Output connections of a wind sensitive interneurone with motor neurones innervating flight steering muscles in the locust

Summary The output connections of a bilaterally symmetrical pair of wind-sensitive interneurones (called A4I1) were determined in a non-flying locust (Schistocerca gregaria). Direct inputs from sensory neurones of specific prosternai and head hairs initiate spikes in these interneurones in the prothoracic ganglion.The interneurone with its axon in the right connective makes direct, excitatory connections with the two mesothoracic motor neurones innervating the pleuroaxillary (pleuroalar, M85) muscle of the right forewing, but not with the comparable motor neurones of the left forewing. The connections can evoke motor spikes.The interneurones also exert a powerful, but indirect effect on the homologous metathoracic pleuroaxillary motor neurones (muscle 114), and a weaker, indirect effect on subalar motor neurones of the hindwings. No connections or effects were found with other flight motor neurones, or motor neurones innervating hindleg muscles, including common inhibitor 1 which also innervates the pleuroaxillary muscle.One thoracic interneurone with its cell body in the right half of the mesothoracic ganglion and with its axon projecting ipsilaterally to the metathoracic ganglion receives a direct input from the right A4I1 interneurone.These restricted output connections suggest a role for the A4I1 interneurones in flight steering.Abbreviations DCMD descending contralateral movement detector - EPSP excitatory postsynaptic potential - TCG tritocerebral commissure giant (interneurone)     

Alpha-Glycerophosphate dehydrogenase (insoluble) and lactic dehydrogenase activities in the skeletal muscles of two insects.

The flight muscle preparations of the dragonfly Pantala flavescens and the aquatic beetle Cybister confusus showed extremely low levels of lactic dehydrogenase activity and high levels of alpha-glycerophosphate dehydrogenase (insoluble) activity. The activities of these two enzymes in the leg muscle of the beetle were approximately the same (1:1), but lactic dehydrogenase activity was several times higher than that in the flight muscles of both Insects. These results have been interpreted as indicating the high energy-yielding demands of the flight muscles during continuous sustained activity, while the leg muscles of the beetle which are involved in swimming activity derive their energy predominantly through anaerobic glycolysis.     

Functional properties of locust locomotor muscles

The ultrastructure of the muscle fibers and the electrical constants and responses of the membrane to microapplication of L-glutamate and acetylcholine were investigated in the longitudinal flight muscle and the flexor tibiae ofLocusta migratoria migratorioides. The twitch flight muscle differs from the slower leg muscle in the smaller size of its sarcomeres and the lower values of the space attenuation factor of the electrotonic potential, time constant, and resistance of the membrane. Microapplication of sodium L-glutamate at strictly definite points of the fibers of both muscles evoked depolarization responses of the membrane. In experiments on normal and denervated muscle, during microapplication of acetylcholine, changes in the level of the membrane potential were never observed. It is concluded that L-glutamic acid is the excitatory mediator of the twitch and slow muscle systems of insects.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 532–538, September–October, 1977.     

Specificity and localisation of lipoprotein lipase in the flight muscles of Locusta migratoria

Using natural lipoproteins as substrates, lipase activity has been measured in leg muscle, fat body, midgut and flight muscles of Locusta migratoria. The enzymic activity in the flight muscles is higher than in those other tissues tested, confirming the potential of the flight muscles to utilise lipids at high rates. In addition, a membrane-bound lipoprotein lipase can be extracted from flight muscle. The flight muscle enzyme activity shows a marked substrate specificity; at lipoprotein concentrations equivalent to those found normally in flown or resting locusts respectively, the enzyme hydrolyses diacylglycerols associated with lipoprotein A+ (present in the haemolymph of flown or adipokinetic hormone-injected locusts) at about 4 times the rate of those associated with lipoprotein Ayellow (which is the major lipoprotein in resting locusts). In addition, the hydrolysis of lipids carried by lipoprotein Ayellow is dramatically reduced in the presence of lipoprotein A+. These observations indicate that the enzyme plays a specific role in the uptake of lipids at the flight muscles to ensure a smooth transition from carbohydrate to lipid based metabolism during flight.     

Origin and development of the dorso-ventral flight muscles in Chironomus (Diptera; Nematocera)

The origin and development of the dorso-ventral flight muscles (DVM) was studied by light and electron microscopy in Chironomus (Diptera; Nematocera). Chironomus was chosen because unlike Drosophila, its flight muscles develop during the last larval instar, before the lytic process of metamorphosis. Ten fibrillar DVM were shown to develop from a larval muscle associated with myoblasts. This muscle is connected to the imaginal leg discso that its cavity communicates with the adepithelial cells present in the disc; but no migration of myoblasts seems to take place from the imaginal leg disc towards the larval muscle or vice versa. At the beginning of the last larval instar, the myoblasts were always present together with the nerves in the larval muscle. In addition, large larval muscle cells incorporated to the imaginal discs were observed to border on the area occupied by adepithelial cells, and are probably involved in the formation of 4 other fibrillar DVM with adepithelial cells. Three factors seem to determine the number of DVM fibres: the initial number of larval fibres in the Anlage, the fusions of myoblasts with these larval fibres and the number of motor axons in the Anlage. The extrapolation of these observations to Drosophila, a higher dipteran, is discussed.     

Differential catabolism of muscle protein in Garden Warblers (Sylvia borin): flight and leg muscle act as a protein source during long-distance migration

Samples of flight and leg muscle tissue were taken from migratory garden warblers at three different stages of migration: (1) pre-flight: when birds face an extended flight phase within the next few days, (2) post-flight: when they have just completed an extended flight phase, and (3) recovery: when they are at the end of a stop-over period following an extended flight phase. The changes in body mass are closely related to the changes in flight (P<0.001) and leg muscle mass (P<0.001), suggesting that the skeletal muscles are involved in the protein metabolism associated with migratory flight. From pre- to post-flight, the flight and the leg muscle masses decrease by about 22%, but are restored to about 12% above the pre-flight masses during the recovery period. Biochemical analyses show that following flight a selective reduction occurred in the myofibrillar (contractile) component of the flight muscle (P<0.01). As this selective reduction accounts only for a minor part of the muscle mass changes, sarcoplasmic (non-contractile) and myofibrillar proteins of both the flight and leg muscle act as a protein source during long-distance migration. As a loss of leg muscle mass is additionally observed besides the loss in flight muscle mass, mass change seems not to be strictly associated with the mechanical power output requirements during flight. Whereas the specific content of sarcoplasmic proteins in the flight muscle is nearly twice as high as that in the leg muscle (P<0.001), the specific content of myofibrillar proteins differs only slightly (P < 0.05), being comparably low in both muscles. The ratio of non-contractile to contractile proteins in the flight muscle is one of the highest observed in muscles of a vertebrate.     

A histochemical study of the muscles of Drosophila melanogaster.

The thoracic muscles of Drosophila melanogaster can be classified into two classes, the fibrillar and the tubular muscles, on morphological grounds. Histochemical techniques were used to characterize these two classes of muscle according to their content of various enzymes (alpha-glycerophosphate, NAD-dependent isocitrate, malate and succinate dehydrogenases, fumarase, acid phosphatase, adenosine triphosphatase and acetylcholinesterase) and of glycogen. These investigations showed that the two muslces types are histochemically very different and, further, that the morphologically similar tubular muscles are heterogeneous with respect to their enzyme content. In particular, the tergal depressor of the trochanter of the second leg, the largest of the tubular muslces, has considerably less of all the enzymes studied, with the exception of acetylcholinesterase, than all the other tubular muscles examined. The histochemical techniqes were also used to follow the changes in enzyme levels that occur during development of the indirect flight muscle fibres. All the enzymes that are present in adult flight muslces showed an increase in staining intensity throughout muscle development. Some minor differences were observed in the time of appearance and rate of increase of intensity of the different enzymes.     

Localization of connectin-like proteins in leg and flight muscles of insects

In leg muscle sarcomeres of a beetle, approximately 6 mum sarcomere length at rest, projectin ( approximately 1200 kDa) was located on the myosin filament up to 2 mum from the both ends of the filament, using immunofluorescence and immunoelectron microscopy. On the other hand, projectin linked the Z line to the myosin filament and bound on the myosin filament in beetle flight muscle, approximately 3-4 mum sarcomere length at rest. Connectin-like protein ( approximately 3000 kDa) was detected by immunoblot tests in beetle, bumblebee and waterbug leg muscles. Immunofluorescence and immunoelectron microscopic observations revealed that the connectin-like protein linked the myosin filament to the Z line in beetle leg muscle.     

Effect of ecdysterone and juvenoid on the developmental involution of flight muscles in Acheta domestica

Morphogenesis and degeneration of the flight muscles in Acheta domestica was studied. The dorso-longitudinal flight muscles (DLMs) degenerate during the fourth day after adult ecdysis and the dorso-ventral flight muscles (DVMs) on the fifteenth day. In the presence of an intact innervation the degeneration of the DLMs can be retarded for 2 days by the injection of ecdysterone into very young adults. This retardation may also result in hypertrophy of the muscle fibres. The injection of ecdysterone, even in high doses, did not affect the flight muscle remnants. No notable changes have been found in the degeneration of DLMs by ovarectomy. Thus, the degeneration of flight muscles and the development of ovaries appear to be independent processes.The DLMs are homogeneous in fibre pattern in respect to succinic dehydrogenase, an important oxidative enzyme, and to ATPase activity, but the muscle fibres do not show any phosphorylase activity.     

Apterous mediates development of direct flight muscles autonomously and indirect flight muscles through epidermal cues

Two physiologically distinct types of muscles, the direct and indirect flight muscles, develop from myoblasts associated with the Drosophila wing disc. We show that the direct flight muscles are specified by the expression of Apterous, a Lim homeodomain protein, in groups of myoblasts. This suggests a mechanism of cell-fate specification by labelling groups of fusion competent myoblasts, in contrast to mechanisms in the embryo, where muscle cell fate is specified by single founder myoblasts. In addition, Apterous is expressed in the developing adult epidermal muscle attachment sites. Here, it functions to regulate the expression of stripe, a gene that is an important element of early patterning of muscle fibres, from the epidermis. Our results, which may have broad implications, suggest novel mechanisms of muscle patterning in the adult, in contrast to embryonic myogenesis.     

Sodium dodecyl sulfate gel electrophoresis studies of connectin-like high molecular weight proteins of various types of vertebrate and invertebrate muscles

Using an SDS gel electrophoresis method, connectin, very high molecular weight (approximately 10(6) dalton) protein, was detected in an SDS extract of whole tissues of various types of muscles of vertebrates and invertebrates. Connectin bands were clearly recognized in all the types of striated muscles (skeletal and cardiac) of the vertebrates examined: rabbit, chicken, turtle, snake, newt, frog, and fish. This was also the case with skeletal muscle of prochordate, Amphioxus. In invertebrates, the situation was much complicated. Connectin-like protein bands were detected in C. elegans (nematode), but not in earthworm (annelid). Smaller sizes of proteins (approximately 10(6)) were faintly found in molluscan adductor muscles. In arthropods, connectin-like proteins were clearly detected in some muscles (e.g., claw muscles of crab and crayfish; leg muscles of several insects) but not at all in other muscles (e.g., tail muscles of crayfish and shrimp; thoracic muscles of some insects). These peculiar observations might be related to the presence of such specific elastic proteins as projectin in honeybee flight muscle. The present study has revealed that connectin is an elastic protein of vertebrate striated muscle, skeletal and cardiac muscles.     

昆虫飞行肌蛋白质

昆虫飞行肌的肌原纤维不仅含有粗肌丝、细肌丝、纤肌丝,还含有很多其它蛋白质参与肌原纤维的组装和调节,文章介绍了10余种蛋白质的结构、功能及其在肌原纤维中的位置和功能,对于了解昆虫飞行肌的发育和探索昆虫飞行能力差异的原因具有重要意义。     

Development of fast singing muscles in a katydid

In males of the katydid Neoconocephalus robustus, mesothoracic wings are used in flight (wing stroke frequence = 20 Hz) and stridulation (200 Hz), while the metathoracic wings are used in flight alone. Most mesothoracic wing muscles produce much briefer isometric twitches than metathoracic counterparts. The mesothoracic first tergocoxal muscle (TCX1) has a twitch duration (onset to 50% relaxation, 35 degrees C) of 6-8 ms and the metathoracic TXC1 a twitch duration of 12-15 ms. The TCX1 muscles from animals one and two instars from adulthood produce twitches similar in duration to those of the adult metathoracic TCX1. The twitch duration of the mesothoracic TCX1 acquires its adult brevity gradually over the first 5 days of adult life. Both TCX1 muscles increase greatly in size and mitochondrial content around the time of the terminal molt. During this period the mesothoracic TCX1 develops narrower myofibrils and a smaller ratio of fibril volume to sarcoplasmic reticulum volume than is characteristic of the metathoracic TCX1. Changes in the ultrastructure of the mesothoracic TCX1 precede changes in contraction kinetics around the time of the terminal molt so that there is not a strict correlation between muscle structure and performance during the period of rapid growth.     

Power and control muscles of cicada song: structural and contractile heterogeneity

Sound production in cicadas is powered by a pair of large muscles whose contractions cause buckling of cuticular tymbals and thereby create sound pulses. Sound is modulated by control muscles that alter the stiffness of the tymbals or change the shape of the abdominal resonance chamber. Muscle ultrastructure and contractile properties were characterized for the tymbal muscle and two control muscles, the ventral longitudinal muscle and the tymbal tensor, of the periodical cicada Magicicada septendecim. The tymbal muscle is a fast muscle that is innervated by a single motoraxon. The control muscles are an order of magnitude less massive than the tymbal muscles, but their innervation patterns were considerably more complex. The tensor muscle is innervated by two axons, each of which evokes rather slow twitches, and the ventral muscle is innervated by at least six axons, some of which produce fast and the others slow contractions. Muscle contraction kinetics correlated well with ultrastructure. Fibers of the tymbal muscle and the portions of the ventral muscle thought to be fast were richly supplied with transverse tubules (T-tubules) and sarcoplasmic reticulum (SR); slow portions of the ventral muscle and the tensor muscle had relatively little SR.Abbreviations SR sarcoplasmic reticulum - TTS transverse tubular system - VLM ventral longitudinal muscle     

Structural and functional development of cricket ring muscles

The sizes of the unifunctional dorsal longitudinal (DLM) and bifunctional subalar (SA) metathoracic flight muscles of the cricket Teleogryllus oceanicus increase by more than an order of magnitude between the second instar before the terminal molt and the tenth day of adult life. During the same developmental period isometric twitch duration (onset to 50% relaxation, 25 degrees C) varies little, while muscle mitochondrial content increased by a factor of ten as measured by stereological analysis of electron micrographs and citrate synthase activity (mumoles citrate . min-1 . gm protein-1, 25 degrees C). The wing muscles of adults have abundant sarcoplasmic reticulum (SR), narrow myofibrils, and a high volume density of mitochondria. At two molts from adulthood muscles that will later be used in flight behavior also have narrow myofibrils and abundant SR, but unlike muscles at later stages, nymphal muscles have a low volume density of mitochondria. At the terminal molt muscles have at least as much SR as is seen in muscles at the tenth day of adult life, and the myofibrils are also more narrow at the earlier stage. Since there is significant variation in muscle structure and little change in twitch duration during late development, the efficacy of the SR in releasing and resequestering CA2+ is seemingly lower in muscles at the terminal molt, a time of rapid muscle growth.     

Glycerol kinase activities in muscles from vertebrates and invertebrates

1. Glycerol kinase (EC 2.7.1.30) activity was measured in crude extracts of skeletal muscles by a radiochemical method. The properties of the enzyme from a number of different muscles are very similar to those of the enzyme from rat liver. Glycerol kinase from locust flight muscle was inhibited competitively by l-3-glycerophosphate with a K(i) of 4.0x10(-4)m. 2. The activity of glycerol kinase was measured in a variety of muscles from vertebrates and invertebrates in an attempt to explain the large variation in the activity of this enzyme in different muscles. 3. In vertebrates glycerol kinase activities were generally higher in red muscle than in white muscle; the highest activities (approx. 0.2mumole/min./g. fresh wt.) were found in the red breast muscle of some birds (e.g. pigeon, duck, blue tit) whereas the activities in the white breast muscle of the pheasant and domestic fowl were very low (approx. 0.02mumole/min./g.). 4. On the basis of glycerol kinase activities, muscles from insects can be classified into three groups: muscles that have a low enzyme activity, i.e. <0.3mumole/min./g. (leg muscles of all insects studied and the flight muscles of cockroaches and the tsetse fly); muscles that have an intermediate enzyme activity, i.e. 0.3-1.5mumoles/min./g. (e.g. locusts, cockchafers, moths, water-bugs); and muscles that have a high enzyme activity, i.e. >1.5mumoles/min./g. (e.g. bees, wasps, some blowflies). 5. The function of glycerol kinase in vertebrate and insect muscles that possess a low or intermediate activity is considered to be the removal of glycerol that is produced from lipolysis of triglyceride or diglyceride by the muscle. Therefore in these muscles the activity of glycerol kinase is related to the metabolism of fat, which is used to support sustained muscular activity. A possible regulatory role of glycerol kinase in the initiation of triglyceride or diglyceride lipolysis is discussed. 6. The function of glycerol kinase in the insect muscles that possess a high activity of the enzyme is considered to be related to the high rates of glycolysis that these muscles can perform. The oxidation of extramitochondrial NADH, and therefore the maintenance of glycolysis, is dependent on the functioning of the glycerophosphate cycle; if at any stage of flight (e.g. at the start) the rate of mitochondrial oxidation of l-3-glycerophosphate was less than the activity of the extramitochondrial glycerophosphate dehydrogenase, this compound would accumulate, inhibit the latter enzyme and inhibit glycolysis. It is suggested that such excessive accumulation of l-3-glycerophosphate is prevented by hydrolysis of this compound to glycerol; the latter would have to be removed from the muscle when the accumulation of l-3-glycerophosphate had stopped, and this would explain the presence of glycerol kinase in these muscles and its inhibition by l-3-glycerophosphate.     

中华绒螯蟹蜕壳过程中肌肉的组织学、超微结构及主要蛋白质含量的变化

为探讨中华绒螯蟹(Eriocheir sinensis)蜕壳前后肌肉组织的形态特征变化, 采用石蜡切片、电镜及生物化学方法, 研究了中华绒螯蟹蜕皮过程中步行足和腹部肌肉的组织学、超微结构及主要蛋白质含量的变化。结果显示: 相对于蜕皮间期, 步行足在蜕皮前后组织学形态特征无明显变化; 超微结构在蜕皮前无明显变化, 蜕皮后可见肌原纤维纵裂及肌小节横裂现象, 表明蜕皮后外骨骼硬化的过程伴随着肌肉的生长。相对于蜕皮间期, 腹部肌肉在蜕皮前后组织学特征变化明显: 蜕皮前肌束间隙增大, 蜕皮后肌束内肌纤维间隙增大。电子显微镜观察显示, 蜕皮前肌原纤维在内部降解, 出现空洞, 肌原纤维边缘降解, 导致肌原纤维间隙增大; 蜕皮后肌原纤维重新组装、重建, 恢复到间期正常形态。生物化学研究发现, 蜕皮前后步行足和腹部肌肉中肌原纤维蛋白和可溶性蛋白含量的变化同其结构特征的变化相一致。以上研究结果表明, 中华绒螯蟹肌肉组织的结构特征同蜕皮周期密切相关。     

Oogenesis-flight syndrome in crickets: age-dependent egg production, flight performance, and biochemical composition of the flight muscles in adult female Gryllus bimaculatus

Age-dependent changes in flight performance, biochemical composition of flight muscles, and fresh mass of the flight muscles and ovaries were analysed in adult female two-spotted crickets, Gryllus bimaculatus. After the final moult the flight muscle mass increased significantly to a maximum at days 2 and 3. On day 2 the highest flight activity was also observed. Between days 2 and 3 the ovary weight started to rapidly increase due to vitellogenic egg growth, which continued at a high rate until day 10. With the onset of ovarial growth, flight performance decreased and the flight muscles started to histolyse. A high correlation between flight muscle mass and the content of protein, lipid, glycogen, and free carbohydrate in the flight muscle indicated that energy-rich substrates from the degrading flight muscles were used to fuel oogenesis, although flight muscle histolysis can provide only a small fraction of the substrates needed for egg production. In general, there was a clear trade-off between egg production and flight ability. Surprisingly, however, some females possessed well-developed ovaries but displayed no signs of flight muscle histolysis. This observation was corroborated by flight experiments which revealed that, although most flying females had small ovaries, some of them carried an appreciable amount of mature eggs, and thus, somehow managed to evade the oogenesis-flight syndrome.