Showing papers by "University of Bern published in 1972"

Acid — base reactions of the TiO2 (Anatase) — water interface and the point of zero charge of TiO2 suspensions

Abstract: The protolytic behaviour of the TiO2 (Anatase)-water interface was investigated by potentiometric titration of finely divided TiO2 suspended in 3 M NaClO4. The experimental data could be explained assuming the following equilibria: $$\begin{gathered} - Ti - OH_2 ^ + \leftrightarrows - Ti - OH + H^ + ; \hfill \\ Ka_1 = \frac{{[H^ + ]( - Ti - OH)}}{{( - Ti - OH_2 ^ + )}} \hfill \\ - Ti - OH \leftrightarrows - Ti - O^ - + H^ + ; \hfill \\ Ka_2 = \frac{{[H^ + ]( - Ti - O^ - )}}{{( - Ti - OH)}}. \hfill \\ \end{gathered}$$

The influence of two diphosphonates on calcium metabolism in the rat.

Abstract: SUMMARY 1. The effects of two diphosphonates, disodium ethane-I-hydroxy-l,1-diphosphonate (EHDP) and disodium dichloromethylene diphosphonate (C1,MDP) on several variables of calcium metabolism have been measured in the intact rat using the model of Aubert & Milhaud (1960). 2. The animals were bred from weaning on a diet containing 1 -3% calcium. At the age of 54 days they were switched to a diet with 0.5% calcium. Some of the animals were also given daily injections of one of the diphosphonates from the day the intake was decreased. The doses of the compounds were 0-01-10 mg of P kg body wt.-' day-'. 3. C12MDP caused a decrease in the rates of bone formation (Vo+) and bone resorption (Vo-), and these effects were proportional to the logarithm of the dose of the compound. There was a small increase in the retention of calcium due to a decrease in the endogenous faecal calcium. 4. EHDP in doses of up to 1 mg of P kg-' day-' decreased bone resorption but had little effect on bone formation. The retention of calcium increased due to an increased absorption of dietary calcium and a decreased endogenous faecal calcium. EHDP at a dose of 10 mg of P kg-' day-' caused a further fall in Vo- but also a great decrease in Vo + which was larger than the fall in Vo - . The net absorption of calcium was diminished, the urinary excretion of calcium was increased, the retention of calcium was greatly diminished and there was a greatly diminished ash content in the femur. Thus, for equal doses of up to 1 mg of P kg-' day-', C1,MDP was more potent in decreasing bone turnover than EHDP, but the two compounds caused a similar increase in the retention of calcium. At high doses EHDP inhibited the mineralization of epiphyseal cartilage. 5. These results are discussed in relation to the possible clinical applications of the diphosphonates.

Solar wind composition experiment.

Abstract: The Apollo 16 SWC experiment is a continuation of the earlier experiments; however, an essential change was introduced in the solar wind particle collection technique. Platinum surfaces were incorporated in the collector foil, and use was made of a layer technique for distinguishing particles of different energies and different directions of arrival. The improvements and the expanded scope of the Apollo 16 experiment, relative to the earlier SWC experiments, can be summarized as follows: elimination of possible residual dust contamination by treating the platinum foil sections with dilute hydrofluoric acid before analysis; increased accuracy of solar wind argon abundance; determination of solar wind albedo; and search for helium in the energy range above approximately 40 KeV/nucleon.

Relation between alkaline phosphatase and Ca 2+ -ATPase in calcium transport.

Abstract: SEVERAL recent studies suggest that at least part of the effect of vitamin D on intestinal calcium transport may be mediated by a calcium-stimulated ATPase (Ca ATPase) situated in the brush borders of intestinal mucosal cells1. Intestinal brush borders are known to contain several other enzymes which may be involved in digestion and transport, but the relationship between them is poorly understood2. In the case of the disaccharidases, the question of the number of enzymes responsible for the various activities has been raised3. Alkaline phosphatase is also present in brush borders but its function is unknown. During studies of the effect of various agents On intestinal calcium transport we noted a close correlation between the activities of alkaline phosphatase and Ca ATPase. We therefore wondered whether the activities might be due to a single enzyme species. Haussler et al.4 and Norman et al.5 have also noted a close relationship between the two activities under a variety of conditions but Holdsworth6 thinks the two activities are not related. We report here further evidence, based on denaturation by heat and on various dietary manipulations in the rat, which suggest that the two enzymes may be part of a single enzyme complex.

The effect of repetitive stimulation at low frequencies upon the electrical and mechanical activity of single muscle fibres.

Abstract: 1. The effect of repetitive stimulation at low frequencies (0.2–5/sec) upon isometric twitch tension was analysed in isolated muscle fibres of the frog. 2. The number of twitches until tension decreased to 10–20% of the original value (fatigue effect) was 5000–10000 in unpoisoned fibres at 20° C, 400–800 in CN-poisoned fibres at 10° C, 1800–2500 in CN-poisoned fibres at 20° C and 100–200 in CN and IAA-poisoned fibres at 1° C. 3. In fatigued fibres the overshoot of the action potential was often only a few millivolts lower than in normal fibres, the spike duration was longer, and the after-potential was increased. 4. In completely exhausted fibres, which developed no tension when they were activated, the effective memrane resistance was extremely low, the resting potential was high, and early and late after-potentials were absent. Since an exchange of external Cl by SO4 caused no depolarization, it is suggested that the decrease in resistance is due to an increase in potassium conductance. 5. A reduction of the external sodium concentration from 115 to 46 mM abolished the overshoot of the action potential, while twitch tension remained unaltered. 6. In fatigued fibres normal twitch height could be restored by the addition of caffeine, and maximal contracture tension could be obtained after a complete depolarization in a potassium sulphate solution which contained caffeine. 7. From the results quoted under 3, 5, and 6 it is concluded that neither an alteration in the action potential nor an exhaustion of energy reserves or a failure in the contractile mechanism can be regarded as the cause of fatigue. 8. In fatigued fibres the S-shaped curve which relates peak tension to membrane potential (threshold curve) was shifted by about 20 mV to more positive potentials. In addition maximal contractile strength was frequently no longer attained, even after complete depolarization. 9. The rate by which the contractility of depolarized fibres can be reactivated after a sudden repolarization, and probably also the steady relation between the state of the contractile system and membrane potential, were equal in normal and fatigued fibres. 10. Fibres recovered from fatigue within one to three hours. 11. From the results quoted under 8 and 9 it is tentatively suggested that a decline of the concentration of an “activator of contraction”—localized in some part of the tubular system—is the cause of the observed deficiency in excitation—contraction coupling.

A stereological method for estimating volume and surface of sarcoplasmic reticulum.

Abstract: SUMMARY The stereological analysis of volume and surface of sarcoplasmic reticulum tubules in muscle cells meets with particular problems because these structures are (a) highly oriented in the longitudinal direction of the muscle cells, (b) lined up in parallel, (c) periodically arranged in relation to sarcomeres and (d) internally symmetrical in analogy to sarcomere symmetry. On the whole this system may be characterized as a parallel linear array of units with translational-reflexive symmetry. On the basis of a simple model it is demonstrated that the problems of sampling and stereological measurement can be overcome if a combination of oblique and transverse sections are used. The procedure can be simplified to operate exclusively with oblique sections only slightly inclined to the transverse plane if a small systematic error can be accepted.

On automation of perimetry.

Abstract: A method enabling a fully automated computer analysis of the visual field is described. Starting from the most probable assumptions about the sensitivity distribution within the visual field, this distribution is approximated in 4 steps. Decisions are based on probability theory. Every analytical step builds up on the conclusions reached in the preceding one. The theoretical limits of the method in regard to the degree of approximation of the true sensitivity function are discussed in detail. The spatial resolution is determined by the density of the questions per area of visual field. For a grid constant of 3°, the spatial resolution of sensitivity defects varies between 4 and 7°. Otherwise, the quality of the approximation varies within large limits and depends on prior knowledge of the expected sensitivity distribution and on the noise in the system. This includes the patient's threshold fluctuation and the reliability of the answers. The whole analytical program was tested on a large number of artificial visual fields contained in computer storage which were then tested by the main program. It is shown that even in the presence of large sensitivity fluctuations and a considerable fraction of erroneous answers by the patient the method is still able to extract the data which are essential from the clinical point of view.

Fundamental mode radiation with solid-state lasers

Abstract: Optical pumping of solid-state lasers induces thermal lensing in the laser crystal. This lansing determines the beam properties in the resonator; the TEM 00 -mode radiation is limited to a small laser rod volume and it depends on the pump power. Especially with pulse-pumped systems, the generation of stable fundamental mode radiation could only be obtained with low efficiency. Laser resonators with optimum TEM 00 mode output were studied considering the thermal lensing. A kind of resonator was found, the radiation of which is insensitive to thermal distortions. The following is determined by parameters g_{1}, g_{2} : \frac{1}{g_{1}}=2g_{2} +^{1} (\frac{a}{b})^{2} + 2\frac{a}{b} , where a and b are distances between rod ends and mirrors, a and b being the distances between the two mirrors and the lens. The predicted beam behavior was verified experimentally with a high repetition rate YAG laser. A high-precision laser drilling machine was constructed with this design. Because of the insensitive properties, reproducible material processing was achieved in industrial use.

The Eck fistula rat: definition of an experimental model.

Abstract: Fifty-nine male Sprague-Dawley rata were subjected to an end-to-side portacaval shunt and compared with appropriate controls. During the first ten days after the operation, the liver weights decreased from an average of 4.2 to 2.3% of the body weight and thereafter remained at this level. Testicular atrophy also occurred regularly but only after the tenth postoperative day. Three weeks after the operation, the body weight of shunted rats had decreased by an average of 20%, whereas sham operated controls gained 17%. These changes were related to food intake and coprophagy. Hyper-ammonaemia developed gradually and levelled off at about 500 (μg/100 ml. Other alterations were more variable in severity. Spontaneous motor activity decreased to 12–77% of the preoperative value and was significantly correlated with changes in body weight. The electrocorticographic pattern was characterized by an average increase in rapid waves to 205% after five to six weeks, whereas the slow waves remained unchanged. These studies have established a standard of reference for further investigations with this animal model.

The influence of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on the development of experimentally induced urinary stones in rats.

Abstract: 1. Bladder stones composed of calcium hydrogen phosphate dihydrate, calcium oxalate mono- and di-hydrate and magnesium ammonium phosphate hexahydrate (struvite) were successfully induced in rats by various dietary manipulations and by implanting zinc pellets in the bladder. 2. The effect of a diphosphonate, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP), given in the drinking water at concentrations of 0·0025, 0·05 and 0·5% (w/v), on the size and composition of these stones was examined. 3. All the concentrations of EHDP decreased the weight of the calcium oxalate calculi. In contrast, only the highest concentration of EHDP inhibited calcium hydrogen phosphate stone formation and the magnesium ammonium phosphate stones were unaffected. 4. The difference between the effects on calcium oxalate and magnesium ammonium phosphate stones is consistent with the finding that EHDP inhibited the precipitation of calcium oxalate from solution in vitro but had only a slight effect on magnesium ammonium phosphate precipitation. 5. It is suggested that EHDP might be of use in the prevention of some types of urinary stones in man.

Currents, stress tensor and generalized unitarity in conformal invariant quantum field theory

Abstract: Matrix elements of internal symmetry currents and energy momentum density tensor are constructed in Migdal Polyakov conformal invariant bootstrap field theory. Their 3-point functions satisfy Bethe Salpeter equations which determine any free coefficients that may still occur in the conformal invariant Ansatz. Ward identities are verified for alln-point functions. They imply correct equal time current commutation relations. A proof of generalized unitarity is also given. Various equivalent forms of the propagator bootstrap are discussed. Our algebraic techniques also yield an eigenvalue equation for first order correction to the exactly conformal invariant theory, assuming the latter is Gell-Mann Low large momentum asymptote of a renormalizable finite mass theory.

Relationship between pyrophosphate, amorphous calcium phosphate and other factors in the sequence of calcificationin vivo

Abstract: The amounts of inorganic pyrophosphate (PPi), orthophosphate and calcium have been measured in resting, proliferating, hypertrophic and calcified cartilage from foetal calf epiphyses and also in cancellous, periosteal and compact bone. In the cartilage samples, the content of PPi increased progressively in the order named above, from values of 8.59 μg P/g dry weight in resting cartilage to 236 μg P/g dry weight in calcified cartilage. However, the ratio of PPi to orthophosphate followed the reverse relationship and was highest in the resting zone and fell dramatically as the tissue calcified. The possible role of PPi in inhibiting the precipitation of amorphous calcium phosphate (ACP) and in the slowing the transformation of ACP to hydroxyapatite (HA) in calcifying tissues is discussed in relation to other factors, such as collagen, magnesium, phospholipids and proteinpolysaccharides, which might also influence the processin vivo. At present, no single factor can be identified as a proven physiological regulator.

The value of stereology in analysing structure and function of cells and organs.

Abstract: I N T R O D U C T I O N It has become a fashion, maybe even an obligation, to ask about the relevance of a certain branch of science for society. The noble days of pure research, whose exclusive aim was to advance knowledge without regard to its usefulness, seem over. We have asked society to commit itself to the advancement of science. It has followed suit by investing over the past decades a large and ever-increasing fraction of the social product in the support of scientific research. NOW society demands its dividends : we are asked as scientists to reconsider the ultimate goals of our endeaveour and to commit ourselves and our scientific activity to the advancement of the well-being of mankind, of society. A theoretical, abstract field such as stereology may appear particularly far away from such commitment. It has certainly not made headlines in the short years of its existence, but it is still worse: many scientists don’t even know the word, which was coined 10 years ago at a meeting of biologists and engineers in Germany (cf. Bach, 1963) to unify those activities which had been going on for a number of years in as widely separated fields as metallurgy and biology, all striving for three-dimensional interpretation of sectioned materials. It seems therefore in order that we open this third congress on stereology by considering for a while the value of stereology for the advancement of the well-being of mankind, by considering its social relevance, before we turn to the discussion of its mathematical principles and to methods of practical application. Can stereology make any contributions whose significance surpasses that of academic endeavour for its own sake ? This question may well be asked, because at first glance stereology may appear as nothing more than a play-ground for some mathematicians who like to juggle point sets, topological parameters and probability theory in an unusual way, offering morphologists a further way of pursuing their obsolete art of describing Structures, be it the composition of rocks or of metal alloys, or that of biological organs. I would like to demonstrate that stereology is indeed an important link in the chain of bio-medical research concerned with maintaining and protecting the health of man.

Sources of Blood Glucose in the Rat Fetus

Abstract: Extract: Pregnant Sprague-Dawley rats from the 18th to the 21st day of gestation were fasted for 16 hr and anesthetized, and a constant infusion of uniformly labeled glucose-14C and of glucose-2-3H was started. The purpose was to see if the regulation of fetal blood glucose concentration differed from the maternal during fasting. The results are given in Figures 2 and 3. During the course of the infusions, the specific activity of glucose was, at all points measured, two to four times lower in the fetal than in the maternal serum. The higher fetal than maternal supply of blood glucose could be derived either from gluconeogenesis or from glycogenolysis in the fetus. In vitro studies indicate that the fetal rat liver is unable to perform gluconecgenesis. Therefore, the placenta was investigated for the presence of a gluconeogenetic pathway. Placenta slices showed no ability to convert pyruvate into glucose (Fig. 8). No phosphoenolpyruvate carboxykinase (EC. 4.1.1.32) activity could be found in placenta homogenates. The possibility of the presence of gluconeogenesis in the rat fetus has been investigated in vivo. Intraperitoneal injections of pyruvate-2-14C and glycerol-1, 3-14C were given to 1-day-old newborns, prematures (fetuses which were delivered 1 day prior to term), and fetuses in situ. The 1-day-old newborns do convert both substrates to glucose, with averages of 50 and 70%, respectively, of serum radioactivity being due to glucose-14C, thus proving the validity of this way of investigating gluconeogenesis in vivo. The prematures did not synthesize glucose from pyruvate, but glucose synthesis occurred from glycerol, an average of 70% of serum radioactivity being due to glucose-14C. The fetuses which were injected in situ did not synthesize glucose from either one of the two substrates. These experiments would seem to exclude fetal gluconeogenesis as the source of fetal blood glucose in the constant infusion experiments mentioned above. Fetal hepatic glycogenolysis can account only in part for the higher dilution of the specific activity of glucose in the fetus after a 16-hr fast. The data in Table I show that at the time when the constant infusions were started (after a 16-hr fast) the fetal liver glycogen concentration had diminished from 111 ± 5 to 82 ± 10 mg/g wet weight, as compared to the fed state. This decrease is too small to account for the higher fetal than maternal dilution of blood glucose specific activity, or for the maintenance of unchanged blood glucose levels in the fetus after a 16-hr fast (86 ± 8 and 92 ± 11 mg/100 ml, respectively). An unknown mechanism leading to the privileged situation of the fetus with regard to blood glucose levels during a fasting state must be postulated. Speculation: Gluconeogenesis is inactive in the rat fetus, as investigated by in vivo and in vitro methods. Fetal hepatic glycogenolysis cannot be the only source of fetal blood glucose during fasting.

Isolation and some properties of the heparin-neutralizing factor (PF4) released from human blood platelets.

Abstract: Der in Form eines hochmolekularen Komplexes von den Plattchen freigesetzte, heparinneutralisierende Faktor (PF 4) konnte reversibel in ein Trager-Material und ein aktives Protein (Molekulargewicht ca. 30000) aufgespalten werden.