Dwelling quietly in the rich club: brain network determinants of slow cortical fluctuations

For more than a century, cerebral cartography has been driven by investigations of structural and morphological properties of the brain across spatial scales and the temporal/functional phenomena that emerge from these underlying features. The next era of brain mapping will be driven by studies that consider both of these components of brain organization simultaneously—elucidating their interactions and dependencies. Using this guiding principle, we explored the origin of slowly fluctuating patterns of synchronization within the topological core of brain regions known as the rich club, implicated in the regulation of mood and introspection. We find that a constellation of densely interconnected regions that constitute the rich club (including the anterior insula, amygdala and precuneus) play a central role in promoting a stable, dynamical core of spontaneous activity in the primate cortex. The slow timescales are well matched to the regulation of internal visceral states, corresponding to the somatic correlates of mood and anxiety. In contrast, the topology of the surrounding ‘feeder’ cortical regions shows unstable, rapidly fluctuating dynamics likely to be crucial for fast perceptual processes. We discuss these findings in relation to psychiatric disorders and the future of connectomics.     

Cloning of chromosome I DNA from Saccharomyces cerevisiae: analysis of the FUN52 gene, whose product has homology to protein kinases.

A gene whose product has homology to protein kinases and is closely related to the Aspergillus nidulans nimA cell-cycle gene was identified on chromosome I of the yeast, Saccharomyces cerevisiae. This gene has been temporarily designated FUN52, where FUN is the acronym for 'function unknown now'. In A. nidulans, nimA is required to enter mitosis. In addition, overexpression of nimA causes premature onset of mitosis and cell cycle arrest. In contrast, S. cerevisiae cells that were either deleted for FUN52 or were overexpressing it had no detectable growth phenotypes. FUN52 proved to be the same as the previously identified KIN3 gene [Jones and Rosamond, Gene 90 (1990) 87-92] that was reported to map on chromosome VI.     

Adenine Nucleotide Changes Associated with the Initiation of Sporulation in Bacillus subtilis

At the end of the exponential growth phase of Bacillus subtilis, there is a decrease in the energy level of the cell, whether expressed as adenosine triphosphate concentration or adenylate energy charge. Phosphate limitation of exponentially growing cells produces a similar decrease in the energy level of the cell, and sporulation is derepressed in the presence of 10 mM glucose. A reduction in the tryptophan concentration of the medium during phosphate limitation of the tryptophan auxotroph B. subtilis 168 prevented the decrease in energy charge. Cells do not sporulate under these conditions. Energy charge values of 0.30 to 0.35 found during sporulation do not lead to cell death.     

Morphological and pharmacological basis for pulmonary ventilation in Amphiuma tridactylum

Summary The lung of the giant salamander, Amphiuma tridactylum, is divided into respiratory alveoli by muscular septa that increase the surface area of the lung as well as provide a mechanism for its almost complete collapse during exhalation. The epithelium of the internal surface is of two types: respiratory, composed of a single layer of pneumocytes overlying anastomosing capillaries, and non-respiratory, composed of ciliated cells and mucus-secreting goblet cells. Non-respiratory epithelium covers the apical edges of the septa, whereas the respiratory epithelium lines the alveoli. The smooth muscle of the septa and walls of the lung was studied in preparations of uninflated and acetylcholine-contracted lung. The muscle cells are ultrastructurally similar to other types of smooth muscle but are surrounded by extraordinary amounts of extracellular matrix, containing collagen and elastic fibers and numerous fine fibrils of unknown composition. Smooth muscle in isolated lung strips contracted in a dose-dependent manner when treated with acetylcholine or methacholine; contraction was blocked by atropine. Responses of lung strips to adrenergic agents were limited; only high doses of adrenalin caused slight relaxation of previously contracted muscle. These observations support the hypothesis that contraction of pulmonary smooth muscle is responsible for the ventilatory efficiency of the lung.