bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphomonoesterase Content and Localization in the Meso-and Metanephros of the Chick Embryo
Authors: Junqueira L. C. U. 
Published: April 2021

ABSTRACT
Chemical determinations were made of the alkaline and acid phosphatase content of meso-and metanephros of chick embryos between 4 days of incubation and 6 days after hatching. Histochemical localization of alkaline phosphatase and of ribonucleaseremovable basiphilia was also studied in these organs.
A study of the data obtained suggest the following conclusions : The acid and alkaline phosphatase activity of the mesonephros increases from the 4th to the 16th day, decreasing from then onwards.The acid and alkaline phosphatase activity of the metanephros increases from the 11 th to the 16th day, decreasing slowly to the 20th day. A rapid rise is observed after hatching.The alkaline phosphatase activity that is diffusely located in the cells of recently formed secretory tubules of the meso-and metanephros polarizes to the brush border zone later on.Ribonuclease-removable basiphilia, abundant in the mesonephric tubules up to the 6th day of incubation, decreases from then onwards.The metanephric blastema and tubules present a high concentration of ribonuclease-removable basiphilia up to the 13th day. From then on its content decreases in the whole organ with the exception of certain groups of cells still in differentiation.
The possible correlation between these findings and meso-and metanephros differentiation and function is discussed.
Mounting Collodion Sections before Staining
Authors: Richardson K. C. 
Published: April 2021

ABSTRACT
In the standard textbooks on microscopical technique many ways are quoted for attaching collodion sections to slides before staining. With some of these methods the attachment is so precarious that extra care is needed during the manipulations of staining and dehydration : with others the section is covered with a film of collodion or stuck to a layer of gelatine. Such supporting films, however, often take up some of the stain. The method to be described is simple and reliable and can be applied to all types of collodion technique, ranging from thin sections cut in collodion-paraffin or low viscosity nitrocellulose, to the large, thick sections commonly cut from collodion blocks hardened by evaporation or chloroform and stored in alcohol. In each case it is possible to remove the collodion immediately after mounting so that the section becomes comparable with a routine paraffin section, and will withstand prolonged treatment even in hot solutions without becoming detached.
Observations concerning the Specificity of the Acid Haematein Test for Phospholipines
Authors: Casselman W. G. Bruce , George O. T. 
Published: April 2021

ABSTRACT
Studies with synthetic enantiomeric a-phosphatidic acids, a-phospholipines, and related compounds, and with highly purified, natural lipine fractions confirm that Baker’s ‘acid haematein test (controlled by the pyridine extraction test) is a method for the histochemical recognition not of lipine in general, but of phospholipine’. A true positive reaction is also given by certain phosphatidic acids.
Histochemical Distribution of 5-Nucleotidase in Snake Tissues: Presence of 5-Nucleotidase and Absence of Alkaline Phosphomonoesterase in Venom Glands of the Rattlesnake
Authors: Bragdon D. E. , Mcmanus J. F. A. 
Published: April 2021

ABSTRACT
Activity of the specific alkaline phosphatase, 5-nucleotidase, is intense in the epithelium and secretion of the rattlesnake venom gland. Non-specific alkaline phosphatase activity is lacking. Thyroid epithelium, the smooth muscle of great vessels, and (inconstantly) smooth muscle of abdominal hollow viscera show greater 5-nucleotidase than nonspecific activity. These findings confirm the specificity of 5-nucleotidase.
Cell Shrinkage caused by Fixatives and Paraffin-wax Embedding in Ordinary Cytological Preparations
Authors: Ross K. F. A. 
Published: April 2021

ABSTRACT
A series of measurements was made of the diameters of the cells and nuclei of the primary spermatocytes of the snail Helix aspersa in preparations made by embedding in paraffin wax after fixation in a number of different cytological fixatives. These were compared with similar measurements made on the living spermatocytes mounted in suitable saline solutions, and the shrinkage that the cells underwent as a result of fixation and embedding in each case was calculated from the medians of the size-distributions recorded.
The results showed that the amount of shrinkage varies to some extent according to the fixative employed—picric acid gave the greatest linear cell-shrinkage (about 40 per cent.) and Sanfelice’s fluid by far the least (about 13 per cent.); but with this one exception the differences in final cell-size were not very great, and represent a linear shrinkage to about 67 per cent, and a volume shrinkage to about 30 per cent, of the original dimensions of both cell and nucleus.
The Golgi Apparatus and Lipoidal Bodies in Exocrine and Endocrine Cells in the Pancreas of Man
Authors: Lacy Dennis 
Published: April 2021

ABSTRACT
The cells of the pancreas of a woman were studied by means of Aoyama’s and Baker’s methods with the following results:
A canal-like Golgi apparatus and lipoidal bodies are observed in both exocrine and endocrine cells. The size of the apparatus and the number of lipoidal bodies are in inverse ratio in both cell types.
These results do not support the theory that the Golgi apparatus as seen in fixed cells is the result of the metallic impregnation of lipoidal bodies.
Metachromatic Dye-Substrate Interactions
Authors: Sylvan Bengt 
Published: April 2021

ABSTRACT
From the interactions between azure A and various substrates with different physical and chemical characteristics, some suggestions are made as to the nature of the metachromatic colour reaction. The following essential factors are necessary for the appearance of metachromasia.
The orderly alignment of dye molecules is favoured if the molecules present hydrophobic and hydrophilic parts. The distribution of electro-negative surface charges of the substrate determines the alignment of dye molecules and the degree of metachromasia. A certain minimum intercharge distance (interplanar), possibly about 5 A, is a prerequisite for metachromasia. The degree of metachromasia increases when the intermolecular distance between adjacent dye molecules aggregated to the substrate surface becomes less than 5 A. The presence of water is essential for metachromatic interaction.
The observed spectral absorption shifts are explained by the assumption that new bonds appear between adjacent dye molecules. The necessary energy requirements are of the order of about 8 cal./mol. In the case of azure A, various types of intermolecular bonds are discussed: hydrogen bonds or perhaps hydrogen bonds plus oxygen-sulphur bridges. It seems very likely that water molecules may be intercalated between adjacent dye molecules as suggested by Scheibe and Sheppard.
Since the dye and many organic substrates form polydisperse colloidal solutions and since further the dye-substrate interactions often imply the appearance of micellar aggregates and precipitates in in vitro experiments, spectrophotometric data should be interpreted with great caution. Evidence is presented indicating that the heterogeneity of the sol systems in many instances renders spectrophotometry useless. The desired colour changes are instead conveniently registered by microscopy with transmitted light.
Available data indicate that the electro-negative surface charge density is the essential characteristic of the various substrates for the conditioning of metachromatic dye-substrate interaction.
The Value of ‘Spreading Factors’ in the Demonstration of Tissue Neural Elements
Authors: Weddell G. , Pallie W. 
Published: April 2021

ABSTRACT
A description is given of the value of ‘spreading factor’ (hyaluronidase) used in conjunction with various neurohistological methods for the display of tissue neural elements. It has been shown that after its use nerve fibres and their terminals in a variety of tissues, including the cornea, closely resemble those seen in fresh specimens of cornea under phase-contrast conditions. The specimens prepared after treatment with hyaluronidase are almost free from artifacts. The staining or impregnation process can be controlled with certainty and precision to produce evenly stained specimens in the tissues we have used. It is suggested that some tissues may need special treatment to obtain optimal results. The use of ‘spreading factor’ makes it possible to determine the cause of the artifacts commonly observed after employing standard neurohistological techniques. The rationale of using ‘spreading factor’ in conjunction with neurohistological techniques is discussed.
Relations between Metachronism and the direction of ciliary beat in metazoa
Authors: Knight-Jones E. W. 
Published: April 2021

ABSTRACT
In various ciliated epithelia one can distinguish either symplectic, antiplectic, dexio-plectic, or laeoplectic metachronal waves, according to whether the effective beat of their cilia is with, against, to the right of, or to the left of, the direction of movement of the waves. In a given epithelium the relation between the direction of the waves and the direction of beat is constant.
Symplectic waves are probably associated with the transport of large particles, or viscous masses of mucus; antiplectic and diaplectic waves are better suited for creating water currents. It is unusual to find both dexioplectic and laeoplectic waves in the same animal; indeed, it is the rule for only one of these two types of metachronism to occur throughout a given systematic group. Dexioplectic waves are found in Protochordata, primitive Spiralia, the velum of Eulamellibranchiata, Phoronidea, Brachiopoda, Bdelloidea, and Melicertida; laeoplectic waves are found in Chaetopterus, Mollusca generally, Bryozoa, and Ploima. The incidence of dexioplectic and laeoplectic meta-chronism is not influenced by morphological reversals of symmetry such as the situs inversus. The relation between the direction of beat and the direction of the waves is therefore probably determined by cytological or stereochemical factors, rather than by gross morphology.
Experiments on the Mechanism of Silver Staining: Part I. Impregnation
Authors: Peters A. 
Published: April 2021

ABSTRACT
In the impregnating stage of silver staining, there are essentially two different reactions taking place between the silver ions and the sections of fixed tissue. A sub-stantial part of the silver is combined with the tissue in the unreduced form, and a smaller part is reduced to produce silver nuclei which form centres on which the de-veloping agents can deposit additional silver derived from the combined (reducible) silver fraction.
A study of the effect of pH and time of impregnation, as well as of the specific blocking of chemically active protein end-groups upon the reducible silver fraction, suggests that this is chiefly combined with histidine and that it is not limited to the sites of the final differential staining. Except for the cell nuclei, the reducible silver shows a uniform distribution throughout the section; the amount taken up is in equilibrium with the silver ion concentration in the impregnating bath.
The fraction present as silver nuclei increases progressively with time, with in-creasing pH, and with the temperature of the impregnating bath. Silver ions appear to be converted to silver nuclei by a process of physical reduction, and once formed, the nuclei are quite stable.
Deposition of silver nuclei, necessary for differentiation of the stain, only occurs after impregnation between pH 7·5 and 9·0. In addition, it is only within this range that a sufficient amount of reducible silver is taken up to produce deep staining after development.
The Transition to Air Breathing in Fishes
Authors: Graham Jeffrey B. 
Published: April 2021

ABSTRACT
The armoured catfish, Ancistrus chagresi, is a facultative air breather and uses its stomach as an air-breathing organ (ABO). Comparisons of control fish and fish that had become acclimated to hypoxia and air breathing for 14–21 days were carried out to assess the effects of this treatment on bimodal (aerial and aquatic) gas exchange capacity. Hypoxia acclimation elicits physiological and biochemical changes that enable A. chagresi to increase O2 utilization both by its gills in hypoxic water and by its ABO. Compared with control fish, hypoxia-acclimated Ancistrus have a higher blood-O2 affinity and more haemoglobin (Hb) and can maintain a higher aquatic oxygen consumption rate in hypoxic water. They also have a 25 % larger ABO volume, are able to hold each air breath longer, and can reduce ABO O2 partial pressure to a lower level. In both groups, respiratory CO2-release occurs primarily through the gills. An air breath instantly causes tachycardia and a reduction in the frequency and amplitude of branchial ventilation. Their lower cardiac and gill ventilation rates in hypoxia and during air breathing suggest that hypoxia-acclimated fish are more adapted for hypoxia than are control fish. During the period an air breath is held in the ABO, hypoxia-acclimated fish exhibit more coordinated phase shifts in gill ventilation and cardiac rates. These may favour an initial phase of efficient aerial O2 uptake from the ABO and transport through the body followed by a period of aquatic CO2 release from the gills.
Prey Capture Hydrodynamics in Fishes: Experimental Tests of Two Models
Authors: Lauder George V. 
Published: April 2021

ABSTRACT
Three experimental modifications of the feeding mechanism in the bluegill sunfish (Lepomis macrochirus Rafinesque: Centrarchidae) were performed to distinguish between two alternative hydrodynamic models of the high-speed suction-feeding process in fishes. These two models make different predictions about the change in slope of the regression line representing the relationship between buccal and opercular cavity pressures, and the three experiments provide a critical test of the models. The results from all three tests unequivocally support (1) the concept of the gill bars as a resistant element within the mouth cavity functionally dividing it into buccal and opercular cavities, (2) the negligible role of lateral movement of the gill cover (operculum) in generating negative mouth cavity pressures, and (3) the large pressure differentials previously reported between the buccal and opercular cavities. Measured pressures conform neither in relative magnitude nor waveform with pressures predicted from theoretical mathematical models. Inertial effects and accelerational flows are key aspects of high-speed suction feeding.
Swimming and Diving in Tufted Ducks, Aythya Fuligula, with Particular Reference to Heart Rate and Gas Exchange
Authors: Woakes A. J. , Butler P. J. 
Published: April 2021

ABSTRACT
In six tufted ducks there was a linear relationship between heart rate and oxygen consumption when swimming at different velocities. Mean oxygen consumption at mean duration of voluntary dives was 3·5 times resting and not significantly different from that at maximum sustainable swimming speed. Contrary to an earlier report (Prange & Schmidt-Nielsen, 1970), leg beat frequency increased with increased swimming speed.
Although heart rate at mean dive duration was 51% higher than the resting value, it was a significant 59 beats min−1 lower than predicted from the heart rate/oxygen consumption relationship obtained during swimming. This relationship is, therefore, of no use for predicting oxygen consumption from heart rate during diving, nor incidentally during transient changes during air breathing.
It is concluded that during voluntary diving in tufted ducks there is a balance between the cardiovascular responses to forced submersion (bradycardia, selective vasoconstriction) and to exercise in air (tachycardia and vasodilatation in active muscles), with the bias towards the latter.
Fast Continuous Swimming of Saithe (Pollachius Virens): a Dynamic Analysis of Bending Moments and Muscle Power
Authors: Hess F. , Videler J. J. 
Published: April 2021

ABSTRACT
This paper deals with the hydrodynamics and internal dynamics of fish swimming. Our analysis starts from kinematic data obtained for fast swimming saithe, and treats the fish as a flexible elongated body. The distribution along the body of the lateral bending moment and the bending power generated inside the fish are computed as well as the power spent on the water. The computed thrust implies a drag coefficient (based on wetted surface area) of about 0·007, which is probably an over-estimate. Our major result is that the bending moment does not travel as a running wave from head to tail like the lateral body curvature does, but behaves as a standing wave. The left and right sides produce alternate contractions simultaneously over the whole body length. This finding is in agreement with myographic data from the literature.
The Kinematics of Swimming in Anuran Larvae
Authors: Wassersug Richard J. , Hoff Karin Von Seckendorf 
Published: April 2021

ABSTRACT
The kinematics of swimming in tadpoles from four species of anurans (Rana catesbeiana Shaw, Rana septentrionalis Baird, Rana clamitans Latreille and Bufo americanus Holbrook) was studied using computer-assisted analysis of high speed (⩾200 frames s− 1) ciné records.
Tadpoles exhibit the same positive, linear relationship between tail beat frequency and specific swimming speed commonly reported for sub-carangiform fishes. Tadpoles show an increase in the maximum amplitude of the tail beat with increasing swimming speed up to approximately 4 lengths s− 1. Above 4 lengths s− 1, amplitude approaches an asymptote at approximately 25% of length. Tadpoles with relatively longer tails have lower specific amplitudes. Froude efficiencies for tadpoles are similar to those reported for most subcarangiform fishes. Bufo larvae tend to have higher specific maximum amplitude, higher tail beat frequencies, lower propeller efficiencies (at least at intermediate speeds) and substantially less axial musculature than do comparable-sized Rana larvae. These differences may relate to the fact that Bufo larvae are noxious to many potential predators and consequently need not rely solely on locomotion for defence. Tadpoles exhibit larger amounts of lateral movement at the snout than do most adult fishes. The point of least lateral movement during swimming in tadpoles is at the level of the semi-circular canals, as assumed in models on the evolution of the vertebrate inner ear. Passive oscillation of anaesthetized and curarized tadpoles at the base of their tail produces normal kinematics in the rest of the tail. This supports the idea that muscular activity in the posterior, tapered portion of the tadpole tail does not serve a major role in thrust production during normal, straightforward swimming at constant velocity. The angle of incidence and lateral velocity of the tail tip as it crosses the path of motion are not consistent with theoretical predictions of how thrust should be generated. The same parameters evaluated at the high point of the tail fin (approximately midtail) suggest that that portion of the tail generates thrust most effectively. Ablation of the end of the tail in passively oscillated tadpoles confirms that the terminal portion of the tadpole tail serves to reduce excessive amplitude in the more anterior portion of the tail, where most thrust is generated. The posterior portion of the tail is important in reducing turbulence around a tadpole. It may also function to produce thrust during irregular, intricate movements, such as swimming backwards. Tadpoles are comparable to subcarangiform fishes of similar size in their maximum swimming speed and mechanical efficiency, despite the fact that they have much less axial musculature and lack the elaborate skeletal elements that stiffen the fins in fishes. The simple shape of the tadpole tail appears to allow these animals efficient locomotion over short distances and high manoeuvrability, while maintaining the potential for rapid morphological change at metamorphosis.
Electroneutral Na+-2 Cl−-Leucine Cotransport by Lobster Hepatopancreatic Brush-Border Membrane Vesicles
Authors: Ahearn Gregory A. , Clay Laurel P. 
Published: April 2021

ABSTRACT
Uptake of L-[3H]leucine by lobster hepatopancreatic brush-border membrane vesicles was stimulated by a transmembrane NaCl gradient (o&gt;i), but not by identical gradients of NaSCN or other Cl− salts (e.g. K+, Li+, NH4+, Cs+ or choline), suggesting that amino acid transfer depended upon both Na+ and Cl−. In NaCl medium at acidic pH, leucine uptake was largely electroneutral and unresponsive to a transmembrane potential generated by permeable anions; however, in Na+-free medium, amino acid transport was strongly electrogenic under the same conditions. Leucine influx occurred by a combination of two carrier processes at physiologically acidic pH. One exhibited an influx Kt of 0·59 mmol 1−1, a JM of 390pmol mg protein−1 s−1 and a cotransport stoichiometry of 1 Na+ : 2 Cl+: 1 leucine. This process was most strongly cis-inhibited by the nonpolar amino acids phenylalanine, methionine and isoleucine, and most weakly inhibited by the more polar species methylaminoisobutyric acid (MeAlB), hydroxyproline, glutamate and arginine. The second leucine carrier system showed a very low binding affinity and could not be distinguished from diffusion, was Na+-and Cl−-independent, and was cis-inhibited by more polar amino acids such as lysine, hydroxyproline, MeAIB, alanine and glutamate. These results suggest that brush-border leucine transport in lobster hepatopancreas at acidic pH may occur by a combination of a modified L-system, that includes ion cosubstrates, and either by a second undefined Na+-independent process with a broad structural specificity or by multiple Na+-independent processes.
The Effects of External Salinity on the Drinking Rates of the Larvae of Herring, Plaice and Cod
Authors: Tytler P. , Blaxter J. H. S. 
Published: April 2021

ABSTRACT
Drinking responses to salinity change in the larvae of herring (Clupea harengus L.), plaice (Pleuronectesplatessa L.) and cod (Gadus morhua L.) were measured from the time course of uptake of dextran labelled with tritium, following immersion in solutions of 32‰ and 16‰ sea water. The yolk sac and first feeding larval stages of all three species drink in both salinities. Furthermore, post-yolk sac stages appear to adjust their drinking rates to compensate for different salinities in a manner similar to that of the adults. Drinking rates in 32‰ sea water are approximately double those in 16‰. Mass-related drinking rates of larvae are higher than those in adults, but the differences do not match the differences in surface area to mass ratios, suggesting that larval skin is less permeable to water than is adult gill epithelium. Water absorption is indicated by the evidence of concentration of dextran in the gut. The estimates of drinking rates from tritiated dextran uptake are supported by epifluorescence microscopical measurements of the uptake of fluorescein isothiocyanate dextran.
Cardiac Response to Voluntary Diving in Tufted Ducklings (Aythya Fuligula)
Authors: Keijer E. , Butler P. J. , Woakes A. J. 
Published: April 2021

ABSTRACT
Heart rate was monitored in tufted ducklings during first-ever and subsequent voluntary whole-body dives. Although the cardiac response to first-ever dives varied between individuals, the average response to these dives, to the following 20 dives, and to dives of longer duration closely resembled the response seen in adult tufted ducks. These results indicate that the cardiac response to voluntary diving in the tufted duck does not result from habituation of the classical bradycardia seen during involuntary diving.