bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Vascular and Extravascular Volumes of Eel Muscle in Response to Catecholamines: The Function of the Caudal Lymphatic Heart
Authors: Davie Peter S.
Published: April 2021

Vascular volume changes in an isolated saline-perfused eel tail preparation in response to catecholamines were small (< 2 %) and are explicable in terms of changes in volume of pre-capillary resistance vessels. Extravascular-extracellular (interstitial) volume increased less than 3 % during infusion of adrenaline (AD) at concentrations of 1 × 10−6 to 1 × 10−3 M. Injection of doses of AD and noradrenaline (NA) between 1 nmol and 100 nmol caused maximum interstitial volume changes of less than 11%. Isoprénaline caused only very small changes in vascular and interstitial volumes. Caudal lymph heart frequency increased when high concentrations (> 1 × 10−6 M) and doses (> 1 nmol) of AD and NA were administered. Caudal lymph heart frequency increases were significantly correlated with changes in outflow after vascular volume adjustments. One function of the caudal lymph heart is to return interstitial fluid to the vascular system.
Long-Term Submergence At 3 °C of the Turtle, Chrysemys Picta Bellii, In Normoxic and Severely Hypoxic Water
Authors: Jackson Donald C. , Ultsch Gordon R.
Published: April 2021

Plasma [Na+], [K+], and [Cl-] were measured on blood sampled periodically from turtles submerged in Na-equilibrated (low-O2) or air-equilibrated (high-O2) water. Plasma osmolality and total [Ca2+] and [Mg2+] were measured on selected samples. Previously we reported that a severe metabolic acidosis developed under these conditions; in low-O2 turtles, plasma [lactate-], rising to over 200 m-equiv/1, was only partially buffered by [HCO3-], which fell from 40 to 5 m-equiv/1.

The balance of the buffering was accomplished by changes in strong ions which included (in low-O2) a fall in [Cl−] from 79·5 ±1·4 m-equiv/1 to below 60 m-equiv/1, a rise in [Ca2+] from 3 to over 100 m-equiv/1, and a rise in [Mg2+] from 3 to over 30 m-equiv/1. Together, all ionic changes balanced the increase in [lactate-], but this analysis is tentative because we do not know the distribution of Ca2+ and Mg2+ between free and bound forms in vivo. Plasma osmolality rose from 233 ±4·1 to 382 ± 12·4 mosmol after 162 days in low-O2, even though the turtles showed a gain in body weight. The ionic changes that occurred in plasma also occurred in the pericardial and peritoneal fluids, suggesting general extracellular fluid participation in lactate buffering. Bladder urine contained significant concentrations of both lactate and calcium, indicating that some acid excretion may have occurred during the submergence.
An Endogenous Crepuscular Rhythm of Rainbow Trout (Salmo Gairdneri) Photomechanical Movements
Authors: Douglas R. H.
Published: April 2021

The position of the epithelial pigment and cones in the retina of Salmo gairdneri was determined during extended periods of darkness in fish entrained to both artificial and natural light/dark cycles. An endogenous rhythm of such photomechanical movements, unique among species so far examined, was observed in both groups of fish, with two peaks of light adaptation coincident with dawn and dusk. It is suggested that such an apparently non-adaptive physiological rhythm is related to the behavioural pattern of trout and reveals a basic crepuscular organisation. No endogenous rhythm was observed in continual light. These results suggest that control of photomechanical changes in rainbow trout has two components : an endogenous component, that causes the bimodal pattern in maintained darkness, and a direct effect of light, that maintains light adaptation throughout a normal day.
The Transition to Air Breathing in Fishes
Authors: Graham Jeffrey B. , Baird Troy A.
Published: April 2021

In response to progressive aquatic hypoxia, the armoured loricariid cat-fishes Ancistrus chagresi and Hypostomus plecostomus become facultative air-breathers and utilize their stomachs as accessory air-breathing organs. Hypostomus initiates air breathing at a higher aquatic O2 tension than does Ancistrus (60 v. 33 mmHg). Once begun, the air-breathing frequencies of both species increase with decreasing ; the frequency of Ancistrus, however, is greater than and increases more with hypoxia than does that of Hypostomus, which appears to be a more efficient air breather.

Hypoxia acclimation reduces the air-breathing rate of both species. A larger rate reduction occurs in Ancistrus, which, however, continues to require more frequent breaths than Hypostomus. Hypoxia acclimation does not affect the air-breathing threshold of either species, suggesting that external O2 receptors initiate facultative air breathing.

In progressive aquatic hypercapnia Ancistrus has a lower air-breathing CO2 threshold (8·7 mmHg) than Hypostomus (12·8 mmHg). However, in some tests, individual fish of both species did not initiate air breathing even at . as high as 21 mmHg. Also, air breathing evoked by hypercapnia was short-lived; both species quickly compensated for this gas and resumed exclusively aquatic respiration within a few hours of exposure. Thus, CO2 is not an important regulator of air breathing in these species. Between 25 and 35 °C, the air breathing threshold of Ancistrus is temperature-independent, but air-breathing frequency increases with temperature.

Ancistrus and Hypostomus do not breathe air in normoxic (air-saturated) water; their air-breathing responses are evoked by environmental hypoxia. This is fundamentally different from other fish species that breathe air in normoxia in order to meet heightened metabolic demands. Also, the facultative air-breathing adaptations of Ancistrus and Hypostomus differ in scope and magnitude from those utilized by species that breathe air in normoxia and adapt to hypoxia by increasing air-breathing rate.
Energetics and mechanics of terrestrial locomotion. I. Metabolic energy consumption as a function of speed and body size in birds and mammals
Authors: Taylor C. R. , Heglund N. C. , Maloiy G. M. O.
Published: April 2021

This series of four papers investigates the link between the energetics and the mechanics of terrestrial locomotion. Two experimental variables are used throughout the study : speed and body size. Mass-specific metabolic rates of running animals can be varied by about tenfold using either variable.

This first paper considers metabolic energy consumed during terrestrial locomotion. New data relating rate of oxygen consumption and speed are reported for: eight species of wild and domestic artiodactyls; seven species of carnivores ; four species of primates ; and one species of rodent. These are combined with previously published data to formulate a new allometric equation relating mass-specific rates of oxygen consumed during locomotion at a constant speed to speed and body mass (based on data from 62 avian and mammalian species):

where has the units ml O2 s−1 kg−1; Mb is in kg; and vg is in m s−1. This equation can be expressed in terms of mass-specific rates of energy consumption (Ėmetab/Mb) using the energetic equivalent of 1 ml O2 = 20·1 J because the contribution of anaerobic glycolysis was negligible :

where Ėmetab/Mb has the units watts/kg.

This new relationship applies equally well to bipeds and quadrupeds and differs little from the allometric equation reported 12 years ago by Taylor, Schmid-Nielsen & Raab (1970). Ninety per cent of the values calculated from this general equation for the diverse assortment of avian and mammalian species included in this regression fall within 25 % of the observed values at the middle of the speed range where measurements were made. This agreement is impressive when one considers that mass-specific rates of oxygen consumption differed by more than 1400% over this size range of animals.
Sensory alteration of motor patterns in the stomatogastric nervous system of the spiny lobster Panulirus interruptus
Authors: Sigvardt Karen A. , Mulloney Brian
Published: April 2021

Stretching the pyloric region of the lobster’s stomach in a manner that resembles pyloric dilation triggers a prolonged burst of impulses in two interneurones with axons in the inferior ventricular nerve (IVN). The burst is activated in the oesophageal ganglion by sensory axons that traverse the lateral ventricular nerves, the dorsal ventricular nerve and the stomato-gastric nerve. These sensory axons do not appear to make synaptic contacts in the stomatogastric ganglion. Electrical stimulation of sensory branches of the pyloric nerve triggers similar bursts in the IVN interneurones. The burst of impulses in the IVN interneurones lasts from 2 to 30 s and the impulse frequency ranges from 10 to 80 Hz in different parts of the burst. Once triggered, burst structure and burst duration are independent of the intensity or duration of stimuli applied to the sensory nerves. These bursts alter both the gastric and pyloric motor patterns. The IVN interneurones make a complex pattern of synapses with stomatogastric neurones. These are: pyloric dilators (PD) -excitation and slow inhibition; ventricular dilator (VD) -excitation ; gastric mill (GM) neurones -inhibition; lateral posterior gastric neurones (LPGN) -inhibition ; and Interneurone I (Int 1) -excitation and slow inhibition. The size of the p.s.p.s at each of these synapses depends on the duration and impulse-frequency of the burst in the presynaptic neurones, which in turn alters the firing patterns of the stomatogastric neurones in various ways.
Sodium and chloride transport in the isolated intestine of the earthworm,Lumbricus terrestris(L.)
Authors: Cornell John C.
Published: April 2021

Measurements of electrical potential difference (PD), short-circuit current (SCC) and unidirectional fluxes of sodium and chloride were made across portions of the intestine. Based on the results, the intestine can be divided into at least four physiologically distinct regions. These four physiological regions, designated from anterior to posterior as R I–fl, R III A, R III B and R IV, do not completely correspond to the four anatomically distinct regions of the intestine. The PD (serosal side positive) in R I–II, R III A, R III B and R IV is 1·08, 12·4, 5·61 and 31·7 mV, respectively. The SCC in these same regions is 9·9, 50·4, 49·7, and 16·4μA cm2, respectively. When short-circuited, net sodium and net chloride fluxes in the above regions are –0·36 and –0·27, 1·46*** and –0·92*, 1·74*** and –0·06 and 0·01*** and 0·07 μmol cm-2 h-1, respectively. Positive fluxes indicate net mucosal to serosal movements and asterisks indicate significant net fluxes (* P < 0·05, *** P < 0·001). There is good agreement between the SCC and net sodium transport in R III B. In the other regions of the intestine the ionic basis of the SCC has not been completely explained. The properties of the intestine in vitro appear to make the intestine well suited for the task of conserving sodium, a function which the intestine performs in vivo.
Saccadic eye movements are coordinated with head movements in walking chickens
Authors: Pratt David W.
Published: April 2021

Saccadic eye movements during walking were studied in chickens using cinematography. Saccades were made during about 80% of the thrust phases of head bobbing, and not made in the hold phases. The coordination of saccades with head movements maintains clear vision for the largest possible proportion of the time. The absence of saccades in hold phases and in some thrusts is probably not the result of insufficient time to organize a saccade.
Energetics and mechanics of terrestrial locomotion. II. Kinetic energy changes of the limbs and body as a function of speed and body size in birds and mammals
Authors: Fedak M. A. , Heglund N.C. , Taylor C.R.
Published: April 2021

This is the second paper in a series examining the link between energetics and mechanics of terrestrial locomotion. In this paper, the changes in the kinetic energy of the limbs and body relative to the centre of mass of an animal (EKE, tot) are measured as functions of speed and body size. High-speed films (light or X-ray) of four species of quadrupeds and four species of bipeds running on a treadmill were analysed to determine EKE, tot . A mass-specific power term, ĖKE, tot/Mb was calculated by adding all of the increments in EKE. during an integral number of strides and dividing by the time interval for the strides and body mass. The equations relating ĖKE, tot /M6 and speed were similar for all bipeds and quadrupeds regardless of size. One general equation for the rate at which muscle and tendons must supply energy to accelerate the limbs and body relative to the centre of mass seems to apply for all of the animals :

where Ė′KE, tot/Mb has the units W kg-1 and vg is ground speed in m s-1. Therefore, Ė′KE, tot/Mb does not change in parallel with the mass-specific rate at which animals consume energy (Ėmetab/Mb), either as a function of speed or as a function of body size.
Water loss and nitrogen excretion in sharp-nosed reed frogs (Hyperolius nasutus:anura, Hyperoliidae)
Authors: Withers Philip C. , Hillman Stanley S. , Drewes Robert C. , Sokol Otto M.
Published: April 2021

Sharp-nosed African reed frogs, Hyperolius nasutus Gunther, are small (0·4 g) hyperoliids which have minimal rates of evaporative water loss (4·5 mg g−1 h−1; 0·3 mg cm−2 h−1) that are only 1/10 to 1/20 that of a typical frog, Hyla regilla, of comparable size ( 171 mg g−1 h−1,4·8 mg cm−2 h−1). The surface-area-specific resistance to water flux of H. nasutus dorsal skin (96–257 sec cm−1) is similar to that of other ‘waterproof’ frogs (300–400), of cocooned frogs (40–500), and of desert reptiles (200–1400). However, H. nasutus can greatly increase the rate of evaporative water loss during radiative heat stress by mucous gland discharge, and by exposing the ventral skin.

Urea is the principal nitrogenous waste product of H. nasutus and uric acid comprises less than 1 % of the total nitrogen excretion for both H. nasutus and H. regilla. Other ‘waterproof’ frogs, in contrast, are uricotelic.

Lethal dehydration requires less than two weeks in H. nasutus, despite its low surface-area-specific rate of water loss, because of its small size and concomitantly high surface-to-volume ratio. The rate of urea accumulation during dehydration was 23 mM g−1 day−1, which is sufficiently low that urea accumulation would not be lethal before the frog had succumbed to dehydrational death. Consequently, there appears to be little or no selective advantage for uricotely in small ‘waterproof’ frogs, such as H. nasutus.
The respiratory metabolism of temperature-adapted flatfish at rest and during swimming activity and the use of anaerobic metabolism at moderate swimming speeds
Authors: Duthie Garry G.
Published: April 2021

The standard oxygen consumption and the oxygen consumption during measured swimming activity have been determined in three flatfish species at 5, 10 and 15 °C. The relationship between weight and standard oxygen consumption for flatfish conform to the general relationship Y = aWb. On an interspecies basis, standard oxygen consumption of flatfish is significantly lower than that of roundfish. A semilogarithmic model describes the relationship between oxygen consumption and swimming speed for the three species. Values for maximum oxygen consumption, metabolic scopes and critical swimming speeds are low in comparison to salmonids. The optimum swimming speeds and critical swimming speeds of flatfish are similar. It is suggested that, over long distances, flatfish adopt a strategy of swimming at supercritical speeds with periods of intermittent rest to repay the accrued oxygen debt. Elevated lactic acid levels in flounder white muscle after moderate swimming indicate an additional 15 % anaerobic contribution to the cost of locomotion as calculated from aerobic considerations.
Water-electrolyte balance in goldfishCarassius auratus, under constant and diurnally cycling temperature conditions
Authors: Houston A. H. , Koss T. F.
Published: April 2021

The effects of acclimation to constant and diurnally cycling temperatures upon water-electrolyte regulation were examined in goldfish held at 20, 25, 30 and 25 ± 5 °C, and sampled at 03.00, 09.00, 15.00 and 21.00 h. Plasma and epaxial muscle levels of Na, K, Ca, Mg, Cl and water were determined. Using Cl space as an indicator of extracellular phase volume, mean cellular cation concentrations were estimated. Fish held at constant temperature exhibited significant diurnal variations in all ions except plasma magnesium and muscle potassium. With the exception of muscle choride, however, the occurrence of peak and/or minimum concentrations tended to be inconsistent in relation to specific sampling times. Somewhat more regularity was apparent in terms of dark or light periods. Under constant temperature conditions plasma Cl increased with increasing temperature, while Na declined. Plasma magnesium was consistently higher at 25 °C than at either 20 or 30 °C. This was true of muscle Mg as well and, generally, also of Na, K and CL Water content tended to rise at higher temperatures in these animals, as did cellular phase volume, while extracellular phase volume was reduced. Exposure to cycling temperatures was associated with a number of significant departures from the pattern seen at constant temperature. Ionic concentrations tended to be lower. By comparison with animals sampled at constant temperature and comparable times, diurnal stability was greater. In several instances (e.g. muscle Cl− and K+, cellular and extracellular phase volumes) variations with temperature were significantly different. This was also the case with ion pairs such as K and Na, and Ca and Mg. These observations raise obvious questions regarding the validity of earlier descriptions of water-electrolyte status in species normally exposed to fluctuating temperatures. The variations seen under cycling temperature conditions, however, appeared to be adaptively appropriate. Reductions in plasma ion levels, for example, would tend to reduce costs of ionic regulation. The stability of plasma: cellular K concentrations should desensitize muscular excitability in relation to changing temperature conditions. This was also true of cellular levels of generally stimulating (Mg, K) and generally inhibitory ions (Ca, Na) known to influence metabolic processes.
Energetics and mechanics of terrestrial locomotion. IV. Total mechanical energy changes as a function of speed and body size in birds and mammals
Authors: Heglund N. C. , Fedak M. A. , Taylor C. R. , Cavagna G. A.
Published: April 2021

This is the nal paper in our series examining the link between the energetics and mechanics of terrestrial locomotion. In this paper the kinetic energy of the limbs and body relative to the centre of mass (EKE,tot of paper two) is combined with the potential plus kinetic energy of the centre of mass (ECM,tot of paper three) to obtain the total mechanical energy (excluding elastic energy) of an animal during constant average-speed locomotion. The minimum mass-specific power required of the muscles and tendons to maintain the observed oscillations in total energy, Ėtot/Mb, can be described by one equation : where Ėtot/Mb is in W kg−1 and vg is in m s−1. This equation is independent of body size, applying equally as well to a chipmunk or a quail as to a horse or an ostrich. In marked contrast, the metabolic energy consumed by each gram of an animal as it moves along the ground at a constant speed increases linearly with speed and is proportional to Mb−0·3. Thus, we have found that each gram of tissue of a 30 g quail or chipmunk running at 3 m s−1 consumes metabolic energy at a rate about 15 times that of a 100 kg ostrich, horse or human running at the same speed while their muscles are performing work at the same rate. Our measurements demonstrate the importance of storage and recovery of elastic energy in larger animals, but they cannot confirm or exclude the possibility of elastic storage of energy in small animals. It seems clear that the rate at which animals consume energy during locomotion cannot be explained by assuming a constant efficiency between the energy consumed and the mechanical work performed by the muscles. It is suggested that the intrinsic velocity of shortening of the active muscle motor units (which is related to the rate of cycling of the cross bridges between actin and myosin) and the rate at which the muscles are turned on and off are the most important factors in determining the metabolic cost of constantspeed locomotion. Faster motor units are recruited as animals increase speed, and equivalent muscles of small animals have faster fibres than those of larger animals. Also, the muscles are turned on and off more quickly as an animal increases speed, and at the same speed a small animal will be turning muscles on and off at a much higher rate. These suggestions are testable, and future studies should determine if they are correct.
Long-term submergence at 3 degrees C of the turtle Chrysemys picta bellii in normoxic and severely hypoxic water. III. Effects of changes in ambient and subsequent air breathing
Authors: Ultsch Gordon R. , Jackson Donald C.
Published: April 2021

Western Painted Turtles, Chrysemys picta bellii (N = 5), were maintained submerged and apneic for 90 days: days 0–21 in severely hypoxic water ( = 0–5 mmHg), days 22–43 aerated water ( ∼ 160 mmHg), and days 44–90 again in hypoxic water. From day 90 onward, the water was aerated and the turtles were allowed access to the air ; water and air temperatures were maintained at 3 °C.

Arterial blood samples were taken periodically and analysed for , pH, [Na+], [K+], [Cl−], [lactate−], [glucose] and haematocrit. Plasma [HCO3−] was calculated for all samples and total plasma calcium was measured on samples from two animals.

Each exposure to low water caused progressive lactic acidosis and a transient respiratory acidosis with an accompanying fall in plasma [Cl−] and rise in plasma [K+] and [calcium]. During the intervening period in aerated water, blood pH recovered significantly (from 7·33 to 7·74 in 7 days), due primarily to a fall in , (from 233 to 10·6 mmHg), while [lactate−] remained unchanged (at about 50 mM), and [HCO3−] rose slightly. Plasma [K+] promptly returned to nearly normal values.

When permitted to breathe on day 90, the three surviving turtles rapidly restored pH to normal by pronounced hyperventilation ( < 5 mmHg). Metabolic acidosis, however, disappeared slowly with a for [lactate−] and [HCO3−] restoration of about 2 weeks.

We conclude that a wintering turtle can stabilize or even slightly improve its acid-base and ionic status by moving from an anoxic environment to well-oxygenated water. Further improvement can be gained by breathing air, but recovery proceeds at a very slow rate if the animal remains at 3 °C.
On Peripheral Control Mechanisms Acting on the Central Pattern Generators for Swimming in the Dogfish
Authors: Grillner Sten , Wallén Peter
Published: April 2021

When sinusoidal movements were artificially imposed on the tail region of the curarized spinal dogfish during ‘fictive locomotion’ the coordinated burst pattern recorded in the ventral roots was effectively entrained to follow movement frequencies above as well as below the resting rate. The entrainment was characterized by: (1) a broad range of effective movement frequencies and amplitudes (down to a few degrees) ; (2) frequency-dependent timing of entrained bursts to the movement; (3) constant burst durations at low and moderate frequencies; (4) incomplete entrainment in response to high or low movement frequencies combined with a low amplitude; (5) entrainment was still present when mean position of movement was displaced laterally; (6) effects persisted when the tail region was devoid of skin and muscle tissue.

Entrainment effects may be explained by the activation of stretch receptors on either side of the vertebral column-spinal cord, exciting the presumed central pattern generators (CPGs) in the hemisegments ipsilateral to the stretch, while inhibiting the contralateral CPGs.
Effect of Maintained Hypoxic Exposure on the CrayfishOrconectes Rusticus: II. Modulation of Haemocyanin Oxygen Affinity
Authors: Wilkes P. R. H. , McMahon B. R.
Published: April 2021

Haemolymph Na+, Cl−, K+, Mg2+, Ca2+, Cu2+ and protein levels, in vivo postbranchial acid-base status (total CO4, pH and ), in vitro haemolymph buffer value, Bohr value and oxygen affinity were measured before and after a -week period in which control crayfish were maintained at normoxia and experimental crayfish were maintained at an ambient oxygen tension of 50–55 torr. Analysis of haemolymph Cu2+ and protein levels in control and experimental crayfish indicated no increase in haemocyanin and therefore oxygen carrying capacity of the haemolymph. Although the Bohr value was not significantly different between control and experimental crayfish, the haemocyanin oxygen affinity was elevated in the hypoxic crayfish by two mechanisms. The first was dependent upon the haemolymph H+ concentration, i.e. a Bohr shift resulting from a respiratory alkalosis. The second mechanism was independent of haemolymph H+ concentration in that at a given pH haemolymph from experimental crayfish had a significantly higher oxygen affinity. The decrease in P50 probably cannot be attributed to a specific cation effect.
Re-Examination of Presumed Feeding Motor Activity in the Isolated Nervous System of Pleurobranchaea
Authors: McClellan Andrew D.
Published: April 2021

In most isolated gastropod nervous systems, presumed feeding motor patterns are thought to be represented by the alternating motor activity in buccal roots, which underlies rhythmic radula movement. Since this movement accompanies several types of behaviour in the gastropod Pleurobranchaea (McClellan, 1979, 1980, 1982), the presumed feeding motor activity in the isolated nervous system of this animal was re-examined in more detail. Alternating buccal root activity was shown here to be associated with other types of behaviour besides feeding, and is, therefore, not sufficiently unique to serve as a ‘neural correlate’ for feeding in Pleurobranchaea and presumably other gastropods. Unlike the isolated nervous systems of most gastropods, which generate only one buccal rhythm, that of Pleurobranchaea generates two different buccal motor patterns which alternate: (1) a slow ‘primary’ rhythm whose behavioural identity is unclear, and (2) brief periods of a relatively fast rhythm which underlie bouts of vomiting. In general, a buccal rhythm generated by an isolated gastropod nervous system can only be assigned a function if there are features of the rhythm that are unique to only one of the several behavioural responses involving the buccal mass.
The Contribution of the Branchial Heart to the Accessory Branchial Pump in the Octopoda
Authors: Smith P. J. S.
Published: April 2021

Experimental and anatomical observations upon the Octopoda suggest that the branchial hearts are not the sole contributors to the increase in venous blood pressure between the anterior vena cava and the afferent branchial vessel.

The lateral venae cavae are proposed as an additional source of pressure generation, thus contributing to the octopod accessory branchial pump.
Bone Strength in Small Mammals and Bipedal Birds: Do Safety Factors Change With Body Size?
Authors: Biewener Andrew A.
Published: April 2021

Measurements of the cross-sectional geometry and length of bones from animals of different sizes suggest that peak locomotory stresses might be as much as nine times greater in the limb bones of a 300 kg horse than those of a 0·10 kg chipmunk. To determine if the bones of larger animals are stronger than those of small animals, the bending strength of whole bone specimens from the limbs of small mammals and bipedal birds was measured and compared with published data for large mammalian cortical bone (horses and bovids). No significant difference (P > 0·2) was found in the failure stress of bone over a range in size from 0·05–700 kg (233 ± 53 MN/m1 for small animals compared to 200 ± 28 MN/m2 for large animals). This finding suggests that either the limb bones of small animals are much stronger than they need to be, or that other aspects of locomotion (e.g. duty factor and limb orientation relative to the direction of the ground force) act to decrease peak locomotory stresses in larger animals.
A Dual Effect of Cobalt Ions on the Spontaneous Release of Transmitter At Insect Motor Nerve Terminals
Authors: Washio Hiroshi
Published: April 2021

The effect of extracellular cobalt on the frequency of miniature excitatory post-synaptic potentials (MEPSPs) was studied in cockroach leg muscle fibres that had been depolarized with 20·8 mm-K saline. Cobalt ions had a dual effect on the spontaneous release of transmitter, an inhibitory action being followed by an acceleratory. A reciprocal relationship between Ca2+ and Co2+ was found for both the inhibitory and acceleratory effects. The equilibrium dissociation constant for Co2+ as a competitive antagonist of spontaneous release ranged from 0·4 to 0·65 mm. It is concluded that Co2+ is much more potent than Mg2+ in suppressing spontaneous transmitter release at the insect neuromuscular junction. The antagonism by extracellular Co2+ appears to occur only at the external surface site on the terminal membrane.
The Distribution and Molecular Characteristics of the Tanning Hormone, Bursicon, in the Tobacco Hornworm Manduca Sexta
Authors: Taghert Paul H. , Truman James W.
Published: April 2021

The distribution and molecular properties of the tanning hormone bursicon were studied using an isolated wing biological assay. Wing cuticle tanning activity was measured in saline homogenates of the central nervous system and selected muscles. Activity was detected in all ganglia of the nervous system in both the prepupal and pharate adult developmental stages. In both stages, this activity was predominantly located in the abdominal portion of the nervous system. The titres in all ganglia, except the suboesophageal, increased during metamorphosis. Of the various non-neural tissues examined, only the closer muscle of the spiracle contained detectable levels of activity.

All activity in the nervous tissue was sensitive to proteolytic digestion; it could not be mimicked by any of the 17 putative transmitter and/or hormonal substances tested. Partial purification of the tanning activity indicated an apparent molecular weight of 20–30 K.

The partially purified material (from gel filtration) resembled the hormone bursicon in the following three ways : its titre in the tissue declined following normal bursicon release ; it could be recovered from the haemolymph during normal bursicon release; it could be released from isolated nervous tissue following high potassium stimulation in a calcium-dependent manner.

It was concluded that the hormone bursicon represents most if not all the tanning activity present in the central nervous system, that it is widely distributed in that tissue and that it is present as a peptide (or class of peptides) with homogeneous size and charge.
Thermal Acclimation in A Crustacean Neuromuscular System
Authors: Stephens Philip J. , Atwood Harold L.
Published: April 2021

Effects of temperature on the muscle fibre membrane and synapses of stretcher muscle preparations made from autotomized limbs of the Pacific shore crab (Pachygrapsus crassipes) were investigated. Acclimation of the crabs to different temperatures modified properties of both muscle fibre membrane and synapses. Increased temperature produced an increase in membrane potential of the muscle fibres. A semi-log plot of these data revealed two linear phases of the membrane potential-temperature relationship, with a change in slope near the acclimation temperature. Maximum values for excitatory junction potential (EJP) amplitude and time constant of EJP decay, and minimum values for facilitation were obtained at temperatures close to the acclimation temperature. It is suggested that the decline in EJP amplitude and time constant of decay produced by deviations in temperature from the acclimation temperature is compensated for by an increase in the amount of facilitation. In this way, maximum tension can be produced by the stretcher muscle in a range of at least 8 °C around the acclimation temperature.
Effects of Temperature on the Endogenous Activity and Synaptic Interactions of the Salivary Burster Neurones in the Terrestrial SlugLimax Maximus
Authors: Prior David J. , Grega Debra S.
Published: April 2021

The activity of the endogenously active salivary burster neurones (SBs) shows temperature acclimation and has characteristic cold and warm Blockade temperatures. Temperature acclimation affects the upper and lower limits of the temperature range over which SBs are active. The absolute range, in centigrade degrees, during warming, is unaffected by acclimation. Acclimatization of burster activity is a slow response to the mean ambient temperature. There is increased synchrony of activity between the right and left salivary bursters at low temperature which is correlated with an increased electrical coupling between the SBs and protractor motoneurones (B7s). There is a corresponding increase in the input resistance of B7 at low temperatures.
Progressive Processing of Ingested Water in the Gut of Sea-Water Teleosts
Authors: Kirsch R. , Meister M. F.
Published: April 2021

The European eel’s oesophagus, stomach and anterior and posterior intestine were perfused separately, in vivo. The oesophagus and anterior intestine play a major part in processing of ingested water. Serosal potential differences to mucosal measured in vivo were positive in all gut segments.

The Cl− concentrations of luminal contents in different parts of the gut were measured in nine species of sea-water teleosts. The progressive decrease in Cl− concentration resulted from local processing of the ingested sea water, and the beginnings of the oesophagus and of the intestine were the major processing sites.
Intracellular and extracellular acid-base status as a function of temperature in the freshwater channel catfish,Ictalurus punctatus1
Authors: Cameron James N. , Kormanik Gregg A.
Published: April 2021

The relationship between acid-base status and temperature was studied in the channel catfish, Ictalurus punctatus. The change in blood pH with temperature had a slope of – 0· 0132/°C and involved both a decrease in total CO2 at higher temperatures, and a significant rise in arterial The acid-base changes in the intracellular compartment were similar to those in the blood, except that for red and white muscle the slope of the change in pH with temperature had a slightly higher value (– 0·0185 and – 0·0147, respectively), and for heart muscle it had a smaller value (– 0·0117).

The net whole-body excretion of acid or base in response to temperature change was relatively small : 0·40 m-mole. kg-1 net OH- was excreted in response to an increase from 22 to 31 °C, and 0·31 m-mole. kg-1 net H+ was excreted in response to change from 25 to 15 °C. In both cases approximately half was excreted renally and half branchially.

Using information on the volumes and buffer capacities of the various body fluid compartments as well as the information above, the ratio of imidazole to phosphate intracellular buffers was calculated to be 5·1 to 1. The amount of intercompartmental (active) transfer required to make temperature adjustments is strongly dependent on the buffer ratio, and on the Without the observed changes in with temperature, the transfer requirement would have been 3 to 4 times larger.
Factors Regulating the Mechanical Properties of Holothurian Dermis
Authors: Motokawa Tatsuo
Published: April 2021

Tensile tests and creep tests were performed on the dermis of the sea cucumber Stichopus chloronotus (Brandt). Chemical stimulation of the dermis with coelomic fluid of the sea cucumber, or with artificial sea water containing a high concentration of potassium, increased both the elastic stiffness and the viscosity. Methanol extraction of the coelomic fluid revealed two factors: a methanol-soluble factor that stiffens the dermis, and a methanol-insoluble factor that softens it. These factors affected the mechanical properties of other echinoderm connective tissue (the catch apparatus of sea-urchin spine) in a similar way to the holothurian dermis.
Ventilatory Currents in the Mantle of Cephalopods
Authors: Wells M. J. , Wells J.
Published: April 2021

In Octopus and Sepia the inhalant water stream is sucked in to each side of the mantle cavity and passes into the centre of the corresponding gill. From here it runs counter-current to the blood vessels in the secondary gill lamellae and out into a common cavity created by expansion of the posterior part of the mantle. On exhalation the flow runs centrally, bypassing the gills and out through the funnel. This paper deals with the anatomy that ensures this pattern of flow, and with measurement of the , at various points in the mantle in normoxia and hypoxia. Utilization of oxygen from the respiratory stream is often better than 50% and the of the exhalant water is regularly lower than the likely arterial .
Abdominal Motoneurone Responses Elicited by Flexion of a Crayfish Leg
Authors: Page Charles H. , Jones Kenneth A.
Published: April 2021

Flexion of the mero-carpal joint of the leg of a partially dissected Pro-cambarus initiated an intersegmental reflex in the superficial extensor (SEMNs) and flexor (SFMNs) abdominal motoneurones. When flexion induced a full extension of the abdomen, as in intact crayfish, there was a discharge of the 5 SEMN exciters and the SFMN peripheral inhibitor throughout the extension. The extension antagonists -the SEMN peripheral inhibitor and the five SFMN exciters-discharged one or two spikes immediately following the stimulus, which suggests that more than one inter-ganglionic interneurone must be excited to activate the neuronal pathway which mediates the abdominal extension.
The Cockroach DCMD Neurone
Authors: Edwards Donald H.
Published: April 2021

The responses of the cockroach descending contralateral movement detector (DCMD) neurone to moving light stimuli were studied under both light- and dark-adapted conditions. With light-adaptation the response of the DCMD to two moving 2° (diam.) spots of white light is less than the response to a single spot when the two spots are separated by less than 10° (Fig. 2). With light-adaptation the response of the DCMD to a single moving light spot is a sigmoidally shaped function of the logarithm of the light intensity (Fig. 3 a). With dark-adaptation the response of a DCMD to a single moving light spot is a bell-shaped function of the logarithm of the stimulus intensity (Fig. 3b). The absolute intensity that evokes a threshold response is about one-and-a-half log units less in the dark-adapted eye than in the light-adapted eye. The decrease in the DCMD’s response that occurs when two stimuli are closer than 10°, and when a single bright stimulus is made brighter, indicates that lateral inhibition operates among the afferents to the DCMD. It is shown that this inhibition cannot be produced by a recurrent lateral inhibitory network. A model of the afferent path that contains a nonrecurrent lateral inhibitory network can account for the response/intensity plots of the DCMD recorded under both light-adapted and dark-adapted conditions. The threshold intensity of the DCMD is increased if a stationary pattern of light is present near the path of the moving spot stimulus. This is shown to be due to a peripheral tonic lateral inhibition that is distinct from the non-recurrent lateral inhibition described earlier. It is suggested that the peripheral lateral inhibition acts to adjust the threshold of afferents to local background light levels, while the proximal non-recurrent network acts to enhance the acuity of the eye to small objects in the visual field, and to filter out whole-field stimuli.
Alkyl-Fullerene Materials of Tunable Morphology and Function
Authors: Neal Edward A , Nakanishi Takashi
Published: April 2021

The self-assembly of molecules into complex superstructures underpins the functionality of many biological processes and physical materials. Many such structures stem from amphiphilic monomer units, with attractions and repulsions between their ends determining the structure and state of the assembled system under equilibrium, which affect its function.

The photophysical and electronic properties of fullerene (C60) have been extensively studied and proven useful in the fabrication of a variety of devices. The simple attachment of alkyl side chains can convert this highly crystalline solid into an alkyl-C60 hydrophobic amphiphile, in which alkyl-alkyl and C60-C60 interactions determine the state, phase, morphology, or architecture of the substance, while the optoelectronic properties of C60 are retained.

In this award article, lipid membranes, crystalline nanostructures, mesophases, and even room-temperature liquid alkyl fullerenes formed through this approach are described. In each case, the effects of chain selection and substitution on morphology and function are explained. The ways in which the inherent properties of C60 can be adapted for particular applications are detailed, such as in superhydrophobic surfaces and photoconductive devices. Thereafter, drawing on these advances, the application of the alkyl chain attachment approach to other functional π-conjugated cores is demonstrated using some examples of functional molecular liquids.
Kefir Is a Viable Exercise Recovery Beverage for Cancer Survivors Enrolled in a Structured Exercise Program
Authors: SMOAK PETER , HARMAN NICHOLAS , FLORES VICTORIA , KISIOLEK JACOB , PULLEN NICHOLAS A. , LISANO JONATHAN , HAYWARD REID , STEWART LAURA K.
Published: April 2021

Purpose

This study investigated the effects of 12 wk of postexercise kefir consumption in cancer survivors who have undergone chemotherapy and/or radiation therapy.

Methods

All participants were enrolled in a structured exercise training program and separated into kefir (KEF) or control (CON) treatment groups. KEF consumed 8 oz. of kefir after exercise sessions (3 d·wk−1) for 12 wk. Outcome measures included assessments for body size and composition, aerobic fitness and muscular strength, medical history, and psychological state at pre- and postintervention time points. Blood was collected and analyzed for C-reactive protein (CRP), interleukin 6 (IL-6), and lipopolysaccharide (LPS) concentrations, and LPS-stimulated whole blood IL-6 and tumor necrosis factor α production were obtained using enzyme-linked immunosorbent assays at both time points. Monocyte numbers and phenotype were obtained using flow cytometry.

Results

Participants (N = 24; 9 males and 15 females) were an average of 61 ± 9.9 yr old. Kefir consumption was associated with 6.3% (P = 0.034) improvements in lean body mass, as well as 51.4% (P = 0.046), 39.3% (P = 0.017), and 64.7% (P = 0.021) improvements in measures of depression, fatigue, and gastric distress, respectively. KEF also experienced a significant 35.4% (P = 0.01) reduction in circulating LPS along with an 18.0% increase (P < 0.001) in classical monocytes % and a 22.3% decrease (P = 0.04) in nonclassical monocytes %. There were no significant changes in any other variables.

Conclusion

Twelve weeks of kefir consumption improved lean body mass, depression, fatigue, gastric distress, and a biomarker of gut dysbiosis. Kefir improved overall and classical monocyte numbers. Kefir should be considered as a component of a postexercise dietary regimen for cancer survivors.
The The effect of Fasting during Ramadan on the Kidney functions of Stage III-IV Chronic Kidney Disease Patients
Authors: Karatas Ahmet , Canakci Ebru , Kasko Arici Yeliz , Kaya Mervegul , Sayim Beyza
Published: April 2021

Objectives: Examine the effect of fasting during Ramadan on kidney functions in patients with chronic kidney disease.

Methods: The study was conducted on 130 patients with stage III-IV chronic kidney disease (CKD), who were admitted to the Ordu University nephrology polyclinic during the month before Ramadan and one month after Ramadan in 2019. Blood samples were taken in the morning after 12 hours of fasting.

Results: There was a statistically significant difference between BUN in the fasting group before and after the month of Ramadan. The median BUN before Ramadan was 26.65 mg/dl, the median after Ramadan was 24.05 mg/dl (p=0.004).There was a statistically significant difference between the nonfasting groups before and after Ramadan with respect to creatinine level. Median creatinine before Ramadan was 1.69 mg/dl,and the median after Ramadan was 1.86 mg/dl (p <0.001).There was a statistically significant difference between the fasting groups before and after Ramadan with respect to creatinine levels. Fasting group ,the median before Ramadan was 1.5 mg/dl, and the median after Ramadan was 1.42 mg/dl (p = 0.038).The impact of independent variable of fasting, using linear regression was found to be statistically significant (ppost-<0.001). The eGFR was 14.826 points higher in those who fasted after Ramadan than in those who did not.

Conclusion: Fasting during the month of Ramadan does not deteriorate kidney functions and even leads to a moderate improvement in kidney functions. Taking these results into consideration, fasting may be advised for patients with stage III-IV CKD who want to fast and remain in stable condition.

doi: https://doi.org/10.12669/pjms.37.4.3661

How to cite this:Karatas A, Canakci E, Arici YK, Kaya M, Sayim B. The effect of Fasting during Ramadan on the Kidney functions of Stage III-IV Chronic Kidney Disease Patients. Pak J Med Sci. 2021;37(4):972-978. doi: https://doi.org/10.12669/pjms.37.4.3661

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Noninvasive exploration of Cardiac Autonomic Neuropathy by heart rate and blood pressure variability analysis in Type 2 Diabetic patients
Authors: Naz Tallat , Memon Noor un Nisa , Afzal Kamran , Shakir Ambreen
Published: April 2021

Objectives: To determine the prevalence of asymptomatic cardiac autonomic neuropathy and its association with risk factors among patients with Type-2 diabetes mellitus (T2DM)

Methods: The present case-control study was conducted at Department of Medicine, Civil Hospital, Dow University of Health Sciences (DUHS), Karachi, Pakistan during the period September` 2016 to May` 2017. After taking informed consent, subjects from both genders, 72 healthy controls and 72 clinically diagnosed T2DM diabetic patients, age between 30-65 years were selected by non-probability sampling technique. After taking medical history and demographics, Cardiac Autonomic Neuropathy (CAN) was identified by using Ewing`s cardiac autonomic reflex tests (CARTs) and association of risk factors was also investigated.

Results: Severe CAN was identified in 13.9% of T2DM patients while in none of the healthy controls. HR response to deep breathing test was most sensitive (sensitivity= 90%) among all tests. The most common symptoms were Numbness (75.9%) and constipation (69%), resting heart rate and diabetes duration was significantly associated with DCAN.

Conclusions: CAN was highly prevalent in diabetic population that may lead to nephropathy and retinopathy in future. It is highly recommended to use sensitive and simple CARTs in clinics for early detection and early treatment of CAN.

doi: https://doi.org/10.12669/pjms.37.4.3675

How to cite this:Naz T, Memon NN, Afzal K, Shakir A. Noninvasive exploration of Cardiac Autonomic Neuropathy by heart rate and blood pressure variability analysis in Type 2 Diabetic patients. Pak J Med Sci. 2021;37(4):1020-1024.  doi: https://doi.org/10.12669/pjms.37.4.3675

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.