bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Varied Culturing and Experimental Temperature on Electrical Membrane Properties in Paramecium
Authors: Martinac Boris , Machemer Hans 
Published: April 2021

ABSTRACT
Effects of temperature on the electrical properties of the Paramecium membrane were investigated under constant current and voltage-clamp stimulation. With cells cultured at 18 °C, the resting potential was largely stable with experimental temperatures varied over the range of 10–25 °C, whereas action potential amplitude and membrane input resistance were inversely related to temperature increases. During voltage clamp, the early calcium current was increased, the time-to-peak decreased, and the early conductance increased with temperature. Similar modifications of the culturing temperature did not affect the resting potential, input resistance and stimulus-response relationship of the action potential, but the early conductance was reduced with increase in temperature. Possible effects of long- and short-term temperature changes upon intraciliary calcium concentration are discussed.
Influence of Hydration of The Environment On the Pattern of Nitrogen Excretion by Embryonic Snapping Turtles (Chelydra Serpentina)
Authors: Packard Gary C. , Packard Mary J. , Boardman Thomas J. 
Published: April 2021

ABSTRACT
Flexible-shelled eggs of common snapping turtles were incubated on wet and dry substrates. More than 70 % of the waste nitrogen accumulating in eggs on both substrates was in the form of urea, and less than 25 % was in the form of ammonia. Low levels of soluble urate were detected in eggs late in incubation, but insoluble urate was never present. Accumulation of ammonia and soluble urate was unaffected by the hydration of the environment, but more urea accumulated late in incubation in eggs on the wet substrate than in those on the dry substrate. Thus, embryos are ureotelic throughout development, and the pattern of accumulation of the primary nitrogenous waste is influenced by hydration of the environment.
Movements and Active Moments of Bull Sperm Flagella as a Function of Temperature and Viscosity
Authors: Rikmenspoel Robert 
Published: April 2021

ABSTRACT
Detailed measurements were made of the movements and waveforms of bull sperm flagella over a temperature range of 5 to 37 °C and over a range of external viscosities of 1–3600 × 10−3Pas−1*. The data obtained were used for an evaluation of the internal active moments in the flagella, using exact, large amplitude, algebra. The results of the calculations show that the axoneme in bull sperm flagella can produce the forces necessary to power the flagellar motion over the entire range of conditions. The calculations further suggest that no other structure in the bull sperm flagella has a forceproducing function.
Aerial Versus Aquatic Oxygen Consumption in Larvae of the Clawed Frog, Xenopus Laevis
Authors: Feder Martin E. , Wassersug Richard J. 
Published: April 2021

ABSTRACT
Tadpoles of Xenopus laevis Daudin can extract oxygen from both air and water. When these larvae have access to air, aerial oxygen uptake averages 16·6 % of total oxygen consumption in normoxic water, and increases to 100% of net oxygen consumption in hypoxic water. Neither anaerobiosis nor increased buccopharyngeal ventilation occur in response to hypoxia. If tadpoles are prevented from surfacing to breathe air, they can maintain normal oxygen consumption through aquatic respiration alone in normoxic water, but not in hypoxic water. Unlike air-breathing larvae, exclusively water-breathing larvae respond to aquatic hypoxia by increasing their buccal pumping rate and by accumulating lactate. Even though Xenopus larvae can survive without air for many days, aerial respiration is necessary for other functions: tolerance of hypoxia, normal feeding, locomotion and buoyancy regulation.
Active Potassium Ion Transport Across the Caterpillar Midgut: I. Tissue Electrical Properties and Potassium Ion Transport Inhibition
Authors: Thomas M. V. , May T. E. 
Published: April 2021

ABSTRACT
Active potassium ion transport by isolated midguts of Spodoptera littoralis andManduca sexta caterpillars has been studied by electrical means. In contrast to previous studies, the electrical properties of the midguts remained essentially constant for several hours; this improvement probably results from use of an experimental saline that more closely resembles caterpillar haemolymph. The active transport could be abolished by anoxia and by a number of chemical agents, of which trimethyl tin chloride (effective at 10−9M) was the most potent. Some of these substances, including trimethyl tin chloride, may have been acting directly on the potassium ion transport system. The results of varying the ionic composition of the saline suggest that potassium is the only cation that can be transported at a significant rate. However, the rate of potassium ion transport is increased by the simultaneous presence of other inorganic cations.
Experiments to determine the ‘reversal potential’ for the active transport pathway, by varying the potassium ion concentration, suggested that this parameter was not a constant, and thus the active transport system could not be modelled by a simple equivalent electrical circuit, although the midgut epithelium is not unique in this respect. Therefore, the tissue electrical properties could not readily be correlated with the energetics of the potassium transport process, but the results are nevertheless consistent with a potassium ion: ATP ratio of greater than one, if ATP is indeed the primary energy source.
Active Potassium Ion Transport Across the Caterpillar Midgut: II. Intracellular Microelectrode Studies
Authors: Thomas M. V. , May T. E. 
Published: April 2021

ABSTRACT
Intracellular microelectrodes were used to record from individual cells in midguts isolated from Spodoptera littoralis caterpillars. Recorded potentials, referenced to the basal (haemolymph) surface, showed a bimodal distribution, with maxima in the ranges 0 to –10 and –30 to –40 mV. In experiments where the fluorescent dye Lucifer Yellow CH was iono-phoresed from the recording microelectrode, fluorescence was associated with single cells only for membrane potentials more negative than –25 mV. Examination of tissue sections showed these cells to be of both columnar and goblet types, in an approximate 2:1 ratio. This conclusion conflicts with that of a previous study on other caterpillar species, in which it was concluded that the goblet cells had basal membrane potentials of only a few mV. Attempts to discriminate between the two cell types by resistance measurements were unsuccessful. The resistance values obtained were substantially higher than those in the previous study, although they are consistent with those predicted from the overall tissue resistance. The major electrical effect of potassium ion transport inhibition by 1 m-KCN was on the apical membrane, supporting the view that the potassium pump is located there. The major initial effect of potassium ion removal was on the basal membrane, which is as expected if this membrane is permeable primarily to potassium. Our inability to discriminate between goblet and columnar cells by any electrical criterion suggests that both cell types may be able to transport potassium.
The Specific Power Output Of Aerobic Muscle, Related To The Power Density Of Mitochondria
Authors: Pennycuick C. J. , Rezende Marcio A. 
Published: April 2021

ABSTRACT
A simple theory is proposed to account for the quantity of mitochondria present in aerobic muscles. Attention is restricted to muscles adapted to operate aerobically at a well-defined ‘operating frequency’. For this special case, it is shown that the volume ratio of mitochondria to myofibrils should depend on the power density of mitochondria, and the operating frequency, but not on the mechanical properties of the myofibrils. If the underlying assumptions are valid, this would mean that the specific power output of such muscles could be determined by examination of electron micrographs.
We provisionally estimate that the inverse power density of mitochondria, in flight muscles running at a high temperature, is in the range 1·010−6 to 1·310−6 m3 W–1, that is, that a little over 1 ml of mitochondria is required to sustain 1 W of mechanical power output. On this basis, a muscle with equal volumes of mitochondria and myofibrils should be able to deliver a specific power of about 430 W kg–1, at an operating frequency around 40 Hz for non-fibrillar, or 230 Hz for fibrillar muscle. The limiting specific power should be twice this level in either case, i.e. about 860Wkg–1.
It is predicted that a survey of flight muscles should yield a straight-line relationship between wing-beat frequency and the volume ratio of mitochondria to myofibrils, in a set of muscles of the same general type. It is not known whether lack of exercise, either on a long-term or short-term basis is likely to affect this. As a preliminary to such a survey, we have examined the pectoralis muscles of domesticated quail, and a wild house sparrow. Both showed a high level of variability in the mitochondria: myofibril ratio, but this may be due, at least in part, to sampling artifacts caused by the shape of mitochondrial arrays. The quail showed distinct populations of aerobic and non-aerobic fibres, apparently identical to those described in wild birds with similar flight requirements by George & Berger (1966), but the quantity of mitochondria in the aerobic fibres was less than half that expected, by comparison with other species.
Jumping Performance of Frogs (Rana Pipiens) as a Function of Muscle Temperature
Authors: Hirano Michio , Rome Lawrence C. 
Published: April 2021

ABSTRACT
This study was performed to determine whether or not the power generated by frog muscles during maximal jumps increases two- to three-fold with a 10 °C increase in temperature as it does in isolated preparations. We found that peak power increased 2·7-fold between 14 and 25 °C, and then remained constant to 30 °C. During jumps at 14 and 25 °C, the extensor muscles of the legs appeared to generate the same power as the maximum power output found in isolated frog muscle preparations, thus suggesting that the total cross section of the extensors is active during maximal jumps. We also found that jump distance was linearly related to peak power generation.
Foetal and Adult Blood Oxygen Affinities of the Viviparous Seaperch, Embiotoca Lateralis
Authors: Ingermann Rolf L. , Terwilliger Robert C. , Roberts Michael S. 
Published: April 2021

ABSTRACT
The high oxygen affinity of foetal versus adult blood is an almost universal characteristic of viviparous vertebrates; a notable exception is the cat (Novy & Parer, 1969). There is also likely to be a difference in the oxygen affinities of foetal and adult blood in the teleostean fish, the seaperch Embiotoca lateralis Agassiz. Our studies of E. lateralis foetal and adult haemoglobins and erythrocytes have shown several mechanisms which are likely to facilitate oxygen transfer to the foetal fish by increasing foetal blood oxygen affinity with respect to that of adult blood. Proposed mechanisms include structurally distinct foetal and adult haemoglobins with foetal haemoglobin having the higher oxygen affinity, lower foetal erythrocyte nucleoside triphosphate (NTP, primarily ATP) concentrations, and possibly, lower mean corpuscular haemoglobin concentrations (MCHC) in foetal cells (Ingermann & Terwilliger, 1981a, b, 1982a). It is necessary, however, to see if the oxygen affinity of foetal whole blood is greater than that of adult blood as predicted from purified haemoglobin oxygen binding and erythrocyte characteristics. Consequently, we have measured the oxygen affinities of foetal and adult whole bloods under comparable conditions.
Use of A Ventilated Capsule and Tritiated Water to Measure Evaporative Water Losses in A Tenebrionid Beetle
Authors: Nicolson S. W. , Louw G. N. , Edney E. B. 
Published: April 2021

ABSTRACT
Evaporative water losses (EWL) in arthropods have traditionally been measured by gravimetric methods (Loveridge, 1980), although electronic sensing of water has recently been employed (Hadley, Stuart & Quinlan, 1982; Hadley & Quinlan, 1982). Difficulties are encountered in separating the cuticular and respiratory components of total transpiration. Cuticular water loss has frequently been measured in freshly killed specimens with blocked spiracles, and the results subtracted from the total EWL of living animals to obtain values for respiratory transpiration. Unfortunately, however, cuticular transpiration is higher in dead than in living arthropods (e.g. Hadley, 1970) and is further augmented by the appreciable damage to the cuticular waterproofing caused by blocking the spiracles (Beament, 1959). An additional problem arises when surface areas are estimated from standard equations, in order to express cuticular EWL in units independent of body weight. Loveridge (1980) has suggested that such estimates of surface area may be as much as an order of magnitude too low. We describe here an alternative technique using tritiated water (THO) and ventilated capsules to determine transpiration rates across small, known areas of cuticle in living insects. Tenebrionid beetles were selected as experimental animals and, because of the anatomy of their respiratory system, our method has also proved suitable for direct measurement of water losses from the subelytral cavity.
In Vitro Studies on the Role of the Brain and Prothoracic Glands in the Pupal Diapause of Manduca Sexta
Authors: Bowen M. F. , Bollenbacher W. E. , Gilbert L. I. 
Published: April 2021

ABSTRACT
Pupal diapause in the tobacco hornworm, Manduca sexta (Johannson), is characterized by the absence of an increased ecdysteroid titre in the haemolymph during the first week of pupal life as measured by radioimmunoassay. This virtual absence of the steroid moulting hormone is thought to be responsible for the diapause state and it is apparently a consequence of the failure of the diapausing pupal prothoracic glands (PG) to synthesize ecdysone at an increased rate. In Manduca, this apparent failure of PG activation during diapause may be in response to two endocrinological circumstances: the curtailment of PTTH release as opposed to its synthesis and transport, and the development of refractoriness of the gland to stimulation by PTTH. The former was examined by measuring PTTH activity present in brains and brain-retrocerebral complexes of diapausing and non-diapausing pupae and the latter by assessing PG biosynthetic activity in vitro in the presence and absence of PTTH.
Hypoxic Acclimation in the Lamprey, Lampetra Fluviatilis: Organismic and Erythrocytic Responses
Authors: Nikinmaa Mikko , Weber Roy E. 
Published: April 2021

ABSTRACT
Acute exposure of Lampetra fluviatilis to hypoxia ( = 40–50 mmHg) resulted in a large increase in ventilation frequency and a significant increase in O2 consumption (from 40 to 60 mg kg−1h−1 at 8 °C). After 1 week’s hypoxia, the O2 consumption decreased (from 60 to 50 mg kg−1 h−1), indicating the existence of slow, acclimatory changes that remove some of the strain from the ventilatory response. The hypoxic animals had a higher blood O2 affinity than the normoxic controls. This acclimatory response is not the result of a decreased allosteric interaction between the haemoglobin and erythrocytic organic phosphates, as in teleost fish, but is attributable partly to dilution of haemoglobin within the red cells and partly to an increase in the intracellular pH. The intraerythrocytic pH of hypoxic animals, measured with a freeze-thaw method, was higher than the plasma pH, suggesting that protons are not passively distributed.
Localization of tones and noise in the horizontal plane by unrestrained house mice (Mus musculus)
Authors: Ehret Günter , Dreyer Angelika 
Published: April 2021

ABSTRACT
House mice (Mus musculus, outbred strain NMRI) were trained to locate loudspeakers at the margin of a wire-mesh covered circular platform. Sound signals were tone bursts of 1, 15, 50 and 80 kHz and noise bursts (bandwidth 15–80 kHz). Localization acuity as represented by orientation angles (α) toward the speaker was determined at 5 radial distances from the centre of the platform. If the animals could localize under closed-loop conditions (with repetitive stimulation), the distributions of (α) showed a significant peak at the speaker position (0°) and mean orientation angles for the different stimuli all varied around 0°. Distributions of (α) from open-loop tests were not peaked, i.e. mice did not localize the sound source. We calculated the median angle (β) of the distributions of orientated runs and used (β) as a measure for the accuracy of localization. Smallest values of α were 12° for 1 kHz, 15 ° for 15 kHz, 9·5 ° for 50 kHz, 8·5 ° for 80 kHz tone bursts and 7 ° for the noise bursts. The results are discussed in relation to possible localization mechanisms in mice.
Contractility and 45Ca fluxes in heart muscle of flounder at a lowered extracellular NaCl concentration
Authors: Gesser H. , Mangor-Jensen A. 
Published: April 2021

ABSTRACT
The twitch force of isolated electrically paced ventricular strips of flounder, Platichthys flesus L., increased after lowering the extracellular sodium chloride concentration by 50 mmol l−1. This response was markedly reduced by replacing the sodium chloride with either Tris-HCl or sucrose, so that osmolarity was unchanged.
The 45Ca efflux decreased and the 45Ca influx increased when the extracellular sodium concentration was lowered. In contrast, changing only the osmolarity had no observable effect on these fluxes.
An increased resting tension appeared in strips exposed to a Na+-, Ca2+-free solution. This was transient at an unchanged osmolarity but became permanent at an osmolarity lowered by 100 mosmol l−1.
These results suggest that both a lowered Na0 and a lowered osmolarity have a positive inotropic effect, due respectively to an increased cellular uptake of Ca2+ and a redistribution of cellular Ca2+.
Antarctic Fish Blood: Respiratory Properties and the Effects Of Thermal Acclimation
Authors: Tetens Vilhelm , Wells Rufus M. G. , DeVries Arthur L. 
Published: April 2021

ABSTRACT
The effects of thermal acclimation on whole blood oxygen affinity were examined in the antarctic fish Pagothenia borchgrevinki. 4·5 °C-acclimated fish had a P50 value of 26·7 mmHg at pH 8·4, compared to 20·7 mmHg for −1·5 °C-acclimated fish. The apparent heat of oxygenation, ΔH = −26·7 kJ mol−1, is comparable to values for temperate species. Warm-acclimation was followed by an increased ATP:Hb4 molar ratio, resulting in an augmentation of the thermal effect on oxy-haemoglobin affinity. This may be considered adaptive in a constantly well oxygenated environment, where oxygen loading at the gills is secured. Unloading to the tissues is thereby enhanced, supporting an elevated rate of aerobic metabolism at higher temperatures. In vivo blood pH was high, between 8·10 and 8·25 at − 1·5 °C. Astrup titration revealed arterial CO2 tensions of less than 0·8 mmHg, indicating relative hyperventilation and low oxygen extraction efficiency in antarctic fish. Blood oxygen affinities of four antarctic nototheniid species were low (P50 between 11·9 and 20·7 mmHg at pH 8·1 and -1·5 °C) in comparison with the temperate speciesNotothenia angustata (P50 = 10·8 mmHg). The zoarcid Rhigophila dearbomi had a high blood oxygen affinity (P50 = 4·3 mmHg). Blood oxygen-binding properties are discussed in relation to the polar environment, mode of life, and the concept of cold adaptation.
Neural Involvement in the Control of Salivary Gland Degeneration in the Ixodid Tick Amblyomma Hebraeum
Authors: Harris Robert A. , Kaufman William R. 
Published: April 2021

ABSTRACT
We have developed a simple, quantitative assay to monitor salivary gland function in ixodid ticks. Salivary glands of engorged (l·0–3·0 g), or partially engorged (0·40–1·0 g), Amblyomma hebraeum Koch lose virtually all secretory function within 4 days after engorgement. Salivary glands from partially-fed ticks (0·20–0·30 g) lose 75 % of their secretory ability by 4 days post-removal, but retain this level of function for at least another 11 days. Partially-fed ticks (0·20–0·30 g) removed from the host for 4 days and then allowed to re-attach and resume feeding for a further 2 days, recover much of their lost function. Cutting the opisthosomal nerves of partially-fed ticks (0·40–1·0 g) inhibits salivary gland degeneration. Excising the seminal receptacle from partially-fed ticks (0·40–1·0 g) inhibits salivary gland degeneration. Replacement of the seminal receptacle permits salivary gland degeneration to proceed normally. The factor from the seminal receptacle appears to be distinct from tick salivary gland degeneration factor (TSGDF; Harris & Kaufman, 1981). Injecting a crude extract of male genital tracts into large, partially-fed ticks (0·40–1·0 g), which had had their seminal receptacles removed, caused virtually complete salivary gland degeneration. Such ticks, when injected with an extract of male salivary glands, showed no such degeneration. This suggests that the factor associated with mating originates in the male and is transferred to the female during copulation.
Serotonergic innervation and modulation of the stomatogastric ganglion of three decapod crustaceans (Panulirus interruptus, Homarus americanus and Cancer irroratus)
Authors: Beltz Barbara , Eisen Judith S. , Flamm Robert , Harris-Warrick Ronald M. , Hooper Scott L. , Marder Eve 
Published: April 2021

ABSTRACT
The serotonergic innervation of the stomatogastric ganglion (STG) of three decapod crustacean species, Panulirus interruptus, Homarus americanus and Cancer irroratus, was studied. Immunohistochemical techniques were used to study the distribution of serotonin-like staining in regions of the stomatogastric system in the three species. In C. irroratus and H. americanus, but not in P. interruptus, serotonin-like staining was found in fibres in the stomatogastric nerve and in neuropil regions of the STG. High performance liquid chromatography confirmed the presence of serotonin in STG of C. irroratus and H, americanus, but serotonin was not found in STG of P. interruptus. Electrophysiological experiments showed that the pyloric motor output of the STG of all three species was influenced by bath applications of serotonin. The STG of P. interruptus responded to serotonin concentrations as low as 10−9M; however the STG of the other two species did not respond until serotonin concentrations in excess of 10−6 M were applied. We conclude that serotonin may play a hormonal role in the control of the STG of P. interruptus, but is likely to be a neurotransmitter released by inputs to the STG of H. americanus and C. irroratus.
Unusual Phase Relationships Between The Forewings And Hindwings In Flying Dragonflies
Authors: Alexander David E. 
Published: April 2021

ABSTRACT
Flying insects can generally be divided into two groups: ‘primitive’ orders with forewings and hindwings that move independently (for example, Odonata, Orthoptera, Isoptera) and more ‘advanced’ orders with wings that are functionally one pair, with the fore- and hindwings in contact so as to function as one wing (for example, Hymenoptera, Lepidoptera, Homoptera), or with only one pair of wings that functions primarily as a lifting surface (for example, Diptera, Strepsiptera).