Electromyography; uses and limitations

A normal muscle at rest emits no detectable electric current, but in action, in diseases of the muscle and in denervation it emits electric impulses characteristic of these states. The impulses can be amplified and studied through the sonic and oscilloscopic patterns they create. These patterns are sufficiently different so that simple atrophy of disuse can be distinguished from the denervation that may be associated with it. Since denervation can be localized to individual muscles and thence to the nerves controlling them, electromyography serves much the same function as myelography, with comparable accuracy and with greater safety and simplicity. It aids in the diagnosis of several muscular diseases of children and adults. Because electromyographic changes due to injury do not appear until 18 to 21 days later, a study made soon after injury can either disclose or rule out preexisting lesions. Then a later study indicating denervation is objective evidence that any disability is due to the injury in question.     

Bryophyte evolution and geography

The three extant Divisions comprising the bryophytes extend, as fossils, well back into Palaeozoic time. Bryophyte origin is part of the rise of terrestrial, vascularized, plants with sporopollenin-walled spores in the Silurian. Before the end of Carboniferous time, bryophyte lines were widely present. Separation of Gondwana and Laurasia by the Permian Tethys Sea and subsequent widespread desert episodes fragmented an already diversified bryoflora subjecting it to intense selective pressure. The cool, mesic climate of southern Gondwana provided a refugium for austral bryophytes. Warmer and drier climates of the Permo-Triassic Laurentian-Laurasia favoured drought-adapted or niche-specific groups creating marked systematic discontinuities. The Angaran wet, probably cool, temperate region provided refuge for basic stock for much of today's rich holarctic and wet ‘tropical’ bryofloras. Climatic changes, correlated with tectonic events and the rise of angiosperms, opened habitats favourable for a diversity explosion. Despite demonstrated potential for long-distance dispersal, modern distributions are mostly linked with total floras or establishment on islands prior to niche saturation. Remnants of Gondwanan bryoflora persist in high southern latitudes as disjunctions with the possibility that the folded ranges of the African Cape have been an insular fragment at higher latitudes becoming attached shortly after angiosperm diversification. Floras of southern India and east Africa have common features but the Himalayan flora shows evidence that the Gondwanan flora of the Indian plate was lost during the movement through desert and tropical latitudes; neotropical and palaeotropical floras are distinctive. Much of the northern Australian bryoflora is recently Malesian-derived while the southeast shows strong austral influence and commonality with New Zealand. Tropical Pacific island floras are mostly Malesian-derived but with both holarctic and austral elements present as in Hawaii and the Society Islands. Holarctic bryoflora is circum-polar with temperate areas of Euro-American and far eastern elements floristically bound by disjunct and vicariad species. Kroeber Coefficients of Correlation differ as Pacific island floras are compared and Guttman-Lingoes Smallest Space Coordinates indicates floristic subgroups within Polynesia. Although these and other mathematical treatments yield potentially promising results, the methods are yet unrefined and there is some uncertainty whether characteristics of numbers or of organisms are implicit in the summations.     

Control of the alary muscles of locust dorsal diaphragm

ABSTRACT. The heartbeat in whole, intact, adult Locusta migratoria R.F. was characterized by a regular rate but apparently irregular amplitude. Cutting segmental nerves often eliminated apparent amplitude fluctuations, and electrically shocking a segmental nerve in the whole animal evoked apparent amplitude changes corresponding to the shocks. Saline-perfused tissue preparations showed that the apparent amplitude fluctuations could be duplicated by segmental nerve stimulation, and that the fluctuations were due largely to contractions of the alary muscles of the dorsal diaphragm which shifted the position of the heart chamber without a change in volume. The alary muscles are each multi-terminally innervated by one motor axon. Neurally-evoked postsynaptic potentials facilitated and summated, and the diaphragm muscles began visibly contracting at stimulation rates as low as 2 Hz. Stimulation at higher frequencies caused greater depolarization of the muscle fibres with no indication of electrically-excited responses. The alary muscles were insensitive to perfusion with acetylcholine, l -glutamate, l -aspartate, dopamine, octopamine, noradrenaline, proctolin, 5-hydroxytryptamine, or gamma aminobutyric-acid in saline at concentrations up to 10^-3M. Larval or adult brain extracts of Locusta at 10 μg/μl and diluted 1:5 in saline caused uniform contractions of the alary muscle preparation, while perfusion of skeletal muscle extracts produced no response.     

Aeolid nudibranchs (Gastropoda: Opisthobranchia) of the family Tergipedidae from New Zealand waters

Four species of the genus Cuthona Alder & Hancock are recorded for the first time. Two of these species are Cuthona beta (Baba & Abe, 1964) and C. alpha Baba & Hamatani, 1963: although the local specimens differ in some features, principally ceratal arrangement, length of the radula and colour, the differences are considered too slight to warrant separation. The other two are new, being distinguished by a combination of features: C. scintillans sp. nov. by the large size reached (24 mm), rhinophores, oral veil and number of ceratal rows (13), the rounded foot-angles, green diverticula and yellow surface pigmentation, and number of denticles on the largest radular teeth (9); C. reflexa sp. nov. by the simple colouration, short radula (30 teeth), terminal position of the cusp, a very short or no vagina and the renal opening above the anus.
The name Tergipedidae (= Cuthonidae) is given priority and its use reviewed. Three subfamilies are recognized viz. Cuthonellinae, Cuthoninae and Tergipedidinae, each founded on the division of the digestive gland. Thirteen genera are listed, but only seven are firmly established as being distinctive and belonging to the family; one of the remaining six, Guyvalvoria Vayssiere, 1906, is certainly valid, but, because the ceratal arrangement is only superficially known, its place in the family could not be determined.