The isolation of mitochondria from dipteran flight muscle

Procedures for the isolation of mitochondria from dipteran flight muscle have been investigated in an attempt to determine the extent and to identify the causes of deterioration associated with isolation. In the light of the results obtained isolation procedures have been improved by minimising mechanical damage, avoiding the development of anoxic conditions, and by the use of an isolation medium of a more physiological nature, containing the potassium salt of an organic anion as the principal osmoeffector, phosphate as the principal buffer, and low concentrations of free Mg²⁺. The oxidative capacity of mitochondria isolated by the improved method is adequate to support the in vivo requirements of the flight system.     

The Fluid Processing Apparatus: from flight hardware to electron micrographs

Sweet clover seeds were grown in the Fluid Processing Apparatus (FPA) flown on STS-54 (January 1993) and STS-60 (February 1994). After germination and seedling growth for 40 hours, seedlings were fixed in space. Electron microscopy was used to examine the seedling ultrastructure to verify that fixation occurred and preserved the samples. Micrographs revealed well-preserved cell structure and the presence of calcium precipitates indicating complete fixation. FPA is a useful piece of hardware for preservation/fixation during spaceflight.     

The evolution of vertebrate flight

Flight–defined as the ability to produce useful aerodynamic forces by flapping the wings–is one of the most striking adaptations in vertebrates. Its origin has been surrounded by considerable controversy, due in part to terminological inconsistencies, in part to phylogenetic uncertainty over the sister groups and relationships of birds, bats and pterosaurs, and in part to disagreement over the interpretation of the available fossil evidence and over the relative importance of morphological, mechanical and ecological specializations. Study of the correlation between functional morphology and mechanics in contemporary birds and bats, and in particular of the aerodynamics of flapping wings, clarifies the mechanical changes needed in the course of the evolution of flight. This strongly favours a gliding origin of tetrapod flight, and on mechanical and ecological grounds the alternative cursorial and fluttering hypotheses (neither of which is at present well-defined) may be discounted. The argument is particularly strong in bats, but weaker in birds owing to apparent inconsistencies with the fossil evidence. However, study of the fossils of the Jurassic theropod dinosaur Archaeopteryx , the sister-group of the stem-group proto-birds, supports this view. Its morphology indicates adaptation for flapping flight at the moderately high speeds which would be associated with gliding, but not for the slow speeds which would be required for incipient flight in a running cursor, where the wingbeat is aerodynamically and kinematically considerably more complex. Slow flight in birds and bats is a more derived condition, and vertebrate flapping flight apparently evolved through a gliding stage.     

The influence of flight on the phospholipid metabolism in insect flight muscle

Males of the American cockroach, Periplaneta americana, received an injection of 32P-orthophosphates and the specific activity of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) was determined after 120 min of in vivo incorporation. If the insects were forced to fly for 10 min immediately before the end of the experiment, the specific activity (S.A.) of PC and PE was lowered by 34.3 and 31.0%, respectively, that of PI by 17.5%. If the animals were allowed to rest for 10 min after cessation of flight, the S.A. of PC and PE did not differ significantly from the controls, whereas that of PI rose by 91.0% above the control value. These effects cannot be due to changes in precursor labelling (glycerophosphate and phosphoarginine were measured) and reflect changes in the rate of phospholipid biosynthesis. The possibility is discussed that mechanisms regulating the rate of phospholipid biosynthesis are involved.     

The science of coprolite analysis: The view from Hinds cave

This paper explores some of the new perspectives resulting from re-examination of the pollen data from my 1978 comprehensive analysis of 100 coprolites from one of the earliest identified prehistoric latrines in North America. Of particular interest are the empirical results of previously unavailable pollen concentration calculations for some of the prehistoric specimens as well as a time-series of 82 modern fecal specimens produced during an experiment yielding data on the rate of elimination of specific pollen grains from the human system. Experimental data of all sorts are needed to extend coprolite analyses and interpretations, particularly from pollen-ingestion studies conducted with more volunteers over long periods of time. Parasitological studies of human coprolites will benefit from experimental data to determine the fate of the constituents of human feces ingested by dogs. The application of specialized techniques at the microscope, such as Intensive Systematic Microscopy ([Dean, G., 1998. Finding a needle in a palynological haystack. In: Bryant, V.M., Wrenn, J.H. (Eds.), New Developments in Palynomorph Sampling, Extraction, and Analysis. Am. Assoc. of Stratigraphic Palynologists Foundation., Contribs Series No. 33, pp. 53-59]), to locate and quantify rare pollen types needs to be explored. Easy and useful ways to express the abundance of macroremains in a coprolite are also needed.     

The paramyosin of insect flight muscle

Paramyosin has been extracted and purified from the flight muscle of the insects Lethocerus cordofanus, Lethocerus maximus (water bugs), Heliocopris japetus (dung beetle) and Pachnoda ephippiata (rosechafer beetle). The subunit molecular weight, estimated by sodium dodecyl sulphate electrophoresis, is 107,000 ± 6000. The intrinsic sedimentation constant is 3.17 S and circular dichroism measurements give about 87 % helix, showing that the molecule is likely to be a two-chain rod.The amino acid composition of insect paramyosins resembles that of molluscan and annelid paramyosins except that the Glu/Asp ratio is higher. The amino acid analysis of insect tropomyosin is also given. Electron microscopy of tactoids shows an axial periodicity of 732 ± 8 Å or 146 Å with fine structure differing from that of molluscan tactoids.The proportion of paramyosin in the myofibrils, estimated by densitometry of stained gels, is 6.3% in L. cordofanus and 9.5% in rosechafer, and the ratio of myosin to paramyosin in L. cordofanus is 8.2. The possibility that paramyosin is a core protein of the myosin filaments is discussed.