Strategies in Neuroendocrine Neurophysiology

SYNOPSIS. Hormonal effects on selected indicators of neuralactivity are reviewed with reference to neuroendocrine mechanisms.The nature of brain recordings and their advantages and disadvantagesin neuroendocrine applications are discussed. The problems oflocalization of neuroendocrine mechanisms in place and timeare presented, with indications of which processes may be bestsuited to neurophysiological analysis.     

Palaeozoic tropical rainforests and their effect on global climates: is the past the key to the present?

Wetland forests, known as coal forests, extended over large areas of the palaeotropics during the Late Carboniferous and the Permian Periods. They were initiated during the Serpukhovian Age as a response to lowering sea levels having exposed large areas of continental shelf. They expanded dramatically during the late Bashkirian Age, but then contracted by over one‐half during the Kasimovian Age. The estimated loss of carbon sink probably resulted in an annual increase in atmospheric CO₂ of about 2–5 ppm, and coincided with clear evidence of global warming in both the northern and southern high latitudes. A return to cooler conditions in very Early Permian times coincided with an expansion of the palaeotropical coal forests in the Far East, but this was short‐lived and most of the rest of the Permian was a time of global warming. The Palaeozoic evidence clearly confirms that there is a correlation between levels of atmospheric CO₂ and global climates. However, care must be taken in extrapolating this evidence to the present‐day tropical forests, which do not act as a comparable unsaturated carbon sink.     

Variations in attack behaviours between Glossina palpalis gambiensis and G. tachinoides in a gallery forest suggest host specificity

Tsetse flies Glossina palpalis gambiensis and G. tachinoides are among the major vectors of sleeping sickness (Human African Trypanosomiasis‐HAT) and nagana (African Animal Trypanosomiasis – AAT) in West Africa. Both riparian species occur sympatrically in gallery forests of south west Burkina Faso, but little is known of their interspecies relationships although different authors think there may be some competition between them. The aim of this study was to check if sympatric species have different strategies when approaching a host. A man placed in a sticky cube (1 m × 1 m × 1 m) and a sticky black‐blue‐black target (1 m × 1 m) were used to capture tsetse along the Comoe river banks in a Latin Square design. The number and the height at which tsetse were caught by each capture method were recorded according to species and sex. Glossina p. gambiensis was more attracted to human bait than to the target, but both species were captured at a significantly higher height on the target compared with the human bait (P < 0.05). No significant difference in heights was found between G. tachinoides and G. p. gambiensis captured on targets (33 and 35 cm, respectively, P > 0.05). However, catches on human bait showed a significant difference in height between G. tachinoides and G. p. gambiensis (22.5 and 30.6 cm, respectively, P < 0.001). This study showed that these sympatric species had different attack behaviours to humans, which is not the case with the target. The implications of these findings are discussed.     

Phyllotaxis, phenology and architecture in Cephalotaxus, Torreya and c(Coniferales)

In Amentotaxus, Cephalotaxus and Torreya there is a regular seasonal alternation of foliage leaves and bud-scales, with foliage leaves largely preformed, i.e. initiated in the season before they expand. On most plagiotropic shoots phyllotaxis in the production of foliage leaves may be either bijugate ( Cephulotaxus, Torreya ) or decussate ( Amentotaxus ). In bijugate phyllotaxis successive leaf pairs originate at an angle of about 68° to each other, i.e. approximately one-half of the 'ideal' or Fibonacci angle of 137.5°. Secondary leaf orientation in Cephulotaxus and Torreya , by twisting of the leaf base, produces the dorsiventrality of plagiotropic shoots, whereas in Amentotaxus secondary orientation involves a twisting of the stemc as well as the leaf base. In Cephalotaxus cc condition is constant in the production of the numerous but imprecise number of bud-scales and in the production of foliage leaves. However, in Torreya the phyllotaxis changes from bijugate in the production of foliage leaves to decussate in the production of bud-scales, which are constant in number (about eight pairs). This allows a precise analysis of the biphasic production of leaf primordia in the seasonal cycle. The phyllotactic change in Torreya may not be the result of reported changes in shoot apex dimensions since Cephalotaxus , with its constant phyllotaxis, has a comparable seasonal change in apex dimensions. Information on architecture, chirality and cone morphology is also included.