway. The effect of treatment was assessed neurochemically by analyzing at the cellular level the functional activity of basal ganglia output structures and the subthalamic nucleus using the expression levels of the mRNAs coding for glutamic acid decarboxylase and cytochrome oxidase, respectively, as molecular markers of neuronal activity. The present study shows that treatment with glutamate antagonists, and particularly with AMPA antagonists, alone or in combination with L-DOPA, reverses the overactivity of the subthalamic nucleus and its target areas induced by nigrostriatal denervation. These results furnish the neurochemical basis for the potential use of glutamate antagonists as therapeutic agents in Parkinson's disease.     

Solution conformation of an immunogenic peptide from HRV2: comparison with the conformation found in a complex with a Fab fragment of an anti-HRV2 neutralizing antibody

The conformation of a [15]-peptide (H-VKAETRLNPDLQPTE-NH₂) from VP2 of rhinovirus HRV2 complexed with a Fab fragment was previously shown by X-ray crystallographic studies to be similar to the one found in the corresponding region of HRV1A. Antibodies raised against this peptide bind to and neutralize HRV2. In order to identify structural features preserved in solution that may explain the ability of this short peptide to mimic the structure of the protein surface, the peptide has been studied by NMR in aqueous solution as well as under denaturing conditions. The peptide is shown to be a random coil in solution. However, the sequence forming a 3₁₀ helix in the complex is biased into a helical conformation according to NOE intensity data as well as from urea and pH titrations. This sequence adopts the same conformation in an unrelated protein. NOE data suggest that a β-turn found in the complex may be sampled in solution. Also, Glu4, interacting with Arg6 in the crystal, has a reduced pK_a value in solution. It is concluded that the local structure present in the random coil state of VP2(156–170) contains enough information to direct the production of antibodies that bind to and neutralize HRV2. © 1998 European Peptide Society and John Wiley & Sons, Ltd.     

Stature estimation in extinct Aónikenk and the myth of Patagonian gigantism

The Aónikenk were a hunter-gatherer group that inhabited the southern extreme of Patagonia at European Contact and became extinct at the end of the 19th century. The myth of Patagonian gigantism developed around these aborigines from early Spanish explorer accounts. In this study, the postcranial remains belonging to the Aónikenk (Patagonia) and the Selk'nam (Tierra del Fuego) preserved at the Instituto de la Patagonia (UMAG, Chile) have been measured, using standard metrics. Different stature estimations for these groups have been generated, by using the different regression formulae available. Aónikenk male stature appears to be between 174 and 178 cm on average, whereas the Selk'nam are considerably shorter. In addition, stature estimations from Spanish populations dating to the contact period have been compiled for comparison. While it can be concluded that the Aónikenk probably presented the highest stature values of all Meso- and South American populations, it is suggested that the perception of their gigantism could be partially attributed to the real difference in stature (probably more than 10 cm) between these aborigines and contemporaneous Europeans. Am J Phys Anthropol 105:545–551, 1998. © 1998 Wiley-Liss, Inc.