Motor supply of the dorsal longitudinal muscles,I: homonomy and ontogeny of the motoneurones in locusts (Insecta,Caelifera)

The neural supply of the dorsal lingitudinal muscles in successive segments from the prothorax to the pregenital abdomen of adult and larval instar locusts (Locusta migratoria and Schistocerca gregaria) has been studied. Stainings have also been carried out for embryos. The whole complement consists of three muscles, of which one or both of the smaller ones degenerate in the pterothoracic segments during early imaginal life. Based on morphological criteria, several motoneurone types can be distinguished. The neural set is almost identical for all segments, independent of the general organization of each segment. At about 65% of embryogenesis, all neurone types can be identified with respect to soma position and basic features of the central branching pattern. By the end of embryogenesis, a dendritic pattern is established which resembles the adult pattern in all major aspects. The reiteration of homonomous elements suggests that they form part of the basic segmental neural Bauplan generated early in embryogenesis. This study of muscles and motoneurones forming identifiable, reiterated neuromuscular units can serve as a segmental matrix for a comparative study comprising other phylogenetic groups of the Tracheata.Abbreviations DLM dorsal longitudinal muscle - DUM dorsal unpaired median - M muscle (number) - MN motoneurone - N nerve (number)     

Motor innervation of the supercontracting longitudinal ventro-lateral muscles of the blowfly larva

The gross motor innervation of the abdominal longitudinal ventro-lateral muscles of the larva of Calliphora erythrocephala is described. Two of these muscles, 6A and 7A, are innervated by the same two multiterminally-ending axons, and thus comprise a single motor unit. No difference is found between the axon diameters in the main nerve trunks, but there is a difference where the axons run over the muscle surface. Only the dorsal, inner, surface of the muscle is innervated. Electro-physiological results show two sizes of EPSP: the large fast EPSP presumably corresponds to the thicker axon and the small slow one to the thinner axon. Preliminary work indicates that it is not possible to distinguish between the two axons with electron microscopy; the presynaptic regions possess both ‘classical’ synaptic and ‘neurosecretory’ type vesicles, and have no glial cell covering.     

Auditory input to motor neurons of the dorsal longitudinal flight muscles in a noctuid moth (Barathra brassicae L.)

Summary Motor neurons innervating the dorsal longitudinal muscles of a noctuid moth receive synaptic input activated by auditory stimuli. Each ear of a noctuid moth contains two auditory neurons that are sensitive to ultrasound (Fig. 1). The ears function as bat detectors. Five pairs of large motor neurons and three pairs of small motor neurons found in the pterothoracic ganglia innervate the dorsal longitudinal (depressor) muscles of the mesothorax (Figs. 2 to 5). In non-flying preparations the motor neurons receive no oscillatory synaptic input. Synaptic input to a cell resulting from ultrasonic stimulation is consistent and can be either depolarizing or hyperpolarizing (Figs. 6 to 9). Quiescent neurons only rarely fire a spike in response to auditory inputs. Motor neurons in flying preparations receive oscillatory synaptic drive from the flight pattern generator and usually fire a spike for each wingbeat cycle (Figs. 10 to 12). Ultrasonic stimulation can provide augmented synaptic drive causing a neuron to fire two spikes per wingbeat cycle thus increasing flight vigor (Fig. 11). The same stimulus presented on another occasion can also inhibit spiking in the same motor neuron, but the rhythmic drive remains (Fig. 12). Thus, when the flight oscillator is running auditory stimuli can modulate neuronal responses in different ways depending on some unknown state of the nervous system. Sound intensity is the only stimulus parameter essential for activating the auditory pathway to these motor neurons. The intensity must be sufficient to excite two or three auditory neurons. The significance of these responses in relation to avoidance behavior to bats is discussed.     

Extraocular muscles in the lamprey, Lampetra fluviatils L. II. Motor end plates

Motor innervation and particularly the structure of motor end plates (MEPs) was studied in the extraocular muscles of the lamprey, Lampetra fluviatilis L., by light and electron microscopy. Each muscle is supplied with numerous thin motor nerve fibres. Motor end plates are located at their ends or along their course. Two motor end plate types were distinguished: en grappe-like plates with a low acetylcholinesterase (AChE) activity were observed on thin muscle fibres, whilst en plaque-like plates with a high AChE activity were found on thick mitochondria-rich and thick multifibrillar muscle fibres. The postsynaptic membrane of the former MEP type does not show the presence of infoldings, MEPs located on thick mitochondria-rich fibres show occasional infoldings, whereas the postsynaptic membrane of MEPs present on thick multifibrillar fibres reveals numerous infoldings. Motor end plates present in the extraocular muscles in the lamprey possess features typical for higher vertebrates and elasmobranch fishes, as well as for Tunicata.     

Ultrastructure of the muscles of the dorsal diaphragm in Locusta migratoria

Summary The alary muscles of Locusta migratoria adults make up the major tissue of the dorsal diaphragm which separates pericardial and perivisceral sinuses in the abdomen. The alary muscles are striated with a sarcomere at rest measuring about 9 m. The Z-line has a staggered-beaded arrangement with A-bands and I-bands readily discernable. Thick myofilaments are surrounded by 10 or more thin filaments. The sarcoplasm has few mitochondria near the area of the Z-line, dyads are present and sarcoplasmic reticulum is poorly developed. Axons which innervate the alary muscle are either contained within invaginated folds of the sarcolemma of the muscle cells or the muscle cells send finger-like projections to envelop the axons. The synaptic terminals contain synaptic vesicles between 40 and 45 nm in diameter and a few electron-dense granules near or less than 170 nm in diameter. Away from synaptic terminals the axon profiles show few or no granules. The axons are accompanied everywhere by well-developed glial cells. This then is not typical neurosecretomotor innervation, however, the presence of electron-dense granules suggests the possibility of peptidergic neurotransmission.     

On relations between sets: II

The notion of relations between sets, defined in a previous publication (Bull. Math. Biophysics,23, 233–235, 1961) is generalized and some biological examples are given. A generalization ton-ary relation is suggested.     

Bipedicle strap flaps in reconstruction of longitudinal dorsal skin defects of the digits

Dorsal skin defects in which the loss of integument is longitudinal in shape are not uncommon after injury by rotating machinery and by glass shearing along the length of the digit. This shape of defect is difficult to reconstruct with commonly used flaps but lends itself to reconstruction by the use of longitudinal bipedicle strap flaps moved across the dorsum of the finger from lateral to medial. A variant of this traditional technique was used in the reconstruction of 28 dorsal digital defects. The incidence of these defects and the need for this reconstructive technique were analyzed by a review of 1077 patients with dorsal digital injuries treated in a 6-year period between 1989 and 1995. Approximately 20 percent of all dorsal digital injuries requiring flap reconstruction were suitable for reconstruction with bipedicle strap flaps.     

Organismic sets: II. Some general considerations

The theory of organismic sets, developed in previous papers (Bull. Math. Biophysics,29, 139–152; 389–393; 643–647) is further generalized. To conform better with some biological and sociological facts the basic definitions are made more general. The conclusion is reached that every organismic setS _o is in general the union of three disjoined subsetsS _o1 ,S _o2 andS _o3 . Of these the subsetS _o1 , called the “core” is equivalent to an organismic set defined in previous publications. Its functioning is essential for the functioning ofS _o . The subsetsS _o2 andS _o3 , taken alone, are not organismic sets. The first of them is responsible for such biological or sociological functions which are not necessary for the “immediate” survival ofS _o but which are important for adaptation to changing environment and are therefore essential for a “long range survival.” The second one,S _o3 , is responsible for biological or social functions which are irrelevant for the survival ofS _o . Biological and sociological examples ofS _o2 andS _o3 are given. In addition to the fundamental theorem established in the first of the above mentioned papers, three new conclusions are derived. One is that in organismic sets of order higher than zero not all elements are specialized. The second is that every organismic set of order higher than zero is mortal. The third is that with increasing specialization the intensities of some activities in some elements ofS _o are reduced. Again the biological and sociological examples are given. At the end some very general speculations are made on the possible relation between biology and physics and on the possibility of “relationalizing” physics.     

Function of the dorsal fin in bluegill sunfish: Motor patterns during four distinct locomotor behaviors

The median fins of fishes are key features of locomotor morphology which function as complex control surfaces during a variety of behaviors. However, very few studies have experimentally assessed median fin function, as most workers focus on axial structures. In particular, the dorsal fin of many teleost fishes possesses both spiny anterior and soft posterior portions which may function separately during locomotion. We analyzed the function of the soft region of the dorsal fin and of the dorsal inclinator (Di) muscles which are the primary muscles responsible for lateral flexion. We used electromyography to measure in vivo Di activity, as well as activity of the red myomeric muscles located at a similar longitudinal position. We quantified motor patterns during four locomotor behaviors: braking and three propulsive behaviors (steady swimming, kick and glide swimming, and C-starts). During the three propulsive swimming behaviors, the timing of Di activity was more similar to that of ipsilateral red myomeric muscle rather than to contralateral myomeric activity, whereas during braking the timing of activity of the Di muscles was similar to that of the contralateral myomeric musculature. During the three propulsive behaviors, when the Di muscles had activity, it was consistent with the function of stiffening the soft dorsal fin to oppose its tendency to bend as a result of the body being swept laterally through the water. In contrast, activity of the Di muscles during braking was consistent with the function of actively flexing the soft dorsal fin towards the side of the fish that had Di activity. Activity of the Di muscles during steady speed swimming was generally sufficient to resist lateral bending of the soft dorsal fin, whereas during high speed kick and glide swimming and C-starts, Di activity was not sufficient to resist the bending caused by resistive forces imposed by the water. Cumulative data from all four behaviors suggest that the Di muscles can be activated independently relative to the myomeric musculature rather than having a single phase relationship with the myomeric muscle common to all of the observed behaviors. © 1996 Wiley-Liss, Inc.     

The arterial blood supply of the skin flap of the dorsal foot

The dorsal foot skin supplied by the arteria dorsalis pedis the dorsal venous arch, the peroneal sensory nerves and the musculus extensor digitorum brevis is a very good myocutaneous flap. The material on which the study was carried out, consisted of 20 feet from standard cadavers, injected with a mixture of terebenthene and minium through the arteria tibialis anterior. The m. extensor digitorum brevis is 6.1 cm long, 1.7 cm wide, 3.9 mm thick. It is mainly supplied by the a. dorsalis pedis and its branches: the a. tarsea dorsalis (constant) and the a. metatarsea dorsalis (12 of 20 specimens). The average diameter of the a. dorsalis pedis at the upper limit of the m. extensor retinaculum was 2.14 mm and this was chosen as the most proximal limit of the dorsalis pedis flap. The a. tarsea dorsalis was present in all the specimens, with a diameter of 0.95 mm at its origin and a length of 35 mm. On average, this artery divided into four branches to the m. dorsalis pedis. The a. metatarsea dorsalis was present in 12 of 20 specimens, with an average diameter of 0.53 mm and a length of 22 mm. On average, this artery divided into three branches to the m. dorsalis pedis. We drew three lines in the proximal, middle and distal third of each flap design and calculated the sum of arterial branch sections with our lines. We think this provides a reasonable indication of the comparative richness of the cutaneous blood supply in the flap. The mean number of cutaneous branches was 10 in the proximal third, 6.7 in the middle third (13 if branches supplying the m. extensor pedis brevis are included) and 5 in the distal third. The myocutaneous dorsalis pedis arterialized flap can be safely used as an island flap to cover the ankle or heel and as a free flap for palm defects.