The control of pacemaker modulations for social communication in the weakly electric fish Sternopygus

Summary Nearly sinusoidal electric organ discharges (EODs) of the weakly electric fish Sternopygus, occur at a regular rate within a range from 50 to 200 Hz and are commanded by a medullary pacemaker nucleus (Pn). During courtship and aggression, the rate of EODs is modulated as smooth EOD-frequency rises or brief EOD-interruptions (Hopkins 1974b). The present study examines the control of such modulations. Rises were elicited by L-glutamate stimulation of the diencephalic prepacemaker nucleus, the only previously known source of input to the Pn. We demonstrate an additional input to the Pn, the sublemniscal prepacemaker nucleus (SPPn). L-glutamate stimulation of this area caused EOD-interruptions.The Pn contains electrotonically coupled pacemaker cells which generate the rhythm of the EODs, as well as relay cells which transmit the command pulse to the spinal motor neurons that innervate the electric organ. Pacemaker cells recorded intracellularly during EOD-interruptions continued firing at their regular frequency but with slightly increased jitter. Relay cells, on the other hand, were strongly depolarized and fired spikelets at a greatly increased frequency during EOD-interruptions. Thus EOD-interruptions were caused by SPPn input to relay cells that caused their massive depolarization, blocking the normal input from pacemaker cells without greatly affecting pacemaker cell firing characteristics.Application to the Pn of an antagonist to NMDA-type glutamate receptors blocked EOD-frequency rises and EOD-interruptions. Antagonists to quisqualate/ kainate receptor-types were ineffective.Abbreviations EOD Electric Organ Discharge - JAR Jamming Avoidance Response - Pn pacemaker nucleus - PPn diencephalic prepacemaker nucleus - SPPn sublemniscal prepacemaker nucleus     

Periclinal penetration of potassium permanganate into mature cuticular membranes ofAgave andClivia leaves: new implications for plant cuticle development

Staining cuticular membranes ofAgave americana andClivia miniata en bloc with potassium permanganate results in a strong contrast in the interior cuticular layer while the exterior part remains unstained. This is not caused by a selective chemical reaction with the interior part but by the unidirectional penetration of the reagent from the interior side, the outside being protected by the cuticle proper. In transverse cryosections of the cuticular membrane, permanganate penetrates nearly as easily into the exterior cuticular layer as into the interior one giving the same contrast. However, compared with the periclinal penetration into the cuticle proper this penetration is accelerated five-to tenfold by the polysaccharide network within the cuticular layer which serves as a distribution-channel system. Periclinal penetration into the cuticle proper occurs independently in each cutin penetration unit included between two obvious lucent lamellae and further divided into subunits.     

Leaving the meristem behind: The genetic and molecular control of leaf patterning and morphogenesis

Leaves, which play an essential role in plant photosynthesis, share common features such as being flat structures, but also show an impressive variability in their sizes and shapes. Following its initiation in the meristems, leaf development is patterned along three polarization axes to establish its basic architecture. This process is further complicated in the case of compound leaves with the formation of new growth axes. Growth and differentiation must be properly coordinated to regulate the size and the flatness of the leaf. This review provides an overview of the genetic and molecular regulatory networks underlying leaf development, with an emphasis on leaf polarity and the comparison of simple and compound leaves.     

A Neural Network for Predicting the Stability of DNA/DNA Duplexes

A back-propagation neural network method has been developed to predict the stability of DNA/DNA duplexes. Calculated T_m with the present parameters fits the experimental values within reasonable errors (AD = 1.86 K, SEP = 1.99151, R2 = 0.9894 for NN1; AD = 1.59667 K, SEP = 2.03824, R2 = 0.99371 for NN2), and it has the advantage that the determinations of thermodynamic parameters are not needed.     

Active Ingredients and Anti‐Arthritic Mechanisms of Ba‐Wei‐Long‐Zuan Granule Revealed by 1H‐NMR‐Based Metabolomics Combined with Network Pharmacology Analysis

Ba‐Wei‐Long‐Zuan granule (BWLZ) is a traditional herbal preparation. It has been widely used for the treatment of rheumatoid arthritis (RA). However, its active ingredients and mechanisms of action are still unclear. The present study aims to reveal the active compounds and anti‐arthritic mechanisms of BWLZ against collagen‐induced arthritis (CIA) by using ¹H‐NMR‐based metabolomics, molecular docking and network pharmacology methods. After 30 days of administration, BWLZ could effectively improve the metabolic disorders in CIA rats. The anti‐arthritic effect of BWLZ was related to its restoration of 16 disturbed serum metabolites. Molecular docking and network analysis showed that 20 compounds present in BWLZ could act on multiple targets. Among them, coclaurine and hesperidin showed the highest hit rates for target proteins related to both metabolic regulation and RA, indicating that these two compounds might be potential active ingredients of BWLZ. Moreover, pathway enrichment analysis suggested that the anti‐arthritic mechanisms of BWLZ might be attributed to its network regulation of several biological processes, such as steroid hormone biosynthesis, mTOR signaling pathway, alanine, aspartate and glutamate metabolism, and synthesis and degradation of ketone bodies. These results provide further evidence for the anti‐arthritic properties of BWLZ and are beneficial for its quality control and clinical application. The potential targets and biological processes found in this study may provide valuable information for further studying the molecular mechanisms of BWLZ against RA. In addition, our work provides new insights for revealing the active ingredients and regulatory mechanisms of complex herbal preparations.