bluuebunny/crossref_metadata_2025 huggingface dataset:
Muscular Basis of Buccal Pressure: Inflation Behavior in the Striped Burrfish Chilomycterus Schoepfi
Authors: Wainwright Peter C. , Turingan Ralph G.
Published: April 2021

We examined the relationship between commonly measured features of cranial muscle activity and the magnitude of sub-and superambient pressure measured inside the buccal cavity of the striped burrfish Chilomycterus schoepfi during inflation behavior. Buccal pressure was recorded simultaneously with electromyographic (EMG) records of activity from three expansive-phase muscles (levator operculi, levator pectoralis and hyohyoideus abductor) and three compressive-phase muscles (adductor mandibulae, protractor hyoideus and protractor pectoralis) in eight individuals. We quantified EMG activity in approximately 30 inflation cycles per fish by measuring the burst duration, rectified integrated area, intensity of activity (area divided by duration) and onset time relative to the onset of subambient pressure at the beginning of the cycle. Multiple regressions were calculated separately for data from each fish to investigate the relationships between pressure and EMG variables. The percentage of variation in minimum buccal pressure or area under the subambient pressure curve explained by the multiple-regression models ranged among individuals from approximately 52 to 84 %. The regression models accounted for more variation in peak pressure and the integrated area of superambient pressure; r2 ranged from 76 % to 97 %. The strong relationship between EMG activity and superambient buccal pressure suggests that the latter is probably a direct function of the strength of compressive-muscle contraction. In contrast, the magnitude of subambient pressure is a complex function of the area of the oral opening and the rate of buccal expansion, factors that do not appear to be as directly indicated by the degree of muscle activity.
Size-Dependent Neural Integration Between Genetically Different Colonies of a Marine Bryozoan
Authors: Shapiro Daniel F.
Published: April 2021

Although the formation of genetic chimeras is rare in the animal kingdom, it has long been known that colonial marine invertebrates fuse under natural conditions, forming genetic chimeras. I report here an example of selective, partial fusion. When small colonies of the encrusting marine bryozoan Membranipora membranacea grow into contact, they usually become behaviorally coordinated: if one colony is disturbed, both colonies will simultaneously retract their feeding structures (lophophores). As a first step towards understanding the fitness consequences of this type of apparent fusion, I examine its mechanistic basis. Using assays of zooid behavior, electrophysiological recordings and 14C-labeled metabolites, I demonstrate that physiological integration between M. membranacea colonies is both partial and temporary. Specifically, this study demonstrates (1) that behavioral coordination is the result of neural integration between colonies, (2) that coordinated colony pairs do not exchange metabolites, and (3) that neural integration is a temporary phenomenon that is terminated as colonies grow larger. Additionally, I show that only those zooids at the middle of the intercolony border mediate neural integration. Partial physiological integration between M. membranacea colonies could be a highly specific interaction that increases the potential benefits of fusion (i.e. neural integration) while minimizing the potential costs (i.e. resource parasitism).
Does the Avian Ophthalmic Nerve Carry Magnetic Navigational Information?
Authors: Beason Robert C. , Semm Peter
Published: April 2021

The bobolink (Dolichonyx oryzivorus) uses the earth’s magnetic field as one source of directional information for its migratory orientation. However, the location and structure of the magnetoreceptors that transduce the magnetic information to the nervous system are unknown. Because treatment with a strong magnetic pulse results in a change in the direction of orientation, one of the receptors is thought to involve a magnetizable material such as magnetite. The effects of the magnetizing treatment can be abolished (i.e. the bird returns to its original orientation) by blocking the ophthalmic branch of the trigeminal nerve, but the ability of the bird to select and maintain a direction is not affected. These results are consistent with the hypothesis that a magnetizable material such as magnetite is part of the magnetoreceptors that are associated with the ophthalmic nerve.
Uptake, Excretion and Respiration of Sucrose and Amino Acids by the Pea Aphid Acyrthosiphon Pisum
Authors: Rhodes J. D. , Croghan P. C. , Dixon A. F. G.
Published: April 2021

Ingestion, excretion and respiration in aphids were studied using artificial diets labelled with radioactive sucrose or amino acids. The rate of ingestion of a 25 % w/v sucrose diet was 12.4 nl mg–1 h–1 and the honeydew excretion rate was 5.3 nl mg–1 h–1, about 43 % of the volume ingested during the same period. The concentration of sugars in the honeydew was equivalent to 0.53 mol l–1 sucrose and 69 % of the sucrose ingested was assimilated. The amino acid concentration of honeydew was 24.6 mmol l–1 and 94 % of the ingested amino acids were assimilated. Respiration was measured by collecting respired 14CO2 using a chamber which allowed the aphids to feed during the experiments on 14C-labelled artificial diets. While feeding on a 25 % w/v sucrose diet, sucrose was respired at the rate of 1.32X10–6 mmol mg–1 h–1, equivalent to 0.354 μl O2 mg–1 h–1, which was 14.6 % of the rate of ingestion. There was no evidence that reducing the dietary sucrose concentration from 22 to 11 % w/v had any effect on the rate at which sucrose was respired. Amino acids were respired at a rate of 0.14X10–6 mmol mg–1 h–1, which was 6.4 % of the rate of ingestion. Dietary sucrose was oxidised in preference to amino acids.
The effects of salinity change on the exercise performance of two Atlantic cod (Gadus morhua) populations inhabiting different environments
Authors: Nelson J , Tang Y , Boutilier R
Published: April 2021

The objective of this study was to determine whether differences in exercise physiology between Atlantic cod (Gadus morhua) populations from different salinity environments could be changed by acclimating individuals of each population to the natural salinity of the comparison population. The exercise-associated blood chemistry of cod from the brackish Bras d'Or lakes, which had previously been shown to be quite different from that of 'open-ocean' cod, changed to resemble the blood chemistry of their oceanic relatives after only 2 months of acclimation to full-strength salinity. In contrast, the blood chemistry of cod from the Scotian Shelf of the Northwest Atlantic Ocean showed little change after 2 months of acclimation to brackish water. These results demonstrate that the degree of osmoconformity to changes in environmental salinity is a population-specific not a species-specific trait. The blood chemistry differences between populations and salinities did not translate into differences in exercise performance: i.e. critical swimming speeds were statistically uniform across all combinations of population and salinity, although performance was more varied in fish swimming in 'non-native' waters. Other 'whole-animal' physiological characteristics, such as metabolic rate and the aerobic cost of transport, were dependent upon both population origin and the environmental salinity. Vigorous swimming was more energetically expensive at full-strength salinity than at 20 salinity, yet estimates of standard (i.e. resting) metabolic rate were lower for full-strength salinity. Environmental salinity also influenced the relative appearance of lactate and metabolic acid in the extracellular fluid compartment, with full-strength salinity favouring the relative appearance of lactate in the blood. Multivariate statistical analyses of this data set showed that, in contrast to other fish species and studies, differences in blood oxygen transport appear to account for some of the swimming performance differences seen in Atlantic cod at 2 °C. The two experimental populations were cleanly separated by a principal components analysis, regardless of the salinity to which they were acclimated, confirming our earlier contention that these cod populations are physiologically distinct. A key feature of that distinctness is the greater phenotypic plasticity exhibited by the population from the more euryhaline, more eurythermal environment.
Plasticity of Fish Muscle Mitochondria with Thermal Acclimation
Authors: Guderley Helga , Johnston Ian A.
Published: April 2021

Short-horned sculpin Myoxocephalus scorpius were acclimated to 5 and 15 °C to evaluate the impact of thermal acclimation upon maximal rates of substrate oxidation by mitochondria and upon the thermal sensitivity of their ADP affinity. Cold acclimation virtually doubled maximal rates of pyruvate oxidation at all experimental temperatures (2.5, 7.5, 12.5 and 20 °C). Rates of palmitoyl carnitine oxidation were also enhanced by cold acclimation, but to a lesser degree. At their respective acclimation temperatures, the mitochondria attained similar rates of pyruvate oxidation. For warm-acclimated sculpin, the Q10 values for mitochondrial pyruvate and palmitoyl carnitine oxidation were higher between 2.5 and 7.5 °C than between 7.5 and 12.5 °C or between 12.5 and 20 °C. In contrast, for cold-acclimated fish, the Q10 values did not differ over these thermal ranges. The Arrhenius activation energy for pyruvate oxidation was reduced by cold acclimation (from 70 to 55 kJ mol–1), whereas that for palmitoyl carnitine oxidation was unchanged (approximately 75 kJ mol–1). Cold acclimation did not alter the ADP affinity of mitochondria at low temperatures but markedly increased the apparent Km for ADP (Km,app) at 12.5 and 20 °C. At the acclimation temperatures, mitochondrial ADP Km,app values did not differ. The loss of ADP affinity at higher temperatures may represent a cost of the enhanced maximal oxidative capacity achieved during cold acclimation.
The Effects of Cyanobacteria and the Cyanobacterial Toxin Microcystin-Lr on Ca2+ Transport and Na+/K+-ATPase in Tilapia Gills
Authors: Bury N. R. , Flik G. , Eddy F. B. , Codd G. A.
Published: April 2021

The effects of cytotoxic substances from cyanobacteria on ionic transport processes in tilapia (Oreochromis mossambicus) were examined. Inhibitory effects on ionic transport including whole-body Ca2+ fluxes and P-type ATPases of the gill were found. The compounds tested were (1) purified microcystin-LR (MC-LR), a heptapeptide hepatotoxin produced by the cyanobacterium Microcystis aeruginosa, (2) extracts from M. aeruginosa strain PCC 7820, a strain producing MC-LR and other microcystin variants, and (3) extracts of M. aeruginosa CYA 43, a strain producing toxins including small quantities of MC-LR. Whole-body Ca2+ influx was inhibited by a 24 h exposure to extracts of M. aeruginosa CYA 43 and 7820, but not by exposure to an equivalent amount (90 mg l-1) of purified MC-LR. Shorter exposure times (4 h) were ineffective. Fish exposed to extracts from M. aeruginosa CYA 43 showed significant plasma hypocalcaemia. Both strains of M. aeruginosa inhibited Ca2+ uptake by basolateral plasma membrane vesicles (BLMVs), endoplasmic reticulum (ER) and mitochondria, as well as BLMV K+-dependent p-nitrophenol phosphatase (pNPPase) activity. The hydrophobic fractions of the cyanobacterial extracts were the most potent, inhibiting BLMV, ER and mitochondrial Ca2+ uptake by up to 99 %, but they were less inhibitory of BLMV K+-dependent pNPPase activity. Purified MC-LR was without effect on these preparations. In conclusion, cytotoxic substances from cyanobacteria have the potential to disrupt normal physiological processes dependent upon Ca2+ transport processes in tilapia gills.
A Primary Cation Transport by a V-Type Atpase of Low Specificity
Authors: Küppers J. , Bunse I.
Published: April 2021

The enzyme involved in outward K+ transport in insect epithelia belongs to the family of V-ATPases. Evidence has been reported relating the generation of the K+ gradient to a primary electrogenic proton transport via a distinct electrophoretic nH+/K+ antiport.

The subject of this paper is the transport of K+ at a thread hair sensillum of the cockroach in situ. We recorded changes in the voltage and resistance of the ion-transporting membrane and of shifts in pH caused by inhibition of energy metabolism and by putative inhibitors of a proton/cation exchanger. The results are supplemented by previous determinations of the K+ activities in the same preparation. In cockroach hair sensilla, the ion transport generates a membrane voltage of 105 mV. We found that the transport rendered the positive output compartment alkaline with respect to the cytoplasm by 1.0 pH unit compared with the pH at equilibrium distribution, and we infer that proton transport cannot be the process that energizes the generation of the K+ gradient.The ion transport created an electrochemical potential difference for protons, Δ ηH, of approximately 4.5 kJ mol–1, while the potential difference for K+, Δ ηK, amounted to approximately 11 kJ mol–1. Both potential differences are directed to the cytosol. It follows from Δ ηK/ Δ ηH that an antiport would have to be electrophoretic to drive K+ by LTH and it should, therefore, contribute to the membrane conductance. Amiloride and harmaline did not significantly change the pH in the adjacent spaces and did not affect the voltage or the resistance of the transporting membrane. Previous determinations of the impedance have shown that the ATP-independent conductance of this membrane is small, supporting the conclusion that it lacks an electrophoretic antiport.

From these results, we deduce that K+ transport in cockroach sensilla is not secondary to a proton transport and an electrochemical proton gradient. The phenomena observed match the performance of a primary, electrogenic, cation-translocating ATPase of the type deduced from analyses of the short-circuit current at the midgut epithelium of lepidopteran larvae. The validity of the H+ transport/antiport hypothesis is discussed.
Inhibition of Voltage-Dependent Ca2+ Influx by Extracellular ATP in Salivary Cells of the Leech Haementeria Ghilianii
Authors: Wuttke Werner A. , Munsch Thomas , Deitmer Joachim W.
Published: April 2021

The effects of extracellular ATP on intracellular free Ca2+ concentration ([Ca2+]i) and depolarization-induced elevations of [Ca2+]i were investigated in salivary cells of the leech Haementeria ghilianii using the fluorescent Ca2+ indicator Fura-2. Simultaneously, the membrane potential was monitored or controlled by voltage-clamp. The cell membrane was depolarized either by transient elevations of the extracellular K+ concentration ([K+]o) to 90 mmol l−1 or by depolarizing steps under voltage-clamp. The resulting transient elevations of [Ca2+]i (Ca2+ transients) could be repeatedly elicited with little variability in amplitude. Ca2+ transients were completely inhibited by 2 mmol l−1 Ni2+ or in Ca2+-free saline. The transients are, therefore, dependent on Ca2+ influx from the external medium through voltage-gated Ca2+ channels. The Ca2+ influx was rapidly and reversibly inhibited by extracellular application of ATP. The effect was dose-dependent with a threshold concentration below 10−7 mol l−1. A 50 % reduction in the amplitude of Ca2+ transients was obtained by application of 1–2 μmol l−1 ATP or ATP--y-S (apparent IC50, 1.6 μmol l−1 ATP) and Ca2+ transients were almost completely inhibited by 30–100 μmol l−1 ATP. Resting [Ca2+]i, the resting membrane potential and membrane potential changes induced by 90 mmol l−1 [K+]o were not affected by ATP. Adenosine (10 μmol l−1) did not affect resting [Ca2+]i, the resting membrane potential or membrane potential changes induced by 90 mmol l−1 [K+]o and had little effect on Ca2+ transients. Suramin, an antagonist of vertebrate P2 receptors, was without effect on the inhibitory actions of ATP. We conclude that activation of a suramin-insensitive purinoceptor by ATP inhibits Ca2+ influx through voltage-gated Ca2+ channels in the salivary cells of Haementeria ghilianii.
Honeybee Waggle Dance: Recruitment Success Depends on the Dance Floor
Authors: Tautz Juergen
Published: April 2021

The waggle dance of the honeybee Apis mellifera, used to recruit nestmates to a food source, takes place on the surface of the combs in the dark hive. The mechanism of information transfer between dancer and follower bees is not entirely understood.

The results presented here reveal a novel factor that must be brought into any consideration of this mechanism, namely that the nature of the floor on which the bees dance has a considerable influence on the recruitment of nestmates to a food source. Dancers on combs with open empty cells recruit three times as many nestmates to a food source as dancers on capped brood cells.
Membrane Energization by Proton Pumps is Important for Compartmentalization of Drugs and Toxins: a New Type of Active Transport
Authors: Moriyama Yoshinori
Published: April 2021

Many organelles are energized by proton pumps: mitochondria form an inside-negative membrane potential by means of the respiratory chain and endomembrane structures, such as lysosomes and synaptic vesicles, establish an internal acidic pH by means of a vacuolar-type H+-ATPase (V-ATPase). Various amphipathic drugs such as local anesthetics and neuron blockers are accumulated in acidic organelles upon energization by proton pumps. However, this process does not require any transporters specific for the drugs: these drugs penetrate through the lipid bilayer against a concentration gradient so as to accumulate inside the energized organelles. Essentially the same transport process takes place in liposomes that have been reconstituted with purified V-or F-ATPase. Various hydrophobic cations are also accumulated in mitochondria by a similar mechanism. The energy-dependent but transporter-independent accumulation does not belong to the known transport categories and seems to represent a new type of transport which may be important for understanding the mode of action of drugs and toxins.
Function of the Intercostal Muscles in Trotting Dogs: Ventilation or Locomotion?
Authors: Carrier David R.
Published: April 2021

Although the intercostal muscles play an important role in lung ventilation, observations from fishes and ectothermic tetrapods suggest that their primary function may be locomotion. To provide a broader understanding of the role these muscles play in locomotion, I measured ventilatory airflow at the mouth and activity of the fourth and ninth intercostal muscles in four dogs trotting on a treadmill. During rest and thermoregulatory panting, activity of the intercostal muscles was associated with inspiratory and expiratory airflow. However, during trotting, activity of the interosseous portions of the intercostal muscles was correlated with locomotion. When ventilation and stride cycles were not synchronized, activity of the interosseous intercostal muscles stayed locked to the locomotor events and drifted in time relative to ventilation. In contrast, activity of the parasternal portion of the internal intercostal muscles was always associated with inspiratory airflow. These observations suggest that, in dogs, locomotion is the dominant function of the interosseous portions of the intercostal muscles. However, the parasternal intercostal muscles are primarily inspiratory in function.
Oxidative Stress and Antioxidants in Overwintering Larvae of Cold-Hardy Goldenrod Gall Insects
Authors: Joanisse Denis R. , Storey Kenneth B.
Published: April 2021

Antioxidant and pro-oxidant systems were studied in overwintering larvae of two cold-hardy gall insect species, the freeze-tolerant fly Eurosta solidaginis and the freeze-avoiding moth Epiblema scudderiana. An increase in the levels of the oxidized form of glutathione suggested slight oxidative stress in both species during the winter. Freeze-tolerant Eurosta solidaginis larvae generally had decreased activities of antioxidant enzymes in the winter, indicating that these larvae do not face increased challenge from oxidative stress during the numerous freeze–thaw events they experience. Instead, existing defences must be sufficient to prevent any damage. By contrast, increased winter activities of antioxidant enzymes in freeze-avoiding Epiblema scudderiana suggest that these larvae must defend against the formation of reactive oxygen species. This may result from the oxidative nature of winter metabolism in these larvae, as well as a dependence on lipid oxidation as their fuel over this season. Xanthine dehydrogenase activity decreased dramatically in both species during the autumn, reducing the potential for the formation of the pro-oxidant xanthine oxidase. Indeed, xanthine oxidase activity fell to undetectable levels by winter in Epiblema scudderiana and was not detectable at any time in Eurosta solidaginis.
Measurement of Crustacean Hyperglycaemic Hormone Levels in the Edible Crab Cancer Pagurus During Emersion Stress
Authors: Webster S. G.
Published: April 2021

The effects of emersion stress upon circulating hyperglycaemic hormone (CHH) levels in the edible crab Cancer pagurus were investigated using a highly specific and sensitive radioimmunoassay, with an antiserum directed against HPLC-purified C. pagurus CHH. Emersion resulted in hyperglycaemia and immediate hypoxia, as shown by rapid hyperlactaemia. CHH levels increased dramatically during the first hour of emersion, from almost undetectable levels to around 17 pmol l−1, thereafter increasing to around 30 pmol l−1 after 4 h of emersion. Short-term air exposure experiments demonstrated that significant increases in CHH levels (up to 3.5 pmol l−1) could be detected during the first 15 min of emersion. Although CHH appears to be fairly stable in haemolymph in vitro, injected CHH was cleared extremely rapidly from the haemolymph in vivo. The results suggest that emersion results in rapid, massive and prolonged exocytosis of CHH from the sinus gland. The sensitivity of the assay and the utility of this crab model may be useful in further studies to elucidate the control of CHH release in crustaceans.
Salinity Change and Cell Volume: the Response of Tissues from the Estuarine Mussel Geukensia Demissa
Authors: Neufeld Douglas S. , Wright Stephen H.
Published: April 2021

The response of cell volume to changes in external salinity was assessed in four tissues (gill, mantle, hemolymph cells and ventricle) of the estuarine mussel Geukensia demissa by using one or more of the following three indicators of cell volume response: changes in cell dimensions, cell water space and cell solute content. All three techniques indicated that short-term volume regulation was generally absent from gill tissue. Lateral cell height in gills, measured using differential interference contrast (DIC) microscopy, increased by approximately 20 % after an abrupt exposure to reduced salinity (60 % artificial sea water, ASW). There was significant variability in the observance of a regulatory volume decrease (RVD) subsequent to the initial swelling; cells remained swollen for 1 h after low-salinity exposure in two-thirds of the trials, while there was a return of cell volume towards control values in the remaining one-third of the trials. Lateral cell height increased linearly when salinity was gradually decreased from 100 to 60 % ASW over 135 min. Cell height then returned to control values when the salinity was abruptly returned to 100 % ASW, indicating that an RVD was not elicited by a slow change in salinity of the type normally encountered by estuarine mussels. Cumulative cell water space in gills increased by 47 % after exposure to 60 % ASW and the cells remained swollen for at least 4 h, returning to control values when gills were returned to 100 % ASW. Consistent with the overall lack of an RVD, there was only a small decrease (approximately 5 %) in cumulative osmolyte content (primarily taurine, betaine and K+) after 4 h in 60 % ASW. Decreases in both cell water space and osmolyte content after 3 weeks of acclimation to 60 % ASW indicated a long-term RVD of approximately 60 %.

Individual cells in the mantle epithelium also generally lacked an RVD in response to lowered salinity. Both abrupt and gradual decreases in salinity caused an increase in mantle cell height to a maximum of 25–30 %, and cell height returned to the control height when salinity was abruptly returned to 100 % ASW. Corresponding with the lack of an RVD in individual mantle cells, there was no change in solute content of the mantle tissue after 4 h of exposure to low salinity. The response of the volume of spherical hemolymph cells to 1 h of abrupt exposure to low salinity, calculated from measured cell diameters, likewise indicated that an RVD is generally lacking in these hemolymph cells. In the ventricle, however, there was a significant decrease in amino acid and betaine content after 4 h of exposure to low salinity, suggesting tissue-specific variability in the cellular response to salinity change.

The consistent lack of a short-term RVD in many tissues may serve to avoid large energetic expenditures associated with repeated volume regulation in the face of the frequent, short-term changes in salinity encountered by estuarine mussels.
Design of the Oxygen and Substrate Pathways: I. Model and Strategy to Test Symmorphosis in a Network Structure
Authors: Taylor C. Richard , Weibel Ewald R. , Weber Jean-Michel , Vock Ruth , Hoppeler Hans , Roberts Thomas J. , Brichon Gérard
Published: April 2021

This first paper in a series develops a model of structure–function relationships for the oxygen and substrate pathways of oxidative metabolism in working muscle. This will be used in the subsequent experimental papers in asking how biological structures are designed if they serve more than one function and whether one function can be served by more than one structural pathway. We have used the concept of symmorphosis to address this question; in its original form, it postulates that no more structure is built and maintained at each step in a pathway than is required to meet functional demands. The concept of symmorphosis was developed to deal with the problem of modelling the pathway for oxygen from the environment to mitochondria, essentially a single series of interconnected transfer steps. In the present context, the application of this concept is more complex. Both oxygen and substrates are transported directly from the blood to the mitochondria in what appear to be shared steps. The flows along this direct pathway are adjusted during muscular work. However, substrates have an additional option. They can be stored intracellularly as lipid droplets or glycogen, and thus their supply to mitochondria can occur in two steps separated in time: from capillaries to stores during rest, and from stores to mitochondria during work. The integrated pathways have a network structure and the functional flows are partitioned to different branches of the network, and we must ask whether the partitioning of fluxes is related to design constraints. The principle of symmorphosis predicts that the best use is made of the available options and that the design of each step is matched to the specific functional demand in view of a balance to be achieved over the entire network. This will be tested in subsequent papers by determining maximal flows for oxygen, carbohydrates and lipids through each of the transport steps and their respective structural capacities, comparing dogs and goats, animals of the same size whose maximal oxidative capacities differ by more than twofold. Finally, we will ask whether the principle of symmorphosis can be extended to apply to network systems.
Design of the Oxygen and Substrate Pathways: V. Structural Basis of Vascular Substrate Supply to Muscle Cells
Authors: Vock Ruth , Weibel Ewald R. , Hoppeler Hans , Ordway George , Weber Jean-Michel , Taylor C. Richard
Published: April 2021

This paper quantifies the structural capacity of the transport steps for oxygen, glucose and fatty acids from the blood in capillaries to the cytosol of muscle cells and compares it with maximal rates of oxygen and substrate transport measured in the same animals and reported in the preceding papers of this series. Dogs have relatively more muscle per unit body mass than goats (37 versus 26 %), but the maximal rate of oxidation per gram of muscle is still larger in the dog by a factor of 1.55. The maximal rates of substrate supply from the circulation are similar in both species. We predict that these differences in physiological parameters should be matched by proportional differences in structural capacity. We find that capillary volume and surface area are matched to maximal oxygen demand. The rate of vascular substrate supply is proportional neither to the capillary surface area nor to the length of intercellular junctions. The sarcolemmal surface area per gram of muscle is the same in both species. Using the physiological data presented in the companion papers of this series, we have calculated the maximal flux densities of circulatory glucose and fatty acids across the capillary wall and the sarcolemma. We find, for both substrates, that the flux densities across the sarcolemma reach a maximum at nearly the same level and at low exercise intensities in both species. In contrast, the flux densities across the capillary surface and the endothelial junctions are higher in goats than in dogs. We conclude that the capillaries are designed for O2 supply up to maximal rates of oxidation but not for the supply of the substrates (glucose and fatty acids) at the rates required at high exercise intensities. These are limited by the transport capacities of the sarcolemma.
Optomotor Control of Course and Altitude in Drosophila Melanogaster is Correlated With Distinct Activities of at Least Three Pairs of Flight Steering Muscles
Authors: Heide Gerhard , Götz Karl G.
Published: April 2021

Flight control in the fruitfly Drosophila melanogaster is achieved by minute sets of muscles on either side of the thorax. Control responses of wings and muscles were elicited during fixed flight by moving a striped pattern in front of the eyes. For example, pattern motion from the lower right to the upper left signals to the test fly a rotatory course deviation to the right and simultaneously a translatory altitude displacement downwards. The counteracting response to the displacement of the retinal image is an increase in thrust and lift on the right, accomplished mainly by increasing the wingbeat amplitude (WBA) on that side. A comparison of such responses with the simultaneously recorded action potentials in the prominent basalar muscles M.b1 and M.b2 and axillary muscles M.I1 and M.III1 on either side suggests that three of these muscles act on the WBA more or less independently and contribute to the optomotor control of course and altitude.

During flight, M.b1 is almost continuously active with a frequency equal to or slightly below 1 spike per wingbeat cycle. The spikes occur within a narrow phase interval of this cycle, normally at the beginning of the transition from upstroke to downstroke. However, the visual stimulus described above causes a substantial phase lead in M.b1 on the right; the spikes occur shortly before the end of the upstroke. Such phase shifts are accompanied by comparatively smooth ‘tonic’ responses of the WBA. The activities of M.b2 and M.I1 are normally very low. However, the stimulus described above activates M.b2 on the right in a phase interval approximately two-thirds into the upstroke and M.I1 on the left in a phase interval at the beginning of the downstroke. The spikes tend to occur in bursts. These bursts are correlated with WBA-increasing ‘hitches’ (rapid changes in amplitude) on the right and WBA-decreasing hitches on the left. As fast ‘phasic’ responses, the burst-induced hitches are likely to account for the course-controlling ‘body saccades’ observed during free flight. For unknown reasons, M.I1 is activated by pattern motion but cannot conceivably assist the other muscles in altitude control. Unlike its homologues in larger flies (Musca domestica, Calliphora erythrocephala), M.III1 does not participate in optomotor flight control. Its activation seems to support the termination of flight and wing retraction at rest.

The essential properties of the three pairs of muscles M.b1, M.b2 and M.I1 resemble those found in larger flies; the muscles are controlled by motion detectors with muscle-specific ‘preferred directions’ in the hexagonal array of retinal elements. Optomotor control of the three pairs of muscles in Drosophila melanogaster could explain most, but not all, of the WBA responses recorded so far.
Extracellular Ca2+ and its Effect on Acid Extrusion in the Crayfish Stretch Receptor Neurone
Authors: Moser H. , Mair N. , Fresser F.
Published: April 2021

In the stretch receptor neurones of the crayfish Astacus astacus, the intracellular pH (pHi), the intracellular Na+ concentration ([Na+]i) and the membrane potential (Em) were measured simultaneously using ion-selective and conventional microelectrodes. Normal Astacus saline (NAS), and salines containing varying amounts of Ca2+ (Ca2+-NAS) but of constant ionic strength, with Na+, Mg2+ or Ba2+ as substituting ions, were used to investigate the effects of extracellular Ca2+ concentration ([Ca2+]o) on pHi and pHi regulation, on [Na+]i and on Em. The maximum rate of pHi recovery was used as a measure of pHi regulation. Acid loads were imposed using the NH4+/NH3 rebound technique. [Ca2+]o affected pHi, pHi regulation, [Na+]i and Em. The magnitudes of the effects were inversely related to [Ca2+]o and were specific to the ion used for [Ca2+]o substitution. Compared with controls, increasing [Ca2+]o threefold (in exchange for Na+) elicited some alkalization, a 7 % faster maximum rate of pHi recovery and generally lower values of [Na+]i. In low-Ca2+ or Ca2+-free NAS (substitutions by Na+ or Mg2+), pHi became more acid, the maximum rate of pHi recovery was reduced by up to 50 % and [Na+]i was generally higher. The effects were faster and larger at lower [Ca2+]o, and stronger with Na+ than with Mg2+ as the substituting ion. In Ca2+-free NAS (Ca2+ substituted for by Ba2+), the effects on pHi, on the maximum rate of pHi recovery and on [Na+]i were generally small. In this respect, Ba2+ had similar physiological properties to Ca2+ and was almost equally effective. Changes in Em, including rapid depolarizations and occasional burst activity in Ca2+-free NAS, indicate that alterations in the properties of the membrane, such as a change in its permeability or selectivity, are occurring. Measurements of [Na+]i support this view. In addition, Ba2+per se induced a (small) depolarization, as shown when Ba2+ was present in NAS or in low-Ca2+ NAS. Changes in [Ca2+]o affected [Na+]i. *[Na+]i is defined as [Na+]i determined at the onset of the maximum rate of pHi recovery, and the ratio *[Na+]i/[Na+]o at that instant was calculated. A linear relationship between the maximum rate of pHi recovery and the *[Na+]i/[Na+]o ratio was found, irrespective of the amount and of the ion species used for [Ca2+]o substitution. This is strong evidence that pHi and pHi regulation were indirectly affected by [Ca2+]o, which altered membrane properties and thus caused a change in [Na+]i. We could find no evidence for a direct contribution of [Ca2+]o to acid extrusion or to a direct modulatory action on the transport protein of the Na+/H+ antiporter.
Periodic Fluctuations in the Numbers of Animals: Their Causes and Effects
Authors: Elton C. S.
Published: April 2021

Four main points are dealt with :— (a) The widespread existence of fluctuations in the numbers of animals. (b) The existence, in many birds and mammals, of periodic fluctuations (p.f.). (c) The cause of the latter, which must be some periodic climatic change acting over wide areas. (d) The effects of fluctuations in general, and in particular of the p.f., on the method of evolution and other biological phenomena. A short sketch is given of what is known about short-period climatic cycles (2 to 20 years), and their causes. P.f. of lemmings have an average period of about 312 years. The maxima in numbers occur synchronously in North America and Europe, and probably all round the arctic regions. The varying hare in Canada has a period of 10 to 11 years. The only regular periods shown by the animals dealt with are the short one of 312 years and the longer one of 10 to 11 years. The former is probably more marked in the arctic and the other further south. The sandgrouse p.f. point to the existence of an 11-year climatic cycle in the deserts of Central Asia. The effects of these p.f. on evolution must be very great, although at present problematical; but the following suggestions are made :— (a) Natural selection of some characters must be periodic. (b) There will be different .types of natural selection at the maxima and minima of numbers. (c) The struggle for existence, and therefore natural selection, tend to cease temporarily during the rapid expansion in numbers from a minimum, and new mutations have then a chance to get established and spread, i.e. without the aid of natural selection. This might happen only rarely. (d) This would explain the origin and survival of non-adaptive characters in a species. (e) On the other hand periodic reduction in numbers will act as an important factor causing uniformity in the species. (f) The opposing factors (c) and (e) will vary much in different species, and the problem will require the combined attentions of mathematicians, and of ecologists working on the methods of regulation of the numbers of animals. (g) This mechanical uniformity factor, since it acts independently of natural selection, explains how a particular structure or habit may evolve, when it only has a general adaptive significance.
A pH Method for Determining the Carbon Dioxide Exchanges of Marine, Brackish - Water, and Freshwater Organisms
Authors: Bruce John Ronald
Published: April 2021

The pH method of determining carbon dioxide exchange has hitherto been available only for freshwater and marine organisms, the necessary determinations of the relation between pH, excess base and CO2-content having been made, in the one case by Prideaux, and in the other by M’Clendon and co-workers.

In order to extend the method to the study of organisms inhabiting brackish waters, of excess base content between that of fresh water and sea water, the determinations of Buch have been utilised, and have been recalculated to a common basis with the foregoing.

The combined results have been plotted as a series of regular curves, which should be of value in comparative metabolic studies of littoral and estuarine forms.
A Minute-Like III-Chromosome Recessive in Drosophila Melanogaster
Authors: Mohr Otto L.
Published: April 2021

Among the numerous cases of mutant changes with multiple effects the so-called “Minutes” discovered by Bridges form an interesting group. In 1919 Bridges discovered the first mutant of this type, the Ill-chromosome dominant mutant Minute, the most obvious characteristic of which is “that all the bristles of the fly, especially those on the thorax, the scutellum and the head, are much more slender and considerably shorter than normal” (Bridges and Morgan, 1923). In most Minute flies the minuteness of the bristles is the only departure from normal that is readily seen. But there is also a tendency for the flies to be paler in general colour, to show a dark trident pattern, to be smaller in size, and to have blunter and dull-coloured wings. This aggregate of somatic peculiarities is accompanied by the following fundamental characteristics : considerably delayed hatching, frequent female sterility, and lowered viability.
Reactions of Daphnia to Simultaneous Light and Electrical Stimuli
Authors: Robertson J. A.
Published: April 2021

Experiments were carried out with Daphnia to see whether the phototropism and galvanotropism which they exhibit would, when the animals were exposed simultaneously to light and to electric current at right angles to each other, induce a resultant reaction such as occurs in many phototropic animals when exposed to two sources of light simultaneously.

Considering the rather difficult nature of the material (consequent on the number of small specimens present, the prevalence of quiescence or inhibition, and the all too frequent modifiability and variability of behaviour among some individuals in the cultures), the following results may, I think, be seen sufficiently clearly: A resultant reaction in the large specimens, doubtfully in the small ones; positivation, by the current, of the photonegative large specimens, but not of the small animals ; kathodic galvanotropism in the large, but not in the small individuals. The threshold value of the current, for galvanotropic reaction alone, and for resultant reaction and positivation, has been found; and finally the latter threshold value has been shown to be independent of the light intensity. The current threshold for resultant reaction, with the light intensities tried, is seen to be the same as that for kathodic galvanotropism alone.
Gonad Grafts in the Fowl
Authors: Greenwood A. W.
Published: April 2021

A histological examination has been made of material from 19 cases of gonad grafts in fowls, from the series of transplantation experiments performed by G. F. Finlay. While some of the ovary grafts remain typically ovarian in structure, many show extensive changes due to a secondary proliferation of the sex cords and their further differentiation into tubules of a definitely spermatic type. Most of the testis grafts are either in active spermatogenesis or are composed of an intimate mixture of active and atrophic tubules ; in 2 cases they consist of atrophic tubules only. It is suggested that the formation of atrophic tubules may be due, apart from environmental conditions, to mechanical pressure. Islets of typical “luteal” cells are present in the interstices between the inactive tubules in the testis grafts, and are not associated with a henny type of plumage. In ovarian grafts “luteal” tissue is found in the thecæ of the follicles, as in the normal ovary, and also in the region of undifferentiated sex cord tissue and tubules. It has not been possible exactly to determine the origin of the new proliferation of the sex cords in the ovarian grafts. It would appear that they may be derived from the germinal epithelium and also from the intra-ovarian epithelial elements represented by the degenerating medullary cords. There appears to be some time relation involved in the formation of the secondary proliferation of the sex cords in the ovarian grafts, since (with one exception) none are found in grafts made later than the fourth day after hatching. Two cases of an activated right gonad in the ovariot-omised female are described, of which one shows typical ovarian structure. The hypothesis is put forward that the right gonad is female fundamentally in constitution, and if it differentiated under a specific stimulus (normally characteristic of the female chick at an early stage of incubation but exceptionally reproduced at a later stage in development) an ovary would be formed.
Some Factors of Animal Development
Authors: Spemann H.
Published: April 2021

The conception of centres of animal organisation or differentiation was formed as the result of the knowledge of certain fundamental facts discovered in the course of experimental studies on amphibian embryos in early stages of development. In the formulation of the problem the following simple considerations were taken into account.
The Respiration of Tyroglyphus Farinae
Authors: Hughes T. E.
Published: April 2021

This investigation into the reactions of Tyroglyphus farinae to varying concentrations of carbon dioxide and oxygen and to the presence of small quantities of hydrocyanic acid, was carried out in order to obtain some insight into the respiratory activities of the mite, very little being known of its physiological reactions. As a necessary preliminary, its reactions to humidity were determined. T. farinae belongs to the family Tyro-glyphidae and respires by direct diffusion through the body surface, since no tracheae are present. These mites infest stored food material, being found on grain, flour and meal. They are associated with the micro-organisms of decay and it might be expected that the gaseous conditions under which they live differ considerably from those of ordinary air. It was decided, therefore, to isolate cultures and to investigate the gaseous changes produced by the organisms in the culture and the effect of such changes on the mites present. The respiratory quotient in normal air was also determined, together with the quotient obtained in the presence of an M/1000 solution of potassium cyanide. The reactions of the mite to varying concentrations of carbon dioxide, oxygen and water vapour in the atmosphere were also determined.
The Determination of Total Volatile Acids in Blood
Authors: Mcanally R. A.
Published: April 2021

In order to study the absorption of volatile acids from the alimentary canal of the ruminant it was necessary to adopt a method of determining the concentration of these acids in the blood.
The Absorption of Sodium Ortho-Iodo-Hippurate from the Rumen of Lambs
Authors: Barcroft J. , Mcanally R. A. , Phillipson A. T.
Published: April 2021

Previous work (Phillipson & McAnally, 1942) indicates that absorption from the rumen is not only possible, as was shown by Trautmann (1933), but is rapid enough to prevent passage to the abomasum of volatile acid present in the rumen, although these acids are present in the rumen in a high concentration. This evidence is remarkable, as the epithelium lining the rumen is stratified and squamous qualities not usually associated with membranes through which there is active absorption.
The Biology and Behaviour of Ptinus Tectus Boie (Coleoptera, Ptinidae), A Pest of Stored Products
Authors: Bentley E. W.
Published: April 2021

Ptinus tectus adults react to a humidity gradient by collecting in the drier region. The reaction to a given difference of humidity is most intense at low humidities; it declines to nothing at about 75-90% R.H. and increases again at 90-100% R.H. No such variation has previously been found. A kinetic mechanism of reaction is involved. The higher the humidity the higher the locomotory activity over a period of a week. Desiccated animals are more active than normal ones. At low humidities they show a much weakened reaction towards drier air; at high humidities the normal reaction is reversed and the animals collect in the wetter region. Desiccated animals given water to drink immediately begin to behave like normal ones. Some of the humidity receptors appear to be located on the antennae. Removal of the distal joint increases the intensity of reaction in high humidities, but the interpretation of this is questionable. The reaction remains strong when up to five joints are amputated and then it declines. When only one or more of the last three joints remain, a reversed reaction occurs, similar to that shown by desiccated individuals. This suggests that there are two kinds of humidity receptors, the first kind being mainly located distally on the antennae and some of the second kind being either on the basal joint or not on the antennae at all. Attempts to identify humidity receptors were not successful.