bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role Of CaCO3 Dissolution as A Source of HCO3− for the Buffering of Hypercapnic Acidosis in Aquatic and Terrestrial Decapod Crustaceans
Authors: Henry R. P. , Kormanik G. A. , Smatresk N. J. , Cameron J. N. 
Published: April 2021

ABSTRACT
Blood calcium concentrations are elevated during a hypercapnic acidosis in the terrestrial crab Gecarcinus lateralis, but not in the aquatic Callincetes sapidus. The increase occurs concomitantly with a rise in blood HCO3− and partial restoration of resting blood pH values. It is believed that in G. lateralis that a source of CaCO3, possibly the shell, is being dissolved for buffering purposes.
Haemodynamic Responses to Haemorrhage in the Snake, Elaphe Obsoleta Obsoleta
Authors: Lillywhite Harvey B. , Smith Laurens H. 
Published: April 2021

ABSTRACT
Haemodynamic responses to graded haemorrhage were studied in unanaesthetized black ratsnakes (Elaphe o. obsoleta) wherein fixed percentages of the blood volume were removed at regular intervals over periods which varied from one to several hours. Initially measured whole blood volumes averaged about 6 % of the body mass and were determined from plasma dilutions of Evans blue dye or the bleeding and washing out of red cells. In response to haemorrhage, heart rate increased, haematocrit decreased, plasma protein concentration decreased, and arterial pressure remained relatively constant until a critical blood loss at which pressure dropped precipitously. Critical volume deficits occurred at the withdrawal of 63-122% of the initially measured blood volume. It appears that cardiovascular reflexes assist the regulation of arterial pressure during haemorrhage; additionally, there occurs a progressive and significant restitution of plasma volume owing to the absorption of extravascular fluid. Fluid volumes absorbed by the circulation during haemorrhage replaced 20–71 % of the haemorrhaged blood loss and were correlated with the magnitude of the critical volume deficit. Body movements increased arterial pressure by improving venous cardiac return.
Cellular Discrimination Processes in Metal Accumulating Cells
Authors: Simkiss K. 
Published: April 2021

ABSTRACT
A technique is described for investigating cellular fluxes and the accumulation of metal ions in the hepatopancreas of the snail Helix aspersa. The method involves the simultaneous administration of double isotopes into the haemocoel and the subsequent detection of these metals in tissues and granule materials. By comparing in vivo and in vitro data it is possible to detect two separate accumulation systems which appear to correspond with metallothionein and pyrophosphate granules. It is also possible to obtain some information of the nature of possible cellular transport systems.
The Exoskeleton and Insect Proprioception
Authors: Zill Sasha N. , Moran David T. 
Published: April 2021

ABSTRACT
In the cockroach tibia, the activities of campaniform sensilla that monitor cuticular strain have been recorded in free-walking animals. In walking, sensillum firing is correlated with myographic activity of the flexor and extensor tibiae muscles. The specific activity of a single campaniform sensillum depends upon the orientation of its cuticular cap. In slow walking, proximal sensilla, whose ovoid cuticular caps are oriented perpendicular to the leg long axis, fire in bursts that are initiated just prior to the onset of extensor tibiae activity in the stance phase of locomotion. The firing frequency within bursts of proximal sensilla is generally inversely related to the frequency of the slow extensor tibiae motoneurone and ceases when motoneurone activity exceeds 200 Hz. Distal campaniform sensilla, oriented parallel to the leg long axis, only fire when slow extensor tibiae activity exceeds 300 Hz. In slow walking, distal sensillum activity typically occurs as a short intense burst near the end of the stance phase of the step cycle, when slow extensor frequency is maximal. Distal sensillum firing is greatly increased when forward progression is impeded. The patterns of afferent activity seen in slow walking indicate that the campaniform sensilla function in load compensation and limitation of muscle tensions. The proximal sensilla respond to initial loading of the leg and can reflexly excite the slow extensor motoneurone in compensation. The distal sensilla respond to cuticular strains that result from large extensor contractions and can reflexly inhibit the slow motoneurone. In rapid walking, activities of both subgroups of campaniform sensilla shift in phase relative to slow extensor firing. Proximal sensilla activity occurs after the onset of slow extensor firing. Distal sensilla bursts follow the termination of slow extensor activity. These phase shifts limit the reflex functions of the tibial campaniform sensilla in rapid walking. Shifts in phase of afferent activity may contribute to the need for central programming of locomotion.
Sensory Fields and Properties of the Oesophageal Proprioceptors in the Mollusc, Philine
Authors: Dorsett D. A. , Sigger J. N. 
Published: April 2021

ABSTRACT
The buccal ganglia of Philine each contain four mechanosensory neurones that are proprioceptors in the oesophageal wall. The sensory fields of the three small receptors are bilateral and separate from each other, but two are overlapped by the more extensive field of the largest cell. The sensory field of each receptor overlaps that of its contralateral homologue. The receptors respond to touch or stretch of the oesophageal wall or certain nerve trunks with a rapid burst of impulses, which adapt quickly to repetitive stimulation. The soma spike is characterized by a large undershoot that summates at high-impulse frequencies to hyperpolarize the cell. Repetitive stimulation leads to the axon spike failing to propagate to the soma. Blocking most probably occurs at a branch point on the main axon within the ganglion. Impulses generated in one part of the axon normally propagate to all parts of the cell. Conduction velocity increases in the axon as the soma is approached. Conduction velocity may vary in different branches of the axon.
Axon/Schwann-Cell Relationships in the Giant Nerve Fibre of the Squid
Authors: Villegas Jorge 
Published: April 2021

ABSTRACT
This communication summarizes the experimental evidence obtained in the giant nerve fibre of the tropical squid Sepioteuthis sepioidea, on the nature of the mechanism responsible for the long-lasting effects of axonal excitation on the membrane potential of the Schwann cell. In these nerve fibres the propagation of a train of nerve impulses by the axon is followed by a prolonged hyperpolarization of the Schwann cell which can be reproduced, or modified,.by the external application of cholinergic compounds. The presence and exact localization of the different components of the acetylcholine system directly involved in such Schwann-cell responses was detected by means of pharmacological, histochemical and chemical procedures. Thus, the results of the experiments herein discussed revealed that, under physiological conditions: the Schwann cell is able to synthesize, store and release acetylcholine; and that it has acetylcholine receptors of the nicotinic type, and acetylcholinesterase enzyme activity in its plasma membrane. On the other hand, the axon has low acetyltransferase activity and acetylcholine concentration in its axoplasm, and a high acetylcholinesterase activity in its axolemma. It was also found that acetylcholine hyperpolarizes the Schwann cell by increasing its relative permeability to the potassium ion. The distribution pattern of the acetylcholine system indicates that it operates as a feedback mechanism for the regulation of the Schwann-cell membrane potential and ionic permeability following axonal excitation.
Studies on Cultured Schwann Cells: The Induction of Myelin Synthesis, and the Control of Their Proliferation by A New Growth Factor
Authors: Brockes J. P. , Fryxell K. J. , Lemke G. E. 
Published: April 2021

ABSTRACT
We have recently described the use of immunological methods to identify and purify rat Schwann cells. In dissociated cultures of neonatal sciatic nerve, all of the cells can be identified by antigenic criteria as either Schwann cells or fibroblasts. The fibroblasts may be removed by treatment with antiserum to the Thy-1 antigen and complement. The purified Schwann cells have been used to study the regulation of the expression of myelin components, and the stimulation of Schwann cell division by a soluble growth factor.
Among the components of myelin, we have concentrated on the peripheral myelin glycoprotein P0, which constitutes 50–60% of the protein in peripheral myelin. We have studied the distribution of P0in vitro and in vivo by immunofluorescence, immuno-autoradiography on SDS gels, and solidphase radioimmunoassay. Our results support the hypothesis that P0 is induced specifically as a consequence of the interaction between the Schwann cell and the myelinated type of axon. The level of P0 in the myelin membrane is at least 1000-fold higher than in the Schwann cell membrane.
Purified Schwann cells divide very slowly in a conventional tissue culture medium. This has alowed us to purify a new growth factor from extracts of brain and pituitary, tentatively named Glial Growth Factor (GGF). The activity resides in a basic protein with a native molecular weight of 6×104 daltons and a subunit molecular weight of 3 ×104 daltons, which is active at levels comparable to those of epidermal growth factor. GGF is mitogenic for Schwann cells, astrocytes and muscle fibroblasts.
Perspectives on the Cell Biology of Glia
Authors: Nicholls John 
Published: April 2021

ABSTRACT
From the vantage point of 1981, advances in our understanding of glial cells over the last 20 years seem at once significant, provocative and high in promise. It is sobering to remember that at that time speculation about their role included a spectrum of romantic possibilities, from blood-brain barrier to memory, from constituting the total extracellular space of the brain to playing a key role in learning, from being essential for the neuronal action potential to producing impulses themselves, from ferrying vital materials into and out of neurones to having no function at all other than support. Unfortunately, the ratio of speculation to sound experimental observations was so high that, apart from continuing contributions from anatomists, to be interested in glia was almost disreputable, somewhat akin to dabbling in parapsychology or memory transfer.
Mechanisms of Ionic Homeostasis in the Central Nervous System of An Insect
Authors: Treherne J. E. , Schofield P. K. 
Published: April 2021

ABSTRACTExtracellular ionic homeostasis in an insect central nervous system involves a peripheral intercellular diffusion barrier, an extracellular matrix and neuroglial cation transport.The peripheral location of the barrier in the superficial neuroglia is confirmed by intracellular recording from glial cells identified by peroxidase injection. This barrier protects the underlying neurones from large changes in ionic composition of the blood-plasma, but renders them more susceptible to fluctuations in ion composition resulting from neuronal signalling within the very restricted extracellular system. Because of the peripheral intercellular barrier, sodium movements between the blood and the extracellular fluid are largely transcellular and are mediated by ion pumps on the perineurial and underlying glial membranes. It is suggested that the homeostatic role of the neuroglial ion pumps is augmented by an anion matrix which functions as an extracellular sodium reservoir. It is proposed that during depletion of extracellular sodium, this cation is released by the matrix to maintain the sodium activity in the fluid at the axon surfaces.
K+ Changes in the Extracellular Space of the Spinal Cord and Their Physiological Role
Authors: Syková Eva 
Published: April 2021

ABSTRACT
K+ accumulates in the intercellular space as a result of neuronal activity. The changes in extracellular K+ concentration, Δ [K]e (estimated by K+-selective microelectrodes), depends on neuronal activity, on the density of discharging neurones and the removal of the accumulated K+ by diffusion, active transport and current flow through cells. In the mammalian as well as the amphibian spinal cord a single volley in a peripheral nerve increases [K]e by 0·2–0·5 mmol.1−1, while tetanic stimulation (100 Hz) by 7–8 m-mol.l−1, with a maximum in the lower dorsal horn. Increased [K]e was also found in lumbar segments when the somatosensory cortex of the cat and medulla of the frog were stimulated. In the frog spinal cord, the tactile stimulation of the hindlimb evoked Δ [K]e by about 0·1 mmol.1−1, nociceptive stimulation by 0· 2–1·0 mmol.1−1. Spontaneous Δ [K]e and dorsal root potentials (DRPs) were observed at various intervals after stimulation, associated with the decay phase of Δ [K]e.
It was shown that primary afferent depolarization (PAD) consists of two components: the ‘early’ component (mediated by GABA and depressed by picrotoxin or bicuculline) and the ‘late’ K+ component (potentiated by picrotoxin and bicuculline). Even when increased [K]e produces PAD, this does not mean that it also results in presynaptic inhibition. It was found that the Δ [K]e produced depolarization of motoneurones and neuroglia and there is every reason to believe that this also applies to the interneurones. Evidence is available that an increase of [K]e up to 6 mmol. 1−1 facilitates impulse transmission in the spinal cord while higher levels result in its inhibition.
Transfer of Habituation Shows an Interaction Between Neuronal Circuits of the Gill Withdrawal Reflex in Aplysia Californica
Authors: Goldberg Jeff , Lukowiak Ken 
Published: April 2021

ABSTRACT
The gill withdrawal reflex (GWR) and its subsequent habituation can be evoked by tactile stimulation of the siphon or gill when the CNS is either intact or removed. It has been suggested that the neural circuits that mediate the GWR evoked at these two loci are parallel and independent. We provide three lines of evidence which show that these circuits interact and, therefore, comprise a single integrated system. Firtly, siphon and gill stimulation evoked similar excitatory responses in the central gill motor neurones. Secondly, the GWR habituated by repetitive stimulation at one locus was dishabituated by stimulation of the other locus. Thirdly, transfer of habituation occurred. Although the transfer was seen neurally at the level of central gill motor neurones, transfer of habituation also occurred after the CNS was removed. Therefore, the neuronal circuits mediating the reflexes evoked at the siphon and gill interact within both the CNS and PNS. The PNS is largely responsible for mediating this gill behaviour that is based on such interactions, while the CNS provides suppressive and facilitatory plasticity to these responses to enable Aplysia to better adapt to a changing environment.
Long-Term Submergence at 3 °C of the Turtle, Chrysemys Picta Bellii, in Normoxic and Severely Hypoxic Water
Authors: Ultsch Gordon R. , Jackson Donald C. 
Published: April 2021

ABSTRACT
Survival and blood acid-base status were measured on freshwater turtles (Chrysemys picta bellii Gray) that were submerged at 3 °C in either aerated (high O2) or Na-equilibrated (low O2) water. Results from catheterized turtles, without access to air under these conditions, and from non-catheterized turtles which were either apnoeic (in high O2 and low O2 water) or in high O2 water with access to air, are compared.
Under the most adverse conditions (catheterized, submerged, low O2), survival duration was 126 ± 14 (X ± s.E.) days, and 2 of the 10 turtles so treated were still alive after 177 days, although their condition was poor. Apnoeic, high O2 turtles generally survived longer and were in better condition despite a skin fungus condition that selectively affected these animals. Six of ten non-catheterized high O2 turtles were still alive after 189 days without breathing.
All apnoeic turtles developed an acidosis which, except for a transient hypercapnia in low O2 turtles, was a metabolic acidosis attributable to elevated lactic acid. Acidosis was most severe in low O2 turtles in which peak plasma lactates exceeded 200 mm. High O2 turtles, as judged by higher blood and lower lactate concentrations, were able to extract dissolved O2 from the water and support a significant portion of their metabolic requirements by aerobic metabolism. Our data indicate that wintering turtles can remain alive for up to 6 months, even while totally anoxic and severely acidotic, but that the acid-base state and probably the recovery potential are significantly improved if dissolved O2 is available for extra-pulmonary uptake.
Neural Lesions Can Cause Dendritic Sprouting of an Undamaged Adult Insect Motoneurone
Authors: Pitman Robert M. , Rand Kathryn A. 
Published: April 2021

ABSTRACT
The effect of nerve lesions upon the dendritic branching of the metathoracic ‘fast’ coxal depressor motoneurone in the adult cockroach, Peri-planeta americana has been studied by intracellular cobalt injection. Dendrites may sprout after several nerve trunks entering the metathoracic ganglion are lesioned. Direct surgical damage to the neurone is not a pre-requisite for sprouting. New sprouts may extend into regions of the ganglion or into nerve trunks which the neurone would not normally occupy. The developing sprouts appear to grow preferentially within regions containing degenerating nerve fibres. The nerve sprouts frequently have varicosities along their length and at their ends.
Sensory and Motor Neurones Responsible for the Local Bending Response In Leeches
Authors: Kristan William B. 
Published: April 2021

ABSTRACT
Intracellular recordings were made from identified mechanosensory neurones (T and P cells) and longitudinal muscle motor neurones of leeches Hirudo medicinalis and Macrobdella decora while the skin was electrically stimulated to produce local bending responses. The stimulus intensity required to produce local bending was found to activate the mechanosensory neurones at physiological firing rates. For a given stimulation frequency, intracellular activation of the mechanosensory neurones produced the same local bending response as did skin stimulation. Hyperpolarization sufficient to block the propagation of the afferent impulses into the central nervous system eliminated the local bending response to skin stimulation. Stimulating identified longitudinal muscle motor neurones at frequencies observed during the local bending response produced body wall movements similar to those seen in local bending. Hyperpolarization of the motor neurones to block impulse initiation abolished local bending. Mechanosensory neurone to longitudinal muscle motor neurone connexions were demonstrated to be effective and reliable, but polysynaptic for all but the previously documented monosynaptic connexions from mechanosensory neurones onto the L motor neurone (Nicholls & Purves, 1970). It is concluded that the previously identified mechanosensory and motor neurones are exclusively responsible for the local bending response.
Transient Rhythms in the Swimming Activity ofSarsia Tubulosa(Hydrozoa)
Authors: Leonard Janet L. 
Published: April 2021

ABSTRACTMaximum entropy spectral analysis (MESA) was used to assess the contribution of endogenous rhythms to the timing of swim bouts in a hydro-zoan jellyfish, Sarsia tubulosa M. Sars. The results show that the high degree of variability in Sarsia swimming activity is due largely to the number of rhythms which may contribute to the behaviour and to the transient nature of these rhythms. I conclude that the ability to ‘choose’ among behavioural rhythms may be a widespread behavioural mechanism in cnidarians and I suggest that, in Sarsia, these transient behavioural rhythms may originate in activity of the marginal pacemaker system.
The Influence of Experimental Anaemia On Blood Acid-Base Regulation In Vivo and In Vitro in the Starry Flounder (Platichthys Stellatus) and the Rainbow Trout (Salmo Gairdneri)
Authors: Wood Chris M. , McDonald D. G. , McMahon B. R. 
Published: April 2021

ABSTRACT
Severe experimental anaemia caused a rise in and an associated fall in pH (respiratory acidosis) in arterial and venous blood of both flounder and trout in vivo. In some trout, but not in flounder, there was also a rise in blood lactate, indicating metabolic acidosis. In vitro, blood buffer capacities declined with haematocrit, a factor which contributed to the extent of the acidoses in vivo. However, haematocrit did not influence the pK1 of the plasma system or the actual measurement of blood pH. The Donnan ratio for varied linearly with pH over the range 7·0–7·6, indicating a passive distribution of across the trout erythrocyte. The present data, together with other recent results, indicate that the teleost red blood cell does play a role in plasma dehydration and CO2 excretion, and therefore opposes the theory of Haswell & Randall (1978) that the erythrocyte is functionally impermeable to .
Water Vapour Absorption by the Desert Burrowing Cockroach, Arenivaga Investigata: Evidence Against A Solute Dependent Mechanism
Authors: O’donnell M. J. 
Published: April 2021

ABSTRACT
Solute concentrations were measured in the frontal bodies and hypopharyngeal bladder surfaces, which form the absorption system of Arenivaga. Measured values were compared with the concentrations necessary to lower relative humidity to the absorption threshold, 81% R.H. The predominant inorganic solutes, measured by instrumental neutron activation analysis, were Na, K, and Cl. Their concentrations were 2–3 orders of magnitude below those necessary for absorption. Quantities of a variety of hydrophilic organic molecules were determined with fluorometric reagents. Concentrations of free amino acids, peptides, reducing sugars and polyhydroxyl alcohols were negligible in frontal bodies and on bladder surfaces. Frontal bodies did not appear to be active sites of protein or polysaccharide synthesis, because they did not accumulate significant amounts of radio-labelled amino acids and glucose injected into the hemolymph. The results of this and previous studies indicate strongly that absorption in Arenivaga differs markedly from the solute-dependent schemes which have been proposed for other arthropods.
Ventricular Haemodynamics in the Monitor Lizard Varanus Exanthematicus: Pulmonary and Systemic Pressure Separation
Authors: Burggren Warren , Johansen Kjell 
Published: April 2021

ABSTRACT
The haemodynamics of the anatomically undivided ventricle of the monitor lizard Varanus exanthematicus have been examined by measurements of blood pressure and flow. Central blood , and pH were also measured.
Intracardiac pressure measurements show the ventricle to be functionally divided throughout systole into a high pressure pump (cavum arteriosum : ‘mean’ pressure 89 cm H2O) perfusing the systemic circulation, and a low pressure pump (cavum pulmonale: ‘mean’ pressure 40 cm H2O) perfusing the pulmonary circulation. Hypoxia produced by asphyxia or N2 breathing changed systolic pressures in the ventricular cava, but never resulted in superimposable pressure waveforms which would have indicated a break-down from ventricular division into two pressure pumps. Diastolic pressures were superimposable in the ventricular cava under all conditions.
Analysis of blood and O2 content revealed the potential for nearly complete separation of left and right atrial blood in the ventricle, but both left-to-right and right-to-left shunts of considerable magnitude could also develop.
The varanid heart with its systolic pressure separation allows the development of high blood pressure gradients capable of driving a large cardiac output through the high impedance systemic vascular beds. Concurrently, the low impedance pulmonary circuit is perfused at a much reduced blood pressure, circumventing filtration of plasma into the lungs and impairment of gas exchange. Haemodynamically this situation resembles that present in crocodilians and the homeothermic vertebrates.