bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Tubular Network Associated with the Brush-Border Surface of the Aedes Aegypti Midgut: Implications for Pathogen Transmission by Mosquitoes
Authors: Zieler Helge , Garon Claude F. , Fischer Elizabeth R. , Shahabuddin Mohammed 
Published: April 2021

ABSTRACT
The mosquito Aedes aegypti is capable of transmitting a variety of pathogens to man and to other vertebrates. The midgut of this insect has been well-studied both as the tissue where the first contact occurs between ingested pathogens and the insect host, and as a model system for blood meal digestion in blood-sucking insects. To understand better the nature of the midgut surface encountered by parasites or viruses, we used scanning electron microscopy to identify the most prominent structures and cell morphologies on the luminal midgut surface. The luminal side of the midgut is a complex and layered set of structures. The microvilli that are found on most, but not all, cells are covered by a network of fine strands that we have termed the microvilli-associated network (MN). The MN strands are membranous, as shown by a membrane bilayer visible in cross sections of MN strands at high magnification in transmission electron micrographs. The MN is found in blood-fed as well as unfed mosquitoes and is not affected by chitinase treatment, suggesting that it is not related to the chitinous peritrophic membrane that is formed only after blood feeding. The cells in the midgut epithelium have two distinct morphologies: the predominant cell type is densely covered with microvilli, while cells with fewer microvilli are found interspersed throughout the midgut. We used lectins to probe for the presence of carbohydrates on the midgut surface. A large number of lectins bind to the luminal midgut surface, suggesting that a variety of sugar linkages are present on the structures visualized by electron microscopy. Some of these lectins partially block attachment of malaria ookinetes to the midgut surface in vitro. Thus, the mosquito midgut epithelium, like the lining of mammalian intestines, is complex, composed of a variety of cell types and extensively covered with surface carbohydrate that may play a role in pathogen attachment.
The Scaling of Carbon Dioxide Release and Respiratory Water Loss in Flying Fruit Flies (Drosophila Spp.)
Authors: Lehmann Fritz-Olaf , Dickinson Michael H. , Staunton Jocelyn 
Published: April 2021

ABSTRACT
By simultaneously measuring carbon dioxide release, water loss and flight force in several species of fruit flies in the genus Drosophila, we have investigated respiration and respiratory transpiration during elevated locomotor activity. We presented tethered flying flies with moving visual stimuli in a virtual flight arena, which induced them to vary both flight force and energetic output. In response to the visual motion, the flies altered their energetic output as measured by changes in carbon dioxide release and concomitant changes in respiratory water loss. We examined the effect of absolute body size on respiration and transpiration by studying four different-sized species of fruit flies. In resting flies, body-mass-specific CO2 release and water loss tend to decrease more rapidly with size than predicted according to simple allometric relationships. During flight, the mass-specific metabolic rate decreases with increasing body size with an allometric exponent of −0.22, which is slightly lower than the scaling exponents found in other flying insects. In contrast, the mass-specific rate of water loss appears to be proportionately greater in small animals than can be explained by a simple allometric model for spiracular transpiration. Because fractional water content does not change significantly with increasing body size, the smallest species face not only larger mass-specific energetic expenditures during flight but also a higher risk of desiccation than their larger relatives. Fruit flies lower their desiccation risk by replenishing up to 75 % of the lost bulk water by metabolic water production, which significantly lowers the risk of desiccation for animals flying under xeric environmental conditions.
Dorsal Unpaired Median Neurones in the Insect Central Nervous System: Towards a Better Understanding of the Ionic Mechanisms Underlying Spontaneous Electrical Activity
Authors: Grolleau Françoise , Lapied Bruno 
Published: April 2021

ABSTRACT
The efferent dorsal unpaired median (DUM) neurones, which include octopaminergic neurones, are among the most intensively studied neurones in the insect central nervous system. They differ from other insect neurones in generating endogenous spontaneous overshooting action potentials. The second half of the 1980s is certain to be considered a turning point in the study of the ion channels underlying the electrical activity of DUM neurones. Recent advances made using the patch-clamp technique have stimulated an increasing interest in the understanding of the biophysical properties of both voltage-dependent and voltage-independent ion channels. Patch-clamp studies of DUM neurones in cell culture demonstrate that these neurones express a wide variety of ion channels. At least five different types of K+ channel have been identified: inward rectifier, delayed rectifier and A-like channels as well as Ca2+- and Na+-activated K+ channels. Moreover, besides voltage-dependent Na+ and Ca2+-sensitive Cl− channels, DUM neurones also express four types of Ca2+ channel distinguished on the basis of their kinetics, voltage range of activation and pharmacological profile. Finally, two distinct resting Ca2+ and Na+ channels have been shown to be involved in maintaining the membrane potential and in regulating the firing pattern. In this review, we have also attempted critically to evaluate these existing ion channels with regard to their specific functions in the generation of the different phases of the spontaneous electrical activity of the DUM neurone.
Object Fixation by The Blowfly During Tethered Flight in a Simulated Three-Dimensional Environment
Authors: Kimmerle Bernd , Eickermann Judith , Egelhaaf Martin 
Published: April 2021

ABSTRACT
The ability of flies to detect and fixate objects moving relative to their background was investigated in a flight simulator during translational tethered flight. The fly experienced optic flow that depended on its own actions and reactions in a similar way as in free-flight (closed-loop) conditions. Fixation of an object required turning responses towards it. The simulated distances between the fly, object and background were varied systematically by changing the velocities with which the object and the background pattern moved from the frontal to the back part of the fly’s visual field. Fixation responses were only elicited when the object was simulated to be closer than the background. The fly’s fixation performance was better with close than with more distant objects. Since, under many stimulus conditions, fixation responses were either elicited or entirely failed to be elicited, it is concluded that object fixation behaviour is gated in the visuo-motor pathway.
Horizontal Flight of A Swallow (Hirundo Rustica) Observed In A Wind Tunnel, With A New Method for Directly Measuring Mechanical Power
Authors: Pennycuick C. J. , Hedenström Anders , Rosén Mikael 
Published: April 2021

ABSTRACT
A swallow flying in the Lund wind tunnel was observed from the side and from behind, by two synchronised high-speed video cameras. The side-view camera provided a record of the vertical position of a white mark, applied to the feathers behind and below the eye, from which the vertical acceleration was obtained. The rear-view camera provided measurements of the mean angle of the left and right humeri above horizontal. From these data, the force acting on the body, the moment applied by each pectoralis muscle to the humerus and the rotation of the humerus were estimated and used to analyse the time course of a number of variables, including the work done by the muscles in each wing beat. The average mechanical power turned out to be more than that predicted on the basis of current estimates of body drag coefficient and profile power ratio, possibly because the bird was not flying steadily in a minimum-drag configuration. We hope to develop the method further by correlating the mechanical measurements with observations of the vortex wake and to apply it to birds that have been conditioned to hold a constant position in the test section.
The Macrophage in Acute Neural Injury: Changes in Cell Numbers Over time and Levels of Cytokine Production in Mammalian Central and Peripheral Nervous Systems
Authors: Leskovar Alenka , Moriarty Loren J. , Turek John J. , Schoenlein Ingrid A. , Borgens Richard B. 
Published: April 2021

ABSTRACT
We evaluated the timing and density of ED-1-positive macrophage accumulation (ED 1 is the primary antibody for the macrophage) and measured cytokine production by macrophages in standardized compression injuries to the spinal cord and sciatic nerves of individual rats 3, 5, 10 and 21 days post-injury. The actual site of mechanical damage to the nervous tissue, and a more distant site where Wallerian degeneration had occurred, were evaluated in both the peripheral nervous system (PNS) and the central nervous system (CNS) at these time points. The initial accumulation of activated macrophages was similar at both the central and peripheral sites of damage. Subsequently, macrophage densities at all locations studied were statistically significantly higher in the spinal cord than in the sciatic nerve at every time point but one. The peak concentrations of three cytokines, tumor necrosis factor α (TNFα), interleukin-1 (IL-1) and interleukin-6 (IL-6), appeared earlier and were statistically significantly higher in injured spinal cord than in injured sciatic nerve. We discuss the meaning of these data relative to the known differences in the reparative responses of the PNS and CNS to injury.
Central Circuitry in the Jellyfish Aglantha Digitale: III. the Rootlet and Pacemaker Systems
Authors: Mackie G. O. , Meech R. W. 
Published: April 2021

ABSTRACT
Tactile stimulation of the subumbrella of Aglantha digitale was found to evoke an escape swimming response similar to that evoked by stimulation of the outer surfaces of the margin but that does not involve the ring giant axon. Evidence is presented that conduction around the margin takes place via an interconnected system of rootlet interneurones. Confocal microscopy of carboxyfluorescein-filled axons showed that the rootlet neurones run out from the bases of the motor giant axons within the inner nerve ring and come into close contact with those of the neighbouring motor giant axons on either side. Transmission between the rootlet neurones has the properties of chemical synaptic transmission. A distinct type of fast excitatory postsynaptic potential (rootlet PSP) was recorded in motor giant axons following stimulation of nearby axons in 3–5 mmol l−1 Mn2+, which lowered the PSP below spike threshold. Immune labelling with anti-syntaxin 1 showed structures tentatively identified as synapses in the inner nerve ring, including some on the rootlet neurones. Neuromuscular junctions were not labelled.
A secondary consequence of stimulating motor giant axons was the triggering of events in the pacemaker system. Triggering was blocked in 105 mmol l−1 Mg2+, indicating a synaptic link. Activity in the pacemaker system led indirectly to tentacle contractions (as described in earlier papers in this series), but the contractions were not as sudden or as violent as those seen when escape swimming was mediated by the ring giant axon. Events triggered in the pacemaker system fed back into the motor giants, producing postsynaptic potentials that appeared as humps in the spike after-potential. The conduction velocity of events propagating in the relay system was increased when the rootlet pathway was simultaneously excited (piggyback effect).
With the addition of the rootlet pathway, the number of identified systems concerned with locomotion, feeding and tentacle contractions comes to fourteen, and the list is probably nearly complete.
Ion Channel Activity From The Midgut Brush-Border Membrane Of Gypsy Moth (Lymantria Dispar) Larvae
Authors: Peyronnet Olivier , Vachon Vincent , Schwartz Jean-Louis , Laprade Raynald 
Published: April 2021

ABSTRACT
Ion channels from the midgut apical membrane of gypsy moth (Lymantria dispar) larvae were studied following mechanical fusion of brush-border membrane vesicles with planar phospholipid bilayer membranes. In symmetrical 300 mmol l−1 KCl (pH 9.0), nine different channels with conductances ranging from 27 to 795 pS and linear current/voltage relationships were resolved. In the presence of a KCl gradient across the bilayer (450 mmol l−1cis/150 mmol l−1trans), 11 different conductance levels ranging from 16 to 850 pS were detected. The channels were slightly cationic: the zero-current reversal potential was shifted by −5 mV to −21 mV compared with symmetrical KCl conditions, corresponding to pK/pCl permeability ratios of 1.5–8.0. Most channels were neither voltage-dependent nor Ca2+-sensitive and displayed complex gating kinetics. Addition of Ba2+ or Cs+ to both sides of the bilayer had little effect on channel activity, but fewer distinct channels were observed when KCl was replaced by potassium gluconate, suggesting an effect of Cl− on channel activity. A reduced number of channels was also detected when KCl was replaced by N-methyl-D-glucamine-HCl. Under asymmetrical N-methyl-D-glucamine-HCl conditions, only anionic channels were observed. They exhibited current rectification (35 pS at negative voltages and 81 pS at positive voltages) and were strongly voltage-dependent.
Adhesion Measured on the Attachment Pads of Tettigonia Viridissima (Orthoptera, Insecta)
Authors: Jiao Yuekan , Gorb Stanislav , Scherge Matthias 
Published: April 2021

ABSTRACT
The tarsi of the cricket Tettigonia viridissima bear flexible attachment pads that are able to deform, replicating the profile of a surface to which they are apposed. This attachment system is supplemented by a secretion produced by epidermal cells and transported onto the surface of the pad through the pore canals of the pad cuticle. This study shows that the secretion alone is necessary, but not sufficient, for adhesion. To account for the full adhesive force, the deformation of the pad and the resulting changes in contact area were considered. In two series of experiments, the adhesive properties of the secretion and the adhesion of the whole pad were measured using a force tester, the sensitivity of which ranged from micronewtons to centinewtons.
The adhesive forces of the secretion measured between a smooth sapphire ball with a diameter of 1.47 mm and a flat silicon surface ranged from 0.1 to 0.6 mN. In a control experiment on the silicon surface without secretion, no adhesive force was measured. There was no dependence of the adhesive force on the applied compressive force.
When an intact pad was pulled off a flat silicon surface, the adhesive force increased with increasing applied compressive force, but it did not increase further once the applied force exceeded a certain value. The saturated adhesive force, ranging from 0.7 to 1.2 mN, was obtained at applied forces of 0.7–1.5 mN. The hemispherical surface of the pad had a larger contact area and demonstrated greater adhesion under a larger applied force. Adhesion became saturated when a pad was deformed such that contact area was maximal. The tenacity (the adhesive force per unit area) was 1.7–2.2 mN mm−2.
Control Of Epithelial Cl− Secretion By Basolateral Osmolality In The Euryhaline Teleost Fundulus Heteroclitus
Authors: Marshall W. S. , Bryson S. E. , Luby T. 
Published: April 2021

ABSTRACT
Euryhaline teleost fish adapt rapidly to salinity change and reduce their rate of ion secretion on entry to fresh water. Killifish (Fundulus heteroclitus) transferred from full-strength sea water to fresh water showed large reductions in plasma [Na+] and osmolality at 6 h which were corrected by 24 h. To mimic this in vitro, a hypotonic shock of 20–70 mosmol kg−1 was applied on the basolateral side of opercular epithelia. This hypotonic shock reversibly reduced the short-circuit current (Isc, equivalent to the rate of secretion of Cl−) in a dose-dependent fashion, with a 40 mosmol kg−1 hypotonic shock reducing Isc by 58±4.6 % in 40 min. Similar reductions in [NaCl], but with added mannitol to maintain osmolality, were without effect, indicating that the effect was purely osmotic. Hypotonic inhibition of Isc was accompanied by reductions in epithelial conductance (Gt) but no significant change in transepithelial potential (Vt). The hypotonic inhibition was apparently not Ca2+-mediated because Ca2+-depleted salines, thapsigargin and ionomycin all failed to block the reduction in Isc produced by hypotonic shock. The inhibition was not mediated via a reduction in intracellular cyclic AMP level because cyclic AMP levels, measured by radioimmunoassay, were unchanged by hypotonic shock and by 1.0 μmol l−1 clonidine (which inhibits Isc by changing intracellular [Ca2+]) but were increased markedly by 1.0 μmol l−1 isoproterenol, a positive control. The protein tyrosine kinase inhibitor genistein (100 μmol l−1), but not its inactive analogue daidzein, inhibited Isc in normal osmolality but produced a stimulation of Isc after hypotonic shock (and after clonidine treatment). The inhibitory effects of genistein and hypotonicity were not additive, suggesting that the same portion of the Isc was inhibited by both treatments. These data are consistent with a model for Cl− transport regulation involving tyrosine phosphorylation in cell-swelling-induced inhibition of Cl− secretion when euryhaline teleosts adapt to fresh water.
Chloride Conductance Across Toad Skin: Effects of Ionic Acclimations and Cyclic Amp and Relationship to Mitochondria-Rich Cell Density
Authors: Rozman A. , Gabbay S. , Katz U. 
Published: April 2021

ABSTRACT
The anionic conductance across toad (Bufo viridis) skin was studied using the voltage-clamp technique following long-term (more than 10 days) acclimation to NaCl and KCl solutions. The non-specific baseline conductance was approximately 0.6 mS cm−2 and was similar in skins from all acclimation conditions. The voltage-activated Cl− conductance (GCl) was maximal in skins from distilled-water- and KCl-acclimated toads (&gt;3 mS cm−2) and was greatly reduced following acclimation to NaCl solutions. Cyclic AMP (EC50=13 μmol l−1) and isobutylmethyl xanthine (IBMX) (EC50=69 μmol l−1) exerted different effects on the activated conductance. IBMX only sensitized the activated conductance, whereas cyclic AMP (CPTcAMP) at high concentrations induced an increase in anionic conductance that was insensitive to electrical potential. Furthermore, external Cl− was not required for the stimulatory effect of cyclic AMP, and the conductive pathway had low selectivity. The effects of the two agonists were reversible and depended on the acclimation conditions. Following electrical measurements, the skin of the toads was removed and stained with silver to measure mitochondria-rich cell density (Dmrc). There was no correlation between Dmrc and Cl− conductance in the present study.
Selective Heating of Vibrissal Follicles In Seals (Phoca Vitulina) and Dolphins (Sotalia Fluviatilis Guianensis)
Authors: Mauck Björn , Eysel Ulf , Dehnhardt Guido 
Published: April 2021

ABSTRACT
The thermal characteristics of the mystacial vibrissae of harbour seals (Phoca vitulina) and of the follicle crypts on the rostrum of the dolphin Sotalia fluviatilis guianensis were measured using an infrared imaging system. Thermograms demonstrate that, in both species, single vibrissal follicles are clearly defined units of high thermal radiation, indicating a separate blood supply to these cutaneous structures. It is suggested that the high surface temperatures measured in the area of the mouth of the follicles is a function of the sinus system. In seals and dolphins, surface temperature gradually decreased with increasing distance from the centre of a follicle, indicating heat conduction from the sinus system via the follicle capsule to adjacent tissues. It is suggested that the follicular sinus system is a thermoregulatory structure responsible for the maintenance of high tactile sensitivity at the extremely low ambient temperatures demonstrated for the vibrissal system of seals. The vibrissal follicles of odontocetes have been described as vestigial structures, but the thermograms obtained in the present study provide the first evidence that, in Sotalia fluviatilis, the follicles possess a well-developed sinus system, suggesting that they are part of a functional mechanosensory system.
Size Matters: Ontogenetic Variation in the Three-Dimensional Kinematics of Steady-Speed Locomotion in the Lizard Dipsosaurus Dorsalis
Authors: Irschick Duncan J. , Jayne Bruce C. 
Published: April 2021

ABSTRACT
Although many studies have investigated how locomotor capacities change with size, few studies have examined whether different-sized individuals within a species have similar kinematics during locomotion. We quantified the skeletal limb morphology and the three-dimensional kinematics of the hindlimb of four sizes (4–66 g) of the lizard Dipsosaurus dorsalis moving steadily at both the walk–run transition (50 % duty factor) and at a moderately fast speed of 250 cm s−1. We used analyses of variance to test whether limb movements changed with size and to determine whether size and speed had interactive effects on kinematics. The disproportionately long hindlimbs of smaller lizards partly contributed to their relatively greater (i.e. adjusted by snout–vent length) values of linear kinematic variables. Both relative linear and angular kinematics changed significantly with both size and speed, both of which had widespread interactive effects. By having more extension of the knee and ankle joints, and thus a relatively higher hip height during stance, the slow-speed movements of small lizards displayed some of the characteristics of the fast-speed movements in larger lizards. Further, approximately one-fifth and two-fifths of the strides of the two smallest size classes were digitigrade at the lower and higher speeds, respectively, whereas the two largest size classes always had a plantigrade foot posture. Some of the most striking effects of size on kinematics were most evident at the lower of the two speeds. Unlike interspecific studies, which show that the limbs often become more crouched with decreased size, the more extended limbs of smaller lizards in this study suggest that variation in size alone cannot be the causal reason for differences in limb posture.
Terrestrial Locomotion in the Black-Billed Magpie: Kinematic Analysis of Walking, Running and Out-of-Phase Hopping
Authors: Verstappen Myriam , Aerts Peter , Damme Raoul Van 
Published: April 2021

ABSTRACT
The inter-limb kinematic patterns of walking, running and out-of-phase hopping in black-billed magpies (Pica pica) were studied using high-speed video recordings. The flexion/extension patterns of the joints were similar between the gait types, suggesting that the within-leg control of the angular excursions is similar. This result is further supported by the fact that running and hopping are alternative gaits at speeds higher than walking; however, magpies show a preference for hopping. Moreover, only small differences occur between the kinematic patterns of the two limbs during out-of-phase hopping, during which the legs are believed to have different functions. The hindlimb kinematic patterns of magpies are like those of other flying and more terrestrial bird species; however, striking differences are found in comparison with humans at the level of the internal angles. This is probably due to the differences in the morphology and configuration of their legs.