Studies on the lack of cooperativity in the melting of lipid bilayers

The gel-to-fluid first-order melting transition of lipid bilayers is simulated by the use of a microscopic interaction model which includes a variable number of lipid-chain conformational states. The results suggest that the experimental observation of ‘continuous melting’ in pure wet lipid bilayers, rather than being ascribed to the presence of impurities, may be explained as a result of kinetically caused metastability of intermediate lipid-chain conformations.     

Na+, Cl− cotransport in Ehrlich ascites tumor cells activated during volume regulation (regulatory volume increase)

Ehrlich ascites cells were preincubated in hypotonic medium with subsequent restoration of tonicity. After the initial osmotic shrinkage the cells recovered their volume within 5 min with an associated KCl uptake. The volume recovery was inhibited when NO-3 was substituted for Cl-, and when Na+ was replaced by K+, or by choline (at 5 mM external K+). The volume recovery was strongly inhibited by furosemide and bumetanide, but essentially unaffected by DIDS. The net uptake of Cl- was much larger than the value predicted from the conductive Cl- permeability. The undirectional 36Cl flux, which was insensitive to bumetanide under steady-state conditions, was substantially increased during regulatory volume increase, and showed a large bumetanide-sensitive component. During volume recovery the Cl- flux ratio (influx/efflux) for the bumetanide-sensitive component was estimated at 1.85, compatible with a coupled uptake of Na+ and Cl-, or with an uptake via a K+,Na+,2Cl- cotransport system. The latter possibility is unlikely, however, because a net uptake of KCl was found even at low external K+, and because no K+ uptake was found in ouabain-poisoned cells. In the presence of ouabain a bumetanide-sensitive uptake during volume recovery of Na+ and Cl- in nearly equimolar amounts was demonstrated. It is proposed that the primary process during the regulatory volume increase is an activation of an otherwise quiescent, bumetanide-sensitive Na+,Cl- cotransport system with subsequent replacement of Na+ by K+ via the Na+/K+ pump, stimulated by the Na+ influx through the Na+,Cl- cotransport system.     

Model simulation of heat and water transport dynamics in an airway

Heat and water transport processes in the respiratory tract depend on environmental conditions, breathing patterns, and the physiological state of the respiratory system. To study these processes, we have developed a mathematical model of the dynamics of temperature and water vapor in the radial and axial directions of an idealized trachea. The model is expressed as two implicit finite-difference equations and solved using an alternating-direction algorithm. Using these equations, we simulated the effects of inspired gas temperature and humidity, velocity profile, and flow rate on heat and water transport between the gas and airway wall. Under inspired gas conditions of low temperature or high relative humidity, supersaturation occurs. Increasing either the velocity gradient at the wall or the flow rate increases the heat and water transport rates. However, these rates change by only 10 percent when the velocity gradient is doubled, and by about 35 percent when flow rate undergoes a two-fold change. The model can be used with in-vivo data from the trachea to test hypotheses concerning normal and abnormal heat and water transport.     

Migration Inhibition Studies on Peripheral Leukocytes and Lymph Node Cells from Ruminants with Fascioliasis

Delayed type hypersensitivity against antigens of Fasciola hepatica has been repeatedly documented in infected hosts. Evidence has been presented to suggest that the delayed reactivity may develop earlier in the regional lymph nodes of the parasitized organ than in other lymph nodes of the body (Soulsby 1971).     

Enzymbestimmungen in Erythrocyten bei Kindern mit Down-Syndrom

Zusammenfassung Bei 20 Kleinkindern mit gesicherter freier Trisomie 21 wurden die Aktivitäten von 21 Enzymen des Energie- und des Glutathionstoffwechsels in isolierten Erythrocyten gemessen. Die Aktivitäten der Fructose-6-phosphatkinase, der Lactatdehydrgenase, der Glucose-6-phosphatdehydrogenase, der Glutathionreduktase (NADP) und der Glutamat-Oxalacetat-Transaminase wurden gegenüber gleichaltrigen Kontrollen signifikant erhöht gefunden. Lediglich die etwa 50%ige Steigerung der Fructose-6-phosphatkinase-Aktivität kann im Sinne eines Gen-Dosis-Effektes gedeutet werden.

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Enzyme activities in the erythrocytes of children with Down's syndrom

Summary The activities of 21 enzymes of the energy supplying and the glutathione metabolism were estimated in isolated erythrocytes from children with Down's syndrome aged from 1 to 5 1/2 years. All 20 patients were trisomic for chromosome 21. The following enzymes were estimated by means of optic assays: All glycolytic enzymes, two enzymes of the hexosephosphate shunt and two of the citric cycle, NADP- and NAD-dependent glutathione reductase, glutamic-oxaloacetic transaminase, adenylate kinase, and Mg²⁺-activated ATPase.The activities of five enzymes, i.e. phosphofructokinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, glutathione reductase (NADP), and glutamic-oxaloacetic transaminase, were significantly elevated as compared to age-matched controls. The 50% increase of phosphofructokinase-activity is assumed to provide suggestive evidence for a controlling gene-locus on chromosome 21. The remaining findings are not considered to be directly related to the chromosomal abnormality.

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Direcktor: Prof. Dr. H.-R. Wiedemann

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Nach einem Vortrag auf der 10. Tagung der Gesellschaft für Anthropologie und Human-genetik, Königstein (Ts.), 22.–25. 10. 1967.

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Die Untersuchungen wurden durch die dankenswerte Unterstützung der Deutschen Forschungsgemeinschaft ermöglicht.     

PRODUCTION AND CHARACTERIZATION OF MULTIPLE-LAYERED POPULATIONS OF ANIMAL CELLS

Dense populations containing 129 x 10⁶ Jensen sarcoma, 134 x 10⁶ DON Chinese hamster, 28.9 x 10⁶ WI-38 human diploid, 61.8 x 10⁶ HEp-2 human carcinoma, and 67.4 x 10⁶ WISH human amnion cells were produced from dilute inocula, 0.85 to 5.33 x 10⁶, in 7 to 8 days in a perfusion system using replicate T-60 flasks. Perfusion rates as high as 560 ml medium/day/T-60 were required to maintain pH (to ca ±0.1 unit) and adequate nutrient supplies. The cell densities encountered are described by the term "monolayer equivalents" (M.E.), defined as number of cells per culture divided by number of cells in a monolayer. The M.E.'s for T-60 cultures containing unusually dense populations of 40 x 10⁶ WI-38 and 250 x 10⁶ DON cells (9-day perfusion) were 5 and 17, respectively, and numbers of cells in illustrations of stained cross-sections of membranes from these cultures were in excellent agreement. Threshold M.E.'s exist below which proliferation is the chief cellular activity and above which one or more cell functions may predominate even though proliferation persists. Cellular nutrition and metabolism may change with changes in M.E., as illustrated in different patterns of glutamic acid, proline, and glycine utilization or production in dense vs. dilute WI-38 cell populations. The results indicated that the role of contact inhibition phenomena in arresting cellular proliferation was diminished in perfusion system environments.     

Disinfection of Aerosolized Pathogenic Fungi on Laboratory Surfaces: II. Culture Phase

The effect of several fungicides on laboratory surfaces contaminated with the culture (spore) phase of aerosolized Blastomyces dermatitidis, Coccidioides immitis, and Histoplasma capsulatum was ascertained. The culture (spore) phase was more resistant to the action of the fungicides than was the tissue (yeast) phase. The addition of a wetting agent increased the efficiency of several fungicides. The time required for disinfection with a given concentration of fungicide, or the concentration required to disinfect within a given time, can be determined by interpolating the plotted graphs.