Prototroch structure and innervation in the trochophore larva of Phyllodoce (Polychaeta)

1986 ◽  
Vol 64 (1) ◽  
pp. 176-184 ◽  
Author(s):  
T. C. Lacalli
Keyword(s):  
Complex Structure ◽  
Ultrastructural Level ◽  
The Other ◽  
Tier 2 ◽  
Cholinergic Drugs ◽  
Physical Interference ◽  
Trochophore Larva ◽  
Frontal Organ ◽  
Normal Behavior

The prototroch and prototroch nerve in trochophores of two Phyllodoce species are described at the ultrastructural level and interpreted with reference to the observed normal behavior of larvae during swimming. The prototroch is a complex structure consisting of four tiers of cells of which the second bears the main locomotory cilia. Cells in the other tiers also have cilia but are notable chiefly for the slender processes they send to the prototroch nerve and which evidently contribute to the sheath that surrounds the nerve. Neurociliary synapses were not observed, but the prototroch arrests when the frontal organ is touched and in response to cholinergic drugs. The arrests are only partial in that the cilia continue to beat, but in a restricted register. The mechanism responsible was not identified, but several possibilities are discussed. While the capacity to arrest could be intrinsic to the main trochal cells (i.e., tier 2), the absence of obvious regions of contact between these cells and the prototroch nerve increases the likelihood that the other tiers are also involved. The arrests could in fact result simply from physical interference between the cilia of adjacent tiers. The arrest response in Phyllodoce is compared with that seen in trochal bands in other spiralian larvae.

scholarly journals A Study of the Effects of Rain, Snow and Hail on the Atmospheric Electric Field near Ground

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 996
Author(s):  
Athanasios Karagioras ◽  
Konstantinos Kourtidis
Keyword(s):  
Frequency Distribution ◽  
Complex Structure ◽  
Potential Gradient ◽  
Weather Conditions ◽  
The Other ◽  
Fair Weather ◽  
Northern Greece ◽  
Rain Events ◽  
The Impact ◽  
Bounce Back

The purpose of the present study is to investigate the impact of rain, snow and hail on potential gradient (PG), as observed in a period of ten years in Xanthi, northern Greece. An anticorrelation between PG and rainfall was observed for rain events that lasted several hours. When the precipitation rate was up to 2 mm/h, the decrease in PG was between 200 and 1300 V/m, in most cases being around 500 V/m. An event with rainfall rates up to 11 mm/h produced the largest drop in PG, of 2 kV/m. Shortly after rain, PG appeared to bounce back to somewhat higher values than the ones of fair-weather conditions. A decrease in mean hourly PG was observed, which was around 2–4 kV/m during the hail events which occurred concurrently with rain and from 0 to 3.5 kV/m for hail events with no rain. In the case of no drop, no concurrent drop in temperature was observed, while, for the other cases, it appeared that, for each degree drop in temperature, the drop in hourly mean PG was 1000 V/m; hence, we assume that the intensity of the hail event regulates the drop in PG. The frequency distribution of 1-minute PG exhibits a complex structure during hail events and extend from −18 to 11 kV/m, with most of the values in the negative range. During snow events, 1-minute PG exhibited rapid fluctuations between high positive and high negative values, its frequency distribution extending from −10 to 18 kV/m, with peaks at −10 and 3 kV/m.

scholarly journals Revising Stanley’s footsteps: encountering the ‘other’ in Darkest England (1996) by Christopher Hope

Literator ◽  
2000 ◽  
Vol 21 (1) ◽  
pp. 85-98
Author(s):  
H. Roos
Keyword(s):  
Nineteenth Century ◽  
Complex Structure ◽  
Frame Of Reference ◽  
Point Of View ◽  
The Other ◽  
Central Theme ◽  
Post Colonial ◽  
Black Africa ◽  
Colonial Texts ◽  
Travel Writings

As has now become a familiar image in Hope’s writings, once again ttie idea of looking at a society from the position of an outsider and an exile forms the central theme of Darkest England (1996). In this satirical novel, the tradition of nineteenth-century travel writings set in a colonial context is reversed, undermined, and then remarkably recreated to portray the present-day manifestation of encounters and relations between (black) Africa and the (white) West. Presenting the (fictional) journals of a Khoisan leader, David Mungo Booi, within a dynamic frame of reference to classical colonial texts by, among others, Livingstone and Stanley. Hope writes a new travel report. This essay discusses how, by the reversal of point of view, a change in time and space, and creating a satirical mood, the colonizer and the colonized are interchanged and the original texts are evoked to be rewritten. The notions of Self/Other, colonial /(post-)colonial and primitive/civilized are placed in new and disturbing contexts, adding to the complex structure of this fascinating text.

scholarly journals A NEW SPECIES OF MALDIVEA GERLACH, 1962 (NEMATODA, OXYSTOMINIDAE) FROM FELIDHOO ATOLL (MALDIVES, INDIAN OCEAN) AND AN EMENDED DIAGNOSIS OF THE SUB-FAMILY AND GENUS

2019 ◽  
Vol 20 ◽  
pp. 1-9
Author(s):  
Federica Semprucci ◽  
Maria Balsamo
Keyword(s):  
New Species ◽  
Indian Ocean ◽  
Type Species ◽  
Distal Part ◽  
Complex Structure ◽  
Dorsal Side ◽  
The Other ◽  
Ventral Part ◽  
Endemic Genus ◽  
A New Species

Maldivea Gerlach, 1962 is a possible endemic genus of the Maldivian archipelago for which only M. xarifae Gerlach, 1962 has been described so far. A new species of this genus, M. complexa n.sp., was recently found in Felidhoo atoll. It reveals a more complex structure of gubernaculum than in type species which appears to be divided into two pieces: one is a sort of long wing in the ventral part of the spicule and the other one, more complex, is characterized by several curved stripes which envelop the dorsal side of the spicule distal part. According to the present considerations, diagnoses of Paroxystomininae and Maldivea are emended.

Structural constraints of secondary asymmetry in male external genitalia of Noctuidae

2013 ◽  
Vol 44 (3-4) ◽  
pp. 349-372 ◽  
Author(s):  
Zoltán Varga ◽  
László Ronkay
Keyword(s):  
Reproductive Success ◽  
Complex Structure ◽  
External Genitalia ◽  
The Other ◽  
Structural Constraints ◽  
Asymmetric Structures ◽  
Other Hand ◽  
Spatial Geometry ◽  
Male External Genitalia ◽  
Working Hypotheses

The basic architecture of the external genitalia of Noctuidae (“genital capsula”) is bilaterally symmetric. Secondary asymmetry is well-known in different subfamilies and tribes. We review and interpret the functions and processes which may be responsible for secondary asymmetry (i.e., dissymmetry) of these structures in terms of structural vs. behavioural working hypotheses. We consider the genital structures as correlated elements of a complex structure (“bauplan”) in which some changes in details can be explained by selection due to optimization of the reproductive success. Major pathways of changes are, however, delimited by some structural constraints which appear in parallel in different phyletic lines of trifine Noctuidae. One of these constraints is the subsistence of symmetry in structures with own musculature. On the other hand, some rigid parts without own musculature can evolve more rapidly and divergently in connection with the different allocation of functions. Such asymmetric structures may have some selective advantages due to the more effective stimulation, on one side, and fixation of genital parts during copulation, on the other. Asymmetric structures can effectively enhance the variations of the spatial geometry but without change of the “bauplan” which can be preserved in parallel in different taxonomical groups. It means that the originally symmetric “bauplan” with its homologies can be considered as a phyletic “heritage”, while the functional dissymmetrisation driven by selective optimization is the “habitus” in which numerous homoplasies can occur.

scholarly journals Pac-man motility of kinetochores unleashed by laser microsurgery

2012 ◽  
Vol 23 (16) ◽  
pp. 3133-3142 ◽  
Author(s):  
James R. LaFountain ◽  
Christopher S. Cohan ◽  
Rudolf Oldenbourg
Keyword(s):  
Sister Chromatid ◽  
Living Cells ◽  
The Other ◽  
Mechanical Tension ◽  
Knock Out ◽  
Resistive Force ◽  
Laser Microbeam ◽  
Normal Behavior ◽  
Chromatid Cohesion ◽  
Kinetochore Function

We report on experiments directly in living cells that reveal the regulation of kinetochore function by tension. X and Y sex chromosomes in crane fly (Nephrotoma suturalis) spermatocytes exhibit an atypical segregation mechanism in which each univalent maintains K-fibers to both poles. During anaphase, each maintains a leading fiber (which shortens) to one pole and a trailing fiber (which elongates) to the other. We used this intriguing behavior to study the motile states that X-Y kinetochores are able to support during anaphase. We used a laser microbeam to either sever a univalent along the plane of sister chromatid cohesion or knock out one of a univalent's two kinetochores to release one or both from the resistive influence of its sister's K-fiber. Released kinetochores with attached chromosome arms moved poleward at rates at least two times faster than normal. Furthermore, fluorescent speckle microscopy revealed that detached kinetochores converted their functional state from reverse pac-man to pac-man motility as a consequence of their release from mechanical tension. We conclude that kinetochores can exhibit pac-man motility, even though their normal behavior is dominated by traction fiber mechanics. Unleashing of kinetochore motility through loss of resistive force is further evidence for the emerging model that kinetochores are subject to tension-sensitive regulation.

scholarly journals NaI and CaII interstellar absorption in the field of SN 1987A

1991 ◽  
Vol 148 ◽  
pp. 434-435
Author(s):  
P. Molaro ◽  
G. Vladilo ◽  
S. D'Odorico ◽  
M. Dennefeld ◽  
R. Ferlet ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Layer Structure ◽  
Complex Structure ◽  
The Other ◽  
Interstellar Absorption ◽  
Number Of Components ◽  
Sn 1987A ◽  
Multiple Components ◽  
The Galaxy

We present CaII and NaI spectra for a sample of stars in a 30'×30' field connecting 30 Dor with SN 1987A. Observations were taken with the CES spectrograph linked via fibres with the 3.6m ESO telescope at a resolution of ˜ 6 km s−1. The LMC gas shows a complex structure with both single and multiple components spanning 250 to 300 km s−1. Results can be interpreted using the multi-layer structure suggested by 21 cm observations. Comparing our optical absorptions with 21 cm emissions yields evidence that layers with increasing radial velocity are located one behind the other. The intermediate velocity components are numerous in CaII, but rare in NaI. Towards Sk-69 211, for which we have the highest S/N CaII spectrum, we have detected a number of components comparable to that found in SN 1987A. The 64 km s−1 cloud is detected in a well-confined region of the field, showing remarkable constancy in the radial velocity, which we interpret as evidence that this cloud is located close to the Galaxy.

Nesting success, density, philopatry, and nest-site selection of the Whimbrel (Numenius phaeopus) in different habitats

1983 ◽  
Vol 61 (1) ◽  
pp. 218-225 ◽  
Author(s):  
Margaret A. Skeel
Keyword(s):  
Site Selection ◽  
Nest Site ◽  
Complex Structure ◽  
Nesting Success ◽  
Nest Site Selection ◽  
The Other ◽  
Uniform Density ◽  
Sedge Meadow ◽  
Heath Tundra ◽  
Selection Of

A population of Whimbrels (Numeniusphaeopus) that nested in three distinct habitats near Churchill, Manitoba, was studied from 1973 to 1976. Nest success in the hummock–bog habitat was 86% and was significantly higher than the 54% success in each of the sedge–meadow and heath–tundra habitats. The hummock–bog habitat differed from the other two in several other respects. In the hummock–bog habitat, density of nesting pairs was highest and averaged 0.11 pairs/ha. Distribution of nests tended toward uniform. Density in sedge–meadow and heath–tundra habitats averaged 0.04 and 0.05 pairs/ha, respectively. Philopatry of banded adults to the hummock–bog habitat was considerably higher than to the other two, indicating more stability there. Several attributes of nest placement were important, and the hummock–bog habitat, structurally the most complex, offered more potentially favorable sites. The higher nesting success in the hummock–bog habitat was attributed primarily to the more complex structure of this habitat (crypticity is enhanced) and the higher nesting density (predation is reduced through joint defense).

scholarly journals Gating mechanism of human N-type voltage-gated calcium channel

2021 ◽  
Author(s):  
Yanli Dong ◽  
Yiwei Gao ◽  
Shuai Xu ◽  
Yuhang Wang ◽  
Zhuoya Yu ◽  
...  
Keyword(s):  
Resting State ◽  
Complex Structure ◽  
The Other ◽  
Nociceptive Transmission ◽  
Voltage Gated ◽  
Gating Mechanisms ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Voltage Sensing Domain ◽  
Structural Insights

N-type voltage-gated calcium (CaV) channels mediate Ca2+ influx at the presynaptic terminals in response to action potential and play vital roles in synaptogenesis, neurotransmitter releasing, and nociceptive transmission. Here we elucidate a cryo-electron microscopy (cryo-EM) structure of the human CaV2.2 complex at resolution of 2.8 Å. This complex structure reveals how the CaV2.2, β1, and α2δ1 subunits are assembled. In our structure, the second voltage-sensing domain (VSD) is stabilized at a resting-state conformation, which is distinct from the other three VSDs of CaV2.2 as well as activated VSDs observed in previous structures of CaV channels. The structure also shows that the intracellular gate formed by S6 helices is closed, and a W-helix from the DII-III linker is determined to act as a blocking-ball that causes closed-state inactivation in CaV2.2. Collectively, our structure provides previously unseen structural insights into fundamental gating mechanisms of CaV channels.

scholarly journals The Mpl-ligand or thrombopoietin or megakaryocyte growth and differentiative factor has both direct proliferative and differentiative activities on human megakaryocyte progenitors

Blood ◽  
1995 ◽  
Vol 86 (7) ◽  
pp. 2516-2525 ◽  
Author(s):  
N Debili ◽  
F Wendling ◽  
A Katz ◽  
J Guichard ◽  
J Breton-Gorius ◽  
...  
Keyword(s):  
Ultrastructural Level ◽  
The Other ◽  
Target Cells ◽  
Humoral Factors ◽  
Biologic Activity ◽  
Accessory Cells ◽  
Transitional Cells ◽  
Limiting Dilution

Previously, it was believed that megakaryocytopoiesis was regulated by two types of humoral factors: megakaryocyte colony-stimulating factor (MK-CSF), which acts on progenitors inducing their proliferation, and thrombopoietin (TPO), a megakaryocyte(s) (MK) maturational factor that induces platelet formation. The recently cloned Mpl-ligand (Mpl-L) seems to have both properties in vivo and in vitro and has also been called TPO. However, it cannot be excluded that a part of these activities is due to a synergistic effect with growth factors present in the serum or synthesized by accessory cells. To delineate the precise TPO (Mpl-L) biologic activities, we performed serum-free cultures at limiting cell dilution. Target cells were adult human marrow CD34+CD41+ cells, which represent a highly selected population of late MK progenitor or transitional cells. Cells were purified using a flow cytometer equipped with an automatic cloning design unit. We determined that the recombinant molecule had a biologic activity that reached a plateau at 10 ng/mL. At this concentration, a linear relationship between the average MK number per well and the number of cells seeded (between 1 to 50 cells per well) was observed. At one cell per well, 60% of the wells contained a single MK at day 5 of culture. Half of these wells contained only one large MK, whereas the other half contained several MK (up to 25), demonstrating that TPO has direct proliferative biologic activity. In contrast, at limiting dilution, none of the other cytokines tested (stem cell factor [SCF], interleukin- 6 [IL-6], and erythropoietin [Epo]) were effective, whereas IL-3 showed a mild effect. However, a combination of SCF plus IL-6 plus IL-3 produced similar results as TPO alone. Addition of the other cytokines to TPO did not enhance the cloning efficiency of the CD34+CD41+ cells but increased twofold the average number of MKs per clone. MKs reached a ploidy of 32N and 64N in the presence of TPO. The mean ploidy value was approximately 6 and was not modified by addition of the other cytokines. At the ultrastructural level, a majority of the MKs showed maturational defects related to an imbalance between the synthesis of alpha-granules and demarcation membranes. However, a fraction (about 30%) had a cytoplasmic maturation that exactly mimicked that of marrow MKs. In addition, proplatelet-shedding MKs were observed in the cultures, even at limiting dilution. Such a result was not observed with any other individual cytokines, including the combination of three cytokines.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Effect of Self-stitched Double Fabric’s Properties on Tensile and Permeability Performances

2021 ◽  
pp. X
Author(s):  
R. Befru Büyükbayraktar
Keyword(s):  
Tensile Test ◽  
Tensile Properties ◽  
Confidence Level ◽  
Complex Structure ◽  
Air Permeability ◽  
The Other ◽  
Plain Weave ◽  
Bias Extension Test ◽  
Bias Extension ◽  
Better Than

The double fabrics having a complex structure are used in different areas both technically and aesthetically. In this study, tensile and air permeability properties of self-stitched double fabrics were investigated. Firstly, six different self-stitched double fabrics having the same yarn type, same settings, two different weave types, and three different stitching arrangements were designed and manufactured. Then, the tensile properties of these double fabrics were tested by applying tensile test at warp and weft directions, and bias-extension test at 45° bias direction. The effect of structural properties on tensile and air permeability results was discussed statistically. The tensile properties of self-stitched double fabrics having plain weave types are mostly better than 2/2 twill ones. The differences between tensile properties of self-stitched double fabrics generally were not found statistically significant according to stitching arrangement except the double fabric having plain weave type and higher stitching points. On the other hand, the differences between air permeability properties of all self-stitched double fabrics were found statistically significant at 95 % confidence level in terms of both stitching arrangement and weave type.

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