Biomedical subjects

G Pass

Publications and source records attributed to G Pass.

4 recordsLinked to original sources

PubMed2003

Preparation of serial sections of arthropods using 2,2-dimethoxypropane dehydration and epoxy resin embedding under vacuum.

Improved methods are described for anatomical investigation of small insects and other arthropods using serial semithin sections. The specimens were dehydrated with acidified 2,2-dimethoxypropane and embedded in ERL 4206 epoxy resin under vacuum. This procedure ensures good resin impregnation of thin, long body compartments and appendages. Furthermore, it produces excellent overall preservation of the specimen and its fragile anatomical structures. This procedure saves time and gives excellent results when sectioning difficult arthropod material. A continuous recording of serial semithin sections is possible when diamond knives are used.

Anatomy, Cross-Sectional↗

PubMed2002

Studies on the cardiac physiology of Onychophora and Chilopoda.

Cardiac physiology in Onychophora and Chilopoda has not yet been studied by electrophysiological methods. Here we present ECGs and the first intracellular recordings from dorsal vessel muscle cells in Scolopendra cingulata, Lithobius forficatus and Peripatopsis sp. In Onychophora, a myogenic automatism generates the heart function. In the Chilopoda examined, heartbeat is triggered by a neurogenic automatism that is superimposed over a basic myogenic rhythm, which occurs under experimental conditions. The neuropeptide proctolin and the head peptide have no significant effects in the species investigated. The results are discussed from the viewpoints of comparative physiology and phylogenetics.

Action Potentials↗

PubMed2000

Accessory pulsatile organs: evolutionary innovations in insects.

In addition to the dorsal vessel ("heart"), insects have accessory pulsatile organs ("auxiliary hearts") that supply body appendages with hemolymph. They are indispensable in the open circulatory system for hemolymph exchange in antennae, long mouthparts, legs, wings, and abdominal appendages. This review deals with the great diversity in the functional morphology and the evolution of these accessory pulsatile organs. In primitive insects, hemolymph is supplied to antennae and cerci by arteries connected to the dorsal vessel. In higher insects, however, these arteries were decoupled and associated with autonomous pumps that entered their body plan as evolutionary innovations. To ensure hemolymph supply to legs, wings, and some other appendages, completely new accessory pulsatile organs evolved. The muscular components of these pulsatile organs and their elastic antagonists were recruited from various organ systems and assembled to new functional units. In general, it seems that the evolution of accessory pulsatile organs has been determined by developmental and spatial constraints imposed by other organ systems rather than by changes in circulatory demands.

Animals↗

PubMed1988

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

Innervation 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.

Animals↗