bluuebunny/crossref_metadata_2025_split huggingface dataset:
Different Neural Pathways Coordinate Drosophila Flight Initiations Evoked By Visual and Olfactory Stimuli
Authors: Trimarchi James R. , Schneiderman Anne M. 
Published: April 2021

ABSTRACT
To determine the role played by the giant fiber interneurons (GFs) in coordinating the jumping stages of visually elicited and olfactory-induced flight initiation we have recorded extracellularly from the cervical connective nerve during flight initiation. A spike is recorded from the cervical connective upon brain stimulation that has the same threshold as does activation of the tergotrochanteral muscle (TTM) and dorsal longitudinal muscles (DLMs). A consistent time interval occurs between the spike and activation of the TTM. Thus, the spike probably results from activity in the GFs. The time intervals between the spike and activation of the TTM during GF stimulation and visually elicited flight initiation are similar. These results suggest that the GFs coordinate the activation of the TTM and DLMs during the jumping stage of visually elicited flight initiation.
A spike is also recorded from the cervical connective during olfactory-induced flight initiations, but its shape and the time interval between it and activation of the TTM is different from that observed during GF stimulation. Although some olfactory-induced flight initiations exhibit a pattern of muscle activation indistinguishable from that evoked by GF stimulation, our results indicate that, regardless of the pattern of muscle activation, olfactory-induced flight initiations are not coordinated by the GF circuit. The stereotypic sequence and timing of activation of TTM and DLMs characteristic of the GF pathway can, therefore, be evoked by neurons other than those constituting the GF pathway.
Cholesterol Levels Explain Inverse Compensation of Membrane Order in Brush Border But Not Homeoviscous Adaptation in Basolateral Membranes from the Intestinal Epithelia of Rainbow Trout
Authors: Crockett Elizabeth L. , Hazel Jeffrey R. 
Published: April 2021

ABSTRACT
The role of cholesterol in the thermal adaptation of biological membranes is explored. Physical and chemical responses of membranes to acclimation temperature were evaluated using plasma membrane domains (basolateral and brush border) prepared from intestinal epithelia of 5- and 20 °C-acclimated rainbow trout (Oncorhynchus mykiss). Basolateral membranes (BLMs) exhibit perfect homeoviscous efficacy (indicated by fluorescence depolarization using 1,6-diphenyl-1,3,5-hexatriene), although cholesterol content does not change with acclimation temperature (molar ratios of cholesterol to phospholipid are 0.23± 0.01 from 5 °C-acclimated fish and 0.25±0.02 from 20°C-acclimated fish; mean ± S.E.M.). Reductions (greater than 30 %) in each of the two major saturated fatty acids (16:0 and 18:0), and a 42 % increase in the polyunsaturate 22:6 (n−3) are found in BLMs from fish acclimated to 5 °C compared with membranes from warm-acclimated animals, suggesting that the phospholipid acyl chain composition determines the physical properties of BLMs. In marked contrast, brush-border membranes (BBMs) display opposite trends. BBMs from 5 °C-acclimated fish are more ordered than BBMs from 20 °C-acclimated fish (inverse compensation). Cholesterol content expressed relative to protein or relative to total polar lipid (phospholipid plus glycolipid) is significantly higher in cold-than in warm-acclimated fish, and nearly so (P=0.15) relative to phospholipid (0.31±0.03 in 5 °C-acclimated animals and 0.25±0.02 in 20 °C-acclimated animals). Only minor changes in the acyl composition of BBMs are induced by temperature acclimation. These results suggest that bile, a constituent of the apical microenvironment, may impose unusual requirements for membrane order and/or stability in the brush border.
A Dorsal Light Reflex in a Squid
Authors: Preuss Thomas , Budelmann Bernd U. 
Published: April 2021

ABSTRACT
A dorsal light reflex is described in the squid Lolliguncula brevis. When illuminated from the side in visually homogeneous surroundings, a free-swimming squid rolls the dorsal side of its head and trunk 10–20 ° towards the light. With the trunk restricted in a holder, the squid rolls its head 4–5 ° towards the light; this reaction increases by about 50 % when the statocysts are bilaterally removed and increases further when the neck receptor organ is also destroyed. The results indicate a multi-modal interaction of visual, statocyst and proprioceptive inputs during postural control.
Synthesis of Stress Protein 70 (Hsp70) in Rainbow Trout (Oncorhynchus Mykiss) Red Blood Cells
Authors: Currie Suzanne , Tufts Bruce L. 
Published: April 2021

ABSTRACT
Unlike enucleated mammalian red blood cells (rbcs), the nucleated rbcs of lower vertebrates are capable of protein synthesis and may, therefore, serve as a valuable model to investigate the adaptive significance of stress protein synthesis in cells. This study examined the synthesis of stress protein 70 (Hsp70) in rbcs of the temperature-sensitive rainbow trout Oncorhynchus mykiss in response to heat shock and anoxia. Through western blot analysis, we have demonstrated that rainbow trout rbcs synthesize Hsp70 both constitutively and in response to an increase in temperature. Radioisotopic labelling experiments indicated that the temperature at which Hsp70 synthesis was induced in fish acclimated to 10 °C was between 20 and 25 °C. Actinomycin D blocked de novo Hsp70 synthesis, implying that synthesis of Hsp70 is regulated at the level of transcription in rainbow trout rbcs. Since trout rbcs rely heavily on aerobic metabolism, but may also experience very low oxygen levels within the circulation, we also examined the relative importance of (1) anoxia as a stimulus for Hsp70 synthesis and (2) oxygen as a requirement for protein synthesis under control and heat-shock conditions. We found that trout rbcs were capable of protein synthesis during 2 h of anoxia, but did not increase Hsp70 synthesis. Moreover, rbcs subjected to combined anoxia and heat shock exhibited increases in Hsp70 synthesis that were similar in magnitude to those in cells exposed to heat shock alone. The latter results suggest that rainbow trout rbcs are (1) able to synthesize non-stress proteins during anoxia, (2) capable of tolerating periods of reduced oxygen availability without increased synthesis of stress proteins and (3) able to maintain the integrity of their heat-shock response even during periods of anoxia.
Species-Specific Action And Distribution Of Tachykinin-Related Peptides In The Foregut Of The Cockroaches Leucophaea Maderae And Periplaneta Americana
Authors: Nässel Dick R. , Eckert Manfred , Muren J. Eric , Penzlin Heinz 
Published: April 2021

ABSTRACT
Nine tachykinin-related peptides (TRPs) have been isolated from the brain and intestine of the cockroach Leucophaea maderae. In the present investigation, two of the nine TRPs, LemTRP 1 and 5, were tested for their ability to stimulate contractions in the foregut of the cockroaches L. maderae and Periplaneta americana in vitro. The two LemTRPs and the related locust peptide locustatachykinin I (LomTK I) induced contractions in the foregut of P. americana in a dose-dependent manner, but had no myostimulatory action in L. maderae. A half-maximal response for the LemTRPs and LomTK I was obtained at 5×10−9 mol l−1. In both species, the neuropeptide proctolin stimulated foregut contractions. Using an antiserum to LomTK I, we demonstrated that in both species there are LomTK-like-immunoreactive (LomTK-LI) cell bodies and fibers within the ganglia and nerves of the stomatogastric nervous system. However, correlated with the species-specific action of the TRPs, we found efferent LomTK-LI nerve fibers supplying muscle fibers in the foregut of P. americana, but not in L. maderae. In both cockroach species, there is a rich supply of proctolin-immunoreactive fibers to the foregut muscle. Some of the LomTK-LI fibers supplying the P. americana foregut muscle contain co-localized proctolin immunoreactivity. These fibers appear to be derived from a large cell body in the frontal ganglion which also displayed co-localized immunoreactivities. Since TRP-containing neurons are restricted to the nerves and ganglia of the stomatogastric nervous system both in P. americana and L. maderae, TRPs may be involved in the control of foregut movements in both species, but in P. americana the control may be more complex with the additional peripherally projecting LomTK-LI neurons.
Arousal Shifts in Quiescent Locusts
Authors: Schuppe H. , Burrows M. 
Published: April 2021

ABSTRACT
Locusts are usually quiescent at night, but this state can be interrupted by spontaneous periods of motor activity, or arousals, that can also be induced by exposure to light stimuli. To investigate whether repeated arousing stimulation has any lasting effect on behaviour, locusts were confronted at night with a series of 1 s light stimuli. Groups of three stimuli at intervals of 60 s were repeated 11 times at 10 min intervals during the first experimental night, and three stimuli at intervals of 90 s were repeated at 15 min intervals during the next night. Arousals and the effects of stimulation were monitored as changes in the spike activity of muscles in the basal part (the scapus) of the right antenna. In the early part of the night preceding the presentation of the light stimuli, neither 60 s nor 90 s periods were present as significant peaks in spontaneous changes in spike activity. The initial stimulus of a series evoked an arousal response that habituated on repetition of the stimulus. The end of the series of stimuli was followed by changes in spike activity that tended to have the same periodicity as the preceding stimuli. Furthermore, a single light stimulus at the end of the night evoked changes in spike activity that again tended to have the same periodicity as the preceding entraining stimuli. Repeated stimulation may therefore establish a memory trace for the period of stimulation that can be recalled either spontaneously or by the application of an appropriate external stimulus.
Neither Respiration Nor Cytochrome c Oxidase Affects Mitochondrial Morphology in Saccharomyces Cerevisiae
Authors: Church Cynthia , Poyton Robert O. 
Published: April 2021

ABSTRACT
Previous studies have reported that mitochondrial morphology and volume in yeast cells are linked to cellular respiratory capacity. These studies revealed that mitochondrial morphology in glucose-repressed or anaerobically grown cells, which lack or have reduced levels of respiration, is different from that in fully respiring cells. Although both oxygen deprivation and glucose repression decrease the levels of respiratory chain proteins, they decrease the expression of many non-mitochondrial proteins as well, making it difficult to determine whether it is a defect in respiration or something else that effects mitochondrial morphology. To determine whether mitochondrial morphology is dependent on respiration per se, we used a strain with a null mutation in PET100, a nuclear gene that is specifically required for the assembly of cytochrome c oxidase. Although this strain lacks respiration, the mitochondrial morphology and volumes are both comparable to those found in its respiration-proficient parent. These findings indicate that respiration is not involved in the establishment or maintenance of yeast mitochondrial morphology, and that the previously observed effects of oxygen availability and glucose repression on mitochondrial morphology are not exerted through the respiratory chain. By applying the principle of symmorphosis to these findings, we conclude that the shape and size of the mitochondrial reticulum found in respiring yeast cells is maintained for reasons other than respiration.
The Concentration-Dependence of Crf-Like Diuretic Peptide: Mechanisms of Action
Authors: Clark Thomas M. , Hayes Timothy K. , Holman G. M. , Beyenbach Klaus W. 
Published: April 2021

ABSTRACT
The mechanism of action of synthetic CCRF-DP, the corticotropin-releasing factor (CRF)-related diuretic peptide of the salt marsh mosquito Culex salinarius, was investigated in isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti. A low concentration of CCRF-DP (10−9 mol l−1) caused a small but insignificant increase in transepithelial secretion of NaCl and fluid, but significantly reduced transepithelial voltage and resistance without a change in short-circuit current, pointing to the stimulation of passive Cl− transport through the paracellular pathway as the principal mechanism of a mild diuresis. Significant changes in voltage and resistance but not in short-circuit current were duplicated by the ionophore A23187 (0.4 μmol l−1), suggesting Ca2+ as a second messenger at 10−9 mol l−1 CCRF-DP. A high concentration of CCRF-DP (10−7 mol l−1) significantly increased transepithelial secretion of NaCl and fluid and significantly increased short-circuit current, pointing to the stimulation of active Na+ transport through the transcellular pathway as the mechanism of a strong diuresis. This effect was mimicked by dibutyryl-cAMP, suggesting cAMP as a second messenger at 10−7 mol l−1 CCRF-DP. Dibutyryl-cGMP had no effects. These results suggest dose-dependent, receptor-mediated effects of CCRF-DP that target discrete transport pathways via discrete second messengers: low concentrations of CCRF-DP cause a mild diuresis, apparently via Ca2+-mediated effects on paracellular Cl− transport, and high concentrations cause a strong diuresis via cAMP-mediated effects on active transcellular Na+ transport in addition to the effects on the paracellular pathway.
Confocal Laser Scanning and Electron Microscopical Studies on Osmoregulatory Epithelia in the Branchial Cavity of the Lobster Homarus Gammarus
Authors: Haond C. , Flik G. , Charmantier G. 
Published: April 2021

ABSTRACT
The adult lobster Homarus gammarus is a weak hyper-regulator at low salinity. The objective of this study was to locate the ion-transporting tissues in the branchial chamber of this species, using electron microscopy and confocal laser scanning microscopy with a fluorescent vital stain for mitochondria, DASPMI, which is widely used to locate mitochondria-rich cells in ion-transporting epithelia of fish. A thick mitochondria-rich epithelium is present on the inner side of the branchiostegite and over the entire surface of the epipodites. Ultrastructural observations confirm that this tissue has features typical of an ion-transporting epithelium. When the lobster is transferred to low salinity, these epithelia undergo marked ultrastructural changes, such as an increase in thickness related to the development of basolateral infoldings, the appearance of numerous vesicles and an increase in height of the apical microvilli. In the gills, the branchial filaments are lined by a thin and poorly differentiated epithelium, containing numerous mitochondria; no significant ultrastructural changes were observed in the gills of animals acclimated to low salinity. In summary, in H. gammarus, no evidence of osmoregulatory structures was found in the gills. Differentiated ion-transporting epithelia are present in the branchial cavity, on the inner side of the branchiostegite and on the epipodites; these organs are probably involved in osmoregulation.
Long-Term Adaptation of Ca2+-Dependent Behaviour in Paramecium Tetraurelia
Authors: Preston Robin R. , Hammond Jocelyn A. 
Published: April 2021

ABSTRACT
Prolonged exposure to KCl has long been recognized to modify swimming behaviour in Paramecium tetraurelia, a phenomenon known as ‘adaptation’. In this study, we have investigated behavioural adaptation systematically. A 24 h exposure to 30 mmol l−1 KCl deprived cells of the ability to respond behaviourally to two established chemoeffectors. We also explored the effects of 30 mmol l−1 KCl on the duration of backward swimming induced by Ba2+ and Mg2+. A brief (60 min) exposure prevented cells from swimming backwards in response to either cation, but recovery was rapid (&lt;60 min) following a return to control medium. Prolonged (48 h) exposure caused a more persistent loss of response to Ba2+, so that several hours was now required for recovery. Surprisingly, responses to Mg2+ reappeared during 6–8 h in KCl, with backward swimming durations increasing to more than 300 % of control values after 26 h. Thus, we can distinguish two phases to adaptation. The short-term phase is characterized by an inability to respond behaviourally to most stimuli and might be adequately explained in terms of Ca2+ channel inactivation and K+-induced shifts in membrane potential. The long-term phase is characterized by enhanced responses to Mg2+ (and also to Na+), suggesting that a more extensive reprogramming of membrane excitability may occur during chronic K+-induced depolarization.
Digging in Sand Crabs: Coordination of Joints in Individual Legs
Authors: Faulkes Zen , Paul Dorothy H. 
Published: April 2021

ABSTRACT
Sand crabs use their multi-jointed legs to dig into sand. Combined movement and electromyogram (EMG) analyses showed that the pattern of intra-leg coordination in the legs of two sand crabs of different families (Blepharipoda occidentalis and Emerita analoga) is similar in legs 2 and 3, but very different in leg 4. For example, the sequence of proximal joint movements in legs 2 and 3 is elevation, retraction, depression and protraction (similar to backward walking in most decapods), but the sequence of proximal joint movements in leg 4 is elevation, protraction, retraction and depression (similar to forward walking). The synergies are the same during leg movements in sea water and in sand, suggesting that the same motor programme is used in both situations. At the transition from sea water into sand, however, both the frequency and amplitude of the EMG potentials increase, and the phasing of the motor output to leg 2 (and presumably leg 3) changes from proportional (both power and return strokes co-vary with period) to return stroke constant (power strokes co-vary much more with period than do return strokes). The motor output to leg 4 remains intermediate between proportional and return stroke constant in sea water and in sand. On the basis of the segmental specialisation of the motor patterns for the legs, we hypothesize that sand crab digging may be an evolutionary mosaic of disparate ancestral locomotor behaviours.
Burrow Ventilation in the Tube-Dwelling Shrimp Callianassa Subterranea (Decapoda: Thalassinidea):I. Morphology and Motion of the Pleopods, Uropods and Telson
Authors: Stamhuis Eize J. , Videler John J. 
Published: April 2021

ABSTRACT
The morphology of the pleopods, uropods and telson of the tube-dwelling shrimp Callianassa subterranea have been studied using dissection microscopy and scanning electron microscopy. The kinematics of these appendages were examined by motion analysis of macro-video recordings of ventilating shrimps in transparent artificial burrows. The pleopods show the usual crustacean biramous anatomy, but all segments are rostro-caudally flattened. The protopodite bears a triangular medially oriented endopodite and a scoop-shaped exopodite. The contralateral endopodites are linked by the appendix interna, ensuring a perfect phase relationship between contralateral pleopods. The outer rims of the exopodites are fringed with long fern-leaf-like plumose setae bearing flattened setules. These setae have very mobile joints and can be turned caudally. The slits between contralateral endopodites have rims of leaf-like setae as well. Setae of the same leaf-like type fringe the uropods, but these are non-motile. The telson has a narrow fringe of leaf-like setae, locally interrupted by long mechanoreceptory setae.
A shrimp, wandering through the burrow or resting, holds its pleopods against the abdomen with the exopodites and their setal fringes retracted medially. The uropods are folded medially as well, probably to reduce the shrimp’s drag. During ventilation, the uropods are extended against the tube wall, leaving only a small opening for flow ventral from the telson, and the pleopods beat at a frequency of approximately 1 Hz (0.9±0.2 Hz). Fourier analysis of pleopod kinematics showed that the motion pattern of the first flow-generating pleopod pair (PP1) consisted mainly of the first harmonic (75 %) and to a lesser extent of the third harmonic (20 %), resulting in almost perfect sinusoidal motion. The motion patterns of PP2 and PP3 could be modelled by assigning pure sinusoids with a 120 ° phase shift and a rostro-caudal ranking to the three pairs of pleopods.
Burrow Ventilation in the Tube-Dwelling Shrimp Callianassa Subterranea (Decapoda: Thalassinidea):II. The Flow in the Vicinity of the Shrimp and the Energetic Advantages of a Laminar Non-Pulsating Ventilation Current
Authors: Stamhuis Eize J. , Videler John J. 
Published: April 2021

ABSTRACT
The ventilation flow in the vicinity of the pleopod-pumping thalassinid shrimp Callianassa subterranea in an artificial transparent burrow has been mapped using particle image velocimetry. The flow in the tube in front of the shrimp was unidirectional, laminar and steady, with a parabolic cross-sectional velocity profile. The mean flow velocity was 2.0±0.1 mm s−1. The flow passed the thorax of the shrimp along the lateral and ventral sides. Ventral to the abdomen, the flow was dominated by the metachronally oscillating pleopods. The water around a pleopod is accelerated caudally and ventrally during the power stroke, and decelerated to a much lesser extent during the recovery stroke owing to a reduction in pleopod area. On average, the flow ventral to the abdomen converged towards the small opening underneath the telson, simultaneously increasing in velocity. A jet with a core velocity of 18–20 mm s−1 entered the area behind the shrimp from underneath the telson. This caused a separation zone with backflow caudal to the telson. Owing to the high rates of shear, the jet diverged and re-adjusted to a parabolic cross-sectional profile within 1–2 body lengths behind the shrimp, showing no traces of pulsation. The metachronal pleopod movements in combination with the increase in flow velocity at the constriction in the tube caused by the uropods and the telson probably prevented pulsation. The energetic consequences of pulsating and steady flows in combination with several tube configurations were evaluated. The results suggested that, by constricting the tube and keeping the flow steady, C. subterranea saves on ventilation costs by a factor of up to six compared with oscillatory flow in a tube without the tail-fan constriction.