On the Ciliary Mechanisms and Interrelationships of Lamellibranches

1943 ◽  
Vol s2-84 (334) ◽  
pp. 187-256
Author(s):  
DAPHNE ATKINS
Keyword(s):  
The Other ◽  
Muscle Fibres ◽  
Frontal Surface ◽  
Posterior Portion ◽  
Food Groove ◽  
Longitudinal Muscles ◽  
Free Edges

In the gill axes of the Microciliobranchia the most important muscles are longitudinal and transverse. The longitudinal muscles are: (a) those extending from one extremity of the gill axis to the other, inserted on the shell anteriorly, and (b) those in the free posterior portion of the axis, inserted on the shell where the axis becomes attached. Together these muscles act as branchial retractors. Withdrawal of the gills prevents (a) their being caught and crushed by the edges of the shell when the valves are suddenly closed, and (b) excessive fouling with sudden intake of muddy or noxious water. The transverse muscles below the chitinous structure arching the axial food groove serve to draw the demibranchs of a gill together, while those above the arch serve to separate them. Such swaying movements of the demibranchs serve to rid them of unwanted material. In the demibranchs are:--(1) muscles of the free edges. These include (a) muscles responsible for movements of the walls of the food grooves, and (b) longitudinal muscles, which effect antero-posterior contraction and assist the longitudinal muscles of the axis in retraction of the gills; (2) vertical muscles of the demibranchs, found chiefly in the Pteriacea, and responsible for dorso-ventral contraction of the demibranchs; (3) muscles of the interlamellar junctions serving to draw the two lamellae of a demibranch together, expelling the contained water; (4) horizontal muscles of the lamellae, present in forms with plicate and heterorhabdic gills and effecting by their action changes in shape of the frontal surface of the principal filaments and movements of the plicae important in connexion with the ciliary sorting mechanism; their contraction increases the folding of the lamellae and decreases the length of the gill: and (5) fine muscle-fibres forming the intrafilamentar ‘septum’.

III —The Cruciform Muscle of Lamellibranchs

1935 ◽  
Vol 54 ◽  
pp. 17-30 ◽  
Author(s):  
Alastair Graham
Keyword(s):  
Adductor Muscle ◽  
Point Of View ◽  
The Other ◽  
Similar Process ◽  
Muscle Fibres ◽  
Directed Attention ◽  
Posterior Portion ◽  
Adductor Muscles ◽  
Mantle Edge

In 1900 von Ihering directed attention to the presence in certain Lamellibranchs of a special muscle lying in the posterior portion of the ventral mantle edge, close to the inner end of the inhalent siphon. This muscle consisted of two strands, each running diagonally from an origin on one valve to be inserted on the other, and crossing one another in the mid-ventral line so as to form a muscular apparatus with the appearance of a St Andrew's cross. He regarded this cruciform muscle as a specially differentiated group of fibres belonging to the pallial edge, acting as an accessory adductor muscle, a point of view in which he has been followed by all subsequent observers. To this von Ihering added the speculation that it had been by some similar process of specialisation of marginal pallial muscle fibres that the two other true adductor muscles of Lamellibranchs had originated.

scholarly journals The interaction between two trains of impulses converging on the same motoneurone

1929 ◽  
Vol 105 (738) ◽  
pp. 363-371 ◽  
Keyword(s):  
Mechanical Effect ◽  
The Other ◽  
Muscle Fibres ◽  
Flexor Muscle ◽  
Afferent Pathways ◽  
Afferent Nerves ◽  
Maximal Stimulation ◽  
The Common ◽  
The Relationship ◽  
Stimulation Of

It was shown in an earlier paper (7) that if maximal stimulation of either of two different afferent nerves can reflexly excite fractions of a given flexor muscle, there are generally, within the aggregate of neurones which innervate that muscle, motoneurones which can be caused to discharge by either afferent (i. e., motoneurones common to both fractions). The relationship which two such afferents bear to a common motoneurone was shown, by the isometric method of recording contraction, to be such that the activation of one afferent, at a speed sufficient to cause a maximal motor tetanus when trans­mitted to the muscle fibres, caused exclusion of any added mechanical effect when the other afferent was excited concurrently. This default in mechanical effect was called “occlusion.” Occlusion may conceivably be due to total exclusion of the effect of one afferent pathway on the common motoneurone by the activity of the other; but facilitation of the effect of one path by the activation of the other when the stimuli were minimal suggests that, in some circumstances at least, the effect of each could augment and summate with th at of the other at the place of convergence of two afferent pathways. Further investigation, using the action currents of the muscle as indication of the nerve impulses discharged by the motoneurone units, has now given some information regarding the effect of impulses arriving at the locus of convergence by one afferent path when the unit common to both is already discharging in response to impulses arriving by the other afferent path. Our method has been to excite both afferent nerves in overlapping sequence by series of break shocks at a rapid rate and to examine the action currents of the resulting reflex for evidence of the appearance of the rhythm of the second series in the discharge caused by the first when the two series are both reaching the motoneurone.

Some Mitochondrial Changes in Denervated Muscle

1968 ◽  
Vol 3 (1) ◽  
pp. 49-54
Author(s):  
R. MILEDI ◽  
c. R. SLATER
Keyword(s):  
Microscopic Study ◽  
Electron Microscopic Study ◽  
The Other ◽  
Muscle Fibres ◽  
Rat Diaphragm ◽  
Denervated Muscle ◽  
Electron Microscopic ◽  
Normal Appearance ◽  
Characteristic Picture

An electron-microscopic study was made of the mitochondria in normal and denervated rat diaphragm muscles. Two types of structurally different muscle fibres were found: one type had a well-defined M-line, while the other did not. The mitochondria in normally innervated muscle are regularly arranged at both sides of the Z-line. The mitochondria are very long and branched, and surround the myofibrils at the level of the Z-line. In transverse sections of the muscle fibres the worm-like mitochondria give a very characteristic picture. After denervation the mitochondria are smaller and less regularly arranged. In transverse sections of the muscle fibres the mitochondria have small circular profiles. This contrasts sharply with the normal appearance and makes it possible to distinguish normal from denervated fibres. The mitochondrial changes can be detected less than 24 h after denervation.

Memoirs: On the Reproductive Processes of the Earthworm, Lumbricus Terrestris

1925 ◽  
Vol s2-69 (274) ◽  
pp. 245-290
Author(s):  
A. J. GROVE
Keyword(s):  
Body Wall ◽  
Seminal Fluid ◽  
Lumbricus Terrestris ◽  
The Body ◽  
The Other ◽  
Reproductive Processes ◽  
Longitudinal Muscles ◽  
Earthworm Lumbricus

During the sexual congress of L.terrestris, the co-operating worms become attached to one another in a head-to-tail position in such a way that segments 9-11 of one are opposed to the clitellum of the other, and vice versa. At these points the attachment between the worms is an intimate one, assisted by the secretion of the glands associated with the diverticula of the setal pores found in certain segments, and is reinforced by the mutual penetration of the setae into the opposed body-surfaces. There is also a slighter attachment between segment 26 of one and 15 of the other. Each worm is enclosed in a slime-tube composed of mucus secreted from the epidermis. The exchange of seminal fluid is a mutual one. The fluid issues from the apertures of the vasa deferentia in segment 15, and is conducted beneath the slime-tube in pit-like depressions in the seminal grooves, which extend from segment 15 to the clitellum on each side of the body, to the clitellum, where it accumulates in the space between the lateral surfaces of segments 9-11 of one worm and the clitellum of the other. Eventually it becomes aggregated into masses in the groove between segments 9 and 10, and 10 and 11, and passes thence into the spermathecae. The seminal groove and its pit-like depressions are brought into existence by special muscles lying in the lateral blocks of longitudinal muscles of the body-wall.

The Dogfish Neuromuscular Junction: Dual Innervation of Vertebrate Striated Muscle Fibres?

1972 ◽  
Vol 10 (3) ◽  
pp. 657-665
Author(s):  
Q. BONE
Keyword(s):  
Neuromuscular Junction ◽  
Nerve Terminal ◽  
Striated Muscle ◽  
Dense Core ◽  
The Other ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Nerve Fibres ◽  
Different Types ◽  
Motor End Plate

In the myotomal muscles of the dogfish, Scyliorhinu canicula, there are 2 major types of fibre. The red fibres at the periphery of the myotome receive a distributed en grappe pattern of innervation. There are subjunctional folds at these endings, and the nerve terminals contain vesicles around 50 nm in diameter. In contrast to this, the white twitch fibres of the myotome are innervated focally, by 2 nerve fibres passing to the same motor end-plate. These 2 fibres contain vesicles of different types. One type of nerve terminal contains vesicles around 50 nm in diameter; these terminals resemble those upon the red fibres. The other contains vesicles up to 100 nm in diameter, frequently possessing a dense core. It is suggested that the white twitch fibres of dogfish are innervated by 2 separate axons, possibly containing different transmitter substances.

The Action of the Eyecup Muscles of the Crab, Carcinus, During Optokinetic Movements

1968 ◽  
Vol 49 (2) ◽  
pp. 223-250
Author(s):  
M. BURROWS ◽  
G. A. HORRIDGE
Keyword(s):  
Large Amplitude ◽  
Optokinetic Nystagmus ◽  
Wide Spectrum ◽  
Muscle Tension ◽  
The Other ◽  
Fibre Types ◽  
Muscle Fibres ◽  
Exact Form ◽  
Slow Movement ◽  
The One

1. The actions of the nine eyecup muscles of the crab during horizontal optokinetic movements are described. 2. Each muscle includes a wide spectrum of fibre types, ranging from phasic, with sarcomere lengths of 3-4 µm., through intermediate, to tonic fibres with sarcomeres of 10-12 µm. Each muscle receives at least one slow and one fast motoneuron, but no inhibitory supply. The slow axons predominantly innervate the tonic muscle fibres while the fast axons innervate the phasic ones. 3. Slow movement and the position of the eyecup in space are controlled by the frequency of slow motoneuron discharges. All muscles collaborate at every position. The phasic system is recruited during rapid eyecup movements of large amplitude. 4. In optokinetic nystagmus the exact form of the impulse sequences are described for each muscle. They are the consequence of a visually driven central programme which takes no account of the movement which it generates. Movements in opposite directions involve different central programmes; the one is not merely the reverse of the other. There is no effective proprioceptive feedback from the eyecup joint or from muscle tension receptors.

scholarly journals Flying High—Muscle-Specific Underreplication in Drosophila

Genes ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 246 ◽  
Author(s):  
J. Spencer Johnston ◽  
Mary E. Zapalac ◽  
Carl E. Hjelmen
Keyword(s):  
Flow Cytometry ◽  
Dna Synthesis ◽  
Salivary Glands ◽  
Genome Size ◽  
Flight Muscle ◽  
S Phase ◽  
The Other ◽  
Tissue Type ◽  
Flight Muscles ◽  
Longitudinal Muscles

Drosophila underreplicate the DNA of thoracic nuclei, stalling during S phase at a point that is proportional to the total genome size in each species. In polytene tissues, such as the Drosophila salivary glands, all of the nuclei initiate multiple rounds of DNA synthesis and underreplicate. Yet, only half of the nuclei isolated from the thorax stall; the other half do not initiate S phase. Our question was, why half? To address this question, we use flow cytometry to compare underreplication phenotypes between thoracic tissues. When individual thoracic tissues are dissected and the proportion of stalled DNA synthesis is scored in each tissue type, we find that underreplication occurs in the indirect flight muscle, with the majority of underreplicated nuclei in the dorsal longitudinal muscles (DLM). Half of the DNA in the DLM nuclei stall at S phase between the unreplicated G0 and fully replicated G1. The dorsal ventral flight muscle provides the other source of underreplication, and yet, there, the replication stall point is earlier (less DNA replicated), and the endocycle is initiated. The differences in underreplication and ploidy in the indirect flight muscles provide a new tool to study heterochromatin, underreplication and endocycle control.

Further studies on the sporocyst capable of producing miracidia

1975 ◽  
Vol 49 (3) ◽  
pp. 167-171 ◽  
Author(s):  
A. Mohandas
Keyword(s):  
The Other ◽  
Muscle Fibres ◽  
Snail Species

AbstractSporocysts capable of producing active miracidia were recovered from the upper branchial chamber of the snail species, Melania tuberculata and M.scabra. The non-ocellate miracidium was characterised by the presence of 22 epidermal plates in four tiers, an apical gland with four nuclei and two penetration glands. Sporocysts were of two types, one producing active miracidia and the other in which daughter sporocysts and miracidia were found. These sporocysts were characterised by the presence of bunches of circular muscles at intervals and also by the presence of a network of muscle fibres at the anterior and posterior one fifth regions. Development of the miracidia took place in compartments. Histochcmical tests were carried out as regards glycogen, protein, lipids and phosphomonoesterases.

scholarly journals Note on the Regeneration of the Gill of Mytilus edulis

1931 ◽  
Vol 17 (2) ◽  
pp. 551-566 ◽  
Author(s):  
D. Atkins
Keyword(s):  
Food Supply ◽  
General Circulation ◽  
Sea Water ◽  
The Other ◽  
Experimental Conditions ◽  
Cut Edge ◽  
Retarding Effect ◽  
Gill Filaments ◽  
Food Groove ◽  
Optimum Salinity

Experiments have shown that the gill of Mytilus is capable of regeneration, and that this may occur in less than eight months. It may be confined to the formation of a food grove at the cut edge of the gill, without appreciable regeneration in length of the gill filaments. Regeneration of a food groove appears always to occur at the cut edge, if the ends of the descending and ascending filaments are able to touch and so to fuse. On the other hand, regeneration of gill filaments does not seem to occur invariably, and when it does the rate is slow, at least under experimental conditions and in mussels of a length of about 7·0 to 8·0 cm., such as were used for the experiments: it is possible that regeneration would occur more surely and rapidly in young mussels, but owing to the thinness of the shell they would be more difficult to wedge open without fracturing. Coulthard (6, p. 136), however, says that “The rate of growth is independent of size in the mussel, being apparently influenced only by the environment.” Perhaps the lack of an abundant food supply under the conditions of the experiments should be taken into consideration, though it is well known that in general the amount of food available to an animal has little influence on regeneration (9, p. 27). The salinity of the water in general circulation is about 36–37°/oo, that is, higher than normal sea-water, which is about 35°/oo, and would be considerably higher than the optimum salinity for growth (see Flattely and Walton, 7, p. 81). This may also possibly have a retarding effect on the initiation of regeneration and the rate.

scholarly journals Studies on the Comparative Physiology of Digestion

1923 ◽  
Vol 1 (1) ◽  
pp. 15-64
Author(s):  
C. M. YONGE
Keyword(s):  
Muscle Fibres ◽  
Visceral Mass ◽  
Amylolytic Enzyme ◽  
Excretory Function ◽  
Organic Debris ◽  
Ciliary Action ◽  
Homologous Structure ◽  
Food Groove ◽  
Micro Organisms ◽  
Food Value

The observations recorded in this paper on the feeding, the alimentary organs, and the digestive processes in Mya arenaria, may be epitomised as follows:-- 1. The food consists of organic debris, sand particles, and micro-organisms suspended in food currents, which are created by the ciliary action of the gills, and conveyed to the mouth by ciliary currents on the surface of the gills and labial palps. 2. Particles are carried towards the ventral margin of the demibranchs, where they are caught in the currents created by the large cilia present in the region of the marginal food groove, and carried towards the mouth. A third anterior current, also created by large cilia, runs along the gill axis. 3. The direction of the ciliary currents on the labial palps has been described in detail, and the view expressed that the ciliary mechanism present on the inner face of the palps is devoted entirely to the separation of the food into large and small particles, the former being despatched to the tip of the palp, and the latter carried forward to the mouth. 4. Coarser particles which do not reach the gills, and other particles rejected by the gills and palps, are carried away by ciliary currents present on the visceral mass and mantle, and are finally expelled from the mantle chamber. 5. The anatomy and histology of the alimentary canal and the hepatopancreas have been described. 6. The presence of muscle fibres in the wall of the gut is practically restricted to the œsophagus and rectum, but the entire alimentary tract, with the exception of the area of the gastric shield, is ciliated and abundantly provided with mucussecreting glands. 7. The presence of ciliary currents in all parts of the gut has been demonstrated. 8. The ciliary currents present in the stomach have been described, and the definite separation of the food into larger and smaller particles, particularly by the mechanism of the grooved area, has been shown. The larger particles are carried straight into the intestine and the smaller particles to the base of the gastric shield, where they are caught in the substance of the tip of the style. 9. The universal presence of phagocytes or wandering cells throughout the gut has been noted, and their special activity in the grooved area of the stomach described. The balance of evidence has been shown to be in favour of the view that they are nutritive in function, although they may also have an excretory function, as they have been shown to be capable of ingesting matter of absolutely no food value. 10. The histology of the style-sac, the origin of the style, and the ciliary currents present in the sac have been described. 11. The mature style has been described and evidence brought forward to prove that it is an albuminoid mass saturated with an amylolytic enzyme, which is revolved, and, at the same time, pushed forward into the stomach by the action of the various cilia present on the epithelium of the style-sac. The tip bears against the gastric shield and is gradually worn down against this surface and through the action of the hepatopancreatic secretion. 12. The permanence of the style in Mya has been shown to be due to its protection from the corroding effects of the protease present in the hepatopancreatic secretion owing to the possession of a separate style-cæcum. 13. The importance of the style as a factor in the evolution of the higher Lamellibranchs, the presence of an homologous structure in certain of the Gastropods, and the question of its taxonomic importance have been touched upon. 14. The periodicity of digestion, as contrasted with the mechanical regularity of feeding, has been discussed. 15. The absence of digestive enzymes in the intestine, together with the evidence of previous workers, has been advanced in favour of the assertion that digestion takes place in the stomach only, and absorption in the stomach, mid-gut, and rectum. 16. The hepatopancreatic secretion has been shown to possess amylolytic, proteolytic, and lipolytic enzymes, and the action of these has been examined. 17. The style enzyme has been examined and found to reduce starch and glycogen but not sucrose. The optimum medium has been shown to be neutral, the optimum temperature to lie near 32°C, and the temperature of destruction at 51°C. Experiments in which the concentration of the enzyme and substrate were varied gave results which prove that the style enzyme has the typical properties of such a substance. 18. The presence of reserve supplies of glycogen and fat has been shown.

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