bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metamorphosis of Research on Ion-Coupled Metabolite Transport
Authors: Slayman Clifford L. 
Published: April 2021

ABSTRACT
A defining moment in the history of active transport research came in August 1960, in a symposium at the Czeckoslovak Academy of Sciences, which became known among membrane biologists as the Prague Symposium (Kleinzeller and Kotyk, 1961). By that date, the enzymatic nature of sodium transport in animal cells had been demonstrated (Skou, 1957) and a generalized concept of transport-related, vectorial metabolism was being formulated (Mitchell, 1961). Specifically concerning uptake of organic metabolites, a pivotal observation had been made by Riklis and Quastel (1958): that active transport of sugars by intestinal villus membrane is dependent upon sodium ions in the luminal bathing solution. This finding was extended by Crane et al. (1961), who suggested in Prague that sugar and sodium ions might be simultaneously transported, and was further discussed by Mitchell. Subsequently, both Crane and Mitchell elaborated hypotheses of ion-coupled sugar transport: Na+–glucose in mammalian intestine (Crane, 1962) and H+–galactoside in Escherichia coli (Mitchell, 1962), which became incorporated into a comprehensive picture of proton-linked ‘chemiosmotic’ processes in bioenergetics.
Ca2+ Transport in Saccharomyces Cerevisiae
Authors: Cunningham Kyle W. , Fink Gerald R. 
Published: April 2021

ABSTRACT
Cytosolic free Ca2+ is maintained at submicromolar levels in budding yeast by the activity of Ca2+ pumps and antiporters. We have recently identified the structural genes for two Ca2+ pumps, PCM1 and PMR1, which are required for Ca2+ sequestration into the vacuole and secretory organelles, respectively. The function of either Ca2+ pump is sufficient for yeast viability, but deletion of both genes is lethal because of elevation of cytosolic [Ca2+] and activation of calcineurin, a Ca2+-and calmodulin-dependent protein phosphatase. Calcineurin activation decreases Ca2+ sequestration in the vacuole by a putative Ca2+ antiporter and may also increase Ca2+ pump activity. These regulatory processes can affect the ability of yeast strains to tolerate high extracellular [Ca2+]. We propose a model in which the cellular response to changes in the environmental levels of Ca2+ is mediated by calmodulin and calcineurin which, in turn, modulate the various types of Ca2+ transporters.
The Lactose Permease Meets Frankenstein
Authors: Kaback H. Ronald , Frillingos Stathis , Jung Heinrich , Jung Kirsten , Privé Gilbert G. , Ujwal M. L. , Weitzman Cindy , Wu Jianhua , Zen Kevin 
Published: April 2021

ABSTRACTThe lactose permease (lac) of Escherichia coli is a paradigm for membrane transport proteins. Encoded by the lacY gene, the permease has been solubilized, purified to homogeneity, reconstituted into phospholipid vesicles and shown to catalyse the coupled translocation of β-galactosides and H+ with a stoichiometry of unity. Circular dichroism and other spectroscopic approaches demonstrate that the purified permease is about 80% helical. Based on hydropathy analysis of the primary amino-acid sequence, a secondary structure has been proposed in which the protein has 12 hydrophobic domains in α-helical conformation that traverse the membrane in zigzag fashion connected by hydrophilic loops. A variety of other approaches are consistent with the model and demonstrate that both the N and C termini are on the inner surface of the membrane, and studies on an extensive series of lac permease/alkaline phosphatase fusion proteins provide exclusive support for the topological predictions of the 12-helix motif. This presentation concentrates on the use of site-directed fluorescence spectroscopy to study structure–function relationships in the permease.
Measurement of Water and Carbon Dioxide Loss From Insects Using Radioactive Isotopes
Authors: Croghan P. C. , Noble-Nesbitt J. , Appel A. G. 
Published: April 2021

ABSTRACT
A method is described for investigating the rate of loss of water and carbon dioxide from terrestrial insects by absorbing tritiated water and 14CO2 from a gas stream flowing past the insect. The loss of water and carbon dioxide can be studied simultaneously with a time resolution (nominal) down to 2 min.
The theoretical and experimental bases of analysing the data are considered in detail. The determination of the efflux rate constant for water is straightforward and, if an estimate of surface area is available, the efflux rate constant can be converted to a permeability coefficient. In the case of 14CO2 loss, the interpretation is complicated by the presence of other compartments within the body that can be labelled with 14C. A multicompartment model of 14C exchange is developed and a method of obtaining the efflux rate constant of 14CO2 is described. The efflux rate constant for 14CO2 can be used to estimate CO2 output.
Motor Pattern of the Stinging Response in the Honeybee APIS Mellifera
Authors: Ogawa H. , Kawakami Z. , Yamaguchi T. 
Published: April 2021

ABSTRACT
In the stinging response of the worker honeybee (Apis mellifera), rhythmic movements of the lancets on the stylet are produced by alternating contractions of a set of stinging muscles (a protractor, M198, and a retractor, M199) on each side during co-contraction of the frucula muscles (M197s) on both sides. In this study, stinging movements were elicited by tactile stimulation to the sternum in isolated abdomens, in intact animals and in preparations in which the connectives between the sixth and terminal abdominal ganglia were cut. There was a close relationship among the following three temporal variables of stinging motoneurone pattern: the interval between successive bursts of a stinging muscle, the duration of a burst and the time lag between the bursts of homologous stinging muscles on both sides. All of these variables increased linearly as the sting was inserted deeper into a soft object and the tension on the lancets increased.
When sensory nerves from the proprioceptors (campaniform sensilla on the tapering sting shaft and hair plates at the basal cuticular plate) were cut on both sides, the relative timing of bursts of homologous stinging muscles on both sides and antagonistic stinging muscles on each side became more variable. When a proprioceptive input was removed from one side during penetration of the sting, the frequency of the bursts of stinging muscles was higher and the duration of bursts was shorter on the cut side than on the intact side; nevertheless, a sting muscle was still activated out of phase with its antagonistic muscle on the ipsilateral side and its homologous muscle on the contralateral side.
These results suggest that the motor pattern driving the rhythmic movements of stinging muscles is produced by a central pattern generator consisting of a pair of oscillators located in the terminal abdominal ganglion and that the precise timing of the motor pattern in a hemiganglion is controlled mainly by proprioceptive inputs on its own side.
Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae:III. Goblet Valve PATENCY
Authors: Moffett David F. , Koch Alan , Woods Robin 
Published: April 2021

ABSTRACT
The midgut epithelium of lepidopteran insect larvae contains characteristic goblet cells possessing an apical cavity surrounded by goblet cell apical membrane (GCAM) and guarded from the gut lumen by a valve-like structure. The currently accepted model of active K+ secretion by the midgut of lepidopteran insect larvae locates the major active step at the GCAM, implying that actively transported K+ reaches the gut lumen by passing through the valve.
The major question for these studies was whether K+ could pass through the valve by diffusion in free solution. Using tetramethylammonium (TMA+) as a surrogate for K+, and exploiting the high sensitivity of standard K+-selective ion-exchange resin to quaternary amines, we used K+-selective intracellular electrodes to measure the rate of access of apically applied TMA+ to the goblet cavity.
TMA+ failed to gain access to more than half of the cavities. For those cavities to which it did gain access, the influx and efflux rates and predicted equilibrium concentrations of TMA+ were too low to be consistent with diffusive exit of transported K+ along the same path. Upon superfusion with cytochalasin E, a disrupter of actin-based cytoskeleton, the TMA+ influx rates immediately increased for those cavities previously accessible to TMA+, but not for those previously inaccessible. Increases in TMA+ influx suggestive of spontaneous valve opening were not observed. The results are consistent with an indirect route of access of TMA+ to goblet cavities.
We conclude that goblet valves are closed in vitro. Assuming that the goblet cavity is part of the transport route, actively transported K+ must exit the cavity to the gut lumen by a mechanism that does not involve diffusion in free solution.
Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae : IV. A Multicompartment Model Accounts for Tetramethylammonium Entry into Goblet Cavities
Authors: Koch Alan , Moffett David F. 
Published: April 2021

ABSTRACT
A quantitative model was developed to explain the kinetics of tetramethylammonium (TMA+) movement into and out of the goblet cavities of posterior midgut cells of Manduca sexta based on the data of the accompanying paper, which indicated that TMA+ does not enter the goblet cavity directly from the lumen.
The model has two cellular compartments between the lumen and goblet cavity; these have been tentatively identified as the columnar cell and goblet cell cytoplasm. Five transmembrane pathways are included: from lumen to columnar cell, from columnar cell to goblet cell, from goblet cell cytoplasm to goblet cell cavity, and across the basal membrane of each cell type. These pathways need not be channels; they could use endocytotic or exocytotic mechanisms or, in the case of the cell-to-cell passage, septate junctions. However, in all cases, transfer is proportional to the electrochemical gradient.
The model was tested against the results obtained after exposure to TMA+ in short-circuited and open-circuited tissues as well as results from an open-circuited tissue that did not develop a large transepithelial potential. Although driving forces for TMA+ across the membrane barriers were quite different in the different experimental conditions, the transfer coefficients from lumen to columnar cell, from columnar to goblet cell and from both cells across the basal membrane were the same. The only transfer coefficient that changed between short-circuit and open-circuit conditions was that from goblet cell cytoplasm to goblet cavity. This value was high under short-circuit conditions (when K+ transport activity is high), but low under open-circuit conditions (when K+ transport activity is low).
The model suggests a hypothesis in which TMA+ enters the goblet cavity by an indirect route across the cell membrane of columnar cells, and thence passes to the goblet cell cytoplasm through intercellular junctions. Results from experiments with cytochalasin E suggest that the actin-based cytoskeleton is involved in limiting cell–cell coupling. In this model, TMA+ passes from the goblet cell cytoplasm to the goblet cavity via the K+/nH+ antiport believed to mediate active transepithelial K+ transport. However, although actively transported K+ is believed to pass from goblet cavity to lumen, TMA+ cannot.
Sound Production in Crickets
Authors: Stephen R. O. , Hartley J. C. 
Published: April 2021

ABSTRACT
The calls of male Gryllus bimaculatus were digitally recorded under four different conditions: in air; in 80 % He/20 % O2; with the tympana occluded with wax in air and finally in the helium/oxygen mixture. The principal frequency component, usually referred to as the carrier frequency, was analysed in a large sample of chirps recorded in the four conditions. In all four recording conditions, the principal frequency component was found to vary from chirp to chirp. The mean of the distribution of the principal frequency component was different in the four recording conditions. Insects with occluded tympana produced in air a greater dispersion of the principal frequency component than insects with normal functioning ears.
The spectrum of an individual chirp generally contained two frequency components, the principal component, which was related to the plectrumfile strike rate, and a second component, which was related to the free vibration of the wings. The subalar air space volume is shown to act as an acoustic resonator and is important in the filtering and amplification of the sound signal. These observations were confirmed by a model stridulatory system. The model system shows that the resonant frequency of the subalar space is dependent upon the square root of the effective volume of the space.
The results suggest that song generation in crickets is a dynamic process involving an auditory feedback control loop. The singing insects appear to be able to control the plectrum–file strike rate as well as the resonant frequency of the subalar space by changing the relative position of the wings and the abdomen, hence varying the volume.
Non-Linear Dynamics of Neurochemical Modulation of Mosquito Oviduct and Hindgut Contractions
Authors: Messer Adam Catton , Brown Mark R. 
Published: April 2021

ABSTRACT
Microphysiological techniques and computer-based methods of data acquisition and analysis were used to investigate the dynamics of neurochemical action on spontaneous contractions of continuously perfused oviducts and hindguts isolated from female mosquitoes (Aedes aegypti). Proctolin, leucomyosuppressin (LMS), serotonin and octopamine, which are known to modulate insect muscle contractions, and a mosquito neuropeptide, Aedes Head Peptide I (Aea-HP-I), which inhibits host-seeking behavior, were tested in the bioassays. LMS depressed contractile activity in oviducts at concentrations above 10−12 mol l-1, but hindguts did not respond to concentrations below 10−6 mol l-1. Hindgut contractions spontaneously restarted in 10−6 mol l-1 LMS, but only washing out LMS restored activity in oviducts. LMS changed the amplitude of the oviduct contractions, but the dynamics of contraction remained steady. Following recovery of contractions in LMS, hindgut tissues contracted with a more regular pattern.
Serotonin and octopamine had an identical action on oviduct and hindgut tissues. At concentrations greater than 10−8 mol l-1, serotonin eliminated the refractory period between contractions and thus increased the contraction frequency of oviducts. Though the contractions appeared chaotic, state-series analysis proved that serotonin-treated oviducts contracted rhythmically. Above 10−6 mol l-1, serotonin extinguished normal hindgut peristalsis and induced regular fluttering of the anteriormost portion of the hindgut, an effect possibly related to diuresis following the blood meal.
Proctolin failed to stimulate both oviduct and hindgut contractions at concentrations up to 10−6 mol l-1, but at 10−8 mol l-1 induced contractions of cricket hindgut preparations. Aea-HP-I had no effect on either tissue at 10−6 mol l-1 or lower concentrations.
State-series analysis, based on simple manipulations of experimental data, permitted direct observation of the dynamics of oviduct and hindgut contractile activity.
The length dependence of work production in rat papillary muscles in vitro
Authors: Layland Joanne , Young Iain S. , Altringham John D. 
Published: April 2021

ABSTRACT
The influence of length on work production was investigated for rat papillary muscles using the work loop technique. Active and passive length–force relationships were first determined under isometric conditions and the length for maximum force production (Lmax) was derived. Starting from different lengths within the physiological range, a series of work loops was generated using the stimulation phase shift, strain amplitude and cycle frequency previously found to be optimal for power output at 37 °C. The relationship between muscle length and net work was used to determine the length at which work output was maximal (Lopt).
In order to examine the dynamic passive properties of the muscles, unstimulated muscles were subjected to the same regime of sinusoidal oscillation as used for the active loops. From the hysteresis loops, lengthening work (work done to extend the passive muscle), passive shortening work (work returned during shortening) and net energy loss (hysteresis) could be measured.
The decline in net work production at lengths greater than 95 %Lmax could largely be attributed to the rapid and non-linear increase in muscle stiffness and the increase in net energy loss over this range of lengths.
The physiological significance of the length–work relationship is considered and the mechanical properties of active and passive papillary muscles are discussed with reference to sarcomere length and cardiac muscle ultrastructure.
Voltage-dependence of ciliary activity in the ciliate Didinium nasutum
Authors: Pernberg Joachim , Machemer Hans 
Published: April 2021

ABSTRACT
In the gymnostome ciliate Didinium nasutum, swimming behaviour depends upon the cyclic activity of about 3000 cilia. The normal beating mode, resulting in forward swimming of the cell, is characterized by a posteriad effective beat (18 ° left of the longitudinal axis) at a frequency of approximately 15 Hz. Activation of depolarization-sensitive ciliary Ca2+ channels leads to an increase in intracellular Ca2+ concentration and a change in the beating mode. Following rapid reorientation, the effective stroke is anteriad (24 ° right of the longitudinal axis) and the beating frequency is about 26 Hz, resulting in fast backward swimming of the cell. In response to minor depolarizations, and hence small increases in cytoplasmic Ca2+ concentration, the cilia inactivate. Frequency increase and reversal in beat orientation share a single threshold level of membrane potential, since both changes of the beating mode occur simultaneously.
Reliability of Stomach Temperature Changes in Determining Feeding Characteristics of Seabirds
Authors: Wilson Rory P. , Pütz Klemens , Grémillet David , Culik Boris M. , Kierspel Mandy , Regel Jana , Bost Charles A. , Lage Jochim , Cooper John 
Published: April 2021

ABSTRACT
We examined the accuracy of stomach temperature archival units (STAUs), which are typically used to determine feeding activity in marine endotherms, with regard to determination of the time of prey ingestion as well as the number of prey items ingested and their masses. Units were deployed in nine species of free-living seabirds, where feeding conditions were uncontrolled, eight species of captive seabirds, where feeding conditions could be partially controlled, and in laboratory stomach simulations, where variables could be strictly controlled. The quality of data obtained on the timing of feeding, the mass ingested and the number of prey items ingested was subject to two main sources of error (i) those induced by changes in animal activity and (ii) those resulting from the physical form of the STAUs themselves. Animal activity factors considered important included the following: variability in (a) body temperature, (b) stomach blood perfusion, (c) consistency of stomach contents and (d) stomach churning and changes in body orientation. The physical form (size and buoyancy) of the STAU affected the location of the unit within the stomach, and thus the likelihood that ingested prey comes into contact with the sensor. The timing of prey ingestion can generally be determined accurately; however, considerable errors in mass estimates can occur if data acquired using STAUs are not critically assessed. An understanding of these sources of errors will allow researchers to construct STAUs appropriate to the species being studied and to analyze data critically so that errors are reduced.
Matrotrophic Viviparity In The Yellowtail Rockfish Sebastes Flavidus
Authors: Macfarlane R. Bruce , Bowers Michael J. 
Published: April 2021

ABSTRACT
A capacity for matrotrophic viviparity was established in the yellowtail rockfish Sebastes flavidus (Teleostei: Scorpaeniformes). The incorporation of radiolabel into embryos from [14C]phosphatidylcholine present in the maternal serum during gestation provided the first in vivo demonstration of matrotrophy of phospholipid for any viviparous teleost and of any nutrient for a member of the genus Sebastes. Radiolabel content increased as embryos progressed through ontogeny.
Serum proteins of 170 kDa, present in vitellogenic and embryogenic females, but not in earlier stages, in immature females or in males, indicated the presence of vitellogenin in pregnant females and, thus, the potential for matrotrophic supplementation to yolk sequestered before fertilization. The retention of higher molecular mass proteins and highly phosphorylated proteins and the maintenance of total protein content in yolk during early to mid embryogenesis argue for exogenous maternal supply during gestation. As ovarian development proceeded from the oocyte through successive embryonic stages, the distribution of yolk proteins shifted from higher (67–97 kDa) to lower molecular masses (&lt;70 kDa).
The results of these experimental studies corroborate data from field investigations showing that yellowtail rockfish can matrotrophically supplement embryo nutrients obtained before fertilization. Thus, yellowtail rockfish represent a teleost species positioned within the viviparity continuum and not at its extremes.
Function Of Metal-Ion Homeostasis In The Cell Division Cycle, Mitochondrial Protein Processing, Sensitivity To Mycobacterial Infection And Brain Function
Authors: Supek Frantisek , Supekova Lubica , Nelson Hannah , Nelson Nathan 
Published: April 2021

ABSTRACT
A novel Saccharomyces cerevisiae mutant, unable to grow in the presence of 12.5 mmol l−1 EGTA, was isolated. The phenotype of the mutant is caused by a single amino acid change (Gly149 to Arg) in the essential yeast cell division cycle gene CDC1. The mutant could be suppressed by overexpression of the SMF1 gene, which codes for a plasma membrane Mn2+ transporter. We observed that the yeast SMF1 gene shares homology with the mouse Nramp gene. Nramp (Bcg) was cloned as a gene responsible for mouse resistance to infection with mycobacteria and is identical with the Ity and the Lsh genes conferring resistance to infection by Salmonella typhimurium and Leishmania donovani, respectively. Although the cloning of Nramp identified the gene responsible for the resistance of mice to mycobacteria, its function is unknown. We propose that the mammalian protein, like the yeast transporter, is a Mn2+ and/or Zn2+ transporter. Following the phagocytosis of a parasite into the phagosome, the macrophage produces reactive oxygen and/or nitrogen intermediates that are toxic for the internalized bacteria. The survival of the pathogen during the burst of macrophage respiratory activity is thought to be partly mediated by microbial superoxide dismutase (SOD), which contains Mn2+ or Fe2+ in its active centre. Nramp may transport Mn2+ from the extracellular milieu into the cytoplasm of a macrophage and, after the generation of the phagosome, remove Mn2+ from the organelle. Thus, the Mn2+-depletion of the phagosome microenvironment by the Nramp gene product may be a rate-limiting step in the metalloenzyme’s production by the engulfed bacteria. This limitation will restrict the mycobacterial ability to produce active enzymes such as SOD and prevent the propagation of the ingested microorganisms. Conversely, an increased concentration of Mn2+ in the phagosome caused by a defective Nramp transporter (Bcgs) may promote the growth of the mycobacteria and render the organism sensitive to the pathogen.
We use a similar approach to identify, clone and study other metal-ion transporters.