Heiner Birkenbeil

Morphology of neurones associated with the antennal heart of Periplaneta americana (Blattodea, Insecta)

SummaryInnervation of the antennal heart, an independent accessory circulatory motor in the head of insects, was investigated in the cockroach Periplaneta americana by use of axonal cobalt filling and transmission electron microscopy. The muscles associated with this organ are innervated by neurones located in a part of the suboesophageal ganglion, generally considered to be formed by the mandibular neuromere. Dorsal unpaired median (DUM) and paired contralateral neurones were stained. The axons of all these neurones run along the circumoesophageal connectives and through the paired nervus corporis cardiaci III into the corpora cardiaca. They pass through these organs forming fine arborizations there and exit anteriorly as a small pair of nerves which terminate at the antennal heart-dilator muscles. Numerous branches of these nerves extend beyond the lateral borders of the large transverse dilator muscle and terminate in the ampullar walls of the antennal heart. These neurosecretory fibres form neurohaemal areas which obviously release their products into the haemolymph, which is pumped into the antennae. The possible functions of the neurones associated with the antennal heart are discussed with respect to both, their role as a modulatory input for the circulatory motor and as a neurohormonal release site.

The distribution of a proctolin-like immunoreactive material in the terminal ganglion of the cockroach, Periplaneta americana L.

SummaryNeurons with proctolin-like immunoreactivity were mapped in the terminal ganglion of Periplaneta americana. The effect of different fixation methods on the variability of immunostaining is described and discussed. The appearance of immunoreactive presynaptic terminals, described here for the first time in insects, points to a function of proctolin as neurotransmitter or neuromodulator in the central nervous system of P. americana besides its known role in the periphery. Proctolin-like immunoreactivity was shown in pre- and postsynaptic profiles. Synaptic contacts are described in detail.

Ultrastructure of the prothoracic gland cells of the last instar of Galleria mellonella in relation to the state of development

SummaryThe prothoracic glands of the last instar of Galleria mellonella undergo characteristic alterations of their cellular fine structure closely related to cellular activity. During progressive secretory activity of the gland cells there are extensive plasmalemmal infoldings and formation of a pronounced lacunar system. Mitochondria of the active cell phase are characterized by a specific increase in size and paler colour of the matrix. In contrast to the alterations, nuclei, ER and Golgi cisterns do not undergo any submicroscopic changes during the different phases of cellular activity. The relationships between the substructural phenomena and the specific phases of cellular activity are discussed.

Ultrastructural and immunocytochemical investigation of ecdysteroid secretion by the prothoracic gland of the waxmoth Galleria mellonella

SummaryThe formation and secretion of ecdysteroid by the prothoracic gland cells of Galleria mellonella (Insecta, Lepidoptera) were investigated electron microscopically and immunocytochemically. The moulting hormone ecdysone becomes first evident in vesicles and tubules of the smooth endoplasmic reticulum (SER). The SER forms secretory granules in which ecdysone was shown immunocytochemically. The Golgi apparatus seems not to be directly involved in ecdysone secretion. The secretory granules are released from the cells by exocytosis.

Electron microscopical-immunocytochemical evidence of ecdysteroids in the prothoracic gland of Galleria mellonella.

SummaryFixation of prothoracic glands of Galleria mellonella with a solution containing saponin permits immunocytochemical staining of the entire gland. By this means ecdysteroids were demonstrated electron microscopically to be present in the hyaloplasm and microtubules.

The ultrastructure of a hitherto unrecognized gland, the cephalic gland in the head of Orconectes limosus which produces ecdysteroids ☆

Abstract The fine structural morphology of a hitherto unrecognized cephalic gland is described. Changes in the nuclei and cytoplasmic components of the gland cells during the molting cycle are specified and the hormonal control of the cephalic gland by the eyestalk system is discussed.

Protein kinase A and C are “Gatekeepers” of capacitative Ca2+ entry in the prothoracic gland cells of the silkworm, Bombyx mori

Application of protein kinases A and C inhibitors to the prothoracic glands cells of the silkworm, Bombyx mori, resulted in slow and gradual increases in intracellular Ca(2+) ([Ca(2+)](i)). Pharmacological manipulation of the Ca(2+) signalling cascades in the prothoracic gland cells of B. mori suggests that these increases of [Ca(2+)](i) are mediated neither by voltage-gated Ca(2+) channels nor by intracellular Ca(2+) stores. Rather they result from slow Ca(2+) leak from plasma membrane Ca(2+) channels that are sensitive to agents that inhibit capacitative Ca(2+) entry and are abolished in the absence of extracellular Ca(2+). Okadaic acid, an inhibitor of PP1 and PP2A phosphatases, blocked the increase in [Ca(2+)](i) produced by the inhibitors of protein kinase A and C. The combined results indicate that the capacitative Ca(2+) entry channels in prothoracic gland cells of B. mori are probably modulated by protein kinases A and C.

Ultrastructure of the Y-organ of Astacus astacus (L.) (Crustacea) in relation to the moult cycle.

SummaryThe electron microscopical investigation of Y-organs of Astacus astacus revealed that during intermoult (stage C) the cytoplasm is poorly developed and that it increases at premoult (stage D). It then shows the typical signs of steroid production, namely agranular endoplasmic reticulum and mitochondria of the tubular type. Furthermore, a larger type of mitochondria with a regular pattern of internal structure is described.

Immuno-electron-microscopic evidence of ecdysteroids in Y-organ of Orconectes limosus (Crustacea, Decapoda)

SummaryEcdysone was demonstrated by ultrastructural immunocytochemistry to be present in the mitochondria of the Y-organs of the crayfish Orconectes limosus. This is in remarkable contrast to the prothoracic glands of insects and suggests substantial differences in the biosynthesis of the same hormone, ecdysone, in crustaceans and insects.

Untersuchungen zur Methodik des ultrastrukturellen immuncytochemischen Nachweises von Ecdysteroiden

Summary The investigations were carried out with prothoracic glands of Galleria mellonella . The influence of various fixation media on the preservation of the ultrastructure and on the immunocytochemical staining of the steroid ecdysone was studied. An immunocytochemical staining technique for ecdysone is described allowing the ultrastructural localization of ecdysone in different cellular compartments.