bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Aspects of the Structure and Cytology of the Gills of Lampetra fluviatilis
Authors: Morris R. 
Published: April 2021

ABSTRACT
A description is given of the structure and vascularization of the lampern gill.
A comparison of the cellular components of the gill epithelium taken from lamperns at various stages of their spawning migration show that certain types of cells are common to all animals. These include the cells covering the gill platelets, the mucous cells, and certain basal cells from which others originate. The mucous cells are quite different in structure from those of teleosts.
There is a progressive loss of large acidophilic cells from certain regions of the gill filament as animals enter fresh water during the earlier stages of the spawning migration. These cells are similar in both structure and location to those described as chloride excretory cells from the gills of marine teleosts. They are typically large, flask-shaped cells with basal nuclei and they are filled with rod-shaped or spherical mitochondria. It is believed that they are responsible for the extra-renal excretion of monovalent ions during the process of marine osmoregulation in the lampern. The chloride excretory cells are very numerous in a limited number of fresh-run animals which are able to osmoregulate in 50% sea water.
In the normal course of events the chloride excretory cells are replaced by a smaller type of cell which is also rich in mitochondria, but unlike the excretory cells these lie at the surface of a transitional epithelium. It is argued that these cells may be responsible for ion uptake from fresh water in the maturing animal.
In male lamperns, large glandular cells of unknown function appear in the gill epithelium as the animal nears the time of spawning.
The Coelomocytes of Holothuria leucospilota
Authors: Endean R. 
Published: April 2021

ABSTRACT
Morula-shaped cells, structurally similar to fibre-producing cells occurring in the blood and test of an ascidian, Pyura stolonifera, have been found in the coelomic fluid and Cuvierian tubules of Holothuria leucospilota.
The morula-shaped cells of the holothurian are formed from primitive amoebocytes. They contain globules, each of which consists of a central core of proteinaceous material associated with an unidentified iron compound. A film of polysaccharide materia1, containing granules of a lipo-protein nature, surrounds the core. Part, at least, of the polysaccharide is mucopolysaccharide. It is believed that the materials present in the globules are precursors of collagenous connective tissue fibres.
The mean value of the iron content of the corpuscles was found to be 0·12 g per 100 g dry weight. The iron is organically bound but does not appear to have chemical relationship to haem or other similar iron-porphyrin compounds.
Fibrous processes arise from many morula-shaped cells when they are cytolysed with distilled water.
In hanging-drop preparations some morula-shaped cells eject globules which trail fibres. It is believed that the globules are directly involved in fibre-production.
Granules, similar in many respects to the globules of the morula-shaped cells of the holothurian, have been found in vertebrate fibroblasts.
Activity of the corpora allata during pupal diapause in mimas tiliae (lepidoptera)
Authors: Highnam K.C. 
Published: April 2021

ABSTRACT
Histological observation indicates that the corpora allata of Mimas tiliae are secretory during pupal diapause, but become inactive by the end of the low-temperature period which terminates diapause.
Removal of the corpora allata, together with the corpora cardiaca, from the dia- pausing pupa increases the thickness of the hypodermis and decreases the number of fat-body inclusions (compared with operated controls), but does not result in any visible signs of diapause break.
The oxygen uptake of the pupa increases by about 60% by the end of the low- temperature period, compared with the diapausing pupa.
It is probable that the corpora allata play some part in the maintenance of diapause, possibly by exercising some control over the fat-body metabolism. This role is subservient to that of the neurosecretory cells in the brain, together with their associated corpora cardiaca.
The Fine Structure and Morphological Organization of the Peripheral Nerve-fibres and Trunks of the Cockroach (Periplaneta americana)
Authors: Hess Arthur 
Published: April 2021

ABSTRACT
Sections of the peripheral nerve-trunks of the metathoracic leg of the cockroach (Periplaneta americana) were studied with the electron microscope. Paraffin sections were also prepared and stained. Protargol succeeds in staining the nerve-fibres. Osmium tetroxide, a modified Weigert procedure, and Luxol fast blue stain the myelin sheaths, as does mercuric bromphenol blue, a protein stain. The axoplasm is relatively free of formed elements; it contains mitochondria. The myelin sheath, when present on the largest and also some smaller fibres, consists of about two or three loose over-lapping processes of Schwann cells, covered by their plasma membranes, enclosing lipid-like droplets and having a beaded appearance. Between the nerve-fibres in the nerve-trunk is Schwann-cell cytoplasm, which arises from Schwann cells that sur-round the whole nerve-trunk. The same fold of Schwann-cell membrane may enter into the formation of the myelin sheath around more than one nerve-fibre. Several small non-myelinated fibres, which may be as small as 0 · 3 μ. in diameter or less, may be enclosed in the same fold of Schwann-cell membrane. Outside of the Schwann-cell layer and surrounding the nerve-trunk is a thin layer of connective tissue, which does not send trabeculae into the interior of the nerve. Tracheae and tracheoles accompany the nerve but are not included within the sheaths surrounding a nerve-trunk, even near the termination of the nerve-fibres in muscle. The structure of the cockroach peripheral nerve is compared with that described by previous investigators, with that of other insects, and with invertebrate and vertebrate nerve.
Observations on the Non-calcareous Component of the Shell of the Lamellibranchia
Authors: Beedham G. E. 
Published: April 2021

ABSTRACT
A comparison has been made between the staining reactions and histochemical properties of the non-calcareous material (conchiolin) from the different layers of the shells of Anodonta cygnea, Mytilus edulis, and Ostrea edulis. Acid hydrolysates of the conchiolin protein have been analysed qualitatively by paper chromatography.
The composition of the conchiolin in Anodonta confirms the view that corresponding layers of the valves and ligament represent modifications of the same layers of the shell. In this bivalve, the properties of the outer layers of the valves and ligament are closely comparable with each other, and also with those of the periostracum and the fusion layer of the ligament. All these regions consist of a quinone-tanned protein, hydrolysates of which are rich in phenolic amino-acids, especially tyrosine, and in glycine.
Much of the periostracal conchiolin in Mytilus shows basically the same properties as the periostracum in Anodonta. However, the outer layers of the valves and ligament in Ostrea and Mytilus each exhibit progressively greater specialization compared with the situation in Anodonta. This is most marked in Mytilus where these components differ completely in character.
The conchiolin in the inner shell layers differs markedly in composition from that in the outer layers in Anodonta and Ostrea and from the periostracum in Mytilus. Hydrolysates of its protein constituent contain appreciably more aspartic acid and glutamic acid but much smaller amounts of phenolic amino-acids. The protein is only lightly tanned. Although in these properties the corresponding inner layers of the valves and ligament appear fundamentally alike, each component has certain specialized features. It is suggested that the modifications shown by the protein of the inner ligament layer, which is characterized by a high content of proline and methionine, are correlated with the specialized function of this region of the shell.
Some Aspects of Cuticular Organization of the Branchiopod, Streptocephalus dichotomus
Authors: Krishnan G. 
Published: April 2021

ABSTRACT
The structural features of the cuticle of Streptocephalus are described. The epicuticle and endocuticle, unlike those of other Crustacea, stain alike and show similar chemical characters (apart from the absence of chitin in the epicuticle). This feature appears to be related to the absence of tanning of the cuticle, which remains soft and colourless in all stages of growth. In the epicuticle the outermost very thin layer, whose presence can be inferred from chemical tests, seems to correspond to the outer epicuticle of Crustacea, but this layer lacks histological distinctness. The protein constituent of the cuticle is unlike that of other arthropod cuticles so far studied. It differs markedly from arthropodin or sclerotin and recalls collagen. The significance of the peculiarities of the cuticle is discussed. It is suggested that the structure and chemical characteristics of the cuticle may indicate that it represents a generalized and unspecialized condition of the arthropod cuticle.
Observations on the Genital System and Alimentary Canal of a Lamiid Beetle, Nupserha bicolor
Authors: Dutt N. 
Published: April 2021

ABSTRACT
The genital system and alimentary canal of both sexes of adult Nupserha bicolor s.sp. postbrunnea have been examined. In the female, the posterior end of the rectum is enclosed within a membranous jacket. The membranous jacket represents the tenth segment and is much more prominent than in the male. The jacket enclosing the rectal end runs a short course parallel with the vaginal passage through a common chitinous capsule representing the ninth segment, in which the openings of the anus and the genital passage lie. The chitinous capsule thus looks like a ‘cloacal chamber’. It disappears when the ovipositor is shot out. In the male, the posterior end of the rectum runs straight to the anus. The anus is located within the membranous remnant of the tenth segment. In the genitalia of the female, one remarkable peculiarity is observed distally in the eighth tergite of the adult female. At this level, the eighth tergite and the dorsal portion of the intersegmental membrane between the eighth and ninth segments lie superimposed upon one another and unite medially. On one side a condyle and an oblique socket are formed. The condyle of each side projects into the socket of the other side to form a ball-and-socket apparatus. The mechanism disappears proximally in the eighth tergite. The structure is absent in the male.
Metabolic Changes Associated with Endocrine Activity and the Reproductive Cycle in Xenopus Laevis
Authors: Zwarenstein H. , Shapiro H. A. 
Published: April 2021

ABSTRACT
Throughout the normal reproductive cycle in Xenopus laevis the serum calcium level is higher in females than in males. The reproductive cycle in females is associated with changes in the serum calcium level and in ovarian activity. In male toads the serum calcium remains remarkably constant except for a slight rise during the breeding season. Captivity first causes a rise and then a steady decline in the serum calcium level of females. Both phases are accompanied by a progressive involution of the ovaries. The serum calcium of males is unaffected by captivity. It is suggested that seasonal variations in the amount of solar radiation and inadequate illumination during captivity are the main agencies influencing serum calcium (through the pituitary and parathyroid glands) and ovarian activity (through the anterior lobe of the pituitary).
Ultraviolet Sensitivity and Spectral Opponency in the Locust
Authors: Osorio D. 
Published: April 2021

ABSTRACT
Intracellular recordings in the medulla of the locust optic lobe reveal units showing u.v. sensitivity and spectral opponency. Previously only a single population of photoreceptors had been recorded in the locust retina, with peak sensitivity from 450—480 nm. Behavioural measurements show that the dorsal light response is elicited only by u.v. light, unlike the optomotor response whose spectral sensitivity is probably attributable to inputs from the green-sensitive cells. The possibility that the cells described may be involved in maintenance of level flight is discussed.
The in vivo Regeneration of Goldfish Rhodopsin and Porphyropsin
Authors: Tsin Andrew T. C. , Flores Janie M. 
Published: April 2021

ABSTRACT
Goldfish with retinas rich in either rhodopsin or porphyropsin were illuminated with bright light and then placed in the dark room to allow visual pigment regeneration. The kinetics of this in vivo pigment regeneration were followed by sampling these animals at regular time intervals. The first-order kinetic rate constant for the initial period of porphyropsin regeneration at 20°C was 8·3 × 10−3 nmol kg−1 body weight min−1 and the half-life of this reaction was 83 min. At 30°C, the rate constant was increased to 1·4 × 10−2nmol kg−1 body weight min−1, yielding a reduced half-life of 49 min. This suggests that the Q10 of porphyropsin regeneration is about 1·7. In goldfish retinas enriched with rhodopsin (62% rhodopsin and 38% porphyropsin), the initial phase of visual pigment regeneration (at 30°C) proceeded at a slower rate (first-order rate constant: 6·5 × 10−3 nmol kg−1 body weight min−1; half-life of reaction = 106 min) than the rate of porphyropsin regeneration. This suggests that the high proportion of rhodopsin in the retina of goldfish held at 30°C is not a direct result of a faster rate of regeneration of rhodopsin than of porphyropsin.
Swim Initiation in the Leech by Serotonin-Containing Interneurones, Cells 21 and 61
Authors: Nusbaum Michael P. , Kristan William B. 
Published: April 2021

ABSTRACT
Two pairs of serotonin-containing neurones, designated cells 21 and 61, were characterized physiologically and anatomically in the hirudinid leeches Macrobdella decora and Hirudo medicinalis. Both of these cells are bilaterally paired interneurones and each cell is weakly electrically coupled to the other serotonin-containing cells both intra- and interganglionically. Cells 21 and 61 are excited polysynaptically by individual identified mechano-sensory neurones. Segmental nerve shock sufficient to elicit an episode of swimming strongly excites cells 21 and 61, which then tend to generate bursts of impulses that are phase-locked to the swim motor pattern. Intracellular stimulation of either cell 21 or cell 61 often causes the initiation of swimming, acting in parallel with the nonserotonergic swim-initiator cell 204. Cells 61 and 204 are also weakly electrically coupled. The latency to swim onset by stimulating cell 21 or 61 is similar to that of cell 204 and different from that of the serotonergic Retzius cell. This result, with those in the accompanying paper (Nusbaum, 1986), suggests that unlike the Retzius cell and similar to cell 204, cells 21 and 61 synaptically contact cells of the swim central pattern generator (CPG).
Spontaneous Locomotor Activity in Arctic Charr Measured by a Computerized Imaging Technique: Role of Brain Serotonergic Activity
Authors: Winberg Svante , Nilsson Göran E. , Spruijt Berry M. , Höglund Urban 
Published: April 2021

ABSTRACT
Using a computerized video-image analysis system, spontaneous locomotor activity was measured in dominant and subordinate individuals of Arctic charr (Salvelinus alpinus) and in individuals treated with inhibitors of serotonin (5-HT) synthesis and re-uptake. Arctic charr were put together in pairs. After 1 week, subordinate individuals were found to have elevated brain levels of 5-hydroxyindoleacetic acid, a major 5-HT metabolite, suggesting an increase in serotonergic activity. The subordinate individuals had significantly lower spontaneous locomotor activity than the dominant fish. Similarly, Arctic charr displayed a significantly reduced locomotor activity when their serotonergic activity was stimulated by the specific 5-HT re-uptake inhibitor zimeldine. In contrast, fish treated with the 5-HT synthesis inhibitor p-chlorophenylalanine showed a significant increase in locomotor activity. Dominant, subordinate and pharmacologically treated fish all had very similar activity rhythms for the 18h test period. Thus, neither the previous social experience nor the pharmacological treatment seemed to affect the diurnal activity rhythm per se. Taken together, these results suggest that the brain serotonergic system inhibits locomotor activity and support the possibility that 5-HT is involved in the inhibition of locomotor activity displayed by subordinate fish.
Adaptations to a Terrestrial Existence by the Robber Crab Birgus Latro: VIII. Osmotic and Ionic Regulation on Freshwater and Saline Drinking Regimens
Authors: Taylor H. H. , Greenaway P. , Morris S. 
Published: April 2021

ABSTRACT
Crabs supplied with deionized water (DIW) and food maintained constant haemolymph osmolality, [Na] and [Cl]. Drinking of 300, 600 or 1000mosmolkg−1 sea water (300SW, 600SW, 1000SW) elevated Na and Cl concentrations, which restabilized by 12 days on the 300SW and 600SW regimens but continued to rise on the 1000SW regimen. [Ca] increased slightly on all regimens. [K] changed only on the 1000SW regimen. Haemolymph [Mg] was poorly regulated on all saline regimens, doubling after 47 days on the 1000SW regimen.
Urine was always isosmotic to haemolymph, had twice the [K] and a lower [Ca]. Changes in urinary ion concentrations paralleled those in the haemolymph, indicating that the antennal organs are unimportant in ionic regulation. Changes in ionic composition of the branchially modified urine (P) reflected drinking water concentrations on a mole-for-mole basis (except for [Mg]), confirming the regulatory role of P. Water and ion budgets indicate reingestion of 70–90% of filtered urine. Branchial ion uptake and reingestion allow variable reclamation of 70–99.9% of filtered Na, Ca, Mg and Cl and 37–96% of K. Crabs drank DIW daily (mean rate, 16.2 g kg−1 day−1) and released P intermittently (intervals ranged from less than 1 to more than 6 days; mean 5.8 g kg−1 day−1). Provision of 300SW and 600SW doubled drinking rate and trebled P output. Intense initial drinking of 1000SW (58.1 g kg−1 day−1) was not maintained. Return to DIW after 1000SW stimulated very high drinking rates initially (119 g kg−1 day−1).
Birgus can vary P composition rapidly and widely (less than 100mosmolkg−1 and 20mmol l−1 [NaCl] to more than 1000mosmolkg−1 and 500mmol l−1 [NaCl] within 1 day) and sometimes produce P that is hyperosmotic to the haemolymph. Production of P hyperosmotic to the drinking water and increased drinking rate permit a gain of osmotically free water to balance evaporation when drinking 300SW and 600SW, but not 1000SW. Adjustments to the volume and composition of the P appear to be more important than ‘behavioural osmoregulation’.
Inhibition of The Respiratory Pattern-Generating Neurons by an Identified Whole-Body Withdrawal Interneuron of Lymnaea Stagnalis
Authors: Inoue T. , Takasaki M. , Lukowiak K. , Syed N. I. 
Published: April 2021

ABSTRACT
Respiration and the whole-body withdrawal are two incompatible behaviors in the freshwater snail Lymnaea stagnalis. Whole-body withdrawal behavior is believed to be higher on the behavioral hierarchy than respiratory behavior. A central pattern generator (CPG) underlies respiratory behavior; whole-body withdrawal is mediated by a network of electrically coupled neurons. In this study, we provide evidence that the behavioral hierarchy between the whole-body withdrawal and the respiratory behaviors is established at the interneuronal level. We demonstrate that an identified whole-body withdrawal interneuron inhibits both muscular and neuronal components of the respiratory behavior in Lymnaea stagnalis.
A pair of identified, electrically coupled interneurons, termed left and right pedal dorsal 11 (L/RPeD11), coordinates the whole-body withdrawal behavior in Lymnaea stagnalis. In the present study, RPeD11 inhibited spontaneously occurring respiratory CPG activity in isolated brain preparations. In addition, electrical stimulation of RPeD11 in a semi-intact preparation also inhibited respiratory CPG interneuron RPeD1.
The synaptic connections between RPeD11 and the respiratory CPG neurons RPeD1 and visceral dorsal 4 (VD4) persisted in the presence of high-Ca2+/high-Mg2+ saline, suggesting the possibility that they may be monosynaptic.
In a semi-intact preparation (lung–mantle, pneumostome and central nervous system), electrical stimulation of RPeD11 induced pneumostome and columellar muscle contractions while inhibiting the activity of RPeD1. Moreover, mechanical stimulation of the respiratory orifice, the pneumostome, excited RPeD11, while its effects on the respiratory CPG neuron (RPeD1) were inhibitory.
To determine the monosynaptic nature of connections between RPeD11 and the respiratory CPG neurons in the intact nervous system, we constructed these synapses in culture. RPeD11 and individual respiratory interneurons were isolated from their respective ganglia and co-cultured under conditions that support neurite outgrowth. Following neuritic overlap, RPeD11 was found to establish inhibitory synapses with the respiratory interneurons, supporting the hypothesis that these synaptic connections are likely to be monosynaptic in the intact central nervous system.
Environmental Acidity and White Muscle Recruitment During Swimming in the Brown Trout (Salmo Trutta)
Authors: Day N. , Butler P. J. 
Published: April 2021

ABSTRACT
Electromyographic recordings show that, for adult brown trout swum up to their critical swimming speed (Ucrit) in a flume at neutral pH, white muscle recruitment occurred when speeds approached 1 body length s−1 (BL s−1) and continued to Ucrit (approximately 2 BL s−1) at both winter (5 °C) and summer (15 °C) acclimation temperatures. However, in the majority of fish swum up to Ucrit at sublethal acidic pH, continuous white muscle recruitment did not occur, although all swam above 1 BL s−1. Any observed electrical activity of the white muscle in these individuals was, at best, intermittent. Consequently, the mean Ucrit of these fish was approximately half that of fish swum at neutral pH. In all fish at sublethal pH, red muscle activity was observed for the whole duration of the exercise period, showing that swimming speeds greater than 1 BL s−1 were achieved largely aerobically. Fish that were chased around a tank at sublethal pH appeared lethargic in their escape response, exhibiting little or no burst swimming. Other observed effects of exposure to sublethal pH, which may have affected swimming capacity, included increases in the resting levels of blood and muscle ammonia, reduced muscle glycogen stores and reduced muscle ion concentrations.