Response Heterogeneity in Adductor Muscle Efferents of the Surf Clam

1967 ◽  
Vol 46 (3) ◽  
pp. 585-597
Author(s):  
DEFOREST MELLON ◽  
GEORGE J. MPITSOS
Keyword(s):  
Structural Organization ◽  
Adductor Muscle ◽  
Type I ◽  
Type Ii ◽  
Nerve Roots ◽  
Surf Clam ◽  
Type I Cells ◽  
Efferent Pathway ◽  
I Cells ◽  
Two Populations

1. Two populations of neurons in the visceroparietal ganglion of the surf clam have been identified as efferent to the posterior adductor muscle. Both populations are driven by input from the cerebrovisceral connectives and the posterior pallial nerves. The latter pathways originate in tactile receptors on the siphons and posterior mantle. 2. Cells designated as type I respond to input over the four major nerve roots by compound postsynaptic potentials, and to input over the adductor muscle nerves by facilitating strictly excitatory potentials. Type II neurons respond in a purely excitatory manner to input over all pathways tested. It is suggested that pharmacological analysis of the input excitatory synaptic contacts on type I cells would have implications for the structural organization of molluscan neuropile. 3. Neither efferent pathway has yet been identified in terms of functional connexions made at the periphery. It is assumed from behavioural observations that type I cells are motoneurons controlling phasic contraction of the adductor, but electro-physiological confirmation of this is still wanting.

scholarly journals ULTRASTRUCTURE OF THE CAROTID BODY

1966 ◽  
Vol 30 (3) ◽  
pp. 563-578 ◽  
Author(s):  
T. J. Biscoe ◽  
W. E. Stehbens
Keyword(s):  
Blood Vessels ◽  
Schwann Cells ◽  
Carotid Body ◽  
Nerve Fibers ◽  
Nerve Endings ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Type I Cells ◽  
I Cells

An electron microscope investigation was made of the carotid body in the cat and the rabbit. In thin-walled blood vessels the endothelium was fenestrated. Larger vessels were surrounded by a layer of smooth muscle fibers. Among the numerous blood vessels lay groups of cells of two types covered by basement membranes. Aggregates of Type I cells were invested by Type II cells, though occasionally cytoplasmic extensions were covered by basement membrane only. Type I cells contained many electron-opaque cored vesicles (350 to 1900 A in diameter) resembling those in endocrine secretory cells. Type II cells covered nerve endings terminating on Type I cells and enclosed nerve fibers in much the same manner as Schwann cells. The nerve endings contained numerous microvesicles (∼500 A in diameter), mitochondria, glycogen granules, and a few electron-opaque cored vesicles. Junctions between nerve endings and Type I cells were associated with regions of increased density in both intercellular spaces and the adjoining cytoplasm. Cilia of the 9 + 0 fibril pattern were observed in Type I and Type II cells and pericytes. Nonmyelinated nerve fibers, often containing microvesicles, mitochondria, and a few electron-opaque cored vesicles (650 to 1000 A in diameter) were present in Schwann cells, many of which were situated close to blood vessels Ganglion cells near the periphery of the gland, fibrocytes, and segments of unidentified cells were also seen. It was concluded that, according to present concepts of the structure of nerve endings, those endings related to Type I cells could be efferent or afferent.

Effects of oligohydramnios on lung growth and maturation in the fetal rat

2002 ◽  
Vol 282 (3) ◽  
pp. L431-L439 ◽  
Author(s):  
Joseph A. Kitterman ◽  
Cheryl J. Chapin ◽  
Jeff N. Vanderbilt ◽  
Nicolas F. M. Porta ◽  
Louis M. Scavo ◽  
...  
Keyword(s):  
Fetal Lung ◽  
Alveolar Type ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lung Growth ◽  
Type I Cells ◽  
Fetal Lung Development ◽  
Fetal Rat ◽  
I Cells

Oligohydramnios (OH) retards fetal lung growth by producing less lung distension than normal. To examine effects of decreased distension on fetal lung development, we produced OH in rats by puncture of uterus and fetal membranes at 16 days of gestation; fetuses were delivered at 21 or 22 days of gestation. Controls were position-matched littermates in the opposite uterine horn. OH lungs had lower weights and less DNA, protein, and water, but no differences in saturated phosphatidylcholine, surfactant proteins (SP)-A and -B, and mRNA for SP-A, -B, -C, and -D. To evaluate effects on epithelial differentiation, we used RTI40 and RTII70, proteins specific in lung to luminal surfaces of alveolar type I and II cells, respectively. At 22 days of gestation, OH lungs had less RTI40 mRNA ( P < 0.05) and protein ( P < 0.001), but RTII70 did not differ from controls. With OH, type I cells (in proportion to type II cells) covered less distal air space perimeter ( P < 0.01). We conclude that OH, which retards lung growth, has little effect on surfactant and impedes formation of type I cells relative to type II cells.

Freeze-substitution and Postembedding Immunocytochemistry on Rat Taste Buds: G-Proteins, Calcitonin Gene-related Peptide, and Choline Acetyl Transferase

1997 ◽  
Vol 3 (1) ◽  
pp. 53-69 ◽  
Author(s):  
Bert Ph.M. Menco ◽  
Maya P. Yankova ◽  
Sidney A. Simon
Keyword(s):  
Freeze Substitution ◽  
Taste Buds ◽  
Taste Bud ◽  
Type I ◽  
Type Ii ◽  
Choline Acetyl Transferase ◽  
Type I Cells ◽  
Dense Core Granules ◽  
Electron Dense Core ◽  
I Cells

Abstract: We have explored freeze-substitution combined with low-temperature embedding in rat taste buds for postembedding immunocytochemistry. A major difference in taste bud cells that were rapidly frozen without prior chemical fixation and those that were fixed and cryoprotected before freezing was that electron-dense core granules were virtually absent. The antibodies used in these initial studies were directed against calcitonin gene-related peptide (CGRP), a peptide commonly found in nociceptive neurons; the α-subunits of two G-proteins involved in bitter and sweet taste transduction; and choline acetyl transferase (ChAT), an enzyme involved in the synthesis of acetylcholine. Anti-CGRP immunolabeled a subpopulation of unmyelinated perigemmal neurons; anti-Gqα labeled a larger subpopulation of these neurons and the microvilli of cells that were most likely from Type II vallate taste buds. α-Gustducin was found in cytoplasm of Type II and/or III cells and probably in microvilli of Type I cells of vallate taste buds. The best labeling results were obtained with anti-ChAT, which stained microvilli and lateral membranes of some Type II vallate taste bud cells, and the cytoplasm of some other Type II and/or III vallate cells. In addition, anti-ChAT labeled electron-opaque materials inside taste bud pores of vallate papillae, but, under the same conditions, not granules of Type I cells or most of the vesicles in von Ebner's glands. These data suggest that we can not assume a priori that the contents of the electron-dense core granules of Type I cells, or even of those of von Ebner's glands, contain the precursors of the taste bud pore–dense substances.

A Study of the Enteric Plexuses in Some Amphibians

1951 ◽  
Vol s3-92 (17) ◽  
pp. 55-77
Author(s):  
MARGARET GUNN
Keyword(s):  
Myenteric Plexus ◽  
Proximal Part ◽  
Nerve Cells ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Nerve Fibres ◽  
Type I Cells ◽  
Splanchnic Nerves ◽  
I Cells

1. The extrinsic nerve-supply to the gut in the frog (Rana temporaria) is contained in the vagus and splanchnic nerves--both of which appear to contain parasympathetic and sympathetic fibres. 2. The vagus supplies the gut from the proximal part of the oesophagus to the most proximal part of the intestine. The splanchnic nerves supply the gut from the oesophagus to the rectum. 3. No vagal fibres accompany the splanchnic nerves. 4. A possible explanation is given for the variable effects produced on stimulation of the extrinsic nerves supplying the gut. 5. A plexus of nerve-fibres is present i n the submucosa which probably corresponds to Meissner's plexus of mammals, but no nerve-cells are present. 6. In the myenteric plexus the nerve-cells are commonly grouped int o ganglia in the oesophagus and stomach, but in theintestine the nerve-cells are fairly evenly distributed, distinct ganglia not being present. 7. Cells of three types have been found corresponding to Dogiel's three types. Type I cells are of two varieties: (a) large, strongly argyrophi l cells which are multi-polar possessing numerous short dendrites and a very prominent axon; (b)smaller cells having a prominent axon and often unipolar. Type I cells are enclosed in capsules. Type II cells are small multipolar cells with long dendrites. Type III cells are small multipolar cells with shorter dendrites and an axon bearing no collaterals. 8. Cells in the oesophagus and stomach are entirely of Type I. In the intestine these cells are present in fairly large numbers at the most proximal end, but throughout the rest of the intestine they only occur commonly close to the attachment of the mesentery, where they are found singly and fairly evenly spaced. 9. Cells of Types II and III occur only in the myenteric plexus of the intestine, where they are distributed fairly evenly, not forming distinct ganglia. 10. It is suggested that the Type II and III cells formed the original autonomic nerve plexus of the gut, the Type II cells being motor and the Type III sensory. The Type I cells are the post-ganglionic cells of the parasympathetic system and are an additional motor contribution to the plexus. 11. The endings of th e pre-ganglionic parasympathetic fibres on the ganglion cells may take any of three forms: (a) pericellular varicose endings which occur on the large variety of Typ e I cell; (b) pericapsular varicose endings which are borne by the smaller variety of Type I cell; and(c) club-shaped endings occurring on the larger Type I cells. 12. The type of synapse formed by the processes of cells of Types II and III consists of the simple endings of their processes on the cell bodies or dendrites of other cells, or the passing contact of their processes with the bodies of other cells. 13. Fine varicose fibrils have been observed on the surface of muscle-cells. These are presumably the distal ends of the cell processes and sympathetic fibres which form the motor endings. 14. The types of sensory endings which have been found are: (a) typical sensory varicose endings spread out in the submucosa of the oesophagus and rectum; those in the oesophagus originating from vagal fibres; and (b) Pacinian corpuscle in the sub-mucosa of the intestine. 15. The ‘interstitial cells of Cajal’ form an apparently anastomosing network in the gut-wall which appears to be distinct from the anastomosing Schwann plasmodium which covers the nerve-fibres.

scholarly journals UTP regulation of ion transport in alveolar epithelial cells involves distinct mechanisms

2009 ◽  
Vol 297 (3) ◽  
pp. L439-L454 ◽  
Author(s):  
Chuanxiu Yang ◽  
Lijing Su ◽  
Yang Wang ◽  
Lin Liu
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Alveolar Epithelial Cells ◽  
Alveolar Type ◽  
Channel Blockers ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Type I Cells ◽  
I Cells

UTP is known to regulate alveolar fluid clearance. However, the relative contribution of alveolar type I cells and type II cells to this process is unknown. In this study, we investigated the effects of UTP on ion transport in type I-like cell (AEC I) and type II-like cell (AEC II) monolayers. Luminal treatment of cell monolayers with UTP increased short-circuit current ( Isc) of AEC II but decreased Isc of AEC I. The Cl− channel blockers NPPB and DIDS inhibited the UTP-induced changes in Isc (Δ Isc) in both types of cells. Amiloride, an inhibitor of epithelial Na+ channels (ENaC), abolished the UTP-induced Δ Isc in AEC I, but not in AEC II. The general blocker of K+ channels, BaCl2, eliminated the UTP-induced Δ Isc in AEC II, but not in AEC I. The intermediate conductance (IKCa) blocker, clofilium, also blocked the UTP effect in AEC II. The signal transduction pathways mediated by UTP were the same in AEC I and AEC II. Furthermore, UTP increased Cl− secretion in AEC II and Cl− absorption in AEC I. Our results suggest that UTP induces opposite changes in Isc in AEC I and AEC II, likely due to the reversed Cl− flux and different contributions of ENaC and IKCa. Our results further imply a new concept that type II cells contribute to UTP-induced fluid secretion and type I cells contribute to UTP-induced fluid absorption in alveoli.

Low permeabilities of MDCK cell monolayers: a model barrier epithelium

1997 ◽  
Vol 273 (1) ◽  
pp. F67-F75 ◽  
Author(s):  
J. P. Lavelle ◽  
H. O. Negrete ◽  
P. A. Poland ◽  
C. L. Kinlough ◽  
S. D. Meyers ◽  
...  
Keyword(s):  
Mdck Cells ◽  
Collecting Duct ◽  
Type I ◽  
Thick Ascending Limb ◽  
Type Ii Cells ◽  
Type Ii ◽  
Type I Cells ◽  
A Cell ◽  
Apical Membranes ◽  
I Cells

Barrier epithelia such as the renal collecting duct (in the absence of antidiuretic hormone) and thick ascending limb, as well as the stomach and mammalian bladder, exhibit extremely low permeabilities to water and small nonelectrolytes. A cell culture model of such epithelia is needed to determine how the structure of barrier apical membranes reduce permeability and how such membranes may be generated and maintained. In the present studies, the transepithelial electrical resistance and isotopic water and urea fluxes were measured for Madin-Darby canine kidney (MDCK) type I and type II cells, as well as type I cells expressing the mucin protein, MUC1, in their apical membranes. Although earlier studies had found the unstirred layer effects too great to permit measurement of transepithelial permeabilities, use of ultrathin semipermeable supports in this study overcame this difficulty. Apical membrane diffusive water permeabilities were 1.8 +/- 0.4 x 10(-4) cm/s and 3.5 +/- 0.5 x 10(-4) cm/s in MDCK type I and type II cells, respectively, at 20 degrees C. Urea permeability in type I cells at the same temperature was 6.0 +/- 0.9 x 10(-6) cm/s. These values resemble those of other barrier epithelial apical membranes, either isolated or in intact epithelia, and the water permeability values are far below those of other epithelial cells in culture. Transfection of MDCK type I cells with the major human urinary epithelial mucin, MUC1, led to abundant expression of the fully glycosylated form of the protein on immunoblots, and flow cytometry revealed that virtually all the cells expressed the protein. However, MUC1 had no effect on water or urea permeabilities. In conclusion, MDCK cells grown on semipermeable supports form a model barrier epithelium. Abundant expression of mucins does not alter the permeability properties of these cells.

Electrical filtering in gerbil isolated type I semicircular canal hair cells

1996 ◽  
Vol 75 (5) ◽  
pp. 2117-2123 ◽  
Author(s):  
K. J. Rennie ◽  
A. J. Ricci ◽  
M. J. Correia
Keyword(s):  
Membrane Potential ◽  
Hair Cells ◽  
Semicircular Canal ◽  
Input Resistance ◽  
Constant Current ◽  
Type I ◽  
Type Ii ◽  
Peak Voltage ◽  
Type I Cells ◽  
I Cells

1. Membrane potential responses of dissociated gerbil type I semicircular canal hair cells to current injections in whole cell current-clamp have been measured. The input resistance of type I cells was 21.4 +/- 14.3 (SD) M omega, (n = 25). Around the zero-current potential (Vz = -66.6 +/- 9.3 mV, n = 25), pulsed current injections (from approximately -200 to 750 pA) produced only small-amplitude, pulse-like changes in membrane potential. 2. Injecting constant current to hyperpolarize the membrane to around -100 mV resulted in a approximately 10-fold increase in membrane resistance. Current pulses superimposed on this constant hyperpolarization produced larger and more complex membrane potential changes. Depolarizing currents > or = 200 pA caused a rapid transient peak voltage before a plateau. 3. Membrane voltage was able to faithfully follow sine-wave current injections around Vz over the range 1-1,000 Hz with < 25% attenuation at 1 kHz. A previously described K conductance, IKI, which is active at Vz, produces the low input resistance and frequency response. This was confirmed by pharmacologically blocking IKI. This conductance, present in type I cells but not type II hair cells, would appear to confer on type I cells a lower gain, but a much broader bandwidth at Vz, than seen in type II cells.

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