bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitric Oxide Loading of the Salivary Nitric-Oxide-Carrying Hemoproteins (Nitrophorins) in the Blood-Sucking BUG Rhodnius Prolixus
Authors: Nussenzveig Roberto H. , Bentley David L. , Ribeiro JosÉ M. C. 
Published: April 2021

ABSTRACT
The salivary glands of the blood-sucking bug Rhodnius prolixus are formed by a single layer of binucleated epithelial cells surrounded by a double layer of transversely oriented smooth muscle cells. The epithelial cells are rich in rough endoplasmic reticulum and mitochondria and have abundant microvillar projections towards the gland lumen. This cell layer surrounds a relatively large cavity where abundant secretory material is stored. Epithelial cells produce an intense and generalized NADPH diaphorase reaction, in contrast to other tissues such as brain, Malpighian tubules and skeletal muscle. Ultrastructural analysis of the osmiophilic reaction product indicates that it is localized within cytoplasmic vacuoles, a similar location to that of NADPH diaphorase (NO synthetase) activity in neuronal cells of vertebrates. Measurements of the time course of protein accumulation, NADPH diaphorase activity and the degree of nitrosylation of hemoproteins (nitrophorins) in the salivary glands of Rhodnius prolixus nymphs after a blood meal indicate that the nitrophorins are synthesized and accumulate when NO production is low (with a 25 % loading of the nitrophorins during the fourth-to fifth-instar molt). NO loading of the nitrophorins increases to 90 % after the molt, concomitant with a large increase in the salivary NADPH diaphorase activity. It is concluded that synthesis of NO occurs within the epithelial cells while the nitrophorins are stored extracellularly. It is hypothesized that the luminally oriented microvilli may serve as a diffusion bridge to direct intracellularly produced NO into the luminal cavity, where the nitrophorins are stored.
Cellular Metabolic Homeostasis During Large-Scale Change in Atp Turnover Rates in Muscles
Authors: Hochachka P. W. , Mcclelland G. B. 
Published: April 2021

ABSTRACT
The term homeostasis traditionally refers to the maintenance of a relatively constant internal milieu in the face of changing environmental conditions or changing physiological function. Tissues such as skeletal and cardiac muscles must sustain very large-scale changes in ATP turnover rate during equally large changes in work. In many skeletal muscles, these changes can exceed 100-fold. In unique biological circumstances (for example, during periods of oxygen limitation, vasoconstriction and hypometabolism), tissues such as skeletal muscles may be obliged to sustain further decreases in ATP turnover rates and operate for varying periods at seriously suppressed ATP turnover rates. Examination of a number of cellular and whole-organism systems identifies ATP concentration as a key parameter of the interior milieu that is nearly universally ‘homeostatic’; it is common to observe no change in ATP concentration even while the change in its turnover rate can increase or decrease by two orders of magnitude. A large number of other intermediates of cellular metabolism are also regulated within narrow concentration ranges, but none seemingly as precisely as is [ATP]. In fact, the only other metabolite in aerobic energy metabolism that is seemingly as ‘homeostatic’ is oxygen – at least in working muscles. The central regulatory question is how such homeostasis of key intermediates in pathways of energy supply and energy demand is achieved.
Hypometabolic Homeostasis in Overwintering Aquatic Amphibians
Authors: Boutilier R. G. , Donohoe P. H. , Tattersall G. J. , West T. G. 
Published: April 2021

ABSTRACT
Many amphibians encounter conditions each winter when their body temperature is so low that normal activities are suspended and the animals enter into a state of torpor. In ice-covered ponds or lakes, oxygen levels may also become limiting, thereby forcing animals to endure prolonged periods of severe hypoxia or anoxia. Certain frogs (e.g. Rana temporaria) can dramatically suppress their metabolism in anoxia but are not as tolerant as other facultative vertebrate anaerobes (e.g. turtle, goldfish) of prolonged periods of complete O2 lack. Many overwintering amphibians do, however, tolerate prolonged bouts of severe hypoxia, relying exclusively on cutaneous gas exchange. Rana temporaria overwintering for 2 months in hypoxic water ( approximately 25 mmHg) at 3 °C progressively reduce their blood to levels characteristic of water-breathing fish. The result is that blood pH rises and presumably facilitates transcutaneous O2 transfer by increasing Hb O2-affinity. Even after months of severe hypoxia, there is no substantial build-up of lactate as the animals continue to rely on cutaneous gas exchange to satisfy the requirements of a suppressed aerobic metabolism. Our recent experiments have shown that the skeletal muscle of frogs oxyconforms in vitro to the amount of O2 available. The cellular basis for the oxyconformation of skeletal muscle is unknown, but the hypothesis driving our continuing experiments theorises that metabolic suppression at a cellular level is synonymous with suppressed ion leak across cellular membranes.
Perireceptor Mechanisms Sustaining Olfaction at Low Salinities: Insight from the Euryhaline Blue Crab Callinectes Sapidus
Authors: Gleeson Richard A. , Wheatly Michele G. , Reiber Carl L. 
Published: April 2021

ABSTRACT
As the blue crab Callinectes sapidus moves from sea water to fresh water, the ‘exposed’ chemosensory dendrites in the olfactory sensilla (aesthetascs) undergo changes in length that are positively correlated with environmental salinity. In this study, we demonstrate the following. (1) The responses of the olfactory receptor cells of freshwater-acclimated crabs are reduced relative to those of seawater-acclimated animals, but increase with a time course comparable to the increase in dendrite length when these crabs are transferred to sea water. (2) The olfactory response of seawater-acclimated crabs is lost and the chemosensory dendrites osmotically ablated if the aesthetascs are acutely exposed to low salinity. However, maintaining iso-osmotic conditions with mannitol preserves both the physiological response and the structural integrity of the dendrites. (3) The flux of [14C]thiocyanate and 22Na between the hemolymph and sensillar lymph of the aesthetascs indicates continuity between these fluid compartments. (4) There is a net efflux of Na+ from the hemolymph through the aesthetascs in freshwater-acclimated crabs, and measurements of electrical potential across the antennules suggest that this efflux largely derives from passive diffusion. (5) Dendrites in the aesthetascs of crabs acclimated to brackish water are intermediate in length between those of freshwater- and seawater-acclimated animals. Together, our findings suggest that, at low salinities, the efflux of Na+ (and probably other ions) from the hemolymph generates an ionic/osmotic microenvironment within the aesthetascs that sustains the structural and functional integrity of the olfactory dendrites. We propose that the length of these dendrites, and consequently the olfactory response, is constrained by the distance over which this microenvironment can be effectively maintained.
Embryos of Artemia Franciscana Survive Four Years of Continuous Anoxia: The Case for Complete Metabolic Rate Depression
Authors: Clegg James S. 
Published: April 2021

ABSTRACT
Encysted gastrula embryos of the crustacean Artemia franciscana have acquired an array of adaptations that enable them to survive a wide variety of environmental extremes.The present paper shows that at least 60 % survive 4 years of continuous anoxia at physiological temperatures (20–23 °C) when fully hydrated. Although these embryos appear to carry on a metabolism during the first day of anoxia, no evidence for a continuing metabolism throughout the subsequent 4 years was obtained. During this period, there were no measurable changes in the levels of their stored, mobilizable carbohydrates (trehalose, glycogen, glycerol). Calculations indicate that, if these carbohydrates are being utilized at all during anoxia, the rate is at the least 50 000 times lower than the aerobic rate (lower limit of detection). Indications of proteolysis during prolonged anoxia were sought but not found. Under starvation conditions, the life span of larvae produced from embryos that had undergone 4 years of anoxia was not significantly different from that of larvae produced by embryos that had not experienced anoxia. Thus, all substrates and other metabolites required to support embryonic development to the nauplius, as well as endogenous (unfed) larval growth and molting, are retained during 4 years of anoxia. It is not possible to prove experimentally the absence of a metabolic rate in anoxic embryos under physiological conditions of hydration and temperature. Nevertheless, on the basis of the results presented here, I will make the case that the anoxic embryo brings its metabolism to a reversible standstill. Such a conclusion requires that these embryos maintain their structural integrity in the absence of measurable biosynthesis and free energy flow and are thus an exception to a major biological generality. Potential mechanisms involved in their stability are discussed.
Vascular Peripheral Resistance and Compliance in the Lobster Homarus Americanus
Authors: Wilkens Jerrel L. , Davidson Glen W. , Cavey Michael J. 
Published: April 2021

ABSTRACT
The peripheral resistance to flow through each arterial bed (in actuality, the entire pathway from the heart back to the pericardial sinus) and the mechanical properties of the seven arteries leaving the lobster heart are measured and compared. Resistance is inversely proportional to artery radius and, for each pathway, the resistance falls non-linearly as flow rate increases. The resistance of the hepatic arterial system is lower than that predicted on the basis of its radius. Body-part posture and movement may affect the resistance to perfusion of that region. The total vascular resistance placed on the heart when each artery is perfused at a rate typical of in vivo flow rates is approximately 1.93 kPa s ml−1. All vessels exhibit adluminal layers of fibrils and are relatively compliant at pressures at or below heart systolic pressure. Arteries become stiffer at pressures greater than peak systolic pressure and at radii greater than twice the unpressurized radius. The dorsal abdominal artery possesses striated muscle in the lateral walls. This artery remains compliant over the entire range of hemolymph pressures expected in lobsters. These trends are illustrated when the incremental modulus of elasticity is compared among arteries. All arteries should function as Windkessels to damp the pulsatile pressures and flows generated by the heart. The dorsal abdominal artery may also actively regulate its flow.
The Effects of Adrenaline on the Work- and Power-Generating Capacity of Rat Papillary Muscle In Vitro
Authors: Layland Joanne , Young Iain S. , Altringham John D. 
Published: April 2021

ABSTRACT
The work loop technique was used to examine the effects of adrenaline on the mechanics of cardiac muscle contraction in vitro. The length for maximum active force (Lmax) and net work production (Lopt) for rat papillary muscles was determined under control conditions (without adrenaline). The concentration of adrenaline producing the maximum inotropic effect was determined. This concentration was used in the remainder of the experiments. Sinusoidal strain cycles about Lopt were performed over a physiologically relevant range of cycle frequencies (4–11 Hz). Maximum work and the frequency for maximum work increased from 1.91 J kg−1 at 3 Hz in controls to 2.97 J kg−1 at 6 Hz with adrenaline. Similarly, maximum power output and the frequency for maximum power output (fopt) increased from 8.62 W kg−1 at 6 Hz in controls to 19.95 W kg−1 at 8 Hz with adrenaline.
We suggest that the power–frequency relationship, derived using the work loop technique, represents a useful index with which to assess the effects of pharmacological interventions on cardiac muscle contractility.
Variation in Normalized Isometric Tetanic Force of Isolated Fast-Twitch Muscle Fibres of Rana Temporaria
Authors: Buschman H. P. J. , Van Der Laarse W. J. , Stienen G. J. M. , Elzinga G. 
Published: April 2021

ABSTRACT
The origin of the threefold variation found previously in isometric force normalized to cross-sectional area of single fast-twitch tibialis anterior muscle fibres of the frog Rana temporaria was studied by using (1) a strictly defined stimulus protocol, and (2) influencing the condition of the frog using artificial hibernation. Variation in normalized force was found to be influenced by the length of the rest period between tetani. After a long rest (&gt;6 h), tetanic force production was less than for a tetanus produced after 1 h. The length of the rest period accounted for a factor of 1.24 of the total variation in normalized force. The condition of the frog also influenced normalized force production. Little variation in normalized force was observed between different fibres from the same animal, whereas a significant difference was found between animals. After artificial hibernation, force normalized to cross-sectional area remained unchanged, but force normalized to dry mass per unit length increased; the total variation increased from a factor of 1.37 to a factor of 1.64. Force normalized to muscle protein mass per unit length, however, was not affected by artificial hibernation. We conclude that variation in normalized tetanic force can be partly reduced by standardization of the stimulation protocol and normalization to protein content per unit length.
Dragonfly Flight: III. Lift and Power Requirements
Authors: Wakeling J. M. , Ellington C. P. 
Published: April 2021

ABSTRACT
A mean lift coefficient quasi-steady analysis has been applied to the free flight of the dragonfly Sympetrum sanguineum and the damselfly Calopteryx splendens. The analysis accommodated the yaw and accelerations involved in free flight. For any given velocity or resultant aerodynamic force (thrust), the damselfly mean lift coefficient was higher than that for the dragonfly because of its clap and fling. For both species, the maximum mean lift coefficient was higher than the steady CL,max. Both species aligned their strokes planes to be nearly normal to the thrust, a strategy that reduces the required for flight and which is different from the previously published hovering and slow dragonfly flights with stroke planes steeply inclined to the horizontal. Owing to the relatively low costs of accelerating the wing, the aerodynamic power required for flight represents the mechanical power output from the muscles. The maximum muscle mass-specific power was estimated at 156 and 166 W kg−1 for S. sanguineum and C. splendens, respectively. Measurements of heat production immediately after flight resulted in mechanical efficiency estimates of 13 % and 9 % for S. sanguineum and C. splendens muscles, respectively.
CO2 Release Patterns in Drosophila Melanogaster: The Effect of Selection for Desiccation Resistance
Authors: Williams Adrienne E. , Rose Michael R. , Bradley Timothy J. 
Published: April 2021

ABSTRACT
We used laboratory natural selection on insects as a means of investigating the role of patterns of gas exchange in desiccation resistance. We used 15 populations of Drosophila melanogaster: five selected for desiccation resistance, five control populations and five ancestral populations. Using flow-through respirometry, we found that D. melanogaster from all populations produced irregular peaks of CO2 release. To quantify the height and frequency of these peaks, we used the standard error of a linear regression (SER) through the recordings of CO2 release. The values for the SER were significantly larger in the populations selected for desiccation resistance than in the control and ancestral populations. Occasionally, highly periodic peaks of CO2 release were observed in the desiccation-resistant populations only. Maximum SER was found to be strongly correlated with survival time in dry air among selection treatments, but not among individuals within a population. Access to dietary water resulted in lower SER values. These data demonstrate that gas exchange is physiologically controlled in Drosophila melanogaster and that the pattern of gas exchange can change under selection. The relationship between these CO2 release patterns and classic discontinuous ventilation is discussed.
Changes in Midgut Active Ion Transport and Metabolism During Larval–Larval Molting in the Tobacco Hornworm (Manduca Sexta)
Authors: Chamberlin M. E. , Gibellato C. M. , Noecker R. J. , Dankoski E. J. 
Published: April 2021

ABSTRACT
Ion transport and metabolism in the posterior midgut before, during and after the molt to the fifth instar of the tobacco hornworm Manduca sexta were investigated. In situ measurements reveal that the transepithelial potential difference of the posterior midgut falls during the molting process. This finding was confirmed by in vitro experiments in which it was demonstrated that both the transepithelial potential and the short-circuit current are lower in molting fourth instars compared with feeding fourth instars. The short-circuit current increases after ecdysis, with a maximal rate being achieved approximately 4 h after the molt. Resumption of feeding after the molt is not necessary to initiate this increase in active ion transport. The metabolic organization of the tissue also changes during the molting process. The maximal activities of glycolytic enzymes and 3-hydroxyacyl-CoA dehydrogenase, an enzyme of lipid β-oxidation, decrease during the molting process and increase after ecdysis. Although citrate synthase activity, an index of maximal aerobic capacity, decreases during the molt and increases again after ecdysis, tissue respiration is the same in feeding fourth instars and molting larvae. This result indicates that a greater percentage of maximal aerobic capacity is used during molting and that energy may be diverted to cell proliferation and differentiation and away from the support of active ion transport at this time.
Behavioral Response to Ultrasound by The Tiger Beetle Cicindela Marutha Dow Combines Aerodynamic Changes and Sound Production
Authors: Yager David D. , Spangler Hayward G. 
Published: April 2021

ABSTRACT
Tethered flying tiger beetles, Cicindela marutha, respond to trains of bat-like ultrasonic pulses with a short-latency, multi-component behavior. The head rolls to one side, the metathoracic legs kick to the opposite side, the elytra swing backwards towards the hindwings and pronate, the hindwings increase their stroke excursion and frequency, and the plane of the hindwing motion tilts forward. In addition, the beetles produce trains of ultrasonic clicks typically containing 100–200 clicks in response to a 1 s stimulus. The clicks average 85–90 dB SPL at 2 cm. The latencies for hindwing changes and elytra swing in response to stimuli more than 10 dB over threshold are 90–110 ms; the latency to clicking is 120–150 ms. Neither the head roll nor the leg kick appears to be directional relative to the sound source. The behavioral response is broadly tuned with greatest sensitivity at 30–60 kHz and mean behavioral thresholds of 75–80 dB SPL. Physiological audiograms from the auditory afferents show substantially greater sensitivity and sharper tuning than the behavioral response, which suggests that tiger beetles may use their hearing in other contexts as well as during flight. The combination of aerodynamic components and arctiid-moth-like clicking may provide these insects with a powerful defense against attack by echolocating bats.
Factors Contributing to Seasonal Increases in Inoculative Freezing Resistance in Overwintering Fire-Colored Beetle Larvae Dendroides Canadensis (Pyrochroidae)
Authors: Olsen T. Mark , Sass Sandra J. , Li Ning , Duman John G. 
Published: April 2021

ABSTRACT
The insects and microarthropods that vary seasonally in susceptibility to cross-cuticular inoculation by external ice (inoculative freezing) represent a phylogenetically diverse group; however, few studies have explored possible mechanisms experimentally. This study documents seasonally variable inoculative freezing resistance in Dendroides canadensis beetle larvae and combines immunofluorescence, in vivo removal of epicuticular lipids and in vitro chamber studies to explore the roles of seasonal modification in the cuticle and in epidermal and hemolymph antifreeze proteins (AFPs). Seasonal cuticular modifications contribute to the inhibition of inoculative freezing since more cold-hardy larvae froze inoculatively when epicuticular waxes were removed with hexane and, in in vitro chamber experiments, cuticle patches (with the underlying epidermis removed) from winter larvae provided greater protection from inoculative freezing than did cuticle patches from summer larvae. The results indicate that seasonal modifications in epidermal and hemolymph AFPs contribute most strongly to the inhibition of inoculative freezing. Subcuticular epidermal AFPs were present in immunocytochemically labeled transverse sections of winter larvae but were absent in summer ones. Winter integument patches (cuticle with epidermis) were more resistant to inoculative freezing than were summer integument patches. Integument patches resisted inoculative freezing as well as live winter-collected larvae only when hemolymph AFP was added. The results also suggest that some integumentary ice nucleators are removed in cold-hardy larvae and that AFP promotes supercooling by inhibiting the activity of these nucleators.
Sound Production in the Collared Dove: A Test of the ‘Whistle’ Hypothesis
Authors: Ballintijn Mechteld R. , Cate Carel Ten 
Published: April 2021

ABSTRACT
The mechanism of sound production in the collared dove Streptopelia decaocto was studied to test the validity of the ‘whistle’ model and to analyze the role of vocal tract resonances. In this study, the vocalizations of six male adult doves were recorded both in normal air and in a mixture of 80 % helium and 20 % oxygen (heliox). Depending on the way in which the syrinx operates, the spectral structure of the vocalizations is expected to show specific changes in heliox. The effects of heliox differed substantially depending on the type of vocal element. Except for a significant decrease in amplitude, unmodulated elements, i.e. elements with a constant frequency, were relatively unaffected by heliox. In contrast, modulated elements, i.e. elements with an abrupt increase in frequency, showed a gradual increase in frequency with increasing helium concentration. This specific increase in frequency stopped when the modulation frequency was 1.5 times the base frequency, even when the helium concentration was increased further. In some individuals, a frequency band of half the base frequency was also observed. In general, the proportion of modulated elements also showed a significant decrease. The lack of change in the fundamental frequency of the unmodulated elements and in the base frequency of the modulated elements indicates that these vocalizations are not produced like a whistle. It is more likely that they are the result of vibration of the syringeal membranes. Generally, vocal tract resonances do not play an active role in the modification of vocalizations, although they might enhance the fundamental frequency passively. The results suggest that the almost pure tonal vocalizations are produced as such in the syrinx and undergo limited modification when passing through the vocal tract. The effect of heliox on the modulation frequency suggests (1) that different sound-producing mechanisms may underlie different types of vocalizations, and (2) that resonance properties of the vocal system may be involved in the production or modification of the modulation frequency.