A Maximum of Temperature in the Middle Ionosphere
J. FUCHS1 has already pointed out the fact that from the change of electron-density (N) with height (h) conclusions as to the temperature in the ionosphere can be drawn. It was, however, not possible then to carry out exact calculations for two reasons: first, the electron-density was only known to be dependent on the apparent height (h′), and secondly, the process of electron loss was not known in more detail, so that Fuchs had to calculate with a recombination-coefficient constant as to space and time.
The role of bone marrow in the immune response.
Publisher Summary This chapter summarizes the various experimental findings related to the source and function of various immunocompetent cells to define the functions of these cell types with respect to the induction of the humoral and cell mediated immune responses. The chapter evaluates the role of the bone marrow as a source of and as an influence upon stem cells and immunocompetent cell precursors and presents a scheme of cellular interactions culminating in antibody formation that incorporate the findings of all investigations to date in a variety of animal species. The scheme presents the specific multicellular pathways composed of a number of specialized cells rather than the single cell pathway characterized by a single, pluripotential immunocompetent cell. Furthermore, it also appears to supply the microphages as well as the cells that constitute the cellular infiltrations in cell-mediated immune reactions. A better understanding of the immune processes and the cellular events and interactions that lead to the humoral and cell-mediated immune responses will greatly facilitate the comprehension of the etiology, pathogenesis, and management of the immune deficiency syndromes, autoimmune states, and related diseases and will hasten the evolution of more rational and scientifically based approaches to prevent the graft-versus-host reaction and the graft rejection by the host.
Pharmacokinetics of amikacin and chloramphenicol in the aqueous humor of rabbits
Composite data describing ocular pharmacokinetics are unreliable because of intersubject variation. To address this problem, an animal model was developed in which multiple aqueous samples from single subjects were obtained. Following direct anterior chamber or intravenous administration of amikacin or chloramphenicol, pharmacokinetic analysis of drug concentrations in the serum and anterior chamber was performed by using a nonlinear least-squares regression program. The number of anterior chamber paracenteses performed did not alter the beta elimination rates or percent penetration into the anterior chamber. The aqueous humor and peripheral-compartment terminal slopes were identical. These data indicate that complete ocular concentration-time curves can be obtained without altering antibiotic pharmacokinetics. Following direct injection into the anterior chamber, the elimination rates for both antibiotics followed a one-compartment model, whereas those following intravenous administration best fit an open, first-order, two-compartment model. Following intravenous administration, the anterior chamber elimination rate constants for both drugs were equal to that of the serum and significantly longer than that following direct injection. The elimination rates of both drugs following direct injection were similar. Systemic administration resulted in drug levels in aqueous humor that persisted longer than those following direct injection. Chloramphenicol, a lipophilic compound, gave higher mean concentrations in aqueous humor than did amikacin. Our model provides a new approach which rigorously examines ocular pharmacokinetics and provides data which suggest that for selected compounds the parenteral route of administration is preferable.