Changes In Physical State Research Articles

The effect of synchronization on the modal selection in classical cepheids

The coupled self-exciting oscillator model is investigated in the non-resonant case and applied to classical cepheids. The modal selection in these models is explained as the result of the synchronization caused by the mutual interaction between different modes. By using linear adiabatic coupling coefficients, it is shown that the fundamental mode suppresses the first overtone mode marginally in short-period classical cepheids. The double periodicity of several cepheids is expected as the result of a small change of physical state in the outer envelopes of these stars.

Influence of membrane fluidity changes upon the imprinting of polypeptide hormones in Tetrahymena

1. 1. Hormonal imprinting is a physiological phenomenon, in which after the first encounter the receptorial and functional responses of a cell change for future occasions. 2. 2. The present experiments demonstrate (using Tetrahymena as a model cell) that the imprinting is very sensitive to the changes in membrane physical state. 3. 3. Cultivation of Tetrahymena cells in 28 or 15°C or in ergosterol-supplemented media caused only quantitative differences in the imprinting; however, the process of cooling (shift-down) or reheating (shift-up) resulted in a false reaction. 4. 4. The combined treatment by ergosterol and cooling completely abolished the imprinting. 5. 5. These results indicate that hormonal imprinting is a membrane-dependent process.

Mood, sexuality, hormones and the menstrual cycle. I. Changes in mood and physical state: description of subjects and method.

Mood and physical symptoms through the menstrual cycle were investigated in 55 women with normal ovulatory cycles. One-third had attended a clinic with severe premenstrual syndrome (clinic PMS group); the remainder were volunteers either with a history of PMS (non-clinic PMS group) or without (no PMS group). Each cycle was divided into six hormonally distinct phases on the basis of repeated hormone measurement. Self-ratings of "well-being" reached their maximum in the late follicular phase, declining throughout the luteal half of the cycle. This pattern was pronounced and statistically significant in the "clinic" and "nonclinic PMS" groups. In all three groups, "physical distress" increased during the second half of the cycle to reach a maximum in the late luteal phase. A clear temporal relationship was therefore demonstrated between mood, physical state, and hormonal phases of the cycle. It remains uncertain whether changes in the "clinic" group were extreme forms of a normal pattern or were qualitatively different.

Mg2+-mediated change in lipid fluidity enhances the reconstituted H+-ATPase activity.

The results by using ANS fluorescent probe and spin labels 5-NS show that the fluidity of L. (H+-ATPase) +Mg2+ (H+-ATPase from pig heart mitochondria reconstituted in the presence of Mg2+) is less than that of L. (H+-ATPase) -Mg2+ (proteoliposome reconstituted in the absence of Mg2+). But no significant difference in fluidity has been observed when both reconstituted systems were monitored by using spin labels 12-NS and 16-NS. This indicates that Mg2+ may cause changes in fluidity of the lipid molecules near the surfaces of the bilayers, but does not affect significantly the fluidity of the deeper layer of the reconstituted system. It is tentatively supposed that in the presence of Mg2+, enhancement of activities of reconstituted H+-ATPase may be due to the Mg2+-mediated change in physical state of the lipids in the more superficial region of lipid bilayers so as to ensure a suitable conformation of ATPase complex, thereby possessing higher activity.

Changes of membrane fluidity in erythrocytes of lead-exposed workers.

We have studied the effect of lead on the fluidity of erythrocyte membrane to clarify if lead can interact in vivo with biological membranes. Erythrocyte membranes were chosen in our study because a decrease of red cell osmotic fragility is also evident in the absence of laboratory and clinical signs of anaemia. The study was undertaken using the Electron Spin Resonance technique with two spin labels 5-doxyl stearate and 16-doxyl-stearate, which probe the physical state of the polar surface and the inner core of the membrane respectively. Red blood cells and erythrocyte ghosts were prepared from the blood of workers occupationally exposed to lead and from healthy controls. The determinations of Pb blood, Pb urine, urine coproporphyrin and delta-aminolevulinic acid showed an increased internal dose of lead, but the ordinary metabolic and haematological parameters were in the normal range. Our results show that in lead workers there is a change in chemical physical state both in erythrocytes and erythrocyte ghosts consistent with a decrease of membrane fluidity, which is evident in the surface as well as in the inner core of the membrane. The degree of membrane fluidity modification does not appear correlated with blood lead level. Changes in the membrane structural organization could be the molecular basis of some pathological alterations induced by lead.

Rapid-solidification phenomena

AbstractA series of alloy powders has been compacted using the dynamic powder compaction process and the regions of rapid melting and solidification formed studied in detail. Technologically, such regions are of importance because they represent the bond regions between particles where microstructural transformations are most likely to occur. In the present context these regions are important because they represent microsamples which have suffered extreme, but reasonably well defined, changes of physical state and, most notably, have solidified under extremely high and deducible cooling rates. The microstructures found within these microsamples have been examined and the relevance of the commonly used relationships between microstructure size and cooling rate discussed.

Changes in the fatty acid composition of the gill phospholipids in Gammarus duebeni with degree of gill contamination

Abstract The fatty acid composition of the gill lipids from Gammarus duebeni have been compared in relation to the degree of contamination of the gills by lipophilic materials. The results indicate that at higher levels of gill contamination a greater proportion of polyunsaturated 20:5 fatty acid occurs in the gill phospholipids. We suggest this may be a response to a change in the physical state of the gill membranes resulting from the contamination.

Escherichia coli B membrane stability related to cell growth phase : Measurement of temperature dependent physical state change of the membrane over a wide range

Escherichia coli B cytoplasmic and outer membrane from cells in different growth phases showed different chemical compositions. In freezing, logarithmic phase cells showed a marked permeability increase in the outer as well as the cytoplasmic membrane. Whereas, in the stationary phase cells no such change in membrane permeability was observed. Cooling of phospholipids and lipopolysaccharides with trans-parinaric acid showed a distinct fluorescence increase from room temperature to far below 0°C. In the outer membrane the fluorescence similar to that of lipopolysaccharides was shown. The outer membranes of cells in different growth phases showed similar temperature-dependent fluorescence changes. The cytoplasmic membrane exhibited a temperature-dependent fluorescence similar to that of the phospholipids. The onset temperature of the increase in fluorescence differed with the cells at different growth phases. The presence of EDTA and MgCl 2 modified the fluorescence changes in the membranes from cells in logarithmic phase. Whereas, in the membranes from cells in stationary phase no such effect was observed. These results suggest that the organizational stability of the membranes from cells in stationary phase is a fundamental basis of the membrane's resistance to the freezing damage.

Membrane fluidity and enzyme activities in brush border and basolateral membranes of the dog kidney.

The physical state of membrane lipids and relationships with the activity of Na+-K+-ATPase and alkaline phosphatase were studied in basolateral and brush border membranes of the dog kidney. Fluorescence polarization and electron spin resonance experiments demonstrate that basolateral membranes are much more fluid than brush border membranes. This can be accounted for by a difference in fluidity of the lipid part of the membranes. Broad (43-17 degrees C) thermotropic transitions are observed in liposomes made from total lipid extracts of brush border and basolateral membranes. Fluorescence data strongly suggest that thermotropic transitions also occur in intact membranes and that a change in membrane physical state may take place around the physiological temperature. A nonlinear Arrhenius plot for the Na+-K+-ATPase activity in basolateral membranes (breakpoint 21 degrees C) provides additional support for the existence of a lipid liquid leads to gel transition in antiluminal plasma membranes. A break in the Arrhenius plot of alkaline phosphatase activity is also observed but at a temperature significantly higher (26 degrees C) than that of the end of the thermotropic transition. "Room temperature" appears as a critical zone for lipid physical state and activities of both enzymes.

Permeability of thermally damaged skin V: Permeability over the course of maturation of a deep partial-thickness wound

The permeability of eschar is an important factor governing rational approaches to topical control of burn wound sepsis. Previous work has shown the burn wound to have a highly variable permeability immediately after burning depending on the manner of burning. But the burn is also a dynamic wound and its physical state changes during the process of maturation. The present studies are an early attempt to characterize wound permeability as a function of maturation. Hairless mice were burned dorsally for 15 seconds on a metal surface maintained at 80°C. The time and temperature conditions were chosen to effect a deep partial-thickness to full-thickness injury on the animal. Mice were sacrificed daily post burn over a 2-week period and the permeabilities of 3H-methanol and 14C-butanol through the excised eschar were measured. The eschar permeability coefficients were directly compared to permeability coefficients for the same compounds found with abdominal skin sections taken concurrently from each animal. It was observed that the branding initially caused a 50 per cent increase in the permeability of methanol and a 300–400 per cent increase in the permeability of butanol. These factors held over the first 4 to 5 days of maturation. Thereafter permeabilities tended to increase, gradually at first, but accelerating to a maximum which was observed at approximately 10 days. At the maximum, methanol's permeability was 20 times and butanol's 12 times their normal values. For both compounds permeability of eschar decreased past the maximum until termination of the studies at 14 days.

Exocytosis in mammalian cells. VI. Temperature dependence of pancreatic exocrine secretion.

The effects of temperature on amylase secretion in vitro have been measured under stimulated and nonstimulated conditions. In both cases a very rapid decrease of secretory rate was observed between 37 and 25 degrees C (60-70%). The decrease is less pronounced between 25 an 15 degrees C. Between 15 and 13 degrees C a drop of secretory activity (10%) was observed under stimulation whereas an increase was measured in absence of stimulus. At lower temperatures the rate of secretion falls again abruptly. These results show that the secretory pattern of amylase from pancreas in vitro as a function of temperature is very different under stimulated and nonstimulated conditions. We suggest that the abrupt change of secretory activity between 15 and 13 degrees C could correspond to a change of physical state of the membranes involved in the exocytosis process.

Estimate and prediction of high-head dam stability

The problems associated with dam construction on hard and soft rocks in tectonically complex regions are reviewed. An additional factor in such areas is the incidence of seismic activity. Characteristics of the foundation rocks that have to be taken into account are: rock type; heterogeneity resulting from interstratification and lateral facies changes; changes in physical state brought about by weathering and hydrothermal alteration; large fault structures breaking the foundation rocks into discrete units; overstressed state of rocks and local stress concentrations; deconsolidation due to load removal on erosion and excavation.

Response to sexual films as a function of anxiety level.

72 subjects between the ages of 18 and 30 yr. were shown 2 sexually explicit films. 12 males and 12 females were classified as high, medium, and low in anxiety according to their scores on the Taylor Manifest Anxiety Scale. Multiple analysis of variance showed no significant differences in the sexual stimulation, thought change, or ratings of change in physical state for subjects' level of anxiety or sex. This was true for films showing one and two couples. These findings do not support an inverse relationship between anxiety and favorable response to sexually explicit films. 95% of the subjects reported some degree of sexual arousal to each film. A significant number of subjects (a) reported an increase in the pleasantness of physical state and thoughts for both films and (b) preferred the film they found to be more sexually stimulating. The positive reaction to the films provides a basis for their possible clinical use.

Effects of low temperature and lipid modification on the proliferation of cultured mammalian cells

The effects of temperature on cell proliferation have been determined for two mouse lines: LM cells, a spontaneously transformed line, and R1 cells, a variant line which displays a less transformed phenotype and which was derived from LM cells by treatment with concanavalin A. Low temperature has a selective effect on the extent of proliferation of LM cells. At 28 °C, LM cells grow to only one-fourth the density which they achieve at 36 °C, whereas R1 cells grow to approximately the same maximal density at both these temperatures. Shifting the growth temperature to 36 °C results in further proliferation of LM cells grown to maximal density at 28 °C. Shifting the temperature of growth from 36 to 28 °C arrests the proliferation of only those LM cell cultures that have already attained the highest density which can be achieved when LM cells are grown entirely at 28 °C. The influence of exogenously incorporated fatty acids on proliferation of LM cells has been determined at different temperatures. At 36 °C, a temperature near the physiological range, none of the fatty acid supplements caused increases in maximal growth density. Most fatty acid supplements caused decreases, but there was no correlation between the fatty acids which caused a decreased extent of proliferation at 36 °C and any change in lipid physical state which these fatty acids would be likely to produce. At 28 °C, there is a marked decrease in the maximal density which LM cells achieve. This phenomenon is reversed by fatty acid supplements (oleic and linolenic acids) which contain cis-olefinic bonds and which decrease the critical temperatures for lectin binding and lectin-mediated agglutination phenomena. Fatty acid supplements which increase the critical temperatures for these phenomena, nonadecanoic acid and elaidic acids, have little effect or are growth inhibitory at 28 °C.

The effect of dissolved organic matter in sea water on the uptake of mixed individual hydrocarbons and number 2 fuel oil by a marine filter-feeding bivalve ( Mercenaria mercenaria)

Laboratory studies, using the marine bivalve Mercenaria mercenaria, were performed to examine the role that naturally occurring surfactant dissolved organic matter (DOM) plays in mediating the process of hydrocarbon uptake. The uptake of a simple hydrocarbon mixture consisting of an n-alkane, hexadecane and an aromatic hydrocarbon, phenanthrene was studied as was the uptake of Number 2 fuel oil. Removal of DOM from the seawater uptake media, by activated charcoal, results in: (1) a statistically significant increase in the uptake of hexadecane; (2) no change in the amount of phenanthrene taken up; and (3) a sevenfold increase in the quantity of No. 2 fuel oil taken up by the clam. The uptake of the ‘saturated’ fraction of the fuel oil increased 17 times when DOM was removed and the ‘aromatic’ fraction increased five times. The findings indicate that solubilization of saturated hydrocarbons by the DOM results in their being taken up less readily by the filter-feeding bivalve. When this DOM is removed, these hydrocarbons are retained more readily by the animal's gill due to changes in the hydrocarbons' physical state in seawater. The increase in the uptake of the ‘aromatic’ fraction of fuel oil in the absence of DOM may reflect a co-solubilization of aromatic and saturated hydrocarbon components.

Multiple thermal discontinuities in glucose-6-phosphatase activity

The temperature dependence of glucose-6-phosphatase ( d-glucose-6-phosphate phosphohydrolase EC 3.1.3.9) was studied in rat liver and kidney microsomal fractions. Arrhenius plots were non-linear and showed four distinct discontinuities in enzyme activity over the temperature range 2–41°C. The discontinuities occurred at approx. 39, 30, 20 and 12°C in the liver and were similar to this in the kidney. Changes in the energy of activation for the enzyme were noted at approx. 20°C in both tissues. The multiple discontinuities in glucose-6-phosphatase activity are viewed as a reflection of complex reorganization and/or change in physical state of the membrane components, primarily lipid.

Changes in composition, biosynthesis, and physical state of membrane lipids occurring upon aging of Mycoplasma hominis cultures

During the progression of Mycoplasma hominis cultures from the early logarithmic phase to the stationary phase of growth, the total phospholipid content of the cell membranes decreased. Measurement of the amount of the various phospholipids during the growth cycle showed that a decrease in the phosphatidylglycerol (PG) content, accompanied by an increase in the phosphatidic acid content, occurred upon aging of the culture. Pulse labeling experiments revealed that the PG, once formed, is relatively stable, undergoing no detectable turnover in growing cultures of M. hominis. No changes in the fatty acid composition of the membrane phospholipids were observed on aging of the culture, with palmitic acid predominating throughout the growth cycle. The preferential incorporation of palmitate into the phospholipid fraction is apparently caused by the higher activity of the membrane-bound acyl-coenzyme A (CoA):alpha-glycerophosphate transacylase with palmityl-CoA rather than with oleyl-CoA as substrate. The activity of the soluble acyl-CoA synthetase was the same whether palmitate or oleate served as substate. M. hominis membrane preparations contained a PG-synthetase system catalyzing the incorporation of L-alpha-glycerol-3-phosphate into PG. The activity of the PG synthetase system was markedly dependent on the age of the culture, being highest in cells from the early exponential phase of growth while declining sharply thereafter, and thus probably responsible, in part, for the decrease in PG content upon aging of the cells. Electron paramagnetic resonance spectra of a spin-labeled fatty acid incorporated in M. hominis membranes revealed a marked decrease in the freedom of motion of the spin label on aging of the culture. It is proposed that this decrease is due primarily to the decrease in the lipid-to-protein ratio of the membranes and has a marked effect on the activity of membrane-associated enzymes and transport systems.

Spreading of solid glycerides and phospholipids at the air—water interface

The equilibrium spreading pressures ( π e ) of a series of glycerides and phospholipids have been determined at various temperatures. Pure mono, di- and triglycerides and phosphatidylethanolamines can spread spontaneously from the crystal to form monomolecular films at the air—water interface, whereas phosphatidylcholines (lecithins) only spread from the liquid-crystal (i.e., at temperatures above the crystal or gel to liquid crystal transition temperature, T c ). Film pressures of up to 50 m N m −1 can be attained. Glycerides and phosphatidylcholines form liquid expanded monolayers in equilibrium with the bulk lipid while phosphatidylethanolamines can form both condensed and liquid expanded films. Liquid expanded monolayers are stable with respect to the bulk, lipid phase when π< π e ; compression of such monolayers to pressures π> π e leads to collapse and formation of bulk, lipid phase without significant overcompression. Condensed monolayers of phosphatidylcholine are metastable ( π e = 0 when T < T c ) and significant overcompression is observed before collapse to the gel or the monohydrate occurs. The equilibrium spreading pressures increase linearly with temperature until changes in physical state of the bulk lipid occur. On fusion or transition to a liquid crystalline state, the temperature coefficient of the equilibrium spreading pressure changes sign. The enthalpies and entropies of spreading are used to gain information on the structure of the lipid monolayers. The entropy of spreading and thus the order in the resulting monolayer is about midway between that of the crystal and the melt, depending on whether the compound spreads to a condensed or liquid expanded monolayer.

The physical state dependence of carboxypeptidase Aalpha and Agamma kinetics.

Spectrochemical probes have demonstrated that the conformations of carboxypeptidase A (EC 3.4.12.2) differ in solution and in the crystalline state. Detailed kinetic studies of carboxypeptidase A(alpha) and A(gamma) crystals and solutions now show that the physical state of the enzyme is also a critical parameter that affects the function of the A(alpha) and A(gamma) enzymes in the same manner. The kinetic profiles and the corresponding kinetic constants of substrate hydrolysis are, therefore, important functional indices of the known conformational differences of the enzyme in these two physical states. The complex kinetic behavior of this enzyme, however, precludes meaningful comparisons of activity measurements for crystals and solutions obtained at only one substrate concentration. Underlying differences in varying substrate-inhibiting or -activating binding modes can result in either high or low activity ratios, concealing the true, functional consequences of the change in physical state. Thus, for all substrates examined, crystallization of the enzyme markedly reduces catalytic efficiency, k(cat), from 20- to 1000-fold. Equally as important, the substrate inhibition, apparent in solution for some di- and depsipeptides, is abolished with crystals, while for longer substrates the normal solution kinetics may acquire activation with the crystals. Hypothetical modes of substrate-enzyme interaction, generated by superimposing substrate models on the crystal structure of carboxypeptidase to simulate kinetics in solution, have failed to detect both of these changes, which affect inhibitory or activating binding modes. The only structure of carboxypeptidase yet published and that of its functionally inert complex with the pseudosubstrate, glycyl-L-tyrosine, derive from a unique form of carboxypeptidase A(alpha) crystals. These crystals differ from all others with regard both to their spectral properties and activity toward carbobenzoxy-glycyl-L-phenylalanine, which is 30% of that in solution, though the significance of this value cannot be gauged without knowledge of the relevant kinetic constants. The rapidly accumulating evidence for functional and conformational differences between crystals and solutions and the recent stress on the nonproductive aspects of the carboxypeptidase A(alpha)-glycyl-L-tyrosine complex, based on 30% site occupancy, suggest that the functional implications of its structural features require reevaluation.

Living with long-term home dialysis.

Eleven of the 22 patients receiving home dialysis in the spring of 1973 from the dialysis unit of a university medical center hospital were interviewed to determine what factors might help or hinder patient adjustment to chronic renal failure alleviated by home dialysis. Two interviewers, following a relaxed protocol, talked with patients at home and recorded the interviews on tape and in notes. Four areas were identified in which well-adjusted patients differed significantly from those poorly adjusted: extent of change in physical or mental state due to disease, source and extent of financial support, role and relationship of helper to patient, and the importance that the patient perceived dialysis to have in his daily life. From the typical patients' profiles, some tentative suggestions to enhance patient adjustment are offered.