bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effector caspases are dispensable for the early nuclear morphological changes during chemical-induced apoptosis
Authors: Johnson V. L. , Ko S. C. W. , Holmstrom T. H. , Eriksson J. E. , Chow S. C. 
Published: April 2021

ABSTRACT
Nuclear morphological changes during apoptosis are very distinct and effector caspases have been implicated to play a central role in these processes. To investigate this in greater detail we examined the effect of blocking caspase activity and its activation on the nuclear morphological change in Jurkat T cells undergoing apoptosis after staurosporine treatment. In the presence of caspase inhibitors, like benzyloxycarbonyl-Val-Ala-Asp fluoro-methylketone (z-VAD-FMK), N-acetyl Tyr-Val-Ala-Asp chloromethylketone (Ac-YVAD-CMK) and benzyloxy-carbonyl-Asp-Glu-Val-Asp (OMe) fluoromethylketone (z-DEVD-FMK), staurosporine-treated Jurkat cells displayed a nuclear morphological change distinct from that of normal and apoptotic cells. This nuclear morphological change is an early event, characterised by convoluted nuclei with cavitations, and clumps of chromatin abutting to inner regions of the nuclear envelope between the nuclear pores. Both the nuclear envelope and endoplasmic reticulum were grossly dilated. This pre-apoptotic nuclear change precedes the externalisation of phosphatidylserine, chromatin condensation and DNA laddering, and can be dissociated from the formation of high molecular weight DNA fragments and cell shrinkage. Although cytochrome c efflux from the mitochondria and the processing of caspase-3 were observed in Jurkat cells with pre-apoptotic nuclear morphology, caspase-2, -6, -7 and -8 were not activated. In the presence of z-DEVD-FMK or Ac-YVAD-CMK, caspase-3 was processed to both the p17 and p20 fragments in staurosporine-treated cells, but only to p20 fragment in the presence of z-VAD-FMK. However, the caspase-3 substrate, poly(ADP ribose) polymerase was not cleaved in the presence of z-VAD-FMK, despite &gt;70% of the cells have pre-apoptotic nuclei. In addition, caspase-3 null MCF-7 cells also undergo pre-apoptotic nuclear change when treated with staurosporine in the presence of caspase inhibitors, indicating that caspase-3 is not required for the early nuclear morphological change in cells undergoing apoptosis. Although cell death in staurosporine-treated Jurkat cells was markedly delayed, they eventually die without discernible downstream apoptotic features. Other apoptotic stimuli like etoposide and the heavy metal chelator, N,N,N’,N’-tetrakis (2-pyridylmethyl) ethylenediamine also induced this nuclear morphological change in Jurkat cells in the presence of z-VAD-FMK. In summary, the effector caspases are not involved in early nuclear morphological change, which precedes the conventional hallmark morphological changes associated with chemical-induced apoptosis.
Insect Cardioactive Peptides: II. Neurohormonal Control of Heart Activity by Two Cardioacceleratory Peptides In the Tobacco Hawkmoth, Manduca Sexta
Authors: Tublitz Nathan J. , Truman James W. 
Published: April 2021

ABSTRACT
The physiological characteristics of two cardioacceleratory peptides (CAPs) were analysed in the tobacco hawkmoth, Manduca sexta, to determine if either CAP functioned as a cardioregulatory neurohormone.
In vivo heart recordings from pharate and newly emerged adults revealed a dramatic increase in heart rate associated with wing-spreading behaviour. Bioassay of whole blood taken from wing-spreading (WS) animals indicated the presence of a stage-specific, blood-borne cardioacceleratory factor(s). Gel filtration of WS blood identified two cardioacceleratory factors which co-eluted with the two CAPs.
A depletion of the ventral nerve cord levels of both CAPs was observed during WS behaviour. Measurements of blood CAP levels showed that the peak CAP titres were coincident with the initiation of WS behaviour. Experimental manipulations that delayed the onset of WS behaviour also prevented CAP release. High potassium incubation evoked the release of both CAPs in a calcium-dependent manner. In vivo injections of CAPi or CAP2 caused a dose-dependent increase in heart rate.
These results confirm the hypothesis that both CAPs function as cardioregulatory neurohormones during wing-spreading behaviour in Manduca sexta.
Habituation of Swimming Activity in the Medicinal Leech
Authors: Debski Elizabeth A. , Friesen W. Otto 
Published: April 2021

ABSTRACT
Tactile stimulation (light stroking) of a body wall flap attached to the ventral nerve cord of the medicinal leech evokes episodes of swimming activity. This swimming response undergoes habituation, involving changes in swim initiation and swim maintenance.
Repeated stimulation of the body wall flap evoked swimming activity between three and 39 times before this response failed. During repetitive stimulation, the length of swim episodes decreased by about 50%. The number of swim episodes which could be elicited was not correlated with swim episode length. Following habituation, swim initiation showed significant spontaneous recovery, but swim episode length returned only to 60% of control values. In preparations where spontaneous recovery was followed by rehabituation, the number of swim episodes elicited declined with each habituation-recovery sequence. Additional stimulation immediately following habituation trials had a dual effect: recovery of the swimming response was delayed, but the lengths of swim episodes following spontaneous recovery were increased. Pinching the body wall flap immediately restored the swimming response in an habituated preparation. Swim initiation habituated more rapidly during stimulation of anterior body wall flaps than during stimulation of mid-body or posterior flaps. However, swim length was independent of this regional variation in swim responsiveness. The number of swim episodes elicited by stimulation of body wall flaps attached to posterior or anterior segments depended upon whether this segment was stimulated before or after other flaps. In contrast, in mid-body segments there was no evidence for such stimulus generalization. The lengths of swim episodes elicited during sequential stimulation of several body wall flaps were independent of the stimulation sequence. We propose that separate processes control swim initiation and swim maintenance. These processes must be repeated in most, if not all, of the segmental ganglia of the leech ventral nerve cord.
Swimming In The Pteropod Mollusc, Clione limacina II. Physiology*
Authors: Satterlie Richard A. , Spencer Andrew N. 
Published: April 2021

ABSTRACT
The central pattern generator (CPG) for swimming in Clione limacina was localized in cutting experiments. A separate pattern generator for each wing is located in the ipsilateral pedal ganglion. The CPGs are tightly coupled but can be isolated by severing the pedal commissure. Removal of the cerebral ganglia results in a decrease in swim frequency and regularity suggesting descending modulation of the CPGs.
Two classes of pedal neurones display firing patterns in phase with swimming movements. One class, swim motor neurones, are further divided into depressor and elevator groups. Motor neurone recordings show complex subthreshold activity consisting of alternate depolarizations and hyperpolarizations. The complex activity is in antiphase in antagonistic motor neurones. Significant motor neurone-motor neurone interactions do not occur centrally as neither electrical coupling nor chemical synaptic interactions could be demonstrated. Injected currents do not alter the motor neurone firing rhythm or the swimming rhythm.
Motor neurone cell bodies are located in the lateral region of the ipsilateral pedal ganglion, near the emergence of the wing nerve. Each motor neurone provides a single axon to the wing nerve which branches repeatedly in the wing. Each motor neurone has an extremely large innervation field, some covering up to half of the wing area.
The second class of pedal neurones that display firing patterns in phase with either wing upswing or downswing are pedal-pedal inter neurones. Each swim interneurone provides axon branches in both pedal ganglia and the axon runs in the pedal commissure. Interneurone axon branches occur in the lateral neuropile of each pedal ganglion, in the region of motor neurone branching. The swim interneurones presumably play a major role in bilateral coordination of the wings and are involved in pattern generation since injected currents were found to accelerate or slow the firing rhythms of interneurones and motor neurones, and wing movements.
Partitioning of Body Fluids and Cardiovascular Responses to Circulatory Hypovolaemia in the Turtle, Pseudemys Scripta Elegans
Authors: Smits Allan W. , Kozubowski Mark M. 
Published: April 2021

ABSTRACT
Investigations were conducted (1) to measure the steady state compartmentation of body fluids and (2) to assess the efficacy of blood volume and pressure maintenance during haemorrhage-induced hypovolaemia in the pond turtle, Pseudemys scripta elegans. The pre-haemorrhage blood volume, as determined by tracer dilution of 51Cr-labelled erythrocytes, averaged 6·89 ±0·33% of the body mass, and was part of comparatively large extracellular (40·2 ± 0·70%) and total body fluid volumes (75·25 ± 1·48%). Turtles exhibited progressive reductions in systemic arterial pressure throughout a cumulative haemorrhage of −48% of their original blood volume, despite dramatic increases in heart rate and comparatively large magnitudes of transcapillary fluid transfer from interstitial to intravascular spaces. Arterial blood pressure returned to pre-haemorrhage values 2h after experimental haemorrhage ceased, concomitant with the restoration of the original blood volume. Our results support arguments made in previous studies that the resistance to fluid movement between vascular and extravascular locations in reptiles is comparatively low. Furthermore, the haemodynamic responses of turtles to experimental hypovolaemia suggest that barostasis through adjustments in vascular tone is less effective than that observed in other reptiles.
Serotonin Modulates the Central Pattern Generator for Locomotion in the Isolated Lamprey Spinal Cord
Authors: Harris-Warrick Ronald M. , Cohen Avis H. 
Published: April 2021

ABSTRACT
The central pattern generator for locomotion in the spinal cord of the lamprey can be activated in vitro by the addition of D-glutamate to the bathing saline. Serotonin has no effects when bath-applied alone, but it modulates the D-glutamate-activated swimming pattern. Three major effects are observed: (1) a dose-dependent reduction in the frequency of rhythmic ventral root burst discharge; (2) enhancement of the intensity of burst discharge, due in part to the recruitment of previously inactive motoneurones; (3) prolongation of the intersegmental phase lag. Motoneurone activation appears to result from enhanced synaptic drive from the central pattern generator; no direct effects of serotonin on the motoneurones themselves (resting potential, input resistance or threshold for action potential generation) were observed. Theoretical and experimental studies suggest that the prolongation of the intersegmental phase lag results at least in part from differential effects of serotonin on segmental oscillators in different parts of the spinal cord. Isolated caudal pieces of the cord were more strongly affected by serotonin than isolated rostral pieces. We propose that serotonin may be an endogenous modulator of the central pattern generator for locomotion in the lamprey. It may have a role in the generation of a family of related undulatory movements (swimming, crawling, burrowing) by a single central pattern generator.
Strand Receptors Associated with the Femoral Chordotonal Organs of Locust Legs
Authors: Bräunig Peter 
Published: April 2021

ABSTRACT
The so-called flexor strand of the femoral chordotonal organ of the locust jumping leg was found to be innervated by a single sensory neurone with its cell body in the metathoracic ganglion. The strand is therefore a new mechanoreceptor of the strand receptor class. It is sensitive to extension of the femoro-tibial joint. The innervation is rather unusual in the hind leg as well as in the fore and middle legs.
Effect of Limb Mass and its Distribution on the Energetic Cost of Running
Authors: Myers M. J. , Steudel K. 
Published: April 2021

ABSTRACT
Functional morphologists have traditionally regarded cost of locomotion as an important influence on the design of locomotor structures. If cost of locomotion is an important constraint in the natural selection of these structures, it should be possible to show that animals differing in limb morphology also differ in their locomotor costs. In previous experiments on three species of cursorial mammals differing considerably in limb structure, no such differences were detected. Since the factors that determine the rate of energy consumption of a running animal are not well understood, we felt that the effect of limb morphology on cost could best be examined in a system in which only the inertial properties of limbs were varied while other factors remained constant. Consequently, we have measured changes in the rate of energy consumption of running human subjects produced by artificial alterations in limb inertial properties. Other variables that might influence cost have been controlled. We found that the cost of adding a given mass to the limbs is significantly greater than adding it to the centre of mass and that this effect becomes more pronounced as the limb loads are moved distally. Thus a clear effect of limb mass and its distribution on cost of locomotion has been demonstrated.
Water Transport Across the Short-Circuited Midgut of the American Silkworm
Authors: Zerahn Karl 
Published: April 2021

ABSTRACT
The midgut of the American silkworm transports potassium actively from the blood-side to the lumen (Harvey & Nedergaard, 1964) and when the midgut is short-circuited, the short-circuit current (ISC) is approximately equivalent to the active K transport. The rate of movement of water has been considered to be low. It has been measured as 9 ±70μl h−1 (N=3) from blood-side to lumen in an open system (Nedergaard, 1972). In the closed system described by Harvey, Haskell & Zerahn (1967) the water flow could be monitored from the shape and size of the midgut and it was obvious that the movement of water was small.
Determination of Pure Voltage-Dependent Ca2+ Current In Paramecium Caudatum and Its Inhibition By Divalent Cations
Authors: Wehner Frank , Hildebrand Eilo 
Published: April 2021

ABSTRACT
Voltage-dependent Ca2+ currents in Paramecium caudatum were studied under voltage clamp conditions. To separate Caz+ inward currents from concomitant K+ outward currents, the voltage-dependent Ca2+ conductance was temporarily inactivated by a preceding depolarization. The remaining currents were then subtracted from the overall currents measured in the absence of a prepulse. In this way pure Ca2+ currents could be obtained up to a depolarization of 100 mV, which is about 50 mV below the theoretical Ca2+ equilibrium potential (ECa). Ca2+ currents were maximal at a depolarization of 35 mV and declined with further approach to ECa, but they did not reverse sign in the voltage range tested.
In the presence of Mg2+, Co2+, Mr2+ or Ni2+, the Ca2+ inward currents decreased to a different extent. From experiments where these cations were added at different concentrations and from measurements at different Ca2+ concentrations in the absence of other divalent cations the following ratio of apparent dissociation constants could be derived: kNi: kCo: kCa: kMn: kMg = 1:3:4·3–4·7: 5:6·5. With a confidence of 95% the absolute value of kCa lies between 40 and 130μmoll−1. These results indicate that Ca2+ and other divalent cations compete for binding sites at the Ca-channel and thus determine excitability. Indirect effects due to changes of the surface potential are discussed.
Evidence for High-Affinity Ca2+-ATPase Activity And Atp-Driven Ca2+-Transport in Membrane Preparations of the Gill Epithelium of the Cichlid Fish Oreochromis Mossambicus
Authors: Flik Gert , Van Rijs Jeanne H. , Wendelaar Bonga Sjoerd E. 
Published: April 2021

ABSTRACT
A high-affinity Ca2+-ATPase activity was demonstrated among the phosphatase activities in plasma membranes of tilapia branchial epithelium: its characteristics (K0·5 = 0·063 μmoll−1 Ca2+, Vmax = 6·02μmnol P,h −1 mg−protein at 37°C) resemble those of Ca2+-translocating enzymes present in mammalian erythrocytes or enterocytes. The ratio of this Ca2+-ATPase activity to Na+/K+-ATPase activity was 1:20·4. Radioimmunoassayable calmodulin was demonstrated in the Ca2+-ATPase-containing membrane fraction.
ATP-dependent Ca2+-transport was demonstrated in tight-vesicle preparations of the branchial cell membranes; 30% of the vesicles in the preparation were inside-out, 44% were right-side-out and 26% were leaky. The characteristics of the active Ca2+-transport activity are consistent with a Ca2+-extrusion mechanism involving high-affinity Ca2+-ATPase activity.
The branchial Ca2+-transport activity per fish, as calculated on the basis of the transport activity determined for the vesicle preparation, is of the order of the branchial Ca2+-influx rates observed in vivo. The data provide the first biochemical evidence for active Ca2+-transport in plasma mem-branes of branchial epithelium. A model is presented for the mechanism of active transepithelial Ca2+-transport in fish gills.
Intracellular Recordings of Neck Muscle Motoneurones During Eye Cleaning Behaviour of the Cricket
Authors: Hensler Klaus 
Published: April 2021

ABSTRACT
Intracellular recordings were made from prothoracic neurones of crickets which were free to move in a quite normal way. During the head roll component of eye cleaning, the motoneurones (MNs) to the driving muscles, dorso-ventral neck muscles 55, 56 and 60, received excitatory and/or inhibitory input from several spiking neurones. The discharge patterns of these MNs were basically identical to those in intact animals.
Lesion of connectives showed that the motor pattern of eye cleaning is generated by a complex neural network in the prothoracic and the suboesophageal ganglia, in which both neck connectives are involved.
Single electric shocks to the axons of the interommatidial mechanoreceptors through which eye cleaning is elicited evoked an EPSP followed by an IPSP with a latency of about 10 ms in all MNs of the three muscles on both sides. During repeated stimulation of the receptors this input is predominantly inhibitory.
The Relationship Between Lung Volume, Respiratory Drive and Breathing Pattern in the Turtle, Chrysemys Picta
Authors: Milsom W. K. , Chan P. 
Published: April 2021

ABSTRACT
Induced changes in resting lung volume (VLR) in the turtle Chrysemys picta (Schneider) had no effect on resting levels of minute ventilation in animals breathing room air but did change their breathing pattern. Increasing VLR caused an increase in the number of breaths in each episode (burst) of breathing but a reduction in the incidence of such breathing bursts and thus an increase in the length of periods of breath-holding. The data indicate that these effects were largely the consequence of changes in lung volume per se rather than changes in lung gas stores.
Although both hypoxia and hypercapnia stimulated ventilation via increases in tidal volume and breathing frequency, they produced distinct changes in breathing pattern. While hypoxia (3% O2) caused an increase in the number of bursts of breathing (B/min) and reduced the number of breaths (b) in each burst (b/B), hypercapnia (5% CO2) increased both B/min and b/B. These data suggest that the size and incidence of bursts of breathing must be under separate control. One consequence of the different effects of hypoxia and hypercapnia on breaths per burst (b/B) was that hypoxic-hypercapnic gas mixtures (3% O2+5% CO2) failed to stimulate ventilation as much as hypercapnia alone.
Administration of hypoxic, hypercapnic and hypoxic-hypercapnic gas mixtures to elevate respiratory drive eliminated the effects of changes in VLR on breathing pattern. Thus, although changes in VLR are important in the control of breathholding in animals breathing air, their effect decreases as respiratory drive increases.
Binocular Spatial Localization in the Praying Mantis
Authors: Rossel Samuel 
Published: April 2021

ABSTRACT
The way in which mantids localize the direction and the distance of their prey has been analysed, to clarify the importance of binocular interactions. The results suggest the following major points: Binocular interactions coordinate monocular directional information, such that the direction in which a mantid fixates its prey is intermediate between the image directions in the two eyes (Figs 3, 4).Binocular interactions elaborate the disparity between the monocular images, thus providing the mantid with a means of estimating the distance of its prey (Fig. 5 ; Tables 1, 2).
The above findings, together with the known visual recognition tasks performed by the mantid, finally allow the formulation of a simple neuronal model of binocular vision.
The Effects of Mechanical Work on Electrolyte and Water Distribution in Amphibian Skeletal Muscle
Authors: Boutilier R. G. , Emilio M. G. , Shelton G. 
Published: April 2021

ABSTRACT
The present experiments were undertaken to confirm whether the increase in haematocrit that consistently accompanies the build-up of lactate in amphibian muscle cells during exercise can be explained in terms of a movement of water from the blood into the active muscles.
Electrically stimulated sartorius and gastrocnemius muscles isolated from Rana ridibunda and Xenopus laevis had consistently higher total water contents than their paired control muscles. In both instances, it was the intracellular water volume which gave rise to the increase in total muscle water. These results were corroborated in vivo by sampling gastrocnemius muscles from exercising and resting Xenopus laevis. Analyses of tissue electrolyte levels in the working muscles of each experimental series showed an increase in intracellular [lactate−] and [Na+]. A corresponding decline in cellular [K+] occurred in concert with increases in extracellular [K+],
In saline-perfused gastrocnemii of Xenopus, the uptake of vascular water was proportional to the total mechanical work performed. Saline leaving the femoral vein of isotonically contracting gastrocnemius muscles had a greater osmotic pressure than that of the arterial perfusate, whereas arterio-venous osmolality differences of control muscles were negligible. Calculations show that the haemoconcentration during exercise in vivo can be attributed at least in part to a net flow of plasma water to osmotically enriched muscle cells.
Phorbol Esters, Protein Phosphorylation and the Regulation of Neuronal Ion Channels
Authors: Kaczmarek L. K. 
Published: April 2021

ABSTRACT
Protein kinase C is an enzyme whose activity is modulated by its lipid environment and which is fully activated by diacylglycerol in the presence of phosphatidyl serine and calcium ions. This kinase is highly enriched in the nervous systems of both vertebrates and invertebrates. The activity of protein kinase C can be stimulated in intact cells by certain synthetic diacylglycerols as well as by phorbol esters which substitute for endogenous diacylglycerol. The effects of such activators on the endogenous electrical properties of neurones, as well as on synaptic transmission, have recently been investigated in several vertebrate and invertebrate preparations of neurones. One example is that of the bag cell neurones of Aplysia which, in response to brief stimulation, generate a prolonged discharge during which the height of their action potentials is increased. Exposure of isolated bag cell neurones to activators of protein kinase C results in the enhancement of their action potentials through an increase in the amplitude of their voltage-dependent calcium current. This is caused by the unmasking of a previously inactive species of calcium channel in the plasma membrane.