Biomechanical study of shaft fracture with the butterfly fragment: software simulation.

The specific traumatic mechanism that leads to the formation of the butterfly fragment is debated in literature. The aim of the present study is to analyze the biomechanics of fractures with a "butterfly" fragment, using a software that simulates the movement of the lines of force (and related iso-displacement points) that occur on the bone, when traumatic forces are applied on it. We have shown that the formation of the butterfly fragment derives from the application of three forces (compression, torsion and bending) with the bending force that acts by increasing the curvature of the long bone.

Consistent behavioral phenotype differences between inbred mouse strains in the IntelliCage.

The between-laboratory effects on behavioral phenotypes and spatial learning performance of three strains of laboratory mice known for divergent behavioral phenotypes were evaluated in a fully balanced and synchronized study using a completely automated behavioral phenotyping device (IntelliCage). Activity pattern and spatial conditioning performance differed consistently between strains, i.e. exhibited no interaction with the between-laboratory factor, whereas the gross laboratory effect showed up significantly in the majority of measures. It is argued that overall differences between laboratories may not realistically be preventable, as subtle differences in animal housing and treatment will not be controllable, in practice. However, consistency of strain (or treatment) effects appears to be far more important in behavioral and brain sciences than the absolute overall level of such measures. In this respect, basic behavioral and learning measures proved to be highly consistent in the IntelliCage, therefore providing a valid basis for meaningful research hypothesis testing. Also, potential heterogeneity of behavioral status because of environmental and social enrichment has no detectable negative effect on the consistency of strain effects. We suggest that the absence of human interference during behavioral testing is the most prominent advantage of the IntelliCage and suspect that this is likely responsible for the between-laboratory consistency of findings, although we are aware that this ultimately needs direct testing.

Arguments against and alternatives for an extracellular surfactant layer in the alveoli of mammalian lung.

It is generally believed that lung alveoli contain an extracellular aqueous layer of surfactant material, which is allegedly required to prevent alveolar collapse at small lung volume; the surfactant's major constituent is a fully saturated phospholipid, referred to as dipalmitoyl lecithin or DPL. I herein demonstrate that the surfactant hypothesis of alveolar stability is fundamentally wrong. Although DPL is synthesized inside type II epithelial cells and stored in the typical inclusion bodies therein and lowers surface tension to zero in the surface balance, there is no evidence to the effect that type II cells secrete the DPL surfactant into the aqueous intra-alveolar layer which is shown by electron microscopy in support of the surfactant theory. To the contrary, all the evidence indicates that, when seen, such an extracellular layer is an artifact. This is probably upon the damage glutaraldehyde inflicts onto alveolar structures during fixation of air-inflated lung tissue. Furthermore, several cogent arguments invalidate the belief that an extracellular layer of DPL and serum proteins is present in the alveoli of normal lung. In light of these arguments, a surface tension role of DPL in alveolar stability is excluded. Three hypotheses for an alternative role of DPL in respiration mechanics are proposed. They are: (a) alveolar clearance by viscolytic and surfactant action (bubble or foam formation) on the aqueous systems which are present in lung alveoli during edema and in prenatal life and which would otherwise be impervious to air; (b) homeostasis of blood palmitate in normal lung; (c) modulation of the elasticity of terminal lung tissue by the intact inclusion bodies and parts thereof inside type II cells in normal lung.

Electromagnetic modulation of biological processes: influence of culture media and significance of methodology in the Ca-uptake by embryonal chick tibia in vitro.

The present studies are aimed at establishing molecular correlations in the interaction of very low frequency electromagnetic fields with biological systems. Ca-uptake by chick embryo tibia rudiment in short-term culture was a useful model. Tibiae of 8- to 10-day-old chick embryos were incubated 60 min in simplified culture media in the presence of 45Ca at 37.5 +/- 0.5 degrees C either inside or outside pulsating electromagnetic fields. Radioactivity count in the medium was the most accurate method for determining Ca-uptake by the rudiment. The effect of the fields on the Ca-uptake depended markedly on the chemical composition of the culture medium: bicarbonate was indispensable; glucose or sucrose was important; phosphate was potentiating; ethanol, Mg2+, and NaF were stimulating. The field had no effect in (a) blank medium without tibia, (b) tibiae that had been altered by fixation with aqueous glutaraldehyde, (c) nonliving artificial systems endowed with great or small ion sorption capacity. The unique bicarbonate effect with living systems and the passive behavior of nonliving ion sorbing systems prompt the suggestion that the electromagnetic field probably couples with specific processes, such as a bicarbonate-dependent Ca2+ ATPase and the active ion transport, at the cell membrane level. The molecular mechanisms remain to be established.

Electromagnetic modulation of biological processes: bicarbonate effect and mechanistic considerations in the Ca-uptake by embryonal chick tibia in vitro.

Electromagnetically induced currents pulsating at very low frequency stimulated calcium uptake by chick embryo tibia rudiments only when bicarbonate was present in the culture medium. A bicarbonate-dependent Ca2+-ATPase might be implicated in coupling of the electromagnetic signal with processes that promote Ca-transport and storage in bone tissue.

Electromagnetic modulation of biological processes: ATPase function and DNA production by Raji cancer cells in vitro.

Addition of either ATP or ouabain to the culture medium markedly depressed thymidine incorporation into DNA in Raji cells. The electromagnetic field, pulsating at very low frequency, did not affect DNA synthesis in normal culture media nor did it alter its ouabain-inhibition, but it partially reversed the ATP-inhibition. In spite of the presence of ATP, ouabain prevented stimulation of ATPase and DNA synthesis by the field. Although no mechanism is known for the action of either ATP or the field, the results may be interpreted in light of existing speculations. In the absence of the field, external ATP may go into an ATP pool that either blocks ATPase or feeds adenyl cyclase, which hinders DNA synthesis. In contrast, the electromagnetic field may either turn off adenyl cyclase or simply stimulate the ATP-depressed ATPase.

Surface properties of membrane systems: interaction of electrolyte and lipid with Ca2+ ionophores.

When spread from organic solvents onto electrolyte solutions, the Ca2+ ionophores A23187 (I) and X537A (II) formed films with relatively high surface pressures potentials. Ionophores I had collapse pressures between 16 and 19 dynes/cm and nearly equal surface activity on distilled water and on 1000 mEq of either sodium chloride or calcium chloride. Film pressure did not reveal appreciable ion selectivity. However, the surface potential of I on calcium chloride solution was higher than that on sodium chloride, and the potential difference, delta(deltaV), of 40 mv was independent of the electrolyte concentration. In contrast, the ion selectivity of II was dependent on the electrolyte concentrations since the delta(deltaV) value between calcium chloride and sodium chloride was maximal (130 mv) on 1000 mEq and negligible on 500- and 2000-mEq salt solutions. The isotherms of phospholipid-ionophore films were markedly different from those of the individual components, although they revealed ionophore characteristics at low film pressures and phospholipid behavior at high film pressures. The magnitude of the surface potential indicated that dipalmitoyl phosphatidylcholine enhanced, whereas mitochondrial lipid and cardiolipin reduced, the preference of the two ionophores for Ca2+ over Na+. Since the ion selectivity was manifested most at both high electrolyte and high lecithin concentrations, the ionophore probably prefers the low dielectric constant of neutral lipid membranes to complex with the selected cation.

Surface properties of membrane systems: interaction of ketamine with monomolecular films of ganliosides and mitochondrial lipids.

Ketamine solutions did not form a film (pi=0) but had an appreciable surface potential (delta V=500 mv), indicating a significant array of +/- oriented charge dipoles at the air-water interface, as opposed to calcium chloride solutions whose delta V was zero. The delta V values of ganglioside films spread on the aqueous phase varied in the order water less than sodium chloride less than calcium chloride less than ketamine hydrochloride. At equivalent concentrations, calcium chloride was 500 times as effective as sodium chloride, and ketamine at the clinical concentrations of 10-20 microgram/ml (36-72 micrometer) was 6000 times as effective as calcium chloride in raising the surface potential of gangliosides; the delta V effect with mitochondrial lipid was in the reverse order; water less than sodium chloride = ketamine hydrochloride less than calcium chloride. This calcium-ketamine inversion indicates a unique specificity of ketamine for gangliosides. Since ketamine acts on the brain and did not affect mitochondrial respiration, the surface potential data suggest that part of the mechanism of action of ketamine could be its interaction with synaptic surfaces and, specifically, with the sialic acid of gangliosides and/or glycoproteins present on the synaptic membrane surface.

Cultured lung cells: interplay effects of beta-mimetics, prostaglandins and corticosteroids in the biosynthesis of dipalmitoyl lecithin.

Cell lines derived from type II lung cells were used to study interplays of substances affecting incorporation of labeled precursors [1(-14)C]palmitate and [methyl-3H]choline into phosphatidyl choline. Ethanol stimulated markedly biosynthesis of dipalmitoyl phosphatidyl choline in cloned rabbit lung cells; the stimulating action of ethanol was reduced very much by cortisol and less by ritodrine. In the presence of 0.1 microM isoproterenol, two prostaglandins, E2 and F2alpha, caused marked depressions in the incorporation of both precursors by cell line A 549 derived from human lung adenocarcinoma. One concluded that among the agents studied, ethanol and cortisol are potent antagonists, and so were also the prostaglandins and isoproterenol.

Effect of serum albumin on dynamic force-area curve of dipalmitoyl lecithin.

In line with previous findings at 25 degrees C, solutions of serum albumin in the subphase stabilized the surface activity of DPL spread films at 25 degrees C as well as 37 degrees C. In contrast, films adsorbed from mixtures of DPL and albumin exhibitied a marked inhibitory action of the albumin on DPL activity. The inhibitory effect increased with the relative protein concentration but, with albumin/DPL ratios smaller than 2, the DPL activity was regained gradually with cycling. With larger albumin/DPE negative effect of albumin was counteracted by higher temperatures (37 degrees C vs 25 degress C) and modest cholesterol concentrations; with greater cholesterol concentrations the known inhibitory effect of cholesterol prevailed. The inhibitory effect of albumin was potentiated by humidity; saturation of the atmosphere with water vapor at 37 degrees C abolished the DPL character of DPL-RSA mixtures and prevented its return (zero surface tension) upon reversal of the atmosphere from saturated water vapor to dry air. The data are important in the interpretation of the surface activity of pulmonary washings and other pulmonary extracts.

Effects of prostaglandins E2 and F2alpha on lecithin biosynthesis by cultured lung cells.

Transformed cells from human lung carcinoma (Line A549), resembling type II pneumocytes, were cultured in monolayer at 37 degrees C and incubated for five hours with 3H-choline and 14C-palmitate in the presence of various concentrations of prostaglandins (PGS) E2 and F2alpha. In the control (no PG) the level of % palmitate incorporation was 13.5 x as high as that of choline, after taking isotope dilution into account. Between the concentrations studied, 0.1 and 10 muM, both prostaglandins stimulated markedly the incorporation of both precursors, though choline up to 3 x better than palmitate. This was indicated by a change in the palmitate/choline incorporation ratio from 13.5 to as low as 4.2. At the lowest PG concentration, 0.1 muM, PGE2 was much more effective than PGF2alpha in stimulating the incorporation of both precursors.

Surface properties of membrane systems. Transport of staphylococcal delta-toxin from aqueous to membrane phase.

Hemolytic delta-toxin from Staphylococcus aureus was soluble in either water, methanol or chloroform/methanol (2 : 1, v/v). The toxin spread readily from distilled water into films with pressures (pi) of 10 dynes/cm on water and 30 dynes/cm on 6 M urea; from chloroform/methanol it produced 40 dynes/cm pressure on distilled water. The toxin adsorbed barely from water (pi = 1 dyne/ cm) but it did rapidly from 6 M urea (pi = 35 dynes/cm). The protein films had unusually high surface potentials, which increased with the film pressure and decreased with increasing both pH and urea concentration in the aqueous phase. The fluorescence of 1-aniline 8-naphthalene sulfonate with delta-toxin was much greater than that with RNAase and dipalmitoyl phosphatidylcholine itself, indicating probably a marked lipid-binding character of the toxin. By circular dichroism the alpha-helix content of delta-toxin was 42% in water, 45% in methanol, 24% in 6 M urea. Infrared spectroscopy showed predominant alpha-helix in both 2H2O and deuterated chloroform/methanol as well as in films spread from either solvent on 2H2O. In spreading from 6 M [2H]urea, in which the major infrared absorption was that of [2H]urea with peaks at 1600 and 1480 cm(-1), the delta-toxin film showed prevalently non-alpha-helix structures with major peak intensities at 1633 cm(-1) > 1680 cm(-1), indicating the appearance of new beta-aggregated and beta-antiparallel pleated sheet structures in the film. The data prove that (1) high pressure protein films can consist of alpha-helix as well as non-alpha-helix structures and, differently from another cytolytic protein, melittin, delta-toxin does not resume the alpha-helix conformation in going into the film phase from the extended chain in 6 M urea; (2) conformational changes are important in the transport of proteins from aqueous to lipid or membrane phase; (3) delta-toxin is by far more versatile in structural dynamics and more surface active than alpha-toxin.