bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation of the Fibrillar Muscles in the Bumblebee During Warm-Up, Stabilization of Thoracic Temperature and Flight
Authors: Heinrich Bernd , Kammer Ann E. 
Published: April 2021

ABSTRACT
Extracellular action potentials and thoracic temperatures (TTh) were simultaneously recorded from the fibrillar flight muscles of Bombus vosnesenskii queens during preflight warm-up, during stabilization of TTh in stationary bees, and during fixed flight. In most stationary bees during warm-up and during the stabilization of the rate of heat production, as calculated from thoracic temperature and passive rates of cooling, is directly related to the frequency of action potentials in the muscles. The rate of heat production increases throughout warm-up primarily because of a greater spike frequency at higher TTh. In stationary bees during the stabilization of TTh at different ambient temperatures (TA) the fibrillar muscles are activated by any in a continuous range of spike frequencies, rather than only by on-off responses. Regulation of TTh in stationary bees may involve not only changes in the rate of heat production but also variations of heat transfer from the thorax to the abdomen. During fixed flight the fibrillar muscles are usually activated at greater rates at the initiation of flight than later in flight, but the spike frequency and thus heat production are not varied in response to differences in TA and heating and cooling rates. During fixed flight TTh is not regulated at specific set-points; TTh appears to vary passively in accordance with the physical laws of heating and cooling. Differences in the TTh of bees in free and in fixed flight are discussed with regard to mechanisms of thermoregulation.
The Antennular Activities of the Hermit Crab, Pagurus Alaskensis (Benedict)
Authors: Snow P. J. 
Published: April 2021

ABSTRACT
The antennular activities of the hermit crab, Pagurus alaskensis, were studied with the aid of motion pictures taken at speeds of 50, 200 and 400 frames/sec. Most movements of the antennule represent one of four types of antennular activity: flicking, rotation, wiping and withdrawal. These activities are described in detail. Water resistance forces contribute to the timing and duration of some antennular movements. Flicking occurs non-rhythmically and flicks of the left and right antennules ail never synchronized. The factors which influence the mean frequency of flicking are discussed. The timing of joint movements during a flick, and the morphology of the outer flagellum and the aesthetasc hairs, appear to be adapted to facilitate splaying of the aesthetascs. It is proposed that this splaying might facilitate the chemoreceptive process by circulating water around the aesthetasc hairs. During antennular wiping the endopodites of the 3rd maxillipeds are used to remove debris caught amongst the aesthetasc hairs. Light mechanical stimulation of the aesthetascs is sufficient to elicit wiping. The antennules are reflexively withdrawn from certain stimuli either by extension or by slow or fast flexion. The functional significance of the withdrawal reflexes are discussed in relation to the stimuli involved and the form of the reflexes. Continued application of certain stimuli to the antennules, eyestalks, antennae or body results in tonic flexion withdrawal which involves postural modifications of the antennules, eyestalks and antennae.
The Mechanism of the Pupal Gin Trap
Authors: Bate C. M. 
Published: April 2021

ABSTRACT
Despite partial degeneration of the larval muscles and reorganization of the nervous system, pupae of the privet hawk moth, Sphinx ligustri, show simple behaviour patterns including abdominal flexion and twirling, and a movement which closes the gin trap. The gin trap closes when the motor neurones driving muscles in the ipsilateral half of the adjacent anterior segment discharge together in a brief high-frequency volley. The system which excites the volley is restricted to these motor neurones and is. activated only by input at a high frequency from triggering receptors. A second system excites efferent neurones in several segments and is driven by triggering and non-triggering receptors. Therefore at low input frequencies the discrimination between the two kinds of receptors disappears. Motor patterns associated with twirling movements drive the efferent neurones. in a sequence which interferes with their simultaneous response to triggering inputs. The arrangement of the closure system shows that the afferent neurones are separated from the efferent neurones by at least one intemeurone.
Mechanisms of Ciliary Co-ordination in Ctenophores
Authors: Tamm Sidney L. 
Published: April 2021

ABSTRACT
An experimental analysis of ciliary metachronism was performed on ctenophores of two types: those with a continuation of the ciliated groove running between adjacent comb plates (lobates), and those in which the ciliated grooves end at the first plate of each comb row (cydippids and beroids). The results showed that the comb plates of cydippids and beroids are co-ordinated by mechanical forces arising from the movement of the plates themselves. Only along the ciliated grooves and at their junctions with the comb rows is a neuroid conduction process likely in this group of ctenophores. Ctenophores with an interplate ciliated groove, on the other hand, do not depend on mechanical interaction between active plates for co-ordination. Instead, the lobates use neuroid conduction at the junction between the interplate ciliated groove and the comb plate, at the junction between adjacent interplate ciliated grooves, and probably along the ciliated grooves and interplate ciliated grooves as well. Ciliary co-ordination may therefore be entirely neuroid in lobate ctenophores. In both types of ctenophores the comb plates may be triggered to beat by depolarization of the comb-plate cells. Electrical excitation of a plate could be caused by mechanical deformation of its base arising from the motion of the preceding plate (in cydippids and beroids), or by a neuroid process at the interplate ciliated groovecomb plate junction (in lobates). These findings resolve a long-standing controversy over the mechanism of ciliary co-ordination in ctenophores.
The Mechanism of the Pupal Gin Trap
Authors: Bate C. M. 
Published: April 2021

ABSTRACT
Pupae of the privet hawk moth Sphinx ligustri are equipped with defensive devices known as gin traps. The function of the traps depends on a discrimination between receptors inside and outside their margins. The traps close when the sensilla within them are disturbed. There is no consistent difference in the response of the trichoid sensilla inside and outside the traps. Discriminations between them must depend on a difference in their central connexions. There is no fusion of the afferent axons from individual receptors in the region of the gin trap. Maps of the triggering and non-triggering receptors show that the pupa does not discriminate between receptors inside and outside the trap, but between receptors at different points on the antero-posterior axis. The distinctive feature of the triggering receptors may be their position in a segmental antero-posterior gradient.
The time Course of Pacemaker Inhibition in the Hydroid Tubularia
Authors: Josephson R. K. , Rushforth N. B. 
Published: April 2021

ABSTRACT
Stimulating the DOS, a conducting system in Tubularia, inhibits spontaneous firing of the principal pacemaker systems of the polyp, the NP and HP systems. The overall inhibition is greater the greater the stimulus frequency and there is rebound from inhibition at the end of the stimulation period. The latent period for NP inhibition is 0·4–0·6 sec and the duration of inhibition is 4–5 sec. The time course and extent of NP inhibition is independent of stimulus frequency except at high frequency where there is diminishing effectiveness of inhibition with time. HP inhibition has a similarly long latent period and even longer duration, lasting 15–20 sec. HP inhibition from successive stimuli can sum to produce a more intense effect. The behavioural significance of the inhibition seems to be to reduce spontaneous polyp movements during food capture and ingestion.
Relative Contribution of Synaptic and Non-Synaptic Influences to Response Decrements in A Post-Synaptic Neurone
Authors: Stephens Cathy Lamar 
Published: April 2021

ABSTRACT
Repeated trans-synaptic stimulation of the giant neurone in the abdominal ganglion from Aplysia californica produced decrements of nervous activity. Although the EPSP amplitude decreased during the stimulation, the firing probability of the post-synaptic neurone continued to decrease after the amplitude had reached a constant low value. When the cell was hyperpolarized and stimulated until the EPSP had decreased to a constant low value, the firing probability immediately after removal of the hyperpolarization was the same as with no previous stimulation. These results and previous work suggest that a process occurring in the post-synaptic neurone, independent of synaptic modification, may contribute significantly to habituation-like phenomena.
Cardiovascular and Respiratory Changes During Heat Stress in Rainbow Trout (Salmo Gairdneri)
Authors: Heath Alan G. , Hughes G. M. 
Published: April 2021

ABSTRACT
Trout were subjected to a steady increase in water temperature (1·5 °C/h) from 15 °C until death occurred, while several respiratory and cardiovascular parameters were monitored. Oxygen consumption increased during the warming (Q10 = 2·35 between 16 and 20 °C). At the higher temperatures the increase was more marked (Q10= 4·96 between 20 and 26 °C). Ventilatory frequency increased during the rising temperature with a general levelling off observed above 23 °C. The amplitude of the pressure changes in the buccal and opercular cavities increased more than did the ventilatory frequency. Further analysis of the differential pressure across the gills suggests that the adjustment of respiratory pumping to the increased oxygen demand is predominantly in the volume pumped per stroke (cycle). Heart rate rose steadily with the increasing temperature until about 24– 25 °C, when a bradycardia usually became evident. Synchrony between the heart beat and the respiratory pumps was observed in some preparations at the higher temperatures. Blood pressure increases during the warming were more marked in the ventral aorta than in the dorsal aorta. At the highest temperatures, abnormal cardiac cycles were frequently observed. Arterial oxygen content declined slightly during warming and venous oxygen content dropped to zero above 23 °C. It is suggested that cardiovascular adjustments may be a limiting factor in this type of stress.
Masking of Auditory Responses in the Medulla Oblongata of Goldfish
Authors: Enger Per S. 
Published: April 2021

ABSTRACT
The nervous activity of single auditory neurones in goldfish brain have been measured. Four types of acoustic stimuli were used, (1) pure tones, (2) noise of one-third octave band width, (3) noise of one-octave band width with centre frequency equal to the pure tone, and (4) white noise. Except for white noise, these stimuli produced the same response to equal sound pressures. The white noise response was less, presumably because the frequency range covered by a single neurone is far narrower than the range of white noise. The conclusion has been reached that for low-frequency acoustic signals, the acoustic power over a frequency band of one to two octaves is integrated by the nervous system. The masking effect of background noise on the acoustic threshold of single units to pure tones is strongest when the noise band has the same centre frequency as the test tone. In this case the tone threshold increases linearly with the background noise level. When the noise band was centred at a different frequency from the tone, the masking effect decreased at a rate of 20–22 dB/octave for the first one-third octave for a tone frequency of 250 Hz. For a tone of 500 Hz the masking effect of lower frequencies was stronger and was reduced by only some 9 dB/octave for the first one-third octave.
The Ionic Properties of the Capsular Fluid Bathing Embryos of Lymnaea Stagnalis and Biomphalaria Sudanica (Mollusc A: Pulmonata)
Authors: Taylor H. H. 
Published: April 2021

ABSTRACT
The cations sodium, potassium, calcium and magnesium are always at a higher concentration in the capsular fluid (perivitelline fluid) of Lymnaea stagnalis and Biomphalaria sudanica than in the bathing medium. The concentration of each ion is a complex function of the concentrations of all ions in the medium and of pH. Typical values for the ratio of capsular concentration to medium concentration for Lymnaea capsules isolated in slightly alkaline water of average hardness are 2·4–5 for monovalent and 18–40 for divalent cations. Lowering the pH of the medium from 8·5 to 4·0 reduces the capsular concentrations of monovalent ions by about 45% and of divalent ions by about 85%. Consideration of the potential difference between the capsular fluid and the medium, and comparison of the monovalent and divalent ion ratios, indicates that a Donnan equilibrium exists across the capsular membrane. On dilution of the medium the above ratios may rise more than tenfold and the potential difference may rise from about 23 mV to above 60 mV (inside negative). It is concluded that the capsular fluid/membrane system buffers the internal cation activities against changes in external cation activities, particularly in the case of calcium. It is suggested that the ‘calcium-buffer’ may be important in maintaining ion-uptake mechanisms near saturation, in reducing the permeability of the embryo to salts and water, in maintaining cellular adhesion and in morphogenesis. The fluxes of 22Na+ and 45Ca2+ across the capsular membrane have half-times of 40–100 sec and about 300 sec respectively. The membrane offers little resistance to the free diffusion of these ions.
The Effects of Derivatives of Adenosine 3′,5′-Monophosphate on Fluid Secretion by the Salivary Glands of Calliphora
Authors: Berridge M. J. 
Published: April 2021

ABSTRACT
The nature of the cyclic AMP-receptor interaction was analysed by testing a range of cyclic nucleotides on the isolated salivary glands of adult blowflies. All compounds containing modifications in the region of ribose or the phosphate ring were inactive. One compound, adenosine 3′,5′-phosphorothioate, appeared to compete with cyclic AMP. A number of nucleotides with alterations restricted to the base region of the molecule could stimulate secretion equally as well as cyclic AMP. These observations indicate that during the action of cyclic AMP the phosphate ring and ribose sugar are critical whereas the adenine ring plays a relatively unspecific role.
Motor Activity During Walking in the Cockroach Periplaneta Americana
Authors: Delcomyn F. , Usherwood P. N. R. 
Published: April 2021

ABSTRACT
The patterns of electrical activity of selected muscles of the rear legs were studied during locomotion in unrestrained, freely moving cockroaches. During walking, muscle potentials in both extensor and flexor muscles were always grouped into bursts separated by periods of silence, with one burst occurring per step. During very slow walking, the occurrence of flexor and extensor bursts was synchronized with, respectively, the flexion and extension movements of the leg. At increasingly greater speeds of locomotion, the movements of the leg lagged increasingly behind the muscle activity, so that during very fast walking the extensor or flexor burst often began while the preceding leg movement was not quite half completed. ‘Slow’ extensor and’fast’ flexor bursts were studied in detail. The frequency of impulses within each extensor burst was usually steady, but sometimes declined in the middle or increased at the end of a burst. Frequency within’fast’ flexor bursts was often more varied, but there was no systematic change in frequency with any other parameter which was examined. For’slow’ extensor bursts, the duration of each burst, the number of impulses per burst and the mean interval between impulses in a burst each increased significantly as the duration of the associated step increased, i.e., there was a positive correlation between each pair of parameters. The rate at which the number of impulses per burst and mean interval per burst changed as a function of step duration was often significantly higher for steps shorter than about 300 msec than for longer ones. For’fast’ flexor bursts, the duration of each burst, the number of impulses per burst and the mean interval per burst were each extremely variable ; a weak correlation with step duration could only be demonstrated for the latter. However, both mean interval and the number of impulses per burst were positively correlated with the duration of the burst from which they were taken. The data qualitatively support current models of step generation in insects, but also suggest that a useful distinction could be made between very slow walking (below 3–4 steps per sec), termed ambling, and faster walking.
Electrophysiological Identification of Neurones and Neural Networks in the Perioesophageal Ganglion Complex of the Marine Pulmonate Mollusc, Onchidium Verruculatum
Authors: Katayama Yoshifumi 
Published: April 2021

ABSTRACT
The marine pulmonate mollusc, Onchidium verruculatum, has many giant neurones in the perioesophageal ganglion complex. Twenty of them were visually identified by their relative locations, sizes, and pigmentations under the dissecting microscope, and electrophysiologically by their input-output patterns. The relationship among and between the giant neurones was investigated on 190 pairs of neurones, arbitrarily paired from 20 neurones, by intrasomatic recordings. There were two excitatory and two inhibitory direct connexions. There were two pairs receiving synchronous excitatory inputs and two pairs receiving synchronous inhibitory inputs. Two pairs of neurones showed a similar activity pattern and one pair showed an alternating activity pattern. A tentative neural network was constructed for one of identified neurones, r-PP i in the r-PPG (right pleuroparietal ganglion). The results and the firing patterns of neurones are discussed.
Repetitive Firing in Molluscan Giant Neurones
Authors: Magura I. S. , Zamekhovsky I. Z. 
Published: April 2021

ABSTRACT
The repetitive responses of molluscan neurones to steady injected outward current have been examined using intracellular microelectrodes. Voltage-clamp experiments were also performed to investigate the participation of transport mechanisms for potassium current in neurones during firing. The maximum rate of rise of action potentials usually decreases during repetitive firing. Simultaneously an increasing duration of the falling phase of spikes is observed. The peak level of spikes in most cases is relatively stable if external Ca2+ concentration exceeds 3−4 mM. The peak level of action potentials markedly decreases during firing in solutions with low Ca2+ concentration. A similar effect is observed if the Ca2+ ions in normal Ringer solution are completely replaced by Mg2+ ions. With increasing external Ca2+ concentration the maximum rate of rise of action potentials becomes more stable during repetitive firing. With increasing external Ca2+ concentration the steady-state inactivation of fast transient potassium channels is removed. Increase in Ca2+ concentration (in range from 10–40 mM) is roughly equivalent to a hyperpolarization of 7–8 mV. Experiments with TEA show that in some neurones of Limnea stagnalis the last transient potassium channels participate in carrying potassium current during the falling phase of the action potentials at the beginning of repetitive firing. The role of potassium inactivation as well as of Ca2+ ions in mechanisms which stabilize the peak level of action potentials during repetitive firing is discussed.
On the Feeding Mechanism of the Copepods, Calanus Finmarchicus and Diaptomus Gracilis
Authors: Cannon H. Graham 
Published: April 2021

ABSTRACT
Calanus finmarchicus and Diaptomus gracilis both feed automatically when swimming slowly and steadily through the water. A feeding current is produced which is filtered by the stationary maxillae. Food so obtained is passed on to the mandibles by the maxillulary endites and setae on the bases of the maxillipeds. The feeding current is a vortex passing through the mouth parts which results automatically from the swimming activities of the antennae, mandibular palps and maxillules. The feeding vortex is caused to pass through the maxillae by the combined activities of the maxillipeds and the maxillulary exites. The former suck water into the filter chamber between the maxillae while the latter suck it out through the maxillary setae. The views of Storch and Pfisterer on the feeding mechanism of Diaptomus gracilis are criticised. There is no powerful antero-posterior swimming current as described by these authors. The swimming current is in the form of a vortex encircling the body and most marked at the sides in the angle between the body and the antennules.
Observations on Ovulation in the Rabbit
Authors: Walton A. , Hammond J. 
Published: April 2021

ABSTRACT
Ovulation has been directly observed in the anaesthetised rabbit. The follicle ruptures, on the average, about 10 hr. after coitus but there is some variation and all follicles do not rupture simultaneously. Ovulation is not the invariable consequence of the normal growth of the follicles and, although confined to those which are mature, is independent of the actual size attained. Ovulation is accompanied by increased vascularity of the follicle. The principal cause of rupture is the rapid distension of the follicle by marked secretory activity. The ovum is carried out in the flow of this secretion. Ovulation in the rabbit is initiated by some component of the orgasm which accompanies coitus rather than by the mechanical stimulus of the penis or the presence of semen in the vagina. Corpora lutea are not formed if the follicle is ruptured artificially and this effect is not due to operative trauma but to the absence of some effect of coitus necessary for the formation of the luteal tissue. Artificial rupture or ablation of ripe follicles is followed by an immediate compensatory growth of new follicles. Blood follicles formed from those artificially ruptured do not inhibit this compensatory growth.
Intracellular Oxidation-Reduction Studies
Authors: Chambers Robert , Pollack Herbert , Cohen Barnett 
Published: April 2021

ABSTRACT
A New approach to the problems of cellular metabolism was opened by J. and D. Needham (8) who used the micro-injection of reversible indicators to determine the oxidation-reduction intensity of living protoplasm. Prerequisites for this work were the elaboration of a series, as yet incomplete, of such indicators, and the electrometric standardisation of the position of each dye on the scale of reduction (or oxidation) electrode potential by Clark, Cohen and their co-workers (1, 4, 5, 7). Discussions of the various theoretical phases of oxidation-reduction and their possible applications to the study of life processes are found in the papers of Clark and Cohen (5).