bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurones in the Leech That Facilitate An Avoidance Behaviour Following Nearfield Water Disturbances
Authors: Mistick Dyane C. 
Published: April 2021

ABSTRACT
A multimodal, multisegmental interneurone (Röhde’s fibre, RF) and previously identified mechanoreceptors (T-cells) are shown to respond to nearfield disturbances. Both the T-cells and RF can fire for hundreds of milliseconds following a brief stimulus, and both have subthreshold excitatory synapses onto motor neurones that cause longitudinal contraction of the body wall, an avoidance response. Natural stimulation or electrical stimulation of T-cells in one hemiganglion causes synaptic excitation of T-cells in adjacent ipsilateral hemiganglia and re-excitation of T-cells in the hemiganglion stimulated. A model of repetitive T-cell activity that incorporates previously described synapses among T-cells is presented: the T-cells in adjacent ipsilateral hemiganglia form a reverberatory circuit, re-exciting one another via electrical synapses; repetitive firing is terminated by synaptic inhibition onto T-cells provided by an interneurone excited by the T-cells. With repeated stimulation (0·1–0·2 Hz, 0·2 ms pulses) of a segmental root (directly exciting all the T-cells of a hemiganglion), the number of T-cell impulses per stimulus decreases. Facilitation of inhibition may contribute to the response decrement. The T-cell-RF pathway is investigated. T-cell stimulation can elicit RF impulses in the same and in adjacent ganglia. The long delay between mechanoreceptor stimulation and a response in the interneurone suggests that spatial and temporal summation of T-cell inputs may be required to reach firing threshold in the interneurone. The impulse frequency of the RF response was compared for a travelling surface wave that is approaching a segment v. one that is moving away from the segment. It was found that the frequency was greater as the stimulus approaches; this should allow more effective temporal summation of the subthreshold synaptic potentials which RF evokes in motor neurones that cause longitudinal contraction of the body wall. Therefore, the probability of contraction is greater in segments toward which a stimulus is moving.
Chemical Excitation of the Proventriculus of the Polychaete Worm Syllis Spongiphila
Authors: Anderson M. , Mrose H. 
Published: April 2021

ABSTRACT
The myoepithelial cells of the proventriculus of Syllis spongiphila (which are composed of only one or two sarcomeres that may reach 40 μm in length) are innervated by excitatory and inhibitory nerve fibres. Experiments were performed to examine the chemical excitation of these cells. We found that acetylcholine (ACh) mimics the excitatory transmitter and that the postsynaptic receptors appear to be nicotinic. Bath application of ACh (10−5 to 10−4 M), carbamylcholine (Carb, 10−4 to 10−3 M) or nicotine (10−4 to 10−3 M), but not muscarine (10−4 to 10−3 M), elicited overshooting depolarizations followed by prolonged depolarized plateaus. Iontophoresis of ACh or Carb (0·1–1·0 M) elicited depolarizing responses which, when elicited in trains, exhibited increased rise times to peak and decreased amplitudes to a plateau level; these results suggest the occurrence of desensitization of the postsynaptic receptors. Depolarizations elicited by indirect stimulation or by iontophoresis of ACh were reduced in amplitude by D-tubocurarine (10−5 to 5 × 10−4 M) in a dose-related and reversible manner. Atropine (10−6 to 10−4M) had no effect on responses elicted by indirect stimulation. Small potential changes superimposed on responses to cholinergic agents applied in the bath or iontophoretically were abolished in Ca2+-free ASW, Ca2+-free+ 1 mm EGTA ASW or in ASW containing 4–6 HIM Mn2+. These small potential changes are likely to be from activity in neurones that receive cholinergic synapses. Carb and nicotine applied in the bath consistently induced more overshooting peaks than did ACh, and the plateaus of the responses to ACh were of lower amplitude than those of the responses to Carb. In addition, responses to iontophoretic pulses of ACh were prolonged in the presence of 10−4 and 10−3 neostigmine. These data suggest the presence of an esterase in the nerve-muscle junctions of the proventriculus.
The Hydrodynamics of Rheotaxis in the Plaice (Pleuronectes Platessa L.)
Authors: Arnold G. P. , Weihs D. 
Published: April 2021

ABSTRACT
Plaice resting on the bottom of a flume respond to the current with a clearly defined pattern of behaviour. A simple hydrodynamic model which relates the slip-speed (Us) and lift-off speed (UL) to the physical forces acting on the fish has been verified experimentally using freshly killed fish and a rigid model. With an asymmetric semi-ellipsoid shape and a fineness ratio of 14 the plaice appears to be morphologically adapted to have minimum drag when heading into the current. As a result of this streamlined shape the lift force experienced by the fish is 10–20 times greater than the drag force, and the rheotactic behaviour therefore appears to be principally adapted to counteract hydrodynamic lift. Values of Us and UL, above which live fish must expend energy against the current, are exceeded for much of each tidal cycle in the southern North Sea. The model is of general application to benthic organisms in flowing water for Reynolds numbers between 104 and 106; outside these limits some modification of the constants is required.
The Metabolic Cost of Flight in Unrestrained Birds
Authors: Torre-Bueno J. R. , Larochelle J. 
Published: April 2021

ABSTRACT
Oxygen consumption and carbon dioxide production were measured during flight in unrestrained starlings by a new method. Mean RQ after the first 30 min of flight was 0·691±0·08 ( ± S.D.). Mean rate of carbon dioxide production was 19·7±2·2 ml CO2/min, which corresponds to a metabolic rate of 8·9 ± 1 W. Metabolic rate during flight did not change significantly over a range of air speeds from 8 to 18 m/s and birds would not fly at speeds outside of this range. Current theories of bird flight predict a large change in metabolic rate over the same range of speeds. Wingbeat frequency was constant at 12 ±0·5 Hz. Wingbeat amplitude reached a minimum at a speed of 14 m/s and increased at both higher and lower speeds. Angle between the body and horizontal was least at high speeds and increased at low speeds. As existing theories do not take into account the change of drag resulting from changes in body attitude, this may be a cause of the discrepancies between theory and observation.
An Electromyographic Analysis of Forelimb Muscles During Overground Stepping in the Cat
Authors: English Arthur W.M. 
Published: April 2021

ABSTRACT
The patterns of activity of 33 forelimb muscles during unrestrained over ground stepping in eight adult cats were analysed using intramuscular electromyography. Three general patterns were found. Some muscles began activity during the first extension epoch (E1) and ceased near the end of the third extension epoch (E3) and were considered extensors. Others, considered flexors, began activity just prior to the flexion (F) epoch and ceased at or just after the onset of E1. Other muscles showed a biphasic pattern of activation; one period of activity occurring during F, the other during the extension epochs. In all regions of the limb, individual muscles displayed variation in the onset and time course of activity. The results are interpreted in terms of a model of locomotor generation which proposes specific neural output to individual muscles. Muscles of the shoulder region are proposed to act mainly to produce translatory and rotatory movements of the scapula associated with lengthening the step. Muscles of the elbow region and antebrachium are interpreted as playing roles both in producing flexion extension movements and in the absorption of energy. The latter group are considered especially suitable to energy absorption because of their pennate arrangement of muscle fasciculi and their long tendons.
Quantitative Mapping of Cutaneous Receptive Fields in Normal and Operated Leeches, Limnobdella
Authors: Fett Michael J. 
Published: April 2021

ABSTRACT
The receptive fields and physiological properties of the sensitive cutaneous mechanoreceptive neurones in the leech Limnobdella australis were found to be very similar to those previously described in Hirudo medicinalis. Following separation from the central nervous system (C.N.S.), the distal dendrite stump and cutaneous receptive field remained unchanged for at least 160 days. There was little spreading of receptive fields into regions of skin isolated from the C.N.S. for at least 184 days. Cutting one dendrite of a mechanoreceptive neurone which has two major dendrites produced little change in the receptive field of the intact dendrite. Abnormalities were found in most of the receptive fields of operated leeches, irrespective of the site of operation. These abnormalities were not seen in normal leeches.
The Dimensions of the Gills of Two Species of Loach, Noemacheilus Barbatulus and Cobitis Taenia
Authors: Robotham P.W.J. 
Published: April 2021

ABSTRACT
The gill area to body weight relationship of two species of loach, Noemacheilus barbatulus (L.) and Cobitis taenia (L.) was measured. It was found that the secondary lamellar area and the total length of the gill filaments were independently related to the lengths of the fish in each of the species. Both these measurements were similar in the two species. The number of secondary lamellae per mm of gill filament was independent of fish length, and was greater in C. taenia than in N. barbatulus (45·5 and 36·4 respectively), being the main factor for the far greater total gill area/g calculated for C. taenia than for N. barbatulus (507·9 and 316 mm2/g respectively). These gill area measurements are, in general, higher than those of other freshwater fish. It is suggested that this is related to the sedentary burrowing habits of the two species.
The Relationship of the External Surface Area of Birds to Skin Surface Area and Body Mass
Authors: Walsberg Glenn E. , King James R. 
Published: April 2021

ABSTRACT
Data from 12 bird species reveal that skin surface area averages 23 % larger than the external surface area of the plumage. Use of skin surface area instead of the area of the external plumage surface may produce large errors in heattransfer analyses.
Cilioexcitatory and Cilioinhibitory Processes Initiated by Light on Two Identifiable Neuronal Pigments in Mytilus Edulis
Authors: Paparo Anthony A. , Murphy Judith A. 
Published: April 2021

ABSTRACT
Two neuronal chromoproteins (red-haemoprotein and yellow-caroteno-protein) initiate changes in ciliary activity on the gill of Mytilus. Photic, electrical and chemical stimulation of these chromoproteins correlate with fluctuations in ionic (calcium and iron) deposits in gill bulk tissue samples. Microspectrophotometric measurements of chromoprotein spectral band patterns reveal two or three absorption maxima for carotenoprotein and haemoprotein respectively. Under aerobic conditions, cilioinhibition and cilioexcitation results after activation of carotenoprotein or haemoprotein respectively. Carotenoproteins are only engaged during gradual anoxia. Immediate anoxia renders both chromoproteins inoperative. Changes in ciliary activity initiated by photic stimulation of neuronal chromoproteins are abolished by denervation of the gill. It is postulated that photoactivation and/or release of specific neurotransmitters lead to transformations in chromoproteins with subsequent neuronal regulation of gill ciliary activity.
Identification of Active Cell in Potassium Transporting Epithelium
Authors: Blankemeyer James T. , Harvey William R. 
Published: April 2021

ABSTRACT
Epithelial ion transport regulates the environment of cells and modulates the environment inside them, making possible the evolution of eukaryotic organisms. Analysis of the transport process requires that the route taken by ions as they are actively transported across epithelia be known. The route can be determined by locating ion pumps electrically and by measuring transport pool sizes kinetically provided that the epithelial structure is simple enough to enable the results to be interpreted in cellular terms. The route by which potassium is actively transported across the lepidopteran midgut is demonstrated here by a combination of electrical and kinetic analyses.
Two sorts of cells, goblet and columnar cells, are distinguished by their electrical properties. The goblet cell is identified as the site of active potassium transport, the pump being localized in its apical membrane. The goblet cells are electrically coupled with columnar cells only when midguts that have been isolated from diet-reared larvae are short circuited. A corollary to this result is that the size of the pool of potassium which is involved in transport should be small when the goblet cells are not coupled with columnar cells and should become large when they are coupled. This corollary has been confirmed by direct measurement of the transport pools using isotope tracer kinetic analysis.
This is the first time that the cell type responsible for active ion transport in a polymorphic tissue has been identified directly by physiological means.
The Source of Short-Circuit Current Across Locust Rectum
Authors: Williams D. , Phillips J. E. , Prince W. T. , Meredith J. 
Published: April 2021

ABSTRACT
Recta of desert locusts were mounted as flat sheets in ‘Ussing-type’ chambers and various parameters of tissue viability were monitored. The trans-epithelial resistance, the electropotential difference, the short-circuit current (Isc), and unidirectional fluxes of 22Na+, 36C1− and 42K+ all remained relatively constant during the 3rd and 4th h. The direction of the Isc indicated a net transport of either anions to the haemocoel, or cations to the lumen side. This current was abolished by KCN and was sensitive to temperature (Q10 = 2·4). There was a rapid decline in Isc over the first 2 h, which could be abolished by substituting NO3− or SO42− for Cl− in the bathing medium, indicating that this fall in current is due to a decline in the rate of Cl− transport. Measurements of 36C1− fluxes under short-circuit conditions confirm this interpretation. In the steady-state (3rd and 4th h), however, the same anion substitutions had no effect on Isc. Concurrent flux measurements indicated that net Na+ and K+ transport to the haemocoel side equals or slightly exceeds that of Cl−in the same direction. Consequently all of the Isc must be due to unidentified ion transport processes. Transport of H+ to the lumen, or HCO3− and organic anions to the haemocoel side, is proposed.
Sodium Fluxes and Exchange Pumps: Further Correlates of Osmotic Conformity in the Nerves of An Estuarine Bivalve (Mytilus Edulis)
Authors: Willmer P. G. 
Published: April 2021

ABSTRACT
Analysis of sodium loss from Mytilus cerebro-visceral connectives indicated a slow efflux component attributable to movement across the cellular membranes. This component was significantly slowed at 4 °C, or by treatment with DNP, ouabain or K-free media; this implies that a conventional Na/K exchange pump contributes to cellular efflux. Dose-response curves for the effects of ouabain on cellular Na efflux gave preliminary indications of a significant increase in the sodium pump frequency in connectives from mussels adapted to 25 % salinity relative to those from too % salinity. Assays of ATPase activity in the connectives showed a 63 % increment in the Na/K-activated enzyme in 25 %-adapted tissues, with no significant change in the magnesium-activated enzyme. The Na/K-ATPase also exhibited a marked shift in its optimal sodium requirement, from 100 mM at 100% salinity to 50mM at 25% salinity; these figures are close to the respective values of [Na+]i determined for the axons under such conditions. [3H]ouabain binding studies confirmed that there was an increment in active sodium pumping sites (in this case of 76 %) in dilute-adapted nerves. Pump frequencies were in the range of 1000–4000 sites/μm2, in agreement with previous studies of invertebrate nerve membranes. The significance of extra pumping capacity for sodium (and potassium) ions in the dilute adapted tissues is considered in relation to the electrophysiological functioning, volume regulation and solute balance of the nerves of an osmoconformer.
Forces on the Tail Surface of Swimming Fish: Thrust, Drag and Acceleration in Bluefish (Pomatomus Saltatrix)
Authors: Dubois Arthur B. , Ogilvy Christopher S. 
Published: April 2021

ABSTRACT
Pressures on the right and left sides of the tails of swimming bluefish were measured and found to have a range of +5·9 to −5·9 cm H20. The pressures were resolved into their forward and lateral vectorial components of force to allow calculation of forward and lateral force and power at speeds ranging from 0·26 to 0·87 m/s. The peak to peak changes in force of acceleration of the body, measured with a forward accelerometer averaged 209 g or 2·05 N at 0·48 m/s, and were compared with the maximum to minimum excursions of forward tail force averaging 201 g or 1·97 N at the same speed. The mean difference was 8 g, S.D. of the mean difference ±29, S.E. of mean difference ± 10 g. Mean tail thrust was calculated as the time average of tail force in the forward direction. It averaged 65 g, or 0·64 N, at 0·48 m/s. The mean forward power was 0·34 N m/s at 0·48 m/s. The drag of the gauges and wires accounted for 10% of this figure. The mean lateral power of the tail was 1·28 N m/s at a mean speed of 0·48 m/s. The propulsive efficiency of the tail, calculated as the ratio of forward power to forward plus lateral power, was found to be 0 20 S.D. ± 0·04, S.E. ±0·01 and was not related to speed. This suggests that 80% of the mechanical power of the tail was wasted. Turbulence in the water may have contributed to this large drag and low tail efficiency.
Oxygen Consumption in the Lizard Genus Lacerta in Relation to Diel Variation, Maximum Activity and Body Weight
Authors: Cragg Patricia A. 
Published: April 2021

ABSTRACT
Diel recordings of under a 12 h Light/12 h Dark regime, constant light or constant dark reveal a strong endogeneous diurnal rhythm in L. sicula. L. vivipara show an exogeneous rhythm with activity occurring only in the light whilst L. viridis have a weak endogeneous rhythm that is modified by behavioural factors and inhibited by dark. Standard (or basal) can only be attained after several hours in an ‘indifferent’ environment, shielded from extraneous stimuli. Measurements must be at night (light or dark) for unrestrained L. sicula and in the dark (day or night, restrained or unrestrained) for L. vivipara and L. viridis. Intrageneric std (ml h−1 STPD) = 0·328 W0·76 or 0·216 W0·77 for 1- or 3-days starvation at 30 °C for 0·2 to 34 g Lacerta. Intrageneric maximum (determined for 30 to 60 s of provoked activity during the day) = 2·66 W0·747at 30 °C for 1-days starvation. Respiratory exchange ratio, R = 0·75 or 0·85 for std after 1 or 3 days starvation and 0·95 and 1·45 for mean daily and max . High R values are considered a result of anaerobic metabolism and hyperventilation during activity.
Measurement of Single Nephron Filtration Rate in the Kidney of the River Lamprey, Lampetra Fluviatilis L
Authors: Moriarty R. J. , Logan A. G. , Rankin J. C. 
Published: April 2021

ABSTRACT
The reliability of [3H]inulin as a reference substance for the measurement of glomerular filtration rate (GFR) in river lampreys was investigated. Simultaneously measured renal clearances of [3H]inulin and [14C]-polyethylene glycol (PEG) were not significantly different. Recoveries of [3H]inulin in the urine following its injection into the proximal tubule and urinary duct averaged 83·5 ± 4·0% (n = 14) and 93·0 ± 4·6% (n = 9) respectively. No evidence was obtained to suggest penetration of the tubular wall by [3H]inulin following its introduction into peritubular capillaries. Gel-filtration of lamprey plasma and urine produced no signs of any significant degradation of the inulin to fructose. [3H]inulin recoveries, though significantly below 100% (P &lt; 0·001), were considered adequate to justify its use after allowing for possible sources of error. A mean single nephron filtration rate (SNGFR) value of 7·02 ± 0·27 nl/ min (n = 89) was obtained from the kidneys of anaesthetized freshwater lampreys. [51Cr]EDTA was found to be totally unsuitable for the measurement of GFR in this species.
The Effect of the H-ion Concentration on Protozoa, as Demonstrated by the Rate of Food Vacuole Formation in Colpidium
Authors: Mills Sylvia M. 
Published: April 2021

ABSTRACT
In a short communication to the British Association at Leeds (1927) Saunders pointed out that the average number of vacuoles ingested by Colpidium in a given time, when fed with suspensions of Indian ink, varied with the H-ion concentration. The present series of experiments represent an attempt to analyse in greater detail the effect of the hydrogen-ion concentration on Colpidium, particularly in respect to its effect on the formation of food vacuoles. The work was carried out under the direction of Mr J. T. Saunders, to whom I owe my thanks for much help.
The Growth of Fish
Authors: Gray J. , Setna S. B. 
Published: April 2021

ABSTRACT
Certain scales of Salmonoid fish exhibit a series of concentric ridges or circuli, the number of which increases with the size of the whole fish. Each year of normal growth is recorded on the scale of a salmon by a concentric band which is more or less sharply divided into two regions, (i) in which the concentric ridges are relatively wide apart, (ii) in which the ridges are closer together. It is tolerably certain that the first region is formed whilst the fish is in the sea, and the second region whilst the fish is in estuarine or fresh water ; roughly speaking the two regions mark the summer and winter periods respectively. The factor or factors responsible for the difference between winter and summer circuli are not fully understood. There are two possibilities. The variation in width may be dependent on an inherent rhythm upon which external factors may exert little or no control ; or the variation may be due to variations in the external environment of the fish. In view of the high economic importance of the facts, curiously little experimental data are available for a solution of the problem.
The Adaptation of Gunda Ulvae to Salinity
Authors: Pantin C. F. A. 
Published: April 2021

ABSTRACT
Whereas it is well known that most organisms cannot survive sudden large changes in the salinity of the external medium yet estuarine organisms have developed powers of resistance to them. Recent work, particularly that of Schlieper (1929), has thrown some light on the behaviour of estuarine animals in diluted sea water.
A Lamarckian Experiment Involving A Hundred Generations with Negative Results
Authors: Agar W. E. 
Published: April 2021

ABSTRACT
The experiment was devised to find out whether regeneration of the dorsal branch of the second antenna of Simocephalus and Daphnia, repeated for many generations, would result in an improvement in the regeneration (which is very imperfect) or in any other alteration in the process. Neither the character nor extent of the regeneration was influenced in any measurable degree in any of the experimental lines, even after 100 generations, nor was the normal growth of the antenna affected.
A similar experiment, except that selection was practised in addition, likewise produced negative results, confirming both the lack of the Lamarckian effect and the inefficacy of intraclonal selection.