Culture of fetal mouse liver in plastic chambers: a new technique for organ culture.

A new technique for organ culture which uses plastic culture chambers and the advantages of the cellophane-sheet technique is described with the results of a study of cultivations of fetal mouse liver. Two chambers, each containing cells, were placed in gas permeable roller tubes and rotated at 0.1 rpm in a CO2-air gassed incubator. The fetal mouse liver cells developed electron microscopic features similar to those of the in vivo adult liver by 9 days of cultivation. The albumin content and tyrosine aminotransferase (TAT) activity were detected in the cultivated liver. TAT activity was further induced by prednisolone. These results indicate that potential of this culture method for the study of physiological and pathological processes.     

Aspects in practical neutron dosimetry with ionization chambers

Summary The calibration procedure to determine the absorbed dose within a phantom irradiated with fast neutrons is described for ionization chambers. A comparison between values of the neutron dose determined with paired ionization chambers and values of the neutron fluence measured with a fission chamber (²³⁸U) is given. The comparison indicates the energy variation of the fast neutrons within a phantom irradiated with 14 MeV neutrons.Dedicated to Prof. Dr. Dr. h. c. mult. B. Rajewsky on the occasion of his 80th birthday.     

Sedimentation equilibrium of proteins in density gradients.

The technique of sedimentation equilibrium in density gradients in the analytical ultracentrifuge has been applied to the study of proteins. A variety of effects and procedures including the use of density marker beads, the effects of pressure on buoyant density and pH, and the calculation of compositional density gradient proportionality constants and density--refractive index relations have been developed. The buoyant densities of twenty-four proteins have been measured and hydration values computed. The buoyant titrations of six proteins have been measured. These data have been interpreted in terms of the buoyant titrations which have been obtained for six ionizable homopolypeptides, five copolypeptides, two non-ionizable homopolypeptides and three chemically modified proteins. Spectropolarimetry and potentiometric titrations were employed to further interpret these data. Approximate values for dissociation constants, numbers of ionizable residues, and the nature of ions bound or dissociated upon ionization have been obtained. The relation between potentiometric and buoyant titrations and the use of density gradient centrifugation as a probe for protein structure have been explored.     

Dosimetry in magnetic fields with dedicated MR-compatible ionization chambers

MR-integrated radiotherapy requires suitable dosimetry detectors to be used in magnetic fields. This study investigates the feasibility of using dedicated MR-compatible ionization chambers at MR-integrated radiotherapy devices. MR-compatible ionization chambers (Exradin A19MR, A1SLMR, A26MR, A28MR) were precisely modeled and their relative response in a 6MV treatment beam in the presence of a magnetic field was simulated using EGSnrc. Monte Carlo simulations were carried out with the magnetic field in three orientations: the magnetic field aligned perpendicular to the chamber and beam axis (transverse orientation), the magnetic field parallel to the chamber as well as parallel to the beam axis. Monte Carlo simulation results were validated with measurements using an electromagnet with magnetic field strength upto 1.1 T with the chambers in transverse orientation. The measurements and simulation results were in good agreement, except for the A26MR ionization chamber in transverse orientation. The maximum increase in response of the ionization chambers observed was 8.6% for the transverse orientation. No appreciable change in chamber response due to the magnetic field was observed for the magnetic field parallel to the ionization chamber and parallel to the photon beam.Polarity and recombination correction factor were experimentally investigated in the transverse orientation. The polarity effect and recombination effect were not altered by a magnetic field.This study further investigates the response of the ionization chambers as a function of the chambers’ rotation around their longitudinal axis. A variation in response was observed when the chamber was not rotationally symmetric, which was independent of the magnetic field.     

Human bone marrow colony formation in diffusion chambers. Normal values.

In situ hybridization techniques have previously employed a series of manipulations to effect denaturation of chromosomal DNA and reannealing of DNA-RNA hybrids. This report presents a new protocol which combines the denaturation and reannealing processes. DNA is heated in a solution of 50% formamide, 50% 4 × SSC containing the RNA to be hybridized. After l h at 70 °C the preparation is slowly cooled to 37 °C over a period of 6 h and incubated at 37 °C for an additional 10 h. This technique eliminates the possibility of premature reannealing of the DNA while employing hybridization conditions which, in vitro, lead to accurate base pairing.     

Sedimentation of a suspension in a centrifugal field.

To model centrifugal sedimentation of biological suspensions, the time history of sedimentation of particles in a centrifugal field was considered for two geometries: a tube and a cylindrical container. The Kynch theory for batch gravitational settling in Cartesian coordinates based on mass conservation was extended to include a centrifugal sedimentation force, cylindrical coordinates, and the Hawksley-Vand hindered settling model. The resulting quasi-linear partial differential equation was solved by the method of characteristics. The combination of radial dependence of the sedimentation force and cylindrical geometry in the centrifugal case results in several differences in the time-position history diagram of the sedimentation process compared to the gravitational case. First, instead of a region of uniform concentration equal to the initial concentration, a region of concentration that is continuously decreasing with time results. Second, in the region of particle accumulation, curved constant concentration contours result instead of straight lines. Finally, a secondary shock that is dependent upon the initial concentration and the radius ratio of the rotating vessel appears in the centrifugal case. The time history of the concentration for a particle suspension with an initial concentration typical of blood is presented.     

In situ studies with membrane diffusion chambers of antibiotic resistance transfer in Escherichia coli.

Coliform bacteria were isolated from raw sewage and sewage effluent-receiving waters and tested for their antibiotic susceptibility patterns and their ability to transfer antibiotic resistance to Escherichia coli K-12 C600. An environmental isolate of E. coli (MA527) capable of transferring antibiotic resistance to C600 was mated, both in vitro and in situ, with an antibiotic-sensitive E. coli environmental isolate (MA728). In situ matings were conducted in modified membrane diffusion chambers, in the degritter tank at the Grant Street (Melbourne, Fla.) sewage treatment facility, and in the sewage effluent-receiving waters in Melbourne, Fla. The transfer frequencies in situ were 3.2 x 10(-5) to 1.0 x 10(-6), compared with 1.6 x 10(-4) to 4.4 x 10(-5) observed in vitro. Transfer was shown to occur in raw sewage but was not detected in the effluent-receiving waters. The presence of a 60-megadalton plasmid species in both donor and transconjugants, but not in the recipients, provided physical evidence for the transfer of antibiotic resistance in situ.     

Culture of fetal mouse liver in plastic chambers: A new technique for organ culture

Summary A new technique for organ culture which uses plastic culture chambers and the advantages of the cellophane-sheet technique is described with the results of a study of cultivations of fetal mouse liver. Two chambers, each containing cells, were placed in gas permeable roller tubes and rotated at 0.1 rpm in a CO₂-air gassed incubator. The fetal mouse liver cells developed electron microscopic features similar to those of the in vivo adult liver by 9 days of cultivation. The albumin content and tyrosine aminotransferase (TAT) activity were detected in the cultivated liver. TAT activity was further induced by prednisolone. These results indicate the potential of this culture method for the study of physiological and pathological processes. This work was supported in part by a Grant-in-Aid for Cancer Research from the Ministry of Education, Science and Culture, Japan and Science Technology Agency, Japan.     

Radiation effect on the proliferating capillaries in rat transparent chambers.

The revascularization of the devascularized area in rat transparent chambers by the proliferating blood vessels was studied quantitatively on the changes of vascularity. On the vascularizing border, a hypervascular zone about 0-5 mm wide was formed. The border advanced constantly at 0-020 cm a day. Vascular density was fixed in the repaired area. The vascular length and repaired area increased on parabolic curves. The chambers were irradiated with single doses of 50, 100, 200, 400, 1000, 2000, and 4000 rad of 30Co gamma-rays, and the effects on the advance of the border were examined. With 200 rad and more, significant inhibition, greater with bigger doses, was seen in the advance of the borders. Regression of the borders also occurred. Irradiation with over 1000 rad destroyed the hypervascular zones.     

Sedimentation equilibrium in macromolecular solutions of arbitrary concentration. I. Self-associating proteins

Relations describing sedimentation equilibrium in solutions of self-associating macromolecules at arbitrary concentration are presented. These relations are obtained by using scaled-particle theory to calculate the thermodynamic activity of each species present at a given radial distance. The results are expected to be valid for solutions of globular proteins under conditions such that interactions between individual solute molecules may be approximated by a hard-particle potential. Sedimentation equilibria in solutions containing either a nonassociating solute or a solute that self-associates according to several different schemes are simulated using the derived relations. The results of these simulations are presented in terms of the dependence of apparent weight-average molecular weight upon solute concentration. Simple empirical relations are presented for estimating the true weight-average molecular weight from the apparent weight-average molecular weight, without reference to any particular self-association scheme. The weight-average molecular weight estimated in this fashion is within a few percent of the true weight-average molecular weight at all experimentally realizable solute concentrations ( < 400 g/L).     

Overestimation of respiration rates in commercially available clamp-on leaf chambers. Complications with measurement of net photosynthesis

The possible interference when measuring gas exchange with respiratory CO₂ produced under the gasket of commercially available clamp‐on leaf chambers was investigated. Two of these chambers were compared with a leaf chamber that accommodated an entire leaf without clamping it under a gasket. An overestimation of dark respiration rate (R_D) by 55% was found with Plantago major leaves, a species with homobaric leaves that have high resistance for lateral gaseous transport. The percentage was similar in the heterobaric Ficus benjamina, but was 32% in the highly porous homobaric Nicotiana tabacum. Net photosynthetic rate at low photon flux density was underestimated by 35% in the clamp‐on chamber. However, the gasket effect was not detectable at light saturation because the error was small in comparison with the high photosynthetic rates. Estimation of respiration in the light (R_L) in Nicotiana as derived from CO₂ exchange at low CO₂ concentrations was complicated by three factors. The inward diffusion of respiratory CO₂ from under the gasket was added to a diffusion of CO₂ from outside through the gasket material and through the leaf, which produced an even larger error in R_L in comparison with R_D at ambient CO₂. These errors are significant for estimations of carbon gain at whole plant and canopy level and also at the leaf level when photosynthetic rates are low. Possible improvements in gasket design and corrections of CO₂ exchange measurements for the gasket effect are discussed.     

Residual particle free rough surfaces after rough blasting with steel grit in total hip arthroplasty]

INTRODUCTION: Several shot peening and grit blasting techniques are used to modify the surface in the production of hip endoprostheses. A number of publications in maxillo- facial- surgery and orthopedic surgery demonstrated significant contamination on alumina blasted surfaces. Latest research studies suspected an association between surface contamination and early failure of endoprostheses associated with third body wear. Additionally, the European standard EN 12010 requires surfaces free of residual particles. The aim of this study is to evaluate the effects of rough blasting using steel grit followed by a pH dependent cleaning procedures with regard to complying with EN 12010. MATERIAL AND METHOD: Ti6Al7Nb rods were rough blasted 1 time using steel grit ("Stahldrahtkorn", hardness: 56 HRC; R+K Draht GmbH, Leisnig). All blasting procedures were carried out with a special grit blasting device with direct pressure. One Ti6Al7Nb rod each was grit blasted with 3 and 4 bar pressure and 10 rods with 5 bar pressure. Surface roughness was measured by means of Mitutoyo- Surftest 301 three times before and after grit blasting. The mean value was calculated. A field emission scanning electron microscopy (SEM, LEO 1525) was used for the detection of residual particles on the surface of the rods with a backscattered electron detector. RESULTS: By rough blasting using steel grit a mean roughness of 54,9 microm and a maximum roughness of 61,4 microm could be achieved. The surface of all rods showed a considerable contamination with steel particles after grit blasting. After the a pH- dependent cleaning procedure a residual particle free surface was detected in all samples. DISCUSSION: The European standard EN 12010 can be fulfilled using rough blasting with steel grit followed by a pH dependent cleaning procedure.