The responses of central acoustic and vibratory interneurones in bushcrickets and locusts to ultrasonic stimulation

ABSTRACT. Analysis of the ultrasonic content of the calling songs of two tettigoniids, Decticus verrucivorus L. and Tettigonia cantans Fuessly, showed that the major secondary energy peaks in the ultrasonic range are only about 15–20 dB below the main audible frequency peaks. The song of the acridid, Locusta migratoria L., contains no appreciable secondary peaks at ultrasonic frequencies, Bifunctional acoustic-vibratory interneurones are present in the ventral nerve cord of all three species. They are divided into three categories, according to their response characteristics: VS (vibration and sound), S (sound) and V (vibration) neurones. All the unit-types capable of coding sound signals in the ventral cord (VS and S neurones) are sensitive to frequencies of up to 100 kHz, with one exception (S3). In tettigoniids, three of these unit-types are more sensitive at ultrasonic frequencies than they are at the audible frequencies of their conspecific songs. Among the vibratory neurones (V), one unit-type receives inhibitory inputs from ultrasonic acoustic primary receptors. The possible importance of ultrasonic perception in the natural environment is briefly discussed.     

Immunocompetence, mast cells and sexual behaviour

This paper reports a provocative and novel observation. Specifically, we have shown that in Ring Doves Streptopelia roseogrisea, following a brief period of courtship, cells of the immune system–mast cells–appear in the brain. This is surprising in that it has long been thought that the blood-brain barrier prevents the movement of blood-borne cells into the parenchyma (neural tissue) of the brain. The conditions under which these cells appear, their chemical and ultrastructural features and their potential in neuroendocrine signalling functions are discussed. The significance of these cells for the expression of behaviour and their specific role in the medial habenula (the brain area to which they migrate) remain to be explored. While our research has focused on a domesticated, laboratory bird species, the relationship between sexual behaviour and immunocompetence has long been of interest in field work and in studies on the evolution of sexual behaviour. It is hoped that this work, now in its infancy, will bridge field and laboratory, as well as providing a forum for integrating mechanistic and evolutionary concepts in neuro-im-muno-endocrinology.     

Spatial partitioning of secretory cargo from Golgi resident proteins in live cells

Background  

To maintain organelle integrity, resident proteins must segregate from itinerant cargo during secretory transport. However, Golgi resident enzymes must have intimate access to secretory cargo in order to carry out glycosylation reactions. The amount of cargo and associated membrane may be significant compared to the amount of Golgi membrane and resident protein, but upon Golgi exit, cargo and resident are efficiently sorted. How this occurs in live cells is not known.     

Immunocompetence, mast cells and sexual behaviour

This paper reports a provocative and novel observation. Specifically, we have shown that in Ring Doves Streptopelia roseogrisea , following a brief period of courtship, cells of the immune system–mast cells–appear in the brain. This is surprising in that it has long been thought that the blood-brain barrier prevents the movement of blood-borne cells into the parenchyma (neural tissue) of the brain. The conditions under which these cells appear, their chemical and ultrastructural features and their potential in neuroendocrine signalling functions are discussed. The significance of these cells for the expression of behaviour and their specific role in the medial habenula (the brain area to which they migrate) remain to be explored. While our research has focused on a domesticated, laboratory bird species, the relationship between sexual behaviour and immunocompetence has long been of interest in field work and in studies on the evolution of sexual behaviour. It is hoped that this work, now in its infancy, will bridge field and laboratory, as well as providing a forum for integrating mechanistic and evolutionary concepts in neuro-immuno-endocrinology.     

Evaluation of trichothecene and nontrichothecene mycotoxins produced byFusarium in soybeans

Each of 12 cultures ofFusarium, comprising four species, isolated from moldy soybeans suspected of being involved in illness of wild geese, were grown separately in autoclaved moist rice, in autoclaved moist soybeans, and in surface sterilized-disinfected soybeans, assayed for various mycotoxins, and fed to rats. Four additional cultures that produced known toxins on rice were also grown on soybeans as controls. All isolates, except one ofF moniliforme, grown in rice resulted in weight loss of rats, and that one resulted in weight gain; 12 of the isolates caused death. One isolate ofF poae grown in soybeans caused death when consumed by rats, but none of the other 15 resulted in weight loss or overt injury. Much larger amounts of zearalenone, deoxynivalenol (DON), T-2 toxin, neosolaniol, T-2 tetraol, wortmannin, and moniliformin were produced by the cultures on rice than on soybeans, but more HT-2 toxin was produced by one isolate ofF poae grown on soybeans than when grown on rice. Soybeans appear to be a poor substrate for elaboration of most of the toxins produced by the isolates tested.