Pathways and fine structure of neurons forming the nervi corporis allati II of the cockroach Periplaneta americana (L.).

By back-filling the nervus corporis allati II (NCA2) with Co2+ and precipitating the sulfide, two groups of somata (A and B) are revealed on the ipsilateral side of the subesophageal ganglion (SG). These occur anteroventrally, adjacent to the midsaggital plane. Group A consists of two cells; group B of five. Their processes form two discrete tracts issuing dorsoposteriorly into the neuropile between and slightly behind the circumesophageal connectives (CEC). After producing separate arborization fields in the dorsal neuropile, the tracts circumscribe the base of the ipsilateral CEC, unite, and their seven fibers enter NCA2 anteriorly. Prograde diffusion reveals 4--6 NCA2 axons penetrating the corpus allatum (CA) near a cap-like neurohemal organ. These axons form the transverse allatal tract (TAT), from whence they branch amongst the CA cells, and into the "cap", the postallatal nerves, and the opposite CA. Electron microscopy of transverse sections demonstrates nine neurosecretory axons entering the SG through NCA2. Proximal to the CA, NCA2 consists of a central bundle of neurosecretory axons and a peripheral zone confluent with the CA "cap". Depending upon the level of sectioning, there are 7--20 axons at the center, and seven pass into the TAT. The peripheral zone has the structure of a neurohemal organ.

Locations and central projections of neurons associated with the retrocerebral neuroendocrine complex of the cockroach Periplaneta americana (L.).

Retrograde diffusion and precipitation of Co2+ reveals in the ipsilateral pars lateralis (PL) and contralateral pars intercerebralis (PI) of the brain neurons that enter the corpus cardiacum (CC), and, possibly, the corpus allatum (CA) on each side. The PL group consists of 29.6 +/- 8.4 somata that fill. Of these, 5.6 +/- 0.6 exceed 25 micrometer in diameter, 14.3 +/- 2.7 range from 15--25 micrometer, and 9.6 +/- 7.6 are smaller than 15 micrometer. After CoCl2 was applied to the right CC-CA of two males, 239 and 265 somata in the left PI stained. Except for 16 ranging from 30--45 micrometers and chiefly located anteriorly, a majority of these somata measured 10--25 micrometer. The only somata revealed by staining whole brains with the performic acid-resorcin fuchsin method are neurosecretory cells 10--20 micrometer in diameter located within the PI. In starved adult males there are 92.4 +/- 8.1 on the right, and 93.2 +/- 6.9 on the left. The largest somata in the PL group contain numerous granules that stain with paraldehyde fuchsin. These somata also fill with Co2+, and belong to neurosecretory cells that extend into the CC-CA. The cerebral distribution of branches from the PL group, and the relationship of these to the corpora pedunculata, central body, and arborizations from the PI decussation are described.

Eye disk differentiation in the wax moth: induction in vitro.

Ecdysterone-induced differentiation of Galleria mellonella compound eyes in vitro is critically dependent on the age of the donor. It is greatest in explants from young prepupae, decreases with increasing donor age, and is absent in explants from 4-6 hour pupae. Failure of eye disks from pupae to differentiate in vitro seems to be the consequence of exposing them to culture conditions at a susceptible time in their development for, unlike eye disks from prepupae, they do not develop when removed from the medium and implanted into competent hosts. The explants most responsive in vitro are more liable to submerge, with resulting inhibition of development. Three media allow differentiation of adult eye structures, and one of these is suitable without adding macromolecular compounds. Ecdysterone is essential, and will elicit ommatidia formation when it is added to the medium at concentrations ranging from 0.1-20 mug/ml. Rubrosterone is ineffective at 1.0 mug/ml of medium. In the best-differentiated explants each ommatidium consists of 8-10 pigmented retinal cells surrounding a rhabdom-like core, and their axons can be traced to an enlarged optic nerve. Crystalline cones, adult cuticle in the form of facets (corneal lenses), and pigment cells also are formed.