Neurosecretory cells in the optic lobes of the brain and activity rhythms in Lycosa tarentula (Araneae: Lycosidae)

Several paired groups of neurosecretory cells (NS) were identified in the dorsal cortical neurons of the optic lobes of the brain of Lycosa tarentula (Araneae). Two large bottle-shaped cells (NS A1, A2) and a cluster of ca. 20 smaller cells (NS B) were found between the lamina and medulla of the anterior median eyes (AM). The forward oriented bundles of NS B axons run alongside large fibres linked to the synaptic zones of the indirect eyes. In front of the arcuate body, an islet of about 10 fusiform cells (NS C1) sends short axons close to the internal cortical border. Other large cells (NS C2, C3) are found from the medulla of the AM to the anterior border of the central body. Their long axons end deeply in the brain neuropil. NS B and C1 function synchronously. The secretory cycles of NS A1 and A2 seem to be in opposition. The activity of these three types of NS depends on the phase of the day. Anatomical relationships of NS A, B and C1 with visual afferent/efferent fibres via synaptic buttons indicate a role of these cells in the modulation of circadian rhythms of visual and locomotor activity. On the other hand, NS C2 and C3, the functioning of which is not synchronous, might be involved in the modulation or control of the elementary movements of L. tarentula when active or at rest.     

Iron levels in the human brain: A post-mortem study of anatomical region differences and age-related changes

The link between brain iron homeostasis and neurodegenerative disease has been the subject of extensive research. There is increasing evidence of iron accumulation during ageing, and altered iron levels in some specific brain regions in neurodegenerative disease patients have been reported.Using graphite furnace atomic absorption spectrometry after microwave-assisted acid digestion of the samples, iron levels were determined in 14 different areas of the human brain [frontal cortex, superior and middle temporal, caudate nucleus, putamen, globus pallidus, cingulated gyrus, hippocampus, inferior parietal lobule, visual cortex of the occipital lobe, midbrain, pons (locus coeruleus), medulla and cerebellum (dentate nucleus)] of n = 42 adult individuals (71 ± 12 years old, range: 53–101 years old) with no known history or evidence of neurodegenerative, neurological or psychiatric disorders.It was found that the iron distribution in the adult human brain is quite heterogeneous. The highest levels were found in the putamen (mean ± SD, range: 855 ± 295 μg/g, 304–1628 μg/g) and globus pallidus (739 ± 390 μg/g, 225–1870 μg/g), and the lowest levels were observed in the pons (98 ± 43 μg/g, 11–253 μg/g) and medulla (56 ± 25 μg/g, 13–115 μg/g).Globally, iron levels proved to be age-related. The positive correlation between iron levels and age was most significant in the basal ganglia (caudate nucleus, putamen and globus pallidus).Compared with the age-matched control group, altered iron levels were observed in specific brain areas of one Parkinson's disease patient (the basal ganglia) and two Alzheimer's disease patients (the hippocampus).