Freezing point and melting point of barnacle muscle fibers

1983 ◽  
Vol 61 (10) ◽  
pp. 1116-1121
Author(s):  
Jean-Pierre Caillé

The freezing point and the melting point of myoplasm were measured with two experimental models. In all samples, a supercooled stage was reached by lowering the temperature of the sample to approximately −7 °C, and the freezing of the sample was mechanically induced. The freezing process was associated with a phase transition in the interstices between the contractile filaments. In intact muscle fibers, the freezing point showed a structural component (0.43 °C), and the melting point indicated that the intracellular and the extracellular compartments are isotonic. When the sample of myoplasm, previously inserted in a cylindrical cavity was incubated in an electrolyte solution, the freezing point showed a structural component similar to that of the intact muscle fiber, but the melting point was lower than the freezing and the melting points of the embedding solution. This was interpreted as evidence that the counterions around the contractile filaments occupied a nonnegligible fraction of the intracellular compartment.

The object for which the present investigation was undertaken was to study the spontaneous crystallisation of mixtures of two substances which form mixed crystals and possess a minimum, or eutectic, freezing point. According to Cady, naphthalene and monochloracetic acid are such a pair of substances, and possess a minimum melting point of 53°·5 for the eutectic mixture of 29·4 per cent, naphthalene, 70·6 per cent, monochloracetic acid. We have attempted to verify Cady’s freezing and melting point curves, but, although our experiments confirm the former, we were quite unable to verify the latter. Pickering mentions four modifications of monochloracetic acid, and traces the freezing point curves for three of them. Our study of mixtures of monochloracetic acid and naphthalene has not given us the information we expected concerning the composition of the “mixed crystals” which separate spontaneously from a solution, but it has led to interesting results concerning the spontaneous crystallisation of the different modifications of a substance dissolved in another substance which is not polymorphous. The Different Modifications of Monochloracetic Acid and their Mutual Transformations . Microscopic examination of crystals of monochloracetic acid obtained from fusion or solution show clearly that three different modifications α, β , and γ of the acid exist. These modifications have melting points 61˚˙5, 55°, and 50°; they are formed on the microscope slide under different circumstances, each modification yielding rhombs quite distinct from those of the two other modifications. If fused monochloracetic acid be cooled suddenly it crystallises as the γ -modification in rhombs having a plane angle of about 59°. If these rhombs be touched they at once transform into the β -modification and give rhombs having a plane angle of about 72°; or occasionally the γ -rhombs are transformed at once into the stable a-modification of the acid, which exists as broad needles having an acute angle of 43˚. The transformation from γ to α takes place much more rapidly than the transformation from γ to β . Similarly, if rhombs of β are formed on a microscope slide they may be at once transformed into the α -modification by inoculating with a fragment of α . Each transformation is accompanied by a rise of temperature. A remarkable feature of the change is that the more stable modification crystallises with sharp edges in the solid mass of the less stable substance, as though it were growing in a liquid.


1979 ◽  
Vol 73 (3) ◽  
pp. 343-368 ◽  
Author(s):  
J M Russell ◽  
M S Brodwick

Unidirectional chloride-36 fluxes were measured in internally dialyzed barnacle giant muscle fibers. About 50--60% of the Cl efflux was irreversibly blocked by the amino-group reactive agent, 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid (SITS), when it was applied either intra- or extracellularly. Similarly, Cl influx was also blocked by SITS. No significant effect on [Cl]i of SITS was noted in intact muscle fibers. However, the rate of net Cl efflux from muscle fibers which were Cl-loaded by overnight storage at 6 degrees C could be slowed by SITS treatment. Two classes of anions were defined based upon their effects on Cl efflux. Methanesulfonate and nitrate inhibited Cl efflux either when they replaced external chloride or when they were added to a constant external chloride concentration. The other group of anions (propionate, formate) stimulated both Cl efflux and influx and such stimulation could be blocked by SITS. Propionate influx was not nearly as large as the stimulated Cl efflux and was unaffected by SITS. Neither the effects of SITS nor those of the anion substitutes could be simply accounted for by changes in the membrane resting potential or conductance. These results suggest a mediated transport system for chloride across the barnacle sarcolemma.


The death of Mr. C. T. Heycook, which took place oil June 3, removes from among us one who has gained the affection of generations of Cambridge men and who was a pioneer in an important branch of inorganic chemistry. Heycock was the younger son of Frederick Heycock, of Braunston, Oakham, and was born on August 21, 1858; he received his early education at the Grammar Schools of Bedford and Oakham, and entered King's College, Cam-bridge, as an Exhibitioner in 1877, taking the Natural Sciences Tripos in 1880. For many years he taught Chemistry, Physics and Mineralogy for the Cambridge examinations and in 1895 he was elected to a Fellowship at King’s College, becoming a College lecturer and Natural Sciences Tutor in the following year, lie was elected a Fellow of the Royal Society in 1895 and was awarded the Davy Medal in 1920 for his work on alloys. His original work on the metals attracted the attention of the Goldsmiths Company who endowed a Readership in Metallurgy at Cambridge; he was appointed to this office in 1908 and held it until his retirement in 1928. He was admitted to the Livery of the Gold-smiths Company in 1909 and to the Court in 1913; he acted as Prime Warden during the year 1922-1923 and took a been interest in the work of the Company’s Assay Office. Notwithstanding the exacting character of his work as a Cambridge coach, Heycock joined with his lifelong friend, F. H. Neville, F.R.S., in a comprehensive study of the metals and their alloys; this partnership, which was only dissolved by the death of Neville in 1915, led to a remarkable series of papers in which novel directions of investigation were mapped out and developed. Before entering upon this joint work, Heycock had had some experience as an investigator; in 1876 he published a not on the spectrum of indium in conjunction with Mr. A. W. Clayden, M. A., and in 1882 he contributed a paper on the atomic weight of rubidium at the British Association meeting. Heycock and Neville’s first joint paper was published in 1884 and described a redetermination of the molecular weight of ozone by the diffusion method. The first of the series of papers on the metals was published in 1889 and dealt with the depression of the freezing points of metals brought about by others dissolved therein; in this, and later papers, it was shown that the addition of small amounts of a second metal depresses the freezing point of the first to an extent (1) directly proportionate to the weight, of metal added, and (2) in rough inverse proportion to the atomic or molecular weight of the added metal. Raoult’s law for ordinary solutions was thus extended to alloys and a method indicated for calculating the latent heat of fusion of a metal by the application to the freezing point depressions of the now well-known van't Hoff equation. At the outset mercury thermometers were used in the temperature measurements and only alloys of low melting points could be studied: the introduction by H. L. Callendar of the platinum resistance pyrometer made it possible to extend the scope of the investigation to metals of high melting point. At that time the melting points of silver, gold and copper were not known with any degree of accuracy, partly because of the difficulty of making the physical measurements, partly because the necessity for using metals of high chemical purity and for protecting them from contamination during melting had not been recognised. A number of fixed points on the platinum resistance pyrometer had to be established before the study of alloys of high melting points was undertaken; these fixed points were determined with the aid of Dr. E. H. Griffiths, F. R. S., and with such accuracy that the results obtained by their use have not since been seriously affected. Thus, Heycock and Neville determined the melting point of Levol’s alloy as 778.7° C. and used this constant as a secondary fixed point; a very recent determination by the Washington Bureau of Standards gives the melting point as 779.4°.


2004 ◽  
Vol 52 (4) ◽  
pp. 479-487 ◽  
Author(s):  
Cs. Pribenszky ◽  
M. Molnár ◽  
S. Cseh ◽  
L. Solti

Cryoinjuries are almost inevitable during the freezing of embryos. The present study examines the possibility of using high hydrostatic pressure to reduce substantially the freezing point of the embryo-holding solution, in order to preserve embryos at subzero temperatures, thus avoiding all the disadvantages of freezing. The pressure of 210 MPa lowers the phase transition temperature of water to -21°C. According to the results of this study, embryos can survive in high hydrostatic pressure environment at room temperature; the time embryos spend under pressure without significant loss in their survival could be lengthened by gradual decompression. Pressurisation at 0°C significantly reduced the survival capacity of the embryos; gradual decompression had no beneficial effect on survival at that stage. Based on the findings, the use of the phenomena is not applicable in this form, since pressure and low temperature together proved to be lethal to the embryos in these experiments. The application of hydrostatic pressure in embryo cryopreservation requires more detailed research, although the experience gained in this study can be applied usefully in different circumstances.


2008 ◽  
Vol 580-582 ◽  
pp. 319-322 ◽  
Author(s):  
Manabu Tanaka ◽  
Kentaro Yamamoto ◽  
Tashiro Shinichi ◽  
John J. Lowke

Study of current attachment at thermionic cathode for TIG arc at atmospheric pressure is attempted from numerical calculations of arc-electrodes unified model. The calculations show that the maximum temperature of arc plasma close to the cathode tip for W-2% ThO2 reaches 19,000 K and it is the highest value in comparison with the other temperatures for W-2% La2O3 and W-2% CeO2, because the current attachment at the cathode tip is constricted by a centralized limitation of liquid area of ThO2 due to its higher melting point. The calculations also show that, in cases of W- 2% La2O3 and W-2% CeO2, the liquid areas of La2O3 and Ce2O3 are widely expanded at the cathode tip due to their lower melting points and then produce uniform current attachments at the cathode. It is concluded that the current attachment at thermionic cathode is strongly dependent on work function, melting point and Richardson constant of emitter materials.


1976 ◽  
Vol 30 (1) ◽  
pp. 197-212
Author(s):  
Daniel F. Wolff ◽  
Osvaldo A. Alvarez ◽  
Fernando F. Vargas

1998 ◽  
Vol 78 (2) ◽  
pp. 359-391 ◽  
Author(s):  
BARRY M. MILLMAN

Millman, Barry M. The Filament Lattice of Striated Muscle. Physiol. Rev. 78: 359–391, 1998. — The filament lattice of striated muscle is an overlapping hexagonal array of thick and thin filaments within which muscle contraction takes place. Its structure can be studied by electron microscopy or X-ray diffraction. With the latter technique, structural changes can be monitored during contraction and other physiological conditions. The lattice of intact muscle fibers can change size through osmotic swelling or shrinking or by changing the sarcomere length of the muscle. Similarly, muscle fibers that have been chemically or mechanically skinned can be compressed with bathing solutions containing very large inert polymeric molecules. The effects of lattice change on muscle contraction in vertebrate skeletal and cardiac muscle and in invertebrate striated muscle are reviewed. The force developed, the speed of shortening, and stiffness are compared with structural changes occurring within the lattice. Radial forces between the filaments in the lattice, which can include electrostatic, Van der Waals, entropic, structural, and cross bridge, are assessed for their contributions to lattice stability and to the contraction process.


2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Man Huang ◽  
Bin Tang ◽  
Jianliang Jiang ◽  
Renqiu Guan ◽  
Huajun Wang

The freeze-thaw duration is one of the important factors affecting the change of rock properties. However, this factor has not formed a unified standard in the freeze-thaw cycle test. This study uses saturated tuff samples taken from eastern Zhejiang, China, as research objects to explore the change law of the time required for the rock to reach a full freeze-thaw cycle. Measured results show that the total duration of the freeze-thaw cycle presents an increasing power function with the increase in the number of freeze-thaw cycles. The freezing process is divided into three phases: initial freezing, water-ice phase transition, and deep freezing. The melting process is also divided into three phases: initial melting, ice-water phase transition, and deep melting. The time required for the ice-water phase change stage of the melting process does not change with the increase in the number of freeze-thaw cycles, while the other stages increase as a power function. The proportion of duration of each stage in the freezing process does not change with the increase in the number of cycles. By contrast, the duration proportion of the initial melting phase in the melting process decreases, and the deep melting phase increases. Experimental results of the freeze-thaw cycles of tuff demonstrate that the freeze-thaw duration of the freeze-thaw cycles within 40 times can be set to 9 h. The freezing and melting processes are 6 and 3 h, respectively.


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