Gary Chiang Oniscus Asellus Research Papers

R. Gary Chiang and C.G.H. Steel
Department of Biology, York University, M3J 1P3 North York, ON, Canada
Brain Research. 1987 Volume 402, Issue 1, Pages 49-57.

Changes during the moult cycle in the bursting firing pattern of the electrical activity recorded extracellularly from the sinus gland of the terrestrial isopod, Oniscus asellus.

Ongoing electrical activity of the sinus gland (SG) of the terrestrial isopod, Oniscus asellus, was recorded extracellularly from almost intact breeding or non-breeding females to delineate the major times of neurohormone release during the moult cycle. In intermoult, SGs discharged in long bursts (10-50 s) at high frequency (10-45 Hz), and their activity ratios (total burst duration divided by total time the SG was monitored) ranged from 0.22 to 0.73. At premoult initiation when release of moult-inhibiting hormone is expected to decline, a decrease in SG activity occurred. It rose again in early premoult in parallel with increases in ecdysteroid titre; declined again in late premoult during peak ecdysteroid titres; increased again just prior to posterior ecdysis, and was very low during posterior ecdysis itself. Activity increased immediately after posterior and anterior ecdysis suggesting the release of neurohormones involved in calcification of the new cuticle. Burst duration was ca. two-fold longer in breeding compared to non-breeding females during early premoult suggesting the release of neurohormones involved in vitellogenesis, and before anterior ecdysis suggesting release of neurohormones involved in egg deposition. Thus, the release of neurohormones occurred during 4 major periods in each moult cycle, clearly demonstrating a relationship between SG activity in situ, and the physiological events dependent on SG hormones.

R. Gary Chiang and C.G.H. Steel
Department of Biology, York University, M3J 1P3 North York, ON, Canada
Brain Research. 1986, Volume 377, Issue 1 , Pages 83-95.

Electrical activity of the sinus gland of the terrestrial isopod, Oniscus asellus: characteristics of identified potentials recorded extracellularly from neurosecretory terminals.

Spontaneously occurring neurosecretory action potentials recorded extracellularly from the sinus gland (SG) of the terrestrial isopod, Oniscus asellus, are of 5 types (A through E) identified by their amplitudes and patterns of discharge. Type A have the largest (200-450 microV) and type E the smallest (25-50 microV) amplitude. Types A, B and C originate from the bulb of the SG, and discharge at high frequencies (30-60 Hz) in coordinated bursts ranging from seconds to several minutes in duration. Coordination of their discharges suggests a mechanism for synchronizing bursting activity among different cell types. Types D and E originate from the lateral extension of the SG, and discharge at low frequencies (0.5-1.0 Hz) for prolonged periods (5-10 min). Their activity is not synchronized with discharges of other potentials. Following transection of the brain through the lateral part of the central protocerebral neuropile, A, B and C potentials are eliminated whereas D and E potentials remain active. This result suggests A, B and C potentials arise from neurosecretory cells (NSCs) whose cell bodies are located in the medial protocerebrum, and D and E potentials arise from NSCs identified in the optic lobe. Alterations in the appearance of action potentials following exposure to salines deficient in Na+ or Ca2+, or containing tetrodotoxin or cobalt, reveal that A and B potentials are primarily Ca2+ dependent whereas C potentials are both Ca2+ and Na+ dependent.

R. Gary Chiang, C.A. Knobloch, D.M. Singleton, C.G.H. Steel, K.G. Davey
Department of Biology, York University, M3J 1P3 North York, ON, Canada
Journal Neuroscience Methods. 1985 Volume 15, Issue 1, Pages 15-20.

Recording electrophysiological data on video tape: a superior and less costly alternative to conventional tape recorders.

Electrical potentials recorded extracellularly from the sinus gland of the isopod, Oniscus asellus, were stored on video tape with the aid of a digital-audio (DA) processor and a video cassette recorder (VCR). The DA processor transforms the analog signal to digital pulses of equal amplitude and converts these pulses into a television signal for recording on video tape. In playback, the DA processor reconverts the pulses to an analog signal with negligible distortion. When viewed on the oscilloscope screen, electrical potentials reproduced by this method were indistinguishable from electrical potentials recorded 'live' from the sinus gland. However, electrical potentials recorded from the same sinus gland and reproduced by a conventional FM tape recorder were easily differentiated from the 'live' recording. The special effects inherent in the VCR (e.g. stop action, frame advance) also permitted detailed analysis of spontaneously occurring electrical potentials. Special effects were not possible with the FM tape recorder. The price, ease of operation and ability to produce extremely high quality recordings, makes the DA processor and VCR an exceptional system for storing electrophysiological data.

R. Gary Chiang and C.G.H. Steel
Department of Biology, York University, M3J 1P3 North York, ON, Canada
Brain Research. 1985, Volume 331, Issue 1, Pages 142-4.

Coupling of electrical activity from contralateral sinus glands.

Bursts of electrical activity recorded extracellularly from the sinus gland (SG) of the isopod, Oniscus asellus, occur synchronously in right and left SGs. Synchronization results from the electrical activity of two physiologically identifiable neurosecretory cell (NSC) types in one SG being coupled to the electrical activity of their respective contralateral counterparts. Furthermore, the coupling mechanism which serves to coordinate hormone release from contralateral SGs appears to differ for each of the two NSC types.

R. Gary Chiang and C.G.H. Steel
Department of Biology, York University, M3J 1P3 North York, ON, Canada
Tissue Cell. 1985. Volume 17, Issue 3, Pages 405-15

Ultrastructure and distribution of identified neurosecretory terminals in the sinus gland of the terrestrial isopod, Oniscus asellus.

An ultrastructural study of the sinus gland of the terrestrial isopod, Oniscus asellus, reveals that this structure consists of two regions: the bulb, which is attached by a narrow stalk to the optic lobe, and the lateral extension, which extends from the bulb along the optic tract to the compound eye. The bulb has a distal region containing only neurosecretory terminals, and a proximal region containing terminals, glial cells, and axons that give rise to the distally located terminals. In total, the sinus gland contains five types of terminals which can be distinguished by their location and the appearance of their neurosecretory granules. Three terminal types are located in the bulb and two in the lateral extension. The size of the terminals in the bulb varies among the three types, but the number of terminals is approximately the same for each type. Conversely, the two terminal types in the lateral extension are similar in size, but differ in number. Axons of two terminal types in the bulb can be traced to the central region of the protocerebrum; axons of one terminal type in the bulb and of terminals in the lateral extension can be traced to the optic lobe.