bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of yeast V-ATPase mutants lacking Vph1p or Stv1p and the effect on endocytosis
Authors: Perzov Natalie , Padler-Karavani Vered , Nelson Hannah , Nelson Nathan 
Published: April 2021

SUMMARYSubunit a of V-ATPase in the yeast Saccharomyces cerevisiae, in contrast to its other subunits, is encoded by two genes VPH1 and STV1. While disruption of any other gene encoding the V-ATPase subunits results in growth arrest at pH 7.5, null mutants of Vph1p or Stv1p can grow at this pH. We used a polyclonal antibody to yeast Stv1p and a commercially available monoclonal antibody to Vph1p for analysis of yeast membranes by sucrose gradient fractionation, and two different vital dyes to characterize the phenotype of vph1 ▵ and stv1 ▵mutants as compared to the double mutant and the wild-type cells. Immunological assays of sucrose gradient fractions revealed that the amount of Stv1p was elevated in the vph1 ▵ strain, and that vacuoles purified by this method with no detectable endosomal contamination contain an assembled V-ATPase complex, but with much lower activity than the wild type. These results suggest that Stv1p compensates for the loss of Vph1p in the vph1 ▵ strain. LysoSensor Green DND-189 was used as a pH sensor to demonstrate unexpected changes in vacuolar acidification in stv1▵ as the Vph1p-containing V-ATPase complex is commonly considered to acidify the vacuoles. In the vph1 ▵ strain, the dye revealed slight but definite acidification of the vacuole as well. The lipophilic dye FM4-64 was used as an endocytic marker. We show that the null V-ATPase mutants, as well as the vph1 ▵ one, markedly slow down endocytosis of the dye.
Temperature adaptation inGillichthys(Teleost: Gobiidae)A4-lactate dehydrogenases
Authors: Fields Peter A. , Kim Yong-Sung , Carpenter John F. , Somero George N. 
Published: April 2021

SUMMARYAlternative conformations of proteins underlie a variety of biological phenomena, from prion proteins that cause spongiform encephalopathies to membrane channel proteins whose conformational changes admit or exclude specific ions. In this paper, we argue that conformational differences within globular `housekeeping' enzymes may allow rapid adaptation to novel environments. Muscle-type lactate dehydrogenases (A4-LDHs) from the gobies Gillichthys seta and G. mirabilis have identical amino acid sequences but show potentially adaptive differences in substrate affinity (apparent Michaelis constants for pyruvate, KmPYR) as well as differences in thermal stability. We examined the A4-LDH of each species using fluorescence spectroscopy, near- and far-ultraviolet circular dichroism (CD)spectroscopy and hydrogen/deuterium exchange (H/D) Fourier-transform infrared spectroscopy to determine whether structural differences were apparent, the extent to which structural differences could be related to differences in conformational flexibility and whether specific changes in secondary or tertiary structure could be defined. The fluorescence spectra and far-ultraviolet CD spectra of the A4-LDH from the two species were indistinguishable, suggesting that the two conformations are very similar in secondary and tertiary structure. Apparent melting temperatures(Tm) followed by fluorescence and CD spectroscopy confirmed that the G. mirabilis A4-LDH is more thermally stable than the G. seta form. H/D exchange kinetics of Gillichthys A4-LDH was described using double-exponential regression; at 20 °C, G. seta A4-LDH has a higher exchange constant, indicating a more flexible and open structure. At 40°C, the difference in H/D exchange constants disappears. Second-derivative analysis of H/D exchange infrared spectra indicates that α-helical, but not β-sheet structure, differs in conformational flexibility between the two forms. Second-derivative ultraviolet spectra indicate that at least one of the five tyrosyl residues in the Gillichthys LDH-A monomer is located in a more hydrophobic environment in the G. mirabilis form. Homology models of A4-LDH indicate that Tyr246 is the most likely candidate to experience a modified environment because it is involved in subunit contacts within the homotetramer and sits in a hinge between a staticα-helix and one involved in catalytic conformational changes. Subtle differences in conformation around this residue probably play a role both in altered flexibility and in the potentially adaptive differences in kinetics between the two A4-LDH forms.
Torque patterns of the limbs of small therian mammals during locomotion on flat ground
Authors: Witte Hartmut , Biltzinger Jutta , Hackert Rémi , Schilling Nadja , Schmidt Manuela , Reich Christian , Fischer Martin S. 
Published: April 2021

SUMMARYIn three species of small therian mammals (Scandentia: Tupaia glis, Rodentia: Galea musteloides and Lagomorpha: Ochotona rufescens) the net joint forces and torques acting during stance phase in the four kinematically relevant joints of the forelimbs (scapular pivot,shoulder joint, elbow joint, wrist joint) and the hindlimbs (hip joint, knee joint, ankle joint, intratarsal joint) were determined by inverse dynamic analysis.Kinematics were measured by cineradiography (150 frames s-1). Synchronously ground reaction forces were acquired by forceplates. Morphometry of the extremities was performed by a scanning method using structured illumination.The vector sum of ground reaction forces and weight accounts for most of the joint force vector. Inertial effects can be neglected since errors of net joint forces amount at most to 10 %. The general time course of joint torques is comparable for all species in all joints of the forelimb and in the ankle joint. Torques in the intratarsal joints differ between tailed and tail-less species. The torque patterns in the knee and hip joint are unique to each species.For the first time torque patterns are described completely for the forelimb including the scapula as the dominant propulsive segment. The results are compared with the few torque data available for various joints of cats(Felis catus), dogs (Canis lupus f. familiaris),goats (Capra sp.) and horses (Equus przewalskii f. caballus).
The Influence of Various Physical and Biological Factors of the Environment on Honeybee Activity. An Examination of the Relationship Between Activity and Nectar Concentration and Abundance
Authors: Butler C. G. 
Published: April 2021

ABSTRACT
As the quantity of nectar of a given species of plant becomes smaller, irrespective of its sugar concentration, so the number of bees working that species of plant becomes reduced. This is not due to old bees that have been working this crop for some time deserting it in favour of a more profitable crop, but to the natural death of these old bees and the fact that their places are not taken by new bees. Young foragers are not attracted to the crop concerned because its presence is not communicated to them by the old bees still working upon it. The range of nectar concentration (% total carbohydrate) in the flowers of many species of plants growing in a given district varies from day to day and even from hour to hour. Such changes are almost certainly directly due to changes in the atmospheric humidity. The changes are greatest in flowers, such as hawthorn, with relatively unprotected nectaries. Honeybees respond to the concentration of nectar secreted by the flowers of plants, working in the greatest numbers on those plants with the highest nectar concentration. When two or more species of ‘bee-plants’ are in flower simultaneously the species which will attract most honeybees will be that in the flowers of which the nectar is most highly concentrated. This accounts for the occasional failure of honeybees to work the flowers of fruit trees when other flowers are available to them. Both nectar abundance and nectar concentration appear to have considerable effect upon honeybee activity. From the data at present available it appears correct to conclude tentatively that nectar concentration decides in the first instance which species of plant will be visited in preference to others in flower at the same time, and that nectar abundance then determines the proportion of the foraging population of a colony which will work the flowers in question.
Transpiration Through the Cuticle of Insects
Authors: Wigglesworth V. B. 
Published: April 2021

ABSTRACT
The cuticle of most insects is an effective barrier to the evaporation of water. Since the work of Kühnelt (1928,1939) it has been known that this impermeability is a property of the outermost layer. It is usually ascribed to the epicuticle—defined as the layer, of the order of 1 μ in thickness, that is not penetrated by the pore canals, contains no chitin, and resists solution in cold concentrated hydrochloric or sulphuric acids. From chemical tests Kühnelt concluded that the epicuticle contained fatty acids and cholesterol-like bodies. He therefore refers to it as a ‘lipoid cuticula’.
An Improved Radiation Integrator for Biological Use
Authors: Gunn D. L. , Kirk R. L. , Waterhouse J. A. H. 
Published: April 2021

ABSTRACT
A new radiation integrator is described similar to one previously described by Buxton. Methods of construction are given in detail to facilitate the standardization of future instruments. Instruments of different sensitivities have been constructed by the use of either alcohol or water as the volatile liquid. The alcohol instruments can be used for determining changes in intensity over short periods of time; the water instruments are of most value for determining the mean daily intensity of sunshine. The instruments have been calibrated against absolute measurements with a pyrheliometer. Compared with previous instruments of the same type a very much improved efficiency has been obtained. The value of this type of instrument for work in the field is discussed; its limitations are briefly indicated.
Facilitation in Sea Anemones
Authors: Ross D. M. 
Published: April 2021

ABSTRACT
The action of a number of drugs which affect the neuromuscular systems of vertebrates has been examined on the sea anemone, Calliactis parasitica. In contrast to their action in vertebrates, no drugs directly cause contraction in the muscles of the anemone. Some drugs of the group which act at cholinergic junctions in the vertebrates, including acetylcholine itself, were ineffective on Calliactis. Atropine and nicotine, of the same group, had depressant effects. Some drugs of the group which act at adrenergic junctions in vertebrates, including adrenaline itself, were ineffective on Calliactis. On the other hand, tyramine, tryptamine and 933 F enhanced and sensitized the response to nervous excitation. Thus responses to single stimuli occurred, whereas normally responses only follow the second and subsequent stimuli. Cocaine enhanced and ergotoxine depressed the responses of Calliactis in a manner analogous to their effects in vertebrates. No significant effects were observed with other substances, including strychnine, veratrine, histamine, betaine and tetramethylammonium hydroxide. The limitation of the drug effects to enhancement and sensitization supports the view that neuromuscular transmission in Calliactis cannot be a simple chemical process as in the vertebrates. In general the results support the hypothesis that there is a separate process of sensitization which must precede the excitation of the muscle in these animals. On the other hand, the drugs which have sensitizing effects on Calliactis do not possess all the properties that would be expected of a natural ‘sensitizer’ or ‘facilitator’ carrying out this process of sensitization at the nerve ending.
Facilitation in Sea Anemones
Authors: Ross D. M. 
Published: April 2021

ABSTRACT
Extracts of the sea anemones, Calliactis parasitica and Metridium senile, have been prepared and their effects on the neuromuscular response of these anemones tested. The presence of extract sensitizes the organism so that a response is given to a single stimulus, whereas normally this occurs only on the second and subsequent stimuli. No other significant effects were observed. The sensitizing effect of the extract differs from the effect of a sensitizing drug like tyramine; it appears more quickly, more regularly, and it is rarely accompanied by an increase in the size of the muscular contraction. The fact that a substance with sensitizing properties has been detected in anemones supports the view that a ‘sensitizer’or’ facilitator’ exists and takes part in neuromuscular transmission in these animals. Nevertheless, the extract, like the sensitizing drugs, lacks some of the properties that would be expected of a true ‘sensitizer’ or ‘facilitator’.
Blood Pressure and Pulse Rate in the Foetal Sheep
Authors: Barcroft Joseph , Barron D. H. 
Published: April 2021

ABSTRACT
A method (the needle method) is described for the measurement of the pressure in the stream going through a vessel. In the foetal sheep the needle method applied to the umbilical artery gives substantially the same results as the mercurial manometer applied to the carotid, until about half-way through the gestation period. As gestation proceeds the needle method applied at the first moment at which it can be applied to the umbilical artery (or a branch) gives readings substantially lower, and increasingly lower as gestation proceeds, than does the mercurial manometer read at the first moment at which it can be read. The discrepancy is due to the sum of a number of causes which are discussed, but of these the most important is an actual rise of pressure between the time of delivery and the completion of the dissections contingent on the use of the mercurial manometer. The cause of this is not at present demonstrated, but either or both of two factors may be concerned : (a) a dulling of the central nervous system which weakens the depressor reflfex; (b) the establishment of a greater degree of vasomotor tone consequent on the bombardment of the central nervous system with sensory stimuli. The pulse rates in utero and just after delivery of the foetus into a saline bath at 39 –40°C. (the umbilical circulation being unimpaired) are not significantly different. The pulse rate quickens up to the 70th-8oth day, after which it becomes slower as gestation proceeds. If both vagi be severed, the pulse rate tends to quicken throughout gestation. The pulse, therefore, comes increasingly under vagus inhibition from the Soth-qoth day onwards. Even after the vagi have been cut after the 120th day (it has not been tried before) adrenalin in sufficient quantity will cause a further quickening of the pulse. The earliest date at which stimulation of the peripheral end of the right vagus was observed to slow the heart was the 77th day. On the 85th day peripheral stimulation of the left vagus also failed, but succeeded on the 101st day. Central stimulation of the left vagus, with the right vagus intact, produced slowing on the 77th day. Slowing of the heart synchronous with rise of arterial pressure has been observed on the 11th day. Slowing of the heart which bears evidence of being reflex has been obtained by raising the blood pressure (clamping the cord) on the 121st day and by injection of adrenalin on the 118th day. Approaching term both the carotid sinus and cardiac depressor mechanisms are functional. Lowering of the blood pressure as the result of stimulation of the central end of the vagus and with both vagi severed can be demonstrated late in gestation.
Studies on Tapeworm Physiology
Authors: Smyth J. D. 
Published: April 2021

ABSTRACT
Unidentified plerocercoids of the family Diphyllobothriidae were removed aseptically from the coelomic cavity of Gasterosteos aculeatus and cultivated at 40°C. in various liquid nutrient and saline media under sterile conditions. The most successful results were obtained with peptone-broth+10% horse serum in which larvae remained active and behaved normally for 10 days. Broth without peptone gave poor results (max. 2 days) but the addition of peptone (max. 7 days) greatly improved the activity. The addition of glucose or yeast to peptonebroth was not significantly beneficial. Survival times in all nutrient media were considerably longer than the periods of normal behaviour. In strength Locke’s saline, the maximum period of normal behaviour was 4 days. The addition of glucose (0·25-1 %) to this saline was detrimental to the behaviour of the larvae. Histochemical investigation showed that fresh larvae were rich in glycogen but almost fat-free. The occurrence of glycogen in larvae after cultivation in various nutrient and non-nutrient media was such that no conclusions regarding the carbohydrate metabolism could be drawn. All larvae after cultivation, however, contained great quantities of intracellular fat, from which it was concluded that fat is a by-product of metabolism. During cultivation in the more favourable media, larvae became firmly attached to the walls of the culture tube by means of their bothria; the strobila also became greatly elongated, and segmented in some cases. Histological examination failed to detect mitosis in the nuclei of the strobila and it was concluded that growth of the strobila had not taken place. The elongation of the strobila was presumed to be a result of the relaxation of the longitudinal musculature. Of eight larvae kept in broth+1% peptone+ 0·5% glucose at room temperatures, seven still showed active undulation on exposure to light after 80 days’ cultivation.
The Physiology of Sea-Urchin Spermatozoa
Authors: Rothschild Lord 
Published: April 2021

ABSTRACT
An investigation has been made into the causes of the interrelated phenomena of Senescence and the Dilution Effect in the spermatozoa of Echinus esculentus. The Dilution Effect is the increase in O2 uptake and in movement observed when a concentrated sperm suspension, obtained by partial dilution of semen, is diluted with sea water. The supernatant sea water obtained by centrifuging partially metabolized sperm suspensions contains no substances which depress the respiration or motility of the spermatozoa of the same species. This supernatant sea water has a small but definite protective action on spermatozoa in maintaining but not increasing their O2 consumption. The effect is enhanced by agitating the suspensions before centrifugation, E. esculentus spermatozoa do not glycolyse aerobically, anaerobically, or in the presence of 5% O2 in CO. The absence of aerobic acid production proves that the reduced O2 uptake per sperm of dense suspensions is not due to a lowering of the pH of the medium. As the Dilution Effect is observed in manometric experiments in which CO2 is continuously and adequately removed, neither accumulation of CO2 nor a reduction in pH resulting from the accumulation of CO2 are responsible for the reduced O2 uptake of dense suspensions. The O2 uptake of dense sperm suspensions ( &gt; 109 sperm/ml.) is altered by changes in O2 tension. O2 consumption in 100% oxygen is nearly double that in 10% O2 in Ns. An increase in O2 tension has no stimulating action on dilute suspensions. An atmosphere of 100% O2 has a gradual toxic effect on dense and dilute sperm suspensions. Carbon monoxide has a greater inhibitory action on dilute than on concentrated sperm suspensions. The difference between the effects of varying O2 tensions or CO on dense and dilute suspensions is partly, or perhaps wholly, due to gaseous diffusion being a limiting factor. This may partly explain the Dilution Effect. Apart from photo-reversibly inhibiting respiration, CO exerts an irreversible toxic influence on sea-urchin spermatozoa. Illumination of spermatozoa with a wave-length of light outside the region of photo-chemical absorption by CO cytochrome oxidase enables visual examination to be made in the presence of CO. The O2 uptake of a suitable concentration of spermatozoa is 70% inhibited by 5% O2 in CO. The same inhibition occurs when the suspension is illuminated by light of wave-length 548 mμ, but there is no equivalent decrease in motility. After motility and respiration have ceased sea-urchin spermatozoa still contain oxidizable substrates and the appropriate dehydrogenases as evidenced by their ability to reduce methylene blue in an evacuated Thunberg tube.
Studies on Animal Carotenoids
Authors: Steven D. M. 
Published: April 2021

ABSTRACT
The principal carotenoids of the trout are b-carotene, lutein and astacene. Carotenoids occur in the skin, muscles, ovary, liver and eyes, but the different types are distributed in a characteristic way in the various tissues. Carotene is found in significant amounts only in the liver and ovaries; lutein and astacene together in the skin, muscles and ovaries; lutein alone in the eyes. Xanthophylls, mainly lutein, occur also in the liver. Other carotenoids occur in trace amounts only. The lutein and astacene of skin are in the form of esters. They are located in the xanthophores and erythrophores, of which they are the characteristic pigments. Yellow areas of skin yield mainly lutein, red areas mainly astacene, and their concentration in all parts of the skin is normally several times greater than in any other tissue. In muscle and ovaries both lutein and astacene are present as free hydroxy-carotenoids. Liver contains both free and esterified xanthophylls, the eye tissues only esters. The concentration of the different carotenoid fractions in various tissues was measured with a photoelectric colorimeter in terms of standard preparations of pure carotenoids. Direct measurements of the absorption spectra of xanthophores and erythrophores show that the former contain only lutein, the latter only astacene. Living xanthophores show absorption maxima at 487, about 450 and at 425 mμ; erythrophores a single maximum close to 490 mμ. The maxima in the blue-green are displaced some 10 –12 mμ towards the red from their positions in hexane. The concentration of pigment in fully contracted chromatophores was estimated by a visual matching method. Xanthophores were found to contain about 0 ·00001 –0 ·00003 γ of lutein per cell, erythrophores about 0 ·00020 –0 ·00035 γ per cell. Trout kept on a diet low in carotenoids lose most of their red and yellow pigments. Astacene disappears from the skin, and the lutein falls to about one-sixth of the normal level. Feeding with natural foods rich in carotenoids may restore the skin coloration, and fish reared on a natural diet develop normal wild-type pigmentation. Supplements of pure carotenoids added to the basal diet failed to raise the pigment levels of depigmented fish. Trout do not appear to be able to convert one type of carotenoid to another.
A Simplified Ultra-Micro Kjeldahl Method for the Estimation of Protein and Total Nitrogen in Fluid Samples. of Less Than 1·0μ1
Authors: Shaw J. , Beadle L. C. 
Published: April 2021

ABSTRACT
An ultra-micro modification of the Kjeldahl method is described whereby nitrogen can be estimated in a blood sample of less than 1 μl. Volume. This is simpler than previously described methods as regards apparatus and procedure. The separate estimations of protein and total nitrogen are also introduced. For samples containing 1·0-10·0 μg. N the standard deviation is 0·02-0·04 μg. N. Preliminary tests indicate that for 0·1-1·0 μg. N the standard deviation would be of the order of 0·006-0·008 μg. N.
The Site of Formation of Hypotonic Urine in the Nephridium of Lumbricus
Authors: Ramsay J. A. 
Published: April 2021

ABSTRACT
Methods for the collection of samples of urine from different parts of the nephridium of Lumbricus are described. The osmotic pressures of these samples have been measured by determination of freezing-point depression and have been compared with the osmotic pressure of the medium surrounding the nephridium. The results of this comparison indicate that the ability to form hypotonic urine is certainly present in the wide tube, is possibly present in the middle tube and is probably not present in the narrow tube. The analogy between the nephridium and the vertebrate nephron is discussed.