bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations on the Structure of Hydra as seen with the Electron and Light Microscopes
Authors: Hess Arthur , Cohen A. I. , Robson Elaine A. 
Published: April 2021

ABSTRACT
Sections of hydra studied with the electron microscope show various structures which have been identified by referring to control histological sections and to previous descriptions. Certain features have also been examined in frozen-dried sections under the light microscope.
In the ectoderm, epithelio-muscular cells contain various organelles, and also smooth longitudinal muscle-fibres with which mitochondria may be associated. The so-called ‘supporting fibres’ appear to be thin bundles of muscle-fibres. Although points of contact exist between muscle-fibres, there appears to be no cytoplasmic continuity. The muscle-fibres insert on the mesogloea, and appear to be separated from it by two membranes, one belonging to the cytoplasm surrounding the musclefibre and the other to the mesogloea.
The mesogloea is extracellular and quite distinct from the intracellular muscle-fibres. It appears granular and sometimes presents an indistinct fibrous background. In frozen-dried material the mesogloea stains blue with Mallory’s method, while the muscle-fibres stain red.
Two main types of cells are found in the endoderm. Among these, some of the digestive cells contain transverse muscle-fibres, but they are less distinct than the longitudinal ectodermal fibres. Otherwise the digestive cells vary much in structure, but generally they contain vacuoles and their free surface is thrown into villi covered with small granules. The ‘foamy gland cells’ are filled with much larger vacuoles containing granular material. The vacuoles are discharged together with portions of cytoplasm, and at this stage lamellated double membranes and mitochrondria appear between the vacuoles. Both types of cell possess two flagella, which show a typical ultrastructure and are surrounded by a thick membrane.
Various other cells of the ectoderm are distinguished by their characteristic appearance. Cnidoblasts, for instance, have been found to contain an extensive system of intercommunicating vacuoles bounded by membranes, and do not resemble the interstitial cells. In unexploded penetrant nematocysts the tube is preformed and the butt and stylets can also be seen. The special gland-cells of the pedal disk show large, electron-dense granules which are extruded from the cell without any cytoplasm. A relatively thick homogeneous layer on the surface of the pedal disk is distinguished by the electron microscope.
The Formation and Properties of the Organic Matrix of Reptilian Tooth Enamel
Authors: Poole D. F. G. 
Published: April 2021

ABSTRACT
A number of features of enamel formation in the lizard Agama atricollis are described. The behaviour and properties of the ameloblasts indicate that the process of enamel formation is similar to the corresponding process in mammals; the fibrous enamel matrix appears to be formed from outgrowths of the cytoplasm of these cells. Inter-prismatic material, as it is known in mammals, is not produced, so that reptilian matrix tends to be uniformly fibrous. Nevertheless, the fibres are initially arranged in groups corresponding to the ameloblasts. There is no distinct pre-enamel stage because matrix production is immediately followed by a limited influx of mineral in an elementary state, converting the matrix into an basiphil form. Striae of Retzius may be due to periodic pauses in the normal process of matrix production enabling the ameloblasts to assimilate and secrete mineral. Before the onset of final calcification, the matrix seems to undergo a modification rendering it capable of influencing the size and orientation of mineral crystallites.
The organic matrix has a refractive index of 1-57 and has no intrinsic birefringence. However, in suitable liquids the parallel fibres produce a positive form birefringence. If paraffin wax is allowed to crystallize on the matrix, optically negative streaks are formed parallel with the fibres, perhaps as the result of crystal overgrowth.
Evidence obtained indicates that this reptilian type of ectodermal enamel is a likely precursor of the mammalian prismatic type. The evolution from one to the other could have been achieved in a comparatively simple step.
Variability of Behaviour of Aggregating Cellular Slime Moulds
Authors: Shaffer B. M. 
Published: April 2021

ABSTRACT
A description is given of the development of certain structures—centre, stream, and ring—formed by the amoebae of four species of Dictyostelium and Polysphondylium during aggregation, and of the outcome of experimentally cutting a stream, recombining lengths of stream in simple geometrical relationships, and excising a centre. In all cases there is a high degree of intraspecific variation in behaviour, and it is not possible to predict, except in terms of rough probability, what the future course of development will be. An amoeba at this stage of the life cycle can exist in one of four main states. In the first, it is unaggregated and cannot react chemotactically; in the second, it is unaggregated but can react; in the third, it is in a stream moving towards a centre or has properties similar to those of a stream cell; and in the fourth, it is in a centre and nearly stationary. Though an enormous variety of patterns may be produced by large numbers of interacting amoebae, their behavioural repertory may be considered, without too much simplification, to be restricted to approaching these four states in various sequences and at various rates. Most of these sequences can be observed over a wide range of environmental conditions. Changes in humidity produce the greatest effect: the drier the culture, the stronger the drift from the first state to the fourth. It is suggested that variability is occasioned by the simplicity of the mechanisms controlling development.
The Effect of Acetic Acid on Cytoplasmic Inclusions
Authors: Baker John R. 
Published: April 2021

ABSTRACT
Acetic acid at 5 % is not necessarily destructive of cytoplasmic inclusions. Hermann’s fluid gives excellent mitochondrial preparations if tissues are postosmicated for several days at 34° C. The mitochondria are blackened by this treatment. Mann’s fluid with the addition of 5 % of acetic acid gives, on postosmication, very good preparations of the ‘Golgi apparatus’ of certain cells.
Spermateleosis in Fasciola hepatica
Authors: Gresson R. A. R. 
Published: April 2021

ABSTRACT
The stages of spermateleosis and the structure of the spermatozoon of Fasciola hepatica were studied in smears of fixed material and in preparations of living tissue examined under phase-contrast microscopy.
Smears were fixed in Bouin’s picro-formol and in Flemming without acetic. Smears were also prepared according to the Feulgen technique.
The nucleus of the late spermatid undergoes elongation and grows out from the distal end of the cell. An extension of cytoplasm gives rise to the sperm-tail or flagellum. The spermatozoon becomes free of the greater part of the cytoplasm of the spermatid; the latter remains as a residual mass.
The spermatozoon consists of a nucleus and a flagellum. The latter is probably composed of an axial filament surrounded by a thin sheath of cytoplasm.
The Functional Anatomy of the Mid-gut of Larvae of the Ant, Myrmica
Authors: Weir J. S. 
Published: April 2021

ABSTRACT
The functional anatomy of the mid-gut of larvae of Myrmica rubra microgyna Brian and Brian is described.
Observations have been made on the modes of formation of the two distinct types of peritrophic membrane, which may correspond to the primary and secondary peritrophic membrane of Wigglesworth.
These membranes are highly developed independently and the hypothesis is advanced that they have different functions. Further, it is suggested that the corresponding structures in adult Apis do not represent, as advanced by earlier workers, an intermediate stage in the evolution of the peritrophic membrane, and in its mode of formation.
Synaptic Relations in the Atrial Nervous System of Amphioxus
Authors: Bone Quentin 
Published: April 2021

ABSTRACT
A detailed description of the system of peripheral nerve-cells upon the gut and diverticulum of amphioxus (Branchiostoma) is given; it is shown experimentally by means of degeneration experiments that these cells are connected with the central nervous system by their own axons, which run in the dorsal-root nerves. The form and connexion of the cells are described, special attention is paid to the problems of the multinucleate cells in the plexus, and to the occurrence of possible asynaptic connexion between neighbouring nerve-cells. No sheath-cells have been observed upon the peripheral nerve-fibres, either within the atrial plexus or upon the dorsal-root nerve bundles ; earlier misinterpretations of the nuclei of the cells of the epineurium around the dorsal nerve bundles are discussed. The origin of the atrial system in ontogeny is discussed; it is suggested that it arises in an analogous manner to the enteric plexuses of vertebrates, by outgrowth from the central nervous system. The part that this system of nerve-cells plays in the life of the animal is not known.
Finally, the relation of this system of cells to that found upon the guts of other groups of animals is discussed, and it is concluded that the system is not homologous with the enteric systems of nerve-cells in the vertebrates.
Note on the Use of Bromophenol Blue for the Histochemical Recognition of Protein
Authors: Baker John R. 
Published: April 2021

ABSTRACT
There is not sufficient evidence to prove that bromophenol blue is a reliable histochemical reagent for the recognition of protein. It is a powerful acid dye, capable of making direct links with basic groups in tissue-constituents (and perhaps also with certain acidic groups, through mercury).
The ‘Posterior Lobes’ of Nephtys: Observations on three New England Species
Authors: Clark R. B. 
Published: April 2021

ABSTRACT
The disposition of the prostomial mucus-glands in Nephtys picta, N. incisa, and N. bucera provides additional evidence that the posterior lobes, which are attached to the supra-oesophageal ganglion of species such as N. californiensis and N. caeca, have been formed by the posterior migration of prostomial epidermal mucus-cells. In N. picta there are few mucus-cells in the prostomium. In N. incisa there are many, and some at the sides of the prostomium occur in clumps and project into the prostomial cavity. In N. bucera there are numerous mucus-cells, but they are massed at the sides of the prostomium and open to the exterior over a narrow zone. The cell-bodies are in intimate contact with the sides of the supra-oesophageal ganglion and lie within the membranes investing the brain. Subsequent evolution of the prostomial mucus-glands has led to the accumulation of their cell-bodies in the posterior part of the supra-oesophageal ganglion in the form of posterior lobes.
The CO2 dissociation curves and the buffering of crab’s muscle and nerve preparations
Authors: Cowan S. L. 
Published: April 2021

ABSTRACT
The CO2 binding powers of frog’s blood (Wastl and Seliskar, 1925), muscle (Fenn, 1928; Stella, 1929) and nerve (Fenn, 1928) have been investigated by equilibrating the substance under examination with known partial pressures of CO2 and determining the amounts (of CO2) which were chemically combined. Hence, from the CO2 dissociation curve, the pH inside the tissue was calculated by means of the Henderson-Hasselbalch equation; also, from the slope of the curve showing the connection between the partial pressure of CO2 and the pH, the variation of the buffering power of the tissue, as defined by Van Slyke (1922), with pH could be calculated.
The Effects of Hypercapnia on the Arterial Acid-Base Status in the Tegu Lizard, Tupinambis Nigropunctatus
Authors: Glass M. L. , Heisler N. 
Published: April 2021

ABSTRACT
The effects of hypercapnia on the arterial acid-base status of the Tegu lizard, Tupinambis nigropunctatus (Spix), were studied at 25 °C. Arterial increased over the first 2 h of hypercapnia causing a fall in arterial plasma pH (pHa) of about 0·17 units with ≈4% CO2 and about 0·3 units with ≈7 % CO2. In both conditions, plasma pH increased slightly (≈ 0·02 units) between 2 and 72 h. Plasma [HCO3−] rose during the initial increase of (by approx. 5·5 mmol l−1 with ≈7 % CO2; approx. 1·9 mmol l−1 with ≈4% CO2) during the first 2h, and further increased by 4 mmol I-1 between 2 and 72 h of hypercapnia, while did not change. The increases of plasma [HCO3−] resulted in a recovery of pH, by 38 or 32 % (≈4 and ≈7 % CO2, respectively) relative to the fall of pHa that would occur at constant [HCO3−].
The limited and incomplete compensation of pHa during environmental hypercapnia is consistent with data for other air-breathing ectothermic vertebrates, and contrasts with the typical response of water-breathing fish, in which compensation is usually complete.
Amiloride-Sensitive Sodium Flux and Potentials in Perfused Carcinus Gill Preparations
Authors: Lucu Čedomil , Siebers Dietrich 
Published: April 2021

ABSTRACT
Sodium and chloride fluxes, as well as transbranchial potentials (TBP) were studied in isolated perfused gill filaments of the crab Carcinus mediterraneus. Experiments were carried out in media that were either hyposmotic to the perfusion solution (asymmetrical conditions) or isosmotic (symmetrical conditions).
Fluxes were found to be diffusional in gills under asymmetrical conditions; amiloride induced an inhibitory effect on influxes, without affecting TBP.
Under symmetrical conditions, TBP was −7·6 ±2·3 mV, suggesting that the electrogenic ion pump contributes significantly to the development of TBP. Immediately after addition of 2·5 × 10−4mol l−1 amiloride to the external solution, sodium influxes were reduced to 31% of those in the control group, and TBP was significantly hyperpolarized from −7·6 to −14·8 mV. The absence of Ca2+ under symmetrical conditions diminished TBP hyperpolarization.
Half-maximal inhibition of sodium influxes by amiloride was at 7× 10−5 mol 1-1. This low amiloride affinity is typical of low resistance leaky epithelia. Sodium transport is discussed as an amiloride-affected influx, probably as a Na/H antiport.
The Salivary Catechol Oxidase/Peroxidase Activities of the Mosquito Anopheles Albimanus
Authors: Ribeiro José M. C. , Nussenzveig Roberto H. 
Published: April 2021

ABSTRACT
Salivary gland homogenates from adult female Anopheles albimanus mosquitoes relaxed aortic rings preconstricted with noradrenaline (NA). This relaxation is slow and is due to destruction of NA. Incubation of NA with the homogenate yielded a product with a spectrum consistent with the corresponding adrenochrome. Oxidation of NA was enhanced by a superoxide generation system and inhibited by the combined action of superoxide dismutase and catalase. Additionally, peroxidase activity on both synthetic (o-dianisidine) and biologically active (serotonin) substrates was also present in the salivary gland homogenates, this latter activity requiring hydrogen peroxide. Noradrenaline oxidation, serotonin and o-dianisidine peroxidation and vasodilation all co-elute with a heme protein of relative molecular mass 50000, as determined by molecular sieving chromatography. Peroxidase activity was localized in the posterior (female-specific) lobes of salivary glands and was also detected in nitrocellulose membranes probed by hungry mosquitoes. Protein and peroxidase activities were significantly lower in salivary glands of mosquitoes after probing and feeding on blood. It is suggested that adult female Anopheles albimanus mosquitoes contain a salivary heme peroxidase that functions during blood finding and blood feeding by destroying hemostatically active biogenic amines released by the vertebrate host during tissue destruction.
Regenerating Adult Cockroach Dorsal Unpaired Median Neurones In Vitro Retain their In Vivo Membrane Characteristics
Authors: Newland P. L. , Smith P. J. S. , Howes E. A. 
Published: April 2021

ABSTRACT
The ability of differentiated neurones to recover from disease or injury depends upon both intrinsic and extrinsic factors. Whereas most mammalian neurones have a limited capacity for regeneration, regulated, in part, by physical and chemical cues in the brain microenvironment (Bray et al. 1987; Caroni and Schwab, 1988, 1989), invertebrates, and in particular insects, exhibit a far greater capacity for repair of central neurones and circuits (Treherne et al. 1988). Studies of the cues that regulate the regenerative process are made easier by the use of individual, identified neurones, cultured under controlled conditions. Invertebrates are particularly useful in this regard; neurones from mature nervous systems of both annelids and molluscs have been grown successfully in culture and their growth can be influenced by changes in the culture conditions (Acklin and Nicholls, 1990; Dagan and Levitan, 1981; Ready and Nicholls, 1979; Syed et al. 1990). Routine and long-term culture of identified neurones from the insect central nervous system (CNS) has proved more elusive, preventing the use of neurones from these well-studied systems. Recently, however, cultures of cockroach (Howes et al. 1991), locust (Kirchoff and Bicker, 1992) and moth (Hayashi and Levine, 1992) adult neurones have been described.
Consequences of Catecholamine Release on Ventilation and Blood Oxygen Transport During Hypoxia and Hypercapnia in an Elasmobranch (Squalus Acanthias) and a Teleost (Oncorhynchus Mykiss)
Authors: Perry Steve F. , Gilmour Kathleen M. 
Published: April 2021

ABSTRACT
The marine dogfish (Squalus acanthias) and the seawater-adapted rainbow trout (Oncorhynchus mykiss) were exposed to acute environmental hypercapnia or hypoxia to evaluate (i) the dynamics of catecholamine release into the circulation and (ii) the impact of catecholamine release on gill ventilation and blood oxygen transport. This comparison was undertaken to test the hypothesis that the pattern and consequences of catecholamine release differ in the two species according to the presence or absence of a Root effect and a red blood cell (rbc) β-adrenergic response.
Hypercapnia and hypoxia elicited marked increases in plasma catecholamine levels in the trout but not in the dogfish. In the trout, catecholamine release occurred abruptly during hypoxia when arterial decreased below 2.7 kPa. In the dogfish, plasma catecholamine levels remained stable during hypoxia even when fell below 2.0 kPa.
Trout and dogfish displayed pronounced hyperventilatory responses during both hypercapnia and hypoxia. In trout, the hyperventilatory response consisted of an increase in ventilation amplitude (estimated by opercular cavity pressure changes) with no change in ventilation frequency (fV), whereas in the dogfish, both amplitude (estimated by spiracular cavity pressure changes) and fV increased significantly. The use of an extracorporeal circulation and frequent blood sampling demonstrated that plasma catecholamine levels and ventilation amplitude were not correlated during hypoxia in either species.
During hypercapnia in trout, the bolus injection of a catecholamine cocktail (final nominal circulating levels 200 nmol l−1 adrenaline, 50 nmol l−1 noradrenaline) caused a rapid (within 2 min) 33 % reduction in ventilation amplitude that persisted for 3 min; fV was unaffected. This hypoventilatory response occurred concurrently with activation of rbc Na+/H+ exchange and an increase in arterial blood O2 content and O2 specifically bound to haemoglobin (O2/Hb). During hypoxia in trout, a similar injection of catecholamines activated rbc Na+/H+ exchange and increased O2/Hb yet was without effect on ventilation amplitude or fV. In dogfish during hypercapnia or hypoxia, injection of a catecholamine cocktail (final nominal circulating levels 125 nmol l−1 adrenaline, 125 nmol l−1 noradrenaline) caused slight but significant reductions in fV (3–4 min−1) without affecting ventilation amplitude. Catecholamine injections did not affect blood oxygen transport in dogfish.
The results demonstrate significant differences in the nature of catecholamine release in dogfish and trout that may reflect, in part, the absence of a Root effect and rbc adrenergic Na+/H+ exchange in the elasmobranch. The present data do not support the hypothesis that circulating catecholamines play a major role in controlling breathing during hypoxia or hypercapnia.
In vivo oocyte hydration in Atlantic halibut (Hippoglossus hippoglossus); proteolytic liberation of free amino acids, and ion transport, are driving forces for osmotic water influx
Authors: Finn Roderick Nigel , Østby Gunn C. , Norberg Birgitta , Fyhn Hans Jørgen 
Published: April 2021

SUMMARY
The in vivo swelling and hydration of maturing oocytes of Atlantic halibut Hippoglossus hippoglossus were studied in order to characterise the osmotic mechanism underlying oocyte hydration in oviparous marine teleosts that spawn pelagic eggs. Sequential biopsies from two females, spanning four hydration cycles, were examined by osmometry, solute analysis and electrophoresis of dissected hydrating oocytes and ovulated eggs. The hydration cycle of the biopsied halibuts lasted 33–54 h. The majority of ovarian oocytes existed in a pre-hydrated condition (individual wet mass approx. 3.7 mg, diameter approx. 1.87 mm, 63 % H2O) with easily visible, non-coalesced, yolk platelets. Group-synchronous batches of the pre-hydrated oocytes increased in individual wet mass, diameter and water content to reach the ovulated egg stage of approximately 15 mg, 3.0 mm and 90 % H2O, respectively. The yolk osmolality of the hydrating oocytes was transiently hyperosmotic to the ovarian fluid (range 305–350 mOsmol l–1) with a peak osmolality of about 450 mOsmol l–1 in oocytes of 6–8 mg individual wet mass. The transient hyperosmolality was well accounted for by the increase in oocyte content of free amino acids (FAAs; approx. 2300 nmol oocyte–1), K+ (approx. 750 nmol oocyte–1), Cl– (approx. 900 nmol oocyte–1), total ammonium (approx. 300 nmol oocyte–1) and inorganic phosphate (Pi; approx. 200 nmol oocyte–1) when relating to the increase in cellular water. The oocyte content of Na+ did not increase during the hydration phase. Extensive proteolysis of yolk proteins, in particular a 110 kDa protein, correlated with the increase in the FAA pool, although the latter increased by approx. 20 % more than could be accounted for by the decrease in the oocyte protein content. Both indispensable and dispensable amino acids increased in the FAA pool, and particularly serine, alanine, leucine, lysine, glutamine and glutamate. Taurine content remained stable at approx. 70 nmol oocyte–1 during oocyte hydration. The results show that final hydration of Atlantic halibut oocytes is caused by an osmotic water uptake in which FAAs, derived mainly from the hydrolysis of a 110 kDa yolk protein, contribute approximately 50 % of the yolk osmolality and ions (Cl–, K+, Pi, NH4+) make up the balance.