A Comparative Histological Study of the Tube-feet of two Regular Echinoids

The histology of the suckered and peristomial tube-feet of the two regular echinoids Cidaris cidaris (Cidaroida) and Echinus esculentus (Diadematoida) is described; of these orders the Cidaroida is the more primitive. The suckered tube-feet of both urchins have a connective-tissue sheath the fibres of which branch extensively before inserting at the disk, and in which are embedded numerous spicules, enlarged distally to form a supporting skeleton of the disk. A series of levator muscles, separate from the retractors of the stem, raise the centre of the disk during adhesion, and this activity also probably squeezes mucus from a series of glands opening at the disk surface. In Cidaris a second series of glands, goblet cells in the disk epithelium, are operated by special short muscle-fibres running between them; these cells and the muscles are absent in Echinus. In Cidaris sensory cells are apparently scattered over the entire disk surface, whereas in Echinus they appear to be mainly concentrated in a ring round the disk periphery. The peristomial tube-feet of both urchins are not suckered; the levator muscles are absent, and the disk, supported by a less complex calcareous skeleton, contains mainly sensory cells and mucous glands. The possible derivation of the diadematoid, clypeasteroid, and spatangoid tube-foot plans from that of the cidaroid is discussed. The differences in ornamentation of the regions of the test which bear the tube-feet are discussed functionally, the main conclusion being that a tube-foot whose activity is at all angles to the test requires a wider base than one whose activity is mainly perpendicular; this is shown to be the case in spatangoids also. A respiratory function for Stewart's organs in the Cidaroida is suggested.

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Studies on Locust Neuromuscular Physiology in Relation to Glutamic Acid

Journal of Experimental Biology ◽

10.1242/jeb.60.3.673 ◽

1974 ◽

Vol 60 (3) ◽

pp. 673-705 ◽

Cited By ~ 2

Author(s):

A. N. CLEMENTS ◽

TERRY E. MAY

Keyword(s):

Amino Acids ◽

Connective Tissue ◽

Glutamic Acid ◽

Diffusion Barrier ◽

Muscle Fibres ◽

Magnesium Ions ◽

Calcium And Magnesium ◽

Nerve Muscle ◽

Connective Tissue Sheath ◽

Calcium And Magnesium Ions

1. Two nerve-muscle preparations were used to investigate the physiology of the locust retractor unguis muscle in relation to L-glutamic acid. These were an ‘isolated preparation’, in which the muscle and its nerve were dissected out, and a ‘perfusedfemur preparation’, in which the muscle suffered no mechanical disturbance. 2. Exposure of the nerve--muscle preparations to glutamate caused a variety of responses, some of which were shown to be abnormal and due to the experimental conditions. 3. When locust femora were perfused with saline or haemolymph the retractor unguis muscles were much more severely affected by glutamate if the hydrostatic pressure was slightly raised. At raised pressures the perfused-femur preparations were particularly prone to give repetitive and spontaneous contractions. 4. Analysis of haemolymph from adult male locusts showed that it contained, on average, 0-2 mmol/1 L-glutamate, 45 mol/1 total non-peptide amino acids, 5-0 mmol/1 calcium, and 11-6 mmol/1 magnesium. It was calculated that approximately 50% of the calcium and 75% of the magnesium ions are bound to amino acids, and that approximately 25% of the glutamic acid is bound to divalent metal ions. 5. The isolated preparations were severely affected by glutamate at the concentration at which it occurs in haemolymph, and it was concluded that in the intact locust some mechanism must protect the neuromuscular synapses from haemolymphg lutamate. No evidence could be obtained of the sequestration of glutamate by haemocytes, or of binding of glutamate to haemolymph proteins. 6. Calcium and magnesium ions reduced the sensitivity of nerve-muscle preparations to glutamate to a greater extent than could be accounted for by the formation of amino acid-metal complexes. This suggests that the protection afforded by calcium and magnesium involves an interaction of the metal ions with the neuromuscular system itself. 7. The retractor unguis muscle was much less sensitive to glutamate when it was contained within an undissected femur than in an isolated preparation. It was concluded that the muscle is normally protected from haemolymph glutamate by a diffusion barrier which is damaged on dissection. 8. Comparison of the fine structure of retractor unguis muscles, fixed either after dissection or while still contained within the femur, showed that dissection normally caused a partial separation of muscle fibres and damage to the connective tissue sheath, with the resultant exposure of some nerve endings. The connective tissue sheath may constitute the postulated diffusion barrier. 9. The excitatory synapses of the locust retractor unguis muscle are believed to be isolated from haemolymph glutamate by a diffusion barrier, which is tentatively identified with the connective tissue sheath that binds the muscle fibres together. Calcium and magnesium ions reduce the sensitivity of nerve-muscle preparations to glutamate, and may have such a role in the living insect.

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Histological Study on the Oesophagus and Crop in Various Species of Wild Bird

Avian Biology Research ◽

10.3184/175815509x12474789336122 ◽

2009 ◽

Vol 2 (3) ◽

pp. 161-164 ◽

Cited By ~ 3

Author(s):

Ebrahim Rajabi ◽

Abolghasem Nabipour

Keyword(s):

Smooth Muscle ◽

Connective Tissue ◽

House Sparrow ◽

Histological Study ◽

Thick Layer ◽

Muscle Fibres ◽

Muscularis Mucosa ◽

Loose Connective Tissue ◽

Tunica Adventitia ◽

Thoracic Part

The histology of the oesophagus and crop was studied in six species of birds: Rock Dove, Collared Dove, Rose-ringed Parakeet, Kestrel, House Sparrow and Linnet. In species, the epithelium of oesophagus and crop was a keratinised stratified squamous. The lamina propria was a loose connective tissue containing glands. Glands were either purely mucous or seromucous (mixed). In the rock dove, rose-ringed parakeet and collared dove, there were no glands either in the cervical part of oesophagus or in the crop. There were differences in the histochemistry of glands’ secretions. The muscularis mucosa was present as a thick layer of smooth muscle fibres. The tunica submucosa was a loose connective tissue containing vessels and nerves. The tunica muscularis consisted of smooth muscle and was surrounded by the tunica adventitia at the cervical part of the oesophagus and crop, and by the tunica serosa at the thoracic part of the oesophagus.

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Cholinergic Motor Control of Sea Urchin Tube Feet: Evidence for Chemical Transmission without Synapses

Journal of Experimental Biology ◽

10.1242/jeb.88.1.281 ◽

1980 ◽

Vol 88 (1) ◽

pp. 281-292

Author(s):

E. FLOREY ◽

M. A. CAHILL

Keyword(s):

Electrical Stimulation ◽

Connective Tissue ◽

Outer Surface ◽

Muscle Fibres ◽

Nerve Terminals ◽

Tissue Layer ◽

Connective Tissue Layer ◽

Electrical Stimuli ◽

Tube Feet ◽

Chemical Transmission

Isolated tube feet of Strongylocentrotus franciscanus contract briefly when the outer epithelium is touched. Similar twitch-like contractions can be induced by electrical stimulation of the outer surface of the tube foot. These responses appear to be chemically mediated. The following evidence indicates that the transmitter substance may be acetylcholine (ACh): ACh causes muscle contraction. This effect and that of electrical stimuli is potentiated by anticholinesterase agents and is antagonized by cholinergic blocking agents. Anaesthesia with chloralhydrate or chloretone abolishes responsiveness to mechanical or electrical stimulation but not to ACh. Desensitization with carbachol prevents responses to ACh and to mechanical or electrical stimulation. There are no neuromuscular synapses and no axons can be detected which cross the connective tissue layer which separates the muscle fibres from the subepithelial nerve plexus. The latter is known to contain conspicuous amounts of ACh; nerve terminals containing clear vesicles invest the outer surface of the connective tissue layer. All evidence indicates that chemical transmission involves diffusion of ACh (released from activated nerve terminals) across this connective tissue layer which is around 5 μm thick in fully extended tube feet but may have a thickness of 20 or even 25 μm in less extended ones. Calculations based on equations describing transmitter diffusion prove the feasibility of such a mechanism. Note:

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Histological Study of Human Thyroid Gland Relative Proportion of Parenchyma and Stroma in Thyroid Glands of Bangladeshi People

Update Dental College Journal ◽

10.3329/updcj.v1i2.13981 ◽

2013 ◽

Vol 1 (2) ◽

pp. 17-20

Author(s):

Md Enayet Ullah ◽

Hasna Hena ◽

Rubina Qasim

Keyword(s):

Thyroid Gland ◽

Histological Study ◽

Relative Proportion ◽

Age Groups ◽

Human Thyroid ◽

Structural Units ◽

Thyroid Glands ◽

Group A ◽

Group B ◽

Connective Tissue Sheath

Deep cervical fascia forms a connective tissue sheath around the thyroid gland. Delicate trabeculae and septa penetrate the gland indistinctly dividing the gland into lobes and lobules which in turn composed of follicles.1,2,3 These follicles are structural units of thyroid gland which varies greatly in size and shape.4 The number of follicles varies in different age groups. The study was carried out to see the percentage of area occupied by follicles in the stained section of thyroid glands in different age groups. The collected samples were grouped as A (3.5 20yrs), B (21- 40yrs) & C (41 78yrs). Percentage of area occupied by follicles was (58.55±10.72) in group A, (63.79±12.35) in group B + (63.39±8.29) in group C.DOI: http://dx.doi.org/10.3329/updcj.v1i2.13981 Update Dent. Coll. j. 2011: 1(2): 17-20

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The Ultrastructure of the Perineurium in two Insect Species, Carausius Morosus and Periplaneta Americana

Journal of Cell Science ◽

10.1242/jcs.2.1.119 ◽

1967 ◽

Vol 2 (1) ◽

pp. 119-128

Author(s):

S. H. P. MADDRELL ◽

J. E. TREHERNE

Keyword(s):

Connective Tissue ◽

Periplaneta Americana ◽

Fluid Transport ◽

Insect Species ◽

Carausius Morosus ◽

Insect Central Nervous System ◽

Connective Tissue Sheath ◽

Extracellular Sodium ◽

Perineurial Cells ◽

Cellular Layer

The organization of the perineurium in two insect species (Carausius morosus and Periplaneta americana) has been examined with the electron microscope. In both species this cellular layer has been found to possess an extensive system of tortuous channels between the lateral cell walls. These channels are open at the outer margin adjacent to the fibrous connective-tissue sheath, but appear to be closed at the inner margin by regions of septate desmosomes and/or ‘tight’ junctions. There is an increased surface area at the inner margin of the perineurial cells produced by the presence of long inwardly directed flanges. An electron-dense coat has also been identified on the cytoplasmic side of the type II perineurial cell membranes at points of contact with the underlying extracellular system and at the outer surface adjacent to the connective-tissue sheath. This organization of the perineurium is strikingly similar to that observed in a variety of fluid-secreting epithelia and its possible function in fluid transport is discussed in relation to the available evidence on the physiology of the insect central nervous system. It is suggested, contrary to some earlier suppositions, that the perineurium may not be primarily involved in the control of the extracellular sodium level and that this regulation may be effected at a deeper level in the central nervous tissues.

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A case of Giant Perifollicular Fibroma - a Diagnostic Challenge

Serbian Journal of Dermatology and Venerology ◽

10.2478/sjdv-2020-0004 ◽

2020 ◽

Vol 12 (1) ◽

pp. 19-21

Author(s):

Raghavendra Rao ◽

Srilatha Parampalli Srinivas ◽

Varsha M. Shetty

Keyword(s):

Connective Tissue ◽

Head And Neck ◽

Neck Region ◽

Diagnostic Challenge ◽

Head And Neck Region ◽

Internal Malignancy ◽

Essential Tool ◽

Proliferative Lesion ◽

Connective Tissue Sheath

AbstractPerifollicular fibroma (PFF) is a rare proliferative lesion originating from the perifollicular connective tissue sheath. It may be congenital or acquired manifesting as skin colored to pink, asymptomatic papules of 1-5 mm in size. They are commonly distributed in the head and neck region. Multiple PFFs may be associated with internal malignancy or as a part of Birt-Hogg-Dube syndrome. Histopathology serves as an essential tool in clinching the diagnosis. Herein we report a case of giant congenital PFF.

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Non-motile sensory cilia and neuromuscular junctions in a ctenophore independent effector organ

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1965.0042 ◽

1965 ◽

Vol 162 (988) ◽

pp. 333-350 ◽

Cited By ~ 51

Keyword(s):

Neuromuscular Junctions ◽

Ciliated Cell ◽

Sensory Nerve ◽

Spatial Summation ◽

Muscle Cells ◽

Sensory Cells ◽

Muscle Fibres ◽

Water Displacement ◽

Single Finger ◽

Effector Organ

Non-motile cilia of the (9 + 2) pattern, having a specialized onion-like root structure, act as sensitive receptors of water displacement and thereby detect vibrations of small objects in the water nearby. These receptors are situated on sensory nerve cells on finger-like processes up to 1 cm long, on the surface of the ctenophore Leucothea ( = Eucharis) multicornis . In response to vibration a single finger can shoot outwards as an independent effector by an extension of its mesogloeal hydrostatic skeleton, acted on by circular and transverse muscle fibres which run mainly through the mesogloea. A copepod which may be hit is immobilized, presumably by a poisonous secretion. Retraction is brought about by longitudinal ectodermal fibres. The neuromuscular junctions have presynaptic vesicles of 30 to 50 nm diameter, a cleft of 15 to 20 nm wide, and occur at discrete points far from each other on the muscle cells, suggesting that excitation is propagated along the muscle fibres. No direct connexion has been traced between a sensory ciliated cell and a muscle fibre, but sensory cells connect with nerve net neurons and these form synapses with each other and with muscle cells. There are numerous nerve fibres in the epithelium and synapses with vesicles on one side of a cleft 12 to 15 nm wide occur between them sufficiently closely for spatial summation to be possible. The separate co-ordination of movements of extension, retraction and bending requires that certain types of sensory cells be connected specifically, if in directly, with muscle fibres of a particular directionality. This provides a primitive example of specificity of connexions which must imply two overlapping nerve nets.

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Subcutaneous reaction to silicone in ventriculoperitoneal shunts

Journal of Neurosurgery ◽

10.3171/jns.1974.41.3.0367 ◽

1974 ◽

Vol 41 (3) ◽

pp. 367-371 ◽

Cited By ~ 26

Author(s):

Oscar Sugar ◽

Orville T. Bailey

Keyword(s):

Cerebrospinal Fluid ◽

Connective Tissue ◽

Fibrous Connective Tissue ◽

Subcutaneous Implantation ◽

Content Type ◽

Ventriculoperitoneal Shunts ◽

Silicone Tubing ◽

Connective Tissue Sheath ◽

Fine Print

✓Silicone tubing (Silastic) used for ventriculoperitoneal shunts induces a fibrous connective tissue sheath around the tubing in children and adults. Two children examined 8 and 3 years after subcutaneous implantation showed a complete tube of dense fibrous connective tissue around the silicone tubing. The reaction was entirely quiescent. These tubes of connective tissue were apparently capable of conveying cerebrospinal fluid for some months after the silicone tubing was disconnected from the pump or pulled out of the abdomen.

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The Connective Tissue Sheath of the Locust Nervous System: A Histochemical Study

Journal of Cell Science ◽

10.1242/jcs.s3-100.51.401 ◽

1959 ◽

Vol s3-100 (51) ◽

pp. 401-412

Author(s):

DOREEN E. ASHHURST

Keyword(s):

Nervous System ◽

Connective Tissue ◽

Collagen Type ◽

Histochemical Study ◽

Locusta Migratoria ◽

System A ◽

Large Numbers ◽

Connective Tissue Sheath ◽

Cellular Layer ◽

Sheath Cells

The connective tissue sheath surrounding the nervous system of Locusta migratoria has been studied histochemically. It consists of an outer non-cellular layer, the neural lamella, and an inner layer of cells, the sheath-cells. The neural lamella has been identified as being composed of a collagen-type protein and neutral mucopolysaccharide on the evidence of its histochemical reactions and the identification of hydroxyproline by paper chromatography in a hydrolysate of the neural lamella. The sheath-cells possess large numbers of lipochondria composed of phospholipids and cerebrosides, and small spherical mitochondria. The cytoplasm also contains lipids (some of which may be cerebrosides), glycogen, and RNA.

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