Diversity in electrical behavior of autonomic neurons associated with the gastrointestinal tract.
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Animals↗
Biomedical subjects
B F King
Publications and source records attributed to B F King.
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Arizona↗
A filter paper sandwich method using small volumes of reagents for the detection of antigens electrophoretically transferred onto nitrocellulose.
A method is described which allows antigens electrophoretically 'blotted' onto nitrocellulose to be probed using small volumes (less than 0.3 ml) of antibody solutions. Reagent volumes required for this method are more than 10-fold lower than the minimum volumes attainable using either custom made or commercial incubation trays. The procedure is simple and economical and should be applicable to any situation where it is desirable to either conserve or reduce the amount of screening reagent used.
Antibodies, Monoclonal↗
The fine structure of the placenta and chorionic vesicles of the bush baby, Galago crassicaudata.
The fine structure of the placental villi and the chorionic vesicles of the bush baby, Galago crassicaudata, were examined. The placenta was of the diffuse epitheliochorial type. The trophoblastic epithelium of the placental villi consisted of cells joined by tight junctions and desmosomes. The apical borders of these cells interdigitated with corresponding processes on the uterine epithelial cells. The fetal capillaries indented the trophoblastic cells later in gestation, and the trophoblast over the capillaries was correspondingly thinner with advancing gestation. The trophoblast of the villi was characterized by numerous lipid droplets and moderate amounts of granular endoplasmic reticulum (ER). The apical cytoplasm often had many mitochondria as well as small electron-dense vesicles and tubules. Uterine epithelial cells contained agranular ER and a well-developed Golgi apparatus. The apical cytoplasm contained numerous granules often with an electron-dense content. The uterine epithelial cells appeared to be secretory, contributing to the electron-dense material found between the fetal and maternal cells. Fetal capillaries were of the continuous type, whereas occasional fenestrae were observed in maternal capillaries. Recesses in the trophoblastic epithelium occurred at the tips, sides, and bases of the villi. These areas had taller trophoblastic cells that appeared to be more active in phagocytosing uterine content. The chorionic vesicles are invaginations of the chorion opposite the mouths of uterine glands. A layer of columnar trophoblastic cells covered the villi of the vesicles. These cells had abundant vacuoles and coated pits and vesicles. The mesodermal component of the chorionic vesicles included a capillary network and a layer of smooth muscle cells in the wall of the vesicle. It was concluded that the trophoblast of the placental villi is engaged in both hemotrophic and histotrophic nourishment of the embryo. The specialized chorionic vesicles are particularly important in providing histotrophic nutrients to the embryo, especially the secretions of the uterine glands. The similarity of the chorionic vesicles to the areolae of other species suggests they may be the pathway by which iron is transported from mother to fetus, perhaps by receptor-mediated endocytosis of macromolecules derived from uterine gland secretions.
Animals↗
Mechanoreceptor pathways from the distal colon to the autonomic nervous system in the guinea-pig.
Electrophysiological and histological techniques were used to trace sensory pathways for stretch mechanoreceptor fibres from the distal colon to dorsal root ganglia. Extracellular and intracellular recording techniques revealed sensory pathways for mechanoreceptors to the prevertebral sympathetic ganglia but no further centrally. Histological studies involving the retrograde transport of horseradish peroxidase revealed sensory pathways from the distal colon to the spinal cord, mainly to the level of the second lumbar vertebra. Few (less than 2000) fibres were involved; their perikarya were small (ca. 25 micron). Sensory perikarya in spinal ganglia in the guinea-pig could be categorized into two populations, F and H cells, after a previously defined nomenclature for murine spinal ganglion cells. F and H cells were distinguished initially by their times to decay by 50% of the action potential. H cells took three times as long to repolarize. F and H cells were distinguished further by their electrical properties including membrane potential, input resistance and amplitude and duration of the after-potential following the action potential. Both F and H cells showed unusual time-dependent rectification following either depolarizing or hyperpolarizing current pulses. Threshold currents to show rectification were different for F and H cells. When taken in conjunction with conduction velocities, the electrophysiological evidence may assist in identifying sensory neurones. For example, H cells appeared to have slow conducting (C fibre) axons. From the lack of electrophysiological evidence and limited histological support for major central sensory pathways, it is concluded that stretch mechanoreceptor information from the colon of the guinea-pig is referred mainly to the prevertebral ganglia with minimal involvement of the spinal cord.
Action Potentials↗
Intracellular recordings from vagally innervated intramural neurons in opossum stomach.
Intracellular recordings were made from intramural neurons in parafascicular ganglia in the opossum stomach. These ganglia were situated between the myenteric and subserosal plexuses and were found lying adjacent to vagal nerve fascicles. The neurons at these ganglia showed active and passive electrical properties similar only to S/type I enteric neurons. They received a complex innervation from preganglionic vagal fibers. These parasympathetic nerves elicited three distinct transmission processes in intramural neurons: fast and slow excitation (excitatory postsynaptic potentials, EPSP) and slow inhibition (inhibitory postsynaptic potential, IPSP). Fast EPSPs were cholinergically mediated via postjunctional nicotinic receptors, with convergence of numerous cholinergic fibers in several vagal fascicles to individual neurons. When seen, slow EPSPs increased neuronal excitability, whereas slow IPSPs decreased excitability.
Animals↗
An electrophysiological study of inferior mesenteric ganglion of the dog.
Intracellular recordings were made in vitro from 430 sympathetic neurons in the inferior mesenteric ganglion (IMG) of the dog. Ganglion cells had resting membrane potentials between -35 and -70 mV; input resistance (Rin) was approximately 22 M omega. Cell rheobase to depolarizing current was 0.3 nA, and the action potential elicited was 80-100 mV in amplitude followed by an afterhyperpolarization of up to 15 mV in size, which decayed to the resting membrane potential over a range of 50-500 ms. Neurons were classified as either phasic (188 of 280) or tonic (92 of 280) firing cells, depending on their discharge pattern in response to depolarizing current. Two hundred eight of 430 neurons showed continuous electrical activity in the form of spontaneous excitatory postsynaptic potentials, 2-5 mV in amplitude. Continuous electrical activity was unaffected by tetrodotoxin (3 X 10(-6) M) but abolished by hexamethonium (10(-4) M). A small number of cells (21 of 430) adopted a repetitive firing pattern not associated with injury discharge. These cells may have been pacemaking neurons. Stimulation of peripheral and central nerves resulted in multiple synaptic input to ganglion cells. There was marked convergence of excitatory fibers to any one cell. Evoked synaptic potentials were abolished by hexamethonium (10(-4) M). Synaptic input from peripheral and central nerves could not be correlated with location of postganglionic neurons in the IMG. The possibility of neuronal intercommunication and dissemination of central and peripheral commands is discussed.
Action Potentials↗
Isolation and partial characterization of the basal cell membrane of human placental trophoblast.
The function of the syncytiotrophoblast in maternal-fetal exchange is related to the properties of its microvillous (maternal-facing) and basal (fetal-facing) plasma membranes. We have previously reported the properties of the microvillous membrane (Smith, C.H., Nelson, D.M., King, B.F., Donohue, T.M., Ruzycki, S.M. and Kelley, L.K. (1977) Am. J. Obstet. Gynecol. 128, 190-196), and now describe the purification and partial characterization of the basal plasma membrane. Sonication and incubation with EDTA were used to isolate selectively the basal cell membrane. These steps were followed by a more conventional purification by centrifugation. The trophoblast was disrupted and its microvillous membrane and cytoplasmic contents were removed by sonication. The exposed basal cell membrane was selectively released from the underlying basal lamina by sonication in the presence of EDTA and further purified by discontinuous Ficoll gradient centrifugation. The material at the 4-10% Ficoll interface consisted of smooth membrane vesicles with internal microfilaments. It was 45-fold enriched in dihydroalprenolol binding activity and 11-fold enriched in ouabain binding activity. Other enzymatic analyses, including alkaline phosphatase, cytochrome-c oxidase, cytochrome-c reductase and galactosyl transferase indicated low contamination by other organelles. This procedure yields a preparation of relatively high purity which should be suitable for investigation of transport and other functions of the basal surface membrane of trophoblast. In principle, the purification procedures used may be applicable to other transporting epithelia.
Alkaline Phosphatase↗
A fine structural and cytochemical study of the rhesus monkey yolk sac: endoderm and mesothelium.
This study has examined the fine structure and some cytochemical characteristics of the endodermal and mesothelial cells of the rhesus monkey yolk sac between 25 and 66 days of gestation. The endodermal cells were characterized by abundant granular endoplasmic reticulum, some agranular endoplasmic reticulum, a well-developed Golgi apparatus, and numerous large mitochondria. During the earlier part of the period studied, endodermal cells had a few acid phosphatase and arylsulfatase-positive lysosomes and moderate numbers of catalase-positive microperoxisomes. During the later stages of development, large granules (believed to be lysosomes) with a heterogeneous content were numerous in the cytoplasm. Mesothelial cells showed fewer development changes. Throughout this period they were usually flattened cells with long microvilli, small mitochondria, and limited amounts of granular endoplasmic reticulum. The mesothelial cells had acid phosphatase reaction product in the Golgi region and occasional large vesicles, but were negative for arylsulfatase and catalase. One specimen was incubated at 37 degrees C in the presence of horseradish peroxidase in order to examine endocytosis. Both the mesothelial cells and endodermal cells internalized the peroxidase into a variety of cytoplasmic vesicles. Based on their cytology, the endodermal cells may function in the synthesis of serum proteins during this period, as has been suggested in other species. They may also be involved in lipid metabolism. The mesothelial cells appeared less synthetically active, but evidence suggested that they may be involved in collagen and extracellular matrix production. The endocytic activity displayed by both cell types may indicate a role in fluid and metabolite transfer across the epithelia. The cytology of both cell types was very similar to that described for human yolk sacs, suggesting that the rhesus monkey may be a useful species in which to study the maturation of yolk sac function.
Animals↗
The permeability of human amniotic epithelium: studies using lanthanum as a tracer.
To study the permeability of human amniotic epithelium to small molecular weight substances, pieces of nonplacental amnion, with attached chorion laeve and decidua, were exposed to solutions containing lanthanum salts and processed for electron microscopy. Lanthanum penetrated the intercellular spaces and often reached the basal lamina region. In addition, some lanthanum was bound to the glycocalyx of the microvilli on the apical surfaces of the cells. Little lanthanum was found deep to the basal lamina. The results suggest the intercellular pathway is of major importance in the movement of small molecules across amniotic epithelium.
Amnion↗
The organization of actin filaments in human placental villi.
The surface of the syncytial trophoblast of the human placenta is covered by a microvillous (brush) border that is in direct contact with maternal blood. Because of this location, it is the site of a variety of transport, enzymatic and receptor activities vital to many placental functions. The organization of the brush border as well as other features of placental villus organization may well be influenced by the distribution of cytoplasmic actin filaments. In order to determine the distribution of actin filaments in human placenta, small pieces of villi were briefly fixed in glutaraldehyde, permeabilized with saponin, and incubated in solutions containing subfragment 1 of myosin (S1). After S1 decoration of actin filaments, tissue was fixed in glutaraldehyde containing tannic acid in order to better visualize the polarity of the filaments, and prepared for electron microscopic examination. The microvilli each contained a core of actin filaments running from the tip of the microvillus to the apical cytoplasm. Most of the actin filaments displayed a distinct polarity, with the S1 arrowheads pointing away from the microvillar tips. These filaments extended only a short distance into the apical cytoplasm. There appeared to be another group of actin filaments in a matlike arrangement in the apical cytoplasm. Coated pits and vesicles were often observed between the microvilli. There appeared to be no clear association between the coated pits and decorated actin filaments, but this was difficult to establish with certainty because of the close proximity of the microvilli. Bundles of actin filaments were sometimes observed near the basal cell surface of the syncytial trophoblast, and in pericytes and capillary endothelial cells in the cores of the villi.(ABSTRACT TRUNCATED AT 250 WORDS)
Actins↗
The organization of actin filaments in the brush border of yolk sac epithelial cells.
The yolk sac epithelium offers a potentially interesting cell type in which to examine brush border cytoskeletal organization because it functions not only in absorption across the microvillous membrane, but also has numerous coated pits at the bases of the microvilli which function in endocytosis. In this study we have examined the organization of actin filaments in the brush border of yolk sac endodermal cells using myosin S1 subfragment decoration. Microvilli contained bundles of actin filaments polarized such that the arrowheads pointed away from the microvillar tips. The bundles continued into the apical cytoplasm as short rootlets that intermingled with a poorly developed layer of other filaments, some of which were actin, running parallel to the apical cell surface (i.e., in the terminal web region). Decorated microfilaments were sometimes associated with coated pits and vesicles, but it was difficult to distinguish direct membrane-filament interaction from coincidental associations brought about by close proximity of coated vesicles to actin filaments emerging from the microvilli. A prominent peripheral band of microfilaments of mixed polarity was present at the level of the zonula adherens. This band of filaments may act as a contractile ring. Tension of the contractile ring, together with a poorly developed terminal web, may produce the domeshaped apical surface characteristic of these cells.
Actins↗
The permeability of nonhuman primate vaginal epithelium: a freeze-fracture and tracer-perfusion study.
The lining of the vaginal mucosa in primates is a keratinized stratified squamous epithelium. As in other structurally similar epithelia, one function of the vaginal epithelium is to provide a barrier between the external environment and the underlying tissues. The vaginal lining is aglandular and the source of true vaginal fluid has been suggested to be the intercellular channels of the epithelium. On the other hand, other structurally similar epithelia have been shown to have a barrier to the movement of water-soluble molecules through these channels. In the present study, we have examined the permeability of rhesus monkey vaginal epithelium to lanthanum and horseradish peroxidase. Both tracer molecules penetrated the intercellular channels in the lower layers of the epithelium, but were excluded from the channels at and above the granular layer. Neither tracer penetrated significantly between cells at the free surface of the epithelium and usually did not penetrate between cells in the upper layers to any degree from the cut edges of the biopsy. These results are consistent with tracer studies in other structurally similar epithelia and strongly suggest that the upper layers of vaginal epithelium present a barrier to the movement of water-soluble molecules through the intercellular channel system. Freeze-fracture analysis of the epithelium revealed gap junctions and desmosomes between cells in the lower layers, but the former disappear in the upper layers. Unlike other keratinizing epithelia that have been described, random intramembranous particles do not disappear from the plasma membranes of the fully differentiated cells. Fracture planes through the upper layers reveal particle-free lamellae in the intercellular spaces, supporting the idea that intercellular lipids may be one of the components that limits the permeability of the intercellular spaces in this epithelium.
Animals↗
Ultrastructure of the nonhuman primate vaginal mucosa: epithelial changes during the menstrual cycle and pregnancy.
Ultrastructural changes in the vaginal epithelium of the rhesus monkey during the menstrual cycle and pregnancy were studied by scanning and transmission electron microscopy. During the menstrual cycle, the epithelium was keratinized but varied in thickness. Cells of the basal and parabasal layers were polyhedral in shape but as they differentiated they accumulated glycogen and filaments. Cells in the intermediate layers had keratohyaline and membrane-coating granules. Cells in the superficial layers had a thickened cell envelope, abundant keratin filaments, electron-dense intercellular material, and focal tight junctions. The epithelial surface had numerous microridges and numerous adherent bacteria; bacteria were rare on desquamating cells. The epithelium remained keratinized for about the first month of gestation, then underwent "mucification." The cells contained abundant granules and Golgi apparatus. Concomitant with this transformation, bacteria were no longer adherent to the epithelial surface and the surface cells had microvilli instead of microridges. The epithelial changes during pregnancy were roughly associated with the changing pattern of steroid hormone secretion during gestation.
Animals↗
The fine structure of the placental labyrinth in the sloth, Bradypus tridactylus.
The placental labyrinth of the three-toed sloth (Bradypus tridactylus) was examined by electron microscopy. The material available was from two fetuses of 55 mm and 150 mm crown-rump length (CRL). The placenta of the younger specimen was a transition form between the syndesmochorial type and the endotheliochorial type. The interhemal membrane of the 55 mm CRL specimen consisted of the following components: 1) hypertrophied maternal endothelial cells surrounding the maternal vessels; 2) a small amount of extracellular material and spindle-shaped cells, both presumed to be of maternal origin; 3) a layer of syncytial trophoblast that had an unusual, reticulated or sponge-like appearance; and 4) the fetal capillary endothelium. In addition, the fetal connective tissue contained hypertrophied mesenchymal cells that were characterized by abundant granular endoplasmic reticulum. The placenta of the 150 mm CRL fetus was poorly preserved, but it was possible to determine that the placenta was of the endotheliochorial type. There was a close apposition of maternal endothelium and trophoblast. The results confirmed virtually all of lhe light microscopic observations of Wislocki (1927; 1928b). The ultrastructure of the sloth interhemal membrane is compared to that of other endotheliochorial placentas, particularly that of the shrew, with which it shows many cytological similarities.
Animals↗
A freeze-fracture study of the guinea pig yolk sac epithelium.
The yolk sac epithelium functions in endocytic absorption of macromolecules from the uterine lumen and in maintaining permeability barriers between the maternal (uterine) compartment and underlying fetal compartments. In this study, cell membranes and intercellular junctions of the guinea pig yolk sac were examined using the freeze-fracture technique. Intramembranous particle (IMP) distribution and size were examined in microvilli, intermicrovillous membrane, and endocytic pits. IMPs on the P-fracture face were not evenly distributed within these membrane domains and the IMPs were of several sizes. In addition, short filamentous strands sometimes bridged between the cytoplasm and the E-face of endocytic pit membranes. These results indicated that the regions of yolk sac cell membrane involved in endocytosis did not have unusual numbers or distributions of IMPs compared to other membrane regions. The intercellular junctions between endoderm cells consisted of zonulae occludentes, gap junctions, and desmosomes. The zonula occludens usually consisted of four or five interconnected strands or ridges, and were elaborately developed where three cells abutted one another. Gap junctions were infrequent, small, and often associated with the zonula occludens. Desmosomes were observed both as typical macular structures and as more extensive, elongated structures. These results confirm previous thin-section studies of yolk sac indicating the presence of tight junctions. However, the extent of development of tight junctions does not correlate with the regard absence of a potential difference across yolk sac epithelium. The presence of gap junctions does not confirm results of previous freeze-fracture studies of other yolk sacs.
Animals↗
Cell surface specializations and intercellular junctions in human amniotic epithelium: an electron microscopic and freeze-fracture study.
Cell surface specializations and intercellular junctions of human term amniotic epithelium were examined by conventional thin-section electron microscopy, after staining with the cationic probes ruthenium red and cationic ferritin, and by freeze-fracture methods. Desmosomes were the predominant type of intercellular junction and often the most apical of the junctional types. In freeze-fracture replicas, desmosomes were characterized by roughly circular areas of large, often irregular, P-face intramembranous particles. Gap junctions were identified in the laterobasal regions between cells. In thin sections they were characterized by a narrow intercellular space, and in freeze-fracture replicas had a typical plaquelike arrangement of P-face intramembranous particles and E-face depressions. Hemidesmosomes at the basal cell surface were characterized by occasional large particles and clusters of particles on both the E and P fracture faces. No evidence of tight junctions was found. The apical cell surface was heavily stained by both ruthenium red and cationic ferritin, indicating the negatively charged nature of this surface. Ruthenium red penetrated between the epithelial cells and bound to anionic materials on the lateral cell surfaces, especially at the location of desmosomes. Below the base of the intercellular cleft, large ruthenium red-positive granules were present in the extracellular matrix. The possibility that the anionic substances in the intercellular region may contribute to the control of permeability in the amniotic epithelium is discussed.
Amnion↗
Developmental changes in rhesus monkey placental villi and cell columns. Scanning electron microscopy.
Developing rhesus monkey placentas were analyzed by scanning electron microscopy with special attention directed toward defining stages in the development of the villus branches. The initial phase in formation of villi was the conversion of reticulated trabeculae of syncytial trophoblast into chorionic villi by growth and proliferation of cell columns of cytotrophoblast. These villi were stout and unbranched. The second phase of development appeared to be the longitudinal splitting of the villi and cell columns to form groups of parallel branches but there was a common insertion of these into the basal plate. The third phase in formation of villi, which appeared to begin at about the same time as the longitudinal splitting occurred, was the outgrowth of large-diameter side branches in a zone nearer the chorionic plate. At about 38-40 days of gestation the next stage in villus formation occurred, characterized by the emergence of numerous, small syncytial sprouts. Continued proliferation of villi at later stages of gestation resulted in a decreased diameter of the terminal villi and an increasing complexity in the course of fetal capillaries.
Animals↗