bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Size of Living Bacteria
Authors: Ross K. F. A. 
Published: April 2021

ABSTRACT
The difficulties involved in the direct measurement, by eyepiece-micrometer or from photomicrographs, of small microscopic objects such as living bacteria are discussed. The accuracy with which this can be done is limited by the numerical aperture of the optical system and the wavelength of light used. With visible light it is scarcely possible to determine the dimensions of an object more accurately than to the nearest O’4 μ. It also seems probable, from the nature of the diffraction pattern at the edges of images of objects of circular cross-section such as bacteria, that direct measurement of the width of the image will tend to give an underestimate of the true width of the object.
An interference microscope enables thickness measurements to be made that are not subject to these particular limitations, because with it, the phase-change in the light passing through the middle of a bacterium can be measured very accurately. This phase-change is proportional to the product of the refractive index of the bacterium minus that of the mounting medium, and its true thickness.
Two methods were used to determine the mean thickness of the living bacilli in a number of different cultures of Lactobacillus bulgaricus. With the first, the mean refractive index of the bacilli was measured directly by the method of immersion refractometry first used by Barer and Ross (1952), and phase-change measurements were made on the bacilli mounted in dilute saline. Their mean thickness was calculated from these measurements. With the second method, phase-change measurements were made on the bacilli mounted in saline and also mounted in protein solutions with refractive indices ranging from 1·365 to 1·376; and, from these, both their mean thickness and their mean refractive index were calculated.
The phase-change measurements were made with a Smith interference microscope and half-shade eyepiece (manufactured by Messrs. Charles Baker).
The values for the mean thickness of the living L. bulgaricus from 14 different cultures obtained by the first method ranged from 1-13 μ to i·23 μ·, and those from 9 different cultures obtained by the second method ranged from 1 ·02 μ to 1 · 14 μ. The mean refractive indices of the latter calculated by the second method agreed very closely with that obtained by immersion refractometry, and differed by a maximum of o·oo9 in all the cultures measured. It therefore seems unlikely that the mean thickness measurements obtained by either method are wrong by more than about ±o·1 μ.
The Origin of the Metazoa and the Stigma of the Phytoflagellates
Authors: Fauré-Fremiet E. 
Published: April 2021

ABSTRACT
It is well known that in various phytoflagellates one of the flagella is connected with the eye-spot or stigma. In the case of Chromulina psammobia the more differentiated structure of the eye-spot+flagellum complex seems analogous to that of a retinal rod with its connective cilium binding the external segment and the cell-body.
It is tempting to draw a parallel between this finding of comparative cytology and a hypothesis on the origin of Metazoa proposed first by J. R. Baker, and subsequently by A. C. Hardy.
A Simultaneous Coupling Azo Dye Technique Suitable for Whole Mounts
Authors: Lewis P.R. 
Published: April 2021

ABSTRACT
A method based on the familiar coupling azo dye technique has been devised for the study of enzyme distribution in thick specimens. Its application to the study of esterase distribution in whole tadpoles of Xenopus laevis is described in detail. It can also be used to show the distribution of alkaline phosphatase, both in Xenopus tadpoles and in limbs dissected from chick embryos. It has proved useful in embryological studies both for teaching and for research.
Observations on the Developmental Cytology of the Fundic Region of the Rabbit’s Stomach, with Particular Reference to the Peptic Cells
Authors: Menzies Gordon 
Published: April 2021

ABSTRACT
1. The first oxyntic cells, differentiating from a non-mucoid cell, appear on the 23 rd day of the foetal life of the rabbit.
2. Bowie-positive granules appear in most epithelial cells during foetal life, reach a maximum on the 27th day, and then almost disappear before birth.
3. The first peptic cells containing Bowie-positive granules appear a few hours after birth. They increase after the end of the first week until the adult condition is reached.
4. During the first 4 weeks of postnatal life the pepsinogen granules contain a mucinogen component. This is lost between the fourth and sixth weeks. The loss starts in cells at the base of the glands and proceeds up the tubules towards the crypts.
5. Pepsinogen granules containing a mucinogen component are strongly eosinophil.
6. The first ‘mature’ peptic granules, that is ones that are Bowie-positive, PAS-negative and non-eosinophil, appear at the fourth week of postnatal life.
7. Mucous neck-cells (of Bensley) begin to appear at the end of the sixth week of postnatal life. Their development is being further investigated.
The Cytoplasmic Inclusions of Nyctotherus macropharyngeus: Histochemical Studies
Authors: Dutta G. P. 
Published: April 2021

ABSTRACT
The cytoplasm of Nyctotherus macropharyngeus contains lipid bodies, mitochondria, and carbohydrate bodies. The lipid bodies consist of neutral lipids, most probably triglycerides, and protein. The mitochondria are rod-shaped. The carbohydrate bodies are formed by the coalescence of smaller spheres, which appear to arise in close association with the mitochondria. The external part of the smaller spheres is PAS-positive.
The osmotic pressure and saline content of the blood of Petromyzon Fluviatilis
Authors: Galloway T. McL. 
Published: April 2021

ABSTRACT
The composition of the body fluids of the most primitive Craniata, namely the cyclostomes, is of considerable general interest in relation to the theory advanced by Bunge in 1894 and by Macallum in 1904 that the saline composition of vertebrate blood is related to the saline composition of the primitive sea from which they originally emerged. This theory has recently been criticised by Pantin (1931), who has reviewed the literature of the subject.
Stimulation of Neuritic Outgrowth in an Undamaged Molluscan Interneurone
Authors: Allison P. , Benjamin P. R. 
Published: April 2021

ABSTRACT
Axotomy of neurones from a variety of invertebrate groups induces sprouting and regrowth of neuritic processes (reviewed by Anderson, Edwards & Palka, 1980). However, direct surgical damage is not a necessary prerequisite for inducing sprouting. For instance, Altrup & Kolde (1982) and Bulloch (1984) showed that damage to non-neural tissue could induce sprouting and Pitman & Rand (1981) showed that neural lesions can cause dendritic outgrowth of an undamaged insect neurone. We report here that a similar phenomenon to the latter occurs in the gastropod mollusc Lymnaea stagnalis. We have previously shown that lesioning the axon of the giant pedal interneurone (RPeDl) induces sprouting and subsequent recovery of synaptic connectivity (Allison & Benjamin, 1985; Benjamin & Allison, 1985). Here similar techniques were used to lesion the Lymnaea CNS, but instead of crushing connectives containing the axon of RPeDl, we lesioned a part of the CNS not occupied by RPeDl processes. This induced limited, but statistically significant, increases in the number of processes in the posterior three ganglia of the CNS, when normal and lesioned preparations were compared.
Control of Rectal Gland Secretion in the Dogfish (Squalus Acanthias) : Steps in the Sequence of Activation
Authors: Erlij D. , Rubio R. 
Published: April 2021

ABSTRACT
We measured the venous and arterial pressure, as well as the rate of secretion and content of cyclic AMP and high energy phosphate compounds, of the rectal gland of the anaesthetized dogfish, Squalus acantinas (L.). Intravenous infusion of isotonic solutions produced a very large increase in the rate of secretion by the rectal gland. The increase in secretion was preceded by an increase in venous blood pressure, but arterial blood pressure was not modified. Injections of small doses of veratridine stimulated gland secretion when given in the vicinity of the heart but not when given in the dorsal aorta. During volume expansion the creatine phosphate and ATP content of the gland were markedly reduced, while ADP and AMP as well as cyclic AMP content were increased. We conclude that: (a) volume expansion leads to the release of a message that activates adenyl cyclase in the gland; (b) the increased venous pressure may be the initial signal in the sequence that leads to the release of the activating messenger; (c) there is a receptor mechanism in the atrial and cardiac region that triggers the sequence that activates glandular secretion; (d) the reduction in the content of high energy phosphate compounds during volume expansion is caused by an increase in energy expenditure, probably due to gland secretion.
Exoskeletal Strain: Evidence for a Trot–Gallop Transition in Rapidly Running Ghost Crabs
Authors: Blickhan R. , Full R. J. , Ting L. 
Published: April 2021

ABSTRACT
Equivalent gaits may be present in pedestrians that differ greatly in leg number, leg design and skeletal type. Previous studies on ghost crabs found that the transition from a slow to a fast run may resemble the change from a trot to a gallop in quadrupedal mammals. One indication of the trot–gallop gait change in quadrupedal mammals is a distinct alteration in bone strain. To test the hypothesis that ghost crabs (Ocypode quadrata) change from a trot to a gallop, we measured in vivo strains of the meropodite of the second trailing leg with miniature strain gauges. Exoskeletal strains changed significantly (increased fivefold) during treadmill locomotion at the proposed trot–gallop transition. Maximum strains attained during galloping and jumping (1000×10−6–3000×10−6) were similar to the values reported for mammals. Comparison of the maximum load possible on the leg segment (caused by muscular tension) with the strength of the segment under axial loading revealed a safety factor of 2.7, which is similar to values measured for jumping and running mammals. Equivalent gaits may result from similarities in the operation of pedestrian locomotory systems.
The Physiology of Bottlenose Dolphins (Tursiops Truncatus): Heart Rate, Metabolic Rate and Plasma Lactate Concentration During Exercise
Authors: Williams Terrie M. , Friedl W. A. , Haun J. E. 
Published: April 2021

ABSTRACT
Despite speculation about the swimming efficiency of cetaceans, few studies have investigated the exercise physiology of these mammals. In view of this, we examined the physiological responses and locomotor energetics of two exercising adult Tursiops truncatus. Oxygen consumption, heart rate, respiratory rate and post-exercise blood lactate concentration were determined for animals either pushing against a load cell or swimming next to a boat. Many of the energetic and cardiorespiratory responses of exercising dolphins were similar to those of terrestrial mammals. Average heart rate, respiratory rate and oxygen consumption for dolphins pushing against a load cell increased linearly with exercise levels up to 58kg for a female dolphin and 85kg for a male. Oxygen consumption did not increase with higher loads. Maximum rate of oxygen consumption ranged from 19.8 to 29.4 ml O2 kg−1 min−1, which was 7–11 times the calculated standard metabolic rate of the dolphins. Blood lactate concentration increased with exercise loads that exceeded . The maximum lactate concentration was 101.4 mgdl−1 (11.3mmol l−1) for the male, and 120.6 mgdl−1 (13.6mmol l−1) for the female. When swimming at 2.1ms−1, heart rate, respiratory rate and post-exercise blood lactate concentration of the dolphins were not significantly different from values at rest. The cost of transport at this speed was 1.29±0.05J kg−1 min−1. The energetic profile of the exercising bottlenose dolphin resembles that of a relatively sedentary mammal if the exercise variables defined for terrestrial mammals are used. However, the energetic cost of swimming for this cetacean is low in comparison to that of other aquatic and semi-aquatic mammals.
Dihydropyridine and Ryanodine Binding in Ventricles From Rat, Trout, Dogfish And Hagfish
Authors: Thomas Marion J. , Hamman Brian N. , Tibbits Glen F. 
Published: April 2021

ABSTRACT
In the adult mammalian heart, the majority of Ca2+ required for contraction is released from the sarcoplasmic reticulum (SR) via the Ca2+-release channel or ryanodine receptor (RyR). Such release is dependent upon a relatively small influx of Ca2+ entering the cell across the sarcolemma (SL) by means of the L-type Ca2+ channel or the dihydropyridine receptor (DHPR). In lower vertebrates, there is indirect evidence suggesting that Ca2+ influx across the SL may be sufficient to support contraction in the absence of Ca2+ release from the SR. This apparent difference in myocardial excitation–contraction (E–C) coupling was investigated further by determining DHPR and RyR densities in ventricular homogenate preparations from rat, trout, dogfish and hagfish. DHPR Bmax values (means ± S.E.M.) were highest in rat (0.30±0.01 pmol mg−1), lower in trout (0.16±0.01 pmol mg−1) and dogfish (0.27±0.03 pmol mg−1), and slightly above the level of detection in hagfish (0.03±0.01 pmol mg−1). The DHPR dissociation constants (Kd) of 40–70 pmol l−1 in these three species were of similar magnitude. RyR binding revealed both high-and low-affinity sites in all species. RyR Bmax for the high-affinity site was greatest in the rat (0.68 pmol mg−1), lower in trout (0.19 pmol mg−1) and dogfish (0.07 pmol mg−1) and lowest in hagfish (0.01 pmol mg−1). The RyR Kd1 values for the high-affinity sites were comparable in all preparations (range 12–87 nmol l−1). The quantitative expression of RyRs in these species is consistent with the relative amount of SR present as indicated in physiological experiments and electron micrographs. Taking into consideration myocyte morphology of teleost and elasmobranch species, the data are consistent with a greater reliance on Ca2+ influx across the SL during E–C coupling in lower vertebrates, although a functional role for Ca2+ release from the SR in the more active species awaits further investigation.
Performance limits of labriform propulsion and correlates with fin shape and motion
Authors: Walker Jeffrey A. , Westneat Mark W. 
Published: April 2021

SUMMARYLabriform locomotion, which is powered by oscillating the paired pectoral fins, varies along a continuum from rowing the fins back and forth to flapping the fins up and down. It has generally been assumed (i) that flapping is more mechanically efficient than rowing, a hypothesis confirmed by a recent simulation experiment, and (ii) that flapping should be associated with wing-shaped fins while rowing should be associated with paddle-shaped fins. To determine whether these hypotheses and the results of the simulation experiment are consistent with natural variation, we compared the steady swimming performance (critical swimming speed) of four species of labrid fish (Cirrhilabrus rubripinnis, Pseudocheilinus octotaenia, Gomphosus varius and Halichoeres bivittatus) selected to form two pairs of closely related species that vary in fin shape and in the direction of fin motion. The results were consistent with expectations. Within each pair, the species with the best swimming performance also had (i) a fin shape characterized by a higher aspect ratio, a longer leading edge relative to the trailing edge fin rays and the center of fin area located closer to the fin base, and (ii) a steeper (more dorsoventral) stroke plane.
Two swimming modes in Trachymedusae; bell kinematics and the role of giant axons
Authors: Meech Matthew E. , Mills Claudia E. , Haddock Steven H. D. , Meech Robert W. 
Published: April 2021

ABSTRACT
Although members of the Rhopalonematidae family (Cnidaria, Hydrozoa, Trachymedusae) are known to exhibit unusually powerful jet swimming in addition to their more normal slow swimming behaviour, for the most part, reports are rare and anecdotal. Many species are found globally at depths of 600–2000 m, and so observation and collection depend on using remotely operated submersible vehicles. With a combination of in situ video footage and laboratory measurements, we have quantified kinematic aspects of this dual swimming motion and its electrophysiology. The species included are from two Rhopalonematidae clades; they are Colobonema sericeum, Pantachogon haeckeli, Crossota millsae and two species of Benthocodon. Comparison is made with Aglantha digitale, a species from a third Rhopalonematidae clade brought to the surface by natural water movement. We find that although all Rhopalonematidae appear to have two swimming modes, there are marked differences in their neural anatomy, kinematics and physiology. Giant motor axons, known to conduct impulses during fast swimming in A. digitale, are absent from C. sericeum and P. haeckeli. Slow swimming is also different; in C. sericeum and its relatives it is driven by contractions restricted to the base of the bell, whereas in A. digitale it is driven by contractions in the mid-bell region. These behavioural differences are related to the position of the different clades on a ribosomal DNA-based phylogenetic tree. This finding allows us to pinpoint the phylogenetic branch point leading to the appearance of giant motor axons and escape swimming. They place the remarkable dual swimming behaviour of members of the Rhopalonematidae family into an evolutionary context.
Studies on the Feeding and Nutrition of Tuberolachnus Salignus (Gmelin) (Homoptera, Aphididae)
Authors: Mittler T. E. 
Published: April 2021

ABSTRACT
It has generally been supposed that the uptake of large quantities of plant sap by aphids is the direct result of suction. Zweigelt (1914) has questioned this concept, and Kennedy & Mittler (1953) have thrown further doubt on the supposition that aphids are typical ‘sucking’ insects. The present paper sets out results, obtained in a study of the uptake of phloem sap by Tuberolachnus salignus (Gmelin), which may help to clarify this question.
Polarized Light and the Orientation of Two Marine Crustacea*
Authors: Bainbridge Richard , Waterman Talbot H. 
Published: April 2021

ABSTRACT
Quantitative experiments are described, designed to test the hypothesis that underwater polarized light is used for orientation by aquatic animals as that of the blue sky is by terrestrial arthropods. Studied in the laboratory the littoral mysid, Mysidium gracile, was found capable of orientation relative to the e vector in a vertical beam of linearly polarized light. Statistically significant preference was shown by this animal for aligning its longitudinal axis at right angles to the plane of polarization. A secondary slight preference was shown for swimming parallel with the plane and the degree of random orientation was often high (40% mean). The littoral prawn, Palaemon northropi, when released in quiet water far enough from the bottom and the shore to prevent visual contact, was found to swim on relatively straight horizontal courses for appreciable distances in forty-one out of sixty-one tests. The mean length of these runs was 24 · 5 m., the maximum 119 m.; swimming velocities up to about 1 km./hr. were measured. The sun’s position seems to be the only directional clue not controlled in these tests, and the general direction of the runs is significantly correlated with the direction of the sun, being at right angles to it. It is thus concluded that this animal can use the sun, either directly or through the polarization pattern, as a celestial compass.
The Absorption Of Water By Plant Tissue In Relation To External Hydrogen-Ion Concentration
Authors: Pearsall W. H. , Ewing J. 
Published: April 2021

ABSTRACT
In previous papers we have considered in some detail the properties of plant tissues in relation to the hydrogen-ion concentration of the external medium, and our observations have led us to regard some of those properties as being due to the behaviour of the proteins present in the tissues, and in particular to the positions of the isoelectric points of those predominant in the tissues. It is now proposed to consider the water absorption of plant tissues from a similar point of view, and to correlate the results of such a study with the data obtained when the swelling and precipitation of proteins over a pertinent range of hydrogen-ion concentration are investigated.
Nitrogen Excretion in Ascidiacea
Authors: Goodbody Ivan 
Published: April 2021

ABSTRACT
The evidence for the occurrence of storage excretion in ascidians is reviewed. Most species probably store uric acid or purine bases in some form. The renal concretions of Ascidia nigra and Phallusia mammillata contain 50-60 % uric acid, the remainder of the concretion is unidentified but is non-nitrogenous and is not calcium carbonate. In Ascidiella aspersa the concretion is predominantly composed of calcium carbonate and there is no significant quantity of uric acid or purine base. Uric acid is also identified in Molgula manhattensis, Polycarpa obtecta, Pyura vittata and Herdmania momus. Storage excretion probably results from a deficiency in the uricolytic enzyme system. It is concluded that while protein metabolism is ammonotelic, purine meta-bolism is uricotelic or xanthotelic.
Studies on Salt and Water Balance inMyxine Glutinosa(L.)
Authors: Morris R. 
Published: April 2021

ABSTRACTThe myxinoids are a marine group of cyclostomes whose blood shows some similarities to the sea water in Which they live, even when they are moved to more dilute environments. Reviews by Morris (1960) and more recently by Robertson (1963) emphasize that the plasma is slightly hypertonic to the environment and that during the course of ionic regulation divalent ions are reduced in the plasma relative to sea water (Smith in Cole, 1940; Robertson, 1954; Bellamy & Chester Jones, 1961). Thus the main work of ionic regulation seems to fall on the tissues themselves. Here, potassium partly replaces sodium, whilst phosphate and perhaps amino acids take the place of chlorides (Robertson, i960; Bellamy & Chester Jones, 1961). The osmotic deficit between the plasma and the tissues seems to be made up in part by unidentified organic acids and by large amounts of trimethylamine oxide which, according to Bellamy & Chester Jones, reaches concentrations comparable with those found in marine elasmobranchs.